637 in the thaw-siphon technique, results in a continuous left-toright shift in the equilibrium composition, whilst the temperature remains constant. Heat exchange is further enhanced by the continuous reduction in the mass of the system resulting from the siphoning of liquid phase. as

gram done on this patient, and without this definiuve investigation the diagnosis remains in doubt. Division of Neurosurgery, Ohio State University Hospital, Columbus, Ohio 43210, U.S A.

JOSEPH H. GOODMAN

Red Cross Blood Transfusion Service,

Queensland Division, G.P.O.Box 157, Brisbane, Queensland 4001, Australia

LOW-DOSE INSULIN INFUSIONS IN DIABETIC PATIENTS WITH HIGH INSULIN REQUIREMENTS to Dr Lowy (Aug. 19, p. 429), the reason uninvestigation (Aug. 5, p. 283) was not to show whether two injections of insulin daily are more effective than one, but to show that the total dose of intravenously infused insulin necessary to maintain adequate glucose homreostasis was much smaller than that required when subcutaneous mJections, either as single or multiple injections, were used. It is quite possible that the twice daily regimen of insulin is better

SIR,-In reply

derlying

NEGATIVE NALOXONE EFFECTS ON SERUM-PROLACTIN

ERNEST C. MASON

our

because insulin absorption is more efticlent when it is given in smaller doses and in forms which are more rapidly absorbed.’I This may be relevant to the success of subcutaneous infusions of insulin.2 It is also of interest that patients with mild type-n diabetes can be injected with 100 units of ultralente insulin merely to obtain adequate glucose homoeostasis without inducing hypoglycaemia.3 It is possible that slowly absorbed insulins in higher concentrations and larger volumes are more vulnerable to degradation in the subcutaneous tissue. We stated clearly in our paper that the patients’ glucose homoeostasis after their admission to hospital (both before and after infusions) was similar to that before admission. The blood-glucose after admission was in the range shown in the table (values obtained in our clinic during previous 12 months). The first two values in fig. 3 in all patients are consistent with this. Furthermore, despite an arbitrary attempt to reduce patients’ insulin dose after infusion, their requirements did not differ significantly. Since all injections of insulin during admission were supervised by doctors and/or nurses, it is that our observations can be explained by discrepancies between prescribed and injected doses of insulin. We agree with Lowy that measurements of free insulin in the plasma would have enabled us to assert further our point about subcutaneous degradation of insulin. Finally, it is relevant to mention that Halban et al.4 have shown that 15-251( of subcutaneously injected insulin in dogs is biochemically altered within 15min of injection.

unlikely

Metabolic Unit,

Department of Chemical Pathology, Royal Free Hospital, London NW3 2QG

P. DANDÒNA

INJURY OF CERVICAL SPINE SIR,-Scoppetta and Vaccari05 reported a hyperextension injury of the cervical spine causing a central cord syndrome in a football player. Their description leaves some question as to whether this is a correct diagnosis in that a herniated cervical HYPEREXTENSION

disc at the c7,8 level with lateral displacement could cause a c8 radiculopathy as well as some long-tract involvement on the same side. Persistent painful parxsthesix in a dermatomal distribution can occur in both the central cord syndrome and with herniated cervical disc. There was apparently no myelo1. Binder, C. Absorption of Injected Insulin. Copenhagen, 2. Pickup, J C, Keen, H., Parsons, J A., Alberti, K. G

1969. M. M Br med. J.,

1978, i, 204. 3. Holman, R. R., Turner, R C. Clin. Sci. mol. Med. 1976, 51, 18P. 4. Halban, P, and others Diabetes, 1978, 27, suppl 2, abst. 36, 439. 5 Scoppetta, C., Vaccario, M Lancet, 1978, i, 1269

SIR,-Gold et al.’ reported a significant decrease in serumprolactin in six Macaca arctoides 30-180 min after infusion of the narcotic-antagonist naloxone hydrochloride (0.2 mg/kg) and

suggested that alterations in serum-prolactin may be a physiological marker of naloxone’s behavioural effects. Using a double-blind, counterbalanced, crossover design, we measured serum-prolactin (samples collected through an indwelling catheter) in man at 30, 15, and 0 min before and 0, 15, and 30 min after a 20 min intravenous infusion of 20 mg naloxone hydrochloride (Narcan-Endo Laboratories) on 1 day and of placebo on another. Naloxone and placebo were given to 8 normal people, 12 psychiatric patients with manic symptoms (8 of whom were receiving antipsychotic drugs), and 4 depressive patients. The dose of naloxone was similar to that

MEAN

(S.E.M.)

SERUM-PROLACTIN BEFORE AND AFTER INFUSION

WITH NALOXONE HYDROCHLORIDE

(20 mg) AND PLACEBO

Gold et al.and samples were collected at times similar to those in earlier animal experiments.23 prolactin was measured as described previously.4 Naloxone had no effect on serum-prolactin in normal people or in psychiatric patients (see table), whether or not serumprolactin was initially raised by antipsychotic drugs. Furthermore, although manic symptoms appeared to decrease after naloxone infusion, naloxone had no significant effect on serum-prolactin in the group of 12 patients with these symptoms

given by

(F=0.60, d.f.=1/11). While our results do not support the findings of Gold et al.’ the hypothesis they advanced, it must be noted that naloxone’s effect on serum-prolactin seems to occur within a very narrow dose-range; we used a relatively short post-infusion blood-collection period (30 min); and we infused naloxone slowly over 20 min. These factors may have contributed to our negative result. Alternatively, humans may be less responsive to the prolactin-lowering effects of naloxone than are rodents and lower primates. The possibility of species differences m the prolactin response to naloxone merits further investigation. or

This work was supported by M.R.I.S. grants no. 4576 and 6911 and N.I.M.H. grant ao. 1P50MH30914-01. D. S. is recipient of N.I.M.H. research scientist award MH70183-05 and N.I.D.A. grant no.

DA01568-03. Research Service, San Diego Veterans Administration and Department of Psychiatry, University of California at San Diego School of Medicine, California, U.S.A.

Hospital,

DAVID JANOWSKY LEWIS JUDD LEIGHTON HUEY NORTON ROITMAN DONAL PARKER DAVID SEGAL

1. Gold, M.S, Redmond, D.E, Donabedian, R. K. Lancet, 1978, i, 323. 2. Shaar, C. J., Frederickson, C. A., Dininger, N. B., Jackson, L. Life Sci.

1977, 21, 853 3. Bruni. J.F, VanVugt, D., Marshall, S., Meites, J ibid. p. 461. 4 Parker, D C, Rossman, L G., Vanderlaan, E. F. J. clin Endocr Metab.

1973, 36, 119

Low-dose insulin infusions in diabetic patients with high insulin requirements.

637 in the thaw-siphon technique, results in a continuous left-toright shift in the equilibrium composition, whilst the temperature remains constant...
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