530 INHALED

SILICA, LUNG, AND KIDNEY SIR,-Some of the points raised by your editorial of July 1 (p. 22) merit amplification. Participation of the macrophage in silicotic fibrogenesis rests on experimental evidence that, after ingestion of quartz by rat peritoneal or pulmonary macrophages, a cell and particle free extract contained a factor or factors which, on application to independently grown fibroblasts, stimulated

the production of hydroxyproline without provoking cell proliferation. Extracts from untreated, disintegrated macrophages lacked comparable stimulatory effect, and, after membrane damage by silica, a further step is evidently required for the elaboration or release of the macrophage fibrogenic factor (M.F.F.). Control procedures suggested that among compact minerals and quartz effect may be peculiar. The original observations have now been confirmed by a variety of techniques, and the M.F.F. appears to be non-lipid in nature.2 Silicon evidently has a role in bone growth, connective tissue and endo3

crine metabolism, atherosclerosis, and dementia. Although the initial study indicated that formation of the M.F.F. did not depend on an immunological mechanism, you invoke, in the absence of evidence, such a response as a means of maintaining the macrophage supply. Recent observations, however, suggest the participation of systemic recruitment by a positive-feedback mechanism from lung to marrow with lipid(s), possibly phospholipids, as the intermediary.2 The lipids employed were extracted from rat lungs with silicainduced alveolar lipo-proteinosis.4 The experimental lesion closely parallels the human disorder,5 and because the condition is essentially a lipidosis, with dipalmitoyl lecithin (D.P.L.) the main component, the term alveolar lipo-proteinosis is now appropriate. The cells which initially lie in the alveoli are principally macrophages rather than type-u epithelial cells shed into the lumen. Silica stimulates type-ii cells both to proliferate and to augmented secretion of D.P.L., but protein accumulation is a comparatively minor event. In experimental lipo-proteinosis elimination of surfactant material is doubled but formation is trebled and thus accounts for the development of the disease.4 Accelerated silicosis in man further links inhalants with the development of alveolar lipo-proteinosis, but nodular silicotic lesions are not characteristic, the fibrosis being more diffuse and irregularly disposed amongst alveoli loaded with lipids.2 The existence of the M.F.F., although established by means of a simple inorganic compound, may be relevant to the ubiquitous phenomenon of fibrosis in other disease states. Institute of Occupational Medicine, Edinburgh EH8 9SU

A. G. HEPPLESTON

PHYSIOTHERAPY AND LUNG FUNCTION read the article by Dr Newton and Mr Stephenson (July 29, p. 228) with interest, but was soon disappointed at the contrast between the three lines devoted to the description of the physiotherapy given-the topic being evaluated-and the detailed analysis of the patient’s lung function. Though 15 min is the physiotherapy time, no details are given of the treatment. Four techniques are mentioned, but what proportion of time was spent on them? Was this standardised or left to the discretion of the physiotherapist? What was the position of the patient in relation to the affected area of the lung? All these factors might affect the outcome. Postural drainage was not given if the patient could not tolerate

SiR,—I started

to

Heppleston, A. G., Styles, J. A. Nature. 1967, 214, 521. Heppleston, A. G. in Biochemistry of Silicon and Related Problems (edited by G. Bendz and I. Lindqvist); p. 357. New York, 1978. 3. Bendz, G., Lindqvist, I. (editors). Biochemistry of Silicon and Related Problems. New York, 1978. 4. Heppleston, A. G., Fletcher, K., Wyatt, I. Br. J. exp. Path. 1974, 55, 384. 5. Heppleston, A. G., Young, A. E. J. Path. 1972, 107, 107. 1. 2.

came into this category? They must be a treatment separate surely group. Did the three physiotherapists thanked at the end of the paper standardise their practice? Were they similarly experienced-i.e., basic grade and newly qualified or more senior with special experience with chest patients? Physiotherapy needs to be evaluated, but papers such as this contribute little to our knowledge. I hope that in the randomised trial which has been started in Leeds, usual scientific practice is being followed and the treatment under investigation will be fully described.

it, but how many patients

Health Services Research Unit, University of Kent at Canterbury, Canterbury, Kent CT2 7NF

CECILY PARTRIDGE

to Dr Newton and Mr Stewhose follows.-ED.L. phenson, reply

***This letter has been shown

SIR,-Mrs Partridge is asking who the physiotherapists and what did they do. All three were fully qualified and with four, three, and two years’ clinical experience, including

were

three months special chest experience before the trial began. The treatment given was standardised as follows: (1) Breathing exercises, five lateral costal breaths and five diaphragmatic breaths with inspiration to total lung capacity and relaxed expiration to functional residual capacity. (2) Postural drainage was given to all patients with percussion and vibration in the prone, supine, and both lateral positions for three minutes in each position. Twenty-four patients had the base of the bed elevated 18 in (45 cm) to drain the lower lobes. The remaining nine patients were treated with the bed flat. As the patients had chronic bronchitis rather than localised bronchiectasis it was not appropriate to position for a specific area of the lung. Incidentally we note that S Gaw was misprinted once as S. Waw and abbreviated incorrectly to S.G. (1/lung volume) in table I. This should have read S. Gaw/1 lung volume. DUNCAN A. G. NEWTON St. James’s University Hospital, Leeds LS9 7TF A. STEPHENSON PROPHYLAXIS AGAINST POSTOPERATIVE PULMONARY EMBOLISM

SIR,-We were interested in the letter of Mr Powley (July 29, p. 261) in which he emphasises the side-effects and difficulties in giving prophylactic low-dose heparin. We too have a bee in the bonnet, but it is that patients should receive the most effective available prophylaxis. For general surgical patients there is now evidence from three prospective controlled trials’-3 that low-dose heparin prevents fatal pulmonary embolism. Powley’s solution, electrical calf-muscle stimulation, has not always been effectiveand accidental burns have been inflicted.5 It has also been shown to be inferior to low-dose heparinwhich in our opinion must be considered the method of choice for general surgeons. A slightly increased incidence of wound haematomas and consumption of nursing-time are undoubted consequences of low-dose heparin therapy. Rather than resort to less effective methods would it not be preferable to seek to eliminate the side-effects of the proven method? Heparin consists of at least five fractions7 with varying ratios of antithrombotic to anticoagulant activity. One or more of these fractions might be as effective as parent heparin against thromboembolism and yet free of hxmorrhagic complications. More immediately, methods of giving low-dose heparin that are economical of 1. Sagar, S. Br. med.J. 1974, i, 153. 2. International Multicentre Trial. Lancet, 1975, ii, 45. 3. Kiil, J., Axelsen, F., Kill. J., Andersen, D. ibid. 1978, i, 1115. 4. De Jode, L. R., Khurshid, M., Walther, W. W. Br. med. J. 1970, iv, 56. 5. Browse, N. L., Negus, D. ibid. 1970, iii, 615. 6. Rosenberg, I. L., Evans, M., Pollock, A. V. ibid. 1975, i, 649. 7. Lane, D. A., MacGregor, I. R., Michalski, R., Kakkar, V. V. Thromb. Res.

1978, 12, 257.

531

nursing-time have recently become available, namely readyfilled syringes and jet injection,8 both of which successfully reduce nursing-time needed for giving low-dose heparin.9 With jet injection, time taken is one third of that with standard methods. Lastly, we disagree with the statement that the crusade for low-dose heparin was started by Sharnoff. As early as 1935, Crafoord 10 gave repeated small doses of heparin to surgical patients by intravenous injection, to prevent thromboembolism. The method was abandoned after successful use in 325 cases because the doses were difficult to give. The lesson is clear. Department of Surgery, Queen Elizabeth Hospital, Birmingham B15 2TH

J.

BLACK

C. J. L. STRACHAN

EICOSAPENTAENOIC ACID AND PREVENTION OF ATHEROSCLEROSIS

SIR,-As suggested by Dr Dyerberg and colleagues (July 15, enrichment of tissue lipids with eicosapentaenoic acid rather than with polyunsaturated fatty acids in may be more appropriate in the prevention of thrombosis and atherosclerosis in the western world. E.P.A. can replace arachidonic acid (A.A.) as a precursor of prostaglandin synthesis and is transformed into prostacyclin (P.G.I3) and thromboxane A3, which is not a platelet pro-aggregating agent. The hypothesis advanced by Dyerberg and colleagues is mainly based on studies in the Eskimo community in Greenland, which reveal a low incidence of acute myocardial infarction. Eskimos have a lower serum-A.A. and a higher serum-E.P.A. than western populations.’ This fatty-acid pattern is thought to result from the fatty-acid content of Eskimo food which is mainly of marine origin.2 We have some data from Italians on the A.A. and E.P.A. content of structural lipids-such as those of red-blood cellswhich reflect the fatty-acid content of the habitual diet more accurately than serum lipids. In the framework of a controlled trial of primary prevention of coronary heart-disease,3 4 262 fatty-acid gas-chromatographic analyses of total red-blood-cell lipids were done in males aged 44-63, randomly selected from people allocated to both treatment and control groups. Red-blood-cell fatty-acid content was examined within a more extensive study of hypocholesterolaemic diets. The average content of A.A. (C20:4 co-6) and E.P.A. (C20:5 w-3) was 6.611.9% and 2.312.5%, respectively, with a mean A.A./E.P.A. ratio of 2.8. The mean cholesterol level was

117), (E.P.A.) general, p.

224.5137.76 mg/dl.

subjects the E.P.A. value was considerably higher (13-3±5-2% of total fatty acids) with a remarkable inversion of A.A/E.P.A. ratio (0-2). Mean serum-cholesterol was In 14

mg/dl. 13 subjects were on their usual diet, while 1 subject, affected by hyperlipoproteinxmia type IIA, was on a hypocholesterolxmic polyunsaturated diet. The investigation of nutritional habits with a qualitative questionnaire did not allow the detection of a common dietary factor, likely to be responsible for the high tissue levels of 214.4137.3

E.P.A. Centro per la Lotta alle Malattie Dismetaboliche e all’ Artenosclerosi, Università di Roma, 00161 Rome, Italy

FRANCESCO ANGELICO PIERO AMODEO

8. Black, J., Nagle, C. J., Strachan, C.J. L. Br. med. J. 1978, ii, 95. 9. Black, J., Strachan, C.J. L. Br. J. Surg. (in the press) (abstract). 10. Crafoord, Acta med scand. 1941, 107, 116. C 1. Dyerberg, J., Bang, H. O., Hjorne, N. Am.J. clin. Nutr. 1975, 28, 958. 2. Bang, H. O., Dyerberg, J., Hjorne, N. Acta med. scand. 1976, 200, 69. 3. W.H.O. European Collaborative Group. Int. J. Epidem. 1974, 3, 219. 4. Research Group of the Rome Project of Coronary Heart Disease Prevention. Ann Ist. Super. Sanità, 1976, 44, 262.

QUOTAS IN NORTHERN REGION SIR,-We, the undersigned consultant obstetricians and gynaecologists and paediatricians in the Northern Regional Health Authority, wish to make it clear to the general public that the Department of Health and Social Security has ignored professional advice about safe medical staffing levels for maternity units in this region. The Royal College of Obstetricians and Gynxcologists has constantly advised that, for the safety of baby and mother, REGISTRAR

every viable obstetric unit should have at least two resident doctors of registrar grade, capability, and experience. On this criterion the Northern region is already short of seven registrars. The D.H.S.S. now proposes to reduce our inadequate even further with the loss of a further five registrars. Rates for stillbirths and postnatal deaths are significantly higher in the U.K. than in comparable countries elsewhere in Europe, whereas twenty years ago British obstetric practice resulted in significantly lower death-rates than in comparable countries. Furthermore, the loss of babies in the Northern region is significantly higher than the national average. We feel that as a direct result of D.H.S.S. policy there will be continuing unnecessary wastage of babies. We do not see reductions in the incidence of spasticity which we feel the community is entitled to expect. We are also concerned about the risks to mother. The practice of safe modern obstetrics implies adequately staffed units. That situation does not exist in the Northern region today. We urge our professional colleagues to put whatever pressure they can on the Department to make them face up to their continuing responsibilities to women having

staffing

children. Maternity and Gynæcological Department, Preston Hospital, North Shields, Tyne and Wear NE29 0LR P. J. MASKERY GORDON MACKAY R. LAYTON JAMES COSBIE ROSS DAVID BARBER GORDON ANDERSON J. M. MONAGHAN JOHN MCGLONE D. SPANTON P. J. ADAMS D. C. GALLOWAY IAN MATHIE TONY BROWN A. P. KENNA J. D. BELL E. N. HEY J. W. PLATT F. M. ELDERKIN

S. COHEN F. S. JOHNSON A. P. B. MITCHELL JOHN ATKINS ROGER GOMERSALL ALAN COXON R. BROWN D. M. SHEPPARD J. M. KING ROBIN DOWIE HAROLD JONES REX GARDNER R. RANGECROFT J. ANGUS W. D. ELLIOTT C. E. COOPER M. B. R. ROBERTS F. W. ALEXANDER

MICHAEL BURKE

PETER SILVERSTONE RONALD FRANCIS BARBARA CASE EDWARD PLATTS E. N. MCKENZIE W. Y. SINCLAIR R. BROWN F. J. COCKERSOLE J. W. FOULDS J. S. FRASER W. DAWSON BEN MURRAY TREVOR BROUGH I. H. GRANT ALAN CRAFT MARGARET TAYLOR C. DIAS E. M. CARR-SAUNDERS

CAREERS FOR NON-MEDICAL SCIENTISTS

SIR,-I read with

Professor Millar’s letter scientists in fulltime medical research to accept the fate of oblivion after a short spell in research. At Guy’s Hospital alone there are over sixty such scientists who, unlike Millar’s praying mantis, do not expect sexual acstasy to accompany such oblivion. Indeed, there can be few who agree with Millar’s policy of despair: it is hardly a rational approach to a major problem in medical research. There must be found an equitable way to marry "project" research with humane treatment of those who carry it out. At Guy’s Hospital a group of scientists have formed an association whose principal aim is to seek a career structure and prospects of reasonable job security for those pursuing fulltime medical research. We shall be pleased to hear from anyone who is similarly concerned.

(Aug. 19,

p.

some amazement

431) recommending untenured

,

Clinical Science

Laboratories,

Guy’s Hospital, London SE1 9RT

WILSON HARVEY,

Association of Researchers in Medical Sciences

Prophylaxis against postoperative pulmonary embolism.

530 INHALED SILICA, LUNG, AND KIDNEY SIR,-Some of the points raised by your editorial of July 1 (p. 22) merit amplification. Participation of the mac...
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