Biomedical subjects

Roberto Gil

Publications and source records attributed to Roberto Gil.

11 recordsLinked to original sources

PubMed2006

High-dose ziprasidone-induced acute dystonia.

There are few clinical data describing the relative risks of extrapyramidal symptoms (EPS) at higher doses of ziprasidone (i.e., greater than 160 mg/day) when compared to lower doses. We report on a patient who displayed no EPS with ziprasidone 160 mg/day for several months, but did display marked, acute dystonic reactions on ziprasidone 240 mg/day. The observations from the present case indicate that high-dose, ziprasidone-induced acute dystonia may occur even if no such side effects have been experienced at doses up to and including 160 mg/day.

Adult↗

PubMed2006

Serotonin 1A receptor availability in patients with schizophrenia and schizo-affective disorder: a positron emission tomography imaging study with [11C]WAY 100635.

BACKGROUND: Postmortem and positron emission tomography (PET) studies have reported several alterations in serotonin 1A receptor (5-HT(1A)) binding parameters in patients with schizophrenia. This study examines 5-HT(1A) availability in vivo in individuals with schizophrenia and schizo-affective disorder. MATERIALS AND METHODS: Twenty-two medication-free individuals with schizophrenia or schizo-affective disorder and 18 healthy subjects underwent PET scans with [(11)C]WAY 100635. Regional distribution volumes (V(T), in milliliters per gram) were derived using a two-tissue compartment kinetic model. Outcome measures for 5-HT(1A) availability included binding potential (BP) and the specific to nonspecific equilibrium partition coefficient (V(3)''). Eleven brain regions with high density of 5-HT(1A) were included in the analysis. RESULTS: No significant differences were observed in regional BP or V(3)'' between patients and controls. No significant relationships were observed between regional 5-HT(1A) availability and symptom severity. CONCLUSION: The postmortem literature reports increased 5-HT(1A) binding in the prefrontal cortex in schizophrenia. This study did not detect differences in 5-HT(1A) binding. Whereas in two recently published PET studies, one reports increased binding in the temporal lobe while the other reports decreased binding in the amygdala. These inconsistencies suggest that the alterations demonstrated in postmortem studies cannot be reliably detected at the resolution achieved with PET. This raises the question as to whether major changes in the level of expression of the 5-HT(1A) receptor play a role in the pathophysiology of schizophrenia.

Adult↗

PubMed2006

Effects of warm water inflows on the dispersion of pollutants in small reservoirs.

The effects of the warm water discharged by a nuclear power plant (NPP) into a small reservoir are studied. A case study is presented (José Cabrera NPP-Zorita Hidráulica Reservoir) with experimental data of the reservoir stratification and predicted data of the dispersion of radioactive pollutants from operative or accidental releases. The vertical and longitudinal temperature profiles, electrical conductivity and transparency of the reservoir water were measured for an annual cycle. The results indicate that the continuous warm water discharge from the NPP causes permanent and artificial reservoir stratification. The stratification is significant within 1500 m upstream and 1000 m downstream from the warm water outfall. The pollutant dispersion has been predicted by using a flow model based on N(T) perfect-mixing compartments in series with feedback. The model parameter, N(T), is calculated from the longitudinal diffusion coefficient. The prediction of pollutant dispersion by means of this model shows that the stratification slows down the vertical mixing in the whole water body, and reduces the reservoir volume that is effective for the dilution and dispersion of pollutants. This means that, in the case of a radioactive pollutant release, the reservoir radioactivity level could increase significantly.

Animals↗

PubMed2006

Etiological heterogeneity and intelligence test scores in patients with schizophrenia.

Previous research has indicated that patients with a family history of schizophrenia show a greater degree of cognitive and neuropsychological impairment than patients without a family history. We examined the neurocognitive performance, using the WAIS-R, of 51 patients with a family history (familial) and 103 patients without a family history (sporadic) to determine if differences exist that may help to explain the heterogeneous neuropsychological profile of the illness. The family history groups did not differ with respect to gender, diagnosis, ethnicity, age, age of onset, education or duration of illness. Multivariate analyses, covarying for age of onset and education, showed the sporadic group performed significantly better than the familial group on the digit symbol and object assembly subtests, with a trend level difference in overall performance IQ score. Additionally, we identified significant gender differences in favor of males for full scale and verbal IQ, the information, digit span, block design, and arithmetic subtests, and at a trend level, the picture assembly subtest. The family history group differences reflect relative dysfunction in visual attention and scanning, visuomotor control, and spatial processing and reasoning. Overall, the results suggest that sporadic patients have better perceptual-organizational skills and faster speed of processing.

Adult↗

PubMed2006

Modeling the Entrepeñas Reservoir.

The Entrepeñas Reservoir is a monomictic reservoir located in River Tagus (Spain). The aim of this work is to establish a feasible model to predict the depth of the thermocline that is developed in the reservoir during the period of natural thermal stratification. Entrainment, eddy diffusion, inflow of external energy, and other factors are considered to calibrate the parameters of the model. The methodology involves the measure of actual temperature and electrical conductivity profiles, use of meteorological data and reservoir parameters, and selection and application of several models from the literature. The calculations and predictions are integrated to a software packet that is able to predict thermocline depth and water temperature profile during a 1-year period on a day-by-day basis. In the thermocline depth, the prediction error, on the basis of real data, is less than 6% and, in the water temperature, it is 2 degrees C.

Computer Simulation↗

PubMed2005

Alcohol dependence is associated with blunted dopamine transmission in the ventral striatum.

BACKGROUND: A decrease in dopamine type 2 receptors (D2) and mesolimbic dopamine transmission predisposes animals to consume alcohol. This study measured D2 receptors and dopamine transmission in human alcohol-dependent (AD) subjects using positron emission tomography (PET) and [11C]raclopride. METHODS: Fifteen AD and 15 healthy control (HC) subjects were scanned before and after a psychostimulant challenge (amphetamine .3 mg/kg intravenous). The outcome measures for baseline D2 receptor availability were binding potential (BP) and the equilibrium partition coefficient (V3''). Amphetamine-induced [11C]raclopride displacement was measured as the difference in V3'' between the two scans. RESULTS: [11C]raclopride BP was significantly reduced by 16.6% in the limbic striatum, 19.2% in the associative striatum, and 21.3% in the sensorimotor striatum in AD subjects compared with HC. The alcohol-dependent subjects showed a blunting of amphetamine-induced dopamine release in the limbic striatum: [11C]raclopride displacement was -5.2% +/- 3.6% in AD subjects compared with -13.0% +/- 8.8% in HC. However, no significant difference in [11C]raclopride displacement was seen in the associative (-4.6% +/- 5.8% in AD subjects vs. -6.7 +/- 5.4% in HC) and sensorimotor (-12.3% +/- 7.3% in AD subjects vs. -13.7 +/- 7.5% in HC) subdivisions of the striatum between the two groups. CONCLUSIONS: Alcohol dependence was associated with a decrease in D2 receptors in each striatal subdivision, whereas amphetamine-induced dopamine release was reduced in the limbic striatum only.

Adult↗

PubMed2005

Serotonin transporter availability in patients with schizophrenia: a positron emission tomography imaging study with [11C]DASB.

BACKGROUND: Postmortem studies have reported several alterations in serotonin transporter (SERT) binding parameters in patients with schizophrenia. The aim of this study was to compare SERT availability in vivo in patients with schizophrenia and matched control subjects. METHODS: Ten medication-free patients with schizophrenia and 10 healthy subjects underwent positron emission tomography (PET) scans for 90 min after 11C-3-amino-4-(2-dimethylaminomethylphenylthio)benzonitrile ([11C]DASB) injection. Metabolite-corrected arterial input function was measured. Regional distribution volumes (mL/g) were derived with a two tissue compartment kinetic model. Outcome measures for SERT availability included binding potential (BP) and the specific-to-nonspecific equilibrium partition coefficient (V3''). Ten brain regions with high density of SERT and where SERT availability can be reliably quantified with [11C]DASB were included in the analysis. RESULTS: No significant differences were observed in regional BP or V3'' between patients and control subjects. No significant relationships were observed between regional SERT availability and severity of positive, negative, and depressive symptoms. CONCLUSIONS: This study failed to detect alterations of SERT availability in patients with schizophrenia; however, this study does not rule out the possibility that schizophrenia might be associated with alterations of SERT density in the cortical regions, where the [11C]DASB-specific binding signal is too low for reliable quantification of SERT.

Adult↗

PubMed2005

Altered prefrontal dopaminergic function in chronic recreational ketamine users.

OBJECTIVE: Ketamine is a noncompetitive antagonist at the glutamatergic N-methyl-D-aspartate (NMDA) receptor that is used in human and animal medicine as an injectable anesthetic. The illegal use of ketamine as a recreational drug is rapidly growing. Very little is currently known about the consequences of repeated ketamine exposure in the human brain. Animal studies indicate that the prefrontal dopaminergic system is particularly vulnerable to the toxic effects of repeated administration of NMDA antagonists. In this study, dopamine D1 receptor availability was assessed by using positron emission tomography and the selective D1 receptor radioligand [11C]NNC 112 in a group of 14 recreational chronic ketamine users and matched healthy subjects. METHOD: History of ketamine abuse was confirmed in subjects by hair analysis. [11C]NNC 112 binding potential was measured with kinetic analysis using the arterial input function. RESULTS: Dorsolateral prefrontal cortex D1 receptor availability was significantly up-regulated in chronic ketamine users ([11C]NNC 112 binding potential: mean=1.68 ml/g, SD=0.40) relative to comparison subjects (mean=1.35 ml/g, SD=0.35). No significant differences were noted in other cortical, limbic, or striatal regions. In the chronic ketamine user group, dorsolateral prefrontal cortex [11C]NNC 112 binding potential up-regulation was significantly correlated with the number of vials of ketamine (with a vial representing approximately 200-300 mg of ketamine) used per week. CONCLUSIONS: Chronic ketamine users exhibited a regionally selective up-regulation of D1 receptor availability in the dorsolateral prefrontal cortex, a phenomenon observed following chronic dopamine depletion in animal studies. These data suggest that the repeated use of ketamine for recreational purposes affects prefrontal dopaminergic transmission, a system critically involved in working memory and executive function.

Adult↗

PubMed2004

Terpenoids from Microliabum polymnioides.

The phytochemical study of M. polymnioides led to the isolation of two sesquiterpene lactones namely: 11alphaH-dihydrozaluzanin E and 1beta-hydroxy-4-oxo-11betaH-4-noreudesman-6,12-olide. Their structures were determined by spectroscopic methods. The relative stereochemistry was established by a combination of coupling constant analysis, NOESY correlations and molecular modeling. Three related known sesquiterpene lactones were also identified, and these data were used for chemotaxonomical purposes.

Lactones↗

PubMed2002

Prefrontal dopamine D1 receptors and working memory in schizophrenia.

Studies in nonhuman primates documented that appropriate stimulation of dopamine (DA) D1 receptors in the dorsolateral prefrontal cortex (DLPFC) is critical for working memory processing. The defective ability of patients with schizophrenia at working memory tasks is a core feature of this illness. It has been postulated that this impairment relates to a deficiency in mesocortical DA function. In this study, D1 receptor availability was measured with positron emission tomography and the selective D1 receptor antagonist [11C]NNC 112 in 16 patients with schizophrenia (seven drug-naive and nine drug-free patients) and 16 matched healthy controls. [11C]NNC 112 binding potential (BP) was significantly elevated in the DLPFC of patients with schizophrenia (1.63 +/- 0.39 ml/gm) compared with control subjects (1.27 +/- 0.44 ml/gm; p = 0.02). In patients with schizophrenia, increased DLPFC [11C]NNC 112 BP was a strong predictor of poor performance at the n-back task, a test of working memory. These findings confirm that alteration of DLPFC D1 receptor transmission is involved in working memory deficits presented by patients with schizophrenia. Increased D1 receptor availability observed in patients with schizophrenia might represent a compensatory (but ineffective) upregulation secondary to sustained deficiency in mesocortical DA function.

Adult↗

PubMedDate not supplied

The determination of longitudinal dispersion coefficients in rivers.

The dispersion coefficient of several sections of two Spanish rivers (Tagus and Ebro) is calculated using different methods. The aim of the study is to accurately know the effects of accidental leaks from two nuclear power plants that are placed upstream. Experimental data from tracer injections as well as data from hydraulic parameters were used to calculate the dispersion coefficient. Two methods based on tracer curves fit the experimental data well. One method is based on the time at which the tracer concentration is half the maximum concentration; the other method is based on the variance of the tracer curve distribution. An alternative method based on governmental data of velocity profiles and correlations of hydraulic parameters was also used. The results of this method are strongly sensitive to small variations in the stream flowrate. A new correlation is proposed to predict the dispersion coefficient with an error smaller than the one provided by other correlations in the literature.

Diffusion↗