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PubMedDate not supplied

Long-term exposures to higher environmental temperature and body temperature: effect of chlorpromazine in relation to hypothalamic GABA.

Treatment with a single dose of chlorpromazine (CPZ; 1 mg/kg, ip) at room temperature (28 degrees +/-0.5 degrees C) significantly reduced body temperature by its anticholinergic action. Long-term exposures to higher environmental temperature (40 degrees +/-0.5 degrees C, 2 h/day, for 30 consecutive days) increased body temperature significantly by reduction of hypothalamic GABAergic activity, but this increase in body temperature was attenuated from that observed with a single exposure to higher environmental temperature (40 degrees C for 2 h). Treatment with a single dose of CPZ on the last day of 30 consecutive days of exposures to higher environmental temperature increased body temperature of rats more than that observed with long-term exposures to higher environmental temperature possibly due to (i) reduction of hypothalamic GABAergic activity, (ii) heat dissipation and (iii) reverse-anticholinergic action of CPZ at higher environmental temperature.

Animals↗

PubMed1999

Local brain surface temperature compared to temperatures measured at standard extracranial monitoring sites during posterior fossa surgery.

Mild hypothermia is assumed to protect against secondary brain injury. However, the accuracy of brain temperature estimation remains debatable if direct measurement in the target area is to be avoided or is impossible. Furthermore, intracerebral temperature gradients exist, especially under intraoperative conditions. We aimed to establish how brain surface temperatures (TBrain) relate to temperatures taken at standard sites in posterior fossa surgery. Ten patients undergoing cerebellopontine angle tumor removal were monitored for TBrain, esophageal temperature (TEso), bladder temperature (TBlad), ipsi- and contralateral tympanic membrane (TTymp-I, TTymp-C), and scalp temperatures (TScalp). During monitoring, TEso increased from 35.3+/-0.2 degrees C to 36.0+/-0.3 degrees C. After dura opening, TBrain was -0.14+/-0.1 degrees C below TEso. At the end of tumor removal, this difference increased to -0.43+/-0.31 degrees C (P < 0.05). TTymp-C was -0.29+/-0.18 degrees C below TBrain at dura opening. TTymp-C reflected the behavior of TEso adequately (r = 0.938), however, with a mean difference of -0.39+/-0.04 degrees C. In contrast, TTymp-I readings closely followed temperature changes in the area of surgery. TBlad reflected TEso except in periods of rapid temperature changes. In posterior fossa (PF) surgery, local TBrain is most accurately reflected by TEso. For clinical use TBlad and TTymp-C are also sufficient to assess brain surface temperature in the PF. Intraoperative surface cooling of the brainstem is less than the previously described cooling rate of exposed cerebral cortex.

Adult↗

PubMed1988

Effects of urethane, ambient temperature and injection route on rat body temperature and metabolism due to endotoxins.

1. We have investigated the influence of environmental temperature, anaesthesia and route of administration on rectal temperature and other metabolic responses to two preparations of bacterial endotoxin in male adult Wistar rats. 2. Urethane anaesthesia, environmental temperatures of 20 and 28 degrees C, subcutaneous (S.C.) and intraperitoneal (I.P.) routes of administration and butanol and trichloroacetic acid (TCA) extracts of E. coli endotoxin (1.2 mg/kg) were used. 3. In addition to rectal temperature, serum zinc, albumin and urea concentrations and liver protein, RNA and zinc contents were measured. 4. Fevers were produced by injections of both endotoxins, by either route at 28 degrees C. Butanol-extracted endotoxin produced a more rapid response than the TCA extract via the I.P. route whereas the TCA extract produced a higher temperature than the butanol extract when the S.C. route was used. 5. Fevers were inhibited at an environmental temperature of 20 degrees C and by anaesthesia, while the former had no effect on compositional changes the latter inhibited the fall in serum zinc in response to subcutaneous doses of either endotoxin and the increase in liver zinc content in response to the butanol extract of endotoxin. 6. At 20 degrees C a marked fall in rectal temperature occurred in conscious rats 2 h after receiving the TCA but not the butanol extract of endotoxin. Temperature depression was more severe when endotoxin was administered by the I.P. route. 7. Serum urea was elevated in conscious rats by the TCA extract of endotoxin via both routes but only by the I.P. route for the butanol extract of endotoxin. In anaesthetized animals only the TCA extract of endotoxin raised serum urea concentration when given intraperitoneally. 8. Serum albumin and liver protein and RNA were unaffected by endotoxin injections over the 7 h time course of the study. 9. Rectal temperature responses to endotoxins were influenced in direction and magnitude by all variables employed in the study, while compositional changes were unaffected by environmental temperature but influenced to varying degrees by urethane anaesthesia and the route of administration employed.

Anesthesia↗

PubMed2002

Temperature effects and genotype-temperature interactions on sex determination in the European sea bass (Dicentrarchus labrax L.).

The effect of temperature on sex-ratios in 27 families of sea bass reared in the same tank from the fertilization stage onward was investigated. An excess of males (68%) was found in the groups that were reared at high temperature (mean +/- standard deviation: 20+/-1 degrees C) until they reached the mean size of 8.1 cm (Standard Length, 149 days post-fertilization [p.f.]). Masculinization was higher (89% of males) in the groups maintained at low temperature (13 degrees C), from fertilization to a mean length of 6.5 cm (346 days p.f.). Shifts from high to low temperature at 8.1cm and from low to high temperature at 6.5 cm had no consequence on the sex-ratio. The percentage of males showing intratesticular oocytes was higher at low temperature (63%) than at high temperature (36%), suggesting that these males may be sensitive fish that have been masculinized by environmental factors. Fish sampled in the groups reared at high (2,200 fish) and low (500 fish) temperature were genotyped on three microsatellite loci. This allowed them to be assigned to the breeders used in the crossing design, thus permitting an analysis of parental influence on sex-ratios. In groups reared at high temperature, both parents had a significant additive effect on the percentage of females, and the interaction between sire and dam was not significant. Genotype temperature interactions were also detected and their existence suggests the interesting possibility of selecting nonsensitive genotypes in breeding programs.

Adaptation, Physiological↗

PubMed2007

Determination of regional brain temperature using proton magnetic resonance spectroscopy to assess brain-body temperature differences in healthy human subjects.

Proton magnetic resonance spectroscopy ((1)H MRS) was used to determine brain temperature in healthy volunteers. Partially water-suppressed (1)H MRS data sets were acquired at 3T from four different gray matter (GM)/white matter (WM) volumes. Brain temperatures were determined from the chemical-shift difference between the CH(3) of N-acetyl aspartate (NAA) at 2.01 ppm and water. Brain temperatures in (1)H MRS voxels of 2 x 2 x 2 cm(3) showed no substantial heterogeneity. The volume-averaged temperature from single-voxel spectroscopy was compared with body temperatures obtained from the oral cavity, tympanum, and temporal artery regions. The mean brain parenchyma temperature was 0.5 degrees C cooler than readings obtained from three extra-brain sites (P < 0.01). (1)H MRS imaging (MRSI) data were acquired from a slice encompassing the single-voxel volumes to assess the ability of spectroscopic imaging to determine regional brain temperature within the imaging slice. Brain temperature away from the center of the brain determined by MRSI differed from that obtained by single-voxel MRS in the same brain region, possibly due to a poor line width (LW) in MRSI. The data are discussed in the light of proposed brain-body temperature gradients and the use of (1)H MRSI to monitor brain temperature in pathologies, such as brain trauma.

Adult↗

PubMed2005

Absolute temperature, temperature changes and stroke risk: a case-crossover study.

Studies suggest that there is an association between weather patterns and ischemic stroke risk. Exposure to a sudden decrease in temperature may increase stroke risk through altering blood viscosity and/or by triggering infections. We investigated the association between ischemic stroke risk and change in temperature. We used a case-crossover study design with 303 consecutive patients admitted to Heidelberg University, Department of Neurology over a one and a half year period (Aug 1998-Jan 2000). We used one day before stroke as the hazard (case) period matched to two control periods 2-7 days before and after stroke onset and took both ambient maximum temperature and the 24-hour difference in maximum temperature as exposure. There was no risk associated with ambient maximum temperature at all lag times and in all subgroup analyses. For the 24-hour difference, large changes in temperature (>5 degrees C) were associated with an increased risk of acute ischemic stroke regardless of whether the change was negative or positive. The odds ratio for temperature increases >5 degrees C compared to no change in temperature was 2.0 (95% confidence interval (CI): 0.7-5.9) at a lag time of 3 days. We found no relevant relation between temperature and stroke risk. The results suggest that the risk of ischemic stroke may increase with large day-to-day variations upwards or downwards in temperature.

Adolescent↗

PubMed1988

Effects of temperature and temperature gradients on ion-sensitive microelectrodes.

Ion-sensitive microelectrodes are widely used in studies of mammalian tissues. Often the tissue is maintained at 37 degrees C, some 10-15 degrees C above room temperature. The temperature difference between the room and the preparation was found to be capable of altering the measured ion potential by as much as 10 mV. The change depended on 3 factors: the temperature dependence of the Nernst slope, the temperature dependence of the interference factor, and the thermoelectric potential induced by the temperature difference between the two ends of the ion-exchanger column. Certain combinations of these changes can cancel each other, resulting in spurious but apparently temperature-insensitive readings. The first two factors can produce errors when the temperature of calibration differs from the temperature of the tissue being measured. Serious errors in measurements of ion concentration can also occur, due to all 3 factors, if a temperature gradient exists across the ion exchanger column; this situation can easily occur when recording from exposed mammalian tissues. The use of a short ion-exchanger column will reduce but not eliminate effects due to a temperature gradient.

Animals↗

PubMed2004

Effect of high-temperature on high-performance liquid chromatography column stability and performance under temperature-programmed conditions.

Six commercially available analytical (4.1 or 4.6 mm i.d.) columns were evaluated under temperature-programmed high-temperature liquid chromatography (HTLC) conditions to access their stability and performance at extreme temperatures. Seven components consisting of acidic, basic and neutral compounds were analyzed under temperature-programmed conditions and solvent gradient conditions using three different mobile phase compositions (acidic, basic and neutral). Each column was checked with a two-component test mix at various stages of the evaluation to look for signs of stationary phase collapse. Three zirconia based stationary phases studied exhibited column bleed under temperature-programmed conditions. The other three columns, a polydentate silica column, a polystyrene-divinylbenzene (PS-DVB) polymeric column, and a graphitic carbon column performed well with no evidence of stationary phase degradation. The R.S.D. for the retention times and efficiencies were less than 10% for most conditions, and not more than 15% during the course of the evaluation for each column. The polydentate silica stationary phase was temperature programmed to 100 degrees C, the PS-DVB stationary phase was temperature programmed up to 150 degrees C, and the graphitic carbon column was used with temperature programming up to 200 degrees C. Comparable peak capacities and similar retention behaviors were observed under solvent gradient and temperature-programmed conditions. Temperature programming with dynamic mobile phase preheating can replace solvent gradient analysis without a loss of peak capacity when used with 4.1 or 4.6 mm columns.

Chromatography, High Pressure Liquid↗

PubMed2006

Interstitial temperature mapping during Prolieve transurethral microwave treatment: imaging reveals thermotherapy temperatures resulting in tissue necrosis and patent prostatic urethra.

OBJECTIVES: Temperature mapping of the prostate during transurethral microwave thermotherapy and imaging of the resultant zones of tissue necrosis have been previously performed using several commercial systems. This study was performed using the Prolieve Thermodilatation System, which simultaneously compresses the prostate with a 46F balloon circulating heated fluid and delivering microwave energy into the prostate. METHODS: Interstitial temperature mapping during Prolieve treatment was performed on 10 patients with benign prostatic hyperplasia using 24 temperature sensors arrayed throughout the prostate. Voiding cystourethrograms were performed on 3 additional patients treated without temperature mapping to document the patency of the prostatic urethra 1 hour after treatment. Gadolinium-enhanced magnetic resonance imaging studies were performed on all patients 1 week after treatment to determine the extent and pattern of tissue necrosis resulting from transurethral microwave thermotherapy. RESULTS: Interstitial temperature mapping found that the heating pattern generated by the Prolieve system created average peak temperatures of 51.8 degrees C an average of 7 mm away from the prostatic urethra. These temperatures were greater near the bladder neck and mid-gland than toward the prostatic apex. Subtherapeutic temperatures were seen adjacent to the urethra, consistent with the viable tissue seen on gadolinium-enhanced magnetic resonance imaging sequences. Magnetic resonance imaging also revealed necrotic zones that were consistent with sustained temperatures greater than 45 degrees C. Voiding cystourethrograms showed widely patent prostatic urethras 1 hour after treatment. CONCLUSIONS: Transurethral microwave thermotherapy with the Prolieve Thermodilatation System produced sustained therapeutic temperatures that resulted in tissue necrosis while maintaining viable tissue surrounding a temporarily dilated prostatic urethra.

Body Temperature↗

PubMed1998

Constant temperature monitoring: a study of temperature patterns in the postanesthesia care unit.

Patients admitted to the PACU from the operating room exhibit fluctuations in core body temperature during the course of their stay in the PACU. Some patients present with normothermia and experience temperature decreases later in their stay. PACU policy does not dictate that temperatures be measured at a predetermined frequency in the absence of hypothermia; thus, it is possible that hypothermia may not be detected at its onset. The major purpose of this study was to describe the core body temperature patterns of postsurgical patients during the PACU stay. Secondary objectives were to (1) identify at which point in time patients become hypothermic and (2) describe length of stay in patients who develop hypothermia. Hypothermia was defined as a core tympanic temperature of less than 35.5 degrees C. A descriptive design was used using a convenience sample of 150 elective surgical patients over the age of 1 month who were normothermic on admission to the PACU. Data were analyzed using descriptive statistics. Concurrent tympanic and continuous axillary temperatures were monitored for comparison and trend monitoring. Temperatures showed clinically significant decreases into the hypothermic range (< 35.5 degrees C). Fifty-seven percent of the sample (n = 86) had temperatures that dropped after PACU admission and another 13% fell below 35.5 degrees C. Hypothermia occurred within the first 15 minutes of the PACU stay. The average length of stay for those that developed hypothermia was 1.83 hours. Monitoring temperatures more frequently will result in detecting hypothermia at its onset. Nurses may use the axillary device as a trend for continuous monitoring. Length of stay may be shortened if temperature management is embraced by the PACU nurse.

Adolescent↗

PubMed1995

Rhythms of temperature selection and body temperature are out of phase in the golden hamster.

Body temperature, locomotor activity, and thermoregulatory behavior of freely moving golden hamsters maintained in a spatial thermocline were measured over several weeks. The thermoregulatory behavior of temperature selection exhibited a robust daily rhythm 180 degrees out of phase with the rhythms of body temperature and locomotor activity. However, the parameters of the body temperature rhythm (rhythmicity, mean level, and amplitude) were not significantly affected by the thermoregulatory behavior. Although the observed phase difference between the rhythms of temperature selection and body temperature might suggest that thermoregulatory behavior is modulated to oppose (rather than to defend) the rhythm of body temperature, the absence of effect of temperature selection on the parameters of the body temperature rhythm fails to reveal the physiological significance of such opposition. Further studies are necessary to establish the physiological significance of the rhythm of temperature selection.

Animals↗

PubMed2005

Cochlear temperature correlates with both temporalis muscle and rectal temperatures. Application for testing the otoprotective effect of hypothermia.

CONCLUSIONS: During systemic hypothermia, the internal temperature of the rat cochlea correlates best with the temporalis muscle and rectal temperatures. These positive correlations will be used in future studies to assess the efficacy of mild and moderate hypothermia to protect hearing against the progressive loss caused by electrode insertion in a clinically relevant model of cochlear implantation trauma. OBJECTIVE: To monitor the internal temperature of the cochlea during induced systemic hypothermia using a reference tissue instead of an internal cochlear temperature probe. MATERIAL AND METHODS: The temperatures of the cochlea, brain, temporalis muscle and rectum were determined during periods of normothermia (37 degrees C), mild (33 degrees C) and moderate (30 degrees C) hypothermia and slow rewarming in anesthetized adult Fisher rats. These values were compared using statistical analysis to establish the best correlations between the temperature of the cochlea and the temperature at the three other temperature measurement sites. RESULTS: The strongest correlations with the internal temperature of the cochlea during the induction of mild-to-moderate hypothermia were obtained for the temperatures of the ipsilateral temporalis muscle and rectum.

Animals↗

PubMedDate not supplied

Incubation of turtle eggs at different temperatures: do embryos compensate for temperature during development?

Freshwater turtle eggs are normally subjected to fluctuations in incubation temperature during natural incubation. Because of this, developing embryos may make physiological adjustments to growth and metabolism in response to incubation at different temperatures. I tested this hypothesis by incubating eggs of the Brisbane river turtle Emydura signata under four different temperature regimes, constant temperatures of 24 degrees C and 31 degrees C throughout incubation, and two swapped-temperature treatments where incubation temperature was changed approximately halfway through incubation. Incubation at 31 degrees C took 42 d, and incubation at 24 degrees C took 78 d, with intermediate incubation periods for the swapped-temperature treatments. Hatchling mass, hatchling size, and total oxygen consumed during development were similar for all incubation regimes. The pattern of oxygen consumption during the last phase of incubation as reflected by rate of increase of oxygen consumption, peak oxygen consumption, and fall in oxygen consumption before hatching was determined solely by the incubation temperature during the last phase of incubation; that is, incubation temperature during the first phase of incubation had no influence on these factors. Thus there is no evidence of temperature compensation in growth or development during embryonic development of E. signata eggs.

Analysis of Variance↗

PubMed2005

Temperature acclimation of photosynthesis: mechanisms involved in the changes in temperature dependence of photosynthetic rate.

Growth temperature alters temperature dependence of the photosynthetic rate (temperature acclimation). In many species, the optimal temperature that maximizes the photosynthetic rate increases with increasing growth temperature. In this minireview, mechanisms involved in changes in the photosynthesis-temperature curve are discussed. Based on the biochemical model of photosynthesis, change in the photosynthesis-temperature curve is attributable to four factors: intercellular CO2 concentration, activation energy of the maximum rate of RuBP (ribulose-1,5-bisphosphate) carboxylation (Vc max), activation energy of the rate of RuBP regeneration (Jmax), and the ratio of Jmax to Vc max. In the survey, every species increased the activation energy of Vc max with increasing growth temperature. Other factors changed with growth temperature, but their responses were different among species. Among these factors, activation energy of Vc max may be the most important for the shift of optimal temperature of photosynthesis at ambient CO2 concentrations. Physiological and biochemical causes for the change in these parameters are discussed.

Acclimatization↗

PubMed1997

Temperature guided radiofrequency catheter ablation of myocardium: comparison of catheter tip and tissue temperatures in vitro.

Temperature monitoring during RF ablation has been proposed as a means of controlling the creation of the lesion. However, in vivo studies have shown poor correlation between lesion size and catheter tip temperature. Thus, we hypothesized a difference between catheter tip and tissue temperatures during RF catheter ablation, and that this difference may depend on flow passing the ablation site, tip electrode length, and catheter-tissue orientation. In vitro studies were performed using four different ablation catheters (tip electrode length: 2, 4, or 6 mm) with a thermistor or a thermocouple as temperature sensor. Set temperature was 70 degrees C and pulse duration was 30 seconds. Pieces of porcine left ventricle were immersed in a bath of isotonic saline-dextrose solution at 37 degrees C. The ablation catheters were positioned perpendicularly, obliquely, or parallel to the endocardium. A temperature sensor was inserted from the epicardial side and positioned 1 mm beneath the catheter-tissue interface. Experiments were made with a flow of 200 mL/min passing the ablation site or with no flow. The catheter tip and tissue temperatures differed significantly (P < 0.0001) during ablation. This difference increased with time, with flow passing the ablation site, with the length of the tip electrode, and when the catheter was positioned perpendicularly or obliquely to the endocardium as compared to the parallel catheter-tissue orientation (P < 0.05). In conclusion, the tissue temperature may far exceed the catheter tip temperature, and intramyocardial superheating resulting in steam formation and popping may occur despite a relatively low catheter tip temperature.

Animals↗

PubMed2000

Production of pectate lyases and cellulases by Chryseomonas luteola strain MFCL0 depends on the growth temperature and the nature of the culture medium: evidence for two critical temperatures.

Several extracellular enzymes that are responsible for plant tissue maceration were detected in culture supernatant of the psychrotrophic bacterium Chryseomonas luteola MFCL0. Isoelectrofocusing experiments showed that pectate lyase (PL) activity resulted from the cumulative action of three major isoenzymes, designated PLI, PLII, and PLIII. Cellulolytic activity was also detected in culture supernatants. These enzymes exhibited different behaviors with respect to growth temperature. PLII was not regulated by temperature, whereas PLI and PLIII were regulated similarly by growth temperature. Maximal levels of PLI and PLIII were produced at 14 degrees C when cells were grown in polygalacturonate-containing synthetic medium and at around 20 to 24 degrees C in nutrient broth. In contrast, thermoregulation of cellulolytic activity production differed from thermoregulation of PL. The level of cellulolytic activity was low in all media at temperatures up to 20 degrees C, and then it increased dramatically until the temperature was 28 degrees C, which is the optimal temperature for growth of C. luteola. Previously, we defined the critical temperature by using the modified Arrhenius equation to characterize bacterial behavior. This approach consists of monitoring changes in the maximal specific growth rate as a function of temperature. Our most striking result was the finding that the temperature at which maximum levels of PLI and PLIII were produced in two different media was the same as the critical temperature for growth observed in these two media.

Cellulase↗

PubMed1970

Thermoelectrically cooled temperature-gradient apparatus for comparative cell and virus temperature studies.

Establishment of a near-linear temperature gradient in an incubator has been accomplished by the application of heat to one terminus of a conducting body, normally a metal bar, and the removal of heat from the other terminus of the conducting body. Such incubators have been complex and unwieldy because of the need for mechanical refrigeration. We have described a simplified temperature gradient incubator which uses thermoelectric module cooling coupled with electric heating. Along the gradient, 20 stations in two parallel rows of 10, each accommodating a 30-ml plastic cell culture flask, were continually monitored by an electronic thermometer, and the temperatures were recorded. By manipulation of two simple potentiometer controls, any temperature gradient between 0 and 50 C could be obtained. Minor deviations which occurred between theoretically perfect and obtained temperature gradients were reproducible and readily measured. The gradient incubator was particularly applicable to (i) simultaneously studying a given biological activity over the entire temperature range supporting the growth of a given cell, virus, or microorganism, or (ii) precisely defining the upper or lower temperature limits of a biological system by 10-point determinations. Preliminary experiments have demonstrated the usefulness of the apparatus in characterizing the temperature limits for growth in vitro of cells of reptilian cell lines. The gradient incubator was also successfully utilized for the characterization of the effect of temperature on the efficiency of plating of amphibian viruses and possible temperature variants of those viruses.

Animals↗

PubMed1988

Relationship of scrotal surface temperature measured by infrared thermography to subcutaneous and deep testicular temperature in the ram.

The right testis of 9 anaesthetized rams was removed from the parietal tunica vaginalis and replaced by a surrogate testis (water-filled balloon) through which water of known temperature was circulated. Thermistors were inserted in the surrogate testis, between the scrotal skin and parietal tunica vaginalis on the right side, and deep within the intact left testis. Scrotal surface temperatures over the surrogate and intact testes were measured by infrared thermography. Scrotal surface temperature was correlated (P less than 0.01) with both subcutaneous (r = 0.95) and surrogate (r = 0.91) testicular temperature. The temperature differential between scrotal surface (30.1 +/- 0.1 degrees C) and deep testicular temperature over the intact side (34.9 +/- 0.09 degrees C) was 4.8 degrees C at an ambient temperature between 24.0 and 26.6 degrees C. Contact with the scrotal skin is not required to measure scrotal surface temperature by infrared thermography. This, coupled with the close association between scrotal surface temperature and that of underlying structures, will enhance our ability to understand better testicular temperature regulation and scrotal/testicular function.

Animals↗