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41.
42.
William J. Aspden Alexandra Rao Katherine Rose Paul T. Scott Iain J. Clarke Timothy E. Trigg John Walsh Michael J. D'Occhio 《Domestic animal endocrinology》1997,14(6)
Anterior pituitary gland contents of LH and LHß- and α-subunit mRNAs, and circulating concentrations of LH and testosterone, were determined in bulls treated with the LH-releasing hormone (LHRH) agonist deslorelin. Brahman (Bos indicus) bulls (14-month-old) were allocated to two groups and received the following: Control (n = 5), no treatment; Deslorelin (n = 4), four deslorelin implants (approximately 200 μg total deslorelin/day) for 36 d. Plasma concentrations of LH were higher in bulls treated with deslorelin on Day 1, had returned to typical levels by Day 8, and did not differ for control bulls and bulls treated with deslorelin from Day 8 to Day 29. Pituitary content of LH on Day 36 was reduced (P < 0.001) in bulls treated with deslorelin (33 ± 4 ng/mg) compared with control bulls (553 ± 142 ng/mg). Relative pituitary content of LHß-subunit mRNA was also reduced on Day 36 in bulls treated with deslorelin (Control, 0.65 ± 0.10; Deslorelin, 0.22 ± 0.04; P = 0.003). However, α-subunit mRNA relative content did not differ (Control, 0.73 ± 0.15; Deslorelin, 1.06 ± 0.12; P > 0.05). Plasma concentrations of testosterone were increased over the period of the experiment in the bulls treated with deslorelin compared with control bulls. This is the first demonstration of reduced pituitary content of LHß-subunit mRNA and LH, and unaltered content of α-subunit mRNA, in bulls treated with LHRH agonist. This was associated with apparently typical plasma concentrations of LH and elevated plasma testosterone. The anterior pituitary in bulls treated with LHRH agonist, therefore, undergoes classical desensitization and downregulation, but plasma LH and testosterone are not suppressed. 相似文献
43.
The effect of meal size and frequency on plasma volume, plasma aldosterone concentration and urinary Na and K clearances was determined in ponies. A daily maintenance ration of hay-grain pellets was provided either as a multiple feeding regimen, ie, 12 equal portions fed at 2-hour intervals, or as single large feedings, ie, half the ration fed every 12 hours at 0800 and 2000 hours. Only the effect of the single morning feeding was studied, using the latter regimen. Serial measurements of plasma volume were made by use of an indicator-dilution technique and indocyanine green (0.15 mg/kg of body weight, IV) that allowed repeated determinations at 2-hour intervals. Ingestion of the single large meal caused a 15% decrease in plasma volume by the end of a 1-hour feeding period. Feeding hypovolemia was confirmed by a coincident increase in plasma protein concentration (12%) and, in separate experiments, by analysis of postfeeding changes in the elimination of Evans blue dye. Plasma aldosterone concentration was significantly (P less than 0.05) increased from 2 to 5 hours after feeding. Urinary Na clearance decreased in response to feeding and remained lower than the prefeeding value until 9 hours after feeding. Urinary K clearance increased from prefeeding and reached a peak value between 5 and 7 hours after feeding. Creatinine clearance was unaffected. In contrast, the aforementioned variables were unchanged during the multiple regimen. Results indicate that ingestion of a large concentrate meal by ponies causes periprandial hypovolemia, activation of the renin-angiotensin-aldosterone system, and a subsequent antinatriuresis-kaliuresis that lasts for several hours. 相似文献
44.
45.
Daniel J. Archambault Eduardo Marentes Wayne Buckley John Clarke Gregory J. Taylor 《Euphytica》2001,117(2):175-182
We have developed a seedling-based bioassay that iscapable of identifying low Cd-accumulating phenotypes(homozygous and heterozygous) after 96–120 h ofexposure. Our experiments were conducted using109Cd as a tracer at subtoxic concentrations tosimulate conditions that might be experienced in thefield. Supply of Cd (10-11 M) to 4-d oldseedlings for 0–8 h resulted in no differences in rootand leaf Cd content between the low (TL05) and high(TL04) Cd-accumulating isolines. Increasing time ofexposure produced significant differences in leaf Cdaccumulation between isolines, with differencesbecoming most pronounced after the bulk of appliedcadmium ( 95%) was depleted from absorption solutions( 72 h). Similar results were obtained with8-d old seedlings, where differences between genotypeswere more pronounced in young leaves (2nd leaf) orshoot bases. Individuals from five low and highCd-accumulating near isogenic pairs (50individuals/isoline) were screened using Cdconcentration of shoot bases as the screeningcriterion. Mean scores within each isoline pair weresignificantly different, although overlap ofindividual scores was observed at intermediate foliarCd concentrations. The 2nd leaf to root Cdcontent ratio, which reflects root to shoottranslocation, provided a better parameter todistinguish low from high Cd-accumulating isolines. Plants used for this bioassay could also be rescuedfor subsequent experimental crosses, providing a rapidand cost-effective tool for early detection of the lowCd-accumulating phenotype. 相似文献
46.
Summary A CODASYL type database has been created for plant propagation records. The existence and history of plants can be recorded in such a way that details of parentage and offspring can be traced. Plants that have undergone similar treatments and events or that have similar characteristics can be located and other information assisting the management of the propagation experiments is recorded. Containing this information, the database is a model of experimental plant propagation. 相似文献
47.
Pre-harvest sprouting of wheat grain can cause economic losses especially in cultivars with low levels of seed dormancy. The
aim of this study was to determine genotype differences in embryo sensitivity to germination in response to exogenous (+/–)
cis-trans ABA treatments at different concentrations. Six white and four red seed-colored bread wheat genotypes that differed in dormancy
were grown in a field near Swift Current, Saskatchewan in 2000 as a randomized complete block design with four replicates.
The seed samples from this experiment were germinated in a controlled environment at 20 °C without light. The exogenous ABA
treatments were 0 μM – whole seed (control), 0 μM-embryos, 25 μM – embryos and 50 μM – embryos. The ABA experiment was a factorial
design with four randomized complete blocks with four ABA treatments in all combinations with the ten genotypes. A weighted
(by day) germination index (WGI) was calculated for each genotype in each ABA treatment. Genotypes differed in response to
ABA. The genotypes, ABA concentration and genotype by ABA concentration interaction effects were significant (p ≤ 0.05). Excised embryos showed significantly decreased dormancy in most of the experimental genotypes. The addition of exogenous
ABA enhanced embryo dormancy of most genotypes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
48.
Breeding territoriality in birds means that a certain proportion of the adult population may breed in suboptimal habitats or not breed at all. Non-breeding birds, or floaters, can have a `buffer effect' on breeding population size. Farmland bird declines in Britain are measured and analysed in terms of numbers of territory-holding birds. We use a population dynamics model to illustrate how, because of the buffer effect of floaters, there can be a time lag between the start of total population decline and detectable breeding population decline. Differences in the timing of declines of closely related farmland birds could therefore be due to slight differences in their population dynamics, rather than differences in their response to agricultural change. 相似文献
49.
L M Atkins D J Miner G S Sittampalam C D Wentling 《Journal of the Association of Official Analytical Chemists》1987,70(4):610-617
An integrated approach is presented for the establishment of purified protein and peptide reference standard materials suitable for both biological and chemical assays. Preliminary considerations, handling and storage conditions, and a variety of chemical methods for defining the reference standards are examined in detail. Of the chemical methods, liquid chromatography (LC), amino acid analysis, Kjeldahl protein assay, electrophoresis, and ion chromatography are key assays in determining the potency, purity, and identity of the reference standard preparation. Finally, the role of liquid chromatography in assessing reference standards for identity and chemical purity is examined and correlated with other methods. 相似文献
50.
Effect of gamma-irradiation on beef myoglobin 总被引:1,自引:0,他引:1