Metabolic network simulation using logical loop algorithm and Jacobian matrix

A novel method to accomplish efficient numerical simulation of metabolic networks for flux analysis was developed. The only inputs required are the set of stoichiometric balances and the atom mapping matrices of all components of the reaction network. The latter are used to automatically calculate isotopomer mapping matrices. Using the symbolic toolbox of MATLAB the analytical solution of the stoichiometric balance equation system, isotopomer balances and the analytical Jacobian matrix of the total set of stoichiometric and isotopomer balances are created automatically. The number of variables in the isotopomer distribution equation system is significantly reduced applying modified isotopomer mapping matrices. These allow lumping of several consecutive isotopomer reactions into a single one. The solution of the complete system of equations is improved by implementing an iterative logical loop algorithm and using the analytical Jacobian matrix. This new method provided quick and robust convergence to the root of such equation systems in all cases tested. The method was applied to a network of lysine producing Corynebacterium glutamicum. The resulting equation system with the dimension of 546 x 546 was directly derived from 12 isotopomer balance equations. The results obtained yielded identical labeling patterns for metabolites as compared to the relaxation method.     

Ontogenic profile of some antioxidants and lipid peroxidation in human placental and fetal tissues

Reactive oxygen species (ROS) pose a serious threat to maternal and fetal health during pregnancy. However, there is little information on the oxidative damage caused by ROS and its protection during prenatal life. The present study highlights the status of various antioxidants in human placental and fetal tissues at different phases of gestation. The activity profile of scavenging enzymes, superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase as well as the concentrations of non-enzymatic antioxidants, ascorbic acid, -tocopherol, bilirubin and glutathione have been determined in human placental whole homogenate, placental brush border membrane and fetal liver over gestational periods ranging from 6 weeks of pregnancy till birth. The ontogenic profile of lipid peroxidation, a marker of oxidative damage has also been investigated in the feto-placental system. Catalase, superoxide dismutase and glutathione reductase activities increased significantly, but glutathione peroxidase activity remained almost the same throughout development. Except - tocopherol and bilirubin, the concentrations of other non-enzymic scavengers followed a significant increasing trend with advancement of pregnancy. Results indicate that there is gradual suppression of lipoperoxide formation with the progress of gestation to protect the fetus against oxygen toxicity.     

Ascorbic acid induced degradation of beta-glucan: Hydroxyl radicals as intermediates studied by spin trapping and electron spin resonance spectroscopy

The formation of hydroxyl radicals in beta-glucan solutions treated with ascorbic acid and iron(II) was demonstrated by ESR spin trapping based methods. Two different spin traps were tested, namely DMPO which is commonly used to detect hydroxyl radicals, and POBN often used to detect carbon centered radicals. The experiments performed showed that the presence of iron(II) with DMPO led to low DMPO-OH adduct stability and further to DMPO dimerization. The level of hydroxyl radicals formed during the beta-glucan radical mediated degradation was evaluated using two ESR spin trapping methods based on the use POBN together with either 2% (v/v) EtOH or DMSO. The addition of ascorbic acid together with iron(II) in beta-glucan solution led to an immediate maximal production of hydroxyl radicals while the presence of ascorbic acid alone led to a progressive production of radical. Further hydroxyl radicals were found to be formed when iron(II) was added alone in beta-glucan solutions. The viscosity loss observed in the three last mentioned beta-glucan solutions were found to relate with the formation of hydroxyl radicals. These data confirm the involvement of hydroxyl radical in the beta-glucan degradation.     

Myosin Ia is required for CFTR brush border membrane trafficking and ion transport in the mouse small intestine

In enterocytes of the small intestine, endocytic trafficking of CFTR channels from the brush border membrane (BBM) to the subapical endosomes requires the minus-end motor, myosin VI (Myo6). The subapical localization of Myo6 is dependent on myosin Ia (Myo1a) the major plus-end motor associated with the BBM, suggestive of functional synergy between these two motors. In villus enterocytes of the Myo1a KO mouse small intestine, CFTR accumulated in syntaxin-3 positive subapical endosomes, redistributed to the basolateral domain and was absent from the BBM. In colon, where villi are absent and Myo1a expression is low, CFTR exhibited normal localization to the BBM in the Myo1a KO similar to WT. cAMP-stimulated CFTR anion transport in the small intestine was reduced by 58% in the KO, while anion transport in the colon was comparable to WT. Co-immunoprecipitation confirmed the association of CFTR with Myo1a. These data indicate that Myo1a is an important regulator of CFTR traffic and anion transport in the BBM of villus enterocytes and suggest that Myo1a may power apical CFTR movement into the BBM from subapical endosomes. Alternatively, it may anchor CFTR channels in the BBM of villus enterocytes as was proposed for Myo1a's role in BBM localization of sucrase-isomaltase.     

特发性右心室流出道室性心律失常射频消融术后复发因素分析

目的:探讨特发性右心室流出道室性心律失常射频消融术后,患者室性心律失常复发的原因,旨在为进一步降低复发率提供线索。方法:1999年12月至2009年12月,在解放军总医院老年心血管内科住院行导管射频消融的特发性右心室流出道室性心律失常患者共145例(男55例,女90例),治疗终点为室性心律失常消失,不能被心室电刺激和静滴盐酸异丙肾上腺素诱发,术后1天复查动态心电图并电话随访观察疗效。结果:在145例患者中,即刻成功136例,成功率为93.8%。随访23.8±6.7月,共有9例患者复发,复发率为6.62%。9例复发患者再次行射频消融术的靶点局部激动(34.0±7.6 ms)明显早于第一次射频消融术(30.4±8.5 ms)(P<0.05);靶点起搏与自发心律失常体表心电图QRS波形的符合数(11.8±0.45)大于第一次射频消融术(11.1±0.78)(P<0.05);复发患者第一次手术在最早激动点处单极标测r波的出现比例大于第二次手术(P<0.05),再次手术均成功。结论:导管射频消融治疗特发性右心室流出道室性心律失常是有效、可行的方法。靶点标测欠精确是术后复发的主要原因。     

曲美他嗪对肺动脉栓塞所致右心衰竭的保护作用

目的：评价曲美他嗪（TrimetazidineTMZ）对肺动脉栓塞所致右心衰竭的保护作用,及其对MMP-2,MMP-9和TIMP-1mRNA在右心室中表达的影响。方法：雄性wistar大鼠随机分为三组：右心衰竭组（RHF）左侧股静脉注射1％玻球微粒3mV100g;等量生理盐水注射为对照组（CON）;曲美他嗪治疗组（TMZ）为肺动脉栓塞后给TMZl0mg／kg／天。6周后各组大鼠首先进行经胸超声评价右心功能后取材进行病理学检测,以及RT—PCR检测右心室MMP-2,MMP-9,TIMP-1mRNA表达水平。结果：RHF组大鼠超声检测发现右心室内径扩大并伴有三尖瓣反流,三尖瓣环收缩期峰值位移下降（TAPSE）;Masson染色显示右心室纤维化增加;RTPCR结果显示MMP-2,MMP-9和TIMP-1mRNA表达水平明显升高;经TMZ治疗组大鼠右心室内径减小,TAPSE增加,而MMP-2,MMP-9和TIMP-1mRNA表达水平下降。结论：曲美他嗪能够抑制右心室纤维化,改善右心功能,可能与调节MMP-2,MMP-9和TIMP-1表达水平有关。     

Alterations in brush border membrane enzymes,carbohydrate metabolism and oxidative damage to rat intestine by potassium bromate

The acute toxicity of potassium bromate (KBrO₃) on rat small intestine was studied in this work. Animals were given a single oral dose of KBrO₃ (100 mg/kg body weight) and sacrificed 12, 24, 48, 96 and 168 h after the treatment; control animals were not given KBrO₃. The administration of KBrO₃ resulted in a reversible decline in the specific activities of several BBM enzymes. Lipid peroxidation, protein oxidation and hydrogen peroxide levels increased while total sulfhydryl groups and reduced glutathione decreased in KBrO₃-treated rats indicating induction of oxidative stress in the intestinal mucosa. The activities of anti-oxidant and carbohydrate metabolic enzymes were also altered upon KBrO₃ treatment. The maximum changes in all the parameters were 48 h after administration of KBrO₃ after which recovery took place, in many cases almost to control values after 168 h. Histopathological studies supported the biochemical findings showing extensive damage to the intestine at 48 h and recovery at 168 h. These results show that a single oral dose of KBrO₃ causes reversible oxidative damage to the intestine.     

S-allyl cysteine in combination with clotrimazole downregulates Fas induced apoptotic events in erythrocytes of mice exposed to lead

Background

Chronic lead (Pb^2 +) exposure leads to the reduced lifespan of erythrocytes. Oxidative stress and K⁺ loss accelerate Fas translocation into lipid raft microdomains inducing Fas mediated death signaling in these erythrocytes. Pathophysiological-based therapeutic strategies to combat against erythrocyte death were evaluated using garlic-derived organosulfur compounds like diallyl disulfide (DADS), S allyl cysteine (SAC) and imidazole based Gardos channel inhibitor clotrimazole (CLT).

Methods

Morphological alterations in erythrocytes were evaluated using scanning electron microscopy. Events associated with erythrocyte death were evaluated using radio labeled probes, flow cytometry and activity gel assay. Mass spectrometry was used for detection of GSH-4-hydroxy-trans-2-nonenal (HNE) adducts. Fas redistribution into the lipid rafts was studied using immunoblotting technique and confocal microscopy.

Results

Combination of SAC and CLT was better than DADS and CLT combination and monotherapy with these agents in prolonging the survival of erythrocytes during chronic Pb^2 + exposure. Combination therapy with SAC and CLT prevented redistribution of Fas into the lipid rafts of the plasma membrane and downregulated Fas-dependent death events in erythrocytes of mice exposed to Pb^2 +.

Conclusion and general significance

Ceramide generation was a critical component of Fas receptor-induced apoptosis, since inhibition of acid sphingomyelinase (aSMase) interfered with Fas-induced apoptosis during Pb^2 + exposure. Combination therapy with SAC and CLT downregulated apoptotic events in erythrocytes by antagonizing oxidative stress and Gardos channel that led to suppression of ceramide-initiated Fas aggregation in lipid rafts. Hence, combination therapy with SAC and CLT may be a potential therapeutic option for enhancing the lifespan of erythrocytes during Pb^2 + toxicity.     

经胸超声胸骨右缘切面对Stanford A型主动脉夹层诊断价值的研究

目的:通过经胸超声心动图获取胸骨右缘升主动脉长短轴切面观察Stanford A型主动脉夹层患者的升主动脉结构,探讨对该类患者进行检查时该切面的应用价值。方法:31例经CTA或手术证实为A型主动脉夹层的连续性患者,超声心动图检查除常规通过胸骨左缘切面观察升主动脉结构外,均做胸骨右缘切面以进一步观察升主动脉结构,包括最大内径,有无撕脱内膜及内膜活动情况,同时应用常规胸骨左缘切面和胸骨右缘切面对A型主动脉夹层能够清晰显示出的病例比例加以比较。结果:胸骨左缘切面能够清晰显示升主动脉结构9例,占比例29%。胸骨右缘切面能够清晰显示升主动脉结构20例,比例65%。将两种切面结合能够清晰显示升主动脉结构的比例升高到74%。胸骨右缘肋间切面测得的升主动脉最大径线数值与CTA结果的一致性更好。结论:胸骨右缘肋间切面对A型主动脉夹层显示的清晰度更好,有助于临床诊断,具有重要的参考价值,值得临床广泛推广。