Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Isolated rat lung cell suspensions were prepared by collagenase digestion of the lung stroma. These cells were functionally competent as judged, among other criteria, by their constant rates of oxygen uptake and glucose utilization. An important metabolic feature of these cells is that they display very high glycolytic rates. At least 60% of the glucose utilized was converted to lactate, regardless of the glucose concentration in the medium. The state of reduction of the nicotinamide system, as indicated by the lactate-to-pyruvate ratio, was normal, thus indicating that the high glycolytic fluxes are not related to poor oxygenation of the preparation. Utilization of glucose displayed Michaelis-Menten saturation type kinetics with a Vmax of 331 nmol/10(6) cells per h and an apparent Km of 2.4 mM. These values were not affected by the presence of ouabain (0.1 mM), mannoheptulose (5 mM), or insulin (1 mU/ml), whereas phloridzin produced a drastic inhibition of glucose utilzation showing an apparent Ki of 0.4 mM. The substitution of sodium by K+ or Li+ as the predominant cations in the incubation medium does not alter rates of glucose utilization. Optimal pH for glucose utilization was within the physiological range with a more pronounced inhibitory effect at alkaline pH's. The intracellular concentration glucose was found to be low. This finding, in conjunction with a Q10 (27-37 degrees C) for glucose utilization above 2.0 and the differential effects of D- and L-glucose on production, seems to indicate that a stereospecific glucose transport system exists in lung cells. Several findings point to glucose transport into the lung cells as a probable rate-limiting step for its metabolism:1) the activity of the glycolytic enzymes largely exceeded the observed rate of glucose utilization;2) the decrease in enzyme activity during starvation was not accompanied by a decreased glycolytic flux, suggesting that factors other than enzyme activity, perhaps the supply of fuel, are rate limiting in the overall process of glucose breakdown;3) fructose was able to increase lactate production in the presence of saturating concentrations of glucose. These additive effects of glucose and fructose seem to support the point of view that it is not the glycolytic machinery but the supply of fuel which is rate limiting for glucose utilization by isolated rat lung cells.
 ...
PMID:Metabolic features of isolated rat lung cells. I. Factors controlling glucose utilization. 1 58

Sulphate uptake by Anacystis nidulans under aerobic conditions in the light was found to be sensitive to metabolic poisons, such as N,N'-dicyclohexylcarbodiimide and carbonyl cyanide m-chlorophenyl hydrazone. It was also depressed by darkness. The sulphate absorption is an energy-dependent process. Sulphate uptake was also inhibited by chromate and selenate. Osmotic shock strongly affected sulphate uptake. This effect could be interpreted by a loss of a binding protein involved in the absorption of sulphate. Osmotic shock also depressed oxygen production in light and oxygen consumption in darkness; however, shocked cells were able to grow normally. Sulphate uptake was strongly enhanced by sulphate starvation, but this enhancement was partly prevented by chloramphenicol. Apparently sulphate starvation depressed the synthesis of a carrier involved in the transport of sulphate. During sulphate starvation the membrane potential, measured by the uptake of triphenylmethylphosphonium, increases. This may be due to changes in the membrane.
 ...
PMID:Dependence of sulphate uptake by Anacystis nidulans on energy, on osmotic shock and on sulphate stravation. 2 Aug 62

A simple defined medium (neisseria defined medium) was devised that does not require iron extraction to produce iron-limited growth of Neisseria meningitidis (SDIC). Comparison of this medium to Mueller-Hinton broth and agar showed nearly identical growth rates and yields. The defined medium was used in batch cultures to determine the disappearance of iron from the medium and its uptake by cells. To avoid a number of problems inherent in batch culture, continuous culture, in which iron and dissolved oxygen were varied independently, was used. Most of the cellular iron was found to be nonheme and associated with the particulate fraction in sonically disrupted cells. Nonheme and catalase-heme iron were reduced by iron starvation far more than cytochromes b and c and N,N,N',N'-tetramethylphenylenediamine-oxidase. The respiration rate and efficiency also decreased under iron limitation, whereas generation times increased. The iron-starved meningococcus took up iron by an energy-independent system operating in the first minute after an iron pulse and a slower energy-dependent system inhibited by respiratory poisons and an uncoupler. The energy-dependent system showed saturation kinetics and was stimulated nearly fourfold by iron privation. In addition, to determine the availability to the meningococcus of the iron in selected compounds, a sensitive assay was devised in which an iron-limited continuous culture was pulsed with the iron-containing compound.
 ...
PMID:Iron in Neisseria meningitidis: minimum requirements, effects of limitation, and characteristics of uptake. 10 16

The decrease in resting oxygen consumption induced by starvation was found to occur not only in euthyroid rats but also in hypothyroid and even in hypothyroid animals treated with triiodothyronine. Furthermore, the effectiveness of triiodothyronine was decreased when given to hypothyroid animals.
 ...
PMID:Starvation-induced decreased sensitivity of resting metabolic rate to triiodothyronine. 22 60

Rat kidney microsomes have been found to catalyze the hydroxylation of medium-chained fatty acids to the omega- and (omego-1)-hydroxy derivatives. This reaction, which requires NADPH and molecular oxygen, is a function of monooxygenase system present in the kidney microsomes, containing NADPH-cytochrome c reductase and cytochrome P-450K. NADH is about half as effective as an electron donor as NADPH and there is an additive effect in the presence of both nucleotides. Cytochrome P-450K absorbs light maximally at 452-3 nm, when it is reduced and bound to carbon monoxide. The extinction coefficient of this complex is 91 mM(-1) cm(-1). Electrons from NADPH are transferred to cytochrome P-450K via the NADPH-cytochrome c reductase. The reduction rate of cytochrome P-450K is stimulated by added fatty acids and the reduction kinetics reveal the presence of endogenous substrates bound to cytochrome P-450K. Both cytochrome P-450K concentration and fatty acid hydroxylation activity in kidney microsomes are increased by starvation. On the other hand, phenobarbital treatment of the rats has no effect on either the hemoprotein or the overall hydroxylation reaction and 3,4-benzpyrene administration induces a new species of cytochrome P-450K not involved in fatty acid hydroxylation. Cytochrome P-450K shows, in contrast to liver P-450, high substrate specificity. The only substances forming enzyme-substrate complexes with cytochrome P-450K are the medium-chained fatty acids and certain derivatives of these acids. The chemical requirements for substrate binding include a carbon chain of medium length and at the end of the chain a carbonyl group and a free electron pair on a neighbouring atom. The distance between the binding site for the carbonyl group and the active oxygen is suggested to be in the order of 16 A. This distance fixes the ratio of omega- and (omega-1)-hydroxylated products formed from a certain fatty acid by the single species of cytochrome P-450K involved. The membrane microenvironment seems also to be of importance for the substrate specificity of cytochrome P-450K, since removal of the cytochrome from the membrane lowers its binding specificity to some extent. A comparison between the liver and kidney cytochrome P-450 systems suggests that the kidney cytochrome P-450K system is specialized for fatty acid hydroxylation.
 ...
PMID:Fatty acid hydroxylation in rat kidney cortex microsomes. 24 Oct 11

Performance characteristics of the central nervous, cardiovascular, respiratory and muscular systems in man postoperatively have received little investigative attention, despite the well known syndrome of postoperative fatigue. The impairmen in perception and psychomotor skills that has been shown to result from caloric restriction, bedrest, sedation and sleep deprivation suggests that a similar deficit may occur after surgical procedures. After a simple elective surgical procedure, maximal oxygen uptake decreases and the adaptability of heart rate to submaximal workloads is impaired. Similar deleterious effects on cardiorespiratory performance have been documented with starvation and bedrest; an understanding of cardiorespiratory performance postoperatively awaits further investigation. Maximal muscular force of contraction is also impaired by caloric restriction and bedrest, suggesting that similar effects may be seen in the postoperative state, although this has not been studied. A better understanding of the syndrome of postoperative fatigue could be achieved by a descriptive analysis of physiologic performance postoperatively. Such descriptive data could form the basis for objective evaluation of therapeutic measures intended to improve performance, such as nutritional supplementation and pharmacologic intervention. The observation that exercise with the patient in the supine position may decrease the impairment in maximal aerobic power otherwise expected in immobilized patients suggests that controlled exercise therapy may be of value in reducing physiologic impairment postoperatively.
 ...
PMID:Understanding postoperative fatigue. 35 38

The pool of coenzyme A--glutathione mixed disulfide (CoASSG) rapidly increased 2.0 times in response to oxygen starvation and 1.5 times in response to glucose starvation but did not change following ammonia starvation. The increase in the CoASSG pool resulted from an increase in the CoASSG fraction of the CoA pool from 42 to 66--93%. Fluoride, cyanide, chloramphenicol, and rifampicin all caused similar increases. Aerobic growth on fermentable sugars resulted in CoASSG making up 40--55% of the CoA pool while growth on nonfermentable carbon sources or anaerobic fermentation resulted in CoASSG replacing acetyl CoA and free CoA to make up 85--95% of the CoA pool. The CoASSG:ATP ratio varied inversely with the growth rate in two groupings of carbon sources made up of either fermentable or nonfermentable molecules. Cultures grown aerobically on fermentable sugars exhibited a lower CoASSG:ATP ratio reflecting the lower proportion of CoASSG in the CoA pool.
 ...
PMID:Levels of coenzyme A--glutathione mixed disulfide in Escherichia coli. 35 37

Nitrogen-starved cultures of the alga Anabaena cylindrica 629 produced hydrogen and oxygen continuously for 7 to 19 days. Hydrogen production attained a maximum level after 1 to 2 days of starvation and was followed by a slow decline. The maximum rates were 30 ml of H2 evolved per liter of culture per h or 32 mul of H2 per mg of dry weight per h. In 5 to 7 days the rate of H2 evolution by the more productive cultures fell to one-half its maximum value. The addition of 10(-4) to 5 X 10(-4) M ammonium increased the rate of oxygen evolution and the total hydrogen production of the cultures. H2-O2 ratios were 4:1 under conditions of complete nitrogen starvation and about 1.7:1 after the addition of ammonium. Thus, oxygen evolution was affected by the extent of the nitrogen starvation. Thermodynamic efficiencies of converting incident light energy to free energy of hydrogen via algal photosynthesis were 0.4%. Possible factors limiting hydrogen production were decline of reductant supply and filament breakage. Hydrogen production by filamentous, heterocystous blue-green algae could be used for development of a biophotolysis system.
 ...
PMID:Hydrogen production by nitrogen-starved cultures of Anabaena cylindrica. 40 9

To evaluate the effects of substrate deficiency on cerebral function, metabolism, and blood flow during seizures, rats were injected intravenously with bicuculline (1.2 mg.kg-1) following a 24-hour period of starvation. During the course of seizures, blood glucose concentrations fell, and when they were reduced to below about 3 mumol.gm-1, cerebral function, metabolism, and blood flow altered. Changes in function involved the transition of an electroencephalographic pattern of bursts and suppression into one of frequent or sparse single spikes. Oxygen consumption, which initially increased at least twofold, fell toward normal or subnormal values in the single-spike period. Cortical blood flow was markedly reduced, and there was an attenuated response to carbon dioxide administration. Simultaneously, a small but clear fall was detected in the cerebral phosphorylation potential, and concentrations of glycolytic metabolites (including lactate) and citric acid cycle intermediates were reduced. Changes in amino acids and ammonia were somewhat similar to those observed in insulin-induced hypoglycemia, but since the amino acid pool did not fall, the experiments failed to give evidence that amino acids serve as oxidative substrates. The perturbation of cerebral energy state (and of levels of carbohydrate substrates and amino acids) was reversed by glucose administration; but since neither this procedure nor additional bicuculline injections could cause resumption of continuous seizure activity, the results suggest that cellular substrate depletion may have given rise to a sustained disturbance of synaptic transmission.
 ...
PMID:Effects of bicuculline-induced seizures on cerebral metabolism and circulation of rats rendered hypoglycemic by starvation. 42 77

Detailed studies of hepatic metabolism of lipemic BHE and nonlipemic Wistar rats were conducted. Hepatic lipogenic capacity was varied through the use of starvation or meal feeding. Livers were clamped in precooled copper plates and used for the assay of glycolytic, gluconeogenic, and lipogenic metabolites. Redox and phosphorylation states were calculated. Mitochondrial metabolism was evaluated through studies of the oxygen consumption of isolated mitochondria and through the study of the activities of the alpha-glycerophosphate and malate aspartate shuttles and ATPase. BHE rats have higher phosphorylation states, higher redox ratios, and lower shuttle activities and oxygen consumption by isolated mitochondria than their Wistar cohorts. The differences in oxidative phosphorylation, redox and phosphorylation states, and in the various shuttle activities suggest that BHE liver cells are geared towards lipogenesis at the expense of oxidative phosphorylation. It appears that the activity of the shuttles is controlled in part by phosphorylation state which in turn appears to affect respiration. We theorize from these data that genetically determined differences in the structure and function of the mitochondrial membrane (and perhaps the cell membrane as well) may affect the communication (via metabolites and adenine nucleotides) between the cytosol and mitochondria. Subtle differences in the exchange of metabolites and/or adenine nucleotides across the mitochondrial membrane could thus explain the lipogenic tendency of the liver of the BHE rat and the subsequent development of maturity onset hyperlipemia and hyperglycemia in this strain of rat.
 ...
PMID:Studies on the control of lipogenesis: strain differences in hepatic metabolism. 43 Feb 26


1 2 3 4 5 6 7 8 9 10 Next >>