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Biomedical subjects

H K Choi

Publications and source records attributed to H K Choi.

120 records · Page 7Linked to original sources
PubMed1988

Octahedral complexes of anti-cancer Pt(IV)(cyclohexyldiamine) agents with 9-methylguanine.

The compounds [Pt(IV)(dach)(9-methylguanine)2X2]2+ (X = Cl, OH) have been prepared and structurally characterized. Their existence shows that it is possible to accommodate two purine bases (in a cis configuration) and four other ligands around a Pt(IV) atom. The geometries of these complexes have very different orientations of the guanine rings as compared to their corresponding Pt(II) counterparts.

Antineoplastic Agents↗
PubMed1983

Preservation of the ureteral blood supply in rat renal transplantation.

A new technique of preserving ureteral blood supply in heterotopic rat renal transplantation is described. This entails leaving an intact gonadal artery in continuity with the donor aortic stump, which is anastomosed to the recipient aorta. Comparison of this technique with conventional methods wherein the spermatic artery is ligated revealed a marked decrease in the incidence of ureteral complications with the former. Preservation of adequate blood supply to the ureter in experimental rat renal transplantation provides more consistent results and lessens the risk of unnecessary animal loss.

Animals↗
PubMed1977

Intoxication caused by interaction of chloramphenicol and phenytoin.

A patient with a brain tumor and seizures who was receiving maintenance doses of phenytoin was given chloramphenicol on three occasions. Her neurological status was both complicated and obscured by the reoccurrence of phenytoin intoxication. Retrospective drug analysis showed a marked elevation of serum concentrations of phenytoin during each course of chloramphenicol.

Chloramphenicol↗
PubMedDate not supplied

Effect of adding non-volatile oil as a core material for the floating microspheres prepared by emulsion solvent diffusion method.

Eudragit microspheres, to float in the gastrointestinal tract, were prepared to prolong a gastrointestinal transit time. To enhance their buoyancy, non-volatile oil was added to the dispersed phase. When an oil component was not miscible with water, over 90% was entrapped within the microspheres and prolonged the floating time of the microspheres. Depending on the solvent ratio, the morphologies of the microspheres were different and the best result was obtained when the ratio of dichloromethane:ethanol:isopropanol was 5:6:4. As the isopropanol portion increased, the time to form microspheres was delayed and the amount of fibre-like substance produced was decreased, due to the slow diffusion rate of the solvent. Compared with microspheres prepared without non-volatile oil, the release rate of the drug from microspheres was faster in all cases tested, except the microspheres containing mineral oil. The solubility of the drug in the non-volatile oil affected the release profiles of the drugs. The non-volatile oil tends to decrease the glass transition temperature of prepared microspheres and change the release profile. The internal morphology of the microspheres was slightly different depending on the entrapped oil phase used. Tiny spherical objects were present at the inner surface of microspheres and the inside of the shell.

Acrylates↗
PubMedDate not supplied

Development of oral drug delivery system using floating microspheres.

Floating acrylic resin microspheres with an internal hollow structure were prepared by a solvent diffusion and evaporation method. The yield of microspheres depended on the diffusion rate of ethanol and/or isopropanol in the organic phase. They were successfully produced when a mixture of ethanol and isopropanol was used instead of ethanol alone. The mixing ratio of components in the organic phase affected the size and the yield of microspheres and the best results were obtained at the volume ratio of ethanol:isopropanol:dichloromethane (8:2:5). Direct introduction of the organic phase into the aqueous phase through a glass tube also significantly improved the yield by avoiding the contact of organic phase with the surface of water. The optimum rotation speed and temperature were 250 rpm and 25 degrees C, respectively. Several different drugs with various physico-chemical properties were used as model drugs for encapsulation and release tests. When a drug had low solubility in dichloromethane and high solubility in both water and a mixture of ethanol/isopropanol, the loading efficiency was the lowest. The release profiles were significantly different depending on the solubility of a drug in the release medium and the physico-chemical properties of an encapsulated drug.

2-Propanol↗
PubMedDate not supplied

Multinucleation of koilocytes is actually multilobation.

In order to clarify the complete cytomorphology of cytopathic changes as a consequence of human papillomavirus (HPV) infection, we performed three-dimensional (3D) reconstruction from confocal fluorescent images. After confirming 22 HPV types using a DNA chip, we performed 3D confocal image restoration in human uterine cervical swab samples and corresponding tumor tissues. On restoration of 3D confocal images, the multinucleated feature of koilocytes was revealed to be multilobation of a single nucleus, as opposed to true multinucleation.

Cell Nucleus↗
PubMedDate not supplied

MR imaging of intersexuality.

Intersexuality involves an intermingling of the characteristics of each sex in varying degrees as a result of some flaw in embryonic development. Accurate demonstration of genital anatomy is essential for proper gender assignment and for treatment of intersexual disorders. Genital anatomy is well demonstrated with MR imaging, which offers unsurpassed soft-tissue contrast, multiplanar capability, and no radiation exposure. Intersexual disorders can be categorized into female pseudohermaphroditism, male pseudohermaphroditism, gonadal dysgenesis or agenesis, and true hermaphroditism. In female pseudohermaphroditism, MR images show normal internal female genitalia with masculinized external genitalia. In male pseudohermaphroditism, MR images show normal or mildly defective testes with incompletely masculinized external genitalia. In gonadal dysgenesis, combinations of normal, dysgenetic, and streak gonads are seen on MR images; in gonadal agenesis, no gonads are evident. In true hermaphroditism, both testicular and ovarian tissue is seen on MR images. MR imaging is essential for management of intersexual disorders.

Adult↗
PubMedDate not supplied

Cryopreservation of Taxus chinensis suspension cell cultures.

A simple cryopreservation method for suspension cells of Taxus chinensis was established. In this procedure 7 days old suspension cells were used without any pre-culture treatment. At first, cells were incubated in cryoprotectant solution (0.5M DMSO and 0.5M glycerol) on ice for 30 min and then frozen at a cooling rate of 1 degree C/min to -40 degrees C prior to immersion in liquid nitrogen. The average viability of frozen-thawed cells was between 30 to 40%. The recovery of cryopreserved cells in liquid nitrogen for 1 month was accomplished. After rapid thawing, cells were transferred to solid medium and cultivated for 4-6 weeks. The treatment of trehalose as a cryoprotectant enhanced re-growth of frozen-thawed cells. The stable maintenance of paclitaxel biosynthetic ability in cryopreserved cells was confirmed by comparing with that of regularly sub-cultured suspension cells.

Cell Survival↗
PubMedDate not supplied

The effect of vasoactive intestinal polypeptide (VIP) on rabbit cavernosal smooth muscle contractility.

Vasoactive intestinal polypeptide (VIP) has emerged as a possible candidate for a nonadrenergic, noncholinergic inhibitory neurotransmitter in penile erection. In this study, the effect of VIP and its relationship to the adrenergic and cholinergic mechanisms were examined using isolated corpus cavernosal strips from the rabbit penis. The mechanism of action of VIP on corporal relaxation was investigated with respect to the activation of cyclic GMP and the mobilization of calcium and potassium ions. VIP caused a dose-dependent relaxation of the cavernosal strip. Pretreatment with VIP had no effect on the contraction induced by norepinephrine, phenylephrine, and clonidine. VIP had no synergistic effect on the relaxation produced by acetylcholine or isoproterenol. Neither atropine nor propranolol had any blocking effect on the VIP-induced relaxation. Methylene blue decreased the VIP-induced relaxation of the cavernosal strip. VIP had no effect on the contraction induced by KCl at either 20 or 80 mM. In calcium-free high-potassium physiologic salt solution, VIP inhibited the calcium-induced contraction. These results suggests that the mechanism of action of VIP is not mediated through classical adrenergic and cholinergic neurotransmission on rabbit cavernosal strips, but that VIP may exert its action by the activation of cyclic GMP, which may be associated, in part, with the inhibition of calcium influx.

Animals↗
PubMedDate not supplied

ANCA-positive vasculitis associated with allopurinol therapy.

The triggers that induce ANCA-positive vasculitis are largely unknown. In a minority of cases, however, the disease appears to be medication-induced. This report provides the first description of a case of ANCA-positive vasculitis associated with allopurinol treatment.

Allopurinol↗