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

The promoter region of the pColV-K30-encoded operon specifying biosynthesis and transport of the siderophore aerobactin was subjected to deletion analysis to determine the smallest DNA sequence affording iron regulation of a iucA'-'lacZ gene fusion. A 78-base-pair (bp) region containing the main (P1) promoter retained the character of inducibility under iron starvation. A 250-bp fragment carrying this sequence was examined for protection against DNase I by the Fur protein, the product of a gene (fur) required for negative control of several iron-regulated functions. The DNase I footprints, in the presence of various divalent heavy-metal ions added as corepressors, revealed two contiguous binding sites with different lengths and affinities for Fur. Increased concentrations of the protein appeared to elicit formation of repressor oligomers which bind to the upstream and downstream regions of the P1 promoter in a metal-dependent fashion, but with a presently undefined stoichiometry. The primary site for Fur binding spans 31 bp and contains two overlapping symmetry dyads which share the sequence 5'-TCATT-3'. It also contains extensive homology with a 19-bp consensus sequence for iron-regulated genes as deduced from comparison with the fhuA and fepA putative promoter sequences.
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PMID:Operator sequences of the aerobactin operon of plasmid ColV-K30 binding the ferric uptake regulation (fur) repressor. 329

Mutations in three Escherichia coli K12 genes, tonB, exbB and the newly discovered semA, reduce sensitivity to the low Mr polypeptide antibiotic microcin E492. The products of the tonB and exbB genes were previously shown to be involved in the uptake of siderophore-complexed iron and in the action of a number of colicins. Strains mutated at or close to semA (collectively referred to as sem mutations) remained fully sensitive to these colicins, and grew as well as wild-type strains under conditions of iron starvation. Expression of a number of sem-lacZ operon fusions was not affected by iron limitation, and sem mutations did not affect the production of iron-regulated outer membrane proteins which are known or thought to be involved in iron uptake. Hfr conjugation and P1 phage transduction experiments indicated that semA is located close to pabB at 40 min on the E. coli K12 chromosome. This places semA close to the mng locus, wherein mutations result in decreased manganese sensitivity. However, strains carrying the semA mutation exhibited increased manganese sensitivity.
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PMID:Microcin-E492-insensitive mutants of Escherichia coli K12. 330 33

The essential metal copper, zinc and iron content in starved virgin and pregnant rat tissue has been studied. The copper content of the whole rat, which was actually increased in pregnant rats, decreased in starved pregnant rats. The differences were significant in 19-day pregnant rats. The total copper content of the conceptus was not affected by starvation. Iron distribution and net tissue content showed the same pattern as that of copper. With regard to zinc, however, there was a decrease of its content associated with starvation in rat tissue. This decrease was statistically significant on the 21st day of gestation both in the mother and in fetuses, which marks a difference compared with the copper-iron pattern. It must be pointed out, however, that--with the significant exception of zinc--the maternal stores of the metals are enough to supply the fetus during starvation despite significant reductions in the maternal reserves.
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PMID:Combined pregnancy and starvation effects on rat tissue iron, zinc and copper contents. 334 20

Circadian variations in plasma iron levels were first reported in humans in 1937. Influences of the sleeping pattern and of plasma cortisol and adrenaline levels on these variations as well as the reproducibility of the phenomenon itself are discussed controversially in the literature. The influence of food intake, however, was not considered in most of the studies and is therefore subject of this investigation. Circadian plasma iron and plasma transferrin variations were determined in rabbits and compared under free access to food and under starvation (caecotrophy was not prevented). Population-mean-cosinor analysis of circadian plasma iron concentrations showed similar variations in the fed and starved condition (mesor: 116.6 micrograms/dl vs 118.1 micrograms/dl, acrophase 0752 hr vs 0728) except for a significant increase of the circadian amplitude under free access to food (30.9 micrograms/dl vs 22.3 micrograms/dl, P less than 0.05). There was no variation in plasma transferrin, which shows that 24 hr variations in plasma iron are not caused by modulation of plasma transferrin. These findings demonstrate a circadian rhythm for plasma iron, the amplitude of which is increased by food intake.
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PMID:Influence of food intake on the 24-hr variations of plasma iron concentration in the rabbit. 337 Jul 17

In Erwinia chrysanthemi, conditions of iron starvation initiate production of a catechol-type siderophore and enhance production of three outer membrane polypeptides. Twenty-two mutants affected in the different stages of this iron assimilation system were isolated by mini-Mu insertion mutagenesis. All of them failed to induce systemic soft rot on axenically grown Saintpaulia plants. From the siderophore auxotrophs and the iron uptake mutants, clones having recovered the missing function(s) were isolated by using the in vivo cloning vector pULB113 (RP4::mini-Mu). An R-prime plasmid containing a ca. 35.5-kilobase-pair DNA insert was identified. Restoration of the iron functions restored partially, if not completely, the virulence of the parental strain.
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PMID:Systemic virulence of Erwinia chrysanthemi 3937 requires a functional iron assimilation system. 337 73

The effects of starvation and refeeding of 2-wk-old turkey poults on serum and tissue levels of zinc, copper and iron were investigated. Serum concentrations of zinc and copper declined during 4 d of starvation. Refeeding for 24 h following a period of starvation restored serum copper to levels similar to those in the fed controls but failed to elevate zinc levels. Liver concentrations and total quantities of zinc, copper and iron increased throughout starvation. Refeeding the starved poults reduced hepatic metal concentrations but caused a further increase in total metal content. This was apparently related to the large increase in liver mass, and the effect was most pronounced in poults starved 1 d prior to refeeding. Starvation also caused an increased zinc concentration and content and a reduced copper content in the pancreas, duodenal mucosa and kidney. Iron content of the pancreas and kidney increased during starvation, but that of the duodenal mucosa declined. Starvation evoked a progressive increase in the cytosolic zinc concentration from liver, pancreas, duodenal mucosa and kidney. A major part of this increase was accounted for as zinc bound to metallothionein (MT). Refeeding rapidly reduced cytosolic and MT-bound zinc in each of these tissues. It was concluded that starvation and refeeding had major effects on tissue trace metal status. A function is proposed for MT during starvation as a mechanism for the conservation of body zinc stores. Zinc, released as a consequence of tissue catabolism, is repartitioned into a soluble storage site (MT), which can be rapidly mobilized to meet the demands of new tissue synthesis once anabolic metabolism resumes.
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PMID:Effects of starvation and refeeding on tissue zinc, copper and iron in turkey poults. 357 61

Under iron-starvation conditions, the different Yersinia species expressed various iron-regulated proteins. Among them, two high-molecular-weight outer membrane proteins were synthesized in high-virulence-phenotype Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica serovars O:8 and O:Tacoma but were present neither in low-virulence phenotype Y. enterocolitica serovars O:3 and O:9 nor in avirulent Y. frederiksenii, Y. kristensenii, Y. intermedia, and Y. enterocolitica serovar O:39. Thus, the degree of virulence correlates with the presence of the two high-molecular-weight proteins in Yersinia species.
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PMID:Expression of iron-regulated proteins in Yersinia species and their relation to virulence. 379 33

Haemophilus influenzae grown on enriched medium containing protoporphyrin IX rather than hemin was iron starved by the addition of the chelator ethylenediamine di-o-hydroxyphenylacetic acid. Iron starvation could be overcome in each of 33 H. influenzae type b isolates by 30% Fe-saturated human transferrin but not by human lactoferrin. Among nontypeable H. influenzae, 28 of 35 isolates, including 2 of 3 systemic isolates, were able to utilize Fe-transferrin. None of 18 H. parainfluenzae isolates was able to use Fe-transferrin. Iron starvation of H. influenzae type b resulted in increased amounts of three membrane proteins of 94,000 to 98,000 daltons.
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PMID:Haemophilus influenzae can use human transferrin as a sole source for required iron. 387 64

In summary, anemia developing in a patient with cancer can be due to several different factors. A relative failure of erythropoiesis, in conjunction with a modestly shortened erythrocyte survival, is the most likely explanation for the anemia and can occur in patients with or without bone marrow invasion. Several theories have been proposed to explain the mechanism of limited red cell production in cancer. Internal iron starvation and cancer toxic factors have been widely implicated. Immunoglobulin inhibitors of erythropoiesis occur in the rare entity, pure red cell aplasia, which is sometimes associated with thymomas. Autoimmune hemolytic anemia and microangiopathic hemolytic anemia can also occur in patients with solid cancers, pointing out the need for a complete evaluation of anemia in any patient with recent-onset anemia. Successful treatment and prognostic implications of anemia in cancer is dependent on proper diagnosis.
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PMID:Anemia in cancer. 389 Oct 30

Manganese is accumulated in Bacillus subtilis by a highly specific active transport system. This trace element "pump" is insensitive to added magnesium or calcium and preferentially accumulates manganese in the presence of cobalt, iron, and copper. Manganese uptake in B. subtilis is inhibited by cyanide, azide, pentachlorophenol, and m-chlorophenyl carbonylcyanide hydrazone. The uptake of manganese follows Michaelis-Menten kinetics, and the net accumulation of manganese is regulated by increasing the V(max) after exposure to manganese-starvation conditions and by decreasing the V(max) for manganese uptake during growth in excess manganese. The K(m) remains constant during these regulatory changes in V(max). Manganese accumulated during growth is exchangeable for exogenous manganese and can be released from the cells by toluene (which causes leakage but not lysis) or by lysis with lysozyme. Two stages can be distinguished with regard to intracellular manganese during the process of growth and sporulation. During logarithmic growth, B. subtilis maintains a relatively constant internal manganese content, which is a function of the external manganese concentration following approximately a Langmuir adsorption isotherm. At the end of log phase, net accumulation of manganese slows. A second phase of net manganese accumulation begins at about the same time during sporulation as the accumulation of calcium begins. The manganese accumulated during growth and early sporulation is exchangeable and therefore relatively "free"; intracellular manganese is converted later during sporulation into a bound form that cannot be released by toluene or lysozyme.
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PMID:Manganese transport in Bacillus subtilis W23 during growth and sporulation. 463


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