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Biomedical subjects

M J Cho

Publications and source records attributed to M J Cho.

At least 127 records · Page 7Linked to original sources
PubMed1989

The electrodiagnosis of the carpal tunnel syndrome.

The carpal tunnel syndrome is one of the most commonly discussed subjects among the public, as well as the medical community, these days. Even though this is a rather simple nerve compression, which can be easily corrected, the carpal tunnel syndrome can induce further complications, sometimes leading to total disability of the patient. Early, proper diagnosis and treatment is very vital. Unfortunately, the exact pathomechanism and proper diagnosis is yet to be seen. As electromyographers, the authors would like to re-visit this debatable carpal tunnel syndrome emphasizing the electrodiagnosis. Among the electrodiagnostic tests, comparison of distal motor or sensory latency of the median nerve to the ulnar nerve along with amplitude of the response, was found to be the most sensitive test. Also, the C6 cervical radiculopathy and the pronator syndrome can present similar clinical pictures and require a differentiation. After successful surgery many patients still complain of subjective residual symptoms. The electrophysiologic findings do not correspond to the clinical progress in many cases. The authors also experienced that most of the victims, following successful surgery, still would benefit from a proper exercise program including instruction for proper body mechanics before they return to their previous activities, to lessen the undesirable complications including the reflex sympathetic dystrophy.

Carpal Tunnel Syndrome↗
PubMed1988

Cellular uptake of a fluid-phase marker by human neutrophils from solutions and liposomes.

In assessing the feasibility of utilizing the phagocytic activity of polymorphonuclear leukocytes (PMNs) for a more efficient drug delivery to the cell, the uptake of the fluid-phase marker lucifer yellow CH (LY) at 37 degrees C by human PMNs from LY-containing liposomes was compared with that from solutions. In the presence of 10% autologous serum, the LY uptake at 37 degrees C via phagocytosis of a given PMN source when the concentrations of PMN, LY, and total lipid were in the range of 10(7) cells/ml, 0.5 mg/ml, and 50 mumol/ml, respectively. As expected, the LY uptake via phagocytosis was critically dependent upon the LY entrapment efficiency in the liposome preparation. Interestingly, little LY uptake was found when the serum was heat inactivated (56 degrees C x 30 min). The serum effect was upon liposome vesicles rather than upon the cells. The present study demonstrates that the use of particular drug carriers for targeted drug delivery to PMNs and possible to an extravascular site mediated by the cell infiltration is a viable approach.

Adult↗
PubMed1988

Comprehensive clinical and statistical analysis of hemophilia in Korea.

A Total of 498 cases of hemophilia which were reported by sixteen medical centers in Korea were reviewed and analyzed. Hemophilia A comprised 425 cases (85.3%) and the remaining 73 cases (14.7%) were hemophilia B. One case was female and all other cases were male. There were known hemophilia patients in the family in 43.0% of cases and the involved members were brothers, maternal cousins, maternal uncles, and maternal grandfathers in descending order of frequency. The major symptoms of the patients were hemorrhagic, such as easy bruising and hemarthrosis followed by prolonged bleeding after trauma and soft tissue hematoma. The incidence of hemarthrosis increased significantly with age. The pediatric age group below the age of 15 consisted of 67.1% of the cases. According to the age at diagnosis, half (54.2%) of the severe cases were diagnosed before the age of 1 year. APTT was prolonged over 40 seconds in all cases and 291 cases showed severe prolongation over 80 seconds. Of 498 cases 273 cases (54.8%) belonged to the severe form (factor VII or IX level, less then 1%), whereas 182 cases (36.5%) and 43 cases (8.7%) belonged to the moderate (factor VIII or IX, 2-5%) and mild form (factor VIII or IX, 6-25%), respectively, Chronic arthropathy was present in 236 cases (49.6%), and the incidence increased significantly with age. The management of chronic arthropathy most commonly employed was rehabilitation in 25.4% of cases, but in 50.8% no management was given at all. The involved joints in descending order of frequency were knees, elbows and ankles. The complications were intracranial hemorrhage, Gl bleeding and nerve palsy in 48, 24, and 13 cases, respectively.

Adolescent↗
PubMed1988

Refractoriness to platelet transfusion after single-donor consecutive platelet transfusions and its relationship to platelet antibodies.

In thirty patients with acute leukemia and severe aplastic anemia receiving random single donor platelet transfusions, the development of refractoriness by consecutive platelet transfusions with cytapheresis and its relationship to the appearance of anti-platelet antibodies were investigated. The median number of platelet transfusions inducing refractoriness was 13 times, and 20% of the patients remained unrefractory despite of the repeated multiple platelet transfusions up to 20 to 25 times. The results of anti-platelet antibody tasts by the enzyme-linked immunosorbent assay(ELISA) and immunofluorescent techniques(IFT) showed no statistically significant relationship with the refractoriness (p greater than 0.1). Although there was significant correlation between the results of ELISA and IFT, both tests were insufficient to find out refractoriness even with the use of pooled platelets from multiple donors as target cells. This study shows that 13 single donor platelet transfusions result in refractoriness, that both ELISA and IFT are insufficient to detect refractoriness despite of their significant correlation, and that other methods than these are needed in order to detect alloimmunization.

Adolescent↗
PubMed1987

Purification of heat-labile enterotoxin from an enterotoxin from an enterotoxigenic Escherichia coli of human origin by monoclonal immunoaffinity chromatography.

Heat-labile enterotoxin (LT) was purified from an enterotoxigenic Escherichia coli 015H11 of human origin. The purification steps included French pressure cell disruption of the bacteria, salting-out, DEAE-Sephacel on chromatography. Application of this procedure resulted in a 95.1-fold purification of LT with a yield of 19.9% as determined by rabbit ileal loop assay. The final LT preparation showed only one protein-staining band on polyacrylamide gel electrophoresis, indicating that the purified LT was homogeneous.

Animals↗
PubMed1986

Sequentially labile water-soluble prodrugs of alprazolam.

A 1,4-benzodiazepine analogue alprazolam (1) undergoes ring-opening hydrolysis under acidic conditions to form a triazolobenzophenone (2). At a neutral pH, 2 rapidly and quantitatively cyclizes back to 1. This facile reversible reaction was utilized in developing water-soluble prodrugs of 1 in which the "solubility anchoring" acyl moieties are formyl, acetyl, succinyl, glycyl, leucyl, and gamma-aminobutyryl groups. These compounds were prepared directly from 2 and corresponding acids through DCC coupling in a 1:1 mixture of H2O and THF. They should be stable in aqueous media at room temperature. Promoieties used should be nontoxic at an intended dose level. In vitro human serum hydrolysis study showed that only glycyl and leucyl amides were able to regenerate 1 within a reasonable period of time. Ex vivo competitive receptor binding assay in mice with [3H]flunitrazepam indicated that leucyl amide prodrug should be able to produce a rapid onset of the intrinsic central nervous system activity of 1 when parenterally administered. For all compounds studied, the final outcome of the biological response appears to be kinetically controlled, rather than by an unfavorable equilibrium, particularly by the first step in which the amide bond is hydrolyzed in vivo.

Alprazolam↗
PubMed1985

Serum-catalyzed hydrolysis of metronidazole amino acid esters.

Glycine (Gly), alanine (Ala), valine (Val), leucine (Leu), isoleucine (Ile), phenylalanine (Phe), and lysine (Lys) esters of metronidazole were synthesized using dicyclohexylcarbodiimide (DCC) coupling or a mixed-anhydride route, using tert-butyloxycarbonyl (tert-Boc) amino acids. Human serum-catalyzed hydrolysis of these esters at 37 degrees C give half-lives varying from 4.5 min for the Phe ester to 96 h for the Ile ester. Also determined was the pH-rate profile for hydrolysis in aqueous buffers at 25 degrees C. A linear relationship was observed between the logarithmic value of the hydrolysis rate constant in serum and that of the OH- -catalyzed hydrolysis of cationic esters. This finding may indicate that the esters studied are "equally" poor substrates for binding to the enzymes in serum and, thus, the difference observed in the serum-catalyzed hydrolysis rate is solely derived from the chemical lability of an ester bond. Interestingly, the extent of chemical activation observed in the buffer system appears to be amplified in the serum-catalyzed hydrolysis.

Amino Acids↗
PubMed1983

Kinetics and equilibrium of the reversible alprazolam ring-opening reaction.

Alprazolam underwent a facile 1,4-benzodiazepine ring-opening reaction in an acidic aqueous solution to form a benzophenone compound. The reaction was demonstrated by means of UV, IR, and 1H- and 13C-NMR spectroscopy. Its reverse cyclization reaction to alprazolam occurred when an acidic solution was neutralized. Both the ring-opening and the cyclization rate constants were obtained from the overall rate constant measured at 25 degrees over a pH range of 0.5--8.0; the latter was measured by monitoring the UV spectral change of the reaction. Although the equilibrium was favored for the benzophenone compound in acidic solutions, it was possible to directly measure the cyclization rate at three acidic pH values by providing a sink condition for the product, alprazolam, using a biphasic reaction system. The bell-shaped cyclization rate pH profile was interpreted in terms of a change in the rate-determining step. The pH profile of the ring-opening rate showed an inflection point indicating a different reactivity of mono- and dicationic alprazolam. The apparent equilibrium between alprazolam and the benzophenone compound at a given pH was estimated from the rate constants for the ring-opening and cyclization reactions. The results agree with the apparent pKa measured by a conventional UV spectrophotometry and a titration technique. The pKa of monocationic alprazolam, the reactive species for the covalent hydration, was determined from the pH dependence of the initial absorbance when an alprazolam solution is acidified.

Alprazolam↗
PubMed1982

Metronidazole phosphate--a water-soluble prodrug for parenteral solutions of metronidazole.

To develop a parenteral solution of relatively water-insoluble metronidazole (2-methyl-5-nitro-1H-imidazole-1-ethanol), its phosphate ester was synthesized via two routes. One route utilized 2-cyanoethyl phosphate and the other utilized pyrophosphoryl tetrachloride. The first method used dicyclohexylcarbodiimide as a coupling agent and the cyanoethyl group was removed under mild alkaline conditions. The second method was a one-step procedure in which free acid of metronidazole phosphate was isolated as a crystalline solid. The solubility of metronidazole in various solvents was determined at 25 degrees. From the pH-dependence of its aqueous solubility, the pKa of the conjugate acid of metronidazole was estimated to be 2.62, which agreed well with the pKa values of other nitroimidazoles. Metronidazole phosphate behaved as a zwitterionic compound in an acidic medium with a minimum solubility at pH 2.0. At pH 7, its solubility was approximately 50 times that of metronidazole. The phosphate ester was so soluble at pH higher than 7 that it was difficult to measure the solubility accurately. In human serum, the hydrolysis of metronidazole phosphate followed zero-order kinetics at an initial concentration of 0.25 mg/ml or higher, presumably due to enzyme saturation (0.035 mg/ml/hr at 37 degrees). A reversed-phase HPLC procedure was adopted to monitor the appearance of metronidazole and the disappearance of metronidazole phosphate. Subcutaneous administration of metronidazole phosphate to rats produced a blood level of bioactivity comparable to that observed after administration of metronidazole.

Animals↗
PubMed1982

Reduced hydrolytic lability of epoprostenol in the presence of cationic micelles.

The rapid hydrolysis of epoprostenol to 6-keto-prostaglandin F1 alpha is hydronium ion-catalyzed even at pH 10 or higher. In the presence of 1.0% hexadecyltrimethylammonium chloride, the rate was reduced significantly (1580-fold at pH 2 and 283-fold at a physiological pH). This decrease in the hydrolysis rate is attributed to two causes: favorable partitioning of epoprostenol in the micellar phase and electrostatic repulsion between the hydronium ion and the cationic micellar surface.

Catalysis↗
PubMed1978

Molecular interaction between E-prostaglandins and selected polymers and its potential utilization in oral dosage form design.

Coacervate formation was observed between some E-prostaglandins and povidone in acetonitrile. This molecular interaction was studied using differential scanning calorimetry, IR spectrophotometry, and light microscopy. The structural requirements for coacervate formation between E-prostaglandins and povidone were investigated. Possible utilization of this molecular interaction in the development of E-prostaglandin formulations was explored. The dissolution rate of some insoluble E-prostaglandin esters increased when they were coprecipitated with povidone and polyethylene glycol. For example, the p-hydroxybenzaldehyde semicarbazone ester of 16,16-dimethyldinoprostone dissolved about 200 times faster as a povidone coprecipitate than did the control mixture. Enhancement of the dissolution rate was observed for the povidone coprecipitates of dinoprostone and its p-acetylphenyl and beta-naphthyl exters but not for the p-phenylphenyl ester. Fast dissolving dispersions of the E-prostaglandin esters also could be prepared with the water-insoluble cross-linked polyvinylpyrrolidone. This type of dispersion was nonglassy and easily dispersible in water. Thus, it might have certain advantages over the classical soluble povidone coprecipitates in terms of ease of handling. The degree of enhancement in dissolution of dispersions of cross-linked polyvinylpyrrolidone and E-prostaglandin esters is apparently dependent on the structure of the esters. The potential dissolution enhancement may be related to the strength of the interaction between the macromolecule and the esters, as indicated by the qualitative relationship between the extent of adsorption of the prostaglandins to cross-linked polyvinylpyrrolidone and the dissolution rate enhancement.

Administration, Oral↗
PubMed1978

Phase solubility analysis and PMR study of complexing behavior of dinoprostone with beta-cyclodextrin in water.

The mechanism of inclusion compound formation by dinoprostone (prostaglandin E2) with beta-cyclodextrin was studied by phase solubility analysis and PMR spectroscopy. As indicated by the linear increase of aqueous solubility of dinoprostone with beta-cyclodextrin concentration, some types of molecular interactions definitely exist between dinoprostone and the complexing ligands. The temperature dependence of a 1:1 complex formation constant yielded the following thermodynamic data at 20 degrees : deltaG degrees = -4.11 kcal/mole, deltaH degrees = 7.20 kcal/mole, and deltaS degrees = 10.5 e.u. Since water was the solvent system, these parameters appear to be largely determined by solvent reorganization through hydrogen bonding rather than solely by the binding of desolvated free dinoprostone and beta-cyclodextrin entities. PMR data indicate that dinoprostone is included within the cavity and also interacts with protons on the exterior of the beta-cyclodextrin molecule. A model consisting of a 1:1 complex, in which a dinoprostone molecule is partially included within the cavity and the remainder of the molecule extends around the edge of the opening of the cavity to the exterior of the beta-cyclodextrin molecule, is proposed as the most probable structure of this inclusion compound.

Chemical Phenomena↗
PubMed1978

Chemical stability of prostacyclin (PGI2) in aqueous solutions.

The rate constant for the hydrolysis of prostacyclin (PGI2) to 6-keto-PGF1alpha was measured by monitoring the UV spectral change, over a pH range 6 to 10 at 25 degrees C and the total ionic strength of 0.5 M. The first-order rate constant (kdegreesobs) extrapolated to zero buffer concentration follows an expression, kdegreesobs = kH+ (H+), where kH+ is a second-order rate constant for the specific acid catalyzed hydrolysis. The value of kH+ obtained (3.71 x 10(4) sec-1 M-1) Is estimated approximately 700-fold greater than a kH+ value expected from the hydrolysis of other vinyl ethers. Such an unusually high reactivity of PGI2 even for a vinyl ether is attributed to a possible ring strain release that would occur upon the rate controlling protonation of C5. A Brønsted slope (alpha) of 0.71 was obtained for the acid (including H3O+) catalytic constants, from which a pH independent first-order rate constant for the spontaneous hydrolysis (catalyzed by H2O as a general acid) was estimated to be 1.3 x 10(-6) sec-1. An apparent activation energy (Ea) of 11.85 Kcal/mole was obtained for the hydrolysis at pH 7.48, from which a half-life of PGI2 at 4 degrees C was estimated to be approximately 14.5 min. when the total phosphate concentration is 0.165 M (cf. 3.5 min. at 25 degrees C).

Buffers↗
PubMed1977

Nucleophilic addition of bisulfite ion to prostaglandins E2 and A2: implication in aqueous stability.

Evidence is presented to indicate that the bisulfite ion (HSO3-) adds across the C-9 carbonyl group of dinoprostone (prostaglandin E2) and across the delta 10,11- bond of prostaglandin A2. At room temperature, the apparent equilibrium constant, determined by phase solubility analysis, circular dichroism, UV spectroscopy, and partitioning, for the formation of the bisulfite adduct of dinoprostone is about 7.5 M-1 at neutral pH. From this result and a free energy relationship reported in the literature for the thermodynamics of nucleophilic addition to carbonyl groups, it is concluded that the chemical reactivity of the C-9 carbonyl group of dinoprostone is not high enough to improve aqueous stability through reversible one-step nucleophilic reactions. However, from a series of kinetic experiments, it is concluded that the equilibrium is extremely favorable for the formation of the bisulfite adduct of prostaglandin A2 over pH 4-8 at room temperature. The second-order rate constant for the attack of sulfite ion (SO3 2-) to prostaglandin A2 is 1.75 sec-1 M-1.

Chemical Phenomena↗
PubMed1977

Prostaglandin prodrugs. 5.1 Prostaglandin E2 ethylene ketal.

In order to improve the chemical stability of prostaglanding E2 (2), prostaglanding E2 ethylene ketal (1) was prepred by direct ketalization of 2 with ethylene glycol in benzene. To establish a quantitative assessment of 1 as a chemically stable and orally active prodrug of 2, the hydrolysis of 1 to 2 and the subsequent dehydration of 2 to prostaglandin A2 (3) were followed at 25 degrees C and six pH's ranging from 2.0 to 6.5 by means of a high-pressure liquid chromatographic procedure. Kinetic results clearly indicate that 1 should be quantitively hydrolyzed back to the parent drug 2 dehydration of 2 to 3 are in the order of 1 h and 14 days, respectively. The preliminary data on the biological response after oral administration of 1 appeared to indicate the 1 is bioequivalent to 2.

Acetals↗
PubMed1975

Solubilization and stabilization of the cytotoxic agent coralyne.

Kinetic studies were carried out on the ring opening of the quaternary nitrogen cation, coralynium ion (I), to yield 6'-acetylpapaverine (III), on the cyclization of III to yield I, and on a photochemical reaction undergone by I in aqueous solutions exposed to visible light. From the results, it was concluded that: (a) I and III are in facile equilibrium in aqueous solution but appreciable amounts of III do not exist in dilute solutions with pH values below 10: (b) the photochemical reaction of I in water (presumably a photohydration) can be reversed by lyophilization, by heatiing, and by increasing the pH of solutions to values greater than 12; (c) the photochemical reaction of I can be inhibited by protecting the aqueous solutions from visible light, and the rate in the presence of light can be reduced by increasing the concentration of I in the solution; and (d) although the chloride and sulfoacetate salts of I react identically and have similar solubilities in water, it is possible to prepare more concentrated and, hence, more stable solutions of the sulfoacetate salt by including sodium hydroxide in the solvent. The solubility of coralyne chloride remains about the same in dilute sodium hydroxide as in water.

Antineoplastic Agents↗