693 inconsistent, and these studies
were abandoned, overby the description of the hepatitis B antigens and, more recently, by animal and immunoelectronmicroscopic observations pertinent to hepatitis A.
obtained) and our modified co-agglutination test for every test.
were
In neither case would he be using reagents with a short shelflife, Workers who use the co-agglutination method to detect other antigen-antibody reactions may also find that the separate addition of antiserum and staphylococcal strain saves them
shadowed
considerable labour. Cross-Infection Reference Laboratory, Ceniral Public Health Laboratory, London NW9 5HT
W. R. MAXTED ANDROULLA EFSTRATIOU M. T. PARKER
SIR,-In bronchial asthma, exercise-induced symptoms can be a disabling and socially restricting feature of the disease.I At a clinic visit a 38-year-old male patient whose main complaint was of wheezing induced by running, also volunteered that he developed similar symptoms during sexual intercourse. The asthmatic features often interfered with the satisfactory completion of coitus and were causing considerable strain on his marital relationship. After this, three further male patients aged 25-40, with exercise-induced asthma, were asked specifically about the possible onset of symptoms during intercourse. All these patients, surprisingly, admitted to considerable sexual difficulties because of the onset of their typical symptoms of wheezing and dyspnrea. None had been asked previously about this feature of their condition, nor had they wished to mention this aspect because of embarrassment. After prophylactic therapy had been started (two with disodium cromoglycate, two with a steroid aerosol), all had a general improvement in their asthma. Two indicated that while on therapy their sexually induced asthmatic symptoms were eliminated, and in the two others the difficulties were considerably modified. The mechanism of this reaction is unlikely to be different from that of asthma initiated by other forms of exercise such as running or cycling. Anxiety and emotional factors may have played a part, but in this group with exercise-induced features predominating, these factors are unlikely to be significant. It is conceivable, however, that sexual activity in bed, by disturbing the surrounding house-dust mite population may provide an allergen challenge in sensitised individuals. It is only through increased awareness and specific questioning that the frequency of angina pectoris occurring during intercourse in patients with coronary heart-disease has been demonstrated.2 "Sexercise" induced asthma may also be common but overlooked both by the family doctor and the respiratory physician. The successful outcome in this group of patients serves to demonstrate the need for a direct approach in those at risk. IAN S. SYMINGTON
JAMES W. KERR
INHIBITION OF PHYTOHÆMAGGLUTININ TRANSFORMATION BY SERUM OF PATIENTS WITH FULMINANT HEPATITIS
Sn,—Dr Dupuy and his colleagues (Sept. 11,
they
were
It may be that inhibition of P.H.A transformation is associated with hepatitis B (4/6 of Dupuy’s cases were known to be associated with hepatitis B) and that the inconsistency encountered in earlier studies was related to our inability properly to identify octiologically distinct varieties of hepatitis. Virus Laboratory, Department of Microbiology, Institute of Child Health, London WC1N 1EH
SEXERCISE-INDUCED ASTHMA
Department of Respiratory Medicine, Western Infirmary and Knightswood Hospital, Glasgow
as
p.
578)
describe the inhibition of phytohasmagglutinin transformation
oy serum of patients with fulminant viral hepatitis. This was ?1 described by Mella and myself in 1967and 1968.4 Subsequently several attempts were made by my laboratory by others to investigate this finding further. The results 1 McNeill, R S., Nairn, J. R., Millar, J. S., Nairn, C. G. Q. Jl Med. 1966,
137, 55 2 Hellerstein, H. K., Fnedman, E. H. Archs intern. Med. 1970, 125, 987. 3 Mell a. B, Lang, D. J. Science, 1967, 155, 80. 4 Mella B, Lang, D. J. Ann N.Y. Acad Sci 1968, 155, 880.
DAVID J. LANG
BREAST IS BEST FOR CORONARY PROTECTION
SiR,—Your contributor (Aug. 21, p. 412) has a hunch that "breast is best", but admits his reasons are largely related to the emotional and behavioural bonding of mother and baby. But he overlooks a wealth of circumstantial evidence which points to coronary protection being a likely benefit of breast
feeding. Non-lipid-containing histological changes in the coronary arteries of infants and young children which are almost certainly predisposing to later atherosclerosis have been described by many pathologists, 1-3 notably Osborn.4These changes have been found in children who have died from gastroenteritis, other infections, or any condition associated with dehydration and collapse, and also in those killed accidentally in whom there was no obvious preceding disease. With a variety of associations, but no proof of causation, they must be referred to as non-specific. Often no doubt, and usually in lowrisk countries in which atherosclerosis and its complications are rare, injury is followed by repair. However, given a later unfavourable nutritional environment in the form of a modern Western-type diet, it is probable that the increased permeability of the arterial wall and changes which predispose to the infiltration, retention, and accumulation of low-density lipoproteins predispose to atherosclerosis. Osborn described the pathological changes in 1500 young people aged 0-20 years. Since serial observations in an individual are impossible, conclusions had to be based on the spectrum of pathological changes from the accumulation of mucopolysaccharides to fully developed atherosclerotic plaques. In infants with no history of relevant preceding disease, causes are likely to be nutritional. He closely questioned more than 100 mothers and concluded that the lesions described were more frequent and severe in the predominantly bottlefed and uncommon or mild in those predominantly breast-fed. Clearly only a prospective study can be conclusive. It is therefore reasonable to consider the differences between human and cow’s milk and the likelihood of their being responsible for the early changes in the coronary arteries. Breast milk has evolved as a perfect and all-sufficient food for the first twelve months of life or longer while cow’s milk has evolved for very different needs. The only similarities in the two varieties lie in the water and, perhaps, the sugar. Total protein in cow’s milk is much higher and its constituent aminoacid pattern is very different. Antibodies are present in the blood of many infants and this immunological response could itself damage the arterial wall and also increase platelet adhesiveness and aggregation which can have harmful effects.6 Cow’s milk is grossly deficient in essential fatty acids. They amount to only 25% of the concentration in human milk in 1. Moon, H. D. Circulation, 1957, 16, 268. 2. Daoud, A. et al. Exp. mol. Path. 1964, 3, 475. 3. Pesonen, E. Atherosclerosis, 1974, 20, 173. 4. Osborn, G. R. Incubation Period of Coronary
Thrombosis; p. 177. London,
1963. 5. Osborne, G. R. Colloq. int. C.N.R.S. 1967, no. 169. 6. Davies, D. F. Am. Heart J. 1971, 81, 289. 7. György, P. Am. J. clin. Nutr. 1971, 24, 970.