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W T Gibson

Publications and source records attributed to W T Gibson.

32 records · Page 2Linked to original sources
PubMed1983

Interactions of C12 surfactants with the skin: studies on enzyme release and percutaneous absorption in vitro.

Using an in vitro penetration cell, it has been shown that enzymes (acid phosphatase, lactate dehydrogenase and N-acetylglucosaminidase) are released from rat-skin slices in response to contact with two irritant C12 surfactants, sodium laurate and sodium lauryl sulphate, but not with the non-irritant sodium lauroyl isethionate. About 3-5 hr contact of the stratum corneum with surfactant and a long incubation time (24 hr) were required for enzyme release. Adsorption and penetration of the two effective surfactants was also studied and the results for sodium lauryl sulphate suggested a relationship between enzyme release and adsorption of surfactant. However, no such simple relationship was observed for sodium laurate, emphasizing the complex nature of surfactant interactions with the skin.

Adsorption↗
PubMed1983

Interactions of C12 surfactants with the skin: changes in enzymes and visible and histological features of rat skin treated with sodium lauryl sulphate.

Rat skin was treated with 35 mM-sodium lauryl sulphate (SLS) and samples were taken after one, three or five treatments, or 24 hr after the fifth treatment for measurement of enzyme release and epidermal enzyme levels. Release of acid phosphatase (AP) and lactate dehydrogenase (LDH) was significantly higher than in controls after five treatments with SLS, and epidermal levels of AP, LDH and N-acetylglucosaminidase were also higher than in controls in skin taken 24 hr after the fifth treatment. The relationship of these changes to the irritant response, assessed visually and histologically, was investigated in two out of three experiments. Although the timing of the irritant response was variable, enzyme release accompanied the development of erythema and oedema in each case, and extensive enzyme release was associated histologically with epidermal oedema and an increase in dermal leucocytes. The increase in epidermal enzyme activities also followed the development of the reaction to SLS, and it seemed to be related to epidermal thickening.

Acetylglucosaminidase↗
PubMed1983

Fibronectin distribution during the development of fetal rat skin.

Fibronectin distribution during fetal rat skin development has been studied immunocytochemically at the light and electron microscope level from 16 days of gestation to birth. The dermal-epidermal junction, the dermis, and connective tissue around developing muscle were shown by light microscopy to be heavily stained throughout this period. The development of hair follicles from about 18 days onward was not associated with any consistent change in fibronectin distribution. The heavy staining of the upper dermis was associated with a high density of mesenchymal cells, and immunoelectron microscopy revealed fibronectin on the surface of many of these cells and in association with the surrounding fine collagen fibrils. At the dermal-epidermal junction, both follicular and interfollicular, fibronectin was localized mainly in the plasma membrane and lamina lucida regions of the basement membrane, and there was also staining associated with the underlying fine collagen fibrils. These observations are further evidence for the proposed role of fibronectin as a mediator of the cell-matrix interactions which are of importance for tissue development and maintenance.

Animals↗
PubMed1983

Fibronectin in cultured rat keratinocytes: distribution, synthesis, and relationship to cytoskeletal proteins.

The aim of this study was to investigate whether epidermal cells can synthesise fibronectin and whether the distribution of this glycoprotein is related to the adhesion and cytoskeletal organisation of these cells. The production of fibronectin by newborn rat epidermal cells was shown by indirect immunofluorescence staining of cultures grown in the absence of a feeder layer using an antiserum which had been cross-adsorbed with foetal calf serum proteins to remove antibodies which recognised serum fibronectin. The distribution of fibronectin in areas of cell-cell and cell-substratum contact, characteristically in the form of short radial stitches, was examined in more detail using immunoelectron microscopy with colloidal gold as marker. This showed the close proximity of fibronectin to the cell membrane, with the ventral surface and fine cellular processes showing the heaviest labelling, and also revealed evidence of a relationship between external fibronectin and internal structure in epidermal cells. Immunofluorescence showed that tonofilaments (keratin) and microtubules were present as fibrillar arrays but were not related to fibronectin distribution. Vimentin and desmin were absent. Actin was distributed as a circumferential bundle of filaments, with finer stands running radially to the edge. The latter were reminiscent of the radial fibronectin stitches and a spatial correspondence between fibronectin and actin was confirmed by double-label immunofluorescence which revealed many instances of overlap and colinearity of actin and fibronectin filaments. The ability of keratinocytes to produce fibronectin suggests that these cells can contribute to the formation of the basement membrane in skin. The localisation of fibronectin and its close association with actin also suggests that it is involved in keratinocyte adhesion and is related to the internal organisation of these cells.

Actins↗
PubMed1982

Changes in epidermal acid phosphatase levels in response to chemical irritation.

Topical sodium laurate produced little or no immediate change in the amount of rat epidermal acid phosphatase but the levels of thid enzyme progressively increased to reach a maximum at about 3 days. This coincided with acanthosis and thickening of the stratum granulosum, indicating epidermal repair. The increase depended o protein synthesis as it could be blocked by treatment with cycloheximide. This inhibitory effect was associated histologically with loss of the stratum granulosum, supporting the belief that the expression of acid phosphatase is closely linked with this layer during normal keratinization.

Acid Phosphatase↗
PubMed1979

Fibronectin distribution in epithelial and associated tissues of the rat.

Specific antiserum was used to investigate the distribution of the extracellular glycoprotein, fibronectin, in rat skin and tongue tissue by light and electron microscopy with immunofluorescence and immunoperoxidase techniques. We conclude that fibronectin is absent from stable, differentiated parts of tissues, such as the sebaceous glands or the matrix, medulla, cortex, and cuticles of the hair and the inner and outer root sheaths, or even in tissues in which there is some cell movement, such as the epidermis. It is, however, characteristic of sites at which cell division is occurring in contact with an extracellular scaffolding, such as basement membrane or loose connective tissue. Conspicuous examples were in the glassy membrane and connective tissue sheath associated with the follicular epithelium, the basement membrane underlying vascular endothelial cells, the connective tissues surrounding and investing nerve and muscle fibre bundles, and the dermal connective tissue where fibronectin was often associated closely with collagen fibres. At the basement membrane of the dermal/epidermal junction, fibronectin occurred at the plasma membrane of the basal cells and in the lamina lucida area. There was no correlation with specific areas of cell-substrate adhesion, such as the hemidesmosomes. The endoplasmic reticulum of fibroblasts stained strongly suggesting that these cells represent a major site of synthesis.

Animals↗
PubMed1978

Collagenolytic cathepsin activity in rabbit peritoneal polymorphonuclear leucocyte granules.

Collagenolytic cathepsin activity was detected in lysed rabbit peritoneal polymorphonuclear leucocytes. The pH optimum was around 3, and activity was greatly enhanced by the presence of cysteine and EDTA. Digestion of polymeric collagen resulted in the release of alpha, beta, and gamma-chains. Collagenolytic cathepsin activity was associated mainly with the granule fraction isolated from homogenates by differential centrifugation. The granule fraction was further fractionated by isopycnic density-gradient centrifugation, and the collagenolytic cathepsin activity was shown to be associated with the azurophil and tertiary granules, both lysosome-like organelles.

Animals↗
PubMedDate not supplied

A mechanistic study of evolvability using the mitogen-activated protein kinase cascade.

Evolvability is a function of the way genetic variation interacts with the mechanisms that produce the phenotype. We explore an explicitly mechanistic way of studying the evolvability of phenotypes that are produced by a relatively simple genetic mechanism, the mitogen-activated protein kinase (MAPK) cascade. We developed a quantitative model of MAPK activation that can be used to study the effects of genetic variation on the various components of this signaling cascade. We show how some standard tools of applied mathematics, such as steady-state formulations and nondimensionalization, can be used to elucidate the relative importance of variation in each gene of this mechanism. We also give insights into non-intuitive patterns of dependence and trade-off among the genes. The mechanism produces several different phenotypes (ultrasensitivity to stimulation, switch-like behavior, amount of MAPK-PP delivered, persistence of MAPK-PP activity), each of which is sensitive to different (but partially overlapping) combinations of genes. We show that the mechanism imposes clear limitations on the evolvability of each of the different phenotypes of the pathway, even in the presence of genetic variation in the components of the mechanism. This approach to the study of evolvability is generally applicable and complements the traditional approach through statistical genetics by providing a mechanistic understanding of the genetic interactions that produce the phenotype.

Biological Evolution↗