Comparative cytologic study of nephron structure in higher vertebrates

A comparative study of the cytological characteristics of the epithelial lining of the nephron and collecting tubules was performed in 9 species of reptiles, 19 species of birds and 12 species of mammals. Representatives of each class of higher vertebrates were shown to have certain specific features of the epithelial lining of different parts of the nephron. Differentiation of various areas of the proximal part of the nephron proceded in phylogeny with different intensity and the maximum specialization was characteristic of the most proximal portion of this part of the nephron. In the cells of the proximal parts of nephrons of some reptiles there were phenomena of apocrine secretion. Evolution of the distal part of the nephron developed to form a loop and differentiation of the distal convoluted segment. The higher differentiation of the epithelial lining of the nephron distal part in birds and mammals, unlike in reptiles, seems to be associated with a more considerable functional specilization of this part. In the cytochemical characteristics of the epithelium of the uriniferous and collecting tubules of kidneys of higher vertebrate animals there are common regularities in the distribution of RNA, proteins and some enzymes. The polysaccharide content is maximum in the epithelial cells of kidneys of reptiles.     

Traveler's diarrhea

Travellers' diarrhea afflicts up to 50 percent of tourists in certain geographic regions. It is a syndrome caused by a variety of pathogens, the most common of which is enterotoxigenic E. coli. Other responsible pathogens include salmonellae, shigellae, Entamoeba histolytica, Yersinia enterocolitica, Giardia lamblia and virus-like agents, seldom vibrios. Symptoms persist for only a few days and are only serious in 1/5 of the cases.     

Mechanisms for the transendothelial migration of HIV-1-infected monocytes into brain

HIV-1 penetration of the brain is a pivotal event in the neuropathogenesis of AIDS-associated dementia. The establishment of productive viral replication or up-regulation of adhesion molecule expression on brain microvascular endothelial cells (BMVEC) could permit entry of HIV into the central nervous system. To investigate the contribution of both, we inoculated primary human BMVEC with high titer macrophage-tropic HIV-1 or cocultured them with virus-infected monocytes. In both instances, BMVEC failed to demonstrate productive viral replication. Cell to cell contact between monocytes and microvascular endothelium resulted in E-selectin expression on BMVEC. BMVEC. cocultured with LPS-activated HIV-infected monocytes expressed even higher levels of E-selectin and vascular cell adhesion molecule-1 (VCAM-1). Transwell assays supported a role of soluble factors, from virus-infected monocytes, for the induction of adhesion molecules on BMVEC. To verify the in vivo relevance of these findings, levels of adhesion molecules were compared with those of proinflammatory cytokines and HIV-1 gene products in brain tissue of AIDS patients with or without encephalitis and HIV-seronegative controls. E-Selectin, and to a lesser degree VCAM-1, paralleled the levels of HIV-1 gene products and proinflammatory cytokines in brain tissue of subjects with encephalitis. Most importantly, an association between macrophage infiltration and increased endothelial cell adhesion molecules was observed in encephalitic brains. Monocyte binding to encephalitic brain tissue was blocked with Abs to VCAM-1 and E-selectin. These data, taken together, suggest that HIV entry into brain is, in part, a consequence of the ability of virus-infected and immune-activated monocytes to induce adhesion molecules on brain endothelium.