The rodent dominant lethal assay: a proposed format for data presentation that alerts to pseudo-dominant lethal effects

The rodent dominant lethal (DL) germ cell mutagenicity assay is the primary test for possible human germ cell mutagens. As such, it occupies a critical regulatory position. DL assay data are often difficult to assess because of the quantity of data involved, and because several related assay parameters require to be considered simultaneously. To reduce this difficulty a schematic method of data presentation is proposed and illustrated. This method enables the most pertinent assay data and parameters to be viewed and considered simultaneously. Using this format of data presentation, existing DL studies on cyclophosphamide, methylnitrosourea, diethylhexylphthalate, divinyl sulphone, methyl methanesulphonate, 6-mercaptopurine and ethylenethiourea are re-analysed.     

A comparison of the glutathione S-transferases of trout and rat liver.

1. Cytosol from trout liver, gills and intestinal caeca has substantial glutathione S-transferase activity. 2. Gel-exclusion and ion-exchange chromatography suggest that trout liver has several glutathione S-transferases with different molecular weights and ionic charges. 3. A component capable of binding lithocholic acid eluted together with glutathione S-transferase activity. Some of the transferase activity did not elute together with binding activity. 4. The enzymic activity from trout liver was less stable at 37 degrees C than that from rat liver. 5. The glutathione S-transferases of fish liver have a similar specific activity to those of rat liver but different molecular properties.     

HSP27 expression regulates CCK-induced changes of the actin cytoskeleton in CHO-CCK-A cells

We investigated how heat shock protein 27 (HSP27)and its phosphorylation are involved in the action of cholecystokinin(CCK) on the actin cytoskeleton by genetic manipulation of Chinesehamster ovary (CHO) cells stably transfected with the CCK-A receptor. In these cells, as in rat acini, CCK activated p38 mitogen-activated protein (MAP) kinase and increased the phosphorylation of HSP27. Thiseffect could be blocked with the p38 MAP kinase inhibitor SB-203580.Examination by confocal microscopy of cells stained with rhodaminephalloidin showed that CCK dose-dependently induced changes of theactin cytoskeleton, including cell shape changes, which were coincidentwith actin cytoskeleton fragmentation and formation of actin filamentpatches in the cells. To further evaluate the role of HSP27, CHO-CCK-Acells were transfected with expression vectors for either wild-type(wt) or mutant (3A, 3G, and 3D) human HSP27. Overexpression of wt-HSP27and 3D-HSP27 inhibited the effects on the actin cytoskeleton seen afterhigh-dose CCK stimulation. In contrast, overexpression ofnonphosphorylatable mutants, 3A- and 3G-HSP27, or inhibition ofphosphorylation of HSP27 by preincubation of wt-HSP27 transfected cellswith SB-203580 did not protect the actin cytoskeleton. These resultssuggest that phosphorylation of HSP27 is required to stabilize theactin cytoskeleton and to protect the cells from the effects of highconcentrations of CCK.

     

Phosphorylated compounds in soybeans [Glycine max (L.) Merr.] as affected by phosphorus levels in solution

Summary Phosphorylated compounds in four varieties of soybeans (Lincoln and Clark, sensitive; Chief and L9, tolerant) were studied in relation to plant sensitivity to high phophorus supply as indicated by reduced dry matter yield. Total P in all tissues indicated that sensitive varieties took up P from solution more readily than tolerant ones, especially at low P levels. Tolerant varieties had a greater protein synthesis rate at high solution P concentration, while sensitive varieties reached a maximum rate at a lower P concentration.Paper No. 7083, Scientific Journal Series, Minnesota Agricultural Experiment Station