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Biomedical subjects

H L Chang

Publications and source records attributed to H L Chang.

68 records · Page 4Linked to original sources
PubMed1976

Release by human chromosome 3 of the block at G1 of the cell cycle, in hybrids between tsAF8 hamster and human cells.

A temperature-sensitive mutant of Syrian hamster cells, AF8 was fused with simian-virus-40-transformed Lesch-Nyhan fibroblasts; LNSV, in the presence of beta-propiolactone-inactivated Sendai virus. The AF8 cells grow well at 33.5 degrees but are arrested in mid G1 period when shifted to 39 degrees. The LNSV cells are deficient in hypoxanthine guanine phosphoribosyltransferase. The hybrid clones were selected in hypoxanthine-aminopterin-thymidine medium at 39 degrees. A total of 20 clones was isolated and karyotyped. All clones contained most of the hamster chromosomes and one to eight human chromosomes. The preferential retention of human chromosome 3 was observed in 100% of the metaphases of all clones. In nine of the clones, the only human chromosome present was chromosome 3. The results indicate that human chromosome 3 is responsible for conferring to the hybrid cells the ability to grow at nonpermissive temperature for AF8 cells, i.e., the ability to overcome the G1 block. These findings, together with other reports in the cell cycle may be regulated by genes located on different chromosomes.

Antigens, Viral↗
PubMed1975

Relation of structure to function in bacterial endotoxins. VIII. Biological activities in a polysaccharide-rich fraction.

This is the first report describing in vivo biologic activities elicited by a non-toxic, polysaccharide-rich, water soluble fraction obtained by partial acidic hydrolysis from endotoxic lipopolysaccharide. The two activities present in this preparation were a) mouse bone marrow cell colony formation stimulation (CSF) and b) protection of mice against lethal irradiation. With polysaccharide-deficient rough mutants of salmonella minnesota, the CSF-inducing activity could be restricted to the "core" region of the LPS structure. Sixty-minute hydrolysis with 1 N HCl at 100 degrees C or 0.1 M sodium metaperiodate oxidation at cold room temperature completely abolished CSF-inducing activity of the preparation, whereas it showed considerable resistance to mild alkaline hydrolysis. These findings indicate that the active component in this preparation is carbohydrate in nature. Lipid preparations from smooth LPS or from Re rough mutants are either much less active or completely inactive in the above two assays. The fully active polysaccharide rich preparation was found to be inert in seven other characteristic endotoxicity parameters.

Adjuvants, Immunologic↗
PubMedDate not supplied

Effects of ibuprofen on arylamine N-acetyltransferase activity in human colon tumor cells.

The inhibition of arylamine N-acetyltransferase (NAT) activity by ibuprofen was determined in a human colon tumour (adenocarcinoma) cell line. Two assay systems were employed, one with cellular cytosols (9000 g supernatant) and the other with intact colon tumour cell suspensions. The NAT activity in a human colon tumour cell line was inhibited by ibuprofen in a dose-dependent manner in both systems, i.e. the greater the concentration of ibuprofen in the reaction, the greater the inhibition of NAT activities in both systems. The data also indicated that ibuprofen decreases the apparent Km and Vmax of NAT enzyme from human colon tumour cells in both systems examined. This report is the first demonstration to show that ibuprofen affects human colon tumour cell NAT activity.

2-Acetylaminofluorene↗
PubMedDate not supplied

Effects of aspirin on arylamine N -acetyltransferase activity and DNA adducts in human bladder tumour cells.

Aspirin (acetylsalicylic acid) was used to determine the inhibition of arylamine N-acetyltransferase (NAT) activity and DNA adduct formation in a human bladder tumour cell line (T24). The activity of NAT was measured by high-performance liquid chromatography, assaying for the amounts of N-acetyl-2-aminofluorene and N-acetyl-p-aminobenzoic acid and remaining 2-aminofluorene and p-aminobenzoic acid. Two assay systems were used: one with cytosol and the other with intact cells. High-performance liquid chromatography was also used to analyse for the 2-aminofluorene-DNA adducts. Intact bladder tumour cells were used. The results demonstrated that NAT activity and 2-aminofluorene-DNA adduct formation in human bladder tumour cells were inhibited by acetylsalicylic acid in a dose-dependent manner. The effects of acetylsalicylic acid on the values of the apparent K(m) and V(max) were also determined in both examined systems. The data also indicated that acetylsalicylic acid decreased the apparent values of K(m) and V(max) from human bladder tumour cells in both cytosol and intact cells.

2-Acetylaminofluorene↗
PubMedDate not supplied

Influences of bradykinin and substance P on the met-enkephalin-like peptide content in the rat incisor pulp.

The present study was aimed to examine possible influences of bradykinin (BK) and substance P (SP) on met-enkephalin (ME)-like peptide content in the rat incisor pulp. Des-Arg9-[Leu8]-BK, a potent BK-antagonist, significantly reduced the increased content of ME-like peptides induced by noxious stimulation, while the effect of BK-antagonist was reversed in combination with BK. Morphine decreased the increased content of ME-like peptides. Ethylketocyclazocine, a kappa-agonist, also decreased the increased content of the peptides. From these results, it was suggested that BK might be a trigger in the increase of ME-like peptide content induced by noxious stimulation and, in contrast, ME-like peptides in the pulp might inhibit BK release from the pulp in a negative feedback mechanism. On the other hand, [D-Pro2,D-Trp7,9]-SP, a potent SP-antagonist, did not show any significant influence to ME-like peptide content in the pulp. Furthermore, the content was not changed following cutting of inferior alveolar nerve. From these results, it was suggested that ME-like peptides in the pulp cells might be independent on SP-containing nerves in the pulp.

Animals↗
PubMedDate not supplied

Inhibition of N-acetyltransferase activity and DNA-2-aminofluorene adducts by glycyrrhizic acid in human colon tumour cells.

Glycyrrhizic acid (GA) was tested for inhibition of arylamine N-acetyltransferase (NAT) activity in a human colon tumour (adenocarcinoma) cell line (colo 205). Two assay systems were performed, one with cellular cytosols (9000g supernatant), the other with intact colon tumour cell cultures. The NAT activity in a human colon tumour cell line was inhibited by GA in a dose-dependent manner in both types of systems examined. The data also indicated that GA decreased the apparent values of K(m) and V(max) of NAT enzymes from human colon tumour cells in both examined systems. The DNA-2-aminofluorene adduct formation in human colon tumour cells were inhibited by GA. This report is the first to demonstrate that GA does inhibit human colon tumour cell NAT activity and DNA adduct formation.

4-Aminobenzoic Acid↗
PubMedDate not supplied

Lip lead as an alternative measure for lead exposure assessment of lead battery assembly workers.

This study investigated lead exposures of lead battery assembly workers in Taiwan. A special attempt was made to evaluate the use of lip lead as an alternative index for occupational lead exposure. Ninety-six of 113 workers from a lead battery plant were recruited as study subjects. Air lead; lead loadings on workers' sleeves, gloves, hands, cheeks, and lips; and blood lead were determined for exposure assessment. A questionnaire also was administered to collect information on work history, suspected exogenous lead sources, and personal behavior and activities. Geometric means of total air lead at different subareas ranged from 0.070 (2.5 geometric standard deviation [GSD]) to 0.159 (1.8 GSD) mg/m3. Geometric means of respirable air lead level for different subgroups of workers varied from 0.009 (2.0 GSD) to 0.032 (1.9 GSD) mg/m3, whereas those of the blood lead level ranged from 22.4 (1.3 GSD) to 44.5 (1.3 GSD) microg/dL. The heaviest lead loadings were found for plate-processing workers (e.g., 66.4 [1.5 GSD] on gloves, 0.80 [3.7 GSD] on cheeks, and 0.79 [3.2 GSD] microg/cm2) on bare-hands after washing. Blood lead level was significantly correlated with lead levels in air, lead loadings on lips, and bare hands after washing (r=0.24-0.30). Results of multiple regression analysis showed that only lip lead had a significant effect on the blood lead, whereas respirable air lead and personal behavior had only mild effects in this model. It was concluded that lip lead level may be used as an alternative index of lead exposure to facilitate the estimation of lead uptake through ingestion.

Cheek↗
PubMedDate not supplied

Effects of the immunomodulator tilorone on the acetylation of 2-aminofluorene and DNA-2-aminofluorene adducts in the rats.

The present studies were undertaken to determine the effect of tilorone dihydrochloride (a synthetic interferon inducer) on the in vivo acetylation of 2-aminofluorene and DNA-2-aminofluorene adducts. For in vivo examination, pretreatment with tilorone dihydrochloride (50 mg/kg) 48 hr prior to the administration of 2-aminofluorene (50 mg/kg) resulted in a 35% and 29% increase in the fecal and urinary recovery of N-acetyl-2-aminofluorene and a 52% increase in the metabolic clearance of 2-aminofluorene to N-acetyl-2-aminofluorene. Following the exposure of rats to the 2-aminofluorene with or without pretreatment with tilorone dihydrochloride, DNA-2-aminofluorene adducts were determined in liver, bladder, lung and also in circulating leukocytes. The DNA-2-aminofluorene adducts in liver were increased by pretreatment with tilorone dihydrochloride. This is the first demonstration of tilorone-induced increasing in N-acetylation of carcinogens and DNA-carcinogen adducts in vivo.

2-Acetylaminofluorene↗
PubMedDate not supplied

Short liquid chromatographic method for determination of zearalenone and alpha-zearalenol.

A rapid method has been developed for the determination of zearalenone and alpha-zearalenol, using liquid-liquid partition for sample extract cleanup followed by liquid chromatography (LC) with fluorescence detection. The same extract can also be used for determination of aflatoxin by LC. Relative standard deviations for the method based on duplicate analyses are 4.18% for artificially contaminated samples and 13.92% for naturally contaminated samples. The method was compared with the AOAC method of extraction and column chromatography extract cleanup, using the same LC conditions for quantitation for both methods. Results showed a correlation coefficient of 0.990 with a mean zearalenone content by this method of 987.8 ppb, and 732.6 ppb by the official AOAC method. The detection limit of this method is 2.2 ppb for zearalenone and 1.5 ppb for alpha-zearalenol.

Animal Feed↗
PubMedDate not supplied

Rapid determination of deoxynivalenol (vomitoxin) by liquid chromatography using modified Romer column cleanup.

A modification of the Romer method for determining deoxynivalenol (DON) provides rapid sample cleanup and includes liquid chromatographic (LC) quantitation. The method was evaluated using wheat, wheat flour, and other wheat products. The sample is extracted with acetonitrile-water (84 + 16), and an aliquot of the extract is subjected to activated charcoal-alumina column chromatography. The extract is then evaporated and diluted to volume with mobile phase, and DON is quantitated using liquid chromatography. The relative standard deviation based on duplicate samples is 6.07%. The detection limit is 30 ppb based on 2 X signal/noise ratio. Results by this method compared with the results obtained by the Scott GC method showed a correlation coefficient of 0.992 with a mean vomitoxin content of 779 ppb by this method and 716 ppb by the Scott method for 14 samples.

Chromatography, Liquid↗