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Biomedical subjects

J C Cowan

Publications and source records attributed to J C Cowan.

At least 55 records · Page 3Linked to original sources
PubMed1986

Nitrate tolerance.

Nitrates are widely used in anginal prophylaxis. In spite of the fact that the concept of nitrate tolerance was first put forward many years ago, the question of tolerance has remained controversial. There is widespread agreement that tolerance does occur to the effects of nitrates on arterial pressure. In contrast, tolerance to the venous and pulmonary effects is disputed. Similarly, the possibility of tolerance to the antianginal effects remains at issue. In this review, I discuss the factors which may have contributed to conflicting results in different studies, in particular recent findings on the rapidity of onset and reversal of tolerance. Tolerance develops rapidly on initiation of treatment and disappears equally rapidly on its discontinuation. In addition, tolerance appears to be a function of plasma nitrate profile. It is most likely to occur when plasma nitrate levels are constant and least likely when nitrate levels fluctuate. Furthermore, the provision of a daily nitrate free interval may protect against the development of tolerance. I then discuss the implications of these findings for patient management. They suggest that nitrate prophylaxis should not be used continuously, if this can be avoided. Rather, prophylaxis should be tailored to the individual to provide protection at times of maximum susceptibility, while allowing nitrate levels to fall at other times. The adequacy of antianginal protection with drug regimens incorporating a nitrate free interval requires further assessment. Similarly, the possibility that a nitrate free interval might lead to withdrawal effects and exacerbation of angina needs to be excluded.

Angina Pectoris↗
PubMed1984

Aortic root abscess complicating bacterial endocarditis. Demonstration by computed tomography.

A 68 year old man with an aortic valve prosthesis was admitted to hospital with Staphylococcus aureus endocarditis. Despite antibiotic treatment he continued to be pyrexial. Computed tomography identified a probable abscess between the root of the aorta and the left atrium. The presence of an abscess in this location was subsequently confirmed at operation. Computed tomography is a useful additional diagnostic method for identifying this potentially lethal complication of bacterial endocarditis.

Abscess↗
PubMed1982

Central somatosensory conduction time from 10 to 79 years.

Somatosensory evoked potentials were recorded simultaneously from the neck and scalp following stimulation of the median nerve at the wrist in 83 normal subjects aged 10-79 years. The central somatosensory conduction time was measured by subtracting the peak latency of the major response from the upper cervical area (N14) from that of the primary cortical response (N20). The central conduction time remained constant between 10 and 49 years but increased abruptly by approximately 0.3 msec between the fifth and sixth decades. Following this increase there was no further change in the central conduction time. Changes with age in the amplitude of N14 and N20 differed both from the changes in latency and from each other. The amplitude of N14 was stable between 10 and 39 years but then declined progressively. The amplitude of N20 deceased between 10 and 39 years and then increased until the end of the seventh decade.

Adolescent↗
PubMed1982

Somatosensory evoked potentials in patients with supraclavicular brachial plexus injuries.

In 12 patients with traumatic lesions of brachial plexus, we studied somatosensory evoked potentials by stimulation of median, radial, and ulnar nerves at the wrist and by recording at the arm, Erb point, cervical spinal cord, and contralateral cortex. Results after median nerve stimulation in patients with upper trunk lesions were normal. Patients with C5/6 root avulsion had either normal, delayed, or absent responses at the cervical cord and cortex, depending on the presence of complicating distal lesions. In patients with particular involvement of C7 root, results were normal after median and ulnar stimulation but were abnormal after radial nerve stimulation. In patients with multiple root avulsions and flail anesthetic arm, no potentials could be recorded from the cervical cord or contralateral cortex, regardless of which nerve was stimulated. For relevant information, it was important to stimulate nerves having roots near the anatomic site of the lesion as determined clinically and electromyographically.

Adolescent↗
PubMed1979

Dairy products.

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Dairy Products↗