共查询到20条相似文献,搜索用时 31 毫秒
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Chinchilla "big" and "little" gastrins 总被引:1,自引:0,他引:1
Gastrin heptadecapeptides (gastrins I and II which differ in the presence of sulfate on the tyrosine of the latter) have been purified and sequenced from several mammalian species including pig, dog, cat, sheep, cow, human and rat. A 34 amino acid precursor ("big" gastrin), generally accounting for only 5% of total gastrin immunoreactivity, has been purified and sequenced only from the pig, human, dog and goat. Recently we have demonstrated that guinea pig (GP) "little" gastrin is a hexadecapeptide due to a deletion of a glutamic acid in the region 6-9 from its NH2-terminus and that GP "big" gastrin is a 33 amino acid peptide. The chinchilla, like the GP, is a New World hystricomorph. This report describes the extraction and purification of "little" and "big" gastrins from 31 chinchilla antra. Chinchilla "little" gastrin is a hexadecapeptide with a sequence identical to that of the GP and its "big" gastrin is a 33 amino acid peptide with the following sequence: (See text) 相似文献
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J Fogg 《BMJ (Clinical research ed.)》1971,3(5777):770-771
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W C Steinmann 《BMJ (Clinical research ed.)》1982,285(6348):1091-1093
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野生生物、野生动植物和野生来源的定义及范畴 总被引:3,自引:0,他引:3
关于野生生物、野生动植物和野生来源的定义是科学研究、物种保护和政策管理工作 ,特别是野生动植物立法和执法方面经常遇到的问题。对见于各种法规和文献中的野生生物、野生动植物、野生来源、人工繁殖、人工培植、天然、人工合成等概念的定义进行了分类、比较与分析 ,讨论了这些概念的相对性和使用范畴 ,提出了野生动植物的简要定义 ,并指出了这些概念的定义需根据实际需要而发展调整。 相似文献
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Two mutants, 1 with small, pollen-less anthers (OR-EA) and another with "pin" flowers (EMS 13-2), in contrast to "thrum" flowers found in normal periwinkle (Catharanthus roseus) plants, were isolated after induced mutagenesis in strain OR and cultivar, "Dhawal," respectively. Inheritance of these 2 traits, pollen-less anthers, and pin flowers was studied by crossing the mutants with their respective parental strains. Segregation ratios observed in F(2) and testcross generations of the cross OR-EA x OR suggested that the pollen-less anthers trait was determined by duplicate recessive genes. Data obtained from F(2) and F(3) generations of the cross involving mutant EMS 13-2 with pin flowers and its parental variety Dhawal, suggested that production of pin (mutant) and thrum (normal) flowers was under the control of inhibitory epistatic interaction between 2 independently inherited genes. 相似文献
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B Przybylska 《Zeitschrift für mikroskopisch-anatomische Forschung》1989,103(2):329-335
Both qualitative and quantitative comparative studies of "dark" and "light" pinealocytes of the porcine pineal gland have been carried out. These cells differ from each other in their electronic density of cytoplasm, shape of nucleus, the structure of membrane bound dense bodies and the number of microtubules and smooth endoplasmic reticulum. The membrane bound dense bodies--characteristic structures of pig pinealocytes as well dense core vesicles occur in both types of cells. The relative volume of the majority of the cells' organellae apart from the Golgi apparatus, also do not show any significant difference. The results obtained support a functional basis for pinealocyte differentiation in the porcine pineal gland. 相似文献
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"Old" human erythrocytes showed a 21.2% decrease in cell surface area and a 2% decrease in the number of WGA receptor sites, but a 27% increase in the distribution density of the WGA (lectin) receptor site, when compared with "young" human erythrocytes. For a list of lectin abbreviations, see Materials and methods). Both "young" and "old" erythrocytes exhibited very weak binding activity for 125I-labeled PNA, but there was no difference in binding activity for PNA between "young" erythrocytes and "old" ones. Compared with "young" erythrocytes, decreases in the number and distribution density of receptor sites for five lectins including LPA, Con A, RCA-II, SBA and BPA on the cell surface were observed in aged erythrocytes. "Old" erythrocytes also showed a decrease in the number of PHA-E receptor sites, while the distribution density of the same receptor site remained unchanged. In view of these and other observations, it is thought that human erythrocyte aging is accompanied by elimination of some glycoconjugates which have affinity for six lectins, LPA, Con A, RCA-II, PHA-E, SBA and BPA, whereas no WGA receptor-containing glycoconjugates are released from erythrocyte membranes. Elimination of the glycoconjugates results in shrinkage of erythrocytes to reduce their cell surface areas. 相似文献
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Cerny R Lwigale P Ericsson R Meulemans D Epperlein HH Bronner-Fraser M 《Developmental biology》2004,276(1):225-236
Cartilage of the vertebrate jaw is derived from cranial neural crest cells that migrate to the first pharyngeal arch and form a dorsal "maxillary" and a ventral "mandibular" condensation. It has been assumed that the former gives rise to palatoquadrate and the latter to Meckel's (mandibular) cartilage. In anamniotes, these condensations were thought to form the framework for the bones of the adult jaw and, in amniotes, appear to prefigure the maxillary and mandibular facial prominences. Here, we directly test the contributions of these neural crest condensations in axolotl and chick embryos, as representatives of anamniote and amniote vertebrate groups, using molecular and morphological markers in combination with vital dye labeling of late-migrating cranial neural crest cells. Surprisingly, we find that both palatoquadrate and Meckel's cartilage derive solely from the ventral "mandibular" condensation. In contrast, the dorsal "maxillary" condensation contributes to trabecular cartilage of the neurocranium and forms part of the frontonasal process but does not contribute to jaw joints as previously assumed. These studies reveal the morphogenetic processes by which cranial neural crest cells within the first arch build the primordia for jaw cartilages and anterior cranium. 相似文献
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We report on the elucidation of two separate pathways of spore germination in a plant pathogenic fungus Colletotrichum gloeosporioides f. sp. aeschynomene. Conidia of the fungus can germinate either from one side or from both sides, depending on external conditions. In shake culture that includes an extract made up from fresh peas, the unicellular conidium divides and one of the two cells develops a germ tube. On a solid surface this germ tube differentiates an appressorium. In rich medium without pea extract, germination is highly similar to Aspergillus spore germination: the conidium swells, forms a single germ tube and then divides and forms a second germ tube. Conidia that germinate in a rich medium do not form appressoria even on a solid surface and are non-pathogenic. In rich medium, cAMP stimulates germination in rich liquid cultures and induces appressoria formation on a hard surface. In pea extract cAMP induces swelling and formation of irregular germ tubes and appressoria. Our results suggest that plant surface signals induce pathogenic-specific spore germination in a cAMP-independent manner. cAMP is required for saprophytic germination and for appressorium formation. 相似文献
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Collinson S 《BMJ (Clinical research ed.)》2001,323(7310):451; author reply 452-451; author reply 453