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At least 577 records · Page 32Linked to original sources
PubMed1998

L-type Ca2+ current in fish cardiac myocytes: effects of thermal acclimation and beta-adrenergic stimulation.

A patch-clamp analysis of L-type Ca2+ current in ventricular myocytes of cold- and warm-acclimated rainbow trout (Oncorhynchus mykiss) and crucian carp (Carassius carassius) hearts was performed. Trout were acclimated at 4 and 17 degrees C and carp at 4 and 24 degrees C for a minimum of 4 weeks. Ventricular myocytes were isolated by enzymatic dissociation using collagenase and trypsin. Marked species-specific differences were noted in Ca2+ current density and its ss-adrenergic regulation. The density of basal Ca2+ current in crucian carp (6.9-7.4 pA pF-1) was almost double that of trout (4.2-4.5 pA pF-1) ventricular myocytes. Maximal beta-adrenergic stimulation increased Ca2+ current by approximately 2.3-fold in trout but by only 1.4-fold in crucian carp, so that Ca2+ current densities in the presence of 10 micromol l-1 isoprenaline were almost equal in trout (8.6-10.5 pA pF-1) and carp (9.6-10.4 pA pF-1) cardiac cells. Direct activation of adenylate cyclase by forskolin (10 micromol l-1) was also associated with similar interspecies differences in the stimulation of Ca2+ current. Thermal acclimation did not change either the density or the kinetics of L-type Ca2+ current in crucian carp ventricular myocytes. In trout cardiac cells, thermal acclimation had no effects on the density of Ca2+ current, but the rate of current inactivation was accelerated after acclimation to cold temperature. As a consequence of faster current decay, the contribution of sarcolemmal Ca2+ current to total cellular [Ca2+] was smaller in cold-acclimated than in warm-acclimated trout. The responses of Ca2+ current to maximal beta-adrenergic stimulation by isoprenaline or to direct activation of adenylate cyclase by forskolin were not changed by thermal acclimation in either species. It is concluded (1) that the density of sarcolemmal Ca2+ current is not increased after acclimation to cold, (2) that sarcolemmal Ca2+ influx through L-type Ca2+ channels can make a significant contribution to contractile [Ca2+] in both teleost species studied and (3) that ss-adrenergic stimulation of Ca2+ current is more important in modulating cardiac contractility in trout than in carp.

Acclimatization↗
PubMed2000

Hypothermia-related deaths--Alaska, October 1998-April 1999, and trends in the United States, 1979-1996.

Hypothermia is defined as an unintentional lowering of the core body temperature to < or = 95 F (< or = 35 C) (1). It is a medical emergency with a high fatality rate (2). In the United States, hypothermia-related deaths can occur anywhere, including in states with milder climates (e.g., Georgia and North Carolina) where weather systems can cause rapid changes in temperature. However, the highest hypothermia-related death rates in the United States occur in northern states, where winter is characterized by moderate to severe cold temperatures (e.g., Alaska and Montana), and western states, where profound declines in nighttime temperatures may occur at high elevations (e.g., New Mexico). From October 1998 through April 1999, 16 deaths attributed to hypothermia (International Classification of Diseases, Ninth Revision [ICD-9], codes E901.0, E901.8, and E901.9; excludes man-made cold [E901.1]) were reported to the Alaska State Medical Examiner. This report describes selected cases of hypothermia-related deaths in Alaska during October 1998-April 1999; compares age-, sex-, and race-specific rates in Alaska and the rest of the United States during 1979-1996; and summarizes trends for hypothermia-related deaths in the United States during 1979-1996.

Adolescent↗
PubMed1996

Profilin is required for the normal timing of actin polymerization in response to thermal stress.

We have used a fluorometric assay to determine the relative amounts of polymerized actin (F-actin) in wild-type and profilin mutant yeast cells. Our results indicate that profilin plays a role in maintaining normal F-actin levels in response to shifts to high temperature. Cells lacking profilin display a greater drop in F-actin levels upon such temperature shifts, and are slower to recover to initial F-actin levels than are wild-type cells. Interestingly, shifts to cold temperatures result in rapid increases of F-actin levels in wild-type and profilin null cells. We have further determined that shifting to high-osmolarity growth conditions causes a relatively slow decrease in F-actin levels in wild-type cells, and a small but rapid increase in the F-actin levels in profilin null cells. Profilin null cells contain normal concentrations of F-actin while growing exponentially at room temperature, indicating that profilin is not essential for maintaining F-actin concentrations during steady-state growth. Our data suggest that actin is inherently unstable in vivo at high temperatures, and that profilin helps to maintain actin in its filamentous state at these temperatures, perhaps by stimulating actin polymerization in a proper temporal and spatial fashion.

Actins↗
PubMed2004

Global patterns of plant leaf N and P in relation to temperature and latitude.

A global data set including 5,087 observations of leaf nitrogen (N) and phosphorus (P) for 1,280 plant species at 452 sites and of associated mean climate indices demonstrates broad biogeographic patterns. In general, leaf N and P decline and the N/P ratio increases toward the equator as average temperature and growing season length increase. These patterns are similar for five dominant plant groups, coniferous trees and four angiosperm groups (grasses, herbs, shrubs, and trees). These results support the hypotheses that (i) leaf N and P increase from the tropics to the cooler and drier midlatitudes because of temperature-related plant physiological stoichiometry and biogeographical gradients in soil substrate age and then plateau or decrease at high latitudes because of cold temperature effects on biogeochemistry and (ii) the N/P ratio increases with mean temperature and toward the equator, because P is a major limiting nutrient in older tropical soils and N is the major limiting nutrient in younger temperate and high-latitude soils.

Climate↗
PubMed1981

Regional and transmural myocardial temperature distribution in cold chemical cardioplegia: significance of critical coronary arterial stenosis.

There is a growing recognition of discrepancies in myocardial temperatures during cold chemical cardioplegia. This study was designed to determine the extent to which coronary arterial stenosis just sufficient to abolish vasodilatory reserve in the working heart, but still compatible with myocardial viability ("critical stenosis"), limits heat transfer from the heart during cardioplegic infusion compared to complete coronary occlusion and no stenosis (control). In nine dogs, temperatures were measured from the subepicardium, midwall, and subendocardium of the left ventricle in the distributions of the circumflex (CCA) and left anterior descending (LAD) coronary arteries plus the aortic root, septum, mediastinum, and ventricular cavities. Cardiopulmonary bypass was instituted with core cooling to 28 degrees C. Three infusions of cold (4 degrees C), radioactive microsphere-labeled, potassium chloride arresting solution were periods of reperfusion. The data (mean +/- SEM) indicate that myocardial cooling was transmurally uniform under all conditions, but was significantly impaired (p less than 0.01) in the CCA region by both critical stenosis (17.4 degrees +/- 1.2 degrees C) and occlusion (23.6 degrees +/- 0.4 degrees C) compared to control (8.3 degrees +/- 0.5 degrees C), because of reduced perfusate flow to regional tissues (4 = 0.62, p less than 0.001). These findings show that coronary artery lesions, including those compatible with myocardial viability, impose a severe constraint on myocardial heat transfer and point to a need for improved cardioplegic technique.

Animals↗
PubMed1979

Effects of contingent versus yoked temperature feedback on voluntary temperature control and cold stress tolerance.

Twenty-four male internals (locus of control) and 24 externals were instructed to increase finger temperature under one of three conditions: (1) contingent feedback (CF), (2) yoked sham feedback (YF), or (3) no feedback (NF). Five 13-min training sessions were given. Feedback was then removed and subjects tested for voluntary temperature control. Finally, the cold pressor test, a laboratory analogue of natural cold stress, was administered under no-feedback conditions. Results demonstrated voluntary control of peripheral temperature following contingent feedback training, but not after yoked feedback temperature training. Contrary to expectation, the acquisition of voluntary control did not attenuate the stress response to thermal pain. Differences between internals and externals throughout the study were generally insignificant.

Biofeedback, Psychology↗
PubMed1993

Spin trapping of superoxide radicals following stimulation of neutrophils with fMLP is temperature dependent.

Oxygen radical formation by human neutrophils stimulated with a chemotactic peptide, formyl-methionyl-leucyl-phenylalanine (fMLP), was studied through the use of spin trapping and superoxide dismutase-inhibitable reduction of oxidized cytochrome c. Both methods provided comparable data on temperature-dependent kinetics of superoxide radical formation, but hydroxyl radicals were also detected in spin-trapping experiments. When superoxide generation was monitored at 37 degrees C, the respiratory burst lasted only a few minutes. If the neutrophils were stimulated at 37 degrees C, but superoxide measurements were done at room temperature, the respiratory burst was again transient. However, neutrophils persistently generated superoxide when both stimulation and subsequent measurements were performed at room temperature. In the presence of the actin polymerization inhibitor, cytochalasin B, superoxide generation was persistent, even when measurements were conducted at 37 degrees C. A possible explanation for these observations is that the fMLP receptor complexes quickly aggregate and are internalized at physiological temperature, but not at room temperature. Very little superoxide was formed if cells were kept at a temperature of 4 degrees C for 1 h prior to fMLP addition, which is consistent with decreased expression of the fMLP receptor at cold temperatures.

Cytochalasin B↗
PubMed1986

Nucleotide binding by myosin in glycerol-extracted rabbit skeletal muscle fibres at temperatures between -35 degrees C and 10 degrees C.

Glycerol-extracted rabbit psoas fibres were incubated at temperatures between -35 degrees C and +10 degrees C in a low-ionic-strength relaxing solution containing 50% ethyleneglycol, 100 microM [3H]MgATP, 1 mM [14C]mannitol and less than 0.01 microM Ca2+. The fibres were then rinsed in a solution containing 1 mM ATP and the bound nucleotide eluted in trichloroacetic acid; all these operations were carried out at the cold temperature. Residual bound nucleotide was eluted with trichloroacetic acid at room temperature. The fibres were found to bind approximately 180 microM nucleotide, which is consistent with binding to the enzymatic site of myosin. The eluate, obtained in the cold, was analysed on poly(ethyleneimine)-cellulose for its ATP and ADP content. At temperatures down to -22 degrees C most of the bound nucleotide was ADP and there was little variation of this fraction with temperature. As the temperature was lowered below -22 degrees C the ATP fraction rose sharply; by -35 degrees C it predominated. These results are similar in type to those found by Biosca et al. [(1984) Biochemistry 23, 1947-1953] on isolated subfragment 1, but are displaced to a much lower temperature range. Thus in a muscle fibre only a low thermal energy is needed for myosin to hold its nucleotide in a constant balance between ATP and ADP.

Adenosine Diphosphate↗
PubMedDate not supplied

False-negative syphilis screening due to change in temperature.

BACKGROUND AND OBJECTIVES: Inaccurate test results for syphilis may cause an individual to experience serious effects. GOAL OF THE STUDY: Investigate potential sources of error and test limitations causing false-negative reactions. STUDY DESIGN: In 5 months, two laboratories screened 2,232 patients for syphilis by the Rapid Plasma Reagin (RPR) test. RESULTS: The hospital laboratory reported 5.3% (64/1,210) of patients' test as reactive on initial screening, and the research laboratory found 6.4% (78/1,210) reactive. Fourteen reactive patients were incorrectly reported negative by the hospital laboratory, as confirmed by both laboratories. A refrigerated centrifuge in the hospital laboratory possibly caused sera to be cooled before testing, producing false-negative results. When its temperature was adjusted from 4 degrees C to 27 degrees C, an additional 1,022 samples tested were consistent between the two laboratories. CONCLUSION: Cold temperature produces false-negative reactions for syphilis screenings in patients' samples with titers < 1:4 dilution. Patients' samples with titers > or = 1:16 dilution were not affected. According to this study, incorrect temperatures for test sera can alter testing outcomes. Therefore, test manufacturer's directions must be strictly followed.

Bias↗
PubMed1995

Effect of ambient temperature and humidity on performance of blood glucose meters.

The accuracy of four blood glucose meters (Accutrend, ExacTech Companion, Medisense Companion 2, and Glucometer III) was tested at temperatures ranging from 4 to 44 degrees C (control solutions) and 8 degrees C, 24 degrees C, and 36 degrees C (venous blood) and at humidities of 60% and 80%. Low and high temperatures resulted in a number of statistically significant changes in glucose readings with all meters. However, Accutrend, Medisense Companion 2, and Glucometer III were 100% clinically accurate at all temperatures. With the ExacTech Companion, only 70.8% of control solution and 55.6% of venous blood results were clinically accurate. The main errors were: (1) cold temperatures lowered the result so that euglycaemic levels erroneously read in the hypoglycaemic range and hyperglycaemic levels gave a better than actual result and (2) hot temperatures increased the result whereby hypoglycaemic levels falsely gave a euglycaemic result. Weather conditions at which blood glucose meters may be operated can affect results and potentially lead to errors in clinical decisions.

Blood Glucose↗
PubMed1962

Temperature.

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Body Temperature↗