Oxygen effect in the radiolysis of proteins:: V. Histones

Histones of calf thymus were irradiated with X-rays in different phosphate solutions under nitrogen and air. Degradation of the monomer core histones, formation of aggregates and of fragments were determined by electrophoresis and HPL-gelchromatography. Under nitrogen loss of monomer histones are caused by aggregation, under air by fragmentation. No influence of the different ionic conditions was observed. The G-value for degradation is smaller under air than under nitrogen. These results for histones are compared with the oxygen effect of other proteins.     

Atomic absorption spectroscopy in the v.u.v.-range: determination of bromine

The conditions for the determination of elements by atomic absorption spectroscopy (AAS) in the vacuum-ultraviolet range are discussed. The requirements for the absorption vessel are considered and the equilibrium concentrations of possible dissociation products of different chemical compounds are calculated. In this way it is possible to estimate the detection limit attained with such an AAS arrangement. When losses by diffusion of sample vapour are disregarded a theoretical value of 5 × 10^?10 g Br results. AAS measurements are described using a special graphite oven in conjunction with a vacuum-ultraviolet monochromator. For KBr as a representative substance we obtained the experimental detection limit of 1.5 × 10^?9 g Br with Br I 148.86 nm.     

Calcium alkoxyalanates : II. Advances in the synthesis

Simple syntheses of calcium alkoxyalanates starting from NaAlH₄, CaCl₂ and alcohols involving evolution of hydrogen and separation of sodium chloride are reported. More complex methods, which allow the preparation of calcium alkoxyllalanates without loss of hydride hydrogen from NaAlH₄, CaCl₂, NaOR and AlX₃ (X = OR, Cl) have also been developed.     

Epicardial development in the rat: a new perspective.

Development of the epicardium is critical to proper heart formation. It provides all of the precursor cells that form the coronary system and supplies signals that stimulate cardiac myocyte proliferation. The epicardium forms from mesothelial cells associated with the septum transversum and is referred to as the proepicardium (PE). Two different methods by which these PE cells colonize the developing heart have been described. In avians, PE cells form a bridge to the heart over which PE cells migrate onto the heart. In fish and mammals, PE cells form vesicles of cells that detach from the mesothelium, float through the pericardial cavity, and attach to the heart. A previous study of rat PE development investigated this process at the histological level. Protein markers have been developed since this study. Thus, we investigated this important developmental process coupled with these new markers using other visualization techniques such as scanning electron microscopy (SEM) and confocal microscopy. Finally, a novel, three-dimensional (3-D) culture system was used to confirm the identity of the PE cells. In this study, we found convincing evidence that the rat PE cells directly attach to the heart in a manner similar to that observed in avians.     

Blood lead proficiency testing: overview of the federally sponsored program in the U.S.

External proficiency testing is a proven method for improving the quality of laboratory measurements, including lead in blood. Several proficiency testing programs exist to fill this need. This article describes the U.S. federally sponsored Blood Lead Proficiency Testing Program. Three specimens, composed of blood from dosed cows, are distributed to participants each month. Target values are determined by a group of 10 referee laboratories. Participant performance has shown steady improvement over time.