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981.
982.
983.
Potassium translocation in yeast mitochondria and its relationship to ergostrol biosynthesis. 总被引:3,自引:2,他引:1 下载免费PDF全文
The energy-dependent transport and accumulation of K+ in respiring mitochondria has been found to inhibit the S-adenosylmethionine: delta-24-sterol methyltransferase enzyme of Saccharomyces cerevisiae. Potassium cation translocation is discussed as a possible regulatory mechanism over the biosynthesis of ergosterol. 相似文献
984.
Zisca R. Dixon Betty J. Burri Andrew Clifford Edwin N. Frankel Barbara O. Schneeman Elizabeth Parks Nancy L. Keim Teresa Barbieri Mei-Miau Wu Alice K.H. Fong Mary J. Kretsch Anne L. Sowell John W. Erdman Jr. 《Free radical biology & medicine》1994,17(6):537-544
The effect of consuming a low carotene diet (≈60 μg carotene/day) on oxidative susceptibility and superoxide dismutase (SOD) activity in women living in a metabolic research unit was evaluated. The diet had sufficient vitamins A, E, and C. The women ate the diet supplemented with 1500 μg/day β-carotene for 4 days (baseline), then the unsupplemented diet for 68 days (depletion), followed by the diet supplemented with > 15,000 μg/day carotene for 28 days (repletion). Production of hexanal, pentanal, and pentane by copper-oxidased plasma low density lipoproteins from carotene-depleted women was greater than their production of these compounds when repleted with carotene. Erythrocyte SOD activity was depressed in carotene-depleted women; it recovered with repletion. Thiobarbituric acid reactive substances in plasma of carotene-depleted women were elevated and diminished with repletion. Dietary carotene seems to be needed, not only as a precursor of vitamin A, but also to inhibit oxidative damage and decrease oxidation susceptibility. 相似文献
985.
Melissa Parks 《Science activities》2020,57(2):77-87
AbstractMaximizing classroom time to include meaningful content-based learning with fun engaging activities that simultaneously challenge and encourage students is a hallmark of a successful school day. This article shares one instructional approach that does a model eliciting activity (MEA). A MEA is a real-world, problem-based scenario framed around a fictitious client who writes a letter in which the client poses a problem for students to address. Students use the engineering design process to brainstorm, create, and test models, then compose written and oral responses to the client citing evidence to justify their solution. The content of the client letter is created by the classroom teacher and based on the Next Generation Science Standards, the teacher wishes to address. The depth of the content addressed is at the teacher’s discretion and may vary depending on sequence of lessons within the unit of study, developmental readiness of students, and standard(s) selected. 相似文献
986.
The Douglas fir terpene α-pinene was shown to inhibit the growth of a variety of bacteria and a yeast. Other terpenes of the Douglas fir, including limonene, camphene, and isobornyl acetate, were also inhibitory to Bacillus thuringiensis. All terpenes were inhibitory at concentrations normally present in the fir needle diet of Douglas fir tussock moth larvae. The presence of such terpenes in the diet of these insects was found to strongly influence the infectivity of B. thuringiensis spores for the Douglas fir tussock moth larvae. The terpene α-pinene destroyed the cellular integrity and modified mitochondrial activity in certain microorganisms. 相似文献
987.
Botanists have long been aware of the floristic similarities between eastern Asia and eastern North America. Most who have considered this classic disjunction pattern have suggested that it arose through range disruption of a flora that was once more widely distributed in the Northern Hemisphere. There is less agreement on the timing of this process, with suggestions ranging from the Paleocene to the Neogene. In this study, molecular markers from two different plant genomes were used to assess the degree of genetic divergence between the two interfertile, morphologically similar species of the genus Liriodendron, i.e., L. tulipifera and L. chinense. Resulting molecular divergence estimates were translated into approximate dates of separation, independent of evidence from the fossil record. Allozyme data (Nei's genetic identity = 0.434) suggested a divergence time of 10–16 million years before present, whereas sequence divergence in the plastid genomes (1.24%) led to an estimate of approximately 11–14 million years before present. A review of the paleobotanical literature indicated that the fossil floras that included, or might have included Liriodendron could not have survived in Beringia after the late Miocene and the onset of southward-migrating Arctic air masses on the North American continent. This interpretation suggests a minimum time of separation of approximately 13 million years before present. Thus, both molecular data sets and the paleobotanical evidence concur in suggesting a divergence time of 10–16 million years before present. Interspecific compatibility and relative morphological stasis must have, therefore, persisted from at least the late Miocene. We emphasize the need for similar studies in other genera, especially those that have both a reasonable Tertiary fossil history and extant species in mesic temperate refugia in Asia, Europe, and western as well as eastern North America. 相似文献
988.
989.
Two Genetically Separable Phases of Growth Inhibition Induced by
Blue Light in Arabidopsis Seedlings 总被引:8,自引:3,他引:5
High fluence-rate blue light (BL) rapidly inhibits hypocotyl growth in Arabidopsis, as in other species, after a lag time of 30 s. This growth inhibition is always preceded by the activation of anion channels. The membrane depolarization that results from the activation of anion channels by BL was only 30% of the wild-type magnitude in hy4, a mutant lacking the HY4 BL receptor. High-resolution measurements of growth made with a computer-linked displacement transducer or digitized images revealed that BL caused a rapid inhibition of growth in wild-type and hy4 seedlings. This inhibition persisted in wild-type seedlings during more than 40 h of continuous BL. By contrast, hy4 escaped from the initial inhibition after approximately 1 h of BL and grew faster than wild type for approximately 30 h. Wild-type seedlings treated with 5-nitro-2-(3-phenylpropylamino)-benzoic acid, a potent blocker of the BL-activated anion channel, displayed rapid growth inhibition, but, similar to hy4, these seedlings escaped from inhibition after approximately 1 h of BL and phenocopied the mutant for at least 2.5 h. The effects of 5-nitro-2-(3-phenylpropylamino)-benzoic acid and the HY4 mutation were not additive. Taken together, the results indicate that BL acts through HY4 to activate anion channels at the plasma membrane, causing growth inhibition that begins after approximately 1 h. Neither HY4 nor anion channels appear to participate greatly in the initial phase of inhibition. 相似文献