In situ formation of leak-free polyethylene glycol (PEG) membranes in microfluidic fuel cells.

Membraneless microfluidic fuel cells operated under two co-laminar flows often face serious fuel cross-over problems, especially when flow rates are close to zero. In this study, we show that polyethylene glycol (PEG) monomers can be cross-linked inside microfluidic channels to form leak-free PEG membranes, which prevent mixing of two incompatible electrolyte solutions while allowing diffusion of certain molecules (e.g. glucose) and ions. By using PEG monomers of different molecular weights and cross-linking conditions, we are able to tailor selectivity of the membrane to allow passage of glucose while blocking larger molecules such as trypan blue. As a proof of principle, a microfluidic fuel cell with a PEG membrane and two incompatible electrolytes (acid and base) is demonstrated. Thanks to the leak-free nature of the PEG membrane, these two electrolytes do not mix together even at very slow flow rates. This microfluidic fuel cell is able to generate a voltage up to ∼450 mV from 10 mM of glucose with a flow rate of 20 µL min-1. This microfluidic fuel cell is potentially useful as a miniature power source for many applications.

Systemic modelling of human bioenergetics and blood circulation.

This work reviews the main aspects of human bioenergetics and the dynamics of the cardiovascular system, with emphasis on modelling their physiological characteristics. The methods used to study human bioenergetics and circulation dynamics, including the use of mathematical models, are summarised. The main characteristics of human bioenergetics, including mitochondrial metabolism and global energy balance, are first described, and the systemic aspects of blood circulation and related physiological issues are introduced. The authors also discuss the present status of studies of human bioenergetics and blood circulation. Then, the limitations of the existing studies are described in an effort to identify directions for future research towards integrated and comprehensive modelling. This review emphasises that a multi-scale and multi-physical approach to bioenergetics and blood circulation that considers multiple scales and physiological factors are necessary for the appropriate clinical application of computational models.

A quasi two-dimensional model for sound attenuation by the sonic crystals.

Sound propagation in the sonic crystal (SC) along the symmetry direction is modeled by sound propagation through a variable cross-sectional area waveguide. A one-dimensional (1D) model based on the Webster horn equation is used to obtain sound attenuation through the SC. This model is compared with two-dimensional (2D) finite element simulation and experiment. The 1D model prediction of frequency band for sound attenuation is found to be shifted by around 500 Hz with respect to the finite element simulation. The reason for this shift is due to the assumption involved in the 1D model. A quasi 2D model is developed for sound propagation through the waveguide. Sound pressure profiles from the quasi 2D model are compared with the finite element simulation and the 1D model. The result shows significant improvement over the 1D model and is in good agreement with the 2D finite element simulation. Finally, sound attenuation through the SC is computed based on the quasi 2D model and is found to be in good agreement with the finite element simulation. The quasi 2D model provides an improved method to calculate sound attenuation through the SC.

Cathepsin G inhibitor prevents ultraviolet B-induced photoaging in hairless mice via inhibition of fibronectin fragmentation.

BACKGROUND: Cathepsin G, a serine protease that is activated by ultraviolet (UV) radiation, increases matrix metalloproteinase-1 (MMP-1) expression in fibroblasts through fibronectin (Fn) fragmentation and promotes the conversion of proMMP-1 to active MMP-1. OBJECTIVES: This study investigated whether [2-[3-[[(1-benzoyl-4-piperidinyl)methylamino]carbonyl]-2-naphthalenyl]-1-(1-naphthalenyl)-2-oxoethyl]-phosphonic acid (KPA), a cathepsin G inhibitor, plays any role in extracellular matrix (ECM) damage in an in vitro 3D dermal equivalent (DE) and an in vivo ultraviolet B (UVB)-irradiated hairless mice. METHODS: We examined the potential ECM-protective effects of a cathepsin G inhibitor in an in vitro 3D DE model and an in vivo UVB-irradiated hairless mouse skin model. RESULTS: Among five known serine protease inhibitors, KPA showed the strongest potency and selectivity against cathepsin G. KPA inhibited the cathepsin G-mediated MMP-1 increase and alleviated the downregulation of mRNAs encoding collagen and tissue inhibitor of matrix metalloproteinase-1 in an in vitro 3D DE model. Most importantly, topical application of KPA (0.025%) to the dorsal skin of hairless mice enhanced collagen expression and attenuated UVB-induced Fn fragmentation and upregulation of MMP-2 and MMP-9 activities. CONCLUSIONS: Cathepsin G inhibitors may be useful for the prevention of UVB-induced photoaging through amelioration of ECM damage and MMP upregulation.

Procoagulant and prothrombotic effects of the herbal medicine, Dipsacus asper and its active ingredient, dipsacus saponin C, on human platelets.

BACKGROUND: In spite of the growing popularity of herbal medicines and natural food supplements, their effects on cardiovascular homeostasis remain largely unknown, especially regarding pro-thrombotic risks. OBJECTIVE: In the present study, 21 herbal tea extracts were screened for the procoagulant activities on platelets, an important promoter of thrombosis to examine if herbal medicines or natural products may have prothrombotic risks. We discovered that Dipsacus asper (DA), known to have analgesic and anti-inflammatory effects, potently induced procoagulant activities in platelets. We tried to identify the active ingredient and elucidate the underlying mechanism. RESULTS: Among 10 major ingredients of DA, dipsacus saponin C (DSC) was identified as a key active ingredient in DA-induced procoagulant activities. DSC-induced procoagulant activities were achieved by the exposure of phosphatidylserine (PS) and PS-bearing microparticle generation that were caused by the alteration in the activities of phospholipid translocases: scramblase and flippase. These events were initiated by increased intracellular calcium and ATP depletion. Notably, DSC induced a series of apoptotic events including the disruption of mitochondrial membrane potential, translocation of Bax and Bak, cytochrome c release and caspase-3 activation. The key roles of apoptotic pathway and caspase activation were demonstrated by the reversal of DSC-induced PS exposure and procoagulant activities with the pretreatment of caspase inhibitors. Interestingly, EGTA reversed DSC-induced procoagulant activities and apoptotic events suggesting that an intracellular calcium increase may play a central role. These results were also confirmed in vivo where platelets of the rats exposed to DSC or DA exhibited PS exposure. Most importantly, DSC or DA administration led to increased thrombus formation. CONCLUSION: These results demonstrate that herbal medicines or natural products such as DA or DSC might have prothrombotic risks through procoagulant activation of platelets.

New index for categorising cardiac reentrant wave: in silico evaluation.

Based on the similarity between a reentrant wave in cardiac tissue and a vortex in fluid dynamics, the authors hypothesised that a new non-dimensional index, like the Reynolds number in fluid dynamics, may play a critical role in categorising reentrant wave dynamics. Therefore the goal of the present study is to devise a new index to characterise electric wave conduction in cardiac tissue and examined whether this index can be used as a biomarker for categorising the reentrant wave pattern in cardiac tissue. Similar to the procedure used to derive the Reynolds number in fluid dynamics, the authors used a non-dimensionalisation technique to obtain the new index. Its usefulness was verified using a two-dimensional simulation model of electrical wave propagation in cardiac tissue. The simulation results showed that electrical waves in cardiac tissue move into an unstable region when the index exceeds a threshold value.

Design of photonic crystals with multiple and combined band gaps.

We present and use an algorithm based on convex conic optimization to design two-dimensional photonic crystals with large absolute band gaps. Among several illustrations we show that it is possible to design photonic crystals which exhibit multiple absolute band gaps for the combined transverse electric and magnetic modes. The optimized crystals show complicated patterns which are far different from existing photonic crystal designs. We employ subspace approximation and mesh adaptivity to enhance computational efficiency. For some examples involving two band gaps, we demonstrate the tradeoff frontier between two different absolute band gaps.

Pharmacokinetic evaluation of an oral tablet form of low-molecular-weight heparin and deoxycholic acid conjugate as a novel oral anticoagulant.

This study was designed to develop a solid oral dosage form of deoxycholic acid (DOCA)-conjugated low-molecular-weight heparin (LMWH) and to evaluate its oral absorption, distribution, and metabolic stability for the prospect of providing an orally bioavailable LMWH. The LMWH derivative (LHD) was synthesised and then formulated with solubilisers and other pharmaceutical excipients to form a solid tablet. Its absorption and distribution after oral administration were evaluated in mice, rats, and monkeys. The in vitro metabolic stability of LHD was examined by liver microsome assays. More than 80% of LHD was released from the tablet within 60 minutes, guaranteeing rapid tablet disintegration after oral administration. Oral bioavailability of LHD in mice, rats and monkeys were 16.1 ± 3.0, 15.6 ± 6.1, and 15.8 ± 2.5%, respectively. After the oral administration of 131I-tyramine-LHD, most of the absorbed drug remained in the blood circulation and was eliminated mainly through the kidneys. LHD was hardly metabolised by the liver microsomes and showed a stable metabolic pattern similar to that of LMWH. In a rat thrombosis model, 10 mg/kg of orally administered LHD reduced thrombus formation by 60.8%, which was comparable to the anti-thrombotic effect of the subcutaneously injected LMWH (100 IU/kg). Solid tablets of LHD exhibited high oral absorption and statistically significant therapeutic effects in preventing venous thromboembolism. Accordingly, LHD tablets are expected to satisfy the unmet medical need for an oral heparin-based anticoagulant as an alternative to injectable heparin and oral warfarin.

Glass transition temperature influence on crosslinked and entangled polymer interfaces.

The influence of glass transition temperature (Tg) on crosslinked and entangled polymer interfaces was investigated using coarse grained molecular dynamics (MD). A crosslinked polymer interface and an entangled polymer interface were built and the Tg for each system were obtained by confining a thin film between two rigid walls. The physical properties of each system above and under Tg were compared. The mechanical properties were also explored by pulling the interfaces apart at different temperature. The results are qualitatively agreed with experimental observations. Furthermore, the present results show that, when under tensile loading at temperature higher than Tg, the entangled interface exhibits strain softening while the crosslinked thin film is still able to show strain hardening. The different performances may due to that, at high temperature, the high mobility of monomers tend to unravel the entangled chain in linear polymer system while in crosslinked system, monomers with high mobility tend to arrest the void and decrease the void propagation.

Multiscale modeling of polymers-bridging the molecular continuum divide.

A method to reduce the degrees freedom in molecular mechanics simulation is presented. Although the approach is formulated for amorphous materials, it is equally applicable to crystalline materials. The method is selectively applied to regions where molecular displacements are expected to be small while simultaneously using classical molecular mechanics for regions undergoing large deformation. Its accuracy and computational efficiency are demonstrated through the simulation of a polymer-like substrate indented by a rigid indentor. The region directly below the indentor is modelled by classical molecular mechanics while the region further away has the degrees of freedom reduced by about 50 times.

Doxorubicin-induced platelet cytotoxicity: a new contributory factor for doxorubicin-mediated thrombocytopenia.

BACKGROUND: Doxorubicin (DOX) is a widely used anticancer drug for solid tumors and hematologic malignancy, but its active use is hampered by serious adverse effects, including thrombocytopenia. Although bone marrow toxicity of DOX has been suggested to be the sole mechanism underlying the reduced platelet counts, the direct effects of DOX on platelets have never been examined. OBJECTIVE: Here, we investigated the DOX-induced platelet cytotoxicity and its underlying mechanism in an effort to elucidate the contribution of platelet cytotoxicity to DOX-induced thrombocytopenia. RESULTS: In freshly isolated human platelets, DOX induced platelet cytotoxicity in a time-dependent and concentration-dependent manner. Reactive oxygen species (ROS) generation, decreased glutathione levels and subsequent protein thiol depletion were shown to underlie the DOX-induced platelet cytotoxicity. Conspicuously, DOX-treated platelets displayed apoptotic features such as caspase-3 activation, reduced mitochondrial transmembrane potential, and phosphatidylserine exposure. Decreased glutathiolation of procaspase-3 was shown to be a link between protein thiol depletion and caspase-3 activation. It is of note that DOX-mediated platelet cytotoxicity was significantly enhanced by shear stress, a common complicating factor in cancer patients. These in vitro results were further confirmed by an in vivo animal model, where administration of DOX induced a platelet count decrease, ROS generation, caspase-3 activation, protein thiol depletion, and damaged platelet integrity. CONCLUSION: We demonstrated that DOX can directly induce platelet cytotoxicity through ROS generation, decreased glutathione levels, and protein thiol depletion. We believe that this study provides important evidence for the role of DOX-induced platelet cytotoxicity in the development of thrombocytopenia in DOX-treated patients.

Significance of water molecules in the inhibition of cylin-dependent kinase 2 and 5 complexes.

Interest in CDK2 and CDK5 has stemmed mainly from their association with cancer and neuronal migration or differentiation related diseases and the need to design selective inhibitors for these kinases. In the present paper, eight Molecular Dynamics (MD) simulations are carried out to examine the importance of structure and dynamics of water in the active site of both CDK2 and CDK5 complexes with roscovitine and indirubin analogues. Together with previous results, the current work shows a highly conserved water-involved hydrogen bonding (HB) network in both CDK2- and CDK5-indirubin combinations to complete information from the X-ray crystallography. The simulations suggest the importance of such a network for combining the inhibitor to the host protein as well as the significance of using an activated CDK as a template when designing new inhibitors. Different binding patterns of roscovitine in CDK2 and CDK5 are detected during the simulations because of the different binding conformations of the group on the C2 side chain, which might offer a clue toward finding highly selective inhibitors with regards to CDK2 and CDK5.

The activation and inhibition of cyclin-dependent kinase-5 by phosphorylation.

Despite the very similar 3-dimensional structures as reflected by the more than 60% identity in amino acid sequences, CDK2 and CDK5 have very different functions and characteristics. Phosphorylation on a conserved Thr14 can inhibit activities of both the kinases, but phosphorylating another conserved Tyr15, however, can lead to totally opposite inhibition and stimulation consequences in CDK2 and CDK5. Our molecular dynamics (MD) simulations suggest a similar inhibition mechanism of phosphorylation on the Thr14 as in the CDK2 system. In both the systems, the kinase activities are inhibited by the phosphorylation because it causes ATP phosphate moiety misalignment and changes in the Mg2+ ion coordination sphere, which have been proven to be critical for the phosphate group of the ATP transferring to the hydroxyl group on the serine in the substrate peptide. The calculations indicate that ATP adopts a more favorable conformation and location in the phosphorylated Tyr15 complex to facilitate the interactions with the substrate and the Mg2+ is wrapped more strongly by the phosphate group than in the unphosphorylated system, which might be favored by the transfer reaction.

Transfer of 137Cs to rice plants from various paddy soils contaminated under flooded conditions at different growth stages.

Soil blocks from 18 paddy fields around three Korean nuclear power plant sites were put into lysimeters. Greenhouse experiments were carried out to investigate the (137)Cs transfer from these paddy soils to rice plants for its deposition at different growth stages. A solution of (137)Cs was applied to the flooded lysimeters at 2-3 different stages. The applied (137)Cs was mixed with the topsoil only at the pre-transplanting application. The transfer was quantified with a transfer factor based on the unit-area deposition (TF(a), m(2)kg(-1)-dry). The TF(a) in the pre-transplanting application showed a remarkable variation with the soils. However, the differences in the mean values among the study sites were not statistically significant. The straw TF(a) was 2-3 times higher than the corresponding seed value. The early-tillering stage and booting stage applications resulted in a higher transfer than the pre-transplanting application by factors of, on an average, 2 and 16 for the straws, and 3 and 25 for the hulled seeds, respectively. The (137)Cs transfer was found to correlate negatively with the soil pH and positively with the organic matter content. Based on the present results, the representative (137)Cs TF(a) values for the rice are proposed for use in the whole of Korea for the deposition at three different growth stages.

Plant uptake and downward migration of 85Sr and 137Cs after their deposition on to flooded rice fields: lysimeter experiments with and without the addition of KCl and lime.

In order to study the plant uptake and downward migration of radiostrontium and radiocesium deposited on to a flooded rice field, 85Sr and 137Cs were applied to the standing water over an acidic sandy soil in planted lysimeters. The plant uptake was quantified with the areal transfer factor (TFa, m2 kg(-1)-dry plant). Following the spiking 14 days after transplanting, the TFa values for the hulled seeds were 3.9 x 10(-4) for 85Sr and 1.4 x 10(-4) for 137Cs, whereas those for the straws were 1.3 x 10(-2) and 3.2 x 10(-4), respectively. The 137Cs TFa from the spiking at the anthesis/milky-ripe stage was several times higher than that from the earlier spiking, whereas the difference was much less in the 85Sr TFa. Such an increase in the 137Cs TFa was attributed mainly to an enhanced plant-base uptake. The addition of KCl and lime after the spiking significantly reduced the TFa values of both radionuclides. The reducing effect was greater for the later spiking. An appreciable fraction of the applied activity leached out of the lysimeter for 85Sr, whereas a negligible fraction leached for 137Cs. The leaching was remarkably increased by the KCl and lime addition for both. A conspicuous localization of 137Cs with respect to the soil surface was observed. In a batch experiment, the 137Cs concentration in the standing water decreased more rapidly than that of 85Sr, both of which were fitted to the power functions of the elapsed time. To add KCl and lime slowed such decreases to lessen the distribution coefficients (Kd) of both 85Sr and 137Cs.

Induction of marked apoptosis in mammalian cancer cell lines by antisense DNA treatment to abolish expression of DENN (differentially expressed in normal and neoplastic cells).

We previously reported the isolation of the novel human DENN gene, which is differentially expressed in normal and neoplastic cells. DENN is identical to MADD (mitogen-activated protein kinase-activating death domain), which interacts with tumor necrosis factor receptor 1 through their death domains. DENN is also homologous to Rab3 GEP, a rat Rab3 GDP/GTP exchange protein. Real-time reverse transcription-polymerase chain reaction analysis showed that DENN expression in cancer cell lines was 26-50 times that in normal cells. The Jurkat human leukemia, PLC/PRF/5 human hepatoma, and NS-1 mouse myeloma cell lines as well as the MRC-5 human fetal lung and Vero monkey kidney cell lines were treated successfully with four separate DENN-targeted antisense oligodeoxynucleotides (ODNs) to abrogate DENN expression. Quantitative assessment of cell viability and apoptosis by flow cytometry via fluorescein diacetate and propidium iodide membrane-integrity tests, terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate-biotin nick end-labeling, and annexin V assays showed that antisense silencing of DENN resulted in markedly more pronounced cell death in cancer cells compared with nonmalignant cells. Antisense-treated cell lines exhibited extensive loss of DNA content, forming distinct sub-G(1) peaks, while cell proliferation diminished significantly. Ultrastructural features of programmed cell death in cells subjected to antisense ODNs were authenticated by electron microscopy. In contrast, transfection of cell lines with a plasmid construct to achieve DENN overexpression augmented cellular proliferation and could reverse the apoptotic effect of antisense and staurosporine treatment. Our findings suggest that DENN is intimately involved in anti-apoptotic and cell-survival processes.

Tissue free water tritium and organically bound tritium in the rice plant acutely exposed to atmospheric HTO vapor under semi-outdoor conditions.

Potted rice plants were exposed to atmospheric HTO in a box outdoors for 1 h at 9 different times from booting to yellow-ripe stages. It is indicated that the leaf TFWT concentration may reach equilibrium within 1 h in clear weather. The plant TFWT concentration decreased at a rapid rate for the first several hours and at a much slower rate thereafter. The decrease till harvest was by factors of 600-95,000 depending on the plant parts and exposure times. The time course of the ear OBT concentration was characterized by the exposure time. After exposure at the booting to heading stages, the leaf OBT concentration decreased rapidly for the first several hours and then very slowly. The plant OBT concentration was initially about 2 orders of magnitude lower, but at harvest an order of magnitude higher, than the TFWT concentration. The OBT concentration in hulled seeds at harvest varied with exposure times by a factor of 70, being highest in the exposure performed at the earlier stage of rapid grain growth. Also in this exposure, the plant total OBT was greatest due to the seed OBT.

2,2-Dimethyl-4,5-diaryl-3(2H)furanone derivatives as selective cyclo-oxygenase-2 inhibitors.

A series of 2,2-dimethyl-5-[4-(methylsulfonyl)phenyl]-4-phenyl-3(2H)furanones was prepared and evaluated for their ability to inhibit cyclo-oxygenase-2 (COX-2).

Cochlear model with three-dimensional fluid, inner sulcus and feed-forward mechanism.

A three-dimensional model of the guinea pig cochlea using the phase-integral method is presented. This model incorporates the viscous fluid effects in the cochlea, dimensional and material property variation along the cochlear duct and the active feed-forward mechanism of the outer hair cells. Two degrees of freedom of the basilar membrane are considered, which results in two traveling waves propagating along the duct for a given frequency. Basilar membrane response with the active feed-forward mechanism compares favorably with published experimental measurements.

Prostaglandin H synthase and lipoxygenase mediated activation of xenobiotics in platelets.

To investigate the involvement of prostaglandin H synthase (PHS) and lipoxygenase (LPO) in the activation of xenobiotics in platelets, platelet sonicates were preincubated with alpha-naphthol. Protein covalent binding of alpha-naphthol was measured following addition of arachidonic acid. Protein covalent binding was increased in a dose-dependent manner until it plateaued at 500 microM arachidonic acid. Pretreatment by two inhibitors of PHS, aspirin and indomethacin, resulted in a dose-dependent inhibition of alpha-naphthol-induced covalent binding, confirming PHS involvement. In addition, pretreatment by a LPO inhibitor, nordihydroguaiaretic acid (NDGA), also prevented covalent binding substantially, showing that LPO may be an alternative pathway for xenobiotic activation in platelets. Furthermore, combined treatment of aspirin and NDGA almost abolished the increase of alpha-naphthol-induced covalent binding, suggesting that PHS and LPO are both major pathways for xenobiotic activation in platelets.