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Biomedical subjects

M Schwartz

Publications and source records attributed to M Schwartz.

At least 775 records · Page 43Linked to original sources
PubMed1978

Specificity and crossreactivity of idiotypes of murine antibodies induced by poly(Tyr,Glu)-poly(DLAla)-poly(Lys) and poly(Phe,Glu)-poly(DLAla)-poly(Lys).

Antibodies elicited against the two synthetic polypeptides, poly(Tyr,Glu)-poly(DLAla)-poly(Lys) [(T,G)-A-L] and poly(Phe,Glu)-poly(DLAla)-poly(Lys) [(Phe,G)-A-L], are crossreactive although the humoral responses to these immunogens are under different genetic controls. The fine specificity of the antibodies elicited by the two polypeptides was studied in the present work. Antisera against (Phe,G)-A-L bind both (125)I-labeled (T,G)-A-L and iodinated modified (Phe,G)-A-L. However, while the binding to (T,G)-A-L could be inhibited completely with the two antigens, the binding to (Phe,G)-A-L was inhibited completely with (Phe,G)-A-L and only partially with (T,G)-A-L. The binding of (125)I-labeled (T,G)-A-L to antisera against (T,G)-A-L was inhibted more efficiently by the homologous antigen than by (Phe,G)-A-L although both antigens completely inhibited the binding. (T,G)-A-L specific antibodies were purified on (T,G)-A-L immunoadsorbents from antisera of high and low responder mice to (T,G)-A-L immunized with (Phe,G)-A-L. (Phe,G)-A-L specific antibodies that did not bind (T,G)-A-L were isolated from the effluent of these columns. By use of anti-idiotypic antibodies of guinea pig against C3H.SW antibodies to (T,G)-A-L it was shown that (T,G)-A-L specific antibodies isolated from antisera against (Phe,G)-A-L of C3H.SW and C3H/DiSn mice possess part of the idiotypic determinants existing on antibodies of C3H.SW obtained by immunization with (T,G)-A-L. In contrast, antibodies to (Phe,G)-A-L that did not bind (T,G)-A-L did not share idiotypic determinants with C3H.SW antibody molecules against (T,G)-A-L. These results suggest that the B cell repertoire expressed by high and low responders to (T,G)-A-L after immunization with (Phe,G)-A-L is similar and represents only part of that of high responders immunized with (T,G)-A-L.

Animals↗
PubMed1978

Protein Ia and the lamB protein can replace each other in the constitution of an active receptor for the same coliphage.

Protein Ia and the lamB protein are both located in the outer membrane of Escherichia coli K-12. The lamB protein is known to be the receptor for phage lambda. Datta et al. [Datta, D. B., Arden, B. & Henning, U. (1977) J. Bacteriol. 131, 821--829] recently isolated a phage called TuIa that uses protein Ia for its adsorption. While phage TuIa fails to grow on ompB mutants, which lack protein Ia, we show here that host-range mutants of TuIa can be isolated that do grow on ompB strains. These host-range mutants fail to grow on ompB lamB double mutants, but retain the ability of the parental phage to grow on ompB+ lamB strains. They are therefore apparently able to use either protein Ia or the lamB protein for their adsorption. Genetic evidence suggests that essentially the same site on the lamB protein may be interacting with phage lambda or the host-range mutants of phage TuIa.

Bacterial Proteins↗
PubMed1978

Mutations altering the cellular localization of the phage lambda receptor, an Escherichia coli outer membrane protein.

Two mutant strains of Escherichia coli have been isolated in which the cellular location of an outer membrane protein, the phage lambda receptor (the lamB gene product), is altered. These mutations were initially selected in a strain containing a lamB-lacZ fusion. In the parent strain the protein coded for by the hybrid gene is located, at least in part, in the outer membrane. In the mutants it is located in the cytoplasm. The mutations responsible for the alteration of cellular location lie very early in the lamB gene, in a region corresponding to the NH2-terminus of the lambda receptor protein. One of these mutations is a small deletion internal to the lamB gene. When this mutation is present in an otherwise wild-type lamB gene, the protein produced is of lower molecular weight than normal receptor. The other mutation behaves as a point mutation; when it is present in an otherwise normal lamB gene, reversion can be demonstrated. The molecular weight of this mutant protein, which is located in the cytoplasm, is larger than that of the wild-type gene product by approximately 2000. It is suggested that these two mutations are in the portion of the lamB gene coding for a signal sequence and thereby block export of the protein.

Bacterial Proteins↗
PubMed1978

Mechanism of colicin E3 production in strains harboring wild-type or mutant plasmids.

As previously reported by others, more than 90% of the colicin E3 synthesized soon after induction of colicinogenic bacteria was found to be cell bound, about half of it being in a salt-extractable state at the cell surface. Evidence is presented that the colicin molecules remain preferentially bound to the cell which produced them, rather than being secreted and randomly distributed in the cell population. Secretion of colicin E3 may in fact never occur, all or most of the colicin found free in the medium perhaps being released during lysis of the producing cells long after induction. Among 19 mutant plasmids selected on the basis of their inability to produce an active colicin, only 3 were found to code for a protein which although it lacked any bactericidal activity, had the same molecular weight as wild-type colicin E3 and displayed a reaction of immunological identity with it. These three inactive colicins fail to be exported to the cell surface and seem to be blocked at some intermediate stage in the export process.

Bacterial Proteins↗
PubMed1978

Hurler/Scheie phenotype. Report of an inbred sibship with tapeto-retinal degeneration and electron-microscopie examination of the conjuctiva.

An inbred sibship with corneal opacities and deficient alpha-L-iduronidase activity showed signs of a Hurler/Scheie phenotype. The children were of normal intelligence. In one of the children, electron microscopy of the conjunctiva showed membrane-bound intracellular vacuoles and the electroretinogram was extinguished. The consanguinity of the parents is taken to indicate the presence of homozygosity of a mutant gene different from both the Hurler and Scheie mutants, thus rejecting the concept of a genetic compound in our patients.

Child↗
PubMed1978

Difficulties in comparing catecholamine-related enzymes from the brains of schizophrenics and controls.

The catecholamine-forming and metabolizing enzyme tyrosine hydroxylase, dopa decarboxylase, dopamine-beta-hydroxylase, phenylethanolamine N-methyltransferase, and catecholamine-O-methyltransferase, as well as the endogenous inhibitor of dopamine-beta-hydroxylase were compared in the brains of schizophrenics and controls. While there were no statistically significant differences in the enzyme or inhibitor activity between groups, tbre was a decided trend toward a decreased enzyme activity in the brains of the schizophrenics. From another set of control brains it was found that changes in human enzyme activity following death are variable and may be dependent on how the brains were handled. Thus, it is unclear whether the apparent differences between schizophrenics and controls were present when they were alive or occurred after death.

Adult↗
PubMed1978

The mode of interaction with macrophages of two ordered synthetic polypeptides which differ in their thymus dependency.

The mode of interaction with macrophages of two ordered synthetic polypeptides (Tyr-Tyr-Glu-Glu)-poly(DLAla)--poly(Lys), (T-T-G-G)-A--L, and (Tyr-Glu-Tyr-Glu)-poly(DLAla)--poly(Lys), (T-G-T-G)-A--L, which differ in their requirements for T-B cell co-operation in the process of antibody production, was compared. The binding of the two radiolabelled antigens to the surface of peritoneal adherent cells, their uptake by the cells and the rate of their degradation were investigated. Macrophages were found to be capable of degrading both poly-peptides with the same efficiency. (T-G-T-G)-A--L, the antigen which is less T-dependent, was bound to macrophage surfaces more readily than (T-T-G-G)-A--L, the T-dependent antigen, however, its uptake by the cells was found to be lower. Thus, (T-G-T-G)-A--L remains for a longer period in the form of a membrane bound polyvalent antigen.

Animals↗
PubMed1977

Uridine phosphorylase from Escherichia coli. Physical and chemical characterization.

Uridine phosphorylase from Escherichia coli has been purified to homogeneity. The enzyme was found to have a molecular weight of 176000 and to consist of 8 probably identical subunits with molecular weights of 22000. These numbers were determined from equilibrium centrifugations in the analytical ultracentrifuge, from dodecylsulphate gel electrophoresis and from amino acid analysis. Moreover the following physico-chemical constants were determined: s020,w = 8.2 x 10(-13) s, upsilon2 = 0.751 cm3/g, A1%280 (1 cm) = 6.73 and a specific activity of 183 units/mg towards uridine. The enzyme shows some activity towards deoxyuridine and thymidine. The activity is not impaired through substitution by bromo, fluoro or methyl groups in the 5-position of the uracil base, but no enzymatic activity is observed when cytosine base is used in the nucleoside substrate.

Amino Acids↗