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In order to quantitate DNA, RNA and glycogen contents of developing macrophages, blood monocytes were obtained from 19 healthy human subjects and examined after 0, 2, 4 and 6 days of suspension culture. Cytochemical staining was carried out by standard methods using Feulgen, cuprolinic blue and PAS. All specimens from all subjects were stained at the same time. Examination was carried out in an integrating microdensitometer, the staining intensities of individual cells being measured at appropriate wavelengths. Over the 6 days of culture, highly significant increases took place in RNA and glycogen, but no significant change was found in DNA content. These findings are taken to indicate that increased protein synthesis and the building up of fuel reserves are features of macrophage development but that S phase DNA replication does not occur.

Measurements of dry mass were made on developing human macrophages in suspension culture using a scanning and integrating microinterferometer. The mean dry mass (+/- SEM) of day 0 monocytes of 19 healthy individuals was 53.6 +/- 2.4 pg. There was a significant increase in cellular dry mass over the period of culture, mean values at 2, 4 and 6 days being 61.1, 79.8 and 110.4 pg, respectively. A comparison of the results with those obtained previously by ultrastructural morphometry inferred that there is a disproportionate increase in the water content of macrophages during development. The technique may have potential for investigating changes in mononuclear phagocytes in clinical states.

A simple morphological method is described whereby the numbers of nuclei in different types of skeletal muscle fibre may be determined. The method allows for the anisotropy of skeletal muscle fibres and the non-random distribution of their nuclei. The advantages in the use of a morphological (rather than a biochemical) method are discussed, together with possible applications of the method in the study of changes which occur in skeletal muscle in adaptation to stress and in disease.

Skeletal muscles consist of an heterogeneous population of muscle fibres. A method for deriving an index of contiguity for any of the fibre types is proposed. This term is defined as the proportion of the total boundary length (interface) of a fibre type which is in contact with fibres of the same type. It can be measured on any type of skeletal muscle independently of its composition. Values for the index of contiguity for the two major types of fibre in normal and hypertrophic extensor digitorum longus muscles of the mouse do not seem to differ.

The metric properties of several important components of muscle, the capillaries, the myonuclei and also the cross-sectional areas of type I and type II fibres in the extensor digitorum longus muscle of the mouse have been studied using techniques appropriate for anisotropic tissues. Myonuclear volume density (Nv) was found to be increased by 70% whilst capillary length density (Lv) was increased by 50%. The results were analysed using multivariate statistical analysis (MANOVA) which is necessary for the multiple comparisons which inevitably occur in any morphometric investigation. The mitochondrial distribution within type I fibres was analysed using two-way ANOVA to study the effect of exercise on the mitochondrial contents of the inner, intermediate and outer zones of the muscle fibre. Significant differences in the mitochondrial content in the various zones were found. Exercise was found to increase mitochondrial contents in all three zones.

Ultrastructural characteristics of human blood eosinophils have been analysed by morphometric methods in 18 healthy adults. Data were obtained relating to whole cell, nucleus, mitochondria and specific granules. No significant differences were found between the eosinophils of the 9 male and 9 female subjects. The results provide normal values against which changes in eosinophils in disease states may be assessed.

Morphometric methods have been used to analyse the ultrastructural characteristics of human blood monocytes in 20 normal adults. Data were obtained relating to whole cell, nucleus and mitochondria and, using a method not previously applied to blood cells, for the distribution of heterochromatin and euchromatin. The results provide a normal baseline against which monocyte changes in disease can be assessed.