Rod Outer Segments Research Articles

Heterogeneous flexibility can contribute to chromatin segregation in the cell nucleus.

The highly and slightly condensed forms of chromatin, heterochromatin and euchromatin, respectively, segregate in the cell nucleus. Heterochromatin is more abundant in the nucleus periphery. Here we study the mechanism of heterochromatin segregation by modeling interphase chromosomes as diblock ring copolymers confined in a rigid spherical shell using molecular dynamics simulations. In our model, heterochromatin and euchromatin are distinguished by their bending stiffnesses only, while an interaction potential between the spherical shell and chromatin is used to model lamin-associated proteins. Our simulations indicate that in the absence of attractive interactions between the nuclear shell and the chromatin, most heterochromatin segregates towards the nuclear interior due to the depletion of less flexible heterochromatin segments from the nuclear periphery. This inverted chromatin distribution,which is opposite to the conventional case with heterochromatin dominating at the periphery, is in accord with experimental observations in rod cells. This "inversion" is also found to be independent of the heterochromatin concentration and chromosome number. The chromatin distribution at the periphery found in vivo can be recovered by further increasing the bending stiffness of heterochromatin segments or by turning on attractive interactions between the nuclear shell and heterochromatin. Our results indicate that the bending stiffness of chromatin could be a contributor to chromosome organization along with differential effects of HP1α-driven phase segregation and of loop extruders and interactions with the nuclear envelope and topological constraints.

Low-error, high-speed, and large-scale hardware implementation of retinal photoreceptor cells: Cone and rod cells

In recent times, there has been a significant focus on creating prosthetics and medical interventions to aid in the treatment of diseases, recovery, and the improvement of biological functions. Researchers have particularly directed their attention toward developing hardware models for delicate biological parts such as the brain, heart, nervous system, and. One area of particular interest is the retina, which is the thinnest and innermost layer of the eye. This research paper focuses on the development of a high-speed and low-error hardware implementation for retinal cone and rod cells. Current mathematical models often use multiple nonlinear functions to describe the behavior of these cells. However, these nonlinear functions can sometimes be limiting in terms of speed. In this study, we explore the use of trigonometric functions to approximate the non-linear properties of retinal cone and rod cells, allowing for improved performance. The results of the simulation show that the suggested model is in line with the functioning of primary cone and rod cells, particularly in relation to time characteristics, dynamic response, and margin of error. By implementing the proposed model in Large-Scale (300 cell) on a Virtex-5 Field Programmable Gate Array (FPGA) board, notable benefits were observed. One of these advantages includes increasing the synthesis frequency of the proposed model by 3.35 and 3.44 times faster than the original model for the cone cell and rod cell, respectively. Another advantage is the ability to implement 300 cells of the proposed models on the FPGA, compared to the implementation of a single cell of the original models, with only a two-fold increase in the amount of hardware resources used. The proposed framework is legitimate and features a compact hardware size and suitable network frequency, as demonstrated by the outcomes from implementing the hardware on the Virtex-5 reconfigurable board (FPGA).

Ablation of Fatty Acid Transport Protein-4 Enhances Cone Survival, M-cone Vision, and Synthesis of Cone-Tropic 9-cis-Retinal in rd12 Mouse Model of Leber Congenital Amaurosis.

The canonical visual cycle employing RPE65 as the retinoid isomerase regenerates 11-cis-retinal to support both rod- and cone-mediated vision. Mutations of RPE65 are associated with Leber congenital amaurosis that results in rod and cone photoreceptor degeneration and vision loss of affected patients at an early age. Dark-reared Rpe65-/- mouse has been known to form isorhodopsin that employs 9-cis-retinal as the photosensitive chromophore. The mechanism regulating 9-cis-retinal synthesis and the role of the endogenous 9-cis-retinal in cone survival and function remain largely unknown. In this study, we found that ablation of fatty acid transport protein-4 (FATP4), a negative regulator of 11-cis-retinol synthesis catalyzed by RPE65, increased the formation of 9-cis-retinal, but not 11-cis-retinal, in a light-independent mechanism in both sexes of RPE65-null rd12 mice. Both rd12 and rd12;Fatp4-/- mice contained a massive amount of all-trans-retinyl esters in the eyes, exhibiting comparable scotopic vision and rod degeneration. However, expression levels of M- and S-opsins as well as numbers of M- and S-cones surviving in the superior retinas of rd12;Fatp4-/ - mice were at least twofold greater than those in age-matched rd12 mice. Moreover, FATP4 deficiency significantly shortened photopic b-wave implicit time, improved M-cone visual function, and substantially deaccelerated the progression of cone degeneration in rd12 mice, whereas FATP4 deficiency in mice with wild-type Rpe65 alleles neither induced 9-cis-retinal formation nor influenced cone survival and function. These results identify FATP4 as a new regulator of synthesis of 9-cis-retinal, which is a "cone-tropic" chromophore supporting cone survival and function in the retinas with defective RPE65.

A vector system for single and tandem expression of cloned genes and multi-colour fluorescent tagging in Haloferax volcanii.

Archaeal cell biology is an emerging field expected to identify fundamental cellular processes, help resolve the deep evolutionary history of cellular life, and contribute new components and functions in biotechnology and synthetic biology. To facilitate these, we have developed plasmid vectors that allow convenient cloning and production of proteins and fusion proteins with flexible, rigid, or semi-rigid linkers in the model archaeon Haloferax volcanii. For protein subcellular localization studies using fluorescent protein (FP) tags, we created vectors incorporating a range of codon-optimized fluorescent proteins for N- or C-terminal tagging, including GFP, mNeonGreen, mCherry, YPet, mTurquoise2 and mScarlet-I. Obtaining functional fusion proteins can be challenging with proteins involved in multiple interactions, mainly due to steric interference. We demonstrated the use of the new vector system to screen for improved function in cytoskeletal protein FP fusions, and identified FtsZ1-FPs that are functional in cell division and CetZ1-FPs that are functional in motility and rod cell development. Both the type of linker and the type of FP influenced the functionality of the resulting fusions. The vector design also facilitates convenient cloning and tandem expression of two genes or fusion genes, controlled by a modified tryptophan-inducible promoter, and we demonstrated its use for dual-colour imaging of tagged proteins in H. volcanii cells. These tools should promote further development and applications of archaeal molecular and cellular biology and biotechnology.

In search of the molecular mechanisms of adaptation memory in rods: basic activity of phosphodiesterase

Retinal rods, the photoreceptors responsible for twilight vision, are capable of adapting to a wide range of light levels. The molecular mechanisms of light adaptation have been well studied, but an interesting question is what changes occur in the phototransduction cascade after the adaptive light stimuli are eliminated. Previously, we showed the phenomenon of adaptation memory in amphibian rods: after background illumination photoreceptor sensitivity to light remained reduced for several minutes, while the dark current recovered within 20—30 s. This suggests the existence of additional, as yet unknown, regulatory mechanisms of the phototransduction cascade that act after the adaptive effect of light. In search of specific mechanisms that could explain the effect of adaptation memory, we performed electrophysiological experiments on isolated frog rods to evaluate the basal activity of the effector enzyme of the phototransduction cascade, the phosphodiesterase type 6, in the dark and after saturating background illumination. It was found that the post-adaptation state of rods was characterized by increased basal phosphodiesterase activity, which gradually decreased to the dark level within tens of seconds after turning off the adaptive illumination. These results also suggest that the components of the phototransduction cascade may undergo some unstudied changes after light adaptation.

The rod cell, a small form of Candida albicans, possesses superior fitness to the host gut and adaptation to commensalism.

Candida albicans deploys various morphological forms through complex switching mechanisms, ensuring its survival and thriving as a commensal or pathogen in vastly different human niches. In this study, we demonstrate that a novel ''rod'' morphological form of C. albicans coexists and is interchangeable with previously reported white, gray, and opaque forms, constituting a tetra-stable phenotypic switching system. Rod cells arise from the efg1 mutant of SC5314 cells or from the clinical BJ1097 strain cultured under glucose-free conditions. They are characterized by a distinct gene expression profile and can be stably maintained through in vitro passaging or in vivo inhabitation of the gastrointestinal (GI) tract of mice. Remarkably, the majority of the efg1 mutant cells become rod cells in N-acetylglucosamine (GlcNAc)-containing medium, and the GlcNAc sensor Ngs1 is instrumental in converting the white or gray cells to the rod cells. Conversely, glucose inhibits rod cells through Cph1; consequently, the loss of Cph1 in the efg1 mutant cells permits their conversion to rod cells in glucose-replete media. Notably, rod cells of the efg1/ cph1 mutant display superior adaptation and longer persistence in the murine GI environment than wild-type white cells. Taken together, these findings establish rod cells as a previously unappreciated form that is not only morphologically and transcriptionally distinguishable but also defined by specific genetic and environmental determinants, shedding light on complex fungus-host interactions.

Thresholds and mechanisms of human magnetophosphene perception induced by low frequency sinusoidal magnetic fields

BackgroundVirtually everyone is exposed to power-frequency MF (50/60 Hz), inducing in our body electric fields and currents, potentially modulating brain function. MF-induced electric fields within the central nervous system can generate flickering visual perceptions (magnetophosphenes), which form the basis of international MF exposure guidelines and recommendations protecting workers and the general public. However, magnetophosphene perception thresholds were estimated 40 years ago in a small, unreplicated study with significant uncertainties and leaving open the question of the involved interaction site. MethodsWe used a stimulation modality termed transcranial alternating magnetic stimulation (tAMS), delivering in situ sinusoidal electric fields comparable to transcranial alternating current stimulation (tACS). Magnetophosphene perception was quantified in 81 volunteers exposed to MF (eye or occipital exposure) between 0 and 50 mT at frequencies of 20, 50, 60 and 100 Hz. ResultsReliable magnetophosphene perception was induced with tAMS without any scalp sensation, a major advantage as compared to tACS. Frequency-dependent thresholds were quantified using binary logistic regressions hence allowing to establish condition dependent probabilities of perception. Results support an interaction between induced current density and retinal rod cells. ConclusionBeyond fundamental and immediate implications for international safety guidelines, and for identifying the interaction site underlying phosphene perception (ubiquitous in tACS experiments), our results support exploring the potential of tAMS for the differential diagnosis of retinal disorders and neuromodulation therapy.

C9ORF72 Deficiency Results in Neurodegeneration in the Zebrafish Retina.

Hexanucleotide repeat expansions within the gene C9ORF72 are the most common cause of the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). This disease-causing expansion leads to a reduction in C9ORF72 expression levels in patients, suggesting loss of C9ORF72 function could contribute to disease. To further understand the consequences of C9ORF72 deficiency in vivo, we generated a c9orf72 mutant zebrafish line. Analysis of the adult female spinal cords revealed no appreciable neurodegenerative pathology such as loss of motor neurons or increased levels of neuroinflammation. However, detailed examination of adult female c9orf72-/- retinas showed prominent neurodegenerative features, including a decrease in retinal thickness, gliosis, and an overall reduction in neurons of all subtypes. Analysis of rod and cone cells within the photoreceptor layer showed a disturbance in their outer segment structure and rhodopsin mislocalization from rod outer segments to their cell bodies and synaptic terminals. Thus, C9ORF72 may play a previously unappreciated role in retinal homeostasis and suggests C9ORF72 deficiency can induce tissue specific neuronal loss.

NR2E3 loss disrupts photoreceptor cell maturation and fate in human organoid models of retinal development.

While dysfunction and death of light-detecting photoreceptor cells underlie most inherited retinal dystrophies, knowledge of the species-specific details of human rod and cone photoreceptor cell development remains limited. Here, we generated retinal organoids carrying retinal disease-causing variants in NR2E3, as well as isogenic and unrelated controls. Organoids were sampled using single-cell RNA sequencing (scRNA-Seq) across the developmental window encompassing photoreceptor specification, emergence, and maturation. Using scRNA-Seq data, we reconstruct the rod photoreceptor developmental lineage and identify a branch point unique to the disease state. We show that the rod-specific transcription factor NR2E3 is required for the proper expression of genes involved in phototransduction, including rhodopsin, which is absent in divergent rods. NR2E3-null rods additionally misexpress several cone-specific phototransduction genes. Using joint multimodal single-cell sequencing, we further identify putative regulatory sites where rod-specific factors act to steer photoreceptor cell development. Finally, we show that rod-committed photoreceptor cells form and persist throughout life in a patient with NR2E3-associated disease. Importantly, these findings are strikingly different from those observed in Nr2e3 rodent models. Together, these data provide a road map of human photoreceptor development and leverage patient induced pluripotent stem cells to define the specific roles of rod transcription factors in photoreceptor cell emergence and maturation in health and disease.

A Biochemical and Histological Assessment of Postmortem Changes to the Eyes of Domestic Pigs: A Preliminary Study.

The Postmortem Interval (PMI) is the time from the death of an animal to its discovery. From a veterinary forensic standpoint, an accurate estimation of the PMI is of particular importance, especially with the observed increase in deaths of domestic and wild animals. A preliminary study was conducted using the eyes of domestic pigs. A biochemical analysis was conducted on the vitreous humor of the eye, whilst a histological analysis was conducted on the retina. The eyes were stored at +4 °C and changes were assessed at time intervals of 0, 12, 24, 48, and 120 h. The biochemical analysis during the PMI established a decrease in sodium, chlorine, and glucose concentrations, and a rise in potassium concentration. Accordingly, a simple linear regression showed a significant correlation between changes in concentrations of sodium (Na+), potassium (K+), chloride (Cl-), and glucose, in relation to the PMI. The histological analysis showed evident morphological changes in the retina, which included homogenization of the rod and cone cells, pyknosis of the outer nuclear layer, homogenization of the outer plexiform layer, pyknosis of the inner nuclear layer, homogenization of the inner plexiform layer, and pyknosis of the nuclei of the ganglion layer of the retina.

Possible retinotoxicity of long-term vardenafil treatment

Phosphodiesterase (PDE) inhibitors – such as vardenafil – are used primarily for treating erectile dysfunction via increasing cyclic guanosine monophosphate (cGMP) levels. Recent studies have also demonstrated their significant cardioprotective effects in several diseases, including diabetes, upon long-term, continuous application. However, PDE inhibitors are not specific for PDE5 and also inhibit the retinal isoform. A sustained rise in cGMP in photoreceptors is known to be toxic; therefore, we hypothesized that long-term vardenafil treatment might result in retinotoxicity. The hypothesis was tested in a clinically relevant animal model of type 2 diabetes mellitus. Histological experiments were performed on lean and diabetic Zucker Diabetic Fatty rats. Half of the animals were treated with vardenafil for six months, and the retinal effects were evaluated. Vardenafil treatment alleviated rod outer segment degeneration but decreased rod numbers in some positions and induced changes in the interphotoreceptor matrix, even in control animals. Vardenafil treatment decreased total retinal thickness in the control and diabetic groups and reduced the number of nuclei in the outer nuclear layer. Müller cell activation was detectable even in the vardenafil-treated control animals, and vardenafil did not improve gliosis in the diabetic group. Vardenafil-treated animals showed complex retinal alterations with improvements in some parameters while deterioration in others. Our results point towards the retinotoxicity of vardenafil, even without diabetes, which raises doubts about the retinal safety of long-term continuous vardenafil administration. This effect needs to be considered when approving PDE inhibitors for alternative indications.

Scotopic and Photopic Conventional Visual Acuity and Hyperacuity - Binocular Summation.

The purpose of this study was to determine and compare binocular summation (BiS) of conventional visual acuity (cVA) versus hyperacuity (hVA) for photopic and scotopic luminance conditions as a potential biomarker to assess the outcome of interventions on binocular function. Sixteen young adults (age range [years] = 21-31; 8 women; cVA logMAR < 0.0) participated in this study. The Freiburg Visual Acuity Test (FrACT) was used for VA testing and retested on another day. Both cVA and hVA were determined for dark grey optotypes on light grey background. Participants underwent 40minutes of dark adaptation prior to scotopic VA testing. Binocular and monocular VA testing was performed. The eye with better VA over the 2 days of testing was selected, the BiS was quantified (binocular VA - better monocular VA) and repeated measures ANOVAs were performed. Binocular VA exceeded monocular VA for all luminance conditions, VA-types, and sessions. We report BiS estimates for photopic and scotopic cVA and hVA, (logMAR BiS ± SEM [decimal BiS]): photopic = -0.01 ± 0.01 [1.03] and -0.06 ± 0.03 [1.15]; and scotopic = -0.05 ± 0.01 [1.12] and -0.11 ± 0.04 [1.28], respectively). Improvement for binocular vision estimates ranged from 0.01 to 0.11 logMAR. A repeated-measures ANOVA (RM ANOVA) did not reveal significant effects of LUMINANCE or VA TYPE on BiS, albeit a trend for strongest BiS for scotopic hVA (15% vs. 28%, photopic versus scotopic, respectively) and weakest for photopic cVA (3% vs. 12%, photopic versus scotopic conditions, respectively). Our results indicate that BiS of VA is relevant to scotopic and photopic hVA and cVA. It appears therefore a plausible candidate biomarker to assess the outcome of retinal therapies restoring rod or cone function on binocular vision. Binocular summation of visual acuity might serve as a clinical biomarker to monitor therapy outcome on binocular rod and cone-mediated vision.

Investigation on Vision System: Digital FPGA Implementation in Case of Retina Rod Cells.

The development of prostheses and treatments for illnesses and recovery has recently been centered on hardware modeling for various delicate biological components, including the nervous system, brain, eyes, and heart. The retina, being the thinnest and deepest layer of the eye, is of particular interest. In this study, we employ the Nyquist-Based Approximation of Retina Rod Cell (NBAoRRC) approach, which has been adapted to utilize Look-Up Tables (LUTs) rather than original functions, to implement rod cells in the retina using cost-effective hardware. In modern mathematical models, numerous nonlinear functions are used to represent the activity of these cells. However, these nonlinear functions would require a substantial amount of hardware for direct implementation and may not meet the required speed constraints. The proposed method eliminates the need for multiplication functions and utilizes a fast, cost-effective rod cell device. Simulation results demonstrate the extent to which the proposed model aligns with the behavior of the primary rod cell model, particularly in terms of dynamic behavior. Based on the results of hardware implementation using the Field-Programmable Gate Arrays (FPGA) board Virtex-5, the proposed model is shown to be reliable, consume 30 percent less power than the primary model, and have reduced hardware resource requirements. Based on the results of hardware implementation using the reconfigurable FPGA board Virtex-5, the proposed model is reliable, uses 30% less power consumption than the primary model in the worth state of the set of approximation method, and has a reduced hardware resource requirement. In fact, using the proposed model, this reduction in the power consumption can be achieved. Finally, in this article, by using the LUT which is systematically sampled (Nyquist rate), we were able to remove all costly operators in terms of hardware (digital) realization and achieve very good results in the field of digital implementation in two scales of network and single neuron.

Acute Myeloid Leukemia in a Three-Year-Old Girl Mimicking Chronic Myeloid Leukemia in Blast Crisis, Challenge in Diagnosis and Treatment in Limited-Resourced Health Care Facility: A Case Report

Introduction: : Acute myeloid leukemia (AML) is the second most common hematologic cancer in childhood. Clinically, AML has similar symptoms to other types of leukemias, and diagnosis remains a challenge due to limited access to pediatric hemato-oncology diagnostic examination. This study aims to report AML in a 3-year-old girl who was first suspected of Chronic Myeloid Leukemia (CML) in blast crisis, using a combination of clinical-hematology parameters and conventional morphology examination in a limited-resourced healthcare facility. Case Presentation: A 3-year-old girl was referred from a rural Eastern Indonesia hospital with symptoms of prolonged fever, leucocytosis, severe anemia, and severe thrombocytopenia. In the previous hospital, the patient had a history of hyperleukocytosis and peripheral blood smear suspected of CML in blast crisis. A peripheral blood smear was repeated in our hospital and showed findings of Auer rod cells suggesting AML. Two bags of packed red cells and 2 thrombocyte concentrations were administered before referral for further diagnostic evaluation with bone marrow aspiration. Bone marrow aspiration revealed multiple nucleoli suggested for AML with FAB classification as M4 subtypes, and she received chemotherapy in a tertiary hospitalConclusions: With limited resources, suspicion based on persistent clinical symptoms, routine hematology tests, and peripheral blood smear examination are important to distinguish AML from CML in blast crisis. Understanding clinical hematology parameters and peripheral blood smears is the first step in AML diagnosis pathway and decision for further diagnostic referral. Supportive therapy and early recognition of oncologic emergency must be done before referral to a tertiary referral hospital.

The Impact of Photopigment Bleaching on the Human Rod Photoreceptor Subretinal Space Measured Via Optical Coherence Tomography.

The purpose of this study was to investigate rod photopigment bleaching-driven intrinsic optical signals (IOS) in the human outer retina and its measurement repeatability based on a commercial optical coherence tomography (OCT) platform. The optical path length of the rod photoreceptor subretinal space (SRS), that is, the distance between signal bands of rod outer segment tips and retinal pigment epithelium, was measured in 15 healthy subjects in ambient light and during a long-duration bleaching white-light exposure. On 2 identical study days (day 1 and day 2 [D1 and D2]), light stimulation resulted in a significant decrease in rod SRS by 21.3 ± 7.6% and 19.8 ± 8.5% (both P<0.001), respectively. The test-retest reliability of the SRS maximum change of an individual subject was moderate for single measures (intraclass correlation coefficient [ICC] = 0.730, 95% confidence interval [CI] = 0.376, 0.900, P<0.001) and good for average measures (ICC = 0.844, 95% CI = 0.546, 0.947, P<0.001). The mean area under the stimulus response curve with values of 14.8 ± 9.4 and 15.5 ± 7.5µm × minutes (P=0.782) showed excellent agreement between the stimulus response on D1 and D2. Intermittent dark adaptation of the retina led to an initial increase of the SRS by 6.1% (P=0.018) and thereafter showed a decrease toward baseline, despite continued dark adaptation. The data indicate the potential of commercial OCT in measuring slow IOS in the outer retina suggesting that the rod SRS could serve as a biomarker for photoreceptor function. The presented approach could provide an easily implementable clinical tool for the early detection of diseases affecting photoreceptor health.

Lipoarabinomannan mediates localized cell wall integrity during division in mycobacteria

The growth and division of mycobacteria, which include clinically relevant pathogens, deviate from that of canonical bacterial models. Despite their Gram-positive ancestry, mycobacteria synthesize and elongate a diderm envelope asymmetrically from the poles, with the old pole elongating more robustly than the new pole. The phosphatidylinositol-anchored lipoglycans lipomannan (LM) and lipoarabinomannan (LAM) are cell envelope components critical for host-pathogen interactions, but their physiological functions in mycobacteria remained elusive. In this work, using biosynthetic mutants of these lipoglycans, we examine their roles in maintaining cell envelope integrity in Mycobacterium smegmatis and Mycobacterium tuberculosis. We find that mutants defective in producing mature LAM fail to maintain rod cell shape specifically at the new pole and para-septal regions whereas a mutant that produces a larger LAM becomes multi-septated. Therefore, LAM plays critical and distinct roles at subcellular locations associated with division in mycobacteria, including maintenance of local cell wall integrity and septal placement.

Retinal response to light exposure in BEST1-mutant dogs evaluated with ultra-high resolution OCT

Mutations in BEST1 cause an autosomal recessive disease in dogs where the earliest changes localize to the photoreceptor-RPE interface and show a retina-wide micro-detachment that is modulated by light exposure. The purpose of this study was to define the spatial and temporal details of the outer retina and its response to light with ultra-high resolution OCT across a range of ages and with different BEST1 mutations. Three retinal regions were selected in each eye: near the fovea-like area, near the optic nerve, both in the tapetal area, and inferior to the optic nerve in the non-tapetal area. The OS+ slab thickness was defined between the peak near the junction of inner and outer segments (IS/OS) and the transition between basal RPE, Bruch membrane, choriocapillaris and proximal tapetum (RPE/T). In wildtype (WT) dogs, two tapetal regions showed additional hyperscattering OCT peaks within the OS+ slab likely representing cone and rod outer segment tips (COST and ROST). The inferior non-tapetal region of WT dogs had only one of these peaks, likely ROST. In dogs with BEST1 mutations, all three locations showed a single peak, likely suggesting optical silence of COST. Light-dependent expansion of the micro-detachment by about 10 um was detectable in both tapetal and non-tapetal retina across all ages and BEST1 mutations.

Perifoveal retinal thickness changes after intravitreal aflibercept injection for choroidal neovascularization in age-related macular degeneration

ObjectiveThere has been some concern that anti-vascular growth factor treatment accelerates the development of macular atrophy in eyes with neovascular age-related macular degeneration. During the treatment with aflibercept, the thickness of choroid may decrease. This may lead to photoreceptor death. The rod cells are more susceptible to atrophic changes than cones during the disease. We aimed to find any thickness changes in the perifoveal outer nuclear layer, where the highest density of rods is found, during the aflibercept intravitreal injection therapy. Materials and MethodsRetrospectively, forty-two patients who were treated for age-related macular degeneration with choroidal neovascularization were included in the study. After the first three loading doses, intravitreal injections were repeated every two months. Outer nuclear layer thicknesses were measured 2000 µm away from the center of the fovea with OCT, at a total of 20 points, located at 180 and 90°. The mean of these measurements was obtained before the treatment and 1 year after the therapy. Results were compared by using the Wilcoxon Rank Test. ResultsThe mean visual acuity was 1,11±0,287 logMAR at the beginning and increased to 0,53±0,32 LogMAR after. Perifoveal thickness was significantly reduced when compared with the thickness before the treatment (p = 0.039, p < 0.05). This result was also significantly lower than the control group thicknesses (p = 0.035, p < 0.05). ConclusionAnti-VEGFs can cause loss of phagocytic functions of RPE. The mechanism of the observed thinning of the ONL may be described as follows: VEGF emitted by the RPE normally helps to maintain the choriocapillaris. Thus, injecting an anti-VEGF intravitreally causes RPE atrophy, which leads to a decrease in the choroidal vascular index. This in turn causes first the rods, and later the cones, that are part of the outer nuclear layer, to start to die and disappear, hence the thinning of this layer. As aflibercept consists of parts of the extracellular domain of both the VEGFR1 and VEGFR2 receptors, that are held together by a human IgG1 backbone, this makes the binding of aflibercept to VEGF-A and VEGF-B stronger as compared to the binding of the previously used ranibizumab or bevacizumab (by nearly a factor 100 in the case of the most abundant isoform VEGF-A 165). Besides, aflibercept also binds very well to placental growth factor (PIGF), which is also associated with several ocular diseases.

WITHDRAWN: Investigating the ERG a-wave and Retinal Diseases with Rod Equivalent Circuit Model Based on the APD

Most empirically supported mathematical models of rod cells lack theoretical support from actual physical devices. Therefore, this paper proposes an equivalent circuit model for the rod is proposed based on the photoconductive properties of the avalanche photodetector (APD) and combined with the electrical properties of the rod. The model employs the photodetector to simulate the source of the photocurrent in outer segments of rod cells and takes into account the electrical properties of the inner and outer segments, the nucleus, and the synaptic terminals. It successfully simulates the trans-retinal voltage generated by the intracellular and extracellular flow of photocurrent in the outer segment of dark-adapted rods. Moreover, the typical waveform characteristics of two retinal diseases, the enhanced short wavelength sensitivity (SWS) cone syndrome and retinitis pigmentosa (RP), are investigated on the basis of electroretinogram (ERG) a-wave. This will further elucidate the function of the visual system and the ERG a-wave characteristics of the related diseases. Comparison with published experimental results validates the reliability of the model presented. Our study provides new ideas and strategies for the diagnosis of retinal diseases and provides some theoretical support for the application of photodetectors in the fabrication of artificial retinal devices.

Minicells as an Escherichia coli mechanism for the accumulation and disposal of fluorescent cadmium sulphide nanoparticles

BackgroundBacterial biosynthesis of fluorescent nanoparticles or quantum dots (QDs) has emerged as a unique mechanism for heavy metal tolerance. However, the physiological pathways governing the removal of QDs from bacterial cells remains elusive. This study investigates the role of minicells, previously identified as a means of eliminating damaged proteins and enhancing bacterial resistance to stress. Building on our prior work, which unveiled the formation of minicells during cadmium QDs biosynthesis in Escherichia coli, we hypothesize that minicells serve as a mechanism for the accumulation and detoxification of QDs in bacterial cells.ResultsIntracellular biosynthesis of CdS QDs was performed in E. coli mutants ΔminC and ΔminCDE, known for their minicell-producing capabilities. Fluorescence microscopy analysis demonstrated that the generated minicells exhibited fluorescence emission, indicative of QD loading. Transmission electron microscopy (TEM) confirmed the presence of nanoparticles in minicells, while energy dispersive spectroscopy (EDS) revealed the coexistence of cadmium and sulfur. Cadmium quantification through flame atomic absorption spectrometry (FAAS) demonstrated that minicells accumulated a higher cadmium content compared to rod cells. Moreover, fluorescence intensity analysis suggested that minicells accumulated a greater quantity of fluorescent nanoparticles, underscoring their efficacy in QD removal. Biosynthesis dynamics in minicell-producing strains indicated that biosynthesized QDs maintained high fluorescence intensity even during prolonged biosynthesis times, suggesting continuous QD clearance in minicells.ConclusionsThese findings support a model wherein E. coli utilizes minicells for the accumulation and removal of nanoparticles, highlighting their physiological role in eliminating harmful elements and maintaining cellular fitness. Additionally, this biosynthesis system presents an opportunity for generating minicell-coated nanoparticles with enhanced biocompatibility for diverse applications.Graphical