Pathogenesis of retinal dystrophy in the Royal College of Surgeons rat.

The Royal College of Surgeons (RCS) rat is an animal with genetically transmitted progressive retinal dystrophy. We compared histopathologically the RCS rat retina with normal age-matched control retinas (Long-Evans rats) using light and scanning electron microscopy. Retinal degeneration begins with alteration of the rod outer segments. There is a progressive involvement of the entire retina, with all layers affected by 45 days. The three-dimensional view obtained with scanning electron microscopy provides another perspective on the pathogenetic changes of the RCS retina.

Preservation of retinal function in the RCS rat by laser treatment.

The Royal College of Surgeons (RCS) rats have been used as a model for human retinitis pigmentosa. Studies on these animals have shown that the degeneration of the retina is associated with a buildup of debris produced by shed rod outer segment discs. It has been reported that localized laser lesions can increase phagocytosis in these rats. This study examined the effect of laser burns on the function of the retina of the RCS rats. One eye of 19-day-old RCS rats was treated with laser and the other eye used as control. The retinal function was measured by electroretinography at 5, 10, 15, 20, 25, 30, and 40 days after lesioning. The morphology of the retina was examined at 24 and 43 days after laser treatment. The results show that the retinal function in the treated eye was improved at all intervals and that this improvement was significant at 15, 20, and 25 days. Morphologic examination showed a significant reduction in debris accumulation in the area of the laser spot. However, at sites distal to the laser burns, no morphologic difference between the treated and untreated eyes was noted. It is concluded that the progress of retinal dysfunction in the RCS rats can be retarded by laser treatment.

The developmental changes in plasma adrenal androgens during infancy and adrenarche are associated with changing activities of adrenal microsomal 17-hydroxylase and 17,20-desmolase.

The plasma concentrations of dehydroepiandrosterone, androstenedione, and dehydroepiandrosterone sulfate decrease during the first year of life, remain low during childhood, and then increase during adrenarche. To determine whether alterations in adrenal enzyme activity might explain the changing secretory pattern of the adrenal androgens, we measured human adrenal microsomal 3 beta-hydroxysteroid dehydrogenase-isomerase, 17,20-desmolase, 17-hydroxylase, and 21-hydroxylase activities. 12 adrenals from individuals aged 3 mo to 60 yr were studied. The patients were divided into three groups based upon the age of the patient when the adrenal glands were obtained: group 1, infants aged 3--8 mo (n = 3); group 2, preadrenarchal or early adrenarchal children aged 2--9 yr (n = 4); and group 3, adults aged 20--60 yr (n = 5). The mean activity of the 17,20-desmolase, 17-hydroxylase, and 21-hydroxylase fell by 50% and that of 3 beta-hydroxysteroid dehydrogenase-isomerase activity rose 80% from group 1 to 2. A fourfold increase in 17,20-desmolase (P less than 0.002) and 17-hydroxylase (P less than 0.001) activity and a doubling in 21-hydroxylase activity (P less than 0.005) occurred between groups 2 and 3. We conclude that the decline in plasma adrenal androgens after birth appears to be associated with a rise in 3 beta-hydroxysteroid dehydrogenase-isomerase and a fall in 17,20-desmolase and 17-hydroxylase activity. The subsequent increase in plasma adrenal androgen concentration during adrenarche is coincident with a rise in 17,20-desmolase and 17-hydroxylase activity.