排序方式： 共有29条查询结果，搜索用时 15 毫秒
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Waseem Akbar Anilkumar Gowda Jeffrey E Ahrens Jason W Stelzer Robert S Brown Scott L Bollman John T Greenplate Jeffrey Gore Angus L Catchot Gus Lorenz Scott D Stewart David L Kerns Jeremy K Greene Michael D Toews David A Herbert Dominic D Reisig Gregory A Sword Peter C Ellsworth Larry D Godfrey Thomas L Clark 《Pest management science》2019,75(3):867-877
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Seventeen seasonally anovulatory light horse mares were treated daily, starting January 5 (d 1), for 28 d with GnRH analog (GnRH-A; 50 ng/kg BW) and(or) thyrotropin-releasing hormone (TRH; 5 microg/kg BW) in a 2 x 2 factorial arrangement of treatments to test the hypothesis that combined treatment may stimulate follicular growth and development. Ovaries were examined via ultrasonography and jugular blood samples were collected every 3 d. Frequent blood samples were collected after treatment injections on d 1, 2, 4, 7, 11, 16, and 22; on d 29, all mares received an i.v. mixture of GnRH, TRH, sulpiride, and EP51389 (a growth hormone secretagogue) to assess pituitary responsiveness. No consistent effects (P > 0.1) of treatment were observed for plasma LH, FSH, prolactin, or thyroxine concentrations in samples collected every 3 d. The only effect on ovarian follicle numbers was a reduction in number of follicles 11 to 19 mm in diameter due to TRH treatment (P = 0.029). No mare ovulated during treatment. On the days of frequent sampling, mean LH (P = 0.0001) and FSH (P = 0.001) concentrations were higher in mares receiving GnRH-A and tended to increase from d 1 through 7. In contrast, mean prolactin (P = 0.001) and thyroid-stimulating hormone (P = 0.0001) concentrations were high in mares receiving TRH on d 1 but rapidly decreased thereafter. When mares were administered the secretagogue mixture on d 29, the LH response was greater (P = 0.0002) in mares that had previously received GnRH-A but the FSH response was not affected (P > 0.1); the prolactin response was greater (P = 0.014) and the TSH response was smaller (P = 0.0005) in mares that had previously received TRH. Surprisingly, an immediate growth hormone response to EP51389 was absent in all mares. In conclusion, daily GnRH-A treatment stimulated plasma LH and FSH concentrations immediately after injection; although no long-term elevation in preinjection concentrations was achieved, the responses gradually increased over time, indicating a stimulation of gonadotropin production and storage. Daily treatment with TRH stimulated plasma TSH and prolactin concentrations, but the response diminished rapidly and was minimal within a few days, indicating a depletion of pituitary stores and little or no stimulation of production. There was no beneficial effect of adding TRH treatment to the daily GnRH-A regimen. 相似文献
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CH Annandale PC Irons VP Bagla UI Osuagwuh EH Venter 《Reproduction in domestic animals》2010,45(2):250-255
The objectives of this work were to determine the site of persistence of lumpy skin disease virus (LSDV) in bulls shedding the virus in semen for a period longer than 28 days, to determine if the virus is present in all fractions of semen and to study lesions that developed in the genital tract. Six serologically negative postpubertal bulls were experimentally infected with a virulent field isolate of LSDV. The polymerase chain reaction (PCR) was performed on sheath washes, vesicular fluid, supernatant and cell‐rich fractions of semen from day 10 to day 26 postinfection (p.i.). Bulls that were positive by PCR on the whole semen sample collected on day 28 p.i. were slaughtered and tissue samples from their genital tracts submitted for histopathological evaluation, immunoperoxidase staining, virus isolation and PCR. Two of the bulls developed severe lumpy skin disease (LSD) and were found to be shedding viral DNA in their semen on day 28 p.i. Viral DNA was identified in all semen fractions from all bulls, but mostly from the cell‐rich fraction and from the severely affected bulls. The PCR assay was positive on postmortem samples of testes and epididymides from the two severely affected bulls. Virus could be recovered from the testes of these two bulls and from the epididymis of one of them. Immunoperoxidase staining was positive for LSDV staining in sections of testes and epididymides exhibiting necrosis. This study suggests that the testis and epididymis are sites of persistence of LSDV in bulls shedding virus in semen for prolonged periods and revealed that viral DNA is present in all fractions of the ejaculate. 相似文献
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S Gür G Türk E Demirci A Yüce M Sönmez Ş Özer EH Aksu 《Reproduction in domestic animals》2011,46(2):289-295
The aim of this study was to determine the changes in diameter of corpus luteum (CL), maternal progesterone (P) concentration, lipid peroxidation and non‐enzymatic antioxidant levels along with enzymatic antioxidant activities in pregnant ewes bearing single and twin foetuses. The ewes were selected from healthy animals that were brought to the abattoir for slaughtering. The ewes were divided into three groups: Group 1 (non‐pregnant, non‐oestrous, n = 30), Group 2 (pregnant bearing a single foetus, n = 30) and Group 3 (pregnant bearing twin foetuses, n = 12) after they were slaughtered. Pregnant ewes were in the first half of the pregnancy. The diameter of CL and P concentration of pregnant ewes bearing a single foetus or twin foetuses were found higher than that found in non‐pregnant ewes. Similarly, the P concentration of pregnant ewes bearing twin foetuses was higher than that found in pregnant ewes bearing a single foetus. Malondialdehyde (MDA) level in pregnant ewes bearing twin foetuses was higher than that found in both non‐pregnant and pregnant ewes bearing a single foetus. The serum glutathione (GSH) level and glutathione‐peroxidase (GSH‐Px) activity of pregnant ewes bearing twin foetuses were found lower than that found in non‐pregnant ewes. Additionally, the GSH‐Px activity of pregnant ewes bearing twin foetuses was found lower than that found in pregnant ewes bearing a single foetus. No significant difference was found between pregnant ewes bearing female and male foetus with respect to diameter of CL, P concentration and oxidative stress parameters. There were significant positive correlations between foetal number (0, 1, 2) and diameter of CL, P concentration, MDA level, and between P concentration and diameter of CL, MDA level. However, significant negative correlations were found between foetal number (0, 1, 2) and GSH level, GSH‐Px activity, and between P concentration and GSH‐Px activity. In conclusion, the diameter of CL enlarges, P production increases and oxidant/antioxidant balance impairs because of the gestation stress in ewes during pregnancy. 相似文献
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Shoot cuttings were harvested fromfour-year-old, loblolly pine hedges in March andSeptember of 1987, and placed into a series offactorial combinations of cutting length, diameterclass, and the presence/absence of a terminal bud toassess effects on rooting and field performance.Average rooting in the March trial was 50 percent andonly 20 percent for the September trial; however, thebest treatment in March yielded 100 percent rooting.Terminal bud status did not appear to influencepercent rooting. Shorter cuttings (5.1 or 7.6 cm)with an average diameter of 2 or 3 mm tended to rootbetter and develop more roots. Field performance ofthe rooted cuttings through age five suggests that theoriginal cutting does not require a terminal bud, butthe best set of morphological traits differ dependingon bud status. Considering both rooting ability andfield growth with an original tip bud present, thebest cutting dimensions were 5.1 or 7.6 cm long and 2or 3 mm in diameter. Without a tip bud present,cutting dimensions were restricted to 7.6 or 10.2 cmlong and 3 mm in diameter. Number of main roots wasa weak predictor of tree height or dbh at age five. 相似文献
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During unequal cell divisions a mitotic spindle is eccentrically positioned before cell cleavage. To determine the basis of the net force imbalance that causes spindle displacement in one-cell Caenorhabditis elegans embryos, we fragmented centrosomes with an ultraviolet laser. Analysis of the mean and variance of fragment speeds suggests that the force imbalance is due to a larger number of force generators pulling on astral microtubules of the posterior aster relative to the anterior aster. Moreover, activation of heterotrimeric guanine nucleotide- binding protein (Gprotein) alpha subunits is required to generate these astral forces. 相似文献
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Rebecca G. Martone Robin Naidoo Theraesa Coyle Bertine Stelzer Kai M.A. Chan 《水产资源保护:海洋与淡水生态系统》2020,30(6):1208-1219
- Facing public concern over costs related to top‐predator reintroductions and conservation, ecosystem services such as ecotourism are often used to evoke benefits that outweigh or offset those costs. Quantifying these benefits using rigorous scientific methods can provide confidence to policymakers and other stakeholders that predators can in fact deliver positive outcomes to people living alongside them. The evaluation of these benefits is often anecdotal or qualitative, however, and empirical quantifications are rare.
- In coastal marine ecosystems, sea otter reintroduction is seen as a conservation success to some but a bane to others. The contribution of sea otters (Enyhdra lutris) to tourism revenue is touted as a crucial ecosystem service benefit to offset the loss of shellfish harvesting and associated revenue, but remains unquantified, weakening the favourable reception of conservation action.
- The potential economic benefits of sea otters associated with tourism and the extent to which benefits are realized were evaluated based on: (i) choice‐experiment surveys of tourists; and (ii) interviews with tourism operators in British Columbia.
- Sea otters were a strong factor in people's choices regarding wildlife viewing, and sea otters could have large benefits for local economies. Alongside socio‐economic characteristics, tourism experience influences tourists’ preferences. Tourism operators did not perceive sea otters as strongly influencing tourist choice, highlighting the gap that can occur between the perception and the reality of tourist preferences, leading to missed opportunities for the alignment of economic development with conservation actions.
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Measurements of the partitioning of rhenium (Re) between garnet and silicate liquid from 1.5 to 2.0 gigapascals and 1250 degrees to 1350 degreesC show that Re is compatible in garnet. Oceanic island basalts (OIBs) have lower Re contents than mid-ocean ridge basalt, because garnet-bearing residues of deeper OIB melting will retain Re. Deep-mantle garnetite or eclogite may harbor the missing Re identified in crust-mantle mass balance calculations. Oceanic crust recycled into the upper mantle at subduction zones will retain high Re/Os (osmium) ratios and become enriched in radiogenic 187Os. Recycled eclogite in a mantle source should be easily traced using Re abundances and Os isotopes. 相似文献