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Biomedical subjects

H H Chung

Publications and source records attributed to H H Chung.

35 records · Page 2Linked to original sources
PubMed1992

Biochemical and biological activity of phosphorylated and non-phosphorylated ras p21 mutants.

In contrast to all cellular ras oncogenes which carry a single activating mutation at codon 12, 13 or 61, all known retroviral ras oncogenes have two mutations at codons 12 and 59. To understand the role of the mutation at codon 59, we have constructed plasmids containing genes for Harvey ras: p21(Gly-12,Thr-59) and p21(Val-12,Thr-59). Escherichia coli expressed proteins and their respective phosphorylated (Pi) and non-phosphorylated (non-Pi) proteins were purified to 95% homogeneity by ion-exchange chromatography and gel filtration. GTPase, autophosphorylation and nucleotide exchange activities of the mutants were studied. When the mutants were microinjected into Xenopus oocytes, the non-phosphorylated forms of p21(Gly-12,Thr-59) and p21(Val-12,Thr-59) showed high activity. Surprisingly, their phosphorylated forms were inactive. These results suggest that threonine at position 59 endows the protein with transforming activity but that phosphorylation of the residue inhibits biological activity. A structural interpretation of the observation is presented.

Animals↗
PubMed1992

[The functional assessment of chronic pain patients activity of daily living and psychosocial disability].

The purpose of this study was to investigate the impact of activity of daily living and psychosocial function in patients with chronic nonmalignant pain. From Jun. 1989 to Nov. 1989, one hundred and eleven cases were assessed by Sickness Impact Profile (SIP) and Taita Symptom Check List (TSCL) to evaluate the disabilities associated with chronic pain. Patients showed significant impairment in the functions of physical psychosocial work and recreational activities. It was also apparent that the psychosocial disabilities were more severe than physical disabilities. Specifically, they showed anxiety depression and significant somatization. Analysis by stepwise multiple regression indicates that sex age educational level employment status diagnosis and pain intensity were the significant influencing factors related to the disabilities of activity of daily living and psychosocial function. The results supported the validity of the SIP as a measurement of functional status with chronic pain patients. Specifically, the psychosocial dimension was significantly correlated with the psychological and psychosocial distress categories of the TSCL. Based upon its reliability validity breadth of assessment and ease of administration, the SIP appeared to be well suited for the assessment of patients with chronic pain and for evaluating the efficacy of multidisciplinary pain treatment.

Activities of Daily Living↗
PubMed1987

Development of immunoassay methods by use of liposomes.

In order to develop liposomes for use in an immunoassay system, the preparation of immune liposomes and their characterization have been investigated. Liposomes have potential use in extremely sensitive analytical immunoassays, in addition to serving as an attractive drug delivery system. This liposome immunoassay system is based on membrane immunochemistry and an enzymatic reaction. An intense yellow color, easily detectable with the naked eye, was produced quite rapidly by the lysis of bovine serum albumin (BSA)-labeled, alkaline phosphatase-entrapped liposomes in the presence of anti-BSA rabbit serum and active complement under alkaline conditions. Sensitive detection is possible because of the antigen-antibody complex reaction, which leads to liposome lysis and an enzymatic reaction. The liposome immunoassay method offers a rapid, simple, and sensitive testing procedure which can quantitatively and qualitatively determine the presence or absence of antigenic materials and antibodies.

Amines↗
PubMed1985

Effects of purified ginseng saponins on multilamellar liposomes.

To elucidate the mode of interaction between purified ginseng saponins and liposomes, the effects of ginseng saponins at concentrations below and above their critical micelle concentration on the osmotic behavior of liposomes were observed. Liposomes composed of egg phosphatidylcholine (PC), phosphatidic acid (PA) and/or cholesterol (Ch) behave as an ideal osmometer and this activity was described by the linear relationship between (1/A450)3/2 and Cin/Cout. Total saponin prepared from the lateral roots of ginseng cultivated in Korea interacted with multilamellar liposomes and prevented them from behaving as an ideal osmometer. 20-S-Protopanaxadiol saponin showed similar activity but 20-s-protopanaxatriol saponin had weak activity. Ginsenoside Rb1 whose genin is 20-S-protopanaxadiol, disturbed osmotic behavior of Ch-free liposomes but not Ch-containing liposomes as monomers and lyzed both liposomes as micelles. Rg1 whose genin is 20-S-protopanaxatriol, showed no activity on liposomes with or without Ch. It can be suggested that ginseng saponins may interact with and destroy liposomal membranes and that structure of sugar moiety is an important factor to their activities. Ch is not a target in this interaction but suppresses the activity of ginseng saponins.

Brassica↗
PubMed1983

Molecular interaction between riboflavin and salicylic acid derivatives in nonpolar solvents.

The interaction of riboflavin-2',3',4',5'-tetrabutyrate (I) with salicylic acid (II), aspirin (acetylsalicylic acid, III), and salicylamide (IV) has been spectroscopically investigated to determine the binding mechanism. NMR and absorption spectra were measured in nonpolar solvents. The association constant K of the formation of complex was calculated from the absorption spectra. Compounds I and II form a 1:1 cyclic hydrogen-bonded dimer through the N-3 proton and the C-2 carbonyl oxygen of the isoalloxazine ring, and the carboxylic hydroxyl proton and carbonyl oxygen of II. Compounds I and III form a 1:1 cyclic hydrogen-bonded dimer by the same mode. Compound IV forms a 1:1 cyclic hydrogen-bonded dimer with I through the N-3 proton and the C-2 carbonyl oxygen of the isoalloxazine ring, and the amino proton and the carbonyl oxygen of IV. Salicylates produce marked changes in the absorption spectra of I. These spectral changes are attributed to the formation of the hydrogen-bonded dimer. It appeared that the strongest complex was formed with salicylic acid, a weaker one with aspirin, and an even weaker one with salicylamide.

Chemical Phenomena↗
PubMed1982

Interaction between flavins and alcohols.

The effect of alcohols on the spectral properties of riboflavin derivatives in non-polar solvent was studied by various spectroscopic methods in order to support the view point that alcohol may directly interact with the isoalloxazine moiety of FAD and enhance the catalytic activity of D-amino acid oxidase (DAAO). The most likely association complex between alcohol and riboflavin is 1 : 1 stoichiometric complex through the 3-N imino and the 2-C carbonyl groups of the isoalloxazine ring and the hydroxyl group of alcohols. It appears that methanol has a larger association constant than any other alcohols, and the association constant decreases with the increase in carbon number and with the steric requirement of the alkyl group of alcohols.

Alcohols↗
PubMedDate not supplied

Cervical cancer incidence and survival in Korea: 1993-2002.

This study examined the incidence rates, histologic and stage distribution, and long-term survival rates of patients with cervical cancer in Korea. A total of 44,182 patients diagnosed with cervical cancer between 1993 and 2002 were reported to the Korea Central Cancer Registry and the Gynecologic Oncology Committee of Korean Society of Obstetrics and Gynecology. The age-standardized incidence rates were 19.0, 17.8, and 15.1 per 100,000 women in 1993-1995, 1996-1998, and 1999-2002, respectively. The incidence rates of adenocarcinoma (AC) have been in the range between 1.2 in 1993-1995 and 1.4 in 1999-2002, while those of squamous cell carcinoma declined from 15.1 in 1993-1995 to 12.2 in 1999-2002. The 5-year relative survival rate was 79.2%. Relative survival rates, according to stage by the FIGO, at 5 years were 94.2%, 69.7%, 38.9%, and 21.1% for stages I, II, III, and IV respectively. Relative survivals improved between 1993 and 1997, probably due to the introduction of cervical cancer screening and effective treatment. The incidence rates of AC have been constant despite decreased cervical cancer in Korea. Introduction of cervical cancer screening and effective treatment may have contributed to the improved relative survival.

Adenocarcinoma↗