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

There are two pathways for replication of plasmids derived from bacteriophage lambda (so-called lambda plasmids) in Escherichia coli. One pathway is based on the assembly of the new replication complex at ori lambda, and the second requires activity of the replication complex inherited by one of two daughter plasmid copies after each replication round. Although these two replication pathways proceed at the same time in the host cell, we previously found conditions for specific elimination of the pathway based on the assembly of the new replication complex; thus, replication is restricted to that carried out by the heritable replication complex. These conditions are (i) the relaxed response to amino acid starvation and (ii) temperature upshift of the culture of cells harboring the lambda crotsPts1 plasmid. Here we asked whether the replication complex is inherited randomly by one of two daughter plasmid copies or whether the inheritance is preferred by one particular copy, that containing the parental DNA r strand or that bearing the l strand. We performed density shift experiments which allowed us to separate plasmid DNA molecules replicated by the heritable replication complex from those devoid of the replication complex and therefore not able to replicate. Then, [3H]thymidine-labelled plasmid DNA strands were separated and hybridized to membrane-bound ssDNA containing a fragment of either the r or l strand of lambda DNA. We found roughly equal efficiency of hybridization to both r and l strands in all experimental systems used. Therefore, we conclude that the lambda replication complex is randomly inherited by one of two daughter plasmid copies rather than preferentially inherited by either the copy carrying the parental r strand or that containing the l strand.
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PMID:Random inheritance of the replication complex by one of two daughter lambda plasmid copies after a replication round in Escherichia coli. 961 64

In our previous paper [Oubihi et al. (1998) Anal. Biochem., 257, 169-175], we have shown that a polyacrylamide-derived synthetic glycopolymer with GlcNAcbeta side chains, termed PAP(GlcNAcbeta), is useful as a solid phase acceptor substrate for the ELISA-based analyses of soluble beta1,4(-)galactosyltransferase (GalT) activity in milk. This method is now used to assay detergent-solubilized cellular GalT. The glycopolymer coated on polystyrene plates was shown to be highly stable against the non-ionic and ionic detergents tested (0 approximately 5% solutions of Triton X-100 and SDS). Such stability made it possible to incubate the ELISA plate with detergent-solubilized GalT and to wash the ELISA plate with SDS solution after the GalT reaction, leading to high accuracy and sensitivity of this assay. The GalT activity was assayed using this method for 1% Triton X-100 extracts of various tissue samples of mice and several cultured cell lines. The results showed that the specific GalT activity of tissue extracts was low in brain and intestine, and high in ovary, muscle, and kidney. As for the cultured cell lines, COS7, COMMA-1D and C2C12 cells showed high specific activity, while CHO and MDCK cells showed low activity. The myoblast C2C12 had a slight increase in GalT activity during starvation-induced cell differentiation. On the other hand, GaIT-I transcript estimated by RT-PCR rather decreased during C2C12 cell differentiation, suggesting a differentiation-dependent switch in GalT isozymes. Taken all together, the ELISA-based assay using PAP(GlcNAcbeta) as a solid phase acceptor substrate was demonstrated to be a useful method for the assay of membrane-bound galactosyltransferases.
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PMID:An ELISA-based assay for detergent-solubilized cellular beta 1,4-galactosyltransferase activity. Use of a polyacrylamide derivative with GlcNAc-beta side chains as a solid phase acceptor substrate. 1083 Apr 94

Genes encoding polypeptides of an ATP binding cassette (ABC)-type ferric iron transporter that plays a major role in iron acquisition in Synechocystis sp. strain PCC 6803 were identified. These genes are slr1295, slr0513, slr0327, and recently reported sll1878 (Katoh et al., J. Bacteriol. 182:6523-6524, 2000) and were designated futA1, futA2, futB, and futC, respectively, for their involvement in ferric iron uptake. Inactivation of these genes individually or futA1 and futA2 together greatly reduced the activity of ferric iron uptake in cells grown in complete medium or iron-deprived medium. All the fut genes are expressed in cells grown in complete medium, and expression was enhanced by iron starvation. The futA1 and futA2 genes appear to encode periplasmic proteins that play a redundant role in iron binding. The deduced products of futB and futC genes contain nucleotide-binding motifs and belong to the ABC transporter family of inner-membrane-bound and membrane-associated proteins, respectively. These results and sequence similarities among the four genes suggest that the Fut system is related to the Sfu/Fbp family of iron transporters. Inactivation of slr1392, a homologue of feoB in Escherichia coli, greatly reduced the activity of ferrous iron transport. This system is induced by intracellular low iron concentrations that are achieved in cells exposed to iron-free medium or in the fut-less mutants grown in complete medium.
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PMID:Genes essential to iron transport in the cyanobacterium Synechocystis sp. strain PCC 6803. 1129 96

The KdpB polypeptides in the cyanobacterium Anabaena torulosa were shown to be two membrane-bound proteins of about 78 kDa, expressed strictly under K(+) deficiency and repressed or degraded upon readdition of K(+). In both Anabaena and Escherichia coli strain MC4100, osmotic and ionic stresses caused no significant induction of steady-state KdpB levels during extreme potassium starvation.
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PMID:Regulation of potassium-dependent Kdp-ATPase expression in the nitrogen-fixing cyanobacterium Anabaena torulosa. 1154 45

Glucose-6-phosphatase (G6Pase), an enzyme found mainly in the liver and the kidneys, plays the important role of providing glucose during starvation. Unlike most phosphatases acting on water-soluble compounds, it is a membrane-bound enzyme, being associated with the endoplasmic reticulum. In 1975, W. Arion and co-workers proposed a model according to which G6Pase was thought to be a rather unspecific phosphatase, with its catalytic site oriented towards the lumen of the endoplasmic reticulum [Arion, Wallin, Lange and Ballas (1975) Mol. Cell. Biochem. 6, 75--83]. Substrate would be provided to this enzyme by a translocase that is specific for glucose 6-phosphate, thereby accounting for the specificity of the phosphatase for glucose 6-phosphate in intact microsomes. Distinct transporters would allow inorganic phosphate and glucose to leave the vesicles. At variance with this substrate-transport model, other models propose that conformational changes play an important role in the properties of G6Pase. The last 10 years have witnessed important progress in our knowledge of the glucose 6-phosphate hydrolysis system. The genes encoding G6Pase and the glucose 6-phosphate translocase have been cloned and shown to be mutated in glycogen storage disease type Ia and type Ib respectively. The gene encoding a G6Pase-related protein, expressed specifically in pancreatic islets, has also been cloned. Specific potent inhibitors of G6Pase and of the glucose 6-phosphate translocase have been synthesized or isolated from micro-organisms. These as well as other findings support the model initially proposed by Arion. Much progress has also been made with regard to the regulation of the expression of G6Pase by insulin, glucocorticoids, cAMP and glucose.
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PMID:The glucose-6-phosphatase system. 1187 77

V-ATPases are complex proteins consisting of a peripheral, ATP-hydrolysing V(1) complex and a membrane-bound H(+)-translocating V(o) complex. The plasma membrane V-ATPase from the tobacco hornworm (Manduca sexta) midgut is made up of eight different V(1) and four different V(o) subunits. During starvation and moulting, V-ATPase activity decreases as a result of the dissociation of the V(1) complex from the V(o) complex. To determine whether subunit biosynthesis is reduced during periods of enzyme inactivity, we measured the transcript levels and transcriptional activities of V-ATPase genes. Northern blots revealed the downregulation of almost all V-ATPase transcripts during starvation. During moulting, transcript levels of the three V-ATPase genes examined, mvB, mvG and mvd, also decreased, and this decrease was negatively correlated with the titre of 20-hydroxyecdysone (20-HE) and positively correlated with the titre of juvenile hormone (JH). To test the biological significance of these correlations, we injected both hormones into feeding larvae and measured transcript levels several hours later. A short-term increase and a long-term decrease in levels of mRNA were observed after 20-HE injection, whereas JH injection had no significant effect. Immunohistochemical studies of the midgut epithelium revealed that 20-HE injection led to changes in goblet cell morphology and in the subcellular distribution of the V(1) complex comparable with the situation during the moult and during starvation. Reporter gene assays in Sf21 cells using mvB, mvG and mvd promoters to initiate transcription of firefly luciferase led, after incubation of the cells with 20-HE, to results comparable with those obtained in the injection experiments. These findings suggest that putative ecdysone-responsive elements are present in all three promoters. Taken together, our results suggest that the expression of V-ATPase genes is controlled in a coordinated manner by ecdysteroids.
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PMID:Expression of Manduca sexta V-ATPase genes mvB, mvG and mvd is regulated by ecdysteroids. 1191 65

The kdpFABC operon, coding for a high-affinity K(+)-translocating P-type ATPase, is expressed in Escherichia coli as a backup system during K(+) starvation or an increase in medium osmolality. Expression of the operon is regulated by the membrane-bound sensor kinase KdpD and the cytosolic response regulator KdpE. From a nitrogen-fixing cyanobacterium, Anabaena sp. strain L-31, a kdpDgene was cloned (GenBank accession no. AF213466) which codes for a KdpD protein (365 amino acids) that lacks both the transmembrane segments and C-terminal transmitter domain and thus is shorter than E. coli KdpD. A chimeric kdpD gene was constructed and expressed in E. coli coding for a protein (Anacoli KdpD), in which the first 365 amino acids of E. coli KdpD were replaced by those from Anabaena KdpD. In everted membrane vesicles, this chimeric Anacoli KdpD protein exhibited activities, such as autophosphorylation, transphosphorylation and ATP-dependent dephosphorylation of E. coli KdpE, which closely resemble those of the E. coli wild-type KdpD. Cells of E. coli synthesizing Anacoli KdpD expressed kdpFABC in response to K(+) limitation and osmotic upshock. The data demonstrate that Anabaena KdpD can interact with the E. coliKdpD C-terminal domain resulting in a protein that is functional in vitro as well as in vivo.
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PMID:A chimeric Anabaena/ Escherichia coli KdpD protein (Anacoli KdpD) functionally interacts with E. coli KdpE and activates kdp expression in E. coli. 1211 59

Classic Hodgkin's disease (cHD) is a lymphoid neoplasia characterized by few malignant Hodgkin and Reed-Sternberg (H-RS) cells, embedded in an abundant background of non-tumour cells. We have previously demonstrated the expression in primary H-RS cells of the receptor tyrosine kinase (RTK) c-kit; here we describe its functional role in the cross-talk between H-RS cells themselves with neighbouring cell populations. In particular, we analysed the expression of c-kit and its ligand stem cell factor (SCF) in a panel of HD-derived cell lines and fibroblasts from HD-involved lymph nodes (HDF). While c-kit was expressed by HD-derived cell lines, usually in the absence of SCF, this latter molecule, in its soluble and/or membrane-bound (mb) form, was in turn expressed at a high level by primary HDF. In vitro adhesion between HD-derived cell lines and HDF was mainly mediated by c-kit/SCF interactions, and this phenomenon was significantly inhibited by an excess of soluble SCF or by neutralizing anti-c-kit monoclonal antibodies. Furthermore, both soluble and mb-SCF increased growth and colony survival of HD-derived cell lines; these effects were significantly enhanced upon co-stimulation of H-RS cells with interleukin 9. Finally, soluble SCF was able to partially rescue H-RS cells from apoptosis induced by serum starvation. Taken together, our data indicated the expression of functional c-kit receptor by H-RS cells and suggests a role of SCF in the pathobiology of cHD.
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PMID:Hodgkin and Reed-Sternberg cells express functional c-kit receptors and interact with primary fibroblasts from Hodgkin's disease-involved lymph nodes through soluble and membrane-bound stem cell factor. 1219 85

The response of tobacco (Nicotiana tabacum) suspension-cultured cells (BY-2) to nutrient starvation was investigated. When the cells that were grown in Murashige-Skoog medium containing 3% (w/v) sucrose were transferred to the same medium without sucrose, 30 to 45% of the intracellular proteins were degraded in 2 d. An analysis with sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that proteins were degraded nonselectively. With the same treatment, protease activity in the cell, which was measured at pH 5.0 using fluorescein thiocarbamoyl-casein as a substrate, increased 3- to 7-fold after 1 d. When the cysteine protease inhibitor (2S,3S)-trans-epoxysuccinyl-L-leucylamido-3-methyl-butane (10 [mu]M) was present in the starvation medium, both the protein degradation and the increase in the protease activity were effectively inhibited. Light microscopy analysis showed that many small spherical bodies accumulated in the perinuclear region of the cytosol 8 h after the start of the inhibitor treatment. These bodies were shown to be membrane-bound vesicles of 1 to 6 [mu]m in diameter that contained several particles. Quinacrine stained these vesicles and the central vacuole; thus, both organelles are acidic compartments. Cytochemical enzyme analysis using 1-naphthylphosphate and [beta]-glycerophosphate as substrates showed that these vesicles contained an acid phosphatase(s). We suggest that these vesicles contribute to cellular protein degradation stimulated under sucrose starvation conditions.
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PMID:Autophagy in Tobacco Suspension-Cultured Cells in Response to Sucrose Starvation. 1222 58

Alkaline phosphatases (ALPs) are glycosylated, membrane-bound enzymes that hydrolyze various monophosphate esters at an optimum high pH and are present in nearly all living organisms. In Escherichia coli, extracellular phosphate (Pi) limitation induces the ALP gene, indicating a role of extracellular Pi in ALP gene regulation. However, little is known about similar mechanisms in mammalian cells. Previously, we reported that Pi starvation increased the tissue-nonspecific ALP (TNSALP) activity and regulated its expression in the mouse stromal cell line ST2, derived from mouse bone marrow. In the present study, we further examined the effects of Pi starvation on the mechanism of TNSALP induction. The specific activity of TNSALP increased markedly after treatment by Pi starvation for 5 days and RT-PCR analysis revealed that the mRNA of the bone morphogenetic protein-4 (BMP-4) gene was highly stimulated. The combination of Pi depletion and mouse BMP-4 receptor IA/Fc chimera down-regulated the TNSALP activity. These results indicated that Pi depletion stimulates the TNSALP activity for the Pi supplementation, and that this system may involve the signaling pathway of the BMP-4 gene at the transcription level.
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PMID:Phosphate depletion enhances bone morphogenetic protein-4 gene expression in a cultured mouse marrow stromal cell line ST2. 1244 13


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