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The ultrastructural features of oocyte differentiation were studied in the marine triclad Cercyra hastata. Oocytes at several stages of maturation, each surrounded by follicle cell projections, are present within each of the two ovaries. A pre-vitellogenic and a vitellogenic stage have been detected in the oogenesis of C. hastata. The pre-vitellogenic stage is mainly characterized by an increase in the nuclear and nucleolar volume and activity, and the appearance and development of cortical granule precursors which are elaborated by the Golgi complex. In early phases of the vitellogenic stage, intense delamination and blebbing of the nuclear envelope occurs which probably contributes to an increase in number of cytoplasmic membranes and to transfer of nuclear material to the cytoplasm. The rough endoplasmic reticulum is extensively developed an often assumes a 'whorl' array. Several areas of yolk precursor formation appear in the whorls. Numerous 2-5 micrometers protein yolk globules are subsequently formed which appear surrounded by a double membrane (cisternae of the smooth endoplasmic reticulum) and become randomly distributed throughout the cytoplasm of mature oocytes. The peripheral ooplasm is occupied by a monolayer of electron-dense cortical granules. Finally, the evolutionary significance of the autosynthetic mechanism of yolk production is discussed.

Three cases of acute myeloid leukemia with megakaryocyte predominance are reported. In the first case megakaryocytosis was particularly evident in bone marrow, liver and spleen. In the second case high content of megakaryocytes was observed in the bone marrow and spleen, during the preleukemic phase only. Third case exhibited a strong predominance of megakaryocytes exclusively within the bone marrow. The characteristics of such observations and their nosologic position within myeloproliferative disorders group are discussed, with special reference to modern views concerning myeloid leukemia.

The uptake of exogenous 32Pi into the membrane proteins of intact erythrocytes was measured in 8 patients with Duchenne muscular dystrophy. No abnormalities were noted after autoradiographic analysis. This contrasts with earlier results obtained when isolated membranes were phosphorylated with gamma-[32P]ATP, and suggests a possible reinterpretation of those experiments.

Cerebral electrical field mapping in a patient with a clinically pure cerebellar syndrome showed the field maximum at the Pz electrode position. Flash visual evoked potentials also showed, in addition to the occipital response, a late positive peak at 344 ms at Pz. The findings suggest that the Pz electrode may at times record far field activity from the cerebellum.

A case of naevoid basal cell carcinoma syndrome with clusters of Langerhans' and lymphoid cells in the inflammatory peritumoral infiltrate, is reported. Electron microscopy shows intercellular contacts between eight to ten lymphoid cells and a single Langerhans' cell. These contacts occur over limited areas of the cell membranes by means of zones of high electron density on the outer edge of the cytoplasm. The functional significance of this finding is discussed, bearing in mind that recent observations have established certain analogies between Langerhans' and interdigitating reticulum cells. The latter might, within the thymus-dependent region of the lymph nodes, contribute to the formation of a micro-environment favourable to certain immunological activities of T-lymphocyte populations.

The two most common sonographic abnormalities in the kidneys of 23 tuberous sclerosis (TS) patients ranging in age from newborn to 30 years are angiomyolipomas (12/23) (AML) and renal cysts (10/23). These usually both occur in the same patient with only 9 cases (39%) having sonographically normal kidneys. Of the 14 affected patients, 2 had cysts without AML and 4 others had AML without cysts. The sonographic appearance of an AML varied from a large 6 cm solid mass with little increased echogenicity (1/12) to subtle small (4 mm) extremely echogenic regions in the periphery of the kidney (11/12). The sonographic appearance of the cysts were anechoic lesions varying in size from 2 mm to 2 cm with thin uniform posterior walls and posterior enhancement. Renal lesions are found more frequently with increasing age. Sonography is the preferred screening procedure for the renal lesions of T.S.