Abstract
The hyaloid vessels form a capillary network on the inner surface of the retina. These capillaries are embedded in the vitreous humor, and they lack a glial investment. The intercellular spaces of the retina communicate with the ocular cavity, as can be evidenced by following the penetration of tracer substances. Hence, there is an extracellular diffusion pathway between hyaloid capillaries and retinal neurons, without interposition of glial cells. Trypan blue and ferrocyanide were not detected within the vitreous humor nor the retina after systemic injection. To this extent, at least, the hyaloid capillaries functionally resemble central nervous system capillaries. Intravascular injections of horseradish peroxidase established the absence of vesicular transfer across the endothelium of the hyaloid capillaries. In addition, quintuple-layered junctions between endothelial cells prevented the intercellular passage of the enzyme. It is likely, therefore, that the only pathway across the endothelium of the hyaloid capillaries is through the plasmalemma of the endothelial cells.
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Selected References
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- BENNETT H. S., LUFT J. H., HAMPTON J. C. Morphological classifications of vertebrate blood capillaries. Am J Physiol. 1959 Feb;196(2):381–390. doi: 10.1152/ajplegacy.1959.196.2.381. [DOI] [PubMed] [Google Scholar]
- FARQUHAR M. G., PALADE G. E. Junctional complexes in various epithelia. J Cell Biol. 1963 May;17:375–412. doi: 10.1083/jcb.17.2.375. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Farquhar M. G., Palade G. E. Cell junctions in amphibian skin. J Cell Biol. 1965 Jul;26(1):263–291. doi: 10.1083/jcb.26.1.263. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Graham R. C., Jr, Karnovsky M. J. The early stages of absorption of injected horseradish peroxidase in the proximal tubules of mouse kidney: ultrastructural cytochemistry by a new technique. J Histochem Cytochem. 1966 Apr;14(4):291–302. doi: 10.1177/14.4.291. [DOI] [PubMed] [Google Scholar]
- KEILIN D., HARTREE E. F. Purification of horse-radish peroxidase and comparison of its properties with those of catalase and methaemoglobin. Biochem J. 1951 Jun;49(1):88–104. doi: 10.1042/bj0490088. [DOI] [PMC free article] [PubMed] [Google Scholar]
- KELLENBERGER E., RYTER A., SECHAUD J. Electron microscope study of DNA-containing plasms. II. Vegetative and mature phage DNA as compared with normal bacterial nucleoids in different physiological states. J Biophys Biochem Cytol. 1958 Nov 25;4(6):671–678. doi: 10.1083/jcb.4.6.671. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kuffler S. W., Nicholls J. G. The physiology of neuroglial cells. Ergeb Physiol. 1966;57:1–90. [PubMed] [Google Scholar]
- LUFT J. H. Improvements in epoxy resin embedding methods. J Biophys Biochem Cytol. 1961 Feb;9:409–414. doi: 10.1083/jcb.9.2.409. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lasansky A., De Fisch F. W. Potential, current, and ionic fluxes across the isolated retinal pigment epithelium and choriod. J Gen Physiol. 1966 May;49(5):913–924. doi: 10.1085/jgp.49.5.913. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lasansky A. Functional implications of structural findings in retinal glial cells. Prog Brain Res. 1965;15:48–72. doi: 10.1016/s0079-6123(08)60939-5. [DOI] [PubMed] [Google Scholar]
- MUIR A. R., PETERS A. Quintuple-layered membrane junctions at terminal bars between endothelial cells. J Cell Biol. 1962 Feb;12:443–448. doi: 10.1083/jcb.12.2.443. [DOI] [PMC free article] [PubMed] [Google Scholar]
- REYNOLDS E. S. The use of lead citrate at high pH as an electron-opaque stain in electron microscopy. J Cell Biol. 1963 Apr;17:208–212. doi: 10.1083/jcb.17.1.208. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Reese T. S., Karnovsky M. J. Fine structural localization of a blood-brain barrier to exogenous peroxidase. J Cell Biol. 1967 Jul;34(1):207–217. doi: 10.1083/jcb.34.1.207. [DOI] [PMC free article] [PubMed] [Google Scholar]
- SABATINI D. D., BENSCH K., BARRNETT R. J. Cytochemistry and electron microscopy. The preservation of cellular ultrastructure and enzymatic activity by aldehyde fixation. J Cell Biol. 1963 Apr;17:19–58. doi: 10.1083/jcb.17.1.19. [DOI] [PMC free article] [PubMed] [Google Scholar]
- WATSON M. L. Staining of tissue sections for electron microscopy with heavy metals. J Biophys Biochem Cytol. 1958 Jul 25;4(4):475–478. doi: 10.1083/jcb.4.4.475. [DOI] [PMC free article] [PubMed] [Google Scholar]