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At least 235 records · Page 13Linked to original sources
PubMed2000

Mechanism and prevention of cold storage-induced human renal tubular cell injury.

BACKGROUND: The recent observation that cold storage of kidneys and tubular cells causes marked increase in free radical-catalyzed F2-isoprostanes suggests that radicals might be formed during cold storage. As cold temperature is associated with reduced metabolic and enzymic activity, the notion that cold temperature causes free radical production appeared less tenable. The objective was, therefore, to seek direct evidence for the free radical production during the cold storage of human renal tubular cells, and to define the roles of extrinsic and intrinsic antioxidants in cold-induced cell injury. METHODS: Human renal tubular cells were cold-stored at 4 degrees C for varying duration in University of Wisconsin solution and subjected to mRNA analysis, biochemical measurements, and cytoprotective studies. RESULTS: Cold storage caused a time-dependent reduction in glutathione levels, and an increase in the formation superoxide, hydrogen peroxide, and hydroxyl radicals. Cold-induced lactate dehydrogenase (LDH) release, ATP depletion, DNA damage, and membrane degradation were suppressed with the inclusion of antioxidant 2-methyl aminochroman or deferroxamine. The cells that were structurally protected with antioxidants were also intact functionally, as they had significantly improved cell proliferation. To examine the effect of cold on intrinsic antioxidant gene expression, antioxidant mRNA levels were analyzed using reverse transcription-polymerase chain reaction. The gene expression of mitochondrial Mn-superoxide dismutase (SOD), but not of cytosolic Cu,Zn-SOD or of glutathione peroxidase expression increased with cold exposure. The oxidant-sensitive gene heme oxygenase I increased slightly with 48-hr cold storage. CONCLUSIONS: Cold storage of human tubular cells causes marked increase in free radicals. These are likely of mitochondrial origin as there is a differential inducement of Mn-SOD gene, and are causal to cold-induced cell injury as extrinsic antioxidants abrogated the injury. Our findings support the strategy of adding antioxidants to preservation solutions or the strategy of pre-conditioning the organs to oxidative stress to minimize cold storage-induced organ damage.

Adenosine↗
PubMed1977

An improved HRP method for the study of central nervous connections.

The HRP tract-tracing method has been modified by the introduction of cryoprotective agents, thereby allowing the enzymatic reaction to take place at sub-zero temperatures. By using cold temperatures the enzymatic reaction can be better controlled, which in turn makes it possible to "push" the method to its maximum without obtaining excessive crystallization. The addition of antifreeze agents, however, changes the acid-base phenomena, which in turn have to be adjusted by the use of appropriate buffers. The overall result is a considerable increase in efficiency as compared with the commonly used HRP procedure.

Acid-Base Equilibrium↗
PubMed2006

Histamine and its receptors modulate temperature-preference behaviors in Drosophila.

Temperature profoundly influences various life phenomena, and most animals have developed mechanisms to respond properly to environmental temperature fluctuations. To identify genes involved in sensing ambient temperature and in responding to its change, >27,000 independent P-element insertion mutants of Drosophila were screened. As a result, we found that defects in the genes encoding for proteins involved in histamine signaling [histidine decarboxylase (hdc), histamine-gated chloride channel subunit 1 (hisCl1), ora transientless (ort)] cause abnormal temperature preferences. The abnormal preferences shown in these mutants were restored by genetic and pharmacological rescue and could be reproduced in wild type using the histamine receptor inhibitors cimetidine and hydroxyzine. Spatial expression of these genes was observed in various brain regions including pars intercerebralis, fan-shaped body, and circadian clock neurons but not in dTRPA1-expressing neurons, an essential element for thermotaxis. We also found that the histaminergic mutants showed reduced tolerance for high temperature and enhanced tolerance for cold temperature. Together, these results suggest that histamine signaling may have important roles in modulating temperature preference and in controlling tolerance of low and high temperature.

Animals↗
PubMed2005

Seasonal adjustments in body mass and thermogenesis in Mongolian gerbils (Meriones unguiculatus): the roles of short photoperiod and cold.

Seasonal adjustments in body mass and thermogenesis are important for the survival of small mammals during acclimatization in the temperate zone. To determine the contributions of short photoperiod and cold temperatures to seasonal changes in thermogenesis and body mass in Mongolian gerbils (Meriones unguiculatus), body mass, basal metabolic rate (BMR), nonshivering thermogenesis (NST), energy intake and energy digestibility were determined in seasonally acclimatized and laboratory acclimated animals. Body mass showed significant seasonal changes and decreased to a minimum in winter. Both BMR and NST increased in winter, and these changes were mimicked by exposing animals to short photoperiod or cold temperatures in the animal house. Digestible energy intake also increased significantly in winter, and also during exposure of housed animals to both short photoperiod and cold. These results suggest that Mongolian gerbils overcome winter thermoregulatory challenges by increasing energy intake and thermogenesis, and decreasing body mass to reduce total energy requirements. Short photoperiod and cold can serve as effective environmental cues during seasonal acclimatization.

Acclimatization↗
PubMed2005

[Treatment of freezing injury].

Report on therapeutic procedures in patients with second and third degree congelations (frostbite) on the feet. Two mechanisms of tissue damage caused by exposure to cold temperature will be discussed pathophysiologically: direct freezing injuries and cell death through intra and extracellular ice crystal formation as well as transient and finally irreversible tissue damage due to decreased perfusion. The condition of decreased perfusion results from persistent vaso-constriction induced by cold temperature, increased blood viscosity, sludge phenomenon and occlusion by platelet thrombi in the microvasculature. Frostbite beyond the erythematous stage should be treated primarily with a parenteral therapy in order to improve the hemorrheologic parameters, in particular within the micro-vascular compartment. Colloidal plasma volume expander such as 10% dextran solution is used to increase the intravascular volume. This solution (with its coating effect) and pentoxifyllin lowers the aggregation of erythrocytes and platelets. The latter will also be favourably influenced by the use of iloprost or acetylsalicylic acid. Iloprost as a stable metabolite of prostacyclin is a powerful vasodilator which attenuates the peripheral vascular resistance and activates fribrinolysis. Pentoxifyllin is considered to lower pathologically increased levels of fibrinogen. Both drugs may protect against damage of the vascular endothelium. Based on their pharmacological effects the above-mentioned drugs may improve tissue perfusion and therefore tissue damage caused by frostbite can be limited. However, an important factor is to strictly avoid bacterial infections in the cold-damaged tissue.

Blood Viscosity↗
PubMed1980

Capacity of old versus young male rats to release thyrotropin (TSH), thyroxine (T4) and triiodothyronine (T3) in response to different stimuli.

Serum TSH, T4 and T3 were measured by radioimmunoassay (RIA) in 20-24 month old and 6-8 month old Long-Evans male rats during basal conditions, and upon exposure to cold temperature (4 degrees C), injection of ovine TSH, thyroidectomy, and T4 or T3 treatment. Basal serum TSH values in the old and young rats were similar, but serum T4 and T3 levels in the old rats were significantly lower than in the young rats. No differences were observed in TSH release between old and young rats in response to cold temperature, but old rats whowed no rise in serum T4, TSH administration produced a significantly smaller increase in serum T4 in old rats, but similar increases in serum T3 in old and young rats. No differences were observed between old and young rats in the rise of serum TSH after thyroidectomy, or in the fall of serum TSH after T4 or T3 administration. These results are believed to indicate that the primary cause for reduced thyroid function in old rats lies in the thyroid gland itself.

Aging↗
PubMed1984

Temperature-dependent deacylation of molecular species of phosphatidylcholine by microsomal phospholipase A2 of thermally acclimated rainbow trout, Salmo gairdneri.

Using the ratios of kinetic parameters, V/Km, the deacylation of different molecular species of 1-palmitoyl,2-acyl phosphatidylcholine via microsomal phospholipase A2 (PLA2) was studied in liver tissue of thermally acclimated rainbow trout (Salmo gairdneri). In general, PLA2 from fish acclimated to cold temperatures showed an order of preference for the acyl moieties of 18:1 greater than 18:2 greater than 18:0. Trout acclimated to warm temperatures generally preferred 18:0 PC, but the actual order of preference depended on the temperature of the assays and the presence of endogenous lipids in the enzyme preparation. At 5 C, the particulate (microsomal) enzyme preferred 18:0 greater than 18:2 greater than 18:1, but a lipid-free preparation of the enzyme preferred 18:2 greater than 18:0 greater than 18:1. At 20 C, particulate enzyme preferred 18:1 greater than 18:0 greater than 18:2 but purified enzyme preferred 18:0 greater than 18:2 greater than 18:1. Thus, assay temperature and the presence of microsomal lipids had a greater effect on PLA2 from fish acclimated to warm temperatures than fish acclimated to cold temperatures. The substrate preference of PLA2 is discussed with reference to the previously observed changes in membrane fatty acid composition that occur with thermal acclimation in rainbow trout.

Acclimatization↗
PubMed2006

Growth and leaf physiology of monkeyflowers with different altitude ranges.

Every species is limited both geographically and ecologically to a subset of available habitats, yet for many species the causes of distribution limits are unknown. Temperature is thought to be one of the primary determinants of species distributions along latitudinal and altitudinal gradients. This study examined leaf physiology and plant performance under contrasting temperature regimes of sister species of monkeyflower, Mimulus cardinalis and Mimulus lewisii (Phrymaceae), that differ in altitude distribution to test the hypothesis that temperature is the primary determinant of differences in fitness versus altitude. Each species attained greatest aboveground biomass, net photosynthetic rate, and effective quantum yield of photosystem II when grown under temperatures characteristic of the altitudinal range center. Although both species exhibited greater stem length, stomatal conductance, and intercellular CO2 concentration in hot than in cold temperatures, these traits showed much greater reductions under cold temperature for M. cardinalis than for M. lewisii. Survival of M. lewisii was also sensitive to temperature, showing a striking decrease in hot temperatures. Within each temperature regime, the species native to that temperature displayed greatest growth and leaf physiological capacity. Populations from the altitude range center and range margin of each species were used to examine population differentiation, but central and marginal populations did not differ in most growth or leaf physiological responses to temperature. This study provides evidence that M. cardinalis and M. lewisii differ in survival, growth, and leaf physiology under temperature regimes characterizing their contrasting low and high altitude range centers, and suggests that the species' altitude range limits may arise, in part, due to metabolic limitations on growth that ultimately decrease survival and limit reproduction.

Altitude↗