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1.
A novel experimental method was developed which allows the determination of the threshold concentration of sucrose by use of a linear sucrose gradient in water. With this method a continuous tasting of the test-liquid is possible. A panel of 15 persons experienced in taste-testing was used. Three gradients of different steepness were applied: 0 to 1.5% (w/w) sucrose in 2 min (I), 3 min (II) and 4 min (III). The results of the new method were compared with those of the standard method (DIN). With gradients I and II we found values which were significantly higher than those of the standard method (I: 0.49% (w/w); II: 0.46% (w/w); DIN: 0.31% (w/w)), whereas with gradient III the same threshold value was found as with the DIN-Method (III: 0.32% (w/w)). 相似文献
2.
The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs. 相似文献
3.
The compulsory dispute settlement regime included in the 1982 Law of the Sea Convention is recognized as one of the most comprehensive in a modern international convention. Yet, in the recent application of this regime, the question has arisen as to whether the procedural prerequisites associated with the LOS Convention's compulsory dispute settlement mechanism are so arduous as to avoid binding and compulsory jurisdiction in most instances. This article addresses that question by examining, in particular, the reasoning of the Southern Bluefin Tuna arbitration tribunal, which found Article 281 of Section 1 of the LOS Convention to bar jurisdiction to the compulsory dispute settlement mechanism prescribed by the Convention, and offers suggestions as to how states might distinguish or overcome the barriers imposed by the Southern Bluefin Tuna tribunal in future cases. 相似文献
4.
Caveolae are present in almost all cells and concentrate a wide variety of signaling molecules, receptors, transporters, and ion pumps. We have investigated the distribution of the ryanodine receptor, the Na(+)/Ca(2+) exchanger, the predominant Na(+) channel isoform rH1, and the L-type calcium channel, Ca(v)1.2, relative to the muscle-specific caveolin isoform, caveolin-3, in adult rat ventricular myocytes. Three-dimensional immunofluorescence images were deconvolved and analyzed. Caveolin-3 colocalizes with all of these molecules at the surface of the cell, but there is no significant colocalization between caveolin-3 and either the Na(+)/Ca(2+) exchanger or the Na(+) channel in the cell interior. The distribution of the surface colocalization indicates that the caveolae that colocalize with each molecule form distinct populations. This organization indicates that there are multiple populations of caveolae separable by location and occupants. In the interior of the cell, caveolin-3 shows a marked colocalization with a population of ryanodine receptors that are separate from those within the dyad. Because of their location, the signaling molecules contained within these caveolae may have preferred access to the neighboring nondyadic ryanodine receptors. 相似文献
5.
T. WORTHINGTON P. S. KEMP P. E. OSBORNE A. DILLEN J. COECK M. BUNZEL‐DRÜKE M. NAURA J. GREGORY K. EASTON 《Freshwater Biology》2012,57(3):602-611
1. Availability of suitable habitat is a prerequisite for species reintroduction success, and to ensure population persistence, investigations of a species’ habitat utilisation throughout its life history should be conducted as part of a feasibility study. 2. Habitat utilisation models for burbot, Lota lota, developed using data from field studies conducted in France and Germany and information from the literature were used to assess the feasibility of reintroducing burbot into rivers of its former native range in eastern England. 3. Per cent tree roots, aquatic vegetation and flow types were important predictors of adult burbot abundance. Furthermore, the habitat utilisation models were supplemented with information from the literature, which suggested that off‐channel habitat such as wetlands and backwaters is important for spawning and nursery stages. 4. An assessment of the habitat availability in the rivers of the burbot’s former native range using variables related to spawning and nursery and adult life stages showed that although adult habitat was widely distributed, the availability of spawning and nursery habitat was less abundant, potentially limiting successful reestablishment. 5. Potential suitable habitat was concentrated in the central and southern areas of the species’ former English distribution. Overall, rivers of the burbot’s former range potentially afford suitable habitat to sustain a reintroduced population. However, sites should be preferentially selected on the basis of having appropriate spawning and nursery areas. 相似文献
6.
The couplons of the cardiomyocyte form nanospaces within the cell that place the L-type calcium channel (Cav1.2), situated on the plasmalemma, in opposition to the type 2 ryanodine receptor (RyR2), situated on the sarcoplasmic reticulum. These two molecules, which form the basis of excitation–contraction coupling, are separated by a very limited space, which allows a few Ca2+ ions passing through Cav1.2 to activate the RyR2 at concentration levels that would be deleterious to the whole cell. The limited space also allows Ca2+ inactivation of Cav1.2. We have found that not all couplons are the same and that their properties are likely determined by their molecular partners which, in turn, determine their excitability. In particular, there are a class of couplons that lie outside the RyR2-Cav1.2 dyad; in this case, the RyR2 is close to caveolin-3 rather than Cav1.2. These extra-dyadic couplons are probably controlled by the multitude of molecules associated with caveolin-3 and may modulate contractile force under situations such as stress. It has long been assumed that like the skeletal muscle, the RyR2 in the couplon are arranged in a structured array with the RyR2 interacting with each other via domain 6 of the RyR2 molecule. This arrangement was thought to provide local control of RyR2 excitability. Using 3D electron tomography of the couplon, we show that the RyR2 in the couplon do not form an ordered pattern, but are scattered throughout it. Relatively few are in a checkerboard pattern—many RyR2 sit edge-to-edge, a configuration which might preclude their controlling each other's excitability. The discovery of this structure makes many models of cardiac couplon function moot and is a current avenue of further research 相似文献
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Axial Tubules of Rat Ventricular Myocytes Form Multiple Junctions with the Sarcoplasmic Reticulum 总被引:1,自引:0,他引:1
Ryanodine receptors (RyRs) are located primarily on the junctional sarcoplasmic reticulum (SR), adjacent to the transverse tubules and on the cell surface near the Z-lines, but some RyRs are on junctional SR adjacent to axial tubules. Neither the size of the axial junctions nor the numbers of RyRs that they contain have been determined. RyRs may also be located on the corbular SR and on the free or network SR. Because determining and quantifying the distribution of RyRs is critical for both understanding and modeling calcium dynamics, we investigated the distribution of RyRs in healthy adult rat ventricular myocytes, using electron microscopy, electron tomography, and immunofluorescence. We found RyRs in only three regions: in couplons on the surface and on transverse tubules, both of which are near the Z-line, and in junctions on most of the axial tubules—axial junctions. The axial junctions averaged 510 nm in length, but they occasionally spanned an entire sarcomere. Numerical analysis showed that they contain as much as 19% of a cell's RyRs. Tomographic analysis confirmed the axial junction's architecture, which is indistinguishable from junctions on transverse tubules or on the surface, and revealed a complexly structured tubule whose lumen was only 26 nm at its narrowest point. RyRs on axial junctions colocalize with Cav1.2, suggesting that they play a role in excitation-contraction coupling. 相似文献