Pericapillary collagen in the human thymus: implications for the concept of the 'blood-thymus' barrier.

The deposition of collagen in the walls of capillary-size blood vessels was studied in 95 human thymuses with respect to the site of deposition, extent of the change and relation to age and degree of involution. When examined by electron microscopy the collagen was found to be situated between the 2 basement membranes of the so-called 'double-layered' capillaries characteristic of the thymus of many species. This results in the formation of substantial 'collars' of collagen around a proportion of the blood vessels examined. Few such collars are seen before birth, but their number and thickness increase markedly during the 1st year of life. The relationship of these changes to the degree of involution is less apparent. The significance of these changes to thymic structure and function is discussed in relation to cell traffic through the thymus and the postulated 'blood-thymus barrier', the existence of which is seen to be in some doubt.

X-ray microanalysis of the Michaelis-Gutmann bodies of malakoplakia.

The Michaelis-Gutmann (MG) inclusion bodies of three cases of malakoplakia (prostate, testis, colon) were studied by X-ray microanalysis to determine their elemental composition. Calcium and phosphorus were consistently found. Iron was detected in a few bodies. No other elements were detected. The electrondense laminations were of similar composition to the core material. Small aggregates of electron-dense material containing calcium and phosphorus were also occasionally seen in phagolysosomes. These observations are consistent with view that MG bodies arise by a process of phagolysosomal coalescence and mineralisation.

Skin window cellularity and macrophage changes in Hodgkin's and non-Hodgkin's lymphomas.

The cutaneous inflammatory response in patients with Hodgkin's and non-Hodgkin's lymphomas was investigated by light and scanning electron microscopy and compared with that of healthy subjects at 24 and 48 h. Both groups of patients showed a reduction in overall cellularity and statistically significant differences in macrophage surface morphology. In macrophages from healthy subjects, microvilli predominated but in lymphoma patients, cells with ruffles and/or ridges (resembling blood monocytes) were more frequent. In healthy subjects, the percentage of macrophages with predominant microvilli increased between day 1 and day 2. It is suggested that both the cellular response and the maturation (or activation) of macrophages are impaired in lymphomas.

Scanning electron microscopy of skin window cells of normal subjects.

With critical-point dried specimens, skin window cells of normal subjects showed a wealth of surface detail with no evidence of underlying nucleus or organells. Cells interpreted as neutrophils were characterized by delicate curved surface folds and variable numbers of fine filopodia; macrophages were larger and usually covered with tightly-packed clusters of knob-like microvilli, their periphery showing many filopodia and broader projections. Some macrophage filopodia took origin from the free surface of the cell and extended outwards to be attached to the coverslip for part of their extent, giving a 'fly-leg' appearance. Filopodial communications between cells were also present. With slow-dried preparations, the cells were flattened and a putative nuclear profile was evident. In these preparations quantitative analysis was made of various cell parameters comparing neutrophils and macrophages. The significance of these features has been discussed in relation to the in vivo inflammatory response as revealed by cell contact with a glass surface. The technique might be useful for studying haematogenous cells in certain disease states.

The morphology of uveal malignant melanomas. An in vitro study using the scanning electron microscope.

Scanning electron microscopy (S.E.M.) has been performed on tissue cultures obtained from four choroidal malignant melanomas. The morphology of these cells has been demonstrated using this technique. Microvilli were found to present on the surfaces of all cells studied. These microprocesses often formed a connection between the cell and the cover slip, or other tumour cells. Rounded vesicles were demonstrated on the surfaces of some cells. It is possible that some of the larger vesicles contained melanosomes.

Scanning electron microscopy of exudative macrophages in malignant lymphoma.

The possible value of scanning electron microscopy (SEM) of skin window preparations in the clinical situation has been investigated with reference to 48-hour macrophages in 26 patients with malignant lymphoma. The preparations were processed for SEM using critical point drying and sputter coating. Identification of macrophages was made with reference to light microscopy both of parallel preparations and of specimens already studied by SEM. Distinctive SEM appearances were present in most of the patients. Although many macrophages were similar to those from normal subjects, the majority showed a more variable morphology including the presence of ruffles and coarse ridge-like profiles. Highly significant differences were found on statistical analysis. It is suggested that immaturity of the 48-hour macrophages is present in some patients with malignant lymphoma (perhaps reflecting the macrophage dysfunction already described in these diseases). The findings indicate the potential clinical application for this technique.

Occupational argyria; light and electron microscopic studies and X-ray microanalysis.

Microscopic studies have been performed on skin biopsies from five patients with occupational argyria. Small brown-black granules were present in the dermis on light microscopy and were intensely refractile with dark-field illumination. Electron microscopy showed that the granules were electron-dense, round or oval in shape and varied in size from 30 nm to 100 nm. They were most numerous in relation to the basal lamina of the eccrine sweat glands, but were also present in relation to the basal lamina of the epidermis and dermal elastic fibres. X-ray microanalysis confirmed that many of the granules contained silver and sulphur. However, selenium, mercury, titanium and iron were also identified and it is probable that these elements were deposited in the skin also as a result of occupational exposure.