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781.
A method was developed which allowed the ultrastructural study of septal formation in the basidiomycete Polyporus biennis. The method involved fixing and embedding single clamp connections. Clamp connections with septa at desired developmental stages were located by light microscopy. The septum grew by the incorporation of vesicles of wall material precursors. The rim of the developing septum was drawn centripetally inwards by a contracting collar of microfilaments within a darkly staining matrix. The inflation of the central pore swelling was governed by realigned microfilaments. The parenthesomes were formed, starting at the apex, by the utilization of the microfilament/matrix material lying along the septum. On completion of the parenthesomes a transient striated structure, governed by microfilaments, was formed in the pore channel and the areas enclosed by the parenthesomes. The maturation of the septum involved the laying down of ER along the septum and the occlusion of each end of the pore channel. 相似文献
782.
Presence and genetic polymorphism of an epithelial mucin in milk of the goat (Capra hircus). 总被引:3,自引:0,他引:3
W M Campana R V Josephson S Patton 《Comparative biochemistry and physiology. B, Comparative biochemistry》1992,103(1):261-266
1. Analysis of individual samples of goat's milk by SDS-PAGE confirmed that they contain a polymorphic, high molecular weight (M(r) greater than 205 kDa) glycoprotein. 2. On SDS-gels, the polymorphism takes the form of two bands of variable mobility which usually stain with equal intensity. This polymorphism resembles that detected in milk mucins of other species and is best explained by an expression of codominant genes containing variable numbers of a tandemly repeated 60-base segment. 3. Analysis of milk fractions provided evidence that the goat mucin is exclusively a membrane protein, and that it can be purified from other fat globule proteins by gel filtration and peanut lectin affinity chromatography. 4. Among proteins in the goat milk fat globule, the mucin appears to be a strong immunogen but the resulting antibodies applied to Western blots only stained the cow's milk mucin mildly and the guinea pig and human milk mucins not at all. 相似文献
783.
784.
Methylcholanthrene transformed mouse fibroblast cells can be induced to synthesize prostaglandins by a short term incubation with various vasoactive agents including serum, bradykinin and thrombin or in response to mechanical detachment from the culture dish. The ability of the cells to synthesize prostaglandins upon stimulation changes during growth of the culture on the dish; the response is maximal on the first day after inoculation and decreased sharply thereafter. Feeding of the cells with fresh growth medium enhances prostaglandin production induced by all stimuli. The difference in the cell response during growth is probably not due to change of prostaglandin synthetase activity since the specific enzyme activities assayed with microsomal preparations of cells harvested from the first and third day culture are similar. However, analysis of the cellular content of arachidonic acid after saponification of the total lipid extract of cells harvested at different days of growth reveals that the level of arachidonic acid per cell during growth is parallel to the response to stimuli. It is maximal on the first day and decreases sharply on the second day and stays low on the third day. Our study suggests that the level of arachidonic acid in the cell governs the extent of prostaglandin synthesis upon stimulation. 相似文献
785.
786.
Following the intestinal absorption of dietary benzo[a]pyrene (BP) by the killifish, this compound becomes incorporated along with dietary triglycerides into membrane-bound fat vacuoles within the intestinal epithelial cell (1985. J. Lipid Res. 26: 428-434). These vacuoles, arising from the smooth endoplasmic reticulum, are important transient structures involved in both the uptake and metabolism of dietary BP and, presumably, other lipophilic toxicants as well. In the present study we used subcellular fractions isolated from the intestines of spot (Leiostomus xanthurus), a teleost fish, to study factors that influence the metabolism of BP in a fat vacuole/microsomal system. Triglyceride-solubilized BP is capable of diffusion from fat vacuoles to microsomal enzymes. Increases in the concentration of fat vacuoles decrease the availability of BP to microsomal BP hydroxylase. The effect of fat vacuoles on the activity of BP hydroxylase becomes more pronounced as the concentration of BP in our test system decreases. Addition of cytosolic glutathione transferases to the fat vacuole/microsomal system enhances the activity of BP hydroxylase. Examination of binding of 3H-labeled BP to killifish (Fundulus heteroclitus) intestinal cytosolic proteins in vivo indicated that a large fraction of the radioactivity was associated within glutathione transferase. These results suggest that dietary fat inhibits metabolism of low levels of BP in the intestine. A consequence of this would be greater exposure of peripheral tissues to dietary carcinogens. 相似文献
787.
Compatibility of high-intensity strength and endurance training on hormonal and skeletal muscle adaptations 总被引:8,自引:0,他引:8
788.
789.
Jeffrey R. Patton 《Molecular biology reports》1990,14(2-3):177-178
790.
Andrea Swei Philip V. Brylski Wayne D. Spencer Shana C. Dodd James L. Patton 《Conservation Genetics》2003,4(4):501-514
The geographic genetic structure, based onsequence variation of an 810 base pair fragmentof the mitochondrial cytochrome b gene,is described for populations of five subspeciesof the Little Pocket Mouse, Perognathuslongimembris, from Southern California. Oneof these, P. l. pacificus (Pacific PocketMouse), is listed as Endangered by the U.S.Federal Government. Sixty-two uniquehaplotypes were recovered from 99 individualssampled. Phylogenetic analyses of thesevariants do not identify regionallyreciprocally monophyletic lineages concordantwith the current subspecies designations, butmost haplotypes group by subspecies in networksgenerated by either statistical parsimony ormolecular variance parsimony. Moreover, asubstantial proportion of the total pool ofhaplotype variation is attributed to thesesubspecies, or to local populations withingeographic segments of each, indicating theirrelative evolutionary independence. The pooledextant populations of the endangered PacificPocket Mouse exhibit the same levels ofnucleotide and haplotype diversity as other,presumptively less-impacted populations ofadjacent subspecies, although the sample fromDana Point, Orange County, has markedly lowhaplotype diversity in comparison to allothers. These populations also show a geneticsignature of population expansion rather thanone of decline. Both pieces of evidence are atodds with current empirical populationestimates, which reinforces the fact thatpresent-day patterns of genetic diversity arethe product of coalescent history and will notnecessarily reflect recent anthropogenic, orother, perturbations. Comparison of haplotypevariation within and among extant populationsof the Pacific Pocket Mouse with those obtainedfrom museum samples collected more than 70years ago suggests that the pattern ofpopulation differentiation and diversity was inplace before the post-World War II exponentialurbanization of Southern California. 相似文献