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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.
Neuromodulative actions of cytokines 总被引:11,自引:0,他引:11
C M Blatteis 《The Yale journal of biology and medicine》1990,63(2):133-146
Interleukin 1, interferon alpha 2, and tumor necrosis factor alpha are cytokines that centrally mediate various reactions typical of the host defense responses to infection. The preoptic-anterior hypothalamus is an important, but not exclusive, integrative and controlling region for several of these effects. Although these cytokines display some common functional activities (e.g., pyrogenicity, somnogenicity), the characteristics of the responses they induce are different. Their effects, moreover, can be evoked or suppressed selectively, indicating that the neuronal substrates and/or neuromodulators used are distinct, each possessing discrete but partially overlapping sensory combinations. Nevertheless, it is not yet obvious how these systems are organized and integrated in host defense. It is also unclear whether these cytokines are elaborated peripherally and gain access to the brain or whether they are induced centrally. The available data suggest that circulating cytokines probably do not penetrate the brain but may activate elements in the organum vasculosum laminae terminalis. This site appears to be critically important for the production of the centrally mediated effects of blood-borne cytokines; it is speculated that the cytokines evoke there local signals that transduce their message; serotonin may be linked to these signals. 相似文献
3.
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
4.
Fever and regional blood flows in wethers and parturient ewes 总被引:1,自引:0,他引:1
Blatteis C. M.; Hales J. R.; Fawcett A. A.; Mashburn T. A. Jr 《Journal of applied physiology》1988,65(1):165-172
To determine whether the reported absence of fever in full-term-pregnant ewes might be associated with shifts of regional blood flows from thermogenic tissues to placenta during this critical period, fevers were induced twice by injections of Escherichia coli lipopolysaccharide (LPS, 0.25 microgram/kg iv) into each of six Merino ewes from 8 to 1 days prepartum, and their regional blood flow distribution was measured with radioactive, 15-microns-diam microspheres before and during the rise in fever (when their rectal temperature had risen approximately 0.4 degree C). Unexpectedly, fever always developed, rising to heights not significantly different at any time before parturition [4-8 days prepartum = 0.81 +/- 0.23 degree C (SE); 1-3 days prepartum = 0.75 +/- 0.17 degree C) and similar to those in three wethers treated similarly (0.90 +/- 0.10 degree C). Generally, during rising fever, blood flow in the ewes shifted away from heat loss tissues (e.g., skin, nose) to heat production tissues (e.g., shivering muscle, fat) and cardiac output increased; blood flow through redistribution organs (e.g., splanchnic bed) decreased. The reverse occurred during defervescence. Utero-placental blood flow remained high in the febrile ewes. These regional blood flow distributions during febrigenesis and lysis are essentially the same as those during exposures to ambient cold and heat, respectively. Some differences in the responses of cardiac output and its redistribution, however, were apparent between wethers and pregnant ewes. We conclude that 1) the previously reported "absence of fever in the full-term-pregnant sheep" should not be regarded as a general phenomenon and 2) full-term-pregnant sheep support fever production without sacrificing placental blood flow. 相似文献
5.
6.
The thermoregulatory responses to 10 degrees C (for 3 h) were investigated in 1) 12 natives from sea level (lowlanders) at 150 m, and on arrival at 3,350 and 4,340 m; 2) 6 of these during a 6-wk sojourn at 4,360 m, and on return to sea level; and 3) 5 natives from each of the two altitudes (highlanders) in their respective habitat, and after descent to 150 m. The cold-induced increase in the rate of O2 consumption (Vo2) of the lowlanders was significantly smaller at both altitudes than at sea level. It did not recover substantially during the 6 wk at altitude, but was restored to its initial rate on return to sea level. By contrast, visible shivering activity was augmented on arrival at altitude. It persisted throughout the 6 wk there, but was greatly depressed on return to sea level, despite the increased Vo2. Mean skin temperatures (Tsk) stabilized in the cold at significantly higher values at altitude. Rectal temperature (Tre) decreased similarly at all altitudes. Vo2 of the highlanders in the cold was significantly greater at sea level than at their resident altitudes, although shivering activity was less intense; Tsk stabilized at significantly lower levels at 150 m than at either altitude. These results indicate that altitude exposure reduces the calorigenic response of man to cold, and that this effect is not moderated by acclimatization to altitude, yet is reversible immediately on descent to sea level. The component of cold thermogenesis which appeared to be reduced by altitude exposure was nonshivering thermogenesis rather than visible shivering. 相似文献
7.
8.
Pasquier CM; Promponas VI; Varvayannis NJ; Hamodrakas SJ 《Bioinformatics (Oxford, England)》1998,14(8):749-750
Summary : FT is a tool written in C++, which implements the Fourier
analysis method to locate periodicities in aminoacid or DNA sequences. It
is provided for free public use on a WWW server with a Java interface.
Availability : The server address is http://o2.db. uoa.gr/FT Contact :
shamodr@atlas.uoa.gr
相似文献
9.
Background
Paulinella chromatophora is a freshwater filose amoeba with photosynthetic endosymbionts (chromatophores) of cyanobacterial origin that are closely related to free-living Prochlorococcus and Synechococcus species (PS-clade). Members of the PS-clade of cyanobacteria contain a proteobacterial form 1A RubisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) that was acquired by horizontal gene transfer (HGT) of a carboxysomal operon. In rDNA-phylogenies, the Paulinella chromatophore diverged basal to the PS-clade, raising the question whether the HGT occurred before or after the split of the chromatophore ancestor. 相似文献10.