PMC

Modeling of the light-induced backscattering increase from the base of the rod OS. (A) Electron micrograph of the base of a mouse rod OS from the recent study of Ding et al. (). Reprinted with permission from Vadim Arshavsky (Duke University, Durham, NC). The “rod OS base” as defined for the backscattering model (red dashed region) is a cylindrical portion of the rod comprising three elements: the IS component (colored yellow); the OS component, comprising eight basal discs in various stages of assembly (pale purple); and the intervening extracellular space (cyan). In this instance, Ding et al. showed that eight basal disc membranes remain fused with the plasma membrane and would thus contribute to an elevated water permeability of the rod OS base. (B) Depiction of a 3D model of the rod OS component of the base (i.e., portion of based disc composed of nascent discs). A dielectric mixing model was developed that combines the predicted time-varying refractive index of the basal discs dictated by osmotically induced swelling, and Gα_t and Gβ₁γ₁ dissociation and solubilization, with portions of the rod OS base that are IS (yellow) or extracellular (cyan). (). (C) Fractional increases in the length of the main (“middle”) portion of the rod OS and the basal discs predicted by the model. (D) Changes in the refractive indexes of the basal and middle portions of the rod OS predicted by the model along with the unchanging refractive index of the rod IS. (E) Rod OS swelling data from (solid black circles), with prediction of the osmo-elastic model (red curve). (F) “IS/OS” (rod OS base) backscatter data (solid black circles) adjusted from the measured value of S²_OCT converted to equivalent Fresnel reflectivity compared with the model prediction (red curve) ().

Rod length determination and rod morphologies of flgG mutants. (A) Total rod length was determined by first measuring the distance between the distal edge of the MS ring and the distal edge of the L ring as the length of the whole rod. WT, wild type. (B) Isolated polyrods allowed for proximal-rod length determination. Then the proximal-rod length was subtracted from the whole-rod length to obtain the distal-rod length. flgG*, flgG mutant. (C) Electron micrographs of the flagellar basal structures with various rods found in flgG(G183R) mutant TH10080. (Top) The filamentous rod only, without further structures attached; (middle) the filamentous rod directly attached to the filament but not through the hook; and (bottom) the filamentous rod attached to the hook and filament.

Diagrams showing a reconstruction of the ultrastructure of Bihospites bacati n. gen. et sp. Relationships between C-shaped rod apparatus, nucleus, cytostomal funnel, feeding pocket, flagellar pocket and vestibulum, as inferred from serial transmission electron microscopy (TEM), scanning electron microscopy (SEM), and light microscopy (LM). A. Cell viewed from the right side showing the positions of the nucleus (N), the C-shaped main rod (r), the accessory rod (ar), and the cytostomal funnel (cyt) in relation to the feeding pocket (FeP), the flagellar pocket (FP) and the vestibulum (vt); Vf = ventral flagellum; Df = dorsal flagellum; Db = dorsal basal body; Vb = ventral basal body. B. Diagram emphasizing the relationship between nucleus (N), main rod (r), and folded accessory rod (ar). The diagram is divided into three sections; and the nucleus removed from the top section for clarity. Posterior end of the main rod positioned at the level of the vestibulum on the ventral side of the nucleus. This rod extends posteriorly and then encircles the posterior, dorsal and anterior ends of the nucleus before terminating on the ventral side of the nucleus just above the vestibulum; therefore, this rod is C-shaped. The folded accessory rod runs along the C-shaped main rod for most of its length, terminating at the same point just above the vestibulum; however, on the ventral side of the nucleus, the posterior end of the accessory rod extends both anteriorly, defining the cytostomal funnel (cyt), and ventrally toward the ventral basal body.

Growth of processes by rod cells is reduced with Pak or LIMK inhibition; blockage of Ca²⁺ influx furthers the effect of LIMK inhibition. (A) Left: Cartoon of regional designations for rod cell processes. In the intact retina, axonal processes grow from the basal/nuclear pole, whereas calycal processes that surround the outer segment grow from the apical/ellipsoidal pole. Right: Representative rod cells with rod opsin labeling from DMSO control, 10 μM BMS-5-, and 10 μM Nc plus 10 μM BMS-5-treated cultures after 3 days. Cells in control, untreated cultures show the most growth. Scale bar: 10 μm. (B) Length of the longest process from three regions (overall, longest process regardless of region of origin; basal, from the cell surface close to the nucleus; apical, from the cell surface close to the ellipsoid) of each rod cell. Pak inhibition with 1 μM IPA-3 reduced process growth of rod cells after 3 days in culture from all regions, compared to control. In control cells, length of apical and basal processes is similar; in IPA-3-treated group, basal processes shortened significantly more than apical processes. n = 3 animals, 12 cultures, 360 rod cells, ∼180 cells per group; *P < 0.05, **P < 0.005. (C) LIM kinase inhibition with 10 μM BMS-5 reduced process growth overall and from the basal but not the apical pole. Blockage of Ca²⁺ influx increased the effect of LIMK inhibition and reduced process growth from basal and apical regions. n = 3 animals, 18 cultures, 540 rod cells, ∼180 cells per group; *P < 0.05, **P < 0.01, ***P < 0.001; (B) Student's t-test; (C) 1-way ANOVA.