Search results for "Arctic"
showing 10 items of 565 documents
Phylogenetic analysis of the Antarctic genus Oswaldella Stechow, 1919 (Hydrozoa, Leptomedusae, Kirchenpaueriidae)
1999
A cladistic study was carried out on known species of the characteristically Antarctic genus Oswaldella, adopting as out-groups some other genera included in the family Kirchenpaueriidae. The analysis resulted in a cladogram with low CI in which no relationship between genera can be depicted. However, the hypothesis of monophyly of the genus Oswaldella is corroborated, being supported in our cladogram by five synapomorphies (although all are homoplastic with other taxa or reversed within the species of the genus). The basal relationships of the genus are uncertain, but three species groups are distinguishable within Oswaldella: 1) the O. incognita group, 2) the O. Antarctica group, and 3) a…
A 5500-year oxygen isotope record of high arctic environmental change from southern Spitsbergen
2017
The oxygen isotope composition of chironomid head capsules in a sediment core spanning the past 5500 years from Lake Svartvatnet in southern Spitsbergen was used to reconstruct the oxygen isotope composition of lake water (δ18Olw) and local precipitation. The δ18Olw values display shifts from the baseline variability consistent with the timing of recognized historical climatic episodes, such as the Roman Warm Period, the Dark Ages Cold Period and the ‘Little Ice Age’. The highest values of the record, ca. 3‰ above modern δ18Olw values, occur at ca. 1900–1800 cal. yr BP. Three negative excursions increasing in intensity toward the present, at 3400–3200, 1250–1100, and 350–50 cal. yr BP, are…
Taste, a new incentive to switch to (R)-praziquantel in schistosomiasis treatment.
2009
Background Praziquantel (PZQ) is the drug compound of choice in the control and treatment of schistosomiasis. PZQ is administered as a racemate, i. e. 1∶1 mixture of enantiomers. The schistosomicidal activity arises from one PZQ-enantiomer, whereas the other enantiomer does not contribute to the activity. The WHO's Special Programme for Research and Training in Tropical Diseases (TDR) has assigned the low-cost preparation of pure schistosomicidal (−)-PZQ a key priority for future R&D on PZQ, but so far this transition has not happened. PZQ has two major administration drawbacks, the first being the high dose needed, and its well documented bitter and disgusting taste. Attempts of taste-mask…
Soil fungal community composition does not alter along a latitudinal gradient through the maritime and sub-Antarctic
2012
We investigated the relationships between fungal community composition, latitude and a range of physicochemical parameters in 58 soils sampled from a 2370 km latitudinal gradient between South Georgia (54 S, 38 W) in the sub-Antarctic and Mars Oasis (72 S, 68 W) on Alexander Island in the southern maritime Antarctic. Our study, which is based on approximately ten times the number of samples used in previous similar studies, indicates that latitude and its associated environmental parameters are not related to fungal community composition. Significant changes in the composition of soil fungal communities were observed in relation to gradients of the ratio of total organic carbon to nitrogen,…
Comprehensive dataset of shotgun metagenomes from stratified freshwater lakes and ponds
2020
AbstractStratified lakes and ponds featuring steep oxygen gradients are significant net sources of greenhouse gases and hotspots in the carbon cycle. Despite their significant biogeochemical roles, the microbial communities, especially in the oxygen depleted compartments, are poorly known. Here, we present a comprehensive dataset including 267 shotgun metagenomes from 41 stratified lakes and ponds mainly located in the boreal and subarctic regions, but also including one tropical reservoir and one temperate lake. For most lakes and ponds, the data includes a vertical sample set spanning from the oxic surface to the anoxic bottom layer. The majority of the samples were collected during the o…
The Valanginian positive carbon isotope event in Arctic Russia: Evidence from terrestrial and marine isotope records and implications for global carb…
2010
The data presented here comprise Ryazanian–Valanginian carbon isotope ratios analyzed from fossil wood and belemnites from the shallow marine Boyarka River succession in Siberia. Additional belemnite carbon isotope ratios from the Izhma River succession (also Ryazanian–Valanginian) in Russia are also presented. The wood-derived and belemnite-derived isotope ratios are considered to primarily reflect changes in the terrestrial and marine carbon isotope reservoirs respectively. The δ13Ccarb and δ13Cwood records reveal a distinct mid-Valanginian positive carbon isotope excursion, with the initiation occurring near the Boreal Russian michalskii–polyptychus zone boundary, which is broadly time-e…
S. haematobium as a Common Cause of Genital Morbidity in Girls: A Cross-sectional Study of Children in South Africa
2013
Background Schistosoma (S.) haematobium infection is a common cause of genital morbidity in adult women. Ova in the genital mucosal lining may cause lesions, bleeding, pain, discharge, and the damaged surfaces may pose a risk for HIV. In a heterogeneous schistosomiasis endemic area in South Africa, we sought to investigate if young girls had genital symptoms and if this was associated with urinary S. haematobium. Methodology In a cross-sectional study of 18 randomly chosen primary schools, we included 1057 schoolgirls between the age of 10 and 12 years. We interviewed assenting girls, whose parents had consented to their participation and examined three urines from each of them for schistos…
Adaptation of microphysical and chemical instrumentation to the airborne measuring platform Iljushin I1-18 ‘Cyclone’ and flight regime planning durin…
1997
Abstract In 1993 the joint Russian-German Research Project ‘Arctic Haze’ started (see the Introduction and editorial note of this issue, by Jaenicke, Khattatov, Jaeschke and Leiterer). Besides CAO, four German groups were involved. To the present three airborne measuring campaigns have been performed. In total 251 h of flight within altitudes up to 8.7 km were flown in the western and eastern part of the arctic leading to a comprehensive set of data of the northern arctic hemisphere. The measurements were conducted aboard the Russian research aircraft I1-18 ‘Cyclone’ which was used by CAO in numerous scientific projects mainly in the former USSR. This 4 engined turboprop aircraft is well eq…
Physical oceanography, sea-bed photographs and videos of benthos from the Weddell Sea taken with remote operated vehicle CHEROKEE during POLARSTERN c…
2010
The marine ecosystem on the eastern shelf of the Antarctic Peninsula was surveyed 5 and 12 years after the climate-induced collapse of the Larsen A and B ice shelves. An impoverished benthic fauna was discovered, that included deep-sea species presumed to be remnants from ice-covered conditions. The current structure of various ecosystem components appears to result from extremely different response rates to the change from an oligotrophic sub-ice-shelf ecosystem to a productive shelf ecosystem. Meiobenthic communities remained impoverished only inside the embayments. On local scales, macro- and mega-epibenthic diversity was generally low, with pioneer species and typical Antarctic megabent…
Identifying and validating the presence of guanine-quadruplexes (G4) within the blood fluke parasite schistosoma mansoni
2021
Schistosomiasis is a neglected tropical disease that currently affects over 250 million individuals worldwide. In the absence of an immunoprophylactic vaccine and the recognition that mono-chemotherapeutic control of schistosomiasis by praziquantel has limitations, new strategies for managing disease burden are urgently needed. A better understanding of schistosome biology could identify previously undocumented areas suitable for the development of novel interventions. Here, for the first time, we detail the presence of G-quadruplexes (G4) and putative quadruplex forming sequences (PQS) within the Schistosoma mansoni genome. We find that G4 are present in both intragenic and intergenic regi…