Effects of 2-fluoroestradiol on lipid metabolism in the ovariectomized rat

Biological activities of estrogen molecules are altered by fluorination of ring A, and the resulting impairment to form catechols. 2-fluoroestradiol (2-F-E2) has been found to be devoid of carcinogenic action despite its high estrogenic potency; its metabolic effects are so far unknown. This study was designed to investigate the effects of 2-F-E2 on lipid metabolism, as compared to those of estradiol-17 beta(E2). Ovariectomized rats received E2 or 2-F-E2 by s.c. injection at a dose of 60 micrograms for three consecutive days. Parameters measured were weights of parametrial fat depots, fat cell volumes, levels of triacylglycerol and acylcholesterol in plasma, and enzymatic responses to the estrogens in isolated parametrial fat cells as evaluated in terms of lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) activities. 2-F-E2 and E2 were found to produce comparable decreases in fat depots, cell volumes and plasma levels of acylcholesterol whereas plasma triacylglycerol was unchanged. Both estrogens decreased LPL, and increased HSL activities to the same extent. Thus, 2-F-E and E2 exhibited comparable effects on lipid metabolism. These effects appeared to depend mainly on the estrogenic potency of these molecules, and to be distinct from their carcinogenic action. Despite its high estrogenic potency, 2-F-E2 was found to be slightly less estrogenic than E2.     

Cell enlargement and growth-induced water potentials

Understanding the origin and role of growth-induced water potentials helps to explain how cell enlargement is inhibited without a decrease in turgor when water is depleted in the soil or more rapidly lost by transpiration. In many cases, changes in growth-induced water potentials probably cause the inhibition initially, but eventually the cell walls lose extensibility and specific proteins accumulate so that metabolic changes in the walls probably limit later growth.     

The dynamics of cohort selection

The dynamics of cohort selection in age-structured populations is explored in a series of computer simulations using a single-locus two-allele model. Cohort selection is a directional process which is a consequence of genetically determined inter-cohort variation in the magnitude of expression of interference behavior; its essential premise is that all genotypes of a given age are equally susceptible to interference and that no advantage accrues to the interfering genotype. In these simulations, allele frequency, population size, intensity of interference, and reproductive apportionment are all major determinants of evolutionary rates. The generality of this process is demonstrated and an analysis of the observed frequency-dependent effects is presented. Cohort selection is distinct from other kinds of selection and may be an important cause of the persistence of interference behavior (culminating in acts of spite) within animal populations.     

Light-driven ATP formation from 32Pi by chloroplast thylakoids without detectable labeling of ADP, as measured by rapid mixing and acid quench techniques

The labeling of ATP and ADP in the first few milliseconds of exposure of chloroplast thylakoids to light, 32Pi, and ADP has been measured. At least 4 mol of ATP/mol of coupling factor 1 (CF1)-ATPase can be formed without detectable labeling of membrane-bound or free ADP. Such results are consistent with ADP and not AMP as the primary acceptor of Pi in photophosphorylation. Evidence is presented demonstrating that quenching with perchloric acid, as used in these and earlier experiments, is satisfactory for the measurement of the amount and nature of membrane-bound nucleotides.