Stretching the Rules: Monocentric Chromosomes with Multiple Centromere Domains

The centromere is a functional chromosome domain that is essential for faithful chromosome segregation during cell division and that can be reliably identified by the presence of the centromere-specific histone H3 variant CenH3. In monocentric chromosomes, the centromere is characterized by a single CenH3-containing region within a morphologically distinct primary constriction. This region usually spans up to a few Mbp composed mainly of centromere-specific satellite DNA common to all chromosomes of a given species. In holocentric chromosomes, there is no primary constriction; the centromere is composed of many CenH3 loci distributed along the entire length of a chromosome. Using correlative fluorescence light microscopy and high-resolution electron microscopy, we show that pea (Pisum sativum) chromosomes exhibit remarkably long primary constrictions that contain 3-5 explicit CenH3-containing regions, a novelty in centromere organization. In addition, we estimate that the size of the chromosome segment delimited by two outermost domains varies between 69 Mbp and 107 Mbp, several factors larger than any known centromere length. These domains are almost entirely composed of repetitive DNA sequences belonging to 13 distinct families of satellite DNA and one family of centromeric retrotransposons, all of which are unevenly distributed among pea chromosomes. We present the centromeres of Pisum as novel ``meta-polycentric'' functional domains. Our results demonstrate that the organization and DNA composition of functional centromere domains can be far more complex than previously thought, do not require single repetitive elements, and do not require single centromere domains in order to segregate properly. Based on these findings, we propose Pisum as a useful model for investigation of centromere architecture and the still poorly understood role of repetitive DNA in centromere evolution, determination, and function

Crabs, scallops, fish, and more: barcoding the marine fauna of the North Sea

Background: During the last years, the effectiveness of DNA barcoding for animal species identification has been proven in many studies, analyzing both vertebrate and invertebrate taxa. In terms of marine organisms, however, most barcoding studies typically focus on economically relevant species, for example, fish, as well asonthedocumentationof hotspots of species diversity, for example, tropical coral reefs or regions of the almost unexplored deep sea regions. In contrast to this, species diversity of “well-known” habitats is nearly neglected. As part of our running project we started to build up a comprehensive DNA barcode library for the metazoan taxa of the North Sea, one of the most extensively studied ecosystems of the world. The North Sea is characterized by a highamountof anthropogenic pressure such as intensive fishing and ship traffic as well as offshore installations. Environmental parameters (e.g., depth, sediment characteristics, temperature, and salinity) of this semi-enclosed shelf sea follow a distinct pattern: high seasonal fluctuations can be observed in southern areas, but low fluctuations are given in the northern regions. This heterogeneity is also displayed in macrobenthic community structures, with a lower number of species in the shallow southern parts (i.e., the German Bight) and more species in the central and northern North Sea. In addition to this, species with a typical Mediterranean-Lusitanean distribution are also known to occur in parts of the North Sea where oceanic influences prevail. Results: Our barcode library includes a broad variety of taxa, including typical taxa of marine barcoding studies, for example, fish or decapod crustaceans. Our on-growing library also includes groups that are often ignored as cnidarians, parasitic crustaceans, echinoderms, mollusks, pantopods, polychaets, and others. In total, our library includes more than 4200 DNA barcodes of more than 600 species at the moment. By using the Barcode of Life Data Systems (BOLD), unique BINs were identified for more than 90% of the analyzed species. Significance: Our data represent a first step towards the establishment of a comprehensive DNA barcode library of the Metazoa of the North Sea. Despite the fact that various taxa are still missing or are currently underrepresented, our results clearly underline the usefulness of DNA barcodes to discriminate the vast majority of the analyzed species. It should be also kept in mind that the benefits of DNA barcoding are not restricted to taxonomic or systematic research only. The rise of modern high-throughput sequencing technologies will change biomonitoring applications and surveys significantly in the coming years. Following this, reference datasets such as ours will become essential for a correct identification of specimens sequenced as part of a metabarcoding study. This is especially true for the North Sea, a marine region that has been massively affected by cargo ship traffic, the exploitation of oil and gas resources, offshore wind parks, and in particular extensive long-term fisheries

Interaction between Experiment, Modeling and Simulation of Spatial Aspects in the JAK2/STAT5 Signaling Pathway

Fundamental progress in systems biology can only be achieved if experimentalists and theoreticians closely collaborate. Mathematical models cannot be formulated precisely without deep knowledge of the experiments while complex biological systems can often not be understood fully without mathematical interpretation of the dynamic processes involved. In this article, we describe how these two approaches can be combined to gain new insights on one of the most extensively studied signal transduction pathways, the Janus kinase (JAK)/ signal transducer and activator of transcription (STAT) pathway. We focus on the parameters of a model describing how STAT proteins are transported from the membrane to the nucleus where STATs regulate gene expression. We discuss which parameters can be measured experimentally in different cell types and how the unknown parameters are estimated, what the limits of these techniques and how accurate the determinations are

Preservation of a Preglacial Landscape Under the Center of the Greenland Ice Sheet

Continental ice sheets typically sculpt landscapes via erosion; under certain conditions, ancient landscapes can be preserved beneath ice and can survive extensive and repeated glaciation. We used concentrations of atmospherically produced cosmogenic beryllium-10, carbon, and nitrogen to show that ancient soil has been preserved in basal ice for millions of years at the center of the ice sheet at Summit, Greenland. This finding suggests ice sheet stability through the Pleistocene (i.e., the past 2.7 million years). The preservation of this soil implies that the ice has been non-erosive and frozen to the bed for much of that time, that there was no substantial exposure of central Greenland once the ice sheet became fully established, and that preglacial landscapes can remain preserved for long periods under continental ice sheet

Dopamine-dependent scaling of subthalamic gamma bursts with movement velocity in patients with Parkinson’s disease

Gamma synchronization increases during movement and scales with kinematic parameters. Here, disease-specific characteristics of this synchronization and the dopamine-dependence of its scaling in Parkinson’s disease are investigated. In 16 patients undergoing deep brain stimulation surgery, movements of different velocities revealed that subthalamic gamma power peaked in the sensorimotor part of the subthalamic nucleus, correlated positively with maximal velocity and negatively with symptom severity. These effects relied on movement-related bursts of transient synchrony in the gamma band. The gamma burst rate highly correlated with averaged power, increased gradually with larger movements and correlated with symptom severity. In the dopamine-depleted state, gamma power and burst rate significantly decreased, particularly when peak velocity was slower than ON medication. Burst amplitude and duration were unaffected by the medication state. We propose that insufficient recruitment of fast gamma bursts during movement may underlie bradykinesia as one of the cardinal symptoms in Parkinson’s disease

GDP per Capita Differentials between Nations: Patterns and Models

Seit den 70er Jahren erscheint die Welteinkommensverteilung zwischen den Nationen polarisiert in arm und reich. Dieses Phänomen kann theoretisch mithilfe des Solow Wachstumsmodells erklärt werden. Der Nachweis wurde auf drei Arten geführt. Als erstes wurde graphisch gezeigt, dass Änderungen der Annahmen bezüglich der Sparquote, des Bevölkerungswachstums sowie der Sparquote des Humankapital im erweiterten Solow Wachstumsmodell zu Bipolarität führen können. Die zweite Vorgehensweise war analytisch: eine endogene Sparquote wurde in das Solow Wachstumsmodell eingefügt, für welches dann die Gleichgewichte bestimmt wurden. Es konnte gezeigt werden, dass es zur Polarisierung kommt. Schließlich wurde ein empirisch determiniertes Solow Wachstumsmodell formuliert. Die Sparquote sowie die Bevölkerungswachstumsrate wurden mithilfe von Regressionen geschätzt und in das Modell integriert. Hieraus wurden anschließend die Gleichgewichte bestimmt

Investigating Evaporation Of Melting Ice Particles Within A Bin Melting Layer Model

Single column models have been used to help develop algorithms for remote sensing retrievals. Assumptions in the single-column models may affect the assumptions of the remote sensing retrievals. Studies of the melting layer that use single column models often assume environments that are near or at water saturation. This study investigates the effects of evaporation upon melting particles to determine whether the assumption of negligible mass loss still holds within subsaturated melting layers. A single column, melting layer model is modified to include the effects of sublimation and evaporation upon the particles. Other changes to the model include switching the order in which the model loops over particle sizes and model layers; including a particle sedimentation scheme; adding aggregation, accretion, and collision and coalescence processes; allowing environmental variables such as the water vapor diffusivity and the Schmidt number to vary with the changes in the environment; adding explicitly calculated particle temperature, changing the particle terminal velocity parameterization; and using a newly-derived effective density-dimensional relationship for use in particle mass calculations. Simulations of idealized melting layer environments show that significant mass loss due to evaporation during melting is possible within subsaturated environments. Short melting distances, accelerating particle fall speeds, and short melting times help constrain the amount of mass lost due to evaporation while melting is occurring, even in subsaturated profiles. Sublimation prior to melting can also be a significant source of mass loss. The trends shown on the particle scale also appear in the bulk distribution parameters such as rainfall rate and ice water content. Simulations incorporating observed melting layer environments show that significant mass loss due to evaporation during the melting process is possible under certain environmental conditions. A profile such as the first melting layer profile on 10 May 2011 from the Midlatitude Continental Convective Clouds Experiment (MC3E) that is neither too saturated nor too subsaturated is possible and shows considerable mass loss for all particle sizes. Most melting layer profiles sampled during MC3E were too saturated for more than a dozen or two of the smallest particle sizes to experience significant mass loss. The aggregation, accretion, and collision and coalescence processes also countered significant mass loss at the largest particles sizes because these particles are efficient at collecting smaller particles due to their relative large sweep-out area. From these results, it appears that the assumption of negligible mass loss due to evaporation while melting is occurring is not always valid. Studies that use large, low-density snowflakes and high RH environments can safely use the assumption of negligible mass loss. Studies that use small ice particles or low RH environments (RH less than about 80%) cannot use the assumption of negligible mass loss due to evaporation. Retrieval algorithms may be overestimating surface precipitation rates and intensities in subsaturated environments due to the assumptions of negligible mass loss while melting and near-saturated melting layer environments

Analysis Of A Parallel Stratiform Mesoscale Convective System During The Midlatitude Continental Convective Clouds Experiment

During the Midlatitude Continental Convective Clouds Experiment, a PS MCS traversed north-central Oklahoma on 11 May 2011. In-situ measurements of the stratiform precipitation region were obtained from six horizontal flight legs flow by the University of North Dakota Citation II Weather Research Aircraft in conjunction with measurements collected using a multitude of ground-based radars and a dense balloon sounding network specifically set up for the MC3E project. Winds were nearly unidirectional south-southwesterly over Oklahoma and southern Kansas, which created the parallel stratiform characteristics. Gamma functions were fit to ten-second averaged two-dimensional cloud probe spectra. Comparisons of N0, μ, and λ with values from McFarquhar et al. (2007) show the microphysical processes in the parallel stratiform region are similar to those in trailing stratiform regions. The similarities between the 11 May 2011 PS MCS and the simulated one from Parker (2007) show that basic kinematic features of these events are understood