Identification and Characterization <Emphasis Type="Italic">in silico</Emphasis> of Meiotic DNA

A method of in silico search for specific repetitive DNA sequences related to the synaptonemal complex (meiDNA) in mammalian genomes was developed. A study of the distribution of these repeats over chromosomes revealed their scarcity on the Y chromosome and a decrease in recombination frequency in regions enriched in meiDNA. The results are discussed in context of the model of the looplike meiotic chromosome organization during the formation of the synaptonemal complex.__________Translated from Genetika, Vol. 41, No. 5, 2005, pp. 697–701.Original Russian Text Copyright © 2005 by Grishaeva, Dadashev, Bogdanov.     

Structure of Mitochondria and Activity of Their Respiratory Chain in Successive Generations of Yeast Cells Exposed to He-Ne Laser Light

The data on the aftereffect of He-Ne laser light (λ = 632.8 nm) on mitochondria of yeasts in late log phase were reviewed. The quantitative analysis of the ultrathin cell sections demonstrated a nonuniform thickness of the giant branched mitochondria typical for budding yeasts. Exposure to a dose of 460 J/m² (accelerating cell proliferation and activating respiratory chain enzymes, cytochrome c oxidase and NADH dehydrogenase), changed the macrostructure of the giant mitochondria—much of the narrow regions of the mitochondrial tube with profiles ≤0.06 μm² were expanded (while no signs of organelle damage were observed). Such mitochondria are characterized by increased relative surface area of the cristae, which can be due to the activation of their respiration and ATP synthesis. The number of associations between mitochondria and endoplasmic reticulum increased in irradiated cells in early log phase, which reflects the increased capacity of mitochondria to uptake Ca²⁺. Altered giant mitochondria configuration can increase the efficiency of both energy transfer and Ca²⁺ propagation through the cytoplasm. __________ Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 6, 2005, pp. 672–683. Original Russian Text Copyright ? 2005 by Manteifel, Karu.     

The problem of invaders in the Caspian Sea in the context of the findings of new zoo- and phytoplankton species from the Black Sea

In April 2004, an expedition to the Caspian Sea discovered the species in the Middle Caspian not previously described in this sea. These species preliminary identified as Oithona similis Claus 1963, Sagitta setosa Muller 1847, and Calanus euxinus (Hulsemann) are the main representatives of edible plankton of the Black Sea; most likely they were introduced into the Caspian Sea with ballast waters of ships passing through the Volga-Don Canal. At present, it is difficult to say if these species will be established in the Caspian Sea; if so, they will clearly become a valuable food resource for planktophagous fish in the Caspian Sea. In addition, we discovered two diatom species typical for the Black Sea phytoplankton, Pseudo-nitzschia seriata (Cleve) H. Peragallo and M. Peragallo and Cerataulina pelagica (Cleve) Hendey which invaded the Caspian Sea in recent years. Pseudo-nitzschia seriata synthesizes a toxin (domoic acid) and can become harmful for the basin in the case of mass bloom. We discuss the problem of spontaneous invasion of alien species from the Black Sea and their effect on the Caspian ecosystem in the context of these findings.Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 1, 2005, pp. 78–87.Original Russian Text Copyright © 2005 by Shiganova, Musaeva, Pautova, Bulgakova.     

Range expansion by moose into coastal temperate rainforests of British Columbia, Canada

Ranges of species are dynamic and respond to long‐term climate change and contemporary effects such as habitat modification. We report here that moose (Alces alces) have recently colonized coastal temperate rainforests of British Columbia, Canada. Contrary to recent publications, field observations of moose and their sign, combined with their occurrence in wolf (Canis lupus) faeces, suggest that moose are now widespread on the coastal mainland and occur on least three islands. Traditional ecological knowledge (information accumulated by aboriginal peoples about their environment) suggests that colonization occurred during the mid 1900s, concomitant with logging of major watersheds that bisect the Coast Mountain Range. Range expansion by moose may have ecological consequences such as alteration of predator–prey dynamics and transmission of disease to native deer (Odocoileus hemionus).     

Visualizing environmental correlates of species geographical range limits

Although many studies have treated aspects of species geographical distributions and numerous approaches exist for understanding overall ecological correlates of distributions, software tools for exploring environmental correlates of distributional limits are relatively few. We focused on the challenge of understanding spatial correlates of distributional limits, and developed an extension to arcview that provides a simple, univariate test and visualization for such explorations. The ‘Boundary U‐test’ seeks out environmental variables that show steep gradients associated with user‐defined boundaries across geography. We illustrate the tool and its applications with an example of the likely historical distribution of Mexican wolf (Canis lupus).     

Comparing and evaluating process-based ecosystem model predictions of carbon and water fluxes in major European forest biomes

Process‐based models can be classified into: (a) terrestrial biogeochemical models (TBMs), which simulate fluxes of carbon, water and nitrogen coupled within terrestrial ecosystems, and (b) dynamic global vegetation models (DGVMs), which further couple these processes interactively with changes in slow ecosystem processes depending on resource competition, establishment, growth and mortality of different vegetation types. In this study, four models – RHESSys, GOTILWA+, LPJ‐GUESS and ORCHIDEE – representing both modelling approaches were compared and evaluated against benchmarks provided by eddy‐covariance measurements of carbon and water fluxes at 15 forest sites within the EUROFLUX project. Overall, model‐measurement agreement varied greatly among sites. Both modelling approaches have somewhat different strengths, but there was no model among those tested that universally performed well on the two variables evaluated. Small biases and errors suggest that ORCHIDEE and GOTILWA+ performed better in simulating carbon fluxes while LPJ‐GUESS and RHESSys did a better job in simulating water fluxes. In general, the models can be considered as useful tools for studies of climate change impacts on carbon and water cycling in forests. However, the various sources of variation among models simulations and between models simulations and observed data described in this study place some constraints on the results and to some extent reduce their reliability. For example, at most sites in the Mediterranean region all models generally performed poorly most likely because of problems in the representation of water stress effects on both carbon uptake by photosynthesis and carbon release by heterotrophic respiration (R_h). The use of flux data as a means of assessing key processes in models of this type is an important approach to improving model performance. Our results show that the models have value but that further model development is necessary with regard to the representation of the some of the key ecosystem processes.     

Adenomatous polyposis coli influences micronuclei induction by PhIP and acrylamide in mouse erythrocytes

Micronucleus (MN) induction in erythrocytes of multiple intestinal neoplasia (Min) mice with heterozygous Apc mutation was measured after s.c. injections of acrylamide, glycidamide, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and colchicine, and compared with wild-type (wt) mice. Since Apc influences microtubule dynamics, we wanted to test whether Min-mice were more sensitive to the production of MN than wild-type mice. We also examined the effect of pre-treatment with cytosine β-D-arabinofuranoside (Ara C) and hydroxyurea, which inhibit ligation of DNA strand breaks in the repair of DNA adducts. All compounds induced a significant increase in MN in both strains of mice with the following potencies: acrylamide < glycidamide < PhIP. No difference in the induction of MN was seen between Min-mice and wt-mice exposed to acrylamide, glycidamide or colchicine without pre-treatment. However, in Min-mice, PhIP treatment induced much less MN than in wt-mice, with about four- and six-fold increase in MN in Min-mice and wt-mice, respectively. A reduced ability to repair PhIP adducts may be the reason for the lower induction of MN in Min-mice. Treatment with Ara C and hydroxyurea, to increase sensitivity, gave more than a four-fold increase in MN, but strongly reduced proliferation. Pre-treatment with Ara C and hydroxyurea made the Min-mice slightly more sensitive to MN induction by glycidamide compared to wt-mice. We conclude that Min-mice are less sensitive than wt-mice to MN induction by PhIP that forms bulky DNA adducts, while Min-mice and wt-mice are equally sensitive to MN induction by acrylamide and glycidamide that form DNA base adducts.     

Stability and specificity of heterodimer formation for the coiled-coil neck regions of the motor proteins Kif3A and Kif3B: the role of unstructured oppositely charged regions.

We investigated the folding, stability, and specificity of dimerization of the neck regions of the kinesin-like proteins Kif3A (residues 356-416) and Kif3B (residues 351-411). We showed that the complementary charged regions found in the hinge regions (which directly follow the neck regions) of these proteins do not adopt any secondary structure in solution. We then explored the ability of the complementary charged regions to specify heterodimer formation for the neck region coiled-coils found in Kif3A and Kif3B. Redox experiments demonstrated that oppositely charged regions specified the formation of a heterodimeric coiled-coil. Denaturation studies with urea demonstrated that the negatively charged region of Kif3A dramatically destabilized its neck coiled-coil (urea1/2 value of 3.9 m compared with 6.7 m for the coiled-coil alone). By comparison, the placement of a positively charged region C-terminal to the neck coiled-coil of Kif3B had little effect on stability (urea1/2 value of 8.2 m compared with 8.8 m for the coiled-coil alone). The pairing of complementary charged regions leads to specific heterodimer formation where the stability of the heterodimeric neck coiled-coil with charged regions had similar stability (urea1/2 value of 7.8 m) to the most stable homodimer (Kif3B) with charged regions (urea1/2 value of 8.0 m) and dramatically more stable than the Kif3A homodimer with charged regions (urea1/2, value of 3.9 m). The heterodimeric coiled-coil with charged extensions has essentially the same stability as the heterodimeric coiled-coil on its own (urea1/2 values of 7.8 and 8.1 m, respectively) suggesting that specificity of heterodimerization is driven by non-specific attraction of the oppositely unstructured charged regions without affecting stability of the heterodimeric coiled-coil.