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W J Larsen

Publications and source records attributed to W J Larsen.

41 records · Page 3Linked to original sources
PubMed1977

Structural diversity of gap junctions. A review.

Gap junctions are plasma membrane specializations characterized as aggregates of intramembranous particles in two apposed membranes meeting particle-to-particle in the 2-4 nm intermembrane 'gap'. Recent thin-section and freeze-fracture evidence has revealed significant structural variations of gap junctional structure at various stages of development and from different organisms and tissues. It is suggested that a comparative analysis of these differences may provide clues to the specific biological functions(s) of these ubiquitous organelles.

Animals↗
PubMed1976

Cell remodeling in the fat body of an insect.

The fat body of the Lepidopteran, Calpodes ethlius, undergoes major functional changes during larval-adult metamorphosis. These changes occur in conjunction with extensive cell remodeling - a process whereby one population of cellular organelles is destroyed and replaced by another during development. Fat body organelles including mitochondria, microbodies, and RER are destroyed on a massive scale shortly before pupation (Locke and Collins, 1965; Locke and McMahon, 1971) a new populations of each are regenerated shortly after emergence of the adult. In addition, protein, lipid and RNA reserves formed shortly before pupation and multivesicular bodies formed shortly before emergence are secreted into the haemocoel during the first few days of adult life. Electron microscopic studies using tracer techniques, cytochemical and enzyme localization procedures, and sterological analyses have been undertaken to determine the time course and mechanism of organelle regeneration and the fate of reserves stored in the fat body.

Acid Phosphatase↗
PubMed1975

Opaque deposits on gap junction membranes after glutaraldehyde-calcium fixation.

When cloned hybrid cells (A/Bm-5) were grown to confluence and fixed in glutaraldehyde-calcium, electron-opaque deposits were observed on the cytoplasmic faces of plasma membrane. Deposits were most abundant at gap junctions. Deposits were often precisely paired, cell-to-cell, across the gap junctional membranes, and these paired deposits were frequently equivalent in size. This relationship was most often observed on long profiles of gap junctions, in contrast to the asymmetric distribution of larger deposits commonly found on short junctional profiles. Deposits were present with or without heavy metal staining but did not appear when calcium was omitted from the fixative. Fixation at room temperature yielded more and larger deposits than fixation at 0 degrees C. The significance of these observations is discussed with regard to the possible binding of calcium at fixed membrane sites or the precipitation of calcium by anions produced by enzymes located at the gap junction.

Calcium Chloride↗
PubMed1974

The membrane junctions in communicating and noncommunicating cells, their hybrids, and segregants.

Human Lesch-Nyhan cells, which are coupling and have gap junctions, were fused with mouse cl-lD cells, which are noncoupling and lack gap junctions. The resulting hybrid cells were coupling and had gap junctions while they contained the nearly complete complement of parent chromosomes. As the hybrid cells lost human chromosomes, clones appeared among the segregants, which had reverted to the noncoupling and junction-deficient trait of the mouse parent cell. The human cell appears to contribute a genetic factor to the hybrids that corrects the junctional deficiency of the mouse cell.

Animals↗