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91.
Fred A. Opmeer J. Peter H. Burbach Victor M. Wiegant Jan M. van Ree 《Life sciences》1982,31(4):323-328
The influence of chronic morphine exposure on the biotransformation of β-endorphin (βE) was investigated using the myenteric plexus-longitudinal muscle of guinea-pig ileum. A membrane preparation was incubated with βE and the degradation of βE as well as the accumulation of several βE fragments in the incubation medium were followed with time. The levels of peptides were determined by specific radioimmunoassays after separation by high-pressure liquid chromatography. It was found that exposure to morphine did not affect the disappearance of βE, but altered the time course of accumulation of βE fragments. In fact, the accumulation of γ-endorphin, α-endorphin and des-tyrosine1-α-endorphin was enhanced, while that of des-tyrosine1-γ-endorphin was not changed. Additionally, the disappearance of γ-endorphin appeared to be stimulated by morphine exposure. These data provide evidence that the fragmentation of βE is changed by chronic morphine exposure in such a way that the turn-over of γ-endorphin is increased. 相似文献
92.
A series of unstable mono- and di-esters of the tetracyclic diterpene ingenol were isolated from the pro-inflammatory ether-soluble fraction of the latex of Euphorbia kamerunica. The esters were isolated by a neutral process involving column and thin-layer chromatography. The monoesters were identified by spectroscopic methods and hydrolysis reactions as ingenol-3-decanoate, ingenol-3-dodecanoate, ingenol-5-hexadienoate and ingenol-5-octenoate and the diesters as 20-acetyl-ingenol-3-octenoate and 20-acetyl-ingenol-3-angelate. 相似文献
93.
Nonrandom mating with respect to color is well documented in the dimorphic Lesser Snow Goose. A set of mathematical models and data from the long-term study at La Pérouse Bay, Manitoba, Canada are used to examine various hypotheses advanced to explain the mechanisms behind the assortative mating. Among the factors considered are mate choice based on familial color, accidental formation of genetically unrelated families, and nonuniform distribution of colors in the region where mate selection occurs. 相似文献
94.
95.
South-Central European fossil hominids dated to the Upper Pleistocene exhibit a distinct morphological and metric continuum in supraorbital form from early Neandertal (Krapina), through late Neandertals (Vindija), to early Upper Paleolithic hominids. The supraorbital morphologies pertinent to this continuum are documented, and the alterations in size and morphology are discussed ralative to the function of supraorbital superstructures and their relationship to overall craniofacial form. It is concluded that this continuum most likely reflects localized transition between Neandertals and modern man in this region of Europe. 相似文献
96.
Genes Affecting the Expression of Cytochrome c in Yeast: Genetic Mapping and Genetic Interactions 总被引:33,自引:4,他引:29
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The four mutant genes, cyc2, cyc3, cyc8 and cyc9, that affect the levels of the two iso-cytochromes c in the yeast Saccharomyces cerevisiae have been characterized and mapped. Both cyc2 and cyc3 lower the amount of iso-1-cytochrome c and iso-2-cytochrome c; whereas, cyc8 and cyc9 increase the amount of iso-2-cytochrome c. The cyc2, cyc3, cyc8 and cyc9 genes are located, respectively, on chromosomes XV, I, II and III, and are, therefore, unlinked to each other and unlinked to CYC1, the structural gene of iso-1-cytochrome c and to CYC7, the structural gene of iso-2-cytochrome c. While some cyc3 mutants are completely or almost completely deficient in cyotchromes c, none of the cyc2 mutants contained less than 10% of parental level of cytochrome c even though over one-half of the mutants contain UAA or UAG nonsense mutations. Thus, it appears as if a complete block of the cyc2 gene product still allows the formation of a residual fraction of cytochrome c. The cyc2 and cyc3 mutant genes cause deficiencies even in the presence of CYC7, cyc8 and cyc9, which normally cause overproduction of iso-2-cytochrome c. We suggest that cyc2 and cyc3 may be involved with the regulation or maturation of the iso-cytochromes c. In addition to having high levels of iso-2-cytochromes c, the cyc8 and cyc9 mutants are associated with flocculent cells and other abnormal phenotypes. The cyc9 mutant was shown to be allelic with the tup1 mutant and to share its properties, which include the ability to utilize exogenous dTMP, a characteristic flocculent morphology, the lack of sporulation of homozygous diploids and low frequency of mating and abnormally shaped cells of alpha strains. The diverse abnormalities suggest that cyc8 and cyc9 are not simple regulatory mutants controlling iso-2-cytochrome c. 相似文献
97.
The sesquiterpene lactones isolated from species in the genus Artemisia have been reviewed in an attempt to better understand the phylogeny and systematics of the four sections (subgenera), Abrotanum, Absinthium, Dracunculus and Seriphidium, proposed by Besser in 1829. The absence of hair on the receptacle is the only morphological characteristic separating species of Abrotanum from the species of Absinthium. There are no chemical characteristics segregating the species in these two subgenera since both produce eudesmanolides and guaianolides that are identical or biosynthetically similar. This suggests that the two subgenera could be combined into one (Artemisia) as proposed by Poljakov. The subgenus Seriphidium is composed of two geographical groups, one in the Old World and the other in the New World. The Old World species almost exclusively produce sesquiterpene lactones in the eudesmanolide class whereas the New World species (section Tridentatae) produce eudesmanolides and guaianolides, many of the latter being identical or structurally related to the sesquiterpene lactones in New World Abrotanum species. The chemical data in conjunction with geographic distributions suggest that the subgenus Seriphidium is polyphyletic and that the section Tridentatae originated from Abrotanum. Consequently, the Tridentate should be recognized as a subgenus separate and distinct from the Old World Seriphidium. There was insufficient information from the subgenus Dracunculus for interpretation. 相似文献
98.
Summary In the present study the development of the bovine acrosome was investigated using conventional electron-microscopical techniques as well as the phosphotungstic-acid (PTA) technique (Rambourg 1967) including enzymatic digestion experiments. As in other species and in accordance with previous light-microscopical studies (Clermont and Leblond 1955) four phases of acrosomal differentiation can be discerned: the Golgi-phase, cap-phase, acrosome-phase, and maturation-phase.In the bull no internal pattern of the acrosomal content can be observed, either with conventional uranyl acetate-lead citrate staining or with the PTA-techniques. Our results support the observation in other species (Fawcett et al. 1971) that no intrinsic polymerization or crystallization process of the acrosomal content is responsible for acrosomal shaping. Some of our results suggest the influence of external forces on acrosomal development in the bull. During the cap-phase and the acrosome-phase accumulations of smooth endoplasmic reticulum and a layer of fine filaments can be observed in the Sertoli-cell cytoplasm, immediately adjacent to the developing acrosome. A temporary influence of these structures on acrosomal development seems possible. The PTA-positive staining of the developing bovine acrosome is probably due to the presence of acrosomal glycoproteins; however, our results do not exclude the possibility that molecules other than glycoproteins contribute to the positive PTA-staining of the developing acrosome.Supported by a grant from the Deutsche Forschungsgemeinschaft 相似文献
99.
Summary This report describes a female infant with a 47,X,del(X)(p11),+21 karyotype who has clinical features of both Down and Turner syndromes. The majority of her clinical features are suggestive of Down syndrome. 相似文献
100.
Marsh white seedless grapefruit were treated with the 2-diethylaminoethanol esters of the following acids: benzoic, phenylacetic, hydrocinnamic, 4-phenylbutyric, 5-phenylvaleric, valeric, hexanoic, heptanoic, octanoic, nonanoic, 5-chlorovaleric, cyclohexanecarboxylic, phenoxyacetic, p-chlorophenoxyacetic, 3-phenoxypropionic, cinnamic and p-chlorocinnamic. Several of these esters, in particular the hexanoate, 4-phenylbutyrate and cinnamate, caused the accumulation of large amounts of β-carotene. The effects of the hexanoate and of 2-phenoxytriethylamine, which causes only lycopene accumulation, were studied as functions of time. The hexanoate caused the rapid accumulation of lycopene during the first day. The amount of lycopene then began to decrease and that of β-carotene increased until, after 14 days, β-carotene was the major pigment. 2-Phenoxytriethylamine caused rapid lycopene accumulation during the first day and a slow steady increase afterwards. Thus, the mode of action of the β-carotene inducers may be similar to that of the lycopene inducers except that the former are probably rapidly hydrolysed by the esterase(s) in the flavedo, so that they no longer inhibit the cyclase(s), and β-carotene is accumulated at the expanse of lycopene. 相似文献