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1.
KM Morton SL Catt FK Hollinshead WMC Maxwell G Evans 《Reproduction in domestic animals》2004,39(6):454-461
Cumulus-oocyte complexes from hormone-stimulated 3-4-week-old (n=43) and 6-7-week-old (n=12) prepubertal lambs were matured in vitro and incubated with unsorted, or X- or Y-spermatozoa separated with a high-speed cell sorter (SX MoFlo)frozen-thawed. Presumptive zygotes were then cultured to the blastocyst stage, and transferred to recipients fresh or after cryopreservation (frozen). Oocyte cleavage was higher (p <0.05) with unsorted (515/926, 55.6%) than X- or Y-spermatozoa (261/672, 38.8% and 229/651, 35.2%, respectively) and blastocyst formation (% zygotes) by Day 9 of in vitro culture was lower (p <0.05) for X- (102/261, 39.1%) than unsorted spermatozoa (249/515, 48.3%), but did not differ between Y-spermatozoa (103/229, 45.0%) and unsorted spermatozoa, or between X- and Y-spermatozoa (p >0.05). For fresh embryos, survival to term was 50.0% (3/6) for unsorted, 0.0% (0/6) for X- and 16.7% (1/6) for Y-spermatozoa-derived embryos (p >0.05), and for frozen embryos was 4.0% (2/50) for unsorted, 9.1% (2/22) for X- and 2.9% (1/34) Y-spermatozoa-derived embryos (p >0.05). Of the two lambs born from X-spermatozoa-derived embryos, one was female (50%), and from the two Y-spermatozoa-derived lambs, both were male (100%), demonstrating that lambs can be produced after the transfer of fresh and cryopreserved IVP embryos derived from prepubertal lamb oocytes and frozen-thawed sex-sorted sperm. 相似文献
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Performance records on 41,184 Red Angus cattle were analyzed and estimates of parameters calculated for absolute growth rate, relative growth rate and restricted selection indices. Heritability estimates for birth weight, 205-d weight, 365-d weight and postweaning gain were .46 +/- .02, .39 +/- .02, .40 +/- .02 and .36 +/- .02, respectively. Heritability estimates for preweaning, postweaning and postnatal relative growth rates were identical (.33 +/- .02). Heritability estimates for restricted selection indices were .31 +/- .02, .33 +/- .02 and .31 +/- .02 for weaning index, yearling index and postweaning index, respectively. The genetic correlation between preweaning and postweaning absolute growth rate was .15. The genetic correlation between consecutive measurements of relative growth rate (RGR) was -.33. Genetic correlations of birth weight with preweaning RGR and postnatal RGR were -.68 and -.71, respectively. Correlations among measures of relative growth rate using simulated data were similar to correlations of actual data, indicating that these relationships are the result of numerator/denominator relationships and not biological causes. The genetic correlation between weaning and postweaning indices was near zero. Small genetic coefficients of variation for preweaning and postnatal relative growth rates indicate further problems with the expression of growth in this manner. Restricted selection indices exhibited much larger genetic coefficients of variation than measurements of RGR. Genetic standard deviations were 7.8%, 7.2% and 13.7% of the means for weaning, yearling and postweaning indices, respectively. 相似文献
4.
The collisional reaction probabilities of several atmospheric species on bulk sulfuric acid surfaces indicate that heterogeneous processes may be important in tropospheric chemistry. 相似文献
5.
KM Blackwood 《Science (New York, N.Y.)》1996,273(5277):909-912
Side-chain ferroelectric liquid crystalline polymers are currently used in a number of applications, including displays and electrical sensors. Comparisons with existing technologies and materials indicate that relative to ceramics, such polymers have lower figures of merit but offer greater durability in sensor applications. 相似文献
6.
Mutation to herbicide resistance maps within the psbA gene of Anacystis nidulans R2 总被引:11,自引:0,他引:11
A psbA gene encoding the target of photosystem II herbicide inhibition, the 32,000-dalton thylakoid membrane protein, has been cloned from a mutant of Anacystis nidulans R2, which is resistant to 3-(3,4-dichlorophenyl)-1,1-dimethylurea-(diuron). A cloned DNA fragment from within the coding region of this gene transforms wild-type cells to herbicide resistance, proving that mutation within psbA is responsible for that phenotype. The mutation consists of a single nucleotide change that replaces serine at position 264 of the wild-type protein with alanine in that of the diuron-resistant mutant. 相似文献
7.
A modeling study of atmospheric diffusion indicates that emission from power plants contributed only a modest percentage of the yearly average concentration of sulfur dioxide at ground level in the most polluted areas of Cook County, Illinois, during 1968. 相似文献
8.
JH Golden FJ DiSalvo JMJ Frechet J Silcox M Thomas J Elman 《Science (New York, N.Y.)》1996,273(5276):782-784
The preparation and analysis of inorganic-organic polymer nanocomposites consisting of inorganic nanowires and multiwire "cables" in a random-coil organic polymer host is reported. Dissolution of inorganic (LiMo3Se3)n wires in a strongly coordinating monomer, vinylene carbonate, and the use of a rapid polymerization in the presence of a cross-linking agent produce nanocomposites without phase separation. Polymerization of dilute solutions yields a material containing mostly (Mo3Se3(-))n mono- and biwires, 6 to 20 angstroms in diameter and 50 to 100 nanometers long. Polymerization of more concentrated liquid crystalline solutions yields a nanocomposite containing oriented multiwire cables, 20 to 40 angstroms in diameter and up to 1500 nanometers long, that display optical anisotropy and electrical conductivity. 相似文献
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10.
Dennis L. Golden DVM Clinton D. Lothrop Jr DVM PhD 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1988,2(3):121-125
A retrospective study on stored plasma from normal dogs and dogs with pituitary dependent hyperadrenocorticism (PDH), pituitary dependent hyperadrenocorticism controlled by mitotane (o,p'-DDD),* iatrogenic hyperadrenocorticism, and hypoadrenocorticism was conducted to determine if alterations in aldosterone production exist in these disorders. The plasma aldosterone concentration (PAC) was measured by radioimmunoassay immediately before and 1 hour after adrenocorticotropic hormone (ACTH) administration (0.5 IU/kg, intravenously [IV]). PACs increased significantly when ACTH was administered to normal dogs. Dogs with PDH had a lower baseline PAC, but their PAC increased to levels similar to that of normal dogs after ACTH administration. In dogs with PDH controlled by o,p'-DDD therapy, the response to ACTH was significantly less than that of normal dogs or dogs with untreated PDH. Dogs with iatrogenic hyperadrenocorticism had a lower baseline and post-ACTH PAC than normal dogs. Dogs with hypoadrenocorticism had a normal basal PAC, but showed no significant increase in PAC following ACTH administration. These findings suggest that PACs are significantly altered in a variety of adrenal diseases, and that the ACTH stimulation test may be useful when evaluating aldosterone secretion in adrenopathic disorders. In addition, at therapeutic dosages, o,p'-DDD treatment was associated with a decrease in basal and post-ACTH PACs in dogs with PDH. 相似文献