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Biomedical subjects

W Wassilev

Publications and source records attributed to W Wassilev.

At least 19 recordsLinked to original sources
PubMed1999

Scanning and transmission electron microscopic study of visceral and parietal peritoneal regions in the rat.

The visceral peritoneum of intraabdominal organs (spleen, stomach, liver, small intestine), omentum majus and the parietal peritoneum of the anterior abdominal wall and the diaphragm were studied in adult Wistar rats by combined scanning and transmission electron microscopy (SEM, TEM). In general, the peritoneal surface consisted of a mesothelium composed of cubic, flat or intermediate cell types delimited by a basal lamina. Cubic mesothelial cells predominated in parenchymal organs (spleen, liver) and were characterized by prominent and indentated nuclei, a cytoplasm richly supplied with organelles, a dense microvillous coat, basal invaginations and elaborate intercellular contacts. Flat mesothelial cells were observed in the intestinal, omental and parietal peritoneum (tendinous diaphragm, abdominal wall) and showed elongated nuclei, scant cytoplasm, a poorly developed organelle apparatus and sparsely distributed microvilli. An intermediate mesothelial cell type was described within the gastric peritoneum characterized by a central cytoplasmic protrusion at the nuclear region containing most of the cytoplasmic organelles and by thin finger-like cytoplasmic processes. The submesothelial connective tissue layer was composed of collagen fiber bundles, fibroblasts and free cells (macrophages, granulocytes, mast cells) and contained blood and lymphatic vessels. In the spleen, elastic fibers formed a membranous structure with intercalated smooth muscle cells. Mesothelial openings were observed as tunnel-like invaginations within the hepatic peritoneum and as clusters of peritoneal stomata within the parietal peritoneum of the anterior abdominal wall and the muscular diaphragm. The round or oval openings of the peritoneal stomata were frequently occluded by overlapping adjacent mesothelial cells and their microvillous coat or obstructed by cellular material. At the side of the peritoneal stomata the mesothelial cell layer was interrupted to allow a direct access to the underlying submesothelial lymphatic system. The mesothelium and lymphatic endothelium shared a common basal lamina. The endothelial cells were discontinuous and displayed valve-like plasmalemmatic interdigitations facilitating an intercellular transport of fluids and corpuscular elements from the peritoneal cavity to the submesothelial lymphatic lacunae. The findings underline the morphological heterogeneity of the peritoneum in visceral and parietal regions, suggesting different functional implications, and further support the presence of extra-diaphragmatic peritoneal stomata.

Abdominal Muscles↗
PubMed1998

A scanning electron microscopy study of peritoneal stomata in different peritoneal regions.

Peritoneal stomata constitute the principal pathways for the drainage of intraperitoneal contents from the peritoneal cavity to the lymphatic system and have been claimed to be exclusively restricted to the peritoneal surface of the diaphragm. This concept has been revised by the demonstration of peritoneal stomata in the omental, mesenteric, ovaric and pelvic peritoneum. Therefore, the aim of this study was to further assess peritoneal surfaces of several other abdominal organs and of the abdominal wall with special reference to the occurrence of peritoneal stomata. The peritoneum covering the spleen, stomach, intestine, liver, diaphragm and anterior abdominal wall obtained from rats was examined by scanning electron microscopy. Whereas the splenic and hepatic peritoneal surfaces were composed of uniformly distributed cuboidal mesothelial cells, the gastric and intestinal peritoneal surfaces were arranged in parallel folds composed of prominent mesothelial cells with elongated finger-like cytoplasmic processes. In addition to diaphragmatic peritoneal stomata, mesothelial openings were also found on the peritoneal surfaces covering the anterior abdominal wall and the liver. The parietal peritoneal stomata were arranged in clusters, oval in shape and delimited by flattened mesothelial cells exposing the underlying submesothelial connective tissue. The hepatic mesothelial openings formed by deep channel-like gaps of adjacent cuboidal mesothelial cells were almost completely occluded by a dense microvillous coat. As the submesothelial connective tissue was not identifiable with certainty, the mesothelial openings were regarded as corresponding to stoma-like structures. These findings yield further evidence that peritoneal stomata are obviously not confined to the diaphragmatic area but extend to other peritoneal regions. It is therefore suggested that these extra-diaphragmatic parietal and visceral peritoneal surfaces contribute to the absorption capacity of the entire peritoneum and are subsequently involved in either therapeutic procedures or pathological processes affecting the peritoneal cavity.

Animals↗
PubMed1994

Tubular networks in soleus muscle fibers of the rat following tenotomy. I. Spatial organization.

Complex systems of tubules, 30-40 nm in diameter, were observed in myofibers of the soleus muscle of Wistar rats following experimental transection of the Achilles tendon. The appearance of these systems varied remarkably, depending upon the plane of sectioning. The spacial arrangement of the tubules was reconstructed by comparing several sections through individual systems. Such reconstructions revealed that they are networks of tubular elements arranged in an hexagonal pattern. A three-dimensional wire model was prepared, illustrating the spatial organization of the tubular systems. The model consists of four groups of lattices with a honeycomb-like arrangement. The lattices of each group are parallel to one another, and intersect those of the other groups at an inclination of 60 degrees.

Animals↗
PubMed1976

[The development of hair and the restoration of innervation in the skin transplants in man].

Various areas in 7 local flaps and in 6 free skin grafts from the back, abdomen and thigh, applied to the palm and fingers and retained for periods extending from several months to 17 years are studied. After the second year, the transplants display virtually complete recovery of the sensation for pain, touch, pressure and temperature. The hair roots in the transplants have varying thickness and reveal changes in the structure of the connective-tissue and outer epithelial sheath (Figs. 1, 2). The sebaceous glands are enlarged. Isolated sebaceous glands are encountered which do not communicate with the hair roots. In the upper layers of the corium bundles of myelin nerve fibers are observed, giving off small groups of 2-4 fibers each, with slightly ascending direction relative to the hair roots (Fig. 3). The nerve fibers break down into branches which are furthermore ramified into smaller branches, forming palisade-like endings along the outer epethelial sheath of the hair root (Figs. 4-8). They number 15-25, being usually thin, with a discrete number of thickenings, and resemble the normal fibers running along the hair roots of the donor site (Figs. 9, 10). No capsulated receptors, characteristic of the surrounding skin, are noted in the transplants. Hence, it is assumed that most likely, the endings of the regenerated nerve fibers along the hair roots, although uncapsulated and with identical structure, provide for perceiving the types of sensation, inherent of the hairy and glabrous human skin.

Female↗