ABSTRACT
Retinal multielectrode array (MEA) recording allows us to examine the action potentials of retinal ganglion cells and field potentials of photoreceptors and bipolar cells. In addition to studying the retinal circuitry, it has become one of the standard examination tools for the characterization of stem cell-derived retinal transplantation in degenerated retinas. Besides the detection of responses to simple light stimulation, it is also necessary to consider the spatial correlation of the graft and the electrodes, in order to unbiasedly reveal the locally reconstructed retinal circuitry after transplantation. Here, we introduce our newly developed protocol of MEA recording and analysis that may serve as a standard for evaluating transplanted retinas.
Subject(s)
Retina/physiology , Stem Cells/physiology , Transplants/physiopathology , Action Potentials/physiology , Animals , Disease Models, Animal , Mice , Microelectrodes , Photic Stimulation/methods , Retinal Degeneration/physiopathology , Retinal Ganglion Cells/physiologyABSTRACT
BACKGROUND: The mouse ether-a-go-go-related gene 1a (mERG1a, mKCNH2) encodes mERG K(+) channels in mouse cardiomyocytes. The mERG channels and their human analogue, hERG channels, conduct IKr. Mutations in hERG channels reduce IKr to cause congenital long-QT syndrome type 2, mostly by decreasing surface membrane expression of trafficking-deficient channels. Three cDNA sequences were originally reported for mERG channels that differ by 1 to 4 amino acid residues (mERG-London, mERG-Waterston, and mERG-Nie). We characterized these mERG channels to test the postulation that they would differ in their protein trafficking and biophysical function, based on previous findings in long-QT syndrome type 2. METHODS AND RESULTS: The 3 mERG and hERG channels were expressed in HEK293 cells and neonatal mouse cardiomyocytes and were studied using Western blot and whole-cell patch clamp. We then compared our findings with the recent sequencing results in the Welcome Trust Sanger Institute Mouse Genomes Project (WTSIMGP). CONCLUSIONS: First, the mERG-London channel with amino acid substitutions in regions of highly ordered structure is trafficking deficient and undergoes temperature-dependent and pharmacological correction of its trafficking deficiency. Second, the voltage dependence of channel gating would be different for the 3 mERG channels. Third, compared with the WTSIMGP data set, the mERG-Nie clone is likely to represent the wild-type mouse sequence and physiology. Fourth, the WTSIMGP analysis suggests that substrain-specific sequence differences in mERG are a common finding in mice. These findings with mERG channels support previous findings with hERG channel structure-function analyses in long-QT syndrome type 2, in which sequence changes in regions of highly ordered structure are likely to result in abnormal protein trafficking.
Subject(s)
Cloning, Molecular , Ether-A-Go-Go Potassium Channels/metabolism , Long QT Syndrome/metabolism , Myocytes, Cardiac/metabolism , Animals , Animals, Newborn , ERG1 Potassium Channel , Ether-A-Go-Go Potassium Channels/genetics , Genetic Predisposition to Disease , HEK293 Cells , Humans , Ion Channel Gating , Long QT Syndrome/genetics , Membrane Potentials , Mice, 129 Strain , Mutation , Phenotype , Protein Transport , Sequence Analysis, DNA , Time Factors , TransfectionABSTRACT
INTRODUCTION: We investigated the mechanism by which the MERG1a K+ channel increases ubiquitin proteasome proteolysis (UPP). METHODS: Hindlimb suspension and electro-transfer of Merg1a cDNA into mouse gastrocnemius muscles induced atrophy. RESULTS: Atrophic gastrocnemius muscles of hindlimb-suspended mice express Merg1a, Murf1, and Mafbx genes. Electrotransfer of Merg1a significantly decreases muscle fiber size (12.6%) and increases UPP E3 ligase Murf1 mRNA (2.1-fold) and protein (23.7%), but does not affect Mafbx E3 ligase expression. Neither Merg1a-induced decreased fiber size nor Merg1a-induced increased Murf1 expression is curtailed significantly by coexpression of inactive HR-Foxo3a, a gene encoding a transcription factor known to induce Mafbx expression. CONCLUSIONS: The MERG1a K+ channel significantly increases expression of Murf1, but not Mafbx. We explored this expression pattern by expressing inactive Foxo3a and showing that it is not involved in MERG1a-mediated expression of Murf1. These findings suggest that MERG1a may not modulate Murf1 expression through the AKT/FOXO pathway.
Subject(s)
Ether-A-Go-Go Potassium Channels/metabolism , Gene Expression Regulation/genetics , Muscle Proteins/metabolism , SKP Cullin F-Box Protein Ligases/metabolism , Ubiquitin-Protein Ligases/metabolism , Analysis of Variance , Animals , ERG1 Potassium Channel , Ether-A-Go-Go Potassium Channels/genetics , Forkhead Box Protein O3 , Forkhead Transcription Factors/genetics , Forkhead Transcription Factors/metabolism , Functional Laterality , Gene Transfer Techniques , Hindlimb Suspension , Male , Mice , Muscle Proteins/genetics , Muscle, Skeletal , Muscular Atrophy/genetics , RNA, Messenger/metabolism , SKP Cullin F-Box Protein Ligases/genetics , Time Factors , Tripartite Motif Proteins , Ubiquitin-Protein Ligases/geneticsABSTRACT
PURPOSE: To report a case of globe perforation and linear retinal tear after periocular acupuncture therapy which resulted in persistent temporal field defect with normal retinal function evidenced by multifocal electroretinogram (MERG). CASE SUMMARY: A 42-year-old female presented with decreased visual acuity and pain in her right eye after a periocular acupuncture therapy for blepharospasm. At initial presentation, the best corrected visual acuity (BCVA) was 0.08 in the injured eye and the intraocular pressure was 15 mmHg. Ultrasonography showed minimal vitreous hemorrhage and fundus examination revealed a linear retinal tear in the posterior pole sparing the macula. Consequently, barrier laser photocoagulation was performed around the lesion. The patient suffered from metamorphopsia and persistent decreased visual acuity even after 3 months. On fundus examination, epiretinal membrane with macular pucker was observed on the macula. Spectral domain optical coherence tomography (SD-OCT) revealed retinal nerve fiber layer defect with a full-thickness posterior wall tear. Multifocal electroretinogram showed normal retinal function; however, Humphrey visual field test demonstrated field defect corresponding to the injury. A 25-gauge pars plana vitrectomy was performed with membranectomy and ILM peeling. One month postoperatively, improvement in BCVA and metamorphopsia was achieved; however, the scotomata remained unchanged. CONCLUSIONS: Ocular perforation or retinal tear caused by an acupuncture needle is a rare condition that has not been reported previously in Korea. Furthermore, no case of traumatic visual field defect with preserved retinal function has been reported elsewhere. Hence, the authors present a case of isolated visual field defect without retinal dysfunction following full-thickness retinal tear caused by an acupuncture needle.
Subject(s)
Adult , Female , Humans , Acupuncture , Acupuncture Therapy , Blepharospasm , Disaccharides , Epiretinal Membrane , Eye , Intraocular Pressure , Korea , Light Coagulation , Needles , Nerve Fibers , Retinal Perforations , Retinaldehyde , Tomography, Optical Coherence , Vision Disorders , Visual Acuity , Visual Field Tests , Visual Fields , Vitrectomy , Vitreous HemorrhageABSTRACT
PURPOSE: To investigate the effects of transcorneal electrical stimulation (TES) on eyes that have a branch retinal artery occlusion (BRAO). SUBJECTS AND METHOD: We studied two eyes having a BRAO, with an interval between the onset of symptoms and the beginning of treatment of >16 weeks (longstanding cases), and in three eyes with an interval of <16 weeks (fresh cases). The visual functions of the eyes were assessed by the best-corrected visual acuity (BCVA), multifocal electroretinograms (mfERGs), and automated static perimetry with the Humphrey field analyzer (HFA). The mfERGs were recorded before and 1 month after the TES, and perimetry with the HFA was done before and at 1 and 3 months after the TES. The amplitudes and implicit times of the N1, P1, and N2 components of the mfERGs were analyzed. RESULTS: TES did not alter the BCVA significantly in all eyes, but it led to a significant increase in the amplitude of the N2 wave of the mfERGs (P < 0.01). The amplitude of the N1-P1 was also increased but not significantly. The implicit times of N1 (P < 0.01) and P1 (P < 0.05) were significantly shorter than that before the TES. The mean deviation of the HFA was increased after the TES but only in the longstanding cases. CONCLUSION: Our results indicate that TES improves the visual function in eyes with BRAO, mainly in longstanding cases.
ABSTRACT
PURPOSE: To investigate the correlation between the severity of diabetic retinopathy and the responses of multifocal electroretinogram (mERG). METHODS: The amplitude and peak time of mERG was evaluated in a group of 88 diabetics and 20 control subjects. The severity of diabetic retinopathy was determined according to the ETDRS scale using color fundus photographs and fluorescein angiograms. RESULTS: The amplitudes of the summed mERG and the central seven hexagons were significantly lower in diabetic patients compared with control subjects, and the more severe the diabetic retinopathy was , the less the amplitude was (P<0.05). The peak times of the summed mERG and the central seven hexagons were significantly delayed in diabetic patients, and the peak time was increased in parallel with the severity of retinopathy (P<0.05). These significant correlations between mERG responses and the severity of diabetic retinopathy was maintained even after the exclusion of patients with diabetic macular edema. CONCLUSIONS: The macular function in diabetic patients is correlated with the grade of diabetic retinopathy, and mERG may have a clinical application in evaluating macular function in these patients.
Subject(s)
Humans , Diabetic Retinopathy , Fluorescein , Macular EdemaABSTRACT
ObjectiveTo study the correlations among age,sex,eye and mERG results.Methods60 normal eyes of 46 volunteers were divided into 6 groups at different ages.RETIscan 3.12 system of Rodenstock was used to carry out mERG examination.ResultsVariation of mERG parameters among normal eyes was significant.Age,sex and eyes have little influence on mERG results,except latency A was longer in male than in female.The size of pupil and fixation were found to influence the results directly.ConclusionsCare should be exercised in explaining the results.Disease history and other examinations shoud be taken into consideration.Attention should be given to the changes in wave-form and vision mountain in addition to amplitudes and latencies.