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Biomedical subjects

A J Reynolds

Publications and source records attributed to A J Reynolds.

17 recordsLinked to original sources
PubMed1992

Prediction of early social and academic adjustment of children from the inner city.

Investigated predictors of five measures of early school adjustment for an ethnically diverse cohort of 683 inner-city kindergartners and first graders. Data from 2 consecutive years were collected from teachers, school records, and children. A multiple-regression preduction model significantly explained children's competence behavior, problem behavior, reading achievement, mathematics achievement, and school absences. Prior adjustment and sociodemographic factors explained a majority of the variance in adjustment. Perceived quality of parent involvement was signifcantly related (in the expected direction) to all five outcomes. Exposure to life events was significantly associated in the expected direction with competence behavior, problem behavior, and school absences but not with reading and mathematics achievement. Together, parent involvement and life-event variables explained as much as 12% of the variance in adjustment independent of sociodemographic and prior adjustment factors. The role of family and school factors in the adjustment of children at risk is discussed [corrected].

Absenteeism↗
PubMed1992

Cultured dermal papilla cells induce follicle formation and hair growth by transdifferentiation of an adult epidermis.

Adult rat pelage follicle dermal papilla cells induced follicle neogenesis and external hair growth when associated with adult footpad skin epidermis. They thus demonstrated a capacity to completely change the structural arrangement and gene expression of adult epidermis--an ability previously undocumented for cultured adult cells. Isolation chambers ensured that de novo follicle formation must have occurred by eliminating the possibility of cellular contributions, and/or inductive influences, from local skin follicles. These findings argue against previous suggestions of vibrissa follicle specificity, and imply that the potential for hair follicle induction may be common to all adult papilla cells.

Animals↗
PubMed1991

Dermal cell populations show variable competence in epidermal cell support: stimulatory effects of hair papilla cells.

A study was made of the comparative abilities of adult rat vibrissa dermal papilla cells, skin fibroblasts and 3T3 cells to support the initial attachment and subsequent growth and division of directly associated newborn rat skin basal epidermal cells. These associations were made under sub-optimal conditions; that is, in the absence of specific epidermal growth-promoting supplements, in order to assess more accurately the epidermal sustaining capacities of each dermal support. Analysis of epidermal cell counts and close photographic scrutiny revealed that low-passage dermal papilla cells, closely followed by transformed dermal papilla cells, were conducive to the successful attachment and subsequent proliferation of epidermal cell populations under three different experimental protocols. In contrast, skin fibroblasts did not support epidermal cell growth under any circumstances. These findings are particularly interesting in that they constitute a rare in vitro example of epidermal cells that are not only supported, but also encouraged to proliferate, by an actively dividing adult skin-derived dermal cell population.

Animals↗
PubMed1991

Hair follicle stem cells? A distinct germinative epidermal cell population is activated in vitro by the presence of hair dermal papilla cells.

Germinative epidermal cells in the lower end bulb region of anagen hair follicles are highly active, and give rise to hair fibres through rapid proliferation and complex differentiation. They have often been termed hair follicle stem cells, but owing to difficulties in isolation and identification their properties have previously only been clearly documented in vivo. We aimed to isolate and culture germinative cells in vitro, and used microdissection methods to dissect a small but identifiable group of cells from complete follicles. Transmission electron microscopy confirmed that the isolated cells were identical to germinative epidermal cells in situ. SDS-PAGE was used to show that they did not have the same protein composition as epidermis from their immediate proximity (overlying hair matrix), or from other follicular (outer root sheath) and interfollicular (skin basal) regions. Moreover, the germinative cells were found to display morphology and in vitro behaviour that distinguished them from comparative epidermal cells. When cultured in media and on substrata normally conducive to epidermal cell growth they remained in a quiescent state, and did not divide or differentiate. In contrast to other epidermal cells that formed typical pavement-like arrangements, germinative cells remained uniformly small, round and closely packed. However, when cultured in association with hair follicle dermal papilla cells they were radically stimulated into proliferative and aggregative behaviour. Furthermore, they were able to form organotypic-like structures, and exceptionally for skin-derived cell recombinations, a distinct basal lamina at the papilla-germinative cell junction. These results provide evidence that hair follicle germinative cells have intriguing properties that distinguish them from other follicular epidermis. The finding that they can be activated by dermal papilla cells reflects the intimate nature of the papilla-germinative cell relationship in situ, and should facilitate research into hair growth control mechanisms. The nature of germinative cells is discussed in the wider context of hair follicle stem-cell terminology.

Animals↗
PubMed1991

Smooth muscle alpha-actin is a marker for hair follicle dermis in vivo and in vitro.

We have examined the expression of smooth muscle alpha-actin in hair follicles in situ, and in hair follicle dermal cells in culture by means of immunohistochemistry. Smooth muscle alpha-actin was present in the dermal sheath component of rat vibrissa, rat pelage and human follicles. Dermal papilla cells within all types of follicles did not express the antigen. However, in culture a large percentage of both hair dermal papilla and dermal sheath cells were stained by this antibody. The same cells were negative when tested with an antibody to desmin. Overall, explant-derived skin fibroblasts had relatively low numbers of positively marked cells, but those from skin regions of high hair-follicle density displayed more smooth muscle alpha-actin expression than fibroblasts from areas with fewer follicles. 2-D SDS-PAGE confirmed that, unlike fibroblasts, cultured papilla cells contained significant quantities of the alpha-actin isoform. The rapid switching on of smooth muscle alpha-actin expression by dermal papilla cells in early culture, contrasts with the behaviour of smooth muscle cells in vitro, and has implications for control of expression of the antigen in normal adult systems. The very high percentage of positively marked cultured papilla and sheath cells also provides a novel marker of cells from follicle dermis, and reinforces the idea that they represent a specialized cell population, contributing to the heterogeneity of fibroblast cell types in the skin dermis, and possibly acting as a source of myofibroblasts during wound healing.

Actins↗
PubMed1991

Note on adolescents' time-use and scientific literacy.

This study investigated the relative influence of self-reported, out-of-school experiences on 13-yr.-olds' scientific literacy, including the often studied variables of homework time and television time. Results, based on a national probability sample of 3,116 students, indicated that time spent doing homework, reading, and viewing television programs with an educational focus had significant and positive independent influences on scientific literacy net of home environment and students' background factors. Viewing television programs that emphasized entertainment negatively contributed to scientific literacy. The number of hours of television viewed was unrelated to literacy. Factors associated with the transition to adolescence, dating, and peer relations, were negatively related to scientific literacy. Findings were discussed in regard to improving students' performances in science.

Achievement↗
PubMed1991

The middle schooling process: influences on science and mathematics achievement from the longitudinal study of American youth.

The purpose of this longitudinal study was to develop and test a model of middle school science and mathematics achievement with a national probability sample of 3,116 seventh-grade public school students. Eighth-grade achievement was viewed as a function of readiness attributes on entry into seventh grade and intervening parent, peer, self, and classroom affective and behavioral measures. Data were collected from students and parents over three time periods in seventh and eighth grade. Results of a revised structural model showed that prior achievement in science and math was a strong mediator of effects in the process of schooling. Grades in sixth grade, parental expectations, parent educational attainment, and motivation had moderately strong indirect effects on eighth-grade achievements. Also notable was the positive direct influence of perceptions of classroom context on science and math achievement growth and the negative direct influence of sex (in favor of girls) on science achievement growth. Cross-validation on a split-half sample did not disconfirm the model. It was concluded that while prior achievement had a dominant influence in the schooling process, other variables including parental expectations, motivation, and classroom context do contribute to the schooling process and can be a focal point for improving school success. These and other factors, though helpful, may be most effective well before the middle school years.

Achievement↗
PubMed1980

Papaverine and hepatotoxicity.

Six of 14 patients receiving a sustained release papaverine preparation developed abnormal liver function tests. One patient had jaundice and another abnormal liver histology on a biopsy specimen. This is only the third report of impaired liver function following the administration of papaverine--a drug which has been used in clinical medicine for over 100 years.

Aged↗