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Biomedical subjects

M Hwang

Publications and source records attributed to M Hwang.

16 recordsLinked to original sources
PubMed1996

Effect of combination of suboptimal concentrations of P-glycoprotein blockers on the proliferation of MDR1 gene expressing cells.

Pharmacologically active in vivo doses of P-glycoprotein (Pgp) blockers, specifically verapamil, Cremophor EL and PSC833 cause toxicity in addition to that from the concomitantly used cancer chemotherapeutic drugs. It was shown before that these blockers cause different types of toxicities in vivo. We found that these 3 chemically distinct Pgp blockers exert different biophysical effects on the membranes of L1210 MDR cells. They also affect the general metabolism of these cells differently, but all block affinity labeling of Pgp. We could also show that the combination of suboptimal doses of these blockers can restore the uptake of the Pgp substrate rhodamine 123 into L1210MDR, 3T3MDR and KB-VI cells and can reduce the survival rate of these cells when treated in combination with daunorubicin. Our results suggest that the combination of suboptimal doses of these Pgp blockers may be advantageous in clinical practice.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

ERCC4 (XPF) encodes a human nucleotide excision repair protein with eukaryotic recombination homologs.

ERCC4 is an essential human gene in the nucleotide excision repair (NER) pathway, which is responsible for removing UV-C photoproducts and bulky adducts from DNA. Among the NER genes, ERCC4 and ERCC1 are also uniquely involved in removing DNA interstrand cross-linking damage. The ERCC1-ERCC4 heterodimer, like the homologous Rad10-Rad1 complex, was recently found to possess an endonucleolytic activity that incises on the 5' side of damage. The ERCC4 gene, assigned to chromosome 16p13.1-p13.2, was previously isolated by using a chromosome 16 cosmid library. It corrects the defect in Chinese hamster ovary (CHO) mutants of NER complementation group 4 and is implicated in complementation group F of the human disorder xeroderma pigmentosum. We describe the ERCC4 gene structure and functional cDNA sequence encoding a 916-amino-acid protein (104 kDa), which has substantial homology with the eukaryotic DNA repair and recombination proteins MEI-9 (Drosophila melanogaster), Rad16 (Schizosaccharomyces pombe), and Rad1 (Saccharomyces cerevisiae). ERCC4 cDNA efficiently corrected mutants in rodent NER complementation groups 4 and 11, showing the equivalence of these groups, and ERCC4 protein levels were reduced in mutants of both groups. In cells of an XP-F patient, the ERCC4 protein level was reduced to less than 5%, consistent with XPF being the ERCC4 gene. The considerable identity (40%) between ERCC4 and MEI-9 suggests a possible involvement of ERCC4 in meiosis. In baboon tissues, ERCC4 was expressed weakly and was not significantly higher in testis than in nonmeiotic tissues.

Amino Acid Sequence↗
PubMed1995

Induction of depersonalization by the serotonin agonist meta-chlorophenylpiperazine.

Sixty-seven subjects, including normal volunteers and patients with obsessive-compulsive disorder, social phobia, and borderline personality disorder, received ratings of depersonalization after double-blind, placebo-controlled challenges with the partial serotonin agonist meta-chlorophenylpiperazine (m-CPP). Challenge with m-CPP induced depersonalization significantly more than did placebo. Subjects who became depersonalized did not differ in age, sex, or diagnosis from those who did not experience depersonalization. There was a significant correlation between the induction of depersonalization and increase in panic, but not nervousness, anxiety, sadness, depression, or drowsiness. This report suggests that serotonergic dysregulation may in part underlie depersonalization.

Adult↗
PubMed1995

Correction of chromosomal instability and sensitivity to diverse mutagens by a cloned cDNA of the XRCC3 DNA repair gene.

The mutagen-sensitive CHO line irs1SF was previously isolated on the basis of hypersensitivity to ionizing radiation and was found to be chromosomally unstable as well as cross-sensitive to diverse kinds of DNA-damaging agents. The analysis of somatic cell hybrids formed between irs1SF and human lymphocytes implicated a human gene (defined as XRCC3; x-ray repair cross-complementing), which partially restored mitomycin C resistance to the mutant. A functional cDNA that confers mitomycin C resistance was transferred to irs1SF cells by transforming them with an expression cDNA library and obtaining primary and secondary transformants. Functional cDNA clones were recovered from a cosmid library prepared from a secondary transformant. Transformants also showed partial correction of sensitivity to cisplatin and gamma-rays, efficient correction of chromosomal instability, and substantially improved plating efficiency and growth rate. The XRCC3 cDNA insert is approximately 2.5 kb and detects an approximately 3.0-kb mRNA on Northern blots. The cDNA was mapped by fluorescence in situ hybridization to human chromosome 14q32.3, which was consistent with the chromosome concordance data of two independent hybrid clone panels.

Animals↗
PubMed1995

Four novel mutations underlying mild or intermediate forms of alpha-L-iduronidase deficiency (MPS IS and MPS IH/S).

The alpha-L-iduronidase deficiency diseases (Mucopolysaccharidosis I) cover a spectrum of clinical severity ranging from the very severe (Hurler syndrome, MPS IH) through an intermediate (Hurler/Scheie syndrome, MPS IH/S) to a relatively mild form (Scheie syndrome, MPS IS). Numerous mutations of the gene encoding alpha-L-iduronidase (IDUA) are known in Hurler syndrome, but only three in the other disorders. We report on novel mutations of the IDUA gene in one patient with the Scheie syndrome and in three patients with the Hurler/Scheie syndrome. The novel mutations, all single base changes, encoded the substitutions R492P (Scheie), and X654G, P496L, and L490P (Hurler/Scheie). The L490P mutation was apparently homozygous, whereas each of the others was found in compound heterozygosity with a Hurler mutation. The deleterious nature of the mutations was confirmed by absence of enzyme activity upon transfection of the corresponding mutagenized cDNAs into Cos-1 cells. These results provide additional information for genotype-phenotype correlations.

Adult↗
PubMed1994

Acute procedural results in the treatment of 30 coronary artery bifurcation lesions with a double-wire atherectomy technique for side-branch protection.

Percutaneous treatment of bifurcation lesions has been consistently shown to be associated with lower acute success rates, higher initial complication rates, and an increased rate of restenosis when compared with findings in nonbifurcation lesions. Recent analysis of data from a CAVEAT subgroup suggests that directional atherectomy of bifurcation lesions can improve initial success rates and lower restenosis rates but at the cost of high complication rates. Reports from several angioplasty series document improved success rates and lower complication rates with the use of a two-wire technique to protect side branches when treating bifurcation lesions. Our experience with a two-wire atherectomy technique that uses a nitinol wire to protect important side branches is presented.

Adult↗
PubMed1993

Immunoaffinity purification of dietary heterocyclic amine carcinogens.

Cooking meats produces a family of heterocylic aromatic amines that are carcinogens in rodents and genotoxic in many short-term assays. Concern that these compounds may be human carcinogens has prompted us to develop immunochemical methods for quantifying these compounds in the human diet and for identifying the parent compounds and metabolites in urine and feces. Previously reported monoclonal antibodies to 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 6-phenyl-2-amino-1-methylimidazo[4,5-f]pyridine (PhIP) were used to purify by immunoaffinity these known mutagens and cross-reacting structural analogs from well-done cooked beef and urine samples. Materials recovered from the immunoaffinity columns were subsequently separated by HPLC to purify the known mutagens from cross-reacting chemicals that co-purify by immunoaffinity. Immunoaffinity chromatography was found to be a rapid means of quantifying individual known mutagens, with a minimum of precolumn sample clean-up required. In addition, this procedure has yielded several new mutagens present in cooked meats that are apparently structural analogs of PhIP. Immunoaffinity techniques were also used to purify metabolites from the urine of rats and humans exposed to MeIQx or PhIP. For MeIQx-exposed rats, the combination antibodies immunoconcentrated 75% of the total urinary radioactivity. Analysis of PhIP metabolites recovered from antibody columns is facilitated by the intrinsic fluorescence of PhIP and its metabolites, providing sufficient sensitivity to monitor individuals for the levels of PhIP excreted following consumption of typical western diets.

Animals↗
PubMed1991

Immunochemical detection of rodent hepatic and urinary metabolites of cooking-induced food mutagens.

Monoclonal antibodies, previously selected to bind either 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were evaluated to determine their binding properties with several known metabolites of these compounds purified from rat hepatocyte cultures. Both 2-N- and 5-substituted MeIQx metabolites were recognized by antibodies AIA-2 and AIA-11, while antibodies AIA-1 and AIA-12 bound N-substituted metabolites only. Anti-PhIP antibodies bound N-hydroxy-PhIP, N-sulfinamide-glutathione-PhIP and N-hydroxy-glucuronide-PhIP. Immunoaffinity columns incorporating these antibodies were used to concentrate and purify both the unmetabolized parent compounds and several relatively non-polar metabolites from the urine of rats exposed either to MeIQx or PhIP. Several of these metabolites corresponded with available standards of previously identified polar conjugate metabolites, e.g. N-sulfamate-MeIQx and N(OH)-gluc-PhIP, while others are as yet unidentified. Immunoaffinity chromatography is demonstrated as a promising means of selectively concentrating metabolites of PhIP and MeIQx from urine.

Animals↗
PubMed1989

Monoclonal antibodies to 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP) and their use in the analysis of well-done fried beef.

Four monoclonal antibodies, PhIP-1, -2, -3 and -4, have been produced that bind to PhIP (2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine), a mutagenic aromatic amine produced in meat by cooking. The immunogen was an analog of PhIP conjugated to a carrier protein through the 2-amino group of PhIP, leaving the pyridine and phenyl rings unmodified. The antibodies show a range of binding specificities for PhIP and its structural analogs, with PhIP-1 being the most highly selective, requiring the entire PhIP molecule with the exception of the exocylic amino group to be present for recognition. A competition enzyme linked immunosorbent assay (ELISA) incorporating these antibodies was developed and applied to the analysis of fried meat extracts differing in mutagen content. In extracts of fried beef, more PhIP-like material was found than would be expected based on chemical estimates of the amount of PhIP, suggesting that frying produces other compounds that are structurally similar to PhIP. These PhIP-like compounds were separated from PhIP using HPLC. Addition of creatinine to the beef prior to frying increased both the mutagenicity of the extracts and the amount of PhIP-like material. Microwave pre-treatment prior to frying reduced both immunochemical reactivity and mutagenicity.

Antibodies, Monoclonal↗
PubMed1988

Monoclonal antibodies for the immunoassay of mutagenic compounds produced by cooking beef.

A family of 2-amino-N-methylimidazoazaarene (AIA) mutagens are produced in meats by cooking, and are of concern as potential carcinogens in the human diet. These are potent genotoxins in bacterial mutation assays, but are present only in trace quantities in cooked foods. Conventional analytical chemistry methods have allowed us to identify six members of the AIA class, but these methods are much too labor-intensive for us to quantify mutagens in large numbers of meat samples. To improve the assay of these mutagens we have developed six monoclonal antibodies (named IQ-1, IQ-2, AIA-1, AIA-2, AIA-4, and AIA-7) and demonstrated their utility in an immunoassay for cooked food mutagens. Each antibody has its own unique binding selectivity pattern; some are compound-specific, and some class-specific. A comparison was made between cooked beef extracts that differed 200-fold in mutagenic activity. The high-mutagen extract had significantly more material that was immunologically cross-reactive with the anti-AIA antibodies than did the low-mutagen extract. Taken as a set, these antibodies will allow rapid quantitation of foods for several AIA mutagens, and will aid in the isolation and characterization of other AIAs and AIA-metabolites.

Animals↗
PubMed1985

Isolation and characterization of the Streptomyces cattleya temperate phage TG1.

A temperate actinophage, TG1, was isolated from soil by growth on Streptomyces cattleya and has been shown to be potentially useful for the cloning of DNA in this organism and other streptomycetes. It forms stable lysogens by integration at a unique site on the chromosome. The phage genome consists of 41 kb of double-stranded DNA with cohesive ends. It has unique sites for ClaI, NdeI, PstI, SmaI, and XbaI. The PstI site has been shown to be in a dispensable region of the phage genome. Deletions (2 kb in length) were obtained which retain this site and should be useful for the cloning of DNA.

Attachment Sites, Microbiological↗