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R Blanco

Publications and source records attributed to R Blanco.

At least 109 records · Page 6Linked to original sources
PubMed1996

Action potentials in axonless horizontal cells isolated from the rabbit retina.

Axonless horizontal cells were enzymatically dissociated from the retinae of adult rabbits. Whole-cell patch-clamp recordings were made on dissociated cells and voltage- and ligand-induced currents were studied. When membrane potential was measured in the current-clamp configuration, current pulses injected into the cell induced repetitive action potentials. When the cells were depolarised by bath application of kainic acid (KA, 30 microM), a train of fast-repetitive action potential was evoked. Also, a slow long-lasting calcium action potential kept the cells depolarised long after the cessation of the KA application. These findings indicate for the first time that horizontal cells of the mammalian retina are able to produce trains of action potentials.

Action Potentials↗
PubMed1996

Acute febrile toxic reaction in patients with refractory rheumatoid arthritis who are receiving combined therapy with methotrexate and azathioprine.

OBJECTIVE: To assess the frequency and clinical features of an acute febrile toxic reaction (AFTR) in patients with refractory rheumatoid arthritis (RA) receiving combined therapy with methotrexate (MTX) and azathioprine (AZA). METHODS: A cohort of 43 RA patients being treated with MTX/AZA combination therapy were studied. In all of them, RA had been refractory to single-therapy disease-modifying antirheumatic drugs. We analyzed the frequency and clinical features of AFTR, which consisted mainly of the development of fever, leukocytosis, and cutaneous leukocytoclastic vasculitis when AZA was added to the MTX regimen. RESULTS: Four of the 43 patients (9.3%) who had been receiving long-term, well-tolerated treatment with MTX (mean +/- SD 375.5 +/- 159.5 days, range 227-561 days) developed AFTR shortly (mean +/- SD 25.7 +/- 13.6 days, range 17-46 days) after the addition of AZA to the regimen. The AFTR resolved rapidly (3 +/- 1.4 days) after discontinuation of AZA and MTX. In 2 cases, rechallenge with AZA and MTX was linked to a new flare of AFTR. CONCLUSION: The knowledge of this side effect is particularly important because it mimics a severe infectious complication related to immunosuppressive therapy, and because rechallenge can produce severe toxicity. Most of the new combined therapies for RA do not seem to be more toxic than single-drug treatment. Nevertheless, clinicians should be aware of a possible increase in side effects due to drug interactions or some other unidentified mechanism.

Acute Disease↗
PubMed1996

Complex segregation analysis of non-myoclonic idiopathic generalized epilepsy in families ascertained from probands affected with idiopathic epilepsy with tonic-clonic seizures in Antioquia, Colombia.

In an attempt to identify the possible role of major genes, multifactorial inheritance, and cohort effects in the susceptibility to idiopathic epilepsy with generalized tonic-clonic seizures of the awakening type (GTCS), complex segregation analysis was performed in 196 nuclear families ascertained through affected probands with idiopathic epilepsy with GTCS belonging to the Paisa community of Antioquia (Colombia). Models postulating no transmission, single major locus (dominant and recessive) only, and multifactorial component only, were rejected. Since the codominant single major locus model could not be rejected and models that assign no major locus to transmission, no polygenic component to transmission, and no transmission of the major effect were rejected, complex segregation analysis suggested that a major autosomal codominant allele together with a multifactorial component (mixed model) best explained clustering of idiopathic epilepsy with GTCS in families of the Paisa community. The deficit of transmission of heterozygotes (0.17) is compatible with the existence of epistasis acting on a major gene whose frequency was estimated to be 0.0211. Its transmission variance accounts for 81% of the susceptibility to idiopathic epilepsy with GTCS. The complementary variance (19%) is due to the polygenic component.

Alleles↗
PubMed1996

Selective c-Jun overexpression is associated with ionizing radiation-induced apoptosis in the developing cerebellum of the rat.

Immunohistochemistry to Bcl-2, Bax, c-Myc, c-Fos, Fos-related, c-Jun, Jun B and Jun D was used to study the involvement of these factors in ionizing radiation-induced apoptosis in the cerebellum of the developing rat. Selective c-Jun overexpression was observed during the whole process of radiation-induced cell death. Furthermore, c-Jun overexpression was restricted to apoptotic cells, as shown by double labeling with the method of in situ labeling of nuclear DNA fragmentation and c-Jun immunohistochemistry. This is the first in vivo evidence that selective c-Jun overexpression is associated with apoptotic cell death in the developing nervous system following ionizing radiation.

Animals↗
PubMed1996

Transforming growth factor-alpha (TGF-alpha) and epidermal growth factor-receptor (EGF-R) immunoreactivity in normal and pathologic brain.

Transforming growth factor alpha (TGF-alpha) and epidermal growth factor-receptor (EGF-R) immunoreactivity is observed in the majority of neurons, and in maturing astrocytes, in the developing and adult brain of humans and different species of animals. TGF-alpha and EGF-R co-localize in most neurons and maturing astrocytes, suggesting that most TGF-alpha-producing cells are EGF-R-expressing cells. TGF-alpha and EGF-R immunoreactivity decrease in damaged areas following different insults. However, EGF-R appears in reactive glia, mostly reactive astrocytes, within and surrounding the damaged areas. TGF-alpha and EGF-R immunoreactivity is found in neurons of patients affected by Alzheimer's disease and other forms of dementia, and in neurons of patients suffering from epilepsy owing to different causes, thus pointing to the conclusion that TGF-alpha does not play a significant role in these pathologies. However, EGF-R immunoreactivity occurs in reactive astrocytes and microglia in subacute but not chronic lesions in human cases. Since TGF-alpha is a membrane-anchored growth factor, which may be cleaved leading to the formation of soluble forms, and both the membrane-anchored and soluble forms have the capacity to activate the EGF-R, it is feasible that TGF-alpha in the nervous system may act upon EGF-R-containing neurons through different mechanisms. In addition to distant effects resulting from the release of soluble TGF-alpha, local effects may be produced by establishing direct cell-to-cell contacts (juxtacrine stimulation), or in cells expressing both TGF-alpha and EGF-R (autocrine stimulation).

Animals↗
PubMed1996

The effects of GABA and glycine on horizontal cells of the rabbit retina.

Intracellular and patch-clamp recordings have been used to characterize GABA-activated channels in axonless horizontal cells (ALHC) of the rabbit retina. In our intracellular recordings on an everted eyecup preparation, GABA depolarized the horizontal cells (HC), diminished their light response amplitude and slowed the response rise time. Glycine showed similar effects on the HC light responses. In our whole cell patch-clamp recordings on dissociated ALHC, all HCs responded to 3 microM GABA but none to glycine, even at 100 microM. Dose-response relationship for GABA gave EC50 values around 10 microM and Hill slopes of 1.3. Whole-cell current-voltage (I-V) relationships of GABA-activated currents reversed close to the predicted Cl- equilibrium potential. Partial replacement of intracellular Cl- with isothetionate shifted the GABA reversal potential to a more negative value. Muscimol (30 microM), a GABAA agonist mimicked the effect of GABA, but baclofen (30 microM), a GABAB agonist and cis-aminocaprionic acid (30 microM), a GABAC agonist did not elicit any effect on ALHC. Responses to GABA were blocked by the GABAA receptor antagonist bicuculline (10 microM) and picrotoxin (100 microM). According to our results, we conclude that ALHC express GABA receptors coupled to ion channels, and they correspond to GABAA receptor subtypes.

Animals↗
PubMed1996

[Molecular and genetic features of fragile X syndrome].

The fragile-X syndrome is the most frequent cause of sexlinked mental retardation. In the majority of the cases the mutation responsible for the Martin Bell syndrome is produced when an expansion of the (CGG)n repetition is present in the region 5' of the exón 1 of the gene for X-fragile mental retardation 1 (FMR1), together with a hipermethylation in the CpG promoter region of the gene. The result of this situation is the absence of FMRP protein coded by the gene. The correlation between length of the (CGG)n sequences and of the X-fragile phenotype has permitted a more precise diagnosis of affected and carrier individuals by means of direct DNA analysis. Nevertheless the molecular genetic basis of the instability and expansion of the (CGG)n sequence represents a problem not yet resolved. Two polymorphic microsatellite (AC)n repetitions, FRAXAC1 and FRAXAC2 that flank the FMR-1 gene have been recently described. It has been suggested that some haplotypes of FRAXAC1 and FRAXAC2 could be associated to long (CGG)n repetitions and that these haplotypes would confer more instability to the repeated fragment thus increasing the probability of expansion. It has also been described that the (CGG)n repetition of the FMR-1 gene is interrupted by AGG trinucleotides and that the loss of one AGG would be an important mutational event in the generation of predisposing unstable alleles of of the X-fragile syndrome.

Chromosome Mapping↗
PubMed1996

Idiopathic epilepsy with generalized tonic clonic seizures in Antioquia, Colombia: is the joint Amerindian and Negroid racial admixture the cause of its high prevalence?

Most Colombian populations stem from the admixture of Caucasians, Amerindians and Negroids. In the world, these two latter ethnical groups show a significantly higher prevalence of epilepsy than the former one. We tested the hypothesis that the high prevalence of idiopathic epilepsy with generalized tonic clonic seizures found in the Antioquian population (Paisas), from Colombia, is due to their possible joint Negroid and Amerindian ethnic components. We have previously demonstrated that inheritance is the principal factor for developing epilepsy in this community. Analyses of racial admixture, heterogeneity between populations, genetic distance, and phyletic relationships were performed among epileptic and non epileptic samples from the Antioquian community. Also Caucasians, Spaniards, Basques, Jews, Chileans, Negroids, Amerindians and Mongoloids were included in the analysis. Four highly polymorphic blood systems were used as genetic markers: RH, MNS, ABO and FY. They were chosen because of their high discriminant power in these ethnic groups. In the population affected with idiopathic epilepsy, the estimated Negroid and Amerindian rates of admixture were low (3% and 14%, respectively). Although, these degrees of admixture can be explained due to common ancestral origins, the estimated proportion of Amerindian admixture in the epileptic affected population, was significantly higher than the estimated for the Non affected Antioquian population. The latter finding is consistent with the analysis of heterogeneity between populations that discriminated epileptic population from non epileptic Antioquian population (p < 0.05). Epileptic and non epileptic Paisas clustered in topology with Caucasians, very close to Spaniards and Basques and highly distant from Negroids and Amerindians. Thus, far, the origin of the high prevalence of idiopathic epilepsy in the Antioquian (Paisa) population cannot be explained by the hypothetical joint Negroid and Amerindian ethnical admixture, but using additional genetic markers and other methods of racial estimation of admixture it is necessary to corroborate if the Amerindian admixture component is significantly higher in the epileptic population than in the non epileptic Paisa population.

Black People↗
PubMed1996

[Genetic factors study in family aggregation of schizophrenia in Santiago, Chile].

BACKGROUND: Genetic epidemiological studies indicate that genetic factors contribute to a familial aggregation of schizophrenia. The form of inheritance has not been elucidated but most studies have been done in Caucasian populations. AIM: To study the form of inheritance of schizophrenia in an urban population of Santiago, Chile, containing an admixture of Spanish origin individuals with Southamerican aborigines. SUBJECTS AND METHODS: Forty four randomly selected schizophrenic probands, 22 female, aged 28 to 48 years old, were studied. From them, an extensive genealogical reconstitution was performed. Probands and relatives were interviewed using the structured interview CIDI and DSM-III-R check-list. Schizophrenia was diagnosed using DSM-III-R criteria. Complex segregation analysis was done using Pointer program. RESULTS: The hypothesis of a multifactorial inheritance, without the participation of major genes, could not be rejected. Likewise, the major dominant and co-dominant gene forms of transmission could not be rejected. CONCLUSIONS: Our results show the participation of a major dominant locus and a multifactorial component in the inheritance of schizophrenia, as has been reported elsewhere.

Adult↗
PubMed1995

[Giant cell arteritis. A study of 191 patients].

BACKGROUND: The aim of the present was to study the clinical features of a wide series of patients with giant cell arteritis (GCA) diagnosed with accurate criteria and to evaluate the sensitivity of the criteria proposed by the ACR for classification of GCA. METHODS: A retrospective analysis of 191 patients with GCA, 184 of whom were diagnosed by biopsy and 7 due to their clinical manifestations was carried out. RESULTS: The age was 73 +/- 7 years with the most frequent symptoms being headache (87%), abnormalities in the temporal arteries (75%), general malaise (60%), rheumatic polymyalgia (49%) and mandibular claudication (40%). The frequency of GCA was equal in both genders although the most complex syndrome was observed in women with a greater frequency of polymyalgia (p < 0.005), jaw claudication (p < 0.01) and anemia (p < 0.01). The patients with polymyalgia were characterized by a predominance of the polymyalgic syndrome in the initial phases and a higher frequency of amaurosis. Out of 47 patients with amaurosis, 23 remained with permanent unit or bilateral blindness. Unilateral biopsy of the temporal artery was diagnosed in 91% of the cases (CI 95%; 86 to 95%) increasing to 96.3% (CI 95%; 92 to 98%) on biopsy of both arteries. Ninety-eight percent of the patients (CI 95%; 95 to 99%) had 3 or more GCA criteria for classification as GCA. CONCLUSIONS: The clinical manifestations of giant cell arteritis in Spain, with the exception of an equal frequency in both sexes, are similar to that described in other series of patients selected with strict criteria. The present data confirm the sensitivity of the criteria proposed by the ACR for the classification of giant cell arteritis although its application does not avoid the need for temporal artery biopsy for diagnosis. Unilateral biopsy is usually suffice in most of the cases.

Aged↗
PubMed1995

Association between alleles of the transforming growth factor alpha locus and cleft lip and palate in the Chilean population.

Two RFLPs at the TGFA locus were studied in 39 unrelated Chilean (Caucasoid-Mongoloid) patients with non-syndromic cleft lip/palate [CL(P)] and 51 control individuals. A highly significant association between BamHI A2 allele and CL(P) was detected (chi 2 = 6.00; P = 0.014), while no association was found between TaqI RFLPs and clefting. No significant differences were found when comparing genotypes by type of cleft and a positive or negative family history of clefting. Our results seem to support rather definitively the association between TGFA and clefting but do not support the hypothesis that TGFA is a major causal gene of CL(P).

Alleles↗
PubMed1995

Amoeboid microglial response following X-ray-induced apoptosis in the neonatal rat brain.

The phagocytic response following X-ray-induced apoptosis in the neonatal rat brain was examined by immunohistochemistry with the antibodies OX-6 and OX-42 which recognize MHC class II antigens and the CR3 complement receptor, respectively. Few OX-6-immunoreactive cells were observed in control rats, and in rats irradiated at postnatal day 2 and examined during the first 2 postnatal weeks. However, a transient increase in the number of OX-42-immunoreactive amoeboid microglia, containing large numbers of apoptotic cells, occurred at 6, 24 and 48 h after irradiation when compared with age-matched controls. These results show that X-ray-induced apoptosis promotes a short-lasting phagocytic response.

Animals↗