Partitioning of mercury in aqueous biphasic systems and on ABEC™ resins

Poly(ethylene glycol)-based aqueous biphasic systems (PEG-ABS) can be utilized to separate and recover metal ions in environmental and hydrometallurgical applications. A concurrent study was conducted comparing the partitioning of mercury between aqueous layers in an ABS [Me-PEG-5000/(NH₄)₂SO₄] and partitioning of mercury from aqueous solutions to aqueous biphasic extraction chromatographic (ABEC-5000) resins. In ammonium sulfate solutions, mercury partitions to the salt-rich phase in ABS, but by using halide ion extractants, mercury will partition to the PEG-rich phase after formation of a chloro, bromo or iodo complex. The efficacy of the extractant increases in the order Cl⁻<Br⁻<I⁻. This behavior is also observed using the ABEC resins where halo complexes of mercury will adsorb to the resin from (NH₄)₂SO₄ solutions with retention following the same order. The onset of mercury extraction or adsorption is different for the three extractants, occurring at the lowest extractant concentration for I⁻, followed by Br⁻, and then Cl⁻. Fluoride does not extract mercury. Extraction or adsorption of mercury is improved at the lowest halide concentrations in the presence of sulfuric acid. The addition of sulfuric acid to (NH₄)₂SO₄ solution results in ABEC retention of mercury even in the absence of halide extractant.     

The distribution of centrosomes in endothelial cells of non-wounded and wounded aortic organ cultures

Summary The distribution of centrosomes in porcine vascular endothelial cells of the thoracic aorta maintained in organ culture was determined in en face preparations using immunofluorescence. Rectangular pieces of aorta that had the distal half (with respect to the heart) of their endothelial surface gently denuded with a scalpel blade and pieces with intact endothelium were cultured for up to 96 h. At time 0, centrosomes were found to be preferentially oriented toward the heart, both in the cells of intact monolayers and in cells at the wound edge. This distribution was maintained in the intact monolayers for at least 24 h, but by 72 h the number of centrosomes in the center of the cells exceeded the number oriented toward the heart as the cells changed from a fusiform to a polygonal shape. The centrosomes of most endothelial cells at the wound edge began to redistribute themselves within the first 24 h in culture, moving from a position toward the heart to a position either in the center of the cell or away from the heart. By 72 h, the majority of centrosomes in endothelial cells at the wound edge were oriented away from the heart toward the denuded region. It is concluded that the centrosomes in the endothelial cells maintained in organ culture respond to injury in a manner similar to those grown in monolayer cell culture except that the reorientation of centrosomes occurs more slowly.     

The number of acetylcholinesterase molecules in the rat megakaryocyte.

A megakaryocyte cell series from rat bone marrow has been examined by the isotopic di-isopropyl fluorophosphate (DFP) method for esterases. After complete reaction with 32P-DFP, the numbers of DFP-reacted molecules inindividual cells havebeen determined by beta trackauto-radiography. Previous work has shown the percentage of organophosphate-sensitive sites in these cells which can be taken as active centers of acetylcholinesterase (AChase). Combining these data, the absolute numbers of organophosphate-sensitive esterase molecules and AChase molecules per cell were determined. Histograms show a narrow spread of values within each of four size classes from megakaryoblast to fully mature megakaryocyte, but, with means increasing 4-fold through this series, approximately in proportion to cell volume. A rat megakaryoblast has 2 X 10(6) AChase molecules, and a megakaryocyte (of 48-micro diameter) has 7.6 X 10(6) molecules. The apparent turnover number of the enzyme for intracellular reaction with substrate is calculated and compared with turnover numbers available for other AChases.     

Spina bifida and anencephaly: miscarriage as possible cause.

In two retrospective Liverpool surveys the domestic, family, dietary, and medical environments of the mothers of children affected by anencephaly or spina bifida, or both (ASB) were examined. None seemed to be of more than minor importance and the findings of others were therefore examined to see if they suggested a major factor. The most promising lead came from the hypothesis that ASB is usually due to an interaction between twin fetuses or between a fetus and residual trophoblastic material from the previous normal pregnancy, particularly when this is of the opposite sex to the propositus. The sex finding was not confirmed. It was noted that hydatidiform moles, like children with ASB, were usually female and that moles and choriocarcinomas on the one hand and children with ASB on the other occurred in mothers of similar ages, but were to some extent reciprocal in geographical incidence. This suggested that trophoblastic disease might be a factor common to all three and if so then one would expect the frequency of miscarriages to be higher immediately before than immediately after the birth of an ASB child, since mole and choriocarcinoma seldom follow a normal pregnancy. An analysis of published data confirmed that this was almost certainly so. Hence residual pathological trophoblastic material from either a previous miscarriage or a co-twin may interact unfavourably with another fetus to produce ASB and this may be the primary cause of the condition. The hypothesis is consistent with the observed lack of concordance in twins, the high incidence in females, the maternal age effect, and the greater prevalence in social classes IV and V.     

Dorsal medullary oxytocin, vasopressin, oxytocin antagonist, and TRH effects on gastric acid secretion and heart rate

Injections of oxytocin and TRH (11 picomoles), centered on the dorsal motor nucleus of the vagus, substantially increased gastric acid secretion. Additionally, oxytocin, but not TRH, simultaneously produced a consistent reduction in heart rate. Vasopressin injected into the same locus, at doses of 11 and 110 picomoles, had no effect on either function. Both the gastric and cardiac effects of oxytocin were eliminated by the central injections of oxytocin antagonist dEt₂Tyr(Et)Orn⁸Vasotocin (ETOV; 6 picomoles) or peripheral administration of atropine (300 μg/kg, IP). Application of oxytocin or TRH to the area postrema, at double the dosage (22 picomoles) yielded no consistent effects on either gastric secretion or heart rate. These findings indicate that oxytocin in the dorsal motor nucleus of the vagus may act as a regulator of vagally-mediated gastric and cardiovascular functions while TRH effects, in this medullary area, seem limited to the regulation of gastric function.