高含硫管道氢致开裂的分形效应及扩展速率计算

氢致开裂是高含硫气田集输管网、长输管网管线钢失效的主要模式之一,为明确管道氢致开裂的机理与过程,对其开裂模式进行了研究。对氢质量浓度在金属裂尖扩展过程中的变化规律进行分析,考虑分形效应的影响,对氢致裂纹的动力学模型进行修正,提出了氢致裂纹扩展的直裂纹-剪切带分形模型:在Gerberich对氢致开裂研究的基础上,基于裂尖的氢化作用与裂纹扩展过程中存在的耦合因素,将断裂过程区的形状与裂纹的扩展长度进行结合,构建了氢致开裂裂纹扩展各阶段分形速率的表达式,得到了更为合理的基于分形效应的氢致开裂数学模型。以材质为16Mn和20钢的天然气管道为例,分别计算了母材与焊缝处的氢致裂纹扩展速率,对比得出两种材料抗H2S的性能,研究结果对于高含硫管道材料的选择具有一定指导意义。     

番茄青枯病抗性相关根际微生物的研究进展

由茄科雷尔氏菌（Ralstonia solanacearum）侵染引起的植物细菌性青枯病（Bacterial wilt）素有“植物癌症”之称,是一种毁灭性土传细菌病害。目前,青枯病已成为制约我国番茄生产的主要病害之一。抗青枯病番茄品种表现出与劣质农艺性状连锁遗传的问题一直没有得到解决,而且番茄青枯病抗性主要为数量遗传,不利于优良抗病品种的选育。根际微生物参与调控植物免疫系统,提高寄主植物青枯病抗性,反之,寄主植物的健康状况也能够影响根际微生物群落组成,根际微生物在番茄青枯病防治中具有重要作用。对抗青枯病番茄根际微生物群落特征及微生物群落形成的影响因素进行总结,讨论了根际微生物参与调控番茄青枯病抗性遗传的作用机制,并对利用有益根际微生物调控番茄青枯病研究方向的热点进行展望,为番茄青枯病诱导抗性机制的解析、遗传育种以及番茄青枯病的防治与品种的合理布局提供有效参考。     

Artificial induction of maturation and fertilization in the Japanese eel, Anguilla japonica

Repeated injections of salmon pituitary extract (20 mg per fish per week) induced vitellogenesis in feminized, cultivated Japanese eels (Anguilla japonica). Oocytes were attained at the migratory nucleus stage after 11 or 12 injections. Addition of 17,20-dihydroxy-4-pregnen-3-one (DHP) into the incubation medium induced germinal vesicle breakdown (GVBD) in the oocytes at the migratory nucleus stage. An injection of DHP (2 µg g^-1 BW), given 24h after an injection of salmon pituitary extract (20 mg fish^-1), succeeded in inducing maturation and ovulation in females which contained occytes at the migratory nucleus stage. Most fish ovulated 15–18h following the DHP injection. Eggs that were ovulated within 15h after the DHP injection showed high fertility and hatchability, but eggs ovulated 18 or 21h after the DHP injection, showed considerably lower fertility and hatchability. A delay between ovulation and stripping of the eggs rapidly decreased both the fertility and hatchability within 6–9h after ovulation, indicating that artificial fertilization must be carried out immediately after ovulation. Repeated injections of human chorionic gonadotropin (hCG) at a concentration of 1 IU g^-1 BW week^-1 induced spermatogenesis, spermiation, and the acquisition of potential for sperm motility in cultivated males. Most males spermiated after the fifth or sixth injection of hCG, and the milt weight gradually increased and remained constant (1–2 g) from the 11th to 31th injection. Sperm motility peaked 24h after each weekly injection, and decreased from the 3^rd day after the injection. Potassium ions are an essential constituent for the maintenance of motility in the eel spermatozoa. Artificial seminal plasma containing 15.2 mM KCl is applicable as a milt diluent. Using these techniques developed for female and male eels, we have succeeded in obtaining many fertilized eggs from cultivated eels.     

Steroidogenesis during induced oocyte maturation and ovulation in the African catfish,Clarias gariepinus

Changes in ovarian steroidogenesis accompanying oocyte maturation and ovulation were studied in the African catfish,Clarias gariepinus. Laboratory-reared females with postvitellogenic ovaries were treated with pimozide and LHRH-analogue. The plasma gonadotropin levels were determined by means of a homologous radioimmunoassay, the condition of the ovaries was studied by histological examination of the follicles, and the steroidogenetic capacity of the ovaries was analyzed byin vitro incubation of tissue fragments for 3 h with [³H]-pregnenolone and [³H]androstenedione as precursors. Data were collected at regular intervals between 0 and 16 h after pimozide-LHRH analogue administration.Until 4 h after the beginning of the experiments the plasma gonadotropin levels did not rise above 25 ng/ml, the ovaries remained in the stage of postvitellogenesis, and testosterone was the main end product of steroidogenesis. Four hours later the gonadotropin concentration in the blood had risen to more than 150 ng/ml, and the ovaries had entered the stage of germinal vesicle migration. At the same time steroidogenesis shifted towards the production of 17,20-dihydroxy-4-pregnen-3-one, 5-pregnane-3, 17-diol-20-one, 5-pregnane-3,6,17-triol-20-one, 5-pregnane-3,17,20-triol and 5-pregnane-3,6,17,20-tetrol. During the subsequent stage of germinal vesicle breakdown the plasma gonadotropin level remained high, and the synthesis of the C₂₁-steroids showed a further increase. Simultaneously, the production of some C₁₉-steroid glucuronides was enhanced. The preovulation and especially the postovulation stages were accompanied by a gradual decrease in steroidogenic capacity of the ovaries, even though the plasma gonadotropin level remained high. It is concluded that the prematuration surge of gonadotropin influences the activity of enzymes involved in steroidogenesis, leading to a reduced C_17,20-lyase and to an augmented activity of the enzymes 20-hydroxysteroid dehydrogenase (HSD), 5-reductase, 3-HSD, 6-hydroxylase and UDP-glucuronosyltransferase. During ovulation the activity of all steroidogenic enzymes, including such key enzymes as 3-HSD and 17-hydroxylase, gradually decreases.Not only 17,20-dihydroxy-4-pregnen-3-one, but also the 5-reduced pregnanes may be involved in inducing oocyte maturation and/or ovulation. The very polar triol and tetrol products may function, together with the steroid glucuronides as sex pheromones.A preliminary account of these results was presented at the XIII Conference of European Comparative Endocrinologists, Belgrade, September 7–12, 1986     

Angiotensins stimulate in vitro ovulation and contraction of brook trout (Salvelinus fontinalis) follicles

The effects of salmon angiotensin I (sAI) and human angiotensin II (hAII) on in vitro ovulation of preovulatory (preOV) brook trout (Salvelinus fontinalis) follicles were investigated. Both angiotensins increased levels of ovulation above that in controls after 12 hours of incubation. The increase was statistically significant in incubates with greater than 1 M hAII. The effects of the angiotensins on follicle contraction were also studied indirectly by measuring the decrease in weight of punctured follicles taken prior to germinal vesicle breakdown. At 1 M, both angiotensins significantly decreased the weight of punctured follicles after 16 hours of incubation. The angiotensin-stimulated decrease in weight was not blocked by indomethacin (10 g/ml), indicating that follicle contraction was not prostaglandin-dependent. The data indicate that angiotensins might be directly involved in brook trout ovulation and the stimulatory effects of angiotensins on ovulation may be attributed to their effects on follicle contraction.This work was supported by NIH grant #HD25924-02.     

Effects of pimozide and LHRH-Aa on carp (Cyprinus carpio L.) oocyte maturation and ovulationin vivo

Effects of pimozide (Pim) and [(D-Ala⁶, Pro⁹-NEt) LHRH] (LRH-Aa) on common carp oocytes maturation and ovulationin vivo under laboratory and commercial fisheries farm conditions were investigated.Although injections of Pim and LRH-Aa at the doses of 10 mg and 50 µg/kg body weight respectively, did not increase mGtH levels (66.7–155.8 mg/ml) as much as injections of carp pituitary extract (chh) (382.1 ng/ml), induced GtH levels were high enough to induce ovulation. Changes in the ovary caused by Pim and LRH-Aa were similar to those induced by chh, and Pim injected together with LRH-Aa in a single injection gave the same results concerning ovulation induction as when they were applied separately at 6h interval.     

Effects of exogenous neurohormone, gonadotropin (GtH) and dopaminergic drugs on the serum GtH content and ovulatory responsiveness of wild catfish, Silurus asotus (Linnaeus, 1758)

Wild female catfish Silurus asotus (Linnaeus, 1758) were injected with domperidone (DOM) alone, [d ‐Ala⁶, Pro⁹ Net]‐luteinizing hormone‐releasing hormone (LHRH‐A) alone once or twice, LHRH‐A plus DOM once or twice simultaneously at 6‐h intervals, LHRH‐A plus carp pituitary extract (CPE) twice simultaneously at 6‐h intervals and LHRH‐A plus human chorionic gonadotropin (HCG) twice simultaneously 6 h apart respectively. The results indicated that injection of LHRH‐A at a dosage of 0.01–0.02 μg g^?1 body weight (BWt) alone induced a low but significant increase in serum gonadotropin (GtH) (P<0.05) and resulted in a very low ovulation rate, while DOM at a dosage of 5 μg g^?1 BWt alone did not induce an increase in the serum GtH levels and ovulation; in contrast, LHRH‐A at a dosage of 0.01 μg g^?1 BWt plus DOM at a dosage of 5 μg g^?1 BWt (termed the Linpe technique) increased the serum GtH (P<0.05) significantly and induced an ovulatory rate of 100%, while LHRH‐A plus CPE or HCG resulted in an increase in the serum GtH (P<0.05) and high ovulatory rate, although the latency period was longer when fish were given LHRH‐A plus HCG or CPE.     

Effects of animal liver and bile extracts on biochemical values of rat ethanol‐induced fatty liver

The purposes of this study were to assess the improvement of fatty liver induced by ethanol with animal liver and bile extracts. This research aimed to increase the economic values of animal liver and bile extracts and used these to reduce damage of ethanol‐induced fatty liver. Extracts came from animal liver and bile, including pig bile powder, pig liver extract, a mixture of pig bile powder and pig liver extract, chicken bile powder, chicken liver extract, and a mixture of chicken bile powder and chicken liver extract, and these were fed to Long‐Evans rats. The results showed that rats fed ethanol for long terms could increase values of aspartate transaminase, cholesterol, γ‐glutamy‐transferase and alkaline phosphatase. Pig bile powder could decrease the values of aspartate transaminase, cholesterol and γ‐glutamy‐transferase. The significances also decreased on aspartate transaminase, γ‐glutamy‐transferase and aspartate transaminase, which were carried out with the pig liver extract treatment. These results suggest pig bile and liver extracts have high potential to improve rats' ethanol‐induced fatty liver with serum biochemical parameters.