Attempt to detect recombination between B-F and B-L genes within the chicken B complex by serological typing,in vitro MLR,and RFLP analyses

In search for recombinants within the chicken major histocompatibility B complex, 1155 animals from crosses between the congenic lines CB (B¹²) and CC (B⁴) were tested with alloantibodies and monoclonal antibodies for the B-F (class I), B-L (class II), and B-G (class IV) antigens and by mixed lymphocyte reaction. The absence of detectable recombination was confirmed by restriction fragment length polymorphism analysis with B-L and B-F probes. Together with previous reports, this indicates that the distance between the B-F and B-L loci is below 0.01 centimorgan.     

Antigen-presenting cell-T cell interaction in the chicken is MHC class II antigen restricted

The involvement of the MHC in the recognition of Ag by avian T lymphocytes was analyzed. PBL from chickens primed with keyhole limpet hemocyanin in vivo were induced to synthesize DNA in an in vitro response to specific Ag. Responding cells were T cells as judged by immunofluorescence staining. In vivo Ag-primed PBL were stimulated in vitro with specific Ag and further propagated in the presence of IL-2. Subsequent Ag-specific T cell proliferation required the presence of Ag-pulsed peripheral blood adherent cells (APC). T cell responses were restricted by the MHC of the APC; Ag presented by allogeneic APC did not support T cell proliferation. By using MHC-recombinant chicken lines, the gene products controlled by MHC class II loci were shown to restrict the T cell-APC interaction. This conclusion was substantiated by the inhibition of the Ag-specific T cell response by a mAb against chicken MHC class II gene products but not by a mAb against chicken MHC class I gene products.     

Simultaneous degradation of the herbicides 2,4-dichlorophenoxyacetic acid and 2-(2-methyl-4-chlorophenoxy)propionic acid by mixed bacterial cultures

The simultaneous degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-(2-methyl-4-chlorophenoxy)propionic acid (mecoprop) was achieved by two mixed cultures in the absence of any additional carbon or energy substrates. Mecoprop was not completely degraded by either of the two cultures, nor did addition of 2,4-D affect the degradation of mecoprop. The cultures completely degraded 2,4-D, and the degradation was uninfluenced by the addition of mecoprop. Nearly complete dechlorination of the mixture of two herbicides was achieved by both cultures, on the basis of the total amount of the two herbicides degraded. During the course of the reaction, however, the expected values of chloride were not met. Cell growth continued after the degradation of the parent substrates ceased. Although the mecoprop degradation did not continue to completion, spectral and growth data indicated that the metabolites which had accumulated during the reaction were degraded upon further incubation.     

Hydrolysis of phospholipid monolayers by human spermatozoa. Inhibition by male contraceptive gossypol

Monomolecular films of phospholipid were used to study the interaction of intact human spermatozoa with model membranes. Exclusively with negatively charged phosphatidylglycerol monolayers rapid penetration of spermatozoa into the monolayer with subsequent hydrolysis of the lipid was triggered by the addition of 5 mM calcium into the medium. The results suggest the localization of a calcium-dependent phospholipase A2 at the outer acrosomal or plasma membrane of human spermatozoa with its active site exposed to the external environment. Preincubation of the cells with 100 microM gossypol completely abolished the ability of human spermatozoa to hydrolyze or penetrate monolayers of phosphatidylglycerol. The inhibition of the phospholipase activity by gossypol may contribute to the unknown contraceptive mechanisms of this non-steroidal male antifertility agent.     

Increased endogenous retroviral gene expression is a consequence of lymphocyte activation

Plasma cells of line 151(5) chickens have been shown to express elevated levels of endogenous retroviral envelope glycoprotein (VEG), measured relative to levels expressed by both immature B cells and resting peripheral B lymphocytes. In this study we analyzed the relationship between peripheral blood lymphocyte (PBL) maturation and the level of VEG expression. A culture system was developed that would support maturation of pokeweed mitogen-activated peripheral B lymphocytes. As analyzed by cytofluorometry, both Ig+ and Ig- lymphoblasts present in the pokeweed mitogen-stimulated cultures expressed detectable levels of VEG in contrast to bursacytes and PBL. Similarly, Ig- blasts, which were present in concanavalin A-stimulated cultures of PBL and presumed to represent activated T cells, were also positive for the expression of VEG. Immature T cells, i.e., thymocytes, although negative by immunofluorescence analysis, expressed VEG at levels that were detectable by radioimmunochemical techniques. These results indicate that T cells as well as B cells constitutively express VEG, and that mitogenic activation of the resting lymphocyte induces an increase in VEG expression.     

Studies on the growth ofThiobacillus ferrooxidans

Summary Uranyl sulphate (0.2–0.9 mM) inhibited ferrous iron oxidation by growing cultures ofThiobacillus ferrooxidans. The addition of 5–100 mM uranium to the cultures caused immediate cessation of carbon dioxide fixation, rapid loss of viability and gradual depression of ferrous iron oxidation. Virtually no uranium was found in washed cells grown in the presence of subtoxic to toxic amounts of uranyl sulphate. Uranium-poisoned organisms appeared plasmolyzed in electron micrographs. Cultures tolerant to 5 mM UO₂ ²⁺ were develoepd by successive subculturing in increased uranium concentrations. The tolerance was maintained during subculturing in uranium-free medium. Frequency of mutants resistant to 1.0 and 1.5 mM UO₂ ²⁺ was 1 per 1.3×10⁶ and 1 per 9.0×10⁸, respectively. The frequency was increased in the presence of 15–150 mM nickel, zinc and manganese. In liquid cultures, bivalent cations and EDTA alleviated the toxicity of 2 mM uranyl sulphate.     

Bacterial Oxidation of Sulfide Minerals in Column Leaching Experiments at Suboptimal Temperatures

The purpose of the work was to quantitatively characterize temperature effects on the bacterial leaching of sulfide ore material containing several sulfide minerals. The leaching was tested at eight different temperatures in the range of 4 to 37°C. The experimental technique was based on column leaching of a coarsely ground (particle diameter, 0.59 to 5 mm) ore sample. The experimental data were used for kinetic analysis of chalcopyrite, sphalerite, and pyrrhotite oxidation. Chalcopyrite yielded the highest (73 kJ/mol) and pyrrhotite yielded the lowest (25 kJ/mol) activation energies. Especially with pyrrhotite, diffusion contributed to rate limitation. Arrhenius plots were also linear for the reciprocals of lag periods and for increases of redox potentials (dmV/dt). Mass balance analysis based on total S in leach residue was in agreement with the highest rate of leaching at 37 and 28°C. The presence of elemental S in leach residues was attributed to pyrrhotite oxidation.