Penetrating keratoplasty for corneal amyloidosis in familial amyloidosis, Finnish type.

PURPOSE: To analyze the outcome of penetrating keratoplasty (PK) to the first eye for corneal amyloidosis in familial amyloidosis, Finnish type (FAF). DESIGN: Single-center, retrospective, nonrandomized, interventional, noncomparative case series. PARTICIPANTS: Thirty-one eyes of 31 patients with FAF. INTERVENTION: All patients with FAF who had their first PK in Helsinki University Eye Hospital between January 1, 1990, and August 1, 2011, were identified and a retrospective analysis of the patient charts was performed. MAIN OUTCOME MEASURES: Best spectacle-corrected visual acuity (BCVA), intraoperative and postoperative complications, graft survival, reason for graft failure, and frequency of regrafting. RESULTS: The median follow-up period was 32 months (range, 5-114). After 24 months, the median BCVA was 1.15 on a logarithm of the minimum angle of resolution scale (20/280; mean, 1.1; SD, 0.5) in comparison with the preoperative median BCVA of 1.3 (20/400; mean, 1.3; SD, 0.4). At 24 months, 3 of 18 eyes (17%) had a visual acuity of ≥0.5 (20/63) and 13 of 18 grafts (72%) were clear. Rejection occurred in 6 of 31 primary grafts (19%). Graft failure occurred in 16 of 31 eyes and resulted from surface complications in 11 eyes and additionally from rejection in 5 eyes. Seven eyes needed regrafting (twice in 1 eye). Complications were frequent in the early and late postoperative periods. Presence of preoperative corneal or graft neovascularization was an indicator of a high risk of graft failure and poor visual outcome. CONCLUSIONS: In a minority of FAF patients, PK improves vision. Owing to the high failure risk and guarded visual prognosis after PK, it is important that both the surgeon and the patient have realistic expectations. It may be reasonable to limit PK to cases with bilateral advanced disease. It seems reasonable to optimize ocular surface health and to delay PK.

Femtosecond Laser-Assisted Intrastromal Relaxing Incisions After Penetrating Keratoplasty: Effect of Incision Depth.

PURPOSE: To correlate the efficacy of femtosecond laser-assisted intrastromal relaxing incisions after penetrating keratoplasty with the posterior depth of corneal incisions. METHODS: Twenty eyes of 20 patients were treated for regular postoperative penetrating keratoplasty astigmatism. Sutures had been removed and refraction had stabilized. Ultrasound pachymetry was used to calculate incisional depth. Femtosecond laser-assisted paired arcuate incisions were made inside the graft stroma, leaving 90 µm of intact anterior cornea including epithelium. The intact posterior corneal margin was 10% of the measured corneal thickness for 10 patients (10% group) and 125 µm for the remaining 10 patients (125-µm group). Follow-up visits consisted of biomicroscopy, intraocular pressure measurement, fundus examination, and topographic evaluation using anterior segment optical coherence tomography at 1 and 3 months. Postoperative corneal thickness and the depth of incisions were measured with optical coherence tomography. RESULTS: Corrected distance visual acuity improved from 0.5 to 0.3 logMAR (Snellen: 20/63 to 20/40, P < .05) in the 10% group and remained constant in the 125-µm group. The refractive cylinder decreased by 34% in the 10% group (range: 0% to 60%), but did not change in the 125-µm group. The topographic anterior cylinder decreased in both groups by 48% (range: 0% to 67%) and 13% (range: 0% to 38%), respectively. The smaller the posterior intact corneal margin, the higher the surgically induced astigmatism (P < .05). CONCLUSIONS: Efficacy of femtosecond laser-assisted intrastromal relaxing incisions is correlated with the posterior depth of the incisions. The deeper incisions were more effective.

Impact of amphiphilic biomass-dissolving ionic liquids on biological cells and liposomes.

The toxicity of some promising biomass-dissolving amidinium-, imidazolium-, and phosphonium-based ionic liquids (ILs), toward two different cell lines, human corneal epithelial cells and Escherichia coli bacterial cells, was investigated. In addition, dynamic light scattering (DLS) and ζ potential measurements were used to study the effect of the ILs on the size and surface charge of some model liposomes. Capillary electrophoresis (CE) was used for determination of the electrophoretic mobilities of the liposomes and for determination of the critical micelle concentration (cmc) of the ILs. The toxicity of the phosphonium ILs was highly dependent on the longest linear chain of the IL, due to increasing hydrophobicity, with the long-chain phosphonium ILs being toxic while the shorter-chain versions were significantly less toxic or not toxic at all. Amidinium and imidazolium ILs showed no significant effect on the cells, within the concentration range used. Moreover, the more hydrophobic ILs were found to have a major effect on the surface charges and size distributions of the model liposomes, which can lead to disruption of the lipid bilayer. This indicates that the cytotoxicity is at least to some extent dependent on direct interactions between ILs and the biomembrane.

Antievaporative mechanism of wax esters: implications for the function of tear fluid.

The tear film lipid layer (TFLL) is considered to act as an evaporation barrier and to maintain the tear film intact between blinks. In vitro methods have, however, failed to reproduce this evaporation-retarding effect. Wax esters (WEs) are a major component of the TFLL. Close to their bulk melting temperature, WEs have been found to retard the evaporation of water, but the nature of this mechanism has remained unclear. We studied the interfacial organization of WE films by measuring their isochors and isotherms and evaporation-retarding effect, and we imaged these films by Brewster angle microscopy (BAM). Behenyl palmitoleate (BP) was used as a representative WE because it resembles the WEs found in meibum. At low temperatures, BP forms solid monolayer crystals in which the molecules are organized in a bulk-like extended conformation. Within approximately 3 °C below the bulk melting temperature, these solid monolayer domains coexist with a fluid monolayer film. At temperatures above the bulk melting temperature, BP forms a completely fluid monolayer in which the molecules are in a hairpin conformation. A fluid hairpin monolayer of BP does not significantly retard evaporation, whereas a solid monolayer decreases evaporation by >50%. The results provide a molecular-level rationale for the evaporation-retarding properties of WEs close to their melting temperature.

Increased intravitreal angiopoietin-2 levels associated with rhegmatogenous retinal detachment.

PURPOSE: To explore factors related to pathogenesis of rhegmatogenous retinal detachment (RRD) and development of proliferative vitreoretinopathy (PVR), vitreous levels of angiopoietin-1 and -2 (Ang-1 and -2), previously undefined in RRD, transforming growth factor-(TGF) ß1, vascular endothelial growth factor (VEGF), erythropoietin (EPO) and proteolytic mediators of extracellular matrix remodelling (MMP-2 and -9) were compared in eyes with RRD and eyes with idiopathic macular hole or pucker. METHODS: Vitreous samples were collected from 117 eyes with RRD (study group) and 40 eyes with macular hole or pucker (control group). Growth factors were measured by ELISA and matrix metalloproteinases (MMPs) by gelatin zymography. RESULTS: The mean vitreous concentrations of Ang-2, MMP-2, and MMP-9 were higher (all p < 0.01), whereas concentration of VEGF was lower (p = 0.01) in eyes with RRD relative to controls. Logistic regression analysis identified Ang-2 concentration as a novel marker of RRD (p = 0.0001, OR 48.7). Ang-1, EPO, and total TGF-ß1 levels were not significantly different between the groups. However, TGF-ß1 and MMP-2 were increased in eyes with total RRD compared to those with local RRD (p ≤ 0.05). In eyes with PVR, no differences were observed in any studied marker as compared with non-PVR eyes. CONCLUSIONS: Current results reveal Ang-2 as a key factor upregulated in RRD. It may co-operate with fibrosis-associated factors and contribute to vascular complications such as breakdown of blood-eye barrier and PVR development.

Treatment of postoperative keratoplasty astigmatism using femtosecond laser-assisted intrastromal relaxing incisions.

PURPOSE: To investigate the effectiveness of femtosecond laser-assisted intrastromal relaxing incisions for astigmatism management and establish laser treatment parameters. METHODS: Sixteen eyes of 16 patients had regular astigmatism after penetrating keratoplasty. All sutures had been removed and the refraction was stabilized. Paired arcuate intrastromal incisions were made 180° apart within the graft stroma with a femtosecond laser preserving the epithelium. Follow-up examinations were performed at 1 week, 2 weeks, 1 month, and 3 months. RESULTS: The logMAR corrected distance visual acuity (CDVA) improved from 0.50 ± 0.29 to 0.32 ± 0.23 (Snellen 20/63 to 20/40). Refractive and topographic anterior cylinders decreased from 6.8 ± 2.2 diopters (D) to 3.7 ± 1.7 D and from 9.5 ± 4.8 D to 4.4 ± 2.1 D, respectively. Stabilization of topographic cylinder was observed 1 month postoperatively. The worse the preoperative CDVA was and the higher the preoperative values for the refractive and topographic cylinders were, the higher the surgically induced changes were. Anterior side cut angles at 90° and 120° produced similar results. A bulge of incision occurred in one eye requiring compression sutures. CONCLUSIONS: Significant improvement in CDVA and refractive and topographic cylinders indicated a good effect of femtosecond laser-assisted intrastromal relaxing incisions in reducing astigmatism. No advantage between 90° and 120° anterior side cut angles was found. No infections were recorded and no patient expressed discomfort.

Hyperosmolarity-induced lipid droplet formation depends on ceramide production by neutral sphingomyelinase 2.

Hyperosmolarity (HO) imposes a remarkable stress on membranes, especially in tissues in direct contact with the external environment. Our efforts were focused on revealing stress-induced lipid changes that precede the inflammatory cytokine response in human corneal epithelial cells exposed to increasing osmolarity. We used a lipidomic analysis that detected significant and systematic changes in the lipid profile, highly correlated with sodium concentrations in the medium. Ceramides and triglycerides (TGs) were the most-responsive lipid classes, with gradual increases of up to 2- and 3-fold, respectively, when compared with control. The source of ceramide proved to be sphingomyelin hydrolysis, and neutral sphingomyelinase 2 (NSM2) activity showed a 2-fold increase 1 h after HO stress, whereas transcription increased 3-fold. Both TG accumulation and IL-8 secretion were shown to be dependent on ceramide production by specific knock-down of NSM2. In HCE cells, diglyceride acyltransferase 1 was responsible for the TG synthesis, but the enzyme activity had no effect on cytokine secretion. Hence, NSM2 plays a key role in the cellular response to hyperosmolar stress, and its activity regulates both cytokine secretion and lipid droplet formation.

Dry eye symptoms are increased in mice deficient in phospholipid transfer protein (PLTP).

In the tear fluid the outermost part facing the tear-air interface is composed of lipids preventing evaporation of the tears. Phospholipid transfer protein (PLTP) mediates phospholipid transfer processes between serum lipoproteins and is also a normal component of human tears. To study whether PLTP plays any functional role in tear fluid we investigated PLTP-deficient mice, applying functional and morphologic analyses under normal housing and experimentally induced dry eye conditions. Aqueous tear fluid production, corneal epithelial morphology, barrier function, and occludin expression were assessed. In mice with a full deficiency of functional PLTP enhanced corneal epithelial damage, increased corneal permeability to carboxyfluorescein, and decreased corneal epithelial occludin expression were shown. These pathologic signs were worsened by experimentally induced dry eye both in wild-type and PLTP knock-out mice. Deficiency in the production of tear PLTP in mice is accompanied by corneal epithelial damage, a feature that is typical in human dry eye syndrome (DES). To complement animal experiments we collected tear fluid from human dry eye patients as well as healthy control subjects. Increased tear fluid PLTP activity was observed among DES patients. In conclusion, the presence of PLTP in tear fluid appears to be essential for maintaining a healthy and functional ocular surface. Increased PLTP activity in human tear fluid in DES patients suggests an ocular surface protective role for this lipid transfer protein.

Role of neutral lipids in tear fluid lipid layer: coarse-grained simulation study.

Tear fluid lipid layer (TFLL) residing at the air-water interface of tears has been recognized to play an important role in the development of dry eye syndrome. Yet, the composition, structure, and mechanical properties of TFLL are only partly known. Here, we report results of coarse-grained simulations of a lipid layer comprising phospholipids, free fatty acids, cholesteryl esters, and triglycerides at the air-water interface to shed light on the properties of TFLL. We consider structural as well as dynamical properties of the lipid layer as a function of surface pressure. Simulations revealed that neutral lipids reside heterogeneously between phospholipids at relatively low pressures but form a separate hydrophobic phase with increasing surface pressure, transforming the initial lipid monolayer to a two-layered structure. When the model of TFLL was compared to a one-component phospholipid monolayer system, we found drastic differences in both structural and dynamical properties that explain the prominent role of neutral lipids as stabilizers of the TFLL. Based on our results, we suggest that neutral lipids are able to increase the stability of the TFLL by modulating its dynamical and structural behavior, which is important for the proper function of tear film.

Comparison of lipid sinks in sequestering common intoxicating drugs.

Intravenous lipid emulsion is a recommended treatment for local anesthetic intoxication. The lipid sink theory hypothesizes that the mechanism behind the lipid treatment is the entrapment of toxic drugs in plasma, preventing them from reaching target receptors. Lipid sink treatment has also been used as a last refuge treatment for severe tricyclic antidepressant intoxication with seemingly beneficial results. We selected three drugs, i.e. amiodarone, ketamine, and amitriptyline, that can cause severe intoxication and compared their interactions with two commercial fat emulsions (Intralipid® and ClinOleic®) and one synthetic liposome (80:20 mol% phosphatidylcholine/phosphatidylglycerol) dispersion. The interaction studies were carried out by capillary electrokinetic chromatography and the retention factors and distributions constants of the drugs were calculated. The results demonstrate that there is stronger interaction between the drugs and the synthetic liposome dispersion than with the commercial emulsions.

Chromatographic lipid profiling of stress-exposed cells.

Lipidomics is an emerging field of science not only due to its integral part of cell biology and biophysics but also due to the key role of lipids in the modulation of membrane physical properties, signaling, and cell death regulation. The aim of this study was to characterize changes in N-palmitoyl ceramide concentration and in the global lipid profile in macrophages challenged by oxidized low-density lipoprotein and nutrient deprived hepatocytes. For this purpose, a quantitative targeted method based on gas chromatography-mass spectrometry for the determination of total N-palmitoyl ceramide concentrations in the cellular membranes of cells under stress was used. Ultrahigh-performance liquid chromatography-quadrupole-time of flight mass spectrometry was applied for the comprehensive profiling of lipids. In essence, we found that both models of cellular stress caused an increase in N-palmitoyl ceramide levels. In addition, increased levels of other ceramides were observed as well as up- and down-regulation of several other lipid species.

Temperature-induced structural transition in-situ in porcine lens--changes observed in void size distribution.

The function of mammalian ocular lens is to provide a sharp image to the retina. Accordingly, the lens needs to be transparent and minimize light scattering. To do so the lens fiber cells first loose intracellular organelles, organize the cytoplasm and arrange the fiber cell membranes. Because the fiber cells are metabolically inactive, the plasma membrane becomes the only cellular organelle and consequently, the phase behavior of these membranes determines the physiological state of the lens. Previous studies have shown that lipids extracted from the nuclear and cortical region of human lens show a temperature-induced phase transition close to the body temperature. Yet, the physiological function of this phase transition is not known, and even the presence of the phase transition in intact lenses is unknown. Positron annihilation lifetime spectroscopy (PALS) was used to characterize the sub-nanometer-sized local structure of intact porcine lens and these studies were complemented with differential scanning calorimeter and mass spectrometric analysis in extracted porcine lens lipids. Using PALS, we present evidence for the presence of a temperature-dependent structural transition centered at 35.5 degrees C in-situ in clear extracted porcine lenses. Further studies employing extracted lens lipids and purified egg-yolk sphingomyelin and cholesterol mixtures suggest that the nano-scale transition emerges from the phase behavior of lens lipids. Based on our results, PALS seems to be a viable method for gaining additional information on biological tissues, especially since it enables non-destructive studies on intact tissues.

Molecular organization of the tear fluid lipid layer.

The tear fluid protects the corneal epithelium from drying out as well as from invasion by pathogens. It also provides cell nutrients. Similarly to lung surfactant, it is composed of an aqueous phase covered by a lipid layer. Here we describe the molecular organization of the anterior lipid layer of the tear film. Artificial tear fluid lipid layers (ATFLLs) composed of egg yolk phosphatidylcholine (60 mol %), free fatty acids (20 mol %), cholesteryl oleate (10 mol %), and triglycerides (10 mol %) were deposited on the air-water interface and their physico-chemical behavior was compared to egg-yolk phosphatidylcholine monolayers by using Langmuir-film balance techniques, x-ray diffraction, and imaging techniques as well as in silico molecular level simulations. At low surface pressures, ATFLLs were organized at the air-water interface as heterogeneous monomolecular films. Upon compression the ATFLLs collapsed toward the air phase and formed hemispherelike lipid aggregates. This transition was reversible upon relaxation. These results were confirmed by molecular-level simulations of ATFLL, which further provided molecular-scale insight into the molecular distributions inside and dynamics of the tear film. Similar type of behavior is observed in lung surfactant but the folding takes place toward the aqueous phase. The results provide novel information of the function of lipids in the tear fluid.

Interaction of phospholipid transfer protein with human tear fluid mucins.

In addition to circulation, where it transfers phospholipids between lipoprotein particles, phospholipid transfer protein (PLTP) was also identified as a component of normal tear fluid. The purpose of this study was to clarify the secretion route of tear fluid PLTP and elucidate possible interactions between PLTP and other tear fluid proteins. Human lacrimal gland samples were stained with monoclonal antibodies against PLTP. Heparin-Sepharose (H-S) affinity chromatography was used for specific PLTP binding, and coeluted proteins were identified with MALDI-TOF mass spectrometry or Western blot analysis. Immunoprecipitation assay and blotting with specific antibodies helped to identify and characterize PLTP-mucin interaction in tear fluid. Human tear fluid PLTP is secreted from the lacrimal gland. MALDI-TOF analysis of H-S fractions identified several candidate proteins, but protein-protein interaction assays revealed only ocular mucins as PLTP interaction partners. We suggest a dual role for PLTP in human tear fluid: (1) to scavenge lipophilic substances from ocular mucins and (2) to maintain the stability of the anterior tear lipid film. PLTP may also play a role in the development of ocular surface disease.

Interaction and localization of the retinitis pigmentosa protein RP2 and NSF in retinal photoreceptor cells.

RP2 is a ubiquitously expressed protein encoded by a gene associated with X-linked retinitis pigmentosa (XLRP), a retinal degenerative disease that causes severe vision loss. Previous in vitro studies have shown that RP2 binds to ADP ribosylation factor-like 3 (Arl3) and activates its intrinsic GTPase activity, but the function of RP2 in the retina, and in particular photoreceptor cells, remains unclear. To begin to define the role of RP2 in the retina and XLRP, we have conducted biochemical studies to identify proteins in retinal cell extracts that interact with RP2. Here, we show that RP2 interacts with N-ethylmaleimide sensitive factor (NSF) in retinal cells as well as cultured embryonic kidney (HEK293) cells by mass spectrometry-based proteomics and biochemical analysis. This interaction is mediated by the N-terminal domain of NSF. The E138G and DeltaI137 mutations of RP2 known to cause XLRP abolished the interaction of RP2 with the N-terminal domain of NSF. Immunofluorescence labeling studies further showed that RP2 colocalized with NSF in photoreceptors and other cells of the retina. Intense punctate staining of RP2 was observed close to the junction between the inner and outer segments beneath the connecting cilium, as well as within the synaptic region of rod and cone photoreceptors. Our studies indicate that RP2, in addition to serving as a regulator of Arl3, interacts with NSF, and this complex may play an important role in membrane protein trafficking in photoreceptors and other cells of the retina.

Visualizing spatial lipid distribution in porcine lens by MALDI imaging high-resolution mass spectrometry.

The intraocular lens contains high levels of both cholesterol and sphingolipids, which are believed to be functionally important for normal lens physiology. The aim of this study was to explore the spatial distribution of sphingolipids in the ocular lens using mass spectrometry imaging (MSI). Matrix-assisted laser desorption/ionization (MALDI) imaging with ultra high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to visualize the lipid spatial distribution. Equatorially-cryosectioned, 12 microm thick slices of tissue were thaw-mounted to an indium-tin oxide (ITO) glass slide by soft-landing to an ethanol layer. This procedure maintained the tissue integrity. After the automated MALDI matrix deposition, the entire lens section was examined by MALDI MSI in a 150 microm raster. We obtained spatial- and concentration-dependent distributions of seven lens sphingomyelins (SM) and two ceramide-1-phosphates (CerP), which are important lipid second messengers. Glycosylated sphingolipids or sphingolipid breakdown products were not observed. Owing to ultra high resolution MS, all lipids were identified with high confidence, and distinct distribution patterns for each of them are presented. The distribution patterns of SMs provide an understanding of the physiological functioning of these lipids in clear lenses and offer a novel pathophysiological means for understanding diseases of the lens.

Liposomes for entrapping local anesthetics: a liposome electrokinetic chromatographic study.

Bupivacaine is a lipophilic, long-acting, amide class local anesthetic commonly used in clinical practice to provide local anesthesia during surgical procedures. Several cases of accidental overdose with cardiac arrest and death have been reported since bupivacaine was introduced to human use. Recent case reports have suggested that Intralipid (Fresenius Kabi) is an effective therapy for cardiac toxicity from high systemic concentrations of, e.g. bupivacaine, even though the mechanism behind the interaction is not fully clear yet. Our long-term aim is to develop a sensitive, efficient, and non-harmful lipid-based formulation to specifically trap harmful substances in vivo. In this study, the in vitro interaction of local anesthetics (bupivacaine, prilocaine, and lidocaine) with Intralipid or lipid vesicles containing phosphatidylglycerol, phosphatidylcholine, cardiolipin, cholesterol, and N-palmitoyl-D-erythro-sphingosine (ceramide) was determined by liposome electrokinetic chromatography. The interactions were evaluated by calculating the retention factors and distribution constants. Atomic force microscopy measurements were carried out to confirm that the interaction mechanism was solely due to interactions between the analytes and the moving pseudostationary phase and not by interactions with a stationary lipid phase adsorbed to the fused-silica wall. The heterogeneity of the liposomes was also studied by atomic force microscopy. The liposome electrokinetic chromatography results demonstrate that there is higher interaction between the drugs and negatively charged liposome dispersion than with the commercial Intralipid dispersion.

Interaction of a commercial lipid dispersion and local anesthetics in human plasma: implications for drug trapping by "lipid-sinks".

Interactions between Intralipid dispersion and local anesthetics (bupivacaine, prilocaine, and lidocaine) were investigated. The amount of bupivacaine (the most cardiotoxic analyte of the local anesthetics studied) entrapped in Intralipid in the presence of plasma was studied using an off-line filtration and solid phase extraction method combined with capillary zone electrophoresis for quantification of free unbound bupivacaine. To confirm interactions between the analytes and Intralipid at lower concentrations, direct injection mass spectrometry was used. The use of immobilized Intralipid chromatography-atmospheric pressure ionization-ion trap mass spectrometry in the study of interactions between drugs and Intralipid dispersion is demonstrated. Finally, interactions between Intralipid dispersion and local anesthetics were investigated by electrokinetic capillary chromatography. The electrophoretic mobility of the Intralipid dispersed phase was calculated using the iterative procedure and a homologous series of alkyl phenyl benzoates (C(1)-C(6)), and the retention factors for the analytes were determined.

Proteomics of photoreceptor outer segments identifies a subset of SNARE and Rab proteins implicated in membrane vesicle trafficking and fusion.

The outer segment is a specialized compartment of vertebrate rod and cone photoreceptor cells where phototransduction takes place. In rod cells it consists of an organized stack of disks enclosed by a separate plasma membrane. Although most proteins involved in phototransduction have been identified and characterized, little is known about the proteins that are responsible for outer segment structure and renewal. In this study we used a tandem mass spectrometry-based proteomics approach to identify proteins in rod outer segment preparations as an initial step in defining their roles in photoreceptor structure, function, renewal, and degeneration. Five hundred and sixteen proteins were identified including 41 proteins that function in rod and cone phototransduction and the visual cycle and most proteins previously shown to be involved in outer segment structure and metabolic pathways. In addition, numerous proteins were detected that have not been previously reported to be present in outer segments including a subset of Rab and SNARE proteins implicated in vesicle trafficking and membrane fusion. Western blotting and immunofluorescence microscopy confirmed the presence of Rab 11b, Rab 18, Rab 1b, and Rab GDP dissociation inhibitor in outer segments. The SNARE proteins, VAMP2/3, syntaxin 3, N-ethylmaleimide-sensitive factor, and Munc 18 detected in outer segment preparations by mass spectrometry and Western blotting were also observed in outer segments by immunofluorescence microscopy. Syntaxin 3 and N-ethylmaleimide- sensitive factor had a restricted localization at the base of the outer segments, whereas VAMP2/3 and Munc 18 were distributed throughout the outer segments. These results suggest that Rab and SNARE proteins play a role in vesicle trafficking and membrane fusion as part of the outer segment renewal process. The data set generated in this study is a valuable resource for further analysis of photoreceptor outer segment structure and function.