Darla J. Higgs

Laminar dispersion in flow-injection analysis.

Simple expressions are given for the dispersion and the travel times of samples in simple flow-injection analysis systems. The sum of these two quantities is the total residence time of the sample in the system. The expressions are based on numerical solutions of the diffusion-convection equation. Preliminary experiments are in agreement with the derived simple expressions, as are peak curve shapes. Diffusion coefficients can be obtained in a straightforward manner.

Characterization of the selenium in rat liver mitochondria as glutathione peroxidase

Summary A large part of the radioselenium in liver mitochondria prepared from rats given 0.1 ppm Se as Na 2 75 SeO 3 in the drinking water can be solubilized by a procedure combining extraction with hypotonic Tris buffer-ethanol and freeze-thawing. The radioselenium in this extract binds to DEAE-Sephadex but can be eluted as a single main radioactive peak with salt solution of relatively low ionic strength. Gel filtration of the radioactive peak fractions from the DEAE-Sephadex column through Sephadex G-150 yielded 2 radioactive peaks, the larger of which was associated with significant glutathione peroxidase activity. These findings are consistent with the concept that most of the selenium in mitochondria exists in the form of glutathione peroxidase.

Microcomputer control and data system for automated multiple flow injection analysis.

Introduction Flow injection analysis has been shown to be a versatile technique for the analyses of many types of samples using unsegmented continuously flowing streams. Several recent reviews have discussed a variety of aspects of this field 1-5]. The automated version of flow injection analysis (usually called automated multiple flow injection analysis or AMFIA) is attractive for those laboratories processing large numbers of samples or which require good precision, and several workers have been exploring this type of flow injection analysis [6-25]. There are three general types of AMFIA systems (Figure 1): the standard configuration with low or medium dispersion, the titration system with the large dispersion and the dilution system with low dispersion [22]. Each type of AMFIA configuration requires precise control of the sample tray, probe and sample injection valve. The dilution system also requires the operation of a fraction collector. Data must be acquired and processed by both the standard and titration systems. In this communication methods are described for the automation of all three types of AMFIA systems. The system described uses the Rockwell AIM-65 microcomputer, some associated electronics and layered user-oriented software. This work is a continuation of earlier efforts to provide full automation of AMFIA systems [22,23]. Malmstadt et al and Slanina et al have also described the use of computers for the control of FIA systems 19,24,25 ].

Selenium Catalysis of Swelling of Rat Liver Mitochondria and Reduction of Cytochrome c by Sulfur Compounds

Schwarz and Foltz (1957) discovered that trace amounts of selenium in the diet could protect vitamin E-deficient rats against liver necrosis. This fundamental discovery led to the recognition of “selenium-responsive” deficiency diseases in several different animal species (Nesheim and Scott, 1961; Schubert et al., 1961). The status of selenium as an essential nutrient in its own right was assured when beneficial effects due to the element were observed even in animals fed sufficient vitamin E (McCoy and Weswig, 1969; Thompson and Scott, 1969).