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At least 343 records · Page 19Linked to original sources
PubMed1978

Crystallographic studies on D-amino acid oxidase.

D-amino acid oxidase, a flavoprotein from hog kidneys, has been crystalized in two different forms. Orthorhombic prisms have been obtained from the enzyme.benzoate complex at pH 8.3; the space group is C2221 and the cell dimensions are a = 325A, b = 138.8 A, c = 200 A. At lower pH values, the enzyme crystallizes in trigonal prisms with a = b = 116.0 A, c = 399 A, space group P3112 or its enantiomorph. The two crystal forms have been obtained at 28 degrees C while at 4 degrees C only weak evidence of crystallization has been detected. In both crystalline modifications, the protein is highly associated.

D-Amino-Acid Oxidase↗
PubMed1976

IgM-mediated, T cell-independent suppression of humoral immunity.

The immunological unreactive state occurring in (T,G)-A-L nonresponder mice after secondary antigen challenge was investigated. Syngeneic IgM anti-(T,G)-A-L antibody-containing plasma, transferred at the time of the time of primary challenge, induced persistent suppression of autologous specific antibody production. Removal of plasma IgM with goat anti-mu antisera removed the ability of the plasma to supress. The induction and maintenance of the suppressed state were not different in thymectomized or sham-thymectomized animals. Primed animals subjected to graft-vs-host reaction (GVHR) at the time of secondary challenge switched over to IgG production. Animals suppressed by passive antibody transfer reacted to GVHR, at the time of secondary challenge, with specific IgM but not IgG antibody production. Transfused normal spleen cells partially abrogated suppression only when (suppressed) hosts had been lethally irradiated. Spleen cells from antigen-plus-antibody suppressed donors, upon transfer to previously normal, syngeneic hosts, were less immunocompetent than spleen cells from untreated donors. These data are consistent with a model of IgM mediated, T cell-independent persistent suppression of humoral immunity.

Animals↗
PubMed1979

Metal-free southern bean mosaic virus crystals.

Native southern bean mosaic virus contains a significant number of Mg2+ and Ca2+ ions. These can be removed by treatment with EDTA causing the virus to swell by 7% in radius at alkaline pH values. The swollen virions are susceptible to protease and nuclease digestion. They are likely to be an intermediate during assembly and disassembly. Crystals of the metal-free virus have been grown and were found to be approximately isomorphous with the orthorhombic type III southern bean mosaic virus crystals (Akimoto, T., Wagner, M.A., Johnson, J.E., and Rossmann, M.G. (1975) J. Ultrastruct. Res. 53, 306-318), although the cell dimensions are longer by 2%. Native rhombohedral type II crystals disintegrate on changing the pH or increasing the ionic strength of the mother liquor. Damage can be prevented by addition of ethylene glycol. At alkaline pH values, these crystals also show a 2% increase in their cell dimensions as well as a significant alteration in their diffraction patterns. In the type II and III crystals, the viruses pack with only their 5-fold axes in contact. Thus, the difference of the apparent swelling in solution and in the crystals may be one of differential swelling over the virus surface.

Calcium↗
PubMed1979

Nature of the stimulus leading to lymphocyte-induced angiogenesis.

Experiments are described that characterize the nature of the stimulus leading to lymphocyte-induced angiogenesis (LIA), a reaction previously shown to reflect a local in vivo graft-vs-host reaction. The studies demonstrate that circulating cells of the host animal provide the stimulation essential for activation of donor lymphocytes and that the major allogeneic stimulus in congenic lines of mice is correlated with I-region disparity, primarily associated with IA-controlled determinants. The results are readily compatible with the hypothesis that is proposed that LIA is in large part of the consequence of the release of soluble mediators or lymphokines that may act either directly on endothelial cells or indirectly by activating macrophages, which in turn generate the vascular reaction.

Animals↗