46 research outputs found
Genetic Determinants of Time Perception Mediated by the Serotonergic System
Background: The present study investigates neurobiological underpinnings of individual differences in time perception. Methodology: Forty-four right-handed Russian Caucasian males (18–35 years old) participated in the experiment. The polymorphism of the genes related to the activity of serotonin (5-HT) and dopamine (DA)-systems (such as 5-HTT, 5HT2a, MAOA, DAT, DRD2, COMT) was determined upon the basis of DNA analysis according to a standard procedure. Time perception in the supra-second range (mean duration 4.8 s) was studied, using the duration discrimination task and parametric fitting of psychometric functions, resulting in individual determination of the point of subjective equality (PSE). Assuming the ‘dual klepsydra model ’ of internal duration representation, the PSE values were transformed into equivalent values of the parameter k (kappa), which is a measure of the ‘loss rate ’ of the duration representation. An association between time representation parameters (PSE and k, respectively) and 5-HT-related genes was found, but not with DArelated genes. Higher ‘loss rate ’ (k) of the cumulative duration representation were found for the carriers of genotypes characterized by higher 5-HT transmission, i.e., 1) lower 5-HT reuptake, known for the 5-HTTLPR SS polymorphism compared with LL, 2) lower 5-HT degradation, described for the ‘low expression ’ variant of MAOA VNTR gene compared with ‘high expression ’ variant, and 3) higher 5-HT2a receptor density, proposed for the TT polymorphism of 5-HT2a T102C gene compared with CC
Characterisation of the Nematode Community of a Low-Activity Cold Seep in the Recently Ice-Shelf Free Larsen B Area, Eastern Antarctic Peninsula
Background: Recent climate-induced ice-shelf disintegration in the Larsen A (1995) and B (2002) areas along the Eastern Antarctic Peninsula formed a unique opportunity to assess sub-ice-shelf benthic community structure and led to the discovery of unexplored habitats, including a low-activity methane seep beneath the former Larsen B ice shelf. Since both limited particle sedimentation under previously permanent ice coverage and reduced cold-seep activity are likely toinfluence benthic meiofauna communities, we characterised the nematode assemblage of this low-activity cold seep and compared it with other, now seasonally ice-free, Larsen A and B stations and other Antarctic shelf areas (Weddell Sea and Drake Passage), as well as cold-seep ecosystems world-wide.Principal Findings: The nematode community at the Larsen B seep site differed significantly from other Antarctic sites in terms of dominant genera, diversity and abundance. Densities in the seep samples were high (.2000 individuals per 10 cm2) and showed below-surface maxima at a sediment depth of 2–3 cm in three out of four replicates. All samples were dominated by one species of the family Monhysteridae, which was identified as a Halomonhystera species that comprised between 80 and 86% of the total community. The combination of high densities, deeper density maxima and dominance of one species is shared by many cold-seep ecosystems world-wide and suggested a possible dependence upon a chemosynthetic food source. Yet stable 13C isotopic signals (ranging between 221.9760.86% and 224.8561.89%) were indicative of a phytoplankton-derived food source.Conclusion: The recent ice-shelf collapse and enhanced food input from surface phytoplankton blooms were responsible for the shift from oligotrophic pre-collapse conditions to a phytodetritus-based community with high densities and low diversity. The parthenogenetic reproduction of the highly dominant Halomonhystera species is rather unusual for marine nematodes and may be responsible for the successful colonisation by this single species
Russian education possible perspectives
This article contains information about possible reforms in pre-school, elementary school, secondary and high school education, based on conducted surveys, researches of legislative acts on education in different countries and on the studies of scientific articles on related topics. It will be discussed in details such aspects as New Zealand's program (including a Montessori infant-toddler environment), elementary school dividing reform, secondary school social classes, high school special lectures, poor families and their educational problems, developing of separate education system.184-18
Nematode species distribution patterns at the Håkon Mosby Mud Volcano (Norwegian Sea)
The Ha°kon Mosby Mud Volcano (HMMV) is a methane seep that is densely
populated by the bacteria Beggiatoa spp. as well as by tubeworms of the Family
Siboglinidae. Analyses of samples from seven stations located in five different
habitats (bare sediments, bacterial mats, siboglinid fields, sediments with small
patches of siboglinids and areas of ‘normal’ sea floor) revealed differences in
the density and species-level diversity of nematode communities. Total densities
increased from stations inside the mud volcano and on its rim towards the
‘normal’ areas outside the volcano. Nematode species diversity was similar in
samples from the siboglinid fields and the bare HMMV sediments. However,
the sediment with patches of siboglinids collected outside the volcano was
characterised by a diverse nematode community comprising 47 species, whereas
the control sediments without siboglinids yielded only 27 species. The nematode
assemblage at the bacterial mat site included only two identified species,
Halomonhystera disjuncta and Sabatieria ornata, with H. disjuncta being
strongly dominant. Terschellingia distlamphida, S. ornata and Aponema ninae
dominated nematode communities at the siboglinid fields and in bare HMMV
sediments. Species dominating at stations inside the caldera were found in
comparable low densities in the sediment with siboglinid patches collected outside
the volcano, but were missing in the background samples, where species of
Endeolophos, Acantholaimus and Desmoscolex were dominant. Species diversity
generally decreased with sediment depth. A subsurface-dwelling nematode community
was observed in the siboglinid fields and the bare sediments. Background
sediments showed a sharp decline with 18–20 species at 0–2 cm versus
three species at 3–5 cm sediment depth. The trophic composition of the nematode
fauna at the HMMV showed a prevalence of deposit feeders at almost all
stations, whereas background sediments exhibited a uniform distribution of
non-selective and selective deposit feeders and epistrate feeders. The high percentage
of deposit feeders inside the mud volcano could be related to the
grain-size distribution and the significantly higher bacterial biomass compared
to the control sediments