Joseph L. Craft

Development of the outer plexiform layer in albino rats

The development of the outer plexiform layer (OPL) at the posterior pole was studied in albino rats, ages 1 to 18 days. Light microscopic observations were consistent with previous reports that within the first postnatal week neuroepithelial cells migrate into outer and inner nuclear layers with formation of the intervening OPL. The relation of neural and glial cells was consistent with the suggestion of others that guidance by glial cells influences the radial organization of the developing neural retina. The new observations presented in this paper raise the possibility that the horizontal orientation of neural processes in the outer plexiform layer depends upon guidance of glial cells.

Human Retinal Dysplasia

We studied the ultrastructure of the four types of dysplastic rosettes and compared them with retinoblastoma rosettes. Dysplastic rosettes have morphologic characteristics intermediate between the normal photoreceptor layer and retino-blastoma rosettes; Müller cells contribute to the formation of dysplastic but not neoplastic rosettes. Abnormality in the relationship between the retina and the retinal pigment epithelium is frequent in cases with spontaneously occurring retinal dsyplasia and is consistent with previous observations that the retinal pigment epithelium influences the development of retinal morphology and function. We believe the normal developmental sequence of cell death and disappearance of necrotic cells may have gone awry in retinal dysplasia.

Kainic acid induces mitoses in mature retinal neurones in rats

Abstract Injection of kainic acid into the vitreous of rats causes mitoses to develop in the inner nuclear layer of the retina. The mitoses appear to be in amacrine cells. Sustained depolarization, which has been shown to be mitogenic for spinal cord neurones cultured in vitro, is presumably the mitogenic stimulus in retinal neurones exposed to kainic acid.

Histologic and Ultrastructural Characteristics of Temporal Arteritis

Temporal artery biopsy is an easily performed procedure of low morbidity that produces valuable information in establishing a diagnosis and guiding therapy as well as providing tissue for further pathologic and immunologic research aimed at understanding and ultimately controlling this disease. The pathogenesis of temporal arteritis remains unresolved. In an effort to clarify this question, 19 temporal arteries demonstrating typical arteritic changes by light microscopy were also examined by transmission electron microscopy. At the light microscopic level, a granulomatous inflammation, often containing giant cells, was found in all layers of the vessel but most commonly concentrated within the internal or external border of the muscular media. The internal elastic lamina was usually fragmented and surrounded by inflammatory cells. Segmented subintimal fibromuscular hyperplasia and lymphocytic and plasma cell infiltration of the adventitia were nondiagnostic but suggestive findings commonly observed. Ultrastructural alterations were most striking in the muscular media. Degenerating smooth muscle cells with elongated mitochondria, dilated rough endoplasmic reticulum, and autophagic vacuoles containing electron-dense material were observed. Macrophages and giant cells contained degenerated smooth muscle cell basement membrane within phagocytic vacuoles, and macrophages were found within smooth muscle. Although frequently found in the vicinity of macrophages and giant cells, disrupted elastic lamina was not demonstrated in phagocytic cells.

Retinal anomalies in trisomy 18

The eyes of three patients with trisomy 18, the second most common human autosomal trisomy, were examined histopathologically. In the posterior retina transmission and scanning electron microscopic examinations reveal cytological details characteristic of immature neural retinas. We are able to confirm the report that the posterior retinal pigment epithelium in trisomy 18 has a paucity of mature melanosomes and, in fact, resembles human albino retinal pigment epithelium. The association of hypopigmentation and retinal immaturity suggests pigmentation plays a role in the control of the maturation of the neural retina. Die Augen von drei Patienten mit Trisomie 18, die zweithäufigste menschliche autosome Trisomie, wurden histopathologisch untersucht. Transmission- und rasterelectronmikroskopische Befunde zeigen zytologische Einzelheiten in der hinteren Netzhaut, die für unreife Neuralretina charakteristisch sind. Wir sind in der Lage das Ergebnis zu bestätigen, daß bei der Trisomie 18 das Pigmentepithel der hinteren Netzhaut einen Mangel an reifen Malanosomen aufweist und dem Netzhautpigmentepithel eines menschlichen Albinos ähnelt. Der Zusammenhang zwischen Hypopigmentierung und unreifer Netzhaut legt nahe, daß bei der Kontrolle des Reifungsprozesses der Neuralretina die Pigmentierung eine Rolle spielt.