[The adventitional and intervascular reticulin fibers of the human retina]

Glial fibrillary acidic protein in the retina of the developing albino rat: an immunoperoxidase study of paraffin-embedded tissue

The peroxidase-anti-peroxidase method was used on paraffin-embedded material to demonstrate the distribution of glial fibrillary acidic (GFA) protein, an astrocyte-specific protein, in the developing retina of the albino rat. At birth activity was scant and was confined to scattered, poorly differentiated cells in the inner retinal layers near the optic disc. At 3 days primitive astrocytes which displayed GFA protein activity were confined to the stratum opticum near the optic disc. With increasing age these cells were found at greater distances from the optic disc and began to assume the appearance of typical fibrous astrocytes. By 30 days the perikarya of these cells were confined almost exclusively to the region between the nerve fiber layer and the inner limiting membrane. The processes of these cells terminated either in suckerlike end-feet upon blood vessels or, to a lesser extent, ended in relation to axon fascicles of the nerve fiber layer. A second population of GFA protein-active cells existed as perivascular glia which were found upon vessels in the inner portion of the stratum opticum in young animals. In the mature retina perivascular glia were found on vessels throughout the stratum opticum and in the inner portion of the inner plexiform layer. Unequivocal staining of Müller cells or their processes was not obtained. The best staining was obtained with fixatives containing minimal concentrations of aldehydes, especially in tissue from younger animals. The fixative which gave the best preservation of cellular structure along with preservation of GFA protein antigenicity was Perfix (Fischer Scientific Company).

Perivascular and intervascular reticular fibers of the retina

We demonstrated the existence in the retina of an argyrophilic perivascular membrane comparable in all respects to that which exists throughout the vascular system. We compared our findings by light microscopy with those previously reported. We identified, by electron microscopy, the normal general location of the network between the basal laminae of the glial and vessel cells and demonstrated its selective staining with silver methenamine. These perivascular fibers, intercapillary strands, and bridges develop in relation to the process of retinal vascularization and the potential for forming these fibers is reactivated in senility and disease, as in diabetes. We summarized the evidence by concluding that these fibers are most likely composed of reticulin; it appears provable that in the past there may have been some confusion with neural fibers.