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621.
The sexual cycle of the cuttlefish, Sepia officinalis, fromthe northern part of the Bay of Biscay was followed over severalyears (1988 to 1990 and 1992 to 1993). Successive maturity stagesare reached at the same time regardless of site in the northernpart of the Bay. In this area, the majority of cuttlefish reproduceduring their second year of life (group II) whereas the remainderreproduce in their first year (group I). The first visible signsof sexual development concern the testis in males and the genitaltract in females. Males mature earlier than females: the firstspermatophores appear in July (group II) and October (groupI) while mature eggs appear from December (group II) and March(group I). The breeding season lasts from about mid-March tolate June (3.5 months). (Received 2 February 1996; accepted 30 May 1996) 相似文献
622.
Quantification of the histochemical reaction for alkaline phosphatase activity using the indoxyl-tetranitro BT method 总被引:5,自引:0,他引:5
Summary The indoxyl—tetranitro BT method for the demonstration of alkaline phosphatase activity has been optimized and its validity for quantitative histochemistry tested. The study has been performed with model films of polyacrylamide gel incorporating homogenate of rat liver and with cryostat sections from the same livers. Addition of polyvinyl alcohol to the incubation medium greatly improved the localization of the final reaction product in cryostat sections. In polyacrylamide films, the formazan production specifically due to alkaline phosphatase was highest when using a medium containing 100mm Tris-HCl buffer, pH 9.0, 0.2–1.0mm substrate, 0.32mm 1-methoxyphenazine methosulphate, 10mm MgCl2, 5mm sodium azide and 1mm tetranitro BT. For the incubation of cryostat sections in the presence of polyvinyl alcohol, the same medium could be used but the optimum concentrations of substrate and tetranitro BT appeared to be 1–2mm and 5mm respectively. The test minus control reaction was specific for alkaline phosphatase activity and could be inhibited completely with tetramisole. The test minus control reaction was linear with time up to 30 min with model films and up to 15 min with cryostat sections. The formazan production was also linear with the amount of homogenate incorporated in model films and with section thickness up to 18 µm and therefore, the reaction obeyed the Beer—Lambert law. Variation of the substrate concentration yielded aK
M of 0.05mm for aqueous media and aK
M of 0.55mm for polyvinyl alcohol-containing media. The inhibition with tetramisole appeared to be competitive withK
i = 0.07mm for aqueous media andK
i = 0.7mm for polyvinyl alcohol-containing media. These values indicate that the indoxyl—tetranitro BT method is considerably more sensitive than any metal salt or diazonium salt method developed so far. It is concluded that the optimized method described here is a specific, sensitive and valid quantitative histochemical method for the demonstration of alkaline phosphatase activity. 相似文献
623.
624.
丹酚酸B对高糖日粮小鼠消化系统自由基水平的影响 总被引:1,自引:0,他引:1
本文研究了丹酚酸B(salvianolic acid B,Sal B)对灌注及长期摄食高糖小鼠活性氧自由基(reactive oxygen species,ROS)的影响.结果表明:灌胃高糖使小鼠全血ROS于1.5 h达到最大值,灌胃葡萄糖的ROS释放量显著高于蔗糖(P<0.05);灌胃高糖使小鼠血糖浓度于0.5 h达到最高,灌胃葡萄糖的小鼠血糖浓度有高于灌胃蔗糖的小鼠血糖浓度的趋势(P>0.05);添加Sal B后并没有改变灌胃高糖小鼠的全血ROS释放和血糖浓度变化趋势,但有降低血糖趋势(P>0.05),显著减少了ROS的释放量(P<0.05);添加Sal B后显著降低长期高糖膳食小鼠的全血、肝脏、胰腺、胃、十二指肠、空肠和回肠的ROS释放量. 相似文献
625.
626.
The habitats and foods used by a sample of marked individuals and by the whole population of Oystercatchers Haematopus ostralegus wintering on the Exe estuary, South Devon, are described. In the spring and early summer, only a few hundred immatures were present. Two thousand adults and several hundred juveniles arrived in late summer from the breeding grounds and remained until the following spring. The majority of the birds were then adults. At low water, most adults fed on the mussel Mytilus edulis beds and ate mussels. Most individuals specialised on this prey and ate little else. Some adults fed on mud-flats and sandflats within the estuary and along the coast, and specialised on a mixture of Nereis diversicolor and Scrobicularia plana or on Cerastoderma edule or Littorina spp. Though some juveniles ate mussels from the time they arrived, most did not. In winter, they took Scrobicularia on mudflats, earthworms Lumbricidae and leatherjackets Tipulidae larvae in fields and Spisula and mussels along the coast. At other times of year they mainly ate Nereis. However, as they grew older, more birds began to specialise on mussels, especially in their second, third and fourth summers when the adults were away. At high water, most birds roosted at the mouth of the estuary or along the coast. However, several hundred fed in the fields in winter with more doing so late in the winter on warm days on Neap tides when less time was available for feeding on the estuary in daylight. Birds feeding on Nereis and Scrobicularia at low water were most often seen in the fields, irrespective of age. Birds feeding on Mytilus and Littorina occurred there rarely, but no bird eating Cerastoderma was seen there. The findings are discussed in relation to age differences in feeding skills and ability to compete successfully with other birds. 相似文献
627.
InRosa hybridaL. cv. Ruidriko Vivaldi®, theeffect of position on growth and development potentials of axillarybuds was investigated by single internode cuttings excised alongthe floral stem and its bearing shoot. The experiments werecarried out in both glasshouses and in a phytotron. The studyfirstly concerned the development of the primary shoot fromthe onset of bud growth until anthesis. The primary shoot wasthen bent horizontally to promote the growth of the two mostproximal secondary buds, the collateral buds, already differentiatedinside the primary bud. They gave rise to basal shoots. In thebasipetal direction, the axillary buds along the floral stemexhibited both an increase in the lag time before bud growthand a decrease in bud growth percentage, demonstrating the existenceof a physiological basipetal gradient of inhibition intrinsicto the buds or due to short range correlations. The same basipetalgradient of inhibition was observed along the floral stem andits bearing shoot, demonstrating that the age of the bud wasnot a major factor in determining the rate of bud growth. Afterbending the primary shoot, the percentage of collateral budgrowth was also affected by the cutting position. The more proximalthe cutting, the lower the sprouting ability of collateral buds.The growth potential of these buds appeared to be already determinedinside the main bud before cutting excision.Copyright 1998 Annalsof Botany Company Axillary bud; basal shoot; cutting; development; endodormancy; growth; paradormancy; position; primary shoot;Rosa hybridaL.; rose; secondary bud; topophysis. 相似文献
628.
629.
630.
临床决策能力是一个医生的必备能力之一,是医学教育中必要且重要的培养目标之一。目前对医学生临床决策能力的培养没有形成完备的体系,一般安排在高年级阶段进行,为时较晚。如何把临床决策能力的培养融入低年级基础课中,以尽早开展能力训练值得探索研究。本研究以医学遗传学课程为例,结合探究式教学方式的特点,模拟临床决策思维过程的各细分模块,优化了课程设计,探索在低年级课程中融入临床决策能力的培养。结果提示:探究式课程设计能充分调动学生主动性,增加学生分析、思考的投入;在教师引导下,促使学生依循临床决策思维的过程得到有效地训练。最后,整理分析了探究式课程设计及实践的思路,总结了设计原则和要点,反思了教学中的经验得失。 相似文献