Genomic Consequences of Ecological Speciation in Astyanax Cavefish

The cave environment is consistently radically different than the surface environment because it lacks light, and animals adapting to cave life are subject to strong selective forces much different than those experienced by their ancestors who evolved in the presence of light. As such, their divergence from surface ancestors and eventual speciation is likely to be driven by the shift in ecology. We report here that hybrids between cave and surface Astyanax mexicanus fishes produce offspring with allelic frequencies that differ significantly from Mendelian expectations both for transmission ratios and for independent assortment of unlinked markers. Comparison of allelic content of DNA from fin clips and sperm pools show that the transmission ratio distortion likely occurs during spermatogenesis. Departures from expectations of independent assortment are essentially epistatic phenomena generating linkage disequilibrium. A novel analysis of the epistatic interactions reveals an apparent network of interactions among genes known or suspected to be involved in cave adaptation, implying that the epistasis arose as a “by product” of the divergence due to cave adaptation.     

<Superscript>15</Superscript>N natural abundance of fossil peat reflects the influence of animal-derived nitrogen on vegetation

'¹⁵N signatures of fossil peat were used to interpret past ecosystem processes on tectonically active subantarctic Macquarie Island. By comparing past vegetation reconstructed from the fossil record with present-day vegetation analogues, our evidence strongly suggests that changes in the '¹⁵N signatures of fossil peat at this location reflect mainly past changes in the proportion of plant nitrogen derived from animal sources. Associated with uplift above sea level over the past 8,500 years, fossil records in two peat deposits on the island chronicle a change from coastal vegetation with fur and elephant seal disturbance to the existing inland herbfield. Coupled with this change are synchronous changes in the '¹⁵N signatures of peat layers. At two sites ¹⁵N-enriched peat '¹⁵N signatures of up to +17‰ were associated with a high abundance of pollen of the nitrophile Callitriche antarctica (Callitrichaceae). At one site fossil seal hair was also associated with enriched peat '¹⁵N. Less ¹⁵N enriched '¹⁵N signatures (e.g. -1.9‰ to +3.9‰) were measured in peat layers which lacked animal associated C. antarctica and Acaena spp. Interpretation of a third peat profile indicates continual occupation of a ridge site by burrowing petrels for most of the Holocene. We suggest that ¹⁵N signatures of fossil peat remained relatively stable with time once deposited, providing a significant new tool for interpreting the palaeoecology.     

Prolactin messenger ribonucleic acid concentrations throughout the ovine estrous cycle: assessment relative to prolactin serum and pituitary amounts

Prolactin (PRL) mRNA concentrations were assessed by nucleic acid hybridization assays in pituitaries of ewes representing the defined stages of the ovine estrous cycle. Concomitantly, pituitary and serum PRL concentrations were measured in these ewes using radioimmunoassays. It was observed that PRL serum, pituitary and mRNA concentrations tended to increase near the time of the gonadotropin preovulatory surge, particularly between 24 hrs before behavioral estrus to 5 hours after estrus. However, the changes in PRL mRNA, serum and pituitary concentrations were shown not to be statistically significant. These data suggest that PRL production during the sheep estrous cycle is maintained without dramatic changes in synthesis or secretion.     

A polymorphism of the complement regulatory protein MCP (membrane cofactor protein or gp45-70)

Membrane cofactor protein (MCP or gp45-70) is a recently described regulatory glycoprotein of the complement system which binds iC3 or C3b and is present on human platelets, T cells, B cells, monocytes, and mononuclear-derived cell lines. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, MCP migrates as a doublet with an Mr of the upper band of 63,000 and the lower band of 58,000. The same pattern was found on all cell populations in a given individual and was stable over time. In order to further characterize the two band pattern on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, MCP was isolated by affinity chromatography or immunoprecipitation from 72 healthy unrelated donors. All individuals expressed both bands and, based on the densitometric scanning of gels, three patterns were noted: upper band predominant in 65%, approximately equal distribution of upper and lower bands in 29%, and lower band predominant in 6%. These observed phenotypic frequencies fit with expectations based on Hardy-Weinberg equilibrium for a two-allele system. Family studies also support this model as none of the 26 offspring had a phenotype that deviated from the expected, assuming an autosomal codominant model of inheritance. These results are consistent with a simple two-allele system that controls the expression of the two bands of MCP.     

Hormonal regulation of estradiol biosynthesis, aromatase activity, and aromatase mRNA in rat ovarian follicles and corpora lutea

To determine the molecular basis for changes in aromatase (P450arom) activity in rat ovarian follicles and corpora lutea, seven clones for rat P450arom cDNA have been identified and isolated from a rat granulosa cell λgtll cDNA expression library using a 62 mer deoxyoligonucleotide probe (derived from an amino acid sequence of purified human placental aromatase) and a human placental P450arom cDNA probe. One of the rat P450arom cDNA clones contained an insert 1.2 kb in size. Both the human 1.8 kb cDNA and the rat 1.2 kb cDNA probes hybridized to a single species of P450arom mRNA that was 2.6 kb in size. Northern blot analysis revealed that corpora lutea isolated on day 15 of pregnancy contained high amounts of P450arom mRNA, whereas granulosa cells of antral follicles of hormonally primed, hypophysectomized rats (i.e., those from which mRNA was isolated to construct the cDNA library) contained only low amounts of P450arom mRNA. The lower amounts of P450arom in granulosa cells of preovulatory follicles in the estradiol-follicle-stimulating hormone primed hypophysectomized rats were unexpected because follicles incubated in medium containing testosterone substrate produce more estradiol than do corpora lutea isolated on day 15 of pregnancy and incubated under similar conditions. Additional studies will determine the hormonal events responsible for the elevated amounts and constitutive maintenance of P450arom mRNA and aromatase activity in luteal cells in vivo and in vitro.     

C-terminal bombesin sequence requirements for binding and effects on protein synthesis in Swiss 3T3 cells.

The active-site serine of the extracellular beta-lactamases of Streptomyces cacaoi and Streptomyces albus G has been labelled with beta-iodopenicillanate. The determination of the sequence of the labelled peptides obtained after trypsin digestion of the denatured proteins indicate both enzymes to be class A beta-lactamases. Surprisingly the two Streptomyces enzymes do not appear to be especially homologous, and none of them exhibited a high degree of homology with the Streptomyces R61 DD-peptidase. Our data confirm that, as a family of homologous enzymes, class A is rather heterogeneous, with only a small number of conserved residues in all members of the class.     

Calcitonin gene-related peptide immunoreactivity in airway epithelial cells of the human fetus and infant

Summary Calcitonin gene-related peptide-immunoreactive cells were identified within the epithelium of distal conducting airways in the human fetus and infant. Several peptides and amines, including calcitonin, have been identified previously within a specific population of airway epithelial cells. These cells, referred to as pulmonary neuroendocrine cells, are postulated to be airway chemoreceptors responsible for changes in ventilation and perfusion in response to changes in airway gas composition. Calcitonin gene-related peptide immunoreactive cells could be identified throughout the period of development studies (20 weeks gestation to 3 months of age), but were present in only limited numbers in less than 50% of individuals (n=23). In contrast, large numbers of calcitonin gene-related peptide immunoreactive cells were identified in 100% of infants (1–3 months, n=5) with bronchopulmonary dysplasia. The differential processing of mRNA transcribed from the calcitonin gene in neural and non-neural tissue suggests that calcitonin, rather than calcitonin gene-related peptide, is the primary product of translation in pulmonary neuroendocrine cells. However, considering the potent vasodilatory and bronchoconstrictive effects of calcitonin gene-related peptide, its presence in pulmonary neuroendocrine cells, even in small amounts, may be important in controlling pulmonary vaso- and/or bronchomotor tone. The presence of large numbers of calcitonin gene-related peptide immunoreactive cells in infants with bronchopulmonary dysplasia suggests that calcitonin gene-related peptide may be one further agent contributing to the pulmonary pathophysiology seen in this disease.     

Rhodobacter capsulatus strain BK5 possesses a membrane bound respiratory nitrate reductase rather than the periplasmic enzyme found in other strains

Rhodobacter capsulatus strain BK5 possesses a membrane bound respiratory nitrate reductase rather than the periplasmic enzyme found in other strains. The enzyme in strain BK5 is shown to be both functionally and structurally related to the nitrate reductase of Paracoccus denitrificans and Escherichia coli.Abbreviation TMAO trimethylamine-N-oxide