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Biomedical subjects

Y Kim

Publications and source records attributed to Y Kim.

At least 703 records · Page 39Linked to original sources
PubMed1993

A new method for computed tomography image compression using adjacent slice data.

RATIONALE AND OBJECTIVES: The authors developed and subjectively evaluated an interslice compression algorithm that explores the redundancy among adjacent slices of an x-ray computed tomography (CT) scan. This algorithm has been compared to an intraslice compression algorithm based on the two-dimensional discrete cosine transform. METHODS: Nine x-ray CT head images from three patients were compressed with this interslice method at compression ratios of 5:1, 10:1, and 15:1. The same images were also compressed with the intraslice method at the same ratios. Six radiologists judged quality of randomly selected compressed and decompressed images compared to that of the originals. The evaluation data were analyzed statistically with the analysis of variance and Tukey's multiple comparison. Kappa-like statistics (Williams index and O'Connell and Dobson indexes) were also calculated to measure the agreement among readers beyond the amount expected by chance. RESULTS: The interslice coding algorithm showed significantly better quality than the intraslice method at significance level 0.05, even though there was no difference in the objective distortion measure (signal-to-noise ratio). Also, the quality of 10:1 compressed images with the interslice coding algorithm was not significantly different from that of the originals at level 0.05. While large variations in agreement occurred among readers, the overall agreement was statistically significant. CONCLUSIONS: By using adjacent slice information in compressing x-ray CT images, significantly better quality in compressed and decompressed images was achieved. While 10:1 compressed images with the interslice algorithm were not significantly different from the originals in quality at level 0.05, effect on diagnostic accuracy remains to be investigated.

Algorithms↗
PubMed1993

Treatment of hyperlipidemia in chronic progressive renal disease.

Experiments in animal models suggest that correcting abnormalities in lipid metabolism could help slow the rate of functional decline in patients with chronic progressive renal disease. Circumstantial evidence in humans also suggests that lipids may play a role in the pathogenesis of glomerulosclerosis. Nevertheless, large controlled clinical trials examining the effect of lipid-lowering strategies on renal disease progression have not been carried out. However, the recent development of antilipemic agents that appear to be safe and effective in patients with renal disease should make it possible to determine whether treating hyperlipidemia will reduce the rate of renal disease progression.

Animals↗
PubMed1993

Identification of methyl jasmonate and salicylic acid response elements from the nopaline synthase (nos) promoter.

Transgenic tobacco plants carrying a fusion between the nopaline synthase (nos) promoter and chloramphenicol acetyltransferase (CAT) reporter gene (cat) were studied for their inducibility by salicylic acid (SA) or methyl jasmonate (MJ) treatments. Either chemical significantly increased CAT activity to a level much higher than that achieved by wounding. Northern blot analysis showed a corresponding increase in mRNA levels. After 20 h of induction of flowering plants, the response to MJ treatment was weaker in old leaves compared with young leaves, whereas the SA response was stronger in old leaves. Kinetic experiments showed that the SA response was much faster than the MJ response, suggesting that the induction mechanism of the nos promoter by these chemicals may differ. Deletion analysis showed that both SA and MJ responses require the DNA sequence between -119 and -112 from the transcription initiation site. This region contains the hexamer sequence (TGACGT) that has been found to be an important regulatory element for several promoters. The MJ response was also reduced by deletions of the CAAT box region or the sequence between -112 and -101, whereas the SA response was not significantly affected by these deletions. This suggests that the nos upstream region containing the hexamer motif is essential for the SA or MJ response and that the CAAT box region and the sequence immediately downstream from the hexamer motif are required for maximum induction by MJ.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1993

Agreement of visual scoring of sleep stages among many laboratories in Japan: effect of a supplementary definition of slow wave on scoring of slow wave sleep.

The purpose of this study was to elucidate the agreement of visual scoring of all-night polysomnographic recordings among many scores from different laboratories. Ten scorers including the author from different laboratories in Japan scored the same paper recordings of two young male subjects. We calculated the agreement rate for each stage using an epoch by epoch analysis. In both records, the agreement rates for stages 2 and R were high; on the contrary, those for stages 3 and 4 were low. After adding a supplementary definition of high voltage slow wave in deep sleep, we scored the first NREM period of another subject. The mean agreement rate for stage 3 among 10 scorers was significantly higher than those of the two former subjects. However, the agreement for stage 4 did not change so much. This result demonstrates that there is much interrater (laboratory) variability of visual scoring, especially in slow wave sleep. When the result of automatic scoring is compared to that of the visual scoring to evaluate the reliability of automatic scoring, these findings must be considered.

Adult↗
PubMed1993

Lovastatin inhibits proliferation of rat mesangial cells.

Products of intracellular mevalonate metabolism are essential for cell growth and proliferation. Lovastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, blocks the formation of mevalonate and its metabolites, and has been shown to inhibit proliferation of several cell types. In vivo, lovastatin has reduced mesangial cellularity and glomerular injury in experimental renal disease. In this study, we investigated the effects of lovastatin on DNA replication and proliferation in rat glomerular mesangial cells. Growth-arrested mesangial cells were exposed to medium containing 10% fetal bovine serum to stimulate mitogenesis. Lovastatin (1-20 microM) caused a significant (P < 0.05) dose-dependent reduction in DNA synthesis ([3H]thymidine incorporation) which was completely prevented in the presence of exogenous mevalonate (100 microM). Lovastatin (1 microM) inhibited cell proliferation by 90% over a 5-d period, and this was largely overcome by added mevalonate. Exogenous low density lipoprotein (100 micrograms/ml) did not prevent lovastatin inhibition of DNA synthesis. The isoprenoid end product isopentenyl adenine (5 or 50 microM) had little effect on DNA synthesis and cell proliferation in lovastatin-blocked cells. By contrast, the isoprenoid farnesol (5 microM) largely prevented lovastatin inhibition of DNA synthesis. We conclude that mevalonate metabolism is essential for mesangial cell proliferation, possibly through the production of the isoprenoid farnesol. Moreover, the action of lovastatin to reduce experimental glomerular injury may involve a direct effect on mesangial cells.

Adenine↗
PubMed1993

Oxidative modification of low-density lipoproteins by mesangial cells.

Because hypercholesterolemia and mesangial cell proliferation may be important in the pathogenesis of glomerulosclerosis, the effects of low-density lipoprotein (LDL) on human mesangial cell proliferation were evaluated. Native LDL (20 to 200 micrograms/mL) caused a dose-dependent increase in (3H)thymidine incorporation and increased mesangial cell numbers over 96 h. The mitogenic effect of LDL was partially blocked by the inhibition of cytochrome P-450, but not by the inhibition of cyclooxygenase or lipoxygenase pathways. Higher LDL concentrations (1,000 to 2,000 micrograms/mL) inhibited (3H)thymidine incorporation and reduced cell numbers, possibly as a result of the oxidative modification of LDL, indicated by an increase in thiobarbituric reactive substances. This peroxidation of LDL involved superoxide, because superoxide dismutase and butylated hydroxytoluene prevented it, whereas hydroxyl radical scavengers were without effect. Native LDL subjected to chemical oxidation by copper sulfate also inhibited mesangial cell proliferation. These results suggest that low concentrations of LDL may stimulate human mesangial cell proliferation, which may, in turn, cause the production of reactive oxygen molecules. Moreover, the oxidative modification of LDL may mediate the toxic effects of high LDL concentrations on human mesangial cells.

Antioxidants↗
PubMed1993

An application of phase spectral analysis to amplitude-modulation following response.

A phase spectral analysis developed by Fridman (1982) was applied to the detection of amplitude-modulated frequency following response (AMFR) and its clinical usefulness was evaluated. A 1000 Hz sinusoidally amplitude-modulated tone with a modulation frequency of 40 Hz and a modulation depth of 90% was delivered to the right ear of 10 normal-hearing subjects. According to Fridman's technique, an ensemble of sweeps was divided into 10 groups and group averages were obtained. Then phase variances were calculated using fast Fourier transform for the group averages. In order to determine the optimal conditions of analysis for constructing an automatic detection program using phase spectral analysis, frequency spacing, number of sampling points and number of sweeps averaged per group were investigated. The sensitivity of phase spectral analysis for automatic detection of AMFR was also evaluated. The results suggested that the optimal number of sampling points and frequency spacing are 512 points and 4.9 Hz (observation window 204.8 ms), respectively. Concerning the average number of sweeps, the synchrony measure of the frequency component corresponding to the modulation frequency increased as the number of sweeps increased. Furthermore, it was demonstrated that threshold determination by phase spectral analysis is more sensitive than detection of the threshold by visual analysis of waveform configuration.

Adult↗
PubMed1993

The mevalonate pathway: importance in mesangial cell biology and glomerular disease.

Products of intracellular mevalonate metabolism are critical for the growth and proliferation of eukaryotic cells. These products include cholesterol and several nonsterol isoprenoids. The isoprenoid farnesyl is a particularly important intermediate in the mevalonate pathway. Farnesyl can be used to synthesize cholesterol and can also bind covalently to several low molecular mass GTP-binding proteins such as p21 ras. Farnesylated p21 ras may be critical for mitogenic signalling stimulated by growth factors such as platelet-derived growth factor. Inhibitors of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase, such as lovastatin and compactin, block the production of mevalonate and its metabolites. These agents have been shown to inhibit proliferation of many cell types. Recently we demonstrated that lovastatin inhibited proliferation of cultured glomerular mesangial cells. Lovastatin inhibition was overcome by the simultaneous addition of either mevalonate or farnesol, but not by exogenous low density lipoprotein cholesterol. These results suggested that farnesyl is critical for mesangial cell proliferation. In several experimental models of renal disease, chronic lovastatin administration reduced the extent of glomerular injury. The beneficial effects of lovastatin have been attributed to lowering of circulating lipid and lipoprotein levels. In view of recent data, however, it is possible that lovastatin may act to reduce glomerular injury, at least in part, through a direct action on mesangial cell proliferation.

Animals↗
PubMed1993

Interaction between beta blockers and epinephrine on hemodynamics of spontaneously hypertensive rats.

Hypertensive patients treated with nonselective beta adrenergic blocking agents may show remarkable hemodynamic changes with administration of epinephrine clinically. We have attempted to investigate the effects of the interaction between beta blockers (a nonselective beta blocker, pindolol, and a cardioselective beta blocker, acebutolol) and a solution of 2% lidocaine containing 1:80,000 epinephrine on the hemodynamics of conscious spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY), as compared with the normotensive rats. The blood pressures (systolic and diastolic) and heart rate were measured indirectly by the photoplethysmographic tail cuff method. All drugs were administered intraperitoneally. We found that: (1) epinephrine with pindolol or acebutolol pretreatment did not cause significant hemodynamic changes in WKY; (2) in SHR, epinephrine in combination with pindolol induced remarkable hemodynamic changes (in particular, increase in diastolic blood pressure), which were prevented by phentolamine pretreatment, whereas epinephrine with acebutolol pretreatment induced no significant hemodynamic changes in these animals; (3) epinephrine in combination with pindolol caused pulmonary congestion or edema in SHR; this was confirmed by both quantitative analysis and histological investigations. These results suggest that pindolol blocked both beta 1 and beta 2 receptors, and therefore, this resulted in exaggerated alpha effects of epinephrine, a remarkable systemic vasoconstriction, and pulmonary congestion. In a clinical setting, great caution should be paid to the hypertensive patients, who are being treated with nonselective beta blockers, if epinephrine-containing local anesthetics are administered.

Acebutolol↗
PubMed1992

Conformation of beta-methylmelibiose bound to the ricin B-chain as determined from transferred nuclear Overhauser effects.

Transferred nuclear Overhauser effect (TRNOE) experiments have revealed a change in the torsion angles about the alpha-1-6 glycosidic bond of methyl beta-melibioside upon binding of the melibioside to the ricin B-chain (Rb). A full relaxation rate matrix simulation of experimental buildup curves aided in quantitative interpretation of 1D selective inversion recovery TRNOE experiments. The data are consistent with a model in which both major (omega approximately 170 degrees) and minor (omega approximately -60 degrees) conformers for methyl beta-melibioside are significantly populated in solution while the Rb/methyl beta-melibioside complex has little of the minor conformer populated. The results indicate that the ricin B-chain excludes binding of certain ligand conformations on the basis of unfavorable interactions between the protein surface and remote portions of the disaccharide system.

Ligands↗
PubMed1992

Amplification and characterization of an inverted repeat from the Chlamydomonas reinhardtii mitochondrial genome.

Based on the nucleotide (nt) sequences of cob and L2a, two oligodeoxyribonucleotides (oligos) were synthesized and used in the polymerase chain reaction (PCR) to amplify the termini of the Chlamydomonas reinhardtii mitochondrial (mt) genome. A 0.8-kb PCR product was detected by agarose-gel electrophoresis when using unligated mt DNA as the template for PCR. This may have indicated the presence of a naturally occurring circular mt DNA molecule that acted as the PCR template. The 0.8-kb DNA could also be amplified from the linear mt DNA via an intramolecular jump during PCR. The sequence data from the 0.8-kb PCR product, and the right 0.6-kb and left 1-kb terminal fragments of the linear mt DNA, along with Southern hybridization analysis, indicated that a 0.49-kb inverted repeat (IR) sequence is present at the right and left termini of the linear mt DNA. The IR contains A+T-rich clusters, as well as numerous short direct repeats (DR) and IR, and might be involved in the recombination, replication and expression of the C. reinhardtii mt genome.

Animals↗
PubMed1992

Molecular cloning and characterization of catechol 2,3-dioxygenases from biphenyl/polychlorinated biphenyls-degrading bacteria.

Catechol 2,3-dioxygenases were cloned from Alcaligenes sp. KF711, Pseudomonas putida KF715, and Achromobacter xylosoxidans KF701 which are biphenyl/polychlorinated biphenyls-degrading bacteria. All of the cloned enzymes were purified by preparative polyacrylamide gel electrophoresis (PAGE). The purified catechol 2,3-dioxygenases were significantly different from one another in ring-fission activities to catechol and its derivatives. The catechol 2,3-dioxygenase from Alcaligenes sp. KF711 exhibited higher ring-fission activity to 4-chlorocatechol than those from P. putida KF715 and A. xylosoxidans KF701. In electrophoretic mobilities, the three enzymes were different from one another on nondenaturing PAGE but the same on SDS-PAGE.

Alcaligenes↗
PubMed1992

Solid phase synthesis of the proteinase of bovine leukemia virus. Comparison of its specificity to that of HIV-2 proteinase.

The 126-residue proteinase (PR) of bovine leukemia virus (BLV) was synthesized by solid-phase peptide synthesis and its activity was shown using various oligopeptide substrates representing cleavage sites in BLV, human T-cell leukemia virus type 1 (HTLV-1), murine leukemia virus (MuLV) and human immunodeficiency virus type 1 (HIV-1). The specificity of the BLV PR was also compared to that of chemically synthesized human immunodeficiency virus type 2 (HIV-2) PR. Many of the peptides were cleaved at the expected site, however, 6 out of 15 were hydrolyzed only by one of the PRs. Furthermore, one BLV peptide was processed differently by the two enzymes. These results, together with the relative activities and the lack of inhibition of BLV PR by two HIV-1 PR inhibitors, suggest that the BLV PR specificity is substantially different from that of HIV PRs.

Amino Acid Sequence↗