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PubMed2003

Cold shock response and major cold shock proteins of Vibrio cholerae.

When exponentially growing Vibrio cholerae cells were shifted from 37 degrees C to various lower temperatures, it was found that the organism could adapt and grow at temperatures down to 15 degrees C, below which the growth was completely arrested. There was no difference between the patterns of the cold shock responses in toxinogenic and nontoxinogenic strains of V. cholerae. Gel electrophoretic analyses of proteins of cold-exposed cells revealed significant induction of two major cold shock proteins (Csps), whose molecular masses were 7.7 kDa (CspA(VC)) and 7.5 kDa (CspV), and six other Csps, most of which were much larger. We cloned, sequenced, and analyzed the cspV gene encoding the CspV protein of V. cholerae O139 strain SG24. Although CspA(VC) and CspV have similar kinetics of synthesis and down-regulation, the corresponding genes, cspA and cspV, which are located in the small chromosome, are not located in the same operon. A comparative analysis of the kinetics of synthesis revealed that the CspV protein was synthesized de novo only during cold shock. Although both CspA(VC) and CspV were stable for several hours in the cold, the CspV protein was degraded rapidly when the culture was shifted back to 37 degrees C, suggesting that this protein is probably necessary for adaptation at lower temperatures. Northern blot analysis confirmed that the cspV gene is cold shock inducible and is regulated tightly at the level of transcription. Interestingly, the cspV gene has a cold shock-inducible promoter which is only 12 nucleotides from the translational start site, and therefore, it appears that no unusually long 5' untranslated region is present in its mRNA transcript. Thus, this promoter is an exception compared to other promoters of cold shock-inducible genes of different organisms, including Escherichia coli. Our results suggest that V. cholerae may use an alternative pathway for regulation of gene expression during cold shock.

Bacterial Proteins↗

PubMed1989

Nociceptive neurons in rat superior colliculus: response properties, topography, and functional implications.

1. Extracellular recordings were made from single superior colliculus neurons in urethane-anesthetized rats in response to mechanical and/or thermal stimulation of the skin. In addition to those activated by low-threshold (LT) tactile stimuli, many neurons responded preferentially, or solely, to noxious stimuli. Two functionally defined subtypes of nociceptive neurons were distinguished: wide-dynamic-range (WDR) neurons, which responded optimally to noxious stimuli but also to innocuous stimuli; and nociceptive-specific (NS) neurons, which responded solely to frankly noxious stimuli. The thermal thresholds were 42-45 degrees C, and the stimulus-response relationships were positively accelerating power functions with exponents of 2.9 (WDR) and 3.1 (NS). 2. WDR neurons also responded to cooling of the skin to temperatures below 24 degrees C. Like noxious heat responses, cold responses were monotonically graded as the intensity of the cold stimulus was increased. Thus the temperature sensitivity of thermal-sensitive neurons in the superior colliculus appeared to be tuned to detect large deviations from ambient skin temperature in either direction once threshold is reached. 3. LT neurons were somatotopically organized, with the head and forelimbs rostral and the trunk and hindlimbs caudal. The limbs were generally represented further lateral in the structure, whereas more proximal body parts were more medial. Nevertheless, there was extensive overlap of body parts especially in areas of transition. Thus, a "block-to-block" or "area-to-area" rather than a "point-to-point" representation of the body surface was evident. 4. The nociceptive representation did not violate the general LT somatotopy but neither was it coextensive. Virtually all nociceptive neurons had trigeminal receptive fields and were thus heavily represented in the rostral superior colliculus, where the LT face representation was also located. No nociceptive neurons were present in the caudal one-third of the structure. A general dorsal-to-ventral segregation of somatosensory neurons also was noted, so that in a given electrode penetration, LT neurons usually were the most superficial, WDR neurons were just below these, and NS neurons were deepest of all. 5. The presence of overlapping LT and nociceptive trigeminal representations in the superior colliculus seems particularly adaptive in view of the fact that rodents use their vibrissae for exploring their environment and thus put rostral body parts at risk during such behaviors.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1986

The ventral septal area: electrophysiological evidence for putative arginine vasopressin projections onto thermoresponsive neurons.

The present experiments were conducted to identify thermoresponsive neurons in the ventral septal area and to characterize such units with respect to their connectivity to potential sources of arginine vasopressin in this area (the paraventricular nucleus and the bed nucleus of the stria terminalis) and to other brain regions (fornix and amygdala). Single unit in vivo microelectrode techniques were used to classify warm responsive, cold responsive, dynamic, biphasic and phasically active thermoresponsive neurons in the ventral septal area which altered their spontaneous activity in response to thermal stimulation of the scrotal skin. The fornix provided a large number of primarily inhibitory afferents to ventral septal thermoresponsive neurons while the amygdala projection consisted of approximately equal excitatory and inhibitory inputs. Electrical stimulation of the paraventricular nucleus resulted in orthodromic inhibition in 9 of 12 thermoresponsive units while projections from the bed nucleus of the stria terminalis appeared to preferentially inhibit warm responsive neurons in this area. These findings implicate the ventral septal area in thermoregulatory pathways by identifying neurons in this area responsive to peripheral thermal stimulation. Further, evidence in support of arginine vasopressin acting in this area to influence thermoregulation is provided by the identification of the paraventricular nucleus and bed nucleus of the stria terminalis as possible sources of afferents to the ventral septal area, and the characterization of the influence of this afferent input on thermoresponsive neurons in this region.

Action Potentials↗

PubMed1996

RbfA, a 30S ribosomal binding factor, is a cold-shock protein whose absence triggers the cold-shock response.

The cold-shock response, characterized by a specific pattern of gene expression, is induced upon a downshift in temperature and in the presence of inhibitors of ribosomal function. Here, we demonstrate that RbfA of Escherichia coli, considered to be involved in ribosomal maturation and/or initiation of translation, is a cold-shock protein. Shifting the rbfA mutant to a lower temperature resulted in a constitutive induction of the cold-shock response accompanied by slower growth at low temperatures, while shifting the rbfA mutant that overproduces wild-type RbfA resulted in an increase in total protein synthesis accompanied by faster growth adaptation to the lower temperature. Furthermore, the cold-shock response was also constitutively induced in a cold-sensitive 16S rRNA mutant at low temperatures. Accompanying the transient induction of the cold-shock response, we also report that shifting E. coli from 37 degrees C to 15 degrees C resulted in a temporary inhibition of initiation of translation, as evidenced by the transient decrease in polysomes accompanied by the transient increase in 70S monosomes. The accumulative data indicate that the inducing signal for the cold-unadapted non-translatable ribosomes which are converted to cold-adapted translatable ribosomes by the association of cold-shock proteins such as RbfA. Therefore, the expression of the cold-shock response, and thus cellular adaptation to low temperature, is regulated at the level of translation. The data also indicate that cold-shock proteins can be translated by ribosomes under conditions that are not translatable for most mRNAs.

Bacterial Proteins↗

PubMed1997

Increased transcript level of RBM3, a member of the glycine-rich RNA-binding protein family, in human cells in response to cold stress.

Although the cold-shock responses of microorganisms have been extensively investigated, those of mammalian cells are just beginning to be understood. Recently, CIRP, a member of the glycine-rich RNA-binding protein (GRP) family, has been identified as the first cold-shock protein in mammalian cells. Here, we report that RBM3, another member of the GRP family, is induced in human cells in response to cold stress (32 degrees C). RBM3 transcripts were constitutively expressed in all cell lines examined including K562, HepG2, NC65, HeLa, and T24 cells. In all of them, the transcript levels of RBM3 were increased at 24 h after the 37 to 32 degrees C temperature down-shift. In NC65 cells, the kinetics of RBM3 induction was different from that of CIRP. Protein synthesis inhibitors cycloheximide and puromycin induced RBM3 transcripts, but cadmium chloride, H2O2, ethanol, and osmotic shock had no effect. Combined with the different tissue distribution of expression, these results suggest that RBM3 and CIRP play distinct roles in cold responses of human cells.

Carcinoma, Hepatocellular↗

PubMed2026

Genome-wide identification of WOX transcription factors and functional characterization of WOX4 and WOX13 involved in cold stress response in Malus baccata.

INTRODUCTION: Cold stress is a major abiotic threat to apple production. Malus baccata has exceptional cold hardiness and is widely used as a superior cold-resistant rootstock. The WUSCHEL-related homeobox (WOX) transcription factor family regulates plant growth, development and stress adaptation, whereas the functions of WOX genes in cold tolerance of M. baccata remain elusive. METHODS: In the present work, 19 MbWOX family members were identified and characterized at the genome-wide level. Evolutionary analysis, cis-element prediction, transcriptome profiling and real-time quantitative PCR (RT-qPCR) were performed to screen core cold-responsive genes. Overexpression vectors were constructed and transformed into Arabidopsis seedlings for functional verification. RESULTS: Evolutionary analysis revealed that segmental duplication drove the expansion of the MbWOX family, and these genes contained a variety of stress-responsive cis-elements. Combined transcriptome and RT-qPCR analyses confirmed that MbWOX4 and MbWOX13 were core cold-responsive genes with distinct expression patterns. The two genes participated in cold signal transduction by interacting with different transcription factor networks. Functional tests revealed that MbWOX4 and MbWOX13 isoforms differentially modulated seedling cold tolerance under low-temperature stress.

Malus baccata↗

PubMedDate not supplied

Cold stress response in patients with severe burns after beta-blockade.

Adrenergic receptor blockade has been shown to be of benefit in the treatment of adverse cardiovascular changes in patients with burns during the hypermetabolic phase. This article examines the stress response to cold exposure in adults and children with 33% to 95% total body surface area burns with and without beta-blockade. Resting energy expenditures were measured by indirect calorimetry; the test subjects were exposed to mean temperatures of 27.5 degrees C (room temperature) or 24.6 degrees C (cold). The mean resting energy expenditure at ambient room temperature in patients with burns without beta-blockade was 1411 +/- 70 kcal/m2/day (mean +/- SEM). This value was 142% of that predicted for normal control subjects without burns. When placed in a cold temperature, patients with burns significantly increased their resting energy expenditures by 160% of predicted values, whereas patients with similar burns and beta-blockade increased their resting energy expenditures by 156%. Adults with septic burns had a mean resting energy expenditure 198% of the predicted value. These patients did not significantly increase their resting energy expenditures when they were exposed to cold either with or without beta-blockade. Data suggest that patients with septic burns already have a maximal metabolic response and that cold stress does not further increase this response. Males, ages 17 to 54 years, were found to increase their resting energy expenditures by 11.4 kcal/m2/day for each percent total body surface area burn. We conclude that beta-blockade with propranolol in therapeutic doses may be used in patients with burns without adversely affecting the cold stress response.

Adrenergic beta-Antagonists↗

PubMed1990

Effects of fasting and refeeding on the level of uncoupling protein mRNA in rat brown adipose tissue: evidence for diet-induced and cold-induced responses.

Brown adipose tissue (BAT) is characterized by the existence of a unique mitochondrial protein (uncoupling protein or UCP) that uncouples oxidative phosphorylation and thus allows heat production. Its role in thermogenesis has been emphasized in recent years in response to cold stress (nonshivering thermogenesis, NST) as well as to hyperphagia (diet-induced thermogenesis, DIT). The present work was a first attempt to determine whether varying nutritional conditions could affect UCP gene expression. Total RNA was isolated from interscapular BAT and hybridized with a cDNA probe for UCP. Changes in UCP mRNA level were studied in rats fasted and refed for various periods at 23 or 28 degrees C. A 2 d fast at 23 degrees C reduced UCP mRNA level, whereas refeeding increased it. A prolonged starvation (53 h) induced an unexpected rise in UCP mRNA, which was associated with a fall in body temperature. Increasing the ambient temperature to thermoneutrality (28 degrees C) suppressed the fall in body temperature as well as the rise in UCP mRNA, which could then be characterized as a cold-induced response. Under the same environmental conditions (28 degrees C), refeeding still triggered a sharp, though transient, increase in UCP mRNA, showing that DIT was dissociated from NST.

Adipose Tissue, Brown↗

PubMed1998

Effect of amezinium metilsulfate on the finger skin vasoconstrictor response to cold stimulation and venoconstrictor response to noradrenaline.

Orthostatic hypotension can be caused by an inadequate vasoconstrictor response. The effects of amezinium on vasoconstrictor response to sympathetic stimulation and to exogenous noradrenaline were investigated and compared with those of midodrine. In 8 healthy men, the following experiments were performed after a single oral dose of 10mg of amezinium, 2mg of midodrine or a placebo. First, finger-tip blood flow (FTBF) was recorded using a laser Doppler flowmeter before and during the contralateral hand cooling and a reduction ratio of FTBF was calculated as an index of the vasoconstrictor response. Second, dose-response curves to increasing doses (1-512ng/min) of noradrenaline infused locally to the dorsal hand vein were determined using a linear variable differential transformer. The reduction ratio of FTBF was significantly increased (p<0.05) by amezimium [placebo, 75.9 +/- 9.8(mean +/- SD)%; amezinium, 85.1 +/- 7.9%; midodrine, 78.1 +/- 9.3%]. The infusion rate of noradrenaline producing a half-maximum venoconstriction was significantly decreased (p<0.05) by amezinium (placebo, 40.6 +/- 33.9 ng/min; amezinium, 21.0 +/- 21.3 ng/min; midodrine, 33.2 +/- 31.5 ng/min). These findings indicate that amezinium increases the vasoconstrictor response to sympathetic stimulation and to noradrenaline in normal subjects, and this mechanism might contribute to the improvement by amezinium of the symptoms of orthostatic hypotension.

Adrenergic alpha-Agonists↗

PubMed1976

Effects of diets on cold tolerance and metabolic responses to cold in fasted rats.

Effects of high-fat and high-protein diets on cold tolerance in fasted rats were investigated. High-fat diets caused significant increases in body weight, blood-free fatty acids (FFA), ketone bodies and glucose, while high-protein diet did not modify any of these parameters. Rats on high-fat diets that were exposed to cold after clipping exhibited an intermediate cold tolerance as assessed by the rate of fall in colonic temperature between control rats on a standard diet and cold-acclimated rats. The extent of increase of blood FFA and decrease of blood glucose due to cold exposure was less in the high-fat diet group than in control group, but greater than in cold-acclimated group. The lower fall in colonic temperature due to cold exposure was signifcantly associated with less increase in blood FFA and less decrease in blood glucose. In this relation the high-fat diet group was also intermediate between the control and cold-acclimated groups. The high-protein diet did not make any difference in cold tolerance and cold-induced changes in blood metabolites as compared with those in control standard diet, although it resulted in a marked increase in urinary nitrogen excretion. These results indicate that a high-fat diet could exert a significant favorable effect on cold tolerance in fasted rats, but the effect would not be as much as as in cold acclimated rats.

Adaptation, Physiological↗

PubMed1990

The effect of clothing on the initial responses to cold water immersion in man.

The protection provided by three clothing assemblies against the cold shock response was investigated. Nine healthy male volunteers each undertook three two minute head-out immersions into stirred water at 10 degrees C. The subjects wore a different clothing assembly for each immersion, these were: a) Swimming trunks only; b) Conventional clothing (equivalent to RN No 8s); c) Conventional clothing plus windproof/shower-proof clothing (RN foul-weather clothing Mk III). The cardiac, ventilatory and thermal responses of the subjects were examined before and during the immersions. No significant differences were found between the magnitude of the responses recorded on immersion when conventional clothing or foul-weather clothing were worn. Mean skin temperature was lower (P less than 0.05) and respiratory frequency and minute ventilation were higher (P less than 0.05) on immersion in swimming trunks compared to the other two conditions. It is concluded that when policies for the use of immersion protective clothing are being formulated, consideration should be given to all of the potentially hazardous responses associated with cold water immersion.

Adult↗

PubMed1988

Vasoconstrictor response to cold in forestry workers: a prospective study.

In a five year prospective study of the vasoconstrictor response to cold 37 forestry workers were investigated in 1978 and again in 1983. The subjects were classified into three groups: group A (n = 13): no subjective finger symptoms in 1978 and continued sawing until 1983; group B (n = 12): no symptoms in 1978 and stopped sawing before 1983; group C (n = 12): vibration induced white finger (VWF) in 1978. A cold provocation test measuring the finger systolic blood pressure with a cuff and strain gauge technique during combined body cooling and finger cooling to 30 degrees, 15 degrees, and 6 degrees C was applied to all subjects at both investigations. In 1978 all groups had an increased cold response when compared with that of 20 non-exposed controls (p less than 0.05), and the response was more exaggerated in group C than in groups A and B (p less than 0.01). From 1978 to 1983 the vasoconstrictor response increased in group A (p less than 0.05), was in group B (p greater than 0.10), and improved in group C (p less than 0.05). The changes in cold response in groups A and C were significantly larger than the within day variation of the method (p less than 0.01). The aggravation of group A indicates that a further five years use of anti-vibration chain saws induced an increased hyperreactivity in the vasoconstrictor mechanisms but led to subjective symptoms of VWF in only one subject. The improvement in group C was in accordance with the improvements of subjective finger symptoms and was associated with a previous shift from saws without vibration damping devices to anti-vibration saws and with cessation of work. The results of group C indicate that VWF may improve or subjectively disappear if exposure to vibration is reduced or stopped. The cold provocation test was more sensitive than the Taylor-Pelmear stage assessments (p<0.05). The test may be of guidance in evaluation preventive measures.

Adolescent↗

PubMed1997

Responses of cutaneous A-fiber nociceptors to noxious cold.

Responses of cutaneous nociceptors to natural stimuli, particularly mechanical and heat stimuli, have been well documented. Although nociceptors are excited by noxious cold stimuli, there have been few studies of their stimulus-response functions for cold stimuli over a wide range of stimulus temperatures. Furthermore, the proportion of nociceptors excited by noxious cold is not clear. In the present study, we examined responses of mechanosensitive A delta-nociceptors and low-threshold mechanoreceptors to a wide range of cold stimuli that included stimulus temperatures <0 degrees C. Electrophysiological recordings were made from single primary afferent fibers in the saphenous nerves of anesthetized rats. Cutaneous sensory receptors were classed according to their conduction velocity and subgrouped functionally according to their responses evoked by mechanical, heat, and cold stimuli (0 degrees C). Responses evoked by a wide range of cold stimulus intensities that included stimuli considered innocuous and noxious (painful) were then assessed. Stimuli of 20 to -20 degrees C were delivered to the receptive field via a 1-cm2 contact thermode from a base temperature of 32 degrees C. Stimuli were applied in descending order of 2 degrees C decrements. Stimulus ramp rate was 5 degrees C/s, and stimulus temperatures were applied for a duration of 10 s. A total of 90 A fibers was studied, of which 61 were nociceptors and had conduction velocity in the A delta-range (2-30 m/s). Nociceptors were classed initially as mechanical, mechanoheat, and mechanocold nociceptors. The remaining 29 fibers were low-threshold mechanoreceptors with conduction velocity in the A delta- or A beta-range (>30 m/s). These were subgrouped according to their adaptive properties as slowly or rapidly adapting, and according to whether they were excited by hair movement (hair follicle afferent fibers). All nociceptors were excited by noxious cold. Only 30% of nociceptors were considered sensitive to cold on initial classification with the use of a cold stimulus of 0 degrees C. However, all nociceptors were excited by stimulus intensities <0 degreesC. Response thresholds for cold ranged from 14 to -18 degrees C (-4.6 +/- 1.07 degrees C, mean +/- SE). The total number of impulses, discharge rate, and peak discharge increased monotonically as intensity of cold stimuli increased. Power functions were used to determine the rate at which the number of impulses increased as stimulus intensity increased. The slopes of power funcions ranged from 0.12 to 2.28 (mean 1.07 +/- 0.13). Most mechanoreceptors were not excited by cold stimuli. The only types of mechanoreceptors that responded reliably to cold stimuli were the slowly adapting mechanoreceptors. Responses usually occurred during the temperature ramp when the skin temperature was decreasing. There was no evidence that mechanoreceptors encoded the intensity of cold stimuli at intensities above or below 0 degrees C, because evoked responses did not increase with intensity of cold stimuli. It is concluded that the proportion of cutaneous A delta-nociceptors excited by noxious cold stimuli has been underestimated in previous studies. All nociceptors were excited by stimulus temperatures <0 degrees C and encoded the intensity of cold stimuli. It is therefore likely that cutaneous A delta-nociceptors contribute to the sensation of cold pain, particularly pain produced by stimulus temperatures <0 degrees C.

Action Potentials↗

PubMed2001

Interpretation of the finger skin temperature response to cold provocation.

OBJECTIVES: To compare alternative methods of interpreting the response of finger skin temperature (FST) to cold provocation for the detection of the abnormal cold response observed in vibration-induced white finger (VWF). METHOD: The FST response to cold provocation was measured in 36 male subjects: 12 office workers, 12 manual workers and 12 manual workers with symptoms of VWF. The FSTs were monitored continuously on the distal phalanges of all five fingers of a test hand for 2 min before, for 5 min during, and for 10 min following, immersion of the test hand in water at 15 degrees C. Of the fingers investigated, 147 were reported not to exhibit blanching and 33 were reported to exhibit blanching. Twenty-one alternative methods of interpreting the response of FSTs to cold provocation were assessed. These were grouped as: (1) areas above the response profile (i.e. the area above the curve showing the FSTs as a function of time during cooling and recovery), (2) areas below the response profile, (3) absolute temperatures during and following cold provocation, (4) percentage differences in FSTs, (5) the times taken for FSTs to rise by specified amounts and (6) rates of change of FSTs. Differences in the response to cooling between those fingers reported to blanch and the fingers not reported to blanch were tested, and receiver operating characteristics (ROCs) were used to compare the sensitivity and specificity of the various measures to symptoms of VWF. RESULTS: The areas above the response profile, areas below the response profile, percentage FSTs, absolute FSTs and rates of change of FSTs tended to discriminate between healthy and unhealthy subjects on a group basis. However, some of these methods of interpreting the FST response to cold provocation did not show a high sensitivity or specificity to vascular dysfunction on individual fingers. The area above the response profile, the percentage of initial temperature at the fifth minute of recovery and the maximum temperature during the 10-min recovery period, were found to show the highest sensitivity and specificity to symptoms of vascular dysfunction. CONCLUSIONS: The method chosen to interpret the FST response to cold provocation affects the ability of the test to detect an abnormal cold response. The area above the response profile, the percentage of initial temperature at the fifth minute of recovery and the maximum temperature achieved during a 10-min recovery period appear to be the most suitable measures for monitoring vascular function in workers exposed to hand-transmitted vibration. It is suggested that the FST response to cold provocation should be interpreted with respect to the state of initial blood flow.

Adult↗

PubMed1995

The cold-shock response in bacteria.

The 'cold shock' response that occurs when exponentially growing Escherichia coli at 37 degrees C are transferred to 10 degrees C leads to the cesation of most protein synthesis, however, about 14 'cold shock' proteins continue to be made. These 'cold shock' proteins facilitate growth at low temperatures. Central to the regulation of this switch in gene expression is the 200 fold induction in the relative rate of synthesis of a small cold-shock protein only 70 amino acids in length, known as CS7.4. There is a remarkable conservation through evolution of the primary sequence found in this small cold shock protein and that of a nucleic acid binding domain within the Y-box family of eukaryotic gene regulatory proteins. Parallel studies on CS7.4 and the Y-box proteins have elucidated both molecular mechanisms regulating the cold shock response and a novel site for the regulation of eukaryotic gene expression.

Amino Acid Sequence↗

PubMed1985

Sympathetic and local vasoconstrictor response to cold in vibration induced white finger.

To study the relative roles of sympathetic and local vasoconstrictor response to cold in vibration induced white finger (VWF) seven lumberjacks with bilateral VWF and seven age matched controls were investigated. During body cooling finger systolic blood pressure was measured with a cuff technique simultaneously on one affected finger on each hand at 30 degrees, 15 degrees, and 6 degrees C. Both affected fingers had an increased vasoconstrictor response at 15 degrees and 6 degrees C compared with the control group (p less than or equal to 0.05). During unilateral sympathetic nerve block the cold provocation test was repeated on both fingers. The unblocked finger affected by VWF showed no significant difference in the cold response between the two cold provocation tests (p greater than 0.10). The local cold response of blocked finger did not differ from that of the control group (p greater than 0.10). The sympathetic vasoconstrictor response to cold was estimated as the difference between the cold response before nerve block and the cold response during nerve block. The median sympathetic vasoconstrictor response at 6 degrees C was about twice as large as the local response during nerve block (p less than 0.05). The results indicate that the sympathetic vasoconstrictor response to cold plays the dominant part in VWF.

Aged↗

PubMed1999

Adaptive response to cold temperatures in Vibrio vulnificus.

The effectiveness of rapid chilling or freezing of oysters to reduce Vibrio vulnificus levels in shellfish may be compromised by product handling procedures that permit cold adaptation. When a V. vulnificus culture was shifted from 35 degrees C to 6 degrees C conditions, it underwent transition to a non-culturable state. Cells adapted to 15 degrees C prior to change to 6 degrees C condition, however, remain viable and culturable. In addition, cultures adapted to 15 degrees C were able to survive better upon freezing at -78 degrees C compared with cultures frozen directly from 35 degrees C. Inhibition of protein synthesis by addition of chloramphenicol in a V. vulnificus culture immediately prior to the exposure to the adaptive temperature eliminated inducible cold tolerance. These results suggest that cold-adaptive "protective" proteins may enhance survival and tolerance at cold temperatures. In addition, removal of iron from the growth medium by adding 2,2'-Dipyridyl prior to cold adaptation decreased the viability by approximately 2 logarithm levels. This suggests that iron plays an important role in adaptation at cold temperatures. Analysis of total cellular proteins on an SDS polyacrylamide gel electrophoresis, labeled with 35S-methionine during exposure at 15 degrees C, showed elevated expressions of a 6-kDa and a 40-kDa protein and decreased expression of an 80-kDa protein. These results suggest that, for V. vulnificus, survival and tolerance at cold temperatures could be due to the expression of cold-adaptive proteins other than previously documented major cold shock proteins such as CS7.4 and CsdA. In this study, for the first time we have shown that exposure to an intermediate cold temperature (15 degrees C) causes a cold adaptive response, helping this pathogen remain in culturable state when exposed to a much colder temperature (6 degrees C). This adaptive nature to cold temperatures could be important for shellfish industry efforts to reduce the risk of V. vulnificus infection from consuming raw oysters.

Adaptation, Physiological↗

PubMed1986

Stimulation of ventromedial hypothalamus induces cold defense responses in conscious rabbits.

The involvement of the ventromedial hypothalamus (VMH) in thermoregulatory responses, which include heat production and heat loss responses, was investigated by the method of electrical stimulation. Electrical stimulation of the VMH caused a rise in rectal temperature, accompanied by the enhancement of heat production: O2 consumption and shivering. In addition, a reduction in heat loss was observed, including decreases in skin temperature (Ts), respiratory rate, and body surface area resulting from a huddled posture. In this study, stimulation of the lateral hypothalamus and other regions near the VMH had no effect on thermoregulatory responses. beta-Blocker (propranolol, 1 mg/kg iv) injected 20 min before stimulation lessened O2 consumption by approximately 10% and attenuated the reduction in Ts during VMH stimulation, whereas alpha-blockade (phentolamine, 1 mg/kg iv) was ineffective. These results indicate that most of the increase in O2 consumption during VMH stimulation was due to the occurrence of shivering but that some component of it could be due to nonshivering thermogenesis. They also indicate that the VMH, either directly or by converging influences, is involved in the activation of thermoregulatory responses to cold stress.

Adrenergic beta-Antagonists↗