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排序方式: 共有294条查询结果,搜索用时 15 毫秒
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Locoweed (Astragalus lentiginosus) was fed to ewes from 70 to 100 days of pregnancy. Ewes were killed at 100, 115, 130, and 145 days, and selected tissues were collected from both the dam and the fetus for histologic examination. Neurovisceral cytoplasmic vacuolation and neuroaxonal dystrophy decreased in dam and fetus with time after the feeding of locoweed was discontinued. 相似文献
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Components of the organic matter have been studied in three soils from adjacent sites with different long-term treatments: soil I, prolonged arable cultivation; soil II, 17 years under grass after prolonged arable cultivation; and soil III, old pasture. Contents of total organic C in the top 15cm were 0.9% in soil I. 1.7% in soil II and 4.8% in soil III. The light fraction, comprising partially decomposed materials with a specific gravity < 2.06, represented greater proportions of the organic C in soils II and III (20–23 per cent) than in soil I (8.5 per cent). The light fraction of soil III had a relatively high N content.The proportions of the soil organic C released, by hydrolysis, as neutral sugars, uronic acids, amino sugars, amino acids and phenolic acids were generally similar in the three soils, although uronic acids and phenolic acids constituted somewhat greater proportions in soils II and III than in I.The light fractions contained greater proportions of neutral sugars and phenolic acids, and smaller proportions of amino sugars and amino acids than the whole soils. 相似文献
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PC Sereno DB Dutheil M Iarochene HCE Larsson GH Lyon PM Magwene CA Sidor DJ Varricchio JA Wilson 《Science (New York, N.Y.)》1996,272(5264):986-991
Late Cretaceous (Cenomanian) fossils discovered in the Kem Kem region of Morocco include large predatory dinosaurs that inhabited Africa as it drifted into geographic isolation. One, represented by a skull approximately 1.6 meters in length, is an advanced allosauroid referable to the African genus Carcharodontosaurus. Another, represented by a partial skeleton with slender proportions, is a new basal coelurosaur closely resembling the Egyptian genus Bahariasaurus. Comparisons with Cretaceous theropods from other continents reveal a previously unrecognized global radiation of carcharodontosaurid predators. Substantial geographic differentiation of dinosaurian faunas in response to continental drift appears to have arisen abruptly at the beginning of the Late Cretaceous. 相似文献
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小鼠血清抗磺胺二甲氧嘧啶抗体的研制 总被引:1,自引:0,他引:1
曹盛丰 《上海交通大学学报(农业科学版)》2007,25(2):96-98,119
将磺胺二甲氧嘧啶(SDM)与载体牛甲状腺球蛋白(BTG)偶联,构建SDM完全抗原SDM-BTG。用SDM-BTG免疫小鼠,诱导小鼠产生血清抗SDM抗体。ELISA检测表明:SDM-BTG免疫小鼠所产生的多克隆抗体与SDM-BSA包被抗原的结合有较强的特异性和较高的亲和力。 相似文献
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不同栽培模式及施氮量对半旱地冬小麦氮素累积及分配的影响 总被引:6,自引:0,他引:6
【目的】研究不同栽培模式和施氮量对半旱地栽培条件下冬小麦-夏玉米轮作体系中冬小麦地上部氮素累积、分配及利用效率的影响。【方法】在陕西关中地区进行了田间试验,以常规栽培为对照,比较了补灌、覆草和垄沟等栽培模式及0,120,240 kg/hm2施氮水平,对冬小麦连续2年(2004和2005年)不同生长期各部位氮素累积量的影响。【结果】在补灌模式下,2004和2005年成熟期冬小麦叶片和茎秆的氮素累积量较其他模式低,氮素分配率也较低,而籽粒的氮素分配率较高;施用氮肥显著增加了各生长时期冬小麦叶片、茎秆、颖壳和穗轴以及籽粒的氮素累积量,当氮肥施用量由120增加到240 kg/hm2时,除籽粒外,成熟期冬小麦叶片、茎秆、颖壳和穗轴的氮素残留量均随之明显增加。与不同栽培模式相比,施用氮肥对冬小麦不同器官中氮素分配的影响较小。随着氮肥施用量的增加,氮肥利用效率、氮肥农学效率和氮肥生理效率均呈降低趋势。在不同栽培模式中,连续2年补灌栽培模式下冬小麦的氮肥利用效率、氮肥农学效率以及氮肥生理效率均较高,而其他栽培模式下这3个指标年际间的变化较大。【结论】施用氮肥可显著增加冬小麦各生长时期不同器官的氮素累积量,但对氮素在不同器官中分配比例的影响较小;与施用氮肥相比,不同栽培模式对冬小麦氮素的累积、分布无明显影响;冬季补灌有利于提高冬小麦的氮素效率。 相似文献
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Effects of Addition of Tissue‐Type Plasminogen Activator in In Vitro Fertilization Medium on Bovine Embryo Development and Quality 下载免费PDF全文
F Krania E Dovolou CA Rekkas EK Theodosiadou I Pappas GS Amiridis 《Reproduction in domestic animals》2015,50(1):112-120
Plasminogen activators/Plasmin system plays pivotal role in regulating reproductive functions of mammals. Here, we examined the effects of modification of in vitro fertilization medium (IVF medium) with the addition of tissue‐type plasminogen activator (t‐PA), on bovine embryo development and quality, assessed by quantification of expression of various genes related to metabolism, oxidation, implantation and apoptosis. In addition, plasminogen activator activity (PAA) and plasminogen activator inhibition (PAI) were measured in the spent media. After conventional IVM, 2016 cumulus‐oocyte complexes (COCs) were divided into four groups with modified composition of the IVF medium containing t‐PA and/or its inhibitor epsilon‐aminocaproic acid (control, t‐PA, t‐PA+ε‐ACA, ε‐ACA). Presumptive zygotes were cultured for 8 days in synthetic oviductal fluid (SOF) medium; gene expression studies were carried out on morulae and blastocysts. t‐PA alone significantly suppressed cleavage and blastocyst formation rates, but this effect was neutralized by the addition of ε‐ACA. PAA in the treated group was significantly reduced by ε‐ACA, but without total elimination. Significant differences were detected in the expression of genes related to apoptosis and/or cell cycle arrest (BAX, BCL2L1, KAT2B) between embryos produced in t‐PA‐modified media and controls, giving an overall notion that the inferior developmental competence of treated embryos may be attributed to apoptotic phenomena induced by t‐PA. In conclusion, it appears that excessive t‐PA content in the IVF media, suppresses blastocyst formation rate, possibly due to induction of apoptotic phenomena. 相似文献