缺氧小鼠脑中神经节苷脂和单胺类神经递质水平

脑缺氧和缺氧后的再灌注常导致一系列复杂的生理生化改变．通过小鼠重复缺氧后,观察其脑组织中的神经节苷脂和单胺类递质水平变化情况,发现重复缺氧时,随着缺氧次数的增加,a．神经节苷脂水平（以唾液酸含量表示）非常明显地持续下降(P<0.01),其中GM1与GD1b相对组分百分比值下降尤为突出(GM1:P<0.05,GD1b:P<0.01); b.单胺类神经递质中NE和DOPA水平下降,DA和HIAA水平升高(P<0.01)．结果提示脑组织经重复缺氧后,中枢神经组织细胞膜受到一定程度的损伤,其结果可能影响到单胺类神经递质的合成、释放、重摄取和贮存的全过程;据此推测脑组织缺氧时神经节苷脂与单胺类神经递质水平改变时存在着相互联系．     

Channel modulators affect PGE(2) binding to bovine aortic endothelial cells

PGE(2), PGF(2alpha) and the thromboxane agonist U-46619 bind to bovine aortic endothelial cells and compete on the same binding site with similar affinity. In addition, binding remains unaffected by prolonged exposure to the ligand. These characteristics differ significantly from those of any known G-coupled prostaglandin receptor. Binding of PGE(2) to the cells is reduced in the presence of the cyclic nucleotides cGMP and cAMP, and is unaffected by protein kinase inhibitors. Removal of permeable cyclic nucleotides from the cell medium results in a fast and complete restoration of PGE(2) binding to the cells, suggesting that both cyclic nucleotides reduce PGE(2) binding by a reversible interaction with the prostaglandin-binding site, without the involvement of second messenger-activated protein kinases. Our data further show that binding of prostaglandins to bovine aortic endothelial cells is sensitive to heavy metals and to activators and blockers of calcium, ATP-sensitive K(+) and chloride channels. Nickel, a specific cyclic nucleotide-gated (CNG) channel activator, decreases PGE(2) binding and so do the CNG channel activators Rp-8-Br-PET-cGMPS and Sp-8-Br-PET-cGMPS. On the other hand, the calcium channel blockers pimozide, diltiazem as well as LY-83,583, a guanylate cyclase inhibitor, which were reported to block CNG channels, enhance PGE(2) binding. The sensitivity of PGE(2) binding to selective CNG channel modifying agents, as well as the rapid and reversible interaction with cyclic nucleotides, may suggest that the common low-affinity prostanoid-binding site on bovine aortic endothelial cells is associated with a molecular entity, which possess several properties of a CNG channel.     

Stimulation of colonic mucosal growth associated with oxidized redox status in rats

Limited data in animal models suggest that colonic mucosa undergoes adaptive growth following massive small bowel resection (SBR). In vitro data suggest that intestinal cell growth is regulated by reactive oxygen species and redox couples [e.g., glutathione (GSH)/glutathione disulfide (GSSG) and cysteine (Cys)/cystine (CySS) redox]. We investigated the effects of SBR and alterations in redox on colonic growth indexes in rats after either small bowel transection (TX) or 80% midjejunoileal resection (RX). Rats were pair fed +/- blockade of endogenous GSH synthesis with buthionine sulfoximine (BSO). Indexes of colonic growth, proliferation, and apoptosis and GSH/GSSG and Cys/CySS redox potentials (E(h)) were determined. RX significantly increased colonic crypt depth, number of cells per crypt, and epithelial cell proliferation [crypt cell bromodeoxyuridine (BrdU) incorporation]. Administration of BSO markedly decreased colonic mucosal GSH, GSSG, and Cys concentrations in both TX and RX groups, with a resultant oxidation of GSH/GSSG and Cys/CySS E(h). BSO did not alter colonic crypt cell apoptosis but significantly increased all colonic mucosal growth indexes (crypt depth, cells/crypt, and BrdU incorporation) in both TX and RX groups in a time- and dose-dependent manner. BSO significantly decreased plasma GSH and GSSG, oxidized GSH/GSSG E(h), and increased plasma Cys and CySS concentrations. Collectively, these data provide in vivo evidence indicating that oxidized colonic mucosal redox status stimulates colonic mucosal growth in rats. The data also suggest that GSH is required to maintain normal colonic and plasma Cys/CySS homeostasis in these animal models.     

Computer simulation of plastocyanin interaction with cytochrome f and photosystem I in cyanobacterium Phormidium laminosum

The paper is devoted to computer simulation of complex formation of protein plastocyanin with transmembrane pigment-protein complex photosystem I and subunit f of cytochrome b ₆ f complex in the cyanobacterium Phormidium laminosum. The computer algorithm considers diffusion and electrostatic interactions of protein molecules. The computer models have shown that electrostatic interactions in the cyanobacterium play a less important role than in higher plants because of different electrostatic potentials created by charged amino acid residues on the protein surfaces.     

The use of epon embedding with the Falck-Hillarp technique to preserve the serotonin-associated fluorescence of endocrine and mast cells in the rat stomach.

Epon embedding was used with the Falck-Hillarp Technique in a study of rat gastric endocrine cells in order to improve morphological resolution. The epon embedding not only produced excellent morphological results, but also resulted in the long-term preservation, now for 10 years of the serotonin-associated fluorescence in the gastric endocrine and mast cells.     

Changes in myelin structure and fatty-acid tail ordering upon nerve fiber excitation

Using laser interference microscopy and Raman spectroscopy of frog myelinated nerve, it has been found that upon a train of action potentials passing along the fiber, the phase height (refractive index) of paranodal myelin declines while the ordering of fatty-acid tails therein increases. In contrast, at the node of Ranvier where excitation is generated, both the phase height of the axoplasm and the ordering of axolemmal lipid tails decline. It is supposed that such changes in myelin are caused by desorption of membrane-bound Ca²⁺.