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Biomedical subjects

C Larsen

Publications and source records attributed to C Larsen.

At least 109 records · Page 6Linked to original sources
PubMed1984

Increase in glucuronide conjugation of aflatoxin P1 after pretreatment with microsomal enzyme inducers.

Microsomes prepared from livers of chickens given enzyme inducers had increased capability to convert aflatoxin P1 to its glucuronide conjugate. This capability was 190% +/- 19 and 184% +/- 13 of control values (mean +/- S.E., N = 4) 96 h after intraperitoneal administration of 80 mg/kg beta-naphthoflavone or 3-methylcholanthrene, respectively. Glucuronidation of aflatoxin P1 was also increased 15 days after 500 mg/kg i.p. of a polychlorinated biphenyl mixture (to 471% +/- 111). Fifteen days on a low protein diet (containing 54% of normal levels) did not alter aflatoxin glucuronidation. Increased glucuronidation after administration of inducers was due to increased specific activity of the microsomal enzymes.

Aflatoxins↗
PubMed1984

Organophosphate detoxification related to induced hepatic microsomal enzymes of chickens.

Detoxification of the organophosphate malathion in its activated form (malaoxon) was increased in livers of chickens given microsomal enzyme inducers (beta-naphthoflavone, 3-methylcholanthrene, butylated hydroxytoluene (BHT), or polychlorinated biphenyls). Positive correlations between inducer and microsomal enzyme activity were demonstrated for beta-naphthoflavone with demethylation of p-nitroanisole and for 3-methylcholanthrene and for BHT with cytochrome P450/448 and cytochrome b5. Malaoxon detoxification decreased in correlation with decreases in quantities of cytochrome P450/448 in birds fed a low-protein diet. Prediction of malaoxon detoxification was aided by using enzyme activities as dependent variables in the regression model, although only in birds given BHT were all of the 5 enzymes necessary for providing the best predictive model.

Animals↗
PubMed1983

A new spectrophotometric method for the selective determination of ampicillin, amoxycillin and cyclacillin in the presence of polymers and other degradation products.

A rapid and convenient spectrophotometric method is described for the quantitative determination of ampicillin and other amino-penicillins. The method involves conversion of the penicillins to the corresponding piperazine-2,5-dione derivatives by heating in an alkaline sorbitol-zinc ion solution for 10 min at 60 degrees C and subsequent treatment of these derivatives with 1 M sodium hydroxide to give a highly absorbing product with lambda(max) at 322 nm. Since an intact beta-lactam moiety and a free amino group in the side-chain of the penicillin molecules are required for the piperazinedione formation, the method is highly selective. The method was found to be free of interference from polymerization and other degradation products and its application to assess the stability of the amino-penicillins was demonstrated.

Journal Article↗
PubMed1983

Drug metabolism in adult white leghorn hens--response to enzyme inducers.

1. Adult hens were given a mixture of polychlorinated biphenyls (0.5 and 2 g/kg Aroclor 1254), 3-methylcholanthrene (80 mg/kg) or beta-napthoflavone (80 mg/kg). 2. beta-Napthoflavone elevated activities of both microsomal and nonmicrosomal enzymes 48 hr after dosing, with cytochrome P-450 p-nitroanisole O-demethylase, aniline hydroxylase, and glutathione S-epoxytransferase at 319% +/- 25, 157% +/- 12, 410% +/- 26 and 120% +/- 3 of control values, respectively. 3. Aroclor 1254 and 3-methylcholanthrane also elevated microsomal enzyme activities, but did not increase the activity of glutathione S-epoxytransferase. 4. Drug metabolizing capability in control and experimental hens differed from that in rats and mice.

Aniline Hydroxylase↗
PubMed1982

Antigenic variation of Borrelia hermsii.

At least 24 different serotypes were detected in populations of Borrelia hermsii that originated from a single organism. These serotypes were identified by staining with specific fluoresceinated antisera prepared against cloned populations of living organisms of each type. In the order of decreasing frequency, the 10 types more often encountered were 7, which was clearly dominant, and 2, 17, 24, 13, 2, 1, 21, 11, and 12. Each of the 24 types were shown to change to 7 or more other serotypes. Spirochetemia in mice was persistent, and relapses occurred when the concentration of organisms was sufficient for detection by visual means. After mice were inoculated with a single organism, peak spirochetemia usually occurred on day 4, after which clearance of organisms occurred, and an apparently pure population was replaced by a mixed population consisting of as many as seven variants. These types persisted for 2-3 d before being replaced by other types. Conversions occurred constantly and were independent of relapses. The rate of conversion in mice treated with cyclophosphamide to delay antibody production was comparable to that of controls. Spontaneous conversion was clearly demonstrated in tubes of fortified Kelly's medium inoculated with a single organism of type 7 or 21. 11 different variants appeared in eight cultures of type 21 by the time growth had reached 4 X 10(6)-10(7) organisms/ml. The rate of spontaneous change was estimated to be or approximately 10(-4)-10(-3) per cell per generation.

Antigens, Bacterial↗
PubMed1977

Polymerization of penicillins. IV. Separation, isolation and characterization of ampicillin polymers formed in aqueous solution.

Polymeric substances formed from ampicillin sodium in aqueous solution have been separated according to charge by anion-exchange chromatography on a column of DEAE-Sephadex A-25 using a linear sodium chloride gradient at a constant pH of 7.4. The separated materials, ranging in size from the monomer to the octamer, have been characterized by various functional-group analyses. A homogeneous well-defined ampicillin dimer, tetramer and hexamer have been isolated from the effluent in high yields. The separation and isolation of the ampicillin polymers permit a conclusive establishment of their structures, which in turn has confirmed previous suggestions that the polymers are formed through a chain process involving aminolysis of ampicillin at the beta-lactam carbonyl moiety by the amino group of the side-chain of a second ampicillin molecule.

Ampicillin↗