Chain length heterogeneity of nucleosomal DNA in mouse liver after dimethylnitrosamine administration

The effect of dimethylnitrosamine on the nucleosomal structure of mouse liver chromatin was studied. After a single oral dose of dimethylnitrosamine (2–75 mg/kg body weight 45 min before sacrifice) liver nuclei were isolated and incubated with micrococcus nuclease. Nucleosomes were separated on sucrose density gradients. There were no differences in nucleosomal sedimentation velocities between preparations from control and dimethylnitrosamine treated animals. The supernatant obtained after centrifugation of the lysed nuclei (2 min at 4,000 g _av) and nucleosomal peak fractions were used for isolation of DNA. DNA was heat denatured in 7 M urea or formamide. After electrophoresis on polyacrylamide gels areas under mononucleosomal DNA and smaller fragments were measured and compared with the total DNA area. The increase in DNA fragmentation was dimethylnitrosamine dose response dependent. When expressed as per cent of controls it amounted to 106% for 2 mg; 115% for 10 mg; 127% for 25 mg; 164% for 75 mg dimethylnitrosamine/kg body weight. A good correlation between mobility and log of chain length of 174 RF DNA-Hae III digest was obtained in nondenaturing 5% polyacrylamide gels and denaturing non-aqueous formamide polyacrylamide gels but not in 12% polyacrylamide gels containing 7 M urea. DNA of mononucleosomal peak fractions contained 200 and that of dinucleosomal peak fractions 400 nucleotides. Fragmentation of DNA was closely related to in vivo dimethylnitrosamine treatment but was not detected in measurements of protein-DNA complexes in the chromatin. It was disclosed on denaturation of DNA followed by polyacrylamide gel electrophoresis.Abbreviations DMN dimethylnitrosamine - SDS sodium dodecyl sulfate The work was supported by Grant Number 1 R0 1 CA26642-01, awarded to A.v.d.D. by the National Cancer Institute, DHEW     

Cytochrome P450 3A4 is the major enzyme responsible for the metabolism of laquinimod, a novel immunomodulator.

In the present study, the involvement of cytochrome P450 enzyme(s) in the primary metabolism of laquinimod, a new orally active immunomodulator, has been investigated in human liver microsomes. Hydroxylated and dealkylated metabolites were formed. The metabolite formation exhibited single enzyme Michaelis-Menten kinetics with apparent KM in the range of 0.09 to 1.9 mM and Vmax from 22 to 120 pmol/mg/min. A strong correlation between the formation rate of metabolites and 6beta-hydroxylation of testosterone was obtained within a panel of liver microsomes from 15 individuals (r2 = 0.6 to 0.94). Moreover, ketoconazole and troleandomycin, specific inhibitors of CYP3A4 metabolism, demonstrated a significant inhibition of laquinimod metabolism. Furthermore, in incubations with recombinant CYP3A4, all the primary metabolites were formed. In vitro interaction studies with CYP3A4 substrates and possible concomitant medication demonstrated that laquinimod inhibits the metabolism of ethinyl estradiol with an IC50 value of about 150 microM, which is high above the plasma level of laquinimod after clinically relevant doses. Ketoconazole, troleandomycin, erythromycin, prednisolone, and ethinyl estradiol inhibited the metabolism of laquinimod, and IC50 values of 0.2, 11, 24, 87, and 235 microM, respectively, were calculated. In conclusion, the present study demonstrates that laquinimod is a low affinity substrate for CYP3A4 in human liver microsomes. The likelihood for in vivo effects of laquinimod on the metabolism of other CYP3A4 substrates is minor. However, inhibitory effects on the metabolism of laquinimod by potent and specific inhibitors of CYP3A4, such as ketoconazole, are anticipated and should be considered in the continued clinical program for laquinimod.     

Disability,coping and quality of life in individuals with muscular dystrophy: a prospective study over five years

Purpose : The present study investigates progressive muscular dystrophy over a five year period. The purpose is twofold: to describe changes over time and to investigate relations between disability, coping and quality of life. Method : The study group comprised 45 adults (16 men and 29 women), with an average age of 44 years. All were assessed in 1991 and 1996, with the following instruments: the ADL staircase, the Self-report ADL, the Mental Adjustment to Cancer scale, the Sickness Impact Profile and the Psychosocial well-being questionnaire (Kaasa). Results : Increasing disability was accompanied by an increase in dependence on others and a significant deterioration of health-related quality of life and with regard to 'Satisfaction'. The predominant type of coping was 'Fighting spirit', whilst 'Fatalism' showed the greatest decline over time. 'Ambulation' and the ADL staircase correlated with 'Physical index' on the SIP. Correlations between disability, coping and quality of life were moderate. The results can serve as a basis for planning and evaluation of recurring rehabilitation for persons with MD.     

A Bisensory Method for Odor and Irritation Detection of Formaldehyde and Pyridine

A bisensory method was developed for determining the psychometric functions and absolute thresholds for odor and sensory irritation of two odorous irritants. Individual and group thresholds for formaldehyde or pyridine were measured for 31 age-matched subjects (18?C35?years old). P ₅₀ absolute thresholds were for formaldehyde odor 110?ppb (range 23?C505), for pyridine odor 77?ppb (range 20?C613), and for pyridine irritation 620?ppb (range 90?C3,656); too few subjects?? formaldehyde irritation thresholds were possible to determine (human exposures limited to 1?ppm). In spite of large interindividual differences, all thresholds for irritation were higher than for odor. The average slopes of the 62 psychometric functions for odor and the 32 possible for sensory irritation were highest for formaldehyde odor (83% per log ppb) and equal for pyridine odor and irritation (68% per log ppb). The bisensory method for measuring odor and sensory irritation jointly produced detection functions and absolute thresholds compatible with those earlier published; however, a steeper slope for sensory irritation than odor was expected for pyridine. The bisensory method is intended for measuring odor and sensory irritation to broadband mixtures and dynamic exposures, like indoor air.