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Biomedical subjects

P S Lin

Publications and source records attributed to P S Lin.

At least 19 recordsLinked to original sources
PubMed1979

Scanning electron microscope study of a new irrigation method in endodontic treatment.

The effectiveness of a newly developed perforated endodontic irrigation needle, with its distal aperture sealed, was compared to conventional endodontic irrigation procedures. In all instances 5 percent sodium hypochlorite was used since the delivery system, rather than the irrigant, was being evaluated. A base line group in which all soft tissue was described was also included. The results indicate that the perforated endodontic irrigation needle is a very effective instrument for the cleansing of instrumented root canals.

Dental Instruments↗
PubMed1979

Diminution of L cell microvilli following exposure to 25-hydroxycholesterol.

The effect of sterol depletion on the topology of mouse L cells was studied by scanning electron microscopy. Treatment of cells with 25-hydroxycholesterol inhibited the synthesis of cellular sterol and diminished the number of microvilli on the cell surface. Simultaneous addition of mevalonic acid or cholesterol to cells during treatment with the inhibitor prevented the loss of microvilli. These results demonstrate that cholesterol is important in maintaining the ultrastructure of the surface membrane of nucleated mammalian cells.

Cell Membrane↗
PubMed1979

Ultrastructural changes of cultured human amnion cells by Clostridiu difficile toxin.

The ultrastructure of the surface of primary human amnion monolayer cells undergoing cytopathology induced by Clostridium difficile toxin was examined by scanning electron microscopy. Our observations indicated that the type and distribution of cell surface projections were altered dramatically by this toxin. The patterns of such surface changes were specific for the two different types of cells found in this cell culture. Cells with demarcated borders showed rearrangement of microvilli into globular chains or ridges which lined up with the branching membrane. Cells without demarcated borders exhibited studlike microvilli, all arranged into ridges or globular chains. These changes were noted after 1 h of toxin exposure and persisted without further progression, in spite of continued toxin exposure, up to 48 h. These data indicate that C. difficile produces a cytolytic toxin and that scanning electron microscopy may be useful in determining toxin-cell interactions.

Amnion↗
PubMed1978

The selection of a stable rat hepatoma variant with concomitant increase in ploidy and permeability to glycerol.

By repeated selection for longer survival in an isotonic solution of glycerol, a stable subline of Novikoff rat hepatoma cells has been isolated. The cells exhibit markedly increased resistances to osmotic lysis in isotonic solutions of glycerol. They are twice as large and have twice as many chromosomes as cells of the parental line. It is suggested that the osmotic stress procedure can be extended for the selection of numerous kinds of mutants and can be used as a method of analysis of membrane properties.

Animals↗
PubMed1978

Phenotypic modification of SV40-transformed hamster lymphoid cells in vivo.

Explants of simian virus 40 (SV40)-induced lymphoid tumors yield SV40-T-antigen-positive derivatives that differ from GD248 lymphocytes propagated in suspension culture, (or in vivo), in the following respects: polygonal shape, adhesion to culture substrates in vitro, phagocytic capacity, lack of immunoglobulin and a chromosome complement at least twice that of GD248 lymphocytes. When GD-248 lymphocytes are propagated as suspension in vitro, no such adherent variants can be detected. However, sequential in vivo passage of GD248 lymphocytes obtained from the suspension-culture lines also yield adherent cell lines upon explanation in vitro. Injection of adherent cells into hamsters produces tumors with histological features of reticulum cell sarcoma.

Animals↗
PubMed1978

Modification of rat thymocyte membrane properties by hyperthermia and ionizing radiation.

Thymocytes are one the most widely used cell models for the study of radiation-induced interphase death. This cell-type was chosen for the study of hyperthermic and radiation effects on two membrane-related processes implicated in the interphase death of cells: Na+-dependent 2-aminoisobutyric acid (AIB) transport and cyclic 3'-5' adenosine monophsophate formation. The response of AIB transport to heat is dose-dependent, but the biphasic thermal response curve (AIB uptake versus time) differs fom the sigmoidal radiation response curve. Heating thymocytes for 20-30 min at 43 degrees C stimulates AIB uptake. Additional heating at 43 degrees C, however, markedly reduces AIB uptake. Despite the immediate stimulating effect of heat (30 min at 43 degrees C), the thymocyte has already developed irrepairable impairments, as demonstrated by the fractionated heating experiments. The heat-induced impairment of AIB uptake is mainly on the Na+-dependent component of neutral amino-acid transport, affecting primarily the maximal rate of uptake, i.e. Vmax. Additional evidence for heat-induced plasma membrane damage is the alteration in cAMP levels. Heating thymocytes for 30 min or longer at 43 degrees C causes a massive rise in cAMP level within the cell. This differs from thymocytes exposed to radiation where no rise in cAMP is observed.

Aminoisobutyric Acids↗
PubMed1978

Impairment of Na+-dependent amino acid transport in a cultured human T-cell line by hyperthermia and irradiation.

We have examined the effects of hyperthermia and radiation on the ability of a human T-leukemic lymphocyte line (Molt-4) to transport the Na+-dependent amino acid, 2-aminoisobutyrate (AIB). Heating Molt-4 at 43 degrees for 1 to 4 hr damages the ability of these cells to accumulate AIB. The damage to the transport system at 43 degrees impairs only the maximal rate of AIB uptake, i.e., Vmax. The thermal effect on AIB transport parallels the radiation effects observed for this system. Preliminary data indicate that heat and radiation may induce irreversible transitions in the tertiary or quaternary structure of a plasma membrane protein involved in regulating Na+-dependent amino acid transport. However, the mechanism by which heat and radiation damage this protein is different.

Aminoisobutyric Acids↗
PubMed1977

Hyperthermic treatment (43 degrees C) rapidly impedes attachment of fibroblasts to culture substrates.

Hyperthermic (43 degrees C) exposure of Chinese hamster fibroblasts for more than 30 min, either in suspension or as a monolayer, significantly inhibits their ability to attach to the culture substrate. This finding as well as the effect of hyperthermia on membrane proteins and on surface topology are rapidly expressed and differ from the inhibition of colony formation which is a later effect of hyperthermia on reproductive ability.

Animals↗
PubMed1977

Simian virus 40-specific proteins in the membranes of simian virus 40-transformed hamster and mouse cells.

Membranes of simian virus 40-transformed hamster lymphocytes and phagocytes, as well as of transformed mouse fibroblasts, contain two classes of antigenic virus-specific protein. The isoelectric points of these proteins, as defined by isoelectric focusing/immune electrophoresis are at pH 4.5 and 4.7. The molecular weights of the pI 4.5 and pI 4.7 components, determined by isoelectric focusing/dodecyl sulfate polyacrylamide electrophoresis, lie near 58,000 and 90,000-110,000, respectively. The pI 4.5 and pI 4.7 proteins are tentatively identified with the surface (transplantation) and U antigens, respectively.

Animals↗
PubMed1977

Transformation by simian virus 40 induces virus-specific, related antigens in the surface membrane and nuclear envelope.

Nucleus- and mitochondrion-free membranes from hamster lymphocytes transformed by simian virus 40 (SV40), GD248 cells, cause guinea pigs to produce immune sera that reveal the presence in GD248 plasma membranes and mitochondria of two types of glycoprotein that are not detected in membranes of normal lymphocytes [Schmidt-Ullrich, R., Thompson, W. S. & Wallach, D. F. H. (1977) Proc. Natl. Acad. Sci. USA 74, 643-647]. Indirect immune fluorescence of living, SV40-transformed T19 hamster reticulum cells, Balb/c 3T3 mouse fibroblasts, and W18 VA2 human fibroblasts, using the antisera against GD248 membrane, at 4 degrees produced a distinct cell surface fluorescence; however, above 20 degrees , staining at the nuclear perimeter, the SV40 U-antigen reaction, becomes equally prominent. In SV40-transformed cells that had been fixed in cold acetone, as well as in purified GD248 nuclei, thermostable U-antigen staining is dramatic, but there is no reaction for nuclear T-antigen. Rabbit antisera against T19 cells gave immunofluorescence reactions equivalent to those obtained with the antisera against GD248 cells. Normal guinea pig or rabbit sera and cells that had not been transformed by SV40 gave no reaction. Our sera from tumor-bearing hamsters gave only nuclear T-antigen fluorescence. The results indicate the presence of related, SV40-specific antigens in the surface membranes, nuclear envelope, and possibly other intracellular organelles of SV40-transformed cells.

Antigens, Viral↗