PLATELET ADHESIVENESS

91 at present, unrelated to the size of the hospital, I feel that the remarkable thing is that large hospitals are able to undertake any research at all, when they are attempting so much for both inpatients and outpatients, with their present inadequate consultant establishments. In our hospital group of over 1700 beds, one of our two consultants has to spend half his sessions in another hospital group of over 1400 beds. Has Mr. Williams any figures for the ratio of consultants to patients in the hospitals for the mentally subnormal in this country, and has he really any evidence to support his assertion that " the average I.Q. of the patients is often well over 50 " ? W. ALAN HEATON-WARD.

MALIGNANT MELANOMA OF THE SKIN SIR,-Your leading article (Dec. 4) prompts us to give here preliminary details of the Queensland Melanoma Project. This investigation started in July, 1963, with a grant to the Princess Alexandra Hospital from the Queensland Cancer Fund. Since then all new cases of malignant melanoma occurring in Queensland have been recorded in the research unit at this hospital. In the first twelve months, 251 microscopically proven cases of all types were registered from a population of 1,700,000. This corresponds to an incidence of about 14 per 100,000 population per year-seven times higher than the incidence you cite in Europe. The reason for this disturbingly high incidence is not known but is the subject of detailed epidemiological study. In Queensland, in contrast to the distribution of cutaneous melanomata cited in your annotation, a third of the lesions occur on the lower limb, a third on the trunk, a sixth on the upper limb, and a sixth on the head and neck. As you mentioned, early diagnosis is not always easy but the history of change is of paramount importance. In Queensland, patients "

"

with any skin blemish tend to seek medical advice early, and this is reflected in the fact that almost half the melanomata are 1 cm. or less in size when excised. " That local excision of a malignant melanoma should be followed by prophylactic dissection of the regional nodes is widely accepted, but we regard this policy as not proven for malignant melanoma as it occurs in Queensland. Because our prospective survey has been in progress for only 21/2 years, we are not yet in a position to discuss prognosis, but in this time we have already accumulated much data on over 500 patients with microscopically confirmed melanoma. NEVILLE DAVIS J. J. HERRON Princess Alexandra Hospital, G. R. C. MCLEOD. Queensland, Australia. "

PLATELET ADHESIVENESS that platelet adhesiveness is greater in whole blood than in platelet-rich plasma was reported previously by Hellem.2 Hellem’s carefuly documented observations provide a starting-point from which a new approach to platelet behaviour has developed; for he found that red-cell extracts increased platelet adhesiveness, and Gaarder et awl. went on to show that the active principle of these extracts was adenosine diphosphate. J. R. A. MITCHELL Department of the R. HAMPTON J. Regius Professor of Medicine, M. J. G. HARRISON. Radcliffe Infirmary, Oxford.

SIR,-Mr. Caspary’s observation1

*t* This letter has been shown reply follows.-ED. L.

to

Mr.

Caspary,

whose

SIR,-Dr. Mitchell and his colleagues rightly take me to task to refer in my paper to the classic monograph by Hellem.1 Hellem’s observations have provided a point of

for much work on platelet adhesiveness including All who make measurements in whole blood and platelet-rich plasma are of course aware of the higher figures given by the former, and it is a failure of communication that this, rather than the efficacy of even a very few red blood-cells in increasing stickiness, should have been taken by Dr. Mitchell as the point of my article. Hellem with mixtures of 20-80% hsematocrit value and found " an almost linear relation between the number of red cells in the plasma and platelet adhesiveness 11.4 He also recorded that a watersoluble adhesiveness-promoting factor, later shown to be adenosine diphosphate5 (A.D.P.), could be liberated from washed red cells by trauma or lysis. My own experiments have extended Hellem’s and showed that a hxmatocrit of as little as 2% is enough to produce the results obtained from whole blood, though Hellem found a hasmatocrit of 50% necessary.6 His measurements relied on forcing suspensions of varying viscosity through a glass-bead bed so that traumatic as well as " simple " A.D.P. release might have operated in producing his linear relation. My findings raise the question whether liberation of A.D.P. from small numbers of red cells of varying

departure my

experimetted

"

fragility " during manipulation may not

the results obtained in whole blood. nmo’rpRR tn tfst

Caspary, E. A. Lancet, 1965, ii, 1273. Hellem, A. J. Stand. J. clin. Lab. Invest. 1960, 12, suppl. 51. Gaarder, A., Jonsen, J., Laland, S. Hellem, A. J., Owren, P. A. Nature, Lond. 1961, 192, 531.

govern substantially Experiments are in

this nnRsihiHtv

Medical Research Council, Demyelinating Diseases Research Unit, Newcastle upon Tyne, 2.

E. A. CASPARY.

PRESSOR EFFECT OF 5-HYDROXYTRYPTAMINE

SIR,-Your leading article

on pressor attacks during treatwith monoamine-oxidase (M.A.o.) inhibitorswas of great interest. Do bananas, in view of their high content of 5-hydroxytryptamine, produce, in patients treated with M.A.o. inhibitors, a picture like the carcinoid syndrome, or hypertensive crises ? To be on the safe side I warn patients on these drugs against bananas, as well as of the already known contraindications. Medical Unit, Victoria Hospital, F. SAW-LAN IP. Candos, Mauritius.

ment

AMNIOTIC FLUID IN ABRUPTIO PLACENTÆ SIR,-The passage of meconium is an accepted feature of foetal hypoxia. Yet in abruptio placenta:, where there is inevitably foetal hypoxia or anoxia, the amniotic fluid is normally clear. In 54 consecutive cases of abruptio placentae at this hospital where the infants were stillborn and weighed more than 51/2 lb. (21/2 kg.), there were only 5 cases in which the amniotic fluid was meconium-stained. In these 5 cases the foetus was at term. The incidence of meconium in the amniotic fluid is much less if the more premature labours and live births are considered. The explanation of this failure to pass meconium may lie in part in the prematurity of many of the foetuses, for certainly the premature foetus is less likely to pass meconium than is the one at or

beyond

term.

But

a more

basic

reason

may be that

substance, which inhibits the movement of the foetal bowel, is reaching the foetus either from the maternal circulation or from the retroplacental clot. 5-hydroxytryptamine (5-H.T.) may be such a substance, and, liberated from the platelets of the retroplacental clot, may well be the factor causing the increased uterine tonus. 5-H.T. reaching the foetus might prevent the passage of meconium, because it has the some

property of relaxing the circular muscle of the human colon. The action of 5-H.T. on the internal anal sphincter is unknown, but one might expect a substance which relaxes the colonic muscle to constrict this sphincter. Simpson

for failing 1. 2. 3.

own.

4. 5.

6. 7.

Memorial

Maternity Pavilion, 3. Edinburgh, Hellem, A. J. See footnote 2, p. 63. Gaarder, A., Jonsen, J., Laland, S., Hellem, Lond. 1961, 192, 531. Hellem, A. J. See footnote 2, p. 37. Lancet, 1965, i, 945.

W. G. PATERSON. A.

J., Owren, P.A. Nature,