Rapid bioassay as indicator of potentially harmful effects for dioxin-like compounds in sample of Ya-Er Lake, China: Requirements for clean-up and comparison to chemical analysis

A rapid bioassay was established measuring the extracts of wildlife samples which were taken from Ya-Er Lake area, China. In extracts of these samples containing PCDD/Fs and PCBs, bioassay and chemically derived TCDD-equivalents (TEQs) were nearly identical. Our results indicate this bioassay is an excellent complement to chemical residue analysis and a useful tool in understanding the complex interactions of halogenated hydrocarbons. However, it must be mentioned that the proper prior clean-up method is very important for using the bioassay.

Interference Effects in Hyperfine Induced 2s2p P-3(0), P-3(2) -> 2s(2) S-1(0) Transitions of Be-like Ions

In this paper, we explored the characteristics of the interference effects between perturbative states in hyperfine induced 2s2p P-3(0), P-3(2) -> 2s(2) S-1(0) transitions of Be-like ions. It was found that the interference effects non-monotonically change with increasing atomic number Z in these two transitions. The strongest interference effect is near Z = 9 for 2s2p P-3(0), -> 2s(2) (1)S(0)transition and near Z = 7 for the other.

Net-like Ferromagnetic Mnsb Film Deposited on Porous Silicon Substrates

MnSb films were deposited on porous silicon substrates by physical vapor deposition (PVD) technique. Modulation effects due to the substrate on microstructure and magnetic properties of the MnSb film's were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and measurements of hysteresis loops. SEM images of the MnSb films indicate that net-like structures were obtained because of the special morphology of the substrates. The net-like MnSb films exhibit some novel magnetic properties different from the unpatterned referenced samples. For example, in the case of net-like morphology, the coercive field is as low as 60 Oe.

Microfluidic effects of transporting signaling components in cell coculture chips

A theoretical model has been developed to investigate the microfluidic transport of the signaling chemicals in the cell coculture chips. Using an epidermal growth factor (EGF)-like growth factor as the sample chemical, the effects of velocities and channel geometry were studied for the continuous-flow microchannel bioreactors. It is found that different perfusion velocities must be applied in the parallel channels to facilitate the communication, i.e., transport of the signaling component, between the coculture channels. Such communication occurs in a unidirectional way because the signaling chemicals can only flow from the high velocity area to the low velocity area. Moreover, the effect of the transport of the signaling component between the coculture channels on the growth of the monolayer cells and the multicellular tumor spheroid (MTS) in the continuous-flow coculture environment were simulated using 3D models. The numerical results demonstrated that the concentration gradients will induce the heterogeneous growth of the cells and the MTSs, which should be taken into account in designing the continuous-flow perfusion bioreactor for the cell coculture research.

Effects of Pallas' viper (Agkistrodon halys pallas) venom on blood coagulation and characterization of a prothrombin activator

The action of Pallas' viper (Agkistrodon halys pallas) venom on blood coagulation was examined in vitro and a strong anticoagulant effect was observed. This action was abolished after treatment with a specific inhibitor of phospholipase A(2) activity (p-bromophenacyl bromide), revealing a procoagulant action in low concentrations of treated venom (around 1 mu g/ml). The effect of the venom an haemostasis was further characterized by measuring its ability to activate purified blood coagulation factors. It is concluded that A. halys pallas venom contains prothrombin activation activity. A prothrombin activator (aharin) was purified from the venom by Sephadex G-75 gel filtration and ion-exchange chromatography on a Mono-Q column. It consisted of a single polypeptide chain, with a mol. wt of 63,000. Purified aharin possessed no amidolytic activity on chromogenic substrates. It did not act on other blood coagulation factors, such as factor X and plasminogen, nor did it cleave or clot purified fibrinogen. The prothrombin activation activity of aharin was readily inhibited by ethylenediamine tetracetic acid (a metal chelator), but specific serine protease inhibitors such as diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride had no effect on it. These observations suggest that, like those prothrombin activators from Echis carinatus and Bothrops atrox venoms, the prothrombin activator from A. halys pallas venom is a metalloproteinase. (C) 1998 Elsevier Science Ltd. All rights reserved.

A novel bradykinin-like peptide from skin secretions of the frog, Rana nigrovittata

A bradykinin-like peptide has been isolated from the skin secretions of the frog Rana nigrovittata. This peptide was named ranakinin-N. Its primary structure, RAEAVPPGFTPFR, was determined by Edman degradation and mass spectrometry. It is structurally related to bradykinin-like peptides identified from skin secretions of other amphibians. Ranakinin-N is composed of 13 amino acid residues and is related to the bradykinin identified from the skin secretions of Odorrana schmackeri, which is composed of 9 amino acid residues. Ranakinin-N was found to exert concentration-dependent contractile effects on isolated guinea pig ileum. cDNA sequence encoding the precursor of ranakinin-N was isolated from a skin cDNA library of R. nigrovittata. The amino acid sequences deduced from the cDNA sequences match well with the results from Edman degradation. Analysis of different amphibian bradykinin cDNA structures revealed that the deficiency of a 15-nucleotide fragment (agaatgatcagacgc in the cDNA encoding bradykinin from O. schmackeri) in the peptide-coding region resulted in the absence of a dibasic site for trypsin-like proteinases and an unusual -AEVA- insertion in the N-terminal part of ranakinin-N. The -AEAV- insertion resulted in neutral net charge at the N-terminus of ranakinin-N. Ranakinin-N is the first reported bradykinin-like peptide with a neutral net charge at the N-terminus. Copyright (C) 2007 European Peptide Society and John Wiley & Sons, Ltd.

The Effects of Visual Object Size in The Depth Perception in KM Mouse

Whether mice perceive the depth of space dependent on the visual size of object targets was explored when visual cues such as perspective and partial occlusion in space were excluded. A mouse was placed on a platform the height of which is adjustable. The platform located inside a box in which all other walls were dark exception its bottom through that light was projected as a sole visual cue. The visual object cue was composed of 4x4 grids to allow a mouse estimating the distance of the platform relative to the grids. Three sizes of grids reduced in a proportion of 2/3 and seven distances with an equal interval between the platform and the grids at the bottom were applied in the experiments. The duration of a mouse staying on the platform at each height was recorded when the different sizes of the grids were presented randomly to test whether the Judgment of the mouse for the depth of the platform from the bottom was affected by the size information of the visual target. The results from all conditions of three object sizes show that time of mice staying on the platform became longer with the increase in height. In distance of 20 similar to 30 cm, the mice did not use the size information of a target to judge the depth, while mainly used the information of binocular disparity. In distance less than 20 cm or more than 30 cm, however, especially in much higher distance 50 cm, 60 cm and 70 cm, the mice were able to use the size information to do so in order to compensate the lack of binocular disparity information from both eyes. Because the mice have only 1/3 of the visual field that is binocular. This behavioral paradigm established in the current study is a useful model and can be applied to the experiments using transgenic mouse as an animal model to investigate the relationships between behaviors and gene functions.

Enriched environment experience overcomes the memory deficits and depressive-like behavior induced by early life stress

Stress in early life is believed to cause cognitive and affective disorders, and to disrupt hippocampal synaptic plasticity in adolescence into adult, but it is unclear whether exposure to enriched environment (EE) can overcome these effects. Here, we rep

DOPAMINE D2 RECEPTOR MECHANISMS CONTRIBUTE TO AGE-RELATED COGNITIVE DECLINE - THE EFFECTS OF QUINPIROLE ON MEMORY AND MOTOR-PERFORMANCE IN MONKEYS

The D2 dopamine (DA) receptor agonist, quinpirole, was characterized in young adult monkeys, young reserpine-treated monkeys and aged monkeys to assess the contribution of DA to age-related loss of prefrontal cortical (PFC) cognitive function, Monkeys were tested on a delayed response memory task that depends on the PFC, and a fine motor task that taps the functions of the motor cortex, In young adult monkeys, low quinpirole doses impaired performance of the PFC and fine motor tasks, while higher doses improved memory performance and induced dyskinesias and ''hallucinatory-like'' behaviors. The pattern of the quinpirole response in reserpine-treated monkeys suggested that the impairments in delayed response and fine motor performance resulted from drug actions at D2 autoreceptors, while the improvement in delayed response performance, dyskinesias and ''hallucinatory-like'' behaviors resulted from actions at postsynaptic receptors. In aged monkeys, low doses of quinpirole continued to impair fine motor performance, but lost their ability to impair delayed response performance. The magnitude of cognitive improvement and the incidence of ''hallucinatory-like'' behaviors were also reduced in the aged animals, suggesting some loss of postsynaptic D2 receptor function, The pattern of results is consistent with the greater loss of DA from the PFC than from motor areas in aged monkey brain (Goldman-Rakic and Brown, 1981; Wenk et al., 1989), and indicates that DA depletion contributes significantly to age-related cognitive decline.

WATER-QUALITY CHANGES AND EFFECTS ON FISH POPULATIONS IN THE HANJIANG RIVER, CHINA, FOLLOWING HYDROELECTRIC DAM CONSTRUCTION

Since its completion in 1973 the Danjiangkou Dam has markedly changed downstream flows, water levels, temperatures, sediment loads and other water quality characteristics in downstream reaches of the Hanjiang River. There have been changes in the growth, spawning behaviour and overwintering condition of local fish populations, in the composition and abundance of food organisms and in the composition of the commercial fish catch. Despite the changed environment and the absence of a fish pass, fish populations are still able to grow and spawn under the new regime. Where conditions are like those of the Hanjiang River, dams may not necessarily have calamitous consequences for fishery production.

Quantum Confinement Effects and Electronic Properties of SnO2 Quantum Wires and Dots

On the basis of the density functional theory (DFT) within local density approximations (LDA) approach, we calculate the band gaps for different size SnO2 quantum wire (QWs) and quantum dots (QDs). A model is proposed to passivate the surface atoms of SnO2 QWs and QDs. We find that the band gap increases between QWs and bulk evolve as Delta E-g(wire) = 1.74/d(1.20) as the effective diameter d decreases, while being Delta E-g(dot) = 2.84/d(1.26) for the QDs. Though the similar to d(1.2) scale is significantly different from similar to d(2) of the effective mass result, the ratio of band gap increases between SnO2 QWs and QDs is 0.609, very close to the effective mass prediction. We also confirm, although the LDS calculations underestimate the band gap, that they give the trend of band gap shift as much as that obtained by the hybrid functional (PBE0) with a rational mixing of 25% Fock exchange and 75% of the conventional Perdew-Burke-Ernzerhof (PBE) exchange functional for the SnO2 QWs and QDs. The relative deviation of the LDA calculated band gap difference Lambda E-g compared with the corresponding PBE0 results is only within 5%. Additionally, it is found the states of valence band maximum (VBM) and conduction band minimum (CBM) of SnO2 QWs or QDs have a mostly p- and s-like envelope function symmetry, respectively, from both LDA and PBE0 calculations.

Effects of different modified underlayer surfaces on growth and optical properties of InGaN quantum dots

InGaN/GaN quantum dots were grown on the sapphire (0 0 0 1) substrate in a metalorganic chemical vapor deposition system. The morphologies of QDs deposited on different modified underlayer (GaN) surfaces, including naturally as grown, Ga-mediated, In-mediated, and air-passivated ones, were investigated by atomic force microscopy (AFM). Photo luminescence (PL) method is used to evaluate optical properties. It is shown that InGaN QDs can form directly on the natural GaN layer. However, both the size and distribution show obvious inhomogeneities. Such a heavy fluctuation in size leads to double peaks for QDs with short growth time, and broad peaks for QDs with long growth time in their low-temperature PL spectra. QDs grown on the Ga-mediated GaN underlayer tends to coalesce. Distinct transform takes place from 3D to 2D growth on the In-mediated ones, and thus the formation of QDs is prohibited. Those results clarify Ga and In's surfactant behavior. When the GaN underlayer is passivated in the air, and together with an additional low-temperature-grown seeding layer, however, the island growth mode is enhanced. Subsequently, grown InGaN QDs are characterized by a relatively high density and an improved Gaussian-like distribution in size. Short surface diffusion length at low growth temperature accounts for that result. It is concluded that reduced temperature favors QD's 3D growth and surface passivation can provide another promising way to obtain high-density QDs that especially suits MOCVD system. (c) 2004 Elsevier Ltd. All rights reserved.

Net-like ferromagnetic MnSb film deposited on porous silicon substrates

MnSb films were deposited on porous silicon substrates by physical vapor deposition (PVD) technique. Modulation effects due to the substrate on microstructure and magnetic properties of the MnSb film's were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and measurements of hysteresis loops. SEM images of the MnSb films indicate that net-like structures were obtained because of the special morphology of the substrates. The net-like MnSb films exhibit some novel magnetic properties different from the unpatterned referenced samples. For example, in the case of net-like morphology, the coercive field is as low as 60 Oe. (c) 2006 Elsevier B.V. All rights reserved.

Effects of seed dot layer and thin GaAs spacer layer on the structure and optical properties of upper In(Ga)As quantum dots

The structure and optical properties of In(Ga)As with the introduction of InGaAlAs or InAlAs seed dot layers are investigated. The area density and size homogeneity of the upper InGaAs dots are efficiently improved by the introduction of a buried layer of high-density dots. Our explanation for the realization of high density and size homogeneity dots is presented. When the GaAs spacer layer is too thin to cover the seed dots, the upper dots exhibit some optical properties like those of a quantum well. By analyzing the growth dynamics, we refer to this kind of dot as an empty-core dot. (C) 2003 American Institute of Physics.

The effects of pre-irradiation on the formation of Si1-xCx alloys

Carbon ions were implanted into crystal Si to a concentration of (0.6-1.5)at% at room temperature. Some samples were pre-irradiated with S-29(i)+ ions, while others were not pre-irradiated. Then the two kinds of samples were implanted with C-12(+) ions simultaneously, and Si1-xCx alloys were grown by solid phase epitaxy with high-temperature annealing. The effects of preirradiation on the formation of Si1-xCx alloys were studied. If the dose of implanted C ion was less than that for amorphizing Si crystals, the implanted C atoms would like to combine with defects produced during implantation, and then it was difficult for Si1-xCx alloys to form after annealine, at 950 degreesC. Pre-irradiation was advantageous for Si1-xCx alloy formation. With the increase of C ion dose, the damage produced by C ions increased. Pre-irradiation was unfavorable for Si1-xCx, alloy formation. If the implanted C concentration was higher than that for solid phase epitaxy solution, only part of the implanted C atoms form Si1-xCx alloys and the effects of pre-irradiation could be neglected. As the annealing temperature was increased to 1050 degreesC, Si1-xCx alloys in both pre-irradiated and unpreirradiated samples of low C concentration remained, whereas most part of Si1-xCx alloys in samples with high C concentration vanished.