115 research outputs found
Ostracods as ecological and isotopic indicators of lake water salinity changes: the Lake Van example
Ostracods are common lacustrine calcitic microfossils. Their faunal
assemblage and morphological characteristics are important ecological
proxies, and their valves are archives of geochemical information related to
palaeoclimatic and palaeohydrological changes. In an attempt to assess
ostracod ecology (taxonomic diversity and valve morphology) combined with
valve geochemistry (δ18O and δ13C) as
palaeosalinity indicators, we analysed sedimentary material from the
International Continental Scientific Drilling Program (ICDP) Ahlat Ridge site
from a terminal and alkaline lake, Lake Van (Turkey), covering the last
150 kyr. Despite a low species diversity, the ostracod faunal assemblage
reacted sensitively to changes in the concentration of total dissolved salts
in their aquatic environment. Limnocythere inopinata is present
throughout the studied interval, while Limnocythere sp. A is
restricted to the Last Glacial period and related to increased lake water
salinity and alkalinity. The presence of species belonging to the genus
Candona is limited to periods of lower salinity. Valves of
Limnocytherinae species (incl. L. inopinata) display nodes (hollow
protrusions) during intervals of increased salinity. Both the number of noded
valves and the number of nodes per valve appear to increase with rising
salinity, suggesting that node formation is related to hydrological changes
(salinity and/or alkalinity). In contrast to Lake Van's bulk
δ18O record, the δ18O values of ostracod valves
do record relative changes of the lake volume, with lower values during high
lake level periods. The δ13C values of different species
reflect ostracod habitat preferences (i.e. infaunal vs. epifaunal) but are
less sensitive to hydrological changes. However, combined with other proxies,
decreasing Holocene δ13C values may indicate a freshening of
the lake water compared to the low lake level during the Last Glacial period.
The Lake Van example underscores the significance and value of coupling
ostracod ecology and valve geochemistry in palaeoenvironmental studies of
endorheic lake basins.</p
A role for the mevalonate pathway in early plant symbiotic signaling
Rhizobia and arbuscular mycorrhizal fungi produce signals that are perceived by host legume receptors at the plasma membrane and trigger sustained oscillations of the nuclear and perinuclear Ca(2+) concentration (Ca(2+) spiking), which in turn leads to gene expression and downstream symbiotic responses. The activation of Ca(2+) spiking requires the plasma membrane-localized receptor-like kinase Does not Make Infections 2 (DMI2) as well as the nuclear cation channel DMI1. A key enzyme regulating the mevalonate (MVA) pathway, 3-Hydroxy-3-Methylglutaryl CoA Reductase 1 (HMGR1), interacts with DMI2 and is required for the legume-rhizobium symbiosis. Here, we show that HMGR1 is required to initiate Ca(2+) spiking and symbiotic gene expression in Medicago truncatula roots in response to rhizobial and arbuscular mycorrhizal fungal signals. Furthermore, MVA, the direct product of HMGR1 activity, is sufficient to induce nuclear-associated Ca(2+) spiking and symbiotic gene expression in both wild-type plants and dmi2 mutants, but interestingly not in dmi1 mutants. Finally, MVA induced Ca(2+) spiking in Human Embryonic Kidney 293 cells expressing DMI1. This demonstrates that the nuclear cation channel DMI1 is sufficient to support MVA-induced Ca(2+) spiking in this heterologous system
Syntheses, characterization, density functional theory calculations, and activity of tridentate SNS zinc pincer complexes
A series of tridentate SNS ligand precursors were metallated with ZnCl2 to give new tridentate SNS pincer zinc complexes. The zinc complexes serve as models for the zinc active site in liver alcohol dehydrogenase (LADH) and were characterized with single crystal X-ray diffraction, 1H, 13C, and HSQC NMR spectroscopies and electrospray mass spectrometry. The bond lengths and bond angles of the zinc complexes correlate well to those in horse LADH. The zinc complexes feature SNS donor atoms and pseudotetrahedral geometry about the zinc center, as is seen for liver alcohol dehydrogenase. The SNS ligand precursors were characterized with 1H, 13C, and HSQC NMR spectroscopies and cyclic voltammetry, and were found to be redox active. Gaussian calculations were performed and agree quite well with the experimentally observed oxidation potential for the pincer ligand. The zinc complexes were screened for the reduction of electron poor aldehydes in the presence of a hydrogen donor, 1-benzyl-1,4-dihydronicotinamide (BNAH). The zinc complexes enhance the reduction of electron poor aldehydes. Density functional theory calculations were performed to better understand why the geometry about the zinc center is pseudo-tetrahedral rather than pseudo-square planar, which is seen for most pincer complexes. For the SNS tridentate pincer complexes, the data indicate that the pseudo-tetrahedral geometry was 43.8 kcal/mol more stable than the pseudo-square planar geometry. Density functional theory calculations were also performed on zinc complexes with monodentate ligands and the data indicate that the pseudo-tetrahedral geometry was 30.6 kcal/mol more stable than pseudo-square planar geometry. Overall, the relative stabilities of the pseudo-tetrahedral and pseudo-square planar systems are the same for this coordination environment whether the ligand set is a single tridentate SNS system or is broken into three separate units. The preference of a d10 Zn center to attain a tetrahedral local environment trumps any stabilization gained by removal of constraints within the ligand set
Syntheses, Characterization, Density Functional Theory Calculations, and Activity of Tridentate SNS Zinc Pincer Complexes Based on Bis-Imidazole or Bis-Triazole Precursors
A series of tridentate pincer ligands, each possessing two sulfur- and one nitrogen-donor functionalities (SNS), based on bis-imidazole or bis-triazole salts were metallated with ZnCl2 to give new tridentate SNS pincer zinc(II) complexes [(SNS)ZnCl]+. The zinc complexes serve as models for the zinc active site in liver alcohol dehydrogenase (LADH) and were characterized with single crystal X-ray diffraction, 1H, 13C, and HSQC NMR spectroscopies, electrospray mass spectrometry, and elemental analysis. The zinc complexes feature SNS donor atoms and pseudotetrahedral geometry about the zinc center, as is seen for liver alcohol dehydrogenase. The bond lengths and bond angles of the zinc complexes correlate well to those in horse LADH. The SNS ligand precursors were characterized with 1H, 13C, and HSQC NMR spectroscopies, elemental analysis, and cyclic voltammetry, and were found to be redox active. Gaussian calculations were performed and agree with the experimentally observed oxidation potentials for the pincer ligand precursors. The zinc complexes were screened for the reduction of electron-poor aldehydes in the presence of a hydrogen donor, 1-benzyl-1,4-dihydronicotinamide (BNAH), and it was determined that they enhance the reduction of electron-poor aldehydes. The SNS zinc pincer complexes with bis-triazole ligand precursors exhibit higher activity for the reduction of 4-nitrobenzaldehyde than do SNS zinc pincer complexes with bis-imidazole ligand precursors. Quantitative stoichiometric conversion was seen for the reduction of pyridine-2-carboxaldehyde via SNS zinc pincer complexes with either bis-imidazole or bis-triazole ligand precursors
500,000 Years of Environmental History in Eastern Anatolia: The PALEOVAN Drilling Project
International Continental Scientific Drilling Program
(ICDP) drilled a complete succession of the lacustrine sediment
sequence deposited during the last ~500,000 years in
Lake Van, Eastern Anatolia (Turkey). Based on a detailed
seismic site survey, two sites at a water depth of up to 360 m
were drilled in summer 2010, and cores were retrieved from
sub-lake-floor depths of 140 m (Northern Basin) and 220 m
(Ahlat Ridge). To obtain a complete sedimentary section, the
two sites were multiple-cored in order to investigate the paleoclimate
history of a sensitive semi-arid region between the
Black, Caspian, and Mediterranean seas. Further scientific
goals of the PALEOVAN project are the reconstruction of
earthquake activity, as well as the temporal, spatial, and
compositional evolution of volcanism as reflected in the deposition
of tephra layers. The sediments host organic matter
from different sources and hence composition, which will be
unravelled using biomarkers. Pathways for migration of continental
and mantle-derived noble gases will be analyzed in
pore waters. Preliminary 40Ar/39Ar single crystal dating of
tephra layers and pollen analyses suggest that the Ahlat
Ridge record encompasses more than half a million years of
paleoclimate and volcanic/geodynamic history, providing
the longest continental record in the entire Near East to
date
Chronic social stress increases nitric oxide-dependent vasorelaxation in normotensive rats
The aim of this study was to examine oxidative load and endothelium-dependent vasorelaxation in the serotonin pre-constricted femoral artery (FA) of Wistar-Kyoto (WKY) rats exposed to chronic social stress produced by crowding in the presence or absence of ascorbic acid (AsA) in working solution. Adult male rats were randomly divided into control (living space: 480 cm2/rat) or stressed (living space: 200 cm2/rat) groups for 8 weeks. Blood pressure and heart rate, determined using tail-cuff plethysmography, were not influenced by stress vs. control. Conjugated dienes (CD) and concentrations of thiobarbituric acid-reactive substances (TBARS) were measured in the left ventricle and liver (for assessment of oxidative load) and were found unchanged by chronic crowding. The nitric oxide (NO)-dependent component of endothelium-dependent relaxation was investigated in the FA using a wire myograph. In both the presence and absence of AsA, acetylcholine-induced relaxation of the FA of stressed rats significantly exceeded that of the controls, which was associated with an increase of the NO-dependent component. In conclusion, the data showed that chronic crowding did not produce oxidative stress in the organs investigated and indicate that elevation of NO production during chronic stress is an important way of adaptation, which may prevent normotensive rats from the development of stress-induced hypertension
Therapeutic implications of improved molecular diagnostics for rare CNS-embryonal tumor entities: results of an international, retrospective study
BACKGROUND: Only few data are available on treatment-associated behavior of distinct rare CNS-embryonal tumor entities previously treated as "CNS-primitive neuroectodermal tumors" (CNS-PNET). Respective data on specific entities, including CNS neuroblastoma, FOXR2 activated (CNS NB-FOXR2), and embryonal tumor with multi-layered rosettes (ETMR) are needed for development of differentiated treatment strategies. METHODS: Within this retrospective, international study, tumor samples of clinically well-annotated patients with the original diagnosis of CNS-PNET were analyzed using DNA methylation arrays (n=307). Additional cases (n=66) with DNA methylation pattern of CNS NB-FOXR2 were included irrespective of initial histological diagnosis. Pooled clinical data (n=292) were descriptively analyzed. RESULTS: DNA methylation profiling of "CNS-PNET" classified 58(19%) cases as ETMR, 57(19%) as HGG, 36(12%) as CNS NB-FOXR2, and 89(29%) cases were classified into 18 other entities. Sixty-seven (22%) cases did not show DNA methylation patterns similar to established CNS tumor reference classes. Best treatment results were achieved for CNS NB-FOXR2 patients (5-year PFS: 63%±7%, OS: 85%±5%, n=63), with 35/42 progression-free survivors after upfront craniospinal irradiation (CSI) and chemotherapy. The worst outcome was seen for ETMR and HGG patients with 5-year PFS of 18%±6% and 22%±7%, and 5-year OS of 24%±6% and 25%±7%, respectively. CONCLUSION: The historically reported poor outcome of CNS-PNET patients becomes highly variable when tumors are molecularly classified based on DNA methylation profiling. Patients with CNS NB-FOXR2 responded well to current treatments and a standard-risk-CSI based regimen may be prospectively evaluated. The poor outcome of ETMR across applied treatment strategies substantiates the necessity for evaluation of novel treatments
Muszyca u ludzi wywołana przez Lucilia sericata
Myiasis is a rare, worldwide, human disease with seasonal variation, caused by developing larvae of a variety of fly species. It can be dangerous when infestations penetrate into the brain. In the available literature, we have found only a few papers concerning ear myiasis caused by Lucilia sericata. Here, we report 2 cases of aural myiasis. Early intervention (surgical removal, occlusion) in these cases should prevent complications. Larvae, for further examination, should be killed by immersion in very hot water, then preserved in an ethanol
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