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

The composition and antibiotic permeability barrier of the outer membrane of Serratia marcescens were assessed in cells grown in vivo and in vitro. Intraperitoneal diffusion chambers implanted in rats were used for the in vivo cultivation of bacteria. Outer membranes isolated from log-phase bacterial cells recovered from these chambers were compared with membranes isolated from cells grown in vitro. Analysis revealed that the suspected 41-kilodalton porin and the OmpA protein were recovered on sodium dodecyl sulfate-polyacrylamide gels in equal quantities. Several high-molecular-weight proteins, thought to be iron starvation induced, appeared in the diffusion chamber-grown cells. The outer membrane permeability barriers to cephaloridine were similar in in vivo- and in vitro-grown cells based on permeability coefficient calculations. The permeability coefficient of cephaloridine in S. marcescens cells (30.3 x 10(-5) to 38.9 x 10(-5) cm s-1) was greater than that obtained for an Escherichia coli strain expressing only porin OmpC but smaller than those obtained for the E. coli wild type and a strain expressing only porin OmpF. Functional characterization of the suspected porin was performed by using the planar lipid bilayer technology. The sodium dodecyl sulfate-0.4 M NaCl-soluble porin from both in vitro- and in vivo-grown cells showed an average single-channel conductance in 1 M KCl of 1.6. A partial amino acid sequence (19 residues) was obtained for the S. marcescens porin. The sequence showed a very high homology to the E. coli OmpC porin. These data identified the S. marcescens outer membrane 41-kilodalton protein as a porin by both functional and amino acid analyses. Also, the methodology used allowed for efficient growth and recovery of diffusion chamber-grown bacterial cells and permitted identification of specific in vivo-induced changes in bacterial cell membrane composition.
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PMID:Outer membrane and porin characteristics of Serratia marcescens grown in vitro and in rat intraperitoneal diffusion chambers. 215 67

It has been shown previously that starvation of the trypanosomatid protozoan Crithidia luciliae for purines and/or inorganic phosphate results in increased levels of a surface membrane-associated 3'-nucleotidase/nuclease (3'-N'ase) activity which hydrolyzes both 3'-ribonucleotides and nucleic acids, thereby permitting the organisms to transport these essential nutrients across their cell membranes. A polypeptide with the requisite catalytic properties has been identified by an in situ gel activity assay following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In current studies, differential synthesis of the protein responsible for the 3'-N'ase activity was not demonstrable by comparisons of SDS-PAGE patterns of nutrient-replete or purine-starved parasites metabolically labeled with either [35S]methionine, [3H]leucine, or [3H]tyrosine. However, surface labeling of nutrient-replete and purine-starved cells revealed the enhanced expression of an 125I surface-labeled 43-kDa protein which comigrated with the 3'-N'ase activity in one- and two-dimensional electrophoretic systems. The amount of this surface-labeled peptide correlated with the level of 3'-N'ase activity as measured by test tube assay. Refeeding adenosine to purine-starved cells led to the loss of both the enzyme activity and the surface iodinatable 43-kDa band as a result of renewed cell division. Starvation of these organisms for phosphate also led to the enhanced expression of the 43-kDa radioiodinatable band. The results indicated that the 3'-N'ase protein, itself, is differentially expressed at the cell surface under conditions which lead to increased enzyme activity.
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PMID:Crithidia luciliae: starvation for purines and/or phosphate leads to the enhanced surface expression of a protein responsible for 3'-nucleotidase/nuclease activity. 216 51

The characteristics of the uptake of L-homocysteine by cultures of human umbilical vein endothelial cells have been examined. Uptake occurred by Na(+)-dependent and Na(+)-independent systems, but was essentially independent of the pH of the uptake medium. The Na(+)-independent system corresponded to system L, being totally inhibited by the presence of beta-2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH) a system L analogue. It was concluded on the basis of starvation experiments coupled with failure to detect any inhibition in the presence of 2-methylaminoisobutyric acid (MeAIB), a system A analogue, that the Na(+)-dependent uptake was wholly accounted for by system ASC. The kinetic properties of systems L and ASC were determined by omitting Na+ from the uptake medium and incorporating BCH in the medium, respectively. It has been concluded on the basis of the inhibitory effects of a number of amino acids that uptake of homocysteine occurs by those systems which transport cysteine.
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PMID:Homocysteine uptake by human umbilical vein endothelial cells in culture. 220 77

Folic acid plays a central role in anabolic metabolism by supplying single-carbon units at varied levels of oxidation for both nucleotide and amino acid biosyntheses. It has been proposed that 5-amino-4-imidazole carboxamide riboside 5'-triphosphate (ZTP), an intermediate in de novo purine biosynthesis, serves as a signal of cellular folate stress and mediates a physiologically beneficial response to folate stress in Salmonella typhimurium (B. R. Bochner, and B. N. Ames, Cell 29:929-937, 1982). We examined the physiological response of Escherichia coli to folate stress induced by the drugs psicofuranine, trimethoprim, and sodium sulfathiazole or by p-aminobenzoic acid (pABA) starvation. Analysis of nucleotide pools showed that psicofuranine or trimethoprim treatment of a prototrophic strain or growth of a pABA auxotroph on limiting pABA induced the production of the nucleotide ZTP, as previously observed in S. typhimurium by Bochner and Ames. Accumulation of ZTP and its precursor 5-amino-4-imidazole carboxamide riboside 5'-monophosphate (ZMP) did not correlate well with folate stress in E. coli, as measured by determination of the folate/protein ratios of extracts of treated cells. Treatment of cells with psicofuranine caused a marked accumulation of 5-amino-4-imidazole carboxamide ribonucleotides (Z-ribonucleotides) but a statistically insignificant drop in the folate/protein ratio of cell extracts. Sodium sulfathiazole treatment at a drug concentration that led to a threefold drop in the growth rate and in the folate/protein ratio of treated cells led to little accumulation of Z-ribonucleotides in E. coli A purF his+ strain which produces ZTP and ZMP when treated with trimethoprim was constructed. In this strain, histidine represses the synthesis of both ZMP and ZTP. Treatment of cells of this strain with trimethoprim resulted in a decrease in the folate/protein ratio of cell extracts, but a blockade of Z-ribonucleotide accumulation did not affect the extent of folate depletion seen in treated cells and had only a small effect on the resistance of this strain to growth inhibition by trimethoprim. The patterns of protein expression induced by treatment of this strain with trimethoprim or psicofuranine were examined by two-dimensional electrophoretic resolution of the total cellular proteins. No differences in protein expression were seen when the treatment were performed in media containing or lacking histidine. These studies failed to provide evidence in E. coli for a folate stress regulon controlled by ZTP.
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PMID:Role of purine biosynthetic intermediates in response to folate stress in Escherichia coli. 225 81

The activity of amino acid transport System A in avian fibroblasts was increased following incubation of the cells in a medium in which most of the NaCl normally present had been isoosmotically replaced by sucrose. This increase was detectable after 2 h of incubation, reached a maximum at about 4 h, and remained constant thereafter. Transfer of treated cells back to a normal medium resulted in decay of the induced transport activity, with a half-life of less than 2 h. Kinetic analysis revealed that the increase in transport activity arose from an increase in Vmax, with little change in Km. This induction of System A activity did not occur if an inhibitor of either RNA or protein synthesis was present in the modified medium. The use of various different solutes as replacements for NaCl in the incubation medium showed that, although each replacement caused a decrease in both cellular Na+ content and protein synthesis, only disaccharides produced the increase in amino acid transport activity. In addition, estimates of cell volume indicated that, even under iso-osmotic conditions, incubation in the sucrose-containing medium caused initial cell shrinkage, followed by swelling. It is concluded that this induction of System A activity is associated with a volume regulatory process and that this process probably accounts for the parallel responses previously observed when cells were incubated in hyperosmolar media. Induction of amino acid transport activity by this process is distinct from adaptive regulation, caused by amino acid starvation; but the two processes are not strictly additive, and so appear to converge at some step.
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PMID:Induction of amino acid transport activity in chick embryo fibroblasts by replacement of extracellular sodium chloride with disaccharide. 238 93

Bacteria from members of the families Enterobacteriaceae and Pseudomonadaceae were grown under phosphate-deficient (0.1 to 0.2 mM Pi) conditions and examined for the production of novel membrane proteins. Of the 17 strains examined, 12 expressed a phosphate-starvation-induced outer membrane protein which was heat modifiable in that after solubilization in sodium dodecyl sulfate at low temperature the protein ran on gels as a diffuse band of higher apparent molecular weight, presumably an oligomer form, which shifted to an apparent monomer form after solubilization at high temperature. These proteins fell into two classes based on their monomer molecular weights and the detergent conditions required to release the proteins from the peptidoglycan. The first class, expressed by species of the Pseudomonas fluorescens branch of the family Pseudomonadaceae, was similar to the phosphate-starvation-inducible, channel-forming protein P of Pseudomonas aeruginosa. The second class resembled the major enterobacterial porin proteins and the phosphate-regulated PhoE protein of Escherichia coli. Using a protein P-trimer-specific polyclonal antiserum, we were able to demonstrate cross-reactivity of the oligomeric forms of both classes of these proteins on Western blots. However, this antiserum did not react with the monomeric forms of any of these proteins, including protein P monomers. With a protein P-monomer-specific antiserum, no reactivity was seen with any of the phosphate-starvation-inducible membrane proteins (in either oligomeric or monomeric form), with the exception of protein P monomers. These results suggest the presence of conserved antigenic determinants only in the native, functional proteins.
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PMID:Phosphate-starvation-induced outer membrane proteins of members of the families Enterobacteriaceae and Pseudomonodaceae: demonstration of immunological cross-reactivity with an antiserum specific for porin protein P of Pseudomonas aeruginosa. 241 13

A large-scale purification scheme was developed for lipopolysaccharide-free protein P, the phosphate-starvation-inducible outer-membrane porin from Pseudomonas aeruginosa. This highly purified protein P was used to successfully form hexagonal crystals in the presence of n-octyl-beta-glucopyranoside. Amino-acid analysis indicated that protein P had a similar composition to other bacterial outer membrane proteins, containing a high percentage (50%) of hydrophilic residues. The amino-terminal sequence of this protein, although not homologous to either outer membrane protein, PhoE or OmpF, of Escherichia coli, was found to have an analogous protein-folding pattern. Protein P in the native trimer form was capable of maintaining a stable functional trimer after proteinase cleavage. This suggested the existence of a strongly associated tertiary and quaternary structure. Circular dichroism studies confirmed these results in that a large proportion of the protein structure was determined to be beta-sheet and resistant to acid pH and heating in 0.1% sodium dodecyl sulphate.
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PMID:Large-scale purification and biochemical characterization of crystallization-grade porin protein P from Pseudomonas aeruginosa. 245 38

Paranoiac and related mutants of Paramecium tetraurelia display altered membrane excitability. We describe an extension of behavioral characterizations of the paranoiac, fast-2, and tetraethylammonium-insensitive mutants, comparing in detail their reactions to sodium stimulation under standard culture conditions, when grown at various temperatures and when starved. We also use freeze-fracture electron microscopic techniques to analyze in these stocks the morphology of organized arrays of membrane particles, the ciliary plaques. This group of mutants is diverse, showing differences in behavior under standard culture conditions and different reactions to temperature and starvation stresses. Ciliary plaque morphology is altered in some, but not all, of the mutants. The possibility is discussed that these plaques may be sites of potassium or sodium transport.
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PMID:Phenotypic characterization of paranoiac and related mutants in Paramecium tetraurelia. 245 66

The influence of sodium molybdate and sodium tungstate on formate dehydrogenase activity was studied in H2-CO2-grown cultures of Methanobacterium formicicum. Depletion of molybdate from the growth medium resulted in a 75-fold decrease of intracellular molybdenum and a 35-fold decrease in enzyme activity; however, growth rate and cell yields were not influenced. By using an indirect enzyme-linked immunoassay, the amount of formate dehydrogenase approximated 3% of the total protein in cells grown in the presence of molybdate. Molybdenum-starved cells contained approximately 15-fold less formate dehydrogenase protein; Western blot (immunoblot) analysis revealed that both subunits of the enzyme were synthesized. Molybdenum starvation resulted in an increase in the amount of mRNA that hybridized to fdh-specific DNA. The results indicated an inverse relationship between the amount of transcript and the amount of formate dehydrogenase protein detected in response to molybdenum starvation. The addition of 1 mM tungstate to molybdate-containing media resulted in nearly complete loss of enzyme activity and decreased the intracellular concentration of molybdenum 10-fold. Cells grown in the presence of tungstate synthesized high amounts of inactive formate dehydrogenase and contained mRNA that hybridized to fdh-specific DNA in amounts similar to that in cells grown with sufficient molybdate. Inactive formate dehydrogenase, purified from cells grown in the presence of tungstate, had the same subunit composition and contained amounts of molybdopterin cofactor, albeit metal-free, comparable to those in the active enzyme.
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PMID:Effect of molybdenum and tungsten on synthesis and composition of formate dehydrogenase in Methanobacterium formicicum. 245 11

Neutral amino acid transport by system A was investigated in the epithelial cell lines MDCK and MDCK-T1. The latter line is a chemically induced, oncogenically transformed line derived from MDCK. Inducers of differentiation, sodium butyrate and 5-azacytidine, and a tumor promoter, TPA, were used as probes to delineate pathways of regulation involved in system A response to a variety of physiological conditions and agents. Azacytidine, an inhibitor of DNA methylation, and butyrate, an enhancer of histone acetylation, inhibited expression of system A, had little effect on system ASC, and slightly stimulated system L. Inhibition of system A expression by butyrate and azacytidine occurred under different conditions. Increases in system A activity due to amino acid starvation or transformation were inhibited by butyrate but not by azacytidine. Repressed system A activity, normally observed in the presence of high levels of amino acids, was more sensitive to azacytidine than to butyrate. The tumor promoter, TPA, stimulated system A activity in MDCK cells under normal growth conditions but did not stimulate activity in amino acid-starved MDCK cells or in MDCK-T1 cells. Stimulation of system A activity by TPA was prevented by prior exposure to butyrate but not to azacytidine. These results suggest 1) that system A expression observed in growing amino-acid-repressed MDCK cells is modulated by an azacytidine-sensitive mechanism and 2) that the elevated expression of system A activity induced by amino acid starvation, by chemical transformation to MDCK-T1, and by TPA is modulated by a butyrate-sensitive mechanism.
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PMID:Effects of 5-azacytidine, sodium butyrate, and phorbol esters on amino acid transport system A in a kidney epithelial cell line, MDCK: evidence for multiple mechanisms of regulation. 245 37


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