摘要:

The present study determined the effect of the full range of humidities on the deswelling function of the human cornea. The closed-eye deswelling function and the open-eye deswelling responses for five different levels of humidity (0%, 25%, 60%, 85%, and 100%) were assessed for 8 normal, young-adult subjects. Open-eye corneal deswelling for the 8 subjects was unaffected by relative humidities from 0 to 100%. Therefore, osmotically-driven corneal thinning effect of tear evaporation does not significantly contribute to the deswelling function of the human cornea. We conclude, contrary to recent reports, that the endothelial pump is the primary mechanism that maintains normal corneal thickness and provides recovery from stromal edema.

ISSN:0271-3683    

DOI:10.3109/02713689109001757

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

This study examines the distribution of laminin and fibronectin in the rat lens capsule during development. Both these extracellular matrix glycoproteins are localised in the interspace between presumptive lens and presumptive retina as well as in their basal laminae. The lens capsule arises from multilayering of the basal lamina of the lens cells. Immunofluorescence localises both laminin and fibronectin in the capsule at 16 days of embryonic development, although reactivity for fibronectin is much weaker than for laminin. In the 19 day embryo only laminin is detected. This indicates that during embryonic development fibronectin becomes a minor component of lens cell ECM and is not accumulated in the developing capsule.The roles of laminin and fibronectin in promoting cell migration during development were analysed in explant cultures. Lens epithelial explants from 16, 17 and 19 day old embryos and neonatal rats were grown on a laminin or fibronectin substratum. Lens cells from all ages of rats migrated on the laminin substratum, whereas lens cells progressively lost the ability to migrate on a fibronectin substratum as the age of the donor increased. This developmental loss of ability to migrate on fibronectin in vitro coincides with the developmental loss of fibronectin from the lens capsule in vivo. Therefore, we propose that whilst both laminin and fibronectin may be important for promoting migration of lens cells on their substratum at early stages of lens morphogenesis, during development laminin takes over as the key molecule that promotes migration on the capsule.

ISSN:0271-3683    

DOI:10.3109/02713689109001758

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

The potential difference (PD), short circuit current (SCC) and resistance (R) of rabbit retina-retinal pigment epithelium-choroid-sclera preparations were measured in a modified Ussing chamber. The rabbits were kept in 14 hour light/10 hour dark cycle conditions for 14 days: tissues were taken for measurement at 1.5, 6, 13, 20 and 23 hours after the start of the fifteenth light period. Significant variations in PD and SCC were observed 6 hours into the light cycle while the resistance remained constant during the test period. When in a second experiment the fifteenth light period was replaced by darkness, the highest PD and SCC values recorded occurred 12 hours after the time when the light period should have started in the normal light/dark cycle. In a third experiment the fifteenth light period was replaced by darkness and the retina was removed. There were variations in the PD and SCC as in the second experiment but the SCC peak was reduced in amplitude. From these preliminary studies it is suggested that these variations may be circadian in origin and may be related to variations in retinal function.

ISSN:0271-3683    

DOI:10.3109/02713689109001759

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

The concentration of epidermal growth factor (EGF) in tear fluid (TF) was recently shown to decrease with increasing tear fluid flow (TFF). The purpose of the present study was to clarify the effects of ocular surface disease on the TF EGF concentrations. Tear fluid samples (n=243) were collected from diseased eyes by means of blunted glass capillaries. The time of collection was measured for each sample, and the tear fluid flow in the capillaries (TFFc) was calculated. The concentration of human EGF (hEGF) was determined using a time-resolved immunofluorometric assay (TR-IFMA). For statistical analysis diagnosis-dependent multi-grouping was performed and the data of the patient groups were compared to the data for a control group. The control material consisted of 271 TF samples collected from healthy eyes before (n=59) and after stimulation of reflex tearing (n=212). It was shown that TF specimens of patients (n-243) contained significantly (p<0.001) less EGF (mean 952 pg/ml) than the TF of healthy control individuals before (n=59 samples; mean 6589 pg/ml) or after stimulation of reflex tearing (n=212 samples; mean 2762 pg/ml). The EGF concentration of every patient group was significantly lower than that found in the TF of control individuals both before and during reflex tearing (p<0.001). The rate of EGF released with TF during collection did not differ significantly between the various groups of patients or from that released with the TF of normal individuals before induction of reflex tearing. The rate of hEGF released with tear fluid was, however, significantly lower in patients (mean 347 fg/s) than in healthy eyes during reflex tearing (mean 1400 fg/s; p<0.001). Ocular surface disease is thus associated with a decreased presence of hEGF in TF.

ISSN:0271-3683    

DOI:10.3109/02713689109001760

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

Alpha crystallin from the bovine lens has been digested with cyanogen bromide, and the major fragment (CB-1) has been purified using reverse phase HPLC. Characterization of this fragment by Edman degradation and antisera to synthetic peptides indicates that it originates from alpha-A crystallin, but lacks the N-terminal methionine and the last 35 amino acids from the C-terminus of the molecule. The purified CB-1 fragment binds as well as native alpha crystallin to lens membrane, but is unable to self-assemble into the correct size of high molecular weight oligomeric complexes characteristic of the intact alpha-A chain. Together, these results demonstrate that the alpha-A chain is comprised of at least two functional domains, one of which is involved in binding of alpha-A crystallin to lens membrane, and another which is necessary for correct self-assembly of the molecule into high molecular weight oligomers.

ISSN:0271-3683    

DOI:10.3109/02713689109001761

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

A procedure is described for the preparation of a tissue fraction enriched in basal-lateral membranes of the epithelium of ciliary body dissected from abattoir-derived cow eyes. Microscopical methods established the viability of the epithelial cells in the dissected tissue. A two-step homogenization procedure was employed. First, mild trituration with a Potter-Elvehjem tissue grinder was used to release the epithelial cells with minimal disintegration of the stroma and muscle components. Then, complete vesicula-tion of the released material was induced with a Dounce homogenizer. This material was fractionated through sequential differential and (Ficoll 400) equilibrium density gradient centrifugation steps. The procedure led to the isolation of a fraction enriched 16.8±5.5 (±SE, n-5) fold in Na +K+-ATPase activity with respect to the initial homogenate. Using a method to artificially generate pH gradients it was demonstrated that the preparation contained sealed vesicles and that the membranes of these vesicles exhibited a K+selectivity consistent with a plasma membrane origin.

ISSN:0271-3683    

DOI:10.3109/02713689109001762

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

The organization of immunoglobulin heavy chain (IgH), light chain (kappa and lambda) and T cell receptor (TCR) beta chain gene loci in 10 patients with ocular adnexal pseudolymphoma was investigated. Eight of them showed IgH gene rearrangement in at least one of the 3 restriction enzymes-digested DNAs extracted from ocular adnexal neoplasms. In contrast, none of them exhibited clonal TCR beta chain gene rearrangement. The configuration of bcl-1, bcl-2 and c-myc oncogenes was also studied by Southern blot technique. Two patients had a rearranged joining region, IgH-containing fragment that comigrated with the rearranged bcl-1 fragment. C-myc gene rearrangement was found in only one patient who also had bcl-1 gene rearrangement. In ocular adnexal pseudolymphoma, none demonstrated bcl-2 gene rearrangement; however, in bone marrow cells, one patient with systemic lymphadenopathy exhibited both IgH and bcl-2 gene rearrangements. Three genotypic subsets of these ocular adnexal pseudolymphoma can be identified by the configuration of IgH gene and related oncogenes: with germline configuration of IgH gene and bcl-1, bcl-2 and c-myc oncogenes; with rearrangement of IgH gene but germline configuration of these oncogenes; and with recombination between rearranged IgH and bcl-1 genes. These results suggest in ocular adnexal pseudolymphoma a spectrum of clonal change evolving from polyclonal to monoclonal B-population, and further to monoclonal B-population with rearranged bcl-1, c-myc and/or bcl-2 oncogenes.

ISSN:0271-3683    

DOI:10.3109/02713689109001763

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

To assess the potential of fluoroquinolones as topical antimicrobial agents, we evaluated in vitro the antimicrobial activity of five fluoroquinolones (ciprofloxacin, norfloxacin, ofloxacin, pefloxacin, and temafloxacin), as well as genta-micin, tobramycin, and cefazolin against 96 isolates of common bacterial corneal pathogens. Ciprofloxacin and temafloxacin were the most active quinolones [minimal inhibitory concentration inhibiting 90% of stains (MIC90) of 1 ug/ml], followed by ofloxacin (MIC90 2 ug/ml), and norfloxacin and pefloxacin (MIC90s 4 ug/ml). In contrast, gentamicin and tobramycin MlCggs were 32 and 64 ug/ml, respectively; cefazolin MIC90 was>2040 ug/ ml. The corneal epithelial cytotoxicity of the fluoroquinolones also was evaluated utilizing an in vitro assay of 3H-thymidine uptake of rabbit corneal epithelial cell cultures. The least to greatest toxicity of the fluoroquinolones were as follows: ciprofloxacin and temafloxacin

ISSN:0271-3683    

DOI:10.3109/02713689109001764

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

Three soft drug analogs of atropine have been tested for mydriatic activity in rabbits' eyes and their in vitro metabolic pathway has been investigated in rat, rabbit and human blood. The three soft drugs were found to produce an equieffective mydriatic activity to atropine and tropicamide. At equieffective concentrations, their durations were shorter with AUC's 12–21% that of 0.25% atropine and 44–80% that of 0.2% tropicamide. The untreated control eyes were observed to dilate after unilateral ocular administration of atropine, but not with unilateral soft drug treatment. In vitro stability studies showed that the soft ethyl analog was less stable in rat blood and rat liver homogenate than in rabbit or human blood. The metabolic product of the soft ethyl derivative in biological media was proven to be the corresponding inactive acidic metabolite predicted by the soft drug design. The ultrashort durations and the potentially nontoxic systemic properties of the soft mydriatics offer promise for use in ophthalmoscopy and in other ocular procedures where a short acting anticholinergic type of mydriatic would be indicated.

ISSN:0271-3683    

DOI:10.3109/02713689109001765

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

The influence of lipophilicity on the conjunctival penetration of beta blockers in the pigmented rabbit was investigated and compared with that on corneal penetration. The beta blockers were hydrophilic sotalol, atenolol, nadolol, pindolol, and acebutolol; lipophilic metoprolol, timolol, oxprenolol, levobunolol, labetalol, and alprenolol; and the very lipophilic propranolol and betaxolol. Drug penetration was evaluated by using the isolated pigmented rabbit conjunctiva and cornea in the modified Ussing chamber and was monitored by reversed phase HPLC. The conjunctiva was more permeable to all the beta blockers than was the cornea. A sigmoidal relationship, rather than the familiar parabolic relationship, best described the influence of lipophilicity on both conjunctival and corneal drug penetration. The ratio of corneal to conjunctival permeability coefficients was most sensitive to changes in log PC within the region of 1.5 and 2.5. Outside of this region, the ratio was relatively independent of changes in lipophilicity. For several beta blockers, their intrinsic sympathomimetic activity may play a minor role in influencing their conjunctival and corneal penetration.

ISSN:0271-3683    

DOI:10.3109/02713689109001766

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor