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Biomedical subjects

L V Johnson

Publications and source records attributed to L V Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1986

Wheat germ agglutinin induces compaction- and cavitation-like events in two-cell mouse embryos.

The lectin wheat germ agglutinin (WGA) has been observed to induce morphological events similar to compaction and cavitation in 2-cell mouse embryos. In vitro exposure of embryos to WGA results in increased apposition between blastomeres and the subsequent formation of a large intercellular cavity. As is the case for cavitation normally associated with blastocyst formation, WGA-induced cavitation can be inhibited by ouabain, suggesting a requirement for ATPase activity. However, WGA-induced effects are not inhibited by cytoskeletal disruptive agents or inhibitors of a variety of synthetic and metabolic functions. WGA may induce the observed effects by triggering the premature onset of developmental events normally involved in the processes of compaction and cavitation or, perhaps, by inducing morphologically similar changes as a result of the crosslinking of cell surface lectin-binding molecules and regional inhibition of ATPase function.

Actin Cytoskeleton↗
PubMed1986

Interphotoreceptor matrix domains ensheath vertebrate cone photoreceptor cells.

The retinal interphotoreceptor matrix (IPM) occupies the space between the neural retina and the retinal pigmented epithelium (RPE), two neuroectoderm-derived epithelia. While the IPM appears to be a major route by which photoreceptor cells receive vital metabolic factors, relatively little is known concerning its structure and function. The studies reported here describe the presence of specialized domains of the IPM that ensheath cone, but not rod, inner and outer segments in pig, monkey, and human retinae. These cone extracellular matrix sheaths are chemically and structurally distinct from the remainder of the IPM as revealed by their specific binding of the lectin peanut agglutinin (PNA) and their structural stability during physical dissociation of the retina. Biochemical studies suggest that the PNA-binding components of the cone matrix sheaths are trypsin-sensitive glycoproteins. These structures may play a role in establishing a specialized microenvironment for cone photoreceptors, maintaining proper orientation of cone outer segments, and/or facilitating cone-RPE interactions.

Animals↗
PubMed1985

An oviductal fluid glycoprotein associated with ovulated mouse ova and early embryos.

This study documents a molecular change in the murine ovum related to its exposure to oviductal fluid. Wheat germ agglutinin (WGA) identifies a 215-kDa glycoprotein band (GP215) that is associated with ovulated oocytes and early embryos obtained from the oviduct, but is absent from preovulatory oocytes. GP215 is present in ovarian bursal fluid, oviductal fluid, oviductal epithelial cell extracts, and medium conditioned by oviductal tissue in vitro. Preovulatory oocytes acquire GP215 after in vitro incubation in ovarian bursal fluid. Thus, it appears likely that GP215 is secreted by the oviductal epithelium and becomes intimately associated with the ovum following ovulation.

Animals↗
PubMed1984

Application of acrylamide as an embedding medium in studies of lectin and antibody binding in the vertebrate retina.

The use of acrylamide as an embedding medium for vertebrate retinal tissue and its applicability to lectin and antibody-based cytochemical studies is described. The acrylamide technique has numerous advantages over those using fresh-frozen or paraffin embedded material. The morphological integrity of retinal tissue prepared in acrylamide is equivalent to that obtainable with paraffin and superior to that of fresh-frozen material. In addition, this technique alleviates problems often encountered with the thermal and chemical treatments required in the paraffin method. The acrylamide technique allows the localization of lectin and antibody-binding sites essentially unaltered by the fixation and embedding protocol, as in frozen sections, while maintaining tissue morphology similar to that of paraffin-embedded tissue. It is hoped that this approach will be useful to other workers in vision research employing lectin, antibody or other cytochemical approaches to the study of cellular structure and function.

Acrylamide↗
PubMed1984

Specific binding of peanut lectin to a class of retinal photoreceptor cells. A species comparison.

Although lectins have been used to study surface oligosaccharides of photoreceptor cells in intact retinas and dissociated retinal cells, the specificity of lectin binding to cones versus rods in a variety of species has not been examined closely. The authors previously found that application of fluorescein isothiocyanate (FITC)-conjugated peanut agglutinin (PNA), a lectin with high affinity for galactose-galactosamine disaccharide residues, to cryostat sections of unfixed mouse retina results in staining that is confined to synaptic regions and a subpopulation of photoreceptor cells. To further investigate the possibility that PNA binding is specific for cone photoreceptors, the authors extended their studies to include the duplex retinas of fish, rabbit, monkey, and human in addition to the cone-dominant retina of the chick. These studies show that PNA binding is specific for cone inner and outer segments and also is likely to be associated with the large synaptic pedicles of cone photoreceptor cells. In addition, the authors compared PNA binding with that of Ricinus communis agglutinin I (RCA), another lectin that preferentially binds terminal D-galactose moieties. While RCA does bind to cones in the species examined, it also binds to a lesser extent to rod photoreceptor inner segments. The pattern of binding of RCA in other regions of the retina differs markedly from that of PNA. Significantly, RCA serves as a specific marker for retinal vasculature in the human, monkey, and mouse. These results suggest that certain PNA-binding macromolecules may be important in defining the molecular and cellular specificity of cone photoreceptor cells and that PNA may provide a means for the isolation of cones and cone-specific molecules. RCA may prove to be of value in monitoring vascular changes associated with normal development and pathologic conditions.

Animals↗
PubMed1983

Selective lectin binding of the developing mouse retina.

A battery of eight lectins with different carbohydrate specificities was used to study changes in glycoconjugate expression during cell differentiation in the mouse retina. The lectins tested included concanavalin A (Con A), wheat germ agglutinin (WGA), soybean agglutinin (SBA), peanut agglutinin (PNA), Ulex europaeus agglutinin (UEA), Ricinus communis agglutinin I (RCA), Dolichos biflorus agglutinin (DBA), and Limulus polyphemus agglutinin (LPA). Unfixed frozen sections of adult and early postnatal mouse retina were treated with fluorescein isothiocyanate-conjugated lectins and examined by fluorescence microscopy. The results showed selective lectin binding in both cellular and synaptic retinal layers of the adult mouse and throughout postnatal development. In general, an increase in intensity of fluorescent lectin staining during retinal development was observed for Con A, WGA, DBA, LPA, RCA, and PNA. This suggests an increase in the expression or accessibility of carbohydrate moieties during development. SBA and UEA showed little to no binding to adult or neonatal retina. Retinal vasculature was intensely stained by RCA, both during development and in the adult. All lectins binding to adult or neonatal retinal layers showed some degree of reactivity with the inner segment region of photoreceptor cells. However, only Con A, PNA and WGA bound to photoreceptor outer segments, suggesting significant differences in the glycosylated components of inner and outer segment membranes. PNA bound specifically to a subpopulation of photoreceptor cells and to discrete regions within the outer synaptic layer. The pattern of PNA binding suggests that this lectin binds preferentially to cone photoreceptor inner and outer segments and cone synaptic pedicles rather than to rod photoreceptor cells. This marked specificity of PNA binding suggests that it may provide a basis for the physical separation of cone and rod photoreceptor cells.

Age Factors↗
PubMed1982

Decreased uptake and retention of rhodamine 123 by mitochondria in feline sarcoma virus-transformed mink cells.

A reduce uptake and retention of the mitochondria-specific membrane potential probe rhodamine 123 by feline sarcoma virus (FeSV)-transformed mink fibroblasts (64F3) has been detected. The decreased accumulation of rhodamine 123 by 64F3 mitochondria is not due to abnormal plasma membrane dye permeability, since after microinjection of the dye these cells are still unable to retain the dye at levels comparable to the untransformed parental cells, CCL 64. Nigericin, an ionophore that mediates an electrically neutral exchange of protons for potassium ions resulting the elimination of the pH gradient across the mitochondrial membrane and a compensatory increase in mitochondrial membrane potential with continued respiration, increases both the dye uptake and the retention time in transformed 64F3 cells. These results suggest that mitochondria in FeSV-transformed mink cells may have an abnormally low mitochondrial membrane potential accompanied by a relatively high pH gradient. Since anioic metabolites such as pyruvate and glutamate are accumulated by mitochondria in proportion to the delta pH across the mitochondrial membrane, the abnormal mitochondria described here may contribute to the abnormal metabolic state of FeSV-transformed cells.

Animals↗
PubMed1981

Monitoring of relative mitochondrial membrane potential in living cells by fluorescence microscopy.

Permeant cationic fluorescent probes are shown to be selectively accumulated by the mitochondria of living cells. Mitochondria-specific interaction of such molecules is apparently dependent on the high trans-membrane potential (inside negative) maintained by functional mitochondria. Dissipation of the mitochondrial trans-membrane and potential by ionophores or inhibitors of electron transport eliminates the selective mitochondrial association of these compounds. The application of such potential-dependent probes in conjunction with fluorescence microscopy allows the monitoring of mitochondrial membrane potential in individual living cells. Marked elevations in mitochondria-associated probe fluorescence have been observed in cells engaged in active movement. This approach to the analysis of mitochondrial membrane potential should be of value in future investigations of the control of energy metabolism and energy requirements of specific biological functions at the cellular level.

Animals↗
PubMed1980

Localization of mitochondria in living cells with rhodamine 123.

The laser dye rhodamine 123 is shown to be a specific probe for the localization of mitochondria in living cells. By virtue of its selectivity for mitochondria and its fluorescent properties, the detectability of mitochondria stained with rhodamine 123 is significantly improved over that provided by conventional light microscopic techniques. With the use of rhodamine 123, it is possible to detect alterations in mitochondrial distribution following transformation by Rous sarcoma virus and changes in the shape and organization of mitochondria induced by colchicine treatment.

Animals↗
PubMed1977

Alkaline phosphatase activity in the preimplantation mouse embryo.

Alkaline phosphatase (AP) activity has been assayed in frozen sections of preimplantation mouse embryos by an azo-dye cytochemical method. The results indicate that during preimplantation mouse development AP activity is first expressed between the 8- and 16-cell stages and develops in all cells by the late morula stage. During blastocyst formation AP activity is lost or greatly reduced in trophoblast cells while activity is maintained in the inner cell mass.

Alkaline Phosphatase↗