Introduction

Incipient diabetic retinopathy is characterized by increased vascular permeability and progressive vascular occlusion. The substrate of vascular occlusion is the formation of nonperfused, acellular capillaries within the retina. The primary morphologic change in the diabetic retina is the loss of pericytes that precedes the formation of acellular capillaries. Pericytes play an important role in the development and maturation of the vascular system. Under non-hyperglycemic conditions, pericytes have a survival- and growth-inhibiting effect on endothelial cells. Under hyper-glycemic conditions, the protective function of pericytes on endothelial cells is traded for the increased repair capacity of the capillary endothelium. It was previously thought that pericyte loss is the result of toxic product accumulation and induction of destructive cellular signals generated within the pericyte. In contrast, new experimental data indicate that pericyte dropout may result from regulations that induce pericyte elimination as an active process. The prevention of acellular capillaries without the rescue of pericyte loss in experimental diabetic retinopathy suggests that the endothe-lium is the primary therapeutic target, and that restoration of pericyte coverage in retinal capillaries may not be necessary for the prevention of diabetic retinopathy.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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