PubMed Health⌕ Search

Biomedical subjects

D Skerrow

Publications and source records attributed to D Skerrow.

13 recordsLinked to original sources
PubMed1989

Relationship of the final alpha-keratin compositions in dyskeratoses to those along the normal keratinization pathway: aetiological and diagnostic significance.

The final alpha-keratin compositions attained in the outer horny layer of 16 dyskeratoses have been compared with the series of compositions which is produced during normal epidermal differentiation. In each case, the abnormal outer horny layer composition corresponded with that of normal basal, spinous, granular or inner horny cells, with, in some cases, the addition of alpha-keratins characteristic of hyperproliferating/regenerating keratinocytes. The results have implications for the aetiology of these diseases. In addition, the distinction between the alpha-keratin patterns in certain of the conditions was sufficiently clear to allow the use of the technique as a non-invasive aid to diagnosis.

Epidermis↗
PubMed1989

Changes to desmosomal antigens and lectin-binding sites during differentiation in normal human epidermis: a quantitative ultrastructural study.

During epidermal differentiation, desmosomes undergo a series of changes in their abundance, structure and properties, which has previously been defined by conventional electron microscopy and the use of antibodies to desmosomal proteins at the light-microscope level. Such changes in a major adhesive organelle would be expected to have a significant role in the maintenance of epidermal organization, and therefore require more detailed characterization. In the present study, modifications to certain desmosomal components in normal human epidermis have been located and quantified by immunogold electron microscopy. Antibodies to desmosomal protein dp3 and glycoprotein dg1 were used to label the cytoplasmic regions of the junctions and lectins concanavalin A (ConA) and wheat germ agglutinin (WGA) to probe the extracellular glycosylated material. Binding was measured at histologically defined levels and expressed as gold particles per microns of desmosome length (linear particle density: LPD). In addition, desmosome frequency, expressed as the percentage of the cell membrane length occupied by desmosomes, was measured. Highly significant changes in desmosome frequency, diameter and LPD were observed between epidermal strata and, in basal and upper horny cells, between different regions of the same cell surface. These parameters rose to a maximum in the spinous or granular layers: their subsequent decrease continued without interruption across the interface between the living and terminally differentiated horny layers. Remaining reactivity with antibodies, but not lectins, was almost completely abolished immediately before the final disintegration of the desmosome structure in the lower horny layer. In contrast, numerous large, highly immunoreactive desmosomes were retained up to the outer surface in the grossly thickened horny layer found in callus. Though the overall pattern of a rise followed by a fall was similar for all parameters measured, differences were observed between probes. Thus, the extent of the rise in available antigen between the lateral and apical surfaces of the basal cell was greater for dg1 than for dp3; the subsequent decrease in dp3 antigens in upper epidermal layers was more rapid than that for dg1, and changes to both antigens preceded those to lectin-binding sites. These results show that differences in desmosome frequency and in the size and antibody-binding characteristics of individual junctions underlie the heterogeneous distribution of desmosomal components within epidermis that is found by light-microscope immunocytochemistry. They further suggest that the disintegration of desmosomes within normal horny layer, which is an essential preliminary to desquamation, is the culmination of a sequence of events that begins in the upper living tissue and initially involves cytoplasmic components.(ABSTRACT TRUNCATED AT 400 WORDS)

Antigens↗
PubMed1987

Epidermal alpha-keratin is neutral-buffer-soluble and forms intermediate filaments under physiological conditions in vitro.

Undenatured bovine epidermal alpha-keratin has been solubilized in a low-ionic-strength buffer at physiological pH (5 mM Tris-HCl/25 mM 2-mercaptoethanol (pH 7.5). The particles in this buffer were multimeric, retaining their characteristic polypeptide chain composition and alpha-helical coiled-coil structure. They were shown by sucrose density gradient centrifugation to be in true solution and to have a narrow size distribution. Upon the addition to this solution of monovalent or divalent cations up to physiological concentrations, the alpha-keratin rapidly assembled into intermediate filaments which showed a high tendency to aggregate laterally and disassembled if returned to low-ionic-strength conditions. This behaviour closely resembles that of other intermediate filament proteins, but it is the first time that alpha-keratins have been shown to be neutral-buffer-soluble and to assemble from such solutions into intermediate filaments under physiological conditions in vitro. This is in direct contrast to the reported properties of alpha-keratins after urea denaturation and the system appears to be appropriate for studying aspects of alpha-keratin intermediate filament formation.

Animals↗
PubMed1987

Dissection of the bovine epidermal desmosome into cytoplasmic protein and membrane glycoprotein domains.

Epidermal desmosomes contain two main regions. The core consists of a pair of membranes, one on either side of a cross-striated intercellular space bisected by a denser midline. The cytoplasmic compartment comprises a dense plaque deposited on the cytoplasmic surface of each membrane and a diffuse layer occupying the zone between the plaque and attached alpha-keratin filaments. Analysis of isolated desmosomes by SDS-PAGE has shown the presence of four major protein (dpl-4) and three major glycoprotein (dgl-3) bands, which have been allocated to the cytoplasmic and core compartments, respectively. In the present paper, we report the use of urea to fractionate this complex structure, both in situ and following isolation with citrate buffer, pH2.6. Extraction of the living layers of bovine epidermis with 9M-urea, pH7.5, resulted in rapid removal of the dense desmosomal plaques, followed by separation and vesiculation of desmosomal membranes. The resistance of the plaque to urea increased abruptly at the transition between living epidermis and dead, dehydrated horny layer. A similar sequence of morphological changes accompanied the extraction of isolated desmosomes with urea. Analysis of residues and extracts of isolated desmosomes by SDS-PAGE confirmed the selectivity of 9 M-urea, pH7.5, for the cytoplasmic compartment. The four major desmosomal proteins, dpl-4 (Mr240, 215, 90 and 83 (X 10(3)), respectively) predominated in the extracts. Desmosomal membranes, both paired and vesiculated, consisted almost entirely of the three desmosomal glycoproteins dgl-3 (Mr150, 120 and 110 (X 10(3)), respectively). These results provide evidence that all three desmosomal glycoproteins are integral membrane proteins. The separation of desmosomal membranes by urea, which is not accompanied by additional loss of proteins, further suggests that desmosomal adhesion is based on interactions between membrane components with no separate extracellular molecules being involved. The dissection of the desmosome by urea into two topographically and biochemically distinct domains should facilitate further studies on the molecular basis of desmosomal adhesion and alpha-keratin filament binding.

Animals↗
PubMed1983

Tonofilament differentiation in human epidermis, isolation and polypeptide chain composition of keratinocyte subpopulations.

Epidermal tonofilaments are intermediate filaments with an unusually complex polypeptide chain composition which undergoes profound changes during differentiation. Assessment of the possible functional significance of these changes requires their correlation with defined stages of keratinocyte differentiation. Methods have, therefore, been developed for the isolation of the four keratinocyte subpopulations from human epidermis in high yield and purity without detectable damage to tonofilament chains. Trypsinization at 4 degrees C yielded sheets of granular and horny layers and a suspension of basal and spinous cells. Granular cells were removed from the horny layer sheets by mechanical action and basal cells separated from spinous cells by selective attachment to collagen. The living cell fractions were representative, by morphological and ultrastructural criteria, of their counterparts in situ. Analysis of the keratinocyte subpopulations by SDS-PAGE revealed directly their tonofilament chain composition. Basal cells contain two quantitatively major tonofilament chains (Mr 58000 and 50000). A third major chain (Mr 70000) is only synthesised suprabasally when the cells lose their ability to divide. The Mr 50000 chain is removed before the granular cell stage and several minor chains are present in the spinous and granular cells. Two chains appearing for the first time in horny cells probably result from processing during the terminal stages of differentiation. It is suggested that synthesis of the Mr 70000 chain in suprabasal keratinocytes is normally linked with their loss of mitotic ability. This may be significant in the skin disease psoriasis in which synthesis of the Mr 70000 chain is defective and the epidermis hyperproliferates.

Cell Differentiation↗
PubMed1982

The proteins of living psoriatic epidermis.

Psoriatic epidermis has a rapid rate of turnover and produces a stratum corneum with an abnormal tonofilament composition. One polypeptide chain, (Mr 70,000) is absent or greatly decreased in relative amount and two other chains, (Mr 63,000 and 55,000), which are normally modified in the living cells, persists into the stratum corneum. Increasing the turnover of normal epidermis has been shown to cause the persistence of 63 and 55 kilodalton chains in the stratum corneum but does not affect the relative amount of 70 kilodalton chain. It has, therefore, been suggested that, in psoriasis, the deficiency of the 70 kilodalton chain may occur prior to or simultaneously with the induction of increased tissue turnover. In the present study, the polypeptide chain composition of living psoriatic epidermis has been examined. It is shown that the relative amounts of 70 kilodalton chain in psoriatic stratum corneum and involved living epidermis from the same site are not significantly different. The abnormality is, therefore, already present in the living cells and it appears that, in psoriasis, the synthesis of the 70 kilodalton chain is defective. The uninvolved epidermis of psoriatics is intermediate between normal and involved psoriatic epidermis both in the ability to synthesise the 70 kilodalton chain and to modify the 63 and 55 kilodalton chains. Comparisons of amino acid compositions of proteins containing different proportions of 70 kilodalton chain suggest that it has a considerably higher content of glycine and serine than the other tonofilament chains. These studies suggest that the 70 kilodalton chain may be functionally different from the other tonofilament chains. The defect in its synthesis in psoriasis is a relatively early event and may be involved with the induction of increased tissue turnover or induced by the same abnormal conditions as the increased tissue turnover.

Amino Acids↗
PubMed1982

A comparative study of psoriatic and non-psoriatic buccal mucosa.

Buccal mucosa biopsies from patients (seven with and seven without psoriasis) were studied using autoradiography and SDS polyacrylamide gel electrophoresis. The flash labelling indices were similar in psoriatic and non-psoriatic patients and the SDS-gel patterns showed variable amounts of 70,000 mol. wt (70K) protein which did not correlate with the presence or absence of psoriasis or with individual labelling indices. An increased labelling occurred at the edges of autoradiographs from psoriatic patients due either to increased penetration of label or to trauma. The possibility of this being a Koebner effect is discussed.

Adult↗
PubMed1978

Protein modifications during the keratinization of normal and psoriatic human epidermis.

Studies on the polypeptide chain compositions of human stratum corneum and callus have shown that characteristic modifications of the epidermal fibrous protein occur during normal eqidermal keratinization. The polypeptide chain composition of psoriatic scale differs from that of both normal stratum corneum and callus. A major constituent, the alpha-chain (Mr = 70 000) of the epidermal fibrous protein is either absent or greatly decreased in amount in psoriatic sacle. This chain is, however, present in normal amounts in the uninvolved epidermis of psoriatics and, during effective treatment, returns to normal levels in the previously involved areas. It is concluded that this is a major, reversible difference between involved psoriatic epidermis and uninvolved psoriatic or normal epidermis and that it most probably results from a defect in the synthesis of the alpha-chain.

Adolescent↗