巴美肉羊发情期外周血E2和P4浓度变化规律与排卵数关系研究

绵羊在发情周期中各生殖激素浓度变化与卵泡发育、成熟和排卵有着密切的关系。为了研究巴美肉羊血清生殖激素的动态变化及其与排卵数关系,试验采用电化学法,测定了12只成年母羊发情期血清中2种类固醇激素(E₂和P₄)的浓度水平,分析其动态变化规律,并用SAS 9.0的方差分析程序分析激素浓度与排卵数的关系。结果表明,两种激素在排单卵组和排双卵组绵羊间变化规律不同,E₂在排单卵组表现为先下降后升高的变化趋势,在排双卵组表现为持续下降趋势;P₄在排单卵组表现为持续上升的趋势,在排双卵组为先上升后下降的变化趋势。排单卵和排双卵组绵羊在各时间点的E₂和P₄激素浓度差异均不显著(P＞0.05)。     

The Expanding Role of Recombinant Gonadotropins in Assisted Reproduction

Using recombinant gonadotropins for assisted reproduction of domestic species is still in its infancy. Yet, the purity, potency and pathogen-free nature of recombinant gonadotropins make them attractive alternatives to tissue-derived gonadotropic agents. In this study, the authors summarize the work to date using recombinant gonadotropins to enhance the - fertility of domestic animals and they discussed their recent studies examining the biopotency of single chain analogues of human gonadotropins. In these studies, single chain analogues of follicle stimulating hormone (Fcα), chorionic gonadotropin (CGβα) or a gonadotropin construct with dual activity (FcCGβα) were administered to sheep pre-treated with antisera directed against GnRH. Ovulation was induced 3 days after analogue administration using hCG (1000 IU, iv). Although Fcα or CGβα alone induced only modest oestradiol production during the pre-hCG period, serum concentrations of oestradiol were markedly increased (p < 0.05) 3 days after administration of FcCGβα or the Fcα + CGβα combination. Final ovarian weight was significantly increased (p < 0.05) in animals receiving Fcα, Fcα + CGβα or FcCGβα. Collectively, these observations demonstrate that the single chain analogues of the human gonadotropins are active in sheep.     

Shikimate accumulation in nine weedy species following glyphosate application

Glyphosate is commonly used in a variety of weed control scenarios and plants respond biochemically by continuing to attempt to push carbon through the shikimate pathway. The result is an accumulation of shikimate in sensitive plants in the days immediately after application. This research determined shikimate accumulation dynamics in nine problematic plant species from 0 to 6 days after treatment (DAT). Ambrosia artemisiifolia, Trifolium repens and Conyza canadensis showed rising concentrations through 6 DAT to >4000 mg L^?1. Chenopodium album, Xanthium strumarium and Urochloa platyphylla showed concentrations levelling off to a constant of about 2000 mg L^?1. Ambrosia trifida, Amaranthus palmeri and Polygonum pensylvanicum generally showed lower levels of shikimate accumulation and concentrations were decreasing after 3 DAT. No apparent relationships were evident between shikimate accumulation pattern and plant growth rate or speed of glyphosate activity. There also appeared to be no pattern in the shikimate accumulation trends that would allow for an informed decision as to which of these species would be most likely to develop glyphosate resistance. Shikimate concentrations were in agreement between field and glasshouse conditions for C. canadensis, but did not agree with those from A. palmeri.     

蓟马取食对苜蓿氨基酸组成及含量的影响

为了探究蓟马取食对苜蓿(Medicago sativa L.)氨基酸组成及含量的影响,本研究以'草原2号'(Medicago varia Martin.'Caoyuan No.2')感蓟马品种和'草原4号'(Medicago sativa L.'Caoyuan No.4')抗蓟马品种为材料,分别进行牛角花齿蓟马(Odo...     

Protection of recently shorn sheep against adverse weather using plastic coats

Sheep cold stressed for 10.5 h had plastic coats applied then the cold stress was continued. In 9 of 10 sheep (test group) showing hypothermia at the time coats were applied, body temperatures had returned to near normal 2.5 h later and to normal in 13.5 h. One sheep severely hypothermic before the coat was applied did not improve and was killed after 2.5 h. Sheep that were cold stressed without coats (wet controls) developed marked hypothermia and were killed between 10.5 h and 21 h. Rectal temperatures remained normal in controls that were cold stressed with coats on (coated wet controls) and in the controls not subjected to wetting (dry controls). Plasma cortisol increased markedly in the cold stressed sheep until plastic coats were applied, but the levels had fallen to normal levels 20 h later. Serum thyroxine levels increased at a faster rate in the test group and in wet controls than in the dry controls and coated wet controls during the first 9 h of cold stress. In 4 sheep of the test group energy utilisation increased markedly and remained high for a variable time after coats were applied then gradually returned to pre-cold stress levels. Liver tyrosine aminotransferase levels of the wet controls were markedly elevated compared to levels found in the test group sheep killed 79.5 h after coats were applied. Histological changes in the spleen and liver of wet controls was absent or only mildly present in the test group sheep. There was severe depletion of muscle and liver glycogen in the wet controls compared with the test group sheep, which were similar to the dry controls and coated wet controls.     

A visual assessment technique for estimating seagrass standing crop

1. Ground-truthing techniques for measuring seagrass standing crop need to be simple, precise, non-destructive and quick. 2. Mellors (1991) designed a visual assessment technique for estimating above-ground seagrass biomass. This paper builds on Mellors' work and presents a modified method for estimating standing crop which uses a six-point ordinal scale (excluding zero). 3. Being non-destructive, this technique is ideally suited for resource assessment in environmentally sensitive areas and, being quick, is potentially useful when threats are imminent. 4. Statistical methods and data presented in this study will allow sample size/statistical power relationships to be estimated for any comparable study and therefore negate the need to conduct pilot surveys. © 1997 John Wiley & Sons, Ltd.