As part of Korean retinal prosthesis project, we have provided preliminary experimental results regarding voltage parameters for the stimulation of chemically degenerated rabbit retina. Since our APB-treated chemically degenerated retina is only ON-pathway blocked, now we switch our experiments to more appropriate retinal degeneration model, genetically degenerated retina model (RD mouse: rd/rd (C3H/HeJ)). Before studying with RD mouse, we started control experiments with normal SD rat to understand characteristics of retinal ganglion cell activity with postnatal maturation in rodents. Ganglion cell activities were recorded with 8x8 multi-electrode array. Moving spontaneous bursts appeared until postnatal day of 15. During pre-eye opening period, no light evoked response appeared. After postnatal day of 2 weeks (post-eye opening period), ON-, OFF- and ON/OFF response appeared. The fractional distributions of ON, OFF, and ON/OFF ganglion cell is about 40%, 50%, and 5%. The percentage (%) of light evoked response in each dorso-temporal, ventral, and dorso-nasal area of eye is about 50%, 37.5% and 12.5%, respectively. We concluded that the optimal period for experiment in rodent is about postnatal day of 2~3 weeks.
Animals ; Ganglion Cysts ; Mice ; Rats* ; Retina ; Retinal Degeneration ; Retinal Ganglion Cells* ; Retinaldehyde* ; Rodentia ; Visual Prosthesis

BACKGROUND: The clinical significance of mean platelet volume (MPV), platelet distribution width (PDW) and megathrombocyte index (MTI) is not clear. METHODS: We examined platelet indices in 900 cases of patients with hematologic disorders and compared them with those of the control to predict thrombopoiesis in the bone marrow. MPV and PDW were measured by Coulter Counter STKS (U.S.A). We calculated megathrombocyte index (MTI, the percentage of megathrombocytes) in the peripheral blood film using ocular micrometer, and examined megakaryocyte number in the bone marrow aspirates. RESULTS: In patients with acute leukemia, and aplastic anemia, MPV and MTI were lower than the control but PDW was higher. In myeloproliferative disorders, all platelet indices were higher, and in ITP (idiopathic thrombocytopenic purpura), MPV and MTI were higher but PDW was not significantly different. MTI was higher in complete remission than initial acute leukemia. All platelet indices were not significantly different between pre- and post-BMT in AML. But in aplastic anemia, MPV and MTI were higher in post-BMT than pre-BMT. MTI was a better index to screen than MPV in the decreased megakaryocyte group, but in increased megakaryocyte group, there was no difference in screening ability between MPV and MTI. CONCLUSIONS: The platelet indices in peripheral blood may be good markers for predicting thrombopoiesis in hematologic disorders and in post chemotherapy of acute leukemia. In addition, after BMT of aplastic anemia, these indices could be used as valuable markers of engraftment.
Anemia, Aplastic ; Blood Platelets* ; Bone Marrow ; Drug Therapy ; Humans ; Leukemia ; Mass Screening ; Mean Platelet Volume ; Megakaryocytes ; Myeloproliferative Disorders ; Thrombopoiesis

Retinal prosthesis is regarded as the most feasible method for the blind caused by retinal diseases such as retinitis pigmentosa (RP) or age related macular degeneration (AMD). Recently Korean consortium launched for developing retinal prosthesis. One of the prerequisites for the success of retinal prosthesis is the optimization of the electrical stimuli applied through the prosthesis. Since electrical characteristics of degenerate retina are expected to differ from those of normal retina, we performed voltage stimulation experiment both in normal and degenerate retina to provide a guideline for the optimization of electrical stimulation for the upcoming prosthesis. After isolation of retina, retinal patch was attached with the ganglion cell side facing the surface of microelectrode arrays (MEA). 8x8 grid layout MEA (electrode diameter: 30micrometer, electrode spacing: 200micrometer, and impedance: 50 k omega at 1 kHz) was used to record in-vitro retinal ganglion cell activity. Mono-polar electrical stimulation was applied through one of the 60 MEA channel, and the remaining channels were used for recording. The electrical stimulus was a constant voltage, charge-balanced biphasic, anodic-first square wave pulse without interphase delay, and 50 trains of pulse was applied with a period of 2 sec. Different electrical stimuli were applied. First, pulse amplitude was varied (voltage: 0.5~3.0 V). Second, pulse duration was varied (100~1,200microns). Evoked responses were analyzed by PSTH from averaged data with 50 trials. Charge density was calculated with Ohm's and Coulomb's law. In normal retina, by varying the pulse amplitude from 0.5 to 3 V with fixed duration of 500 microns, the threshold level for reliable ganglion cell response was found at 1.5 V. The calculated threshold of charge density was 2.123 mC/cm2. By varying the pulse duration from 100 to 1,200microns with fixed amplitude of 2 V, the threshold level was found at 300microns. The calculated threhold of charge density was 1.698 mC/cm2. Even after the block of ON-pathway with L-(1)-2-amino-4-phosphonobutyric acid (APB), electrical stimulus evoked ganglion cell activities. In this APB-induced degenerate retina, by varying the pulse duration from 100 to 1200 microns with fixed voltage of 2 V, the threshold level was found at 300microns, which is the same with normal retina. More experiment with APB-induced degenerate retina is needed to make a clear comparison of threshold of charge density between normal and degenerate retina.
Electric Stimulation ; Electrodes ; Fees and Charges ; Ganglion Cysts ; Interphase ; Jurisprudence ; Macular Degeneration ; Microelectrodes ; Prostheses and Implants ; Retina ; Retinal Diseases ; Retinal Ganglion Cells ; Retinaldehyde ; Retinitis Pigmentosa ; Visual Prosthesis

No abstract available.
Cholesterol* ; Female ; Hypertension, Pregnancy-Induced* ; Lipoproteins* ; Metabolism* ; Pregnancy ; Pregnancy*

Retinal prosthesis is regarded as the most feasible method for the blind caused by retinal diseases such as retinitis pigmentosa or age-related macular degeneration. One of the prerequisites for the success of retinal prosthesis is the optimization of the electrical stimuli applied through the prosthesis. Since electrical characteristics of degenerate retina are expected to differ from those of normal retina, we investigated differences of the retinal waveforms in normal and degenerate retina to provide a guideline for the optimization of electrical stimulation for the upcoming prosthesis. After isolation of retina, retinal patch was attached with the ganglion cell side facing the surface of microelectrode arrays (MEA). 8x8 grid layout MEA (electrode diameter: 30micrometer, electrode spacing: 200micrometer, and impedance: 50 k omega at 1 kHz) was used to record in-vitro retinal ganglion cell activity. In normal mice (C57BL/6J strain) of postnatal day 28, only short duration (<2 ms) retinal spikes were recorded. In rd/rd mice (C3H/HeJ strain), besides normal spikes, waveform with longer duration (~100 ms), the slow wave component was recorded. We attempted to understand the mechanism of this slow wave component in degenerate retina using various synaptic blockers. We suggest that stronger glutamatergic input from bipolar cell to the ganglion cell in rd/rd mouse than normal mouse contributes the most to this slow wave component. Out of many degenerative changes, we favor elimination of the inhibitory horizontal input to bipolar cells as a main contributor for a relatively stronger input from bipolar cell to ganglion cell in rd/rd mouse.
Animals ; Electric Stimulation ; Electrodes ; Ganglion Cysts ; Macular Degeneration ; Mice ; Microelectrodes ; Prostheses and Implants ; Retina ; Retinal Diseases ; Retinal Ganglion Cells ; Retinaldehyde ; Retinitis Pigmentosa ; Visual Prosthesis

No abstract available.
Carcinoma, Transitional Cell*

Since the output of retina for visual stimulus is carried by neurons of very diverse functional properties, it is not adequate to use conventional single electrode for recording the retinal action potential. For this purpose, we used newly developed multichannel recording system for monitoring the simultaneous electrical activities of many neurons in a functioning piece of retina. Retinal action potentials are recorded with an extra-cellular planar array of 60 microelectrodes. In studying the collective activity of the ganglion cell population it is essential to recognize basic functional distinctions between individual neurons. Therefore, it is necessary to detect and to classify the action potential of each ganglion cell out of mixed signal. We programmed M-files with MATLAB for this sorting process. This processing is mandatory for further analysis, e.g. poststimulus time histogram (PSTH), auto-correlogram, and cross-correlogram. We established MATLAB based protocol for waveform classification and verified that this approach was effective as an initial spike sorting method.
Action Potentials ; Classification ; Electrodes ; Ganglion Cysts ; Microelectrodes ; Neurons ; Retina ; Retinal Ganglion Cells* ; Retinaldehyde*

No abstract available.
Ectopia Cordis*

No abstract available.
Sterilization, Tubal*

It is expected that synaptic construction and electrical characteristics in degenerate retina might be different from those in normal retina. Therefore, we analyzed the retinal waveform recorded with multielectrode array in normal and degenerate retina using principal component analysis (PCA) and independent component analysis (ICA) and compared the results. PCA is a well established method for retinal waveform while ICA has not tried for retinal waveform analysis. We programmed ICA toolbox for spatiotemporal analysis of retinal waveform. In normal mouse, the MEA spatial map shows a single hot spot perfectly matched with PCA-derived ON or OFF ganglion cell response. However in rd/rd mouse, the MEA spatial map shows numerous hot and cold spots whose underlying interactions and mechanisms need further investigation for better understanding.
Animals ; Ganglion Cysts ; Mice* ; Passive Cutaneous Anaphylaxis ; Principal Component Analysis ; Retina ; Retinaldehyde* ; Spatio-Temporal Analysis*