Letter: Clean start for the retinal pigment epithelium.
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Biomedical subjects
Publications and source records attributed to L Feeney.
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The sulfated material which locates in the basal membrane of ciliary body epithelium when immature rat eyes are incubated with Na235SO4 was studied. On the basis of its chromatographic behavior compared with standard preparations, we conclude that the material consists of sulfatides.
A light and electron microscopical study of subretinal fluid removed at surgery for rhegmatogenous retinal detachment showed a heterogeneity of cell types originating from the neural retina, pigment epithelium, and wandering cells of the blood. Subcellular organelles sedimenting in the centrifuged pellets could be identified as to cell of origin, health of the parent cell, and time since cell rupture. Acellular specimens were typical of angiomatous detachments or long-standing rhegmatogenous detachments. Because various mechanisms of cellular pathophysiology contribute to the destructive and reparative processes during retina detachment, the cytologic analysis of subretinal fluid becomes a useful tool in understanding the biological processes that affect visual recovery or impairment after successful retinal detachment surgery.
A new type of hereditary cataract was predicted in the deer mouse (Peromyscus maniculatus) by the presence of syndactyly of the hind feet. Early morphologic changes were found in the equatorial cells that differentiated into new lens fibers. Later swelling at the anterior and posterior poles of these cells produced lens opacities. Anterior and posterior subcapsular cataracts progressed to a hypermature shrunken lens.
Immature and adult rat eyes were bisected and incubated with 35-SO4 and 3-U-galactose in short-term pulse-chase experiments. Autoradiographs (ARG) of the tissue revealed that very little sulfate is incorporated by the peripheral neural retina, the pigment epithelia of the retina, ciliary body, or iris. The inner, inverted optic cup cells at the ora serrata, i.e., those that are undergoing differentiation into the unpigmented epithelium of the ciliary body, incorporate large amounts of 35-sulfate into "fixable" macromolecules. The sulfate label is chased from the apically located Golgi apparatus to the basal surface of these cells within one hour. Ultrastructurally, these cells are beginning to develop lateral and basal invaginations of the plasma membrane characteristic of the adult secretory epithelial cells. Electron microscopic ARG show label associated with the plasma membranes. The sulfated macro-molecules at this site appear to be glycolipids and glycoproteins rather than glycosaminoglycans. The preferential synthesis of these macromolecules and their placement at the cellular site of aqueous humor production suggests a role for these sulfated substances in establishing, and perhaps maintaining, that secretory process. 3-H-galactose was incorporated into "fixable" macromolecules to some degree by all the neuroepithelial cells. After chase incubation, ARG showed a high concentration of label in differentiated retinal pigment epithelium (RPE), but not in undiffenentiated peripheral RPE. Ciliary body unpigmented and pigment epithelium, and iris muscle cells incorporate galactose, but to a lesser degree than either RPE or corneal endothelial cells.
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In this study we analyzed several aspects of protein secretion by thyroid follicular cells. The study was carried out on intact thyroid lobes obtained from newborn rats and incubated in vitro. The fate of leucine-(3)H incorporated into protein within follicular cells of untreated and thyrotropic hormone (TSH)-treated lobes was traced by quantitative electron microscope radioautography. Our findings indicate that protein synthesized by the rough-surfaced endoplasmic reticulum during a pulse exposure to leucine-(3)H is released relatively slowly by this organelle. Approximately 1 hr after onset of the pulse, a peak of radioactive protein appears in the Golgi region. The significance of this peak is not clear. Newly synthesized secretory protein passes through the apex of follicular cells without being concentrated or temporarily stored there in the form of large secretory droplets. Passage probably takes place via small vesicles which are intermingled among diverse small vesicles at the apex of the cells as well as in the Golgi region. Exposure of the lobes to TSH in the incubation medium for 45 or 90 min does not stimulate incorporation of leucine-(3)H into protein. Acute stimulation with TSH does, however, modify the movement of secretory protein within the exocrine secretory apparatus of the follicular cell. It accelerates the arrival of the protein at the apex of follicular cells, and it accelerates the release of the protein into the follicular lumen.
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