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PubMed1987

Psychophysical experiments of thermoperception in human teeth.

Clinically inconspicuous anterior teeth of subjects 18-53 years of age were stimulated by means of an electrically controlled thermode of 0.5 degree C, 35 degrees C and 71 degrees C for 60 s. In two sets of experiments testing vital anterior teeth the cold stimuli were correctly identified significantly above chance level, making the existence of cold receptors inside the tooth probable. No evidence of a corresponding warm perception in human anterior teeth was found. These results were corroborated in a third experiment by comparative testing of 75 anterior teeth--25 devital and 50 vital--for a possible stimulus spread to other than intradental neural structures. Local surface anaesthesia of the tissues adjacent to the teeth significantly reduced the subject's ability to correctly identify cold stimuli. Investigating the effect of cold stimulus temperatures (0.5 degree C, 15 degrees C and 25 degrees C), no significant difference in correct cold perception was found when the two lower temperatures were applied, while with the 25 degrees C stimulus correct cold perception was at chance level. The latency of correct cold responses increased significantly when stimuli of 15 degrees C instead of 0.5 degree C were applied (t-test p less than 0.05). The latency of correct cold responses (0.5 degrees C) was not significantly influenced by surface anaesthesia. It increased significantly, however, when devital teeth were tested with the 0.5 degree C stimulus (t-test; p less than 0.01).

Adult↗
PubMed1984

Hypothalamic neuronal responses to iontophoretic application of morphine in rats.

Effects of thermal stimulation of the scrotum and of iontophoretic application of morphine on the activity of neurones in the preoptic anterior hypothalamic area were observed in 30 urethane-anaesthetised rats. The proportions of cold-responsive, warm-responsive and thermally unresponsive units were 20.7, 28.3 and 51%, respectively, of the total number of neurones tested. Iontophoretic application of morphine to neurones in the preoptic anterior hypothalamic area in rats resulted in excitation of the majority of cold-responsive cells and inhibition of the majority of warm-responsive cells tested. However, most of the thermally unresponsive cells were unaffected by application of morphine. These results provide a neuronal basis for the hypothesis that morphine, when administered directly into the hypothalamus, facilitates heat production and inhibits heat loss, which leads to hyperthermia.

Animals↗
PubMed1975

Responses to cold in the midbrain sonar center of hibernating and tropical bats.

The central gray matter of the bat midbrain, when electrically stimulated, causes the animal to produce a string of species-specific biosonar cries. Changes in this response with progressive cooling were studied in tropical homeothermic bats and in temperate hibernating bats. The species of hibernators chosen often move between hibernacula in the winter, flying and echolocating at low body temperatures (Tb). It was found that the midbrain "sonar center" exhibits a differential response to cooling that depends on the thermal propensities of the animal and its natural environment. Tropical bats followed a Q10 similar to that reported for other nonhibernating mammals and ceased responding at Tb 14-15 degrees C. Temperate zone-hibernating bat brains showed a relative insensitivity to temperature change and still responded at Tb 4-5 degrees C. Individual sonar cries within a string showed that duration was correlated with temperature but amplitude was unaffected. The study provides data for the functional separation of some parameters of biosonar and gives further evidence for differential nervous function in eurythermal versus stenothermal animals.

Adaptation, Physiological↗
PubMed2001

Differential expression of two HSP70 transcripts in response to cold shock, thermoperiod, and adult diapause in the Colorado potato beetle.

Partial clones for two members of Leptinotarsa decemlineata inducible 70kDa heat shock protein family (LdHSP70A and B) were developed using RT-PCR. LdHSP70A, but not LdHSP70B, was upregulated during adult diapause. The ability of L. decemlineata to express these two genes in response to subzero temperatures depended on the thermal history of the beetles. Chilling diapausing beetles increased the rate at which both LdHSP70A and B were expressed following a cold shock at -10 degrees C. Following cold shock at -10 degrees C, LdHSP70B expression peaked after 3h at 15 degrees C for chilled diapausing individuals, decreasing to near background levels by the sixth hour. In contrast, nonchilled diapausing beetles expressed their highest level of LdHSP70B only after 6h at 15 degrees C. Diapausing beetles exposed to a thermoperiod with a mean temperature of either 0 or -2.5 degrees C expressed significantly higher levels of both LdHSP70A and B than beetles exposed to constant 0 or -2.5 degrees C. These results demonstrate that the expression of LdHSP70A and B is differentially regulated in response to diapause and environmental conditioning.

Journal Article↗
PubMed1976

Metabolic reactions to changes in core and skin temperature in man.

The metabolic cold response, i.e. the increase in oxygen consumption above that for the given activity in a neutral environment, was measured in 7 subjects during cooling, resting or swimming in cold water (14, 16, 18, 20degrees C) and during rewarming in air (Ta 20, 30, 40degrees C), bicycling or resting. Esophageal temperatures varied between 38 and 34degrees C. Mean skin temperature was considered as equal to water temperature during cooling, and ranged between 25-35degrees C during rewarming in the different environments. Both central and peripheral cold stimulation induced metabolic cold responses. The skin temperature was the dominating factor in determining the response, especially in transient states. During rewarding a rising skin temperature suppressed the effects of even very low core temperatures.

Adult↗
PubMed1985

Effects of insulin on thermoregulatory responses and hypothalamic neuronal activity.

In the first series of experiments, the effects of administration of insulin (0.04-0.12 IU/microliter) into the preoptic anterior hypothalamic area on thermoregulatory responses were assessed in unanesthetized rats at various ambient temperatures (Ta). Intrahypothalamic administration of insulin induced a dose-dependent rise in rectal temperature. At Ta = 8 degrees C, the hyperthermia in response to insulin was due to increased metabolism, whereas at Ta = 30 degrees C, the hyperthermia was due to cutaneous vasoconstriction. However, at Ta = 22 degrees C, the insulin-induced hyperthermia was due to both increased metabolism and cutaneous vasoconstriction. In the second series of experiments, the effects of intracerebroventricular administration of insulin on 35 hypothalamic units classified as cold-responsive, warm-responsive, or thermally unresponsive were assessed in 35 rats anesthetized with urethane. It was found that the majority (80%) of the warm-responsive units were depressed by insulin, whereas the majority (70%) of the cold-responsive units were excited by insulin. The data indicate that insulin acts on the hypothalamic thermally responsive neurons to induce hyperthermia by promoting an increase in heat production and/or vasoconstriction.

Action Potentials↗
PubMed1983

Inhibition of the TSH secretion by histamine in male rats.

The effect of histamine (HA) on the cold-stimulated and the TRH-induced TSH secretion was studied in male rats utilizing HA and specific HA antagonists and histaminergic drugs as tools. L-histidine (1000 and 1500 mg/kg ip) inhibited the cold-stimulated but not the TRH-induced TSH secretion. Mepyramine (5-50 mg/kg ip) and cimetidine (50-250 mg/kg ip) had no effect on the TSH-cold-response, but the TRH-induced TSH secretion was enhanced by them. HA (1 mg/kg sc), 2-pyridylethylamine (2PEA; 10 mg/kg ip) and impromidine (1 mg/kg sc) decreased the TRH-induced TSH secretion but did not affect the TSH cold-response. When infused into the third ventricle HA (1-50 micrograms/rat), impromidine (0.1 and 1.0 microgram/rat) and 2PEA (50 micrograms/rat) decreased the cold-stimulated TSH-secretion. The locus of the inhibitory action of HA seems to be both at the anterior pituitary, where it is mediated through H1- and H2-receptors and in the hypothalamus, where the effect appears to be mediated through H2-receptors. At least a part of this particular action might be explained by other mechanisms since neither H1- nor H2-receptor antagonists were able to counteract the effect of HA.

Animals↗
PubMed2005

Cold shock response of the UspA1 outer membrane adhesin of Moraxella catarrhalis.

Colonization of the human nasopharynx exposes Moraxella catarrhalis, a common cause of otitis media in children and exacerbations of chronic obstructive pulmonary disease in adults, to sudden downshifts in temperature, occurring when the host breathes cold air. We investigated whether in vitro cold shock influences the expressions of the outer membrane adhesins UspA1 and hemagglutinin, which are considered virulence factors, and of an M. catarrhalis homolog of recA, a housekeeping gene, which in Escherichia coli is induced by cold shock. Quantitative real-time reverse transcriptase PCR was used for measuring mRNA copy number. A screening experiment revealed that a cold shock at 26 degrees C maximally induced the copy number of uspA1. In comparison with 37 degrees C conditions, a 1-hour cold shock at 26 degrees C increased copy numbers of uspA1 and recA by 2.5-fold (11.2 +/- 1.8 versus 4.5 +/- 0.8 copies/CFU) and 2.7-fold (0.30 +/- 0.10 versus 0.11 +/- 0.06), respectively, but did not induce transcription of hag. Exposure to 26 degrees C increased surface expression of UspA1, as assessed by fluorescence-activated cell sorter analysis, and resulted in a significant increase in adherence of strain O35E to Chang human conjunctival cells (97.1% +/- 2.0% versus 48.3% +/- 9.2% at 37 degrees C; P = 0.01). Cold shock induction of uspA1 and recA was detected in strains belonging to either phylogenetic subpopulation of M. catarrhalis (16S rRNA types 1 and 2/3) and was most pronounced in type 2/3 strains (4- to 25-fold for uspA1), which do not express detectable amounts of UspA1 protein at 37 degrees C. These data indicate that cold shock at a physiologically relevant temperature of 26 degrees C induces the expression of at least one virulence factor (UspA1). To our knowledge, no similar data are available for other nasopharyngeal pathogens.

Adhesins, Bacterial↗
PubMed1978

Physiological responses of women to thermal stress: a review.

The recent increase in women's participation in physically challenging activities prompted this review of female responses to heat and cold (68 references). Relevant sex differences include hormone levels, anthropometric factors, and body composition. Many studies show that women are less heat tolerant than men, particularly when physical work is required. Much of the difference is related to women's relatively low level of physical fitness and lack of heat acclimatization, which are in turn a result of their traditionally sedentary lifestyle. When work load is adjusted relative to individual capacity, females respond to heat stress much as males do. Acclimatization mechanisms are the same. Women generally have lower sweat rates, an appropriate adjustment to lesser cooling needs. The menstrual cycle has no meaningful effect on heat tolerance. Cold response reflects individual subcutaneous fat thickness, and women have an advantage there, but in extreme cold exposure they may be handicapped by their small muscle mass. Sex per se is but a small factor in determining human thermal responses; individual body size, physical fitness, and state of acclimatization play for more important roles.

Acclimatization↗
PubMed2006

Effect of bonding systems on post-operative sensitivity from posterior composites.

PURPOSE: To compare post-operative sensitivity from posterior composites lined with bonding systems that utilize either a self-etching primer or phosphoric acid conditioner. METHODS: Occlusal cavities on homologous contralateral posterior teeth in 28 selected subjects were lined with either One-Step Plus (a bonding system that utilizes phosphoric acid conditioner) or Clearfil SE Bond with a self-etching primer, and then restored with a hybrid resin composite. Post-operative sensitivity was assessed subjectively by asking the patient to classify pain from the restored tooth into none, mild or severe; and objectively by measuring the time it took for the patient to feel cold sensation when standardized ice stick was placed against the mid-buccal surface of the tooth. RESULTS: Subjective assessment showed that post-operative sensitivity was mild with either of the bonding systems; and marginal homogeneity test showed no statistically significant difference in the prevalence of post-operative sensitivity (P> 0.05), although there was a trend towards decreasing sensitivity with Clearfil SE Bond as post-operative period increased (P= 0.027). In the objective assessment, repeated measures of ANOVA showed that cold response measurements increased significantly with postoperative period only in the teeth lined with Clearfil SE Bond (P< 0.05), indicating decreasing post-operative sensitivity. However, paired t-test showed no significant difference between the cold response measurements obtained for the two bonding systems (P> 0.05).

Acid Etching, Dental↗
PubMed1993

Arabidopsis thaliana cor15b, an apparent homologue of cor15a, is strongly responsive to cold and ABA, but not drought.

We previously described a cold-regulated (cor) gene from Arabidopsis thaliana, cor15a (formerly cor15), that encodes a 15 kDa polypeptide that is targeted to chloroplasts (C. Lin and M. Thomashow, Plant Physiol 99 (1992): 519-525). Here we describe an apparent homologue of cor15a, cor15b. cor15b is located immediately downstream from cor15a (within 1 kb) and has the same relative 5' to 3' orientation as cor15a. The predicted coding regions for the two genes are 82% identical at the nucleic acid sequence level. Transcripts for cor15b, like those of cor15a, increase dramatically in response to low temperature and exogenous application of ABA. However, only cor15a transcripts accumulate to high levels in response to drought. The cor15a/cor15b gene pair is the third case in which A. thaliana cold-regulated genes have been found to exist as tandem gene pairs with the members of each pair being differentially regulated.

Abscisic Acid↗
PubMed1984

Effects of endurance fitness on responses to cold water immersion.

The purpose of this study was to determine if the changes in selected blood hormones and substrates, metabolic rate, and rectal temperature (Tre) in nine males after immersion in 10 degrees C water, while clad in standard flight suits, were related to the level of aerobic fitness. Fitness was evaluated by the blood lactate response to submaximal exercise. Immersion time (IT) was defined as the time required for a 1 degrees C decrease in Tre and averaged 38.5 (range: 21-62) min. Metabolic rate increased 3.4 times the resting rate. Lactate, free fatty acids, triiodothyronine and thyroxine increased by 81%, 38%, 11%, and 8%, respectively, in contrast to insulin which decreased by 32%, with all changes being statistically significant (p less than 0.05). Glucagon increased slightly but not significantly (p = 0.11) while glucose levels did not change. The IT was correlated directly with a measure of aerobic fitness, with relative body fat, and with the T3 levels postimmersion (p less than 0.05). The results suggest that the aerobic fitness level can significantly influence the cooling rate during water immersion.

Adult↗
PubMed2002

Genome-wide transcriptional profiling of the Bacillus subtilis cold-shock response.

The transcriptome of Bacillus subtilis was analysed at different time points (30, 60 and 90 min) after a temperature downshift from 37 to 18 degrees C using DNA macroarrays. This approach allowed the identification of around 50 genes exhibiting an increased mRNA level and around 50 genes exhibiting a decreased mRNA level under cold-shock conditions. Many of the repressed genes encode enzymes involved in the biosynthesis of amino acids, nucleotides and coenzymes, indicating metabolic adaptation of the cells to the decreased growth rate at the lower temperature. The strongest cold-inducible gene encodes fatty acid desaturase, which forms unsaturated fatty acids from saturated phospholipid precursors, thereby increasing membrane fluidity. The cold-shock-induced increase of mRNA levels of the classical cold-shock genes cspB, cspC and cspD could be verified. Furthermore, besides many genes encoding proteins of unknown function, some genes encoding ribosomal proteins were transcriptionally up-regulated, which points to an adaptive reprogramming of the ribosomes under cold-shock conditions. Interestingly, the amount of mRNA specified by the operon ptb-bcd-buk-lpd-bkdA1-bkdA2-bkdB, which encodes enzymes involved in degradation of branched-chain amino acids, also increases after a temperature downshift. As cells utilize the isoleucine and valine degradation intermediates alpha-methylbutyryl-CoA and isobutyryl-CoA for synthesis of branched-chain fatty acids, this finding reflects the adaptation of membrane lipid composition, ensuring the maintenance of appropriate membrane fluidity at low temperatures. The results of the DNA array analyses were verified for several selected genes by RNA slot-blot analysis and compared with two-dimensional PAGE analyses.

Bacillus subtilis↗
PubMed1992

A comparison of guanfacine, bunazosin, atenolol and nadolol on blood pressure and plasma noradrenaline responses to cold pressor testing.

1. The role of the presynaptic adrenoceptor subtypes in man was investigated based on observation of the changes in blood pressure (delta BP) and plasma noradrenaline concentration (delta NA) with the cold pressor test (CPT). 2. The CPT was well reproducible for BP and NA when performed at a 2 week interval in patients with mild hypertension. 3. After administration for 4 weeks, guanfacine (Gf; alpha 2-adrenoceptor agonist) decreased the delta NA response to CPT. 4. After administration for 2 or 4 weeks, bunazosin (Bu; alpha 1-adrenoceptor antagonist) atenolol (At; beta 1-adrenoceptor antagonist) and nadolol (Nd; non-selective beta-adrenoceptor antagonist) did not affect the delta NA response to CPT. 5. Both Gf and Bu decreased the systolic blood pressure response (delta SBP) to CPT after 4 weeks of the administration. Neither At nor Nd significantly changed the delta SBP response to CPT. 6. It is likely that Gf stimulated the presynaptic alpha 2 adrenoceptors at the sympathetic nerve endings as well as the central alpha 2 adrenoceptors, inhibiting the release of noradrenaline. It is unlikely that Bu, At and Nd exerted any clearly defined action on the presynaptic adrenoceptors in human hypertensive subjects.

Adrenergic alpha-Antagonists↗