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81.
Several quinolizidine alkaloids, including various angelate esters, are known from the genus Pearsonia. In a detailed variation study which included 98 samples from nine of the 11 species, large qualitative and quantitative differences were recorded. The observed variation is ascribed to the following: 1, species (the alkaloids of some species and subspecies are diagnostically different); 2, provenance (various populations of the same species may have unique combinations of alkaloids); 3, developmental stage (in P. cajanifolia there is a marked decreased in esterification towards the end of the growing season); 4, plant parts extracted (seeds, for example, have high concentrations of hydroxylated lupanine-type alkaloids and only small amounts of esters). These results highlight some of the problems associated with the use of alkaloids as taxonomic characters. 相似文献
82.
大鼠离体左室乳头肌固定于最适初长位,逐步递减“后荷”获得一系列等张收缩的张力、长度缩短程度和速度。结果发现:(1)收缩末期张力-长度关系(ESTLR)为指数曲线,回归方程 T=ar~(-bL)-K 拟合的优度明显高于线性方程拟合的优度(P<0.001),其中 a,k 分别代表总张力和静息张力,b 为曲线的弯曲度;(2)在高钙(4mmol/L)或去甲肾上腺素(NE10~(-6)mol/L)作用下,ESTLR 右上移位,a,b 和无张力缩短速度 L_O 均增大(P均<0.01),尤以高钙时的变化更明显,(3)NE 使张力-速度曲线的右上移位比高钙显著。这提示大鼠离体心肌的 ESTLR 呈非线性特征,参数 a,b 及长度轴截距 L_O 对收缩强度的变化敏感,但对收缩速度改变的敏感性可能比经典的力学指标低。 相似文献
83.
S. M. Beckstrom-Sternberg Loren H. Rieseberg Khiem Doan 《Plant Systematics and Evolution》1991,175(3-4):125-138
Helianthus petiolaris andH. niveus are polytypic species which are morphologically distinct at the periphery of their ranges but intergrade in areas of sympatry.Helianthus niveus includes both annual and perennial members, whereasH. petiolaris is strictly annual. Chloroplast DNA and nuclear ribosomal DNA restriction site data were used to reconstruct the evolutionary history of populations of the two species. Cladistic analyses reveal the following: (1) neither species is monophyletic; (2) the annual habit is derived once in this complex; and (3) the region of morphological intergradation appears to be primary in origin. The significance of interbreeding versus common descent in defining species concepts is discussed in relation to the above cladistic analyses. 相似文献
84.
H. Ohno T. Yahata K. Yamashita A. Kuroshima 《International journal of biometeorology》1988,32(1):52-55
Seven male students were studied to observe the effects of acute cold exposure (at 10°C for 60 min) on erythrocyte concentrations of glycolytic intermediates in summer and in winter. The subjects shivered slightly but frankly in both experiments. Significant decreases were observed in the concentrations of pyruvate and lactate during body cooling in summer, but not in winter. The lactate concentration remained significantly reduced 15 min after cold exposure. After 60 min of cold exposure in summer, a negative crossover point appeared to exist between phosphoenolpyruvate and pyruvate and erythrocyte pyruvate kinase activity showed a significant decrease. No seasonal difference was observed in the initial control values of the intermediates measured. From these results and the fact that glucose, pyruvate and lactate are evenly distributed between erythrocytes and plasma, it is likely that erythrocytes and skeletal muscles need less fuel substrate, glucose during cold exposure in winter than in summer, suggesting that an increased economy of energy for homeostasis is achieved. 相似文献
85.
Ihsan M. Said Sami K. Abdel-Hafez Fadwa M. Al-Yaman 《International journal for parasitology》1988,18(8):1111-1114
,
and
1988. Morphological variation of Echinococcus granulosus protoscoleces from hydatid cysts of human and various domestic animals in Jordan. International Journal for Parasitology 18: 1111–1114. Rostellar hook morphology of protoscoleces was employed to study the possible existence of Echinococcus granulosus strains in humans and various domestic animals in Jordan. A distinct form in the donkey was evident as the protoscoleces from this host did not share any characteristics with those from the other hosts examined. Sheep, goats and cattle appeared to be affected by another form since the protoscoleces from their hydatid cysts shared six out of nine characteristics studied. Protoscoleces of camel and human cysts shared seven out of nine characteristics studied and they were different in six characteristics from protoscoleces from other hosts. Differences observed among the three forms may reflect strain variation of E. granulosus in this country. 相似文献
86.
The hatching distributions of rainbow trout (Salmo gairdneri) with different genotypes at eight loci are compared in two experiments with the same strain. Embryos were incubated at temperatures colder (5 and 8°C) and warmer (12°C) than normally experienced by these fish (9.5°C). At hatching, embryos were separated into five hatching groups representing the chronological order of hatching. There is no significant correlation between multilocus heterozygosity and hatching time at any temperature in either experiment. Fish in the middle of the hatching distribution had the highest average heterozygosity. In both experiments, heterozygotes at the majority of loci examined tended to hatch relatively later within the hatching distribution at 12°C than at both 5 and 8°C. Fish with different genotypes atPgm2 andCk1 showed significant differences in hatching time that were consistent between experiments.Ck1 heterozygotes hatched sooner than homozygotes at 8°C but later at 12°C.Pgm2 heterozygotes hatched later than homozygotes at all temperatures and significantly later in four of five cases. At the other loci examined, however, the relative hatching distributions of fish with particular genotypes were not significantly different or repeatable between experiments.This research was supported by National Science Foundation Grant BSR-8300039 awarded to Dr. Fred W. Allendorf. Moira M. Ferguson was supported by a postgraduate scholarship from the Natural Sciences and Engineering Research Council of Canada. 相似文献
87.
Andrew S. Pullin 《Entomologia Experimentalis et Applicata》1986,41(3):237-242
The variation in response to photoperiod and temperature of different populations of the peacock butterfly, Inachis io (L.) (Lepidoptera: Nymphalidae), was investigated to test the extent to which species can adjust their response to the environment, and therefore maximise their reproductive potential. The photoperiodic (adult) diapause induction response varies between populations, and appears to be finely tuned to the local conditions. There is however variation within populations and the response can be adjusted in a population by selective breeding. The developmental rate is not significantly different between three latitudinally distinct populations, over the range of temperatures tested, and pupal weights are similar at given temperatures. However, pupal weights increase with decreasing development temperature. The implications of these findings are discussed with reference to modelling life history strategies.
Résumé Inachis io (L.), observable dans une grande partie de l'Europe, y présente des différences quant au cycle biologique, au voltinisme et à la durée du développement. Trois populations provenant de la zone de transition entre monovoltinisme et bivoltinisme ont été échantillonnées pour examiner les différences de réponses à la photopériode et à la température, et pour évaluer l'étendue des possibilités d'adaptation de cette espèce à l'environnement et ainsi optimaliser son potentiel reproductif. L'induction photopériodique de la diapause est de type jour long pour toutes les souches examinées, mais la photopériode critique 50 (CPh50) varie suivant les populations et paraît étroitement ajustée aux conditions locales. Il y a cependant assez de variabilité à l'intérieur des populations pour que le seuil puisse être rapidement abaissé dans chaque population par des expériences d'élevage sélectif. Par contre, la vitesse de développement ne varie pas significativement entre les populations pour la gamme de température: 15–27°C. Les poids de chrysalides ne diffèrent pas suivant les populations, bien qu'ils augmentent quand la température de dévelppement diminue. On peut penser que des modèles, prédisant que la diminution du nombre de générations pendant une saison sera accompagnée d'une prolongation de la durée de développement et d'une augmentation de la taille, et que ceci est d'origine génétique et non le résultat seul du refroidissement de l'environnement, ne tiendront pas compte de l'absence de variation entre populations dans la relation entre température et développement.相似文献
88.
Wolfgang Hofmann 《Hydrobiologia》1986,143(1):119-121
A succession of morphs from Bosmina coregoni f. coregoni to B. c. f. thersites, which vary in shell and antennule characters, occurred in an undated 176 cm long sediment core from the Neversdorfer See (N. Germany). 相似文献
89.
A genetic locus controlling the electrophoretic mobility of an acid phosphatase in the rat (Rattus norvegicus) is described. The locus, designed Acp-2, is not expressed in erythrocytes but is expressed in all other tissues studied. The product of Acp-2 hydrolyzes a wide variety of phosphate monoesters and is inhibited by l(+)-tartaric acid. Inbred rat strains have fixed either allele Acp-2a or allele Acp-2b. Codominant expression is observed in the respective F1 hybrids. Backcross progenies revealed the expected 1:1 segregation ratio. Possible loose linkage was found between the Acp-2 and the Pep-3 gene loci at a recombination frequency of 0.36±0.06.Supported by the Deutsche Forschungsgemeinschaft (Grant Be 352/15) and by a grant from the Alexander-von-Humboldt-Stiftung (VB2-FLF). 相似文献
90.