Effect of a changed temperature regime on the benthos of a norwegian regulated river

The lowermost 20 km of the River Surna, north-western Norway receives cool water during summer from a hypolimnetic release mountain reservoir. The benthic fauna is completely dominated by insects. Benthic densities immediately below the power station are much lower than at all other localities. Although benthic densities increase downstream of the power station, they never exceed the densities above. The dominant insect group, chironomids, can be divided into four categories according to their abundance and distribution above and below the power station: (1) rare or absent above, but common or abundant below; (2) abundant or common above but rare or absent below; (3) slightly less abundant below; (4) unchanged abundance. No major differences in the species composition were recorded for stonefilies, mayflies and caddisflies.     

Cloning and characterization of a cDNA encoding a novel subtype of rat thyrotropin-releasing hormone receptor

A cDNA encoding a thyrotropin-releasing hormone (TRH) receptor expressed in the pituitary was previously cloned (De La Pena, P., Delgado, L. M., Del Camino, D., and Barros, F. (1992) Biochem. J. 284, 891-899; De La Pena, P., Delgado, L. M., Del Camino, D., and Barros, F. (1992) J. Biol. Chem. 267, 25703-25708; Duthie, S. M., Taylor, P. L., Anderson, J., Cook, J., and Eidne, K. A. (1993) Mol. Cell Endocrinol. 95, R11-R15). We now describe the isolation of a rat cDNA encoding a novel subtype of TRH receptor (termed TRHR2) displaying an overall homology of 50% to the pituitary TRH receptor. Introduction of TRHR2 cDNA in HEK-293 cells resulted in expression of high affinity TRH binding with a different pharmacological profile than the pituitary TRH receptor. De novo expressed receptors were functional and resulted in stimulation of calcium transient as assessed by fluorometric imaging plate reader analysis. The message for TRHR2 was exclusive to central nervous system tissues as judged by Northern blot analysis. Studies of the expression of TRHR-2 message by in situ hybridization revealed a pattern of expression remarkably distinct (present in spinothalamic tract, spinal cord dorsal horn) from that of the pituitary TRH receptor (present in hypothalamus, and ventral horn of the spinal cord, anterior pituitary). Therefore, we have identified a novel, pharmacologically distinct receptor for thyrotropin-releasing hormone that appears to be more restricted to the central nervous system particularly to the sensory neurons of spinothalamic tract and spinal cord dorsal horn, which may account for the sensory antinociceptive actions of TRH.     

Microprocesses of metal dusting on nickel and Ni-base alloys

Microstructural and microchemical investigations were carried out on nickel and Inconel 600 after exposure to strongly carburizing atmospheres at temperatures of about 600 to 650°C to study their metal dusting behaviour. Contrary to iron and low-alloy steels, where metal dusting proceeds via the formation and disintegration of a metastable carbide M₃C, both nickel and Inconel 600 directly disintegrate. Inside the metal this disintegration proceeds by formation of thin graphite filaments of nearly 10 nm in diameter, the atomic basal planes of which are oriented perpendicular to the surface thus effecting a high reactivity at the growth front. Subsequently, fine particles or larger parts of the metal surface layer are released, which are buried in the deposited graphite layer on the surface. In case of Inconel 600, containing Cr with mass contents of about 15%, the disintegration can be delayed by the formation of a chromium oxide layer, but no safe protection against metal dusting is obtained.     

Zur natrium- und kaliumbestimmung mit ionensensitiven elektroden

Zusammenfassung Obwohl sie zu den häufigsten Elementen gehören, zählen die Bestimmungen des Natriums und Kaliums in der Lebensmittelchemie zu den Ausnahmen. Da zwischen der Kochsalzaufnahme und dem Bluthochdruck ein Zusammenhang zu bestehen scheint, nimmt das Interesse an der tatsächlichen Kochsalzaufnahme ständig zu.Vorgestellt wird die Natrium- und Kaliumbestimmung mit Hilfe von ionensensitiven Elektroden, die Vorteile gegenüber der AAS aufweisen. Hierbei ist besonders die minimale Probenvorbereitung zu nennen. Die Methode ist nicht auf Getreideprodukte oder Backwaren beschränkt, sondern läßt sich nach Änderung der Vorbereitung auf praktisch alle Lebensmittel anwenden. Die Richtigkeit und Genauigkeit der Bestimmung konnte durch Vergleiche und Zusatzversuche bestätigt werden.

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Determination of sodium and potassium by ion-sensitive electrodes

Summary Although sodium and potassium belong to the most common elements, their determination in foods is rarely carried out. Because there seems to be a relationship between the consumption of sodium chloride and hypertension there is a growing interest in the actual intake of sodium chloride.Ion-sensitive electrodes are utilized for the determination of sodium and potassium with obvious advantages over the AAS, particularly by requiring a minimum of sample preparation. The method is applicable for practically all types of foods. Recovery rates were 96–102% and the reliability was verified by comparison with other methodology.

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Nr. 5011 der Veröffentlichungen der Bundesforschungsanstalt für Getreide- und Kartoffelverarbeitung, Detmold     

Optische Methoden zur Charakterisierung von hochpolymeren Fasern. 1. Methodik der Interferenzmikroskopie

Density and orientation describe, besides other characteristics, the structure of high polymers. They can be obtained as a function of the radius by measurement of the refraction index of the fibre. The influence of refraction of light on the obtained index of refraction n(r) is demonstrated by an optical model of the fibre. For fibres having a radius R < 30 μm and changes in the refraction index < 0.02 the influence of refraction is less than ± 0.0002 and therefore of no significance for most textile fibres. Important is the exact adaption of the refraction index of the embeding medium to the margin of the fibre. The computed index at the margin of the fibre takes always the refraction index of the embeding medium. An incorrect adaption can be traced up to 0.2·R into the fibre. A spline function used for the approximation of the relative displacement of interference fringes gives the opportunity to calculate extreme variations in refractive index, this is demonstrated using hollow fibres filled with paraffin-oil. Using a HeNe-laser interference-holographie became possible.     

Decidable properties of monadic recursive schemas with a depth parameter

Summary Monadic table counter schemas (MTCS) are defined as extensions of recursive monadic schemas by incorporating a depth-of-recursion counter. The family of languages generated by free MTCS under Herbrand interpretation is shown to be the family of ETOL languages. It is proven that the halting and divergence problems are decidable for free MTCS and that the freedom problem is decidable. Most of these results are obtained using results on regular control sequences from L system theory.     

RNA helicases: versatile ATP-driven nanomotors

RNA helicases are a large family of molecular motors that utilize nucleoside triphosphates to unwind RNA duplexes and to remodel RNA protein complexes. In this review, we discuss the structure and function of RNA helicases with an emphasis on the potential application of these enzymes to control conformational changes in nanoassemblies that contain RNA.     

Frequency distribution and signal formation around a vessel

We describe the NMR signal formation properties of a single vessel. Instead of assuming the frequency distribution to be a simple Lorentzian or Gaussian one, we take into account that the frequency distribution around the vessel is a complex function. Considering the static dephasing regime we find a relationship between signal formation and frequency distribution. Analytical expressions for the frequency distribution in a voxel and the magnetization decay are obtained. In the case of small volume fractions of blood and week magnetic fields the results can be used for describing signal formation processes in a vascular network. A relationship between the frequency distribution and the properties of the vascular network is derived. The magnetization decay in different time regimes is discussed. The result is relevant for describing signal formation processes around a vessel for arbitrary pulse sequences.