Modeling metal bioaccumulation in the invasive mussels Dreissena polymorpha and Dreissena rostriformis bugensis in the rivers Rhine and Meuse

The metal-specific covalent index and the species-specific size-based filtration rate were integrated into a biokinetic model estimating metal bioaccumulation in mussels from the dissolved phase and phytoplankton. The model was validated for zebra (Dreissena polymorpha) and quagga (Dreissena rostriformis bugensis) mussels in the rivers Rhine and Meuse, the Netherlands. The model performed well in predicting tissue concentrations in different-sized zebra mussels from various sampling sites for (55) Mn, (56) Fe, (59) Co, (60) Ni, (82) Se, (111) Cd, (118) Sn, and (208) Pb (r(2) =0.71-0.99). Performance for (52) Cr, (63) Cu, (66) Zn, (68) Zn, and (112) Cd was moderate (r(2) <0.20). In quagga mussels, approximately 73 to 94% of the variability in concentrations of (82) Se, (111) Cd, (112) Cd, and (208) Pb was explained by the model (r(2) =0.73-0.94), followed by (52) Cr, (55) Mn, (56) Fe, (60) Ni, and (63) Cu (r(2) =0.48-0.61). Additionally, in both zebra and quagga mussels, average modeled concentrations were within approximately one order of magnitude of the measured values. In particular, in zebra mussels, estimations of (60) Ni and (82) Se concentrations were equal to 51 and 76% of the measurements, respectively. Higher deviations were observed for (52) Cr, (59) Co, (55) Mn, (56) Fe, (111) Cd, (63) Cu, and (112) Cd (underestimation), and (66) Zn, (68) Zn, (208) Pb, and (118) Sn (overestimation). For quagga mussels, modeled concentrations of (66) Zn and (68) Zn differed approximately 14% from the measured levels. Differences between predictions and measurements were higher for other metals.     

Biological studies of new organotin(IV) complexes of thioamide ligands

New organotin(IV) complexes with heterocyclic thioamides 2-mercapto-benzothiazole (Hmbzt), 5-chloro-2-mercapto-benzothiazole (Hcmbzt) and 2-mercapto-benzoxazole (Hmbzo) of formulae [(C(6)H(5))(3)Sn(mbzt)] (1), [(C(6)H(5))(3)Sn(cmbzt)] (3) and [(C(6)H(5))(2)Sn(cmbzt)(2)] (4), together with the already known [(C(6)H(5))(3)Sn(mbzo)] (2), [(n-C(4)H(9))(2)Sn(cmbzt)(2)] (5) and [(CH(3))(2)Sn(cmbzt)(2)] (6) were used to study their influence on the peroxidation of oleic acid. The influence of complexes (3)-(6) upon peroxidation of oleic acid showed that the formation of reactive radicals caused the initiation of the chain radical oxidation of the substrate. The influence of complexes (1)-(6) upon the catalytic peroxidation of linoleic acid by the enzyme lipoxygenase (LOX) was also studied and compared to those of cisplatin. Compounds (1)-(6) were finally tested for in vitro cytotoxicity against leiomyosarcoma cells.     

An evaluation of methods for the stratified analysis of clustered binary data in community intervention trials

A simulation study is conducted in a community intervention setting. Several methods of stratified analysis of clustered binary data are compared in terms of empirical significance and empirical power levels. They are the Mantel-Haenszel test statistic (chi(2) (MH)), the adjusted Mantel-Haenszel test statistic of Donald-Donner (chi(2) (DD)), Rao-Scott (chi(2) (RSN) and chi(2) (RSP)), and Zhang-Boos (chi(2) (ZBN) and chi(2) (ZBP)), Wald (chi(2) (W)), robust Wald (chi(2) (RW)), score (chi(2) (S)), robust score (chi(2) (RS)), and the test statistic based on generalized linear mixed model (GLMM) (chi(2) (GLMM)). When rho not equal 0, chi(2) (MH) has inflated type I error, and it should not be used when observations are correlated. The results also warn of the use of chi(2) (RSN) and chi(2) (RW) due to their poor performance in terms of empirical significance level. chi(2) (ZBP) and chi(2) (GLMM) have better empirical significance levels as compared to other statistics; however, chi(2) (ZBP) tends to have lower empirical powers than other statistics when the number of clusters (N) is less than 24. chi(2) (RSP) provides the highest empirical powers when rho > or = 0.1 and N < or = 12. When rho < or = 0.01, we recommend the use of chi(2) (RS) and chi(2) (GLMM) since they have better overall performance in terms of empirical significance levels and empirical power levels.     

Synthesis, antibacterial, antifungal activity and interaction of CT-DNA with a new benzimidazole derived Cu(II) complex

The ligand [C(16)H(10)O(2)N(4)S(2)] L has been synthesized by the condensation reaction of 2-mercaptobenzimidazole and diethyloxalate. The ligand L was allowed to react with bis(ethylenediamine)Cu(II)/Ni(II) complexes to yield [C(20)H(22)N(8)S(2)Cu]Cl(2)1 and [C(20)H(22)N(8)S(2)Ni]Cl(2)2 complexes. The Ni(II) complex was synthesized only to elucidate the structure of the complex. The complexes 1 and 2 were characterized by elemental analyses, IR, NMR, EPR, UV-vis spectroscopy and molar conductance measurements. Both the complexes are ionic in nature and possess square-planar geometry. The binding of the complex 1 to calf thymus DNA was investigated spectrophotometrically. The absorption spectra of complex 1 exhibits a slight red shift with "hyperchromic effect" in presence of CTDNA. Electrochemical analysis and viscosity measurements were also carried out to ascertain the mode of binding. The complex 1 in the absence and in presence of CT DNA in aqueous solution exhibits one quasi-reversible redox wave corresponding to Cu(II)/Cu(I) redox couple at a scan rate of 0.2 V s(-1). The shift in DeltaE(p), E(1/2) and I(pa)/I(pc) values ascertain the interaction of calf thymus DNA with copper(II) complex. There is decrease in viscosity of CTDNA which indicates that the complex 1 binds to CTDNA through a partial intercalative mode. The antibacterial and antifungal studies of the [C(7)H(6)N(2)S], [C(4)H(16)N(4)Cu]Cl(2,) [C(16)H(10)N(4)S(2)O(2)] and [C(20)H(22)N(8)S(2)Cu]Cl(2) were carried out against S. aureus, E. coli and A. niger. All the results reveal that the complex 1 is highly active against the bacterial strains and also inhibits fungal growth.     

A study of photon interaction parameters in some commonly used solvents.

Various parameters of dosimetric interest such as mass attenuation coefficients, effective atomic numbers and electron densities of some commonly used solvents such as acetonitrile (C(4)H(3)N), butanol (C(4)H(9)OH), chlorobenzene (C(6)H(5)Cl), diethylether (C(4)H(10)O), ethanol (C(2)H(5)OH), methanol (CH(3)OH), propanol (C(3)H(7)OH) and water (H(2)O) were computed in the wide energy range of 10 keV-100 GeV. A comparative study of two different methods used to compute effective atomic numbers has been done. It is observed that in the intermediate energy region (0.1-5 MeV), the mass attenuation coefficient values becomes almost the same for all the solvents, and the effective atomic number and electron density show almost constant values, whereas significant variation is observed in both lower (10-100 keV) and higher (5 MeV-100 GeV) energy regions for all the solvents, which may be due to the dominance of different partial interaction processes in different energy regions.     

Azanonaboranes [(RNH(2))B(8)H(11)NHR] as possible new compounds for use in boron neutron capture therapy

The synthesis and biological in vitro and in vivo activities of possible new compounds for Boron Neutron Capture Therapy (BNCT) are reported. The azanonaboranes of the type [(RNH(2))B(8)H(11)NHR] are water-soluble when hydrophilic groups are introduced. The reaction of B(9)H(13)SMe(2) with primary amines yields azanonaboranes. Five compounds with different numbers of hydroxypropyl groups have been isolated: [(HO(CH(2))(3)NH(2))B(8)H(11)NHCH(3)] (4), [(HO(CH(2))(3)NH(2))B(8)H(11)NH(CH(2))(3)OH] (2), [((HO(CH(2))(3))(2)NH)B(8)H(11)NHCH(3)] (6), [((HO(CH(2))(3))(2)NH)B(8)H(11)NH(CH(2))(3)OCH(3)] (11) and [((HO(CH(2))(3))(2)NH)B(8)H(11)NH(CH(2))(3)OH] (8). In vitro experiments as judged by cloning survival tests showed that two of the synthesised compounds are not toxic. The in vivo experiments were carried out with C3H/He mice bearing SCCVII tumours and C57 mice bearing B16 tumours. Compounds 2 and 6 have no particular affinity to any tissue, but are excluded from the brain.     

Homologation of mexiletine alkyl chain and stereoselective blockade of skeletal muscle sodium channels

The optical isomers (-)-(S)- and (+)-(R)-3-(2, 6-dimethylphenoxy)-2-methyl-1-propanamine (Me2), homologues of the antiarrhythmic and antimyotonic drug mexiletine (Mex), were synthesized and assayed as new potential antimyotonic agents. As observed with Mex, Me2 exhibits an enantioselective behaviour. Tests carried out on sodium currents of single muscle fibres of Rana esculenta demonstrated that (-)-(S)- and (+)-(R)-Me2 were less potent than Mex in producing tonic block, but showed a higher use-dependent block. (-)-(S)-Me2 and (-)-(R)-Mex were also used to study the excitability of muscle fibres of myotonic ADR mice, a phenotype of a recessive form of low G(Cl) myotonia. (-)-(S)-Me2 reduced spontaneous discharges and after discharges better than (-)-(R)-Mex in agreement with the use-dependent block of sodium currents.     

New perfluoroalkylated amphiphilic methacrylates bearing sulfinyl group as monomers for biomedical applications: water content and oxygen permeability of their copolymers with DEGMA

Perfluoroalkylated methacrylates 7a-c bearing sulfinyl group within a straight-chain ester group, i.e. CH(2)=C(CH(3))CO(2)CH(2)CH(2)S(O)-CH(2)CH(2)CF(2)(CF(2)CF(2))(n)CF(3) (n=1-3) were prepared by two alternative synthetic sequences from 2-[(polyfluoroalkyl)sulfanyl]ethanols HOCH(2)CH(2)SCH(2)CH(2)CF(2)(CF(2)CF(2))(n)CF(3) (n=1-3) in overall yields of 88-91%. Copolymers of 7a-c with diethylene glycol methacrylate (DEGMA) prepared in bulk under radical conditions display high transparency, increased water content and good oxygen permeability properties, which are advantageous for their application in ophthalmology and as prosthetic materials.     

The efficiency of energy utilization in growing cattle consuming fresh perennial ryegrass (Lolium perenne cv. Melle) or white clover (Trifolium repens cv. Blanca)

1. Twenty Friesian steers (225 kg live weight) were fed on mid- (M) (June-July) and late- (L) (August-September) season crops of either fresh perennial ryegrass (Lolium perenne cv. Melle) (G) or white clover (Trifolium repens cv. Blanca) (C). Each of the forage diets was offered at three restricted planes of nutrition above maintenance to compare the effect of forage species on the efficiency of energy utilization. All diets were harvested daily from swards of regrowth forage of intended equivalent digestibility. 2. Faecal and urine excretions were measured for 7 and 5 d respectively, followed by two consecutive 24 h measurements of methane, carbon dioxide and oxygen exchange in open-circuit respiration chambers. 3. The apparent digestibility of the energy in perennial ryegrass (0.759) was marginally higher (P less than 0.01) than that in white clover (0.748); the mid- and late-season forages were of similar (P greater than 0.05) digestibilities. Metabolizable energy (ME): digestible energy (DE) in diet G (0.837) was significantly (P less than 0.001) different from that in diet C (0.812). The partition of energy losses when expressed as MJ/GJ gross energy intake (GEI) indicated that energy lost as methane was not significantly different (P greater than 0.05) either between forages (G 62.8, C 63.4) or between seasons (M 63.2, L 63.1). Energy excretion in urine was higher for cattle fed on diet C (77.5) compared with diet G (60.5) (P less than 0.001). Heat production was similar (P greater than 0.05) between forages (G 480, C 478), but lower (P less than 0.01) for L (471) compared with M(486). Energy retention (by difference) was lower (P less than 0.001) for diet C (132) than G (156) and for M (138) than L (149) (P less than 0.05). 4. Parallel-line analysis of unscaled ME intake (MEI) in relation to retained energy (RE; MJ/d) indicated that the efficiency of utilization (kt) was similar (P greater than 0.05) between perennial ryegrass (0.42) and white clover (0.46). Linear extrapolation of the values to zero energy retention indicated that maintenance requirements of ME (Em; MJ/d) were 23.3 for diet G and 28.8 for diet C. The extrapolated Em when expressed in relation to a measured fasting heat production (FHP) of 22.8 (MJ/d) resulted in a derived efficiency of utilization of ME for maintenance (km) of 0.97 (G) and 0.79 (C), suggesting an underestimate of Em for diet G.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effect of increasing the dietary (n-3) to (n-6) polyunsaturated fatty acid ratio on murine liver and peritoneal cell fatty acids and eicosanoid formation

An incremental increase in the dietary (n-3):(n-6) polyunsaturated fatty acid (PUFA) ratio from 0 to 1.93 in diets containing 15% fat (wt/wt) decreased the total (n-6) PUFA content of phospholipids of the liver and peritoneal cells (macrophage) in mice from 43.1 and 33.6 mol/100 mol to 16.0 and 12.3 mol/100 mol with a concomitant increase of 27.6 and 16.1 mol/100 mol in (n-3) PUFA, respectively. Consumption of (n-3) PUFA increased hepatic (n-3) PUFA levels without changing total PUFA (46.35 vs. 46.87 mol/100 mol), whereas macrophage PUFA levels were decreased. The synthesis of sulfidopeptide leukotrienes (SP-LT) (LTC4 and LTE4) was progressively reduced by increasing dietary (n-3) PUFA, i.e., there was a reduction of 76% in mice fed a diet containing a (n-3):(n-6) PUFA ratio of 1.93 compared with the control diet. The 5-series SP-LT (LTC5 and LTF5) were produced in all animals consuming (n-3) PUFA and accounted for 62% of all SP-LT synthesized in mice fed the diet containing a 1.93 (n-3):(n-6) PUFA ratio. Synthesis of 6-keto-prostaglandin F1 alpha decreased 81% in mice fed a diet containing a (n-3):(n-6) PUFA ratio of 1.93 whereas prostaglandin E2 synthesis decreased 44% in mice fed diets with (n-3):(n-6) ratios ranging from 0.41 to 1.93.     

Organotin(IV) complexes of 2-pyridineformamide-derived thiosemicarbazones: antimicrobial and cytotoxic effects

Reaction of n-butyltin trichloride [(n-Bu)SnCl(3)] with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me) and N(4)-ethyl (H2Am4Et) derivatives gave [(n-Bu)Sn(2Am4DH)Cl(2)] (1), [(n-Bu)Sn(2Am4Me)Cl(2)] (2), and [(n-Bu)Sn(2Am4Et)Cl(2)] (3). Thiosemicarbazones as well as their tin complexes are active as antimicrobials against the growth of Candida albicans and Salmonella typhimurium and were highly active against malignant glioblastoma. The cytotoxic activity of complexes 1-3 is similar. Among the studied compounds [(n-Bu)Sn(2Am4DH)Cl(2)] (1) was the most active as antiproliferative (cytostatic) agent. Thiosemicarbazones and their tin(IV) complexes proved to be more potent as cytotoxic agents than cisplatin. All the compounds were able to induce apoptosis.     

Optical resolution of (+/-)-all-trans-3-hydroxyretinal by use of high-performance liquid chromatography.

Racemic all-trans-3-hydroxyretinal (3-OH-RAL) (1) was converted by a reaction with (-)-camphanic acid chloride (CpCl) into a diastereomixture of camphanates (2a) and (2b) which was separated by preparative high-performance liquid chromatography (HPLC) to give two esters (2a) and (2b) in pure state, respectively. Saponification of (2a) and (2b) independently afforded optically active (3S)- and (3R)-3-OH-RALs (3a) and (3b), respectively, whose absolute structures were determined by circular dichroism (CD) spectra. Racemic 3-OH-RAL was separated to two peaks by HPLC using chiral column (ChiraSpher, Merck). Cochromatography with authentic specimens (3a) and (3b) showed that the peak with a short retention time corresponded to (3R)-isomer and the other to (3S).     

Lipoprotein(a) levels and apolipoprotein(a) isoforms related to life style risk factors

Lipoprotein(a) [Lp(a)] has been considered to be a predictor of premature coronary heart disease and other cardiovascular diseases. Lp(a) levels are largely genetically determined, but the detailed mechanism of Lp(a) elevation is uncertain. We examined the association between Lp(a) levels and apolipoprotein(a) [apo(a)] phenotypes as well as that of Lp(a) level and other various conditions. The subjects were 280 healthy Japanese (102 males and 178 females) aged 39 to 70 years who were living in a rural community in 1992. We obtained apo(a) phenotypes determined by SDS-PAGE as well as Lp(a) levels and other cardiovascular risk factors. We combined apo(a) phenotypes form 4 groups according to molecular weights (from high apo(a) molecular weight to low: I, II, III and IV). Lp(a) levels were associated with apo(a) phenotype-groups, that is, they were inversely associated with apo(a) molecular weight. Small apo(a) phenotypes were less frequent than large ones. The median Lp(a) level was higher in smoking (29.2 mg/dL) than in non-smoking subjects (18.5 mg/dL) in phenotype-group III. Adjusted means of total cholesterol and fibrinogen levels in apo(a) phenotype-group IV were the highest of all phenotype-groups. Age, apo(a) phenotype, smoking status, total cholesterol and fibrinogen were positively correlated with Lp(a) levels by multiple regression analysis. Lp(a) levels were found to be mainly associated with apo(a) phenotype, but varied broadly within the same apo(a) phenotype at various conditions, such as smoking status and high total cholesterol.     

应用基因重组细胞模型研究苯并[a]芘的细胞毒性和遗传损伤效应

目的 利用经基因重组构建的具有细胞色素P450 1A1(CYP1A1)代谢活性的人支气管上皮细胞(16HBE)为体外模型,研究苯并[a]芘[B(a)P]的细胞毒性和遗传效应改变.方法 应用实时定量PCR方法检测细胞的CYP1A1和微粒体环氧化物水解酶(mEH)的mRNA水平.细胞分0、1、5、10、20 μmol/L B(a)P处理组,应用胞质分裂阻滞微核细胞组学技术综合评价B(a)P的有害生物效应,其中核分裂指数、细胞凋亡率和细胞坏死率等指标评价B(a)P的细胞毒性,微核、核质桥和核芽的发生率检测B(a)P的遗传损伤效应.结果 CYP1A1和mEH在16HBE-CYP1A1细胞中有较高表达,mRNA相对含量分别是7.8×10~(-4)和0.030.B(a)P作用后,16HBE-CYP1A1细胞1、5、10、20μmol/L处理组核分裂指数分别为1.92±0.04,1.71±0.01,1.61±0.04,1.41±0.01,低于对照组(2.08±0.03);双核细胞率分别为(76.33±3.51)%、(66.33±0.58)%、(51.67±1.53)%、(39.00±1.00)%,低于对照组的(82.67±6.66)%;细胞坏死率分别为(1.93±0.42)%、(2.20±0.53)%、(8.07±0.90)%、(15.27±2.80)%,高于对照组的(0.47±0.11)%,差异均有统计学意义(F值分别为899.94、303.33、240.87,P值均<0.01).而凋亡细胞随着B(a)P作用剂量的增加出现先增高后降低的趋势,分别为(1.20±0.53)%、(2.00±0.20)%、(1.47±0.12)%、(1.20±0.00)%、(1.20±0.00)%.遗传损伤效应分析中发现,随B(a)P作用浓度的增加,核质桥发生率随之增加,分别为(4.67±2.89)‰、(7.33±1.53)‰、(10.67±2.08)‰、(11.00±1.00)‰;核芽发生率也随之增加,分别为(2.33±0.58)‰、(4.00±1.00)‰、(5.00±1.00)‰、(7.67±1.16)‰,均有剂量-效应关系(F值分别为50.23、121.09,P值均<0.01).在B(a)P低于10 μmol/L组中,微核率也随B(a)P作用浓度的增加而升高,分别为(8.33±3.21)‰、(14.67±1.15)‰,但在20 μmol/L组,微核率为(16.67±2.88)‰,低于10 μmol/L处理组[(17.67±2.08)‰].在空载质粒细胞16HBEV中,细胞毒性出现较晚,在5、10、20 μmol/L组中,微核、核质桥和核芽的发生率[分别为(6.37±2.08)‰、(9.33±1.52)‰、(9.33±3.21)‰;(4.33±1.53)‰、(6.00±2.65)‰、(5.33±1.53)‰;(2.33±0.58)‰、(3.33±1.16)‰、(3.67±1.16)‰]没有明显的组间改变.结论 B(a)P代谢活化后可导致遗传损伤效应增加,这可能与细胞的核分裂指数降低、细胞坏死率增加或细胞凋亡受抑制有关.     

Effects of mercury and selenite on delta-aminolevulinate dehydratase activity and on selected oxidative stress parameters in rats

The present study evaluates the effects of Na(2)SeO(3) and HgCl(2) on kidney and liver of adult rats. In vivo, HgCl(2) (17 micromol/kg, sc) reduced ascorbic acid levels in liver ( approximately 15%), whereas in kidney it reduced ALA-D activity ( approximately 60%) and ascorbic acid levels ( approximately 35%) and increased TBARS content ( approximately 50%). Na(2)SeO(3) (17 micromol/kg, sc) exposure increased the content of nonprotein thiol groups in liver (35-60%) and kidney ( approximately 50-160%), partially prevented mercury-induced ALA-D inhibition in kidney, and completely prevented a mercury-induced increase of TBARS content and decrease of ascorbic acid levels in kidney. In vitro, HgCl(2) and Na(2)SeO(3) inhibited renal and hepatic ALA-D, while HgCl(2) increased TBARS in renal and hepatic tissue preparations. Na(2)SeO(3) increased the rate of glutathione oxidation in vitro. Results indicated that Na(2)SeO(3) protected against HgCl(2) effects in vivo (prevention of mercury interaction with thiol groups and of mercury-induced oxidative damage). In vitro, Na(2)SeO(3) did not prevent mercury effects, but potentiated ALA-D inhibition by mercury, probably due to its ability to oxidize thiol groups.     

Ileal endogenous nitrogen recovery is increased and its amino acid pattern is altered in pigs fed quebracho extract

Ileal endogenous nitrogen recovery (ENR) in pigs (9 +/- 0.6 kg body weight) was estimated simultaneously using the (15)N-isotope dilution technique ((15)N-IDT) and the peptide alimentation ultrafiltration (UF) method. Diets were cornstarch, enzyme-hydrolyzed casein with no (control) or high (4%) content of quebracho extract (Schinopsis spp.) rich in condensed tannins. The amino acid (AA) pattern of the ENR was also determined. The ENR of pigs fed the quebracho diet was higher (P = 0.0001) than that of pigs fed the control diet [6.00 vs. 1.95 g/kg dry matter intake (DMI) for the (15)N-IDT and 5.18 vs. 1.49 g/kg DMI for the UF method, respectively]. With the (15)N-IDT, ENR values were 0.44-0.79 g/kg DMI (24%) higher (control P = 0.0032, quebracho P = 0.0002) than for the UF method. Apparent nitrogen digestibility depended on diet (69.0% quebracho vs. 86.0% control, P = 0.0001). Real nitrogen digestibility (RD-N) determined by the UF method was higher (P = 0.0001) for the control than for the quebracho diet (91.4 vs. 88.2%). Corresponding values for the (15)N-IDT did not differ (P = 0.0569) between diets (92.8 vs. 91.4%). The (15)N-IDT gave higher values for RD-N of both diets (control P = 0.0030, quebracho P = 0.0002) compared with the UF method. Endogenous AA recoveries (g/kg DMI) were increased 300% (P = 0.0001) and the AA-pattern of ENR was changed (P from 0.0001 to 0.7530 for different AA) by the quebracho diet. A constant AA-pattern of ENR cannot be assumed. Despite limitations of both techniques, the (15)N-IDT and the UF method gave similar results with respect to ENR.     

重铬酸钾和氧化还原物质反应致质粒DNA断链

目的　在体外研究六价铬化合物诱导质粒ＤＮＡ 链断裂的作用。方法　采用质粒松弛法。结果　重铬酸钾（０ ．５ ｍｍｏｌ／Ｌ） 、抗坏血酸（１ ｍｍｏｌ／Ｌ） 、谷胱甘肽（５ ｍｍｏｌ／Ｌ） 或过氧化氢（１７ｍｍｏｌ／Ｌ） 单独作用都不能诱导明显的ＤＮＡ 单链断裂。然而,将重铬酸钾和具有氧化还原功能的物质与ＤＮＡ 共同温浴,发现重铬酸钾和抗坏血酸、谷胱甘肽或过氧化氢反应后可明显诱导质粒ＤＮＡ 单链断裂。重铬酸钾和过氧化氢（１７ ｍｍｏｌ／Ｌ） 还诱导质粒ＤＮＡ 双链断裂。结论　抗坏血酸、谷胱甘肽和过氧化氢可能在重铬酸钾的致癌过程中起重要作用。     

Effects of Aroclor 1242 and different fish-based diets on vitamins A1 (retinol) and A2 (3,4-didehydroretinol), and their fatty acyl esters in mink plasma

The effects of a 21-week exposure to Aroclor 1242 (1mg per day in feed) on plasma concentrations of vitamins A(1) (retinol) and A(2) (3,4-didehydroretinol) and their principal fatty acyl esters (A(1)-16:0, A(2)-16:0 (palmitates), A(1)-18:1n-9; A(2)-18:1n-9 (oleates), and A(1)-18:0; A(2)-18:0 (stearates)) were studied in young female mink (Mustela vison) fed a diet based on freshwater smelt. These vitamin levels were also examined in mink fed diets containing Baltic herring or fatty marine fish. In the Aroclor-exposed smelt-fed mink, the plasma concentrations of A(1) and A(2) esters were significantly lower than the levels in controls fed the uncontaminated smelt diet. In addition, the A(2) esters reacted more sensitively to the polychlorinated biphenyls than did A(1) esters. In contrast, in the plasma of the exposed mink the level of alcoholic A(1) was normal, and transport of thyroxine (T(4)) and nonspecific lipoprotein transport of major lipids were not impaired. Despite the large dietary supply of vitamin A(2) and high levels of plasma A(2) esters, the mink fed freshwater smelt had only trace amounts of alcoholic vitamin A(2) in their plasma. The concentrations of A(1) and A(2) esters in the plasma of all the mink studied correlated with the hepatic total concentrations of the vitamins. Thus, in carnivores that have nonspecific lipoprotein transport of vitamin A esters, determination of plasma levels of the esterified vitamins may be a useful nondestructive way to estimate stores of the vitamin A analogs in the body and to assess the organochlorine-induced decrease in the vitamin stores.     

Use of the youth risk behavior survey to monitor trends for nutrition and physical activity in a Midwest city school district

BACKGROUND: The Youth Risk Behavior Survey (YRBS) was used by a city school district (approximately 11,000 students) in the upper Midwest to monitor trends for nutrition and physical activity (PA) behaviors both within and between years and to compare with national 2003 data. METHODS: Independent random samples were obtained in 1999 (387 middle school [MS] and 931 high school [HS]), in 2001 (322 MS and 367 HS), and in 2003 (658 MS and 1026 HS). A two-sample test of proportions was used. RESULTS: Within each survey year, a higher proportion of MS compared to HS reported positive behaviors with some exceptions: (1) an increased proportion of HS having daily physical education (PE) and (2) a reduced proportion of HS reporting media time. Within 2003, a lower proportion of district females compared to males (MS and HS) reported participation in many measured behaviors. District trends overtime indicated a reduced proportion: (1) drinking milk (MS and HS), (2) eating breakfast (HS), and (3) watching television (MS). Trends overtime indicated an increased proportion: (1) using computers for fun (MS and HS), (2) participating in moderate PA (MS), and (3) daily PE (HS). District HS compared to national (2003) indicated a higher proportion: (1) drinking milk, (2) getting moderate PA, and (3) taking daily PE. District HS compared to national indicated a lower proportion: (1) at risk of overweight, (2) overweight, and (3) watching television. CONCLUSIONS: Analysis of district YRBS trends provides both a database for informed decisions by the school district and an assessment model for other districts.     

Calculating the energy values of foods: towards new empirical formulae based on diets with varied intakes of unavailable complex carbohydrates.

A statistical analysis has been made by generalised linear regression of the relationship between the availability of digestible energy (DE) and the intakes of dietary gross energy (E) and of dietary 'fibre' or unavailable complex carbohydrate (U), for published observations on 43 human diets with varied intakes and sources of U (2-93 g daily) and varied intakes of E (7598-15104 kJ or 1816-3610 kcal daily). Simple formulae were devised also for the availability of metabolizable energy (ME) assuming urinary energy losses of 30 kJ or 7 kcal/g nitrogen (N) intake. For the calculation of DE and ME in mixed human diets with accuracy greater than obtained with previously published methods, the following linear formulae are proposed and their limitations discussed: DE (kJ) = 0.96E(kJ)-9U(g) ME (kJ) = 0.96E(kJ)-9U(g)-30N(g) DE (kcal) = 0.96E(kcal)-2U(g) ME (kcal) = 0.96E(kcal)-2U(g)-7N(g) The equations devised are used to identify atypical observations on faecal energy excretion, and their possible causes are considered. In particular diets high in whole-grain cereal cause faecal energy losses greater than predicted by these equations which is possibly explained by more carbohydrate reaching the colon than expected from current compositional analytical methods.