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

The question of whether lymphocytes which have once been activated and have completed one or several cell cycle(s) can return to the G0 phase and stay ready for a new activation (G0-G1 transition), rather than simply die, was investigated. To do so interleukin 2 (IL-2) was removed from cultures of continuously proliferating human T lymphocytes and the formation of resting (G0) cells was measured. Kinetic analyses in freshly prepared peripheral blood lymphocytes (PBL) revealed that the onset of detectable RNA synthesis and the appearance of structures binding the anti-Tac antibody occurred simultaneously. This allowed the expansion of the definition of G0 T lymphocytes as cells having a low RNA (and DNA) content, and no Tac antigen. When cultured human T cells proliferating continuously by means of IL-2 were characterized in terms of their distribution in the cell cycle, 7 days after the initial PHA stimulation, it could be demonstrated that very few cells were in the G0 phase, supporting the concept of direct S/G2/M-G1 transition. However, when IL-2 was removed from the cultures, the [3H]thymidine incorporation per 10(4) cells and correspondingly the number of cells in the S/G2/M and G1 phases were reduced drastically and during the following 72-hr period, the number of G0 cells increased markedly. Restimulation of such in vitro formed G0 cells, under conditions permitting observation of their shift from the G0 to G0 phase, demonstrated that most cells could respond normally. Based on these observations, it was concluded that IL-2 not only ensures T-lymphocyte survival and proliferation, but IL-2 starvation induces many continuously proliferating T lymphocytes to stop cycling and to return to the G0 phase of the cell cycle where they remain functional.
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PMID:Lymphokine regulation of human lymphocyte proliferation: formation of resting G0 cells by removal of interleukin 2 in cultures of proliferating T lymphocytes. 661 Apr 79

Depressed cell-mediated immunity and decreased insulin-like growth factor I (IGF-I) are observed in malnourished humans. To study the interaction among nutrition, IGF-I, and cytokines, healthy volunteers (six men and four women, aged 21-38 yr, weighing 93-124% of ideal body weight) were subjected to a 7-day fast (mineral water only). Fasting steadily decreased serum IGF-I from 247 +/- 29 (prefast) to 87 +/- 10 ng/mL (postfast; P < 0.0001), total T cells (CD3+) from 1499 +/- 68 to 1308 +/- 70 x 10(9) (P < 0.0001), and T helper cells (CD4+) from 997 +/- 62 to 856 +/- 55 x 10(9) (P < 0.001). Peripheral blood mononuclear cells were isolated and cultured in serum-free RPMI 1640 for 24 h. Fasting attenuated peripheral blood mononuclear cell production of interleukin-2 in response to various concentrations of phytohemagglutinin P [PHA-P; 347 +/- 48 (prefast) vs. 135 +/- 52 pg/mL (postfast) when challenged with 3 micrograms/mL PHA-P; P < 0.005 when comparing dose-response curves (1-100 micrograms/mL PHA-P)]. Although the approximately 3-fold suppression of interleukin-2 and IGF-I in subjects fasted for 1 week is not likely to affect immune function significantly, our results with this short term model of nutrient restriction provide insight into possible mechanisms for immune suppression in chronic starvation.
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PMID:Decreased interleukin-2 production from cultured peripheral blood mononuclear cells in human acute starvation. 910 May 92

Paracoccus denitrificans degraded poly(3-hydroxybutyrate) (PHB) in the cells under carbon source starvation. Intracellular poly(3-hydroxyalkanoate) (PHA) depolymerase gene (phaZ) was identified near the PHA synthase gene (phaC) of P. denitrificans. Cell extract of Escherichia coli carrying lacZ--phaZ fusion gene degraded protease-treated PHB granules. Reaction products were thought to be mainly D(--)-3-hydroxybutyrate (3HB) dimer and 3HB oligomer. Diisopropylfluorophosphonate and Triton X-100 exhibited an inhibitory effect on the degradation of PHB granules. When cell extract of the recombinant E. coli was used, Mg(2+) ion inhibited PHB degradation. However, the inhibitory effect by Mg(2+) ion was not observed using the cell extract of P. denitrificans.
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PMID:Identification of the intracellular polyhydroxyalkanoate depolymerase gene of Paracoccus denitrificans and some properties of the gene product. 1126 73

Regulation of medium-chain-length polyhydroxyalkanoate biosynthesis in Pseudomonas aeruginosa and Pseudomonas putida was studied conducting PHA accumulation experiments and transcriptional analysis of PHA biosynthesis genes with wild type strains and rpoN-negative mutants. In P. putida PHA accumulation was RpoN-independent, whereas in P. aeruginosa PHA accumulation was RpoN-dependent. Transcriptional analysis applying reverse transcriptase-polymerase chain reaction showed strong induction of phaG, encoding the transacylase, under nitrogen starvation in P. putida KT2440 and the respective rpoN-negative mutant, indicating an RpoN-independent regulation of phaG. No transcription of phaG and no PHA accumulation was detected in the rpoN-negative mutant of P. aeruginosa neither from gluconate nor from octanoate as carbon source. Alginate-overproducing mutant P. aeruginosa FRD1 showed strongly decreased PHA accumulation from gluconate but no difference in phaC1 (encoding the PHA synthase) transcription, indicating that alginate biosynthesis competes with PHA biosynthesis regarding acetyl-CoA as precursor for both biopolymers. Transcription of phaF and phaI-F was nitrogen independent.
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PMID:Regulation of polyhydroxyalkanoate biosynthesis in Pseudomonas putida and Pseudomonas aeruginosa. 1526 31

Aspects of the biological significance of the bisecting N-acetylglucosamine (GlcNAc) structure on N-glycans introduced by beta1,4-N-acetylglucosaminyltransferase III (GnT-III) in Neuro2a cell differentiation are demonstrated. The overexpression of GnT-III in the cells led to the induction of axon-like processes with numerous neurites and swellings, in which beta1 integrin was localized, under conditions of serum starvation. This enhancement in neuritogenesis was suppressed by either the addition of a bisecting GlcNAc-containing N-glycan or erythroagglutinating phytohemagglutinin (E(4)-PHA), which preferentially recognizes the bisecting GlcNAc. GnT-III-promoted neuritogenesis was also significantly perturbed by treatment with a functional blocking anti-beta1 integrin antibody. In fact, beta1 integrin was found to be one of the target proteins of GnT-III, as confirmed by a pull-down assay with E(4)-PHA. These data suggest that N-glycans with a bisecting GlcNAc on target molecules, such as beta1 integrin, play important roles in the regulation of neuritogenesis.
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PMID:beta1,4-N-Acetylglucosaminyltransferase III potentiates beta1 integrin-mediated neuritogenesis induced by serum deprivation in Neuro2a cells. 1653 77

Transcription factors are key components of regulatory networks that control development, as well as the response to environmental stimuli. We have established an experimental pipeline in Caenorhabditis elegans that permits global identification of the binding sites for transcription factors using chromatin immunoprecipitation and deep sequencing. We describe and validate this strategy, and apply it to the transcription factor PHA-4, which plays critical roles in organ development and other cellular processes. We identified thousands of binding sites for PHA-4 during formation of the embryonic pharynx, and also found a role for this factor during the starvation response. Many binding sites were found to shift dramatically between embryos and starved larvae, from developmentally regulated genes to genes involved in metabolism. These results indicate distinct roles for this regulator in two different biological processes and demonstrate the versatility of transcription factors in mediating diverse biological roles.
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PMID:Genome-wide identification of binding sites defines distinct functions for Caenorhabditis elegans PHA-4/FOXA in development and environmental response. 2017 64

The nucleotide composition of key enzymes involved in medium-chain-length polyhydroxyalkanoates (mcl-PHA) synthesis was analyzed in two newly isolated strains of Pseudomonas. The isolated strains were tested for their abilities to synthesize polyhydroxyalkanoates using three different substrates as a carbon source: sodium octanoate, oleic acid, and sodium gluconate. Both analyzed strains were able to accumulate mcl-PHA in a range from 2.07 to 21.40%, which depended on the substrate used. Potential nitrogen-dependent regulation of mcl-PHA synthesis was analyzed by cell cultivation in nitrogen-limiting and non-limiting conditions. The analyzed strains demonstrated an incremental increase of mcl-PHAs in response to nitrogen starvation when oleic acid and sodium gluconate were applied as the carbon source. The transcriptional analysis showed that the induction of gene coding for PHA synthases was correlated with an increment in mcl-PHAs content. Both analyzed strains revealed differences in terms of the studied gene's expression, showing a dependence on the carbon source used.
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PMID:The influence of nitrogen limitation on mcl-PHA synthesis by two newly isolated strains of Pseudomonas sp. 2020 56

PHA was a kind of biodegradable polymer produced by mixed microorganisms. In recent years, 3-stage PHA synthesis process (including substrate hydrolysis, culture selection, and PHA synthesis) was commonly used for PHA production. In this kind of process, culture selection is the key stage, which directly affects the PHA production efficiency. In order to deal with sludge bulking occurred in the culture selection system, this paper analyzes the influence of substrate concentration on culture selection efficiency as well as operation stability. Under different influent substrate concentrations of 560 mg x L(-1), 1 120 mg x L(-1) and 1 680 mg x L(-1), we confirmed that influent substrate concentration (COD) of 1 120 mg x L(-1) is the most suitable parameter for the bacteria enriching process after a long period of time under short SRT. After 94 days of cultivation, we achieved 50% of PHA content, 0.7145 COD/COD of PHA conversion rate and 0.191 2 mg x (mg x h)(-1) of specific PHA storage rate at the end of batch tests with nutrient starvation. The study also confirmed that glycogen level in cells has a close relationship with its PHA synthesis ability, which shows its potential to predict the enrichment efficiency.
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PMID:[Influence of substrate concentration on PHA production using fermented sugar cane as substrate]. 2394 47

We studied the effects of early weaning on immunocompetence and parasite resistance in a precocial rodent Acomys cahirinus. We hypothesized that if parasite resistance is energetically expensive and nutritional and immunological support from mothers are necessary for the long-term health of offspring, then early weaned animals would be immunologically weaker and less able to defend themselves against parasites than later weaned animals. We weaned pups at 14, 21 or 28 days after birth and assessed their immunocompetence and resistance against fleas Parapulex chephrenis when they attained adulthood. Immunocompetence was assessed using leukocyte concentration (LC) and a phytohaemagglutinin injection assay (PHA test). To estimate resistance against fleas, we measured performance of fleas via the number of produced eggs and duration of development and resistance to starvation of the flea offspring. We found a significant positive effect of weaning age on the PHA response but not on LC. The effect of age at weaning on flea egg production was manifested in male but not female hosts, with egg production being higher if a host was weaned at 14 than at 28 days. Weaning age of the host did not affect either duration of development or resistance to starvation of fleas produced by mothers fed on these hosts. We conclude that even in relatively precocial mammals, weaning age is an important indicator of future immunological responses and the ability of an animal to resist parasite infestations. Hosts weaned at an earlier age make easier, less-resistant targets for parasite infestations than hosts weaned later in life.
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PMID:Age at weaning, immunocompetence and ectoparasite performance in a precocial desert rodent. 2494 45

The response of a mixed-microbial-culture (MMC) biomass for PHA accumulation was evaluated over a range of relative nitrogen (N) and phosphorus (P) availabilities with respect to the supply of either complex (fermented whey permeate - FWP) or simpler (acetic acid) organic feedstocks. Fed-batch feed-on-demand PHA accumulation experiments were conducted where the feed N/COD and P/COD ratios were varied ranging from conditions of nutrient starvation to excess. A feast-famine enrichment (activated sludge) biomass, produced in a pilot-scale aerobic sequencing batch reactor on FWP and with a long history of stable PHA accumulation performance, was used for all the experiments as reference material. FWP with N/COD ratios of (2, 5, 15, 70 mg/g all with P/COD = 8 mg/g) as well as simulated FWP with nutrient starvation (N/COD = P/COD = 0) conditions were applied. For the acetic acid accumulations, nutrient starvation as well as N/COD variations (2.5, 5, 50 mg/g all with P/COD = 9 mg/g) and P/COD variations (0.5, 2, 9, 15 mg/g all with N/COD = 10 mg/g) were evaluated. An optimal range of combined N and P limitation with N/COD from 2 to 15 mg/g and P/COD from 0.5 to 3 mg/g was considered to offer consistent improvement of productivity over the case of nutrient starvation. Productivity increased due to active biomass growth of the PHA storing biomass without observed risk for a growth response overtaking PHA storage activity. PHA production with respect to the initial active biomass was significantly higher even in cases of excess nutrient additions when compared to the cases of nutrient starvation. The 24-h PHA productivities were enhanced as much as 4-fold from a base value of 1.35 g-PHA per gram initial active biomass with respect nutrient starvation feedstock. With or without nutrient loading the biomass consistently accumulated similar and significant PHA (nominally 60% g-PHA/g-VSS). Based on results from replicate experiments some variability in the extant biomass maximum PHA content was attributed to interpreted differences in the biomass initial physiological state and not due to changes in feedstock nutrient loading. We found that the accumulation process production rates for mixed cultures can be sustained long after the maximum PHA content of the biomass was reached. Within the specific context of the applied fed-batch feed-on-demand methods, active biomass growth was interpreted to have been largely restricted to the PHA-storing phenotypic fraction of the biomass. This study suggests practical prospects for mixed culture PHA production using a wide range of volatile fatty acid (VFA) rich feedstocks. Such VFA sources derived from residual industrial or municipal organic wastes often naturally contain associated nutrients ranging in levels from limitation to excess.
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PMID:Polyhydroxyalkanoate (PHA) storage within a mixed-culture biomass with simultaneous growth as a function of accumulation substrate nitrogen and phosphorus levels. 2584 83


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