Chloral hydrate effects on oogenesis in Marsilea vestita Hook. et Grev

Chloral hydrate [3.5 × 10^?2 M] applied to archegonium of Marsilea vestila during oogenesis modifies the asymmetry of the gametic mitoses and the nuclear migrations. Multinucleate female gametes are obtained whose polarity is disturbed. At the ultrastructural level, the distribution of the organelles is changed profoundly. The ‘fertilization cone’ disappears, and there is increased vacuolation associated with myelin figures in the cytoplasm and the appearance of filament bundles. The nuclei also contain vacuoles and myelin figures.     

Ultrastructural changes in vitro of rat liver nucleoli in response to polyamines

Summary Structural alterations of the nucleoli of rat liver cells were noted when these nuclei were isolated with spermidine or spermine rather than magnesium. When 5–10 mM spermidine or spermine were used to isolate the nuclei, the nucleoli were a) larger, b) contained numerous and sometimes large lacunae, and c) were less aggregated and had prominent chromatin caps. These chromatin caps gave the nucleolus a ring-shaped appearance in the light microscope. These findings, coupled with physiological data that indicate that polyamines enhance nucleolar RNA polymerase activity (Russell et al., 1971), suggest that spermidine and spermine may be involved in the control of ribosomal RNA synthesis. To our knowledge, this is the first instance of the direct stimulation of ribosomal RNA synthesis during nuclear isolation.Supported by USPHS Grant NS-07934.     

Ultrastructural changes in the gallbladder mucous membrane during temporary experimental ischemia]

Temporary ischemia of the gall bladder was induced in rabbits by ligation of the gall bladder artery with silk. Histological examination revealed vascular disorders, such as hyperemia, blood stasis and focal hemorrhages. Electron microscopic studies showed the presence of increased number dark epithelial cells, expansion of intercellular area, loosening of the basal membrane and defects in it with invagination of the epithelial cells into the submucous layer. The most striking changes were discovered after a thrice-repeated 30-minute occlusion of the gall bladder artery. The degree of destructive changes proved to depend on the number of stimulated spasms (occlusions) and not on the duration of ischemia. This gives grounds to believe that multiple circulatory disorders participated in the complicated pathogenesis of cholecystitis.