University of Hamburg

About: University of Hamburg is a education organization based out in Hamburg, Germany. It is known for research contribution in the topics: Population & Laser. The organization has 45564 authors who have published 89286 publications receiving 2850161 citations. The organization is also known as: Hamburg University.

The Arctic Ocean Response to the North Atlantic Oscillation

Abstract: The climatically sensitive zone of the Arctic Ocean lies squarely within the domain of the North Atlantic oscillation (NAO), one of the most robust recurrent modes of atmospheric behavior. However, the specific response of the Arctic to annual and longer-period changes in the NAO is not well understood. Here that response is investigated using a wide range of datasets, but concentrating on the winter season when the forcing is maximal and on the postwar period, which includes the most comprehensive instrumental record. This period also contains the largest recorded low-frequency change in NAO activity—from its most persistent and extreme low index phase in the 1960s to its most persistent and extreme high index phase in the late 1980s/early 1990s. This longperiod shift between contrasting NAO extrema was accompanied, among other changes, by an intensifying storm track through the Nordic Seas, a radical increase in the atmospheric moisture flux convergence and winter precipitation in this sector, an increase in the amount and temperature of the Atlantic water inflow to the Arctic Ocean via both inflow branches (Barents Sea Throughflow and West Spitsbergen Current), a decrease in the late-winter extent of sea ice throughout the European subarctic, and (temporarily at least) an increase in the annual volume flux of ice from the Fram Strait.

The African coelacanth genome provides insights into tetrapod evolution

Abstract: The discovery of a living coelacanth specimen in 1938 was remarkable, as this lineage of lobe-finned fish was thought to have become extinct 70 million years ago. The modern coelacanth looks remarkably similar to many of its ancient relatives, and its evolutionary proximity to our own fish ancestors provides a glimpse of the fish that first walked on land. Here we report the genome sequence of the African coelacanth, Latimeria chalumnae. Through a phylogenomic analysis, we conclude that the lungfish, and not the coelacanth, is the closest living relative of tetrapods. Coelacanth protein-coding genes are significantly more slowly evolving than those of tetrapods, unlike other genomic features. Analyses of changes in genes and regulatory elements during the vertebrate adaptation to land highlight genes involved in immunity, nitrogen excretion and the development of fins, tail, ear, eye, brain and olfaction. Functional assays of enhancers involved in the fin-to-limb transition and in the emergence of extra-embryonic tissues show the importance of the coelacanth genome as a blueprint for understanding tetrapod evolution.

Three-dimensional reconstitution of embryonic cardiomyocytes in a collagen matrix: a new heart muscle model system.

Abstract: A method has been developed for culturing cardiac myocytes in a collagen matrix to produce a coherently contracting 3-dimensional model heart tissue that allows direct measurement of isometric contractile force. Embryonic chick cardiomyocytes were mixed with collagen solution and allowed to gel between two Velcro-coated glass tubes. During culture, the cardiomyocytes formed spontaneously beating cardiac myocyte-populated matrices (CMPMs) anchored at opposite ends to the Velcro-covered tubes through which they could be attached to a force measuring system. Immunohistochemistry and electron microscopy revealed a highly organized tissue-like structure of alpha-actin and alpha-tropomyosin-positive cardiac myocytes exhibiting typical cross-striation, sarcomeric myofilaments, intercalated discs, desmosomes, and tight junctions. Force measurements of paced or unpaced CMPMs were performed in organ baths after 6-11 days of cultivation and were stable for up to 24 h. Force increased with frequency between 0.8 and 2.0 Hz (positive "staircase"), increasing rest length (Starling mechanism), and increasing extracellular calcium. The utility of this system as a test bed for genetic manipulation was demonstrated by infecting the CMPMs with a recombinant beta-galactosidase-carrying adenovirus. Transduction efficiency increased from about 5% (MOI 0.1) to about 50% (MOI 100). CMPMs display more physiological characteristics of intact heart tissue than monolayer cultures. This approach, simpler and faster than generation of transgenic animals, should allow functional consequences of genetic or pharmacological manipulation of cardiomyocytes in vitro to be studied under highly controlled conditions.

A consensus approach toward the standardization of back pain definitions for use in prevalence studies

Abstract: A modified Delphi study conducted with 28 experts in back pain research from 12 countries. OBJECTIVE. To identify standardized definitions of low back pain that could be consistently used by investigators in prevalence studies to provide comparable data. SUMMARY OF BACKGROUND DATA. Differences in the definition of back pain prevalence in population studies lead to heterogeneity in study findings, and limitations or impossibilities in comparing or summarizing prevalence figures from different studies. METHODS. Back pain definitions were identified from 51 articles reporting population-based prevalence studies, and dissected into 77 items documenting 7 elements. These items were submitted to a panel of experts for rating and reduction, in 3 rounds (participation: 76%). Preliminary results were presented and discussed during the Amsterdam Forum VIII for Primary Care Research on Low Back Pain, compared with scientific evidence and confirmed and fine-tuned by the panel in a fourth round and the preparation of the current article. RESULTS. Two definitions were agreed on a minimal definition (with 1 question covering site of low back pain, symptoms observed, and time frame of the measure, and a second question on severity of low back pain) and an optimal definition that is made from the minimal definition and add-ons (covering frequency and duration of symptoms, an additional measure of severity, sciatica, and exclusions) that can be adapted to different needs. CONCLUSION. These definitions provide standards that may improve future comparisons of low back pain prevalence figures by person, place and time characteristics, and offer opportunities for statistical summaries.