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PubMed1983

Induction of endotoxin tolerance with nonpyrogenic O-antigenic oligosaccharide-protein conjugates.

We prepared a dodecasaccharide, specific for the O-antigenic polysaccharide chain of Salmonella typhimurium (O-antigens 4 and 12), by the partial hydrolysis of the O-polysaccharide chain, utilizing bacteriophage 28B endo-alpha-L-rhamnosidase. The dodecasaccharide was shown by chemical and spectroscopical analyses to be totally devoid of lipid A and core oligosaccharide. By coupling this dodecasaccharide to human serum albumin, a glycoconjugate (DODECA-4809-ITC-HSA) was prepared and found to be (i) nonpyrogenic, (ii) unable to gelate a Limulus amoebocyte lysate, and (iii) unable to induce early-phase pyrogenic tolerance to endotoxin. Rabbits immunized either intravenously (with the glycoconjugate suspended in saline) or intrapopliteally (with the glycoconjugate suspended in Freund complete adjuvant) developed a significant although modest pyrogenic tolerance against challenge with the O-antigenic homologous S. typhimurium lipopolysaccharide (P less than 0.025 and P less than 0.01 for immunized and control rabbits, respectively). The evoked tolerance was O-antigen specific since no pyrogenic tolerance against challenge with lipopolysaccharide from S. thompson (possessing identical lipid A and core oligosaccharide structures but differing in the O-antigen polysaccharide chain) could be seen (P greater than 0.1). These results demonstrate that a nonpyrogenic O-antigenic polysaccharide hapten, when coupled to an immunogenic carrier protein, evokes immune responses which mediate significant, although modest, late-phase tolerance and is capable of partly reducing the pyrogenic activity of the O-antigenic homologous lipopolysaccharide.

Animals↗
PubMed1993

Effect of naloxone on the habituation of novelty-induced hypoalgesia: the collateral inhibition hypothesis revisited.

Repeated daily administration of the opiate receptor antagonist naloxone prior to hotplate tests provokes longer paw-lick latencies by attenuating the habituation of novelty-induced hypoalgesia. This hypoalgesia has been found to persist when pain tests are subsequently conducted following saline administration. The present experiments were conducted to determine whether the substrates mediating the hypoalgesia observed during naloxone and saline tests are similar or distinct. Neither the hypoalgesia observed during naloxone nor saline tests were affected by the induction of tolerance to the hypoalgesic effect of morphine, suggesting that both effects are mediated by nonopioid antinociceptive mechanisms. Previous work from our laboratory demonstrated that the hypoalgesia observed during naloxone tests is inhibited by clonidine, enhanced by yohimbine, and unaffected by prazosin and phentolamine. In the present article, we report a similar pattern of results for the hypoalgesia observed during saline tests. It is concluded that the substrates mediating both effects are similar. The results are discussed in relation to the possibility that an opioid substrate involved in habituative learning may be inhibitory on a nonopioid antinociceptive substrate.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed2001

Expressed sequence tags from a NaCl-treated Suaeda salsa cDNA library.

Past efforts to improve plant tolerance to osmotic stress have had limited success owing to the genetic complexity of stress responses. The first step towards cataloging and categorizing genetically complex abotic stress responses is the rapid discovery of genes by the large-scale partial sequencing of randomly selected cDNA clones or expressed sequence tags (ESTs). Suaeda salsa, which can survive seawater-level salinity, is a favorite halophytic model for salt tolerant research. We constructed a NaCl-treated cDNA library of Suaeda salsa and sequenced 1048 randomly selected clones, out of which 1016 clones produced readable sequences (773 showed homology to previously identified genes, 227 matched unknown protein coding regions, 16 anomalous sequences or sequences of bacterial origin were excluded from further analysis). By sequence analysis we identified 492 unique clones: 315 showed homology to previously identified genes, 177 matched unknown protein coding regions (101 of which have been found before in other organisms and 76 are completely novel). All our EST data are available on the Internet. We believe that our dbEST and the associated DNA materials will be a useful source to scientists engaging in stress-tolerance study.

Blotting, Northern↗
PubMed1988

Tolerance to intrathecal oxymetazoline-induced analgesia, with paradigm-dependent cross-tolerance to intrathecal morphine.

Male, Sprague-Dawley rats, implanted with intrathecal (i.t.) catheters, were given repeated i.t. injections of morphine (40 nmol), oxymetazoline (100 nmol) or saline (10 microliter) at 12-h intervals for 3 days. Antinociception was determined 1 or 1.5 hr after each injection using the tail-flick and paw-pressure tests. Complete tolerance to i.t. morphine and oxymetazoline developed within 72 and 24 hr, respectively. Antinociception after i.t. oxymetazoline (100 nmol) in morphine-tolerant rats, and after i.t. morphine (20 nmol) in oxymetazoline-tolerant rats, was not significantly different from their respective effects in saline-pretreated rats. These data suggest an absence of cross-tolerance between morphine and oxymetazoline in the rat spinal cord. In a separate group of rats, the continuous i.t. infusion of morphine (26 nmol/hr) produced significant antinociception; tolerance to morphine developed within 36 hr. The antinociceptive effect of i.t. oxymetazoline (100 nmol) was significantly attenuated in rats pretreated with continuous i.t. morphine as compared to saline-pretreated rats. In rats pretreated with continuous i.t. oxymetazoline, cross-tolerance to morphine could not be determined due to severe adverse effects during oxymetazoline infusion. The results of this study suggest that functional cross-tolerance between morphine and alpha adrenoceptor agonists in the spinal cord cannot be excluded on the basis of repeated i.t. injection experiments alone.

Analgesia↗
PubMed1987

Nitrate tolerance: the lack of effect of N-acetylcysteine.

The hemodynamic and antianginal effects of 30 mg of isosorbide dinitrate (ISDN) were assessed in 12 patients with chronic stable angina after initial dosing and after 7 to 10 days of therapy four times daily. During early therapy, ISDN produced significant hemodynamic and antianginal effects that persisted over a 3 hr observation period. During sustained therapy there was attenuation of the hemodynamic effects at rest, and treadmill exercise time to the onset of angina and to the development of moderate angina was increased 1 hr after dosing; no effect was apparent at 3 hr. During this state of nitrate tolerance, patients were treated with an infusion of normal saline or 100 mg/kg N-acetylcysteine and exercise testing was repeated. N-Acetylcysteine did not change the hemodynamic findings at rest or during exercise and there was no improvement in exercise tolerance. It is apparent that the short-term administration of reduced sulfhydryl groups does not reverse tolerance to the hemodynamic and antianginal effects of isosorbide dinitrate in an exercise test model.

Acetylcysteine↗
PubMed1996

Loss of tolerance to morphine after a change in route of administration: control of within-session tolerance by interoceptive conditioned stimuli.

Tolerance to morphine analgesia (tail-immersion test) was examined after manipulation of two aspects of a tolerance test: 1) the route of drug administration and 2) the time interval between the test dosing and the tolerance test. The intravenous (IV) and intraperitoneal (IP) routes were used, together with a novel test for tolerance in which the test morphine was infused IV just 2 min before measuring the opiate effect. The first experiment validated this test as an assay for tolerance by examining the log dose-response (LDR) curve changes produced by daily IP injection with 0, 20 or 200 mg/kg morphine; the IV test confirmed the expected parallel shift to the right and flattening of the LDR curve. In the second experiment, all rats of two groups were injected once daily for 3 weeks with 20 mg/kg morphine and with saline except that one group received the morphine IV (and saline IP), the other morphine IP (saline IV). The results indicated route-specific tolerance. On a test using 20 mg/kg given IV morphine, tolerance was significantly greater in rats treated with IV morphine than in those treated IP. However, a larger effect on tolerance was produced by a pretest application of 5 mg/kg morphine 30 min before the actual tolerance test. This manipulation was designed to "prime" short-term, adaptive processes hypothesized to occur within a normal tolerance test session as morphine is taking effect. The tolerance on the test increased (equivalent to 2 to 3 fold shift in the LDR curve) when the pretest morphine was given with the same route as the chronic morphine, regardless of treatment group. It was concluded that opiate tolerance may be modulated by conditioned stimuli produced by morphine acting through different routes. These interoceptive cues appear to modulate rapidly acquired and short-lived adaptive processes taking place within a given test session.

Analgesics, Opioid↗
PubMed1992

Rapid tolerance and cross-tolerance as predictors of chronic tolerance and cross-tolerance.

Hypothermia and motor impairment (tilt-plane) tests were used to assess the phenomenon of rapid tolerance to ethanol and cross-tolerance to various alcohols, benzodiazepines, and barbiturates that differ in lipid:water partition coefficients. The hypothermic and motor impairment responses to ethanol were significantly reduced on day 2 in rats receiving ethanol (2 doses of 2 g/kg each for the hypothermia test and 2.3 and 1.7 g/kg for the tilt-plane test) 24 and 22 h earlier compared to the control group pretreated with saline. Ethanol pretreatment resulted in rapid cross-tolerance, on both tests, to the various alcohols (n-propanol, n-butanol, and t-butanol) and the benzodiazepines (chlordiazepoxide, diazepam, oxazepam, and flurazepam) tested. Ethanol pretreatment also conferred clear rapid cross-tolerance to barbital and phenobarbital, but did not result in rapid cross-tolerance to pentobarbital, secobarbital, amobarbital, or thiopental. The results on rapid cross-tolerance on both tests seen in these studies parallel the results obtained in chronic tolerance and cross-tolerance studies reported recently. These results suggest that rapid tolerance and cross-tolerance can be used as predictors of chronic tolerance and cross-tolerance.

Alcohols↗
PubMed2000

Spinal PKC activity and expression: role in tolerance produced by continuous spinal morphine infusion.

It has been hypothesized that spinal morphine tolerance results from protein kinase C (PKC) mediated phosphorylation. Chronic lumbar intrathecal (i.t.) infusion of morphine (20 nmol/microl/h) was shown to produce antinociception on day 1 (d1) that disappeared by d5 (tolerance). On d6, a bolus i.t. probe dose of morphine (60 nmol) produced a more profound antinociception in saline-infused rats than in morphine-infused rats. Coinfusion of morphine with a PKC inhibitor, chelerythrine, prevented tolerance to the probe morphine dose. Bolus i.t. chelerythrine or GF109203X (GF), another PKC inhibitor, on d5, but not the inactive homologue of GF Bisindolymaleimide V, also blocked development of tolerance after 24 h. I.t. morphine infusion, but not saline, produced a 2-fold increase in dorsal horn PKC phosphorylating activity and in the expression of PKCalpha/gamma. Bolus chelerythrine on d5 after spinal morphine infusion blocked upon an increase in PKC activity, confirming that at the behaviorally active dose the drug had the intended biochemical effect upon spinal PKC activity. PKC activity and protein expression did not change when assessed 1 h after bolus i.t. morphine in naive rats. Thus, tolerance produced by morphine infusion is dependent upon an increase in local phosphorylating activity by PKC. Blocking the PKC activity prevents expression of the morphine tolerance.

Alkaloids↗
PubMed1999

Immunoglobulin E suppression and cytokine modulation in mice orally tolerized to beta-lactoglobulin.

This study was designed to confirm the tolerogenic properties of beta-lactoglobulin in a mouse model and to assess specific oral tolerance induction in humoral and cellular compartments. BALB/c mice were fed beta-lactoglobulin (BLG) or whey proteins at different ages and subsequently intraperitoneally challenged 5 days later with both BLG and a non-specific antigen, ovalbumin (OVA). Three weeks later, oral tolerance induction was analysed in CMP-fed, versus saline-fed mice, by measuring specific seric and intestinal antibody responses, delayed-type hypersensitivity (DTH), specific splenocyte proliferation, and cytokine secretion patterns. Three-week-old mice fed high doses of either whey proteins or BLG (respectively 3 mg/g or 5 mg/g of body weight) were found to achieve oral tolerization. At humoral and mucosal levels, anti-BLG immunoglobulin E (IgE) were suppressed in these groups when compared with saline fed mice. With respect to cellular responses, systemic DTH and lymphocyte proliferation to BLG were also inhibited in CMP-fed mice. Weaning time was determined to be the best period for oral tolerance induction. Kinetic analyses showed however, that a minimum of 2 weeks was required for oral tolerance detection. Finally, cytokine profiles indicated a reciprocal decrease of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) versus an increase of IL-10 and transforming growth factor-beta (TGF-beta) secretions in tolerized mice. Taken together, these results clearly showed that oral administration of high doses of cows' milk proteins can induce significant hyposensitization in mice, in a specific inhibition of T helper 1 (Th1) lymphocytes with the participation of suppressor cytokines.

Age Factors↗
PubMed2005

Cold, salinity and drought stresses: an overview.

World population is increasing at an alarming rate and is expected to reach about six billion by the end of year 2050. On the other hand food productivity is decreasing due to the effect of various abiotic stresses; therefore minimizing these losses is a major area of concern for all nations to cope with the increasing food requirements. Cold, salinity and drought are among the major stresses, which adversely affect plants growth and productivity; hence it is important to develop stress tolerant crops. In general, low temperature mainly results in mechanical constraint, whereas salinity and drought exerts its malicious effect mainly by disrupting the ionic and osmotic equilibrium of the cell. It is now well known that the stress signal is first perceived at the membrane level by the receptors and then transduced in the cell to switch on the stress responsive genes for mediating stress tolerance. Understanding the mechanism of stress tolerance along with a plethora of genes involved in stress signaling network is important for crop improvement. Recently, some genes of calcium-signaling and nucleic acid pathways have been reported to be up-regulated in response to both cold and salinity stresses indicating the presence of cross talk between these pathways. In this review we have emphasized on various aspects of cold, salinity and drought stresses. Various factors pertaining to cold acclimation, promoter elements, and role of transcription factors in stress signaling pathway have been described. The role of calcium as an important signaling molecule in response to various stress signals has also been covered. In each of these stresses we have tried to address the issues, which significantly affect the gene expression in relation to plant physiology.

Acclimatization↗
PubMed1999

Acquisition and expression of conditioned hypoalgesia in morphine-naive and morphine-tolerant rats.

The present study used a within-subject design to examine acquisition and expression of conditioned hypoalgesia in 50 male Wistar rats. Morphine-naive rats preexposed to a heat stressor with saline were hypoalgesic when subsequently tested for latencies to tail flick or paw lick. However, morphine-tolerant rats preexposed to the heat stressor with saline failed to display hypoalgesia when tested for latencies to tail flick, but showed hypoalgesia when tested for latencies to paw lick. Taken together, these findings suggest that expression of conditioned hypoalgesic responses in morphine-tolerant rats may depend on the nociceptive test used. Both morphine-naive and morphine-tolerant rats preexposed to the heat stressor with morphine failed to display hypoalgesia on either the tail-flick or the hot-plate test, demonstrating that morphine's ability to block acquisition of conditioned hypoalgesia is independent of the test used to assess nociceptive sensitivity.

Analgesics, Opioid↗
PubMed1978

Development of tolerance to the analgesic effect of clonidine in rats. Cross-tolerance to morphine.

The influence of chronic treatment with clonidine on analgesia produced by clonidine and morphine was studied in rats. Electrical stimuli were applied to the tail, and analgesia was measured as increase in the threshold voltage that elicited vocalisation. Twenty-two hours after the last of 14 injections of increasing doses of clonidine over 7 days, the acute analgesic effects of both clonidine and morphine were reduced, i.e. tolerance had developed. Pretest vocalisation thresholds (voltage) were unchanged by long-term treatment with clonidine, or, respectively, saline. Contrarywise, acute administration of clonidine enhanced the effect of morphine. The tolerance developed after long-term treatment with clonidine might be associated with changes in brain noradrenaline mechanisms.

Analgesics↗
PubMed1985

Tolerance to morphine-induced analgesia in mice: magnetic fields function as environmental specific cues and reduce tolerance development.

Mice receiving daily injection of morphine (10 mg/kg) developed tolerance to morphine-induced analgesia, such that after 5-7 days of treatment their thermal response (paw licking) latencies in the hot plate test were indistinguishable from those of control animals. Exposure to a rotating magnetic field for thirty minutes before the daily morphine administrations significantly reduced the development of tolerance. These magnetic exposures also significantly increased over 7-10 days the basal nociceptive thresholds and paw licking response latencies of saline treated mice. Control and sham exposed mice that were fully tolerant to the analgesic effects of morphine failed to show any tolerance to morphine-induced analgesia when exposed to the magnetic stimuli prior to injection. Likewise, the partial tolerance to morphine shown by mice exposed to the rotating magnetic field pre-injection environmental cues was eliminated when control or sham pre-injection cues lacking the magnetic stimuli were provided. In all cases tolerance to morphine-induced analgesia was evident in the subsequent re-test with the original cues. These results indicate that magnetic field exposure can reduce the development of tolerance to the analgesic effects of morphine. They also show that magnetic stimuli function as significant environmental cues for the development of tolerance to morphine-induced analgesia. This suggests that magnetic stimuli affect both the associative (classical conditioning) and non-associative (physiological, pharmacological) mechanisms involved in the development of opiate tolerance.

Analgesia↗
PubMed1995

Increases in gill cytosolic corticosteroid receptor abundance and saltwater tolerance in juvenile coho salmon (Oncorhynchus kisutch) treated with growth hormone and placental lactogen.

Juvenile coho salmon (Oncorhynchus kisutch) were injected with one of two recombinant bovine hormones, growth hormone (bGH; 5.0 and 0.5 micrograms.g-1 body wt) or placental lactogen (bPL; 5.0, 0.5, and 0.05 micrograms.g-1 body wt) to determine the effect on growth, plasma cortisol concentration, cytosolic corticosteroid receptors (CR) in the gills, and the development of hypoosmoregulatory ability. One week following a single injection or six weekly injections of bGH or bPL, the fish were measured and sampled for CR concentration and Na+,K(+)-ATPase activity in the gills. Fish were also challenged with salt water (salinity 25%) for 24 hr to determine saltwater tolerance at the end of the 6-week treatment. Treatment with bPL and bGH significantly increased weight and length of the fish. The 0.05-micrograms bPL dose significantly elevated plasma cortisol concentration, whereas all other hormone treatments did not affect cortisol levels. bPL and bGH also significantly increased CR concentration and Na+,K(+)-ATPase activity in the gills. The perturbation in plasma sodium concentration was least in animals receiving the highest dose of bPL and the bGH-treated animals following transfer to seawater. An increase in cytosolic CR by bGH and bPL may increase responsiveness of the gills to cortisol and partially account for the increase in Na+,K(+)-ATPase activity and greater ability to regulate plasma sodium in seawater as exhibited by the experimental groups.

Animals↗
PubMed1983

Tolerance to amphetamine anorexia: role of learning versus body weight settling point.

Three experiments were conducted to clarify the role of learning and body weight settling point in the development of tolerance to amphetamine anorexia. In the first experiment, rats that had become tolerant to the suppressant effect of amphetamine on milk intake were anorexic when subsequently offered other foods or water during a transfer test. These results appear to support a conditioning interpretation, which predicts a loss of tolerance when cues associated with drug administration are altered. Subsequent experiments examined the long-term effect of changing diets. In Experiments 2 and 3, rats made tolerant with milk as the diet showed prolonged anorexia when switched to Purina pellets or slightly bitter milk. However, when switched from pellets or adulterated milk to milk, tolerant rats were anorexic only 1 day and then ingested significantly more of the new diet. These results are inconsistent with a conditioning interpretation. Further analysis revealed that tolerant rats maintained their weight below the level of saline controls despite the recovery of food intake. Moreover, the level at which they maintained their weight varied with the palatability of the diet. These results suggest that amphetamine lowers the settling point for body weight and that tolerance does not develop to this effect (cf. Stunkard, 1981). From this perspective, the reinstatement of prolonged anorexia when apparently tolerant rats were switched to a less palatable diet can be understood as an attempt to attain a lower weight level.

Animals↗
PubMed1987

Perceived self-efficacy and pain control: opioid and nonopioid mechanisms.

In this experiment, we tested for opioid and nonopioid mechanisms of pain control through cognitive means and the relation of opioid involvement to perceived coping efficacy. Subjects were taught cognitive methods of pain control, were administered a placebo, or received no intervention. Their pain tolerance was then measured at periodic intervals after they were administered either a saline solution or naloxone, an opiate antagonist that blocks the effects of endogenous opiates. Training in cognitive control strengthened perceived self-efficacy both to withstand and to reduce pain; placebo medication enhanced perceived efficacy to withstand pain but not reductive efficacy; and neither form of perceived self-efficacy changed without any intervention. Regardless of condition, the stronger the perceived self-efficacy to withstand pain, the longer subjects endured mounting pain stimulation. The findings provide evidence that attenuation of the impact of pain stimulation through cognitive control is mediated by both opioid and nonopioid mechanisms. Cognitive copers administered naloxone were less able to tolerate pain stimulation than were their saline counterparts. The stronger the perceived self-efficacy to reduce pain, the greater was the opioid activation. Cognitive copers were also able to achieve some increase in pain tolerance even when opioid mechanisms were blocked by naloxone, which is in keeping with a nonopioid component in cognitive pain control. We found suggestive evidence that placebo medication may also activate some opioid involvement. Because placebos do not impart pain reduction skills, it was perceived self-efficacy to endure pain that predicted degree of opioid activation.

Female↗
PubMed1978

A comparison of methods for measurement of rectal potential difference in man: effects of rectal infusion of amiloride.

1. Two methods for measurement of rectal potential difference in man were compared. A saline-filled catheter technique gave more reproducible results and was better tolerated by patients than the solid probe technique. 2. Infusion of amiloride at a concentration of 4 x 10(-6) mol/l in saline produced a variable fall of potential difference in six normal subjects. Dose-response curves in two subjects showed that complete inhibition of rectal difference occurred at 4 x 10(-5) mol/l and 4 x 10(-6) mol/l respectively. 3. This finding provides additional evidence that rectal potential difference in man results from electrogenic ion transport across the mucosal epithelial cell.

Adult↗
PubMed1999

Water potential and ionic effects on germination and seedling growth of two cold desert shrubs.

We tested expectations that two desert shrubs would differ in germination and seedling relative growth rate (RGR) responses to Na and Ψ(s) stress. The study species, Chrysothamnus nauseosus ssp. consimilis and Sarcobatus vermiculatus (hereafter referred to by genus), differ in their distribution along salinity gradients, with Chrysothamnus inhabiting only less saline areas. In growth chamber studies, declining Ψ(s) (-0.82 to -2.71 MPa) inhibited germination of both species, and Chrysothamnus was less tolerant of Ψ(s) stress than Sarcobatus. Germination fell below 10% for Chrysothamnus at -1.64 MPa (NaCl and PEG), and for Sarcobatus at -2.4 MPa PEG. Neither species exhibited ion toxicity. There was substantial ion enhancement for Sarcobatus in lower Ψ(s), allowing for 40% germination in -2.71 MPa NaCl. For seedling RGR, species were not different at -0.29 or -0.82 MPa (0 and 100 mmol/L NaCl, respectively), but Chrysothamnus RGR declined substantially at -1.3 MPa (200 mmol/L NaCl). The greater stress tolerance of Sarcobatus was not associated with a lower RGR under nonsaline conditions. Species differences in seed and seedling Ψ(s) stress tolerance probably contribute to the restricted distribution of Chrysothamnus to less saline areas. The Na uptake of Sarcobatus seedlings enhances its ability to deal with declining Ψ(s) and establish in more saline areas.

Journal Article↗