摘要:

Twenty male albino rabbits were studied. Four animals served as controls; the remaining 16 animals represented the treated group. All the treated animals were exposed to the same amount of energy delivered by the excimer laser (pulse rate: 20 Hz, fluence 250mJ/cm2; number of pulses: 6032; cumulative UV dose 1508 J/cm2) and were divided into eight groups of 2 animals each (four eyes). Samples of aqueous humor and lens were obtained at the following intervals: 5, 10, 20 and 40 min and 1,2,3 and 4 weeks after photorefractive keratectomy (PRK). The levels of reduced and oxidized glutathione, hydrogen peroxide, ascorbic acid and malondialdehyde were determined.Aqueous humor analyses, twenty min after PRK, showed no significant differences with pre-treatment values, while the observed variations in lens were constantly present over the entire follow-up period (one month).These findings suggest that the biochemical lens alterations induced by PRK may represent the earliest events relevant to cataractogenesis in the rabbit.

ISSN:0271-3683    

DOI:10.3109/02713689608995825

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

The distribution of leucine aminopeptidase, aminopeptidase III, prolyloligopeptidase and acylpeptidehydrolase activities in different regions of a bovine lens was determined and correlated with the distribution of crystallin fragments (measured as<18 kDa protein) and water-insoluble proteins in the same lens. A gradient of activity was observed for all the peptidases tested, with the highest specific activity present in the cortical fibers which decreased to one half or below in the inner cortical fibers and nucleus. An inverse correlation between peptidase activities and the amount of crystallin fragments was observed in different regions of the lens. However, a direct correlation between the water-insoluble protein content and the crystallin fragments was observed in all fibers of the same lens. The amount of crystallin fragments and the amount of water-insoluble proteins increased from 2.7% and 8% in the outer cortical fibers to 13% and 68% in the nucleus of the same lens. The water-insoluble fraction from both cortical and nuclear fibers however displayed 4–5 fold more crystallin fragments compared to that present in the water-soluble fraction of the same preparation.When the bovine lens cortical and nuclear extracts were tested for their ability to hydrolyze the peptide substrate, Ile-Ser-bradykinin, the cortical extract was found to be at least ten times superior to the nuclear extract. Prior inactivation of prolyloligopeptidase and other serine proteases by diisopropylfluorophos-phate however diminished the ability of the cortical extract to hydrolyze peptide substrates. Bovine lens cortical extract was able to completely hydrolyzeα-melanocyte stimulating hormone as well as N-Acetyl-Met-Asp-Arg-Val-Leu-Ser-Arg-Tyr showing the presence of active acylpeptidehydrolase facilitating the complete hydrolysis of N-terminally blocked peptides. The human lens extract was found to contain both diisopropylfluorophos-phate sensitive and resistant enzymes capable of hydrolyzing peptide substrates.

ISSN:0271-3683    

DOI:10.3109/02713689608995826

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

The content of the meibomian gland lipid exprimate is known, but little is known about the phospholipids that comprise the glandular cells. The purpose of the present study is to identify and quantitate the phospholipid complement of the meibomian gland cells that produce the lipid secretion of meibomian oil and which is vital to tear film stability.Eyelids (n = 50) were excised from rabbits, and after surgical removal of surrounding tissues, the tarsal plates with and without expressing meibomian oil were extracted and phospholipids of the plates quantified by31P nuclear magnetic resonance (NMR).Seventeen phospholipids were quantified from tarsal plates expressed of oil and tarsal plates containing meibomian oil: alkylacylphosphatidylcholine (AAPC), dihydrosphingomyelin (DHSM), dimethylphosphatidylethanolamine, diphosphatidyl-glycerol (cardiolipin), ethanolamine plasmalogen (EPLAS), lyso-ethanolamine plasmalogen, lysophosphatidylcholine, lysophos-phatidylethanolamine, lysophosphatidylserine, phosphatidic acid, phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol, phosphatidylinositol, phosphatidylserine, sphingomyelin (SM), sphingosylphosphorylcholine. The six zwit-terionic and neutral phospholipids, DHSM, EPLAS, PE, SM, AAPC, and PC together comprise 79.5% of the total meibomian gland phospholipid profile (in meibomian oil this value is 84.2%). The zwitterionic and neutral phospholipids dominate meibomian gland phospholipid profiles. Since the meibomian gland cells undergo holocrine secretion and form the meibomian gland secretion, such a composition is consistent with the hypothesis that a chemically stable lamellar surfactant layer phospholipids bind non-polar meibomian oil to the aqueous layer of the tear film.

ISSN:0271-3683    

DOI:10.3109/02713689608995827

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

An abundant 1.05 kb human lacrimal gland mRNA has been characterized by cDNA cloning. It encodes a predicted 180 residue, 20546 Da secreted protein, with a charge of +11 at pH 7 and 24.5% proline, designated as Basic Proline-rich Lacrimal Protein (BPLP). Southern blot analysis is consistent with a singleBPLPgene. BPLP lacks any distinct repetitive structure, and is unrelated to the salivary proline-rich protein super-family. The pre-proprotein shows modest overall similarity to a superfamily comprising human PRPb, the mouse MSG proteins, and rat VCS-αl, VCS-β1 and submandibular apomucin. BPLP also contains a domain with similarity to the Zp2 protein domain found in several otherwise unrelated proteins. Northern blot analysis indicated that theBPLPgene is also expressed at modest levels in the human submandibular gland, andin situhybridization demonstrated expression ofBPLPin the secretory end-pieces of the human lacrimal gland. TheBPLPcDNA clone defines a new human tear protein, and should provide a useful phenotypic marker of differentiation inin vitrostudies of lacrimal gland function.

ISSN:0271-3683    

DOI:10.3109/02713689608995828

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

This study investigated the effects of dipyridamole in isolated porcine ciliary arteries (diameter 200–250μm).Isolated porcine ciliary arteries were suspended in myograph chambers filled with modified Krebs-Ringer solution (37°C; 95% O2/5% CO2) for isometric tension recording.Dipyridamole induced concentration-dependent relaxations of porcine ciliary arteries with endothelium precontracted with thromboxane analogue U-46619 (10-6M), KC1 (50 mM), or endothelin-1 (10-8M). Removal of the endothelium of the ciliary vessels and preincubation of the arteries with L-NAME (10-SM), or indomethacin (10-5M), or the combination of the two drugs significantly reduced the relaxation to dipyridamole (p = 0.002–0.03). Similar vascular responses could be observed in a time-dependant analysis of the effect of a single concentration dipyridamole (10-4M). The stimulator of CAMP forskolin also caused relaxations. Endothelin-1 (10-12-10-7M) and U-46619 (1010-10−6M) induced potent contractions of porcine ciliary arteries. Preincubation with dipyridamole (10−5M) reduced contractions to endothelin-1 as compared to control (p<0.004), while contractions to U-46619 were only slightly affected under these conditions (n.s.).These findings demonstrate that dipyridamole is a vasodilator in porcine ciliary arteries. Endothelial nitric oxide and prosta-cyclin contribute importantly to the effects of dipyridamole. Further studies are required to show whether these properties of dipyridamole may also occurin vivoand offer clinical use in patients with ocular vasospasms and other ophthalmic vascular dysfunctions.

ISSN:0271-3683    

DOI:10.3109/02713689608995829

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Lipid peroxidation has been associated with a number of specific manifestations related both to lens aging and cataract development. The assessment of the effect of various naturally occurring prooxidants as well as the development of antioxidant strategies has often been limited by the lack of appropriate and simple experimental models. In this study we discuss the adaptation of a method based on the incorporation of a fluorescent probe (parinaric acid) into biological membranes to monitor early stages of lipid peroxidation. After establishing the appropriate conditions, the method can be successfully applied to study peroxidation in bovine lens membranes, allowing for the evaluation of the effect of several free radical generating systems, including the following metal-dependent initiators: axorbate/ iron, hydrogen peroxide/copper and cumene hydroperoxidel copper. The inhibitory effect of the chelating agent diethylene-triaminepenta-acetic acid and the competitive hydroxyl radical scavenger sorbitol, was consistently observed on parinaric acid degradation, on hydroxyl radical yield and on the amount of thiobarbituric acid reactive material produced. It could be shown that oxidative degradation of the probe gives direct information on lens membrane susceptibility to a specific peroxidation system. Parinaric acid can therefore be used as an efficient oxidation probe to evaluate oxidative damage inflicted to lens membranes by different systems, allowing also the evaluation of the antioxidant effect of various drugs including those with potential anticataractogenic effect.

ISSN:0271-3683    

DOI:10.3109/02713689608995830

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Severe retinopathy of prematurity (ROP) occurs in the smallest and sickest of premature infants. We hypothesized that, in a rat model of oxygen induced retinopathy, abnormal neovascularization would occur more frequently in larger litters where the pups are subject to postnatal growth retardation. Four litters of newborn Sprague-Dawley rats were studied; rats were randomly mixed to form two large litters (n = 25 each) and two small litters (n = 10 each). All litters were exposed to 7 days cyclic hyperoxia and hypoxia followed by 5 days in room air. ADPase stained retinae were evaluated in a masked manner for the presence and severity of abnormal neovascularization. Fluorescein perfused retinae were digitized and the ratios of vascularized:total retinal area were calculated using computer assisted image analysis. As expected, final weight in the large litters was less than in the small litters (15.3±3.8g vs. 23.4±2.1g, p<0.001). Neovascularization occurred in 53% of rats in the large litters vs. 15% in the small litters (p = 0.009). Rats with retinae demonstrating neovascularization were smaller than those without (16.2±4.7g vs. 19.6±5.0g, p = 0.016). The severity of neovascularization in clock h was inversely correlated with final weight (rs= -0.35, p = 0.01) and ratio of vascularized:total retina area (rs= -0.46, p<0.001). Smaller rat pups raised in larger litters, with resultant growth retardation, develop more frequent and more severe abnormal retinal neovascularization. Our results correlate with clinical experience in the premature infant.

ISSN:0271-3683    

DOI:10.3109/02713689608995831

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Corneal transmittance in pigmented rabbits was measured at ultraviolet and visible wavelengths from the ratio of fluorescence of dyes in the anterior chamber to fluorescence of the same dyes in a quartz cuvette. Aqueous humor was drained through a limbal incision and the anterior chamber was reformed with a mixture of a viscoelastic material and a fluorophore (fluorescein, O-methyl pyranine, or sulforhodamine B). Excitation spectra, emission spectra, or both were measured in the anterior chamber with a new scanning ocular fluorophotometer, at wavelengths between 250 nm and 700 nm. Fluorescence spectra were also measured from the same fluorophore in a quartz cuvette. External transmittance of the cornea was calculated at each wavelength from the ratio of fluorescence in the anterior chamber to fluorescence in the cuvette. Transmittance was 93%±1.4% (mean±SD, n = 8 rabbits) at 500 nm and was 89% to 93% between 370 nm and 500 nm. Transmittance decreased to 82%±5.7% at 350 nm, to 50%±5.9% at 310 nm, and to less than 2% at 290 nm. Between 370 nm and 500 nm, the wavelength range most frequently used in fluorophotometry, average transmittance varied by less than 5%. These results suggest that fluorescence measured at two or more wavelengths within this spectrum needs little if any correction for differential attenuation by the cornea. At wavelengths shorter than 370 nm, measurements should be corrected. This technique provides a simple and minimally invasive means of studying visible and ultraviolet transparency of the cornea in the living eye.

ISSN:0271-3683    

DOI:10.3109/02713689608995832

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Naphthalene-induced cataract in rat lenses can be completely prevented by AL01576, an aldose reductase inhibitor (ARI). In an attempt to understand the mechanism of this inhibition, several ARIs were examined to compare their efficacies in preventing naphthalene cataract, using bothin vitroandin vivomodels. Two classes of ARIs were tested: One group including AL01576, AL04114 (a AL01576 analog) and Sorbinil contained the spiro-hydantoin group, while Tolrestat contained a carboxylic acid group. Furthermore, to clarify if aldose reductase played a role in naphthalene-induced cataractogenesis in addition to its role in sugar cataract formation, a new dual cataract model was established for ARI evaluations. This was achieved by feeding rats simultaneously with high galactose and naphthalene or incubating rat lenses in culture media containing high galactose and naphthalene dihydrodiol. Under these conditions, both cortical cataract and perinuclear cataract developed in the same lens. It was found that at the same dosage of 10 mg/kg/day, both AL01576 and AL04114 completely prevented all morphological and biochemical changes in the lenses of naphthalene-fed rats. Sorbinil was less efficacious, while Tolrestat was inactive. AL01576 showed a dose-response effect in preventing naphthalene cataract and at 10 mg/kg/day, it was also effective as an intervention agent after cataractogenesis had begun. With the dual cataract model, Tolrestat prevented the high galactose-induced cortical cataract but showed no protection against the naphthalene-induced perinuclear cataract. AL01576, on the other hand, prevented both cataract formations. Results for dulcitol and glutathione levels were in good agreement with the morphological findings. AL04114, an ARI as potent as AL01576 but without its property for cytochrome P-450 inhibition, displayed similar efficacy in preventing naphthalene cataract. Based on these results, it was concluded that the prevention of the naphthalene cataract probably results from inhibition of the conversion of naphthalene di-hydrodiol to 1,2-dihydroxynaphthalene and that the effect of the ARIs cannot be explained by their inhibition of the dihydrodiol dehydrogenase activity of aldose reductase.

ISSN:0271-3683    

DOI:10.3109/02713689608995833

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

This study was undertaken to determine whether there are age-related changes in the specific activities of several glycosidases in fresh retinal pigment epithelial cells (RPE) isolated from the posterior pole of human donor eyes. One hundred and twenty-one pairs of eyes from human donors, between the ages of 43 and 95 years, were obtained from the National Disease Research Interchange (NDRI, Philadelphia, PA) and the Cleveland Ohio Eye Bank within 18 to 24 h of death. None had histories of diabetes, hepatitis, HIV infection, intraocular surgery, or documented age-related macular degeneration, although several older donors with evidence of drusen were included in the study. RPE cells were isolated from the posterior third of the retina using the conventional rush method and homogenized with a glass, Broeck tissue grinder. All post-nuclear supernatants were anlayzed for glycosidase activity; a smaller number of nuclear pellets were assayed to verify that the majority of the enzyme activity was associated with the post-nuclear sypernatants. Glycosidase activity was quantitated fluorometrically by measuring the enzymatic release of umbelliferone from synthetic substrate preparations, specific for each enzyme. Total protein was determined by a micro BCA protein assay. Regression analysis revealed statistically significant age-related decreases for the specific activities ofα-mannosidase (p = 0.000l),β-galactosidase (p = 0.0001),N-acetyl-β-glucosaminidase (p = 0.0001), andN-acetylβgalactosaminidase (p = 0.0001) in fresh human donor RPE cells taken from the region of the posterior third of the retina that included the macula. Mannose andN-acetyl-glucosa-mine are major carbohydrate monomers of the oligosaccaride chains of human rhodopsin, and a realtively high percentage of the oligosaccharide chains are galactosylated. Defects in their degradation may lead to the accumulation of undigested residual material in the RPE.

ISSN:0271-3683    

DOI:10.3109/02713689608995834

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor