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Query: UMLS:C0392674 (exhaustion)
 13,658 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new selection procedure has been developed for isolating prototrophic relaxed mutants of Klebsiella pneumoniae. Two mutants were isolated. One of them showed a fully relaxed phenotype, while the other one behaved in a semi-relaxed way. The wild-type strain, as well as the rel mutants exerted similar patterns to their E. coli counterparts in RNA, protein, ppGpp and pppGpp accumulation during amino starvation, carbon source shift-down and nitrogen starvation. Both mutants became stringent after introducing an F'-factor carrying the relA+ allele from Escherichia coli. The relaxed phenotype could be recovered by curing the F'-factor. Some of the pleiotropic consequences of rel mutations found in E. coli are present in the Klebsiella mutants also while some of them are absent. The mutants are defective in dinitrogen fixation after the exhaustion of limiting ammonium from the culture medium. However, their merodiploid derivatives, carrying the E. coli relA+ allele, showed the wild-type level of nitrogenase activity under the same conditions.
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PMID:Isolation and characterization of prototrophic relaxed mutants of Klebsiella pneumoniae. 626 22

To investigate the hypothesis that circulating glucose levels may affect exercise performance and the severity of hyperthermic injury, rats were made hypoglycemic (n = 12, IV insulin, 4 U) or hyperglycemic (n = 12, IP glucose, 750mg) before exercise in the heat to hyperthermic exhaustion (Tco = 42.5-43 degrees C). The endurance of rats administered glucose was significantly greater than insulin-treated controls (n = 12). Hematocrit levels were unaffected by exercise in control and insulin-treated rats, but were significantly (p less than 0.01) increased in those glucose-treated. Lactate levels were increased (p less than 0.001) post-run in all groups, and these increments were exacerebated in glucose-treated rats. Glucose levels pre-run were decreased by insulin and increased by glucose, and remained depressed (p less than 0.01) post-run in the insulin-treated group. Potassium concentrations were reduced (p less than 0.05) by insulin administration. Urea nitrogen and creatinine were increased (p less than 0.001) post-run in all groups. We concluded that, while hyperglycemic rats had increased endurance compared to hypoglycemic animals, mortality of at least 50% in all groups was unaffected by circulating glucose levels.
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PMID:Hypo- and hyperglycemia in rats: effects on endurance and heat/exercise injury. 636 46

Cultures of Streptomyces venezuelae released acidic metabolites during nitrogen-limited growth on glucose. The main products were pyruvic acid and alpha-ketoglutaric acid. Variation in the extent of acid production was observed; spores of the parental strain 13s gave approximately 10% of low-producing colonies when plated on acid-base indicator medium. Examination of one low producer, strain PC 51-5, showed that differences in acid production became apparent only in low-glucose media containing manganese. In both strains PC 51-5 and 13s, uptake of alpha-keto-[5-14C]glutaric acid occurred by diffusion and no marked differences in permeability to alpha-ketoglutarate were detected. However, differences were observed in the activity of alpha-ketoglutarate dehydrogenase. In cultures of strain PC 51-5, the specific activity of the enzyme increased throughout growth, whereas in the parental strain activity decreased and could not be detected in older mycelium. Loss of enzyme activity was accompanied by excretion of alpha-ketoglutaric acid and failure to assimilate the product after glucose exhaustion. The results suggest that accumulation of pyruvic and alpha-ketoglutaric acids in S. venezuelae cultures grown in glucose-containing media may be due to regulatory suppression of the dehydrogenases by this carbon source.
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PMID:Excretion of alpha-keto acids by strains of Streptomyces venezuelae. 649 38

To determine the effects of low-dosage organophosphate administration on exercise in a hot environment, malathion (7.5 mg/day, 4 days) was administered IP to rats, and effected a 35% (p less than 0.01) reduction in plasma cholinesterase levels. Treadmill endurance (9.14 m/min, no incline, 35 degrees C ambient) was unaffected when the animals were exercised to hyperthermic exhaustion (Tre approximately 43 degrees C). While rates of heat gain were similar between groups, malathion-treated rats displayed higher Tsk (p less than 0.05) at a number of sampling times during the treadmill run. While creatine phosphokinase levels were unaffected by either cholinesterase inhibition or exercise in the heat, lactate dehydrogenase activities were increased (p less than 0.01) in both groups following hyperthermic exhaustion. Although plasma levels of lactate, potassium, urea nitrogen, and creatinine were all significantly (p less than 0.01) increased as a result of exercise in the heat, these increments were not exacerbated by cholinesterase inhibition. Results generally indicated that at this moderate level cholinesterase inhibition, malathion administration did not adversely affect physiological, physical, or thermoregulatory efficacy.
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PMID:Malathion administration: effects on physiological and physical performance in the heat. 665 21

Six endurance-trained and heat-acclimatized adult males ran for 1 h (or until exhaustion) at room temperature (23.8 degrees C) on three occasions. The work loads approximated 37, 56, and 74% of the subjects' aerobic capacities. Venous blood samples were drawn, and urine was collected before and immediately after each exercise bout. Metabolic cost was partitioned by energy substrate, and metabolic water production was quantified from urinary nitrogen, oxygen, and carbon dioxide production. Total body water loss was recorded as the decrease in body weight during the exercise. All subjects completed 1 h of exercise at the two lower exercise intensities but, due to exhaustion, averaged only 35.5 min at the highest work intensity. There were no significant changes in plasma volume after the exercise bouts. Metabolic water production increased with increasing work intensity as did the fraction of total caloric expenditure derived from carbohydrate metabolism. Plasma protein content significantly increased at all levels of exercise intensity. Metabolic water production alone would be of minimal help in plasma volume maintenance and thermoregulation during endurance exercise.
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PMID:Effects of endurance exercise on metabolic water production and plasma volume. 670 69

Previous studies have established that older (16 wk) and more obese rats conserve body protein during prolonged starvation. This adaptation is due in part to a curtailment of muscle proteolysis. To determine whether this response occurs also in younger rats and whether protein is conserved at sites other than muscle, studies were conducted in young 6-wk-old rats previously fed either a chow or a high-fat diet before starvation. Fat feeding caused a marked increase in adipose mass and prolonged survival. Whereas chow-fed rats survived the fast for approximately 5 days, fat-fed rats lived for 10 days and diminished their excretion of nitrogen for at least 6 days, indicative of protein conservation. Despite the ability of fat-fed rats to survive the fast longer, protein was conserved in only a few organs. The timing and magnitude of protein loss from liver, kidney, intestine, and lung was similar to that in chow-fed rats, and little protein was lost during the fast from brain, stomach, skin, and soleus muscle in either group. In fat-fed rats, cardiac and skeletal muscle were the principle tissues in which protein was conserved, and this adaptation was lost when body fat stores were nearing exhaustion. In both groups nitrogen excreted in the urine early in the fast was derived mainly from protein lost from muscle, liver, and to a lesser extent intestine. Later in the fast, the principal source was muscle. These findings indicate that during starvation in the rat the conservation of protein occurs principally in skeletal and cardiac muscle. They also suggest that the ability of the rat to conserve protein is dependent on the size of its lipid stores.
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PMID:Sites of protein conservation and loss during starvation: influence of adiposity. 672 Sep 43

Adult, male rats (300-325 g) were treated with pyridostigmine bromide (n = 22) or saline (n = 22) to quantitate the effects of cholinesterase inhibition (64%) on the ability to work (9.14 m/min, level treadmill) in the heat (35 degrees C). Pyridostigmine-treated rats had a mean endurance of 23 min, whereas saline-treated animals ran for nearly 35 min (P less than 0.001). Rates of rectal and skin temperature increments were significantly higher (P less than 0.001) in pyridostigmine-treated rats as were water losses (P less than 0.001). Exercise in the heat to hyperthermic exhaustion effected anticipated increments in circulating urea nitrogen, creatinine, lactate dehydrogenase, and potassium levels, whereas pyridostigmine pretreatment had additive effects on lactate and creatine kinase concentrations. Additionally, pyridostigmine elicited a significant (P less than 0.01) hyperglycemia before exercise, an effect noted also with other organophosphate simulants. We concluded that pyridostigmine-induced cholinesterase inhibition had a variety of debilitating effects during work in the heat.
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PMID:Effects of pyridostigmine on ability of rats to work in the heat. 672 66

Saccharomyces cerevisiae does not show a noticeable Pasteur effect (activation of sugar catabolism by anaerobiosis) when growing with an excess of sugar and nitrogen source, but it does do so after exhaustion of the nitrogen source in the medium (resting state). We have found that this different behavior of growing and resting S. cerevisiae seems due to differences in the contribution of respiration to catabolism under both states. Growing S. cerevisiae respired only 3 to 20% of the catabolized sugar, depending on the sugar present; the remainder was fermented. In contrast, resting S. cerevisiae respired as much as 25 to 100% of the catabolized sugar. These results suggest that a shift to anaerobiosis would have much greater energetic consequences in resting than in growing S. cerevisiae. In resting S. cerevisiae anaerobiosis would strongly decrease the formation of ATP; as a consequence, various regulatory mechanisms would switch on, producing the observed increase of the rate of glycolysis. The greater significance that respiration reached in resting cells was not due to an increase of the respiratory capacity itself, but to a loss of fermentation which turned respiration into the main catabolic pathway. The main mechanism involved in the loss of fermentation observed during nitrogen starvation was a progressive inactivation of the sugar transport systems that reduced the rate of fermentation to less than 10% of the value observed in growing cells. Inactivation of the sugar transports seems a consequence of the turnover of the sugar carriers whose apparent half-lives were 2 to 7 h.
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PMID:Mechanisms of appearance of the Pasteur effect in Saccharomyces cerevisiae: inactivation of sugar transport systems. 674 5

In experiments with mongrel male rats the asparaginase and adenosine deaminase activities in the liver tissue and adenosine deaminase in blood serum were determined under different conditions of parenteral nutrition. The intraperitoneal administration of the preparations of parenteral nitrogen nutrition-aminosol and amikin (0.25 g of conditioned protein per 100 g of body weight) against a background of protein deficiency and exhaustion is shown to cause no changes as compared to the control of these enzymes activity in the liver tissue and blood serum. The asparaginase activity in the liver increases noticeably with the dose of aminosol and amikin up to 0.5 g of conditioned protein per 100 g of body weight and the adenosine deaminase activity undergo no essential changes. A statistically significant decrease in the adenosine deaminase activity is observed only under administration of aminosol against a background of protein deficiency. Under oral feeding of rats with amikin in the composition of protein-free (0.5 g of conditioned protein per 100 g of body weight), as distinct from its parenteral administration, the asparaginase activity in the liver is considerably lower. The adenosine deaminase activity in the liver and blood serum is not practically changed. A part of the nitrogen excreted from the organism with urea and ammonia under protein deficiency is supposed to be a product of deamination of endogenic purine and pyrimidine derivatives.
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PMID:[Dynamics of asparaginase and adenosine deaminase activity in the liver with intraperitoneal administration of aminosol and amikin preparations of parenteral nitrogen nutrition]. 680 84

The connection between the kinetics of citrate-isocitrate overproduction by Saccharomycopsis lipolytica in glucose media and the specific activities of the enzymes being related to overproduction has been investigated. The specific activities of citrate synthase, aconitate hydratase, NAD+-linked and NADP+-linked isocitrate dehydrogenase decline significantly after exhaustion of the nitrogen source, whereas the activity of the pyruvate carboxylase remains relatively constant and corresponds to changes of the production rate. The results are compared with those obtained by fermentations in n-alkane media and discussed in relation to mechanisms of overproduction.
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PMID:[Enzymatic study of citrate-isocitrate accumulation in yeast with glucose as the carbon source]. 686 52


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