Stephen J. Girsch

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Lens fibers are coupled by communicating junctions which contain a 28-kDalton protein (MIP26) believed to be the main component of the cell-to-cell channel. To study the permeability properties and regulation of these channels, anin vitro system has been developed in which MIP26 isolated from calf lens is incorporated into liposomes and the resulting(More)
The major intrinsic protein (MIP26) of bovine lens membranes, purified by HPLC, was incorporated into liposomes and planar bilayers. Permeability of MIP26 channels was studied in liposomes by a spectrophotometric osmotic-swelling assay, and channel electrical properties were monitored in planar bilayers following liposome fusion. Particle formation in(More)
A study of the membranes of human lens fiber cells revealed a very high protein to lipid ratio, which tended to increase with aging and in brunescent cataract. Phospholipids were more abundant than cholesterol, cholesterol esters, and other neutral lipids. With aging and cataract formation, a marked decrease in membranes phospholipid content occurred.(More)
Lens fiber junctions contain cell-to-cell channels believed to be composed of a 28.2 kD protein (MIP26). Previous evidence indicates that calmodulin (CaM) is involved in the regulation of channel permeability by changing the conformation of the C terminal chain of MIP26. A study of the amino acid sequence of MIP26 has revealed an amphiphilic segment of the(More)
Lens gap junction channels are studied in a reconstituted system obtained by incorporating into liposomes, with or without calmodulin, the lens junction protein (MIP26) and its trypsin-cleaved product (MIP21) that lacks the C-terminal arm. Channel permeability is studied with an osmotic swelling assay. MIP26 and MIP21 liposomes swell in sucrose or(More)
Much of the capacity of tissues to respond to signals as well integrated systems is due to the existence of direct cell-to-cell communication pathways. This type of communication, usually referred to as cell coupling, is based on the presence of cell-to-cell channels permeable to ions, metabolites, and regulatory compounds. The cell-to-cell channels are(More)
Lens fiber cells are coupled by communicating junctions that comprise over 50% of their appositional surfaces. The main intrinsic protein (MIP26) of lens fibers is a 28.2 kDa protein that forms large gap junction-like channels in reconstituted systems. Previously, we have shown that Ca(++)-activated calmodulin (CaM) regulates the permeability of(More)
The lens junction protein (MIP26), and its trypsin cleavage product (MIP21), isolated from calf fiber cells, are incorporated into liposomes and the permeability and gating of the resulting channels are studied spectrophotometrically by an osmotic swelling assay. Liposomes incorporated with either protein and loaded with Dextran T-10 swell when placed in(More)
Lens fibers are coupled by communicating junctions, clusters of cell-to-cell channels composed of a 28-kD intrinsic membrane protein (MIP26). Evidence suggests that these and other cell-to-cell channels may close as a result of protein conformational change induced by activated calmodulin. To test the validity of this hypothesis, we have measured the(More)
A calcium activated photoprotein, termed mnemiopsin, which emits bioluminescence upon the addition of calcium ion, has been isolated from the Ctenophore, Mnemiopsis leidyi, and purified by hollow fiber techniques. The system is similar to aequorin, from the jellyfish Aequorea, except that mnemiopsin can be light-inactivated. Separation of mnemiopsin from(More)