PubMed Health⌕ Search

Biomedical subjects

M M Castro

Publications and source records attributed to M M Castro.

18 recordsLinked to original sources
PubMed2000

Structural study of the interaction of vanadate with the ligand 1,2-dimethyl-3-hydroxy-4-pyridinone (Hdmpp) in aqueous solution.

The interaction of vanadate with the ligand 1,2-dimethyl-3-hydroxy-4-pyridinone (Hdmpp) was studied in aqueous solution using a combination of multinuclear NMR and EPR spectroscopies, as well as potentiometry and cyclic voltammetry. The different species in solution were identified and characterized, and their pKa values and stability constants determined. The vanadium complexes formed in solution are strongly dependent on media composition (ionic strength, presence of buffer), pH and metal-to-ligand ratio (M:L). Two major species--V(V)/dmpp and V(V)/(dmpp)2--are formed in a 140 mM NaCl solution within the pH range 4.5 to 9.0, when M:L = 1:2. In the presence of excess ligand (M:L < or = 1:5), only the 1:2 complex is present, and at pH < 4 paramagnetic species are detected by EPR in solution, thus indicating a reducing capacity of the ligand. Cyclic voltammetry shows that redox processes in solution are not just electron transfer, but are accompanied by chemical reactions. The pK, values and stability constants were determined both by 51V NMR spectroscopy and potentiometry. The present results have a particular interest in the understanding of the aqueous solution chemistry in aerobic conditions of bis(1,2-dimethyl-3-hydroxy-4-pyridinonato) oxovanadium(IV) complex, VO(dmpp)2, a vanadium compound with potential insulin-mimetic properties.

Deferiprone↗
PubMed2000

Drugs in prehistory: chemical analysis of ancient human hair.

Concern about drug abuse in modern populations has led to the development of specific methods for identification of cocaine, opiates and cannabis in human hair. Drug use in prehistory can provide indirect evidence of interpopulational contact and social stratification. This paper reports drug evaluation in nineteen ancient hair samples from archaeological sites in northern Chile. Each sample was tested for the presence of traces of cocaine, opiates and cannabis, in order to establish a standard methodology for studies of drug use among prehistoric groups. Although results are negative, this absence of evidence could be due to two main causes: (1) the individuals evaluated did not use any drugs, which does not mean that other members of their cultural group did, or (2) the wide range of known drugs studied did not consider some group specific drugs, derived from local or imported plants, thus meaning that a greater drug range must be tested. In any case, our study confirms that drug testing in prehistoric samples is viable. However, in order to determine what kind of substances were used in prehistoric times new patterns that incorporate all drugs which are not part of the western pharmacopeia must be created. Finally, a methodology for the study of drug use among prehistoric groups using ancient hair samples is described.

Cannabinoids↗
PubMed1999

Competition between Li+ and Mg2+ in neuroblastoma SH-SY5Y cells: a fluorescence and 31P NMR study.

Because Mg2+ and Li+ ions have similar chemical properties, we have hypothesized that Li+/Mg2+ competition for Mg2+ binding sites is the molecular basis for the therapeutic action of lithium in manic-depressive illness. By fluorescence spectroscopy with furaptra-loaded cells, the free intracellular Mg2+ concentration within the intact neuroblastoma cells was found to increase from 0. 39 +/- 0.04 mM to 0.60 +/- 0.04 mM during a 40-min Li+ incubation in which the total intracellular Li+ concentration increased from 0 to 5.5 mM. Our fluorescence microscopy observations of Li+-free and Li+-loaded cells also indicate an increase in free Mg2+ concentration upon Li+ incubation. By 31P NMR, the free intracellular Mg2+ concentrations for Li+-free cells was 0.35 +/- 0. 03 mM and 0.80 +/- 0.04 mM for Li+-loaded cells (final total intracellular Li+ concentration of 16 mM). If a Li+/Mg2+ competition mechanism is present in neuroblastoma cells, an increase in the total intracellular Li+ concentration is expected to result in an increase in the free intracellular Mg2+ concentration, because Li+ displaces Mg2+ from its binding sites within the nerve cell. The fluorescence spectroscopy, fluorescence microscopy, and 31P NMR spectroscopy studies presented here have shown this to be the case.

Binding Sites↗
PubMed1997

Influence of vanadate on glycolysis, intracellular sodium, and pH in perfused rat hearts.

Vanadium compounds have been shown to cause a variety of biological and metabolic effects including inhibition of certain enzymes, alteration of contractile function, and as an insulin like regulator of glucose metabolism. However, the influence of vanadium on metabolic and ionic changes in hearts remains to be understood. In this study we have examined the influence of vanadate on glucose metabolism and sodium transport in isolated perfused rat hearts. Hearts were perfused with 10 mM glucose and varying vanadate concentrations (0.7-100 microM) while changes in high energy phosphates (ATP and phosphocreatine (PCr)), intracellular pH, and intracellular sodium were monitored using 31P and 23Na NMR spectroscopy. Tissue lactate, glycogen, and (Na+, K+)-ATPase activity were also measured using biochemical assays. Under baseline conditions, vanadate increased tissue glycogen levels two fold and reduced (Na+, K+)-ATPase activity. Significant decreases in ATP and PCr were observed in the presence of vanadate, with little change in intracellular pH. These changes under baseline conditions were less severe when the hearts were perfused with glucose, palmitate and beta-hydroxybutyrate. During ischemia vanadate did not limit the rise in intracellular sodium, but slowed sodium recovery on reperfusion. The presence of vanadate during ischemia resulted in attenuation of acidosis, and reduced lactate accumulation. Reperfusion in the presence of vanadate resulted in a slower ATP recovery, while intracellular pH and PCr recovery was not affected. These results indicate that vanadate alters glucose utilization and (Na+, K+)-ATPase activity and thereby influences the response of the myocardium to an ischemic insult.

3-Hydroxybutyric Acid↗
PubMed1990

Tm(DOTP)5-: a 23Na+ shift agent for perfused rat hearts.

Tm(DOTP)5-, the thulium(III) complex of 1,4,7,10-tetraazacyclododecane-N,N',N',N'''-tetra(methylenephos p hon ate), is introduced as a 23Na+ shift agent for use in discrimination of the NMR resonances of intra- and extracellular 23Na+ ions in perfused rat hearts. The novel shift agent is directly compared to the widely used Dy(TTHA)3- (dysprosium(III) triethylenetetraminehexaacetate).

Animals↗
PubMed1990

Influence of global ischemia on intracellular sodium in the perfused rat heart.

Intracellular [Na+], [H+], and [ATP] and mechanical performance were measured in the isovolumic perfused rat heart during ischemia. The concentration of intracellular sodium, [Na+]i, was determined by atomic absorption spectroscopy under control conditions, and [Na+]i was monitored by 23Na NMR spectroscopy at 1-min intervals under control conditions and during global ischemia. [ATP], [H+], and [Pi] were measured by 31P NMR in a separate group under identical conditions. The control [Na+]i measured by atomic absorption was 30.7 +/- 3.3 mM (mean +/- SD, n = 6), and [Na+]i measured by NMR was 6.2 +/- 0.5 mM (n = 3). Brief ischemia (10 min) was associated with a 54% increase in [Na+]i which reversed completely with reperfusion. Developed pressure also returned to control values upon reperfusion. Prolonged ischemia (30 min) produced continuous further accumulation of sodium (0.53 mM/min, r2 = 0.99). [H+] also increased approximately linearly early in ischemia (0.084 microM/min, r2 = 0.97). The rate of increase in [Na+]i was more than 4000 times greater than the increase in [H+] on a molar basis. Nevertheless, [H+]/[Na+]i increased early in ischemia because the proportional change in [H+] was greater than that in [Na+]i. These results indicate that (1) intracellular sodium measured by NMR in the functioning heart is about 20% of total intracellular sodium; (2) intracellular acidosis and accumulation of sodium develop simultaneously during global ischemia; (3) increased intracellular sodium content is not in itself an indicator of irreversible injury; and (4) recovery of mechanical performance is associated with return of [Na+]i (measured by NMR) to baseline after brief ischemia. The mechanism of the increase in sodium content detected by NMR is unknown.

Animals↗
PubMed1989

Interaction of vanadate with monosaccharides and nucleosides: a multinuclear NMR study.

Proton, 13C and 51V nuclear magnetic resonance spectroscopy has been used to study the interaction of vanadate with several molecules containing more than one hydroxyl group, including various aldoses and nucleosides. The aldoses D-mannose and D-ribose mainly form tridentate complexes, of trigonal bipyramidal geometry, with vanadate at pH 7. These sugars use three consecutive hydroxyl groups, cis to each other, of their pyranose forms to bind vanadate in those cyclic triesters. Other aldoses, like D-glucose, which do not have this unique structural characteristic, do not form tridentate complexes, but can form weaker bidentate cyclic diesters using two consecutive pyranose cis hydroxyl groups. Of course, the pyranose forms of D-mannose and D-ribose, as well as the furanose form of D-ribose, also yield cyclic diesters of vanadate. All these aldoses form weak monodentate noncyclic monoesters of tetrahedral geometry using a single hydroxyl group. The nucleosides uridine, cytidine and adenosine form two complexes of trigonal bipyramidal geometry with vanadate. In these complexes, having 1:1 and 2:1 ligand-to-metal stoichiometries, the nucleosides form cyclic diesters with vanadate using their C2, and C3, hydroxyl groups.

Adenosine↗
PubMed1989

Multinuclear NMR study of the interaction of vanadate with mononucleotides, ADP, and ATP.

The interaction of vanadate with 5'-mononucleotides, ADP, ATP, and various molecules containing some of their chemical moieties was studied in aqueous solution in the pH region of 5-9 using proton, 13C, 31P, and 51V nuclear magnetic resonance (NMR) spectroscopy. All the compounds studied formed noncyclic vanadate esters through interaction of monovanadate or divanadate with the hydroxyl groups of the ribose ring. Noncyclic anhydrides were also formed with the phosphate groups of ribose 5-phosphate, the mononucleotides, ADP, ATP, phosphate, pyrophosphate, and tripolyphosphate. In particular, ADP and ATP analogs resulted from AMP (AMPV and AMPV2) and from ADP (ADPV). Cyclic esters of trigonal bipyramidal geometry resulted from the interaction of vanadate with two ribose ring cis hydroxyl groups. AMP, CMP, and UMP formed two such complexes of 1:1 and 1:2 stoichiometries, similar to what has been observed for uridine and other nucleosides. However, 2'-deoxy-AMP does not yield this type of complexes. ADP and ATP also form similar cyclic ester complexes with vanadate, which does not chelate their pyrophosphate and tripolyphosphate moieties. Nevertheless, the separate pyrophosphate (PP) and tripolyphosphate (PPP) ligands form cyclic anhydrides of octahedral geometry with vanadate. However, their binding to vanadate is weaker than that of the ribose ring of nucleotides. Competition experiments between ethylene glycol and phosphate (P), pyrophosphate (PP), or tripolyphosphate (PPP) show that the relative strength of the interaction of these ligands with vanadate is PP greater than ethylene glycol greater than PPP greater than P.

Adenosine Diphosphate↗
PubMed1986

One-lane sequence analysis of oligodeoxyribonucleotides.

Treatment of 5'-end 32P-labeled oligodeoxyribonucleotides with 0.4 M aqueous piperidinium formate, pH 2, at 37 degrees C for 6 h, followed by treatment with 1 M aqueous piperidine at 90 degrees C for 6 h, produces, after electrophoresis through 27% polyacrylamide sequencing gels, one-dimensional distributions of radioactivity from which the base sequences can be deduced. The order of intensities for the bands signaling the various bases is G greater than A greater than C greater than T. The spacing from a given band to the next higher band in the ladder was base characteristic, the order of band spacings being G greater than T greater than or equal to A greater than C. In contrast to the one-cleavage one-lane DNA sequencing method reported earlier (B. J. B. Ambrose and R. C. Pless, 1985, Biochemistry 24, 6194-6200), which was based on treatment of end-labeled DNA with hot aqueous piperidine in the presence of sodium chloride, the present method produces a salt-free hydrolysate, thus minimizing electrophoretic irregularities in the fastest moving bands.

Autoradiography↗
PubMed1985

Base pairing involving deoxyinosine: implications for probe design.

The thermal stability of oligodeoxyribonucleotide duplexes containing deoxyinosine (I) residues matched with each of the four normal DNA bases were determined by optical melting techniques. The duplexes containing at least one I were obtained by mixing equimolar amounts of an oligonucleotide of sequence dCA3XA3G with one of sequence dCT3YT3G where X and Y were A, C, G, T, or I. Comparison of optical melting curves yielded relative stabilities for the I-containing standard base pairs in an otherwise identical base-pair sequence. I:C pairs were found to be less stable than A:T pairs in these duplexes. Large neighboring-base effects upon stability were observed. For example, when (X,Y) = (I,A), the duplex is eight-fold more stable than when (X,Y) = (A,I). Independent of sequence effects the order of stabilities is: I:C greater than I:A greater than I:T congruent to I:G. This order differs from that of deoxyguanosine which pairs less strongly with dA; otherwise each deoxyinosine base pair is less stable than its deoxyguanosine counterpart in the same sequence environment. Implications of these results for design of DNA oligonucleotide probes are discussed.

Hydrogen Bonding↗
PubMedDate not supplied

Lanthanide complexes of aminophosphonates as shift reagents for 7Li and 23Na NMR studies in biological systems.

A systematic NMR characterization of various Dy(III) complexes of linear and macrocyclic aminophosphonates as 7Li and 23Na NMR shift reagents for biological systems was undertaken. Their efficacy as shift reagents (SR) was tested under constant aqueous solution ionic strength conditions at pH 7.5 as a function of rho = [SR]/[M+]. Further characterization of the two best SRs, Dy(PcPcP)2(7-) and Dy(DOTP)5-, led to the conclusion that, although quite sensitive to solution pH and the presence of alkali metal ions and Mg2+ and Ca2+, these complexes were stable towards hydrolysis by phosphatases. The lack of precipitation of its solutions in the presence of Ca2+, allowed the choice of Dy(DOTP)5- as the best overall SR for biological studies. Other SRs, like Dy(TTHA)3-, although less sensitive to pH and to divalent ions, require significantly higher concentrations to yield the same shifts, leading to large bulk susceptibility artifacts in perfused tissues and organs.

Alkaline Phosphatase↗
PubMedDate not supplied

Non-traumatic acute abdomen: videolaparoscopic approach.

BACKGROUND AND OBJECTIVE: Although videolaparoscopy has been considered a safe method for many elective procedures, its use in traumatic and non-traumatic acute abdomen needs to be evaluated. The aim of this article is to evaluate the role of videolaparoscopy in non-traumatic acute abdomen as a method of diagnosis and treatment. METHODS: Between January 1992 and December 1996, 462 patients' charts were reviewed, retrospectively. Patients were admitted to the emergency room of São Rafael Hospital with symptoms of non-traumatic acute abdomen. Routine investigation of abdominal pain was performed in all patients, followed by videolaparoscopy. The laparoscopic procedures were done with four main purposes: diagnosis (ie, enteritis); diagnosis and treatment (ie, appendicitis); treatment only, when the diagnosis was known (ie, acute cholecystitis); and in cases where the conversion to conventional laparotomy was necessary, indicating the best incision. RESULTS: The vast majority of patients had inflammatory causes of acute abdomen (82.03%); others causes were hemoperitoneum (11.03%), bowel obstruction (3.25%), perforation of a hollow viscera (1.74%), vascular occlusion (1.3%), and negative laparoscopy (0.65%). CONCLUSIONS: This study shows that laparotomy was necessary in only 7.14% of the patients. The videolaparoscopic approach was used for diagnosis (99.35%) and treatment (92.86%) of patients with acute abdomen.

Abdomen, Acute↗
PubMedDate not supplied

Videolaparoscopic approach of the splenic cyst: a case report.

The authors report a case of an asymptomatic 30-year-old female patient with an extensive cystic lesion continuous with the splenic parenchyma. A review of the literature and use of a videolaparoscopic approach to the treatment of these lesions is presented.

Adult↗
PubMedDate not supplied

Videolaparocholecystectomy: casuistry of 1000 cases.

Despite the ongoing evolution in the medical treatment of biliary pathology, the standard of treatment for gallstones remains cholecystectomy. There are no alternative treatments that have shown the same efficacy as surgery. Current alternative treatments have shown high recurrence and failure rates. Cholecystectomy remains the gold standard for management of gallstones. The surgical access of laparoscopic cholecystectomy accomplished by Mouret in 1987 allows for a reduction in operative trauma, hospital stay, postoperative pain and convalescence. These factors permit a faster return to normal activities. Today, laparoscopic cholecystectomy is performed in almost all medical centers around the world; however, the procedure is not free of complications. The objective of this study was to analyze our first 1000 cases of laparoscopic cholecystectomy, giving emphasis to the morbidity and mortality of the procedure.

Adolescent↗