bluuebunny/crossref_metadata_2025 huggingface dataset:
Transmittance Enhancement in Textured Silicon Solar Cells
Authors: de Lima Monteiro D. W. , Honorato F. P. , Nakamura L. , Tavares Branco J. R. , Freitas T. O.
Published: November 2007

There is a growing demand to improve solar-cell efficiency. Among several methods under investigation, surface texturization is an important alternative. This paper presents an alternative texturization of crystalline silicon to improve solar-cell efficiency. The method is based on anisotropic etching of bulk silicon and requires only a single exposure mask and two etching steps with a KOH aqueous solution. The surface texture consists of smooth hemispherical cavities that have their parameters accurately controlled. There is no need for a lithographic mask or intricate technology processes to obtain the hemispherical cavities. By this method, it is possible to increase both the frontal surface exposed to light and the depletion region. That implies in a higher probability of photon collection, contributing to the improvement of the conversion efficiency of the device. The textured silicon solar-cell transmittance under small incident angles during the day is improved compared to a flat surface, increasing the generated photocurrent.
Annealing Temperature Dependence of 1550 NM Emission of Hydrogenated Amorphous Silicon Films Co-Deposited with Erbium
Authors: Figueira D. , Mustafa D. , Tessler L. R. , Frateschi N. C.
Published: November 2007

We present an experimental study of the influence of annealing temperature in the room temperature 1550 nm (~0.8eV) photoluminescence (PL) of Er3+ co-deposited with silicon on silicon dioxide matrix to be used for light emission in microdisk resonators.
Structure and Optical Properties of ZnO Thin Films Prepared by Reactive e- Beam Evaporation
Authors: Sabino M. E. , Falcao V. D. , Muniz E , Diniz A. S. , Branco J. R.
Published: November 2007

Zinc oxide has been used as transparent and conducting oxide film in solar cells and electrochromic devices. In this work, ZnO thin films have been deposited by reactive electron beam evaporation technique with argonoxygen plasma assistance. The films have been deposited on glass substrate. After the deposition, the films were annealed at 550ºC during 2 hours in an oxidant atmosphere to improve its optical properties. The films were characterized by atomic force microscopy, UV/VIS/NIR spectroscopy and X-ray diffraction. The films are adherent and present high roughness, low transmittance and low crystallinity. After the thermochemical treatment there was an increase in optical transmittance, in crystallinity and a decrease of the absorption coefficient in the visible spectral region. Furthermore, the results of atomic force microscopy and DRX indicate that this treatment promotes a significant change of the surface texture and of the grain size.
Comparison of Plasma Parameters Obtained with Planar Probe and Optical Spectrometer
Authors: Swart L. , Daltrini A. M. , Moshkalyov S. A. , Verdonck Patrick
Published: November 2007

A planar probe and an optical spectrometer were employed to analyze some parameters in an inductively coupled plasma (ICP). The analyses were performed in Ar, Ar+SF6 and O2 plasmas at 40 mTorr. Typical probe results indicate an ion current of 10-3 A/cm2 and an electron temperature (high energy tail) between 1-2 eV in measurements at high powers. At low powers a distinct discharge regime is observed, typically with low density (low ion current) and high electron temperature. Even though a quantitative analysis has not been done yet, the optical emission studies also showed the presence of these two regimes.
Study of Mode Transitions in Inductively Coupled Plasmas
Authors: Daltrini A. M. , Moshkalyov S. A. , Monteiro M. J. , Machida M. , Besseler E.
Published: November 2007

The transitions between low density and high density modes in an inductively coupled plasma reactor were studied by the measurements of different spectral line emissions in Ar plasmas. A described model for metastable atoms shows that the ratio of the emissions Ar 811.5 nm / Ar 750.4 nm is similar to the contribution of metastable ionization in electron production (two-step ionization). Then, the influence of the metastable atoms in the transition triggering was identified, mainly at high pressures. Also, the measurements show that metastable atoms can be a source for the sustaining of the H mode in the hysteresis region.
Effects of the Secondary Electron Emision Coefficent on the Generation of Charged Particles in RF Oxygen Discharge
Authors: Roberto Marisa , Verboncoeur John , Verdonck Patrick , Cizzoto Elias
Published: November 2007

Radio-frequency oxygen discharges have several applications for plasma processing such as etching and surface modification. In order to investigate the structure of O2 discharges between parallel plates at 13.56 MHz, we used the particle-in-cell plus Monte Carlo collision model. A sustaining voltage of 500sinωt V is used for pressures of 20 and 200 mTorr. The dominant process of generation of negative oxygen ions is dissociative attachment, while the loss processes are electron impact detachment, mutual neutralization and detachment. For 20 mTorr pressure processes, dominant positive and negative ions O2+ and O- have a maximum density at the centre and the electron density is two orders of magnitude less than that of these ions. However at a higher pressure, for the 200 mTorr case, the charge density profiles become broader. As the secondary electron emission from the electrodes increases, the electron density also increases as a result of high ionization rates.
Connexin-32 acts as a downregulator of growth of thyroid gland
Authors: Prost Gaëlle , Bernier-Valentin Françoise , Munari-Silem Yvonne , Selmi-Ruby Samia , Rousset Bernard
Published: November 2007

Thyroid epithelial cells communicate through gap junctions formed from connexin (Cx)32, Cx43, and Cx26. We previously reported that reexpression of Cx32 in “gap junction-deficient” FRTL-5 and FRT thyroid cell lines induces a reduction of cell proliferation rate and an activation of expression of cell differentiation. The present study aimed at determining whether Cx32 could exert similar regulatory functions in vivo. We investigated morphological and functional characteristics of thyroid gland of Cx32-deficient mice (Cx32-KO), mice overexpressing Cx32 selectively in the thyroid (Cx32-T+), and Cx32-KO mice with a thyroid-selective Cx32 complementation obtained by crossing Cx32-KO and Cx32-T+ mice. In basal conditions, Cx32-KO mice did not present any detectable thyroid alteration, whereas Cx32-T+ mice showed a thyroid hypoplasia (20% reduction) associated with a slight increase in thyroid functional activity. Under thyrotropin stimulation (following sodium perchlorate treatment), Cx32-KO mice developed a larger goiter (≤65% increase) than wild-type littermates, whereas Cx32-T+ mice exhibited the same thyroid hyperplasia as wild-type mice. Restoration of Cx32 expression in the thyroid of Cx32-KO mice abrogated the thyroid growth increase related to Cx32 deficiency. All together, these data show that Cx32 acts as a downregulator of growth of thyroid gland; an excess of Cx32 limits growth of thyroid cells in the basal state, whereas a lack of Cx32 confers an additional growth potential to TSH-stimulated thyroid cells.
Loss of stearoyl-CoA desaturase 1 inhibits fatty acid oxidation and increases glucose utilization in the heart
Authors: Dobrzyn Pawel , Sampath Harini , Dobrzyn Agnieszka , Miyazaki Makoto , Ntambi James M.
Published: November 2007

Stearoyl-CoA desaturase (SCD) is a lipogenic enzyme that catalyzes the synthesis of monounsaturated fatty acids (FA). SCD1 deficiency activates metabolic pathways that promote FA β-oxidation and decrease lipogenesis in liver. In the present study, we show that FA transport and oxidation are decreased, whereas glucose uptake and oxidation are increased in the heart of SCD1−/−mice. Protein levels of FA transport proteins such as FA translocase/CD36 and FA transport protein as well as activity of carnitine palmitoyltransferase 1, the rate-limiting enzyme for mitochondrial fat oxidation, were significantly lower in the heart of SCD1−/−mice compared with SCD1+/+mice. Consequently, the rate of palmitoyl-CoA oxidation was decreased significantly in the heart of SCD1−/−mice. mRNA levels of peroxisome proliferator-activated receptor-α, a key transcription factor controlling genes of FA oxidation, were significantly reduced in SCD1−/−mice. Phosphorylation of insulin receptor substrate-1 (IRS-1) and the association of αp85 subunit of phosphatidylinositol 3-kinase with IRS-1 were significantly higher under both basal and insulin-stimulated conditions in SCD1−/−hearts. This increased insulin sensitivity translated to a 1.8-fold greater 2-deoxyglucose uptake and 2-fold higher rate of glucose oxidation in the myocardium compared with SCD1+/+counterparts. The results suggest that SCD1 deficiency causes a shift in cardiac substrate utilization from FA to glucose by upregulating insulin signaling, decreasing FA availability, and reducing expression of FA oxidation genes in the heart. This increase in cardiac insulin sensitivity and glucose utilization due to SCD1 deficiency could prove therapeutic in pathological conditions such as obesity that are characterized by skewed cardiac substrate utilization.
Evaluation of LEXF/FXLE rat recombinant inbred strains for genetic dissection of complex traits
Authors: Voigt Birger , Kuramoto Takashi , Mashimo Tomoji , Tsurumi Toshiko , Sasaki Yoshiyuki , Hokao Ryoji , Serikawa Tadao
Published: November 2007

Recombinant inbred (RI) strains are formed from an outcross between two well-characterized inbred stains followed by at least 20 generations of inbreeding. RI strains can be utilized for the analysis of many complex phenotypic traits. The LEXF/FXLE RI strain set consists of 34 RI strains derived by reciprocal crossing of LE/Stm and F344/Stm. Here we report on genetic dissections of complex traits using this RI set and their parental strains. We have developed strain distribution patterns for 232 informative simple sequence length polymorphism markers. The framework map covers the rat genome except for chromosome Y. Seventy-six phenotype parameters, which included physiological and behavioral traits, were examined for these RI lines. Quantitative trait locus (QTL) analysis of these parameters revealed 27 significant and 91 suggestive QTLs, illustrating the potential of this RI resource for the detection of underlying gene functions for various phenotypes. Although this RI set was originally developed to study susceptibility to chemical-induced tumors, it has been shown to be equally powerful for a wide spectrum of traits. The LEXF/FXLE RI strains have been deposited at the National Bio Resource Project for the Rat in Japan and are maintained under specific pathogen-free conditions. They are available at http://www.anim.med.kyoto-u.ac.jp/nbr .
Dissociation of obesity and insulin resistance in transgenic mice with skeletal muscle expression of uncoupling protein 1
Authors: Katterle Yvonne , Keipert Susanne , Hof Jana , Klaus Susanne
Published: November 2007

We evaluated the effect of skeletal muscle mitochondrial uncoupling on energy and glucose metabolism under different diets. For 3 mo, transgenic HSA-mUCP1 mice with ectopic expression of uncoupling protein 1 in skeletal muscle and wild-type littermates were fed semisynthetic diets with varying macronutrient ratios (energy % carbohydrate-protein-fat): HCLF (41:42:17), HCHF (41:16:43); LCHF (11:45:44). Body composition, energy metabolism, and insulin resistance were assessed by NMR, indirect calorimetry, and insulin tolerance test, respectively. Gene expression in different organs was determined by real-time PCR. In wild type, both high-fat diets led to an increase in body weight and fat. HSA-mUCP1 mice considerably increased body fat on HCHF but stayed lean on the other diets. Irrespective of differences in body fat content, HSA-mUCP1 mice showed higher insulin sensitivity and decreased plasma insulin and liver triglycerides. Respiratory quotient and gene expression indicated overall increased carbohydrate oxidation of HSA-mUCP1 but a preferential channeling of fatty acids into muscle rather than liver with high-fat diets. Evidence for increased lipogenesis in white fat of HSA-mUCP1 mice suggests increased energy dissipating substrate cycling. Retinol binding protein 4 expression in white fat was increased in HSA-mUCP1 mice despite increased insulin sensitivity, excluding a causal role in the development of insulin resistance. We conclude that skeletal muscle mitochondrial uncoupling does not protect from the development of obesity in all circumstances. Rather it can lead to a “healthy” obese phenotype by preserving insulin sensitivity and a high metabolic flexibility, thus protecting from the development of obesity associated disturbances of glucose homeostasis.
A Cooperative Recurrent Neural Network for Solving L1 Estimation Problems with General Linear Constraints
Authors: Xia Youshen , Kamel Mohamed S.
Published: November 2007

The constrained L1 estimation is an attractive alternative to both the unconstrained L1 estimation and the least square estimation. In this letter, we propose a cooperative recurrent neural network (CRNN) for solving L1 estimation problems with general linear constraints. The proposed CRNN model combines four individual neural network models automatically and is suitable for parallel implementation. As a special case, the proposed CRNN includes two existing neural networks for solving unconstrained and constrained L1 estimation problems, respectively. Unlike existing neural networks, with penalty parameters, for solving the constrained L1 estimation problem, the proposed CRNN is guaranteed to converge globally to the exact optimal solution without any additional condition. Compared with conventional numerical algorithms, the proposed CRNN has a low computational complexity and can deal with the L1 estimation problem with degeneracy. Several applied examples show that the proposed CRNN can obtain more accurate estimates than several existing algorithms.
The High-Conductance State of Cortical Networks
Authors: Kumar Arvind , Schrader Sven , Aertsen Ad , Rotter Stefan
Published: November 2007

We studied the dynamics of large networks of spiking neurons with conductance-based (nonlinear) synapses and compared them to networks with current-based (linear) synapses. For systems with sparse and inhibition-dominated recurrent connectivity, weak external inputs induced asynchronous irregular firing at low rates. Membrane potentials fluctuated a few millivolts below threshold, and membrane conductances were increased by a factor 2 to 5 with respect to the resting state. This combination of parameters characterizes the ongoing spiking activity typically recorded in the cortex in vivo. Many aspects of the asynchronous irregular state in conductance-based networks could be sufficiently well characterized with a simple numerical mean field approach. In particular, it correctly predicted an intriguing property of conductance-based networks that does not appear to be shared by current-based models: they exhibit states of low-rate asynchronous irregular activity that persist for some period of time even in the absence of external inputs and without cortical pacemakers. Simulations of larger networks (up to 350,000 neurons) demonstrated that the survival time of self-sustained activity increases exponentially with network size.
The Presidency, Regionalism, and Distributive Politics in South Korea
Authors: Horiuchi Yusaku , Lee Seungjoo
Published: November 2007

Although whether there is political influence on distributive policies is now indisputable, important debates have emerged about how politics distorts distributive policy outcomes. In this article, the authors improve the understanding of distributive politics by focusing on South Korea. They argue that because of Korea-specific institutional and cultural settings, an incumbent president allocates disproportionately larger amounts of pork-barrel benefits not only to his own turf but also to his rival's, while distributing smaller amounts to regions where votes are more evenly divided between the camps. This uneven distribution results from his aspiration to achieve dual objectives: to secure his “graceful retirement” and to achieve uninterrupted operation of government during his term. Using municipality-level data, the authors show that this U -shaped relationship between vote and money is statistically significant for both the Kim Young Sam (1993 to 1997) and Kim Dae Jung administrations (1998 to 2002).
What You See and What You Get
Authors: Rohlfing Ingo
Published: November 2007

In a recent contribution to this journal, Munck and Snyder found that many studies suffer from a deficient application of qualitative and quantitative methods. They argue that the combination of small- n and large- n analysis represents a viable method for promoting the production of knowledge. Recently, Evan Lieberman proposed nested analysis as a rigorous approach for comparative research that builds on the complementary strengths of quantitative and qualitative analysis. In this paper, the author examines the methodological potential of nested inference to advance comparative political analysis, arguing that the specific methodological problems of nested designs have not been fully appreciated. It is shown that, under certain circumstances, nothing is gained from a nested analysis. On the contrary, one might lose more than one gains compared to single-method designs. The author suggests specific methodological principles that take these problems into account to make nested analysis fruitful for comparative studies.
Rebuilding at Gunpoint: A City-Level Re-Estimation of the Brady Law and RTC Laws in the Wake of Hurricane Katrina
Authors: La Valle James M.
Published: November 2007

The aftermath of Hurricane Katrina saw a sharp spike in gun-violence, which necessarily re-focused criminological research on the persistent question of how best to prevent gun-related violence. However, a Critical Review published by a National Academy of Science Research Council strongly suggests that previous research evaluating gun-policy outcomes may be unacceptably flawed methodologically, casting serious doubt upon the validity of the results. The research here presented adjusts for those flaws to revise our current knowledge of the effects two of the most common gun-interventions— the Brady Law and “right to carry” Laws—may exert on gun homicide rates and total homicide rates. The Brady Law is found exert a slight but statistically significant effect on both outcomes whereas “right to carry” laws fail to exert statistically significant deterrent effects on either outcome, and both results provisionally contradict earlier gun-policy outcome research, much as the academy report critically suggests.
An Alcohol Policy Evaluation of Drinking and Driving in Hillsborough County, Florida
Authors: Grohosky Amanda R. , Moore Kathleen A. , Ochshorn Ezra
Published: November 2007

Driving under the influence (DUI) is a serious crime that contributes to approximately 9% of traffic-related crashes, injuries, and fatalities in the state of Florida. Specifically, Hillsborough County, which includes Tampa, has the highest rate of DUI-related occurrences in the state of Florida. There are several gaps in policy, enforcement, and treatment that need to be addressed before Hillsborough County can shed this dubious distinction. To this end, 15 key stakeholders involved in alcohol policy were interviewed about law enforcement, judicial, and treatment issues. Several obstacles to reducing DUI crime emerged: inadequate case preparation time, case overload, prosecution challenges such as leniency and inconsistency in sentencing, and the need for more collaboration between law enforcement, the judicial system, and treatment providers. Suggested recommendations included the addition of a DUI court, stricter legal and treatment requirements, and mandatory blood testing.
Violence Against Girls Provokes Girls' Violence
Authors: Schaffner Laurie
Published: November 2007

Young women adjudicated delinquent in juvenile court report suffering inordinate amounts of emotional, physical, and sexual trauma in early childhood and adolescence. In addition, adolescent girls' arrests for violent crimes rose dramatically in the 1990s. This article explores the relationship between those two factors. Drawing from interviews with court-involved girls, this article highlights two contexts in which girls committed aggressive offenses: an incidence of intimate violence in a lesbian relationship and a stabbing in self-defense against sexual assault. I argue that the trauma witnessed and experienced from prior childhood and adolescent injuries—much of it experienced in private—contributed to girls' coming to the attention of public authorities.
Violence and Desire in Beijing
Authors: Xiying Wang  , Ho Petula Sik Ying
Published: November 2007

In Mainland China, there is a lack of public awareness of and systematic research on dating violence and incest. This article fills a gap in the research in this area by examining a woman's lived experience of father–daughter incest and dating violence. The article adopts the standpoint of third-wave feminists and highlights women's agency and resistance to abuse. Meng Xi, the subject of the case study in this article, is regarded as a “survivor” rather than a “victim,” and her various strategies of resistance—in particular, how she talks about her body and linghun (intelligence soul), and uses the two as sites of resistance—are examined. The article sheds light on the desire and sexuality of women in contemporary China, and especially the struggle between spiritual and material pursuits.
Evaluating classroom dialogue Reconciling internal and external accountability
Authors: Laverty Megan , Gregory Maughn
Published: November 2007

In this article we present an instrument to be used by students and professors to evaluate classroom dialogue. We begin with an explanation of the classroom community of inquiry and why we value it as a pedagogical approach. We then describe our different reasons for evaluating classroom dialogue — including institutional, professional and pedagogical accountability — and describe the inherent conflicts among these reasons. We explain how our evaluation instrument was designed to ameliorate these conflicts. We recount a number of theoretical and practical problems we encountered in designing and implementing the instrument and explain how we attempted to overcome these problems. We conclude the article by describing the advantages and disadvantages of our instrument in light of our analysis of data gathered from its first implementation.
Combined Policies and Ideologies in an American International School
Authors: Ramalho Elizabeth Murakami
Published: November 2007

Immersed in host countries around the globe, American international schools serve about a quarter of a million Americans. These schools can often be perceived as representatives of U.S. schools in the international setting. This study has a twofold purpose: to introduce students to the philosophy, policies, and practices of American schools overseas and to provide ethical considerations in the diffusion and implementation of policies that influence teaching and learning practices.
Short-term BMP-4 treatment initiates mesoderm induction in human embryonic stem cells
Authors: Zhang Pengbo , Li Jian , Tan Zhijia , Wang Chengyan , Liu Ting , Chen Lin , Yong Jun , Jiang Wei , Sun Xiaomeng , Du Liying , Ding Mingxiao , Deng Hongkui
Published: November 2007

Human embryonic stem cells (hES cells) have unlimited self-renewal capacity and can differentiate into most, if not all, possible cell types. This unique property makes them valuable not only for investigation of early developmental processes, but also for regenerative medicine. Mesoderm-derived cardiac cells and hematopoietic cells both have the potential for various therapeutic applications. However, efficient induction of hES cell differentiation into mesoderm remains a challenge. Here, we showed that treatment of hES cells with bone morphogenetic protein-4 (BMP-4) exhibited differential effects: long-term treatment results in trophoblast and extra-embryonic endoderm differentiation, whereas short-term treatment can promote early mesoderm induction. The induction of mesoderm in hES cells occurs at a high efficiency as measured using several markers, such as Brachyury, WNT3, and MIXL1 expression. Moreover, these mesoderm progenitor cells can differentiate into cardiac and hematopoietic lineages in vitro. Further analysis showed that the mesoderm-inducing capacity of BMP-4 requires endogenous FGF and TGF-β/Nodal/activin signaling activities. Thus, our results uncover a novel role for BMP-4 in regulation of hES cell differentiation and should provide insights into the mechanism of mesoderm induction in hES cells.
Pim-1 and Pim-2 kinases are required for efficient pre–B-cell transformation by v-Abl oncogene
Authors: Chen Ji-Long , Limnander Andre , Rothman Paul B.
Published: November 2007

The precise mechanisms by which Abl oncogenes transform hematopoietic cells are unknown. We have examined the role of Pim kinases in v-Abl–mediated transformation. In v-Abl transformants, expression of Pim-1 and Pim-2, but not Pim-3, is dependent on Abl kinase activity. Transformation assays demonstrate that v-Abl cannot efficiently transform bone marrow cells derived from Pim-1−/−/Pim-2−/− mice. Ectopic expression of either Pim-1 or Pim-2 in Pim-1−/−/Pim-2−/− cells restores transformation by v-Abl, strongly suggesting that either Pim-1 or Pim-2 is required for v-Abl–mediated tumorigenesis. Interestingly, the combined deficiency of Pim-1, Pim-2, and Suppressor of Cytokine Signalling (SOCS)-1 resulted in partial restoration of v-Abl transformation efficiency. In addition, Pim kinases are involved in modification of SOCS-1 and in regulating SOCS-1 protein levels in v-Abl–transformed cells. Furthermore, Pim kinases regulate the proapoptotic proteins Bcl-XS and BAD. Pim kinases inhibit the expression of Bcl-XS. Pim deficiency decreases the phosphorylation levels of BAD, whereas ectopic expression of Pim-1 increases the amount of phospho-BAD. This correlates with an increased protection from apoptosis in Abl transformants expressing Pim kinases. Together, these data suggest that Pim kinases play a key role in the v-Abl transformation, possibly via participating in modulation of SOCS-1 and via regulating the apoptotic signaling.
Interleukin-27 directly induces differentiation in hematopoietic stem cells
Authors: Seita Jun , Asakawa Masayuki , Ooehara Jun , Takayanagi Shin-ichiro , Morita Yohei , Watanabe Nobukazu , Fujita Koji , Kudo Motoshige , Mizuguchi Junichiro , Ema Hideo , Nakauchi Hiromitsu , Yoshimoto Takayuki
Published: November 2007

Interleukin (IL)-27, one of the most recently discovered IL-6 family cytokines, activates both the signal transducer and activator of transcription (STAT)1 and STAT3, and plays multiple roles in pro- and anti-inflammatory immune responses. IL-27 acts on various types of cells including T, B, and macrophage through the common signal-transducing receptor gp130 and its specific receptor WSX-1, but the effect of IL-27 on hematopoietic stem cells (HSCs) remains unknown. Here, we show that IL-27 together with stem cell factor (SCF) directly acts on HSCs and supports their early differentiation in vitro and in vivo. CD34−/lowc-Kit+Sca-1+lineage marker− (CD34−KSL) cells, a population highly enriched in mouse HSCs, were found to express both IL-27 receptor subunits. In vitro cultures of CD34−KSL cells with IL-27 and SCF resulted in an expansion of progenitors including short-term repopulating cells, while some of their long-term repopulating activity also was maintained. To examine its in vivo effect, transgenic mice expressing IL-27 were generated. These mice exhibited enhanced myelopoiesis and impaired B lymphopoiesis in the bone marrow with extramedullary hematopoiesis in the spleen. Moreover, IL-27 similarly acted on human CD34+ cells. These results suggest that IL-27 is one of the limited cytokines that play a role in HSC regulation.
α2β1 integrin expression in the tumor microenvironment enhances tumor angiogenesis in a tumor cell–specific manner
Authors: Zhang Zhonghua , Ramirez Norma E. , Yankeelov Thomas E. , Li Zhengzhi , Ford Laura E. , Qi Ying , Pozzi Ambra , Zutter Mary M.
Published: November 2007

To define the role of the α2β1 integrin in pathologic angiogenesis, we investigated tumor-associated growth and angiogenesis in wild-type and α2-null mice. Our findings reveal that the α2β1 integrin plays an important role in angiogenesis via regulation of VEGFR1 expression. When challenged with B16F10 melanoma cells, mice lacking α2β1 integrin ex-pression exhibit increased tumor angiogenesis associated with up-regulated VEGFR1 expression. In contrast, there was no α2β1 integrin-dependent difference in the angiogenic response to Lewis lung carcinoma (LLC) cells. Interestingly, whereas B16F10 cells secrete high levels of placental growth factor (PLGF), LLC cells produce high levels of VEGF, but low levels of PLGF. The α2β1 integrin-dependent difference in angiogenesis was restored to LLC cells by expression of PLGF, strongly suggesting that the angiogenic phenotype and tumor growth in the α2-null host is dependent on specific interactions between the tumor cell and the genetically defined integrin repertoire of the host microenvironment. Thus integrin α2-null mice represent an example of genetic alterations of “the soil” determining response to the “seed.”
Spleen tyrosine kinase Syk is critical for sustained leukocyte adhesion during inflammation in vivo
Authors: Frommhold David , Mannigel Ingrid , Schymeinsky Jürgen , Mocsai Attila , Poeschl Johannes , Walzog Barbara , Sperandio Markus
Published: November 2007

Background

During inflammation, β2-integrins mediate leukocyte adhesion to the endothelium accompanied by the activation of the spleen tyrosine kinase Syk.

Results

We investigated leukocyte adhesion and rolling in cremaster muscle venules before and during stimulation with fMLP using mice with aSyk-/-hematopoietic system. In unstimulated venules,Syk-/-leukocytes adhered less efficiently than control leukocytes while rolling was similar betweenSyk-/-and control leukocytes. During fMLP-superfusion, control mice showed significantly increased adhesion accompanied by reduced rolling. ForSyk-/-leukocytes, an increase in adhesion with a concomitant decrease in rolling was only observed during the first three minutes during fMLP stimulation, but not at later time points. We also investigated leukocyte spreading against the vessel wall during fMLP stimulation and found a significant impairment of spreading forSyk-/-leukocytes. Additional in vitro experiments revealed that the adhesion and spreading defect seen inSyk-/-chimeric mice was due to compromised β2-integrin-mediated outside-in signaling.

Conclusion

We provide substantial evidence for an important role of Syk in mediating β2-integrin dependent outside-in signaling leading to sustained leukocyte adhesion and spreading during the inflammatory response in vivo.
Dynamic and redundant regulation of LRRK2 and LRRK1 expression
Authors: Biskup Saskia , Moore Darren J , Rea Alexis , Lorenz-Deperieux Bettina , Coombes Candice E , Dawson Valina L , Dawson Ted M , West Andrew B
Published: November 2007

Background

Mutations within the leucine-rich repeat kinase 2 (LRRK2) gene account for a significant proportion of autosomal-dominant and some late-onset sporadic Parkinson's disease. Elucidation of LRRK2 protein function in health and disease provides an opportunity for deciphering molecular pathways important in neurodegeneration. In mammals, LRRK1 and LRRK2 protein comprise a unique family encoding a GTPase domain that controls intrinsic kinase activity. The expression profiles of the murine LRRK proteins have not been fully described and insufficiently characterized antibodies have produced conflicting results in the literature.

Results

Herein, we comprehensively evaluate twenty-one commercially available antibodies to the LRRK2 protein using mouse LRRK2 and human LRRK2 expression vectors, wild-type and LRRK2-null mouse brain lysates and human brain lysates. Eleven antibodies detect over-expressed human LRRK2 while four antibodies detect endogenous human LRRK2. In contrast, two antibodies recognize over-expressed mouse LRRK2 and one antibody detected endogenous mouse LRRK2. LRRK2 protein resides in both soluble and detergent soluble protein fractions. LRRK2 and the related LRRK1 genes encode low levels of expressed mRNA species corresponding to low levels of protein both during development and in adulthood with largely redundant expression profiles.

Conclusion

Despite previously published results, commercially available antibodies generally fail to recognize endogenous mouse LRRK2 protein; however, several antibodies retain the ability to detect over-expressed mouse LRRK2 protein. Over half of the commercially available antibodies tested detect over-expressed human LRRK2 protein and some have sufficient specificity to detect endogenous LRRK2 in human brain. The mammalian LRRK proteins are developmentally regulated in several tissues and coordinated expression suggest possible redundancy in the function between LRRK1 and LRRK2.
Breastfeeding and childhood asthma: a six-year population-based cohort study
Authors: Fredriksson Pia , Jaakkola Niina , Jaakkola Jouni JK
Published: November 2007

Background

The question of the protective effect of breastfeeding on development of asthma has raised substantial interest, but the scientific evidence of the optimal duration of breastfeeding is controversial.

Methods

The authors elaborated the optimal duration of breastfeeding with respect to the risk of asthma primarily, and secondarily to the risk of persistent wheezing, cough and phlegm in school age in a population-based cohort study with the baseline in 1991 and follow-up in 1997. The study population comprised 1984 children aged 7 to 14 years at the end of the follow-up (follow-up rate 77). Information on breastfeeding was based on the baseline survey and information on the health outcomes at the follow-up.

Results

There was a U-shaped relation between breastfeeding and the outcomes with the lowest risk with breastfeeding from four to nine months for asthma and seven to nine months for persistent wheezing, cough and phlegm.

Conclusion

Our results suggest a U shape relation between duration of breastfeeding and risk of asthma with an optimal duration of 4 to 6 months. A true concave relation would explain the inconsistent results from the previous studies.
Carbohydrate restriction and dietary cholesterol modulate the expression of HMG-CoA reductase and the LDL receptor in mononuclear cells from adult men
Authors: Mutungi Gisella , Torres-Gonzalez Moises , McGrane Mary M. , Volek Jeff S. , Fernandez Maria Luz
Published: November 2007

The liver is responsible for controlling cholesterol homeostasis in the body. HMG-CoA reductase and the LDL receptor (LDL-r) are involved in this regulation and are also ubiquitously expressed in all major tissues. We have previously shown in guinea pigs that there is a correlation in gene expression of HMG-CoA reductase and the LDL-r between liver and mononuclear cells. The present study evaluated human mononuclear cells as a surrogate for hepatic expression of these genes. The purpose was to evaluate the effect of dietary carbohydrate restriction with low and high cholesterol content on HMG-CoA reductase and LDL-r mRNA expression in mononuclear cells. All subjects were counseled to consume a carbohydrate restricted diet with 10–15% energy from carbohydrate, 30–35% energy from protein and 55–60% energy from fat. Subjects were randomly assigned to either EGG (640 mg/d additional dietary cholesterol) or SUB groups [equivalent amount of egg substitute (0 dietary cholesterol contributions) per day] for 12 weeks. At the end of the intervention, there were no changes in plasma total or LDL cholesterol (LDL-C) compared to baseline (P > 0.10) or differences in plasma total or LDL-C between groups. The mRNA abundance for HMG-CoA reductase and LDL-r were measured in mononuclear cells using real time PCR. The EGG group showed a significant decrease in HMG-CoA reductase mRNA (1.98 ± 1.26 to 1.32 ± 0.92 arbitrary units P < 0.05) while an increase was observed for the SUB group (1.13 ± 0.52 to 1.69 ± 1.61 arbitrary units P < 0.05). Additionally, the LDL-r mRNA abundance was decreased in the EGG group (1.72 ± 0.69 to 1.24 ± 0.55 arbitrary units P < 0.05) and significantly increased in the SUB group (1.00 ± 0.60 to 1.67 ± 1.94 arbitrary units P < 0.05). The findings indicate that dietary cholesterol during a weight loss intervention alters the expression of genes regulating cholesterol homeostasis.
The Warwick-Edinburgh Mental Well-being Scale (WEMWBS): development and UK validation
Authors: Tennant Ruth , Hiller Louise , Fishwick Ruth , Platt Stephen , Joseph Stephen , Weich Scott , Parkinson Jane , Secker Jenny , Stewart-Brown Sarah
Published: November 2007

Background

There is increasing international interest in the concept of mental well-being and its contribution to all aspects of human life. Demand for instruments to monitor mental well-being at a population level and evaluate mental health promotion initiatives is growing. This article describes the development and validation of a new scale, comprised only of positively worded items relating to different aspects of positive mental health: the Warwick-Edinburgh Mental Well-Being Scale (WEMWBS).

Methods

WEMWBS was developed by an expert panel drawing on current academic literature, qualitative research with focus groups, and psychometric testing of an existing scale. It was validated on a student and representative population sample. Content validity was assessed by reviewing the frequency of complete responses and the distribution of responses to each item. Confirmatory factor analysis was used to test the hypothesis that the scale measured a single construct. Internal consistency was assessed using Cronbach's alpha. Criterion validity was explored in terms of correlations between WEMWBS and other scales and by testing whether the scale discriminated between population groups in line with pre-specified hypotheses. Test-retest reliability was assessed at one week using intra-class correlation coefficients. Susceptibility to bias was measured using the Balanced Inventory of Desired Responding.

Results

WEMWBS showed good content validity. Confirmatory factor analysis supported the single factor hypothesis. A Cronbach's alpha score of 0.89 (student sample) and 0.91 (population sample) suggests some item redundancy in the scale. WEMWBS showed high correlations with other mental health and well-being scales and lower correlations with scales measuring overall health. Its distribution was near normal and the scale did not show ceiling effects in a population sample. It discriminated between population groups in a way that is largely consistent with the results of other population surveys. Test-retest reliability at one week was high (0.83). Social desirability bias was lower or similar to that of other comparable scales.

Conclusion

WEMWBS is a measure of mental well-being focusing entirely on positive aspects of mental health. As a short and psychometrically robust scale, with no ceiling effects in a population sample, it offers promise as a tool for monitoring mental well-being at a population level. Whilst WEMWBS should appeal to those evaluating mental health promotion initiatives, it is important that the scale's sensitivity to change is established before it is recommended in this context.
Student Perspectives on Curricular Change: Lessons from an Undergraduate Lower-Division Biology Core
Authors: Casem Merri Lynn
Published: November 2007

Inquiry-based laboratories are acknowledged as the preferred method of instruction for development of research skills. Much has been written about changes in student performance associated with inquiry, but less is known about how students view the inquiry-based format or whether they perceive a benefit from this type of instruction. The Student Assessment of Learning Gains (SALG) survey was used to evaluate and compare student reactions to the new, inquiry-based laboratories of a lower-division undergraduate curriculum, from implementation to the present (an interval of 3 yr). Initial student response to the format and value of the inquiry labs improved over time. The quality of the graduate teaching assistants and the clarity of the laboratory manual were important variables influencing student perception. A student's perception of his/her retention of lab-related skills was strongly associated with perceptions of gains in those skills. Student responses reflect their most current laboratory experience and not a cumulative effect of participation in the core series of courses. Student success in the inquiry format was not associated with gender or status as a transfer student. The majority of students believe that their experiences in the lower-division inquiry labs have prepared them for upper-division course work.
Criticism and Interpretation: Teaching the Persuasive Aspects of Research Articles
Authors: Gillen Christopher M.
Published: November 2007

Research articles are an excellent tool for promoting active learning about the scientific process. One difficulty in teaching research articles is that they address a professional audience and often seek to be persuasive as well as informative. This essay discusses pedagogical strategies that are intended to help students differentiate the purely informative aspects of research articles, such as descriptions of the methods and results, from the persuasive aspects, such as interpretation of results and critical evaluation of the work of other scientists.
Using Literature and Innovative Assessments to Ignite Interest and Cultivate Critical Thinking Skills in an Undergraduate Neuroscience Course
Authors: Lynd-Balta Eileen
Published: November 2007

Science education reform initiatives emphasize 1) the value of concepts over facts; 2) the benefits of open-ended, inquiry-based problem-solving rather than protocols leading to a single correct answer; and 3) the importance of a multidisciplinary approach to teaching that is not confined by departmental boundaries. Neuroscientists should be at the forefront of this movement by the very nature of the discipline we study. Neuroscience is a relatively new field that integrates diverse subjects (anatomy, physiology, pharmacology, molecular biology, computer science, and psychology) and experimental advances are constantly changing and expanding our understanding of brain function. How can we convey this excitement in the classroom? The project described in this article uses nonscientific literature to introduce a scientific topic of study. In addition, the multitask assignment requires the acquisition of content knowledge and the development of critical thinking skills. As students explore the topic from multiple perspectives, they recognize the interconnectedness of science and society and confront ethical and moral issues related to science. A comparison of exam scores, essay responses, engagement level, as well as students' own reflections, demonstrates that inclusion of the project does not sacrifice content knowledge, rather it enhances the overall learning process.
How Golden is Silence? Teaching Undergraduates the Power and Limits of RNA Interference
Authors: Kuldell Natalie H.
Published: November 2007

It is hard and getting harder to strike a satisfying balance in teaching. Time dedicated to student-generated models or ideas is often sacrificed in an effort to “get through the syllabus.” I describe a series of RNA interference (RNAi) experiments for undergraduate students that simultaneously explores fundamental concepts in gene regulation, develops cutting-edge laboratory skills, and embraces student-directed learning. Students design a small interfering RNA (siRNA) against luciferase, add it to cells expressing this gene, and then quantitatively assess the siRNA's effect on both intended and unintended targets, using a luciferase assay and a DNA microarray. Because both RNAi and microarray technologies are relatively new, with no clear consensus on their analysis or limitations, students are encouraged to explore different approaches to the design of their reagents and interpretations of their data. The ability to creatively formulate a hypothesis-driven experimental approach to a scientific question and to critically evaluate collected data is stressed. Equally important, this experiment emphasizes how modern scientific ideas emerge, are debated, tested, and decided.
Beverage-Agarose Gel Electrophoresis: An Inquiry-based Laboratory Exercise with Virtual Adaptation
Authors: Cunningham Steven C. , McNear Brad , Pearlman Rebecca S. , Kern Scott E.
Published: November 2007

A wide range of literature and experience has shown that teaching methods that promote active learning, such as inquiry-based approaches, are more effective than those that rely on passive learning. Gel electrophoresis, one of the most common laboratory techniques in molecular biology, has a wide range of applications in the life sciences. As such, we chose it as a platform to expose high school and undergraduate students to the active process of scientific inquiry in general, while specifically teaching electrophoresis. First, we optimized DNA electrophoresis in the laboratory by using common beverages instead of standard media (e.g., Tris-based media). Second, we adapted this laboratory process of progressive optimization to a Web-based format in which students had to achieve all the same steps of optimization by performing serial electrophoreses. And third, we evaluated the use of this entirely Web-based virtual laboratory exercise in high school and undergraduate biology courses. Students learned fundamental and practical principles of electrophoresis, while experiencing the essential inquiry-based process of optimizing a technique, and they also enjoyed it. Our findings provide a readily accessible, inexpensive, and intriguing technique for teaching electrophoresis and the progressive optimization of a laboratory technique.
A Summer Program Designed to Educate College Students for Careers in Bioinformatics
Authors: Krilowicz Beverly , Johnston Wendie , Sharp Sandra B. , Warter-Perez Nancy , Momand Jamil
Published: November 2007

A summer program was created for undergraduates and graduate students that teaches bioinformatics concepts, offers skills in professional development, and provides research opportunities in academic and industrial institutions. We estimate that 34 of 38 graduates (89%) are in a career trajectory that will use bioinformatics. Evidence from open-ended research mentor and student survey responses, student exit interview responses, and research mentor exit interview/survey responses identified skills and knowledge from the fields of computer science, biology, and mathematics that are critical for students considering bioinformatics research. Programming knowledge and general computer skills were essential to success on bioinformatics research projects. General mathematics skills obtained through current undergraduate natural sciences programs were adequate for the research projects, although knowledge of probability and statistics should be strengthened. Biology knowledge obtained through the didactic phase of the program and prior undergraduate education was adequate, but advanced or specific knowledge could help students progress on research projects. The curriculum and assessment instruments developed for this program are available for adoption by other bioinformatics programs at http://www.calstatela.edu/SoCalBSI .