The development of the dilator muscle in the iris of the albino rat

Pre‐ and Postnatal Development of the Eye: A Species Comparison

“…Between PND4 and PND6, the iris begins to elongate, and the cellularity of anterior stroma begins to decrease (Inagaki et al, ). At PND5, the basal layer of the pars iridica retinae contains a discrete eosinophilic coloration compatible, with the myofilaments forming the pupillary dilator muscle of the iris (Lai, ). By PND12 to PND14, basal epithelial cells in the dilator region have fully differentiated into myoepithelial cells, and by PND20, the pupillary dilator muscle is fully differentiated into adult form (Lai, ).…”

Cytoskeleton in neuroectodermally derived epithelial and muscle cells of the human iris and ciliary body.

“…Quite surprisingly, although no convincing immunoreaction for cytokeratins was detected in the epithelial portion of the anterior iris epithelium, in many eyes individual dilator fibers in its muscular portion reacted with MAb CAM 5.2 and CY-90 to CK 8 and 18. Co-expression of cytokeratins, vimentin, and desmin in human muscle cells is also found in the uterus, heart, and certain blood vessels, in which cytokeratin immunoreactivity likewise is weak and restricted to a heterogenous subpopulation of muscle fibers (28,34,41,42).…”

“…Although the mammalian sphincter and dilator muscles are both derivatives of the anterior iris epithelium (16)(17)(18), the former was completely devoid of vimentin and cytokeratins. This was even more striking since the ciliary muscle, which is thought to originate from cranial neural crest, co-expressed vimentin and desmin (19,20).…”

“…Primary murine monoclonal antibodies (MAb) against cytokeratin 4 (Clone 215 B8, IgGi; Lot 12269420-01; Boehringer Mannheim, Mannheim, Germany) (diluted 1:35), an epitope common to cytokeratins 5 and 6 (Clone D5/16 B4, IgG1; Lot 12269820-01; Boehringer Mannheim) (diluted 1:35), cytokeratin 7 (Clone LdS68, IgGl; Lot 69F4800; Sigma, St Louis, MO) (diluted 1:32000) (21), cytokeratin 13 (Clone KS-lA3, IgGl; Lot 78F-4806; Sigma) (diluted 1:500) (22), three MAb to different epitopes on cytokeratin 18 (Clone CK5, IgG1; Lot 37F-4958; diluted 1:400; Clone CY-90, IgGl; Lot 49F-4815; diluted 1:3000; and Clone KS-B17.2, IgGi, Lot 128F-4805; diluted 1:500) (all from Sigma) (7,22,23), cytokeratin 19 (Clone BA17, IgG1; Lot 109; Dakopatts, Glostrup, Denmark) (diluted 1:lOO) (24), a monoclonal antibody against an epitope common to cytokeratins 8 and 18 (Clone CAM 5.2, IgGza; Lot M0910; Becton Dickinson, Mountain View, CA) (diluted 1:2) (25), and an MAb to a conformational epitope common to most cytokeratin polypeptides, including 8, 18, and 19 (Clone lu-5, IgGl; Lot 10968525-01; Boehringer Mannheim) (diluted 1:lO) (26) were commercially obtained. Murine MAb to vimentin (Clone V9, IgGl; Lot 48F4827) (diluted 1:750) (27,28), desmin (Clone DE-U-10, IgGi; Lot 117F 4809) (diluted 1:400) (29), and a-smooth muscle actin (Clone 1A4, IgG2,; Lot 98F-4808) (diluted 1:SOOO) (30) were also purchased from Sigma, and another mouse MAb to vimentin (Clone Vim 3B4, IgG2,; Lot 11454322-01) (diluted 1:20) was obtained from Boehringer Mannheim.…”

“…During embryonic development, invagination of the optic vesicle gives rise to the optic cup, the outer layer of which differentiates into the retinal pigment epithelium, the outer pigmented layer of the ciliary epithelium, and the anterior epithelium of the iris, which in turn gives rise to the mammalian dilator and sphincter muscles (16)(17)(18). In contrast, the ciliary muscle may originate from cranial neural crest (19,ZO).…”