MicroRNA Regulation in Extreme Environments:Differential Expression of MicroRNAs in the Intertidal Snail Littorina littorea During Extended Periods of Freezing and Anoxia

Several recent studies of vertebrate adaptation to environmental stress have suggested roles for microRNAs (miRNAs) in regulating glo- bal suppression of protein synthesis and/or restructuring protein expression patterns. The present study is the first to characterize stress-responsive alterations in the expression of miRNAs during natural freezing or anoxia exposures in an invertebrate species, the intertidal gastropod Littorina littorea. These snails are exposed to anoxia and freezing conditions as their environment constantly fluctuates on both a tidal and seasonal basis. The expression of selected miRNAs that are known to influence the cell cycle, cellular signaling pathways, carbohydrate metabolism and apoptosis was evaluated using RT-PCR. Compared to controls, significant changes in expression were observed for miR-1a-1, miR-34a and miR-29b in hepatopancreas and for miR-1a-1, miR-34a, miR-133a, miR-125b, miR-29b and miR-2a in foot muscle after freezing exposure at 6 °C for 24 h (P < 0.05). In addition, in response to anoxia stress for 24 h, significant changes in expression were also observed for miR-1a-1, miR-210 and miR-29b in hepatopancreas and for miR-1a-1, miR-34a, miR-133a, miR-29b and miR-2a in foot muscle (P < 0.05). Moreover, protein expression of Dicer, an enzyme responsible for mature microRNA processing, was increased in foot muscle during freezing and anoxia and in hepatopancreas during freezing. Alterations in expression of these miRNAs in L. littorea tissues may contribute to organismal survival under freezing and anoxia.     

Genomic affinities in Arachis section Arachis (Fabaceae): molecular and cytogenetic evidence

Section Arachis is the largest of nine sections in the genus Arachis and includes domesticated peanut, A. hypogaea L. Most species are diploids (x=10) with two tetraploids and a few aneuploids. Three genome types have been recognized in this section (A, B and D), but the genomes are not well characterized and relationships of several newly described species are uncertain. To clarify genomic relationships in section Arachis, cytogenetic information and molecular data from amplified fragment length polymorphism (AFLP) and the trnT-F plastid region were used to provide an additional insight into genome composition and species relationships. Cytogenetic information supports earlier observations on genome types of A. cruziana, A. herzogii, A. kempff-mercadoi and A. kuhlmannii but was inconclusive about the genome composition of A. benensis, A. hoehnei, A. ipaensis, A. palustris, A. praecox and A. williamsii. An AFLP dendrogram resolved species into four major clusters and showed A. hypogaea grouping closely with A. ipaensis and A. williamsii. Sequence data of the trnT-F region provided genome-specific information and showed for the first time that the B and D genomes are more closely related to each other than to the A genome. Integration of information from cytogenetics and biparentally and maternally inherited genomic regions show promise in understanding genome types and relationships in Arachis.     

Partial recovery of neutrophil functions during prolonged hypothermia in pigs

The changes in circulation and migration of mature and immature neutrophils during 12 h of hypothermia have been studied using an experimental pig model. At 29 degrees C the number of circulating neutrophils fell from 5 +/- 1.1 at 37 degrees C to 3.5 +/- 0.6 X 10(9)/l and then remained unchanged while hypothermia was maintained. The number of circulating immature neutrophils did not fall during hypothermia. During hypothermia, hydrocortisone failed to stimulate the release of mature and immature neutrophils from the bone marrow. In contrast, endotoxin caused a profound neutropenia followed by a gradual increase in the number of circulating mature neutrophils, which by 6 h, was similar to the number circulating before endotoxin administration. At 29 degrees C the number of circulating immature neutrophils also fell following endotoxin but then increased over the number circulating before endotoxin administration by approximately 10-fold. Compared with neutrophil migration at 37 degrees C, very few mature or immature neutrophils migrated to an inflammatory site during the 12 h of hypothermia (29 degrees C). Unlike hypothermia in vitro, where neutrophil function may improve with time in vivo, neutrophil function remains compromised.     

The simple repeat poly(dT-dG).poly(dC-dA) common to eukaryotes is absent from eubacteria and archaebacteria and rare in protozoans

Genomic DNA from a wide variety of prokaryotic and eukaryotic organisms has been assayed for the simple repeat sequence poly(dT-dG).poly(dC-dA) by Southern blotting and DNA slot blot hybridizations. Consistent with findings of others, we have found the simple alternating sequence to be present in multiple copies in all organisms in the animal kingdom (e.g., mammals, reptiles, amphibians, fish, crustaceans, insects, jellyfish, nematodes). The TG element was also found in lower eukaryotes (Saccharomyces cerevisiae, Neurospora crassa, and Dictyostelium discoideum) and at a much lower frequency in protozoans (Oxytricha fallux and Tetrahymena thermophila). The sequence was also repeated in high copy number in a higher plant (Zea mays) as well as at very high levels in a unicellular green alga (Chlamydomonas reinhardi). Although the copy number of the repeat per haploid genome was generally proportional to genome size, there was a greater-than-1,000-fold variation in the number of (TG)25/100-kb genomic DNA. By contrast, no eu-or archaebacterium--including Myxococcus xanthus, whose life cycle is very similar to that of the slime mold Dictyostelium discoideum, and Halobacter volcanii, whose genome contains other repeated sequences-- was found whose genomic DNA contained this sequence in detectable amounts. A computer search also failed to find the TG element in human mitochondrial DNA.      

The use of infants in drug research when there is no direct benefit to them: a survey of Canadian health care professionals serving on ethics committees.

Canadian health care professionals and lawyers serving on ethics committees were questioned about their views on pharmacokinetic research in newborn infants who are not likely to benefit directly from the results. Of the 50 respondents 13 felt that blood samples should be taken only for therapeutic reasons; 10 of the 13 argued that additional blood samples should not be taken, because there is no direct benefit to the infant; and 8 felt that proxy consent cannot be given for invasive nontherapeutic research. Four of the five participating lawyers would not permit additional blood samples to be taken. Of the 37 respondents who would permit additional blood samples to be taken, 27 felt that the number of samples taken should depend on the researcher''s justification for that number of samples; only 7 of the respondents had a clear idea of what the "upper limit" of the number of blood samples should be.     

Protein evolution in different cellular environments: cytochrome b in sharks and mammals

DNA sequences for the mitochondrial cytochrome b gene were determined for 13 species of sharks. Rates and patterns of amino acid replacement are compared for sharks and mammals. Absolute rates of cytochrome b evolution are six times slower in sharks than in mammals. Bivariate plots of the number of nonsynonymous and silent transversions are indistinguishable in the two groups, however, suggesting that the differences in amino acid replacement rates are due primarily to differences in DNA substitution rates. Patterns of amino acid replacement are also similar in the two groups. Conserved and variable regions occur in the same parts of the cytochrome b gene, and there is little evidence that the types of amino acid changes are significantly different between the groups. Similarity in the relative rates and patterns of protein change between the two groups prevails despite dramatic differences in the cellular environments of sharks and mammals. Poor penetrance of physiological differences through to rates of protein evolution provides support for the neutral theory and suggests that, for cytochrome b, patterns of evolution have been relatively constant throughout much of vertebrate history.