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PubMed1999

Gelatinase A and TIMP-2 expression in the fibrous sclera of myopic and recovering chick eyes.

PURPOSE: Myopia, or nearsightedness, is characterized by excessive lengthening of the ocular globe and is associated with extracellular matrix remodeling in the posterior sclera. The activity of gelatinase A, a member of the matrix metalloproteinase family, has been shown to increase in the posterior sclera during the development of induced myopia in several species. In the present study, the distribution and relative expression of gelatinase A and its associated inhibitor, tissue inhibitor of metalloproteinases (TIMP)-2, were measured within the fibrous scleras of experimentally myopic (form-deprived) eyes, control eyes, and eyes recovering from form deprivation to better understand the mechanisms that regulate scleral remodeling and the rate of ocular elongation. METHODS: Total RNA was extracted from the posterior scleras of form-deprived chick eyes, eyes recovering from deprivation myopia, and paired contralateral control eyes, and subjected to northern blot analysis analyses using cDNA probes to chicken gelatinase A and TIMP-2. The distribution of gelatinase A and TIMP-2 mRNAs was evaluated by in situ hybridization on frozen sections of chick scleras using 33P-labeled RNA probes. Gelatinase A activity within the fibrous scleras of form-deprived eyes and paired contralateral recovering eyes was evaluated by gelatin zymography. RESULTS: Northern blot analysis indicated that the relative expression of gelatinase A was increased by 128% in deprived eyes (P = 0.009), whereas after 1 day of recovery, levels were decreased by 80% in scleras from recovering eyes (P = 0.005). In contrast, TIMP-2 expression was significantly decreased (-53%, P = 0.027) in the posterior scleras of form-deprived eyes. No significant differences were detected in levels of TIMP-2 expression between recovering eyes and paired control eyes. In situ hybridization indicated that most of the gelatinase A transcripts were present in the fibrous layer of the posterior scleras from form-deprived and recovering eyes. CONCLUSIONS: Changes in the steady state levels of gelatinase A and TIMP-2 mRNA lead to changes in gelatinase activity within the fibrous sclera and mediate, at least in part, the process of visually regulated ocular growth and scleral remodeling.

Animals↗
PubMed1995

Increased latent gelatinase activity in the sclera of visually deprived chicks.

PURPOSE: Gelatinase activity was measured in the normal chick sclera and in sclera of form-deprived (myopic) eyes to assess the role of this metalloproteinase in ocular elongation associated with experimental myopia. METHODS: Gelatinases were extracted from anterior and posterior regions of normal chick sclera and sclera from eyes that had been form-vision deprived for 11 days. Gelatinase activity in the extracts was determined by measuring the digestion of 3H-gelatin after incubation with the extracts in the absence or presence of 1 mM aminophenylmercuric acetate (APMA) to activate latent gelatinases. Scleral gelatinases were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis gelatin zymography and immunoprecipitation analyses. RESULTS: No significant differences were detected in gelatinase activity between normal and deprived posterior sclera in the absence of APMA. However, when scleral extracts were incubated with APMA, extracts from the posterior sclera of deprived eyes contained significantly more gelatinase activity than paired controls (+127%, P = 0.0105). In contrast, no differences in active or latent gelatinase activity were detected in extracts from the anterior sclera. Removal of tissue inhibitors of metalloproteinases (TIMP) from control scleral extracts by reduction and alkylation resulted in a 222% increase in gelatinolytic activity after APMA-activation (P < or = 0.001), whereas similar treatment of deprived scleral extracts resulted in only a 76% increase in gelatinolytic activity (P < or = 0.001). A 65/58-kd doublet was the major gelatinolytic species from control and deprived posterior sclera that represent the proenzyme and active forms of the 72-kd gelatinase (MMP-2). CONCLUSIONS: These data indicate that visual deprivation is associated with an increased amount of the 72-kd progelatinase and a decreased amount of TIMP within the posterior sclera. Therefore, an imbalance between the levels of 72-kd progelatinase and its inhibitor may play a role in the remodeling processes of the posterior sclera during the development of form-deprivation myopia.

Animals↗
PubMed1991

Increased aggrecan (cartilage proteoglycan) production in the sclera of myopic chicks.

A previously characterized chick model of myopia was used to evaluate biochemical changes in the sclera which are associated with ocular enlargement and myopia. Chicks were monocularly occluded for 10 days and the DNA, hydroxyproline, and glycosaminoglycan contents of the sclera were compared between the normal and the myopic eyes. No significant differences could be detected in total DNA or hydroxyproline content. There was, however, a 34% increase in glycosaminoglycans and a 20.7% decrease in cell density within the posterior sclera of myopic eyes. The biosynthesis of scleral proteoglycans was determined by measuring 35SO4 incorporation in the sclera of chicks visually occluded for 5, 10, and 15 days. No differences could be detected in 35SO4 incorporation into the cornea or the anterior sclera. However, 35SO4 incorporation was significantly increased in the posterior sclera of myopic eyes by 64% at Day 5, 39% at Day 10, and 49% at Day 15. When fractionated on Sepharose CL-4B, scleral proteoglycans were resolved into two peaks which were identified by Western blot analysis as aggrecan (cartilage proteoglycan) and decorin. Furthermore, Western blot and dot blot analyses indicated that significantly more aggrecan core protein was present in the sclera of myopic eyes compared with equivalent amounts of sclera from control eyes. These results indicate that increased synthesis and accumulation of aggrecan, which increases the volume of extracellular matrix in the posterior sclera, are responsible for the ocular enlargement observed in this model of myopia.

Aggrecans↗
PubMed1999

Residual ethanol content of donor sclera after storage in 95% ethanol and saline rinse of various durations.

PURPOSE: Some surgeons are wary of using alcohol-preserved sclera for allografts because they fear a toxic effect on surrounding tissue after placement. We set out to determine the amount of ethanol remaining in scleral allograft material after storage in 95% ethanol. METHODS: Sixty half scleras from 30 donors were preserved in 95% ethanol for an average of 31+/-14 days (range, 11 to 50 days). Rehydration was performed by soaking each half sclera in 4 ounces of balanced salt solution. Half scleras were randomly assigned to six groups of 10 each. Assays for ethanol were performed on the following groups: no balanced salt solution soak and balanced salt solution soak for 10 minutes, 20 minutes, 30 minutes, 40 minutes, and 50 minutes. Ethanol assay was performed by Headspace Gas Space Chromatography at ChemaTox Laboratory, Inc, Boulder, Colorado. RESULTS: The 10 half scleras without balanced salt solution soak had a mean ( SD) ethanol level of 175+/-14.1 mg per g of sclera. After 10 minutes of balanced salt solution s oak, the level decreased to 7.57+/-1.56 mg per g, then 3.77+/-3.02 mg per g at 20 minutes, 1.59+/-0.61 mg per g at 30 minutes, 1.07+/-0.30 mg per g at 40 minutes, and 0.96+/-0.26 mg per g at 50 minutes. Approximately 96% of the ethanol is leeched out of the half sclera by 10 minutes and 98% by 20 minutes. CONCLUSIONS: For sclera preserved in 95% ethanol, soaking in balanced salt solution for 20 minutes or longer leeches approximately 98% of the ethanol from the preserved donor sclera.

Drug Residues↗
PubMed2006

Small leucine rich repeat proteoglycans (SLRPs) in the human sclera: identification of abundant levels of PRELP.

PURPOSE: The small leucine rich proteoglycan (SLRP) family is made up of several members which are thought to guide matrix assembly and organization through protein:protein and/or protein:carbohydrate interactions. In order to better characterize the composition of the scleral extracellular matrix, gene and protein expression of several members of the SLRP family were evaluated in the human sclera from donors aged 2-93 years of age. METHODS: Semi-quantitative and quantitative RT-PCR analyses were performed on RNA isolated from human donor sclera using primers for decorin, fibromodulin, PRELP (proline arginine rich end leucine-rich protein), biglycan, chondroadherin, and lumican. Additionally, the protein expression and distribution of the SLRP family member, PRELP, was determined in the human sclera through western blot detection and immunohistochemistry. RESULTS: Semi-quantitative and quantitative PCR analysis showed that all six SLRPs were expressed in the human sclera, with PRELP exhibiting the highest steady state mRNA levels, relative to that of the other SLRPs (p<0.001, ANOVA). Further analysis of PRELP in the human sclera by western blot analysis indicated that PRELP contained a 45 kDa core protein with short unsulfated keratan sulfate side chains and appeared in greatest abundance in sclera during the fourth decade of life. CONCLUSIONS: These results suggest that several SLRP proteoglycans are expressed in the human sclera and provide the first description of the PRELP protein in the human sclera. The relative abundance of PRELP mRNA and protein in the human sclera, and the observed age-related variation in scleral PRELP expression suggests that PRELP may play a critical role in regulating the biomechanical properties of scleral extracellular matrix.

Adolescent↗
PubMedDate not supplied

Viability of bacteria in glycerin and ethanol preserved sclera.

BACKGROUND: Sclera is commonly preserved in glycerin or ethanol before being used for ophthalmic surgery. The purpose of this study was to determine the ability of bacteria to survive in sclera preserved in glycerin or ethanol. METHODS: Fresh sclera was inoculated with Staphylococcus aureus, Streptococcus pneumoniae, or Pseudomonas aeruginosa and transferred to preservative vials containing glycerin, 95% ethanol, or trypticase soy broth (control) and stored at room temperature. Pieces of sclera were removed from preservative at designated intervals over a 14-day period. The sclera was then homogenized, plated on blood agar, and incubated at 37 degrees C. Colonies were counted at 24, 48, and 72 hours. RESULTS: S. pneumoniae, P. aeruginosa, and S. aureus were recovered from glycerin preserved sclera for up to 12 hours, 1.5 days, and 8 days, respectively. No bacteria was recovered from the ethanol preserved sclera. CONCLUSIONS: Bacteria cannot be recovered from ethanol preserved sclera but can survive in glycerin preserved sclera for at least 8 days. Ethanol may offer advantages over glycerin as a scleral preservative due to its greater antibacterial activity.

Bacteria↗
PubMed1993

[Histological observations on the sclera in uveal effusion].

The author performed sclerectomy in six cases of uveal effusion syndrome and examined the excised sclera histologically. From the findings of the sclera during the surgery and histological findings of the excised sclera, uveal effusion syndrome was divided into three groups: 1) nanophthalmos, 2) non-nanophthalmos with hypertrophic sclera, 3) non-nanophthalmos with normal thick sclera. In all cases, glycosaminoglycans were found to be deposited around the scleral collagen fibers. In the nanophthalmic eyes (group 1) and non-nanophthalmic eyes with the hypertrophic sclera (group 2), much glycosaminoglycans were demonstrated around the collagen bundles and enlarged the collagen bundle spaces. In these groups, sclerectomy procedures were successful and, based on the successful result of the operation, the cause of uveal effusion was considered to be disturbance of outflow of intraocular fluid through the hypertrophic sclera. In non-nanophthalmic eyes with normal thick sclera (group 3), few glycosaminoglycans was demonstrated around the collagen bundles with less abnormality, and sclerectomy procedure was not effective. In this group, the occurrence of uveal effusion was another cause but abnormal sclera.

Adult↗
PubMed1997

Effect of pterygium morphology on pterygium recurrence in a controlled trial comparing conjunctival autografting with bare sclera excision.

OBJECTIVES: To compare success rates of conjunctival autografting and bare sclera excision for primary and recurrent pterygium in the tropics and to evaluate risk factors for pterygium recurrence. METHODS: A prospective, controlled clinical trial was performed in which 123 primary and 34 recurrent pterygia, matched for age and pterygium morphology, were randomized in 2 separate studies to receive either bare sclera excision or conjunctival autograft. The surgical procedures were performed by one surgeon and reviewed at 1, 3, 6, and 12 months after surgery by an independent observer. Pterygium morphology was clinically graded as atrophic, intermediate, or fleshy according to an assessment of pterygium translucency. Risk factors were assessed using likelihood ratio tests. Weibull curves were used to estimate recurrence rates allowing for the interval censoring. RESULTS: In the group with primary pterygium (mean follow-up, 15.1 months), 38 (61%) of the 62 cases of bare sclera excision (heretofore referred to as the bare sclera group) had pterygium recur in contrast with 1 (2%) of the 61 cases of conjunctival autograft (heretofore referred to as the conjunctival autograph group) (P<.001, likelihood ratio X2 test). Nontranslucency, or fleshiness of the pterygium, and not age was a significant risk factor for recurrence in the bare sclera group (P<.001, likelihood ratio X2 test). In the group with recurrent pterygium (mean follow-up, 13.2 months), 14 (82%) of the 17 bare sclera group had pterygium recur, while no recurrences occurred among 17 cases in the conjunctival autograft group. Nontranslucency was again a highly significant factor for recurrence (P<.001, likelihood ratio X2 test). CONCLUSIONS: Pterygium recurrence is related to pterygium morphology and fleshiness of the pterygium is a significant risk factor for recurrence if bare sclera excision is performed. Conjunctival autografting for primary and recurrent pterygium is effective in reducing pterygium recurrence compared with bare sclera excision.

Adult↗
PubMed1995

Reduced extracellular matrix in mammalian sclera with induced myopia.

The purpose of this study was to learn whether visual form deprivation, which produces myopia in the deprived eye, alters the scleral extracellular matrix in tree shrew, a mammal closely related to primates. Axial myopia was induced in 10 tree shrews by monocular deprivation imposed with a translucent diffuser. The other eye in each animal was an untreated control. After 21 days of deprivation the refractive state and axial component dimensions were measured and the eyes were assayed for levels of DNA, hydroxyproline, and sulfated glycosaminoglycans (GAGs) in samples of the sclera and the cornea. In comparison to the open control eye, the deprived eyes became myopic and elongated. In the sclera, DNA levels were not significantly changed from the control eye. Sulfated GAG levels were significantly lower in the deprived eyes, as compared to the control eyes, at the posterior pole (-15.6%), at the nasal equatorial region (-18.1%), and in the rest of the sclera (-11.6%). The hydroxyproline level was significantly lower only at the posterior pole (-11.8%). Levels of sulfated GAGs were significantly reduced relative to DNA and relative to hydroxyproline in the total sclera. No significant changes were found in the cornea. The lower level of sulfated GAGs throughout the sclera of the deprived eyes, as compared with the control eyes, suggests that the deprived sclera contained less proteoglycan, or that the proteoglycans were less glycosylated or less sulfated. In contrast, the regional reduction of hydroxyproline suggests that collagen accumulation was specifically reduced only at the posterior pole of deprived eyes. These results suggest that form deprivation slows or reverses the normal process of extracellular matrix accumulation in the sclera of this mammal. This may allow the sclera to be more distensible, permitting the vitreous chamber elongation and resultant myopia.

Animals↗
PubMed2004

Collagen crosslinking of human and porcine sclera.

PURPOSE: To develop methods of collagen crosslinking the sclera to increase its biomechanical strength for the treatment of progressive myopia. SETTING: Department of Ophthalmology, Technical University of Dresden, Dresden, Germany. METHODS: Sagitally oriented scleral strips of 4.0 mm x 8.0 mm were prepared from 5 human postmortem eyes and 50 porcine cadaver eyes and treated with various crosslinking methods including physical crosslinking by combined riboflavin-ultraviolet A (UVA) or rose bengal/white-light irradiation and chemical crosslinking by incubation with glucose, ribose, glyceraldehyde, and glutaraldehyde solutions. Parallel scleral strips from the same eye were used as untreated controls. After crosslinking, stress-strain measurements of the treated and control scleras were performed using a microcomputer-controlled biomaterial tester. RESULTS: A statistically significant increase in scleral rigidity was found after crosslinking with riboflavin-UVA, with a rise in stress in treated porcine (157%) and human (29%) sclera, and after treatment with glyceraldehyde, with a rise in stress in treated porcine (487%) and human (34%) sclera, and with glutaraldehyde, with a rise in stress in treated porcine (817%) and human sclera (122%) at 8% strain. The other crosslinking methods proved ineffective. The untreated human sclera had a 4-fold higher stiffness than porcine sclera. CONCLUSIONS: Collagen crosslinking induced by riboflavin-UVA, glyceraldehyde, and glutaraldehyde led to a significant increase in biomechanical strength in human and porcine sclera. Using these methods, collagen crosslinking might become a treatment possibility for progressive myopia. Future animal and clinical studies must determine the best application methods and the long-term effects of increased crosslinking on scleral rigidity and prevent potential toxicity or serious side effects.

Animals↗
PubMed1999

Regulation of the mechanical properties of tree shrew sclera by the visual environment.

Experiments in several species have shown that the axial elongation rate of the developing eye can be increased or decreased by manipulating the visual environment, indicating that a visually guided emmetropization mechanism controls the enlargement of the vertebrate eye during postnatal development. Previous studies in tree shrews (Tupaia glis belangeri) suggest that regulation of the mechanical properties of the sclera may be an important part of the mechanism that controls the axial elongation rate in this mammal. To learn whether the mechanical properties of the sclera change when the axial elongation rate is increased or decreased under visual control, uniaxial mechanical tests were performed on 3-mm wide strips of tree shrew sclera. The creep rate was measured under 1, 3, and 5 g of tension, maintained for 30 min at each level. The modulus of elasticity was calculated from the elastic extension that occurred when the force was increased from 0 to 1 g, 1 to 3 g, and 3 to 5 g. Both were measured in the sclera of both eyes from animals exposed to four experimental conditions: (1) Normal development, at intervals from the day of natural eyelid opening (day 1 of visual experience [VE]) to greater than 5 years of age; (2) Monocular form deprivation (MD), for varying lengths of time; (3) Recovery from MD; (4) Monocular -5 D lens treatment. The creep rate was low in normal animals (1-2% elongation/h), did not change significantly between day 1 and day 75 of VE, and was not significantly different between the two eyes. Four days of MD produced a 200-300% increase in creep rate in the sclera from deprived eyes. Creep rate remained similarly elevated after 11 and 21 days of MD. After 2 days of recovery, which followed 11 days of MD, the creep rate of sclera from the recovering eyes was below normal levels. In animals that wore a monocular -5 D lens for up to 21 days, creep rate increased, and then decreased, in concert with the increase, and decrease, in axial elongation rate as the eyes compensated for the lens. The modulus of elasticity of the sclera was not significantly affected by any manipulation. The temporal correspondence between changes in axial elongation rate and changes in creep rate support the hypothesis that regulation of the time-dependent mechanical properties of fibrous mammalian sclera plays a role in controlling axial elongation rate during both normal emmetropization and the development of refractive errors.

Animals↗
PubMed1990

Regional glycosaminoglycans composition of the human sclera.

Human sclera from different parts of the normal adult eye was analyzed for content of uronic acid and the distribution of specific glycosaminoglycan types. Uronic acid is widely determined as representative of glycosaminoglycans in biological substances and variations of about 2-fold were found. Differences of up to 50% were detected in the relative abundance of hyaluronic acid and of dermatan sulphate, depending on the site on the globe from which the sample was taken. Sclera from around the papilla was found to be rich in content of dermatan sulphate. Sclera from the posterior eyeball showed a higher percentage of chondroitin sulphate as compared with sclera from equator and limbus. Equatorial sclera was richer in hyaluronic acid than posterior sclera. Sclera from the posterior eyeball showed a higher content of uronic acid as compared with sclera from equator and limbus. This work is an addition to the understanding of the scleral biochemistry and this finding may have some relevance in connection with ocular disease, as the proteoglycans and their content of glycosaminoglycans play a key role in the regulation of collagen fibril assembly and in the biomechanical strength of collagen fibrils.

Aged↗
PubMed2000

Diffusion of high molecular weight compounds through sclera.

PURPOSE: To determine the in vitro permeability of the sclera to high molecular weight compounds and the relationship between scleral permeability and molecular size. METHODS: Fresh rabbit sclera was mounted in a two-chamber diffusion apparatus, and its permeability to sodium fluorescein, fluorescein isothiocyanate (FITC)-conjugated bovine serum albumin, FITC-IgG, and FITC dextrans ranging in molecular weight from 4 to 150 kDa was determined by fluorescence spectrophotometry. Electron microscopy was used to assess the impact of the experimental design on scleral ultrastructural integrity. The effect of the diffusion apparatus on scleral hydration was examined. Rabbit scleral permeability was compared with previously reported data for human and bovine sclera. RESULTS: Scleral permeability decreased with increasing molecular weight and molecular radius, consistent with previous human and bovine data. Molecular radius was a better predictor of scleral permeability than molecular weight. The sclera was more permeable to globular proteins than to linear dextrans of similar molecular weight. The experimental apparatus did not alter scleral ultrastructure. Permeability of rabbit sclera was similar to human sclera but greater than bovine sclera. CONCLUSIONS: Large molecules, such as IgG, diffuse across sclera in a manner consistent with porous diffusion through a fiber matrix. Transscleral delivery of immunoglobulins and other large compounds to the choroid and retina may be feasible.

Animals↗
PubMed2002

Altered collagen fibril formation in the sclera of lumican-deficient mice.

PURPOSE: To better understand the role of lumican (corneal keratan sulfate proteoglycan) in the scleral extracellular matrix, collagen fibril size, shape, and organization were evaluated in the sclera of wild-type mice and in mice homozygous or heterozygous for a null mutation in the lumican gene. METHODS. Anterior and posterior sclera from 6-month-old wild-type (lum+/lum+) and lumican-deficient mice (lum+/lum- and lum-/lum-) were analyzed by transmission electron microscopy. In addition, lumican was characterized in the sclera of wild-type and lumican-deficient mice by Western blot analyses. RESULTS: Lumican was present in the mouse sclera as an approximately 48-kDa core protein containing short glycosaminoglycan side chains consisting of moderate- to low-sulfated keratan sulfate. The wild-type mouse sclera consisted of irregularly arranged lamellae of collagen fibrils with an average diameter of 47.37 +/- 0.648 nm in the anterior sclera and 54.68 +/- 0.342 nm the posterior sclera. Collagen fibrils in the sclera of lumican mutant mice (lum+/lum- and lum-/lum-) were significantly larger in diameter in anterior (72.61 +/- 0.445 and 84.47 +/- 0.394 nm, respectively) and posterior (75.92 +/- 0.361 and 80.90 +/- 0.490 nm, respectively) scleral regions compared with wild-type mice (P < 0.001). CONCLUSIONS: The results of the present study indicate that null mutations in one or both alleles of the lumican gene result in significant defects in scleral collagen fibril formation that could lead to alterations in ocular shape and size and severely affect vision.

Animals↗
PubMed2003

[Experimental study of using xenologous sclera as wrapping materials for hydroxy apatite(HA)].

OBJECTIVE: Use xenologous sclera (pig sclera) as wrapping materials for hydroxyapatite (HA) ocular implants in enucleated New Zealand white rabbits. METHODS: Ten rabbits were unilaterally enucleated and the sockets implanted with 10 mm HA spherical implants. All implants were wrapped with pig sclera. The rabbits were killed 4 weeks later and the sockets were examined clinically for inflammation and implant exposure. Exenterated specimens were assessed histopathologically for inflammation and vascularization. RESULTS: No clinical evidence of implant exposure or extrusion was detected in rabbits receiving pig sclera wrapped implants. Histopathologically the xenologous (pig) sclera displayed moderate inflammation, as well as maintain its lamellar arrangement without disruption. Fibrovascular ingrowth was complete in all implants. CONCLUSION: Xenologous (pig) sclera behaves similar clinically to homologous sclera as a wrapping material for spherical HA ocular implants in a rabbit model, and may represent a reasonable alternative to sclera in such procedures in humans.

Animals↗
PubMed1987

The dermatan sulfate proteoglycans of bovine sclera and their relationship to those of articular cartilage. An immunological and biochemical study.

Dermatan sulfate proteoglycans were isolated from adult bovine sclera and adult bovine articular cartilage. Their immunological relationships were studied by enzyme-linked immunosorbent assays using polyclonal antibodies raised against the large and small dermatan sulfate proteoglycans from sclera and a polyclonal and monoclonal antibody directed against the small dermatan sulfate proteoglycans from cartilage. The small dermatan sulfate proteoglycans from sclera and cartilage displayed immunological cross-reactivity while there was no convincing evidence of shared epitope(s) with the larger dermatan sulfate proteoglycans, nor did these larger proteoglycans share any common epitopes with each other. A hyaluronic acid binding region was detected immunologically on the larger scleral dermatan sulfate proteoglycan but was absent from the larger dermatan sulfate proteoglycan of cartilage and both the small dermatan sulfate proteoglycans. These antibodies were used in immunofluorescence microscopy to localize the scleral proteoglycans and molecules containing these epitopes in the eye. The large scleral dermatan sulfate proteoglycan was restricted to sclera while molecules related to the small scleral and cartilage proteoglycans were found in the sclera, anterior uveal tract, iris, and cornea. Amino acid sequencing of the amino-terminal regions of the core proteins of the small dermatan sulfate proteoglycans from sclera and articular cartilage showed that all the first 14 amino acids analyzed were identical and the same as reported earlier for the small bovine skin and tendon dermatan sulfate proteoglycans. These studies demonstrate that the larger dermatan sulfate proteoglycans of sclera and cartilage are chemically unrelated to each other and to the smaller dermatan sulfate proteoglycans isolated from these tissues. The latter have closely related core proteins and probably represent a molecule with a widespread distribution in which the degree of epimerization of glucuronic acid and iduronic acid varies between tissues.

Amino Acid Sequence↗
PubMed1997

Transscleral diode laser cyclophotocoagulation on autopsy eyes with abnormally thinned sclera.

BACKGROUND AND OBJECTIVE: To determine, using autopsy eyes, whether diode laser energy adjustments are indicated in patients with thin sclera. MATERIALS AND METHODS: In the laboratory, the superior 180 degrees of sclera at the limbus was dissected to the level of barely visible anterior uvea and the opposite 180 degrees of sclera served as the control in three human cadaver eyes. A contact G-probe was placed at the limbus, and settings of a diode laser were increased in increments from 1.0 to 9.0 J at 4 burns per setting in each location. RESULTS: On gross examination, circular hypopigmented lesions were seen in the ciliary body (CB) beginning at 3.0 J in thin sclera and at 5.0 J in normal sclera. On light microscopic examination of thin scleral sections, CB damage began at 2.9 J and CB/ciliary body epithelium (CBE) damage occurred beginning at 3.5 J. In normal sclera, minimal CB/CBE changes occurred at 6.0 to 7.5 J. No scleral damage was visible in either the experimental or the control groups. CONCLUSION: Cycloablation energy adjustments are indicated on eyes with abnormally thin sclera to achieve similar histologic end points using the diode laser.

Basement Membrane↗
PubMed1997

Growth of the two layers of the chick sclera is modulated reciprocally by visual conditions.

PURPOSE: Although visual deprivation causes increased ocular elongation and myopia in both birds and mammals, changes in sclera appear to be in opposite directions. Because avian sclera has a cartilaginous layer as well as the fibrous layer found in mammals, we examined whether the scleral responses to various visual manipulations differ between the two layers. METHODS: To produce increases in ocular elongation and myopia, monocular diffusers or negative lenses were fitted to eyes. Conversely, to produce decreases in ocular elongation, diffusers were removed (restoring normal vision) or monocular positive lenses were fitted. Scleral layers were then dissected apart, and incorporation of labeled precursors into glycosaminoglycans (GAGs), DNA, and protein was assessed. Tissue coculture experiments were used to assess humoral interactions between scleral layers and with the choroid. RESULTS: In the cartilaginous layers, the incorporation of label into proteoglycans and DNA was significantly higher in eyes elongating faster than normal because of wearing diffusers or negative lenses and significantly lower than normal in eyes elongating slower than normal because of removal of the diffuser or wearing positive lenses. In the fibrous layers, the reverse was the case. Coculturing cartilaginous sclera from normal eyes with fibrous sclera from myopic or recovering eyes produced the same increase or decrease in sulfate incorporation into GAGs in the cartilaginous layer as though the tissue measured was from the animal providing the conditioning tissue. Coculturing with choroid, especially from recovering eyes, also inhibited cartilaginous sclera. CONCLUSIONS: The fibrous layer of the avian sclera shows changes in sulfate incorporation into GAGs during deprivation and recovery from deprivation in the same direction as does the mammalian sclera, whereas the cartilaginous layer changes in the opposite direction. The responses of the cartilaginous layer may be controlled by the fibrous layer, although they are influenced by the choroid as well.

Animals↗