Thyroid hormone improves the mechanical performance of the post-infarcted diabetic myocardium: A response associated with up-regulation of Akt/mTOR and AMPK activation

Objective

Thyroid hormone (TH) is shown to be protective against cardiac and pancreatic injury. Thus, this study explored the potential effects of TH treatment on the functional status of the postinfarcted diabetic myocardium. Diabetic patients have worse prognosis after acute myocardial infarction (AMI).

Materials/Methods

AMI was induced by left coronary ligation in rats previously treated with 35 mg/kg streptozotocin (STZ), (DM-AMI). TH treatment was initiated at 2 weeks after AMI and continued for 6 weeks (DM-AMI + TH), while sham-operated animals served as control (DM-SHAM).

Results

TH treatment increased cardiac mass, improved wall stress and favorably changed cardiac geometry. TH significantly increased echocardiographic left ventricular ejection fraction (LVEF%): [54.2 (6.5) for DM-AMI + TH vs 37 (2.0) for DM-AMI, p < 0.05]. TH treatment resulted in significantly increased insulin and decreased glucose levels in serum. The ratios of phosphorylated (p)-Akt/total Akt and p-mTOR/total mTOR were increased 2.0 fold and 2.7 fold in DM-AMI + TH vs DM-AMI respectively, p < 0.05. Furthermore, the ratio of p-AMPK/total AMPK was found to be increased 1.6 fold in DM-AMI + TH vs DM-AMI, p < 0.05.

Conclusion

TH treatment improved the mechanical performance of the post-infarcted myocardium in rats with STZ-induced diabetes, an effect which was associated with Akt/mTOR and AMPK activation.     

Leukotrienes stimulate pepsinogen secretion from guinea pig gastric chief cells by a nitric oxide-dependent pathway

Leukotrienes (LTs) are involved in many inflammatory conditions including gastric damage induced by nonsteroidal anti-inflammatory drugs. Although LTs stimulate acid secretion, the effect they exert on pepsinogen secretion is unknown. The aim of this study was to investigate whether LTs stimulate pepsinogen secretion by isolated chief cells and to identify the intracellular messengers that mediate this action. Isolated chief cells were incubated with concentrations of LTB₄, LTC₄, LTD₄, or LTE₄ ranging from 0.1 pmol/L to 10 μmol/L, and pepsinogen release, intracellular calcium and inositol(1,4,5)-trisphosphate (IP₃) concentrations were measured. Nitric oxide generation was determined by the amount of citrulline generated during incubation. All four LTs caused a concentration-dependent stimulation of pepsinogen secretion with 50% effective concentration of 0.05-0.1 nmol/L and a dose-dependent increase in cytoplasmic free calcium and IP₃ concentration. The LTB₄ and LTD₄ antagonists caused selective, concentration-dependent inhibition of LTB₄- and LTD₄-induced pepsinogen secretion, calcium mobilization, and IP₃ generation. All four LTs increased NO generation, and the effect was inhibited by LTB₄ and LTD₄ antagonists and an NO synthase inhibitor N^G-monomethyl-l-arginine and reversed by l-arginine. N^G-monomethyl-l-arginine caused a 50%–60% reduction of LT-induced pepsinogen release. Each of the four LTs caused a fivefold increase in 5′-cyclic guanosine monophosphate. LTs are powerful stimulators of pepsinogen secretion in isolated chief cells and act via occupancy of specific cell-surface receptors.     

Sustained phosphorylation of Bid is a marker for resistance to Fas-induced apoptosis during chronic liver diseases

BACKGROUND & AIMS: Increased rates of apoptosis have been reported to play a role in the pathophysiology of many disorders, including liver diseases. Conversely, genetic mutations that result in impairment of programmed cell death have been associated with cancer development. However, apoptosis resistance can also be the result of nongenetic stress adaptation, as seen in the cancer-prone metabolic liver disease hereditary tyrosinemia. To clarify whether stress-induced apoptosis resistance is a general feature of chronic liver diseases, an animal model of chronic cholestasis was examined. METHODS: Studies were performed with mice before and 2 weeks following bile duct ligation and with Fah-/- and Fah/p21-/- mice before and after NTBC withdrawal. RESULTS: Here we show that bile duct ligation induced profound resistance against Fas monoclonal antibody-mediated hepatocyte death. The apoptosis signaling pathway was blocked downstream of caspase-8 activation and proximal to mitochondrial cytochrome c release. In controls, activation of the Fas receptor resulted in rapid dephosphorylation of Bid and its subsequent cleavage, whereas Bid remained phosphorylated and uncleaved in chronic cholestasis and other models of hepatic apoptosis resistance. CONCLUSIONS: We propose a model in which the phosphorylation status of Bid determines the apoptotic threshold of hepatocytes in vivo. Furthermore, resistance to apoptosis in chronic cholestasis may contribute to the long-term risk of cancer in this setting.     

Control of cardiac myofilament activation and PKC-betaII signaling through the actin capping protein, CapZ

Actin capping protein (CapZ) anchors the barbed ends of sarcomeric actin to the Z-disc. Myofilaments from transgenic mice (TG-CapZ) expressing a reduced amount of CapZ demonstrate altered function and protein kinase C (PKC) signaling [Pyle WG, Hart MC, Cooper JA, Sumandea MP, de Tombe PP, and Solaro RJ., Circ. Res. 90 (2002) 1299-306]. The aims of the current study were to determine the direct effects of CapZ on myofilament function and on PKC signaling to the myofilaments. Our studies compared mechanical properties of single myocytes from TG-CapZ mouse hearts to wild-type myocytes from which CapZ was extracted using PIP(2). We found that myofilaments from CapZ-deficient transgenic myocardium exhibited increased Ca(2+) sensitivity and maximum isometric tension. The extraction of CapZ from wild-type myofilaments replicated the increase in maximum isometric tension, but had no effect on myofilament Ca(2+) sensitivity. Immunoblot analysis revealed that the extraction of CapZ was associated with a reduction in myofilament-associated PKC-beta(II) and that CapZ-deficient transgenic myofilaments also lacked PKC-beta(II). Treatment of wild-type myofilaments with recombinant PKC-beta(II) reduced myofilament Ca(2+) sensitivity, whereas this effect was attenuated in myofilaments from TG-CapZ mice. Our results indicate that cardiac CapZ directly controls maximum isometric tension generation, and establish CapZ as an important component in anchoring PKC-beta(II) at the myofilaments, and for mediating the effects of PKC-beta(II) on myofilament function.     

Comparison of synaptic plasma membrane and synaptic vesicle polypeptides by two-dimensional polyacrylamide gel electrophoresis.

Extracts of chick brain synaptic plasma membranes, synaptic vesicles, and mixtures of membranes and vesicles were examined by electrophoresis on two-dimensional polyacrylamide gels by a modification of the O'Farrell technique. Synaptic plasma membranes had twenty-one major polypeptides; synaptic vesicles had seventeen. Thirteen major polypeptides were common to both fractions. The similarities between the synaptic vesicle and synaptic plasma membrane patterns are unlikely to be due to contamination of one fraction by the other or to contamination of both fractions by microsomes, synaptoplasm or mitochondria. Our findings are consistent with mixing of membrane proteins occurring during exocytosis but it remains to be shown that these synaptic subfractions are not contaminated by a type of membrane for which markers are not yet available.     

EGTA与EDTA溶液去除根管壁玷污层能力的比较

目的：比较EGTA与EDTA去除根管玷污层的能力，为临床应用提供实验依据。方法：新鲜拔除24颗牙齿分为4组，即：15％EDTA、5％EGTA、10％EGTA、15％EGTA。实验组又分为：根管预备后冲洗(简称：甲组)，边扩边冲洗组(简称：乙组)。常规开髓、拔髓后15％EDTA、5％EGTA、10%EGTA、15％EGTA分别冲洗根管，剖开根管后在扫描电镜下观察根管壁玷污层及根管壁牙本质小管开口情况。结果：15％EDTA无论在根管上、中、下1／3均能较理想去除根管壁玷污层，牙本质小管开口清楚、密集。5％EGTA去除根管玷污层效果欠佳，而10％、15％EGTA效果较好。结论：15％EDTA，10%、15％EGTA均有较好去除根管壁玷污层的能力，而且冲洗效果与注射针头进入深度密切相关。     

Supplementation with branched-chain amino acids attenuates hepatic apoptosis in rats with chronic liver disease

Branched-chain amino acids (BCAA) can function as pharmacologic nutrients for patients with decompensated cirrhosis. However, the effects of BCAA at the early stage of chronic liver disease are not clear. We hypothesized that early BCAA supplementation would attenuate the progression of chronic liver disease. The present study examined the effects of BCAA supplementation on the progression of chronic liver disease in rats caused by injected carbon tetrachloride (CCl₄). Sprague-Dawley rats were fed with a casein diet (control group) or the same diet supplemented with BCAA (BCAA group) for 11 weeks, and all rats were repeatedly injected with CCl₄. Food intake did not significantly differ between control and BCAA groups during the experimental period. Plasma alanine aminotransferase activities gradually increased during the experimental period in both groups but peaked later in the BCAA group. Liver fibrosis was more evident in the control group. Levels of connective tissue growth factor messenger RNA were significantly lower in the livers of rats in the BCAA group than in the control group. Terminal deoxynucleotidyl transferase–mediated deoxyuridine 5-triphosphate nick end labeling assays found considerably more hepatic apoptosis in the control group. Liver cytosolic cytochrome c levels and expression of the proapoptotic Bax protein in the mitochondrial fraction were significantly lower in the BCAA group than in the control group. These results suggest that supplementation with BCAA delays the progression of chronic liver disease caused by CCl₄ in rats by attenuating hepatic apoptosis.     

EGTA对SLET细胞TCR/CD3复合物介导的[Ca2+]i反应的影响

目的 :证实SLE患者T细胞功能异常是否与其生物化学信号传导异常有关以及EGTA对其影响 ,探讨SLE的发病机理。方法 :用CD3单抗与羊抗鼠二抗IgG相交联刺激T细胞并用EGTA干预后 ,分别粘附细胞仪连续观察 10minT细胞 [Ca2 + ]i的变化 ,并评价 [Ca2 + ]i反应与CD3分子的相关性。结果 :正常人和SLE患者T细胞 [Ca2 + ]i反应的基准值相似 (P =0 .10 5 ) ;SLE患者高峰值、平台值T细胞的 [Ca2 + ]i反应明显高于正常对照 (P <0 .0 0 1,P <0 .0 0 1) ;加入EGTA后二者 [Ca2 + ]i反应有显著差异 :二者的T细胞CD3阳性率无差异 (P =0 .6 6 5 )。结论 :SLE患者T细胞TCR/CD3介导的信号转导途径存在异常 ,且不受EGTA的影响 ,可能是贮存库 [Ca2 + ]i释放的增加所致。     

A serine proteinase in the penetration glands of the hexacanths of Hymenolepis diminuta (Cestoda, Cyclophyllidea)

 Histochemically demonstrable activity of a serine proteinase was detected in the penetration glands of Hymenolepis diminuta hexacanths. At the optimal pH of 8.4 the enzyme hydrolyzed N-blocked l-aminoacyl- and N-blocked l-peptidyl-naphthylamides bearing l-arginine at the P₁ subsite. The proteinase did not require either Ca²⁺ or Mg²⁺ for its activity and was insensitive to 1 mM EGTA and 1 mM EDTA. Organic fluorophosphates inhibited it, whereas thiol-blocking compounds did not. At operative pH values of 4.8 and 3.8 generated during electrophoresis in a stacking and a resolving gel, respectively, the proteinase migrated toward the cathode. When examined for proteolytic activity at the optimal pH of 8.4, the separated enzyme produced a single band of gelatinolysis in a gelatin-containing polyacrylamide gel. During in vitro maintenance of the hexacanths, the secretion from their penetration glands formed a mucous cyst surrounding the individual larvae. The cyst was resistant to and protected the hexacanths from the proteolytic activity of trypsin, papain, and proteinases extracted from the gut of the beetle Tenebrio molitor (the host). Hexacanths extracted from the hemocoel of T. molitor at 24 and 48 h after infection were surrounded by similar mucous cysts. Consequently, roles in penetration and protection for the secretion from the penetration glands are postulated. Received: 18 January 1995 / Accepted: 20 May 1995     

Solubilization and separation of divalent cation dependent adenosinetriphosphatase in native gradient polyacrylamide slab gel

A new method for the simultaneous solubilization and separation of different cation dependent adenosinetriphosphatases after non-denaturing polyacrylamide gel electrophoresis is described. Using a gradient system, 3 distinct divalent cation dependent adenosinetriphosphatase bands (Mg2+-, Ca2+-, and Mg2+ + Ca2+-dependent) could be separated on the same gel from NP-40 solubilized brain microsomal preparations. This indicates that these 3 adenosinetriphosphatases represent distinct molecular species.