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David R. Nelson 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2013,368(1612)
The world we live in is a biosphere influenced by all organisms who inhabit it. It is also an ecology of genes, with some having rather startling effects. The premise put forth in this issue is cytochrome P450 is a significant player in the world around us. Life and the Earth itself would be visibly different and diminished without cytochrome P450s. The contributions to this issue range from evolution on the billion year scale to the colour of roses, from Darwin to Rachel Carson; all as seen through the lens of cytochrome P450. 相似文献
3.
George John Acton 《Phytochemistry》1974,13(8):1303-1310
The light-dependent increment in RNase activity (which is ribosome bound in cell extracts) is distributed as a gradient increasing from base to hook of lupin hypocotyls. No evidence was found of non-specific or of specific activation of pre-formed enzyme molecules following isolation, either before or after (latent activity) destruction of particles. The autodegradation capacity of ribosomes isolated from irradiated cells was almost double that of ribosomes from etiolated tissue. It is proposed that association between the bulk of the light-controlled RNase fraction and lupin ribosomes results from binding of soluble protein. It is not clear whether binding is specific or an artifact of isolation. 相似文献
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5.
Feral and laboratory flocks of rock doves () show a pattern of grouped sequential exploitation when simultaneously presented with two dispersed, depleting patches of seed. This behavior contrasts with the ideal free distribution pattern shown when patches are small and concentrated. Grouped sequential exploitation consists of two phases: all pigeons first land together and feed at one patch, then leave one by one for the other patch. Departure times of individuals for the second patch are correlated with feeding rate at patch 1, which is in turn correlated with position in the dominance hierarchy. The decision to switch from patch 1 to patch 2 improves individual feeding rates in all cases, but is done slightly later than it should according to optimal foraging theory. 相似文献
6.
新的抑癌基因家族--ASPP 总被引:2,自引:0,他引:2
P53是重要的抑癌基因之一的产物,其在抑制肿瘤功能的重要方面是诱导凋亡的能力。但多年来P53诱导凋亡的机制还不清楚,最近发现的ASPP蛋白较好的解释了这个问题,ASPP蛋白能和P53结合形成复合物,再作用于原凋亡基因的启动子区域,从而诱导细胞凋亡的发生,ASPP表达水平的改变能影响P53与DNA结合的能力,进而控制细胞是进入凋亡还是进入停滞的途径,影响P53诱导肿瘤抑制的效应。 相似文献
7.
Antibacterial activity of Turkish propolis and its qualitative and quantitative chemical composition 总被引:7,自引:0,他引:7
The antibacterial activity of propolis from different regions of Turkey was studied, accompanied by TLC and GC-MS analyses of its chemical composition and spectrophotometric quantification of the most important active principles. All six samples were active against the bacterial test strains used; however, samples 1 (Yozgat), 2 (Izmir) and 3 (Kayseri) were more active than samples 4 (Adana), 5 (Erzurum) and 6 (Artvin). By TLC comparison all samples were found to contain poplar taxonomic markers but in samples 4 (Adana), 5 (Erzurum) and 6 (Artvin), different substances were observed, which were not present in P. nigra L. bud exudate. The typical poplar samples 1 (Yozgat), 2 (Izmir) and 3 (Kayseri) displayed very similar phenolic and flavonoid content. Samples 4 (Adana), 5 (Erzurum) and 6 (Artvin) were characterized by low phenolic and very low flavonoid concentrations. Qualitative analysis by GC-MS revealed that sample 4 (Adana) contained diterpenic acids and high percent of cinnamyl cinnamate, sample 5 (Erzurum)-significant amounts of hydroxy fatty acids and triterpenic alcohoLs, and sample 6 (Artvin)-phenolic glycerides, characteristic for the bud exudate of Populus euphratica Oliv. The results confirm the importance of phenolics for propolis antibacterial activity, and the significance of P. nigra L. as a propolis source, which provides the hive with the best defense against microorganisms. 相似文献
8.
A Comparison of Bone Mineral Density and Its Predictors in HIV-Infected and HIV-Uninfected Older Men
《Endocrine practice》2021,27(12):1225-1231
ObjectiveBone health in older individuals with HIV infection has not been well studied. This study aimed to compare bone mineral density (BMD), trabecular bone score (TBS), and bone markers between HIV-infected men and age- and body mass index (BMI)-matched HIV-uninfected men aged ≥60 years. We investigated the associations of risk factors related to fracture with BMD, TBS, and bone markers in HIV-infected men.MethodsThis cross-sectional study included 45 HIV-infected men receiving antiretroviral therapy and 42 HIV-uninfected men. Medical history, BMD and TBS measurements, and laboratory tests related to bone health were assessed in all the participants. HIV-related factors known to be associated with bone loss were assessed in the HIV-infected men.ResultsThe mean BMD, TBS, and osteopenia or osteoporosis prevalence were similar among the cases and controls. The HIV-infected men had significantly higher mean N-terminal propeptide of type 1 procollagen and C-terminal cross-linking telopeptide of type I collagen levels. Stepwise multiple linear regression analysis demonstrated that low BMI (lumbar spine, P = .015; femoral neck, P = .018; and total hip, P = .005), high C-terminal cross-linking telopeptide of type I collagen concentration (total hip, P = .042; and TBS, P = .010), and low vitamin D supplementation (TBS, P = .035) were independently associated with low BMD and TBS.ConclusionIn older HIV-infected men with a low fracture risk, the mean BMD and TBS were similar to those of the age- and BMI-matched controls. The mean bone marker levels were higher in the HIV group. Traditional risk factors for fracture, including low BMI, high C-terminal cross-linking telopeptide of type I collagen level, and low vitamin D supplementation, were significant predictors of low BMD and TBS. 相似文献
9.
J Matousek 《Animal genetics》1994,25(Z1):45-50
Injection of mouse scrotum with the bull seminal ribonuclease (BS RNase) isolated from bull seminal vesicle fluid inhibited spermatogenesis and caused a decrease in the weight of the testes. Long-term injection of BS RNase evoked the production of antibodies which reached the titre 524448. These antibodies did not prevent the aspermatogenic action of BS RNase in vivo when a twofold higher amount of this enzyme was injected into mouse scrotum. Aspermatogenesis was reversible in both the first and second part of the experiment. During the period of aspermatogenesis the males were sterile. Increasing the amount of BS RNase injections in the second part of experiments caused aspermatogenesis around 3 months. No malformations were observed among offspring of males recovered from the first stage of aspermatogenesis. The antigen—antibody complex prepared in vitro and injected into testes of mice evoked the same degree of aspermatogenesis as the enzyme itself. 相似文献
10.
Effects of the supply levels and ratios of nitrogen and phosphorus on seed traits of Chenopodium glaucum
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《植物生态学报》2018,42(9):963
全球氮沉降不仅改变土壤氮和磷的有效性, 同时也改变氮磷比例。氮磷供应量、比例及其交互作用可能会影响植物种子性状。该研究在内蒙古草原基于沙培盆栽实验种植灰绿藜(Chenopodium glaucum), 设置3个氮磷供应量水平和3个氮磷比例的正交实验来探究氮磷供应量、比例及其交互作用对灰绿藜种子性状的影响。结果发现氮磷供应量对种子氮浓度、磷浓度和萌发率影响的相对贡献(15%-24%)大于氮磷比例(3%-7%), 而种子大小只受氮磷比例的影响。同时氮磷供应量和比例之间的交互作用显著影响种子氮浓度和磷浓度。同等氮磷比例情况下, 低量养分供应提高种子氮浓度、磷浓度和萌发率。氮磷比例只有在养分匮乏的环境中才会对种子大小和萌发率产生显著影响。总之, 灰绿藜种子不同性状对氮或磷限制的敏感性不同, 同时种子性状也对养分限制表现出适应性和被动响应。 相似文献