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Biomedical subjects

J Michl

Publications and source records attributed to J Michl.

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

The effect of growth-promoting alpha-globulin (GPAG) on the incorporation of exogenous DNA into L-cells. I. Incorporation of isologous and heterologous 3H-DNA.

Isologous and heterologous 3H-DNA (optimum concentration 25 microgram/ml of medium) are incorporated into L-cells from the medium during short-term incubation (up to 60 min). The incorporation of DNA is stimulated by a protein complex from calf serum--the growth-promoting alpha-globulin (GPAG) in the concentration 0.8 mg/ml of medium), which is rapidly taken into cells by pinocytosis. GPAG increases the frequency of incorporation of exogenous 3H-DNA into L-cells and the quantity of DNA incorporated. The quantity of 3H-DNA incorporated is further increased on the incubation of L-cells in a medium containing the complex 3H-DNA + GPAG, which is formed by the joint preincubation of the two components at 37 degrees C (20 hr); under these conditions the quantity of DNA incorporated is 150% greater than when 3H-DNA is used alone. GPAG acts as an activator of exogenous DNA transfer, stimulates its pinocytosis by the cells, and at the same time accelerates its intracellular transfer to the cell nuclei.

Alpha-Globulins↗
PubMed1978

Effect of growth-promoting alpha-globulin on the incorporation of exogenous DNA into L cells. II. Fate of exogenous 3H-DNA after incorporation into recipient cells.

GPAG stimulates the uptake of exogenous 3H-DNA by L cells and facilitates its retention in host cell nuclei during 48-h postcultivation; the nuclei contain 1.5 times more radioactivity than GPAG-free controls. Owing to the well-known properties of GPAG, the formation of the 3H-DNA-GPAG complex may affect the incorporation of exogenous 3-H-DNA and its intracellular transport and retention in the host cell nuclei.

Alpha-Globulins↗
PubMed1977

Proliferative capacity constant of metazoan cells in culture.

Proliferative capacity of metazoan cells in culture may be defined quantitatively by using GPAG-supplemented medium. For this purpose an expression called proliferative capacity constant (KPC) was introduced. KPC represents the logarithm of GPAG concentration over which the mitotic activity of cells is induced.

Alpha-Globulins↗
PubMed1976

2-Deoxyglucose selectively inhibits Fc and complement receptor-mediated phagocytosis in mouse peritoneal macrophages. I. Description of the inhibitory effect.

Incubation of normal or thioglycollate-elicited mouse peritoneal macrophages with 2-deoxy-D-glucose (2-dG) inhibits the capacity of these macrophages to phagocytize IgG- or complement-coated particles via their Fc and C3 receptors. 2-dG has no inhibitory effect on the capacity of these macrophages to phagocytize latex or zymosan particles, which are ingested in the absence of specific opsonins, and it does not inhibit binding of IgG- or C3-coated particles to their respective receptors on the macrophage's plasma membrane. 2-dG exerts its inhibitory effect on the macrophage and not on the opsonized particle. The inhibition is independent of particle size, occurs within 15-30 min of addition of this glucose analogue to the medium at 37 degrees C, cannot be overcome by supra-agglutinating amounts of opsonizing antibody, and is completely reversible by substitution of 5.5 mM glucose for 50 mM 2-dG in the medium. Addition of equimolar amounts of glucose or mannose, but not of fructose, galactose, fucose, or glucosamine, to medium containing 50 mM 2-dG results in substantial reversal of the inhibitory effect of 2-dG on Fc and C3 receptor mediated phagocytosis.

Animals↗
PubMed1976

2-Deoxyglucose selectively inhibits Fc and complement receptor-mediated phagocytosis in mouse peritoneal macrophages II. Dissociation of the inhibitory effects of 2-deoxyglucose on phagocytosis and ATP generation.

Macrophages incubated in 2-deoxy-D-glucose (2-dG)-containing medium showed a marked decrease in cellular ATP content, and were unable to ingest IgG- and complement-coated erythrocytes via the corresponding membrane receptors for these ligands. However, the inhibitory effects of 2-dG on Fc- and C3 receptor-mediated phagocytosis were not a consequence of lowered macrophage ATP levels since addition of glucose or mannose to the culture medium restored the capacity of the macrophages to ingest IgG- and C3-coated particles without increasing ATP levels. These results indicate that Fc- and C3 receptor-mediated phagocytosis (opsonin dependent) differs qualitatively from the ingestion of latex and zymosan particles (opsonin independent); they suggest that the same regulatory molecules govern the responses of phagocytic cells to signals initiated by both the Fc and C3 receptors. The possibility that these molecules are regulated by glycosylation is discussed.

Adenosine Triphosphate↗
PubMed1976

Contact inhibition of pleiotropin pinocytosis as a critical factor in metazoan cell ageing.

For the biosynthesis of macromolecules in amounts sufficient for indefinite growth or survival in dividing as well as in nondividing metazoan cells, a specific serum protein is required. As the addition of this factor to the medium triggers off a chain of events which leads to RNA, DNA, and protein synthesis, we have called it the pleiotropin. Pleiotropin is taken into the cells by pinocytosis. Pinocytic uptake of pleiotropin is strongly inhibited by a mutual cell-to-cell contact; diploid cells in the stage of contact inhibition of pleiotropin pinocytosis are nutritionally limited, and some changes in life processes may be expected. In continouous culture and in tissues in vivo, these changes may accumulate and ultimately result in an irreversible damage of cells so that old cells are characterized by a low pinocytic activity and by a reduced formation of macromolecules. As pleiotropin increases the saturation density and prolongs the life span of diploid cells in vitro, it is suggested that the loss of division potential in metazoan cells is not a programmed event at the cellular level and that the ageing of static cell populations may be caused by the same nutritional deficiency as that of proliferating cells.

Aging↗
PubMed1975

[Possibilities of a quality control in the diagnosis of tuberculosis (author's transl)].

A method is described which allows a quality control for demonstrating mycobacteria in the diangosis of tuberculosis. It does not test the differentiating procedures, but the manner of culturing and concentrating the bacteria by applying a statistical evaluation of serial experiments, thus allowing the statistically proven determination of the bacterial count. For this an evaluation method given by Cavalli-Storza was employed.

Bacteriological Techniques↗