Biologische beobachtungen an Janthina

Ohne Zusammenfassung     

Unique peptide-binding motif for Mamu-B*037:01: an MHC class I allele common to Indian and Chinese rhesus macaques

Indian and Chinese rhesus macaques are often used in biomedical research. Genetic analyses of the major histocompatibility class I region have revealed that these macaques display a substantial level of polymorphism at Mamu-A and Mamu-B loci, which have been subject to duplication. Only a few Mamu class I allotypes are characterised for their peptide-binding motifs, although more information of this nature would contribute to a better interpretation of T cell-mediated immune responses. Here, we present the results of the characterisation of the functional properties of Mamu-B*037:01, an allotype commonly encountered in rhesus macaques of Indian and Chinese origin. Mamu-B*037:01 is seen to have a strong preference for acidic amino acids at the third residue, and for arginine, lysine, and tyrosine at the carboxyl terminus. This peptide-binding motif is not described in the human population.     

Evolutionary classification of toxin mediated interactions in microorganisms

A trade-off between the parameters of Lotka–Volterra systems is used to give verifications of relations between intrinsic growth rate and limiting capacity and the stability type of the resulting dynamical system. The well known rock–paper–scissors game serves as a template for toxin mediated interactions, which is best represented by the bacteriocin producing Escherichia coli bacteria. There, we have three strains of the same species. The producer produces a toxin lethal to the sensitive, while the resistant is able to protect itself from that toxin. Due to the fact that there are costs for production and for resistance, a dynamics similar to the rock–paper–scissors game results. By using an adaptive dynamics approach for competitive Lotka–Volterra systems and assuming an inverse relation (trade-off) between intrinsic growth rate (IGR) and limiting capacity (LC) we obtain evolutionary and convergence stable relations between the IGR’s and the LC’s. Furthermore this evolutionary process leads to a phase topology of the population dynamics with a globally stable interior fixed point by leaving the interaction parameters constant. While the inverse trade-off stabilizes coexistence and does not allow branching, toxicity itself can promote diversification. The results are discussed in view of several biological examples indicating that the above results are structurally valid.     

A skew in poo: Biases in primate fecal isotope analysis and recommendations for standardized sample preparation

Feces are a treasure trove in the study of animal behavior and ecology. Stable carbon and nitrogen isotope analysis allows to assess the dietary niches of elusive primate species and primate breastfeeding behavior. However, some fecal isotope data may unwillingly be biased toward the isotope ratios of undigested plant matter, requiring more consistent sample preparation protocols. We assess the impact of this potential data skew in 114 fecal samples of wild bonobos (Pan paniscus) by measuring the isotope differences (Δ¹³C, Δ¹⁵N) between bulk fecal samples containing larger particles (>1 mm) and filtered samples containing only small particles (<1 mm). We assess the influence of fecal carbon and nitrogen content (ΔC:N) and sample donor age (subadult, adult) on the resulting Δ¹³C, Δ¹⁵N values (n = 228). Additionally, we measure the isotope ratios in three systematically sieved fecal samples of chimpanzees (Pan troglodytes verus), with particle sizes ranging from 20 μm to 8 mm (n = 30). We found differences in fecal carbon and nitrogen content, with the smaller fecal fraction containing more nitrogen on average. While the Δ¹³C values were small and not affected by age or ΔC:N, the Δ¹⁵N values were significantly influenced by fecal ΔC:N, possibly resulting from the differing proportions of undigested plant macroparticles. Significant relationships between carbon stable isotope ratios (δ¹³C) values and %C in large fecal fractions of both age groups corroborated this assessment. Δ¹⁵N values were significantly larger in adults than subadults, which should be of concern in isotope studies comparing adult females with infants to assess breastfeeding. We found a random variation of up to 3.0‰ in δ¹³C and 2.0‰ in nitrogen stable isotope ratios within the chimpanzee fecal samples separated by particle sizes. We show that particle size influences isotope ratios and propose a simple, cost-effective filtration method for primate feces to exclude larger undigested food particles from the analysis, which can easily be adopted by labs worldwide.     

Racemization of chlorthalidone in the presence of liposomes

The extent of racemization of (+)-chlorthalidone as a function of pH is examined. The minimum of the log K/pH curve is pH 3. The reaction mechanism of inversion is postulated to involve a carbenium cation over the entire pH range and a ring opening reaction in the alkaline range. The influence of liposomes on the inversion rate is also studied, retardation of the racemization rate being observed with increasing liposome concentration. A model of drug distribution between liposome phase and aqueous phase based on the Nernst distribution principle is presented and reaction kinetic aspects are considered. © 1993 Wiley-Liss, Inc.     

Über die Geotaxis von Convoluta Roscoffensis

Zusammenfassung Convoluta reagiert in ungereiztem Zustande im allgemeinen negativ geotaktisch, auf mechanische Reize hin wird sie positiv geotaktisch. Als Receptor der Schwerkraftsreize ist mit großer Wahrscheinlichkeit die Statocyste anzusprechen. Die geotaktischen Krümmungen geschehen durch Muskelkontraktionen, die normale Fortbewegung dagegen geschieht durch den Cilienschlag. Wenn auf das Tier außer der Schwerkraft noch die Zentrifugalkraft einwirkt, stellt sich das Tier mit physikalischer Genauigkeit in die Resultante beider Kräfte ein. Daraus ist zu folgern, daß normalerweise qualitativ und quantitativ die Schwerkraft die geotaktische Orientierung bewirkt.Vorliegende Arbeit wurde im August und September 1927 an der zoologischen Station zu Roscoff (Bretagne) durchgeführt. Zu großem Dank bin ich Herrn Prof. Ch. Péréz-Paris für die Überlassung des Arbeitsplatzes verpflichtet. Der Aufenthalt in Roscoff war mir durch eine Spende der Notgemeinschaft der deutschen Wissenschaft ermöglicht, wofür ich dieser Körperschaft hier meinen herzlichen Dank ausdrücke.