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Biomedical subjects

M McGregor

Publications and source records attributed to M McGregor.

At least 73 records · Page 4Linked to original sources
PubMed1989

New growth elicited in adult leech mechanosensory neurones by peripheral axon damage.

1. New growth in cutaneous mechanosensory neurones elicited by axotomy or axon crush was studied using intracellular injection of horseradish peroxidase at different times after the lesion, ranging from a few days to over a year. 2. Cutting or crushing major, large-calibre axon branches of mechanosensory neurones elicits sprouting of new processes, either centrally within the ganglion neuropile or at the site of the lesion in the peripheral nerve. In contrast, cutting or crushing fine-calibre axon branches supplying accessory parts of the receptive field does not elicit sprouting of the main arbor or main axon branches. 3. Different modalities of mechanosensory neurone respond differently to lesions of their axons. Cutting the axons of high-threshold units responding to noxious stimulation of the skin elicits sprouting of additional processes from the axon hillock region within the central nervous system (CNS), whereas cutting or crushing the axons of low-threshold cells responding to light touch of the skin elicits sprouting at the site of the lesion only, and not within the CNS. 4. In addition to the new growth directed into the peripheral nerve, damaged nociceptive neurones also form new processes that wrap the somata of particular cells within the ganglion. 5. Sprouted processes of axotomized neurones are retained for long periods after the lesion (up to 425 days). 6. The electrical properties of touch and nociceptive cells were studied between 1 and 60 days after axotomy, by intracellular recording from the centrally located cell bodies. The amplitude, width and maximum dV/dt of the action potential and after-hyperpolarization, as well as the resting potential and input resistance, did not change significantly after axotomy, despite the considerable process sprouting known to occur during this time.

Action Potentials↗
PubMed1989

Restoration of flow in acute coronary obstructive syndromes: consequences of different management strategies.

Although much necessary evidence is not yet available, there is sufficient information from recent therapeutic trials to necessitate a nationwide review of the management of acute coronary obstructive syndromes. On the basis of present information it is evident that, in addition to heparin, all patients suffering from suspected acute myocardial infarction should receive immediate low dose aspirin which should be continued for one to six months. This treatment, if generally applied, can be expected to save 1200 lives per year in Canada at negligible cost. Addition of intravenous streptokinase infusion to all patients (in whom there are no contraindications) available for treatment from 0 to 24 h from the onset, can be expected to save an additional 1088 lives at an additional cost of approximately $11,000 per life. Other thrombolytic agents involve additional cost and the gains in terms of mortality are not yet demonstrated. The evidence for thrombolytic treatment in acute unstable angina is still uncertain but the treatment of all cases with aspirin from the earliest possible moment is clearly indicated.

Angina Pectoris↗
PubMed1987

Selection of medical students--are all matriculation examinations equivalent?

The marks achieved by students vary significantly with the type of matriculation examination written. In particular, students who write the examination set by the Transvaal Education Department score significantly higher matriculation marks than other students but score the same in the first year at medical school as other students. These students have an undeserved advantage in the selection process.

Educational Measurement↗
PubMed1987

Selection of medical students--are interview evaluations consistent?

We report an attempt to evaluate the consistency of interviews used in the selection of medical students. We found that when two teams of two or three members each interviewed candidates independently, the difference between marks (on a scale of 0-10) was less than 2.5 in 90% of comparisons and less than 1.4 in 75%. When candidate variation was eliminated by use of televised interviews differences between teams were reduced. We conclude that teams of two or three interviews can evaluate candidates with acceptable consistency. On the other hand, evaluations by individuals are less consistent and probably should not be used for categorical evaluations.

College Admission Test↗
PubMed1987

Combination of theophylline and salbutamol for arrhythmias in severe COPD.

We conducted a single-bind placebo controlled study using 24-hour continuous ambulatory electrocardiographic recordings. The arrhythmogenic potential of the combination of salbutamol and theophylline was investigated in 25 ambulatory subjects with severe chronic airflow obstruction (mean age 65 +/- 8 SD, mean FEV1 31 percent +/- 13 SD predicted). Asymptomatic arrhythmias were very prevalent in the study population: 76 percent of the patients had runs of supraventricular tachycardia while 24 percent had runs of ventricular tachycardia. Individual arrhythmia frequency showed greater between-test variability than previously described in non-COPD subjects. The mode of administration of salbutamol may have affected arrhythmia frequency in that subjects using aerosol nebulizers had more ventricular extrasystoles than those using metered dose inhalers. Although the addition of theophylline to salbutamol significantly increased heart rate and supraventricular extrasystoles, there was no statistically significant increase in ventricular arrhythmias.

Aged↗
PubMed1987

A comparison of the effectiveness of spinal manipulative therapy for low back pain patients with and without spondylolisthesis.

The effectiveness of spinal manipulative therapy for low back pain is compared between two groups of patients: a small group (25) of patients with lumbar spondylolisthesis and a larger group (260) of patients without spondylolisthesis. This data, which was collected from a previously published study on the effectiveness of manipulation for chronic low back pain, shows that the results of manipulative treatment are not significantly different in those patients with or without lumbar spondylolisthesis.

Adolescent↗
PubMed1986

Mechanisms of transient myocardial ischemia.

The second Pisa Conference nine years ago established the frequency of transient reduction of coronary flow, as a cause of angina. Understanding of mechanisms remains very incomplete and there is great overlap between different clinical syndromes. The following facts appear established: Episodes of spontaneous ischemia are frequently asymptomatic and may occur even in patients with classic stable angina of effort: Large coronary arteries exhibit tone; they do not take part in autoregulation: In the presence of advanced organic obstruction, large coronary artery tone may be sufficiently increased by physiological alpha-adrenergic stimulation to provoke ischemia. The following deductions seem justifiable: Clinically, increased large coronary tone can be suspected as a cause of ischemia when there is a background of severe organic coronary narrowing with effort angina, when rest attacks occur in association with stimuli such as cold or isometric stress and when their frequency can be reduced by alpha blockade: Spasm, as distinct from physiological increase in tone, can be suspected when there is minimal organic disease, an absence of effort angina and when attacks are unrelated to stress: The mechanism of spasm is unknown; it may be associated with intimal trauma and probably is more frequent in the presence of early atherosclerotic change: Spasm may be simulated by pseudo-spasm where a physiological increase in tone may cause marked luminal narrowing at a site of still pliable quite mild intimal proliferation; it may be suspected when apparent localised spasm is associated with diffuse acute narrowing of all coronary arteries. Apart from the smooth muscle, acute luminal narrowing with rest angina can result from coronary thrombosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1985

The effect of a prostacyclin analogue (Iloprost) on skin temperature.

Skin temperature was measured in the forearms of 8 healthy volunteers to study the effect of transdermal application of a stable prostacyclin analogue (Iloprost). Local skin temperature was significantly increased 24 hours and 48 hours after application of the drug when compared with an area of control skin. The effect had worn off by 72 hours. At a dose of 25 micrograms there were no systemic effects of vasodilatation or antiplatelet behaviour, but when the dose was increased to 75 micrograms there was a decreased rate of platelet aggregation for 24 hours. Histology of a skin biopsy suggested that the increase in skin temperature was due to vasodilatation and not acute inflammatory reaction. The results of this pilot study suggest that transdermal application of Iloprost is a suitable vehicle for administration of the drug and a prospective randomised trial is proposed for patients with Raynaud's Syndrome.

Administration, Topical↗
PubMed1984

The role of intimal hyperplasia in arterial spasm.

It has been postulated that even moderate spasm in an artery with intimal hyperplasia can produce organ hypoxia because there is an excessive reduction in the diameter of the lumen. To test this hypothesis we created intimal hyperplasia in one femoral artery in five pigs and then induced arterial spasm by administering ergonovine maleate. Arterial spasm did not produce a greater reduction in the luminal diameter of the femoral artery with intimal hyperplasia than it did in the normal femoral artery. Until further evidence appears this hypothesis must be viewed with caution.

Animals↗