Functional analysis of secreted and transmembrane proteins critical to mouse development.

We describe the successful application of a modified gene-trap approach, the secretory trap, to systematically analyze the functions in vivo of large numbers of genes encoding secreted and membrane proteins. Secretory-trap insertions in embryonic stem cells can be transmitted to the germ line of mice with high efficiency and effectively mutate the target gene. Of 60 insertions analyzed in mice, one-third cause recessive lethal phenotypes affecting various stages of embryonic and postnatal development. Thus, secretory-trap mutagenesis can be used for a genome-wide functional analysis of cell signaling pathways that are critical for normal mammalian development and physiology.     

Isolation of chrysotalunin,a red pigment from a New Zealand soil

Summary Benzene extraction of Te Kopuru sand, a podzol located in the subtropical region of New Zealand, yielded a high melting pigment. Spectroscopic data showed it to be the bianthraquinone chrysotalunin. This is the first report of its occurrence in the Southern hemisphere soil.Acknowledgment. The authors wish to thank Dr B. K. G. Theng, Soil Bureau, D.S.I.R., Lower Hutt, for the sample of the Te Kopuru sand podzol humus B horizon and Dr D. J. Wright of the Chemistry Department, University of Canterbury, for the high resolution mass spectral data.     

Nitroglycerin inhibits the phosphorylation of intermediate filament proteins rather than myosin light chain on porcine coronary artery sustained contraction

The smooth muscle relaxation induced by nitroglycerin is hypothesized to be mediated by an increase in the cytoplasmic concentration of guanosine 3′,5′-monophosphate (cGMP) and subsequent dephosphorylation of the 20-kilodalton myosin light chain (MLC). We investigated this hypothesis in procine coronary arterial smooth muscle stimulated with histamine (3 μM) or K⁺ (30 mM). Stimulation of [³²P]Pi-labeled muscle with histamine or K⁺ for 2 min resulted in a four- or 6.2-fold increase, respectively, in the incorporation of³²P into MLC. After 48 min of exposure to histamine. MLC phosphorylation decreased to the basal level and the phosphorylation of desmin, synemin, and of three unidentified cytosolic proteins was increased. K⁺ stimulation resulted in a sustained increase of MLC phosphorylation but had no effect on the phosphorylation of desmin, synemin, or the three unidentified cytosolic proteins. Application of nitroglycerin (1 μM) 48 min after histamine stimulation inhibited the phosphorylation of desmin, synemin, and the three cytosolic proteins. The sustained phase of histamine-induced contraction was also inhibited to a greater extent then the acute phase of histamine-induced contraction and both the acute and sustained phases of K⁺-induced contraction. These results suggest that MLC phosphorylation is required for both phases of K⁺-induced contraction, whereas phosphorylation of intermediate filament proteins is required for the sustained phase of histamine-induced contraction. Intermediate filament proteins, rather than MLC, may also be the target for the relaxant action of nitroglycerin during histamine-induced sustained contraction.