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Biomedical subjects

B A Gilchrest

Publications and source records attributed to B A Gilchrest.

At least 127 records · Page 7Linked to original sources
PubMed1990

Cultured epidermal autografts and allografts: a study of differentiation and allograft survival.

Cultured epidermal sheets were examined before and at various times after grafting on skin ulcer beds. Before grafting, the sheet consisted of four to five layers of keratinocytes with incomplete differentiation. Ten days after grafting, graft recipient sites showed compact hyperkeratosis, a normal-appearing epidermis, and a flat dermoepidermal junction. At 6 months, the stratum corneum had a basket-weave appearance but the dermoepidermal junction remained flat. Monoclonal antibodies to keratins 14 and 10 showed normal basal and suprabasal localization, respectively. Electron microscopy showed a normal basement membrane with anchoring fibrils. LH7:2, a monoclonal antibody that binds to the type VII collagen molecule, stained the dermoepidermal junction in all biopsy specimens. AE-1, an antibody that stains suprabasal cells in hyperproliferative skin, was expressed suprabasally for up to 12 weeks after healing (16 weeks after grafting), but expression was confined to the basal layer at 18 weeks after healing (6 months after grafting). Anti-involucrin staining was found in the deeper layers of the epidermis up to 12 weeks after healing (16 weeks after grafting) but had receded to a normal distribution in upper spinous and granular layers at 18 weeks (6 months after grafting). Overall, the histologic patterns observed in recipient sites during the first 4 months after grafting resembled those observed for 10 to 14 days in newly healed epidermis and in hyperproliferative states such as psoriasis. In four sex-mismatched graft sites, specimens were reacted with a biotinylated probe to the Y chromosome by in situ hybridization. Lack of Y chromosome-positive cells suggested that host keratinocytes had replaced the allografts. Multilocus DNA analysis in one patient confirmed this observation. Our data suggest that an altered state of epithelial maturation persists for several months after culture grafting, with restoration of the normal pattern by 6 months. No differences were detected between autografted and allografted sites.

Cells, Cultured↗
PubMed1990

Variable keratin polypeptide profile in human stratum corneum.

Stratum corneum samples obtained from 46 members in three generations of seven families were analyzed for keratin pattern by gel electrophoresis. All these samples of apparently normal upper arm skin expressed the 55 kDa, 56.5 kDa, and 65 kDa keratin proteins; while only 28%, 20% and 48% of the samples expressed the 50 kDa, 58 kDa, and 67 kDa proteins, respectively. The keratin phenotype was identical in all members of two families (9 individuals) and variable in members of five other families (37 individuals), in whom the patterns were consistent with autosomal dominant inheritance. These results demonstrate inter-individual variations in stratum corneum keratin pattern and may reflect either polymorphism of genes coding for the various keratin polypeptides or a post transcriptional modification of mature keratins by proteolytic digestion.

Adolescent↗
PubMed1990

The senile epidermis: environmental influences on skin ageing and cutaneous carcinogenesis.

There is a wealth of new knowledge regarding mechanisms of carcinogenesis and their interaction with senescence and environmental insults, particularly on the effects of UV irradiation on the skin. Innovations and advances in tissue culture techniques now permit in vitro studies of keratinocytes and other benign and malignant skin-derived cells. The ageing processes and cutaneous neoplasia, therefore, can now be studied at the cellular level. New insights regarding the interrelationship of ageing, environment and cutaneous neoplasia are close at hand. Depletion in the number of Langerhans cells and suppression of their function in ageing and UV-exposed skin may allow tumour cells to overcome the host's defence system. The potential increase in UV irradiation due to depletion of the ozone layer may increase the incidence of skin tumours. Carcinogenesis involves three distinct steps: initiation, promotion, and malignant conversion. The mechanism has been studied in mice, where it is suggested the c-ras oncogene may play an important role.

Animals↗
PubMed1990

Cellular and molecular mechanisms of cutaneous aging.

There are two major theories of aging: the programmatic theory states that aging is an inherent genetic process, and the stochastic theory states that aging represents random environmental damage. Processes that are associated with cellular damage and aging are the production of free radicals (a process much enhanced after ultraviolet irradiation) and an increasing number of errors during DNA replication. Cellular manifestations of intrinsic aging include decreased life span of cells, decreased responsiveness of cells to growth signals, which may reflect loss of cellular receptors to growth factors, and increased responsiveness to growth inhibitors. All these findings are more pronounced in cells derived from photodamaged skin. Molecular manifestations of intrinsic aging, studied mainly in fibroblasts, are altered membrane composition, adhesion properties, production of extracellular matrix, and activity of the enzyme catalase. Molecular changes as a result of photoaging are less well characterized; published studies mainly target differences in composition of the extracellular dermal matrix.

Adult↗
PubMed1990

Actinic injury.

Sun exposure has multiple well-documented acute and chronic effects of substantial medical importance. The most extensively studied of these are the effects on the skin. Acute effects include sunburn, phototoxic and photoallergic reactions, altered immunoreactivity, and a variety of photosensitivity disorders. Chronic effects include photoaging and photocarcinogenesis. Photoprotection is central to both prevention and treatment.

Animals↗
PubMed1990

Skin aging and photoaging.

Multiple surveys suggest that at least two-thirds of the elderly have complaints regarding their skin and that a similar percentage have one or more medically significant dermatologic disorders. Appreciation of the age-associated changes in normal skin and of the separate process of photoaging allows more effective patient counselling and treatment.

Aged↗
PubMed1990

Cultured epidermal grafts in the treatment of leg ulcers.

Cultured epidermal grafts offer a major advance in the treatment of burns and other disabling skin wounds in which there are few other available treatments. Cultured allografts offer immediate availability, obviating skin biopsies. Theoretically, they could be grown in advance, cryopreserved, and stored in skin banks. They provide rapid coverage of wounds and produce prompt relief of pain and healing that continues for many weeks after the graft has been applied. Their mechanism of action has not been elucidated, but it seems likely that the allografted cells do not survive permanently and are gradually replaced by host epithelial cells. Release of growth factors by cultured allografts may contribute significantly to their wound healing properties. Whatever their mechanism of action, they promote rapid epithelialization at least in small chronic wounds. Especially for the elderly patient with nonhealing ulcers, they offer an alternative treatment option that is simple, painless, and noninvasive.

Biological Dressings↗
PubMed1989

[Ca2+]i independent mitogenesis in cultured human fibroblasts revealed by single cell microfluorimetry.

A transient rise in intracellular free Ca2+ concentration ([Ca2+]i) has been implicated in mitogenic induction of cell division. Individual human foreskin fibroblasts in confluent cultures examined with the Ca2+ indicator Fura-2 and a fluorescence microscope-imaging system had a basal [Ca2+]i which varied markedly from cell-to-cell. A transient serum-induced rise in [Ca2+]i was demonstrated the magnitude of which was directly correlated with the basal [Ca2+]i level. In contrast to serum-induced increase in [Ca2+]i, exposure to an elevated level of extracellular Ca2+, which is at least equally mitogenic for fibroblasts, did not alter the basal [Ca2+]i of single subconfluent cells or confluent cells. Elevated extracellular Ca2+ does not exert its mitogenicity via a transient rise in [Ca2+]i.

Benzofurans↗
PubMed1989

Treatment of children with port-wine stains using the flashlamp-pulsed tunable dye laser.

Thirty-five children, three months to 14 years of age, with disfiguring port-wine stains were treated with a flashlamp-pulsed tunable dye laser. All had complete clearing of the stains after an average of 6.5 laser treatments to each lesional area; skin over bony prominences required approximately half as many sessions as skin on the cheek. Children less than seven years old required fewer sessions (mean +/- SD, 5.8 +/- 1.1) than older children (7.1 +/- 1.1; P less than 0.05). Treated skin was identical in texture and color to adjacent normal skin in 33 (94.3 percent) of the children, whereas 2 (5.7 percent) had small, isolated, depressed scars in areas accidentally traumatized soon after laser treatment. The only other side effect was transient hyperpigmentation, which occurred in 20 patients (57 percent). These results can be attributed to two distinguishing characteristics of the flashlamp-pulsed tunable dye laser: an emission wavelength of 577 nm, theoretically ideal for selective absorption by the intravascular target oxyhemoglobin, and a pulse duration of 360 microseconds, which closely matches the thermal relaxation time for dermal blood vessels and hence avoids diffuse nonspecific thermal necrosis with subsequent scarring of the treated skin.

Adolescent↗
PubMed1989

Effect of donor age and prior sun exposure on growth inhibition of cultured human dermal fibroblasts by all trans-retinoic acid.

The effect of retinoic acid on human fibroblasts was studied in a cell culture model of chronologic aging and photoaging. During early exponential phase, all trans-retinoic acid significantly stimulated growth rate of adult arm-derived dermal fibroblasts but not of newborn or adult foreskin-derived fibroblasts. Retinoic acid also significantly reduced saturation density in most young adult arm-derived lines and all 24 lines derived from old adult arm and foreskin. However, four of ten young adult outer arm (relatively sun-exposed) and one of ten young adult inner arm (relatively sun-protected) fibroblasts lines increased their saturation density in response to retinoic acid. These data suggest that prior sun exposure and/or donor age may influence cellular responsiveness to retinoic acid. Neither the stimulatory nor the inhibitory effect of retinoic acid could be attributed to cell density, to breakdown of retinoic acid in culture, to nutrient depletion or to serum dependency. However, stationary phase fibroblasts from all sites (foreskin, inner and outer arm) showed an increase in filopodia and in intracellular actin after treatment with retinoic acid that was roughly proportional to the degree of growth inhibition, irrespective of donor age. We suggest that retinoic acid induces premature density dependent growth inhibition at least in part by increasing filopodia-mediated cell contact that is in turn directly related to an increase in fibrillar actin.

Adult↗
PubMed1989

Phenolic and tyrosyl ring iodothyronine deiodination by the Caco-2 human colon carcinoma cell line.

Thyroid hormone metabolism was studied in the human Caco-2 colon carcinoma cell line, which at confluence exhibits several functions of differentiated enterocytes. Cells were harvested two to 17 days after reaching confluence. Intact cells and homogenates were tested for deiodination of [125I]-labeled substrates. Small amounts of thyroxine (T4) were converted by homogenates to 3,3',5'-triiodothyronine (rT3), 3,3'-diiodothyronine (3,3'-T2), and 1-, with no detectable production of 3,5,3'-triiodothyronine (T3) by homogenates or cells. rT3 was converted to 3,3'-T2 and 1- with an apparent Michaelis constant (Km) for rT3 of 24 nmol/L; 6-n-propyl-2-thiouracil (PTU) had a 50% inhibitory concentration of 30 nmol/L and abolished rT3 5'-deiodination at 1 mmol/L in the presence of 20 mmol/L dithiothreitol (DTT). T3 was deiodinated to 3,3'-T2 and 3'-monoiodothyronine (3'-T1) with an apparent Michaelis constant (Km) for T3 of 5.7 nmol/L; this reaction was not inhibited by 1 mmol/L PTU. Phenolic and tyrosyl ring deiodinating activities were maximal four and six days, respectively, after the cells reached confluence. Homogenates of cells grown in standard medium containing fetal calf serum had fivefold higher rT3 5'-deiodinating activity than cells grown in a serum-free defined culture medium, reflecting a fivefold difference in the apparent Vmax with no difference in the apparent Km for rT3. There was no difference in T3 5-deiodination rates in homogenates of Caco-2 cells grown in the two media until 12 days postconfluence, when cells grown in standard medium had higher activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Carcinoma↗
PubMed1989

Interferon and the epidermis: implications for cellular senescence.

Human keratinocytes are epithelial cells that cover the external surface of the body and function primarily to protect against physical, chemical and biological injury. Since 1975, serial cultivation of disaggregated human keratinocytes in vitro has been possible and these cultures have been utilized to assess in vitro physiological age. As has been demonstrated in human dermal fibroblasts harvested from donors of different ages, human epidermal keratinocytes from older donors manifest a decreased proliferative response to serum and to selected mitogens when compared to younger donors. Recent work suggests an increased sensitivity to negative growth modulators as well. The epidermis constantly renews itself. In normal skin, the majority of the cells in the germinative, basal cell layer are blocked in Go and do not cycle unless stimulated. Interferons (IFN) are a family of glycoproteins well known for their antiviral activity and their ability to inhibit growth and alter the behavior of various normal and transformed cell types, both in vitro and in vivo. As such, we examined intact skin for the presence of negative modulators of growth and demonstrated the presence, by immunofluorescence and Western blotting, of a protein of approximate molecular weight 40 kilodaltons with polyclonal antiserum directed against recombinant IFN-alpha. Extracts from healthy, non-virally infected keratinocyte cultures contained IFN activity as determined by viral plaque inhibition assays. Further, we have demonstrated that IFN inhibits the growth of the human keratinocyte in a non-cytotoxic, reversible manner and that the keratinocytes harvested from older adult donors are significantly more sensitive to the growth inhibitory effects of IFN than are the keratinocytes of young donors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Treatment of skin ulcers with cultured epidermal allografts.

Thirty-six skin ulcers in 23 patients were treated with cultured allogeneic epidermal sheets derived from neonatal foreskin. In 73% of ulcers, there was complete healing within 8 weeks, with a mean healing time of 3.3 weeks. In the other 27%, there was reduction in ulcer size of 35% to 93% by 8 weeks after grafting. In 30 painful ulcers, pain was markedly relieved within 24 hours of grafting. The healing pattern suggested that the cultured epidermal sheets acted by stimulation of host keratinocytes to divide and migrate rather than by permanent acceptance of the allograft. Of the 26 ulcers that healed within 8 weeks, 23 (88.5%) remained healed for follow-up periods of 10 to 18 months (mean 13.7 months), with an overall mean duration of healing of 13 months.

Adult↗
PubMed1989

Skin aging and photoaging: an overview.

As the population ages, common skin disorders of the elderly demand greater attention. Moreover, the many clinical, histologic, and physiologic changes that characterize old skin are increasingly implicated in its vulnerability to environmental injury and certain diseases. Thus it behooves dermatologists to study the basic biologic process of aging in the skin and the separable process of photoaging, which itself is a major clinical problem. To date studies at the cellular level have demonstrated major functional losses, particularly in proliferative capacity between infancy and adulthood, with definite further loss between early and late adulthood and as a result of chronic sun exposure. Continued careful, quantitative assessment of aging and photoaging in human skin both in vivo and in vitro will be critical to a better understanding of these processes and particularly to their successful therapeutic modification.

Aged↗
PubMed1989

Human melanogenesis is stimulated by diacylglycerol.

The intracellular signal pathways that mediate pigmentation in human skin are unknown. We now report that a diacylglycerol (DAG) analogue 1-oleoyl-2-acetyl-glycerol (OAG) 25-100 microns strikingly increased the melanin content of cultured human melanocytes in a dose dependent manner without altering growth rate. The pigment increase occurred within 24 h, was accompanied by increased incorporation of the melanin precursor L-3,4-dihydroxyphenyl alanine (DOPA), required new protein synthesis, and was completely blocked by the protein kinase C (PKC) inhibitors H-7 and sphingosine. A PKC-inactive DAG isomer had no effect on melanin per cell. These results implicate protein kinase C and its effector DAG in melanogenesis.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

Regulation of human melanocyte growth, dendricity, and melanization by keratinocyte derived factors.

Epidermal pigmentation involves the synthesis of melanin in melanocytes and its transfer to surrounding keratinocytes, where it functions in photoprotection. To investigate the possible role of the keratinocyte in regulating pigmentation, human keratinocytes were incubated for 24 h in a defined culture medium, which was then transferred to pure human melanocyte cultures. After 1 week, the conditioned medium produced a fourfold increase in melanocyte yield and a seven-fold increase in total melanin. Increased melanocyte dendricity was clearly visible within 24 h as well. Ultrafiltration of the keratinocyte-conditioned medium suggested approximately one-half of the growth promoting activity as well as most of the dendricity and melanization stimulating activities were of low molecular weight (less than 500 Da). High molecular weight fractions stimulated only melanocyte growth. Of the several known keratinocyte-derived factors tested, none could be implicated as a mediator of the observed effects. Basic fibroblast growth factor, known to stimulate melanocyte growth in some culture systems, failed to stimulate growth, dendricity, or melanin content when added to the complete non-conditioned medium. Interleukin-1 alpha, interleukin-1 beta, 12-hydroxyeicosatetraenoic acid, prostaglandin E2, leukotriene B4, and adenosine 3',5'-cyclic monophosphate analogues also had no effect. These studies demonstrate that keratinocytes in vitro release factors that modulate melanocyte behavior and expand our understanding of controls for human epidermal pigmentation.

Cell Division↗