Relaxation Techniques

Relax Your Mind

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Tj and T2 relaxation proton density and weighting

Relaxation is comprised of two distinct processes, both of which occur exponentially, but are independent of each other and have different time constants (T1 and T2). The T1 relaxation reflects nuclei falling back from the high to the low energy state, where T1 (the spin-lattice relaxation time constant) is the time for 63 recovery of the longitudinal magnetization (Mz). The T2 relaxation reflects the decay of transverse magnetization (My) due to loss of phase coherence among the precessing nuclei (spin-spin relaxation), where T2 denotes the time at which the transverse magnetization has decayed to 37 4 of its maximum strength. T1 relaxation is always longer than T2 relaxation. The strength of the tissue signal also depends upon the proton density (PD), i.e. the number of hydrogen nuclei present per unit area of tissue. T1 and T2 relaxation and proton density of fluids, water and fat-based tissues Fluids have long T1 relaxation times (about 1500 - 2000 ms), tissues that are...

Relaxation rates of neoplastic tissues

An early NMR study 2 in rats revealed that Ti relaxation times were nearly three times longer in 3 Novikoff hepatomas compared to 5 normal liver specimens. The T2 relaxation times were about twice as long in the tumors. Subsequently, these authors reported that a combined Ti and T2 normalized NMR malignancy index distinguished cancerous and normal tissues in 36 colon samples, 22 of 23 breast samples and 26 of 29 lung samples 3 . However, in a more recent study 4 human surgical samples of malignant and normal large bowel, while showing statistically significant differences in Ti and T2 relaxation times, these differences were considered too small to use the NMR method alone for diagnosis (p. 51).

Relaxation strategies

Relaxation strategies are based on the notion that individuals with social phobia experience extreme physiological arousal that interferes with performance. Applied relaxation involves training in three skills. First, the patients learn to attend to the physiological sensations of anxiety. Second, the patients learn to relax quickly while engaging in everyday activities. Finally, the patients learn to apply relaxation skills in anxiety-provoking situations. (90 Applied relaxation thus combines relaxation and exposure to help individuals cope with anxiety-provoking situations. Treatment studies suggest that applied relaxation is superior to delayed treatment (91, and as effective as social skills training. (,92 However, applied relaxation was less effective than cognitive treatment in one study.(91) Research has demonstrated minimal improvement in social phobia symptoms when relaxation techniques are not combined with exposure 61,62)

Relaxation Of Muscle Cell

After Ca2+ binds to calmodulin, the resulting complex stimulates the activity of NO synthase, an enzyme that catalyzes formation of NO from O2 and the amino acid arginine. Because NO has a short half-life (2-30 seconds), it can diffuse only locally in tissues from its site of synthesis. In particular NO diffuses from the endothelial cell into neighboring smooth muscle cells, where it triggers muscle relaxation (Figure 13-30). The effect of NO on smooth muscle is mediated by the second messenger cGMP, which can be formed by an intra-cellular NO receptor expressed by smooth muscle cells. Binding of NO to the heme group in this receptor leads to a conformational change that increases its intrinsic guanylyl cyclase activity, leading to a rise in the cGMP level. Most of the effects of cGMP are mediated by a cGMP-dependent protein kinase, also known as protein kinase G (PKG). In vascular smooth muscle, protein kinase G activates a signaling pathway that results in...

B1 NMR Relaxation of aD and 1H in Aqueous Solutions of 3Lactoglobulin

Deuterium Nmr Mobility

Proton, deuterium, and oxygen-17 NMR relaxation can be used to investigate the amount and mobility of water bound to proteins. In this example, we illustrate the analysis of pulsed NMR relaxation data for 2D and 'H nuclei of water in a protein solution for such a system. Figure 8.2 shows typical proton relaxation results for an aqueous solution of the protein 3-lactoglobulin A. The transverse relaxation data gave a Figure 8.2 Proton NMR peak intensities vs. delay time r for 0.061 g 3-lactoglobulin A g H20 at pH 6.2,30 C. Longitudinal relaxation data (T , o) from inversion recovery experiment with line representing best fit to single exponential model in eq. (8.2) and transverse relaxation data (7 2, ) from spin-locking measurements with line representing best fit to sum of two exponentials in eq. (8.4). (Reprinted with permission from 3 , copyright by Academic Press.) Figure 8.2 Proton NMR peak intensities vs. delay time r for 0.061 g 3-lactoglobulin A g H20 at pH 6.2,30 C....

B3b Models for Deuterium Relaxation in Protein Solutions

The simplest model of protein hydration is a two-state one, where water (i.e., D20) exchanges chemically between a bound and a free state. Using the general approach to equilibrium problems described in Chapter 6 and making the reasonable assumption that for bound water is much less than that of free water, the observed longitudinal relaxation time is 7 ru relaxation time of 2D for bound water, T ,o relaxation time of 2D for free water, where the relaxation times have been replaced by the corresponding relaxation rates (Ri l 7 ). The frequency (oj)-dependent relaxation rates 0bs and i i are distinguished from the frequency independent Rifl ones for free water. In other words, the frequency dependent component of the measured deuterium relaxation rate is directly proportional to the longitudinal relaxation rate of the deuteriums in water bound to the protein. A consequence of eq. (8.8) is that the fastest of the dynamic processes dominates the observed field dispersion of the...

Fundamentals of NMR Relaxation

Relaxation is a general term used to describe the movement of a system toward equilibrium after an injection of energy. When atomic nuclei in a molecule are excited in a pulsed nuclear magnetic resonance (NMR) experiment, the excited state may exist for a rather long time, often seconds to minutes 1 , Characteristic relaxation times estimated in an NMR experiment can be used to provide information about molecular motion. In the following paragraphs, we provide a simplified summary of pulsed NMR relaxation. The reader may consult texts on this subject for further details 1, 2 , where M0 is the magnetization at thermal equilibrium, and T is a characteristic relaxation time called the longitudinal relaxation time. Longitudinal denotes that the z component of the magnetization is of importance here. When the magnetization is moved away from the z direction, it will return to the 2 axis with a time constant Tx. where A* is the limiting peak height at long times and Rt 1 Tj is the...

Molecular Tumbling And Nmr Relaxation

Molecular Tumbling Rate

What is the mechanism of spins dropping down from the ft state to the a state and fanning out around the two cones, and what determines the rates (R1 1 T1 and R2 1 T2)ofNMR relaxation These processes are intimately tied to the motion of molecules as they tumble ( reorient ) in solution in their rapid Brownian motion, and measurement of the NMR relaxation parameters T1 and T2 can even give us detailed information about molecular dynamics (motion) from the point of view of each spin in the molecule. A simplified model of these physical processes and their consequences for NMR will help you to understand the effect of molecular size on relaxation and the NOE. The nucleus cannot simply transfer energy to molecular motions (vibration, rotation, translation, etc.) by collisions because the nucleus is not really attached to the rest of the molecule. The tiny nucleus sits in a vacuum very far from the bonding electrons that hold the molecule together, and its only mechanism for interaction...

Impaired Relaxation of Arterioles to Vasodilator Stimuli

In addition to an enhanced response to vasoconstrictor stimuli, arterioles of hypertensive animals exhibit an impaired relaxation in response to a variety of vasodilator stimuli including hypoxia, shear stress, and endothelium-dependent vasodilators, such as acetylcholine (ACh). Impaired relaxation of arterioles to endothelium-dependent vasodilator stimuli such as ACh has also been demonstrated in human hypertensive patients. The impaired vascular relaxation in hypertensive individuals has been proposed to be due to a reduced production of endothelium-derived vasodilator compounds, such as nitric oxide (NO) or vasodilator prostaglandins, and or to an enhanced release of vasoconstrictor factors (e.g., thromboxane or prostaglandin H2) from the endothelium. The reduction in endothelium-dependent dilation mediated by NO also may result from increased levels of oxidative stress in the tissue, which would destroy NO and reduce its availability for mediating vascular relaxation. There is...

Imagery and relaxation

There is a wide range of relaxation methods including progressive relaxation, imagery training, biofeedback, meditation, hypnosis, and autogenic training, but little evidence to indicate superiority of any one approach. Furthermore, there is little evidence to support the presumption that insomniacs are hyperaroused in physiological terms or that relaxation has its effect through autonomic change. At the cognitive level, these techniques may act through distraction and the promotion of mastery. During relaxation the mind focuses upon alternative themes such as visualized images or physiological responses. In meditation the focus is upon a 'mantra' and in self-hypnosis upon positive self-statements. Relaxation may be effective for thought processes that are anxiety-based, confused, and which flit from topic to topic.


The equilibrium state is characterized by a complete lack of coherence (random phase), a slight excess of population in the a state (N 2 + 5), and a deficit in the j state (N 2 - 5). Anything that perturbs this equilibrium (e.g., an RF pulse) will be followed immediately by a process of relaxation back to the equilibrium state that can take as long as seconds to reestablish. Relaxation is extremely important in NMR because it not only determines how long we have to wait to repeat the data acquisition for signal averaging, but it also determines how quickly the FID decays and how narrow our NMR lines will be in the spectrum. Relaxation is also the basis of the nuclear Overhauser effect (NOE), which can be used to measure distances between nuclei one of the most important pieces of molecular information we can obtain from NMR. 5.5.1 Relaxation After a 90 Pulse

Muscle Relaxation

Benzodiazepines have the capacity to depress polysyn-aptic reflexes and have been shown to decrease decere-brate rigidity in cats and spasticity in patients with cerebral palsy. What is not clear is whether they can, in humans, relax voluntary muscles in doses that do not cause considerable central nervous system depression. Nevertheless, benzodiazepines, such as diazepam, are often prescribed for patients who have muscle spasms and pain as a result of injury. In these circumstances, the sedative and anxiolytic properties of the drug also may promote relaxation and relieve tension associated with the condition.

Assessment of the airway

In addition to assessment of the airway, the presence of ventilatory effort should also be monitored. Phonation, detection of breath sounds, particularly using a stethoscope applied over the upper trachea and both lung fields, and the feel of breath on the hand are readily observable clinical signs. In the presence of spontaneous ventilatory effort an obstructed airway may present with paradoxical chest movements. As the diaphragm contracts the abdominal contents descend, causing the girth to increase, while at the same time the chest wall collapses and a tracheal tug is evident as the more mobile tissues of the neck are drawn down towards the thoracic inlet. This alternates with relaxation of the diaphragm and contraction of the abdominal muscles, reversing the abdominal and thoracic movements.

The Brain and Related Structures in CT

The two major types of MRI images (MRI T1 and MRI T2) are related to the effect of RP on protons and the reactions of these protons (relaxation) when the RP is turned off. In general, those cancelled out protons return slowly to their original magnetic strength. The image constructed from this time constant is called T1 (Fig. 1-2). On the other hand, those protons that achieved a higher energy level (were not cancelled-out) lose their energy more rapidly as they return to their original state the image constructed from this time constant is T2 (Fig. 1-3). The creation of a T1-weighted image versus a T2-weighted image is based on a variation in the times used to receive the echo from the relaxed protons.

Continence Abnormalities

Obstetric trauma is the most important etiologic factor in the pathogenesis of fecal incontinence in women. There is evidence that hormonal changes during pregnancy lead to smooth muscle relaxation attributed to progesterone. Relaxin is an ovarian hormone that peaks late during pregnancy and leads to connective tissue remodeling in the pelvic floor.23 With parturition, there is stretching of the levators, stretching and tearing of the rectovaginal septum, stretching of the vaginal wall, and compression of the pudendal nerves against the pelvic side wall. All these factors may contribute to fecal incontinence.

Proton NMR titration method

Repeated measures of spin-lattice relaxation rate 1 T1 and spin-spin relaxation rate 1 T2 provide data to measure hB the hydration of limit of all water bound to the backbone of protein and also give a good measure of hRa. The method was first applied in 1986 to the globular protein lysozyme (Fullerton et al., 1986c), as shown in Fig. 1.8. Results were nearly identical in general form to the more recent results measured for collagen in 2006 (Fullerton et al., 2006c). The correlation of NMR titration results with the structural information provided by collagen provides the framework to correlate specific types of hydration compartments with slowed water motions. The plots of spin echo relaxation times and amplitudes in Fig. 1.9 show sharp changes at hydration capacities near the monolayer hydration capacity hM as T2 relaxation is dominated by slowed motion of protein tumbling when surface water is lost.

Dynamic hyperinflation

In normal subjects at rest, the end-expiratory lung volume (functional residual capacity (FRC)) corresponds to the relaxation volume ( Vr) of the respiratory system, i.e. the lung volume at which the elastic recoil pressure of the respiratory system is zero. Pulmonary hyperinflation is defined as an increase of FRC above the predicted normal value. This may be due to increased Vr as a result of loss of elastic recoil (e.g. emphysema) or to dynamic pulmonary hyperinflation, which is said to be present when the FRC exceeds Vr. Dynamic hyperinflation exists whenever the duration of expiration is insufficient to allow the lungs to deflate to Vr prior to the next inspiration. This tends to occur under conditions in which expiratory flow is impeded (e.g. increased airway resistance) or when the expiratory time is reduced (e.g. increased breathing frequency). Expiratory flow may also be retarded by other mechanisms such as persistent contraction of the inspiratory muscles during expiration...

Effects of dynamic hyperinflation on work of breathing and mechanical performance of inspiratory muscles

Fig. 1 Volume-pressure diagram of the relaxed respiratory system showing the increase in elastic work caused by dynamic hyperinflation area A, elastic work for a breath that starts from the relaxation volume Vr area B, elastic work for a similar breath to A but starting from a volume 29 per cent VC higher than Vr. In case B, the intrinsic PEEP is 15 cmH2O, as indicated by the upper circle.

Magnetic Resonance Imaging MRI

How are MR signals sampled and processed to produce the kinds of pictures that we are used to seeing the brain's anatomy in fine detail First, different tissues have different relaxation times i.e. times of emitting the absorbed RF energy pulse, which form the basis of contrast in the MR image. For example, fat has a shorter relaxation time than does tissue or water. Pulse sequences are a series of RF pulses and gradients applied in a precise reproducible manner which are varied to emphasize different tissue types relative to their respective relaxation times (Fig. 2). So-called T1-weighted images emphasize grey-white brain tissue

The SH model predicts both vibrational dynamics and enzyme activity changes

Enzyme activity, vibration, and hydrogen exchange all show compartmental capacities that correlate with predictions of the SHM. Furthermore, the SHM relates fast conformational fluctuations in the picosecond range to hydration of the protein backbone. As globular lysozyme consists of two domains with both a-helix and b-sheet components, it leads to the hypothesis that fast fluctuations are vibrations of tightly bound protein secondary structures. Additionally, backbone water bridges participate in tight hydrogen bonding between amide and carbonyl groups, which predicts a monotonic increase in the proton exchange rate as the number ofbackbone amide protons associated with water increases with each bridge until all sites are fully occupied at hB 0.217 g g. The slow relaxation process starts to increase above hB 0.217 g g where the SH model predicts DWC form around the water bridges. DWC cover charge sites on the immobilized water bridges and remaining polar sites on the side chains of...

Intentionality in biological systems

The case that intentional processes, as defined in the quotation by Searle, are seen throughout biological systems is made first through an example. This serves to highlight particular features of intentional processes that are unique to biological processes, and indeed help to define them. Blood pressure is regulated by a number of mechanisms including a circuit from receptors in the arterial wall (baroreceptors), via nerves to the brainstem, and further nerves to muscles in the arteries that alter blood pressure through contraction and relaxation. The electrical impulses in the nerves, and in the brain stem, carry information about blood pressure, and hence meet Searle's definition. This formulation would not present difficulties for most physiologists but it would for Searle on the grounds that there is a lot that is different between the workings of the mind and the regulation of blood pressure. This is indeed true and so our task is to show the ways in which intentionality is the...

Magnetic Resonance Imaging

The T1 component (or spin-lattice relaxation) depends on the time taken for the protons to realign themselves with the magnetic field and reflects the way the protons interact with the 'lattice' of surrounding molecules and their return to thermal equilibrium. The T2 compound (spin-spin relaxation) is the time taken for the protons to return to their original 'out of phase' state and depends on the locally 'energised' protons and their return to electromagnetic equilibrium.

Diffusionweighted imaging

The basic idea is that protons move within and between cells by random motion. Typically, a proton may travel around 20 pm in 100 ms by this Brownian motion or diffusion. The rate of diffusion will be greatest for protons that are moving freely through the cerebrospinal fluid and less for protons constrained by physical barriers such as myelinated cell membranes. The rate of diffusion affects the spin-spin relaxation time, with rapidly diffusing protons tending to relax more quickly. To acquire images that are weighted by differences in diffusion, two extra gradients are briefly applied during a spin echo sequence. (1)

Exogenous and endogenous contrast agents

The first involves the administration of an exogenous contrast agent, such as gadolinium diethylenetriaminepentaacetic acid ( Gd-QTPA). Gd-DTPA has marked paramagnetic properties causing a local change in the effective magnetic field. When given intravenously as a bolus while the subject is exposed to experimental stimulation, Gd-DTPA causes locally increased field strength in those regions (and only those regions) that are neurally activated by the stimulus. This effect on the field alters the magnetic resonance properties of protons, namely the spin-spin relaxation time, creating tissue contrast between brain regions activated by the stimulus and regions that are not activated. The second approach involves exploiting the existence of an endogenous contrast agent. Iron in deoxygenated haemoglobin has paramagnetic properties similar to Gd-DTPA. It also does not diffuse out of the vascular compartment. Neural activity causes a local reduction in the ratio of deoxygenated to oxygenated...

Gradient echo sequence

In gradient echo imaging, the process of spin-spin relaxation (dephasing) is first accelerated by briefly applying a gradient to the magnetic field shortly after the excitation pulse. Then, at some time (TE 2) after the excitation pulse, a second gradient is applied to reverse the process of dephasing, causing rephasing and a signal maximum or echo some time (TE) after excitation. The sequence is repetitively applied with a constant time interval between consecutive excitations (TR). The objective is to manipulate spin-spin relaxation by brief perturbations of the external magnetic field rather than by supplying additional pulses of radiofrequency energy as in spin echo imaging. Frequency- and phase-encoding gradients are applied to locate the sources of signal in three-dimensional space (see Ch pteri2.3.7).

The Role of Second Messengers in Receptormediated Responses

For example contraction, secretion, relaxation, or altered metabolism. The total process of converting the action of an external signal (e.g., norepinephrine interacting with its receptor) to a physiological response (e.g., vascular smooth muscle contraction) is called signal transduction. The specific second-messenger pathways constitute a highly versatile signaling system that can modify (stimulate or inhibit) numerous cellular processes including secretion, contraction and relaxation, metabolism, neuronal excitability, cell growth, and apoptosis. The second messengers that participate in signal transduction include cyclic adenosine monophosphate (cAMP), diacylglycerol, and inositol triphosphate. Once liberated within the cell, second messengers will activate specific

Use of Nanoparticles in Biomedical Imaging A Historical Perspective

Although magnetic nanoparticles were reported to have the ability to modulate MR relaxation times in the late 1970s (Ohgushi et al., 1978), their applicability as MR contrast agents were not explored until the mid-1980s (Mendonca Dias and Lauterbur, 1986 Renshaw et al., 1986a,b). Also during this time, liposomes entered the arena of non-invasive imaging as paramagnetic agents for MR imaging (Unger et al., 1988), iodinated agents for computed tomography (Havron et al., 1981 Ryan et al., 1983), and radioactive agents for nuclear medicine (Morgan et al., 1981). In addition, ultrasound bubbles were introduced for sonographic purposes (Widder and Simeone, 1986). In the 1990s, quantum dots were introduced for fluorescent imaging (Alivisatos, 1996 Chan and Nie, 1998) (Figure 1.1) including non-invasive imaging in rodents.

Effects on Nonvascular Smooth Muscle

Smooth muscle of the gastrointestinal tract is generally relaxed by catecholamines, but this may depend on the existing state of muscle tone. Usually motility of the gut is reduced by catecholamines while the gastrointestinal sphincters are contracted. Catecholamines appear to produce relaxation of the gut through an action on -adrenoceptors on ganglionic cells. Activation of these receptors reduces acetylcholine release from cholinergic neurons. Catecholamines also may produce gastrointestinal relaxation through an action on ( 2-adrenoceptors on smooth muscle cells. Contraction of the sphincters occurs through an action on aradreno-ceptors. These effects are quite transient in humans and therefore have no therapeutic value. Uterine muscle contains both a- and (-adrenocep-tors, which mediate contraction and relaxation, respectively. The response of the human uterus to cate-cholamines is variable and depends on the endocrine balance of the individual at the time of amine administration...

Conventional precordial compression

Chest compressions are applied by the rescuer who places the heel of one hand over the lower half of the victim's sternum and the other hand on top of the first hand. Downward force displaces the sternum for a distance of 3.5 to 5 cm for adult patients. The compressions are repeated at a rate of 80 to 100 min with equal compression-relaxation intervals.

BAdrenoceptor Agonists

Agonists of b-adrenoceptors have been used for many years as bronchodilators in the treatment of asthma, and they remain the most widely used group of bronchodilators in therapy. Epinephrine, an agonist exhibiting relative selectivity for b-adrenoceptors, was the first b agonist used in the treatment of asthma. Through the years, agonists have been developed that are selective for the b-adrenoceptor mediating human airway smooth muscle relaxation, viz. the b2-adrenoceptor. Examples of drugs of this type include albuterol (salbutamol), fenoterol, terbutaline, and metaproterenol. Further development has led to drugs, such as formoterol and salmeterol, which exhibit longer residence times in the airways and consequent increases in duration of action 29 . Stereoisomers of

Imaging of the Genitourinary Tract in Females

Pelvic organ prolapse and pelvic floor relaxation are common problems in older multiparous women, affecting approximately 16 of women aged 40 to 56 years.1 A detailed knowledge of pelvic anatomy is paramount for the proper evaluation and management of such patients. Although a thorough pelvic examination is always indicated, even experienced clinicians may be misled by the physical findings, having difficulty differentiating among cystocele, enterocele, and high rectocele by physical examination alone. Depending on the position of the patient and strength of the Valsalva maneuver, the surgeon may be limited in his or her ability to accurately diagnose the components of pelvic prolapse. Furthermore, with uterine prolapse, the cervix and uterus may fill the entire introitus, making the diagnosis of concomitant anterior and posterior pelvic prolapse even more difficult. Regardless of the etiology of the support defect, the surgeon must identify all aspects of vaginal prolapse and pelvic...

Polarization Transfer Schemes

Once spectral resolution is optimized, (13C,15N) evolution and detection dimensions can be connected by through-space, through-bond, or relaxation-mediated transfer pathways along the polypeptide chain (Figure 2.1). Amino acid types and intraresidue interactions are, perhaps, most easily obtained from (13C,13C) broadband correlation spectra. Such experiments can involve through-bond44-46 or through-space interactions. For the latter, (13C,13C) interactions may be actively recoupled (see Refs. 6, 47 for recent reviews), or they may rely on (13C,13C) transfer facilitated by multiple-(1H) spin effects.4849 Discrimination of intraresidue or interresidue transfer can be easily established by rendering the dipolar (N,C) transfer chemical-shift selective. For this purpose, the conventional Hartmann-Hahn cross-polarization condition50,51

Mechanism Of Action

Dicyclomine (Bentyl), oxybutynin (Ditropan), and tolterodine (Detrol) are nonselective smooth muscle relaxants that produce relatively little antagonism of muscarinic receptors at therapeutic concentrations. The mechanism of relaxation is not known. Finally, some other classes of drugs can act in part as muscarinic antagonists. For example, the antipsychotics and antide-pressants produce antimuscarinic side effects (e.g., dry mouth).

Nmr Data Acquisition And Acquisition Parameters

(a) Wait for a period of time called the relaxation delay for spins to reach thermal equilibrium The audio signals must be converted into a list of numbers, which is the only language that a computer understands. This is done by sampling the voltage of each signal at regular intervals of time and converting each analog voltage level into an integer number. Thus, an FID becomes a long list of numbers, which is stored in the computer memory. As the same FID is acquired over and over again, repeating the sequence (relaxation delay pulse-acquire FID), each new list of numbers is added to the list stored in memory. This process is called sum to memory. As more and more scans or transients are acquired, the signal-to-noise ratio of this sum improves. 3.6.1 Relaxation Delay D1 (Varian) or RD (Bruker) Usually the acquisition (pulse-FID) is repeated a number of times in order to sum the individual FIDs and increase the signal-to-noise ratio. In this case, a delay must be inserted before each...

Rectoanal Inhibitory Reflex

The rectoanal inhibitory reflex is thought to have a role in the fine adjustments of continence. Rectal distension, usually with small volumes (10-30mL), causes a contraction of the external anal sphincter followed by a pronounced internal anal sphincter relaxation. This reflex enables the sensory mucosa of the anal canal to sample the contents of the distal rectum and the patient to distinguish between gas, liquid, and solid stool. This reflex is absent or abnormal in patients with Hirschsprung's disease, Chagas' disease, dermatomyositis, and scleroderma.

Intrinsic Brain Tumors and Functional Mapping

Intraoperative, invasive, functional mapping using cortical stimulation techniques is time consuming and requires modification of the anesthetic regimen. Patients need to be awake for assessment of language function, but light anesthesia without muscle relaxation is adequate for motor mapping. Unlike pre-operative non-invasive mapping, this technique does

Excitationcontraction Coupling

The physiological processes that begin with cardiac sar-colemmal membrane depolarization and culminate in contraction are collectively defined as myocardial excitation-contraction coupling. Depolarization of the cardiac myocyte sarcolemmal membrane during the action potential results in the intracellular entry of extracellular calcium. The major regulators of the transsarcolem-mal entry of calcium include L-type calcium channels and autonomic receptors (Fig. 15.1). These membrane-bound proteins all contribute to the influx of a minute quantity of calcium from outside the cell into the myocyte. The entry of this small quantity of calcium causes the release of the large reservoir of calcium stored in the sarcoplasmic reticulum (SR) through the SR calcium release channel (ryanodine receptor). This large reservoir of calcium interacts with tropomyosin to allow the actin and myosin filaments to overlap, resulting in systolic myocardial contraction. Diastolic relaxation results from the...

Types Of Muscle Tissue

Shortly after the acetylcholine is released, cholinesterase begins to destroy it. Such a rapid destruction of the acetylcholine prevents it from re-stimulating the muscle until another nerve impulse reaches the neuromuscular junction. Figure 2-2 illustrates the relaxation of the muscle tissue. (1) Anatomy. Cardiac muscle is made up of branched, striated fibers and responds to stimuli as if it were a single muscle fiber. Cardiac tissue is responsible for the propulsion of blood through the circulatory system. The contraction and relaxation of the heart move the blood. (2) Physiology. The same chemical substances are found in smooth muscle as are found in skeletal muscle. Contraction of smooth muscle tissue occurs by the activation by ions--just the same as with skeletal muscles Contraction occurs during depolarization of the muscle membrane, and it stops after repolarization. Smooth muscle tissue does not contract as rapidly as skeletal muscle tissue....

Stimulation of Vascular MaxiK Channels

A recent report suggests that estradiol may also produce vascular relaxation in an en-dothelium-independent manner by stimulating smooth muscle Maxi-K channel gates directly.59 Maxi-K channels are key modulators of vascular smooth-muscle tone. Estrogen appears to activate the Maxi-K channel through binding to this membrane receptor's P subunit. Opening of these channels would cause K+ efflux, membrane repolarization, and closure of voltage-dependent Ca2+ channels, leading to a decrease in intracellular Ca2+ and relaxation of blood vessels.

Nervous System Innervation of the Lower Urinary Tract

Isoproterenol, less by epinephrine, and least by norepi-nephrine. When stimulated, beta receptors elicit an inhibitory effect on detrusor muscle contraction. Two subtypes of beta receptors exist, B1 and B2. Beta 1 receptors are located in the cardiovascular system. The beta 2 receptors are located throughout the bladder, but to a greater extent are within the bladder body. Beta receptor stimulation in the LUT inhibits bladder contraction and causes receptive relaxation of the detrusor to allow for increasing bladder volumes, without increasing intravesical pressure (detrusor compliance). Prostaglandins Detrusor relaxation Adenosine 5'-triphosphate Opioids Urethral relaxation Nitric oxide Opioids Urethral contraction Serotonin Epinephrine Supporters of micturition

Nervous System Regulation of Lower Urinary Tract Function

During filling, the normal bladder has a minimal change in intravesical pressure until capacity is reached. At low volumes, the elastic and viscoelastic properties are primarily responsible for compliance. Elasticity allows the constituents of the bladder wall to stretch without a significant increase in bladder wall tension. The viscoelasticity of the bladder causes stretch to induce an increase in tension, followed by a decay when filling stops. In the animal model, it has been shown that at a certain level of bladder disten-tion, spinal sympathetic reflexes facilitory to bladder storage, are evoked. This allows smooth muscle relaxation of the bladder by beta receptor stimulation (accommodation). Spinal sympathetic reflexes inhibit parasympathetic activity at the level of the parasympathetic ganglia during filling. Clinically, detrusor compliance may be altered by any processes that can damage the elastic tissues (chronic cystitis, radiation, ischemia, etc.) or neurologic...

Relationship of the spinecho phenomenon to magnetic field inhomogeneity

Loss of phase coherence ( dephasing ) means loss of RF signal. Part of this loss is due to spin-spin relaxation, expressed by T2, which is an inherent property of the material. The observed rate of decay of phase coherence denoted by T2*, is always faster than T2, because of inhomogeneities of the magnetic field. The part of dephasing due to inhomogeneities can be cancelled by the spin-echo maneuver, in which a 180 RF pulse is applied after termination of the 90 RF pulse. The latter serves to re-gather the transverse relaxation vectors so that they emit a strong signal 14, 15 .

Definition Of A Muscle Relaxant

A skeletal muscle relaxant may be defined as an agent that reduces skeletal muscle tone. Even when muscles are at rest, there is a certain amount of tension or tautness that is present. This remaining degree of contraction of skeletal muscle is called skeletal muscle tone. It is believed that skeletal muscle tone results entirely from nerve impulses originating from the spinal cord. If these nerve impulses are blocked in some manner, the result is decreased skeletal muscle tone skeletal muscle relaxation. The degree of skeletal muscle relaxation ranges from partial to complete depending upon the effectiveness of the skeletal muscle relaxant being used and its site of activity.

Mechanism of Vasodilator Action

The vasodilator action of the nitrates to be produced. The nitrate receptor possesses sulfhydryl groups, which reduce nitrate to inorganic nitrite and nitric oxide (NO). The formation of nitrosothiols, and possibly free NO, has been proposed to stimulate intracellular soluble guanylate cyclase, which leads to an increase in in-tracellular cyclic guanosine monophosphate (GMP) formation (Fig. 17.1). The increase in GMP results in vascular smooth muscle relaxation, possibly through inhibition of calcium entry via L-type calcium channels, decreased calcium release from the sarcoplasmic reticu-lum, or via an increase in calcium extrusion via a sar-colemmal Ca++-adenosine triphosphatase (ATPase).

Blood Oxygen Level Determination

Functional MRI (fMRI) refers to MRI of the brain performed while the subject is performing a specific task. For instance, a patient may be asked to repeatedly touch their thumb and forefinger together while being scanned, and this action causes a small change in blood flow to a specific motor center in the brain. The change in blood flow induced by this action causes a change in the ratio of deoxyhemoglobin to oxyhemoglobin. Deoxyhemoglobin is paramagnetic and relaxes relatively faster on T2*-weighted images than does oxyhemoglobin. This small change in signal can be detected and is known as blood oxygen level determination scans as it depends on the deoxy oxy hemoglobin ratio. The differential in T2* relaxation can be exploited to generate difference maps that are thought to reflect activity in the brain. It is important to note that this technique does not necessarily measure tissue oxygenation, i.e., the partial pressure of oxygen within tissue. Rather, it reflects the available...

Intraoperative Navigation

Frame-based and frameless sterotactic systems are quite useful as well (Fig. 10.5c). They can be used in planning the scalp flap, the craniotomy and the resection. However, the accuracy of these systems relies on concordance between brain position and pre-operative imaging studies. Therefore, alterations in brain volume or shifts of the intracra-nial contents during resection may render these guidance systems less useful as the resection progresses. Intraoperative imaging systems allow the neurosurgical oncologist to bring the post-operative gold standard into the operation. Currently these systems are expensive, often cumbersome and prolong the surgery. However, they combine the advantages of IOUS and stereotaxy.

Ion Channels and Vasodilation

Vasodilators tend to have effects on smooth muscle ion channels that oppose those of vasoconstrictors (Figure 3). In general, they reduce Ca2+ influx by a number of mechanisms (see Figure 3), leading to a reduction in intracellular Ca2+, smooth muscle relaxation, and vasodilation. The only exceptions to this pattern are vasodilators that act through the cAMP-PKA signaling cascade. Voltage-gated Ca2+ channels are phosphorylated by PKA, leading to their activation. Although counter to the general Ca2+-lowering trend induced by most dilators, this increased activity in voltage-gated Ca2+ channels may provide local Ca2+ to maintain the activity of BKCa channels (see Figure 1), despite a general lowering of intracellular Ca2+ by other means. Vasodilators such as acetylcholine, bradykinin, ATP, and histamine lead to relaxation of vascular smooth muscle and decreases in arteriolar tone in intact arterioles by stimulating the release of vasodilator substances from endothelial cells. Ion...

Clinical Development

A genetic basis for drug response is not a new concept. As early as 1902, Archibald Garrod hypothesized that genetic variance in a biochemical pathway for the detoxification of a foreign substance was the cause of alcap-tonuria (Garrod, 1902). During World War II, it was noted that hemolysis related to antimalarial treatment was much more common among African American soldiers, leading to the identification of inherited variants of glucose-6-phosphate dehydrogenase (G-6-PD). It was during this time that scientists discovered that the prolonged muscle relaxation and apnea after suxamethonium in some patients was due to an inherited deficiency of a plasma cholinesterase. Peripheral neuropathy was observed in a significant number of patients treated with the antituberculosis drug isoniazid, leading to the identification of genetic differences in acetylation pathways.

Vascular Tone Vasodilatation EDHF

In the mid-1980s, it became apparent that endothelium-dependent vasorelaxation could not always be completely accounted for by the actions of PGI2 and NO. It had been known for some time that isolated arteries could be relaxed (or dilated) by factors such as acetylcholine (ACh), bradykinin (BK), and adenosine diphosphate (ADP). However, whereas the relaxation could be abolished by the removal or damaging of the endothelial layer, the relaxation was not always completely blocked by the combined inhibition of PGI2 and NO synthesis. It was further noted that the PGI2 NO-independent relaxation was associated with smooth muscle hyperpolarization. These findings prompted some investigators to conclude that an additional relaxing factor must exist they termed it endothelium-derived hyperpolarizing factor (EDHF) 1 .

Sexual Arousal Disorder

Sexual arousal disorder is the persistent or recurrent inability to attain or maintain sexual excitement, which causes personal distress. This disorder includes poor vaginal lubrication, decreased genital sensation, and poor vaginal smooth muscle relaxation. Arousal disorders are primarily physiologic in nature and can often result from pelvic and colorectal surgery and other pelvic disorders, various medications, atherosclerosis, cigarette smoking, and vascular disease. This disorder most closely parallels ED in the male. In fact, a condition of hyperactive sexual arousal disorder, analogous to the priapism state in the male, has also been described.

Mechanism of EDHFMediated Vasodilatation

An agonist binds to its receptor on the endothelium. This binding initiates a cascade of events that leads to an elevation of endothelial cytosolic free calcium ( Ca2+ j). Calcium ionophores, such as A23187, have also been demonstrated to initiate EDHF-mediated dilations by producing an increase in endothelial Ca2+ r (2) Elevated endothelial Ca2+ j stimulates endothelial calcium-sensitive K channels (KCa) and promotes hyperpolarization of the endothelium. Elevated endothelial Ca2+ also results in activation of other pathways that may be important modulators of the EDHF-dependent mechanism. (3) The endothelial hyper-polarization then promotes smooth muscle hyperpolariza-tion by a mechanism that is still quite controversial. One of the prevailing ideas is that hyperpolarization is conducted directly via myoendothelial gap junctions, which form electrical couplings between adjacent smooth muscle and endothelial cells. There is pharmacological, electrophysio-logical, and histological...

Continuouswave Lowpower Irradiation Of One Resonance

The following sections examine three techniques that all use low-power irradiation of a proton resonance in a proton-observe experiment. Homonuclear decoupling involves irradiation at a proton peak during the acquisition period in order to eliminate a J coupling to another proton resonance. This is similar to selective heteronuclear decoupling in that it is used to identify J coupling relationships between nuclei. Presaturation and NOE difference involve irradiation of a signal during the relaxation delay period, either to eliminate an unwanted signal (presaturation) or to observe the enhancement of z magnetization (Mz) of protons that are close in space to the irradiated proton (NOE difference). In either case the purpose of the irradiation is saturation to equalize the populations of the two energy levels (spin states). All three of these experiments are being replaced by new methods using shaped pulses and pulsed field gradients (Chapter 8) Selective 1D TOCSY for identifying J...

Physiology of Female Sexual Function

The underlying physiologic processes in both normal female sexual function and FSD are not yet well understood. Normal female sexual function is based on an interaction between intact anatomic, vascular, and neurologic factors. Sexual arousal is marked by physiologic changes secondary to increased genital blood flow, which leads to vaginal congestion and lubrication, facilitating intercourse. The normal vascular response is a result of cavernosal and arteriole smooth muscle relaxation via the androgen-dependent nitric oxide synthase system during sexual stimulation and arousal. This produces a vascular engorgement of the vestibule and clitoris. Vaginal lubrication is a transudate of serum that results from this normal increase of pelvic blood flow with arousal. Patients with arousal disorders may complain of decreased vaginal lubrication and dyspareunia.

Relationship between Endothelial Membrane Potential VJ and Endothelial [Ca2i

Handful of studies have evaluated the relationship in endothelium from intact arteries. In cultured endothelial cells, Ca2+ influx has been shown to be notably modulated by endothelial Vm. As the endothelial cell becomes more hyperpolarized, the driving force for Ca2+ entry is increased and greater Ca2+ influx results following agonist stimulation 8 . If this relationship were to hold true for endothelium within intact arteries, then one possible effect of stimulating endothelial KCa channels (and thus hyperpolarizing the endothelium) would be to promote greater Ca2+ influx in response to EDHF-dependent agonists. In this scenario, the effect of KCa channel blockers on the EDHF-mediated response could be to prevent endothelial Ca2+ from reaching a critical threshold. However, from the few studies that have addressed this issue in intact arteries, the relationship between endothelial Vm and endothelial Ca2+ is uncertain. When high K+ has been used to nonselectively inhibit all K+...

Acute psychological effects of cannabis use

Cannabis produces euphoria and relaxation, perceptual alterations (including time distortion, and impaired short-term memory and attention), and intensification of ordinary sensory experiences, such as eating and listening to music.(2) The most common unpleasant psychological effects are anxiety and panic reactions.(2) These may be reported by naive users and they are a common reason for discontinuing use.(2)

Summary of Endothelial [Ca2i in EDHFMediated Vasodilatation

J., and Plane, F. (1996). Relative importance of endothelium-derived hyperpolarizing factor for the relaxation of vascular smooth muscle in different arterial beds. In Endothelium-Derived Hyperpolarizing Factor (P. M. Vanhoutte, ed.), Vol. 1, pp. 173-179. Harwood Academic Publishers. 4. Zygmunt, P. M., and Hogestatt, E. D. (1996). Role of potassium channels in endothelium-dependent relaxation resistant to nitroarginine in the rat hepatic artery. Br. J. Pharmacol. 117, 1600-1606. 6. Nagao, T., Illiano, S., and Vanhoutte, P. M. (1992). Heterogeneous distribution of endothelium-dependent relaxations resistant to NG-nitro-l-arginine in rats. Am. J. Physiol. 263, H1090-H1094. This article is

Why So Many Peptidergic Neuromodulators

In the Aplysia feeding circuit, nine members of the myomodulin family of peptides have been identified as co-transmitters of a motor neuron (Brezina et al. 1995). They either potentiate or depress muscle contraction however, they may also accelerate relaxation rate. All nine myomodulins enhanced L-type Ca2+ currents, forming the basis of potentiation and fast relaxation of muscular contractions, whereas their effects on a specific K+ current the basis of depression

Pharmacological Actions

The hemodynamic effects of diazoxide are similar to those of hydralazine and minoxidil. It produces direct relaxation of arteriolar smooth muscle with little effect on capacitance beds. Since it does not impair cardiovascular reflexes, orthostasis is not a problem. Its administration is, however, associated with a reflex increase in cardiac output that partially counters its antihyperten-sive effects. Propranolol and other p-blockers potentiate the vasodilating properties of the drug. Diazoxide has no direct action on the heart. Although renal blood flow and glomerular filtration may fall transiently, they generally return to predrug levels within an hour.

The Fourier transform

The relaxation of the nuclei after exposure to the RF pulse generates a current in the coils surrounding the scanned organ. This current is electronically converted into a time signal c(t) FID. The measured MRS signal is a mixture of various frequencies that decay in intensity over time, with the rate of decay varying among the components. As noted earlier, this recorded signal or FID is a heavily packed, oscillating function, whose information content cannot be visually discerned directly in the time domain.

P NMR data for NTP analogs with modified triphosphate chains

In the phosphorus magnetic resonance spectra of NTP analogs by the changes in the chemical shifts of the phosphorus atoms, phosphorus-phosphorus coupling constants, and relaxation parameters compared to those for the unmodified NTP. In Table 3.11, the 31P NMR data on the chemical shifts and geminal phosphorus-phosphorus coupling constants are presented for many of the known NTP analogs with modifications in the triphosphate fragment. Instead of presenting the original NMR data, all the information was generalized in the form of differences of chemical shift and coupling constant values (A5, AJ) compared to those for the unmodified NTP.

Positioning Incision and Exposure

The patient positioning, appropriate incision placement, and selection of the optimal approach for tumor exposure are the critical elements of successful meningioma surgery. The patient is positioned in such a way that the patient's safety is maximized. Moreover, the ideal position must allow for an approach that provides complete exposure of the tumor and the involved surrounding bone and dura. At the same time, maximal brain relaxation must be achieved by use of gravity and uncompromised venous drainage. The head should be no lower than the level of the heart, regardless of the position selected, and undue severe neck rotation or flexion must be avoided. In addition, surgeon's comfort for the duration of surgery must be

Confirmation of brain edema

Measurements of contrast or radionuclide uptake, but interpretation depends on the size of the markers. MRI is a very sensitive but less specific imaging technique. It is particularly useful for detecting edema in the white matter. Magnetic resonance relaxation time, mapping, and marker-enhanced imaging can be used to interrogate blood-brain barrier integrity. Extravasation of larger molecules into the surrounding tissue can be visualized using marker substances.

Endothelial cells and other cell types

Blood vessels are lined with a single layer of flat cells, endothelial cells this lining is called the endothelium (Fig. 4.19). The whole endothelium in humans is large, weighing around 1.5 kg, with an area similar to that of a football pitch. Endothelial cells provide a smooth lining that reduces resistance to blood flow, but they are also very active in a number of ways. They regulate the contraction or relaxation of blood vessels (by sending signals to the muscle surrounding the vessel), they provide a (regulatable) barrier to prevent cells and large molecules leaving the circulation and entering the surrounding tissue, and they also prevent blood clotting (unless there is damage to the vessel wall). We will consider the first of these functions since it is relevant to metabolism. It was recognised in 1980 that endothelial cells could produce a substance that caused blood vessels to dilate (by relaxation of the smooth muscle layer of the vessel). This substance was called...

Retropubic Therapy for Stress Incontinence

Since 1949, when Marshall et al.1 first described retropubic urethrovesical suspension for the treatment of stress urinary incontinence, and since Burch's landmark article in 1961,2 retropubic procedures have emerged as consistently curative. Although numerous terminologies and variations of retropubic repairs have been described, the basic goal remains the same to suspend and stabilize the anterior vaginal wall, and thus the bladder neck and proximal urethra, in a retropubic position. This prevents their descent and allows for urethral compression against a stable suburethral layer. We select a retropubic approach (versus a vaginal approach) depending on many factors, including the need for laparotomy for other pelvic disease, the amount of pelvic organ relaxation, and whether a vaginal or abdominal procedure will be used to suspend the vagina. Additionally, the age and health status of the patient, and the preferences of the patient and surgeon are also determining factors. We...

Cardiovascular Circulatory Patterns

The pulmonary cycle begins in the right ventricle of the heart. Contraction of the right ventricular wall applies pressure to the blood. This forces the tricuspid valve closed, and the closed valve prevents blood from going back into the right atrium. The pressure forces blood past the semilunar valve into the pulmonary trunk. Upon relaxation of the right ventricle, backpressure of the blood in the pulmonary trunk closes the pulmonary semilunar valve. The blood then passes into the lungs through the pulmonary arterial system. Gases are exchanged between the alveoli. This blood, now saturated with oxygen, is collected by the pulmonary veins and carried to the left atrium of the heart. This completes the pulmonary cycle.

Connexins and Vascular Tone

Gap junctions contribute to regulation of vascular tone. Thus, pharmacologic agents and connexin mimetic peptides, which inhibit gap junctional communication, also inhibit vasodilation. In fact, the well-documented phenomenon of conducted vasodilatation in conduit arteries is explained by longitudinal NO conduction along the vascular wall through gap junctions. Further, connexin-mimetic peptides inhibit the transmission of endothelial hyperpolarization to underlying smooth muscle cells, consistent with a role for heterologous endothelial-vascular smooth muscle communicating junctions in so-called endothelium-derived hyperpolarizing factor (EDHF)-induced vasodilation 8 . EDHF-type vessel relaxation mediated by gap-junctional communication is more prominent for small than large vessels. This is consistent with the finding that functional gap-junctional communication is present in small vessels as indicated by the presence of Ca2+ waves that propagate between endothelial cells 9 .

Respiratory support

Prior to intubation of the trachea, an attempt should be made to ensure that the stomach is empty when respiratory muscle weakness has developed slowly and is not likely to progress with great rapidity. Therefore patients should remain nil by mouth for at least 4 h. In an emergency the stomach may be emptied by inserting a nasogastric tube. The patient should be preoxygenated for approximately 5 min and then anesthesia induced with a suitable induction agent (e.g. propofol, etomidate, thiopental (thiopentone), or midazolam). Muscle relaxation should be ensured with a non-depolarizing muscle relaxant (e.g. atracurium or vecuronium). A cuffed endotracheal tube should be inserted and the cuff inflated while an assistant maintains cricoid pressure, which should only be released once the airway is secured adequately and the endotracheal cuff inflated.

Physiological consequences Lower neuron

Higher centers and local reflex arcs. Loss of this inhibition leads to both a higher firing rate in the lower motor neuron and a loss of reflex relaxation of antagonistic muscle groups during movement. The effects on the a motor neuron are an increased basal tone, manifesting clinically as rigidity. Clinically, spasms are the result of exaggerated uncoordinated reflex responses to minimal stimuli.

Other psychotherapies

Few acute controlled trials of other therapies have been published. Two large-scale studies of individual behavioural therapy are available. In a comparison of behavioural therapy with insight-orientated therapy, antidepressant drugs, and relaxation, the behavioural approach was more effective than insight-orientated therapy (which tended to fair worst overall), but differences between treatments had largely disappeared at 3 months' follow-up. (68 Hersen et al.(69) randomly allocated 125 depressed females to antidepressant drug treatment, social skills training plus antidepressants, social skills training plus placebo or dynamic therapy plus placebo, and found similar outcome in all groups.

Middle Fossa Approach

The patient is positioned supine with the head turned to the contralateral side, with the ear uppermost. Brain relaxation using osmotic diuretics and or lumbar CSF drainage is mandatory. A pre-auricular incision is used and a middle fossa free flap craniotomy performed. This must be made as low as possible to minimize the amount of bone that needs to be removed with ronguers. The petrous bone is then exposed extradurally. The arcuate eminence and greater petrosal nerve are useful landmarks to localize the internal auditory canal. Once located, the internal auditory canal must be opened widely. The dural sleeve is opened along the long axis of the canal. The position of the facial nerve is confirmed. The tumor is then excised, with careful dissection from the nerves and vessels in the canal. The cochlear nerve is usually only revealed once the tumor has been resected. A small plug of fat is placed in the tumor bed. The dura is repaired and the craniotomy closed in standard fashion.

Supplemental Reading

A 77-year-old man is admitted to the hospital for a coronary artery bypass. He has been treated with a p-blocker (Tenormin 100 mg per day), which he took every morning. He is induced with propofol 1 mg kg, fentanyl 5 g kg and vecuronium 8 mg for muscle relaxation. After 3 minutes a decreasing heart rate becomes a worry for the anesthesiologist. The heart rate continues to fall until it reaches 38 BPM. At this point the patient's blood pressure is 80 60 and the anesthesiologist gives atropine 0.4 mg and ephedrine 10 mg. This treatment results in a stable patient. What effects were most likely produced by the anesthesia procedure Could this have been avoided

Measuring Ferritin Iron in Vivo

The bulk of brain iron is stored in ferritin molecules 66,149,150 and an in vivo MRI method called field-dependent relaxation rate (R2) increase (FDRI) can obtain specific measures of the iron content of ferritin molecules (ferritin iron) 59,74,118 . Ferritin, a spherical protein in which upwards of 90 of tissue nonheme iron is stored 149-151 , can sequester iron (as well as other transition metals such as zinc) and may function as a general metal detoxicant 152,153 . Although not a direct measure of other transition metals, FDRI measures of ferritin iron may be pertinent to the overall transition metal storage capacity of different brain tissues. In brain, iron is by far the most abundant transition metal 115,134,135,154 and in this context, the age-related increases of brain ferritin iron levels in normal individuals likely has implications for the homeo-static mechanisms of other transition metals 116,117,152,153,155 . The FDRI method takes advantage of the fact that ferritin...

Empirically evaluated treatments

Systematic desensitization( l5) has been used successfully in the treatment of specific phobias since the mid-1960s. Combining progressive relaxation and graduated imaginal exposure to the feared stimulus, systematic desensitization has been demonstrated to be superior to psychotherapy in some cases (116,11Zand 118) but not others.(H9) Wolpe(H5) contended that systematic desensitization works by the principle of reciprocal inhibition, which asserts that the sympathetic response associated with anxiety is incompatible with, and thus inhibited by, the parasympathetic response that occurs during deep muscle relaxation. Therefore, pairing parasympathetic activation with the feared stimulus leads to the conditioning of relaxation to the phobic stimulus. More recently, theorists have taken the position that the exposure component is responsible for the efficacy of systematic desensitization, while the decrease in autonomic arousal achieved by relaxation enhances habituation to the feared...

Management of specific phobia

Several investigations suggest that tailoring treatment to individual response patterns will improve outcome. For example, patients with a profile of heightened physiological reactivity may respond preferentially to applied relaxation, while patients with a profile characterized by avoidance may respond better to in vivo exposure.(121) Patients who experience their anxiety primarily in the form of anxious thoughts may respond better to cognitive techniques than patients whose symptoms are characterized more by somatic arousal.(139)

Psychological treatments

Almost anything that can help the patient accomplish the actual exposure appears to be useful and helpful. For instance, manuals and computer programs, as well as telephone-based supervision and encouragement have been shown to be effective. Although many therapists utilize relaxation techniques, applied relaxation has been the most widely utilized and effective. Many therapists employ breathing retraining, encouraging people who hyperventilate to slow their breathing by utilizing their diaphragm. Although both have been shown to be effective and are widely utilized, other studies suggest they may not be essential components of treatment, and their use does vary. Cognitive-based treatments involving education, breathing retraining, and applied relaxation primarily involve a systematic programme of cognitive restructuring and

Types And Causes Of Hypertension

Endothelial cells are important mediators of vasoconstriction and vasodilatation. This mediation is brought about by the production of nitric oxide (a vasodilator) by the endothelium.2829 Inhibition of platelet aggregation relaxation are some ways nitric oxide can affect the body.30 Alterations in L-arginine, a compound that forms nitric oxide, can lead to a decrease in nitric oxide production and high blood pressure. While not directly related to nitric oxide, cyclooxygenase (COX) can cause vascular damage by producing superoxide anions and prostanions31 (see Figure 10.1).

Tensiontype headache

Physiotherapy is the treatment of choice for musculoskeletal symptoms accompanying frequent episodic or chronic tension-type headache. In stress-related illness, lifestyle changes to reduce stress, and relaxation and or cognitive therapy to develop stress-coping strategies, are the treatment mainstays. Prophylactic medication has a limited role. Amitriptyline is first-line in most cases, withdrawn after improvement has been maintained for 4-6 months. Long-term remission is not always achievable, especially in long-standing chronic tension-type headache. A pain management clinic may be the final option.

Management of anxiety and stressrelated disorders

Behaviour therapy, involving relaxation and gradual exposure to the precipitating situation, is of proven value in phobic disorders and in panic disorder when there is avoidance behaviour. A clinical psychologist should assess the patient and organise treatment if behaviour and cognitive therapy are considered appropriate. Phenelzine is a useful adjunct to psychological methods of treatment. Drug treatment is more important in spontaneous panic attacks phenelzine, imipramine, and paroxetine have been shown to be effective.

Reactive Oxygen and Nitrogen Species

Nitric oxide and superoxide anion react very efficiently and inactivate each other as they form peroxynitrite. Thus, the bioactivity of nitric oxide depends, in part, on its interaction with superoxide. Increased levels of superoxide impair relaxation of cerebral arteries in response to endothelium-dependent stimuli. Kontos and Wei were the first to provide evidence that superoxide inactivates nitric oxide (EDRF) in vivo.

Biological Effects

In contrast to BNP and ANF, the C-type natriuretic peptide (CNP) has minor effects upon natriuresis and diuresis. CNP seems to possess an anti-proliferative action on smooth muscle cells in vitro and induces vasodilatation as well as relaxation of smooth muscle cells in the bronchi.

Development of the disorder

Bulimia nervosa starts in a similar way although the age of onset is typically some years later, and shape and weight concerns usually antedate the dieting. The dietary restriction resembles that seen in anorexia nervosa and it leads to weight loss sufficient to result in anorexia nervosa in about a quarter of cases. (As a result of referral bias, this proportion is higher in cases seen in specialist centres.) In the remaining cases there is also weight loss but it is less extreme. After a variable length of time (generally within 3years) dietary control breaks down with the patient's dieting becoming punctuated by episodes of overeating. At first, the episodes of overeating may be modest in size and intermittent, but gradually they become larger and more frequent. As a result, the lost weight is regained and body weight returns to near its original level. By this point the disorder tends to be self-perpetuating. At some stage in this sequence of events, self-induced vomiting and...

Detection of DNA doublestrand breaks by the comet assay

The alkaline comet assay, described earlier, which includes incubation at high pH before and during electrophoresis, is the most common variant now employed. The alkaline comet assay identifies both single- and doublestrand breaks because the two strands of DNA are uncoiled at the breaks by alkaline denaturation. The idea came about that if the assay is performed in neutral buffers (pH 10), it detects only double-strand breaks because the DNA is not unwound. However, it now seems likely that both single- and double-strand breaks are identified by the comet assay at neutral pH (Collins et al., 1997 Olive et al., 1991). The reasoning is as follows. Treatment of cells with detergents and or high NaCl removes membranes, cytoplasm, and nucleoplasm and disrupts nucleosomes (histones are solubilized by high salt or ionic detergents, such as SDS). The nucleoid that is left consists of nuclear matrix and DNA that is negatively supercoiled consequent to the turns that the double helix had made...

AM a Vasoactive Hormone

By endothelial cells and vascular smooth muscle cells. AM is a powerful hypotensive peptide. Its vasodilator effects are mediated in part by an elevation of cytoplasmic cAMP leading to relaxation of vascular smooth muscle cells. In addition, AM acts on endothelial cells it stimulates nitric oxide production via calcium-dependent activation of endothelial nitric oxide synthase, which also contributes to vasodilatation. AM regulates vascular smooth muscle cell proliferation, inhibits endothelial apoptosis, promotes angiogenesis, and regulates blood coagulation and fibrinolysis. Transgenic overexpressing and knockout models further emphasize that AM is crucial to vascular morphogenesis and function.

Role of AM in the Microcirculation

Endothelial cells have been shown to contain an elaborate microfilament system allowing active actin- and myosin-based cell contraction. In peripheral endothelium, activation of cell contraction and disturbance of junctional organization subsequently result in the induction of inter-endothelial gaps followed by enhanced paracellular endothelial permeability. An increased intracellular cAMP level in endothelial cells has been known to decrease the basal permeability properties of the barrier and attenuate the increase in permeability when the endothelial cells are exposed to inflammatory agents. AM, as an autocrine paracrine hormone, is a potent stimulator of cAMP elevation in endothelial cells. AM can stabilize the barrier function of endothelial cells by a cAMP-dependent relaxation of the microfilament system, thereby preventing endothelial cell contraction and paracellular fluid flux.

Hemodynamic alterations

However, glucocorticoids are also of prime importance in maintaining adequate cardiovascular function as shock may occur in glucocorticoid deficiency. Glucocorticoid deficiency is associated with reduced myocardial contractility which responds to corticosteroid treatment. Withdrawal of glucocorticosteroid treatment in patients with chronic hypoadrenalism results in a pronounced fall in lymphocyte b 2-adrenergic receptor density, which may reflect changes in cardiovascular b-receptors, and a reduced cAMP response to isoprenaline. This is associated with impaired left ventricular relaxation and diastolic filling which may contribute to cardiovascular failure in adrenal crisis. Patients with substituted chronic hypoadrenalism have significantly lowered levels of plasma epinephrine (with normal norepinephrine levels), indicating that high local adrenocortical glucocorticoid concentrations are necessary for normal epinephrine production via adrenal medullary enzyme induction. This may have...

Use of SPIOs for Clinical Liver Imaging

Abstract Superparamagnetic iron oxide (SPIO) particles are as MR contrast media composed of iron oxide crystals coated with dextran or carboxydextran. These particles are sequestered by phagocytic Kupffer cells in the normal reticuloendothelial system (RES), but are not retained in tumor tissue. Consequently, there are significant differences in T2 T2* relaxation between normal RES tissue and tumors. This results in an increased lesion conspicuity and detectability. The introduction of SPIO has been expected to substantially increase the detectability of hepatic metastases. For focal hepatocellular lesions, it has been documented that SPIO-enhanced MR imaging exhibits slightly better diagnostic performance than dynamic helical CT in the detection of hypervascular hepatocellular carcinoma (HCC). A combination of dynamic and static MR-imaging technique using Tj- and T2 -imaging criteria appears to provide clinically more useful patterns of enhancement. SPIO-enhanced MR imaging also...

BOX 93 MRI Parameters for Orbital Study

In particular, cystic or vascular lesions are better characterized on MRI and its multisequenced parameters.5-7 For example, a lymphangioma of the orbit can be suggested with a high level of confidence based on the T1- and T2-weighted relaxation characteristics (Figure 9.8).6

Guanylate Cyclase cGMP and Vascular Smooth Muscle

Interestingly, NO was found to be released along the entire lengths of the neurons studied, confirming its ability to affect putative target cells in the three-dimensional space surrounding all parts of the releasing cell. In the vascular system, NO is released constitutively from endothelial cells and nervi vasorum, exerting its relaxant effect on neighbouring smooth muscle cells. Here, the principal molecular target for NO is the enzyme guanylate cyclase which, when activated by NO, converts guanosine triphos-phate (GTP) into cGMP. This so-called second messenger facilitates smooth muscle relaxation through hyperpolarization of the sarcolemma, involving activation of potassium channels and or closure of voltage-dependent calcium channels, both of which are known to be modulated by NO in a variety of cell types. Although several mechanisms have been proposed to explain cGMP-evoked relaxation, the most likely mechanism may involve activation of...

Cerebral Autoregulation

In 1902, Bayliss reported direct contraction and relaxation of canine hindlimb arteries in response to increase and decrease, respectively, of intravascular pressure 15 . This phenomenon, referred to as the Bayliss effect , was attributed to intrinsic properties of vascular smooth muscle cells, and formed the basis of the myogenic hypothesis of autoregulation. Importantly, contraction occurs in response to an increase in transmural pressure rather than intraluminal pressure alone and, as such, can be thought of as a vascular stretch response . The single most important piece of evidence supporting the myogenic hypothesis is the presence of stretch-activated cation channels (SACCs) in myocytes. These channels have been shown to be present in a wide variety of cells, including all three types of muscle cells, in addition to epithelial and endothelial cells. Experimentally, SACCs are studied by the patch clamp technique, their minute currents recorded via a cell-attached microelectrode...

T Hypointense Lesions

Correlations have been found between Tl-hypointense lesion load in the brain and the development of cerebral atrophy (Sailer et al., 2001). This has been noted even in the first years after presentation with a CIS (Dalton et al., 2002). Compared to Tl-isointense lesions, Tl-hypointense lesions exhibit a lower NAA (van Walderveen et al., l999 Brex et al., 2000) indicating more severe axonal damage or loss. They have also been shown to have more prolonged Tl relaxation time and a higher concentration of myoinositol (Brex et al., 2000) as already discussed, the latter may indicate increased glial cellularity either as a response or a contributory mechanism to tissue damage.

Basic Concepts And Techniques

The sensitivity of an NMR experiment depends on the gyromagnetic ratio (y) of the nuclei that are being prepared and the y of the detected nuclei. This sensitivity is further increased if the nuclei under preparation and detection are highly abundant. The potential to significantly enhance the sensitivity of heteronuclear correlation experiments via inverse detection, particularly of low-y nuclei such as 15N and 13C, was recognized at the early stages of the development of two-dimensional NMR.17-19 The basic idea is to make use of the large y, which, first of all, provides a large magnetic moment that leads to a large induction voltage in the receiver coil. Second, most solution-state inverse-detected experiments take advantage of the high equilibrium magnetization of protons by coherent transfer of polarization.1819 Because the transverse relaxation has negligible effects on the timescale needed for CT via isotropic scalar couplings, transfer efficiencies close to 100 are possible in...

Pharmacological Aspects

For one to several minutes and is followed by sedation, relaxation, and tranquility lasting up to an hour. This latter period is sometimes called being on the nod. All effects have largely dissipated within 3 to 5 hours, which requires the user to inject at frequent intervals.

Central Nervous System

Alcohol is primarily a CNS depressant, and the degree of depression is directly proportional to the quantity of ethanol consumed. However, behavioral stimulation can be found after ingestion of small amounts of ethanol. This stimulation is expressed as decreased social and psychological inhibition and is most likely the result of a depression of inhibitory pathways in the brain with release of cortical activity. The behavioral and physiological effects are associated with different blood ethanol concentrations. As the blood ethanol concentration begins to increase, behavioral activation, characterized by euphoria, talkativeness, aggressiveness, and loss of behavioral control, generally precedes the overt CNS depression induced by ethanol. At progressively higher blood ethanol concentrations, the stage of relaxation is transformed into decreased social inhibitions, slurred speech, ataxia, decreased mental acuity, decreased reflexive responses, coma, and, finally, death resulting from...

Myosin Light Chain Kinase MLCK

Endothelium Structure

Actin and myosin are the major contractile components in the cytoskeleton. The cross-bridge movement between actin and myosin provides a mechanical basis for not only the maintenance of centripetal tension but also the development of contractile force in cells during physical or chemical stimulation. In vascular endothelial cells, the interaction between actin and myosin is mainly governed by the phos-phorylation status of the regulatory myosin light chain (MLC). Two major mechanisms control the activity of MLC. On one hand, myosin light-chain kinase directly phosphorylates MLC at Thr-18 and or Ser-19, resulting in MLC activation and actin-myosin binding. On the other hand, myosin-associated protein phosphatase dephosphory-lates MLC and thus counteracts the MLCK effect, leading to cell relaxation. Certain types of agonists and cells can

Beta Band Erd And

Berger was the first to identify a beta rhythm (18-22 Hz) as the characteristic frequency of the motor cortex.65 This was confirmed in a thorough study by Jasper and Penfield who did bipolar recording from the cortical surface in epilepsy patients.66 In the resting individual, the dominant frequency in the motor cortex was about 25 Hz, but premotor areas registered a slower beta rhythm (17-22 Hz). Beta in the motor cortex was blocked by voluntary movement, namely clenching the contralateral fist, or by somatosensory stimulation.66 The beta ERD only lasted about 1 sec even though fist clenching was maintained, the beta oscillation resumed as before. It was blocked again when the subject relaxed. Also about 1 sec after relaxation there could be a brief burst of mu rhythm at about half the beta frequency (12 Hz). For Jasper and Penfield, the return of beta during a sustained contraction represented a state of equilibrium of activity permitting again a synchronization of unit discharge....

Neuromuscular Blocking Agents

In some types of surgery (for example, abdominal surgery) it is highly advantageous to have the patient's skeletal muscles (for example, abdominal surgery) in a state of relaxation. Most general anesthetic agents do not produce a sufficient level of skeletal muscle relaxation. Therefore, neuromuscular blocking agents are administered to achieve the desired muscle relaxation effects. Two commonly used neuromuscular blocking agents

An example of a 13C spectrum

Figure 8.16 shows the J mod spectrum of salbutamol sulphate. As can be seen the J mod 13C spectrum of salbutamol is much simpler than its proton spectrum. The carbons can be assigned as follows A 3 26 C 3 58.8 E 3 61 D 3 70.4 3 3116 2 + 63 127.1 5 3 129.5 1 3 133 and 4 3 156 (carbons 3 and 5 are shifted upheld through being ortho to an OH group). The signal due to carbon B is missing and this illustrates one of the problems of l3C NMR which is that the relaxation times of the carbon atoms tend to vary more widely than those for protons in 'H NMR and thus their signals may be missed or not fully accumulated. This is particularly true for quaternary carbons and it can be seen in Figure 8.16 that the quaternary carbons 1, 4 and 5 give weaker signals than the other carbons which have protons attached. In the case of quaternary carbon B, its signal has been completely missed. Thus the signals

Arteriovenous Malformations

There are several general principles and techniques that are useful during AVM surgery. The techniques used to resect AVMs in specific locations, such as perisylvian, parasagittal, medial temporal and parahippocampal, trigonal, intra-ventricular, basal ganglia or posterior fossa, are beyond the scope of this chapter but are reviewed in detail by other authors. Surgical AVM excision should be an elective procedure, even in patients with ruptured AVMs. In these patients, waiting at least 3 or 4 weeks allows the patient to recover and the hematoma to liquefy, which can greatly facilitate surgery. We routinely administer steroids, anticonvulsants and prophylactic antibiotics before and during AVM resection, particularly for supratentorial AVMs. The use of lumbar CSF drainage or mannitol for brain relaxation is individualized after careful study of all imaging studies. Frameless stereo-taxy or intraoperative ultrasound is useful to help localize deep AVMs, whereas electrophys-iologic...

B 3 a Field Dispersion in Protein Solutions

NMR relaxation provides additional molecular information if it can be done at a series of frequencies. The general observation in NMR frequency dependence experiments in solutions of proteins is that the longitudinal NMR relaxation rates (R, l 7 ) of 2D nuclei are independent of the field at very low NMR frequencies. As NMR frequency (and magnetic field strength) increases, Ri gradually decreases in a sigmoid-shaped curve until finally it becomes independent of the frequency and field strength 7 , An example, shown in Figure 8.5 illustrates the field dispersion of the NMR relaxation. Figure 8.5 Influence of frequency on the 2D-NMR longitudinal relaxation rate for a 30.6 mg mL-1 solution of a-hemocyanin in 80 D20 20 H20. The solid curve represents the best fit of the model in Table 8.3 with two correlation times (i.e., k 2), with tCil 180 ns and tc 2 1070 ns. (Reprinted with permission from 7 , copyright by Elsevier.) Figure 8.5 Influence of frequency on the 2D-NMR longitudinal...

The autonomic nervous system

There are some exceptions to this rule. For instance, the sympathetic nervous system controls sweat secretion via cholinergic fibres (i.e. using acetyl-choline as their transmitter). In addition, the sympathetic nervous system has cholinergic fibres that innervate the blood vessels in skeletal muscle in order to cause relaxation of the vessels. The significance of this will be considered in more detail later (Section 8.4.5). But most aspects of metabolism that it controls involve adrenergic impulses (i.e. liberation of noradrenaline).

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Relaxation Audio Sounds Autumn In The Forest

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