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Biomedical subjects

H Maisel

Publications and source records attributed to H Maisel.

At least 73 records · Page 4Linked to original sources
PubMed1983

Lens actin: purification and localization.

Actin was purified from the chick lens using DEAE-52 column chromatography followed by hydroxylapatite chromatography. The antibody produced against the purified actin cross-reacted specifically with lens actin from other species in addition to smooth and skeletal muscle actin and labelled the stress bundles of cultured fibroblasts. Actin was localized, using immunological methods, primarily to the plasma membrane of the epithelial and fiber cells of the chick and human lens. Actin filaments were also identified by HMM S-1 labeling in bovine cortical fiber cells. Using this procedure, the actin filaments were found throughout the fiber cell but were mainly concentrated near the plasma membrane and in cell processes. They formed a population distinct from the beaded filaments. The initial DEAE-52 column chromatography was also useful in the initial purification of lens fiber cell intermediate filament protein and two species of beta-crystallins.

Actins↗
PubMed1982

Calmodulin binds to chick lens gap junction protein in a calcium-independent manner.

A biochemically active conjugate of calmodulin and tetramethylrhodamine isothiocyanate (CaM-RITC) was synthesized. When incubated with sections of chick lens, this conjugate bound to the surface membranes of lens fiber cells in the presence of absence of calcium. Incubation of lens sections with antibodies to gap junction protein of lens completely blocked the binding of the conjugate to cell membranes, whereas serum from nonimmunized animals or antibodies to others lens proteins reduced the binding only slightly. By means of a gel overlay procedure, 125I-labeled calmodulin was found to bind to the gap junction protein of lens, also in a calcium-independent manner. These results support the concept that calmodulin may interact with and regulate gap junctions in living cells.

Animals↗
PubMed1982

Actin filaments of lens fiber cells.

Filaments of typical actin morphology can be isolated from acetone powder of lens fiber cells. These filaments, which react with heavy meromyosin, are also present in native form in the water-insoluble fraction of the lens. These findings indicate that native actin filaments exist in the lens fiber cells distinct from the beaded filaments.

Actins↗
PubMed1982

Synthesis of cytoskeletal and membrane polypeptides by the organ cultured chicken lens.

The synthesis of cytoskeletal and membrane polypeptides of the chick lens epithelium, superficial cortical fiber cells and deep cortical fiber cells was studied in the organ-cultured lens. The synthetic activity of the cytoskeletal polypeptides was restricted to the epithelium and superficial cortical fiber cells while membrane polypeptides were synthesized by deep cortical fiber cells as well. None of the polypeptides was observed to be synthesized by the lens nuclear fiber cells.

Animals↗
PubMed1981

Electron microscopy supports a fibrous substructure for lens intermediate filaments.

The substructure of intermediate filaments from bovine lens cortical fiber cells was investigated by electron microscopy. Native filaments and synthetic ones regenerated from the total cytoskeletal extract and from the three purified subunits were examined. The morphologies from these various sources were essentially identical, with the exception that filaments reconstituted from one of the purified polypeptides were much shorter, very contorted and showed strings of aggregated protein. The solid cylindrical, unbranching filaments consisted of a helical arrangement of at least two, 5 nm diameter strands. The evidence indicated that each strand was composed of two, 2 nm diameter protofilaments which were also helically constructed (right-handed) with a periodicity of 11.6 nm. Intermediate filament diameter varied widely (8-14.8 nm, average 11.3 nm) and in a direct, linear manner relative to the apparent progression (helical) angle of the strands across the filaments face. These conclusions were obtained from observations on negatively stained intact filaments and reconstituted 4.4 nm fibrils and on positively stained transverse sections of fixed and embedded filaments.

Animals↗
PubMed1980

Subunit characterization of lens intermediate filaments.

The intermediate filaments from the bovine ocular lens can be fractionated into three 54000 dalton polypeptides (alpha, beta and gamma) which are present in equimolar quantities and differ from one another with respect to isoelectric point, two-dimensional peptide map pattern and total amino acid composition. The polypeptides, for which the name lentin is proposed, were purified from the 8 M urea extract of the water-insoluble residue of the cortical fiber cells by ion-exchange chromatography on DE- and CM-cellulose. The regeneration of native-appearance filaments from each purified fraction, or combinations thereof, definitively established the three polypeptides as the subunit species. Additionally, small diameter 'protofilaments' were regenerated when one or two fractions were utilized, but not when all three fractions were combined. This, together with the fact that the stoichiometric yield of the three species was invariably equimolar, suggests that alpha, beta, and gamma may be distinct entities not related by artifactual interconversion.

Amino Acids↗
PubMed1980

Polypeptides of the lens fibre cell intracellular matrix.

The cytoskeletal proteins of the vertebrate lens fibre cell comprise polypeptides raging in mol.wt from 43,000 to 250,000 daltons. The main intermediate filament polypeptide of the pickerel, Northern frog, chick, bovine, and human lens has a mol.wt of 54,000 daltons. Peptide analysis revealed that the chick 54,000 dalton protein was more similar to the bovine protein than to the pickerel protein.

Animals↗
PubMed1980

The surface morphology of embryonic and adult chick lens-fiber cells.

The surface morphology of lens fibers in embryonic and adult chicken lenses has been studied by scanning electron microscopy. As the elongating epithelial cells enter into a state of terminal differentiation they elaborate a number of cellular processes interconnecting neighboring fibers. The interlocking devices take the shapes of balls on a short stalk, tonguelike flaps, and fingerlike processes that fit into complementarily shaped sockets, imprints, and fingerprints, respectively, of adjoining fibers. Gap junctions comprising more than 50% of the fiber-cell membrane may serve as ultrastructural interlocking devices. The interlocking devices and gap junctions are probably necessary to maintain fiber order--a critical requirement for lens transparency. With increase maturation, the uniform morphology of the fibers and their interlocking devices is lost. The highly repetitive ordered alignment of young uniformly shaped fiber cells acts to minimize large-particle scatter. The results of this study show a progressive loss of uniform shape and order in chicken fibers of advanced maturity. This phenomenon of lens development may be the basis for the increase in light scattering seen in aged lenses of other species such as man.

Animals↗
PubMed1979

Age changes in the skeleton of the human lens.

The cytoskeleton of the human lens (newborn, 24 year-old and 80 year-old) was studied by morphological methods. Actin and intermediate (10 nm) filaments were identified in the epithelial cells of all the lenses. In the newborn lens intermediate filaments and chains of protein were found in cortical and nuclear fiber cells. Many intermediate filaments and protein chains in the elongated form were observed in the superficial cortical fiber cells of the 24 year-old lens. However, in the deep cortical cells the number of intermediate filaments decreased and the protein chains became more coiled and aggregated. In the nuclear region the protein chains were markedly aggregated and intermediate filaments were absent. The 80 year-old fiber cells contained only protein aggregates in the fiber cells. While the size of the chain backbone corresponds to actin, the conclusive demonstration that it is actin remains to be shown.

Actins↗