An instrument for checking the radioactivity in shielded syringes.

A description is given of an instrument that can be used for checking, to within ten percent, the radioactivity in shielded syringes. The unit is simple in design and construction and easy to use. The lead shield of the syringe does not have to be removed, since only radiation emitted along the direction of the barrel is detected. A range of syringe sizes can be accommodated and, whilst the instrument is calibrated for 99Tcm with activities in the range 1-10 mCi, both higher and lower activities and other radionuclides can be used. Each measurement takes only a few seconds and the activity of radiopharmaceuticals can be routinely checked immediately before injection.

Instability of cerebral blood-flow in insulin-dependent diabetics.

Cerebral blood-flow (CBF) was measured in 23 insulin-dependent diabetics before and 2--3 h after insulin/breakfast. In 10 of these patients CBF changed significantly during the day, with a significant fall in 9. In 3 patients who had the greatest falls in CBF there was a concomitant sensation of an impending faint. Thus CBF is unstable in insulin-dependent diabetics in contrast to control subjects in who there is little or no variation. Sudden falls in CBF in insulin-dependent diabetics may explain the symptoms of impending faint without hypoglycaemia; such falls would also be relevant to the pathogenesis of strokes in these patients.

The effect of beta-adrenergic receptor blocking drugs on cerebral blood flow.

1 Cerebral blood flow (CBF) was measured by the 133xenon inhalation method in 33 newly-diagnosed hypertensive patients prior to commencing therapy. 2 Blood pressure was treated by using a varying sequence of four different drugs, namely labetalol, metoprolol, oxprenolol and sotalol, each of which is a beta-adrenergic receptor blocking agent, but with differing additional properties. 3 CBF measurements were repeated when blood pressure was controlled. No significant change in CBF was found with any of the four drugs, in contrast to the fall which has been reported when drugs of this type are administered acutely.

Cerebral blood flow in diabetes mellitus: evidence of abnormal cerebrovascular reactivity.

Cerebral blood flow (CBF) was studied at normocapnia and after a challenge with 5% CO2 in 59 diabetic patients and 28 controls. There was a significant age-related decline in CBF in both groups, which suggests that diabetes does not affect the rate of decrease of CBF with age. After CO2 challenge CBF increased in most of the controls; in the patients CBF increased in 23, decreased in 26, and remained stable in 10. Thus the reactivity of cerebral blood vessels in diabetics is altered. Diabetics have diminished cerebrovascular reserve and are thus at increased risk of cerebrovascular disease because they are unable to compensate when necessary with an increased CBF.

Effect of oxprenolol on stage-fright in musicians.

The effect of 40 mg oxprenolol on stage-fright was assessed in 24 musicians in a double-blind crossover trial. Musical performance judged by two professional assessors was found to improve. Greatest improvement was seen on the first performance and in those most affected by nervousness.

Age as a factor affecting lithium therapy.

1 We examined the case notes of 82 psychiatric out-patients (aged 21-84 years) receiving lithium prophylaxis and with steady-state plasma lithium levels. 2 The mean weight-related daily dose of lithium prescribed decreased by about 50% between the third and eight decades. 3 The corresponding steady-state plasma lithium levels showed a less marked tendency to decrease, this only being seen in the seventh and eighth decades. 4 In patients aged 50 years or over the daily lithium dose required to give a plasma level of 1 mmol l-1 (0.50 mmol kg-1) was significantly lower than that (0.65 mmol kg-1) in patients aged under 50 years (P less than 0¿5, Student's t-test). In patients aged 70-79 years this dose was 31% lower than in patients under 50 years. However, interindividual variation was great and it was estimated that age only contributed about 14% to the total interpatient variation. 5 Of the 36 patients under 50 years of age, 42% had minor lithium side-effects and 17% were not optimally controlled with lithium. The corresponding figures for the 46 'older' patients were 46% and 28%. 6 Generally the 50% dosage reduction seemed necessary to compensate for an age-related decrease in lithium excretion and to reduce lithium side effects to a level comparable to that acceptable in younger patients.