Calcium signaling in platelets VARGA‐SZABO, D.; BRAUN, A.; NIESWANDT, B.
Journal of thrombosis and haemostasis,
July 2009, Volume:
7, Issue:
7
Journal Article
Peer reviewed
Open access
Agonist‐induced elevation in cytosolic Ca2+ concentrations is essential for platelet activation in hemostasis and thrombosis. It occurs through Ca2+ release from intracellular stores and Ca2+ entry ...through the plasma membrane (PM). Ca2+ store release is a well‐established process involving phospholipase (PL)C‐mediated production of inositol‐1,4,5‐trisphosphate (IP3), which in turn releases Ca2+ from the intracellular stores through IP3 receptor channels. In contrast, the mechanisms controlling Ca2+ entry and the significance of this process for platelet activation have been elucidated only very recently. In platelets, as in other non‐excitable cells, the major way of Ca2+ entry involves the agonist‐induced release of cytosolic sequestered Ca2+ followed by Ca2+ influx through the PM, a process referred to as store‐operated calcium entry (SOCE). It is now clear that stromal interaction molecule 1 (STIM1), a Ca2+ sensor molecule in intracellular stores, and the four transmembrane channel protein Orai1 are the key players in platelet SOCE. The other major Ca2+ entry mechanism is mediated by the direct receptor‐operated calcium (ROC) channel, P2X1. Besides these, canonical transient receptor potential channel (TRPC) 6 mediates Ca2+ entry through the PM. This review summarizes the current knowledge of platelet Ca2+ homeostasis with a focus on the newly identified Ca2+ entry mechanisms.
Two different silver colloids were prepared by chemical reduction of silver nitrate with trisodium citrate and hydroxylamine hydrochloride to compare their characteristics in relation to their ...possible use in surface-enhanced Raman scattering (SERS) spectroscopy. The morphology and plasmon resonance of the single nanoparticles and aggregates integrating these colloids were characterized by means of UV−vis absortion spectroscopy and scanning electron microscopy, revealing important differences between each type of nanoparticle as concerns their physical properties. These metallic systems also manifested differences in the aggregation and the adherence to glass surfaces, revealing significant differences in the chemical surface properties of these nanoparticles. SERS and surface-enhanced IR also indicated the presence of interference bands which can overlap the spectra of the analyte, mainly in the case of the citrate colloid. All these differences have an important influence on the applicability of these nanostructured systems in SERS. In fact, the enhancement factor and spectral pattern of the SERS obtained by using alizarin as a molecule probe are different.
Over the past 60 years a rich sample of experimental results concerning the inclusive production of
π
-
mesons has been obtained spanning a range from about 3 GeV to 13 TeV in interaction energy. ...This paper attempts a model-independent overview of these results with the aim at obtaining an internally consistent data description on a dense grid over the three inclusive variables transverse momentum, rapidity or Feynman
x
F
and interaction energy. The study concentrates on the non-perturbative sector of the strong interaction by limiting the transverse momenta to
p
T
<
1.3 GeV/c. The three-dimensional interpolation which is mandatory and necessary for this aim is shown to provide a controlled systematic precision of better than 5%. This accuracy allows for a critical inspection of each of the 40 experiments concerned in turn. It also allows precision tests of some of the physics concepts developed around inclusive processes like energy scaling, “thermal” production and the evolution of transverse momenta.
Integrins in platelet activation NIESWANDT, B.; VARGA‐SZABO, D.; ELVERS, M.
Journal of thrombosis and haemostasis,
July 2009, Volume:
7
Journal Article
Peer reviewed
Open access
Heterodimeric receptors of the β1 and β3 integrin families mediate platelet adhesion and aggregation in hemostasis and thrombosis. In resting platelets, integrins are expressed in a low‐affinity ...state but they shift to a high‐affinity state and efficiently bind their ligands in response to cellular activation. This review summarizes recent advances in understanding the functional regulation and (patho‐) physiological significance of individual platelet integrins with a special focus on studies in genetically modified mice. It is now recognized that β1 and β3 integrins have partially redundant roles in the adhesion process and that their activation is regulated by similar mechanisms, involving Ca2+‐dependent and ‐independent signaling events and essential functions of talin‐1 and kindlin‐3 in the terminal activation step.
Gaseous detectors are one of the popular particle tracking technologies in high energy physics, and there are multiple applications where the detectors must tolerate outdoor conditions, e.g. in the ...emerging field of muography. Gaseous tracking detectors are attractive choices due to their high efficiency, good resolution and large sensitive area at a reasonable cost and low weight, but to achieve these, the gas system is usually not sealed. Continuous gas flow results gas consumption and thus regular gas cylinder replacement which limits applicability. In this paper we present a practical solution to reduce gas flow to a negligible level, keeping the construction cost-efficient and low weight, by a properly chosen buffer tube at the end of the gas line, which makes the system able to withstand large temperature and pressure fluctuations.
The influence of bed depth on the performance of aerated horizontal constructed wetlands was investigated at the pilot plant scale. Two horizontal flow subsurface constructed wetlands (HF) ...intensified units of different bed depth (HF1: 0.90 m and HF2: 0.55 m, 0.8 m and 0.5 m water level, respectively) were fitted with forced aeration, while a third one (HFc, 0.55 m bed depth, 0.5 m water level) was used as control and not aerated. The three HF units were operated in parallel, receiving the same municipal wastewater pre-treated in a hydrolytic up-flow sludge blanket anaerobic digester. Applied surface loading rates (SLR) ranged from 20 to 80 g biochemical oxygen demand (BOD5)/m2·d and from 3.7 to 6.7 g total nitrogen (TN)/m2·d, while it ranges from 6 to 23 g BOD5/m2·d and from 1.1 to 1.7 g TN/m2·d in the control unit. Removal of total suspended solids (TSS) and BOD5 was usually close to a 100 % in all units, whilst chemical oxygen demand (COD) removal was higher for the HF1 unit (97 % on average, range of 96-99 %) than for HF2 (92 %, 82-98 %) and HFc (94 %, 86-99 %). TN removal reached on average 33 % (16-43 %) in HFc, 37 % (10-76 %) in HF2 and 51 % (21-79 %) in HF1. High TN removal required a longer aeration time for nitrification and higher effluent recirculation ratio to enhance denitrification. The results indicate that artificial aeration and a high bed depth allows to increase the SLR by a factor of 4 in HF1 but only by a factor of 2 in HF2.
A full-scale hybrid constructed wetland (CW) was built to treat mixed effluent derived from a winery and tourist establishment. The treatment system consisted of a hydrolytic upflow sludge bed (HUSB) ...digester for suspended-solids removal, a vertical-flow (VF) constructed wetland and three parallel subsurface horizontal-flow (HF) constructed wetlands. The HUSB reduced TSS loads to 72–172
mg
L
−1, helping to prevent clogging, while organic loads for the wastewater entering the VF ranged from 422 to 2178
mg
COD
L
−1 and from 216 to 1379
mg
BOD
5
L
−1. At an average hydraulic loading rate (HLR) of 19.5
mm
d
−1 and average surface loading rates (SLR) of 30.4
g
COD
m
−2
d
−1 and 18.4
g
BOD
5
m
−2
d
−1, the overall VF
+
HF CW system reached average removal efficiencies of 86.8% of TSS, 73.3% of COD, and 74.2% of BOD
5. The system also removed 52.4% of total Kjeldhal nitrogen (TKN), 55.4% of NH
3-N and 17.4% of phosphates. While the VF unit showed high removal rates, the HF unit operated at lower removal rates than those previously reported. The CW units showed rapid adaptation to low pH values. A linear-regression analysis indicated that the independent variables SLR and temperature determined more than 95% of the variation in performance and efficiency of the CW system and offered simple mathematical models for design and system-description purposes.
The validity of the Kubelka-Munk (K-M) theory was investigated to determine the IR absorption spectra of wood based on diffuse reflection infrared Fourier transform (DRIFT) measurements taken on ...photodegraded samples. After analysing plenty of DRIFT spectra of wood and examining the shape of the K-M equation, it can be concluded that the measured K-M function can be used as an absorption spectrum if the values of the function are below 14 K-M units. Above this limit, the K-M theory, which was created for poorly absorbing materials, does not give the absorption of wood properly. If a matt aluminium plate is used as a background material and the values are between 14 and 40, absorption changes can be calculated after normalisation of the spectra. This normalising manipulation is only successful if there is an absorption peak close to the examined one which does not change its absorption during the photodegradation.
The main operational problem of subsurface flow constructed wetlands (CWs) is clogging of granular medium, a phenomenon related to the accumulation of different types of solids that lead to a ...reduction of the infiltration capacity of the gravel bed. It is generally accepted that the application of a good wastewater pre-treatment is essential for the long-term operation of subsurface flow CW. Anaerobic digesters (ADs) could help to the aim of clogging prevention. Two combined AD-CW treating either municipal or winery wastewater were designed and monitored for trough performance and efficiency parameters, solids accumulation and hydraulic conductivity, over a long term period. CW operated at high organic loading rates in terms of TCOD and BOD5 while suspended solids loading rates and solids accumulation in CW were lower. In turn, CW maintained an adequate hydraulic conductivity and low rates of solids accumulation.
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