PubMed Health⌕ Search

Biomedical subjects

G Savard

Publications and source records attributed to G Savard.

At least 19 recordsLinked to original sources
PubMed2001

Precise half-life measurement for the superallowed 0(+)-->0(+) beta emitter (74)Rb: first results from the new radioactive beam facility (ISAC) at TRIUMF.

Presently, the world data for superallowed beta decay leads to a result in disagreement (at the 98% confidence level) with the predictions of the minimal standard model for the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. Precise data for the superallowed 0(+)-->0(+) beta decay of (74)Rb would provide a critical test of the nucleus-dependent isospin symmetry-breaking corrections that must be calculated for these superallowed Fermi beta decays. The present work reports the first precise measurement of the half-life for (74)Rb ( t(1/2) = 64.761+/-0.031 ms). The data were obtained at the radioactive beam facility (ISAC) at TRIUMF using a beam of approximately 4000 (74)Rb ions s(-1).

Journal Article↗
PubMed2000

Psychiatric assessment of candidates for epilepsy surgery.

Patients with medically intractable epilepsy often present with comorbid psychiatric diseases. When referred to a program for the surgical treatment of the epilepsies, these patients benefit from a pre-admission psychiatric assessment with a view to lessen the chances of a psychiatric crisis during the pre- and postoperative investigations. This article proposes a practical approach to the psychiatric assessment and monitoring of adult candidates to the surgery of epilepsy. It emphasizes, in agreement with a world literature review, that definitive psychiatric contraindications to this elective surgery are few, and that adverse long-term psychiatric outcomes are less frequent when good seizure outcome is achieved.

Epilepsy↗
PubMed1999

Psychosis after resection of ganglioglioma or DNET: evidence for an association.

PURPOSE: David Taylor and Murray Falconer suggested that some patients may develop a psychotic illness after resection of a ganglioglioma that led to intractable seizures. They implied that the mechanism of this association remained unclear. This concept is currently not universally accepted (M. Trimble, personal communication). METHODS: We studied six children or young adults from four centers who developed psychosis after resection of a ganglioglioma or dysembryoplastic neuroepithelioma (DNET). RESULTS: All patients were operated on because of intractable epilepsy. The lesions involved mainly the temporal lobe. Patients had good outcomes for seizure control. In none of the six was potentially psychogenic medication used nor were the psychotic symptoms postictal in nature. The psychosis was schizophreniform with paranoid features and prominent depressive symptoms. Although some behavioral abnormalities were described preoperatively, none had been psychotic before operation. This type of psychotic reaction was not encountered in the four centers in a comparable period after resection of other types of lesions. This complication is rare; it occurred in only one of 39 patients who had such a lesion resected. CONCLUSIONS: Psychotic illness may rarely occur after resection of a ganglioglioma or DNET for treatment of intractable epilepsy. This does not seem to occur after removal of other types of lesions. Because the patients had good outcomes for seizures, the mechanism may be related to "forced normalization." The original observations of Taylor and Falconer are confirmed by this study; the reasons for the selective occurrence, however, remain speculative.

Adolescent↗
PubMed1998

Case study: neurological brain waves causing serious behavioral brainstorms.

A case highlighting the association of epilepsy with psychopathology is reported. The patient suffered a rare and extreme behavioral disturbance, characterized by persistent disruptive behavior and intermittent bizarre and violent outbursts. These outbursts often appeared purposeful, but some of them were later diagnosed as ictal manifestations of temporal lobe epilepsy. Temporal lobectomy resulted in remission both of the epilepsy and of the more persistent behavioral disturbance. lctal behavioral change was masked by interictal behavioral disturbance, leading to delayed diagnosis and prolonged psychosocial dysfunction. It is important to record the paroxysmal abnormal behavior with simultaneous electroencephalographic recording if there is a suspicion of organic disease. Physical and psychosocial factors in the relationship between epilepsy and extreme psychiatric disturbance are considered. This case demonstrates how successful epilepsy treatment may produce amelioration of associated psychiatric disturbance.

Attention Deficit and Disruptive Behavior Disorder↗
PubMed1997

Results of surgical treatment in temporal lobe epilepsy with chronic psychosis.

The combination of psychosis and refractory temporal lobe epilepsy is not rare. However, patients with chronic interictal psychosis and refractory epilepsy are rejected from many epilepsy surgery programmes purely on psychiatric grounds. It is often assumed that disturbed behaviour will prevent adequate preoperative evaluation or that the patients are unable to provide informed consent for preoperative investigations and for surgery. The observation that the psychosis usually does not improve after operation and fears of an exacerbation of psychosis with post-surgical seizure remission, analogous to 'forced normalization', are further deterrents to surgery in these patients. We describe five patients with the dual diagnoses of medically intractable temporal lobe epilepsy and chronic psychosis who underwent temporal lobe resection. The patients were able to provide informed consent and were easily managed during preoperative investigation. Seizure outcome has been excellent in all. Neither temporal lobe resection nor remission of seizures influenced the nature or evolution of the psychosis. Subjectively the patients functioned better in activities of daily living and freedom from seizures improved integration into psychiatric treatment facilities. With appropriate psychiatric intervention, patients with chronic psychosis and refractory epilepsy can participate in presurgical investigation successfully, and can undergo surgery uneventfully.

Adult↗
PubMed1994

Elevated dopa decarboxylase activity in living brain of patients with psychosis.

The hypofrontality theory of the pathogenesis of schizophrenia predicts that cortical lesions cause psychosis. During a search for abnormalities of catecholaminergic neurotransmission in patients with complex partial seizures of the mesial temporal lobe, we discovered an increase of the rate of metabolism of an exogenous dopa tracer (6-[18F]fluoro-L-dopa) in the neostriatum of a subgroup of patients with a history of psychosis. When specifically assayed for this abnormality, patients with schizophrenia revealed the same significant increase of the rate of metabolism in the striatum. The finding is consistent with the theory that a state of psychosis arises when episodic dopamine excess is superimposed on a trait of basic dopamine deficiency in the striatum. The finding is explained by the hypothesis that cortical insufficiency, a proposed pathogenetic mechanism of both disorders, causes an up-regulation of the enzymes responsible for dopa turnover in the neostriatum as well as the receptors mediating dopaminergic neurotransmission.

Adult↗
PubMed1994

Morbidity of chronic recording with intracranial depth electrodes in 170 patients.

A consecutive series of 170 patients who have been submitted to intracranial depth electrode recordings is reviewed to assess the overall morbidity of the technique. Most patients had bitemporal and frontal electrodes inserted and were monitored for an average period of 18 days. A surgically amenable focus was found in 85% of the cases. There were 4 cases of infection including 2 cerebral abscesses which required surgical evacuation. One patient with frontal lobe atrophy developed an acute subdural hematoma after electrode implantation. There was no death or neurological deficit in the entire series. Morbidity was encountered mainly in the neuropsychological sphere, several patients having developed transient postictal psychosis after repetitive seizures. Our recording technique has been associated with low surgical morbidity. Patients undergoing depth electrode recordings should be closely monitored to minimize the occurrence of psychotic episodes associated with drug withdrawal and increased seizure frequency.

Adult↗
PubMed1992

Plasma disposition and hemodynamic effects of a single oral dose of isosorbide dinitrate in human males and females.

The goal of the present work was to determine the plasma disposition and hemodynamic effects of isosorbide dinitrate (ISDN) in human males and females. Fourteen healthy human volunteers took part in the study; seven males, 21.7 +/- 2.5 y (SD), and seven females, 20.7 +/- 3.4 y. Measurements of forearm blood flow (FBF), vascular conductance (FVC), and venous capacitance (Cv) were obtained by venous occlusion plethysmography, whereas blood pressure was measured by automatic sphygmomanometry. Blood samples were taken through a catheter placed in the antecubital vein at 0, 15, 30, 45, 60, 90, 120, 360, 480, 720, and 1440 min following a single 10 mg oral dose of ISDN. Plasma concentrations of ISDN and its mononitrate metabolites, isosorbide-2-mononitrate (2-ISMN) and isosorbide-5-mononitrate (5-ISMN), were determined by large bore capillary column gas-liquid chromatography. Hemodynamic measurements were made at corresponding experimental times up to 480 min. No differences were observed in the disposition of ISDN, 2-ISMN or 5-ISMN between the male and female volunteers. In addition, the plasma concentrations of ISDN and its mononitrate metabolites did not consistently correlate with the hemodynamic changes of the individual subjects. Diastolic blood pressure was significantly decreased for a 0.5 h period starting at 30 min, which was the time at which plasma ISDN concentrations peaked, and which preceded the time when the plasma concentrations of 2-ISMN and 5-ISMN were maximal. These observations indicate that, for a single 10 mg oral dose of ISDN, there were no gender-dependent differences in the plasma disposition of the parent drug or its mononitrate metabolites, and the vascular changes responsible for the decrease in diastolic blood pressure in these volunteers occurred in vascular beds other than those of skeletal muscle as represented by forearm blood flow.

Administration, Oral↗
PubMed1990

Muscle blood flow and muscle metabolism during exercise and heat stress.

The effect of heat stress on blood flow and metabolism in an exercising leg was studied in seven subjects walking uphill (12-17%) at 5 km/h on a treadmill for 90 min or until exhaustion. The first 30 min of exercise were performed in a cool environment (18-21 degrees C); then subjects moved to an adjacent room at 40 degrees C and continued to exercise at the same speed and inclination for a further 60 min or to exhaustion, whichever occurred first. The rate of O2 consumption, 2.6 l/min (1.8-3.3) (average from cool and hot conditions), corresponded to 55-77% of their individual maximums. In the cool environment a steady state was reached at 30 min. When the subjects were shifted to the hot room, the core temperature and heart rate started to rise and reached values greater than 39 degrees C and near-maximal values, respectively, at the termination of the exercise. The leg blood flow (thermodilution method), femoral arteriovenous O2 difference, and consequently leg O2 consumption were unchanged in the hot compared with the cool condition. There was no increase in release of lactate and no reduction in glucose and free net fatty acid uptake in the exercising leg in the heat. Furthermore, the rate of glycogen utilization in the gastrocnemius muscle was not elevated in the hot environment. There was a tendency for cardiac output to increase in the heat (mean 15.2 to 18.4 l/min), which may have contributed to the increase in skin circulation, together with a possible further reduction in flow to other vascular beds, because muscle blood flow was not reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Muscle blood flow during isometric activity and its relation to muscle fatigue.

The effect of isometric exercise on blood flow, blood pressure, intramuscular pressure as well as lactate and potassium efflux from exercising muscle was examined. The contractions performed were continuous or intermittent (5 s on, 5 s off) and varied between 5% and 50% maximal voluntary contraction (MVC). A knee-extensor and a hand-grip protocol were used. Evidence is presented that blood flow through the muscle is sufficient during low-level sustained contractions (less than 10% MVC). Despite this muscle fatigue occurs during prolonged contractions. One mechanism for this fatigue may be the disturbance of the potassium homeostasis. Such changes may also play a role in the development of fatigue during intermittent isometric contractions and even more so in the recovery from such exercise. In addition the role of impaired transport of substances within the muscle, due to long-lasting daily oedema formation, is discussed in relation to fatigue in highly repetitive, monotonous jobs.

Adult↗
PubMed1988

Skeletal muscle glucose uptake during dynamic exercise in humans: role of muscle mass.

To study the role of muscle mass in glucoregulation, six subjects worked with the knee extensors of one leg on a specially constructed cycle ergometer. The knee extensors of one leg worked either alone or in combination with the knee extensors of the other leg and/or with the arms. Substrate usage was measured across both knee extensors by femoral arterial and venous catheterization and measurement of femoral venous blood flow. Glucose uptake by the working knee extensors was absolutely (by approximately 20%) or relatively decreased when arm cranking was added to knee extensions. The decrease in glucose uptake was not compensated for by increased uptake of free fatty acids but was accompanied by decreases in plasma insulin and increases in plasma epinephrine and norepinephrine. During work with large muscle masses, arterial lactate increased to approximately 6 mM, and net leg lactate release reverted to net lactate uptake. Decreased glucose uptake could not be explained by decreased perfusion. It is concluded that thigh muscle glucose uptake is affected by the size of the total muscle mass engaged in exercise. The decrease in thigh glucose uptake, when arm cranking was added and O2 uptake was increased above 50% of maximum aerobic capacity, may be elicited by neuroendocrine adjustments or lactate-induced inhibition of glycolysis and may represent a mechanism for protecting against premature hypoglycemia during prolonged exercise.

Adult↗
PubMed1988

Epileptic Munchausen's syndrome: a form of pseudoseizures distinct from hysteria and malingering.

A young woman with seizures and status epilepticus sought and obtained hospitalization in at least 25 hospitals in the province of Quebec between 1980 and 1987. She was thought to have uncontrolled epilepsy; her treatment led to intoxication with anticonvulsants and once to anesthesia for three consecutive periods of 7 days each. The nonepileptic nature of her attacks was proven and a diagnosis of Munchausen's syndrome made. She was transferred to a psychiatric center where she committed suicide. We found no documented cases of epileptic chronic factitious disorder in the literature.

Adult↗