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Biomedical subjects

G Savard

Publications and source records attributed to G Savard.

28 records · Page 2Linked to original sources
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↗
PubMed1987

Noradrenaline spillover during exercise in active versus resting skeletal muscle in man.

Increases in plasma noradrenaline (NA) concentration occur during moderate to heavy exercise in man. This study was undertaken to examine the spillover of NA from both resting and contracting skeletal muscle during exercise. Six male subjects performed one-legged knee-extension so that all measurements could be made both in the exercising and in the resting leg. Subjects exercised for 10 min at each of 50% and 100% of the peak performance capacity of the leg. Leg blood flow was measured by thermodilution and blood samples were drawn for the determination of plasma NA and adrenaline, first in the resting leg and then in the exercising leg. To calculate NA spillover, the extraction of NA (NAe) or of adrenalin (Ae) is required: NAe was measured by repeating the experiment under constant [3H]NA infusion following a 40-min rest period. During exercise, NA spillover was significantly larger in the exercising leg than in the resting leg both during 50% and 100% leg exercise. These results suggest that contracting skeletal muscle may contribute to a larger extent than resting skeletal muscle to increasing the level of plasma NA during exercise. Contractile activity may influence the NA spillover from skeletal muscle by a presynaptic and/or postsynaptic influence on the sympathetic nervous activity to this tissue.

Adult↗
PubMed1986

Role of hemoglobin and capillarization for oxygen delivery and extraction in muscular exercise.

Through the years the role of the various links in the transport of oxygen in the human body has been discussed extensively, and especially whether one of these links could be singled out as limiting oxygen uptake during exercise. In his thesis work Lars Hermansen dealt with several of these variables related to oxygen transport and uptake. Two of these were the hemoglobin concentration of the blood (Hb) and skeletal muscle capillarization. These are the focus of this article. It can be demonstrated that variation in arterial oxygen content due to different Hb concentrations is fully compensated for at the level of the muscle, i.e. the amount of oxygen delivered to contracting muscles is adjusted by a variation in the blood flow so that it is the same regardless of Hb concentration in the range of 118-172 g X l-1. At the systemic level, with a large fraction of the muscle exercising, this causes an increase in submaximal heart rate and a lowering in maximal oxygen uptake in people with low as compared to normal or high Hb concentration. The primary significance of an enlarged capillary network in the muscle does not appear to be for accommodating a larger flow, but rather to allow for a long enough mean transit time and large enough surface area for optimal exchange of gases, substrates and metabolites.

Capillaries↗
PubMedDate not supplied

Postictal psychosis after partial complex seizures: a multiple case study.

Bouts of unusually frequent partial complex seizures originating in the temporal lobe, that sometimes became secondarily generalized, induced psychotic episodes in 9 patients. In 7, the increase in seizures occurred at a time when antiepileptic drugs (AEDs) were being reduced during intensive EEG monitoring with a view to surgical treatment of intractable epilepsy. According to DSM-III-R criteria, the postictal psychosis resembled an organic delusional syndrome which was paranoid in 7 and schizophreniform in 1 and an organic mood syndrome in 1. A high incidence of ictal fear, of bilateral independent epileptogenic discharge, and of small foreign tissue lesion were unexpected findings and appeared to represent risk factors, especially in patients otherwise handicapped by an epileptic personality disorder. Recognition of postictal psychosis in this setting and in others is important both prognostically and therapeutically. Postictal psychosis does not constitute a contraindication to surgical treatment of epilepsy.

Adult↗
PubMedDate not supplied

Acute postictal psychosis: a stereo EEG study.

An acute psychosis characterized by auditory hallucinations and paranoid delusions developed in a 19-year-old man with temporal lobe epilepsy after he had a cluster of seizures when antiepileptic drugs (AEDs) had been gradually discontinued. Continuous sterotactic depth and epidural EEG recordings confirmed that this was a postictal rather than an ictal event. Acute postictal psychosis is a self-limited condition phenomenologically distinct from ictal or postictal confusion.

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