Biomedical subjects

M A Babizhayev

Publications and source records attributed to M A Babizhayev.

At least 19 recordsLinked to original sources

PubMed2005

Immunostimulating activities of the novel peptidomimetic L-glutamyl-histamine.

An original representative of histamine-containing peptidomimetics L-glutamyl-histamine (L-Glu-Hist) was synthesized and characterized as a cytokine mimic leading to cellular responses of improved specificity. The energy-minimized 3-D conformations of L-Glu-Hist derived from its chemical structure resulted in stabilization for Fe(2+) chelating complexes. L-Glu-Hist accelerated the decrease of ferrous iron in the ferrous sulphate solution in a concentration-dependent mode and showed the ferroxidase-like activity at concentrations less than 3 mm in the phenanthroline assay, whereas in the concentration range 3-20 mm L-Glu-Hist restricted the availability of Fe(2+) to phenanthroline due to binding of ferrous ions in chelating complexes. L-Glu-Hist showed a stimulatory effect on phosphatidylcholine liposomal peroxidation (LPO) catalysed by the superoxide anion radical (O(2) (*))-generating system (Fe(2+)+ ascorbate) at low (less or about 1 mm) L-Glu-Hist concentrations and both revealed the inhibitory effect on LPO in this system of high ( approximately 10 mm) L-Glu-Hist concentration. L-Glu-Hist released O(2) (*) in concentrations which stimulated [(3)H]-thymidine incorporation into DNA and proliferation of mouse spleen lymphocytes and mononuclear cells from human blood. The structural peptide-like analogues of L-Glu-Hist such as L-Glu-Trp, carcinine (beta-alanylhistamine), but not L-Pro-Glu-Trp were active in stimulating thymidine incorporation and in inducing proliferation of mononuclear cells compared to mitogen concanavalin A at doses 2.5-25.0 microg/ml. Our data provide evidence that L-Glu-Hist may act as a very fast and sensitive trigger for lymphocyte proliferation and immunoregulation.

Animals↗

PubMed2003

Hydration properties of the molecular chaperone alpha-crystallin in the bovine lens.

Topographic studies of crystalline fractions from different morphological layers of the young adult bovine lens were conducted. Crystallin profiles were obtained for each lens layer, using thin-layer isoelectric focusing in polyacrylamide gel (IEF). Water soluble (WS) crystallins from the lens equator revealed a separation into HM (high molecular weight) alpha(L)-, beta(H)-, beta(L)-, beta(S)-, and gamma-crystallins. The nature of the water insoluble (WI) protein fraction in the separated lens layers reflected the aggregated state of alpha(L)-, beta(L)-, beta(S)-, and gamma-crystallins in different regions of the lens, concealed in the central cavity of the alpha-crystallin chaperone model. The IEF data demonstrate a possible chaperone-like function for alpha-crystallin in the nucleus and inner cortex of the lens, but not in the outer cortex. The water binding properties of bovine lens alpha-crystallin, calf skin collagen, and bovine serum albumin (BSA) were investigated with various techniques. The water adsorptive capacity was obtained in high vacuum desorption experiments volumetrically, and also gravimetrically in controlled atmosphere experiments. The NMR spin-echo technique was used to study the hydration of protein samples and to determine the spin-spin relaxation times (T(2)) from the protons of water adsorbed on the proteins. Isolated bovine lenses were sectioned into 11-12 morphological layers (from anterior cortex through nucleus to posterior cortex). The water content in relation to dry weight of proteins was measured in individual morphological lens layers. During water vapor uptake at relative humidity P/P(0) = 0.75, alpha-crystallin did not adsorb water suggesting that hydrophobic regions of the protein are exposed to the aqueous solvent. At relative humidity P/P(0) = 1.0, the adsorption of water by alpha-crystallin was 17% with a single component decay character of spin echo (T(2) = 3 msec). Addition of water to alpha-crystallin to about 50% of its weight/weight in the protein sample showed T(2) = 8 msec with only one single component decay of the spin-echo signal. The single component decay character of the spin echo indicates water tightly bound by alpha-crystallin. Under a relative humidity P/P(0) = 1.0, collagen and BSA adsorbed, correspondingly, 19.3 and 28% of water and showed a two-component decay curve with T(2) about 5 and 40 msec. The findings demonstrate the presence of two water fractions in collagen and BSA which are separated in space. The IEF data suggest a tight binding of water with alpha-crystallin with similar distribution patterns in the lens layers. To conclude, it was found that alpha-crystallin can immobilize water to a greater extent than other proteins such as collagen and BSA. These results shed new light on structural properties of alpha-crystallin and its superhydration properties and have important implications for understanding the mechanism of the chaperone-like action of this protein in the lens and non-ocular tissues.

Aging↗

PubMed2001

N-Acetylcarnosine, a natural histidine-containing dipeptide, as a potent ophthalmic drug in treatment of human cataracts.

A study was designed to document and quantify the changes in lens clarity over 6 and 24 months in 2 groups of 49 volunteers (76 eyes) with an average age of 65.3 +/- 7.0 enrolled at the time of diagnosis of senile cataracts of minimal to advanced opacification. The patients received N-acetylcarnosine, 1% sol (NAC) (26 patients, 41 eyes = Group II), placebo composition (13 patients, 21 eyes) topically (two drops, twice daily) to the conjunctival sac, or were untreated (10 patients, 14 eyes); the placebo and untreated groups were combined into the control (reference) Group I. Patients were evaluated upon entry, at 2-month (Trial 1) and 6-month (Trial 2)-intervals for best corrected visual acuity (b/c VA), by ophthalmoscopy and the original techniques of glare test (for Trial 1), stereocinematographic slit-image and retro-illumination photography with subsequent scanning of the lens. The computerized interactive digital analysis of obtained images displayed the light scattering/absorbing centers of the lens into 2-D and 3-D scales. The intra-reader reproducibility of measuring techniques for cataractous changes was good, with the overall average of correlation coefficients for the image analytical data 0.830 and the glare test readings 0.998. Compared with the baseline examination, over 6 months 41.5% of the eyes treated with NAC presented a significant improvement of the gross transmissivity degree of lenses computed from the images, 90.0% of the eyes showed a gradual improvement in b/c VA to 7-100% and 88.9% of the eyes ranged a 27-100% improvement in glare sensitivity. Topographic studies demonstrated less density and corresponding areas of opacification in posterior subcapsular and cortical morphological regions of the lens consistent with VA up to 0.3. The total study period over 24 months revealed that the beneficial effect of NAC is sustainable. No cases resulted in a worsening of VA and image analytical readings of lenses in the NAC-treated group of patients. In most of the patients drug tolerance was good. Group I of patients demonstrated the variability in the densitometric readings of the lens cloudings, negative advance in glare sensitivity over 6 months and gradual deterioration of VA and gross transmissivity of lenses over 24 months compared with the baseline and 6-month follow-up examinations. Statistical analysis revealed the significant differences over 6 and 24 months in cumulative positive changes of overall characteristics of cataracts in the NAC-treated Group II from the control Group I. The N-acetylated form of natural dipeptide L-carnosine appears to be suitable and physiologically acceptable for nonsurgical treatment for senile cataracts.

Age Factors↗

PubMed2000

The natural histidine-containing dipeptide Nalpha-acetylcarnosine as an antioxidant for ophthalmic use.

The naturally occurring compound Nalpha-acetylcarnosine is proposed as a prodrug of L-carnosine that is resistant to enzymatic hydrolysis by carnosinase. Eyes of rabbits were treated with 1% Nalpha-acetylcarnosine, L-carnosine, or placebo and extracts of the aqueous humor from the anterior eye chamber were analyzed for imidazole content by reverse-phase analytical high performance liquid chromatography (HPLC) and thin-layer (TLC) and ion-exchange chromatographic techniques. Topical administration of pure L-carnosine to the rabbit eye did not lead to accumulation of this compound in the aqueous humor over 30 min in concentration exceeding that in the placebo-treated matched eye. Nalpha-Acetylcarnosine showed dose-dependent hydrolysis in its passage from the cornea to the aqueous humor, releasing L-carnosine after l5-30 min of ocular administration of the prodrug in a series of therapeutic modalities: instillation < or = subconjunctival injection < or = ultrasound-induced phoresis. Different treatment techniques showed excellent toleration of 1%Nalpha-acetylcarnosine by the eye. Once in the aqueous humor, L-carnosine might act as an antioxidant and enter the lens tissue when present at effective concentrations (5-l5 mM). The advantage of the ophthalmic prodrug Nalpha-acetylcarnosine and its bioactivated principle L-carnosine as universal antioxidants relates to their ability to give efficient protection against oxidative stress both in the lipid phase of biological membranes and in aqueous environments. Nalpha-Acetylcarnosine is proposed for treatment of ocular disorders that have a component of oxidative stress in their genesis (cataracts, glaucoma, retinal degeneration, corneal disorders, ocular inflammation, complications of diabetes mellitus, and systemic diseases).

Administration, Topical↗

PubMed1999

Cellular signalling and free-radical modulating activities of the novel peptidomimetic L-glutamyl-histamine.

A novel histamine-containing peptidomimetic, L-glutamyl-histamine (L-Glu-Hist), has been synthesized and characterized as a possible cytokine mimic which might lead to cellular responses of improved specificity. The energy-minimized 3-D conformations of L-Glu-Hist derived from its chemical structure stabilize Fe2+-chelating complexes. L-Glu-Hist concentration-dependently accelerates a decrease in ferrous iron in ferrous sulfate solution and shows ferroxidase-like activity at concentrations less than 3 mM in the phenanthroline assay, whereas in the concentration range 3-20 mM it restricts the availability of Fe2+ to phenanthroline by chelation of iron ions. At low concentrations (less than or about 1 mM), L-Glu-Hist stimulates peroxidation of phosphatidylcholine in liposomes catalyzed by a superoxide anion radical (O2)-generating system (Fe2+ + ascorbate) and, at high concentrations (*10 mM), it suppresses lipid peroxidation (LPO) in liposomes. The stimulation of LPO by L-Glu-Hist is related to its ability at low concentrations (*0.05 mM) to release O2 free radicals as determined by the superoxide dismutase-inhibitable reduction of cytochrome c. The release of O2 by L-Glu-Hist might result from its ferroxidase-like activity, while its inhibition of LPO is due to chelation of Fe2+, prevention of the formation of free radicals, and degradation of lipid hydroperoxides at 5-20 mM L-Glu-Hist concentrations. L-Glu-Hist releases O2 at concentrations which stimulate [3H]thymidine incorporation into DNA and proliferation of mouse spleen lymphocytes and also of mononuclear cells from human blood. The induction of lymphocyte proliferation by L-Glu-Hist is dose-dependent in the 0.01-0.05 mM concentration range, although the maximal stimulation of LPO in the O2-dependent system is observed at higher L-Glu-Hist concentrations (*1 mM). Thus, low concentrations of oxygen free radicals released by L-Glu-Hist may provide a very fast, specific, and sensitive trigger for lymphocyte proliferation and immunoregulation.

Animals↗

PubMed1998

Photoprotector and antioxidant properties of histamine-containing peptidomimetics in the photooxidation of glycyltryptophan.

The natural imidazole-containing dipeptide carnosine in vitro exhibits several antioxidant properties; however, in vivo its activity is limited due to enzymatic hydrolysis. A family of original histamine-containing peptidomimetics, i.e., carcinine (beta-alanylhistamine), N-acetylcarcinine (N-acetyl-beta-alanylhistamine), and L-prolylhistamine, which exhibit significant resistance to dipeptidases and retain antioxidant activity, was synthesized. The effect of these compounds on chemiluminescence of glycyltryptophan (Gly-Trp) associated with its photooxidation at the wavelengths over 280 nm and oxidation photosensitized by riboflavin and Rose Bengal was studied. It is shown that all three peptidomimetics efficiently react with singlet oxygen with the rate constant 9.107 M-1.sec-1, exhibit free-radical scavenging activity in the course of riboflavin-sensitized Gly-Trp oxidation (C50% = 8-15 mM), and quench the photoexcited triplet states of the molecules. Unlike these peptidomimetics, carnosine does not react with superoxide generated during the photooxidation of Gly-Trp in the used test system. The data demonstrate photoprotector and antioxidant properties of histamine-containing peptidomimetics in the photooxidation of biological molecules.

Antioxidants↗

PubMed1996

N alpha-acetylcarnosine is a prodrug of L-carnosine in ophthalmic application as antioxidant.

The naturally occurring compound N alpha-acetylcarnosine (NAC) is proposed as the prodrug of L-carnosine (C) resistant to enzymatic hydrolysis by human serum carnosinase. Rabbit eyes were treated with 1% NAC, C or placebo and extracts of the aqueous humor from the anterior eye chamber were analyzed for imidazole content by reverse phase analytical high performance liquid chromatography (HPLC), thin-layer (TLC) and ion-exchange chromatographic techniques. The topical administration of pure C to the rabbit eye did not lead to accumulation of this compound in the aqueous humor over 30 min in concentration exceeding that in the placebo-treated matched eye. NAC showed dose-dependent hydrolysis in its passage from the cornea to the aqueous humor, releasing C after 15. 30 min of ocular administration of prodrug in a series of therapeutical modalities: instillation < or = subconjunctival injection < or = ultrasound induced phoresis. Different treatment techniques showed excellent toleration of 1% NAC by the eye. Once in the aqueous humor, C might act as an antioxidant and enter the lens tissue when present at effective concentrations (5-15 mmol/l). The advantage of the ophthalmic prodrug NAC and its bioactivated principle C as universal antioxidants relates to their ability to give efficient protection against oxidative stress both in the lipid phase of biological membranes and in an aqueous environment. NAC is proposed to treat ocular disorders which have the component of oxidative stress in their genesis (cataracts, glaucoma, retinal degeneration, corneal disorders, ocular inflammation, complications of diabetes mellitus, systemic diseases).

Animals↗

PubMed1996

Failure to withstand oxidative stress induced by phospholipid hydroperoxides as a possible cause of the lens opacities in systemic diseases and ageing.

Lipid peroxidation (LPO) is a causative factor of cataract. The increased concentrations of primary molecular LPO products (diene conjugates, lipid hydroperoxides) and end fluorescent LPO products, were detected in the lipid moieties of the aqueous humor samples obtained from patients with senile and complicated cataracts as compared to normal donors. The degrees of lens clouding were assessed quantitatively by measuring the optical density indices and areas of equidensities using digital image analysis. Human cataractous lenses showed decreased activity of glutathione peroxidase (GPX, catalyzing reduction of organic hydroperoxides including hydroperoxides of lipids). The apparent Km for tert-butylhydroperoxide was 0.434 mM for human normal and cataractous lens GPX. When lenses were exposed for 1 h at 37 degrees C to linoleic acid hydroperoxide (LOOH, 0.5 mM) or egg phosphatidyl-choline hydroperoxide (PLOOH, 1 micro mol per 112 micro mol of phospholipid) in liposomes suspended in the incubation medium, normal, immature and mature human cataractous lenses showed a significant loss in the residual content of liberated LOOH to 62%, 38% or 17%, correspondingly, but little or no reduction was observed with PLOOH in liposomal membranes. Human, rabbit or mice transparent or immature cataractous lenses induced significantly more absorbance changes in conjugated diene, iodometric and TBA-reactive substance measurements when incubated with liposomal membranes which were decreased in the presence of free radical scavengers and antioxidant enzymes (EDTA, SOD, L-carnosine, chelated iron, catalase). Injection into the vitreous body of the rabbit eye of a suspension of liposomes prepared from phospholipids containing LPO products induced the development of posterior subcapsular cataract. Saturated liposomes did not cause clouding of the lens. This modelling of cataract was accompanied by accumulation of fluorescing LPO products in the vitreous body, aqueous humor and the lens and also by a fall in the concentration of GSH in the lens. The peroxidative damage to the lens cell membranes and biomolecules induced in the lack of reductive detoxification of phospholipid hydroperoxides is proposed as the triggering mechanism of cataractogenesis.

Aged↗

PubMed1996

Isoelectric focusing of crystallins in microsections of calf and adult bovine lens. Identification of water-insoluble crystallins complexing under nondenaturing conditions: demonstration of chaperone activity of alpha-crystallin.

Topographic studies of crystallin fractions from the young adult bovine lens revealed that lenses do not have a homogeneous distribution of crystallins. There are, however, gradual differences between the cortices and the nucleus. The isolated lenses were separated mechanically into lens equator and inner cylinder. The latter was then sectioned in a special sectioning machine into 11-12 morphological layers (from anterior cortex through nucleus to posterior cortex). Matters of the lens sections were separated into water-soluble (WS) and water-insoluble (WI) crystallins. The WI fractions were solubilized with 100% formamide, or dissolved into 7 M urea. Crystallin profiles were obtained for each lens layer, using thin-layer isoelectric focusing in polyacrylamide gel. WS crystallins from the lens equator revealed a separation into HM-, alpha L-, beta H-, beta L-, beta S- and gamma-crystallins. The WI fractions of the layers dissolved in urea gave a separation into the individual HM- (3 components), alpha L- (4 components), beta- (6 component groups), beta S- (2 components) and gamma- (11 components) crystallins in the different morphological layers. The results confirm that a significant age-related increase in several beta- and gamma-crystallins incorporated into alpha-crystallins exists in the patterns of WI fractions of the different layers from lenses of 2.2 and 5.9 years. The WI crystallins solubilized in formamide showed only the presence of HM weight and alpha-crystallin moieties, due to the action of chaperone activity of alpha-crystallin. The nature of the WI protein fraction in the separated lens layers reflected to the aggregated state of: alpha L-, beta L-, beta S- and gamma-crystallins in the different regions of the lens, concealed in the central cavity of the alpha-crystallin chaperone model.

Aging↗

PubMed1994

L-carnosine (beta-alanyl-L-histidine) and carcinine (beta-alanylhistamine) act as natural antioxidants with hydroxyl-radical-scavenging and lipid-peroxidase activities.

Carnosine (beta-alanyl-L-histidine) and carcinine (beta-alanylhistamine) are natural imidazole-containing compounds found in the non-protein fraction of mammalian tissues. Carcinine was synthesized by an original procedure and characterized. Both carnosine and carcinine (10-25 mM) are capable of inhibiting the catalysis of linoleic acid and phosphatidylcholine liposomal peroxidation (LPO) by the O2(-.)-dependent iron-ascorbate and lipid-peroxyl-radical-generating linoleic acid 13-monohydroperoxide (LOOH)-activated haemoglobin systems, as measured by thiobarbituric-acid-reactive substance. Carcinine and carnosine are good scavengers of OH. radicals, as detected by iron-dependent radical damage to the sugar deoxyribose. This suggests that carnosine and carcinine are able to scavenge free radicals or donate hydrogen ions. The iodometric, conjugated diene and t.l.c. assessments of lipid hydroperoxides (13-monohydroperoxide linoleic acid and phosphatidylcholine hydroperoxide) showed their efficient reduction and deactivation by carnosine and carcinine (10-25 mM) in the liberated and bound-to-artificial-bilayer states. This suggests that the peroxidase activity exceeded that susceptible to direct reduction with glutathione peroxidase. Imidazole, solutions of beta-alanine, or their mixtures with peptide moieties did not show antioxidant potential. Free L-histidine and especially histamine stimulated iron (II) salt-dependent LPO. Due to the combination of weak metal chelating (abolished by EDTA), OH. and lipid peroxyl radicals scavenging, reducing activities to liberated fatty acid and phospholipid hydroperoxides, carnosine and carcinine appear to be physiological antioxidants able to efficiently protect the lipid phase of biological membranes and aqueous environments.

Antioxidants↗

PubMed1994

Lipid peroxide and reactive oxygen species generating systems of the crystalline lens.

Lipid peroxidation (LPO) could be one of the mechanisms of cataractogenesis, initiated by enhanced production of oxygen free radicals in the eye fluids and tissues and impaired enzymatic and non-enzymatic defences of the lens. The increased concentrations of primary molecular LPO products (diene conjugates, lipid hydroperoxides) and end fluorescent LPO products were detected in the lipid moiety of the aqueous humor samples obtained from patients with cataract as compared to normal donors. Isolated human transparent and cataractous lenses and normal mouse and rabbit lenses were incubated with liposomes in organ culture in the presence and absence of LPO inhibitors, free radical scavengers and enzymes (catalase, superoxide dismutase (SOD)) in order to examine the potential of the lenses to induce LPO in the surrounding medium. LPO assayed spectrophotometrically were diene and triene conjugates, and malonaldehydes (MDA) were determined as thiobarbituric acid-reactive material. A chemiluminescence detection catalysed by peroxidase was used to measure H2O2 and O2-. was assayed spectrophotometrically using cytochrome C reduction. The level of lipid peroxides in liposomes was significantly (2.5-4.5-fold) higher after 3 h of incubation of the transparent lenses (or the lenses at the initial stage of cataract) than after the proper time of incubation of human mature cataractous lenses and virtually no oxidation of liposomes was detected in the absence of the lens. LPO in this system was decreased in the presence of free radical scavengers and enzymes that degrade H2O2 (EDTA, SOD, L-carnosine, chelated iron and catalase). The most effective agent was EDTA which chelates the free metal cations required to generate O2-. radicals that initiate the free radical process culminating in LPO. Lenses generated more H2O2 into the medium in the presence of exogenous ascorbate. Release of the oxidants, (O2-., H2O2, OH. and lipid hydroperoxides) by the intact lenses in the absence of respiratory inhibitors indicates that these metabolites are normal physiological products inversely related to the lens life-span potential (maturity of cataract) generated, probably, through the metal-ion catalysed redox-coupled pro-oxidant activation of the lens reductants (ascorbic acid, glutathione).

Adult↗

PubMed1994

Tinting effect of ultraviolet radiation on intraocular lenses of polymethyl methacrylate.

Intraocular lenses (IOL) made of polymethyl methacrylate (PMMA) lack an important yellowish pigment useful as a filter in the visual process and in the protection of the retina from short wavelength light. It was found that the PMMA used for IOL manufacturing can be tinted by dry exposure to mercury near-UV emitting lamp (emission maximum, 365 nm, light bandwidth +/- 140 nm; irradiance of 50-100 W/sq m as measured at the PMMA surface; time of exposure 70-100 h, room temperature). The UV irradiated samples were stored in the atmosphere of N2 under the heating-protected and clean conditions. The IOL sample holder allowed to remove IOL loops and their fixation areas from the zone of the passing light. The absorptive properties of IOLs treated with UV light were similar to those of young human lenses. Raman vibration and fluorescence spectral analyses of IOLs have shown that the yellow colour and its intensity in the irradiated samples depends on the presence of conjugated C = C and C = O groups (pi-pi conjugation) in the chemical composition of PMMA. When the PMMA samples were exposed for 70 h to a high level of UV radiation (50-100 W/sq m) no damage was seen with scanning electron microscopy at both side surfaces of the IOLs. The PMMA water exhaustive extracts made by 70 h of UV radiation exposure did not show any cytological damage when injected into the cell cultures of fibroblasts. The threshold for optical breakdown in PMMA was detected by 100 h of UV radiation at the level of exposure equivalent to at least 20,000 times levels for expected ambient UV exposure to PMMA within the eye. A rigorous quality index defined as the ratio of the line C = C/C = O stretching mode intensities was introduced for the UV-absorbing PMMA photostability. The findings suggest an applicability of the photochemical tinting and further research to test the efficacy and safety of UV-absorbing chromophore induction in the PMMA IOLs.

Absorption↗

PubMed1993

Immunohistochemical monitoring of the effect of a synthetic fibronectin-like peptide (Arg-Gly-Asp) on the age-related changes in the isolated human corneoscleral tissue of glaucomatous eyes.

Fibronectin, an adhesion glycoprotein has been detected and localized in samples of the trabecular meshwork from eight normotensive and 30 glaucomatous human eyes of various ages by means of the indirect immunoperoxidase staining technique. Fibronectin concentration in the trabecular meshwork tissue was evaluated by morphometric analysis. Deposits of the adhesion glycoprotein fibronectin were shown to be spread in the ocular drainage outflow system from patients along with progressive primary open-angle glaucoma (POAG). The fibronectin level quantitatively evaluated in serial cross-sections of trabecular meshwork, appeared to be increased during ageing and more rapidly in the event of POAG development. The active amino acid sequence in fibronectin is an arginine-glycine-aspartic acid tripeptide (Arg-Gly-Asp) and it was shown that the synthetic Arg-Gly-Asp peptide specifically inhibited the adhesive function of fibronectin in trabecular meshwork samples when incubated for 30 min at a concentration of 1-2 mg/ml. The peptide concentration necessary for a 50% decrease of the maximal fibronectin level in the trabecular meshwork specimen derived from patients with moderately advanced POAG stage, was about 1 mg/ml. Immunohistochemical staining exhibited a fainter fibronectin staining in trabecular tissues including the external trabecular layers and subendothelial region of Schlemm's canal, in samples incubated with the synthetic peptide compared with the same tissue explants before peptide treatment. It may be concluded that the adhesion control system is likely to play an important role in development and maintenance of tissue architecture and specialization of the normal human trabecular meshwork.

Aged↗

PubMed1992

Peroxide-metabolizing systems of the crystalline lens.

The ability of transparent and cataractous human, rabbit and mice lenses to metabolize hydrogen peroxide in the surrounding medium was evaluated. Using a chemiluminescence method in a system of luminol-horseradish peroxidase and a photometric technique, the temperature-dependent kinetics of H2O2 decomposition by lenses were measured. The ability of opaque human lenses to catalyze the decomposition of 10(-4) M H2O2 was significantly decreased. However, this was reversed by the addition of GSH to the incubation medium. Incubation of the mice lenses with the initial concentration H2O2 10(-4) M led to partial depletion of GSH in normal and cataractous lenses. Human cataractous lenses showed decreased activities of glutathione reductase, glutathione peroxidase (catalyzing reduction of organic hydroperoxides including hydroperoxides of lipids), superoxide dismutase, but no signs of depletion in activities of catalase or glutathione peroxidase (utilizing H2O2). The findings indicated an impairment in peroxide metabolism of the mature cataractous lenses compared to normal lenses to be resulted from a deficiency of GSH. An oxidative stress induced by accumulation of lipid peroxidation products in the lens membranes during cataract progression could be considered as a primary cause of GSH deficiency and disturbance of the redox balance in the lens.

Aged↗

PubMed1992

ESR spin label and ultrastructural monitoring of protein-lipid interactions in the lens fiber-cell plasma membranes in relation to human ageing and cataractogenesis.

The Electron Spin Resonance (ESR) technique and the protein spin labels 2,2,4,4,9-pentamethyl-1,2,3,4-tetrahydro-gamma-carboline-3-oxyl and 4-(N-maleimido)-2,2,6,6-tetramethylpiperidine-1-oxyl were used in this study to probe the fluidity and binding ability to protein functional groups in human lens membranes. The image and the stage of cataract as well as the ultrastructural characteristics of the lens fiber cell membranes were evaluated in parallel studies. ESR measurements in membrane structures of the transparent lenses of different ages have shown that the sorbtion parameter of the carboline label on the surface of protein-lipid components was usually weakly expressed but increased with aging and the extent of immobilization of the bound label was not significant. At different stages of the lens opacification the carboline analogue spin label increasingly bound to the lens membranous structures. A spin label signal can be enhanced by addition to the samples of the paramagnetic probe K3Fe(CN)6. The maleimide spin label bound to the protein SH-groups in the cataractous lens membranes at a slow rate, however in transparent lenses a gradual increase of the rapidly binding phase of this label could be detected. The results show an appearance of at least two types of the reactive SH-groups in membranes of human transparent lenses. The electron microscopic studies suggested that the age-related and cataractogenic changes in the lens matter are accompanied by deterioration of the lenticular fiber plasma membranes and formation of the coalescing globules with a diameter of 220-500 nm. At the stage of cataract with advanced opacities, which is biochemically characterized by the increase in number of the carboline label binding sites with the surface proteins and annular lipids of membranes, a mass of amorphous aggregates filled with the electron-grey debris is formed contributing to significant scatter of light. It appears, therefore, that the suggested ESR spin label technique can be effectively used to monitor the aggregation process of protein membrane components which takes place during human cataractogenesis.

Adult↗

PubMed1992

Image analysis of the lens opacities induced in developing chick embryo by glucocorticoid.

Glucocorticoid-induced cataracts in chick embryos were monitored by an image analysis system. Opacities in the lens visually showed a complex pattern with significant changes in the cortical and nuclear regions. An electronic image analyser produced an image in which contrast represented different zones of lens opacification in the frontal plane and documented objective lens findings such as the precise topography of the opacities, density and opacity measurements, geometric measurements of boundary surfaces and of regional areas. Parameters of lens clouding were evaluated quantitatively by measuring the optical density index and the area of the zones of clouding outlined with equi-densities. The light intensity standard graded different morphological areas of the lens into up to 256 grey levels. The data were entered and stored quantitatively into a computer. The lens images thus picked up by the TV camera and digitally stored in a frame buffer of the measuring system could be reliably transformed into a 2-D or 3-D picture of lens clouding. The approach demonstrated by the current study provides a sensitive and meaningful measure of cataractous changes for lens laboratory research.

Animals↗

PubMed1991

Changes in fibronectin staining in the human lens during ageing and cataractogenesis.

The content and localization of fibronectin, an extracellular glycoprotein, in the serial sections of lenses of normal human donors and cataractous patients of different ages were determined by the indirect immunoperoxidase staining technique. This was followed by the evaluation with quantitative morphometric analysis. It was shown that fibronectin was present in the area of cell contacts as single deposits of faint orange-brown stained material in the lens samples of young donors. The fibronectin level was raised in lens sections from aged donors. Its accumulation was detected mostly within the spaces of the lens fiber cells. At different stages of cataractogenesis a dramatic decrease of the fibronectin content was detected in the lens sections obtained from patients of different ages. A new linear spectrophotometric technique was developed for evaluation of the lens transparency, to correlate the lens opacity with corresponding histological data obtained from the immunostaining technique. Morphological studies performed further suggested that the lens fiber cell plasma membrane structures were deteriorated. This was observed as changes of fibronectin staining in the lens sections at different periods of human ageing and cataract development. It is concluded that a decrease of fibronectin staining in the human lens is an indication for the structural damage of the lens fiber cell plasma membranes during ageing and cataractogenesis.

Adult↗

PubMed1991

Modulative effects of cell adhesion peptide (Arg-Gly-Asp-Ser) on the aggregation of stimulated platelets from ophthalmic patients.

Adhesion proteins are cofactors in the aggregation of human platelets, and can mediate the ADP-induced response of these cells. It was shown that the synthetic cell adhesion peptide, Arg-Gly-Asp-Ser inhibits the aggregation of platelets from normal donors and ophthalmic patients with diabetic retinopathy, glaucoma and retinal vein occlusion. This effect increases in the relative order of activity retinal vein occlusion greater than or equal to glaucoma greater than or equal to diabetic retinopathy greater than control. Deaggregation due to the peptide appeared to be diminished in the order control (normal) greater than diabetic retinopathy greater than glaucoma greater than retinal vein occlusion after its addition at the maximum of aggregation curve. It is concluded that there are differences in the ability of Arg-Gly-Asp-Ser peptide to block the fibronectin adhesion receptor on ADP stimulated platelets from different clinical groups.

Adenosine Diphosphate↗