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.     

Restriction mapping of the rRNA genes from Artemia larvae

A restriction endonuclease analysis of the genes coding for the ribosomal RNA from Artemia larvae has shown that these genes consist of a repeat unit of 16.2 kilobase pairs (10.7 Mdaltons) and that the repeat unit seems to be homogeneous in size.     

The abnormal phosphorylation of spectrin in human hereditary spherocytosis

The phosphorylation of the proteins of the erythrocyte membrane of patients suffering from hereditary spherocytosis is investigated in intact erythrocytes by their incubation in the presence of radioactive inorganic phosphate. Examination of the phosphorylated components by high-resolution two-dimensional gel electrophoresis reveals only one defect in the pathological membranes, a depressed phosphorylation of the smaller polypeptide of spectrin; band 2. The phosphorylation of band 2 is measured with reference to the phosphorylation of syndein ($\text{2.1 + 2.2 + 2.3}$). In patients showing overt clinical symptoms and for whom splenectomy is advocated the phosphorylation of band 2 is depressed by approx. 70%. After splenectomy the phosphorylation of membrane proteins is restored to normal levels.     

Effect of transforming growth factor beta (TGF-β) on ATP citrate lyase in isolated hepatocytes

Summary Transforming growth factor beta (TGF-) activates ATP citrate lyase in freshly isolated rat liver hepatocytes in a time dependent manner. Maximal stimulation of the enzyme occurred with less than thirty minutes of incubation of the cells with TGF-. The half maximal effect on the enzyme determined in hepatocytes incubated with TGF- for 10 min at 37°C was elicited by TGF- concentrations in the 10^–11 – 10^–12 M range. The potential role of TGF- stimulation of ATP citrate lyase activity in new membrane synthesis is discussed.     

Citric acid excretion and precipitation of calcium citrate in the rhizosphere of white lupin (Lupinus albus L.)

Abstract. White lupin ( Lupinus albus L.) was grown for 13 weeks in a phosphorus (P) deficient calcareous soil (20% CaCO₃, pH(H₂O)7.5) which had been sterilized prior to planting and fertilized with nitrate as source of nitrogen. In response to P deficiency, proteoid roots developed which accounted for about 50% of the root dry weight. In the rhizosphere soil of the proteoid root zones, the pH dropped to 4.8 and abundant white precipitates became visible. X-ray spectroscopy and chemical analysis showed that these precipitates consisted of calcium citrate. The amount of citrate released as root exudate by 13-week-old plants was about 1 g plant⁻¹, representing about 23% of the total plant dry weight at harvest. In the rhizosphere soil of the proteoid root zones the concentrations of available P decreased and of available Fe, Mn and Zn increased. The strong acidification of the rhizosphere and the cation/anion uptake ratio of the plants strongly suggests that proteoid roots of white lupin excrete citric acid, rather than citrate, into the rhizosphere leading to intensive chemical extraction of a limited soil volume. In a calcareous soil, citric acid excretion leads to dissolution of CaCO₃ and precipitation of calcium citrate in the zone of proteoid roots.     

Sodium channel opening as a precursor to inactivation

The time constant of the process producing the delay in Na inactivation development as determined by the two pulse method (_delay) was extracted and compared to that of the slowest Na activation process ₃ for the I _Na during the conditioning pulse of that same determination. _delay and two pulse inactivation _c values were computer generated using a nonlinear least squares algorithm. _h and single pulse inactivation _h values were independently generated for each determination also with the aid of the computer using the same non-linear least squares algorithm. In one determination at 2 mV, _c was 4.68 and _delay 0.494 ms while _h was 4.70 and ₃ 0.491 ms for a _c/_h of 0.996 and a _delay/₃ of 1.006. Mean _delay/₃ from five determinations in four axons, both Cs and K perfused, and spanning a potential range of-27 to 2mV was 1.068. The precursor process to inactivation is channel opening. Some fraction of channels presumably inactivate via another route where prior channel opening is not required.     

Functional reconstitution of rat ovarian LH/hCG receptor into proteoliposomes

Rat ovarian membrane LH/hCG receptor was solubilized in various detergents and reconstituted into proteoliposomes. Upon removal of sodium cholate by active absorption on Bio-Beads SM-2, the functional interaction between receptor and adenylate cyclase was restored. Adenylate cyclase was stimulated by hCG, HCG+GTP or GppNHp and NaF. Reconstituted proteoliposomes bound more ¹²⁵I-hCG (528 fmol/mg protein) than membrane-bound receptors (384 fmol/mg protein). There was no difference, however, in the relative affinity of reconstituted receptor preparations for hCG.     

Recovery of plastids from photooxidative damage: Significance of a plastidic factor

Glyoxysomal citrate synthase (gCS) was purified from crude extracts of watermelon (Citrullus vulgaris Schrad.) cotyledons, yielding a homogenous protein with a subunit MW of 48 kDa. The enzyme was selectively inhibited by 5,5-dithiobis-(2-nitrobenzoic acid), allowing quantification in the presence of the mitochondrial isoenzyme (mCS). Differences were also observed with respect to inhibition by ATP (k _i=2.6 mmol · l^-1 for gCS, k _i=0.33 mmol · l^-1 for mCS). The antibodies prepared against gCS did not cross-react with mCS. The immunocytochemical localization of gCS by the indirect protein A-gold procedure was restricted to the glyoxysomal membrane or the peripheral matrix of glyoxysomes. Other compartments, e.g. the endoplasmic reticulum, were not labeled. Xenopus oocytes were used for the translation of watermelon polyadenylated RNA (poly(A)⁺RNA). A translation product with a MW of 51 kDa was immunoprecipitated by the anti-gCS antibodies. It was absent in controls without poly(A)⁺RNA or with preimmune serum. A similar translation product was also immunoprecipitated after cell-free synthesis of watermelon poly(A)⁺RNA in a reticulocyte system, in contrast to the in-vivo labeled gCS (48 kDa). It was concluded that gCS is synthesized as a higher-molecular-weight precursor.Abbreviations DTNB 5,5-dithiobis-(2-nitrobenzoic acid) - gCS glyoxysomal citrate synthase - gMDH glyoxysomal malate dehydrogenase - k _i inhibitor constant - mCS mitochondrial citrate synthase - OAA oxaloacetate - poly(A)⁺RNA polyadenylated RNA - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis