缺氧大鼠心肌α1,β肾上腺素能受体的变化

为了探讨α_1、β肾上腺素能受体在大鼠缺氧性心脏肥大进程中的作用,本研究应用放射配基结合法观察了不同缺氧时间大鼠心室α_1、β肾上腺素能受体变化的动态过程,同时也观察了α_1、β受体阻断剂在预防缺氧性心肌肥大发生中的作用。缺氧10d后,测定右心室重量及组织学检查未见右心室肥大,但此时心室肌α_1受体数量从对照组的27.49±1.25增加到33.80±0.90fmol/mg蛋白(P<0.05);β受体从对照组的51.80±7.60下降到25.10±2.30fmol/mg蛋白(P<0.01)。缺氧20和30d后α_1受体进一步增加到40.70±1.43和32.30±1.96fmol/mg蛋白(P<0.05);β受体分别为27.90±2.30和42.80±1.70fmol/mg蛋白(P<0.05)。缺氧20和30d后右心室重量指数明显高于对照组,在整个缺氧过程中α_1、β受体的亲和性(K_d)未见明显变化,未见左心室肥大。缺氧同时应用α_1受体阻断剂(哌唑嗪4mg·kg~(-1)·d~(-1))30d,可明显预防缺氧所致的右心肥大;而β受体阻断剂(心得安10mg·kg~(-1)·d~(-1))没有此种作用。由此可见,在缺氧所致右心肥大之前,心肌α_1受体数量即明显升高,α_1受体阻断剂可以预防缺氧引起的右心肥大。     

Vanadate stimulates system A amino acid transport activity in skeletal muscle. Evidence for the involvement of intracellular pH as a mediator of vanadate action.

Sodium orthovanadate caused a 2-fold stimulation of system A transport activity in soleus muscle, as assessed by the uptake of the nonmetabolizable analog 2-(methylamino)isobutyric acid (MeAIB). The effect of vanadate on system A was rapid, concentration-dependent and was characterized by an increased Vmax without modification of Km for MeAIB. Under these conditions, vanadate also activated 3-O-methylglucose uptake and lactate production. The effects of vanadate on muscle metabolism showed a complex interaction with the effects of insulin. Thus, the stimulatory effects of vanadate and insulin on MeAIB and 3-O-methylglucose uptake were not additive; however, the effects of insulin and vanadate on lactate production were additive. In spite of the lack of additivity, insulin- and vanadate-induced stimulation of system A differed in their sensitivity to gramicidin D, being the vanadate effect more susceptible to inhibition by gramicidin D than the insulin effect. System A transport activity shows a dependence on pH, and recent results suggest the presence of critical histidine residues on the A carrier that may be responsible for its pH dependence (Bertran, J., Roca, A., Pola, E., Testar, X., Zorzano, A. & Palacín, M. (1991) J. Biol. Chem. 266, 798-802). In this regard, a rise in extracellular pH led to a substantial activation of system A. Furthermore, lowering of muscle intracellular pH induced by ethylisopropylamiloride (EIPA), a specific inhibitor of sodium/proton exchange activity, led to inhibition of system A. This suggests that critical histidine residues are present in an intracellular localization on the A carrier. Furthermore, the rate of muscle glycolysis was also altered in response to a rise in extracellular pH or to EIPA treatment. Regarding the mechanisms involved in vanadate action, vanadate treatment in the incubated soleus muscle did not cause any significant stimulation of tyrosine kinase activity after partial purification of muscle insulin receptors. On the other hand, vanadate but not insulin caused a substantial increase in muscle intracellular pH as assessed by 5,5'-dimethyloxazolidine-2,4-dione equilibrium. This effect of vanadate on intracellular pH was not due to activation of the sodium/proton exchanger, since it was not blocked by EIPA. Based on these findings, we suggest that alkalinization of muscle intracellular pH might mediate the effects of vanadate on system A and on glycolysis.     

Ageing-related changes in Mycoplasma canadense membranes.

Fluidity and composition of cell membranes during progression of Mycoplasma canadense cultures grown in a serum-free medium was assessed. The fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene at 25 degrees C of intact cells and liposomes in the exponential and stationary phases of growth was compared. A decrease in fluidity and an increase in the ratio of saturated to unsaturated fatty acids was detected in cell membranes on aging. Nevertheless, membrane density remained unaltered although the molar ratio of cholesterol to phospholipids decreased. It is proposed that the increase in lipid order is primarily due to the increase in the ratio of saturated to unsaturated membrane fatty acids, being the diminished molar ratio of cholesterol to phospholipids involved in the reduced unsaturated fatty acid uptake.     

Effect of continued exposition to ethanol on activity of the ammonium and fructose transport systems in Saccharomyces cerevisiae var. ellipsoideus

Ethanol and cycloheximide inhibited the function of the ammonium transport system in growing cultures of Saccharomyces cerevisiae var. ellipsoideus measured as methylamine uptake. The effect was reversible with ethanol and irreversible with the antibiotic. The kinetic data are consistent with a reduction of the number of active carrier molecules located in the plasma membrane. In contrast, neither ethanol nor cycloheximide affected the specific rate of fructose uptake.     

Tyrosine protein phosphorylation is required for protein kinase C-mediated proliferation in T cells.

We have studied the role of tyrosine kinase in PMA-stimulated T cells. Protein kinase C (PKC)-mediated D10A cell proliferation is inhibited by the specific inhibitor of tyrosine kinase, tyrphostin. This inhibitor selectively blocks the mRNA expression of the proto-oncogene c-myc in response to the phorbol ester, PMA. On the other hand, the same doses of this inhibitor do not affect the mRNA expression of the proto-oncogene c-fos in PMA-stimulated D10A cells. Phorbol esters induce in this T cell line the tyrosine phosphorylation of a unique protein of 42 kDa and the enzyme PKC is required for this activity.     

The interplay of LncRNA ANRIL and miR‐181b on the inflammation‐relevant coronary artery disease through mediating NF‐κB signalling pathway

This study was designed to investigate whether ANRIL affected the aetiology of coronary artery disease (CAD) by acting on downstream miR‐181b and NF‐κB signalling. Altogether 327 CAD patients diagnosed by angiography were included, and mice models of CAD were established. Human coronary endothelial cells (HCAECs) and human umbilical vein endothelial cells (HUVECs) were also purchased. In addition, shRNA‐ANRIL, shRNA‐NC, pcDNA3.1‐ANRIL, miR‐181b mimic, miR‐181b inhibitor and miR‐NC were transfected into the cells. The lipopolysaccharides (LPS) and pyrrolidine dithiocarbamate (PDTC) were also added to activate or deactivate NF‐κB signalling. Both highly expressed ANRIL and lowly expressed miR‐181b were associated with CAD population aged over 60 years old, with smoking history, with hypertension and hyperlipidemia, with CHOL H 4.34 mmol/L, TG ≥ 1.93 mmol/L and Hcy ≥ 16.8 μmol/L (all P < 0.05). Besides, IL‐6, IL‐8, NF‐κB, TNF‐α, iNOS, ICAM‐1, VCAM‐1 and COX‐2 expressions observed within AD mice models were all beyond those within NC and sham‐operated groups (P < 0.05). Also VEGF and HSP 70 were highly expressed within AD mice models than within NC and sham‐operated mice (P < 0.05). Transfection of either pcDNA‐ANRIL or miR‐181b inhibitor could significantly fortify HCAECs’ viability and put on their survival rate. At the meantime, the inflammatory factors and vascular‐protective parameters were released to a greater level (P < 0.05). Finally, highly expressed ANRIL also notably bring down miR‐181b expression and raise p50/p65 expressions within HCAECs (P < 0.05). The joint role of ANRIL, miR‐181b and NF‐κB signalling could aid in further treating and diagnosing CAD.     

Reaction mechanism of organoselenium-catalyzed <Emphasis Type="Italic">syn</Emphasis>-dichlorination of alkenes: a DFT study

A new method for the syn-dichlorination of alkenes at room temperature has been proposed by Denmark et al. The method uses diselenide (PhSeSePh) as the precatalyst, benzyltriethylammonium chloride (BnEt₃NCl) as the source of chlorine, and an N-fluoropyridinium salt as the oxidant to recover the catalyst. This approach has achieved exquisite diastereocontrol on a number of alkene substrates. In this paper, we report the results of DFT calculations we performed to study the mechanism of this reaction. We were able to identify a reasonable reaction path, including the intermediate and transition-state structures. The results also indicate that PhSeCl₃, rather than PhSeCl, is the active catalyst.     

Targeted Gene Deletion in <Emphasis Type="Italic">Cordyceps militaris</Emphasis> Using the Split-Marker Approach

The macrofungus Cordyceps militaris contains many kinds of bioactive ingredients that are regulated by functional genes, but the functions of many genes in C. militaris are still unknown. In this study, to improve the frequency of homologous integration, a genetic transformation system based on a split-marker approach was developed for the first time in C. militaris to knock out a gene encoding a terpenoid synthase (Tns). The linear and split-marker deletion cassettes were constructed and introduced into C. militaris protoplasts by PEG-mediated transformation. The transformation of split-marker fragments resulted in a higher efficiency of targeted gene disruption than the transformation of linear deletion cassettes did. The color phenotype of the Tns gene deletion mutants was different from that of wild-type C. militaris. Moreover, a PEG-mediated protoplast transformation system was established, and stable genetic transformants were obtained. This method of targeted gene deletion represents an important tool for investigating the role of C. militaris genes.     

Single‐Crystalline Nanomesh Tantalum Nitride Photocatalyst with Improved Hydrogen‐Evolving Performance

Tantalum nitride (Ta₃N₅) with a suitable bandgap (≈2 eV) is regarded as one of the most promising photocatalysts for efficient solar energy harvesting and conversion. However, Ta₃N₅ suffers from low hydrogen production activity due to the low carrier mobility and fast carrier recombination. Thus, the design of Ta₃N₅ nanostructures to facilitate charge carrier transport and improve photocatalytic performance remains a challenge. This study reports a new type of ultrathin (≈2 nm) Ta₃N₅ nanomesh with high specific surface area (284.6 m² g^?1) and excellent crystallinity by an innovative bottom‐up graphene oxide templated strategy. The resulting Ta₃N₅ nanomeshes demonstrate drastically improved electron transport ability and prolonged lifetime of charge carriers, due to the nature of high surface area and excellent crystallinity. As a result, when used as photocatalysts, the Ta₃N₅ nanomeshes exhibit a greater than tenfold improvement in solar hydrogen production compared to bulk counterparts. This work provides an effective and generic strategy for designing 2D ultrathin nanomesh structures for nonlayered materials with improved catalytic activity.