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91.
Using whole cottonseed as a lipid source, silage-based diets that were isocaloric and isonitrogenous yet varied in lipid level were fed to multiparous cows. In Experiment 1, 48 cows (n = 12 per treatment) were allotted to 1 of 4 treatments where diets were formulated to supply 3.9, 4.3, 5.3 and 6.3% of total lipid. In Experiment 2, 66 cows (n = 22 per treatment) were allotted to 1 of 3 treatments where diets were formulated to supply 3.1, 5.5 and 8.3% of total lipid. Length of the first ovarian cycle, length of the first normal estrous cycle, postpartum intervals to onset of ovarian luteal activity and to first estrus were not affected by diet (P>0.10) in either experiment. Mean progesterone (P(4)) concentrations for first normal estrous cycles were not different (P>0.10) in either experiment. Anestrous periods were divided into 3 phases for analyses: Phase I) parturition to onset of ovarian luteal activity, Phase II) first ovarian luteal activity and Phase III) first normal estrous cycle. No differences were observed in P(4) concentrations during any phase of the postpartum period. In conclusion, isocaloric and isonitrogenous diets with increasing levels of lipid had no effect on reproductive performance in suckled beef in these experiments. 相似文献
92.
Threonine dehydratase, the first enzyme in isoleucine biosynthesis, catalyzes deamination and dehydration of threonine to produce 2-ketobutyrate and ammonia. An antimetabolite, 2-(1-cyclohexen-3(R)-yl)-S-glycine (CHG), inhibits the plant enzyme. CHG inhibits the growth of Black Mexican Sweet corn (Zea mays) cells and of Arabidopsis thaliana plants. The herbicidal effects of CHG can be reversed by 2-ketobutyrate, other intermediates of isoleucine biosynthesis, and by isoleucine itself. These results suggest that the herbicidal effects observed with CHG are a consequence of inhibition of threonine dehydratase. The enzyme could be a potential target site for an herbicide screening program. 相似文献
93.
华中地区小家鼠生物学特性观察 总被引:8,自引:2,他引:6
华中地区农村小家鼠的个体较小,主要栖息于农舍,终年繁殖,繁殖高峰期为7月和8月,1-3月为繁殖低谷期;种群数量高峰在9月,低谷期在7-8月,冬季的种群数量水平较高,呈后峰型。在较高的密度条件下,雌鼠的怀孕率降低,性成熟延缓。 相似文献
94.
玉米细胞两种质膜囊泡的制备和鉴别 总被引:3,自引:0,他引:3
细胞质膜是细胞进行物质交换、能量转换及信息传递等重要生命活动的关键部位,现已成为细胞生物学、植物生理学和生物化学的重要研究领域。但目前对植物细胞质膜。:研究远远落后于对其它材料质膜的研究,其中一个重要原因就是制备高度纯化的具有特定朝向的密实质股囊泡比较困难,而不同的研究目的分别需要正向型(ROV)和内侧外翻型(IOV)两种质膜囊泡。我们在前人方法基础上加以改进,成功地制备了基本上为两种取向的密实质膜囊泡,并已用于质膜十”一泵和铁氰化钾还原酶的研究[’j。材料与方法1材料玉米(he_)农大65的种子。奎叮… 相似文献
95.
大袋峨Cryptotheleavariegata(Snellen)是目前我国主要的森林害虫之一,近年在河南、安徽、山东、江苏等省的泡桐基地泛滥成灾,严重影响了林木的生长。现将其变温下的有效积温的研究结果整理如下。(一)经观察测定,大袋蛾的卵期、幼虫期、蛹期及其历期温度列于表l~羊(雄蛹数据略)。(二)各虫态的发育起点温度与有效积温自然变温条件下为:幼虫蛹蛹恒温条件下为:蛹(三)发生期检验在林间,1990年大袋蛾产卵高峰期为5月25日,1991年雄幼虫化蛹高峰期为5月1日,产卵高峰期为6月7日。我们利用获得的大经峨冬虫态的C、K值,根据1990… 相似文献
96.
1.豹斑石豆兰 新种 图1:5—6Bulbophyllum colomaculosum Tsi et S. C. Chen, sp. nov.Species nova B. obrieniano Rolfe proxima, a quo differt petalis margine dentatis.Herba epiphytica. pseudobulbi aggregati ovati, ca. 4 cm longi, medio 1.5—1.8 cm lati, 相似文献
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Maize (Zea mays L.) leaf acetyl-CoA carboxylase (ACCase) was purified about 500-fold by ammonium sulfate fractionation and gel filtration and blue Sepharose affinity and anion-exchange chromatography. Most ACCase activity (85%) recovered from the anion-exchange column was found in a highly purified fraction (specific activity 5.5 [mu]mol acid-stable product min-1 mg-1) that consisted primarily of a single 227-kD biotinylated polypeptide. The fraction represented 29% of the original activity and was designated ACCase I. A second partially purified ACCase activity (ACCase II) eluted earlier during anion-exchange chromatography, contained a single biotinylated polypeptide of 219 kD, was poorly recognized by antiserum raised against the ACCase I polypeptide, and was less inhibited by the herbicides haloxyfop or sethoxydim than was ACCase I. ACCase I and II both utilized propionyl-CoA as substrate about 50% as effectively as acetyl-CoA, and neither utilized methylcrotonyl-CoA. Immunoprecipitation with antiserum and protein blotting of crude extracts of leaf, embryo, and endosperm tissue and suspension cells indicated that most ACCase activity in these tissues was immunologically similar and consisted of ACCase I. Only leaves contained significant amounts of the ACCase II polypeptide; however, no ACCase II polypeptide was found in isolated mesophyll chloroplasts. The ACCase I and II polypeptides appear to be subunits of distinct ACCase isoforms. 相似文献