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PubMedDate not supplied

Racial differences in blood pressure and forearm vascular responses to the cold face stimulus.

The mechanisms responsible for the higher incidence of essential hypertension in blacks than in whites are the object of much research attention. One hypothesis is that the development of hypertension in blacks is associated with exaggerated blood pressure reactivity, particularly those responses mediated by vasoconstriction. Racial differences in blood pressure responses to cold stimulation of the forehead, a known alpha-adrenergic vasoconstrictive stimulus, were examined in health, college-age males. Compared to white subjects, black subjects exhibited significantly greater increases in systolic and diastolic blood pressure, as well as increases in forearm vascular resistance, in response to cold stimulation. This preliminary evidence of increased peripheral vascular reactivity in blacks suggests that known racial differences in hypertension prevalence might derive in part from physiological differences in sympathetic nervous system reactivity.

Adolescent↗
PubMed1996

Differential mRNA stability of the cspA gene in the cold-shock response of Escherichia coli.

Exposure of bacterial cells to temperature changes induces the synthesis of a set proteins. We investigated the control of expression of the cspA gene, coding for the major cold-shock protein of Escherichia coli. This protein was shown to be transiently induced upon shift to low temperature. We demonstrated that the cspA mRNA is extremely unstable at 37 degrees C with a half-life of approx. 10 s. Upon shift to 15 degrees C cspA mRNA becomes highly stable. This mRNA stability is transient and is lost once the cells are adapted to the low temperature. Transcription fusions of lacZ containing part or most of the cspA gene do not show the rapid degradation at high temperature. Our results suggest that mRNA stability plays a major role in the control of the cspA gene. The expression of cspA is also regulated, to a smaller extent, by the relative increase in transcription after transfer to low temperature. A model by which cspA mRNA is regulated in response to temperature shift is discussed.

Bacterial Proteins↗
PubMed2005

Expressed sequence tags from the Yukon ecotype of Thellungiella reveal that gene expression in response to cold, drought and salinity shows little overlap.

Thellungiella salsuginea (also known as T. halophila) is a close relative of Arabidopsis that is very tolerant of drought, freezing, and salinity and may be an appropriate model to identify the molecular mechanisms underlying abiotic stress tolerance in plants. We produced 6578 ESTs, which represented 3628 unique genes (unigenes), from cDNA libraries of cold-, drought-, and salinity-stressed plants from the Yukon ecotype of Thellungiella. Among the unigenes, 94.1% encoded products that were most similar in amino acid sequence to Arabidopsis and 1.5% had no match with a member of the family Brassicaceae. Unigenes from the cold library were more similar to Arabidopsis sequences than either drought- or salinity-induced sequences, indicating that latter responses may be more divergent between Thellungiella and Arabidopsis. Analysis of gene ontology using the best matched Arabidopsis locus showed that the Thellungiella unigenes represented all biological processes and all cellular components, with the highest number of sequences attributed to the chloroplast and mitochondria. Only 140 of the unigenes were found in all three abiotic stress cDNA libraries. Of these common unigenes, 70% have no known function, which demonstrates that Thellungiella can be a rich resource of genetic information about environmental responses. Some of the ESTs in this collection have low sequence similarity with those in Genbank suggesting that they may encode functions that may contribute to Thellungiella's high degree of stress tolerance when compared with Arabidopsis. Moreover, Thellungiella is a closer relative of agriculturally important Brassica spp. than Arabidopsis, which may prove valuable in transferring information to crop improvement programs.

Algorithms↗
PubMed1988

Thermal responses of ventromedial hypothalamic neurons in vivo and in vitro.

The ventromedial hypothalamic neurons were recorded in anesthetized rats and in slice preparations. Whereas almost all thermosensitive neurons (27 out of 28) in the slice preparations showed warm sensitivity, cold-responsive neurons were recorded more frequently than warm-responsive ones during preoptic thermal stimulation in anesthetized rats. These results suggest that most cold-responsive neurons excited by preoptic cooling in the anesthetized rats were influenced by synaptic inputs.

Animals↗
PubMed2000

Lung function response to cold air challenge in asthmatic and healthy children of 2-5 years of age.

The aim of the study was to assess feasibility, sensitivity, specificity, predictive value, and repeatability of cold, dry air challenge (CACh) as a diagnostic test for asthma in young children 2 to 5 yr of age. Response to a 4-min single-step isocapnic CACh was measured in 38 asthmatics and 29 control subjects. Specific airway resistance (sRaw) by whole body plethysmography was the primary outcome. In addition, lung function was measured as respiratory resistance by the interrupter technique (Rint) and respiratory resistance and reactance at 5 Hz (Rrs5, Xrs5) by the impulse oscillation technique. At baseline, lung function measures differed significantly between asthmatics and healthy control subjects. CACh was readily performed in young children. Response was expressed as change from baseline in numbers of within-subject standard deviation (SDw). Hyperresponsiveness defined as change in lung function of more than 3 SDw was detected by sRaw in 26 of 38 asthmatics versus 2 of 29 control subjects, by Rint in 12 of 38 asthmatics versus 1 of 29 control subjects, by Xrs5 in 9 of 38 asthmatics versus zero of 29 control subjects and by Rrs5 in 7 of 38 asthmatics versus 1 of 29 control subjects. Thus sRaw had the highest sensitivity (68%). Specificity ranged from 93 to 100%. The correlation coefficient between sRaw responses to CACh repeated within 8 wk was 96%. In conclusion, CACh is feasible in young children age 2 to 5 yr. Whole body plethysmography (sRaw) was superior in separating asthmatics from healthy control subjects. Change in sRaw in response to CACh may be used as a diagnostic test for asthma in young children.

Asthma↗
PubMed1982

Contact lenses in extreme cold environments: response of rabbit corneas.

Contact lenses are worn by many individuals in military and civilian populations. Anecdotal reports have described contact lenses "sticking" and "freezing" to the eye during extreme cold conditions. However, some articles indicate the advantages of wearing contact lenses in cold environments. Military operations frequently taken place in cold regions; therefore, we need to known whether contact lenses can be worn safely in extreme cold. Rabbits were fitted with hard (polymethyl methacrylate) contact lenses and exposed to -28.9 degrees C temperatures with winds up to 78 mph (125 km/hr) for 3-hr periods. The wind-chill factor in these conditions exceeded -67.8 degrees C. No effects of the cold or contact lenses were seen in 85% of the eyes. A few of the eyes, both with contact lenses and without, showed mild superficial fluorescein staining of the cornea which cleared within a few ours after exposure. Histologic examination of the corneas revealed no abnormalities attributable to the cold. Inasmuch as this study showed that rabbits wearing contact lenses in extreme cold suffered no acute deleterious effects to the eyes, the research can be expanded to include human subjects.

Animals↗
PubMed1987

Comparison between hypothalamic thermoresponsive neurons from duck and rat slices.

Neuronal thermoresponsiveness in the preoptic and anterior hypothalamic (PO/AH) region of a bird and a mammal were compared in vitro by recording the activity of 48 units from ducks and 37 units from rats in tissue slices subjected to temperature changes. Warm-responsive units were found in similar proportions in duck and rat PO/AH slices. The average degrees of thermoresponsiveness did not differ between the two species. Neurons exhibiting thresholds of warm responsiveness had higher threshold temperatures (2P less than 0.01) in duck (38.8 +/- 0.2 degrees C) than in rat (37.4 +/- 0.4 degrees C) slices (means +/- standard errors). Firing rates at threshold temperatures and thermoresponsiveness below and above thresholds did not differ between ducks and rats. During synaptic blockade in a Ca2+-free/high-Mg2+ medium, warm-responsiveness was retained in 9 out of 13 units in duck slices and in 8 out of 13 units in rat slices. In two instances in ducks and in one case in rats positive temperature coefficients were converted into negative temperature coefficients. Among two cold-responsive units tested in duck slices one retained its cold-responsiveness. It is concluded that in vitro evaluation of PO/AH neuronal thermoresponsiveness in a bird and a mammal has not revealed differences at the single unit level which might explain the diverging contributions of the avian and mammalian hypothalamus to deep body temperature perception.

Action Potentials↗
PubMedDate not supplied

Sex differences and incentive effects on perceptual and cardiovascular responses to cold pressor pain.

OBJECTIVE: Sex differences in pain perception have been widely reported, with women typically displaying greater pain sensitivity than men, but the mechanisms underlying these differences remain unclear. One possible explanation suggests that men are more motivated to tolerate and suppress expressions of pain because of the masculine sex role, whereas the feminine sex role encourages pain expression and produces lower motivation to tolerate pain among women. METHODS: To examine the influence of motivation on perceptual and cardiovascular responses to pain among women and men, different levels of monetary incentive (high vs. low incentive) were provided to a group of 81 healthy young adults undergoing the cold pressor pain procedure. It was anticipated that men would have greater endogenous motivation and would therefore be less affected by the external incentive. RESULTS: Men had higher pain thresholds and tolerances and lower pain ratings than women, but the incentive condition produced no significant effect on pain responses. Resting blood pressure was positively correlated with pain tolerance among the low incentive group, whereas blood pressure reactivity to the cold pressor predicted pain tolerance in the high incentive group. CONCLUSIONS: Thus, monetary incentive did not influence pain responses, but the relationship between cardiovascular measures and pain responses was influenced by the incentive manipulation. Potential explanations for the observed results are presented, and the implications for applying the biopsychosocial model to pain research are discussed.

Adult↗
PubMed2004

Uncoupling protein 2 and 3 in marsupials: identification, phylogeny, and gene expression in response to cold and fasting in Antechinus flavipes.

We searched for the presence of uncoupling protein genes so far unknown in marsupials and monotremes and identified uncoupling protein 2 (UCP2) and UCP3 full-length cDNAs in libraries constructed from the marsupials Antechinus flavipes and Sminthopsis macroura. Marsupial UCP2 is 89-90% identical to rodent UCP2, whereas UCP3 exhibits 80% identity to mouse UCP3. A phylogenetic tree including all known UCPs positions the novel marsupial UCP2 and UCP3 at the base of the mammalian orthologs. In the 5'-untranslated region of UCP2 a second open reading frame encoding for a 36-amino acid peptide was identified which is highly conserved in all vertebrate UCP2 transcripts. Analysis of tissue specificity in A. flavipes with homologous cDNA probes revealed ubiquitous presence of UCP2 mRNA and striated muscle specificity of UCP3 mRNA resembling the known expression pattern in rodents. Neither UCP2 nor UCP3 gene expression was stimulated in adipose tissue and skeletal muscle of cold exposed A. flavipes. However, UCP3 mRNA expression was upregulated 6-fold in heart and 2.5-fold in skeletal muscle as reported for rodents in response to fasting. Furthermore, UCP3 mRNA seems to be coregulated with PDK4 mRNA, indicating a relation to enhanced lipid metabolism. In contrast, UCP2 gene expression was not regulated in response to fasting in adipose tissue and skeletal muscle but was diminished in the lung and increased in adipose tissue. Taken together, the sequence analysis, tissue specificity and physiological regulation suggest a conserved function of UCP2 and UCP3 during 130 million years of mammalian evolution.

Amino Acid Sequence↗
PubMed2005

Vasomotor response to cold stimulation in human capsaicin-induced hyperalgesic area.

Cooling the skin induces sympathetically driven vasoconstriction, with some vasoparalytic dilatation at the lowest temperatures. Neurogenic inflammation, on the other hand, entails vasodilatation. In this study we investigated the balance between vasoconstriction and vasodilatation in an area of experimentally induced secondary hyperalgesia (2 degrees HA), in response to low-temperature stimulations. Fourteen healthy volunteers were exposed to three 30-s long cold stimuli (20, 10, and 0 degrees C) applied, at three adjacent sites, before (baseline) and 8 min after intradermal injection of 50 microg capsaicin to the volar forearm. The cold stimuli were applied distally to the injection site within the 2 degrees HA. Blood flux (BF) and skin temperatures were measured at four different regions (proximally, and distally to the capsaicin injection and at the 0, 10, and 20 degrees C thermode sites) all within the 2 degrees HA. The vascular measurements were conducted five times. Results showed a marked increase in BF after baseline cold stimulation (P<0.001) at the 0 degrees C compared with the three other sites. In addition, vasodilatory effect (elevated BF) was found following the capsaicin injection compared with baseline for all regions (P<0.001): the non-cooled area was dilated by 450+/-5.1%; The vasoconstrictive effect for the 10 and 20 degrees C did not overcome the capsaicin vasodilatation, but did reduce it, with dilatation of 364+/-7.0% and 329+/-7.3%, respectively. For 0 degrees C, a dilatation of 407+/-6.5% was seen. It is concluded that in this experimental model, and potentially in the equivalent clinical syndromes, vasodilatation induced by the inflammation is only slightly reduced by cold stimulation such that it is still dominant, despite some cold-induced vasoconstriction.

Adult↗