Tag-Trigger-Consolidation: A Model of Early and Late Long-Term-Potentiation and Depression

Changes in synaptic efficacies need to be long-lasting in order to serve as a substrate for memory. Experimentally, synaptic plasticity exhibits phases covering the induction of long-term potentiation and depression (LTP/LTD) during the early phase of synaptic plasticity, the setting of synaptic tags, a trigger process for protein synthesis, and a slow transition leading to synaptic consolidation during the late phase of synaptic plasticity. We present a mathematical model that describes these different phases of synaptic plasticity. The model explains a large body of experimental data on synaptic tagging and capture, cross-tagging, and the late phases of LTP and LTD. Moreover, the model accounts for the dependence of LTP and LTD induction on voltage and presynaptic stimulation frequency. The stabilization of potentiated synapses during the transition from early to late LTP occurs by protein synthesis dynamics that are shared by groups of synapses. The functional consequence of this shared process is that previously stabilized patterns of strong or weak synapses onto the same postsynaptic neuron are well protected against later changes induced by LTP/LTD protocols at individual synapses.     

Evolution of C4 phosphoenolpyruvate carboxylase

C4 plants are known to be of polyphyletic origin and to have evolved independently several times during the evolution of angiosperms. This implies that the C4 isoform of phosphoenolpyruvate carboxylase (PEPC) originated from a nonphotosynthetic PEPC gene that was already present in the C3 ancestral species. To meet the special requirements of the C4 photosynthetic pathway the expression program of the C4 PEPC gene had to be changed to achieve a strong and selective expression in leaf mesophyll cells. In addition, the altered metabolite concentrations around C4 PEPC in the mesophyll cytoplasm necessitated changes in the enzyme's kinetic and regulatory properties. To obtain insight into the evolutionary steps involved in these altered enzyme characteristics, and even the order of these steps, the dicot genus Flaveria (Asteraceae) appears to be the experimental system of choice. Flaveria contains closely related C3, C3-C4, and C4 species that can be ordered by their gradual increase in C4 photosynthetic traits. The C4 PEPC of F. trinervia, which is encoded by the ppcA gene class, possesses typical kinetic and regulatory features of a C4-type PEPC. Its nearest neighbor is the orthologous ppcA gene of the C3 species F. pringlei. This latter gene encodes a typical nonphotosynthetic C3-type PEPC which is believed to be similar to the C3 ancestral PEPC. This pair of orthologous PEPCs has been used to map C4-specific molecular determinants for the kinetic and regulatory characteristics of C4 PEPCs. The most notable finding from these investigations was the identification of a C4 PEPC invariant site-specific mutation from alanine (C3) to serine (C4) at position 774 that was a necessary and late step in the evolution of C3 to C4 PEPC. The C3-C4 intermediate ppcA PEPCs are used to identify the sequence of events leading from a C3- to a C4-type PEPC.     

The foregut-ossicle system of Dromia wilsoni, Dromia personata and Lauridromia intermedia (Decapoda, Brachyura, Dromiidae), studied with a new staining method

The ossicles of the cardiac and pyloric foregut of three species of decapods: Dromia wilsoni [Fulton and Grant, 1902], Dromia personata [Linnè, 1758] and Lauridromia intermedia [Lauri, 1906] are described and illustrated in detail. Five new ossicles are recognized based on a specific staining-method with Alizarin-Red. The ossicle terminology of the brachyuran foregut is revised now to include 37 ossicles. All described ossicles are documented by drawings and photographs. The two new cardiac ossicles, the prepterocardiac and the postpterocardiac ossicles are narrow ossicles associated with the pterocardiac ossicles at the antero-dorsal margin of the cardiac foregut. The pyloric foregut includes the newly described lateral mesopyloric- and the posterior uropyloric ossicles. These pyloric ossicles are clearly recognizable only in the stained condition. Based on our data we provide new additional evidence for brachyuran monophyly and the paraphyletic status of the podotrematan crabs.     

A Study of the Decomposition of Reed (Phragmites australis ) as a Possible Source of Aquatic Humic Substances by Measuring the Natural Abundance of Stable Carbon Isotopes

The decomposition of leaf and steam litter of reed (P. australis) was measured both in the field and in the laboratory. The breakdown rates, the total carbon and the stable carbon isotope dynamics of reed litter were determined. The stable carbon isotope ratios of isolated humic substances (fulvic and humic acids) were also analysed. The δ¹³C value in reed remains increased from –26‰ to –24‰ for stems and from –27‰ to –26‰ for leaves. The dissolved fulvic and humic acids isolated from the experimental bottles (mean δ¹³C was –27.6‰) and the reservoir water were depleted in ¹³C (mean δ¹³C was –28.6‰) relative to the reed remains. The results show that reed litter is an important source of coloured aquatic humic substances. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Diversity patterns of trait-based phytoplankton functional groups in two basins of a large, shallow lake (Lake Balaton, Hungary) with different trophic state

The application of functional approaches in understanding phytoplankton community-level responses to changes in the environment has become increasingly widespread in recent years. Eutrophication is known to cause profound modifications in ecosystem processes; however, the underlying relationships between environmental drivers and phytoplankton diversity and functioning are complex and largely unknown. Therefore, in the present study, we investigated and compared the temporal diversity patterns of phytoplankton functional groups in the mesotrophic eastern and eutrophic western basin of the shallow Lake Balaton situated in Hungary. Diversity data were derived from taxonomic composition and biomass data corresponding to the years 2005–2006 and 2008–2009. With the use of cluster analysis, phytoplankton species were classified into eight distinct groups representing different combinations of functionally relevant traits including greatest axial linear dimension; surface-to-volume ratio; photosynthetic pigment composition; N₂ fixation; phagotrophic potential; growth form/complexity (unicell, filamentous, colony-, or coenobium-forming); and motility. Our results have revealed that there is a significant inverse relationship between the functional group diversity used in our study and trophic state (total phytoplankton biomass) as opposed to species diversity, where no correlation was observed. In addition, group evenness showed an even stronger negative correlation with trophic state, while species evenness yielded only a weak relationship. The observed variability in functional group diversity suggests that such an approach could provide an efficient means of revealing structural changes in phytoplankton communities, establishing new hypotheses and highlighting fundamental points in ecosystem functioning.     

Structure of the WD40‐domain of human ATG16L1

Autophagy‐related protein ATG16L1 is a component of the mammalian ATG12～ATG5/ATG16L1 complex, which acts as E3‐ligase to catalyze lipidation of LC3 during autophagosome biogenesis. The N‐terminal part of ATG16L1 comprises the ATG5‐binding site and coiled‐coil dimerization domain, both also present in yeast ATG16 and essential for bulk and starvation induced autophagy. While absent in yeast ATG16, mammalian ATG16L1 further contains a predicted C‐terminal WD40‐domain, which has been shown to be involved in mediating interaction with diverse factors in the context of alternative functions of autophagy, such as inflammatory control and xenophagy. In this work, we provide detailed information on the domain boundaries of the WD40‐domain of human ATG16L1 and present its crystal structure at a resolution of 1.55 Å.     

Art history anthropology: a new interdisciplinary overlap using the examples of Caravaggio and Mozart

The established identification of human faces on images may also be applied to paintings. This demands an extension of the known methodology: A check is performed if the depicted trait expressions may occur in nature at all or if they are an "artefact" of artistic freedom. Two cases are presented here, which illustrate an identification and an identity exclusion.     

Genetic variability of the mTOR pathway and prostate cancer risk in the European Prospective Investigation on Cancer (EPIC)

The mTOR (mammalian target of rapamycin) signal transduction pathway integrates various signals, regulating ribosome biogenesis and protein synthesis as a function of available energy and amino acids, and assuring an appropriate coupling of cellular proliferation with increases in cell size. In addition, recent evidence has pointed to an interplay between the mTOR and p53 pathways. We investigated the genetic variability of 67 key genes in the mTOR pathway and in genes of the p53 pathway which interact with mTOR. We tested the association of 1,084 tagging SNPs with prostate cancer risk in a study of 815 prostate cancer cases and 1,266 controls nested within the European Prospective Investigation into Cancer and Nutrition (EPIC). We chose the SNPs (n = 11) with the strongest association with risk (p<0.01) and sought to replicate their association in an additional series of 838 prostate cancer cases and 943 controls from EPIC. In the joint analysis of first and second phase two SNPs of the PRKCI gene showed an association with risk of prostate cancer (OR_allele = 0.85, 95% CI 0.78–0.94, p = 1.3×10⁻³ for rs546950 and OR_allele = 0.84, 95% CI 0.76–0.93, p = 5.6×10⁻⁴ for rs4955720). We confirmed this in a meta-analysis using as replication set the data from the second phase of our study jointly with the first phase of the Cancer Genetic Markers of Susceptibility (CGEMS) project. In conclusion, we found an association with prostate cancer risk for two SNPs belonging to PRKCI, a gene which is frequently overexpressed in various neoplasms, including prostate cancer.