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Whole cells of Mycobacterium phlei were shown to actively accumulate proline, leucine, lysine, tryptophan, histidine, glutamine, and glutamic acid to different steady state levels. The transport of proline, in contrast to that of other amino acids, was found to be insensitive to various respiratory inhibitors, e.g. cyanide, arsenate, azide, and sulfhydryl reagents. However, oxygen was an obligatory requirement for the uptake of proline, as well as for the other amino acids. The results indicate that the energy requirements for proline uptake are different from those of other amino acids. In contrast to the system from Escherichia coli, the mode of energy transduction for the uptake of proline, glutamine, and glutamic acid is different even though these amino acids are shock resistant in the M. phlei system. 相似文献
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Pre-incubation of cells of Saccharomyces cerevisiae with 2 M-ethanol led to decreased rates of L-alanine uptake, H+ efflux and fermentation rate. However, these responses were modified in yeast cells with altered phospholipid composition. Using L-alanine transport and H+ efflux as indices of ethanol tolerance, it was observed that cells enriched with phosphatidylserine had greater tolerance to ethanol. This resulted from altered charge of membrane phospholipids rather than changes in membrane fluidity. It is suggested that the anion:zwitterion ratio of phospholipids may be one of the important determinants of ethanol tolerance in S. cerevisiae. 相似文献
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The morphology, seasonal variation and histochemistry of the sexual segment of the Indian house lizard, Hemidactylus flaviviridis are described. The sexual segment is the hypertrophied portion of the secondary and the tertiary collecting ducts of the kidney in males. The cells of the sexual segment are columnar and are loaded with secretory granules which are predominantly localized in the apical portion. These granules are either free or occasionally clumped to form an “aggregate” towards the basement membrane and are released into the lumen by apocrine secretion. Development of the sexual segment is synchronous with the spermatogenic activity of the testis and maximum development occurs in March and April when the lizards copulate. The sexual segment is secretory from the beginning of October to the end of May and is regressed during sexual quiescence (June and July). It is not developed in females and young of both sexes in any season of the year. Histochemically, the sexual segment granules are saliva resistant and PAS positive, sudanophilic and are positive to the tests for phospholipid, choline and acid phosphatase. An intense esterase activity was localized in the mucosa of the oviduct and cloaca of the female. Sperms are mixed with sexual segment secretions and are transferred to the female during copulation. A possible role for the lipid-rich sexual segment secretion as a source of energy for sperms in the female reproductive tract is discussed. 相似文献
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Prasad P. Phadnis Thilo Schurr Falk Lissner Wolfgang Kaim 《Inorganica chimica acta》2005,358(9):2609-2617
Dinaphthylmethylarsine complexes of palladium(II) and platinum(II) with the formulae [MX2L2] (M = Pd, Pt; L = di(1-naphthyl)methylarsine = Nap2AsMe and X = Cl, Br, I), [M2Cl2(μ-Cl)2L2], [PdCl(S2CNEt2)L], [Pd2Cl2(μ-OAc)2L2] and [MCl2(PR3)L] (PR3 = PEt3, PPr3, PBu3, PMePh2) have been prepared. These complexes have been characterized by elemental analyses, IR, Raman, NMR (1H, 13C, 31P) and UV-vis spectroscopy. The stereochemistry of the complexes has been deduced from the spectroscopic data. The crystal structures of trans-[PdCl2(PEt3)(Nap2AsMe)] and of [Pd(S2CNEt2)2], a follow-up product, were determined. The UV-vis spectra of [MX2L2] complexes show a red shift on going from X = Cl to X = I. The complexes [PdX2L2] and [PtX2L2] are strongly luminescent in fluid solution and in the solid at ambient temperature. 相似文献
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Kumariah Manoharan Thirupathi Karuppanapandian Pritam Bala Sinha Rajendra Prasad 《Journal of Plant Biology》2005,48(4):394-403
We investigated 2,4-D-induced leaf senescence in young mustard seedlings. A set of morphometric, biochemical and molecular
parameters were analyzed to characterize senescence markers. In accordance with earlier reports, chloroplast-membrane degradation
marked the early phase of leaf senescence based on the analysis of the galactolipid fraction. Degradation of grana occurred
earlier to that of the envelope, as revealed by the relative level of their specific galactolipids, namely, monogalactosyl
diglyceride and digalactosyl diglyceride. Phospholipids showed extensive degradation resulting in the accumulation of lyso-derivatives
of major phospholipids and phosphatidic acid (PA) in senescing leaves. Catalase activity was stimulated by 2,4-D and reflected
scavenging of reactive oxygen species. Nuclear DNA degradation, a previously known death signal that represented a point of
no return from progression of senescence, occurred late on the 4th day subsequent to 2,4-D supplementation. AgNO3, an inhibitor of ethylene biosynthesis, inhibited leaf senescence by ca. 54% based on PA content Involvement of 2,4-D, ethylene
and abscisic acid in leaf senescence is discussed in relation to hormonal interplay. 相似文献