bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Glucocorticoids in Pregnancy, Parturition, Lactation, and Nurturing in Melanocortin Receptor 2-Deficient Mice
Authors: Chida Dai , Miyoshi Keiko , Sato Tsuyoshi , Yoda Tetsuya , Kikusui Takefumi , Iwakura Yoichiro
Published: February 2011

Maternal glucocorticoids are critical for fetal development, but overexpression can be deleterious. Previously we established a mouse line deficient in melanocortin receptor 2 (MC2R). MC2R−/− mice have undetectable levels of corticosterone despite high levels of ACTH and defects resembling those in patients with familial glucocorticoid deficiency. Here we analyzed the role of glucocorticoids in pregnancy, parturition, lactation, and nurturing in MC2R−/− mice. MC2R−/− mice were fertile and produced normal litters when crossed with MC2R+/+ mice. However, MC2R−/− females crossed with MC2R−/− males had no live births, and approximately 20% of the embryos at d 18.5 of pregnancy were of normal body size but were dead when born. MC2R−/− pregnant females crossed with MC2R+/+ males had detectable serum corticosterone levels, suggesting the transplacental passage of corticosterone from fetus to mother. MC2R+/− pups delivered from MC2R−/− females crossed with MC2R+/+ males mice thrived poorly with MC2R−/− mothers but grew to adulthood when transferred to foster mothers after birth, suggesting that MC2R−/− females are poor mothers or cannot nurse. MC2R−/− females had normal alveoli, but penetration of mammary epithelium into fat pads and expression of milk proteins were reduced. Myoepithelial cells, which force milk out of the alveoli, were fully developed and differentiated. Pup retrieval behavior was normal in MC2R−/− mice. Exogenous corticosterone rescued expression of milk proteins in MC2R−/− mothers, and the pups of treated mothers grew to adulthood. Our results reveal the importance of glucocorticoids for fetal survival late in pregnancy, mammary gland development, and milk protein gene expression.
Growth Hormone-Dependent Pathogenesis of Human Hepatic Steatosis in a Novel Mouse Model Bearing a Human Hepatocyte-Repopulated Liver
Authors: Tateno Chise , Kataoka Miho , Utoh Rie , Tachibana Asato , Itamoto Toshiyuki , Asahara Toshimasa , Miya Fuyuki , Tsunoda Tatsuhiko , Yoshizato Katsutoshi
Published: February 2011

Clinical studies have shown a close association between nonalcoholic fatty liver disease and adult-onset GH deficiency, but the relevant molecular mechanisms are still unclear. No mouse model has been suitable to study the etiological relationship of human nonalcoholic fatty liver disease and human adult-onset GH deficiency under conditions similar to the human liver in vivo. We generated human (h-)hepatocyte chimeric mice with livers that were predominantly repopulated with h-hepatocytes in a h-GH-deficient state. The chimeric mouse liver was mostly repopulated with h-hepatocytes about 50 d after transplantation and spontaneously became fatty in the h-hepatocyte regions after about 70 d. Infusion of the chimeric mouse with h-GH drastically decreased steatosis, showing the direct cause of h-GH deficiency in the generation of hepatic steatosis. Using microarray profiles aided by real-time quantitative RT-PCR, comparison between h-hepatocytes from h-GH-untreated and -treated mice identified 14 GH-up-regulated and four GH-down-regulated genes, including IGF-I, SOCS2, NNMT, IGFLS, P4AH1, SLC16A1, SRD5A1, FADS1, and AKR1B10, respectively. These GH-up- and -down-regulated genes were expressed in the chimeric mouse liver at lower and higher levels than in human livers, respectively. Treatment of the chimeric mice with h-GH ameliorated their altered expression. h-Hepatocytes were separated from chimeric mouse livers for testing in vitro effects of h-GH or h-IGF-I on gene expression, and results showed that GH directly regulated the expression of IGF-I, SOCS2, NNMT, IGFALS, P4AH1, FADS1, and AKR1B10. In conclusion, the chimeric mouse is a novel h-GH-deficient animal model for studying in vivo h-GH-dependent human liver dysfunctions.
ACTH-Dependent Ultradian Rhythm of Corticosterone Secretion
Authors: Spiga Francesca , Waite Eleanor J. , Liu Ying , Kershaw Yvonne M. , Aguilera Greti , Lightman Stafford L.
Published: February 2011

The activity of the hypothalamic-pituitary-adrenal axis is characterized by an ultradian pulsatile pattern of glucocorticoid secretion. Despite increasing evidence for the importance of pulsatility in regulating glucocorticoid-responsive gene transcription, little is known about the mechanism underlying the pulsatility of glucocorticoid synthesis and release. We tested the hypothesis that pulsatile ACTH release is critical for optimal adrenocortical function. Hypothalamic-pituitary-adrenal activity was suppressed by oral methylprednisolone, and ACTH (4 ng/h) was infused for 24h either as a constant infusion or in 5-min pulses at hourly intervals. Control methylprednisolone-treated rats had very low plasma corticosterone (CORT) levels with undetectable pulses and also had steroidogenic acute regulatory protein (StAR) and cytochrome P450 side-chain cleavage (P450scc) heteronuclear RNA levels reduced to approximately 50% of that seen in untreated animals. Pulsatile but not constant ACTH infusion restored pulsatile CORT secretion, and this was accompanied by parallel rises in StAR and P450scc heteronuclear RNA levels during the rising phase of the CORT pulse, which then fell during the falling phase. The pulsatile pattern of StAR and P450scc was paralleled by pulsatile transcription of the melanocortin 2 receptor accessory protein. Pulsatile ACTH activation of the adrenal cortex not only is critical for the secretion of CORT but also induces episodic transcription of the rate-limiting enzymes necessary for physiological steroidogenic responses. Because constant infusion of identical amounts of ACTH did not activate CORT secretion, pulsatility of ACTH provides a more effective signaling system for the activation of adrenocortical activity.
Early-Life Exposure to Testosterone Programs the Hypothalamic Melanocortin System
Authors: Nohara Kazunari , Zhang Yan , Waraich Rizwana S. , Laque Amanda , Tiano Joseph P. , Tong Jenny , Münzberg Heike , Mauvais-Jarvis Franck
Published: February 2011

In mammals, males consume more food, which is considered a masculinized behavior, but the underlying mechanism of this sex-specific feeding behavior is unknown. In mice, neonatal testosterone (NT) is critical to masculinize the developing brain, leading to sex differences in reproductive physiology. The proopiomelanocortin (POMC) neurons of the hypothalamic arcuate nucleus (ARC) are critical to suppress energy intake and POMC innervation of hypothalamic feeding circuits develops to a large extent neonatally. We hypothesized that NT programs the masculinization of energy intake by programming POMC neurons. We tested this hypothesis by comparing control females and control males (CMs) with female mice neonatally androgenized with testosterone (NTFs). We show that increased food intake in CMs is associated with reduced POMC expression and decreased intensity of neuronal projections from POMC neurons within the ARC compared with control females. We found that NTFs display a masculinized energy intake and ARC POMC expression and innervation as observed in CMs, which can be mimicked by neonatal exposure to the androgen receptor agonist dihydrotestosterone (DHT). NTFs also exhibit hyperleptinemia and a decreased ability of leptin to up-regulate POMC, suppress food intake, and prevent adipose tissue accumulation, independent of signal transducer and activator of transcription 3. However, this leptin resistance is specific to NTFs, is not a consequence of masculinization, and is reproduced by neonatal exposure to estrogen but not DHT. Thus, NT programs a sexual differentiation of POMC neurons in female mice via DHT but also predisposes to leptin resistance and obesity in an estrogen-dependent manner.
GPR30 Activation Opposes Estrogen-Dependent Uterine Growth via Inhibition of Stromal ERK1/2 and Estrogen Receptor Alpha (ERα) Phosphorylation Signals
Authors: Gao Fei , Ma Xinghong , Ostmann Alicia B. , Das Sanjoy K.
Published: February 2011

Although estradiol-17β (E2)-regulated early and late phase uterine responses have been well defined, the molecular mechanisms linking the phases remain poorly understood. We have previously shown that E2-regulated early signals mediate cross talk with estrogen receptor (ER)-α to elicit uterine late growth responses. G protein-coupled receptor (GPR30) has been implicated in early nongenomic signaling mediated by E2, although its role in E2-dependent uterine biology is unclear. Using selective activation of GPR30 by G-1, we show here a new function of GPR30 in regulating early signaling events, including the inhibition of ERK1/2 and ERα (Ser118) phosphorylation signals and perturbation of growth regulation under the direction of E2 in the mouse uterus. We observed that GPR30 primarily localizes in the uterine epithelial cells, and its activation alters gene expression and mediates inhibition of ERK1/2 and ERα (Ser118) phosphorylation signals in the stromal compartment, suggesting a paracrine signaling is involved. Importantly, viral-driven manipulation of GPR30 or pharmacological inhibition of ERK1/2 activation effectively alters E2-dependent uterine growth responses. Overall, GPR30 is a negative regulator of ERα-dependent uterine growth in response to E2. Our work has uncovered a novel GPR30-regulated inhibitory event, which may be physiologically relevant in both normal and pathological situations to negatively balance ERα-dependent uterine growth regulatory functions induced by E2.
Fred Holland: Walking the Line
Authors: Bernard Catherine
Published: February 2011

This essay analyzes the work of a contemporary black artist who reinvents the human body, searching for its limits in works that transform and recycle materials and concepts while challenging viewers’ perceptions. As a link between conceptual art, arte povera, and postmodern discourses, Fred Holland’s sculptures are reflections on life’s impermanence, on human frailty, and on the struggle for survival. He walks the line between the categories that have defined black art in a constant search for reinvention and renewal.
The Clothes Make the Man: Portraits of Emperor Haile Selassie
Authors: Werts Julia Kim
Published: February 2011

The many names and titles of Haile Selassie, Ethiopia’s last emperor, proclaim the grandeur and majesty of his role in the country’s recent history. As elaborate and expressive as the words used to describe him, the role of his physical body as a public embodiment of modernity evoked the spirit of his politics, both at home and abroad. This essay examines how Haile Selassie controlled his visual image, through clothing as well as photography, in order to express his political and cultural agendas.
Steve McQueen: Giardini
Authors: Rocco Vanessa
Published: February 2011

Steve McQueen’s Giardini, a ravishing half-hour dual projection, comprises vignettes recorded around the national pavilions that are the principal organizing spaces of the Venice Biennale. Fluctuating among images of serene nature and images of trash, piles of building materials, and loose dogs on the prowl, Giardini examines vacated public spaces in between the festivities, after the visitors, critics, and journalists have departed. These images conjure a haunted ruin, creating a tension with other images in the film that are more firmly rooted in current sociocultural contexts. In a shorter film in the exhibition, Static, McQueen makes us rethink our preconceptions about the Statue of Liberty from various viewpoints. It is a multisensory subversion that shows how McQueen returns the “physical to . . . the image.”
El Anatsui
Authors: Onafuwa Yemi
Published: February 2011

This review considers the Ghanaian sculptor El Anatsui’s recent work—stitched “cloth” made from recycled liquor-bottle caps—in the context of his entire artistic production and his “remix and recycle” ethos. By transforming glittering gold-colored bottleneck wrappers and silvery bottle caps into a new kind of luxury, Anatsui presents the viewer with an impressive visual coup. Part of the sensation of luxurious beauty is due to the viewer’s awareness of the intensive manual labor that went into making the works. The review also examines the tendency of Anatsui’s recent sculpture to elicit comparisons to woven cloth, chain mail, mosaics, and so on. Anatsui’s own invitation of such semiotic fluidity is considered in light of his work’s titles. The “meaning” of these recent pieces is to be found in two dimensions: the comparative resonances they set up in the viewer’s mind, and the knowledge that these are the works of many hands.
Yinka Shonibare MBE
Authors: Hirsh Jennie
Published: February 2011

This review examines the midcareer retrospective Yinka Shonibare MBE in the context of its third and final venue, the National Museum of African Art in Washington, DC. The survey featured examples of the artist’s familiar interests—the complex relationship between colonial and postcolonial history, art history as archive, European decadence—alongside works that emphasize his more recent focus on cinematic strategies and contemporary global politics. By juxtaposing works in different mediums executed over the past fifteen years, this carefully curated and creatively installed show provided both a vehicle for the artist’s most visually stunning works and a panoptical framework, illuminating the aesthetic and underlying conceptual affinities that subtly bind together the artist’s discrete endeavors.
The Problem Is More Mental Than Economic: Ousmane Sembène in Conversation with Samba Gadjigo
Authors: Gadjigo Samba
Published: February 2011

After more than three years of work, Ousmane Sembène put the finishing touches on his feature film Moolaadé. This film was selected for the Cannes Film Festival (Un Certain Regard) and had its press screening on May 14, 2004, then its debut on May 15. Several hours after the final postproduction on the film, on April 11, 2004, Sembène graciously granted Samba Gadjigo this interview in Rabat, Morocco. Their conversation covers diverse issues such as women in Africa, the role and responsibility of the artist, art and pleasure, cinema and political activism, and Africa and globalization.
Pale Reflections and Fables of Life: George Osodi’s “Real People” of the Niger Delta
Authors: Ugiomoh Frank A. O.
Published: February 2011

Documentary photography, in a very fundamental sense, locates the self and the other in determinate historical relationships. In these relationships documentary photographs usually capture what organized establishments like governments would rather have ignored. Documentary photography is George Osodi’s strong suit. His images of the not so pleasant and the contestatory in the Niger Delta region of Nigeria and the apparent ease with which he confronts the documentary photography genre are the topics of this essay. His photographs embody narratives of diverse contexts that inflect the identity and history of the Nigerian nation in general. In addition, the photographs hint at years of neglect to which the Niger Delta region has been subjected even as it continues to fund government and governance in Nigeria.
From Riot to Austerity: Chris Ofili’s Retrospective at the Tate Britain
Authors: Hynes N. J.
Published: February 2011

The British painter Chris Ofili’s retrospective at the Tate Britain in London shows a painter reinventing his approach to paint in the middle of a successful career. His previous work used multiple layers of cutouts, paint, glitter, resin, and dung, creating a lush Afro-rococo style with its obsessive decoration and its focus on black figuration. It won awards and the admiration of institutions and collectors. The new work employs a reduced palette, eschews glitter, and rewards the extended gaze in a way that his previous excess could not. This recent work also allows the viewer to reflect on juxtapositions of the sacred and profane, the beautiful and ugly, in Ofili’s earlier work and to consider the implications of his strategic shift.
Beyond the Shit Storm: Chris Ofili’s Retrospective at the Tate Britain
Authors: Juncker Kris
Published: February 2011

Inadvertently, Tate Britain may be forecasting the fate of hip-hop and its artistic expression through a midcareer retrospective of Chris Ofili’s work. The exhibition presents a number of stages of his development, with an emphasis on the breakout, commercially successful work involving collage and elephant dung. However, Ofili’s work from the past decade illustrates some surprising new directions, particularly the work from 2005 on, after the artist had moved to Trinidad. In particular, Ofili is now invested in investigating very different, if not classically art-historical, themes through dramatic contrasts in the fluidity and brightness of his media. Whereas Ofili began his career illustrating the popular thematic interests of hip-hop, he is now well distanced from the commercial elite of hip-hop and has grown comfortable weaving his own topics into hip-hop’s increasingly international discourse.
African Screens (Re)viewed from Lisbon
Authors: Sanches Manuela Ribeiro
Published: February 2011

Representations of Africa tend to reproduce old stereotypes, adapted to recent trends but ultimately reproducing, even in postcolonial times, a largely negative and monolithic image of a diverse continent. The same can be said of cinema. A more or less consensual approach to “African cinema” associates it with exoticism, making it into a genre easily recognized by Western audiences. It is this idea of a backward, monolithic Africa that the curators of African Screens, Manthia Diawara and Lydie Diakhaté, intended to challenge. The provocative gesture can be found in the choice of the film screened at the inaugural session, Les saignantes, by Jean-Pierre Bekolo. The same applies to Juju Factory, by Balufu Bakupa Kanyinda. Both films question ideas of “authentic” representations of “Africanness,” introducing a complex cinematic language that shows how contemporary African film not only is diverse in its tendencies but also relates in diverse ways to different trans/national traditions and models.
Uncovering the Frozen Image
Authors: Zeleke Elleni (Centime)
Published: February 2011

This article examines how the Ethiopian Swedish artist Loulou Cherinet portrays the construction of gender and nation as a balancing act between men and women, local and international forces. In particular, the essay focuses on how she forces her audience to confront the fact that if we abstract one of these binaries from the other, we end up with stereotypical stories that do not take us far in understanding our own condition. Yet she also teaches us that the subject’s story never belongs to him or her alone: what we face on the outside turns out to be as important as what we face on the inside.
Translocation dynamics of sorting nexin 27 in activated T cells
Authors: Rincón Esther , de Guinoa Julia Sáez , Gharbi Severine I. , Sorzano Carlos O. S. , Carrasco Yolanda R. , Mérida Isabel
Published: February 2011

Sorting nexin 27 (SNX27) belongs to the sorting nexin family of proteins, which participate in vesicular and protein trafficking. Similarly to all sorting nexin proteins, SNX27 has a functional PX domain that is important for endosome binding, but it is the only sorting nexin with a PDZ domain. We identified SNX27 as a partner of diacylglycerol kinase ζ (DGKζ), a negative regulator of T cell function that metabolises diacylglycerol to yield phosphatidic acid. SNX27 interacts with the DGKζ PDZ-binding motif in early/recycling endosomes in resting T cells; however, the dynamics and mechanisms underlying SNX27 subcellular localisation during T cell activation are unknown. We demonstrate that in T cells that encounter pulsed antigen-presenting cells, SNX27 in transit on early/recycling endosomes polarise to the immunological synapse. A fraction of SNX27 accumulates at the mature immunological synapse in a process that is dependent on vesicular trafficking, binding of the PX domain to phosphatidylinositol 3-phosphate and the presence of the PDZ region. Downmodulation of expression of either SNX27 or DGKζ results in enhanced basal and antigen-triggered ERK phosphorylation. These results identify SNX27 as a PDZ-containing component of the T cell immunological synapse, and demonstrate a role for this protein in the regulation of the Ras–ERK pathway, suggesting a functional relationship between SNX27 and DGKζ.
Electron tomography reveals a flared morphology on growing microtubule ends
Authors: Höög Johanna L. , Huisman Stephen M. , Sebö-Lemke Zsofia , Sandblad Linda , McIntosh J. Richard , Antony Claude , Brunner Damian
Published: February 2011

Microtubules (MTs) exhibit dynamic instability, alternating between phases of growth and shortening, mostly at their uncapped plus ends. Based on results from cryo-electron microscopy it was proposed that growing MTs display mainly curved sheets and blunt ends; during depolymerisation curled ‘ramshorns’ predominate. Observations of MTs in mitotic cells have suggested that the situation in vivo differs from that in vitro, but so far, a clear comparison between in vivo and in vitro results has not been possible because MT end structures could not be correlated directly with the dynamic state of that particular MT. Here we combine light microscopy and electron tomography (ET) to show that growing MT plus ends in the fission yeast Schizosaccharomyces pombe display predominantly a flared morphology. This indicates that MT polymerisation in vivo and in vitro can follow different paths.
Proteomic analysis of endocytic vesicles: Rab1a regulates motility of early endocytic vesicles
Authors: Mukhopadhyay Aparna , Nieves Edward , Che Fa-Yun , Wang Jean , Jin Lianji , Murray John W. , Gordon Kristie , Angeletti Ruth Hogue , Wolkoff Allan W.
Published: February 2011

Texas-Red–asialoorosomucoid (ASOR) fluorescence-sorted early and late endocytic vesicles from rat liver were subjected to proteomic analysis with the aim of identifying functionally important proteins. Several Rab GTPases, including Rab1a, were found. The present study immunolocalized Rab1a to early and late endocytic vesicles and examined its potential role in endocytosis. Huh7 cells with stable knockdown of Rab1a exhibited reduced endocytic processing of ASOR. This correlated with the finding that Rab1a antibody reduced microtubule-based motility of rat-liver-derived early but not late endocytic vesicles in vitro. The inhibitory effect of Rab1a antibody was observed to be specifically towards minus-end-directed motility. Total and minus-end-directed motility was also reduced in early endocytic vesicles prepared from Rab1a-knockdown cells. These results corresponded with virtual absence of the minus-end-directed kinesin Kifc1 from early endocytic vesicles in Rab1a knockdown cells and imply that Rab1a regulates minus-end-directed motility largely by recruiting Kifc1 to early endocytic vesicles.
Nesprin-3 augments peripheral nuclear localization of intermediate filaments in zebrafish
Authors: Postel Ruben , Ketema Mirjam , Kuikman Ingrid , de Pereda José M. , Sonnenberg Arnoud
Published: February 2011

The outer nuclear membrane protein nesprin-3 binds the cytoskeletal linker protein plectin, which are proposed to anchor the intermediate filaments to the nuclear envelope. To investigate the function of nesprin-3 in vivo, we used the zebrafish as a vertebrate model system. Zebrafish nesprin-3 is expressed at the nuclear envelope of epidermal and skeletal muscle cells during development. Unexpectedly, loss of nesprin-3 did not affect embryonic development, viability or fertility. However, nesprin-3-deficient zebrafish embryos showed a reduced concentration of intermediate filaments around the nucleus. Additional analysis revealed the presence of two nesprin-3 isoforms in zebrafish, nesprin-3α and nesprin-3β. Nesprin-3β is only expressed during early development and lacks seven amino acids in its first spectrin repeat that are crucial for plectin binding and recruitment to the nuclear envelope. These seven amino acids are highly conserved and we showed that residues R43 and L44 within this motif are required for plectin binding. Furthermore, several residues in the actin-binding domain of plectin that are crucial for binding to the integrin β4 subunit are also important for the binding to nesprin-3α, indicating partial overlapping binding sequences for nesprin-3α and integrin β4. All this shows that nesprin-3 is dispensable for normal development in zebrafish, but important for mediating the association of the intermediate filament system with the nucleus in vivo.
Using double-stranded RNA to explore the role of heat shock protein genes in heat tolerance in Bemisia tabaci (Gennadius)
Authors: Lü Zhi-Chuang , Wan Fang-Hao
Published: February 2011

The whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) biotype B, is one of the most destructive invasive pests of field and glasshouse crops, and has a high tolerance to heat. Our previous work found that whitefly females are more heat tolerant than males. In the present study, real-time PCR and double-stranded RNA (dsRNA) methods were used to explore the role of heat shock protein (Hsp) genes in whitefly of both sexes; this provided further evidence of the mechanism underlying the differential heat tolerance abilities of females and males. The results showed that both hsp23 and hsp70 mRNA expression levels were higher in females than in males from 37.5 to 42°C, while at the extreme temperature of 44°C the hsp70 mRNA level was higher in males than in females. There was no significant difference in hsp90 mRNA expression between females and males under heat shock conditions. Furthermore, the survival rate of females fed hsp23 or hsp70 dsRNA significantly decreased following heat shock at 44°C for 1 h, but male survival rate was not significantly affected. Additionally, the survival rate of both females and males showed no significant change after they were fed with hsp90 dsRNA. Collectively, the present study shows that the optimum mRNA expression of Hsp genes in females promotes a higher survival rate under heat shock conditions; hsp23 and hsp70 play a key role for heat tolerance in females but not in males, and hsp90 shows no significant role in heat tolerance in either females or males. Further, our study indicates that feeding with dsRNA is an effective method by which to study gene function, and the simplicity of this approach opens the way for further research on gene function in different sexes and diverse groups of species.
Climbing flight performance and load carrying in lesser dog-faced fruit bats (Cynopterus brachyotis)
Authors: MacAyeal Leigh C. , Riskin Daniel K. , Swartz Sharon M. , Breuer Kenneth S.
Published: February 2011

The metabolic cost of flight increases with mass, so animals that fly tend to exhibit morphological traits that reduce body weight. However, all flying animals must sometimes fly while carrying loads. Load carrying is especially relevant for bats, which experience nightly and seasonal fluctuations in body mass of 40% or more. In this study, we examined how the climbing flight performance of fruit bats (Cynopterus brachyotis; N=4) was affected by added loads. The body weights of animals were experimentally increased by 0, 7, 14 or 21% by means of intra-peritoneal injections of saline solution, and flights were recorded as animals flew upwards in a small enclosure. Using a model based on actuator disk theory, we estimated the mechanical power expended by the bats as they flew and separated that cost into different components, including the estimated costs of hovering, climbing and increasing kinetic energy. We found that even our most heavily loaded bats were capable of upward flight, but as the magnitude of the load increased, flight performance diminished. Although the cost of flight increased with loading, bats did not vary total induced power across loading treatment. This resulted in a diminished vertical velocity and thus shallower climbing angle with increased loads. Among trials there was considerable variation in power production, and those with greater power production tended to exhibit higher wingbeat frequencies and lower wing stroke amplitudes than trials with lower power production. Changes in stroke plane angle, downstroke wingtip velocity and wing extension did not correlate significantly with changes in power output. We thus observed the manner in which bats modulated power output through changes in kinematics and conclude that the bats in our study did not respond to increases in loading with increased power output because their typical kinematics already resulted in sufficient aerodynamic power to accommodate even a 21% increase in body weight.
Behavioural evidence for a sleep-like quiescent state in a pulmonate mollusc, Lymnaea stagnalis (Linnaeus)
Authors: Stephenson Richard , Lewis Vern
Published: February 2011

The objective of this study was to determine whether the great pond snail, Lymnaea stagnalis, expresses a sleep-like behavioural state. We found that snails spontaneously enter a relatively brief (22±1 min) quiescent state characterized by postural relaxation of the foot, mantle and tentacles, and cessation of radula rasping. Quiescence was reversed (‘aroused’) by appetitive (sucrose solution) and aversive (tactile) stimuli. Responsiveness to both stimuli was significantly lower in quiescent snails than in active snails. However, tactile stimuli evoked a more sustained defensive response in quiescent snails. Quiescence bouts were consolidated into ‘clusters’ over an infradian timescale and were only weakly affected by time of day. Clusters contained 7±0.5 bouts, lasted 13±1 h and were separated by long (37±4 h) intervals of almost continuous activity. Analysis of Kaplan–Meier survival curves revealed that the quiescent bout duration was described by an exponential probability distribution (time constant 15±1 min). Active bout duration was described by a bi-exponential probability distribution (time constants 62±4 and 592±48 min). We found no evidence for a ‘sleep rebound’ mechanism and quiescence expression appeared to be regulated through stochastic processes causing state transitions to resemble a Markovian random walk. We conclude that Lymnaea is a potentially valuable model system for studies of cellular function in sleep.
Biomechanics of hair cell kinocilia: experimental measurement of kinocilium shaft stiffness and base rotational stiffness with Euler–Bernoulli and Timoshenko beam analysis
Authors: Spoon Corrie , Grant Wally
Published: February 2011

Vestibular hair cell bundles in the inner ear contain a single kinocilium composed of a 9+2 microtubule structure. Kinocilia play a crucial role in transmitting movement of the overlying mass, otoconial membrane or cupula to the mechanotransducing portion of the hair cell bundle. Little is known regarding the mechanical deformation properties of the kinocilium. Using a force-deflection technique, we measured two important mechanical properties of kinocilia in the utricle of a turtle, Trachemys (Pseudemys) scripta elegans. First, we measured the stiffness of kinocilia with different heights. These kinocilia were assumed to be homogenous cylindrical rods and were modeled as both isotropic Euler–Bernoulli beams and transversely isotropic Timoshenko beams. Two mechanical properties of the kinocilia were derived from the beam analysis: flexural rigidity (EI) and shear rigidity (kGA). The Timoshenko model produced a better fit to the experimental data, predicting EI=10,400 pN μm2 and kGA=247 pN. Assuming a homogenous rod, the shear modulus (G=1.9 kPa) was four orders of magnitude less than Young's modulus (E=14.1 MPa), indicating that significant shear deformation occurs within deflected kinocilia. When analyzed as an Euler–Bernoulli beam, which neglects translational shear, EI increased linearly with kinocilium height, giving underestimates of EI for shorter kinocilia. Second, we measured the rotational stiffness of the kinocilium insertion (κ) into the hair cell's apical surface. Following BAPTA treatment to break the kinocilial links, the kinocilia remained upright, and κ was measured as 177±47 pN μm rad–1. The mechanical parameters we quantified are important for understanding how forces arising from head movement are transduced and encoded by hair cells.
Ontogeny of lift and drag production in ground birds
Authors: Heers Ashley M. , Tobalske Bret W. , Dial Kenneth P.
Published: February 2011

The juvenile period is often a crucial interval for selective pressure on locomotor ability. Although flight is central to avian biology, little is known about factors that limit flight performance during development. To improve understanding of flight ontogeny, we used a propeller (revolving wing) model to test how wing shape and feather structure influence aerodynamic performance during development in the precocial chukar partridge (Alectoris chukar, 4 to >100 days post hatching). We spun wings in mid-downstroke posture and measured lift (L) and drag (D) using a force plate upon which the propeller assembly was mounted. Our findings demonstrate a clear relationship between feather morphology and aerodynamic performance. Independent of size and velocity, older wings with stiffer and more asymmetrical feathers, high numbers of barbicels and a high degree of overlap between barbules generate greater L and L:D ratios than younger wings with flexible, relatively symmetrical and less cohesive feathers. The gradual transition from immature feathers and drag-based performance to more mature feathers and lift-based performance appears to coincide with ontogenetic transitions in locomotor capacity. Younger birds engage in behaviors that require little aerodynamic force and that allow D to contribute to weight support, whereas older birds may expand their behavioral repertoire by flapping with higher tip velocities and generating greater L. Incipient wings are, therefore, uniquely but immediately functional and provide flight-incapable juveniles with access to three-dimensional environments and refugia. Such access may have conferred selective advantages to theropods with protowings during the evolution of avian flight.
The protective role of aquaporins in the freeze-tolerant insect Eurosta solidaginis: functional characterization and tissue abundance of EsAQP1
Authors: Philip Benjamin N. , Kiss Andor J. , Lee Richard E.
Published: February 2011

The movement of water and small solutes is integral to the survival of freezing and desiccation in insects, yet the underlying mechanisms of these processes are not fully known. Recent evidence suggests that aquaporin (AQP) water channels play critical roles in protecting cells from osmotic damage during freezing and desiccation. Our study sequenced, functionally characterized and measured the tissue abundance of an AQP from freeze-tolerant larvae of the gall fly, Eurosta solidaginis (Diptera: Tephritidae). The newly characterized EsAQP1 contains two NPA motifs and six transmembrane regions, and is phylogenetically related to an AQP from the anhydrobiotic chironomid Polypedilum vanderplanki. Using a Xenopus laevis oocyte swelling assay, we demonstrated that EsAQP1 increases water permeability to nine times that of simple diffusion through the membrane. In contrast to its high water permeability, EsAQP1 was impermeable to both glycerol and urea. The abundance of EsAQP1 increased from October to December in all tissues tested and was most abundant in the brain of winter larvae. Because the nervous system is thought to be the primary site of freezing injury, EsAQP1 may cryoprotect the brain from damage associated with water imbalance. The sequence, phylogenetic relationship, osmotic permeability, tissue distribution and seasonal abundance of EsAQP1 further support the role of AQPs in promoting freezing tolerance.
The role of the gut in insect chilling injury: cold-induced disruption of osmoregulation in the fall field cricket,Gryllus pennsylvanicus
Authors: MacMillan Heath A. , Sinclair Brent J.
Published: February 2011

To predict the effects of changing climates on insect distribution and abundance, a clear understanding of the mechanisms that underlie critical thermal limits is required. In insects, the loss of muscle function and onset of cold-induced injury has previously been correlated with a loss of muscle resting potential. To determine the cause of this loss of function, we measured the effects of cold exposure on ion and water homeostasis in muscle tissue, hemolymph and the alimentary canal of the fall field cricket, Gryllus pennsylvanicus, during an exposure to 0°C that caused chilling injury and death. Low temperature exposure had little effect on muscle osmotic balance but it dissipated muscle ion equilibrium potentials through interactions between the hemolymph and gut. Hemolymph volume declined by 84% during cold exposure whereas gut water content rose in a comparable manner. This rise in water content was driven by a failure to maintain osmotic equilibrium across the gut wall, which resulted in considerable migration of Na+, Ca2+ and Mg2+ into the alimentary canal during cold exposure. This loss of homeostasis is likely to be a primary mechanism driving the cold-induced loss of muscle excitability and progression of chilling injury in chill-susceptible insect species.
Biomechanics of jumping in the flea
Authors: Sutton Gregory P. , Burrows Malcolm
Published: February 2011

It has long been established that fleas jump by storing and releasing energy in a cuticular spring, but it is not known how forces from that spring are transmitted to the ground. One hypothesis is that the recoil of the spring pushes the trochanter onto the ground, thereby generating the jump. A second hypothesis is that the recoil of the spring acts through a lever system to push the tibia and tarsus onto the ground. To decide which of these two hypotheses is correct, we built a kinetic model to simulate the different possible velocities and accelerations produced by each proposed process and compared those simulations with the kinematics measured from high-speed images of natural jumping. The in vivo velocity and acceleration kinematics are consistent with the model that directs ground forces through the tibia and tarsus. Moreover, in some natural jumps there was no contact between the trochanter and the ground. There were also no observable differences between the kinematics of jumps that began with the trochanter on the ground and jumps that did not. Scanning electron microscopy showed that the tibia and tarsus have spines appropriate for applying forces to the ground, whereas no such structures were seen on the trochanter. Based on these observations, we discount the hypothesis that fleas use their trochantera to apply forces to the ground and conclude that fleas jump by applying forces to the ground through the end of the tibiae.
Synthesis and Fluorescence Tuning of Novel Nitroxides with a Binaphthyl Framework
Authors: Wang Haibo , Jing Linlin , Xiang Zhuo , Liu Peng , Sun Xiaoli , Jiang Ru
Published: February 2011

Four novel nitroxides were synthesized, and the fluorescence tuning of these molecules with the action of different chemical inputs was investigated; the results suggested that these nitroxides could serve as a redox fluorescence switch.
Intercalation Reaction of Carbonate MgAl-layered Double Hydroxide Using Alcohol as Solvent
Authors: Hayashi Aki , Nakayama Hirokazu
Published: February 2011

We succeeded in the first direct intercalation of an organic compound into carbonate layered double hydroxide (LDH) by using alcohol as the solvent at 50 °C. Furthermore, carbonate ion in carbonate LDH was easily exchanged with chloride or nitrate ion in methanol.
Fluorescence Probes for Tyrosine Dephosphorylation Based on Coumarin–Proline Conjugates
Authors: Choi Kihang , Park Bongjeong , Han So-Yeong , Ahn Hee Choon
Published: February 2011

Proline-substituted coumarin compounds were prepared and used as environment-sensitive fluorescence probes. Phosphorylation and dephosphorylation of tyrosine derivatives labeled with the coumarin–proline conjugate induced marked changes in fluorescence intensity allowing phosphatase activity to be monitored.
Snake bites in Moyen Chari district, Chad: a five-year experience
Authors: Bregani Enrico Rino , Maraffi Tommaso , Van Tien Tu
Published: February 2011

Snake bites are of major public health importance in Africa as a cause of morbidity and mortality. Echis ocellatus is responsible for the majority of envenomation cases in West Africa. Antivenom immunotherapy is the only specific treatment available for envenomed patients. From January 1997 to December 2001, 325 patients suffering from snake bites were enrolled in a survey undertaken at Goundi Hospital, Chad. We analysed the percentage of envenomed patients, sex distribution, distribution along the year, lethality, hospital stay and recovery clotting time. Two hundred and ninety-eight patients showed signs of envenomation and were treated with antivenom immunotherapy with three different sera in consecutive periods. Young males were more frequently involved. The overall lethality was 8%. Lethality and hospital stay were significantly different in the differently treated patients. Most of the data in our series were similar to those from other sub-Saharan countries but, overall, the percentage of snake bite victims who were admitted to hospital was higher.
Understanding ribosome assembly: the structure of in vivo assembled immature 30S subunits revealed by cryo-electron microscopy
Authors: Jomaa Ahmad , Stewart Geordie , Martín-Benito Jaime , Zielke Ryszard , Campbell Tracey L. , Maddock Janine R. , Brown Eric D. , Ortega Joaquin
Published: February 2011

Four decades after early in vitro assembly studies demonstrated that ribosome assembly is a controlled process, our understanding of ribosome assembly is still incomplete. Just as structure determination has been so important to understanding ribosome function, so too will it be critical to sorting out the assembly process. Here, we used a viable deletion in theyjeQgene, a recognized ribosome assembly factor, to isolate and structurally characterize immature 30S subunits assembled in vivo. These small ribosome subunits contained unprocessed 17S rRNA and lacked some late ribosomal proteins. Cryo-electron microscopy reconstructions revealed that the presence of precursor sequences in the rRNA induces a severe distortion in the 3′ minor domain of the subunit involved in the decoding of mRNA and interaction with the large ribosome subunit. These findings suggest that rRNA processing events induce key local conformational changes directing the structure toward the mature assembly. We concluded that rRNA processing, folding, and the entry of tertiary r-proteins are interdependent events in the late stages of 30S subunit assembly. In addition, we demonstrate how studies of emerging assembly factors in ribosome biogenesis can help to elucidate the path of subunit assembly in vivo.
Support Vector Machines with the Ramp Loss and the Hard Margin Loss
Authors: Brooks J. Paul
Published: February 2011

In the interest of deriving classifiers that are robust to outlier observations, we present integer programming formulations of Vapnik's support vector machine (SVM) with the ramp loss and hard margin loss. The ramp loss allows a maximum error of 2 for each training observation, while the hard margin loss calculates error by counting the number of training observations that are in the margin or misclassified outside of the margin. SVM with these loss functions is shown to be a consistent estimator when used with certain kernel functions. In computational studies with simulated and real-world data, SVM with the robust loss functions ignores outlier observations effectively, providing an advantage over SVM with the traditional hinge loss when using the linear kernel. Despite the fact that training SVM with the robust loss functions requires the solution of a quadratic mixed-integer program (QMIP) and is NP-hard, while traditional SVM requires only the solution of a continuous quadratic program (QP), we are able to find good solutions and prove optimality for instances with up to 500 observations. Solution methods are presented for the new formulations that improve computational performance over industry-standard integer programming solvers alone.
The Price of Fairness
Authors: Bertsimas Dimitris , Farias Vivek F. , Trichakis Nikolaos
Published: February 2011

In this paper we study resource allocation problems that involve multiple self-interested parties or players and a central decision maker. We introduce and study the price of fairness, which is the relative system efficiency loss under a “fair” allocation assuming that a fully efficient allocation is one that maximizes the sum of player utilities. We focus on two well-accepted, axiomatically justified notions of fairness, viz., proportional fairness and max-min fairness. For these notions we provide a tight characterization of the price of fairness for a broad family of problems.
TECHNICAL NOTE—Exact Analysis of a Lost Sales Model Under Stuttering Poisson Demand
Authors: Chen Jie , Jackson Peter L. , Muckstadt John A.
Published: February 2011

We investigate the (S − 1, S) inventory policy under stuttering Poisson demand and generally distributed lead time when the excess demand is lost. We correct results presented in Feeney and Sherbrooke's seminal paper [Feeney, G. J., C. C. Sherbrooke. 1966. The (S − 1, S) inventory policy under compound Poisson demand. Management Sci. 12(5) 391–411] and note that the stationary distribution of units on order for the general compound Poisson demand case is still an open question.
An Exact Algorithm for the Period Routing Problem
Authors: Baldacci Roberto , Bartolini Enrico , Mingozzi Aristide , Valletta Andrea
Published: February 2011

This paper presents an exact algorithm for solving strategic and tactical multiperiod vehicle routing problems that can be modeled as period vehicle routing problems (PVRPs). The PVRP is defined on a time horizon of several days and consists of assigning appropriate combinations of delivery to customers and designing a set of delivery routes for every day of the planning period. The objective is to service all customers assigned to each day minimizing the overall routing cost. This paper describes an integer programming formulation of the PVRP that is used to derive different lower bounds and an exact solution method. Computational results on test instances from the literature and on new sets of test instances show the effectiveness of the proposed method.
Making Organizational Theory Work: Institutions, Occupations, and Negotiated Orders
Authors: Bechky Beth A.
Published: February 2011

In this essay I argue that organizational theorizing would benefit from incorporating a richer understanding of work and occupations. To demonstrate how, I turn to recent literature analyzing inhabited institutions, occupations as institutions, and occupations as negotiated orders. I explore the theoretical and methodological implications of these approaches to show how they challenge some of our more abstract images of organizations. They do so by grounding their theoretical frameworks in work practices and interaction, interpretation and meaning, and understandings of occupational membership.