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PubMed1989

Central versus peripheral effects on temperature preference and body temperature following alteration of 5-HT in maturing mice.

Experiments were designed to distinguish between central and peripheral effects on temperature preference and body temperature of drugs injected intraperitoneally (IP) in infant mice ranging in age from 3 to 10 days postpartum. These compared a drug restricted to the periphery ("peripheral" drug) with a drug of similar action that reaches the central nervous system (CNS) as well as the periphery. Two different classes of drugs were utilized to test central versus peripheral actions independently with drugs that have different modes of action: 1-aromatic amino acid inhibitors and serotonin receptor antagonists. Although the decarboxylase inhibitor NSD 1015, which reaches the central nervous system from IP injection, can significantly decrease temperature preference (Tpref), the peripheral inhibitor carbidopa had no significant effects on Tpref or on body temperature (Tb). Furthermore, pretreatment with NSD 1015 prevented the elevation of Tpref produced by the serotonin precursor 5-hydroxytryptophan (5-HTP); however carbidopa pretreatment had no effect on the increased Tpref produced by 5-HTP. In other experiments, the peripheral serotonin antagonist BW 501C was not able to prevent elevated Tpref produced by 5-HTP, although the specific 5-HT2 antagonist pirenperone, which reaches the CNS as well as the periphery, blocks the 5-HTP elevation of Tpref. Taking all of these results together, we conclude that the changes in Tb and Tpref following these treatments require a decarboxylase inhibitor or 5-HT antagonist that reaches the CNS. However, the well known and potent peripheral vasoconstrictor action of serotonin requires that peripheral effects of drugs be considered when manipulations are not restricted to the CNS.

5-Hydroxytryptophan↗
PubMed2006

Microinjection of muscimol into caudal periaqueductal gray lowers body temperature and attenuates increases in temperature and activity evoked from the dorsomedial hypothalamus.

Microinjection of the neuronal inhibitor muscimol into the midbrain lateral/dorsolateral periaqueductal gray (l/dlPAG) suppresses increases in heart rate (HR) and mean arterial pressure (MAP) evoked by microinjection of the GABA(A) receptor antagonist bicuculline methiodide (BMI) into the dorsomedial hypothalamus (DMH) in rats. Injection of BMI into the DMH also increases body temperature (Tco) and motor activity. Here, our goal was to extend previous findings by examining the effect of microinjection of muscimol into the PAG on these thermogenic and behavioral responses in conscious freely moving rats. Microinjection of muscimol (300 pmol and 1 nmol) alone into the l/dlPAG reduced baseline Tco without affecting activity, HR, or MAP. Similar injection of a dose that failed to alter baseline Tco (100 pmol) suppressed the increases in Tco evoked from the DMH and significantly attenuated DMH-induced increases in locomotor activity. Whereas microinjection of 1 nmol muscimol into the ldlPAG abolished the increases in Tco evoked from the DMH and in fact lowered body temperature to a degree similar to that seen after this dose of muscimol alone, 1 nmol muscimol at adjacent sites outside the targeted region of the PAG had no significant effect on DMH-induced increases in Tco or any other parameter. These results indicate a role for neuronal activity in the l/dlPAG in (1) the temperature and behavioral responses to disinhibition of neurons in the DMH, and (2) the maintenance of basal body temperature in conscious freely moving rats.

Animals↗
PubMed2003

Mesoporous polybutadiene-modified zirconia for high-temperature packed capillary liquid chromatography: column preparation and temperature programming stability.

In the present study, three different methods for packing of 3 microm PBD-ZrO2 particles in 0.5 mm i.d. glass-lined stainless steel columns have been examined. The two first methods were based on a traditional downstream high-pressure technique using tetrachloromethane (Method I) or aqueous Triton X-100 (Method II) as slurry solvents, while Method III was an upstream high-pressure flocculating method with stirring, using isopropanol both as the slurry and packing solvent. Method I was found to be superior in terms of efficiency, producing 0.5 mm i.d. x 10 cm columns with almost 90,000 plates m(-1) for toluene (R.S.D. = 8.7%, n = 3), using a slurry concentration of 600 mg ml(-1), ACN-water (50:50 (v/v)) as the packing solvent and a packing pressure of 650 bars. For Method I, the slurry concentration, column i.d., column length and initial packing pressure were found to have a significant effect on column efficiency. Finally, the long-term temperature stability of the prepared columns was investigated. In isothermal mode, using ACN-20 mM phosphate buffer, pH 7 (50:50 (v/v)) as the mobile phase, the columns were found to be stable for at least 3,000 void volumes at 100 degrees C. At this temperature, the solute efficiencies changed about 5-18% and the retention factors changed about 6-8%. In temperature programming mode (not exceeding 100 degrees C), on the other hand, a rapid decrease in both column efficiency and retention factors was observed. However, when the columns were packed as initially described, ramped up and down from 50 to 100 degrees C for 48 h and refilled, fairly stable columns with acceptable efficiencies were obtained. Although not fully regaining their initial efficiency after refilling, the solute efficiencies changed about 19-28% (32-37%) and the retention factors changed about 4-5% (13-17%) after running 3,000 (25,000) void volumes or 500 (3,900) temperature programs.

Butadienes↗
PubMed2002

Effects of increased ambient temperature on skin sympathetic nerve activity and core temperature in humans.

The strength of sympathetic vasoconstrictor nerve traffic to the skin has an important role in human thermoregulation since it controls heat loss from the skin by constricting or dilating cutaneous blood vessels. This study sought to clarify the time relationship between a reduction of the vasoconstrictor activity induced by elevating the ambient temperature (Ta), and subsequent change of core temperature (Tty). For this purpose, we recorded peroneal skin sympathetic nerve activity (SSNA), laser Doppler skin blood flow, skin and core (tympanic) temperatures in 11 subjects while increasing Ta from 15 to 30 degrees C during approximately 30 min. We observed a significant suppression of SSNA 7.7 min after Ta rise with marked interindividual variations. Tty displayed an increase with a peak after 8.2 min followed by a successive decrease, which became significant 14 min after the Ta rise. The rate of decrease of vasoconstrictor SSNA correlated both with the rate of decrease of Tty (P<0.01) and the magnitude of the Tty decrease (P<0.0005). A cross-correlogram between SSNA and Tty showed a peak at 7 min (r=0.52). We conclude that a Ta rise-induced reduction of skin vasoconstrictor nerve traffic leads to a core temperature decrease after 7-8 min.

Adult↗
PubMed1998

Thermodynamic analysis of human plasma apolipoprotein C-1: high-temperature unfolding and low-temperature oligomer dissociation.

Thermal and chemical unfolding of lipid-free apolipoprotein C-1 (apoC-1), a 6-kDa protein component of very low density and high-density lipoproteins, was analyzed by far-UV CD. In neutral 1 mM Na2HPO4 solutions containing 6-7 micrograms/mL protein, the apoC-1 monomer is approximately 30% alpha-helical at 0-22 degrees C and unfolds reversibly from about 22-80 degrees C with Tm = 51 +/- 3 degrees C and van't Hoff enthalpy delta Hv(Tm) = 19 +/- 3 kcal/mol. The apparent free energy of the monomer stabilization determined from the chemical unfolding at 0 degree C, delta G(0 degree C) = 2.8 +/- 0.8 kcal/mol, decreases by about 1 kcal/mol upon heating to 25 degrees C. A small apparent heat capacity increment suggests the absence of a substantial hydrophobic core for the apoC-1 molecule. At pH 7, increasing apoC-1 concentration above 10 micrograms/mL leads to self-association and formation of additional alpha-helices that unfold upon both heating and cooling from room temperature. The CD data indicate that the high-temperature transition reflects a complete monomer unfolding and the low-temperature transition reflects oligomer dissociation into stable monomers. This suggests the importance of hydrophobic interactions for apoC-1 self-association. Close proximity between the high- and low-temperature transitions and the absence of a plateau in the chemical unfolding curves recorded from oligomeric apoC-1 indicate marginal oligomer stability and suggest that in vivo apoC-1 transfer is mediated via the complexes with other apolipoproteins and/or lipids.

Acetates↗
PubMedDate not supplied

From time temperature integrator kinetics to time temperature integrator tolerance levels: heat-treated milk.

Six milk compounds were studied as potential intrinsic time temperature integrators (TTIs) for the assessment of heat-treated milk. These include the enzymes alkaline phosphatase and lactoperoxidase, the whey protein beta-lactoglobulin and the chemical compounds hydroxymethylfurfural, lactulose and furosine. In previous research the inactivation/denaturation/formation kinetics of these compounds were analyzed under isothermal and nonisothermal conditions and evaluated for variability of the milk composition. The present paper focuses on the implementation of the TTIs. TTIs are validated with respect to microbiological indices and quality attributes, and a quantitative relationship between the denaturation, inactivation or formation of the TTIs and technological processes is established by construction of general time temperature tolerance (TTT) diagrams. In these diagrams temperature time combinations are presented, which lead to the same formation, inactivation or denaturation of TTIs, or result in the same level of microbiological destruction or quality degradation of the product. TTT-diagrams are very informative since they allow visualization of the impact of a thermal process on milk and evaluation of criteria for evaluating milk authenticity (conformity of the product with the terminology applied). Moreover, the optimum combination of temperature and time of heating may be readily deduced from these diagrams.

Animals↗
PubMed1997

A novel hsp110-related gene, apg-1, that is abundantly expressed in the testis responds to a low temperature heat shock rather than the traditional elevated temperatures.

We isolated a novel hsp110-related gene, apg-1, from a testis cDNA library. The apg-1 transcripts were constitutively expressed in the testicular germ cells and, in some degree, most tissues examined. In a mouse TAMA26 Sertoli cell line, apg-1 transcripts were induced in 2 h by a temperature shift from 32 to 39 degrees C, but not by a shift from 37 to 42 degrees C, the traditional heat stress, or a shift from 32 to 42 degrees C. The heat response pattern of hsp110 expression was similar to that of apg-1. Although induction of a hsp70 transcript was observed in 2 h by a shift from 32 to 39 degrees C, the induction was more apparent by a shift from 37 to 42 degrees C or from 32 to 42 degrees C. Essentially similar differential response patterns were observed among these genes in NIH/3T3 fibroblasts as well. The nuclear run-on assay and the native gel mobility shift assay demonstrated that, by the 32 to 39 degrees C temperature shift, the apg-1 gene was transcriptionally activated, and heat shock factor 1 bound to the heat shock elements in the 5'-flanking region of the apg-1 gene. These results demonstrated that expressions of apg-1, hsp110, and hsp70 could be heat-induced at a temperature lower than the traditional elevated temperatures in somatic cells of both testis and nontestis origin and suggest that the mechanisms regulating the transcript levels of apg-1 and hsp110 are different from those of hsp70. Furthermore, the constitutive expression in germ cells suggests that APG-1 plays a specific role in spermatogenesis as well as in stress response.

3T3 Cells↗
PubMed1978

The effects of plane of nutrition and environmental temperature on the energy metabolism of the growing pig. 1. Heat loss and critical temperature.

1. The heat losses and energy balances of thirty-eight individually housed pigs (initial body-weights 21--38 kg) were measured continuously for periods of 14 d when they were maintained at environmental temperatures of 10, 15, 20, 25 or 30 degrees. At each temperature four levels of feeding were given approximating to once, twice and three times the maintenance energy intake and the ad lib. level. The minimal maintenance energy requirement (M) was calculated to be 440 kJ metabolizable energy (ME)/kg0.75 per d at 25 degrees. 2. ME intake at the ad lib. level decreased from 1965 kJ/kg0.75 per d at 10 degrees to 1202 at 30 degrees. 3. Heat loss calculated from multiple regression analysis decreased to minimum levels between 20 and 25 degrees; 30 degrees was within the hyperthermic zone at each plane of nutrition. 4. The partition of heat loss into its sensible and evaporative components showed that evaporation increased from 25% at 10 degrees to 78% at 30 degrees. 5. Critical temperature was dependent upon food intake and decreased from 23.1 degrees at M to 20.7 degrees at 2M, 18.0 degrees at 3M and 16.7 degrees at 4M. 6. The extra food required to meet extra thermoregulatory heat production per 1 degrees below the effective critical temperature was 0.65 g/kg body-weight per d.

Animal Nutritional Physiological Phenomena↗
PubMed2001

Thermotolerance acquisition in broiler chickens by temperature conditioning early in life--the effect of timing and ambient temperature.

Thermal conditioning of chicks results in improvements in performance and thermotolerance at marketing age. Conditioning has been found to be a sensitive process, dependent on age and the temperature used. The objective of this study was to assess the optimal timing and temperature for the conditioning processes. Six separate trials were conducted on male broiler chickens: the first two aimed to find the optimal age for thermal conditioning (1 to 5 d of age); the other four evaluated the optimal thermal conditioning temperature between 36 and 40.5 C. At 42 d of age chickens were thermally challenged to evaluate their ability to cope with acute heat stress. The highest body weight was achieved when thermal conditioning had been applied at the age of 3 d, and it coincided with low feed intake and higher to significantly higher feed efficiency. These treated chickens showed relatively lower mortality rate under thermal challenge and lower to significantly lower Triiodothyronine (T3) concentration in Trial 2. Chicks that had been thermally conditioned at ambient temperatures (Ta) of 36 and 37.5 C at the age of 3 d demonstrated the best performance characteristics and the ability to reduce T3 concentration to the lowest levels during thermal challenge. It can be suggested, therefore, that a Ta between 36.0 and 37.5 C, applied at 3 d of age is optimum for thermal conditioning of broiler chickens.

Adaptation, Physiological↗
PubMed1965

IMPROVED TEMPERATURE-GRADIENT INCUBATOR AND THE MAXIMAL GROWTH TEMPERATURE AND HEAT RESISTANCE OF SALMONELLA.

An improved all-metal temperature-gradient incubator produces its gradient by means of a bar permanently installed in a near-vertical position with its lower end in a cool constant-temperature water bath and with thermostatically controlled heaters near its top. Bolts hold the incubator in contact with the temperature-gradient bar, and polyurethane foam insulates the entire assemblage during use. Maximal growth temperatures of 34 representative strains of Salmonella were found to be between 43.2 and 46.2 C. In an agar medium with an initial level of 10(6) cells per milliliter, no strain survived 50 C for 48 hr. S. senftenberg 775W showed no greater heat resistance at or near 48 C than did other species or other S. senftenberg strains. However, it was considerably more resistant than other strains at 55 C.

Bacteriological Techniques↗
PubMed1972

Ultrahigh-temperature activation of a low-temperature Bacillus subtilis spore germination system.

Exposure of Bacillus subtilis A spores to 115 to 125 C for several seconds activated a low-temperature germination system that remained dormant after a heat treatment that activated the normal l-alanine- and glucose-stimulated germination systems. The low-temperature germination system was characterized by an optimum temperature lower than that of the l-alanine or glucose germination systems (30 C versus 45 C), germination in the absence of exogenous germination stimulants, and the capacity for heat-induced deactivation and subsequent reactivation. The rates of activation at 115 to 125 C were exponential and were not influenced by a previous heat treatment that activated the l-alanine- or glucose-stimulated germination systems. Although activation of the low-temperature germination system was accompanied by suppression of l-alanine-stimulated germination, it did not appear to be a modification of the l-alanine germination system.

Alanine↗
PubMed1975

Comparison of metabolic, temperature, heart rate and ventilatory responses to exercise at extreme ambient temperatures (0 degrees and 35 degrees C.).

Eight male subjects exercised on a bicycle ergometer for one half to one hour at loads demanding 52 to 59% of Vo2max on two separate occasions, once with ambient temperature held at 0 degrees C and once in a 35 degrees C environment. Throughout exercise and during recovery in a 25 degrees C environment, measurements were made of oxygen consumption, ventilation, heart rate, muscle-rectal-skin temperatures, and blood lactic acid. In the hot condition significant increases in heart rate, blood lactates, sweat loss, muscle, rectal and skin temperature responses were observed. At 0 degrees C Vo2 was significantly elevated during exercise over that in the 35 degrees C condition. Despite the elevated Vo2 response in the cold, higher body temperatures measured in the heat were associated with a significantly higher (P less than .025) recovery Vo2 (x = 866 ml), which was of the magnitude predicted by the van't Hoff-Arrhenius relationship.

Adult↗
PubMed1991

Adrenal and body temperature changes in rabbits exposed to varying effective temperatures.

Eight adult New Zealand White rabbits were exposed individually, in series, to each of 23 effective temperatures (t(eff)) until body temperature (tb) increased 1.1 degrees C or for a period of 2 hours. Body temperature was measured to the nearest 0.1 degree C using FM radio transmitters in the pre-test (baseline) condition and at 2 minute intervals during the test conditions where t(eff) ranged between 21.7 and 34.7 degrees C. The frequency at which the rabbits displayed a 1.1 degree C rise in tb was related to the magnitude of the t(eff), with 100% of the rabbits manifesting this change at t(eff) greater than 30.2 degrees C. At t(eff) of 28.4 through 30.2 degrees C, some, but not all, of the rabbits showed a 1.1 degree C rise in tb whereas none displayed the 1.1 degree C rise in tb at t(eff) below 28.4 degrees C. The mean time necessary for the 1.1 degree C rise in tb was negatively correlated (P less than 0.01) to the magnitude of the t(eff). The significantly (P less than 0.01) elevated plasma corticosterone in rabbits exhibiting 0.6 degree C and 1.1 degree C rise in tb suggests that those animals were stressed physiologically by the experimental procedure. It is concluded that the conditions associated with increased tb induce physiological changes commonly associated with stressors and that the techniques reported herein should be useful in establishing upper environmental temperature limits for housing rabbits.

Animals↗
PubMed1981

Influence of ambient and core temperatures on auditory canal temperature.

UNLABELLED: Ear canal temperature (Tac) is a useful indicator of human body temperature under some laboratory conditions. Tac has also been used in field studies, but problems arise there due to its susceptibility to external influences such as wind. Experiments on five resting subjects in an environmental chamber showed that 1) compared to a warm environment (35 degrees C), a cool one (22 degrees C) produced significant lowering of both Tac and rectal temperature (Tre), 2) the cool condition increased the difference between Tre and Tac, and 3) head treatment (helmet wear, wind) significantly affected Tac. In a second series of experiments, six subjects exposed to the same conditions performed mild exercise to abolish the progressive decline in Tre seen at 22 degrees C. Results showed that Tac still reflected external temperature and continued to show the influence of head treatment. CONCLUSION: Tac has only limited usefulness in aircrew studies or other field work unless subjects can wear a protective helmet throughout the period of data collection.

Adult↗
PubMed1994

Sleep deprivation in the rat at different ambient temperatures: effect on sleep, EEG spectra and brain temperature.

To investigate the relationship between thermoregulation and sleep regulation, rats were sleep-deprived for 3 hours at two different ambient temperatures. Sleep deprivations (SD) were performed at 23 degrees C (SD-23) and at 32 degrees C (SD-32) in the beginning of the 12-h light period in animals chronically implanted with ECoG and EMG electrodes, and with epidural and hypothalamic thermistors. SD-32 enhanced cerebral temperature more than SD-23 at both brain sites. The SD-induced hyperthermia was followed by a fall of brain temperature below baseline. During recovery from either SD procedure, waking was reduced and sleep continuity increased. REM sleep was increased after SD-32. EEG slow-wave activity (spectral power density in the 0.75-4.0 Hz band) exceeded the baseline level in the first 3-h interval of recovery; however, the effects of SD-23 and SD-32 did not differ. In the same time interval, power density in the 1.25-1.5 Hz bin as well as in some bins in the theta and alpha band was higher after SD-32 than after SD-23. The increase in hypothalamic temperature during SD did not correlate with the increase in SWA during recovery. It is concluded that even a brief SD has major repercussions on recovery sleep whereas the extent of cerebral hyperthermia during SD is only a minor factor.

Animals↗
PubMed1996

The telemetric monitoring of heart rate, locomotor activity, and body temperature in mice and voles (Microtus arvalis) during ambient temperature changes.

We have studied the physiological and behavioural responses in small rodents to ambient alterations. For this purpose, voles and mice were exposed to relatively low (12 degrees C) and high (35 degrees C) ambient temperatures, and heart rate (HR), locomotor activity (LA) and body temperature (BT) were recorded using telemetry system. The control HR (at 24 degrees C) of voles was lower than that of mice. The 'heat exposure' decreased HR to 85.0 +/- 3.3% in voles, and to 78.0 +/- 3.2% in mice compared with the mean HR of the same time in the control day. The 'cold exposure' increased the HR to 131.9 +/- 8.8% in voles, and 119 +/- 10.9% in mice. The decreasing rate of HR in heat exposure was smaller in voles than mice, and in cold exposure the increased rate was larger in voles than mice. Cold exposure decreased BT in both species; 96.1 +/- 0.5% in voles and 93.7 +/- 1.0% in mice. The LA was not changed significantly by heat exposure in either species, but was partially increased by cold exposure. These results demonstrate that telemetry was helpful for qualitative and quantitative behavioural studies in small rodents, and confirmed that the physiological and behavioural responses to ambient temperature changes differed between these animals.

Animals↗
PubMed2002

Low-temperature electron microscopy for the study of polysaccharide ultrastructures in hydrogels. II. Effect of temperature on the structure of Ca2+-alginate beads.

Calcium alginate beads were thermally treated at temperatures ranging from 25 degrees C to 130 degrees C for periods of up to 30 minutes. Important modifications to the structure of the alginate beads were shown to be a function of the temperature and period of incubation at each temperature. Modifications to the alginate beads included reduction in size, mechanical resistance, and molecular weight cut-off with increasing temperature and incubation period. Thus, heating 700 microm calcium alginate beads for 20 min at 130 degrees C resulted in a 23% reduction in diameter, 70% increase in mechanical resistance, and 67% reduction in molecular weight cut-off. Incubation of calcium alginate beads containing 2 x 10(6) kDa blue dextran for 20 min at 130 degrees C resulted in no detectable loss of either dye or alginate. This indicates the shrinkage of the beads was due to re-arrangement of the alginate chains within the beads, coupled with loss of water. This hypothesis was verified by direct visual observation of calcium alginate beads before and after thermal treatment using cryo-scanning electron microscopy (cryo-SEM). Unlike other microscopy methods cryo-SEM offers the advantage of extremely rapid freezing which preserves the original structure of the alginate network. As a result cryo-SEM is a powerful tool for studies of hydrogel and capsule structure and formation. Differential scanning calorimetry (DSC) showed that the water entrapped in 2% alginate beads was present in a single state, irrespective of the thermal treatment. This result is attributed to the low alginate concentration used to form the beads.

Alginates↗