ORGANIZATION AND COMPOSITION OF THE AMPHIBIAN YOLK PLATELET. I. INVESTIGATIONS ON THE ORGANIZATION OF THE PLATELET

¹ Department of Biology, New York University, New York 53. N. Y.

1. Yolk platelets of Rana pipiens ovarian eggs were studied by micromanipulation, lysis, histological and electron microscopic techniques. Investigations were carried out on washed, isolated platelets; unwashed, extruded platelets; and platelets in ova.

2. The presence of a surface coat was demonstrated for isolated, washed platelets by micromanipulation and lysis. However, the evidence suggested that this coat might be a preparation artifact. Histological studies also showed a surface coat for platelets in ovo, but evidence indicated that this coat too was an artifact.

3. "Ghost" material (the insoluble residue of platelet suspensions after lysis) was found to be largely made up of follicular and other ovarian membrane fragments.

4. Yolk platelets fixed in ovo were faintly Feulgen-positive.

5. Electron microscopy of osmium-fixed, washed yolk platelets showed a periodic arrangement of yolk components (72 Å periodicity of 36 Å-wide lamellae or bands of closely spaced units). An electron-dense surface was noted on some platelets, but this "coat" showed the same periodic structure as the rest of the platelet.

6. Electron microscopy of YC-fragments (platelet-like material prepared from soluble yolk by a simple precipitation process) showed a close packing of yolk components similar to the packing found for yolk platelets.