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Biomedical subjects

J Krachmer

Publications and source records attributed to J Krachmer.

6 recordsLinked to original sources
PubMed1988

Development of the anchoring structures of the epithelium in rabbit and human fetal corneas.

The sequence of development of the components of the corneal adhesion complex (hemidesmosomes, basal lamina and anchoring fibrils) was studied in rabbit and human fetal corneas using electron microscopy and histochemical localization of type VII (anchoring fibril) collagen. In the rabbit, basal lamina was present at 15 days gestation, followed by hemidesmosomes (HDs) and anchoring fibrils (AFs) at 20 days gestation. Type VII collagen was first localized at 20 days. At 25 days, HDs remained low compared to the adult value. During human corneal development, basal lamina was present at 8 weeks gestation. Through 12 weeks of gestation, no HDs or AFs were discernible nor was there any type VII localization. At 13-19 weeks, HDs and cross-banded AFs were seen, and localization of type VII collagen was first noted. A palisade of filaments extending perpendicularly from the basal lamina into the underlying stroma was discernible from 13 to 27 weeks. A distinct Bowman's layer was present at 19 weeks. By 27 weeks, HDs/micron membrane were greater than or equal to the adult value, and AF penetration into the underlying stroma was also greater than or equal to the adult value. Bowman's layer had not reached adult values by term. These data indicate that after basal lamina deposition, HDs and AFs develop synchronously in both species. In humans the palisade of filaments may be the precursor of Bowman's layer, and the AF network develops within Bowman's layer.

Animals↗
PubMed1987

Actin filament localization in developing and pathologic human corneas.

Actin is associated with motility, cell morphology, and cell-substrate adhesion. The molecular probe NBD phallacidin, which reacts with filamentous actin, was used to study the distribution of actin filaments in the corneal and conjunctival epithelium, stroma, and endothelium. Frozen sections of human fetal eyes from 8 weeks to 40 weeks of gestation were reacted with NBD phallacidin. Pathologic tissues included keratoplasty specimens from patients with hereditary posterior polymorphous corneal dystrophy (PPMD) and surgically excised tissues removed for treatment of epithelial down-growth. Normal human cornea was used as a control. Immunofluorescent staining disclosed actin filament distribution in corneal epithelium as early as 9-10 weeks of gestation. Staining increased with maturation until term. Adult human corneal epithelium showed more pronounced staining of the surface layers. Stromal staining was more extensive in earlier stages of gestation and decreased in later stages of gestation, after 20-21 weeks. In pathologic corneas with posterior polymorphous dystrophy, there was localization of actin, as well as keratin, in the abnormal epithelial-like layers lining the posterior cornea. In epithelial downgrowth, actin and keratin were demonstrated in multilayered squamous epithelium on the anterior iris surface. Actin appears to be involved in migration of corneal epithelial and endothelial cells.

Actin Cytoskeleton↗
PubMed1987

Suprabasal expression of a 64-kilodalton keratin (no. 3) in developing human corneal epithelium.

We have previously shown that a basic 64-kilodalton (no. 3 in the catalog of Moll et al.) and an acidic 55-kilodalton (no. 12) keratin are characteristic of suprabasal cell layers in cultured rabbit corneal epithelial colonies, and therefore may be regarded as markers for an advanced stage of corneal epithelial differentiation. Moreover, using an AE5 mouse monoclonal antibody, we showed that the 64-kilodalton keratin marker is expressed suprabasally in limbal epithelium but uniformly (basal layer included) in central corneal epithelium, suggesting that corneal basal cells are in a more differentiated state than limbal basal cells. In conjunction with previous data implicating the centripetal migration of corneal epithelial cells, our data support a model of corneal epithelial maturation in which corneal epithelial stem cells are located in the limbus, the transitional zone between the cornea and conjunctiva. In the present study, we analyzed the expression of the 64-kilodalton keratin in developing human corneal epithelium by immunohistochemical staining. At 8 weeks of gestation, the presumptive corneal epithelium is composed of a single layer of cuboidal cells with an overlying periderm; neither of these cell layers is AE5 positive. At 12-13 weeks of gestation, some superficial cells of the three- to four-layered epithelium become AE5 positive, providing the earliest sign of overt corneal epithelial differentiation. At 36 weeks, although the epithelium is morphologically mature (four to six layers), AE5 produces a suprabasal staining pattern, this being in contrast to the adult epithelium which exhibits uniform staining.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1984

Defective processing of keratan sulfate in macular corneal dystrophy.

Macular corneal dystrophy is a human genetic disorder characterized by corneal opacities that arise, in part, from a failure to synthesize mature keratan sulfate proteoglycans. The macromolecules in macular corneas and in keratoconus corneas, an abnormality not involving proteoglycans, were biosynthetically labeled with [3H]mannose and [14C]glucosamine in organ culture, and the keratan sulfate proteoglycans were immunoprecipitated with antibodies against the protein core of monkey keratan sulfate proteoglycan. The chondroitin sulfate proteoglycans, which did not react with the antibody, were oversulfated in corneas from patients with macular corneal dystrophy. Characterization of the immunoprecipitates showed that macular corneas did not make keratan sulfate proteoglycan but did synthesize an immunoreactive glycoprotein in nearly equal amounts as keratan sulfate proteoglycan was synthesized by the keratoconus cornea. The oligosaccharides on the immunoprecipitated macular glycoprotein appeared to be normal. However, the macromolecules contained an unsulfated glycoconjugate that was nearly as large as the normal keratan sulfate chains isolated from the keratoconus keratan sulfate-proteoglycan and contained the same relative proportions of labeled glucosamine, mannose, and fucose. This glycoconjugate was resistant to digestion with keratanase. These observations indicate that macular corneal dystrophy is caused by an error in the synthesis of keratan sulfate, possibly involving the specific sulfotransferases involved in sulfation of the lactosaminoglycan backbone of the chains.

Animals↗
PubMed1980

Epithelialization of the corneal endothelium in posterior polymorphous dystrophy.

The unusual cell type present on the posterior corneal surface of posterior polymorphous dystrophy patients has been characterized. In addition to microvilli and desmosomes, these cells contain abundant 10 nm filaments which by immunofluorescent staining were shown to consist of keratin proteins, a marker for epithelial cells.

Cornea↗