Modulation of disk margin structure during renewal of cone outer segments in the vertebrate retina.

摘要: In the process of disk renewal in retinal cone outer segments (COSs), apical displacement disks must be coupled to systematic reductions area and perimeter order retain overall conical geometry. We have quantified these changes segment lengths by morphometric analyses cross sections fully formed taken from basal ends COSs. Specifically excluded are data arising partial or incomplete within COS, which do not conform geometry constitute a minor fraction COS population. Thus, our results address long-range pattern structural affecting major population along length COS. Our indicate that decreases total margin associated with due opposite cilium, i.e., open segment. contrast, average closed remains constant increases slightly direction. The margins frog recently been shown possess distinctive lattice membrane-associated components (Fetter Corless: Invest. Ophthalmol. Vis. Sci. 28:646–657, '87). also examined COSs freeze-fracture, deep-etch technique for evidence mechanism whereby measured may accommodated while maintaining organization segments. regions membrane continuity between plasma membrane, we observed elevated ridges on (1) tend lie parallel segments, (2) similar axial spacing, (3) occasionally demonstrate interconnecting filaments those lattice, (4) appear particulate substructure. The proposed reducing involves tangential lateral edges adjacent membrane. These shifted domains initially give rise plasmalemmal ridges, subsequently disassemble, whose become redistributed features suggest several revisions earlier model morphogenesis (Corless Fetter: J. Comp. Neurol. 257:24–38, '87), was based structure ROS alone. Eckmiller (J. Cell Biol. 105:2267–2277, '87) has represent sites new formation. evaluate consequences geometries local remodelling briefly outline an alternative interpretation is consistent available morphological data.