Granular Accumulations Research Articles

An electron microscope study of nuclear-cytoplasmic exchange in oocytes of Ciona intestinalis

Electron microscope observations of glutaraldehyde-osmium tetroxide fixed oocytes of the tunicate Ciona intestinalis indicate that nuclear-cytoplasmic exchanges are prominent in young oocytes. Dense granular accumulations are noted at various regions on both sides of the nuclear envelope, and under favorable conditions they can be demonstrated to be continuous through the nuclear pores. The basophilic staining reaction of this product and the structural similarity to nucleolar components suggest that the exchange is from the nucleus to the ooplasm. The product transferred (which is Feulgen negative) appears to accumulate in the ooplasm adjacent to the nuclear envelope. The morphological variations observed suggest a subsequent transformation of this material into particulate ribosomes. Mitochondria often show a close association with the extruded ooplasmic masses.

Liquid immiscibility as one factor in chromitite seam formation in the Bushveld igneous complex

Chromite seams from the lower Critical Zone, Farm Ruighoek, Bushveld complex contain chromite grains with centrally located silicate inclusions. The existence of chromite-rich immiscible liquid is postulated on the basis of these silicate inclusions. Chromitite textures indicate that most chromite crystallized directly from the magma and settled to the floor of crystal accumulation accompanied by chromite-rich immiscible droplets that had crystalline margins. . . . The major role of the chromite-rich immiscible liquid may have been to enrich the granular accumulations of chromite by gravity accumulation and crystallizations in place.

Some observations on the anterior pituitary of the domestic fowl with the aid of the electron microscope.

AbstractLipid accumulations in the gonadotrophs of the pituitaries of aging and castrate fowl have been demonstrated. Secretory granules and mitochondria play no part in their formation. Some lipids, perhaps all, occupy the cavities of the ER. The ER is a highly variable organelle, appearing as spherical or irregularly shaped vesicles in gonadotrophs or as lamellae in acidophiles. The Golgi complex is typical of pituitary cells in general. There are no bodies in the enlarged cavities of the complex and convincing evidence for the origin of all secretory granules within the small vesicles of the complex is lacking. Many secretory granules appear to be without membranes and to lie free in the cytoplasmic matrix. Observations on the pituitaries of broody hens confirm earlier conclusions that the broody cells appear during the incubation period and that they are small cells with large nuclei and reduced cytoplasm. The study also confirms the accumulation of secretory granules in laying hens at one side of certain cells which are interpreted to be either LH or FSH producing basophiles. Thiouracil feeding brings about some unexpected granular accumulations in the ER vesicles of thyrotrophs of the fowl pituitary. The granules may fuse to form larger structures with concentric rings. Whether the effect is direct or indirect through the thyroid is uncertain, but thiouracil feeding and thyroidectomy produce similar effects upon the pituitary. The interpretation of these changes remains to be determined.

INTRANUCLEAR AND CYTOPLASMIC ANNULATE LAMELLAE IN TUNICATE OOCYTES

Electron microscope studies were made on various tunicate oocytes at different stages of growth and development. Both the inner and outer lamellae of the perforated nuclear envelope demonstrate considerable blebbing activity. The blebs of the inner lamella detach into the nucleoplasm where they undergo a special type of fusion process resulting in the formation of numerous, usually single, differentiated annulate lamellae of various lengths. The blebbing of the outer layer of the nuclear envelope contributes to the vesicular and granular endoplasmic reticulum characteristically present in the ooplasm and perhaps to the differentiation of cytoplasmic annulate lamellae as well. Cytoplasmic stacks of annulate lamellae frequently have ribosomes associated with them. In addition, granular accumulations are sometimes observed around or between the annuli. The morphological evidence suggests that, at least in many cases, the annuli in the annulate lamellae are patent.

OBSERVATIONS ON THE EFFECT OF MOLYBDENUM ON PLANTS WITH SPECIAL REFERENCE TO THE SOLANACEAE

Summary In view of the similarity between certain cytological changes induced by virus disease and treatment with molybdenum, pot‐and water‐culture experiments were carried out to determine further the effect of this element on plant growth. Sodium molybdate was used throughout. Toxic symptoms were produced with the larger dressings of molybdate, injury being shown at much lower concentrations in solanaceous species than in barley. The shoots of tomato and Solanum nodiflorum turned a golden yellow, and potato tubers a reddish yellow colour when the plants were grown with the larger quantities of molybdate. These colour changes were shown to be due to the presence of yellow globules of a tannin‐molybdenum compound which had formed within the tissues. Blue granular accumulations occurred in large numbers in molybdenum‐treated plants. Their distribution was confined to tissues that contained anthocyanin pigment, and their composition was apparently of an anthocyanin‐molybdenum nature.