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Results for “alpha-Crystallins”

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At least 19 recordsLinked to original sources
PubMed1978

The distribution and relative immunogenicity of calf alpha-crystallin antigenic determinants on different subunits.

In the native alpha-crystallin molecule, 45.9% of all reactive antigenic determinants were found to be located on SH-containing subunits. Of these, the majority (35.3%) were reaggregation dependent, and 10.6% were reactive on monomeric subunits. By contrast, only 10.9% of all antigenic determinants were located on SH-free subunits, and the ratio of aggregation-dependent determinants (4.4%) to those of monomeric subunits (6.5%) was reversed compared to SH-containing subunits. Among all antigenic determinants reactive in native alpha-crystallin, 44.1% were dependent on the presence of both types of subunits. These data indicate that the antigenic determinants requiring subunit interaction were formed from SH-containing and SH-free subunits in a ratio of 1:1. Direct analysis showed that in the alpha-crystallin molecule, the ratio of these subunits is 2:1. The experiments indicate that some conformations of subunits in the native molecule persist in separated subunits. The relative immunogenicity of each type of antigenic determinant expressed as the ratio of the percentage of the determinant reactive in the native calf lens alpha-crystallin to the percentage of corresponding antibodies induced by native alpha-crystallin was found to be close to 1.

Animals↗
PubMed1977

The bicistronic nature of lens alpha-crystallin 14S mRNA.

The A2 and B2 polypeptide chains of calf lens alpha-crystallin are synthesized on a 14S, 1500-nucleotide mRNA and a 10S, 735-nucleotide mRNA, respectively. The 10S mRNA is theoretically compatible with the size of the B2 chain, but the 14S mRNA contains approximately twice the required number of nucleotides necessary for A2 chain synthesis. This fact raises the question of the function of the additional nucleotide sequence in the 14S mRNA. The following observations on 14S mRNA suggest that it may contain an additional cistron. (i) Under a number of denaturing conditions, 14S mRNA continues to retain its initial size characteristics. (ii) In addition to synthesis of the A2 chain, 14S mRNA directs the synthesis of another polypeptide with the same electrophoretic mobility as that of the B2 chain. (iii) Molecular hybridization of the 14S mRNA with the cDNA produced from the 10S mRNA suggests that 2 mol of the cDNA bind to 1 mol of the 14S mRNA. (iv) Examination of the nucleotide sequences of the 10S and 14S mRNAs by two-dimensional maps of RNase A and T1 digests indicates marked similarity. The overall data suggest that the additional cistronic component may carry coding information for an alpha-crystallin polypeptide or a closely related polypeptide species.

Animals↗
PubMed1978

Variations in the soluble alpha-crystallin proteins from human cataractous lenses.

Human cataractous lenses from subjects aged 20-91 years were extracted in tris/glycine buffer and fractionated on Sephadex G-75 column. Four fractions, F1, F2, F3 and F4 identified as alpha-, beta1-, beta2- and gamma-crystallin were obtained. Gel electrophoresis of alpha-crystallin in polyacrylamide containing 6M urea revealed changes in polypeptide composition, colouration; variation in band pattern and mean mobility. The relative mobilities of the protein bands were used to calculate coefficient of similarity within the same age group and among different age groups.

Adult↗
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↗
PubMed1978

Cell division, cell elongation and the co-ordination of crystallin gene expression during lens morphogenesis in the rat.

A quantitative analysis of cell division and cell elongation was carried out during lens morphogenesis in the rat. At 13 days of development elongating cells in the posterior part of the lens vesicle (presumptive fibre cells) have a lower mitotic activity than cells in the anterior vesicle. By 14 days these elongating cells do not divide. Thus at 14 days of development the lens can be separated into two compartments; a proliferation compartment in the anterior lens and an elongation compartment in the posterior lens. The three main groups of lens-specific proteins, alpha-, beta- and gamma-crystallins, were localized by immunofluorescence. alpha-crystallin is the first crystallin to be detected and is localized in some lens pit cells at 12 days of development. By 14 days all lens cells contain alpha-crystallin. beta- and gamma-crystallins are detected later at 12 1/2 days and are localized in some cells situated primarily in the posterior part of the lens vesicle. At later stages of development these crystallins are restricted to cells of the elongation compartment, i.e. presumptive fibre and fibre cells. Possible mechanisms that govern the temporal and spatial distribution of crystallins are discussed.

Animals↗
PubMed1979

DNA repair in lens cells during chick embryo development.

When chick lens epithelium is cultured in vitro, differentiation into lens fiber cells is accompanied by DNA degradation. This phenomenom of terminal differentiation was studied in the epithelium from embryos at the 6th and 11th days of development. DNA size and the ability of the cells to repair DNA damage induced by X-rays were analysed in alkaline sucrose gradients. In the 6-day epithelium a rapid degradation and complete lack of DNA repair were recorded. Similar observations have been made in previous studies on the 11-day sample, but here degradation is progressive and occurs after a lag of several days. In the younger epithelium, internal irradiation by [3H]thymidine also had a drastic effect resembling that caused by X-rays. In order to assess the process of differentiation in our experimental system the synthesis of delta- and alpha-crystallins was monitored. Stage-related modifications in the rates of synthesis were recorded. The results confirm that the DNA repair system is impaired during terminal differentiation. The differences observed between the two stages may reflect either a developmental modification in DNA repair mechanisms or a change in the relative proportions of differentiating cells. An hypothesis is proposed in support of the latter case.

Age Factors↗
PubMed1978

Reactivation of nuclei containing lens fiber cells to mitotic growth biochemical and immunochemical analysis.

Nuclei containing lens fiber cells can be reactivated to mitotic growth by transplantation into a suitable culture medium. Reactivated epithelium-like fiber cells are morphologically indistinguishable from cultivated epithelial cells. During reactivation the enzyme pattern of the differentiated fiber cells changes to a pattern closely related to that of cultivated epithelial cells. Moreover dedifferentiation was correlated with an appreciable loss of specific lens proteins (alpha-crystallin). Cytoplasmic shedding and attachment of fiber cells to the substratum are discussed with regard to their role in the reactivation process.

Cell Differentiation↗
PubMed1979

Actin in mammalian lens.

In this paper evidence is provided that one of the protein components of the water-soluble fraction of the calf lens binds specifically to deoxyribonuclease I (DNAse I). On the basis of this property, the polypeptide could be purified by applying DNAse I affinity chromatography. Concomitantly a protein of Mr55000 and a rather large amount of alpha-crystallin copurify with this polypeptide, which has a molecular weight of 42000. Highly purified 42000-Mr protein was also obtained by extraction of the water-insoluble fraction of the calf lens with 2-([tris(hydroxymethyl)methyl]amino) ethanesulfonic acid followed by gel filtration. Amino acid analyses, peptide mapping and electron microscopy show that the protein obtained from both lens fractions is identical to non-muscle actin. Furthermore the amino acid composition of the 55000-Mr protein is identical to hog stomach skeletin and very similar to calf brain desmin.

Actins↗
PubMed1977

Immunopathology of the lens. I. Humoral and cellular immune responses to heterologous lens antigens and their roles in ocular inflammation.

In experimental rabbits heterologous soluble lens proteins consisting of alpha-, beta-, and gamma-crystallins were found to be antigenic; they stimulated a marked antibody response compared to a rather weak T-cell response. The serum antibodies to alpha-crystallins appeared first, to be followed by antibodies to beta- and gamma-crystallins in that order. The rabbits did not respond to heterologous gamma-crystallins unless these were injected with Freund's adjuvant containing mycobacteria. Incomplete Freund's adjuvant (i.e., without mycobacteria) was found to be an inferior immunoaccelerator so far as lens antigens are concerned. The response to lenticular antigens in both magnitude and duration varied in different rabbits, which suggested to us the important role played by a central control mechanism involving the immune response (Ir) genes. Some of the antibodies in potent lens antisera cross-reacted with mitochondria, endoplasmic reticulum (i.e., microsomes), contractile organelles, and cell nuclei. This explains for the first time at least in part the reasons for the widely observed phenomenon of the reactivity of lens antisera with ocular and extraocular structures. Antibodies to soluble lens proteins as detected by immunofluorescence and immunoperoxidase techniques were shown to be of the IgG class. Systemic heterologous immunisation followed by discission of the lens does not lead to the typical changes of phakoallergic endophthalmitis in the rabbit.

Animals↗
PubMed1979

The plasma membrane of the rabbit lens cortical fiber. I. Isolation, characterization, and biosynthesis of two membrane intrinsic polypeptides.

Rabbit lens cortical fiber plasma membrane polypeptides were isolated and two membrane intrinsic proteins were characterized by SDS-PAGE. A polypeptide with a molecular weight of 26 kilodaltons is the major constituent of the plasma membrane. The molecular weight and antigenic properties of the other polypeptide studied are similar to polypeptides of cortical water-soluble alpha-crystalline. Biosynthesis of these two polypeptides was studied. After initially high rates, synthesis of both of these polypeptides decreased considerably and maintained a steady rate for the rest of the culture time.

Animals↗
PubMed1979

The anticomplementary activity of the rabbit lens.

We wished to determine if inhibitors of the complement system are present in the normal rabbit lens. Soluble less extract in various dilutions was incubated with normal human serum (as source of complement). The residual hemolytic activity was measured using sheep erythrocytes sensitized with antisheep rabbit hemolysin. The lens extract was found to contain two heat stable anticomplementary factors of different molecular weights capable of cleaving C2 and C4. Gel filtration showed that one of these factors was located in the alpha-crystalline region. It is suggested that the anticomplementary factors in the lens may be related to a natural mechanism for the modulation of complement mediated lens injury.

Adult↗
PubMed1979

[Immunochemical study of the water-soluble lens proteins in the embryo of Xenopus laevis with the mutation of periodic albinism].

The crystallins of ap mutants of Xenopus laevis have been studied in comparison with those of normal embryos and adults using the complex of immunochemical methods (immunoelectrophoresis, immunodiffusion, immunoadsorption, immunofluorescence, isoelectrofocusing with immunoidentification). The analysis was carried out with antisera to electrophoretic fractions of the mutant lens. 11 organ-specific antigens were found in the lens of both the normal and mutant animals. These proteins are heterogenous by electrophoretic mobility, isoelectrical point, antigenic and species specificity. Each class of crystallins contains antigens which are specific: a) for amphibians only, b) for lower vertebrates, c) for vertebrates in general. No qualitative differences were found between crystallins of the normal and mutant animals. Immunofluorescence analysis has shown that crystalins appear in the normal and mutant embryos practically at the same time. No significant differences in the appearance of specific immunofluorescence between the normal and mutant embryos were found (with various antisera). gamma-crystallins and, perhaps, a part of the primary lens fibers. Alpha-crystallins appear later. gamma-crystallins are first identified the synthesis of which manifests itself at the advanced developmental stages. The quantitative predominance of some beta--gamma-crystallins in the mutant lens detected by us (electrophoresis, isoelectrofocusing) is not related to their earlier synthesis in the embryogenesis.

Albinism↗