克伦特罗对绵羊肝脏氮和挥发性脂肪酸代谢的影响

利用多种慢性血管导管技术研究了β－肾上腺素能受体激动剂克伦特罗（CL，0．8mg.kg^-1，肠系膜静脉给药，每天2次，连续5d)，对绵羊肝脏物质代谢的影响，结果表明，在CL作用下，绵羊肝静脉和门静脉血液中尿素氮浓度分别减少27．48％（P＜0．01）和26．37（P＜0．01），多肽水平也分别下降46．33％（P＜0．01）和21．22％（P＜0．01）。CL还增加进入绵辜肝脏的挥发性脂肪酸（VFA）水平，其中门静脉中乙酸的浓度较对照期增加了11．16％，而肝静中则下降7．84％；门静脉中丙酸和丁酸的浓度也有所增加，此外，CL也可提高肝脏中葡萄糖的异生，提示CL可增加绵羊肝脏中氮的潴留，促进肝脏对VFA的吸收和利用。     

蛋白激酶C抑制剂Staurosporine对血小板聚集、蛋白磷酸化和肌动蛋白聚合的影响

目的：进一步研究蛋白激酶C抑制剂Staurosporine在血小板聚集、蛋白磷酸化、肌动蛋白聚合中的作用。方法：以32P－Na2HPO4标记血小板；以血小板聚集仪测定血小板聚集；以SDS－PAGE分离蛋白质，进行放射自显影；以TritonX－100抽提法沉淀骨架蛋白。结果：（1）1μmol／LStaurosporine完全抑制0．5U／ml凝血酶或10μmol／LPMA诱导的血小板聚集，大部分抑制20μmol／LA23187诱导的血小板聚集。（2）1μmol／LStaurosporine几乎完全抑制0．5U／ml凝血酶、或10μmol／LPMA、或20μmol／LA23187诱导的血小板40kD和20kD蛋白磷酸化。（3）1μmol／LStaurosporine完全抑制0．5U／ml凝血酶或10μmol／LPMA诱导的血小板肌动蛋白聚合。结论：Staurosporine抑制蛋白激酶C的活性．从而抑制血小板的聚集和肌动蛋白聚合；蛋白激酶C在血小板聚集和肌动蛋白聚合中起着重要调控作用。     

Effects of intravenous administration of neurokinin receptor subtype-selective agonists on gonadotropin-releasing hormone pulse generator activity and luteinizing hormone secretion in goats

Recent evidence suggests that neurokinin B (NKB), a member of the neurokinin (tachykinin) peptide family, plays a pivotal role in gonadotropin-releasing hormone (GnRH) pulse generation. Three types of neurokinin receptors (NKRs), NK1R, NK2R and NK3R, are found in the brain. Although NKB preferentially binds to NK3R, other NKRs are possibly also involved in NKB action. The present study examined the effects of intravenous administration of the NKR subtype-selective agonists GR73632 (NK1R), GR64349 (NK2R), and senktide (NK3R) on GnRH pulse generator activity and luteinizing hormone (LH) secretion. Multiple-unit activity (MUA) was monitored in ovariectomized goats (n = 5) implanted with recording electrodes. Characteristic increases in MUA (MUA volleys) were considered GnRH pulse generator activity. Although three NKR agonists dose-dependently induced an MUA volley and an accompanying increase in LH secretion, the efficacy in inducing the volley markedly differed. As little as 10 nmol of senktide induced an MUA volley in all goats, whereas a dose of 1000 nmol was only effective for the NK1R and NK2R agonists in two and four goats, respectively. When the treatment failed to evoke an MUA volley, no apparent change was observed in the MUA or LH secretion. Similar effects of the NK2R and NK3R agonists were observed in the presence of estradiol. The results demonstrated that NK3R plays a predominant role in GnRH pulse generation and suggested that the contributions of NK1R and NK2R to this mechanism may be few, if any, in goats.     

猪组成型雄烷受体激动剂高通量药物筛选模型的建立

构建猪组成型雄烷受体(pgCAR)激动剂体外高通量筛选模型。利用RT-PCR技术从猪肝脏总RNA中扩增出pgCAR基因序列,将测序后正确的pgCAR片段连接到pcDNA 3.1 vector上构建表达载体pcDNA 3.1-CAR;将合成的5个拷贝NR1(Nuclear receptor sites)插入PGL3-TK-promoter构成报告质粒(NR1)5-TK-luc,与PRL-TK报告质粒构成双荧光报告系统。用PEI转染技术将表达载体与报告质粒共转染HepG 2细胞株中,通过检测荧光素酶基因表达状况评价具有生物活性配体化合物对pgCAR激动活性。阳性药苯妥英钠明显提高荧光素酶的表达,最大上调倍增数可达约2.53倍,并且在一定浓度下阳性药与相对荧光酶的活性表达有较好量效关系。     

The prophylactic effect of a dry-cow antibiotic against Streptococcus uberis

The prophylactic use of a dry-cow antibiotic for reducing the incidence of mastitis due to Streptococcus uberis was studied in four seasonally calving dairy herds involving 378 cows. The treatment was a long-acting dry-cow antibiotic preparation administered immediately after the last milking of lactation. New intramammary infections were identified by comparing the bacteriological status of quarters at drying off with that after calving, or through manual udder palpation during the dry period. The administration of dry-cow antibiotic to uninfected quarters at drying off reduced the overall incidence of new infections with Streptococcus uberis from 12.3% for untreated quarters to 1.2% of quarters (p<0.01). The reduction was significant (p<0.01) for both dry-period and post-calving infections. The susceptibility of uninfected quarters to new infection by Streptococcus uberis appeared to be unrelated to the infection status of a cow at drying off. Clinical infections during the dry period were most prevalent (97%) in quarters identified as having open teat canals. Fewer open teat canals (p<0.05) were observed among antibiotic treated quarters over the first 4 weeks of the dry period. Treated quarters had a lower (p<0.05) incidence of new clinical infection during the ensuing lactation and lower somatic cell counts. This did not affect production levels of milk, milk fat or protein. The results clearly indicated a prophylactic benefit for the dry cow antibiotic treatment against new Streptococcus uberis infections during the dry period.     

Non-steroidal ecdysteroid agonist chromafenozide: Gene induction activity, cell proliferation inhibition and larvicidal activity

The activity profile of the most recent commercial non-steroidal ecdysteroid agonist chromafenozide (ANS-118), was evaluated on a comparative basis to methoxyfenozide (RH-2485) that is to date the most potent commercial agonist against Lepidoptera. This was done first at the molecular and cellular level regarding its induction activity of an ecdysteroid-responsive reporter gene and its cell proliferation inhibition activity, and subsequently at the level of larvicidal toxicity. For in vitro experiments three ecdysteroid-responsive insect cell lines were used: Drosophila melanogaster (Diptera) S2 cells, Bombyx mori (Lepidoptera) Bm5 cells and Spodoptera exigua (Lepidoptera) Se4 cells. The in vivo toxicity was scored against two major lepidopteran pests in the world, the beet armyworm S. exigua and the cotton leafworm Spodoptera littoralis. In vitro results revealed that chromafenozide and methoxyfenozide are highly potent against lepidopteran cells compared to dipteran cells, supporting the lepidopteran-specificity of these compounds. Interestingly, in the reporter gene induction experiments and proliferation inhibition experiments, a slightly higher efficacy was observed in S2 compared to Bm5 cells at high concentrations of chromafenozide and methoxyfenozide. Our analysis shows the high potency and efficacy of the chromafenozide compound as an ecdysteroid agonist towards lepidopteran insects at a level that is similar to methoxyfenozide.     

Biochemical mechanisms of methoxyfenozide resistance in the cotton leafworm Spodoptera littoralis

BACKGROUND: Methoxyfenozide is a lepidopteran‐specific insecticide that belongs to a new group of insecticides, the non‐steroidal ecdysteroid agonists, also called moulting accelerating compounds (MACs). To investigate the risk of resistance and possible mechanisms conferring resistance to methoxyfenozide, the authors selected in the laboratory for a resistant strain of the cotton leafworm Spodoptera littoralis (Boisd.), which is a representative lepidopteran model and an important pest in cotton and vegetables worldwide, with a high risk for resistance development. RESULTS: After selection with methoxyfenozide during 13 generations, toxicity data showed that the selected strain developed fivefold resistance to methoxyfenozide in comparison with the susceptible strain. Measurement of the detoxification enzymes demonstrated that the monooxygenase (MO) activity was 2.1 times higher in the selected strain, whereas there was no change for esterases and glutathione‐S‐transferases. When the inhibitors piperonyl butoxide (PBO), S,S,S‐tributyl phosphorotrithioate (DEF) and diethyl maleate were tested as synergists, the respective synergistic ratios were 0.97, 0.96 and 1.0 for the susceptible strain, and 2.2, 0.96 and 1.1 for the resistant strain. The significant synergistic effect by PBO concurs with the increased MO activity in the selected strain. CONCLUSION: Taken overall, the present study supports the importance of MO‐mediated metabolism in resistance to methoxyfenozide, directing tactics to fight against resistance development for this novel group of insecticides. Copyright © 2009 Society of Chemical Industry