Sporophore production ofAgaricus bisporus in aseptic environments

Production of mature sporophores ofAgaricus bisporus was achieved for the first time in amended, autoclaved soil, gamma-sterilized soil, and soil-extract agar medium. The initiation of sporophores was triggered by metabolites of soil-inhabiting bacteria, particularly nodule forming isolates. Whether a single metabolite or several metabolites of these bacteria caused formation of sporophores could not be established; however, biotin alone when added to soil extract medium produced comparable results. The potentiality of different bacteria to induce sporophore formation varied considerably within species and isolates.Amino acids favored vegetative growth ofA. bisporus, but failed to induce formation of sporophores. Organic acids supported luxuriant growth and poor sporophore formation. Among several growth-promoting substances and vitamins, biotin induced abundant formation of mature sporophores.The authors are thankful to Dr. C. Corke, Department of Soil Microbiology, University of Guelph, Ontario, for providing some bacterial cultures used in this study.     

Embryogenesis and plant regeneration from tissue culture of Canada wildrye,Elymus canadensis L.

Somatic embryogenesis and plant regeneration of Canada wildrye (Elymus canadensis L.) from tissue culture was investigated by culturing immature embryos and inflorescences on MS medium containing 2 mg/l 2,4-D. The optimum size of explants for maximum embryogenic callus formation was 1.0 to 1.5 mm for embryos and 4 to 6 cm for inflorescences. Plant regeneration from the subcultured embryogenic callus was attempted monthly using hormone-free MS medium or MS medium with 0.5 mg/1 2,4-D and 0.3 mg/l GA3. Three hundred and fifty seven plantlets were regenerated from the callus cultures of both explant sources during a six month period. Ten chlorophyll deficient plants accounting for 2.8% of the total regenerants were observed. One plant with white striped leaves survived and was found to be an octoploid.Abbreviations GA3 gibberellic acid - MS Murashige and Skoog (1962) - 2,4-D 2,4-dichlorophenoxyacetic acid     

Evidence for the presence of disulfide bridges in opioid receptors essential for ligand binding. Possible role in receptor activation

The mobility of purified mu opioid binding protein in SDS-polyacrylamide gek electrophoresis is sensitive to the presence of reducing agents. In the presence of increasing concentrations of DTT the apparent molecular weight increases in a stepwise fashion from 53 kDa to 65 kDa. This reduction in mobility is attributed to the successive breakage of disulfide bridges, resulting in an increasingly asymmetric molecule. Treatment of cell membranes from various brain areas with reducing agents, such as DTT, produced a concentration-dependent inhibition of opioid binding. Sensitivity to DTT inhibition varied between receptor types, mu greater than delta much greater than kappa. For mu receptors, agonist binding was considerably more sensitive to DTT than antagonist binding. Inhibition by DTT is readily reversible and is unaffected by Na+ and/or Mg2+ ions. Reversibility may be partially prevented by the inclusion of a low concentration of a reducing reagent such as glutathione which does not inhibit binding but blocks reformation of disulfide bonds. Scatchard analysis of saturation data shows that DTT causes a pronounced decrease in binding affinity with little effect on receptor number. It is suggested that disulfide bonds are essential for ligand binding and that cleavage of one or more of these bonds may play a role in opioid receptor activation by agonists.