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Biomedical subjects

R E Malcolm

Publications and source records attributed to R E Malcolm.

6 recordsLinked to original sources
PubMed1984

Short term reductions in cerebral muscarinic receptor concentration of the mouse after in vivo administration of cycloheximide.

[3H]quinuclidinyl benzilate ([3H]QNB) was used to investigate the effects of administration of cycloheximide to mice on the concentration of muscarinic receptors in the cerebral cortex. A single subcutaneous (s.c.) injection of cycloheximide (3.5 mg/kg) reduced receptor concentration by 18% afer an apparent latency of 1 hr. A single intraperitoneal (i.p.) injection of 3.5 mg/kg produced a 14% reduction in muscarinic receptor concentration 20 min after injection. After both s.c. and i.p. administration the effects of cycloheximide were reversible, dose-related and maximal at a dose of 3.5 mg/kg. The maximum reductions in receptor concentrations obtained were 13-18%. Multiple doses of cycloheximide did not produce greater falls in receptor concentration than single doses and did not prevent its return towards control levels. Treatment of mice for 10 day with cycloheximide reduced muscarinic receptor concentration to 71% of the control at 3 days after stopping administration; receptor levels returned to control values 35 days after the last dose of cycloheximide. Treatment of mice with cycloheximide had no effect on the affinity of [3H]QNB for the receptor and, in vitro, 10(-4)M cycloheximide did not have any significant effect on the binding of the radiolabel.

Animals↗
PubMed1982

Semicircular canals: measurement of endolymphatic and cupular displacements at threshold.

The left horizontal semicircular canal of the leopard frog (Rana pipiens) was exposed and the entire intact nerve was draped over a platinum-iridium hook for recording action potentials (a.p.'s). The preparation was then rotated sinusoidally in the horizontal plane at 0.3 Hz with varying angular displacements. The arm of the canal was then transected, and a fine micropipette ligated in place in one end of the arm. Artificial endolymph was pumped into and out of the canal at the same frequency, while the amplitude of the displacement was varied from sub-threshold to supra-threshold values as determined from the resulting a.p. train. By comparing the two a.p. trains, it was determined that the movement of endolymph in the canals was 5.3 x 10(-8) cm3/deg/s, and that the threshold displacement of the midpoint of the cupula was 7.6 x 10(-5) cm (0.76 micrometers).

Action Potentials↗
PubMed1980

The use of nicotine chewing gum as an aid to stopping smoking.

Two hundred and ten subjects entered a trial to test the use of a chewing gum containing nicotine as an aid to stopping smoking. They were divided into three groups: nicotine chewing gum, placebo chewing gum, and control. The trial was double blind between the two chewing gum groups. After 1 month the percentage of confirmed non-smokers in the nicotine gum group was 34%, in placebo chewing gum group 37% and the control group 24%. By 6 months most of the non-smokers had relapsed, but the nicotine gum group (23%) was more successful than the placebo (5% or the control group (14%).

Adolescent↗
PubMed1979

Oculogravic illusion in response to straight-ahead acceleration of CF-104 aircraft.

Experimental subjects wore goggles that restricted monocular vision to a luminous line fixed relative to the head, and they were exposed on one occasion to a straight-ahead acceleration of an aircraft and on another occasion to a tilting chair. The magnitude of change of direction of the resultant accleration was the same on both occasions, but the perceived movement of the luminous line from the two stimuli was very different. In response to the aircraft stimulus, the oculogravic illusion was experienced and the luminous line was perceived as tilting relative to the subject, in response to the tilting chair stimulus, the line was perceived as remaining fixed relative to the subject. It was concluded that the oculogravic illusion, as experienced in the aircraft (and previously in centrifuges), is a true illusion and not merely a fact of physics.

Acceleration↗
PubMed1978

Deception among smokers.

Subjects in two different clinical trials who had been advised to stop smoking were asked if they had done so. Some 22% of subjects (11 out of 51) in the first trial and 40% (33/82) in the second trial who said they had stopped smoking were found to have raised carboxyhaemoglobin concentrations. Deception appears to be common in people trying to stop smoking.

Adolescent↗