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Mitochondrial DNA sequence diversity and the colonization of Scandinavia by house mice from East Holstein 总被引:3,自引:0,他引:3
43.
Fructan exohydrolase from grasses 总被引:8,自引:6,他引:2
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MICHAEL P. KOONCE PAULA M. GRISSOM MARY LYON THERESA POPE J. RICHARD McINTOSH 《The Journal of eukaryotic microbiology》1994,41(6):645-651
Cytoplasmic dynein is a high molecular weight, microtubule-based mechanochemical ATPase that is believed to provide motive force for a number of intracellular motilities, including transport of membrane-bound organelles. Cytoplasmic dynein also localizes to the mitotic spindles of some organisms and to the kinetochore regions of some condensed chromosomes, where it may play an active role in spindle assembly, spindle position, and/or chromosome movement during cell division. Despite active research efforts from a number of laboratories, little detail is yet available about dynein-based cellular activities. This paper describes our efforts to characterize cytoplasmic dynein from Dictyostelium and to use this protist as a molecular genetic factory to probe structure-function relationships of this molecule. 相似文献
45.
Wheat (Triticum aestivum L.) embryos form in dynamically-regulatedovular environments. Our objectives were to improve developmentof cultured immature wheat embryos by simulating, in vitro,abscisic acid (ABA) levels and O2 tensions as found in wheatovules during zygotic embryogenesis. We characterized from intactwheat kernels embryo respiration, embryo morphology and embryoand endosperm + ABA levels at 13, 19 and 25 d post-anthesis(DPA). Young (13 DPA) embryos were then excised and culturedin vitro, where they were exposed to 0·2 or 2·Ommol m3 ±ABA and 2.·1, 2·5 or 7·4mol m3 (6, 7 and 21%, respectively) gaseous O2. At 6and 12 d in culture, + ABA levels, embryo respiration and embryomorphology were characterized by treatment. Thirteen-day-oldembryos from two different plant populations differed by 17-foldin initial ABA content. However, this difference did not affectprecocious germination in vitro, nor did it affect the amountof exogenous ABA required to reduce precocious germination by40%. In this respect, embryos from both populations were equallysensitive to exogenous ABA. Cavity sap O2 levels (2·1to 2·5 mol m3) were much more effective in preventingprecocious germination of cultured embryos than were cavitysap levels of ABA (0·2 to 2·0 mmol m3).The combination of physiological levels of both ABA and O2 largelynormalized DW accumulation and embryo morphology without alteringendogenous + ABA levels. Residual respiration of cultured embryoswas higher than that of embryos grown in situ, and was not influencedby the exogenous O2 and ABA treatments Key words: Abscisic acid, embryo development, oxygen tensions, respiration, wheat 相似文献
46.
The effect of consumption of bitter taste substances (caffeine and beer) to bitter taste sensitivity was examined by 19 healthy adults. For individual taste sensitivity, detection thresholds were used on 6 bitter substances (caffeine, iso-alpha-acids: beer bittering agents, quinine sulfate, L-tryptophan, L-phenylalanine and glycyl-L-phenylalanyl-L-phenylalanine) and 3 non-bitter substances (L-aspartic acid, aspartame and NaCl). Nonusers of caffeine had significantly higher sensitivity (lower threshold) for caffeine compared to moderate and heavy users. Slight consumers of beer had significantly higher sensitivity for iso-alpha-acids relative to heavy users of beer, Iso-alpha-acids were not detected in saliva in acute dosing test by using 6 subjects. The correlations between thresholds of 6 bitter substances were calculated. Significant correlations (p < 0.01) were noted in 2 cases between caffeine and quinine, and iso-alpha-acids and L-trypothan. These data suggest the significant relation between individual bitter taste sensitivity and the consumption of caffeine and beer (iso-alpha-acids). 相似文献
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1IntroductionHongKongliesonthesouthcoastofChinabetweenlatitudes22?9'-22?TNandlon-gitudesl13?2'Nl14?0'E.ItconsistsofasectionoftheChinesemainland(KowloonandtheNewTerritories,782km2)andnumerousislands,ofwhichthelargestareLantauIsland(142km2)andHongKongIsland(78km2).Thetotalareais1076km2.Thetopographyisextremelyrugged,reaching957matthehighestpoint,TaiMoShah,intheNewTerrito-ries.HongKong'spopulationof6millionpeopleisconcentratedonthelimitednaturalflatland,whichhasbeenextendedbycoastalrecla… 相似文献
49.
ANDERS FORSMAN RICHARD SHINE 《Biological journal of the Linnean Society. Linnean Society of London》1995,55(4):273-291
Females of Lampropholis delicata are dimorphic for colour pattern, the difference between morphs being the presence or absence of a distinct white mid-lateral stripe. A less distinct striped morph occurs also in males. We evaluated alternative hypotheses for the maintenance of this polymorphism by examining temporal and spatial variation in morph frequency, testing for differential selection among morphs using data on body size and reproductive traits from preserved specimens, and experimentally manipulating colour pattern in free-ranging lizards of both sexes, to assess the influence of the lateral stripe on survival rates. We found that the relative frequency of striped individuals varied among populations and decreased from north to south in both sexes, coincident with an increasing incidence of regenerated tails. Morph frequencies did not change through time within a population. Striped gravid females appeared to survive better and produced larger clutches than did non-striped females. In our experimental study, the relationship between survival and colour morph differed between the two sexes; males painted with a white lateral stripe had lower survival than control (brown stripe) males, but survival did not differ between striped and control females. The different response in the two sexes may be due partly to differences in temperature and microhabitat selection. We propose that the white lateral stripe decreases susceptibility to predators in gravid females but increases risk of predation in males, especially in combination with low temperatures. The polymorphism might be maintained by: (1) opposing fitness consequences of the stripe in males and females; (2) sex-specific habitat selection; and (3) gene flow in combination with spatial variation in relative fitness of the two morphs. 相似文献
50.