Reduced release of nitric oxide to shear stress in mesenteric arteries of aged rats

We hypothesized that aging is characterized by a reduced release of nitric oxide (NO) in response to shear stress in resistance vessels. Mesenteric arterioles and arteries of young (6 mo) and aged (24 mo) male Fischer 344 rats were isolated and cannulated. Shear stress (15 dyn/cm(2))-induced dilation was significantly reduced and shear stress (1, 5, 10, and 15 dyn/cm(2))-induced increases in perfusate nitrite were significantly smaller at all shear stress levels in vessels of aged rats. Inhibition of NO synthesis abolished shear stress-induced release of nitrite. Furthermore, shear stress (15 dyn/cm(2))-induced release of nitrate was significantly higher and total nitrite (nitrite plus nitrate) was significantly lower in vessels of aged rats. Tiron or SOD significantly increased nitrite released from vessels of aged rats, but this was still significantly less than that in young rats. Superoxide production was increased and the activity of SOD was decreased in vessels of aged rats. There were no differences in endothelial NO synthase (eNOS) protein and basal activity or in Cu/Zn-SOD and Mn-SOD proteins in vessels of the two groups, but extracellular SOD was significantly reduced in vessels of aged rats. Maximal release of NO induced by shear stress plus ACh (10(-5) M) was comparable in the two groups, but phospho-eNOS in response to shear stress (15 dyn/cm(2)) was significantly reduced in vessels of aged rats. These data suggest that an increased production of superoxide, a reduced activity of SOD, and an impaired shear stress-induced activation of eNOS are the causes of the decreased shear stress-induced release of NO in vessels of aged rats.     

大鼠肢体预缺血减小心肌缺血-再灌注后的梗塞范围

在氨基甲酸乙酯麻醉大鼠上观察肢体预缺血(limb ischemic preconditioning,LIP)对缺血-再灌注(ischemia—reperfusion,IR)心肌的影响,旨在探讨LIP对IR心肌有无保护效应,并明确腺苷和神经通路是否参与此效应。所得结果如下:(1)在心脏缺血30 min和再灌注120 min过程中,梗塞心肌占缺血心肌的51.48±0.82％。(2)LIP时心肌梗塞范围为35.14±0.88％,较单纯心肌缺血-再灌注时显著减小(P<0.01),表明LIP对心肌有保护作用。(3)事先切断股神经可取消LIP的保护效应。(4)股动脉内局部给予腺苷(10nmol/kg),可模拟LIP对心肌的保护作用;心肌梗塞范围是37.28±1.68％,而股静脉内注射同等剂量腺苷则无保护作用。(5)股动脉内预先应用腺苷A.受体拈抗剂8-环戊-1,3-二丙基嘌呤(DPCPX)(32 nmol/kg)可部分阻断LIP诱发的心肌保护效应。以上结果表明,肢体短暂预缺血可减小心肌缺血-再灌注后的梗塞范围,而局部释放的腺苷和由此所激活的相关的神经通路在LIP的心肌保护中起重要作用。     

Antinematodal activity and the mechanism of the antimicrobial peptide, HP (2-20), against Caenorhabditis elegans

The peptide HP (2-20), derived from the N-terminal sequence of Helicobacter pylori ribosomal protein L1 (RPL1), has a nematicidal activity against eggs and worms of Caenorhabditis elegans. Eggs treated with HP (2-20) (69%) has a higher fluorescence intensity with propidium iodide staining, which was similar to that of melittin (82%) but higher than untreated cells (5.7%). Confocal microscopy showed that the peptides were located in the shell of the eggs and the inner and outer surfaces of the worms. HP (2-20) therefore may exert its antinematodal activity by disrupting the structure of the egg's shell and the cell membrane via pore formation or by direct interaction with the lipid bilayers in a detergent-like manner.     

Functional characterization and purification of the secretin receptor expressed in baculovirus-infected insect cells

Structural insights into Class II G protein-coupled receptors have been limited by the absence of a plentiful and highly enrichable source such as rhodopsin in the Class I family. With structural differences predicted to exist between these families, and with the key importance of an intact, disulfide-bonded amino-terminal domain for the Class II receptors, an overproduction and purification scheme is critically important. In this work, we have established and characterized a baculoviral expression and purification system for the secretin receptor. Hemagglutinin epitope-tagged wild-type rat secretin receptor construct was expressed using the recombinant baculovirus/Sf9 insect cell-based system, achieving a level of expression substantially higher than that previously achieved in Chinese hamster ovary (CHO-SecR) cells. Receptor expressed in Sf9 cells had similar affinity for secretin (Ki=1.4+/-0.2 nM) and similar potency to stimulate intracellular cAMP in response to this hormone (EC50=194+/-45 pM) as did wild-type receptor expressed in CHO cells. Receptors from Sf9 cells were also affinity labeled saturably and specifically by a photolabile secretin analogue. The receptors were purified to homogeneity by solubilization with sodium deoxycholate, selective ammonium sulfate precipitation, gel filtration and immunoaffinity purification. This expression system should facilitate the structural characterization of this receptor and its important amino-terminal domain.     

Development of glutamic acid decarboxylase 65 (GAD65) autoantibody assay using biotin-GAD65 fusion protein

We evaluated a biotin-glutamic acid decarboxylase 65 (GAD65)-based enzyme-linked immunosorbent assay (B-ELISA) to detect GAD65 autoantibodies (GAD65Ab) in 78 sera from individuals with newly diagnosed type 1 diabetes. The GAD65Ab index of patients with type 1 diabetes (mean value of GAD65Ab index of 1.891) was significantly higher than those in 50 sera from healthy control group (mean value of 0.068). The intra- and inter-assay coefficients of variation (CV) were calculated to be 1.042 and 10.703%, respectively. The specificity of the B-GAD65 ELISA was comparable to the standard radioimmunoassay (RIA) which is routinely used in the laboratory. We describe the optimal conditions of the binding kinetics from each assay-step for the detection of GAD65Ab using the WHO standard serum 97/550 as a model autoantibody serum. We concluded that incubation times of 15, 90, and 90 min for step 1 (pre-incubation of Biotin14-GAD65 with serum), step 2 (binding the Ab/Ag complex to NeutrAvidin plate), and step 3 (incubation with HRPO-anti-human IgG), respectively, along with human serum dilutions of 1:50, would provide an optimal assay signal within a relatively short timeframe.     

Phorbol esters affect skeletal muscle glucose transport in a fiber type-specific manner

Recent evidence has shown that activation of lipid-sensitive protein kinase C (PKC) isoforms leads to skeletal muscle insulin resistance. However, earlier studies demonstrated that phorbol esters increase glucose transport in skeletal muscle. The purpose of the present study was to try to resolve this discrepancy. Treatment with the phorbol ester 12-deoxyphorbol-13-phenylacetate 20-acetate (dPPA) led to an approximately 3.5-fold increase in glucose transport in isolated fast-twitch epitrochlearis and flexor digitorum brevis muscles. Phorbol ester treatment was additive to a maximally effective concentration of insulin in fast-twitch skeletal muscles. Treatment with dPPA did not affect insulin signaling in the epitrochlearis. In contrast, phorbol esters had no effect on basal glucose transport and inhibited maximally insulin-stimulated glucose transport approximately 50% in isolated slow-twitch soleus muscle. Furthermore, dPPA treatment inhibited the insulin-stimulated tyrosine phosphorylation of insulin receptor substrate (IRS)-1 and the threonine and serine phosphorylation of PKB by approximately 50% in the soleus. dPPA treatment also caused serine phosphorylation of IRS-1 in the slow-twitch soleus muscle. In conclusion, our results show that phorbol esters stimulate glucose transport in fast-twitch skeletal muscles and inhibit insulin signaling in slow-twitch soleus muscle of rats. These findings suggest that mechanisms other than PKC activation mediate lipotoxicity-induced whole body insulin resistance.     

Dot-blot hybridization and RT-PCR detection of extra small virus (XSV) associated with white tail disease of prawn Macrobrachium rosenbergii

The availability of specific and reliable detection methods is essential for monitoring the health status of farmed species, particularly for viral diseases. Extra small virus (XSV), a virus-like particle, is associated with Macrobrachium rosenbergii Noda virus (MrNV) in white tail disease (WTD) of M. rosenbergii. We developed 2 genome-based detection methods for the identification of XSV, namely dot-blot hybridization and a single-step RT-PCR. Detection limits were established and are ca. 2.5 pg and 5 fg of viral RNA for dot-blot hybridization and RT-PCR, respectively. Application of the methods to field samples indicated that some animals positively diagnosed with MrNV did not contain XSV, at least within the detection limit of the methodology. This raises the question of the actual role of XSV and its interactions with MrNV in WTD of M. rosenbergii.     

Small molecule biaryl FSH receptor agonists. Part 2: Lead optimization via parallel synthesis

Potent small molecule biaryl diketopiperazine FSH receptor agonists such as 10c (EC(50)=13 nM) and 11f (EC(50)=1.2 nM) were discovered through the design, synthesis and evaluation of three biaryl diketopiperazine optimization libraries with over 300 compounds. These libraries were prepared via solid-phase parallel synthesis using a cyclization-release method.     

Degradation of target protein in living cells by small-molecule proteolysis inducer

Ubiquitin-dependent proteolysis of cellular proteins is one of the major pathways to regulate protein function posttranslationally. Here we demonstrate a potentially general method of degrading any targeted proteins by the ubiquitin-dependent proteolysis in living cells, using small-molecule proteolysis inducer (SMPI).     

Synthesis and evaluation of tacrine-E2020 hybrids as acetylcholinesterase inhibitors for the treatment of Alzheimer's disease

Tacrine-E2020 hybrids and some related compounds were prepared and their bioactivities on the Alzheimer's disease were assayed. The optimum hybrid inhibitor 3 is 37-fold more potent and 31-fold more selective than tacrine in vitro.