Inhibition of epidermal metabolism and DNA-binding of benzo[a]pyrene by ellagic acid

Ellagic acid, a common plant phenol, was shown to be a potent inhibitor of epidermal microsomal aryl hydrocarbon hydroxylase (AHH) activity in vitro, and of benzo[a]pyrene (BP)-binding to both calf thymus DNA in vitro and to epidermal DNA in vivo. The in vitro addition of ellagic acid (0.25-2.0 microM) resulted in a dose-dependent inhibition of AHH activity in epidermal microsomes prepared from control or carcinogen-treated animals. The I50 of ellagic acid for epidermal AHH was 1.0 microM making it the most potent inhibitor of epidermal AHH yet identified. In vitro addition of ellagic acid to microsomal suspensions prepared from control or coal tar-treated animals resulted in 90% inhibition of BP-binding to calf thymus DNA. Application of ellagic acid to the skin (0.5-10.0 mumol/10 gm body wt) caused a dose-dependent inhibition of BP-binding to epidermal DNA. Our results suggest that phenolic compounds such as ellagic acid may prove useful in modulating the risk of cutaneous cancer from environmental chemicals.     

Genetic mapping of bovine mitochondrial DNA from a single animal

Using a physical map of bovine mitochondrial DNA derived from the liver of a single Holstein cow, we have determined the location of the genes specifying the large and small riibosomal RNAs by hybridization analysis and electron microscopic observations of R-loop forms. Also, the position of the origin of DNA replication (D-loop) has been located by electron microscopy. Additionally, the direction of D-loop expansion and the polarity of the large and small ribosomal RNA genes were determined.     

SAHA treatment overcomes the anti-apoptotic effects of Bcl-2 and is associated with the formation of mature PML nuclear bodies in human leukemic U937 cells

Bcl-2 protects tumor cells from the apoptotic effects of various antineoplastic agents. Increased expression of Bcl-2 has been associated with poor response to chemotherapy in various malignancies, including leukemia. Therefore, bypassing the resistance conferred by anti-apoptotic factors such as Bcl-2 represents an attractive therapeutic strategy against cancer cells, including leukemic cells. We undertook this study to examine whether SAHA (suberoylanilide hydroxamic acid) overcomes the resistance by Bcl-2 in human leukemic cells, with a specific focus on the involvement of PML-NBs. Experiments were conducted with Bcl-2-overexpressing human leukemic U937 cells. Since we previously demonstrated that overexpression of Bcl-2 attenuates resveratrol-induced apoptosis in human leukemic U937 cells, resveratrol-treated U937 cells were used as a negative control. The present study indicates that SAHA at 1-7 μM, the dose range known to induce apoptosis in various cancer cells, overcomes the anti-apoptotic effects of Bcl-2 in Bcl-2-overexpressing human leukemic U937 cells. Notably, we observed that SAHA-induced formation of mature promyelocytic leukemia (PML) nuclear bodies (NBs) correlates with overcoming the anti-apoptotic effects of Bcl-2 in human leukemic U937 cells. Thus, PML protein and the formation of mature PML-NBs could be considered as therapeutic targets that could help bypass the resistance to apoptosis conferred by Bcl-2. Elucidating exactly how PML regulates Bcl-2 will require further work.     

草酸二甲酯对小鼠亚急性吸入毒性的实验研究

为了研究草酸二甲酯吸入染毒对小鼠的急性毒性,观察吸入染毒后小鼠活动状况、记录心电图、计算LD50,实验结束后取血、检测血液学、血液cTnI和生化指标;取脏器,计算脑、心、肝、脾、肺、肾、卵巢、睾丸、附睾脏器系数,观察其病理组织学改变。结果显示,小鼠吸入草酸二甲酯后出现抽搐、烦躁不安、心电图异常等中毒反应,LD50为2.065 4×10-4g/cm3,脑、心、肝、脾、肺、肾、睾丸、卵巢脏器系数明显升高,血液学、血生化指标和cTnI水平出现了异常变化,与对照组比较具有显著性差异(P0.05或P0.01);心、肺、肝、小肠和肾组织出现了严重受损。由此可见,草酸二甲酯吸入染毒具有较强的毒性,可引起小鼠心电图、血液中cTnI水平、血液学和血生化指标异常改变,可导致心、肺、肝、小肠和肾脏出现病变。本实验为乙二醇合成过程中产生的碳酸二甲酯职业危害防治提供实验依据。     

Guava leaf volatiles and dimethyl disulphide inhibit response of Diaphorina citri Kuwayama to host plant volatiles

The Asian citrus psyllid, Diaphorina citri Kuwayama, vectors the causal pathogen of huanglongbing (HLB), which is likely the most important disease affecting worldwide citrus production. Interplanting citrus with guava, Psidium guajava L., was reported to reduce D. citri populations and incidence of HLB. We describe a series of investigations on the response of D. citri to citrus volatiles with and without guava leaf volatiles and to synthetic dimethyl disulphide (DMDS), in laboratory olfactometers and in the field. Volatiles from guava leaves significantly inhibited attraction of D. citri to normally attractive host‐plant (citrus) volatiles. A similar level of inhibition was recorded when synthetic DMDS was co‐released with volatiles from citrus leaves. In addition, the volatile mixture emanating from a combination of intact citrus and intact guava leaves induced a knock‐down effect on adult D. citri. Compounds similar to DMDS including dipropyl disulphide, ethyl‐1‐propyl disulphide, and diethyl disulphide did not affect the behavioural response of D. citri to attractive citrus host plant volatiles. Head‐space volatile analyses were conducted to compare sulphur volatile profiles of citrus and guava, used in our behavioural assays, with a gas chromatography‐pulsed flame photometric detector. DMDS, produced by wounded guava in our olfactometer assays, was not produced by similarly wounded citrus. The airborne concentration of DMDS that induced the behavioural effect in the 4‐choice olfactometer was 107 pg/ml. In a small plot field experiment, populations of D. citri were significantly reduced by deployment of synthetic DMDS from polyethylene vials compared with untreated control plots. Our results verify that guava leaf volatiles inhibit the response of D. citri to citrus host plant volatiles and suggest that the induced compound, DMDS, may be partially responsible for this effect. Also, we show that field deployment of DMDS reduces densities of D. citri and thus may have potential as a novel control strategy.     

Fibrillar seeds alleviate amyloid-β cytotoxicity by omitting formation of higher-molecular-weight oligomers

Amyloid-β (Aβ) peptides can exist in distinct forms including monomers, oligomers and fibrils, consisting of increased numbers of monomeric units. Among these, Aβ oligomers are implicated as the primary toxic species as pointed by multiple lines of evidence. It has been suggested that toxicity could be rendered by the soluble higher-molecular-weight (high-n) Aβ oligomers. Yet, the most culpable form in the pathogenesis of Alzheimer’s disease (AD) remains elusive. Moreover, the potential interaction among the insoluble fibrils that have been excluded from the responsible aggregates in AD development, Aβ monomers and high-n oligomers is undetermined. Here, we report that insoluble Aβ fibrillar seeds can interact with Aβ monomers at the stoichiometry of 1:2 (namely, each Aβ molecule of seed can bind to two Aβ monomers at a time) facilitating the fibrillization by omitting the otherwise mandatory formation of the toxic high-n oligomers during the fibril maturation. As a result, the addition of exogenous Aβ fibrillar seeds is seen to rescue neuronal cells from Aβ cytotoxicity presumably exerted by high-n oligomers, suggesting an unexpected protective role of Aβ fibrillar seeds.     

Glyceraldehyde-3-phosphate dehydrogenase activity studied under physiological conditions with a linear assay.

An assay method for glyceraldehyde-3-phosphate dehydrogenase in which none of the primary products accumulate and which gives linear kinetics under physiological conditions has been developed. It is based on the use of the 1,3-diphosphoglycerate produced by the enzyme for the formation of NADPH, while the NADH produced is recycled with an auxiliary system. Revised Km values at pH 7.4 for the muscle (rabbit and rat) enzyme are: glyceraldehyde-3-P, 50 μM; NAD, 100 μM; Pi, 10 mM. The rat erythrocyte enzyme gave similar values except for glyceraldehyde-3-P which was 300 μM. Cooperativity for NAD⁺ tends to be positive but is a variable parameter.     

Role of G(i/o)-Src kinase-PI3K/Akt pathway and caveolin-1 in β₂-adrenoceptor coupling to endothelial NO synthase in mouse pulmonary artery

Activation of the β₂-adrenoceptor (β₂-AR) elicits an endothelial nitric oxide synthase (eNOS)-dependent relaxation in mouse pulmonary artery, which, contrary to the muscarinic receptor-dependent relaxation, is preserved in hypoxic pulmonary arterial hypertension. We therefore characterized the signaling pathways underlying the β₂-AR-mediated eNOS activation, with special focus on G_i/o proteins, protein kinases and caveolae. Functional studies (for evaluation of vasorelaxant response), Western blotting (for assessment of eNOS and caveolin-1 phosphorylation) and transmission electron microscopy (for visualization of caveolae) were conducted in pulmonary arteries from wild-type or caveolin-1 knockout mice. In wild-type isolated arteries, relaxation to the selective β₂-AR agonist procaterol was reduced by inhibitors of G_i/o proteins (pertussis toxin, PTX), phosphatidylinositol 3-kinase (PI3K; wortmannin or LY 294002), Akt (Akt inhibitor X) and Src-kinase (PP2) and by cholesterol depletion (using methyl-β-cyclodextrin). Procaterol induced eNOS phosphorylation at Ser¹¹⁷⁷, which was prevented by PTX, PP2 or Akt inhibitor. Procaterol also promoted caveolin-1 phosphorylation at Tyr¹⁴, which was decreased by PTX or PP2. Caveolin-1 gene deletion resulted in endothelial caveolae disruption in mouse pulmonary artery and in potentiation of procaterol-induced relaxation. Unlike procaterol, acetylcholine-induced relaxation was unaffected by PTX, methyl-β-cyclodextrin or caveolin-1 gene deletion. To conclude, the mouse pulmonary endothelial β₂-AR is coupled to a G_i/o-Src kinase-PI3K/Akt pathway to promote eNOS phosphorylation at Ser¹¹⁷⁷ leading to a NO-dependent vasorelaxation. Caveolin-1 exerts a negative control on this response that is abrogated by its phosphorylation at Tyr¹⁴, through a G_i/o-Src kinase pathway. Since pulmonary β₂-AR- and muscarinic receptor-mediated relaxations differentiate in their respective signaling pathways leading to eNOS activation and sensitivities during hypoxia-induced pulmonary arterial hypertension, mechanisms underlying eNOS activation might be key determinants of pulmonary endothelial dysfunction.     

从人发中连续提取亮氨酸和胱氨酸工艺初探

介绍了一种从人发中连续提取亮氨酸和胱氨酸的新工艺。人发用盐酸水解后 ,将水解液减压赶酸 ,再直接加入邻二甲苯 - 4-磺酸沉淀亮氨酸 ,所得沉淀经氨解及后续的精制过程可得亮氨酸精品 ,沉淀亮氨酸后所得的母液按传统的工艺用液氨和得胱氨酸粗品 ,再经一次精制中和可得胱氨酸精品。亮氨酸和胱氨酸的收率分别可达 4 .9%和 7.8% ,产品质量符合日本味之素标准