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Summary Maximum lipase production byAspergillus foetidus was obtained from cultures grown in the medium of 2% olive oil and 0.5% sucrose. The optimal conditions for the production of lipases in the Multigen fermenters were found to be at 500rpm with an airflow of 1.5 liter per mimute. Immobilization of the fungal source was found to be infeasible in natural polymers. 相似文献
14.
A system was established for introducing cloned genes into white clover (Trifolium repens L.). A high regeneration white clover genotype was transformed with binary Agrobacterium vectors containing a chimaeric gene which confers kanamycin resistance. Transformed kanamycin resistant callus was obtained by culturing Agrobacterium inoculated stolon internode segments on selective medium. The kanamycin resistance phenotype was stable in cells and in regenerated shoots. Transformation was confirmed by the expression of an unselected gene, nopaline synthase in selected cells and transgenic shoots and by the detection of neomycin phosphotransferase II enzymatic activity in kanamycin resistant cells. Integration of vector DNA sequences into plant DNA was demonstrated by Southern blot hybridisation. 相似文献
15.
The two gene pairs encoding H2A and H2B play different roles in the Saccharomyces cerevisiae life cycle. 总被引:14,自引:7,他引:7 下载免费PDF全文
We have isolated Saccharomyces cerevisiae mutants bearing deletions of one or the other of the two divergently transcribed gene pairs encoding H2A and H2B. The deletions produced diverse effects on the yeast life cycle. Deletion of TRT1, one of the H2A-H2B gene pair sets, affected mitotic growth, sporulation, spore germination, the heat shock response, and exit from the stationary phase; deletion of TRT2, the other H2A-H2B gene pair set, had negligible effects on these same processes. Using a genetic complementation assay, we found that the differential effects of the deletions could be attributed to two features of the gene sets: first, the expression of the TRT1 gene pair, but not the TRT2 gene pair, could compensate for the absence of its partner; second, the protein subtypes encoded by the two gene pairs appear to have different functions in the heat shock response. 相似文献
16.
Heat resistance of Listeria: strain differences and effects of meat type and curing salts 总被引:3,自引:1,他引:2
The heat resistances of 27 strains of Listeria monocytogenes and two strains of L. innocua were compared in broth heated at 57°C. No strain was exceptionally resistant. The heat resistance of a representative isolate of L. monocytogenes was compared in fresh and cured beef and chicken, and an equation was derived to predict the time necessary to achieve a '7D' inactivation at temperatures between 50 and 70°C. 相似文献
17.
J A Luckey H Drossman A J Kostichka D A Mead J D''''Cunha T B Norris L M Smith 《Nucleic acids research》1990,18(15):4417-4421
A major challenge of the Human Genome Initiative is the development of a rapid, accurate, and efficient DNA sequencing technology. A major limitation of current technology is the relatively long time required to perform the gel electrophoretic separations of DNA fragments produced in the sequencing reactions. We demonstrate here that it is possible to increase the speed of sequence analysis by over an order of magnitude by performing the electrophoresis and detection in ultra thin capillary gels. An instrument which utilizes these high speed separations to simultaneously analyze many samples will constitute a second generation automated DNA sequencer suitable for large-scale sequence analysis. 相似文献
18.
M A Jones Z Cao C J Norris W Anderson E Hemmick M J Harper 《Prostaglandins, leukotrienes, and essential fatty acids》1990,39(4):267-275
Day-6 pregnant rabbits were anesthetized and subjected to a mid-ventral laparotomy. [3H] Prostaglandin F2alpha) (PGF2alpha) [3H]PGE2, [14C]Urea or [14C]Sucrose were instilled into the uterine lumen via the uterotubal junction. The amounts instilled/uterine horn were respectively 3.7 +/- 0.3, 3.5 +/- 0.3, 5.7 +/- 1.3 and 2.7 +/- 1.6 muCi in 20mul of buffer. Animals were killed at 1, 2, 9, 19 or 21 h after radioactive instillation, and the amounts of radioactivity in blastocysts, uterine tissue, peritoneal cavity washings and urine evaluated by liquid scintillation spectrometry. A gradient of radioactivity was observed from the uterotubal junction to the cervical end of the uterus. Large amounts of [3H]PG were found in the injected horn and associated blastocysts with a considerable crossover to the non-injected horn, but little in the associated blastocysts. Much of the blastocysts associated- [3H]PG remained unmetabolized. Large amounts of metabolized [3 H] were found in urine. [14C]Urea was taken up by uterine tissue in the injected horn, but there was little cross over to the non-injected horn. Urea was also found in urine. Much of the [14C]Sucrose remained in the injected horn, and little was recovered from the urine. It was found that at 9 h, but not at 19 h, after [3 H]PG instillation, the PG was localized at the site of the blastocysts in the injected but not in the contralateral horn. Significantly more [3H]PGF2alpha than [3H]PGE2 was localized in this situation. [14C]Urea was not localized at the site of the blastocysts in urea injected horns. (ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
19.
F Furukawa M B Lyons L A Lee S N Coulter D A Norris 《Journal of immunology (Baltimore, Md. : 1950)》1988,141(5):1480-1488
A strong association between anti-SS-A/Ro and anti-SS-B/La antibodies and skin lesions has been well documented in subacute cutaneous lupus erythematosus and neonatal lupus erythematosis in which 70 to 80% of patients are female. In order to better understand the mechanisms of the influence of sex hormones on cutaneous lupus, we designed immunopathological in vitro experiments to evaluate the effects of estradiol and other sex steroids on the binding of SS-A/Ro- and SS-B/La-specific antibodies to cultured human keratinocytes from neonates. Cultured human keratinocytes incubated with antisera specific for SS-A/Ro or SS-B/La Ag were fixed with either acetone or paraformaldehyde and then analyzed in indirect immunofluorescent assays or by FACS analysis to detect cell surface IgG binding as an indirect measure of SS-A/Ro and SS-B/La Ag expression on the cell surface of keratinocytes. Estradiol (10(-5) to 10(-7) M) augmented binding of antiserum probes on the surface of cultured keratinocytes, with 10(-7) M estradiol showing the highest induction of cell surface binding of antisera specific for SS-A/Ro plus SS-B/La Ag (24.5% of cells were positive). In contrast, dihydrotestosterone, testosterone, and progesterone showed no augmentation. The augmentation by estradiol was partially inhibited by the antiestrogen nafoxidine. Estradiol augmented the relative incidence and absolute number of small or cuboidal cells binding antibodies specific for SS-A/Ro and SS-B/La Ag, whereas the number and incidence of larger differentiated cells binding anti-SS-A/Ro and anti-SS-B/La decreased significantly in cell cultures stimulated with estradiol. Flow cytometric analysis utilizing monospecific anti-SS-A/Ro or anti-SS-B/La sera showed that estradiol induced binding of anti-SS-A/Ro in 13.1% of cultured keratinocytes, of anti-SS-A/La in 14.4%, and of sera specific for both Ag in 21.4%. This direct association between estradiol and the augmentation of binding to the cell surface of human keratinocytes of IgG from antisera specific for SS-A/Ro and SS-B/La Ag may be a trigger factor of immunologic damage in lupus and may be important in the different sex rates observed in skin manifestation of subacute cutaneous and neonatal lupus erythematosis. 相似文献
20.
For 15 months, the composition and abundance of drift vegetation were determined from a plantdominated fringing reef at Galeta Point, Caribbean Panama. Five nets located downstream of the reef platform continuously sampled 1.0–1.3 ha of reef flat which included 137–202 m of fore reef. Time series and multiple correlation analysis were done to evaluate the dependence of drift biomass on selected physical and biological factors. Export and import rates and turnover times were derived and compared between the dominant species. Floating leaves, branches, and seeds of higher plants were the major components of imported drift with 52% of the dry weight mass, followed by algae and seagrass each with 19%, the water hyacinth Eichhornia with 2%, and floating tar with 8%. Exported biomass from the reef platform was higher in the dry-season (late November–March) than in the wet-season (April-early November). Within the 1.0–1.3 ha sampling area, export estimates ranged from 37–294 kg mo-1 for the seagrass Thalassia, 3–171 kg mo-1 for the alga Laurencia, and 3–74 kg mo-1 for the alga Acanthophora. Multiple correlation models indicated that meteorological and hydrographic conditions explained between 31 to 65% of the variance in the drift biomass and that the best predictors of exported biomass were tidal elevation and wind speed (3 week lag). Export rates increased with high tides and strong winds and decreased with elevated water temperatures. Autocorrelations of drift biomass were generally highest at 2 week intervals, suggesting that the quantity of drift removed from the platform was, in part, related to spring and neap tide cycles. Export rates were also affected by the morphology of the vegetation, development of uprights, and location on the reef platform. Import rates of terrestrial-plant debris, the hyacinth Eichhornia, the seagrass Syringodium, and the brown alga Sargassum did not exhibit pronounced seasonal patterns in abundance and averaged 60.2, 1.9, 1.1, and 2.7 g d-1m-1, respectively. Wind speed was negatively correlated with Sargassum abundance, suggesting that strong winds depleted it from nearshore waters. Floating tar averaged about 10 g d-1m-1, the highest reported in the Caribbean. The plant-dominated fringing reef at Galeta Point is shown to be a major source, as well as a recipient, of drift vegetation. 相似文献