摘要:

Protein-mixed disulfides (PSSG) were formed by interaction of glutathione disulfide (GSSG) with lens crystallins. Total water-soluble crystallins andα-crystallin purified on a Sephacryl S-200 column were separately incubated with 0, 2, 4, and 8 mM (final concentrations) GSSG overnight and then dialyzed to remove unbound GSSG and GSH. Either TPCK-treated trypsin or TLCK-treatedα-chymotrypsin were added to about 200μg crystallin samples and incubated for 20 min at room temperature. Reactions were terminated by boiling in SUS-mercaptoethanol-Tris (pH 6.8) solution and subjected to electrophoresis on 10% polyacrylamide slab gels. Comparison of SDS-PAGE patterns of proteolysis with or without GSSG treatment showed that GSSG at a concentration of 2 mM or higher reduced or abolished proteolysis ofα-crystallin by trypsin but not byα-chymotrypsin. The protective effect of GSSG was greater withα-crystallin than withβ-crystallins. Addition ofα-crystallin-mixed-disulfide to an assay system in which trypsin was hydrolyzing N-α-benzoyl-DL-arginine-P-anilide (BAPNA) inhibited the tryptic activity. Direct addition of GSSG or nativeα-crystallin had no significant inhibitory effect on trypsin. Based on these results, it is speculated thatα-crystallin glutathione mixed-disulfide appears to become resistant to trypsin probably by non-competetive inhibition of the enzyme.

ISSN:0271-3683    

DOI:10.3109/02713688609015108

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

We have been able to analyze the autocorrelation function of the light scattered from the rabbit lensin vivoin terms of a two component, exponential fit. We have measured the intensity and the decay rate associated with each of these two components as a function of age and position in the lens. As far as is possible we have interpreted these results in terms of molecular changes in the state of association of the protein constituents in the aging rabbit lens. These studies suggest that the method of quasielastic light scattering spectroscopy can provide a useful probe of the protein modifications that occur in both normal and cataractous human lenses.

ISSN:0271-3683    

DOI:10.3109/02713688609015109

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

The importance of membrane -SH groups in the epithelium and posterior fiber cells of rabbit lens was demonstrated by employing a non-penetrating sulfhydryl reagent parachloromercuribenzoate sulfonic acid (PCMBS). Both fiber cell and epithelial membrane preparations contain substantial amounts of -SH, 31nmoles/mg membrane protein. PCMBS-treatment of anterior and posterior surfaces of the lens leads to dramatic increases in the calcium influx across both anterior and posterior surfaces, indicating that the importance of membrane -SH groups is not limited to the epithelium. When the entire lens is bathed in PCMBS (0.1mM) for short duration and transferred to normal medium, calcium continues to increase from 0.4mM to nearly 1mM over a 20 hr period. At this point in time, GSH levels are normal, indicating that intracellular GSH does not gain access to PCMBS-binding sites. In contrast, external GSH or cysteine, at lower levels (5mM) quickly reverses PCMBS binding with membrane -SH groups and leads to near normal levels of lens calcium during subsequent culture. This in addition to the fact that PCMBS is not found in the cell interior where GSH levels are undiminished, suggests that the critical -SH groups involved in control of barrier properties are externally located where little protection from intracellular GSH is afforded. These data indicate that aqueous humor GSH may play a critical role in maintaining reduced -SH groups controlling membrane permeability located on the surface of membranes.

ISSN:0271-3683    

DOI:10.3109/02713688609015110

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

The effect of retrobulbar lidocaine administration on ocular and optic nerve blood flow was studied in phakic rabbit eyes using a radioactive microsphere (85Sr) technique. Blood flow measurements were performed 15 minutes after retrobulbar injection of 40 mg of lidocaine in ethanol to the right eye of each rabbit. Blood flow measurements were determined for the iris, scraped ciliary processes, choroid, retina, and optic nerve. There was no statistically significant (P<0.05) difference in lidocaine treated eyes compared to contralateral control eyes. An identical volume of retrobulbar ethanol alone had no effect on regional blood flow.

ISSN:0271-3683    

DOI:10.3109/02713688609015111

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

An in vitro animal model was used to characterize the protective effect of glucose on lenses subjected to oxidative stress. Paired rat lenses were incubated in TC-199 medium for six hours in the presence of an oxidant (0.06 mM H2O2, superoxide produced from 5 mM purine, or hydroxyl radical) and 2 mM glucose (control) or no glucose (experimental). Soluble hexokinase (HK) specific activity and lactate production were measured. 0.06 mM H2O2inactivates 48% of the hexokinase in the absence of glucose; with glucose present hexokinase activity is reduced only 26%. Control experiments without oxidants show a statistically insignificant difference between hexokinase activities in the 0 and 2 mM groups, suggesting that the changes observed are not simply due to the presence or absence of glucose. Hexosemonophosphate shunt activity increases nearly 2.5-fold in the presence of 0.06 mM H2O2and 2.0, 4.0 or 5.5 mM glucose. This suggests that the loss of hexokinase (a -SH enzyme) in the presence of H2O2and 0 mM glucose is due to NADPH production inadequate to offset the oxidative stress on enzyme -SH groups. FPLC analysis suggests that type II HK is more susceptible to oxidative inactivation than type I, and further studies have shown that this inactivation is localized to the capsule/epithelium. Lactate levels were measured and controls (without oxidants) were run, to obtain a baseline value for fresh lenses and assess the contribution of endogenous glucose to lactate production. H2O2levels in superoxide and hydroxyl radical media were measured, and the protective effects of mannitol and catalase were also determined.

ISSN:0271-3683    

DOI:10.3109/02713688609015112

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

About 55% of the acyl groups of dog and human vitreous are unsaturated fatty acids. The major components are oleate (18: 1, n-9) and arachidonate (20: 4, n-6) with moderate amounts of linoleate (18: 2, n-6) and docosahexaenoate (22: 6, n-3). Palmitate (16: 0) and stearate (18: 0) are the major saturated fatty acids. There are no significant changes between ages 37–82 years in the fatty acyl group content and composition of human vitreous. In vitreous from Irish setters with hereditary rod-cone dysplasia (RCD) the levels of oleate are decreased with a concomitant increase in arachidonate. [1-−14C] Arachidonic acid was actively incorporated into canine vitreous glycerolipids both in vitro and in vivo. The incorporation was mainly into phosphatidylinositol, triacylglycerol, phosphatidylcholine and phosphatidylethanolamine. There were some differences in the pattern of incorporation between human and dog and between in vivo and in vitro incubations of canine vitreous. Glycerolipid acylation was significantly increased in phosphatidylinositol and phosphatidylcholine in RCD canine vitreous. The pattern of incorporation of [U-14C]docosahexaenoic acid into vitreous glycerolipids was different from arachidonic acid incorporation. Although vitreous did not produce any measurable enzymatic synthesis of cyclooxygenase and lipoxygenase products from [1-−14C]-arachidonic acid in vitro, there was significant generation of autooxidation products. These results suggest an active lipid metabolism in vitreous.

ISSN:0271-3683    

DOI:10.3109/02713688609015113

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

The effect of dopamine and SK&F 82526 on cyclic AMP metabolism in ocular tissues has been examined. Thein vitroincubation of human and bovine ciliary body with these agonists produced a dose-dependent increase in endogenous levels of cyclic AMP. This stimulation was blocked by the selective DA1receptor antagonist SK&F 83566, but not by theβ-receptor antagonist propranolol. The response to SK&F 82526 was stereoselective, with SK&F R-82526 being approximately 100 times more potent than SK&F S-82526 in this preparation. This stimulation of ciliary body cyclic AMP content was not observed in the rabbit or cat, nor was it seen in human, bovine or rabbit iris tissue. These data suggest that adenylate cyclase linked dopamine receptors are present in both human and bovine ciliary body.

ISSN:0271-3683    

DOI:10.3109/02713688609015114

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

The response of the ciliary processes of the rabbit eye to water-soluble marihuana-derived material (MDM) has been examined with light and electron microscopy. Following intravenous injection of MDM, the processes undergo considerable swelling within 1 hour followed by thrombus formation in the capillaries and extravasation of red cells. Later phases include the formation of cysts between the non-pigmented and pigmented cell layers of the ciliary epithelium. The ciliary process edema coincides with the initial hypertensive phase seen after intravenous MDM, while the hematogenous response coincides with the fall in intraocular pressure. Following intravitreal injection of MDM, a similar pattern of structural changes occurs that accompanies a fall in intraocular pressure that lasts for several days; because the physiological response occurs over a longer time course (14–20 hours) relative to intravenous administration where the intraocular pressure changes occur rapidly, the ciliary process swelling phase does not result in an increase in intraocular pressure. The physiologic changes in the eye caused by MDM appear to be related to the induction of a general inflammatory response in the ciliary processes, with a primary effect on the vascular system.

ISSN:0271-3683    

DOI:10.3109/02713688609015115

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

ISSN:0271-3683    

DOI:10.3109/02713688609015116

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

An Outline of Ophthalmology by Roger L. Coakes and Patrick J. Holmes Sellors, published by John, Wright&Sons Ltd., Techno House, Redcliffe Way, Bristol BS1 6NX, England; 1985; 195 pages with illustrations.

ISSN:0271-3683    

DOI:10.3109/02713688609015117

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor