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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Winter survival for numerous cold-blooded animals includes freeze tolerance: the ability to endure the conversion of as much as 65% of total body water into extracellular ice. Selected molecular adaptations underlying freeze tolerance (e.g. cryoprotectants, ice nucleating proteins) have been widely studied, but the full range of metabolic adjustments needed for freeze endurance remains unknown. 2. Recent studies using gene screening techniques are providing a different approach to the search for biochemical responses that support freezing survival by identifying genes and proteins that are up-regulated by freezing or thawing in freeze-tolerant amphibians and reptiles. 3. Screening of a cDNA library from wood frog liver revealed the freeze-induced up-regulation of genes coding for the alpha- and gamma-subunits of fibrinogen (a plasma clotting protein), the mitochondrial ADP/ATP translocase and a novel 10 kDa protein containing a nuclear exporting sequence. 4. Northern blotting revealed that these genes were differentially responsive to two of the component stresses of freezing (dehydration and anoxia), indicating that different genes are induced by signals radiating either from cell volume change or oxygen deprivation during freezing. 5. Freeze up-regulation of fibrinogen synthesis in liver and other organs appears to be a damage repair response that anticipates a need for enhanced plasma clotting capacity to deal with ice crystal damage to capillary beds. 6. Up-regulation of ADP/ATP translocase in frog liver is linked with ischaemia resistance and studies with freeze-tolerant turtles have shown that other genes encoding proteins involved in mitochondrial energetics (NADH-ubiquinone oxido-reductase subunit 5, cytochrome C oxidase subunit 1) are also up-regulated by both anoxia and freezing exposures. 7. These studies are making major advances in our understanding of freeze tolerance as a natural phenomenon and also highlight new key areas that can be targeted by applied interventions for the optimization of medical cryopreservation techniques for cells, tissues and organs.
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PMID:Living in the cold: freeze-induced gene responses in freeze-tolerant vertebrates. 1002 71

Animal and plant uncoupling protein (UCP) homologues form a subfamily of mitochondrial carriers that are evolutionarily related and possibly derived from a proton/anion transporter ancestor. The brown adipose tissue (BAT) UCP1 has a marked and strongly regulated uncoupling activity, essential to the maintenance of body temperature in small mammals. UCP homologues identified in plants are induced in a cold environment and may be involved in resistance to chilling. The biochemical activities and biological functions of the recently identified mammalian UCP2 and UCP3 are not well known. However, recent data support a role for these UCPs in State 4 respiration, respiration uncoupling and proton leaks in mitochondria. Moreover, genetic studies suggest that UCP2 and UCP3 play a part in energy expenditure in humans. The UCPs may also be involved in adaptation of cellular metabolism to an excessive supply of substrates in order to regulate the ATP level, the NAD(+)/NADH ratio and various metabolic pathways, and to contain superoxide production. A major goal will be the analysis of mice that either lack the UCP2 or UCP3 gene or overexpress these genes. Other aims will be to investigate the possible roles of UCP2 and UCP3 in response to oxidative stress, lipid peroxidation, inflammatory processes, fever and regulation of temperature in certain specific parts of the body.
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PMID:The uncoupling protein homologues: UCP1, UCP2, UCP3, StUCP and AtUCP. 1062 Apr 91

The osmoregulatory isoform of dihydroxyacetone phosphate (DHAP) reductase (Osm-DHAPR) is an enzyme unique to Dunaliella, photosynthetic unicellular green algae adapted to extreme environments. This is the first report of purification of an isoform of DHAP reductase from Dunaliella, specifically the osmoregulatory isoform that is involved in the synthesis of free glycerol for osmoregulation in extreme environments, such as high salinity. The Osm-DHAPR is cold labile, inactivated by ammonium sulfate, forms a strong complex with Rubisco, and is unstable in the absence of glycerol. These difficulties have been addressed, and a four-step procedure has been developed to purify the Osm-DHAPR from Dunaliella tertiolecta: precipitation of Rubisco by polyethylene glycol, followed by successive chromatography on DEAE cellulose, Sephacryl S-200, and Red Agarose. Yield of the purified enzyme was 3.6%, with a specific activity of 938 micromol.min-1.mg-1 of protein and a subunit molecular mass of approximately 38 kDa. A maximum specific activity of 2580 micromol.min-1.mg-1 of protein could be achieved by assay with 150 mM NaCl. The Osm-DHAPR had little preference for NADH or NADPH, but it is highly specific for DHAP. Other metabolites of glycolysis, the tricarboxylic acid cycle, and the C3 reductive photosynthetic carbon cycle were not reduced by the enzyme. The purified enzyme was stimulated three-fold by 150 to 250 mM NaCl/KCl and by 25 mM MgCl2. Detergents, lipids, or long-chain acyl CoA derivatives, all of which inhibited the chloroplastic glyceride form of DHAP reductase, did not affect the activity of Osm-DHAPR. The Osm-DHAPR has different properties than the other chloroplastic isoform of DHAP reductase from plants and algae for glycerol phosphate formation and triglyceride synthesis.
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PMID:Osmoregulatory isoform of dihydroxyacetone phosphate reductase from Dunaliella tertiolecta: purification and characterization. 1192 56

Cold stress effects on the expression of genes for respiratory chain enzymes were investigated in potato (Solanum tuberosum L., cv. Desiree) leaves. The nda1 and ndb1 genes, homologues to genes encoding the non-proton-pumping respiratory chain NADH dehydrogenases of Escherichia coli and yeast, were compared to genes encoding catalytic subunits of the proton-pumping NADH dehydrogenase (complex I). Using a real-time PCR system, we demonstrate a specific and gradual decrease of the NDA1 transcript after exposing the plants to 5 degrees C. After 6 days of cold treatment the NDA1 transcript abundance is 10% of the original level. This decrease is accompanied by specific decreases of immunodetected NDA protein and internal rotenone-insensitive NADH oxidation in mitochondria isolated from cold-treated plants. The alternative oxidase is not cold-induced neither at the protein nor at the activity level. The results are discussed in relation to the recent finding that the nda1 gene expression is completely light-dependent.
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PMID:Cold stress decreases the capacity for respiratory NADH oxidation in potato leaves. 1206 13

The mitochondrial glycerol phosphate dehydrogenase (mGPD) is important for metabolism of glycerol phosphate for gluconeogenesis or energy production and has been implicated in thermogenesis induced by cold and thyroid hormone treatment. mGPD in combination with the cytosolic glycerol phosphate dehydrogenase (cGPD) is proposed to form the glycerol phosphate shuttle, catalyzing the interconversion of dihydroxyacetone phosphate and glycerol phosphate with net oxidation of cytosolic NADH. We made a targeted deletion in Gdm1 and produced mice lacking mGPD. On a C57BL/6J background these mice showed a 50% reduction in viability compared with wild-type littermates. Uncoupling protein-1 mRNA levels in brown adipose tissue did not differ between mGPD knockout and control pups, suggesting normal thermogenesis. Pups lacking mGPD had decreased liver ATP and slightly increased liver glycerol phosphate. In contrast, liver and muscle metabolites were normal in adult animals. Adult mGPD knockout animals had a normal cold tolerance, normal circadian rhythm in body temperature, and demonstrated a normal temperature increase in response to thyroid hormone. However, they were found to have a lower body mass index, a 40% reduction in the weight of white adipose tissue, and a slightly lower fasting blood glucose than controls. The phenotype may be secondary to consequences of the obligatory production of cytosolic NADH from glycerol metabolism in the mGPD knockout animal. We conclude that, although mGPD is not essential for thyroid thermogenesis, variations in its function affect viability and adiposity in mice.
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PMID:Normal thyroid thermogenesis but reduced viability and adiposity in mice lacking the mitochondrial glycerol phosphate dehydrogenase. 1209 99

Radiolabeled pyruvate, glucose, glucose-6-phosphate, acetate, and malate are all variously utilized for fatty acid and glycerolipid biosynthesis by isolated pea (Pisum sativum L.) root plastids. At the highest concentrations tested (3-5mM), the rates of incorporation of these precursors into fatty acids were 183, 154, 125, 99 and 57 nmol h-1 mg-1 protein, respectively. In all cases, cold pyruvate consistently caused the greatest reduction, whereas cold acetate consistently caused the least reduction, in the amounts of each of the other radioactive precursors utilized for fatty acid biosynthesis. Acetate incorporation into fatty acids was approximately 55% dependent on exogenously supplied reduced nucleotides (NADH and NADPH), whereas the utilization of the remaining precursors was only approximately 10 and 20% dependent on added NAD(P)H. In contrast, the utilization of all precursors was greatly dependent (85-95%) on exogenously supplied ATP. Palmitate, stearate, and oleate were the only fatty acids synthesized from radioactive precursors. Higher concentrations of each precursor caused increased proportions of oleate and decreased proportions of palmitate synthesized. Radioactive fatty acids from all precursors were incorporated into glycerolipids. The data presented indicate that the entire pathway from glucose, including glycolysis, to fatty acids and glycerolipids is operating in pea root plastids. This pathway can supply both carbon and reduced nucleotides required for fatty acid biosynthesis but only a small portion of the ATP required
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PMID:The Utilization of Glycolytic Intermediates as Precursors for Fatty Acid Biosynthesis by Pea Root Plastids. 1222 67

The present study compares the exogenous NAD(P)H oxidation and the membrane potential ([delta][psi]) generated in mitochondria isolated from different tissues of an important agricultural crop, sugar beet (Beta vulgaris}. We observed that mitochondria from taproots, cold-stored taproots, and in vitro-grown tissue cultures contain a functional NADH dehydrogenase, whereas only those isolated from tissue cultures displayed a functional NAD(P)H dehydrogenase. It is interesting that the NADH-dependent [delta][psi] of mitochondria from cold-stored taproots and from tissue cultures was not affected by free Ca2+ ions, whereas free Ca2+ was required for the mitochondrial NADPH oxidation by in vitro-grown cells and cytosolic NADH oxidation by mitochondria from fresh taproots. A tentative model accounting for the different response to Ca2+ ions of the NADH dehydrogenase in mitochondria from cold-stored taproots and tissue cultures of B. vulgaris is discussed.
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PMID:Oxidation of External NAD(P)H by Mitochondria from Taproots and Tissue Cultures of Sugar Beet (Beta vulgaris). 1223 47

Accumulation of polyols in insects is well known as a cold-hardening response related to overwintering or to protection against cold shock. The silverleaf whitefly (Bemisia argentifolii, Bellows and Perring) is a major insect pest in tropical and subtropical regions where heat stress and desiccation pose formidable threats to survival. We found that sorbitol levels increased ten-fold when whiteflies were exposed to elevated temperatures. Sorbitol levels rose from 0.16nmolwhitefly(-1) at 25 degrees C to 1.59nmolwhitefly(-1) at 42 degrees C. Sorbitol levels fluctuated diurnally under glasshouse and field conditions increasing ten-fold from morning to early afternoon. Feeding experiments on artificial diets showed that both temperature and dietary sucrose concentration were key factors influencing sorbitol accumulation. Cell free extracts prepared from adult whiteflies catalyzed NADPH-dependent fructose reduction, but were unable to reduce glucose with either NADPH or NADH. Radiotracer experiments with labeled glucose and fructose showed that fructose was the immediate precursor of sorbitol. Thus, sorbitol synthesis in the whitefly is apparently unconventional, involving conversion of fructose by a novel NADPH-dependent ketose reductase. We propose that sorbitol accumulation is a mechanism for thermoprotection and osmoregulation in the silverleaf whitefly, allowing the insect to thrive in environments conducive to thermal and osmotic stress.
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PMID:A thermoprotective role for sorbitol in the silverleaf whitefly, Bemisia argentifolii. 1276 42

Venous-systemic oxygen persufflation (VSOP) was performed in rat livers stored at 4 degrees C in either UW or HTK preservation solution. Since tissue anoxia is associated with a transformation of cellular NAD+ to NADH and the latter fluoresces upon UV-epiillumination, homogeneity and intensity of liver oxygenation could be analysed by intravital microscopic detection of NADH fluorescence. VSOP resulted in a significant decrease of the NADH signal, documenting effective tissue oxygenation in both UW and HTK. This effect was quite homogeneous (spatial variance < 15%). After 48 h of cold storage tissue levels of ATP (mumol/g dry weight) were increased upon VSOP in UW to 17.3 +/- 4.8 but only to 2.9 +/- 0.6 in HTK, while ATP amounted to less than 0.4 without VSOP in either of the groups. It is concluded that VSOP is an appropriate tool to prevent alterations of the hepatic redox status during ischemic preservation in UW and HTK. Metabolic preservation of energy-rich adenine nucleotides seems to be largely improved in combination with UW compared with HTK.
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PMID:[Differential effect of preservative solutions (UW vs HTK) on mitochondrial redux status and energy metabolism during liver ischemia with oxygen persufflation]. 1451 79

Hypothermic perfusion of the heart decreases oxidative phosphorylation and increases NADH. Because O(2) and substrates remain available and respiration (electron transport system, ETS) may become impaired, we examined whether reactive oxygen species (ROS) exist in excess during hypothermic perfusion. A fiberoptic probe was placed on the left ventricular free wall of isolated guinea pig hearts to record intracellular ROS, principally superoxide (O(2)(-).), and an extracellular reactive nitrogen reactant, principally peroxynitrite (ONOO(-)), a product of nitric oxide (NO.) + O(2)(-). Hearts were loaded with dihydroethidium (DHE), which is oxidized by O(2)(-). to ethidium, or were perfused with l-tyrosine, which is oxidized by ONOO(-) to dityrosine (diTyr). Shifts in fluorescence were measured online; diTyr fluorescence was also measured in the coronary effluent. To validate our methods and to examine the source and identity of ROS during cold perfusion, we examined the effects of a superoxide dismutase mimetic Mn(III) tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP), the nitric oxide synthase inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME), and several agents that impair electron flux through the ETS: menadione, sodium azide (NaN(3)), and 2,3-butanedione monoxime (BDM). Drugs were given before or during cold perfusion. ROS measured by DHE was inversely proportional to the temperature between 37 degrees C and 3 degrees C. We found that perfusion at 17 degrees C increased DHE threefold versus perfusion at 37 degrees C; this was reversed by MnTBAP, but not by l-NAME or BDM, and was markedly augmented by menadione and NaN(3). Perfusion at 17 degrees C also increased myocardial and effluent diTyr (ONOO(-)) by twofold. l-NAME, MnTBAP, or BDM perfused at 37 degrees C before cooling or during 17 degrees C perfusion abrogated, whereas menadione and NaN(3) again enhanced the cold-induced increase in ROS. Our results suggest that hypothermia moderately enhances O(2)(-). generation by mitochondria, whereas O(2)(-). dismutation is markedly slowed. Also, the increase in O(2)(-). during hypothermia reacts with available NO. to produce ONOO(-), and drug-induced O(2)(-). dismutation eliminates the hypothermia-induced increase in O(2)(-).
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PMID:Hypothermia augments reactive oxygen species detected in the guinea pig isolated perfused heart. 1464 63


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