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FILE NAME Brakes BRK DATE 1963 June 15 DOC BRK019 DOCUMENT DESCRIPTION Journal Article - Pulmonary Asbestosis - African Medical Journal uth African Medical e Town 15 June 1963 Journal : Afrikaanse Tydskrif vir Geneeskunde Volume 37 No. 24 Deel 37 Kaapstad 15 Junie 1963 EDITORIAL : VAN DIE REDAKSIE PULMONARY ASBESTOSIS Il the pneumoconioses or dust diseases asbestosis would ar to be the most serious from many points of view in follow a relatively short exposure instead ears as in silicosis while the morbidity rate as rmined by radiological means has been much re- ed by measures to lessen the inhalation of asbestos in factories bestos workers in those with e reduction in it can still be very 44-5 with 20 or more years exposure and 10-15 years exposure frequency of pulmonary tuberculosis e post era and the equally striking increase in cancer in most countries makes it difficult to assess ncreased liability of present sufferers from asbes- to these two complications Clearly the data obtained or more years ago have little validity now while chial carcinoma has such a range of frequency in rent countries that conclusions based on world aver- are hardly acceptable In the case of pulmonary tuber- sis the British figure for the association of this disease fatal cases of asbestosis in the years 1932 was 4. while in the same period the figure was 57.1 in cases of silicosis But in one part of Germany sen more recent findings published in 1960 show that culosis as a complication of silicosis was still very while the association with asbestosis only % little more than twice the tuberculosis figure he whole population in that region. e cancer rate in silicosis is not appreciably r than in the general population but in asbestosis its ency is estimated to be about ten times that of simi- ge groups both in Britain and in Germany recent years the matter has been extended by the acceptance by most pathologists of malignant mesoma as an entity and the even more tardy appreciathat mesothelioma of the pleura may be associated asbestosis occupations where pneumoconiosis of mineral origin azard those affected are normally the miners and sonally the workers handling the material in bulk after there is no danger as a rule to those who deal the manufactured goods containing the raw material rned With asbestos it is otherwise In Canada where It quarters of the world's production of asbestos ned the miners would appear to suffer little asis and show no significantly increased cancer of the but in South Africa at least the miners and even living in the vicinity of the mines may develop asis and pleural mesothelioma st cases of asbestosis however result not from min- ut from employment in asbestos factories Today os is used in so many industries and is a constituent many manufactured goods that the occupations asbestos is a potential hazard are too many to rate here Workers at risk include such unlikely is the garage worker employed in under car spraying and more obvious ones such as those employed in lagging pipes with asbestos or those concerned with the manufacture of asbestos cement roof and floor tiles ceiling boards etc. or with the use of them such as builders and builders labourers While the modern use of asbestos expands the field of potential inhalers of asbestos fibres the risk of asbes- tosis is limited and it is unlikely that these occupations will lead to a marked increase in pulmonary asbestosis The effect of the inhalation of a small quantity of asbestos fibres insufficient to produce pulmonary asbestosis but possible in many of the occupations indicated has been put on quite a different footing by two recent papers by Thomson and his colleagues in this Journal In the first paper Thomson described 6 cases of mesothelioma pleural and peritoneal where there was no diffuse pul- monary asbestosis of the ordinary type but only a few small foci of asbestosis at the bases of the lower lobes It was stressed that this limited basal asbestosis produced no signs or symptoms was likely to be overlooked at autopsy unless sections from the lung amined microscopically In only one of there a history of exposure to asbestos bases were exthese cases was This paper was followed by what appears to be the first investigation into the extent to which urban dwellers are exposed to the inhalation of asbestos fibres Thomson et al examined the bases of lungs for asbestos bodies by a simple smear technique and found that more than a quarter of the subjects over the age of 15 years in the autopsy services of the Groote Schuur Hospital Cape Town showed asbestos bodies supporting their conten- tion that the inhalation of asbestos fibres was now an might significant urban hazard They did not find that it was a hazard today and were more concerned with what happen in the future They emphasized that the world's production of asbestos is increasing at a staggering rate and is now eight times what it was 35 years ago and that today containing products are ubiquitous especially in urban areas Thomson et al also drew attention to a simple but important fact which seems to have been overlooked so far from the medical and public health points of view This is that the very reason for the use of asbestos in in- dustry resistance to heat acid alkali oxidation and reduction in fact its virtual indestructibility the reason why it may become progressively more dangerous to man Wind and water may disperse asbestos fibres but they cannot destroy them Asbestos is now accumulating on the surface of the earth mainly in the cities at the rate of 2,400,000 long tons per annum motor vehicles are discharging asbestos dust from brake drums clutches silencers and under coatings and modern buildings may contain asbestos products from the roof to the base- ment The indestructibility of asbestos makes this to some extent cuprulative and in effect we may be creating such 629 ra 100 G. for it ae he eS Set Se ie eae aes+ COT OS AL ST SS 4 Sri AYER cat a re red: ee aCe Tears ree ney ae 630 S.A. MEDICAL JOURNAL 15 June 1963 an asbestos environment in cities that in the future basal asbestosis may become almost universal and mesothelioma of the pleura and become common tumours in urban dwellers peritoneum may These observations and opinions are new and we await confirmation of these findings from other countries they may well be confirmed as regards the frequency of asbestos bodies in the lungs of urban dwellers It would seem a hard turn of fate that the avoidance of ordinary pulmonary asbestosis might lead to an increased frequency of mesothelioma of the pleura or peritoneum presumably because the patient lives longer and the carcinogenic action of asbestos has a longer time to act We hope the fears for the future expressed by Thomson et al are unjusti- fied but it may be desirable to pay heed to their warnings at least to the extent of restricting some unnecessary and possibly dangerous uses of asbestos Lungen 1. Bohlig H. Jacob G. and M^...llerH. 1960 Die Asbestose der Stuttgart Thieme 2. Sutherland C. L. 1940 Lancet 1 893 3. Wirth J. 1960 Op cit.,, 4. Doll R. 1955 Brit J. Industr Med 12 81 5. Cartier P. 1952 Arch Industr Hyg 5. 262 6. Van der School H. C. M. 1952 Ned T. Geneesk 102. 1124 7. Wagner J. C. SlegSlgeggss C. A. and MarMacrchhaandnd P. ( 196)0 BrBriit t J. Industr Med 17 260 8. 8. Braun O. and Truan P. 1958 Arch Industr Hyg 17 634 9. 9. Sleggs C. A. Marchand P. and Wagner J. C. 1961 S. Afr Med 10. Brugsch H. G. and Bavley H. 1961 New Engl J. Med 265 379 11. Thomson J. G. 1962 S. Afr Med J. 36 759 12. Thomson J. G. Kaschula R. O. C. and MacDonald R. R. R. R. 1963: Ibid 37 77 Feasible * Zo. Me etry 3 t i BAKTERIE^ LEGENETIKA Daar was n tyd toe dit aanvaar was dat die klassieke genetiese wette en beginsels nie op organismes en veral bakterie^ van toepassing was nie Bakterie^ reproduseer vegetatief en hul mikroskopiese grootte het hulle ongeskik vir sitologiese studies gemaak Vir baie jare was dit aanvaar dat daar fundamentele verskille beide geneties en fisiologies tussen ho^r diere en organismes bestaan en dat die wette wat op die een van toepassing is nie vir die ander geld nie Maar gesien in die lig van die moderne fundamentele eenvormigheid tussen alle biologiese wetenskappe is dit duidelik dat hierdie opvatting verkeerd was Gemeenskaplike grond is gevind deur die intensiewe studie van bakteri^le genetika wat slegs in die laaste twee dekades op die voorgrond getree het Vandag is hierdie vak die brandpunt van die biologiese wetenskappe en het al selfs sov^'r gevorder dat dit amper die tergende vraag wat is lewe kan verklaar Jacob en Wollmanverdeel die historiese ontwikkeling van bakteri^le genetika in sekere tydvakke Gedurende die laaste helfte van die 19de eeu is mikrobiologie as eksperimentele wetenskap ingestel en aandag is hoofsaaklik bestee aan die isolasie en morfologiese beskrywing van nuwe spesies Van 1900 tot 1940 is n groot aantal variasies van bakterie^ ge^fldentifiseer bestudeer en beskrywe en hieruit is die vak bakteri^le genetika gebore In die laaste tydvak beginnende 1940 word bakteri^le oorerwing ontleed en geko^rdineerin die lig van die klassieke genetiese teorie^ Klassieke genetika ontleed die aard van komplekse dikwels essensi^le eienskappe In teenstelling daarmee analiseer bakteri^le genetika op die molekul^"re vlak en gee n beter begrip van basiese sellul^"re meganismes Ook dien dit as n handige instrument waarmee die struktuur en funksie van biologiese sisteme bepaal kan word Treffende bewys dat daar n chemiese basis vir oorerwing bestaan is gelewer toe n bakteri^le eienskap omvorm is deur desoksieribonukle~ensuur D.N.S. wat uit n pneumokokkale mutant berei is Soortgelyke ingrypende waarnemings is in die afgelope 20 jaar met bakteri^ gedoen waarvoor verskeie faktore verantwoordelik is Om slegs n paar te noem Bakteri^ kan weens hulle onge^wenaarde voortplantingsnelheid in n kort tyd tot enorme getalle aangroei Die bakteri^lesel se oorerwingsfaktore is vasgel^" deur n enkele lini^"re struktuur die bakteri^le chromosoom bestaande uit D.N.S. wat die makromolekul^"repatroon van die bakterium beheer Bak- teri^ se genetiese materiaal is relatief onstabiel Mutasies kom spontaan voor in n gegewe gene in een uit elke honderd miljoen verdelings Eksperimentele metodes in bakteri^legenetika tref deur hul eenvoud akkuraatheid en berekenbaarheid waarmee analiese uitgevoer kan word Die fundamentele probleme van genetika het hierdeur binne die bestek van die genetikus geval Van die ... abs, merkwaardigste bydraes op hierdie gebied is inderdaad gemaak deur fisici en biochemici In 1953 beskrywe Watson en Crick Nobelpryswenners van 1962 die struk- 2oH tuur van D.N.S. gebaseer op chemiese analiese en kristal- ws lografiese studies wat allerwe^ as n biochemiese triomf Abe, aanvaar is Hiervolgens sou D.N.S. bestaan uit twee poli- oe nukleotied wat spiraalsgewyse rondom n sentrale as gedraai is Die ruggraat van elke spiraal bestaan uit fosfodiester Die basisse op n gegewe vlak van at lat die een ketting word met behulp van waterstofbande ge- bind aan basisse op die ooreenstemmende vlak van die ander ketting Waterstofbindings kan weens strukturele Dae redes net plaasvind tussen die basis adenien en guaniensitosien sodat die een ketting dan die spie^lbeeld van die ander is Dit is verbasend watter belangrike FT biologiese gevolgtrekkinge van hierdie model gemaak kan word Dit lewer bewys van D.N.S. se molekul^"rerepli- kasie die aaneenlopende lini^"re volgorde van basis gee aanleiding tot n bepaalde genetiese kode en spesifisi- teit terwyl dit ook verklaring vir mutasies aan die Cea hand gee Hierdie model dien verder as voorbeeld van Ce n nuwe studierigting naamlik molekul^"re biologie wat daargestel is hoofsaaklik deur die toedoen van bakteri^le dec en genetika Hoe ver ons reeds vandag gevorder het RB van die klassieke sitologie blyk uit die feit dat as die wor genetika van dierlike somatiese selle op hierdie grondslag ontwikkel moet word dit dan n direkte uitvloeisel van bakteri^le en genetika is wat weer op hulle hulle ontstaan aan weefselkulture te danke het beurt Die sentrale posisie wat atoomfisika vandag in die fisiese wetenskappe beklee kan ons vergelyk met molekul^"re biologie in die biologiese wetenskappe Vandag se teorie is die praktyk van m^re In hoeverre bakteri^le genetika die natuurwette gaan be^flnvloedhang af van die sukses waarmee die teorie^ wat sodanig verkry is op ander biologiese sisteme toegepas kan word 1. Jacob F. en Wollman E. L. 1961 Bacteria London Academic Press Sexuality and the Genetics of 2. Avery O. T. McLeod C. M. en McCarthy M. 1944 J. Exp M 2.. 79. 137 3. Watson J. D. en Crick F. H. C. 1953 Nature Lond 171 737 i 4