摘要:

Cytochrome oxidase (CYO), a key enzyme in the respiratory chain, was observed as an indicator of retinal metabolism after an in vivo blue light exposure.Thirty Sprague-Dawley rats were exposed to optic radiation of 404 nm with a retinal dose of 110kJ/m2. Immediately after exposure, the CYO activity in the pigment epithelium, in the outer and inner segments of photoreceptors, and in the outer plexiform layer of the exposed retina, was reduced to one—third—to—half of the control level. However, there was an increase in CYO activity in the exposed retina one day after exposure. One week after exposure, the CYO activity in the inner segment and the outer plexiform layer was higher, while the activity in the other two layers was lower, than that at one day, although still higher than in the control. Two weeks after exposure, the CYO activity in the four retinal layers returned to the level of the control retina, as did the activity four weeks after. After exposure, no ophthalmoscopically visible retinal change and no lightmicroscopically evident morphological alterations were found. There was no retinal edema or loss of photoreceptor cells.The observed alteration in CYO activity after blue light exposure may represent an inhibition of retinal metabolism. The inhibition was reversible. If this compensation mechanism is overwhelmed, retinal damage may occur.

ISSN:0271-3683    

DOI:10.3109/02713689209033480

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

Changes occurring at the membrane are believed to be the decisive factors in the initiation of diabetic cataract. During diabetic hyperglycemia lens crystallins were shown to undergo glycation. Several studies indicated that glycation brings about protein conformational changes thus implicated in cataractogenesis. Since the membrane proteins are the first targets for glycation, in this study we measured the glycation of alkali washed urea-insoluble membrane proteins from control and diabetic rats by two different methods, phenyl-boronate affinity chromatography and [3H]NaBH4reduction, and confirmed by amino acid analysis. There was a significant increase in the glycation of membrane proteins in diabetic cataract lenses when compared to controls. It appears that lysine is the major site of glycation. Concomitant to early glycation, there was an increase in non-tryptophan fluorescence (Ex: 350 nm/Em: 440 nm) in the diabetic lens membrane proteins suggesting the presence of advanced glycation mediated protein cross-links. In order to identify whether the major membrane intrinsic protein, MIP26, undergoes glycation, we isolated MIP26 along with its degradatory product MIP22 as one peak on molecular sieve HPLC. HPLC isolated MIP26/MIP22 was further separated on SDS-PAGE followed by slicing and counting. This analysis revealed that MIP26 and MIP22 were more or less equally glycated in controls, however, in diabetic rats glycation of MIP22 was glycated slightly higher than MIP26. Moreover, the proportion of MIP22 increased by about 2-fold in diabetic lenses compared to controls. Thus it appears that major glycation sites are still retained in MIP22 in diabetic rat lenses.In vitroglycation studies with bovine lens membranes were also done using14C glucose, followed by SDS-PAGE and autoradiography. The major protein glycatedin vitroalso seems to be MIP26. Interestingly, MIP22 was less glycated than MIP26in vitro.

ISSN:0271-3683    

DOI:10.3109/02713689209033481

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

Chlorpromazine (CPZ) has been used extensively in the treatment of psychiatric disorders, and has recently been shown to possess systemic anti-inflammatory properties as well. To investigate the potential effects of CPZ on ocular inflammation, we evaluated its action on endotoxin-induced uveitis (EIU) in Lewis rats. At three different dosage levels, CPZ produced highly significant reductions in the mean aqueous aspirate inflammatory cell counts and histological inflammatory scores as compared to controls treated with vehicle only. Analysis of aqueous fluid demonstrated a similar decrease in protein concentration and phospholipase A2 (PLA-2) activity in the treated animals. The ability of CPZ to inhibit the development of EIU may be related to its properties as a calcium channel blocker and inhibitor of the enzyme phospholipase A2.

ISSN:0271-3683    

DOI:10.3109/02713689209033482

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

Cells of keratoconus corneas have been reported to produce higher levels of collagenolytic/gelatinolytic enzymatic activities than do cells of normal corneas. The current study investigates the contribution of 1) specific enzyme gene products, and 2) the degree to which these proteins are present in the activated forms, to the increased enzymatic activities. We demonstrate that two neutral gelatinolytic enzymes, a 66/59 kD form and a 92 kD form, can be directly extracted from both normal and keratoconus corneas. These enzymes are identified as the pro- and activated forms of MMP-2 and as the pro-form of MMP-9, specific members of the matrix metalloproteinase family. Normal and keratoconus corneas show no significant differences in amounts or types of extractable neutral gelatinases, nor in the amounts or types that they synthesize in culture. Furthermore, in both the normal and keratoconus corneas, gelatinases are found primarily in the inactive form. These studies suggest the possible importance of changes in proteinase inhibitor levels to the characteristic biochemical features of keratoconus corneas.

ISSN:0271-3683    

DOI:10.3109/02713689209033483

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

Rodent photoreceptor dystrophies are characterized by late stage ingrowth of retinal blood vessels into the retinal pigment epithelium (RPE) where they proliferate. Some of these vessels develop the fenestrated phenotype of the choriocapillaris (CC). To determine if development of fenestrae in these endothelial cells is a function of the duration of time the endothelial cell had been encapsulated by the RPE, we did an ultrastructural morphometric study of these vessels in urethane induced photoreceptor degeneration in Long-Evans rats. Retinas of animals aged 20, 24, 40 and 56 weeks were studied.The fraction of vessel profiles within the RPE that had fenestrated endothelial cells increased from 10% to 90% between 20 to 56 weeks. The average number of fenestrae per vessel increased approximately 25 fold between 20 and 24 weeks but stabilized after that, despite a decrease in the number of vessels present at 56 weeks. A large number of degenerated retinal vessel profiles were seen in the RPE at 40 weeks. These facts support the idea that the presence of the RPE induces endothelial cell fenestrae, and also show that a complex process of remodelling including proliferation and degeneration is occurring in these vessels. Analogies between the basic cell biology of neovascularization occuring in these rodent models and that of proliferative diabetic retinopathy and age-related macular degeneration are discussed.

ISSN:0271-3683    

DOI:10.3109/02713689209033484

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

The healing of alkali-injured corneas is characterized by the persistence of polymorphonuclear leukocytes (PMN) in tissues and recurrent corneal epithelial defects. It has been suggested that the proteolytic enzymes secreted by PMN may account in part for the recurrent epithelial defects in the alkali-burned corneas. Cytoplasmic keratins, which form intracellular intermediate filaments, participate in the formation of hemidesmosomes and play a key role in the focal adhesion of epithelial cells to the basement membranes. The K3/K12 keratin pair is a major constituent of differentiated and stratified corneal epithelium. We have recently cloned the cDNA encoding the rabbit K12 keratin. In the present study we examined the expression of K12 keratin during the healing of alkali-burned rabbit corneas by slot-blot and in situ hybridization. Our results indicate that in normal cornea K12 keratin is equally expressed in all cell layers of stratified corneal epithelium and suprabasal layers of limbal epithelium, but not in bulbar conjunctival and other epithelia, i.e., lens, iris, and retinal pigment epithelium. The basal cells of the detached regenerating epithelium of the injured cornea express a very low level of K12 keratin. These observations are consistent with the notion that defective expression of K3/K12 keratins may play a role in the abnormal attachment of the regenerating epithelium to the basement membrane.

ISSN:0271-3683    

DOI:10.3109/02713689209033485

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

The lacrimal gland stores retinyl esters which are synthesized by the enzyme acyl CoA:retinyl acyl transferase. Retinol is released from retinyl ester reserves by retinyl ester hydrolase (REH). Since the lacrimal gland secretes retinol, this gland should also contain this enzyme. To identify bile saltdependent REH activity, rabbit lacrimal glands were homogenized in 0.05 M Trismaleate buffer, and enzyme activity was determined in the tissue homogenate, in the membrane fraction and in the cytosolic fraction by measurement of production of retinol from retinyl palmitate (nmol retinol produced/mg protein/h). In the lacrimal gland, production of retinol was optimal in the presence of 200 mM CHAPS at pH 7. The REH activity in the presence of 1000μM retinyl palmitate was 2.38 $pM 0.18 nmol/mg/h in the homogenate, 1.13 $pM 0.16/ nmol/mg/h in membranes and 3.25 $pM 0.26 nmol/mg/h in cytosol. By comparison, REH activity in rabbit liver was 6.58 $pM 0.75 nmol/mg/h. The REH activity in lacrimal gland was not affected by vitamin A deficiency. These data are consistent with the presence of retinyl ester hydrolase activity in the lacrimal gland and provide further evidence that this gland is adapted for metabolism and secretion of retinol.

ISSN:0271-3683    

DOI:10.3109/02713689209033486

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

Protein kinase C (PKC) has been implicated in cell proliferation and differentiation. Multiple forms of PKC have been isolated, principally from the brain where PKC is most abundant. In rabbit corneai epithelium, two distinct major peaks of PKC activity were resolved by hydroxyapatite column chromatography. Peak 2, with 65% of the total PKC activity, corresponds to $aL-PKC, based on its mobility in the column and Western blot analysis using specific monoclonal antibodies. Peak 1 did not react with either polyclonal or monoclonal antibodies to PKC $aL-,β-, andγ-isoforms suggesting the presence of isoforms specific to the corneai epithelium, or of another member of the PKC family.To investigate possible changes in the amounts of the various PKC subspecies during wound healing, the enzyme activities of the isolated subspecies were assayed 2, 5, and 7 days after corneai de-epithelialization. Two days after wounding, by which time the migratory limbal epithelium had covered the denuded area, total PKC activity was unchanged but $aL-PKC activity had increased to 77% of the total activity, compared with 65% in nonwounded epithelium. An increased proportion of $aL-PKC activity was also observed 5 and 7 days after wounding, during which time proliferation of epithelium continued. We hypothesize that $aL-PKC plays a role in long-term responses after injury such as gene expression and corneai epithelial proliferation. Moreover, these studies indicate that the cornea provides a good model ofin vivowound healing for PKC studies.

ISSN:0271-3683    

DOI:10.3109/02713689209033487

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

ISSN:0271-3683    

DOI:10.3109/02713689209033488

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

LBP-32 is a cell surface and cytoplasmic protein which is thought to both mediate cell attachment to laminin and play a role in translation initiation. In the present study, antisense RNA for LBP-32 was used to document its cellular mRNA expression pattern in newborn mouse eye.In situhybridization revealed that LBP-32 was distributed uniformly through the retina as well as over anterior oblique muscle, in corneal and lens epithelial cells and in capillary endothelial cells of the choroid. This unique cell-specific expression raises interesting questions of the role of LBP-32 in eye development.

ISSN:0271-3683    

DOI:10.3109/02713689209033489

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor