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Female Wistar rats were trained in a Skinner-box, 30 trials per day in a dark room to establish operant defence conditioning. Training started with a light (15 s), then combined with footshock for further 8 s. When the rats learned to press the key to avoid footshock within 15 s, conditioned response was considered established. After the rats reached a conditioning rate (CR) above 80% for 5 days, cannulae were implanted into caudate-putamen. Two to three days later, Met-enkephalin (MEK) or bestatin (an aminopeptidase inhibitor) was injected bilaterally into caudate-putamen. 30 min, 2 h, 24 h and 48 h after injection, conditioning tests were conducted, with each session consisting of 30 trials. Control experiments were done when 0.9% NaCl (NS) was injected. After injection of NS, CR maintained above 80% in all 4 test sessions. MEK (60 ng/rat) or bestatin (10 micrograms/rat) significantly lowered the CR during the 30 min and 2 h test session. In the latter case, the latency (L) was also prolonged. However both CR and L returned to the control level in the 24 h and 48 h test sessions. Naloxone (2 mg/kg, i.p.) blocked the conditioning-depression effect of bestatin. No significant alteration was seen in locomotor activity after MEK or bestatin injection. The results suggest that enkephalin in caudate-putamen may be involved in the regulation of retrieval of conditioning. Bestatin mimics the effect of MEK on conditioning reflex probably by increasing production of endogenous enkephalin. 相似文献
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Carbonates and rare shales of the ca 700-800 Ma old Draken Conglomerate Formation, northeastern Spitsbergen, preserve a record of environmental variation within a Neoproterozoic tidal flat/lagoon complex. Forty-two microfossil taxa have been recognized in Draken rocks, and of these, 39 can be characterized in terms of their paleoenvironmental distributions along a gradient from the supratidal zone to permanently submerged lagoons. Supratidal to subtidal trends include: increasing microbenthic diversity, increasing abundance and diversity of included allochthonous (presumably planktonic) elements, decreasing sheath thickness of mat-building organisms (with significant taphonomic consequences), and an increasing sediment/fossil ratio in fossiliferous rocks. Five principal and several minor biofacies can be distinguished. The paleoecological resolution obtainable in the Draken Conglomerate Formation rivals that achieved for most Phanerozoic fossil deposits. It documents the complexity and diversity of Proterozoic coastal ecosystems and indicates that both environment and taphonomy need to be taken into explicit consideration in attempts to understand evolutionary trends in early fossil record. Three species, Coniunctiophycus majorinum, Myxococcoides distola, and M. chlorelloidea, are described as new; Siphonophycus robustum, Siphonophycus septatum, and Gorgonisphaeridium maximum are proposed as new combinations. 相似文献
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Sørensen BS Fukata H Jensen PS Andersen AH Christiansen K Fukasawa H Westergaard O 《Plant physiology》1991,95(2):659-662
We have investigated cauliflower (Brassica oleracea) topoisomerase II with respect to its interaction with DNA and demonstrate that the enzyme shares the characteristics of topoisomerase II purified from a variety of phylogenetically remote organisms. In the presence of the 2-nitroimidazole Ro 15-0216, cauliflower topoisomerase II-mediated DNA cleavage is extensively stimulated (approximately 20-fold) only at a site recognized as a major cleavage site for the enzyme in the absence of drug. The conservation of the enzyme's DNA specificity in the presence of Ro 15-0216 is in contrast to the effect exerted by traditional topoisomerase II inhibitors, which cause enzyme-mediated cleavage to take place at a multiple number of DNA sites. Ro 15-0216 may therefore prove useful as a tool in the elucidation of the enzyme's DNA interaction sites and its involvement in nucleic acid metabolism in plant cells. 相似文献
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Repeated transvaginal ultrasound guided puncturing of visible follicles was performed for ovum pick-up (OPU) during Periods A and B, each of which lasted 3 mo. During Period A, 10 cows (A) were used in the study. Period B commenced 1 mo after Period A and two groups of animals were used. The first group (B1) consisted of 9 of 10 cows from Group A. The second experimental group of animals in Period B consisted of 11 cows (B2) which had not been submitted to previous puncture. During the study, all visible follicles larger than 3 mm were punctured and aspirated three times, on Day 3 or 4, Day 9 or 10 and Day 15 or 16 of the estrous cycle. The mean estrous cycle length (+/- SEM) after repeated follicle puncture did not differ among the three groups and was 22.3 +/- 0.4, 22.5 +/- 0.4 and 22.1 +/- 0.3 d for groups A, B1 and B2, respectively. The mean total number (+/- SEM) of punctured follicles per estrous cycle in Group A (13.1 +/- 0.5) was significantly larger than in Groups B1 (11.2 +/- 0.4) and B2 (11.6 +/- 0.4). The largest number of follicles punctured for ovum pick-up in all three groups was always on Day 3 or 4 of the estrous cycle: 4.9 +/- 0.3 follicles; the mean (+/- SEM) number of punctured follicles on Day 9 or 10 and Day 15 or 16 was significantly (P<0.05) lower: 3.4 +/- 0.2 and 3.9 +/- 0.2, respectively. In Period A, primarily 3- to 5-mm follicles were punctured per estrous cycle, while 6- to 10-mm follicles were predominantly punctured in Period B (P<0.05). Recovery rate of oocytes on Day 3 or 4, Day 9 or 10 and Day 15 or 16 were 53, 50 and 52%, respectively. Most oocytes (P<0.05) were aspirated from follicles smaller than 10 mm. 相似文献
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