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PubMed1999

Cold shock response and low temperature adaptation in psychrotrophic bacteria.

Psychrotrophic bacteria are capable of developing over a wide temperature range and they can grow at temperatures close to or below freezing. This ability requires specific adaptative strategies in order to maintain membrane fluidity, the continuance of their metabolic activities, and protein synthesis at low temperature. A cold-shock response has been described in several psychrotrophic bacteria, which is somewhat different from that in mesophilic microorganisms: (i) the synthesis of housekeeping proteins is not repressed following temperature downshift and they are similarly expressed at optimal and low temperatures (ii) cold-shock proteins or Csps are synthesized, the number of which increases with the severity of the shock (iii) a second group of cold-induced proteins, i.e. the cold acclimation proteins or Caps, comparable with Csps are continuously synthesized during prolonged growth at low temperature. Homologues to CspA, the major cold-shock protein in E. coli, have been described in various psychrotrophs, but unlike their mesophilic counterparts, they belong to the group of Caps. Although they have been poorly studied, Caps are of particular importance since they differentiate psychrotrophs from mesophiles, and they are probably one of the key determinant that allow life at very low temperature.

Adaptation, Physiological↗
PubMed2006

Enhanced cold and desiccation tolerance in diapausing adults of Culex pipiens, and a role for Hsp70 in response to cold shock but not as a component of the diapause program.

Culex pipiens L. reared under diapause-inducing conditions (short daylength; 18 degrees C) were more cold tolerant and desiccation resistant than their nondiapausing counterparts (long daylength; 18 degrees C). Upon cold exposure (-5 degrees C), diapausing mosquitoes reared at 18 degrees C survived nearly twice as long as nondiapausing mosquitoes reared at 18 degrees C and 10 times longer than nondiapausing mosquitoes reared at 25 degrees C. Thus, rearing temperature provided partial protection against low temperature injury in nondiapausing mosquitoes, but maximum resistance to cold was attained by the diapause state. In this species, the supercooling point is not a good indicator of cold tolerance. Both diapausing and nondiapausing females had supercooling points of approximately -16 degrees C, but diapausing as well as nondiapausing females died at temperatures well above the supercooling point, suggesting that low temperature mortality was due to indirect chilling injury. Diapause also conferred greater resistance to desiccation (1.6-2-fold increase in survival) compared with the nondiapause state. The gene encoding a 70-kDa heat shock protein, hsp70, was not up-regulated (i.e., more highly expressed) as a part of the diapause program, nor was it up-regulated by desiccation stress, but it was up-regulated during recovery from cold shock. Cx. pipiens thus differs from a number of other diapausing insect species that are known to developmentally up-regulate hsp70 during diapause.

Amino Acid Sequence↗
PubMed1987

Bombesin alters the sympathetic nervous system response to cold exposure.

The accumulation of dopamine in interscapular brown fat, heart, kidney and mesenteric white fat has been used as an index of sympathetic nervous activity in rats in which dopamine beta-hydroxylase has been blocked. Intracerebroventricular administration of bombesin impaired the cold-induced increase of dopamine accumulation in interscapular brown fat but not in other tissues. These studies provide evidence that bombesin acts within the central nervous system to modify efferent sympathetic nervous system responses to cold exposure in a viscerotopically specific manner. This action of bombesin is consistent with the other central nervous system actions of this peptide, i.e. inhibition of heat production and disruption of thermoregulation.

Adipose Tissue, Brown↗
PubMed1982

Quantitative observations on thermal and metabolic responses to cold of workers using vibrating tools.

Quantitative observations on thermal and metabolic responses of 32 patients exposed to moderate cold of vibration hazards due to using chain saw were performed. In this study, many cases showed trends of both in increase of metabolic rate and decrease of mean skin temperatures. The ratio of 60 min mean value of the increase of metabolic rate/decrease of mean skin temperature is 3.5 +/- 2.60. Twenty-two patients (68.8%) indicated the value larger than 3. There are many with markedly large increase in metabolic rate in those who affected Raynaud's phenomenon. It can be suggested that many of the patients with the vibration hazards indicate an decrease of the cold tolerance ot the moderate cold exposure.

Adult↗
PubMed1987

Time relationships and reversal by two indoleamines of the pinealectomy-inhibited thyrotropin secretion in male rats.

Time relationships and mediators of the inhibitory effect of pinealectomy on cold-induced TSH secretion were studied in male Sprague-Dawley rats. Pinealectomy but not sham operation significantly reduced the TSH cold-response (30 min at +4 degrees C) in 6-8 week-old rats on the 3rd postoperative day. Longer postoperative periods resulted in gradual attenuation of the effect of pinealectomy. Pinealectomy did not modify basal TSH levels on the 3rd or 7th postoperative day. Melatonin, arginine vasotocin and crude pineal extracts failed to antagonise the suppressed cold-response in pinealectomised rats. 5-Hydroxytryptamine and 6-methoxy-tetrahydro-beta-carboline, however, antagonised partially but significantly the pinealectomy-induced reduction in TSH cold-response. Although transient, the suppression of cold-stimulated TSH secretion by pinealectomy may be caused by lack of two pineal indoleamines 5-hydroxytryptamine and/or 6-methoxy-tetrahydro-beta-carboline.

Animals↗
PubMed1994

Sensory nerve conduction during cold pressor response in humans.

A study was carried out to find the correlation, if any of autonomic responses and experimental pain induced during the cold pressor test (CPT) with the median nerve sensory conduction velocity (SCV). In 19 healthy subjects who volunteered for the study, the nondominant hand of each was subjected to the CPT and, pain parameters, heart rate, blood pressure and SCV were recorded. Dominant median nerve SCV was measured by orthodromic stimulation of the index finger and evoked responses were recorded at the wrist. In each subject, 32 evoked action potential responses were averaged to determine the SCV. Median nerve SCV of 57.8 +/- 5.2, 56.6 +/- 5.1, 57.0 +/- 5.2 and 57.8 +/- 5.1 m/sec were recorded before, during, immediately after and after ten minutes of the CPT, respectively. The SCV and the amplitude of the evoked response were significantly (P < 0.001 and P < 0.01 respectively) decreased during the CPT. A significant relationship (P < 0.05) was found between nerve conduction parameters and diastolic blood pressure recorded before the CPT. These findings suggest that sympathetic overactivity and/or cold induced pain interacts with sensory conduction in the contralateral median nerve so as to decrease its conduction velocity. There also exists a relationship between SCV and vasomotor mechanisms controlling peripheral resistance, and hence the diastolic pressure.

Adolescent↗
PubMed2003

Cold induction of Arabidopsis CBF genes involves multiple ICE (inducer of CBF expression) promoter elements and a cold-regulatory circuit that is desensitized by low temperature.

The Arabidopsis CBF1, 2, and 3 genes (also known as DREB1b, c, and a, respectively) encode transcriptional activators that have a central role in cold tolerance. CBF1-3 are rapidly induced upon exposing plants to low temperature, followed by expression of CBF-targeted genes, the CBF regulon, resulting in an increase in plant freezing tolerance. At present, little is known about the cold-sensing mechanism that controls CBF expression. Results presented here indicate that this mechanism does not require a cold shock to bring about the accumulation of CBF transcripts, but instead, absolute temperature is monitored with a greater degree of input, i.e. lower temperature, resulting in a greater output, i.e. higher levels of CBF transcripts. Temperature-shift experiments also indicate that the cold-sensing mechanism becomes desensitized to a given low temperature, such as 4 degrees C, and that resensitization to that temperature requires between 8 and 24 h at warm temperature. Gene fusion experiments identified a 125-bp section of the CBF2 promoter that is sufficient to impart cold-responsive gene expression. Mutational analysis of this cold-responsive region identified two promoter segments that work in concert to impart robust cold-regulated gene expression. These sequences, designated ICEr1 and ICEr2 (induction of CBF expression region 1 or 2), were also shown to stimulate transcription in response to mechanical agitation and the protein synthesis inhibitor, cycloheximide.

Acclimatization↗
PubMed2006

Developmental response to cold stress in cranial morphology of Rattus: implications for the interpretation of climatic adaptation in fossil hominins.

Adaptation to climate occupies a central position in biological anthropology. The demonstrable relationship between temperature and morphology in extant primates (including humans) forms the basis of the interpretation of the Pleistocene hominin Homo neanderthalensis as a cold-adapted species. There are contradictory signals, however, in the pattern of primate craniofacial changes associated with climatic conditions. To determine the direction and extent of craniofacial change associated with temperature, and to understand the proximate mechanisms underlying cold adaptations in vertebrates in general, dry crania from previous experiments on cold- and warm-reared rats were investigated using computed tomography scanning and three-dimensional digitization of cranial landmarks. Aspects of internal and external cranial morphology were compared using standard statistical and geometric morphometric techniques. The results suggest that the developmental response to cold stress produces subtle but significant changes in facial shape, and a relative decrease in the volume of the maxillary sinuses (and nasal cavity), both of which are independent of the size of the skull or postcranium. These changes are consistent with comparative studies of temperate climate primates, but contradict previous interpretations of cranial morphology of Pleistocene Hominini.

Adaptation, Biological↗
PubMed1989

Hyperventilation response to cold water immersion: reduction by staged entry.

Staged immersion of humans into cold water was investigated to determine whether the hyperventilation response could be reduced by this behavioral technique. A simple, two-stage procedure involving immersion to the waist for 30 s before full immersion to neck level was compared to non-staged immersion. For the staged immersion, maximum values of respiratory minute volume and respiratory frequency were significantly reduced by 35% and 38%, respectively, from the maxima observed for non-staged immersion. These results indicate that if staged immersion into cold water is possible, it can attenuate the hyperventilation response and, therefore, the probability of sudden drowning. We recommend that this knowledge be incorporated into teaching programs concerning cold water safety.

Adult↗
PubMed2005

Aberrant neural responses to cold pressor challenges in congenital central hypoventilation syndrome.

Patients with congenital central hypoventilation syndrome (CCHS), a condition characterized by impaired ventilatory responses to chemoreceptor stimulation, do not show the normal increase in respiratory rate and respiratory-related heart rate variation to cold forehead stimulation, a challenge that bypasses central chemoreceptors. We hypothesized that a forehead cold pressor challenge would reveal abnormal neural response patterns, as assessed by functional magnetic resonance imaging, in brain regions that are responsible for the integration of cold afferent stimulation with respiratory and cardiovascular output in patients with CCHS. Primary sensory thalamic and cortical areas for the forehead showed diminished responses in 13 patients with CCHS (ventilator dependent during sleep but not waking, no Hirschsprung's disease) compared with 14 control subjects, despite initial signal changes in the cortex being similar in both groups. Cerebellar cortex and deep nuclei; basal ganglia; and middle to posterior cingulate, insular, frontal, and temporal cortices showed reduced signal rises in patients with CCHS. Areas within the frontal and anterior cingulate cortices exhibited marked signal declines in control subjects but little change in patients with CCHS. No response occurred in either group in the dorsal medulla, but medial and ventral medullary areas showed enhanced signals in patients with CCHS. The cold pressor stimulation did not recruit dorsal medullary sites that would be affected by PHOX2B (a mutation of which is associated with the syndrome) expression in either group but demonstrated deficient cerebellar and medial medullary influences that, by action on rostral sites, may underlie the loss of respiratory responses.

Adolescent↗
PubMed1983

Beta-receptor stimulation by adrenaline elevates plasma noradrenaline and enhances the pressor responses to cold exposure and isometric exercise.

Isoprenaline 3.5-35 ng/kg/min, salbutamol 17.5-175 ng/kg/min and prenalterol 1-32 micrograms/kg were given intravenously (i.v.) to 10, 12 and nine subjects with borderline hypertension respectively. For a given chronotropic effect the effects on plasma noradrenaline were in the order: salbutamol greater than isoprenaline greater than prenalterol, indicating that the increase in noradrenaline was a beta 2-receptor-mediated response. This was supported by the antagonistic effects of atenolol and propranolol on this response. Adrenaline 30 ng/kg/min i.v. raised plasma adrenaline by a factor of 10 in 17 subjects with borderline hypertension. Plasma noradrenaline rose from 218 +/- 29 to 264 +/- 35 pg/ml (mean +/- s.e.m., P less than 0.05). The increments in blood pressure and plasma noradrenaline in response to cold exposure and isometric exercise were greater during the adrenaline infusion than during saline. This effect of adrenaline was antagonized by propranolol 0.5 mg i.v. These in vivo results lend support to the view that adrenaline may act as a physiological modulator of sympathetic neurotransmission by facilitating the release of noradrenaline through activation of presynaptic beta 2-type receptors.

Acclimatization↗
PubMed1994

The effects of warming by active and passive means on the subsequent responses to cold water immersion.

Two experiments were undertaken to investigate the effects of warming the body upon the responses during a subsequent cold water immersion (CWI). In both experiments the subjects, wearing swimming costumes, undertook two 45-min CWIs in water at 15 degrees C. In experiment 1, 12 subjects exercised on a cycle ergometer until their rectal temperatures (Tre) rose by an average of 0.73 degree C. They were then immediately immersed in the cold water. Before their other CWI they rested seated on a cycle ergometer (control condition). In experiment 2, 16 different subjects were immersed in a hot bath (40 degrees C) until their Tre rose by an average of 0.9 degrees; they were then immediately immersed in the cold water. Before their other CWI they were immersed in thermoneutral water (35 degrees C; control condition). Heart rate in both experiments and respiratory frequency in experiment 1 were significantly (P < 0.05) higher during the first 30 s of CWI following active warming. In experiment 1, the rate of fall of Tre during the final 15 min of CWI was significantly (P < 0.01) faster when CWI followed active warming (2.46 degrees C.h-1) compared with the control condition (1.68 degrees C.h-1). However, this rate was observed when absolute Tre was still above that seen in the control CWIs. It is possible, therefore, that if longer CWIs had been undertaken, the two temperature curves may have converged and thereafter fallen at similar rates; this was the case with the aural temperature (Tau) seen in experiment 1 and the Tau and Tre in experiment 2. It is concluded that pre-warming is neither beneficial nor detrimental to survival prospects during a subsequent CWI.

Adult↗
PubMed2006

Stronger nasal responsiveness to cold air in individuals with rhinitis and asthma, compared with rhinitis alone.

BACKGROUND: We have previously proposed that, compared with rhinitis alone, the constellation of upper and lower airway allergic disease is a manifestation of a more severe form of a syndrome affecting the entire airway. If this is correct, not only the lower, but also the upper airways of patients with asthma and rhinitis should demonstrate more abnormalities compared with patients with rhinitis alone, including higher sensitivity to irritant factors. Objective To test the hypothesis that, a previously well-studied natural nasal stimulus, cold, dry air (CDA), produces a stronger response in subjects with allergic rhinitis (AR) and asthma compared with subjects with AR alone. METHODS: We performed nasal provocation with CDA on 24 individuals with asthma and rhinitis and 17 with rhinitis alone. Prior to and after the challenge, nasal symptoms were recorded using visual analogue scales and nasal lavages were performed to determine histamine and lysozyme levels. RESULTS: The two groups reacted differently to CDA: after the challenge, patients with rhinitis and asthma reported significantly higher scores for nasal congestion, rhinorrhea and lacrimation. Also in this group, significant increases in histamine and in lysozyme levels in nasal lavage fluids were induced by CDA. In subjects with rhinitis alone, CDA failed to increase histamine or lysozyme levels above baseline. The CDA-induced change from baseline in histamine was significantly higher in the patients with rhinitis and asthma, compared with the rhinitis-only group. CONCLUSION: Patients with AR and asthma have stronger nasal responsiveness to CDA compared with patients with rhinitis alone. This observation is consistent with the notion that compared with rhinitis alone, the presence of asthma and rhinitis signifies a higher degree of functional abnormality of the entire airway.

Adult↗
PubMed1985

Urinary responses to cold temperature during water immersion.

If cold temperature combines with ambient water pressure to stimulate the Henry-Gauer reflex in humans, then free water clearance (CH2O) should be greater during immersion in cold water (29.8 degrees C) than during exposure to cold air (14.8 degrees C) or immersion in thermoneutral water (35 degrees C). Urinary responses to these environments were compared with control measurements made during 6 h of sitting in thermoneutral air (27.6 degrees C). CH2O was not significantly greater in cold water than in the other environments. Rather, the diuretic response was characterized by an increased osmolar clearance (P less than 0.05). Cold temperature and water pressure additively raised urinary output during cold water immersion, with ambient water pressure accounting for two-thirds of the urinary water loss. An elevated rate of sodium excretion (P less than 0.05) began significantly earlier in cold water than in thermoneutral water. This effect of low temperature might have resulted from cold-induced vasoconstriction, since cold temperatures was observed to reduce the foot volume. Sodium excretion was inversely proportional to vital capacity, indicating a responsiveness of the kidney to expansion of the central blood volume. In addition to the effects of water pressure and cold temperature, urinary function was also sensitive to time. The rate of potassium excretion was significantly elevated at min 199 of exposure to all environments. Failure of CH2O to increase above control values indicated that the human diuretic response to cold water immersion is atypical for the Henry-Gauer reflex.

Body Temperature Regulation↗
PubMed1998

Thermoregulatory responses to cold: effects of handwear with multi-layered clothing.

BACKGROUND: Thermoregulatory responses were studied during rest and exercise in men wearing diverse handwear with an extended cold-weather clothing system [ECWCS]. The ECWCS (thermal insulation = 3.6 clo (1 clo = thermal resistance approximately 0.155 m2.K.W(-1)); weight = 10.1 kg) incorporates skin-tight polypropylene underwear, polyester/cotton fatigues, polyester-insulated liners, balaclava, vapor-barrier boots, and polytetrafluroethylene [PTFE]-lined outer garments. METHODS: Six fit males each rested (M = 71 W.m(-2) and performed treadmill exercise (M = 171 W.m(-2)) while wearing the following handwear with the ECWCS: a light duty glove (LD, clo = 0.86), a heavy duty glove (HD, clo = 1.05), or an Arctic mitten (AM, clo = 1.46). Cold exposures were at Ta = 0 degrees C, -20 degrees C, and -30 degrees C; rh = 20%; wind speed = 10.34 m.s(-1). Exposure was a target period of 120 min designated as maximal endurance time (ET, min). All experiments were performed on separate days. Rectal (Tre), middle finger (Tmf), and mean weighted skin (Tsk) temperatures were recorded continuously; oxygen uptake and heart rate were measured periodically and total body weight loss msw, g.h(-1)) was determined after each run. RESULTS: During rest at 0 degrees C, the ECWCS maintained Tre at 37 degrees C for the maximal ET with all handwear configurations; for each lower ambient condition, steady-state Tre dropped -0.2 degrees C per each 10 C decrease in Ta.Tmf at or near 5 degrees C prior to the maximal ET was the basis for premature attrition; Tsk of 29.4 degrees C was associated with subjective thermal discomfort. ET was predicted adequately by combining Tmf, heat production, Tre and Tsk. CONCLUSIONS: The ECWCS with specific handwear furnish adequate ET in cold-dry ambients provided that ventilation and removal of extra layers is an option during heavy exercise and thermal insulation is not decreased by body moisture.

Adult↗
PubMed2003

Expression of human aromatase (CYP19) in Escherichia coli by N-terminal replacement and induction of cold stress response.

CYP19 (P450arom) catalyzes the aromatization reaction of C19 steroids leading to estrogens. While readily expressed in insect cells, the human P450arom has been a difficult P450 to express in Escherichia coli at useful levels. In the present study, we replaced the N-terminal sequence in human CYP19 with the corresponding sequences of other microsomal P450s (CYP2C11 and CYP17) that are efficiently expressed in E. coli. Although the N-terminal replacement alone was not sufficient for the expression, human P450arom was successfully expressed up to the level of 240nmol/l culture by the combination of the N-terminal replacement and the induction of cold stress response by 1 microg/ml chloramphenicol. Membrane fractions containing the expressed P450arom catalyzed aromatization of androstenedione with a specific activity of 4.9 nmol/min/nmol P450. Our results are important to provide large quantities of human P450arom as an active form for structure-function studies.

Amino Acid Sequence↗
PubMed1981

Changes in mitochondrial components of hamster brown adipose tissue in response to cold acclimation.

Cold acclimation of hamsters was found to result in an increase in cytochrome concentration relative to ATPase activity in brown adipose tissue mitochondria, but not in liver mitochondria. These data lend support to the hypothesis that the uncoupled respiration characteristic of non-shivering thermogenesis is the result of an adaptive change in the composition of brown adipose tissue mitochondria in response to cold acclimation.

Acclimatization↗