Crystalloid inclusions in the connective tissue of spider venom gland

Résumé Nous décrivons des inclusions cristallines observées dans l'élytre extracellulaire des glandes venimeuses deLoxosceles reclusa.     

A new model of glucocorticoid-induced metanephric maldevelopment

A new experimental model of glucocorticoid-induced tubular cyst formation has been developed in metanephric organ culture. The addition of cortisol (1.4 X 10(-5) M) to chemically defined serum-free culture medium produces cystic changes during in vitro nephrogenesis . The model isolates the role of glucocorticoids in experimental cyst formation.     

Okinonellins A and B,two novel furanosesterterpenes,which inhibit cell division of fertilized starfish eggs,from the marine spongeSpongionella sp

Cellular and Molecular Life Sciences - Two novel furanosesterterpenes, okinonellins A (1) and B (2), have been isolated from the spongeSpongionella sp. Both compounds inhibit cell division of...     

Temperature-induced hand inversion inBacillus subtilis macrofibers

Cellular and Molecular Life Sciences -     

Responses to the H-2Kba mutant involve recognition of syngeneic Ia molecules

Conventional antigens appear to be recognized by T lymphocytes only when associated with major histocompatibility complex (MHC) antigens. Using antigen-specific proliferation as a model for helper T lymphocytes, it has been demonstrated that Ly1+T cells recognize antigen presented in association with syngeneic Ia molecules. In contrast to responses to conventional antigens, however, a large number of studies have suggested that the stimulation of alloreactive Ly1+T cells, and helper T cells specific for allogeneic cytotoxic T lymphocyte (CTL) responses, involve the direct recognition of Ia alloantigens. For the generation of optimal allogeneic CTL activity it has been proposed that Ly1+T cells recognize allo-Ia antigens directly and provide help to pre-CTLs that respond to allo-H-2K and/or D determinants. Thus, the B6.C.H-2bm1 mutant (bm1, formerly referred to as Hz1), which is believed to consist of a substitution of two amino acids in the H-2Kb antigen, has presented a paradox, for it can stimulate strong mixed lymphocyte culture (MLC), graft versus host and CTL responses by T cells of H-2b haplotype mice in the apparent absence of any alloantigenic differences in the I region. We now present evidence that the stimulation of proliferative and helper T cells by the mutant B6.C.H-2bm1 results from the H-2Kba antigen being recognized in the context of syngeneic Ia determinants. Thus responses to both conventional antigens and allogeneic MHC gene products may proceed via the recognition of antigen in the context of self Ia molecules.     

Identification of the V factor needed for synthesis of the iron-molybdenum cofactor of nitrogenase as homocitrate

Nitrogenase catalyses the ATP-dependent reduction of N2 to NH3, and is composed of two proteins, dinitrogenase (MoFe protein or component I) and dinitrogenase reductase (Fe protein or component II). Dinitrogenase contains a unique prosthetic group (iron-molybdenum cofactor, FeMoco) comprised of Fe, Mo and S, which has been proposed as the site of N2 reduction. Biochemical and genetic studies of Nif- (nitrogen fixation) mutants of Klebsiella pneumoniae which are defective in nitrogen fixation, have shown that the nifB, nifQ, nifN, nifE and nifV genes are required for the biosynthesis of FeMo-co. Recently, a system for in vitro synthesis of FeMoco was described. The assay requires at least the nifB, nifN and nifE gene products, and a low-molecular-weight factor (V factor) produced in the presence of the nifV gene product. We have used this system to study FeMoco biosynthesis. We report here the isolation of V factor and identify it as homocitric acid ([R]2-hydroxy-1,2,4-butanetricarboxylic acid).     

Cholera toxin genes: nucleotide sequence, deletion analysis and vaccine development

Nucleotide sequence and deletion analysis have been used to identify the regulatory and coding sequences comprising the cholera toxin operon (ctx). Incorporation of defined in vitro-generated ctx deletion mutations into Vibrio cholerae by in vivo genetic recombination produced strains which have practical value in cholera vaccine development.