Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Among corneal dystrophies, the keratoconus is one of the most frequently observed among young adults. A clinico pathological case is reported in a 13-year-old-girl of African origin. The diagnosis of bilateral keratoconus was established based on the obvious changes of the corneal curvature and thickness. After an unsuccessful attempt to improve vision with contact lenses, a keratoplasty was finally performed on one side to remove the pathological cornea. Its histopathological study found the characteristic changes of keratoconus: breaks of Bowman's layer and corneal thinning.
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PMID:[Bilateral keratoconus: a case report]. 1247 58

In this 21 st century, it is predicted that blindness caused by corneal disorders which are difficult to prevent or treat will increase. It is important to study the pathogenesis, prevention, and treatment of these corneal disorders. Two corneal disorders, keratoconus and corneal dystrophy, were investigated to elucidate the pathogenesis by using molecular biological or molecular genetic techniques. Corneal transplantation is performed to restore vision of patients with corneal disorders, but the condition of the donor corneal endothelium is the key to maintaining transparency of the grafted cornea. We investigated the function or cell cycle mechanism of corneal endothelium at the level of the gene, and we also studied induced genes of endothelial cells during preservation of donor corneas. 1. Keratoconus: We searched for keratoconus patients with questionnaires sent to 141 hospitals in the 23 Wards of Tokyo. The incidence of patients was estimated to be 12.4 x 10(-5) for males and 6.7 x 10(-5) for females. The male/female ratio was 1.7: 1.0. The number of male patients was low when compared with studies reported 17 years ago. Rupture of Descemet's membrane in males was significantly higher than in females. Genesis of incidence: Apoptosis-related gene expression in thinning of the cornea was analyzed with cDNA microarrays, using mRNA isolated from cultured keratocytes of normal human corneas and keratoconus corneas. The expression of tumor necrosis factor alpha-induced protein 6(TNFAIP 6) was more enhanced, while insulin growth factor binding protein 5(IGFBP 5) was less expressed in keratoconus patients. 2. Corneal dystrophy: In corneal dystrophy related to four candidate genes such as transforming growth factor beta-induced(TGFBI) gene, membrane component 1 surface maker 1(M 1 S 1) gene, carbohydrate sulfotransferase gene 6(CHST 6), and collagen type VIII alpha-2(COL8 A 2) gene, 208 Japanese and 42 Vietnamese families were analyzed for the gene mutation and studied for the frequency of gene mutation and differences of clinical features. About 80% of Japanese with corneal dystrophies had mutation of the TGFBI gene and about 70% of them had Avellino corneal dystrophy. However, in Vietnamese patients, mutations were found in both the TGFBI gene (lattice corneal dystrophy; the phenotype gene was His 626 Arg) and in the CHST gene. The difference in frequency in gene mutations was significant between the two nationalities. Moreover, a novel corneal dystrophy associated with Asp 123 His mutation in TGFBI gene was found in one Vietnamese family. 3. Corneal endothelial cell: 1) gene expression: We performed random sequence and homology research analysis of 1,000 clones from a rabbit corneal endothelial cDNA library. Forty-five genes, including collagen type VIII alpha-1, were listed for the frequently observed cDNA in the library. 2) gene transfection: One of the causes of a growth-arrested state in human corneal endothelium was thought to be the presence of transforming growth factor-beta (TGF-beta) in aqueous humor. The transfection of Smad 7 gene, which blocks the signal, showed proliferation of the endothelial cells in the presence of aqueous humor. This suggests that there may be a possible practical application for using gene transfection with a non-viral DNA vector or with an adenovirus vector.
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PMID:[The pathogenesis and treatment of corneal disorders]. 1261 Aug 36

The authors suggested the method of intraoperative dot-type keratocompression to localize the zones of ectasia in keratoconus. Corneocompression is made before corneal transplantation under the monitoring of the operation microscope by a special corneocompressor (from the keratoconus top to its periphery). The sagging degree of the examined corneal portion proportionate to its thinning is in the focus of attention. Simultaneously, the ectasia zone is marked by a 1% solution of brilliant green, after which a decision is made on the possibility of its radical incision by trepans of various sizes, ranging from 7.5 to 11 mm. Penetrating keratoplasty was made by using this method in 116 patients (147 eyes) with keratoconus of degrees III-IV according to Amsler. Better refractive results, including a higher visual acuity and a lower degree of postoperative astigmatism in long-term follow-ups ranging from 2 to 12 years, were ensured in the main group (77 patients, 93 eyes) versus the control group (39 patients, 54 eyes). Finally, the authors suggested, on the basis of their own experience, an operational classification of keratoconus.
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PMID:[Penetrating keratoplasty in keratoconus by using the method of intraoperative corneal compression]. 1293 99

Keratoconus is a debilitating corneal thinning disease that principally develops in the second and third decades of life. Our group previously developed a novel approach to studying keratoconus, based on the observation that there is a gradient of damage across the keratoconic cone. We identified a number of cellular characteristics of keratoconus such as discrete incursions of fine cellular processes from the anterior keratocytes in association with localised indentation of the basal epithelium, and increased levels of the lysosomal enzymes Cathepsin B and G in aberrant keratocytes, located beneath compromised regions of Bowman's layer, but also deeper in the stroma. Enzyme activity by these cells seemed to be causing localised structural degradation of the anterior stroma, leading to near-complete destruction of both Bowman's layer and the stroma, often necessitating a full-thickness corneal graft for sight restoration. This current study extends our initial findings by investigating the role of corneal nerves passing between the stroma and epithelium at the sites of early degradative change observed previously, and may be facilitating the keratocyte-epithelial interactions in this disease. Cells in sections of normal and keratoconic human corneas were labelled with the fixable fluorescent viability dye 5-chloromethylfluorescein diacetate, antibodies to alpha-tubulin (nerves), alpha3beta1 integrin, Cathepsin B and G, and the nuclear dye DAPI, and then examined with a confocal microscope. Anterior keratocyte nuclei were seen wrapping around the nerves as they passed through the otherwise acellular Bowman's layer, and as the disease progressed and Bowman's layer degraded, these keratocytes were seen to express higher levels of Cathepsin B and G, and become displaced anteriorly into to the epithelium. Localised nerve thickenings also developed within the epithelium in association with Cathepsin B and G expression, and appeared to be very destructive to the cornea. Insight into the molecular mechanisms of keratoconic disease pathogenesis and progression can be gained from the process of extracellular matrix remodelling known from studies of connective tissues other than the cornea, and wound healing studies in the cornea. Further studies are required to determine how well this model fits the actual molecular basis of the pathogenesis of keratoconus.
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PMID:Involvement of corneal nerves in the progression of keratoconus. 1295 50

We report a patient with a sufficiently thick cornea (593 microm) and no topographic signs of keratoconus preoperatively who developed iatrogenic keratoconus 2 months after repeat laser in situ keratomileusis (-4.00 -1.00 x 20) performed 5 months after the primary procedure (-10.50 -1.00 x 55). After penetrating keratoplasty, macrophotography showed severe multidirectional "macrostriae" of the stromal bed. On histologic evaluation, excessive thinning of the residual stromal bed to a minimum of 75 microm in the valleys and a maximum of 200 microm at the peaks of the macrostriae were documented. The flap thickness was 225 microm in the center. The thicker-than-intended flap (160 microm) is thought to be the cause of the severe complication of the LASIK procedure.
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PMID:Penetrating keratoplasty for iatrogenic keratoconus after repeat myopic laser in situ keratomileusis: histologic findings and literature review. 1467 Apr 35

A candidate for refractive surgery presented with classic (type I) Ehlers-Danlos syndrome (EDS). Clinical examination revealed blue sclera, limbus-to-limbus corneal thinning, myopia, and astigmatism. Orbscan (Bausch & Lomb) pachymetry mapping provided a striking demonstration of the limbus-to-limbus thinning with a central corneal thickness of 360 microm in the right eye and 383 microm in the left eye and midperipheral corneal thickness ranging from 370 to 438 microm and 376 to 434 microm, respectively. Despite the theoretical biomechanical weakness from the thin cornea and defective collagen, regular surface topography was maintained without the development of keratoconus. Although all types of EDS remain a contraindication to laser refractive surgery, Orbscan mapping provides a valuable insight into corneal shape and thickness in this condition.
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PMID:Orbscan mapping in Ehlers-Danlos syndrome. 1531 10

A 27-year-old man had excimer photoastigmatic keratectomy in the right eye and laser in situ keratomileusis in the left eye for the treatment of equivalent myopia. Preoperative slitlamp examination did not reveal evidence of keratoconus, central corneal pachymetry was 485 microm in the right eye and 500 microm in the left eye, and corneal topography revealed asymmetric bow-tie astigmatism with inferior steepening in the right eye and a small area of inferior steepening in the left eye. Twenty-two months after surgery, the patient complained of poor vision in the left eye. Slitlamp examination of the left eye revealed central corneal thinning and protrusion, with a Fleischer ring within the flap. Corneal topographic evaluation revealed a stable map in the right eye and central corneal steepening indicative of keratectasia in the left eye.
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PMID:Photorefractive keratectomy versus laser in situ keratomileusis to prevent keratectasia after corneal ablation. 1561 36

The cause of keratoconus is unknown. However, an earlier report demonstrated magnesium deficiency in keratoconus patients, and suggested that magnesium deficiency could pathologically affect the mechanisms of the cornea. Experimental and clinical papers concerning a possible relationship between keratoconus and magnesium deficiency were reviewed. These studies have demonstrated molecular and cellular alterations specific to the keratoconic cornea, including: thinning and fragmentation of membranes, degenerated cells and collagen fibres, swelling of the mitochondria, and biochemical abnormalities in protein synthesis. Similar alterations have reportedly been induced by magnesium deficiency. This review suggests a possible relationship between the specific keratoconic disorders and the alteration induced by magnesium deficiency at the intracellular and extracellular levels. Although the etiology of keratoconus is still unknown, this paper may give some new ideas for further experimental and clinical studies on the etiology of keratoconus.
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PMID:The possible relationship between keratoconus and magnesium deficiency. 1564 77

Keratoconus, a non-inflammatory thinning of the cornea, is a leading indication for corneal transplantation. For its causation, we propose a "Cascade Hypothesis" stating that keratoconus corneas have abnormal or defective enzymes in the lipid peroxidation and/or nitric oxide pathways leading to oxidative damage. The accumulation of oxidative, cytotoxic by-products causes an alteration of various corneal proteins, triggering a cascade of events, (i.e. apoptosis, altered signaling pathways, increased enzyme activities, fibrosis). This hypothesis is supported by biochemical, immunohistochemical and molecular data presented in this review. Based upon this evidence, one can speculate that keratoconus patients should minimize their exposure to oxidative stress. Protective steps should include wearing ultraviolet (UV) protection (in the contact lenses and/or sunglasses), minimizing the mechanical trauma (eye rubbing, poorly fit contact lenses) and keeping eyes comfortable with artificial tears, non-steroidal anti-inflammatory drugs and/or allergy medications.
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PMID:The cascade hypothesis of keratoconus. 1630 9

Keratoconus is a noninflammatory, progressive disease with ectasia and thinning of the corneal stroma, leading to decrease visual acuity related to asymmetrical irregular astigmatism and myopia. Currently, patients with keratoconus who are contact lens intolerant, are primarily treated by penetrating keratoplasty. When the cornea is transparent, other options may be considered. There are several studies about intrastromal rings implantation, in eyes with keratoconus. The major objective of corneal ring implantation is to reshape the abnormal cornea without removing corneal tissue or touching the central cornea.
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PMID:[Present views concerning surgery treatment of keratoconus]. 1641 14


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