Characterization of the color related receptor mosaic in the ground squirrel retina

Light microscopic and histochemical studies reveal that the retina of the European ground squirrel (Citellus citellus L.) contains a mosaic pattern of two cone types and a small population of rods. A minority (7%) of the cones can be characterized by their ellipsoids having larger diameters and increased staining density over the majority population. Exposure to green light selectively elicited intense NBT-diformazan labeling in the major population of cones while the larger diameter cone type was labeled after blue illumination. The two cone subpopulations are probably the blue and green cone types of ground squirrel protanopic color vision.     

视网膜色素变性视网膜的组织病理和超微结构观察

目的：探讨视网膜色素变性的病理改变及其发病机制。 方法：对1例常染色体显性遗传性视网膜色素变性患者的视网膜进行组织病理和超微结构观察．结果：视网膜各层组织均有变性改变和结构紊乱，并有区域性差异，后极部变性较周边部为重．视网膜色素上皮细胞病变与感光细胞病变程度密切相关，但后者似较前者为重．感光细胞的超微结构有明显变性改变，尤以外节变性，线粒体变性、胞浆内脂褐索沉着为突出。结论：超微结构变化提示感光细胞能量代谢系统和(或)自噬系统功能障碍。 （中华眼底病杂志，1997，13：24-26）     

Additive manufacturing of porous titanium metaphyseal components: Early osseointegration and implant stability in revision knee arthroplasty

AimsMetaphyseal cones and sleeves are components used in revision knee arthroplasty to ensure load transfer, encourage bone on-growth and prevent stress shielding. Additive manufacturing of titanium alloy implants is a novel technique with limited clinical outcome reports in the literature. The aim of this study was to determine radiographic evidence of osseointegration and early results of a single manufacturer porous titanium metaphyseal components in the proximal tibia.MethodsWe retrospectively reviewed the prospectively collected database of two institutions. Patients who underwent revision knee arthroplasty using porous titanium components by a single manufacturer were identified. Immediate post-operative and latest follow-up radiographs were independently analysed by 2 reviewers to determine metaphyseal bone contact and level of osseointegration in relevant Knee Society Radiographic Evaluation and Scoring System zones.Results22 patients (15 males; 7 females) with a mean age of 71 (49–92) years were included. The mean follow-up period was 14 months (2–44 months). Cones were used in 16 patients and sleeves in 6. Interobserver reliability assessment showed substantial agreement (weighted Kappa 0.71, (95% CI: 0.60, 0.81). There was significant correlation between the bone contact in the immediate postop radiograph and osseointegration at final follow-up (kendall’s tau-b: 0.698, p < 0.001). Infection free prosthetic joint survival was 20/22 at final follow-up.ConclusionPorous titanium metaphyseal components produced with additive manufacturing provided excellent osseointegration and no early clinical failures. Partial or complete contact of the cone with native bone in the immediate postoperative radiograph resulted in osseointegration in all cases.     

Development and Verification of Novel Porous Titanium Metaphyseal Cones for Revision Total Knee Arthroplasty

Background

Porous metaphyseal cones are widely used in revision knee arthroplasty. A new system of porous titanium metaphyseal cones has been designed based on the femoral and tibial morphology derived from a computed tomography–based anatomical database. The purpose of this study is to evaluate the initial mechanical stability of the new porous titanium revision cone system by measuring the micromotion under physiologic loading compared with a widely-used existing porous tantalum metaphyseal cone system.

Studies on cell migration and axon guidance in the developing distal auditory system of the mouse

The events that take place along the potential route of distal auditory axons (future vestibular component) prior to and during their outgrowth were examined morphologically using timed mouse embryos. During embryonic (E) day 9.5 a discrete zone of cell death appears in the rostrolateral wall of the otic cup. Necrosis is accompanied by outward migration of epitheloid cells from the same region of the otic wall. Temporally and spatially correlated with these two events is the widening of extracellular spaces between otic neuroepithelial cells and the breakdown of basement membrane. During E 10.5 migrating epitheloid cells condense to form a funnel-shaped configuration. This cellular "funnel" begins narrowly at the dorsorostrolateral wall of the otocyst and broadens as it reaches the auditory ganglion. During E 11.5 through E 12.5, "pioneer" distal auditory axons take a circuitous route and ascend from the auditory ganglion to enter the otocyst. Axons extend toward the otocyst moving along cells of the "funnel," maintaining an orientation similar to that of the cells that compose it. Axon growth cones enter the otocyst at sites devoid of basement membrane and invade the wall of the otocyst moving tangentially along radially arranged cells that bridge the otocyst and the "funnel." These observations demonstrate that a preformed, funnel-shaped tissue exists along the future route of the auditory fibers. We suggest that the "funnel" may influence the growth and directionality of distal auditory axons as they extend from the auditory ganglion to the wall of the otocyst. At the otic wall, the transition provided by "bridge" epitheloid cells, together with the absence of basement membrane at specific sites of the otic wall, provide the auditory axons with a route into the otocyst.     

Morphology of bipolar cells labeled by DAPI in the rabbit retina.

The morphology, distribution, and coverage of certain cone bipolar cell types were investigated in rabbit retina. Brief in vitro incubation of isolated rabbit retina in the fluorescent dye 4,6-diamino-2-phenylindole labeled only a few cell types in the inner nuclear layer. Intracellular injection of Lucifer Yellow into these types showed them to be horizontal cells and cone bipolar cells. All stained bipolar cells ramified in sublamina a of the inner plexiform layer (IPL) and formed three classes. Two types ranged from 20 to 60 microns in diameter in both plexiform layers; the other large bipolar cell was 40-70 microns in diameter in the outer plexiform layer (OPL) and up to 150 microns in diameter in the IPL. The brightest type was narrowly stratified in the outer portion of sublamina a. Its density increased from about 500 cells/mm2 in the periphery to about 2,500 cells/mm2 in the visual streak. Staining of neighboring cells of this type showed that processes in the IPL rarely crossed, but often converged at a common site so as to impart a "honeycomb" appearance to a single sublayer of retina. The other small bipolar cell was similar in density and coverage, but stratified diffusely throughout sublamina a. The large bipolar cell stratified narrowly in the distal portion of sublamina a and was more sparsely distributed. Whether determined by staining adjacent cells or by density vs. area calculations, coverage in the OPL approached 1 for each type, as did coverage in the IPL for the two types with narrow fields.     

Assessing Interocular Symmetry of the Foveal Cone Mosaic

PurposeTo test the hypothesis that foveal cone topography is symmetrical between contralateral eyes.MethodsWe used adaptive optics scanning light ophthalmoscopy to acquire images of the foveal cone mosaic in each eye of 58 subjects with normal vision (35 female, 23 male). Cones were semiautomatically identified over a 300 × 300-µm foveal area. From these cone coordinates, maps of cone density were derived, and we extracted estimates of peak cone density from each map. Mosaic regularity was assessed using Voronoi cell area regularity (VCAR). Average roundness and average area of the 70%, 75%, 80%, 85%, and 90% of peak density isodensity contours were evaluated.ResultsThe average peak cone density for right eyes was 180,286 cones/mm² (n = 49) and for left eyes was 182,397 cones/mm² (n = 45), with a mean absolute difference of 6363 cones/mm² (n = 43). Peak density, cone spacing, VCAR, and average area within the isodensity contours of fellow eyes were not significantly different (P = 0.60, P = 0.83, P = 0.30, and P = 0.39, respectively). However, the average roundness of the isodensity contours was 2% more circular in the right eyes than in the left eyes (P = 0.02).ConclusionsThere is interocular symmetry of peak foveal cone density, mosaic regularity, and area encompassing the most densely packed cells in subjects with normal vision. The origin and significance of the observed interocular difference in average roundness of the isodensity contours are unclear.     

Motion Perception of Short-Wavelength Sensitive Cones in Glaucoma Using Random Dots Moving

Purpose: To determine whether motion perception of short-wavelength sensitive (SWS) cones is capable of predicting primary open angle glaucoma (POAG) optic neuropathy. Methods: Motion perceptions of SWS cones were isolated by Blue random dot stimulus displayed on the Yellow background, then the detecting displacement threshold of motion perception from SWS cone in POAG was measured, and compared with the age-matched normal group.Results: The detecting displacement thresholds of motion perception from SWS cones in 8 sites of 15 degrees were all elevated in POAG compared with the normal group. Conclusion: These findings suggest that motion perception of SWS cones may reveal preclinical visual nerve damage in early POAG. Eye Science 2001; 17:176 ~ 179.     

Distinct contribution of cone photoreceptor subtypes to the mammalian biological clock

Ambient light detection is important for the synchronization of the circadian clock to the external solar cycle. Light signals are sent to the suprachiasmatic nuclei (SCN), the site of the major circadian pacemaker. It has been assumed that cone photoreceptors contribute minimally to synchronization. Here, however, we find that cone photoreceptors are sufficient for mediating entrainment and transmitting photic information to the SCN, as evaluated in mice that have only cones as functional photoreceptors. Using in vivo electrophysiological recordings in the SCN of freely moving cone-only mice, we observed light responses in SCN neuronal activity in response to 60-s pulses of both ultraviolet (UV) (λ_max 365 nm) and green (λ_max 505 nm) light. Higher irradiances of UV light led to irradiance-dependent enhancements in SCN neuronal activity, whereas higher irradiances of green light led to a reduction in the sustained response with only the transient response remaining. Responses in SCN neuronal activity decayed with a half-max time of ∼9 min for UV light and less than a minute for green light, indicating differential input between short-wavelength–sensitive and mid-wavelength–sensitive cones for the SCN responsiveness. Furthermore, we show that UV light is more effective for photoentrainment than green light. Based on the lack of a full sustained response in cone-only mice, we confirmed that rapidly alternating light levels, rather than slowly alternating light, caused substantial phase shifts. Together, our data provide strong evidence that cone types contribute to photoentrainment and differentially affect the electrical activity levels of the SCN.

In addition to rods and cones, light is also sensed in the retina by a specialized subset of melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs). ipRGCs incorporate input from rod and cone photoreceptors (1). Two types of cone photoreceptors are present in the murine retina: short-wavelength–sensitive cones (S-cones; λ_max 360 nm), which are maximally sensitive to ultraviolet (UV) light, and mid-wavelength–sensitive cones (M-cones; λ_max 508 nm), which are maximally sensitive to green light (2). The ipRGCs project to the suprachiasmatic nuclei (SCN) of the hypothalamus, hereby subserving photoentrainment of the major pacemaker for circadian rhythms in physiology and behavior (3). The ablation of ipRGCs results in the loss of photoentrainment of circadian rhythms to the environmental light–dark (LD) cycle (1). Although rod and cone photoreceptors are not essential for entrainment of the biological clock to the external LD cycle, both rod and cone photoreceptors influence the SCN, which is evidenced by the experimental finding that mice can entrain to an LD cycle in the absence of melanopsin (4, 5). In addition, recordings in SCN of melanopsin-deficient mice show preservation of sustained light responses in the SCN, the magnitude of which seems unaffected by the absence of melanopsin (6, 7).Whereas rods are capable of driving photoentrainment at a wide range of light intensities (8), the majority of cone-only (Opn4^−/−Gnat1^−/−) mice, which lack melanopsin and functional rod signaling, show surprisingly large interindividual differences in their ability to entrain to LD cycles of white light, and some of them exhibit a positive phase angle of entrainment (9, 10). However, phase-shifting responses in mice lacking M-cones are attenuated (11, 12), which contradicts the reduced ability of Opn4^−/−Gnat1^−/− mice to entrain to an LD cycle. The question is, therefore, to what extent cones contribute to photic entrainment and whether S- and M-cones contribute similarly to the entrainment of the circadian clock.Photoentrainment is dependent on light-induced changes in SCN neuronal activity (13, 14). Typically, SCN neurons respond to light with a transient increase in SCN electrical activity followed by a sustained component throughout light exposure. Together, rod and cone photoreceptors can mediate light responses at the level of the SCN, including both the fast and the sustained components (6, 7, 15). These findings are consistent with rod- and cone-mediated responses recorded in ipRGCs (16–18). In this study, we determined the specific contribution of the S- and M-cone photoreceptors to circadian photoreception. We performed behavioral and in vivo electrophysiological recordings in Opn4^−/−Gnat1^−/− mice to determine the effects of λ_max 365 nm (UV) and λ_max 505 nm (green) light on photoentrainment and on light-induced responses in electrical activity of SCN neurons. Furthermore, we assessed the capability of Opn4^−/−Gnat1^−/− mice to phase shift in response to intermittent monochromatic light pulses aimed to stimulate the UV- or green-sensitive cones.     

Early‐stage development of human induced pluripotent stem cell‐derived neurons

Recent advances in human induced pluripotent stem cells (hiPSCs) offer new possibilities for biomedical research and clinical applications. Differentiated neurons from hiPSCs are expected to be useful for developing novel methods of treatment for various neurological diseases. However, the detailed process of functional maturation of hiPSC‐derived neurons (hiPS neurons) remains poorly understood. This study analyzes development of hiPS neurons, focusing specifically on early developmental stages through 48 hr after cell seeding; development was compared with that of primary cultured neurons derived from the rat hippocampus. At 5 hr after cell seeding, neurite formation occurs in a similar manner in both neuronal populations. However, very few neurons with axonal polarization were observed in the hiPS neurons even after 48 hr, indicating that hiPS neurons differentiate more slowly than rat neurons. We further investigated the elongation speed of axons and found that hiPS neuronal axons were slower. In addition, we characterized the growth cones. The localization patterns of skeletal proteins F‐actin, microtubule, and drebrin were similar to those of rat neurons, and actin depolymerization by cytochalasin D induced similar changes in cytoskeletal distribution in the growth cones between hiPS neurons and rat neurons. These results indicate that, during the very early developmental stage, hiPS neurons develop comparably to rat hippocampal neurons with regard to axonal differentiation, but the growth of axons is slower. © 2015 The Authors. Journal of Neuroscience Research Published by Wiley Periodicals, Inc.