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Biomedical subjects

M E Thompson

Publications and source records attributed to M E Thompson.

At least 91 records · Page 5Linked to original sources
PubMed1983

Local cerebral blood flow increases during auditory and emotional processing in the conscious rat.

Local cerebral blood flow was measured in rats by the 14C-labeled iodoantipyrine technique with quantitative autoradiography during the processing of environmental stimuli. Presentation of a tone increased blood flow in the auditory but not the visual pathway. When the animal had previously been conditioned to fear the tone, blood flow additionally increased in the hypothalamus and amygdala. Local cerebral blood flow can thus be used to detect patterns of cerebral excitation associated with transient (30- to 40-second) mental events in experimental animals.

Acoustic Stimulation↗
PubMed1983

Electrical brain activity and cardiovascular function during amygdaloid kindling in the dog.

Two lines of evidence converged to suggest that amygdaloid kindling would produce alterations in cardiovascular responsiveness. First, stimulation of the amygdala produces changes in heart rate and blood pressure. Second, the amygdala is the most sensitive region of the brain for kindling. Our objectives were to document the electrical brain activity, cardiovascular responses, and behavioral manifestations associated with the development of generalized convulsions during amygdaloid kindling in the dog. Kindling in the dog was marked by its rapidity and lack of graded stages, resulting in two identifiable stages. The first, afterdischarge stage, was characterized by increased electrical brain activity in the stimulated amygdala but not in the ipsilateral anterior or posterior hypothalamus, or contralateral amygdala. Increased blood pressure was closely related to the activity of the stimulated amygdala, and a gradual increase in heart rate was unrelated to activity at any of the recording sites. Behavioral manifestations were confined to head and neck movements. The second, convulsion stage, was typified by increased activity in both amygdalae and in the anterior hypothalamic recording sites, indicating generalized involvement of both hemispheres. Blood pressure was significantly increased consistent with the behavioral manifestations of bilateral tonic-clonic convulsion. Heart rate during the convulsion was not significantly different from that during the afterdischarge stage. This experiment, therefore, demonstrated that kindling in the dog follows a substantially different progression from that reported in other species and that kindled afterdischarges in the amygdala had a potent effect on blood pressure, even in the absence of generalized convulsions.

Amygdala↗
PubMed1983

Indexes of intravascular hemolysis, quantification of coagulation factors, and platelet survival in patients with porcine heterograft valves.

Ten patients with porcine heterograft valves who were not receiving anticoagulant agents were evaluated to determine the effect of the valve on red blood cell survival and on platelet activation and consumption as measured by (1) quantification of the coagulation mechanism, (2) platelet function studies, and (3) 51-chromium platelet survival time. There was no evidence of significant intravascular hemolysis as determined by the reticulocyte count, serum iron and iron binding capacity, serum bilirubin level, or lactic dehydrogenase activity. The coagulation profile and the platelet function studies were normal. No statistically significant difference was found in the platelet survival time in the 10 patients with porcine heterograft valves (half-life 3.2 +/- 0.8 days) and the 11 normal control subjects (half-life 3.6 +/- 0.6 days) (p greater than 0.2). The finding of a normal platelet survival time in patients with porcine heterograft valves is consistent with clinical experience indicating that this device is associated with a low incidence of systemic embolization, approximating 3% per year.

Adult↗
PubMed1983

The effects of cardiovascular drugs on the defibrillation threshold and the pathological effects on the heart using an automatic implantable defibrillator.

Internal defibrillating leads were implanted in 6 dogs through a left thoracotomy and in 6 pigs through a subxiphoid approach. The effects of digoxin (0.04 mg per kilogram of body weight), procainamide (15 mg per kilogram), and propranolol (0.2 mg per kilogram) on the defibrillation threshold was determined 30 to 60 minutes following intravenous administration. Resultant blood levels were equal to or greater than therapeutic levels. Individually these drugs resulted in no appreciable change in the defibrillation threshold from baseline. Pathological study of the myocardium obtained from 6 dogs that underwent more than two hundred shocks each did not demonstrate any abnormality. The 6 pigs were reliably defibrillated, this indicating that thoracotomy is not required for successful implantation. The automatic implantable defibrillator is not the definitive treatment for recurrent ventricular arrhythmias, but is a practical regimen of therapy for a select group of high-risk, out-of-hospital patients. These observations advance our knowledge of the use of this device and give more assurance for future implantation in this select group of patients.

Animals↗
PubMed1983

Mitral valve prolapse and agoraphobia.

Of 46 female agoraphobic patients, three had definite and four had probable mitral valve prolapse--a total prevalence of only 15%. There were no significant differences between patients with mitral valve prolapse and the rest of the sample on demographic and clinical variables, nor did the groups differ significantly on measures of psychological symptoms assessed before and after treatment. These negative findings support recent reports indicating that agoraphobia associated with mitral valve prolapse may be indistinguishable from agoraphobia without mitral valve prolapse.

Adolescent↗
PubMed1982

Blood culture positivity: suppression by outpatient antibiotic therapy in patients with bacterial endocarditis.

Recognition of the increasing prevalence of outpatient antibiotic use prompted this review of 32 patients with verified infectious endocarditis. The results of 161 quantitative blood cultures obtained before definitive therapy were correlated with clinical information to determine whether outpatient antibiotic administration influenced blood culture positivity. In 17 patients receiving outpatient antibiotics, 56 (64%) of 88 blood cultures obtained before definitive treatment were positive, whereas all cultures obtained from 15 patients without recent antibiotic exposure were positive. Notably, seven patients showed a phase of total suppression, and two patients showed a phase of partial suppression of blood culture positivity after discontinuation of outpatient antibiotic treatment. Consequently, patients with recent antibiotic exposure and suspected endocarditis should have blood cultures obtained initially and periodically throughout the phase of potential suppression of bacteremia to optimize the chance of obtaining a positive result.

Ambulatory Care↗
PubMed1981

Corticosterone secretion after inhibition of prostaglandin synthesis by indomethacin.

Systemic indomethacin (Ind) administration decreased prostaglandin F (PGF) content of the rat adrenal to less than 1.4 pg/mg. This was less than 5% of the adrenal PGF content in the gelatin-treated (Gel) control group (34 pg/mg). Basal plasma corticosterone levels were increased by the Ind treatment. Since the calculated metabolic clearance rate for corticosterone was unchanged, this increase was attributed to an enhanced adrenal secretion rate that was secondary to elevated plasma ACTH concentration. Ether exposure in the presence of Ind did not stimulate a normal rise in plasma corticosterone or adrenal corticosteroidogenesis. Adrenal responsiveness to exogenous ACTH was reduced after Ind treatment. There was a normal rise in plasma ACTH levels following ether exposure confirming the adrenal as the site of inhibition. Systemic Ind treatment thus appears to have two sites of action in altering plasma corticosterone levels: 1) a direct effect on the adrenal, inhibiting normal secretion in response to acute elevations of plasma ACTH, and 2) an action at the pituitary or hypothalamic level, eliciting an increase in basal ACTH secretion.

Adrenal Cortex↗
PubMed1981

Lead systems for internal ventricular fibrillation.

We examined the feasibility of using a standby automatic implantable defibrillator and established thresholds for internal defibrillation. The implantable defibrillator senses ventricular fibrillation and delivers an electrical impulse for defibrillation. Two lead systems for the device have been investigated. System I consists of two 12-cm2 silicone-covered titanium mesh patches attached to the atrial and diaphragmatic pericardial surfaces. System II has an identical diaphragmatic patch and a titanium spring catheter, with a 12-cm2 surface area of conductivity, placed transvenously in the right atrium. Both systems were implanted by thoracotomy in 12 dogs (mean weight 20 kg) and by a subxiphoid approach in 10 pigs (mean weight 20 kg). The defibrillation threshold (lowest energy required for 80% success) was determined periodically for 54 weeks in the dogs (615 trials) and at 6 weeks for the pigs (100 trials). In dogs, the mean defibrillation threshold with system I leads at 4 weeks was 10.5 J and did not change significantly over a 54-week period (p greater than 0.05). Similar results were obtained in the pig at 4 weeks. The defibrillation thresholds for both lead systems in dogs and pigs using a transpleural thoracotomy or a subxiphoid approach are satisfactory for an implantable defibrillator that produces 20-35 J.

Animals↗
PubMed1981

Evidence that thyrotropin and prolactin are not secreted by the posterior pituitary of the rat.

After eutopic hypophysectomy of the host, transplants under the renal capsule of three whole pituitaries or of the adenohypophysis alone were capable of maintaining plasma PRL concentration equal to or greater than that of intact controls. The basal plasma TSH levels in rats with these types of heterotopic pituitaries was below that of intact controls but was significantly increased by TRH or chronic antithyroid treatment. Rats with posterior pituitary (intermediate and neural lobe) heterotopic transplants were incapable, under any conditions tested, of raising the plasma PRL or TSH concentration above that seen in hypophysectomized controls without pituitary transplants. In a further experiment, selective extirpation of the anterior or posterior lobe of the eutopic pituitary was performed. Plasma concentrations of TSH and PRL in rats with anterior lobectomy were not significantly different from those of hypophysectomized controls but were significantly higher than those of hypophysectomized controls in rats with posterior lobectomy. These data indicate that only the adenohypophysis secretes physiologically significant quantitites of these two hormones. (Endocrinology 108: 382, 1981)

Animals↗
PubMed1980

Lung growth in response to altered metabolic demand in hamsters: influence of thyroid function and cold exposure.

This study examines the relation between whole body O2 requirements and lung growth. 6-week-old hamsters were exposed to cold (5 degrees C) or injected with thyroid hormone. These treatments elevated O2 consumption by 26% over a 28-day period. Both alveolar surface area and total lung air volume were increased by approximately 25% in each group. Morphometric data suggest that lung enlargement was due to an increase in the number or complexity, rather than size of individual alveolar units. Further elevating O2 demand by increasing thyroid dosage did not enhance lung size beyond the level observed with the lowest dose used. Depressing metabolic rate with an antithyroid drug for four weeks had no effect on lung structure (in this animal model). Results indicate that in hamsters, increased physiologic O2 demand may be met to a certain extent by augmentation of the pulmonary diffusing surface.

Animals↗