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At least 1,405 records · Page 78Linked to original sources
PubMed1984

On the presence of a metalloprotease in human skin fibroblasts that degrades the human skin elastic fiber system.

Succinyl-trialanine paranitroanilide, a specific synthetic substrate of elastases, was shown to be hydrolyzed by Triton X-100 extracts of human skin fibroblasts at near neutral pH. The neutral endopeptidase has been partially purified by ion exchange chromatography (DEAE Sephadex) and affinity chromatography using an AH-Sepharose (Ala)3 column. The enzyme has been purified 85-fold and appears to be a metalloprotease as shown by its inhibitory profile. In its partially purified form, the neutral endopeptidase was found inactive toward benzoyl arginine paranitroanilide, benzoyl tyrosine paranitroanilide, azocasein, type I collagen, and [3H]ligamentum nuchae-insoluble elastin. Structural glycoprotein microfibrils isolated from porcine aorta are extensively degraded by this neutral protease. It could also hydrolyze, but to a lesser extent, insoluble elastin purified from human aortas; it was, however, found inactive toward bovine ligamentum nuchae elastin. Its potentiality to degrade the human skin elastic fiber system (namely elastic fibers, oxytalan, and elaunin fibers) has been assessed by a morphometric analysis of the length of these fibers (on tissue sections appropriately stained to identify the components of the elastic fiber system) prior to and after enzyme action. Analysis of the data obtained by morphometry indicated that this neutral protease attacked rapidly both elaunin and oxytalan fibers of human dermis, but only slowly the mature elastic fibers.

Cells, Cultured↗
PubMed1985

Evaluation of anchoring fibrils and other components of the dermal-epidermal junction in dystrophic epidermolysis bullosa by a quantitative ultrastructural technique.

To examine the possibility that differences in the structure and population density of anchoring fibrils (AF) and other components of the dermal-epidermal junction might distinguish between genetically and clinically distinct varieties of dystrophic epidermolysis bullosa (DEB), a controlled ultrastructural morphometric study of nonseparated keratinocyte-associated dermal-epidermal junction was undertaken in a total of 17 patients with DEB. Seven patients had dominant DEB, 3 had localized recessive DEB, and 7 had severe, generalized recessive DEB. Nonlesional, unscarred skin was obtained from standard body regions. Criteria for the identification of AF were a mandatory union with the lamina densa and the presence of central banding and/or fanning of the extremities. No AF were detected in 9 technically suitable samples from patients with severe recessive DEB. Structurally normal AF were present, but significantly reduced in number, in both dominant and localized recessive DEB, compared with site-matched samples from 12 healthy adults. There was no difference in AF characteristics between dominant and localized recessive DEB, or between sites of predilection and nonpredilection for blisters. The presence or absence of albopapuloid lesions in dominant DEB did not influence AF counts. There was no difference in numbers of hemidesmosomes, basal cell plasmalemmal vesicles, or dermal microfibril bundles in any group of DEB patients compared with controls. Thus, although severe mutilating DEB can be distinguished by routine transmission electron microscopy, the dominant and localized recessive forms cannot be differentiated on the basis of AF structure or numbers.

Adult↗
PubMed1984

Ultrastructural morphometry of normal human dermal-epidermal junction. The influence of age, sex, and body region on laminar and nonlaminar components.

To obtain baseline data for future studies on such processes as wound healing, carcinogenesis, and blistering, a morphometric analysis of the dermal-epidermal junction was undertaken on normal skin from 3 or 4 standard sites on the arm and leg of 12 subjects aged 20-60 years. Lamina densa was thinner in females than in males (p less than 0.01) but no sex difference was apparent for lamina lucida. Both laminar elements were thinner beneath melanocytes than beneath keratinocytes. Sex, age, and body region had no apparent influence on numbers of hemidesmosomes or basal cell plasmalemmal vesicles, nor was there a significant variation of these structures among individuals. Numbers of dermal microfibril bundles diminished with age (p less than 0.01). Anchoring fibril counts varied widely both among individuals (p less than 0.025) and within the same subject; there were fewer in the upper arm compared with different parts of the leg (p less than 0.005). These results emphasize the importance of appropriate controls in studies of physiologic and pathologic conditions involving the dermal-epidermal junction.

Adult↗
PubMed1995

Skin fibroblasts are the only source of nidogen during early basal lamina formation in vitro.

The purpose of this study was to determine whether nidogen, the linkage protein of the basal lamina, is of epidermal or dermal origin. The development of the basal lamina was studied in an in vitro skin model. Preputial fibroblasts seeded onto a nylon mesh attached, proliferated, and developed a rich extracellular matrix (dermal model). Preputial keratinocytes were added to the dermal model to form a keratinocyte dermal model that ultrastructurally resembled in many respects human skin. Ultrastructural analysis revealed early stages of dermal development, including an incomplete basal lamina, aggregates of dermal filamentous material connecting to the lamina densa, bundles of 10-nm microfibrils, formation of premature hemidesmosomes, anchoring filaments, and anchoring fibrils. The cell origin of nidogen was determined in the dermal model and in the epidermal and dermal components of the keratinocyte dermal model. Specific antibodies and a cDNA probe for nidogen were used for immunofluorescence microscopy, Western and Northern blots, and for in situ hybridization studies. Our data show that fibroblasts are the only source of nidogen during early basal lamina formation. Although fibroblasts can synthesize nidogen and deposit it in the dermal matrix, no basal lamina will form unless they are recombined with keratinocytes. This suggests that the epidermis plays a major regulatory role in the production and assembly of nidogen into the basal lamina.

Basement Membrane↗
PubMed1993

Culturing keratinocytes and fibroblasts in a three-dimensional mesh results in epidermal differentiation and formation of a basal lamina-anchoring zone.

The purpose of this study was to characterize an in vitro co-culture model in which fibroblasts grown in a three-dimensional nylon mesh were recombined with human keratinocytes. The cultures were kept for 3 and 5 weeks and then processed for electron microscopy. Keratinocytes showed reconstruction of an epidermis consisting of a basal layer with hemidesmosomes, a stratified epithelium with tonofilaments and desmosomes, a granular layer with keratinosomes and keratohyaline granules, and a transitional stratum corneum. Anchoring filaments, lamina densa, anchoring fibrils, bundles of elastin-associated microfibrils (diameters 10 nm) and fine collagen fibrils were formed. Collagen fibrils near the epidermis were much thinner than those in the lower levels. The present study shows that the dermal model containing metabolically active fibroblasts in their natural environment will support epidermal morphogenesis and differentiation including the formation of a basal lamina and anchoring zone.

Basement Membrane↗
PubMed1976

Oxytalan, elaunin, and elastic fibers in the human skin.

The elastic system of normal human skin was studied by light and electron microscopy. By light microscopy three different types of fibers were observed: oxytalan, elaunin, and elastic. The most superficial ones (oxytalan fibers) are very thin and directed perpendicularly to the dermoepidermal junction. They start from a plexus with the tinctorial characteristics of elaunin fibers which is connected with the thicker elastic fibers of the reticular dermis. At the electron microscopic level the oxytalan fibers are formed by bundles of tubular microfibrils 10 to 12 nm in diameter. In the deepest layers of the dermis an amorphous material is seen in the core of these bundles. In the elaunin fibers the amorphous material is sparse, while in the elastic fibers it is abundant and compact.

Adolescent↗
PubMed1981

Ultrastructural studies of elastotic material and elastic fibers in aged skin before and after autoclaving.

Elastotic material and aged elastic fibers of patients with solar elastosis before and after autoclaving was studied using the tannic acid stain as well as the conventional stain. The amorphous matrix of the elastotic material and the elastic fibers stained positive with the tannic acid stain. In the fibrous form of elastotic material and in the elastic fibers both electron-dense inclusions and the amorphous matrix remained unchanged after autoclaving, while microfibrils were removed. In the amorphous form the fine granular component and round bodies were removed after autoclaving, and the moderately electron-dense amorphous component with a reticular or net-like appearance remained. It has been suggested that the elastotic degenerative changes are (1) expansion of the electron-dense inclusions to form a larger part of the fiber; (2) transformation of the inclusions into moderately electron-dense material, composing mainly of a fine granular component and an amorphous one; and (3) disorganization of the moderately electron-dense material.

Aged↗
PubMed1982

Antibody-independent binding of Clq and activation of serum complement by human skin in vitro.

By exposing frozen sections of human skin to fresh normal human serum, binding and activation of complement was observed. Attached complement components Clq, C4, and C3 were detected by immunofluorescence microscopy using anticomplement conjugates. Isolated Clq bound to the same structures as serum Clq, C4, and C3 and binding of C4 and C3 was dependent on binding of Clq. The complement components bound to capillary endothelial cells and to fibrillar structures in the dermis and reacted with the epidermis. Complement binding dermal fibrillar structures in adult skin were scant but abundant in fetal skin. They had similar distribution as "microfibrils" demonstrable by human autoantibodies. Antibody independence of the Clq binding was shown using isolated Clq and by the observed constant and reproducible binding of complement of normal sera lacking antibodies to the described target structures. The observations suggest that antibody independent binding of complement should be considered as a possible mechanism leading to dermal complement deposition in vivo.

Adult↗
PubMed1979

Biochemistry of the elastic fibers in normal connective tissues and its alterations in diseases.

The elastic fibers present in various connective tissues of the body are responsible for physiologic elasticity of the organs. These fibers consist of 2 distinct components, elastin and the elastic fiber microfibrils. Controlled synthesis and balanced interaction of these 2 components are essential for normal fibrillogenesis. The intracellular biosynthesis of elastin by connective tissue cells, such as smooth muscle cells, involves assembly of the polypeptide chains on the membrane-bound ribosomes, hydroxylation of some prolyl residues to hydroxyproline, and secretion of the polypeptides packaged in Golgi vacuoles. In the extracellular space the elastin molecules assemble into fiber structures which are stabilized by the synthesis of complex covalent cross-links, desmosines. Recently, aberrations in the structure or metabolism of elastin have been detected in a variety of heritable and acquired diseases affecting skin and other connective tissues. These conditions include pseudoxanthoma elasticum, cutis laxa, and elastosis perforans serpiginosa, as well as arteriosclerosis and other degenerative changes of the vascular connective tissues.

Amino Acids↗
PubMed1983

Immunohistochemical studies of amyloid P component distribution in normal human skin.

The distribution of amyloid P component (AP) in normal human skin was investigated by a light and electron microscopic immunoperoxidase technique, using antibodies to serum amyloid P component (SAP). AP, or an immunologically cross-reactive protein, was found to be specifically localized to the microfibrils of papillary oxytalan fibers and to the peripheral microfibrillar mantle surrounding the elastin core of mature elastic fibers in the reticular dermis; collagen fibers were not stained with anti-SAP. AP was not detected in the dermal-epidermal basement membrane or in the basement membranes surrounding dermal papillary blood vessels and eccrine structures. These findings, which establish the detailed distribution of normal tissue AP in the skin, provide a basis for further studies of the function and behavior of this protein in health and disease.

Amyloid↗
PubMed1982

Structural abnormalities in the dermal collagen and elastic matrix from the skin of patients with inherited connective tissue disorders.

Skin from patients with inherited disorders of connective tissue metabolism (EDS Types I-IX, Marfan's syndrome, osteogenesis imperfecta, spondyloepiphyseal dysplasia, and cutis laxa) has been examined by light and transmission electron microscopy for defects in the collagen and elastic fibrous connective tissue which may explain the clinical disorder and/or correlate with the biochemical defect (where known). Alterations were observed in the organization of the dermis and in the individual collagen and elastic fibers. The major alterations observed among collagen fibrils were hieroglyphic-shaped fibrils, collagen flowers, unravelled fibrils and fibrils of normal shape but abnormally large or small diameters or a mixed population of both. Elastic fibrils were sometimes fragmented, highly branched, granular, densely stained and had inclusions suggestive of cellular debris. These changes appeared to be a consequence of degradative processes. Other fibers were seen with a paucity of elastin matrix associated with the microfibrils or with totally separate deposition of the two elastic fiber components. Such fibers were barely visible by light microscopy. Alterations were observed in tissue concurrently regardless of whether the biochemical defect was related to only one of these connective tissue structures. The observations support an hypothesis that alterations in one component of the connective tissue matrix may influence the deposition and structure of others, ultimately, modifying the overall organization and mechanical properties of the tissue.

Adult↗
PubMed1988

An ultrastructural study of ultraviolet-induced elastic fiber damage in hairless mouse skin.

Ultrastructural visualization of mouse elastic fibers has been hampered by the small size and sparseness of the fibers. Furthermore, with conventional uranyl acetate and lead citrate stains, the elastin matrix remains electron-lucent so that even severe elastosis is elusive. The addition of tannic acid to the staining procedure renders the elastin matrix extremely electron dense and easily located even at low scanning power. Microfibrils, as with conventional stains, are electron-dense and clearly visible. This study describes, with the aid of tannic acid, normal hairless mouse elastic fibers and their progressive degeneration with increasing exposure to ultraviolet radiation. Results with the two staining methods are contrasted. In addition, photodamaged mouse and human elastic fibers are compared for differences and similarities.

Animals↗
PubMed1975

The epidermal-dermal junction.

Ultrastructurally, the epidermal-dermal junction is composed of four component areas:(1) the basal cell plasma membrane with its specialized attachment devices or hemidesmosomes, (2) an electron-lucent area, the lamina lucida, (3) the basal lamina, and (4) the sub-basal lamina fibrous components, including anchoring fibrils, dermal microfibril bundles, and collagen fibers. The light microscopic "basement membrane" comprises only the sub-basal lamina fibrous zone. Other cell types, including melanocytes and Merkel cells, are also found at the epidermal-dermal junction. Structures at the junction derive their origin from the epidermis and dermis: the basal lamina is primarily of epidermal origin, the anchoring fibrils of dermal origin. The junction serves the following functions: (1) epidermal-dermal adherence, (2) mechanical support for the epidermis, and (3) a barrier to the exchange of cells and of some large molecules across the junction.

Animals↗
PubMed1975

Epidermolysis bullosa dystrophica-recessive: a possible role of anchoring fibrils in the pathogenesis.

The purpose of this study was to define the ultrastructural defects and pathogenesis of epidermolysis bullosa dystrophica-recessive (EBD-R). The only consistent ultrastructural alteration found in EBD-R was an absence of anchoring fibrils. In many specimens of nonblistered, nontraumatized EBD-R skin, absence of anchoring fibrils was the only ultrastructural abnormality observed. The possibility that lack of anchoring fibrils was a secondary change resulting from previous blistering and scarring was eliminated by our observation that anchoring fibrils were consistently absent in the never previously blistered skin of two newborns with EBD-R. In experimentally traumatized skin, the epidermis and dermis separated in the region of the epidermal-dermal junction normally occupied by anchoring fibrils. Basal lamina and dermal microfibril bundles appeared to be normal. Using recombinant grafts, we demonstrated that anchoring fibrils were not formed by EBD-R dermis when combined with EBD-R epidermis or normal epidermis. Anchoring fibrils were formed when normal dermis was combined with normal and EBD-R epidermis. These studies indicate that the defect in EBD-R resides in the dermis and that the defect may be associated with impaired formation of anchoring fibrils.

Adolescent↗
PubMed2005

Apparent fragility of African hair is unrelated to the cystine-rich protein distribution: a cytochemical electron microscopic study.

A feature of black African hair is an apparent increased fragility of the hair shaft compared to other ethnic groups (as measured by the tensile force needed to break the hair fibre). This has certain similarities to that reported for trichorrhexis nodosa (weathering secondary to physical damage) and trichothiodystrophy [a genetic disorder associated with reduced cystine (sulphur)-rich proteins and increased fragility]. In the present study, the distribution of the cystine-rich proteins in the hair of black Africans was compared to that of Caucasian and Asian volunteers, plus patients with trichorrhexis nodosa and trichothiodystrophy, using transmission electron microscopy and specific silver stains. It was found that the silver staining pattern of the hair shafts of black Africans was similar to that observed for Caucasians, Asians and also patients with trichorrhexis nodosa. The cuticular cells exhibited an electron dense A layer and exocuticle, and in the cortex the microfibrils forming the macrofibres were outlined by electron-dense material. This contrasts with the abnormal distribution of the cystine-rich proteins seen in trichothiodystrophy. This study is the first formal comparison of the cystine-rich proteins in the various racial groups and shows that there is no abnormality in their distribution in black African hair shafts compared to the other ethnic groups. Therefore, the excessive structural damage observed in the African hair shafts is consistent with physical trauma (resulting from grooming) rather than an inherent weakness due to any structural abnormality.

Africa↗
PubMed1991

Sclerotic fibromas of the skin.

We report a case of a 34-year-old Japanese woman with a fibrous tumor on the left palm that fulfilled the criteria of sclerotic fibroma of the skin. Immunohistochemically, the tumor cells were positive for vimentin, but negative for S-100 protein and neuron-specific enolase. Ultrastructurally, the cross-striations of collagen microfibrils were less prominent. Our case supports the concept that sclerotic fibroma of the skin is a distinctive lesion which may represent a hamartoma of the skin.

Adult↗
PubMed1985

Effect of aculeacin A, a wall-active antibiotic, on synthesis of the yeast cell wall.

A wall-active, amphophilic antibiotic aculeacin A significantly but incompletely inhibited in vitro the activity of beta-(1,3)glucan synthase prepared from highly susceptible yeasts Saccharomyces cerevisiae and Candida albicans. In contrast, comparable cell-free preparations from S. cerevisiae active in chitin synthase or mannan synthase were insensitive to the antibiotic, suggesting selectivity of its action in synthesis of the yeast cell wall. An electron microscopic study of the effects of aculeacin A at 0.31 micrograms/ml, the optimally active concentration, on osmotically stabilized C. albicans cells revealed morphological alterations in both cell walls and cell membranes. Deformation in contour and derangement of the layered structure of the cell wall were prominent. In addition, massive fibrous material of beta-glucan-like microfibrils was occasionally extruded from the cell surface. Accompanying this effect on the cytology of the cell wall, ultrastructural and functional impairment of the cell membrane was demonstrated by transmission and freeze-fracture electron microscopic techniques. These data suggest that aculeacin A affects synthesis of the yeast cell wall through not only selective blockage of beta-(1,3)glucan synthase, as a result of a primary interaction with the cell membrane, but also inhibition of the fabrication of beta-glucan or other wall components into well-organized cell walls.

Antifungal Agents↗
PubMed1987

Effect of aculeacin A on reverting protoplasts of Candida albicans.

Protoplasts of Candida albicans were prepared by digestion with Zymolyase and the effect of aculeacin A, a wall-active antibiotic, on the synthesis of microfibrillar structures by the protoplasts incubated for 5 hr in an osmotically stabilized medium was studied using several electron microscopical techniques. Chemical analyses of the protoplasts before and after reversion with or without the antibiotic were also performed. Aculeacin A not only inhibited synthesis of microfibrils mainly composed of alkali-insoluble beta-glucan, but also their assembly to form thicker bundles. The antibiotic appeared to have no effect on other wall components constituting the surface structure of reverting protoplasts. These data confirmed our previous postulation that aculeacin A is a specific and potent inhibitor of beta-glucan synthesis as well as biogenesis of cell walls including beta-glucans in susceptible yeasts.

Alkalies↗