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排序方式: 共有1365条查询结果,搜索用时 15 毫秒
1.
In September 2014, a pod of seven sperm whales (Physeter macrocephalus) was stranded along the Adriatic coast of Southern Italy. Concentrations of 20 essential and non-essential trace elements were quantified in the brain, muscle, liver and kidneys of three female sperm whales, which died in this event.The essential elements copper, iron, manganese and zinc showed low ranges of variability, suggesting a homeostatic physiological control, while selenium concentrations were associated with age. Molybdenum, nickel and chromium showed low ranges of concentrations and no evidence of preferential accumulation in selected organs. Very low concentrations of the non-essential elements cadmium, lead, tin and vanadium were detected in all tissues, suggesting a minor impact of these pollutants on the sperm whale populations of the Mediterranean Sea. Aluminum was revealed to have relatively high concentrations, together with a high variability between tissues and individuals, reaching the highest values in the kidneys and muscle of the oldest female, which was pregnant; the rare earth elements – lanthanum and cerium – were also detected in the kidneys of this female, indicating that pregnancy probably influenced metal concentrations in body tissues.  相似文献   
2.
Correlation between spermathecal morphology and mating systems in spiders   总被引:2,自引:0,他引:2  
This study tested predictions regarding male mating preferences which were based on some aspects of female reproductive morphology which may influence sperm precedence patterns in six species of spiders. Males of two species, whose 'conduit' spermathecal design has been associated in previous studies with first male sperm precedence, showed the predicted preference for associating with immature females about to moult to maturity rather than mature females. Those of a third species, however, associated indiscriminately with mature and penultimate instar females. As predicted, males of three other species with 'cul-de-sac' spermathecal morphology did not associate preferentially with immature females. Immature females were avoided in two of the species, but not in the third. One of the species with cul-de-sac spermathecae showed, as predicted, lack of a strong first male advantage in sperm precedence. These data give only limited confirmation of the predictions.  相似文献   
3.
Protamine of the archaeogastropod mollusc Monodonta turbinata has been isolated and characterized. With a mass of 13,476 Da, it is the largest known prolamine. Amino acid sequence of this protamine (106 residues) was established from data provided by automated sequence analysis and mass spectrometry of the protein and of its fragments. The primary structure of the NH2-terminal region exhibits repetitive sequence motifs Basic-Ser (mainly R-S) and both central and COOH-terminal regions are composed by arginine clusters. The amino acid sequence of Monodonta turbinata protamine shows structural similarities with other protamines from invertebrates and from birds and mammals.  相似文献   
4.
Synopsis Turbot sperm motility is observed using dark field microscopy and stroboscopic illumination combined with video recording. Sperm motility is triggered by dilution of spermatozoa in sea water or in non ionic media (glucose or saccharose), presenting osmotic pressure ranging from 300 to 2100 mOsmol. The percentage of motile spermatozoa reaches 100% under conditions of osmotic pressure of 300 to 1100 mOsmol and pH close to 8.0. In full sea water, glucose or saccharose solutions an agglutination of spermatozoa is observed; this is prevented by addition of bovine serum albumin (5 mg ml–1). Immediately after transfer in activation solutions, 100% spermatozoa are motile in most samples freshly stripped. This percentage drops suddenly between 15 and 30% after 70 to 100 sec. The beat frequency remains at a constant value of 50 Hz during 40 s post activation and then drops suddenly between 15 and 30 Hz. The spermatozoa velocity is about 200 micrometers s–1 during 30 to 40 s and then declines to a stable value of 100 micrometers s–1 at 50 s post activation. After 1.20 mn, more and more spermatozoa become motionless. The minimum calculated and averaged distance covered during 1.20 min, is about 12 mm. The high performances of turbot spermatozoa motility are interpreted as a compensatory mechanism for the low sperm production.  相似文献   
5.
《Cryobiology》2016,73(3):210-215
Several methods are currently available for selection when conducting sperm cryopreservation, however, these methods might cause different degrees of damage on sperm DNA. The aim of the this study is to compare the effects of storage at −80 °C (in ultra-low temperature refrigerator) and at −196 °C (in liquid nitrogen) on sperm DNA damage, thus to provide a reference for choosing the right method according to different aims. We randomly collected 28 semen samples from college students of Chongqing city. The samples stored at −80 °C were neat semen samples and the samples stored at −196 °C were mixed with additional cryoprotectants. Each sample was subjected to two freezing-thawing cycles, and the sperm DNA damage levels of fresh and thawed samples were measured by single cell gel electrophoresis (SCGE) and sperm chromatin structure assay (SCSA). Both SCGE and SCSA assays showed cryopreservation induced significant damage to sperm DNA. However, storage at −196 °C lead to more severe damage to sperm DNA than storage at −80 °C measured by SCSA. Sperm DNA damage increased simultaneously with the higher frequency of freezing-thawing cycles. We concluded that storage of neat semen samples at −80 °C had milder damage to sperm DNA than storage at −196 °C mixed with cryoprotectants. To avoid additional sperm DNA damage, repeated freezing and thawing should be prevented.  相似文献   
6.
Nevertheless, a nonviable sperm population is present in the cauda epididymidis of many species. Degenerating spermatozoa release enzymes that could have detrimental effects on the viability of neighboring cells, and they are source of autoantigens that induce an autoimmune response if they escape the blood-epididymis barrier. Does the epididymis have specialized protective mechanism(s) to segregate the viable sperm population from defective spermatozoa? Previously, we identified a fibrinogen-like protein-2 (fgl2) that specifically binds to and polymerizes into a cocoon-like complex coating defective spermatozoa and sperm fragments. The objective of the present study is to identify the subunit composition of the fgl2-containing oligomers both in the soluble and cocoon-like complex. Our proteomic studies indicate that the 260/280 kDa oligomers (termed eFGL) contain two distinct disulfide-linked subunits; 64 kDa fgl2 and 33 kDa fgl1. Utilizing a PCR-based cloning strategy, the 33 kDa polypeptide has been identified as fibrinogen-like protein-1 (fgl1). Immunocytochemical studies revealed that fgl1 selectively binds to defective spermatozoa in the cauda epididymidis. Northern blot analysis and in situ hybridization demonstrated the high expression of fgl1 in the principal cells of the proximal cauda epididymidis. Co-immunoprecipitation analyses of cauda epididymal fluid, using anti-fgl2, demonstrate that both fgl1 and fgl2 are present in the soluble eFGL. Our study is the first to show an association of fgl1 and fgl2 both in the soluble and in the sperm-associated eFGL. We conclude that our results provide new insights into the mechanisms by which the potentially unique epididymal protein functions in the recognition and elimination of defective spermatozoa.  相似文献   
7.
Our previous studies showed that Brewbaker and Kwack salts, which have been widely used in pollen germination and sperm isolation, are not appropriate for the maintenance of isolated maize (Zea mays L.) sperm cells. In the present study, we have characterized the effects of each BKS component salt on the integrity of isolated sperm cells using hemacytometry. At 0.01 and 0.1 mM, there were no differences in cell number between control and any salt-treated cells except a 22% decrease with 0.1 mM MgSO4 at 48 h. At the 1 mM level, cell number decreased with time in the presence of Ca(NO3)2 and MgSO4, with loss of integrity of most cells at 48 h, while KNO3 and H3BO3 had little or no effect. Further characterization of calcium-induced reduction in cell integrity using flow cytometry showed that depletion of possible residual free calcium by addition of EGTA to the suspension medium improved cell longevity and viability. Exposure of isolated sperm cells to 1 mM calcium had no effect on cell integrity and viability in 5 h; however, only 12% of cells remained intact at 24 h. The reduction in cell integrity was hastened when cells were pretreated with the calcium ionophore A23187 prior to exposure to 1 mM calcium, with a 54% reduction in cell number at 1 h and complete cell lysis at 24 h. However, depletion of cytosolic free calcium by pretreatment of cells with the calcium ionophore followed by resuspension in the presence of EGTA resulted in rapid reduction of cell integrity as well. These results collectively suggest that maize sperm cells are sensitive to exogenous free calcium; however, a certain level of cytosolic free calcium is necessary for maintenance of integrity. Mechanisms of calcium-induced reduction in cell integrity are discussed along with possible roles of the sensitivity of sperm cells to calcium in fertilization.  相似文献   
8.
Carbohydrates and fertilization in animals   总被引:7,自引:0,他引:7  
A frequently used mechanism for sperm-egg recognition in many species involves complementary protein-carbohydrate interaction. The usual paradigm includes complex glycoconjugates in reproductive tract fluids or on the eggs which are recognized by carbohydrate-binding proteins on the sperm surface. Various glycoconjugates are utilized in the steps of sperm capacitation, sperm binding to the egg extracellular matrix and vitelline membrane and induction of the acrosome reaction. Several types of complex glycoconjugates are involved in these processes, including proteoglycans, lactosaminoglycans, sulfated fucose-containing glycoconjugates, and glycoproteins. There appear to be some structural similarities between active glycoconjugates; they are large in molecular weight and complex, and they are often sulfated, fucosylated, and attached to a protein through serine or threonine residues. In some species, the protein core of the glycoconjugates also participates in the interaction by limiting the binding of carbohydrates to sperm only of the relevant species, likely by providing the proper steric arrangement for the interaction. In other cases the protein core seems to serve more as a crosslinker of the carbohydrate moieties. This review discusses the types of glycoconjugates implicated in fertilization and the complementary lectin-like proteins found on sperm.  相似文献   
9.
Myosin associated with the male germ cells of angiosperms interacts with actin, promoting transport of the non-motile generative and later sperm cells in the pollen tube. Myosin localizing on the sperm cell plasma membrane seems negligible in Plumbago, as reflected by the absence of: (i) anti-myosin labeling using immunoelectron microscopy, (ii) sperm motility on actin matrices, and (iii) electrophoretic movement changes after addition of antibody. Sperm cells injected directly into actively streaming Nitella internodal cells, however, follow actin bundles and their movement is sensitive to ATP and Mg2+. This may be based on simple charge binding since negatively charged latex beads also migrate on actin, whereas neutral or positively-charged latex beads do not. Sperm cells are negatively charged according to capillary microelectrophoresis, whereas killed sperm cells, which are positively charged do not migrate. The sperm cell that normally fertilizes the egg has a higher calculated charge (8.277 × 103 esu/cm2) compared with the sperm cell that fuses with the central cell (6.120 × 103 esu/cm2). Received: 15 December 1998 / Accepted: 21 January 1999  相似文献   
10.
哺乳动物及人精子膜离子通道的研究进展   总被引:3,自引:0,他引:3  
Ma XH  Shi YL 《生理科学进展》1998,29(2):109-114
离子的跨膜转动对精子的生理活动起重要的作用。近年,应用膜片钳及人工膜重组等研究通道有关的电生理技术,人们直接观察到哺乳动物及人精子膜上K、Na^+、Ca^2+、Cl通道的存在。这些结果为揭示精子成熟、获能精卵结合反应等生理过程的某些细节提供了有有的资料,特别是对人精子膜的研究,还为临床应用提供了可能。  相似文献   
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