||"Individual islet masses averaged 200µm in diameter [BNID 111274]. Large ovoid cells at the
surface have been designated as beta cells, and smaller pyramidal cells as alpha
cells (Fig. 1). This identification was based on information from transmission
electron microscopy regarding size, shape and location of these two cell types.
An additional criterion was that the smaller pyramidal cells did not show any
surface response to glucose stimulation. In transmission electron micrographs,
beta cells are seen at the surface as well as the center of islet masses. These
rounded or ovoid cells have a diameter averaging 10µm and contain granules
about 0.20-0.25µm in diameter. The smaller alpha cells have a pyramidal shape
(Fig. 2). No attempt was made to distinguish alpha2 cells from alpha1 or delta
cells in the present study...With scanning electron microscopy, beta cells in unstimulated islet preparations
appear rounded or oval and have a diameter averaging 10µm (Fig. 3)."