Biomedical subjects

A S Johnson

Publications and source records attributed to A S Johnson.

9 recordsLinked to original sources

PubMed1990

The role of hydrophobicity and electronic factors in regulating alcohol inhibition of cytochrome P-450-mediated aniline hydroxylation.

The role of hydrophobicity and electronic factors in regulating alcohol inhibition of cytochrome P-450-mediated aniline p-hydroxylation has been investigated by the formulation of quantitative structure-activity relationships. The activity of linear primary alcohols and unhindered linear secondary alcohols shows a linear dependence on log P, where P is the octanol-water partition coefficient. Hindered primary and secondary alcohols are less active than this relationship predicts. An equation describing the activity of both hindered and unhindered primary and secondary alcohols shows that alcohol inhibition of aniline hydroxylation is regulated by hydrophobicity and steric effects. No role for electronic factors can be discerned. Similarities are found between alcohol inhibition and the binding of alkyl amines to cytochrome P-450, suggesting that alcohols may bind to the amine binding site.

Alcohols↗

PubMed1990

Prevalence of eating disorders in the psychiatric emergency room.

A random sample of 143 patients from a centralized psychiatric emergency service with a catchment area of one million people was studied. A two-stage interview was conducted for diagnosis of DSM-III-R eating disorders. Of those reporting active bingeing, 14.5% were men, and 22.4% were women. No cases of anorexia nervosa were discovered. Bulimia nervosa was diagnosed in 3.0% of the women and 2.6% of the men. Race and marital status were unrelated to bingeing or to any eating disorder diagnosis. Many patients never had discussed their eating behaviors before with a therapist.

Adolescent↗

PubMed1989

Pattern of caries experience in permanent molars in a 15-year-old African population.

Some epidemiologic studies from Africa report higher DMF values in second than in first molars. It is generally accepted that the maturation of dental enamel influences the susceptibility of teeth to caries. The purpose of the present study was to test the hypothesis that DMF values of second molars will be higher than those of first molars if the first molars have reached a high degree of maturation before being exposed to increased cariogenic challenge. The study was carried out in a group of 15-year-old students attending secondary schools in Botswana (n = 287). The results showed that in children who assumingly had had a traditional diet during childhood the DMF values were higher in second molars than in first molars. In children who grew up in a more urbanized setting, the results were opposite. The observed differences were due to differences in caries experience in first molars only. The DMF values of second molars did not vary among the groups. Oral hygiene, sugar consumption and knowledge level at age 15 seemed to have no effect upon the caries pattern studied. It is concluded that the results support the hypothesis tested.

Adolescent↗

PubMed1986

A method for reducing the noise generated in digitizing or analog recording of EEG data.

Magnetic recording and/or analog-to-digital conversion add noise to the data. This paper describes a method for reducing the noise added to EEG data by recording and digitizing. A linear filter is described which pre-emphasizes the EEG before recording or digitizing; a second filter then recovers the original signal after playback. The technique can result in a factor of 10 (20 dB) improvement of the signal-to-noise ratio of high frequency EEG components.

Analog-Digital Conversion↗

PubMed1968