Trace elements in rock salt and their bioavailability estimated from solubility in acid

In this study, 18 partly commercially available samples of rock salt from Austria, Germany, Pakistan, Poland, Switzerland, and Ukraine were investigated with respect to their content of trace elements using instrumental neutron activation analysis. Elements detected were Al, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Eu, Fe, Hf, La, Mn, Na, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Th, and Zn, some of them only in individual cases. An estimation of the bioavailability of these trace elements was performed by dissolving an equivalent of the sodium chloride samples in diluted hydrochloric acid (simulating stomach acid), filtering off the insoluble components, and analyzing the evaporated filtrate. It could be shown that in most cases bioactive trace elements like Fe can be found in rock salt in the form of almost insoluble compounds and are therefore not significantly bioavailable, whereas thorium, for example, was partly bioavailable in two cases. A significant contribution to the recommended daily intake of metal trace elements by using rock salt for nutrition can be excluded.     

Book reviews

Ohne Zusammenfassung

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Book reviews

     

Preparation and discharge of secretion in the subcommissural organ of the rat

Summary The secretion of the subcommissural organ (SCO) of the rat was studied by means of immunocytochemistry at the electron-microscopic level with the use of (1) the polar embedding medium Lowicryl K4M at -30° C, (2) the protein A-gold technique, and (3) a rabbit antiserum against bovine Reissner's fiber (see Sterba et al. 1981).Two different substructures of the ependymal and the hypendymal SCO-cells display a positive immunocytochemical reaction: (1) sacs containing flocculent secretion, which originate from the granular endoplasmic reticulum, and (2) vacuoles filled with fine granular secretion, which are pinched off from the Golgi apparatus. The secretory material of the sacs and the vacuoles is discharged both (i) apically into the cerebrospinal fluid and (ii) basally into intercellular spaces of the SCO-hypendyma. The apically released secretion is condensed to a lamina-like formation, which more caudally assumes the form of Reissner's fiber. The route of the basally released secretion remains, however, vague. The periodically striated bodies, which were thought to be morphological mediators of the discharge of the secretion into the capillaries, are never labeled by gold particles.Supported by grants from the Ministry for Science and Technology of the German Democratic RepublicThe expert technical assistance of Mrs. B. Wolff, Mrs. S. Mehnert, Mrs. E. Siebert, Mrs. Ch. Schneider, and Mrs. I. Seifert is gratefully acknowledged     

Evidence for stanniocalcin and a related receptor in annelids

Stanniocalcin (STC) is a prime example of a hormone whose discovery in fish led to its subsequent discovery in mammals. STC is considered to be first and foremost a vertebrate polypeptide hormone with regulatory effects on ion transport, mitochondrial function and steroid hormone synthesis. The gene is widely expressed in both fishes and mammals, and the hormone can operate via both local and endocrine signaling pathways. In spite of the growing catalogue of vertebrate hormones and receptors with homologues in invertebrates, the notion that there might be an invertebrate STC homolog has received scant attention to date. In the present study, we have provided evidence for STC in annelid worms (freshwater leeches). Western blot analysis revealed the presence of two STC immunoreactive (STCir) proteins in leech tissue extracts of 100 and 193 kDa. These same extracts significantly lowered the rate of gill calcium transport upon injection into fish. Similarly, fish STC increased the rate of whole body calcium uptake when administered to leeches, and STC receptors of high affinity were identified on isolated leech plasma membranes. Two discrete populations of STC-positive cells were also identified in leeches using antibodies to fish STC and fish STC cRNA probes. One of the cell types was confined to the skin. The second cell type was confined to the coelomic cavity and identified as an adipose cell, which in leeches is a major repository of fat. Collectively, the data constitutes compelling evidence for the existence of STC-related proteins and receptors in annelids that share structural and functional similarities with those in vertebrates.     

Elektronenmikroskopische Untersuchungen über die Reaktion der Pituizyten nach Hypophysenstieldurchtrennung bei Rana esculenta

Zusammenfassung Etwa 2 Tage nach Durchtrennung des Hypophysenstiels beginnen die Pituizyten der Froschhypophyse (Rana) die degenerierenden sekrethaltigen Axone zu phagozy tieren. Nach 3–4 Tagen werden die Neurosekretgranula in den Einschlußkörpern immer mehr zusammengedrängt und verlieren schließlich ihren elektronendichten Inhalt. Die Hüllen der Elementargranula verwandeln sich mit eingelagerten Lysosomen zu membranösen, sehr stark osmiophilen Körpern, die sich schließlich langsam auflösen.Die mitotische Aktivität der Pituizyten ist während des Abbaues gesteigert. Zwischen Gefäßen und Pituizyten bestehen enge räumliche Beziehungen. Die Fähigkeit zur Phagozytose wird als Grundfunktion der Pituizyten angesehen.

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Electron microscopical investigation on the reaction of the pituicytes after stalk section in Rana esculenta

Summary About 2 days after transsection of the pituitary stalk the pituicytes of the frog neurohypophysis (Rana) start to phagocytate the degenerating neurosecretory axons. After 3–4 days the neurosecretory granules inside the inclusion bodies are compressed more and more and finally their electron-dense contents disappear. The membranes of the elementary granules together with lysosomes alter into membranous highly osmiophilic bodies slowly dissolving at last.During the desintegration of nerve endings the mitotic activity of the pituicytes increases. Blood vessels and pituicytes are closely connected.It is supposed that the ability of phagocytosis represents a basic function of the pituicytes.