N-acetylglucosaminyltransferase substrates prepared from glycoproteins by hydrazinolysis of the asparagine-N-acetylglucosamine linkage. Purification and structural determination of oligosaccharides with mannose andN-acetylglucosamine at the non-reducing termini

Sixteen asparagine-linked oligosaccharides ranging in size from (Man)₂(GlcNAc)₂ (Fuc)₁ to (GlcNAc)₆(Man)₃(GlcNAc)₂ were obtained from human ₁-acid glycoprotein and fibrinogen, hen ovomucoid and ovalbumin, and bovine fetuin, fibrin and thyroglobulin by hydrazinolysis, mild acid hydrolysis and glycosidase treatment. The oligosaccharides hadN-acetylglucosamine at the reducing termini and mannose andN-acetylglucosamine residues at the non-reducing termini and were prepared for use asN-acetylglucosaminyltransferase substrates. Purification of the oligosaccharides involved gel filtration and high performance liquid chromatography on reverse phase and amine-bonded silica columns. Structures were determined by 360 MHz and 500 MHz proton nuclear magnetic resonance spectroscopy, fast atom bombardment-mass spectrometry and methylation analysis. Several of these oligosaccharides have not previously been well characterized.Abbreviations bis bisecting GlcNAc - DMSO dimethylsulfoxide - FAB fast atom bombardment - Fuc l-fucose - Gal d-galactose - GLC gas-liquid chromatography - GlcNAc or Gn N-acetyl-d-glucosamine - HPLC high performance liquid chromatography - Man or M d-mannose - MES 2-(N-morpholino)ethanesulfonate - MS mass spectrometry - NMR nuclear magnetic resonance - PIPES piperazine-N,N-bis(2-ethane sulfonic acid) the nomenclature of the oligosaccharides is shown in Table 1.     

Pituitary and Leydig cell function in boars actively immunized against gonadotrophin-releasing hormone

Crossbred boars were (a) immunized against GnRH conjugated to human serum globulin (200 micrograms GnRH-hSG) in Freund's adjuvant at 12 weeks of age and boosted at weeks 18 and 20 (N = 10), (b) served as controls and received hSG only in adjuvant (N = 10), or castrated at weaning (N = 10). At 24 weeks of age (immediately before slaughter), the boars were challenged with saline or pig LH (1 microgram/10 kg body weight). After slaughter, fresh testicular fragments were incubated with pig LH (0.05 and 0.2 ng/2 ml medium) to assess the effects of immunization on Leydig cell function. Pituitary contents of LH and FSH, and testicular LH receptor content were also measured. The results indicated that plasma LH and testosterone concentrations, pituitary LH content, testicular LH receptor content, testis and sex accessory organ weights were significantly reduced in GnRH-immunized boars compared to hSG-adjuvant controls. However, plasma and pituitary FSH content were not affected by high antibody titres generated against GnRH. The testicular testosterone response to exogenous LH in vivo and in vitro was significantly reduced (P less than 0.05) in GnRH-immunized boars. These results indicate that active immunization against GnRH impairs pituitary and Leydig cell functions in boars.     

Genome rearrangement in top3 mutants of Saccharomyces cerevisiae requires a functional RAD1 excision repair gene.

Saccharomyces cerevisiae cells that are mutated at TOP3, a gene that encodes a protein homologous to bacterial type I topoisomerases, have a variety of defects, including reduced growth rate, altered gene expression, blocked sporulation, and elevated rates of mitotic recombination at several loci. The rate of ectopic recombination between two unlinked, homologous loci, SAM1 and SAM2, is sixfold higher in cells containing a top3 null mutation than in wild-type cells. Mutations in either of the two other known topoisomerase genes in S. cerevisiae, TOP1 and TOP2, do not affect the rate of recombination between the SAM genes. The top3 mutation also changes the distribution of recombination events between the SAM genes, leading to the appearance of novel deletion-insertion events in which conversion tracts extend beyond the coding sequence, replacing the DNA flanking the 3' end of one SAM gene with nonhomologous DNA flanking the 3' end of the other. The effects of the top3 null mutation on recombination are dependent on the presence of an intact RAD1 excision repair gene, because both the rate of SAM ectopic gene conversion and the conversion tract length were reduced in rad1 top3 mutant cells compared with top3 mutants. These results suggest that a RAD1-dependent function is involved in the processing of damaged DNA that results from the loss of Top3 activity, targeting such DNA for repair by recombination.     

Pyruvate is transported by a proton symport inLactobacillus plantarum 8014

Pyruvate is a key metabolic intermediate and the substrate for diacetyl and acetoin synthesis. The mechanism of pyruvate transport was determined inLactobacillus plantarum by use of cells and membrane vesicles. In the cells, protonophores inhibited pyruvate transport, whereas valinomycin did not. Pyruvate was accumulated against a gradient in membrane vesicles. The transport rate and the degree of accumulation increased as the proton gradient increased, but an imposed K potential of –61mV did not drive pyruvate transport. The maximum transport rate (35 nmol/min/mg protein) and accumulation ratio (162-fold) were at pH 3.0, with an apparent Km value of 35 M. These results suggested that pyruvate was transported by a proton symport.     

Tin compounds inhibit the plasma cell response to metallic tin

Injection of metallic tin powder causes intense proliferation of plasma cells in draining lymph nodes of Lewis rats. Pretreatment orally with soluble tin salts prevents this response to subsequently injected metallic tin. In the present work, pretreatment with tin salts by parenteral injection was just as effective as addition to the drinking water. This new approach made the following experiments possible. Poorly soluble tin compounds were found to be inhibitory when injected parenterally. Tin salts injected parenterally into one of two rats joined in parabiotic union prevented the plasma cell response to metallic tin in both parabionts. The transfer of the inhibitory effect via the cross-circulating blood represents significant progress toward understanding the mechanisms involved. The evidence suggests the possibility that tin salts elicit an intermediary substance or process that is responsible for inhibition of the plasma cell response to metallic tin.     

Comparative testing of disinfectant and antiseptic products using proposed European suspension testing methods

The development of standard suspension test methods for disinfectants and antiseptics for adoption in Europe is described. Evaluation of a range of disinfectant agents and products currently used in the UK under conditions as proposed for these tests indicates that the majority of products diluted in water of standard hardness showed satisfactory activity producing a 4·5–5 log reduction in viable count within 5 min against Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecium, Proteus mirabilis and Candida albicans in the absence and presence of 1% albumin. All the products, when diluted with distilled water, produced greater than 5 log reduction in 60 min.