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991.
E N Amuzu-Aweh P Bijma B P Kinghorn A Vereijken J Visscher J AM van Arendonk H Bovenhuis 《Heredity》2013,111(6):530-538
Prediction of heterosis has a long history with mixed success, partly due to low numbers
of genetic markers and/or small data sets. We investigated the prediction of heterosis
for egg number, egg weight and survival days in domestic white Leghorns, using
∼400 000 individuals from 47 crosses and allele frequencies on
∼53 000 genome-wide single nucleotide polymorphisms (SNPs). When heterosis is
due to dominance, and dominance effects are independent of allele frequencies, heterosis
is proportional to the squared difference in allele frequency (SDAF) between parental pure
lines (not necessarily homozygous). Under these assumptions, a linear model including
regression on SDAF partitions crossbred phenotypes into pure-line values and heterosis,
even without pure-line phenotypes. We therefore used models where phenotypes of crossbreds
were regressed on the SDAF between parental lines. Accuracy of prediction was determined
using leave-one-out cross-validation. SDAF predicted heterosis for egg number and weight
with an accuracy of ∼0.5, but did not predict heterosis for survival days. Heterosis
predictions allowed preselection of pure lines before field-testing, saving
∼50% of field-testing cost with only 4% loss in heterosis. Accuracies
from cross-validation were lower than from the model-fit, suggesting that accuracies
previously reported in literature are overestimated. Cross-validation also indicated that
dominance cannot fully explain heterosis. Nevertheless, the dominance model had
considerable accuracy, clearly greater than that of a general/specific combining
ability model. This work also showed that heterosis can be modelled even when pure-line
phenotypes are unavailable. We concluded that SDAF is a useful predictor of heterosis in
commercial layer breeding. 相似文献
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993.
The photoperiodic response of diapause induction is studied in females of five subtropical and warm‐temperate zone populations of Nezara viridula (L.) (Heteroptera: Pentatomidae) in Japan (26.4–34.7°N; 127.4–135.7°E). Laboratory tests at 25 °C demonstrate that both warm‐temperate and subtropical populations have pronounced photoperiodic responses of adult diapause induction. Under short‐day conditions (LD 10 : 14 h), 73–100% of females enter diapause, whereas, under long‐day conditions (LD 15 : 9 h), 87–100% of females are nondiapause and reproduce. When the critical photoperiod for diapause induction is plotted against the latitude of origin of each population, the data points do not show the expected tendency of increasing critical photoperiod northwards but, instead, vary between 12 h 15 min and 13 h 30 min. It is suggested that adults from different populations of such a highly migratory species move often among subtropical islands (by themselves or being assisted by typhoons), thus constantly destabilizing the photoperiodic responses. Although important for general synchronization of seasonal development in the tropics and subtropics, winter diapause might not be so critical for survival in mild winters in these zones. Such circumstances might make the selective pressure over the photoperiodic response less severe in the tropics and subtropics than in the temperate zone. It is suggested that the current climate warming might contribute to this situation as well by promoting polewards migrations and lessening the selective pressure of overwintering conditions. 相似文献
994.
Dorothy M. Fragaszy Sophie A. Barton Sreinick Keo Rushi Patel Patrícia Izar Elisabetta Visalberghi Michael Haslam 《American journal of primatology》2020,82(7):e23156
Wild bearded capuchin monkeys (Sapajus libidinosus) habitually use stone hammers to crack open palm nuts and seeds on anvils. This activity requires strength, balance, and precise movement of a large stone with respect to the item placed on an anvil. We explored how well young monkeys cope with these challenges by examining their behavior and the behavior of adults while they cracked palm nuts using a stone. Using video records, we compared actions of six juvenile (2–5 years) and six adult (7+ years) wild monkeys during their first 20 strikes with one unfamiliar ellipsoid, quartzite stone (540 g), and the outcomes of these strikes. Compared with adults, juveniles cracked fewer nuts, performed a more diverse set of exploratory actions, and less frequently placed one or both hands on top of the stone on the downward motion. Adults and juveniles displayed similar low frequencies of striking with a slanted trajectory, missing the nut, and losing control over the nut or stone after striking. These findings indicate that young monkeys control the trajectory of a stone adequately but that is not sufficient to crack nuts as effectively as adults do. Compared with juveniles, adults more quickly perceive how to grip the stone efficiently, and they are able to adjust their grip dynamically during the strike. Young monkeys develop expertise in the latter aspects of cracking nuts over the course of several years of regular practice, indicating that perceptual learning about these aspects of percussion occurs slowly. Juvenile and adult humans learning to use stones to crack nuts also master these features of cracking nuts very slowly. 相似文献
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998.
Liu Hong Habiba Sultana Karina Paulius Guoquan Zhang 《The Journal of steroid biochemistry and molecular biology》2009,114(3-5):180-185
Bone marrow mesenchymal stem cells (MSCs) are considered a potential cell source for stem cell-based bone tissue engineering. However, noticeable limitations of insufficient supply and reduction of differentiation potential impact the feasibility of their clinical application. This study investigated the in vitro function of steroids and gender differences on the proliferation and differentiation of rat MSCs. Bone marrow MSCs of age-matched rats were exposed to proliferation and osteogenic differentiation media supplements with various concentrations of 17β-estradiol (E2) and dexamethasone. Cell proliferation was measured by MTS assay; osteogenic markers and steroid-associated growth factors and receptors were evaluated by ELISA and real-time PCR. The results revealed that supplements of E2 and dexamethasone increase MSC proliferation in a biphasic manner. The optimal dose and interaction of steroids required to improve MSC proliferation effectively varied depending on the gender of donors. Supplementation of E2 effectively improves osteogenic differentiation markers including ALP, osteocalcin and calcium levels for MSCs isolated from both male and female donors. The mRNA of TGF-β1 and BMP-7 are also up-regulated. However, effective doses to maximally improve osteogenic potentials and growth factors for MSCs are different between male and female donors. The relationship between steroid receptors, osteogenic markers and cytokines are also varied by genders. The outcomes of the present study strongly indicate that steroids potentially function as an effective modulator to improve the capacity of MSCs in bone regeneration. It provides crucial information for improving and optimizing MSCs for future clinical application of bone regeneration. 相似文献
999.
《水生昆虫》2012,34(2):189-205
The abundance and taxonomic composition of the aquatic insect fauna were investigated, with focus on adult water bugs, water beetles and water scavenger beetles (Heteroptera: Nepomorpha and Gerromorpha, and Coleoptera: Hydradephaga and Hydrophilidae) in two different freshwater habitats: (1) a periodically flooded area of the Special Zoological Reserve in Kopa?ki rit Nature Park, Croatia; and (2) melioration canals in the wider area of the Nature Park during 2005. Aquatic insects are generally abundant in various water systems, including floodplains that are exposed to water level fluctuations. Our aims were (1) to determine abundance and species richness in relation to habitat type; (2) to determine the influence of high flood peaks and oscillations during high water levels on the diversity of aquatic Coleoptera and Heteroptera in the flooded area; and (3) to identify characteristic species associated with each habitat type. We collected 71 species; 41 were captured at canals and 64 at the flooded area. Diversity of the two habitat types varied depending on the months but there were remarkable differences in species pool and their abundance. Both high and low water levels as well as oscillations during high water levels had major influence on species assemblages at the flooded area. Diversity of aquatic Coleoptera and Heteroptera was higher when the water level decreased after high water level peaks. A total of 11 species fulfilled the criteria for specificity and were sufficiently abundant to be suitable species characteristic for these two habitats. A higher proportion of significant characteristic species was present in the flooded area than in the canals. The presence of two Red List species of water beetles (Graphoderus bilineatus De Geer, 1774 and Berosus geminus Reiche et Saulcy, 1856) and nine significant characteristic species at the flooded area clearly indicates that the contribution of floodplains in maintaining freshwater biodiversity is not only important regionally but also at the international level. Also, our results suggest that the power of high water levels is an important factor that can be used in analyses on aquatic Coleoptera and Heteroptera assemblages, showing the uniqueness of large floodplain areas. 相似文献
1000.
《Electromagnetic biology and medicine》2013,32(2):236-243
The objective of the current work was to simulate radiofrequency ablation (RFA) with theoretical and realistic computational models, which correspond to single-compartment models and clinical scenarios. A 3D model in a cubic region of 12 cm edge was studied representing either a homogeneous model or real clinical scenarios in three human tissues, i.e., liver, lung and kidney. An active electrode was placed at the center of the model. Various tumor sizes (1–3 cm) and source voltages (10–30 V) were investigated for the second case of a two-compartment model. In the case of a 3-cm tumor in diameter, the electrical and thermal problems (at steady state) were solved to calculate the temperature distribution within the tumor and tissue. Lesion volume was quantified using the Arrhenius equation and the isothermals of 50 and 60 °C. The physical properties of all materials were constant during the simulations, i.e., no changes with temperature were considered. It was found that tumor conductivity was low to achieve significant damage in the tumor; in all clinical scenarios, saline-enhanced RFA was necessary and led to a more efficient tumor destruction. It was also shown that highly perfused tissues, such as liver and kidney, block the energy deposition within them, in contrast to lung, and, thus, require a further saline enhancement. Finally, the effect of perfusion on lesion size was studied, and it was concluded that tumor perfusion was more significant than surrounding tissue perfusion. 相似文献