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PubMed1987

Characterization of chromosome aberrations induced by incubation at a restrictive temperature in the mouse temperature-sensitive mutant tsFT20 strain containing heat-labile DNA polymerase alpha.

tsFT20 cells derived from a mouse mammary carcinoma cell line, FM3A, which has temperature-sensitive DNA polymerase alpha activity (Y. Murakami, H. Yasuda, H. Miyazawa, F. Hanaoka, and M. Yamada, Proc. Natl. Acad. Sci. USA, 82:1761-1765, 1985) were rapidly committed to death after temperature upshift to 39 degrees C. tsFT20 cells synchronized in S phase were more sensitive to the restrictive temperature than exponentially growing cells. In order to gain insight into the processes from the interruption of DNA synthesis to cell death, we analyzed chromosome aberrations induced in tsFT20 cells which had been incubated for 2 or 4 h at the restrictive temperature and then cultured at the permissive temperature. The majority of metaphase cells showed extensive chromosome aberrations such as chromatid gaps, breaks, and exchanges; chromosome pulverizations; their mixed types; and ring chromosomes. Analyses with the use of cell synchronization and autoradiography revealed that chromosome aberrations were induced only in the cells which synthesized DNA during incubation at 39 degrees C. We classified the chromosome aberrations into five types: gap or break type; exchange type; pulverization type; complex type; and ring type. The temporal order of the appearance of these types of chromosome aberrations was found to be the above described order. It was further found that cycloheximide dramatically repressed the induction of chromosome aberrations, and metaphases with many chromosome aberrations exhibited a large number of sister chromatid exchanges. These results indicate that abnormal cessation of DNA replication in tsFT20 cells at the restrictive temperature due to the inactivation of DNA polymerase alpha results in cell death via induction of double-strand breaks which lead to chromosome aberrations as well as sister chromatid exchanges.

Animals↗

PubMed1980

Somitogenesis in amphibian embryos. III. Effects of ambient temperature and of developmental stage upon pattern abnormalities that follow short temperature shocks.

Temperature shocks of a few minutes duration at 37 degrees C to tail-bud embryos of Rana induce zones of abnormal segmentation along the somite files subsequently produced. The immediate result of a temperature shock is a temporary arrest of development as a whole, following which the schedule of somite determination and formation is resumed at the normal rate. It is during the period immediately following this that the zone of abnormal somite pattern is determined. Thus the length of the abnormal zone reflects the total time taken by the morphogenetic system to recover from the disturbance, and might depend upon variables affecting both the duration of the initial arrest and the duration of the recovery period itself. Observations are presented demonstrating how the length of abnormal zones, caused by a temperature shock of any particular severity, are affected by three variables; (1) the ambient temperature to which the embryos were adapted before shock, (2) the ambient temperature of post-shock development, (3) the stage in somitogenesis, i.e. the number of somites already formed at the time of shock. The data (in this and previous papers of the series) support models postulating that the spatial periodicity in cell behaviour, that is somite morphogenesis, reflects a normal interaction between two hidden aspects of development, one a wavefront of cellular activation passing down the body axis, and the other having the character of a temporal periodicity throughout the tissue. Temperature shock, as well as halting the wavefront (i.e. stopping development) temporarily, leads to a subsequent period during which there is only gradual recovery of normal co-ordination between the periodicity within cells of the tissue and the wavefront progress. It is the relative rate of this recovery, alone, that is responsible for variation in the length of the abnormal zone.

Animals↗

PubMed1995

Autophagic death after cell cycle arrest at the restrictive temperature in temperature-sensitive cell division cycle and secretory mutants of the yeast Saccharomyces cerevisiae.

When virgin temperature-sensitive mutant cdc28 cells of the yeast Saccharomyces cerevisiae were incubated at restrictive temperatures, they continued to grow, reaching a maximum of 3.3-fold the original size after 24 h. The protein and RNA levels increased during the first 24 h, then gradually decreased. The cells that reached the maximal size lost proliferative activity and synthesized less protein. After a 72-h incubation, cellular components, protein, RNA and DNA, were progressively degraded, resulting in extensive fragmentation within 7 days. Light and electron microscopic observation revealed that cdc28 cells incubated at the restrictive temperature for 24 h were enriched with double-unit membranes in the cytoplasm, and the vacuoles were filled with autophagic body-like structures. After 7 days most cellular contents were lost, and the membrane systems were fragmented. The protein synthesis inhibitor cycloheximide added at 24 h inhibited degradation of protein for at least 7 days suggesting that protein synthesis was involved in the activation of autophagic death. All other temperature-sensitive cdc and secretory (sec) mutants tested showed similar morphological changes when arrested in the cell division cycle at the restrictive temperature. In contrast, the temperature-insensitive wild-type cells grew normally at 38 degrees C and only a few percent of them underwent autolysis 7 days after transfer to the stationary phase. These results suggested that the yeast cells underwent autophagic death when arrested at any stage of the cell division cycle, whereas those arrested at the stationary phase rarely underwent autophagic death.

Autophagy↗

PubMed1976

Effects of temperature and wind on facial temperature, heart rate, and sensation.

Skin temperature measurements of the face have shown that the cheek cools faster than the nose and the nose faster than the forehead. The cooling effect of wind is maximum at wind speeds between 4.5 and 6.7 m/s. Cold winds produce significant bradycardia, which is, however, much more pronounced during the expiratory phase of respiration. A significant correlation was noted between cooling of face and the reflex bradycardia observed. Similarly, a very significant correlation was noted between drop in skin temperature and subjective evaluation of cold discomfort. Consequently, the drop in skin temperature, reflex bradycardia, and subjective evaluation are parameters which are directly affected by cold wind and can be used as adequate indicators of the degree of discomfort. When comparing the present results with the windchill index, it was found that in the zone described as "dangerously cold" the index fits well with the physiological measurements. In the zone described as "bitterly cold," the index by comparison with actual skin temperature measurements and subjective evaluation underestimates the cooling effects of combined temperature and wind by approximately 10 degrees C.

Adult↗

PubMed1985

Effects of temperature acclimation on rabbit metabolic rate and rectal temperature.

The metabolic rates and rectal temperatures of cold-(10 degrees C), warm-(20 degrees C) and heat-(30 degrees C) acclimated rabbits were measured at 10, 20 and 30 degrees C. When the logarithm of metabolic rate was plotted against the logarithm of body weight, no differences could be demonstrated between the slopes of the lines obtained for each of the nine experimental groups. Metabolic rate, expressed as kcal h-1 kg-1, kcal h-1 kg-3/4 and kcal h-1 kg-2/3, was mass-independent for most of the experimental conditions. The rabbits were able to maintain constant rectal temperature during cold or heat exposure only when previously acclimated to these temperature extremes. The increase in metabolic rate of cold-acclimated rabbits observed during cold exposure seemed to be too low to explain the maintenance of rectal temperature. The lower metabolic rate of heat-acclimated rabbits exposed to heat probably played an important role in preventing increased rectal temperatures.

Acclimatization↗

PubMed1996

Infrared tympanic temperature as a predictor of rectal temperature in warm and hot conditions.

BACKGROUND: Infrared (IR) thermometry has been proposed as a rapid, non-invasive means of monitoring core temperature. However, it has not been validated for use in warm to hot environments. HYPOTHESIS: IR tympanic temperature (Tty) accurately predicts rectal temperature (Tre) during simulated marching in warm and hot conditions. METHODS: Tty, and thermistor-derived Tre, aural canal (Tac) and cheek skin (T cheek) temperatures were monitored in seven males during 100 min of treadmill walking, in combat uniforms, at 5 km.h-1, slope 6%, in warm (30 degrees C, 60% RH) and hot (40 degrees C, 30% RH) conditions. RESULTS: Tty was significantly different to Tre in hot, but not warm, conditions. Final Tty was 0.2 degrees C < Tre in warm, but 0.4 degrees C > Tre in hot, conditions. From 60-100 min of the warm trial, Tty predicted Tre with a standard error of estimate (SEE) of 0.15 degrees C (r = 0.9, p < 0.0001). In a multiple regression model, the combination of Tty, Tac, and Tcheek reduced this SEE to 0.1 degrees C. In the H trial, from 60-100 min Tty predicted Tre with a SEE of 0.21 degrees C (r = 0.7, p < 0.0001). Tty and Tac correlated significantly in both trials. CONCLUSIONS: (1) the IR method should provide useful estimates of Tre in the field provided the influence of ambient conditions is taken into account; (2) the IR method is not as reliable as rectal monitoring in distinguishing accurately between degrees of heat strain; and (3) Tre prediction with the IR device may be improved in warm conditions if skin temperatures are combined with Tty.

Adult↗

PubMedDate not supplied

Calibration of water proton chemical shift with temperature for noninvasive temperature imaging during focused ultrasound surgery.

The present work was performed to calibrate water proton chemical shift change with tissue temperature in vivo to establish a method of quantitative temperature imaging during focused ultrasound surgery. The chemical shift change measured with a phase-mapping method using spoiled gradient-recalled acquisition in steady state (SPGR) (TR = 26 msec, TE = 12.8 msec, matrix = 256 x 128) was calibrated with the corresponding temperature elevation (0-50 degrees C, 32-84 degrees C in absolute temperature) measured with a copper-constantan thermocouple (.05-mm-diameter bare wires) in rabbit skeletal muscle (16 animals) under focused ultrasound exposures (10-100 W radiofrequency [RF] power, 20-second sonication). A linear calibration with a regression coefficient of (-8.76+/-.69) x 10(-3) ppm/degrees C (P < .01 [P, significance level]) was obtained. Temperature distributions during a 20-second sonication were visualized every 3.3 seconds with a 2.3-mm3 spatial resolution and 4 degrees C temperature uncertainty.

Animals↗

PubMed2002

Temperature accuracy and temperature gradients in solution-state NMR spectrometers.

In solution-state NMR spectrometers, there is a systematic deviation between the temperature of the sample and the temperature reported by the spectrometer. In addition, temperature gradients are often present in the sample. The size of both the temperature deviations and the temperature gradients depends on several factors, including the temperature, the flow rate of the heating/cooling gas, and the amount of radiofrequency heating.

Journal Article↗

PubMed2001

Temperature measurement in microfluidic systems using a temperature-dependent fluorescent dye.

A technique is described for the measurement of fluid temperatures in microfluidic systems based on temperature-dependent fluorescence. The technique is easy to implement with a standard fluorescence microscope and CCD camera. In addition, the method can be used to measure fluid temperatures with micrometer spatial resolution and millisecond time resolution. The efficacy of the method is demonstrated by measuring temperature distributions resulting from Joule heating in a variety of microfluidic circuits that are electrokinetically pumped. With the equipment used for these measurements, fluid temperatures ranging from room temperature to 90 degrees C were measured with a precision ranging from 0.03 to 3.5 degrees C-dependent on the amount of signal averaging done. The spatial and temporal resolutions achieved were 1 microm and 33 ms, respectively.

Journal Article↗

PubMed2000

Temperature trends over the past five centuries reconstructed from borehole temperatures

For an accurate assessment of the relative roles of natural variability and anthropogenic influence in the Earth's climate, reconstructions of past temperatures from the pre-industrial as well as the industrial period are essential. But instrumental records are typically available for no more than the past 150 years. Therefore reconstructions of pre-industrial climate rely principally on traditional climate proxy records, each with particular strengths and limitations in representing climatic variability. Subsurface temperatures comprise an independent archive of past surface temperature changes that is complementary to both the instrumental record and the climate proxies. Here we use present-day temperatures in 616 boreholes from all continents except Antarctica to reconstruct century-long trends in temperatures over the past 500 years at global, hemispheric and continental scales. The results confirm the unusual warming of the twentieth century revealed by the instrumental record, but suggest that the cumulative change over the past five centuries amounts to about 1 K, exceeding recent estimates from conventional climate proxies. The strength of temperature reconstructions from boreholes lies in the detection of long-term trends, complementary to conventional climate proxies, but to obtain a complete picture of past warming, the differences between the approaches need to be investigated in detail.

Journal Article↗

PubMed2000

Metallic low-temperature resistivity in a 2D electron system over an extended temperature range

We report measurements of the zero-field resistivity in a dilute 2D electron system in silicon at temperatures down to 35 mK. This extends the previously explored range of temperatures in this system by almost an order of magnitude. On the metallic side, the resistivity near the metal-insulator transition continues to decrease with decreasing temperature and shows no low-temperature upturn. At the critical electron density, the resistivity is found to be temperature independent in the entire temperature range from 35 mK to 1 K.

Journal Article↗

PubMed1972

Aftereffects of low and high temperature pretreatment on leaf resistance, transpiration, and leaf temperature in xanthium.

Leaf resistance for water vapor (total diffusion resistance minus boundary layer resistance), transpiration, and leaf temperature were measured in attached leaves of greenhouse-grown Xanthium strumarium L. plants that had been pretreated for 72 hours with high (40 C day, 35 C night), or low (10 C day, 5 C night) air temperatures. Measurements were made in a wind tunnel at light intensity of 1.15 cal cm(-2) min(-1), air temperatures between 5 and 45 C, and wind speed of 65 cm sec(-1). Leaf resistances in low temperature pretreated plants were higher (8 to 27 sec cm(-1)) than in controls or high temperature pretreated plants (0.5 to 3 sec cm(-1)) at leaf temperatures between 5 and 25 C. Thus, the pretreatment influenced stomatal aperture.

Journal Article↗

PubMed1999

Room-temperature and low-temperature structure of Nd1-xCaxMnO3 (0.3 </= x </= 0.5).

The structure of the insulating manganites Nd(1-x)Ca(x)MnO(3) (0.3 </= x </= 0.5) has been studied against temperature using electron diffraction and neutron diffraction. At room temperature, the three compounds with x = 0.3, 0.4 and 0.5 exhibit the orthorhombic GdFeO(3)-type structure (a approximately 2(1/2)a(p), b approximately 2a(p), c approximately 2(1/2)a(p)). Below the charge-ordering temperature of approximately 250 K, a doubling of the lattice is observed along the a axis which could be interpreted as an ordering of the d(z(2)) Mn(3+) orbitals. The low-temperature polymorph has ortho-rhombic symmetry for x = 0.5 and monoclinic symmetry for x = 0.4 and 0.3. The low-temperature structure of the x = 0.4 sample was refined using neutron diffraction data. The HREM study at room temperature confirms the average GdFeO(3)-type structure and indicates the existence of defective areas with a lower symmetry.

Journal Article↗

PubMed2001

Temperature-dependent neutron powder diffraction study of the Ba(OD)(2) polymorphs: a new low-temperature phase.

The structural behaviour of both low-temperature beta- and high-temperature alpha-Ba(OD)(2), barium dihydroxide-d, was investigated at temperatures between 10 and 552 K by neutron powder diffraction. While the beta phase (P2(1)/n) remains stable to the lowest temperature investigated, the quenchable alpha phase (Pnma) shows a reversible orthorhombic-to-monoclinic phase transition between 100 and 150 K. The structure of the new alpha(m) phase (P2(1)/n) is quite similar to that of the alpha phase. This behaviour is unusual as a metastable phase transforms to another metastable phase. The Pnma <--> P2(1)/n low-temperature phase transition is driven by an order-disorder mechanism, mainly caused by one of the D atoms, which is disordered on positions off the mirror plane, mimicking a special position on the mirror plane in the orthorhombic phase. Refinements of the alpha phase above the phase transition indicate this disorder across the mirror plane through a conspicuously high isotropic displacement parameter if compared to the other D atoms. At low temperature the energy of the vibration is lowered and the D atom is frozen at a general position in a correlated way, thus violating the mirror plane and reducing the space-group symmetry.

Journal Article↗

PubMed1976

Body temperature responses at different ambient temperatures following injections of prostaglandin E1 and noradrenaline into the brain.

Since prostaglandins of the E series have been implicated in the production of fever by pyrogens, we have applied them directly to the anterior-hypothalamic preoptic area of uunanesthetized rats at various ambient temperatures. In this paper we have determined accurately the region of the brain of the rat from which temperature responses can be produced by local injection. In addition we present evidence to suggest that the responses to local injections of PGE1 are relatively unaffected by environmental temperatures, whereas those in response to injections of noradrenaline are influenced by ambient temperature. These results are discussed in light of similar findings with respect to the response to pyrogens in that it is relatively unaltered by ambient temperature. This work lends further support to the hypothesis that pyrogens act in the hypothalamus by releasing prostaglandins.

Amygdala↗

PubMed1995

The influence of colonic temperature changes in anaesthetised rats on tail skin temperatures and repeated testing of tail-flick latencies.

Tail-flick (TF) response latencies were measured in pentobarbitone-anaesthetized rats and variations with time, body and tail temperatures and 5 tail stimuli positions analysed with a mixed model analysis of variance. Variation with time was not significant. Highly significant differences (P < 0.001) were found between tail-flick latencies (TFLs) for tail temperatures and stimulus position. The most proximal tail position showed significantly different relationships for TFL with time and body temperature from other positions. The method described allows multiple TFLs to be measured in 1 animal with the potential of reducing the total number of animals in an experiment. Tail stimuli positions from proximal to distal sites showed a variation in response from 4.3 sec (95% CI: 4.2, 4.4) to 6.7 sec (95% CI: 6.6, 6.9). Rat tail stimulus position should therefore be standardised to allow reproducible measures of TFL and body temperature maintained within normal limits. TFLs were found to be abnormal at body temperatures above 39 degrees C.

Analysis of Variance↗

PubMed1995

Effects of age, reproductive status and ambient temperature on skin temperature regulation in the female rat.

In the present study, we evaluated a large population of aged Long-Evans female rats for the occurrence of spontaneous tail skin temperature (TST) surges. Young (5-7 months) normally cycling (NC) rats and aged (19-29 months), repeated pseudopregnant (PP) and constant estrous (CE) rats were placed in an environmentally controlled room with ambient temperatures of 24-25 degrees C or 29-30 degrees C and TST was monitored at 5 min intervals for 2 h. In young NC and aged PP rats, the incidence of TST surges (flushes) was 8-17% at low and 28-33% at high ambient temperature. Old CE rats exhibited a flushing incidence of 21% and 74% at ambient temperatures of 24-25 degrees C and 29-30 degrees C, respectively. The observed flushing episodes did not differ in their duration or amplitude among the three groups of rats. However, at both low and high ambient temperature, the frequency of flushes were significantly higher in old CE rats. Collectively, these data indicate that reproductive status, rather than age, is the important determinant of TST stability in the female rat. Further, elevated estrogen associated with the CE state may compromise, while elevated progesterone associated with the PP state has a protective effect on the stability of TST in the female rat.

Aging↗

PubMed1999

Rectal temperature time of death nomogram: sudden change of ambient temperature.

Cooling experiments on dummies known as body-like cooling were performed with sudden decrease and increase of ambient temperature in the order of 15 degrees C. In the case of a sudden decrease of ambient temperature, a second 'temperature plateau' occurs which is shorter than the known plateau at the beginning of body cooling. The cooling curves can be described mathematically by a three-step procedure based on the two-exponential term of the 'nomogram method'. The second plateau at the beginning of the second cooling phase in sudden decreased ambient temperature requires a lower value of the constant A (1.15) compared with the known value (1.25) at the beginning of body cooling. In the case of a sudden increase of ambient temperature in the order of 15 degrees C no procedure could be found to model the cooling curves mathematically.

Air↗