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Biomedical subjects

K C Chen

Publications and source records attributed to K C Chen.

At least 145 records · Page 8Linked to original sources
PubMed1981

Aryl hydrocarbon hydroxylase activity induced by injected diesel particulate extract vs inhalation of diluted diesel exhaust.

The effects of long-term inhalation of diluted diesel exhaust on aryl hydrocarbon hydroxylase activity (AHH) and cytochrome P-450 content in lung and liver microsomes were investigated in male Fischer-344 rats and compared with repeated parenteral administration of organic solvent extracts of hydrocarbons adsorbed on the diesel particulate surface during the combustion process. The animals were exposed to concentrations of 750 micrograms m-3 or 1500 micrograms m-3 of diesel particulates from a 5.7L GM diesel engine 20 h per day, 5 1/2 days per week for up to 9 months or treated by repeated IP injections of diesel particulate extract (dissolved in corn oil) from the same engine at several dose levels for 4 days. No significant effects of long-term inhalation exposure were observed in liver microsomal AHH activity. A slight decrease in lung microsomal AHH activity was found in rats following 6 months of exposure to diesel exhaust at the particulate concentration of 1500 micrograms m-3. The total mass of particles deposited in the lung during the inhalation exposure was estimated and an equivalent dose of extractable hydrocarbons was administered intraperitoneally; no increase in AHH activity was observed in the lung or liver microsomes. In contrast, 1.4- to 9-fold increases in AHH activity were observed in liver and lung microsomes of rats pretreated by intraperitoneal doses 10-50 times larger than the most conservative estimate of the deposited lung burden. No changes in cytochrome P-450 content were observed in the microsomes of rat liver after inhalation or injection treatment studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerosols↗
PubMed1981

Nonspecific vaginosis.

Nonspecific vaginosis (NSV) is a very common clinical syndrome with characteristic clinical, biochemical, and microbiologic features. There is a thin, malodorous homogeneous, grey, nonpurulent vaginal discharge. The discharge usually has a pH greater than 4.5, contains "clue cells" on wet mount examination, and produces a "fishy" odor when mixed with 10% potassium hydroxide. The discharge contains an increased concentration of at least seven amines which are presumably produced by bacterial decarboxylases; and several volatile and non-volatile organic acid metabolites of anaerobic bacteria. Although the pathogenesis of NSV is not understood, the normal, lactobacillus-dominated microbial flora is replaced by Gardnerella (Haemophilus) vaginalis and certain anaerobic species. Treatment with sulfonamide creams or oral tetracycline is usually ineffective. Ampicillin is often effective, but metronidazole appears to be the most effective antimicrobial for this condition. The optimal dose of metronidazole, and the need for treatment of sex partners, require further study.

Amines↗
PubMed1980

Glutathione and mercapturic acid conjugations in the metabolism of 2,4-dinitrobromobenzene.

The formation of glutathione (GSH) conjugate in the detoxification of [Ring-UL-14C]-2,4-dinitrobromobenzene (DNBB) was investigated using rat liver cytosolic fraction. The mercapturic acid conjugate in rats was also studied by collection of urine of rats dosed with radioactive DNBB by intraperitoneal injection. The glutathione replaced the labile bromo atom and formed the conjugate, S-(2,4-dinitrophenyl)glutathione. The GSH conjugate was confirmed by amino acid analysis and by mass spectroscopy as well as co-cochromatography with the synthetic compound. The amount of formation of GSH conjugate was dependent on the amount of GSH added in the incubation mixture. When [Ring-UL-14C]-DNBB was dosed to rats, 69% and 17% of the radiocarbon was excreted via the urine and feces within 72 hours, respectively. The major radioactive metabolite present in the acid urine of DNBB treated was S-(2,4-dinitrophenyl)mercapturic acid accounting for 60% of the administered dose of radiocarbon. The mercapturic acid conjugate was identified similarly to methods used for identification of GSH conjugate. The data demonstrated that GSH conjugate, formed initially and then subsequently converted into the mercapturic acid excreted in the urine, was the major metabolic pathway in the metabolism of 2,4-dinitrobromobenzene.

Acetylcysteine↗
PubMed1979

Amine content of vaginal fluid from untreated and treated patients with nonspecific vaginitis.

We examined the vaginal washings from patients with nonspecific vaginitis (NSV) to seek biochemical markers and possible explanations for the signs and symptoms of this syndrome. Seven amines were identified including methylamine, isobutylamine, putrescine, cadaverine, histamine, tyramine, and phenethylamine. These amines may contribute to the symptoms of NSV and may contribute to the elevated pH of the vaginal discharge. They may also be partly responsible for the "fishy" odor that is characteristic of vaginal discharges from these patients. Among the seven amines, putrescine and cadaverine were the most abundant and were present in all vaginal discharges from each of ten patients before treatment. These amines are produced in vitro during growth of mixed vaginal bacteria in chemically defined medium, presumably by decarboxylation of the corresponding amino acids. We hypothesize the anaerobic vaginal organisms, previously shown to be quantitatively increased in NSV, are responsible for the amine production, because metronidazole inhibited the production of amines by vaginal bacteria in vitro, and Haemophilus vaginalis did not produce amines. H. vaginalis did release high concentrations of pyruvic acid and of amino acids during growth in peptone-starch-dextrose medium, whereas, other vaginal flora consumed both pyruvic acid and amino acids in the same medium during growth. These findings suggest that a symbiotic relationship may exist between H. vaginalis and other vaginal flora in patients with NSV.

Amines↗
PubMed1979

Glutathione and mercapturic acid conjugations in the metabolism of naphthalene and 1-naphthyl N-methylcarbamate (carbaryl).

The formation of glutathione (GSH) conjugate in the detoxification of [1-14C]-naphthalene and [naphthyl-14C]-carbaryl was investigated using rat liver homogenate. The mercapturic acid conjugate in rats was also investigated by collection of urine after intraperitoneal injection of 14C substrates. The formation of water-soluble metabolites in vitro from naphthalene was dependent on the amount of glutathione added, but this was not seen in carbaryl metabolism. In vitro, the metabolism of [1-14C]-naphthalene produced 50% GSH conjugates in the incubation mixture, whereas in vivo the metabolism of this compound produced 65% mercapturic acid conjugate in the urine. There was no evidence of GSH or mercapturic acid conjugate in the metabolism of [naphthyl-14C]-carbaryl in vitro and in vivo. This conclusion was made by comparing the nature and chemical characteristics of GSH and mercapturic acid conjugates formed in [1-14C]-naphthalene metabolism. With the aid of the specific enzyme (e.g. beta-glucuronidase and sulfatase) and acid hydrolysis, the water-soluble metabolites of [naphthyl-14C]-carbaryl were tentatively recognized as glucuronide or sulfate conjugated mainly with 5,6-dihydro-5,6-dihydroxycarbaryl or N-hydroxy-methyl carbaryl and their hydrolytic products. This data demonstrated that the substituent group on the naphthalene molecule may affect the significance of GSH conjugation.

Acetylcysteine↗
PubMed1978

Neisseria pili proteins: amino-terminal amino acid sequences and identification of an unusual amino acid.

The amino-terminal amino acid sequences of the pili proteins from four antigenically dissimilar strains of Neisseria gonorrhoeae, from Neisseria meningiditis, and from Escherichia coli were determined. Although antibodies raised to the pili protein from a given strain of gonococcus cross-reacted poorly or not at all with each of the other strains tested, the amino-terminal sequences were all identical. The meningococcal protein sequence was also identical with the gonococcal sequence through 29 residues, and this sequence was highly homologous to the sequence of the pili protein of Moraxella nonliquifaciens determined by other workers. However, the sequence of the pili protein from E. coli showed no similarity to the other sequences. The gonococcal and meningococcal proteins have an unusual amino acid at the amino termini, N-methylphenylalanine. In addition, the first 24 residues of these proteins have only two hydrophilic residues (at positions 2 and 5) with the rest being predominantly aliphatic hydrophobic amino acids. The preservation of this highly unusual sequence among five antigenically dissimilar Neisseria pili proteins implies a role for the amino-terminal structure in pilus function. The amino terminus may be directly or indirectly (through preservation of tertiary structure) important for the pilus function of facilitating attachment of bacteria to human cells.

Amino Acid Sequence↗
PubMed1978

A system for studying effects of microwaves on cells in culture.

An improved design of the fluid-filled waveguide-exposure chamber is described for studying effects of microwave radiation on cells in vitro. The system with a micropipette sample holder may be used as a prototype to isolate the apparent nonthermal factor of microwave radiation on cells in culture from those effects resulting from cell temperature rise. This system also allows more precise calibration of incident and absorbed microwave energies. Compared with control, somatic cells of the Chinese hamster exhibited a lower rate of growth and difference in morphology after 2450 MHz microwave radiation for 20 min at a power density of 500 mW/cm2.

Animals↗
PubMed1977

Extremity of semantic differential ratings in deaf and hearing subjects.

A comparison was made separately by sex of 19 deaf and 19 hearing Ss on mean semantic differential ratings of contradictory concept-pairs. There were nine deaf males, 10 deaf females, 11 hearing males, and eight hearing females with mean ages of 23.00, 21.90, 20.73, and 19.75, respectively. It was hypothesized that the deaf would make less extreme ratings of concept-pairs than hearing Ss and that they would shift their ratings of contradictory concept-pairs closer to the mean of the original ratings of the single concepts comprising the pairs. It was found that both predictions were true only for deaf males. Deaf females did not differ from hearing Ss.

Adult↗