Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The hydroxymethylglutaryl-coenzyme A reductase (mevalonate:NADP+ oxidoreductase, EC 1.1.1.34) system in Fusarium oxysporum, a soil inhabiting plant pathogen, has been examined. Two forms of the enzyme catalyzing the conversion of hydroxymethylglutaryl-coenzyme A were obtained in the supernatant after precipitation at 75% (NH4)2SO4 saturation of the soluble culture extract which was previously separated from cell wall, mitochondria and microsomes. The two forms of the enzyme were separated electrophoretically. A third form, contained in the precipitate obtained at 35--75% (NH4)2SO4 saturation of the same extract, was further purified by Sephadex G-50 column chromatography. This purified form moved as a single band in sodium dodecyl sulphate electrophoresis and in immunological tests and has a molecular weight of 11 000. The apparent Michaelis constant for the substrate hydroxymethylglutaryl-coenzyme A is 21 micron at 2 micron NADP. NADPH is a more efficient reductant on a molar basis than NADH for the deacylation of the hydroxymethylglutaryl-coenzyme A substrate. Optimum activity of the enzyme was obtained at pH 7.4 and 37 degrees C. The enzyme demonstrated no cold sensitivity but rather was more stable at 4 degrees C than at 25 degrees C. The protection with dithiothreitol, though minimal compared to other systems, was more effective at the higher temperature.
 ...
PMID:Hydroxymethylglutaryl-coenzyme A reductase. Purification and properties of the enzyme from Fusarium oxysporum. 2 7

Inactivation of apo-glyceraldehyde-phosphate dehydrogenase (D-glyceraldehyde-3-phosphate: NAD+ oxidoreductase(phosphorylating) (EC 1.2.1.12) from rat skeletal muscle at 4 degrees C in 0.15 M NaC1, 5 mM EDTA, 4 mM 2-mercaptoethanol pH 7.2 is a first-order reaction. The rate constant of inactivation depends on protein concentration. With one molecule of NAD bound per tetrameric enzyme, a 50 per cent loss in activity is observed and the rate constant of inactivation becomes independent of the protein concentration over a 30-fold range. Two moles of NAD bound per mole of enzyme fully protect it against inactivation. NADH affords a cooperative effect on enzyme structure similar to that of NAD. Inactivation of 7.8 S apoenzyme is reflected in its dissociation into 4.8-S dimers. In the case of enzyme-NAD1 complex, no direct relationship between the extent of inactivation and dissociation is observed, suggesting that these two processes do not occur simultaneously; we may say that dissociation is slower than inactivation. A mechanism in which the rate-limiting step for inactivation is a conformational change in the tetramer occurring prior to dissociation and affecting only the structure of the non-liganded dimer, is consistent with the experimental observations. Inorganic phosphate protects apoenzyme against inactivation. Its effect is shown to be due to the anion binding at specific sites on the protein with a dissociation constant of 2.6 plus or minus 0.4 mM. The NaC1-induced cold inactivation of glyceraldehyde-phosphate dehydrogenase is fully reversible at 25 degrees C in the presence of 20 mM dithiothreitol and 50 mM inorganic phosphate. The rate of reactivation is independent of protein concentration. Inactivated enzyme retains the ability to bind specific antibodies produced in rabbits, but diminishes its precipitating capability.
 ...
PMID:Cold inactivation of glyceraldehyde-phosphate dehydrogenase from rat skeletal muscle. 16 22

Triiodothyronine (T3) treatment induced marked hypertrophy of the brown adipose tissue (BAT), similar to that observed in cold-acclimated animals, although partly due to fat deposition. Similar to cold acclimation, T3 treatment also increased the oxidation of succinate by tissue slices without concomitant increase in isolated mitochondria. It is therefore suggested that thyroid hormones, like cold acclimation, effect conformational changes in the mitochondria, leading to greater expression of the succinic oxidase in the tissue. T3 treatment was not followed by any change in the respiratory activity of tissue slices in the presence of alpha-GP. Likewise, no change was found either in other oxidative activities tested in isolated mitochondria (e.g., NADH and cytochrome oxidases) or in the concentration of the components of the electron transport chain in the mitochondria.
 ...
PMID:Metabolic activity of brown adipose tissue in T3-treated hamsters. 18 8

15 min cold exposure of rats adapted to cold results in switching on a pathway of the fast oxidation of extramitochondrial NADH in the isolated liver mitochondria. This pathway is sensitive to mersalyl and cyanide, resistant to amytal and antimycin A, and can be stimulated by dinitrophenol. A portion of the endogenous cytochrome c pool can easily be removed by washing mitochondria of the cold-exposed rats. A scheme is discussed, postulating desorption of the inner membrane-bound cytochrome c into intermembrane space of mitochondria, resulting in formation of a link between the non-phosphorylating NADH-cytochrome c reductase in the outer mitochondrial membrane and cytochrome c oxidase in the inner membrane. It is suggested that such an oxidative pathway is involved in the urgent heat production in liver in response to the cold treatment.
 ...
PMID:Activation of the external pathway of NADH oxidation in liver mitochondria of cold-adapted rats. 20 43

Thermal acclimation of rainbow trout (Salmo gairdneri) taken from 20 degrees C to 7 degrees C resulted in adaptation of mitochondrial function, as evidenced by increases in the specific activities of NADH- and succinate-cytochrome c reductase of 1.93- and 2.7-fold respectively. Mitochondria from both gill and liver obeyed the Boyle-van't Hoff relationship in the range from 400 to 60 mosM. Thermal acclimation had no effect on the osmotic properties of liver mitochondria, whereas gill mitochondria from cold-acclimated trout were more sensitive to osmotic swelling than mitochondria from warm-acclimated individuals. The non-electrolyte permeability of liver mitochondria was assessed by optically monitoring mitochondrial swelling rates in isosmotic solutions of urea, glycerol, mannitol and glucose. Two parameters of mitochondrial swelling were determined: (a) initial swelling rates, d(1/A)dt, and (b) swelling constants, ks, derived from the time required to swell a fixed volume. Regardless of the assay temperature or the permeant employed, liver mitochondria from cold-acclimated trout exhibited greater initial swelling rates than mitochondria from warm-acclimated trout, indicating properties of temperature-compensated permeability. The apparent ranking of nonelectrolyte permeabilities was urea greater than glycerol greater than mannitol greater than glucose. ks values for urea and glycerol from cold-acclimated trout were greater than values typical of warm-acclimated populations; however ks values for glucose and mannitol were not influenced by thermal acclimation. Regardless of the permeant considered, activation energies for ks values were 3- to 5-fold greater than those for initial swelling rates. The time course of mitochondrial swelling consists of two components, an initial rapid swelling phase characterized by a half-life of 3-12 seconds, and a slower swelling phase characterized by a half life of 1-6 minutes. Initial swelling rates, which approximate the rapid swelling component, are considered to be the least ambiguous index of permeability, whereas ks values are more complex and strongly influenced by the slower swelling component.
 ...
PMID:The effects of temperature and thermal acclimation upon the osmotic properties and nonelectrolyte permeability of liver and gill mitochondria from rainbow trout (Salmo gairdneri). 81 88

Cold acclimation caused the following changes in the brown adipose tissue (BAT) of the hamster: the relative weight of the tissue increased, it color darkened, the multilocular structure predominated, and tissue protein content increased while fat content decreased. There was also an increase in the mitochondrial protein content. Heat acclimation had the opposite effects, i.e., the color became lighter, total and mitochondrial protein decreased, fat content increased, and tissue structure was mostly unilocular. Accordingly, cold acclimation was accompanied by increased tissue respiration in the presence of chi-glycerophosphate (chi-GP) and succinate, whereas heat acclimation reduced the respiratory activity of the tissue with these substrates. Isolated BAT mitochondria from cold-acclimated animals increased activities of chi-GP and NADH oxidase, whereas the activities of succinic and cytochrome oxidases and the amount of mitochondrial cytochromes were unchanged. The effects of heat acclimation were more pronounced: there was a decrease in the activities of chi-GP, succinic, NADH, and cytochrome oxidases, as well as in the cytochrome a and a3 content. When respiration of tissue slices on succinate was compared to the maximal potential respiration, as measured with mitochondria disrupted by freezing and thawing, it was found that the relative activity (slices vs. disrupted mitochondria) was highest in cold-acclimated animals and decreased progressively with increasing acclimation temperatures. It is suggested that the differences in the apparent activity of the mitochondria were due to changes in the conformation of the mitochondria as a result of acclimation.
 ...
PMID:Metabolic adaptations in brown adipose tissue of the hamster in extreme ambient temperatures. 96 55

The protective effect of a new oligomeric derivative of prostaglandin B2, known as OC-5186, was evaluated using time-sharing spectrofluorometry in the cold-preserved rat liver. Experiments were divided into three groups: in group A, a 5000 ng dose of OC-5186 was administered via the peripheral vein, 1000 ng via the portal vein, and 200 ng/ml in University of Wisconsin (UW) solution; in group B, the OC-5186 dosage was ten times greater than that in group A; in group C (control group), liver procurement and storage were performed without OC-5186. At 0, 12, and 24 h after cold preservation at 4 degrees C, the liver was perfused for 30 min at 12 degrees C with oxygenized Krebs-Henseleit solution, after which the perfusate was switched to deoxygenized Krebs-Henseleit solution. Time sharing spectrofluorometry was used to follow NADH fluorescence at 450 nm with a 360-nm excitation wavelength, as well as the reflectance of cytochrome aa3 with 605 minus 620 nm from oxidation to reduction. Rate constants of NADH fluorescence and cytochrome aa3 reflectance were used as indices of integrity of the mitochondrial respiratory chain. In group C, the rate constant of NADH fluorescence decreased significantly (P < 0.05) from the control value of 8.31 +/- 0.21 x 10(-3) (sec-1) to 4.97 +/- 0.15 x 10(-3) and 5.58 +/- 0.16 x 10(-3) (mean +/- SEM) at 12 and 24 h after cold preservation, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Protective effect of a prostaglandin oligomer on liver mitochondria in situ: time-shared measurements of fluorescence and reflectance in the cold-preserved rat liver. 141 8

Time-dependent changes in the viability of rat liver graft during cold preservation with Euro-Collins solution were evaluated with NADH fluorometry. Correlation between the fluorometric analysis, 1-week survival rate after liver transplantation, and mitochondrial ATP synthesis activity in the early phase after transplantation was studied. Fluorometric study: Rat livers were preserved at 0 degree-4 degrees C for 0-48 h in Euro-Collins solution and then reperfused for 15 min with oxygenated Krebs-Henseleit solution at 4 degrees C. The amplitude (R x A) between the oxidized and the reduced steady-state NADH fluorometric trace and the velocity (R x V) of the trace were determined to evaluate the mitochondrial respiratory chain. The R x A and R x V remained at levels higher than 90% of control after 6-h preservation, while the R x A of the 9-h preservation group and the R x V of the 12-h preservation group decreased significantly compared with those of the control and the 6-h preservation group. Survival study: a 100% survival rate after transplantation was achieved in the 6-h preservation group, whereas the rates were 18.8% and 0% in the 9- and 12-h preservation groups respectively. These survival rates correlated closely with the time-dependent decrease of the fluorometric parameters. Study of mitochondrial phosphorylative activity and energy charge 3 h after transplantation: With fresh grafts, the decrease in hepatic energy charge after transplantation was reduced to 0.79 from the control value of 0.86 by a 30% increase in mitochondrial ATP synthesis ability.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Low-temperature fluorometric technique for evaluating the viability of rat liver grafts after simple cold storage. 151 64

We studied the efficacy of defibrotide, a prostacyclin-stimulating agent, in preventing ischemia reperfusion injury in Wistar rat heart by using three experimental models: (1) hearts from donors were perfused with the drug (32 mg/kg/hr) during 15, 30, 45, and 60 min of cold ischemia following 5, 10, and 15 min of warm ischemia; (2) hearts from donors treated with the drug were cold-stored for 12 or 24 hr; and (3) procured hearts perfused with the drug were isografted, after 30 or 60 min of warm ischemia, in recipient rats treated daily with defibrotide. Hearts perfused with saline and/or vehicle of the drug were used as controls. At the end of established ischemia times, and after 30 min, and 2, 4, 7 and 14 days from transplantation, hearts were rapidly cooled in liquid nitrogen. ATP, ADP, AMP, cAMP contents, and NAD+/NADH ratios were evaluated in prepared tissue extracts. Cardiac ATP and ADP levels and NAD+/NADH ratios were significantly higher in defibrotide-treated organs than in controls. Isografted defibrotide-treated hearts were also significantly preserved, with respect to controls, from the loss of ATP levels until rejection occurred. Our results demonstrate the protective activity of the drug against the myocardial metabolic damage due to ischemia-reperfusion.
 ...
PMID:Protection of rat heart from damage due to ischemia-reperfusion during procurement and grafting by defibrotide. 192 39

The presence of redox systems in microsomes of brown adipose tissue (BAT) in cold exposed rats was investigated and compared with liver. BAT microsomes showed high activity of lipid peroxidation measured both by the formation of malondialdehyde (MDA) and by oxygen uptake. NADH and NADPH dependent cytochrome c reductase activity were present in both BAT and liver microsomes. Aminopyrine demethylase and aniline hydroxylase activities, the characteristic detoxification enzymes in liver microsomes could not be detected in BAT microsomes. BAT minces showed very poor incorporation of [1-14C]acetate and [2-14C]mevalonate in unsaponifiable lipid fraction compared to liver. Biosynthesis of cholesterol and ubiquinone, but not fatty acids, and the activity of 3-hydroxy-3-methyl glutaryl CoA reductase appear to be very low in BAT. Examination of difference spectra showed the presence of only cytochrome b5 in BAT microsomes. In addition to the inability to detect the enzyme activities dependent on cytochrome P-450, a protein with the characteristic spectrum, molecular size in SDS-PAGE and interaction with antibodies in double diffusion test, also could not be detected in BAT microsomes. The high activity of lipid peroxidation in microsomes, being associated with large oxygen uptake and oxidation of NADPH, will also contribute to the energy dissipation as heat in BAT, considered important in thermogenesis.
 ...
PMID:Microsomal redox systems in brown adipose tissue: high lipid peroxidation, low cholesterol biosynthesis and no detectable cytochrome P-450. 210 21


1 2 3 4 5 6 7 8 9 10 Next >>