NUCLEAR DIFFERENCES BETWEEN THE ARGYROPHIL (= A1) AND NON-ARGYROPHIL (= A2) PANCREATIC A CELLS IN THE DUCK

ABSTRACT Previous investigations have shown that the A cells in the islets of Langerhans do not constitute a homogeneous cell group, but can be divided into two distinct fractions, on the basis of the presence (= A1 cells) and the absence (= A2 cells) of an argyrophil reaction. In order to asses the biological significance of this finding, it is important in the first instance to study, whether the A cells show any other mutual differences. In a comparison of the A1 and A2 cells within the dark A cell islets from ducks, significant differences were obtained with regard to nuclear size and eccentricity. The larger nuclear size in the A1 cells is possibly an expression of the higher functional activity in these cells. The findings support the concept of two different forms of the A cells.

THE SPECIFICITY OF THE ARGYROPHIL REACTION IN THE ISLETS OF LANGERHANS IN MAN

ABSTRACT By studying the Islets of Langerhans in man in thin Bouin fixed paraffin sections, first after impregnation with silver, and subsequently after removal of the silver, stained with Gomori's chrome-haematoxylin or aldehyde-fuchsin, it was possible to assess the specificity of the argyrophil reaction. Reports in the literature that some of the B cells were also silver impregnated could not be confirmed. On the other hand, the argyrophil reaction was not characteristic for all the A cells, since a minority of them were not blackened. In agreement with these observations, the considerably higher frequency of silver cells over A cells, previously reported in connection with comparative differential cell counts on the same human pancreas material, was shown to be only apparent.

SOME ASPECTS OF SILVER IMPREGNATION OF THE ISLETS OF LANGERHANS IN THE RAT

ABSTRACT By using a modification of Davenport's alcoholic silver nitrate method for impregnating nerves, it was possible to obtain a distinct argyrophil reaction on thin paraffin sections from rat pancreas which had been fixed either in formalin or Bouin's solution. Since this was followed by a removal of silver with subsequent granule staining according to Gomori, it became clear that the distinctly blackened cells comprised only some of the A cells. Some post-mortem change seemed to be an essential prerequisite of the argyrophil reaction, since this almost completely failed to appear after fixation in an ice-cold Bouin's solution. The reducing material was considerably resistent to acids; strongly blackened islet cells could be observed even after refixation in hydrochloric acid at a pH of 0.5. Although a preoxidation, e. g. with an acid solution of potassium permanganate, is essential for the differentiation of the islet cells with the modern granule stains, such treatment results in the argyrophil reaction becoming weaker or not appearing at all. Actual blackening, except in the case of those A cells, which could be distinguished as silver cells even after a short time, could not be produced by lengthening the impregnation time, but instead, the argyrophil reaction tended to decrease after a certain optimal period. The observation that among those cells, which by granule staining were classified as A cells, a separate fraction with distinctly blackened cytoplasm could be distinguished, led to the suggestion that the blackened cells should be called A1 cells and the remaining ones, A2 cells.