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Biomedical subjects

J Wakely

Publications and source records attributed to J Wakely.

34 records · Page 2Linked to original sources
PubMed1979

The effect of cytochalasin B on chick mesoderm cells as studied by scanning electron microscopy.

The effects of cytochalasin B (CCB) on chick mesoderm cells in vivo was examined by scanning electron microscopy (SEM). The embryos were mounted for New Culture and the mesoderm exposed by dissecting off the endoderm. Cytochalasin B was suspended in saline and the embryos flooded with the suspension. Control embryos were treated with saline alone. The embryos were reincubated for varying times at 37 degrees C. In the treated embryos the mesoderm cells were rounded and separated from each other. Many had long branched processes and rough surfaces. These changes became more pronounced as treatment time was increased. They were also reversible on reincubating treated embryos in the absence of cytochalasin B. The morphological changes produced by CCB are thought to be due to an effect on the cytoskeleton, either a direct disruptive effect or detachment of skeletal microfilaments from the cell membrane. There may also be a direct removal of cell surface materials leading to the observed surface roughening of treated cells.

Animals↗
PubMed1979

The chick embryo late primitive streak and head process studied by scanning electron microscopy.

Changes in cell shape during the formation of the head process and regression of Hensen's node have been examined by scanning electron microscopy in a series of chick embryos from stage -5 to stage -8. The endoderm was removed from embryos mounted for New culture so that the mesoderm could be viewed from the ventral surface. As the primitive streak shortens its cells flatten and lose the flap-like processes characteristic of earlier stages. The notochord differentiates and its cells become transversely orientated, then re-align along the embryonic axis between stage 6 and stage -8. At the same time a split or cleft appears between notochord and head mesoderm, and extracellular fibrils are formed which are the first sign of the formation of a notochordal sheath.

Animals↗
PubMed1978

Endoderm regeneration in the chick embryo studied by SEM.

Regeneration of the area pellucida endoderm of the chick embryo was studied by scanning electron microscopy (SEM). A new endoderm was formed by in situ changes in the shape and relationships of mesoderm cells. Initially the cells flattened and lost their processes except along cell boundaries. Later even these processes were lost and an epithelium was formed. The area of regenerated endoderm coincided with the area of mesoderm at the time of endoderm removal, confirming the mesodermal origin of the new layer. Remnants of the original endoderm did not contribute to the regenerated layer. Contact inhibition was observed at the boundary between original and regenerated endoderms.

Animals↗
PubMed1977

Scanning electron microscopy of the development of the mesoderm layer in chick embryos.

The distribution of mesoderm, the structure of mesoderm cells and relationship between mesoderm and ectoderm were examined by SEM in embryos at stages 3 to 5. The mesoderm was displayed by removal of the endoderm and by fracturing the embryos through mesoderm containing regions. Within the mesoderm layer four zones could be distinguished by their cell shape and arrangement--the primitive streak, a multilayered compact area around the margins of the area pellucida, multilayered and loosely arranged cells near the primitive streak and a flattened monolayer of cells around the advancing lateral and anterior edges of the mesoderm sheet. Secretion of basement membrane by the ectoderm was seen to precede the arrival of mesoderm cells. This suggests that ectoderm alone can synthesize basement membrane without mesodermal contribution.

Animals↗
PubMed1977

Scanning electron microscope study of the extracellular matrix between presumptive lens and presumptive retina of the chick embryo.

The three-dimensional architecture of the intercellular matrix contained in the interspace between the presumptive lens and optic vesicle of the chick embryo was examined by scanning electron microsocpy. The fibrous structure of the basement membranes lining the space was demonstrated. The space was shown to be filled with a dense fibrous meshwork. The reaction of basement membranes and interspace contents to enzymic digestion is described. The functional significance of the arrangement of fibres in the interspace is discussed.

Animals↗
PubMed1977

Scanning electron microscopy (SEM) of the chick embryo primitive streak.

The structure of the cells forming the primitive streak was examined by SEM in a series of embryos at Hamburger and Hamilton's stages 2--5. Specimens were prepared by stripping the endoderm from fresh embryos in New Culture and by fracturing whole fixed embryos along and at right angles to the primitive streak. At all stages of examination the SEM appearance of cells within the privitive streak was quite different from that of ectodermal, endodermal or mesodermal cells away from the streak. Streak cells were closely packed, lay with their long axes directed from ectoderm to endoderm and possessed many flat leaf-like processes. By contrast the ectoderm formed a columnar epithelium, the endoderm a flat epithelium and the mesoderm was a layer of loosely arrangedcells with long. thin processes. Within the streak SEM did not show any differences between cells that could identify them specifically as future endoderm or mesoderm cells. It was concluded that during gastrulation all the cells migrating through the primitive streak have the same appearance regardless of their eventual destination in the embryo. This structure may be attributable to the type of movement made by cells during invagination.

Animals↗
PubMed1976

Cytochemical localization of transport adenosine triphosphatase in the ferret placenta.

The distribution of transport adenosine triphosphatase in the ferret placenta was examined cytochemically by light and electron microscopy. The enzyme was detected in the syncytiotrophoblast but was absent from maternal tissues. It appeared to be associated with cytoplasmic processses on syncytiotrophoblast surfaces directly related to foetal or maternal capillaries. The functional significance of transport adenosine triphosphatase is discussed with reference to the transport of solutes between the maternal and foetal circulation across the trophoblast layer.

Adenosine Triphosphatases↗