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At least 469 records · Page 26Linked to original sources

PubMed2004

A novel salt-tolerant L-myo-inositol-1-phosphate synthase from Porteresia coarctata (Roxb.) Tateoka, a halophytic wild rice: molecular cloning, bacterial overexpression, characterization, and functional introgression into tobacco-conferring salt tolerance phenotype.

l-myo-Inositol-1-phosphate synthase (EC 5.5.1.4, MIPS), an evolutionarily conserved enzyme protein, catalyzes the synthesis of inositol, which is implicated in a number of metabolic reactions in the biological kingdom. Here we report on the isolation of the gene (PINO1) for a novel salt-tolerant MIPS from the wild halophytic rice, Porteresia coarctata (Roxb.) Tateoka. Identity of the PINO1 gene was confirmed by functional complementation in a yeast inositol auxotrophic strain. Comparison of the nucleotide and deduced amino acid sequences of PINO1 with that of the homologous gene from Oryza sativa L. (RINO1) revealed distinct differences in a stretch of 37 amino acids, between amino acids 174 and 210. Purified bacterially expressed PINO1 protein demonstrated a salt-tolerant character in vitro compared with the salt-sensitive RINO1 protein as with those purified from the native source or an expressed salt-sensitive mutant PINO1 protein wherein amino acids 174-210 have been deleted. Analysis of the salt effect on oligomerization and tryptophan fluorescence of the RINO1 and PINO1 proteins revealed that the structure of PINO1 protein is stable toward salt environment. Furthermore, introgression of PINO1 rendered transgenic tobacco plants capable of growth in 200-300 mm NaCl with retention of approximately 40-80% of the photosynthetic competence with concomitant increased inositol production compared with unstressed control. MIPS protein isolated from PINO1 transgenics showed salt-tolerant property in vitro confirming functional expression in planta of the PINO1 gene. To our knowledge, this is the first report of a salt-tolerant MIPS from any source.

Amino Acid Sequence↗

PubMedDate not supplied

Cold tolerance in hatchling painted turtles (Chrysemys picta): supercooling or tolerance for freezing?

We studied tolerance for cold in hatchling painted turtles (Chrysemys picta) from Lake Metigoshe, Bottineau County, North Dakota, to determine whether neonates in populations near the northern limit of distribution rely on a tolerance for freezing or on a capacity for supercooling to survive their first winter of life. We placed hatchlings individually into artificial hibernacula constructed in jars of damp, loamy sand and then cooled the jars to approximately -0.45 degrees C, which was below the equilibrium freezing point for water held by the sand but above that for body fluids of the neonatal turtles. A piece of ice next was placed on the surface of the sand in each jar to induce freezing of the soil water. After the soil water had frozen to an equilibrium, the temperature in the jars was lowered by 1 degrees C/d to minima averaging -2.5 degrees C, -4.5 degrees C, -6.5 degrees C, and -10.5 degrees C in different treatments. These temperatures were maintained for varying periods, so that animals in each treatment were exposed to temperatures below the equilibrium freezing point for their body fluids for a total of 11 d. Thirty of 32 hatchlings survived exposure to -2.5 degrees C; 24 of 32 survived at -4.5 degrees C; 14 of 32 withstood -6.5 degrees C; and 7 of 32 tolerated -10.5 degrees C. Freezing exotherms were detected in temperature profiles for turtles that succumbed but not in those for hatchlings that survived. Thus, the ability of hatchlings to withstand subzero temperatures for extended periods apparently requires that they avoid freezing. Although other workers contend that tolerance for freezing is the key to survival over winter by hatchling painted turtles from the region of Lake Metigoshe, our findings indicate that neonates rely primarily on their ability to remain unfrozen and supercooled.

Animals↗

PubMed2003

Anoxia tolerance in rice seedlings: exogenous glucose improves growth of an anoxia-'intolerant', but not of a 'tolerant' genotype.

This study demonstrated that, in rice seedlings, genotypic difference in tolerance to anoxia only occurred when anoxia was imposed at imbibition, but not at 3 d after imbibition. When seeds were imbibed and grown in anoxia, IR22 (anoxia-'intolerant') grew much slower and had lower soluble sugar concentrations in coleoptiles and seeds than Amaroo (anoxia-'tolerant'), while Calrose was intermediate. After 3 d in anoxia, the sugar concentrations in embryos and endosperms of anoxic seedlings were nearly 4-fold lower in IR22 than in Amaroo. Sugar deficit in the embryo of IR22 is presumably due to the limitation of sugar mobilization rather than the capacity of transport as shown by similar sugar accumulation ratios of 1.8 between embryo and endosperm in IR22 and Amaroo at 3 d in anoxia. With 20 mol m-3 exogenous glucose, coleoptile extension and fresh weight increments in anoxic seedlings of IR22 were much closer to those in the two other genotypes, nevertheless protein concentration remained lowest on a fresh weight basis in the coleoptiles of IR22; indicating that protein synthesis has a lower priority for energy apportionment during anoxia than processes crucial to coleoptile extension. In contrast to these responses to anoxia imposed at imbibition, IR22 had nearly the same high tolerance to anoxia as Calrose and Amaroo, when anoxia was imposed on seedlings subsequent to 48 h aeration followed by 16 h hypoxic pretreatment. In fact, coleoptiles of anoxic IR22 had higher sugar concentrations and grew faster than Calrose, and exogenous glucose had no effect on the coleoptile extension of IR22. Excised coleoptile tips of IR22 and Amaroo with exogenous glucose had similar rates of ethanol production and were equally tolerant to anoxia. In conclusion, much of the anoxia 'intolerance' of IR22 when germinated in anoxia could be attributed to limited substrate availability to the embryo and coleoptile, presumably due to slow starch hydrolysis in the endosperm.

Adaptation, Physiological↗

PubMed2006

Wounding increases salt tolerance in tomato plants: evidence on the participation of calmodulin-like activities in cross-tolerance signalling.

Cross-tolerance is the phenomenon by which a plant resistance to a stress results in resistance to another form of stress. It has previously been shown that salt stress causes the accumulation of proteinase inhibitors and the activation of other wound-related genes in tomato plants (Solanum lycopersicum). However, very little is known about how different stresses interact with one another, and which are the signalling components that interrelate the responses triggered by different stress types. In the present work, it is shown that mechanical wounding increases salt-stress tolerance in tomato plants through a mechanism that involves the signalling peptide systemin and the synthesis of JA. Data are also provided indicating that calmodulin-like activities are necessary for the downstream signalling events that lead to cross-tolerance between wounding and salt stress. Finally, evidence was gathered supporting the hypothesis that LeCDPK1, a Ca2+ -dependent protein kinase from tomato previously described in our laboratory, could participate in this cross-tolerance mechanism interrelating the signalling responses to wounding and salt stress.

Abscisic Acid↗

PubMed1994

Cloning of organic solvent tolerance gene ostA that determines n-hexane tolerance level in Escherichia coli.

A variety of genes are involved in determining the level of organic solvent tolerance of Escherichia coli K-12. Gene ostA is one of the genes contributing to the level of organic solvent tolerance. This gene was cloned from an n-hexane-tolerant strain of E. coli, JA300. A JA300-based n-hexane-sensitive strain, OST4251, was converted to the n-hexane-tolerant phenotype by transformation with DNA containing the ostA gene derived from JA300. Thus, the cloned ostA gene complemented the n-hexane-sensitive phenotype of OST4251.

Cloning, Molecular↗

PubMed2003

Improved estimation of human neck tensile tolerance: reducing the range of reported tolerance using anthropometrically correct muscles and optimized physiologic initial conditions.

Unlike other modes of loading, the tolerance of the human neck in tension depends heavily on the load bearing capabilities of the muscles of the neck. Because of limitations in animal models, human cadaver, and volunteer studies, computational modeling of the cervical spine is the best way to understand the influence of muscle on whole neck tolerance to tension. Muscle forces are a function of the muscle's geometry, constitutive properties, and state of activation. To generate biofidelic responses for muscle, we obtained accurate three-dimensional muscle geometry for 23 pairs of cervical muscles from a combination of human cadaver dissection and 50(th) percentile male human volunteer magnetic resonance imaging and incorporated those muscles into a computational model of the ligamentous spine that has been previously validated against human cadaver studies. To account for multiple origins, insertions, and lines of action, 82 muscle partition pairs, including nonlinear passive and active elastic components, were included in the model. Using optimization, we determined physiologically appropriate levels of muscle activation for each of the 23 muscles simulating relaxed (no pre-impact awareness) and tensed (pre-impact awareness) states. Unlike all prior neck models, both of these states of activation were mechanically stable in an upright neutral anatomic position resisting gravity as an initial condition prior to tensile loading. Tensile forces were then applied to the models at the head center of gravity at 500 N/s. Both states of activation predicted injury above C3, consistent with clinically observed tensile neck injuries. Using these more physiologically reasonable estimates of muscle activation significantly narrowed the range of estimates of 50(th) percentile male tolerance to tensile loading. Specifically, while the ligamentous spine fails in tension at an average of 1.8 kN and the total muscle activation predicts neck failure at 4.8 kN, the optimized muscle forces resulted in a whole neck tolerance of 3.1 kN and 3.7 kN for the relaxed and tensed neck, respectively. Moreover, these techniques provide quantitative estimates of load sharing between the neck musculature and ligamentous spine that will be useful in the creation of next generation ATD necks.

Journal Article↗

PubMed1992

A characterization of nicotine-induced tolerance: evidence of pharmacological tolerance in the rat.

The present studies were conducted in order to confirm and extend previous findings that the mechanisms of tolerance to the behaviorally disruptive effects of nicotine in a operant model were primarily pharmacological. Both the traditional methodology employing the determination of dose response curves before and after chronic drug administration and a methodology which omits the generation of dose response curves were utilized in these investigations of nicotine-induced tolerance. Rats developed tolerance to both pre- and post-session administration of nicotine, suggesting that the mechanisms of tolerance to the disruptive effects of nicotine are primarily pharmacological. The mechanisms underlying these effects, however, remain to be evaluated.

Journal Article↗

PubMed1995

Tolerance and cross-tolerance to the response rate-decreasing effects of µ opioids in morphine-maintained squirrel monkeys.

The purpose of the present experiment was to assess the degree of tolerance and cross-tolerance to the response rate-decreasing effects of opioids with different degrees of intrinsic efficacy at the mu receptor. The mu opioids included buprenorphine, etorphine, l-methadone, morphine, and sufentanil. Lever pressing of squirrel monkeys was maintained by a fixed-ratio (FR) 30 schedule of food presentation, and dose-effect curves for each drug were obtained prior to, during, and after daily administrations of morphine. Each of the mu opioids, and the non-opioid pentobarbital, dose-dependently decreased response rates. Daily administration of morphine produced approximately a 0.9 log unit rightward shift in the morphine dose-effect curve. During this chronic-morphine phase of the experiment, the dose-effect curve for pentobarbital was not shifted consistently, whereas the dose-effect curves for buprenorphine, etorphine, l-methadone, and sufentanil were shifted between 0.4 and 0.6 log unit to the right. Therefore etorphine, l-methadone and sufentanil, mu opioids thought to have high intrinsic efficacy, and buprenorphine, a mu opioid thought to have low intrinsic efficacy, all produced a smaller degree of cross-tolerance than that observed for morphine, and pentobarbital, a non-opioid, did not produce cross-tolerance.

Journal Article↗

PubMed1980

Fixed combination mezlocillin/oxacillin injected intramuscularly. Comparative study of local tolerability compared with ampicillin and determination of effectiveness and tolerability in the treatment of surgical and urinary tract infections.

The results of two studies on tolerability and efficacy of mezlocillin/oxacillin are reported. The pain caused by i.m. injection of 1 g (20% solution) of the fixed antibiotics combination mezlocillin/oxacillin is compared with that caused by 1 g ampicillin. The injection volume was 5 ml. The statistical analysis of the patients' statements indicates a better tolerance of the fixed antibiotics combination mezlocillin/oxacillin than of ampicillin. The second study was determined the clinical efficacy and tolerability of mezlocillin/oxacillin in the treatment of wound infections, biliary tract infections, urinary tract infections, appendicitis and peritonitis. 19/20 patients were clinically cured after about 7 days o treatment with i.m. injections of 1.5 g mezlocillin/oxacillin in 6 ml of a 25% aqueous solution t.i.d. Treatment had to be discontinued after 3 days in one case because of a generalized exanthema. No other side effects were reported. These studies show that both the i.m. injection o the 20% solution of 1 g mezlocillin/oxacillin combination and the 25% solution of 1.5 g of this combination are tolerated without problems.

Adolescent↗

PubMed1989

Relationship between glucose tolerance, insulin secretion, and insulin action in non-obese individuals with varying degrees of glucose tolerance.

Plasma glucose and insulin concentration following a 75 g oral glucose challenge and glucose uptake during a hyperinsulinaemic glucose clamp study were determined in 50 non-obese individuals. The study population was divided into five groups on the basis of their glucose tolerance: normal, impaired glucose tolerance, Type 2 (non-insulin-dependent) diabetes mellitus with fasting plasma glucose of less than 8 mmol/l, between 8-15 mmol/l, and more than 15 mmol/l. The plasma insulin response was significantly greater (p less than 0.001) than normal in those with either impaired glucose tolerance or Type 2 diabetes and a fasting plasma glucose concentration less than 8 mmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗

PubMed2006

Glucose tolerance at age 58 and the decline of glucose tolerance in comparison with age 50 in people prenatally exposed to the Dutch famine.

AIMS/HYPOTHESIS: People who were small at birth have an increased risk of type 2 diabetes in later life. People who were in utero during the Dutch famine had decreased glucose tolerance and raised insulin concentrations at age 50. We aimed to evaluate whether prenatal famine exposure leads to more rapid progression of impaired glucose/insulin homeostasis with increasing age. METHODS: We performed an OGTT in 702 men and women at age 50 and in 699 men and women at age 58, all born as term singletons immediately before, during or after the 1944-1945 Dutch famine. RESULTS: People who had been exposed to famine in utero had significantly higher 120-min glucose concentrations at age 58 compared with people who had not been exposed to famine (difference=0.4 mmol/l, 95% CI 0.1 to 0.7, adjusted for sex and BMI). Glucose tolerance deteriorated between the age of 50 and 58. The unadjusted 120-min glucose concentrations rose by 0.2 mmol/l (95% CI 0.0 to 0.4), while 120-min insulin concentrations had increased by 64 pmol/l (95% CI 48 to 82). There were no differences in the rates of glucose and insulin level increase between the famine-exposed group and the unexposed group (p=0.28 for the difference in increase in glucose concentrations and p=0.09 for insulin concentrations). CONCLUSIONS/INTERPRETATION: Although we confirmed that undernutrition during gestation is linked to decreased glucose tolerance, the effect does not seem to become more pronounced at age 58 as compared with age 50.

Adult↗

PubMed2000

Pathophysiology of opioid tolerance and clinical approach to the opioid-tolerant patient.

The physiologic basis for opioid tolerance has been elucidated, resulting in a better understanding of this problem. As a result of this ongoing effort, patients exhibiting opioid tolerance can now expect better pain management both in the postoperative period and during the course of their treatment. This article outlines the pathophysiology of opioid tolerance and a practical clinical approach to this problem.

Analgesics, Opioid↗

PubMed1987

Lipoprotein analyses in varying degrees of glucose tolerance. Comparison between non-insulin-dependent diabetic, impaired glucose tolerant, and control populations.

Atherosclerosis is the major cause of death in diabetic patients. Lipoproteins and lipids are frequently altered in non-insulin-dependent diabetes. These lipoprotein alterations are of interest because of their possible role in the origin of the accelerated atherosclerosis found in diabetes. Because of the link between lipoproteins and diabetes, serum lipids and lipoproteins were measured in 215 middle-aged patients (107 female, 108 male) with varying degrees of glucose tolerance: control subjects, subjects with impaired glucose tolerance (IGT), and patients with non-insulin-dependent diabetes mellitus (NIDDM). In male subjects, levels of fasting total triglycerides were significantly greater in those with NIDDM compared with control subjects. In female subjects, fasting total cholesterol levels were significantly greater in NIDDM compared with IGT. Both high-density lipoprotein (HDL) cholesterol and HDL2 cholesterol values were significantly lower in both sexes with NIDDM compared with control subjects. Low-density lipoprotein (LDL) cholesterol levels were elevated in the male subjects with IGT. No differences in HDL cholesterol or its subfractions were seen in both sexes with IGT compared with control subjects. Bivariate analyses showed that the reduced HDL cholesterol and HDL subfraction levels were most closely associated with both total triglycerides and weight. This study shows that reduced HDL cholesterol and HDL2 cholesterol levels occur in NIDDM, whereas persons with "impaired glucose tolerance" do not have the dramatic alterations in HDL levels.

Arteriosclerosis↗

PubMed1988

Neonatal tolerance induction to Mlsa. II. T cells induce tolerance to Mlsa.

We have investigated the ability of murine T cell lines to induce neonatal tolerance to Mlsa (minor lymphocyte stimulating). Mlsb mice were injected within 24 hr of birth with MHC (major histocompatibility complex) identical T cell lines generated by culturing responders from Mlsa strains with stimulators from Mlsb strains. Injected mice were tested at 6 to 8 weeks of age for responses in either primary mixed leukocyte reaction or IL-2 limiting dilution analysis. Mlsa specific responses by injected tolerant mice relative to noninjected controls were reduced by 92-98% in MLR and by 2- to 10-fold in IL-2 LDA. In contrast, responses against third-party MHC antigens by either the injected or the noninjected mice were identical. Fifty percent of all mice injected with the T cell lines were tolerant to Mlsa. These results strongly suggest that murine T cells express the Mlsa gene product.

Animals↗

PubMed1983

Tolerance develops to LSD while the drug is exerting its maximal behavioral effects: implications for the neural bases of tolerance.

Tolerance to a test dose of 50 mg/kg of LSD occurred within 0.5-1.0 h following an initial dose of 10 mg/kg of the drug, using limb flicking and abortive grooming as behavioral indices in the cat. These findings represent an example of very rapidly developing drug tolerance using a behavioral index. These data are discussed within the context of hypotheses concerning the neurochemical bases of tolerance to LSD.

Animals↗

PubMed1985

Prolactin analgesia: tolerance and cross-tolerance with morphine.

The development of acute tolerance to prolactin-induced analgesia in mice was identified by using the writhing test. This tolerance was antagonised by naltrexone pretreatment indicating a role of an opioid mechanism. Cross-tolerance between morphine and prolactin was observed with regard to analgesia. These data show that prolactin mimics morphine properties as far as analgesia is concerned and serve as evidence supporting prolactin-opioid interaction.

Analgesics↗

PubMed1985

Opioid dependence in the guinea-pig myenteric plexus is controlled by non-tolerant and tolerant opioid receptors.

The experiments concerned the association of opioid dependence with specific opioid receptors. Previous investigations have demonstrated that tolerance may be confined to only one type of opioid receptor. These findings could suggest that dependence develops invariably only with receptors which have been rendered tolerant. We report here that in the guinea-pig isolated ileum, which has been made selectively tolerant to a mu-receptor agonist, naloxone may precipitate a sign of dependence at mu-receptors chronically activated and at naive kappa-receptors. Furthermore, suppression of the withdrawal contracture in preparations rendered dependent on a mu-receptor agonist can be achieved by very low concentrations of a kappa-agonist, e.g. dynorphin A. These findings challenge the current concept that confines drug dependence only to that opioid receptor type which has been activated chronically.

Animals↗

PubMed1991

Effects of the analgesic agent tramadol in normal and arthritic rats: comparison with the effects of different opioids, including tolerance and cross-tolerance to morphine.

The effects of the analgesic agent tramadol (0.1-1 mg/kg i.v.) were compared to those of the mixed agonist-antagonist analgesics nalbuphine (1 mg/kg i.v.) and buprenorphine (3 micrograms/kg i.v.) in the vocalization threshold to paw pressure test. Normal and Freund's adjuvant-induced arthritic rats were used. We have shown previously that these animals used as a model of clinical pain exhibit an enhanced sensitivity to morphine (0.1-1 mg/kg i.v.), with a rapid development of tolerance after repetitive low doses, a response not observed in normal rats. In the present study, the antinociceptive effects of tramadol, buprenorphine and nalbuphine were enhanced (by 2- to 5-fold) in arthritic compared to normal rats. In this model, these effects were significantly reduced by a dose of naloxone (0.1 mg/kg i.v.) that completely antagonized the effect of morphine. In this model, the antinociceptive effect of tramadol (1 mg/kg i.v.) was comparable to that of nalbuphine (1 mg/kg i.v.), buprenorphine (3 micrograms/kg i.v.) and morphine (1 mg/kg i.v.). Repeated administration of low doses of tramadol twice daily for 4 days to arthritic rats did not induce tolerance, in contrast to nalbuphine, buprenorphine, and morphine. In addition, no cross-tolerance between tramadol and morphine was observed in these animals.

Animals↗