NON-FUNCTIONING PITUITARY ADENOMAS DO NOT REGRESS DURING BROMOCRIPTINE THERAPY BUT POSSESS MEMBRANE-BOUND DOPAMINE RECEPTORS WHICH BIND BROMOCRIPTINE

Dopaminergic binding to membranes from 20 well-characterized non-functioning pituitary tumours was investigated using the radioligand [3H]spiperone; nine had failed to regress during pre-operative bromocriptine therapy. Five macroprolactinomas and six normal pituitaries were similarly investigated. High affinity dopaminergic binding sites were defined in all tissues studied. Mean dissociation constants were similar for the three groups (0.92, 0.55 and 0.51 nmol/l, respectively) but mean site numbers were greater in the prolactinomas (698) than in non-functioning tumours (131) or normal pituitaries (136 fmol/mg protein). In a pool of non-functioning tumour membranes ligand competition experiments confirmed that binding was dopaminergic. Stereospecificity was demonstrated using the (+) and (-)isomers of butaclamol. Bromocriptine was present in three non-functioning tumours that had been exposed to the drug within 24 h of surgery and it largely prevented [3H]spiperone binding; membrane washing restored [3H]spiperone binding to control values. We conclude that non-functioning tumours possess high affinity membrane-bound dopaminergic binding sites similar to those in normal pituitary and macroprolactinomas, but apparently fewer in number than in the latter. Though bromocriptine binds to dopamine receptors on non-functioning tumours in vivo, this does not result in tumour regression.     

USE OF MANDATORY MINUTE VOLUME VENTILATION IN THE PERIOPERATIVE MANAGEMENT OF A PATIENT WITH MYASTHENIA

The anaesthetic and postoperative management of a patient withestablished myasthenia gravis, using a mandatory minute volumesystem (MMV), are described. Before operation the patient wasreceiving large doses of anticholinesterases and steroids. Theanaesthetic and postoperative drug therapy and management weresimplified by the use of the MMV system.     

EFFECT OF POSITIVE AND NEGATIVE EXPIRATORY PRESSURE ON RENAL FUNCTION

The effects of positive and negative and expiratory pressureon renal function have been studied in adult greyhounds witha normal blood volume and without evidence of cardiorespiratorydisease. Positive expiratory pressure (+10 cm H₂O) resultedin a decrease of urine volume, glomerular filtration rate andrenal blood flow which returned towards normal following removalof the positive pressure. Negative expiratory pressure ( –6 cm H₂O) resulted in opposite changes in renal function.     

Paediatric Low Vision – A Survey

ABSTRACT This paper reports the results of a survey conducted at a paediatric low vision clinic, of all children examined in the eight year period 1974 to 1981. The data provide a unique opportunity to identify the ophthalmic characteristics of children with low vision. The major cause of low vision in these children has been identified, examined and compared with the results of similar studies. Other characteristics studied are distance and near vision, the type of low vision aids used and the nature of primary education undertaken by the children. The results are discussed to provide information to improve paediatric low vision care.     

THE SHORT METYRAPONE TEST: COMPARISON OF THE PLASMA ACTH RESPONSE TO METYRAPONE WITH THE CORTISOL RESPONSE TO INSULIN-INDUCED HYPOGLYCAEMIA IN PATIENTS WITH PITUITARY DISEASE

After a single dose of 2 g metyrapone given with a snack at 2300 h, blood was taken for estimation of plasma adrenocorticotrophin hormone (ACTH) concentrations at 0800 h the next morning from normal individuals and from patients with pituitary disease. Plasma ACTH concentrations following metyrapone were significantly lower in patients with pituitary disease with no evidence of anterior pituitary hormone deficiency (mean 90.0 +/- SD 63.9 ng/l) when compared with normal individuals (mean 182.5 +/- SD 14.1 ng/l, P leads than 0.01) but significantly greater than in patients with pituitary disease in whom a deficiency of one or more anterior pituitary hormones was demonstrated (mean 50.8 +/- SD 14.1 ng/l, P less than 0.01). It is concluded that the short metyrapone test is a sensitive method of detecting minor degrees of impairment of the negative feedback control of aCTH secretion that would be unrecognized by conventional assessment by insulin-induced hypoglycaemia. The clinical relevance of impaired ACTH release in response to a single dose of metyrapone in patients with pituitary tumours, in whom pituitary function is otherwise shown to be adequate, needs to be determined.     

CHOLINERGIC BLOCKADE WITH PIRENZEPINE IMPROVES CARBOHYDRATE TOLERANCE AND ABOLISHES THE GH RESPONSE TO MEALS IN NORMAL SUBJECTS

Pretreatment of normal male volunteers with the cholinergic muscarinic receptor-blocking drug pirenzepine (200 mg p.o.) abolishes the delayed GH response to a meal stimulus. In addition, the glycaemic and insulin responses to meals are significantly reduced following this dose of pirenzepine. The data suggest that the effect of pirenzepine on the glucose response to meals is at least partly independent of the inhibition of GH release. Our findings are of relevance to the further investigation of cholinergic muscarinic antagonist in diabetes mellitus.