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Biomedical subjects

A J Reynolds

Publications and source records attributed to A J Reynolds.

At least 19 recordsLinked to original sources
PubMed1996

Human hair follicle regeneration following amputation and grafting into the nude mouse.

In this study we investigated the capacity of the human hair follicle to regenerate a fiber-forming bulb after its amputation. We removed the bases from terminal follicles from a variety of sites and transplanted the follicles onto athymic mice, either still attached to a skin graft or as subcutaneous implants of individual follicles. External hair growth was observed on the skin grafts, and histology of the follicles revealed restoration of dermal papillae and follicle bulb structures. This result suggests that the capacity of hair follicles to regenerate their lower structures after removal, which was first demonstrated on whisker follicles, may be a general phenomenon. It emphasizes the importance of specific cellular subpopulations within the follicle and the role of dermal-epidermal interactions in adult follicle activities.

Animals↗
PubMed1996

Hair matrix germinative epidermal cells confer follicle-inducing capabilities on dermal sheath and high passage papilla cells.

Low passage cultured dermal papilla cells from adult rats stimulate complete hair follicle neogenesis when re-implanted into heterotypic skin. In contrast, cultured sheath cells are non-inductive despite sharing other behavioural characteristics (a common lineage and in situ proximity) with papilla cells. However, since sheath cells can behave inductively in amputated follicles after regenerating the papilla, this poses the question of what influences the sheath to papilla cell transition? During reciprocal tissue interactions specific epidermal cues are crucial to skin appendage development, and while in vivo assays to date have focussed on dermal interactive influence, our aim was to investigate epidermal potential. We have previously observed that hair follicle epidermal cells display exceptional interactive behaviour when combined with follicle dermal cells in vitro. Thus in the present study, hair follicle germinative, outer root sheath or skin basal epidermal cells were separately combined with each of three non-inductive dermal cell types (high passage papilla, low passage sheath or fibroblast) and then implanted into small ear skin wounds. The sheath/germinative and papilla/germinative cell implants repeatedly induced giant vibrissa-type follicles and fibres. In complete contrast, any single cell type and all other forms of recombination were consistently non-inductive. Hence, the adult germinative epidermal cells enable non-inductive adult dermal cells to stimulate hair follicle neogenesis, effectively, by altering their 'status', causing the sheath cells to 'specialise' and the 'aged' papilla cells to 'rejuvenate'.

Animals↗
PubMed1996

Cognitive and family-support mediators of preschool effectiveness: a confirmatory analysis.

Investigated in this study were the mediators of the effects of preschool intervention on children's school achievement in sixth grade. A confirmatory structural model developed in a previous study of third graders was tested with 360 low-income, mostly black children who were available at the 3-year follow-up. The model incorporated cognitive readiness at kindergarten entry and parent involvement in school (rated by teachers and parents) as primary mediators of preschool effectiveness. In sixth grade (age 12), preschool participation at ages 3 or 4 was significantly associated with higher reading achievement, higher math achievement, and with lower incidence of grade retention. Cognitive readiness and parent involvement in school significantly mediated the estimated effects of preschool participation on school achievement and grade retention 7 years postprogram. Teacher ratings of school adjustment, school mobility, and grade retention also contributed to the transmission of effects. This integrated model fit the data better than several alternative models, including those based on the cognitive-advantage and family-support hypotheses.

Achievement↗
PubMed1995

Effect of diet and training on muscle glycogen storage and utilization in sled dogs.

Two groups of eight Alaskan huskies fed either a high-fat (HFD; 60% kcal from fat and 15% kcal from carbohydrate) or a high-carbohydrate diet (HCD; 60% kcal from carbohydrate and 15% kcal from fat) performed standard aerobic (1 h at 4 m/s on a 0% slope) and anaerobic (3 min at 6.7 m/s on a 10% slope) tests before and after training. Before and immediately after each exercise test, venous blood samples were collected and analyzed for lactate and pyruvate, and muscle biopsies were obtained under local anesthesia from the semitendinosus muscle and analyzed for total muscle glycogen (TMG) concentration. Training was associated with a significant increase in preexercise TMG in both diet groups; this effect was most marked in the HCD. There was no effect of diet or training on TMG utilization during the aerobic tests. The rate of TMG utilization during the anaerobic tests was between 20 and 40 times greater than that measured during the aerobic tests. The pre- to postexercise change in TMG was dependent on preexercise TMG in the HCD and HFD for both anaerobic tests (HCD: P < 0.01, r = 0.81; HFD: P < or = 0.03, r = 0.66). It is concluded that the increased glycogen storage associated with the HCD was more than offset by the more rapid rate of glycogen utilization in this group. HFD facilitated carbohydrate sparing during intense exercise and should thus be a better dietary strategy for endurance in sled dogs.

Analysis of Variance↗
PubMed1995

New approach to percutaneous muscle biopsy in dogs.

The size and quality of muscle specimens obtained by use of a percutaneous biopsy technique were studied. All biopsies were performed under local anesthesia, using an 11-gauge biopsy needle. The mean +/- SEM size of specimens obtained from 128 biopsies of the semitendinosus muscles of 16 Alaskan Huskies was 23.8 +/- 4.4 mg. All biopsy specimens were of sufficient quality to permit histochemical differentiation of the fiber types by use of myosin ATPase staining. An additional 8 biopsy specimens were obtained from 1 dog and analyzed for muscle glycogen content. These specimens contained 50.6 +/- 7.2 mmol of glucose/kg of muscle wet weight. This modified biopsy procedure was free of notable complications, and repeatable use produced specimens of adequate size and quality for histologic and biochemical analysis. It is concluded that this procedure is a safe and reliable alternative to open biopsy for diagnosis and management of neuromuscular, metabolic, and nutritional myopathies.

Animals↗
PubMed1994

Hair follicle reconstruction in vitro.

The in vitro creation of a follicular structure capable of hair growth from cultured adult cells has long been an aim of researchers in hair biology. Basal outer root sheath cells (ORS) attached to the hair follicle glassy membrane (GM) were isolated and cultured, where they revealed greater replicative potential and longevity than ORS cells from plucked fibres. Hair follicles were reconstructed in vitro using the collagenous shells of rat vibrissa follicles as natural containers for 4 hair follicle cell types. Basal ORS cells were initially seeded onto the residual vibrissa GM, and cultured dermal papilla, dermal sheath and germinative epidermal cells were then added. Histology revealed that after 2 or 3 weeks in combined culture, cell interactions and tissue morphogenesis had resulted in the formation of irregular but recognizable hair fibres, produced from unusual bulb structures. To our knowledge this represents the first example of adult cell populations instigating the de novo creation of hair fibres in a culture dish. While the usefulness of the current methodology relates immediately to hair growth research, the generation of hair follicles and fibres in vitro establishes the enormous potential of this type of interactive work for practical purposes.

Adult↗
PubMed1994

Lipid metabolite responses to diet and training in sled dogs.

Two groups of Alaskan Huskies were fed either a high fat (HFD) or a high carbohydrate diet 4 wk before and during an 8-wk conditioning program. Aerobic bouts of exercise were performed before and after conditioning. Blood samples taken before and after each exercise test were analyzed for serum concentrations of free fatty acids (FFA), triglycerides (TG), vitamin E, glucose and serum lipase activity. The post-exercise FFA and TG values were greater in the HFD group both before and after training. There were no significant differences in plasma vitamin E or in serum lipase activity between diet groups. It is concluded that after an adequate period of adaptation, prolonged feeding of a HFD safely enhances the availability of local and peripheral lipid stores during exercise. Although the elevated levels of FFA and TG associated with HFD suggest enhanced potential for performance, further study of more prolonged and possibly more intense exercise is necessary to confirm this theory.

Animals↗
PubMed1994

Hair follicle stem cells: characteristics and possible significance.

All four of the principle dermal and epidermal cell types from the adult hair follicle (dermal papilla and sheath, germinative epidermal and outer root sheath) can now be grown in culture. The germinative epidermal cells from the source of the hair fibre appear to be the most visually distinctive of these populations, but all four can be morphologically, synthetically and behaviourally distinguished from general interfollicular skin cells. The germinative population also most obviously exhibit many classical stem cell attributes, but the interactive and inductive capabilities of all of the cell types, in addition to their multipotential natures, highlights that they all share an intriguing level of developmental flexibility.

Animals↗
PubMed1993

Dermal-epidermal interactions--follicle-derived cell populations in the study of hair-growth mechanisms.

All skin appendage development is initiated by a series of dermal-epidermal interactions. These continue to underpin adult hair follicle activities through the specialized follicular cell populations--indeed the inductive properties of isolated dermal papillae from adult vibrissa follicles are well established. Far less is known about the influence of adult follicle epidermis on dermal cells, or inductive properties of papilla cells from other follicle types. Cultured papilla cells, unusually, are able to support the proliferation of skin epidermal cells during simple association in culture, but do not produce more elaborate organization or differentiation. However, germinative epidermal cells from the follicle base are morphologically and behaviorally distinct from other epidermal populations, and in simple association with papilla cells interact to form complex structures with a distinct basal lamina. That hair follicle germinative cells have an important influence on dermal cells is further demonstrated by in vivo recombinations, where germinative cells interact with otherwise non-inductive follicle dermal sheath cells to initiate follicle formation and hair growth. In vitro, several follicle cell populations assembled within the capsule of a vibrissa follicle and grown in a three-dimensional culture system produce hair-type fibers. When cultured pelage follicle dermal papilla cells are implanted alone into footpad skin under controlled conditions, new pelage-type follicles and fibers are induced. This emphasizes the power and universal nature of inductive influences from papilla cells, and underlines the dermatologic potential of cell manipulations. The transdifferentiation of the footpad epidermis is a powerful biologic phenomenon normally only seen in embryonic-type association experiments.

Aging↗
PubMed1993

A quantitative study of the differential expression of alpha-smooth muscle actin in cell populations of follicular and non-follicular origin.

Alpha-smooth muscle actin (ASMA) is an actin isoform present in the filaments of smooth muscle cells, myofibroblasts, and a specific region of hair follicle dermal sheath in vivo. We employed double immunofluorescence, two-dimensional electrophoresis, Western blots and DNA, protein, and actin isoform determinations to quantify the relative levels of ASMA in four populations of cultured hair follicle dermal cells, and fibroblasts derived from three regions of adult and comparable areas of 4-d rat skin. Although follicle sheath populations were morphologically similar, they contained variable proportions of cells that expressed ASMA. Tissue from the most positive region in situ, the lower/mid sheath, also gave rise to the most positive cells in culture (98%), followed by the end bulb (85%) and then upper sheath (50%). The follicle dermal cells (including papilla 81%) displayed and maintained levels of expression well above those obtained for adult (below 10%) or 4-d (9-40%) fibroblasts, and even cultured smooth muscle cells. It was also confirmed that levels of expression in adult fibroblasts could be positively correlated with hair follicle density in the biopsies from which they were initiated. Differential expression of ASMA in follicle subpopulations provides an insight into how their behavior may be linked to their specialized functions, for example, their likely involvement in the mechanics of the hair cycle. Moreover, the proposition that hair follicle dermal cells represent unappreciated constituents of general skin fibroblast cultures has substantial implications.

Actins↗
PubMed1993

Induction of hair growth in ear wounds by cultured dermal papilla cells.

In the adult hair follicle the dermal papilla plays a crucial role in the dermal-epidermal interactions that control hair production and events of the growth cycle. It has previously been shown that cultured cells from rat vibrissa follicle dermal papillae can stimulate hair growth when implanted into amputated follicles. This study investigated the effects of implanting low-passage cultured papilla cells into small incisional wounds in the rat ear pinna. The groups of fibers that emerged from wound sites were much larger than local hairs, and often had vibrissa-type characteristics. Later-passage papilla cells or cultured skin fibroblasts failed to elicit the same response. Histology revealed that big follicles were formed when papilla cells were trapped between the cut edges of the epidermis. Abnormally large follicles were seen at wound sites many months post-operatively. Independent of epidermal influence, cultured papilla cells in the wound dermis formed rounded papilla-like aggregates that also persisted until biopsy. A previously described method of wrapping papilla cells in glabrous epidermis was less successful in percentage terms but resulted in the production of one very large vibrissa-type follicle and fiber. These results further illustrate that the inductive powers and developmental information retained by cultured dermal papilla cells parallel the properties of their embryonic precursors; the findings may have implications for human hair growth.

Animals↗
PubMed1993

Human hair follicle germinative epidermal cell culture.

Isolated human hair follicle germinative epidermal cells were observed in vitro for the first time. When cultured alone, this small, round, novel cell type did not grow, divide, take on an outer root sheath-type appearance, or display any obvious signs of epidermal differentiation. We have previously described comparable cells from rat vibrissa follicles. However, in combination with human hair follicle dermal papilla populations, the germinative epidermal cells were stimulated into proliferative and complex interactive behaviors. This included the formation of composite organotypic structures containing not only impressively intact basement membrane, but also the hair-specific form, glassy membrane.

Cell Adhesion↗
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↗