Signature of Al11Sm3 fragments in undercooled Al90Sm10 liquid from ab initio molecular dynamics simulations

An ab initio molecular dynamics (MD) simulation is performed to investigate the structural evolution in Al(90)Sm(10) liquid from 1500 to 900 K. Development of Al(11)Sm(3) local order upon rapid cooling is suggested by the Honeycutt-Anderson (HA) index analysis and the appearance of a predominant Sm-Sm-Sm bond angle around 90° when the liquid approaches the melting point (∼920 K). Direct structural evidence of Al(11)Sm(3) fragments at 900 K is obtained using an atomic cluster alignment method developed recently. Meanwhile, development of strong icosahedral short range order (ISRO) and a non-negligible amount of fcc-type clusters around Al in the system are also observed. These results suggest that fcc Al and Al(11)Sm(3) crystalline phases would compete strongly with the formation of an amorphous phase that exhibits ISRO in the diffusionless solidification limit upon rapid quenching.

An ab initio calculation study of silicon and carbon binary clusters C7Si(n) (n = 1-7)

Binary C(7)Si(n) (n = 1-7) clusters are studied using density functional calculations at the level of B3LYP/6-311G(d). Lowest-energy structures have been determined theoretically and their properties such as binding energies, second differences in energy and highest-occupied and lowest-unoccupied molecular orbital gaps have been analyzed. It is found that the lowest-energy structures of the C(7)Si(n) (n = 1-7) clusters change from linear to planar when n ≥ 3, and in the planar structures C atoms prefer to form five- and six-membered rings surrounded by extra Si atoms in the form of the C(2)Si units.

Competitive diamond-like and endohedral fullerene structures of Si70

We performed first-principles calculations to study the structure and stability of Si(70) cluster. The results from the density functional theory calculation with the Becke-Lee-Yang-Parr and B3LYP exchange-correlation functionals suggest that a diamond-like Si(70) isomer is the most stable structure, in contrast to endohedral fullerenes of Si(70). On the other hand, an endohedral fullerene of Si(16)@Si(54) was found to be slightly lower in energy than the diamond-like Si(70) if the Predew-Burke-Ernzerhof functional is used. Our calculation results suggest that around n = 70, the endohedral fullerene and diamond-like isomer are expected to be competitive. The calculated IR vibration spectra, ionization potential, and inverse mobilities were also calculated and discussed.

Electronic structure and transport of a carbon chain between graphene nanoribbon leads

The electronic structure and transport property of a carbon chain between two graphene nanoribbon leads are studied using an ab initio tight-binding (TB) model and Landauer's formalism combined with a non-equilibrium Green's function. The TB Hamiltonian and overlap matrices are extracted from first-principles density functional calculations through the quasi-atomic minimal basis orbital scheme. The accuracy of the TB model is demonstrated by comparing the electronic structure from the TB model with that from first-principles density functional theory. The results of electronic transport on a carbon atomic chain connected to armchair and zigzag graphene ribbon leads, such as different transport characters near the Fermi level and at most one quantized conductance, reveal the effect of the electronic structure of the leads and the scattering from the atomic chain. In addition, bond length alternation and an interesting transmission resonance are observed in the atomic chain connected to zigzag graphene ribbon leads. Our approach provides a promising route to quantitative investigation of both the electronic structure and transport property of large systems.

Structures of Pb(n) (n = 21-30) clusters from first-principles calculations

Neutral lead clusters Pb(n) (n = 21-30) were studied using a genetic algorithm (GA)/tight-binding (TB) search combined with density functional theory (DFT)-Perdew-Burke-Ernzerhof (PBE) calculations. The calculated results show that the Pb(n) (22 ≤ n ≤ 30) clusters favor endohedral cage structures with two (Pb(22 - 26)) or three (Pb(27 - 30)) endohedral atoms. The binding energies, stabilities, and highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps of the Pb(n) clusters were also discussed. The results from our calculations also indicate that Pb(24) and Pb(28) are especially stable clusters compared with their neighbors.

Stabilities and fragmentation energies of Si(n) clusters (n = 2-33)

The structures of Si(n) (n = 2-33) were confirmed by genetic algorithm (GA)/tight binding (TB) search and ab initio calculations at the B3LYP/6- 311++G(2d) and PW91/6-311++G(2d) level, respectively. The fragmentation energies, binding energies, second differences in energy, and highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps in the size range 2≤n≤33 were calculated and analyzed systematically. We extended the cluster size involved in the fragmentation analyses up to Si(33), and studied the multi-step fragmentations of Si(n). The calculated result is similar to the fragmentation behavior of small silicon clusters studied previously, showing that Si(6), Si(7), and Si(10) have relatively larger stabilities and appear more frequently in the fragmentation products of large silicon clusters, which is in good agreement with the experimental observations.

A first-principles divide-and-conquer approach for electronic structure of large systems and its application to graphene nanoribbons

We demonstrate an efficient and accurate first-principles method to calculate the electronic structure of a large system using a divide-and-conquer strategy based on localized quasi-atomic minimal basis set orbitals recently developed. Tight-binding Hamiltonian and overlap matrices of a large system can be constructed by extracting the matrix elements for a given pair of atoms from first-principles calculations of smaller systems that represent the local bonding environment of the particular atom pair. The approach is successfully applied to the studies of electronic structure in graphene nanoribbons. This provides a promising way to do the electronic simulation for large systems directly from first principles.

Efficient first-principles simulation of noncontact atomic force microscopy for structural analysis

We propose an efficient scheme to simulate noncontact atomic force microscopy images by using first-principles self-consistent potential from the sample as input without explicit modeling of the atomic force microscopy tip. Our method is applied to various types of semiconductor surfaces including Si(111)-(7x7), TiO2(110)-(1x1), Ag/Si(111)-(sqrt[3]xsqrt[3])R30 degrees, and Ge/Si(105)-(1x2) surfaces. We obtain good agreement with experimental results and previous theoretical studies, and our method can aid in identifying different structural models for surface reconstruction.

American ginseng berry juice intake reduces blood glucose and body weight in ob/ob mice

Diabetes is a serious chronic metabolic disease and has a significant impact on patients' lives and the health care system. We previously observed that the organic solvent extract of American ginseng berry possessed significant antidiabetic effects in obese diabetic ob/ob mice after intraperitoneal injection. If American ginseng berry is useful as a dietary supplement, simple preparation and oral intake would be a convenient, safe, and practical means for consumers. In this study, the simply prepared berry juice was first analyzed using high-performance liquid chromatography, and then administered orally in the ob/ob mice. The animals received daily berry juice 0.6 mL/kg or vehicle for 10 consecutive days. The results indicated that oral juice administration significantly lowered fasting blood glucose levels, and this effect continued for at least 10 d after cessation of the treatment. Data from intraperitoneal glucose tolerance test demonstrated that there was a notable improvement in glucose tolerance in the juice treated group. In addition, the berry juice significantly reduced body weight. Our data suggest that ginseng berry juice, as a dietary supplement, may have functional efficacy in consumers with diabetes.

Simultaneous identification of Bulbus Fritillariae cirrhosae using PCR-RFLP analysis

Bulbus Fritillariae (BF) is the most commonly used antitussive herb in China. There are nine species of Fritillaria recorded as the drug BF in the Chinese Pharmacopoeia. Bulbus Fritillariae cirrhosae (BF cirrhosae) is a group that includes four species of BF; these four species come from wild sources with higher efficiency and lower toxicity compared to the other five species of BF. Due to reasons of carelessness and reduced costs, the other five species are often sold as BF cirrhosae. Analysis through appearance, microscopic and chemical techniques has limitations. Identifying botanical resources is a primary step in the standardization of herbal medicine. In the present article, the internal transcribed spacer 1 (ITS1) regions of the nuclear ribosomal DNA (nrDNA) of nine species and one variety of Fritillaria genus have been sequenced. A mutation site in the ITS1 region among BF cirrhosae and other species of BF has been found and can be recognized by the restriction endonuclease SmaI. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the nuclear ribosomal ITS1 region was used to differentiate BF cirrhosae from other species of BF and is a successful method in distinguishing the subgroups.

Oxidation Pattern of Small Silicon Oxide Clusters: Structures and Stability of Si6On (n = 1−12)

We have performed systematic ab initio calculations to study the structures and stability of Si(6)O(n)() clusters (n = 1-12) in order to understand the oxidation process in silicon systems. Our calculation results show that oxidation pattern of the small silicon cluster, with continuous addition of O atoms, extends from one side to the entire Si cluster. Si atoms are found to be separated from the pure Si cluster one-by-one by insertion of oxygen into the Si-O bonds. From fragmentation energy analyses, it is found that the Si-rich clusters usually dissociate into a smaller pure Si clusters (Si(5), Si(4), Si(3), or Si(2)), plus oxide fragments such as SiO, Si(2)O(2), Si(3)O(3), Si(3)O(4), and Si(4)O(5). We have also studied the structures of the ionic Si(6)O(n)(+/-) (n = 1-12) clusters and found that most of ionic clusters have different lowest-energy structures in comparison with the neutral clusters. Our calculation results suggest that transformation Si(6)O(n)+(a) + O --> Si(6)O(n+1)+(a) should be easier.

Quantum size effect on the diffusion barriers and growth morphology of Pb/Si(111)

An intriguing growth morphology of Pb islands on a Si(111) surface is observed in our STM experiments: the growth of a Pb layer on Pb islands with unstable heights starts from the periphery and moves towards the center, while the nucleation of the next layer on stable Pb islands starts away from the periphery. Using first-principles total energy calculations, we have studied the diffusion barriers of Pb adatoms on a freestanding Pb(111) film as a function of film thickness. The diffusion barriers are found to be very low (<60 meV), and a bi-layer oscillation due to the quantum size effect (QSE) is observed, with a lower barrier on the odd-layered, relatively unstable Pb films. The diffusion barrier difference between the odd- and even-layered film is as large as 40 meV. The observed unusual growth can be attributed to this big difference in the diffusion barriers due to QSE.

Molecule intrinsic minimal basis sets. II. Bonding analyses for Si4H6 and Si2 to Si10

The method, introduced in the preceding paper, for recasting molecular self-consistent field (SCF) or density functional theory (DFT) orbitals in terms of intrinsic minimal bases of quasiatomic orbitals, which differ only little from the optimal free-atom minimal-basis orbitals, is used to elucidate the bonding in several silicon clusters. The applications show that the quasiatomic orbitals deviate from the minimal-basis SCF orbitals of the free atoms by only very small deformations and that the latter arise mainly from bonded neighbor atoms. The Mulliken population analysis in terms of the quasiatomic minimal-basis orbitals leads to a quantum mechanical interpretation of small-ring strain in terms of antibonding encroachments of localized molecular-orbitals and identifies the origin of the bond-stretch isomerization in Si4H6. In the virtual SCF/DFT orbital space, the method places the qualitative notion of virtual valence orbitals on a firm basis and provides an unambiguous ab initio identification of the frontier orbitals.

Molecule intrinsic minimal basis sets. I. Exact resolution of ab initio optimized molecular orbitals in terms of deformed atomic minimal-basis orbitals

A method is presented for expressing the occupied self-consistent-field (SCF) orbitals of a molecule exactly in terms of chemically deformed atomic minimal-basis-set orbitals that deviate as little as possible from free-atom SCF minimal-basis orbitals. The molecular orbitals referred to are the exact SCF orbitals, the free-atom orbitals referred to are the exact atomic SCF orbitals, and the formulation of the deformed "quasiatomic minimal-basis-sets" is independent of the calculational atomic orbital basis used. The resulting resolution of molecular orbitals in terms of quasiatomic minimal basis set orbitals is therefore intrinsic to the exact molecular wave functions. The deformations are analyzed in terms of interatomic contributions. The Mulliken population analysis is formulated in terms of the quasiatomic minimal-basis orbitals. In the virtual SCF orbital space the method leads to a quantitative ab initio formulation of the qualitative model of virtual valence orbitals, which are useful for calculating electron correlation and the interpretation of reactions. The method is applicable to Kohn-Sham density functional theory orbitals and is easily generalized to valence MCSCF orbitals.

Ganoderma lucidum extract inhibits proliferation of SW 480 human colorectal cancer cells

AIM

Ganoderma lucidum is a commonly used Chinese herb and an important ingredient in traditional Chinese medicine herbal formulations for immune dysfunction related illnesses. The effects of this medicinal mushroom on human colorectal cancer cells have not yet been evaluated. In this study, we investigated the effects of Ganoderma lucidum extract using SW 480 human colorectal cancer cell line.

MATERIALS AND METHODS

Two different fractions of Ganoderma lucidum extract, i.e., a fraction containing mainly polysaccharides (GLE-1), and a triterpenoid fraction without polysaccharides (GLE-2) were analyzed. Their antiproliferative activity was evaluated by cell proliferation assay and 3H-thymidine incorporation assay. Scavenging effects of DPPH radical were assessed using ESR-spectroscopy.

RESULTS

Our data showed that both GLE-1 and GLE-2 significantly inhibited the proliferation of SW 480 cells. The inhibitory effect of GLE-2 was much stronger than that of GLE-1. GLE-1 inhibited DNA synthesis in the cells and reduced the formation of DPPH radicals.

CONCLUSION

Ganoderma lucidum extract inhibits proliferation of human colorectal cancer cells and possesses antioxidant properties.

Structure and stability of oxygen adsorption on Si(n) (n = 5-10) clusters

The structures, binding energies, and electronic properties of one oxygen atom (O) and two oxygen atoms (2O) adsorption on silicon clusters Si(n) with n ranging from 5 to 10 are studied systematically by ab initio calculations. Twelve stable structures are obtained, two of which are in agreement with those reported in previous literature and the others are new structures that have not been proposed before. Further investigations on the fragmentations of Si(n)O and Si(n)O2 (n = 5-10) clusters indicate that the pathways Si(n)O --> Si(n-1) + SiO and Si(n)O2 --> Si(n-2) + Si2O2 are most favorable from thermodynamic viewpoint. Among the studied silicon oxide clusters, Si8O, Si9O, Si5O2 and Si8O2 correspond to large adsorption energies of silicon clusters with respect to O or 2O, while Si8O, with the smallest dissociation energy, has a tendency to separate into Si7 + SiO. Using the recently developed quasi-atomic minimal-basis-orbital method, we have also calculated the unsaturated valences of the neutral Si(n) clusters. Our calculation results show that the Si atoms which have the largest unsaturated valences are more attractive to O atom. Placing O atom right around the Si atoms with the largest unsaturated valences usually leads to stable structures of the silicon oxide clusters.

Diffusion, coalescence, and reconstruction of vacancy defects in graphene layers

Diffusion, coalescence, and reconstruction of vacancy defects in graphene layers are investigated by tight-binding molecular dynamics (TBMD) simulations and by first principles total energy calculations. It is observed in the TBMD simulations that two single vacancies coalesce into a 5-8-5 double vacancy at the temperature of 3000 K, and it is further reconstructed into a new defect structure, the 555-777 defect, by the Stone-Wales type transformation at higher temperatures. First principles calculations confirm that the 555-777 defect is energetically much more stable than two separated single vacancies, and the energy of the 555-777 defect is also slightly lower than that of the 5-8-5 double vacancy. In TBMD simulation, it is also found that the four single vacancies reconstruct into two collective 555-777 defects which is the unit for the hexagonal haeckelite structure proposed by Terrones et al. [Phys. Rev. Lett. 84, 1716 (2000)].

Potential Energy Surfaces of SimOn Cluster Formation and Isomerization

The reaction paths for formation and isomerization of a set of silica SimOn (m = 2,3, n = 1-5) nanoclusters have been investigated using second-order perturbation theory (MP2) with the 6-31G(d) basis set. The MP2/6-31G(d) calculations have predicted singlet ground states for all clusters excluding Si3O2. The total energies of the most important points on the potential energy surfaces (PES) have been determined using the completely renormalized (CR) singles and doubles coupled cluster method including perturbative triples, CR-CCSD(T) with the cc-pVTZ basis set. Although transition states have been located for many isomerization reactions, only for Si3O3 and Si3O4 have some transition states been found for the formation of a cluster from the separated reactants. In all other cases, the process of formation of SimOn clusters appears to proceed without potential energy barriers.

Ab initio molecular dynamics simulation of liquid Al88Si12 alloys

First-principles molecular dynamics simulations are carried out to study the structures, dynamics, and electronic properties of liquid Al88Si12 in the temperature ranging from 898 to 1298 K. The temperature dependence of static structure factors, pair correlation functions, and electronic density-of-states are investigated. The structural properties obtained from the simulations are in good agreement with the x-ray diffraction experimental results.

Effect of chain connectivity on the structure of Lennard-Jones liquid and its implicationon statistical potentials for protein folding

Statistical contact potentials and bead-spring models have been widely used for computational studies of protein folding. However, there has been speculation that systematic error may arise in the contact energy calculations when the statistical potentials are deduced under the assumption that the chain connectivity in proteins can be ignored. To address this issue, we have performed molecular-dynamics simulations to study the structure and dynamics of a simple liquid system in which the beads are either connected or unconnected with springs. Results from the present study provide useful information for assessing the accuracy of the statistical potentials for protein structure simulations.

Heat-induced transformation of nanodiamond into a tube-shaped fullerene: a molecular dynamics simulation

Heat-induced structural transformation in nanodiamond of diameter approximately 1.4 nm is investigated by tight-binding molecular dynamics simulations using the environment-dependent tight-binding carbon potential. The nanodiamond is found to transform into a tube-shaped fullerene via annealing. Three interesting mechanisms for promoting inner carbon atoms of the nanodiamond into the surface carbon atoms of the tubular structure are observed. The "flow-out" mechanism prevails at temperatures lower than 2500 K and the "direct adsorption" and "push-out" mechanisms are observed at higher temperatures.

Pharmacological and behavioral analysis of the effects of some bivalent ligand-based monoamine reuptake inhibitors

Novel piperidine-based bivalent ligands were prepared in enantiomerically pure form and evaluated for their ability to inhibit reuptake of dopamine (DA), serotonin (5-HT), and norepinephrine (NE) into rat brain nerve endings (synaptosomes). In this study, we have succeeded in using (1) the length of the linking chain connecting the two piperidine-based monomer units and (2) the absolute configuration of the piperidine monomer as a means to tailor activity and selectivity at the three monoamine transporters tested. In this series, the bivalent ligand 16, comprised of two (+)-trans-piperidine units linked by a pentamethylene spacer, exhibits a combination of high DA transporter (DAT) and 5-HT transporter (SERT) activity (K(i) = 39 nM and 7 nM, respectively). Piperidine 16 is capable of reducing cocaine's locomotor effects in mice while not having any effect on locomotion when tested alone. Additionally, compound 16 (1-10 mg/kg) does not substitute for cocaine in drug discrimination studies in rats. However, the analogous bivalent ligand 15 comprised of two (-)-trans-piperidine units, which is SERT selective, was less effective in antagonizing cocaine's locomotor stimulant activity. The piperidine-based bivalent inhibitors described herein constitute a new class of monoamine reuptake inhibitors that exhibit varying levels of monoamine transporter activity and selectivity, and these ligands may serve as lead candidates in the discovery of new therapeutics to treat a range of neurological disorders including cocaine addiction.

[Effect of Tripterygium wilfordii on Th1, Th2 cytokines production in asthma patients]

OBJECTIVE

To observe the effect of Tripterygium wilfordii on Th1, Th2 cytokines in asthma patients for further study on the therapeutic mechanism.

METHODS

Twelve patients of middle or severe asthma were treated by Tripterygium polyglucoside 40 mg or 60 mg daily for 4 weeks. Blood of patients was colleted before and after treatment for serum and peripherol blood mononuclear cells (PBMC) preparation. The prepared PBMCs were stimulted in vitro with Concanavalin A (ConA) for 6 hrs and followed by culturing with Triptolide for 24 hrs and then the supernatant was collected. The concentration of interleukin-2(IL-2), -4(IL-4), -5(IL-5) and interferon-gamma(IFN-gamma) in serum and in the supernatant were detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Serum levels of IL-2, IL-4 and IL-5 of patients decreased significantly after treatment of Tripterygium polyglucoside (P < 0.01), but IFN-gamma level was under the detection sensitivity both before and after treatment. Triptolide could inhibit PBMC to secrete IL-2, IL-4 and IL-5 in vitro (P < 0.01), but IFN-gamma was also under the detection sensitivity.

CONCLUSION

The marked inhibition of Th2 cytokine expression by Tripterygium was the important mechanism of it in treating asthma. But the fact that Tripterygium also showed inhibition on Th1 cytokine indicated that the inhibition of Tripterygium on Th2 and Th1 cytokines was non-specific.

Unique dynamic appearance of a Ge-Si ad-dimer on Si(001)

We carry out a comparative study of the energetics and dynamics of Si-Si, Ge-Ge, and Ge-Si ad-dimers on top of a dimer row in the Si(001) surface, using first-principles calculations. The dynamic appearance of a Ge-Si dimer is distinctively different from that of a Si-Si or Ge-Ge dimer, providing a unique way for its identification by scanning tunneling microscopy (STM). Its "rocking" motion, observed in STM, actually reflects a 180 degrees rotation of the dimer, involving a piecewise-rotation mechanism. The calculated energy barrier of 0.74 eV is in good agreement with the experimental value of 0.82 eV.

Role of the Metal/Semiconductor interface in quantum size effects: Pb /Si(111)

Self-organized islands of uniform heights can form at low temperatures on metal/semiconductor systems as a result of quantum size effects, i.e., the occupation of discrete electron energy levels in the film. We compare the growth mode on two different substrates [Si(111)- (7x7) vs Si(111)- Pb(sqrt[3]xsqrt[3] )] with spot profile analysis low-energy electron diffraction. For the same growth conditions (of coverage and temperature) 7-step islands are the most stable islands on the (7x7) phase, while 5-step (but larger islands) are the most stable islands on the (sqrt[3]xsqrt[3] ). A theoretical calculation suggests that the height selection on the two interfaces can be attributed to the amount of charge transfer at the interface.

The Na+-driven Cl-/HCO3- exchanger. Cloning, tissue distribution, and functional characterization

The Na(+)-driven Cl(-)/HCO(3)(-) exchanger is an important regulator of intracellular pH in various cells, but its molecular basis has not been determined. We show here the primary structure, tissue distribution, and functional characterization of Na(+)-driven chloride/bicarbonate exchanger (designated NCBE) cloned from the insulin-secreting cell line MIN6 cDNA library. The NCBE protein consists of 1088 amino acids having 74, 72, and 55% amino acid identity to the human skeletal muscle, rat smooth muscle, and human kidney sodium bicarbonate cotransporter, respectively. The protein has 10 putative membrane-spanning regions. NCBE mRNA is expressed at high levels in the brain and the mouse insulinoma cell line MIN6 and at low levels in the pituitary, testis, kidney, and ileum. Functional analyses of the NCBE protein expressed in Xenopus laevis oocytes and HEK293 cells demonstrate that it transports extracellular Na(+) and HCO(3)(-) into cells in exchange for intracellular Cl(-) and H(+), thus raising the intracellular pH. Thus, we conclude that NCBE is a Na(+)-driven Cl(-)/HCO(3)(-) exchanger that regulates intracellular pH in native cells.

Laser-induced graphitization on a diamond (111) surface

We report an atomistic simulation study of laser-induced graphitization on the diamond (111) surface. Our simulation results show that the diamond to graphite transition occurs along different pathways depending on the length of the laser pulse being used. Under nanosecond or longer laser pulses, graphitization propagates vertically into bulk layers, leading to the formation of diamond-graphite interfaces after the laser treatment. By contrast, with femtosecond (0.2-0.5 ps) laser pulses, graphitization of the surface occurs layer by layer, resulting in a clean diamond surface after the ablation. This atomistic picture provides an explanation of recent experimental observations.

Insulin secretion and differential gene expression in glucose-responsive and -unresponsive MIN6 sublines

We have established two sublines derived from the insulin-secreting mouse pancreatic beta-cell line MIN6, designated m9 and m14. m9 Cells exhibit glucose-induced insulin secretion in a concentration-dependent manner, whereas m14 cells respond poorly to glucose. In m14 cells, glucose consumption and lactate production are enhanced, and ATP production is largely through nonoxidative pathways. Moreover, lactate dehydrogenase activity is increased, and hexokinase replaces glucokinase as a glucose-phosphorylating enzyme. The ATP-sensitive K(+) channel activity and voltage-dependent calcium channel activity in m14 cells are reduced, and the resting membrane potential is significantly higher than in m9 cells. Thus, in contrast to m9, a model for beta-cells with normal insulin response, m14 is a model for beta-cells with impaired glucose-induced insulin secretion. By mRNA differential display of these sublines, we found 10 genes to be expressed at markedly different levels. These newly established MIN6 cell sublines should be useful tools in the analysis of the genetic and molecular basis of impaired glucose-induced insulin secretion.

The interactions between soybean trypsin inhibitor and delta-endotoxin of Bacillus thuringiensis in Helicoverpa armigera larva

No significant difference in larval mortality was observed when a sublethal dose of Bacillus thuringiensis (Bt) var. kurstaki HD-1 crystal was supplemented with soybean trypsin inhibitor (STI) in the artificial diet fed to Helicoverpa armigera in the laboratory, but supplementing a nonlethal dose of crystal with STI in the diet led to a pronounced reduction of larval growth. This concentration of crystal and two lower concentrations of STI alone had no significant effects on larval growth. The results of substrate-gel electrophoresis demonstrated that the proteases in the H. armigera midgut fluid responsible for the degradation of protoxin consisted of at least four proteases with molecular weights of 71, 49, 36, and 30 kDa. All four proteases could utilize casein also as the substrate. When larvae were fed with STI or Bt + STI, the proteolytic activities of the 49-kDa enzyme disappeared, and the activities of the other three enzymes were reduced. Enzyme assays also indicated that feeding larvae with diets containing Bt, STI, or Bt + STI significantly decreased the specific activities of larval general proteases and the trypsin-like enzyme. The protein concentration of midgut fluid was elevated, especially in the larvae fed on the diets containing STI and Bt + STI. Both in vitro and in vivo studies showed that the degradation of protoxin and toxin could be inhibited by soybean trypsin inhibitors, but when the incubation time was prolonged, the protoxin could be degraded completely, while the degradation of toxin was inhibited further. This suggested that the retention time of toxins in the larval midgut was extended and synergism between insecticidal crystal protein and soybean trypsin inhibitor occurred, which showed as the inhibition of H. armigera larval growth.

Correlations between the scanning tunneling microscopy imaged configurations and the electronic structure on stepped Si(111)-( 7x7) surfaces

We have observed the dependence of the scanning tunneling microscopy (STM) imaged atom intensity within the (7x7) unit cell on stepped Si(111) as a function of the tunneling voltage. Pronounced differences from the corresponding atom intensity on the flat surface are observed for the contrast of atoms on the low versus the high side of the step and for the contrast between the faulted versus unfaulted subcells of the (7x7) structure. These differences can be accounted for by changes in the electronic structure within the (7x7) subcells adjacent to the step. Calculations of the local density of states and the STM images using a tight-binding method are in excellent agreement with the experimental results.

Synthesis of 3,3',5-trihydroxybiphenyl-2-carboxylic acid, a component of the bitterest natural product amarogentin and its coenzyme A and N-acetyl cysteamine thiol esters

3,3',5-Trihydroxybiphenyl-2-carboxylic acid (6), an ester component of the bitter-tasting natural products amarogentin and amaroswerin, was synthesized in six steps in 13.6% overall yield. Its N-acetyl cysteamine thiol ester (9) and its coenzyme A thiol ester (8), a likely biosynthetic precursor of the amarums, were also prepared.

Dose dependence and time course of smoke inhalation injury in a rabbit model

The dose dependence and time course of smoke inhalation injury were determined in a rabbit model. Animals were insufflated with 18-90 breaths of cotton smoke or room air (control) at a rate of 18 breaths/min and tidal volume of 12 ml/kg. Smoke-exposed animals exhibited dose-related histologic effects with progressive deterioration of respiratory function during the postexposure period of observation (96 h). The smoke-exposed rabbits had reproducible injuries to both airway mucosa and lung parenchyma, manifested by disruption and sloughing of airway and alveolar epithelia, and exudation of protein-rich fluid and leukocytes into the airway and alveolar spaces. Significant effects were evident by 24 h postexposure. Smoke inhalation also affected the respiratory burst of alveolar macrophages. Generation of superoxide anions by alveolar macrophages at 48 h postexposure was increased significantly after smoke inhalation (54 breaths). The present rabbit model should be useful for studying the interactions between pulmonary epithelial cells and leukocytes after smoke inhalation and for determining the role that abnormal functioning of alveolar macrophages plays in the development of smoke inhalation injury.

Subacute pituitary apoplexy-analysis of 17 cases

We retrospectively study 17 cases (total cases 197), receiving surgery at Kaohsiung Medical College Hospital, which are proved to be subacute pituitary apoplexy via preoperative computerized tomograms, magnetic resonance imagings, operative findings and pathological proof. Fourteen patients had headache; 15 cases were with visual disturbance including visual defect, blindness. One case was found incidentally to have a cerebral vascular attack. None of these cases received bromocriptine. Preoperative computerized tomograms (CT) aided the initial diagnosis and magnetic resonance imaging (MRI) is preferred for radiological investigation in displaying the metabolic products of hemorrhage within the pituitary tumors. Operative findings revealed xanthochromic fluid with liquid-like tumor debris or chocolate-like content. All these patients received hormone supplement when pituitary apoplexy was highly suspected.

Cotton smoke inhalation primes alveolar macrophages for tumor necrosis factor-alpha production and suppresses macrophage antimicrobial activities

The present study determined the effects of cotton smoke inhalation on the functioning of alveolar macrophages (mphi). Smoke inhalation led to dose-dependent impairment of respiratory gas exchange by 48 h postexposure and pulmonary edema by 96 h. Maximal effects were observed in animals ventilated with 54 breaths of cotton smoke (3-min exposure, 18 breaths/min). Macrophages were obtained at 48 h postexposure by bronchoalveolar lavage of rabbits subjected to 54 breaths of smoke or room air (control). Phagocytosis of opsonized bacteria and adherence to solid substratum were reduced in smoke-exposed mphi. Smoke inhalation primed mphi for release of tumor necrosis factor-alpha (TNF-alpha) induced by lipopolysaccharide (LPS). Smoke-exposed mphi were also primed for TNF-alpha release induced by phorbol myristate acetate, which suggests that the priming event occurred downstream of protein kinase C activation in the signal transduction pathway. Further, smoke exposure attenuated the inhibitory effects of phosphodiesterase inhibitors on LPS-induced TNF-alpha release. Thus, the priming event may be mediated through cAMP and/or protein kinase A. The data indicate that cotton smoke inhalation suppresses the antimicrobial activities of alveolar mphi and can lead to excessive mphi production of TNF-alpha. These mphi effects would be expected to contribute to the pathophysiological abnormalities associated with smoke inhalation injury.

Evidence for pH sensitivity of tumor necrosis factor-alpha release by alveolar macrophages

Alveolar macrophages (m phi) participate in inflammatory and immune responses in acidic microenvironments such as the interstitial fluids of tumors and abscesses. Two plasmalemmal H+ extruders interact to control the acid-base status of alveolar m phi, namely a V-type H+ pump (V-ATPase) and a Na+/H+ exchanger. The present study examined the effects of extracellular pH (pHo) and H+ transport inhibitors on tumor necrosis factor-alpha (TNF-alpha) release induced by endotoxin (lipopolysaccharide) in rabbit alveolar m phi. The amount and activity of TNF-alpha in m phi-conditioned media were determined by enzyme-linked immunosorbent assay and L929 fibroblast bioassay, respectively. TNF-alpha release was suppressed progressively at lower pHo values (< or = 7.0). Also, bafilomycin A1 (a specific inhibitor of V-ATPases) significantly reduced the amount and activity of TNF-alpha in m phi-conditioned media (pHo 7.4). However, bafilomycin caused a significant increase in the nonspecific cytotoxicity (i.e. bioactivity insensitive to TNF-alpha antibody) of m phi-conditioned media. The effects of bafilomycin specifically on TNF-alpha release followed a time course similar to that of acidic pHo, suggesting that both treatments acted on similar events in the lipopolysaccharide signal transduction pathway. Amiloride (an inhibitor of Na+ transporters including the Na+/H+ exchanger) also suppressed TNF-alpha release but displayed a time course of action different from the acidic pHo or bafilomycin.

Triterpenoid saponins from Aster auriculatus

Three new triterpenoid saponins, auriculatusaponins A, B, and C, along with one known saponin, 3- O-beta-glucuronylolean-12-en-28-oic acid 28-( O-alpha-rhamnopyranosyl-(1-->2)-alpha-arabinopyranosyl) ester were isolated from roots of Aster auriculatus. On the basis of spectral and chemical evidence, auriculatusaponins A, B, and C were determined as 3beta- O-beta-glucuronyl-16-oxo-12-ene-28-noroleanane, 3beta- O-beta-glucuronyl-16alpha- trans-feruloyloxy-12-en-oleanane, and 3- O-beta-glucopyranosyl-16alpha-hydroxy-olean-12-ene-28-oic acid 28- O-carboxymethyl ester, respectively.

Neolignan glycosides from Pedicularis longiflora

Four new neolignan glucosides, longiflorosides A, B, C and D, in addition to one known neolignan glucoside, dehydro-diconiferyl alcohol-4-O-beta-D-glucopyranoside were obtained from whole plants of Pedicularis longiflora. The structures of these compounds were determined mainly on spectral evidence.

Cellular distribution of the P2X4 ATP receptor mRNA in the brain and non-neuronal organs of rats

RNA blot analysis has shown that an ionotropic ATP receptor P2X4 is widely distributed, as compared with other P2X subtypes. Cellular distribution of the P2X4 ATP receptor mRNA was investigated by in situ hybridization technique in the brain and non-neuronal organs. In the brain, transcripts of the P2X4 were widely distributed in various regions, with the highest signals in the cerebellar Purkinje cells and granule cells. In other organs, intense and selective expression was detected in seminiferous tubules of the testis and intestinal crypts of the colon, suggesting an involvement of ATP in spermatogenesis and intestinal secretion. A low but significant level of the P2X4 mRNA was detected in the adenohypophysis and the cortex of the adrenal gland. The tissue- or cell-specific expression of the P2X4 mRNA is of importance to understand the functional roles of the purinergic transmission system.

A family of sulfonylurea receptors determines the pharmacological properties of ATP-sensitive K+ channels

We have cloned an isoform of the sulfonylurea receptor (SUR), designated SUR2. Coexpression of SUR2 and the inward rectifier K+ channel subunit Kir6.2 in COS1 cells reconstitutes the properties of K(ATP) channels described in cardiac and skeletal muscle. The SUR2/Kir6.2 channel is less sensitive than the SUR/Kir6.2 channel (the pancreatic beta cell KATP channel) to both ATP and the sulfonylurea glibenclamide and is activated by the cardiac K(ATP) channel openers, cromakalim and pinacidil, but not by diazoxide. In addition, SUR2 binds glibenclamide with lower affinity. The present study shows that the ATP sensitivity and pharmacological properties of K(ATP) channels are determined by a family of structurally related but functionally distinct sulfonylurea receptors.

Cloning and pharmacological characterization of a fourth P2X receptor subtype widely expressed in brain and peripheral tissues including various endocrine tissues

We have isolated cDNA encoding a fourth member (P2X-4) of the ATP receptor P2X receptor family from a rat pancreatic islet cDNA library. Rat P2X-4 is a protein of 388 amino acids which shares 50%, 49%, and 47% identity with P2X-1, P2X-2, and P2X-3, respectively, and has two putative transmembrane segments. Rat P2X-4 mRNA is widely expressed in brain and peripheral tissues, including various endocrine tissues, and it is also expressed in various hormone-secreting cell lines. We have heterologously expressed the cloned P2X-4 in Xenopus laevis oocytes and have characterized its pharmacological properties. ATP, its analogs and ADP activate cation-selective ion channels. The order of agonist potency is ATP ADP 2-methyl- thioATP(2MeSATP) >> alpha beta-methelene-ATP (alpha betameATP). ATP-evoked currents are only partially blocked by suramin, reactive blue-2, or H2DIDS. The present study suggests that P2X-4, with pharmacological properties distinct from those of P2X-1+, P2X-2, and P2X-3, mediates extracellular ATP-induced biological effects in non-neuronal cells, including endocrine cells, as well as in neuronal cells.

Early effects of smoke inhalation on alveolar macrophage functions

Alveolar macrophage (AM) dysfunctions have been implicated in the pathogenesis of smoke inhalation lung injury. We investigated the early (within 70 min) effects of smoke inhalation on AM. The cells were recovered by bronchoalveolar lavage from rabbits ventilated with cotton smoke for 5 min followed by O2/room air for 60 min (smoke-exposed) or with room air in place of smoke (control). Smoke injury caused arterial blood carboxyhaemoglobin levels to increase 11-fold and reduced arterial blood PO2 (measured approximately 1 h postinjury) by 25 per cent. Scanning electron micrographs revealed denudation of plasmalemmal pseudopods in smoke-exposed AM. Smoke exposure suppressed both AM adherence to plastic and phagocytosis of opsonized bacteria. Basal superoxide (O2-) production was elevated in smoke-exposed AM, compared with controls, whereas PMA-stimulated O2- production was unaffected. Smoke-exposed AM had reduced basal secretion of tumour necrosis factor-alpha (TNF-alpha), but displayed a greater TNF response to stimulation with LPS than did control cells. LPS-stimulated TNF-alpha releases from control and smoke-exposed AM were suppressed by phosphodiesterase inhibitors pentoxifylline and theophylline, and were enhanced by the lipoxygenase inhibitor, MK886. The early responses of AM to smoke inhalation lung injury are consistent with activation of O2- production and priming of TNF-alpha release, concurrent with a functional down regulation of phagocytosis.

Human gastric inhibitory polypeptide receptor: cloning of the gene (GIPR) and cDNA

Gastric inhibitory polypeptide (GIP), which is released from the gastrointestinal tract, stimulates insulin secretion from pancreatic beta cells and plays a crucial role in the regulation of insulin secretion during the postprandial phase. We have isolated the human gene (GIPR) and cDNA encoding the GIP receptor by a combination of the conventional screening and polymerase chain reaction procedures. Human GIP receptor cDNA encodes a protein of 466 amino acids that is 81.5 and 81.2% identical to the previously cloned hamster and rat GIP receptor, respectively. Hydropathic analysis shows the presence of a signal peptide and seven potential transmembrane domains, a feature characteristic of the VIP/glucagon/secretin receptor family of G protein-coupled receptors. The human GIPR gene is about 13.8 kb long, consists of 14 exons, and carries 17 Alu repeats.

Experimental studies on early treatment of schistosomal infection with artemether

An early treatment with artemether given in appropriate regimens was tested in mice, rabbits and dogs for prevention purposes. Artemether was administered intragastrically (ig) to the hosts on day 7 after infection with Schistosoma japonicum cercariae at a single dose, and the same dose of artemether was repeated every 1 or 2 weeks for 2-4 times. As a result, most of the female worms were killed before their oviposition with female worm reduction rates of 90-100%, resulting in protection of the host from damage induced by schistosome eggs. When rabbits were treated ig with artemether 10 mg kg-1 on day 7 after infection, followed by repeated dosing every week for 4 times, some parameters related to acute schistosomiasis, such as temperature, eosinophil count and eggs in the feces were negative, and low specific antigen and antibody levels in serum were seen. Further study showed that the appropriate regimens of Artemether were also effective in early treatment of reinfection with cercariae. When rabbits infected with 48-52 cercariae once every other day for 5 times were treated ig with artemether 15 mg kg-1, followed by repeated dosing every 1 or 2 week for 2- 3 times, the female worm reduction rates were 92.1-98.4%. Histopathological examination of the livers showed that the above-mentioned early treatment with Artemether exhibited a promising protective effect on dogs and rabbits. The major features included normal appearance of the liver resembling those of uninfected dogs and rabbits; few or no dispersed miliary egg tubercles appeared on the surface of the liver; the structure of the hepatic lobules was normal with normal arrangement of the liver bundles; few or no eggs appeared in the portal vein area and there was apparent diminution of total egg granuloma, comprising inflammatory, fibrous or scarred egg granuloma. On the basis of above-mentioned results, early treatment with Artemether could be recommended for field trial for controlling acute schistosomiasis, reducing infection rate and intensity of infection.