Energy of K-momentum dark excitons in carbon nanotubes by optical spectroscopy

Phonon sideband optical spectroscopy determines the energy of the dark K-momentum exciton for (6,5) carbon nanotubes. One-phonon sidebands appear in absorption and emission, split by two zone-boundary (K-point) phonons. Their average energy locates the E11 K-momentum exciton 36 meV above the E11 bright level, higher than available theoretical estimates. A model for exciton-phonon coupling shows the absorbance sideband depends sensitively on the K-momentum exciton effective mass and has minimal contributions from zone-center phonons, which dominate the Raman spectra of carbon nanotubes.

Effects of cilostazol on thrombospondin-1 (TSP-1) expression changes in the myocardium of diabetic rats

Myocardial protective effects of the phosphodiesterase 3 inhibitor, cilostazol, in streptozotocin-induced diabetic rats were investigated. Four weeks after induction of diabetes, we measured thrombospondin-1 (TSP-1) expression in the left ventricular myocardium. Microstructural and ultrastructural changes were also analysed. Four weeks after the induction of diabetes there were significant differences in body weight and blood glucose between the control, diabetic and cilostazol-treated diabetic animals. TSP-1 expression was significantly increased in the myocardium of diabetic rats compared with the control group. Although significantly higher than the control group, TSP-1 expression was significantly lower in the cilostazol group compared with the diabetes group. There were obvious ultrastructural changes in the myocardium of diabetic rats, which were rarely seen in cilostazol-treated diabetic rats. In conclusion, this study provides experimental evidence that cilostazol treatment of diabetic rats effectively prevents pathological myocardial alterations, possibly via the down-regulation of TSP-1 expression.

Direct measurement of the lifetime of optical phonons in single-walled carbon nanotubes

Time-resolved anti-Stokes Raman spectroscopy has been applied to probe the dynamics of optical phonons created in single-walled carbon nanotubes by femtosecond laser excitation. From measurement of the decay of the anti-Stokes Raman signal in semiconducting nanotubes of (6,5) chiral index, a room-temperature lifetime for G-mode phonons of 1.1+/-0.2 ps has been determined. This lifetime, which reflects the anharmonic coupling of the G-mode phonons to lower-frequency phonons, is important in assessing the role of nonequilibrium phonon populations in high-field transport phenomena.

A phase II study of nilotinib administered to patients with imatinib resistant or intolerant chronic myelogenous leukemia (CML) in chronic phase (CP), accelerated phase (AP) or blast crisis (BC) who also failed dasatinib

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Background: Nilotinib and dasatinib are two new second generation tyrosine kinase inhibitors used in the treatment of imatinib-resistant/intolerant CML. There is limited data regarding the efficacy and safety of these therapies when given sequentially. Methods: This phase II open-label study was designed to evaluate the safety and efficacy of nilotinib at a dose of 400mg BID in CML-CP, -AP, and -BC pts who previously received and either failed or were intolerant to imatinib and dasatinib. Results: A total of 42 pts are reported - CP (16), AP (9), and BC (17 total; 13 myeloid, 4 lymphoid). Overall 10 (24%) pts had extramedullary disease at baseline. For all pts, median time from first diagnosis was 16.8 (0.6–265) months. The median duration of nilotinib exposure was 81 days with median dose intensity of 800mg/day. A total of 13 (31%) pts with dasatinib failure remain on treatment, 29 (69%) discontinued (6 for AEs, 16 for disease progression). CP: Of the 16 pts, 5 (31%) had a MCyR (3 complete, 2 partial). Complete hematologic response (CHR) was reported in 5/13 (39%) pts without CHR at baseline. Disease progression only occurred in 2 pts. AP: 2/9 (22%) pts had a return to chronic phase (RTC), 6 pts were not evaluable and there was 1 death. Disease progression occurred in 5 pts. BC: 3/17 (18%) achieved CHR, 1 (6%) had RTC, and 4 (24%) pts had disease progression. For all pts, the most common Grade 3/4 AEs reported were thrombocytopenia (26%), neutropenia (24%), and anemia (7%) pts. Conclusions: Nilotinib has significant clinical activity in CML-CP, AP, and BC patients who have failed imatinib and dasatinib. Nilotinib is safe and well tolerated, consistent with its kinase selectivity profile.

No significant financial relationships to disclose.

Systems approach to modeling the neuronal CPG for leech swimming

This paper proposes a mathematical model of the neuronal central pattern generator (CPG) for leech swimming. The model is developed through the "systems approach" where dynamical components and their connections are first identified through input/output data from physiological experiments and then integrated into a chain of nonlinear oscillators. Our approach leads to a model of moderate complexity when compared with existing models developed through biophysical principles. We show through numerical simulations that our model can successfully reproduce the phase coordination observed in the isolated nerve cord of the leech CPG. As a byproduct, a prediction is obtained for the intrinsic period gradient along the nerve cord.

Modulation of the oxidative stress and nuclear factor kappaB activation by theaflavin 3,3'-gallate in the rats exposed to cerebral ischemia-reperfusion

The major pathobiological mechanisms of IR injury include excitotoxicity, oxidative stress, and inflammation. TF3, a major constituent of black tea, possesses biological functions such as anti-oxidative and anti-inflammatory activities. The purpose of this study was to verify the neuronal protective potential of TF3 and its mechanisms against cerebral IR injury in rats. TF3 administration (10 and 20 mg.kg-1) ameliorated the infarct volume. TF3 also decreased the content of MDA and NO. TF3 significantly increased the activity of SOD and GSH-Px, which were reduced by IR injury. Administration of TF3 decreased mRNA and protein expression of COX-2 and iNOS. DNA binding and Western blotting revealed an increase in NF-kappaB activation and IkappaB depletion in IR brain tissue. Pretreatment with TF3 markedly inhibited IRinduced increase in nuclear localization of NF-kappaB, and preserved IkappaB in the cytoplasm. The results show that TF3 exerts protective effects against cerebral IR injury by reducing oxidative stress and modulating the NF-kappaB activation.

Photoluminescence from intertube carrier migration in single-walled carbon nanotube bundles

Photoluminescence (PL) identifies spectroscopic signatures of intertube transfer of optically pumped carriers in single-walled carbon nanotube (SWNT) ensembles. Resonant photoexcitation of large band gap SWNTs produces strong PL from smaller band gap SWNTs. Magnetic alignment measurements associate the energy-transfer PL peaks with the formation of SWNT bundles, suggesting that efficient coupling results from physical contact.

Systems-level modeling of neuronal circuits for leech swimming

This paper describes a mathematical model of the neuronal central pattern generator (CPG) that controls the rhythmic body motion of the swimming leech. The systems approach is employed to capture the neuronal dynamics essential for generating coordinated oscillations of cell membrane potentials by a simple CPG architecture with a minimal number of parameters. Based on input/output data from physiological experiments, dynamical components (neurons and synaptic interactions) are first modeled individually and then integrated into a chain of nonlinear oscillators to form a CPG. We show through numerical simulations that the values of a few parameters can be estimated within physiologically reasonable ranges to achieve good fit of the data with respect to the phase, amplitude, and period. This parameter estimation leads to predictions regarding the synaptic coupling strength and intrinsic period gradient along the nerve cord, the latter of which agrees qualitatively with experimental observations.

mda-7 gene transfer sensitizes breast carcinoma cells to chemotherapy, biologic therapies and radiotherapy: correlation with expression of bcl-2 family members

Current therapies used in the treatment of breast cancer are limited by systemic toxicity, rapid drug metabolism and intrinsic and acquired drug resistance. We have previously shown that adenoviral-mediated transfer of the melanoma differentiation-associated gene-7 (mda-7) elicits growth inhibition and apoptosis in various tumor types. Here, we evaluate the effects of Ad-mda7, alone and in combination with other therapies, against a panel of nine breast tumor cell lines and their normal counterparts; we report selective Ad-mda7-mediated p53-independent growth inhibition, G2/M cell cycle arrest, and apoptosis. In vivo, Ad-mda7 induced p53-independent tumor growth inhibition (P<0.004) in multiple xenograft models. We then evaluated the combination of Ad-mda7 with agents commonly used to treat breast cancer: radiotherapy (XRT), Tamoxifen, Taxotere, Adriamycin, and Herceptin. These agents exhibit diverse modes of action, including formation of bulky adducts, inhibition of DNA replication (Adriamycin, XRT), damage to microtubules (Taxotere), nonsteroidal estrogen antagonists (Tamoxifen), or Her2/neu receptor blockade (Herceptin). Treated with conventional anticancer drugs or radiation, MDA-7-expressing cells display additive or synergistic cytotoxicity and apoptosis that correlates with decreased BCL-2 expression and BAX upregulation. In vivo, animals that received Ad-mda7 and XRT underwent significant reduction of tumor growth (P<0.002). This is the first report of the synergistic effects of Ad-mda7 combined with chemotherapy or radiotherapy on human breast carcinoma cells.

Combinatorial synergy induced by adenoviral-mediated mda-7 and Herceptin in Her-2+ breast cancer cells

The melanoma differentiation-associated gene-7 (mda-7) is a member of the interleukin-10 cytokine family and a novel tumor suppressor gene. Adenoviral-mediated mda-7 (Ad-mda7) gene transfer has tumor-specific growth inhibitory and proapoptotic effects in a broad spectrum of cancer cells. In breast cancer cells, adenoviral-induced mda-7 expression triggers antiproliferative effects by downregulation of survival signals, such as Bcl-2 and Akt. The anti-human epidermal growth factor receptor-2 (Her-2) monoclonal antibody, Trastuzumab (Herceptin), increases the sensitivity of Her-2/neu-overexpressing breast cancer cells to chemotherapeutic agents and radiotherapy. In this study, we evaluate the effects of treatment with Ad-mda7 and Herceptin combination therapy in a panel of Her-2/neu-overexpressing cell lines, and in established tumors in nude mice. Compared to individual treatments, the combination of Ad-mda7 and Herceptin elicits supra-additive antitumor activity in Her-2/neu-overexpressing tumor cell lines: increased cell death, cell cycle block and apoptosis. The Ad-mda7 and Herceptin interaction was shown to be synergistic by isobologram analysis. Ad-mda7 does not alter cell surface Her-2/neu levels, but the combination of Ad-mda7+Herceptin results in increased expression of cell surface E-cadherin with concomitant translocation of beta-catenin from the nucleus to the cell membrane. In vivo, the combination of Ad-mda7 and Herceptin showed significantly increased antitumor activity (P<0.003) against Her-2/neu-overexpressing tumors. These data suggest that the combination of Ad-mda7 with Herceptin may be a novel therapy for breast cancer patients whose tumors overexpress Her-2/neu. The observed synergistic effect may improve treatment options for otherwise poorly responsive, Her-2-positive, breast cancer patients.

Purification and characterization of an intracellular beta-glucosidase from the methylotrophic yeast Pichia pastoris

Pichia pastoris beta-glucosidase was purified to apparent homogeneity by salting out with ammonium sulfate, gel filtration, and ion-exchange chromatography with Q-Sepharose and CM-Sepharose. The enzyme is a tetramer (275 kD) made up of four identical subunits (70 kD). The pH optimum is 7.3, and it is fairly stable in the pH range 5.5-9.5. The temperature optimum is 40 degrees C. The purified beta-glucosidase is effectively active on p-/o-nitrophenyl-beta-D-glucopyranosides (p-/o-NPG) and 4-methylumbelliferyl-beta-D-glucopyranoside (4-MUG) with Km values of 0.12, 0.22, and 0.096 mM and Vmax values of 10.0, 11.7, and 6.2 micromol/min per mg protein, respectively. It also exhibits different levels of activity against p-nitrophenyl-1-thio-beta-D-glucopyranoside, cellobiose, gentiobiose, amygdalin, prunasin, salicin, and linamarin. The enzyme is competitively inhibited by gluconolactone, p-/o-nitrophenyl-beta-D-fucopyranosides (p-/o-NPF), and glucose against p-NPG as substrate. o-NPF is the most effective inhibitor of the enzyme activity with Ki value of 0.41 mM. The enzyme is more tolerant to glucose inhibition with Ki value of 7.2 mM for p-NPG. Pichia pastoris has been employed as a host for the functional expression of heterologous beta-glucosidases and the risk of high background beta-glucosidase activity is discussed.

Sensory feedback mechanism underlying entrainment of central pattern generator to mechanical resonance

Rhythmic body motions observed in animal locomotion are known to be controlled by neuronal circuits called central pattern generators (CPGs). It appears that CPGs are energy efficient controllers that cooperate with biomechanical and environmental constraints through sensory feedback. In particular, the CPGs tend to induce rhythmic motion of the body at a natural frequency, i.e., the CPGs are entrained to a mechanical resonance by sensory feedback. The objective of this paper is to uncover the mechanism of entrainment resulting from the dynamic interaction of the CPG and mechanical system. We first develop multiple CPG models for the reciprocal inhibition oscillator (RIO) and examine through numerical experiments whether they can be entrained to a simple pendulum. This comparative study identifies the neuronal properties essential for the entrainment. We then analyze the simplest model that captures the essential dynamics via the method of harmonic balance. It is shown that robust entrainment results from a strong, positive-feedback coupling of a lightly damped mechanical system and the RIO consisting of neurons with the complete adaptation property.

Humanin delays apoptosis in K562 cells by downregulation of P38 MAP kinase

Humanin (HN) is a newly identified neuroprotective peptide. In this study, we investigated its antiapoptotic effect and the potential mechanisms in K562 cells. Upon serum deprivation, expression of HN in K562 cells decreased and its intracellular distribution changed from cytoplasm to cell membrane. In HN stably transfected K562 cells, apoptosis was delayed compared with control vector transfected cells as measured by flow cytometry. Furthermore, analysis of different mitogen-activated protein (MAP) kinases activity revealed that extracellular signal-regulated kinase (ERK) pathway was inhibited while p38 signaling was activated following serum deprivation in K562 cells. And in HN transfected K562 cells, ERK downregulation was not affected, but p38 activation was suppressed, which may responsible for the delayed apoptosis in these cells. Activation of the ERK signaling pathway by phorbol myristate 13-acetate (PMA) and sorbitol protected K562 cells from serum deprivation induced apoptosis. Additionally, overexpression of HN reduced megakaryocytic differentiation of K562 cells. The present data outline the role of ERK and p38 MAP kinases in serum deprivation induced apoptosis in K562 cells and figure out p38 signaling pathway as molecular target for HN delaying apoptosis in K562 cells.

Effect of 2.1 MPa and 4.1 MPa H2O2 exposure on auditory brain stem evoked potential in mice

Brain auditory evoked potential (BAEP) in mice exposed to hyperbaric H2O2 pressure was monitored to reveal the correlation between altered synaptic transmission and hydrogen narcosis or isobaric HPNS. Inter peak latencies and wave amplitudes were selected as indices of assessment. The animals were exposed either to He-O2 or H2-O2 at 2.1 MPa and 4.1 MPa. Results showed that synaptic transmission was inhibited to various extents. The inhibition was partly due to the narcotic effect of hydrogen, which was added to the effect caused by hydrostatic pressure. On the other hand, asymmetrical reaction of each segment in the neuro-network might be responsible for the occurrence of HPNS.