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E Rivas

Publications and source records attributed to E Rivas.

At least 19 recordsLinked to original sources
PubMed2005

Differential role of dopamine in drug- and lithium-conditioned saccharin avoidance.

Rats learn to avoid palatable saccharin solutions that predict the systemic administration of reinforcing drugs as well as malaise-inducing lithium chloride (conditioned saccharin avoidance, CSA). In the present study the involvement of dopamine (DA) transmission in the acquisition of morphine, nicotine and lithium-conditioned CSA was investigated in a two-bottle choice paradigm. Nicotine tartrate (0.2 and 0.4 mg/kg s.c.) administered 15 min after saccharin presentation induced CSA, with a maximum effect at 0.4 mg/kg. The DA D1 receptor antagonist, SCH 39166 (0.1 mg/kg s.c.) and the DA D2 receptor antagonist raclopride (0.3 mg/kg s.c.), administered immediately after saccharin, prevented CSA induced by the lower but not by the higher dose of nicotine. However, combined administration of the two antagonists prevented CSA induced by the higher dose of nicotine. SCH 39166 prevented CSA induced by all morphine doses while raclopride prevented only CSA induced by the lowest dose of morphine (1.75 mg/kg). CSA induced by different doses of lithium given by the same schedule of drug-CSA (i.e. two pairings, 15 min after saccharin) was not affected by SCH 39166. However SCH 39166 impaired the acquisition of lithium-CSA when lithium was given 60 min after saccharin. In contrast, raclopride failed to affect lithium-CSA independently from the delay between saccharin and lithium. These results suggest that DA can play different roles in drug- and in lithium-CSA and are consistent with a different mechanism of drug- as compared to lithium-CSA.

Analysis of Variance↗
PubMed2005

Autosomal dominant congenital fibre type disproportion: a clinicopathological and imaging study of a large family.

Congenital fibre type disproportion (CFTD) is considered a non-progressive or slowly progressive muscle disease with relative smallness of type 1 fibres on pathological examination. Although generally benign, CFTD has a variable natural course and severe progression has been observed in some patients. The pathogenesis of the disorder is unknown and many authors consider CFTD a syndrome with multiple aetiologies rather than a separate clinical entity. A positive family history has been reported in about 40% of cases, but the inheritance pattern is not clear. Both autosomal recessive and dominant modes of inheritance have been suggested. The present paper describes a large, multigenerational kindred that has an inherited myopathy fulfilling the histological criteria of CFTD, with autosomal dominant transmission and high penetrance. The clinical picture, remarkably similar in all affected family members, started in early infancy with mild limb muscle weakness. There was slow progression of symptoms into adulthood, with moderate to severe, mainly proximal, muscle weakness without loss of ambulation. Muscle biopsy from two affected individuals demonstrated predominance of small type 1 muscle fibres without other significant findings. Nerve conduction studies were normal and needle electromyography showed a myopathic pattern. MRI examination performed on three patients from successive generations showed involvement of proximal limb and paraspinal muscles. The clinical and pathological homogeneity in the present family, together with the lack of additional histological abnormalities after decades of disease progression in two affected individuals, supports this being a distinct myopathy with fibre type disproportion. Whether the disease in this family can be regarded as a form of the congenital myopathy known as CFTD or rather a unique condition sharing histological features with CFTD needs further investigation. This is, to our knowledge, the largest kindred with muscle fibre type disproportion reported to date. Our data confirm autosomal dominant inheritance, and this is the first MRI document of this disorder.

Adult↗
PubMed2004

Beta-sarcoglycanopathy (LGMD 2E) in a Spanish family.

Out of 10 autosomal recessive limb-girdle muscular dystrophies reported, 4 are caused by mutations in the genes encoding for sarcoglycans (alpha-, beta-, gamma- and delta-SG). Beta-sarcoglycanopathy (limb-girdle muscular dystrophy 2E) is a genetically heterogeneous disorder which usually presents a severe progressive clinical course. A complete immunohistochemical evaluation of the sarcoglycan complex should be carried out to direct the mutation analysis approach. The present report concerns a Spanish family with a genetically confirmed beta-sarcoglycanopathy. The patient, a 16-year-old female, offspring of a consanguineous marriage, developed a severe limb-girdle muscular dystrophy with a Duchenne-like phenotype. Muscle biopsy showed dystrophic changes and complete absence of the four sarcoglycans. Genetic analysis demonstrated homozygosis for the M100K missense mutation in exon 3, encoding for the proximal extracellular domain. The parents and one sister were found to be carriers. Missense mutations affecting this domain result in the instability of the entire sarcoglycan complex and lead to severe phenotypes as seen in non-sense mutations.

Adolescent↗
PubMed2003

[A brain tissue bank in a neuropathology laboratory. Basic methodology].

The Meixoeiro Hospital Brain Bank (BB) was established at the end of 2002. A BB is a tissue collection and storage system, established under the best conditions to carry out prospective morphological, biochemical or molecular studies. The BB should ideally be supported by a donor program, although samples may also be obtained from autopsy material from patients with neurodegenerative diseases. Recruitment of control cases from brains without neurological diseases is basic. The main goal of a BB is to provide brain tissue for research. Each case requires accurate clinical data, a definite diagnosis and optimal conditions of tissue preservation. The use of protocols to standardize the handling and processing of tissues, data recruitment and neuropathological diagnosis is fundamental to assure the quality and homogeneity of samples. Close collaboration between neuropathologists, neurologists and other specialists is essential in all the process. Although important advances in the tissue banking field have been achieved, the number of donors in Spain still remains low. Stronger institutional support as well as public awareness through better diffusion of the information is necessary to increase the number of donors and improve BB development.

Brain↗
PubMed2002

[Extra-naso-pharyngeal angiofibroma: report of a new case and review of literature].

Juvenile nasopharyngeal angiofibromas are vascular neoplasms, which originate characteristically in the posterior lateral wall of the nasopharynx. Although angiofibromas extend beyond the nasopharynx commonly, sometimes they can have their origin outside nasopharynx. We present an unusual case of extranasopharyngeal angiofibroma. A high level of suspicion is essential for an adequate diagnosis and treatment of these neoplasms.

Adolescent↗
PubMed2001

Noncoding RNA gene detection using comparative sequence analysis.

BACKGROUND: Noncoding RNA genes produce transcripts that exert their function without ever producing proteins. Noncoding RNA gene sequences do not have strong statistical signals, unlike protein coding genes. A reliable general purpose computational genefinder for noncoding RNA genes has been elusive. RESULTS: We describe a comparative sequence analysis algorithm for detecting novel structural RNA genes. The key idea is to test the pattern of substitutions observed in a pairwise alignment of two homologous sequences. A conserved coding region tends to show a pattern of synonymous substitutions, whereas a conserved structural RNA tends to show a pattern of compensatory mutations consistent with some base-paired secondary structure. We formalize this intuition using three probabilistic "pair-grammars": a pair stochastic context free grammar modeling alignments constrained by structural RNA evolution, a pair hidden Markov model modeling alignments constrained by coding sequence evolution, and a pair hidden Markov model modeling a null hypothesis of position-independent evolution. Given an input pairwise sequence alignment (e.g. from a BLASTN comparison of two related genomes) we classify the alignment into the coding, RNA, or null class according to the posterior probability of each class. CONCLUSIONS: We have implemented this approach as a program, QRNA, which we consider to be a prototype structural noncoding RNA genefinder. Tests suggest that this approach detects noncoding RNA genes with a fair degree of reliability.

Algorithms↗
PubMed2001

Computational identification of noncoding RNAs in E. coli by comparative genomics.

Some genes produce noncoding transcripts that function directly as structural, regulatory, or even catalytic RNAs [1, 2]. Unlike protein-coding genes, which can be detected as open reading frames with distinctive statistical biases, noncoding RNA (ncRNA) gene sequences have no obvious inherent statistical biases [3]. Thus, genome sequence analyses reveal novel protein-coding genes, but any novel ncRNA genes remain invisible. Here, we describe a computational comparative genomic screen for ncRNA genes. The key idea is to distinguish conserved RNA secondary structures from a background of other conserved sequences using probabilistic models of expected mutational patterns in pairwise sequence alignments. We report the first whole-genome screen for ncRNA genes done with this method, in which we applied it to the "intergenic" spacers of Escherichia coli using comparative sequence data from four related bacteria. Starting from >23,000 conserved interspecies pairwise alignments, the screen predicted 275 candidate structural RNA loci. A sample of 49 candidate loci was assayed experimentally. At least 11 loci expressed small, apparently noncoding RNA transcripts of unknown function. Our computational approach may be used to discover structural ncRNA genes in any genome for which appropriate comparative genome sequence data are available.

Animals↗
PubMed2000

Synthesis and biological studies of glycosyl dopamine derivatives as potential antiparkinsonian agents.

A new approach to deliver dopamine into the central nervous system, based on the use of D-glucose as transportable agent, has been studied. Glycosyl dopamine derivatives bearing the sugar moiety linked to either the amino group or the catechol ring of dopamine through amide, ester or glycosidic bonds were synthesised as potential antiparkinsonian agents. Studies on the binding to dopamine D2 receptor, in vitro stability, and locomotive effect in mice of the synthetic glycoconjugates are reported.

Animals↗
PubMed2000

Biochemical and biophysical studies of Bacillus subtilis envelopes under hyperosmotic stress.

The behaviour and state of the envelopes from B. subtilis cultures grown in Luria Bertani (LB) medium with and without 1.5 M NaCl are compared. Under hypertonic conditions, the hydrophobicity of the cultures increases. The phospholipid and fatty acid (FA) compositions show important differences: a higher cardiolipin (CL) content [at the expense of phosphatidylglycerol (PG)], and a higher unsaturated and straight chain FA content. The fluidity of the membranes, determined with fluorescent probes, indicates an increase in viscosity of the cytoplasmic membrane. The consequences of these variations in membrane permeability and osmotolerance are discussed.

Bacillus subtilis↗
PubMed2000

[Invagination of the ileum as the etiology of acute abdomen in adults].

In contrast to children, intussusception is an unusual cause of an abdominal emergency in adults. We report on a 65-year-old patient who complained of inconstant crampy abdominal pain for a period of over 6 months. He was admitted to our hospital because of acute intestinal obstruction. Sonography and computer tomography suggested an intussusception. At surgery the diagnosis of an ileo-ileal invagination was confirmed and resection of a segment of the ileum was performed. As shown by macroscopic findings intussusception had existed for several days. Histologically, the underlying disease causing the intussusception was a leiomyoma arising from the submucosa.

Abdomen, Acute↗
PubMed2000

The language of RNA: a formal grammar that includes pseudoknots.

MOTIVATION: In a previous paper, we presented a polynomial time dynamic programming algorithm for predicting optimal RNA secondary structure including pseudoknots. However, a formal grammatical representation for RNA secondary structure with pseudoknots was still lacking. RESULTS: Here we show a one-to-one correspondence between that algorithm and a formal transformational grammar. This grammar class encompasses the context-free grammars and goes beyond to generate pseudoknotted structures. The pseudoknot grammar avoids the use of general context-sensitive rules by introducing a small number of auxiliary symbols used to reorder the strings generated by an otherwise context-free grammar. This formal representation of the residue correlations in RNA structure is important because it means we can build full probabilistic models of RNA secondary structure, including pseudoknots, and use them to optimally parse sequences in polynomial time.

Algorithms↗
PubMed2000

Secondary structure alone is generally not statistically significant for the detection of noncoding RNAs.

MOTIVATION: Several results in the literature suggest that biologically interesting RNAs have secondary structures that are more stable than expected by chance. Based on these observations, we developed a scanning algorithm for detecting noncoding RNA genes in genome sequences, using a fully probabilistic version of the Zuker minimum-energy folding algorithm. RESULTS: Preliminary results were encouraging, but certain anomalies led us to do a carefully controlled investigation of this class of methods. Ultimately, our results argue that for the probabilistic model there is indeed a statistical effect, but it comes mostly from local base-composition bias and not from RNA secondary structure. For the thermodynamic implementation (which evaluates statistical significance by doing Monte Carlo shuffling in fixed-length sequence windows, thus eliminating the base-composition effect) the signals for noncoding RNAs are still usually indistinguishable from noise, especially when certain statistical artifacts resulting from local base-composition inhomogeneity are taken into account. We conclude that although a distinct, stable secondary structure is undoubtedly important in most noncoding RNAs, the stability of most noncoding RNA secondary structures is not sufficiently different from the predicted stability of a random sequence to be useful as a general genefinding approach.

Algorithms↗
PubMed1999

A dynamic programming algorithm for RNA structure prediction including pseudoknots.

We describe a dynamic programming algorithm for predicting optimal RNA secondary structure, including pseudoknots. The algorithm has a worst case complexity of O(N6) in time and O(N4) in storage. The description of the algorithm is complex, which led us to adopt a useful graphical representation (Feynman diagrams) borrowed from quantum field theory. We present an implementation of the algorithm that generates the optimal minimum energy structure for a single RNA sequence, using standard RNA folding thermodynamic parameters augmented by a few parameters describing the thermodynamic stability of pseudoknots. We demonstrate the properties of the algorithm by using it to predict structures for several small pseudoknotted and non-pseudoknotted RNAs. Although the time and memory demands of the algorithm are steep, we believe this is the first algorithm to be able to fold optimal (minimum energy) pseudoknotted RNAs with the accepted RNA thermodynamic model.

Algorithms↗
PubMed1999

In vivo effects of new inhibitors of catechol-O-methyl transferase.

1. The effects of two new synthetic compounds showing in vitro catechol-O-methyl transferase (COMT) inhibitor properties were studied in vivo and compared with the effects of nitecapone and Ro-41-0960. 2. QO IA (3-(3-hydroxy-4-methoxy-5-nitrobenzylidene)-2,4-pentanedione), QO IIR ([2-(3,4-dihydroxy-2-nitrophenyl)vinyl]phenyl ketone), nitecapone and Ro-41-0960 (30 mg kg(-1), i.p.) were given to reserpinized rats 1 h before the administration of L-DOPA/carbidopa (LD/CD, 50:50 mg kg(-1), i.p.). Locomotor activity was assessed 1 h later. All the COMT inhibitors (COMTI), with the exception of QO IA, markedly potentiated LD/CD reversal of reserpine-induced akinesia. Similar results were obtained when the COMTI were coadministered with LD/CD. The effect of compound QO IIR was dose-dependent (7.5-30 mg kg(-1), i.p.). 3. The COMTI (30 mg kg(-1), i.p.) potentiated LD/CD reversal of both catalepsy and hypothermia of reserpinized mice. 4. QO IIR, nitecapone and Ro-41-0960 (30 mg kg(-1), i.p.) reduced striatal 3-methyl-DOPA (3-OMD) levels and increased dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) levels. Compound QO IA was devoid of any effect on striatal amine levels. In contrast to the other inhibitors, Ro-41-0961 reduced HVA levels as well. The effect of QO IIR on striatal amine levels was dose-dependent (7.5-60 mg kg(-1), i.p.) 5. These results suggest that the new compound QO IIR is an effective peripherally acting COMT inhibitor in vivo.

Animals↗
PubMed1998

Osmotic strength blocks sporulation at stage II by impeding activation of early sigma factors in Bacillus subtilis.

In Bacillus subtilis, osmotolerance is a stationary phase-dependent, adaptive response inhibiting sporulation and sharing common regulators with this process. The extent of this inhibition was determined by measuring transcription activity of promoter lacZ fusions to early sigma genes (spoIIG and spoIIA coding for precursors of sigmaE and sigmaF) and to reporters of them (spoIID, spoIIQ and spoIIIG), in the absence and presence of 0.6 M or 1 M NaCl. The transcription activity of these sigma precursors, normally occurring at the onset of the stationary phase, was reduced to 30-50% of their maximal expression in hyperosmotic conditions; expression of genes under their control was, however, more inhibited (<10%). Therefore, sporulation was blocked at the sigma sigmaE and sigmaF activation steps. This assumption was confirmed by electron microscopic examinations of hyperosmotic cultures, which presented asymmetric septa characteristic of stage II mutants. Discussion was focused on the particular composition and/or structure of membranes during hyperosmotic growth and their involvement in the arrest of sporulation.

Bacillus subtilis↗
PubMed1996

Diacylglycerol and the promotion of lamellar-hexagonal and lamellar-isotropic phase transitions in lipids: implications for membrane fusion.

Changes in steady-state fluorescence anisotropy of 1 -(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene TMA-DPH) are applied to the detection of lamellar-hexagonal transitions in egg phosphatidylethanolamine. Even low (2 mole%) proportions of diacylglycerol decrease the hexagonal transition temperature considerably, as confirmed by differential scanning calorimetry. Diacylglycerol is also found to promote a lamellar to "isotropic" (Q(224) cubic) transition in mixtures of phosphatidylcholine: phosphatidylethanolamine:cholesterol. This nonreversible transition is also observed by (31)P nuclear magnetic resonance and detected as a large increase in TMA-DPH steady-state anisotropy. The same technique reveals as well that lysophosphatidylcholine counteracts the effect of diacylglycerol and stabilizes the lamellar phase in both transitions. Diacylglycerol and lysophosphatidylcholine are known to respectively promote and inhibit membrane fusion in a variety of systems. These data are interpreted in support of the hypothesis of a highly bent structural fusion intermediate ("stalk"). They also show the interest of lipid-phase studies in predicting and rationalizing membrane fusion mechanisms.

Calorimetry, Differential Scanning↗