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151.
Gorinstein S Caspi A Zemser M Libman I Goshev I Trakhtenberg S 《The Journal of nutritional biochemistry》2003,14(12):710-716
Moderate beer consumption (MBC) is cardioprotective: it positively influences plasma lipid levels and plasma antioxidant activity in beer-consuming individuals. The connection between MBC and blood coagulation is not clearly defined. Forty-two volunteers were equally divided into experimental (EG) and control (CG) groups following coronary bypass surgery. For 30 consecutive days, only patients of the EG consumed 330 mL of beer per day (about 20 g of alcohol). A comprehensive clinical investigation of 42 patients was done. Blood samples were collected before and after the investigation for a wide range of laboratory tests. The plasma fibrinogen was denatured with 8 M urea and intrinsic fluorescence (IF), hydrophobicity and differential scanning calorimetry (DSC) were used to reveal possible qualitative changes. After 30 days of moderate beer consumption, positive changes in the plasma lipid levels, plasma anticoagulant and plasma antioxidant activities were registered in patients of the EG group. In 17 out of 21 patients of the same group, differences in plasma circulating fibrinogen's (PCF), secondary and tertiary structures were found. The stability of fibrinogen, expressed in thermodynamic parameters, has shown that the loosening of the structure takes place under ethanol and urea denaturation. Also fluorescence stability of PCF was decreased. No changes in the lipid levels, anticoagulant and antioxidant activity or changes in PCF were detected in patients of CG. In conclusion, for the first time after a short term of moderate beer consumption some qualitative changes in the plasma circulating fibrinogen were detected: differences in the emission peak response, fluorescence intensity and all thermodynamic data. Together, with the decrease in the PCF concentration it may lead to an elevation of the blood anticoagulant activity. 相似文献
152.
Weber MH de Oliveira KR Valle SC Schweigert ID Rotta LN Fagundes I Krüger AH Souza K Souza DO Perry ML 《Neurochemical research》2001,26(2):161-166
We have studied the developmental changes of glucose, mannose, fructose and galactose metabolism in rat cerebral cortex. As the animals aged, glucose, mannose and fructose oxidation to CO2 increased, whereas galactose oxidation decreased. Lipid synthesis from glucose and fructose also increased with age, that from mannose decreased and galactose did not change. Cytochalasin B, a potent non-competitive inhibitor of sodium-independent glucose transport, significantly impaired glucose, mannose and galactose metabolism, but had no effect on fructose metabolism. Both galactose or fructose did not change, whereas mannose declined the glucose metabolism. Glucose decreased fructose, galactose and mannose metabolism. Our results show that besides glucose, the metabolism of mannose, galactose and fructose present developmental changes from fetal to adult age, and reinforce the literature data indicating that mannose and galactose are transported by glucose carriers, while fructose is not. 相似文献
153.
Ligand-gated ion channels contain a conserved leucine at position 9′ (L9′) in the M2 transmembrane domain. We used multiple
substitutions at this position in the γ subunit of the mouse acetylcholine receptor (AChR) (γL9′) to examine the role of residue
polarity at this position in the gating process at both the macroscopic and single-channel levels. The midpoint of the macroscopic
dose-response relationship (EC50) and the channel closing rate constant, α, decreased as the polarity of the residue at that position increased, suggesting
a stabilization of the open state of the channel. Both parameters showed similar dependencies on the polarity of the substituted
residue. These data support the notion that during AChR gating, the amino acid at the 9′ position moves into a polar environment,
and that interactions between this residue and the polar environment determine the stability of the open state. Since this
residue is conserved in all other members of the ligand-gated ion channel family, we suggest that a similar mechanism applies
to the other members of the family.
Received: 17 September 1999/Revised: 15 December 1999 相似文献
154.
In patch-clamp experiments on isolated chloroplasts of Peperomia metallica Lind. et Rodig. (Piperaceae), the replacement of 50 mM KCl in a medium with 50 mM NH4Cl strongly influenced the parameters of photocurrent known to reflect the generation of electric potential in thylakoids. The addition of NH+
4to the medium modified the induction curves of the photocurrent as well as the currents induced by single-turnover flashes in preilluminated chloroplasts. Under the action of a prolonged light pulse (1 s), the steady-state current was much higher in the ammonium-containing medium than in the presence of K+. Preillumination of a dark-adapted chloroplast with a 1-s light pulse suppressed the current induced by a single-turnover flash (6 s) in the presence of K+ but caused an elevation (by 50–150%) of the flash-induced current and shortening of its relaxation time in the presence of NH+
4. The origin of different induction kinetics for the photocurrent in K+ and NH+
4 media is partly clear, because ammonium prevents generation of the pH gradient and, subsequently, eliminates the pH-dependent suppression of the electron transport rate. However, this does not explain the origin of NH+
4-dependent photostimulation of the current generated by single-turnover flashes. This phenomenon arises from the thylakoid swelling caused by the accumulation of NH+
4 in the lumen and from the respective changes in the network resistances. The network element most sensitive to thylakoid swelling is the lateral resistance of the lumen: it decreases upon enlargement of the cross-section area. Stimulation of the flash-induced current by preillumination in the presence of NH+
4 was accompanied by accelerated relaxation of the current, indicating that the phenomena observed are caused by the reduction of network resistance involved in the discharge of the membrane capacity. Thus, the light-induced structural changes in the thylakoid system have a marked effect on the currents measured with the patch-clamp technique. 相似文献
155.
Using a cytofluorimetric assay, we found that immunocytes of the mollusc, Mytilus galloprovincialis, express CD10, a surface antigen known to be identical to neutral endopeptidase-24.11 (NEP). The spectrofluorimetric analysis demonstrates that the growth factors PDGF-AB and TGF-beta1 provoke an increase in NEP-like activity in membrane preparations from the immunocytes, but have no effect on the soluble form in the serum. On the other hand, computer-assisted microscopic image analysis reveals that NEP deactivates the PDGF-AB- and TGF-beta1-induced shape changes in immunocytes. However, Western blots show that, in solution, NEP does not cleave PDGF-AB or TGF-beta1, indicating that the inactivation is not due to proteolysis. These results suggest a functional interplay in invertebrate immunocytes between growth factors and NEP, as previously shown in vertebrate cells. 相似文献
156.
157.
158.
Polyelectrolyte-coated microcapsules and their potential applications to biotechnology 总被引:1,自引:0,他引:1
Etsuo Kokufuta 《Bioseparation》1998,7(4-5):241-252
Polyelectrolyte-coated microcapsules can be prepared by adsorption of polyions onto microcapsule surfaces in aqueous solutions
under appropriate pH and ionic conditions. The resulting polyelectrolyte-coated microcapsules provide a promising tool for
studying pH-induced configurational changes in polyions adsorbed onto hydrophobic membranes (capsule walls). An interesting
application of polyelectrolyte-coated microcapsules is the pH-sensitive on/off control of microencapsulated enzyme reactions
through alterations in the substrate permeability of the capsule wall by pH-conditioned configurational changes in the adsorbed
polyion layer. This paper presents an overview of pH-induced conformational changes of polyelectrolytes in solutions, preparation
of polyelectrolyte-coated microcapsules with an immobilized enzyme, and on/off control of the respective enzyme reactions
by pH adjustment.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
159.
ABSTRACT An improved method has been developed for the induction of selfing conjugation in Paramecium. Methyl cellulose induces selfing conjugation simply and efficiently in all species examined. Induction of conjugation by methyl cellulose was characterized in P. caudatum , where it occurred only in sexually mature, mating reactive cells. Conjugation produced sexual offspring and the time course of nuclear processes was substantially the same as that in natural conjugation between cells of complementary mating types. The method is useful for genetic studies in a wide variety of Paramecium species including P. caudatum, P. tetraurelia, P. multimicronucleatum and P. bursaria. 相似文献
160.
Contrasting responses to Pleistocene climate changes: a case study of two sister species Allium cyathophorum and A. spicata (Amaryllidaceae) distributed in the eastern and western Qinghai–Tibet Plateau
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Xinyu Wang Yuanshuo Li Qianlong Liang Lei Zhang Qian Wang Huan Hu Yongshuai Sun 《Ecology and evolution》2015,5(7):1513-1524
It has been hypothesized that species occurring in the eastern and the western Qinghai–Tibet Plateau (QTP) responded differently to climate changes during the Pleistocene. Here, we test this hypothesis by phylogeographic analysis of two sister species, Allium cyathophorum and A. spicata. We sequenced two chloroplast DNA (cpDNA) fragments (accD‐psaI and the rpl16 intron) of 150 individuals, and the nuclear (ITS) region of 114 individuals, from 19 populations throughout the distributional ranges of these species. The divergence between the two species was dated at 779 ‐ 714 thousand years before the present and was likely initiated by the most major glaciation in the QTP. Analysis of chlorotype diversity showed that A. spicata, the species occurring in the western QTP, contains much lower genetic diversity (0.25) than A. cyathophorum (0.93), which is distributed in the eastern QTP. Moreover, multiple independent tests suggested that the A. spicata population had expanded recently, while no such expansion was detected in A. cyathophorum, indicating a contrasting pattern of responses to Pleistocene climate changes. These findings highlight the importance of geographical topography in determining how species responded to the climate changes that took place in the QTP during the Pleistocene. 相似文献