摘要:

The survival time of rabbit corneal endothelial cells in isolated perfused cornea is extended dramatically by the addition of oxygen free radical scavengers. Lipid soluble antioxidants were found to be more effective than water soluble non-enzymatic antioxidants in extending the survival time. The ultrastructural appearance of endothelial cells treated with vitamin E was compared with controls. Vitamin E treated endothelial cells retained normal appearance up to 12h, but without vitamin E, breakdown of the endothelial cells occurred after 6h of perfusion. In these cells the major sites of damage were the mitochondria and the endoplasmic reticulum, whereas the plasma and nuclear membranes appeared normal.

ISSN:0271-3683    

DOI:10.3109/02713689008995196

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

The inhibitory effects of theα2-adren-ergic agonist clonidine and that or dopamine were studied on the adenylate cyclase activity in homogenates of ciliary processes.Clonidine inhibited in a dose-dependent manner basal adenylate cyclase activity as well as that stimulated by isoproterenol or forskolin. However, the adenylate cyclase activity stimulated by isoproterenol was sensitive to at least one order lower inhibitory concentrations of clonidine than basal or forskolin-stimulated adeny-ate cyclase. Dopamine inhibited adenylate cyclase stimulated by isoproterenol considerably less potently than clonidine. The slope of the dopamine dose-response curve was, however, similar to that of the dose -response curve of clonidine. The inhibitory effects of clonidine and dopamine were antagonized by anα2-adrenergic antagonist, yohlmbine, in a manner suggesting a competitive nature of this interaction. On the contrary, the inhibitory effects of neither clonidine nor dopamine were prevented by anα1-adrenergic antagonist, prazosin. In addition, the effect of dopamine was not antagonized by the D2-antagonist, tiapride. Taken together, tnese results strongly indicate that both clonidine and dopamine exert their inhibitory effects by the stimulation ofα2-adrener-gic receptors. Accordingly, they provide experimental evidence that both basal and drug-stimulated adenylate cyclase activity of ciliary processes can be inhibited via stimulation ofα2-adrenergic receptors.The substantially higher sensitivity of isoproterenol-stimulated than basal or forskolin stimulated adenylate cyclase toα2-adrenergic inhibition seems to be a unique feature of this enzyme of ciliary processes. It is suggested that this may reflect an involvement ofα2-adrenergic receptors in the physiological feedback mechanism preventing the over-stimulation of adenylate cyclase of ciliary processes

ISSN:0271-3683    

DOI:10.3109/02713689008995197

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

The inhibitory effect of neuropeptide Y (NPY) was studied on the adenylate cyclase (AC) activity in homogenates of rabbit ciliary processes and compared with that of theα2-adrenergic agonist clonidine (CLN).NPY inhibited basal AC activity as well as AC activity stimulated by isoprotere-nol (ISO), vasoactive intestinal polypep-tide (VIP) or forskolin (FSK). The extent of this inhibition corresponded well to the inhibition elicited by CLN. The inhibitory effects of NPY and CLN appeared to be nonadditive. AC activity stimulated by ISO was considerably more sensitive to the effects of either NPY or CLN than basal, VIP- or FSK-stimulated AC activity.It was inferred that NPY inhibitory effects were mediated by the activation of NPY receptors coupled negatively to the catalytic unit of AC via the inhibitory G1protein. Moreover, involvement of NPY in physiological modulation of AC activity in ciliary processes and in the regulation of aqueous humor formation and intraocular pressure is suggested.

ISSN:0271-3683    

DOI:10.3109/02713689008995198

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

The changes in mouse corneal inflammatory cell population and the phagocytic capability of these cells were studied quantitatively at 24 and 48 hours after eliciting inflammatory cells into the cornea byPseudomonas aeruginosainoculation. Mice were selected for study according to their ability (young adult Swiss-Webster) or inability (aged Swiss-Webster) to restore corneal clarity after bacterial inoculation. Inflammatory cells were recovered from enzymatically disaggregated corneas, nucleated cells counted, and cell viability assessed to be 95% by trypan blue dye exclusion. Polymorphonuclear neutrophilic leukocytes (PMN) and macrophages recovered in this manner showed no significant differences in cell population contribution to the differential leukocyte count, but did show significantly fewer phagocytically active cells in aged when compared with young adult mice. These phagocytosis data were confirmed in a separate study using peripheral blood cells obtained from uninoculated mice of each age. The impaired phagocytic function seen in aged mice may contribute to the failure to resolve corneal clarity observed in these animals afterPseudomonasinfection.

ISSN:0271-3683    

DOI:10.3109/02713689008995199

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

Enolase is a dimeric enzyme of molecular weight of 100,000 daltons, which plays an important role in the glycolytic cycle. The aim of this study was to characterize the enzyme of the chicken lens epithelium and to compare its distribution in different regions of the chicken, duck and turtle lens.Enolase of the chicken lens epithelium was found to be an enzymatically active dimeric protein of molecular weight 100,000 daltons and representingα-enolase. It is a major component of the epithelium comprising 4%, 12% and 46% of the water-soluble protein of chicken, duck and turtle epithelium respectively. Enolase is found in trace amount in the fiber cells of the chicken and duck, but is retained in much greater concentration in the turtle fiber mass as a predominantly inactive enzyme.

ISSN:0271-3683    

DOI:10.3109/02713689008995200

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

Procedures for regenerating visual pigment and restoring phototransduction have been established with freshly isolated, bleached rat retinas. Phosphatidyl choline liposomes containing a 500μM mixture of retinal isomers, including the 9-cis and 11-cis forms, were employed and the results compared with dark-adapted retinas, incubated similarly but without retinal. The following were recovered in a 60 min incubation, rhodopsin (plus isorhodopsin) to 91% of the original rhodopsin concentration, 87% of cGMP and 89% of PHI amplitude at saturation. PIII amplitude vs. log intensity curves gave values of n between 0.6 and l.o andσbetween 85 and 439 quanta/μm2.Human retinas, ranging from 18 to 58 hours postmortem and treated as above, also produced photoresponses. Of the 7 retinas studied so far, rhodopsin has been regenerated to 0.1-0.35 nmol/mg protein, cGMP to 23.5-49.2 pmol/mg protein, and PIII to 20-50μV: in some cases a b-wave was also seen. Values of n varied between 0.6 and 1.0, andσbetween 132 and 3700 quanta/μm2. PIII responses were also seen after retinas, approximately 30 hours postmortem, were incubated for a further 24 hours in fortified medium. After incubation, retinal vacuolation was reduced.

ISSN:0271-3683    

DOI:10.3109/02713689008995201

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

MK-927 is a water soluble, potent inhibitor of human carbonic anhydrase (CA) II in vitro. Topical administration of MK-927 reduces intraocular pressure (IOP) in rabbits. Elevated IOP was produced in cynomolcjus monkey eyes by argon laser photocoagulation of the trabecular meshwork. IOP was measured at 0 hr, 0.5 hr and hourly for 8 hrs in 8 eyes for two baseline days, one day on vehicle and five days of therapy with 2% MK-927 b.i.d., after initial single-dose trials of various concentrations. IOP was not significantly different comparing baseline and vehicle treated days. Significant (p<0.05) reductions of IOP occurred for five days lasting at least 8 hrs after each dosing. At 3 hrs after treatment with vehicle the IOP was 31.6±3.4 (SE) mm Hg. Maximum reduction of IOP occurred at 3 hrs after application of MK-927, the IOP decreasing from day 1 (19.9±1.0 mm Hg) to day 5 (16.5±1.6 mm Hg). MK-927 appear-s to have great clinical potential.

ISSN:0271-3683    

DOI:10.3109/02713689008995202

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

The prejunctional effects of angiotensin II (AII) on stimulation-evoked secretion of3H-norepinephrine (3H-NE) were investigated byin vitromethods in isolated, superfused rabbit iris-ciliary body preparations. AII (0.1–10 nM) concentration-dependently enhanced the field- stimulated release of3H-NE (EC50 = 0.1 nM), nearly doubling evoked neurotrans-mitter release with no apparent effect on spontaneous3H-NE efflux. The response to 1 nM AII was abolished by the selective AII receptor antagonist saralasin([Sar1, Val5, Ala8]-angiotensin II; 500 nM), which alone did not modify3H-NE overflow. All-mediated effects on neurosecretion were partially additive to those of forskolin and were not potentiated by phosphodiesterase inhibition, suggesting that AII utilizes a mechanism other than increased cAMP synthesis to facilitate neurotransraitter release. AII also strongly enhanced calcium ionophore (A23187)-induced3H-NE release in iris-ciliary body segments, indicating that AII can modulate calcium-dependent exocytosis at step(s) distal to calcium influx. These results demonstrate that sympathetic nerves in the rabbit eye contain prejunctional, facilitatory AII receptors, and support the possible involvement of the renin-angiotensin system in regulation of ocular sympathetic neurotransmissionin vivo.

ISSN:0271-3683    

DOI:10.3109/02713689008995203

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

The present results indicate that 30μg/ml copper was toxic to bovine corneal endothelial cells (BCEC) cultured in a serum-free medium (SFM) when the duration of treatment was 72 hours or more. Copper at 10μg/ml, if mixed with 50μg/ml ascorbate 2 to 3 hours before treatment, caused a transient decrease in the number of nuclei/mm2at 72 hour, whereas 10μg/ml copper alone was apparently non-toxic. When 10μg/ml copper was added to 50μg/ml ascorbate at the time of treatment, the toxicity was increased. All the treated cells failed to survive beyond 24 hours, and copper at a lower concentration of 1μg/ml could inhibit the proliferation of BCEC. We propose that copper toxicity on BCEC is augmented by ascorbate possibly through the increased replenishment of Cu+and the subsequent enhanced production of free radicals by copper auto-oxidation.

ISSN:0271-3683    

DOI:10.3109/02713689008995204

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

Transplantation of normal retinal pigment epithelium (RPE) to the subretinal space has been reported to rescue photoreceptors in the RCS rat. Moreover, the rescue effect was surprisingly large considering the relatively small number of RPE cells transplanted. The reason for this widespread rescue of photoreceptors is not known, nor is the mechanism for outer segment phagocytosis in photoreceptors not apposed to the transplanted RPE cells. This suggests that the rescue effect may not be solely mediated by the transplanted cells. We therefore wished to test whether the transplantation surgery itself might contribute to the rescue of RCS photoreceptors. For these control experiments, we performed the surgery on juvenile RCS rats as described by others for the transplantation of RPE but instead of injecting RPE, we injected saline. We sacrificed the RCS control operates two months following surgery. In the area of the surgery (superior retinal quadrant) the outer nuclear layer (ONL) was up to 8–10 photoreceptor cells thick, while at the extreme inferior margin of the retina the ONL was almost eliminated. To investigate the role of temporary retinal detachment in photoreceptor rescue we repeated the above experiment using our trans-corneal approach to the subretinal space. This procedure results in a large temporary retinal detachment and little or no damage to the choroid and sclera. In these cases we found extensive preservation of the ONL extending across both the superior and inferior aspects of the retina. The degree of rescue of photoreceptors that we obtained in these experiments was comparable to (with saline injections) or greater than (with gelatin insertion) that obtained with the RPE cell injection technique. It therefore appears that the rescue of photoreceptors in this animal for at least 2 months (a post surgical time comparable to previous RPE transplantation reports) does not require transplantation of normal RPE cells, but only the surgical manipulation for such transplantation. Furthermore, it appears that temporary retinal detachment alone can induce photoreceptor rescue in the RCS rat.

ISSN:0271-3683    

DOI:10.3109/02713689008995205

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor