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R Diaz

Publications and source records attributed to R Diaz.

At least 37 records · Page 2Linked to original sources
PubMed2001

Regulation of MAP kinase by calcium-sensing receptor in bovine parathyroid and CaR-transfected HEK293 cells.

Regulation of the extracellular signal-regulated kinase 1 and 2 (ERK1/2) pathway by the extracellular calcium (Ca2+o)-sensing receptor (CaR) was investigated in bovine parathyroid and CaR-transfected human embryonic kidney (HEKCaR) cells. Elevating Ca2+o or adding the selective CaR activator NPS R-467 elicited rapid, dose-dependent phosphorylation of ERK1/2. These phosphorylations were attenuated by pretreatment with pertussis toxin (PTX) or by treatment with the phosphotyrosine kinase (PTK) inhibitors genistein and herbimycin, the phosphatidylinositol-specific phospholipase C (PI-PLC) inhibitor U-73122, or the protein kinase C (PKC) inhibitor GF109203X and were enhanced by the PKC activator phorbol 12-myristate 13-acetate. Combined treatment with PTX and inhibitors of both PKC and PTK nearly abolished high Ca2+o-evoked ERK1/2 activation in HEKCaR cells, demonstrating CaR-mediated coupling via both Gq and G(i). High Ca2+o increased serine phosphorylation of the 85-kDa cytosolic phospholipase A2 (cPLA2) in both parathyroid and HEKCaR cells. The selective mitogen-activated protein kinase (MAPK) inhibitor PD98059 abolished high-Ca2+o)-induced ERK1/2 activation and reduced cPLA2 phosphorylation in both cell types, documenting MAPK's role in cPLA2 activation. Thus our data suggest that the CaR activates MAPK through PKC, presumably through Gq/11-mediated activation of PI-PLC, as well as through G(i)- and PTK-dependent pathway(s) in bovine parathyroid and HEKCaR cells and indicate the importance of MAPK in cPLA2 activation.

Animals↗
PubMed2001

Transmission of tuberculosis in Havana, Cuba: a molecular epidemiological study by IS6110 restriction fragment length polymorphism typing.

The combination of molecular and conventional epidemiological methods has improved the knowledge about the transmission of tuberculosis in urban populations. To examine transmission of tuberculosis in Havana, Cuba, with DNA fingerprinting, we studied 51 out of 92 Mycobacterium tuberculosis strains isolated from tuberculosis patients who resided in Havana and whose infection was culture-confirmed in the period from September 1997 to March 1998. Isolates from 28 patients (55%) had unique IS6110 restriction fragment length polymorphism (RFLP) patterns, while isolates from 23 others (45%) had identical patterns and belonged to 7 clusters. Three clusters consisting of six, five and two cases were each related to small outbreaks that occurred in a closed setting. Three other clustered cases were linked to a large outbreak that occurred in another institution. Younger patients were more correlated to clustering than older ones. The finding that 45% of the isolates had clustered RFLP patterns suggests that recent transmission is a key factor in the tuberculosis cases in Havana. The IS6110 RFLP typing made it possible to define the occurrence of outbreaks in two closed institutions.

Adult↗
PubMed2001

Hypothalamic function in response to 2-deoxy-D-glucose in long-term abstinent alcoholics.

BACKGROUND: The body adapts to diverse stressful stimuli with a response characterized by activation of the hypothalamic-pituitary-adrenal (HPA) axis. Chronic alcohol consumption can cause changes in the function of this neuroendocrine system. Although many studies have examined this phenomenon in drinking and recently sober alcoholics, few studies have examined HPA axis function in long-term sober alcoholics. METHODS: To characterize HPA axis function in long-term sober alcoholics, we used a challenge paradigm with 2-deoxy-d-glucose (2-DG). An infusion of 2-DG (a nonmetabolizable glucose analog) induces a well-characterized stress response. In a previous study, our laboratory found an exaggerated corticotropin and cortisol response in alcoholics abstinent 3 weeks; in this investigation we compared the effects of an infusion of 2-DG on 19 healthy volunteers and 20 community-living alcoholics who had been abstinent more than 6 months. RESULTS: In contrast to the previous study, long-term sober alcoholics did not have an exaggerated corticotropin and cortisol response after 2-DG. CONCLUSIONS: Previously observed abnormalities in cortisol regulation in 3-week-sober alcoholics may be related to the acute effects of recent alcohol consumption and withdrawal. Future investigations into the metabolic function of alcoholics, particularly investigations involving the HPA system, should consider the possibility that normalization may not occur until long-term abstinence has been achieved.

Adrenocorticotropic Hormone↗
PubMed2000

Analysis of the polymorphic (GT)(n) repeat at the dopamine beta-hydroxylase gene in Spanish patients affected by schizophrenia.

The presence of a polymorphic (GT)(n) repeat, a microsatellite repeat, at the human dopamine beta-hydroxylase (DBH) gene had been previously investigated in healthy people and in schizophrenic patients. The different DBH genotypes had been found to be associated to different DBH biochemical function, but no differences were found in the allelic and genotype frequencies between schizophrenic and control groups. To further clarify the potential involvement of the variation at the DBH gene in schizophrenia we have studied the DBH (GT)(n) repeat in a sample of 47 Spanish schizophrenic patients, in their healthy relatives (n = 72), and in a control population (n = 74). We have been able to identify five different variants of the DBH gene (A1, A2, A3, A4, A5) in the different groups. Subsequent statistical analysis revealed that the genotypes as well as the allele frequencies did not differ significantly among schizophrenic patients and the control population. Interestingly, the allelic variant A2 and the genotype A4/A2 were significantly more frequent in schizophrenic patients as compared with their healthy relatives. However, the association of the A2 allele with schizophrenia was not supported by the haplotype relative risk analysis of transmitted versus nontransmitted alleles. Therefore, although it will be important to extend the present analysis in a larger sample of schizophrenic patients and controls, our results suggest that the (GT)(n) does not seem to play a major role in the genetics of schizophrenia at least in this group of Spanish schizophrenic patients. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:88-92, 2000.

Alleles↗
PubMed2000

Expression of calcium-sensing receptor gene by avian parathyroid gland in vivo: relationship to plasma calcium.

Calcium-sensing receptor (CaR) gene expression and parathyroid hormone (PTH) content were evaluated in situ in chicken parathyroid glands (PG) in relation to changes in plasma calcium. The CaR gene is expressed by the parathyroid chief cells, the same cells that store and secrete PTH. An increase in plasma calcium, achieved by repletion of vitamin D-deficient chicks with a normal diet, by PTH injection, or during eggshell formation, increased the expression of the CaR gene. Low plasma calcium concentration in vitamin D-deficient chicks or in layers, before or after eggshell formation, was associated with decrease in CaR gene expression in the PG. The level of CaR gene expression was inversely correlated with the PTH content of the PG. The results of this study demonstrate for the first time that, in contrast to mammals, the CaR gene expression in the PG of the chicken is inversely associated with changes in plasma calcium.

Animals↗
PubMed1999

Single-bolus tenecteplase compared with front-loaded alteplase in acute myocardial infarction: the ASSENT-2 double-blind randomised trial.

BACKGROUND: Bolus fibrinolytic therapy facilitates early efficient institution of reperfusion therapy. Tenecteplase is a genetically engineered variant of alteplase with slower plasma clearance, better fibrin specificity, and high resistance to plasminogen-activator inhibitor-1. We did a double-blind, randomised, controlled trial to assess the efficacy and safety of tenecteplase compared with alteplase. METHODS: In 1021 hospitals, we randomly assigned 16,949 patients with acute myocardial infarction of less than 6 h duration rapid infusion of alteplase (< or = 100 mg) or single-bolus injection of tenecteplase (30-50 mg according to bodyweight). All patients received aspirin and heparin (target activated partial thromboplastin time 50-75 s). The primary outcome was equivalence in all-cause mortality at 30 days. FINDINGS: Covariate-adjusted 30-day mortality rates were almost identical for the two groups--6.18% for tenecteplase and 6.15% for alteplase. The 95% one-sided upper boundaries of the absolute and relative differences in 30-day mortality were 0.61% and 10.00%, respectively, which met the prespecified criteria of equivalence (1% absolute or 14% relative difference in 30-day mortality, whichever difference proved smaller). Rates of intracranial haemorrhage were similar (0.93% for tenecteplase and 0.94% for alteplase), but fewer non-cerebral bleeding complications (26.43 vs 28.95%, p=0.0003) and less need for blood transfusion (4.25 vs 5.49%, p=0.0002) were seen with tenecteplase. The rate of death or non-fatal stroke at 30 days was 7.11% with tenecteplase and 7.04% with alteplase (relative risk 1.01 [95% CI 0.91-1.13]). INTERPRETATION: Tenecteplase and alteplase were equivalent for 30-day mortality. The ease of administration of tenecteplase may facilitate more rapid treatment in and out of hospital.

Aged↗
PubMed1999

Clinical significance of thrombocytopenia during a non-ST-elevation acute coronary syndrome. The platelet glycoprotein IIb/IIIa in unstable angina: receptor suppression using integrilin therapy (PURSUIT) trial experience.

BACKGROUND: The significance of thrombocytopenia in patients experiencing an acute coronary syndrome (ACS) has not been examined systematically. We evaluated this condition in a large non-ST-elevation ACS clinical trial, with particular interest paid to its correlation with clinical outcomes. METHODS AND RESULTS: Patients presenting without persistent ST elevation during an ACS were randomized to receive a double-blind infusion of the platelet glycoprotein (GP) IIb/IIIa inhibitor eptifibatide or placebo in addition to other standard therapies including heparin and aspirin. The primary end point was death/nonfatal myocardial infarction (MI) at 30 days, whereas bleeding and stroke were the main safety outcomes. Thrombocytopenia (nadir platelet count <100x10(9)/L or <50% of baseline) occurred in 7.0% of enrolled patients. The time to onset was a median of 4 days in both treatment arms. Patients with thrombocytopenia were older, weighed less, were more likely nonwhite, and had more cardiac risk factors. These patients experienced significantly more bleeding events: they were more than twice as likely to experience moderate/severe bleeding after adjustment for confounders. Univariably, ischemic events (stroke, MI, and death) occurred significantly (P<0.001) more frequently in patients with thrombocytopenia; multivariable regression modeling preserved this association with death/nonfatal MI at 30 days. Neither the use of heparin or eptifibatide was found to independently increase thrombocytopenic risk. CONCLUSIONS: Although causality between thrombocytopenia and adverse clinical events could not be established definitively, thrombocytopenia was highly correlated with both bleeding and ischemic events, and the presence of this condition identified a more-at-risk patient population.

Acute Disease↗
PubMed1999

Manifestations of slow site exchange processes in solution NMR: a continuous Gaussian exchange model.

The effects of site exchange due to slow conformational changes in rapidly rotating molecules in solution are examined in detail. Significant gaps in the currently available theory are filled. The effects of site exchange on the lineshape, decay of a simple spin-echo, decay of the even echoes in a Carr-Purcell-Meiboom-Gill (CPMG) pulse-sequence, and decay of the transverse magnetization in a resonant spin-locking field are investigated. Both trajectory and stochastic operator approaches are formulated and shown to be completely equivalent whenever the dynamics of population transfers among the inequivalent sites is governed by either a stationary or a nonstationary Markov process. A nonstationary Markov process may result from Brownian dynamics (a stationary Markov process) in a larger conformational space that contains the subspace of inequivalent sites. A continuous Gaussian exchange model is formulated in which a nucleus undergoes continuous one-dimensional motion in a harmonic potential well that is located in a linear chemical shift gradient. The effects of this Gaussian exchange model on the lineshape, simple spin-echo decay, and decay of the even echoes of a CPMG pulse train are treated rigorously via the trajectory approach. Compact analytical expressions are obtained for the relevant correlation functions in each case. The relevant decays are found to be exponential in the very short time and long time limits, which are not necessarily experimentally significant in any given case. In the fast exchange limit the relevant decays are exponential at all times, and explicit formulas are given for their decay rates. In the long time limit, all discrete multisite models with the same intrinsic Ro2 at every site are shown to be completely equivalent to a continuous Gaussian model with appropriate relaxation time and variance of the Larmor frequency. The effects of this Gaussian exchange model on the decay of the transverse magnetization in a resonant spin-locking field are treated heuristically by a trajectory approach. The intrinsic contribution (Ro1rho) of rapid rotations and dipole-dipole interactions to relax the transverse magnetizations of two nuclei of the same kind in the presence of a (nearly) resonant spin-locking field is also derived and found to be practically the same as the intrinsic contribution, Ro2, of those same rotations to the simple and CPMG spin-echo decay rates and linewidth. Literature data for the linewidth, decay rate of the CPMG even spin-echoes, and R(1rho) decay rate for the A9-H2 protons of adenines at the central TpA step in the sequence, 5'-GCAGGTTTAAACCTCG-3', are analyzed using the Gaussian exchange model to assess the time-scale and variance of the site exchange process as well as the intrinsic Ro2 rate. Although a single Gaussian exchange process with appropriate parameters can fit these three A9-H2 data rather well, this particular "solution" cannot be reconciled with NMR relaxation data on other protons in the same DNA molecule. Rather good agreement with all of the observations is obtained by using a model of two concurrent Gaussian exchange processes, whose relaxation times, tau = 7 and 460 micros, differ in time-scale by a factor of 65. The insensitivity of R1rho in the presence of a fast site exchange process to much slower concurrent site exchange processes is explicitly demonstrated. Protocols for detecting and characterizing a second slow site exchange process are suggested.

Adenine↗
PubMed1998

The calcium-sensing receptor is localized in caveolin-rich plasma membrane domains of bovine parathyroid cells.

Parathyroid cells have an intracellular machinery for parathyroid hormone (PTH) secretion that is inversely regulated by the extracellular calcium concentration (Ca2+o). The recently characterized Ca2+o-sensing receptor (CaR) is a G protein-coupled, seven-transmembrane receptor mediating the inhibitory effects of high Ca2+o on PTH secretion. The CaR's precise cell surface localization and the signal transduction pathway(s) mediating its inhibitory effects on PTH secretion have not been characterized fully. Here, we demonstrate that the CaR resides within caveolin-rich membrane domains in bovine parathyroid cells. Chief cells within bovine parathyroid glands exhibit a similar pattern of staining for caveolin-1 and for alkaline phosphatase, a glucosylphosphatidylinositol-anchored protein often enriched in caveolae. Purified caveolin-enriched membrane fractions (CEMF) from bovine parathyroid cells are highly enriched in the CaR and alkaline phosphatase. Other signaling proteins, including Gq/11, eNOS, and several protein kinase C isoforms (i.e. alpha, delta, and zeta), are also present in CEMF. Activation of the CaR by high Ca2+o increases tyrosine phosphorylation of caveolin-1 in CEMF, suggesting that CaR-mediated signal transduction potentially involved in Ca2+o-regulated processes in parathyroid cells occur in caveolae-like domains.

Alkaline Phosphatase↗
PubMed1998

Sodium and ionic strength sensing by the calcium receptor.

The calcium-sensing receptor (CaR) is activated by small changes in extracellular calcium [Ca2+]o) in the physiological range, allowing the parathyroid gland to regulate serum [Ca2+]o; however, the CaR is also distributed in a number of other tissues where it may sense other endogenous agonists and modulators. CaR agonists are polycationic molecules, and charged residues in the extracellular domain of the CaR appear critical for receptor activation through electrostatic interactions, suggesting that ionic strength could modulate CaR activation by polycationic agonists. Changes in the concentration of external NaCl potently altered the activation of the CaR by external Ca2+ and spermine. Ionic strength had an inverse effect on the sensitivity of CaR to its agonists, with lowering of ionic strength rendering the receptor more sensitive to activation by [Ca2+]o and raising of ionic strength producing the converse effect. Effects of osmolality could not account for the modulation seen with changes in NaCl. Other salts, which differed in the cationic or anionic species, showed shifts in the activation of the CaR by [Ca2+]o similar to that elicited by NaCl. Parathyroid cells were potently modulated by ionic strength, with addition of 40 mM NaCl shifting the EC50 for [Ca2+]o inhibition of parathyroid hormone by at least 0.5 mM. Several CaR-expressing tissues, including regions of the brain such as the subfornical organ and hypothalamus, could potentially use the CaR as a sensor for ionic strength and NaCl. The Journal guidelines state that the summary should be no longer than 200 words.

Adenosine Triphosphate↗
PubMed1998

Distinct ontogeny of glucocorticoid and mineralocorticoid receptor and 11beta-hydroxysteroid dehydrogenase types I and II mRNAs in the fetal rat brain suggest a complex control of glucocorticoid actions.

Glucocorticoids (GCs) act via intracellular mineralocorticoid (MR) and glucocorticoid receptors (GR). However, it has recently been recognized that GC access to receptors is determined by the presence of tissue-specific 11beta-hydroxysteroid dehydrogenases (11beta-HSDs) that catalyze the interconversion of active corticosterone and inert 11-dehydrocorticosterone. 11beta-HSD type 1 (11beta-HSD1) is a bidirectional enzyme in vitro that acts predominantly as a reductase (regenerating corticosterone) in intact neurons. In contrast, 11beta-HSD type 2 (11beta-HSD2) is a higher affinity exclusive dehydrogenase that excludes GCs from MR in the kidney, producing aldosterone-selectivity in vivo. We have examined the ontogeny of 11beta-HSD mRNAs and enzyme activity during prenatal brain development and correlated this with GR and MR mRNA development. These data reveal that (1) 11beta-HSD2 mRNA is highly expressed in all CNS regions during midgestation, but expression is dramatically reduced during the third trimester except in the thalamus and cerebellum; (2) 11beta-HSD2-like activity parallels closely the pattern of mRNA expression; (3) 11beta-HSD1 mRNA is absent from the CNS until the the third trimester, and activity is low or undectectable; and (4) GR mRNA is highly expressed throughout the brain from midgestation, but MR gene expression is absent until the last few days of gestation. High 11beta-HSD2 at midgestation may protect the developing brain from activation of GR by GCs. Late in gestation, repression of 11beta-HSD2 gene expression may allow increasing GC activation of GR and MR, permitting key GC-dependent neuronal and glial maturational events.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1998

Changes in cultured arterial smooth muscle cells isolated from chicks upon cholesterol feeding.

We have developed cultures of smooth muscle cells (SMC) isolated from arterial hypercholesterolemic chicks (cholesterol-SMC). These cultures are suitable for the study at the molecular level of the changes in arterial SMC induced by a cholesterol diet. By using a strong dose of cholesterol (5%) for 10 d, we obtained very proliferative SMC which became foam cells after 30 d in culture. On the other hand, SMC cultures isolated from control-fed chicks had a lower growth rate than the SMC ones under the same culture conditions. DNA synthesis was fourfold greater in cholesterol-SMC than in control-SMC cultures. Intracellular cholesterol concentrations were the same in both cholesterol and control SMC during the first 14 d of culture but afterward increased in differing ways: after 20 d of culture the cholesterol-SMC increased their cholesterol content to double the control. We give here the results obtained from transmission electron microscopy, lipid analysis, proliferation studies, DNA, RNA and protein synthesis, and then discuss their implications.

Animals↗
PubMed1998

Durability of mitral valve repair for degenerative disease.

BACKGROUND: Degenerative mitral valve disease is the most common cause of mitral regurgitation in the United States. Mitral valve repair is applicable in the majority of these patients and has become the procedure of choice. OBJECTIVE: This study was undertaken to identify factors influencing the durability of mitral valve repair. PATIENTS AND METHODS: Between 1985 and 1997, 1072 patients underwent primary isolated mitral valve repair for valvular regurgitation caused by degenerative disease. Repair durability was assessed by multivariable risk factor analysis of reoperation. It was supplemented by a search for valve-related risk factors for death before reoperation. Three hospital deaths occurred (0.3%); complete follow-up (4152 patient-years) was available in 1062 of 1069 hospital survivors (99.3%). RESULTS: At 10 years, freedom from reoperation was 93%. Among 30 patients who required reoperation for late mitral valve dysfunction, the repair failed in 16 (53%) as a result of progressive degenerative disease. Durability of repair was adversely affected by pathologic conditions other than posterior leaflet prolapse, use of chordal shortening, annuloplasty alone, and posterior leaflet resection without annuloplasty. Durability was greatest after quadrangular resection and annuloplasty for posterior leaflet prolapse and was enhanced by the use of intraoperative echocardiography. Death before reoperation was increased in patients having isolated anterior leaflet prolapse or valvular calcification and by use of chordal shortening or annuloplasty alone. CONCLUSIONS: Repair durability is greatest in patients with isolated posterior leaflet prolapse who have posterior leaflet resection and annuloplasty. Chordal shortening, annuloplasty alone, and leaflet resection without annuloplasty jeopardize late results.

Calcinosis↗
PubMed1998

Anti-phosphatidylcholine antibodies in patients with brucellosis.

An indirect ELISA was adapted to measure individual classes of anti-phosphatidylcholine (PC) antibodies in patients with brucellosis; a comparison was made with patients with other infectious diseases and healthy human controls. Immunoconjugates of alpha, gamma or mu chain specificity were used. The results were compared with those of conventional tests for brucella antibodies, Rose Bengal, microagglutination (MAT) and Coombs tests, as well as with VDRL. The results indicated that although all sera from patients with brucellosis were VDRL negative, 97% of them (30 of 31) had higher levels of IgA or IgG anti-PC antibodies than the healthy control group. The IgM anti-PC antibodies isotype was not discriminatory between both groups. Seven sera (19%) from patients with other infections had values of IgG anti-PC higher than those of the healthy group; three of them were VDRL positive. The mean ELISA values of IgG and IgA anti-PC (serum diluted 1 in 1600) in the brucellosis and healthy groups were: IgG, 0.80 SEM 0.17 versus 0.23 SEM 0.10; and IgA, 0.86 SEM 0.26 versus 0.35 SEM 0.15. The sensitivity and specificity for the ELISA-PC were: IgG, 96.8% and 96.5%, respectively; IgA, 90.3% and 89.7%, respectively. Only one of 14 individuals clinically cured from brucellosis had significant IgG anti-PC antibodies. In contrast, all of these patients gave positive values in the conventional test for brucellosis. No correlation was found between the serum levels of IgA, IgG anti-PC by ELISA-PC and the results of the MAT or Coombs tests.

Agglutination Tests↗