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1.
Auxotrophic mutants of Candida albicans FC18 were induced by a combination of treatments with nitrous acid and UV irradiation. Arginine (Arg-), histidine (His-) and methionine/cysteine (MetA-) auxotrophs were recovered by this means. The Arg- auxotrophs lacked active argininosuccinate lyase (EC 4.3.2.1), the enzyme catalysing the final step in arginine biosynthesis. Thus the locus may be designated arg-4. The mutant strains bearing this mutation did not form germ tubes unless the germination medium contained arginine. 相似文献
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3.
We have used a quantitative titration assay for mixed lymphocyte interactions to determine the additivity of responses of rat lymphocyte populations to simultaneous stimulation with major histocompatibility complex alloantigens from pairs of apparently unrelated rat strains. Our inability to detect strict additive stimulation led us to investigate inclusion among allo-reactive lymphocyte populations. After specific depletion of reactivity to PVG by negative selection through an AO × PVG F1 hybrid rat, AO thoracic duct lymphocytes showed an asymmetrical loss of reactivity to the unrelated strains DA and F344. We suggest that this differential loss of reactivity probably reflects alloantigen sharing among rat strains which had been previously undetected using other less sensitive techniques for the quantitation of lymphocyte reactivity after specific depletion of allo-reactive cells. 相似文献
4.
Serological comparison of bovine T-mycoplasmas 总被引:1,自引:0,他引:1
5.
A review of in vitro mutagenesis assessment of metal compounds in mammalian and nonmammalian test systems has been compiled.
Prokaryotic assays are ineffective or inconsistent in their detection of most metals as mutagens, with the notable exception
of hexavalent chromium. Mammalian assay systems appear to be similarly inappropriate for the screening of metal compounds
based upon the limited number of studies that have employed those compounds having known carcinogenic activity. Although of
limited value as screening tests for the detection of potentially carcinogenic metal compounds, the well-characterized in
vitro mutagenesis systems may prove to be of significant value as a means to elucidate mechanisms of metal genotoxicity. 相似文献
6.
L V Melendez M D Daniel H H Barahona C E Fraser R D Hunt F G Garcia 《Laboratory animal science》1971,21(6):1050-1054
7.
Intestinal cholesterol absorption is specifically inhibited by the 2-azetidinone cholesterol absorption inhibitor ezetimibe. Photoreactive ezetimibe analogues specifically label a 145-kDa protein in the brush border membrane of enterocytes from rabbit small intestine identified as aminopeptidase N (CD13). In zebrafish and mouse small intestinal cytosol, a heterocomplex of Mr 52 kDa between annexin II and caveolin 1 was suggested as a target of ezetimibe. In contrast, in the cytosol and brush border membrane vesicles (BBMV) from rabbit small intestine of control animals or rabbits treated with the nonabsorbable cholesterol absorption inhibitor AVE 5530, both annexin II and caveolin 1 were exclusively present as monomers without any heterocomplex formation. Upon immunoprecipitation with annexin II a 52-kDa band was observed after immunostaining with annexin II antibodies, whereas no staining of a 52-kDa band occurred with anti-caveolin 1 antibodies. Vice versa, a 52-kDa band obtained by immunoprecipitation with caveolin 1 antibodies did not stain with annexin II-antibodies. The intensity of the 52-kDa band was dependent on the amount of antibody and was also observed with anti-actin or anti-APN antibodies suggesting that the 52-kDa band is a biochemical artefact. After incubation of cytosol or BBMV with radioactively labelled ezetimibe analogues, no significant amounts of the ezetimibe analogues could be detected in the immunoprecipitate with caveolin-1 or annexin II antibodies. Photoaffinity labelling of rabbit small intestinal BBMV with ezetimibe analogues did not result in labelling of proteins being immunoreactive with annexin II, caveolin 1 or a 52-kDa heterocomplex. These findings indicate that the rabbit small intestine does not contain an annexin II/caveolin 1 heterocomplex as a target for ezetimibe. 相似文献
8.
Eight pilot-scale in-line filtration trials were performed to evaluate the passage of cyanobacterial cells through drinking water filters after sudden increases in hydraulic loading rates. Trials were performed at 30 °C using two coagulant combinations (aluminum sulfate and cationic polymer or ferric chloride and cationic polymer), two initial filter loading rates (7 or 10 m/h) and two species of morphologically different cyanobacteria (Microcystis aeruginosa or Anabaena flos aquae). The filter was perturbed by instantaneously increasing the hydraulic loading rate by 50%. Filter influent and effluent water qualities were characterized by measuring turbidity, particles and chlorophyll a. The observed post-perturbation filter effluent chlorophyll a peaks were 1.6–48 times greater than the pre-perturbation averages. Chlorophyll a peaks were larger for M. aeruginosa than for A. flos aquae. Chlorophyll a peaks were also larger for the higher (10 m/h) than for the lower (7 m/h) initial filter loading rate. The post-perturbation effluent turbidity peaks were 1.4–7.2 times greater than the pre-perturbation averages. The post-perturbation effluent particle peaks were 6.5–25 times greater than the pre-perturbation averages. These results indicate that particles were a more sensitive indicator of cyanobacterial passage than turbidity. 相似文献
9.
The onset of incubation varies in birds, with many species beginning incubation prior to clutch completion. Here we examine whether early onset is more likely to occur during high temperatures, a critical prediction of the egg-viability hypothesis, which suggest that birds begin incubation prior to clutch completion in order to maintain egg-viability. We examined onset of incubation in tree swallows Tachycineta bicolor at two locations at the extremes of their breeding range, Alaska and Tennessee. A majority of individuals (68%) began incubation prior to clutch completion. While females in Tennessee were more likely to begin incubation early, there was no difference between sites when differences in temperatures inside nestboxes were controlled in analyses. Rather, early onset of incubation was predicted by the proportion of daily temperatures above physiological zero during laying, a critical prediction of the egg viability hypothesis. Both warm weather and early onset led to shorter incubation periods and increased levels of hatching asynchrony. We found no effect of timing of nesting, female body condition index or clutch size on the probability of beginning incubation prior to clutch completion. Our results are consistent with the egg viability hypothesis, not consistent with a threshold clutch size rule, and do not support the hurry-up hypothesis, that individuals breeding later in the season would begin incubation early to reduce the time spent nesting. Overall, our results suggest that broad scale geographic differences in incubation behaviour may be explained by individual-level responses to environmental conditions. 相似文献
10.
A winter bloom dominated by Pseudo-nitzschia calliantha Lundholm, Moestrup et Hasle (Bacillariophyceae), a potential domoic acid producer, is reported for the first time in the Aegean Sea, Greece, in a semi-enclosed embayment (Kalloni Gulf) surrounded by agricultural land and drained by intermittent rivers. Abundances of this species in the inner part of the Gulf during February were extremely high (max 1.1 × 107 cells l−1). The species Alexandrium insuetum Balech (Dinophyceae) was also found in considerable cell numbers (max 1.4 × 105 cells l−1) during the bloom and reached up to 40% of the total biovolume. This study demonstrates an evident cause and effect relationship between nutrient inflows originating from agricultural activities in the watershed and the development of a potential HAB. The massive bloom formation was observed soon after an episodic rainfall event during the fertilizer application period (December to February). A bloom was also observed the following year, but it was less pronounced due to the fact that rainfalls were more evenly spaced in time and were of moderate intensity. 相似文献