bluuebunny/crossref_metadata_2025 huggingface dataset:
Transport from Higher Order g‐Jitter Effects
Authors: NAUMANN ROBERT J.
Published: July 2009

Abstract: Large complex spacecraft, such as the International Space Station (ISS), will have a rich spectrum of vibrational modes that will be excited by crew activity as well as by on‐board mechanical systems. The response of various experiments to this vibratory environment is not completely understood and has been a subject of concern to the users community. Since these vibrations arise for the most part from internal forces, the net acceleration must time‐average to zero. Steady state periodic accelerations applied to a fluid in a completely filled container with an imposed density gradient will drive first‐order flows that time‐average to zero. Likewise, the resulting first‐order thermal and solutal fluctuations time‐average to zero. Over the range of frequencies in the vibrational environment expected on the ISS, the velocity oscillations tend to be nearly 90° out of phase with the thermal and/or solutal fluctuations; consequently, little net transport occurs from the first‐order effects. We must, therefore, examine possible higher‐order effects that can lead to significant net transport. Second‐order flows with non‐zero time averages arise from the non‐linear terms in the flow equations and from incomplete cancellation of first‐order flows if the density gradient changes with time, or if the periodic acceleration has both axial and transverse components relative to the imposed density gradient. The time‐average of such flows can be expressed in terms of the sum of the square of each periodic acceleration, weighted by the appropriate function of the frequency, taken over all frequencies; or as the weighted integral over the power spectral distribution (PSD) of the frequency spectrum. Approximate analytical solutions for these second‐order flows, which agree closely with numerical computations, have been found using a perturbation analysis. These analytical models are then used to predict the effects of the anticipated vibratory environment on various classes of experiments planned for the ISS. Even though these second‐order flows are much smaller than the first‐order flows, it is shown that they can produce significant transport.
Dynamics of Single and Multiple Bubbles and Associated Heat Transfer in Nucleate Boiling Under Low Gravity Conditions
Authors: QIU D. , SON G. , DHIR V. K. , CHAO D. , LOGSDON K.
Published: July 2009

Abstract:Experimental studies and numerical simulation of growth and lift‐off processes of single bubbles formed on designed nucleation sites have been conducted under low‐gravity conditions. Merging of multiple bubbles and lift‐off processes during boiling of water in the parabola flights of KC‐135 aircraft were also experimentally studied. The heating area of the flat heater surface was discretized and equipped with a number of small heating elements that were separately powered in the temperature‐control mode. As such, the wall superheat remained nearly constant during the growth and departure of the bubbles, whereas the local heat flux varied during the boiling process. From numerical calculation it is found that peak of heat flux occurs locally at the contact line of bubble and heater surface. Dry conditions exist inside the bubble base area, which is characterized through a zero heat flux region in the numerical calculation and a lower heat flux period in the experimental results. During the merger of multiple bubbles, dry‐out continues. In both the numerical calculations and experimental results, the bubble lift‐off is associated with an apparent increase in heat flux. Wall heat flux variation with time and spatial distribution during the growth of a single bubble from numerical simulations are compared with experimental data.
Vapor Transport Growth of Organic Solids in Microgravity and Unit Gravity
Authors: ZUGRAV MARIA ITTU , CARSWELL WILLIAM E. , HAULENBEEK GLEN B. , SANGHADASA MOHAN , O'BRIEN SUE K. , GHITA BOGDAN C. , GATHINGS WILLIAM E.
Published: July 2009

Abstract: Thin films of an organic nonlinear optical (NLO) material, N, N‐dimethyl‐p‐(2,2‐dicyanovinyl) aniline (DCVA), have been grown in space and on the ground by physical vapor transport in an effusive ampoule arrangement. The thin film growth technique developed on the ground is a direct result of information gleaned from experiments in microgravity. This paper covers the results of our experimental investigations for establishing “ideal” terrestrial conditions for deposition of a DCVA film. The active control during the deposition process was exercised by three deposition variables: the material source temperature, the background pressure external to the growth ampoule and the substrate temperature. Successful growth occurred when the difference in temperature between the source material and the copper substrate was 14°C and the background nitrogen pressure was such that the transport was either diffusive or convective. A qualitative diffusion limited boundary was estimated to occur at a pressure of approximately 20 torr. We have probed the DCVA thin films with visible‐near infrared reflection absorption spectroscopy, polarized Fourier transform infrared spectrometry, differential interference contrast optical microscopy, and stylus profilometry.
Historical Background and Anticipated Developments
Authors: JORDAN BERTRAND
Published: July 2009

Abstract: Expression profiling using DNA arrays is often believed to have appeared during the second half of the 1990s, and to be based exclusively on nonisotopic methods. In fact, the first article describing the application of cDNA arrays to expression analysis was published in 1992, relied on radioactive labeling, and was a new development of “high‐density” membranes used until then essentially for efficient screening of libraries. Several papers described the use of this technology for simultaneous expression measurement of thousands of genes at the time when the first glass microarrays were published. Simultaneously, oligonucleotide chips, originally developed for resequencing and mutation detection applications, were shown to be capable of expression measurement as well. The three approaches have developed over the years and still coexist, as each of them has specific advantages (and drawbacks); the major issues have become those of data quality, data analysis and storage (ideally in a common public database). Meanwhile, the technology continues to evolve. The most obvious trend is a shift towards using arrays of relatively long oligonucleotides that combine most of the advantages of very long (cDNA) and very short (25‐mer) DNA segments. The search for better detection methods, ideally without labeling of the sample, is continuing, although it seems difficult to reach the required sensitivity. New materials for microarray manufacture and new implementations of existing methods have appeared. In addition, the field is progressively becoming segmented into high gene number, low volume (research) applications on the one hand, and low gene number, high throughput (diagnostic) uses on the other.
IL‐15 Is a Growth Factor and an Activator of CD8 Memory T Cells
Authors: WENG NAN‐PING , LIU KEBIN , CATALFAMO MARTA , LI YU , HENKART PIERRE A.
Published: July 2009

Abstract: Memory lymphocytes, arising from naïve lymphocytes after antigenic stimulation and being long‐lived, are the cellular basis for immunological memory. Recent studies of CD8 T cells suggest that generation of CD8 memory T cells requires the engagement of T cell antigen receptors (TCR) with antigen, yet the maintenance of CD8 memory T cells appears to be dependent on cytokines, such as IL‐15, independent of TCR. Although considerable progress has been made in understanding the molecular and cellular events of TCR‐induced differentiation and proliferation in the past decade, less is known about the mechanisms of IL‐15 action. From a kinetic and comparative analysis of the responses of memory phenotype CD8 T cells to IL‐15 and TCR stimulation in vitro, we found that IL‐15 and anti‐CD3 induce highly similar responses in memory phenotype CD8 T cells as measured by general gene expression profiles, synthesis of effector molecules (IFNγ, TNFβ, granzyme B and perforin), induction of cytotoxicity, and cellular proliferation. These findings indicate that IL‐15 is not only a growth factor but also an antigen‐independent activator for CD8 memory T cells.
A Genomic View of Helper T Cell Subsets
Authors: ROGGE LARS
Published: July 2009

Abstract: Genomic‐scale gene expression profiling in combination with the availability of a draft sequence of the human genome is beginning to revolutionize the way immunology is done. The possibility of measuring levels of gene expression for tens of thousands of genes simultaneously and in a quantitative fashion aids in the definition of a comprehensive molecular phenotype of cells and cellular processes of the immune system in health and disease. T helper lymphocytes are an essential element of appropriate immune responses to pathogens. To achieve effective immunity, T helper cells differentiate into at least two specialized subsets that direct type 1 and type 2 immune responses. Here, I discuss recent progress that has been made in our understanding of the genetic program that controls the development and functional properties of helper T cell subsets.
Complexity of Inflammatory Responses in Endothelial Cells and Vascular Smooth Muscle Cells Determined by Microarray Analysis
Authors: BANDMAN OLGA , COLEMAN ROGER T. , LORING JEANNE F. , SEILHAMER JEFFREY J. , COCKS BENJAMIN G.
Published: July 2009

Abstract: To better understand the molecular basis of vascular cell system behavior in inflammation, we used gene expression microarrays to analyze the expression of 7,075 genes and their response to IL‐1β and TNFα in cultures of coronary artery endothelium and smooth muscle derived from a single coronary artery. The most noticeable difference between the cell types was the considerably greater magnitude and complexity of the transcriptional response in the endothelial cells. Two hundred and nine genes were regulated in the endothelium and only 39 in vascular smooth muscle. Among the 209 regulated genes in the endothelium, 99 have not been previously associated with endothelial cell activation and many implicate the endothelium in unconventional roles. For example, the induced genes include several that have only been associated with leukocyte function (e.g., IL‐7 receptor, EBI‐3 receptor) and others related to antiviral and antibacterial defense (e.g., oligoadenylate synthetase, LMP7, toll‐like receptor 4, complement component 3). In addition, 43 genes likely to participate in signal transduction (eg. IL‐18 receptor, STK2 kinase, STAF50, ANP receptor, VIP receptor, RAC3, IFP35) were regulated providing evidence that a major effect of TNFα and IL‐1β is to alter the potential of the endothelial cell to respond to various other external stimuli.
CD30—Governor of Memory T Cells?
Authors: PODACK ECKHARD R. , STRBO NATASA , SOTOSEC VLATKA , MUTA HIROMI
Published: July 2009

Abstract: CD30 is well recognized as a marker expressed by a heterogeneous group of lymphomas and in several immune and autoimmune disorders. However, the function of CD30 in theses diseases or in the normal immune response has remained unclear. Studying gene expression patterns induced by stimulating CD30 signals on a large granular lymphoma cell line, YT, with an agonistic anti‐CD30 antibody, we found that CD30 signals affected proapoptotic and antiapoptotic genes, regulated cytotoxicity, and controlled molecules regulating T cell traffic. Creating CD30‐L deficient mice and studying CD8 CTL activation and memory responses, it was observed that the absence of CD30‐L resulted in diminished primary clonal expansion of CD8 cells. In addition the absence of CD30‐L abolished clonal contraction after primary expansion and interfered with secondary expansion upon boosting. The studies suggest that CD30 regulates CD8 CTL function and survival during memory responses and is important for clonal contraction.
A Short Domain within Bcl‐3 Is Responsible for Its Lymphocyte Survival Activity
Authors: MITCHELL THOMAS C. , THOMPSON BRUCE S. , TRENT JOHN O. , CASELLA CAROLYN R.
Published: July 2009

Abstract: The NFκB factor Bcl‐3 influences the survival of T cells when they are activated to take part in immune responses. Because treatment of mice with adjuvant results in the increased expression of Bcl‐3 in T cells, where it has survival‐promoting effects, Bcl‐3 may be an important, limiting factor that is supplied to T cells only when they are contributing to an appropriate immune response to infection, and not when spuriously activated by self‐antigens. Although Bcl‐3 is a member of the NFκB/Rel/IκB family of transcription factors, the means by which it promotes T cell survival is not obvious because Bcl‐3 is unique in having an ankyrin repeat domain, like inhibitory IκB proteins, while also possessing domains capable of transcriptional activation, like Rel proteins. In order to understand the basis for the survival activity of Bcl‐3, deletion mutants were engineered and tested in a retroviral gene transfer sytem. We report that most of Bcl‐3 can be deleted without diminishing its ability to prolong the survival of activated T and B cells, and find that its lymphocyte survival domain maps to the vicinity of its first and second ankryin repeats. This information sets the stage for experiments in which a focused search can be made for mediators of Bcl‐3 survival effects.
Antibodies to Neuronal Targets in Neurological and Psychiatric Diseases
Authors: VINCENT ANGELA , DALTON PAOLA , CLOVER LINDA , PALACE JACKIE , LANG BETHAN
Published: July 2009

Abstract: The role of antibodies to specific neuronal and muscle ion channels in the etiology of neuromuscular transmission disorders is now well accepted. In addition, maternal antibodies can cross the placenta and cause neonatal disease or even alter the development of the infant, raising the possibility that some neurodevelopmental conditions could be caused by maternal antibodies. Voltage‐gated ion channels are expressed in the brain as well as at the neuromuscular junction, and in recent years it has become clear that antibodies to some central nervous system (CNS) channels can be associated with CNS disease. This review highlights features of these conditions, preliminary investigations into neurodevelopmental disorders, and areas for further study.
Stress, Leukocyte Trafficking, and the Augmentation of Skin Immune Function
Authors: DHABHAR FIRDAUS S.
Published: July 2009

Abstract: Delayed type hypersensitivity (DTH) reactions represent cell‐mediated immune responses that exert important immunoprotective (resistance to viruses, bacteria, and fungi) or immunopathologic (allergic or autoimmune hypersensitivity) effects. We have used the skin DTH response as an in vivo model to study neuro‐endocrine‐immune interactions. We hypothesized that just as an acute stress response prepares the cardiovascular and musculoskeletal systems for fight or flight, it may also prepare the immune system for challenges (e.g., wounding) that may be imposed by a stressor (e.g., an aggressor). Studies showed that acute (2 hours) stress experienced before primary or secondary cutaneous antigen exposure induces significantly enhanced skin DTH. This enhancement involves innate as well as adaptive immune mechanisms. Adrenalectomy eliminates the stress‐induced enhancement of DTH. Acute administration of physiological concentrations of corticosterone and/or epinephrine to adrenalectomized animals enhances skin DTH. Compared with those in controls, DTH sites from acutely stressed or hormone‐injected animals show significantly greater erythema and induration, numbers of infiltrating leukocytes, and levels of cytokine gene expression. In contrast to acute stress, chronic stress is immunosuppressive. Chronic exposure to corticosterone or acute exposure to dexamethasone significantly suppresses skin DTH. These results suggest that during acute stress, endogenous stress hormones enhance skin immunity by increasing leukocyte trafficking and cytokine gene expression at the site of antigen entry. Elucidation of mechanisms mediating a stress‐induced enhancement of skin immune function is important because such immunoenhancement can have protective (wound healing, resistance to infection) or pathological (allergic or autoimmune hypersensitivity) consequences.
Anti‐Inflammatory Potential of Melanocortin Receptor‐Directed Drugs
Authors: SKOTTNER A. , POST C. , OCKLIND A. , SEIFERT E. , LIUTKEVICIUS E. , MESKYS R. , PILINKIENE A. , BIZIULEVICIENE G. , LUNDSTEDT T.
Published: July 2009

Abstract: Melanocortin receptor‐based drug discovery is particularly active in the field of neuroendocrine systems and is mostly related to food intake and novel obesity therapies. The immunomodulatory and anti‐inflammatory effects of nonpeptidic, low molecular weight compounds activating the melanocortin‐1 receptor (MC1R) provide a new principle for treating various types of inflammation, such as dermal, joint, and gastrointestinal, probably by virtue of the effects acting through modulation of proinflammatory and anti‐inflammatory cytokines. Several reports demonstrate that α‐MSH, for example, has anti‐inflammatory effects in different models. The aim of our study was to design, synthesize, and characterize compounds that bind to and activate the MC1R in vitro. The binding affinities are submicromolar to this receptor, and activation of the receptor (cAMP assay) varies from full agonists to partial agonists as well as antagonists. In vivo, the compounds exert prominent anti‐inflammatory effects, with efficacy in the same range as that of dexamethasone, for example. The potential advantages of MC1R‐based anti‐inflammatory effects versus glucocorticosteroids, for example, are that the latter, albeit exerting prominent anti‐inflammatory effects, also have many side effects that most likely will not characterize an MC1R‐based anti‐nflammatory drug.
Regulation of PPARγ and Obesity by Agouti/Melanocortin Signaling in Adipocytes
Authors: MYNATT RANDALL L. , STEPHENS JACQUELINE M.
Published: July 2009

Abstract: To study the potential biological role of agouti/melanocortin signaling in human adipose tissue, we engineered transgenic mice to overexpress agouti in adipose tissue. The aP2‐agouti transgenic mice become significantly heavier than littermates. The increased body weight is maintained at approximately 15% above nontransgenic mice through 20 weeks and is caused by increased fat mass. The obesity is increased by a high‐fat diet. There is no change in food intake in the aP2‐agouti mice suggesting changes in energy utilization. A possible mechanism is that the agouti/melanocortin signaling regulates levels of PPARγ. PPARγ functions as a major regulator of adipocyte differentiation and as a receptor for the antidiabetic thiazolidinediones. Agouti increases PPARγ protein levels in differentiated 3T3‐L1 adipocytes, and PPARγ expression is elevated in the fat pads of the aP2‐agouti transgenic mice. The modest weight gain observed in the transgenic mice suggests that hypothalamic pathways regulating food intake are intact and the observed adiposity is within ranges that can be achieved by a paracrine mechanism at the adipocyte level.
Proopiomelanocortin Peptides and Sebogenesis
Authors: ZHANG LI , ANTHONAVAGE MIKE , HUANG QIULING , LI WEN‐HWA , EISINGER MAGDALENA
Published: July 2009

Abstract: Previous animal studies have demonstrated that α‐melanocyte‐stimulating hormone (α‐MSH) is a sebotropic hormone in rats and that targeted disruption of melanocortin 5 receptor (MC5‐R) can down‐regulate sebum output in mice. To study the role of proopiomelanocortin (POMC) peptides in the regulation of human sebaceous lipid production and sebocyte differentiation, we established a primary human sebocyte culture system. Sebocytes were derived from normal human facial skin. Differentiation of sebocytes, induced by POMC‐derived peptides such as MSH, adrenocorticotropic hormone (ACTH), or bovine pituitary extract (BPE), resulted in the appearance of prominent cytoplasmic lipid droplets. Partial induction of sebocyte differentiation also was observed in serum‐depleted cultures, but there was very limited spontaneous differentiation in serum‐containing medium. Analysis by high‐performance thin‐layer chromatography (HPTLC) of 14C‐acetate‐labeled lipids showed a dose‐dependent increase in synthesis of sebaceous‐specific lipid (i.e., squalene) induced by NDP α‐MSH. Molecular studies using RT‐PCR showed a low level of human MC5‐R expression under serum‐free condition but a substantial increase after treatment with NDP α‐MSH or BPE. In contrast, MC1‐R expression remained the same, independent of treatment. Our data indicate that expression of MC5‐R correlates with sebocyte differentiation and suggest a regulatory role for MC5‐R in human sebaceous lipid production.
The Gut Hormone Peptide YY Regulates Appetite
Authors: BATTERHAM RACHEL L. , BLOOM STEPHEN R.
Published: July 2009

Abstract:The gut hormone peptide YY (PYY) belongs to the pancreatic polypeptide (PP) family along with PP and neuropeptide Y (NPY). These peptides mediate their effects through the NPY receptors of which there are several subtypes (Y1, Y2, Y4, and Y5). The L cells of the gastrointestinal tract are the major source of PYY, which exists in two endogenous forms: PYY1–36and PYY3–36. The latter is produced by the action of the enzyme dipeptidyl peptidase‐IV (DPP‐IV). PYY1–36binds to and activates at least three Y receptor subtypes (Y1, Y2, and Y5), whereas PYY3–36is more selective for Y2 receptor (Y2R). The hypothalamic arcuate nucleus, a key brain area regulating appetite, has access to nutrients and hormones within the peripheral circulation. NPY neurons within the arcuate nucleus express the Y2R. In response to food ingestion plasma PYY3–36concentrations rise within 15 min and plateau by approximately 90 min. The peak PYY3–36level achieved is proportional to the calories ingested, suggesting that PYY3–36may signal food ingestion from the gut to appetite‐regulating circuits within the brain. We found that peripheral administration of PYY3–36inhibited food intake in rodents and increased C‐Fos immunoreactivity in the arcuate nucleus. Moreover, direct intra‐arcuate administration of PYY3–36inhibited food intake. We have shown that Y2R null mice are resistant to the anorectic effects of peripherally administered PYY3–36, suggesting that PYY3–36inhibits food intake through the Y2R.

In humans, peripheral infusion of PYY3–36, at a dose which produced normal postprandial concentrations, significantly decreased appetite and reduced food intake by 33% over 24 h. These findings suggest that PYY3–36released in response to a meal acts via the Y2R in the arcuate nucleus to physiologically regulate food intake.
Central Serotonin and Melanocortin Pathways Regulating Energy Homeostasis
Authors: HEISLER LORA K. , COWLEY MICHAEL A. , KISHI TOSHIRO , TECOTT LAURENCE H. , FAN WEI , LOW MALCOLM J. , SMART JAMES L. , RUBINSTEIN MARCELO , TATRO JEFFREY B. , ZIGMAN JEFFREY M. , CONE ROGER D. , ELMQUIST JOEL K.
Published: July 2009

Abstract: It is now established that the hypothalamus is essential in coordinating endocrine, autonomic, and behavioral responses to changes in energy availability. However, the interaction of key peptides, neuropeptides, and neurotransmitters systems within the hypothalamus has yet to be delineated. Recently, we investigated the mechanisms through which central serotonergic (5‐hydroxytryptamine, 5‐HT) systems recruit leptin‐responsive hypothalamic pathways, such as the melanocortin systems, to affect energy balance. Through a combination of functional neuroanatomy, feeding, and electrophysiology studies in rodents, we found that 5‐HT drugs require functional melanocortin pathways to exert their effects on food intake. Specifically, we observed that anorectic 5‐HT drugs activate pro‐opiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (Arc). We provide evidence that the serotonin 2C receptor (5‐HT2CR) is expressed on POMC neurons and contributes to this effect. Finally, we found that 5‐HT drug‐induced hypophagia is attenuated by pharmacological or genetic blockade of downstream melanocortin 3 and 4 receptors. We review candidate brain regions expressing melanocortin 3 and 4 receptors that play a role in energy balance. A model is presented in which activation of the melanocortin system is downstream of 5‐HT and is necessary to produce the complete anorectic effect of 5‐HT drugs. The data reviewed in this paper incorporate the central 5‐HT system to the growing list of metabolic signals that converge on melanocortin neurons in the hypothalamus.
Agouti‐Related Protein: Appetite or Reward?
Authors: OLSZEWSKI PAWEL K. , WICKWIRE KATHIE , WIRTH MICHELLE M. , LEVINE ALLEN S. , GIRAUDO SILVIA Q.
Published: July 2009

Abstract:Agouti‐related protein (AgRP) is an orexigenic peptide that acts as an antagonist of the melanocortin‐3 and ‐4 receptors in the hypothalamus. Studies suggest that the melanocortin and opioid systems interact in the control of ingestive behavior. Also, AgRP has been shown to especially increase intake of a palatable diet. Given these observations, we wished to examine whether the effects of AgRP on ingestive behavior resemble those of opioids. AgRP was injected into the hypothalamic paraventricular nucleus in animals given a choice between a palatable sucrose solution and calorically dense chow. As a result of AgRP injection, animals increased intake of chow but not sucrose relative to controls, in contrast to what has been seen with opioid agonists. These results together with prior findings suggest that the primary effect of AgRP is to cause an increase in food intake to satisfy energy needs, though AgRP also has opioid‐like effects, possibly due to melanocortin‐opioid interactions.
Engineering the Melanocortin‐4 Receptor to Control Gs Signaling in Vivo
Authors: SRINIVASAN SUPRIYA , VAISSE CHRISTIAN , CONKLIN BRUCE R.
Published: July 2009

Abstract: G‐protein‐coupled receptors (GPCRs) are the largest known family of cell surface receptors, and they control many important physiological events, including sensory perception, chemotaxis, neurotransmission, and energy homeostasis. However, GPCR signaling can be difficult to study in vivo because of the multitude of GPCRs, the lack of specific synthetic agonists, and the fact that some GPCRs activate multiple signaling pathways. One method to circumvent these problems is to develop an engineered receptor that is unresponsive to its endogenous agonist, yet can be fully activated by synthetic, small‐molecule drugs. Such a receptor, called a receptor activated solely by a synthetic ligand (RASSL), can be rapidly and reversibly activated by a small‐molecule drug and would be a powerful tool to control G‐protein signaling in vivo. Here we present the development of a Gs‐coupled RASSL based on the melanocortin‐4 receptor (MC4R). MC4R couples exclusively to Gs at physiologically relevant concentrations of its endogenous ligand, α‐melanocyte‐stimulating hormone (α‐MSH). Data from human patients and structure‐activity studies have shown that several mutations in MC4R cause a decreased affinity for α‐MSH and can be exploited for RASSL development. Synthetic, small‐molecule agonists of MC4R are now available and can be used to activate mutated receptors in vivo. We are engineering a series of mutations in MC4R to remove the peptide‐binding site while retaining small‐molecule binding and activation. The MC4R Gs RASSL could be used to control many physiological responses associated with Gs signaling such as heart rate, energy homeostasis, and cell proliferation.
Accessory Proteins for Melanocortin Signaling
Authors: HE LIN , ELDRIDGE ADAM G. , JACKSON PETER K. , GUNN TERESA M. , BARSH GREGORY S.
Published: July 2009

Abstract: Switching from eumelanin to pheomelanin synthesis during hair growth is accomplished by transient synthesis of Agouti protein, an inverse agonist for the melanocortin‐1 receptor (Mc1r). The coat color mutations mahogany and mahoganoid prevent hair follicle melanocytes from responding to Agouti protein. The gene mutated in mahogany, which is also known as Attractin (Atrn), encodes a type I transmembrane protein that functions as an accessory receptor for Agouti protein. We have recently determined that the gene mutated in mahoganoid, which is also known as Mahogunin (Mgrn1), encodes an E3 ubiquitin ligase. Like Attractin, Mahogunin is conserved in invertebrate genomes, and its absence causes a pleiotropic phenotype that includes spongiform neurodegeneration.
DNA Polymorphism and Selection at the Melanocortin‐1 Receptor Gene in Normally Pigmented Southern African Individuals
Authors: JOHN PREMILA R. , MAKOVA KATERYNA , LI WEN‐HSIUNG , JENKINS TREFOR , RAMSAY MICHELE
Published: July 2009

Abstract: Skin pigmentation is a polygenic multifactorial trait determined by the cumulative effects of multiple genetic variants and environmental factors. Melanocortin‐1 receptor (MC1R) is one of the genes involved in pigmentation, and has been implicated in the red hair and pale skin phenotype in human Caucasoid individuals. The present study was undertaken to identify variation at the MC1R locus in normally pigmented individuals in two African populations, sub‐Saharan Negroids (22 unrelated individuals) and the San (17 unrelated individuals). The study showed considerable MC1R gene sequence variation with the detection of eight synonymous and three nonsynonymous mutations. This is the first report of nonsynonymous mutations in African individuals in the MC1R gene: L99I was found in a single San individual, S47I was detected in a single Negroid individual, and F196L was detected in five Negroid individuals (5/44; 0.11). The functional significance of these mutations is not known. Three of the eight synonymous mutations found, L106L (CTG → CTA), F300F (TTC → TTT), and T314T (ACA → ACG) (also known as A942G), have been reported previously. T314T was the only variant that showed a significant difference between the Negroid and San populations (0.477 and 0.059, respectively; P= 1.6× 10−5). Its low frequency in the San may be the result of random genetic drift in a population of small size, or selection. Several tests of neutrality of the MC1R coding region in these and other African populations were significant, suggesting that purifying selection (functional constraint) had occurred at this gene locus in Africans. This demonstrates that although some nonsynonymous MC1R mutations are tolerated in individuals with dark skin, this gene has likely played a significant role in the maintenance of dark pigmentation in Africans and normal pigment variation in non‐African populations.
DOTA α‐Melanocyte‐Stimulating Hormone Analogues for Imaging Metastatic Melanoma Lesions
Authors: FROIDEVAUX SYLVIE , CALAME‐CHRISTE MARTINE , SUMANOVSKI LAZAR , TANNER HEIDI , EBERLE ALEX N.
Published: July 2009

Abstract: Scintigraphic imaging of metastatic melanoma lesions requires highly tumor‐specific radiopharmaceuticals. Because both melanotic and amelanotic melanomas overexpress melanocortin‐1 receptors (MC1R), radiolabeled analogues of α‐melanocyte‐stimulating hormone (α‐MSH) are potential candidates for melanoma diagnosis. Here, we report the in vivo performance of a newly designed octapeptide analogue, [βAla3, Nle4, Asp5, D‐Phe7, Lys10]‐α‐MSH3–10 (MSHOCT), which was conjugated through its N‐terminal amino group to the metal chelator 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) to enable incorporation of radiometals (e.g., indium‐111) into the peptide. DOTA‐MSHOCT displayed high in vitro MC1R affinity (IC50 9.21 nM). In vivo [111In]DOTA‐MSHOCT exhibited a favorable biodistribution profile after injection in B16‐F1 tumorbearing mice. The radiopeptide was rapidly cleared from blood through the kidneys and, most importantly, accumulated preferentially in the melanoma lesions. Lung and liver melanoma metastases could be clearly imaged on tissue section autoradiographs 4 h after injection of [111In]DOTA‐MSHOCT. A comparative study of [111In]DOTA‐MSHOCT with [111In]DOTA‐[Nle4, D‐Phe7]‐α‐MSH ([111In]‐DOTA‐NDP‐MSH) demonstrated the superiority of the DOTA‐MSHOCT peptide, particularly for the amount of radioactivity taken up by nonmalignant organs, including bone, the most radiosensitive tissue. These results demonstrate that [111In]DOTA‐MSHOCT is a promising melanoma imaging agent.
Smad3: A Key Player in Pathogenetic Mechanisms Dependent on TGF‐β
Authors: ROBERTS ANITA B. , RUSSO ANGELO , FELICI ANGELINA , FLANDERS KATHLEEN C.
Published: July 2009

Abstract: Transforming growth factor‐β (TGF‐β), a key player in a large variety of physiological and disease processes, signals through transmembrane receptor serine/threonine kinases to activate novel signaling intermediates called Smad proteins, which then modulate transcription of target genes. We have utilized mice with a targeted deletion of Smad3, one of two homologous proteins involved in signaling from TGF‐β/activin, to investigate the function of this particular pathway in transducing such effects of TGF‐β. The dramatic results of the absence of Smad3 on parameters of healing of cutaneous wounds, such as reepithelialization and influx of inflammatory cells, as well as on fibrosis as modeled by radiation fibrosis of skin in mice, suggest that signaling flux through Smad3 is critical for chemotactic activity of TGF‐β, inhibitory effects of TGF‐β on keratinocyte proliferation and migration, and chemoattraction and elaboration of extracellular matrix by fibroblasts in fibrotic diseases. We recently identified a novel molecule, TLP for TRAP‐1‐like protein, which selectively interferes with Smad3 signaling, and are currently investigating whether levels of this protein might be altered in disease to change the relative flow of information from Smad2 and Smad3.
How Proteases Regulate Bone Morphogenesis
Authors: ORTEGA NATHALIE , BEHONICK DANIELLE , STICKENS DOMINIQUE , WERB ZENA
Published: July 2009

Abstract: Matrix metalloproteinases (MMPs) degrade most components of the extracellular matrix (ECM), as well as many non‐ECM molecules. MMPs participate in (1) degradation of ECM to allow cell migration; (2) alteration of the ECM microenvironment resulting in alteration in cellular behavior; (3) modulation of biologically active molecules by direct cleavage or release from ECM stores; (4) regulation of the activity of other proteases; and (5) cell attachment, proliferation, differentiation, and apoptosis. We have sought to understand the role of MMPs during development and tissue repair in transgenic mice. Endochondral bone formation presents a particularly interesting developmental challenge. During this process, an avascular tissue (cartilage) is converted into one of the most highly vascularized tissues (bone) in the vertebrate body. Ossification begins with invasion of the calcified hypertrophic cartilage by capillaries. Apoptosis of the terminal hypertrophic chondrocytes, degradation of the cartilage matrix, and deposition of bone matrix by osteoblasts accompanies neovascularization of the growth plate. Remodeling of ECM results in a cavity filled with vascular channels containing hematopoietic cells. Our results reveal that MMP9, MMP13, and vascular endothelial growth factor are key regulators for the remodeling of the skeletal tissues. They coordinate not only matrix degradation, but also the recruitment and differentiation of endothelial cells, osteoclasts, chondroclasts, and osteoprogenitors.
Induction of Vascular Networks in Adult Organs: Implications to Proangiogenic Therapy
Authors: DOR YUVAL , DJONOV VALENTIN , KESHET ELI
Published: July 2009

Abstract: Most therapeutic proangiogenic approaches rely on the premise that a single factor (e.g., VEGF) can induce new vascular loops properly connected to the existing vasculature of an ill‐perfused organ (e.g., the ischemic myocardium). To gain insights into VEGF‐driven neovascularization in the adult, in general, and to uncover inherent obstacles in VEGF‐based therapeutic angiogenesis, we have used a transgenic system for conditional “on” and “off” switching of VEGF expression in selected adult organs and analytical methods for three‐dimensional visualization of the induced vascular network. VEGF induces massive accumulation of endothelial progenitor cells and their subsequent coalescence into new vascular loops. Continual ramification of the vasculature and fusion of adjacent vessels culminate in formation of hemangioma‐like vessels. In the absence of guiding cues, abnormal branching patterns and random connections with the existing network are formed. Following cessation of the VEGF stimulus, the acquired network undergoes extensive hemodynamic remodeling acting to “normalize” its architecture. Premature withdrawal of VEGF leads to regression of most acquired vessels, thus challenging the utility of therapeutic approaches relying on short stimulus duration. Overproduction of VEGF leads also to highly disruptive edema, thereby emphasizing the need to uncouple VEGF‐induced permeability from its angiogenic activity. This genetic switch system thus highlights remaining problems critical for the implementation of proangiogenic therapy.
Chromatin as a Tool for the Study of Genome Function in Cancer
Authors: URNOV FYODOR D.
Published: July 2009

Abstract: The transition to malignancy requires an extensive reconfiguration of the genome's expression program that does not result entirely from actual changes in primary DNA sequence—i.e., mutation. Epigenetic—meta‐DNA—gene expression states result from an assembly over a given locus of a poorly understood nucleoprotein entity that includes histones and other architectural components of chromatin, nonhistone DNA‐bound regulators, and additional chromatin‐bound polypeptides. This structure is rapidly reestablished in the wake of the DNA replication fork, thus ensuring its persistence in rapidly proliferating cells and thereby yielding an exceptionally stable mode of gene expression. Chromatin is the perfect vehicle for enabling such genome control. During S phase both covalently modified histones and histone‐associated regulatory proteins distribute to the newly synthesized daughter chromatids in a form of ‘molecular dowry’ inherited from the G1 state of the genome, and impose a specific mode of function on the underlying DNA. An extensively studied example of chromatin‐based epigenetic inheritance connects DNA methylation to the targeting of chromatin remodeling and modification. In a broad sense, however, genome reprogramming in cancer is associated with the remodeling of a multitude of regulatory DNA stretches—e.g., promoters, enhancers, locus control regions (LCRs), insulators, etc.—into a specific chromatin architecture. This architectural entity provides a general molecular signature of the cancer epigenome that complements and significantly expands its DNA methylation‐based component.
Unanswered Questions about the Role of Promoter Methylation in Carcinogenesis
Authors: BESTOR TIMOTHY H.
Published: July 2009

Abstract: It has been proposed that tumor suppressor genes can be silenced by ectopic de novo methylation during tumor progression and that this epigenetic silencing is an alternative to mutation in tumor suppressor inactivation during oncogenic transformation. However, methylation may follow inactivation and may not directly participate in tumor progression. There are no genetic data that implicate ectopic de novo methylation in cancer, and no DNA methyltransferase gene has been shown to be mutated in any cancer. Promoter methylation at tumor suppressor loci may be a consequence of transcriptional inactivity imposed by mutations in upstream components of the transcriptional machinery or signal transduction pathways. Current estimates of the importance of epigenetic changes in the etiology of cancer may be inflated, and consequences may have been mistaken for causes in some cases.
Histone Deacetylases: Unique Players in Shaping the Epigenetic Histone Code
Authors: THIAGALINGAM SAM , CHENG KUANG‐HUNG , LEE HYUNJOO J. , MINEVA NORA , THIAGALINGAM ARUNTHATHI , PONTE JOSE F.
Published: July 2009

Abstract: The epigenome is defined by DNA methylation patterns and the associated posttranslational modifications of histones. This histone code determines the expression status of individual genes dependent upon their localization on the chromatin. The silencing of gene expression is associated with deacetylated histones, which are often found to be associated with regions of DNA methylation as well as methylation at the lysine 4 residue of histone 3. In contrast, the activation of gene expression is associated with acetylated histones and methylation at the lysine 9 residue of histone 3. The histone deactylases play a major role in keeping the balance between the acetylated and deacetylated states of chromatin. Histone deacetylases (HDACs) are divided into three classes: class I HDACs (HDACs 1, 2, 3, and 8) are similar to the yeast RPD3 protein and localize to the nucleus; class II HDACs (HDACs 4, 5, 6, 7, 9, and 10) are homologous to the yeast HDA1 protein and are found in both the nucleus and cytoplasm; and class III HDACs form a structurally distinct class of NAD‐dependent enzymes that are similar to the yeast SIR2 proteins. Since inappropriate silencing of critical genes can result in one or both hits of tumor suppressor gene (TSG) inactivation in cancer, theoretically the reactivation of affected TSGs could have an enormous therapeutic value in preventing and treating cancer. Indeed, several HDAC inhibitors are currently being developed and tested for their potency in cancer chemotherapy. Importantly, these agents are also potentially applicable to chemoprevention if their toxicity can be minimized. Despite the toxic side effects and lack of specificity of some of the inhibitors, progress is being made. With the elucidation of the structures, functions and modes of action of HDACs, finding agents that may be targeted to specific HDACs and potentially reactivate expression of only a defined set of affected genes in cancer will be more attainable.
Advances in Solvent‐Resistant Nanofiltration Membranes
Authors: BHANUSHALI D. , BHATTACHARYYA D.
Published: July 2009

Abstract: Nanofiltration (NF) and reverse osmosis (RO) are well‐established membrane technologies for applications involving aqueous streams. The principles of NF transport (diffusion, convection, and Donnan exclusion) are effectively used to develop novel membrane materials and applications in aqueous medium. Use of NF in a non‐aqueous medium holds strong potential for the food, refining, and pharmaceutical industries because of the low energy costs involved with such membrane processes. Further understanding and development of solvent‐resistant NF membranes provides opportunities for various hybrid processing ranging from reactor‐membrane to distillation‐membrane combinations. This paper provides a comprehensive overview of literature results and our own work in the area of non‐aqueous systems. For solvent‐based systems, potential membrane swelling and solvent‐solute coupling needs to be considered for membrane design and transport theories. A simplified transport theory for pure solvents has been developed using solvent (molar volume, viscosity) and membrane properties (membrane surface energy). This model and has been verified with literature data for both hydrophilic and hydrophobic membranes. Membrane characterization and preconditioning aspects need to be given serious consideration for evaluating membrane performance. In addition to permeability and separation results, some novel applications of NF in non‐aqueous solvents are included in this paper.
Effect of Compatibility of PVC/P2 Alloy System on Membrane Structure and Performance
Authors: SUN PATRICIA B. , SUN BENHUI
Published: July 2009

Abstract: The effects of the secondary polymer component (P2) on poly(vinyl chloride) (PVC)/P2 alloy membrane structure and performance were systematically investigated. A series of P2 with varying compatibility with PVC used in this study included vinyl chloride‐vinyl acetate copolymer (VC‐co‐VAc); copolymer of vinyl chloride, vinyl acetate‐maleic anhydride copolymer (VC‐co‐VAc‐co‐MAL); isobutylene‐maleic anhydride copolymer (IB‐co‐MAL); poly(methyl methacrylate) (PMMA); poly(vinylidene dichloride) (PVDC); and styrene‐acrylonitrile copolymer (SAN). Alloy membranes were prepared by means of solution blending—phase inversion technique. On the basis of our experimental results, the compatibility of PVC/P2 was proved to be the most critical factor affecting the alloy membrane structure and performance. Systems with good compatibility, such as PVC/VC‐co‐VAc, are more suitable for preparing membranes with small pore size; whereas systems with partial compatibility, such as PVC/PMMA, are more favored for the formation of large‐pore membranes.
Nonlinear Parameter Estimation for Solution‐Diffusion Models of Membrane Pervaporation
Authors: CAOA BING , HENSON MICHAEL A.
Published: July 2009

Abstract: An optimization‐based procedure for estimating unknown parameters in solution‐diffusion models of membrane pervaporation is presented. Permeation of two components through a polymer membrane is described by distinct solution and diffusion models. The solution model is based on a modified form of Flory‐Huggins theory that accounts for interactions between the two penetrants. The diffusion model is derived from Fick's law, where the diffusion coefficients are allowed to depend on the local concentration of each component in the membrane. A phenomenologic relation is used to account for the effect of temperature on the component fluxes. The solution and diffusion models, as well as the temperature‐flux relation, contain parameters that are not directly measurable. It is shown that these parameters can be estimated effectively from sorption and flux data by the solution of suitably formulated nonlinear optimization problems. The separation of styrene and ethylbenzene with a polyurethane membrane is used to illustrate the parameter estimation procedure.
Hydrophobic Pervaporation
Authors: FIELD ROBERT W. , LOBO VANESSA
Published: July 2009

Abstract: Pervaporation is a relatively new technology. Although hydrophilic pervaporation has become established, hydrophobic pervaporation for recovery of organics from water has not been a commercial success. Technologic reasons for this are suggested. However, as the pressure to include waste minimization and to recycle, as well as pollution prevention, increases, there will be opportunity for the development of new wastewater treatment processes. This may lead to hybrid processes, including a coupling of pervaporation with conventional technology. The hybrid process examined herein is a simple pervaporation‐decanter system that is applicable to organics with limited solubility in water. In this system, the PV unit produces permeate that after condensation gives two liquid phases. The organic phase is relative pure and concentrated (and available for reuse), whereas the aqueous phase can be recycled into the PV feed stream. For a given feed concentration and water purity target, there is a minimum membrane selectivity (αmin) that yields a two‐phase condensate. If the membrane has a selectivity that is just greater than the minimum, the recycle rate of the aqueous phase relative to the feed rate will be very large and likewise the membrane area. Also, for a membrane with known organic permeability, one can define a theoretical Amin, the minimum membrane area required when the separation factor is so high that the aqueous phase is negligible. For membranes with α > αmin, values of the required membrane area, A, have been obtained for various representative duties, and a correlation between α/αmin and A/Amin has been obtained (compare with the Gilliland correlation used in distillation). An approximate relationship is (A/Amin− 1)(α/αmin− 1) = 1. Since αmin and Amin can be calculated readily, this relationship is a shortcut tool that permits estimation of A for any α and any duty. Finally, membrane areas for the above hybrid system and those for PV alone are compared.