Pre‐copulation intervals,copulation frequencies,and initial progeny sex ratios in two biotypes of whitefly,Bemisia tabaci

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is a species complex, and its systematic classification requires controlled crossing experiments among its genetic groups. Accurate information on pre‐copulation intervals, copulation frequencies, and initial frequency of egg fertilization of newly emerged adults is critical for designing procedures for collecting the virgin adults necessary for these experiments. In the literature, considerable variation is reported between B. tabaci populations, with respect to the length of the pre‐copulation interval and the initial frequency of egg fertilization. Here, we used a video‐recording method to observe continuously the copulation behaviour of the Mediterranean/Asia Minor/Africa (B biotype) and the Asia II (ZHJ1 biotype) groups of B. tabaci. We also recorded the initial frequency of egg fertilization, as determined by the sex of the progeny. When adults were caged in female–male pairs on leaves of cotton plants, the earliest copulation events occurred 2–6 h after emergence; at 12 h after emergence 56–84% of the females had copulated at least once, and nearly all (92–100%) had copulated at least once by 36 h after emergence. Both females and males copulated repeatedly. Approximately 80 and 20% of copulation events occurred during the photophase and scotophase, respectively. By 72 h post‐emergence, the females of the B and ZHJ1 biotypes had copulated on average 6.1 and 3.9 times, respectively. When adults were caged in groups on plants 1–13 h after emergence, 30–35% of the eggs deposited during this period were fertilized, and approximately 90% of females were fertilized by the end of the 13 h. Although timing of copulation differed in detail between the two genetic groups, the results demonstrate that B. tabaci adults can start to copulate as early as 2–6 h post‐emergence and the majority of females can become fertilized on the day that they emerge.     

Effects of histamine on bronchial artery blood flow and bronchomotor tone

The effects of aerosolized 5% histamine (10 breaths) on bronchial artery blood flow (Qbr), airflow resistance (RL), and pulmonary and systemic hemodynamics were studied in mechanically ventilated sheep anesthetized with pentobarbital sodium. Histamine increased mean Qbr and RL to 252 +/- 45 and 337 +/- 53% of base line, respectively. This effect was significantly different from base line for 30 min after challenge. The histamine-induced increase in RL was blocked by pretreatment with the histamine H1 receptor antagonist, chlorpheniramine, whereas the histamine-induced elevation in Qbr was prevented by the H2 antagonist, metiamide. Both responses were blocked only when both antagonists were present. Changes in Qbr were not directly associated with alterations in systemic and pulmonary hemodynamics or arterial blood gas composition. In vitro histamine caused a dose-dependent contraction of ovine bronchial artery strips that was prevented by H1 antagonist. The H2 agonist, impromidine, caused relaxation of precontracted arterial strips and was more potent and efficacious than histamine, whereas H1 agonists failed to elicit a relaxant response. Thus these findings indicate that histamine aerosol induces a vasodilation in the bronchial vascular bed; histamine has a direct effect on Qbr that is independent of alterations in RL, systemic and pulmonary hemodynamics, or arterial blood gas composition; and, histamine-induced bronchoconstriction is mediated predominantly by H1-receptors, whereas increased Qbr is controlled predominantly by H2-receptors, probably located in resistance vessels. This local effect of histamine on Qbr may have important implications in the pathophysiology of bronchial asthma and pulmonary edema.     

Generalized transduction in Rhizobium meliloti.

Generalized transduction of Rhizobium meliloti 1021 was carried out by bacteriophage N3. Genetic markers on the chromosome and the pSym megaplasmid were transduced, along with markers on several IncP plasmids. Cotransduction between transposon Tn5 insertions and integrated recombinant plasmid markers permitted correlation of cotransductional frequencies and known physical distances. Bacteriophage N3 was capable of infecting several commonly used strains of R. meliloti.     

高温厌氧条件下纤维素的直接乙醇发酵

本文介绍了出分解纤维素的嗜热厌氧菌Clostridium celluloflavus sp.nov.直接发酵纤维素产乙醇的初步研究、发酵于60℃下进仃,其主要产物为乙醇、乙酸、氢气和二氧化碳。文中介绍了间歇发酵的若干特征与影响发酵的因素,1％纤维素发酵至120小时,大约有70％纤维素被分解;乙醇的转化率约为0.36g/g降解纤维素;发酵液中乙醇浓度达到56至61mM。发酵中乙醇与乙酸浓度的比值因发酵时间与其它发酵条件的不同而不同。     

湖北石松目植物的研究

石松目植物是蕨类植物中经济价值较高的一个类群,除孢子粉供铸造工业使用外,大部份种类供药用,有的种类为酸性土的指示植物。湖北石松种类比较丰富,历年来植物学工作者们在我省采集了大量标本,并对民间使用情况进行过调查,积累了不少有用     

Susceptibility of house flies (Diptera: Muscidae) and five pupal parasitoids (Hymenoptera: Pteromalidae) to abamectin and seven commercial insecticides.

Assays of five commercial insecticides applied as residual sprays at label rates to plywood indicated the most toxic insecticide overall for pteromalid parasitoids of house flies, Musca domestica L., was Atroban (permethrin), followed by Ciodrin (crotoxyphos), Rabon (tetrachlorvinphos), Ectrin (fenvalerate), and Cygon (dimethoate). Insecticide-susceptible house flies were susceptible to all five insecticides (mortality, 62-100%). Flies that were recently colonized from populations on dairy farms in New York were susceptible only to Rabon. Urolepis rufipes (Ashmead) was the most susceptible parasitoid species overall to these insecticides, followed by Muscidifurax raptor Girault & Sanders, Nasonia vitripennis Walker, Pachycrepoideus vindemmiae (Rondani), and Spalangia cameroni Perkins. Compared with susceptible flies, newly colonized flies showed moderate resistance to avermectin B1a (abamectin). Abamectin was more toxic to all of the parasitoids except N. vitripennis and S. cameroni than to newly colonized house flies when exposed for 90 min to plywood boards treated with 0.001-0.1% abamectin. Space sprays with Vapona (dichlorvos) killed all of the parasitoids and susceptible flies and 64% of the newly colonized flies when insects were placed directly in the path of the spray; mortality was substantially lower among flies and parasitoids protected under 5 cm of wheat straw. Space sprays with Pyrenone (pyrethrins) killed greater than 86% of all insects exposed to the spray path except for the newly colonized flies (1% mortality); mortality of insects protected under straw was low (less than 12%) except for S. cameroni (76%). Because responses of the five parasitoids to the different insecticides varied considerably, general conclusions about parasitoid susceptibility to active ingredients, insecticide class, or method of application were not possible.     

Photocleavage of myosin subfragment 1 by vanadate

The heavy chain of myosin's subfragment 1 (S1) was cleaved at two distinct sites (termed V1 and V2) after irradiation with UV light in the presence of millimolar concentrations of vanadate and in the absence of nucleotides or divalent metals. The V1 site cleavage appeared to be identical with the previously described active site cleavage at serine-180, which is effected by irradiation of a photomodified form of the S1-MgADP-Vi complex [Cremo, C. R., Grammer, J. C., & Yount, R. G. (1989) J. Biol. Chem. 264, 6608-6011]. The V2 site was cleaved specifically, without cleavage at the V1 site, first by formation of the light-stable S1-Co2+ADP-Vi complex at the active site [Grammer, J. C., Cremo, C. R., & Yount, R. G. (1988) Biochemistry 27, 8408-8415] and then by irradiation in the presence of millimolar vanadate. By gel electrophoresis, the V2 site was localized to a region about 20 kDa from the COOH terminus of the S1 heavy chain. From the results of tryptic digestion experiments, the COOH-terminal V2 cleavage peptide appeared to contain lysine-636 in the linker region between the 50- and 20-kDa tryptic peptides of the heavy chain. This site appeared to be the same site cleaved by irradiation of S1 (not complexed with Co2+ADP-Vi) in the presence of millimolar vanadate as previously described [Mocz, G. (1989) Eur. J. Biochem. 179, 373-378]. Cleavage at the V2 site was inhibited by Co2+ but was not significantly affected by the presence of nucleotides or Mg2+ ions. Tris buffer significantly inhibited V2 cleavage. From the results of UV-visible absorption, 51V NMR, and frozen-solution EPR spectral experiments, it was concluded that irradiation with UV light reduced vanadate +5 to the +4 oxidation state, which was then protected from rapid reoxidation by O2 by complexation with the Tris buffer. The relatively stable reduced form or forms of vanadium were not competent to cleave S1 at either the V1 or the V2 site. 51V NMR titration experiments indicated that a tetrameric species of vanadium preferentially bound to S1 and to the S1-MgADP-Vi complex, whereas no binding of either the monomeric or dimeric species could be detected. These results suggest that the vanadate tetramer was responsible for the photocleavage of S1 which occurred at both the V1 and V2 sites in the absence of nucleotides or divalent metals.