Tamm-Horsfall protein (THP), a monomeric glycoprotein (M(r) 80 to 100 kDa), is produced by the mammalian kidney's thick ascending limb of Henle cells and excreted into the urine. The function of THP is uncertain. Here we report that a high molecular weight contaminant in sheep THP (sTHP) preparations was identified as sheep IgG by its positive reaction with donkey anti-sheep IgG antibody and with protein G. To answer the question of whether sTHP and sheep IgG co-purified because of a physical interaction between the two proteins, an enzyme-linked immunosorbent assay (ELISA) using immobilized sTHP and soluble sheep IgG was performed. Analysis of the ELISA data identified the presence of two sets of binding sites: a high affinity site (Kd 10(-8) to 10(-9) M) and a lower affinity site (Kd 10(-6) to 10(-7) M) [corrected]. The ELISA detected a similar high affinity interaction between human THP (hTHP) and human IgG. The binding of sheep IgG to immobilized sTHP was inhibited by soluble sTHP. These observations suggest an additional factor to be considered in studies addressing THP's potential immunoregulatory function.

Electron microscopy studies on the morphology of the columnar cells covering the villi in small intestinal loops, which were surgically isolated in 7 day old pigs, showed that the fine structure of those cells is very similar to that in other mammalian species. Upon infection of the loops with TGE virus, virus particles with a diameter of 75 to 88 m~ became visible in the cytoplasm of these absorptive cells. The virus was taken up by pinocytosis, and newly produced particles maturated by budding at smooth cellular membranes particularly in the Golgi apparatus. Cellular morphological changes were first detectable at the microvillar border and appeared to develop concomitantly with virus release. Loss of cells occurred later through desquamation and cell disruption. Atrophied villi were, at 18 hours postinoculation, almost completely covered with newly produced cuboidal cells which ultrastructurally resembled the undifferentiated crypt cells. Gradual differentiation of these cells occured during the following days and at 72 hours postinoculation, they were morphologically similar to normal absorptive cells. A few of the differentiating and differentiated cells were seen to contain virus particles.Arch. ges. Virusforseh. 31/3-4 22

The response of oligodendrocytes, astrocytes, microglia, and pericytes to sciatic neurectomy in young adult rats was studied from l p Epon sections for quantitative cell counts and autoradiography. Two hours after an IP injection of 3H-thymidine animals were killed by aldehyde perfusion at survival periods of 2 , 4, 7, and 14 days postoperative (dpo).At 2 dpo there was a marked increase in the number of labeled microglial cell nuclei and mitotic figures on the experimental side. This activation appeared to involve most of the "resting" microglia, which comprise about 6% of the total neuroglia in the normal ventral horn. A significant numerical increase (over fourfold) in perineuronal and total microglia was seen at 4 dpo followed by a gradual decline. Other findings include minimal chromatolysis in ventral horn neurons, contralateral effects, and a slight proliferative response in and around the central canal. A response was not apparent in the other neuroglia, pericytes, or mononuclear leukocytes. The relationship of the microglia to the multipotential glia of neuroectodennal origin is considered.

Abstract. Three young male Beagle dogs were given daily oral doses of 0.3 mg/kg body weight of crystalline ochratoxin A. Three untreated Beagle dogs served as controls. The principals survived for 11-1 5 days and were killed. Cytomorphologic alterations were seen primarily in the endomembrane system of the renal epithelial cells of the proximal convoluted tubules. Increased amounts of smooth-surfaced membranes were present as linear and concentric arrays and as large and small vesicles in many proximal tubular epithelial cells. Few basilar infoldings of the plasma membrane were present in proximal tubular epithelial cells of the principals, but extracellular basilar labyrinth was extensive in proximal tubular epithelial cells of the control kidney. Many tubular epithelial cells contained lipid droplets and cytoplasmic accumulations of phospholipids. The mitochondria usually appeared normal. Prominent ultrastructural alterations of the interstitium included separation between tubular basement membranes, increase in the number of interstitial cells, well-developed secretory apparatuses in many interstitial cells, and the presence of collagen and amorphous material. Few alterations were found in the epithelial cells of the distal convoluted tubules, but some contained more lipid droplets than normally. No consistent alterations were found in other parts of the nephron.Ochratoxin A is a nephrotoxic fungal metabolite elaborated by certain strains of Aspergillus ochruceus [41], Penicillium viridicatum [42], and other members of the A . ochruceus group [17, 191. These fungi are common contaminants of agricultural commodities [3,4,10,11,24,29,3 11, and the natural occurrence of ochratoxin A has been reported in cereal grains in the United States [12,33,34], Canada [30,31], and Denmark [18]. Although ochratoxin A was primarily a nephrotoxin in the species studied [9,18,23,26,27,37-391,

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