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M C Kenney

Publications and source records attributed to M C Kenney.

At least 55 records · Page 3Linked to original sources
PubMed1986

Decreased fibronectin levels in aqueous humor after corneal injury.

Fibronectin plays an important role in wound healing and cell differentiation. The present study measures fibronectin levels in aqueous humor from injured corneas. In response to transcorneal freezing treatments, a thickened scar-like matrix is deposited on the posterior surface of rabbit corneas. This posterior collagenous layer (PCL) is visible grossly and has a uniform diameter. Aqueous humor from eyes with established posterior corneal scarring has significantly less fibronectin compared with control eye aqueous humor. Tissue culture experiments show that corneal endothelial cells from control eyes and PCL-associated cells from injured eyes produce similar amounts of fibronectin. The marked decline in fibronectin levels in aqueous humor in scarred corneas supports the hypothesis that fibronectin plays a role in the pathological events which result from corneal injury.

Animals↗
PubMed1985

Fibronectin initiates fibrin production by rabbit corneal endothelial cells in vitro.

Confluent rabbit corneal endothelial cells incubated in the absence of serum do not produce fibrinogen. When exogenous fibronectin is added to these cultures, fibrinogen production is observed. Fibronectin concentrations stimulate fibrinogen synthesis by endothelial cells in a dose-response fashion. This direct interaction of fibronectin and fibrinogen may be important in both wound healing processes and pathological states.

Animals↗
PubMed1984

Characterization of the Descemet's membrane/posterior collagenous layer isolated from Fuchs' endothelial dystrophy corneas.

The combined Descemet's membrane (DM) and posterior collagenous layer (PCL) of Fuchs' endothelial dystrophy corneas were isolated and characterized by biochemical and immunofluorescence methods. The amino acid composition of the Fuchs' DM-PCL was similar to age-matched normal Descemet's membranes (DM). As determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and 125I two-dimensional peptide mapping, normal DM and Fuchs' DM-PCL contained the same collagen types [type IV and endothelial cell (EC) collagen], but a slight discrepancy was seen in the electrophoretic mobility of some collagen chains. Immunofluorescence staining localized fibrinogen/fibrin to Fuchs' DM-PCL but not to normal DM. These data suggest that the appearance of 110 nm banded material in sheets and fusiform bundles characteristic of Fuchs' PCL is not due to the presence of a new (abnormal) collagen type but may represent altered assembly of collagen molecules, and that the fibrinolytic system may play a role in the degenerative process of Fuchs' endothelial dystrophy.

Amino Acids↗
PubMed1983

The presence of EC collagen and type IV collagen in bovine Descemet's membranes.

When bovine Descemet's membranes (DMs) were characterized after limited pepsinization the major component in DM was found to be endothelial cell (EC) collagen. Phenol extractions of the undigested pepsin residue recovered only type IV collagen. This study provides evidence that EC collagen may be produced by corneal endothelial cells in vivo.

Amino Acids↗
PubMed1983

Vitamin A augments collagen production by corneal endothelial cells.

When isolated confluent corneal endothelial cells were cultured in delipidized serum, a marked reduction in collagen production was observed. Supplementation of such cultures with vitamin A as either retinol or retinoic acid at concentrations of 10(-6)-10(-7) M was capable of significantly increasing collagen production. In addition, when cultured in normal (non-delipidized) serum, both retinol and retinoic acid were capable of further increasing collagen production by corneal endothelial cells. Such augmentation of collagen production was relatively specific as total protein synthesis was not altered to the same extent, nor was it merely a reflection of changes in total cell number, as such cell numbers were similar in all treatment groups.

Animals↗
PubMed1983

Production of collagen by cells isolated from a retrocorneal fibrous membrane rabbit model.

The morphological and biosynthetic characteristics of cells from an experimentally induced rabbit retrocorneal fibrous membrane (RCFM) model were investigated. By transmission electron microscopy the cells within the RCFM demonstrated overlapping cytoplasmic processes and intercellular junctions, neither of which are fibroblast-like characteristics. The extracellular matrix within the RCFM had a fibrillar and amorphous component. Collagenous biosynthetic products of primary cultures of RCFM cells were compared to normal corneal endothelial cells, which produce mainly type IV collagen and a small amount of type V collagen, and fibroblasts, which produce types I, III and V collagens. The collagenous components produced by the RCFM cells were a combination of types I, V and low molecular weight fragments of type IV collagen. Therefore, these morphological and biochemical data suggest that RCFM cells are a type of modified corneal endothelial cell that produce collagens distinctly different from normal corneal endothelial cells.

Animals↗
PubMed1983

Identification of collagens isolated from bovine Descemet's membrane.

In this study collagens were isolated and identified from a morphologically pure preparation of bovine Descemet's membrane (DM) which was obtained by gentle scraping of the cornea, sieving and subsequent treatment with detergents. An alternative procedure of DM isolation with forceps resulted in stromal contamination of the preparation as verified by light and transmission electron microscopy, and gel electrophoresis. The amino acid profile of collagens isolated by pepsinization and salt precipitation from the pure sample was similar to the analysis of the intact bovine DM. Polyacrylamide gel electrophoresis of this collagen under non-reducing conditions resulted in five major bands: 300 000 daltons (300 K), 200 000 daltons (200 K), 100 000 daltons (100 K) and lower molecular weight fractions (50 K1 and 50 K2). Individual collagen chains were isolated from preparative polyacrylamide gels and characterized by 125I two dimensional peptide mapping patterns. This data suggests that (1) the majority of collagen fragments seen in bovine DM pepsin supernatant are derived from a single genetically distinct collagen molecule, and (2) that type I and V collagens are not major components of bovine DM.

Amino Acids↗
PubMed1982

An ultrastructural analysis of isolated basement membranes in the acellular renal cortex: a comparison study of human and laboratory animals.

Freshly harvested kidneys from New Zealand white rabbits, Sprague-Dawley white rats, rhesus monkeys, and transplant-quality human kidneys were used in this study. Minced renal cortical tissue blocks (less than 2 mm3) were treated with 1 mM EDTA, 3% Triton X-100, 0.025% DNAse, and 4% sodium deoxycholate in an effort to remove all cellular elements and leave the extracellular matrix (ECM) intact. These preparations showed remarkable structural preservation and all components of the ECM, including basement membranes (BMs), maintained their in vivo histoarchitectural relationships. By light microscopy, at least four major BM types were recognizable, including Bowman's capsular BM (BCBM), tubular BM (TBM), glomerular BM (GBM), and peritubular capillary BM (PTCBM). Scanning electron microscopy demonstrated that, despite the lack of supporting interstitium, GBMs in human, monkey, and rat (and rabbit to a lesser degree) exhibit intrinsic structural rigidity such that their convoluted spheroidal shapes are maintained following cell removal. Transmission electron microscopy showed that major BM types are morphologically heterogeneous and vary markedly within and between species. Randomized measurements showed that isolated BM thicknesses (lamina densa only) compared favorably with those reported in cellular preparations. Mean thicknesses of GBMs were within normal ranges in all species with or without power transformations to reduce right-sided skew of distribution curves. In all species, thickness of BCBM greater than TBM greater than GBM greater than PTCBM. The striking morphologic heterogeneity of major BM types demonstrated in the acellular renal cortex is not surprising in view of recent biochemical analyses that show that BMs derived from different sources are compositionally disparate. We conclude that BMs should be evaluated and characterized individually and that morphologic definition of isolated BMs necessary prior to further analysis.

Animals↗
PubMed1982

Structural properties of Type I collagen isolated from chickens with scoliosis.

This study examines biochemically the Type I collagen isolated from skin of chickens that develop idiopathic scoliosis. Previous studies indicate a defect in collagen exists in these chickens. Alpha 1 (I) and alpha 2 chains were separated by gel filtration and carboxymethyl cellulose column chromatography and were then subjected to the analytical techniques of sodium dodecyl sulfate gel electrophoresis, Staphylococcus aureus V8 protease digestion, cyanogen bromide peptide mapping and amino acid analyses. In all categories, the scoliotic alpha 1 (I) and alpha 2 chains were identical to alpha chains isolated from normal chickens. These data suggest that the altered properties of collagen solubility and connective tissue stress relaxation seen in these scoliotic chickens are not a manifestation of an altered primary structure of the alpha chains or post-translational modification affecting chromatographic elution profiles or electrophoretic migration patterns.

Amino Acids↗
PubMed1980

Surface ultrastructure of the isolated avian notochord in vitro: the effect of the perinotochordal sheath.

The perinotochordal sheath (PNS) is a "tube" of extracellular matrix (ECM) that surrounds the avian notochord beginning in the second day of development. Somites, like the notochord, derive from chordamesoblast but are encased by a less substantial perisomitic matrix (PSM). Initially both tissue types exhibit epithelioid characteristics. Somitic cells subsequently disperse, however, while notochordal histoarchitecture is maintained until much later. To test the possible shape-preserving role of the PNS, otochords were isolated from chick embryos by homogenization (which retains the sheath) or by trypsinization (which removes the sheath). Somites were similarly isolated. Tissues were cultured 12-72 hours and studied by LM, SEM and TEM. Mechanically isolated notochords are initially rigid with smooth surfaces. During the culture period a few cells grow outward from cut ends of the notochord, but its overall rod shape and intact PNS are maintained. In contrast, uncultured trypsinized notochords are flaccid, denuded cylinders with numerous cytoplasmic blebs. They adhere to the substratum within 12 hours of culture when a few cells break away from the central tissue rod, migrate laterally, and appear mesenchymal. This cellular dispersion is directional (perpendicular to the long notochordal axis) and continuous (up to 72 hours). At this time a flattened ovoid growth area is formed. Cultured somites form flat circular growth areas within 12 hours of culture irrespective of the isolation method. These data suggest that the maintenance of an epithelial configuration by notochords in vivo may be due in part to physical restraints of the PNS. It seems possible that notochordal secretions (manifested by the formation of a PNS) could result in its compartmentation and axial confinement while its unrestrained somitic relatives are free to disperse.

Animals↗
PubMed1980

Preparation and histoarchitecture of ultrastructurally pure glomerular basement membrane.

Our recent morphological studies showed that basement membranes isolated from renal tubules tended to collapse and form folded sheets while glomerular basement membranes were more resilient. In an effort to study the shapes of various isolated basement membranes in undissociated tissues, a method was developed to remove all cellular elements and leave the extracellular matrix and associated basement membranes intact. Accordingly, transplant quality human kidneys were harvested, perfused with Collin's medium and transported to the laboratory on ice. The renal cortex was then peeled away by blunt dissection, further minced to 2 mm3 and placed in 1 mM EDTA (with gentle intermittent stirring) for 72 h at 4 degrees C. Solubilization of cellular materials was carried out by successive washings with 3% Triton X-100, 0.025% DNAse and 1-4% sodium deoxycholate (all with gentle stirring or shaking at 22 degrees C). Each solution contained 0.1% sodium azide. At the level of fine structure, glomerular, tubular, Bowman's capsular and peritubular capillary basement membranes all maintained their respective shapes and did not collapse. Glomerular basement membrane was particularly striking in this regard and exhibited an open, lobulated form that closely resembled its in vivo histoarchitecture. Moreover, when the acellular tissue blocks were prepared for scanning electron microscopic observation, the glomerular basement membranes exposed at the surface of the block showed a remarkable structural rigidity. These basement membranes were free-standing, convoluted electron-dense sheets, continuous with highly folded central mesangial regions. It seems significant that glomerular basement membranes maintain their in vivo conformation irrespective of the presence of other extracellular matrix components while removal of these materials by organ subfractionation results in folding and general shapelessness of tubular basement membrane. It is possible that in addition to its unique role in filtration, glomerular basement membrane may also serve to preserve glomerular shape, regardless of changing cell populations or alterations in hydrostatic pressures.

Basement Membrane↗
PubMed1979

A new technique for isolation of Descemet's membrane: preliminary studies.

The structure and function of basement membranes have been the subject of extensive investigation. The present study takes advantages of a new experimental procedure to yield ultrastructurally pure basement membranes and applies this methodology to Descemet's membrane, a highly specialized ocular basement membrane. Rabbit Descemet's membranes and associated endothelial cells were mechanically isolated without contaminating stromal elements. The endothelial cells were then solubilized and removed by treatment with detergents as verified by light microscopy and scanning and transmission electron microscopy. The Descemet's membrane remained intact and retained its fibrillar fine structure. Therefore purity of starting material for ongoing morphological and biochemical studies of isolated Descemet's membranes is demonstrated. These investigations will provide a valuable data base for comparison with disease-altered Descemet's membranes.

Animals↗
PubMed1978

Ultrastructural identification of collagen and glycosaminoglycans in notochordal extracellular matrix in vivo and in vitro.

Notochordal extracellular matrix consists of a continuous basal lamina, amorphous materials and microfibrils embedded in the ground substance of low electron density. Together they comprise the notochord sheath and are of considerable interest because of their suspected role in early embryonic tissue interactions. The notochord is particularly well-suited to morphological investigation of extracellular matrix because it is one of the few embryonic epithelia which produces ultrastructurally recognizable stroma in vitro without the advantage of a collagenous substratum. Furthermore, these matrix components produced in vitro are morphologically identical to those observed in vivo. The present study used ruthenium red staining to demonstrate that notochordal microfibrils exhibit collagen-like cross-banding patterns both in vivo and in vitro. Collagenase and testicular hyaluronidase digestion studies designed to localize collagen and glycosaminoglycans show a reduction of microfibrillar diameters by 30-35%. Furthermore, these enzyme treatments frequently result in enhanced striations of microfibrils. When cis-hydroxyproline (a proline analog) or beta-aminoproprionitrile (BAPN, a lathyrogenic compound) is added to the culture medium, a similar reduction in microfibrillar diameters is seen. Moreover, increased ruthenium red-positive surface coats and large collagen fibrils are frequently present in BAPN-treated cultures, implying a stimulatory metabolic effect. We conclude that most, if not all, notochordal extracellular matrix components are composed of both collagen and glycosaminoglycans and suggest that the entire extracellular matrix should be considered a macromolecular composite which acts in concert to induce or stabilize developmental interactions.

Aminopropionitrile↗