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Biomedical subjects

J Overton

Publications and source records attributed to J Overton.

At least 55 records · Page 3Linked to original sources
PubMed1975

Hybrid desmosomes in aggregated chick and mouse cells.

Mouse embryo skin epidermis has been examined during maturation, and stages have been found when desmosomes are first scarce, then increasing in frequency and finally numerous. Cells of skin epithelium from these stages have been combined in reaggregates with cells of the 15-day chick corneal epithelium which also form desmosomes readily. When these two cell types are reaggregated in the presence of cytochalasin B which inhibits cell sorting, they form numerous junctions with each other. Desmosomes in mouse and chick appear similar morphologically except for certain cytoplasmic components. Mouse skin epidermis cells combined with cardiac muscle or intestinal epithelium formed imperfect or no specialized contacts. The possible role of junctions in cell sorting in reaggregates is discussed.

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PubMed1973

Experimental manipulation of desmosome formation.

In the corneal epithelium of the embryonic chick there is a 3- to 4-fold increase in desmosomes between the 15th and 16th days of incubation which has not been noted in earlier studies of this tissue. This finding has made it feasible to study the effects of the local cell environment on desmosome formation. Cells of 15-day corneas which were forming desmosomes rapidly, were dispersed and combined in culture with cells from 10-day corneas which were forming few desmosomes. Surfaces of the same 15-day cell which were confronted with either another 15-day cell or a 10-day cell were compared. Desmosomes formed preferentially on the surface adjacent to a like cell. When 15-day cells were confronted with pigment cells, desmosomes formed almost exclusively on the surface adjacent to a like cell. Evidence for such localized differences on the same cell surface emphasize the importance of the immediate cell environment in desmosome formation. The observation that single desmosome plaques form occasionally on lateral cell surfaces has been noted previously. This finding was confirmed.

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PubMed1969

A fibrillar intercellular material between reaggregating embryonic chick cells.

Lanthanum staining of embryonic chick cell reaggregates reveals an intercellular material composed of fibrils. Fibrillar arrays may be composed of parallel fibrils with a 35 A center-to-center spacing. Fibrils may also be disoriented, long, and tortuous. Newly dissociated cells show little lanthanum staining surface material, but appreciable amounts are present after 6 hr of reaggregation. Examination of intact tissue does not give the same clear evidence of a fibrillar matrix surrounding the cells, but treatment with a number of agents permits observation of intercellular fibrils, and in some cases there is evidence of orientation. Thus fibrillar material must be taken into account in considering mechanisms of cell aggregation.

Animals↗
PubMed1966

Microtubules and microfibrils in morphogenesis of the scale cells of Ephestia kühniella.

The development of scale cells in insects has been studied from the appearance of the first cytoplasmic projection which forms the scale rudiment. This rudiment contains numerous longitudinally oriented microtubules throughout. Immediately under its outer surface lie a series of adjacent but distinct bundles of longitudinally oriented circa 60-A fibrils with a circa 120-A center-to-center spacing. As the rudiment broadens, the microtubules become distributed near the surface. The rudiment finally becomes extremely broad and flattened. Fibril bundles are now widely separated and equally spaced. They still lie immediately below the cell surface. Then the cytoplasm protrudes midway between each fibril bundle to form longitudinal ridges and the major shape changes of the scale have been achieved. The final pattern can thus be related to the cytoplasmic organization of the rudiment. The main cytoplasmic elements which seem important in scale morphogenesis, on the basis of frequency, orientation and grouping, are 60-A fibrils and microtubules.

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