Vanadium biochemistry: the unknown role of vanadium-containing cells in ascidians (sea squirts)

This article reviews several new developments in vanadium biochemistry, as elucidated from studies of ascidians. A hypothesis correlating ascidian blood cell function to anaerobiosis, via two prominent redox constituents, namely vanadium(III) and the tunichromes, a family of metal ion complexing/reducing hydroquinonoid peptides, is presented.     

Inhibition of human platelet lipoxygenase by cyanide

Summary Potassium cyanide inhibited the lipoxygenase activity of a human platelet cytosolic fraction in a concentration-dependent manner (ID₅₀=2 mM). The inhibition was monitored by spectrophotometry (conjugation of diene bonds at 236 nm), by chromatography (inhibition of formation of 12-hydroperoxy eicosatetraenoic acid) as well as by measuring suppression of oxygen consumption. The lipoxygenase activity of intact platelets was also inhibited by KCN as evidenced by the reduction in 12-hydroxy-eicosatetraenoic acid formation in response to thrombin.Acknowledgments. This work was supported in part by NIH grant HL-14890. D.A. was a recipient of the Pharmaceutical Manufacturers Association Advanced Pre-Doctoral Fellowship.     

Distribution of tunichrome and vanadium in sea squirt blood cells sorted by flow cytometry

Specialized blood cells of many tunicates accumulate high concentrations of vanadium and phenolic peptide pigments called tunichromes (TC). In order to determine whether V and TC reside in the same cells, Ascidia nigra and Ascidia ceratodes blood cell subpopulations were isolated by fluorescence-activated cell sorting (flow cytometry) and chemically analyzed. V was found in the spherical, green/grey signet ring cells, and to a lesser degree in the mulberry-shaped, yellow/green morula cells (MRs), whereas free TC was detected mainly in MRs.     

Mouse mutants from chemically mutagenized embryonic stem cells

The drive to characterize functions of human genes on a global scale has stimulated interest in large-scale generation of mouse mutants. Conventional germ-cell mutagenesis with N-ethyl-N-nitrosourea (ENU) is compromised by an inability to monitor mutation efficiency, strain and interlocus variation in mutation induction, and extensive husbandry requirements. To overcome these obstacles and develop new methods for generating mouse mutants, we devised protocols to generate germline chimaeric mice from embryonic stem (ES) cells heavily mutagenized with ethylmethanesulphonate (EMS). Germline chimaeras were derived from cultures that underwent a mutation rate of up to 1 in 1,200 at the Hprt locus (encoding hypoxanthine guanine phosphoribosyl transferase). The spectrum of mutations induced by EMS and the frameshift mutagen ICR191 was consistent with that observed in other mammalian cells. Chimaeras derived from ES cells treated with EMS transmitted mutations affecting several processes, including limb development, hair growth, hearing and gametogenesis. This technology affords several advantages over traditional mutagenesis, including the ability to conduct shortened breeding schemes and to screen for mutant phenotypes directly in ES cells or their differentiated derivatives.