Einflu\ von Diffusionspotentialen auf Membranpotential- und IonenaktivitÄtsmessungen in biologischen Systemen am Beispiel von KCl-Rinderserumalbumin-Lösungen

Zusammenfassung Membranpotentiale und IonenaktivitÄten lassen sich aus EMK-Messungen nur dann nÄherungsweise bestimmen, wenn die Diffusionspotentiale an den beiden Salzbrücken nÄherungsweise berechnet werden können. Unter Benutzung der von Möller, van Os und Overbeek [Trans. Farad. Soc.57, 312 (1961)] gemessenen und durch die Anwesenheit des Rinderserumalbumins (RSA) verÄnderten elektrischen Beweglichkeit von K⁺- und Cl^–-Ionen in RSA-KCl-Lösungen verschiedener Konzentration wurden die überführungszahlen und derideale Anteil des Diffusionspotentials in einer Diffusionsschicht vom Henderson-Typ zwischen verschiedenen RSA-KCl-Lösungen und einer gesÄttigten KCl-Lösung berechnet. Bei dieser, an einer Rechenanlage durchgeführten Rechnung wurde die AktivitÄt der Komponenten durch deren Konzentration ersetzt. Au\erdem wurde der Einflu\ eines vom Wert in einer reinen Salzlösung gleicher Konzentration abweichenden AktivitÄtskoeffizienten für K⁺- und Cl^–-Ionen berechnet, wobei für den AktivitÄtskoeffizienten des Gegenions Werte zwischen 0,2 und 0,7 angenommen wurden. Die Rechnung ergab, da\ bei Anwesenheit des RSA-Moleküls mit einer Ladungszahl von — 22 in der Diffusionsschicht und bei Berücksichtigung der verschiedenen Kombinationen von Coionen- und GegenionenaktivitÄtskoeffizienten das Diffusionspotential einen Wert zwischen + 10 mV und – 10 mV annehmen kann.

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Liquid junction potential, membran potential, and ion activity in bovine serum albumin solutions and biological systems

Summary The determination of membrane potentials and single ion activities — although without strict thermodynamic basis — from e.m.f. measurement to a reasonable approximation presupposes an evaluation of the liquid junction potentials (l.j.p.) at the two salt bridges to the same degree of accuracy.Using the data for the electrical mobility of K⁺- and Cl^–-ions in bovine serum albumin solutions of differing compositions obtained by Möller, van Os, and Overbeek the transport numbers of K⁺ and Cl^– in these polyelectrolyte solutions and theideal part of the liquid junction potential were computed assuming a Henderson-type boundary and replacing activities by concentrations. The contribution of the terms containing various combinations of the activity coefficients for the colons between 0.5 and 0.9 and counter ions between 0.2 and 0.7 to the l.j.p. is of the same order of magnitude as theideal part of the l.j.p. containing the concentration and transport numbers alone. Taking the activity coefficients into account, the l.j.p. may reverse its sign. Practically all values for the l.j.p. are localized in the range between +10 mV and –10 mV.A crude approximation of the l.j.p. at the tip of a salt bridge located in the cytoplasm of a cell shows that even in this case the l.j.p. presumably has similar values.

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Herrn Professor Boris Rajewsky zum 75. Geburtstag gewidmet.     

EDC3 phosphorylation regulates growth and invasion through controlling P‐body formation and dynamics

Regulation of mRNA stability and translation plays a critical role in determining protein abundance within cells. Processing bodies (P‐bodies) are critical regulators of these processes. Here, we report that the Pim1 and 3 protein kinases bind to the P‐body protein enhancer of mRNA decapping 3 (EDC3) and phosphorylate EDC3 on serine (S)161, thereby modifying P‐body assembly. EDC3 phosphorylation is highly elevated in many tumor types, is reduced upon treatment of cells with kinase inhibitors, and blocks the localization of EDC3 to P‐bodies. Prostate cancer cells harboring an EDC3 S161A mutation show markedly decreased growth, migration, and invasion in tissue culture and in xenograft models. Consistent with these phenotypic changes, the expression of integrin β1 and α6 mRNA and protein is reduced in these mutated cells. These results demonstrate that EDC3 phosphorylation regulates multiple cancer‐relevant functions and suggest that modulation of P‐body activity may represent a new paradigm for cancer treatment.     

Adaptive function of duodichogamy: Why do chestnut trees have two pollen emission phases?

Premise

Intersexual mating facilitation in flowering plants has been largely underexplored. Duodichogamy is a rare flowering system in which individual plants flower in the sequence male-female-male. We studied the adaptive advantages of this flowering system using chestnuts (Castanea spp., Fagaceae) as models. These insect-pollinated trees produce many unisexual male catkins responsible for a first staminate phase and a few bisexual catkins responsible for a second staminate phase. We hypothesized that duodichogamy increases female mating success by facilitating pollen deposition on stigmas of the rewardless female flowers through their proximity with attractive male flowers responsible for the minor staminate phase.

Methods

We monitored insect visits to 11 chestnut trees during the entire flowering period and explored reproductive traits of all known duodichogamous species using published evidence.

Results

In chestnuts, insects visited trees more frequently during the first staminate phase but visited female flowers more frequently during the second staminate phase. All 21 animal-pollinated duodichogamous species identified are mass-flowering woody plants at high risk of self-pollination. In 20 of 21 cases, gynoecia (female flower parts) are located close to androecia (male flower parts), typically those responsible for the second minor staminate phase, whereas androecia are often distant from gynoecia.

Conclusions

Our results suggest that duodichogamy increases female mating success by facilitating pollen deposition on stigmas by means of the attractiveness of the associated male flowers while effectively limiting self-pollination.

     

Permutation‐based inference for the AUC: A unified approach for continuous and discontinuous data

We investigate rank‐based studentized permutation methods for the nonparametric Behrens–Fisher problem, that is, inference methods for the area under the ROC curve. We hereby prove that the studentized permutation distribution of the Brunner‐Munzel rank statistic is asymptotically standard normal, even under the alternative. Thus, incidentally providing the hitherto missing theoretical foundation for the Neubert and Brunner studentized permutation test. In particular, we do not only show its consistency, but also that confidence intervals for the underlying treatment effects can be computed by inverting this permutation test. In addition, we derive permutation‐based range‐preserving confidence intervals. Extensive simulation studies show that the permutation‐based confidence intervals appear to maintain the preassigned coverage probability quite accurately (even for rather small sample sizes). For a convenient application of the proposed methods, a freely available software package for the statistical software R has been developed. A real data example illustrates the application.     

IgY Technology: Extraction of Chicken Antibodies from Egg Yolk by Polyethylene Glycol (PEG) Precipitation

Hens can be immunized by means of i.m. vaccination (Musculus pectoralis, left and right, injection volume 0.5-1.0 ml) or by means of Gene-Gun plasmid-immunization. Dependent on the immunogenicity of the antigen, high antibody-titres (up to 1:100,000 - 1:1,000,000) can be achieved after only one or 3 - 4 boost immunizations. Normally, a hen lays eggs continuously for about 72 weeks, thereafter the laying capacity decreases. This protocol describes the extraction of total IgY from egg yolk by means of a precipitation procedure (PEG. Polson et al. 1980). The method involves two important steps. The first one is the removal of lipids and the second is the precipitation of total IgY from the supernatant of step one. After dialysis against a buffer (normally PBS) the IgY-extract can be stored at -20°C for more than a year. The purity of the extract is around 80 %, the total IgY per egg varies from 40-80 mg, dependent on the age of the laying hen. The total IgY content increases with the age of the hen from around 40 mg/egg up to 80 mg/egg (concerning PEG precipitation). The laying capacity of a hen per year is around 325 eggs. That means a total potential harvest of 20 g total IgY/year based on a mean IgY content of 60 mg total IgY/egg (see Table 1).     

Patterns and propensities in reproduction and growth of marine fishes

A number of strong regularities characterize certain very basic biological parameters in marine fishes. For example, the ovulated eggs of fish usually measure approximately 1 mm in diameter. The small, relatively uniform size of the eggs means that almost all fish larvae experience environmental variability at very similar scales, which itself establishes strong constraints for, and links between reproduction and recruitment. Additional constraints emerge from seawater being a poor medium for respiration, which establishes further linkages between growth and mortality. These constraints have produced strongly convergent features, and thence the patterns in reproduction and growth of marine fishes that are presented.