Impairment of mossy fiber long-term potentiation and associative learning in pituitary adenylate cyclase activating polypeptide type I receptor-deficient Mice

The pituitary adenylate cyclase activating polypeptide (PACAP) type I receptor (PAC1) is a G-protein-coupled receptor binding the strongly conserved neuropeptide PACAP with 1000-fold higher affinity than the related peptide vasoactive intestinal peptide. PAC1-mediated signaling has been implicated in neuronal differentiation and synaptic plasticity. To gain further insight into the biological significance of PAC1-mediated signaling in vivo, we generated two different mutant mouse strains, harboring either a complete or a forebrain-specific inactivation of PAC1. Mutants from both strains show a deficit in contextual fear conditioning, a hippocampus-dependent associative learning paradigm. In sharp contrast, amygdala-dependent cued fear conditioning remains intact. Interestingly, no deficits in other hippocampus-dependent tasks modeling declarative learning such as the Morris water maze or the social transmission of food preference are observed. At the cellular level, the deficit in hippocampus-dependent associative learning is accompanied by an impairment of mossy fiber long-term potentiation (LTP). Because the hippocampal expression of PAC1 is restricted to mossy fiber terminals, we conclude that presynaptic PAC1-mediated signaling at the mossy fiber synapse is involved in both LTP and hippocampus-dependent associative learning.

The contribution of schooling in development accounting: Results from a nonparametric upper bound

How much would output increase if underdeveloped economies were toincrease their levels of schooling? We contribute to the development accounting literature by describing a non-parametric upper bound on theincrease in output that can be generated by more schooling. The advantage of our approach is that the upper bound is valid for any number ofschooling levels with arbitrary patterns of substitution/complementarity.Another advantage is that the upper bound is robust to certain forms ofendogenous technology response to changes in schooling. We also quantify the upper bound for all economies with the necessary data, compareour results with the standard development accounting approach, andprovide an update on the results using the standard approach for a largesample of countries.

Horizontal innovation in the theory of growth and development

We analyze recent contributions to growth theory based on the model of expanding variety of Romer (1990). In the first part, we present different versions of the benchmark linear model with imperfect competition. These include the labequipment model, labor-for-intermediates and directed technical change . We review applications of the expanding variety framework to the analysis of international technology diffusion, trade, cross-country productivity differences, financial development and fluctuations. In many such applications, a key role is played by complementarities in the process of innovation.

Influence activity and the organization of research and development

The organizational design of research and development conditions theincentives of the researchers of the research project. In particular,the organizational form determines the allocation of effort of theresearcher between time spent on research and time spent lobbying management. Researchers prefer to spend their time on research. However,the researchers only get utility from performing research if theproject is approved for its full duration. Spending time lobbyingmanagement for the continuation of the researcher s project increasesthe probability that the management observes a favorable signal aboutthe project. Organizing a research joint venture increases theflexibility of the organizational form with respect to the continuationdecision. For low correlation between the signals of the partners aboutthe expected profitability of the project, we find that the organizationof a research joint venture reduces influence activity by the researchersand increases expected profits of the partners. For high correlationbetween the signals, internal research projects lower influence activityby the researchers. We try to relate the correlation of the partnerssignals to the characteristics of basic research versus more appliedresearch projects, and find that the model is consistent with theobservation that research joint ventures seem involved in more basicresearch projects compared to internal R&D departments, whichconcentrate on more applied research.

Comparative transcriptomics of early dipteran development

BACKGROUND: Modern sequencing technologies have massively increased the amount of data available for comparative genomics. Whole-transcriptome shotgun sequencing (RNA-seq) provides a powerful basis for comparative studies. In particular, this approach holds great promise for emerging model species in fields such as evolutionary developmental biology (evo-devo). RESULTS: We have sequenced early embryonic transcriptomes of two non-drosophilid dipteran species: the moth midge Clogmia albipunctata, and the scuttle fly Megaselia abdita. Our analysis includes a third, published, transcriptome for the hoverfly Episyrphus balteatus. These emerging models for comparative developmental studies close an important phylogenetic gap between Drosophila melanogaster and other insect model systems. In this paper, we provide a comparative analysis of early embryonic transcriptomes across species, and use our data for a phylogenomic re-evaluation of dipteran phylogenetic relationships. CONCLUSIONS: We show how comparative transcriptomics can be used to create useful resources for evo-devo, and to investigate phylogenetic relationships. Our results demonstrate that de novo assembly of short (Illumina) reads yields high-quality, high-coverage transcriptomic data sets. We use these data to investigate deep dipteran phylogenetic relationships. Our results, based on a concatenation of 160 orthologous genes, provide support for the traditional view of Clogmia being the sister group of Brachycera (Megaselia, Episyrphus, Drosophila), rather than that of Culicomorpha (which includes mosquitoes and blackflies).

An integrated model of adoption and development of e-commerce in companies

Since the mid-1990s researchers have sought to understand why some firms embark on e-commerceoperations on the Internet while others prefer to wait and see how events unfold. We still have todetermine which variables contribute to explaining the extent to which firms use e-commerce, giventhat to date the literature has not yet offered conclusive evidence on this question. The current workaims to provide an integrated vision of the set of factors influencing the e-commerce adoptionprocess. We use a sample of 2,038 firms of all types that trade their products either with otherorganizations or with end-consumers.