Biomedical subjects

H J Caplan

Publications and source records attributed to H J Caplan.

5 recordsLinked to original sources

PubMed1995

Transient ischemic attacks and minor stroke during sleep. Relationship to obstructive sleep apnea syndrome.

BACKGROUND: It is reported that 13% to 44% of all cerebrovascular accidents (CVAs) occur during sleep. In addition to other well-known risk factors, snoring, sleep apnea, obesity, and daytime sleepiness have been shown to significantly increase the risk of stroke. We describe two cases that support the statistical relationship between snoring, sleep apnea, and CVA during sleep. CASE DESCRIPTIONS: In the first case, motor aphasia was noted in a 64-year-old, 5-ft, 1-in, 218-lb woman when she awakened from sleep at approximately 4 AM. This completely resolved within 3 hours. During her subsequent hospitalization she was found to have severe obstructive sleep apnea that responded well to treatment with nasal continuous positive airway pressure. There has been no recurrence of symptoms in this patient. The second patient was a 59-year-old, 5-ft, 6-in, 260-lb woman who presented to the Sleep Disorders Center with signs and symptoms of severe sleep apnea. In addition, she had awakened from sleep approximately 6 months earlier with numbness and weakness on her right side. Although these symptoms had greatly improved, she continued to complain about residual weakness that was worse on awakening from sleep. Sleep studies confirmed severe obstructive sleep apnea that responded very well to treatment with nasal continuous positive airway pressure. CONCLUSIONS: Snoring and obstructive sleep apnea not only increase the statistical risk of CVA but could be the proximal trigger that precipitates these events during sleep. These two cases provide clinical support for this relationship. Successful diagnosis and treatment of obstructive sleep apnea in the patient with transient ischemic attacks and minor stroke may be an important tool for preventing recurrence.

Female↗

PubMed1975

Frequency of reinforcement as a determinant of extinction-induced aggression during errorless discrimination learning.

Seven pigeons were trained to discriminate without errors between a green keylight and a dark key. The key-pecking response was reinforced in the presence of green, and extinction was in effect in the presence of the dark key. The opportunity to attack a restrained target pigeon was present only during extinction. Both variable-interval 30-sec and fixed-ratio 1 schedules of reinforcement during the positive stimulus induced a higher rate of attack during extinction than a variable-interval 5-min schedule. The highest rate of attack during extinction occurred during the first 20 sec after the positive stimulus terminated. Hence, the withdrawal of the positive condition, rather than the consequences of the pecking response during extinction, appears to be one of the primary factors responsible for attack between pigeons during extinction. Behavioral contrast, defined as a decrease in the rate of responding when the positive stimulus was presented alone, was obtained from the four birds that displayed the lowest overall rates of attack while the three birds with the highest attack rates did not display behavioral contrast. For the birds without contrast, components of the attack response during the positive stimulus presumably competed with and reduced the rate of pecking the key, thereby recluding behavioral contrast.

Aggression↗

PubMed1975

Inhibitory stimulus control following errorless discrimination learning.

Three generalization procedures were used to investigate inhibitory stimulus control following discrimination learning with few errors. Three groups of pigeons acquired a discrimination between a green stimulus (the positive stimulus) and a vertical or horizontal line (the negative stimulus) through differential autoshaping followed by multiple schedule presentation of the two stimuli with gradually increasing stimulus durations. Genereralization testing was along a line-tilt continuum. For one group, the test involved a resistance-to-reinforcement procedure in which responses to all line tilts were reinforced on a variable-interval schedule. For a second group, also tested with the resistance-to-reinforcement procedure, the lines were superimposed on the green field that formerly served as the positive stimulus. A third group was tested in extinction with the combined stimuli. Control groups had no discrimination training but responding to green was nondifferentially reinforced. The control subjects responded more to all line tilts during testing than did the comparable experimental subjects, indicating that the negative stimulus had become an inhibitory stimulus. Both resistance-to-reinforcement groups revealed inhibitory gradients around the negative stimulus, but the gradient for the extinction group was relatively flat. These data are consistent with others that modify Terrace's early conclusion concerning the failure of inhibition to develop during errorless training.

Journal Article↗

PubMed1973

Extinction-induced aggression during errorless discrimination learning.

Pigeons were trained to discriminate without errors between a green light and a dark key. The key-pecking response was reinforced in the presence of green, and extinction was in effect in the presence of the dark key. The duration of the dark key was gradually increased during the first few sessions of conditioning. The opportunity to attack a restrained target pigeon was also present. During discrimination training, the rate of attack in the presence of the dark key was higher for each animal than the operant level, even though most of the animals acquired the discrimination without errors. Furthermore, the rate of attack did not decrease during 45 sessions of discrimination training. Attack also occurred in the presence of the green stimulus, although to a lesser extent than during extinction. Reinforcement during green is a determinant of attack during extinction because removal of reinforcement virtually eliminated attack during extinction.

Journal Article↗

PubMedDate not supplied

An overview of pituitary tumors.

Tumors arising in and around the hypophyseal fossa can cause symptoms by compression of surrounding structures or, in the case of adenomas arising from the adenohypophysis, by hypersecretion of hormones. Until recently, adenomas of the hypophysis have been classified on the basis of light microscopy into chromophobe, eosinophilic and basophilic. Presently available methods of histochemistry, immunocytology, electron microscopy and hormone assays make available a biological classification of these adenomas into two groups: (I) adenomas without secretory activity and (II) adenomas with secretory activity. Amongst the latter are included somatotroph adenomas, prolactin cell adenomas, melanocorticotroph adenomas and thyrotroph adenomas. Many of the large group of tumors formerly called "chromophobe" can now be reclassified amongst the secretory adenomas.

Adenocarcinoma↗