Activity Of Corneal Epithelium Research Articles

The relation between activity in corneal epithelium and haze after LASEK

目的 探讨LASEK治疗近视的效果及手术中角膜上皮的活性与术后发生haze的关系.方法 对LASEK手术105例(210眼)进行随诊观察,手术中根据不同年龄及术前配戴角膜接触镜时间决定酒精浸泡的时间,尽可能缩短酒精浸泡的时间,以保证角膜上皮细胞的活性,减少术后反应及haze的形成.结果 术后裸眼视力达到或超过术前最佳矫正视力者197眼,占93.81%;术后裸眼视力低于术前最佳矫正视力者13眼,占6.19%.发生haze者8眼,占3.8%,均为1级,其中5眼为摘除角膜接触镜后出现角膜上皮缺损,3眼术前为高度近视.结论 LASEK手术安全、有效,不断地提高手术技巧,制作完整的角膜上皮瓣,最大限度地保护角膜上皮细胞活性,可以减少haze的发生。

Characterization of Tetracycline-Inducible BitransgenicKrt12rtTA/+/tet-O-LacZMice

To prepare binary transgenic mouse lines that overexpress reporter genes in a corneal-epithelium-specific manner when induced by doxycycline. A gene-targeting construct containing an internal ribosomal entry site-reverse tetracycline transcription activator (IRES-rtTA) cassette was inserted into the Krt12 allele (keratin 12 gene) to produce a knock-in Krt12(rtTA/+) mouse line through gene-targeting techniques. The Krt12(rtTA/+) knock-in mice were bred with tet-O-LacZ reporter mice to obtain Krt12(rtTA/+)/tet-O-LacZ bitransgenic mice. The expression of the LacZ gene was induced in bitransgenic mice by administration of doxycycline in the drinking water and chow. Administration of doxycycline induced a 15-fold increase of beta-galactosidase activity in the cornea of adult bitransgenic mice (Krt12(rtTA/+)/tet-O-lacZ). Administration of doxycycline either to single transgenic Krt12(rtTA/+) or tet-O-LacZ mice as a control did not induce overexpression of LacZ as it did in the bitransgenic mice. The induction of beta-galactosidase enzyme activity by doxycycline in bitransgenic mice took place in 24 hours and reached a plateau by 2 days. Histochemical analysis also showed that beta-galactosidase induction was limited to the corneal epithelium of bitransgenic mice fed doxycycline. The increased beta-galactosidase activity in corneal epithelium caused by doxycycline returned to basal levels in 4 weeks after the antibiotics were omitted from the diet. A binary mouse model has been successfully established that conditionally overexpresses reporter genes in corneal epithelium. This mouse model will be useful in elucidating signaling pathways of various growth factors and cytokines and gene functions in the maintenance of homeostasis and pathogenesis in the adult mouse cornea.

Caspase-9 activation in hypoxic human corneal epithelial cells.

The purpose of this study was to determine the effect of hypoxia on caspase-8 and -9 gene and protein expression and activity in corneal epithelium. Non-transformed human corneal epithelial cells (HCEC) were cultured in 2% oxygen. A cDNA expression array coupled with densitometric analysis was used to compare relative mRNA expression levels of 96 apoptosis-related genes in hypoxic and normoxic HCEC. Caspase-8, caspase-9, FLIP, Fas, FasL, and TNFalpha protein expression was assessed further using Western blot analysis and ELISA. Caspase-8 and -9 activities were measured using a fluorometric activity assay. Hypoxia did not affect caspase-8 or -9 gene or protein expression in HCEC, however caspase-9 activity was significantly increased. Hypoxia significantly suppressed the activity of caspase-8. FLIP and Fas gene and protein expression were not significantly altered in hypoxic cells compared to normoxic controls. mRNA and protein levels of TNFalpha and TNFR-1 were significantly decreased, while FasL mRNA and proteins levels were significantly increased in hypoxic HCEC. In corneal epithelium stressed by hypoxia caspase-9 activity is upregulated, suggesting that apoptosis proceeds via the mitochondrial pathway. Caspase-8 activity may be suppressed because the loss of TNFalpha and TNFR-1 gene and protein expression inhibits the initial formation of a death signaling complex.

Proliferative Activity of Corneal Epithelium and Specific Features of Morphogenesis in Postmetamorphic Rana arvalisNilss. in Urbanized Areas

The mitotic activity and sizes of corneal epithelial cells in postmetamorphic Rana arvaliswere studied in the populations exposed to different degrees of anthropogenic impact in the city of Yekaterinburg. The studies were conducted at the initial stages of frogs' terrestrial life in three consecutive years. Mitotic activity exhibited a slight positive correlation with the liver index, which indirectly reflects the general metabolic rate in young frogs. The combined estimation of proliferative activity, epithelial cell size, and relative liver weight had the highest information value. There was a relationship between the mitotic index and liver index in young frogs from habitats with the highest level of anthropogenic transformation. This indicates that morphogenesis is well-balanced and is likely to decrease the probability of morphological abnormalities in frogs developing in the unstable environment. This physiological property allows the populations to exist and reproduce in urbanized areas.

Changes in lactate dehydrogenase activity in bovine corneal stroma and epithelium in response to in vitro toxic challenges in the enucleated eye test.

To assess whether changes in lactate dehydrogenase (LDH) activity, as a marker of cell damage, could be detected in corneal stroma and corneal epithelium after toxicity measurements using the enucleated eye test (EET). The corneal surface of isolated bovine eyes was continuously wetted with commercial balanced salt solution (BSS) over 4 h at 37 degrees C and central corneal thickness (CCT) was measured. Initial 5-min challenges were made with dilute solutions of benzalkonium chloride (up to 0.032%) or NaOH (up to 0.4 M). The residual LDH activity in the corneal epithelium and corneal stroma were then assessed. Dose-dependent increases in CCT of up to 70% were measured. A strong correlation (r = -0.961) was found between increases in CCT and decreases in stromal LDH activity, but the correlation was much less (r = -0.512) for epithelial LDH activity. LDH activity can be used as one marker for cell integrity in the corneal stroma and epithelium, although dose-dependent correlations may not be high.

Constitutive Expression of Class 3 Aldehyde Dehydrogenase in Cultured Rat Corneal Epithelium

Mammalian Class 3 aldehyde dehydrogenase (ALDH) is normally associated with neoplastic transformation or xenobiotic induction by aromatic hydrocarbons in liver. However, Class 3 ALDH is constitutively expressed at it's highest specific activity in corneal epithelium. Tissue-specific, differential gene expression is often controlled by alternative, independent molecular pathways. We report here the development of an in vitro corneal epithelium culture system that retains constitutive high expression of the ALDH3 gene. This model system was used to establish, by enzymatic assays, Western and Northern analyses, histochemical and immunocytochemical staining, and 5'3' RACE methodologies that constitutive and xenobiotic induction of Class 3 ALDHs occurs from a single gene. Our results also provide a plausible explanation for the very high Class 3 ALDH activity in mammalian cornea, as the primary mechanism of oxidation of lipid peroxidation-derived aldehydes. Further studies with corneal epithelium suggest the presence of additional mechanisms, other than Ah-receptor-mediated, by which the ALDH3 gene can be differentially regulated in a tissue-specific manner.

Regulation of RNA Polymerase Activity in Corneal Epithelium

Regulation of RNA Polymerase Activity in Corneal Epithelium

Calcium- and phospholipid-dependent protein kinase C and phosphatidylinositol kinase: two major phosphorylation systems in the cornea.

The signaling messengers for the regulation of intracellular calcium-dependent functions involve a phospholipid-sensitive protein kinase (protein kinase C) modulated by diacylglycerol, which is a product of phosphoinositide degradation. We found that protein kinase C activity is two times higher in the epithelium than in the stroma-endothelial layers of the rabbit cornea. 12-0-tetradecanoylphorbol-13-acetate (TPA) and phosphatidylserine stimulate protein kinase C at low Ca2+ concentrations. The TPA-phosphatidylserine stimulated activity of corneal epithelium was recovered in the soluble fraction; in the membrane-bound fraction, a very active phosphatidylinositol kinase accounted for half the basal phosphorylation of the corneal epithelium.

The enzymatic activities in the alkali-burnt rabbit cornea.

Alkali-burnt corneas of the rabbits with 1 N NaOH were studied periodically for enzymatic activities by biochemical methods. There was significant increase of aldolase (ALD) activity both in corneal epithelium and stroma 1, 2, 3 and 4 weeks after alkali burns. Glucose-6-phosphate dehydrogenase (G6PD) activity was significantly decreased in epithelium and was absent in stroma. Thus the breakdown of glucose would be present preferably in the Embden-Meyerhoff pathway instead of the pentose phosphate shunt. Lactate dehydrogenase (LDH) activity of corneal epithelium and stroma was significantly decreased 1, 2, 3, and 4 weeks after alkali burns and the possible pathway of glycolysis might channel to citric acid cycle, in which malate dehydrogenase (MDH) could indicate the important role in this pathway.

Ultraviolet induced lysosome activity in corneal epithelium.

A 5,000 W Xe-Hg high pressure lamp and a double monochromator were used to produce a 3.3 nm half-bandpass ultraviolet radiation at 295 nm. Pigmented rabbit eyes were irradiated with radiant exposures from 140 Jm-2 to 10,000 Jm-2 and evaluated by slit-lamp biomicroscopy, light and electron microscopy. Corneal threshold (Hc) was 200 Jm-2 and lens threshold (HL) was 7,500 Jm-2. The most repeatable and reliable corneal response to these levels of UV was the development of corneal epithelial granules. Histological changes included a loss of superficial epithelial cells and selective UV induced autolysis of the wing cells. It is suggested that the biomicroscopically observed granules are the clinical manifestation of the secondary lysosomes revealed by light and electron microscopy. It is proposed that UV breaks down the primary lysosome membranes to release hydrolytic enzymes which in turn form the secondary lysosomes during autolysis. Extreme levels of radiant exposure at 295 nm result in indiscriminate destruction of all layers of the corneal epithelium, but the posterior cornea was spared.

Dynamics of the mitotic activity in corneal epithelium of white mice during fasting

The dynamics of mitotic activity of corneal epithelium was studied in fasting white mice. The animals were deprived of food for a period of 1 to 6 days. A sharp decrease of mitotic activity, appearing from the second day of fasting, remained on the same level with more prolonged food deprivation as well. In mice which received only carbohydrates (sugar and glucose) the mitotic activity of the corneal epithelium remained normal up to 4 days inclusively; after the fifth day of experiment, however, the mitotic activity decreased. The loss of weight in mice given water only was four times greater then in those fed on carbohydrates.