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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Under iron-starvation conditions of growth, Pseudomonas fluorescens CHA0, a soil isolate involved in phytopathogenic fungi antagonisms, produced, together with pyoverdine, a second iron-chelating compound which was purified and identified by spectroscopy, HPLC and 1H-NMR to be salicylic acid. Mutants unable to synthesize pyoverdine overproduced this compound by a factor of 9-14. The biosynthesis of salicylic acid was under iron control; it was fully inhibited by 5 microM added iron in the growth medium. In contrast, salicylic acid of either bacterial or commercial origin facilitated labeled iron incorporation in iron-starved cells. Based on these two relationships observed with bacterial iron metabolism it is concluded that salicylic acid has a siderophore function for this strain.
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PMID:Iron metabolism in Pseudomonas: salicylic acid, a siderophore of Pseudomonas fluorescens CHAO. 129 72

The extraction of reliable and useful relaxation time data for tissue characterization by NMR requires strict protocols, optimized for each type of biological tissue, which include parameters like storage duration and temperature as well as measurement parameters. Spin-lattice relaxation times in liver tissue vary not only with NMR frequency but also with their "time-after-excision characteristics," while spin-spin relaxation times are almost independent of most parameters which influence T1 at 20 MHz in normal liver tissue (e.g., species, sex, circadian rythm, starvation). T2, however, being more sensitive to water content and pH changes, is well suited for detecting nonspecific tissue alterations (e.g., due to ischemia, chemical toxins). Following the suggestions outlined herein, investigation of at least 120 min of time-after-excision (storage) effects allows the significant distinguishing of various physiological differences in normal liver tissue as well as improvement of early detection of liver pathologies.
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PMID:Liver tissue characterization by in vitro NMR: tissue handling and biological variation. 156 62

31P NMR of superfused resting cartilage demonstrated the presence of phosphocreatine in chondrocytes. Changes in pH and in the NTP level were followed during carbon source starvation. From 31P spectra of perchloric acid extracts, phosphoethanolamine, phosphocholine, and the corresponding glycerol diesters were identified as the major phosphomonoester and phosphodiester components.
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PMID:31P NMR studies of resting zone cartilage from growth plate. 161 20

400 MHz 1H NMR spectroscopy was used to analyze methyl group-containing metabolites in perchloric acid extracts of livers of rats treated with carbon tetrachloride or fed with ethanol-containing liquid diets, and sacrificed with carbon dioxide anoxic euthanasia or pentobarbital euthanasia (with or without 12-18 hour fasting). In all cases, coenzyme A was detected using 1H NMR spectroscopy, but at higher levels for chronic ethanol-treated rats. Propionate was also detected in livers 6 hours after treatment with carbon tetrachloride. The assignments of the 1H NMR resonances in a spectrum of biological origin to these two metabolites have not been previously reported. Another unusual metabolite, 1,2-propanediol, was also observed in dramatically elevated levels in starved rats. The methyl groups for coenzyme A, propionate, and 1,2-propanediol have 1H NMR chemical shifts at 0.73 and 0.87 ppm, 1.18 ppm, and 1.14 ppm (from tetramethylsilane) respectively. In addition to the above mentioned resonances, glutamine, glutamate, proline, acetate, leucine, alanine, lactate, ethanol, beta-hydroxybutyrate, and valine were also observed in the 0.5-2.3 ppm methyl region of the 1H NMR spectra. Biochemical changes were also observed in these latter metabolites. beta-Hydroxybutyrate was increased by chronic ethanol administration; this increase was exacerbated by starvation. Alanine was decreased by chronic ethanol administration. Acetate was increased by chronic ethanol administration except when glycerol was added to the liver or when the rat was starved. We also observed an unassigned triplet at 0.81 ppm, and its appearance seems to be correlated with that of 1,2-propanediol.
Physiol Chem Phys Med NMR 1991
PMID:1H NMR analyses of methyl group-containing metabolites in rat liver extracts--effects of starvation, anoxia, acute glycerol and carbon tetrachloride treatment and chronic ethanol administration on hepatic metabolism. 181 3

The colonic cells of the large intestine are one of the most proliferative tissues of the animal body. The pentose pathway has an essential role in cell division and growth being the only pathway forming ribose 5-P necessary for all nucleotide and nucleic acid sunthesis. The pentose pathway may also provide reducing potential as NADPH for biosynthesis and C-3- C-8 glycolyl compounds. The maximum catalytic capacities of the reactions of the non-oxidative pentose pathway for the conversion of ribose 5-P to hexose and triose phosphates by the proximal and distal colon under feeding and starvation regimes are among the highest in the animal body. The qualitative presence of the oxidative pentose pathway was assessed by measurement of the C-1/C-6 ratio value of 1.67-1.82. Enzymes of the F-type and L-type pentose pathways are present in colonocytes and their maximum catalytic activities in colonocyte cytosol are reported. The contribution of the F-type pentose cycle to the total glucose metabolism of colonocytes, measured by the specific yield method, is negligibly low (approximately 1.5%). Colonic epithelial cells use glucose at a high rate (7.1 +/- 0.33 mumol min-1g-1 dry wt) and 79% of the glucose is converted to lactate. Arabinose 5-P has an intermediary role in the formation of keto pentose, sedoheptulose and hexose phosphates from ribose 5-P by colonocyte cytosol. The intermediary and reaction products of [1-13C] ribose 5-P dissimilation by colonocytes is investigated by 13C NMR spectroscopy. The 13C positional isotope distributions show labelling of C-1 and C-3 of hexose 6-phosphates consistent with either the theoretical predictions of the F-type pentose pathway or of the activities of exchange reactions catalysed by transketolase and/or transaldolase. Measurements of exchange reactions showed that the C-1/C-3 labelling of these compounds is mostly, if not wholly, attributable to exchange catalysis by these group transferring enzymes. The results suggest that the F-type PC has little role in the glucose metabolism of colonocytes and pentose phosphate formation may thus occur by a contribution (approx 20% of the total glucose metabolism) by the alternate L-type pathway.
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PMID:Pentose phosphate pathway in rat colonic epithelium. 196 76

31P-NMR spectroscopy has been used to study the energy metabolism and the NMR visibility of ATP and intracellular Pi of the C6 glioma cell line and rat astrocyte grown on microcarrier beads with the following results. 1. In vivo NMR spectra of C6 glioma cells and rat astrocytes indicate that these cells were able to maintain their level of ATP resonances during a long anoxic period (more than an hour). Both cell types were sensitive to ischemia which induced a loss of ATP resonances within 40 min. Glucose starvation induced by 40% decrease in ATP resonances correlated to a 50% increase in the intensity of the Pi signal. These changes corresponded to a new steady state which could be reversed by reperfusing the cells with a glucose-containing medium. 2. In contrast to in vivo data, 31P-NMR analyses of perchloric acid extracts of cells incubated in a glucose-free medium showed that their ATP and Pi contents were unchanged during starvation. The changes of NMR visibility of the metabolites in living C6 cells were correlated to modifications of their macroscopic longitudinal relaxation times, evolving from 0.30 +/- 0.08 s and 6.6 +/- 1.5 s in the presence of glucose to 0.68 +/- 0.26 s and 3.2 +/- 0.9 s in the absence of glucose for ATP and Pi, respectively. The changes of the NMR detectability of ATP and Pi indicate that changes in their microenvironment occur during glucose starvation, suggesting the existence of different pools of these metabolites within the cells. 3. Under various experimental conditions, i.e. anoxia, ischemia and glucose starvation, rat astrocytes in primary culture showed a very similar behavior to that of C6 cells, suggesting a similar adaptability to the nature of the energy supply for both the normal and the malignant cell.
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PMID:Phosphorus-31 nuclear magnetic resonance of C6 glioma cells and rat astrocytes. Evidence for a modification of the longitudinal relaxation time of ATP and Pi during glucose starvation. 199 80

The recovery of Candida utilis from phosphate starvation was studied using 31P-NMR. The phosphate analogue methylphosphonate was found to be a useful indicator of cytosol pH. Added orthophosphate was rapidly accumulated by the cells and stored mainly In a stable pool of polyphosphate of mean chain-length at least 200 units. Observed pH changes in the medium and cytosol during uptake of orthophosphate and methylphosphonate are consistent with the transport of these compounds across the plasma membrane by a proton/phosphate symport. However, transport of phosphate across the vacuole membrane occurs by a mechanism for which methylphosphonate is not a substrate. In the cytosol pH changes are strongly correlated with changes in orthophosphate concentration, however, this is not the case in the vacuole.
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PMID:A 31P-NMR study of phosphate transport and compartmentation in Candida utilis. 222 70

Methyl phosphonate at concentrations up to 20 mM was found to be non toxic towards the growth of Dictyostelium amoebae and the starvation-induced differentiation program. In contrast, phenyl phosphonate at the same concentrations was found to inhibit growth. Methyl phosphonate possessed good 31P-NMR characteristics for use as a pH probe in Dictyostelium. The entry of methyl phosphonate into the cytoplasm required about 150 min of incubation before an equilibrium was reached with added extracellular methyl phosphonate. A semilogarithmic plot of the efflux of methyl phosphonate out of the amoebae was linear as a function of time, and the kinetic first-order constant was k = 0.016 min-1. The kinetic parameters were consistent with an uptake of methyl phosphonate by fluid-phase pinocytosis. The pH calculated from the chemical shift of the internalized methyl phosphonate signal was found to be pH 7.4 in aerobic Dictyostelium amoebae. The intracellular methyl phosphonate environment turned more acidic in response to anaerobiosis (delta pH = 0.8) or in the presence of a weak acid such as propionate. These pH determinations were in agreement with the values of cytosolic pH derived from the chemical shift of Pi. Methyl phosphonate should be a useful probe for pH measurements in 31P-NMR studies of Dictyostelium in situations where the signal of Pi cannot be attributed with certainty.
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PMID:Methyl phosphonate as a 31P-NMR probe for intracellular pH measurements in Dictyostelium amoebae. 250 63

Despite numerous work on spin-lattice (T1) relaxation in vitro, not much attention has been paid on spin-spin (T2) relaxation until now. In this study we are presenting spin-spin relaxation time measurements of mouse liver tissue in order to estimate the time-after-excision effects. The post mortem behaviour of excised tissue was investigated up to four hours in intervals of about nine minutes. The time course of liver T2 was determined for different temperatures (4 degrees - 40 degrees C) for female mice. In order to describe the similar behaviour of T2 and pH changes in mouse liver after excision, we are suggesting an empirical model to correlate this data. In contrast to T1 results published recently, we found no significant differences in liver T2 time course after excision due to different physiological states like sex, starvation or circadian rhythm. T1/T2-behaviour after tissue excision is discussed in an attempt to separate various relaxation mechanisms.
Physiol Chem Phys Med NMR 1989
PMID:Systematic investigation of degradation effects on spin-spin relaxation times in mouse-liver by low resolution NMR. 260 30

In spite of numerous work on in vitro proton relaxation time investigations of biological tissue, many questions still remain open. In this study we focused on spin-lattice (T1) relaxation time measurements of mouse liver tissue in order to estimate the time-after-excision effects. The post mortem behaviour of excised tissue was measured up to four hours in intervals of about nine minutes. The time course of liver T1 was determined for different temperatures (4 degrees-40 degrees C) for female mice and the effect of starvation (up to 48 hours) on the time course of T1 was investigated for male and female mice at 37 degrees C. We obtained significant differences in liver T1 time course after excision due to different physiological states like sex, starvation and circadian rhythm.
Physiol Chem Phys Med NMR 1989
PMID:Systematic investigation of degradation effects on spin-lattice relaxation times in mouse-liver by low resolution NMR. 261 49


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