排序方式： 共有81条查询结果，搜索用时 30 毫秒
1.
2.
3.
4.
Salmonid sperm pre-incubated at extracellular pH (pHe) values less than about 7.4 do not become motile upon water activation whereas sperm maintained above about pH 8.0 demonstrate maximal motility upon activation. The basis for this permissive effect of elevated pHe on sperm motility is not known. Since it is conceivable that the pH sensitivity of dyneinATPase (the molecular motor that drives flagellar movement) could be the basis of, or contribute to this pH dependency, the pH sensitivity of this enzymatic activity was evaluated in membrane-permeabilized axonemes (isolated flagella) ofsteelhead sperm. DyneinATPase activity was found to be sensitive to pH. This activity in permeabilized axonemes was about 3.5-fold higher at pH 7.6 compared to 7.0. To determine whether the pH sensitivity ofATP regeneration might affect the interpretation of the effect of pH on dyneinATPase activity, the pH sensitivities of creatine kinase and adenylate kinase were established. The rates ofATP generation by these enzymes were insensitive to pH between 6.5 and 8.0. The results of these studies are consistent with the hypothesis that prior maintenance at pHe, in part, controls the potential for sperm motility upon water activation via an influence on dyneinATPase activity. However, the potential for motility ofsteelhead sperm is particularly sensitive to prior maintenance at pHe values between about 7.4 and 8.0 whereas the dyneinATPase activity of permeabilized axonemes was particularly sensitive to pH values between 7.0 and 7.6. Phosphorus NMR spectroscopy was used to determine that sperm intracellular pH (pHi) increased with increasing pHe between 7.0 and 8.5 and pHi was, on average 0.4–0.5 pH units lower than pHe. Therefore the pHe sensitivity of the potential for motility appears to correspond to the pHi sensitivity of dyneinATPase activity. The data indicate that pHi is directly related to pHe and that prior incubation at pHe may, in part, control the sperm's potential for motility upon water activation via an influence on dyneinATPase activity. 相似文献
5.
6.
J Go I Marsh M Gabor V Saunders RL Reece J Frances C Boys LJ Gabor 《Australian veterinary journal》2012,90(12):513-514
Epizootic ulcerative syndrome was diagnosed, and the presence of Aphanomyces invadans confirmed, from an outbreak of clinical disease in wild‐caught bony bream (Nematalosa erebi) from the Darling River near Bourke, in New South Wales, Australia, during 2008. This confirms a significant extension of the agent beyond its historical range. 相似文献
7.
ObjectiveTo investigate the contribution of K+ channels on peripheral antinociception induced by ketamine.Study designProspective experimental study.Animals110 male Wistar rats weighing 160–200 g.MethodsThe paw pressure required to elicit limb flexion was designated as the nociceptive threshold. Hyperalgesia was induced by intraplantar injection of prostaglandin E2. All drugs were administered locally into the right hind paw of rats. Ketamine was administered into the right hind paw 2 hours and 55 minutes after local injection of PGE2. Tetraethylammonium was administered 30 minutes prior to ketamine and the other K+ channel blockers, glibenclamide, dequalinium and paxilline, were administered 5 minutes prior to ketamine.ResultsProstaglandin E2 (2 μg per paw) induced hyperalgesia. Ketamine (10, 20, 40 and 80 μg per paw) elicited a local peripheral antinociceptive effect that was antagonized by a specific blocker of ATP‐sensitive K+ channels, glibenclamide (20, 40 and 80 μg per paw). In another experiment, the non‐selective voltage‐dependent K+ channel blocker tetraethylammonium (30 μg per paw) and small and large conductance blockers of Ca2+‐activated K+ channels, dequalinium (50 μg per paw) and paxilline (20 μg per paw), were ineffective at blocking the effect of a local ketamine injection.Conclusions and clinical relevanceAnalysis of these results provides evidence that ketamine, may in part, induce peripheral antinociceptive effects by ATP‐sensitive K+ channel pathway activation. 相似文献
8.
AbstractCASE HISTORY: A group of 545 pregnant rising 2-year-old Coopdale ewes on a Southland sheep farm were grazed over winter on a fodder beet (Beta vulgaris) crop. Subsequently, 45 out of approximately 750 lambs were born with a variety of skeletal deformities, including shortened limbs, varus and valgus angular limb deformities, palmar grade stance and cranial bowing of the carpus. Analysis of the crop showed the fodder beet contained a low percentage of phosphorus. In addition, 60 out of 460 rising 2-year-old ewes that had been grazed on the fodder beet crop as 1-year-olds had incisor abnormalities and malocclusion.PATHOLOGICAL FINDINGS: Two affected lambs (1-day-old and 3-days-old) with representative clinical signs examined postmortem were found to have markedly enlarged costochondral junctions, and noticeably enlarged long bone metaphyses. In addition, one lamb had a dense band of metaphyseal sclerosis beneath the physes of all long bones examined. Histopathological findings included small islands and columns of chondrocytes and eosinophilic cartilage matrix present in the metaphysis. Metaphyseal trabeculae were disorganised and often lined by accumulations of pale pink osteoid; similar pale pink osteoid was also present in the cortices. Unerupted molar teeth in the affected lambs lacked a layer of enamel, and the dentine was irregular with globular basophilia.DIAGNOSIS: The gross and histopathological lesions were consistent with a diagnosis of rickets.CLINICAL RELEVANCE: Nutritional congenital rickets has not been previously diagnosed in sheep, but is a recognised disease of human infants with vitamin D deficient mothers. The rickets in affected lambs was most likely associated with phosphorus deficiency as a result of the pregnant ewes grazing fodder beet during gestation. While vitamin D deficiency was not definitively ruled out in these cases, practitioners are alerted to the possible effects of feeding phosphorus-deficient fodder beet to ewes for long periods during gestation and to 1-year-old sheep during important growth periods. 相似文献
9.
Climate and vegetation history of the midcontinent from 75 to 25 ka: A speleothem record from crevice cave, missouri, USA 总被引：3，自引：0，他引：3
Four Missouri stalagmites yield consistent overlapping records of oxygen and carbon isotopic changes and provide a climate and vegetation history with submillennial resolution from 75 to 25 thousand years ago (ka). The thorium-230-dated records reveal that between 75 and 55 ka, the midcontinental climate oscillated on millennial time scales between cold and warm, and vegetation alternated among forest, savanna, and prairie. Temperatures were highest and prairie vegetation peaked between 59 and 55 ka. Climate cooled and forest replaced grassland at 55 ka, when global ice sheets began to build during the early part of Marine Oxygen Isotope Stage 3. 相似文献
10.
N Ge CM Wong RL Lingle JD McNeill KJ Gaffney CB Harris 《Science (New York, N.Y.)》1998,279(5348):202-205
The dynamics of two-dimensional small-polaron formation at ultrathin alkane layers on a silver(111) surface have been studied with femtosecond time- and angle-resolved two-photon photoemission spectroscopy. Optical excitation creates interfacial electrons in quasi-free states for motion parallel to the interface. These initially delocalized electrons self-trap as small polarons in a localized state within a few hundred femtoseconds. The localized electrons then decay back to the metal within picoseconds by tunneling through the adlayer potential barrier. The energy dependence of the self-trapping rate has been measured and modeled with a theory analogous to electron transfer theory. This analysis determines the inter- and intramolecular vibrational modes of the overlayer responsible for self-trapping as well as the relaxation energy of the overlayer molecular lattice. These results for a model interface contribute to the fundamental picture of electron behavior in weakly bonded solids and can lead to better understanding of carrier dynamics in many different systems, including organic light-emitting diodes. 相似文献