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

Large free-living amoeba (Chaos carolinensis) can survive in spring water without food intake for several weeks. Starvation is associated with a dramatic change in mitochondrial cristae from random tubular to ordered (paracrystalline) cubic morphology. Whole-cell polarography was used to monitor changes in respiratory activity during fasting. Basal respiration per cell decreased progressively during starvation, while the cyanide-resistant fraction increased. Spectrofluorometric assay of H2O2 and reactive oxygen species (ROS) in cell lysates (using the dye 2',7'-dichlorofluorescein diacetate) indicates greater H2O2 and ROS generation in starved than in fed cells. Fluorescence microscopy of intact cells incubated with the same dye demonstrates that H2O2 and ROS tend to accumulate in vacuoles. A remarkable generation of O2 observed with starved cells after addition of KCN may be explained by release of H2O2 from these compartments into the cytosol, where it can react with catalase. Together, these observations suggest that fasting increases oxidative stress in the amoeba and that this organism has several protective mechanisms to deal with it, including activation of a plantlike alternative oxidase. The hypothesis is forwarded that the cubic structural transition of the mitochondrial inner membrane represents another protective mechanism, reducing oxidative damage by enhancing the efflux of H2O2 and ROS and by reducing the susceptibility of membrane lipids to the oxidants.
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PMID:Fasting induces cyanide-resistant respiration and oxidative stress in the amoeba Chaos carolinensis: implications for the cubic structural transition in mitochondrial membranes. 1209 16

The unicellular green alga Dunaliella bardawil exhibits typical responses to excessive light when starved for sulfate under normal light (60 [mu]E m-2 s-1) but not under low light (14 [mu]E m-2 s-1). Algae were analyzed during several days of sulfate starvation for nonphotochemical quenching of chlorophyll fluorescence in the absence or presence of the uncouplers SF-6847 (SF) or carbonyl cyanide p- trifluoromethoxyphenyl hydrazone. Parallel analyses followed two light-stress responses: (a) violaxanthin conversion to zeaxanthin and (b) accumulation of Cbr, a protein analogous to plant early-light-induced proteins and implicated in zeaxanthin binding. In cells starved under normal light SF inhibited nonphotochemical quenching during the first 24 h, but not from 40 h onward. In cells starved under low light SF inhibited nonphotochemical quenching throughout the starvation period. Under normal light accumulation of zeaxanthin was nearly maximal by 24 h, but Cbr was fully induced only by 40h. Under low light zeaxanthin accumulated slowly but no Cbr was evident. These results suggest that during exposure to excessive light, the initial pH gradient-dependent, Cbr-independent mode of nonphotochemical quenching is modified to become less dependent on pH gradient and requires Cbr.
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PMID:Possible Role of Cbr, an Algal Early-Light-Induced Protein, in Nonphotochemical Quenching of Chlorophyll Fluorescence. 1222 69

1. Evidence is presented that silicon uptake in the diatom Navicula pelliculosa is linked with aerobic respiration. 2. Cyanide, fluoride, iodoacetate, arsenite, azide, and fluoroacetate, at concentrations inhibitory to respiration, were also inhibitory to silicon uptake. 3. 2,4-Dinitrophenol (1 to 2 x 10(-5)M) stimulated respiration by 100 per cent, but almost completely inhibited silicon uptake. 4. The respiratory quotient of non-Si-deficient cells decreased from 0.93 to 0.75 after 4 days of starvation in darkness. Glucose (1 per cent) raised the respiratory quotient of such starved cells to 1.05. 5. Silicate (20 mg. Si/liter) stimulated respiration of unstarved Si-deficient cells by about 40 per cent. The effect of silicate on the respiration of Si-deficient cells which had been starved in darkness for 4 days was less marked. 6. The respiratory quotient of Si-deficient cells decreased from 0.8-0.9 to 0.3 after 4 days of starvation in darkness. The addition of silicate to starved cells raised the quotient to 0.5. This represented a 25 per cent stimulation of oxygen uptake concomitant with a 90 per cent stimulation of carbon dioxide evolution. 7. Glucose (1 per cent) caused an increase of respiratory quotient in starved cells from 0.3 to 0.7-0.8. The addition of silicate had no effect on the R.Q. during the oxidation of exogenous glucose. 8. Substrates (glucose, fructose, galactose, lactate, succinate, citrate, glycerol), which caused a stimulation of respiration in starved cells, also stimulated silicon uptake by those cells. However, the stimulation of silicon uptake (50 to 100 per cent) was not proportional to the respiratory stimulation by these substrates (30 to 300 per cent).
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PMID:Silicon metabolism in diatoms. III. Respiration and silicon uptake in Navicula pelliculosa. 1325 31

Under anaerobiosis, the mitochondrion of Saccharomyces cerevisiae is restricted to unstructured promitochondria. These promitochondria provide unknown metabolic functions that are required for growth. Since high glucose concentrations are mainly fermented by S. cerevisiae during stationary phase (due to nitrogen starvation), an optimized promitochondria isolation procedure was investigated. Firstly, the unusual promitochondria ultrastructure was checked in intact cells by electron microscopy using a cryo-fixation and freeze-substitution method. The rapid response of anaerobic cells toward oxygen justified the adoption of several critical steps, especially during spheroplasting. Control of spheroplasting was accompanied by a systematic analysis of spheroplast integrity, which greatly influence the final quality of promitochondria. Despite the presence of remnant respiratory chain components under anaerobiosis, characterization of isolated promitochondria by high-resolution respirometry did not reveal any antimycin A- and myxothiazol-sensitive NADH and NADPH oxidase activities. Moreover, the existence of a cyanide-sensitive and non-phosphorylating NADH-dependent oxygen consumption in promitochondria was demonstrated. Nevertheless, promitochondria only slightly contribute to the overall oxygen consumption capacity observed in highly glucose-repressed anaerobic cells.
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PMID:Isolation and properties of promitochondria from anaerobic stationary-phase yeast cells. 1503 59

Biochemical estimation of NADH concentration is a useful method for monitoring cellular metabolism, because the NADH/NAD+ reduction-oxidation pair is crucial for electron transfer in the mitochondrial electron chain. In this article, we present a novel method for deriving functional maps of intracellular reduction-oxidation ratio in vivo via measurement of the fluorescence lifetimes and the ratio of free and protein-bound NADH using two-photon fluorescence lifetime imaging (FLIM). Through systematic analysis of FLIM data from the control cells, it was observed that there is a statistically significant decrease in the fluorescence lifetime of both free and protein-bound NADH and the contribution of protein-bound NADH as cells progress from an early to logarithmic to confluent phase. Potassium cyanide (KCN) treatment and serum starvation of cells yielded similar changes. There was a statistically significant decrease in the fluorescence lifetime of protein-bound and free NADH at the early and logarithmic phase of the growth curve and a statistically significant decrease in the contribution of protein-bound NADH relative to that observed in the control cells at all three phases of the growth curve. The imposed perturbations (confluence, serum starvation, and KCN treatment) are all expected to result in an increase in the ratio of NADH/NAD+. Our studies suggest that the fluorescence lifetime of both the free and the protein-bound components of NADH and the ratio of free to protein-bound NADH is related to changes in the NADH/NAD+ ratio.
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PMID:Metabolic mapping of MCF10A human breast cells via multiphoton fluorescence lifetime imaging of the coenzyme NADH. 1620 46

The role of amino acids in trypanosomatids goes beyond protein synthesis, involving processes such as differentiation, osmoregulation and energy metabolism. The availability of the amino acids involved in those functions depends, among other things, on their transport into the cell. Here we characterize a glutamate transporter from the human protozoan parasite Trypanosoma cruzi. Kinetic data show a single saturable system with a Km of 0.30 mM and a maximum velocity of 98.34 pmoles min(-1) per 2 x 10(7) cells for epimastigotes and 20 pmoles min(-1) per 2 x 10(7) cells for trypomastigotes. Transport was not affected by parasite nutrient starvation for up to 3h. Aspartate, alanine, glutamine, asparagine, methionine, oxaloacetate and alpha-ketoglutarate competed with the substrate in 10-fold excess concentrations. Glutamate uptake was strongly dependent on pH, but not on Na+ or K+ concentrations in the extracellular medium. These data were consistent with the sensitivity of the system to the H+ ionophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone, suggesting that transport is driven by H+ concentration gradient across the cytoplasmic membrane. The glutamate transport increased linearly with temperature in a range from 15 to 40 degrees C, allowing the calculation of an activation energy of 52.38 kJ/mol.
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PMID:Biochemical characterization of the glutamate transport in Trypanosoma cruzi. 1637 69

During infection of the cystic fibrosis (CF) lung, Pseudomonas aeruginosa microcolonies are embedded in the anaerobic CF mucus. This anaerobic environment seems to contribute to the formation of more robust P. aeruginosa biofilms and to an increased antibiotic tolerance and therefore promotes persistent infection. This study characterizes the P. aeruginosa protein PA4352, which is important for survival under anaerobic energy stress conditions. PA4352 belongs to the universal stress protein (Usp) superfamily and harbors two Usp domains in tandem. In Escherichia coli, Usp-type stress proteins are involved in survival during aerobic growth arrest and under various other stresses. A P. aeruginosa PA4352 knockout mutant was tested for survival under several stress conditions. We found a decrease in viability of this mutant compared to the P. aeruginosa wild type during anaerobic energy starvation caused by the missing electron acceptors oxygen and nitrate. Consistent with this phenotype under anaerobic conditions, the PA4352 knockout mutant was also highly sensitive to carbonyl cyanide m-chlorophenylhydrazone, the chemical uncoupler of the electron transport chain. Primer extension experiments identified two promoters upstream of the PA4352 gene. One promoter is activated in response to oxygen limitation by the oxygen-sensing regulatory protein Anr. The center of a putative Anr binding site was identified 41.5 bp upstream of the transcriptional start site. The second promoter is active only in the stationary phase, however, independently of RpoS, RelA, or quorum sensing. This is the second P. aeruginosa Usp-type stress protein that we have identified as important for survival under anaerobic conditions, which resembles the environment during persistent infection.
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PMID:The Pseudomonas aeruginosa universal stress protein PA4352 is essential for surviving anaerobic energy stress. 1695 44

A Cu,Zn-superoxide dismutase has been characterized from Scedosporium apiospermum, a fungus which often colonizes the respiratory tract of patients with cystic fibrosis. Enzyme production was stimulated by iron starvation. Purification was achieved from mycelial extract from 7-day-old cultures on Amberlite XAD-16. The purified enzyme presented a relative molecular mass of 16.4 kDa under reducing conditions and was inhibited by potassium cyanide and diethyldithiocarbamate, which are two known inhibitors of Cu,Zn-SODs. Its optimum pH was 7.0 and the enzyme retained full activity after pretreatment at temperatures up to 50 degrees C. Moreover, a 450-bp fragment of the gene encoding the enzyme was amplified by PCR using degenerate primers designed from sequence alignment of four fungal Cu,Zn-SODs. Sequence data from this fragment allowed us to design primers which were used to amplify by walking-PCR the flanking regions of the known fragment. SaSODC gene (890 bp) corresponded to a 154 amino acid polypeptide with a predicted molecular mass of 15.9 kDa. A database search for sequence homology revealed for the deduced amino acid sequence 72 and 83% identity rate with Cu,Zn-SODs from Aspergillus fumigatus and Neurospora crassa, respectively. To our knowledge, this enzyme is the first putative virulence factor of S. apiospermum to be characterized.
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PMID:Molecular cloning and biochemical characterization of a Cu,Zn-superoxide dismutase from Scedosporium apiospermum. 1739 18

The function unknown gene PA2384 of Pseudomonas aeruginosa PAO1 has been previously shown dramatically responsive to iron limitation. In the present study, a bioinformatics analysis showed that PA2384 has a weak similarity to the N-terminus DNA-binding domain of Fur, the well-known ferric uptake regulator. To investigate the potential function of PA2384 in iron regulation a P. aeruginosa PAO1 recombinant (pUCP20::PA2384) over-expressing PA2384 and a PA2384 disrupted mutant PAO1*PA2384 were constructed. Physiological characterization showed that the knockout mutant had a longer lag phase. Genome-scale transcriptional profiles at different growth stages were compared between the wild type and the DeltaPA2384 mutant grown under iron-limiting conditions. The expression of more than 350 genes was affected by the knockout of PA2384. Among them, 71 genes involved in iron uptake were significantly down-regulated in the absence of PA2384. One hundred two quorum sensing (QS) dependent genes displayed differential transcriptions, including genes involved in the biosynthesis of some important virulence factors such as pyocyanin, rhamnolipids and hydrogen cyanide. The transcription of genes responsible for the synthesis of Pseudomonas quinolone signal (PQS) was greatly enhanced by the knockout of PA2384. Furthermore, the knockout of PA2384 also resulted in an altered expression of genes involved in electron transfer, central metabolism, phosphorus starvation and translation. It implies that PA2384 might affect more physiological processes than iron acquisition in P. aeruginosa.
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PMID:Functional characterization of the gene PA2384 in large-scale gene regulation in response to iron starvation in Pseudomonas aeruginosa. 1788 92

Pseudomonas aeruginosa has five terminal oxidases for aerobic respiration. Two of them, the bo(3) oxidase (Cyo) and the cyanide-insensitive oxidase (CIO), are quinol oxidases and the other three, the cbb(3)-1 oxidase (Cbb3-1), the cbb(3)-2 oxidase (Cbb3-2) and the aa(3) oxidase (Aa3), are cytochrome c oxidases. The expression pattern of the genes for these terminal oxidases under various growth conditions was investigated by using lacZ transcriptional fusions and some novel regulatory issues were found. The Aa3 genes were induced under starvation conditions. The Cyo genes were induced by exposure to the nitric oxide-generating reagent S-nitrosoglutathione. The CIO genes were induced by exposure to sodium nitroprusside as well as cyanide. The stationary phase sigma factor RpoS was found to be involved in the expression of the Aa3 and CIO genes. The role of two redox-responsive transcriptional regulators, ANR and RoxSR, was investigated using the anr and roxSR mutant strains. The ANR was involved in the repression of the CIO genes and induction of the Cbb3-2 genes. The other three terminal oxidase genes were not significantly regulated by ANR. On the other hand, all five terminal oxidase genes were shown to be directly or indirectly regulated by RoxSR. The Aa3 genes were repressed but the genes for the other four enzymes were induced by RoxSR. The transcriptome data also showed that some respiration-related genes were regulated by RoxSR, suggesting that this two-component regulatory system plays an important role in the regulation of respiration in P. aeruginosa.
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PMID:Differential expression of multiple terminal oxidases for aerobic respiration in Pseudomonas aeruginosa. 1993 Apr 44


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