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J A Parsons

Publications and source records attributed to J A Parsons.

153 records · Page 9Linked to original sources
PubMed1968

The distribution of DNA among dividing mitochondria of Tetrahymena pyriformis.

A squash technique was developed for log phase Tetrahymena pyriformis which permitted the resolution of over 100 individual mitochondria from a single cell. Mitochondria incorporated thymidine at all stages of the cell cycle, even when nuclear DNA synthesis was not occurring. During the stage of macronuclear DNA synthesis, however, there was a significant increase in the extent of mitochondrial labeling. Low radioautograph background suggests that mitochondrial DNA is synthesized at the mitochondria themselves. All mitochondria incorporated thymidine-3H within one population-doubling time. Grain counts also showed that the amount of mitochondrial label was retained for four generations and that this label remained randomly distributed among all mitochondria during this time. The results are not consistent with any theory of de-novo or "microbody" origin of mitochondria, but do support the hypothesis that mitochondria are produced by the growth and division of preexisting mitochondria. The stability of the mitochondrial DNA and its distribution among daughter mitochondria satisfy two prerequisites for a genetic material. The possibility is discussed that some of the genetic information for the mitochondrion is contained in the DNA associated with this organelle.

Animals↗
PubMedDate not supplied

Interviewer effects on self-reported substance use among homeless persons.

This study examines respondent editing of survey responses to questions regarding substance use. Previous research has identified several types of interviewer effects that may be associated with respondent editing, including direct and social distance effects. Little is known, however, regarding how these potential effects may influence self-reported substance use behavior. Data analyzed for this study were collected as part of a survey of substance use among homeless persons conducted in Cook County, Illinois. A total of 481 respondents were sampled at random in emergency and transitional shelters, soup kitchens, drop-in centers, and single room occupancy (SRO) hotels. Overall, a direct, gender-based effect was observed, with homeless respondents of both genders more willing to reveal substance use behaviors to male interviewers. Some race- and age-related direct effects were also identified, with White and older interviewers obtaining more reports of substance use. These findings yield important evidence regarding respondent editing of self-reported substance use and have implications for the common practice of demographically matching interviewers and respondents.

Adolescent↗
PubMedDate not supplied

Measuring readiness and motivation to quit smoking among women in public health clinics: predictive validity.

We conducted an independent pilot test of the internal consistency, stability, and predictive validity of the instrument presented by Crittenden, Manfredi, Lacey, Warnecke, and Parsons (1994) using a two-wave panel of female smokers in 12 public health clinics. This instrument subdivides the precontemplation stage proposed by Prochaska and DiClemente into three more distinct stages: not contemplating quitting or cutting down, not contemplating quitting, and not contemplating quitting within 6 months. Findings confirm that the instrument is useful for evaluating movement toward quitting for populations that are largely concentrated in the precontemplative stage. The concurrent and predictive validity of the elaborated stages and the reliability and stability of smoking motivation and confidence indicate that the instrument is sensitive enough to track changes in readiness and motivation across the full readiness continuum.

Adult↗