Modeling and dynamic assessment of urban economy–resource–environment system with a coupled system dynamics – geographic information system model

At present, environmental issues associated with rapid economic development are becoming critical concerns that arouse government's and people's particular attention. A large amount of influencing factors and especially their complicated interactions have always thrown confused insights into assessing the dynamic evolvement and sustainable development of urban economy–resource–environment (ERE) system and programming the developing strategies. A combination of system dynamics (SD) and geographic information system (GIS) is expected to explicitly understand the synergic interaction and feedback among a variety of influencing factors in time and space, since SD model can extend the spatial analysis functions of GIS to realize both dynamic simulation and trend prediction of an ERE system development. According to connotation and framework of sustainable development, this study proposes a dynamic combination method of SD–GIS to model and evaluate the urban development in Chongqing city of China suffering from depletion of resource and degradation of environment. To compare different policy inclinations with regard to potential ERE effects, typical scenarios (current, resource, technology and environment scenarios) are designed by adjusting the parameters in the model and changing the specification of some variables. Integrated assessment results indicate that the current ERE system of Chongqing is not sustainable; environment scenario is more effective to sustainable development of urban ERE system in a long run. Under the considerations of development features and regional differences, as well as regular discipline on urbanization, a coordinated combination of environmental, resource and technology scenarios is anticipated to realize sustainable development of urban ERE system.     

pH-dependent aggregate forms and conformation of Alzheimer amyloid beta-peptide (12-24)

The conformational transition to a beta-structure and the aggregation process of Alzheimer amyloid beta-peptide (12-24) [abbreviated as A beta(12-24)] were studied. The influence of sample dissolution methods for the aggregate structure was examined by electron microscopy (EM). The difference in the width of the aggregate of A beta(12-24) depended on the pH immediately after sample dissolution. Two types of sample dissolution methods, F and R, were employed. For dissolution method F, the peptide sample was immediately dissolved in water and then adjusted to pH 2.2 by adding buffer, while for dissolution method R, the peptide was directly dissolved in the buffer solution. In the latter case, the starting pH was 3.0. Slight fibrils (10-12 nm in diameter) were observed with method F, and wider ribbon-like aggregates (17-20 nm in diameter) with method R, despite the same pH range. A difference between methods F and R was also detected in the CD spectra, especially at pHs near 5.0. The CD intensity of the 214 nm band with method R changed with pH, with the highest value at pH 3.7, whereas that with method F was unchanged at pHs below 5.0. The temperature-dependent CD results showed that a thermostable aggregate of A beta(12-24) occurs at higher pHs than 3.0. NMR analysis showed that deprotonation of the C-terminal carboxylate group in A beta(12-24) triggered the aggregate formation, and the transition from a random coil to a beta-conformation in the C-terminal region of V18-V24 was detected on analysis of the (3)Ja(N) coupling constant in the pH range of 2.2 to 3.0.     

24(S)-hydroxycholesterol induces neuronal cell death through necroptosis, a form of programmed necrosis

24(S)-Hydroxycholesterol (24S-OHC) produced by cholesterol 24-hydroxylase expressed mainly in neurons plays an important physiological role in the brain. Conversely, it has been reported that 24S-OHC possesses potent cytotoxicity. The molecular mechanisms of 24S-OHC-induced cell death have not yet been fully elucidated. In this study, using human neuroblastoma SH-SY5Y cells and primary cortical neuronal cells derived from rat embryo, we characterized the form of cell death induced by 24S-OHC. SH-SY5Y cells treated with 24S-OHC exhibited neither fragmentation of the nucleus nor caspase activation, which are the typical characteristics of apoptosis. 24S-OHC-treated cells showed necrosis-like morphological changes but did not induce ATP depletion, one of the features of necrosis. When cells were treated with necrostatin-1, an inhibitor of receptor-interacting serine/threonine kinase 1 (RIPK1) required for necroptosis, 24S-OHC-induced cell death was significantly suppressed. The knockdown of RIPK1 by transfection of small interfering RNA of RIPK1 effectively attenuated 24S-OHC-induced cell death. It was found that neither SH-SY5Y cells nor primary cortical neuronal cells expressed caspase-8, which was regulated for RIPK1-dependent apoptosis. Collectively, these results suggest that 24S-OHC induces neuronal cell death by necroptosis, a form of programmed necrosis.     

Allee threshold and extinction threshold for spatially explicit metapopulation dynamics with Allee effects

In this paper, we investigate a spatially explicit metapopulation model with Allee effects. We refer to the patch occupancy model introduced by Levins (Bull Entomol Soc Am 15:237–240, 1969) as a spatially implicit metapopulation model, i.e., each local patch is either occupied or vacant and a vacant patch can be recolonized by a randomly chosen occupied patch from anywhere in the metapopulation. When we transform the model into a spatially explicit one by using a lattice model, the obtained model becomes theoretically equivalent to a “lattice logistic model” or a “basic contact process”. One of the most popular or standard metapopulation models with Allee effects, developed by Amarasekare (Am Nat 152:298–302, 1998), supposes that those effects are introduced formally by means of a logistic equation. However, it is easier to understand the ecological meaning of associating Allee effects with this model if we suppose that only the logistic colonization term directly suffers from Allee effects. The resulting model is also well defined, and therefore we can naturally examine it by Monte Carlo simulation and by doublet and triplet decoupling approximation. We then obtain the following specific features of one-dimensional lattice space: (1) the metapopulation as a whole does not have an Allee threshold for initial population size even when each local population follows the Allee effects; and (2) a metapopulation goes extinct when the extinction rate of a local population is lower than that in the spatially implicit model. The real ecological metapopulation lies between two extremes: completely mixing interactions between patches on the one hand and, on the other, nearest neighboring interactions with only two nearest neighbors. Thus, it is important to identify the metapopulation structure when we consider the problems of invasion species such as establishment or the speed of expansion.     

Fission yeast MO25 protein is localized at SPB and septum and is essential for cell morphogenesis

Cell morphogenesis is of fundamental significance in all eukaryotes for development, differentiation, and cell proliferation. In fission yeast, Drosophila Furry-like Mor2 plays an essential role in cell morphogenesis in concert with the NDR/Tricornered kinase Orb6. Mutations of these genes result in the loss of cell polarity. Here we show that the conserved proteins, MO25-like Pmo25, GC kinase Nak1, Mor2, and Orb6, constitute a morphogenesis network that is important for polarity control and cell separation. Intriguingly, Pmo25 was localized at the mitotic spindle pole bodies (SPBs) and then underwent translocation to the dividing medial region upon cytokinesis. Pmo25 formed a complex with Nak1 and was required for both the localization and kinase activity of Nak1. Pmo25 and Nak1 in turn were essential for Orb6 kinase activity. Further, the Pmo25 localization at the SPBs and the Nak1-Orb6 kinase activities during interphase were under the control of the Cdc7 and Sid1 kinases in the septation initiation network (SIN), suggesting a functional linkage between SIN and the network for cell morphogenesis/separation following cytokinesis.     

Photo-induced activation of cytochrome P450/reductase fusion enzyme coupled with spinach chloroplasts

Summary Photoactivation of cytochrome P450 monooxygenase was studied using a combination of spinach chloroplasts and yeast microsomes containing rat P4501A1/yeast reductase fusion enzyme. Under illumination, in the reaction mixture, NADP was reduced, transferring electrons to the P450/reductase fusion enzyme to convert 7-ethoxycoumarin to 7-hydroxycoumarin.