摘要:

In vivoexposure of grey squirrels to 40W BLB illumination resulted in alterations in the state of the lens crystallins; mainly in the outer layer of the lens. HPLC revealed an increase of the void volume or crosslinked crystallins and an increase in peptides with molecular weights lower than 20,000 d.In vitroexposure of squirrel lens aqueous extracts to Woods lamp radiation (predominantly 365 nm) led to similar but more exaggerated changes as viewed by high performance liquid chromatography. When viewed by polyacrylamide gel electrophoresis (PAGE), soluble protein crosslinking was also observed. The near-UV absorbing chromophores of low molecular weight present in the lens served as photo-sensitizers that enhanced the protein changes. Sodium azide inhibited the changes, indicating a role for singlet oxygen in the crosslinking.

ISSN:0271-3683    

DOI:10.3109/02713688809031808

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

The influence ofin vitronear-UV radiation exposure on the physical state of the rat lens and on its membrane-bound Na-K-ATPase activity was investigated. Lens swelling was correlated to the appearance of opacities and the inactivation of the enzyme. The results show a significant decrease in the Na-K-ATPase activity which may be an early change leading to osmotic type cataracts. The dose-effect curves obtained for cortical and epithelial enzymes were different. Since the data do not follow a mono-exponential function, the existence of two forms of Na-K-ATPase in the lens is discussed.

ISSN:0271-3683    

DOI:10.3109/02713688809031809

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

Several unsaturated fatty acids are precursors of prostaglandins and leukotrienes. Depending on their precursor, these prostaglandins and leukotrienes have different biological characteristics. The effects of topically administered fatty acids on an experimentally provoked inflammatory keratitis were studied in rabbits. Intrastromal injection with human serum albumin induced in the cornea a ring-shaped infiltration with leukocytes, corneal edema and neovascularization. Arachidonic,γ-linoienic, dihomo-γ-linolenic (DHGL), eicosapentaenoic (EPA) and columbinic acid were given as eye drops in a suspension in hydroxypropylmethylcellulose 0.5% three times daily during the experiment. EPA, DHGL, columbinic, andγ-linolenic, but not arachidonic acid, showed a significant inhibition of either leukocyte infiltration, edema or neovascularization. The inhibitory effects of these fatty acids may be caused by topical inhibition of the formation of prostaglandins and leukotrienes in the arachidonic acid cascade in the rabbit cornea.

ISSN:0271-3683    

DOI:10.3109/02713688809031810

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

The effect of topical administration of 3-isobutyl-methyl-xanthine (IBMX), a potent phosphodiesterase inhibitor, was studied on an experimentally provoked uveitis in rabbits. After presensitization with an intravitreal injection of human serum albumin (HSA), intravenous antigenic challenge induces blood-aqueous barrier breakdown and leukocyte infiltration. The effect of IBMX on the blood-aqueous barrier was determined by scoring the severity of the flare in the anterior chamber and by determination of the levels of ascorbic acid and protein in the aqueous. Treatment with IBMX 1% two times daily, significantly inhibited the breakdown of the blood-aqueous barrier and the increase in PGE2level of the aqueous humor. There was no effect on leukocyte infiltration. The therapeutic effect of IBMX in blood-aqueous barrier protection is comparable with the effect of topical treatment with the corticosteroid medrysone.

ISSN:0271-3683    

DOI:10.3109/02713688809031811

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

α-crystallin can be isolated in two forms depending on the temperature at which the lens is extracted. At 4°C,αC-crystallin is obtained while at 37°C, a smaller molecule,αm-crystallin can be isolated.The apparent molecular weight of bovine foetalαm-andαC-crystallins were determined in 5 different ways using sedimentation velocity, sedimentation equilibrium and intensity fluctuation spectroscopy analyses and the experimentally determined diffusion coefficients, intrinsic viscosity and partial specific volume. Values ranged from 291,000 to 369,000 forαmand from 604,000 to 760,000 forαCdue to the differential effects of the protein's polydispersity on the different methods.Subfractionation of the protein by gel filtration yielded much less polydisperse minimum species populations with molecular weights of 280,000 and 529,000 forαmandαCrespectively.It was concluded thatα-crystallin is probably synthesized as a symmetrical dodecamer and that the polydispersity of most preparations can be attributed to age-related modificationin vivoas well asin vitrosupra-aggregation due to variations in experimental conditions.

ISSN:0271-3683    

DOI:10.3109/02713688809031812

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

The photooxidation of calfγ-crystallin has been Investigated in (a) riboflavin-sensitized reaction and (b) direct photolysis of the tryptophan residues of the protein at 300 nm. Partial insolubilization of the protein is evident by the increase in turbidity of the photolyzed protein solution. The turbidity is diminished when anaerobic conditions are used for irradiation. Spectroscopic studies on the soluble phase of the photolyzed protein reveal significant changes in the near-UV circular dichroism spectrum, suggesting that changes in the tertiary structure of the protein precede insolubilization. Isoelectric focusing analyses reveal that theγ-crystallin polypeptides have more acidic pI's after photooxidation under both conditions. The insoluble protein is highly crosslinked into dimers and higher oligomers via covalent, non-disulfide crosslinks, but inter-subunit crosslinking is negligible in the soluble phase of the photolyzed protein. The mechanism of photooxidation involves the generation of H2O2in the riboflavin-sensitized reaction. In the direct photolysis of tryptophan residues by 300 nm irradiation, there Is a rapid disruption of the protein structure, apparently by the oxidation of the hydrophobic tryptophan residues.

ISSN:0271-3683    

DOI:10.3109/02713688809031813

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

Drusen-like changes In Bruch's membrane following subretlnal Injection of vitreous In the rabbit were studied by electron microscopy. A sequence of changes Is seen that closely panel lets those observed during drusen formation In primates. The Initial event Is the budding of retinal pigment epithelial (RPE) cells Into Bruch's membrane; the buds, which contain cytoplasm and plasma membrane, are connected to the cytoplasm of the parent RPE cell. Most buds are surrounded by basement membrane, but some penetrate RPE basement membrane Into Bruch's membrane. Later, RPE buds completely separate from the parent RPE cell and show degeneration and disintegration. Finally, drusen-like material, Including vesicular, granular, tubular and linear structures. Is dispersed from the bud remnant Into Bruch's membrane. The study described herein thus supports the hypothesis that drusen are the result of budding from the RPE.

ISSN:0271-3683    

DOI:10.3109/02713688809031814

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

The possible role of specific mechanisms involved in the adherence process of immune aggregates to tissue components of the mouse eye was investigated in an experimental animal model. Passive intravenous administration of immunoglobulin aggregates to mice, resulted in the localisation of these aggregates in various organs, including the eye. In the eye a strong localisation was seen in the episcleral capillary plexus, whereas only a weak deposition was seen in the iris, ciliary body and choroid. No deposits were seen in the retina. To investigate the role of specific receptors for immune complexes in the eye, in vitro experiments were performed, whereby immunoglobulin aggregates were layered on cryostat sections of the mouse eye. These in vitro studies also showed an adherence of immune aggregates to the episcleral capillary region, but furthermore a deposition on mast cells scattered throughout the extra-ocular muscles.The in vitro binding of immunoglobulin aggregates to the episcleral capillary plexus could be inhibited by high concentrations of Fc fragments and monomeric IgG, but not with Fab fragments or 0.5 M NaCl. The in vitro adherence of aggregates to mast cells could not be blocked by the inhibitors employed in our study and could therefore be distinguished from the interaction of aggregates with the episcleral capillary plexus. These results indicate that the ocular deposition of immunoglobulin aggregates in the episcleral capillary plexus of the mouse eye is (immune) specific and mediated by Fc receptors.

ISSN:0271-3683    

DOI:10.3109/02713688809031815

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

Topographical corneal thickness changes were monitored in 10 subjects who each wore a hydrogel contact lens with a large central aperture (“donut”lens) for 6 hours. Analysis of local corneal thickness changes indicates that no corneal swelling occurred in the central exposed area of the cornea, but significant swelling occurred in the area of the cornea covered by the lens. The lateral cut-off point of corneal swelling was well-defined, indicating that the contact lens-induced corneal edema did not spread laterally to the exposed area of the cornea over the six-hour wearing period. Swelling of the peripheral cornea covered by the lens was found to be significantly greater with a tightly-fitting, immobile donut lens than with a loosely-fitting lens, suggesting that tear mixing may explain in part the apparent averaging of edema during open-eye wear of hydrogel lenses of varying thickness profile. The possibility that lateral spread of lactate within the stroma may contribute to this apparent averaging of edema was not confirmed in this study. We suggest that rapid metabolism or elimination of lactate in the exposed region of the cornea, or evaporation through the central lens aperture, may have contributed to the maintenance of normal central corneal thickness during open-eye wear of the donut lens.

ISSN:0271-3683    

DOI:10.3109/02713688809031816

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

Both periarterial electrical stimulation (ES) and intraluminal application of noreplnephrine (NE) produced a vasoconstriction in the isolated canine ophthalmic artery (OA). The ES-induced vasoconstrictor response was markedly inhibited by treatment with tetrodotoxin and slightly but significantly depressed by xylazine, a selective alpha-2 adrenoceptor agonist. Moreover, the ES-induced response was enhanced by either DG-5128, a selective alpha-2 adrenoceptor antagonist, or angiotensin II. The inhibitory effect of bunazosin on the ES-induced response was significant, but it was rather small compared with that on the NE-induced response. The NE-induced constriction was not affected by xylazine and DG-5128, but significantly enhanced by angiotensin II. These results indicate that (1) the ES-induced response is mediatedviasympathetic nerve activation, (2) there are inhibitory prejunctional alpha-2 adrenoceptors, (3) there are more postjunctional alpha-1 than postjunctional alpha-2 adrenoceptors in canine OAs, and (4) prejunctional angiotensin II receptors may exist in isolated OA preparations.

ISSN:0271-3683    

DOI:10.3109/02713688809031817

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor