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At least 415 records · Page 23Linked to original sources
PubMed2000

Phosphate starvation-inducible proteins of Bacillus subtilis: proteomics and transcriptional analysis.

The phosphate starvation response in Bacillus subtilis was analyzed using two-dimensional (2D) polyacrylamide gel electrophoresis of cell extracts and supernatants from phosphate-starved cells. Most of the phosphate starvation-induced proteins are under the control of sigma(B), the activity of which is increased by energy depletion. In order to define the proteins belonging to the Pho regulon, which is regulated by the two-component regulatory proteins PhoP and PhoR, the 2D protein pattern of the wild type was compared with those of a sigB mutant and a phoR mutant. By matrix-assisted laser desorption ionization-time of flight mass spectrometry, two alkaline phosphatases (APases) (PhoA and PhoB), an APase-alkaline phosphodiesterase (PhoD), a glycerophosphoryl diester phosphodiesterase (GlpQ), and the lipoprotein YdhF were identified as very strongly induced PhoPR-dependent proteins secreted into the extracellular medium. In the cytoplasmic fraction, PstB1, PstB2, and TuaD were identified as already known PhoPR-dependent proteins, in addition to PhoB, PhoD, and the previously described PstS. Transcriptional studies of glpQ and ydhF confirmed the strong PhoPR dependence. Northern hybridization and primer extension experiments showed that glpQ is transcribed monocistronically from a sigma(A) promoter which is overlapped by four putative TT(A/T)ACA-like PhoP binding sites. Furthermore, ydhF might be cotranscribed with phoB initiating from the phoB promoter. Only a small group of proteins remained phosphate starvation inducible in both phoR and sigB mutant and did not form a unique regulation group. Among these, YfhM and YjbC were controlled by sigma(B)-dependent and unknown PhoPR-independent mechanisms. Furthermore, YtxH and YvyD seemed to be induced after phosphate starvation in the wild type in a sigma(B)-dependent manner and in the sigB mutant probably via sigma(H). YxiE was induced by phosphate starvation independently of sigma(B) and PhoPR.

Alkaline Phosphatase↗
PubMed1969

Relation of the segregative origin of chromosome replication to the origin of replication after amino acid starvation.

Cultures of Escherichia coli 15T(-) and K-12 were labeled with (3)H-thymine before, during, and after amino acid starvation. The number of labeled segregating units was measured by autoradiography of microcolonies derived from the labeled cells. In both strains, labels inserted before starvation and during starvation appeared to segregate as if incorporated into the same polynucleotide strands. However, labels inserted during and after starvation segregated as if incorporated into different polynucleotide strands. In view of previous data, it was concluded that replication after amino acid starvation originates from the region of the chromosome which serves as the origin for replication during normal growth and division.

Autoradiography↗
PubMed1995

The histidyl-tRNA synthetase-related sequence in the eIF-2 alpha protein kinase GCN2 interacts with tRNA and is required for activation in response to starvation for different amino acids.

Protein kinase GCN2 is a multidomain protein that contains a region homologous to histidyl-tRNA synthetases juxtaposed to the kinase catalytic moiety. Previous studies have shown that in response to histidine starvation, GCN2 phosphorylates eukaryotic initiation factor 2 (eIF-2), to induce the translational expression of GCN4, a transcriptional activator of genes subject to the general amino acid control. It was proposed that the synthetase-related sequences of GCN2 stimulate the activity of the kinase by interacting directly with uncharged tRNA that accumulates during amino acid limitation. In addition to histidine starvation, expression of GCN4 is also regulated by a number of other amino acid limitations. Questions that we posed in this report are whether uncharged tRNA is the most direct regulator of GCN2 and whether the function of this kinase is required to recognize each of the different amino acid starvation signals. We show that GCN2 phosphorylation of eIF-2, and the resulting general amino acid control pathway, is stimulated in response to starvation for each of several different amino acids, in addition to histidine limitation. Cells containing a defective aminoacyl-tRNA synthetase also stimulated GCN2 phosphorylation of eIF-2 in the absence of amino acid starvation, indicating that uncharged tRNA levels are the most direct regulator of GCN2 kinase. Using a Northwestern blot (RNA binding) assay, we show that uncharged tRNA can bind to the synthetase-related domain of GCN2. Mutations in the motif 2 sequence conserved among class II synthetases, including histidyl-tRNA synthetases, impair the ability of this synthetase-related domain to bind tRNA and abolish GCN2 phosphorylation of eIF-2 required to stimulate the general amino acid control response. These in vivo and in vitro experiments indicate that synthetase-related sequences regulate GCN2 kinase function by monitoring the levels of multiple uncharged tRNAs that accumulate during amino acid limitations.

Amino Acids↗
PubMed2002

A role for cell cycle proteins in the serum-starvation resistance of Epstein-Barr virus immortalized B lymphocytes.

Epstein-Barr virus (EBV) is a B-lymphotropic human herpes virus that infects B lymphocytes and is associated with a broad spectrum of benign and malignant diseases. B cell infection by EBV causes indefinite cell proliferation that results in the development of immortalized lymphoblastoid cell lines (LCLs). We found that SNU-1103, a latency type III EBV-transformed LCL developed from a Korean cancer patient, resisted the G1 arrest that was normally caused by serum starvation. Western blot analyses revealed several alterations in the expression of key regulatory cell cycle proteins involved in the G1 phase. High expression of cyclin D2 and time-dependent increases in cyclin-dependent kinase 6 (CDK6) and cyclin D3 were observed in SNU-1103 during serum starvation. Very unexpectedly, in SNU-1103, the key G1 phase CDK inhibitor p21CiP1 was expressed at a consistently high level, while p27KiP1 expression was increased. Of three pRb family proteins, pRb expression was reduced and it became hypophosphorylated in SNU-1103 during serum starvation. Instead, p107 and p130 were expressed at consistently high levels in SNU-1103 during serum starvation. In conclusion, compared with an EBV-negative BJAB cell line, multiple cell cycle regulatory proteins were abnormally or inversely expressed in SNU-1103 during serum starvation.

B-Lymphocytes↗
PubMed2002

Occurrence of leu+ revertants under starvation cultures in Escherichia coli is growth-dependent.

BACKGROUND: Many investigations have reported that advantageous mutations occurred more frequently under selective conditions than those under non-selective conditions. This phenomenon is referred to as adaptive mutation. Their characteristics are that adaptive mutations are directed and growth-independent. The idea of directed adaptive mutation had been objected by some reports, however, the idea of growth-independent adaptive mutation has been held till today. RESULTS: In this paper, we have observed that under leucine starvation conditions, leu+ revertants accumulated as a function of time; leu- to leu+ reverse mutation rates and frequencies were higher than those under non starvation conditions; and no divided cells could be monitored by the penicillin method. These results were similar to the time-dependent manner of adaptive mutation from previous reports. However, leucine concentration determinate experiments revealed that certain traces of leucine, which leaked from the E. coli cells, was almost always present in the culture. More numbers of leu+ revertants appeared when the similar cultures were dropped in small areas on the selective plates than when spread on the whole selective plates. These results have shown that mutations under leucine starving conditions are growth-dependent. Fluctuation analysis of leu+ revertants indicated that leu-leu+ mutation occurred spontaneously and randomly. In addition, the spectra of leuB gene in the revertants proved that mutations under selective conditions were not specific or directed. CONCLUSIONS: The above investigations led to the conclusion (1) that the occurrence of leu+ mutations under starvation conditions was growth-dependent. The occurrence mutations was also similar to that under non-starvation conditions (2). Under starvation conditions the mutation rates were higher, and was not constant during the long process.

3-Isopropylmalate Dehydrogenase↗
PubMed1995

Fission yeast TPR-family protein nuc2 is required for G1-arrest upon nitrogen starvation and is an inhibitor of septum formation.

Fission yeast nuc2+ gene encodes a protein of a tetratricopeptide repeat (TPR) family which is conserved throughout evolution. We previously showed that nuc2 is required for exit from the mitotic metaphase. In this study, we present evidence which shows that nuc2 has two additional roles in the cell cycle. We showed that the nuc2 mutant is sterile even at the permissive temperature and septation occurs in the absence of chromosome separation at the restrictive temperature. The nuc2 mutant fails to arrest at the G1 phase upon nitrogen starvation at the permissive temperature which is a prerequisite for conjugation. Upon starvation, however, the nuc2 mutant ceased division normally and induced starvation-dependent gene expression. Therefore, the nuc2 mutant is deficient only for failure to block DNA replication upon starvation. At the lower restrictive temperature, the nuc2 mutant showed a 'cut' phenotype where septation and cytokinesis takes place without the completion of mitosis. Ectopic overexpression of the nuc2+ gene caused multiple rounds of S and M phases in the complete absence of septum formation. We propose that nuc2 is a novel cell cycle regulator essential for three events; firstly for exit from mitosis, secondly for DNA replication restraint under nutrient starvation and thirdly for inhibition of septation and cytokinesis until the completion of mitosis.

Apc3 Subunit, Anaphase-Promoting Complex-Cyclosome↗
PubMed1997

Starvation increases the number of coliform bacteria in the caecum and induces bacterial adherence to caecal epithelium in rats.

OBJECTIVE: To investigate the impact of starvation for 24 and 48 h on the number of coliform bacteria in the caecal contents, on the mucosal adherence of coliform bacteria, and on bacterial translocation in rats. DESIGN: Open prospective study. SETTING: University departments of surgery and microbiology, Sweden. MATERIAL: 46 adult male Sprague-Dawley rats. INTERVENTIONS: 19 rats served as controls, and were fed until samples were taken. Six animals were starved for 24 h and another 15 for 48 h, with free access to water, and then anaesthetised before blood, mesenteric lymph nodes (MLN), caecum, and caecal contents were sampled. To verify bacterial translocation in this strain of rats, another six rats underwent controlled haemorrhage for 60 min to reduce the blood pressure to 55 mm Hg mean arterial pressure (MAP). These rats had free access to food and water before haemorrhage but were allowed only water until samples were taken 24 h after haemorrhage. MAIN OUTCOME MEASURES: Presence and number of coliform bacteria in samples taken from caecal contents, caecal epithelium, MLN, and blood. RESULTS: Starvation for 24 h increased the number of coliform bacteria (colony forming units (CFU)/g) in the caecal contents 25-fold (p < 0.05). Starvation for 48 h further increased the number by a factor of 100. The number of coliform bacteria that adhered to the caecal epithelium increased 3,000 times in rats that had been starved for 48 h (p < 0.001). There was no significant difference in translocation (as indicated by cultures from MLN) between rats that had been fed and those that had been starved for 48 h. In 4 of the 6 rats that were bled and then starved for 24 h there were signs of bacterial translocation, which was significantly more than the 1/19 in fed rats (p < 0.05). CONCLUSION: Starvation increases the number of bacteria in the caecal contents and increases bacterial adherence to the caecal epithelium. These changes may contribute to the previously reported increase in bacterial translocation in starved compared wit fed rats that were subjected to stress. The same changes in the gut were observed in animals subjected to haemorrhagic stress in addition to starvation, and in which bacterial translocation was evident.

Animals↗
PubMed2005

Chromatin supraorganization and extensibility in mouse hepatocytes following starvation and refeeding.

BACKGROUND: The effect of 48 h of starvation and of 48 h of refeeding subsequent to starvation on chromatin supraorganization and extensibility was studied in hepatocytes from adult mice. METHODS: Methods used involved topochemical assays, image analysis, gravity action, and polarization microscopy. RESULTS: Starvation increased the chromatin packing states, especially in areas of noncondensed chromatin, and induced drastic decreases in concanavalin A reactivity due to nuclear matrix glycoproteins and the frequency of nuclei with chromatin extensibility under gravity. Changes in chromatin packing state were accompanied by shifts of nuclear areas of part of the nuclear population to smaller values but did not affect the respective Feulgen-DNA amounts except for a few nuclei. The extent of chromatin unpackaging, but not of frequency of nuclei with formation of extended chromatin fibers, in starved mice that were refed was greater than in well-fed controls. Refeeding induced increase in Feulgen-DNA amounts and regain and redistribution of concanavalin A-reactive nuclear glycoproteins. However, the duration of refeeding used was probably insufficient to reestablish the stereo arrangement of the chromatin-nuclear matrix and to restore chromatin fluidity to the level seen in well-fed mice. CONCLUSIONS: The changes in the liver cell nuclei associated with starvation and refeeding of adult mice involved chromatin supraorganization, hepatocyte proliferation (refeeding), and the loss, regain, and redistribution of nuclear proteins, especially nuclear matrix components, related to chromatin organization and extensibility. These changes are suggested as favoring the silencing and reactivation of transcriptional activities, depending on the organism's nutritional state.

Animals↗
PubMed1999

Differences in fat, carbohydrate, and protein metabolism between lean and obese subjects undergoing total starvation.

Despite extensive experimental studies on total starvation, many of the findings relating to protein, fat (plus ketone body), and carbohydrate metabolism remain confusing, although they become more consistent when considered in relation to the degree of initial obesity. During prolonged starvation, protein loss and percent energy derived from protein oxidation are 2- to 3-fold less in the obese than in the lean; percent urine N excreted as urea is 2-fold less in the obese; and the contribution of protein to net glucose production is only about half in the obese compared to lean subjects. During short-term starvation (first few days) the following differences are reported: hyperketonaemia is typically 2-fold greater in lean subjects, but associated with a 2-fold lower uptake of ketone bodies by forearm muscle; glucose tolerance becomes impaired more in lean subjects; and both protein turnover and leucine oxidation increase in the lean, but may show no significant change in the obese. It is no longer acceptable to describe the metabolic response to starvation as a single typical response. The differences between lean and obese subjects have important physiological implications, some of which are of obvious relevance to survival.

Blood Glucose↗
PubMed1988

Role of glucocorticoids in increased muscle glutamine production in starvation.

The influence of glucocorticoids on muscle glutamine production in starvation was studied by using cortisol-treated or non-cortisol-treated, starved, adrenalectomized rats. Administration of cortisol at physiological doses in vivo (1 mg/100 g body weight) to fasted, adrenalectomized rats increased the muscle ratio of glutamine/glutamate and the activity of glutamine synthetase after only 6 hours. Prior treatment of fasted, adrenalectomized animals with actinomycin D or proflavine abolished these increases by cortisol. Therefore, cortisol induces muscle glutamine synthetase, and this induction can be detected by changes in the fresh-muscle ratio of glutamine/glutamate. Using this ratio as a qualitative indicator of muscle glutamine synthesis, the role of glucocorticoids in modifying muscle glutamine production in starvation was studied. In fresh-frozen soleus, extensor digitorum longus, and diaphragm muscle, starvation led to greater ratios of glutamine/glutamate and higher levels of tyrosine, which are indicative of enhanced muscle protein turnover. These effects were not apparent in starved, adrenalectomized animals but were restored, at least partially, by administering a physiological dose of cortisol. Therefore, glucocorticoids seem essential for promoting muscle glutamine production in starvation probably by inducing the activity of glutamine synthetase.

Adrenal Glands↗
PubMed2006

The phosphate-starvation response of Bacillus licheniformis.

The phosphate-starvation stimulon of Bacillus licheniformis was analyzed at the transcriptional and translational level. The comparison of the transcriptome and the proteome demonstrated that this specific starvation response of B. licheniformis is partially similar to that of B. subtilis. However, it is also shown that B. licheniformis has evolved its own strategies to cope with this nutrient limitation. By means of the secretome analysis the phytase was identified as the most abundant protein under phosphate-starvation conditions. Data of this study indicate that, unlike in B. subtilis, phosphate starvation in B. licheniformis does not induce the SigmaB-dependent general stress response.

6-Phytase↗
PubMed2006

Serial analysis of stable nitrogen and carbon isotopes in hair: monitoring starvation and recovery phases of patients suffering from anorexia nervosa.

Stable nitrogen and carbon isotopic ratios of hair strands of six patients suffering from anorexia nervosa were measured to monitor a dietary change from near starvation to recovery. This paper presents the results of a first-time study of nitrogen and carbon balance of the patients prior to and after admittance to a hospital and therapy. Sequential analysis of the isotopic ratios of hair strands of all patients could be related to the respective body mass index (BMI) of each patient. Our hypothesis concerning the diachronic change in delta15N and delta13C during therapy was met: The delta15N values were inversely related to the BMI, indicating a slow-down in catabolism of bodily protein due to the process of gluconeogenesis during the starvation phase. In contrast, the delta13C values and BMI were in phase: an increase in BMI resulted in an increase in the delta13C values. This rise in delta13C ratios is best interpreted by an increased supply of protein in the diet. Furthermore, delta15N and delta13C were inversely related. We conclude that hair, which is easily and non-traumatically sampled, is an adequate monitor that reflects dietary change and nitrogen balance within days. This isotopic method may also be applied in forensic studies with regard to cases of deprivation, and starvation, and may be a method for investigating starvation in historic populations.

Adult↗
PubMed1990

The value of fat reserves and the tradeoff between starvation and predation.

It is shown that in a range of models, the probability that a forager dies from starvation is, to a good approximation, an exponential function of energy reserves. Using a time and energy budget for a 19g passerine, we explore the consequences, in terms of starvation and predation, of various levels of energy reserves. It is shown that there exists an optimal level L* of reserves at which total mortality (starvation plus predation) is minimized. L* increases when the environment deteriorates as a result of a decrease in either temperature or mean gross gain or an increase in the mean search time. The effect of combined deteriorations is greater than the sum of their individual effects. At L*, the probability of predation is much higher than the probability of starvation. A simple analytic model suggests that this result will be fairly general, but also indicates conditions under which the result might not hold.

Adipose Tissue↗
PubMed1986

Quantitative changes in the lysosomal vacuolar system of rat hepatocytes during short-term starvation. A morphometric analysis with special reference to macro- and microautophagy.

Ultrastructural morphometric analysis was used to study time-dependent variations in macro- and microautophagy in rat hepatocytes. Except during periods of short-term starvation for up to 24 h, animals were kept under standardized conditions of food intake. In hepatocytes of meal-fed rats the volume fraction of macroautophagic vacuoles is significantly higher at 23:00 h, i.e., immediately before food intake, compared to 11:00 h, i.e., 12 h following feeding. During fasting, macroautophagy drops to a low level. Microautophagic vacuoles in hepatocytes of meal-fed rats, sacrificed at 11:00 or 23:00 h respectively, do not show any significant quantitative differences. However, during 12 h of starvation, the volume fraction of microautophagic vacuoles rises significantly, whereas the numerical density remains constant. Subsequently, during the second 12-h period of fasting, the volume fraction of microautophagic vacuoles remains unchanged, but the numerical density increases. Over a period of 24 h of starvation the volume fraction of the total lysosomal system does not change significantly, whereas the numerical density rises. The time-dependent changes of the macroautophagic vacuolar system correlate with the circadian, food-related variations in the protein content of individual hepatocytes from meal-fed animals. The increase in volume fraction and thereafter in number of microautophagic vacuoles, as observed during starvation, coincides with a large decrease in protein content of individual hepatocytes.

Animals↗
PubMed1986

Immunohistochemistry and morphometry of gastrin cells in the rat pyloric antrum during starvation.

The gastrin cells (G cells) in the rat pyloric antrum after 7, 14, 21 and 28 days of starvation were investigated by immunohistochemistry and electron microscopy. In the peroxidase anti-peroxidase method for light microscopy, gastrin immunoreactive cells during starvation markedly decreased in number and size. Quantitative electron microscopy revealed that during starvation the number of electron-lucent granules were greatly reduced, but the number of electron-dense granules increased; the number of intermediate granules were not remarkably changed in G cells. These results may suggest that the synthesis of gastrin and granule maturation were greatly inhibited during long-term starvation.

Animals↗
PubMed1975

Adenylate cyclase and phosphodiesterase in the rat gastric mucosa after starvation, feeding and pentagastrin.

The effects of starvation, feeding and pentagastrin on gastric mucosal adenylate cyclase (AC) and phosphodiesterase (PDE) activity were studied in the rat. 1. Starvation for 24 hrs and 48 hrs reduced both NaF stimulated and basal AC activities. 2. Feeding of starved rats slowly raised the AC activity up to 430% within 4 hrs after feeding. This effect was more pronounced under basal conditions than with NaF stimulation. 3. A single i.p. injection of pentagastrin (125 mug/kg) caused a stimulation of basal AC lasting 45 min, which was followed by a subsequent decrease in the basal and NaF stimulated enzyme activity. 4. PDE activity was not influenced by starvation and feeding but underwent a transient inhibition by pentagastrin. Accordingly gastric mucosal cAMP levels after starvation, feeding and pentagastrin are regulated by changes in AC and not in PDE activity. The rise in AC activity after feeding appears to be related to functions other than H+ and pepsin secretion.

Adenylyl Cyclases↗
PubMed1993

Zonal expression of the glucokinase gene in rat liver. Dynamics during the daily feeding rhythm and starvation-refeeding cycle demonstrated by in situ hybridization.

The abundance and zonal distribution of glucokinase (GK) mRNA were studied in rat liver during a normal 12 h day/12 h night rhythm (dark from 1900 to 0700 hours) and during refeeding after 60 h of starvation. Zonation of GK gene expression was examined by in situ hybridization with a radiolabelled cRNA probe and GK mRNA abundance was determined by Northern blot analysis with a digoxigenin-labelled cRNA probe. GK mRNA appeared to be almost homogeneously distributed throughout the whole daily feeding cycle; yet it was predominantly localized in the perivenous and intermediate zone during refeeding after 60 h of starvation. During the daily feeding rhythm, the total amount of GK mRNA increased quickly with the beginning of the feeding period at 1900 hours reaching a maximum at midnight and then decreased continuously to a basal level at noon. Virtually no GK mRNA was detected after 60 h of starvation. Refeeding caused a rapid increase in GK mRNA to a maximum at 2400 hours followed by a decrease to approximately two-thirds of the maximum value at 0700 hours. If the homogeneous distribution of GK mRNA during the daily feeding rhythm was real rather than apparent because of too low a sensitivity of the cRNA probe, the present results suggest that during the normal circadian cycle the mainly perivenous distribution of GK enzyme activity and protein is regulated preferentially at a translational level. The findings clearly show that during refeeding after 60 h of starvation the GK distribution is controlled predominantly at a pretranslational level.

Animals↗
PubMed1993

Insulin-like growth factors and binding proteins in the fetal rat: alterations during maternal starvation and effects in fetal brain cell culture.

Maternal malnutrition adversely affects fetal body and brain growth during late gestation. We utilized a fetal brain cell culture model to examine whether alternations in circulating factors may contribute to reduce brain growth during maternal starvation; we then used specific immunoassay and western blotting techniques, and purified peptides to investigate the potential role that altered levels of insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs) may play in impaired growth during maternal nutritional restriction. Fetal, body, liver, and brain weight were reduced after 72 hr maternal starvation, and plasma from starved fetuses were less potent than fed fetal plasma in stimulating brain cell growth. Circulating levels of IGF-I were reduced in starved compared to fed fetuses, while levels of IGF-II were similar in both groups. In contrast, [125I]-IGF-I binding assay demonstrated an increase in the availability of plasma IGFBPs following starvation. Western ligand blotting and densitometry indicated that levels of 32 Kd IGFBPs were 2-fold higher in starved compared to fed fetal plasma. Immunoblotting and immunoprecipitation with antiserum against rat IGFBP-1 confirmed that heightened levels of immunoreactive IGFBP-1 accounted for the increase in 32 Kd IGFBPs in starved plasma. Levels of 34 Kd BPs, representing IGFBP-2, were unaffected by starvation. Reconstitution experiments in cell culture showed that IGF-I promoted fetal brain cell growth, and that when they were supplemented with IGF-I, the growth promoting activity of starved fetal plasma was restored to fed levels. These changes were measured using MTT to assess mitochondrial reductase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗