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PubMed1998

Protective effect of ischemic preconditioning on liver preservation-reperfusion injury in rats.

BACKGROUND: Ischemic-preconditioning is a process whereby a brief ischemic episode confers a state of protection against subsequent long-term ischemia-reperfusion injury. Ischemic preconditioning has been studied in heart and liver ischemia-reperfusion injury; however, few studies have been performed in the model of preservation-reperfusion injury in liver transplantation. The current study was designed to evaluate the ability of ischemic preconditioning to protect liver grafts from long-term preservation-reperfusion injury. METHODS: Male Sprague Dawley rats were used as donors and recipients of orthotopic liver transplantation. Ischemic preconditioning was done by interruption of the portal vein and hepatic artery for 5, 10, and 20 min (5-10, 10-10, and 20-10 groups). Reflow was initiated by removal of the clamp for another 10 min in all groups. The liver was removed and placed in a bath with Euro-Collins solution for different preservation times. Tolerance of the transplanted liver to cold ischemia was determined by survival time and liver function tests. Rat tumor necrosis factor was analyzed by a bioassay. Nomega-Nitro-L-arginine methyl ester, L-arginine, or adenosine was administered to block or stimulate the synthesis of nitric oxide (NO) in the rats that received long-term-preserved liver grafts. RESULTS: Twenty percent of syngeneic rats (n=10) that received a liver graft with a 16-hr cold ischemia time in Euro-Collins solution survived for more than 1 day and 10% survived for more than 5 days. In contrast, 87.5% of rats (n=8) that received a liver graft with ischemic preconditioning (10-10 group) and 16 hr of cold ischemia survived for more than 1 day and 75% for more than 5 days. Recipients of liver grafts with ischemic preconditioning had significantly reduced levels of serum aspartate transaminase and tumor necrosis factor-alpha, as well as increased bile flow, compared with recipients of liver grafts without ischemic preconditioning. Blockage of the NO pathway using Nomega-nitro-L-arginine methyl ester, a stereospecific competitive inhibitor of NO formation, attenuated the protective effect of ischemic preconditioning. Administration of one of two precursors of NO synthesis, L-arginine or adenosine, prolonged the survival of rats that received 16-hr-preserved liver grafts. In addition, L-arginine synergized with short-term ischemic pre conditioning (5-10 group) to increase the survival of rats that received a liver graft with a 16-hr cold ischemia time, and the survival rate was 83% after 5 days. Finally, prolonged ischemic preconditioning (> or = 20 min; 20-10 group) resulted in liver damage and loss of function. CONCLUSION: The current results show that ischemic preconditioning protects the liver graft from subsequent long-term cold preservation-reperfusion injury in a rat liver transplantation model. The protective role of ischemic preconditioning may be mediated by the endogenous production of NO.

Animals↗
PubMed2004

Comparative study of the expression profiles of the Cor/Lea gene family in two wheat cultivars with contrasting levels of freezing tolerance.

Expression profiles of a set of Cor/Lea genes were assessed during early stages of cold acclimation in seedlings of two wheat cultivars, which showed contrasting levels of freezing tolerance. These Cor/Lea family members consisted of three EST clones and 13 previously identified cDNA clones of wheat and rye. Northern blot analysis using RNA extracted from seedling leaves and roots showed that most of the genes exhibited a quite similar time-course of expression, although with different expression levels: They rapidly responded to low temperature and their transcript levels reached high plateaus within 3-5 days. The overall gene expression profiles were correlated with the time-dependent development and the level of freezing tolerance under low temperature in the two cultivars. Western blot analysis of protein accumulation further verified this observation. Abscissic acid response was proved for at least four genes. Light was stimulatory to most of the genes, and this positive light response associated with low temperature occurred not only in leaf-specific genes but also in leaf/root-expressed genes. Taken together, the present results suggest that the Cor/Lea gene family represents a major group of downstream genes involved in the ABA-dependent and -independent signal pathways and that most of them are co-regulated in determining freezing tolerance in wheat seedlings.

Journal Article↗
PubMed1997

Cellular mechanisms of cold stress-related immunosuppression and the action of interleukin 1.

Recent studies of the immunomodulatory cytokines, especially interleukin 1 (IL-1), as the mediators of immunoneuroendocrine links have suggested their important physiological role in the development of host resistance during stress reaction. The present study examined the effects of cold stress (-20 degrees C, 20 min) in rats on the value of humoral immune response, lymphocyte activating factor (LAF) production by peritoneal macrophages, as well as IL-1 beta action on lymphocyte proliferation, and the level of general antibody titers. Cold stress exposure led to a considerable elevation of corticosterone (Cs) in rat blood serum and to pronounced suppression of humoral immune response. This kind of experimental stress induced peritoneal macrophages in rats to release LAF without additional stimulation within 24 h after termination of cooling. At the same time LAF production by macrophages after their additional stimulation by LPS in vivo and heat-killed staphylococcus in vitro was decreased during cold stress reaction. Cold stress exposure suppressed the ability of peripheral blood lymphocytes to proliferate in response to concomitant action of IL-1 beta. Immunoprotective effect of rat recombinant IL-1 beta administrated i.p. to rats before cooling was revealed. It is suggested that IL-1 beta modulates immunological and neuroendocrine responses to stress and plays a critical physiological role in realization of stress reaction.

Animals↗
PubMed1994

Differential expression of a gene encoding an acidic dehydrin in chilling sensitive and freezing tolerant gramineae species.

We have characterized a new wheat cold-regulated cDNA clone, Wcor410, that accumulates to equivalent levels in root, crown and leaf tissues during cold acclimation. The Wcor410 cDNA contains an ORF encoding a dehydrin-like glutamate-rich protein of 28 kDa with a pI of 5.1. However, the acidic nature, the absence of the glycine-rich repeat and of the conserved N-terminal region, DEYGNP, suggest that Wcor410 belongs to a different subgroup of the D11 protein family. Northern analysis showed that this gene is expressed only in freezing tolerant gramineae, whereas Southern analysis showed that the Wcor410 gene is present in all monocot species tested. The presence of freezing tolerance-associated genes in sensitive species such as rice and corn is interesting. Characterization of the regulatory factors controlling these genes may help to establish an appropriate strategy to improve freezing tolerance.

Amino Acid Sequence↗
PubMed2005

A global survey of gene regulation during cold acclimation in Arabidopsis thaliana.

Many temperate plant species such as Arabidopsis thaliana are able to increase their freezing tolerance when exposed to low, nonfreezing temperatures in a process called cold acclimation. This process is accompanied by complex changes in gene expression. Previous studies have investigated these changes but have mainly focused on individual or small groups of genes. We present a comprehensive statistical analysis of the genome-wide changes of gene expression in response to 14 d of cold acclimation in Arabidopsis, and provide a large-scale validation of these data by comparing datasets obtained for the Affymetrix ATH1 Genechip and MWG 50-mer oligonucleotide whole-genome microarrays. We combine these datasets with existing published and publicly available data investigating Arabidopsis gene expression in response to low temperature. All data are integrated into a database detailing the cold responsiveness of 22,043 genes as a function of time of exposure at low temperature. We concentrate our functional analysis on global changes marking relevant pathways or functional groups of genes. These analyses provide a statistical basis for many previously reported changes, identify so far unreported changes, and show which processes predominate during different times of cold acclimation. This approach offers the fullest characterization of global changes in gene expression in response to low temperature available to date.

Acclimatization↗
PubMed1998

Rapid development of tolerance to analgesia during remifentanil infusion in humans.

UNLABELLED: Studies in experimental animals have demonstrated a rapidly developing acute tolerance to the analgesic effect of opioids administered by continuous i.v. infusion. The aim of the present study was to determine whether acute tolerance plays an important role in the analgesic effect of remifentanil provided by i.v. infusion to humans. The analgesic effect of remifentanil, infused at a constant rate of 0.1 microg x kg(-1) x min(-1) for 4 h, was evaluated by measuring pain tolerance with thermal (2 degrees C water) and mechanical (pressure) noxious stimulations in 13 paid volunteers. The constant-rate infusion of remifentanil resulted in a threefold increase in pain tolerance with both tests. After reaching its maximum in 60-90 min, the analgesic effect of remifentanil began to decline despite the constant-rate infusion, and after 3 h of infusion, it was only one fourth of the peak value. A comparative rate in the development of acute tolerance measured in terms of time to 50% recovery during infusion was 129 +/- 27 min (mean +/- SD) with the cold water test and 138 +/- 39 min with the pressure test. We conclude that the development of tolerance should be included in the calculations for target-controlled infusions. IMPLICATIONS: Our study shows that tolerance to analgesia during remifentanil infusion is profound and develops very rapidly. The administration of opioids during anesthesia based on target-controlled infusions should include corrections for the development of tolerance.

Adult↗
PubMed1997

Differential sensory block after spinal bupivacaine in volunteers.

We performed this study to determine whether differential sensory block to touch, pinprick, and cold after spinal bupivacaine could be used to predict the dermatomal level of block to transcutaneous electrical stimulation (TES) equivalent to surgical stimulation, onset of tourniquet pain, or magnitude of hemodynamic depression. Eight subjects per group were randomized to receive 3.75, 7.5, or 11.25 mg of 0.75% bupivacaine with 8.25% dextrose in a double-blind fashion. Sensory block was assessed with touch, pinprick, cold, TES at T-12, L-2, S-1, and thigh tourniquet pain. Differential extent of sensory block to touch, pinprick, and cold occurred at the time of offset of tolerance to TES (P < 0.03) and at the time of tourniquet pain (P < 0.05). However, the extent of differential sensory block to touch, pinprick, and cold varied up to 10 dermatomes (2 SD) cephalad to block to TES and up to 7 dermatomes (2 SD) cephalad to the thigh tourniquet at the time of intolerable tourniquet pain. Sensory block to cold did not correlate with hemodynamic depression. Differential sensory block occurs after bupivacaine spinal anesthesia, but is a poor predictor for surgical anesthesia, tourniquet pain, and hemodynamic depression.

Adult↗
PubMed2002

Molecular and biochemical characterization of a cold-regulated phosphoethanolamine N-methyltransferase from wheat.

A cDNA that encodes a methyltransferase (MT) was cloned from a cold-acclimated wheat (Triticum aestivum) cDNA library. Molecular analysis indicated that the enzyme WPEAMT (wheat phosphoethanolamine [P-EA] MT) is a bipartite protein with two separate sets of S-adenosyl-L-Met-binding domains, one close to the N-terminal end and the second close to the C-terminal end. The recombinant protein was found to catalyze the three sequential methylations of P-EA to form phosphocholine, a key precursor for the synthesis of phosphatidylcholine and glycine betaine in plants. Deletion and mutation analyses of the two S-adenosyl-L-Met-binding domains indicated that the N-terminal domain could perform the three N-methylation steps transforming P-EA to phosphocholine. This is in contrast to the MT from spinach (Spinacia oleracea), suggesting a different functional evolution for the monocot enzyme. The truncated C-terminal and the N-terminal mutated enzyme were only able to methylate phosphomonomethylethanolamine and phosphodimethylethanolamine, but not P-EA. This may suggest that the C-terminal part is involved in regulating the rate and the equilibrium of the three methylation steps. Northern and western analyses demonstrated that both Wpeamt transcript and the corresponding protein are up-regulated during cold acclimation. This accumulation was associated with an increase in enzyme activity, suggesting that the higher activity is due to de novo protein synthesis. The role of this enzyme during cold acclimation and the development of freezing tolerance are discussed.

Abscisic Acid↗
PubMed1999

Preservation of frozen yeast cells by trehalose.

Two different methods commonly used to preserve intact yeast cells-freezing and freeze-drying-were compared. Different yeast cells submitted to these treatments were stored for 28 days and cell viability assessed during this period. Intact yeast cells showed to be less tolerant to freeze-drying than to freezing. The rate of survival for both treatments could be enhanced by exogenous trehalose (10%) added during freezing and freeze-drying treatments or by a combination of two procedures: a pre-exposure of cells to 40 degrees C for 60 min and addition of trehalose. A maximum survival level of 71.5 +/- 6.3% after freezing could be achieved at the end of a storage period of 28 days, whereas only 25.0 +/- 1.4% showed the ability to tolerate freeze-drying treatment, if both low-temperature treatments were preceded by a heat exposure and addition of trehalose to yeast cells. Increased survival ability was also obtained when the pre-exposure treatment of yeast cells was performed at 10 degrees C for 3 h and trehalose was added: these treatments enhanced cell survival following freezing from 20.5 +/- 7. 7% to 60.0 +/- 3.5%. Although both mild cold and heat shock treatments could enhance cell tolerance to low temperature, only the heat treatment was able to increase the accumulation of intracellular trehalose whereas, during cold shock exposure, the intracellular amount of trehalose remained unaltered. Intracellular trehalose levels seemed not to be the only factor contributing to cell tolerance against freezing and freeze-drying treatments; however, the protection that this sugar confers to cells can be exerted only if it is to be found on both sides of the plasma membrane.

Biological Transport, Active↗
PubMed1996

Competitive and non-competitive NMDA antagonists block the development of antinociceptive tolerance to morphine, but not to selective mu or delta opioid agonists in mice.

N-Methyl-D-aspartate (NMDA) receptor antagonists have been shown to block the development of antinociceptive tolerance to morphine. Assessment of the effects of NMDA antagonists on development of antinociceptive tolerance to selective opioid mu (mu) and delta (delta) agonists, however, has not been reported. In these experiments, selective mu and delta receptor agonists, and morphine, were repeatedly administered to mice either supraspinally (i.c.v.) or systemically (s.c.), alone or after pretreatment with systemic NMDA antagonists. Antinociception was evaluated using a warm-water tail-flick test. Repeated i.c.v. injections of mu agonists including morphine, fentanyl, [D-Ala2, NMePhe4, Gly-ol]enkephalin (DAMGO) and Tyr-Pro-NMePhe-D-Pro-NH2 (PL017) or [D-Ala2, Glu4]deltorphin, a delta agonist, or s.c. injections of morphine or fentanyl, produced antinociceptive tolerance as shown by a significant rightward displacement of the agonist dose-response curves compared to controls. Single injections or repeated administration of MK801 (a non-competitive NMDA antagonist) or LY235959 (a competitive NMDA antagonist) at the doses employed in this study did not produce behavioral toxicity, antinociception or alter the acute antinociceptive effects of the tested opioid agonists. Consistent with previous reports, pretreatment with MK801 or LY235959 (30 min prior to agonist administration throughout the tolerance regimen) prevented the development of antinociceptive tolerance to i.c.v. or s.c. morphine. Neither NMDA antagonist, however, affected the development of antinociceptive tolerance to i.c.v. fentanyl, DAMGO, or [D-Ala2, Glu4]deltorphin. Additionally, MK801 pretreatment did not affect the development of antinociceptive tolerance to i.c.v. PL017 or to s.c. fentanyl. Further, MK801 pretreatment also did not affect the development of tolerance to the antinociception resulting from a cold-water swim-stress episode, previously shown to be a delta-opioid mediated effect. These data lead to the suggestion that the mechanisms of tolerance to receptor selective mu and delta opioids may be regulated differently from those associated with morphine. Additionally, these findings emphasize that conclusions reached with studies employing morphine cannot always be extended to 'opiates' in general.

Analgesics, Opioid↗
PubMed2002

Cryoprotectin: a plant lipid-transfer protein homologue that stabilizes membranes during freezing.

Plants from temperate and cold climates are able to increase their freezing tolerance during exposure to low non-freezing temperatures. It has been shown that several genes are induced in a coordinated manner during this process of cold acclimation. The functional role of most of the corresponding cold-regulated proteins is not yet known. We summarize our knowledge of those cold-regulated proteins that are able to stabilize membranes during a freeze-thaw cycle. Special emphasis is placed on cryoprotectin, a lipid-transfer protein homologue that was isolated from cold-acclimated cabbage leaves and that protects isolated chloroplast thylakoid membranes from freeze-thaw damage.

Acclimatization↗
PubMed2006

Opioid tolerance and hyperalgesia in chronic pain patients after one month of oral morphine therapy: a preliminary prospective study.

UNLABELLED: There is accumulating evidence that opioid therapy might not only be associated with the development of tolerance but also with an increased sensitivity to pain, a condition referred to as opioid-induced hyperalgesia (OIH). However, there are no prospective studies documenting the development of opioid tolerance or OIH in patients with chronic pain. This preliminary study in 6 patients with chronic low back pain prospectively evaluated the development of tolerance and OIH. Patients were assessed before and 1 month after initiating oral morphine therapy. The cold pressor test and experimental heat pain were used to measure pain sensitivity before and during a target-controlled infusion with the short-acting mu opioid agonist remifentanil. In the cold pressor test, all patients became hyperalgesic as well as tolerant after 1 month of oral morphine therapy. In a model of heat pain, patients exhibited no hyperalgesia, although tolerance could not be evaluated. These results provide the first prospective evidence for the development of analgesic tolerance and OIH by using experimental pain in patients with chronic back pain. This study also validated methodology for prospectively studying these phenomena in larger populations of pain patients. PERSPECTIVE: Experimental evidence suggests that opioid tolerance and opioid-induced hyperalgesia might limit the clinical utility of opioids in controlling chronic pain. This study validates a pharmacologic approach to study these phenomena prospectively in chronic pain patients and suggests that both conditions do occur within 1 month of initiating opioid therapy.

Administration, Oral↗
PubMed1995

Immediate and delayed tolerance of iohexol and ioxaglate in lower limb phlebography: a double-blind comparative study in humans.

RATIONALE AND OBJECTIVES: We compared the tolerance and efficacy of iohexol-300, a nonionic low-osmolar monomer, with those of ioxaglate-320, an ionic low-osmolar dimer, in lower limb phlebography. METHODS: One hundred twenty inpatients were randomly divided into two groups in this double-blind comparative study. Two hundred milliliters of contrast medium (100 ml per leg) was injected intravenously. The immediate tolerance was classified as discomfort (i.e., sensation of warmth, pain, coldness related to the injection) and adverse events occurring up to 1 hr after administration. Delayed tolerance was followed up to 8 days after the examination. The main parameter was immediate adverse events. Image quality was assessed by a radiologist using a visual analog scale. RESULTS: The number of immediate adverse events was significantly higher in the ioxaglate group (p < .02). The more frequent events were digestive disorders and skin rashes; 13 of these events were reported in the ioxaglate group, but none were reported in the iohexol group (p < .001). The other parameters were not significantly different in the two groups. CONCLUSION: We found a similar efficacy and a better tolerance of iohexol-300 than ioxaglate-320 in lower limb phlebography.

Contrast Media↗
PubMed1983

The validity of experimental pain measures.

Forty subjects served in a study investigating the characteristics of experimental pain measures. Subjects indicated when their pain threshold and tolerance levels had been reached with each of three stressors: cold, pressure, and electrical shock. Using the multitrait-multimethod matrix procedure, the measures of threshold and tolerance were found to show both generality and discriminant validity across stressors. Threshold judgements, which emphasize discrimination of nociceptive quality, and tolerance decisions, which indicate an unwillingness to receive more intense stimuli, are not equivalent measures of responsiveness. Both should be obtained in studies involving experimental pain. Stressors, while related, are also not equivalent. Minimum method variance was associated with the discomfort produced by electrical pulse trains.

Adolescent↗
PubMed2002

Drug under test: influenza--Relenza in daily practice. Experience during the influenza season 1999/2000.

A total of 5-7 million cases of the disease, 4.5 million medical certificates, 25,000 admissions to hospital, 15,000 mortalities and direct and indirect costs amounting to several billions - that is the outcome of a "normal" influenza season (data provided by the Influenza Study Group, AGI, of Germany on the 1998/99 season). With zanamivir (Relenza), a selective inhibitor of the influenza-specific neuraminidase, a pharmaceutical product against influenza A and B is now available in Germany for the very first time. In clinical studies, zanamivir reduced not only the duration of the illness and the severity of symptoms, but also the rate of complications and the need for antibiotics. Under practice conditions, the efficacy and tolerability of the anti-influenza product were studied during the 1999/2000 influenza season. In a large observational study in over 1,900 patients, including many patients at risk of asthma and/or chronic obstructive bronchitis, zanamivir (Relenza) improved the symptoms quickly and reliably, and was tolerated very well. The diagnosis of influenza was established clinically to discriminate the disease from colds.

Antiviral Agents↗