摘要:

The effect of adsorbed substances on the properties of the water in various hydrogel contact lens materials was examined by exposing contact lenses (Hydron Zero 4, B&L 70, DuraSoft 3, Vistamarc, and Acuvue) to an artificial tear solution for various periods up to 14 days. The only materials affected were the high-water/ionic lenses which adsorbed a large amount of protein, predominantly lysozyme. In the DuraSoft 3 lenses the equilibrium water content (EWC) dropped from 49% to 46% and the freezing water from 28% to 21%. Similar changes were seen with the Vistamarc lenses. After a 10-day exposure of the Acuvue lens to artificial tears, the EWC decreased from 53% to 47% and the amount of freezing water from 33% to 23%. The decrease in the permeability of water seen with these materials was consistent with the decrease of the freezing water, i.e., the water able to participate in diffusion. Since the content of freezing water determines the transport through hydrogels it can be expected that any lens characteristics that depend upon the amount of this portion of water would be affected by the presence of proteins inside the polymer matrix. We extrapolated that an absolute change of 10% in the amount of freezing water could lead to a decrease in oxygen permeability of as much as 7 Dk units. In view of this work more attention should be given to changes in the properties of lenses during wear, in particular, in the high-water/ionic lenses.

ISSN:0271-3683    

DOI:10.3109/02713689109003440

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

In a physiological medium (134 mM Na+concentration), unidirectional blood-to-aqueous and aqueous-to-blood Na+fluxes across the isolated rabbit ciliary epithelium are large, rendering the detection of a net transport difficult. At 134 mM an active component for Na+may be obscured by diffusional fluxes and a bidirectional Na+-Cl-cotransport. Considering that the active transport saturates at about 30 mM, experiments were performed at this reduced Na concentration to minimize the influence of diffusional pathways. A net blood-to-aqueous Na+flux that ranged from 0.25 to 0.81 /xeq/hr was obtained. Addition of ascorbic acid to the aqueous side under this condition increased the blood-to-aqueous flux with little effect on the flux in the opposite direction. Ouabain inhibited both the Na+and ascorbate-stimulated Na+transport. The increase in blood-to-agueous Na flux by ascorbate was also observed in tissues bathed with [Na+] closer to physiological levels (100 mM). These results indicate that the rabbit ciliary epithelium transports Na into the posterior chamber. Since aqueous ascorbate stimulates Na+transport, it may be implicated in both Na movement and aqueous humor secretion. However, the rate of Na+transport can only account for a small fraction of total aqueous humor production.

ISSN:0271-3683    

DOI:10.3109/02713689109003441

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

The visual threshold for standard and flickering targets was determined and compared in 8 glaucoma patients, 8 glaucoma suspects and 13 normal controls. Using a Goldmann size III standard white light target, 25 points in the central 30°of the visual field were tested. The location of these points was designed to reflect areas of the visual field commonly affected by glaucomatous damage. The same determinations were then repeated with the test target flickering at 25 Hz. All glaucoma patients had elevation of the visual threshold compared to normal controls for both standard and flickering targets. The absolute value of threshold elevation was not significantly different between standard and flickering lights. However, when larger targets were used, flicker thresholds were an average 8 dB higher (p<0.05) in the glaucoma patients compared to the normals, suggesting improved identification of glaucomatous damage with the use of larger flickering targets.

ISSN:0271-3683    

DOI:10.3109/02713689109003442

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

A rapid and highly sensitive reverse-phase HPLC (RP-HPLC) method was used to separate crystallin subunits from human a crystallin. Three distinct peaks were separated; by electrophoretic and immunological analyses the first and second peaks were identified asαB andαA respectively. On the other hand, peak 3 appeared to be a modified form of a crystallin. The ratio ofαA andαB proteins was 3:1 in 1 day old lenses which gradually changed to 2:1 in 17 year old lenses and to 1:1 in the 50 and 82 year old whole lenses and 82 year old lens cortex, with a concomitant increase in the modified a, suggesting thatαA subunits are relatively more involved in aggregation. Analysis of the 82 year old lens nucleus also supported this conclusion. The RP-HPLC analysis of the HMW aggregate fraction showed substantial enrichment of the modified a. TheαA andαB subunits independently reassociated to form polymeric a crystallin whereas the modified a reassociated to form HMW aggregates as shown by molecular sieve HPLC. Hence it appears that the HMW aggregate peak was constituted by modified a crystallin. Only in the peak 3 material the 280nm absorbance was about 2-fold higher than what was expected from the actual protein content. The data suggest that the changes induced by post-translational modifications may have some role in the formation of modified a. The present RP-HPLC method is useful in separating these modifiedαfrom the unmodifiedαA andαB subunits.

ISSN:0271-3683    

DOI:10.3109/02713689109003443

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

Heat lability studies of glutathione peroxidase and glutathione reductase activities were conducted on rabbit, sheep, rat, human, galago, cat and rhesus monkey lens supernatants. These species represent five mammalian orders. Incubation periods were 10.0 minutes in duration, with temperatures ranging from 25-100°C (depending on which enzyme was being investigated). Results obtained for glutathione peroxidase activity demonstrated nearly identical heat lability profiles for human and rhesus monkey lenses. Both species were extremely labile to heat, losing activity at 30°C and becoming totally inactive at temperatures of 50°C (rhesus monkey) and 55°C (human). Their profiles were very dissimilar to those of the other five species investigated, providing evidence for the existence of an evolutionary break. Glutathione reductase activity was extremely stable under conditions of highly elevated temperature for all seven species investigated. The human lens enzyme, the most stable of the species, maintained nearly 100% of its original activity up to 65°C. Lenticular glutathione reductase activity did not reach zero levels in any of the seven species until a temperature of at least 80°C was attained.

ISSN:0271-3683    

DOI:10.3109/02713689109003444

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

The objective of this study was to determine whether the ocular and systemic absorption of topically applied timolol in the pigmented rabbit was significantly affected by the coadministration with other eye medications, including pilocarpine, epinephrine, their prodrugs, phenylephrine, tetracaine, and proparacaine. Twenty-five microliters of 0.65% timolol maleate solutions, both in the presence and absence of a second drug, were instilled to the pigmented rabbit eye. Timolol concentrations in anterior segment tissues were monitored at 30 and 90 min, and the time course of timolol concentration in plasma was monitored over 120 min. All coadministered drugs except proparacaine reduced intraocular timolol concentrations by varying extents depending on the sampling time, while increasing the timolol concentrations in the conjunctiva and sclera. In addition, all coadministered drugs, except pilocarpine, tetracaine, and proparacaine, reduced the systemic absorption of timolol by an average of about 50%. A plausible explanation for the simultaneous reduction in ocular and systemic timolol absorption is changes in tear turnover rate, protein secretion, and binding of timolol to tear proteins, rather than changes in corneal and perhaps conjunctival and nasal permeability, elicited by the second drug. Vasoconstriction on the conjunctival and nasal mucosae is an additional factor possibly contributing to the reduction in systemic timolol absorption by epinephrine, its prodrug, phenylephrine, and perhaps the pilocarpine prodrug. The clinical implication of the above findings is that before instituting combination or multiple drug therapy the possibility of changes in ocular and systemic absorption of the first drug by the second drug must be considered.

ISSN:0271-3683    

DOI:10.3109/02713689109003445

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

Patients with certain systemic deficiencies in the degradation of glycosaminoglycans (GAGs) often suffer from a retinal degeneration similar to that seen in retinitis pigmentosa. This applies to mucopolysaccharidosis (MPS) types I, II, and III, but not to type VI. The retinal pigment epithelium (RPE) is thought to contribute significantly to the synthesis and degradation of proteoglycans in the interphotoreceptor matrix. This raises the possibility that a defect in the synthesis or degradation of GAGs by the RPE may be related to some forms of retinal degeneration. In the present work, RPE from normal and RP donors was investigated for the capacity to correct deficiencies in GAG degradation by cultured skin fibroblasts from patients with different forms of MPS. A cross-correction technique was used in which abnormal increases in the incorporation of35S-sulfate into GAGs by MPS fibroblasts was measured in the absence or presence of RPE cultures. RPE from normal donors corrected the defects in GAG degradation of fibroblasts from patients with MPS I, II, and III, but not MPS VI. The RPE from four donors with retinitis pigmentosa (one autosomal dominant, one sex-linked, and two isolated cases) and one donor with an unclassified isolated retinal degeneration demonstrated the same capacities to correct the MPS deficiencies as did normal RPE. Therefore, although retinitis pigmentosa is a heterogeneous disorder with several possible etiologies, no evidence was found in these five patients for a defect in GAG degradation that resembles the deficiencies of MPS patients.

ISSN:0271-3683    

DOI:10.3109/02713689109003446

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

We investigated the inhibition of proliferation of human retinal pigment epithelial cells in vitro by the 4-quinolone, ciprofloxacin, and the steroid, dexamethasone. The concentration of ciprofloxacin that inhibited growth by 50% (lC50) was found to be 14.1μg/mL Growth was 100% inhibited at 83μg/mL. At 166μg/mL, all the cells became completely detached and appeared dead at the end of seven days. The lC50for dexamethasone in RPE cells was found to be 141μg/mL A dexamethasone concentration of 1.3 mg/mL inhibited proliferation 100% after five days. When the two drugs were combined, the inhibitory effect was found to be additive; i.e., the lC50dose of the two drugs in combination inhibited RPE cell proliferation by 75%. A combination of the two drugs was also tested for retinal toxicity in rabbit eyes. An examination of histological sections and electroretinograms showed that a dose of 100μg of ciprofloxacin, alone or in combination with 200μg of dexamethasone in saline, was not toxic to the rabbit retina. These studies indicate that a combination of ciprofloxacin and dexamethasone has the potential for reducing the risk of PVR formation and aiding in the prevention of endophthalmitis.

ISSN:0271-3683    

DOI:10.3109/02713689109003447

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

We have investigated the effects of endothelin-1 (ET1) on phospholipid hydrolysis and 3H-arachidonic acid (AA) release and prostaglandin synthesis in the rabbit iris sphincter smooth muscle. ET1 actions are concentration- and time dependent with an EC50 for AA release of 1 nM and ti value of 1.5 min. We have identified the AA metabolites released by ET1, employing HPLC, as both cyclooxygenase and lipoxygenase products. The AA released by ET1 appears to derive mainly from the phosphoinositides through phospholipase A2, rather than phospholipase C activation. A key role for phospholipase A2in AA release in the sphincter muscle is supported by the following observations. (1) Pretreatment of the labeled sphincter with the phorbol ester, PDBu (100 nM) inhibited ET1-stimulated IP3formation, but it potentiated ET1-stimulated AA release. (2) Pretreatment of the labeled tissue with isoproterenol (5 M) inhibited ETl-stimulated IP3production without altering AA release. (3) The potency for ET1-stimulated AA release (EC50=1 nM) was much higher than that for IP3formation (EC50=45 nM). (4) There were considerable increases, rather than decreases, in 1, 2-diacyl-glycerol formation (1.2-folds) and its phosphorylated product, phosphatidic acid (2.6-folds) by ET1. It is concluded that in the rabbit iris sphincter ET1 is a potent agonist for AA release and eicosanoid synthesis and that AA is released from phosphoinositides mainly through activation of phospholipase A2.

ISSN:0271-3683    

DOI:10.3109/02713689109003448

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

The goal of the present in vitro study was to determine the ability of unadapted human adenoviral ocular isolates to replicate in the rabbit cornea. Rabbit corneas grown in organ culture (24 well plate) were inoculated topically with 50 ul (5 ul 105pfu) of different ocular adenoviral serotypes (ATCC and clinical isolates). Control wells (no cornea present) were inoculated in a similar fashion. Viral replication was determined by serial aliquots titrated on A549 cells. We demonstrated sustained viral replication over time of all isolates (100%) of Adl, 2, 5, 6, 8, 9, 11 and 37 tested. No isolates (0%) of Ad3, 7A, 19, and 4 demonstrated replication in our model. Peak titers varied among successful serotypes from 102pfu/ml (Adll) to 105PFU/ml (Ad5), and among different isolates of a given serotype. We conclude that the ability of unadapted human Ad serotypes to replicate in rabbit corneas was serotype-dependent, and that subgroup C (Adl, 2, 5, and 6) appeared to be the most successful subgroup.

ISSN:0271-3683    

DOI:10.3109/02713689109003449

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor