bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermoregulation as a function of thermal quality in a northern population of painted turtles, Chrysemys picta
Authors: Edwards A.L. , Blouin-Demers G.
Published: May 2007

Body temperature affects nearly all processes of ectotherms. Reptiles do not generate sufficient body heat to regulate their body temperature internally and therefore use behavioural thermoregulation. We determined whether thermoregulatory effort varied among seasons in an environment where large temporal differences in environmental temperatures (Te) exist. We took 31 297 internal body temperature (Tb) measurements from 18 painted turtles ( Chrysemys picta (Schneider, 1783)) throughout their active season. We estimated Te with physical models and water temperatures. We measured the range of preferred body temperatures (Tset) in a thermal gradient. Tset was 21.3–25.0 °C. We used Tb, Te, and Tset to calculate standard thermoregulation indices (Ex and de – db). An Ex of 40.7% and a de – db of 2.4 °C indicated that painted turtles are moderate thermoregulators, despite inhabiting a high-cost environment. Effort to regulate Tb increased as the thermal quality of the habitat decreased. Thermoregulatory effort was higher when Tset could not be achieved. Painted turtles put more effort in thermoregulation in the early season than in the rest of the season. This within-species pattern follows the pattern seen among species. This study is the first to measure Tb internally and to apply standard thermoregulation indices to free-ranging turtles.
LAYERED CELLULAR AUTOMATA FOR PSEUDORANDOM NUMBER GENERATION
Authors: TAN SYN KIAT , GUAN SHENG-UEI
Published: May 2007

The proposed Layered Cellular Automata (L-LCA), which comprises of a main CA with L additional layers of memory registers, has simple local interconnections and high operating speed. The time-varying L-LCA transformation at each clock can be reduced to a single transformation in the set {Af | f = 1, 2, …, 2n -1} formed by the transformation matrix A of a maximum length Cellular Automata (CA), and the entire transformation sequence for a single period can be obtained. The analysis for the period characteristics of state sequences is simplified by analyzing representative transformation sequences determined by the phase difference between the initial states for each layer. The L-LCA model can be extended by adding more layers of memory or through the use of a larger main CA based on widely available maximum length CA. Several L-LCA (L = 1, 2, 3, 4) with 10- to 48-bit main CA are subjected to the DIEHARD test suite and better results are obtained over other CA designs reported in the literature. The experiments are repeated using the well-known nonlinear functions f30 and f45 in place of the linear function f204 used in the L-LCA. Linear complexity is significantly increased when f30 or f45 is used.
SUPERCONDUCTING QUANTUM POINT CONTACTS AND MAXWELL POTENTIAL
Authors: ALY ARAFA H. , DOUARI JAMILA
Published: May 2007

The quantization of the current in a superconducting quantum point contact is reviewed and the critical current is discussed at different temperatures depending on the carrier concentration as well by suggesting a constant potential in the semiconductor and then a Maxwell potential. When the Fermi wavelength is comparable with the constriction width we showed that the critical current has a step-like variation as a function of the constriction width and the carrier concentration.
TWO-PHOTON CORRELATION OF CHAOTIC LIGHT: A QUANTUM INTERFERENCE PHENOMENON
Authors: SHIH YANHUA , SCARCELLI GIULIANO , BERARDI VINCENZO
Published: May 2007

Two-photon correlation phenomena of chaotic light, including the historical Hanbury Brown and Twiss effect, are essentially the quantum effect of two-photon interference, instead of the classical statistical correlation between intensity fluctuations. To support our view, we analyze a "ghost" imaging experiment with chaotic light for which the classical understanding does not give a satisfactory interpretation. We also provide a two-photon optical picture of ghost imaging with chaotic light in terms of a two-photon phase-conjugate mirror, which suggests lensless imaging applications for radiations for which no effective lens is available.
NUMERICAL CHARACTERIZATION OF ATMOSPHERIC EFFECTS ON AN EARTH–SPACE QUANTUM COMMUNICATION CHANNEL
Authors: ANTONIETTI N. , MONDIN M. , BRIDA G. , GENOVESE M.
Published: May 2007

Quantum communication in free space is the next challenge of telecommunications. Since we want to determine the outcome of a quantum communication by means of single photons, we must understand how a single photon interacts with the atmosphere. In this brief article, some simulation results for realistic and generic atmospheric conditions are reported and discussed.
ENVIRONMENT-INDUCED DECOHERENCE IN NONCOMMUTATIVE QUANTUM MECHANICS
Authors: PRATA JOÃO NUNO , DIAS NUNO COSTA
Published: May 2007

We address the question of the appearance of ordinary quantum mechanics in the context of noncommutative quantum mechanics. We review our derivation of the noncommutative extension of the Hu–Paz–Zhang master equation for a Brownian particle linearly coupled to a bath of harmonic oscillators. As a new contribution, we consider the particular case of an Ohmic regime.
EFFECTS OF CAVITY-FIELD STATISTICS ON ATOMIC ENTANGLEMENT IN THE JAYNES–CUMMINGS MODEL
Authors: GHOSH BIPLAB , MAJUMDAR A. S. , NAYAK N.
Published: May 2007

We study the entanglement properties of a pair of two-level atoms going through a cavity one after another. The initial joint state of two successive atoms that enter the cavity is unentangled. Interactions mediated by the cavity photon field result in the final two-atom state being of a mixed entangled type. We consider the field statistics of the Fock state field, and the thermal field, respectively, inside the cavity. The entanglement of formation of the joint two-atom state is calculated for both these cases as a function of the Rabi angle gt. We present a comparitive study of two-atom entanglement for low and high mean photon number cases corresponding to the different fields statistics.
Development of Small Planar Cells (Ni-YSZ|YSZ|LSM) and Automatic Evaluation of Performance and Deterioration of SOFC
Authors: Yoshida Masayuki , Gomoto Takayuki , Eguchi Koichi
Published: May 2007

Small planar cells consisting of standard component materials (Ni-YSZ| YSZ |LSM) were produced for use with the BEL-SOFC(TM), an automatic SOFC testing system developed for the performance evaluation and deterioration tests for a single cell. The experimental standard data achieved high reliability and reproducibility. The certificated values were decided at 3-measurement temperatures of 800, 900, and 1000oC. A typical current density at 1000oC was 0.699{plus minus}0.1289 A/cm2 at the cell voltage of 0.7 V. For the investigation of the power generation from the cell, the simulated steam-reformate was used as fuel gas. The deterioration behavior at 800oC utilizing methane gas as fuel was also investigated and the mechanism was confirmed to include two steps of reforming and electrode performance reductions.
Fabrication and Characterization of Cermet Supported Cell with SDC Electrolyte
Authors: Zhang Xinge , Robertson Mark , Decès-Petit Cyrille , Qu Wei , Kyong-Bok Min , Tuck Adam , Xie Yongsong , Hui Rob , Kesler Olivera , Maric Radenka , Ghosh Dave
Published: May 2007

Cermet supported cells with Sm0.2Ce0.8O1.9 (SDC) electrolyte have been developed and scaled up to 55mm x 55mm at NRC-IFCI. A solid oxide fuel cell with SDC electrolyte of 10µm in thickness and Ni-SDC anode of 15µm in thickness on a 0.8mm thick Ni-YSZ cermet substrate was fabricated by tape casting, screen printing, and co-firing. A composite cathode, 75 wt% Sm0.5Sr0.5CoO3 (SSCo) + 25 wt% SDC, approximately 50µm in thickness, was printed on the co-fired half-cell, and sintered at 1000{degree sign}C. The cell with effective cathode area of 16 cm2 showed a high electrochemical performance at 600{degree sign}C, and peak power density of 0.9W cm-2 was obtained with hydrogen fuel.
Performance of Ln0.7Sr0.3Fe0.8Co0.2O3-δ (Ln = Pr, La, Gd) Cathodes for Intermediate-Temperature SOFCs Synthesized by a Novel Gel-Combustion Route
Authors: Ruiz de Larramendi Idoia , Lamas Diego G. , Fernández Alejandro , Ruiz de Larramendi José I. , Rojo Teófilo , Walsöe de Reca Noemí E.
Published: May 2007

Iron-cobalt-based perovskite materials with different A-site cations Ln0.7Sr0.3Fe0.8Co0.2O3-δ (Ln = La, Pr and Gd) were investigated for SOFC application as intermediate temperature cathodes. These samples were synthesized by a novel gel combustion process and characterized by X-ray diffraction. The diffraction patterns of the samples were indexed on the basis of an orthorhombic perovskite (GdFeO3-type) structure. The results of scanning electron microscopy showed that all of the powders have mean particle size less than 1 μm. The polarization resistance of the cathodes with samaria-doped ceria as electrolyte was studied by Electrochemical Impedance Spectroscopy. The best performance was obtained for the praseodymium compound, which exhibit an ASR of 0.30 Ω•cm2 at 700{degree sign}C, highly satisfactory value for technological applications, followed by the lanthanum one (0.42 Ω•cm2 at 700{degree sign} C). The ASR values for the gadolinium compound were higher than the others (1.05 Ω•cm2 at 700{degree sign}C).
Differences in regulation of type I collagen synthesis in primary and passaged hepatic stellate cell cultures: the role of α5β1-integrin
Authors: Dodig Milan , Ogunwale Ben , Dasarathy Srinivasan , Li Min , Wang Bingcheng , McCullough Arthur J.
Published: May 2007

Hepatic stellate cells (HSC) differ in their phenotype depending on the initiation and progression of their activation. Our hypothesis was that different mechanisms govern type I collagen synthesis depending on stage of HSC activation. We investigated the role of α5β1-integrin as a regulator of type I collagen gene COL1A1 expression in primary and passaged HSC cultures using transgenic mouse containing type I collagen gene COL1A1 promoter linked to the chloramphenicol acetyltransferase (CAT) reporter gene. The α5β1protein levels increased during the activation and were highest in day 6 primary cultures but decreased in passaged HSC. CAT activity, reflecting COL1A1 expression, was upregulated by α5β1-integrin. Inhibition of α5β1-integrin by echistatin and blocking antibody resulted in reduced transgene activity only in early primary cultures (compared with the control, 53.3 ± 12% echistatin and 58.8 ± 7% blocking antibody, respectively, P < 0.05). Treatment of passaged HSC with either echistatin or blocking antibody had no effect. Fibronectin, an α5β1-integrin ligand, increased transgene activity in primary (210 ± 33%, P < 0.05) but not in passaged HSC cultures (119 ± 8%). This α5β1-integrin effect appears to be at least in part mediated by CCAAT enhancer binding protein-β (C/EBPβ), because fibronectin increased and α5-gene silencing by small interfering RNA decreased C/EBPβ levels. In addition, C/EBPβ knockout mice showed reduced type I collagen synthesis compared with wild-type littermates. Therefore α5β1-integrin is an important regulator of type I collagen production in early primary HSC cultures but appears to have no direct role once the HSC are fully activated.
Pioglitazone reverses insulin resistance and impaired CCK-stimulated pancreatic secretion in eNOS(−/−) mice: therapy for exocrine pancreatic disorders?
Authors: Reddy Raju C. , Hao Yibai , Lee Sae-Hong , Gangireddy Srinivasa R. , Owyang Chung , DiMagno Matthew J.
Published: May 2007

In mice, eNOS (endothelial nitric oxide synthase) maintains in vivo pancreatic secretory responses to carbachol or cholecystokinin octapeptide (CCK-8), maintains insulin sensitivity, and modulates pancreatic microvascular blood flow (PMBF). eNOS(−/−) mice are insulin resistant, and their exocrine pancreatic secretion is impaired. We hypothesized that the reduced exocrine pancreatic secretion in eNOS(−/−) mice is due to insulin resistance or impaired PMBF. To test this hypothesis, we gave eNOS(−/−) and wild-type (WT) mice pioglitazone (20 or 50 mg·kg−1·day−1), an insulin-sensitizing peroxisome proliferator-activated receptor-γ (PPAR-γ) activator, and measured pancreatic protein secretion evoked by CCK-8 (160 pmol·kg−1·h−1, a maximal stimulus). We also measured insulin resistance, serum glucose, C-peptide, insulin, pancreatic RNA digestive enzyme expression, and PMBF (microsphere technique). In WT mice, pioglitazone did not increase CCK-8-stimulated protein output over baseline. In eNOS(−/−) mice, however, pioglitazone substantially increased the low CCK-8-stimulated protein output that is characteristic of these mutant mice ( P < 0.005). Pioglitazone abolished the CCK-8-evoked hyperinsulinemia ( P < 0.005) and increased insulin sensitivity of eNOS(−/−) mice ( P < 0.05), the latter based on hyperinsulinemic-euglycemic clamp studies. Pioglitazone had no effect on PMBF or pancreas mRNA expression of insulin or digestive enzymes. We conclude that in hyperinsulinemic eNOS(−/−) mice, a nonobese model of insulin resistance relevant to diabetes mellitus and possibly chronic pancreatitis, reduced pancreatic secretion is caused, at least in part, by insulin resistance. Insulin-sensitizing PPAR-γ agonists such as pioglitazone may thus simultaneously correct endocrine and exocrine pancreatic disorders.
Responsiveness of the isolated airway during simulated deep inspirations: effect of airway smooth muscle stiffness and strain
Authors: Noble Peter B. , McFawn Peter K. , Mitchell Howard W.
Published: May 2007

In vivo, breathing movements, including tidal and deep inspirations (DIs), exert a number of beneficial effects on respiratory system responsiveness in healthy humans that are diminished or lost in asthma, possibly as a result of reduced distension (strain) of airway smooth muscle (ASM). We used bronchial segments from pigs to assess airway responsiveness under static conditions and during simulated tidal volume oscillations with and without DI and to determine the roles of airway stiffness and ASM strain on responsiveness. To simulate airway dilations during breathing, we cycled the luminal volume of liquid-filled segments. Volume oscillations (15 cycles/min) were set so that, in relaxed airways, they produced a transmural pressure increase of ∼5–10 cmH2O for tidal maneuvers and ∼5–30 cmH2O for DIs. ACh dose-response curves (10−7–3 × 10−3 M) were constructed under static and dynamic conditions, and maximal response and sensitivity were determined. Airway stiffness was measured from tidal trough-to-peak pressure and volume cycles. ASM strain produced by DI was estimated from luminal volume, airway length, and inner wall area. DIs produced substantial (∼40–50%) dilation, reflected by a decrease in maximal response ( P < 0.001) and sensitivity ( P < 0.05). However, the magnitude of bronchodilation decreased significantly in proportion to airway stiffening caused by contractile activation and an associated reduction in ASM strain. Tidal oscillations, in comparison, had little effect on responsiveness. We conclude that DI regulates airway responsiveness at the airway level, but this is limited by airway stiffness due to reduced ASM strain.
Expression of p16Ink4a Compensates for p18Ink4c Loss in Cyclin-Dependent Kinase 4/6–Dependent Tumors and Tissues
Authors: Ramsey Matthew R. , Krishnamurthy Janakiraman , Pei Xin-Hai , Torrice Chad , Lin Weili , Carrasco Daniel R. , Ligon Keith L. , Xiong Yue , Sharpless Norman E.
Published: May 2007

Cell cycle progression from G1 to S phase depends on phosphorylation of pRb by complexes containing a cyclin (D type or E type) and cyclin-dependent kinase (e.g., cdk2, cdk4, or cdk6). Ink4 proteins function to oppose the action of cdk4/6-cyclin D complexes by inhibiting cdk4/6. We employed genetic and pharmacologic approaches to study the interplay among Ink4 proteins and cdk4/6 activity in vivo. Mouse embryo fibroblasts (MEF) lacking p16Ink4a and p18Ink4c showed similar growth kinetics as wild-type MEFs despite increased cdk4 activity. In vivo, germline deficiency of p16Ink4a and p18Ink4c resulted in increased proliferation in the intermediate pituitary and pancreatic islets of adult mice, and survival of p16Ink4a−/−;p18Ink4c−/− mice was significantly reduced due to aggressive pituitary tumors. Compensation among the Ink4 proteins was observed both in vivo in p18Ink4c−/− mice and in MEFs from p16Ink4a−/−, p18Ink4c−/−, or p16Ink4a−/−;p18Ink4c−/− mice. Treatment with PD 0332991, a specific cdk4/6 kinase inhibitor, abrogated proliferation in those compartments where Ink4 deficiency was associated with enhanced proliferation (i.e., islets, pituitary, and B lymphocytes) but had no effect on proliferation in other tissues such as the small bowel. These data suggest that p16Ink4a and p18Ink4c coordinately regulate the in vivo catalytic activity of cdk4/6 in specific compartments of adult mice. [Cancer Res 2007;67(10):4732–41]
Molecular Basis of the Synergistic Antiangiogenic Activity of Bevacizumab and Mithramycin A
Authors: Jia Zhiliang , Zhang Jun , Wei Daoyan , Wang Liwei , Yuan Ping , Le Xiangdong , Li Qiang , Yao James , Xie Keping
Published: May 2007

The impact of antiangiogenic therapy on the Sp1/vascular endothelial growth factor (VEGF) pathway and that of alteration of Sp1 signaling on the efficacy of antiangiogenic therapy is unclear, yet understanding their interactions has significant clinical implications. Treatment with bevacizumab, a neutralizing antibody against VEGF, suppressed human pancreatic cancer growth in nude mice. Gene expression analyses revealed that this treatment substantially up-regulated the expression of Sp1 and its downstream target genes, including VEGF and epidermal growth factor receptor, in tumor tissues, whereas it did not have this effect on pancreatic cancer cells in culture. Treatment with mithramycin A, an Sp1 inhibitor, suppressed the expression of Sp1 and its downstream target genes in both cell culture and tumors growing in nude mice. Combined treatment with bevacizumab and mithramycin A produced synergistic tumor suppression, which was consistent with suppression of the expression of Sp1 and its downstream target genes. Thus, treatment with bevacizumab may block VEGF function but activate the pathway of its expression via positive feedback. Given the fact that Sp1 is an important regulator of the expression of multiple angiogenic factors, bevacizumab-initiated up-regulation of Sp1 and subsequent overexpression of its downstream target genes may profoundly affect the potential angiogenic phenotype and effectiveness of antiangiogenic strategies for human pancreatic cancer. Therefore, this study is the first to show the significance and clinical implications of alteration of Sp1 signaling in antiangiogenic therapy for pancreatic cancer and other cancers. [Cancer Res 2007;67(10):4878–85]
Differential Effects of Targeted Disruption of Thiopurine Methyltransferase on Mercaptopurine and Thioguanine Pharmacodynamics
Authors: Hartford Christine , Vasquez Erick , Schwab Matthias , Edick Mathew J. , Rehg Jerold E. , Grosveld Gerard , Pui Ching-Hon , Evans William E. , Relling Mary V.
Published: May 2007

The recessive deficiency in thiopurine methyltransferase (TPMT), caused by germ-line polymorphisms in TPMT, can cause severe toxicity after mercaptopurine. However, the significance of heterozygosity and the effect of the polymorphism on thioguanine or in the absence of thiopurines is not known. To address these issues, we created a murine knockout of Tpmt. Pharmacokinetic and pharmacodynamic studies of mercaptopurine and thioguanine were done in Tpmt−/−, Tpmt+/−, and Tpmt+/+ mice and variables were compared among genotypes. Methylated thiopurine and thioguanine nucleotide metabolites differed among genotypes after treatment with mercaptopurine (P < 0.0001 and P = 0.044, respectively) and thioguanine (P = 0.011 and P = 0.002, respectively). Differences in toxicity among genotypes were more pronounced following treatment with 10 daily doses of mercaptopurine at 100 mg/kg/d (0%, 68%, and 100% 50-day survival; P = 0.0003) than with thioguanine at 5 mg/kg/d (0%, 33%, and 50% 15-day survival; P = 0.07) in the Tpmt−/−, Tpmt+/−, and Tpmt+/+ genotypes, respectively. Myelosuppression and weight loss exhibited a haploinsufficient phenotype after mercaptopurine, whereas haploinsufficiency was less prominent with thioguanine. In the absence of drug challenge, there was no apparent phenotype. The murine model recapitulates many clinical features of the human polymorphism; indicates that mercaptopurine is more affected by the TPMT polymorphism than thioguanine; and provides a preclinical system for establishing safer regimens of genetically influenced antileukemic drug therapy. [Cancer Res 2007;67(10):4965–72]
The Combined Effects of Xeroderma Pigmentosum C Deficiency and Mutagens on Mutation Rates in the Mouse Germ Line
Authors: Miccoli Laurent , Burr Karen L-A. , Hickenbotham Peter , Friedberg Errol C. , Angulo Jaime F. , Dubrova Yuri E.
Published: May 2007

Spontaneous and induced mutation rates at two expanded simple tandem repeat (ESTR) loci were studied in the germ line of xeroderma pigmentosum group C (Xpc) knockout mice defective in global genome nucleotide excision repair. Spontaneous and radiation-induced mutation rates in homozygous Xpc−/− males were significantly higher than those in isogenic wild-type (Xpc+/+) and heterozygous (Xpc+/−) mice. In contrast, exposure to the monofunctional alkylating agent ethylnitrosourea resulted in similar increases in ESTR mutation rates across all genotypes. ESTR mutation spectra in the germ line of Xpc−/−, Xpc+/− and Xpc+/+ did not differ. Considering these data and the results of other publications, we propose that the Xpc-deficient mice possess a mutator phenotype in their germ line and somatic tissues that may significantly enhance carcinogenesis across multiple tissues. [Cancer Res 2007;67(10):4695–9]
Chemotherapy-Induced Thrombocytopenia Derives from the Selective Death of Megakaryocyte Progenitors and Can Be Rescued by Stem Cell Factor
Authors: Zeuner Ann , Signore Michele , Martinetti Daniela , Bartucci Monica , Peschle Cesare , De Maria Ruggero
Published: May 2007

Thrombocytopenia is a common side effect of chemotherapy, responsible for increased risk of bleeding and delay of treatment schedules in cancer patients. It is currently unknown how chemotherapeutic agents affect platelet production and whether the platelet precursors megakaryocytes represent a direct target of cytotoxic drugs. We investigated the effects of chemotherapeutic agents on primary megakaryocytes by using a culture system that recapitulates in vitro human megakaryopoiesis and found that cytotoxic drugs predominantly destroyed megakaryocytic progenitors at early stages of differentiation. Immature megakaryocytes could be protected from chemotherapeutic agents by the cytokine stem cell factor (SCF), which binds the c-kit receptor expressed on hematopoietic stem and progenitor cells. In chemotherapy-treated megakaryocytes, SCF activated Akt, neutralized the mitochondrial apoptotic machinery, and inhibited caspase activity. Interfering with Akt activation abrogated the antiapoptotic effects of SCF, whereas exogenous expression of constitutively active Akt inhibited drug-induced apoptosis of primary megakaryocytes, indicating the Akt pathway as primarily responsible for SCF-mediated protection of megakaryocyte progenitors. These results indicate apoptosis of megakaryocyte progenitors as a major cause of chemotherapy-induced thrombocytopenia and suggest that SCF may be used to prevent platelet loss in cancer patients with c-kit–negative tumors. [Cancer Res 2007;67(10):4767–4773]
Transcriptional Control of the Human High Mobility Group A1 Gene: Basal and Oncogenic Ras-Regulated Expression
Authors: Cleynen Isabelle , Huysmans Christel , Sasazuki Takehiko , Shirasawa Senji , Van de Ven Wim , Peeters Kristel
Published: May 2007

Several studies have already shown that the high mobility group A1 (HMGA1) gene is up-regulated in most common types of cancer and immortalized tissue culture cell lines. HMGA1 expression is also much higher during embryonic development than in adult life. The elevated expression of HMGA1 in cancer thus likely occurs through oncofetal transcriptional mechanisms, which to date have not been well characterized. In the present study, we have cloned and functionally analyzed the TATA-less 5′-flanking regulatory region of human HMGA1. We identified two proximal regulatory regions that are important for basal transcription and in which specificity protein 1 (SP1) and activator protein 1 (AP1) transcription factors seem to be the regulating elements. In addition, we showed that the HMGA1 promoter is strongly inducible by oncogenic Ras, via a distal regulatory region. An AP1 site and three SP1-like sites are responsible for this inducible activity. An even more convincing finding for a role of oncogenic Ras in the regulation of HMGA1 in cancers is the discovery that HMGA1 up-regulation in the HCT116 colon cancer cell line is abolished when the mutated Ras allele is removed from these cells. Our data constitute the first extensive study of the regulation of basal and Ras-induced human HMGA1 gene expression and suggest that the elevated expression of HMGA1 in cancer cells requires, among others, a complex cooperation between SP1 family members and AP1 factors by the activation of Ras GTPase signaling. [Cancer Res 2007;67(10):4620–9]
Armed Antibodies Targeting the Mucin Repeats of the Ovarian Cancer Antigen, MUC16, Are Highly Efficacious in Animal Tumor Models
Authors: Chen Youjun , Clark Suzanna , Wong Terence , Chen Yongmei , Chen Yvonne , Dennis Mark S. , Luis Elizabeth , Zhong Fiona , Bheddah Sheila , Koeppen Hartmut , Gogineni Alvin , Ross Sarajane , Polakis Paul , Mallet William
Published: May 2007

MUC16 is a well-validated cell surface marker for serous adenocarcinomas of the ovary and other gynecologic malignancies that is distinguished by highly repetitive sequences (“mucin repeats”) in the extracellular domain (ECD). We produced and compared two monoclonal antibodies: one (11D10) recognizing a unique, nonrepeating epitope in the ECD and another (3A5) that recognizes the repeats and binds multiple sites on each MUC16 protein. 3A5 conjugated to cytotoxic drugs exhibited superior toxicity against tumor cells in vitro and in tumor xenograft models compared with antibody-drug conjugates of 11D10. Importantly, drug conjugates of 3A5 were well tolerated in primates at levels in excess of therapeutic doses. Additionally, the presence of circulating CA125 in a rat model did not exacerbate the toxicity of 3A5 drug conjugates. We conclude that targeting the repeat MUC16 domains, thereby increasing cell-associated levels of drug-conjugated antibody, provides superior efficacy in vitro and in vivo without compromising safety. [Cancer Res 2007;67(10):4924–32]
Mutations in BRAF and KRAS Converge on Activation of the Mitogen-Activated Protein Kinase Pathway in Lung Cancer Mouse Models
Authors: Ji Hongbin , Wang Zhenxiong , Perera Samanthi A. , Li Danan , Liang Mei-Chih , Zaghlul Sara , McNamara Kate , Chen Liang , Albert Mitchell , Sun Yanping , Al-Hashem Ruqayyah , Chirieac Lucian R. , Padera Robert , Bronson Roderick T. , Thomas Roman K. , Garraway Levi A. , Jänne Pasi A. , Johnson Bruce E. , Chin Lynda , Wong Kwok-Kin
Published: May 2007

Mutations in the BRAF and KRAS genes occur in ∼1% to 2% and 20% to 30% of non–small-cell lung cancer patients, respectively, suggesting that the mitogen-activated protein kinase (MAPK) pathway is preferentially activated in lung cancers. Here, we show that lung-specific expression of the BRAF V600E mutant induces the activation of extracellular signal–regulated kinase (ERK)-1/2 (MAPK) pathway and the development of lung adenocarcinoma with bronchioloalveolar carcinoma features in vivo. Deinduction of transgene expression led to dramatic tumor regression, paralleled by dramatic dephosphorylation of ERK1/2, implying a dependency of BRAF-mutant lung tumors on the MAPK pathway. Accordingly, in vivo pharmacologic inhibition of MAPK/ERK kinase (MEK; MAPKK) using a specific MEK inhibitor, CI-1040, induced tumor regression associated with inhibition of cell proliferation and induction of apoptosis in these de novo lung tumors. CI-1040 treatment also led to dramatic tumor shrinkage in murine lung tumors driven by a mutant KRas allele. Thus, somatic mutations in different signaling intermediates of the same pathway induce exquisite dependency on a shared downstream effector. These results unveil a potential common vulnerability of BRAF and KRas mutant lung tumors that potentially affects rational deployment of MEK targeted therapies to non–small-cell lung cancer patients. [Cancer Res 2007;67(10):4933–9]
Hint1 Inhibits Growth and Activator Protein-1 Activity in Human Colon Cancer Cells
Authors: Wang Lin , Zhang Yujing , Li Haiyang , Xu Zhiheng , Santella Regina M. , Weinstein I. Bernard
Published: May 2007

There is accumulating evidence that histidine triad (HIT) nucleotide-binding protein 1 (HINT1), a member of the evolutionary highly conserved HIT protein super family, is a novel tumor suppressor. However, the mechanism of action of HINT1 with respect to tumor suppression is not known. In the present study, we found that a series of human colon cancer cell lines displayed various levels of expression of HINT1, with a very low level in SW480 cells. This cell line also displayed partial methylation of the promoter region of the Hint1 gene, and treatment of these cells with 5-azadeoxycitidine increased expression of Hint1 mRNA and protein. Therefore, the decreased expression of HINT1 in SW480 cells seems to be due to epigenetic silencing. Increased expression of HINT1 in these cells, using a retrovirus vector (pLNCX2) that encodes either wild-type (WT) Hint1 or a point mutant (His112/Asn112) of Hint1, inhibited the proliferation of SW480 cells. Because of the important role of the activator protein-1 (AP-1) transcription factor in cancer cells, we examined possible effects of HINT1 on AP-1 transcription factor activity in SW480 cells transfected with an AP-1-luciferase reporter. We found that cotransfection with a pHA-Hint1 plasmid DNA significantly inhibited this activity. Studies with inhibitors indicated that AP-1 activity in SW480 cells requires the activity of c-Jun NH2-terminal kinase (JNK) 2 and not JNK1. Cotransfection with the Hint1 plasmid DNA also inhibited AP-1-luciferase reporter activity in WT mouse embryo fibroblast (MEF) studies, and studies with JNK1 deleted or JNK2 deleted MEFs confirmed the essential role for JNK2, but not JNK1, in mediating AP-1 activity. Recent studies indicate that the protein plenty of SH3 (POSH) provides a scaffold that enhances JNK activity. We found that cotransfection of a plasmid DNA encoding POSH stimulated the phosphorylation of c-Jun and also AP-1 reporter activity, and cotransfection with Hint1 inhibited both of these activities. Furthermore, coimmunoprecipitation studies provided evidence that HINT1 forms an in vivo complex with POSH and JNK. These results suggest that HINT1 inhibits AP-1 activity by binding to a POSH-JNK2 complex, thus inhibiting the phosphorylation of c-Jun. This effect could contribute to the tumor suppressor activity of HINT1. [Cancer Res 2007;67(10):4700–8]
Regulation of Helicobacter pylori cagA Expression in Response to Salt
Authors: Loh John T. , Torres Victor J. , Cover Timothy L.
Published: May 2007

Helicobacter pylori infection and a high dietary salt intake are risk factors for the development of gastric adenocarcinoma. In this study, we tested the hypothesis that high salt concentrations might alter gene expression in H. pylori. Transcriptional profiling experiments indicated that the expression of multiple H. pylori genes, including cagA, was regulated in response to the concentrations of sodium chloride present in the bacterial culture medium. Increased expression of cagA in response to high salt conditions was confirmed by the use of transcriptional reporter strains and by immunoblotting. H. pylori CagA is translocated into gastric epithelial cells via a type IV secretion pathway, and on entry into target cells, CagA undergoes tyrosine phosphorylation and causes multiple cellular alterations. Coculture of gastric epithelial cells with H. pylori grown under high salt conditions resulted in increased tyrosine-phosphorylated CagA and increased secretion of interleukin-8 by the epithelial cells compared with coculture of the cells with H. pylori grown under low salt conditions. Up-regulation of H. pylori cagA expression in response to high salt concentrations may be a factor that contributes to the development of gastric adenocarcinoma. [Cancer Res 2007;67(10):4709–15]
Tumor Suppressor Activity of CCAAT/Enhancer Binding Protein α Is Epigenetically Down-regulated in Head and Neck Squamous Cell Carcinoma
Authors: Bennett Kristi L. , Hackanson Björn , Smith Laura T. , Morrison Carl D. , Lang James C. , Schuller David E. , Weber Frank , Eng Charis , Plass Christoph
Published: May 2007

Tumor suppressor CCAAT enhancer binding protein α (C/EBPα) is a transcription factor involved in cell cycle control and cellular differentiation. In a recent study, microarray expression profiling on head and neck squamous cell carcinoma (HNSCC) samples identified significant C/EBPα down-regulation, correlating with poor prognosis. However, the mechanisms of C/EBPα down-regulation remained elusive. C/EBPα has been previously found to provide an antiproliferative role in lung cancer, and our laboratory showed that its down-regulation involves epigenetic mechanisms. This prompted us to investigate the involvement of epigenetics in down-regulating C/EBPα in HNSCC. Here, we show that C/EBPα is down-regulated in HNSCC by loss of heterozygosity and DNA methylation, but not by gene mutation. We found a consistently methylated upstream regulatory region (−1,399 bp to −1,253 bp in relation to the transcription start site) in 68% of the HNSCC tumor samples, and DNA demethylation using 5-aza-2′-deoxycytidine treatment was able to significantly restore C/EBPα mRNA expression in the HNSCC cell lines we tested. In addition, C/EBPα overexpression in a HNSCC cell line (SCC22B) revealed its ability to provide tumor suppressor activity in HNSCC in vitro and in vivo. In conclusion, we showed for the first time not only that C/EBPα has tumor suppressor activity in HNSCC, but also that it is down-regulated by DNA promoter methylation. [Cancer Res 2007;67(10):4657–64]
Suicide Gene Therapy of Human Colon Carcinoma Xenografts Using an Armed Oncolytic Adenovirus Expressing Carboxypeptidase G2
Authors: Schepelmann Silke , Ogilvie Lesley M. , Hedley Douglas , Friedlos Frank , Martin Janet , Scanlon Ian , Chen Ping , Marais Richard , Springer Caroline J.
Published: May 2007

We have designed a targeted systemic suicide gene therapy that combines the advantages of tumor-selective gene expression, using the human telomerase promoter (hTERT), with the beneficial effects of an oncolytic adenovirus to deliver the gene for the prodrug-activating enzyme carboxypeptidase G2 (CPG2) to tumors. Following delivery of the vector (AdV.hTERT-CPG2) and expression of CPG2 in cancer cells, the prodrug ZD2767P was administered for conversion by CPG2 to a cytotoxic drug. This system is sometimes termed gene-directed enzyme prodrug therapy (GDEPT). Here, we have shown that it is applicable to 10 human colorectal carcinoma cell lines with a direct correlation between viral toxicity and CPG2 production. SW620 xenografts were selected for analysis and were significantly reduced or eradicated after a single administration of AdV.hTERT-CPG2 followed by a prodrug course. The oncolytic effect of adenovirus alone did not result in DNA cross-links or apoptosis, whereas DNA cross-links and apoptosis occurred following prodrug administration, showing the combined beneficial effects of the GDEPT system. The apoptotic regions extended beyond the areas of CPG2 expression in the tumors, indicative of significant bystander effects in vivo. Higher concentrations of vector particles and CPG2 were found in the AdV.hTERT-CPG2 plus prodrug–treated tumors compared with the virus alone, showing an unexpected beneficial and cooperative effect between the vector and GDEPT. This is the first time that a tumor-selective GDEPT vector has been shown to be effective in colorectal carcinoma and that apoptosis and significant bystander effects have been identified as the mechanisms of cytotoxicity within the tumor. [Cancer Res 2007;67(10):4949–55]
Hu/Mu ProtIn Oligonucleotide Microarray: Dual-Species Array for Profiling Protease and Protease Inhibitor Gene Expression in Tumors and Their Microenvironment
Authors: Schwartz Donald R. , Moin Kamiar , Yao Bin , Matrisian Lynn M. , Coussens Lisa M. , Bugge Thomas H. , Fingleton Barbara , Acuff Heath B. , Sinnamon Mark , Nassar Hind , Platts Adrian E. , Krawetz Stephen A. , Linebaugh Bruce E. , Sloane Bonnie F.
Published: May 2007

Proteolysis is a critical regulatory mechanism for a wide variety of physiologic and pathologic processes. To assist in the identification of proteases, their endogenous inhibitors, and proteins that interact with proteases or proteolytic pathways in biological tissues, a dual-species oligonucleotide microarray has been developed in conjunction with Affymetrix. The Hu/Mu ProtIn microarray contains 516 and 456 probe sets that survey human and mouse genes of interest (proteases, protease inhibitors, or interactors), respectively. To investigate the performance of the array, gene expression profiles were analyzed in pure mouse and human samples (reference RNA; normal and tumor cell lines/tissues) and orthotopically implanted xenografts of human A549 lung and MDA-MB-231 breast carcinomas. Relative gene expression and “present-call” P values were determined for each probe set using dChip and MAS5 software, respectively. Despite the high level of sequence identity of mouse and human protease/inhibitor orthologues and the theoretical potential for cross-hybridization of some of the probes, >95% of the “present calls” (P < 0.01) resulted from same-species hybridizations (e.g., human transcripts to human probe sets). To further assess the performance of the microarray, differential gene expression and false discovery rate analyses were carried out on human or mouse sample groups, and data processing methods to optimize performance of the mouse and human probe sets were identified. The Hu/Mu ProtIn microarray is a valuable discovery tool for the identification of components of human and murine proteolytic pathways in health and disease and has particular utility in the determination of cellular origins of proteases and protease inhibitors in xenograft models of human cancer. (Mol Cancer Res 2007;5(5):443–54)
Gα12/13 Basally Regulates p53 through Mdm4 Expression
Authors: Kim Mi-Sung , Lee Sang Min , Kim Won Dong , Ki Sung Hwan , Moon Aree , Lee Chang Ho , Kim Sang Geon
Published: May 2007

Gα12/13, which belongs to the Gα12 family, participates in the regulation of diverse physiologic processes. In view of the control of Gα12/13 in cell proliferation, this study investigated the role of Gα12/13 in the regulation of p53 and mdm4. Immunoblotting and immunocytochemistry revealed that p53 was expressed in control embryonic fibroblasts and was largely localized in the nuclei. Gα12 deficiency decreased p53 levels and its DNA binding activity, accompanying p21 repression with Bcl2 induction, whereas Gα13 deficiency exerted weak effects. Gα12 or Gα13 deficiency did not change p53 mRNA expression. ERK1/2 or Akt was not responsible for p53 repression due to Gα12 deficiency. Mdm4, a p53-stabilizing protein, was repressed by Gα12 deficiency and to a lesser extent by Gα13 deficiency, whereas mdm2, PTEN, β-catenin, ATM, and Chk2 were unaffected. p53 accumulation by proteasomal inhibition during Gα12 deficiency suggested the role of Gα12 in p53 stabilization. Constitutively active Gα12 (Gα12QL) or Gα13 (Gα13QL) promoted p53 accumulation with mdm4 induction in MCF10A cells. p53 accumulation by mdm4 overexpression, but no mdm4 induction by p53 overexpression, and small interfering RNA knockdown verified the regulatory role of mdm4 for p53 downstream of Gα12/13. In control or Gα12/Gα13-deficient cells, genotoxic stress led to p53 accumulation. At concentrations increasing the flow cytometric pre-G1 phase, doxorubicin or etoposide treatment caused serine phosphorylations in Gα12−/− or Gα12/13−/− cells, but did not induce mdm4. Gα12/13QL transfection failed to phosphorylate p53 at serines. Our results indicate that Gα12/13 regulate basal p53 levels via mdm4, which constitutes a cell signaling pathway distinct from p53 phosphorylations elicited by genotoxic stress. (Mol Cancer Res 2007;5(5):473–84)
Incorporating Genotyping Uncertainty in Haplotype Frequency Estimation in Pedigree Studies
Authors: Zhu Wen-Sheng , Fung Wing-Kam , Guo Jianhua
Published: May 2007

Aims: Haplotype frequency estimation is indispensable in studies of human genetics based on haplotypes since studies based on haplotypes are likely to yield more information than those based on single SNP marker. However, most existing algorithms estimate haplotype frequencies under the assumption that all of the genotype data sets are correct. To date, nearly all large genotype data sets have errors, and studies have demonstrated that even a small quantity of genotyping errors can have enormous impact on haplotype frequency estimation. Methods: Although the GenoSpectrum (GS)-EM algorithm which estimates haplotype frequencies incorporating genotyping uncertainty has been presented recently [1], it can only be suitable for independent individuals rather than dependent pedigree data. In this paper, we describe a new EM algorithm, called GS-PEM, that calculates maximum likelihood estimates (MLEs) of haplotype frequencies based on all possible multilocus genotypes (GenoSpectrum) of each member of the pedigrees through making use of the dependence information of relatives. Results and Conclusion: We evaluate the performance of the GS-PEM by simulation studies and find that our GS-PEM can reduce the impact induced by the genotyping errors in haplotype frequency estimation.
Rituximab as a Treatment Option for Refractory Endogenous Anterior Uveitis
Authors: Tappeiner C. , Heinz C. , Specker C. , Heiligenhaus A.
Published: May 2007

Background: To report on anti-CD20 antibody therapy in a patient with uveitis refractive to immunosuppression therapy. Methods: Case report with ophthalmoscopic, optical coherence tomography and fluorescein-angiographic findings. Results: A 49-year-old woman was suffering from bilateral, noninfectious chronic anterior uveitis refractive to corticosteroids and immunosuppressive drugs. Bilateral visual acuity was 20/100 due to cataract and cystoid macular edema (CME). After treatment with rituximab, vision and CME improved, and uveitis was stable until the final visit (follow-up at 12 months). Conclusion: The case report suggests that rituximab may be helpful for selected patients with chronic anterior uveitis refractive to corticosteroids and immunosuppressive medication.
Effect of Ventralis Intermedius Thalamotomy on the Area in the Sensorimotor Cortex Activated by Passive Hand Movements: fMR Imaging Study
Authors: Miyagishima Takaaki , Takahashi Akio , Kikuchi Senichiro , Watanabe Katsushige , Hirato Masafumi , Saito Nobuhito , Yoshimoto Yuhei
Published: May 2007

Stereotactic ventralis intermedius (Vim) thalamotomy is effective for essential tremor (ET) of the limb, but the effect on the activity of the sensorimotor cortex is still unclear. The functional changes in this cortical area of patients with ET after Vim thalamotomy were investigated using functional magnetic resonance (fMR) imaging. Six patients underwent Vim thalamotomy for medically intractable ET, predominantly in the right hand. 1.5-tesla fMR imaging was performed using the blood oxygenation level-dependent sequence, before and after Vim thalamotomy, during passive movements with right wrist flexion and extension. Before and after images were analyzed using SPM99 software. Activation in the sensorimotor cortex and supplementary motor area evoked by wrist passive movement was observed both before and after surgery. Group analysis of changes in the blood oxygenation level-dependent response revealed a significantly smaller activated area postoperatively. Activation at the fundus of the central sulcus was characteristically decreased. All patients showed marked improvement in tremor after Vim thalamotomy. No patient experienced neurological deficits. fMR imaging showed that activation at the fundus of the central sulcus evoked by passive wrist movement was suppressed after Vim thalamotomy in ET patients, probably due to disruption of the thalamocortical pathway. The fundus of the central sulcus (Brodmann area 3a) is likely to be one of the key relays in the tremor circuit.
Genetic Deletion of Pregnancy-Associated Plasma Protein-A Is Associated With Resistance to Atherosclerotic Lesion Development in Apolipoprotein E–Deficient Mice Challenged With a High-Fat Diet
Authors: Harrington Sean C. , Simari Robert D. , Conover Cheryl A.
Published: May 2007

Pregnancy-associated plasma protein–A (PAPP-A), a metalloproteinase in the insulin-like growth factor (IGF) system, is markedly upregulated in human atherosclerotic plaque. To determine whether PAPP-A plays an active role in the development of atherosclerosis, we crossed mice lacking apolipoprotein E (ApoE) with PAPP-A–deficient mice, generating ApoE knock-out (KO), PAPP-A KO, wild-type (WT/WT), and ApoE/PAPP-A double KO (KO/KO) mice. These mice were fed a high-fat diet starting at 7 weeks of age. Total serum cholesterol levels were elevated similarly in the ApoE KO and KO/KO mice and were 10-fold higher than in the WT/WT and PAPP-A KO mice. WT/WT and PAPP-A KO mice showed little or no lesion development even after 20 weeks of diet. ApoE KO mice had a progressive increase in aortic lesion area over 20 weeks of diet. In comparison, lesion area was reduced 60% to 80% in KO/KO mice. Lesions of ApoE KO aortas had 8- to 20-fold increases in PAPP-A, IGFBP-4, and IGF-I mRNA levels compared with nonlesional areas, whereas IGF-I receptor levels were equivalent—conditions for enhanced lesional IGF activity. Consistent with this, an in vivo marker of IGF-I receptor-mediated action was increased 10-fold in lesions from ApoE KO compared with KO/KO aortas. These data indicate that PAPP-A plays a critical role in lesion development in a mouse model of atherosclerosis, at least in part, through amplification of local IGF-I bioavailability.