Biomedical subjects

George A Abrams

Publications and source records attributed to George A Abrams.

4 recordsLinked to original sources

PubMed2003

Ultrastructural basement membrane topography of the bladder epithelium.

The basement membrane underlies epithelium and separates it from deeper tissues. Recent studies suggest that nanoscale topography of the surface of basement membrane may modulate adhesion, migration, proliferation and differentiation of overlying epithelium. This study was performed to elucidate nanoscale topographic features of basement membrane of the bladder. Bladder tissues were obtained from three adult female rhesus macaques. A process was developed to remove the epithelium while preserving the underlying basement membrane, and tissues were evaluated by immunohistochemistry and scanning electron microscopy (SEM). Detailed measurements were made of stereo SEM images to quantitatively define topographic features. Measurements made from multiple SEM images of bladder basement membrane provided the following values for topographic features: mean feature height, 178+/-57 nm; mean fiber diameters, 52+/-28 nm; mean pore diameter, 82+/-49 nm; and mean interpore distance (center to center), 127+/-54 nm. These dimensions are similar to those reported previously for basement membranes of other species and anatomical locations. This information provides a rational basis for design of nanostructured biomaterials to produce composite grafts for repair or replacement of segments of the urinary tract.

Animals↗

PubMed2003

Epithelial contact guidance on well-defined micro- and nanostructured substrates.

The human corneal basement membrane has a rich felt-like surface topography with feature dimensions between 20 nm and 200 nm. On the basis of these findings, we designed lithographically defined substrates to investigate whether nanotopography is a relevant stimulus for human corneal epithelial cells. We found that cells elongated and aligned along patterns of grooves and ridges with feature dimensions as small as 70 nm, whereas on smooth substrates, cells were mostly round. The percentage of aligned cells was constant on substrate tomographies with lateral dimensions ranging from the nano- to the micronscale, and increased with groove depth. The presence of serum in the culture medium resulted in a larger percentage of cells aligning along the topographic patterns than when no serum was added to the basal medium. When present, actin microfilaments and focal adhesions were aligned along the substrate topographies. The width of the focal adhesions was determined by the width of the ridges in the underlying substrate. This work documents that biologic length-scale topographic features that model features encountered in the native basement membrane can profoundly affect epithelial cell behavior.

Actin Cytoskeleton↗

PubMed2002

Conjunctivitis in birds.

There are numerous causative agents of avian conjunctivitis, many of which are associated with systemic disease. A thorough evaluation of the patient's history and habitat is mandatory, and a complete physical examination and ophthalmic examination are required. The owner should be informed at the initial visit that an orderly sequential approach for obtaining diagnostic specimens is required and that a protracted course of treatment may be required to bring about complete, long-lasting resolution of clinical signs.

Animals↗

PubMed2002

Electron microscopy of the canine corneal basement membranes.

The purpose of this study was to characterize the surface topographical features of the epithelial and endothelial (Descemet's) basement membranes of the canine cornea. Corneas were obtained from young, healthy dogs (<2 years old) with no history or evidence of previous ocular disease. The epithelium and endothelium was carefully removed preserving the anterior and posterior basement membranes. The specimens were examined by transmission electron microscopy and scanning electron microscopy. The epithelial and endothelial basement membrane surface topography is an intricate meshwork of pores and fibers measuring in the nanometer size range. The features of the endothelial basement membrane overall are smaller in size than the epithelial basement membrane. These surface topographical features may incite changes in epithelial and endothelial cell behavior.

Animals↗