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)

The metabolic pathways of poly(3-hydroxybutyrate) (PHB) and polyphosphate in the microorganism Alcaligenes eutrophus H16 were studied by H, C, and P nuclear magnetic resonance (NMR) spectroscopy and by conventional analytical techniques. A. eutrophus cells accumulated two storage polymers of PHB and polyphosphate in the presence of carbon and phosphate sources under aerobic conditions after exhaustion of nitrogen sources. The solid-state cross-polarization/magic-angle spinning C NMR spectroscopy was used to study the biosynthetic pathways of PHB and other cellular biomass components from C-labeled acetate. The solid-state C NMR analysis of lyophilized intact cells grown on [1-C]acetate indicated that the carbonyl carbon of acetate was selectively incorporated both into the carbonyl and methine carbons of PHB and into the carbonyl carbons of proteins. The P NMR analysis of A. eutrophus cells in suspension showed that the synthesis of intracellular polyphosphate was closely related to the synthesis of PHB. The roles of PHB and polyphosphate in the cells were studied under conditions of carbon, phosphorus, and nitrogen source starvation. Under both aerobic and anaerobic conditions PHB was degraded, whereas little polyphosphate was degraded. The rate of PHB degradation under anaerobic conditions was faster than that under aerobic conditions. Under anaerobic conditions, acetate and 3-hydroxybutyrate were produced as the major extracellular metabolites. The implications of this observation are discussed in connection with the regulation of PHB and polyphosphate metabolism in A. eutrophus.
 ...
PMID:Nuclear Magnetic Resonance Studies of Poly(3-Hydroxybutyrate) and Polyphosphate Metabolism in Alcaligenes eutrophus. 1634 55

Depending on the moment of cellobiose starvation, Clostridium cellulolyticum cells behave in different ways. Cells starved during the exponential phase of growth sporulate at 30%, whereas exhaustion of the carbon substrate at the beginning of growth does not provoke cell sporulation. Growth in the presence of excess cellobiose generates 3% spores. The response of C. cellulolyticum to carbon starvation involves changes in proteolytic activities; higher activities (20% protein degradation) corresponded to a higher level of sporulation; lower proteolysis (5%) was observed in cells starved during the beginning of exponential growth, when sporulation was not observed; with an excess of cellobiose, an intermediate value (10%), accompanied by a low level of sporulation, was observed in cells taken at the end of the exponential growth phase. The basal percentage of the protein breakdown in nonstarved culture was 4%. Cells lacking proteolytic activities failed to induce sporulation. High concentrations of cellobiose repressed proteolytic activities and sporulation. The onset of carbon starvation during the growth phase affected the survival response of C. cellulolyticum via the sporulation process and also via cell-cellulose interaction. Cells from the exponential growth phase were more adhesive to filter paper than cells from the stationary growth phase but less than cells from the late stationary growth phase.
 ...
PMID:Clostridium cellulolyticum Viability and Sporulation under Cellobiose Starvation Conditions. 1653 70

Post-operative fatigue is a well-known clinical problem even after uncomplicated surgery. In the multifaceted post-operative state, several factors other then the surgical trauma may influence muscular function, such as an insufficient nutritional intake. The aim of this study was to investigate the effect of fasting on work capacity and voluntary skeletal muscle function. Eight healthy lean volunteers, age range 25-43 years, were studied the day before starvation, at the end of the fasting period of 5 days, and after another 3-4 days on a normal diet. Hand grip strength was assessed as maximum voluntary contraction (MVC) and physical working capacity was investigated with successively increased work load on a cycle ergometer until near exhaustion. After 5 days of total starvation, MVC remained unchanged but physical working capacity was reduced from 220 +/- 18 watt to 199 +/- 22 watt (p < 0.05). Corresponding heart rate, estimated effort and leg tiredness were not changed. A poor nutritional intake per se may therefore be a less important factor causing post-operative muscle fatigue than the operation itself.
 ...
PMID:Effect of starvation on work capacity and voluntary skeletal muscle function in man. 1683 61

Information about the functions of extracellular autoregulators, which adapt microorganisms to the stresses "scheduled" in the development cycle of microbial cultures (stresses of new medium, starvation, or space exhaustion (high cell density)) is summarized in the review. In a number of bacteria and yeasts, derivatives of alkylhydroxybenzenes (AHB), particularly of the class of alkyl resorcinols, act as autoregulators with adaptogenic functions. The chemical structure of AHB determines their amphiphility; capacity for physical and chemical interaction with membrane lipids, proteins, and DNA; properties as natural modifiers of biological membranes and enzymes; and the expression of antioxidant activity. Increase of AHB concentration up to the critical level (10(-5)-10(-4) M) results in cessation of cell division and in transition of the microbial culture to the stationary phase; further increase to 10(-4)-10(-3) M induces a transition of some of the cells of a post-stationary culture to the anabiotic state with the formation of cystlike resting cells (CRC), even in non-spore-forming bacteria. AHB participate in the regulation of the phenotypic variability of bacteria. The dynamics of extra- and intracellular concentrations of AHB in growing microbial cultures and the polymodality of their effect determine the adaptogenic functions of AHB as autoinhibitors of culture growth, autoinducers of anabiosis, and autoinhibitors of germination of resting forms. Manifestation of any given function depends on the concentration of AHB, the physiological state of the recipient cells, and on environmental factors. The species nonspecificity of AHB effects points to their significant role in the regulation of the development and functioning of microbial communities.
 ...
PMID:[Adaptive functions of extracellular autoregulators of microorganisms]. 1702 68

Two Podospora mutants carrying mutations modE and modF were persumed to be quiescent defective, because, when grown under glucose limitation, they differed from the wild-type strain in an excess of dry weight production and a reduction of cell survival. New insight on the action of modE and modF mutations was provided by the study of double mutants resulting from the association of modE or modF mutations with unrelated developmental mutations.-ModE and modF were first coupled to three allelic mutations ( modC) that inhibit production of all hyphal cell derivatives (late ramifications, aerial hyphae and protoperithecia). Suppression in the double mutants of the excess of proliferation associated with modE and modF and restoration of normal cell survival indicated that modE and modF result in an uncontrolled production of hyphal cell derivatives in which deregulation is presumed to be responsible for the reduction of cell survival following glucose exhaustion.-ModE and modF were associated with mutations of two genes (modD and modG) which abolish production of hyphal cell derivatives (like modC mutations) but also inhibit the renewal of growth of cells situated in the center of colonies. Investigations of eight of these double mutants showed that modE and modF mutations suppress the inhibitory action of modD and modG on production of hyphal cell derivatives and on growth renewal.-Taken together these results lead to the suggestion that the accomplishment of a quiescent state for cell survival under glucose starvation is the final stage in the differentiation of hyphal cells and prerequisite for the production of derivatives of hyphal cells and for a control of their development.
 ...
PMID:Temporal Action of Mutations Inhibiting the Accomplishment of Quiescence or Disrupting Development in the Fungus PODOSPORA ANSERINA. 1724 50

This study characterized the ability of lactococci to become nonculturable under carbohydrate starvation while maintaining metabolic activity. We determined the changes in physiological parameters and extracellular substrate levels of multiple lactococcal strains under a number of environmental conditions along with whole-genome expression profiles. Three distinct phases were observed, logarithmic growth, sugar exhaustion, and nonculturability. Shortly after carbohydrate starvation, each lactococcal strain lost the ability to form colonies on solid media but maintained an intact cell membrane and metabolic activity for over 3.5 years. ML3, a strain that metabolized lactose rapidly, reached nonculturability within 1 week. Strains that metabolized lactose slowly (SK11) or not at all (IL1403) required 1 to 3 months to become nonculturable. In all cases, the cells contained at least 100 pM of intracellular ATP after 6 months of starvation and remained at that level for the remainder of the study. Aminopeptidase and lipase/esterase activities decreased below detection limits during the nonculturable phase. During sugar exhaustion and entry into nonculturability, serine and methionine were produced, while glutamine and arginine were depleted from the medium. The cells retained the ability to transport amino acids via proton motive force and peptides via ATP-driven translocation. The addition of branched-chain amino acids to the culture medium resulted in increased intracellular ATP levels and new metabolic products, indicating that branched-chain amino acid catabolism resulted in energy and metabolic products to support survival during starvation. Gene expression analysis showed that the genes responsible for sugar metabolism were repressed as the cells entered nonculturability. The genes responsible for cell division were repressed, while autolysis and cell wall metabolism genes were induced neither at starvation nor during nonculturability. Taken together, these observations verify that carbohydrate-starved lactococci attain a nonculturable state wherein sugar metabolism, cell division, and autolysis are repressed, allowing the cells to maintain transcription, metabolic activity, and energy production during a state that produces new metabolites not associated with logarithmic growth.
 ...
PMID:Carbohydrate starvation causes a metabolically active but nonculturable state in Lactococcus lactis. 1729 21

In higher organisms dependent on the regenerative ability of tissue stem cells to maintain tissue integrity throughout adulthood, the failure of stem cells to replace worn out, dead, or damaged cells is seen as one mechanism that limits life span. In these organisms, tumor suppressors such as p53 are central participants in the control of longevity because they regulate stem cell proliferation. Several recent reports have identified p53 as a longevity gene in organisms such as Caenorhabditis elegans and Drosophila melanogaster, which lack proliferative stem cells in all but the germline and have relatively short life spans. This has forced us to reevaluate the role of p53 in the control of life span. We discuss how p53 might regulate longevity in both long- and short-lived species by controlling the activity of insulin-like molecules that operate in proliferating and non-proliferating compartments of adult somatic tissues. We also discuss the hierarchical structure of life span regulation where loss of p53 has life span extending effects. Finally, we suggest a molecular mechanism by which p53 might facilitate the response to severe nutrient deprivation that allows metabolically active cells to survive periods of starvation. Paradoxically, loss of p53 function in these cells would compromise life span.
 ...
PMID:Running on empty: how p53 controls INS/IGF signaling and affects life span. 1859 47

The use of glucose starvation to uncouple the production of recombinant beta-galactosidase from cell growth in Escherichia coli was investigated. A lacZ operon fusion to the carbon starvation-inducible cst-1 locus was used to control beta-galactosidase synthesis. beta-Galactosidase induction was observed only under aerobic starvation conditions, and its expression continued for 6 h following the onset of glucose starvation. The cessation of beta-galactosidase expression closely correlated with the exhaustion of acetate, an overflow metabolite of glucose, from the culture medium. Our results suggest the primary role of acetate in cst-1-controlled protein expression is that of an energy source. Using this information, we metered acetate to a glucose-starved culture and produced a metabolically sluggish state, where growth was limited to a low linear rate and production of recombinant beta-galactosidase occurred continuously throughout the experiment. The cst-1 controlled beta-galactosidase synthesis was also induced at low dilution rates in a glucose-limited chemostat, suggesting possible applications to high-density cell systems such as glucose-limited recycle reactors. This work demonstrates that by using an appropriate promoter system and nutrient limitation, growth can be restrained while recombinant protein production is induced and maintained.
 ...
PMID:Use of glucose starvation to limit growth and induce protein production in Escherichia coli. 1860 Nov 13

The fungus Fusarium fujikuroi (Gibberella fujikuroi MP-C) produces metabolites of biotechnological interest, such as gibberellins, bikaverins, and carotenoids. Gibberellin and bikaverin productions are induced upon nitrogen exhaustion, while carotenoid accumulation is stimulated by light. We evaluated the effect of nitrogen availability on carotenogenesis in comparison with bikaverin and gibberellin production in the wild type and in carotenoid-overproducing mutants (carS). Nitrogen starvation increased carotenoid accumulation in all strains tested. In carS strains, gibberellin and bikaverin biosynthesis patterns differed from those of the wild type and paralleled the expression of key genes for both pathways, coding for geranylgeranyl pyrophosphate (GGPP) and kaurene synthases for the former and a polyketide synthase for the latter. These results suggest regulatory connections between carotenoid biosynthesis and nitrogen-controlled biosynthetic pathways in this fungus. Expression of gene ggs1, which encodes a second GGPP synthase, was also derepressed in the carS mutants, suggesting the participation of Ggs1 in carotenoid biosynthesis. The carS mutations did not affect genes for earlier steps of the terpenoid pathway, such as fppS or hmgR. Light induced carotenoid biosynthesis in the wild type and carRA and carB levels in the wild-type and carS strains irrespective of nitrogen availability.
 ...
PMID:Regulation of carotenogenesis and secondary metabolism by nitrogen in wild-type Fusarium fujikuroi and carotenoid-overproducing mutants. 1904 98

Behavioral changes of animal species can influence the consequence of population dynamics. One of the most remarkable behaviors of animal species is the aggregation by which species can reduce predation risk as a consequence of dilution or the other effects by forming a group. Empirical studies have demonstrated that an incompatibility exists in aggregation since resource competition might become severe at the cost of reducing predation pressure from predatory species. Parental care by supplying the food consumed by adults to their juveniles would reduce the mortality of juvenile due to starvation, but it would reduce the reproduction rate at the same time. In this paper, we study a class of stage-structured resource-consumer models to investigate the effect of behavioral changes on population dynamics. It is shown that under the presence of trade-off in parental care, moderate degrees of parental care will be favored as maximizing the equilibrium density of consumers. For consumer species having a long maturation period, consumer species might get benefit from dilution effects as a result of aggregation despite the elevated resource competition. Aggregation gives rise to two different outcomes in consumer extinction. Resource exhaustion as a consequence of over-exploitation can induce extinction of consumers due to Allee effects if aggregation strongly mediates juvenile survival.
 ...
PMID:Effect of parental care and aggregation on population dynamics. 1953 31


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