In vitro alkylation of calf thymus DNA by acrylonitrile. Isolation of cyanoethyl-adducts of guanine and thymine and carboxyethyl-adducts of adenine and cytosine

Reaction of the rodent carcinogen acrylonitrile (AN) at pH 5.0 and/or pH 7.0 for 10 and/or 40 days with 2'-deoxyadenosine (dAdo), 2'-deoxycytidine (dCyd), 2'-deoxyguanosine (dGuo), 2'-deoxyinosine (dIno), N6-methyl-2'-deoxyadenosine (N6-Me-dAdo) and thymidine (dThd) resulted in the formation of cyanoethyl and carboxyethyl adducts. Adducts were not detected after 4 h. The adducts isolated were 1-(2-carboxyethyl)-dAdo (1-CE-dAdo), N6-CE-dAdo, 3-CE-dCyd, 7-(2-cyanoethyl)-Gua (7-CNE-Gua), 7,9-bis-CNE-Gua, imidazole ring-opened 7,9-bis-CNE-Gua, 1-CNE-dIno, 1-CE-N6-Me-dAdo and 3-CNE-dThd. Structures were assigned on the basis of UV spectra and electron impact (EI), chemical ionization (CI), desorption chemical ionization (DCI) and Californium-252 fission fragment ionization mass spectra. Evidence is presented which strongly suggests that N6-CE-dAdo was formed by Dimroth rearrangement of 1-CE-dAdo during the reaction between AN and dAdo. The carboxyethyl adducts resulted from initial cyanoethylation (by Michael addition) at a ring nitrogen adjacent to an exocyclic nitrogen atom followed by rapid hydrolysis of the nitrile moiety to a carboxylic acid. It was postulated that the facile hydrolysis is an autocatalyzed reaction resulting from the formation of a cyclic intermediate between nitrile carbon and exocyclic nitrogen. AN was reacted with calf thymus DNA (pH 7.0, 37 degrees C, 40 days) and the relative amounts of adducts isolated were 1-CE-Ade (26%), N6-CE-Ade (8%), 3-CE-Cyt (1%), 7-CNE-Gua (26%), 7,9-bis-CNE-Gua (4%), imidazole ring-opened 7,9-bis-CNE-Gua (19%) and 3-CNE-Thy (16%). Thus a carcinogen once adducted to a base in DNA was shown to be subsequently modified resulting in a mixed pattern of cyanoethylated and carboxyethylated AN-DNA adducts. Three of the adducts (1-CE-Ade, N6-CE-Ade and 3-CE-Cyt) were identical to adducts previously reported by us to be formed following in vitro reaction of the carcinogen beta-propiolactone (BPL) and calf thymus DNA. The results demonstrate that AN can directly alkylate DNA in vitro at a physiological pH and temperature.     

连作花生土壤中酚酸类物质的检测及其对花生的化感作用

研究了南方红壤区不同连作年限花生土壤中酚酸物质的种类、含量,及其对花生生长的影响。结果表明:连作花生土壤中对羟基苯甲酸、香草酸和香豆酸随着连作年限的增加而增加,连作10a后3种酚酸总量达11.09mg·kg-1干土,显著高于连作3a和6a的土壤;而土壤中香豆素和苯甲酸含量比较低,且变化没有规律。所有酚酸处理组对花生幼苗的株高和根长表现出抑制作用,对花生幼苗地下部的干鲜重均表现出"低促高抑"的特点。香草酸和香豆酸处理组对花生幼苗地上部的干鲜重表现出"低促高抑"的特点,其他处理组均表现出抑制作用。花生幼苗根系活力随着酚酸处理浓度的增加而降低,花生幼苗的超氧化物歧化酶活力(SOD)、过氧化物酶活力(POD)、丙二醛含量(MDA)则随着酚酸浓度的增加而增加。与只用茄腐镰刀菌孢子悬液浸泡花生种子的对照相比,加入酚酸后,花生种子的病原菌的感染率随着酚酸浓度的增加而增加,发芽率则随着酚酸浓度的增加而下降。以上结果说明,酚酸物质可以抑制花生幼苗的生长和提高花生的发病率,可能是因为酚酸物质破坏花生细胞膜的完整性而使病原菌入侵,影响花生生长,产生连作障碍。     

Selective inhibition of methanogenesis to enhance ethanol and n-butyrate production through acetate reduction in mixed culture fermentation

Acetate reduction is an alternative digestion process to convert organic waste into ethanol. Using acetate for fuel ethanol production offers the opportunity to use organic waste materials instead of sugar-containing feedstock. Methanogenesis, however, competes with acetate reduction for acetate and hydrogen and lowers the final efficiency. The aim of this research is to selectively inhibit methanogenesis and to enhance acetate reduction. Acetate reduction was stimulated in batch tests at pH between 4.5 and 8; and at pH 6 with and without thermal pre-treatment. It was found that methanogenesis was selectively inhibited while acetate reduction was enhanced after thermal pre-treatment incubated at pH 6. Initially the acetate reduction yielded 7.7 ± 3.2 mM ethanol with an efficiency of 60.2 ± 8.7%, but later on it was consumed to form 7.02 ± 0.85 mM n-butyrate with an efficiency of 76.2 ± 14.0%. It was the first time demonstrated that n-butyrate can be produced by mixed cultures from only acetate and hydrogen.     

右美托咪定联合经皮穴位电刺激对混合痔剥扎术后患者肠胃功能及术后疼痛的影响

摘要 目的：探讨右美托咪定联合经皮穴位电刺激对混合痔剥扎术后患者肠胃功能及术后疼痛的影响。方法：选择2022年3月-2022年7月我院行混合痔剥扎术的患者60例,将60例患者随机分为对照组（30例）与观察组（30例）,对照组患者给予右美托咪定镇痛,观察组给予术前经皮穴位电刺激,时间为手术开始前2 min至手术结束,右美托咪定使用方法、剂量同对照组。对比两组患者术前、术后0.5 h、1 h、2 h、3 h的疼痛评分,对比两组患者的术后疼痛疗效,对比两组创面愈合时间、腐肉完全脱落时间、住院时间及胃肠功能恢复情况,对比两组术前、术后的血管活性肠肽、胃动素及胃泌素水平。结果：术前及术后3 h时,两组的疼痛评分对比无统计学意义（P>0.05）;术后0.5 h、1 h、2 h时,观察组的疼痛评分明显较对照组低（P<0.05）。观察组的术后疼痛有效率明显较对照组高,P<0.05。观察组的创面愈合时间、腐肉完全脱落时间及住院时间明显较对照组低（P<0.05）。观察组的肠鸣音恢复时间、术后恶心呕吐发生率及排气时间明显较对照组短（P<0.05）。术前,两组的血管活性肠肽、胃动素及胃泌素水平对比无统计学意义（P>0.05）;术后,两组血管活性肠肽、胃泌素水平升高,胃动素水平降低,且观察组变化幅度明显较对照组低（P<0.05）。结论：右美托咪定联合经皮穴位电刺激可改善混合痔剥扎术后患者肠胃功能及术后疼痛情况。     

Four-site four-electron model for Bi(III)-Bi(V) mixed valence complex

In most quantum models for the four-site four-electron problem the lowest singlet state has two short and two long bonds in the absence of lattice polarization and is called the resonating valence bond (VB) state. It is shown here that if the lattice polarization is large, the ground state is a ‘negative U’ state with valence disproportionation (for example BaBiO₃ with Bi(V) and Bi(III) sites). Furthermore the model shows that the coupling between the pairs on different sites is provided via the VB state.     

Development of permethrin resistance in Culex quinquefasciatus Say in Kuala Lumpur,Malaysia

The resistance status towards permethrin among the laboratory strain, the permethrin-selected strain and four field strains of Culex quinquefasciatus collected in Kuala Lumpur, Malaysia was determined using three standard laboratory methods: WHO larval bioassay, WHO adult bioassay and biochemical microplate assay. Cx. quinquefasciatus permethrin-selected strain larvae were the least susceptible to permethrin with a resistance ratio of 47.28-folds, whereas all field strain larvae of the same species were tolerant to permethrin with resistance ratios of more than 3-folds. In contrast, in adult stage, the permethrin exposed permethrin-selected strain (resistance ratio = 1.27) was found to be more susceptible to permethrin than all permethrin-exposed field strains (resistance ratios = 2.23–2.48). Complete mortalities for all strains of Cx. quinquefasciatus adults proved the effectiveness of the synergist; piperonyl butoxide (PBO). For the biochemical microplate assay, the reduction of the mean optical density of elevated oxidase activity of three field strains upon exposure to PBO confirmed the association between oxidase activity and permethrin tolerance. On the other hand, irregular patterns of the mean optical density of elevated oxidase activity in the laboratory strain, permethrin-selected strain and Jalan Fletcher strain illustrated the gene variation within these mosquito colonies as well as the involvement of other enzyme activities in the permethrin resistance occurred.     

Diversity and abundance of wild host plants of lepidopteran stem borers in two different agroecological zones of Kenya

A survey was carried out between 2004 and 2005 in two ecologically different locations, Kakamega and Muhaka to assess diversity and abundance of wild host plants of lepidopteran stem borers as compared to maize plots during the cropping and non-cropping seasons. Kakamega in Western Kenya is characterized by a Guineo-Congolian rain forest mosaic and Muhaka at the Kenyan coast by a Zanzibar Inhambane mosaic with secondary grassy and woody vegetation. In Kakamega, wild host plants and maize covered 2 and 43% of the surveyed area. No variation in diversity and relative abundance of wild host plants was observed between both the cropping and non-cropping seasons. In Muhaka, the diversity and relative abundance of wild host plant species differed between seasons, with the Shannon Weaver Index (H) of 1.67 and 0.95 for cropping and non-cropping seasons, respectively. Similarly in this location, wild host plant cover varied between cropping (23%) and noncropping (17.9%). During both seasons, this was higher than the maize cover, with 10.7% and 0% for the cropping and non-cropping seasons, respectively. For both localities, the implication of the differences found in the abundance and diversity between the cropping and non-cropping seasons is discussed.     

Influence of crucifer cropping system on the parasitism ofPlutella xylostella (Lep., Yponomeutidae) byCotesia plutellae (Hym., Braconidae) andDiadegma semiclausum (Hym., Ichneumonidae)

Field experiments were conducted to study the influence of cabbage monoculture and mixed cropping on the parasitism of diamondback moth,Plutella xylostella (L.), a destructive pest of all crucifers, by 2 larval parasites,Diadegma semiclausum Hellén andCotesia plutellae Kurdjumov. There was no significant difference in parasitism by either species whether cabbage was planted in insecticide-free monoculture or in mixed cropping with 8 noncrucifers which were sprayed twice a week with chemical insecticides mevinphos, methamidophos and permethrin. Population ofP. xylostella increased as the cabbage plants grew older. Parasitism byC. plutellae was higher soon after cabbage transplanting but decreased as the plants grew older. Parasitism byD. semiclausum was very low soon after cabbage planting but increased as the plants grew older. A significant negative correlation was found betwen parasitism byC. plutellae andD. semiclausum. In a caged field study where only one parasite species was used in an individual cage, parasitism ofP. xylostella by both species decreased as theP. xylostella population increased. This is believed to be due to the absence of competition between the two parasites inside the cage. There was no relationship between host-plant age and parasitism ofP. xylostella larvae by either parasite species.     

Effect of legume-based cropping systems on nitrogen mineralization potential of Vertisol

The quantity and patterns of net mineralization of soil nitrogen (N) were studied in Vertisols under different cropping systems in the semi-arid tropical areas. Eight cropping systems were selected; three contained pigeonpea (PP), one contained PP and cowpea (COP), and two contained chickpea (CP) as legume component crops, one included sequence cropping with nonlegumes during the rainy and postrainy seasons, and one system was kept fallow (F) during the rainy season and sown to sorghum (S) during the postrainy season. Cropping systems with PP as a component crop increased mineralizable N(N _o ) content two-fold in the soil compared with fallow + sorghum (F+S)–F+S system. The N mineralization rate constant (k) was not significantly affected by previous cropping history of the soil; however, a numerically higher rate constant was observed in the COP/PP intercrop, followed by sequential S+safflower (SF) system as compared to the other soils. Mineral N accumulation curves for six soils were more accurately described by the exponential model than the linear model. The active N fraction (N _o /N_tot %) varied between 8 and 16% for different systems and a direct relationship was observed between N _o /N_tot and total N for the soils under diverse cropping systems.ICRISAT JA (1638)