716 in the future ? For religious or other reasons some parents might well reject the idea of contraception or antenatal diagnosis with selective abortion. A further problem arises from the introduction of techniques for antenatal diagnosis. These techniques are complex and require considerable expertise. If a mistake is made and a child with a serious deformity is born, are those individuals who carried out the tests likely to be the subject of litigation ? The Commission’s report is not helpful on this point, but whether or not the defence of " acting in good faith " would be acceptable is a moot point. In the very near future the profession will require expert legal guidance in these matters. Department of Human Genetics, Western General Hospital, Edinburgh EH4 2HU.
A. E. H. EMERY.
DISPENSING DOCTORS SIR,-I was surprised that David McKie (Sept. 7, p. 583), in his article on the disappearing chemist’s shop, did not point out the possible virtues of encouraging more doctors to dispense. To do so would require a new flexibility in the rule preventing doctors dispensing to patients living within a mile of the nearest chemist. But, apart from the fact that doctors are, quite fairly, paid less than chemists for dispensing, and so provide a cheaper service for the N.H.S., the advantages to a patient of receiving drugs from the doctor at the time of prescribing are very real. In ten years in a part-dispensing semirural practice, I provided rural patients with drugs not only in the surgery, but also in their homes, by carrying a portable, limited, but adequately comprehensive range of drugs in a specially designed box in the back of my car. I used to feel sorry for those patients who were denied this service by the existence of the one-mile rule. Cobbetts, Town Row, Rotherfield, Sussex.
J. M. HUGHES.
RAPID CHROMOSOME DIAGNOSIS
SIR,-Dr Smithies and Dr Valmanreported that a cytogenetic diagnosis could be made from bone-marrow cells five hours after the sample had been aspirated. This was an improvement over an eight-hour diagnostic pro-
Method.-l ml. of bone-marrow aspirate was placed in 4 ml of culture medium containing 0-4 ml. of heparin. In the laboratory this specimen was divided into two centrifuge tubes and made up to 10 ml. each with medium enriched with 20% fetal calf serum. 0-2 ml. of colcemid was added to each tube and left to sit at room temperature for one hour. They were then centrifuged at 800 r.p.m. for 5 minutes, the supernatant was discarded, and the cells were washed with phosphate buffer solution. Hypotonic treatment and fixation followed in the usual fashicn. The fixed cells were chilled in the freezer for 15 minutes before air-dried slides were prepared. The slides were stained with a drop of 2% acetic orcein (toluidene-blue if chromosome banding is to follow), a coverslip was added, and the chromosomes were
Some complaints have been voiced by physicians that karyotyping has limited use because of the length of time taken to obtain results. In urgent cases a diagnosis can be made on cultured lymphocytes in three days (without chromosome-banding studies) while karyotyping of bonemarrow cells can be performed within two hours. This simple and rapid technique can be of considerable value to physicians and parents faced with the question of management.
Regional Cytogenetics Laboratory and Department of Pediatrics, McMaster University, Hamilton, Ontario.
C. P. A. B. IRENE C. Y.
VIOLA LEE MACMILLAN A. UCHIDA YEUNG.
SIR,-Dr Thaler and his colleagues (Aug. 24, p. 438) described defective ornithine transcarbamylase (o.T.c.) in the liver of a child with Reye’s syndrome: activity was 20% of normal and Km (for ornithine) was increased 18-fold. The authors did not measure carbamyl-phosphate
synthetase (c.p.s.). We reported the activity (though not the Km) of o.T.c. and c.p.s. in hepatic specimens of two patients with Reye’s syndrome 1; we have since extended these measurements to two additional patients with similar results. They are presented here for their possible bearing on Dr Thaler’s (C.P.S.)
AND ACTIVITY OF CARBAMYL-PHOSPHATE SYNTHETASE IN NORMAL HUMAN ORNITHINE TRANSCARBAMYLASE LIVER AND LIVER OF FOUR PATIENTS WITH REYE’S SYNDROME
cedure mentioned by Shaw.2 We have found that this time can be shortened to two hours. An infant girl was born at 32 weeks’ gestation in severe respiratory distress. The following malformations suggested a clinical diagnosis of 18-trisomy syndrome: microphthalmia, low-set malformed ears, webbed neck, overlapping of index fingers, and rocker-bottom feet. Small dermal patterns (arches and loops) were present on the fingers. When the question of management arose, rapid confirmation of the clinical diagnosis became urgent. A sample of bone-marrow was aspirated from the iliac crest and within two hours the presence of an extra chromosome no. 18 was confirmed in 7 cells. No extraordinary measures were taken to prolong life and the infant died a few hours later. Further confirmation was provided by fluorescent banding of lymphocyte chromosomes prepared from peripheral blood cultures. Similar rapid karyotyping was performed on a sample of fluid obtained before necropsy from the chest of a stillborn girl with a differential diagnosis of 13-trisomy syndrome or Potter’s syndrome. The malformations suggestive of 13 trisomy were cleft lip and palate and polydactyly of both hands. An apparently normal karyotype was quickly demonstrated. Necropsy confirmed a diagnosis of Potter’s syndrome. Subsequent chromosome-banding analysis on a sample of cord blood identified a pericentric inversion of chromosome no. 9 transmitted by the father. 1. 2.
Smithies, A., Valman, H. B. Lancet, 1974, i, 1056. Shaw, A. New Engl. J. Med. 1973, 289, 885.
* Mean t 1 s.D.
One specimen was obtained by the other three at biopsy, necropsy. The results (obtained by published methods2 and expressed in nanomoles citrulline formed per mg. liver protein per minute) were compared with " control " values in two biopsy and eleven necropsy specimens; whether they were obtained by biopsy or necropsy did not seem to affect the values. Mean activity of o.T.c. and c.p.s. in Reye’s syndrome was reduced to 37% and 57% of normal (P<0-005 and 0-01, respectively, using the t test for comparison of means).
1. Brown, T., Brown, H., Lansky, L., Hug, G. New Engl. J. Med. (in the press). 2. Brown, H. in Hepatic Failure (edited by I. N. Kugelmass); p. 63. Springfield, Illinois, 1970.