Hepatic estrogen receptor in the turtle, Chrysemys picta: partial characterization, seasonal changes and pituitary dependence

A hepatic estrogen receptor is described from female turtles, Chrysemys picta. The receptor adheres to DNA after incubation with [3H]estradiol and can be eluted with a linear salt gradient as a single component with an elution maximum of 0.21 M. It is steroid-specific, binding estrogens, but not androgens or progestins. Specific binding saturates between 3 and 7 nM [3H]estradiol-17 beta and Scatchard analysis gave a Kd of 2 X 10(-9) M and a maximal binding capacity of 3.02 fmol/mg protein. Hypophysectomy reduces hepatic estradiol receptor from 70 fmol/g tissue in control animals to non-detectable levels. Growth hormone replacement partially restored the receptor to 36% of control. Significant changes in receptor occur during the ovarian cycle.     

Ionic fluxes induced by topical misoprostol in canine gastric mucosa

We studied the dose response of ionic fluxes in canine chambered gastric segment mucosa to increasing doses of topical misoprostol (0.1, 1, 10, 100, and 1000 micrograms). The fluxes were also correlated with the simultaneous changes in focal gastric mucosal blood flow measured by laser-Doppler flowmetry. After misoprostol administration, there was a dose-dependent increase in focal gastric mucosal blood flow (Emax = 8.23 +/- 3.25 V at 10 micrograms; ED50 = 1.05 micrograms), pH, and the outputs of ions (Na+, K+, Cl-, and HCO3-) and fluid (Emax for pH and fluxes greater than or equal to 1000 micrograms). ED50 values for these outputs ranged from 215.40 to 340 micrograms (mean +/- SE = 279.08 +/- 24.27 micrograms). H+ output showed a dose-dependent decrease to zero at the 10-micrograms dose, the dose at and after which net HCO3- secretion became obvious. The slopes of the dose-response curves for the fluxes of fluid, Na+, K+, Cl-, and HCO3- were significantly different (p less than 0.01) from the slope of the curve for mucosal blood flow changes. There were no correlations between the changes in these fluxes and blood flow changes. Na+ and Cl- were the predominant cation (98.84%) and anion (98.19%), respectively, in the misoprostol-induced secretion. Misoprostol stimulates a composite alkaline gastric nonparietal secretion, predominantly Na+ and Cl-, but also containing K+ and HCO3-. Our results suggest different mechanisms for the effects on nonparietal secretion and focal gastric mucosal blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lymphocyte ecto-5'-nucleotidase activity in infancy: increasing activity in peripheral blood B cells precedes their ability to synthesize IgG in vitro

Ecto-5'-nucleotidase activity was measured in peripheral blood lymphocytes isolated from serial specimens from nine healthy full-term infants and two premature infants at 0, 2, 4, and 6 mo of age. The postnatal nadir in activity was 7.1 +/- 2.0 nmol/hr/10(6) cells, which is the same as the activity in cord blood lymphocytes (7.0 +/- 2 nmol/hr/10(6) cells). The activity rose twofold to 13.2 +/- 3.8 nmol/hr/10(6) cells at 6 mo of age (p less than 0.001, paired t-test), which is similar to the activity in adult peripheral blood lymphocytes (14.1 +/- 6.3 nmol/hr/10(6) cells). This increased activity in total lymphocytes reflects increased activity in the B cell population. B cell ecto-5'-nucleotidase activity in two infants at 12 to 13 mo of age was 19.3 and 25.2 nmol/hr/10(6) cells, values that are four-to fivefold higher than for cord blood B cells (5.6 +/- 2.8 nmol/hr/10(6) cells) and within the normal range for adult B cells (27.9 +/- 12 nmol/hr/10(6) cells). In spite of a greatly expanded peripheral blood B cell population, studies of immunoglobulin biosynthesis in vitro demonstrated that infant peripheral blood B cells are functionally immature with no synthesis of IgG in response to Epstein Barr virus. Thus, the increase in peripheral blood B lymphocyte ecto-5'-nucleotidase activity in infants precedes their acquisition of a capacity for IgG synthesis in vitro. Data from a hypogammaglobulinemic infant revealed a persistently low ecto-5'-nucleotidase activity over a 10-mo period until at 14 mo of age the activity was 8.8 nmol/hr/10(6) cells in total lymphocytes and 13.0 nmol/hr/10(6) cells in B cells, which correlated with in vivo and in vitro evidence of delayed B cell maturation. Thus, ecto-5'-nucleotidase activity may be a useful cell surface marker in studies of human postnatal B cell maturation.     

Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

The maintenance of genetic diversity under host–parasite coevolution in finite,structured populations

As a corollary to the Red Queen hypothesis, host–parasite coevolution has been hypothesized to maintain genetic variation in both species. Recent theoretical work, however, suggests that reciprocal natural selection alone is insufficient to maintain variation at individual loci. As highlighted by our brief review of the theoretical literature, models of host–parasite coevolution often vary along multiple axes (e.g. inclusion of ecological feedbacks or abiotic selection mosaics), complicating a comprehensive understanding of the effects of interacting evolutionary processes on diversity. Here we develop a series of comparable models to explore the effect of interactions between spatial structures and antagonistic coevolution on genetic diversity. Using a matching alleles model in finite populations connected by migration, we find that, in contrast to panmictic populations, coevolution in a spatially structured environment can maintain genetic variation relative to neutral expectations with migration alone. These results demonstrate that geographic structure is essential for understanding the effect of coevolution on biological diversity.