PubMed Health⌕ Search

Biomedical subjects

M Castro

Publications and source records attributed to M Castro.

At least 19 recordsLinked to original sources
PubMed2002

Azimuthal anisotropy of K(0)(S) and Lambda+Lambda production at midrapidity from Au+Au collisions at sqrt[s(NN)]=130 GeV.

We report STAR results on the azimuthal anisotropy parameter v(2) for strange particles K(0)(S), Lambda, and Lambda at midrapidity in Au+Au collisions at sqrt[s(NN)]=130 GeV at the Relativistic Heavy Ion Collider. The value of v(2) as a function of transverse momentum, p(t), of the produced particle and collision centrality is presented for both particles up to p(t) approximately 3.0 GeV/c. A strong p(t) dependence in v(2) is observed up to 2.0 GeV/c. The v(2) measurement is compared with hydrodynamic model calculations. The physics implications of the p(t) integrated v(2) magnitude as a function of particle mass are also discussed.

Journal Article↗
PubMed2002

Midrapidity Lambda and Lambda(macro) production in Au+Au collisions at the square root of [s(NN)]=130 GeV.

We report the first measurement of strange (Lambda) and antistrange (Lambda macro) baryon production from square root of [s(NN)]=130 GeV Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC). Rapidity density and transverse mass distributions at midrapidity are presented as a function of centrality. The yield of Lambda and Lambda; hyperons is found to be approximately proportional to the number of negative hadrons. The production of Lambda; hyperons relative to negative hadrons increases very rapidly with transverse momentum. The magnitude of the increase cannot be described by existing hadronic string fragmentation models alone.

Journal Article↗
PubMed2002

The effect of ethanol on acrylic bone cement.

Prosthesis loosening is a major problem associated with the use of poly(methyl methacrylate) (PMMA) bone cement that may be related to a peri-implant vacuolisation commonly observed at bone-cement interface. Methyl methacrylate (MMA) monomer may be one of the cement components partly responsible for the mentioned vacuolisation due to a cytotoxic effect associated to this compound. Alcoholism has been related to bone necrosis in predisposed individuals. Furthermore, ethanol has been shown to clean material with adherent cement debris during cleaning procedure in laboratory. Consequently, we have decided to study whether ethanol will also be related to an increased liberation of MMA from the polymer matrix. 'In vitro' release studies using PMMA plates were conducted to access the role of ethanol on the liberation of the monomer. Contact angle measurements and surface tension estimation were also carried out in order to find a possible effect of ethanol on surface cement properties. Results suggest that ethanol, even in small quantities, enhances the leaching of the monomer from the polymer matrix, but does not considerably change the wettability properties of the cement surface.

Acrylic Resins↗
PubMed2002

Azathioprine in paediatric inflammatory bowel disease: an Italian multicentre survey.

AIM: To assess the efficacy and safety of azathioprine in a paediatric population with inflammatory bowel disease. PATIENTS AND METHODS: One hundred and twenty-three Italian children treated with azathioprine were studied retrospectively. The treatment duration and causes of its discontinuation, side-effects and variation in corticosteroid dose were assessed. RESULTS: The mean age at inflammatory bowel disease diagnosis was 9.8 +/- 3.6 years, and at the start of azathioprine therapy 11.8 +/- 4.3 years. The mean duration of treatment was 19 +/- 16 months. Fifty patients (41%) stopped treatment due to surgery (12%), prolonged remission (11%), non-response (7%), severe side-effects (7%) and poor compliance (3%). Of the 73 patients (59%) remaining on azathioprine, 11 had never been treated with corticosteroids, 27 were able to stop them and 35 were still on a very low daily dose (91% < 0.3 mg/kg). The difference in the daily corticosteroid dose between the beginning of azathioprine treatment (1 +/- 0.6 mg/kg) and the conclusion of the study (0.18 +/- 0.16 mg/kg) was statistically significant. Side-effects were recorded in 48 of the 123 patients (39%), but only eight required discontinuation of azathioprine. CONCLUSIONS: Azathioprine was efficacious in 70% of patients, but ineffective in 20% and induced severe toxicity in 7%. Corticosteroids were stopped or markedly reduced in 62% of patients, but they were never given in 9%.

Adolescent↗
PubMed2002

Glucocorticoid receptor gene polymorphisms in ACTH-secreting pituitary tumours.

OBJECTIVE: The inhibitory action of glucocorticoids on the hypothalamic-pituitary axis is disrupted in ACTH-secreting pituitary tumours. The molecular events leading to the development of these tumours and their relative resistance to glucocorticoids are unknown. We investigated the presence of mutations and polymorphisms of the glucocorticoid receptor (GR) gene in corticotropinoma and their possible relationship with the tissue-specific resistance to glucocorticoids. DESIGN AND METHODS: DNA or RNA was extracted from 18 corticotropinomas and the GR gene was amplified by the polymerase chain reaction (PCR) or reverse transcriptase-PCR followed by automated direct sequencing. RESULTS: We did not identify any mutation in the coding region and the exon-intron boundary regions of the GR gene. The polymorphism AAT > AGT at codon 363 (N363S) was found in 17% and the polymorphism AAT > AAC at codon 766 (N766N) in 11% of tumours, both in heterozygous state. The polymorphisms at codons 22 and 23, at introns 3 and 4, and at codon 618, previously described in normal population, were not observed. CONCLUSIONS: Our results show that GR gene mutations are rare and unlikely to contribute to the glucocorticoid resistance observed in corticotropinomas. Polymorphisms in the GR gene might confer a selective advantage to tumorigenesis in corticotropinoma. However, there was no relationship between GR gene polymorphism and clinical presentation, tumour size or surgery outcome, suggesting that tumour growth may not be directly related to alterations of the GR gene structure.

Adenoma↗
PubMed2002

Influence of apolipoprotein E polymorphism on plasma vitamin A and vitamin E levels.

BACKGROUND: Plasma concentrations of vitamins A and E are positively correlated with those of concurrent lipids and, on the other hand, lipid levels are influenced by apolipoprotein E polymorphism. Therefore, the effect of this polymorphism on both vitamins was analysed in an adult population. MATERIALS AND METHODS: Subjects were recruited from a working population. Their anthropometric, lifestyle and dietary intake variables and menopausal status were recorded. Their apolipoprotein E phenotype and their plasma vitamins A and E (by high-performance liquid chromatography) and lipid (enzymatically) concentrations were determined after an overnight fast. The associations of the phenotype with vitamins and lipids were studied in men and women separately and controlling for significant covariates. RESULTS: The apolipoprotein E phenotype was associated with the concentrations of total, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol in women, whereas no associations with lipids were found in men. Vitamin A and vitamin E levels were higher in men than in women, but only the difference in the former persisted after lipid adjustment. Apolipoprotein E2 slightly increased vitamin A levels in women, an effect which was still evident with lipid adjustment. Actually, both the apolipoprotein E phenotype and triglyceride were selected as significant predictors of this vitamin by multiple regression. This phenotype did not affect vitamin E levels in either sex. CONCLUSIONS: Lipids do not mediate the effect of gender on vitamin A levels. Apolipoprotein E polymorphism is an independent determinant of vitamin A levels in women. Pending confirmation by others, we propose that enhancement of this vitamin may contribute to the beneficial impact of the epsilon2 allele on human ageing and health.

Adult↗
PubMed2002

Resting energy expenditure in young patients with cystic fibrosis receiving antibiotic therapy for acute respiratory exacerbations.

BACKGROUND: patients with cystic fibrosis commonly have severe malnutrition and growth retardation. Among possible causes of these manifestations are low caloric intake, loss of nutrients and increased resting energy expenditure. This study was designed to assess the influence of antibiotic therapy for infectious exacerbations on resting energy expenditure in young patients with cystic fibrosis. METHODS: We studied 17 patients with cystic fibrosis (mean age, 13.6 years). All were hospitalized to receive intravenous antibiotic therapy (mean duration, 2 weeks) for acute respiratory exacerbations. At the beginning of therapy and after it ended, all patients underwent blood chemical tests, anthropometrical measures, determination of body composition by bioelectrical impedance, spirometry, and indirect calorimetry. RESULTS: Antibiotic therapy led to a significant improvement in biochemical, spirometric variables and in estimated calorimetry measurements expressed in relation to fat-free mass. These findings suggest that infective exacerbations are among the causes of increased resting energy expenditure in young patients with cystic fibrosis. CONCLUSIONS: Indirect calorimetry may prove useful in the diagnosis of infective exacerbations and in monitoring the effect of antibiotic therapy in patients with cystic fibrosis.

Adolescent↗
PubMed2002

Molecular and biochemical screening for the diagnosis and management of medullary thyroid carcinoma in multiple endocrine neoplasia type 2A.

Patients with Multiple Endocrine Neoplasia (MEN) type 2A are at risk for early medullary thyroid carcinoma (MTC). We performed different screening tests for MTC--a recently reported biochemical screening test using omeprazole-induced calcitonin (CT) stimulation and DNA analysis--in fifteen members of two non-consanguineous Brazilian families with MEN 2A. RET proto-oncogene analysis was carried out by direct DNA sequencing of PCR-amplified products for exons 10 and 11. Family 1 showed a germline mutation (C634Y) in three individuals; a sister and a brother with symptomatic MTC; the former also presented with pheochromocytoma and hyperparathyroidism, and her son was a nine-year-old boy of previously unknown status. Family 2 showed the C634R mutation only in the index case, who presented with cutaneous lichen amyloidosis in addition to MTC, pheochromocytoma and hyperparathyroidism. Neither her parents nor her four brothers showed this genetic abnormality, suggesting a de novo RET proto-oncogene mutation in this patient. The controls and patients presented normal basal gastrin levels and a significant increase after omeprazole. Basal CT levels were elevated in patients with MTC and undetectable in control and asymptomatic family members. No subject showed any increase in CT levels after omeprazole treatment. In conclusion, the two most frequent RET proto-oncogene mutations in MEN 2A are present in Brazilian families. In addition, the specificity of basal and omeprazole-stimulated calcitonin is rather limited, and the efficacy of the omeprazole test still needs to be systematically examined. Therefore, RET proto-oncogene analysis must be the first choice for a screening procedure to identify gene carriers in MEN 2A family members and to permit early prophylactic treatment of MTC.

Adolescent↗
PubMed2002

Screening for adenylosuccinate lyase deficiency: clinical, biochemical and molecular findings in four patients.

Adenylosuccinate lyase deficiency is an autosomal recessive defect of purine metabolism. Succinyladenosine (S-Ado) and succinylaminoimidazole carboxamide riboside (SAICAr) are the disease marker metabolites in physiological fluids. The Bratton-Marshall test for detection of SAICAr in urine has been added to the selective screening for inborn errors of metabolism that is carried out in our lab. During the last three years, around 2,000 patients have been screened by this method, resulting in the detection of four new cases with this disease. They all presented with severe psychomotor delay, hypotonia and refractory epilepsy since the neonatal period. The S-Ado/SAICAr ratio in cerebrospinal fluid was below 2, indicating that they correspond to the most severe form of the disease. New missense mutations were found in a heterozygous fashion in three patients. The study of purines in all patients with neurological disease of unknown etiology is highly recommended.

Adenylosuccinate Lyase↗
PubMed2002

Nitrergic modulation of vasopressin, oxytocin and atrial natriuretic peptide secretion in response to sodium intake and hypertonic blood volume expansion.

The central nervous system plays an important role in the control of renal sodium excretion. We present here a brief review of physiologic regulation of hydromineral balance and discuss recent results from our laboratory that focus on the participation of nitrergic, vasopressinergic, and oxytocinergic systems in the regulation of water and sodium excretion under different salt intake and hypertonic blood volume expansion (BVE) conditions. High sodium intake induced a significant increase in nitric oxide synthase (NOS) activity in the medial basal hypothalamus and neural lobe, while a low sodium diet decreased NOS activity in the neural lobe, suggesting that central NOS is involved in the control of sodium balance. An increase in plasma concentrations in vasopressin (AVP), oxytocin (OT), atrial natriuretic peptide (ANP), and nitrate after hypertonic BVE was also demonstrated. The central inhibition of NOS by L-NAME caused a decrease in plasma AVP and no change in plasma OT or ANP levels after BVE. These data indicate that the increase in AVP release after hypertonic BVE depends on nitric oxide production. In contrast, the pattern of OT secretion was similar to that of ANP secretion, supporting the view that OT is a neuromodulator of ANP secretion during hypertonic BVE. Thus, neurohypophyseal hormones and ANP are secreted under hypertonic BVE in order to correct the changes induced in blood volume and osmolality, and the secretion of AVP in this particular situation depends on NOS activity.

Animals↗
PubMed2001

d Macro and (3)He macro production in square root of s(NN) = 130 GeV Au+Au collisions.

The first measurements of light antinucleus production in Au+Au collisions at the Relativistic Heavy-Ion Collider are reported. The observed production rates for d macro and (3)He macro are much larger than in lower energy nucleus-nucleus collisions. A coalescence model analysis of the yields indicates that there is little or no increase in the antinucleon freeze-out volume compared to collisions at CERN SPS energy. These analyses also indicate that the (3)He macro freeze-out volume is smaller than the d macro freeze-out volume.

Journal Article↗
PubMed2001

Measurement of inclusive antiprotons from Au+Au collisions at square root of s(NN) = 130 GeV.

We report the first measurement of inclusive antiproton production at midrapidity in Au+Au collisions at square root of s(NN) = 130 GeV by the STAR experiment at RHIC. The antiproton transverse mass distributions in the measured transverse momentum range of 0.25<p( perpendicular)<0.95 GeV/c are found to fall less steeply for more central collisions. The extrapolated antiproton rapidity density is found to scale approximately with the negative hadron multiplicity density.

Journal Article↗
PubMed2001

Transients due to instabilities hinder Kardar-Parisi-Zhang scaling: a unified derivation for surface growth by electrochemical and chemical vapor deposition.

We propose a unified moving boundary problem for surface growth by electrochemical and chemical vapor deposition, which is derived from constitutive equations into which stochastic forces are incorporated. We compute the coefficients in the interface equation of motion as functions of phenomenological parameters. The equation features the Kardar-Parisi-Zhang (KPZ) nonlinearity and instabilities which, depending on surface kinetics, can hinder the asymptotic KPZ scaling. Our results account for the universality and the experimental scarcity of KPZ scaling in the growth processes considered.

Journal Article↗
PubMed2001

Multiplicity distribution and spectra of negatively charged hadrons in Au+Au collisions at square root of (sNN) = 130 GeV.

The minimum-bias multiplicity distribution and the transverse momentum and pseudorapidity distributions for central collisions have been measured for negative hadrons ( h(-)) in Au+Au interactions at square root of ([s(NN)]) = 130 GeV. The multiplicity density at midrapidity for the 5% most central interactions is dN(h(-))/d(eta)/(eta = 0) = 280+/-1(stat)+/-20(syst), an increase per participant of 38% relative to pp collisions at the same energy. The mean transverse momentum is 0.508+/-0.012 GeV/c and is larger than in central Pb+Pb collisions at lower energies. The scaling of the h(-) yield per participant is a strong function of p( perpendicular). The pseudorapidity distribution is almost constant within /eta/<1.

Journal Article↗