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At least 523 records · Page 29Linked to original sources
PubMed1976

Effect of rapid temperature change on mean body temperature and gill ventilation in carp.

Carp were transferred from 25 degrees C water to a calorimeter at 15 degrees C or from 15 degrees C water to a calorimeter at 25 degrees C. During cooling, dorsal muscle temperature (Tdm) and mean body temperature (Tb) were continuously monitored. During the first minutes Tb changed rapidly, while Tdm changed only slightly. In a 0.468-dg fish, Tdm decreased to two-thirds of the final value in 8.05 min, while Tb attained this value in 3.6 min. Tdm changed faster during heating than during cooling. Carp were also placed in a device where gill ventilation (VG) could be continuously monitored while rapid shifts in the temperature of the inspired water (TPINSP) AND/OR BODY SURFACE (Tbs) were effected. Changing Tinsp and Tbs both effected rate-sensitive changes in VG, although Tinsp was more effective. Decreases in Tinsp or Tbs produced decreases in VG; increases in Tinsp or Tbs had an opposite effect. The fish respiratory system is sensitive to the rate of change of external temperature. This sensitivity provides evidence for the existence of peripheral thermal input to the systems regulating respiration in teleost fish.

Adaptation, Physiological↗
PubMed1981

[Temperature gradients in the skin and heat loss in various environmental temperatures].

Increase of the chamber temperature from 15 degrees to 30 degrees C induced a significant drop in the heat emission and in temperature gradients on the rabbit nose, back and abdomen skin (1.0--1.2 and 2.0--2.5 mm from the surface). The revealed reduction of the temperature gradient values is within limits of thermoreceptor sensitivity. One can assume that the thermoreceptors situated on different skin layers are able to measure the temperature gradients (i. e. the heat flows).

Animals↗
PubMed1985

Effects of high ambient temperature on respiration rate, rectal temperature, fetal development and thyrold gland activity in tropical and temperate breeds of sheep.

The effects of high ambient temperatures on rectal temperature (RT), respiration rate (RR), fetal development and serum thyroxine (T(4)) concentrations were stuaied in two experiments involving 35 ewes and 26 lambs from the following ewe groups: 1) Barbados Blackbelly (B), a tropical breed; 2) Dorset (D), a temperate breed; and 3) Blackbelly x Dorset crosses (BxD). Data were obtained on four B, five D and five BxD ewes exhibiting estrus during the summer (Exp. 1). In Exp. 2, eight B, seven D and six BxD ewes were maintained in two environmental chambers (cool, 22.2C; hot, 33.8C) from day 125 of gestation to seven days before the expected lambing date for each breed group (D and BxD, 140+/-1; B, 144+/-1 day of gestation). The B and BxD ewes were more heat-tolerant than D ewes as measured by significantly lower RT and RR in each experiment. Mean lamb birth weight, crown-rump length, number of functional uterine caruncles and caruncle weight and size did not vary significantly among breed groups or temperature chamber (Exp. 2), and there was no indication that the high temperature imposed caused fetal dwarfing in lambs removed from the uterus at a standard age of seven days before expected parturition. Serum T(4) varied markedly among breed groups (P<0.05) in each experiment with B ewes having the lowest and BxD ewes the highest concentration. In Exp. 1, follicular stage T(4) concentrations in B and BxD ewes were lower (P<0.02) than those during the luteal stage of the estrous cycle. The decrease in D ewes was not significant. High ambient temperature (Exp. 2) depressed T(4) levels in D ewes (P<0.05) and also depressed the pituitary-thyroid response to thyrotropin releasing hormone in D lambs. Such was not the case in B and BxD ewes and their lambs.

Journal Article↗
PubMed2004

Low-temperature stability and high-temperature reactivity of iron-based core-shell nanoparticles.

Iron-based core-shell nanoparticles have been prepared that exhibit low-temperature stability and high-temperature reactivity toward oxygen in solution. The concentration of oxygen was determined from the fluorescence decay of pyrene. At low temperatures (<110 degrees C), the decays are short, indicating oxygen in solution. At higher temperatures (>110 degrees C), the decays become long and are consistent with no oxygen in solution. The change is abrupt, occurring over a narrow temperature range, and reproducible.

Journal Article↗
PubMed2005

Design and preparation of a novel temperature-responsive ionic gel. 2. Concentration modulation of specific ions in response to temperature changes.

We have designed a novel temperature-responsive dialysis system consisting of mixed electrolyte solutions and an ionic gel whose charge density changes in response to temperature changes. The system can modulate the time-concentration profile of just bivalent ions in arbitrary forms by changing the transport modes of the ions in response to the temperature, as long as the system has a sufficient concentration difference of the driving electrolyte for the modulation. The simulation in a model system consisting of mixed KCl and CaCl(2) solutions and the ionic gel shows that the system modulates the time-concentration profile of Ca(2+) ions as a sawtooth waveform and also keeps the concentration a prearranged value for a certain time period by controlling the transport modes of just Ca(2+) ions in two ways: downhill (transport along their own concentration gradient in a system) and uphill (transport against their own concentration gradient), in response to temperature changes. The simulations agree quantitatively with the experiments using a temperature-responsive ionic gel prepared in the previous paper.

Journal Article↗
PubMed2007

Effect of free volume and temperature on the structural relaxation in polymethylphenylsiloxane: a positron lifetime and pressure-volume-temperature study.

The microstructure of the free volume and its temperature dependence in polymethylphenylsiloxane (PMPS) have been examined using positron annihilation lifetime spectroscopy (PALS) and pressure-volume-temperature experiments. The hole-free volume fraction h and the specific hole-free and occupied volumes, Vf=hV and Vocc=(1-h)V, were estimated employing the Simha-Somcynsky (SS) lattice-hole theory. From the PALS spectra analyzed with the new routine LT9.0 the hole size distribution, its mean, , and mean dispersion, sigmah, were calculated. A comparison of with V and Vf delivered a constant specific hole number Nh'. Using a fluctuation approach the temperature dependency of the volume of the smallest representative freely fluctuating subsystem, , is estimated to vary from approximately 8.5 nm3 at Tg to approximately 3 nm3 at T/Tg>or=1.15. Unlike other polymers, the segmental relaxation from dielectric spectroscopy of PMPS follows the Cohen-Turnbull free volume theory almost perfectly in the temperature and pressure ranges between 243 and 279 K and 0 and approximately 100 MPa. This behavior correlates with the small mass of the SS lattice mer which indicates the high flexibility of the PMPS chain. Above 293 K and approximately 150 MPa, the free volume prediction gives relaxation times that are too small, which indicates that effects of thermal energy must be included in the analysis. To quantify the degree to which volume and thermal energy govern the structural dynamics the ratio of the activation enthalpies, Ei=R[(d ln taudT1)]i (tau-relaxation time of alpha relaxation), at constant volume V and constant pressure P, EV/EP, is frequently determined. The authors present arguments for necessity to substitute EV with EVf, the activation enthalpy at constant (hole) free volume, and show that EVf/EP changes as expected: increasing with increasing free volume, i.e., with increasing temperature and decreasing pressure. EVf/EP (=0.04-0.1) exhibits remarkably smaller values than EV/EP (=0.44-0.53), which leads to the inference that the free volume plays a distinctly larger role in dynamics than traditionally concluded from EV/EP. This conclusion is in agreement with the results of our more direct Cohen-Turnbull free volume analysis.

Journal Article↗
PubMed1996

Cool Temperature-Induced Chlorosis in Rice Plants (II. Effects of Cool Temperature on the Expression of Plastid-Encoded Genes during Shoot Growth in Darkness).

It has been proposed that cool temperature-induced chlorosis (CTIC) in Indica cultivars of rice (Oryza sativa L.) is caused by cell growth and plastid development being impeded at cool temperatures. Since it is well known that the overall rate of transcription of plastid-encoded genes changes dramatically during the early phases of plastid development, in this study we focused on the patterns of expression of these genes. Northern blot analysis revealed that the level of 16S rRNA is decreased in a CTIC-sensitive rice cultivar grown at a cool temperature. The expression of the gene for the [beta] subunit of plasmid RNA polymerase (rpoB) was shown to be somewhat disturbed, particularly in terms of its resuppression under cool conditions. The level of transcripts or proteins of plastid-encoded photosynthetic genes was also decreased in a CTIC-sensitive cultivar at a cool temperature. These results suggest that the temperature-dependent inhibition of the onset of gene expression encoding the transcription/translation apparatus may be primarily involved in the mechanism causing CTIC.

Journal Article↗
PubMed1967

Temperature and plant adaptation. I. Interaction of temperature and light in the synthesis of chlorophyll in corn.

The effect of temperature and light intensity have been studied in relation to the greening of etiolated corn (Zea mays cv. Pioneer 309-B) seedlings. Chlorophyll accumulation is rapid at high temperature (28 degrees ) under all conditions of light intensity. At low temperature (16 degrees ), and particularly in combination with high light intensity (3000-4500 ft-c), the accumulation of both chlorophyll and carotene is inhibited.Low pigment content at 16 degrees is not directly due to a block in the pigment synthesizing mechanism, but rather to the photodestruction of chlorophyll prior to its stabilization in the membrane structure of the chloroplast lamellae. The parallel reduction in carotene content at high light intensity is probably a contributing factor, because of its role in protecting chlorophyll from photodestruction. The greater severity of photo-oxidation of chlorophyll at low temperature in corn when compared with wheat, appears to be due to a slower rate of protochlorophyllide synthesis and subsequent esterification. Thus in corn at 16 degrees there is a prolongation of the photosensitive stage during chlorophyll synthesis. Photo-oxidation at 16 degrees has also been shown to be a function of the incident light energy, with the photosynthetic pigments acting as receptors for their own destruction.In comparison with the behavior of corn, wheat seedlings green rapidly at high light intensity at both 16 degrees and 28 degrees . This contrasting temperature response with respect to chlorophyll synthesis may underlie a fundamental difference in adaptation of these 2 species to growth in the temperate zones of the world.

Journal Article↗
PubMed1968

Studies on a maize mutant sensitive to low temperature I. Influence of temperature and light on the production of chloroplast pigments.

A mutant inbred line of Zea mays L. (M11) in which chlorophyll accumulation is particularly sensitive to low temperature is described. Under natural light conditions the chlorophyll content of seedlings is negligible below 17 degrees but is normal at high temperature. Seedlings of M11 can synthesize chloroplast pigments at 16 degrees but at a rate slower than normal. When photo-oxidation is minimized, chlorophyll accumulates, and seedlings can photosynthesize efficiently at low temperature. The primary site of low temperature sensitivity in M11 is the shoot apex where new leaves are developing and undergoing rapid cell expansion. It seems that there is impaired development and associated impaired function of chloroplasts in M11 grown at low temperatures which sensitizes them to rapid photo-oxidation in the light.

Journal Article↗
PubMed2004

All-fiber-optic infrared multispectral radiometer for measurements of temperature and emissivity of graybodies at near-room temperature.

An all-fiber-optic infrared multispectral radiometer for measurements of temperature and emissivity of graybodies at near-room temperature was constructed. Different spectral regions in the radiometer were obtained by use of hollow glass waveguides (HGWs) as filters. Using HGWs instead of bulk filters was advantageous because each HGW can be used as two different spectral filters when a dual-band IR detector is used. In addition, HGWs are much cheaper than the bulk IR filters that are usually used in such applications. For one graybody with a mean emissivity of 0.71, the estimated mean errors obtained for sample temperature, ambient temperature, and sample emissivity for all measured temperatures were 0.50% (approximately 1.65 K), 0.48% (approximately 1.4 K), and 7.3% (approximately 0.052) respectively. For a second graybody with a mean emissivity of 0.8 the estimated mean errors were 0.35% (approximately 1.2 K), 0.48% (approximately 1.4 K), and 5.0% (approximately 0.04), respectively.

Journal Article↗
PubMed2004

Scanning iron temperature lidar for mesopause temperature observation.

We introduce a new method for temperature profile measurements in the mesopause region in the altitude range from 80 to 105 km. A frequency-doubled narrowband alexandrite laser is used to scan the iron resonance line at 386 nm. The isotopic shifts of the iron isotopes and the laser bandwidth are derived by the measurement itself. Neglecting the minor isotopes results in large temperature errors up to 28 K. We discuss the derived temperatures in comparison with results of our potassium temperature lidar. The iron lidar-derived temperatures have typically a statistical error of 0.4 K and vary by less than 10 K, which is due to the daily natural variation. The all-solid-state system, which is compact, can be containerized and deployed at remote locations.

Journal Article↗
PubMed1996

Noninvasive temperature measurement in vivo using a temperature-sensitive lanthanide complex and 1H magnetic resonance spectroscopy.

A new lanthanide complex, praseodymium-2-methoxyethyl-DO3A, was tested as a temperature indicator for 1H magnetic resonance spectroscopy under in vivo conditions, using a 2-T imaging system. The chemical shift of the methoxy group of the compound is strongly temperature dependent. In vitro, a shift change of -0.131 ppm/degree C was found. The signal was shifted by about -24 ppm relative to the water signal, allowing easy water suppression and signal identification in vivo. The body temperatures of eight anesthetized rats were measured in the liver after intravenous administration of 1 mmol/kg of the praseodymium complex under different heating conditions of the animal. The temperatures calculated from the spectra were in good agreement (deviation < +/- 1 degree C) with values obtained simultaneously with a thermocouple placed in the rectum of the animals.

Anesthesia↗
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↗
PubMed1982

Photoperiod-induced changes in temperature-metabolism curve, shivering threshold and body temperature in the pigeon.

A short photophase combined with cold-acclimation changed the shivering threshold of the pigeon from 21 to 14 degrees C. The change of critical temperature was also found in the temperature-metabolism curve. A long photophase both alone and combined with warm-acclimation induced a reduction of body temperature to a lower level (about 2 degrees C) at all ambient temperature, ranging from 5 to 40 degrees C.

Acclimatization↗
PubMed2000

Can skin temperature manipulation, with minimal core temperature change, influence plasma volume in resting humans?

We investigated body-fluid distribution in resting humans, during short-term, whole-body skin temperature modification, in which core temperature changes (DeltaT(c)) were minimal. Seven males participated in hot (36.2 degrees C (s.d. 0.7), 44% relative humidity (rh; s.d. 3)), temperate (22.0 degrees C (s.d. 1.0), 52% rh (s.d. 6)), and cool trials (14.4 degrees C (s.d. 1.6), 74% rh (s.d. 9)), while seated at rest. Total body water (TBW), extracellular fluid (ECF), erythrocyte (RCV) and plasma volumes (PV) were measured using a simultaneous radionuclide dilution technique. In the cold, PV contracted by 205 ml (+/-60) by the end of exposure (p = 0.04), while in the heat, PV expanded 108 ml (+/-123; p = 0.02). Both RCV and TBW remained stable, regardless of the environment. Despite fluid movement across the vascular wall, ECF, interstitial and intracellular volumes were relatively unaffected by skin temperature. It was concluded that, at rest, and with minimal DeltaT(c), the intravascular fluid volume was dependent on prevailing environmental conditions, and its impact on local skin temperature and venomotor tone.

Adult↗
PubMedDate not supplied

Comparison of room temperature and body temperature local anaesthetic solutions.

The injection of local anaesthetic solutions is painful. We report the results of a blinded randomised controlled trial comparing the pain of injection of local anaesthetics at room temperature and body temperature. The results show that local anaesthetic solution injected at body temperature produces significantly less pain than local anaesthetic injected at room temperature.

Anesthetics, Local↗
PubMed1990

Temperature-mediated processes in immunity: differential effects of low temperature on mouse T helper cell responses.

A low culture temperature of 27 degrees C inhibited mouse primary in vitro anti-hapten plaque-forming cell responses to a thymus-dependent (TD) antigen (Ag) (trinitrophenyl-keyhole limpet hemocyanin, TNP-KLH). In contrast, the magnitudes of secondary responses to TNP-KLH or primary responses to a thymus-independent (TI) Ag (TNP-lipopolysaccharide (LPS)) were unaffected. The low-temperature-sensitive step in the primary TD response occurred relatively early and preceded interleukin 2 (IL-2) secretion. Furthermore, the low-temperature-induced suppression could be obviated (rescued) by recombinant IL-2 or IL-4, but not by IL-1. Thus, the low temperature appeared to inhibit the function of virgin Th cells by preferentially affecting T cell-derived interleukin synthesis/secretion and not other cellular activities. These results also imply fundamental differences between the activation requirements of memory and virgin Th cells.

Animals↗
PubMed1975

Hypothalamic temperature during the sleep cycle at different ambient temperatures.

Hypothalamic temperature during complete and incomplete sleep cycles (slow wave sleep followed by fast wave sleep and slow wave sleep followed by arousal, respectively) has been studied in freely moving cats at 20 degrees C and 0 degrees C ambient temperatures. The results show that sleep and thermoregulatory processes interact and, at 0 degrees C ambient temperature, become mutally exclusive. The occurrence of fast wave sleep is related to an opptimum range of hypothalamic temperatures which is specific in each enviromental conditions.

Animals↗