Nuclear selection in monokaryotic oidium formation from dikaryotic mycelia in a basidiomycete,Pholiota nameko

The effect of nuclear dominance in monokaryotic oidium formation from dikaryotic mycelia inPholiota nameko was examined. Over 90% of oidium isolates from dikaryotic mycelia were monokaryotic. Although only one parental nuclear type was recovered from an average of about 80% in these isolates, the nuclear selection process in oidium formation seems essentially to produce split nuclear type composition in oidium products. The hierarchy of relative dominance among the nuclear types of the parental dikaryons in monokaryotic oidium formation was determined. The two hierarchies in nuclear selection between monokaryotic oidium formation and monokaryotic mycelium formation coincided at a level of at least 75%.     

Differences of asymmetrical division between the pseudomycelial and yeast forms of Candida albicans and their effect on multiplication

Unlike asymmetrical division of budding yeast, the daughter cell in the pseudomycelial form of Candida albicans at division was nearly equal in size to the mother cell, it had a larger amount of protein, RNA and active protoplasm (cell size minus vacuolar volume) than the mother cell, and it budded earlier than the mother cell. Results presented here suggest that the cell size control over bud initiation found in budding yeasts is also applicable to the pseudomycelial cells of C. albicans if vacuolar volume is omitted from cell size.     

Localization of nonspecific lipid transfer protein (nsLTP = sterol carrier protein 2) and acyl-CoA oxidase in peroxisomes of pigment epithelial cells of rat retina.

We investigated the localization of nonspecific lipid transfer protein (nsLTP) in rat retina, especially in the pigment epithelial (RPE) cells, by the avidin-biotin-peroxidase complex method on cryosections for light microscopy and by the cryoimmunogold method for electron microscopy. Light microscopic observation revealed that the RPE, inner segment layer, nerve fiber layer, and Müller cells contain nsLTP. In the RPE cells gold particles were exclusively concentrated in the small peroxisomes (microperoxisomes; 0.1-0.3 micron in diameter), which were identified by double staining using anti-nsLTP and anti-catalase antibodies. In the peroxisomes gold particles were distributed homogeneously in the matrices and no preferential binding to the limiting membrane was observed. Acyl-CoA oxidase was also localized in the matrices of the peroxisomes. We suggest that the peroxisomes in RPE cells play important roles in the metabolism of lipids of the outer segment disk membranes, especially in the beta-oxidation of polyunsaturated long-chain and very long-chain fatty acids, such as docosahexaenoic acid which is composed of approximately one third of fatty acids in the disk membranes.     

Distribution of tumor promoters in lipid membranes and changes in membrane structure

The interaction of tumor promoters differing in molecular structure, namely, 12-O-tetradecanoylphorbol 13-acetate (TPA) and teleocidin, with dipalmitoylphosphatidylcholine (DPPC) vesicles was studied. Investigation by Fourier transform infrared spectroscopy clarified the differences between the tumor promoters in the mode of interaction with lipid bilayer membranes. The temperature dependence of the bandwidth of the C-H or C = O stretching absorption of lipid molecules in the presence of tumor promoters relative to that in pure DPPC vesicles indicated that TPA is incorporated into the hydrophobic core of the lipid bilayer membrane whilst teleocidin binds predominantly to the membrane surface. However, both tumor promoters tend to restrict the motion of lipid molecules in membranes. The same conclusion was derived from measurements of steady-state fluorescence polarization, which showed that tumor promoters decreased the membrane fluidity. On the other hand, carboxyfluorescein (CF) leakage from vesicles was enhanced by the addition of TPA below the phase-transition temperature, whereas the effect of teleocidin on steady-state CF leakage was not as significant. It is considered that the difference in the profile of the TPA-induced increase in CF leakage compared to that of teleocidin might be ascribable to a different binding site for each tumor promoter in the membranes.     

Increased frequency of specific alleles of the c-Ha-ras gene in Japanese cancer patients

Summary We have examined the c-Ha-ras locus in 145 cancer patients of a mixed group and 164 normal individuals in Japan for restriction fragment length polymorphisms and compared the allele distributions in normal and cancer populations. The c-Ha-ras gene is highly polymorphic in Japanese as previously reported in Caucasians. Two rare alleles were found to be present with increased frequencies in Japanese cancer patients. These results suggest that genotype analysis of the c-Ha-ras gene could be used to detect cancer-prone individuals.     

Protection of mice against bacterial infection by oral administration of bacterial lipopolysaccharide

The effect of orally administered bacterial lipopolysaccharide (LPS) on host resistance against bacterial infections was studied. LPS orally given for 5 consecutive days prior to infection caused no apparent toxic effect and protected mice against Pseudomonas aeruginosa and Listeria monocytogenes infections.