摘要:

Rabbit corneal endothelial fluxes of sodium, bicarbonate, inulin, and dextran have been measured in ambient solutions containing either 0.5 mM adenosine alone (A), 0.3 mM glutathione alone (G), both adenosine and glutathione, or neither adenosine nor glutathione. Addition of A alone to a solution lacking both additives caused a decrease in both Jstro endo and Jstro str sodium fluxes coupled with an increase in Jstro endo Addition of G alone caused no effect, whereas addition of A and G together caused a decrease in both Jstro endo and Jstro str sodium fluxes and a large increase in Jstro endo net. Addition of A or G caused an increase in Jstro endo bicarbonate flux, but no change in Jstro str flux. Addition of A and G caused an increase in both Jstro endo and Jstro str bicarbonate flux and a decrease in Jstro endo net. None of the solution variations caused an alteration in either inulin or dextran permeability. Since both A and G influence Jstro endo net bicarbonate and sodium transport, this may provide an explanation of the beneficial effects of these compounds on the endothelium to both enhance and prolong corneal thickness and hydration regulation.

ISSN:0271-3683    

DOI:10.3109/02713688209020014

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

Differential scanning calorimetric measurements were performed between−30°C and 15°C. The cortical sections of normal human lenses usually show one endotherm at the melting point, while the nucleus indicates a composite endotherm that can be separated into two endotherms with two melting points. Cataractous human lenses usually have composite endotherms from the cortical, intermediate as well as nuclear regions. We interpret the different endotherms as representing different kinds of freezable water contents: free water and partially bound water. Both in normal and cataractous human lenses, there is an appreciable amount of non-freezable water”The amount of non-freezable water is less in cataractous lenses than in normal lenses, indicating a syneretic process as a cause of cataract formation.

ISSN:0271-3683    

DOI:10.3109/02713688209020015

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

We have measured the change in the phase separation temperature, TC, in calf nuclear homogenate produced by a variety of naturally occurring cellular constituents. For all of the compounds studied, increasing concentrations of test compound were found to lower TC. Phosphorylated nucleotides had the greatest effect, lowering TCby 165–305μ/mole of test compound. Reduced and oxidized glutathione reduced TCby 69 and 100°C/mole, respectively. Smaller effects were observed for amino and ascorbic acids and sugars. The pH of the homogenate was also found to affect TCIn the normal lens, the concentration of each of these constitutents is small. Therefore, for each individual component, the cataract associated decrease in concentration is insufficient to produce the large increase in TCthat has been observed during cataractogenesis in some model systems. However, the superposition of the effects of changes in many cellular constituents (including pH and hydration) could possible produce a change in TCmore consistent with the experimentally observed one. In support of this, we have found that combinations of test compound have an additive effect on the TCof the nuclear homogenate.

ISSN:0271-3683    

DOI:10.3109/02713688209020016

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

Unidirectional Na+and Cl−fluxes were measured across the isolated rabbit iris-ciliary body under short-circuited conditions. Na+fluxes were in the range of 9–13μeq/hr.cm2, and Cl−fluxes varied between 7–12μeq/hrμcm2. A statistically significant net Na+or Cl−flux could not be found. Ouabain, 5×10−5M, did not change the Na+or Cl−flux in either direction despite a marked effect on the short-circuit current (SCC). There was a disagreement between the electrical conductance calculated from unidirectional fluxes and electrical measurements, suggesting the presence of electrically silent exchange mechanisms. Theophylline and isobutyl methylxanthine stimulated the SCC, whereas epinephrine, trifluormethazolamide and diisothiocyanostilbene disulfonic acid inhibited the SCC. Furosemide had a minor inhibitory effect, and the Ca2+ionophore A23187 was without effect. Amphoterlcin B produced a substantial stimulation of the SCC from the aqueous side but an inhibition of the SCC from the blood side. This dual effect is consistent with the presence of Na+-K+pumps in the basolateral membranes of both the pigmented and non-pigmented cell layers of the ciliary body.

ISSN:0271-3683    

DOI:10.3109/02713688209020017

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

Effect of feeding riboflavin deficient diet to rats on lens protein composition was investigated. Total proteins and profile of soluble and insoluble proteins in lenses from rats fed on a riboflavin deficient diet for seven weeks were found to be similar to that of the vitamin supplemented diet. Distribution of high molecular weight protein (above 4×10 daltons) isolated from the 9,900 g supernatant fraction was found to be significantly higher and gamma crystallin was significantly lower in riboflavin deficient group as compared to the normal lenses. However, the distribution of alpha and beta crystallins was not affected. Gel electrophoresis in sodium dodecyl sulfate of soluble lens proteins from riboflavin deficient animals had lower proportions of polypeptide species with molecular weight above 40,000 daltons while insoluble protein fraction had higher proportions of these polypeptide species as compared to control rats.These data suggest that the composition of lens proteins is altered in riboflavin deficiency.

ISSN:0271-3683    

DOI:10.3109/02713688209020018

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

Samples of aqueous humor from rabbits and humans were examined for growth effects on sub-confluent monolayer fibroblast cultures from ocular and extraocular tissues. At a concentration of 20% aqueous by medium volume, both homologous and heterologous aqueous stimulated DNA synthesis in fibroblasts from both species. The stimulation was independent of medium serum. When fibroblasts were exposed to 0 to 100% aqueous in serum-free medium or 0 to 98% aqueous in 2% serum-supplemented medium, no concentration of aqueous was observed in which DNA synthesis was inhibited. However, higher concentrations of aqueous led to increasing cell loss resulting in an apparent net inhibition of culture growth. Net growth effects of aqueous humor were, therefore, dependent upon aqueous concentration and were apparently due to the combined effects of stimulation of proliferation and reduction in cell survival.

ISSN:0271-3683    

DOI:10.3109/02713688209020019

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

Steady currents around the rat lens were measured with a vibrating probe. Inward currents were found at the anterior pole and to a lesser degree at the posterior pole. Outward currents were localized at the equator. These currents were inhibited and even reversed by high concentrations of potassium. Ouabain blocked currents after 24 hrs but not after 6 hrs of exposure. The composition of the medium was not critical. For example, currents were observed in NaCl and in MgSO4solutions.

ISSN:0271-3683    

DOI:10.3109/02713688209020020

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

Treatment of normal lens homogenates with trypsin results in the production of polypeptides of approximately 4,000 and 8,000 daltons. Peptide maps of these components are very similar to polypeptides of comparable molecular weight found only in cataracts with brunescent and opaque nuclei. Together, these results demonstrate that putative proteolysis products producedin vivoduring human cataractogenesis can be mimicedin vitroby the addition of exogeneous proteases to the normal lens homogenate.

ISSN:0271-3683    

DOI:10.3109/02713688209020021

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

Electron micrographs of avian retinal pigment epithelium (RPE) reveal a basal zone of abundant mitochrondria, approximately 15% of which present ring-shaped profiles. We infer that these ring profiles represent cross sections of“donut-shaped”bodies, randomly deployed in the RPE mitochondrial zone. The per cent of all RPE mitochondria which are in the ring form increases with age, and is further increased in chicks reared under continuous light, an environmental condition leading also to light-induced avian glaucoma (LIAG). We calculate that a given mitochondrion, on assuming the ring form, would more than double its surface area. Thus the RPE mitochondria of chicks developing LIAG may present to the surrounding cytoplasm a total surface area more than fourfold greater than in normal chicks.

ISSN:0271-3683    

DOI:10.3109/02713688209020022

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

The avian retinal pigment epithelium (RPE) is well endowed with mitochondria, 10–15% of which appear to be“donut-shaped”. The number of such mitochondria presenting ring profiles varies with the photoperiod, with a peak early in the dark period and a low early in the light period. This cycle is inversely correlated with the diurnal rhythm of plasma thyroxine (T4), but is in phase with the T3cycle. We could detect no effect on the numbers of ring mitochondria when exogenous TSH, T4or T3was injected. Numbers and appearance of ring mitochondrdia were likewise unaltered in chicks breathing pure oxygen or spent air for 15 min. before sacrifice. We speculate that this aberrant mitochondrial form may have some relationship to the processing of shed outer segment discs, also a photoperiod-driven phenomenon. It has been suggested that the daily manufacture of hydrolytic enzymes for breakdown of disc proteins is probably highly energy-expensive. We also note that the peroxidation of the lipid components of these membranes must be another aspect of disc disposal. Ascorbic acid, whose photooxidation in the eye generates hydrogen peroxide, may play a role in this process.

ISSN:0271-3683    

DOI:10.3109/02713688209020023

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor