BB_RADABA: a computer program as a tool for breeding and management of laboratory animals.

The use of well characterized laboratory animals in biomedical research is of importance for quality securing and reproducibility of animal experiments. Therefore, breeders should not only have in mind the reproduction of their animal stocks, but they should also be interested to achieve an optimal resemblance of the animals in the main traits characterizing them as a model of human diseases. Specific software applications which helps the breeders in monitoring the main breeding parameters, selecting suitable breeding pairs and data processing are practically not available. This prompted us to develop a computer program for management of breeding and experimental data, which we called BB_RADABA. In this report we want to give a short survey on this computer program.     

Induced free liquid surface oscillations in a visco-elastic liquid column due to angular temperature fluctuations

The response due to time-fluctuating temperature distribution applied at the free surface of a viscoelastic cylindrical liquid column with no axial dependency has been determined analytically. The amplitude of the radial- and angular velocity as well as the free liquid surface elevation has been presented as a function of the “reduced” forcing frequency of the oscillatory temperature and has numerically been evaluated for an angular temperature field proportional to sin 2φ. It was found, that visco-elasticity as described by the Maxwell model has quite some influence upon the liquid behavior. It shows for larger relaxation times besides the enlarged resonance peak additional peaks below and above resonance. This is particularly evident inside the liquid column, indicating a more pronounced elastic behavior of the liquid.     

Saturation intensity and time response of InGaAs-InGaP MQW opticalmodulators

We report modulation saturation and time response measurements on InGaAs-InGaP MQW modulators. The measurements yield a saturation intensity of (3.7±0.1) kW/cm² for a 0-10 V swing and switching times between 10 and 90 ns, depending on the bias voltage and incident light intensity. The observed dependence indicates that field screening due to carrier build-up is the dominant physical mechanism determining both the speed and the saturation intensity. This conclusion is supported by results of theoretical calculations     

Accumulation of nitrite and sulfite in yeast cells and synergistic depletion of the intracellular ATP content

Summary When nitrite or sulfite are applied to yeast cells below pH 5.0, an enormous intracellular accumulation occurs. It is assumed that nitrite and sulfite penetrate the cell membrane in their undissociated forms as nitrous acid (pK = 3.3) or sulfurous acid (pK =1.8), respectively. Due to the neutral intracellular pH they are trapped inside the cell in their anionic forms, which are impermeable to the cell membrane. It has previously been shown that sulfite causes a rapid depletion of the ATP content of yeast cells [Schimz, K. L. and Holzer, H. (1979) resp. Hinze et al. as above]. Similarly, millimolar concentrations of nitrite decrease the ATP level to less than 10% of the initial value. Nitrite and sulfite in combination deplete the ATP content of yeast cells much stronger than expected for the sum of the separate effects of these compounds (synergistic effect).

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Akkumulation von Nitrit und Sulfit in Hefezellen und synergistischer Abfall des intrazellulären ATP-Gehalts

Zusammenfassung Wenn Hefezellen mit Nitrit oder Sulft bei pH-Werten unter 5,0 inkubiert werden, beobachtet man eine starke intracelluläre Akkumulation von Nitrit, bzw. Sulfit. Es ist anzunehmen, daß Nitrit und Sulfit in ihrer undissoziierten Form als salpetrige Säure (pK=3,3) bzw. schweflige Säure (pK=1,8) penetrieren und dann in den Zellen durch Neutralisation zu den anionischen Formen, die die Zellmembran nicht mehr permeieren können, abgefangen werden. Ähnlich dem früher beschriebenen raschen Abfall des ATP-Gehaltes nach Zusatz von Sulfit in Hefe [Schimz, KL und Holzer H (1979) Arch Microbiol 121:225–229] und in Bakterien [Hinze H, Maier K, Holzer H (1981) Z Lebensm Unters Forsch 172:389-392] verursacht auch Nitrit einen raschen Abfall des ATP-Gehaltes in Hefe auf weniger als 10 % des Anfangswertes. Werden Nitrit und Sulfit in Kombination verabreicht, so beobachtet man einen wesentlich stärkeren Abfall des ATP-Gehaltes als er aus der Summe der Einzeleffekte von Nitrit, bzw. Sulfit zu erwarten wäre (Synergistischer Effekt).

     

Control of yeast neutral trehalase by distinct polyphosphates and ribonucleic acid

Summary The activity of yeast trehalase when assayed at pH 7 in a crude extract was found to increase 2- to 3-fold upon incubation with 0.1 % (v/v) polyethyleneimine or other polycations such as polylysine (0.075-mMol) and calf thymus histories (0.08 mMol). Incubation with 3 mM-Mn²⁺ and 5 mM-Ca²⁺ also led to 3- and 1.6-fold increases in trehalase activity, respectively. The activities of 11 other enzymes assayed in the crude yeast extract did not increase after addition of polyethylene imine. At concentrations of polyethylenemine that maximally stimulated trehalase activity, 97% of the total RNA present in the crude extract, 40% of total protein, and 60% of the polyphosphate (assayed as inorganic phosphate liberated during 7 min incubation at 95 °C and pH O) were found to be precipitated. A similar finding was made with trehalase-stimulating concentrations of Mn²⁺. Activation of trehalase by polyethylene imine rendered this enzyme susceptible to inhibition by a preparation of total yeast RNA, inorganic polyphosphates, and related polyanions. We present further evidence that the removal of a distinct RNA and/or polyphosphate is the basic principle of polyetyleneimine-induced activation of trehalase.A more pronounced stimulation of trehalase activity (4-fold) could be obtained by enzymatic phosphorylation with ATP in the presence of cyclic AMP and Mg²⁺ as described by van Solingen and van der Plaat (1975) [9]. Thus, trehalase 2-fold activated by polyethylene imine was further activated by another 2-fold increase by enzymatic phosphorylation. Conversely, no additional stimulation by polyethylene imine was obtained for the maximally active, phosphorylated enzyme. We conclude that phosphorylation-mediated activation of trehalase is a two-step event, one being the removal of an inhibitor, which can be achieved by polyethylene imine or related cations independent on phosphorylation. The most likely candidate for the inhibitor appears to be a distinct RNA.

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Kontrolle der neutralen Hefen-Trehalase durch bestimmte Polyphosphate und RNA

Zusammenfassung Die in einem rohen Extrakt aus Hefe bei pH 7 gemessene Aktivität von Trehalase nimmt bei der Inkubation mit 0,1% Polyethylenimin oder mit anderen Polykationen, wie Polylysin (0,075 mmol) oder Histon aus Kalbsthymus (0,08 mmol) auf das zwei- bis dreifache zu. Auch die Inkubation mit 3 mmol Mn²⁺ oder 5 mmol Ca²⁺ führt zu einer 3-, bzw. 1,6fachen Zunahme der Trehalase-Aktivität. Die Aktivität von 11 anderen Enzymen, die im rohen Extrakt aus Hefe bestimmt wurden, nimmt nach Zusatz von Polyethylenimin nicht zu. Bei der Inkubation mit Polyethylenimin, das eine maximale Stimulierung der Trehalase-Aktivität bewirkt, werden 97% der gesamten Ribonucleinsäure, 40% des gesamten Proteins und 60% des Polyphosphats (bestimmt als anorganisches Phosphat, das in 7 min bei 95 °C und pH O freigesetzt wird) präcipitiert. Eine gleichartige Präcipitation wurde bei der Inkubation mit Trehalase-stimulierenden Konzentrationen von Mn²⁺ beobachtet. Mit Polyethylenimin aktivierte Trehalase wird durch Ribonucleinsäure aus Hefe, anorganisches Polyphosphat und verwandte Polyanionen gehemmt. Vermutlich führt die Entfernung einer bestimmten Ribonucleinsäure-Fraktion und/oder von Polyphosphat zu der Polyethylenimin-induzierten Aktivierung der Trehalase.Wie von van Solingen und van der Plaat 1975 beschrieben [9], wird eine 4fache Stimulierung von Trehalase durch enzymatische Phosphorylierung mit ATP in der Gegenwart von cyclischem AMP und Mg²⁺ erreicht. Das so durch Phosphorylierung maximal aktivierte Enzym kann durch Zusatz von Polyethylenimin nicht weiter aktiviert werden. Das mit Polyethylenimin 2fach aktivierte Enzym kann jedoch noch einmal 2fach weiter aktiviert werden durch enzymatische Phosphorylierung. Aus diesen Beobachtungen wird geschlossen, daß die durch enzymatische Phosphorylierung bewirkte Aktivierung der Trehalase ein zweistufiger Vorgang ist: Zuerst findet die Entfernung eines Inhibitors statt (dies kann auch mit Polyethylenimin oder mit verwandten Kationen unabhängig von der enzymatischen Phosphorylierung erreicht werden), hierauf folgt weitere Aktivierung durch Konformationsänderung des Enzyms. Wahrscheinlich handelt es sich bei dem durch Phosphorylierung bzw. Behandlung mit Polyethylenimin abgetrennten Inhibitor um eine gewisse Ribonucleinsäure-Fraktion.

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Abbreviation PEI polyethylene imine The followingenzymes are mentioned in the text: Alcohol dehydrogenase Glyceraldehyde-3-phosphate dehydrogenase (1.1.1.12), Malate dehydrogenase (1.1.1.37), Glucose-6-phosphate dehydrogenase (1.1.1.49), Glutamate dehydrogenase (NAD) (1.4.1.2), Glutamate dehydrogenase (NADP) (1.4.1.4), Aspartate -ketoglutarate aminotransferase (2.6.1.1), 6-Phosphofructokinase (2.7.1.11), Neutral trehalase (3.2.1.28), Pyruvate decarboxylase (4.1.1.1), Phosphoenolpyruvate carboxykinase (4.1.1.49).This paper is dedicated to Prof. Dr. Karl Decker on the occasion of his 60th birthday     

On Iron Metabolism and Its Regulation

Iron is a critical metal for several vital biological processes. Most of the body’s iron is bound to hemoglobin in erythrocytes. Iron from senescent red blood cells is recycled by macrophages in the spleen, liver and bone marrow. Dietary iron is taken up by the divalent metal transporter 1 (DMT1) in enterocytes and transported to portal blood via ferroportin (FPN), where it is bound to transferrin and taken up by hepatocytes, macrophages and bone marrow cells via transferrin receptor 1 (TfR1). While most of the physiologically active iron is bound hemoglobin, the major storage of most iron occurs in the liver in a ferritin-bound fashion. In response to an increased iron load, hepatocytes secrete the peptide hormone hepcidin, which binds to and induces internalization and degradation of the iron transporter FPN, thus controlling the amount of iron released from the cells into the blood. This review summarizes the key mechanisms and players involved in cellular and systemic iron regulation.     

Analytical studies on the temperature distribution in spiral plate heat exchangers: Straightforward design formulae for efficiency and mean temperature difference

The temperature distribution in spiral plate heat exchangers has been calculated numerically to obtain the efficiency and the logarithmic mean temperature difference (LMTD) correction factors F as a function of the number of transfer units N, the number of turns n, and the heat capacity rate ratio C. It has been found that the LMTD correction factors, when plotted against the number of transfer units per turn N/n, fall approximately on a single curve. That curve for balanced countercurrent operation (C = −1) can be very closely represented by the simple formula F = (n/N)tanh(N/n). From that simple analytic representation of our numerical results it was concluded that a simpler physical model might exist to represent the overall behaviour of a spiral plate heat exchanger equally well. In fact, a countercurrent cascade of n cocurrent heat exchangers does result exactly in the above-mentioned formula for the LMTD correction factor. From that model the F-factors for other heat capacity rate ratios C (−1 < C 0) can also be calculated and they are in sufficient agreement with the numerical results.     

Efficient material design for diesel particulate filters

This paper will give an overview about the filter development for diesel particulate emission control in automotive applications. The material development for passenger car diesel particulate filters led to new materials like silicon carbide while for heavy duty applications still Cordierite plays a major role. But in the future other materials might also be used for passenger cars. This paper will show the basic difference between both applications and describe the material design in terms of filter properties (base material, back pressure aspects, filtration efficiency, coating impact). Current application on vehicles with catalysed soot filters (CSF) with and without oxidation catalyst will be presented. Furthermore an outlook will be given on materials for catalysed soot filters for the future.