PubMed Health⌕ Search

Biomedical subjects

M Miranda

Publications and source records attributed to M Miranda.

At least 55 records · Page 3Linked to original sources
PubMed2000

Antioxidant and GSH-related enzyme response to a single teratogenic exposure to the anticonvulsant phenytoin: temporospatial evaluation.

BACKGROUND: It has been proposed that the anticonvulsant drug phenytoin (PHT) requires bioactivation to reactive intermediate(s) to achieve its recognized teratogenic potential and that embryonal detoxification power may play a fundamental role in the teratogenic response. On this basis, we sought to investigate the potential effects of a teratogenic exposure to PHT on the activities of antioxidant and GSH-related detoxifying enzymes in gestational murine tissues. METHODS: Pregnant Swiss mice were injected intraperitoneally with 0 (vehicle) or 65 mg/kg of PHT on gestation day (GD) 12 (plug day = GD 1). Biochemical determinations, including activities of glutathione transferase, glutathione peroxidase, glutathione reductase, glyoxalase I, glyoxalase II, catalase, and superoxide dismutase, were carried out on maternal and embryonic/fetal livers and in placentas on GD 14 and 19. RESULTS: The major findings of this study show that (1) organogenesis-stage conceptal tissues have detectable levels of all the tested enzymes; (2) most of the embryonic liver and placental enzymes investigated undergo a significant induction within 48 hr (GD 14) after PHT administration; and (3) in the same tissues a down-regulation of enzyme activities is noted near term (GD 19). CONCLUSIONS: Overall, these findings show that teratogenic exposure to PHT is associated with a modulation of reactive-intermediates-scavenging enzyme activities, and provide further support for role of generation of reactive intermediates in PHT-induced teratogenesis.

Abortion, Veterinary↗
PubMed2000

The effect of pig farming on copper and zinc accumulation in cattle in Galicia (north-western Spain).

Copper and zinc are frequently added at high concentrations to pig diets as growth promoters. Livestock grazing pasture contaminated with pig slurry may, therefore, be at risk from excessive intake of these elements. High liver copper concentrations have been detected in cattle from the agricultural region of Galicia (NW Spain), especially where there is intensive pig farming. The aim of this study was to evaluate whether pig farming does affect accumulation of copper and zinc in cattle in Galicia. Hepatic copper and zinc concentrations in calves were elevated in areas with naturally high levels of these elements in the soil. The densities of young pigs (piglets and growing-finishing pigs), but not reproductive sows, also influenced copper accumulation in calves. Liver copper levels in calves were significantly and positively related to the density of young pigs in the region. In areas with the highest pig densities, more than 20% of the cattle analysed had hepatic copper concentrations that exceeded the potentially toxic concentration of 150 mg/kg fresh weight. There was no evidence that zinc accumulation in calves was affected by pig density.

Animals↗
PubMed2000

Toxic and trace elements in liver, kidney and meat from cattle slaughtered in Galicia (NW Spain).

The aims of this study were to determine the levels of some toxic and trace metals in cattle meat in Spain and to compare them with concentrations in cattle elsewhere and to maximum acceptable levels. Arsenic, cadmium, lead, copper and zinc concentrations in the liver, kidney and muscle (meat) from 438 calves (6-10 months old) and 56 cows (2-16 years old) slaughtered in Galicia (NW Spain) in 1996 were quantified. The arithmetic mean fresh weight concentrations in calf liver, kidney and muscle respectively were 0.043, 0.055, 0.004 mg/kg for arsenic, 0.032, 0.070, 0.001 mg/kg for cadmium, 0.053, 0.052, 0.009 mg/kg for lead, 64.6, 4.91, 0.677 mg/kg for copper and 47.7, 14.4, 47.8 mg/kg for zinc. In cows, these concentrations were 0.046, 0.068, 0.005 mg/kg (arsenic), 0.097, 0.458, 0.001 mg/kg (cadmium), 0.057, 0.066, 0.017 mg/kg (lead), 60.3, 3.67, 1.26 mg/kg (copper) and 59.8, 20.0, 52.7 mg/kg (zinc). Except for copper levels in the liver which were high, metal concentrations in cattle were generally low in Galicia and broadly similar to those in the rest of Europe, Australia and Canada. Arsenic, cadmium and lead concentrations in Galician cattle rarely exceeded acceptable maximum concentrations that have been adopted by many countries. Copper and zinc concentrations in Galician cattle did exceed acceptable maximum concentrations but the frequency with which this occurred depended upon which acceptable maximum concentration was used; regulatory values differ markedly between countries.

Animals↗
PubMed2000

Aldosterone- and testosterone-mediated intracellular calcium response in skeletal muscle cell cultures.

Fast nongenomic steroid actions in several cell types seem to be mediated by second messengers such as intracellular calcium ([Ca(2+)](i)) and inositol 1,4,5-trisphosphate (IP(3)). We have shown the presence of both slow calcium transients and IP(3) receptors associated with cell nuclei in cultured skeletal muscle cells. The effect of steroids on [Ca(2+)](i) was monitored in Fluo 3-acetoxymethyl ester-loaded myotubes by either confocal microscopy or fluorescence microscopy, with the use of out-of-focus fluorescence elimination. The mass of IP(3) was determined by radioreceptor displacement assay. [Ca(2+)](i) changes after either aldosterone (10-100 nM) or testosterone (50-100 nM) were observed; a relatively fast (<2 min) calcium transient, frequently accompanied by oscillations, was evident with both hormones. A slow rise in [Ca(2+)](i) that reached its maximum after a 30-min exposure to aldosterone was also observed. Calcium responses seem to be fairly specific for aldosterone and testosterone, because several other steroid hormones do not induce detectable changes in fluorescence, even at 100-fold higher concentrations. The mass of IP(3) increased transiently to reach two- to threefold the basal level 45 s after addition of either aldosterone or testosterone, and the IP(3) transient was more rapid than the fast calcium signal. Spironolactone, an inhibitor of the intracellular aldosterone receptor, or cyproterone acetate, an inhibitor of the testosterone receptor, had no effect on the fast [Ca(2+)](i) signal or in the increase in IP(3) mass. These signals could mean that there are distinct nongenomic pathways for the action of these two steroids in skeletal muscle cells.

Aldosterone↗
PubMed2000

Biogenesis and function of the yeast plasma-membrane H(+)-ATPase.

One of the most abundant proteins in the yeast plasma membrane is the P-type H(+)-ATPase that pumps protons out of the cell, supplying the driving force for a wide array of H(+)-dependent cotransporters. The ATPase is a 100 kDa polypeptide, anchored in the lipid bilayer by 10 transmembrane alpha-helices. It is structurally and functionally related to the P-type Na(+),K(+)-, H(+),K(+)- and Ca(2+)-ATPases of animal cells and the H(+)-ATPases of plant cells, and it shares with them a characteristic reaction mechanism in which ATP is split to ADP and inorganic phosphate (P(i)) via a covalent beta-aspartyl phosphate intermediate. Cryoelectron microscopic images of the H(+)-ATPase of Neurospora crassa and the sarcoplasmic reticulum Ca(2+)-ATPase of animal cells have recently been obtained at 8 nm resolution. The membrane-embedded portion of the molecule, which presumably houses the cation translocation pathway, is seen to be connected via a narrow stalk to a large, multidomained cytoplasmic portion, known to contain the ATP-binding and phosphorylation sites. In parallel with the structural studies, efforts are being made to dissect structure/function relationships in several P-type ATPases by means of site-directed mutagenesis. This paper reviews three phenotypically distinct classes of mutant that have resulted from work on the yeast PMA1 H(+)-ATPase: (1) mutant ATPases that are poorly folded and retained in the endoplasmic reticulum; (2) mutants in which the conformational equilibrium has been shifted from the E(2) state, characterized by high affinity for vanadate, to the E(1) state, characterized by high affinity for ATP; and (3) mutants with altered coupling between ATP hydrolysis and proton pumping. Although much remains to be learned before the transport mechanism can be fully understood, these mutants serve to identify critical parts of the polypeptide that are required for protein folding, conformational change and H(+):ATP coupling.

Adenosine Triphosphate↗
PubMed2000

Effect of sex on arsenic, cadmium, lead, copper and zinc accumulation in calves.

This study evaluated the effect of sex on the accumulation of arsenic, cadmium, lead, copper and zinc in calves. Samples of liver, kidney, muscle and blood of 312 animals (127 females and 185 males) were analysed after acid digestion using atomic absorption spectrophotometry (AAS). Arsenic was determined by AAS interfaced with continuous flow hydride generation, cadmium and lead by graphite furnace, and copper and zinc by flame. Females accumulated more cadmium, copper and zinc in kidneys than did males. The zinc blood levels in females were higher than in males, whereas copper in liver was higher in males than in females. In the case of arsenic and lead, no significant statistical differences between males and females were found.

Animals↗
PubMed1999

Inhibition of L-tyrosine-induced micronuclei production by phenylthiourea in human melanoma cells.

It was previously found that L-tyrosine oxidation product(s) are cytotoxic, genotoxic and increase the sister chromatid exchange (SCE) levels in human melanoma cells. In this work, the micronucleus assay has been performed on human melanotic and amelanotic melanoma cell lines (Carl-1 MEL and AMEL) in the presence of 1.0, 0.5 and 0.1 mM L-tyrosine concentrations to investigate if melanin synthesis intermediate(s) increase micronuclei production. L-Tyrosine oxidation product(s) increased the frequency of micronuclei in melanoma cells; 0.1 mM phenylthiourea (PTU), an inhibitor of L-tyrosine oxidation by tyrosinase, lowered the micronucleus production to the control levels. The culture of melanoma cells with high L-tyrosine in the culture medium resulted in a positive response to an ELISA-based apoptotic test. For comparison the effect of L-tyrosine on micronuclei production in human amelanotic melanoma cells was also investigated; the micronucleus production in the presence of 1 mM L-tyrosine in the culture medium was lower than that found with melanotic melanoma cells of the same cell line. The data suggest that melanin synthesis intermediates arising from L-tyrosine oxidation may cause micronuclei production in Carl-1 human melanoma cells; the addition of PTU in the presence of L-tyrosine decreased the frequency of micronuclei to about the control values thus the inhibition of melanogenesis may have some clinical implication in melanotic melanoma.

Apoptosis↗
PubMed1999

Effect of tyrosinase inhibitors on Tuber borchii mycelium growth in vitro.

This paper reports the effect of the tyrosinase (monophenol o-diphenol:oxygen oxidoreductase; EC 1.14.18.1) inhibitors diethyldithiocarbamate (DETC), L-tropolone, kojic acid, phenylthiourea (PTU) and L-mimosine on the in vitro growth of Tuber borchii (a white truffle) mycelium. A significant inhibitory effect on mycelium growth was observed for DETC, PTU and L-tropolone (0% growth compared to control at 100 microg ml(-1) DETC, PTU and L-tropolone and at 10 microg ml(-1) DETC and L-tropolone). As a comparison the action of the same inhibitors was also tested on the growth and pigmentation of the mould Cladosporium sphaerospermum. In the presence of CuSO(4) 10(-6) M T. borchii mycelium acquired pigmentation (as rounded aggregates compared to control revealed by SEM microscopy). Tyrosinase activity in the extract from T. borchii mycelium (18-day culture) was detected spectrophotometrically.

Ascomycota↗
PubMed1999

Multiple unfolded states of glutathione transferase bbGSTP1-1 by guanidinium chloride.

Inactivation, dissociation, and unfolding of the homodimeric glutathione transferase (bbGSTP1-1) from Bufo bufo embryos were investigated at equilibrium, using guanidinium chloride (GdmCl) as denaturant. Protein transitions were monitored by enzyme activity, intrinsic fluorescence, far UV circular dichroism, glutaraldehyde cross-linking, and gel-filtration chromatography. At low denaturant concentrations (less than 0.5 M), reversible inactivation of the enzyme occurs. At denaturant concentrations between 0.5 and 1.5 M the enzyme progressively dissociates into structured monomers. At higher denaturant concentrations the monomers unfold completely. Refolding studies indicate that a total reactivation occurs only by starting from the enzyme denatured at concentrations below 0.5 M. The enzyme denatured at GdmCl concentrations higher than 0.5 M only partially refolds. Globally our results indicate that unfolding of the amphibian bbGSTP1-1 is a multistep process, i.e., inactivation of the structured dimer, dissociation into partially structured monomers, followed by complete unfolding.

Animals↗
PubMed1999

Age-dependent ultrastructural alterations and biochemical response of rat skeletal muscle after hypoxic or hyperoxic treatments.

This work deals with the antioxidant enzymatic response and the ultrastructural aspects of the skeletal muscle of young and aged rats kept under hypoxic or hyperoxic normobaric conditions. It is in fact well known that the supply of oxygen at concentrations higher or lower than those occurring under normal conditions can promote oxidative processes that can cause tissue damage. The enzymes investigated were both those directly involved in reactive oxygen species (ROS) scavenging (superoxide dismutase, catalase and selenium-dependent glutathione peroxidase), and those challenged with the detoxication of cytotoxic compounds produced by the action of ROS on biological molecules (glutathione transferase, glyoxalase I, glutathione reductase), in order to obtain a comparative view of the defence strategies used with respect to aging. Our results support the hypothesis that one of the major contributors to the aging process is the oxidative damage produced at least in part by an impairment of the antioxidant enzymatic system. This makes the aged organism particularly susceptible to oxidative stress injury and to the related degenerative diseases, especially in those tissues with high demand for oxidative metabolism.

Aging↗
PubMed1999

Morphology and amplitude values of the P and T waves in the electrocardiograms of Spanish-bred horses of different ages.

This investigation was undertaken to determine values of electrocardiographic parameters in Spanish-bred horses at different stages of growth. The study was carried out on 179 healthy Spanish-bred (Andalusian) horses (98 females and 81 males), which were aged between 1 month and 17 years. The ECGs showed P waves of different configurations. The bifid shape deflection of the P wave was generally more frequent than the simple one in animals from 6 months of age. The first component of bifid P waves (P1) did not vary in a statistically significant way with increasing age, showing a mean value of 0.105 mV. The amplitudes of the P2 (the second component of the bifid P waves) and simple P waves showed statistically significant differences between the age groups. The highest values were found in animals up to 3 months and over 2 years of age. Several configurations of the T wave were observed in the different age groups: a negative shape was generally present for the youngest animals (foals up to 2 years old); the biphasic (/+) pattern became more frequent in animals 3 and 4 years old. In adult horses the positive configuration was the most frequent. No statistically significant differences according to age were found for the amplitude values of the different T-wave configurations.

Aging↗
PubMed1999

[Severe hyponatremia during treatment with fluoxetine].

Serotonin reuptake inhibitors, used as antidepressants, may cause hyponatremia due to a syndrome of inappropriate antidiuretic hormone, specially in elders. Thirty cases with such complication have been reported in the last six years. We report a 76 years old female with a hypertensive cardiopathy and paroxysmal atrial fibrillation treated with amlodipine and sotalol. Five days after starting fluoxetine, the patient presented with a confusional state, gait instability and tremor. Laboratory assessment disclosed a plasma sodium of 115 meq/L. Fluoxetine was discontinued and fluids were restricted. The clinical condition of the patient improved and hyponatremia abated. Hyponatremia must be born in mind as a potential side effect of serotonin reuptake inhibitors.

Aged↗
PubMed1999

[Chorea induced by oral contraceptives. Report of two cases].

We report two women using oral contraceptives, aged 17 and 33 years old, who presented with hemichorea. In both patients all other possible causes of chorea were discarded and the disease disappeared when contraceptives were discontinued. Four months later, the 33 years old patient used again oral contraceptives and chorea reappeared. This rare complication of contraceptive use has been previously reported in young and mainly nulliparous women.

Adolescent↗
PubMed1999

[Adult onset subacute sclerosing panencephalitis. Report of two cases with atypical presentation].

Subacute sclerosing panencephalitis is an infrequent central nervous system viral disease and is a late manifestation of persistent infection by a mutant form of measles virus. Since it affects mainly children and teenagers, the diagnosis in older ages is difficult. Its main clinical symptoms are cognitive impairment, behavioral disturbances and myoclonia. We report two males, aged 21 and 22 years old, presenting with the disease with atypical manifestations. One had a catatonic syndrome and the other, amaurosis. The recognition of the different presentation forms of the disease, endemic in developing countries, allows an earlier diagnosis and a more efficient treatment, when available.

Adult↗
PubMed1999

The effect of intrastriatal injection of liposome-entrapped tyrosinase on the dopamine levels in the rat brain.

Parkinson's disease is a neurodegenerative disorder which is mainly characterized by degeneration of the dopaminergic cells in the nigro-striatal system. Due to a lowered L-tyrosine 3-monooxygenase activity, L-tyrosine is not sufficiently transformed to L-DOPA. To date the most common therapy is the administration of the dopamine precursor L-DOPA, with severe collateral effects. Therefore, the substitution of the lacking tyrosine hydroxylase with tyrosinase might be a novel therapeutical approach that would generate specifically L-DOPA from L-tyrosine. We present here evidence that stereotaxic injection of liposome-entrapped tyrosinase is able to significatively increase the levels of dopamine in the rat brain. The catecholamines L-DOPA, dopamine, L-epinephrine, L-norepinephrine were extracted by acid treatment from the brains and detected by HPLC.

Animals↗
PubMed1999

[Tics disease (Gilles de la Tourette syndrome): clinical characteristics of 70 patients].

BACKGROUND: Tourette's syndrome is a childhood-onset hereditary neurobehavioural disorder believed to occur without geographical restrictions. Although there have been reports of this disorder worldwide just a few are from Latin America. AIM: To report a preliminary experience with a series of 70 patients and to review recent advances in this disorder. PATIENTS AND METHOD: We reviewed patients seen in pediatric and adult neurological clinics in Santiago, Chile, all of whom fulfilled clinical diagnostic criteria for Tourette Syndrome. RESULTS: Seventy patients were studied, 54 males (77.1%) and 16 females (22.8%), their mean age at first evaluation was 13.6 years (range 2-46). The mean age of onset of symptoms was 6.4 (range 2-20), the mean time of follow-up was 3 years. Fifty-eight patients showed simple motor tics (blinking, facial grimacing, shoulder shrugging), whereas dystonic tics like head jerking were seen in 38 patients, torticollis in 6 and oculogyric movements in 2. Complex motor tics like jumping, antics, trunk bending and head shaking were present in 16 subjects. Vocal tics were predominantly of the simple type: sniffing, throat clearing, blowing, and whistling. Complex vocal tics were seen in 12 patients, five cases showed palilalia, 3 echolalia and only six displayed coprolalia (8.5%). Tics were of mild to moderate severity in most patients. Obsessive-compulsive disorder was observed in 22.8% and attention deficit and hyperactivity disorder were present in 35.7%. Forty-five patients (64.2%) had a first degree relative with tics, nine patients (12.8%) had a family history of obsessive-compulsive disorder. The current evidence involving desinhibition of cortico-striatum-thalamic-cortical neuronal circuits in the pathogenesis of this disorder is analyzed. CONCLUSION: Our report supports the recognized clinical homogeneity and genetical basis of Tourette's syndrome regardless of geographical region and ethnic origin.

Adult↗
PubMed1998

Oxidative damage of mitochondrial and nuclear DNA induced by ionizing radiation in human hepatoblastoma cells.

PURPOSE: Since reactive oxygen species (ROS) act as mediators of radiation-induced cellular damage, the aim of our studies was to determine the effects of ionizing radiation on the regulation of hepatocellular reduced glutathione (GSH), survival and integrity of nuclear and mitochondrial DNA (mtDNA) in human hepatoblastoma cells (Hep G2) depleted of GSH prior to radiation. METHODS AND MATERIALS: GSH, oxidized glutathione (GSSG), and generation of ROS were determined in irradiated (50-500 cGy) Hep G2 cells. Clonogenic survival, nuclear DNA fragmentation, and integrity of mtDNA were assessed in cells depleted of GSH prior to radiation. RESULTS: Radiation of Hep G2 cells (50-400 cGy) resulted in a dose-dependent generation of ROS, an effect accompanied by a decrease of reduced GSH, ranging from a 15% decrease for 50 cGy to a 25% decrease for 400 cGy and decreased GSH/GSSG from a ratio of 17 to a ratio of 7 for controls and from 16 to 6 for diethyl maleate (DEM)-treated cells. Depletion of GSH prior to radiation accentuated the increase of ROS by 40-50%. The depletion of GSH by radiation was apparent in different subcellular sites, being particularly significant in mitochondria. Furthermore, depletion of nuclear GSH to 50-60% of initial values prior to irradiation (400 cGy) resulted in DNA fragmentation and apoptosis. Consequently, the survival of Hep G2 to radiation was reduced from 25% of cells not depleted of GSH to 10% of GSH-depleted cells. Fitting the survival rate of cells as a function of GSH using a theoretical model confirmed cellular GSH as a key factor in determining intrinsic sensitivity of Hep G2 cells to radiation. mtDNA displayed an increased susceptibility to the radiation-induced loss of integrity compared to nuclear DNA, an effect that was potentiated by GSH depletion in mitochondria (10-15% intact mtDNA in GSH-depleted cells vs. 25-30% of repleted cells). CONCLUSION: GSH plays a critical protective role in maintaining nuclear and mtDNA functional integrity, determining the intrinsic radiosensitivity of Hep G2. Although the DNA repair is a complex process that is not yet completely understood, the protective role of GSH probably does not seem to involve the repair of classical DNA damage but may relate to modification of DNA damage dependent signaling.

Apoptosis↗