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S Vazquez

Publications and source records attributed to S Vazquez.

At least 19 recordsLinked to original sources
PubMed2005

Quasiclassical trajectory study of the F + CH4 reaction dynamics on a dual-level interpolated potential energy surface.

An ab initio interpolated potential energy surface (PES) for the F + CH4 reactive system has been constructed using the interpolation method of Collins and co-workers. The ab initio calculations have been performed using second-order Möller-Plesset (MP2) perturbation theory to build the initial PES. Scaling all correlation (SAC) methodology has been employed to improve the ab initio calculations and to construct a dual-level PES. Using this PES, a detailed quasiclassical trajectory study of integral and differential cross sections, product rovibrational populations and internal energy distributions has been carried out for the F + CH4 and F + CD4 reactions and the theoretical results have been compared with the available experimental data.

Journal Article↗
PubMed2001

Construction, characterization and immunogenicity of recombinant yellow fever 17D-dengue type 2 viruses.

Chimeric yellow fever (YF)-dengue type 2 (Den 2) viruses were constructed by replacing the premembrane (prM) and envelope (E) genes of YF 17D virus with those from Den 2 virus strains of south-east Asian genotype. Whereas viable chimeric viruses were successfully recovered when the YF 17D C gene and the Den 2 prM gene were fused at the signalase cleavage site, no virus could be rescued from the constructions fused at the viral protease cleavage site. Unlike YF virus that replicated in all the cell lines tested and similar to the Den 2 virus, the recombinant viruses did not replicate in vaccine-production certified CEF and MRC5 cells. Besides, chimeric 17D/Den 2 viruses and their parental viruses reached similar growth titers in Vero and C6/36 cell cultures. Analysis of mouse neurovirulence, performed by intracerebral inoculation, demonstrated that the 17D/Den 2 chimera is more attenuated in this system than the YF 17DD virus. Immunization of mice with this chimera induced a neutralizing antibody response associated with a partial protection against an otherwise lethal dose of mouse neurovirulent Den 2 NGC virus. Overall, these results provide further support for the use of chimeric viruses as an attractive methodology for the development of new live flavivirus vaccines.

Amino Acid Sequence↗
PubMed2001

A study of kynurenine fragmentation using electrospray tandem mass spectrometry.

A combination of accurate mass measurement and tandem mass spectrometry (both product ion and precursor ion scans) have been used to characterize the major fragment ions observed in the ESI mass spectrum of kynurenine. Kynurenine is a metabolite of tryptophan found in the human lens and is thought to play a role in protecting the retina from UV-induced damage. Three major fragmentation pathways were evident, following initial elimination either of ammonia, H2O and CO or the imine form of glycine. The latter is proposed to occur via the formation of an ion-molecule complex. In the case of loss of H2O and CO from deaminated kynurenine, there is evidence for an acylium ion intermediate, which is not observed for the loss of H2O and CO directly from protonated kynurenine. Product ion scans of deuterated kynurenine enabled the elucidation of structural rearrangements that were not evident in the spectra of the native compound. Since UV filter compounds can often only be isolated in small quantities from the lens, this study forms the basis for the characterization of novel UV filter compounds using mass spectrometry. The approach presented here may also be useful for the characterization of related classes of small molecules.

Ammonia↗
PubMed2000

Cross-coupling of highly pyramidalized alkenes: A straightforward access to functionalized tetrasecododecahedradienes

The synthesis and chemical trapping of a highly pyramidalized pentacyclo[6.4.0.0(2,10).0(3,7).0(4,9)]dodec-8-ene containing ketal functions is reported. Its cross-coupling reaction with 3, 7-dimethyltricyclo[3.3.0.0(3,7)]oct-1(5)-ene followed by a [2 + 2] retrocycloaddition reaction gives a straightforward access to functionalized tetrasecododecahedradienes.

Journal Article↗
PubMed2000

Ictal SPECT in paroxysmal non-kinesigenic dyskinesia. Case report and review of the literature.

Purpose: Paroxysmal non-kinesigenic dyskinesia (PNKD) should be included in the list of differential diagnosis in patients with refractory epilepsy. Although the pathophysiological mechanisms that underlie this disorder remain controversial, it is now accepted that the basal ganglia are the anatomical substrate responsible for it.Material and methods: We report a 16-year-old mentally retarded male with PNKD admitted for video-EEG monitoring and ictal SPECT, which showed hyperperfusion on the right caudate and thalamus.Conclusion: This case supports more evidence for the involvement of the caudate nucleus and thalamus in the mechanisms responsible for the production of PNKD.

Journal Article↗
PubMed2000

Characterisation of the major autoxidation products of 3-hydroxykynurenine under physiological conditions.

3-Hydroxykynurenine (3-OHKyn) is a tryptophan metabolite that is readily autoxidised to products that may be involved in protein modification and cytotoxicity. The oxidation of 3-OHKyn has been studied here with a view to characterising the major products as well as determining their relative rates of formation and the role that H2O2 and hydroxyl radical (HO*) may play in modifying the autoxidation process. Oxidation of 3-OHKyn generated several compounds. Xanthommatin (Xan), formed by the oxidative dimerisation of 3-OHKyn, was the major product formed initially. It was, however, found to be unstable, particularly in the presence of H2O2, and degraded to other products including the p-quinone, 4,6-dihydroxyquinolinequinonecarboxylic acid (DHQCA). A compound that has a structure consistent with that of hydroxyxanthommatin (OHXan) was also formed in addition to at least two minor species that we were unable to identify. Hydrogen peroxide was formed rapidly upon oxidation of 3-OHKyn, and significantly influenced the relative abundance of the different autoxidation species. Increasing either pH (from pH 6 to 8) or temperature (from 25 degrees C to 35 degrees C) accelerated the rate of autoxidation but had little impact on the relative abundance of the autoxidation species. Using electron paramagnetic resonance (EPR) spectroscopy, a clear phenoxyl radical signal was observed during 3-OHKyn autoxidation and this was attributed to xanthommatin radical (Xan*). Hydroxyl radicals were also produced during 3-OHKyn autoxidation. The HO* EPR signal disappeared and the Xan* EPR signal increased when catalase was added to the autoxidation mixture. The HO* did not appear to play a role in the formation of the autoxidation products as evidenced using HO* traps/scavengers. We propose that the cytotoxicity of 3-OHKyn may be explained by both the generation of H2O2 and by the formation of reactive 3-OHKyn autoxidation products such as the Xan* and DHQCA.

Amino Acids↗
PubMed2000

SPECT findings in mentally retarded autistic individuals.

The authors examined specific deficits of cerebral blood perfusion in autistic patients as measured with [(99m)Tc]HMPAO single-photon emission computed tomography (SPECT). The study, conducted in an outpatient clinic setting, included a consecutive series of 30 patients with autism and 14 patients with mental retardation but no autism comparable in chronological age, mental age, height, weight, and head circumference. All participants were examined with a comprehensive psychiatric and neuropsychological battery and received a [(99m)Tc]HMPAO SPECT scan. Autistic patients had significantly lower perfusion than the control group in the following brain regions: right temporal lobe (basal and inferior areas), occipital lobes, thalami, and left basal ganglia. The study demonstrated significant perfusion deficits in specific brain areas of moderately to severely mentally retarded autistic patients.

Autistic Disorder↗
PubMed1999

Identification of glutathionyl-3-hydroxykynurenine glucoside as a novel fluorophore associated with aging of the human lens.

A novel fluorophore was isolated from human lenses using high performance liquid chromatography (HPLC). The new fluorophore was well separated from 3-hydroxykynurenine glucoside (3-OHKG) and its deaminated isoform, 4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid O-glucoside, which are known UV filter compounds. The new compound exhibited UV absorbance maxima at 260 and 365 nm, was fluorescent (Ex(360 nm)/Em(500 nm)), and increased in concentration with age. Further analysis of the purified compound by microbore HPLC with in-line electrospray ionization mass spectrometry revealed a molecular mass of 676 Da. This mass corresponds to that of an adduct of GSH with a deaminated form of 3-OHKG. This adduct was synthesized using 3-OHKG and GSH as starting materials. The synthetic glutathionyl-3-hydroxykynurenine glucoside (GSH-3-OHKG) adduct had the same HPLC elution time, thin-layer chromatography R(F) value, UV absorbance maxima, fluorescence characteristics, and mass spectrum as the lens-derived fluorophore. Furthermore, the (1)H and (13)C NMR spectra of the synthetic adduct were entirely consistent with the proposed structure of GSH-3-OHKG. These data indicate that GSH-3-OHKG is present as a novel fluorophore in aged human lenses. The GSH-3-OHKG adduct was found to be less reactive with beta-glucosidase compared with 3-OHKG, and this could be due to a folded conformation of the adduct that was suggested by molecular modeling.

Aging↗
PubMed1996

Neuropsychological, psychiatric, and cerebral blood flow findings in vascular dementia and Alzheimer's disease.

BACKGROUND AND PURPOSE: Psychiatric, neuropsychological, and cerebral blood flow differences between patients with ischemic vascular dementia (IVD) or Alzheimer's disease (AD) were examined. METHODS: A consecutive series of patients who met either the criteria of the National Institute of Neurological Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association for probable AD or the State of California AD Diagnostic and Treatment Centers criteria for probable IVD were included in the study. Twenty consecutive patients with IVD were matched for age, sex, and Mini-Mental State Examination scores with 40 consecutive patients with probable AD. Patients underwent a psychiatric interview, a neuropsychological assessment, and single-photon emission CT imaging with 99mTc-hexamethylpropyleneamine oxime. RESULTS: Patients with IVD showed significantly more severe anosognosia (P<.05) and emotional lability (P<.01) than AD patients, but no significant between-group differences were found in the frequency and severity of depression. IVD patients showed significantly more severe deficits in tests of planning, sequencing (P<.05), and verbal fluency (P<.05) as well as significantly more severe cerebral blood flow deficits in the basal ganglia (P<.01) and the frontal lobes (P<.001) than AD patients. CONCLUSIONS: Patients with IVD showed a relatively more severe dysfunction of the frontal lobes as demonstrated by single-photon emission CT and expressed in specific psychiatric and neuropsychological changes than AD patients matched for age, sex, and severity of dementia.

Aged↗
PubMed1996

GM1-gangliosidosis presenting as nonimmune hydrops fetalis: a case report.

We report a new case of GM1-gangliosidosis diagnosed in a 5 months old baby who was admitted at birth to our Neonatology Unit because of congenital ascites. The antenatal diagnostic techniques, including ultrasound, maternal antibody screen and fetoscopy with fetal karyotyping, as well as postnatal exhaustive study, failed to determine the underlying cause. Because of progressive neurologic deterioration a lysosomal storage disease was suspected and confirmed by skin biopsy. We wish to add a new case of a lysosomal storage disease to the growing list of nonimmune hydrops fetalis etiologies, and to highlight the importance of enzymatic studies in chorionic villous sample or amniotic cultured cells, once the most common conditions associated with fetal ascitis have been ruled out.

Adult↗
PubMed1995

A SPECT study of parkinsonism in Alzheimer's disease.

The authors examined the presence of significant regional cerebral blood flow (rCBF) differences between Alzheimer's disease (AD) patients with and without extrapyramidal signs (EPS). Nine patients with probable AD and EPS (resting tremor or rigidity and bradykinesia) and 9 AD patients without EPS, comparable in age, duration of illness, and global cognitive decline, were studied with [99mTc]HMPAO SPECT. Patients with AD and EPS showed significantly lower rCBF in the superior frontal, superior temporal, and parietal regions of the left hemisphere than AD patients without EPS. Rigidity and bradykinesia independently accounted for the decreased rCBF in these areas. These findings suggest that the presence of EPS in AD may result from dysfunction in specific brain regions.

Aged↗
PubMed1994

[Granulomatous prostatitis. An infrequent diagnosis. Review of our series].

Granulomatous prostatitis is an inflammatory condition of the prostate which presents rarely in the urological practice. It is caused by several specific and unspecific infectious agents, and can also be secondary to prostate surgery or a local reflection of a systemic granulomatous disease. With regard to clinical manifestations and treatment, it is an unspecific entity which has a characteristic histopathology. Its major interest consists on the possibility of it being mistaken for a prostate cancer during physical examination. This paper reviews a series of 7 granulomatous prostatitis, with special emphasis on their histology and ultrasound findings.

Aged↗
PubMed1993

Favored and suppressed patterns of hydrophobic and nonhydrophobic amino acids in protein sequences.

Hydrophobic amino acids of the group Leu, Ile, Val, Phe, and Met (LIVFM) are distributed in favored or suppressed patterns within protein sequences. The frequencies of all five-position combinations of [symbol: see text] = LIVFM and [symbol: see text] = non-LIVFM residues were analyzed in 48 proteins of known crystallographic structure. Some motifs were strongly preferred or suppressed; e.g., [symbol: see text] was favored (z = 3.5), while [symbol: see text] was suppressed (z = -3.4). In longer patterns, [symbol: see text] followed by [symbol: see text] and one [symbol: see text] was favored ([symbol: see text], z = 5.1), while conversion of the single hydrophobic residue to a pair was not ([symbol: see text], z = 0.8). Distributions of certain non-LIVFM amino acids around [symbol: see text] positions in strongly favored patterns were also favored or disfavored (Asp, Glu, Lys, Arg, Asn, Cys, Tyr, and Pro; for each magnitude of z > 2.0). While the strongly favored pattern [symbol: see text] was found in both alpha-helical and beta-strand sequences, it associated significantly with alpha-helices (z = 3.6 for the second-position alpha-helical phi and psi angles) but not with beta-strands (z = -1.1). Certain motifs of LIVFM and non-LIVFM residues might be selected if they lead efficiently to the local nucleations hypothesized to characterize molten globule intermediates in the folding of proteins.

Amino Acid Sequence↗
PubMed1993

Comparison of actual and random-positioning-model distributions of peptide scavenging and T cell-presented sites in antigenic proteins.

In a peptide with a T cell-presented epitope (T site), a folded structure with a hydrophobic surface, 'the scavenger (S) site', may regulate transfer to major histocompatibility complex class II molecules. Three procedures which were proposed to identify T sites selected for amphipathic helical patterns but not T sites. In testing whether S sites lay in or near T sites, we found their linkage was not greater than that generated by a model in which segments of equal length and number to the S and T sites for each protein were distributed at random. This study establishes criteria for evaluation of schemes to predict functional motifs in antigenic proteins.

Amino Acid Sequence↗
PubMed1992

[Therapeutic options in metastatic renal carcinoma].

Within the scope of urogenital tract tumoral diseases, renal adenocarcinoma is the third most frequent neoplasia diagnosed in the adult population. The limited clinical presentations in early analysis and their anarchical behaviour are the cause for 50% to 60% of patients having already developed distant disease at the time of diagnosis. The only curative procedure so far is radical surgery, which is possible when there is a single metastatic site and sometimes even, depending on various factors which will be analyzed, several sites. In these occasions, the traditional therapeutic choices (Hormonotherapy, Chemotherapy, Radiotherapy) have proven to have limited or no efficacy in managing the disease. This fact, together with the successful results obtained in other tumoral processes, have allowed the clinical development of different modalities of Immunotherapy for the management of metastatic renal carcinoma, with results clearly hopeful. This work is a review of the results reported for each of the mentioned therapeutic choices, basically analyzing the role currently played by surgery and immunotherapy in the management of advanced renal carcinoma.

Combined Modality Therapy↗
PubMed1991

Imaging histamine H1 receptors in the living human brain with carbon-11-pyrilamine.

The brain distribution and kinetics of the H1 receptor antagonist, carbon-11-pyrilamine (11C-pyrilamine) were examined in vivo in two baboons and one human by positron emission tomography. After i.v. administration of the tracer, brain activity peaked within 20 min after injection and subsequently decreased, reflecting reversible binding to the receptor. Pretreatment with 1 mg/kg diphenhydramine reduced the brain activity at 70 min by 33%, 29%, 26%, and 23% of the control values in frontal cortex, temporal cortex, hippocampus, and cerebellum, respectively. Coinjection of 1 and 5 mg/kg cold pyrilamine reduced the activity at 70 min by 40%, 36%, 34%, and 30% in frontal, temporal, hippocampus and cerebellum, respectively. The in vivo specific binding to the H1 receptors in different brain regions at 70 min after injection correlated with the in vitro H1 histamine receptors distribution in human brain tissue obtained at autopsy, with high values in the frontal and temporal cortex and low values in cerebellum and brain stem. In the healthy human volunteer study, the value of washout of radioactivity increased by about 50% after injection of 0.7 mg/kg diphenhydramine.

Adult↗
PubMed1990

Dengue hemorrhagic fever in Cuba, 1981: a retrospective seroepidemiologic study.

In Cuba, 2 epidemics of dengue virus occurred: 1 caused by DEN-1 in 1977 and 1 caused by DEN-2 in 1981. The latter was associated with cases of dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS). To study viral risk factors for DHF/DSS, a retrospective seroepidemiological survey was conducted in Cerro, a densely populated district in Havana City. The prevalence of plaque reduction neutralizing antibodies to DEN-1 and DEN-2 viruses was measured in 1,295 individuals (children and adults). Of these, 43.7% were immune to DEN-1 virus and 23.6% to DEN-2 virus. Of those individuals who were immune, 26.1% were immune to DEN-1 virus only, 6% to DEN-2 virus only, and 17.6% to both viruses. The DEN-2 virus infection rate in DEN-1 immune individuals was 3.8 times higher than in non-immune individuals. The 5 DHF/DSS cases in the sample had evidence of DEN-1 virus plus DEN-2 virus infections. Three were children and 2 were young adults. No cases were found in individuals infected with DEN-1 virus or DEN-2 virus only. Children infected by DEN-1 virus followed by DEN-2 virus had a high risk of acquiring DHF/DSS. Blacks and whites were equally infected with DEN-1 and DEN-2 viruses.

Adolescent↗