Cytobios最新文献

Saccharomyces cerevisiae (ale strain) grown in batch culture to stationary phase was tested for its tolerance to heat (50 degrees C for 5 min), hydrogen peroxide (0.3 M) and salt (growth in 1.5 M sodium chloride/YPD medium). Yeast cells which have been exposed previously to heat shock are more tolerant to hydrogen peroxide and high salt concentrations (1.5 M NaCl) than the controls. Their fermentative activity as judged by glucose consumption and their viability, as judged by cell number and density have higher levels when compared with cells not previously exposed to heat shock. Experimental conditions facilitated the isolation of S. cerevisiae ale strain, which was tolerant to heat, and other agents such as hydrogen peroxide and sodium chloride.

The antagonistic effect of enterocin CCM 4231 towards enterococci, staphylococci, Escherichia coli, listeriae and pseudomonads in the cattle slurry environment was assessed during periods of 1 and 2 weeks. The maximum decrease in the viable cells of enterococci and staphylococci (5.39 to 1.1 log CFU ml-1, and 4.3 to 2.3 log CFU ml-1, respectively) was detected on the second day after enterocin CCM 4231 addition to cattle slurry. E. coli cells, listeriae and pseudomonads decreased insignificantly. After 1 week, enterococci were completely inhibited. Staphylococci were suppressed by reaching a 1.8 log CFU ml-1 difference between the experimental and the control samples. A stable suppressive effect of enterocin CCM 4231 on the growth of listerial cells became significant with 2.59 log CFU ml-1 between the experimental and the control samples in the second week of bacteriocin addition. This was demonstrated in an experiment with enterocin addition to slurry which was sterilized and then inoculated with Listeria monocytogenes Ohio culture. Further possibilities of using bacteriocins for the treatment of animal waste are discussed.

Ten strains of two species in the Drosophila buzzatii cluster (D. serido and D. seriema) were examined as to esterase patterns using polyacrylamide gel electrophoresis. The migration rate of esterases, and their substrate specificity to alpha and beta naphthyl acetates, were analysed. Other esterase features such as inhibition behaviour, presence in males and females and location in the head, thorax or abdomen of flies, were also examined. The present data, together with results obtained by others for eight strains of D. koepferae, D. serido, D. seriema and D. buzzatii, show that 69 bands have been detected in the eighteen strains studied. This total number of bands was used for comparison of strains and species by similarity index, analysis of dependence and cluster analysis. The comparisons confirmed the existence of a high degree of similarity among D. seriema strains and among D. koepferae strains, but indicated differentiation among the D. serido strains. Two strains (D69R2 and D69R5) which differed from the others of the latter species, showed closer affinities with D. buzzatii, which indicates the need for further work on those strains classified as D. serido.

A model system of experiments to consider the problem of the origin of eukaryotic cells as well as the prokaryote-to-eukaryote transition was investigated, in terms of the role of nucleic acid-membrane interactions. It was thought worthwhile to consider the importance of DNA-membrane contacts for the organization of the prokaryotic nucleoid. The model for the fusion of four proto-eukaryotic cells was proposed to clarify the prokaryote-to-eukaryote transition as well as the formation of the nuclear pores of eukaryotes from the Bayer's junctions of proto-eukaryotes. The basic requirements following from the cell fusion model suggest such orientation of the cells involved. The obstacles for division of the ancestor cell were excluded by merging. Enormous advantages to the cell metabolism due to the fusion of four proto-eukaryotic cells and an intensive growth of the inner membranous structures resulted.

Sporadic abnormalities in lymphocyte cultures are often attributed to in vitro culture variations of no clinical significance. The data presented here compare the findings from 11,873 cells of 230 patients referred with histories of previous chemical exposure (usually to mixtures of solvents and/or pesticides) with 27,050 cells from 855 patients referred for other reasons. Detection of 0.38% or more, structural abnormalities (approximately 1 in 30 cells) was 27.2 times more likely in exposed persons than in controls and the finding of a single autosomal trisomic cell was 14.4 times more likely in exposed persons. These highly statistically significant findings were similar to the frequencies of abnormalities reported in other studies of persons exposed to benzene, pesticides, herbicides and irradiation. It is recommended that findings of sporadic abnormalities in lymphocytes be routinely recorded, and patients with positive findings followed up to discover whether there are past histories of significant exposures.

The cytotoxin of four strains of Yersinia pseudotuberculosis was characterized using the MDBK cell line and by application of the MTT colorimetric test. The highest cytotoxin yield was obtained in tryptic soy broth medium after 24 h. It was detected in the cell-free culture filtrate, and treatment of the cells with CHAPS as a membrane detergent did not decrease significantly their cytotoxic activity. The cytotoxin was inhibited by trypsinization and by increasing values of either acidity or alkalinity. The cytotoxin was inactivated partially by heating at 70 degrees C for 20 min and totally at 90 degrees C for 10 min. The results obtained indicate that the cytotoxin is protein in nature and produced mainly as free exotoxin.

Bacillus thuringiensis was isolated from 23 of 37 samples obtained from different Jordanian habitats. Of the 37 samples, 187 different spore-forming colonies were selected and thirty (16%) were identified as B. thuringiensis based on their pathogenicity and production of parasporal inclusions. The lethal dose (LD50) of B. thuringiensis indicated a variation in their pathogenicity to Drosophila melanogaster larvae. Sensitivity of the first, the second and the third instar larvae of D. melanogaster showed slight variation in between. The third instar was the most sensitive stage to the pathogen spores.

The productivity of Drosophila prosaltans treated with six concentrations of caffeine (from 50 micrograms/ml to 2,500 micrograms/ml of culture medium) during ten generations (approximately 8 months) decreased in a dosage dependent manner in every generation, but at the end of the treatment the flies in all experiments recovered normal productivity, except for those treated with 2,500 micrograms/ml. Longevity in the tenth generation was significantly reduced in males and females only in the 2,500 micrograms/ml dosage, with males being much more affected than females. In a previous study in which the treatment was done in a single generation, productivity exhibited only a partial recovery when the treatment ceased and longevity was significantly reduced in 1,500 micrograms/ml dosages. The hypothesis of selection occurring in ten generations leading to recovery in productivity and to a reduction in the processes which cause a decrease in longevity is being considered.

Human erythrocytes were exposed at room temperatures to 662 keV gamma radiation at doses up to 60 Gy. The total delta Li+ influx as well as the delta Li+ influx by passive diffusion and Na(+)-K+ pump mechanisms increased linearly with the dose. The rate constant K of Li+ efflux by the Li(+)-Na+ countertransport mechanism through irradiated erythrocyte membranes was reduced by about 35% at the highest dose.

Recent data show that monocyte chemotactic peptide-1 (MCP-1), a chemotactic factor specific for monocytes, may play a central role in regulating the activation of these cells. For this reason, the production of MCP-1 in peripheral blood mononuclear cell (PBMC) cultures of eight healthy subjects, six chronic uraemic subjects under conservative treatment and six chronic uraemic patients undergoing haemodialysis (HD), was assessed. In the latter group of individuals, complement-activating membranes such as cuprophan (CU) were used for 1 month followed by biocompatible non-complement-activating membranes, like polymethylmetacrylate (PMMA) for the next 30 days. The chemotactic index (CI) elicited by PBMC supernatants from patients undergoing dialysis was found to be significantly higher than that obtained by supernatants recovered from normal subjects or uraemic patients on conservative therapy. Furthermore, the CI from PBMC supernatants having had contact with CU membranes was higher than that obtained from PBMC activated by PMMA. Finally, the increased chemotactic ability in the supernatants was closely correlated with the augmented MCP-1 gene expression and production, as assessed by in vitro hybridization studies.