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11.
Bacillus megaterium cells from various growth phases were equally susceptible to the lethal effects of aflatoxin B1. Known surfactants (EDTA and Tween-80) accentuated the effects of aflatoxin B1. Viability and inulin uptake in aflatoxin B1-exposed cells decreased considerably. The effect was concentration dependent. A straight-line relationship observed in the death curve indicated a single target for aflatoxin B1 action in B. megaterium. Leakage of intracellular constituents in B. megaterium was also concentration dependent, and this can be related to the extent of cell membrane damage. 相似文献
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Summary During an earlier investigation, microtubules were observed at the periphery of invasion processes in the developing syncytial tapetum ofTradescantia virginiana L. They were also associated with membranous sacs that accumulate adjacent to tetrads, with putative fusion sites where the tapetal plasmodium is initiated, and, in postmeiotic stages, with the perispore membrane that encloses the developing spore cells. Colchicine was administered to developing flower buds to investigate the roles of these microtubules. The results indicate that microtubules neither initiate nor guide the tapetal invasion of the loculus. The treatments, however, resulted in absence of cell coat from invasion processes and prevention of cell fusion. They also inhibited polarized migration of membrane sacs and removed the associated microtubules. The development of an organized secretory apparatus at the perispore membrane was disrupted, with subsequent disordered deposition of sporopollenin in the extracellular spaces of the partially-fused plasmodium. The results suggest that microtubules participate in the formation and internal spatial organization of the tapetal plasmodium, and establishment of a secretory surface that normally produces sporopollenin at the tapetum-microspore interface. 相似文献
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Hentriacontane, β-sitosterol and ursolic acid have been isolated from roots of Boerhaavia diffusa (Linn). 相似文献
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Simon C. Allen K. Ravi Acharya Kathleen A. Palmer Robert Shapiro Bert L. Vallee Harold A. Scheraga 《Journal of Protein Chemistry》1994,13(7):649-658
The three-dimensional structure of human angiogenin has been determined by X-ray crystallography and is compared here with an earlier model which predicted its structure, based on the homology of angiogenin with bovine pancreatic ribonuclease A. Comparison of the predicted model and crystal structure shows that the active-site histidine residues and the core of the angiogenin molecule, including most of the-strands and-helices, were predicted reasonably well. However, the structure of the surface loop regions and residues near the truncated C-terminus differs significantly. The C-terminal segment includes the active-site residues Asp-116, Gln-117, and Ser-118; Gln-117 in particular has been shown to be important in affecting the ribonucleolytic activity of angiogenin. Also, the orientation of one helix in the model differed from the orientation observed experimentally by about 20°, resulting in a large displacement of this chain segment. The difficulty encountered in predicting the surface loop regions has led to a new algorithm [Palmer and Scheraga (1991),J. Comput. Chem.,12, 505–526; (1992),J. Comput. Chem.,13, 329–350] for predicting the conformations of surface loops. 相似文献
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The ability to withstand thermal stress in a laboratory population of the blowflyLucilia cuprina (measured as per cent adult survival following varying periods of exposure to elevated temperature up to a maximum of 48°C)
was in the order pupa > larva > adult. Pre-exposure to a mild heat shock (37°C) induced tolerance to temperatures which were
otherwise lethal. An analysis of heat shock-induced protein synthesis during development at similar elevated temperatures
presented patterns corresponding to the above observations on thermotolerance. The induced level of synthesis of major heat
shock proteins (viz., 79, 69, 28, 20 and 19 kDa) were greater in larval tissues than in most of the adult tissues except gonads.
The response varied between young (2 days) and old (30 days) adults in a tissue-specific manner. In general, heat shock protein
69 kDa was most abundant in all the tissues studied. Control as well as heat shocked Malpighian tubules of adults uniquely
showed two major [35S]methionine labelled bands corresponding to approximately 62 and 64 kDa. Immunoblots showed the 62 kDa protein to cross react
with an antibody againstHelioihis HSP60. Although the synthesis of the 62 kDa polypeptide was prominent only in Malpighian tubules of adult blowflies, nearly
equal levels of this HSP60 family polypeptide were present in all tissues (control as well heat shocked) except the larval
salivary glands. 相似文献
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3β-hydroxy-5-cholenoic acid was found in the bile and feces of new-born and fetal guinea pigs. The identity of this compound was confirmed by gas chromatography and mass spectrometry. This finding suggests that the formation of chenodeoxycholic acid through 3β-hydroxy-5-cholenoic acid is intermediate in the early life of guinea pigs. Thus, it provides a useful model for studying the details of regulatory factors and significance of this pathway. This study also revealed that, unlike the adult guinea pig, the newborn guinea pig has significant amounts of glycine conjugates of bile acid. 相似文献