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排序方式: 共有177条查询结果,搜索用时 203 毫秒
1.
A method was developed to optimize simultaneous selection for a quantitative trait with a known QTL within a male and a female line to maximize crossbred performance from a two-way cross. Strategies to maximize cumulative discounted response in crossbred performance over ten generations were derived by optimizing weights in an index of a QTL and phenotype. Strategies were compared to selection on purebred phenotype. Extra responses were limited for QTL with additive and partial dominance effects, but substantial for QTL with over-dominance, for which optimal QTL selection resulted in differential selection in male and female lines to increase the frequency of heterozygotes and polygenic responses. For over-dominant QTL, maximization of crossbred performance one generation at a time resulted in similar responses as optimization across all generations and simultaneous optimal selection in a male and female line resulted in greater response than optimal selection within a single line without crossbreeding. Results show that strategic use of information on over-dominant QTL can enhance crossbred performance without crossbred testing. 相似文献
2.
Effect of postnatal development on calcium currents and slow charge movement in mammalian skeletal muscle 总被引:16,自引:3,他引:13 下载免费PDF全文
Single- (whole-cell patch) and two-electrode voltage-clamp techniques were used to measure transient (Ifast) and sustained (Islow) calcium currents, linear capacitance, and slow, voltage-dependent charge movements in freshly dissociated fibers of the flexor digitorum brevis (FDB) muscle of rats of various postnatal ages. Peak Ifast was largest in FDB fibers of neonatal (1-5 d) rats, having a magnitude in 10 mM external Ca of 1.4 +/- 0.9 pA/pF (mean +/- SD; current normalized by linear fiber capacitance). Peak Ifast was smaller in FDB fibers of older animals, and by approximately 3 wk postnatal, it was so small as to be unmeasurable. By contrast, the magnitudes of Islow and charge movement increased substantially during postnatal development. Peak Islow was 3.6 +/- 2.5 pA/pF in FDB fibers of 1-5-d rats and increased to 16.4 +/- 6.5 pA/pF in 45-50-d-old rats; for these same two age groups, Qmax, the total mobile charge measurable as charge movement, was 6.0 +/- 1.7 and 23.8 +/- 4.0 nC/microF, respectively. As both Islow and charge movement are thought to arise in the transverse-tubular system, linear capacitance normalized by the area of fiber surface was determined as an indirect measure of the membrane area of the t-system relative to that of the fiber surface. This parameter increased from 1.5 +/- 0.2 microF/cm2 in 2-d fibers to 2.9 +/- 0.4 microF/cm2 in 44-d fibers. The increases in peak Islow, Qmax, and normalized linear capacitance all had similar time courses. Although the function of Islow is unknown, the substantial postnatal increase in its magnitude suggests that it plays an important role in the physiology of skeletal muscle. 相似文献
3.
Diet of the brown howler monkeyAlouatta fusca in a semi-deciduous forest fragment of southeastern Brazil 总被引:1,自引:1,他引:0
Adriano Garcia Chiarello 《Primates; journal of primatology》1994,35(1):25-34
The diet of a group of six brown howlers was studied weekly during 12 months in a reserve of 250 ha of secondary, mesophytic,
semi-deciduous forest. The phenology of 186 trees of 72 species and 29 families was monitored simultaneously. Scan sampling
was used to record the diet from dawn until dusk on a total of 60 days of observation, yielding 718 hr of animal-observer
contact and 2,943 feeding scans. The diet was composed of leaves (73%), flowers (12%), and fruits (5%), from 68 identified
plant species.Celtis iguanae, Cassia ferruginea, andInga spp. were the main food sources, accounting for approximately 50% of the diet. Young leaves (59%) were preferred to mature
leaves (31%), trees contributing 56% and lianas 41% of the leaf diet. The ingestion of young leaves was correlated to the
availability of these items, however, the correlations were not significant for flowers and fruits. The diet was poorer in
fruits and richer in young leaves of lianas in comparison to other howler monkey species studies, probably as a consequence
of the liana abundance in this forest fragment. 相似文献
4.
5.
For a finite locus model, Markov chain Monte Carlo (MCMC) methods can be used to estimate the conditional mean of genotypic values given phenotypes, which is also known as the best predictor (BP). When computationally feasible, this type of genetic prediction provides an elegant solution to the problem of genetic evaluation under non-additive inheritance, especially for crossbred data. Successful application of MCMC methods for genetic evaluation using finite locus models depends, among other factors, on the number of loci assumed in the model. The effect of the assumed number of loci on evaluations obtained by BP was investigated using data simulated with about 100 loci. For several small pedigrees, genetic evaluations obtained by best linear prediction (BLP) were compared to genetic evaluations obtained by BP. For BLP evaluation, used here as the standard of comparison, only the first and second moments of the joint distribution of the genotypic and phenotypic values must be known. These moments were calculated from the gene frequencies and genotypic effects used in the simulation model. BP evaluation requires the complete distribution to be known. For each model used for BP evaluation, the gene frequencies and genotypic effects, which completely specify the required distribution, were derived such that the genotypic mean, the additive variance, and the dominance variance were the same as in the simulation model. For lowly heritable traits, evaluations obtained by BP under models with up to three loci closely matched the evaluations obtained by BLP for both purebred and crossbred data. For highly heritable traits, models with up to six loci were needed to match the evaluations obtained by BLP. 相似文献
6.
Thiago F. Rodrigues Aline M. B. Mantellatto Mariella Superina Adriano G. Chiarello 《Biological reviews of the Cambridge Philosophical Society》2020,95(1):1-21
Awareness of the natural ecological processes provided by organisms that benefit human well‐being has significantly progressed towards the goal of making conservation a mainstream value. Identifying different services and the species that provide them is a vital first step for the management and maintenance of these so‐called ecosystem services. Herein, we specifically address the armadillos, which play key functional roles in terrestrial ecosystems, including as ecosystem engineers, predators, and vectors of invertebrates and nutrients, although these roles have often been overlooked. Armadillos can control pests, disperse seeds, and be effective sentinels of potential disease outbreaks or bioindicators of environmental contaminants. They also supply important material (meat, medicines) and non‐material (learning, inspiration) contributions all over the Americas. We identify key gaps in the understanding of ecosystem services provided by armadillos and areas for future research required to clarify their functional role in terrestrial ecosystems and the services they supply. Such information will produce powerful arguments for armadillo conservation. 相似文献
7.
CM van der Loos 《Biotechnic & histochemistry》2013,88(3):141-154
Three fixation issues related to immunostaining are discussed here: 1) Generally, a tissue block is fixed, then embedded and sectioned (pre-fixation). The type of fixative applied, crosslinking or coagulating, has an impact on selecting an epitope retrieval method. Individual antigens have a fixation–retrieval characteristic. 2) A long fixation time, especially with crosslinking fixatives, may compromise the result of immunostaining. This negative effect varies among different antigens and can be partially restored by applying a more sensitive/efficient detection system such as tyramide amplification. 3) Sections cut from a fresh frozen tissue block usually are acetone fixed (post-fixation). This was accepted as the “gold standard” for a long time. Post-fixation, however, may have serious consequences for preservation of small peptides leaking from the cut open cells, whereas this is not the case with pre-fixed intact cells. Consequently, the concept of an acetone post-fixed cryostat tissue section as “gold standard” no longer exists and a more appropriate use of the terms immunohistochemistry and immunocytochemistry therefore seems justified. For many antibodies, it is not known whether a formalin fixed, paraffin embedded tissue specimen is appropriate. Suggestions are made for creating a positive control cell block for testing such antibodies. 相似文献
8.
Antonio Politano Vincenzo Formoso Gennaro Chiarello 《Plasmonics (Norwell, Mass.)》2013,8(4):1683-1690
The collective electronic excitations in thin Ag films deposited onto the Ni(111) surface were studied by high-resolution electron energy loss spectroscopy. A broad loss peak at 7.7 eV was assigned to the Ag multipole plasmon, in excellent agreement with calculations based on s-d polarization model. Ag multipole plasmon was excited only at grazing incidence. Furthermore, a strong dependence on the impinging energy exists. Multipole plasmon could be measured only for a very strict range of primary electron beam energies and it was excited by electrons scattered at a reflection plane located just underneath the jellium edge. Such mode was found to be dramatically more sensible to the state of the surface with respect to ordinary surface plasmon. Moreover, we report experimental evidence of interference effects in surface plasmon excitation. 相似文献
9.
Abstract Opportunistic sightings and strandings of Caperea marginata (n=196) from the vicinity of Australia and New Zealand (1884 to early 2007) were used to relate geographic and temporal patterns to oceanographic and broad-scale climatic variability. Records were not uniformly distributed along the coast and more (69%) were from Australia than New Zealand. Seven coastal whale ‘hotspots’ were identified which accounted for 61% of records with locality data. Half of the hotspot records were from southeast (37) and northwest (20) Tasmania—others each had 9–15 events. Upwelling and/or high zooplankton abundance has been documented near all whale hotspots. Records of C. marginata occurred in all months, with 75% in spring and summer. Inter-annual variability showed broad agreement between increased whale records (usually in spring/summer) and strongly positive ‘Niño 3.4’ during 1980–1995 but not thereafter. Coastal upwelling and productivity increase during climatic phenomena such as El Niño and are likely to be quickly beneficial to plankton-feeding whales such as C. marginata. 相似文献
10.
Primate Population Densities and Sizes in Atlantic Forest Remnants of Northern Espírito Santo,Brazil
We surveyed primates in seven fragments of Atlantic forest ranging from 210 to 24,250 ha in Espírito Santo, southeastern Brazil. The objective was to assess their population densities and fragment-specific population sizes in order to discuss the survival of primates in this highly fragmented landscape. We used line-transect sampling for censusing primates and estimated densities via DISTANCE program. Alouatta fusca, Cebus apella, Callicebus personatus, and Callithrix geoffroyi live in the study area. Although variable, primate numbers were higher in larger than in smaller fragments, the likely reasons being the lack of space and food resources (fruits) and higher impact of mesopredators (small cats) in small fragments. The estimated densities are within the range reported for other Atlantic forest sites, except for brown howlers (Alouatta fusca), which were extremely rare. Estimates of population sizes were on the order of several hundreds to thousands of individuals/species in the large-sized fragments (ca. 20,000 ha), while comparable estimates for the other areas indicate <500 individuals/species in the medium-sized reserves (ca. 2,000 ha), and <50 individuals/species in the small fragments (ca. 200 ha). These estimates suggest that only Atlantic forest fragments 20,000 ha can harbor primate populations large enough to escape extinction in the long term. Given that <20% of all protected areas remaining in the Atlantic forest are 20,000 ha, management measures are urgently needed to improve primate conservation in this biome. 相似文献