Effect of 1% sodium hyaluronate (Healon) on a nonregenerating (feline) corneal endothelium

A series of experiments were performed to investigate the effect of 1% sodium hyaluronate (Healon) on the nonregenerating corneal endothelium of the cat. Aqueous humor replacement with 1% sodium hyaluronate resulted in mild, transient elevations of intraocular pressure compared to eyes that were injected with balanced salt solution. Sodium hyaluronate 1% protected the feline endothelium against cell loss incurred by contact with hyaluronate-coated intraocular lenses compared to endothelial contact with lenses that were not coated with sodium hyaluronate. The use of intraoperative 1% sodium hyaluronate, however, did not protect against endothelial cell loss incurred by penetrating keratoplasty or prevent subsequent skin graft-induced corneal homograft rejections. Homograft rejections were milder, however, in some eyes that received grafts coated with 1% sodium hyaluronate. Image analysis of photographs of trypan blue- and alizarin red-stained corneal buttons after trephining, stretching of Descemet's membrane, rubbing against iris-lens preparations, or immediately after penetrating keratoplasty demonstrated that the stretching of the posterior cornea is an important cause of endothelial damage that would not be protected against by a viscoelastic coating.

Postnatal development of corneal endothelium

Comparison specular micrographs of infant and adult corneas from cats, cows, dogs, rabbits, and humans demonstrate that a large decrease in central endothelial cell density occurs during maturation of the cornea. Central endothelial cell counts of developing cat, dog, and rabbit corneas decrease rapidly during the first months of life. This rapid decline in endothelial cell density correlates with growth of the cornea to the adult size. Central endothelial cell counts of adult cat, cow, deer, dog, pig, rabbit, and human corneas are similar (2500 cells/mm2) despite a wide variation in corneal size. Comparison of observed endothelial cell counts with two hypothetical situations, one of unrestricted endothelial mitosis and the other of only endothelial hypertrophy, indicates that hypertrophy of individual cells is primarily responsible for achieving the adult cell density of 2500 cells/mm2 for these species. This observation is true for species that have a high adult endothelial mitotic capacity (rabbit) as well as those that do not (cat). The human cornea is a special case because the decline in central endothelial cell density indicates that a large apparent corneal endothelial cell loss (approximately 45%) occurs early in postnatal development.

Variation in basement membrane topography in human thick skin

Samples of human plantar and palmar skin were excised and incubated in 20 mM EDTA after which the epidermis was gently separated from the dermis with the plane of separation occurring in the lamina lucida. Scanning electron microscopic examination of the dermal component revealed the classically described series of regularly spaced grooves and papillae that characterize the epidermal-dermal junction in thick skin. Primary dermal grooves exhibited evenly spaced tunnels that were originally occupied by sweat gland ducts. The basement membrane (basal lamina) in the primary grooves was relatively smooth but did exhibit a flattened, reticulated pattern at high magnifications. The basement membrane of secondary dermal grooves and papillae was in the form of numerous, elevated microridges off of which septae arose at roughly right angles. The surface appearance of the basement membrane in these areas was that of a honeycomb owing to the numerous compartments and recesses formed by the ridges and septae. Degradation of the basement membrane by trypsin demonstrated that the foundation for the highly folded and compartmentalized basement membrane was composed of dermal collagen fibrils, 60-70 nm in diameter, that were arranged in a series of variably sized, interconnected collagen bundles or walls. Epidermal basal cells extended cytoplasmic (foot) processes into two or more compartments, formed by the ridges and septae, which considerably amplified the basement membrane surface available for epidermal attachment. Scanning electron microscopic studies of the epidermal-dermal junction confirm the variable surface character of this interface previously reported by others using sectioned material.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for corneal endothelial cell hypertrophy during postnatal growth of the cat cornea

Endothelial cell counts made from specular micrographs of 1-month-old kitten and adult cat corneas demonstrate that a progressive increase in endothelial cell size and a reduced endothelial cell density occurs during the postnatal development of the cat cornea. In addition to confirming the difference in cell size, scanning electron micrographs show that kitten endothelial cells are much more pleomorphic than those of the adult. When the number of corneal endothelial cells/mm2 and the size of the whole cornea are calculated for the kitten and adult, hypertrophy rather than mitosis appears to be the principal mechanism responsible for maintaining a confluent endothelial cell monolayer during the postnatal development of the feline cornea. Hypertrophy also appears to play a role in establishing the adult corneal endothelial cell population of the rabbit when the previously published data of others are treated in a similar manner to those of the kitten and adult cat. Thus, endothelial cell hypertrophy plays a role in establishing an "adult" endothelial cell monolayer in species that have a widely divergent corneal endothelial cell mitotic capacity.

The behavior of subcultivated stratified squamous epithelial cells on reconstituted extracellular matrices: initial interactions

Stratified squamous epithelial cells derived from the ventral surface of the rat tongue interact with matrices composed of hydrated dermal collagens (types I and III) and with a bovine basement membrane in distinctly different ways. When compared with the behavior of the cells on the basement membrane, the attachment and subsequent migration of the cells on the collagens were inefficient and slow. The resultant epithelial colonies did, however, stratify and differentiate more rapidly than those formed on the membrane. The fibrillar meshwork of the type III collagen gel provided better initial support for the cells than did the gel of type I collagen in which the fibrils were arranged as coarse aggregates. The physical characteristics of the type III gel also allowed the cells to condense the surface resulting in even better epithelial support. The basement membrane encouraged rapid epithelial coverage of large areas by promoting cell attachment and migration. This important property indicates that epithelial discontinuities can be rapidly repaired, providing the cells can migrate along a preexistent basement membrane. The use of such defined extracellular matrices in culture can provide important insight into the function and structural organization of subepithelial connective tissues and basement membranes.

Penetrating keratoplasty in the cat. A clinically applicable model

A series of 28 consecutive penetrating keratoplasties were performed on adult cats. Donor corneas (n = 14) were maintained in culture medium for 14--24 hours prior to transplantation. Rotational autografts (n = 7) were used to control for cell loss caused by culture maintenance as well as for the effects of surgery. Additional homografts (n = 7) were transplanted following removal of the corneal endothelium to study the extent of host corneal endothelial cell regeneration. Pre- and post-operative endothelial cell counts of the homografts made from specular micrographs demonstrated an average cell loss of 30% one month following surgery. A similar 30% average cell loss was present in the rotational autografts. Clinically, both homografts and autografts remained clear and were near normal in thickness. Homografts lacking endothelium exhibited persistent, severe edema that correlated with the inability of the host corneal endothelium to resurface the graft. Clinical and morphologic evidence of mild homograft rejection as observed in 15% of the animals that received normal homografts. Corneal endothelial cell loss following penetrating keratoplasty in the cat approximates that observed following the same procedure in the human. Additionally, regenerative capacity of the corneal endothelium in the cat, like that of the human, is limited. These features suggest that this cooperative, hardy animal is an excellent model in which to study many aspects of corneal transplantation that have direct application to the treatment of human corneal disease.

Complications associated with bovine corneal endothelial cell-lined homografts in the cat

Cultured bovine corneal endothelial cells were subcultured onto feline corneas from which the native endothelium had been mechanically removed, and transplanted into cats via penetrating keratoplasty. Although the transplants remained thin and clear in the immediate postoperative period, correlative clinical and morphologic analysis disclosed evidence of a host response directed against the heterologous endothelium by the ninth postoperative day. Eyes with rotational autografts or transplanted homografts did not disclose evidence of a similar host response.

A hot wire device for cutting tissue culture flasks

A small hot wire device for cutting plastic culture was can be constructed of steel rod, brass screws, nichrome wire and acrylic plastic sheeting and tubing. The nichrome wire is heated using a variable power transformer. Four sequential cuts are made in the culture flask bottom and the bottom separated from the remainder of the flask. Cultures can be stained, air-dried and cover slips affixed with PVP or epoxy resin. This method of cutting culture ware avoids the formation of small bits of polystyrene generated by rotating discs or saws.

Ultrastructure and histochemistry of the submandibular gland of the European hedgehog, Erinaceus europaeus L. II. Intercalated ducts and granular striated ducts

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