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Biomedical subjects

M Hwang

Publications and source records attributed to M Hwang.

32 records · Page 2Linked to original sources
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↗
PubMedDate not supplied

Amino acid conservation and clinical severity of human glucose-6-phosphate dehydrogenase mutations.

More than a hundred naturally occurring mutations of human glucose-6-phosphate dehydrogenase (G6PD) have been identified at the amino acid level. The abundance of distinct mutation sites and their clinical manifestations make this enzyme ideal for structure-function analysis studies. We present here a sequence and structure combined analysis by which the severity of clinical symptoms resulting from point mutations of this enzyme is correlated with quantified degrees of amino acid conservation within 23 G6PD sequences from different organisms. Our analysis verifies, on a quantitative basis, a widely held notion that clinically severer mutations of G6PD usually occur at conserved amino acids. However, marked exceptions to this general trend exist which are most notably revealed by a number of mutations associated with chronic nonspherocytic hemolytic anemia (class I variants). When mapped onto a homology-derived structural model of human G6PD, these class I mutational sites of low amino acid conservation appear to localize in two spatially distinct clusters, both of which are populated with mutations consisting mainly of clinically severer variants (i.e. class I and class II). These results of computer-assisted analyses contribute to a further understanding of the structure-function relationships of human G6PD deficiency.

Amino Acid Sequence↗