高原低氧对机体无氧代谢阈值的影响

为了探讨高原低氧对机体无氧代谢阈值(AT)的影响,本研究采用Wasserman无创性方法,分别测定了11名新兵在平原(四川淮口,海拔500m)和经空运进驻高原 (西藏错那,海拔4370m)后的第3、5、7和14天的AT。结果表明:新兵进驻高原后AT由平原的813.6±147.4kg·m/min降低到395.5±194.5 kg·m/min(P<0.01);高原低氧引起AT的降低幅度与受试者平原AT的高低呈正相关(r=0.933,P<0.01);进驻高原后第3、5、7天AT维持在较低水平,随后呈上升趋势。但移居高原1年战士的AT仍低于平原水平(P<0.05)。提示,高原低氧能够显著地降低机体的AT,并且AT越高的个体进驻高原后受低氧环境的影响程度越大。     

Superoxide anion scavenging activity of graft chitosan derivatives

Two kinds of graft chitosan derivatives (CMCTS-g-MAS and HPCTS-g-MAS) were prepared by the graft copolymerization of maleic acid sodium onto etherified chitosans-carboxymethyl chitosan (CMCTS) and hydroxypropyl chitosan (HPCTS), respectively. Superoxide anion scavenging activity of the derivatives was evaluated in a luminal-enhanced autoxidaton of pyrogallol by chemiluminescence techniques. Compared with chitosan, the graft chitosan derivatives have much improved scavenging ability against superoxide anion. They have similar 50% inhibition concentrations (IC₅₀s) as ascorbic acid and superoxide dismutase (SOD). Graft chitosan derivatives with hydroxypropyl groups have relatively higher superoxide anion scavenging ability owing to the incorporation of hydroxyl groups. The graft chitosan derivatives (HPCTS-g-MAS 1, 2, and 3) with different grafting percentages exhibit IC₅₀s values ranging from 243 to 308 μg/mL, which could be related to the contents of active hydroxyl and amino groups in the polymer chains.     

蜈龙抗癌颗粒对小鼠移植性肿瘤的治疗实验

目的　观察新药“蜈龙抗癌颗粒”对四种小鼠移植性肿瘤的治疗效果 ,初步探讨该制剂对小鼠的毒副作用。方法　在小鼠急性毒性试验的基础上 ,选择三个剂量对小鼠移植性肿瘤Lewis肺癌、P388白血病、S1 80 肉瘤和H2 2 肝癌进行治疗实验 ,同时检查一批治疗Lewis肺癌实验小鼠的 15项血液学指标和脾脏、胸腺的相对重量。结果与结论　“蜈龙抗癌颗粒”在生药剂量为每日每公斤体重 10、2 5、4 0g(Lewis肺癌、P388白血病 )和每日每公斤体重 15、30、5 0g(S1 80 肉瘤和H2 2 肝癌 )时 ,对小鼠移植性肿瘤有肯定的治疗效果 ,并呈良好的量效关系 ,对小鼠Lewis肺癌的治疗效果最明显。该制剂大剂量时可能对小鼠的造血系统和免疫系统有明显影响。     

褪黑素抑制小鼠卵母细胞的体外成熟

目的:探讨褪黑素(MT)对小鼠卵母细胞的体外成熟的影响.方法:通过卵母细胞自发、次黄嘌呤(HX)阻滞和激素诱导成熟三种体外培养模型研究了褪黑素(MT)对小鼠卵母细胞体外成熟的影响.结果:①0.1 g/L、0.02g/L、0.004 g/L及0.0008 g/L浓度的MT均能显著抑制小鼠卵丘卵母细胞复合体(CEOs)自发成熟过程中第一极体(PB1)的释放(P＜0.01);②动力曲线分析表明,MT对自发成熟的CEOs的GVBD和PB1有显著的推后作用,与对照组相比,处理组的GVBD和PB1分别被推后8～10 h和3～4 h;③0.1 g/L和0.02 g/L两有效浓度的MT还能显著抑制促性腺激素(FSH)诱导的HX阻滞的CEOsGVBD的发生(P＜0.05),对PB1的排出虽有一定的抑制作用,但没有统计学意义;④MT和次黄嘌呤(HX)对CEOs的自发成熟有协同抑制作用(P＜0.01),但在裸卵(DO)自发成熟的阻滞中没有协同效应.结论:MT是调节哺乳动物卵母细胞成熟的重要激素之一,其作用机制可能是通过卵丘细胞实现的.     

Antioxidant effects of American ginseng berry extract in cardiomyocytes exposed to acute oxidant stress

It is postulated that antioxidant properties of American ginseng root mediate its cardioprotective actions. The antioxidant capabilities of the American ginseng root have been demonstrated previously, however, the berry of the American ginseng has not yet been evaluated. In this study, we tested the American ginseng berry extract (AGBE) for its antioxidant effects in cell-free chemical systems using H(2)O(2)/FeSO(4) to generate hydroxyl radicals which were measured by a fluorescent probe, 2', 7'-dichlorofluorescin diacetate (DCFH/DA). Xanthine/xanthine oxidase was used to generate superoxide anion, which was measured by a fluorescent probe dihydroethidium (DHE). We found that AGBE decreased fluorescence significantly, suggesting that AGBE scavenges oxygen free radicals. We further tested whether AGBE (0.1-1 mg/ml) can protect cardiomyocytes from oxidative injury induced by exogenous or endogenous oxidants. Cells were exposed to either H(2)O(2) or antimycin A (a mitochondrial electron transport chain site III inhibitor that augments mitochondrial oxidant production). The resulting oxidant stress was measured using DCFH/DA and the cell death was assessed using propidium iodide staining. Pretreatment with AGBE (1 mg/ml) significantly attenuated DCF fluorescence by 49% or 85% and reduced cell death by 59% or 63% in cells exposed to H(2)O(2) or antimycin A, respectively. When the effects of extracts from berry and root of American ginseng were compared in cardiomyocytes exposed to antimycin A, we observed that AGBE conferred greater antioxidant protection at the same dose. We conclude that AGBE is a potent antioxidant that protects cardiomyocytes against oxidant-mediated injury and this protection is partly mediated by its free radical scavenging properties.     

Characterization of the 3a protein of SARS-associated coronavirus in infected vero E6 cells and SARS patients

Proteomics was used to identify a protein encoded by ORF 3a in a SARS-associated coronavirus (SARS-CoV). Immuno-blotting revealed that interchain disulfide bonds might be formed between this protein and the spike protein. ELISA indicated that sera from SARS patients have significant positive reactions with synthesized peptides derived from the 3a protein. These results are concordant with that of a spike protein-derived peptide. A tendency exists for co-mutation between the 3a protein and the spike protein of SARS-CoV isolates, suggesting that the function of the 3a protein correlates with the spike protein. Taken together, the 3a protein might be tightly correlated to the spike protein in the SARS-CoV functions. The 3a protein may serve as a new clinical marker or drug target for SARS treatment.     

Current concepts on Escherichia coli K1 translocation of the blood-brain barrier

The mortality and morbidity associated with neonatal gram-negative meningitis have remained significant despite advances in antimicrobial chemotherapy. Escherichia coli K1 is the most common gram-negative organism causing neonatal meningitis. Our incomplete knowledge of the pathogenesis of this disease is one of the main reasons for this high mortality and morbidity. We have previously established both in vitro and in vivo models of the blood-brain barrier (BBB) using human brain microvascular endothelial cells (HBMEC) and hematogenous meningitis in neonatal rats, respectively. With these in vitro and in vivo models, we have shown that successful crossing of the BBB by circulating E. coli requires a high-degree of bacteremia, E. coli binding to and invasion of HBMEC, and E. coli traversal of the BBB as live bacteria. Our previous studies using TnphoA, signature-tagged mutagenesis and differential fluorescence induction identified several E. coli K1 determinants such as OmpA, Ibe proteins, AslA, TraJ and CNF1 contributing to invasion of HBMEC in vitro and traversal of the blood-brain barrier in vivo. We have shown that some of these determinants interact with specific receptors on HBMEC, suggesting E. coli translocation of the BBB is the result of specific pathogen-host cell interactions. Recent studies using functional genomics techniques have identified additional E. coli K1 factors that contribute to the high degree of bacteremia and HBMEC binding/invasion/transcytosis. In this review, we summarize the current knowledge on the mechanisms underlying the successful E. coli translocation of the BBB.     

Comparison of hybridization behavior between double and single strands of targets and the application of asymmetric PCR targets in cDNA microarray

Double stranded targets on the cDNA microarray contain representatives of both the coding and noncoding strands, which will introduce hybridization competition with probes. Here, the effect of double and single strands of targets on the signal intensity and the ratios of Cy5/Cy3 within the same slide were compared. The results show that single stranded targets can increase the hybridization efficiency without changing the Cy5/Cy3 ratio. Based on these results, a new strategy was established by generating cDNA targets with asymmetric PCR, instead of conventional PCR, to increase the sensitivity of the cDNA microarray. Furthermore, the feasibility of this approach was validated. The results indicate that the cDNA microarray system based on asymmetric PCR is more sensitive, with no decrease in the reliability and reproducibility as compared with that based on conventional symmetric PCR.     

Increased levels of Wee-1 kinase in G(2) are necessary for Vpr- and gamma irradiation-induced G(2) arrest

Human immunodeficiency virus type 1 (HIV-1) Vpr induces cell cycle arrest at the G(2)/M transition and subsequently apoptosis. Here we examined the potential involvement of Wee-1 in Vpr-induced G(2) arrest. Wee-1 is a cellular protein kinase that inhibits Cdc2 activity, thereby preventing cells from proceeding through mitosis. We previously showed that the levels of Wee-1 correlate with Vpr-mediated apoptosis. Here, we demonstrate that Vpr-induced G(2) arrest correlated with delayed degradation of Wee-1 at G(2)/M. Experimental depletion of Wee-1 by a small interfering RNA directed to wee-1 mRNA alleviated Vpr-induced G(2) arrest and allowed apparently normal progression through M into G(1). Similar results were observed when cells were arrested at G(2) following gamma irradiation. Thus, Wee-1 is integrally involved as a key cellular regulatory protein in the signal transduction pathway for HIV-1 Vpr-induced cell cycle arrest.