Biochemical and cytological heterogeneity of the differentiating cells of the cellular slime mould Dictyostelium discoideum

1. The slug stage of the cellular slime mould Dictyostelium discoideum has been shown to contain two types of cell, which differ in buoyant density. 2. These two cell types also differ in cytological appearance and histochemical behaviour and have very different enzymic activities. 3. Evidence is presented suggesting that the lighter of these two cell types corresponds to cells from the posterior region of the slug (pre-spore cells) and the heavier of the two to cells from the anterior region of the slug (pre-stalk cells).     

Nutrient stress gradient in the bottom 5 cm of fast ice, McMurdo Sound, Antarctica

One-centimeter-scale vertical sampling of fast ice from McMurdo Sound, Antarctica reveals evidence of progressive nutrient limitation with distance above the ice/water interface. Over the bottom 6 cm photosynthetically active radiation increases by between 1.8 and 3 times, C:N increases from 6.8 to 19.8 and δ¹³C increases from −18 to −12. Fatty acid composition also changes with a consistent decline in polyunsaturated fatty acids and a rise in saturated fatty acids. These factors all suggest severe and progressive nutrient limitation with distance from the ice/water interface. Accepted: 5 September 1998     

Electron-spin-resonance studies of the structure and formation of bacterial diazodiphenoquinone pigments (Short Communication)

The formation of diazodiphenoquinone pigments during bacterial oxidations of pyridinediols can be accounted for in terms of a free-radical mechanism similar to that operating for oxidations in vitro involving azasemiquinone radicals. Electron-spin-resonance spectra are of great value in pigment structure determinations.