Biomedical subjects

I Bravo

Publications and source records attributed to I Bravo.

At least 19 recordsLinked to original sources

PubMed2006

Anti-oxidant enzyme activities and expression and oxidative damage in patients with non-immediate reactions to drugs.

Adverse drug reactions with an immunological basis (ADRIB) may involve activation of other concomitant, non-specific mechanisms, amplifying the specific response and contributing to the severity and duration. One concomitant mechanism could be the generation of reactive oxygen species (ROS) and/or their detoxification by anti-oxidants, including anti-oxidant enzymes. We analysed the activity of the anti-oxidant enzymes Cu/Zn-superoxide dismutase (SOD), catalase (CAT) and cellular glutathione peroxidase (GPX), as well as certain markers of oxidative damage (thiobarbituric acid reactive substances (TBARS) and carbonyl content) in peripheral blood mononuclear cells from patients with non-immediate ADRIB using spectrophotometric methods and the anti-oxidant enzymes expression by quantitative real-time reverse transcription-polymerase chain reaction. SOD activity and expression were increased in all types of non-immediate reactions (urticaria, maculopapular exanthema and toxic epidermal necrolysis). Regarding oxidative damage, TBARS were increased in urticaria and maculopapular exanthema, and carbonyl groups in all types of reactions. Our observations indicate that oxidative damage occurs in non-immediate reactions. Carbonyl stress and the inadequacy of the anti-oxidant defences are probable causes.

Adolescent↗

PubMed2003

Drug release kinetics and fronts movement studies from methyl methacrylate (MMA) copolymer matrix tablets: effect of copolymer type and matrix porosity.

Several methyl methacrylate (MMA) copolymers have recently been proposed as an alternative for the formulation of controlled-release matrix tablets. Copolymers were synthesised by free radical copolymerisation of methyl methacrylate with starch or cellulose derivatives and were alternatively dried by oven or freeze-drying techniques. Both the chemical composition and the drying technique were demonstrated to have a considerable influence on the physical properties of the copolymers. The present investigation was focused on the elucidation of the drug release mechanism from MMA copolymer matrices, using anhydrous theophylline as model drug. Drug release experiments were performed from free tablets. Radial drug release and fronts movement were also evaluated using special devices consisting of two Plexiglass discs joined by means of four stainless steel screws. Mathematical analysis of release data was performed using Higuchi, Korsmeyer and Peppas equations and fronts movement was investigated using a colorimetric technique. The drug release rate and the relative positions of the fronts were studied as functions of the type of copolymer and the initial porosity of the tablets. Drug release was controlled mainly by diffusion and the release rate was found to be affected by the drying method and related to the area exposed to the dissolution medium. Three distinct fronts (water uptake, complete wetting, erosion) were observed during the release process and the dynamics of fronts movement confirmed the diffusional mechanism.

Methylmethacrylate↗

PubMed2001

Ethanol inhibits L-arginine uptake and enhances NO formation in human placenta.

The acute effects of ethanol (20-60 mM) on L-arginine uptake and nitric oxide (NO) formation was investigated in human placental cotyledons perfused at constant flow. Ethanol (40 mM) decreased L-[3H]arginine uptake from 27.6 +/- 2.3 to 15.8 +/- 1.3 per cent (P < 0.05) of the injected dose and significantly enhanced NO levels in the perfusate from 0.88 +/- 0.11 to 2.80 +/- 0.39 microM. Ethanol also elicited the constriction of placental vessels. The effects of ethanol (20-60 mM) on L-arginine uptake and endothelial NO synthase (eNOS) activity were also investigated in cultured human umbilical vein endothelial cells (HUVEC). After 60 min of ethanol (40 mM) exposure, basal L-[3H]arginine uptake (4.7 +/- 0.3 pmol/microg protein/min) was inhibited by 60 per cent (P < 0.05). Basal eNOS activity in HUVEC determined under "no flow" (static) conditions was significantly increased (approximately 1.8 fold) by 60 mM ethanol. These data are consistent with a stimulatory effect of ethanol on eNOS activity in both basal and flow-stimulated conditions, which may serve a protective role against its vasoconstrictive acute effect. While acute ethanol administration inhibits L-arginine uptake, the present results do not allow us to speculate on the effects of chronic ethanol exposure on NO formation in the fetoplacental unity.

Arginine↗

PubMed2001

Toxin composition of the toxic dinoflagellate Prorocentrum lima isolated from different locations along the Galician coast (NW Spain).

The DSP toxin composition of 19 Prorocentrum lima isolates from different locations of the Galician rias (Vigo and Pontevedra) was investigated by high performance liquid chromatography coupled with fluorimetric detection. Boiling and freeze/thaw/hydrolyse methodology were applied during extraction to detect OA, DTX1, DTX2 and their esterified derivatives. OA and DTX2 were detected in both free and esterified form, the latter always in very low amounts, whilst DTX1 was always present in the free form. This indicate that the hypothesized self-protection mechanism of toxin storage in the less active esterified forms does not seem to apply to DTX1. A slight increase in the toxin concentration per cell was found during growth, although toxin composition did not vary appreciably. Toxin production and toxin profile varied significantly depending on the isolate. Four groups of P. lima were differentiated by cluster analysis according to their toxin composition. It is noteworthy that one of the clusters comprised all the strains collected from one location characterised by its geographical isolation, whereas the other clusters consisted of isolates from different locations. The differences in the toxin profile from P. lima strains and from the DSP contaminated shellfish, together with the very good correlation between Dinophysis spp occurrence and DSP toxicity in shellfish, support that these planktonic species are the main agents responsible for DSP events in Galicia.

Animals↗

PubMed2000

Subjects with allergic reactions to drugs show in vivo polarized patterns of cytokine expression depending on the chronology of the clinical reaction.

BACKGROUND: The mechanisms involved in adverse drug reactions with an immunologic basis (ADRIB) can be antibody dependent, mainly IgE or T cell dependent (sensitized T cells). These mechanisms are regulated by a number of cytokines, including IL-2, IL-4, IL-5, IFN-gamma, and TNF-alpha, which follow the classical T(H)1/T(H)2 immunologic paradigm. Although evidence for this has been seen in ex vivo studies, the results are heterogeneous, and few in vivo studies have been carried out in subjects with ADRIB. OBJECTIVE: We studied a group of patients who experienced either immediate reactions (n = 10) or nonimmediate reactions (n = 9) to drugs to determine the cytokine pattern profile during the acute stage of the response, as well as after recovery. METHODS: PBMCs were taken at different time intervals of 24 hours or less and 7, 15, and 30 days after the onset of the reaction, and the specific cytokine transcription and production were determined by using quantitative competitive RT-PCR and ELISA, respectively. RESULTS: There was a transient polarized pattern corresponding to a T(H)1 response with IL-2, IFN-gamma, and TNF-alpha in nonimmediate reactions and to a T(H)2 response with IL-4 in immediate reactions. CONCLUSIONS: This is the first in vivo demonstration of these T(H)1/T(H)2 patterns in subjects with ADRIB and confirms that an immunologic process is occurring related to the mechanisms involved in the pathologic manifestation. These findings are relevant to the understanding of the pathophysiologic mechanisms involved in ADRIB, suggesting that further studies in this direction are warranted.

Adult↗

PubMed1999

L-arginine transport at the fetal side of human placenta: effect of aspirin in pregnancy.

L-Arginine transport by the fetal side of human placenta was investigated through the characterization of L-[3H]arginine uptake in isolated perfused cotyledon. Competitive inhibition experiments suggest the presence of at least two transport systems: a Na+-independent, pH-insensitive system inhibitable by cationic amino acids, similar to system y+, and a Na+-dependent system which recognizes both cationic and neutral amino acids only in the presence of Na+, i.e. a Bo,+-like system. The kinetic analysis of L-arginine uptake in the presence of Na+ revealed that the process is mediated by saturable components: a high-affinity system (Km = 167 +/- 18.0 microM; Vmax = 0.174 +/- 0.012 micromol min-1) and a low-affinity carrier (Km = 980 +/- 112 microM; Vmax = 1.60 +/- 0.12 micromol min-1). In the absence of Na+, L-arginine uptake was fitted by one model with a Michaelis-Menten constant of 200 +/- 24.8 microM. These results suggest that the high-affinity component corresponds to the Na+-independent system y+, whilst the low-affinity system may represent the activity of the Na+-dependent Bo,+ transporter. Kinetic studies in placentae taken from aspirin-treated pregnancies showed that L-arginine is transported with a significantly higher affinity (Km = 42.5 +/- 5.7 microM), but with a lower capacity (Vmax = 0.064 +/- 0.003 micromol min-1) than in the non-treated group. The latter finding suggests that aspirin would facilitate the uptake of the NO precursor only at very low arginine concentrations.

Adult↗

PubMed1998

Adrenal-dependent modulation of the catalytic subunit isoforms of the Na+-K+-ATPase in aorta.

Na+-K+-ATPase gene expression and activity were studied in aortas from adrenalectomized (ADX) rats and ADX rats with deoxycorticosterone supplement (ADX-DOCA). Northern analysis of RNA from ADX rats revealed a significant decrease in alpha2-mRNA levels (38.5 +/- 8.3% of control, P < 0.01) that was prevented by DOCA (P < 0.05). A decrease to 55.8 +/- 7.7% in alpha2-isoform protein was observed 8 days after adrenal removal (P < 0.05); DOCA reversed this effect (90.8 +/- 10.5%). Adrenalectomy induced a decrease of 68.5 +/- 4.5% in beta1-mRNA (P < 0.01) and 52.7 +/- 8.3% in ADX-DOCA rats (P < 0.01). Also, a reduction in beta1-isoform protein that was not prevented by DOCA was detected after adrenalectomy (47.1 +/- 11%, P < 0.01). In contrast, no differences in alpha1-mRNA or -protein levels were observed. Vascular sodium pump activity was reduced to 59.8 +/- 4.6% of control values after adrenalectomy (P < 0.01); this reduction was reversed by DOCA. Our data indicate that corticosteroids regulate Na+-K+-ATPase isoform expression and activity in vascular tissue in vivo, suggesting a mineralocorticoid-dependent modulation of alpha2-Na+-K+-ATPase gene expression in aorta, with beta1-isoform expression dependent on the presence of glucocorticoids.

Adrenal Cortex Hormones↗

PubMed1997

Mortality discrimination in acute myocardial infarction: comparison between APACHE III and SAPS II prognosis systems. PAEEC Group.

OBJECTIVE: To compare the Acute Physiology, Age and Chronic Health Evaluation (APACHE) III with the Simplified Acute Physiology Score (SAPS II) in discriminating in-hospital mortality for intensive care unit (ICU) patients with acute myocardial infarction (AMI). DESIGN: Prospective, observational, multicenter study. SETTING: 70 Spanish ICUs. PATIENTS AND PARTICIPANTS: 1711 patients with AMI and representative of Spanish ICUs. MEASUREMENTS AND RESULTS: APACHE III score, APACHE III system probability of death (APACHE III probability), SAPS II score and in-hospital mortality were noted for each patient. Two hundred and twenty three (13.0 %) patients died in the hospital. The sensitivity (+/- SE), specificity (+/- SE), and accuracy (+/- SE) for the APACHE III score were, respectively, 75.8 +/- 2.9, 75.9 +/- 1.1, and 75.9 +/- 1.0. The corresponding figures for APACHE III probability were 75.3 +/- 2.9, 79.2 +/- 1.1, and 78.7 +/- 1.0, and for SAPS II 72.2 +/- 3.0, 75.9 +/- 1.1, and 75.4 +/- 1.0. CONCLUSIONS: The results indicate good discrimination by the three tests. APACHE III probability shows a statistically significant improvement in accuracy and specificity when compared with the two scores.

APACHE↗

PubMed1997

Hypoxanthine uptake at the fetal side of human placenta proceeds through a nucleobase-preferring carrier and a non-saturable process.

Uptake and metabolism of hypoxanthine by human placenta were studied using the single-circulation paired-tracer technique. In isolated cotyledons perfused through the fetal (basal) circulation, at mean pressures of 31.7 +/- 4.0 mmHg and mean flow rates maintained at 5.5 +/- 0.15 ml/min, the [3H]hypoxanthine uptake was 36 +/- 2.4 per cent (16.5 +/- 1.1 pmol/g wet weight). Hypoxanthine uptake was significantly inhibited by unlabelled (mM) hypoxanthine (0.5), adenine (0.5), guanine (0.5) and papaverine (15.0), but was unaffected by nitrobenzylthioinosine (0.01). Adenosine failed to inhibit hypoxanthine uptake. The kinetic analysis of hypoxanthine uptake showed it to be partially mediated by a saturable (apparent K(m) = 12.1 +/- 1.85 microns; Jmax = 7.1 +/- 0.52 nmol/min) and Na(+)-dependent mechanism. A greater fraction of hypoxanthine influx proceeded through a non-saturable process. Thin layer chromatographic analysis of venous perfusate after the intra-arterial injection of [3H]hypoxanthine showed a negligible degradation of nucleobase. These overall results show that hypoxanthine uptake at the fetal side of human placenta occurs by a saturable plus a non-saturable process. The carrier showed specificity for nucleobases and high affinity-low capacity for hypoxanthine. Since the fetal blood concentration of hypoxanthine is normally low, its uptake would be mediated by the high affinity transport system. Because the non-saturable mechanism can be operative at high concentrations of hypoxanthine, it may have primary importance to clear the nucleobase coming from the fetus during intrauterine hypoxia.

Adenine↗

PubMed1997

Endogenous nitric oxide attenuates ethanol-induced vasoconstriction in the human placenta.

The purpose of this study was to clarify the role of endogenous nitric oxide and prostanoids in ethanol-induced perturbation of microcirculation in perfused human placenta. Infusion of ethanol into chorionic plate vessels at 10-65 mM increases perfusion pressure in a concentration-dependent fashion, and is an indicator of fetal-placental vasoconstriction. Simultaneous infusion of N(omega)-nitro-L-arginine, methylene blue and endothelial cell removal significantly enhances the ethanol-induced increase in perfusion pressure. In contrast, sodium nitroprusside attenuates this effect. Indomethacin did not significantly modify the ethanol-induced response. In conclusion, inhibition of the action of endogenous nitric oxide is associated with an increase in fetal-placental vasoconstriction. These results suggest that endogenous nitric oxide acts as a vasodilator that reduces ethanol-induced vasoconstriction, thus improving microcirculation, and leads to decreased placental damage.

Antidotes↗

PubMed1996

Proteinuria and albumin homeostasis in the nephrotic syndrome: effect of dietary protein intake.

Nephrotic syndrome is analyzed in the light of interventions designed to decrease proteinuria and renal injury. The effect of dietary protein intake on urinary protein losses and albumin homeostasis are discussed on the basis of the pathophysiologic mechanisms known to account for changes in renal function of nephrotic patients. In addition, the effect of angiotensin-converting enzyme inhibitors for reduction of proteinuria is discussed in terms of the modulation of glomerular permselectivity and hemodynamics.

Albumins↗

PubMed1996

Comparison of the biochemical properties, regulation and function of ATP-diphosphohydrolase from human placenta and rat kidney.

ATP-diphosphohydrolase (apyrase. EC 3.6.1.5) has both ATPase and ADPase activity that are stimulated by bivalent metals, with Ca2+ being the most effective. The possible physiological function of this enzyme, associated with placental and renal microvilli, is related to the extracellular metabolism of nucleotides. A comparison of the biochemical properties of human placenta and rat kidney apyrase is presented, showing similarities in Mr. bivalent metal stimulation, nucleotide nonspecificity, insensitivity towards specific ATPase inhibitors, and lack of essential sulfhydryl and aliphatic hydroxyl groups. We describe the treatment of membrane preparations from both tissues with different detergents and the isoelectric focusing of the solubilized proteins to partially purify apyrase. An ectoenzyme localization is assigned both in microvillus membranes and in the vasculature on the basis of organ perfusion experiments with nucleotides in the presence of antibodies. Placental and kidney microvillus membranes inhibited ADP-induced platelet aggregation, in agreement with an extracellular role. Initial studies on enzyme regulation suggested the existence of at least two types of modulatory proteins: an activating protein in the cytosol of both tissues, and an inhibitory protein associated with placental microsomes. Possible hormonal regulation was investigated in kidneys using in vivo estradiol treatment, but only slight changes in total apyrase activity were observed.

Animals↗

PubMed1996

[Bacterial urovirulence factors and their association with functional and anatomical abnormalities and recurrence of urinary tract infections in children].

BACKGROUND: Urinary tract infections in children are associated with functional and anatomical abnormalities of the urinary tract, they tend to recur and can cause permanent kidney damage. AIM: To study in children with urinary tract infections, microbiological factors associated to recurrence, functional and anatomical abnormalities of the urinary tract. PATIENTS AND METHODS: A prospective sample of children was incorporated into a follow-up protocol after their first episode of bacteriologically-demonstrated urinary tract infection. In all patients an abdominal ultrasound examination and a mictional urethrocystography were done and the presence of fimbriae was studied in isolated strains of Escherichia coli. RESULTS: Two hundred fifteen cases bad an adequate adherence to the study protocol, 190 caused by E coli. Fimbriated E coli strains were isolated with greater frequency from children with pyelonephritis than from those with a low urinary tract infection (50 and 28% respectively). The absence of fimbriae in E coli strains was associated with a higher risk of recurrent infections (odds ratio = 3, confidence intervals = 2-9.2) and an abnormal urethrocystography (odds ratio = 3, confidence intervals = 1.1-10.2). CONCLUSIONS: These data are consistent with foreign reports and support the need to study adhesins in E coli strains isolated from children with urinary tract infections.

Bacterial Infections↗

PubMed1996

Prognosis value of the expression of Ki-67 for squamous cell carcinoma of the oral cavity.

Ki-67 is a nuclear antigen expressed in G1, S, G2 and M phase of cell cycle and absent in quiescent cells (G0). In some neoplasms, Ki-67 expression has a prognostic value. The purpose of this study was to determine the role of Ki-67 expression like prognostic factor in oral squamous cell carcinoma (OSCC). Monoclonal antibody MIB-1 that recognizes Ki-67 antigen was used. 74 OSCCs were analyzed. 49% of OSCCs did not express Ki-67 antigen. In the Ki-67 positive tumours, the expression was slight in 36.5%, moderate in 10.8% and intense in 10.8% of the cases. In all the positive OSCCs, the distribution of the marking was patchy in different zones of the tumour, moreover, in 65% of the lesions, the positive cells were located mainly in the proximity of intraoral blood vessels. A significantly more intense expression was noted on tumours that had not been differentiated (p < 0.05), with a larger nuclear pleomorphism (p < 0.05) and in lesions that invaded in the form of disassociated neoplastic cells of in small groups of neoplastic cells (p < 0.001). However, the expression of Ki-67 did not correlate with the mitosis count and it had no influence on survival.

Adult↗

PubMed1995

Transport and metabolism of adenosine in the perfused human placenta.

Uptake and metabolism of adenosine by human placenta were studied using the single-circulation paired-tracer technique. When isolated cotyledons were perfused through the fetal (basal) circulation at mean pressures of 36 +/- 3.3 mmHg and mean flow rates of 6.6 +/- 0.3 ml/min the maximal [3H]adenosine uptake was 51.3 +/- 3.9 per cent. The uptake was not changed when the vascular resistance was pharmacologically increased. Adenosine uptake was significantly inhibited by adenosine, inosine and nitrobenzylthioinosine (NBMPR), but was unaffected by hypoxanthine. The kinetic analysis of adenosine transport showed it to be a saturable and, Na(+)-independent process, with a Km of 60.8 microM and a Jmax of 0.148 mumol/min. Thin layer chromatographic analysis showed that about 65 per cent of [3H]adenosine was metabolized (10-30 sec) in a single passage through the fetoplacental circulation. [3H]hypoxanthine and [3H]adenine were the major products recovered in the venous perfusate. In the presence of NBMPR the fractional recovery of [3H]adenine and [3H]phosphorylated derivatives was reduced while that of [3H]hypoxanthine was increased. These overall results show that the uptake of adenosine is a Na(+)-independent, NBMPR-sensitive, carrier-mediated process, which appears to be specific for nucleosides, and suggests that metabolization of adenosine proceeds both intra- and extracellularly.

Adenosine↗

PubMed1993

Serotonin-induced vasoconstriction in human placental chorionic veins: interaction with prostaglandin F2 alpha.

In vitro experiments using isolated rings and perfused segments of human chorionic veins, were designed to determine the effects of serotonin and their interaction with PGF2 alpha on vascular tension and perfusion pressure. These vessels responded vigorously with high sensitivity to the vasoconstrictor effects of serotonin in both experimental designs. Administration of PGF2 alpha also led to constriction of the veins, but this autacoid is at least 100 times less potent than serotonin. When adding PGF2 alpha previously to serotonin to the bathing fluid or to the perfusate, the serotonin response was significantly potentiated, increasing the maximal contractile response in 116 +/- 12% and the perfusion pressure in 180 +/- 25%. Both autacoids probably operate in this vascular bed interacting with each other and playing an important role in the regulation of placental blood flow in vivo.

Analysis of Variance↗

PubMed1993

Stimulation of human T lymphocytes via CD2 and CD3 molecules: establishment of the method and characterisation of proliferating cells.

The in vitro exposure of human lymphocytes to degradation products (Fe, Ni or Co) of metallic biomaterials causes a significant reduction of lymphocytes expressing the molecules involved in T lymphocyte activation, CD2 and CD3. A method is described which was developed for the stimulation of lymphocytes in which both CD2 and CD3 molecules were triggered simultaneously. For this purpose an anti-CD3 monoclonal antibody (mAb) was chemically bound to sheep (SE) or human (HE) erythrocytes, forming SE alpha CD3 or HE alpha CD3 conjugates, respectively, which were used for lymphocyte stimulation. Stimulation via CD2 and CD3 was compared with classical phytohaemagglutinin stimulation as well as with soluble alpha CD3 mAb stimulation. Phenotypical characterisation of DNA synthesising lymphocytes was assessed by autoradiography of 3H-thymidine pulsed cultures combined with immunocytochemical tests. Results indicate that this method of T lymphocyte stimulation via CD2 and CD3 is reliable and consistent, and it seems to be very convenient for the evaluation of immunocytotoxicity of metal ions derived from metallic biomaterials.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1993

L-lysine transport through the basolateral surface of oxyntic glands and plasma membrane of parietal cells isolated from rabbit stomach.

L-lysine uptake was measured in isolated oxyntic glands of rabbit stomach in both Na(+)-containing (1.29 +/- 0.29 nmol.mg-1.(20s)-1) and choline-containing (0.93 +/- 0.15 nmol.mg-1.(20s)-1) medium. Time curves and concentration dependence curves showed higher uptake values in the presence of extracellular Na+. The carrier-mediated uptake of L-lysine fit the Michaelis-Menten equation for one saturable component (Kt = 1.42 mM, Jmax = 0.16 nmol.mg-1.s-1) when sodium was replaced by choline in the medium. Two components are apparent when the kinetic analysis was performed in the presence of Na+: component 1 showed lower affinity (Kt = 4.0 mM) than component 2 (Kt = 0.53 mM). The transport constants for the Na(+)-independent component and for the Na(+)-dependent component 2 (i.e. the high affinity component) are in the range described for system y+ in other cells. L-lysine uptake in the choline-containing medium was inhibited only by cationic amino acids and histidine. In the presence of Na+, both cationic and some neutral (His, Cys, Ala, Leu, Phe) amino acids inhibited L-lysine uptake. These overall results and the ratio of Ki obtained for cationic and neutral amino acids suggest that at the basolateral side of the oxyntic glands cationic amino acids transport is mediated by the system y+ and, probably, an ASC like system. The pH-insensitivity of L-lysine uptake (in the range 6.5 to 8) supports this hypothesis. Results obtained in isolated parietal cells suggest that L-lysine uptake would be primarily mediated by a transporter which resembles the selectivity of system b(o),+.

Amino Acid Transport Systems↗