摘要:

Glyceraldehyde-3-phosphate dehydrogenase has been shown to occur in three different forms in the human adult cataractous lens: a membrane bound form (M) and at least two cytosolic isozymes: I1and I2. Similar Km's for substrate, cofactor and HAsO4, were established for each form and all three forms, to differing degree, require a reduced sulfhydryl group for maximum activity. A variety of phosphonucleosides (ATP, ADP, AMP and 3′5′cyclic AMP) as well as NADH inhibit enzyme activity. Inhibition by ATP is non-competitive whereas cyclic AMP and NADH compete for the cofactor binding site. Chloride ion stimulates and inhibits enzyme activity at low and high concentrations respectively.

ISSN:0271-3683    

DOI:10.3109/02713688509020029

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

86Rb efflux has been studied in normal lenses and in human senile cataracts. The rate constant (Ki) of the efflux gradually increases in cataractous lenses with progression of lens damage. Efflux experiments run in the presence of BaC12 suggest that a progressive activation of BaC12 inhibitable efflux routes occurs in cataractous lenses. In the final stages of opacification the ineffectiveness of BaC12 enriched or Ca++ free media on the efflux suggests that a direct disruption of the lens membranes has occurred.

ISSN:0271-3683    

DOI:10.3109/02713688509020030

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

The corneal endothelium of alloxan diabetic dogs was examined by wide-field specular microscopy and compared to that of age-matched non-diabetic dogs. Computer-assisted morphometry of individual cells showed that the diabetic dog endothelium had marked polymegethism and pleomorphism similar to that previously described in diabetic patients. There also appeared to be a positive correlation between the degree of these endothelial changes and the diabetic control as demonstrated by HbA1concentration.

ISSN:0271-3683    

DOI:10.3109/02713688509020031

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

The Chediak-Higashi syndrome (CHS) is a genetic disorder of man, cats, and four other animal species. Enlarged cytoplasmic granules, including lysosomes and melanosomes, characterize the syndrome. Cats affected with CHS lack funduscopically visible tapeta. In normal cats, the tapetum is the light reflecting cellular layer located in the choroid. The tapetal cells contain bundles of parallel cytoplasmic rods. In this study, eyes from CHS and control cats were examined by light microscopy and transmission electron microscopy. The CHS kittens up to 14 days of age had tapeta which appeared similar to those of the controls. By 28 days of age some of the CHS tapetal rods had degenerated. Degeneration of the tapetal rods progressed rapidly and by 56 days of age there was a dramatic difference in the ultrastructural appearance of the tapetal cells. All the rods had degenerated and the contents of the tapetal cells were disorganized. The tapetal layer gradually thinned over a period of several months until the layer was absent or nearly so in CHS cats over one year of age. This study demonstrated that there is a previously overlooked degenerative component of the Chediak-Higashi syndrome.

ISSN:0271-3683    

DOI:10.3109/02713688509020032

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

Glaucoma was induced in cynomolgus monkeys by photocoagulating the trabecular meshwork with the argon laser. Repeat treatments were often necessary and wide intraocular pressure fluctuations were characteristic.Baseline intraocular pressure was measured with a calibrated pneumatonometer hourly for six hours. On a succeeding day a baseline measurement was made, 50μl of the drug to be tested applied, and six hourly measurements of intraocular pressure repeated. The effects on intraocular pressure of timolol, epinephrine, pilocarpine, vanadate, prostaglandin F2α(PGF2α), forskolin, and corynanthine were tested in at least eight eyes. Significant (p<0.05) reductions of intraocular pressure were produced by 0.5% timolol, 2% epinephrine, 4% pilocarpine, 1% vanadate, 500μg of PGF2αand 1% forskolin. Five per cent corynanthine produced no significant lowering of intraocular pressure.Tonography revealed an increased outflow facility associated with the reduction of intraocular pressure 2 hours after the administration of 4% pilocarpine.This glaucoma animal model may be useful in investigating agents that lower intraocular pressure by a variety of mechanisms.

ISSN:0271-3683    

DOI:10.3109/02713688509020033

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

Prior administration of detergents modulates the effects of epinephrine (epi) in isolated, arterially perfused rabbit eyes. Pretreatment with Tween 80, Triton X-100, digitonin and sodium dodecyl sulphate (SDS) caused a dose-dependent reduction of epi induced vasoconstriction of uveal vessels. There also was a dose-dependent reduction of the epi induced fall in intraocular pressure (IOP) after pretreatment with Tween 80 and Triton X-100; digitonin and SDS enhanced the effects of epi on IOP but these effects were not dose-dependent. Significant effects of all four detergents on the efficacy of epi were irreversible. Digitonin probably increased the affinity of epi for the adrenergic receptor as shown by the decrease of the ED50-value; the three other detergents did not significantly affect the affinity. The sequence of administration of epi and detergents is of minor importance for the effects of Tween 80 and Triton X-100 but differs significantly for the effects of digitonin and SDS.

ISSN:0271-3683    

DOI:10.3109/02713688509020034

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

The calcium-binding characteristics of the EDTA-extractable proteins (EEP) from calf lens fiber membranes were studied by equilibrium dialysis and far-ultraviolet circular dichroism measurements. The EEP proteins appeared to contain binding sites with different affinities for calcium. These sites seem to behave as positively cooperating Ca2+binding sites with a total capacity of 25 mol Ca2+per mol EEP. The mean apparent dissociation constant (KD) for the Ca2+binding sites was determined to be 7.7μM. Calcium binding probably is accompanied by a decrease in the apparentα-helical content of the EEP proteins.The present results indicate that the EEP proteins belong to the group of proteins possessing high affinity and binding capacity for calcium. Because of the high calcium-binding capacity, the EEP proteins possibly function as an intracellular calcium store in the lens. The calcium-sensitivity of the conformational state of the EEP proteins, however, might point to a possible regulating function of these membrane proteins in calcium-dependent cellular processes in the lens.

ISSN:0271-3683    

DOI:10.3109/02713688509020035

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

The synthesis of phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PIP) and phosphatidylinositol-4,5-bisphosphate (PIP2) was studied in the rabbit cornea using (PIP2)32Pand [3H]myo-inositol as precursors. Also, the formation of water—soluble products of the degradation of inositol lipids, inositol-1-phosphate, 1,4-bisphosphate and-1,4,5-trisphosphate, was shown. Corneal epithelium displayed the most active inositol lipid metabolism and endothelium the least when the cornea layers were separately incubated (stroma had intermediate values). In corneal epithelium incubated with [3H]myo-inositol, tritiated glycerophosphorylinositol and water-soluble inositol phosphates were formed. 10 mM LiCl promotes an increase in the inositol phosphates consistent with an inhibitory effect on inositol phosphatase. Cell-free preparations of epithelium incubated with [γ-32P]ATP detected the presence of diacylglycerol kinase, PI kinase and PIP kinase. Endogenous PI was rapidly phosphorylated to PIP within 1 min of incubation, whereas PIP was phosphorylated more slowly. In conclusion, the components of the inositol lipid cycle are present in the cornea, particularly in the epithelium. It is proposed that the control of these pathways may be involved in the transduction of cell signals through the plasma membrane, intracellular calcium ionization and epithelial cell proliferation and differentiation, particularly in wound healing.

ISSN:0271-3683    

DOI:10.3109/02713688509020036

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

Bovine eyes were dissected and separate pools of lens, lens capsule, cornea and vitreous were extracted in guanidine, subjected to ultrafiltration, and examined for their effects on collagenolytic activity. Although lens extract was not inhibitory, the cornea and vitreous both contained Inhibitors of collagenase. More inhibition was present in the filtrate of the vitreous than in the retentate, whereas the total amount of inhibition in the cornea was distributed almost equally between the two fractions. The inhibition observed was dose dependent. The partially purified inhibitors from cornea and vitreous blocked the activity of human skin and tadpole back skin collagenases, but they failed to inhibit the bacterial(Clostridium histolyticum)collagenase. The inhibitor was stable to heating to 60 for 30 minutes and to trypsinization.

ISSN:0271-3683    

DOI:10.3109/02713688509020037

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

A fraction of bovine vitreous extract is a potent inhibitor of mitogen induced lymphocyte proliferationin vitro.Proliferation of lymphocytes induced in culture by lipopolysaccharide was more sensitive to inhibition by this fraction than were cultures of lymphocytes stimulated by Concanavalin A. We were unable to demonstrate such activity in similarly prepared fractions of cornea and lens.

ISSN:0271-3683    

DOI:10.3109/02713688509020038

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor