Evolution of sperm structure and energetics in passerine birds

Spermatozoa exhibit considerable interspecific variability in size and shape. Our understanding of the adaptive significance of this diversity, however, remains limited. Determining how variation in sperm structure translates into variation in sperm performance will contribute to our understanding of the evolutionary diversification of sperm form. Here, using data from passerine birds, we test the hypothesis that longer sperm swim faster because they have more available energy. We found that sperm with longer midpieces have higher levels of intracellular adenosine triphosphate (ATP), but that greater energy reserves do not translate into faster-swimming sperm. Additionally, we found that interspecific variation in sperm ATP concentration is not associated with the level of sperm competition faced by males. Finally, using Bayesian methods, we compared the evolutionary trajectories of sperm morphology and ATP content, and show that both traits have undergone directional evolutionary change. However, in contrast to recent suggestions in other taxa, we show that changes in ATP are unlikely to have preceded changes in morphology in passerine sperm. These results suggest that variable selective pressures are likely to have driven the evolution of sperm traits in different taxa, and highlight fundamental biological differences between taxa with internal and external fertilization, as well as those with and without sperm storage.     

Population characteristics predict responses in moose body mass to temporal variation in the environment

1. A general problem in population ecology is to predict under which conditions stochastic variation in the environment has the stronger effect on ecological processes. By analysing temporal variation in a fitness-related trait, body mass, in 21 Norwegian moose Alces alces (L.) populations, we examined whether the influence of temporal variation in different environmental variables were related to different parameters that were assumed to reflect important characteristics of the fundamental niche space of the moose. 2. Body mass during autumn was positively related to early access to fresh vegetation in spring, and to variables reflecting slow phenological development (low June temperature, a long spring with a slow plant progression during spring). In contrast, variables related to food quantity and winter conditions had only a minor influence on temporal variation in body mass. 3. The magnitude of the effects of environmental variation on body mass was larger in populations with small mean body mass or living at higher densities than in populations with large-sized individuals or living at lower densities. 4. These results indicate that the strongest influence of environmental stochasticity on moose body mass occurs towards the borders of the fundamental niche space, and suggests that populations living under good environmental conditions are partly buffered against fluctuations in environmental conditions.     

Phylogenetic footprinting of non-coding RNA: hammerhead ribozyme sequences in a satellite DNA family of <Emphasis Type="Italic">Dolichopoda</Emphasis>cave crickets (Orthoptera,Rhaphidophoridae)

Background  

The great variety in sequence, length, complexity, and abundance of satellite DNA has made it difficult to ascribe any function to this genome component. Recent studies have shown that satellite DNA can be transcribed and be involved in regulation of chromatin structure and gene expression. Some satellite DNAs, such as the pDo500 sequence family in Dolichopoda cave crickets, have a catalytic hammerhead (HH) ribozyme structure and activity embedded within each repeat.     

DNA sequence profiles of the colorectal cancer critical gene set KRAS-BRAF-PIK3CA-PTEN-TP53 related to age at disease onset

The incidence of colorectal cancer (CRC) increases with age and early onset indicates an increased likelihood for genetic predisposition for this disease. The somatic genetics of tumor development in relation to patient age remains mostly unknown. We have examined the mutation status of five known cancer critical genes in relation to age at diagnosis, and compared the genomic complexity of tumors from young patients without known CRC syndromes with those from elderly patients. Among 181 CRC patients, stratified by microsatellite instability status, DNA sequence changes were identified in KRAS (32%), BRAF (16%), PIK3CA (4%), PTEN (14%) and TP53 (51%). In patients younger than 50 years (n = 45), PIK3CA mutations were not observed and TP53 mutations were more frequent than in the older age groups. The total gene mutation index was lowest in tumors from the youngest patients. In contrast, the genome complexity, assessed as copy number aberrations, was highest in tumors from the youngest patients. A comparable number of tumors from young (<50 years) and old patients (>70 years) was quadruple negative for the four predictive gene markers (KRAS-BRAF-PIK3CA-PTEN); however, 16% of young versus only 1% of the old patients had tumor mutations in PTEN/PIK3CA exclusively. This implies that mutation testing for prediction of EGFR treatment response may be restricted to KRAS and BRAF in elderly (>70 years) patients. Distinct genetic differences found in tumors from young and elderly patients, whom are comparable for known clinical and pathological variables, indicate that young patients have a different genetic risk profile for CRC development than older patients.     

Responsiveness of selected condition measures of herring, Clupea harengus, larvae to starvation in relation to ontogeny and temperature

A laboratory experiment was performed to study the responsiveness of selected condition measures to starvation in herring, Clupea harengus, larvae in relation to temperature and ontogeny. The larvae at two intervals of development, i.e. stage 1 larvae with initial exogenous feeding and stage 2 larvae with established feeding prior to notochord flexion, were reared at three temperatures (5, 8 and 11°C) and subjected to sub-lethal durations of starvation. Temporal changes in standard length, dry weight, DNA concentration (% of dry weight), RNA concentration (% of dry weight), Fulton's condition factor (CF) and RNA/DNA were assessed and compared with fed controls. Starvation led to decreases in dry weight, CF, RNA concentration and RNA/DNA, while it led to an increase in DNA concentration. Higher responsiveness to starvation was observed at higher temperatures, and the magnitude of the changes was higher in stage 2 larvae. The shortest latency in starvation response was found with respect to RNA/DNA which was length independent in the size range studied. RNA/DNA was also significantly related to average DNA growth rate, and the model for DNA growth rate was, SGRDNA=4.49 RNA/DNA + 7.14 T – 0.42 T2 – 37.5 ; n=32, r2=0.85, p < 0.001). While the model seemed to adequately represent the average temperature dependent DNA growth, a relatively low classification success made it unsuitable for depicting individually starving larvae. Critical levels in DNA concentration can be used (2.2% for stage 1 larvae, 2.9% for stage 2 larvae) to differentiate starving larvae (after 3 – 5 days) from feeding larvae. RNA/DNA was the most sensitive and suitable condition index studied in detecting early starvation of herring larvae.     

Day and night temperature responses in Arabidopsis: effects on gibberellin and auxin content,cell size,morphology and flowering time

The effect of 16 different day (DT) and night (NT) temperature combinations (DT and NT 12, 17, 22 and 27 degrees C) on rosette leaf growth, flower stem elongation and flowering time in Arabidopsis thaliana Ler was investigated. Final leaf length decreased with increasing NT due to a combination of reduced elongation period and reduced elongation rate. Final stem length increased with increasing DT due to increased elongation rate, and decreased with increasing NT due to a decrease in elongation period. Under NT 27 degrees C, however, stem elongation rate increased greatly, resulting in the same final stem length as under NT 12 degrees C. The transition to flowering was accelerated by increasing NT. A linear regression analysis was performed to clarify the relationship between final leaf length, final stem length and flowering time with DIF (DT minus NT) and/or ADT (average daily temperature). For all three variables, the effect of DIF depended on ADT and vice versa. The relationship of final stem length with DIF also depended on the temperature range. Increased cell volume in flower stems developing at DT/NT 22/12 degrees C gave rise to longer and thicker stems compared with stems developing at DT/NT 12/22 degrees C. GC-MS analysis (gas chromatography-mass spectrometry) showed that the endogenous level of IAA was 56 % higher in stems grown under DT/NT 22/12 degrees C compared with DT/NT 12/22 degrees C. Of the 12 gibberellins analysed, however, only the level of non-bioactive GA29 was affected by the temperature treatment.     

Oxygen influences benzyladenine and 2,4-dichlorophenoxyacetic acid levels in cultured embryogenic tissue of Norway spruce

It is known that reducing the partial pressure of O₂ influences the induction of somatic embryogenesis. We tested the hypothesis that O₂ causes changes in the endogenous levels of exogenously supplied benzyladenine (BA) or 2,4-dichlorophenoxyacetic acid (2,4-D). Embryogenic tissue of Picea abies was incubated under reduced (2.5, 5 kPa) and ambient (21 kPa) levels of O₂ for 1, 3, 7 and 11 days and the endogenous concentrations of BA and 2,4-D were measured. For all treatments the concentration of BA in the tissue increased until the third day. At day 3, the ratio of BA in the tissue relative to the initial concentration in the medium, was 3.9, 2.8 and 1.9 for tissue incubated under 2.5, 5 and 21 kPa O₂, respectively. The BA concentration then declined gradually. Uptake of 2,4-D was inhibited at low O₂ levels. However, 2,4-D gradually accumulated in tissue grown under hypoxia, so that high levels were reached by day 11. These shifts in the BA and 2,4-D levels also caused a transient increase in the BA to 2,4-D ratio in tissue incubated under hypoxia. Although relevant for the previously reported effects of oxygen on induction of embryogenic tissue, it is unlikely that oxygen-induced alterations in BA and 2,4-D levels alone suffice to explain these findings.     

PepeSearch: Semantic Data for the Masses

With the emergence of the Web of Data, there is a need of tools for searching and exploring the growing amount of semantic data. Unfortunately, such tools are scarce and typically require knowledge of SPARQL/RDF. We propose here PepeSearch, a portable tool for searching semantic datasets devised for mainstream users. PepeSearch offers a multi-class search form automatically constructed from a SPARQL endpoint. We have tested PepeSearch with 15 participants searching a Linked Open Data version of the Norwegian Register of Business Enterprises for non-trivial challenges. Retrieval performance was encouragingly high and usability ratings were also very positive, thus suggesting that PepeSearch is effective for searching semantic datasets by mainstream users. We also assessed its portability by configuring PepeSearch to query other SPARQL endpoints.     

Simvastatin Inhibits Glucose Metabolism and Legumain Activity in Human Myotubes

Simvastatin, a HMG-CoA reductase inhibitor, is prescribed worldwide to patients with hypercholesterolemia. Although simvastatin is well tolerated, side effects like myotoxicity are reported. The mechanism for statin-induced myotoxicity is still poorly understood. Reports have suggested impaired mitochondrial dysfunction as a contributor to the observed myotoxicity. In this regard, we wanted to study the effects of simvastatin on glucose metabolism and the activity of legumain, a cysteine protease. Legumain, being the only known asparaginyl endopeptidase, has caspase-like properties and is described to be involved in apoptosis. Recent evidences indicate a regulatory role of both glucose and statins on cysteine proteases in monocytes. Satellite cells were isolated from the Musculus obliquus internus abdominis of healthy human donors, proliferated and differentiated into polynuclear myotubes. Simvastatin with or without mevalonolactone, farnesyl pyrophosphate or geranylgeranyl pyrophosphate were introduced on day 5 of differentiation. After 48 h, cells were either harvested for immunoblotting, ELISA, cell viability assay, confocal imaging or enzyme activity analysis, or placed in a fuel handling system with [¹⁴C]glucose or [³H]deoxyglucose for uptake and oxidation studies. A dose-dependent decrease in both glucose uptake and oxidation were observed in mature myotubes after exposure to simvastatin in concentrations not influencing cell viability. In addition, simvastatin caused a decrease in maturation and activity of legumain. Dysregulation of glucose metabolism and decreased legumain activity by simvastatin points out new knowledge about the effects of statins on skeletal muscle, and may contribute to the understanding of the myotoxicity observed by statins.