PubMed Health⌕ Search

Biomedical subjects

P Rioux

Publications and source records attributed to P Rioux.

11 recordsLinked to original sources
PubMed1992

Central benzodiazepine receptors in human brain: estimation of regional Bmax and KD values with positron emission tomography.

Studies of central benzodiazepine receptors in the human brain in vivo are now possible using positron emission tomography (PET) and [11C]flumazenil. With the aim of measuring Bmax and Kd in brain regions, we used a two-injection [11C]flumazenil (at high and low specific radioactivity, respectively) pseudo-equilibrium paradigm to evaluate, in seven unmedicated healthy volunteers, the relative merits of three 'reference' structures (pons, hemispheric white matter and corpus callosum) in which the free radioligand concentration in brain tissue was estimated 15-40 min after i.v. injection of the radioligand. By means of high-resolution PET, the Bmax and Kd were calculated for each subject in 18 gray matter structures, based on a two-point Scatchard plot. We found that the use of the corpus callosum as reference often resulted in spurious Bmax and Kd values. The pons was the best reference structure because it provided satisfactory Bmax values (closest to in vitro data) and most consistent Kd values, and was the region easiest to sample on PET images. The pattern of regional Bmax was consistent with that expected from in vitro studies, with values highest in the cerebral cortex, intermediate in the cerebellum, and lowest in the striatum and the thalamus. The Kd values were uniform among regions and were consistent with earlier in vitro and in vivo data. This work documents the feasibility of estimating Bmax and Kd of central benzodiazepine receptors in multiple brain regions for clinical research.

Adult↗
PubMed1992

Regional cerebral oxygen consumption, blood flow, and blood volume in healthy human aging.

Using high-resolution positron emission tomography and the oxygen 15 continuous inhalation method, we examined the changes in cerebral metabolic rate of oxygen, blood flow, blood volume, and oxygen extraction fraction as a function of age in 25 optimally healthy, unmedicated volunteers who ranged in age from 20 to 68 years. Subjects were strictly selected for absence of cerebrovascular risk factors, dementia, or mental disorders; they had neither biological nor clinical abnormalities, and no focal anomaly on computed tomographic scan. Regions of interest were determined according to the anatomical structures defined on corresponding computed tomographic scan cuts obtained using a stereotaxic head-positioning method. This same method was also used for positron emission tomographic imaging. There was no significant effect of aging on PaCO2 values, hematocrit, arterial blood pressure, cholesterol and triglyceride levels, and blood glucose levels. In most cerebral cortex gyri, the cerebral metabolic rate of oxygen significantly decreased with age according to a linear pattern, with the same magnitude (about -6% per decade) in all four lobes and on both sides. This effect of age on cortical cerebral metabolic rate of oxygen persisted when the possible influence of cortical atrophy, gender, and head size were partialled out. In contrast, the white matter, deep gray nuclei, thalamus, and cerebellum were not significantly affected. The cerebral blood volume declined with a similar pattern to cerebral metabolic rate of oxygen, while changes in cerebral blood flow were less significant, presumably because of larger variance of data across subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Thrombi of the right heart. Value of thrombolytic therapy in mobile thrombi].

Seven patients with mobile right heart thrombi, 4 floating and 3 pediculated, were recensed between 1985 and 1990. Two patients were admitted for congestive cardiac failure (Group I) and 5 patients for pulmonary embolism (Group II). Both patients in Group I were treated with heparin without complications. In one case, the size of the thrombus decreased in 10 days whereas, in the second case, it disappeared within 8 days. In Group II, the first patient underwent successful thrombectomy. The other four patients were given thrombolytic therapy (UK = 2, rt-PA = 2) associated with appropriate doses of heparin. In the two patients given UK (3M units the first day followed by 1.2 M units per day for 4 days) the thrombus disappeared in the first 48 hours of treatment. One patient had a recurrent pulmonary embolism after 2 hours' treatment; both patients had a fall in haemoglobin of 3 cg/ml at the second day. The second patient died at the 5th day. In the two patients treated by rt-PA (100 mg/7 hours) the thrombus disappeared within 4 hours of starting therapy. One patient had a probable recurrent pulmonary embolism. Both patients had a fall in haemoglobin of 3 cg/ml at the 2nd day of treatment. Right heart thrombi are rare (168 cases in the literature of which 111 were mobile). The prognosis seems to be related to echocardiographic appearances: mortality of mural thrombi is about 4% compared with 50% in mobile thrombi. Very mobile "worm-like" masses are therapeutic emergencies because of the risk of embolism (about 68%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Angioplasty after failure of thrombolysis in myocardial infarction. Hospital results apropos of 40 consecutive patients].

Intravenous thrombolysis during the acute phase of myocardial infarction is successful in restoring perfusion in 60 to 80% of cases. When it is unsuccessful, there is disagreement about the best approach to adopt. The article reports the results obtained in 40 consecutive patients treated by angioplasty after thrombolysis had been unsuccessful. Reperfusion was achieved in 92.5% of cases, with a hospital mortality rate of 7.5% (2.5% if patients admitted in a stage of cardiogenic shock are excluded). There was no mortality related to the procedure itself and an emergency aorto-coronary by-pass was not required in any case. Since it is accepted that the subsequent prognosis depends on coronary patency, coronary artery assessment after thrombolysis, followed by angioplasty if the occlusion persists seems to be a logical strategy if the myocardial territory is compromised.

Adult↗
PubMed1991

Thrombosis and thrombolysis in unstable angina.

Pathophysiology of unstable angina involves spasm, plaque rupture, activation of platelets, and coagulation. The incidence and frequency of intracoronary thrombus formation are presently under active assessment in order to establish the potential benefit of thrombolytic therapy. A preliminary study was conducted in patients admitted in our coronary care unit for unstable angina with typical clinical and electrocardiographic criteria and with early coronary angiogram. After exclusion of 4 patients with left main coronary stenosis or contraindications for thrombolysis, 16 patients received thrombolytic infusion and 14 underwent a second coronary angiogram. Seven patients had an intracoronary thrombus (6 nonocclusive, 1 occlusive) and at the second angiogram only 3 nonocclusive thrombi were modified (1 disappeared, 2 were reduced). Moreover, the quantitative Coronary Angiography Analysis System (CAAS) in the 11 cases suitable for analysis did not show any significant changes, especially in the Ambrose type IIB lesions. In-hospital clinical outcome was not influenced by thrombolytic therapy (5 ischemic recurrences, 1 fatal myocardial infarction, 4 emergency and 4 elective revascularization procedures). This short series is in agreement with the literature data. Only one third of patients with active unstable angina remains refractory to conventional therapy. The transient benefit of thrombolysis is limited to patients with demonstrated intracoronary thrombi. Clinical or angiographic improvement are not always in correlation and until now do not seem able to prevent short-term recurrences or the need for revascularization procedures.

Adult↗
PubMed1991

[Partial abnormal pulmonary venous return. An underestimated and unknown association in Turner-Ullrich syndrome. Presentation of an original case].

The authors report the case of a 59-year-old woman with a complex cardiac lesion consisting of degenerative major mitral insufficiency masking partial abnormal pulmonary venous return. These cardiac abnormalities fell within a context of genetic disease since the patient had Turner's syndrome, confirmed at the age of 58 by a 45 x 0 karyotype. They detail the originality of the clinical manifestations of partial abnormal pulmonary venous return and review the literature concerning cardiac malformations in Turner's syndrome.

Angiography↗
PubMed1988

[Value of esophageal stimulation for decreasing auricular flutter].

The purpose of this study was to evaluate the effectiveness of trans-esophageal atrial stimulation in decreasing atrial flutters. 31 patients, aged between 26 and 86 years, underwent 38 esophageal stimulations between August 1986 and April 1987. Esophageal stimulation was carried out with a device delivering major stimuli (10 to 20 ms) as well as high voltages (10 to 20 volts). A bipolar probe of permanent intracardiac stimulation was placed behind the left atrium, via a trans-esophageal approach under ECG guidance. Stimulations were carried out at a slightly faster rhythm than that of the atrial flutter, for 1 to 30 seconds with a progressive increase of the stimulation frequency (280 to 960 impulses/min) until either a sinus rhythm or an atrial fibrillation was obtained. A sinus rhythm was obtained immediately (21 times out of 38; 55.3%) and at the 24th hour after temporary atrial fibrillation in 8 additional patients (21%). The reduction percentage at 24 hours was therefore 76.3 p. cent. In 6 patients (15.8%), esophageal stimulation failed and in 3 additional patients, after atrial fibrillation, there was either relapse into flutter, or persistence of atrial fibrillation at the 24th hour. Esophageal stimulation was well tolerated in all cases. There were no local or rhythm complications. In conclusion, trans-esophageal atrial stimulation appears to be effective, easy to implement, economical and well tolerated. Its primary use to decrease atrial flutter seems justified, permitting to avoid in 75 p. cent of the time, recourse to intracardiac atrial stimulation or external shock.

Adult↗
PubMed1987

Effect of exercise on the onset of puberty, gonadotropins, and ovarian inhibin.

Swimming 6 h/day from 11 days of age led to a significant delay of the onset of puberty of female rats compared with the sedentary group. Rats who were in contact with water but without the energy expenditure due to exercise (paddlers) had their vaginal opening in a middle point between control and exercising rats. Vaginal opening occurred at different ages but at a same body weight. Exercise and stress led to a marked decrease of the body weights between 19 and 40 days of age. Serum luteinizing hormone and follicle-stimulating hormone were increased with the exercise program at 30 days of age, whereas no significant differences between groups in serum gonadotropins were observed at 50 days of age. Only the anterior pituitary luteinizing hormone content was increased by exercise in adult rats. Total ovarian proteins were significantly reduced by stress and to a greater degree by exercise. Ovarian inhibin activity is not modified by exercise at 30 days of age, whereas it increased significantly in the exercising group at 50 days of age and to a lesser degree in paddlers. It is therefore suggested that the onset of puberty in rats is dependent on a critical weight and that exercise and stress can delay the onset of puberty. This delay could be explained by a deficiency of hormonal maturational process while exercising until sexual maturity alters the inhibin activity, which suggests that inhibin could play a major role for the normal reproductive function and this could possibly explain the menstrual disturbances in the female athlete.

Animals↗
PubMed1979

Discriminant analysis: methods and program.

Because of the disparity in the results obtained using different methods of discriminant analysis, we have written and used a unique program to test them. These methods can be divided into two groups corresponding to a classical probabilistic approach (i.e., Bayesian methods) or a topological approach (i.e., Sebestyen method).

Bayes Theorem↗
PubMed1979

Intra- and interhemispheric EEG differences quantified by spectral analysis. Comparative study of two groups of schizophrenics and a control group.

In this work we have studied comparatively the relationships between alpha intensity, alpha frequency, root-mean-square amplitude and their standard deviations, versus the location of the four recorded EEG channels: left and right rolando-parietal, left and right parieto-occipital. Twenty-four spectral parameters were computed for each 5-min EEG recording, in the eyes closed situation. The hebephrenic group (36 EEGs from six patients) presented higher values of alpha intensity and RMS amplitudes with low coefficient of variation when compared with the other groups. The left/right rolando-parietal amplitude ratio was 0.73 versus 1.52 for the parieto-occipital ratio. An amplitude hypovariability in the central regions, probably associated with hyperarousal, especially in the left hemisphere, can then be observed in hebephrenics, together with high alpha intensity on the left parieto-occipital area. The two groups of schizophrenics differ from the control group (27 EEGs from 12 subjects) in terms of spectral parameters, the hebephrenic group presenting a possible interhemispheric dysfunction.

Adult↗