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

Phosphorylation of the alpha-subunit of eukaryotic initiation factor 2 (eIF2alpha) is a conserved mechanism regulating protein synthesis in response to various stresses. A screening for negative factors in yeast salt stress tolerance has led to the identification of Gcn2p, the single yeast eIF2alpha kinase that is activated by amino acid starvation in the general amino acid control response. Mutation of other components of this regulatory circuit such as GCN1 and GCN3 also resulted in improved NaCl tolerance. The gcn2 phenotype was not accompanied by changes in sodium or potassium homeostasis. NaCl induced a Gcn2p-dependent phosphorylation of eIF2alpha and translational activation of Gcn4p, the transcription factor that mediates the general amino acid control response. Mutations that activate Gcn4p function, such as gcd7-201, cpc2, and deletion of the translational regulatory region of the GCN4 gene, also cause salt sensitivity. It can be postulated that sodium activation of the Gcn2p pathway has toxic effects on growth under NaCl stress and that this novel mechanism of sodium toxicity may be of general significance in eukaryotes.
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PMID:The protein kinase Gcn2p mediates sodium toxicity in yeast. 1140 81

The survival response of Lactococcus lactis during long-term starvation was investigated. The cells were cultured with different levels of glucose (the sole energy source) and either were kept in the resultant spent medium or transferred to fresh medium (without glucose) for up to 2 years. The survival of the cells during starvation was not dependent on the nature of transition phase, as expected, but on the nature of medium in which the cells were kept. The proliferation of cells, despite the apparent lack of glucose, could have been due to some cells being able to utilize the small amounts of peptides still present in the spent medium or to use energy sources provided by the breakup of dead cells. The 1- and 2-year-old cultures contained cells with vastly changed morphotypes. When these isolates were examined, it was revealed that the original plasmids present in the parent were rearranged in a certain way, and an entirely new plasmid was generated. Changes were also evident in the chromosomal DNA and in gene expression. Furthermore, all of the isolates exhibited a growth advantage relative to the parent cells when grown in energy-limiting media. When they were tested against different types of stresses, they exhibited a higher resistance against the bile salt and hydrogen peroxide stresses compared to the parent. Because of the similar changes observed in the 2-year-old isolates, a similar survival strategy may be operational in those cells that survive for that length of time.
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PMID:Survival response and rearrangement of plasmid DNA of Lactococcus lactis during long-term starvation. 1157 Nov 61

Chromohalobacter marismortui VH1 was screened for its ability to utilise organosulfonate compounds at a range of NaCl concentrations. Only aminomethane sulfonate, of seven sulfonates tested, was utilised. Length of lag phase during growth on aminomethane sulfonate, as either nitrogen and/or sulfur source, increased with increasing NaCl concentration. Cell yields increased linearly with increasing aminomethane sulfonate concentration up to 5 mM. Resting cells pregrown on aminomethane sulfonate as sole nitrogen source exhibited carbon-sulfur bond cleaving [0.123 nmol sulfate accumulated h(-1) (mg cells)(-1)] and sulfite-oxidising [0.185 nmol sulfate accumulated h(-1) (mg cells)(-1)] activities. C. marismortui VH1 is capable of sulfur-starvation deregulated metabolism of aminomethane sulfonate under high salt conditions.
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PMID:Utilisation of aminomethane sulfonate by Chromohalobacter marismortui VH1. 1188 50

The ftsH gene of Caulobacter crescentus has been isolated and identified as a component of the general stress response of this organism. In C. crescentus, ftsH expression is transiently induced after temperature upshift and in stationary phase. Consistent with this, mutants deprived of the FtsH protease are viable at normal growth conditions, but are highly sensitive to elevated temperature, increased salt concentration or the presence of antibiotics. Overexpression of ftsH resulted in an increased salt but not thermotolerance, emphasizing the importance of the FtsH protease in stress response. Mutants lacking FtsH were unable to undergo morphological and physiological adaptation in stationary phase and, upon starvation, experienced a more pronounced loss of viability than cells containing FtsH. In addition, cells lacking FtsH had an increased cellular concentration of the heat shock sigma factor sigma32, indicating that, as in Escherichia coli, the FtsH protease is involved in the control of the C. crescentus heat shock response. In agreement with this, transcription of the heat-induced sigma32-dependent gene dnaK was derepressed at normal temperature when FtsH was absent. In contrast, the groEL gene, which is controlled in response to heat stress by both sigma32 and a HcrA/CIRCE mechanism, was not derepressed in an ftsH mutant. Finally, FtsH is involved in C. crescentus development and cell cycle control. ftsH mutants were unable to synthesize stalks efficiently and had a severe cell division phenotype. In the absence of FtsH, swarmer cells differentiated into stalked cells faster than when FtsH was present, even though the entire cell cycle was longer under these conditions. Thus, directly or indirectly, the FtsH protease is involved in the inherent biological clock mechanism, which controls the timing of cell differentiation in C. crescentus.
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PMID:The FtsH protease is involved in development, stress response and heat shock control in Caulobacter crescentus. 1197 83

Glutamate is concentrated within RBC, but this intracellular glutamate is often ignored in studies of glutamate metabolism in vivo. The objective of this work was to determine the size of the plasma and cellular glutamate pools in rat blood and to clarify the role of RBC in the interorgan transport of glutamate. Approximately 20% of whole-blood glutamate was associated with isolated RBC membranes, but this was easily removed by washing with high salt solutions. Arterial plasma glutamate levels were relatively stable and did not show marked differences with starvation, streptozotocin diabetes or feeding 60% casein diets. In rats fed 5% casein, the plasma glutamate level was slightly higher (P < 0.05) than in most other groups. In contrast, RBC glutamate levels showed considerable variation. In rats consuming 5% casein, cellular glutamate levels were approximately 100% higher (P < 0.05) than in control, starved, diabetic or 20 or 60% casein-fed rats. Cellular glutamate levels were also higher (P < 0.05) in rats fed 60% casein than in those consuming 20% casein or the control diet. Rat erythrocytes in vitro did not take up or release free glutamate, confirming that they do not possess a glutamate transporter. Arteriovenous difference measurements across the portal drained viscera indicated a net glutamate release into the portal vein in control, 60% casein-fed and diabetic rats. In all cases, the net change in blood glutamate across the tissue occurred via the plasma, with no change in cellular glutamate levels. Therefore analyses of glutamate metabolism in rats in vivo may be made confidently using measurements of either whole-blood or plasma glutamate concentrations.
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PMID:Net interorgan transport of L-glutamate in rats occurs via the plasma, not via erythrocytes. 1198 20

Four transcripts homologous to K(+) transporters of the HAK/KT/KUP family have been characterized from the common ice plant (Mesembryanthemum crystallinum). We report tissue-specific expression of McHAK1 and McHAK4 transcripts abundant in roots, leaves, and stems. McHAK2 was predominantly present in stems and McHAK3 in root tissues. By in situ hybridizations, the McHAKs showed signals in the leaf vascular bundles, mesophyll, and epidermal cells as well as in epidermal bladder cells. In mature roots, transcripts were mainly localized to the vasculature, and in differentiated root tips, the strongest signals were obtained from the epidermis. Expression of McHAK1, McHAK2, and McHAK4 complemented a yeast mutant defective in low- and high-affinity K(+) uptake. Growth of the yeast mutant was restored at low-millimolar K(+) concentrations and was inhibited by Rb(+) and Cs(+) but was not affected by Na(+). Transcript levels of McHAK1 and McHAK4 increased by K(+) starvation and by salt stress of 400 mM NaCl in leaves and roots. Expression of McHAK2 and McHAK3 was stimulated in leaves and was transiently induced in roots in response to high salinity with prestress transcript levels restored in salt-adapted plants. We discuss possible roles for such transporters in ion homeostasis at high salinity.
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PMID:The expression of HAK-type K(+) transporters is regulated in response to salinity stress in common ice plant. 1217 62

Alkaline phosphatase (AP) activity is often targeted in enzyme-related histochemistry as probe enzyme to detect neoplastic cells, as marker for primordial germ cells as well as in preimplantation studies, osteoblast differentiation, phosphate starvation in bacteria, yeast and phytoplankton. Moreover, AP-marker activity is a very useful tool in immunohistochemistry to detect gene sequences, antigens and antibodies. Here we describe a novel high resolution fluorescence method to localize AP-activity in cells and tissue sections based on a naphthol-AS azo coupling procedure (Jenfluor ap). This method provides amorphous photostable fluorescent final reaction products without any diffusion artifacts which are visible in conventional fluorescence microscopes as well as in confocal laser scanning and near infrared multiphoton laser scanning microscopes. The superiority of the Jenfluor ap method in comparison to the known Fast Red TR salt as well as the ELF stains is discussed.
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PMID:Jenfluor ap--a novel fluorogenic substrate for in situ detection of alkaline phosphatase activity. 1264 52

Two different groups of haloalkaliphilic, obligately autotrophic, sulfur-oxidizing bacteria belonging to the genera Thioalkalimicrobium and Thioalkalivibrio have recently been discovered in highly alkaline and saline soda lakes. To understand response to their extreme environment and different occurrence in soda lakes, the growth kinetics and competitive behavior of several representatives have been characterized in detail using batch and pH-controlled continuous cultivation. The bacteria belong to the true alkaliphiles, growing within the pH range 7.5-10.6 with maximum growth rate and maximum growth yield at pH 9.5-10. On the basis of their response to salt content, three groups can be identified. All the Thioalkalimicrobium strains and some of the Thioalkalivibrio strains belonged to the moderate halophiles. Some of the Thioalkalivibrio strains from hypersaline soda lakes were extremely salt-tolerant and capable of growth in saturated soda brines. The Thioalkalimicrobium strains demonstrated relatively high specific growth rates, low growth yield, high maintenance, and extremely high rates of thiosulfate and sulfide oxidation. In contrast, the Thioalkalivibrio strains, in general, were slow-growing, high-yield organisms with lower maintenance and much lower rates of oxidation of sulfide and thiosulfate. Moreover, the latter survived starvation much better than Thioalkalimicrobium. Different growth characteristics and salt resistance appear to determine the outcome of the enrichment cultures from different soda lakes: Thioalkalimicrobium dominated in the enrichments with freshly obtained samples from diluted soda lakes at low-medium salinity, while Thioalkalivibrio was the predominant organism in enrichments from aged samples and at hypersaline conditions. In mixed thiosulfate-limited chemostat cultures at low salinity, Thioalkalimicrobium strains (mu(max)=0.33 h(-1)) out-competed Thioalkalivibrio strains (mu(max)=0.15 h(-1)) at D>0.02 h(-1). The overall results suggest that Thioalkalimicrobium and Thioalkalivibrio represent two different ecological strategies.
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PMID:Growth physiology and competitive interaction of obligately chemolithoautotrophic, haloalkaliphilic, sulfur-oxidizing bacteria from soda lakes. 1276 50

Bacteria typically undergo intermittent periods of starvation and adaptation, emulated as diauxic growth in the laboratory. In association with growth arrest elicited by metabolic stress, the differentiating eubacterium Streptomyces coelicolor not only adapts its primary metabolism, but can also activate developmental programmes leading to morphogenesis and antibiotic biosynthesis. Here, we report combined proteomic and metabolomic data of S. coelicolor used to analyse global changes in gene expression during diauxic growth in a defined liquid medium. Cultures initially grew on glutamate, providing the nitrogen source and feeding carbon (as 2-oxoglutarate) into the TCA cycle, followed by a diauxic delay allowing reorientation of metabolism and a second round of growth supported by NH4+, formed during prediauxic phase, and maltose, a glycolytic substrate. Cultures finally entered stationary phase as a result of nitrogen starvation. These four physiological states had previously been defined statistically by their distinct patterns of protein synthesis and heat shock responses. Together, these data demonstrated that the rates of synthesis of heat shock proteins are determined not only by temperature increase but also by the patterns and rates of metabolic flux in certain pathways. Synthesis profiles for metabolic- and stress-induced proteins can now be interpreted by the identification of 204 spots (SWICZ database presented at http://proteom.biomed.cas.cz). Cluster analysis showed that the activity of central metabolic enzymes involved in glycolysis, the TCA cycle, starvation or proteolysis each displayed identifiable patterns of synthesis that logically underlie the metabolic state of the culture. Diauxic lag was accompanied by a structured regulatory programme involving the sequential activation of heat-, salt-, cold- and bacteriostatic antibiotic (pristinamycin I, PI)-induced stimulons. Although stress stimulons presumably provide protection during environmental- or starvation-induced stress, their identities did not reveal any coherent adaptive or developmental functions. These studies revealed interactive regulation of metabolic and stress response systems including some proteins known to support developmental programmes in S. coelicolor.
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PMID:Proteomic studies of diauxic lag in the differentiating prokaryote Streptomyces coelicolor reveal a regulatory network of stress-induced proteins and central metabolic enzymes. 1278 56

Protein expression profiles in yeast cells, in response to salinity stress, were determined using the cleavable isotope-coded affinity tag (cICAT) labeling strategy. The analysis included separation of the mixed protein samples by SDS-PAGE, followed by excision of the entire gel lane, and division of the lane into 14 gel regions. Regions were subjected to in-gel digestion, biotin affinity chromatography, and analysis by nano-scale microcapillary liquid chromatography coupled to tandem mass spectrometry. The novel (13)C-labeled ICAT reagents have identical elution profiles for labeled peptide pairs and broadly spread the distribution of labeled peptides during reversed-phase chromatography. A total of 560 proteins were identified and quantified, with 51 displaying more than 2-fold expression differences. In addition to some known proteins involved in salt stress, four RNA-binding proteins were found to be up-regulated by high salinity, suggesting that selective RNA export from the nucleus is important for the salt-stress response. Some proteins involved in amino acid synthesis, which have been observed to be up-regulated by amino acid starvation, were also found to increase their abundance on salt stress. These results indicate that salt stress and amino acid starvation cause overlapping cellular responses and are likely to be physiologically linked.
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PMID:Protein profiling with cleavable isotope-coded affinity tag (cICAT) reagents: the yeast salinity stress response. 1450 5


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