Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Role Playing”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources
PubMed1991

Trends in the 5' vs. 3' flanks of oligonucleotides in eukaryotic and prokaryotic genomes: the asymmetric roles played by cytosine and guanine.

Studies of sequence context preferences of oligonucleotides composed of (G/C)n and (A/T)m blocks (n + m = 3,4,5) unravel strong patterns. Comparisons of the 5' and 3' nearest neighbor doublets flanking these oligomers reveal the preference of (G/C)2 to be positioned immediately next to the (A/T)m block, enclosing it by (G/C) nucleotides rather than extending the (G/C)n block. That is, for a (G/C)n(A/T)m oligomer and a (G/C)2 doublet, (G/C)n(A/T)m(G/C)2 greater than (G/C)n + 2 (A/T)m. Similarly for an (A/T)m(G/C)n oligomer, (G/C)2(A/T)m(G/C)n greater than (A/T)m(G/C)n + 2. In an analogous manner, (A/T)2 flanking doublets prefer enclosing the (G/C)n blocks, although these patterns are weaker. Here we show a strong, direct relationship between the magnitude of the trends and the presence of Cs in the (G/C)n block in the (G/C)n(A/T)m oligomer, and the presence of Gs in the complementary (A/T)m(G/C)n oligomers. The trends are stronger in eukaryotic than in prokaryotic sequences. They are stronger for longer (G/C)n and shorter (A/T)m blocks. We suggest that the preference for (A/T)m to be enclosed by (G/C) rather than be flanked by them on only one side is related to DNA structure and DNA-protein interaction. Sequences of the (G/C)(A/T)(G/C) type may have more homogeneous minor groove geometry. In particular, the strong G vs. C asymmetry in the trends may be related to pyrimidine-purine junctions, possibly to CG sequences.

Cytosine↗
PubMed1981

Normal and retrograde blood supply to the body of the mandible in the dog. II. The role played by periosteo-medullary and symphyseal anastomoses.

An experimental study was carried out in 8 dogs to delineate the blood supply to the body of the mandible under normal conditions and when the central (medullary) circulation was blocked. A vascular blocking technique combined with selective arterial perfusion using different colored perfusates was used. The results were based on an evaluation of cleared specimens, microradiography and histology. Under normal conditions, the inferior alveolar artery was shown to be the sole source of perfusate to the entire mandibular body, marginal gingiva and the subperiosteal layer, without any contribution from facial artery branches. Several perfused symphyseal anastomoses were found. When the medullary circulation was blocked, retrograde perfusion was evident only in the medullary bone of the frontal region 30 min. after blocking. Marked periosteal and symphyseal vascularity and an increased medullary perfusion were seen 3 days later. 30 days after vascular blocking, perfusion was demonstrated throughout the entire bone including dental pulps. The facial artery was found to be the source of the retrograde perfusion through symphyseal and periosteo-medullary anastomoses in cases with blocked central (medullary) circulation.

Angiography↗
PubMed2003

The role played by neural crest cells in the development of syndrome X: a hypothesis.

This study evaluated the components and the related hormone releasing organs, the mechanism of action of these hormones, and the origins of the cells and organs in a disorder known as metabolic syndrome X, the prevalence of which is rapidly increasing particularly among the adult population of industrial societies. Metabolic syndrome X, involving carbohydrate and lipid metabolism disorders and cardiovascular disorders caused by the release of primary hormones, alpha and beta cells of the islets of Langerhans of pancreas, adrenal gland medulla's chromaffin cells, sympathetic nervous system neurons and ganglia, adenohypophysis, neurohypophysis and hypothalamus, were evaluated for being neuroectodermal and mainly having neural crest origin. Generally the cells, tissues and organs involved are neuroectodermal and especially have neural crest origins; and to conclude, in prevention, diagnosis and treatment of this disorder the priority is the analysis and understanding of the migration, differentiation and adaptation at the target of neural crest cells.

Humans↗
PubMed2003

Apoptosis induced in neuronal cells by oxidative stress: role played by caspases and intracellular calcium ions.

Reactive oxygen species (ROS) have been implicated in the pathophysiology of many neurologic disorders and brain dysfunction. In the same pathological settings evidence has been provided in favour of a participation of intracellular Ca(2+) concentration altered homeostasis in the chain of events leading to neuronal apoptosis. In the present review literature reports and experimental data on the relationship between caspase activation and alteration of intracellular calcium concentrations in the mechanisms triggering neuronal apoptosis are discussed. The data gathered support the conclusion that during oxidative stress in neuronal cells the production of ROS triggers a mechanism that, through the release of cytochrome c from mitochondria and caspase-3 activation, leads to apoptosis; the concomitant ROS-mediated elevation of intracellular Ca(2+) concentration triggers caspase-2 activation but both events do not seem to be involved in cell death.

Animals↗
PubMedDate not supplied

Male/female ratio in centenarians: a possible role played by population genetic structure.

All the demographic surveys on the centenarians have highlighted that females outnumber males. The centenarians' male/female (M/F) ratio reported by most studies ranges between 1:4 and 1:7. A puzzling 1:2 ratio was observed in Calabria, a Southern Italian region. To our knowledge only in Sardinia a similar phenomenon had been previously observed. We have therefore used the data of the Italian Institute of Statistics to figure out the centenarians' M/F ratio in the Italian regions. We found that this ratio gradually decreases from South to North. Such a result is certainly due to many factors. Thus, we have explored the possibility, it is also influenced by the genetic structure of the Italian population. In fact, the distribution of the centenarians' M/F ratio turned out to be significantly correlated with the genetic structure of the Italian population as outlined by the principal component analysis.

Aged↗
PubMed2000

The roles played by crucial free radicals like lipid free radicals, nitric oxide, and enzymes NOS and NADPH in CCl(4)-induced acute liver injury of mice.

Mice were administered a single dose of carbon tetrachloride (CCl(4)) to induce acute liver injury. We found that lactate dehydrogenase (LDH) and glutamic pyruvic transaminase (GPT) levels in serum, as well as the level of thiobarbituric acid reaction substances (TBARS) in liver homogenate increased significantly in a manner both dose dependent and time dependent after CCl(4) administration. Such results suggest that the liver is susceptible to CCl(4) treatment and that lipid peroxidation is associated with CCl(4)-induced liver injury. The spin-trapping electron paramagnetic resonance (EPR) method was used to detect nitric oxide (NO) level in liver. The chemiluminescence method was also employed to measure the NO(2)(-)/NO(3)(-) concentration in serum. The NO levels in liver tissues and NO(2)(-)/NO(3)(-) concentration in serum were found to decrease significantly both in a dose-dependent manner and in time course after CCl(4) treatment. The nitric oxide synthase (NOS) II activity in the liver, in contrast, was found to increase significantly. Our study suggests that not only should the expression of NOS be analyzed but NO organ and blood concentration must be measured in the study of diseases involving nitric oxide. L-arginine treatment had no significant effect on the liver function of CCl(4)-treated mice. It was found that NO donor sodium nitroprusside (SNP; 50 or 100 microg/kg) treatment resulted in decreases of LDH, GPT, and TBARS levels, leading to a protective effect on CCl(4)-treated mice. On the other hand, N(G)-nitro-L-arginine methyl ester (L-NAME, 100 or 300 mg/kg) treatment caused more severe liver damage. Moreover, we have found in an in vitro EPR study that SNP could scavenge lipid peroxyl radical LOO&z.rad;. The above results together suggest that NO may protect CCl(4)-induced liver injury through scavenging lipid radical, inhibiting the lipid peroxidation chain reaction. On the basis of our analysis, we put forth two explanations for the stated discrepancy between NOS II and NO production: (i) NO was used up gradually in terminating lipid peroxidation and (ii) NADPH was depleted (on the basis of correlation evidence only).

Alanine Transaminase↗
PubMed2006

Thermodynamic characterization of triheme cytochrome PpcA from Geobacter sulfurreducens: evidence for a role played in e-/H+ energy transduction.

The facultative aerobic bacterium Geobacter sulfurreducens produces a small periplasmic c-type triheme cytochrome with 71 residues (PpcA) under anaerobic growth conditions, which is involved in the iron respiration. The thermodynamic properties of the PpcA redox centers and of a protonatable center were determined using NMR and visible spectroscopy techniques. The redox centers have negative and different reduction potentials (-162, -143, and -133 mV for heme I, III, and IV, respectively, for the fully reduced and protonated protein), which are modulated by redox interactions among the hemes (covering a range from 10 to 36 mV) and by redox-Bohr interactions (up to -62 mV) between the hemes and a protonatable center located in the proximity of heme IV. All the interactions between the four centers are dominated by electrostatic effects. The microscopic reduction potential of heme III is the one most affected by the oxidation of the other hemes, whereas heme IV is the most affected by the protonation state of the molecule. The thermodynamic properties of PpcA showed that pH strongly modulates the redox behavior of the individual heme groups. A preferred electron transfer pathway at physiologic pH is defined, showing that PpcA has the necessary thermodynamic properties to perform e-/H+ energy transduction, contributing to a H+ electrochemical potential gradient across the periplasmic membrane that drives ATP synthesis. PpcA is 46% identical in sequence to and shares a high degree of structural similarity with a periplasmic triheme cytochrome c7 isolated from Desulfuromonas acetoxidans, a bacterium closely related to the Geobacteracea family. However, the results obtained for PpcA are quite different from those published for D. acetoxidans c7, and the physiological consequences of these differences are discussed.

Cytochromes↗
PubMed2001

Time-resolved optical and infrared spectral studies of intermediates generated by photolysis of trans-RhCl(CO)(PR3)2. Roles Played in the Photocatalytic Activation of Hydrocarbons.

Described are picosecond and nanosecond time-resolved optical (TRO) spectral and nanosecond time-resolved infrared (TRIR) spectral studies of intermediates generated when the rhodium(I) complexes trans-RhCl(CO)L2 (L = PPh3 (I), P(p-tolyl)3 (II), or PMe3 (III)) are subjected to photoexcitation. Each of these species, which are precursors in the photocatalytic activation of hydrocarbons, undergoes CO labilization to form an intermediate concluded to be the solvated complex RhCl(Sol)L2 (A(i)). The picosecond studies demonstrate that an initial transient is formed promptly (<30 ps), which decays to A(i) with lifetimes ranging from 40 to 560 ps depending upon L and the medium. This is proposed on the basis of ab initio calculations to be a metal-to-ligand charge transfer (MLCT) excited state. Second-order rate constants (kCO) for reaction of the A(i) with CO were determined, and these depend on the nature of L and the solvent, the slowest rate being for A(I) in tetrahydrofuran (kCO = 7.1 x 10(6) M(-1) x s(-1)), the fastest being for A(III) in dichloromethane (1.3 x 10(9) M(-1) x s(-1)). Each A(i) also undergoes competitive unimolecular reaction with solvent to form long-lived transients with TRIR properties suggesting these to be Rh(III) products of oxidative addition. Although this was mostly suppressed by the presence of higher concentrations of CO (which trapped A(i) to re-form the starting complexes in each case), both TRO and TRIR experiments indicate that a fraction of the oxidative addition could not be quenched. Thus, the short-lived MLCT state or a vibrationally hot species formed during the decay of this excited state appears to participate directly in C-H activation.

Journal Article↗