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Biomedical subjects

Y H Kwon

Publications and source records attributed to Y H Kwon.

17 recordsLinked to original sources
PubMed1998

Test-retest variability of blue-on-yellow perimetry is greater than white-on-white perimetry in normal subjects.

PURPOSE: To compare long-term fluctuation of blue-on-yellow automated perimetry with white-on-white automated perimetry in normal subjects. METHODS: White-on-white and blue-on-yellow automated perimetry were performed on a Humphrey Visual Field Analyzer and an Octopus perimeter, both modified for blue-on-yellow perimetry. The study sample consisted of 31 eyes of 31 normal subjects for the Humphrey perimeter and 33 eyes of 33 normal subjects for the Octopus perimeter. After one practice session, each subject completed four testing sessions over a period of 2 to 8 weeks, each separated by at least 1 day. Each testing session consisted of both white-on-white and blue-on-yellow perimetry performed on one eye; the order of the tests was alternated for successive sessions. Long-term fluctuation (expressed as statistical variance) was calculated for each test location. Intersubject variability (expressed as statistical variance) across all subjects was determined for each test location. RESULTS: On the Humphrey perimeter, the long term fluctuation for blue-on-yellow perimetry (4.07 +/- 3.07 dB2) was significantly greater than that for white-on-white perimetry (1.97 +/- 0.99 dB2; P < .001). Long-term fluctuation increased as a function of eccentricity for both blue-on-yellow and white-on-white perimetry. Short-term fluctuation was significantly greater for blue-on-yellow (0.46 +/- 0.25 dB) than that for white-on-white perimetry (0.29 +/- 0.19 dB; P < .02). Finally, the intersubject variability was significantly greater in blue-on-yellow (13.2 +/- 2.8 dB2) than it was in white-on-white perimetry (4.25 +/- 1.13 dB2; P < .001). Similar results were found with the Octopus perimeter. CONCLUSIONS: Long-term fluctuation and short-term fluctuation of blue-on-yellow perimetry are greater than those of white-on-white perimetry in normal subjects. The increased long-term fluctuation requires appropriate statistical approaches when evaluating serial change of blue-on-yellow perimetry.

Adult↗
PubMed1998

Orbital melanoma presenting as orbital cellulitis: a clinicopathologic report.

Most choroidal melanomas are diagnosed when the tumor is still relatively small and confined to the globe. Rarely, these tumors can escape detection and extend through the sclera. They can reach a large size and create significant orbital inflammation. The authors describe a 71-year-old man with orbital cellulitis secondary to a necrotic choroidal melanoma that invaded the orbit. This tumor had minimal intraocular involvement with a large extrascleral component. On histopathologic analysis, the lesion was best classified as a spindle B melanoma with epithelioid areas (mixed melanoma). The patient was treated with an enucleation and postoperative radiation. This report demonstrates that malignancies in the orbit can present as acute infections. Early suspicion, diagnosis, and treatment of these lesions offer the best chance for survival.

Aged↗
PubMed1997

Temporal corneal phacoemulsification in patients with filtered glaucoma.

OBJECTIVE: To evaluate the effect of temporal clear corneal phacoemulsification on intraocular pressure (IOP) in eyes that underwent prior trabeculectomy. DESIGN: Retrospective case-control study. PATIENTS: Forty consecutive patients who underwent temporal clear corneal phacoemulsification subsequent to trabeculectomy (trabeculectomy-phacoemulsification group) were identified, and 40 control patients who underwent trabeculectomy alone (trabeculectomy group) were matched to the case patients for length of follow-up, age, IOP, number of antiglaucoma medications, number of 5-fluorouracil injections, race, sex, and diagnosis. MAIN OUTCOME MEASURES: Intraocular pressure before vs 1 year after phacoemulsification in the trabeculectomy-phacoemulsification group compared with IOP in the trabeculectomy group and survival analysis of IOP control after trabeculectomy in the 2 groups. RESULTS: In the trabeculectomy-phacoemulsification group, IOP 1 year after phacoemulsification was not significantly different from the prephacoemulsification IOP value (P = .65). Kaplan-Meier survival analysis showed that the rates of IOP control 3, 6, and 9 years after trabeculectomy in the trabeculectomy-phacoemulsification group were 80%, 66%, and 44%, respectively; in the trabeculectomy group, these were 79%, 69%, and 55%, respectively. These survival curves were not statistically different (P = .55). CONCLUSION: Cataract surgery by temporal clear corneal phacoemulsification in eyes with filtering blebs after trabeculectomy does not adversely affect long-term IOP control.

Aged↗
PubMed1997

Temporal corneal phacoemulsification in filtered glaucoma patients.

PURPOSE: To evaluate the effect of temporal clear corneal phacoemulsification on intraocular pressure (IOP) in eyes that had prior trabeculectomy. DESIGN: Retrospective case-control study. PATIENTS: Forty consecutive patients (cases; TRAB-PHACO group) who underwent temporal corneal phacoemulsification subsequent to trabeculectomy were identified. Forty patients (controls; TRAB group) who had trabeculectomy alone were matched to the cases for length of follow-up, age, IOP, number of anti-glaucoma medications, number of 5-fluorouracil (5-FU) injections, race, sex and diagnosis. MAIN OUTCOME MEASURES: Comparison of IOP before and one year after phacoemulsification in the TRAB-PHACO group, and comparison with the TRAB group. Survival analysis of IOP control after trabeculectomy in the TRAB-PHACO and TRAB groups. RESULTS: In the TRAB-PHACO group, IOP one year after phacoemulsification was not significantly different from the pre-phacoemulsification IOP value (p = 0.65). Kaplan-Meier survival analysis showed that the rates of IOP control at 3, 6 and 9 years after trabeculectomy in the TRAB-PHACO group were 80%, 66% and 44%; in the TRAB group these were 79%, 69% and 55%. These survival curves were not statistically different (p = 0.55). CONCLUSIONS: Cataract surgery by temporal clear corneal phacoemulsification in eyes with filtering blebs after trabeculectomy does not adversely affect long term IOP control.

Aged↗
PubMed1996

Chronic in vivo sodium azide infusion induces selective and stable inhibition of cytochrome c oxidase.

The effect of chronic subcutaneous infusion of sodium azide on the activity of mitochondrial respiratory chain enzymes was investigated in Sprague-Dawley rats. Treatment with approximately 1 mg/kg/h sodium azide induced chronic, partial inhibition of cytochrome c oxidase, whereas the activities of respiratory complexes I and III were not significantly affected. The inhibition of cytochrome c oxidase was evident by 7 days after infusion began, and the effect was stable for at least 3 weeks. The selectivity of azide for cytochrome c oxidase is discussed in the context of other findings of azide effects on enzymes. The results of the present study indicate that the sodium azide infusion paradigm described here provides a useful tool for the evaluation of selective and stable cytochrome oxidase inhibition in vivo.

Analysis of Variance↗
PubMed1996

Variations in dietary protein but not in dietary fat plus cellulose or carbohydrate levels affect cysteine metabolism in rat isolated hepatocytes.

To determine if previously observed effects of dietary protein on hepatic cysteine metabolism were due specifically to increases in dietary protein or to the accompanying decreases in dietary carbohydrate, two experiments were conducted. In one experiment, rats were fed diets that contained different levels of protein vs. an isocaloric mixture of fat + cellulose and a constant amount of carbohydrate. In the other, rats were fed diets that contained a constant amount of protein but different levels of carbohydrate vs. an isocaloric mixture of fat+cellulose. Diets were fed for 2-3 wk and hepatocytes were then isolated. Hepatic cysteine dioxygenase activity increased and cysteinesulfinate decarboxylase and gamma-glutamylcysteine synthetase activities decreased in a stepwise manner when protein was added to the diet at the expense of fat + cellulose. Changes in cysteine dioxygenase, cysteinesulfinate decarboxylase and gamma-glutamylcysteine synthetase activities were consistent with changes in rates of cysteine catabolism, taurine production and glutathione synthesis, respectively, by intact hepatocytes incubated with 0.2 mmol/L cysteine. When the carbohydrate to fat+ cellulose ratio was varied, but the protein level was held constant, little or no change in enzyme activities or levels of metabolite production was observed. Regulation of the activities of enzymes involved in cysteine metabolism is predominantly due to changes in dietary protein intake and not to the associated changes in intake of other dietary macronutrients.

Adenosine Triphosphate↗
PubMed1996

Swelling of the vesicle is prerequisite for PTH secretion.

Unlike most secretory cells, high extra cellular calcium inhibits rather than stimulates hormonal secretion in several cells such as parathyroid cells, Juxtaglomerular cells and osteoclast. To gain further insight into the common but unique stimulus-secretion coupling mechanism in these cells, bovine parathyroid slices were incubated in various conditions of Krebs-Ringer (KR) solution containing essential amino acids. Parathyroid cells showed the inverse dependency of secretion on extra cellular calcium concentration as we expected. Ammonium acetate overcame the inhibitory effect of 2.5 mM of calcium and the maximum effect was as much as the five times of the basal value, while there was a little additive effect under 0 mM CaCl2. PTH secretion was biphasic according to the change of extra cellular osmolarity and the lowest response was observed at 300 mOsm/l. In Na-rich KR solution, high concentration of nigericin (> 10(-4)M) completely overcame the inhibitory effect of 2.5 mM CaCl2 and the maximum stimulatory effect was 8 times greater whereas it was only 2 times greater without CaCl2. In K-rich KR solution that abolished the K-gradient between the extra cellular solution and the cytoplasm, the rate of PTH secretion increased, and furthermore the addition of nigericin increased the rate of secretion significantly. The results above suggested that the osmotic swelling of the secretory vesicle in parathyroid cells might promote exocytosis as in Juxtaglomerular cells. We propose that the swelling of the vesicle is also prerequisite for secretion in several cells inhibited paradoxically by Ca++, whatever the signal transduction pathway for swelling of the secretory granules induced by the lowering of Ca++ in cytoplasm are.

Acetates↗
PubMed1995

IgA response in mice infected with Neodiplostomum seoulensis.

To observe the production of IgA in Balb/c mice with neodiplostomiasis, 20 mice were infected with each 200 metacercariae of Neodiplostomum seoulenis. Sera and the duodenums were obtained 3, 7, 14, 28 days post-infection (PI) from five mice each group. Neodiplostomum specific IgA in serum by the enzyme-linked immunosorbent assay increased from 7 days PI and persisted till 28 days PI. Immunohistochemistry for IgA was done with sections of the duodenum. The IgA-positive reaction was generally seen in the lamina propria and submucosa. Some of epithelial cells were positive at 7 and 14 days PI. The present finding showed that Neodiplostomun specific IgA antibody increased in serum and that there was local reaction of IgA in the mucosa and submucosa of the duodenum but not directly related with worm expulsion.

Animals↗
PubMed1992

Retinogeniculate EPSPs recorded intracellularly in the ferret lateral geniculate nucleus in vitro: role of NMDA receptors.

We used an in vitro preparation of the ferret lateral geniculate nucleus (LGN) to examine the role of the NMDA class of excitatory amino acid (EAA) receptors in retinogeniculate transmission. Intracellular recordings revealed that blockade of NMDA receptors both shortened the time course and reduced the amplitude of fast and slow components of excitatory postsynaptic potentials (EPSPs) evoked by optic tract stimulation. The amplitude and width of the EPSPs mediated by NMDA receptors increased as membrane potential was depolarized towards spike threshold. Individual LGN cells were influenced to varying extents by blockade of NMDA receptors; NMDA and non-NMDA receptor blockade together attenuated severely the entire retinogeniculate EPSP. The dependence of all components of retinogeniculate EPSPs (and action potentials) on NMDA receptor activation supports the hypothesis that the NMDA receptor participates in fast (less than 10 ms) synaptic events underlying conventional retinogeniculate transmission. The voltage dependence of the NMDA receptor-gated conductance suggests strongly that the transmission of retinal information through the LGN is subject to modulation by extraretinal inputs that affect the membrane potential of LGN neurons.

2-Amino-5-phosphonovalerate↗
PubMed1992

Effect of stimulus contrast and size on NMDA receptor activity in cat lateral geniculate nucleus.

1. We studied the effect of varying excitatory and inhibitory drive on the N-methyl-D-aspartate (NMDA) receptor-mediated component of the visual responses of neurons in the cat dorsal lateral geniculate nucleus (dLGN) by varying the contrast and size of stimuli presented to the receptive fields of these cells. 2. Cells were classified as either on- or off-center, X or Y, and lagged or nonlagged. Stimulus contrast, and hence the amount of excitatory drive, was varied by changing the brightness of a spot, whose size and location matched the cell's receptive field center, relative to a fixed background luminance. Responses to varying contrast were collected from each cell before, during, and after iontophoretic application of D-2-amino-5-phosphonovaleric acid (D-APV), a specific NMDA receptor antagonist. From each contrast-response plot, a sigmoidal curve fit yielded five parameters on which we examined the effect of D-APV: the threshold contrast, saturation contrast, contrast at half saturation (C50), slope (gain) at C50, and saturation response. 3. In most cells, application of D-APV reduced both the saturation response and the gain of the contrast-response curve, but did not reduce or change significantly the threshold contrast, saturation contrast, or C50. 4. Cells varied in their sensitivity to D-APV, but for any given cell, the D-APV-sensitive component was nearly always a linear function of the control visual response level. Thus, for a spot of optimal size, there was a constant proportion of the visual response attributable to NMDA receptors, regardless of the amplitude of the response. 5. When the effect of D-APV on the visual responses to an optimal spot at varying contrasts was compared among different classes of dLGN cells, the visual responses of lagged X cells were reduced to a greater extent than those of either nonlagged X cells or the combined population of nonlagged X and Y cells. 6. Stimulus size (spot diameter) was also varied systematically at a fixed contrast to vary the inhibitory drive to dLGN cells. As stimulus size was increased, the response first increased because of increased stimulation of the receptive field center and then decreased because of increasing amounts of surround inhibition. 7. The D-APV-sensitive component of individual cell responses was greater when the stimulus spot was less than or equal to optimal size than when the spot was larger. Thus the contribution of NMDA receptors to the visual response decreased with increasing surround inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1992

Visual projections routed to the auditory pathway in ferrets: receptive fields of visual neurons in primary auditory cortex.

How does cortex that normally processes inputs from one sensory modality respond when provided with input from a different modality? We have addressed such a question with an experimental preparation in which retinal input is routed to the auditory pathway in ferrets. Following neonatal surgical manipulations, a specific population of retinal ganglion cells is induced to innervate the auditory thalamus and provides visual input to cells in auditory cortex (Sur et al., 1988). We have now examined in detail the visual response properties of single cells in primary auditory cortex (A1) of these rewired animals and compared the responses to those in primary visual cortex (V1) of normal animals. Cells in A1 of rewired animals differed from cells in normal V1: they exhibited larger receptive field sizes and poorer visual responsivity, and responded with longer latencies to electrical stimulation of their inputs. However, striking similarities were also found. Like cells in normal V1, A1 cells in rewired animals exhibited orientation and direction selectivity and had simple and complex receptive field organizations. Furthermore, the degree of orientation and directional selectivity as well as the proportions of simple, complex, and nonoriented cells found in A1 and V1 were very similar. These results have significant implications for possible commonalities in intracortical processing circuits between sensory cortices, and for the role of inputs in specifying intracortical circuitry.

Animals↗
PubMed1991

NMDA and non-NMDA receptors mediate visual responses of neurons in the cat's lateral geniculate nucleus.

1. We have examined the effects of iontophoresing specific antagonists to excitatory amino acid receptors on the visual responses of cells in lamina A or A1 of the cat's lateral geniculate nucleus (LGN). 2. Cells were classified as On- or Off-center, X or Y, and lagged or nonlagged. The effects of antagonists were studied while cells were stimulated with spots of the appropriate contrast covering the receptive-field center. 3. The N-methyl-D-aspartate (NMDA) receptor antagonists D-2-amino-5-phosphonovaleric acid (D-APV) and 3-(+/-)-2-carboxypiperazin-4-yl)- propyl-1-phosphonic acid (CPP), when iontophoresed at doses that specifically antagonized NMDA-induced responses but not kainate-induced responses, reduced the responses of all cell types in the LGN, including X and Y cells, lagged and nonlagged cells, and On- and Off-center cells. 4. The non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), when applied at doses that specifically antagonized kainate-induced responses but not NMDA-induced responses, also reduced the visual responses of each of the cell types in the LGN. 5. We analyzed quantitatively the effects of D-APV and CNQX on LGN cells. D-APV reduced the responses of lagged cells to a greater extent than the responses of nonlagged cells. CNQX reduced the responses of lagged and nonlagged cells to a similar extent. There was no difference in the effect of D-APV or of CNQX on X and Y cells or on On- and Off-center cells. 6. We analyzed the effects of the antagonists on separate components of responses, including an early component comprising the first 100 ms of response and a late component comprising the next 300 ms of response. D-APV reduced the late component of lagged cell responses to a greater extent than either the early component of the same cells or the early or late component of nonlagged cells. CNQX had nearly equivalent effects on both response components of all cell types. 7. These data indicate that NMDA and non-NMDA receptors make similar contributions to the responses of On- and Off-center and X and Y cells in the LGN. Lagged and nonlagged cells are not differentiated with respect to the contribution of non-NMDA receptors to their visual responses. The greater contribution of NMDA receptors to the responses of lagged cells is consistent with the large contribution made by these receptors to the late response components of lagged cells.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1989

Mouse transition protein 1 is translationally regulated during the postmeiotic stages of spermatogenesis.

Transition protein 1 (TP1) is a small basic nuclear protein that functions in chromatin condensation during spermatogenesis in mammals. Here, recently identified cDNA clones encoding mouse transition protein 1(mTP1) were used to characterize the expression of the mTP1 mRNA during spermatogenesis. Southern blot analysis demonstrates that there is a single copy of the gene for transition protein 1 in the mouse genome. Northern blot analysis demonstrates that mTP1 mRNA is a polyadenylated mRNA approximately 600 bases long, which is first detected at the round spermatid stage of spermatogenesis. mTP1 mRNA is not detectable in poly(A)+ RNAs isolated from mouse brain, kidney, liver, or thigh muscle. mTP1 mRNA is translationally regulated in that it is first detected in round spermatids, but no protein product is detectable until approximately 3 days later in elongating spermatids. In total cellular RNA isolated from stages in which mTP1 is synthesized, the mTP1 mRNA is present as a heterogeneous class of mRNAs that vary in size from about 480 to 600 bases. The shortened, heterogeneous mTP1 mRNAs are found in the polysome region of sucrose gradients, while the longer, more homogeneous mTP1 mRNAs are present in the postmonosomal fractions.

Animals↗
PubMed1982

Isolation of Drosophila proteins that bind selectively to left-handed Z-DNA.

An affinity column for isolating Z-DNA binding proteins was made by attaching brominated poly(dG-dC) to Sephadex. Proteins from Drosophila nuclei were prepared and those that could bind to Escherichia coli B-DNA were removed from the solution. The remaining proteins were passed over the Z-DNA affinity column and then eluted with NaCl. Using both direct and competitive filter binding assays, we found that the eluted proteins bind to brominated poly(dG-dC) (Z-DNA) and poly(dG-m5dC) but not to poly(dG-dC) (B-DNA), native or denatured E. coli or calf thymus DNA, or brominated oligonucleotides. The proteins also bind to negatively supercoiled plasmids carrying Z-DNA sequences but not to relaxed or linearized plasmids in which the Z-DNA conformation is no longer present. Gel analysis reveals a mixture of several large proteins up to approximately 150,000 daltons.

Binding, Competitive↗