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排序方式: 共有120条查询结果,搜索用时 265 毫秒
111.
M Villani F Cairoli H Kindahl G Galeati M Faustini A Carluccio MC Veronesi 《Reproduction in domestic animals》2006,41(6):544-548
Very little information is available regarding the physiological mechanisms involved in the normal sexual activity in the stallion and, in particular, the endocrine control of reproduction is still not clearly understood. This experiment was designed to determine the short-term effect of sexual stimulation on plasma concentrations of testosterone, cortisol, oestrone sulphate and 15-ketodihydro-PGF(2alpha) in stallions. Semen samples were collected from 10 lighthorse stallions of proven fertility using a Missouri model artificial vagina. At the same time, blood samples were collected from the jugular vein with heparinized tubes, 20 and 10 min before oestrous mare exposure, at exposure and 10, 20, 30 min after dismounting. Testosterone concentrations showed a sharp rise 10 min after mating (p < 0.001), reached a plateau, and then showed a further increase 30 min after mating (p < 0.001). Cortisol concentrations increased 10 min after mating (p < 0.001) and remained at high levels in the subsequent samples taken. A peak of oestrone sulphate was observed 10 min after mating (p < 0.001). 15-Ketodihydro-PGF(2alpha) concentrations decreased rapidly at the moment of the exposure of the stallions to an oestrous mare (p < 0.05), returned to pre-mating concentrations and then decreased again 30 min after mating (p < 0.05). 相似文献
112.
J Rubio-Guillén D González JJ Garde MC Esteso MR Fernández-Santos JE Rodríguez-Gíl N Madrid-Bury A Quintero-Moreno 《Reproduction in domestic animals》2007,42(4):354-357
Assisted sperm morphometry analysis (ASMA) was used in this study to determine the effects of cryopreservation on bull spermatozoa distribution in morphometrically distinct subpopulations. Ejaculates were collected from five bulls and were divided. One portion was diluted at 30 degrees C in a skim milk-egg yolk medium, containing glycerol. A microscope slide was prepared from single extended sperm samples prior to freezing. The remainder of each sample was frozen in nitrogen vapours. After thawing, sperm smears were prepared as described above. All slides were air dried and stained with Hemacolor. The sperm-head dimensions for a minimum of 200 sperm heads were analysed from each sample by means of the Sperm-Class Analyser (SCA), and the mean measurements recorded. Our results showed that applying the ASMA technology and multivariate cluster analyses, it was possible to determine that three separate subpopulations of spermatozoa with different morphometric characteristics coexist in bull ejaculates (large, average and small spermatozoa). The mean values of each sperm head dimension among the three subpopulations of spermatozoa were significantly different (p < 0.001). Besides, there were significant (p < 0.001) differences in the distribution of these three sperm subpopulations between fresh and thawed samples. Thus, the percentage of representation of the subpopulation that includes those spermatozoa whose dimensions are the biggest, decreased from 52.06% in extended fresh samples to 15.51% in the thawed ones. Contrarily, the percent of representation of the subpopulation containing the smallest spermatozoa, increased from 8.70% in extended fresh samples to 34.04% in the thawed ones. In conclusion, the present study confirms the heterogeneity of sperm head dimensions in bull semen, heterogeneity that vary through the cryopreservation procedure. 相似文献
113.
114.
C Soler M Sancho A García MC Fuentes J Núñez H Cucho 《Reproduction in domestic animals》2014,49(1):71-78
South American camelid sperm characteristics are poorly known compared with those of other domestic animals. The long‐term duration of ejaculation makes difficult to gather all the seminal fluid, implying possible ejaculation portion losses. Thus, the aim of this research was to evaluate the characteristics of the morphology and morphometry of the spermatozoa change during ejaculation. The morphometric characterization was tested on nine specimens of the Lanuda breed, using a special artificial vagina. In five of the animals, a fractioning of the ejaculate was performed by taking samples every 5 min. for a total of 20 min. Air‐dried seminal smears were stained with Hemacolor and mounted permanently with Eukitt. Morphometric analysis was carried out with the morphometry module of the ISAS® CASA system. Almost 350 cells were analysed per sample, with a total number of 3207 spermatozoa. Mean values were given as follows: length: 5.51 μm; width: 3.38 μm; area: 17.75 μm2; perimeter: 14.8 μm; ellipticity: 0.24; elongation: 0.56; rugosity: 0.87; regularity: 1.07; and shape factor: 1.41. Different animals showed differences in their morphometric values. When we compared the values from different fractions, only two samples showed differences in morphometric parameter values and four samples showed differences in shape parameters. Multivariate analysis allowed the size classification of the cells into three classes and five classes of shapes. The distribution of classes among fractions showed no differences. Despite the individual morphometric differences observed in some fractions, the characteristics of the sperm head morphometry can be considered constant along the ejaculatory period in the llama. 相似文献
115.
RW Graham EL Lundelius MA Graham EK Schroeder RS Toomey E Anderson AD Barnosky JA Burns CS Churcher DK Grayson RD Guthrie CR Harington GT Jefferson LD Martin HG McDonald RE Morlan HA Semken SD Webb L Werdelin MC Wilson 《Science (New York, N.Y.)》1996,272(5268):1601-1606
Analyses of fossil mammal faunas from 2945 localities in the United States demonstrate that the geographic ranges of individual species shifted at different times, in different directions, and at different rates in response to late Quaternary environmental fluctuations. The geographic pattern of faunal provinces was similar for the late Pleistocene and late Holocene, but differing environmental gradients resulted in dissimilar species composition for these biogeographic regions. Modern community patterns emerged only in the last few thousand years, and many late Pleistocene communities do not have modern analogs. Faunal heterogeneity was greater in the late Pleistocene. 相似文献
116.
MC Lonergan 《Science (New York, N.Y.)》1997,278(5346):2103-2106
Although in principle semiconductor-metal (Schottky) diodes should be tunable by changing the work function of the metal, such flexibility cannot be achieved in a single device and in practice is often limited by interfacial states that cause Fermi-level pinning. A tunable diode is reported based on a hybrid inorganic-organic, n-indium phosphide&cjs3539;poly- (pyrrole)&cjs3539;nonaqueous electrolyte architecture. By electrochemically manipulating the work function of the conjugated polymer poly(pyrrole), the turn-on voltage (more precisely, the forward bias potential required to pass a particular current) of the diode can be continuously and actively tuned by more than 0.6 volt. The work highlights a distinguishing feature of conjugated polymers relative to more traditional semiconductor materials, namely, the ability of dopant ions to permeate conjugated polymers, thereby enabling electrochemical manipulation. 相似文献
117.
Role of Gene Interactions in Hybrid Speciation: Evidence from Ancient and Experimental Hybrids 总被引:6,自引:0,他引:6
LH Rieseberg B Sinervo CR Linder MC Ungerer DM Arias 《Science (New York, N.Y.)》1996,272(5262):741-745
The origin of a new diploid species by means of hybridization requires the successful merger of differentiated parental species' genomes. To study this process, the genomic composition of three experimentally synthesized hybrid lineages was compared with that of an ancient hybrid species. The genomic composition of the synthesized and ancient hybrids was concordant (rs = 0.68, P < 0.0001), indicating that selection to a large extent governs hybrid species formation. Further, nonrandom rates of introgression and significant associations among unlinked markers in each of the three synthesized hybrid lineages imply that interactions between coadapted parental species' genes constrain the genomic composition of hybrid species. 相似文献
118.
MA Stornelli JC Reyna MC Stornelli R Nuñez Favre CA Savignone CM Tittarelli RL de la Sota 《Reproduction in domestic animals》2009,44(S2):287-290
The aim of this study was to asses the variation in the morphology of the seminal epithelium in relation to natural photoperiod in male cats. Tom cats (n = 240) were castrated every other week throughout the year. Each testis was fixed in Bouin's solution and cut into sections. The percentage of tubules with round spermatids (RS), elongated spermatids (ES), tailed spermatids (TS), mature spermatids (MS) and the number of Sertoli cells (SC) and Leydig cells (LC) were recorded in each sample. Testicles from males during short days (SHD) had a higher percentage of tubules with RS and ES compared to testicles from males during long days (LHD, 31.3 ± 0.6 vs 2.1 ± 0.6%, p < 0.001; 30.9 ± 0.7 vs 11.0 ± 0.7%, p < 0.001). Conversely, testicles from males during SHD had a lower percentage of tubules with TS and MS compared to testicles from males during LHD (24.5 ± 0.8 vs 29.7 ± 0.8%, p < 0.01; 13.1 ± 1.2 vs 57.0 ± 1.2%, p < 0.01). Furthermore, testicles from males during SHD had a higher number of SC and lower number of LC compared to testicles from males during LHD (11.4 ± 0.1 vs 8.0 ± 0.1%, p < 0.01; 19.2 ± 1.0 vs 38.0 ± 1.0%, p < 0.01). In conclusion, there are seasonal changes in testis cell morphology in the tom which may be related to seasonal sperm production. 相似文献
119.
F Martínez-Pastor M del Rocío Fernández-Santos ÁE Domínguez-Rebolledo MC Esteso JJ Garde ; Biology of Reproduction Group 《Reproduction in domestic animals》2009,44(3):424-431
The assessment of sperm chromatin status is compulsory in a complete spermiogram. Here we applied the sperm chromatin structure assay (SCSA) and the sperm chromatin dispersion (SCD) test to assess the chromatin status of three fighting bulls. Cryopreserved semen (two straws/bull) were analysed by duplicate after thawing and after 6 h at 37°C with and without oxidative stress (1 m m FE2+ ). Results (SCD: percentage of spermatozoa with halo; SCSA: SD-DFI, %DFI and HDS) were analysed for differences between bulls and treatments, sensitivity and specificity (receiver operating characteristic curves) and repeatability (repeatability coefficients as 2SD of duplicate differences).%DFI for the three bulls was below 2% at 0 h, indicating no risk for fertility according to previous reports. It increased slightly for two of the bulls after FE2+ treatment (%DFI < 5%) and more pronouncedly for the other bull (C, %DFI∼10%), which merits further investigation. SCD rendered higher percentage of halos for bull C, but could not discriminate between samples with and without oxidizing treatment (AUC: 0.52). SCSA (%DFI) showed a high discriminating ability between treatments (AUC: 0.96). The repeatability coefficient was also higher for SCD (5.9) than for %DFI (1.8), indicating lower repeatability for SCD. Overall, %DFI might be the most useful parameter for assessing sperm chromatin on fighting bull. SCD might yield different information than SCSA, hence further research is warranted. 相似文献
120.
Involvement of Protein cAMP‐dependent Kinase,Phospholipase A2 and Phospholipase C in Sperm Acrosome Reaction of Chinchilla lanigera
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MC Gramajo‐Bühler L Zelarayán G Sánchez‐Toranzo 《Reproduction in domestic animals》2016,51(1):150-157
The mechanisms involved in fertilization are the centre of attention in order to determine the conditions required to reproduce in vitro the events that take place in vivo, with special interest in endangered species. Previous data from mouse sperm, where acrosome reaction (AR) occurs more often in the interstitium of the cumulus oophorus, contribute to strengthen the use of progesterone as a physiological inducer of this process. We studied the participation of protein kinase A (PKA), phospholipases A2 and C (PLA2, PLC) in the AR induced by progesterone from Chinchilla epididymal spermatozoa. The addition of db‐cAMP to the incubation medium caused an increase of 58% in the AR, while the use of H89 (30 μm ), a PKA inhibitor, reflected a decrease of 40% in the percentage of reacted gametes. The assays conducted with arachidonic acid showed a maximum increase of 23% in the AR. When gametes were pre‐incubated with PLA2 inhibitors, a dose‐dependent inhibitory effect was observed. The addition of phorbol12‐myristate13‐acetate (10 μm ) revealed higher percentages of AR induction (60%). When PLC was inhibited with neomycin and U73122, a dose‐dependent decrease in AR percentages was observed. Combined inhibition of PKA, PLA2 and PLC, AR values similar to control were obtained. This work shows evidence, for the first time in Chinchilla, that progesterone activates the AC/cAMP/PKA system as well as sperm phospholipases and that these signalling pathways participate jointly and cooperatively in AR. These results contribute to the understanding of the complex regulation that is triggered in sperm after the effect of progesterone. 相似文献