温度驯化对五种鲤科鱼类糖代谢酶活性的影响

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The effect of acclimation temperature on thermal activity thresholds in polar terrestrial invertebrates

In the Maritime Antarctic and High Arctic, soil microhabitat temperatures throughout the year typically range between ?10 and +5 °C. However, on occasion, they can exceed 20 °C, and these instances are likely to increase and intensify as a result of climate warming. Remaining active under both cool and warm conditions is therefore important for polar terrestrial invertebrates if they are to forage, reproduce and maximise their fitness. In the current study, lower and upper thermal activity thresholds were investigated in the polar Collembola, Megaphorura arctica and Cryptopygus antarcticus, and the mite, Alaskozetes antarcticus. Specifically, the effect of acclimation on these traits was explored. Sub-zero activity was exhibited in all three species, at temperatures as low as ?4.6 °C in A. antarcticus. At high temperatures, all three species had capacity for activity above 30 °C and were most active at 25 °C. This indicates a comparable spread of temperatures across which activity can occur to that seen in temperate and tropical species, but with the activity window shifted towards lower temperatures. In all three species following one month acclimation at ?2 °C, chill coma (=the temperature at which movement and activity cease) and the critical thermal minimum (=low temperature at which coordination is no longer shown) occurred at lower temperatures than for individuals maintained at +4 °C (except for the CTmin of M. arctica). Individuals acclimated at +9 °C conversely showed little change in their chill coma or CTmin. A similar trend was demonstrated for the heat coma and critical thermal maximum (CTmax) of all species. Following one month at ?2 °C, the heat coma and CTmax were reduced as compared with +4 °C reared individuals, whereas the heat coma and CTmax of individuals acclimated at +9 °C showed little adjustment. The data obtained suggest these invertebrates are able to take maximum advantage of the short growing season and have some capacity, in spite of limited plasticity at high temperatures, to cope with climate change.     

The presence of an NADP-dependent alcohol dehydrogenase activity in Acinetobacter calcoaceticus

Abstract A soluble NADP-dependent alcohol dehydrogenase activity (EC 1.1.1.2) was found in all five strains of Acinetobacter calcoaceticus tested. In A. calcoaceticus NCIB8250, this dehydrogenase was not induced by growth on ethanol, but was present at approximately the same specific activity when this strain was grown on a variety of carbon sources. The specific activity of the NADP-dependent alcohol dehydrogenase is about 10% of the activity of the NAD-dependent alcohol dehydrogenase found in bacteria grown on ethanol. The distinct biochemical properties of the NADP-dependent dehydrogenase showed that this activity was not due to lack of nucleotide specificity of the NAD-dependent dehydrogenase.     

Isocitrate dehydrogenase activity and its regulation by estradiol in tissues of rats of various ages

The activity and hormonal regulation of NAD- and NADP-linked isocitrate dehydrogenase (EC.1.1.1.41 and EC.1.1.1.42, respectively) in the brain, liver and kidney cortex of female rats of various ages was investigated. The activity of NAD-ICDH of brain was greater than extramitochondrial (-c) or intramitochondrial (-m) NADP-ICDH. In contrast, liver c-NADP-ICDH was much higher than NAD- or m-NADP-ICDH, whereas in kidney cortex the activity of m-NADP-ICDH is dominant over both NAD- and c-NADP-ICDH in all the age group of rats studied. The activity of the NAD-ICDH of brain and all the enzymes of liver and kidney cortex increases until adulthood (33-weeks) and decreases thereafter in old rats (85-weeks). In brain c-NADP-ICDH was much higher in immature (6-weeks) rats and decreases with increasing age of the animal, whereas m-NADP-ICDH showed no significant change with the age of the rats. Bilateral ovariectomy decreases the level of all the three forms of enzyme in all the tissues of 6-, 13- and 33-week rats but failed to show any significant effect in 85-week old rats. Exogenous administration of estradiol induces all the three forms of enzyme in all the tissues of ovariectomized rats. The degree of response is tissue- and age-specific.     

Novel nitrogen sources for growth of Bacillus fastidiosus and their effect on the activity of NADP-dependent glutamate dehydrogenase

Abstract Although Bacillus fastidiosus assimilates ammonium formed internally during growth on urate, allantoin or allantoate via NADP-dependent glutamate dehydrogenase (NADP-GDH), growth on exogenous ammonium as nitrogen source has not been observed. Growth on ammonium, urea and ureidoglycolate, intermediates of the urate degradative pathway, was found to occur if the mineral growth medium containing glycerol as a carbon source was supplemented with both allantoin (0.5 mM) and brain heart infusion (BHI, 0.1%, w/v) or yeast extract. Neither allantoin nor BHI supported growth alone or in combination unless ammonium was present. NADP-GDH activity appeared to be regulated only by the extracellular concentration of allantoin or allantoate. Enzyme activity was not influenced by other nitrogen sources or the intracellular ammonium concentration.     

The influence of acclimation and experimental temperature on glutamate dehydrogenase of carp red lateral muscle (Cyprinus carpio L.)

The dependence of the reaction catalysed by carp red lateral muscle glutamate-dehydrogenase on acclimation and experimental temperature was studied. In addition to quantitative aspects of enzyme temperature compensation, the influence of temperature conditions on kinetic characteristics of the enzyme protein is reported. Results are discussed with respect to temperature capacity adaptation (acclimation).     

Purification and various properties of hyaloplasmic NADP-dependent isocitrate dehydrogenase from the rabbit adrenal gland

NADP-dependent isocitrate dehydrogenase was isolated from the hyaloplasmic fraction of rabbit adrenal glands and purified by ammonium sulfate and polyethylene glycol fractionation and chromatography on DEAE-Sephadex A-50 to a specific activity of 26.8 U/mg with a 53% yield. Polyacrylamide gel electrophoresis revealed one distinct protein band with mobility corresponding to Mr approximately 50 000 in the presence of SDS. Data from gel filtration suggest that the detergent-untreated isocitrate dehydrogenase has a twice as great molecular mass, which is indicative of its dimeric structure of identical subunits. The pH optimum for the adrenal isocitrate dehydrogenase-catalyzed reaction is 7.5-7.7; the apparent activation energy is 61.3 kJ X mol-1. Mn2+ activate the enzyme more effectively than Mg2+. The curve for the dependence of the isocitrate dehydrogenase reaction rate versus D-isocitrate and NADP concentrations is S-shaped. At low substrate or coenzyme concentrations the Hill coefficient is 2.0 and 1.9, respectively, which serves as a kinetic attribute of positive cooperativity of their interaction with isocitrate dehydrogenase. The concentrations of D-isocitrate and NADP providing for the half-maximal rate of the reaction are 3.8 and 6.6 microM, respectively.     

Effects of cold acclimation on the activity levels of creatine kinase, lactate dehydrogenase and lactate dehydrogenase isoenzymes in various tissues of the rat.

The effects of cold acclimation on the activity levels of creatine kinase, lactate dehydrogenase and lactate dehydrogenase isoenzymes in various tissues/ organs of the rat (Rattus norvegicus) were investigated. Male Sprague-Dawley rats were divided into two groups. One group was housed at 4+/-1 degrees C (experimental group) and the other at 24+/-1 degrees C (control group) for six months. The rats were housed in single cages and had access to food and water ad libitum. The tissues/organs investigated were heart, liver, lung, kidney, gastrocnemius muscle and interscapular brown adipose tissue as well as serum. With the exception of lung, (which showed a decrease of 24%) total creatine kinase activity levels were significantly increased (P< 0.05) in all the tissues/organs investigated (17-51%) as well as serum (34%), in cold acclimated animals. Cold acclimation also resulted in significantly increased (P< 0.05) activity levels of lactate dehydrogenase in all the tissues/organs investigated (14-24%) as well as serum (35%). Cold exposure resulted in an increase of the activity levels of all the detectable isoenzymes of lactate dehydrogenase, although not always significant, in all the tissues/organs investigated as well as serum. The M(4)tetramer of lactate dehydrogenase was the only detectable isoenzyme in serum.     

Studies on mechanisms of ornithine decarboxylase activity regulation in regenerating liver

Rat liver (hydrocortisone-induced) ornithine decarboxylase has been shown to be stable when the cytosolic fraction is incubated alone at 37 degrees C, although there is a very rapid and drastic loss of activity after addition of microsomes to the incubation medium. The present paper is concerned with the behaviour of ornithine decarboxylase induced in rat liver by a growth stimulus (partial hepatectomy); comparative studies have been carried out on the enzyme induced by sham operation, or by hydrocortisone. Results show that ornithine decarboxylase from regenerating liver is more stable when incubated with microsomes (from the same source); this higher stability depends both on a lower microsome-bound inactivating capacity and a limited susceptibility of the enzyme to the inactivation. A critical role in modulating the microsome-dependent inactivation appears to be played by low molecular weight cytosolic factors, whose greater content in regenerating liver is likely to be included with the factors above in determining the relative stability of ornithine decarboxylase.     

Differential regulation of the oxidative 11beta-hydroxysteroid dehydrogenase activity in testis and liver

11Beta-hydroxysteroid dehydrogenase (11beta-HSD) Type I enzyme is found in testis and liver. In Leydig cell cultures, 11beta-HSD activity is reported to be primarily oxidative while another report concluded that is primarily reductive. Hepatic 11beta-HSD preferentially catalyzes reduction and the reaction direction is unaffected by the external factors. Recent analysis of testicular 11beta-HSD revealed two kinetically distinct components. In the present study, various steroid hormones or glycyrrhizic acid (GCA), given for 1 week, or thyroxine given for 5 weeks to normal intact rats had different effects on the 11beta-HSD oxidative activity in testis and liver. Deoxycorticosterone, dexamethasone, progesterone, thyroxine, and clomiphene citrate increased testicular 11beta-HSD oxidative activity, but decreased hepatic enzyme activity except for deoxycorticosterone (unchanged). Corticosterone and testosterone decreased 11beta-HSD oxidative activity in testis but not that of liver (which was unchanged). Estradiol, GCA and adrenalectomy lowered oxidative activity of 11beta-HSD in testis and liver, but the degrees of reduction were different. The in vivo effects of glucocorticoids too were different, even in the same organ. Dexamethasone, a pure glucocorticoid, has greater affinity for glucocorticoid receptors (GR) than corticosterone. The direct effects of dexamethasone via GR in increasing testicular 11beta-HSD oxidative activity may override its indirect effects. Possibly, the reverse occurs with corticosterone treatment, as it has both glucocorticoid and mineralocorticoid effects. Because both organs have Type I isoenzyme, the difference in 11beta-HSD oxidative activities of these two organs could be attributable to the presence of an additional isozyme in testis or differences in tissue-specific regulatory mechanisms.     

Hormonal regulation of temperature acclimation in catfish hepatocytes

Summary Protein synthesis (measured by ³H-leucine incorporation) by catfish hepatocytes in culture was enhanced when trace amounts of catfish serum were added. Serum from 15°C-acclimated fish was significantly more effective than serum from 25°C-acclimated fish.Total protein content of the cells was slightly diminished; DNA content was not altered.Added triiodothyronine (T₃) significantly reduced protein synthesis by cultured hepatocytes, more at 25°C than at 15°C culture. Threshold concentration of T₃ was 10^–9 M.Removal of T₃ from serum by exchange resin resulted in increased protein synthesis. Addition of T₃ to that preparation decreased protein synthesis.The concentration of T₃ in serum from 25°C-acclimated catfish is three times greater than the concentration in serum from 15°C-acclimated fish.Increase in protein synthesis after removal of T₃ suggests that there is a blood-borne stimulating factor, more active in cold- than in warm-acclimated fish. The stimulating substance was present after dialysis (2000 Da cutoff) and was partially inactivated by heat.Insulin stimulated protein synthesis; salmon insulin was more effective than bovine insulin. Insulin content did not differ in serum from 15°C- and 25°C-fish.The effects of growth hormone and prolactin were equivocal or negative.The inhibitory effect of T₃ may explain the reduction in metabolism during warm-acclimation. The nature of a stimulating hormone in cold acclimation is unknown.Abbreviations DNA desoxyribonucleic acid - DPM desintegrations per minute - GH growth hormone - HPLC high performance liquid chromatography - LDH lactate dehydrogenase - MEM minimal essential medium - PBS phosphate buffered saline - POPOP 1,4-bis [5-phenyl-2-oxazolyl]benzene 2,2-p-phenylene-bis[5-phenyloxazole] - PPO 2,5-diphenyloxazole - RIA radioimmunoassay - TCA trichloroacetic acid - T ₃ 3,5,5-triiodothyronine - T ₄ thyroxine - VO ₂ oxygen consumption     

Inducibility of liver cytosolic aldehyde dehydrogenase activity in various animal species

1. The inducibility of hepatic cytosolic aldehyde dehydrogenase activity was studied in rat, mouse, guinea pig, chicken, frog, salamander and rainbow trout, by using two different types of inducers of drug metabolism. 2. Phenobarbital (a type I inducer of drug metabolizing enzymes) increased total liver cytosolic aldehyde dehydrogenase activity (up to 20-fold) in a genetically defined substrain of responsive rats (RR) and only slightly, if at all, in a non-responsive substrain (rr). On the contrary, both types of rats showed a highly induced aldehyde dehydrogenase activity after treatment with methylcholanthrene (a type II inducer). Phenobarbital is affecting mainly an isozyme of aldehyde dehydrogenase which is best measured with propionaldehyde as the substrate and NAD as the coenzyme (P/NAD). 3. Administration of phenobarbital to mice produced only a slight increase (2-fold) in the P/NAD aldehyde dehydrogenase activity. 4. Methylcholanthrene treatment caused a 2-fold increase of the hepatic P/NAD aldehyde dehydrogenase activity in the chicken. 5. In the guinea pig, phenobarbital produced an approximate 3-fold increase of the P/NAD activity. Methylcholanthrene had a similar effect, although to a lesser extent. 6. In the salamander, a 4-fold increase was detected in the enzyme activity measured with benzaldehyde as the substrate and NADP as the coenzyme (B/NADP), after treatment with either phenobarbital or methylcholanthrene. 7. The hepatic aldehyde dehydrogenase activities were found unchanged in the rainbow trout, after treatment with phenobarbital or 2,3,7,8-tetrachlorodibenzo-p-dioxin. 8. The rat model remains the only one examined that shares with human hepatocytes strong inducibility of the B/NADP aldehyde dehydrogenase isozyme upon treatment with polycyclic aromatic hydrocarbons.     

Effect of various chemicals on the aldehyde dehydrogenase activity of the rat liver cytosol

The cytosolic activity of aldehyde dehydrogenase (ALDH) was studied in the rat liver, after acute administration of various carcinogenic and chemically related compounds. Male Wistar rats were treated with 27 different chemicals, including polycyclic aromatic hydrocarbons, aromatic amines, nitrosamines, azo dyes, as well as with some known direct-acting carcinogens. The cytosolic ALDH activity of the liver was determined either with propionaldehyde and NAD (P/NAD), or with benzaldehyde and NADP (B/NADP). The activity of ALDH remained unaffected after treatment with 1-naphthylamine, nitrosamines and also with the direct-acting chemical carcinogens tested. On the contrary, polycyclic aromatic hydrocarbons, polychlorinated biphenyls (Arochlor 1254) and 2-naphthylamine produced a remarkable increase of ALDH. In general, the response to the effectors was disproportionate between the two types of enzyme activity, being much in favour for the B/NADP activity. This fact resulted to an inversion of the ratio B/NADP vs. P/NAD, which under constitutive conditions is lower than 1. In this respect, the most potent compounds were found to be polychlorinated biphenyls, 3-methylcholanthrene, benzo(a)pyrene and 1,2,5,6-dibenzoanthracene. Our results suggest that the B/NADP activity of the soluble ALDH is greatly induced after treatment with compounds possessing aromatic ring(s) in their molecule. It is not known, if this response of the hepatocytes is related with the process of chemical carcinogenesis.     

糖皮质激素对血压的调节作用及其机制

糖皮质激素能够通过其允许作用增强血管平滑肌对儿茶酚胺的敏感性,进而提高血管的张力和维持血压。近年来越来越多的证据表明,自发性高血压与糖皮质激素的异常分泌有关。糖皮质激素可以通过心脏、血管内皮细胞、血管平滑肌等不同部位的作用而调节血压。本文就糖皮质激素对血压的调节及其可能的机制作一综述。     

Thiamine phosphates and regulation of the pyruvate dehydrogenase complex activity in rat liver mitochondria

The possibility of thiamine phosphates to participate in the regulation of pyruvate dehydrogenase complex activity on the level of isolated mitochondria is studied. It is shown that an increase in the thiamine diphosphate concentration in incubation medium produces no significant changes in the pyruvate dehydrogenase activity of mitochondria. The pyruvate dehydrogenase activity decreases when mitochondria are incubated with thiamine triphosphate or ATP under different conditions. Thiamine triphosphate is not able to replace ATP in kinase reaction of the isolated complex, but it inhibits reactivation of the complex with exogenase phosphatase; under the same conditions thiamine diphosphate activates phosphatase. Analysis of these data leads to conclusion that under native conditions an increase of the intramitochondrial thiamine triphosphate concentration can produce a drop in the pyruvate dehydrogenase complex activity by inhibition of the phosphatase reaction.     

Increase in chloroplastic thiol groups by SO2 and its effect on light modulation of NADP-dependent glyceraldehyde 3-phosphate dehydrogenase

In broken spinach chloroplasts the total amount of thiol groups is about 3.7 mol mg^-1 chlorophyll. Two thirds are represented by the masked form (which is only titratable after unfolding of the protein). Of the free groups, those reacting with NBD·Cl (1.2–2.0 mol mg^-1 chlorophyll) seem to be undergoing oxidation more readily than those reacting with DTNB (1.0 mol mg^-1 chlorophyll). SO₂ application causes a maximal increase of 25% in free thiols, and doubles the amount of the masked thiols. The light triggered increase in SH, which starts at an elevated level, runs parallel to that of the controls. SO₂ application of 1.8 mg m^-3 (=28 nmol l^-1) for 1 h does not affect the dark level of NADP-GPD but enhances the light modulation by increasing the ratio of activation. This enhancement is explained by an increase in masked thiol groups during the preceding fumigation period.Abbreviations DTNB 5,5 dithiobis-2-nitrobenzene-2-oxa-1,3 diazole - NBD·Cl 7-chloro-4-nitrobenzene-2-oxa-1,3 diazole - PCMB p-chloromercuribenzoate - SDS sodium dodecylsulfate - NADP-GPD NADP-dependent glyceraldehyde 3-phosphate dehydrogenase (EC 1.2.1.13) - HEPES N-2-Hydroxyethylpiperazine-N-2-ethanesulfonic acid - MES 2[N-Morpholino]ethanesulfonic acid - PGA 3-phosphoglyceric acid