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Biomedical subjects

J Baribeau

Publications and source records attributed to J Baribeau.

34 records · Page 2Linked to original sources
PubMed1993

Tardive dyskinesia and associated cognitive disorders: a convergent neuropsychological and neurophysiological approach.

This study sought to assess whether tardive dyskinesia (TD) related differentially to two types of cognitive functioning in schizophrenia. Thirteen schizophrenics with severe formal thought disorders (+FTD) were matched for age, sex, education, chronicity, dosage, hospital care, with 13 schizophrenics selected for absence of or minimal formal thought disorders (-FTD). TD and neuroleptic dosage were analyzed in relation to cognitive and motor tests of the Luria-Nebraska (L-N) battery and to attentional evoked potentials (EPs). EPs were recorded at electrodes Fz, Cz, and Pz, in a dichotic signal detection task (oddball paradigm), during attention and inattention conditions. Group differences on attentional EPs replicated published results with flatter and smaller positive waves in +FTD patients and larger late negative waves (FzN4-N7) in -FTD patients. Controlling for dosage, the following were the best groups discriminators. +FTD schizophrenics presented more severe dyskinesia in the orofacial area and poorer verbal scores on L-N. Severe TD correlated with smaller N1 amplitudes. +FTDs also presented distinct attentional EP deficits with abnormally small P3a, a correlate of deficient categorization and orienting. Neuroleptic dosage was not directly correlated to any single motor or cognitive measure, nor to TD indices. The hypothesis of a differential association of TD with distinct attentional/cognitive disorders was generally supported.

Acoustic Stimulation↗
PubMed1993

Methylene blue inhibits the antithrombotic effect of nitroglycerin.

OBJECTIVES: The aim of this study was to examine whether cyclic guanosine monophosphate (GMP) may be involved in the antithrombotic action of nitroglycerin. BACKGROUND: Nitroglycerin has been shown to inhibit platelet function in vitro by stimulating prostacyclin or inhibiting thromboxane A2 production, or both. Nitroglycerin has also been shown to possess potent antithrombotic properties in vivo. However, the mechanism of this antithrombotic effect is unclear. METHODS: Nitroglycerin was infused to produce a 10% decrease in mean arterial pressure in 27 normal pigs by exposing their circulating arterial blood to porcine aortic media in an ex vivo perfusion chamber. Eight pigs received an infusion of nitroglycerin alone; eight received an infusion of methylene blue, a guanylate cyclase inhibitor, followed by nitroglycerin infusion and five pigs received an infusion of nitroglycerin followed by methylene blue and subsequent infusion of cyclic GMP. RESULTS: With nitroglycerin alone, quantitative autologous indium-111-labeled platelet deposition (x10(6) on the aortic media was decreased to 63.9 +/- 10.4% (p = 0.01) of the baseline control platelet deposition. Methylene blue given before nitroglycerin tended to increase platelet deposition relative to baseline and platelet deposition after nitroglycerin was 142 +/- 35% (p = NS) of baseline value. In pigs that received all three agents, nitroglycerin reduced platelet deposition to 42.3 +/- 12.2% of baseline value; this decrease was then attenuated by subsequent methylene blue infusion but was enhanced by cyclic GMP infusion to 16.4 +/- 3.8% of baseline value (p = 0.006 vs. baseline control and p = 0.02 versus methylene blue infusion). CONCLUSIONS: Guanylate cyclase inhibition with methylene blue abolishes the antithrombotic effect of nitroglycerin, which can be enhanced by cyclic GMP.

Animals↗
PubMed1992

AERPs and clinical evolution of thought disorders over five years.

In a selective attention task, 21 Subjects detected rare randomized targets (P = 0.02) in a set of randomized standard tones. In one condition, Subjects focused their attention and detected targets in one ear, ignoring the other ear, and vice versa in the next condition. AERPs (auditory event-related potentials) were recorded at 5 electrode sites (10-20 system), at Fz, Cz, Pz, C3, C4, in two conditions varying speed of stimulation (randomized interstimulus intervals of 250-750 ms and 750-1500 ms). One group of 7 schizophrenics with the major syndrome of formal thought disorder (+FTD) was compared to 7 schizophrenics without the FTD syndrome (-FTD), and to 7 controls. The schizophrenic group was matched for age, education, sex, medication, hospitalization and intelligence score on abbreviated WAIS test. Ss were re-tested after 5 years following identical experimental and counterbalancing method to the pre-test. At re-test, similarly to pre-test, schizophrenics' AERPs showed smaller amplitudes, longer latencies, smaller attention effects than normals. -FTD schizophrenics showed intermediate values between the +FTD patients and normals. At retest, +FTD schizophrenics showed an aggravation of these AERP abnormalities while -FTD patients seemed to improve with larger amplitudes, faster latencies and better attention effects than at pre-test. Differential correlations between clinical and AERP indices indicated a dissociation between neurophysiological and clinical evolution: factors of dissociation included Andreasen's positive and negative indices of thought disorder, neuropsychological indices on the Luria-Nebraska scales, and severity of psychotic symptoms.

Adult↗
PubMed1989

Effect of lipid-protein interaction on the color of bacteriorhodopsin.

Detergent solubilization and subsequent delipidation of bacteriorhodopsin (bR) results in the formation of a new species absorbing maximally at 480 nm (bR480). Upon lowering the pH, its absorption shifts to 540 nm (bR540). The pK of this equilibrium is 2.6, with the higher pH favoring bR480 (Baribeau, J. and Boucher, F. (1987) Biochim. Biophysica Acta, 890, 275-278). Resonance Raman spectroscopy shows that bR480, like the native bR, contains a protonated Schiff base (PSB) linkage between the chromophore and the protein. However, the Schiff base vibrational frequency in bR480, and its shift upon deuteration, are quite different from these in the native bR, suggesting changes in the Schiff base environment upon delipidation. Infrared absorption and circular-dichroism (CD) spectral studies do not show any net change in the protein secondary structure upon formation of bR480. It is shown that deprotonation of the Schiff base is not the only mechanism of producing hypsochromic shift in the absorption maximum of bR-derived pigments, subtle changes in the protein tertiary structure, affecting the Schiff base environment of the chromophore, may play an equally significant role in the color regulation of bR-derived pigments.

Bacteriorhodopsins↗
PubMed1989

Vasopressin receptors and inositol trisphosphate production in blood vessels of spontaneously hypertensive rats.

To understand the regulation of vasopressin (AVP) receptors in spontaneous hypertension, we investigated the pressor response of AVP in the perfused mesenteric vasculature, AVP binding sites in the membrane preparation of the same vascular bed, and the production of inositol trisphosphate (InsP3) stimulated by AVP in the aorta of spontaneously hypertensive rats (SHR), Wistar-Kyoto rats (WKY), and Wistar rats (WR) at different ages (4-16 weeks). Plasma AVP concentrations were similar in SHR, WKY, and WR at all ages. The density of AVP vascular binding sites was significantly higher in WKY than in SHR and WR at 12 weeks. Receptor affinity was similar in all strains. The pressor response of the mesenteric vasculature to AVP was similar in the three strains of rats at 4 weeks (prehypertensive stage) and increased progressively in SHR compared with WKY and WR at 8 and 12 weeks of age by 43 and 35%, respectively, and by more than 80% at 16 weeks of age (established hypertensive stage). There was no difference in vascular sensitivity to AVP. A significantly increased pressor response to a supramaximal dose of norepinephrine was also found at 16 weeks in SHR, but not in younger rats. InsP3 production in the aorta in response to AVP was increased in SHR at 8, 12, and 16 weeks, compared with WKY and WR. These results suggest that the vascular response to AVP is increased in SHR, in spite of decreased or normal density of binding sites compared with WKY or WR.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗