Effect of vinblastine sulfate on the fine structure of cells of the rat renal corpuscle

Effect of Vinblastine Sulfate on Visceral Epithelial Cells of Rat Renal Corpuscle (Scanning Electron Microscopy)

Visceral epithelial cells (podocytes) of the rat renal corpuscle are highly branched -in shape (1-3) and contain numerous cytoplasmic microtubules (4). In a previous study of podocytes by Tyson and Bulger (4), microtubule loss was induced by intravenous injections of vinblastine sulfate, and then renal tissue was examined by routine transmission electron microscopy. With a vinblastine treatment that resulted in nearly complete absence of microtubules in podocytes, examination of ultrathin sections yielded no evidence that loss of microtubules was accompanied by a change in cell shape. Similar experiments, described below, have now been performed using scanning electron microscopy, in order to facilitate recognition of subtle shape changes that would not be readily apparent in sectioned material.

Modulation of cytoskeletal organization of podocytes during the course of aminonucleoside nephrosis in rats

By immunoelectron microscopy the modulation of cytoskeletal organization of podocytes during the course of puromycin aminonucleoside-induced nephrosis was examined. In control rats, tubulin and vimentin were present, limited to the podocyte cell body and the major processes. Their distribution in the foot processes was virtually negative. Myosin exhibited the same distribution pattern, albeit much more scattered, with no relation to any podocyte organelles or cell structures. Actin was scattered over the fibrillar zones of the cell body and its processes, including the foot processes. In proteinuric rats, loss of foot processes occurred and the glomerular basement membrane was covered by broad cytoplasmic sheets of podocytes, which contained these four subunits of cytoplasmic filaments. Accompanied by the disappearance of proteinuria, the structural organization of the foot processes was completely restored, in which tubulin, vimentin, and myosin were scarcely observed. Our results confirmed that the loss of foot processes is caused by their retraction, and indicated that the specific localization of the podocytic cytoskeleton contributes to the maintenance of the particular cell shape. Its reorganization may account for the structural modification of podocytes.

Microtubules and macrotubules in fish meiosis

During meiosis in the male of a cyprinodontid fish, Aphyosemion splendopleure, and during the organization of the spindle of division, the spindle is made of two types of tubules: microtubules (20-25 nm) and macrotubules (30-50 nm). The macrotubules are associated only with the polar region of the meiotic apparatus and are located outside the spindle of microtubules. At the end of meiosis, the spindle microtubules depolymerize whereas the macrotubules remain. One can find them throughout the entire process of spermiogenesis; later, they disappear only at the end of spermatid maturation. We have studied four populations from Cameroon, three of them with macrotubules.

Cytoskeleton ultrastructure of podocytes and glomerular endothelial cells in man and in the rat

The ultrastructural organization of the cytoskeleton of normal podocytes and glomerular endothelial cells was studied in man (adults and children) and in adult Sprague-Dawley rats. In podocytes of both species, cytoplasmic microtubules (MT) were observed in the cell body close to the Golgi apparatus and along the main axis of the major processes where they formed bundles. A network of intermediate filaments (IF) was observed in the cell body and in the major processes where they sometimes formed bundles parallel to MT, especially in man. Numerous clustered microfilaments (MF) were noticed in the foot processes close to the plasma membrane. In glomerular endothelial cells from both species, networks of MT and IF were observed in the cell body, whereas MF surrounded the endothelial fenestrations. The high degree of organization of the cytoskeleton suggests that it may play an important role in several functions of both cell types.

An electron microscopic study of the effects of vinblastine sulphate on the ultrastructure of the kidney, trachea, liver, peripheral nerve and small intestine of the rat

The effects of vinblastine in high doses on the kidney, liver, trachea, peripheral nerve and small intestine of rats have been studied by scanning and transmission electron microscopy. Dramatic structural changes were seen in glomerular visceral epithelial cells, hepatocytes and small intestinal epithelial cells which appear to be due to the effect of vinblastine on microtubules and possibly also on other proteins and cell membranes. Ciliary microtubules appeared resistant to vinblastine effects.

The effects of vinblastine on acinar cells of the exorbital lacrimal gland of the rat

The effects of vinblastine treatment on acinar cells of the rat exorbital lacrimal gland were studied by electron microscopy. Experimental animals of both sexes were given single intraperitoneal injections of (1) vinblastine (4 mg/kg body weight) at 1 to 24 h before sacrifice; (2) pilocarpine (20 mg/kg b.w.) for 1 h; or (3) vinblastine for 1 h followed by pilocarpine for 1 h. Vinblastine treatment caused a number of changes including autophagocytosis, formation of intracisternal granules, and alteration of secretory granules. These changes varied in extent and onset between male and female rats. In addition, the Golgi apparatus was reduced in size and dispersed throughout the cytoplasm. Mitotic figures were commonly observed. Moreover, vinblastine inhibited the pilocarpine-stimulated degranulation of the acinar cells. In view of the known anti-microtubular action of vinblastine, these results suggest that microtubules are involved in various aspects of the transport, packaging, and secretion of exportable proteins in the lacrimal gland. Additionally, autophagocytosis and alteration of secretory granules may partially result from the interaction of vinblastine with membranes.

Scanning electron microscopic study of the effect of vinblastine on podocytes of rat kidney

Loss of cytoplasmic microtubules was induced in rat renal podocytes by intravenous administration of the microtubule poison, vinblastine sulfate. Scanning electron microscopy was used to study the shape exhibited by podocytes 2, 8, or 12 h after initiation of vinblastine treatment. The podocytes of all vinblastine-treated rats possessed focal enlargements of cellular processes. At 8 and 12 h the focal enlargements were more abundant and often larger than those seen at 2 h. In addition, at the longer exposure times many cellular processes were smaller in diameter than comparable processes of control animals. There was no evidence that a loss of pedicel organization occurred with any of the three treatment times studied. The results suggest that in the absence of microtubules a redistribution of cytoplasm occurred within podocyte processes, resulting in the accumulation of cytoplasmic material at certain sites and a concomitant narrowing of the diameter of processes in other regions. Thus, intact microtubules appear to be essential for normal podocyte shape.

Substructure of solitary cilia in mouse kidney

Recent scanning electron microscopic studies confirm the presence of solitary cilia on most epithelial cells along the mammalian nephron and collecting ducts. By transmission electron microscopy we have found that the axonemata of such cilia consist of a maximal number of 9 doublet and no singlet filaments. 10% of the cross-sectioned cilia contain 9 doublets arranged in peripheral ring (9 + 0 pattern). 30% of the cross-sections contain 8 or 7 doublets in peripheral ring and 1 or 2 doublets in the central region (8 + 1 and 7 + 2 patterns). Serial sections and goniometer tilt reveal the central doublets to originate as dislodged peripheral doublets. 60% of the sectioned cilia contain filament numbers between 8 and 4. In patterns of 5 and 4 filaments single microtubules predominate. The functional significance of these atypical cilia is discussed.

The effect of vinblastine-induced microtubule loss on kidney podocyte morphology

The effect of intravenous injections of vinblastine sulfate on the renal glomerular epithelium was studied by scanning and transmission electron microscopy. Two hours after treatment with vinblastine, microtubules were almost completely lost from the podocyte cell bodies and major processes, and crystalline inclusions of a tubular nature had appeared within the cytoplasm. Coincident with this loss of microtubules, podocyte major processes at first collapsed and then became significantly thinner as they appeared to lose much of their cytoplasm to the nucleated cell body. These observations suggest that microtubules serve to maintain the shape and integrity of podocyte major processes. At no time after vinblastine treatment did we note any alteration in podocyte pedicel morphology.

Effect of vinblastine on the brush border of proximal tubule cells of rat kidney

A vinblastine-induced lesion of the brush border of proximal tubule cells of rat kidney was studied by scanning and transmission electron microscopy. Adult rats were given two tail-vein injections of vinblastine sulfate and then sacrificed either three or sixteen hours after administration of the first injection. The proximal tubules of animals treated with the drug for three hours differed from those of saline-treated controls in possessing (1) well defined areas of apical cell surface devoid of microvilli and (2) fewer microcraters in the brush border. In tubules of animals treated with vinblastine for sixteen hours, the areas devoid of microvilli were much more extensive, and microcraters were less frequently seen. Cilia did not appear to be affected by exposure to the drug and were observed both in regions devoid of microvilli and in areas with a well developed brush border. The mechanism of action of vinblastine in eliciting focal loss of microvilli of proximal tubule cells is not known. Several hypotheses to account for this lesion of the brush border are discussed.

Cytotoxicity of vinblastine and vincristine to pancreatic acinar cells

BALB/c mice were given vinblastine (Velbe), 40 and 200 mg/kg, or vincristine (Oncovin), 20 mg/kg, dissolved in saline as single intraperitoneal injections. Nontreated mice served as controls. Animals were killed 1, 2, 5, and 24 hours and 4 days after the drug administration and small pieces from the pancreas were processed for electron microscopy. Autophagocytotic activity increased 3 hours after the injection and at 5 and 24 hours there were large amounts of autophagic vacuoles containing altered cell organelles and membranous or amorphous debris in the acinar cells. Cell death and acinar atrophy were evident at later time intervals. It was concluded that the vinca alkaloids caused autophagy and degeneration in pancreatic acinar cells and that their inhibitory effect on pancreatic enzyme secretion might depend partly or solely on their cytotoxic action.

Scanning electron microscopy of the distal nephron and calyx of the human kidney

Surface fine structures of human distal nephron, papilla and calyx were studied by use of SEM. Tissue preservation was carried out by perfusion fixation and critical point drying. The various surface features of epithelial cells were visualized in the lower urinary tract.

Fine structure of mammalian renal cilia

Studies were carried out, using transmission electron microscopy, of the cilia of the nephrons of rat and human kidneys. Cilia were observed in the parietal layer of Bowman's capsule, in the proximal tubule, the distal tubule, including the macula densa, and the collecting duct. They had a number of characteristic features, including the presence of a centriole adjacent to the basal body, long, slender cross-striated rootlets, and a typically organized basal body. The shaft of the cilia differed from the typical 9 + 2 pattern of organization. Near the base of the cilia the pattern was 9 + 0. In the middle portion, one or more of the peripheral doublets had been displaced centrally to give an 8 + 1 or a 7 + 2 pattern, while towards the tip the pattern became more irregular and the doublets were reduced to single microtubules. We have hypothesized that these cilia may be vestigial. They may, if motile, have some minor stirring function, or they may play a sensory role, as has been postulated for similarly structured cilia in other sites.

Vinblastine: influence on nerve conduction and synaptic transmission

Vinblastine injected into the eyes of pigeons had a detrimental effect on the amplitude of the postsynaptic evoked potential in the optic tectum; impulse conduction of the optic nerve was not influenced. The depression of the postsynaptic evoked potential was dependent on the dosage. Only 20 and 100 mug vinblastine had an influence; no influence was observed with 10 mug vinblastine. The reversible depression was seen from the third day after injection to between the 21st and the 28th day after injection, and in that period it remained constant. The latency of the response was not influenced by vinblastine.

Microtubule biogenesis and cell shape in Ochromonas. 3. Effects of herbicidal mitotic inhibitor isopropyl N-phenylcarbamate on shape and flagellum regeneration

The role of microtubules and microtubule nucleating sites in the unicell, Ochromonas has been examined through the use of two mitotic inhibitors, isopropyl N-phenylcarbamate (IPC) and isopropyl N-3-chlorophenyl carbamate (CIPC). Although IPC and CIPC have little or no effect on intact microtubules, the assembly of three separate sets of microtubules in Ochromonas has been found to be differentially affected by IPC and CIPC. The assembly of flagellar microtubules after mechanical deflagellation is partially inhibited; the reassembly of rhizoplast microtubules after pressure depolymerization is totally inhibited (however, macrotubules may form at the sites of microtubule initiation or elsewhere); and, the reassembly of the beak set of microtubules after pressure depolymerization may be unaffected although similar concentrations of IPC and CICP completely inhibit microtubule regeneration on the rhizoplast. These effects on microtubule assembly, either inhibitory or macrotubule inducing, are fully reversible. The kinetics of inhibition and reversal are found to be generally similar for both flagellar and cell shape regeneration. Incorporation data suggest that neither IPC nor CIPC has significant effects on protein synthesis in short term experiments. Conversely, inhibiting protein synthesis with cycloheximide has little effect on microtubule regeneration when IPC or CIPC is removed. Although the exact target for IPC and CIPC action remains uncertain, the available evidence suggests that the microtubule protein pool or the microtubule nucleating sites are specifically and reversibly affected. Comparative experiments using the mitotic inhibitor colchicine indicate some similarities and differences in its mode of action with respect to that of IPC and CIPC on assembly and disassembly of microtubules in these cells.