ISSN:0271-3683    

DOI:10.3109/02713689309001825

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Thermal gradients were measured from the cornea to the posterior pole in the eyes of 11 chicks, six of which had the lids of one eye sutured three weeks previously. A comparison was made between eyes that were chronically closed by lid-suture (while still sutured shut) and two types of control eyes: (a) treated controls, which were the non-sutured, contralateral eyes of the lid-sutured chicks and (b) untreated controls, which were the eyes of a different group of chicks in which neither eye had been sutured. The results indicated that transient closing of the eyes of normal, untreated chicks (untreated controls) elevated the ocular temperature by about 1.5°C at the cornea; the extent of thermal elevation diminished as the thermoprobe was advanced towards the posterior pole. In contrast, when the transiently closed eyes in untreated control chicks were compared with the chronically closed eyes of the lid-sutured chicks, the lid-sutured eyes were cooler by 2°-2.5°. When the sutured lids were opened, however, the eyes were isothermal with the untreated control eyes. Moreover, the eyes of lid-sutured chicks were isothermal with their contralateral, non-sutured, control eyes (treated control), whether in the opened or closed state. A comparison of the untreated control eyes and the treated control eyes revealed no differences (except at the cornea) when the eyes were opened; but when the eyes were closed, the treated control eyes were 2°-3°cooler than the untreated control eyes. These results indicate that chronic lid suture produces very different effects on the thermal properties of the eye than does transient lid closure. Chronic lid closure results in a reduction of ocular temperature when the eyes are closed, which may be a consequence of the sutured eye's reduced need for vascular thermoregulation by the choriocapillaris circulation. The differences between lid suturing, which reduces ocular temperature, and the application of goggles, which elevates ocular temperature, are discussed.

ISSN:0271-3683    

DOI:10.3109/02713689309001826

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Using a phoro-accommodometer, accommodation and convergence responses were measured for 17 experimental subjects before and after they ingested 200 mg caffeine. For 16 control subjects accommodation and convergence responses were determined at two test sessions separated by 45 min. For the experimental group, the accommodative response/accommodative stimulus (Ar/As) slope increased 0.05 D/D after ingestion of caffeine, and the response AC/A ratio decreased 3.05Δ/D. The y-intercept of the convergence response/accommodative response increased by 3.7Δin the experimental group. These changes were statistically significant. For the control group, the differences in Ar/As slope, response AC/A ratio, and convergence response/accommodative response y-intercept between first and second test sessions were not statistically significant.

ISSN:0271-3683    

DOI:10.3109/02713689309001827

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Soft drug analogs of methscopolamine (4 a-c) were tested for mydriatic activity in rabbits' eyes. After unilateral administration of equieffective doses, the AUC24hrsand the mydriatic recovery times were found to be significantly lower with tho soft drugs compared to methscopolamine. At equieffective doses, the AUC24hrsfor soft drugs ranged from 22.4% to 60% of that of methscopolamine. Significant dilation of the untreated eye was observed with methscopolamine but not with the soft drugs after unilateral administration. Soft drug 4a exhibited only 10.4% of the AUC6hrs(untreated eye) of that of methscopolamine. Shorter durations of mydriatic action combined with potentially reduced systemic side effects make these compounds candidates for further study, in vitro rabbit transcorneal penetration of soft analog 4a was found to be significantly higher than methscopolamine.

ISSN:0271-3683    

DOI:10.3109/02713689309001828

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

The enzyme adenylyl cyclase has been shown to be important in the regulation of intraocular pressure. We therefore studied the activity of adenylyl cyclase (AC) activity in the rabbit iris/ciliary body (I/CB) after pre-treatment with theβ-adrenergic agonist isoproterenol (ISO) which activates cAMP dependent protein kinase A, and phorbol 12, 13 dibutyrate (PDB) which activates protein kinase C. When I/CB was pre-treated with ISO (1μM) or PDB (1μM), attenuated AC activity (∼35%) resulted when the activity of the enzyme was assessed by rechallenge with isoproterenol. However, when AC activity was assessed by rechallenge with forskolin or prostaglandin, enhanced activity resulted. In an effort to identify the mechanism of this apparent heterologous regulation of AC, studies were performed that showed no significant changes in the density ofβ-adrenergic receptors or the affinity of the receptors for the ligand (125I)-Iodopindolol occurred in ISO or PDB treated tissue. Similarly, in membranes prepared from ISO or PDB treated tissue, no significant changes in the functional activity of the guanine nucleotide binding proteins Gior Gscould be ascertained as assessed by somatostatin inhibition of forskolin-stimulated AC (to assess Gifunction), or in an adenylyl cyclase complementation assay (to assess Gsfunction). However, AC activity stimulated by Mn2+and purified Gswas enhanced (∼2X) following isoproterenol or phorbol ester pre-treatment, suggesting that an alteration at the level of the catalytic subunit of AC resulted from ISO or PDB pre-treatment. Therefore, the assessment of net changes in receptor coupled AC activity induced by phorbol esters or isoproterenol appears to be dependent on the drug used to rechallenge the AC system and cAMP production is dependent on the sum of diverse effects on multiple components of the AC pathway.

ISSN:0271-3683    

DOI:10.3109/02713689309001829

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Gentamicin shows retinal toxicity in rabbits, monkeys, and humans, but its mechanism of toxicity is not understood. Pig eyes, which are anatomically similar to human eyes, were examined with ophthalmoscopy, fluorescein angiography, and light and electron microscopy at time points ranging from 3 to 72 hours after intravitreous injection of 3 mg of gentamicin or vehicle to observe the sequence of toxicity-related changes that occur in the retina. The first ophthalmoscopic changes were retinal hemorrhages at 3 hours, followed by retinal whitening and thickening and vascular nonperfusion detected by fluorescein angiography 48 hours after injection. Vacuolization in the nerve fiber layer and perivascular swelling were seen at 6 hours, and subsequently, extended deeper into the retina. Vascular endothelial cells, photoreceptors, and the retinal pigment epithelium appeared to be spared from the toxic effects of gentamicin. At 48 and 72 hours after injection, numerous large and small retinal vessels showed congestion and leukocyte margination. These changes could not be prevented by increasing the pH of gentamicin to 7.2.These data suggest that gentamicin toxicity is not simply a pH-related phenomenon, that the primary targets of gentamicin toxicity are neurons and glia of the inner retina, and that retinal infarction occurs secondarily, possibly due to leukocytic plugging.

ISSN:0271-3683    

DOI:10.3109/02713689309001830

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Using a modified turbidimetric assay to determine the protein concentration in human tears by precipitation with trichloroacetic acid (TCA) we found lower protein concentrations if compared with other methods for protein determination. This implies that a factor in human tears is able to inhibit the precipitation of protein by TCA.Earlier a coating inhibitory factor in human tears was described which is able to prevent coating of a polyacrylate surface by proteins using a ELISA methodology. Because of the similarity in its behaviour towards protein we investigated whether the same factor could be responsible for both inhibitory effects.A pool of human tears was separated into various fractions using HPLC whereafter inhibitory activity in the turbidimetric and the coating assay could be found in the same fractions. Characterization of the inhibitory factor was performed by minigel-electrophoresis (SDS-PAGE), after which blotting and staining with a lectin (Jacalin) revealed two subunits of a glycoprotein with a molecular weight of 30 and 70 kD. The inhibitory factor also could be isolated if human tears were incubated for 30 min at 100°C whereafter precipitated protein was removed by centrifugation. Inhibitory activity could be detected in the supernatant and an identical glycoprotein profile could be produced after staining with lectin (Jacalin).The results of this study suggest that a soluble glycoprotein serves as a coating and precipitation inhibitor in tears and may play an important role in the protein to protein interaction on the surface of the eye.

ISSN:0271-3683    

DOI:10.3109/02713689309001831

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Parallel arrays of Na+/H+and Cl−/HCO3−antiporters are believed to catalyze the first step of transepithelial electrolyte secretion in lacrimal glands by coupling Na+and Cl−influxes across acinar cell basolateral membranes. Tracer uptake methods were used to confirm the presence of Na+/H+antiport activity in membrane vesicles isolated from rabbit lacrimal gland fragments. Outwardly-directed H+gradients accelerated22Na+uptake, and amiloride inhibited 96% of the H+gradient-dependent22Na+flux. Amiloride-sensitive22Na+influx was half-maximal at an extravesicular Na+concentration of 14 mM.In vitrostimulation of isolated lacrimal acini with 10μM carbachol for 30 min increased Na+/H+antiport activity of a subsequently isolated basolateral membrane sample 2.5-fold, but it did not significantly affect Na+/H+antiport activity measured in intracellular membrane samples. The same treatment increased basolateral membrane Na+, K+-ATPase activity 1.4-fold; this increase could be accounted for by decreases in the Na+, K+-ATPase activities of intracellular membranes. Thus, it appears that cholinergic stimulation causes recruitment of additional Na+, K+-ATPase pump units to the acinar cell basolateral plasma membrane. The mechanistic basis of the increase in basolateral membrane Na+/H+antiport activity remains unclear.

ISSN:0271-3683    

DOI:10.3109/02713689309001832

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Two anti-fibrotic agents were evaluated in vitro for potential application in trabeculectomy. The rate of collagen formation by cultured rabbit corneal fibroblasts was determined by [3H]proline uptake and hydroxylation assay.Incubation of fibroblasts, for 96 hours, with 16 mM 2, 4-pyridine dicarbo-xylic acid (2, 4-PDCA), a competitive inhibitor of prolyl 4-hydroxylase, decreased [3H]OH-proline formation from control by 28.2±3.9%; (average±S.E.M), whereas 10 mM minoxidil, an antihypertensive pyrimidine oxide and a lysyl hydroxylase inhibitor, induced a decrease of 17.3±4.5%. Incubating fibroblasts with a mixture of the two inhibitors, 16 mM 2, 4-PDCA and 10 mM minoxidil, resulted in a further decrease in [3H]proline incorporation of 40.7±5.1%. After 96 hours of incubation with the inhibitors, rabbit corneal fibroblast growth was decreased from control by 17.2±4.2% and 10.5±4.5% for 16 mM 2, 4-PDCA and 10 mM minoxidil, respectively. These effects were dose dependent. The results suggest that both 2, 4-PDCA and minoxidil have an inhibitory effect on collagen formation and may be useful in delaying surgical wound healing.

ISSN:0271-3683    

DOI:10.3109/02713689309001833

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Recently a new technique was reported in which examination of the retina of oxygen reared newborn rats was made using indirect fluorescence microscopy (Invest. Ophthal. Vis. Sci. 31:810). We have now improved this technique and systematically employed it as a means of studying oxygen-induced retinopathy in the newborn rat as an animal model for retinopathy of prematurity (ROP). Immediately after birth, litters of pigmented rats were exposed to an elevated oxygen atmosphere that varied in a cyclic fashion between 40% and 80% every 12 hours for 14 days. Rats raised simultaneously in room air served as controls. At the end of the treatment period, rats were deeply anesthetized, their pupils dilated, and 100μl of 3% sodium fluorescein was administered via tail venipuncture. After angiography, rats were awakened and returned to their mothers in room air for future assessment. Angiography was performed again at 4, 7, 38 or 56 days after oxygen treatment Our results suggest that retinal pathology in the rat model parallels that of the human infant with ROP with respect to loss of patent retinal blood vessels in oxygen and subsequent abnormal vasoproliferation upon return to room air. Angiograms performed on room air-raised control rats at 14 days of age demonstrated our ability to resolve the smallest retinal capillaries. Angiograms conducted at the same age in oxygen-exposed rats revealed extensive areas of retinal non-perfusion and substantial arterio-venous shunting between adjacent primary vessels. If rats were maintained in room air for 4 or 7 days following oxygen exposure, a variety of pathologic signs became obvious including: 1) tortuosity of primary vessels mimicking human“plus disease”, 2) frequent abnormal budding of tertiary vessels and capillaries, 3) retinal fluorescein leaks indicative of hemorrhages and 4) abnormal capillary tufts not evident at the time of removal from oxygen. By 38 and 56 days post-exposure, all four of these phenomena were still observed. Many of these pathologic phenomena could not have been observed with conventional methods currently used for retinal vascular assessment in small animals.

ISSN:0271-3683    

DOI:10.3109/02713689309001834

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor