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Biomedical subjects

J C González

Publications and source records attributed to J C González.

At least 19 recordsLinked to original sources
PubMed2006

Persistent auditory hallucinations.

BACKGROUND: There is still a significant proportion of psychotic patients who suffer from persistent auditory hallucinations (PAH) in spite of treatment. The objective of our study was to analyze those clinical dimensions that characterize persistent hallucinators in comparison with episodic hallucinators. SAMPLING AND METHODS: Ninety-one outpatients with AH were assessed through semistructured interviews. The interviews included the Psychotic Symptom Rating Scales for AH and the Krawiecka scale. They elicited descriptions about the persistence of AH, existence of pleasurable hallucinations and other types of hallucinations. RESULTS: Forty-five patients fulfilled criteria for reported PAH. Persistent hallucinators showed greater scores in frequency and duration of hallucinations, Krawiecka total score and incoherence of speech. Moreover, pleasurable experiences were more frequent in this group of patients. Logistic regression analysis rendered a model with the following variables: duration of voices, degree of control and pleasurable hallucinations. CONCLUSION: Specific dimensions of AH can predict the possibility of treatment resistance.

Adult↗
PubMed2006

Structural and optical characterization of strained free-standing InP nanowires.

The structural and optical properties of high-quality crystalline strained InP nanowires are reported in this article. The nanowires were produced by the vapor-liquid-solid growth method in a chemical-beam epitaxy reactor, using 20 nm gold nanoparticles as catalysts. Polarization-resolved photoluminescence experiments were carried out to study the optical properties of the InP nanowires. These experiments revealed a large blue shift of 74 meV of the first electron-to-heavy hole optical transition in the nanowires, which cannot be solely explained by quantum size effects. The blue shift is mainly attributed to the presence of biaxial compressive strain in the inward radial direction of the InP nanowires. High-resolution transmission electron microscopy Electron and selected area electron diffraction experiments show that the nanowires have high crystal quality and grow along a [001] axes. These experiments also confirmed the presence of 1.8% compressive radial strain and 2% tensile longitudinal strain in the nanowires. A simple theoretical model including both quantum confinement and strain effects consistently describes the actual energy position of the InP nanowires optical emission.

Computer Simulation↗
PubMed2004

Indication of unusual pentagonal structures in atomic-size Cu nanowires.

We present a study of the structural and quantum conductance properties of atomic-size copper nanowires generated by mechanical stretching. The atomistic evolution was derived from time-resolved electron microscopy observations and molecular dynamics simulations. We have analyzed the quantum transport behavior by means of conductance measurements and theoretical calculations. The results suggest the formation of an unusual and highly stable pentagonal Cu nanowire with a diameter of approximately 0.45 nm and approximately 4.5 conductance quanta.

Journal Article↗
PubMed2004

Maternal adrenalectomy affects development of adrenal medulla.

This work investigates the effects of maternal adrenalectomy (ADX) on the development of the adrenal medulla. Adrenal catecholamines (AC) were measured at postnatal day (PN) 1, 8, 12 and 22 in rat offspring of ADX dams and in pups of control dams. The pups of ADX rats showed a reduction in AC concentrations in the adrenal medulla at PN 1, 12 and 22, although these were higher than in the pups of sham dams at PN 8. Further, in the pups of control mothers, there was an increase in ACs during the first two weeks of life whereas pups of ADX mothers only showed increases in noradrenaline, dopamine and adrenaline levels at day 8. These results suggest that maternal absence of corticosterone affects the medulla catecholamine content during development. These data support the idea that a maternal glucocorticoids are involved in the differentiation or/and maturation of the adrenal medulla.

Adrenal Medulla↗
PubMed2004

A possible association between the CCK-AR gene and persistent auditory hallucinations in schizophrenia.

Recent studies have suggested that DNA variations in the CCK-AR gene might predispose individuals to schizophrenia and particularly to auditory hallucinations (AH). The aim of this study is to assess the association between AH, using a specific scale for AH in schizophrenia (PSYRATS), and the CCK-AR polymorphism at 779 in a Spanish sample. A total of 105 DSM-IV schizophrenic patients with AH and 93 unrelated controls were studied. Twenty-two patients were considered as persistent auditory hallucinators, which showed similar clinical and demographic characteristic than patients with episodic AH, but with the exception of the PSYRATS values. The persistent AH group showed an excess of the A1 allele when was compared with episodic or control groups. Our data support the possible role of the CCK-AR gene in the development of persistent AH in schizophrenic patients.

Adult↗
PubMed2004

Role of maternal adrenal glands on the developing serotoninergic and aminoacidergic systems of the postnatal rat brain.

Serotonin, gamma-aminobutyric acid and glutamate, which are regulated by glucocorticoids in the central nervous system, are involved in neuroendocrine functions and the development of the brain. The present study investigates the effect of maternal adrenalectomy on the developing serotoninergic, GABAergic and glutamatergic systems. Neurotransmitter levels were measured in four brain areas of both male and female offspring on postnatal days 1, 8, 12 and 22. At postnatal day 1 and 8, the pups of adrenalectomized dams showed higher concentrations of serotonin than controls in all the brain areas studied. Serotonin levels decreased significantly in males at postnatal day 22 in the hippocampus and cortex. During the first 2 weeks of postnatal life, the lack of maternal corticosterone produced an increase in glutamate and a reduction in gamma-aminobutyric acid concentrations, mainly in males. Further, on postnatal day 1, increased serotonin and glutamate levels and lower levels of gamma-aminobutyric were observed in the hypothalamus of male pups born to adrenalectomized dams. The absence of maternal corticosterone affects the pattern of development of the serotoninergic system, especially in the hippocampus and cortex, and particularly in males. A delay in the maturation of the aminoacidergic systems, mainly of the GABAergic system and in males, was also seen. A sexually dimorphic response to the removal of maternal glucocorticoids was seen in terms of neurotransmitter levels, mainly in the hippocampus and hypothalamus.

Adrenal Glands↗
PubMed2001

Modified mass action law-based model to correlate the solubility of solids and liquids in entrained supercritical carbon dioxide.

The solubility of solids and liquids in supercritical CO2 with added entrainers was modeled with a modified version of the equation of Chrastil to include the effect of entrainers. By considering the formation of the solute-entrainer-solvent complexes an equation is obtained which predicts an exponential increase of solubility with fluid density and/or entrainer concentration. The correlating model was tested by non-linear regression through a computerized iterative process for several systems where an entrainer was present. Four experimental parameters are easily regressed from experimental data, hence the corresponding properties of components such as chemical potentials or critical parameters are not needed. Instead of its simplicity, this thermodynamical model provided a good correlation of the solubility enhancement in the presence of entrainer effect.

Carbon Dioxide↗
PubMed2001

13C/12C isotope ratio MS analysis of testosterone, in chemicals and pharmaceutical preparations.

The 13C/12C ratio can be used to detect testosterone misuse in sport because (semi)-synthetic testosterone is supposed to have a 13C abundance different from that of endogenous natural human testosterone. In this study, gas chromatography/combustion isotope ratio mass spectrometry (GC/C/IRMS) analysis for the measurement of the delta 13C/1000 value of testosterone from esterified forms of 13 pharmaceutical preparations, six reagent grade chemicals and three bulk materials (raw materials used in pharmaceutical proarations) obtained world-wide was investigated after applying a strong acidic solvolytic procedure. Mean delta 13C/1000 values of non esterified (free) testosterone from chemicals and bulk materials of several testosterone esters were in the range: -25.91/-32.82/1000 while the value obtained for a (semi)-synthetic, reagent grade, free testosterone was -27.36/1000. The delta 13C/1000 results obtained for testosterone from the pharmaceuticals investigated containing testosterone esters were quite homogeneous (mean and S.D. of delta 13C/1000 values of free testosterone: 27.43 +/- 0.76/1000), being the range between -26.18 and -30.04/1000. Values described above were clearly different from those reported by several authors for endogenous natural human testosterone and its main metabolites excreted into the urine in non-consumers of testosterone (delta 13C/1000 range: from -21.3 to -24.4/1000), while they were similar to those of urinary testosterone and metabolites from individuals treated with testosterone esters and testosterone precursors. This finding justifies the fact that administration of these pharmaceutical formulations led to a statistical decrease of carbon isotope ratio of urinary testosterone and its main metabolites in treated subjects.

Carbon↗
PubMed2001

In vitro antiplasmodial activity of 4-phenylcoumarins from Exostema mexicanum.

The stem bark of Exostema mexicanum (Rubiaceae) is used in Latin American folk medicine as a quinine substitute for malaria treatment. Bioassay-guided fractionation of lipophilic and hydrophilic extracts from the stem bark and branches yielded two previously undescribed 4-phenylcoumarins: 4',8-dihydroxy-5,7-dimethoxy-4-phenylcoumarin (exomexin A) and 3',4'-dihydroxy-5,7,8-trimethoxy-4-phenylcoumarin (exomexin B). Together with five known derivatives the in vitro activities against a chloroquine-sensitive strain (poW) and a chloroquine-resistant strain (Dd2) of Plasmodium falciparum have been evaluated. The most lipophilic compound, 4',5,7,8-tetramethoxy-4-phenylcoumarin (O-methylexostemin) revealed the strongest antiplasmodial activity (IC50 values: 3.6 microg/ml [poW], 1.6 microg/ml [Dd2]).

Animals↗
PubMed2001

[Progressive diffuse subretinal fibrosis syndrome: a case report].

CASE REPORT: The case of a 63 year old woman presenting fibrous subretinal lesions in the posterior pole on a routine ocular fundus check up is reported. The angiographic study showed a choroidal origin window defect next to hypofluorescence areas. The patient did not complain of vision loss or scotomas at any time. DISCUSSION: This clinical picture could be classified as a progressive subretinal fibrosis syndrome with atypical features. However, a differential diagnosis with other choroidal inflammatory conditions should be carried out even though many authors may consider them as different developmental phases of the same entity.

Choroiditis↗
PubMed2000

Development and validation of a high-performance liquid chromatographic method using fluorimetric detection for the determination of the diarrhetic shellfish poisoning toxin okadaic acid without chlorinated solvents.

A modification of the high-performance liquid chromatographic method with fluorimetric detection method for the determination of diarrhetic shellfish poisoning toxins was developed to completely avoid the use of dangerous chlorinated solvents. The method was validated for the toxin okadaic acid (OA) over a period of 6 months where 12 calibrations were performed and 72 samples were analyzed. Analysis of toxic and non-toxic mussels, clams and scallops demonstrated its selectivity. Linearity was observed in the tested range of interest for monitoring purposes of edible shellfish, from the limit of detection (0.3 microg OA/g hepatopancreas) to 13 microg OA/g hepatopancreas. Intra-assay precision of the method was 7% RSD at the quantification limit (0.97 microg OA/g hepatopancreas at S/N=10). Accuracy was tested in triplicate recovery experiments from OA-spiked shellfish where recovery ranged from 92 to 106% in the concentration range of 0.8 to 3.6 microg OA/g hepatopancreas. Useful information on critical factors affecting calibration and reproducibility is also reported. Good correlation (R=0.87) was observed between the results of the method and those of the method of Lee, after the analysis of 45 samples of mussels from the galician rias.

Calibration↗
PubMed1998

Improvement on sample clean-up for high-performance liquid chromatographic-fluorimetric determination of diarrhetic shellfish toxins using 1-bromoacetylpyrene.

Okadaic acid (OA) and dinophysistoxin-2, two of the main diarrhetic shellfish toxins, can be determined by high-performance liquid chromatography coupled to fluorimetry as pyrenacyl esters. Toxin fluorescent derivatives were obtained after quantitative derivatization with 1-bromoacetylpyrene in acetonitrile. An efficient improvement in the silica gel clean-up procedure of the pyrenacyl derivatives is reported. The clean-up cartridge is washed with hexane-dichloromethane (1:1, v/v), dichloromethane-ethyl acetate (8:2, v/v), and finally the pyrenacyl esters were eluted with dichloromethane-methanol (9:1, v/v). We compare this procedure with other methods already described. Good results were obtained with mussels, scallops and clams. The clean-up procedure showed good robustness when checked against silica and solvents activity. Using samples of mussel hepatopancreas with an OA concentration ranging from 0 to 2 micrograms OA/g hepatopancreas, the inter-assay relative standard deviation ranged from 5.5 to 12.6%.

Animals↗
PubMed1996

Cobalamin-independent methionine synthase from Escherichia coli: a zinc metalloenzyme.

Cobalamin-independent methionine synthase (MetE) from Escherichia coli catalyzes the transfer of a methyl group from methyltetrahydrofolate to homocysteine. Previous work had shown the existence of a reactive thiol group, cysteine 726, whose alkylation led to loss of all detectable enzymatic activity [González, J.C., et al. (1992) Biochemistry 31, 6045-6056]. A site-directed mutation of MetE, Cys726Ser, was constructed to investigate the possible role of this cysteine. The Cys726Ser protein was purified to homogeneity, affording a protein with no detectable activity. To assess the possibility that cysteine726 functions as a metal ligand, inductively coupled plasma-atomic emission spectrometry was performed. The wild-type enzyme contains 1.02 equiv of zinc per subunit; the Cys726Ser mutant does not contain zinc, supporting the view that cysteine726 is required for metal binding. A loss of enzymatic activity is observed upon removal of zinc from the wild-type MetE by incubation in urea and EDTA; activity can subsequently be restored by zinc reconstitution, suggesting that zinc is required for catalysis. Circular dichroism measurements further suggest that there are no major differences in the secondary structures of the wild-type and the Cys726Ser mutant enzymes. Extended X-ray absorption fine structure analysis has established that the average zinc environment is different in the presence of homocysteine than in its absence and is consistent with the changes expected for displacement of an oxygen or nitrogen ligand by the sulfur of homocysteine. A possible model for zinc-dependent activation of homocysteine by MetE is presented.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1995

[Informatics in medical schools and postgraduate education centers for health professionals. Survey on the situation in Spain].

BACKGROUND: Informatics is acquiring an increasing relevance in the medical profession. METHODS: During the year 1993, a survey was carried out at the medical schools (MS) and postgraduate education centres (PEC) in Epidemiology, Public Health and Health Administration of Spain, on the available computer infrastructure and the teaching activities. The percentages of respondents were 81 at the MS and 100 at the PEC. RESULTS: 81% of the MS and 100% of the PEC had a computer laboratory, mainly equipped with personal computers with MS-DOS operating system. The use of general purpose applications was predominant. The number of students using the computer laboratory was very variable (5-300 per day). 48% of the MS organized courses on microcomputer applications. 66% of the MS included subjects related with informatics in the new curricula. CONCLUSIONS: Use of computers in the Spanish MS is heterogeneous. Compared with the Nord-American MS, they do not usually use applications of computer-assisted-instruction. The use of the computers at the PEC is much more generalized.

Curriculum↗
PubMed1995

Characterization of nonradioactive assays for cobalamin-dependent and cobalamin-independent methionine synthase enzymes.

Methionine synthase enzymes catalyze methyl group transfer from 5-methyltetrahydrofolate to homocysteine to give methionine and tetrahydrofolate. Assays for this enzyme activity usually monitor transfer of a 14C-methyl group from the N5-position of methyltetrahydrofolate to homocysteine to produce 14C-methionine that must be purified by anion-exchange chromatography. Alternatively, tetrahydrofolate may be derivatized with a formylating agent under acidic conditions to produce methenyltetrahydrofolate. We report optimization of this reaction for assay of cobalamin-dependent methionine synthase to give an economical method for determining enzyme activity that does not require the use of radioactive compounds. By heating for 10 min in 1 N hydrochloric acid containing 12% formic acid, the enzymatic product tetrahydrofolate is converted into methenyltetrahydrofolate, which absorbs light at 350 nm, while residual substrate 5-methyltetrahydrofolate does not contribute to the absorbance at 350 nm. The assay allows the derivatized product to be characterized in situ with a minimal increase in volume upon acidification. The results of the spectrophotometric assay given here have been compared with the radioactive assay to confirm the validity of the derivatization under the assay conditions. We also report the extension of this assay method for use in activity measurements of cobalamin-independent methionine synthase.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1995

Vitamin-B12-independent methionine synthase from a higher plant (Catharanthus roseus). Molecular characterization, regulation, heterologous expression, and enzyme properties.

Methionine synthases catalyze the formation of methionine by the transfer of a methyl group from 5-methyltetrahydrofolate to homocysteine. This reaction is the last step in L-methionine biosynthesis, and it also serves to regenerate the methyl group of S-adenosylmethionine, a cofactor required for biological methylation reactions. We describe the cloning, expression and characterization of a methionine synthase from the higher plant Catharanthus roseus. cDNAs were identified that encoded a protein of 85 kDa sharing 50% identify with the cobalamin-independent methionine synthase from Escherichia coli (MetE) and 41% identity with a partial sequence of a yeast homolog of MetE. The C. roseus protein was expressed at high levels in E. coli. The enzyme accepts the triglutamate form of methyltetrahydrofolate as a methyl donor but not the monoglutamate form, and it does not require S-adenosylmethionine or cobalamin for activity. The properties indicate that the enzyme is a cobalamin-independent methionine synthase (EC 2.1.1.14). In contrast to the E. coli MetE, the plant protein does not require phosphate or magnesium ions for activity. Immunoblots of plants extracts showed that the protein was localized in the cytosol, and was present in a variety of plant species. A nutritional downshift of the C. roseus cell culture revealed a strong, transient transcriptional activation, but no significant increment in the total level of the protein. The availability of the protein and the cDNA now provide tools to investigate the complexities of methionine biosynthesis in plants.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗