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Results for “Lens crystallins”

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At least 19 recordsLinked to original sources
PubMed1979

Electrical properties of structural components of the crystalline lens.

The electrical properties of the crystalline lens of the frog eye are measured with stochastic currents applied with a microelectrode near the center of the preparation and potential recorded just under the surface. The stochastic signals are decomposed by Fourier analysis into sinusoidal components, and the impedance is determined from the ratio of mean cross power to input power. The data are fit by an electrical model that includes two paths for current flow: one through the cytoplasm, gap junctions, and outer membrane; the other through inner membranes and the extracellular space between lens fibers. The electrical properties of the structures of the lens which appear as circuit components in the model are determined by the fit to the data. The resistivity of the extracellular space within the lens is comparable to the resistivity of Ringer. The outer membrane has a normal resistance of 5 kohm . cm(2) but large capacitance of 10 muF/cm(2), probably because it represents the properties of several layers of fibers. The inner membranes have properties reminiscent of artificial lipid bilayers: they have high membrane resistance, 2.2 megohm . cm(2), and low specific capacitance, 0.8 muF/cm(2). There is so much membrane within the lens, however, that the sum of the current flow across all the inner membranes is comparable to that across the outer surface.

Animals↗
PubMed1978

Ontogeny of lens crystallins in marine cephalopods.

The ontogeny of the lens crystallin antigens throughout development of three marine cephalopod embryos, Loligo vulgaris, Sepia officinalis and Octopus vulgaris has been investigated using the indirect immuno-cytochemical staining against respective homologous anti-total lens protein antiserum. The cellular mechanism of lens development appears to be the same in all species investigated and so does the ontogeny of the lens crystallins. The first positive immuno-fluorescence reaction appears simultaneously and in equal intensities over the lens and lentigenic area confirming the relationship between the two.

Animals↗
PubMedDate not supplied

Immunohistochemical study of crystallin synthesis during morphogenesis of the crystalline lens in mice.

Using indirect immunofluorescence, the sequence of the synthesis of various classes of crystallins during normal morphogenesis of the crystalline lens in mice was shown: The alpha- begin to be synthesized first, then the gamma-, and finally the beta-crystallins. Using mice with hereditary anophthalmia (genotype ey-1/ey-1 ey-2/ey-2) permitted it to be established that the synthesis of alpha-crystallins occurs even when there is no morphogenesis of the crystalline lens. In mice of this genotype, the lens placode, which is reduced as compared to the norm, is resorbed as a rule, and does not develop into the crystalline lens vesicle. Separate cells containing alpha-crystallins were found in cranial epithelium on serial cross sections of the eye area of 13-day-old mutant embryos. Consequently, in ey-1/ey-1 ey-2/ey-2 embryos, alpha-crystallin synthesis takes place even in cells of the resorbed lens placode after brief inducing influence of the optic vesicle. As opposed to alpha-crystallins, synthesis of gamma- and beta-crystallins is detected only when lens fibers have formed. This is characteristic for embryos of ey-1/ey-1 ey-2/ey-2 genotype, as well as for mouse embryos homozygous for the fi gene. Data of the present work indicate that the inducing influence of the optic vesicle is necessary for activation of the genes controlling alpha-crystallin synthesis, while the influence of the retinal rudiment is necessary for derepression of the genes for gamma- and beta-crystallin synthesis.

Animals↗
PubMedDate not supplied

Sugar metabolism in the crystalline lens.

Research on the sugar metabolism of the crystalline lens, past and preent, is reviewed. The chief energy source in the lens is the Embden-Meyerhof pathway; respiration and oxidative phosphorylation become more important as the lens ages. The function of the alpha-glycerophosphate cycle is not fully understood. The mechanisms involved in cataract formation, including those of hypoglycemic cataract and osmotic cataracts, are discussed. Sugar cataracts can be delayed or prevented with such aldose reductase inhibitors as flavonoids. By inhibiting aldose reductase, the formation and accumulation of sugar alcohols is stopped. This approach may be useful as a medical therapy for human diabetic senile cataracts.

Aldehyde Reductase↗
PubMed1979

Aerobic and anaerobic metabolism of the crystalline lens of a poikilotherm; the toad Bufo marinus.

1. The O2 consumption and lactic acid production of the lens of the toad Bufo marinus was measured under various conditions. The energy consumption was very low compared to other amphibian tissues and about 20% of that previously described in the rat lens. About 80% was derived from oxidative metabolism, which is the converse of that seen in mammals. 2. Cyanide abolished O2 consumption and increased lactate production 20-30 times ("Pasteur effect"). 3. Under aerobic conditions about 40% of the energy requirements of the lens are related to the presence of Na in the bathing-media but this was not seen in the presence of CN. 4. Oxidative metabolism was predominant in the outer cortical regions of the lens while glycolysis persisted even in the central nucleus. The energetic requirements of this region were, however, only about 10% of those in the intact lens. 5. Lactate readily leaves the lens and passes into its bathing fluids, and at high rates of glycolysis this occurs more readily across the posterior surface. 6. The results are discussed in relation to the unique physiological needs, structure and situation of the lens.

Aerobiosis↗
PubMed1978

The influence of calcium-free EGTA solution upon membrane permeability in the crystalline lens of the frog.

Potential difference, resistance, cation content, and 86Rb efflux were measured in frog lenses maintained in normal or calcium-free EGTA Ringer's solution. Exposure of the lens to calcium-free solution resulted in a rapid fall in potential and resistance, together with a twofold increase in 86Rb efflux rate. These rapid changes were not due to an alteration in cation distribution between the lens and its environment. However, the alteration in 86Rb efflux rate could be explained on the basis of the fall in potential. These findings suggested that removal of calcium from the bathing medium caused a rapid increase in sodium permeability alone. This suggestion was substantiated by the results of experiments where the response of the lens to low calcium solution was determined in a medium in which 90% of the sodium had been replaced by sucrose.

Animals↗
PubMedDate not supplied

[Na-K-ATPase activity in the normal aging crystalline lens and in senile cataract].

Activity of Na-K-ATPase decreases in normal bovine and human lens with age. In senile cataract this tendency continues to some extent. In most lenses, clear or opaque, the presence of an inhibitor to Na-K-ATPase can be demonstrated. Its activity which is not influenced by a dialysis, seems to vary greatly. So it is impossible for the moment being to draw conclusions on this special point, except perhaps a certain increase of the inhibition during aging.

Adenosine Triphosphatases↗
PubMed1977

[Cytochemical study of various enzymes of the rabbit crystalline lens epithelium].

The activity of a number of enzymes of glycolysis, tricarbonic acids, cycle, pentose phosphatase shunt and some important hydrolases, acid nucleases and adenosine triphosphate among them, was cytochemically determined in the rabbit lens epithelium. The data obtained clearly demonstrate the role the epithelium plays in energy producing processes of the lens, which are connected both with anaerobic and aerobic phases of glucose utilization and its direct oxydation, as well as with synthesis of some substances, with the transport of organic and inorganic molecules.

Acid Phosphatase↗