恒定磁场出生前暴露对仔鼠生长发育的影响

目的:探讨不同强度恒定磁场出生前暴露对仔鼠生后生长发育的影响。方法:将30只孕鼠自怀孕第0天始分别置于不同强度的恒定磁场(0.04T;0.08T;0.12T)中饲养,10只孕鼠作为对照。孕鼠让其自然分娩。仔鼠生后第2、3、8、20、22天分别开始观察和记录耳廓张开、平面翻正、张眼、睾丸下降、阴唇张开的时间。结果:耳廓张开及睁眼的时间在0.12T组分别为4.42±0.48天及14.19±0.94天,较对照组耳廓张开时间4.01±0.47天和睁眼时间13.21±0.79天相比差异有统计学意义,与其他强度磁场组相比无显著性差异.平面翻正、阴唇张开及睾丸下降出现时间在各组间相比差异无统计学意义。结论:恒定磁场出生前暴露可能对仔鼠的生长发育起到一定的影响,这种影响可能与磁场强度具有相关性。随着磁场强度的增加各个器官生长发育的时间相对延长。     

Podocin蛋白对肾小球足细胞的影响

目的：探讨肾小球足细胞裂隙膜蛋白podocin对足细胞形态及蛋白尿的影响.方法：32只体重160g～220g的雄性SD大鼠按阿霉素给药剂量随机分成小剂量组（3.0mg/Kg）、肾病剂量组（7.5mg/Kg）、超剂量组（10.0mg/Kg）、正常对照组.于给药第三周末处死大鼠,用氯化苄乙氧铵比浊法检测大鼠24h尿蛋白量,用免疫胶体金电镜检测大鼠肾小球蛋白podocin的表达和足细胞形态.结果：阿霉素组大鼠24h尿蛋白排泄量明显高于正常对照组,尤以肾病组最明显（P＜0.05）;正常对照组大鼠podocin分布在靠近肾小球基底膜（GBM）的足突基底部,主要定位于裂隙隔膜的胞质面,部分金颗粒也可发现于GBM稍远的足突细胞表面.肾病组肾小球足突广泛融合,免疫胶体金颗粒几乎见不到;超剂量组和小剂量组podocin分布在靠近肾小球基底膜（GBM）的足突基底部,免疫胶体金颗粒数明显少于正常对照组,有部分足突退缩.结论：（1）podocin表达减少或消失可能是导致肾小球足突细胞融合的关键因素（2）蛋白尿的发生与肾小球足细胞裂隙膜蛋白podocin的减少或缺失有关.     

植物铁吸收、转运和调控的分子机制研究进展

铁是植物正常生命活动所必需的微量矿质元素, 铁离子的吸收、转运和利用是一个复杂的过程, 很多基因参与了这一过程。本文对近10年来发现和分离的参与植物铁吸收、转运及调控的基因研究进展进行了综述。根据最近的研究结果, 提出了植物控制铁吸收的分子调控模式(机理I)。     

Relations between carbon dioxide fluxes and environmental factors of Kobresia humilis meadows and Potentilla fruticosa meadows

Carbon dioxide fluxes of Kobresia humilis and Potentillafruticosa shrub meadows,two typical ecosystems in the Qinghai-Tibet Plateau,were measured by eddy covariance technology and the data collected in August 2003 were employed to analyze the relations between carbon dioxide fluxes and environmental factors of the ecosystems.August is the time when the two ecosystems reach their peak leaf area indexes and stay stable,and also the period when the net carbon absorptions of Kobresia humilis and Potentilla photo flux densities (PPFD),the carbon dioxide-uptake rate of the Kobresia humilis meadow is higher than that of the Potentilla fruticosa shrub meadow;where the PPFD are rates of the two ecosystems declined as air temperature increased,but the carbon dioxide uptake rate of the Kobresia humilis meadow decreased more quickly (-0.086) than that of the Potentilla fruticosa shrub meadow (-0.016).Soil moistures exert influence on the soil respirations and this varies with the vegetation type.The daily carbon dioxide absorptions of the ecosystems increase with increased diurnal temperature differences and higher diurnal temperature differences result in higher carbon dioxide exchanges.There exists a negative correlation between the vegetation albedos and the carbon dioxide fluxes.     

Chemical genetics suggests a critical role for lysyl oxidase in zebrafish notochord morphogenesis

As a result of a chemical genetic screen for modulators of metalloprotease activity, we report that 2-mercaptopyridine-N-oxide induces a conspicuous undulating notochord defect in zebrafish embryos, a phenocopy of the leviathan mutant. The location of the chemically-induced wavy notochord correlated with the timing of application, thus defining a narrow chemical sensitivity window during segmentation stages. Microscopic observations revealed that notochord undulations appeared during the phase of notochord cell vacuolation and notochord elongation. Notochord cells become swollen as well as disorganized, while electron microscopy revealed disrupted organization of collagen fibrils in the surrounding sheath. We demonstrate by assay in zebrafish extracts that 2-mercaptopyridine-N-oxide inhibits lysyl oxidase. Thus, we provide insight into notochord morphogenesis and reveal novel compounds for lysyl oxidase inhibition. Taken together, these data underline the utility of small molecules for elucidating the dynamic mechanisms of early morphogenesis and provide a potential explanation for the recently established role of copper in zebrafish notochord formation.     

Rapid and sensitive liquid chromatography-tandem mass spectrometry method for the quantitation of colchicine in human plasma

A rapid and sensitive method to determine colchicine in human plasma by liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed. Colchicine and the internal standard (I.S.), tegafur, were extracted from the matrix with n-hexane:dichloromethane:isopropanol (300:150:15, v/v/v) and separated by reversed-phase high-performance liquid chromatography (HPLC) using formic acid:10 mM ammonium acetate:methanol (1:49:75, v/v/v) as the mobile phase in a run time of 2.5 min. Detection was carried out by electrospray positive ionization mass spectrometry in the multiple-reaction monitoring (MRM) mode. The assay was linear in the concentration range 0.050-10 ng/ml with intra- and inter-day precision (as relative standard deviation (R.S.D.)) of <2 and <7%, respectively. The method was applied to a pharmacokinetic study of colchicine in healthy volunteers given an oral dose of 2.0 mg.     

Analysis of the hypoxia-activated dinitrobenzamide mustard phosphate pre-prodrug PR-104 and its alcohol metabolite PR-104A in plasma and tissues by liquid chromatography-mass spectrometry

PR-104 is a dinitrobenzamide mustard pre-prodrug that is activated by reduction to a cytotoxic hydroxylamine metabolite in hypoxic tumour cells; it has recently commenced Phase I clinical trial. Here, we report two validated methods for the determination of PR-104 and its alcohol hydrolysis product, PR-104A in plasma and tissues across species. A high pH LC/MS/MS method was optimised for rapid and sensitive analysis of both analytes in rat, dog and human plasma. This assay was linear over the concentration range 0.005-2.5 microg/ml for PR-104 and 0.05-25 microg/ml for PR-104A (0.005-2.5 microg/ml for rat). A second method, using a low pH LC separation, was designed to provide higher chromatographic resolution, facilitating identification of metabolites. Both methods were successfully applied to the plasma pharmacokinetics of PR-104 and PR-104A in rats. In addition, cytotoxic reduced metabolites of PR-104A were identified in human tumour xenografts by the higher chromatographic resolution method.     

High performance liquid chromatography with ultraviolet detection for the determination of SYUIQ-5, a novel telomerase inhibitor for cancer therapy: application to an enzyme kinetic study in rat liver microsomes

A sensitive assay for the determination of SYUIQ-5, a novel telomerase inhibitor and anti-tumor drug, in rat liver microsomes was developed by using high-performance liquid chromatography with ultraviolet detection. SYUIQ-5 was incubated in vitro with liver microsomes from rats pre-treated with control vehicle, beta-naphthofIavone, phenobarbital, 20% ethanol or dexamethasone. The analytes were extracted with diethyl ether and separated a C(18) 5-microm analytical column. Elution was conducted with 30 mM dipotassium hydrogen phosphate (pH 8.0)-methanol-triethylamine (30:70:0.05, v/v/v) at a flow-rate of 1.0 ml/min and the detection of UV absorbance was conducted at 278 nm. Intra-day and inter-day precision and accuracy of the method were within 10%. The mean analytical recoveries of SYUIQ-5 ranged from 78.8 to 95.3%. The linearity of the calibration curve was in the range of 1.0-80.0 microM. The lower limit of quantification (LOQ) was 1.0 microM. Kinetic analysis showed that beta-naphthofIavone and dexamethasone significantly induced SYUIQ-5 metabolism, suggesting that cytochrome P450 1A and 3A are the major contributor to SYUIQ-5 metabolism in rat liver microsomes.     

Development and validation of a LC-MS/MS method for the determination of viaminate in human plasma

A sensitive and specific method for determination of viaminate in human plasma by using high-performance liquid chromatography coupled with electrospray tandem mass spectrometry (LC-MS/MS) was developed in this study. The plasma samples were simply deproteinated, extracted, evaporated, and then reconstituted in 200 microl of methanol prior to analysis. Chromatographic separation was carried out on a Shimadzu VP-ODS column (250 mm x 2.0 mm, 5 microm) with a mobile phase of methanol-water (95:5, v/v) at a flow rate of 0.2 ml/min. Quantification was performed in the negative-ion electrospray ionization mode by selected ion monitoring of the product ions at m/z 164 for viaminate and m/z 109 for testosterone propionate which was used as the internal standard. The corresponding parent ions were m/z 446 and m/z 345. A linear calibration curve was observed within the concentration range of 0.10-200 ng/ml. The lowest limit of quantitation (LLOQ) was 0.1 ng/ml. The extraction-efficiency at three concentrations was 100.7, 93.6, and 99.7%. Practical utility of this new LC-MS/MS method was confirmed in pilot pharmacokinetic studies in humans following oral administration.     

Development and validation of a liquid chromatography-tandem mass spectrometry for the determination of BPR0L075, a novel antimicrotuble agent, in rat plasma: application to a pharmacokinetic study

A rapid and sensitive liquid chromatography-tandem mass spectrometric method (LC-MS/MS) had been developed and validated to determine the concentrations of BPR0L075 in rat plasma. After a simple protein precipitation of plasma samples by acetonitrile, BPR0L075 was analyzed on a C(8) column at a flow rate of 0.5 mL/min. The mobile phase consisted of a mixture of 10 mM ammonium acetate containing 0.1% formic acid and acetonitrile (20:80, v/v). Both BPR0L075 (analyte) and the internal standard (BPR0L092) were determined using electro-spray ionization and the MS data acquisition was via multiple reactions monitoring (MRM) in positive scanning model. The MS/MS ion transitions monitored are m/z 342.2/195.2 and 312.5/165.2 for BPR0L075 and BPR0L092, respectively. The low limit of quantitation was 0.5 ng/mL. Each plasma sample was chromatographed within 5 min. The method was validated with respect to linearity, accuracy, precision, recovery, and stability. A good linear relationship was observed over the concentration range of 0.5-1000 ng/mL (r>0.9994). Absolute recoveries ranged from 63.45 to 68.34% in plasma at the concentrations of 2, 40, 400, and 800 ng/mL. The intra- and inter-day accuracy ranged from 92.04 to 111.80%. Intra- and inter-day relative standard deviations were 1.08-3.29% and 1.96-5.46%, respectively. This developed and validated assay method had been successfully applied to a pharmacokinetic study after intravenous injection of BPR0L075 in rats at a dose of 5mg/kg.