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At least 559 records · Page 31Linked to original sources
PubMed2002

Beating the cold: the functional evolution of troponin C in teleost fish.

The sensitivity of the cardiac myocyte contractile element for Ca(2+) decreases with temperature. As myocyte contractility is regulated by changes in cytosolic [Ca(2+)], this desensitizing effect represents a challenge for temperate fish such as the rainbow trout, Oncorhynchus mykiss, living in environments where temperatures are low and variable. To allow cardiac function in a temperate environment it is thought that the comparatively high Ca(2+) sensitivity of trout cardiac myocytes compensates for the effects of low temperature on myocyte contractility. The high Ca(2+) sensitivity of the trout myocyte is due, at least in part, to changes in the amino acid sequence of the thin filament protein, cardiac troponin C (cTnC). cTnC is the Ca(2+)-activated switch that triggers myocyte contraction. The isoform of cTnC cloned from trout ventricle (ScTnC) is 92% identical to mammalian cTnC (McTnC) and is significantly more sensitive to Ca(2+). This result suggests that ScTnC has evolved in trout to allow cardiac function at low temperatures. cTnC also appears to play a role in maintaining cardiac function when temperatures change. Increasing myofibrillar pH according to alpha-stat regulation, as would occur when temperature decreases, increases Ca(2+) sensitivity. A similar increase in pH also sensitizes cTnC to Ca(2+). ScTnC therefore appears critical in maintaining cardiac function in trout at low temperatures as well as during changes in temperature.

Acclimatization↗
PubMed1984

New standards for neutral thermal environment of healthy very low birthweight infants in week one of life.

It is generally accepted that low birthweight infants should be nursed at thermal neutral temperature--the environment in which oxygen consumption is at a minimum. Low birthweight infants do not, however, always show an increase in oxygen consumption at a temperature outside the neutral range, but react with a change in body temperature. We redefined therefore the neutral temperature for these infants as 'the ambient temperature at which the core temperature of the infant at rest is between 36.7 and 37.3 degrees C and the core and mean skin temperatures are changing less than 0.2 and 0.3 degrees C/hour respectively'. Using this definition, new guidelines of the neutral temperature have been made for healthy infants of 29-34 weeks' gestation. The neutral temperature during the first week of life is dependent on gestational age and postnatal age, whereas after the first week it depends on body weight and postnatal age. Using this definition and the guidelines, the appropriate environmental temperature for the individual patient can be chosen.

Body Temperature↗
PubMed1993

Circadian variation in peripheral blood flow in relation to core temperature at rest.

The aim of the present study was to examine the circadian variation in skin blood flow and its relationship to the rhythm of rectal temperature. Eight young men were confined to continuous bed rest for 24 h in a thermoneutral environment. Rectal temperature, oxygen consumption, and peripheral blood flow (laser-Doppler flowmetry and plethysmography) were measured at intervals of 2 h, except at 2400 hours and 0600 hours. According to the cosinor-method, the mean rectal temperature displayed a statistically significant circadian variation with a minimum at 0400 hours. A significant circadian rhythm was also observed in total finger blood flow, finger laser-Doppler flow, and forearm laser-Doppler flow, but not in total forearm blood flow and forehead laser-Doppler flow. The rhythms of rectal temperature and extremity skin blood flow were phased differently, i.e. the decrease in rectal temperature was preceded by an increase in extremity skin blood flow with an average of 4-h time difference. The results would support the idea that circadian rhythm of core temperature is, at least in part, regulated by variation in extremity skin blood flow.

Adult↗
PubMed2006

Structural relaxation of acetaminophen glass.

PURPOSE: The aim is to determine the structural stability of acetaminophen glass with time and temperature change, and to examine the merits of adapting the structural relaxation models of the glassy state for pharmaceuticals. METHODS: Differential scanning calorimetry technique has been used to study the acetaminophen glass after keeping the samples for various periods at fixed temperatures and after keeping at various temperatures for fixed periods. RESULTS: A general formalism for thermodynamic changes during storage in a temperature fluctuating environment is given and the kinetics of the enthalpy and entropy decrease determined. At a fixed temperature, the decrease occurs according to a non-exponential kinetics. For the same storage time, but at different temperatures, the enthalpy and entropy decrease rises to a maximum value at a certain temperature and then declines. The peak appears at the temperature at which the internally equilibrated state of the sample is reached for a fixed storage time. The change in the normalized heat capacity during the heating of acetaminophen has been analysed in terms of a non-exponential, non-linear enthalpy relaxation model. CONCLUSION: A single set of parameters that fit the data for unannealed acetaminophen glass does not fit the calorimetric data for annealed glass. Since acetaminophen molecules form intermolecular hydrogen-bonds in the crystal state and likely to form such bonds more easily in the disordered state, effect of such bonds on structural relaxation is likely to be significant.

Acetaminophen↗
PubMed2005

Improved superfusion technique for rapid cooling or heating of cultured cells under patch-clamp conditions.

We have developed an improved technique for fast cooling and heating of solutions superfusing isolated cells under patch-clamp or calcium imaging conditions. The system meets the requirements for studying temperature dependency of all kinds of ion channels, in particular temperature-gated ion channels. It allows the application of temperature changes within a range of 5-60 degrees C at maximum rates of -40 degrees C/s to 60 degrees C/s. Barrels filled with different solutions are connected to a manifold consisting of seven silica capillaries (320 microm inner diameter, i.d.). A common outlet consists of a glass capillary through which the solutions are applied onto the cell surface. The upper part of this capillary is embedded in a temperature exchanger driven by a miniature Peltier device which preconditions the temperature of the passing solution. The lower part of the capillary carries an insulated copper wire, densely coiled over a length of 7 mm, and connected to a dc current source for resistive heating. The Peltier device and the heating element are electrically connected to the headstage probe which is fixed on to a micromanipulator for positioning of the manifold. The temperature of the flowing solution is measured by a miniature thermocouple inserted into the common outlet capillary near to its orifice which is placed at a distance of less than 100 microm from the surface of the examined cell. The temperature is either manually controlled by voltage commands or adjusted via the digital-to-analog converter of a conventional data acquisition interface. Examples are given of using the device in patch-clamp studies on heterologously expressed TRPV1, TRPM8, and on cultured rat sensory neurons.

Action Potentials↗
PubMed2002

Variability in thermal response of primed and non-primed seeds of squirreltail [Elymus elymoides (Raf.) Swezey and Elymus multisetus (J. G. Smith) M. E. Jones].

Bottlebrush squirreltail [Elymus elymoides (Raf.) Swezey = Sitanion hystrix (Nutt.) J. G. Smith] and big squirrel-tail [Elymus multisetus (J. G. Smith) M. E. Jones = Sitanion jubatum (J. G. Smith)] have a broad geographical distribution and have been identified as high priority species for restoration of degraded rangelands in the western United States. These rangelands exhibit high annual and seasonal variability in seedbed microclimate. The objective of this study was to examine variability in thermal response of both primed and non-primed seeds of these species in the context of field-variable temperature regimes. Seed priming treatments were selected to optimize germination rate in a low-temperature test environment. Primed and non-primed seeds were evaluated for laboratory germination response under 12 constant temperature treatments between 3 and 36 degrees C. Thermal time and base temperature were estimated by regression analysis of germination rate as a function of temperature in the sub-optimal temperature range. The thermal germination model and 6 years of field temperature data were used to simulate the potential germination response under different field planting scenarios. Seed priming reduced the total germination percentage of some seedlots, especially at higher germination temperatures. Seed priming increased the germination rate (reduced the number of days to 50 % germination) by 3.8-8.4 d at 6 degrees C with a mean germination advancement of 6.9 +/- 0.6 d. Maximum germination advancement in the model simulations was 5-10 d for planting dates between I March and 15 May. Model simulations can be used to expand germination analysis beyond simple treatment comparisons, to include a probabilistic description of potential germination response under historical or potential future conditions of seedbed microclimate.

Germination↗
PubMed2006

[Condition and mechanism of formation of mummy in Shanghai region].

To investigates the condition and the mechanism of the formation of mummy in Shanghai region. Three cases of mummy were normaly examinated. It showed that the formation condition of mummy were influenced by season, scene, and the corpse keeping methods etc. In warm and damp southern region in Shanghai, the mummy formation depended on lower temperature, dry environment season, dehydrated and hunger before death, and interfered factors like ventilating and turning over corpse frequently.

Autopsy↗
PubMedDate not supplied

Infant weight and gestational age effects on thermoneutrality in the home environment.

OBJECTIVE: To describe infant temperature in the home environment and explore factors, particularly weight and gestational age at birth, associated with maintenance of thermal neutral temperatures in the home. DESIGN: Continuous abdominal skin temperature was recorded at 1-minute intervals for a 24-hour period in both full-term and preterm infants, using a two-group exploratory design. SETTING: Infants were studied in the home environment. PATIENTS/PARTICIPANTS: Twenty-four preterm and 16 full-term infants were studied at approximately 44 weeks postconceptional age. MAIN OUTCOME MEASURES: Abdominal skin temperature was coded as within, over, or under the thermal neutral zone, and the percentage of time in these thermal conditions was calculated. RESULTS: Regression analysis was conducted, and weight, gestational age, and weight by gestational age interaction were found to be statistically significant predictors of percent of time over and under the thermal neutral zone. Smaller preterm infants were overheated, whereas heavier preterm infants were underheated. Smaller full-term infants were underheated, and heavier full-term infants were overheated. CONCLUSION: Thermal care of infants in the home may be influenced by parental perception of thermal vulnerability relative to weight and gestational age at birth.

Body Temperature Regulation↗