Influence of enkephalinase inhibitors on gastric emptying in mice depends on the nature of the meal

The effects of two enkephalinase inhibitors (thiorphan and acétorphan) and DALAMIDE on gastric emptying of fat or non-fat meals were evaluated in mice. When administered intraperitonally at low doses (0.1 and 0.2 mg/kg) 30 min prior to a fatty (milk) meal, both thiorphan and acetorphan increased significantly (P less than 0.01) gastric emptying; these effects were maximal for 0.2 and 0.1 mg/kg respectively and decreased progressively to be not significant for doses higher than 5 mg/kg for thiorphan and 0.5 mg/kg for acetorphan. Similarly DALAMIDE given IP increased significantly (P less than 0.05) gastric emptying at doses of 0.5 and 1 mg/kg while a slowing of gastric emptying was obtained for 10 times higher doses. The effects of thiorphan (0.2 mg/kg) and DALAMIDE (0.5 mg/kg) were blocked by previous administration of naloxone (0.3 mg/kg) and methyl-naloxone (0.5 mg/kg) while only naloxone (0.3 mg/kg) blocked the slowing effect of high dose of DALAMIDE. Administered prior to a non-fat meal, thiorphan (1 mg/kg) stimulated gastric emptying and inhibited it at higher dosage (10 mg/kg). Neither acetorphan nor DALAMIDE at similar dosages affected the gastric emptying of a non-fat meal and the effects of thiorphan (1 and 0.1 mg/kg) were not blocked by naloxone (0.3 mg/kg). It is concluded that enkephalinase inhibitors (thiorphan and acetorphan) administered systemically stimulate the gastric emptying of a fat meal by increasing enkephalin levels in peripheral tissues, while thiorphan exhibits non-opiate effects on gastric emptying of a non-fat meal.     

A tetrapeptide isolated from hamster embryo with central opiate properties on gastrointestinal motility but not on pain perception

The effects of centrally administered kentsin (H-Thr-Pro-Arg-Lys-OH) on intestinal motility and on pain perception were investigated in rats chronically equipped with lateral ventricle catheters. Intestinal motility was recorded electromyographically from electrodes placed on the duodeno-jejunum; analgesia was evaluated by the hot-plate and tail-flick tests. Kentsin (4.0 ug/kg), injected intracerebroventricularly (ICV) 2 hours after the beginning of a meal, restores the "fasted" i.e. the migrating myoelectric complex of intestinal motility, while a 5 times higher dose administered subcutaneously was inactive. The ICV effect of kentsin was blocked by previous ICV administration of naloxone (400 ug/kg). In contrast, kentsin administered ICV (40 ug/kg) or SC (200 ug/kg) did not affect significantly (P greater than 0.05) the time latency in the two analgesic tests during 90 minutes after its administration and did not significantly modify the analgesic effects of (D5-Ala2, Met5) enkephalinamide. We conclude that kentsin when centrally administered acts on opiate receptors to alter gastrointestinal motility but without effects on pain perception.     

Light Activation of NADP-Malate Dehydrogenase in Guard Cell Protoplasts from Vicia faba L

Light-induced swelling of guard cell protoplasts (GCP) from Vicia faba was accompanied by increases in content of K⁺ and malate. DCMU inhibited the increase of K⁺ and malate, and consequently swelling.

Effect of light on the activity of selected enzymes that take part in malate formation was studied. When isolated GCP were illuminated, NADP-malate dehydrogenase (NADP-MDH) was activated, and the activity reached a maximum within 5 minutes. The enzyme activity underwent 5- to 6-fold increase in the light. Upon turning off the light, the enzyme was inactivated in 5 minutes NAD-MDH and phosphoenolpyruvate carboxylase (PEPC) were not influenced by light. The rapid light activation of NADP-MDH was inhibited by DCMU, suggesting that the enzyme was activated by reductants from the linear electron transport in chloroplasts. An enzyme localization study by differential centrifugation indicates that NADP-MDH is located in the chloroplasts, NAD-MDH in the cytosol and mitochondria, and PEPC in the cytosol. After light activation, the activity of NADP-MDH in guard cells was 10 times that in mesophyll cells on a chlorophyll basis. The physiological significance of light-dependent activation of NADP-MDH in guard cells is discussed in relation to stomatal movement.

     

慢性心功能不全大鼠心脏和血淋巴细胞β-肾上腺素受体的改变

在主动脉与肾动脉缩窄造成的慢性心功能不全大鼠,血浆儿茶酚胺浓度增高;心脏β-肾上腺素受体(β-AR)数量增加,其中β_1-AR及其mRNA增加,而β_2-AR及其mRNA不变;左心房异丙基肾上腺素(ISO)浓度-收缩效应曲线右移;而心肌ISO浓度-cAMP蓄积曲线无显著改变;血淋巴细胞β-AR数量显著减少.结果提示心功能不全时心脏β_1-AR数量增多,但其介导的正性变力效应反而降低,在cAMP生成以后的信号转导过程或心肌收缩成分功能存在障碍,而血淋巴细胞β-AR的改变与心脏β-AR的功能改变平行.     

Changes in endogenous cytokinin levels in partially synchronized cultured tobacco cells

During the course of partially synchronized cell divisions in cultured tobacco (Xanthi) cells the amount of endogenous cytokinins in the butanol-soluble fraction increased 5 to 10 times in 3 hours and paralleled the increase in frequency of mitosis. Among three cytokinins detected in tobacco cells, the activity corresponding to the R_F of authentic zeatin in thin layer chromatography changed in parallel with the mitotic index.     

Identification of Cytokinins of Root Nodules of the Garden Pea, Pisum sativum L

Five cytokinin activities which induced soybean callus proliferation were detected in ethanol extracts of root nodules of the garden pea (Pisum sativum L., cv. Little Marvel). The most active factors among them were identified as zeatin and its riboside on the basis of their mobility on thin layer chromatography in three solvent systems. Smaller activities of zeatin ribotide, isopentenyladenine and its riboside were also detected. Cytokinin activity gradually decreased with the cultivation period, but no qualitative change in the active compounds was found.     

灰飞虱与褐飞虱种内和种间密度效应比较

在人工气候室内比较研究了灰飞虱和褐飞虱在汕优63和秀水11上的种内和种间密度效应对其主要生物学参数的影响,结果表明两种稻飞虱均存在显著的种内竞争,主要表现为随着密度增加,若虫发育历期延长、若虫羽化率下降、雌成虫寿命缩短、每雌产卵量下降。种内密度效应与稻飞虱种类和寄主品种有显著互作关系,灰飞虱种内竞争较褐飞虱明显,二者在适宜寄主上种内竞争更为明显。同时,两种稻飞虱存在着显著的种间密度效应,主要表现为异种存在时的促进作用,即异种共存时若虫历期缩短、若虫羽化率提高、雌虫寿命延长、每雌产卵量增加。种间密度效应也与稻飞虱种类和寄主品种有显著互作关系,两种共存对灰飞虱的有利作用显著大于对褐飞虱的有利作用,在欠适宜寄主上种间互利效应更为明显。最后,本文对稻飞虱种内和种间密度效应的机制和进化意义进行了讨论。     

鸭疫里默氏杆菌Mtan对底物SAH的催化活性

【目的】分析鸭疫里默氏杆菌(Riemerella anatipestifer,RA)不同血清型pfs基因的序列差异,并开展其编码蛋白S-腺苷高半胱氨酸核苷酶(Mtan,又称Pfs)的催化活性研究。【方法】PCR扩增9株不同血清型RA的pfs基因,分析其核苷酸序列的同源性;构建该基因的重组表达载体p Cold-RA-pfs,表达、纯化RA的重组蛋白Mtan(RA-Mtan);测定RA-Mtan对底物S-腺苷同型半胱氨酸(S-adenosylhomocysteine,SAH)的催化活性,运用哈维弧菌报告菌株BB170检测催化底物的自诱导物2(Autoinducer-2,AI-2)活性。【结果】对RA的pfs序列分析结果表明,不同血清型RA的核苷酸一致性在93.9%-100%之间;SDS-PAGE检测结果表明,RA-Mtan呈可溶性表达;酶活测定表明RA-Mtan和禽致病性大肠杆菌(Avain pathogenic Escherichia coli,APEC)的Lux S蛋白共同作用于底物时,可产生浓度为176.7μmol/L的同型半胱氨酸(Homocysteine,HCY);AI-2活性检测结果表明,产生的AI-2具有生物学活性。【结论】RA不同血清型的pfs高度保守,RA pfs基因的编码产物RA-Mtan在体外具有催化SAH的活性,RA-Mtan和禽致病性大肠杆菌的Lux S蛋白共同作用于底物SAH时,能产生有活性的AI-2,为进一步研究pfs对RA的调控作用提供参考。     

非损伤微测技术在植物根系生长发育研究中的应用

进出组织和细胞的无机离子的运输对植物生命极为重要。膜片钳和荧光成像等传统方法技术要求高、设备要求先进且测得的数据很难直接用于样品植株上。"非损伤微测技术"因其具有非损伤性、高的时空分辨率的特点,使其可以在不破坏样品的前提下测到样品的生理特征和生命活动规律,测得的数据生理真实性高,可以直接应用于样品植株上。文章较详细地介绍了运用非损伤微测技术,尤其是用于测量离子流的SIET技术和MIFE技术,及其在测量植物根部净离子流量以研究植物根系生长发育的一些报告。     

Preparation of androsta-1,4-diene-3,17-dione from sterols using Mycobacterium neoaurum VKPM As-1656 strain

A product of microbiological cleavage of the sterols side chain, androsta-1,4-diene-3,17-dione, is toxic for bacteria, in particular, actinobacteria of the genera Mycobacterium and Arthrobacter. Sterols were transformed into androsta-1,4-diene-3,17-dione by culturing the M. neoaurum VKPM An-1656 strain in a high yield, provided that a sorbent was used for elimination of contact between the bacterial cells and the product. Unlike the cholesterol side chain, the more branched chains of phytosterols were cleaved in the presence of M. neoaurum at a high rate only under turbulent stirring of the culture medium, which intensified the formation of hydrocarbonate ion from NaNI3 in situ.