Human muscle cell growth was studied to investigate the nucleo-cytoplasmic ratio during development and ageing. The mean muscle fibre size, as well as the number and size of myonuclei were estimated in human muscle biopsies from normal individuals whose ages ranged from 1 to 71 years. Changes in muscle fibre size were accompanied by similar changes in nuclear number, the size of which remained the same. This resulted in a constant nucleo-cytoplasmic ratio during the age range studied. The role of the satellite cell in the maintenance of this ratio was discussed.

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Summary We have measured the concentrations of mediators of hypersensitivity in the sputum of twenty‐five young, symptomatic cigarette smokers who regularly expectorated and twenty‐three matched non‐smokers with a respiratory infection. The measurements included sputum and blood eosinophils, IgE, IgG, IgA and IgM and also sputum histamine. We found a significant increase of sputum histamine, and a higher sputum/serum ratio of IgE in smokers when compared to non‐smokers. These findings support the view that the bronchial inflammatory response in smokers, as in chronic bronchitis, involves the participation of mediators of hypersensitivity.

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