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Biomedical subjects

S Stenman

Publications and source records attributed to S Stenman.

At least 73 records · Page 4Linked to original sources
PubMed1978

Distribution of a major connective tissue protein, fibronectin, in normal human tissues.

Fibronectin is a major surface-associated glycoprotein of cultured fibroblasts and it is also present in human plasma. Antiserum specific for human fibronectin was used to study the distribution of fibronectin in normal adult human tissues. The protein was detected (a) characteristically in various basement membranes including capillary walls: (b) around individual smooth muscle cells and in the sarcolemma of striated muscle fibers; and (c) in the stroma of lymphatic tissue and as thin fibers in loose connective tissue. The distribution of fibronectin was distinct from that of collagen and elastic fibers, but was very similar to reticulin, as demonstrated by conventional histological staining. The results indicate that fibronectin is a major component of connective tissue matrix. The distribution also indicates that most types of adherent cells abut fibronectin-containing structures. This supports the possible role of fibronectin in cell-cell and cell-matrix interactions in tissues.

Basement Membrane↗
PubMed1978

Fluorescent antibodies and lectins stain intracellular structures in fixed cells treated with nonionic detergent.

Nonionic detergent (NP40) treatment of paraformaldehyde-fixed normal and SV40-transformed human fibroblasts resulted in intracellular penetration of two chosen fluorescent antibodies and Concanavalin A (Con A). After the detergent treatment nuclear SV40 T antigen, cytoplasmic fibronectin glycoprotein and Con A binding sites could be visualized in fluorescence microscopy. The lowest NP40 concentration which made fixed cells permeable was 0.05%. The morphology of cells was preserved better by this new method than by conventional fixation methods, such as acetone treatment. In scanning electron microscopy the surface of the fixed NP40-treated cells had only small rugosities and fine pores. The subsurface cytoskeleton especially was well preserved and had a more distinct fine structure. The improved morphology made it possible to detect a similar distribution of fibronectin and Con A binding sites in the perinuclear endoplasmic reticulum regions.

Antigens, Viral↗
PubMed1977

Localization of amyloid-related serum protein SAA-like material to intermediate (10 nm) filaments of cultured human embryonal fibroblasts.

Further studies are presented on the intracellular localization of the amyloid-related serum protein SAA previously shown to be produced by embryonal fibroblasts. In cultured embryonal fibroblasts, the fine fibrillar cytoplasmic immunofluorescence obtained by anti-SAA was distinguished from that of microfilaments and microtubules. By using electron microscopy and cells treated with drugs known to specifically alter intracellular fibrils, SAA was localized to 10-nm intermediate size filaments. These filaments form characteristic perinuclear bundles upon treatment with drugs such as demecolcine or vinblastine which disrupt micotubules. The results indicate that SAA is a constituent of the intracellular cytoskeleton.

Amyloid↗
PubMed1977

Changes in the distribution of a major fibroblast protein, fibronectin, during mitosis and interphase.

The distribution of a major fibroblast protein, fibronectin, was studied by immunofluorescence and immunoscanning electron microscopy in cultures of human and chicken fibroblasts during different phases of the cell cycle. The main findings were: (a) In interphase cells, the intensity of surface-associated fibronectin fluorescence correlated with that of intracellular fibronectin fluorescence. (b) The intensity of the fluorescence of both surface-associated and intracellular fibronectins was not changed in cells that were synthesizing DNA. (c) Mitotic cells had reduced amounts of surface-associated but not of intracellular fibronectin. The surface fibronectin that remained on meta-, ana-, or telophase cells had a distinct punctate distribution and was also localized to strands attaching the cells to the substratum. Fibronectin strands first reappeared on the surface of flattening cytoplasmic parts of telophase cells. (d) Fibronectin was also detected in extracellular fibrillar material on the growth substratum, particularly around dividing cells. Thus, surface-associated fibrillar fibronectin was present during G(1), S, and G(2) but in cells undergoing mitosis the distribution was altered and the amount appeared to be reduced. The observations on the distribution of surface-associated fibronectin suggest that rather than being involved in growth control this fibronectin plays a structural role in interactions of cells with the environment.

Animals↗
PubMed1976

Changes in expression of fibroblast surface antigen (SFA) during cytodifferentiation and heterokaryon formation.

Fibroblast surface antigen (SF antigen, SFA) is a major glycoprotein antigen detected in connective tissue cells (primitive mesenchymal cells, fibroblasts, and astroglial cells). In this study the expression of SFA was followed during differentiation of the mesenchymal cells of the mouse metanephros and during heterokaryon formation produced by Sendai-virus induced fusion of human fibroblasts and chick red blood cells. It was demonstrated by immunofluorescence that SFA was lost from the kidney mesenchymal cells when they differentiate into epithelial cells of the secretory tubuli. During this process SFA became detectable in the basement membrane formed around the tubuli. In cell fusion experiments human SFA which was present as fibrillar network on the surface of cultured fibroblasts, was gradually lost from the heterokaryons when the incorporated chick nuclei became activated. These two sets of experiments indicate that SFA can be used as a phenotypic marker of cytodifferentiation.

Animals↗
PubMed1976

Expression of immunoglobulin synthesis in human myeloma x non-lymphoid cell heterokaryons: evidence for negative control.

Heterokaryons formed between human myeloma cells and various types of mouse and human non-lymphoid cells loose their cytoplasmic content of lambda light chains, a component of IgE produced by the myeloma parent. This loss of immunoglobulin content was observed regardless of the species origin (mouse or human) of the non-lymphoid partner cell, suggesting that the factors responsible for extinction of this differentiated function are not specific for a species. The kinetics of the loss of immunoglobulin content was essentially identical in the different experiments, since all myeloma X non-lymphoid cell heterokaryons were scored as negative after immunofluorescence staining for lambda chains 4-6 hr after infusion. Myeloma cells treated with inhibitors of protein synthesis (puromycin and cycloheximide) also lost their cytoplasmic content of immunoglobulin after 4 hr. These results indicate that the fusion of myeloma cells with non-lymphoid cells results in an immediate inhibition of immunoglobulin synthesis.

Animals↗
PubMed1975

Expression of SV40 T antigen during the cell cycle of sv40-transformed cells.

The expression of the nuclear SV40-induced T antigen was measured by microfluorimetry on individual, asynchronously growing SV40-transformed cells which had been stained with hamster T-antiserum by the indirect immunofluorescence method. The same individual cells were first measured for T antigen and then for DNA by Feulgen microspectrophotometry. A linear correlation was observed between the two parameters. T antigen expression was also measured in cell populations arrested at different phases of the cell cycle. Results of both types of experiments show that the expression of the gene (s) for T antigen in transformed cells increases during DNA replication and reaches its highest level in G2 nuclei. During mitosis T antigen is found in the cytoplasm.

Animals↗