Choice of function for mortality analysis: Effective forecasting depends on a minimum parameter representation

For nearly two centuries actuaries, statisticians and demographers have sought a parameter space in which the mortality pattern of a population could be located, that would be linked to the larger space of age-specific rates by an analytical formula. Gompertz, Makeham, Brillinger, Wolfenden, Pollard and others have made contributions to this end. Model or reference tables perform a similar task, usually with fewer parameters, but are less easily manipulated. A common means of reducing dimensionality is to map the original space of mortality rates in five-year groups on a straight line in which are located the expectations of life at age zero (ė₀). A small-space representation is advantageous for filling gaps in data. If the only fact known about a country is the fraction of girls who have a living mother, then a one-dimensional set can be indexed on this to provide the full detail of mortality, assuming the unknown mortality is part of that set. For forecasting one would like the succession of life tables for a given population over past times to be representable by points moving in a simple way through a parameter space—ideally in a straight line—over a succession of calendar years. The simpler the curve, the more realistic is likely to be its projection into the future. The Brass relational method provides a trajectory well suited to extrapolation in a space of only two parameters. Some useful extensions of this have recently been devised.     

Synthesis of charged amphipathic nitroxide lipid spin labels and an example of their application in membrane studies

The synthesis of a series of amphipathic nitroxide lipid spin labels is reported. Thus, 12-proxylhexadecanol has been converted into the versatile fatty acid spin label 14-proxylstearic acid. This substance was used to prepare 14-proxylstearyltrimethylammonium methanesulfonate, a positively charged label, and 14-proxylstearylmethyl phosphate sodium salt, a negatively charged label. Also prepared in the doxyl series were quaternary ammonium salts derived from 16-doxyl- and 7-doxylstearic acid. The positively charged and negatively charged proxyl labels were used in a preliminary experiment to investigate the role of charge in their interaction with reconstituted cytochrome oxidase. The average binding affinity of the negatively charged label is approximately 2-fold higher than that of the positively charged label at pH 7.4. At pH 5.5 the average relative affinity for negatively charged label is about 3.5-fold higher than that of positively charged label, suggesting that the ionizable group(s) on the protein can interact with the lipid headgroup.     

Effect of synthetic enantiomeric cannabinoids on platelet aggregation.

The effect of a synthetic pair of enantiomeric cannabinoids on platelet function was evaluated. The nonpsychotropic enantiomer, the 1,1-dimethylheptyl homolog of (+)-(3S,4S)-7-hydroxy-delta-6-tetrahydrocannabinol (HU-211), was found to be more active in inhibiting ADP-induced platelet aggregation than the highly psychotropic (-)-enantiomer (HU-210). The related (+)-(3R,4R) cannabinoid, HU-213, which lacks the 7-hydroxy moiety, exerted its inhibitory effect within a wider range of concentrations. The results indicate a differentiation between psychotropic activity and inhibition of platelet aggregation in the cannabinoid group of compounds.     

Snow-patch foraging by pink-footed geese Anser brachyrhynchus in south Iceland

The pre-nesting feeding behaviour of pink-footed geese was studied in hayfields in southern Iceland during the late spring of 1989. Persistent snow-patches protected underlying grass from the effects of severe night-time frost. Areas within 1 m of snow-patches had significantly greater amounts of green material than those further away; green material contained more than double the protein of brown, dead material, which predominated in open fields. Geese spent nearly 60 times more time feeding within 1 m of snow patches than expected by chance, and 20 times more time within 2–5 m. Their feeding rates here were faster and their step rate slower than further away. In this way, the geese selected the prime forage as soon as it became available.     

Increased cell surface EGF receptor expression during the butyrate-induced differentiation of human HCT-116 colon tumor cell clones

Several clonal sublines of HCT-116 human colon adenocarcinoma cells were isolated and characterized on the basis of their growth characteristics, intrinsic enterocyte-like differentiation (as assessed by alkaline phosphatase and lactase activities), and responses to butyrate, an inducer of colon tumor cell maturation. The HCT-116 sublines were found to be heterogeneous and several phenotypically distinct clones were identified. Further characterization of these clones indicated that the effects of butyrate on cell growth, alkaline phosphatase activity, and lactase activity were distinct and separable. The growth of all of the clones were inhibited by butyrate (IC50 values varied from 0.44 to 1.5 mM), but the effects of this agent on alkaline phosphatase and lactase activities varied widely. In several sublines butyrate had no effect on either enzyme while in others one or both activities were induced. Additionally, the binding of 125I-epidermal growth factor (EGF) to cell surface receptors was found to be proportional to the expression of lactase activity in the cell. The D3 clone and other sublines with intrinsic lactase activities greater than 100 nmol/mg/min expressed a class of high-affinity EGF receptors (e.g., D3 cells had 3.48 X 10(4) EGF receptors/cell with a kd of 0.61 nM). Other clones with less lactase activity had undetectable levels of 125I-EGF binding. In clones which exhibited greater than twofold increases in lactase activity in response to butyrate, the expression of a large number of low-affinity EGF receptors was also induced. In one such clone, the P1 subline, lactase activity was increased from 70 nmol/mg/min to 230 nmol/mg/min after 96 h in 2 mM butyrate, and the expression of EGF receptors was increased from undetectable levels to 1.18 X 10(5) EGF receptors/cell (kd of 3.2 nM). Northern blot analysis indicated that the increased 125I-EGF binding after butyrate treatment may have been due, in part, to a greater than twofold accumulation of EGF receptor mRNA. In addition, the expression of the messages for transforming growth factor alpha (TGF-alpha) and transforming growth factor beta (TGF-beta) was examined in butyrate-treated cells. While TGF-alpha mRNA levels were found to correlate with EGF receptor message levels in the HCT-116 clones, TGF-beta mRNA expression was not found to correlate with the butyrate-induced growth inhibition or with increases in EGF receptor expression, alkaline phosphatase activity, or lactase activity in these cells.