Biomedical subjects
S C Packham
Publications and source records attributed to S C Packham.
Effects of ethanol and carbon monoxide on two measures of behavioral incapacitation of rats.
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Sequelae of carbon monoxide-induced hypoxia in the rat.
Rats were exposed to carbon monoxide, and conduction velocity of ventral caudal nerve (VCN), visual cortical evoked potential (VEP), electroencephalogram, and vital functions were determined in relation to the degree of CO-induced hypoxia. The conduction velocity of VCN and VEP (latency of P2 [second positive deflection of the visual evoked response]) were unaffected until carboxyhemoglobin (COHb) levels reached between 60% and 70%. These levels were maintained for approximately one hour before decreased conduction velocity or increased latency of P2 occurred. Decrease in mean arterial blood pressure resulted in impaired neurological function. Recovery of conduction velocity was discontinuous. Conduction was lost and recovered again within a three-hour period after exposure. It decreased again 9 to 13 days later, recovering in approximately four days. Data on P2 latency after exposure were fragmentary, but suggest that later increases might occur. Similar effects of CO-induced hypoxia on peripheral and central nervous systems were found. Decrease of mean arterial blood pressure was consistently associated with impaired nervous system function.
Trial development of unit response changes during conditioning in cats.
Single-cell and evoked potential (EP) activity in the postcruciate cortex of acutely prepared cats was recorded during a classical conditioning procedure. The temporal pattern of response (PSH) of the neuron was separated into three components, and the trial development of learning changes for these components was examined individually. Changes over trials in the similarity of the EP waveform and the unit PSH were also examined. The unit response components showed changes in response at different trial periods; these changes could not be accounted for by changes at lower brain levels that projected to the cortex. This suggests that local learning changes were taking places in the cortex. The EP-PSH similarity decreased for neurons showing the largest changes in response during conditioning. Since the EP reflects the response of the whole population of neurons and a majority did not show learning changes, this could account for the observed decrease.
Extreme toxicity from combustion products of a fire-retarded polyurethane foam.
The products from nonflaming combustion of wood and a trimethylol-propane-based rigid-urethane foam that was not fire-retarded produced elevated carboxyhemoglobin levels but no abnormal neurological effects. However, when this type of foam contained a reactive phosphate fire retardant, the combustion products caused grand mal seizures and death in rats. The toxic combustion product responsible for the seizures has been identified as 4-ethyl-1-phospha-2,6,7-trioxabicyclo(2.2.2.)octane-1-oxide.
Habituation of cell activity in cat postcruciate cortex.
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Features of spike train related to learning.
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Conditioned leg movement in the cat with massed trials, trace conditioning, and weak US intensity.
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