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Biomedical subjects

S Chacko

Publications and source records attributed to S Chacko.

100 records · Page 6Linked to original sources
PubMed1976

Rings of intermediate (100 A) filament bundles in the perinuclear region of vascular endothelial cells. Their mobilization by colcemid and mitosis.

Vascular endothelial cells cultured from guinea pig aorta or portal vein contain naturally occurring bundles of 100 A (diameter) filaments that completely encircle the nucleus. These rings are phase lucent and birefringent when examined with the light microscope. Perinuclear bundles of 100 A filaments were also seen in endothelial cells in vivo, indicating that they are a normal cytoplasmic component. These filaments did not decorate with S-1, and were not disrupted by glyceination. With these cells, experiments were designed to answer the following questions: (a) does Colcemid have an effect on these naturally occuring bundles? And (b) do these filaments remain during cell division? Endothelial cells grown in the presence of Colcemid were followed over 24 h. The perinuclear ring coiled into a juxtanuclear cap that consisted of disorganized arrays of 100 A filaments. This "coiling" effect was not blocked by cycloheximide, an inhibitor of protein synthesis. In another experiment, dividing cells were examined. During division the bundle of filaments is passively pulled in half into the daughter cells. These bundles did not disappear during the mitosis when mitotic spindle microtubules assemble. These studies suggest that Colcemid may exert a direct effect on 100 A filaments, independent of microtubules. Since these filaments do not disappear during mitosis, it is possible that in these cells the 100 A filaments and tubulin do not share a common pool of precursor proteins.

Animals↗
PubMed1975

Golgi organelle response to the antibiotic X537A.

The effects of the ionophoric antibiotic X537A on cell structure were studied with phase-contrast, fluorescence, and electron microscopy. X537A induced selective vacuolation of the Golgi apparatus of vascular and intestinal smooth muscle, epithelium, plasma cells, and cultured chick heart and guinea pig vascular smooth muscle cells. The swelling of the Golgi apparatus induced by X537A was reversible in the systems examined for reversibility: vascular smooth muscle and cultured chick heart. Myelin figures were common in the Golgi apparatus vacuolated by X537A. Fluorescence microscopy of cultured cells incubated with X537A showed the characteristic blue X537A fluorescence associated with lipid globules in the cultured cells. Incubation of cultured chick heart cells with X537A reduced the beating rate and, after 24-72 h, abolished the sarcomere pattern. The swelling of the Golgi membranes produced by X537A in cultured vascular smooth muscle was associated with inhibition of D-[6-3H]glucosamine and [35S]sulfate incorporation into glycosaminoglycans.

Animals↗
PubMed1975

Phagocytosis by muscle cells.

Electron microscopy of intact tissue and cultured smooth muscle suggested the occurrence of phagocytosis of necrotic cells by normal vascular smooth muscle cells. Phagocytosis was further studied in vitro in muscle cells from guinea pig aorta, guinea pig vas deferens, and striated muscle from chick embryo by light and electron microscopy. The uptake of yeast cells (approximately 2-mum. diameter) into living cultured smooth muscle cells from guinea pig aorta was observed with phase contrast microscopy and differential interference (Nomarski) optics. Periodic acid-Schiff staining showed the yeast cells lined up in the cytoplasm of the muscle cells. Electron microscopy confirmed the uptake of yeast cells by differentiated muscle cells. Some of the yeast in the smooth muscle cells showed signs of disintegration suggesting digestion within the phagosome. Spontaneously contracting cultured smooth, cardiac and skeletal muscle cells incubated with latex spheres (0.3-mum. diameter) showed uptake and sequestration of the spheres. The ability of muscle cells to phagocytose necrotic cells and other particulate matter may be important in atherogenesis and in the repair of tissue after injury.

Animals↗
PubMed1969

The loss of phenotypic traits by differentiated cells. VI. Behavior of the progeny of a single chondrocyte.

A single, functional, mitotically quiescent chondrocyte may be induced to reenter the mitotic cyde, and produce a progeny of over 10(11) cells. Sessile, adherent, polygonal cells deposit matrix, whereas amoeboid, dispersed, flattened fibroblastic cells do not. The prior synthetic history of a cell is of greater importance in determining whether the characteristic chondrogenic phenotype will be expressed, rather than growth in "permissive" or "nonpermissive" medium. Clonal conditions select for stem-like cells, some of whose progeny may become polygonal chondrocytes. The retention of the characteristic chondrogenic phenotype in vitro is favored by pruning the dedifferentiated chondrocytes which arise in these cultures. Dedifferentiated chondrocytes interfere with the deposition and synthesis of chondroitin sulfate by neighboring functional chondrocytes. Possible mechanisms are proposed to explain this type of cell-cell or cell exudate interference. If the progeny of a single, genetically programmed chondrocyte may or may not synthesize chondroitin sulfate, then extragenic sites in the cytoplasm or cell surface must influence the decision as to which cluster of "luxur" molecules the cell will synthesize.

Animals↗
PubMed1969

Effect of 5-bromodeoxyuridine on expression of cultured chondrocytes grown in vitro.

Exposure of cultured cartilage cells to 5-bromodeoxyuridine results in a rapid loss of the ability to synthesize the chondroitin 4-sulfate-protein complex characteristic of the extracellular matrix of differentiated cartilage. UDP-glucose dehydrogenase, UDP-N-acetyl hexosamine 4-epimerase and the enzyme system responsible for catalyzing 3'-phosphoadenosine-5'-phosphosulfate synthesis all progressively decline in activity, while several other cellular processes seem unaffected. However, there are marked morphological changes which may be associated with plasma membrane components or the synthesis of the protein-polysaccharide complex.

Bromodeoxyuridine↗
PubMedDate not supplied

Sexual behaviour, AIDS and poverty in Sub-Saharan Africa.

Within the rapidly progressing pandemic of the acquired immunodeficiency syndrome (AIDS) Sub-Saharan Africa plays a disproportionally large role. The reported data indicate that heterosexual transmission is the predominant cause for the rapid spread in this, one of the world's poorest regions. Prostitution, though poorly understood in the African context, unstable family structure, lack of male circumcision, aversion to, and high cost of, condom use, and risky sexual behaviour, including multiple sexual contacts and partners, are causal and facilitating factors in the rapid spread of HIV infection. Virtually all of these factors are related to poverty. Education and information, which in the absence of an effective curative drug and/or vaccine, would be essential, is also a costly undertaking. Deeper understanding of and increased attention to the economic, as well as social and cultural, parameters of the Sub-Saharan AIDS endemic is needed for the implementation of preventive measures.

Acquired Immunodeficiency Syndrome↗