Search PubMed⌕ Search

Biomedical subjects

Y B Cho

Publications and source records attributed to Y B Cho.

25 records · Page 2Linked to original sources
PubMed1989

Cytochrome c methylation.

In this review, protein methylation is outlined in general terms, highlighting the major amino acids that are methylated and some of the proteins in which they are found. The majority of the review examines the methylation of cytochrome c at Lys-77 of lower eukaryotes as a possible model for methylation studies. Early work involving the purification and characterization of the methyltransferase responsible for this methylation indicated cytochrome c was methylated posttranslationally, yet prior to import into the mitochondria. Methylation in vitro occurred only at the in vivo methylation site and only on cytochrome c. Later studies using in vitro translated apocytochrome c revealed that methylated, as compared with unmethylated, apocytochrome c was imported preferentially into yeast, but not rat liver, mitochondria. Efforts to discover the reasons for this preference have shown that methylation of apocytochrome c dramatically lowers its isoelectric point (against a predicted increase) and decrease its Stokes radius. A possible mechanism for these differences involving the disruption of hydrogen bonds is presented here with space-filling models. Finally, the in vivo significance of this modification is also discussed.

Animals↗
PubMed1984

Preparation of Ng-Monoethyl-L-arginine.

NG-Monoethyl-L-arginine, a putative in vivo product after administration of the potent hepatocarcinogen L-ethionine to rats, has been chemically synthesized by coupling N-ethyl, S- methylthiopseudouronium iodide with alpha-amino-blocked L-ornithine. The structure of the compound as NG-monoethyl-L-arginine was confirmed by 13C NMR. Its elution time on an automatic amino acid analyzer, Rf values using thin-layer chromatography, and isoelectric point have been compared with those of NG-monomethyl-L-arginine.

Arginine↗
PubMedDate not supplied

Short-term effects of iontophoresis on the structure of the guinea pig tympanic membrane.

Guinea pig tympanic membrane was anesthetized iontophoretically. The animals were sacrificed between 2 h and 4 days after the anesthesia and the tympanic membrane was studied histologically by light microscopy and transmission electron microscopy. Edema in the subepidermal connective tissue layer and detachment of the basement membrane from the basal cell layer were observed 2 h after iontophoresis. Eight and 12 h later, the epidermal layer between the handle of the malleus and the bony annulus peeled and retracted towards the bony annulus, leaving only hornified outer epidermis on the fibrous layer. Four days after iontophoresis, the retracted margin of the epidermal layer became greatly thickened and evidence of hyperplasia and migration was observed. This study has demonstrated that iontophoresis of the tympanic membrane produces remarkable histological changes. However, no perforation was observed.

Anesthesia, Local↗
PubMedDate not supplied

In vitro cytotoxicity, pharmacokinetics and ex vivo pharmacodynamics of a new platinum compound, cis-malonato [(4R,5R-4,5-bis(aminomethyl)-1,3-dioxolane-2-spiro-1'-cyclopentane] platinum (II).

The in vitro cytotoxicity of a new platinum complex, cis-malonato [(4R, 5R)-4,5-bis(aminomethyl)-1,3-dioxolane 2- spiro 1' cyclo-pentane]platinum(II) (SKI 2054R) and cisplatin (CDDP) was evaluated against two human stomach adenocarcinoma cell lines (MKN-45 and KATO III) and a human lung adenocarcinoma cell line (PC-14). The in vitro 50% inhibitory concentration (IC50) values of SKI 2054R and CDDP against MKN-45, KATO III, and PC-14 were 1.21 and 0.51, 2.11 and 0.83, and 2.90 and 0.77 micrograms/ml, respectively. The pharma-cokinetic and ex vivo pharmacodynamic studies on SKI 2054R and CDDP were performed in beagle dogs. Equitoxic doses of SKI 2054R and CDDP (7.0 and 3.0 mg/kg, respectively) were administered i.v. bolus to beagle dose in a randomized crossover study. Plasma samples were analyzed for platinum by flameless atomic absorption spectrophotometry. Plasma concentrations of total and ultrafiltrable platinum for the two drugs declined in a biexponential fashion. The mean area under the concentration-tine curve (AUC(0)--> infinity) determined for ultrafiltrable platinum derived from SKI 2054R, as an active component was 6.61 +/- 2.34 micrograms . h/ml (mean +/- S.D.), with an initial half-life of 0.26 +/- 0.14 h, a terminal half-life of 1.57 +/- 0.71 hour, a total clearance of 17.65 +/- 4.99 ml/min/kg, and a steady-state volume of distribution of 1.46 +/- 0.11 l/kg. The ex vivo antitumor activity of SKI 2054R was assessed using the ultrafiltrable plasma against MKN-45, KATO III, and PC-14 by tetrazolium-dye (MTT) assay and was compared with that of CDDP using the antitumor index (ATI) determined from the ex vivo pharmacodynamic results of inhibition rates (%) versus time curves. The mean ATI value recorded for SKI 2054R was higher than that noted for CDDP; however, statistical difference was not observed between SKI 2054R and CDDP, suggesting that the antitumor activity of SKI 2054R is comparable to that of CDDP. These results suggest that SKI 2054R is a new platinum complex which is worth being evaluated further.

Adenocarcinoma↗
PubMedDate not supplied

Pharmacokinetics of a new platinum compound, cis-(glycolato-O,O) [(4R,5R)-4,5-bis(aminomethyl)-1,3-dioxolane-2-spiro-1'-cyclohexane]plat inum (II) in dogs.

A pharmacokinetic study on cis-(glycolato-O,O)/ (4R,5R)-4,5-bis(aminomethyl)-1,3-dioxolane-2-spiro-1'- cyclohexane]platinum(II) (SKI 2032R) was performed in dogs. A single dose of 2.0 mg/kg of SKI 2032R was administered i.v. bolus to three beagle dogs. Plasma samples were analyzed for platinum by flameless atomic absorption spectrophotometry. Plasma concentrations of total and ultrafiltrable platinum for SKI 2032R declined in a biexponential fashion. The mean area under the concentration-time curve (AUC0 --> infinity) determined for ultrafiltrable platinum derived from SKI 2032R, as an active component, was 2.36 +/- 0.23 micrograms. h/ml (mean +/- S.D.), with an initial half-life of 0.23 +/- 0.20 hour, a terminal half-life of 1.32 +/- 0.49 hour, a total clearance of 14.17 +/- 1.50 ml/min/kg, and a steady-state volume of distribution of 1.21 +/- 0.24 l/kg.

Animals↗
PubMedDate not supplied

Pharmacokinetics of platinum following the administration of cis-(glycolato-O,O')[(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1, 3-dioxolane]platinum(II) in dogs.

The pharmacokinetic study on cis-(glycolato-O,O') [(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1,3-dioxolane]-platinum(II) (SKI 2034R, NSC D642489) was performed in beagle dogs. A single dose of 2.0 mg/kg of SKI 2034R was given by i.v. bolus to three beagle dogs. Plasma samples were analyzed for platinum by flameless atomic absorption spectrophotometry. Plasma concentrations of total and ultrafiltrable platinum for SKI 2034R declined in a biexponential fashion. The mean area under the concentration-time curve (AUC0-->infinity) determined for ultrafiltrable platinum derived from SKI 2034R, as an active component, was 2.76 +/- 0.13 micrograms.h/ml (mean +/- S.D.), with an initial half-life of 0.15 +/- 0.09 hour, a terminal half-life of 0.96 +/- 0.12 hour, a total clearance of 12.07 +/- 0.67 ml/min/kg, and a steady-state volume of distribution of 0.82 +/- 0.06 1/kg.

Animals↗