1,4-苯醌对人骨髓干细胞增殖能力的影响

目的 探讨1,4-苯醌(1,4-benzoquinone,1,4-BQ)对人骨髓造血干细胞(hBM-HSCs)和人间充质干细胞(hBM-MSCs)增殖能力的影响.方法 人骨髓样本采自健康自愿者.hBM-HSCs培养采用半固体甲基纤维素培养法,用集落形成实验(CFU)评价不同浓度1,4-BQ( 10、25、50、100μmol/L)对人骨髓红细胞集落(CFU-E)/爆发式红细胞集落(BFU-E)、粒细胞-巨噬细胞系集落(CFU-GM)、粒细胞-红细胞-巨噬细胞-巨核细胞集落(CFU-GEMM)形成的影响.hBM-MSCs分离、培养扩增之后,采用噻唑蓝(MTT)实验评价不同浓度1,4-BQ(1、5、10、25、50、100、200、500、1000 μmol/L)对hBM-MSCs增殖能力影响.结果 CFU实验结果显示,25、50、100 μmol/L1,4-BQ染毒组的集落形成数明显低于对照组,差异有统计学意义(P＜0.05).10μmol/L1,4-BQ染毒组集落形成数与对照组的差异无统计学意义(P＞0.05).MTT的结果显示,当1,4-BQ染毒24h,1,4-BQ浓度在50-200 μmol/L时,细胞存活率下降趋势明显,存在剂量-反应关系;当染毒浓度≥200 μmol/L时,细胞存活率小于5％,与对照组的差异有统计学意义(P＜0.05);当染毒浓度≤25 μmol/L时,细胞存活率与对照组的差异无统计学意义(P＞0.05).结论 1,4-BQ能影响hBM-HSCs的集落形成数和hBM-MSCs的相对存活率,1,4-BQ的血液毒性可能与其对hBM-HSCs和hBM-MSCs增殖能力的抑制有关.     

1,4苯醌对K562细胞自噬的影响及机制

[目的]研究1,4苯醌(1,4-BQ)对人慢性髓系白血病K562细胞自噬的影响及其机制。[方法]选择人慢性髓系白血病K562细胞,采用1,4-BQ、自噬早期抑制剂LY294002和自噬晚期抑制剂氯喹(CQ)进行染毒处理,分为对照组、1,4-BQ染毒组(5、10、20μmol/L)、LY294002组(10μmol/L)、CQ组(10μmol/L)、1,4-BQ(20μmol/L)+LY294002(10μmol/L)组和1,4-BQ(20μmol/L)+CQ(10μmol/L)组。应用MTT法检测细胞增殖率;采用CYTO-ID荧光探针并运用荧光染色法和流式细胞术法对细胞自噬水平进行定性、定量检测;采用丫啶橙染色法检测细胞溶酶体pH值;运用实时定量PCR法和Western blot法检测LC3-Ⅱ和P62自噬相关基因和蛋白的表达水平。[结果]10、20μmol/L的1,4-BQ分别作用K562细胞24、48、72 h后,细胞相对增殖率明显降低(P0.05)。CYTO-ID自噬荧光染料特异性聚集在K562细胞胞质内,随着染毒浓度增加荧光强度明显增强。流式细胞术结果显示,与对照组相比,5、10、20μmol/L 1,4-BQ组自噬水平均明显增加,差异具有统计学意义(P0.05)。丫啶橙染色结果显示,不同浓度1,4-BQ组红色荧光强度均高于对照组,即1,4-BQ组溶酶体pH明显降低。Western blot结果显示,当1,4-BQ浓度为10、20μmol/L时,LC3-Ⅱ和P62蛋白表达量明显高于对照组(P0.05),且在染毒24 h时增幅最大。干预自噬后,与1,4-BQ组相比,1,4-BQ+LY294002组的自噬水平和LC3-Ⅱ蛋白表达量均降低(P0.05)。与1,4-BQ组相比,1,4-BQ+CQ组自噬水平增加(P0.05),而与CQ组的差异无统计学意义。此外,与对照组相比,CQ组LC3-Ⅱ蛋白表达明显增加(P0.05)。与1,4-BQ组相比,1,4-BQ+CQ组LC3-Ⅱ蛋白表达水平差异无统计学意义(P0.05)。[结论]1,4-BQ可引起K562细胞LC3-Ⅱ、P62蛋白表达增加,可能是通过增加自噬体的合成和减少自噬体的降解从而增加细胞自噬。     

1,4-苯醌抑制人骨髓间充质干细胞中copine 1、copine 3的表达

目的建立人骨髓间充质干细胞(hBM-MSCs)体外培养系统,检测1,4-苯醌(1,4-BQ)对hBM-MSCs中copine 1、copine 3表达的影响。方法采用密度梯度离心和流式细胞技术分离、鉴定hBM-MSCs;10、25、50μmol/L1,4-BQ染毒24 h后,实时定量PCR技术和蛋白免疫印迹检测hBM-MSCs中copine 1、copine 3 mRAN和蛋白质表达情况。结果 hBM-MSCs稳定表达CD29、CD44,几乎不表达CD34、CD45;实时定量PCR的结果证实,在mRNA水平1,4-BQ染毒剂量在10μmol/L即可引起copine 1表达降低,25μmol/L可引起copine 3表达水平降低。蛋白免疫印迹试验结果证实1,4-BQ为25μmol/L和50μmol/L分别引起copine 1和copine 3表达降低。结论 1,4-BQ可在转录水平和蛋白质水平抑制hBM-MSCs中copine 1和copine 3的表达,本研究结果有助于进一步阐明苯及其代谢物1,4-BQ的血液毒性机制。     

三甲基氯化锡诱导PC12细胞凋亡的机制

目的 在体外条件下,研究三甲基氯化锡(trimethyltin chloride,TMT)对PC12细胞增殖、细胞凋亡及细胞氧化损伤的作用,并探讨TMT对NF-kB表达的影响.方法 (1)不同浓度TMT(0、0.3125、0.6250、1.2500、2.500、5.000、10.000、20.000 μmol/L)处理PC12细胞24、48 h,噻唑蓝(MTT)法测定细胞存活率;(2)1.25、2.50、5.00、10.00 μmol/L TMT分别染毒PC12细胞12、24h后,流式细胞仪检测检测细胞凋亡率;(3)1.25、2.50、5.00、10.00 μmol/L剂量的TMT染毒PC12细胞6h后,测定活性氯(ROS)和谷胱甘肽(GSH)含量的变化;(4)1.25、2.50、5.00、10.00 μmol/L剂量的TMT染毒PC12细胞12h后免疫印迹法(Western blot)检测核蛋白NF-kB的水平.结果 与溶剂对照组比较,染毒24 h,2.5000、5.0000、10.0000、20.0000 μmol/L TMT剂量组细胞存活率明显下降;染毒48 h,1.2500、2.5000、5.0000、10.0000、20.0000 μmol/L剂量组细胞存活率明显下降,差异均有统计学意义(P＜0.05).1.25、2.50、5.00、10.00 μmol/L TMT染毒细胞12h,凋亡率分别为15.30％±0.75％、18.90％±0.61％、22.00％±0.60％、36.50％±0.66％,染毒24 h凋亡率分别为28.60％±0.40％、43.54％±2.00％、65.73％±0.71％、74.67％±0.40％,明显高于对照组[12 h:(12.80％±1.00％)、24 h:(16.83％±0.25％)],差异均有统计学意义(P＜0.05).1.25、2.50、5.00、10.00 μmol/L剂量组的ROS荧光强度值分别为对照组的1.42、1.71、1.78、1.89倍,差异有统计学意义(P＜0.05).2.50、5.00、10.00 μmol/L组GSH含量分别为(0.17±0.0)、(0.20±0.04)、(0.07±0.03)μmol/μg pro,明显低于对照组(0.30±0.01) μmol/L pro,差异有统计学意义(P＜0.05).2.50、5.00、10.00 μmol/L剂量组NF-kB p65表达的蛋白条带灰度值明显高于对照组,差异有统计学意义(P＜0.05).结论 在本实验条件下,TMT对PC12细胞具有明显抑制增殖和诱导凋亡的作用,其作用可能与氧化应激以及NF-kB信号通路的激活有关.     

1,4-苯醌暴露下小鼠骨髓细胞p15基因表达和甲基化状态

目的 探讨1,4-苯醌(1,4-BQ)暴露下,体外原代培养的小鼠骨髓细胞中抑癌基因p15的mRNA表达及启动子区的甲基化状态.方法 体外分离小鼠骨髓细胞,测定0、0.1、1.0、5.0、10.0、20.0、40.0 μmol/L的1,4-BQ对小鼠骨髓细胞活力的影响,最终确定以0、0.1、1.0、10.0 μmol/L的1,4-BQ染毒骨髓细胞24 h;实时荧光定量聚合酶链反应(PCR)检测p15基因mRNA的表达变化;重亚硫酸盐测序法(BSP)检测启动子区域CpG岛的甲基化状态.结果 1,4-BQ对小鼠骨髓细胞具有剂量依赖的毒性作用,其LC50为8.3 μmol/L(95%CI:4.6～10.6 μmol/L).与对照组(100.0%)比较,10.0、20.0、40.0μmol/L 1,4-BQ染毒组小鼠的骨髓细胞生存率(35.9%、35.8%、30.5%)均明显降低,差异有统计学意义(P＜0.01).10.0μmol/L染毒组p15 mRNA表达为对照组的43%,与对照组比较,1.0和10.0 μmol/L染毒组p15基因mRNA表达量明显下降,差异有统计学意义(P＜0.05或P＜0.01).BSP测序结果显示,染毒组和对照组相同,p15基因启动子区域CpG岛上56个甲基化位点仍保持非甲基化状态.结论 1,4-BQ暴露可导致原代培养的小鼠骨髓细胞中p15基因的mRNA表达量下降,但启动子区域CpG岛的甲基化状态未受影响,提示甲基化不参与1,4-BQ介导的p15基因表达下调.

Abstract：

Objective To detect the expression and the CpG island methylation status of tumor suppressor gene p15 after exposure to 1,4-benzoquinone (1,4-BQ) in primary cultivated C57BL/6J mouse bone marrow cells in vitro. Methods The mouse bone marrow cells were isolated in vitro. The effect of 0, 0.1, 1, 5,10, 20, and 40 μmol/L 1,4-BQ on cell viability (CKK-8) was detected. 0, 0.1, 1, 10 μmol/L 1,4-BQ were used to intoxicate the mouse bone marrow cells for 24 h; Real-time PCR was employed to analyze the mRNA expression level of p15; The bisulfite sequencing PCR (BSP) was used to look into the methylation status of CpG islands in p15 promoter region. Results 1,4-BQ exhibited dose-dependent toxicity to mouse bone marrow cells, and the LC50 was 8.3 μmol/L (95% CI: 4.6-10.6 μmol/L). The mRNA expression of p15 in 10 μ mol/L group was only equivalent to 43% of control group. Compared with control group, the decrease of p15 mRNA expression in 1 and l0 μ mol/L concentration were obvious, and the differences had statistical significance(P＜0.05 or P＜0.01 ). BSP sequencing results were same between the exposure groups and control group, the 56 CpG sites on CpG islands remained in the state of unmethylated. Conclusion mRNA expression of p15 gene decreases after exposure to 1,4-BQ, but the CpG islands menthylation status in promoter is not affected, suggesting that methvlation does not participate in 1,4-BQ-mediated p15 gene expression decrease, other effect mechanisms still need to be investigated.     

甲醛对白血病细胞增殖、凋亡影响研究

目的研究甲醛对白血病细胞在细胞增殖和凋亡方面的影响。方法以急性髓系白血病细胞株HL60、K562为研究对象,在不同浓度甲醛环境下培养,噻唑蓝法检测细胞增殖抑制率;荧光倒置显微镜观察细胞凋亡形态学变化,流式细胞仪测细胞的凋亡率。结果 10、15μmol/L甲醛组HL60、K562细胞均略有增殖,从20μmol/L甲醛组开始,细胞转为增殖抑制,且抑制率随甲醛浓度和时间的增加而增加,100 mmol/L甲醛48 h能抑制86.13%的HL60细胞和91.16%的K562细胞增殖。培养24 h后,对照组、10μmol/L甲醛组HL60、K562细胞的胞核呈弥漫均匀蓝色荧光,30μmol/L甲醛组细胞出现少量核固缩、凝集及凋亡小体,而100μmol/L甲醛组则明显增多。10μmol/L甲醛组的细胞凋亡率与对照组比较,差异均无统计学意义(P>0.05);30μmol/L甲醛组细胞的早期凋亡率与对照组、10μmol/L甲醛组比较,差异均无统计学意义(P>0.05),但晚期凋亡率较两者均显著增加(P<0.05);100μmol/L甲醛组细胞不论早期凋亡率还是晚期凋亡率均较其他组显著增高(P<0.05)。结论较低浓度的甲醛可促...     

1,2-二氯乙烷对体外培养SW620细胞增殖和细胞周期及凋亡的影响

目的 探讨1,2-二氯乙烷(1,2-DCE)对体外培养细胞周期、凋亡和增殖能力的影响.方法 不同浓度1,2-DCE染毒0.5或1h,噻唑蓝(MTT)法检测活细胞相对数和相对活力,流式细胞术(FCM)分析细胞周期和凋亡情况.结果 MTT法检测发现,随1,2-DCE染毒剂量的增加和染毒时间的延长,细胞相对存活率逐渐降低.与二甲亚砜(DMSO)组比较,染毒0.5 h,25、75、100、125、150、175、200 μmol/L 1,2-DCE组的细胞相对存活率降低,差异均有统计学意义(P＜0.05或P＜0.01);染毒1h,75、100、125、150、175、200 μmol/L 1,2-DCE组的细胞相对存活率降低,差异均有统计学意义(P＜0.05或P＜0.01);与0.5 h各组比,175μmol/L组染毒1h的细胞相对存活率降低,差异有统计学意义(P＜0.01);增殖曲线经标准化拟合后发现,染毒0.5 h,1,2-DCE的最适IC50为89.41 μmol/L,95％的可信区间为85.23～93.79μmol/L;染毒1h,1,2-DCE的最适IC50为87.68 μmol/L,95％的可信区间为83.71～91.82 μmol/L.FCM法检测发现,与对照组比较,1,2-DCE染毒1h,25、50、100、150、200 μmol/L组的G0/G1期比例降低,25、50、100 μmol/L组的S期比例降低,25、50、100、150、200 μmol/L组的G2/M期比例升高,差异均有统计学意义(P＜0.05或P＜0.01);但各组均不引起细胞凋亡.结论 1,2-DCE能够抑制体外培养SW620细胞增殖,使细胞周期停滞在G2/M期,但不诱导细胞凋亡.     

PCB153对INS-1细胞毒性作用及机制

目的 探讨2,2＇,4,4＇,5,5＇-六氯联苯(PCB153)对体外培养胰岛β细胞株(INS-1)细胞毒性作用及机制.方法 PCB153设3个剂量组(1、3、6μmol/L),二甲基亚砜(DMSO)为溶剂对照组,染毒INS-1细胞24 h后,检测细胞存活率、凋亡、活性氧(ROS)水平、Caspase 3和Caspase 12等凋亡相关基因表达水平.结果 3、6 μmol/L PCB153剂量组细胞存活率分别为(80.9±8.7)％和(42.2±4.3)％,与对照组比较均有下降(P＜0.05);3μmol/L PCB153剂量组ROS为(9.2±0.4)、凋亡率为(30.7±3.4)％,6μmol/L PCB153剂量组ROS为(13.7±1.6)、凋亡率为(40.4±1.3)％,与对照组比较,ROS水平和细胞凋亡率均增加(P＜0.05);与对照组比较,3 μmol/L PCB153剂量组Caspase 3及3、6μmol/L PCB153剂量组Caspase 12基因表达水平均有增加(P＜0.05).结论 PCB153可诱导INS-1细胞凋亡,氧化应激和内质网信号通路可能参与PCB153对INS-1细胞的毒性作用.     

双(对氯苯基)二氯乙烯与β-六氯化苯对大鼠睾丸支持细胞凋亡的影响

目的 探讨双(对氯苯基)二氯乙烯[1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene,p,p'-DDE]、β-六氯化苯(β-benzenehexachloride,β-BHC)及其联合作用对大鼠睾丸支持细胞凋亡半胱氨酸天冬氨酸蛋白酶(Caspase)途径的影响及其作用机制.方法 以不同浓度的p,p'-DDE、β-BHC(分别为10、30、50 μmol/L)及其联合(10 μmol/L p,p'-DDE+10 μmol/L β-BHC,30 μmol/L p,p'-DDE+30 μmol/L β-BHC,50 μmoL/L p,p'-DDE+50 μmol/L β-BHC)处理大鼠睾丸支持细胞24 h,设Caspase-3抑制剂组(先用100 μmol/L Caspase-3抑制剂Ac-DEVD-CHO处理支持细胞2 h,再用50 μmol/L p,p'-DDE+50 μmol/L β-BHC联合处理),采用四甲基偶氮唑蓝比色法测定支持细胞的活性,吖啶橙/溴化乙锭(AO/EB)双重荧光染色测定支持细胞的凋亡率,RT-PCR法检测Caspase-3、Caspase-8及Caspase-9 mRNA表达量的变化.结果 10、30、50、70 μmol/L p,p'-DDE组吸光度(A值)分别为0.498±0.039、0.481±0.065、0.397±0.032和0.286±0.049,相同浓度β-BHC组A值分别为0.518±0.103、0.490±0.060、0.454±0.054和0.302±0.030,10、30、50 μmol/L p,p'-DDE与β-BHC联合组A值分别为0.483±0.048、0.473±0.058和0.337±0.052,50 μmol/L浓度组与对照组比较,A值降低,差异有统计学意义(t值分别为4.599、2.716、6.537,P＜0.05).AO/EB双重荧光染色分析结果显示,10、30、50 μmol/L各染毒组的支持细胞凋亡率明显升高,与溶剂对照组(9.83±0.95)%、Caspase-3抑制剂Ac-DEVD-CHO组(15.60±2.74)%比较,p,p'-DDE处理组分别为(23.73±2.24)%、(30.03±2.84)%和(38.04±4.98)%,β-BHC处理组分别为(24.42±3.53)%、(30.64±1.06)%和(39.88±0.17)%,联合处理组分别为(37.08±1.71)%、(42.18±3.32)%和(41.25±3.36)%.逆转录(RT)-PCR结果表明,Caspase-3、Cagpase-8及Caspase-9 mRNA表达量随着p,p'-DDE、β-BHC及其联合浓度的增加而增加.结论 p,p'-DDE、β-BHC及其联合作用可通过激活启动Caspase-8和Caspage-9,进而激活下游效应Caspase-3引起支持细胞凋亡.     

氟化钠对人成骨肉瘤MG-63细胞增殖的影响

目的 探讨氟化钠(NaF)对人成骨肉瘤MG-63细胞增殖的影响.方法 以0、10-2、10-1、1、10、102、5×102、103、5×103、104、2×104、4×104 μmol/L NaF染毒MG-63细胞,培养48 h.采用MTI实验观察NaF对MG-63细胞增殖能力的影响,以流式细胞技术检测MG-63细胞周期变化.结果 MTr实验结果显示,MG-63细胞开始有增殖活性时的NaF浓度为102 μmol/L,增殖活性最大时的浓度为5×103 μmol/L,增殖活性受到抑制时的浓度为2×104 μmol/L.流式细胞技术检测结果显示,采用MTT实验中确定的3个关键浓度染毒细胞48 h后,高剂量(2×104 μmol/L)组的MG-63细胞凋亡率最高(6.001％),细胞增殖指数(PI)最低(0.339);中剂量(5×103μmol/L)组的细胞凋亡率最低(2.220％),PI最高(0.632);低剂量(102 μmol/L)组的PI及细胞凋亡率均与对照组无明显差异.结论 NaF对成骨细胞具有双向作用,低浓度下促进细胞增殖,超过一定浓度后因其增殖抑制而使细胞凋亡增加.     

Calcium intake in the elderly: validation of a dietary questionnaire

Epidemiological studies of calcium and osteoporosis have been hampered by the lack of a suitable tool for assessing calcium intake. This report describes a new frequency and amount questionnaire for measuring present and past calcium intake in the elderly. The validity of the questionnaire was tested against two commonly used standards of dietary assessment, five-day duplicate diets and seven-day weighed dietary inventories. The resulting correlation coefficients were, respectively, r = 0.76 and r = 0.69, while that for repeatability was r = 0.84. Furthermore, the questionnaire categorized subjects into thirds of the distribution of intake with almost no gross misclassification. It is suggested that the present findings may be extended to the majority of normal, healthy elderly subjects, implying wide application for the questionnaire in the assessment of calcium intake in the elderly.     

Self-reported health problems among Swedish miners one year after unemployment

Unemployment is considered to be a public health concern sincedeterioration in the health of the unemployed is often anticipated.However, for some groups, such as miners, unemployment mightimprove health due to a cessation of potentially harmful occupationalexposures. This study evaluates the health of 79 miners in oneSwedish iron-ore mine, and 226 age-matched controls from thegeneral population, during one year after the closure of themine. The participants received a questionnaire regarding medicalhistory and subjective symptoms at the beginning of the studyperiod, and after one year. Statistically significant negativeeffects on self-reported health attributable to unemploymentwere not found, although neuropsychiatric symptoms were morecommon among the unemployed miners. The miners reported a statisticallysignificant improvement in grip force (p=0.031). They had asignificantly higher prevalence of symptoms associated withmining related exposures when compared with the population controls;pain in the upper extremities [relative risk (RR)=2.27, 95%confidence interval (Cl)=1.44–3.59), back pain (RR=1.84;Cl=1.237–2.75), vasospastic disease of the fingers (RR=2.05;Cl=1.18–3.57) and obstructive respiratory symptoms (attacksof dyspnea and wheezing: RR=3.67; Cl=1.167–11.6).     

Excès de cas humains et animaux de tularémie en France au cours de l’hiver 2007–2008 : émergence ou phénomène isolé ?

Context

Tularemia is a zoonosis affecting humans and hares in France. We describe the results of surveillance in both species, in 2007 and 2008.

Methods

Human tularemia cases are mandatorily notifiable in France since 2003. In hares, surveillance relies on volunteer hunter associations in all districts of the country. Data from mandatory reports and volunteer surveillance in 2007/2008 were analyzed and compared with previous results.

Results

In 2007/2008, 144 cases were reported in humans and 117 cases in hares. This was a 100% increase compared to previous years. Human cases differed from those of previous years only by the frequency of contact with breeding animals. Human cases without any documented risk exposure were also more frequent.

Conclusion

An increase of tularemia cases occurred in 2007/2008 in both species. Complementary studies are needed to identify the species reservoir in France to understand the causes of this peak of cases.     

Occupational health hazards in mining: an overview

This review article outlines the physical, chemical, biological, ergonomic and psychosocial occupational health hazards of mining and associated metallurgical processes. Mining remains an important industrial sector in many parts of the world and although substantial progress has been made in the control of occupational health hazards, there remains room for further risk reduction. This applies particularly to traumatic injury hazards, ergonomic hazards and noise. Vigilance is also required to ensure exposures to coal dust and crystalline silica remain effectively controlled.     

Manufacture and use of nanomaterials: current status in the UK and global trends

This paper provides an overview of the production and use of nanomaterials (NMs), particularly in the UK. Currently, relatively few companies in the UK are identifiable as NM manufacturers, the main emphasis being the bulk markets in metals and metal oxides, and some niche markets such as carbon nanotubes and quantum dots. NM manufacturing in the UK does not reflect the global emphasis on fullerenes, nanotubes and fibres. Some assumptions have been made about the types of NM that are likely to be imported into the UK, which currently include fullerenes, modified fullerenes and other carbon-based NMs including nanotubes. Many university departments, spin-offs and private companies have developed processes for the manufacture of NMs but may only be producing small quantities for research and development (R&D) purposes. However, some have the potential to scale up to produce large quantities. The nanotechnology industry in the UK has strong R&D backup from universities and related institutions. This review has covered R&D trends at such institutions, and appropriate information has been added to a searchable database. While several companies are including NMs in their products, only a few (e.g. manufacturers of paints, coatings, cosmetics, catalysts, polymer composites) are using nanoparticles (NPs) in any significant quantities. However, this situation is likely to change rapidly. There is a need to collect more information about exposure to NPs in both manufacturing and user scenarios. As the market grows, and as manufacturers switch from the micro- to the nanoscale, the potential for exposure will increase. More research is required to quantify any risks to workers and consumers.     

深圳公立医院管理体制改革制度设计

深圳公立医院管理体制改革实行政事分开、管办分开,在理事会架构下按法定机构模式组建市医管中心,落实公立医院运营管理自主权.作者从当前公立医院管理体制的弊端入手,介绍了深圳市进行公立医院管理体制改革的基本思路及改革方案设计的主要举措,深入剖析了的改革方案的特点,并对改革效果进行了预测.     

Effects of nitrogen dioxide on red blood cells of rats: Changes in components of red cell membranes during in vivo exposure to NO2

Red cell membranes, prepared from red blood cells of rats exposed to 4, 10, or 20 ppm nitrogen dioxide (NO₂) for 1 to 10 days, were examined for evidence of changes in membrane components. Appreciable changes were not found in contents of phospholipid and cholesterol during exposure to 10 ppm NO₂. By contrast, protein content altered with the time of exposure. Moreover, changes in protein composition were observed by employing sodium dodecyl sulfate — polyacrylamide gel electrophoresis. Twenty-four-hour exposure to NO₂ at the concentration above 10 ppm resulted in a marked increase in the percentage of lysophosphatidylethanolamine (LysoPE) to the total phospholipids. The prolonged exposure to 10 ppm NO₂ gave rise to a further increase in LysoPE, whereas the percentage of phosphatidylethanolamine (PE) showed a gradual decrease. A 1-day exposure to 4.0 ppm NO₂ also caused an increase in sialic acid content and decreases in those of PE and hexose. In addition to contents of these components the percentage of LysoPE increased 5 days after exposure and the elevated values were maintained up to the end of exposure period. These results demonstrate that red blood cells in circulation exhibit different membrane properties in terms of lipid and carbohydrate composition during 10 days of exposure to 4.0 ppm NO₂.     

Investigating clusters in the workplace and beyond

Clusters of disease are common and occur in the workplace and in the general community. They often arouse considerable concern among the population. Investigations have sometimes lead to exciting new knowledge, but in general the investigation of clusters is difficult and often unrewarding, especially for community clusters. In the workplace, investigations are more likely to find associations and even new causes, but still many clusters remain enigmatic. Despite this, there are many reasons for investigating clusters, including allaying community concern and identifying uncontrolled exposures. A structure for investigating clusters in the workplace is suggested.