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A similar but clearer example is seen in the exponentialphase of growth of cultured microorganisms. Let us

suppose that 1 mg. of cells is inoculated at zero time, andthis mass increases tenfold each day. If Dr. Widdowsonharvests them at day 3, she will find the total mass is 1 g.(" mean growth-rate 1/3 g. per day "). If, however, she hasthe patience to wait till day 6, the mass is now 1 kg. (" meangrowth-rate 167 g. per day "). What different animalsthese would seem to be.

DENNIS W. K. COTTONPAUL D. MIER.

University Department of Dermatology,Nijmegen,

Netherlands.

CHLORPROPAMIDE AND

CHLORAMPHENICOL

SIR,ŁIn their letter on the interaction between chlor-amphenicol and chlorpropamide (April 11, p. 789), Dr.Petitpierre and Professor Fabre give presumptive evidenceindicating that chlorpropamide is metabolised in patientswith normal renal function. Like chloramphenicol,bishydroxycoumarin increases the half-lives of bothtolbutamide 1,2 and chlorpropamide,3 which also couldlead one to believe that chlorpropamide is metabolisedmore than commonly supposed. The most conclusiveevidence to support this view has recently been presentedby Brotherton et al. They found that as much as 80% oforally administered chlorpropamide can be metabolised indiabetic patients. Apparently technical difficulties accountedfor the early, and now widespread, belief that chlorpro-pamide is not metabolised in man.

PHILIP D. HANSTENSupervisor,

Drug Information Service.Alta Bates Community Hospital,

Berkeley, California 94705.

ALPHA RHYTHM: AN ARTEFACT?

SIR,-Dr. Lippold and Dr. Novotny (May 9, p. 976)suggest that the alpha rhythm is " produced by tremor ofthe extraocular muscles modulating the corneoretinalpotential". The sample of E.E.G. record shown in the

accompanying figure was recorded from a young diabeticwoman of 27 who had both eyes removed because of

complications of bilateral glaucoma at age 24. She wasotherwise neurologically normal and did not wear artificialeyes. The record shows alpha activity and classical reduc-tion to attention. In this particular sample, the primaryrecord was filtered by band pass filters selecting frequenciesin the 8 to 16-cycle-per-second range.The E.E.G. showed an unusual amount of fast activity;

1. Kristensen, M., Hansen, J. M. Diabetes, 1967, 16, 211.2. Solomon, H. M., Schrogie, J. J. Metabolism, 1967, 16, 1029.3. Kristensen, M., Hansen, J. M. Acta med. scand. 1968, 183, 83.4. Brotherton, P. M., Grieveson, P., McMartin, C. Clin. Pharmac.

Ther. 1969, 10, 505.

E.E.G. from bipolar centro-parietal derivation on right (uppertrace) and left (lower trace) sides.The signals have been filtered to select only those frequencies

in the range 8 to 16 cycles per second. At arrow, patient wasasked to add 15 to 19.

the alpha rhythm was asymmetrical and of greatest ampli-tude in the c-p leads. Clearly in this case the alpha rhythmcannot have originated in the manner suggested byDr. Linnold and Dr. Novotnv.

J. C. SHAWJ. FOLEYG. H. BLOWERS.

M.R.C. Clinical Psychiatry Research Unit,Graylingwell Hospital, Chichester, Sussex.

OCCUPATIONAL HEALTH BILL

SIR,-A lull for a general election may stop the legislativewindmill as Dr. Herford’s persistent tilting (March 28,p. 673, and May 9, p. 1006) could not do. He has pointedout forcefully over the years that the school leaver enteringindustry needs more help. This requires secure linksbetween schools, employers, the Careers Advisory Serviceand the Employment Medical Advisory Service if the newlaw is to help the young effectively.The formal links can be improved but they cannot be

forged entirely by legislation. Doctors of the new servicemust have community needs at heart. Not only medicalhazards at work need attention but also health education,prevention of mental as well as physical illness, the handi-capped, and those at special risk, including the young.Their elders also need help-for themselves and in under-standing the young.The Employment Medical Advisory Service should be in

the mainstream of medical care and include the best of

many disciplines. Segregation to the Department ofEmployment and Productivity suggests, but need not mean,a narrower interest than our nation and its conununitiesdeserve.

J. J. McMULLAN.Chesham,Bucks.

MEIOSIS IN AN XYY MALE

SIR,-We should like to comment on the communica-tions by Dr. Hulten and Dr. Evans and his colleagues 2on meiosis in XYY individuals. Dr. Hulten’s reportshowed that most of the spermatocytes at diakinesis contain23 bivalents, including a normal XY bivalent, and a fewcells with 24 structures which were interpreted as 23bivalents including a YY bivalent and an X univalent.Dr. Evans and his colleagues emphasised that most of thespermatogonial metaphases contained 46 chromosomes,but clear counts of 47 chromosomes were found in a fewcells and 1 cell seemed to have 49 chromosomes. Melnyket al.3 have also found chromosome numbers of 46, 47, 48,49, and 50 in spermatogonial-metaphase analysis in twopatients with XYY. We should like to report briefly ourmeiotic study in a 24-year-old XYY individual in whomperipheral-leucocyte cultures and fibroblast cultures ofboth skin and testicular biopsies have shown a 47, XYYconstitution.

Meiotic preparations were made by a modification ofthe air-drying method of Evans et al. A total of 35 primaryspermatocytes at diakinesis and a total of 14 spermatogonialmetaphases were examined. Of the 35 spermatocytes,20 cells contained 23 bivalents including a normal XYbivalent; 6 cells had 24 structures without XY bivalentsbut with an X univalent and a possible Y univalent (nodefinite Y bivalent was identified in any of these cells);2 cells had 24 structures including a normal XY bivalentand 2 univalents of G which are due to early separation1. Hultén, M. Lancet, April 4, 1970, p. 717.2. Evans, E. P., Ford, C. E., Chaganti, R. S. K., Blank, C. E., Hunter,

H. ibid. p. 720.3. Melnyk, J., Vanasek, F., Thompson, H., Rucci, A. J. Annual

Meeting of American Society of Human Genetics, San Francisco,California, Oct. 2-4, 1969; abstr. no. 42.

4. Evans, E. P., Breckon, G., Ford, C. E. Cytogenetics, 1964, 3, 289.

1174

of a G bivalent; and 6 cells had 23 structures but with noclear-cut XY bivalents.Of the 14 spermatogonial metaphases, 3 cells had

46 chromosomes, 5 cells had 47 chromosomes, 4 cells had48 chromosomes, and 2 cells had 49 chromosomes. Thefinding of cells with 46, 47, 48, and 49 chromosomes couldrepresent a repeated non-disjunction of the Y chromo-somes early in the process of differentiation, as suggestedby Melnyk et awl. Apparently most of the spermatogonialcells with extra Y chromosomes are eliminated before

entering first meiotic division; however, the report of anXYY child from an XYY father 5 may indicate one possibleexample of an escape from this elimination.A detailed study of this case will be published.This work was supported by grants from the U.S. Public

Health Service (HD-02552), the Birth Defects Institute, theNew York State Department of Health (C-40629), and theHealth Research Council of the City of New York (I-513).

LILLIAN Y. HSULAWRENCE R. SHAPIROKURT HIRSCHHORN.

Mount Sinai School of MedicineDivision of Medical Genetics,Department of Pediatrics,

New York, andLetchworth Village

Mental Retardation Research Unit,Thiells, New York.

CHROMOSOMES FROM HAIRS

SiR,-The letter from Dr. Engel and his colleaguesconcerning Barr body studies from hairs (April 11, p. 789)prompts me to give a preliminary account of the use ofhair-cells as a source of human chromosomes. Conven-tional methods of examining chromosomes generallyentail the culturing of cells for a period of several days.Exceptions to this are short-term cultures or direct prepara-tions from bone marrow,6-9 or direct preparation ofendometrial tissue.1o I have found that certain facial hairs- moustache, beard, and eyebrow-may be extracted

together with a number of dividing cells at their base.Chromosome preparations from these cells may be madedirect without culture, and have the added advantage thatthe material is readily obtainable without any special tech-nique. It is essential to use hairs which are in an active

phase of growth and have been extracted complete withthe outer sheath; this, however, is not difficult. If thehair taken is not excessively dark (and this can often beavoided) the dispersed granules of pigment in the finalpreparation do not cause serious masking of the chromo-somes.

Suitable hairs are placed in a demecolcine solution (4 g. perml. in Hanks’ balanced salt solution) for approximately 2 hours.The temperature is not critical and satisfactory pretreatmenthas been obtained in the range 12-24°C. The material isthen subjected to 10 minutes’ hypotonic treatment in 0-75%sodium-citrate solution containing 0-2% trypsin (1/250), followedby fixation in acetic alcohol (3/1) for a few minutes. Each hairis then transferred to a drop of 2% orcein in 45% acetic acid ona slide, and the tip of the base of the root cut off with a sharpscalpel. The shaft is discarded, while the basal portion left inthe stain is gently heated several times and left for an hour.(Evaporation may be avoided by enclosing the drop of stain witha glass ring and a coverslip on top.) After an hour the stain isdrained off and the cell mass mounted under a coverslip in a dropof 1 % aceto-orcein. The cells are spread into a single layer bya sharp tap with a needle on top of the coverslip and flattenedby thumb pressure as described by Tjio and Whang.9 Slidesmay be made permanent by the dry-ice methody,12

5. Sundequist, U., Hellström, E. Lancet, 1969, ii, 1367.6. Ford, C. E., Jacobs, P. A., Lajtha, L. G. Nature, Lond. 1958, 181,

1565.7. Bottura, C., Ferrari, I. ibid. 1960, 186, 904.8. Meighan, S. S., Stich, H. F. Can. med. Ass. J. 1961, 84, 1004.9. Tjio, J. H., Whang, J. Stain Technol. 1962, 37, 17.

10. László, J. Lancet, Jan. 31, 1970, p. 246.11. Schultz, J., Macduffee, R. C., Anderson, T. F. Science, N.Y. 1949,

110, 5.12. Conger, A. D., Fairchild, L. M. Stain Technol. 1953, 28, 281.

Although accurate chromosome-counts are beingobtained, further development of the technique is still

required to improve chromosome spreading. A goodpreparation of a relatively thick hair such as from the

moustache, will show between 10 and 40 cells at arrestedmetaphase. Well spread, this should be sufficient to

provide a confident check of the chromosome constitutionof an adult male. Work is at present being carried outusing eyebrow hairs so that children and women may besimilarly screened.

If the technique of hair-cell preparations can be perfected,the advantages it gives are obvious-it is an easy and rapidtechnique which does not necessitate sterile collection orculture of the cells. Also, it causes little inconvenience tothe subject under investigation. In short, it would providean ideal method for screening a large number of individualsfor chromosomal abnormalities.

M. G. DAKE

Department of Biology,St. Thomas’s Hospital Medical School,

London S.E.1.

SEX RATIO IN PHENYLKETONURIA

SIR,-The report of Professor Hsia and Mr. Dobson(May 2, p. 905), showing a predominance of males overfemales in phenylketonuric infants ascertained by Guthrietesting, agrees with our own experience.

In New South Wales, screening is performed by theGuthrie method at the time of discharge from majormetropolitan and country hospitals (6-12 days) and bya State-wide urine-chromatography survey 1 from well-baby centres. This is estimated to provide about an 85%cover. The survey is performed by Dr. Brian Turner of theN.S.W. Department of Public Health, and all infants withpositive tests have been seen at our clinic.

INFANTS REFERRED WITH POSITIVE SCREENING TESTS

Since May, 1968, we have had referred to us from thesurvey 16 infants with positive screening-tests-10 by theGuthrie method and 6 by urine chromatography (seeaccompanying table). The male/female sex-ratio was 10/6.If, however, we separate these into classical P.K.u. and

hyperphenylalaninxmia, the distribution in classical P.K.U.is 3/5 but in hyperphenylalaninasmia 7/1. In a total of 48children with classical phenylketonuria in our clinic, themale/female sex-ratio in this larger group is 26/22.These data show that hyperphenylalaninaemia and classic

P.K.u. occur with equal frequency in N.S.W., and that ourseries of hyperphenylalaninsmia infants shows the pro-nounced male dominance of 7/1. Full details of theseinfants are to be published elsewhere.2 Ascertainmentmethods make it unlikely that we are missing female infantswith hyperphenylalaninsemia. The sex difference seemsreal.

J. S. YUM. T. O’HALLORAN

Departments of Child Health and Biochemistry,Royal Alexandra Hospital for Children,

Camperdown, N.S.W.,Australia.

1. Turner, B., Brown, D. A. Med. J. Aust. 1967, i, 560.2. Yu, J. S., Stuckey, S. J., O’Halloran, M. T. Archs Dis. Childh.

(in the press).