Biomedical subjects

Charlene B Y Kim

Publications and source records attributed to Charlene B Y Kim.

4 recordsLinked to original sources

PubMed2006

Effects of reference electrode location on monopolar-derived multifocal electroretinograms in cynomolgus monkeys.

The purpose of this study is to determine the effect of reference electrode location on the multifocal electroretinographic waveform. Multifocal electroretinograms (mfERGs) were recorded from 20 ocularly normal cynomolgus monkeys. The corneal electrode was an ERG-jet referenced to an ipsilaterally (outer canthus) situated subdermal needle electrode and to the contralateral corneal electrode. Testing was monocular and recordings from both montages were obtained simultaneously. The stimulus array consisted of 103 equal-sized hexagonal elements, which subtended +/-44 degrees about the central visual axis. Mean luminance of the display was 100 cd/m2. First-order (K1) and second-order (first slice) kernels (K2.1) of the mfERG were grouped in (a) 4 rings, representing the central 56 degrees of visual field and (b) in 15-element quadrants. The mfERG waveform measures included amplitude, implicit time, and root mean square (RMS) of the oscillatory potentials (OP) and response waveform. K1 and K2.1 ring and quadrant amplitudes were larger with the contralateral than with the ipsilateral reference, but more notably signal-to-noise ratios (S:N) of the response waveform were always larger with the ipsilateral reference. Implicit times were longer for the contralateral than ipsilateral reference montage. K1 and K2.1 implicit times in males were longer than in females. Quadrant groupings revealed generally larger K1 and K2.1 amplitudes in nasal than in temporal retina.

Animals↗

PubMed2006

Measurement of regional choroidal blood flow in rabbits and monkeys using fluorescent microspheres.

OBJECTIVE: To develop a quantitative measure of regional variation in choroidal blood flow (ChBF). METHODS: Five million 15-microm fluorescent microspheres were injected into the left ventricles of 4 rabbits and 3 monkeys. The fixed globes were bleached, flat mounted, and photomicrographed. After image analysis to locate each microsphere, regional densities and blood flow were determined. RESULTS: Regional variation in ChBF was clearly evident. In the rabbit, a high density of spheres was seen in the visual streak. This was surrounded by a middle peripheral area of low sphere density and a far peripheral region of moderately high density. In the monkeys, sphere density was markedly greater in the macula compared with the periphery. Contour plots produced lines of constant flow that were oval and extended farther nasally than temporally in the monkeys. The ratio of central to peripheral ChBF was much greater in the monkeys than in the rabbits. CONCLUSION: Quantitative assessment of regional ChBF can be performed using a modification of the fluorescent microsphere impaction method. CLINICAL RELEVANCE: This method of determining regional ChBF will be useful for studying the vascular effects of pharmacologic agents and for characterizing animal models of human disease involving the outer retina.

Animals↗

PubMed2006

Multifocal visual evoked potentials in the anesthetized non-human primate.

PURPOSE: To evaluate monkey multifocal visual evoked cortical potentials (mfVEPs) recorded from central and peripheral fields for reliability and isolation from electroretinographic (ERG) activity. METHODS: The mfVEP stimulus consisted of a 7-element hexagonal array that subtended 80 degrees of the central visual field. Recordings were made under intravenous pentobarbital sodium (15 mg/kg) anesthesia. Two monkeys with absent optic nerve and ganglion cell function after combined unilateral optic nerve transection and experimental ocular hypertension (ONT/OHT) were followed longitudinally. In a second study, 16 ophthalmologically normal monkeys were tested once. RESULTS: Testing of the non-transected eye in two transected animals revealed robust first- and second-order kernel, first slice (K1 and K2.1) mfVEPs. Stimulation of the transected eye revealed no contamination of the mfVEP from the concurrently recorded multifocal ERGs. There was complete separation of the root-mean-square (RMS) mfVEP amplitudes from the transected and the fellow eyes tested repeatedly across a 4- to 17- month period. The largest amplitude mfVEP was generated by the central element; however, mfVEPs were recorded from outside the central 20 degrees element. The 16 normal animals showed waveforms similar to the normal eyes of the ONT/OHT animals both in shape and distribution throughout the visual field. A scalar-product measure showed both K1 and K2.1 mfVEPs from central and some peripheral elements were statistically distinct from noise. CONCLUSIONS: mfVEPs can be reliably recorded from non-human primates anesthetized with pentobarbital. Under the recording conditions described, mfVEPs are not contaminated by ERG activity. mfVEPs may be useful in animal models of diseases that differentially affect macular and peripheral visual field responsiveness.

Anesthesia, Intravenous↗

PubMed2004

Interspecies and gender differences in multifocal electroretinograms of cynomolgus and rhesus macaques.

The purpose of this study is to ascertain whether inherent differences exist in the retinal function of two macaque species that are commonly used in experimental glaucoma investigations. We quantified and compared multifocal electroretinograms (mfERGs) from ocularly normal cynomolgus (n = 36) and rhesus (n = 18) monkeys. The stimulus array consisted of 103 equal-sized hexagonal elements, which subtended +/-44 degrees about the central visual axis. Mean luminance of the display was 100 cd/m2. The firstorder kernel (K1) and second-order (first slice) kernel (K2) of the mfERG were averaged into 4 rings radiating from the foveal element, and represented the central 56 degrees of visual field. Fifteen and 30-element segments were used for K1 and K2 quadrant and hemiretinal response determinations, respectively. Response measures for the rings, quadrants, and hemiretinae included K1 amplitude and implicit time, and K1 and K2 oscillatory potentials (OPs) and response amplitude root mean square (RMS). Species, gender, and retinotopic differences were assessed with repeated measures analysis of variance (split plot design). K1 amplitudes of the N1 waves, K1 and K2 OPs and K2 amplitude RMS for the ring, quadrant, and hemiretinal mfERG waveforms were larger in rhesus than in cynomolgus monkeys. Rhesus males (as compared to rhesus females) and cynomolgus females (as compared to cynomolgus males) exhibited larger amplitudes and less delayed implicit times in the central retina. These results demonstrate that species-specific differences in retinal function are evident in cynomolgus and rhesus monkeys. There also were gender-associated differences that varied across species. Thus, investigators should exercise caution when data from species or gender are combined.

Animals↗