Structural features and evolutionary considerations of group IB introns in SSU rDNA of the lichen fungus Teloschistes

Different species of the lichen-forming ascomycete fungus Teloschistes were found to contain group IB introns at position S1506 in the small subunit ribosomal RNA gene. We have characterized the structural organization and phylogeny of the Teloschistes introns Tco.S1506, Tla.S1506, and Tvi.S1506. Common features to all the introns are a small size, a compact RNA structure, and an atypical catalytic ribozyme core sequence motif. Variations in intron sizes, due to sequence extensions in the P1 and P8 loop segments, were observed in different species and isolates. Phylogenetic analyses based on the ITS1-5.8S-ITS2 region as well as the introns show that the Teloschistes S1506 introns represent a distinct evolutionary isolated cluster among the nuclear group I introns. Furthermore, introns from different lineages of Teloschistes villosus appear not strictly vertically inherited probably due to horizontal transfer in one of the lineages.     

Leptin expression in human primary skeletal muscle cells is reduced during differentiation

We found leptin to be strongly expressed in undifferentiated human myoblasts derived from biopsies of the thigh (Musculus vastus lateralis). Both mRNA expression and secretion of leptin were reduced during in vitro differentiation into primary myotubes. However, the expression of the leptin receptor (OB-Rb) mRNA, was unchanged during differentiation of the muscle cells. Administration of recombinant leptin had no effect on leptin, myogenin, myoD, or GLUT4 mRNA expressions during the period of cellular differentiation. A functional leptin receptor was demonstrated by an acute leptin-induced 1.5-fold increase in ERK activity (P = 0.029). Although mRNA expression of regulation of suppressor of cytokine signaling-3 (SOCS-3) mRNA expression was unaltered, leptin significantly stimulated fatty acid oxidation after 6 h measured as acid soluble metabolites (ASM). Palmitic acid (PA), oleic acid (OA), and eicosapentaenoic acid (EPA), known to modulate leptin expression in other tissues, had no effect on mRNA expression or secretion of leptin from human myotubes. In conclusion, we demonstrate that leptin is highly expressed in undifferentiated human myoblasts and the expression is reduced during differentiation to mature myotubes. The role of leptin in these cells needs to be further characterized.     

The geology of the Øvre Heimdalen valley

Øvre Heimdalsvatn is clearly influenced by the geological conditions, and the lake basin and catchment area are determined by the bedrock and the mountain structures. The distribution and characteristics of the loose deposits are decisive for the lake's water budget. The groundwater in the catchment area and the Quaternary deposits near the lake influence the amount and quality of the lake waters.     

Generic ecological impact assessments of alien species in Norway: a semi-quantitative set of criteria

The ecological impact assessment scheme that has been developed to classify alien species in Norway is presented. The underlying set of criteria enables a generic and semi-quantitative impact assessment of alien species. The criteria produce a classification of alien species that is testable, transparent and easily adjustable to novel evidence or environmental change. This gives a high scientific and political legitimacy to the end product and enables an effective prioritization of management efforts, while at the same time paying attention to the precautionary principle. The criteria chosen are applicable to all species regardless of taxonomic position. This makes the assessment scheme comparable to the Red List criteria used to classify threatened species. The impact of alien species is expressed along two independent axes, one measuring invasion potential, the other ecological effects. Using this two-dimensional approach, the categorization captures the ecological impact of alien species, which is the product rather than the sum of spread and effect. Invasion potential is assessed using three criteria, including expected population lifetime and expansion rate. Ecological effects are evaluated using six criteria, including interactions with native species, changes in landscape types, and the potential to transmit genes or parasites. Effects on threatened species or landscape types receive greater weightings.     

Optimal age of maturity in fluctuating environments under r‐ and K‐selection

Optimality models for evolution of life histories have shown that increased environmental stochasticity promotes early age of maturity. Here we argue that if r‐selection for early maturation implies a tradeoff making those phenotypes more sensitive to a change in population size than phenotypes maturing at older ages, K‐selection can favor delayed onset of maturation. We analyze a general stochastic Leslie‐matrix model with a simplified density regulation affecting all survivals equally through a function of the population vector, often called the ‘critical age class’. We show that the outcome of such an age‐dependent r‐ and K‐selection is that the expected value of the ‘critical age class’ is maximized by evolution, a strategy strongly influenced by the magnitude of the environmental stochasticity. We also demonstrate that evolution caused by such density‐dependent selection influences the population dynamics, showing a possible reciprocal effect between ecology and evolution in age‐structured populations. This modeling approach reveals that changes in population size affecting the fitness of phenotypes with different age of maturity may be an important selective agent for variation in onset of reproduction in fluctuating environments. This provides a testable hypothesis for how patterns in the population dynamics should affect life history variation.     

Enhanced cancer cell invasion caused by fibroblasts when fluid flow is present

Biomechanics and Modeling in Mechanobiology - It has been demonstrated that interstitial fluid (IF) flow can play a crucial role in tumor cell progression. Swartz and collaborators (Cancer Cell 11:...     

Mitogenome polymorphism in a single branch sample revealed by SOLiD deep sequencing of the Lophelia pertusa coral genome

We present an initial genomic analysis of the non-symbiotic scleractinian coral Lophelia pertusa, the dominant cold-water reef-building coral species in the North Atlantic Ocean. A significant fraction of the deep sequencing reads was of mitochondrial and microbial origins. SOLiD deep sequencing reads from fragment library experiments of total DNA and PCR amplified mitogenome generated about 21,000 times and 136,000 times coverage, respectively, of the 16,150bp mitogenome. Five polymorphic sites that include two non-synonymous sites in the NADH dehydrogenase subunit 5 genes were detected in both experiments. This observation is surprising since anthozoans in general exhibit very low mtDNA sequence variation at intraspecific level compared to nuclear sequences. More than fifty bacterial species associated with the coral isolate were also sequence detected, representing at least ten complete genomes. Most reads, however, were predicted to originate from the Lophelia nuclear genome.