Increased expression of glucose transporter 3 in gerbil brains following magnesium sulfate treatment and focal cerebral ischemic injury

Glucose is the primary energy substrate for neurons. Glucose transporter 3 (Glut3) localizes at the neuronal cellular membrane, which transports glucose from the extracelluar space into neurons. Ischemia results in an increased energy demand that is associated with profound changes in brain energy metabolism. Magnesium sulfate (MgSO₄) ameliorates ischemia‐induced neuronal death in the rat and gerbil model. We investigated the effects of MgSO₄ administration on the expression of Glut3 in cortex and hippocampus of gerbils during ischemia. The focal cerebral ischemia was produced by unilateral occlusion of the right common carotid artery and right middle cerebral artery. Following ischemia, Glut3 expression increased significantly versus non‐ischemic (contra‐lateral) cortex and hippocampus. MgSO₄ treatment significantly increased the level of Glut3 expression in the non‐ischemic and ischemic cortex and hippocampus. We found that the MgSO₄‐induced increase in Glut3 expression was not reversed by administration of U0126, a MEK kinase inhibitor. These results suggest that other factors may function to modulate the MgSO₄‐induced Glut3 response. In all, our data showed that MgSO₄ increases the expression of Glut3 in the cortex and hippocampus of gerbil brains both in non‐ischemia and ischemia status. However, the MEK signaling pathway might not be involved in MgSO₄‐induced Glut3 expression following focal ischemia. Copyright © 2010 John Wiley & Sons, Ltd.     

桔梗生物学的研究

桔梗既是一种资源植物;又为常用中药,可宣肺祛痰、利咽排脓;并供作菜肴,别具风味,颇受欢迎。不论药用或食用,多年来皆依靠采挖野生资源。近年来,由于荒原减少,再加上只采不育,野生资源日益枯竭,既使过去每年调出量很大的黑龙江省亦感紧缺!为此,我们自1981年以来,对桔梗的生物学进行了一些研究,希望对保护和发展这一资源,乃至引种栽培提供理论依据。     

东北蒿属一新种

本文发表了产于东北的蒿属一新种,即肇东蒿Artemisia zhao-dongensis G.Y.Chang et M.Y.Liu。     

Kinetics of visual pigment regeneration in excised mouse eyes and in mice with a targeted disruption of the gene encoding interphotoreceptor retinoid-binding protein or arrestin.

Photoisomerization of 11-cis-retinal to all-trans-retinal and reduction to all-trans-retinol occur in photoreceptor outer segments whereas enzymatic esterification of all-trans-retinol, isomerization to 11-cis-retinol, and oxidation to 11-cis-retinal occur in adjacent cells. The processes are linked into a visual cycle by intercellular diffusion of retinoids. Knowledge of the mechanistic aspects of the visual cycle is very limited. In this study, we utilize chemical analysis of visual cycle retinoids to assess physiological roles for components inferred from in vitro experiments and to understand why excised mouse eyes fail to regenerate their bleached visual pigment. Flash illumination of excised mouse eyes or eyecups, in which regeneration of rhodopsin does not occur, produced a block in the visual cycle after all-trans-retinal formation; constant illumination of eyecups produced a block in the cycle after all-trans-retinol formation; and constant illumination of whole excised eyes resulted in a block of the cycle after formation of all-trans-retinyl ester. These blocks emphasize the role of cellular metabolism in the visual cycle. Interphotoreceptor retinoid-binding protein (IRBP) has been postulated to play a role in intercellular retinoid transfer in the retina; however, the rates of recovery of 11-cis-retinal and of regeneration of rhodopsin in the dark in IRBP-/- mice were very similar to those found with wild-type (wt) mice. Thus, IRBP is necessary for photoreceptor survival but is not essential for a normal rate of visual pigment turnover. Arrestin forms a complex with activated rhodopsin, quenches its activity, and affects the release of all-trans-retinal in vitro. The rate of recovery of 11-cis-retinal in arrestin-/- mice was modestly delayed relative to wt, and the rate of rhodopsin recovery was approximately 80% of that observed with wt mice. Thus, the absence of arrestin appeared to have a minor effect on the kinetics of the visual cycle.     

A simplified calculation method applied to enzyme inactivation during drying

An approximate method for solving the nonlinear diffusion problem in the case of a power-function variation of the diffusion coefficient with concentration has been applied to a drying process with simultaneous enzyme inactivation. Experimental results obtained by air drying of soybean lipoxygenase entrapped in a glucose calcium-alginate gel are in good agreement with the predicted behavior, whereas hardly any differences occur between the results obtained with the approximate method and those obtained by a numerical solution of the original model.     

Isolation, chemical structure, acute toxicity, and some physicochemical properties of territrem C from Aspergillus terreus.

Territrem C, a new tremorgenic mycotoxin (C28H32O9; molecular weight, 512.20) was isolated from the chloroform extract of rice cultures of Aspergillus terreus 23-1, which also produces territrems A and B. Isolation, acute toxicity, and some physicochemical properties of territrem C are discussed in this paper. The spectral and chemical evidence indicated that the structural difference between territrem C and territrem B (C29H34O9) was in their phenyl moieties: a 4-hydroxy-3,5-dimethoxy phenyl group in territrem C and a 3,4,5-trimethoxy phenyl group in territrem B. It was also demonstrated that territrem B was obtained by methylation of territrem C with dimethyl sulfate.     

Factors affecting the activation of rabbit muscle phosphofructokinase by actin

The consistent application of phosphatase inhibitors and a novel final purification step using a connected series of DE-51, DE-52, and DE-53 anion-exchange chromatography columns facilitate the preparation of electrophoretically homogeneous subpopulations of rabbit muscle phosphofructokinase which differ in their catalytic properties and endogenous covalent phosphate content. A band of "high"-phosphate enzyme (fraction II) flanked by regions of "low"-phosphate enzyme (fractions I and III) is an unusual feature of the final purification profile. Fractions I (containing in this case 0.42 mol of P/82 000 g of enzyme) and II (containing 1.26 mol of P/82 000 g of enzyme) exhibit the most pronounced functional differences of the fractions. Following our original report [Liou, R.-S., & Anderson, S. R. (1980) Biochemistry 19, 2684], both are activated by the addition of rabbit skeletal muscle F-actin. Under the assay conditions, half-maximal stimulation of phosphofructokinase activity occurs at 15.4 nM actin (in terms of monomer) for fraction I and 9.7 nM for fraction II. The low-phosphate enzyme is synergistically activated in the presence of 0.12 microM actin plus 3.0 microM fructose 2,6-bisphosphate, with a marked increase in Vmax, while the high-phosphate enzyme is not. Neither fraction is activated appreciably by the addition of G-actin or the chymotrypsin-resistant actin "core". The covalently cross-linked trimer of actin stimulates the activity of both the low- and high-phosphate enzyme fractions. However, the previously mentioned synergistic activation characteristic of fraction I fails to occur in solutions containing the trimer plus fructose 2,6-bisphosphate. Phosphorylation of fraction I in an in vitro reaction catalyzed by the cAMP-dependent protein kinase causes its properties to become more like those of fraction II. The total amount of covalent phosphate present after in vitro phosphorylation approaches 2 mol of P/82 000 g of enzyme for both fractions.     

Bilateral retinal and brain tumors in transgenic mice expressing simian virus 40 large T antigen under control of the human interphotoreceptor retinoid-binding protein promoter

We have previously shown that postnatal expression of the viral oncoprotein SV40 T antigen in rod photoreceptors (transgene MOT1), at a time when retinal cells have withdrawn from the mitotic cycle, leads to photoreceptor cell death (Al-Ubaidi et al., 1992. Proc. Natl. Acad. Sci. USA. 89:1194-1198). To study the effect of the specificity of the promoter, we replaced the mouse opsin promoter in MOT1 by a 1.3-kb promoter fragment of the human IRBP gene which is expressed in both rod and cone photoreceptors during embryonic development. The resulting construct, termed HIT1, was injected into mouse embryos and five transgenic mice lines were established. Mice heterozygous for HIT1 exhibited early bilateral retinal and brain tumors with varying degrees of incidence. Histopathological examination of the brain and eyes of three of the families showed typical primitive neuroectodermal tumors. In some of the bilateral retinal tumors, peculiar rosettes were observed, which were different from the Flexner-Wintersteiner rosettes typically associated with human retinoblastomas. The ocular and cerebral tumors, however, contained Homer-Wright rosettes, and showed varying degrees of immunoreactivity to antibodies against the neuronal specific antigens, synaptophysin and Leu7, but not to antibodies against photoreceptor specific proteins. Taken together, the results indicate that the specificity of the promoter used for T antigen and/or the time of onset of transgene expression determines the fate of photoreceptor cells expressing T antigen.     

Transfectomas expressing both secreted and membrane-bound forms of chimeric IgE with anti-viral specificity.

Because of the lack of a cell line expressing on surface and secreting human IgE of known Ag specificity, the construction of a transfectoma line possessing such properties would be useful for studying the roles of surface IgE and the effects of anti-IgE antibodies on IgE-producing B cells. Toward this goal, the human genomic DNA segment encompassing the two exons encoding the membrane anchor peptide of epsilon-chain and their flanking regions was sequenced. Hybrid epsilon and kappa genomic DNA comprising the C regions of human epsilon- and kappa-chains and the H and L chain V regions of the murine mAb BAT123, which reacts with the gp120 envelope protein of HIV-1, were constructed. Mammalian expression vectors containing these fusion genes were used to transfect murine myeloma Sp2/0 cells, and transfectants stably expressing on surface and secreting into culture medium chimeric IgE were obtained. The chimeric IgE showed identical Ag-binding properties as the murine mAb BAT123. Acting in concert with the specific peptide Ag polyvalently coupled to a protein carrier, the chimeric antibody could induce histamine release from human blood basophils. These results demonstrate the potential utility of the transfectoma cells and the chimeric IgE in studying the roles of membrane-bound IgE and effects of anti-IgE antibodies on IgE-producing B cells.