The fine structure of the reconstructed neural retina of chick embryos

The fine structure of reconstructed neural retina formed from dissociated neural retinal cells of 6½-day-old chick embryos on the chorio-allantoic membrane of chick embryos was examined with the electron microscope. Three nuclear layers (ganglion cell layer, inner and outer nuclear layers) and two fibrous layers (inner and outer plexiform layers) are found within the reconstructed retina. Both the outer and the inner limiting membranes of the reconstructed structure are constituted from the processes of differentiated Müller cells. The ganglion cell layer consists of two types of cell, though a typical ganglion cell with axonal process is not observed. Optic nerve fibres are not formed. Amacrine cells are recognized within the inner nuclear layer. Differentiation of the inner segment of the photoreceptor cell occurs, but not of the outer segment. Synaptic structures are recognized in the inner plexiform layer, but not in the outer plexiform layer.

THE STRUCTURE OF FLIGHT MUSCLE SARCOSOMES IN THE BLOWFLY CALLIPHORA ERYTHROCEPHALA (DIPTERA)

The electron microscopic structure of sectioned indirect flight muscle fibers of the blowfly Calliphora is described. Particular attention is paid to the organization of the sarcosomes (mitochondria) of this tissue, and this description is accompanied by an account of the appearance of these bodies in negatively stained preparations. In sectioned material, it has been shown that these sarcosomes are similar to other mitochondria in the disposition of the outer and inner limiting membranes, but that the cristae, confluent with the latter, are unusually regular, and form parallel plates, containing circular fenestrations forming cylindrical channels within the matrix. Negatively stained preparations of disrupted sarcosomes reveal that both the outer limiting membrane and the cristae membranes bear large numbers of small particles, similar in appearance to those described by Fernández-Morgán and others in various mitochondria. In Calliphora, these particles consist of a sub-spherical "head" and a cylindrical "stalk," and appear to be arranged on the mitochondrial membranes either randomly distributed, or collected into circular or elongated groups. Recent suggestions concerning the nature of these submitochondrial particles are discussed, and an attempt is made to correlate the aspects of organization of Calliphora sarcosomes, revealed by conventional sectioning of the "intact" structures, and by negative staining of sarcosomal derivatives.