Purification of phosphoinositide-specific phospholipase C from a particulate fraction of bovine brain

The coupling of various agonist receptors to the hydrolysis of phosphoinositides has generated much interest in the nature of the phospholipase C that is activated. Here we report the purification of a bovine brain phospholipase C derived from the particulate fraction. A 1000-fold purification was achieved by a combination of heparin-Sepharose, DEAE-cellulose and gel-permeation chromatography. The purified enzyme appears to be monomeric and under denaturing conditions shows a single staining major polypeptide of molecular mass 154 kDa in SDS gels. The enzyme is specific for phosphoinositides although it shows a marked preference for the polyphosphoinositides. With phosphatidylinositol 4,5-bisphosphate as substrate the enzyme expresses a specific activity of greater than 100 mumol min-1 mg-1. The phospholipase C is activated by Ca2+ (0.1-10 microM). The behaviour of this particulate enzyme is discussed in the context of a agonist-induced phosphatidylinositol hydrolysis.     

It is better to be ignorant of our moral enhancement: A reply to Zambrano

In a recent issue of Bioethics, I argued that compulsory moral bioenhancement should be administered covertly. Alexander Zambrano has criticized this argument on two fronts. First, contrary to my claim, Zambrano claims that the prevention of ultimate harm by covert moral bioenhancement fails to meet conditions for permissible liberty-restricting public health interventions. Second, contrary to my claim, Zambrano claims that covert moral bioenhancement undermines autonomy to a greater degree than does overt moral bioenhancement. In this paper, I rebut both of these arguments, then finish by noting important avenues of research that Zambrano’s arguments motivate.     

Morphogenia: a new genus of the Neotropical tribe Jubini (Coleoptera,Staphylinidae, Pselaphinae) from the Brazilian Amazon

A new genus and species of the large Neotropical pselaphine tribe Jubini is described from Manaus, Brazil, based on material preserved in the Natural History Museum, London. Morphogenia struhli gen. et sp. n. represents the possible sister taxon of the abundant and speciose genus Barrojuba Park, sharing with it the putatively derived condition of anterolaterally shifted vertexal foveae, producing a smoothly convex vertex devoid of fovea or sulci. However, unlike Barrojuba, Morphogenia retains a plesiomorphic antebasal sulcus on the pronotum in both sexes, and additionally lacks elaborate abdominal fovea-like pockets and teeth on the lateral margins of the pronotum that are typical of Barrojuba. The genus is also unusual among jubine genera in lacking the characteristic V- or Y-shaped gular carina. In contrast to the commonly-collected Barrojuba, specimens of Morphogenia are absent in extensive jubine collections housed in museums in the United States, indicating that the new taxon may be relatively scarce or localised.     

Beta-adrenergic agonists and cyclic AMP decrease intracellular resting free-calcium concentration in ileum smooth muscle

Intracellular free-calcium levels were measured in strips of longitudinal smooth muscle from guinea-pig ileum; fura-2 was used as a calcium monitor. At rest the calcium concentration was about 180 nM, and this rose to 300-400 nM following electrical stimulation and during spontaneous calcium transients (all measurements at 23-25 degrees C). Isoprenaline suppressed the spontaneous calcium transients, and reduced the resting calcium level to about 130 nM. This fall in resting calcium concentration was seen even in muscle strips which did not have spontaneous activity. Elevation of intracellular cyclic AMP levels, produced by forskolin or dibutyryl cyclic AMP, mimicked the actions of isoprenaline. We conclude that the relaxant effects of beta-adrenergic agonists of visceral smooth muscle may be explained partly by a fall in intracellular resting free-calcium level, mediated via an increase in cyclic AMP.     

Cation amelioration of aluminum toxicity in wheat

Aluminum is a major constituent of most soils and limits crop productivity in many regions. Amelioration is of theoretical as well as practical interest because understanding amelioration may contribute to an understanding of the mechanisms of toxicity. In the experiments reported here 2-day-old wheat (Triticum aestivum L. cv Tyler) seedlings with 15-millimeter roots were transferred to solutions containing 0.4 millimolar CaCl₂ at pH 4.3 variously supplemented with AlCl₃ and additional amounts of a chloride salt. Root lengths, measured after 2 days in the test solutions, were a function of both Al activity and the cation activity of the added salt. Percent inhibition = 100 {Al³⁺}/({Al³⁺} + K_m + α{C}^β) where {Al³⁺} is the activity of Al³⁺ expressed in micromolar, {C} is the activity of the added cation expressed in millimolar, and K_m (= 1.2 micromolar) is the {Al³⁺} required for 50% inhibition in the absence of added salt. For Ca²⁺, Mg²⁺, and Na⁺ the values of α were 2.4, 1.6, and 0.011, respectively, and the values for β were 1.5, 1.5, and 1.8, respectively. With regard to relative ameliorative effectiveness, Ca²⁺ > Mg²⁺ ≈ Sr²⁺ K⁺ ≈ Na⁺. Other cations were tested, but La³⁺, Sc³⁺, Li⁺, Rb⁺, and Cs⁺ were toxic at potentially ameliorative levels. The salt amelioration is not solely attributable to reductions in {Al³⁺} caused by increases in ionic strength. Competition between the cation and Al for external binding sites may account for most of the amelioration.