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201.
202.
Ustilago maydis, the causal agent of corn smut disease, displays dimorphic growth in which it alternates between a unicellular, nonpathogenic yeast-like form and a dikaryotic, pathogenic filamentous form. Previously, a constitutively filamentous haploid mutant was obtained. Complementation of this mutant led to the isolation of the gene encoding adenylate cyclase, uac1. Secondary mutagenesis of a uac1 disruption strain allowed the isolation of a large number of suppressor mutants, termed ubc, for Ustilago bypass of cyclase, lacking the filamentous phenotype. Analysis of one of these suppressor mutants previously led to the identification of the ubc1 gene, encoding the regulatory subunit of cAMP-dependent protein kinase. In this report we describe the isolation of cosmids containing three new ubc genes, termed ubc2, ubc3, and ubc4. We also describe the morphology of the ubc2, ubc3, and ubc4 mutants in a uac1- background as well as in a background with a functional uac1 gene. In addition, we describe several mutant strains not complemented with any of the genes currently in hand and that are thus presumed to possess mutations in additional ubc genes. Copyright 1998 Academic Press. 相似文献
203.
The taste of polycose in hamsters 总被引:2,自引:2,他引:0
Hamsters show a preference for Polycose, a mixture of starch-derived
glucose polymers, that is as strong as their preference for sucrose.
However, in the hamster, taste aversions to Polycose may be less easily
acquired than taste aversions to sucrose and the qualitative aspects of
Polycose are unknown in this species. In order to examine the taste of
Polycose in the hamster, we utilized a taste-aversion protocol with two
conditioning trials. Animals were trained to avoid one of three different
conditioning stimuli: 50 mM sucrose, 100 mM Polycose and a mixture of 50 mM
sucrose with 100 mM Polycose. Control animals were conditioned with
deionized water. After the second conditioning trial, generalization
testing began for the three conditioning stimuli plus 3 mM citric acid, 300
mM KCI and 30 mM NaCl. The results showed that aversions to Polycose,
sucrose or the Polycose/sucrose mixture cross- generalized, demonstrating
that Polycose and sucrose share a common taste percept in the hamster. None
of the aversions generalized to NaCl, citric acid or KCI. In addition,
comparisons among the patterns of taste generalizations indicated that the
tastes of Polycose and sucrose also had distinct qualitative components.
Finally, although the taste of 100 mM Polycose was more salient than the
taste of 50 mM sucrose, the taste of sucrose could still be detected in a
mixture with Polycose.
相似文献
204.
205.
S. Gedik ME Erdemli M Gul B Yigitcan H Gozukara Bag Z Aksungur 《Biotechnic & histochemistry》2018,93(4):267-276
We investigated repair of acrylamide (AA) induced damage in intestines by administration of crocin. We used 40 male Wistar rats in four groups of 10 animals: control, AA, crocin, and AA + crocin groups. We investigated biochemical and histological changes to small and large intestine. AA ingestion decreased glutathione (GSH) levels and total antioxidant status (TAS) in the intestine compared to the control group, while superoxide dismutase (SOD) and catalase (CAT) activities, and total oxidant status (TOS) and malondialdehyde (MDA) levels were increased. Villi were shortened and villus degeneration was observed in ileum of the AA group. Degeneration of surface epithelium and Liberkühn crypts were observed in colon sections. GSH and TAS levels increased after administration of AA together with crocin, while SOD and CAT levels and TOS and MDA levels decreased; significant recovery of histological damage also was observed. We found that crocin exhibits protective effects on AA induced small and large intestine damage by inhibiting oxidative stress. 相似文献
206.
The growth of the freshwater microalga Scenedesmus obliquus was studied at 30°C in a mineral culture medium with phosphorus concentrations of between 0 and 372 μ
. The values for the specific growth rates, between
and
, fitted a semistructured substrate-limitation model with μm1 = 0·0466 h−1, μm2 = 0·0256 h−1 and
. The specific uptake rate of phosphorus reached a maximum value of qSm1 = 658·01 × 10−4 μmol P mg−1 biomass h−1. 相似文献
207.
Background
Herpes Simplex Virus 2 (HSV-2) is one of the most common sexually transmitted infections (STIs) worldwide and is a risk factor for the acquisition and transmission of other STIs, including HIV. We determined the prevalence and predictors of HSV-2 infection among women screened for a HIV prevention trial in Durban, South Africa. Univariate and multivariate logistic and Cox regression models were used to determine the correlates and predictors of HSV-2 infection at enrolment and seroconversion during the study respectively.Results
Prevalence of HSV-2 at screening was 65% and crude incidence was 22.3 per 100 person-years (PY) (95% CI 20.4–24.3). The HIV seroconversion was significantly higher among those testing positive for HSV-2 at baseline compared to women who were negative [8.7 per 100 person years (PY) versus 5.2 per 100 PY; (p < 0.001)]. In univariate analysis, age was determined to be the most significant predictor for HSV-2 diagnosis, while co-infection with syphilis was also a significant predictor, while age and co-infection with syphilis remained the two most significant predictors of having HSV-2 in multivariate analysis at baseline. Consistent with these results, along with HIV seroconversion, age was also identified as a significant predictor for incidence of HSV-2.Conclusion
Given the unacceptably high prevalence and incidence rates of HSV-2 infection reported here, HSV-2 and general STI education needs to be reinforced in these communities, with a focus on condom education for prevention. HSV-2 has emerged as the most prevalent STI which is most often asymptomatic and unrecognized, and which increases women’s risk of acquiring other STIs, including HIV.208.
209.
210.
The endangered Uluguru Bush Shrike Malaconotus alius is a large, black-headed bush shrike, strictly endemic to the Uluguru Mountains in Tanzania. It has recently been suggested that this species has been misplaced within the genus Malaconotus and might instead be related to Malagasy Vangidae. To assess its systematic affinities, we analysed 1518 bp of sequence data obtained from a nuclear intron (myoglobin intron-2) and a mitochondrial protein-coding gene (ND2) using parsimony, maximum likelihood and Bayesian inference. Both genes strongly support the traditional placement within the genus Malaconotus , suggesting that similarities between the Uluguru Bush Shrike and the Vangidae are due to convergence. These results caution that taxonomic changes should not be made without a proper character analysis (i.e. assignment of character homology). 相似文献