The hypothalamo-hypophysial system of hypophysectomized rats

Summary The median eminence (ME) of hypophysectomized rats was studied by means of light and electron microscopy. Paraldehyde-fuchsin (PAF)-positive material is seen in the external zone (EZ) of the ME 2–5 days after the operation. Its amount gradually increases especially in the caudal part of the ME during the following few days. Some PAF-positive fibers make contact with the subependymally located blood capillaries. In the most caudal region of the recessus infundibuli they penetrate into the third ventricle. PAF-positive material decreases markedly from the ME of rats two months after hypophysectomy and exposure to a 1% salt load. Fibers of types A₁, A₂ and B containing granules of 120–220 nm, 100–150 nm and 80–100 nm in diameter, respectively, are seen in the EZ of the ME in hypophysectomized rats, although almost exclusively A₂- and B-type structures make contact with the primary portal capillaries in intact animals. All types of neurosecretory fibers establish contact with the subependymal nonfenestrated blood capillaries and penetrate the recessus infundibuli. Some neurosecretory terminals of different types make direct contact with the glandular cells of the pars tuberalis or are separated from them by a thin basal lamina. It is assumed that mainly neurosecretory fibers of types A₂ and B are permanently connected with the primary portal capillaries in the EZ of the ME in intact mammals, while the overwhelming majority of fibers of A₁-type shows ingrowth during the course of postoperative reparation. The possible physiological significance of the described changes is discussed.     

Anthozoa from the northern Mid-Atlantic Ridge and Charlie-Gibbs Fracture Zone

An annotated list of deep-sea Anthozoa of the orders Actiniaria, Antipatharia, Scleractinia, Alcyonacea and Pennatulacea collected on the G.O. Sars MAR-ECO cruise to the Mid-Atlantic Ridge between the Azores and the southern tip of the Reykjanes Ridge is given. A total of 33 species is reported of which 32 were identified to species or genus level. The groups most rich in species were Actiniaria (nine species), Scleractinia (eight species) and Pennatulacea (eight species). Scleractinia, Antipatharia and Pennatulacea were mainly represented by species with a wide or cosmopolitan geographical distribution. In contrast, most of the actiniarians had been rarely recorded in the North Atlantic. Three species, Schizopathes affinis Brook, 1889 (Antipatharia), Dendrobrachia multispina Opresko & Bayer, 1991 and Heteropolypus cf. insolitus Tixier-Durivault, 1964 (Alcyonacea) are reported from the North Atlantic for the first time.