摘要:

Various marketed chloramphenicol ophthalmic solutions were compared and various dilutions of Tobrex®Ophthalmic Solution were tested for effectiveness in a Staphylococcus aureus rabbit keratitis model.

ISSN:0271-3683    

DOI:10.3109/02713688509095248

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

Conformational changes in the three crystallinsα-,β-, andγ- in a singlet-oxygen generating system were investigated by fluorescence studies of tryptophan and covalently-bound sulfhydryl probe 4-[(N-iodoacetoxy)N-methyl]amino-7-nitrobenz-2-oxa-l,3-diazole (IANBD). Upon excitation at 295 nm, the tryptophan emission maxima of the crystallins were red-shifted by irradiation with visible light in the presence of the photosensitizer methylene blue.β- crystallin showed the largest shift (A nm) of the emission spectrum. Time course of the fluorescence changes by irradiation showed that the decrease in the tryptophan fluorescence yield occurs most rapidly forβ-crystallins, as compared toα- orγ-crystallins. Fluorescence changes of IANBD-labeled crystallins show a 40% decrease in the fluorescence intensity of the sulfhydryl probe forβ-crystallin after one hour of irradiation. Forα- andγ-crystallin smaller decreases (7% and 15% respectively) were observed. Since all the sulfhydryl groups ofβ-crystallin are known to be exposed on the surface of the protein (Andley et al, 1982, Biochemistry 21, 1853), these results suggest that the pronounced changes in conformation ofβ-crystallin by singlet oxygen may be due to a rapid loss of the protein tertiary structure by oxidation of the sulfhydryl groups. These results have potential significance in understanding the age and cataract-related changes in the ocular lens in view of the fact that several key lens enzymes are associated withβ-crystallins in vivo.

ISSN:0271-3683    

DOI:10.3109/02713688509095249

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

The role of ornithine decarboxylase and polyamines in proliferative vitreoretinopathy (PVR) is ill-defined. An increase in utie activity of this enzyme concurrent with an increase in poly amine levels may be essential in the process of intraocular cellular proliferation. Therefore, in this study, cultured rabbit fibroblasts were exposed to DL-alpha-difluoromethylornithine (alpha-DFMO), a mechanism-based irreversible inactivator of ornithine decarboxylase, alone and in combination with 5-fluorouracil (5-FU). Concentrations of OlmM alpha-DFMO and 0.12 5mM 5-FU decreased rabbit fibroblast cell number by 60% and 65%, respectively, after three days, while with either 5.0mM alpha-DFMO or 0.25mM 5-FU, cell number is decreased by 95%. The effectiveness of inhibitory concentrations of 5-FU and alpha-DFMO together in reducing cell number is additive.

ISSN:0271-3683    

DOI:10.3109/02713688509095250

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

Bovine retinae, devoid of pigment epithelium, were assayed for endogenous melatonin using high-performance liquid chromatography with electrochemical detection (HPLC-EC). A method of extracting the more polar biogenic amines and metabolites was employed, allowing for direct injection of retinal supernatants into the chromatographic column. The results: 1) confirm the presence of melatonin in the bovine retina; 2) provide a“benchmark”of 3.01 ng/retina for normal adult retinae collected during photophase; and 3) indicate that HPLC-EC represents an adequately sensitive instrument for the detection and quantification of melatonin in a single bovine retina.

ISSN:0271-3683    

DOI:10.3109/02713688509095251

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

In the pathogenesis of mycotic infections, adherence of the microbes to surface structures prior to invasion appears to be the initial and essential step in a susceptible host. Adherence and inhibition of adherence of Candida albicans to rabbit corneal surface was investigated in vitro by light and scanning electron microscopic examinations. The results indicate that blastospores of Candida albicans rarely bind to intact corneal epithelium, but consistently adhere to stroma denuded of epithelium. Such adherence was inhibited by concanavalin A. With its strong affinity for the yeast cell wall carbohydrate mannan, concanavalin A may block the site of attachment of yeast cells to the corneal surface.

ISSN:0271-3683    

DOI:10.3109/02713688509095252

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

This study focused on whether changes in lens levels of glutathione and calcium, early events associated with cataract formation, were related or that one might cause the other. The first part of the investigation was concerned with the extent to which an increase in levels of intracellular calcium might alter GSH levels in lens fiber and epithelial cells. The results demonstrate that calcium accumulation, either at 19°c or 370C, did not diminish the concentration of GSH. More importantly, GSH levels did not decline in opaque regions of a calcium-loaded lens. The reciprocal part of the problem focused on whether a decline in lens thiol might lead to an increase in levels of calcium and subsequent opacification. In particular, it was shown that treatment of lenses with parachloromercuribenzene sulphonic acid (PCMBS), a nonpenetrating sulphhydryl probe, resulted in a 10-30% loss of membrane SH groups in the epithelium. Diminished numbers of SH groups was accompanied by chloride fluxes and an increase in membrane permeability to sodium and calcium with an influx of sodium and calcium leading to opacities. It is important to note that these changes occurred in the absence of any change in cellular levels of soluble protein-SH or GSH. Additional experiments suggest that calcium transport was not impaired, as evidenced by lack of inhibition of Ca-ATPase activity in lenses treated with PCMBS. The results suggest that one explanation for opacification is that oxidative insults, which diminish GSH levels, leads to a loss of important membrane SH groups. An increase in membrane permeability to calcium and other ions quickly follows the loss of thiol followed by an accumulation of lens calcium and subsequent opacification.

ISSN:0271-3683    

DOI:10.3109/02713688509095253

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

The hydrolysis of H-retinyl ester was examined in the retinal pigment epithelium (RPE) and neural retina of cattle eyes and compared to that in homogenates of rat liver. The optimum pH for hydrolysis was 4.0-4.5 for RPE and 7.5 - 8.0 for liver. The RPE activity, which shows no variability between individual animals, is localized mainly in the lysosomal fraction of the cell. It is strongly inhibited by bile salts at concentrations as low as 0.2-0.5% and conversely, is strongly activated by Triton X-100, with maximum stimulation found at a concentration of approximately 1%. The apparent Vmax for hydrolysis of labeled retinyl ester in the RPE is 2.7 nmoles/hr/mg protein, a value approximately 1/150 to 1/200 of the rate of retinol esterification in these cells. Little or no hydrolytic activity could be detected in neural retina or in rod outer segments. Studies on the specificity of the RPE retinyl ester hydrolase activity revealed unexpectedly high hydrolytic activity toward both cholesteryl oleate and triolein, approximately 20 and 5 times greater, respectively, than in rat liver. The hydrolytic activity for cholesteryl oleate in the RPE was mainly at pH 3.5, while that for triolein showed three pH maxima, one at pH 4.5-5.0, a second near neutral pH and the third at pH 8. These findings reflect an active and complex pattern of fatty acyl ester lipid-metabolizing enzymes in cattle RPE whose interrelationships to one another require further clarification.

ISSN:0271-3683    

DOI:10.3109/02713688509095254

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

Total outflow facility was measured by two-level constant pressure anterior chamber perfusion in surgically untouched vervet monkeys receiving intracameral infusions of mock aqueous humor without or with isoproterenol. Bolus dl-isoproterenol sulfate doses of 1 to 10μg, corresponding respectively to initial intracameral base concentrations of 2×10−5M and 24410−4M, increased facility 30-50%; higher and lower bolus doses were ineffective, as were 0.1 and 1,g doses of 1-isaproterenol hydrochloride (4×10−6M and 4×10−5M base). Relatively maintained intracameral dl-isoproterenol concentrations of 2×10−7M and 2×10−6M or 1-isooroterenol concentrations of 4×10−7M to 4×10−5M did not significantly increase facility, although there was great variability with the latter agent. Possible reasons for species, investigator, technique, and dosage-associated differences in results are discussed.

ISSN:0271-3683    

DOI:10.3109/02713688509095255

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

Microdiathermy has recently been shown to be effective In the treatment of persistent corneal epithelial recurrent erosion. In order to determine the mechanism of action of microdiathermy on the anterior surface of the cornea, rabbit eyes were treated with microdiathermy and the course of corneal tissue repair studied by electron microscopy. Shortly after treatment, the epithelium is edematous and necrotic and the lamina densa is thickened. Within 24 hours, the epithelium appears healed and some hemidesmosomes are present, but the lamina densa is still thickened. At two weeks the epithelial surface is undulated and protrudes into the stroma in areas where the lamina densa is disrupted. Hemidesmosomes are absent in these regions. Activated fibroblasts are present in superficial stroma. At four weeks following microdiathermy, there is segmental deposition of new lamina densa and a connective tissue zone between the newly deposited lamina densa and the old lamina densa. Hemidesmosomes are present only in areas of newly deposited lamina densa. Between six weeks and three months the epithelial basal surface becomes more uniform with mature hemidesmosomes and the new lamina densa is complete. The old lamina densa remains below it but is no longer present by six months. The mechanism of action for microdiathermy in recurrent erosion is believed to be as follows: in the treated area, epithelium and activated fibroblasts secrete a new connective tissue layer, which provides a suitable substrate to which the epithelium can adhere until it secretes a new lamina densa and hemidesmosome formation can occur.

ISSN:0271-3683    

DOI:10.3109/02713688509095256

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

By incubating preparations enriched in membranes from lens epithelial cells with [γ32P]-ATP and Ca++at 0°C for 15 seconds followed by SDS-PAGE analysis, it was possible to demonstrate a Ca++-dependent [32P]-phosphate incorporation in two polypeptides with Mr 105,000 and 140,000. Treatment of phosphorylated preparations with 0.06 N hydroxylamine at pH 5.4 and 25°C removed the label from both polypeptides indicating that the phosphate was attached to the proteins by an anhydride linkage characteristic of the phosphorylated intermediates of the ATPases. Membrane preparations from sarcoplasmic reticulum and red blood cell studied under the same conditions showed a Ca++-dependent [32P]-phosphate incorporation into polypeptides with Mr 105,000 and 138,000, respectively, corresponding to the phosphorylated intermediates of the Ca++-ATPases present in these preparations. The results suggest the presence of two Ca++-ATPases in lens epithelial cells which, in terms of Mr, appear to be similar to those present if the sarcoplasmic reticulum and the red blood cell plasma membrane, respectively.

ISSN:0271-3683    

DOI:10.3109/02713688509095257

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor