Heavy Metals

Limit test for heavy metals

Many pharmacopoeial monographs contain a limit test for heavy metals. Sometimes the metal is specified, e.g. lead, but often the test is more general. Pharmacopoeial tests often involve precipitation of the metals as their sulphides. A FIA method was developed based upon complex formation between heavy metals and diethyldithiocarbamate (DDC). Figure 3.22 shows the FIA system used for this analysis and illustrates how relatively simple components can be assembled to carry out a complex analytical task. The analysis was achieved by using a segmented flow system where alternate segments of buffer solution + reagent and carbon tetrachloride were produced. In the first extraction coil, the heavy metals in the sample are extracted as their complexes, along with some excess complexing agent, into carbon tetrachloride. In the second extraction coil, the excess reagent in the organic layer is back extracted by the borax solution, which is mixed into the carrier stream. The flow was then passed...

Heavy metals European Pharmacopoeia 248

The test ensures that the substance to be examined has a content of heavy metals, which is below the limit defined in the individual monograph. Heavy metals are in the test defined by the selectivity of the methods to include lead, copper, silver, mercury, cadmium, bismuth, ruthenium, gold, platinum, palladium, vanadium, arsenic, antimony, tin, and molybdenum. The contents of heavy metals in active pharmaceutical ingredients and excipients are tested for two reasons due to the toxicity of the elements, but also because a heavy metal residue is a general marker for the quality of the product. The toxicologically acceptable content of heavy metals in a given substance to be examined is set taking into account its route of administration, size of daily intake, and typical duration of intake. Such calculations impart that a substances taken orally for a short duration in a very low dose could safely be allowed a heavy metal content above 1,000 ppm, whereas a substance given in high...

Preface to the series

The assessment of safe to use starts with the harvested plant material which has to comply with an official monograph. This may require absence of, or prescribed limits of, radioactive material, heavy metals, aflatoxin, pesticide residue, as well as the required level of active principle. This analytical control is costly and tends to exclude small batches of plant material. Large scale contracted mechanized cultivation with designated seed or plantlets is now preferable.

Thermotolerance and Hsp Reallocations in Mammalian Cells

When cells are exposed to a nonlethal heat shock, they can develop a transient resistance against a subsequent heat treatment (Gerner and Schneider 1975). In these so-called thermotolerant cells, damage to cellular structures and functions is either reduced or repaired more rapidly (Laszlo 1992b). Although thermotolerance can develop in the absence of synthesis of Hsp (Kampinga 1993), several observations have indicated that heat-shock proteins play an important role. Firstly, there is a good concordance between the kinetics of the transient heat-induced increase in the expression of Hsp and the kinetics of the induction and decay of thermotolerance (Li and Werb 1982). Also, as mentioned above, agents that induce heat shock proteins, such as heavy metals and ethanol, induce thermotolerance. Conversely, heat causes an increased resistance to these agents (Hahn and Li 1982). Secondly, heat-resistant cell lines (e.g., generated by repeated heating and selection of survivors) have...

Significance Of Impurities In Water For Use In Cell Culture

To avoid interference with the various processes involved in cell culture it is, above all, essential to minimize the presence of biologically active species, for example, endotoxins, bacteria and nucleases. In addition, levels of ionic contaminants, especially multivalent ions and heavy metals, and organic contaminants must be kept low. For ancillary operations, such as initial rinsing of equipment and some media preparation, less tight specifications are acceptable (see Finter et al. 1990).

Air Quality and Deposition in Polluted Areas versus Remote Areas

Deposition of heavy metals including Ni has been monitored systematically in Europe at background sites since the 1990s in the EMEP programme (http www.emep.int index_facts.html). In 2001 the measured Ni deposition varied between 54.6 and 7732.7 ng m 2 57 . The highest deposition was recorded in Svanvik, Norway, at a site located near the Russian border, and under the influence of the Ni-Cu smelters in the Kola Peninsula. The lowest annual Ni deposition was recorded at Irafoss, Iceland. In another study in a polluted area near a Cu-Ni smelter in southwestern Finland, the average annual Ni deposition during 1993-1998 was 64 mg m 2 at 0.5 km from the main stack 58 .

Regional Indicator Surveys The Use of Mosses Lichens Bark

Epiphytic lichens have been extensively used in monitoring as well. The use of lichens as bioindicators of air quality was discovered by the Finnish botanist Nylander in the 19th century, when he noticed that lichens occurred only in the most sheltered locations in the famous Jardins du Luxembourg in Paris 72 . The physiology of lichens makes them sensitive and also vulnerable to air pollutants, especially to high levels of sulfur dioxide (SO2). Therefore, epiphytic lichens are the first to disappear from the immediate surroundings of pollutant sources 72-74 . However, since they obtain their nutrients directly from aerial deposition 75,76 , they are efficient in trapping atmospheric heavy metals in low or moderate pollution conditions 71,77,78 .

Creating Lineage andor Inducible Gene Alteration

Several approaches have been utilized for inducible gene expression in both experimental animals and in culture. Initially, inducible systems involved the use of heat shock, isopropylithio-P-D-galactoside (IPTG), and heavy metals as inducing agents (23,24), but owing to their lack of specificity and toxic side effects, these systems are primarily restricted to use in prokaryotes, yeast, and Drosophila. Unfortunately, at present there is no totally satisfactory inducible system available for use in transgenic mice, though recently several laboratories have reported the successful use of drug- and hormone-inducible systems in mammalian cell culture (25,26). A common aspect of these various approaches is that the majority comprise binary systems involving the use of chimeric transcription factors that can reversibly bind target gene sequences in response to the administered drug or hormone. Modifications of the bacterial tetracycline system (27), the Drosophila ecdysone receptor system...

Nickel Fluxes in Forested Catchments

The atmospheric deposition of heavy metals is dominated by dry deposition of aerosols and particulates 100,101 . Forest canopies are particularly effective in trapping suspended heavy metal aerosols because of the high surface area for interception 102 . It is well known that the precipitation can wash many contaminants from the surfaces of vegetation. Less known is the fate of elements as the solution travels through the soil horizons and moves into streams. Some part of the elements absorbed by plants remain incorporated in stems, leaves, or moss tissues and are released back to the nutrient cycle only after senescence and litter decomposition. Input-output budgets at catchment and stand levels, therefore, are a useful means of describing the mobility, retention and fluxes of elements in the environment 103-108 . considerable areas of peatlands in both catchments, which may be very important to the terrestrial retention observed. Sedimentation of organometal complexes is the main...

The Benefit of Spices

A number of different dental treatments have a toxic effect on the body, but the toxins themselves are either heavy metals or the products of anaerobic bacterial metabolism. Patients who underwent dental treatment at the clinic of Hal A. Huggins, D.D.S., M.S., commonly reported gastrointestinal symptoms. These patients came to Dr. Huggins in the hope that the removal of their mercury-containing dental amalgams, root canals, and cavitations would improve their health. In fact, in the patients who completed their dental treatment with Dr. Huggins, the effect of the treatment on the Most of these patients had amalgam fillings in their mouths. These fillings appeared to be especially hard on the digestion. Amalgam fillings are generally a mixture of mercury, silver, copper, tin, and zinc. It is mercury especially that concerns us here. Although mercury is not the only toxic component of amalgam, it is the most toxic component. Indeed, mercury is the most toxic of the nonradioactive heavy...

Inhibition of Photosynthesis

The photosynthetic apparatus, both its primary photochemical side and its biochemical carbon-fixing part, is one of the most important sites of inhibition by many heavy metals 4 . In all studies investigating this, a much stronger inhibition was found for photosystem II compared with photosystem I. The relative importance of specific inhibition sites, however, strongly depends on the nickel concentration, the irradiance conditions, the organism under investigation and the metal. Most of the work has been carried out with copper and cadmium as the most toxic metals nickel has often been treated only as a side-aspect. In most studies on nickel toxicity published so far, heavy metals were applied to Chlorophyta (higher plants and green algae) in high irradiance or without a dark phase. Under such conditions, direct damage to the PS II reaction center (PS II RC) occurs instead of the formation of Ni-Chls in the antenna. This reaction has been named the 'sun reaction' by K pper et al. 98 ....

Mechanisms of Resistance Against Nickel Toxicity

Plants have developed a number of strategies to resist the toxicity of heavy metals which has been extensively reviewed by many authors (e.g., Prasad and Hagemeyer 5 , K pper and Kroneck 4 , Meharg 132 ). As for mechanisms of damage, this section will focus on recent research and nickel-specific aspects. While metal tolerance is a constitutive feature in plants normally growing on metal-rich habitats such as hyperaccumulators (see Section 4), in Scenedesmus acutus the defense mechanisms were activated only at an elevated level when the cells were actually stressed by metal toxicity 130 .

Exclusion and Sequestration

Many plants detoxify heavy metals by sequestering them in the vacuoles 4 . This plant-specific metal detoxification strategy (animal and bacterial cells do not possess this organelle) provides an efficient form of protection because the vacuole does not contain any sensitive enzymes. When vacuolar sequestration is the major detoxification mechanism, nickel tolerance is often associated with elevated nickel accumulation an extreme form of this sequestration is found in hyperaccu-mulator plants (see Section 4). In most heavy-metal-tolerant plants, the vacuolar sequestration occurs mainly in nonphotosynthetic cells of the epidermis, reducing toxicity to the heavy metal sensitive photosynthetic apparatus 95,136-139 .

Nickel Hyperaccumulation

Plants have developed a number of strategies to resist the toxicity of heavy metals, as discussed in the previous section. Plants that actively prevent metal accumulation inside their cells are called excluders these represent the majority of metal-resistant plants 6 . Other resistant plants deal with potentially toxic metals in just the opposite way, i.e., they actively take up metals and accumulate them. This phenomenon was discovered as early as 1885 by Baumann 152 for zinc accumulation in Thlaspi calaminare, later renamed to Thlaspi caerulescens ssp. calaminare 153 . These plants, which have been named 'hyperaccumula-tors' 7 , are able to actively accumulate several percent of metals in the dry weight of their aboveground parts. This ability provides a promising approach for both cleaning anthropogenically contaminated soils (phytoremediation) and for commercial extraction (phytomining) of metals from naturally metal-rich (serpentine) soils (see Section 4.3.). By now more than 400...

Mechanisms of Nickel Hyperaccumulation

The mechanisms by which hyperaccumulator plants accumulate the enormous amounts of heavy metals in their shoots, and prevent phytotoxicity of these metals, have been a subject of many studies, in particular during the past decade, but many of these mechanisms are still under debate (reviewed, e.g., by Pollard et al. 178 ). When metal concentrations in hyperaccumulators reach toxic levels, several additional resistance mechanisms may become activated. In the mesophyll of Ni-stressed Ni-hyperaccumulating Alyssum and Thlaspi species the concentrations of nickel rises faster than in the epidermis, suggesting that the epidermal sequestration mechanism becomes overloaded so that additional storage sites are needed 95,184 . But even under these circumstances the plants seem to avoid widespread nickel toxicity in the mesophyll, since the Ni accumulation occurs only in a small subset of the mesophyll cells, which are possibly sacrificed in an 'emergency defense' 95 . Under these stress...

Validation Of Raw Materials

Variations in raw materials constitute one of the major sources of problems confronting the pharmaceutical development scientist, production supervisor, or quality control chemist. Variations in materials occur among different suppliers of the same product, depending on the method of transportation chosen, the exposure of materials to undesirable conditions (heat, humidity, oxygen, light), the reliability of the supplier, and the individual supplier's conformance to regulatory requirements in terms of facilities, personnel, operating procedures, and controls. In addition to the important physical characteristics of particle size, surface area, and the like mentioned previously, the manufacturer should check the supplier's assay procedure as part of its own validation program. Other chemical characteristics, such as water content, residue on ignition, and heavy metals, should also be monitored.

Drug Associated Oral Pigmentation

Gingival pigmentation due to heavy metals such as mercury, lead, bismuth, arsenic and others was not rare in the past due to industrial exposure and in some cases therapeutic administration, particularly for the treatment of syphilis. They caused blue, brown or black lines close to the gingival margins due to the deposition of sulphides as a result of reactions with products of the dental plaque. A wide range of drugs can cause more generalised oral pigmentation including antimalarials, phenothiazines and some contraceptive pills 98 . Drugs used in the treatment of HIV infection such as zidovudine and some antifungals such as ketoconazole have also been shown to cause oral pigmentation.

Environmental Exposures

That is not to say that potential environmental risk factors for PD have not been suggested. A universally accepted risk factor for PD is age, as both incidence and prevalence of the disease increase sharply after the age 60 (22). Interestingly, the other factor now accepted as inversely associated with PD is cigarette smoking. A recent meta-analysis of 48 published studies found a statistically significant protective effect of smoking, with a pooled estimate of 0.59 for the relative risk (23). A recent study from our group using family data, which greatly reduces many of the concerns in case-control data, also strongly supports an inverse association with risk for PD (24). Interestingly, the smoking association holds even when individuals have ceased smoking for many years. Two potential biologic mechanisms that have been discussed for this association (i) smoking decreases monoamine oxidase activity, which might be neuroprotective in PD and (ii) nicotine might have a direct...

Use of Nickel Hyperaccumulator Plants for Phytomining and Phytoremediation

Many hyperaccumulators have a good potential to be used for phytoremediation, i.e., to extract and remove heavy metals from anthropogenically contaminated soils, which was first proposed by Chaney 188 and intensively investigated in the following years (recent reviews 4,189-191 ). Some of them even allow for commercially profitable phytomining, i.e., the extraction of metals (mainly nickel) from naturally heavy metal rich soils that are not directly usable as metal ores. After burning of the plants, their ash can be used as a metal ore (first proposed by Baker and Brooks 192 ).

Deciding what to drink

Well water can also have a highly variable content of minerals, mostly in the nonbioavailable form discussed earlier. Well water may also be contaminated with toxic minerals and heavy metals, especially near mountains and mining areas. However, such contamination is not limited to such areas. Drinking any unpurified well water over a prolonged period of time is just another slow version of Russian roulette. Don't do it.

Many Plasmids Help their Host Cells

Plasmids often carry genes for resistance to antibiotics. This protects bacteria both from human medicine and from antibiotics produced naturally in the soil. Plasmids with genes for resistance to toxic heavy metals such as mercury, lead or cadmium protect bacteria from industrial pollution and from natural deposits of toxic mineral. Other plasmids provide genes that allow bacteria to grow by breaking down various industrial chemicals, including herbicides, or the components of petroleum. From the human perspective, such bacteria may be a nuisance or may be useful in cleaning up oil spills or other chemical pollution. Finally, some plasmids provide virulence or colonization factors needed by infectious bacteria to invade their victims and survive the countermeasures taken by the host immune system.

Plasmids may Provide Aggressive Characters

The first plasmids drew attention because they provided their host bacteria with resistance to antibiotics. Other plasmids protect bacteria against heavy metal toxicity. However, many plasmids are known that confer aggressive, rather than defensive properties. These may be sub-divided into two broad groups. Bacteriocin plasmids encode toxic proteins used by certain strains of bacteria to kill related bacteria. Virulence plas-mids carry genes for a variety of characters deployed by bacteria that infect higher organisms, both plants and animals, including humans.

Basic supplement forms

The body requires these elements in very large amounts. Because of this, it is difficult (but not impossible) to overdose on them, as can easily occur with other highly absorbable inorganic salt forms of the mineral elements. This is one reason why taking sea salt is not such a wonderful idea. Sea salt presents most of its mineral elements in the inorganic simple salt form. These elements are absorbed very readily, but they are not associated with the carrier food molecules that allow the effective delivery of small quantities of these elements to the target tissues and target cellular sites. Furthermore, sea salt contains trace to small amounts of many of the highly toxic heavy metals. Having a purely natural source of mineral elements is no guarantee that the equally natural toxic heavy metals are not also present. Colloidal forms of mineral elements are becoming increasingly popular. These forms are advertised as being highly absorbable. However, high...

Functional Gene Arrays FGAs

FGAs contain genes encoding key proteins involved in various environmental processes. Microbial involvement in processes important to ecosystem biogeochemistry such as nitrification, denitrification and sulfate reduction in ocean sediments (Wu et al. 2001 Tiquia et al. 2004), nitrogen fixation in picoplankton communities (Jenkins et al. 2004 Steward et al. 2004), and naphthalene degradation in soils (Rhee et al. 2004) have recently been targets of studies using FGAs. Our laboratory has been actively developing FGAs designed to be comprehensive for the known diversity of microbial functional genes involved in N, C (including methane) and S cycling, as well as genes involved in the biodegradation of organic contaminants and in the resistance to metal toxicity (Wu et al. 2001 Zhou 2003 Rhee et al. 2004 Schadt et al. 2005 Tiquia et al. 2004).

Approaches For Assessment Of Placental Transfer

The ideal approach to determine placental transfer of any compound would be to evaluate it in pregnant women. However, this presents a very obvious ethical dilemma due to the potential risks associated with exposure during pregnancy. Such risks have been highlighted by the unforeseen consequences of the prescription of drugs which have turned out to be pharmaceutical teratogens such as thalidomide and diethylstilbesterol. It is possible to carry out in vivo measurements of chemicals to which pregnant women are unavoidably exposed such as those taken up from the environment e.g., heavy metals, persistent organic pollutants, and medication for conditions such as epilepsy and diabetes through the sampling of adult peripheral blood and cord blood at birth. However, the information that can be obtained from such studies is limited as this information is available for a single time-point only and provides no knowledge about the kinetics of placental transfer. In order to undertake...

IIIB Biological Functions of Three Products of HO1

The bile pigment biliverdin is produced as a consequence of the heme degradation by HO and is then reduced to biliru-bin. Cytoprotection by bilirubin is not an intuitively intriguing concept to most hepatologists, and, as a sign in liver damages, removal of bile pigments is a potential beneficial factor of modern supportive treatment strategies in acute liver failure, such as albumin dialysis (35). On the other hand, cells primed by a wide variety of toxic compounds, such as heavy metals, develop tolerance to subsequent, otherwise lethal injury. Moreover, there is good evidence to suggest a significant role for bile pigments as a cellular antioxidant system (36).

The Nature of Newer Manufactured Nanoparticles

There are a number of bulk-produced nanoparticles that have been used for decades in industry and these are typified by TiO2 and carbon black (CB). In addition to these, the Emerging Nanotechnologies project, conducted by The Woodrow Wilson International Center for Scholars, along with the Pew Charitable Trusts, has identified, as at April 2006, over 200 consumer products into which newer nanotechnology, especially nanoparticles, is incorporated (see The reasons for the rapid expansion in industrial use of this technology are its unique properties due to small size and large reactive surface area. Nanoparticles come in a wide variety of shapes, sizes and chemical compositions. In addition to the spherical shapes observed for particles such as TiO2, shape varieties also include carbon nano-tubes, nanowhiskers and nanofibres. Engineered nanoparticles vary considerably in their size and composition and so would be anticipated to vary in toxicity. Nanotubes and nanowires can range from...

Quality Control of Protein Folding and the Role of Molecular Chaperones in Disease

Protein aggregation in the cell is intimately tied to protein folding and stability. These intrinsic properties of proteins are modified by molecular chaperones. Accumulation of abnormally folded proteins as a result of a variety of stress situations, including hyperthermia, viral infection, ischemia, anoxia, oxida-tive stress, and exposure to heavy metals, triggers the heat shock response, which results in the expression of heat shock proteins (Hsps) in many cellular systems. Constitutively expressed Hsps function as molecular chaperones and participate in protein synthesis, protein folding, protein transport, and protein translocalization processes, and, upon stress, prevent irreversible aggregation of proteins.

Types and sources of polyunsaturated fatty acids

The therapeutic significance of omega-3 PUFAs has been clearly indicated in clinical trials and epidemiological studies (Bucher et al., 2002 Hu et al., 2002). Fatty fish or fish oils are the richest sources of long-chain omega-3 PUFAs, but as already discussed, the dietary intake of fish has decreased. However, fish stocks are also declining and there have been reports indicating the accumulation of heavy metals and pollutants in some fish (Hites et al., 2004). There is thus an urgent need for alternative sources of long-chain omega-3 PUFAs and there is considerable interest in developing new techniques for this purpose. The primary producers of various omega-3 PUFAs in nature are bacteria, algae, fungi, insects and some invertebrates. Other PUFAs are extracted from oily plant seeds (Table 13.2).

Bioremediation Activity

In addition to bioremediation of organic compounds, microorganisms have also been implicated in the bioremediation of heavy metals such as selenium, uranium, cadmium and mercury. Metal remediation can be achieved by precipitation and immobilisation of contaminants (microbes can reduce metal which can result in detoxification and precipitation e.g. mercury is taken up into the cell and delivered to the NADPH-dependent flavoenzyme mercuric reductase, which catalyses the reduction of Hg2+ to volatile, low-toxicity HgO Nascimento and Chartone-Souza 2003), by biosorption (passive sequestration by interaction with live or dead biological material bacteria can be genetically engineered to incorporate metal-binding polysaccharides in their cell surface, or to enhance metal transporters with metal binding metallothioneins in the cytoplasm), or by biomineralisation (formation ofinsoluble metal precipitates by interactions with microbial metabolites thus achieving concentration and reduction in...

Toxicokinetics and Mechanism of Action 211 Toxicokinetics

Following absorption from any route of exposure, cadmium distributes widely throughout the body, with the major portion ending up in the liver and, especially in the kidney. Average cadmium concentrations in the kidney are near zero at birth, and rise with age to a peak (typically around 40-50 g g wet weight) between ages 50 and 60, after which kidney concentrations plateau or decline. Liver cadmium concentrations also begin near zero at birth, increase to typical values of 1-2 g g wet weight by age 20-25, then increase only slightly thereafter 2,3 . The choroid plexus represents the blood-cerebrospinal fluid barrier for heavy metals including cadmium. Cadmium tends to accumulate in the choroid plexus at concentrations much higher than those found in the brain 4,5 .

Modification of aquaporin expression 221 Antisense

There are many examples in the literature of how plant aquaporin function can be assessed using inhibitors, antisense, or RNAi techniques. No doubt that treatment of a complex organism such as a higher plant with inhibitors of aquaporin function, such as heavy metals, could have unforeseen side effects. Furthermore, the use of transgenes to reduce aquaporin expression might downregulate not only the target gene, but also closely related genes. Particularly in plants where complete genome sequence data are not yet available and thus it is not known if closely related aquaporins exist, this is a point ofprecariousness. In both cases it is difficult to completely exclude side

Discussion Risk Assessment of Engineered NPs

The physico-chemical form of the NPs dispersed, adsorbed to other substrate, aggregated or taken up by cells.77 For example, C60 (fullerene) is a hydrophobic nanomaterial, but it can form an aqueous suspended stable colloidal species in water.78 On the other hand, in water elementary carbon particles or nanotubes show a tendency to aggregate.79 The mobility of NPs in aqueous environments is a function of particle transport, transformation and removal mechanism.80 Fluid flow, gravity and diffusion are the primary mechanisms for transport. Ionic strength and pH may be relevant parameters that affect the NP mobility in water. Initial studies of environmental nanotechnologies indicate that iron NPs, used for cleaning up contaminated soil and groundwater, can travel with groundwater over a distance of 20 metres and remain reactive for 4-8 weeks.48 Nanoparticle surface properties (such as large surface area per unit mass, crystalline structure, anionic surface functional groups) make them...

Bioprocess Engineering of Sulfate Reduction for Environmental Technology

Abstract Sulfate reduction can be used in a large number of environmental technologies. Methanogenic bioreactors treating organic wastewater containing sulfate can be negatively affected by the sulfide produced however, it is possible to combine methanogenesis and sulfate reduction when adequate measures are applied. For the treatment of inorganic wastewaters containing sulfate, organic substrates or H2 CO2 are added as electron donors. Alternatively synthesis gas or methane can be used however, the sulfate reduction rates with methane are still extremely low. Heavy metals such as Cu, Zn, Cd, Pb, Ni and Fe can be removed from waste streams by precipitation with biogenic sulfide. Because of differences in solubility products the metals can be selectively precipitated. The insoluble metal sulfides formed can be recovered in order to be reused.

Passive Sulfate Reducing Systems

Microbial sulfate reduction is also regarded as an effective basic mechanism for treating acid or neutral waters contaminated with heavy metals and sulfate, which might simultaneously remove acidity and metals owing to, respectively, the alkalinity produced during sulfate reduction and the very low solubility of metal sulfides (Table 22.4). Application of high-rate sulfate reduction systems for the treatment of mine waters is hampered by too high investment and operating costs. Attempts to overcome these problems have essentially focused on two strategies. Firstly, established industrial technologies can be adapted for the purpose of mine drainage treatment, e.g. by choosing particular low-cost substrates such as whey, methanol or even wastewaters (Rose et al. 1998). The second approach uses SRB in passive processes, e.g. constructed wetlands (Gibert et al. 2004 Markewitz et al. 2004) or reactive walls (Waybrant et al. 1998 Benner et al. 2002). Passive processes have been developed on...

Metal Sulfide Precipitation

Heavy metals such as Cu, Zn, Cd, Pb, Ni and Fe precipitate with biogenic sulfide to form insoluble metal sulfides (Table 22.4), thereby concentrating the metals into an easy separable and sometimes valuable form. In engineered systems, metal sulfide precipitation can be optimized with respect to the rate of biogenic sulfide production, metal precipitate product quality and selective precipitation of metal sulfides. Treatment processes should focus on recovery of the metals also, as metal resources are depleting. Reuse of metals can only become economically and technically feasible when metals are removed selectively and relatively pure metal sludges are produced.

Biogenic Sulfide for Metal Sulfide Precipitation

Several studies have focused on the use of SRB for precipitating metal sulfides in the same reactor systems where the sulfate reduction activity occurs however, a problem associated with this is the metal toxicity to SRB (Chen et al. 2000). Another problem associated with the use of SRB biomass in the metal-precipitation

Enzyme Activities as Indicators of the Functional Status of the Soil Community

Moreno et al. (2001) described mathematical models to calculate the ecological dose ED (expressed as ED5, EDi0 and ED50) values of Cd and Ni for urease and phosphatase activities. It was suggested that the ED values be used to quantitatively assess the impact of heavy metals on soil functioning.

Microbiology of Solid Waste Treatment

There are several disadvantages to this type of waste management. First, only a limited number of sites are available for use near urban and suburban areas. Second, the organic content of landfills anaerobically decomposes very slowly, over a period of at least 50 years. During this time, the methane gas that is produced must be removed. If buildings are constructed before the methane is removed, disastrous gas explosions can occur. Pollutants such as heavy metals and pesticides can leach from landfill sites into the underground aquifers. It is very difficult to purify these aquifers once they have become contaminated.

Microvascular Actions of CO

Hifas Aseptadas

CO is a gaseous product of the HO reaction that utilizes molecular oxygen to oxidatively degrade protoheme IX into biliverdin-IXa, ferrous iron, and the gas. CO has been considered a gaseous mediator analogous to NO that activates soluble guanylate cyclase (sGC) as a common transducer to relax vascular systems. In mammals, HO exists in two forms HO-1 and HO-2. HO-1 is induced by varied stressors such as cytokines, heavy metals, ROS and hypoxia. Excess NO could also cause the HO-1 induction. Microvascular actions of endogenously generated CO was first demonstrated in the liver 10 . Liver constitutes a major organ responsible for detoxification of the hemoglobin-derived heme and biliary excretion of bilirubin-IXa, a product generated from biliverdin-IXa through biliverdin reductase. We

Fragmentation of Monoclonal Antibodies

Antibody Fragmentation Ficin

Papain is inactivated by heavy metals, which complex with its sulfhydryl group. It is often supplied as 'mercuripapain' to prevent autodigestion. Regardless of whether mercury is present or not, it is good practice to chelate any divalent cations with EDTA to ensure maximal activity of the enzyme. Papain should be 'activated' by a brief incubation in 0.1 M Tris-HCl, pH 8.0, containing 2 mM EDTA and 1 mM dithiothreitol, just prior to use.

Distribution of Enzyme Activities with Soil Particles

In soil polluted by heavy metals, urease activity was mainly located in the clay fraction, alkaline and arylsulfatase activities in the silt-sized and clay particles, and xylanase activity was almost equally distributed among the particle-size fractions, with a slightly lower activity in the clay fractions. In agreement with earlier studies, the predominance of enzyme activities in different size fractions appeared independent of soil type, soil management and soil pollution (Kandeler et al. 2000).

Monitoring supplementation

Urine testing for a heavy metal such as mercury can also serve to indicate how fast detoxification is proceeding. Since this detoxification rate is generally very critical to how healthy one is at the moment, such a test can be very useful as well. When a baseline urinary mercury level suddenly doubles or triples, increased exposure to mercury must be presumed, and this must come either from new outside sources or from within, due to an increased rate of detoxification. Furthermore, if the higher urine mercury level is indicating an increased rate of detoxification, it is not usually important to check other urinary heavy metals, since the levels of mercury in the urine will generally track the release rates of other heavy metals and toxins from their internal storage sites.

Peripheral Neuropathy

Peripheral neuropathy is ascribed when peripheral nerves are damaged. This condition is associated with impaired motor, sensory, and or autonomic nerve dysfunction, and may be either inherited such as in Charcot-Marie-Tooth (CMT) disease or acquired. Acquired neuropathies are commonly caused by leprosy (most common world-wide), other diseases (diabetes mellitus, autoimmune disorders, toxins such as alcohol or heavy metals) or nutritional deficiencies (B12 or thiamine).

Soil Proteins as Metal Biosensors

To the observation in laboratory cultures that organisms synthesise met-allothionein and similar proteins as a protective measure against metal toxicity. However, a validation of the putative correlation between bulk protein expression and metal concentration will require further research. It is quite possible that such correlations will prove difficult to establish with confidence given the complex variability of physical and chemical parameters of soils. In such cases, establishing and integrating the responses of several key individual soil organisms may provide a feasible strategy for approximating community-level responses. However, challenges posed by the enormity of the statistical processing capacity needed for such computations may prove insurmountable. Instead, a compartmentalised approach where pools of active and inactive microbial populations are evaluated to derive approximations of overall soil processes is perhaps inevitable.

The methodology of studies of dementia in Parkinsons disease

A major problem in research on dementia in Parkinson's disease has been in the diagnosis of Parkinson's disease itself. The original description of paralysis agitans by Parkinson was, in fact, the identification of a syndrome rather than of a disease. The part played by such agents as heavy metals, infection, and vascular disease was recognized more than 50 years ago. More recently, the importance of drug-induced parkinsonism, where patients generally recover following withdrawal of the drug, has been recognized. The term Parkinson's disease had come to be regarded as synonymous with idiopathic Parkinson's disease and paralysis agitans, and to be a degenerative disease of unknown cause. In spite of the use of standardized methods of diagnosis, recent studies have shown that a substantial proportion of patients diagnosed as suffering from Parkinson's disease in life do not show the expected findings in the brain postmortem. (1213 In the study by Hughes et al.,(12) 80 per cent of cases...

Neurotoxicology and Behavior William K Boyes PhD

Numerous metallic compounds have proven neurotoxic in humans or in experimental animals. The form of the metal compound, whether it is elemental, an inorganic salt, or contained within an organic compound, can strongly influence neurotoxicity. In general, organometallic compounds are more neurotoxic than the inorganic forms due to the greater penetration of these compounds into the brain. In addition, the route of exposure and age of the subject are critical determinants of toxicity. Inhalation exposure to mercury vapor is much more dangerous than oral exposure, for example. Developing organisms are often more sensitive to metals than adults. There is very little information regarding the sensitivity of the aged to metal toxicity, but many now suspect that the aged may be more at risk than young adults. The neurotoxicities of lead, mercury, and manganese compounds are well established in working populations. In addition, a variety of other metals produce neurotoxic effects.

Environmental Factors And Neurodegeneration

Among environmental factors associated, over the years, with an increased risk for AD several studies have been conducted to explore the role of heavy metals on brain development and dementia. Association between aluminum in drinking water and AD was observed, however results are still inconclusive, including positive and negative findings (37,38) conflicting results have been obtained also concerning occupational or environmental exposures to aluminum (29). The homeostasis of zinc, copper, and iron are altered in the brain of AD individuals, and under mildly acidic conditions, such as those believed to occur in AD brain, iron and zinc ions have been observed to induce Ap aggregation, so that their possible implication in the formation of Ap aggregates in the AD brain has been postulated (39). Elevated levels of iron, zinc, and selenium in the brain have been associated with AD (40). The role of copper in Ap aggregation is still controversial APP has copper-binding domains, and there...

Figure

At least three groups of compounds enter the bile. Compounds of group A are those whose concentration in bile and plasma are almost identical (bile-plasma ratio of 1). These include glucose, and ions such as Na+, K+, and Cl . Group B contains the bile salts, bilirubin glucuronide, sulfobromophthalein, procainamide, and others, whose ratio of bile to blood is much greater than 1, usually 10 to 1,000. Group C is reserved for compounds for which the ratio of bile to blood is less than 1, for example, insulin, sucrose, and proteins. Drugs can belong to any of these three categories. Only small amounts of most drugs reach the bile by diffusion. However, biliary excretion plays a major role (5-95 of the administered dose) in drug removal for some anions, cations, and certain un-ionized molecules, such as cardiac glycosides. In addition, biliary elimination may be important for the excretion of some heavy metals.

Metallothioneins

Metallothioneins (MTs) are low molecular weight metal-binding proteins, mainly of intracellular origin, generally elevated during fetal development and exhibiting a significant degree of polymorphism. Since the discovery of the first MT in 1957 as a cadmium-carrying protein in horse kidney (342), and since the realization that production of this type of polypeptide can be induced by various heavy metals, other similar molecules contained in a variety of tissues, including skin and cell cultures, have been identified in many vertebrates, invertebrates, higher

General Comments

There is no conclusive evidence that silver performs any essential function in living organisms. Similar to other heavy metals, the silver ion reacts with nucleo-philic amino acid residues in proteins, attaching to sulfhydryl, amino, imidazole, phosphate, and carboxyl groups of membrane or enzyme proteins, generally resulting in protein denaturation (1). As for a number of other transition metals, this accounts for silver's antibacterial activity. The only significant therapeutic use of silver as the nitrate or its sulfonamides (2,3) is the disinfection of the skin of thermal injury patients, where the antiseptic effect is primarily due to the metal's reactivity with viral and bacterial proteins (4). This protein-denaturing action of the silver ion makes the metal an effective sterilant for water and other beverages, an effect that has been recognized and put to use over centuries in one form or another (e.g., in the use of silver drinking and storage vessels). Currently, finely...

Haem Oxygenase

Nitric oxide, cytokines, heavy metals, hyperoxia, hypoxia, endotoxin, and heat shock 3-5 . HO-1 activity is present in virtually all organs and is thought to primarily account for the cyto-protective properties of HO. HO-2 is a 36 kDa protein that is constitutively active and localized primarily to the brain and testes. HO-3 is a recently cloned isoform of 33 kDa and the exact role of this isoform remains to be defined.

Nickel Deficiency

In most plant species, nickel deficiency is rarely observed because only very minute amounts of this metal are needed for normal metabolism, and the adequate range between limiting and toxic concentrations is exceptionally large compared to other heavy metals (Figure 1 reviewed in detail by Welch 1 and Gerendas et al. 66 ). For this reason, it took a long time before Ni was identified as being essential for plant growth (see above), and nickel has been termed an 'ultra-micronutrient' 90 . However, a recent study 91 on Scots pine (Pinus sylvestris) showed an increased growth after addition of 20 mg nickel per liter of soil, indicating that nickel deficiency may be more common than previously thought. Symptoms of Ni deficiency are a consequence of the lack of urease, which leads both to an accumulation of urea to toxic levels and to a lack of usable nitrogen sources. Visible symptoms of urea toxicity are leaf tip necroses 59,60 , while symptoms of nitrogen deficiency are interveinal...

Nickel Toxicity

For terrestrial higher plants, toxicity thresholds are very hard to predict because often only a small fraction of the total metal in the soil is bioavailable, and the bioavailability varies by orders of magnitude, depending on the ingredients and pH of the soil. Complexation by weak ligands, such as carboxyl groups of organic acids, hardly affects metal uptake into the plants, but complexation by stronger ligands (simulated, e.g., by EDTA addition) decreases nickel uptake and thus toxicity 103 . When considering the impacts of nickel pollution on plants one should keep in mind that nickel is much less toxic to plants than other important environmental contaminants, in particular copper. For submerged waterplants, for example, nickel is more than hundred times less toxic than copper 97,98 . This is particularly important since nickel pollution in most cases occurs together with copper pollution, as described in more detail below. Furthermore, some plant species seem to be able to...

Synthetic

In 1950, two events were decisive in regulation of certifiable colorants (1) several children became sick after consumption of popcorn and candies pigmented with high colorant levels, and (2) the FDA carried out a new toxicity evaluation of colorants, implementing stringent conditions (higher doses and longer durations). After this evaluation, FD&C orange No. 1, FD&C orange No. 2, and FD&C red No. 32 were taken off the list of permitted colorants. All the events associated with certifying colorants led to the appearance of the Delaney clause, and approval of the products became expensive and time-consuming. Consequently, some colorants listed as provisional were taken off after permission expired and only the colorants with the highest economic feasibility survived. Other delisted colors in the United States were FD&C yellows No. 1, 2, and 4 FD&C violet No. 1 and FD&C reds No. 2 and 4. Moreover, of the seven colorants recommended by Hesse, only two remain in the list of approved...

Other Effects

In principle, heavy metals can have a mutagenic effect on the genome, but so far there is no convincing evidence that such effects play a significant role in in vivo heavy metal toxicity in plants. Manusadzianas et al. 97 reported a strong ATPase inhibition at sublethal levels of nickel 90 n.M IC50, in comparison to a lethal concentration (4-day LC50) of 290 iM. Nickel may induce a disturbance in the uptake of essential microelements as mentioned in Section 3.3.1. But while this was confirmed for roots by several authors 117-120 , Quinn et al. 131 showed that it does not occur in the green alga Chlamydomonas. Instead, these authors found a nickel-induced upregulation of several copper-deficiency response genes. As a result, these genes remained active, even under conditions of excess copper. A break-up of colonies of the floating higher aquatic plant Lemna was observed already at 5 iM Ni2+ (or 0.2 iM Cu2+) within 6 h of exposure 101 .

Other Mechanisms

Because of the sensitivity of the photosynthetic apparatus to heavy metal toxicity, plants have developed strategies that specifically protect this part of their metabolism, in addition to the general metal detoxification mechanisms described in Sections 3.4.1-3.4.3. In particular, in plants that accumulate large amounts of metals, the highest metal accumulation is usually found in cell types that are not photosynthetically active (see Sections 3.4.1. and 4.2.). Under conditions of heavy metal toxicity, hyperaccumulator plants seem to reduce the binding of Ni to essential sites (such as Chl) by accumulating the Mg that would be replaced by Ni 95 (see Section 4.2). In this context it is interesting to note that trees grown on high Ni in sand culture exhibited reduced Ni toxicity if an elevated level of magnesium was supplied simultaneously 120 .

Transfer

In addition to mutation, the genetic information in a cell can be altered if the cell gains genes from other cells. The movement of DNA from one cell to another accounts for the rapid spread of resistance to antimicrobial medications and heavy metals in bacterial populations, as described for Shigella earlier in this chapter. The transfer of genes from one bacterium to another is called horizontal gene transfer or lateral gene transfer. DNA passed from the parental cell to daughter cells following DNA replication is termed vertical gene transfer.

Microcheck 810

All members of the microbial world contain plasmids, which in most cases code for unknown functions. Plasmids vary in size, copy number, host range, their genetic composition, and their ability to be transferred to other cells. One of the most important plasmids is the R plasmid, which codes for resistance to various antimicrobial medications and heavy metals.

Test b

Colored salts like copper, chromium, cobalt, and nickel will reduce the sensitivity of the test, and all heavy metals are expected to interfere. No elements are stated to give a false positive reaction, but a number of ions can interfere. Reductants, like tin(II), can reduce Fe3+ to Fe2+ and will (ultimately) give a false negative result. Ions capable of forming strong complexes with the ions of the test are another cause of interference. Fluoride, acetate, oxalate, and tartrate are examples.

Ecogenetic theory

Intense interest in environmental exposures as risk factors for PD developed in the 1980s after reports confirmed that intoxication with the synthetic meperidine derivative, MPTP, could reproduce the features of PD in humans and animals. This stimulated a search for exogenous or endogenous molecules with similar effect. This also prompted a multitude of epidemiological surveys to assess potential environmental risk factors for Parkinson's disease. It is now clear that a number of classes of molecules have an ability to induce parkinsonism in animals and humans. Examples include the mitochondrial toxin rotenone, proteasomal pathway inhibitors and certain heavy metals. In addition, epidemiological surveys, mostly using a case-control experi

Heme Oxygenase

Pathway of disposing toxic heme, but also in the anabolic pathway of producing bioactive molecules like bilirubin pigments and CO, which bring, respectively, the antioxidant and the cGMP-elevating physiologic effects. Thereafter, it was also learned that HO activity could be enhanced not only by heme, the native substrate, but also by various other non-heme agents like endotoxin (LPS), heavy metals, cytokines, mitogens, and hormones (67-74). Indeed, studies have revealed that following induction of HO-1 expression in vascular tissues, there is an increased production of CO and cGMP (75,76). It has also been shown that upregulation of HO-1 expression and consequent overproduction of intracellu-lar bilirubin is associated with protection against the peroxy-nitrite (ONOO)-mediated apoptosis (77), oxidant-dependent microvascular leukocyte adhesion (78), and postischemic myocardial dysfunction (79). In support of this, cells treated with hemin (oxidized heme) had elevated HO-1 expression...

Melanin

A number of in vitro and in vivo studies focus on the role of melanin in virulence. Melanin is a negatively charged, hydrophobic surface capable of binding many substances including antibiotics and heavy metals (Nosanchuk & Casadevall, 2003b). Cn melanin binds to a number of proteins, as well antimicrobial peptides normally produced by the host. Melanin protects Cn from the antimicrobial activity of the peptides protegrin and defensin, by binding and sequestering them (Doering et al., 1999). When wild type and CNLAC1 deletion strains are used to infect mice, there is no difference in lung clearance between the wild type and deletion strains. However, the fungal burden in the brain and spleen is higher for wild type Cn, showing that laccase, and likely melanization, is required for dissemination and or survival outside the lung (Noverr et al., 2004).

Impurity Profile

The FDA guidance document on impurities in drug substances recommends that individual impurities greater than 0.1 should be fully characterized and quantified by a validated analytical method. In addition, the USP permits up to 2 of ordinary nontoxic impurities in APIs. Such impurities may include residual starting materials, intermediates, reagents, by-products, degradation products, catalysts, heavy metals, electrolytes, filtering aids, and residual solvents.

Hsp Knockouts

In order to further characterize specific Hsp70 gene response, Lee and Seo tested Hsp70.1 expression in MEFs with various stressors such as amino acid analog, heavy metals, oxidative stress, hyperosmotic stress (aze-tidine, cadmium chloride, zinc chloride sodium arsenite, hydrogen peroxide, and sodium chloride) (Lee and Seo 2002). In MEFs, Hsp70.1, which is expressed at a higher level than Hsp70.3 under basal and stress conditions, is the only gene induced by hyperosmolarity. Although these authors analyzed Hsp70.1 knockout cells in this study, they did not correlate the lack of Hsp70.1 expression and the ability of the cells to survive. In an additional study, they made this link by testing the effect of osmotic stress in kidney (Shim et al. 2002). When Hsp70.1 mice were exposed to this type of challenge by adding 3 NaCl in their drinking water, they exhibited increased apoptosis in their kidneys.

Immunology

Mercury compounds have been administered for medical purposes since the earliest times, applied directly to the skin, or given by mouth, and more recently by intramuscular or intravenous injection. Hypersensitivity (i.e., contact sensitivity) to mercury as a consequence of medicinal administration was first described in 1895 (93). Like other transition group elements and highly electropositive heavy metals, such as lead and cadmium, mercury can act as a coordination center for electronegative groups (SH groups and disulfide bridges, cysteinyl and histidyl residues) present in proteins, purines, and pteridines. Such complexation can cause conformational changes and hence immunogenicity (94). Hypersensitivity reactions to host proteins haptenized by mercury following skin contact or systemic exposure can be (a) of type I or anaphylactic, mediated by immunoglobulin E (IgE) (presenting clinically as urticaria) (b) of type III or Arthus reactions involving antigen-antibody complexes with...

Table 1601

Most R-plasmids are of moderate to large size and present in 1-2 copies per host cell. Most are self-transmissible at a low frequency, although de-repressed mutants showing high transfer frequency are sometimes found. The original F-plasmid is such a naturally-occurring mutant . R-plasmids belong to a wide range of incompatibility groups. Many carry resistances to one or more antibiotics and or toxic heavy metals and may also carry genes for colicins, virulence factors etc.

Minerals

Protects cells against free radicals also helps neutralize heavy metals such as mercury. Consider supplementing with 10 to 20 micrograms daily of a chelated form. Men with higher levels of selenium appear to have a lower risk of prostate cancer than men with lower levels.

Vitamins

Vitamin C is one of the few supplements that are extremely difficult to overdose. Whether administered orally or intravenously, megadose vitamin C has been shown to be a superlative therapy for heavy-metal poisoning carbon monoxide exposure and poisoning pesticide exposure allergic and toxic shock from snakebite or insect bite and almost all viral diseases studied, including polio, hepatitis, and herpes. Frederick Klenner, M.D., published much of the significant work documenting these marvelous effects of megadose vitamin C.12-15 In many of the conditions listed above, Dr. Klenner would often report clinical cures, with return of blood tests to

Electron Tomography

Various sample preparation methods exist. Conventional techniques for the preparation of biological samples imply a fixation step using aldehydes then a dehydration followed by the infiltration of the specimen by a resin. The preparation is stained with heavy metals (osmium or uranyl acetate) and may be contrasted by lead 31 . Most recent techniques (cryoelectron microscopy or cryo-EM) use cryo-fixation the sample is immobilized by ultra-rapid freezing. Thus the preparation is embedded in vitreous ice. No stain is added and the true density is visualized 32 . Several other methods exists, such as the combination of negative staining and cryo-EM 33 and rapid freezing and freeze substitution 25 .

Tests

The European Pharmacopoeias general Chapter 2.4 Limit tests include 27 monographs, each describing a test developed to assure that any unintended content of a well-defined element or compound is below some critical limit. The reason for limiting the element or compound in question varies from monograph to monograph. Some monographs reveal a residual content of toxic substances, like arsenic and heavy metals, and the reason for limiting their presence is obvious. Others, however, cover clearly harmless elements like chlorides or the alkali metals. In those cases, the reason for limiting their presence is one of general product quality. A well-produced, active pharmaceutical ingredient or excipient need not have a residual content of, for example, inorganic salts used during synthesis. When present, however, they reveal a product of low general quality.

Albumin

In addition to its osmoregulatory function, HSA serves a transport function. Various metabolites travel throughout the vascular system predominantly bound to HSA. These include fatty acids, amino acids, steroid hormones and heavy metals (e.g. copper and zinc), as well as many drugs.

Method e

It is clear from the many articles published in general scientific literature, in pharmacopoeia publications, and even in the European Pharmacopoeia's guide for the general test in the new monograph, that the tests of heavy metals method (a) to (f) have certain limitations. The most important are the limit of detection is in general close to the limits of allowed content comparing sulfide salts of different colors causes problems even though the amount of precipitate is very low certain heavy metals are lost to a high extent during the incineration procedure of methods (c) and (d) the result obtained in methods (c) and (d) puts high demands on the skills of the operator carrying them out and the wet ashing procedure of method (f) is for many substances very time consuming.

Igfi T

And diabetes Higher risk of cancer Recent exposure to environmental factors hypothermia, heavy metals, amino acid analogues, inhibitors of energy metabolism, UV exposure pathological conditions viral infection, fever, inflammation, ischaemia, oxidative stress Ongoing inflammatory process prior to

Effect of pH

The pH of soil can be markedly reduced after sludge application, particularly in the light textured sandy soil with a low buffering capacity, due to nitrification of the NH+-N produced by mineralisation of added organic matter and sulfide oxidation. The decrease in soil pH causes a solubilisation of heavy metals with possible adverse effects on enzyme activities. Liming of these soils raises soil pH values and alleviates the toxicity of metals.

Potential Concerns

Some herbal preparations, particularly some un-branded Asian imports, have been found to contain inactive fillers or adulterants. In one assessment, 24 of imported herbs were found to contain ingredients not on the label. These included specific medications (aspirin, caffeine, diuretics, and even benzodiazepines), not to mention heavy metals, such as lead. Some Asian formulations may also contain animal components. Therefore, it is advisable to buy only products that list the following information botanical name or names,

Antioxidant Activity

Anthocyanins are highly reactive radical scavengers in various in vitro environments. Anthocyanins not only scavenge radicals, but through their ability to bind heavy metals such as iron, zinc, and copper, also prevent the formation of radicals.47 Anthocyanins may also exert antioxidant abilities through the protection or enhancement of endogenous antioxidants (i.e., sparing effect), or through the induction of antioxidant enzymes such as glutathione-S-transferase (GST) and superoxide dismutase (SOD).48,49 Also, there appears to be a synergism between anthocyanins, vitamin C, and other flavonoids which is similar to the reported recycling effect of vitamin E by vitamin C. This effect was observed in an investigation by Rossetto et al.31 where the flavonoid catechin was observed to regenerate malvidin 3-glucosides thereby increasing their antioxidant capacity in a micellar system with induced linoleic acid peroxidation.

Organic Amendments

In general, recent additions of organic residues can stimulate enzyme activities as the result of microbial proliferation or enzyme induction in response to the amendment, if inhibitory substances are not present in organic residues such as heavy metals in municipal solid waste (MSW) compost. Indeed the ratios between acid phosphatase, alkaline phosphatase, a-glucosidase, arylsulfatase, or urease activity and microbial biomass were significantly increased by manure regardless of crop type in historic Sanborn field (Missouri) soil under various cropping and management practices since 1888 (Eivazi et al. 2003). However, repeated annual organic fertilisation can usually lead to lower levels of enzyme activity (Perucci 1992 Marcote et al. 2001) even if constant values were found in some long-term experiments because constant and regular organic addition balanced stimulation and suppression of enzyme activity (Martens et al. 1992). The activities of 3-glucosidase, nitrate reductase,...

Vanadium

Vanadium is an element classified in the group of heavy metals, very common in the natural environment, mainly in the heavy oils, carbon and bituminous materials, where it is associated with the heavy fraction. Vanadium emissions to the atmosphere are produced in areas around siderurgical industries, oil refineries, and cities that use fossil fuels for heating. Some clinical-epidemiological