Population receptive field dynamics in human visual cortex

Seminal work in the early nineties revealed that the visual receptive field of neurons in cat primary visual cortex can change in location and size when artificial scotomas are applied. Recent work now suggests that these single neuron receptive field dynamics also pertain to the neuronal population receptive field (pRF) that can be measured in humans with functional magnetic resonance imaging (fMRI). To examine this further, we estimated the pRF in twelve healthy participants while masking the central portion of the visual field. We found that the pRF changes in location and size for two differently sized artificial scotomas, and that these pRF dynamics are most likely due to a combination of the neuronal receptive field position and size scatter as well as modulatory feedback signals from extrastriate visual areas.     

Shear-induced Crystal Structure Formation in Milk Fat and Blends with Rapeseed Oil

The effect of shear on the rheological properties of anhydrous milk fat (AMF) and blends added 10?C30 w/w% rapeseed oil (RO) was studied. Shear was applied during early crystallization, and the complex modulus |G*| was measured during the final isothermal crystallization. The firmest and most rapidly formed network was achieved when an intermediate shear of 50?s^?1 was applied, and at this shear rate, up to 20?% RO could be added without lowering the final |G*| compared to pure AMF. A similar effect was not obtained at lower or higher shear rates. Solid fat content was unaffected by shear, while fat crystal size decreased upon increasing shear rate. The study indicates that intermediate shear produces a continuous and strong crystal network, while high shear breaks down the microstructure to such an extent that it is difficult to rebuild during subsequent crystallization, thus resulting in lower |G*|.     

Synthesis and evaluation of non-basic inhibitors of urokinase-type plasminogen activator (uPA)

Recent drug discovery programs targeting urokinase plasminogen activator (uPA) have resulted in nonpeptidic inhibitors consisting of amidine or guanidine functional groups attached to aromatic or heteroaromatic scaffolds. There is a general problem of poor oral bioavailability of these charged inhibitors. In this paper, we report the synthesis and evaluation of a series of naphthamide and naphthalene sulfonamides as uPA inhibitors containing non-basic groups as substitute for amidine or guanidine groups.     

Total Synthesis of Septocylindrin B and C-Terminus Modified Analogues

The total synthesis is reported of the peptaibol Septocylindrin B which is related to the well documented channel forming peptaibol antibiotic Alamethicin. Several analogues were synthesized with a modified C-terminus, to investigate the SAR of the terminal residue Phaol. All these peptides were tested for their membrane perturbation properties by fluorescent dye leakage assay and for their antibacterial activity.     

Will Agroforests Vanish? The Case of Damar Agroforests in Indonesia

Resin producing agroforestry in the Krui area of Sumatra in Indonesia is presented as an environmentally friendly, income generating land-use system which contributes to both development and conservation objectives. We studied the change in household income portfolios in three communities in the Krui area. The studies revealed that in the period 1995–2004 agroforestry remained the main source of income. We predict, however, that due to declining resin productivity per hectare, and rising price and demand for timber, an increasing number of farmers will cut their mature agroforests in the near future. At the same time our data suggests that farmers will continue tree planting activities. In result old agroforests may vanish while new ones will be established.

Prolyl oligopeptidase stimulates the aggregation of alpha-synuclein

Despite its thorough enzymological and biochemical characterization the exact function of prolyl oligopeptidase (PO, E.C. 3.4.21.26) remains unclear. The positive effect of PO inhibitors on learning and memory in animal models for amnesia, enzyme activity measurements in patient samples and (neuro)peptide degradation studies link the enzyme with neurodegenerative disorders. The brain protein alpha-synuclein currently attracts much attention because of its proposed role in the pathology of Parkinson's disease. A fundamental question concerns how the essentially disordered protein is transformed into the highly organized fibrils that are found in Lewy bodies, the hallmarks of Parkinson's disease. Using gel electrophoresis and MALDI TOF/TOF mass spectrometry we investigated the possibility of alpha-synuclein as a PO substrate. We found that in vitro incubation of the protein with PO did not result in truncation of full-length alpha-synuclein. Surprisingly, however, we found an acceleration of the aggregation process of alpha-synuclein using turbidity measurements that was reversed by specific inhibitors of PO enzymatic activity. If PO displays this activity also in vivo, PO inhibitors might have an effect on neurodegenerative disorders through a decrease in the aggregation of alpha-synuclein.     

Crustacean Species Richness in Temporary Pools: Relationships with Habitat Traits

We examined species richness separately for cladocerans and ostracods in 52 temporary pools in a small geographical area, relating species richness with habitat traits using multiple regressions. Habitat traits considered included surface area, water depth, permanence and sediment depth. Permanence was an important predictor of species richness of both cladocerans and ostracods. Additionally, variation in ostracod species richness was significantly explained by water depth (negative relationship) and sediment depth (positive relationship). Surface area was not a statistically significant factor in any of our analyses. The importance of permanence supports the hypothesis that extinction due to pool drying is a major driving force behind the structuring of microcrustacean communities in temporary pools.     

In APCs, the autologous peptides selected by the diabetogenic I-Ag7 molecule are unique and determined by the amino acid changes in the P9 pocket.

We demonstrate in this study the great degree of specificity in peptides selected by a class II MHC molecule during processing. In this specific case of the diabetogenic I-A(g7) molecule, the P9 pocket of I-A(g7) plays a critical role in determining the final outcome of epitope selection, a conclusion that is important in interpreting the role of this molecule in autoimmunity. Specifically, we examined the display of naturally processed peptides from APCs expressing either I-A(g7) molecules or a mutant I-A(g7) molecule in which the beta57Ser residue was changed to an Asp residue. Using mass spectrometry analysis, we identified over 50 naturally processed peptides selected by I-A(g7)-expressing APCs. Many peptides were selected as families with a core sequence and variable flanks. Peptides selected by I-A(g7) were unusually rich in the presence of acidic residues toward their C termini. Many peptides contained short sequences of two to three acidic residues. In binding analysis, we determined the core sequences of many peptides and the interaction of the acidic residues with the P9 pocket. However, different sets of peptides were isolated from APCs bearing a modified I-A(g7) molecule. These peptides did not favor acidic residues toward the carboxyl terminus.     

Interaction of thiabendazole with fungal tubulin.

Thiabendazole, 2-(4'-thiazolyl)benzimidazole, at 80 micrometer completely inhibits mitosis in hyphae of Aspergillus nidulans, growing in liquid culture. DNA and RNA synthesis and mycelial growth are only partially inhibited at this concentration. Binding studies with cell-free mycelial extracts from Penicillium expansum showed that thiabendazole competitively inhibits [14C]carbendazim binding to tubulin, which suggests that the antimitotic activity of thiabendazole is based on interference with microtubule assembly. Tubulin from a thiabendazole-resistant and carbendazim-highly sensitive mutant of P. expansum has a lower affinity to thiabendazole and a higher affinity to carbendazim than tubulin from a wide-type strain. This indicates that in this mutant the structure of the binding site is affected. The data presented suggest that several sites of both the tubulin and ligand molecule are involved in the binding of benzimidazole compounds to fungal tubulin.