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Biomedical subjects

J M Simard

Publications and source records attributed to J M Simard.

53 records · Page 3Linked to original sources
PubMed1986

Interactions of scorpion toxins with the sodium channel.

It is evident from the data reviewed that scorpion toxins can be distinguished on the basis of three properties: their effects on Na currents, their specific binding to excitable membranes, and the effects of depolarization and pH on binding and on effect. Additional work with other scorpion toxins is required to establish the degree of correlation between the three properties for each class of toxin. Further investigations with this family of homologous proteins will undoubtedly contribute not only to our understanding of the toxins themselves but also to our understanding of the structure and function of the Na channel.

Amino Acid Sequence↗
PubMed1986

Cavernous angioma: a review of 126 collected and 12 new clinical cases.

The histopathological, clinical, and radiological features of the intracranial cavernous angioma are reviewed, based on an analysis of 138 symptomatic, histologically verified cases. Twelve of the cases are from our own series and 126 were collected from appropriately documented reports in the modern literature. The analysis indicated that, at the time of diagnosis, one-third of the patients (49 cases) were being evaluated for seizures, one-third (40 cases) for clinical evidence of hemorrhage, and one-third (49 cases) for mass lesions. Unlike the other two groups, the group presenting with clinical evidence of hemorrhage was distinguished by a dominant age at the time of diagnosis (41% were diagnosed during the 4th decade of life), by a high incidence of prior neurological evaluation (43%), by a higher rate of diagnosis at autopsy (28%) than at operation, and by the absence of microscopic calcification within the lesion.

Adolescent↗
PubMed1984

Automatic artifact rejection during intraoperative recording of somatosensory evoked potentials. Technical note.

A device is described that performs automatic artifact rejection for somatosensory evoked response analysis in intraoperative and other electrically noisy environments. Although based on amplitude discrimination, rejection is not triggered by the large stimulus-dependent voltage transients associated with somatosensory evoked potentials. The device readily interfaces with commercially available evoked potential equipment.

Electrophysiology↗
PubMed1984

Biochemical and electrophysiological characteristics of toxins isolated from the venom of the scorpion Centruroides sculpturatus.

Recent progress in biochemical, structural and physiological studies has revealed several interesting properties of the toxins from the American scorpion, Centruroides sculpturatus. These toxins, together with similar toxins from other species of scorpions, comprise a unique family of homologous proteins with phylogenetically related structural differences. There is now evidence from both binding and electrophysiological studies that two distinct classes of toxins are present in the venom of C. sculpturatus. One class of toxins markedly slows inactivation of the sodium permeability but has no demonstrable effect on activation, whereas the second class induces a transient shift in the voltage-dependence of activation. Both groups make inactivation incomplete.

Amino Acid Sequence↗
PubMed1983

Spontaneous, rhythmic myoelectric activity induced by scorpion neurotoxin, reduced [calcium]0 and cadmium in chick striated muscle.

The cellular electrical activity accompanying the very slow resting-tension oscillation (period 4-13 min) in chick skeletal muscle caused by scorpion neurotoxin, reduced [Ca2+]0 and Cd2+ was investigated. All three oscillogenic treatments were found to induce spontaneous, periodically recurring, electrical activation of muscle cells, including periodic bursting activity of individual cells. The period of the recurrent electrical activation approximated the period of the resting-tension oscillation. The data suggest that the three oscillogenic treatments act by way of a common mechanism, possibly a critical Ca2+ moiety, to effect the periodic electrical activation of the cells. Analysis of single cell and group discharge activity suggests that the cells are coupled by non-specific, electrotonic interactions, resulting in the integration of their individual periodic activities into a resting-tension oscillation of the whole muscle.

Action Potentials↗
PubMed1982

Oscillation in resting tension of chick skeletal muscle treated with toxin V from scorpion venom, reduced [calcium]o and cadmium.

1. An oscillation in resting tension of the chick biventer cervicis muscle is induced by scorpion toxin (CsT-V), reduced [Ca]o and by Cd2+. Other chick muscles, e.g. semispinalis cervicis, anterior and posterior latissimus dorsi, also oscillate with the same treatments. The period of the oscillation in the biventer cervicis muscle is uniform, averaging 5-6 min. 2. The oscillation and the period are very sensitive to changes in temperature, [Ca]o, [K]o, ouabain and tetrodotoxin [TTX]. The oscillation is resistant to twitch blocking dosages of nicotinic antagonists. 3. The period of the oscillation varies inversely as the temperature (26-37 degrees C), log [K]o and [ouabain] and directly as the log [Ca]o and [TTX]. 4. These data support the inference that the oscillator is postjunctional and results from fluctuation in the electrochemical gradient of ions across the muscle cell membrane. The role, if any, of the Na+, K+ pump in the primary oscillogenic mechanism is not evident from our data.

Animals↗
PubMed1976

Development of telemetric techniques for use in studies of the electrical activity of the brain.

A telemetry system has been designed to transmit two channels of wideband activity (0.2 Hz-2.5 KHz) recorded from high-impedance microelectrodes in the brains of free-moving cats. Thus, both unit activity and slow-wave field activity are accessible without disruption of the animals' behavior. In addition, circuitry is described that conditions the receiver signals, that dicriminates valid subcarrier signals from receiver noise and that automatically aborts data output in the absence of discriminable subcarrier. This receiver signal processing circuitry thus assures the fidelity of the decoded subcarrier, greatly facilitates further machine processing of the data and frees the experimenter from having to continuously monitor the receiver signals to subjectively edit out noisy data.

Animals↗