Evolution of Helix Formation in the Ribosomal Internal Transcribed Spacer 2 (ITS2) and Its Significance for RNA Secondary Structures

Helices are the most common elements of RNA secondary structure. Despite intensive investigations of various types of RNAs, the evolutionary history of the formation of new helices (novel helical structures) remains largely elusive. Here, by studying the nuclear ribosomal Internal Transcribed Spacer 2 (ITS2), a fast-evolving part of the eukaryotic nuclear ribosomal operon, we identify two possible types of helix formation: one type is “dichotomous helix formation”—transition from one large helix to two smaller helices by invagination of the apical part of a helix, which significantly changes the shape of the original secondary structure but does not increase its complexity (i.e., the total length of the RNA). An alternative type is “lateral helix formation”—origin of an extra helical region by the extension of a bulge loop or a spacer in a multi-helix loop of the original helix, which does not disrupt the pre-existing structure but increases RNA size. Moreover, we present examples from the RNA sequence literature indicating that both types of helix formation may have implications for RNA evolution beyond ITS2.     

Lifestyle and Ice: The Relationship between Ecological Specialization and Response to Pleistocene Climate Change

Major climatic changes in the Pleistocene had significant effects on marine organisms and the environments in which they lived. The presence of divergent patterns of demographic history even among phylogenetically closely-related species sharing climatic changes raises questions as to the respective influence of species-specific traits on population structure. In this work we tested whether the lifestyle of Antarctic notothenioid benthic and pelagic fish species from the Southern Ocean influenced the concerted population response to Pleistocene climatic fluctuations. This was done by a comparative analysis of sequence variation at the cyt b and S7 loci in nine newly sequenced and four re-analysed species. We found that all species underwent more or less intensive changes in population size but we also found consistent differences between demographic histories of pelagic and benthic species. Contemporary pelagic populations are significantly more genetically diverse and bear traces of older demographic expansions than less diverse benthic species that show evidence of more recent population expansions. Our findings suggest that the lifestyles of different species have strong influences on their responses to the same environmental events. Our data, in conjunction with previous studies showing a constant diversification tempo of these species during the Pleistocene, support the hypothesis that Pleistocene glaciations had a smaller effect on pelagic species than on benthic species whose survival may have relied upon ephemeral refugia in shallow shelf waters. These findings suggest that the interaction between lifestyle and environmental changes should be considered in genetic analyses.     

The Link between Knowledge,Attitudes and Practices in Relation to Atmospheric Haze Pollution in Peninsular Malaysia

Transboundary haze episodes caused by seasonal forest fires have become a recurrent phenomenon in Southeast Asia, with serious environmental, economic, and public health implications. Here we present a cross-sectional survey conducted among people in Kuala Lumpur and surrounds to assess the links between knowledge, attitudes, and practices in relation to the transboundary haze episodes. Of 305 respondents, 125 were amateur athletes participating in a duathlon event and the remainder were surveyed in an inner-city shopping mall. Across the whole sample, people who possessed more factual information about the haze phenomenon showed significantly higher levels of concern. Duathletes were more knowledgeable than non-duathletes and also more concerned about the negative effects of haze, especially on health. For all people who regularly practice outdoor sports (including people interviewed at the shopping mall), higher levels of knowledge and concerned attitudes translated into a greater likelihood of engaging in protective practices, such as cancelling their outdoor training sessions, while those with greater knowledge were more likely to check the relevant air pollution index on a daily basis. Our results indicate that the provision of accurate and timely information about air quality to residents will translate into beneficial practices, at least among particularly exposed individuals, such as amateur athletes who regularly practice outdoor sports.     

Cloning and restriction fragment length polymorphism analysis of a cDNA for swine PIT-1, a gene controlling growth hormone expression*

A partial swine cDNA which encodes the functional domain of PIT-1 was isolated by the polymerse chain reaction (PCR). The swine PIT-1 cDNA clone is 95% identical at the protein level to the rat Pit-1 gene. Thus, Pit-l's known function in control of rat growth hormone and prolactin expression is likely to be conserved in swine. This swine cDNA clone was used to investigate genetic variability at PIT-1 in several American and Chinese breeds. Polymorphic BamIII fragments were found in pure-bred Meishan animals (n= 13), but only monomorphic fragments in five American breeds (n= 36).     

Seroepidemiological study of human hydatidosis and trichinosis, with the indirect hemagglutination reaction, in San Juan de la Costa County. Osorno, X Region, Chile. 1990-1991]

San Juan de la Costa County (40 degrees 45' South lat., 73 degrees 19' West long.) is located in the Osorno province, South of Chile. Its population is 8,486 inhabitants. The basic economic activities are agriculture, cattle raising, timber production and manufacture of wood and coal. According to official reports, the incidence of human hydatidosis and trichinosis in this locality in 1989 were 24 and 59 per 100,000 respectively. In order to contribute to a better knowledge of the epidemiology of human hydatidosis and trichinosis in San Juan de la Costa County, an indirect hemagglutination test (IHAT) for these parasitoses was performed to 511 randomized people. Nine (1.8%) individuals resulted positive for hydatidosis and twenty four (4.7%) were positive for trichinosis. Some considerations on the corresponding prophylactic measures are proposed.     

Synthesis and expression of genes encoding tuna, pigeon, and horse cytochromes c in the yeast Saccharomyces cerevisiae.

Genes encoding tuna, pigeon, and horse cytochromes c were constructed with synthetic oligodeoxyribonucleotides having preferred codons and portions of the iso-1-cytochrome c-encoding gene from the yeast Saccharomyces cerevisiae. The genes were ligated into an expression vector, which contains the normal 5'- and 3'-untranslated regions of the yeast iso-1-cytochrome c gene, and were integrated in single copy into the chromosome. Yeast strains were also constructed with multiple integrated copies of the pigeon gene. The heterologous and normal mRNA levels of the single-copy strains were equivalent. Although the N-terminal methionines were completely cleaved in the heterospecific proteins, the levels of trimethylation of Lys72 and acetylation of N-terminal glycines ranged from 39-78% and 10-70%, respectively. Horse cytochrome c was produced at a nearly normal level, whereas the pigeon and tuna cytochromes c were produced at approx. 40% of the normal levels. The levels of the cytochromes c and growth of the mutant yeast strains indicated that the heterospecific cytochromes c had approx. 50% specific activity in vivo.