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Biomedical subjects

J Urban

Publications and source records attributed to J Urban.

At least 181 records · Page 10Linked to original sources
PubMed1976

Synthesis of albumin via a precursor protein in cell suspensions from rat liver.

The mechanism of the biosynthesis of albumin was studied in cell suspensions from rat liver. The cells were prepared by continuous perfusion of the liver in situ with 0.05% collagenase and 0.10% hyaluronidase and incubated under conditions optimized for the incorporation of amino acids into protein. Seven minutes after starting the incubation L-[1-14C]leucine was added, followed after 25 min by a 15 or 30-min chase with an 830-fold excess of non-radioactive L-leucine. Total protein, an albumin-like protein, and albumin were isolated from samples withdrawn immediately of total protein was found to remain constant after addition of the non-radioactive L-leucine, whereas that of the albumin-like protein decreased and that of albumin increased with incubation time. The increase in albumin radioactivity accounted for the decrease in radioactivity of the albumin-like protein, suggesting that the latter is a precursor of albumin. The precursor protein differed from albumin by an oligopeptide extension at the N-terminal end.

Albumins↗
PubMed1976

Immunoglobulin E synthesis in parasite infection.

The infection of rats with Nippostrongylus brasiliensis (Nb) larvae enhanced IgE synthesis prior to the formation of IgE antibody specific for parasite antigens. As early as the eighth to tenth day of infection, IgE-bearing lymphocytes appeared in lymph nodes and spleen. At this time, even bone marrow contained IgE-bearing blast cells. The IgE-forming plasma cells were detected in the lymph nodes and spleen at the tenth day and their number reached maximum at the fourteenth day. The proliferation of IgE-bearing lymphocytes in the lymphoid tissues was observed in neonatally thymectomized animals, indicating that T cells are not essential for the development of IgE-B cells in the infected animals. It appears, however, that T cells are involved in the differentiation of IgE-B cells to IgE-forming plasma cells. Nonspecific proliferation of IgE-B cells and their differentiation to IgE-forming plasma cells may explain potentiation of IgE antibody formation against unrelated antigens after infection with N. brasiliensis (Nb). It was also found that T cells specific for parasite antigens were primed by infection with Nb. Evidence was obtained tht Nb-specific T cells raised by the infection collaborated with hapten-specific IgE-B cells and IgG-B cells for the secondary antihapten antibody responses. By contrast, T cells primed by immunization with parasite antigen included in alum exerted the helper function for IgG antibody response but failed to collaborate with IgE-B cells. Dissociation between the helper function for IgE and IgG antibody response indicated that parasite infection generated a favorable condition for priming T cells for the IgE antibody response.

Animals↗
PubMed1976

Effects of a streptococcal lipoteichoic acid on host responses in mice.

A teichoic acid (TA) extracted from Streptococcus pyogenes 1-RP41 was previously shown to be an immunosuppressant under certain conditions (Miller and Jackson, 1973). The TA has now been shown to be a lipoteichoic acid composed of 40% glycerol, 20% alanine, 13% phosphorus, and 8% glucose, with a variable content of fatty acids. Teh presence of the polyglycerol phosphate backbone and fatty acid was required for maximum immunosuppression of the primary immunoglobulin M response to sheep cells. A complex, nonlinear, time-dependent dosage relationship in suppression of the anti-sheep erythrocyte response in mice was observed. TA depressed the anamnestic response to sheep cells in the mouse and could affect this response whether administered before the primary antigen challenge or immediately before the secondary challenge. In distinct contrast, TA enhanced antibody production to Escherichia coli O55:B5 lipopolysaccharide when assessed by counting plaque-forming cells or measuring antilipopolysaccharide serum titers. The TA failed to stimulate a large uptake of [3H]TdR by murine spleen cells; however, it significantly enhanced the clearance of carbon by the reticuloendothelial system.

Animals↗
PubMed1976

Biosynthesis of albumin via a precursor protein in Morris hepatoma 5123tc.

The mechanism of albumin biosynthesis was studied in Morris hepatoma 5123tc in vivo and in hepatoma cell suspensions obtained by solubilizing the intercellular matrix with collagenase and hyaluronidase. In the in vivo experiments, L-[-14C]leucine was injected i.v. into rats bearing hepatomas in the muscles of both hind legs. After 14 min, tumors were removed and homogenized. A protein fraction quantitatively precipitable with antialbumin was isolated from the homogenate by acetone fractionation and precipitation with antiserum against serum albumin. This protein fraction was not homogeneous. With the use of 3 consecutive chromatographies on diethylaminoethyl cellulose, a very highly radioactive albumin-like protein could be separated from a large amount of only slightly radioactive albumin. In hepatoma cell suspensions incubated with L-[1-14C]leucine followed by a chase with excess nonradioactive L-leucine, radioactivity was incorporated first into the albumin-like protein and transferred thereafter into albumin, suggesting that albumin was synthesized via the albuminlike protein as precursor. In vivo, 1.8% of newly synthesized hepatoma protein was albumin or its precursor, compared with 1.2% in cell suspensions.

Albumins↗
PubMed1975

Factors involved in the nutrition of the human lumbar intervertebral disc: cellularity and diffusion of glucose in vitro.

Post-mortem specimens of the human lumbar (L4-L5) intervertebral disc have been studied histologically and physico-chemically. Blood vessels were found only at the margin of the anulus fibrosus and in the vertebral marrow spaces. Contact between disc tissue and marrow spaces occupied about 10% of the bone-cartilage interface. The disc was most cellular at the periphery of the anulus fibrosus and in the hyaline cartilage next to the vertebral bone. Cellularity declined towards the nucleus pulposus where it achieved a low constant value. The cell density of the disc as a whole was about 60000 cells/mm3. For glucose, the diffusion coefficient of the anulus fibrosus and hyaline cartilage end plate was 2.5 cm2/sec and 2.4 cm2/sec respectively at 37 degrees C, comparable to that of cartilage elsewhere. The permeability of the bone-cartilage interface was low, particularly in the peripheral part. Calculations, based on the present findings and derived values for glucose utilization in disc tissue, indicate that nutritional conditions in the intervertebral disc are more critical than, for example, in articular cartilage.

Adolescent↗