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C Cintron

Publications and source records attributed to C Cintron.

At least 19 recordsLinked to original sources
PubMed1991

Immunohistochemistry of proteoglycans in human lamina cribrosa.

Proteoglycans are macromolecular components of connective tissue, which are believed to have an important role in the organization of other extracellular matrix components and in the hydration and rigidity of tissue. Using antibodies to the heparan sulfate-, dermatan sulfate-, and keratan sulfate-proteoglycans core proteins, we used indirect immunofluorescence to determine the presence of these core proteins and to characterized their distribution in the lamina cribrosa of healthy human eyes of various ages. Findings with heparan sulfate-proteoglycan core proteins support the multilayered organization of basement membranes in the lamina cribrosa as proposed in previous reports. Dermatan sulfate-proteoglycan core protein results indicate colocalization with fibrillar collagen. Application of monoclonal antibodies to the glycosaminoglycan side chain disclosed an increasing predominance of chondroitin-4-sulfate over chondroitin-6-sulfate with age. This may indicate a decreasing water-holding capacity of the cribriform plates and suggest a decreasing ability to withstand pressure. This study attempts to identify the core proteins of proteoglycans in human lamina cribrosa and serves as a basis for study of glaucomatous eyes.

Adolescent↗
PubMed1991

Differential roles for two gelatinolytic enzymes of the matrix metalloproteinase family in the remodelling cornea.

We have documented changes in collagenolytic/gelatinolytic enzymes of the matrix metalloproteinase family (MMP) in remodelling rabbit cornea. MMP-2 (65 kDa gelatinase) in the proenzyme form is synthesized by the cells of the normal corneal stroma. After keratectomy the level of MMP-2 is increased in the stroma and enzyme appears in both pro- and activated forms. In addition, corneal cells synthesize MMP-9 (92 kDa gelatinase) in the proenzyme form after keratectomy; expression occurs in both the epithelial as well as stromal corneal layers. Changes in expression of both enzymes are precisely localized to the repairing portion of cornea, but demonstrate important differences in timing that correlate with the timing of specific events of matrix remodelling. Our data suggest that each of the gelatinases plays a different role in tissue remodelling after injury. We hypothesize that MMP-2 performs a surveillance function in normal cornea, catalyzing degradation of collagen molecules that occasionally become damaged. After wounding, this enzyme appears to participate in the prolonged process of collagen remodelling in the corneal stroma that eventually results in functional regeneration of the tissue. MMP-9 expression does not correlate with stromal remodelling, but we suggest that the enzyme might play a part in controlling resynthesis of the epithelial basement membrane.

Animals↗
PubMed1990

Proteoglycan distribution in developing rabbit cornea.

We used a staining procedure specific for sulfated glycosaminoglycans, cuprolinic blue dye (CBD), and immunohistochemical techniques to determine the histological distribution and ultrastructural organization of proteoglycans in developing rabbit cornea. We found several types of CBD-stained structures located throughout the corneal stroma, indicative of the distribution and perhaps the chemical heterogeneity of proteoglycans in this tissue. Keratan sulfate-specific immunohistochemical evidence supports our cytochemical findings. Our results suggest that low-sulfated keratan sulfate proteoglycans are found throughout most of the developing stroma, with the exception of the posterior margin of this tissue. Highly sulfated keratan sulfate proteoglycans in young fetal corneas, initially restricted to the subepithelial stroma, progressively extend to deeper portions of the stroma with development. Dermatan sulfate proteoglycans are located throughout the stroma, including the posterior margin. Invoking a recently published "oxygen-lack hypothesis" and correlating the tissue location of proteoglycans with the source of oxygen, we hypothesize that the distribution of proteoglycans in the developing rabbit cornea is related to the selective synthesis of keratan sulfate glycosaminoglycans under hypoxic conditions.

Animals↗
PubMed1990

Morphologic analyses of proteoglycans in rabbit corneal scars.

Ultrastructural localization of proteoglycans (PGs) in 1-week- to 2-year-old scar was determined by staining with cuprolinic blue dye (CBD) after specific enzymatic digestion of keratan sulfate (KS) glycosaminoglycans (GAGs) or chondroitin sulfate glycosaminoglycans (CSs). High critical electrolyte conditions were maintained for CBD-staining, specific for high-sulfated GAGs. Although KS was detected in the 1-week-old wound, no CBD-stained KS was seen in the anterior stroma adjacent to the wound. The CS was present throughout the 1-week-old wound and adjacent stroma, and PGs were biosynthetically 35SO4-labeled in normal stroma. Subsequently, radioactivity from labeled PGs in normal stroma adjacent to the wound moved into scar tissue during healing. Marked sensitivity of PGs to Chondroitinase ABC indicated an abundance of CS in 2-week-old scars. Punctate CBD-staining and immunohistochemical evidence suggested chemically altered KS is present in the 2-week-old anterior scar. The pattern of CBD-staining in 1- and 2-week scars, after chondroitinase treatment, suggested KS in the younger scar is similar to adult high-sulfated GAG, whereas KS in the 2-week scar contains primarily newly synthesized low-sulfated KS. The latter is consistent with previous immunochemical and biochemical analyses. Cytochemical and immunohistochemical evidence indicated that KS is not present in the 2-week-old posterior scar. By the week 8 of healing, CBD-stained KS was present throughout most of the scar, except along the posterior margin, consistent with earlier stages of healing. The CBD-stained structures in the first 8 weeks of healing were reminiscent of stained GAGs in normal developing cornea. This fetal-like CBD-staining pattern seen in scar, however, changed to that of the normal adult by the 2nd year of healing. The significance of these observations relate to our contention that healing adult cornea recapitulates some ontogenetic events of the normal cornea, and that the nonuniform distribution and chemical properties of GAGs in scar tissue are a function of the movement of existing proteoglycans and de novo synthesis of altered macromolecules.

Animals↗
PubMed1990

Immunolocalization of type VI collagen in developing and healing rabbit cornea.

We have localized type VI collagen in normal developing and corneal scar tissue. Indirect immunofluorescence showed that type VI collagen was distributed throughout the normal stroma and most of the scar. No fluorescence was detected along the posterior margin of the scar and in a retrocorneal membrane continuous with the scar. Since the corneal endothelium in rabbits contributes to the formation of scar tissue and retrocorneal membrane, our observations suggest that the endothelium does not synthesize type VI collagen. Indirect immunoelectron microscopy showed that type VI collagen was located abundantly between collagen fibrils as fine filamentous structures containing beads with a periodicity of 100 nm, consistent with published observations of other tissues. Because these filaments are more prominent when stained with ruthenium red, and predigestion of tissue with Chondroitinase ABC enhances binding of monoclonal antibody to type VI collagen, proteoglycans probably are associated with this collagen in the cornea. Ultrastructural observations supported by previous biochemical analyses show that the proportion of type VI collagen to fibrillar collagen is smaller in scar tissue compared with fetal cornea. The abundance of type VI collagen and its distribution and association with proteoglycans in rabbit corneal tissues suggest that this macromolecule plays a role in the tensile strength and transparency of the stroma.

Animals↗
PubMed1990

Biochemical analyses of proteoglycans in rabbit corneal scars.

Macromolecules from normal rabbit cornea and cornea containing a 2-mm diameter button of scar tissue were biosynthetically labeled with 35S-sulfate and 3H-glucosamine in vivo and in organ culture. Labeled macromolecules, including proteoglycans (PGs) extracted from the normal cornea, scar tissue, and corneal tissue adjacent to the scar with guanidine hydrochloride were chromatographed on DEAE-Sepharose CL-6B columns and eluted with increasing concentrations of NaCl. The elution pattern of corneal macromolecules synthesized in vitro was remarkably similar to that in vivo. In another experiment, corneas having 2-, 4-, and 8-week-old scars were labeled in organ culture and also extracted. Scars synthesized PGs with lower sulfation than those of adjacent corneal tissue. Although PG synthesis in scar decreased with wound age, the synthesis in adjacent cornea remained the same. In a third experiment, PGs extracted from pools of unlabeled 2- and 4-week-old scars, adjacent corneal tissue, and normal corneas were chromatographed on ion-exchange columns and analyzed chemically. The quantity of PGs in scar and adjacent cornea increased with healing time. The ratios of keratan sulfate PG to dermatan sulfate PG in normal cornea, scar, and adjacent cornea was 2.3, 0.6, and 1.5, respectively. The PGs from adjacent corneal tissue had a higher charge density than those from scar. The predominant adjacent-cornea dermatan sulfate PG had a higher charge density than that in normal cornea. The authors conclude that cornea adjacent to the healing wound synthesized PGs measurably different fro those in scar and normal cornea.

Animals↗
PubMed1988

Morphogenesis of rabbit corneal endothelium.

We studied ultrastructurally the development of rabbit corneal endothelium from the 13th day of gestation to 3 days after birth. Precursor corneal endothelial cells, stromal cells, and a vascular network migrate in close association with each other between the developing corneal and lens epithelia. During development, newly deposited extracellular fibrous matrices separate the prospective endothelium from the capillaries and corneal stroma. The extracellular matrix between the apical endothelial surface and the vascular network loses its fibrous appearance early in development. Simultaneously, randomly organized fibrils are deposited on the basal endothelial surface facing the stroma. These fibrils, gradually obscured by the deposition of a nonfibrous component, eventually become part of Descemet's membrane. Early in development, prospective endothelial cells cannot be distinguished morphologically from the overlying corneal stromal cells. Morphologic differentiation of the endothelial cell is characterized by the formation of sinuous lateral borders that interdigitate with those of adjacent cells to form a continuous single-cell layer of tissue. The basal endothelial membrane forms a pitted surface, distinguishing it from the apical cell membrane. Intercellular junctions between lateral membranes, a cilium projecting into the anterior chamber, and deposition of Descemet's membrane on the basal endothelial surface contribute to the polarization of the endothelium. Throughout most of corneal development the vascular pupillary membrane maintains a close association with the apical surface of the differentiating endothelium. We conclude that fetal corneal endothelium develops within a complex extracellular matrix environment and in proximity to the underlying vascular network. These structures play an important role in the morphogenesis of corneal endothelium.

Animals↗
PubMed1988

Organ culture of rabbit cornea: morphological analyses.

Tissues maintained in vitro often undergo changes in the pattern of protein synthesis that result in the deposition of macromolecules quantitatively or qualitatively unrelated to those normally synthesized. In these preliminary studies, we modified published techniques to maintain adult and neonate rabbit corneas in vitro for 24 to 48 h. Measurements of corneal wet weight, and histologic and ultrastructural analyses were made to determine the success of maintaining rabbit corneas in culture. The results show that rabbit corneas can maintain normal corneal hydration and tissue structure for at least 48 h when incubated in Coon's modification of Ham's F12, 5% fetal or newborn calf serum, 2 mM glutamine, and 2% chondroitin sulfate or 2% 50 kDa dextran sulfate at 37 degrees C in a 5% CO2/air atmosphere. In addition, we confirmed previous observations that corneal explants must have a 1 to 2 mm rim of limbal sclera, and the organ placed in the culture dish with the epithelial side down to guard against damage and insure endothelial functioning. Normal ultrastructure of neonate rabbit cornea is also maintained when organ-cultured with these procedures. Moreover, neonate corneas continue to synthesize collagen in culture.

Animals↗
PubMed1988

Immunoanalysis of keratan sulfate proteoglycan from corneal scars.

Corneal keratan sulfate proteoglycan (KSPG) from scar tissue of experimental penetrating corneal wounds in rabbits was analyzed 2-8 weeks after injury using three previously characterized antibodies. Keratan sulfate (KS) was identified in 2 week scars and normal corneal tissue by indirect immunofluorescence using a monoclonal antibody against sulfated KS epitopes. KSPG was measured in unfractionated extracts of scar and of normal corneal tissue using a "sandwich" enzyme-linked immunosorbent assay (ELISA). In extracts of 2 week scars, KSPG molecules reacting with two different anti-KS monoclonal antibodies were 55% and 82% as abundant as in normal tissue extracts. Ion exchange high performance liquid chromatography (HPLC) of tissue extracts found qualitatively similar elution profiles of KSPG antigens from both scar and normal tissues. Direct ELISA of the HPLC-purified KSPG showed identical quantitative binding of antibodies against core protein and KS from normal and scar tissue. KS in the HPLC-purified extracts was sensitive to digestion with endo-beta-galactosidase, whereas core protein antigens were not affected by this enzyme, as expected. Alteration of the antigenic characteristics of the KSPG of scars was detected with a competitive immunoassay using immobilized monoclonal antibodies against KS. KS in extracts from 2, 6, and 8 week scars competed only 5-11% as effectively as KS from normal cornea, although core protein antigens in the scar extracts competed 61-80% as well as those of normal cornea.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Heterogeneity of collagens in rabbit cornea: type VI collagen.

Normal adult rabbit corneas were digested with 5% pepsin and their collagens extracted with acetic acid. Collagen extracts were fractionated by differential salt precipitation. The 2.5 M NaCl fraction was then redissolved with tris buffer and precipitated with sodium acetate. The precipitate contained a high-molecular-weight disulfide-bonded aggregate which, upon reduction with mercaptoethanol, was converted into three distinct polypeptides having molecular weights between 45 and 66 Kd. These physical characteristics, together with the susceptibility of these polypeptides to collagenase and their amino acid composition, identified the high molecular weight aggregate as type VI collagen. Corneas from neonate rabbits and adult corneas containing 2-week-old scars were organ cultured in the presence of [14C] glycine to incorporate radiolabel into collagen. Tissues were digested with 0.02% pepsin and their collagens extracted with formic acid. The total radioactivity of the extracts and tissue residues was determined before the collagens were separated by SDS-polyacrylamide slab gel electrophoresis. Radioactive collagen polypeptides bands were then stained with Coomassie blue, processed for fluorography, and analyzed by densitometry. The results show that: (1) type VI collagen is synthesized by neonate corneas and healing adult corneas; (2) it is not readily solubilized from either corneal tissue by 0.02% pepsin digestion and formic acid extraction; and (3) the proportion of type VI collagen deposited in scar tissue is markedly lower than that found in neonate corneas.

Amino Acids↗
PubMed1988

Heterogeneity of collagens in rabbit cornea: type III collagen.

Whole neonate rabbit corneas and adult corneas containing 2-week-old scars were incubated in the presence of [14C] glycine. Radiolabeled collagen extracted from the corneas and scar tissue were analyzed by sodium dodecylsulfate/polyacrylamide gel electrophoresis and fluorography to determine the types and relative quantity of collagen polypeptides present and synthesized by these tissues. In addition to other collagen types, type III was found in both neonate cornea and scar tissue from adult cornea, albeit in relatively small quantities. Type III collagen in normal cornea was associated with the residue after pepsin digestion and formic acid extraction of the tissue, and the same type of collagen was extracted from scar tissue after similar treatment. Type III collagen-specific monoclonal antibody bound to developing normal corneas and healing adult tissue sections, as determined by immunofluorescence. Antibody binding was localized to the endothelium and growing Descemet's membrane in fetal and neonate corneas, and restricted to the most posterior region of the corneal scar tissue. Although monoclonal antibody to keratan sulfate, used as a marker for stromal fibroblasts, bound to most of the scar tissue, the antibody failed to bind to the posterior scar tissue positive for type III collagen. We conclude that endothelial cells from fetal and neonate rabbit cornea and endothelium-derived fibroblasts from healing wounds of adult cornea synthesize and deposit type III collagen. Moreover, this collagen appears to be incorporated into the growing Descemet's membrane of normal corneas and narrow posterior portion of the scar tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Developmental changes in proteoglycans of rabbit corneal stroma.

Proteoglycans have been extracted from rabbit corneal stromas at developmental stages from fetal to adult. Ion exchange fractionation and gel chromatography show that proteodermatan sulfates decrease in sulfation and relative amount and proteokeratan sulfates increase in sulfation and relative amount during development. There are small increases in size of all of the proteoglycans up to 2 weeks after birth, and the final adult composition is achieved by 8 weeks.

Animals↗
PubMed1986

Development of monoclonal antibodies recognizing collagenase from rabbit PMN; the presence of this enzyme in ulcerating corneas.

Rabbit uterine collagenase was purified from the medium of involuting uterus (1-2 days postpartum) in culture using ammonium sulfate fractionation, DEAE-cellulose, heparin-affinity, and high performance liquid chromatography. The enzyme was purified more than 1600 fold. Hybridoma cell-lines producing monoclonal antibodies were prepared by fusing the spleen cells of mice immunized with the purified enzyme with mouse myeloma cells (Sp2/O-Ag14). The hybridoma cells were selected with HAT medium, cloned, and screened by ELISA. Antibody-producing ascites were prepared by injecting hybridoma cell-lines into the peritoneal cavities of mice. Western-blot analysis indicated that the antibodies recognized a polypeptide having a molecular weight of 52,000. The IgG isolated from the ascites inhibited the enzyme. Indirect immunofluorescent staining demonstrated that polymorphonuclear leukocytes (PMNs) in the superficial layer of alkali-burned corneas contained collagenase, whereas stromal cells and PMNs within the stroma were not stained by the antibodies. Our results suggest that collagenases produced by rabbit PMNs are different from those produced by fibroblasts from cornea. We hypothesize that PMNs in alkali-burned corneas secrete all or most of their collagenases by degranulation at the anterior surface of the cornea, and then continue to migrate into the deeper portion of the stroma.

Animals↗
PubMed1985

Disparate effects of calmodulin inhibitors on corneal epithelial migration in rabbit and rat.

We investigated the effects of two calmodulin inhibitors, trifluoperazine and N-6-aminohexyl-5-chloro-1-naphthalenesulfonamide, on corneal epithelial wound closure in rabbits and rats. Measured, round epithelial defects were made on corneas by gentle scraping. After 20 h in organ culture with or without inhibitor, the remaining wound area was measured and samples were fixed for microscopy. In the rabbit, these inhibitors had little or no effect on the rate of wound coverage. In the rat, however, both trifluoperazine (3-40 microM) and N-6-aminohexyl-5-chloro-1-naphthalenesulfonamide (10-100 microM) inhibited wound closure in a dose-dependent manner. Thus we believe that calmodulin plays a crucial role in epithelial migration in the rat. In the rabbit, there seems to exist a mechanism that is not critically dependent upon an intact calmodulin pathway.

Animals↗
PubMed1985

Different corneal epithelial healing mechanisms in rat and rabbit: role of actin and calmodulin.

The authors investigated the effects of calmodulin inhibitors, trifluoperazine (10-20 microM) and W-7 (25-50 microM), and of cytochalasin B (5 micrograms/ml) on the F-actin distribution, surface morphology, and migration of rat and rabbit corneal epithelial cells in tissue culture. In the rat, actively migrating cells have abundant F-actin-containing stress fibers and numerous cytoplasmic extensions of the plasmalemma. These features, and ultimately cell migration, are inhibited by calmodulin inhibitors and cytochalasin B. In the rabbit, migrating cells are devoid of stress fibers and cytoplasmic extensions. Cell migration is not inhibited by calmodulin inhibitors but is arrested by cytochalasin B. The cell-to-substrate adhesion is reduced by calmodulin inhibitors in both rat and rabbit. These findings corroborate our earlier observations in organ culture studies and support the view that corneal epithelial cell migration is calmodulin-dependent in the rat, while it is not in the rabbit. The complete blockage of migration in both species by cytochalasin B suggests that actin polymerization is critical for corneal epithelial locomotion in both species.

Actins↗
PubMed1984

Fibronectin in developing rabbit cornea.

Fibronectin is believed to be important in tissue morphogenesis. We examined the distribution of fibronectin in developing rabbit cornea by immunohistofluorescence. Cryostat sections of cornea from 13, 15, and 20-day-old fetuses, 3-day neonates, and adults were incubated with affinity-purified fluoresceinated guinea pig anti-rabbit fibronectin antiserum (aFN). aFN bound to components within the presumptive stromal region and along the basal surfaces of corneal and lens epithelia during early stages of mesenchymal invasion. At 15 days of gestation, fluorescence was associated with the stromal extracellular matrix of the cornea, the subepithelial zone, and the lens capsule. In the 20-day fetus an intense aFN fluorescence was present along the inner corneal stromal border coincident with the formation of Descemet's membrane. Fluorescence within the corneal stroma appeared as fine lines, restricted to the collagen lamellae, remaining through birth and disappearing in the adult. Although stromal fluorescence disappeared in the adult, Descemet's membrane continued to fluoresce, albeit to a lesser extent. The results of our studies indicate the presence of fibronectin in developing rabbit cornea. Because fibronectin is important to cell adhesion in vitro, and because intercellular and cell-extracellular matrix interactions, including adhesion, are necessary for tissue morphogenesis, our observation suggests that fibronectin plays an important role in corneal morphogenesis.

Animals↗
PubMed1984

Beta-adrenergic and serotonergic stimulation of rabbit corneal tissues and cultured cells.

The adult rabbit cornea synthesizes cyclic AMP in response to both serotonin and isoproterenol. The authors have examined the postnatal development of these pathways and attempted to localize the responsive cell type(s) by dissection, cell culture, and surgical denervation. Full thickness corneas of neonatal rabbits have beta-adrenergic responses similar to the adult but fail to respond to serotonin until the animals are 9-12 weeks old. When adult corneas are separated into epithelia, stromal, and endothelial layers, only the stromal layer synthesizes cyclic AMP in response to serotonin, whereas all layers respond to isoproterenol. When grown in tissue culture, keratocytes, epithelial, and endothelial cells are unresponsive to serotonin but respond to isoproterenol. Neither adrenergic nor sensory denervation abolishes the corneal adrenergic or serotonergic response pathways. These results indicate that the epithelial cells do not contain the serotonin stimulated, cyclic AMP-mediated pathway as originally postulated. The cell population that does contain this pathway is within the stroma and may be the Schwann cells.

Animals↗