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Biomedical subjects

K Sege

Publications and source records attributed to K Sege.

At least 19 recordsLinked to original sources
PubMed1983

Characterization of an antigen present on testicular cells and preimplantation embryos whose expression is modified by the t12 haplotype.

In attempts to identify cell surface molecules specified by lethal genes in the T/t-complex, we prepared a rabbit antiserum that has cytotoxic activity against testicular cells from males heterozygous for t12, but not against wild type cells. However, anti-t12 serum immunoprecipitates the same major component, a glycoprotein of mol. wt. 87,000 daltons, from galactose-labelled C3H. +/t12 testicular cell lysate and from congenic C3H. +/+ lysate, although the gp87 molecule precipitated from +/t12 cells appears to be more highly galactosylated than the +/+ form. The antigen is heavily glycosylated in both genotypes, since when testicular cells are treated with tunicamycin before immunoprecipitation, a protein of 40,000-42,000 daltons is obtained. Gp87 is also present on pre-implantation embryos, and on teratocarcinoma cells, but is barely detectable on any adult somatic cells examined. Its expression is developmentally regulated during pre-implantation stages, but the temporal pattern of its expression appears to be different between wild type and t12 embryos. Thus, we believe we have identified a molecule that may play a role in the differentiation of testicular cells and pre-implantation embryos, and that is either specified by genes in the t12 haplotype, or responsive in some way to the effects of t12.

Animals↗
PubMed1982

Isolation and characterization of mouse beta 2-microglobulin allotypes.

Two allelic forms of mouse beta 2-microglobulin (beta 2m), the smaller polypeptide chain of the H-2 histocompatibility antigens, were purified from urine and partially characterized. The isoelectric points of the two allotypes are 7.4 (beta 2ma) and 8.1 (beta 2mb). The electrophoretic mobility of beta 2ma is decreased by reduction, whereas the mobility of beta 2mb is not. Urinary beta 2m can replace endogenous beta 2m in mouse H-2 histocompatibility antigens.

Alleles↗
PubMed1982

Expression of histoincompatibility antigens during spermatogenesis in the rat.

The expression of the AgB-SB and -LD (Ia-like) antigens on spermatogenic cells has been investigated by using a protein A-containing Staphylococcus Cowan I rosetting assay. The results show that the Ia-like antigens are present on all spermatogenic cells although the relative expression seems to decrease slightly concomitant with the differentiation. The AgB-SD antigens are detected on spermatogenia, leptotene, and zygotene spermatocytes but not on later developmental stages.

Animals↗
PubMed1981

Role of beta2-microglobulin in the intracellular processing of HLA antigens.

The biosynthesis of HLA-A, -B, and -C antigens was examined in the two lymphoblastoid cell lines DAUDI and RAJI. In RAJI cells the HLA-A, -B, and -C antigen heavy chains become core-glycosylated in the endoplasmic reticulum as evidenced by their sensitivity to endo-H digestion and tunicamycin treatment. Beta2-Microglobulin is present in excess in the endoplasmic reticulum of the RAJI cells and associates with the heavy chain at the time of synthesis of the heavy chain. Pulse-chase experiments demonstrated that the RAJI HLA-A, -B, and -C antigen heavy chains become terminally glycosylated since their changed characteristics included resistance to endo-H digestion, sensitivity to neuraminidase treatment, and incorporation fucose. DAUDI HLA-A, -B, and -C antigen heavy chains are synthesized normally and become core-glycosylated but not terminally glycosylated. Other glycosylated cell surface proteins, like the HLA-DR antigens, display normal glycosylation in DAUDI cells. Therefore it is unlikely that the absence of terminally glycosylated HLA-A, -B, and -C antigen heavy chains is the result of a general defect in the biosynthetic machinery of DAUDI cells. However, DAUDI cells lack the ability to synthesize beta2-microglobulin, the common subunit of all HLA-A, -B, and -C antigens. Therefore, it seems reasonable to conclude that beta2-microglobulin is of importance for intracellular transport of newly synthesized HLA-A, -B, and -C antigens.

Beta-Globulins↗
PubMed1981

Two allelic forms of mouse beta 2-microglobulin.

Two allelic forms of mouse beta 2-microglobulin (beta 2m), the small polypeptide chain of H-2 histocompatibility antigens, have been identified. The two forms can be distinguished by NaDodSO4/polyacrylamide gel electrophoresis. All inbred mouse strains express a single beta 2m isotype. Mice heterozygous for beta 2m synthesize both forms, showing codominant expression of beta 2m alleles. In mice heterozygous for both H-2 and beta 3m, individual H-2 histocompatibility antigens associate with both beta 2m forms. Preliminary structural studies indicate differences in peptide composition between the two forms.

Alleles↗
PubMed1980

On the stoichiometry of the interaction between prealbumin and retinol-binding protein.

The stoichiometry of the interaction between prealbumin and retinol-binding protein was investigated. Gel chromatography analyses of prealbumin on columns equilibrated with retinol-binding protein (RBP)-containing buffers and fluorescence polarization analyses of RBP in the presence of various concentrations of prealbumin demonstrated that 3 molecules of RBP could simultaneously bind to prealbumin. Each RBP molecule seemed to interact with prealbumin with an apparent association constant of about 7.8 X 10(6) M-1. Fab fragments of anti-iudiotypic antibodies raised against anti-RBP antibodies reaced specifically with the RBP-binding sites on prealbumin. Two anti-idiotypic Fab fragments could simultaneously interact with prealbumin. These data strongly suggest that prealbumin exhibits at least two RBP-binding sites.

Binding Sites↗
PubMed1980

Turnover in humans of beta 2-microglobulin: the constant chain of HLA-antigens.

The turnover of beta 2-microglobulin, the common subunit of the HLA antigens, has been examined in normal subjects and in some patients with kidney disorders, multiple myeloma and rheumatoid arthritis. All patients displayed elevated serum levels of beta 2-microglobulin. The plasma disappearance curve of 125I-beta 2-microglobulin demonstrated that the protein has a rapid turnover (t 1/2 = 2.1 h; range 1.1-2.8 h) in normal persons and in patients with a normal glomerular filtration rate. In patients with kidney disorders the impaired renal filtration prolonged the turnover time and led to elevated serum levels of beta 2-microglobulin. Simultaneous measurements of 125I-beta 2-microglobulin in serum and urine allowed estimations of the beta 2-microglobulin net reabsorption in the renal tubuli. Two patients with renal disease reabsorbed 84% and 89%, respectively, of the beta 2-microglobulin filtered in the glomeruli. In normal persons the net reabsorption is close to 100%. In patients with normal kidney function increased serum levels of beta 2-microglobulin seem to be due to an increased synthetic rate of the protein as the elimination rate is normal. HLA antigen heavy chains in serum are present in smaller amounts than beta 2-microglobulin. The present data, therefore, suggest an imbalanced synthesis of the two chains.

Adult↗
PubMed1980

Isolation and partial characterization of a murine cell surface glycoprotein with affinity for exogenously added beta 2-microglubulin.

Exogenously added beta 2-microglobulin (beta 2m) binds to a variety of murine cell types. The 'receptor' for beta 2m has been isolated. The purified 'receptor' comprised a 48,000-dalton chain and occasionally a 25,000-dalton component. Direct crosslinking of beta 2m to the receptor on intact cells gave rise to a single 60,000-dalton beta 2m-'receptor' complex. The molecular characteristics of the 'receptor' were considerably changed on binding beta 2m. The size of the beta 2m-'receptor' complex was increased partly due to enhanced binding of deoxycholate. The 'receptor' was less easily degraded by proteases when beta 2m was bound then when free. The solubilized 'receptor' reacted with a heteroantiserum raised against H-2K and D antigens but did not exhibit any alloantigenic determinants shared with H-2K, D or Ia antigens.

Animals↗
PubMed1979

Demonstration of a murine cell surface component with affinity for exogenous beta 2-microglobulin.

Murine and human beta 2-microglobulin (beta 2m) bind to various types of mouse cells. The binding is saturable and displays a single association constant of about 1 x 10(9) liter/mol. The binding of beta 2m to splenocytes was not affected by a variety of metabolic inhibitors but was temperature-dependent. It is suggested that the beta 2m "receptor" exhibits a temperature-dependent conformational change since the "receptor", whether integrated into the membrane or solubilized by the detergent Triton X-100, binds beta 2m poorly at low temperatures. Spleen T and B lymphocytes display more binding sites than thymocytes, kidney, liver and brain cells. The relative amounts of the beta 2m-binding "receptor" on these cell types are strongly correlated to the relative amounts of H-2 antigens. This correlation is also obvious for the teratocarcinoma cell line F9, which lacks both beta 2m "receptor" and H-2 antigens, but spermatozoa, which express very small amounts of H-2 antigens, have an appreciable amount of the beta 2m "receptor". The latter observation, together with the fact that alloantisera directed against H-2 K and D antigens do not measurably affect the binding of beta 2m to the "receptor", may argue against the notion that the beta 2m "receptor" represents H-2 antigens which have lost their endogenous beta 2m. Normal mouse serum contains a component which inhibits the binding of beta 2m to splenocytes. It is likely that this serum protein is identical to a newly discovered H-2 antigen-like glycoprotein. The beta 2m "receptor" appears to be under the control of the major histocompatibility complex as splenocytes of the H-2f haplotype bind considerably more beta 2m than splenocytes of other haplotypes.

Animals↗
PubMed1978

Use of anti-idiotypic antibodies as cell-surface receptor probes.

Anti-idiotypic antibodies have been raised against antibodies to retinol-binding protein (RBP) and to insulin. After absorption the anti-idiotypic antibodies recognized the antigen-combining sites of the antibodies used as the immunogen but of no other antibodies. Some of the anti-idiotypic antibodies raised against antibodies to RBP bound specifically to rat intestine epithelial cells, which have a physiological cell-surface receptor for RBP. The RBP receptor mediates the uptake of retinol from RBP to the cells. This uptake was abolished in a concentration-dependent manner by the anti-idiotypic antibodies, which obviously competed with RBP for binding to the receptor.Anti-idiotypic antibodies against antibodies to insulin inhibited the binding of (125)I-labeled insulin to isolated rat epididymal fat cells, whereas anti-idiotypic antibodies raised against antibodies to RBP had no effect. Furthermore, on interacting with young rat thymocytes, anti-idiotypic antibodies against antibodies to insulin stimulated the uptake by the cells of alpha-aminoisobutyric acid, thereby mimicking the effect of insulin. These results suggest that in some cases anti-idiotypic antibodies may be useful tools in elucidating structure-function relationships for cell-membrane receptors.

Aminoisobutyric Acids↗