UMLS:C0009443 - FACTA Search

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Query: UMLS:C0009443 (cold)
92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This work reconsiders the GATC motif distribution in a 1.6 Mb segment of the Escherichia coli genome, compared to its distribution in phages and plasmids. At first sight the distribution of GATC words looks random. But when a realistic model of the chromosome (made of average genes having the same codon usage as in the real chromasome), is used as a theoretical reference, strong biasesare observed. GATC pairs such as GATCNNGATC are under-represented while there is a strong positive selection for motifs separated by 10, 19, 70 and 1100 bp. The last class is the only one present in E. coli parasites. It can be ascribed to the triggering sequences of the long-patch mismatch repair system. The 6 bp class overlaps with the consensus of CAP (catabolite activator protein) and FNR (fumarate/nitrate regulator) binding sites, thus accounting for counter-selection. The other classes, which could be targets for a nucleic acid-binding protein, are almost always present inside protein coding sequences, and are members of clusters of GATC motifs. Analysis of the genes containing these motifs suggests that they correspond to a regulatory process monitoring the shift from anaerobic to aerobic growth conditions. In particular this regulation, closing down transcription of a large number of genes involved in intermediary metabolism would be well suited for the cold and oxygen shift from the mammal's gut to the standard environmental conditions. In this process the methylation status of GATC clusters would be very important for tuning transcription, and a DNA binding protein, probably a member of the cold-shock proteins family would be needed for alleviating the effects mediated by slackening of the pace of methylation during the shift.
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PMID:Uneven distribution of GATC motifs in the Escherichia coli chromosome, its plasmids and its phages. 864 25

A multicenter clinical trial conducted by the authors compared the desensitizing efficacy of a new 5 percent potassium nitrate: 0.243 percent sodium fluoride dentifrice along with two clinically proven, commercially available desensitizing dentifrices to a placebo dentifrice. Sensitivity to cold air and tactile stimulation, along with patients' subjective assessments, were evaluated to assess the dentinal desensitizing efficacy of the test dentifrices. Results demonstrated that after four weeks, participants who used the new dentifrice formulation experienced significant decreases in dentinal sensitivity compared to the placebo group for all measured indexes.
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PMID:Assessing the efficacy of three dentifrices in the treatment of dentinal hypersensitivity. 868 88

Because the ferric uptake regulator (fur) appears to be an essential gene in Pseudomonas aeruginosa, resistance to manganese was used as an enrichment to isolate strains carrying point mutations in the fur gene in order to assess its role in the co-ordinate expression of siderophores and exotoxin A (ETA). This report describes a detailed molecular and phenotypic characterization of four mutants and one revertant, which carry point mutations in the fur gene. Two parental strains were used in this study. Three mutants were isolated from the widely used strain, PAO1. One of these, CS (cold sensitive), has a mutation in the 5' non-coding region of the fur gene while the two other mutants derived from this parent have mutations resulting in the following deduced changes in Fur: mutant A2, H86-->R; mutant A4, H86-->Y. The other mutant (C6) and its revertant (C6Rv) were derived from PAO6261, a mutant of PAO1 with a deletion in the anr gene (anaerobic regulation of arginine deiminase and nitrate reduction) that controls anaerobic respiration in P. aeruginosa. Fur from the C6 mutant has an A10-->G mutation while in the C6Rv spontaneous revertant the mutant Gly residue has been changed to Ser at this position. All mutants were examined for alterations in the iron-regulated expression of siderophores and ETA. The A2 and A4 mutants expressed higher levels of siderophores in iron-deficient media and in iron-replete media. The CS mutant constitutively expressed siderophores at 25 degrees C. At 42 degrees C siderophore biosynthesis was iron repressed as in the parental strain PAO1. The deletion of anr in PAO6261 had no apparent effect on the iron-mediated regulation of siderophore synthesis, but the C6 mutant derived from this strain produces siderophores constitutively. The iron-regulated production of siderophores by C6Rv was similar to the parental strain PAO6261 and PAO1. Because one of the parental strains used in this study is an Anr mutant, regulation of ETA production was assessed under aerobic and microaerobic conditions. Iron-dependent repression of ETA synthesis in both parental strains and A2 and A4 mutants was found to be 50-100-fold under aerobic and microaerobic conditions, as assayed by quantitative Western dot-blot assays. By contrast in the CS and C6 mutants, while iron-dependent repression os ETA synthesis was similar to both parental strains under aerobic conditions, ETA production in these mutants was constitutive in a microaerobic environment. RNase protection analysis of toxA and regAB transcription in PAO1, PAO6261 and the C6 mutant corroborated the results of quantitative dot-blot assays of ETA. The mutant Fur proteins were purified and examined for their ability to bind to the promoter of a gene (pvdS) that positively regulates the expression of siderophores and ETA. Fur from the A2 and A4 mutants and from the C6Rv revertant was able to bind to the target DNA, but with reduced affinity by comparison to wild-type Fur. Fur from the C6 mutant in DNase I footprint experiments failed to protect the promoter region of the pvdS gene, but it retained some weak binding activity in gel mobility shift assays. The data presented in this study not only furnish some additional insights into the structure-function relationships of Fur, but also afford novel perspectives of virulence factors in P. aeruginosa under environmental conditions that have not previously been considered.
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PMID:Ferric uptake regulator mutants of Pseudomonas aeruginosa with distinct alterations in the iron-dependent repression of exotoxin A and siderophores in aerobic and microaerobic environments. 888 70

Seven patients underwent cold-steel uvulopalatoplasty with tissue removal similar to that being performed with laser-assisted uvulopalatoplasty. The severity and length of postoperative pain, days out of work, postoperative complications, and efficacy in reducing snoring were assessed. The minimum follow-up period was 6 months. The average length of postoperative pain (inability to eat a completely normal diet) was 6 days. All but one patient underwent only one session of cold-steel uvulopalatoplasty with satisfactory relief of snoring. The remaining patient required two sessions. One patient had some mild postoperative bleeding, which resolved with silver nitrate. Improvement in snoring goes as follows: marked improvement in three patients, moderate improvement in three patients, and slight improvement in one patient. None of the patients had complete resolution or the same degree of snoring. Patients who underwent concomitant oropharyngeal procedures (i.e., tonsillectomy) in addition to cold-steel uvulopalatoplasty tended to have pain for a longer period of time and required a longer convalescence period. Cold-steel uvulopalatoplasty is an inexpensive and viable option to outpatient laser-assisted uvulopalatoplasty for the reduction of snoring in select patients.
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PMID:Efficacy of cold-steel uvulopalatoplasty. 890 50

A cold-regulated operon, rbpA1-rpsU, encodes an RNA-binding protein and a ribosomal protein in Anabaena variabilis M3. The level of expression of this gene cluster was about ten times higher at temperatures below 30 degrees C than at 38 degrees C. To study the role of the RbpA1 protein in vivo, we constructed insertional disruptants of rbpA1. These strains were totally devoid of RbpA1 protein but contained a normal level of the ribosomal protein S21, a product of the rpsU gene. The disruptants were morphologically normal at 38 degrees C, but at 22 degrees C they produced unusual cells at a low frequency. These cells were probably at an initial stage of proheterocyst formation. Various molecular events that are related to heterocyst initiation, namely, excision of the 11-kbp DNA element in nifD and the accumulation of transcripts of xisA and hetR, also occurred in the disruptants at 22 degrees C in the presence of nitrate ions, but these events did not occur in the presence of ammonium ions or at 38 degrees C. The results suggest that RbpA1 is required for enhanced repression of heterocyst initiation at low temperatures in the presence of nitrate. Possible mechanisms of the action of RabA1 are discussed.
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PMID:Disruption analysis of the gene for a cold-regulated RNA-binding protein, rbpA1, in Anabaena: cold-induced initiation of the heterocyst differentiation pathway. 903 67

Reintroduction of high levels of molecular oxygen after a hypoxic period is followed by a burst of nitric oxide (NO), peroxynitrite, and oxygen free radicals (OFR), which are highly cytotoxic. This study indicates that hyperoxic reoxygenation of cyanotic immature hearts on cardiopulmonary bypass (CPB) induces a reoxygenation injury and that, by reducing NO and OFR production during institution of CPB with subsequent reoxygenation under blood cardioplegic arrest, this oxygen-related damage can be avoided and biochemical and functional status improved. Of 25 immature piglets (3-5 kg, two to three weeks old), 6 underwent one hour of CPB including thirty minutes of aortic clamping with substrate-enriched modified blood cardioplegia (hypocalcemic, alkalotic, and hyperosmolar; warm induction-cold replenishment-warm reperfusion) without preceding hypoxia (controls). Nineteen others were made hypoxic (arterial [Po2] 20-30 mmHg) for up to two hours by lowering the fraction of inspired oxygen (FIO2) on ventilator. These hypoxic piglets were then reoxygenated on CPB at different Po2 levels (hyperoxic, normoxic, or hypoxic) for five minutes, followed by the aforementioned blood cardioplegic (BCP) arrest regimen. Myocardial conjugated diene (CD) production as a marker of lipid peroxidation, and NO production, determined as its spontaneous oxidation products, nitrite (NO2-) and nitrate (NO3-), were assessed during blood cardioplegic induction, and antioxidant reserve capacity was determined by incubating myocardium in the oxidant t-butylhydroperoxide (t-BHP). Myocardial function was evaluated from end-systolic elastance (Ees, conductance catheter). Blood cardioplegic arrest caused no functional or biochemical changes in normoxic control immature piglets. In contrast, brief reoxygenation at PO2 > 400 mmHg, followed by BCP-arrest (hyperoxic) resulted in marked CD production (42 +/- 4 vs 3 +/- 1 A233 nm/minute/100 g; P < 0.05), and NO production (4500 +/- 500 vs 450 +/- 32 mmol/minute/100 g; P < 0.05) during blood cardioplegic induction, reduced antioxidant reserve capacity (malondialdehyde [MDA] at 4.0 mM of t-BHP: 1342 +/- 59 vs 958 +/- 50 nM/g protein; P < 0.05), and caused profound myocardial dysfunction; Ees recovered only 21 +/- 2% (vs 104 +/- 7; P < 0.05), despite the blood cardioplegic regimen shown to be cardioprotective in control normoxic piglets. Conversely, controlling initial PO2 to normoxic (100 mmHg) or hypoxic (20-30 mmHg) levels reduced lipid peroxidation (CD production 16 +/- 2, 2 +/- 1 A233nm/minute/100 g) and NO production (1264 +/- 736, 270 +/- 182 mmol/minute/100 g), restored antioxidant reserve capacity (MDA at 4.0 mM of t-BHP: 940 +/- 95, 982 +/- 88 nM/g protein), and allowed significant functional recovery (58 +/- 11% and 83 +/- 8%), in a PO2-dependent fashion. The authors conclude that reoxygenation of hypoxemic immature hearts by initiating hyperoxic CPB causes oxidant-related damage characterized by lipid peroxidation, enhanced NO production, and reduced antioxidants, leading to functional depression that nullifies the cardioprotective effects of blood cardioplegia. These detrimental effects can be reduced in a PO2-dependent fashion by controlling initial PO2 on CPB and subsequent reoxygenation during blood cardioplegic arrest.
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PMID:Nitric-oxide-induced reoxygenation injury in the cyanotic immature heart is prevented by controlling oxygen content during initial reoxygenation. 907 Nov 94

Primary Raynaud's phenomenon (PRP) is characterized by cold- or stress-induced transient attacks of impaired skin circulation in fingers and/or toes. PRP displays seasonal variation with less severe symptoms in the summer. The aetiology has not been clarified. The aims of the present study were (a) to assess the influence of cold exposure on the plasma levels of the nitric oxide (NO) metabolite, nitrate, in patients with PRP and in healthy control subjects; and (b) to investigate whether there is a seasonal variation in these plasma levels. In a group of women with PRP and matched control subjects, venous blood was sampled before and at the end of a 40-min period of whole-body cooling. The study was performed with the same protocol on two occasions; once in the winter and once in the summer. A seasonal variation was detected with higher plasma levels of nitrate in the winter than in the summer, both in PRP and in control subjects. However, the plasma level of nitrate was not changed in response to cold exposure on any occasion, either in the patient or in the control group. Our study indicates that NO formation is up-regulated in response to cold weather in both study groups. However, NO formation does not seem to be increased in response to whole-body cooling, either in PRP patients or in healthy subjects. Further investigations are required to reveal whether the observed seasonal variation in NO formation is a universal phenomenon in man.
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PMID:Plasma nitric oxide metabolite in women with primary Raynaud's phenomenon and in healthy subjects. 917 67

The effect of sodium-nitrite (NaNO2) and potassium nitrate (KNO3) on the outgrowth and toxigenesis of nonproteolytic Clostridium botulinum in vacuum-packed cold-smoked rainbow trout stored for-six weeks was studied in two inoculation studies at slightly abusive storage temperatures of 4 degrees C and 8 degrees C. The depletion rate of nitrite and the reduction rate of nitrate to nitrite as well as the effect of nitrite and nitrate on the shelf-life of the product during eight weeks' storage period were also determined. The nitrite concentrations were reduced from 166 mg/kg +/- 9 (mean +/- SE), to a final concentration of 34 mg/kg +/- 2 and 11 mg/kg +/- 2, and the nitrate concentrations from 686 mg/kg +/- 67 to 465 mg/kg +/- 140 and 427 mg/kg +/- 33 at 4 degrees C and 8 degrees C respectively. The nitrite depletion rate was more rapid at 8 degrees C; nitrate depletion was not significantly affected by temperature. A considerable amount of nitrite was detected in the nitrate-treated samples in the latter half of the storage period. At 4 degrees C the aerobic plate counts were significantly lower in the samples treated with NaNO2 + NaCl and with KNO3 + NaCl as compared to the NaCl-treated controls, while at 8 degrees C the differences were smaller. The sensorial shelf-life of the product was considerably extended by nitrite and nitrate curing. The nitrite and nitrate concentrations used in the present study did not completely inhibit the toxigenesis of nonproteolytic C. botulinum during the six-week storage period, although the number of toxic samples was considerably reduced by nitrite and nitrate curing.
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PMID:Sodium nitrite and potassium nitrate in control of nonproteolytic Clostridium botulinum outgrowth and toxigenesis in vacuum-packed cold-smoked rainbow trout. 923 23

The measured parameters for the formation of peroxynitrous acid via the reaction of acidified hydrogen peroxide with nitrous acid and its self-decomposition corroborate with an earlier suggested mechanism in which H2NO2+ nitrosates H2O2. The activation energies for the formation and decay of peroxynitrous acid have been determined to be 15 and 19 kcal/mol, respectively. We found that perchlorate, nitrate, sulfate and phosphate ions have no effect on the formation and decay rates, whereas chloride ions enhance the rate of the formation of peroxynitrous acid at low peroxide concentrations, and have no effect at high peroxide concentrations. This suggests that at relatively low concentration of H2O2, Cl- competes with H2O2 for H2NO+ to yield NOCl, which may also nitrosate H2O2. Simulation of the experimentally observed parameters for the decay and formation rates suggests that it is not possible to obtain 100% yield of peroxynitrite under any condition. High yields of peroxynitrite were obtained at room temperature using an efficient double mixer where acidified peroxide was mixed with nitrite; after an appropriate delay, the reaction was quenched with strong alkali. An excess of more than 10% of H2O2 over nitrite, or vice versa, is sufficient to get ca. 85-90% of peroxynitrite, almost free from nitrite or H2O2, respectively. The results also suggest that conventional use of ice-cold solutions of the reactants and the alkali solutions is not required if an efficient mixer and appropriate quenching times are available.
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PMID:Determination of optimal conditions for synthesis of peroxynitrite by mixing acidified hydrogen peroxide with nitrite. 955 78

The kinetics and mechanism of reversible cold inactivation of the tetrameric enzyme tryptophanase have been studied. Cold inactivation is shown to occur slowly in the presence of K+ ions and much faster in their absence. The W330F mutant tryptophanase undergoes rapid cold inactivation even in the presence of K+ ions. In all cases the inactivation is accompanied by a decrease of the coenzyme 420-nm CD and absorption peaks and a shift of the latter peak to shorter wavelengths. The spectral changes and the NaBH4 test indicate that cooling of tryptophanase leads to breaking of the internal aldimine bond and release of the coenzyme. HPLC analysis showed that the ensuing apoenzyme dissociates into dimers. The dissociation depends on the nature and concentration of anions in the buffer solution. It readily occurs at low protein concentrations in the presence of salting-in anions Cl-, NO3- and I-, whereas salting-out anions, especially HPO4(2-), hinder the dissociation. K+ ions do not influence the dissociation of the apoenzyme, but partially protect holotryptophanase from cold inactivation. Thus, the two processes, cold inactivation of tryptophanase and dissociation of its apoform into dimers exhibit different dependencies on K+ ions and anions.
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PMID:Cold inactivation and dissociation into dimers of Escherichia coli tryptophanase and its W330F mutant form. 965 98

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