Biomedical subjects

B Fernández

Publications and source records attributed to B Fernández.

At least 19 recordsLinked to original sources

PubMed2006

Anomalous origin of the left coronary artery from the right side of the aortic valve in Syrian hamsters (Mesocricetus auratus).

This study describes the coronary artery distribution patterns associated with the anomalous origin of the left coronary artery from the right side of the aortic valve in Syrian hamsters. The hearts of 15 affected animals were examined by means of a corrosion-cast technique, histology and scanning electron microscopy. The hamsters belonged to a laboratory inbred colony with a high incidence of coronary artery anomalies and bicuspid aortic valves. The aortic valve was tricuspid in eight hamsters and bicuspid in the other seven. In all cases, the right coronary artery was normal, whereas the left main coronary artery trunk arose from the right aortic sinus or from the right side of the ventral aortic sinus when the aortic valve was bicuspid. In 12 specimens, the left main trunk crossed the infundibular septum and then divided into the left circumflex branch and the obtuse marginal branch. In another specimen, the course of the left main trunk was ventral to the right ventricular outflow tract; in the remaining two, it surrounded the aorta dorsally. In man, some of these distribution patterns may cause myocardial ischaemia and sudden death. The present findings prove that the origin of the left coronary artery from the right aortic sinus occurs in primitive mammals such as the Syrian hamster, suggesting that the defect may occur in other mammalian species. Its possible occurrence should be borne in mind in domestic animals, especially in those with signs of myocardial ischaemia after strenuous activity.

Animals↗

PubMed2006

Monitoring biomarkers in fish (Lepidorhombus boscii and Callionymus lyra) from the northern Iberian shelf after the Prestige oil spill.

Hepatic biomarker responses were measured in two demersal fish species (Lepidorhombus boscii and Callionymus lyra) from the northern Iberian shelf associated with the massive Prestige oil spill (POS), five months after the accident. The biomarkers selected were 7-ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), glutathione reductase (GR), catalase (CAT), and DNA integrity. Interspecies differences and spatial variations in biomarker responses were observed along the shelf. GST, GR and CAT activities were significantly elevated in L. boscii in the most oil impacted area (Finisterre) and positively correlated (p<0.05) with POS tar aggregate densities. The lack of previous data from the area together with the existence of chronic background pollution of the shelf implies that the observed biomarker responses cannot be solely attributed to the petroleum hydrocarbon components of the spilled oil. This first biological effect assessment showed that L. boscii is a potentially suitable target species to be used in future biomonitoring programmes along the northern Iberian shelf.

Animals↗

PubMed2006

The expression of nNOS, iNOS and nitrotyrosine is increased in the rat cerebral cortex in experimental hepatic encephalopathy.

The changes in the distribution and amount of nitric oxide (NO) synthases (nNOS and iNOS) and the appearance of nitrotyrosine (NT) in the rat cerebral cortex were investigated following portacaval anastomosis (PCA), an experimental hepatic encephalopathy (HE) model. One month after PCA, rats showed more neurones immunoreactive to nNOS than did control animals. At 6 months post PCA, the number of neurones expressing nNOS had again increased and the intensity of the immunoreactions was stronger. Immunohistochemical analysis also showed that iNOS was increasingly expressed in pyramidal-like cortical neurones and in perivascular astrocytes from 1 to 6 months post PCA. In addition, a significant increase in cerebral iNOS concentration, at both post-PCA periods, was determined by Western blotting. The iNOS induction appears to be correlated with the length of the post-PCA period. PCA also induced the expression of NT, a nitration product of peroxynitrite. NT immunoreactivity was found in pyramidal-like cortical neurones. At 6 months, NT immunoreactivity was also evident in perivascular astrocytes, which was concomitant with a significant increase in NT protein level. PCA therefore not only increases the expression of nNOS but also induces the expression of iNOS and NT in both neurones and astrocytes. Taken together, these findings indicate that the induction of iNOS in pyramidal neurones and cortical astrocytes 6 months after PCA contributes to the generation of NT, and demonstrate the clear participation of NO in the pathogenic process of HE in this model.

Animals↗

PubMed2005

The effect of antagonistic pleiotropy on the estimation of the average coefficient of dominance of deleterious mutations.

We investigate the impact of antagonistic pleiotropy on the most widely used methods of estimation of the average coefficient of dominance of deleterious mutations from segregating populations. A proportion of the deleterious mutations affecting a given studied fitness component are assumed to have an advantageous effect on another one, generating overdominance on global fitness. Using diffusion approximations and transition matrix methods, we obtain the distribution of gene frequencies for nonpleiotropic and pleiotropic mutations in populations at the mutation-selection-drift balance. From these distributions we build homozygous and heterozygous chromosomes and assess the behavior of the estimators of dominance. A very small number of deleterious mutations with antagonistic pleiotropy produces substantial increases on the estimate of the average degree of dominance of mutations affecting the fitness component under study. For example, estimates are increased three- to fivefold when 2% of segregating loci are over-dominant for fitness. In contrast, strengthening pleiotropy, where pleiotropic effects are assumed to be also deleterious, has little effect on the estimates of the average degree of dominance, supporting previous results. The antagonistic pleiotropy model considered, applied under mutational parameters described in the literature, produces patterns for the distribution of chromosomal viabilities, levels of genetic variance, and homozygous mutation load generally consistent with those observed empirically for viability in Drosophila melanogaster.

Computer Simulation↗

PubMed2005

Neuronal and inducible nitric oxide synthase expression in the rat cerebellum following portacaval anastomosis.

In order to determine the role of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in the pathogenesis of experimental hepatic encephalopathy (HE), the expression of both was analyzed in the cerebellum of rats 1 month and 6 months after performing portacaval anastomosis (PCA). In control cerebella, nNOS immunoreactivity was mainly observed in the molecular layer (ML), whereas the Purkinje cells did not express nNOS. However, nNOS expression was detected in the Purkinje cells at 1 month after PCA, correlating with a decrease in nNOS expression in the ML--part of an overall reduction in cerebellar nNOS concentrations (as determined by Western blotting). At 6 months post-PCA, a significant increase in nNOS expression was observed in the ML, as well as increased nNOS immunoreactivity in the Purkinje cells. nNOS immunoreactivity was also observed in the Bergmann glial cells of PCA-treated rats. While no immunoreactivity for iNOS was seen in the cerebella of control rats, iNOS immunoreactivity was significantly induced in the cerebellum 1 month after PCA. In addition, the expression of iNOS was greater at 6 months than at 1 month post-PCA. Immunohistochemical analysis revealed this iNOS to be localized in the Purkinje cells and Bergmann glial cells. The induction of iNOS in astroglial cells has been associated with pathological conditions. Therefore, the iNOS expression observed in the Bergmann glial cells might play a role in the pathogenesis of HE, the harmful effects of PCA being caused by them via the production of excess nitric oxide. These results show that nNOS and iNOS are produced in the Purkinje cells and Bergmann glial cells following PCA, implicating nitric oxide in the pathology of HE.

Animals↗

PubMed2005

Genetic differentiation and estimation of effective population size and migration rates in two sympatric ecotypes of the marine snail Littorina saxatilis.

On exposed rocky shores in Galicia (northwest Spain), a striking polymorphism exists between two ecotypes (RB and SU) of Littorina saxatilis that occupy different levels of the intertidal zone and exhibit an incomplete reproductive isolation. The setting has been suggested to represent ongoing sympatric speciation by ecological adaptation of the two ecotypes to their respective habitats. In this article we address whether or not the ecotypes have developed their own population structures in response to the rigors of their corresponding environments and life histories. We analyzed four to five allozymic loci from three surveys of the same sites, spanning a 14-year period. An experimental design including three localities with two transects per locality and three shore levels allowed studying temporal and spatial population structure and estimation of effective population sizes (N(e)), neighborhood sizes (N(n)), and migration rates (m). Genetic differentiation was significantly lower in RB populations (theta(ST) = 0.067) than in SU ones (theta(ST) = 0.124). Mean estimates of N(e), N(n), and m did not differ significantly between ecotypes, but local ecotype differences in migration between the two closest localities (larger migration rates in RB than in SU populations) could explain the pattern in population differentiation.

Animals↗

PubMed2005

Acute and chronic effects of exposure to a 1-mT magnetic field on the cytoskeleton, stress proteins, and proliferation of astroglial cells in culture.

This paper reports the effects of exposure to static, sinusoidal (50 Hz), and combined static/sinusoidal magnetic fields on cultured astroglial cells. Confluent primary cultures of astroglial cells were exposed to a 1-mT sinusoidal, static, or combined magnetic field for 1h. In another experiment, cells were exposed to the combined magnetic field for 1, 2, and 4h. The hsp25, hsp60, hsp70, actin, and glial fibrillary acidic protein contents of the astroglial cells were determined by immunoblotting 24h after exposure. No significant differences were seen between control and exposed cells with respect to their contents of these proteins, neither were any changes in cell morphology observed. In a third experiment to determine the effect of a chronic (11-day) exposure to a combined 1-mT static/sinusoidal magnetic field on the proliferation of cultured astroglial cells, no significant differences were seen between control, sham-exposed, or exposed cells. These results suggest that exposure to 1-mT sinusoidal, static, or combined magnetic fields has no significant effects on the stress, cytoskeletal protein levels in, or proliferation of cultured astroglial cells.

Actins↗

PubMed2005

Organogenic responses of Pinus pinea cotyledons to hormonal treatments: BA metabolism and cytokinin content.

Isolated cotyledons from mature Pinus pinea L. embryos were cultured in vitro in a factorial combination of 4.4, 10 and 44.4 microM N6-benzyladenine (BA) for 2, 4, 8, 16 and 35 days to optimize shoot regeneration. Incubation of explants in 44.4 microM BA for 4 days, in place of the standard incubation in 4.4 microM BA for 35 days, reduced the entire culture period to 4 weeks. Shortening the culture period had no significant effect on the caulogenic response or the number of buds formed per cotyledon. To establish the relationship between key moments in the caulogenic process induced by 4.4 microM BA and the endogenous concentrations of the active forms of BA and other isoprenoid-type cytokinins (CKs), we examined uptake, metabolism and amount of BA, as well as the amounts of zeatin, dihydrozeatin and their ribosides in P. pinea cotyledons after 1, 2, 6, 12 and 24 h, and 2, 4, 8, 16 and 35 days of exposure to 8-[14C]BA. Uptake and release of BA were associated with water movement between explants and the medium during the first 8 days of culture. The interconvertible forms of BA were the main metabolites formed in the tissues. Inactivation of BA as a result of conjugation or oxidation was insignificant. The endogenous concentration of BA + N6-benzyladenosine was 20-fold higher than the exogenously applied BA during the competence acquisition phase (Days 0-3). The concentration of isoprenoid-type CKs also increased 16-fold and then decreased during this time. Induction of shoot buds (Days 4-8) was characterized by a second peak of BA uptake by explants that triggered the synthesis of N6-benzyladenosine-5 -monophosphate and by the maintenance of isoprenoid-type CKs. Reestablishment of CK homeostasis marked the shift from the induction phase to the shoot development phase in this organogenic process (Days 8-12).

Benzyl Compounds↗

PubMed2005

Down-regulation of astroglial proteins in the rat cerebellum after portacaval anastomosis.

The effect of short-term portacaval anastomosis (PCA) on the expression of specific astroglial markers [glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS)] in the rat cerebellum was examined to determine the influences of PCA on astroglial cells. The results suggest that PCA directly interferes with astroglial cytoskeleton, as indicated by the irregular distribution and reduced expression of GFAP observed after 1 month. PCA also decreased GS immunoreactivity in the Bergmann glial processes of the molecular layer, as well as in astrocytes of the granule cell layer. It might also modulate glutamatergic nervous activity as GS expression was reduced in 1 month post-PCA brains. Moreover, the GFAP and GS levels in PCA-exposed rats were lower than in control rats. This might contribute to the appearance of encephalopathy by increasing extracellular glutamate and/or ammonia concentrations. These results show that short-term PCA interferes with astroglial protein expression, with both GFAP and GS levels falling in astroglial cells.

Animals↗

PubMed2005

Partial nitrification of wastewater from an aminoplastic resin producing factory.

Nitrification via nitrite was studied in two aerobic reactors treating wastewater from an aminoplastic resin producing factory at HRT varying between 1.37-1.89 and 2.45-3.63 days. Both eactors were fed with concentrations of 366, 450, 1099 and 1899 mg N-NH4+/L. In general in the reactor operated at a lower HRT, the nitritation percentage decreased from 87.2 to 21.6%, while the nitratation percentage remained always lower than 2.5% (except in the last period) when the ammonium concentration was increased. This behaviour could be due to the inhibition of the ammonium and nitrite oxidation produced by high free ammonia concentrations up to 179.3 mg N-NH3/L. In the reactor operated at a higher HRT, the nitritation percentage decreased and the nitratation percentage increased from 88.6 to 39.6% and from 0.65 to 35.7%, respectively, due to an increase of the dissolved oxygen concentration from 0.76 to 1.02 mg O2/L. However, when ammonium was fed at a concentration of 1898.7 mg N-NH4+/L, the nitritation increased and the nitratation decreased, probably as a result of the accumulation of free ammonia up to 2.04 mg N-NH3/L, meaning that nitrite oxidizers were inhibited. Nitrite build-up was observed after each modification of ammonium concentration in the feed.

Aerobiosis↗

PubMed2004

Two cases of tetrasomy 9p syndrome with tissue limited mosaicism.

Tetrasomy of short arm of chromosome 9 constitutes a clinically recognizable chromosomal syndrome. Isochromosome 9p shows a strong propensity to tissue-limited mosaicism. It occurs predominantly in peripheral blood cultures, often at a lower frequency or even absent in skin, amniotic fluid or chorionic villous cell cultures. Tissue-limited nature of mosaicism may render prenatal detection of this condition very difficult. Herein, we report two new cases of mosaic tetrasomy 9p. Conventional cytogenetics (CC) and FISH studies demonstrated a differential expression of the mosaicism in several tissues. We review the literature and discuss the implications of these findings in cytogenetic prenatal diagnosis.

Aneuploidy↗

PubMed2004

Mutation-selection balance accounting for genetic variation for viability in Drosophila melanogaster as deduced from an inbreeding and artificial selection experiment.

We carried out an experiment of inbreeding and upward artificial selection for egg-to-adult viability in a recently captured population of Drosophila melanogaster, as well as computer simulations of the experimental design, in order to obtain information on the nature of genetic variation for this important fitness component. The inbreeding depression was linear with a rate of 0.70 +/- 0.11% of the initial mean per 1% increase in inbreeding coefficient, and the realized heritability was 0.06 +/- 0.07. We compared the empirical observations of inbreeding depression and selection response with computer simulations assuming a balance between the occurrence of partially recessive deleterious mutations and their elimination by selection. Our results suggest that a model assuming mutation-selection balance with realistic mutational parameters can explain the genetic variation for viability in the natural population studied. Several mutational models are incompatible with some observations and can be discarded. Mutational models assuming a low rate of mutations of large average effect and highly recessive gene action, and others assuming a high rate of mutations of small average effect and close to additive gene action, are compatible with all the observations.

Animals↗

PubMed2004

Analysis of the estimators of the average coefficient of dominance of deleterious mutations.

We investigate the sources of bias that affect the most commonly used methods of estimation of the average degree of dominance (h) of deleterious mutations, focusing on estimates from segregating populations. The main emphasis is on the effect of the finite size of the populations, but other sources of bias are also considered. Using diffusion approximations to the distribution of gene frequencies in finite populations as well as stochastic simulations, we assess the behavior of the estimators obtained from populations at mutation-selection-drift balance under different mutational scenarios and compare averages of h for newly arisen and segregating mutations. Because of genetic drift, the inferences concerning newly arisen mutations based on the mutation-selection balance theory can have substantial upward bias depending upon the distribution of h. In addition, estimates usually refer to h weighted by the homozygous deleterious effect in different ways, so that inferences are complicated when these two variables are negatively correlated. Due to both sources of bias, the widely used regression of heterozygous on homozygous means underestimates the arithmetic mean of h for segregating mutations, in contrast to their repeatedly assumed equality in the literature. We conclude that none of the estimators from segregating populations provides, under general conditions, a useful tool to ascertain the properties of the degree of dominance, either for segregating or for newly arisen deleterious mutations. Direct estimates of the average h from mutation-accumulation experiments are shown to suffer some bias caused by purging selection but, because they do not require assumptions on the causes maintaining segregating variation, they appear to give a more reliable average dominance for newly arisen mutations.

Computer Simulation↗

PubMed2003

Involvement of the kappa-opioid receptor in the anxiogenic-like effect of CP 55,940 in male rats.

We have studied the possible interaction between three selective opioid-receptor antagonists, nor-binaltorphimine (NB: kappa) (5 mg/kg), cyprodime (CY: mu) (10 mg/kg) and naltrindole (NTI: delta) (1 mg/kg), and the cannabinoid receptor agonist CP 55,940, in the modulation of anxiety (plus-maze) and adrenocortical activity (serum corticosterone levels by radioimmunoassay) in male rats. The holeboard was used to evaluate motor activity and directed exploration. CP 55,940 (75 microg/kg, but not 10 microg/kg) induced an anxiogenic-like effect, which was antagonised by NB. The other effects of CP 55,940 (75 microg/kg), a decreased holeboard activity and stimulation of adrenocortical activity, were not antagonised by any of the three opioid receptor antagonists. CY and NTI, when administered alone, induced marked reductions in motor activity, anxiogenic-like effects and stimulation of adrenocortical activity. The selective kappa-opioid receptor antagonist NB, on its own, did not modify the level of anxiety but stimulated adrenocortical activity. We provide the first pharmacological evidence about the involvement of the kappa-opioid receptor in the anxiogenic-like effect of CP 55,940.

Animals↗

PubMed2003

Wicking assays for the rapid detection of West Nile and St. Louis encephalitis viral antigens in mosquitoes (Diptera: Culicidae).

The recent outbreaks of West Nile (WN) encephalitis and St. Louis encephalitis (SLE) in the United States have highlighted the need for rapid and specific methods of detecting arboviral antigens in mosquitoes. We evaluated rapid, field-usable assays for detecting and differentiating WN and SLE viruses in mosquito pools, based on a patent-pending, immunochromatographic technology (VecTest) formatted on a dipstick. The device provides results in less than 20 min and can be used in laboratories with adequate containment facilities. In laboratory assessments, both the SLE and WN virus tests demonstrated sensitivity comparable with that of an antigen capture ELISA, but less than can be achieved with Vero cell plaque or reverse-transcriptase polymerase chain reaction assays. There was no evidence of cross-reaction when tested with high concentrations of heterologous flavivirus antigens or with Eastern equine encephalitis or Western equine encephalitis viruses. Both the WN and SLE dipstick tests delivered a clear positive result with a single positive specimen in a pool of 50 mosquitoes. This virus assay technology reduces the time required to obtain test results and will allow rapid medical threat assessment and effective targeting of vector control measures.

Animals↗

PubMed2003

[Hepatitis C virus variability and interferon-mediated pathway inhibition].

The most important aim of this study was to describe the hypothetical relationship between the PePHD region variability (related to the synthesis of a cellular enzyme pseudosubstrate) of the hepatitis C virus and the response of patients to interferon therapy. This interaction could be a determining factor in the antiviral effect of interferon. All samples (from 24 patients with chronic hepatitis C infection) were analyzed using a previously described method based on RT-PCR and nested PCR mediated by single-strand conformation polymorphism assay (SSCP). The patients were divided into three groups with respect to the response to therapy: 8 patients with sustained response, 8 patients with transient response and 8 nonresponders. In all samples a low genetic heterogeneity pattern was detected, which was independent of other factors involved in the lack of response to treatment, such as age, sex or viral genotype. This genetic homogeneity is an indirect indication of the importance of the region on viral persistence. However, more studies are needed to evaluate the real role of this sequence on the interaction between cells and the virus.

Adult↗

PubMed2002

Impaired response to insulin associated with protein kinase C in chronic fructose-induced hypertension.

A fructose-enriched diet induces an increase in blood pressure associated with metabolic alterations in rats. Our hypothesis was that an increase in protein kinase C (PKC) activation, reported in the acute period of fructose overload, and an impaired vessel's response to vasoactive substances contribute to maintain elevated blood pressure levels in the chronic period. The aims of this study were to investigate in this animal model of hypertension: (1) if the increase in PKC activation was also found in the chronic stage; (2) the involvement of nitric oxide and insulin in the vessel's response; and plasma atrial natriuretic factor and nitrites/nitrates (nitric oxide metabolites) behavior. We evaluated the effects of: PKC-stimulator 12,13-phorbol dibutyrate, phenylephrine, insulin, nitric oxide synthase-inhibitor NG-nitro-L-arginine methyl esther (L-NAME) and PKC-inhibitor Calphostin C on aortic rings responses of Sprague-Dawley rats: fructose-fed and control. The fructose-fed group showed higher contractility to 12,13-phorbol dibutyrate than the control group in aortic rings pre-incubated with insulin, and this difference disappeared with L-NAME. The response to phenylephrine in rings pre-incubated with Calphostin C was decreased in the fructose-fed group and increased with Calphostin C plus L-NAME. Fructose-fed rats showed higher levels of plasma atrial natriuretic factor and nitrites/nitrates than controls. In conclusion, chronic fructose feeding seems to develop an impaired response to insulin, dependent on nitric oxide, suggesting a PKC alteration. Vasorelaxant agents, such as atrial natriuretic factor and nitric oxide, would behave as compensatory mechanisms in response to high blood pressure.

Animals↗

PubMed2002

Reduced glial fibrillary acidic protein and glutamine synthetase expression in astrocytes and Bergmann glial cells in the rat cerebellum caused by delta(9)-tetrahydrocannabinol administration during development.

In this study we analyzed the responses of cerebellar astroglial cells to pre- and perinatal delta(9)-tetrahydrocannabinol (THC) exposure in three postnatal ages and both sexes. To determine whether THC during development directly modifies astroglial growth, this study investigated the effects of THC on astroglial morphological changes and on the expression of specific astroglial markers (glial fibrillary acidic protein: GFAP and glutamine synthetase: GS). Our results demonstrated that the administration of THC during development has deleterious effects on astroglial maturation in the cerebellum. These results also indicate that THC might interfere with astroglial differentiation in a way dependent on sex. The effect of cannabinoids on the development of cerebellar astroglial cells (astrocytes and Bergmann glial cells) is to reduce protein synthesis, since both GFAP and GS decreased in astroglial cells, not only during THC exposure but also in adult ages. Our data suggest that pre- and perinatal THC exposure directly interferes with astroglial maturation by disrupting normal cytoskeletal formation, as indicated by the irregular disposition of GFAP and the lower GFAP expression observed at all the ages studied. THC exposure during development may also modulate glutamatergic nervous activity since GS expression is reduced in THC-exposed brains. GS expression increased progressively after THC withdrawal, but GS expression had still not reached control values two months after THC withdrawal. This indicates that glutamate uptake is lower in glial cells exposed to THC, since GS expression is lower than in older controls. Consequently, glutamatergic neurotransmission may be affected by cannabinoid exposure during gestation. Therefore, cannabinoids exert developmental toxicity, at least on astroglial cells, which could contribute to fetal brain growth retardation.

Animals↗