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941.
942.
A total of 764 breeding soundness examinations was conducted on beef bulls utilizing the method of examination and criteria for classifying bulls of the Society for Theriogenology. In addition to this examination each bull was subjected to scrotal circumference measurement and to weighing. Classification of the bulls according to breeding soundness potentials was as follows: 88% of the bulls were satisfactory potential breeders, 8% of the bulls were questionable potential breeders and 4% of the bulls were unsatisfactory potential breeders. The proportions of bulls in each classification; satisfactory, questionable, or unsatisfactory; were not different among the four breeds evaluated. The majority of bulls evaluated in this study were between 14 and 36 months of age and weighed between 900 and 1500 pounds. For the ages and weights evaluated, scrotal circumference measurement variances were not closely related to age and weight differences. There was a tendency shown for “Questionable” and “Unsatisfactory Potential Breeders” to have smaller scrotal circumference measurements. The study indicates that Angus, Charolais, Horned Hereford and Polled Hereford bulls of breeding ages and weights should have scrotal circumference measurements of at least 32 centimeters in order to be classified as “Satisfactory Potential Breeders”. 相似文献
943.
944.
B Hollenbach E Scherzinger K Schweiger R Lurz H Lehrach E E Wanker 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1999,354(1386):991-994
We have shown previously by electron microscopy that the purified glutathione S-transferase (GST)-Huntington's disease (HD) exon 1 fusion protein with 51 glutamine residues (GST-HD51) is an oligomer, and that site-specific proteolytic cleavage of this fusion protein results in the formation of insoluble more highly ordered protein aggregates with a fibrillar or ribbon-like morphology (E. Scherzinger et al. (1997) Cell 90, 549-558). Here we report that a truncated GST HD exon 1 fusion protein with 51 glutamine residues, which lacks the proline-rich region C-terminal to the polyglutamine (polyQ) tract (GST-HD51 delta P) self-aggregates into high-molecular-mass protein aggregates without prior proteolytic cleavage. Electron micrographs of these protein aggregates revealed thread-like fibrils with a uniform diameter of ca. 25 nm. In contrast, proteolytic cleavage of GST-HD51 delta P resulted in the formation of numerous clusters of high-molecular-mass fibrils with a different, ribbon-like morphology. These structures were reminiscent of prion rods and beta-amyloid fibrils in Alzheimer's disease. In agreement with our previous results with full-length GST-HD exon 1, the truncated fusion proteins GST-HD20 delta P and GST-HD30 delta P did not show any tendency to form more highly ordered structures, either with or without protease treatment. 相似文献
945.
Spatial, temporal and habitat-related variation in the abundance of large predatory fish at One Tree Reef, Australia 总被引:1,自引:1,他引:0
Patterns of abundance of large piscivorous fish (>200 mm TL) were documented at two spatial and four temporal scales within
the main lagoon of One Tree Reef on Australia’s Great Barrier Reef. Grouper (Serranidae), snapper (Lutjanidae) and wrasses
(Labridae) were the most abundant large piscivores. On a large scale (hundreds of metres), patterns of predator abundance
were consistently greater on the inner edge than centre of the lagoon over a range of temporal scales: days, weeks, months
and years. On a small spatial scale (tens of metres), the abundance of large predatory fish was patchy. At both spatial scales,
fish were consistently aggregated in particular areas and associated with specific structural features of the reef habitat.
Predator abundance was high where live corals were predominant and the topography was more complex. Hence, predation pressure
and its potential effects on the distribution and abundance of prey populations, both in time and space, may vary greatly
within lagoonal environments.
Accepted: 25 May 1997 相似文献
946.
947.
948.
949.
F. Hofhansl W. Wanek S. Drage W. Huber A. Weissenhofer A. Richter 《Biogeochemistry》2011,106(3):371-396
Bulk precipitation and throughfall were collected in a wet lowland rainforest in SW Costa Rica on an event basis to allow
modelling the contributions of dry deposition and canopy exchange to nutrient inputs and internal cycling of nutrients. Estimates
based on bulk precipitation underestimated total atmospheric deposition to tropical rainforests by up to 10-fold ignoring
the contributions of dry deposition. Canopy exchange contributed most of the aboveground inputs to the forest soil of Na+, about half for K+, 10% for P and Mg2+ and negligible for N, C and other elements. Tree species composition did not account for the differences found in net throughfall
between forest sites, and vegetation structure (plant area index) had only a small effect on net throughfall. Forest regrowth
affected net throughfall through reduced soil fertility and differences in leaf traits. Topography most significantly affected
net throughfall via increased dry deposition at sites of higher elevation and via soil fertility and increased canopy exchange
at down slope sites. 相似文献
950.
Recent evidence suggests that the nutritional state of male Mediterranean fruit flies, Ceratitis capitata (Wied.) (medfly), is an important influence on various components of their reproductive biology, including mating success. The objective of the present study was to examine experimentally the effect of temporary starvation on the mating success of wild male C. capitata. Males were maintained on protein–sugar or sugar-only diets, and for each diet we compared the mating success of continuously fed males versus males starved for 18 or 24 h immediately before testing. In trials conducted on field-caged, host trees, males starved for 24 h obtained only about half as many matings as fed males for both diets. However, when the starvation period was 18 h, starved males reared on the protein–sugar diet mated significantly less frequently than fed males, whereas starved males reared on sugar mated as often as fed males. Measurements of male pheromone calling and female attraction revealed that reduced mating success likely reflected the decreased signaling activity of starved males. 相似文献