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PubMed1998

Behavioral approach to the study of the upper limit of temperature tolerance in rats.

A simple test of critical thermal maximum (CTM) to assess a break-down of heat-escape behavior in rats is described. Experiments were performed on 18 unrestrained adult Wistar rats of both sexes. Hypothalamic and intraperitoneal (i.p.) temperatures as well as motor activity were simultaneously and continuously recorded in the rats exposed to heat. When animals were growing restless, as evidenced by an increase in their motor activity, which was usually recorded at hypothalamic temperatures well above 41 degrees C, we started testing CTM. To assess heat-escape behavior we used a precooled cooling bar (a part of a camp-cooler) which was placed at intervals in a climatic chamber. The hyperthermic rats, given the bar for 30 s, mounted it vigorously until they failed at particular levels of brain and body temperatures which were recognized as respective CTM values. Rapid external cooling of rats prevented lethal effects of the heat exposure. We were able to show effects of timing of heat exposure on heat tolerance. We also managed to detect small but significant differences in heat tolerance of warm-reared (an increase), cold-reared (a decrease), and bacterial-endotoxin-treated (an increase) rats. The heat-escape behavior was less heat-resistant than selective brain cooling response which was still present at CTM point. In conclusion, our CTM test is a safe and reliable way to study heat tolerance in rats.

Animals↗
PubMed2003

Expression profiling and bioinformatic analyses of a novel stress-regulated multispanning transmembrane protein family from cereals and Arabidopsis.

Cold acclimation is a multigenic trait that allows hardy plants to develop efficient tolerance mechanisms needed for winter survival. To determine the genetic nature of these mechanisms, several cold-responsive genes of unknown function were identified from cold-acclimated wheat (Triticum aestivum). To identify the putative functions and structural features of these new genes, integrated genomic approaches of data mining, expression profiling, and bioinformatic predictions were used. The analyses revealed that one of these genes is a member of a small family that encodes two distinct groups of multispanning transmembrane proteins. The cold-regulated (COR)413-plasma membrane and COR413-thylakoid membrane groups are potentially targeted to the plasma membrane and thylakoid membrane, respectively. Further sequence analysis of the two groups from different plant species revealed the presence of a highly conserved phosphorylation site and a glycosylphosphatidylinositol-anchoring site at the C-terminal end. No homologous sequences were found in other organisms suggesting that this family is specific to the plant kingdom. Intraspecies and interspecies comparative gene expression profiling shows that the expression of this gene family is correlated with the development of freezing tolerance in cereals and Arabidopsis. In addition, several members of the family are regulated by water stress, light, and abscisic acid. Structure predictions and comparative genome analyses allow us to propose that the cor413 genes encode putative G-protein-coupled receptors.

Acclimatization↗
PubMed2006

Safety, efficacy, and effectiveness of cold-adapted influenza vaccine-trivalent against community-acquired, culture-confirmed influenza in young children attending day care.

OBJECTIVE: The goal was to evaluate the safety, tolerability, and efficacy of an investigational, refrigerator-stable formulation of live attenuated influenza vaccine (cold-adapted influenza vaccine-trivalent) against culture-confirmed influenza, acute otitis media, and effectiveness outcomes in young children in day care over 2 consecutive influenza seasons. METHODS: Children 6 to <36 months of age who were attending day care were assigned randomly in year 1 to receive 2 doses of vaccine or placebo intranasally, 35 +/- 7 days apart. In year 2, subjects received 1 dose of the same treatment as in year 1. RESULTS: A total of 1616 subjects (vaccine: 951 subjects; placebo: 665 subjects) in year 1 and 1090 subjects (vaccine: 640 subjects; placebo: 450 subjects) in year 2 were able to be evaluated for efficacy. The mean age at first vaccination was 23.4 +/- 7.9 months. In year 1, the overall efficacy of the vaccine against influenza subtypes similar to the vaccine was 85.4%; efficacy was 91.8% against A/H1N1 and 72.6% against B. In year 2, the overall efficacy was 88.7%; efficacy was 90.0% against H1N1, 90.3% against A/H3N2, and 81.7% against B. Efficacy against all episodes of acute otitis media associated with culture-confirmed influenza was 90.6% in year 1 and 97.0% in year 2. Runny nose or nasal discharge after dose 1 in year 1 was the only reactogenicity event that was significantly more frequent with cold-adapted influenza vaccine-trivalent (82.3%) than placebo (75.4%). CONCLUSIONS: Cold-adapted influenza vaccine-trivalent was well tolerated and effective in preventing culture-confirmed influenza illness in children as young as 6 months of age who attended day care.

Acute Disease↗
PubMed2004

Cold and heat pain assessment of the human oesophagus after experimental sensitisation with acid.

The aim of the present study was to investigate the effect of thermal stimulation of the oesophagus before and after sensitisation with acid. In 17 healthy subjects a stimulation bag was used to re-circulate water at 5 and 60 degrees C for up to 90 s in the lower part of the oesophagus. The area under the temperature curve was used to assess the caloric load. The thermal stimuli were repeated after perfusion of the oesophagus with acid. The evoked pain intensity and referred pain areas (at the pain threshold) were assessed. At baseline the subjects were able to tolerate less caloric load (42%) for the heat compared to the cold stimuli (P = 0.007). The heat stimuli resulted in an increased referred pain area as compared with the cold stimuli (P = 0.03). Following acid perfusion there was a selective sensitisation to the heat pain stimuli as only 36% of the initial caloric load was tolerated (P = 0.012) whereas the sensation to the cold stimuli was unchanged. After acid perfusion, the referred pain area to the heat pain stimulation increased 49% (P = 0.04) but was not changed to cold stimulation (P = 0.82). After sensitisation the words used to describe the sensations to heat pain stimuli shifted from a warmth quality towards a more burning quality in most subjects. This multi-modal sensory testing study showed that acid sensitises the oesophagus to heat but not to cold pain. This may account for the modality-specific symptoms and hypersensitivity reported in patients suffering from, e.g. gastro-oesophageal reflux disease.

Acids↗
PubMed2004

Oxygen limited thermal tolerance in fish?--Answers obtained by nuclear magnetic resonance techniques.

In various phyla of marine invertebrates limited capacities of both ventilatory and circulatory performance were found to set the borders of the thermal tolerance window with limitations in aerobic scope and onset of hypoxia as a first line of sensitivity to both cold and warm temperature extremes. The hypothesis of oxygen limited thermal tolerance has recently been investigated in fish using a combination of non-invasive nuclear magnetic resonance (NMR) methodology with invasive techniques. In contrast to observations in marine invertebrates arterial oxygen tensions in fish were independent of temperature, while venous oxygen tensions displayed a thermal optimum. As the fish heart relies on venous oxygen supply, limited cardio-circulatory capacity is concluded to set the first level of thermal intolerance in fish. Nonetheless, maximized ventilatory capacity is seen to support circulation in maintaining the width of thermal tolerance windows. The interdependent setting of low and high tolerance limits is interpreted to result from trade-offs between optimized tissue functional capacity and baseline oxygen demand and energy turnover co-determined by the adjustment of mitochondrial densities and functional properties to a species-specific temperature range. At temperature extremes, systemic hypoxia will elicit metabolic depression, thereby widening the thermal window transiently sustained especially in those species preadapted to hypoxic environments.

Acclimatization↗
PubMed2002

Characterization of Sphingomonas sp. Ant 17, an aromatic hydrocarbon-degrading bacterium isolated from Antarctic soil.

Sphingomonas sp. strain Ant 17 was isolated from fuel-contaminated soil collected at Scott Base, Ross Island, Antarctica. We anticipated that Ant 17 would be a good model organism for studying cold climate bioremediation, and therefore determined its biodegradation capabilities and tolerance of potentially growth-limiting environmental conditions. Sphingomonas sp. Ant 17 degrades the aromatic fraction of several different crude oils, jet fuel, and diesel fuel at low temperatures and without nutrient amendment. It utilizes or transforms a broad range of pure aromatic substrates, including hydrocarbons, heterocycles, and aromatic acids and alcohols. Ant 17 grows at temperatures of 1 degree C to 35 degrees C and mineralizes radiolabeled phenanthrene over a range of more than 24 degrees C. This psychrotolerant isolate appears to utilize hydrocarbons more efficiently at low temperatures than would be predicted by mesophilic enzyme kinetics. The optimum pH for growth was 6.4 at 22 degrees C, with extended lag phases observed in more alkaline media. However, there was less effect of pH on lag phase at lower temperatures. Ant 17 displayed greater tolerance to UV irradiation and freeze-thaw cycles than the hydrocarbon-degrading isolate Sphingomonas sp. WPO-1, which may reflect adaptation to its Antarctic soil environment. However, it was more sensitive than expected to desiccation and to low concentrations of NaCl and CaCl(2). Ant 17 was phenotypically stable and lacked detectable plasmids, suggesting a chromosomal location for genes encoding aromatic degradation enzymes. Its broad aromatic substrate range and tolerance of low and fluctuating temperature and low nutrients make Sphingomonas sp. Ant 17 a valuable microbe for examining fuel spill bioremediation in cold soils.

Antarctic Regions↗
PubMed2000

The assessment of dermatomal level of surgical anesthesia after spinal tetracaine.

UNLABELLED: Transcutaneous electrical stimulation (TES), a 60-mA, 50-Hz continuous square wave, has been considered equivalent to surgical incision. We examined whether TES at a smaller current (10 mA) can be used to predict surgical anesthesia and compare the results with sensory block to cold, pinprick, and touch after the administration of spinal tetracaine. Two groups of 40 consecutive patients, 17-69 yr old and 70 yr old or older received a subarachnoid injection of 0. 5% tetracaine in 10% glucose or saline according to the type of surgery. Patients undergoing abdominal surgery received glucose solution, and those scheduled for lower extremities surgery received saline solution, and thus, the resultant four groups of patients were studied. Neural block was assessed by the loss of sensation to cold, pinprick, touch, and TES at 10 mA (T10s), and tolerance (i.e., the loss of pain or discomfort) to TES at 10 (T10p) and 60 (T60) mA. Dermatomal levels of sensory block to cold, pinprick, and touch that were cephalad to T60 varied widely. In contrast, dermatomal levels of T10s and T10p cephalad to T60 were less variable, and the difference between T10s and T60 was the smallest among all the differences in any groups. Our results demonstrate that, regardless of patient age and baricity of a local anesthetic solution, T10s is a good predictor of T60 equivalent to the dermatomal level of surgical anesthesia. IMPLICATIONS: Our results show that the loss of sensation to transcutaneous electrical stimulation at 10 mA, but not cold, pinprick, or touch, is a good predictor of the dermatomal level of block to transcutaneous electrical stimulation at 60 mA, which is considered equivalent to the dermatomal level of surgical anesthesia after the administration of spinal anesthesia.

Abdomen↗
PubMed2002

Resistance of cold- and starvation-stressed Vibrio vulnificus to heat and freeze-thaw exposure.

The effects of cold storage and starvation on the subsequent heat resistance and freeze-thaw resistance of Vibrio vulnificus were studied. Three strains of V. vulnificus were evaluated. Cold stress had no effect on freeze-thaw resistance (P > 0.05). Starvation enhanced freeze-thaw resistance for one strain compared to controls (P < 0.05). V. vulnificus was not heat resistant; control populations were inactivated within 12 min at 47 degrees C. Starvation increased heat tolerance for one strain, but differences were small from a processing perspective (P < 0.05). Cold stress had no effect on heat resistance (P > 0.05). Cold adaptation (holding 4 h at 15 degrees C) enhanced cold temperature (5 degrees C) tolerance. This information will be helpful in the development of methods to minimize V. vulnificus risk.

Adaptation, Physiological↗
PubMed2003

Effect of sequential heat and cold shocks on nuclear phenotypes of the blood-sucking insect, Panstrongylus megistus (Burmeister) (Hemiptera, Reduviidae).

Thermal shocks induce changes in the nuclear phenotypes that correspond to survival (heterochromatin decondensation, nuclear fusion) or death (apoptosis, necrosis) responses in the Malpighian tubules of Panstrongylus megistus. Since thermal tolerance increased survival and molting rate in this species following sequential shocks, we investigated whether changes in nuclear phenotypes accompanied the insect survival response to sequential thermal shocks. Fifth instar nymphs were subjected to a single heat (35 or 40 degrees C, 1 h) or cold (5 or 0 degrees C, 1 h) shock and then subjected to a second shock for 12 h at 40 or 0 degrees C, respectively, after 8, 18, 24 and 72 h at 28 degrees C (control temperature). As with specimen survival, sequential heat and cold shocks induced changes in frequency of the mentioned nuclear phenotypes although their patterns differed. The heat shock tolerance involved decrease in apoptosis simultaneous to increase in cell survival responses. Sequential cold shocks did not involve cell/nuclear fusion and even elicited increase in necrosis with advancing time after shocks. The temperatures of 40 and 0 degrees C were more effective than the temperatures of 35 and 5 degrees C in eliciting the heat and cold shock tolerances, respectively, as shown by cytological analysis of the nuclear phenotypes. It is concluded that different sequential thermal shocks can trigger different mechanisms of cellular protection against stress in P. megistus, favoring the insect to adapt to various ecotopes.

Analysis of Variance↗
PubMedDate not supplied

Antihypertensive action of nifedipine: effects on arteries and veins.

Nifedipine is a calcium-channel antagonist with effective antihypertensive activity and has been suggested for the treatment of high blood pressure as an alternative to vasodilators. The aim of this study was to define the acute effect of nifedipine and in particular the dose-effect relationship, effects on veins, influence on adrenergic reflexes, and effectiveness on hypertension according to severity and etiologic type. The effects of nifedipine on blood pressure, heart rate, forearm blood flow, peripheral vascular resistance, orthostatic and cold reflexes, and venous tone were examined in 45 patients with hypertension of different etiologies (essential, renovascular, and renal parenchymal) and different World Health Organization grades. The antihypertensive effect was dose dependent, but a dose of 20 mg has nearly maximal activity with acceptable side effects. The drug acts by lowering peripheral vascular resistance, and this lowering is directly related to baseline values; therefore, the antihypertensive effect increases with severity of the hypertension. Nifedipine had the same effect in all three etiologic groups of hypertension studied. The drug seems to increase venous tone, since it caused venoconstriction when locally injected in hand veins. Nifedipine did not alter adrenergic reflexes induced by both cold application and standing and was well tolerated. In conclusion, the calcium antagonist nifedipine for its characteristics of action, at least in acute administration, seems to be a useful alternative in the treatment of various forms of hypertension.

Adult↗
PubMed2006

Indole-3-acetic acid improves Escherichia coli's defences to stress.

Indole-3-acetic acid (IAA) is a ubiquitous molecule playing regulatory roles in many living organisms. To elucidate the physiological changes induced by IAA treatment, we used Escherichia coli K-12 as a model system. By microarray analysis we found that 16 genes showed an altered expression level in IAA-treated cells. One-third of these genes encode cell envelope components, or proteins involved in bacterial adaptation to unfavourable environmental conditions. We thus investigated the effect of IAA treatment on some of the structural components of the envelope that may be involved in cellular response to stresses. This showed that IAA-treated cells had increased the production of trehalose, lipopolysaccharide (LPS), exopolysaccharide (EPS) and biofilm. We demonstrated further that IAA triggers an increased tolerance to several stress conditions (heat and cold shock, UV-irradiation, osmotic and acid shock and oxidative stress) and different toxic compounds (antibiotics, detergents and dyes) and this correlates with higher levels of the heat shock protein DnaK. We suggest that IAA triggers an increased level of alert and protection against external adverse conditions by coordinately enhancing different cellular defence systems.

Adaptation, Physiological↗
PubMed2006

A cotton dehydration responsive element binding protein functions as a transcriptional repressor of DRE-mediated gene expression.

Dehydration responsive element binding proteins (DBPs) are members of a larger family of transcription factors that are specific to plants and play an important role in enhancing plant tolerance to environmental stresses such as drought, cold, and high salinity. To gain a better understanding of this type of protein, we reported here a novel DBP protein which functioned as a repressor of transcriptional in tobacco leaf cells. GhDBP1 was preferentially localized to the nucleus of onion epidermis cells and bound specifically to DRE (core sequence, A/GCCGAC) in vitro. In addition, RNA gel-blot analysis showed that expression of the GhDBP1 gene was mainly induced under osmotic stresses conditions such as drought and high salinity. These findings suggest that GhDBP1 can function as a transcriptional repressor for DRE element-mediated gene expression and provides an important insight into the molecular adaptation mechanisms of environmental stresses in cotton plants.

Amino Acid Sequence↗
PubMed1999

Sequence analysis of expressed sequence tags from an ABA-treated cDNA library identifies stress response genes in the moss Physcomitrella patens.

Partial cDNA sequencing was used to obtain 169 expressed sequence tags (ESTs) in the moss, Physcomitrella patens. The source of ESTs was a random cDNA library constructed from 7 day-old protonemata following treatment with 10(-4) M abscisic acid (ABA). Analysis of the ESTs identified 69% with homology to known sequences, 61% of which had significant homology to sequences of plant origin. More importantly, at least 11 ESTs had significant similarities to genes which are implicated in plant stress-responses, including responses which may involve ABA. These included a cDNA associated with desiccation tolerance, two heat shock protein genes, one cold acclimation protein cDNA and five others that may be involved in either oxidative or chemical stress or both, i.e., Zn/Cu-superoxide dismutase, NADPH protochlorophyllide oxidoreductase (PorB), selenium binding protein, glutathione peroxidase and glutathione S transferase. Analysis of codon usage between P. patens and seed plants indicated that although mosses and higher plants are to a large extent similar, minor variations also exists that may represent the distinctiveness of each group.

Abscisic Acid↗
PubMed1993

Splanchnic lactate production in cardiac surgery patients.

OBJECTIVE: To review the pathophysiology of lactic acidosis in patients undergoing open-heart surgery, with special reference to the splanchnic circulation. DATA SOURCE: MEDLINE search of pertinent experimental and clinical research studies. RESULTS: Lactate is an end-product of anaerobic metabolism and is in dynamic equilibrium with its precursor, pyruvate. The ratio of serum lactate to pyruvate concentrations in arterial blood is normally < or = 10:1. In patients with lactic acidemia, measurement of serum pyruvate concentrations may yield valuable clinical information. Lactate/pyruvate ratios > 10:1 suggest that oxygen delivery (DO2) is inadequate to meet metabolic demand, whereas increases in both lactate and pyruvate values with preservation of normal lactate/pyruvate ratios suggest a defect in oxidative utilization (e.g., a fractional increase in the inactive form of the pyruvate dehydrogenase enzyme complex) despite adequate DO2. Meaningful changes in regional oxygen kinetics occur during extracorporeal circulation. Increased production of endogenous vasoconstrictors in response to nonpulsatile flow, together with a decrease in arterial oxygen content resulting from the addition of 2 L of pump prime to the patient's circulation at the beginning of cardiopulmonary bypass, decrease DO2 to the gastrointestinal tract. The effect of this reduction is mitigated, in part, by lowering core temperature and reducing tissue oxygen demand. CONCLUSIONS: The abdominal organs tolerate reductions in DO2 when they are cold (25 degrees C), since gastric intramucosal pH (a marker of inadequate DO2), and hepatic venous lactate/pyruvate ratios and oxygen saturation during the first half of cardiopulmonary bypass are normal. As surgery nears completion and core temperature is increased, tissue oxygen demands escalate. The presence of gastric mucosal acidosis, coupled with lactic acidemia and oxygen desaturation of hepatic venous blood, suggest that delivery of oxygen to the abdominal organs at the conclusion of cardiopulmonary bypass is insufficient to meet demand. A growing proportion of cardiac surgery patients are older and many have concomitant medical problems that can impair their recovery. Useful strategies are needed to reduce the occurrence of splanchnic ischemia in these and other high-risk populations if surgical outcome is to improve in the future.

Coronary Artery Bypass↗
PubMed2004

clpB, a novel member of the Listeria monocytogenes CtsR regulon, is involved in virulence but not in general stress tolerance.

Clp-HSP100 ATPases are a widespread family of ubiquitous proteins that occur in both prokaryotes and eukaryotes and play important roles in the folding of newly synthesized proteins and refolding of aggregated proteins. They have also been shown to participate in the virulence of several pathogens, including Listeria monocytogenes. Here, we describe a member of the Clp-HSP100 family of L. monocytogenes that harbors all the characteristics of the ClpB subclass, which is absent in the closely related gram-positive model organism, Bacillus subtilis. Transcriptional analysis of clpB revealed a heat shock-inducible sigma(A)-type promoter. Potential binding sites for the CtsR regulator of stress response were identified in the promoter region. In vivo and in vitro approaches were used to show that expression of clpB is repressed by CtsR, a finding indicating that clpB is a novel member of the L. monocytogenes CtsR regulon. We showed that ClpB is involved in the pathogenicity of L. monocytogenes since the DeltaclpB mutant is significantly affected by virulence in a murine model of infection; we also demonstrate that this effect is apparently not due to a defect in general stress resistance. Indeed, ClpB is not involved in tolerance to heat, salt, detergent, puromycin, or cold stress, even though its synthesis is inducible by heat shock. However, ClpB was shown to play a role in induced thermotolerance, allowing increased resistance of L. monocytogenes to lethal temperatures. This work gives the first example of a clpB gene directly controlled by CtsR and describes the first role for a ClpB protein in induced thermotolerance and virulence in a gram-positive organism.

Adenosine Triphosphatases↗
PubMed2004

Isolation and molecular characterization of a new CRT binding factor gene from Capsella bursa-pastoris.

A new CRT binding factor (CBF) gene designated Cbcbf25 was cloned from Capsella bursa-pastoris, a wild grass, by the rapid amplification of cDNA ends (RACE). The full-length cDNA of Cbcbf25 was 898 bp with a 669 bp open reading frame (ORF) encoding a putative DRE/CRT (LTRE)-binding protein of 223 amino acids. The predicted CbCBF25 protein contained a potential nuclear localization signal (NLS) in its N-terminal region followed by an AP2 DNA-binding motif and a possible acidic activation domain in the C-terminal region. Bioinformatic analysis revealed that Cbcbf25 has a high level of similarity with other CBF genes like cbf1, cbf2, and cbf3 from Arabidopsis thaliana, and Bncbf5, Bncbf7, Bncbf16, and Bncbf17 from Brassica napus. A cold acclimation assay showed that Cbcbf25 was expressed immediately after cold triggering, but this expression was transient, suggesting that it concerns cold acclimation. Our study implies that Cbcbf25 is an analogue of other CBF genes and may participate in cold-response, by for example, controlling the expression of cold-regulated genes or increasing the freezing tolerance of plants.

Amino Acid Sequence↗
PubMed2000

Molecular responses to dehydration and low temperature: differences and cross-talk between two stress signaling pathways.

Recently, a major transcription system that controls abscisic-acid-independent gene expression in response to dehydration and low temperature has been identified. The system includes the DRE/CRT (dehydration-responsive element/C-repeat) cis-acting element and its DNA-binding protein, DREB/CBF (DRE-binding protein/C-repeat binding factor), which has an AP2 domain. DREB/CBF contains two subclasses, DREB1/CBF and DREB2, which are induced by cold and dehydration, respectively, and control the expression of various genes involved in stress tolerance. Recent studies are providing evidence of differences between dehydration-signaling and cold-stress-signaling cascades, and of cross-talk between them.

Adaptation, Physiological↗
PubMed1998

Gestational cocaine exposure alters postnatal pituitary-adrenal axis activity and stress endurance in rats.

Female pregnant Sprague-Dawley rats were injected once daily with 40 mg/kg cocaine hydrochloride or 0.9% saline from gestational day 12 (GD 12) to GD 21. From postnatal day 21 (PND 21) to PND 60, both male and female offspring were examined for stress response. Treated male and female offspring demonstrated a diminished tolerance to stress as determined by a cold water stress test performed at PND 21, 30 and 40. Base hormonal levels of adrenocorticotropin hormone (ACTH) and corticosterone were not affected by prenatal cocaine exposure in male offspring at PND 30. However, immobilization for 1 hr caused a significant sustained elevation of corticosterone levels at both PND 30 and PND 60 in male treated offspring as compared to the control group. Plasma ACTH levels were also significantly sustained after 1 hr of immobilization at PND 60 for the cocaine-treated male offspring. These results indicate both a diminished capacity to respond to stress and an abnormal heightened reactivity of the pituitary-adrenal axis in offspring exposed to cocaine in utero.

Adrenocorticotropic Hormone↗