81

deficiency of certain essential fatty acids in result of a defect in fatty-acid metabolism.

C.F.

is the

We thank Dr J. A. Raeburn for providing samples from of his patients, and Mrs L. Bain for technical assistance. University Department of Human

Genetics, Hospital, Edinburgh. Department of Pediatrics, Western General Hospital, Edinburgh. University Department of Child Life and Health, Royal Hospital for Sick Children, Edinburgh.

some

Western General

A. E. H. EMERY. K. FARRELL A. J. KEAY.

W. M. MCCRAE.

EQUIVOCAL AMNIOTIC A.F.P. LEVELS ASSOCIATED WITH OPEN SPINA BIFIDA followed by alpha-fetoprotein estimation is now well established as a means of (A.F.P.) diagnosing open neural-tube lesions in high-risk pregnancies. Between 16 and 20 weeks’ pregnancy, the test is generally regarded as highly sensitive, with a wide separation between the upper limit for normal values and the lowest A.F.P. levels associated with open neural-tube lesions.l,2 The following case should, however, sound a note of caution.

SIR,-Amniocentesis

A 31-year-old woman, who gave birth to a female anencephalic in January, 1971, and a normal female in February, 1972, became pregnant again (last menstrual period July 20, 1974). She was advised to have the pregnancy monitored because the risk of recurrence was considered to be about 1 in 20. An ultrasound scan at 17 weeks showed no abnormalities, and an amniocentesis yielded amniotic fluid containing 78 g. per ml. of A.F.P. measured by the Rocket technique3 (upper limit of normal 45 tj.g. per ml.). The serum level, estimated by radioimmunoassay at the same time, was 110 ng. per ml. (this is at the 95th percentile level). Because of the high serum result the amniocentesis was repeated at l8! weeks, this time yielding amniotic fluid containing 50 ;j.g. per ml. (upper level of normal 35 !g. per ml.). Serum taken simultaneously contained 120 ng. A.F.P. per ml. (at the 95th percentile). As the pregnancy appeared to be clinically normal and the amniotic A.F.P. level was falling, and also because the A.F.P. levels in the two amniotic fluids estimated in another laboratory were thought to be only 70 and 31 fig., the pregnancy was allowed to run its normal course. A moderately well-nourished 2-9 kg. female infant was born at term, with a large open myelocele extending from T10 to the lumbar region associated with kyphosis and with almost complete paralysis of the legs and sphincters but no hydrocephalus. In addition, there was an exomphalos containing small intestines. The infant died aged 5 days.

Although the A.F.P. levels were well above the normal values, they were considerably lower than are usually associated with open neural-tube lesions. In addition, the exomphalos might also have led to an increase in the amniotic levels.4 With this case in mind, it might be advisable to view any level above the usual normal range with extreme suspicion and not to be too dogmatic about the ability to detect widely open neural-tube malformations by means of A.F.P. levels in the amniotic fluid between 16 and 20 weeks. Department of Child Health, Welsh National School of Medicine, K. M. LAURENCE Heath Park, SHEILA M. WALKER. Cardiff CF4 4XN. MARY LLOYD General Hospital, B. L. GRIFFITHS. Neath SA11 3SU. 1. 2.

Laurence, K. M. Lancet, 1974, ii, 939. Laurence, K. M. Develop. Med. Child. Neurol. 1974, 16, suppl. 32,

3.

Allen, L. P., Ferguson-Smith, M. A., Donald, I., Sweet, E., Gibson, A. A. M. Lancet, 1973, ii, 522. De Bruijn, H. W. A., Huisjes, H. J. ibid. 1975, i, 525.

BONE-MARROW CELLS RESISTANT TO CHLORAMPHENICOL IN CHLORAMPHENICOLINDUCED APLASTIC ANÆMIA

SIR,-Dr Kern and his colleagues (May 24, p. 1190) important points concerning the effect of

raise many

on human bone-marrow cultures in semi-solid agar, and they suggest that it would be premature to conclude that bone-marrow precursors of patients with chloramphenicol-induced aplastic anxmia are resistant to chloramphenicol in vitro. They found that total inhibition of colony growth for patients and controls occurred over a wide range of chloramphenicol concentrations. It is notoriously difficult to measure the point of total inhibition in pharmacological experiments and we have followed the example of the pharmacologists by estimating the E.D’50’ the concentration of drug required to inhibit response by 50%: the response in this case being colony formation. 1, The accompanying table shows the E.D.óo concentration of chloramphenicol

chloramphenicol

EFFECT OF CHLORAMPHENICOL ON COLONY FORMATION BY HUMAN BONE-MARROW CELLS FROM NORMAL CONTROLS AND PATIENTS WITH

OR

RECOVERED

FROM

APLASTIC

ANEMIA

FOLLOWING

EXPOSURE TO CHLORAMPHENICOL

poor

serum test.

Dr Kern and others’ data.

for normal colony formation, the approximate relevant in our two patients, and the estimated E.D.óo from the data presented by Dr Kern. Control 6 was run in poor serum to attempt to mimic low colony formation found in chloramphenicol-induced aplastic anaemia. The estimated E.D.óo for both Dr Kern’s patients and our own falls outside the values for our controls in all instances suggesting that colony-forming cells in these patients are relatively resistant to chloramphenicol. The E.D’97oó for controls is also given in the table: it indicates the wide variation when attempting to estimate near complete inhibition and the relative resistance of some of the cells in normal marrow. Some of the data in our paper may be explained if early in culture the cells which will form clusters (groups of 4-49 cells) are more resistant to chloramphenicol than the cells which will go on to form colonies (groups of 50 or more cells), the proportion of clusters/colonies being greater in chloramphenicol-induced aplastic anaemia than in controls. It does not explain the relative resistance of colony-forming cells to chloramphenicol outlined in the table. Our own and Dr Kern’s data suggest a shift, towards resistance to chloramphenicol in chloramphenicol-induced

figures

p. 117.

4.

1. 2.

Finney, D. J. 1971 Probit Analysis. Cambridge. Howell, A., Chinn, S., Andrews, T. M., Watts, R. W. E. Clin. Sci. molec. Med. 1974, 46, 619.

82

aplastic anxmia and that using the agar technique it is not possible to corroborate the data of Yunis 4 using a different technique that these cells are sensitive to chloramphenicol. Further studies of myeloid progenitor cell kinetics related to cell morphology in aplastic anxmia are badly needed. A. HOWELL* T. M. ANDREWS R. W. E. WATTS.

Clinical Research Centre, Harrow, Middlesex HA1 3UJ.

ABNORMAL HÆMOGLOBINS IN SOUTH-EAST STAFFORDSHIRE

FINGER CLUBBING SIR,-Your editorial (June 7, p. 1285) omits mention of a hypothesis to explain certain types of clubbing which has experimental evidence to support it.l-3 It was proposed that the engorgement of the finger tips in clubbing is due to dilatation of the arteriovenous anastomoses under the influence of vasodilator material (probably reduced ferritin) normally present in mixed venous blood, which escapes inactivation by the lung because of right to left shunting. As far as I know this theory has not been disproved or

superseded. 6 Friars Walk, Exeter EX2 4AY.

SiR,—There seems to be a high frequency of haemoglobinopathies in both the local and immigrant populations of this part of Great Britain. During the past 3 years we have screened 726 patients (584 immigrants and 142 local population) for abnormal haemoglobins by CAM electroABNORMAL HEMOGLOBINS IN STAFFORDSHIRE POPULATIONS 1

1

,

G. H. HALL.

PREGNANCY AFTER RENAL TRANSPLANTATION

SiR,—The paper by Dr Evans and his colleagues (June 21, p. 1359), which I have just seen for the first time and concerns one of my patients successfully treated by hxmodialysis and cadaver kidney transplantation, contains an error. The dose of azathioprine was in fact 100 and not

50 mg.

daily.

While I would agree with the cautious attitude expressed by the authors towards pregnancy in women after kidney transplantation, it has not been my practice to recommend restrictions in this regard and I was glad to see that comment was made in the paper that the theoretical teratogenic risk has not been confirmed in practice. Department of Surgery, Royal Postgraduate Medical School, Hammersmith Hospital, London W12.

*

Including

1

VITAMINS AND ORAL

homozygote.

phoresis, using Tris buffer pH points are worth noting:

8-9

(see table).

A few

1. Blood-counts and red-cell morphology in these cases of not reveal any consistent pattern but varied from normal to gross abnormality. 2. A knowledge of the geographical origin of a person under investigation for abnormal haemoglobin was very helpful, especially in differentiating Hb S and Hb D traits. An abnormal fraction moving between Hb A and Ain an immigrant from Pakistan invariably indicated Hb D trait, whereas in individuals from the West Indies it was Hb S trait in all cases. So one should be sceptical about an apparent diagnosis of sickle-cell trait in Pakistani immigrants and Hb D trait in West Indians. 3. &bgr;-thalassaemia does exist in the so-called " pure " English population, and is quite common in some villages in Staffordshire (Abbots Bromley and neighbouring areas) which may have historical importance, going as far back as the Roman invasion of Britain. 4. Some of the immigrants have married local girls and have transmitted the abnormal hxmoglobin gene to some of their children. There is a possibility that these children will, in due course, marry English men and women and will again transmit the same abnormal gene to some of their children. If this process goes on, in a few generations these hxmoglobin abnormalities will no longer be uncommon in Britons.

haemoglobinopathies did

We therefore feel that couples of different racial origins who intend to marry should be screened for the presence of abnormal hxmoglobins. It would be interesting to know the views of others on this topic. Department of Hæmatology, Burton Hospitals, Burton-on-Trent, Staffordshire. 3. 4.

M. E. BUCKLEY P. E. BRASSINGTON M. J. LONG.

Howell, A., Andrews, T. M., Watts, R. W. E. Lancet, 1975, i, 65. Yunis, A. A., Harrington, W. J.J. Lab. clin. Med. 1960, 56, 831. *Present address: Department of Medicine, Birmingham University.

RALPH SHACKMAN.

CONTRACEPTIVES

SIR,-As Professor Wynn (March 8, p. 561) points out, reduced levels of ascorbic acid are found in women using oral contraceptives, but the 500 mg. daily that he suggests would be required to normalise blood-levels may be too little for women whose vitamin-C intake has been low for a long time, unless this dose is sustained for several months. Using a lingual test4 for the vitamin, we have found that young women excreting a mean amount of 41-2:26-5 (n=77) mg. ascorbic acid in 24 hours have a plasma-level of 1-0020-255 mg. per 100 ml. (n=31), whereas women in the same age-range using oral contraceptives had plasma-levels of 0-688±0-405 mg. per 100 ml. (n=9), which differs from the control group significantly (P < 0-02). To determine the fate of high-dose supplements of vitamin C, 6 women (using oral oestrogens) were given 3-3 g. ascorbic acid at bedtime; after a night’s sleep their plasma-levels had risen from 0-939 ±0-073 to 1-2060-178 mg. per 100 ml., but within 24 hours it had again fallen to 0-945± 0-184 mg. per 100 ml. Although their plasma-levels rose their first urinary excretion after significantly (P