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.     

A nuclear magnetic resonance study of the glucose metabolism of Hymenolepis diminuta exposed to histamine and serotonin in vitro.

The direct effects of the inflammatory mediators, histamine (HI) and serotonin (SE), on the glucose metabolism of Hymenolepis diminuta in vitro were studied by analyzing the excretory products from culture media, containing D-1-13C-glucose and various concentrations of HI and/or SE, by 1H-nuclear magnetic resonance (n.m.r.) spectroscopy. The results revealed that HI markedly accelerated the glycolysis process by increasing the amount of lactate production. The increased glycolytic activity was reflected in a concentration-dependent increase in glucose uptake. Excretion of acetate was also stimulated by HI. A low concentration of SE significantly increased succinate, acetate and lactate excretions, whereas a high concentration had little effect on lactate production and significantly decreased succinate and acetate excretions. A combination of HI and SE treatment at a low concentration had no significant effect, but at a high concentration showed an additive effect, with an increase in lactate production, a decrease in succinate production and an increase in glucose uptake. Thus this work confirms that HI and SE directly influence, albeit differently, energy metabolism of the tapeworm H. diminuta.     

Nutrition and inflammatory events: highly unsaturated fatty acids (omega-3 vs omega-6) in surgical injury.

Given the poor prognosis and high cost of care for patients with acute inflammatory responses (often leading to organ failure and/or allograft rejection), immunomodulation of this hyperresponse represents an important priority for research in nutritional medicine. The primary goal of nutritional support in inflammatory disease is to provide adequate energy, particularly through use of novel lipids (to alter eicosanoid pathway toward a more regulated inflammatory state), and protein to meet endogenous requirements for tissue repair IL-1 production, and restored cellular function, thus preventing secondary infection (52). Manipulation of macrophage eicosanoid production by use of omega-3 PUFA may reduce the cellular immune response (by competing with arachidonic acid, which produces inflammatory eicosanoids of the 2- and 4-series), whereas inclusion of MCT found in coconut oil may lower the arachidonic acid content of membrane phospholipids. As more data are obtained on the use of such tailored therapies in critically ill patients, a new generation of parenteral and enteral diets will be developed to reduce inflammation and immune dysfunction.     

The telomere terminal transferase of Tetrahymena is a ribonucleoprotein enzyme with two kinds of primer specificity

We have analyzed the de novo telomere synthesis catalyzed by the enzyme telomere terminal transferase (telomerase) from Tetrahymena. Oligonucleotides representing the G-rich strand of telomeric sequences from five different organisms specifically primed the addition of TTGGGG repeats in vitro, suggesting that primer recognition may involve a DNA structure unique to these oligonucleotides. The sequence at the 3' end of the oligonucleotide primer specified the first nucleotide added in the reaction. Furthermore, the telomerase was shown to be a ribonucleoprotein complex whose RNA and protein components were both essential for activity. After extensive purification of the enzyme by a series of five different chromatographic steps, a few small low abundance RNAs copurified with the activity.     

Dynamics of telomere length variation in Tetrahymena thermophila

We have analyzed the mechanism and dynamics of telomere length variation in the macronucleus of Tetrahymena thermophila. In a newly differentiated macronucleus, the average length of the telomeric repeated sequence, (C4A2 X T2G4)n, is closely regulated. In contrast, in vegetatively dividing cells in log phase, all macronuclear telomeric sequences lengthen coordinately by 3-10 bp per generation until up to 1000 bp are added. In both elongated and short telomeres, characteristic single-stranded breaks on both strands are distally located. Reduction of elongated telomeres to their original length involves either the appearance of a novel type of variant cell, incapable of net telomere elongation, or, under stationary phase conditions, a reversible removal of telomeric sequences. The demonstration that telomeres are dynamic structures provides evidence for a model of telomere length regulation by activities that add and remove telomeric repeats.     

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.     

The bioflavonoid quercetin inhibits neutrophil degranulation, superoxide production, and the phosphorylation of specific neutrophil proteins

Quercetin, a C-kinase antagonist, inhibits neutrophil degranulation and superoxide production induced by f-met-leu-phe, solid phase IgG, zymosan treated serum and a phorbol ester (PMA). Quercetin is more effective in inhibiting degranulation (IC50 = 20 uM) than superoxide production (IC50 = 80 microM). Neutrophil activation by PMA is accompanied by the phosphorylation of neutrophil proteins of 205, 170, 130, 91, 77, 67, 56, 47, 39, 34, 27, and 20 kilodaltons; quercetin also inhibits the phosphorylation of these proteins. Dose-response studies indicated that phosphorylation of the 67 kilodalton protein was particularly sensitive to inhibition by quercetin at concentrations that also inhibit neutrophil degranulation and superoxide production. These results suggest that phosphorylation of the 67 kilodalton protein may be an important intracellular reaction associated with neutrophil activation.     

Further characterization of the interaction of histidine-rich glycoprotein with heparin: evidence for the binding of two molecules of histidine-rich glycoprotein by high molecular weight heparin and for the involvement of histidine residues in heparin binding

Rabbit histidine-rich glycoprotein (HRG, 94 kDa) binds heparin with high affinity (apparent Kd 60-110 nM). Eosin Y (1 equiv) bound to HRG was used as a reporter group to monitor associations of HRG with heparins of molecular mass 10, 17.5, and 30 kDa. The stoichiometries of the heparin-HRG complexes were determined by fluorescence and absorbance measurements as well as by analytical ultracentrifugation. Two types of complex form: complexes of 1 heparin:1 HRG and of 1 heparin:2 HRG. The 1:2 complex formation requires a minimum heparin chain length since 17.5-kDa but not 10-kDa heparin binds two HRG molecules. The formation of the 1:2 complexes of the larger heparin fractions is enhanced by divalent copper or zinc (1-10 equiv) bound to HRG. However, metal is not required for complex formation since all sizes of heparin examined interact tightly with HRG in the presence of ethylenediaminetetraacetic acid. Between 0.1 and 0.3 M ionic strength, both 1:1 and 1:2 complexes of heparin with HRG are progressively destabilized. No heparin-HRG complex is found at ionic strengths of 0.5 M. Between pH 8.5 and pH 6.5 both 1:2 and 1:1 complexes are found with 17.5-kDa heparin, but at pH 5.5 only 1:1 complexes are formed. The heparin-HRG interaction is progressively decreased by modification of the histidine residues of HRG, whereas modification of 22 of the 33 lysine residues of HRG has little effect.(ABSTRACT TRUNCATED AT 250 WORDS)