首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   12篇
  完全免费   4篇
  2018年   1篇
  2016年   3篇
  2011年   1篇
  2008年   1篇
  2006年   2篇
  2005年   1篇
  2004年   1篇
  2000年   2篇
  1995年   1篇
  1989年   1篇
  1985年   1篇
  1981年   1篇
排序方式: 共有16条查询结果,搜索用时 46 毫秒
1.
棘尾虫无小核镜像骈体的获得及其生殖行为的实验观察   总被引:3,自引:0,他引:3  
史新柏  丘子健 《动物学报》1989,35(4):364-369
用在分裂期进行显微手术的方法和在陈旧培养中诱导的方法,从贻贝棘尾虫天然无小核系S_(10)中获得了无小核镜像骈体。对骈体的各种生殖行为进行了观察,并用孚尔根和改进的黑色素染色技术揭示了它们的细胞学细节。发现在本文描述的无小核骈体和过去报告的有小核骈体之间,在二分裂和生理再生上没有显著区别。无小核骈体和正常单体S_7之间的接合命运则是多样化的。在630个这样的接合对中,有257对发生了真正的接合并形成接合后体;有153对接合不久包囊化;在其余的220对中,一个接合体吸收了另一个,变成营养型的单体和有小核的骈体。前者占总吸收者的96.8%,后者只占3.2%。对接合和吸收两种情况的细胞学事件进行了详细观察。无小核骈体中的两组细胞质和双套大核能吸引其配偶中的小核,形成自己新的双套大核胚基及小核胚基,在本文的讨论中受到充分注意。  相似文献
2.
The previous study showed involvement of spinal glia in tetanically sciatic stimulation-induced long-term potentiation (LTP) of C-fiber-evoked field potentials in the spinal dorsal horn. In the present study, the electrophysiological recording and paw withdrawal threshold (PWT) to von Frey stimulation were assessed following unilaterally tetanically sciatic stimulation in rats. Tetanic stimuli elicited LTP of both A- and C-fiber-evoked field potentials. After stimulation with the same parameter, bilateral PWTs to mechanical stimuli decreased. Intrathecal administration of fluorocitrate (1 nmol/10 microl), an astrocyte inhibitor, partially inhibited tetanic stimulation-induced reduction of bilateral PWTs. A similar effect also occurred at the contralateral side. And this bilateral inhibition of mechanical threshold lasted 8 days. Similarly, intrathecal administration of d-amino acid oxygenase (50 microg/mul, 10 microl), D-serine inhibitor, partially inhibited tetanic sciatic stimulation-induced reduction of bilateral PWTs for 24 h. The results showed that spinal glia plays an important role in bilaterally mechanical allodynia by tetanic sciatic stimulation of the sciatic nerve.  相似文献
3.
Gao JY  Ren PY  Yang ZH  Li QJ 《Annals of botany》2006,97(3):371-376
BACKGROUND AND AIMS: Gesneriaceae is a pantropical plant family with over 3000 species. A great variety of pollination mechanisms have been reported for the neotropical members of the family, but the details of buzz-pollination and enantiostyly for the family have not been described. We investigated the floral biology and pollination ecology of Paraboea rufescens in Xishuangbanna, south-west China, considering three aspects: (1) the type of enantiostyly exhibited; (2) whether the species is self-compatible; and (3) whether pollinator behaviour could enhance the precision of pollen transfer between flowers of contrasting stylar orientation. METHODS: Flowering phenology was monitored once a month during vegetative growth, and once a week during flowering both in the field and under cultivation. Pollination manipulations and pollinator observation in the field were conducted. KEY RESULTS: Anthesis occurred early during the morning, and flowers remained open for 1-5 d, depending on weather conditions. Controlled pollinations revealed that P. rufescens is self-compatible, and exhibited inbreeding depression in seed set. Plants were pollinator limited in natural populations. The similar stylar deflection among flowers within a plant limits autonomous self-pollination as well as pollination between flowers. Two species of bumble bees (Bombus spp.), Amegila malaccensis and Nomia sp. effectively pollinated P. rufescens. These pollinators visited flowers in search of pollen with almost the same frequency. None of the pollinators appeared to discriminate between left- or right-handed flowers. CONCLUSIONS: Paraboea rufescens exhibits monomorphic enantiostylous flowers and a buzz-pollination syndrome. Floral morphology in P. rufescens and pollinator foraging behaviour seems likely to reduce self-pollination and pollinations between flowers of the same stylar deflection.  相似文献
4.
李莉  邱子健  陈瑛  孙寓娇 《动物学报》2004,50(5):808-816
棘尾虫是细胞表面具有特殊纤毛结构排列方式的复杂下毛类纤毛虫。其镜像骈体的两列纤毛结构几乎完全是左右对称排列 ,一个是正常方式排列的 ,另一个是相反方式排列。本文包括两项移接实验 :1)将棘尾虫口对镜像骈体一侧细胞的后半部分倒转 180°与另一侧细胞的前半部分对接 ;2 )将此种骈体一侧后半部分调转90°与另一侧细胞的前半部分对接。接后定时分期固定接块 ,以蛋白银染色法 ,观察其发育过程及结果。实验 1的发育结果为有的仍形成口对镜像骈体 ;有的成为末端对末端的镜像骈体。实验 2的发育结果为全部成为口对镜像骈体。两项实验结果均可用位置值假说解释 ,实验 1属于位置值插入的结果 ;实验 2为位置值添加的结果。为何实验Ⅰ有的发育成口对镜像骈体有的发育成末端对末端的镜像骈体 ,而实验 2却全部发育成口对镜像骈体呢 ?这是接块发育中是否发生对折的结果。Shietal.(1991)认为与预存的缘棘毛和是否具有完整表膜的面积大小有关系。接块在发育中是否发生对折与接块的伤口一侧面积大小和具完整表膜有关系。接块具完整表膜和缘棘毛的一侧由于新缘棘毛和口围带的发育生长 ,造成该侧的伸张 ,产生前后两接块向伤口一侧对折的压力 ,从而接块发生对折形成口对镜像骈体。我们认为还应有其它因素 :(1)与细胞#0;  相似文献
5.
将贻贝棘尾虫镜像骈体横断后,再将前后切块的左右半细胞做对折骈接。前半部分切块对折后有67%成为左右镜像对称骈体;有33%形成末端对末端的镜像骈体,最后分开成为一正常虫体和一具有反向口围的单体虫。后半部分切块对折后基本上全部形成左右镜像对称骈体。这一事实可用位置值的添加理论来解释。但也显示出预存的缘棘毛在确定形成左右镜像对称骈体或末端对末端的镜像骈体中所起的重要作用。  相似文献
6.
1,6-Dideoxygalactostatin, the mirror image of 1-deoxy-L-fuconojirimycin, was efficiently prepared from 2,3-O-isopropylidene-L-lyxonolactone in four steps and evaluated as a glycosidase inhibitor.  相似文献
7.
The effect of contest and scramble competition on the growth performance of wild and sea-ranched juvenile (0+) brown trout, Salmo trutta, originating from the River Dalälven, Sweden was scrutinised. In a mirror image stimulation (MIS) experiment, and in a 35000 1 stream-water aquarium the trout was studied for three weeks (20 individuals in each of four replicates). Activity in MIS was correlated with swimming activity in the stream-water aquarium. The MIS results could not be used for predicting any social behaviour patterns or the growth performance of a fish. No behavioural differences between the two strains were noted. However, the sea-ranched strain grew faster than the wild one, both in regard to the RNA/DNA ratio and the weight-specific growth rate. Because the strains had the same genetic background and prior to the experiments were raised under similar hatchery condition, the results of this study suggest that the sea-ranching process selects for faster juvenile growth in brown trout. The ultimate mechanisms underlying the faster growth by the domesticated strain probably involves both contest and scramble competition.  相似文献
8.
The effects of the digenean trematode parasite Telogaster opisthorchis on aggression and competitive ability in male upland bullies ( Gobiomorphus breviceps ) were examined using mirror-image stimulation (MIS) techniques and dyadic contests for nest sites between pairs of males. Parasite load had no significant effect on male aggression or success in dyadic contests, nor was aggression a predictor of the likely winner of these contests. The results are discussed with relation to the role of parasites in male-male competition and to possible problems in using MIS techniques for studies on dominance and aggression in fish.  相似文献
9.
Analysis or the development of microtubular structures in the mirror-image doublet cell lines of a hypotrich ciliate,Paraurostyla weissei, revealed several modifications in standard morphogenesis. Ciliary primordia can be formed without prior disaggregation of the preformed marginal cirri, on the left instead of the right hand side of an old row. Two or more overlapping streak segments may originate from disaggregating old marginal cirri, giving rise to two or three cirral rows. Inverted marginal cirri occasionally develop de novo and can be propagated clonally. Thus the modifications in developmental processes concern the positioning of primordia, the number of forming structures and the polarity of these structures. The microtubular triplets in the basal bodies of normal and inverted cirri do not differ, indicating that the large-scale reversal of the overall pattern has no effect on the assembly of microtubular triplets. The study indicates that the control of cytotactic propagation of compound microtubular structures is either modified or partially suppressed in a morphogenetic field where the positional values along one of the main cellular axes (lateral) have been reversed.  相似文献
10.
Summary YoungBunodactis verrucosa Pennant at the 12 tentacle stage are employed to test the applicability of the polar coordinate model to coelenterate regeneration. The animals are cut along every radius into fragments of 3 to 9 segments. Most fragments are patent 3–4 weeks later, but small fragments have a higher mortality rate than large fragments. Some fragments do not regenerate and occasionally tentacles fuse, thereby reducing the number of segments. Small fragments tend to regenerate more tentacies than large fragments, but large fragments may regenerate great numbers of supernumerary tentacles. Twenty-two percent of the fragments restore the missing number of tentacles, while 76% of all fragments produce an even number of tentacles.Fragments restoring the correct numbers of tentacles show a marked tendency to form the correct tentacles (regulative regeneration). Fragments regenerating two less than the number of tentacles already present show a marked tendency to reproduce tentacles of the types already present (miror image formation). Other fragments produce missing segments (forward regeneration), or those already present (reverse regeneration) at lower frequencies.No fragments beginning or ending with the number 1 directive tentacle fail to regenerate entirely, while first cycle segments maximally remote from segment 1 are associated with the absence of regeneration. No fragments beginning or ending with the number 4 directive tentacle fail to undergo forward regeneration, regulate or produce a mirror image when the appropriate number of segments are regenerated. In contrast, segment 4 is associated with a low frequency of reverse regeneration, and second cycle segments cut away from immediate contact with segment 4 show an increase in the frequency of reverse regeneration. Controls through morphogenic substances rather than polar coordinates seem to explain these results. Such substances would control the number and direction of tentacle regeneration.This work was performed while the author was on sabbatical leave from the University of Pittsburgh at the Stazione Zoologica di Napoli. The author gratefully acknowledges the assistance of Mr. Ciro Gargiulo and of Ms. Gisella Princivalli. This work was supported by a travel grant from the United States Italy Cooperative Science Program of the National Science Foundation. The paper is dedicated to Dr. Alberto Monroy whose generosity made it possible  相似文献
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号