Kidney glomerulus

Water moves across cell membranes either by the simple diffusion described above or as the result of osmotic differences across membranes. In the latter case, when water moves in bulk through aqueous pores in cellular membranes due to osmotic forces, any molecule that is small enough to pass through the pores will also be transferred. This movement of solutes is called filtration. Cell membranes throughout the body possess pores of different sizes for example, the pores in the kidney glomerulus are typically 70 nm, but the channels in most cells are <4 nm.2... 

Ammonia is also the major nitrogenous end product in some of the simpler aquatic and marine animal forms, such as protozoa, nematodes, and even bony fishes, aquatic amphibia, and amphibian larvae. Such animals are called am-monotelic. But in many animals, NH3 is toxic, and its removal by simple diffusion is difficult. Thus, in terrestrial snails and amphibia, as well as in other animals living in environments in which water is limited, urea is the principal end product (fig. 22.6). Urea formation also helps to maintain osmotic balance with seawater in cartilagenous fishes. In such animals, most of the urea secreted by the kidney glomerulus is reabsorbed by the tubules. Indeed, the amount of nitrogen excreted by the kidneys of fishes is small com-... 

A4. Andrews, P. M., Investigations of cytoplasmic contractile and cytoskeletal elements in the kidney glomerulus. Kidney Int. 20, 549-562 (1981). 

Xu, B., etal. (2005). Two-dimensional electrophoretic profiling of normal human kidney glomerulus proteome and construction of an extensible markup language (XML)-based database. Proteomics 5, 1083-1096. 

In contrast, the chemical toxicity of uranium is more important than its radiological hazard. In body fluids, uranium is present as soluble U(VI) species and is rapidly eliminated from the body (60% within 24 h Goyer and Clarkson (2001)). It is rapidly absorbed from the gastrointestinal tract and moves quickly through the body. The uranyl carbonate complex in plasma is filtered out by the kidney glomerulus, the bicarbonate is reabsorbed by the proximule tubules, and the liberated uranyl ion is concentrated in the tubular cells. This produces systemic toxicity in the form of acute renal damage and renal failure. 

Kerjaschki D,Vernillo AT,and Farquhar MG. Reduced sialylationof podocalyxin-the major sialoproteinofthe rat kidney glomerulus in aminonucleoside nephrosis.The American Journal of Pathology 118 343-349,1985. 

Fig. 3.2 Relationship of the connective tissue stroma to an epithelium. Fibroblasts secrete unique types of laminin proteins that interact with each other and type IV collagen, to form a basal lamina (yellow) that is tightly attached to the connective tissue (stromal) cells and also to the associated muscle or epithelial cell. The kidney glomerulus is a specialized tissue in which the stroma is absent and endothelial cells and epithelial cells are separated by the basal lamina which filters the blood as the first step in urine collection. The attachment of an epithelium to stromal collagen is discussed in detail in Chap. 5 (Fig. 19-55 in The Molecular Biology of the Cell. B. Alberts et al., 4th Ed. 2002. Garland Science, Taylor Francis Group, NY)...

Heart and kidney (glomerulus) Liver (periportal) Phospholipidosis (lung)... 

The protein a2ju-globulin is filtered by the kidney glomerulus and reabsorbed into the proximal tubules... 

Ap )ears to be a minor form, found in dermis and dentin The main collagen of cartilage, where it forms the main, thin fibrils. Also found in intervertebral disk Often with type I, in extensible tissues such as blood vessels, dermis, and intestine. More abundant in foetal tissues Located in basement membranes, with different chain combinations being associated with specific tissues Lens capsule, kidney glomerulus, aorta, bladder, etc Lung alveoli, kidney glomerulus... 

Mackensie, S., and Scriver, C. R., 1971, Transport of L-proline and Q -aminoisobutyric acid in isolated rat kidney glomerulus, Biochim. Biophys. Acta 241 725. 

The tissues discussed above are examples of cellular permeability, but capillary permeability must now be discussed. The capillaries of the blood-system, like those of the kidney glomerulus (see below), have porous Type 4 membranes and allow the passage of ions and proteins. However the capillaries of the brain are differently structured see blood-brain barrier, in the following. 

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