Band structure asymmetry of bilayer graphene revealed by infrared spectroscopy

We report on infrared spectroscopy of bilayer graphene integrated in gated structures. We observe a significant asymmetry in the optical conductivity upon electrostatic doping of electrons and holes. We show that this finding arises from a marked asymmetry between the valence and conduction bands, which is mainly due to the inequivalence of the two sublattices within the graphene layer and the next-nearest-neighbor interlayer coupling. From the conductivity data, the energy difference of the two sublattices and the interlayer coupling energy are directly determined.

Board-invited review: the biology and regulation of preadipocytes and adipocytes in meat animals

The quality and value of the carcass in domestic meat animals are reflected in its protein and fat content. Preadipocytes and adipocytes are important in establishing the overall fatness of a carcass, as well as being the main contributors to the marbling component needed for consumer preference of meat products. Although some fat accumulation is essential, any excess fat that is deposited into adipose depots other than the marbling fraction is energetically unfavorable and reduces efficiency of production. Hence, this review is focused on current knowledge about the biology and regulation of the important cells of adipose tissue: preadipocytes and adipocytes.

Thickness induced structural changes in polystyrene films

Changes to the structure of polystyrene melt films as measured through the spectrum of density fluctuations have been observed as a function of film thickness down to the polymer radius of gyration (Rg). Films thicker than 4Rg show bulklike density fluctuations. Thinner films exhibit a peak in S(q) near q=0 which grows with decreasing thickness. This peak is attributed to a decreased interpenetration of chains resulting in an enhanced compressibility. Measurements were made using small angle x-ray scattering in a standing wave geometry designed to enhance scattering from the interior of the film compared to interface scattering.

Detection and characterization of amplified fragment length polymorphism markers for clinical mastitis in Canadian Holsteins

Mastitis is the most frequent, complex, and costly disease in dairy cattle. Genetic improvement of milk production traits has accompanied an increased susceptibility to mastitis. To determine genome-wide quantitative trait locus-linked markers for mastitis resistance, a total of 200 cows, comprising 100 top clinical mastitis- (CM) resistant and 100 top CM-susceptible cows, were screened by selective DNA pooling and amplified fragment length polymorphism (AFLP) technique. The AFLP analysis on resistant and susceptible pools using 89 selective primer combinations revealed 27 significant AFLP markers at a false discovery rate (FDR) of < 5%. The most promising AFLP marker was then selected for further characterization. Individual AFLP genotyping of the marker on all selected animals confirmed a significant difference. Sequence analysis detected a single nucleotide polymorphism (A<-->G) responsible for the AFLP polymorphism, which was named CGIL4. The PCR-RFLP analysis indicated that the frequency of allele A was significantly higher in the resistant group. The logistic regression analysis demonstrated that the marker was significantly associated with somatic cell score, CM residual values, and production traits. Radiation hybrid mapping assigned the marker to Bos taurus autosome 22. The present study provides promising markers for marker-assisted selection for CM resistance. Our results also demonstrated the capability of AFLP on selective DNA pools as a method for detection of genome regions containing quantitative trait loci.

Estimation of bioconcentration factors using molecular electro-topological state and flexibility

Bioconcentration assessment is important in the scientific evaluation of risks that chemicals may pose to humans and environment and is a current focus of regulatory effort. In this work, a new QSAR model by adopting electronic topological properties and flexibility of chemicals to predict the bioconcentration factor (BCF) in fish was established based on a large number of diverse compounds. Multiple linear regression (MLR) and partial least squares (PLS) were used to build reliable QSARs, which were evaluated with internal five cross-validations (Qcv2) and an external validation (Qex2). The proposed MLR model showed reasonable predictivity of BCF (Qcv2 = 0.79,Qex2 = 0.79) and included seven molecular descriptors, namely SsCl, SaasC, SaaaC, SsNH2, Hmin, SssO, and Phia. The PLS model (Qcv2 = 0.83, Qex2 = 0.80) was shown to be slightly better than the MLR one in prediction accuracy, using six PLS latent components. In addition, the relationship between the log BCF and the theoretical calculated log Kow was extensively investigated. These studies may help to understand the factors influencing the bioconcentration process of chemicals and to develop alternative methods for prescreening of environmental toxic compounds.

Cyclotron resonance in bilayer graphene

We present the first measurements of cyclotron resonance of electrons and holes in bilayer graphene. In magnetic fields up to B=18 T, we observe four distinct intraband transitions in both the conduction and valence bands. The transition energies are roughly linear in B between the lowest Landau levels, whereas they follow square root[B] for the higher transitions. This highly unusual behavior represents a change from a parabolic to a linear energy dispersion. The density of states derived from our data generally agrees with the existing lowest order tight binding calculation for bilayer graphene. However, in comparing data to theory, a single set of fitting parameters fails to describe the experimental results.

Full-length dystrophin gene transfer to the mdx mouse in utero

In utero gene therapy for genetic diseases, such as muscular dystrophies, offers potential advantages over postnatal treatment including vector delivery at the earliest point in the disease and treatment prior to full maturation of the immune system. This study examines in utero gene delivery of full-length murine dystrophin to the murine mdx model for Duchenne muscular dystrophy using a high-capacity adenoviral vector. We examined dystrophin expression, spread of vector, morphology and specific force production of the tibialis anterior muscle 9 weeks after intramuscular in utero injection. Recombinant dystrophin was expressed in the hindlimb muscles, with the majority of animals having expression in two muscles of the injected hindlimb. The dystrophin-glycoprotein complex was restored in those muscle fibers expressing recombinant dystrophin. Analysis of the percentage of dystrophin-expressing muscle fibers with centrally placed nuclei revealed effective protection from cycles of degeneration and regeneration normally seen in muscle fibers lacking dystrophin. However, due to low levels of muscle gene transfer, further advances in the efficiency of adenoviral vector-mediated gene delivery would be required for clinical applications of in utero gene therapy for primary myopathies such as Duchenne muscular dystrophy.

Association of a single nucleotide polymorphism in the calpastatin gene with carcass and meat quality traits of beef cattle

Calpastatin (CAST) is a naturally occurring protein that inhibits the normal tenderization of meat as it ages postmortem. A SNP was identified in the CAST gene (a G to C substitution) and genotyped on crossbred commercially fed heifers (n = 163), steers (n = 226), and bulls (n = 61) from beef feedlots, and steers (n = 178) from a University of Guelph feeding trial. The association of the CAST SNP with carcass and meat quality traits was studied. Carcass traits included fat, lean, and bone yield; grade fat; LM area; and HCW. Meat quality traits included marbling grade; i.m. fat content of LM; tenderness evaluation of LM (Warner-Bratzler shear force) at 2, 7, 14, and 21 d of postmortem aging; and tenderness evaluation of semitendinosus muscle at 7 d of postmortem aging. The mixed model used in the analyses included fixed effects of CAST genotype, sex, slaughter group, and breed composition (linear covariate); sire was a random effect. For the analysis of shear force, i.m. fat content of LM was also included in the model as a linear covariate. Shear force measures were analyzed within days of postmortem aging and by repeated measures analysis. The CAST SNP allele C was more frequent (63%) in the crossbred population than allele G. The CAST SNP was associated with shear force across days of postmortem aging (P = 0.005); genotype CC yielded beef that was more tender than GG (-0.32 kg +/- 0.13), and CG had intermediate tenderness. The corresponding average allele substitution effect (G to C substitution) was also highly significant (-0.15 +/- 0.05 kg, P = 0.002). A lower percentage of unacceptably tough steaks (shear force > 5.7 kg) at 2 and 7 d postmortem was associated with an increasing number of C alleles (P < or = 0.05). At 7 d postmortem, the percentage of unacceptably tough steaks decreased by 24 and 35%, respectively, for animals carrying 1 and 2 copies of the C allele relative to animals with no C alleles. However, genotype CC had a greater fat yield (+1.44 +/- 0.56%; P = 0.037) than genotype GG, with a corresponding allele substitution effect of 0.67 +/- 0.27% (P = 0.015). Therefore, the CAST SNP allele C was associated with increased LM tenderness across days of postmortem aging and, importantly for the beef industry, had a significant reduction in the percentage of steaks rated unacceptably tough by consumers based on an assumed threshold level.

Photoscattering effect in supercontinuum-generating photonic crystal fiber

A photosensitivity different from that responsible for fiber grating inscription is found in a supercontinuum-generating photonic crystal fiber transmitting intense 818 nm femtosecond pulses. This photosensitivity progressively generates a waveguide at the entrance of the fiber to scatter light of specific wavelengths and is termed as the photoscattering effect. This effect is linked to the ~800 nm photosensitivity in the microlithography of bulk silica glass. While the effect somewhat limits fiber-optic supercontinuum applications, it can be beneficial to produce new photonic devices.

Sterol regulatory element binding transcription factor 1 expression and genetic polymorphism significantly affect intramuscular fat deposition in the longissimus muscle of Erhualian and Sutai pigs

Two experiments were performed to elucidate the role of sterol regulatory element binding transcription factor 1 (SREBF1) in i.m. fat (IMF) deposition in pigs. In Exp. 1, LM samples were removed from 4 male and 4 female Erhualian piglets at 3, 20, and 45 d of age, and SREBF1 mRNA expression level and IMF content were measured. Intramuscular fat content and expression of SREBF1 mRNA was greater (P < 0.05) in females than males at all 3 stages of age, providing initial evidence that the level of SREBF1 mRNA expression is related to IMF deposition in muscle of suckling pigs. Additionally, in Exp. 2 there was a positive correlation between the SREBF1 mRNA level and IMF content (r = 0.67, P < 0.01) in 100 Sutai finishing pigs, a synthetic line produced by crossing Erhualian and Duroc pigs. Single-strand conformation polymorphism (SSCP) analysis of the reverse transcription PCR products of the SREBF1 gene revealed 3 genotypes in Sutai pigs with frequencies of 50% for AA, 36% for AB, and 14% for BB, respectively. Both SREBF1 mRNA level and IMF content in muscle were greater (P < 0.05) in AB and BB animals than in AA animals, whereas no difference in backfat thickness was observed among the 3 genotypes. Sequencing analysis identified 2 SNP at T1006C and C1033T within the open reading frame of the SREBF1 gene (NM_214157). Although both are silent mutations, they affected the secondary structure of SREBF1 mRNA. These results suggest that SREBF1 might play an important role in regulation of muscle fat deposition during postnatal growth of pigs. The SNP identified in the SREBF1 gene suggest that it could be used as a genetic marker to improve IMF content in pigs.

Quantum Hall states near the charge-neutral Dirac point in graphene

We investigate the quantum Hall (QH) states near the charge-neutral Dirac point of a high mobility graphene sample in high magnetic fields. We find that the QH states at filling factors nu=+/-1 depend only on the perpendicular component of the field with respect to the graphene plane, indicating that they are not spin related. A nonlinear magnetic field dependence of the activation energy gap at filling factor nu=1 suggests a many-body origin. We therefore propose that the nu=0 and +/-1 states arise from the lifting of the spin and sublattice degeneracy of the n=0 Landau level, respectively.

Involvement of cellular death in TRAIL/DR5-dependent suppression induced by CD4(+)CD25(+) regulatory T cells

CD4(+)CD25(+) regulatory T cells (Treg) are potent immunosuppressive cells active in controlling normal pathological immune responses. The mechanisms of this suppression have been investigated under various conditions. In this report, tumor necrosis factor-related apoptosis inducing ligand (TRAIL)/death receptor 5 (DR5) was explored as one of the pivotal factors for the suppression and cytotoxicity induced by CD4(+)CD25(+) Treg. Cell death was involved in the suppression induced by activated CD4(+)CD25(+) Treg in vitro. The induction of CD4(+) T cell death was not mediated by the CD95/CD95L pathway, but rather depended upon the upregulation of TRAIL in the Treg. Blocking the TRAIL/DR5 pathway resulted in a significant reduction of the suppressive activity as well as the cytotoxic effects of Treg in vitro. Activated Treg displayed TRAIL-dependent cytotoxicity against CD4(+) T cells in vivo. The prolonged survival of allogeneic skin grafts induced by Treg was inhibited by DR5-blocking antibodies. Our findings suggest that the TRAIL/DR5 pathway is one of the mechanisms used by Treg to regulate immune responses both in vitro and in vivo.

Synergistic activity of PHY906 with capecitabine in pancreatic carcinoma

15116

Background: Preclinical data indicates that PHY906, a traditional Chinese botanical formulation, can reduce chemo-induced gastrointestinal toxicity while simultaneously enhancing therapeutic efficacy of a broad-spectrum of common anticancer agents. Methods: Male NCR athymic nude mice were transplanted with human PANC-1 cells. To determine the best dose of combinational regimen, two dose ranges of capecitabine, 60 and 180 mg/kg bid for 14 consecutive days with two dose ranges of PHY906, 300 and 900 mg/kg bid on days 1–4 and days 8–11 were administered by gavage in the first experiment. In the second experiment, PHY906 was fixed at 500 mg/kg bid at days 1–4 and 8–11 while dose of capecitabine was increased to 360 mg/kg bid for 14 consecutive days. A dose of 180 mg/kg of capecitabine was also included for comparison with previous experiments. In the third experiment, capecitabine at 360 mg/kg was selected to evaluate effect of different doses of PHY906 ranging from 100 mg/kg to 500 mg/kg on enhancement of antitumor activity of capecitabine. PHY906 was always administered 30 minutes prior to capecitabine. Tumor size, body weight and mortality were monitored daily and mice were sacrificed when tumor size reached 10% of body weight or on Day 21. Results: PHY906 showed enhancement of antitumor activity of capecitabine when both doses of PHY906 were co-administered with both doses of capecitabine in first experiment. In second experiment, increase of capecitabine dose from 180 mg/kg to 360 mg/kg significantly increased disparity of tumor growth rates between capecitabine alone and concomitant use of both PHY906 and capecitabine. Similar results were obtained in third experiment using a dose of 360 mg/kg of capecitabine and 500 mg/kg of PHY906 (p= 0.0018) as compared with control, capecitabine or PHY906 alone. Similar observation was found in mice bearing PAN-2 murine pancreatic cancer. Conclusions: The studies demonstrate that PHY906 potentiates antitumor activity of capecitabine in human pancreatic carcinoma xenograft mouse model in all capecitabine and PHY906 dosing regimens examined. Observed effect appeared to be dependant on dosage of capecitabine. Therefore, we are employing a dose intense weekly schedule for capecitabine with PHY906 in a phase I/II study in patients with advanced pancreatic cancer.

No significant financial relationships to disclose.

Randomized phase II study of biweekly gemcitabine (gem)-paclitaxel (pac), gem-carboplatin (carb) and gem-cisplatin (cis) as first-line treatments in metastatic breast cancer (MBC) after anthracycline failure

1099

Background: Biweekly gem-pac and gem-cis regimens have shown promising activity and safety in different tumor types. In MBC biweekly gem-pac is active and well tolerated. The aim of this multi-country study is to evaluate the efficacy and safety of gem in combination with pac, carb or cis on a biweekly schedule in patients (pts) with MBC. Methods: Major eligibility criteria included: tissue diagnosis of stage IV breast carcinoma; prior anthracycline therapy; ECOG performance status (PS) of 0 or 1; and written informed consent. Pts were randomized to receive gem 2500 mg/m2 in combination with pac 150 mg/m2 (Arm A), carb AUC 2.5 (Arm B) or cis 50 mg/m2 (Arm C) on day 1 of 2-week cycles. The primary endpoint was response rate, with safety a secondary endpoint. Results: This interim analysis was planned to occur when patient enrollment had reached 50% (75/150 pts), at which point there were 26 pts in Arm A, 25 in Arm B and 24 in Arm C, with 12 pts still on treatment. The baseline characteristics were similar in the three arms, including mean age (Arm A 50.2 yr, Arm B 46.1, Arm C 47.3); ECOG PS (PS 0: 50.0%, 64.0%, 54.2%); mean number of sites of tumor involvement (2.9, 2.6, 2.7); dominant type of metastasis (visceral: 73.1%, 80.0%, 79.2%); and disease-free interval (<24 mo: 53.8%, 60.0%, 41.7%). The mean number of cycles was 6.4, 6.0 and 5.8. There was a partial response in 5/26 efficacy qualified pts (19.2%), 5/25 pts (20.0%) and 2/23 pts (8.7%) in Arms A, B and C, respectively, stable disease in 10 pts (38.5%), 9 pts (36.0%) and 9 pts (39.1%), and progressive disease in 5 pts (19.2%), 6 pts (24.0%) and 6 pts (26.1%). There were no treatment-related deaths. Conclusions: The three regimens appear to show activity and have manageable toxicity when given on a biweekly schedule.

[Table: see text]

No significant financial relationships to disclose.

Randomized study comparing nab-paclitaxel with solvent-based paclitaxel in Chinese patients (pts) with metastatic breast cancer (MBC)

1038

Background: The results of a large clinical study comparing solvent-based paclitaxel 175 mg/m2 with 130-nM albumin-bound paclitaxel (nab-paclitaxel) 260 mg/m2 demonstrated that nab-paclitaxel had greater efficacy and a favorable safety profile in pts with MBC (Gradishar et al., JCO, 2005; 23:7794). The maximum tolerated dose of nab-paclitaxel was 300 mg/m2 infused over 30 minutes without premedication in Chinese pts with solid tumors (Teng et al., Ai Zheng, 2004;23:1431). The aim of this randomized study is to compare the response rates and to evaluate the safety of nab-paclitaxel with those of solvent-based paclitaxel in Chinese pts with MBC. Methods: In this open-label, multicenter study, 210 pts with MBC were assigned to either solvent-based paclitaxel 175 mg/m2 intravenously (IV) over 3 hours every 3 weeks (q3w) with standard premedication (steroids and antihistamines) or nab-paclitaxel 260 mg/m2 IV over 30 minutes q3w with no premedication for 1–6 cycles. The primary endpoints were the overall response rate (ORR, complete or partial response) and toxicity. Stable disease (SD) at =16 weeks was measured. All pts who received at least 1 dose of study drug were evaluable for study endpoints. Results: 210 pts (median age, 50 years; 70% postmenopausal) were enrolled from 29 June 2005 - 1 August 2006. Efficacy results are summarized in the Table . The common toxicities occurring at =20% were alopecia (78%), peripheral neuropathy (75%, 7% gr 3), neutropenia (65%), leucopenia (60%), myalgia (39%), arthralgia (23%), and nausea (21%) and were similar between groups (P = NS). Gr 3/4 neutropenia, measured on days 1 and 8, were similar between groups (p = 0.202). Conclusions: Compared to solvent- based paclitaxel, treatment with nab-paclitaxel was associated with a higher response rate and longer time to progression without increased toxicity. These comparative data in Chinese pts are almost identical to results previously reported in Caucasian pts (Gradishar et al, JCO, 2005).

[Table: see text]

[Table: see text]