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三疣梭子蟹精子顶体反应前后胞内Ca~(2+)的变化 总被引:1,自引:0,他引:1
应用激光扫描共聚焦显微镜(LSCM)和Fluo-3/AM荧染技术对三疣梭子蟹精子顶体反应前后的胞内Ca2 变化进行了观察和检测.结果显示,在精子顶体反应过程中,胞内Ca2 主要分布在细胞核、穿孔器和胞质膜残存处,胞内Ca2 浓度([Ca2 ]I)总体上呈现先上升后下降的趋势.顶体反应前精子的平均荧光强度为35.95±5.71;穿孔器前伸、顶体囊膜翻转阶段精子的平均荧光强度为66.80±7.35;顶体囊膜脱落、顶体丝形成阶段精子的平均荧光强度为3.87±2.82;上述各阶段间精子荧光强度有极显著差异(P<0.01).顶体反应穿孔器前伸、顶体囊膜翻转阶段的精子相比顶体反应前精子,[Ca2 ]I显著提高;而在顶体囊膜脱落、顶体丝形成阶段,[Ca2 ]I则急剧下降,只在顶体丝基部胞质膜残存处有微量Ca2 存在.初步探讨了三疣梭子蟹精子顶体反应前后胞内Ca2 变化的功能. 相似文献
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应用扫描电镜技术观察了三疣梭子蟹的精卵相互作用。未受精成熟卵表面较光滑、无受精孔,但有许多微孔。成熟卵外被卵膜,内为卵母细胞。在卵自然产出后,精子迅速发生顶体反应使顶体囊外翻并压入卵膜,而核仍留于卵膜外,核辐射臂不收缩且仍附着于卵膜上。三疣梭子蟹为多精着卵和多精入卵膜。精子外翻顶体囊压入卵膜后,核辐射臂陆续回缩直至消失。作用于顶体丝上的卵母细胞主动拖精作用对入卵膜精子的进一步入卵、受精至关重要,环状卵膜突起的向心伸展也有一定的协助作用。探讨了着卵精子的顶体反应、精子入卵膜的机制及卵子在精子入卵过程中的作用 相似文献
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透射电镜下观察长江华溪蟹成熟精子的形态和超微结构。精子呈椭球形,无鞭毛,具数条由核延伸而成的辐射臂精子。由球形的顶体,膜复合体,核杯及辐射臂组成,顶体由头帽,亚帽带,丁体囊及中央管组成。在中央管的基部发现有中心粒。核膜与质膜紧贴在一起形成了精子的界膜。 相似文献
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锯缘青蟹精子超微结构的研究 总被引:20,自引:4,他引:20
利用光镜和电镜观察了锯缘青蟹成熟精子的形态和超微结构。精子呈陀螺形,无鞭毛,在较宽的一端环生着10余辐射臂。精子由球状的顶体、核杯以及核衍生的辐射臂三部分组成。顶体包括顶体管和顶体囊,后者包绕在顶体管的中央管周围,并可分为头帽带,内层和外层区。顶体被杯状的核包裹,仅头帽露于精子表面。成熟的精子中,位于核杯和顶体管之间的核膜出现局部断续或消失,中心粒和一些胞器出现的核杯腔中。 相似文献
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用卵水 (eggwater)对中国对虾纳精囊内精子进行人工诱导顶体反应 ,并分别用透射电镜和SDS—PAGE及复性单向电泳对顶体反应的超微结构变化和蛋白成分的变化进行了研究。结果表明 ,中国对虾精子在人工诱导条件下 3 0min内有 5 0 %以上完成反应。电镜观察证明 ,中国对虾精子的顶体反应可分为两个阶段 :(1 )棘突的收缩 ;(2 )顶体颗粒的释放和顶体帽的消失。在反应过程中许多蛋白被降解 ,且反应开始后精子本身释放出一些水解酶类 ,主要有 2 0 0kDa、1 3 0kDa、66kDa、5 3kDa、48kDa和 41kDa 6种。在对卵水成分的初步分析中发现两种分子量约 2 0 0kDa的蛋白。 相似文献
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采用相同种类卵水诱导的方法对直翅目,蟋蟀科,黄脸油葫芦的受精囊精子的顶体反应过程进行系统观察.发现黄脸油葫芦精子顶体反应可划分为3个阶段,第1阶段,精子质膜膨胀、断裂或丢失;第2阶段,顶体复合体的顶体外层与顶体本体外膜发生融合,囊泡化;第3阶段,顶体复合体大部分脱落,只留有短锥状的顶体位于核前端.据观察,蟋蟀精子质膜不参与囊泡形成,此结果与家蝇及哺乳类的猪、牛、绵羊、猕猴精子的顶体反应结果很相似.经过比较发现卵水对受精囊内精子的诱导率明显高于精巢内,据分析,可能与精子的生理成熟有关,即便受精囊内精子比精巢内精子更趋于成熟.与其他学者的实验结果相比,蟋蟀精子顶体反应率与家蝇的相似,但明显低于其他动物.这可能与动物的授精方式有关. 相似文献
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Ectogenesis, or the use of an artificial womb to allow a foetus to develop, will likely become a reality within a few decades, and could significantly affect the abortion debate. We first examine the implications for Judith Jarvis Thomson’s violinist analogy, which argues for a woman’s right to withdraw life support from the foetus and so terminate her pregnancy, even if the foetus is granted full moral status. We show that on Thomson’s reasoning, there is no right to the death of the foetus, and abortion is not permissible if ectogenesis is available, provided it is safe and inexpensive. This raises the question of whether there are persuasive reasons for the right to the death of the foetus that could be exercised in the context of ectogenesis. Eric Mathison and Jeremy Davis have examined several arguments for this right, doubting that it exists, while Joona Räsänen has recently criticized their reasoning. We respond to Räsänen’s analysis, concluding that his arguments are unsuccessful, and that there is no right to the death of the foetus in these circumstances. 相似文献
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On the diversity of the Cladocera in the tropics 总被引:20,自引:13,他引:7
Henri J. Dumont 《Hydrobiologia》1994,272(1-3):27-38
The mythical concept of an impoverished tropical cladoceran fauna is refuted. On a planetary scale, around half of the cladoceran species presently known occur exclusively in the tropics-subtropics, often with considerable restriction to particular geographical subzones. On a regional (political) scale, the situation is often unclear because of the continued fragmentary nature of studies, and because political units are not a good basis for biogeographical comparisons. At the finest level of resolution (lake-perlake comparisons), there appears to be an upper limit of c. 50 cladoceran species per individual lake. No significant difference between lakes in the temperate zone and in the tropics could be established here. Daphnia is largely absent from the tropics, but is replaced by more Sidids, Moinids, and Bosminids, such that the average cladoceran community in the limnetic zone of a tropical lake is not characterized by less species but rather by lower population densities. This, in turn, is considered a consequence of higher prevalent predation levels in the tropics. 相似文献
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Ronald E. Martin Thomas Servais 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2020,53(1):5-31
We discuss the possible links between the fossil record of marine biodiversity, nutrient availability and primary productivity. The parallelism of the fossil records of marine phytoplankton and faunal biodiversity implicates the quantity (primary productivity) and quality (stoichiometry) of phytoplankton as being critical to the diversification of the marine biosphere through the Phanerozoic. The relatively subdued marine biodiversity of the Palaeozoic corresponds to a time of relatively low macronutrient availability and poor food quality of the phytoplankton as opposed to the diversification of the Modern Fauna through the Mesozoic–Cenozoic. Increasing nutrient runoff to the oceans through the Phanerozoic resulted from orogeny, the emplacement of Large Igneous Provinces (LIPs), the evolution of deep-rooting forests and the appearance of more easily decomposable terrestrial organic matter that enhanced weathering. Positive feedback by bioturbation of an expanding benthos played a critical role in evolving biogeochemical cycles by linking the oxidation of dead organic matter and the recycling of nutrients back to the water column where they could be re-utilized. We assess our conclusions against a recently published biogeochemical model for geological time-scales. Major peaks of marine diversity often occur near rising or peak fluxes of silica, phosphorus and dissolved reactive oceanic phosphorus; either major or minor 87Sr/86Sr peaks; and frequently in the vicinity of major (Circum-Atlantic Magmatic Province) and minor volcanic events, some of which are associated with Oceanic Anoxic Events. These processes appear to be scale-dependent in that they lie on a continuum between biodiversification on macroevolutionary scales of geological time and mass extinction. 相似文献
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Summary A tubular network was found in the terminal endings of the visual receptor cells in the human, the monkey (Macaca mulatta), the cat and the dog. These tubules are arranged in close groups in the vicinity of the synaptic lamellae and the invaginated dendrites. According to the form, diameter, density of the tubules and to the consistence of the network formed by them one can distinguish at these places an initial type (type I), a transitory (type II) and a vesicular one (type III). In the the type III branching, bizarre forms are frequent. The diameter of all the tubules reaches 500–600 Å, their density and walls being the same as in the synaptic vesicles.Similar networks also occur in the axons of the visual receptor cells of the monkey.
Zusammenfassung In den Endigungen der Photorezeptorzellen von Mensch, Affe (Macaca mulatta), Katze und Hund kommen aus Tubuli bestehende Komplexe vor. Organellenartig in geschlossenen Gruppen angeordnet, liegen sie in Nähe der synaptischen Lamellen und der invaginierten Dendriten. An diesen Stellen kann man nach Form, Durchmesser, Dichte und Konsistenz der von den Tubuli gebildeten Komplexe drei Typen unterscheiden: 1. einen initialen (Typus I), 2. einen Übergangstypus (Typus II) und 3. einen vesiculären Typus (Typus III). In letzterem kommen häufig verzweigte, bizarre Formen vor. Der Durchmesser sämtlicher Tubuli erreicht 500–600 Å. Ihre Dichte und ihre Wand gleicht denen der synaptischen Vesikel.Ähnliche Komplexe fanden wir auch in den Axonen der Photorezeptorzellen vom Affen.相似文献
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Methods of amperometry and potentiometric titration were used to follow dark respiration (DR) and apparent photosynthesis (AP) in the fucoids Ascophyllum nodosum (L.) Le Jol, Fucus vesiculosus L., and F. serratus L. from the Barents Sea littoral by the end of the 40-day-long polar night. The macroalgae were shown to manifest species-specific low rates of photosynthesis and respiration. However, in spite of their low photosynthetic status due to the effects of subzero temperature and prolonged low or zero illumination, the macroalgae have been able to restore DR and AP to the initial level already by the day 9; the ability to restore AP depended on the level of illumination. The study of the changes in the carbonate–bicarbonate system in the light and darkness demonstrated that the macroalgae grown in darkness, in contrast to those grown in twilight, could absorb bicarbonate in darkness; however, they lost this capacity after two-day-long illumination at an irradiance of 7 mol/(m2 s). Bicarbonate uptake in darkness and the capacity to restore the systems of photosynthesis and respiration in fucoid cells are discussed in the context of algal energy metabolism under the polar night conditions. 相似文献
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The voltage-gated potassium channel is currently one of the few membrane proteins where functional roles have been mapped onto specific segments of sequence. Although high-resolution structures of the transmembrane portions of three bacterial potassium channels, the tetramerization domain and the cytoplasmic ball are available, their relative spatial arrangement in mammalian channels remains a matter of ongoing debate. Cryo-electron microscopic images of the six transmembrane voltage-gated Kv channel have been reconstructed at up to 18 Å resolution, revealing that the T1 domain tetramerizes and is suspended below the transmembrane segments. However, the resolution of these images is insufficient to reveal the location of the third piece of the puzzle, the inactivating ball domain. We have used the aberrant interactions observed in a series of chimæric channels to establish that an assembled T1 domain restricts access to the cytoplasmic face of the channel, suggesting that the N-terminal ball and chain may be confined in the space between the T1 domain and the transmembrane portion of the channel. 相似文献
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Summary The choriocapillaris is a fenestrated capillary bed located posterior to the retinal pigment epithelium. It serves as the main source of supply to the photoreceptors, retinal pigment epithelium, and other cells of the outer retina. The permeability of these capillaries to intravenously injected ferritin (MW — approx. 480,000; mol. diam. 11 nm) was examined in the mouse, rabbit, and guinea pig, each of which is characterized by a different type of retinal vascularization. In all three species, the bulk of the ferritin remained in the capillary lumina, where it appeared to be blocked at the level of the diaphragmed fenestrae. Some ferritin was present in endothelial cell vacuoles. The results confirm previous work on the rat choriocapillaris and indicate that the barrier function of the choriocapillary endothelium is present even among species in which the retinal circulation differs significantly.Supported by NIH grant EY03418 相似文献
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Summary According to light- and electron-microscopic observations the pineal organ of the 3-day-old chicken consists of a prominent end vesicle and a tapering parenchymal stalk. During this stage the pineal lumen is in open communication with the third ventricle. However, in the 40-day-old chicken, which still possesses a well-developed end vesicle, the proximal portion of the pineal stalk displays regressive changes leading to local fragmentation. At this stage the pineal stalk is reduced, and the pineal lumen is missing. In 1-year-old chickens the parenchyma of the proximal portion of the stalk is further diminished, and in 3-year-old domestic fowl is completely displaced by bundles of collagenous fibers, only some nerve fibers being present. This post-hatching pineal development may reflect the sequence of changes leading from pineal sense organs to pineal glands.This work was supported by a grant-in-aid for Scientific Research from the Ministry of Education, Science and Culture of Japan 相似文献