Structure-activity relationships on hyperglycemia by representatives of the adipokinetic/hyperglycemic hormone family in Blaberus discoidalis cockroaches

Summary Several members of the adipokinetic/hyperglycemic neurohormone family from several different invertebrate species have been prepared by solid-phase peptide synthesis and assayed by a modified in vivo hyperglycemic bioassay in Blaberus discoidalis cockroaches. The hypertrehalosemic hormone (HrTH) is the endogenous hypertrehalosemic factor for B. discoidalis and was the most potent peptide in the assay. The more divergent the sequence of a family member from Blaberus HrTH, the less potent was the bioanalog. Manduca adipokinetic hormone is the most divergent peptide of the family and was totally inactive in the bioassay. Locusta adipokinetic hormone I had reduced maximum activity in the assay, which suggests that Ser⁵ is an important residue for the transduction of the hyperglycemic response. The direct relation between bioanalog similarity to Blaberus HrTH sequence and potency suggests that the hormone and target cell receptor for HrTH have evolved to maintain an optimal fit.Abbreviations AKH adipokinetic hormone - HrGH hyperglycemic hormone - HrTH hypertrehalosemic hormone - RPCH red pigmentconcentrating hormone - CAH cardioacceleratory hormone. Hormone abbreviations are according to the convention of Gäde and Raina (1989) except that the genus names are not abbreviated     

培养大鼠搏动心肌细胞在缺氧和复氧时的电生理观察

应用细胞内微电极技术记录到37个培养大鼠搏动心肌细胞充氮前后和复氧后的电活动参数。结果提示:充氮10min后,最大舒张电位(MDP),最大除极速度(V_(max)),动作电位振幅(APA)和动作电位时程(APD)等参数明显降低;自发节律增快,并出现多种形式的节律失常。83.8％细胞在充氮后30min内停搏,16.2％在50min左右停搏。复氧后,86.5％细胞在5min内复跳,13.5％未能复跳;12.5％复跳细胞在复跳10min内再次停搏。复跳细胞的各项电活动参数在30min内未能恢复到充氮前水平(p<0.05),且呈现不同程度的各类异常电活动。本结果对进一步研究心肌细胞缺氧和复氧损伤有一定意义。     

固氮酶铁钼辅因子FeMo-co在水与非水体系内重组活力与催化活力的比较研究

 本文提出一种测定FeMo-co催化活力的反应体系,用此反应体系,在测定FeMo-co催化活力的过程中,FeMo-co与变种UW45抽提液的重组活性始终保持不变。讨论了水含量、还原剂对FeMo-co催化活力和重组活力的影响。     

Chinese hamster ovary cells continuously secrete a cysteine endopeptidase

Summary The protease activity in serum-free conditioned medium of chinese hamster ovary (CHO) cells was measured using peptidyl (or aminoacyl)-4-methylcoumaryl-7-amides (MCAs) as the substrates. Aminopeptidase increased in level as amounts of nonviable cells increased during cultivation in serum-free medium, indicating that the activity seems to be originated from intracellular proteases. The activity toward Boc-Leu-Arg-Arg-MCA, which was strongly inhibited by p-chloromercuribenzonate and N-ethylmaleimide, was the strongest among those toward peptidyl-MCAs in the conditioned medium within 48 h-cultivation in serum-free medium. In contrast to the case of aminopeptidase activity, the endopeptidase activity decreased in level after 48 h-cultivation although amounts of nonviable cells increases. Thus, CHO cells continuously secrete the cysteine proteases. This work was supported by the management of the Research Association for Biotechnology as a part of the R&D of Basic Technology for Future Industries sponsored by NEDO (New Energy and Industrial Technology Development Organization).     

Radical Cations in Aromatic Hydrocarbon Carcinogenesis

Most carcinogens, including polycyclic aromatic hydrocarbons (PAH), require metabolic activation to produce the ultimate electrophilic species that bind covalently with cellular macromolecules to trigger the cancer process. Metabolic activation of PAH can be understood in terms of two main pathways: one-electron oxidation to yield reactive intermediate radical cations and monooxygenation to produce bay-region diol epoxides. The reason we have postulated that one-electron oxidation plays an important role in the activation of PAH derives from certain common characteristics of the radical cation chemistry of the most potent carcinogenic PAH. Two main features common to these PAH are: 1) a relatively low ionization potential, which allows easy metabolic removal of one electron, and 2) charge localization in the PAH radical cation that renders this intermediate specifically and efficiently reactive toward nucleophiles. Equally important, cytochrome P-450 and mammalian peroxidases catalyze one-electron oxidation. This mechanism plays a role in the binding of PAH to DNA. Chemical, biochemical and biological evidence will be presented supporting the important role of one-electron oxidation in the activation of PAH leading to initiation of cancer.     

Hydration of 3-cyanopyridine to nicotinamide by crude extract nitrile hydratase

Summary The kinetic and stability characteristics of crude extract nitrile hydratase fromBrevibacterium R-312 were studied for the hydration of 3-cyanopyridine to nicotinamide. The enzyme was substrate and product inhibited and had the following kinetic constants:K _m =28 mM;K _p =36 mM;K _s =155 mM;V _m =5.8 mol/min/mg protein (25°C). Itsmaximum temperature and pH (phosphate buffer) were 35°C and 8.0, respectively and it had half-lives of 50 days, 10 days and 1 day at 4°C, 10°C and 25°C, respectively. The crude extract also exhibited amidase activity on nicotinamide, but it became significant only at nicotinamide concentrations greater than 300 mM. Mathematical models for batch and fed-batch hydrations were developed to account for substrate and product inhibitions and for enzyme decay. They predicted to within 10% experimental results for initial substrate and final product concentrations up to 300 mM; the accuracies decreased at higher concentrations primarily because of the relatively rapid hydrolysis of nicotinamide.     

Dominance in demand-feeding behaviour in Arctic charr and rainbow trout: the effect of stocking density

The effects of stocking density on the demand feeding behaviour of Arctic charr Salvelinus alpinus and rainbow trout Oncorhynchus mykiss were evaluated using demand feeders in combination with a monitoring system based on automatic passive integrated transponders. The proportion of total bites accounted for by top-ranked charr and trout decreased from 87 to 15% and from 66 to 15%, respectively, when moving from the lowest to the highest densities, indicating that the ability of the highest-ranked fish to monopolize the demand feeders was reduced at high densities. However, when the individuals were grouped into quartiles, based on their individual rank, both charr and trout ranked within the upper quartile accounted for the majority of bites independent of stocking density (87 and 72% of the total, respectively). Instead of there being a single dominant individual, as was the case under low density conditions, a small group of individuals dominated the actuation of the trigger at high densities. The two species responded differently to crowding, with the total daily bite activity of charr increasing linearly with increasing density, whereas the corresponding relationship was quadratic for rainbow trout, with a peak value at 24 to 36kg m⁻³.     

Electromyograms from radiotelemetry as indicators of reproductive activity in lake trout

One male and one female lake trout, Salvelinus namaycush , were held in a laboratory tank simulating a natural spawning environment. Their behaviour during their reproductive period was videotaped each day for 2 h at dusk. The fish activities were classified into seven types: resting, casual swimming, side-thrusting, chase, chase-nudge, body alignment, shuddering. As the reproductive period progressed the fish became more generally active with a marked increase in interactive behaviours such as pursuit of the female by the male (chasing, chasing-nudging). Around spawning time, shuddering and body alignment activity reached apeak. Each fish was equipped with an internally implanted radiotelemetry package able to detect and transmit continuously over the course of each day signals that reflect production of the electromyograms (EMGs) that accompany fish axial muscle activity (high muscular activity gives low pulse interval times in milliseconds). The lowest EMG pulse intervals corresponded with what, from the video records, appeared to be the time of highest physical activity during the reproductive period–viz. that associated with spawning activity during dusk. Other times during the diel cycles over the reproductive period, except for times of roughly similar duration during early morning (which may also be reflections of spawning) showed considerably lower muscular activity. It is concluded that transmitted EMG records could probably be used as indicators of spawning activity of lake trout in at least some of those places in the field where they cannot normally be located by visual means.     

Integrated cultivation of salmonids and seaweeds in open systems

Bacterial abundance and production in a vertical profile in Lake Kariba (17dgS), Zimbabwe, were affected by solar irradiance. At the surface, 1.87 × 10⁹ bacteria 1^–1 were found and abundance peaked at 10 m (2.5 × 10⁹ bacteria l^-1), then decreasing with depth. Bacterial reproduction at the surface(0.145 µg C1^–1 h^–1) was nearly four times less than the production at 10 m although bacterial numbers were only 26% less. Thus, bacterial production per cell was lower at the surface than deeper down, suggesting that bacterial production is inhibited at the surface.Bacterial production in GF/F filtered lake water in Whirl Pack bags showed an exponential decrease down to 3 m depth. The inhibition was well in accordance with light extinction in the UV region. Phosphatase activity was low in light exposed bags compared to dark, indicating photolysis of extracellular enzymes, or phototransformation of recalcitrant DOM, which substitutes enzyme activity. Hypolimnetic enzyme activity was less affected by solar light than epilimnetic.     

TheisfA mutation inhibits mutator activity and processing of UmuD protein inEscherichia coli recA730 strains

Further studies on theisfA mutation responsible for anti-SOS and antimutagenic activities inEscherichia coli are described. We have previously shown that theisfA mutation inhibits mutagenesis and other SOS-dependent phenomena, possibly by interfering with RecA coprotease activity. TheisfA mutation has now been demonstrated also to suppress mutator activity inE. coli recA730 andrecA730 lexA51(Def) strains that constitutively express RecA coprotease activity. We further show that the antimutator activity of theisfA mutation is related to inhibition of RecA coprotease-dependent processing of UmuD. Expression of UmuD' from plasmid pGW2122 efficiently restores UV-induced mutagenesis in therecA730 isfA strain and partially restores its mutator activity. On the other hand, overproduction of UmuD'C proteins from pGW2123 plasmid markedly enhances UV sensitivity with no restoration of mutability.