Parvalbumin, a Neuronal Protein in Brain Cell Cultures

Dissociated brain cell cultures were derived from 14-day-old embryonic as well as from newborn mice. The cells were grown in a medium containing 10% fetal calf serum. Indirect immunofluorescence was performed using antisera directed against the Ca2+-binding protein parvalbumin (Mr 12,000). In embryonic cultures a large proportion of cells was intensely stained by antiparvalbumin . In double-labelling experiments involving the simultaneous application of antisera against parvalbumin and the neuron-specific enolase, the enolase-containing cells were also parvalbumin-positive and both antisera revealed identical intracellular staining patterns. Conversely, almost no parvalbumin- and enolase-positive cells were present in cultures derived from newborn mice. However, in these cultures many cells were immunoreactive toward the myelin basic protein, an accepted marker for oligodendrocytes. The presence of parvalbumin within the embryonic brain cell cultures was confirmed by analyses of the culture extracts (4 mM EDTA, pH 7.5) by HPLC on reverse-phase supports, two-dimensional polyacrylamide gel electrophoresis, and immunoblotting. The present study suggests that in mouse brain cell cultures, parvalbumin is localized in neurons.     

Male Mating Tactics in Captive Rhesus Macaques (Macaca mulatta): The Influence of Dominance, Markets, and Relationship Quality

Male mating success in a multimale–multifemale group can depend on several variables: body condition, dominance, coalitions, “friendship,” or an exchange of services for mating access. Exchange patterns may also be determined by market effects or social relationships. We studied the mating tactics of males in a captive, multimale–multifemale group of rhesus macaques and the resulting patterns of mating and paternity to determine the influence of dominance rank, mating markets, and relationship quality on their mating tactics. Male rank was positively related to the total number of copulations and the number of mating partners, but did not explain male mating distribution completely. Moreover, male fertilization success was not related to male rank. Males did not exchange grooming for mating access on the same day and neither the supply nor the rank (as a proxy for quality) of receptive females affected the amount of male grooming, suggesting that market effects did not explain male mating access. However, there was a positive correlation between long-term grooming patterns of both males and females and mating access, indicating that social relationships were important for male mating access. Paternity data revealed that these social relationships were also important for male reproductive success. We conclude that both male rank and male–female “friendship” determined male mating access in these rhesus macaques, but that “friendship” was more important in determining paternity, emphasizing the importance of intersex social bonds in male mating success in multimale primate societies.     

A Basic Approach Towards the Development of Bioelectric Bacterial Biosensors for the Detection of Plant Viruses

There is a growing need for virus sensors with improved sensitivity and dynamic range for disease diagnosis, pharmaceutical research, agriculture and homeland security. Membrane‐engineered animal cells bearing antibodies against viral antigens have been previously used for biorecognition biosensors for the ultrarapid (3 min), sensitive (1 ng/ml) detection of plant viruses, such as the cucumber mosaic virus. We here report a new approach for the construction of cell‐based sensors for virus detection, based on membrane (antibody)‐engineered bacteria. The novel method was applied for the detection of tobacco mosaic virus (TMV) and cherry leaf roll virus (CLRV) using sensors containing modified Escherichia coli XL‐1Blue MRF’ bacteria. E. coli membranes have been engineered with electro‐inserted, virus‐homologous antibodies. The detection principle was based on the measurement of changes in the bacterial membrane potential as a result of virus–antibody binding. After optimization of the membrane‐engineering process, the virus detection limit for TMV and CLRV with the bacteria‐based biosensor system was 1 pg/ml, representing a 1000‐fold improvement over currently available methods. Although the novel biosensor is still in its proof‐of‐concept stage of development, its sensitivity and speed (assay time: 60–100 s) could make it a very promising tool for high throughput, field‐based virus screening.     

Crystal Structure of the Multidrug Exporter MexB from Pseudomonas aeruginosa

We report here the crystal structure of the Pseudomonas aeruginosa multidrug exporter MexB, an intensively studied member of the resistance-nodulation-cell division family of secondary active transporters, at 3.0 Å. MexB forms an asymmetric homotrimer where each subunit adopts a different conformation representing three snapshots of the transport cycle similar to the recently determined structures of its close homologue AcrB from Escherichia coli, so far the sole structurally characterized member of the superfamily. As for AcrB, the conformations of two subunits can be clearly assigned to either the binding step or the extrusion step in the transport process. Unexpectedly, a remarkable conformational shift in the third subunit is observed in MexB, which has potential implications for the assembly of the tripartite MexAB-OprM drug efflux system. Furthermore, an n-dodecyl-d-maltoside molecule was found bound to the internal multidrug-binding cavity, which might indicate that MexB binds and transports detergent molecules as substrates. As the only missing piece of the puzzle in the MexAB-OprM system, the X-ray structure of MexB completes the molecular picture of the major pump mediating intrinsic and acquired multidrug resistance in P. aeruginosa.     

Definition of Mafa-A and -B haplotypes in pedigreed cynomolgus macaques (Macaca fascicularis)

The major histocompatibility complex (MHC) class I B gene/allelic repertoire was investigated in a pedigreed population of cynomolgus macaques of mixed Indonesian/Malaysian origin. The Mafa-B alleles detected in this cohort are mostly specific for a given geographic area, and only a small number of alleles appears to be shared with other populations. This suggests the fast evolution of Mafa-B alleles due to adaptation to new environments. In contrast to humans, the B locus in Old World monkeys displays extensive copy number variation. The Mafa-B and previously defined -A gene combinations segregate in families and thus allowed the definition of extended haplotypes. In many cases it was possible to assign a particular Mafa-I allele to one of these Mafa-A/B haplotypes as well. The presence of a large number of stable haplotypes in this cohort of animals, which was pedigreed for up to eight generations, looks promising for developing discriminative MHC typing tools that are less cumbersome. Furthermore, the discovery of 53 unreported Mafa-B sequences expands the lexicon of alleles significantly, and may help in understanding the complex organisation of the macaque B region.