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1.
C onner , D.E. & B euchat , L.R. 1985. Recovery of heat-stressed yeasts in media containing plant oleoresins. Journal of Applied Bacteriology 59 , 49–55.
Oleoresins from seven plants (allspice, cinnamon, clove, garlic, onion, oregano, and thyme) were tested for their effects on eight genera of sublethally heated food-spoilage and industrially important yeasts ( Candida lipolytica, Debaryomyces han-senii, Hansenula anomala, Kloeckera apiculata, Lodderomyces elongisporus, Rhodotorula rubra, Saccharomyces cerevisiae, and Torulopsis glabrata ). All heat-stressed yeasts had increased sensitivity to oleoresins in recovery media. Heated cells were most sensitive to cinnamon oleoresin, a lethal effect being observed to concentrations as low as 5 μg/ml. Results indicate that all eight yeasts underwent metabolic and/or structural injury as a result of exposure to elevated temperature. Whilst changes in sensitivity to oleoresins were not the same for all yeasts, it is concluded that the oleoresins may have a pronounced synergistic or additive effect on thermal inactivation of yeasts in foods. Furthermore, carryover of oleoresins in low dilutions of food to enumeration media could adversely influence the recovery of heat-stressed cells, thus resulting in apparent low populations. 相似文献
Oleoresins from seven plants (allspice, cinnamon, clove, garlic, onion, oregano, and thyme) were tested for their effects on eight genera of sublethally heated food-spoilage and industrially important yeasts ( Candida lipolytica, Debaryomyces han-senii, Hansenula anomala, Kloeckera apiculata, Lodderomyces elongisporus, Rhodotorula rubra, Saccharomyces cerevisiae, and Torulopsis glabrata ). All heat-stressed yeasts had increased sensitivity to oleoresins in recovery media. Heated cells were most sensitive to cinnamon oleoresin, a lethal effect being observed to concentrations as low as 5 μg/ml. Results indicate that all eight yeasts underwent metabolic and/or structural injury as a result of exposure to elevated temperature. Whilst changes in sensitivity to oleoresins were not the same for all yeasts, it is concluded that the oleoresins may have a pronounced synergistic or additive effect on thermal inactivation of yeasts in foods. Furthermore, carryover of oleoresins in low dilutions of food to enumeration media could adversely influence the recovery of heat-stressed cells, thus resulting in apparent low populations. 相似文献
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下丘脑外侧区注射TRH对大鼠胃酸分泌的影响 总被引:2,自引:2,他引:0
本文采用连续收集胃腔灌流法,观察下丘脑外侧区(LHA)注射促甲状腺激素释放激素(TRH)对大鼠胃酸分泌的影响,并分析TRH在LHA促进胃酸分泌的作用机制。结果表明:(1)LHA注射TRH(1μg)明显地刺激胃酸分泌;(2)预先向LHA注射酚妥拉明(10μg)、美多心安(5μg)及胃泌素抗体1μl(1:640)并不影响TRH的泌酸作用,如预先向LHA注射阿托品(5μg)则可消除TRH的泌酸效应;(3)垂体摘除及肾上腺切除均不影响TRH的泌酸作用;(4)隔下迷走神经切断后,LHA注入TRH的泌酸效应仍然出现,但持续时间显著缩短;腹腔交感神经节摘除后,TRH仍能促进胃酸分泌,但分泌量少而平稳。以上结果提示:LHA是TRH中枢泌酸效应的有关结构之一,其中枢机制是通过胆碱能M受体中介的,腹腔交感神经节和膈下迷走神经是TRH泌酸效应的传出途径。前者引起的泌酸反应出现较早且引起泌酸高峰,但持续时间短;后者则引起低平的持续分泌。 相似文献
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Summary We studied the nesting success of Evening Grosbeaks (Coccothraustes vespertinus) inhabiting two areas of the Front Range of the Rocky Mountains of Colorado from 1983–1987. Sixty-four nests were followed during building, incubating, brooding, and fledging; 54.7% were successful (young fledged). The largest number of nests failed during incubation. Nests started later were more successful than nests begun earlier in the season. Failure was most likely due to severe weather, abandonment during building, or predation. Specific habitat characteristics of grosbeak nesting sites and where nests were placed in trees were consistently associated with nesting success. Successful nests, when compared with nests that failed, were: (1) built in more open areas characterized by dispersed vegetation and a higher minimum canopy, (2) oriented in more southerly directions, (3) built closer to the main trunk of the nest tree, and (4) built in larger trees. Current ideas about whether or not birds actually select nest-sites are briefly discussed. We conclude that some grosbeaks optimally select nest sites where the likelihood of producing fledglings is higher than in other areas. 相似文献
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Large scale selection of aluminum-resistant mutants from plant cell culture: expression and inheritance in seedlings 总被引:2,自引:0,他引:2
A. J. Conner C. P. Meredith 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1985,71(2):159-165
Summary A large number of aluminum-resistant variants, selected from non-mutagenized homozygous diploid cell cultures of Nicotiana plumbaginifolia Viv., are characterized. Of 115 variants cloned and reselected from single cells, 67 retained Al resistance in callus cultures after 6–9 months of growth in the absence of Al. There was no association between Al resistance and callus growth in the absence of Al, suggesting that the Al-resistant phenotype is not detrimental in the absence of Al challenge and that Al resistance is not the result of increased vigor. Plants regenerated from initially resistant callus lines that subsequently lost their resistance failed, with one exception, to transmit resistance to their seedling progeny. Fertile plants were regenerated from 40 of the 67 variants that retained stable Al resistance in callus culture. All 40 transmitted Al resistance to their seedling progeny (selfed and backcrossed) in segregation ratios expected for a single dominant mutation. The selfed progeny of many variants also segregated for recessive lethal mutations which were attributed to independent mutations that occurred during cell culture. 相似文献
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中华白蛉的自育性研究 总被引:3,自引:0,他引:3
现场及实验室结果表明,我国黄土高原的大多数中华白蛉(Phlebotomus chinensis)应属自育性品系,它通常在羽化后、吸血前经交配能依靠腹节内脂肪体发育卵泡,一般在产卵后始行吸血。其生理性状是:胃内无血、腹节内有大量块状或条状脂肪体。羽化24小时后,附腺内有暗色颗粒,卵巢内有发育的卵泡。在25℃士1℃下它的生活史分快、慢两型。快型从卵至成虫仅需44—50夭,慢型需要以四龄幼虫滞育,其长短随滞育期而定,最长的滞育期达301天。观察了白蛉幼虫在饥饿状态下对自育性的影响。此外,还比较了吸血白蛉与自育性白蛉的妊卵数。吸血白蛉的妊卵数约较自育性的高出1/5。这种自育性品系的中华白蛉在自然居群约内占92%、主要栖于洞穴内为野栖种类。本文对自育性中华白蛉的生态及其防制策略作了分析和讨论。 相似文献
8.
Helix geometry and hydration in an A-DNA tetramer: IC-C-G-G 总被引:10,自引:0,他引:10
The DNA oligomer of sequence IC-C-G-G has been synthesized, and its X-ray crystal structure solved at a resolution of 2.0 A, using anomalous scattering from iodines in phase analysis: 48 cycles of Jack-Levitt restrained least-squares refinement resulted in a residual error of 19.9% over all data, or 16.5% for two-sigma data. Two double-helical tetramers stack in the crystal to form a continuous octamer, except for the two missing phosphate connections across the center. The octamer has a mean helix rotation of 33.7 degrees (10.7 base-pairs per turn), rise of 2.87 A, mean inclination angle of base-pairs of 14 degrees, and mean base-pair propeller twist of +16.3 degrees. Local variations in both helix rotation and base plane roll angles, including those across the center of the octamer, are as predicted from base sequence by sum functions sigma 1 and sigma 2. The three known DNA octamers: IC-C-G-G/IC-C-G-G, G-G-T-A-T-A-C-C and G-G-C-C-G-G-C-C, make up a graded series in this order, with monotonically changing structural parameters. An exhaustive comparison of torsion angle correlations among the known A helices confirms some structural expectations and reveals some new features. 86 water molecules have been located per double-helical IC-C-G-G tetramer (the asymmetric unit), of which 451/2 per tetramer lie within a first hydrogen-bonded shell of hydration. No ordered water structure is observed comparable to the minor groove spine of hydration in B-DNA. 相似文献
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Sister-chromatid exchange (SCE) induction by the direct-acting bifunctional carcinogen, diepoxybutane (DEB), was investigated in multiple tissues in vivo. The log-log dose SCE response relationship was found to be parallel to that previously reported for DEB induction of lung adenomas. However, the SCE assay is approximately 20 times as sensitive in detecting genotoxic effects of DEB than indicated by the lung adenoma assay. Examination of second and third division cells following various treatment protocols revealed that regardless of the nature of initially induced lesions, they are rapidly repaired with no evidence of persistence beyond 1 cell cycle. 相似文献
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