A cis-element in the 5' untranslated region of the preproinsulin mRNA (ppIGE) is required for glucose regulation of proinsulin translation

Insulin production in pancreatic beta cells is predominantly regulated through glucose control of proinsulin translation. Previously, this was shown to require sequences within the untranslated regions (UTRs) of the preproinsulin (ppI) mRNA. Here, those sequences were found to be sufficient for specific glucose-regulated proinsulin translation. Furthermore, an element 40-48 bp from the 5' end of the ppI mRNA specifically bound a factor present in islets of Langerhans. Glucose-responsive factor binding to this cis-element exhibited temporal and glucose-concentration-dependent patterns that paralleled proinsulin biosynthesis. Mutating this cis-element abolished the ability of ppI mRNA UTRs to confer glucose regulation upon translation. Like the rat 5'UTR, the human ppI 5'UTR conferred glucose regulation of translation. However alternative splicing of the human 5'UTR that disrupts the cis-element abolished glucose-regulated translation. These data indicate that glucose regulation of cis-element/trans-acting factor interaction is a key component of the mechanism by which glucose regulates insulin production.     

黑木耳子实体粉代替部分膳食对高脂模型小鼠营养性肥胖预防作用

本文旨在研究黑木耳粉代替部分膳食对模型小鼠预防营养性肥胖的作用功效。试验选择5周龄健康ICR雄性小鼠48只,随机分为正常对照组(CK)、高脂组(HFD)、阳性药物对照组(PD)和黑木耳粉添加组(AH)。连续饲喂9周,检测小鼠的各项生理生化指标。结果表明：与HFD组相比,AH组小鼠体重、附睾脂肪指数显著降低(P<0.05);Lee’s指数、血清葡萄糖(GLU)含量、甘油三酯(TG)含量和肝脏指数含量极显著降低(P<0.01),血清高密度脂蛋白胆固醇(HDL-C)和肝脏HDL-C含量极显著提高(P<0.01);染色结果观察到AH组小鼠肝脏中脂肪细胞减小,脂质含量降低;附睾脂肪体积减小,附睾细胞形状较规则。高通量测序分析发现,黑木耳粉干预有效改善了小鼠肠道中的变形菌门、螺杆菌属与拟杆菌属的相对丰度。研究结果表明黑木耳有显著预防小鼠营养性肥胖的功效,为黑木耳的开发利用提供依据。     

Hsp105α suppresses Adriamycin-induced cell death via nuclear localization signal-dependent nuclear accumulation

Heat shock protein 105 (Hsp105) is a molecular chaperone, and the isoforms Hsp105α and Hsp105β exhibit distinct functions with different subcellular localizations. Hsp105β localizes in the nucleus and induces the expression of the major heat shock protein Hsp70, whereas cytoplasmic Hsp105α is less effective in inducing Hsp70 expression. Hsp105 shuttles between the cytoplasm and the nucleus; the subcellular localization is governed by the relative activities of the nuclear localization signal (NLS) and nuclear export signal (NES). Here, we show that nuclear accumulation of Hsp105α but not Hsp105β is involved in Adriamycin (ADR) sensitivity. Knockdown of Hsp105α induces cell death at low ADR concentration, at which ADR is less effective in inducing cell death in the presence of Hsp105α. Of note, Hsp105 is localized in the nucleus under these conditions, even though Hsp105β is not expressed, indicating that Hsp105α accumulates in the nucleus in response to ADR treatment. The exogenously expressed Hsp105α but not its NLS mutant localizes in the nucleus of ADR-treated cells. In addition, the expression level of the nuclear export protein chromosomal maintenance 1 (CRM1) was decreased by ADR treatment of cells, and CRM1 knockdown caused nuclear accumulation of Hsp105α both in the presence and absence of ADR. These results indicating that Hsp105α accumulates in the nucleus in a manner dependent on the NLS activity via the suppression of nuclear export. Our findings suggest a role of nuclear Hsp105α in the sensitivity against DNA-damaging agents in tumor cells.     

Characteristics of β-adrenergic receptors in longitudinal muscle membranes of rat uterus: Changes in kinetic properties of the receptor during gestation

Binding characteristics of β-adrenergic receptors of longitudinal muscle membranes isolated from different stages of pregnant rat myometrium were investigated using [³H]dihydroalprenolol. Between Days 15 and 21 of gestation, the ratio of β₁- and β₂-adrenergic receptors of longitudinal membranes was constant. The membranes were found to be predominant in β₂-adrenergic receptors. The concentration of longitudinal muscle β-adrenergic receptors increased significantly during the last 7 days of gestation. Kinetic binding studies implied that the affinity of the membrane β-adrenergic receptors decreased through a slight decrease in the association rate and a large increase in the dissociation rate with progression of pregnancy. A Scatchard plot indicated that longitudinal muscle in β-adrenergic receptors on Days 15 and 18 constitute a single class of independent sites. By contrast, the dissociation kinetics, the convex downward curvature in a Scatchard plot and a Hill coefficient (h) of less than 1.00 of [³H] DHA binding to β-receptors of muscle on Day 21 suggested the existence of negatively cooperative multiple binding sites for β-adrenergic ligand. These results suggest that changes in the dynamics of uterus β-adrenergic receptors play an important role in the onset of labor.     

Determination of human plasma xanthine oxidase activity by high-performance liquid chromatography

An assay for human plasma xanthine oxidase activity was developed with pterin as the substrate and the separation of product (isoxanthopterin) by high-performance liquid chromatography with a fluorescence detector. The reaction mixture consists of 60 μl of plasma and 240 μl of 0.2 M Tris-HCl buffer (pH 9.0) containing 113 μM pterin. With this assay, the activity of plasma xanthine oxidase could be easily determined despite its low activity. As a result, it could be demonstrated that the intravenous administration of heparin or the oral administration of ethanol did not increase plasma xanthine oxidase activity in normal subjects, and also that plasma xanthine oxidase activity was higher in patients with hepatitis C virus infection than in healthy subjects or patients with gout. In addition, a single patient with von Gierke's disease showed a marked increase in the plasma activity of this enzyme, relative to that apparent in normal subjects.     

Structural conservation of the transposon Tam3 family in Antirrhinum majus and estimation of the number of copies able to transpose

We have investigated the organization of the transposon Tam3 family in Antirrhinum majus. Genomic hybridization experiments and characterization of 40 independent Tam3 clones isolated from an A. majus plant revealed that the Tam3 family is quite conserved and the copy sizes are uniform. We did not find any copy with a deleted internal sequence, unlike what is usually observed in other transposons. This exceptionally conserved structure of the Tam3 family was confirmed by PCR and sequencing analyses. Sequencing analysis identified eight copies with sequences completely identical to that of the Tam3 transposase gene. These results suggested that a considerable number of autonomous Tam3 copies are present in the genome of A. majus. Among 24 copies which are surrounded by single copy regions of the genome, 14 copies are present as specific insertions in the line which we used, but absent in other lines. These copies are therefore predicted to be movable. If this ratio is the same for all Tam3 copies in a genome, then a maximum of 60% of the copies are estimated to be movable in the genome. The relatively high frequency of gene tagged by Tam3 might reflect the large number of movable copies in the genome.     

Expression of TGFβ3 RNA during chick embryogenesis: a possible important role in cardiovascular development

Formin was originally isolated as the gene affected by the murine limb deformity (ld) mutations, which disrupt the epithelial-mesenchymal interactions regulating patterning of the vertebrate limb autopod. More recently, a rapidly growing number of genes with similarity to formin have been isolated from many different species including fungi and plants. Genetic and biochemical analysis shows that formin family members function in cellular processes regulating either cytokinesis and/or cell polarisation. Another common feature among formin family members is their requirement in morphogenetic processes such as budding and conjugation of yeast, establishment of Drosophila oocyte polarity and vertebrate limb pattern formation. Vertebrate formins are predominantly nuclear proteins which control polarising activity in limb buds through establishment of the SHH/FGF-4 feedback loop. Formin acts in the limb bud mesenchyme to induce apical ectodermal ridge (AER) differentiation and FGF-4 expression in the posterior AER compartment. Finally, disruption of the epithelial-mesenchymal interactions controlling induction of metanephric kidneys in ld mutant embryos indicates that formin might function more generally in transduction of morphogenetic signals during embryonic pattern formation. Received: 24 September 1998 / Accepted: 30 September 1998     

Oxidative stress and delayed-onset muscle damage after exercise

Reactive oxygen species (ROS) produced during exercise may be involved in delayed-onset muscle damage related to inflammation. To investigate this hypothesis, we studied whether oxidative stress increases nuclear translocation of nuclear factor-kappaB and chemokine expression in skeletal muscle using myotube L6 cells. We also assessed whether prolonged acute exercise could increase these parameters in rats. In L6 cells, H(2)O(2) induced nuclear translocation of p65 and increased the expression of cytokine-induced neutrophil chemoattractant-1 (CINC-1) and monocyte chemoattractant protein-1 (MCP-1), whereas preincubation with alpha-tocopherol limited the increase in these proteins. Sprague Dawley rats were divided into the following groups: rested control, exercised, rested with a high alpha-tocopherol diet, and exercised with a high alpha-tocopherol diet. After 3 weeks of acclimation, both exercise groups ran on a treadmill at 25 m/min for 60 min. Exercise increased nuclear p65, CINC-1, and MCP-1 in gastrocnemius muscle cells, but these changes were ameliorated by the high alpha-tocopherol diet. Increases in myeloperoxidase and thiobarbituric acid-reactive substrates were ameliorated by a high alpha-tocopherol diet, as were the histological changes. Neutrophil activity was not altered by either exercise or a high alpha-tocopherol diet. These results indicate that delayed-onset muscle damage induced by prolonged exercise is partly related to inflammation via phagocyte infiltration caused by ROS and that alpha-tocopherol (an antioxidant) can attenuate such inflammatory changes.