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Biomedical subjects

S D Anderson

Publications and source records attributed to S D Anderson.

At least 145 records · Page 8Linked to original sources
PubMed1977

Somatosensory properties of spinoreticular neurons in the cat.

(1) Spinal cord neurons projecting to the brain stem were studied in cats prepared by decerebration or anesthetized with barbiturate or nitrous oxide and halothane. Antidromic stimulation from the medial pontomedullary reticular formation (MDRF) and midbrain (MB) was used to identify the site of projection. (2) Receptive fields were mapped using adequate stimuli. A variety of noxious stimuli was employed to establish the capacity of these neurons to transmit nociceptive input. (3) Neurons were found to project bilaterally to the MPRF. Of 46 units tested for a more rostral projection, only 13 were activated from the MB electrode. (4) Neurons fall into three categories based on receptive fields: cutaneous, restricted (SR); deep, restricted (DR); and complex, extensive (CE). All 16 SR neurons were located in the dorsal horn and had low thresholds to mechanical stimulation of the skin. Seven discharged maximally to nociceptive inputs. The 34 DR neurons were widely distributed in the spinal gray and responded to pressure upon subcutaneous structures. Although 13 neurons increased their firing rate as the stimulus intensity was increased into the noxious range, nociceptive input could only be established with confidence in 4 neurons. The 38 CE neurons were located ventrally in the spinal gray and had highly convergent inputs from cutaneous and deep receptors. Ten responded maximally to noxious stimulation.

Afferent Pathways↗
PubMed1977

A comparison of oral theophylline and oral salbutamol in exercise-induced asthma.

Ten patients with exercise-induced asthma were premedicated with oral salbutamol and oral theophylline on separate occasions before performing a standardised exercise test. Although both agents produced bronchodilatation, reflected by increases in peak expiratory flow rates (PEFR) at rest, they were generally ineffective in preventing an abnormal post-exercise fall in PEFR. Only one patient was afforded protection by salbutamol and another two patients by theophylline.

Administration, Oral↗
PubMed1976

Effect of beta-adrenergic blockade with alprenolol on ST-segment depression and circulatory dynamics during exercise in patients with effort angina.

1. Nine subjects with severe coronary artery disease were studied during graded "sprint" and "steady-state" exercise before and after intravenous administration of the beta-receptor antagonist alprenolol. During "sprint" workload was increased every minute until maximum work capacity (Wmax) was reached. "Steady-state" exercise was performed at work rates of 0.250, 0.50, and 0.75 of each subject's sprint Wmax. Variables measured included ST-segment depression, changes in heart rate, blood pressure, respiratory gas exchange, and arterial blood composition. Cardiac output (indirect Fick) was measured during "steady-state" exercise. 2. Alprenolol did not alter Wmax during "sprint" but reduced the incidence of angina in both types of exercise. After the drug work capacity was limited by symptoms and signs suggestive of mild left ventricular failure. 3. The relationship between workload (normalized in terms of Wmax) and ST-segment depression was curvilinear. Under control conditions a given rate of work during "steady-state" exercise was assocaited with more marked ST-segment depression than during "sprint". Alprenolol displaced the work-ST-depression curve to the right in each type of exercise; now a given rate of work produced similar ST-depressing during "steady-state" and "sprint" exercise. 4. Alprenolol attentuated the exercise tachycardia during both types of exercise. Cardiac output was lower in "steady-state" exercise after the drug than under control conditions. Metabolic effects included significant reduction in body oxygen consumption after alpreprenolol at 0.25 Wmax and diminished arterial lactate at 0.75 Wmax. The beneficial effects of the drug thus appeared to involve not only cardiac but peripheral effects on beta receptors. 5. Before alprenolol cardiac output was relatively fixed at all workloads, but after the drug there was a work-related rise in output in five out of nine subjects. Comparison with data in normal subjects suggested that in anginal subjects cardiac output at low "steady-state" workloads was inappropriately high.

Adult↗
PubMed1976

Inhaled and oral salbutamol in exercise-induced asthma.

Twenty-one asthmatic patients participated in a single blind, crossover study comparing the effects of aerosol and oral salbutamol (a beta-adrenergic bronchodilator), on exercise-induced bronchospasm. By both routes of administration, salbutamol (albuterol) produced significant bronchodilatation at rest, but only the aerosol effectively prevented post-exercise bronchospasm in most patients. Because exercise-induced bronchospasm is a common problem in children and adults with asthma, these observations are relevant to the drug therapy of these patients. The existence of separate mechanisms for bronchodilatation and the prevention of exercise-induced asthma is postulated. It is possible that differing tissue concentrations of salbutamol are responsible for the observed differences between the 2 routes of administration.

Administration, Oral↗
PubMed1976

Exercise-related changes in plasma levels of 15-keto-13,14-dihydro-prostaglandin F2alpha and noradrenaline in asthmatic and normal subjects.

In an attempt to elucidate the roles of prostaglandin F2alpha and noradrenaline in exercise-induced asthma, plasma levels of these substances were measured at rest, during and after exercise in normal and asthmatic subjects. Changes in airways resistance were assessed by measuring the peak expiratory flow rate. Plasma levels of 15-keto-13,14-dihydro-prostaglandin F2alpha (a relatively stable metabolite of prostaglandin F2alpha) and noradrenaline, at rest, and the changes that occurred during and after exercise, were similar in both the normal and asthmatic subjects. Exercise-induced broncho-constriction occurred in all asthmatic subjects following exercise while no significant change occurred in the peak expiratory flow rates of the normal subjects. At this time, in both groups of subjects, the levels of 15-keto-13,14-dihydro-prostaglandin F2alpha were lower than at rest. The level of noradrenaline observed following exercise were lower than during exercise in all but one subject. It would appear that neither noradrenaline nor prostaglandin F2alpha (or its metabolites) play a significant role in the aetiology of exercise-induced asthma.

Airway Resistance↗
PubMed1976

A trial of an alpha-adrenoreceptor blocking drug (indoramin) in exercise-induced bronchoconstriction.

In 10 patients with exercise-induced asthma oral indoramin, an alpha adrenoreceptor blocking drug, was ineffective in preventing the post-exercise fall in peak expiratory flow rate (PEFR). The values of PEFR at rest increased after administration of indoramin, providing indirect evidence for the existence of alpha receptors in the bronchial smooth muscle of asthmatic subjects.

Adolescent↗
PubMed1975

Exercise-induced asthma.

A review of exercise-induced asthma is presented which describes work that has been carried out by the authors and by other investigators over recent years. The effect of exericse on lung function in asthmatic and normal subjects is compared. The influence of the type and severity of exercise on the response of the asthmatic is noted and the importance this has for interpretation of results. The effects of various drugs on exercise-induced asthma are considered in some detail. The clinical implications of the results of exercise tests in asthmatics, their relatives, and other subjects are considered in terms of the diagnosis and prognosis of asthma and its mode of inheritance. It is concluded that there is as yet no explantation for the mechanism of exercise-induced asthma, but it is a tool of potentially great value for research into the physiology and treatment of clinical asthma.

Acidosis, Respiratory↗
PubMed1975

Inhaled and oral bronchodilator therapy in exercise induced asthma.

Measurements of peak expiratory flow rate during serial exercise tests were used to assess the efficacy of the beta adrenergic stimulants oral terbutaline (5 mg) and fenoterol aerosol (400 micrograms), in preventing post-exercise bronchoconstriction in 18 asthmatic subjects. While both compounds significantly elevated resting levels of peak expiratory flow rate for at least four hours, there were qualitative and quantitative differences in the effects of the two drugs on exercise induced bronchoconstriction. Oral terbulation did not significantly alter the pattern of response to exercise. However, the peak expiratory flow rates before during and after exercise were significantly higher compared with placebo at two, four and six hours after the drug. The importance of examination of actual values for peak expiratory flow rates as well as percentage changes when testing oral bronchodilators is emphasised. Aerosol fenoterol completely blocked post-exercise bronchoconstriction immediately after inhalation and for up to four hours in most subjects. Bronchodilatation occurred in all subjects during exercise in the presence of both the active and placebo drugs. It is postulated that the superiority of the aerosol in blocking exercise induced bronchoconstriction may be function of its activity at the surface of the bronchial mucosa.

Administration, Oral↗
PubMed1975

The use of the treadmill for assessing exercise-induced asthma and the effect of varying the severity and duration of exercise.

Running produces a greater amount of post-exercise bronchoconstriction than other forms of exercise carried out a similar metabolic rates. The treadmill can be used to provide a standardized form of exercise when studying the asthmatic child. The severity of post-exercise bronchoconstriction depends upon the rate of working on the treadmill and the duration of exercise. A maximum response is obtained by six minutes of running at an uphill slope of 10% at a speed of 5 kmph (3 mph). Even with this type of test, there is still considerable variation in the response from time to time and greatest reporducibility is obtained by repeating the test within one week. Treadmill exercise tests may be used in the diagnosis of asthma and in the assessment of its likely severity.

Adult↗
PubMed1972

Exercise asthma.

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Acidosis, Respiratory↗
PubMed1972

Metabolic changes preceding exercise-induced bronchoconstriction.

Five asthmatics aged 25-30 were studied during bicycle ergometer and treadmill exercise. Metabolic and ventilatory changes during exercise were compared with the degree of bronchoconstriction which followed exercise. In all patients bronchoconstriction was greater after treadmill exercise. Contrary to previous suggestions, exercise-induced bronchoconstriction did not seem to be caused by lactic acidosis, increase in minute ventilation, acidaemia, hypocapnia, or change in arterial Po(2)

Acidosis↗