Denitrification under various aeration conditions in Comamonas sp., strain SGLY2

Abstract A number of bacteria were isolated from different anoxic reactors. Those having denitrifying potential were tested for their ability to denitrify under aerobic conditions. The activity of their denitrifying enzymes varied from partial inactivation by oxygen (strains NO2B9 and TCET1) to oxygen-independent activity in a strain named SGLY2 which was tentatively identified as Comamonas sp. The effect of different aeration conditions on growth and on denitrification of SGLY2 was studied more extensively. This strain was able to consume oxygen and nitrate simultaneously with the production of nitrogen and without build-up of nitrite. The dissimilatory nitrate-reductase of nitrate-adapted cells was found to be more active in the presence of oxygen than in micro-aerobic or strictly anaerobic conditions.     

Haematological changes in an Antarctic teleost,Trematomus bernacchii,following stress

The effect of an acute increase in temperature, exhaustive exercise and hypoxia on the haematology of the benthic Antarctic teleost, Trematomus bernacchii was investigated. High temperature and hypoxia caused the biggest changes to the blood, with increases in haematocrit, haemoglobin concentrations and plasma chloride levels. The spleen decreased in mass. Exercise produced the smallest changes. Changes were substantially less than reported for the more active cryopelagic species Pagothenia borchgrevinki. The magnitude of the haematocrit increase is discussed in relation to life-style of fish living in the Antarctic.     

Patterns of sequence variation in the mitochondrial D-loop region of shrews

Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews (genus Sorex) for the region between the tRNA(Pro) and the conserved sequence block-F revealed variable numbers of 79-bp tandem repeats. These repeats were found in all 19 individuals sequenced, representing three subspecies and one closely related species of the masked shrew group (Sorex cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an adjacent 76-bp imperfect copy of the tandem repeats. One individual was heteroplasmic for length variants consisting of five and seven copies of the 79-bp tandem repeat. The sequence of the repeats is conducive to the formation of secondary structure. A termination-associated sequence is present in each of the repeats and in a unique sequence region 5' to the tandem array as well. Mean genetic distance between the masked shrew taxa and the pygmy shrew was calculated separately for the unique sequence region, one of the tandem repeats, the imperfect repeat, and these three regions combined. The unique sequence region evolved more rapidly than the tandem repeats or the imperfect repeat. The small genetic distance between pairs of tandem repeats within an individual is consistent with a model of concerted evolution. Repeats are apparently duplicated and lost at a high rate, which tends to homogenize the tandem array. The rate of D- loop sequence divergence between the masked and pygmy shrews is estimated to be 15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid sequence evolution in shrews may be due either to their high metabolic rate and short generation time or to the presence of variable numbers of tandem repeats.      

大鼠胼胝体内神经肽Y免疫反应阳性纤维的发育

本实验用免疫组织化学ＡＢＣ法研究了大鼠胼胝体内神经肽Ｙ免疫反应阳性（ＮＰＹ－ＩＲ）纤维的生后发育。结果发现,许多ＮＰＹ－ＩＲ纤维在大鼠出生时便存在于胼胝体内。ＮＰＹ－ＩＲ胼胝体纤维的密度在生后１周内继续逐渐增高,在第２周内达到最高峰。之后,ＮＰＹ－ＩＲ胼胝体纤维的密度逐渐下降,至第３周末时接近成年时的水平,即仅有少量ＮＰＹ－ＩＲ纤维存在于胼胝体内。这些结果提示在大鼠早期生后发育过程中许多ＮＰＹ－ＩＲ胼胝体纤维是暂时性的,其作用可能与大脑皮质的机能发育有关。     

Gas-phase enzyme catalysis using immobilized lipase for ester production

Bench-scale reactors were operated in continuous recycle and single-pass modes using immobilized porcine lipase to catalyze gas-phase esterification of ethyl alcohol with two carboxylic acids (acetic acid and propionic acid). Approximately one order of magnitude increases (over uncatalyzed reactions) in conversion were achieved; produc-tion concentrations ranged from 0.1 to 0.5 mM in air, and were affected strongly by substrate concentration and acid-induced enzyme inactivation.     

IN VIVO MEASUREMENT OF ACTIVE OXYGEN PRODUCTION IN THE BROWN ALGA FUCUS EVANESCENS USING 2′,7′-DICHLOROHYDROFLUORESCEIN DIACETATE1

Intracellular production of active oxygen in the brown alga Fucus evanescens C. Ag. was studied by measuring the capacity for in vivo conversion of 2′,7′-dichlorohydrofluorescein diacetate (DCFH-DA) to the fluorescent dye 2′,7′-dichlorofluorescein (DCF), both in emersed and immersed seaweeds. Algae were incubated in seawater containing DCFH-DA under a range of conditions, and it was also possible to load algae with DCFH-DA and then follow subsequent DCF production in emersed tissue. DCF formation was linear for at least 2 h in both darkness and light, with the rate of formation increasing with the light level. DCF formation was temperature dependent. It also increased when algae were treated with H₂O₂ or methyl viologen (paraquat), which disrupts photosystem 1 electron transport and increases O^?₂ production. Exogenous catalase reduced in vivo DCF production, presumably by lowering cellular concentrations of H₂O₂. Hydrogen peroxide was released into the seawater by illuminated algae resulting in external dye conversion to DCF. However, this does not interfere with in vivo measurement of DCF by loaded, washed algae because DCF leakage appeared to be negligible. Internal DCF did not affect photosynthetic oxygen production relative to untreated controls. Overall, our data suggest that DCFH-DA is a potentially very useful probe for studying active oxygen metabolism in seaweeds subjected to environmental stresses.     

A non-metric sequence alignment program

An algorithm for nucleic acid and protein sequence alignment is presented. It is a non-metric local similarity minimal-difference algorithm and in the current implementation, assembles the matching regions found into a pseudo-global format. Its strengths are its speed of execution and the especially convenient presentation of its output. The algorithm is intended for use in sequence melding and local (small-region) similarity searching. It is not designed to replace a metric Needleman-Wunsch-Sellers-type similarity algorithm. The program is written in FORTRAN and is designed to be easily transportable to a variety of computer systems.     

Redox state of cytochrome C in the presence of the 6-hydroxydopamine/oxygen couple: Oscillations dependent on the presence of hydrogen peroxide or superoxide

The reduction of ferricytochrome c in the presence of 6-hydroxydopamine/O₂ mixtures was examined under various reaction conditions. As the autoxidation of 6-hydroxy-dopamine progressed to completion, there were fluctuations in the net redox reactivity between reducing and oxidizing steady states. This was reflected in a sequence of damped oscillations in the redox state of cytochrome c. Corresponding to the time when 6-hydroxydopamine was 75–100% exhausted, reoxidation of the ferrocytochrome c occurred (prevented by catalase or catalase plus Superoxide dismutase). After the H₂O₂, in turn, was mostly consumed, the next phase commenced in which the cytochrome c became reduced for a second time. This reductive phase was 52% inhibited by superoxide dismutase. In the subsequent and final phase of the process, a progressive oxidation of cytochrome c lasting at least 24 h was observed. Of the initial reduction of ferricytochrome c, at most 37% can be attributed to direct reduction by 6-hydroxydopamine or its semiquinone. This initial net reduction of cytochrome c was inhibited 51% by superoxide dismutase and 41% by catalase. However, since either catalase or superoxide dismutase inhibited the autoxidation of 6-hydroxydopamine by at least as much as it slowed the reduction of cytochrome c, their effects in slowing the reduction of cytochrome c resulted largely from the decreased production of those free radicals which reduce ferricytochrome c, and only in part from accelerated removal. Elimination of the actions of transition metal ions (whether by passage of the buffer solutions through Chelex 100 resins or by addition of desferrioxamine to the reaction medium) slowed both the reoxidation and rereduction by up to 96%. Addition of mannitol decreased the rate of the first reoxidation by 25% and increased the rate of the rereduction by 7%. In general, the oscillations are explicable in terms of changes in the steady state levels of O₂ and H₂O₂, with metal ions playing a major role and hydroxyl radicals a minor role in both the reoxidation and rereduction.     

The cholecystokinin antagonist,proglumide, increases food intake in the rat

Cholecystokinin, secreted in response to ingested food entering the duodenum, may play a role in limiting food intake. Inhibition of cholecystokinin should therefore induce an increase in food intake. Proglumide, a specific antagonist of cholecystokinin was used to block the satiety effect of a food preload in rats. A significant increase in food intake was obtained following proglumide injection, thus supporting the hypothesis that cholecystokinin, released by food in the duodenum, acts as a short-term satiety factor.