Biochemical Composition of the Epidermal-dermal Junction and Other Basement Membrane

The epidermo-dermal junction ultrastructurally appears to be high organized, presenting 4 layers: (1) the basal cell plasma membrane, a trilaminar layer with special attachment structures (hemidesmosomes); (2) lamina lucida (rara) an electron-lucent zone with 'anchoring' filaments (vide infra); (3) basal lamina (densa) electron-dense and relatively thick (30-50 nm) and (4) the subbasal fibrous area, composed of 3 different fibrils: (a) 'anchoring fibrils' meshing with the lamina densa upwards and forming and interlocking (a) meshwork with the adjacent anchoring fibrils downwards; (b) dermal microfibril bundles starting from the basal lamina and passing deep in the dermis. The dermal part of these, are in connection with the elastic fibers and ultrastructurally they are identical and; (c) collagen fibers, randomly oriented without connection with the basal lamina. The biochemical composition comprises collagenous and noncollagenous substances: collagens can be divided into 3 groups designated as type IV collagen, type V(AB collagen) and 7S collagen. The non-collagenous materials as yet identified are: bullous pemphigoid antigen (reactive with the bullous pemphigoid antibodies), laminin, heparan-sulfate containing proteoglycan and amyloid P-component (a normal plasma constituent). Functional aspects of basement membrane components: (1) support of a caffolding function assumed by the collagens; (2) attachment of cells of different embryonic origin (fibronectin, PB antigen and laminin); (3)regulation of the permeability (heparan-sulfate proteoglycan and other glycosaminoglycans); and (4) a role in development and morphogenesis (laminin) and type IV collagen). This paper must be read in extenso by those interested in the microstructure and functions of the skin. (I. Capusan - Cluj

The time-dependent rearrangement of the epithelial basement membrane in human skin wounds

In 62 human skin wounds (surgical wounds, stab wounds and lacerations after surgical treatment) we analyzed the immunohistochemical localization of collagen IV in the epithelial basement membrane. In 27 of these wounds the distribution of collagen VII, which represents a specific component of the basement membrane of stratified epithelia, was also analyzed. We were able to demonstrate a virtually identical co-distribution of both collagen IV and VII in the wound area with no significant time-dependent differences in the appearance of both collagen types. Fragments of the epithelial basement membrane could be detected in the wound area from as early as 4 days after wounding and after 8 days a complete restitution of the epithelial basement membrane was observed. In all cases with a wound age of more than 21 days the basement membrane was completely reformed over the former lesional area. The period between 8 and 21 days after wounding was characterized by a wide variability ranging from complete restitution to deposition of basement membrane fragments or total lack of the epidermal basement membrane

Recent advances in understanding brain capillary function

The endothelial cells in brain capillaries form a blood-brain barrier which limits and controls the movements of solutes between blood and brain. These cells contain continuous tight junctions and exhibit a low rate of pinocytosis, resulting in formation of a permeability barrier to macromolecules and many polar compounds. However, brain capillary endothelial cells also contain specialized transport systems that facilitate blood-to-brain transfer of some solutes and actively pump other solutes from brain to blood. Several investigators have developed methods to isolate microvessels from brain or to grow brain capillary endothelial cells in tissue culture. This review summarizes progress made with these model systems and discusses their usefulness in increasing our knowledge of brain capillary function.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50303/1/410140402_ftp.pd

An In Vitro Model of the Glomerular Capillary Wall Using Electrospun Collagen Nanofibres in a Bioartificial Composite Basement Membrane

The filtering unit of the kidney, the glomerulus, contains capillaries whose walls function as a biological sieve, the glomerular filtration barrier. This comprises layers of two specialised cells, glomerular endothelial cells (GEnC) and podocytes, separated by a basement membrane. Glomerular filtration barrier function, and dysfunction in disease, remains incompletely understood, partly due to difficulties in studying the relevant cell types in vitro. We have addressed this by generation of unique conditionally immortalised human GEnC and podocytes. However, because the glomerular filtration barrier functions as a whole, it is necessary to develop three dimensional co-culture models to maximise the benefit of the availability of these cells. Here we have developed the first two tri-layer models of the glomerular capillary wall. The first is based on tissue culture inserts and provides evidence of cell-cell interaction via soluble mediators. In the second model the synthetic support of the tissue culture insert is replaced with a novel composite bioartificial membrane. This consists of a nanofibre membrane containing collagen I, electrospun directly onto a micro-photoelectroformed fine nickel supporting mesh. GEnC and podocytes grew in monolayers on either side of the insert support or the novel membrane to form a tri-layer model recapitulating the human glomerular capillary in vitro. These models will advance the study of both the physiology of normal glomerular filtration and of its disruption in glomerular disease

Bovine corneal endothelium in vitro : Elaboration and organization of a basement membrane

Bovine corneal endothelial cells can be easily grown in culture using conventional techniques. The cultured cells closely resemble the parent, native endothelium. In culture the endothelium synthesizes and deposits, in a polar fashion, a well organized basement membrane that contains molecules which are characteristic of all basement membranes. Membrane deposition continues for at least a year and, during that time, it begins to acquire the unique, ordered substructure characteristic of the native membrane.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23987/1/0000236.pd

MOLECULAR STRUCTURE OF THE EPIDERMAL EXTRACELLULAR SPACES

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65966/1/j.1365-4362.1979.tb01946.x.pd

Genome Sequence of a Lancefield Group C Streptococcus zooepidemicus Strain Causing Epidemic Nephritis: New Information about an Old Disease

Outbreaks of disease attributable to human error or natural causes can provide unique opportunities to gain new information about host-pathogen interactions and new leads for pathogenesis research. Poststreptococcal glomerulonephritis (PSGN), a sequela of infection with pathogenic streptococci, is a common cause of preventable kidney disease worldwide. Although PSGN usually occurs after infection with group A streptococci, organisms of Lancefield group C and G also can be responsible. Despite decades of study, the molecular pathogenesis of PSGN is poorly understood. As a first step toward gaining new information about PSGN pathogenesis, we sequenced the genome of Streptococcus equi subsp. zooepidemicus strain MGCS10565, a group C organism that caused a very large and unusually severe epidemic of nephritis in Brazil. The genome is a circular chromosome of 2,024,171 bp. The genome shares extensive gene content, including many virulence factors, with genetically related group A streptococci, but unexpectedly lacks prophages. The genome contains many apparently foreign genes interspersed around the chromosome, consistent with the presence of a full array of genes required for natural competence. An inordinately large family of genes encodes secreted extracellular collagen-like proteins with multiple integrin-binding motifs. The absence of a gene related to speB rules out the long-held belief that streptococcal pyrogenic exotoxin B or antibodies reacting with it singularly cause PSGN. Many proteins previously implicated in GAS PSGN, such as streptokinase, are either highly divergent in strain MGCS10565 or are not more closely related between these species than to orthologs present in other streptococci that do not commonly cause PSGN. Our analysis provides a comparative genomics framework for renewed appraisal of molecular events underlying APSGN pathogenesis

An electron microscopic autoradiographic study of proline incorporation by mouse lingual epithelium

Mouse lingual epithelium incorporates significant amounts of L-proline-2, 3-H 3 one hour after intraperitoneal injection of the tritiated amino acid. All viable cell strata incorporated approximately equal amounts of proline as assessed by autoradiographic techniques. Grain counts at 30 minutes, 1 hour, 4 hours and 24 hours, the four time periods studied, indicated a progressive incorporation of proline up to 4 hours following injection. Preferential incorporation of proline into any one cell structure or group of structures was not observed. Keratohyalin granules (KHG's) demonstrated incorporated proline; however, usually only one silver grain appeared over each granule, and, based on grain counts, the amount of proline incorporated by KHG's appeared slightly less than the general labeling observed in KHG-containing cells. This finding supports recent biochemical studies which have indicated a considerably lower proline content of keratohyalin than had previously been reported. Significant proline incorporation into the epithelial basal lamina was not observed during the 24 hours of this study. Thus, while recent recombination experiments have conclusively demonstrated that epithelial basal cells synthesize considerable quantities of basal lamina in a 24 hour period; it would appear that epithelial basal cells contribute little to a formed, intact basal lamina. This finding lends credence to the concept of a long basal lamina turnover time.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47661/1/441_2004_Article_BF00307250.pd