bluuebunny/crossref_metadata_2025 huggingface dataset:
A Review of Medical Imaging Informatics
Authors: SINHA USHA , BUI ALEX , TAIRA RICKY , DIONISIO JOHN , MORIOKA CRAIG , JOHNSON DAVID , KANGARLOO HOOSHANG
Published: July 2009

Abstract:This review of medical imaging informatics is a survey of current developments in an exciting field. The focus is on informatics issues rather than traditional data processing and information systems, such as picture archiving and communications systems (PACS) and image processing and analysis systems. In this review, we address imaging informatics issues within the requirements of an informatics system defined by the American Medical Informatics Association. With these requirements as a framework, we review, in four sections: (1) Methods to present imaging and associated data without causing an overload, including image study summarization, content‐based medical image retrieval, and natural language processing of text data. (2) Data modeling techniques to represent clinical data with focus on an image data model, including general‐purpose time‐based multimedia data models, health‐care‐specific data models, knowledge models, and problem‐centric data models. (3) Methods to integrate medical data information from heterogeneous clinical data sources. Advances in centralized databases and mediated architectures are reviewed along with a discussion on our efforts at data integration based on peer‐to‐peer networking and shared file systems. (4) Visualization schemas to present imaging and clinical data: the large volume of medical data presents a daunting challenge for an efficient visualization paradigm. In this section we review current multimedia visualization methods including temporal modeling, problem‐specific data organization, including our problem‐centric, context and user‐specific visualization interface.
Use of an Electric Field in an Electrostatic Liquid Film Radiator
Authors: BANKOFF S. G. , GRIFFING E. M. , SCHLUTER R. A.
Published: July 2009

Abstract: Experimental and numerical work was performed to further the understanding of an electrostatic liquid film radiator (ELFR) that was originally proposed by Kim et al.1 The ELFR design utilizes an electric field that exerts a normal force on the interface of a flowing film. The field lowers the pressure under the film in a space radiator and, thereby, prevents leakage through a puncture in the radiator wall. The flowing film is subject to the Taylor cone instability, whereby a cone of fluid forms underneath an electrode and sharpens until a jet of fluid is pulled toward the electrode and disintegrates into droplets. The critical potential for the instability is shown to be as much as an order of magnitude higher than that used in previous designs.2 Furthermore, leak stoppage experiments indicate that the critical field is adequate to stop leaks in a working radiator.
Large‐Scale Geophysical Flows on a Table Top
Authors: HEGSETH JOHN , AMARA KAMEL
Published: July 2009

Abstract: Results from two similar experimental systems that attempt to create laboratory geophysical analogs in spherical geometry are presented. In the first system, real time holographic interferometry and shadowgraph visualization are used to study convection in the fluid between two concentric spheres when two distinct buoyancy forces are applied to the fluid. The heated inner sphere has a constant temperature that is greater than the outer sphere's constant temperature by ΔT. In addition to the usual gravitational buoyancy from temperature induced density differences, another radial buoyancy is imposed by applying an ac voltage difference, ΔV, between the inner and outer spheres. The resulting electric field gradient in this spherical capacitor produces a central polarization force. The temperature dependence of the dielectric constant results in the second buoyancy force that is especially large near the inner sphere. The normal buoyancy is always present and, within the parameter range explored in our experiment, always results in a large‐scale cell that is axisymmetric about the vertical axis. We have found that this flow becomes unstable to toroidal or spiral rolls that form near the inner sphere and travel vertically upward when ΔT and ΔV are sufficiently large. These rolls start near the center sphere's equator and travel upward toward its top. In the second experimental system, the central force is applied to a highly compressible near‐critical fluid in weightlessness (parabolic flight) and normal gravity. Although a geophysically similar density distribution could not be obtained in the limited time of a parabolic flight, clear influences of the central force on the fluid were observed in both weightlessness and terrestrial experiments.
The Use of Pulsatile Flow to Separate Species
Authors: THOMAS AARON M. , NARAYANAN R.
Published: July 2009

Abstract: Pulsatile motion greatly enhances the mass transfer of a dilute species compared to that due to pure molecular diffusion. If two dilute species are present in a carrier, the mass transfer of the faster diffusing species may be higher, lower, or the same as the slower diffusing species. This depends on the time constants associated with the system and the ability of a species to remain in the fast moving portion of the flow field. The difference in the mass transfer of each species can lead to a separation that can be used in a number of processes including the removal of carbon dioxide from the air. This phenomenon is modeled in an open tube geometry and in the annular space between two concentric cylinders. In annular pulsatile flow, the effect of the inner cylinder being off center from the outer cylinder on the mass transfer and separation is also analyzed. Finally, experimental results are presented to prove the validity of the models and the separation that can be achieved using this process.
Unidirectional Solidification of Magnetostrictive Materials Using a Magnetic Field in Microgravity
Authors: MINAGAWA HIDEKI , KAMADA KEIJI , NAGAI HIDEAKI , NAKATA YOSHINORI , OKUTANI TAKESHI
Published: July 2009

Abstract: Unidirectional solidification experiments of magnetostrictive materials of Tb0.3Dy0.7Fe2−x, (Terfenol‐D) alloy in a static magnetic field and microgravity were performed using the Japan Microgravity Center (JAMIC) free‐fall facilities. When the magnetic field strength was increased from 0T to 3.7 × 10−2 T during unidirectional solidification in microgravity, a 〈111〉 crystallographic alignment of the grains dominated, and the maximum magnetostriction constant increased from 500 ppm to 2,000ppm. For unidirectional solidification in normal gravity, the maximum magnetostriction constant remained at 1,000 ppm for increases in the magnetic field.
Microscale Heat Transfer to Subcooled Water
Authors: LEYSE ROBERT H.
Published: July 2009

Abstract: Exciting heat transfer phenomena have been discovered with a micron‐sized heat transfer element operating in subcooled (20°C) degassed, demineralized water over a wide pressure range (200‐6,000psia) at heat fluxes up to 3,500W/cm2. The platinum heat transfer element (diameter 7.5 microns, length 1.14mm) is installed within a one‐cm3 stainless steel chamber. Sealed electrical terminals penetrate the chamber to effect direct current heating of the platinum element. Pressure is applied pneumatically. The adiabatic heating rate of the element is 6°C per microsecond at 3,700W/cm2; response is essentially instantaneous for the procedure described herein. The direct current voltage and current are measured from which the power and the resistance (temperature) are determined. The following procedure applies: (1) Pressurize the water‐filled stainless steel chamber to 6,000psia. (2) Apply power at 3,000W/cm2. (3) Maintain constant heat flux as pressure is smoothly reduced from 6,000psia to 200psia over a period of 20 seconds. Record voltage, amperage, and pressure at 0.1 second intervals. Heat transfer phenomena thus discovered: (1) Element starting temperature of 370°C at 6,000psia smoothly increased to 380° as pressure was reduced to 3,970psia. (2) At 3,970psia the temperature abruptly stepped upward to 590°C. (3) Temperature smoothly increased to 730°C as pressure was reduced to 3,230psia. (4) In the vicinity of the critical pressure, the temperature turned around and began smoothly decreasing. (5) At 2,350psia, the temperature stepped down from 520 to 350°C. (6) Temperature smoothly decreased to 230°C at 190psia and power was then turned off. Bulk water temperature increased less than 4°C. Controlled gravity (KC‐135) tests are planned.
A Study of Gas‐Liquid Two‐Phase Flow in a Horizontal Tube Under Microgravity
Authors: CHOI BUHONG , FUJII TERUSHIGE , ASANO HITOSHI , SUGIMOTO KATSUMI
Published: July 2009

Abstract: A better understanding of the effect of gravity level on two‐phase flow characteristics is crucial for designing two‐phase heat transport systems and thermal control systems for space. Hence, an experiment was conducted aboard MU‐300 aircraft, as well as at normal gravity using the same horizontal tube, 10mm internal diameter and flow conditions. The experimental results, obtained under Earth, hypergravity (2g), and microgravity environments were compared with previous models. Flow pattern data were compared with data from models for predicting microgravity flow pattern transitions. The mean void fraction under μg and 1g conditions was also compared with the Inoue‐Aoki model for vertical upward annular flow at normal gravity. Frictional pressure drop fitted well with the Lockhart‐Martinelli model, slightly influenced by the change in gravity levels (μg, 1g, and 2g); however, the effect of changing gravity on the pressure drop was insignificant for turbulent flow.
Review of Existing Research on Microgravity Boiling and Two‐Phase Flow
Authors: OHTA HARUHIKO , BABA ATSUSHI , GABRIEL KAMIEL
Published: July 2009

Abstract:This paper describes research objectives on boiling and two‐phase flow under microgravity conditions from both scientific and technological points of view. Existing research for various systems in flow boiling are briefly reviewed and problems indicated for research conducted by available facilities with short microgravity duration. A wide range of experimental subjects that become possible by using different types of test sections is clarified and the validity of long term experiments is emphasized. A first step outline is described for a test loop with interchangeable test sections, such as transparent heated tubes, transparent flat heating surfaces, and narrow channels optimized for individual objectives and restricted by specifications of the facility.
Mechanisms of Steady‐State Nucleate Pool Boiling in Microgravity
Authors: LEE HO SUNG
Published: July 2009

Abstract:Research on nucleate pool boiling in microgravity using R‐113 as a working fluid was conducted using a five‐second drop tower and five space flights ata/g∼ 10−4. A 19 × 38‐mm flat gold film heater was used that allowed cine camera viewing both from the side and the bottom of the heater. It was concluded that for both subcooled and saturated liquids long‐term steady‐state pool boiling can take place in reduced gravity, but the effectiveness of the boiling heat transfer appears to depend on the heater geometry and on the size and the properties of fluids. Heat transfer is enhanced at lower heat flux levels and the CHF increases as the subcooling increases. It was found that several mechanisms are responsible for the steady‐state nucleate pool boiling in the absence of buoyancy. The mechanisms considered here are defined and summarized as bubble removal, bubble coalescence, thermocapillary flow, bubble migration, and latent heat transport.
Sliding‐Cavity Fluid Contactors in Low‐Gravity Fluids, Materials, and Biotechnology Research
Authors: TODD PAUL , VELLINGER JOHN C. , SENGUPTA SHRAMIK , SPORTIELLO MICHAEL G. , GREENBERG ALAN R. , KRANTZ WILLIAM B.
Published: July 2009

Abstract: The well‐known method of sliding‐cavity fluid contactors used by Gosting for diffusion measurements and by Tiselius in electrophoresis has found considerable use in low‐gravity research. To date, sliding‐cavity contactors have been used in liquid diffusion experiments, interfacial transport experiments, biomolecular crystal growth, biphasic extraction, multistage extraction, microencapsulation, seed germination, invertebrate development, and thin‐film casting. Sliding‐cavity technology has several advantages for spaceflight: it is simple, it accommodates small samples, samples can be fully enclosed, phases can be combined, multiple samples can be processed at high sample density, real‐time observations can be made, and mixed and diffused samples can be compared. An analysis of the transport phenomena that govern the sliding‐cavity method is offered. During sliding of one liquid over another flow rates between 0.001 and 0.1m/sec are developed, giving Reynolds numbers in the range 0.1‐100. Assuming no slip at liquid‐solid boundaries shear rates are of the order 1sec−1. The measured consequence is the transfer of 2‐5% of the content of a cavity to the opposite cavity. In the absence of gravity, buoyancy‐driven transport is assumed absent. Transport processes are limited to (1) molecular diffusion, in which reactants diffuse toward one another at rates that depend on their diffusion coefficient and concentration gradient (Fick's second law), (2) solutocapillary (Marangoni) flow driven by surface‐tension gradients, (3) capillary flow (drop spreading) at liquid‐solid three‐phase lines leading to immiscible phase demixing, and (4) vapor‐phase diffusive mass transfer in evaporative processes. Quantitative treatment of these phenomena has been accomplished over the past few years in low‐gravity research in space and on aircraft.
Microgravity Protein Crystallization
Authors: CHAYEN NAOMI E. , HELLIWELL JOHN R.
Published: July 2009

Abstract: Protein crystallography, which has a growing role in the human genome project, is one of the most powerful techniques in modern biology. However, it can only be applied providing suitable crystals can be obtained. The ability to produce suitable crystals is currently the major bottleneck to structure determination. Microgravity, which is used as a tool for improving crystal growth, is a high‐profile enterprise, especially with the upcoming prospects for utilizing the International Space Station, yet the issue of crystallization in microgravity is an extremely controversial one. In spite of numerous experiments conducted in microgravity during 16 years, the reported success rate, measured in terms of various improvements witnessed in the perfection of protein crystals, has been a mere 20%. In this paper we present experimental evidence, supporting previous fluid physics calculations to show that in many cases the potential benefits of the microgravity environment have not been fully exploited. These findings offer an explanation for the low rate of success and open up the possibility for enhancing the efficiency of experimentation in microgravity. Furthermore, these findings extend into a number of other disciplines involving fluid physics.
Space‐Grown Protein Crystals Are More Useful for Structure Determination
Authors: NG JOSEPH D.
Published: July 2009

Abstract:The usefulness of X‐ray data derived from space‐grown protein crystals for calculating a more accurate structure is reviewed here for three model proteins. These include the plant sweetening protein, thaumatin, fromThaumatococcus daniellii; the aspartyl‐tRNA synthetase fromThermus thermophilus; and pea lectin fromPisum sativum. In all three cases, X‐ray diffraction data collected from protein crystals obtained under reduced gravity lead to better defined initial electron density maps, facilitating model building and improved crystallographic statistics. With thaumatin, the phasing power of the anomalous scattering atom, sulfur, is used to determine protein crystal quality in terms of its usefulnessfor abinitio structure determination. Thaumatin crystals grown under microgravity provided improved phasing statistics compared to those of Earth‐grown crystals. Consequently, generating ade novoprotein model of higher quality was facilitated using X‐ray diffraction data from space‐grown crystals. This lends evidence to the possibility that a microgravity environment can favor protein crystal growth and, subsequently, be more useful for structure determination.
Mathematical Model for Diffusion of a Protein and a Precipitant about a Growing Protein Crystal in Microgravity
Authors: ANNUNZIATA ONOFRIO , ALBRIGHT JOHN G.
Published: July 2009

Abstract: Equations are presented that model diffusion of a protein to the surface of a growing crystal in a convection‐free environment. The equations apply to crystal growth solutions that contain both a protein and a protein precipitant. The solutions are assumed ternary and the equations include all four diffusion coefficients necessary for the full description of the diffusion process. The four diffusion coefficients are assumed constant. Effects of crystal/solution moving boundary and the effect of a protein adsorption barrier at the crystal interface are included. The equations were applied to the system lysozyme chloride + NaCl + H2O, which has served as the primary model system for the study of crystal growth of proteins and for which there are now published ternary diffusion coefficients. Calculated results with and without the inclusion of cross‐term diffusion coefficients are compared.
Analysis of B Cell Memory Formation Using DNA Microarrays
Authors: VINUESA CAROLA G. , COOK MATTHEW C. , COOKE MICHAEL P. , MACLENNAN IAN C. M. , GOODNOW CHRISTOPHER C.
Published: July 2009

Abstract: DNA microarray analysis of B cell subsets has identified comprehensive programs of gene expression that distinguish B cells at discrete stages of differentiation. The next task is to identify key genetic signals within these complex programs that regulate the dynamic cellular events during B cell activation in vivo. After stimulation with antigen, naïve B cells proliferate and differentiate, and then produce antibodies. Crucial qualitative differences in antibody responses are observed depending on whether or not B cells receive T cell help during activation. Proteins, lipopolysaccharides, and polysaccharides stimulate T‐dependent (TD), T‐independent type 1 (TI‐1), and type 2 (TI‐2) antibody responses, respectively. Only TD responses generate somatically mutated antibody‐forming (plasma) cells and memory B cells, which produce high affinity anamnestic responses to subsequent antigen challenge. Somatic mutation of immunoglobulin genes occurs during B cell proliferation in germinal centres (GC), which are typical in TD responses but rare in TI responses. However, we have described a model, which is exceptional because numerous large GC form in response to a model TI‐2 antigen, (4‐hydoxy‐3‐nitrophenyl) acetyl (NP)‐Ficoll. Significantly, these GC undergo involution before memory B cells are generated. This model provides an opportunity to investigate the genetic signals that drive memory cell formation, and we have compared global gene expression in TI and TD GC to identify a relatively small number of genes that are differentially expressed between the two prototypic B cell responses. This model demonstrates how genome‐scale technology can be adapted to investigate specific aspects of B cell biology.
Genetic Determinants of Coxsackievirus B3 Pathogenesis
Authors: McMANUS BRUCE M. , YANAGAWA BOBBY , REZAI NANA , LUO HONGLIN , TAYLOR LYDIA , ZHANG MARY , YUAN JANE , BUCKLEY JONATHAN , TRICHE TIMOTHY , SCHREINER GEORGE , YANG DECHENG
Published: July 2009

Abstract:The development of high throughput genomic and bioinformatic analysis tools, coupled with established molecular techniques, has allowed new insights into the pathogenesis of infectious diseases. In humans, coxasackievirus B3 (CVB3) is the primary etiological agent of viral myocarditis, an inflammatory disease process involving the heart muscle. Early host cellular survival and apoptotic mechanisms during viral infections, as well as immune events, affect myocarditis progression and outcome. Therefore, our laboratory has been keenly interested in infectomics, defined here as the transcriptional events of both virus and host. We first elucidated up‐ or downregulated transcriptional activities in CVB3‐infected hearts by mRNA differential display. Further characterization of these regulated genes including Nip21, IP10, and IGTPase, and study of their role in CVB3‐infection are underway. In further dissection of the stages of myocarditis—peak viremia, inflammatory infiltration and tissue repair—we used cDNA microarrays to probe differential gene expression in the myocardium following virus infection. Following virus infection, there are global decreases in metabolic and mitochondrial genes, increases in signaling genes and distinctive patterns in other functional groups. To establish early gene expression profiles in infected cells by themselves, we also used oligonucleotide arrays in anin vitromodel of CVB3 infection. Notably, we have found increased expression of transcription factorsc‐fosandc‐jundown‐stream of extracellular signal‐related kinase, a pathway which is crucial for virus replication and pathogenesis. Our investigations based on gene profiling following CVB3 infection have thus far been fruitful in providing new experimental leads. High throughput genetic analysis has allowed us to simultaneously try on greater than 12,000 potential genetic “glass slippers.” Ourin vitroexperimental plan has enabled us to chart prominent patterns of gene expression, analyzed by novel bioinformatic approaches, and to separate varied and potentially significant gene expression events.
A Functional Genomics Approach to Kaposi's Sarcoma
Authors: MOSES ASHLEE V. , JARVIS MICHAEL A. , RAGGO CAMILO , BELL YOLANDA C. , RUHL REBECCA , LUUKKONEN B.G. MATTIAS , GRIFFITH DIANA J. , WAIT CECILY L. , DRUKER BRIAN J. , HEINRICH MICHAEL C. , NELSON JAY A. , FRÜH KLAUS
Published: July 2009

Abstract: Kaposi's sarcoma (KS) is the most frequent malignancy afflicting acquired immune‐deficiency syndrome (AIDS) patients. Tumor lesions are characterized by spindle cells of vascular origin and vascularization. Kaposi's sarcoma‐associated herpes virus (KSHV) is consistently found in all forms of KS. Infection of dermal microvascular endothelial cells (DMVEC) with KSHV recapitulates spindle cell formation in vitro. We studied this transformation process by DNA microarray analysis comparing the RNA expression profiles of KSHV‐infected and mock‐infected DMVEC. Genes involved in tumorigenesis, angiogenesis, host defense, cell growth and differentiation, transcription, and metabolism were observed to change significantly upon infection with KSHV. One of the most consistently KSHV‐induced genes was the receptor tyrosine kinase and proto‐oncogene c‐Kit. Inhibition of c‐Kit activity with the pharmacological inhibitor of c‐Kit signaling STI571 reversed the KSHV‐induced morphological transformation of DMVEC. Moreover, overexpression studies showed that c‐Kit was sufficient to induce spindle cell formation (Moses et al. J. Virol. 76(16): 8383‐8399). These data demonstrate that microarrays are useful for the identification of pharmacological targets essential for KS tumorigenesis.
Pathophysiology of Cerebral Malaria
Authors: WASSMER SAMUEL C. , COMBES VALÉRY , GRAU GEORGES E.
Published: July 2009

Abstract: Cerebral malaria (CM), one of the most serious complications of Plasmodium falciparum infection, is characterized by the sequestration of infected erythrocytes (IEs) in cerebral microvascular beds. The precise mechanisms involved in the onset of neuropathology remain unknown, but parasite sequestration in the brain, metabolic disturbances, and host immune responses all play a role. Studies in a murine model of CM showed a potential role for host cells, especially platelets, in the pathogenesis of CM. Indeed, urokinase plasminogen activator receptor (uPAR; CD87) deficiency attenuates the severity of CM, most likely by its important role in platelet kinetics and trapping. These results led us to evaluate whether platelets have a role in the human disease. By immunostaining of brain samples from Malawian patients, we determined that the surface of platelet accumulation and the proportion of vessels filled with platelets were significantly higher in patients who died of CM than in those who died of other causes. We then investigated the role of platelets in IE cytoadhesion in vitro, using CD36‐binding IE (IECD36) and CD36‐deficient (CD36DEF) brain microvascular endothelial cells (ECs). Coincubation studies indicated that platelets can induce strong IECD36 binding to CD36DEF ECs and, conversely, can hide constitutively expressed falciparum receptors such as chondroitin sulfate A. Thus, platelets may provide an adhesion receptor to microvascular beds originally devoid of it. This novel mechanism of cytoadhesion may reorient the sequestration of different parasite phenotypes and play an important role in the pathogenesis of severe malaria.
Hypothalamic‐Pituitary‐Adrenocortical and Gonadal Functions in Rheumatoid Arthritis
Authors: CUTOLO M. , SULLI A. , PIZZORNI C. , CRAVIOTTO C. , STRAUB R. H.
Published: July 2009

Abstract: Rheumatoid arthritis (RA) as well as most autoimmune disorders results from a combination of several predisposing factors including the relations between epitopes of the trigger agent (i.e., virus, self‐antigens) and histocompatibility epitopes (i.e., HLA), the status of the stress response system including the hypothalamic‐pituitary‐adrenocortical axis (HPA) and the sympathetic nervous system (SNS), as well as the gonadal hormones (hypothal‐amic‐pituitary‐gonadal axis, HPG), with estrogens implicated as enhancers of the immune response and androgens and progesterone as natural suppressors. The regular observation of reduced cortisol and adrenal androgen secretion during testing in RA patients not treated with glucocoticoids should clearly be regarded as “relative adrenal insufficiency” in the setting of a sustained inflammatory process, as shown by high interleukin (IL)‐6 levels. In polymyalgia rheumatica, several pathogenetic and clinical aspects of the disease might well overlap RA, at least with elderly onset RA (EORA). Therefore, reduced production of adrenal hormones (i.e., cortisol, DHEAS) at baseline in active and untreated patients with polymyalgia rheumatica was detected. The defect was mainly related to altered adrenal responsiveness to ACTH stimulation (i.e., increased 17‐OHP), at least in untreated patients with polymyalgia rheumatica. Finally, normal serum estrogen and low androgen levels, but high synovial fluid estrogen and much lower androgen levels, have been found in RA patients, supporting the fundamental role of the peripheral sex hormone metabolism in the manifestations of the disease.
PACAP in Immunity and Inflammation
Authors: DELGADO MARIO , ABAD CATALINA , MARTINEZ CARMEN , JUARRANZ M. GUILLERMA , LECETA JAVIER , GANEA DOINA , GOMARIZ ROSA P.
Published: July 2009

Abstract:The pituitary adenylate cyclase‐activating polypeptide (PACAP) is a neuropeptide belonging to the VIP/secretin/glucagon family of peptides, produced by the lymphoid cells, which exerts a wide spectrum of immunological functions controlling the homeostasis of immune system through different receptors expressed in various immunocompetent cells. In the last decade, PACAP has been clearly identified as a potent anti‐inflammatory factor that exerts its function by regulating the production of both anti‐ and proinflammatory mediators. In this sense, PACAP prevents death by septic shock, an acute inflammatory disease with a high mortality. In addition, PACAP regulates the expression of costimulatory molecules, inasmuch as this related to the modulation in the shift from Th1 towards Th2 differentiation. We recently reported that PACAP prevents the deleterious effects of arthritis by downregulating both inflammatory and autoimmune components of the disease. Therefore, PACAP and analogs have been proposed as very promising candidates, alternative to other existing treatments, for treating acute and chronic inflammatory and autoimmune diseases, such as septic shock, arthritis, multiple sclerosis, Crohn's disease, or autoimmune diabetes.
Melanocortin Receptors: Ligands and Proteochemometrics Modeling
Authors: WIKBERG J. E.S. , MUTULIS F. , MUTULE I. , VEIKSINA S. , LAPINSH M. , PETROVSKA R. , PRUSIS P.
Published: July 2009

Abstract: The melanocortin receptors exist in five subtypes, MC1–5R. These receptors participate in important regulations of the immune system, central behavior, and endocrine and exocrine glands. Here we provide a short review on MCR subtype selective peptides and organic compounds with activity on the MCRs, developed in our laboratory. Also provided is an overview of our new proteochemometric modeling technology, which has been applied to model the interaction of MSH peptides with the MCRs.
Melanocortin Tetrapeptides Modified at the N‐Terminus, His, Phe, Arg, and Trp Positions
Authors: HOLDER JERRY RYAN , HASKELL‐LUEVANO CARRIE
Published: July 2009

Abstract: The endogenous melanocortin agonists all contain the conserved His‐Phe‐Arg‐Trp sequence proposed to be important for melanocortin receptor selectivity and stimulation. We have generated peptide libraries consisting of over 100 peptides modified at the N‐terminus and at each of the four amino acid positions. These peptides were characterized at the mouse melanocortin MC1, MC3, MC4, and MC5 receptors for agonist or antagonist functional activity. The results from these studies include the identification of a nM MC4 versus MC3 receptor selective (>4700‐fold) agonist (JRH 420–12), a nM MC4 receptor agonist that is a nM MC3 receptor antagonist (JRH 322–18), a nM MC5 receptor selective (>100‐fold) agonist versus the MC1, MC3, and MC4 receptors (FFM 1–60), and side‐chain substitutions that may be utilized for non‐peptide design considerations.
α‐MSH and Desacetyl‐α‐MSH Signaling through Melanocortin Receptors
Authors: MOUNTJOY KATHLEEN G. , WU CHIA‐SHAN JENNY , CORNISH JILLIAN , CALLON KAREN E.
Published: July 2009

Abstract: The functional significance of N‐terminal acetylation of ACTH[1–13]NH2 is unknown. N‐terminal acetylation of ACTH[1–13]NH2 (known as desacetyl‐α‐MSH) to produce α‐MSH enhances some activities of ACTH[1–13]NH2 and virtually eliminates others. To determine whether α‐MSH and desacetyl‐α‐MSH diverge in their coupling to melanocortin receptors in vitro, we measured the sensitivity of MC1, MC3, MC4, and MC5 receptors stably expressed in HEK293 cells to these peptides, functionally coupling them to adenylyl cyclase and a calcium signaling pathway. α‐MSH and desacetyl‐α‐MSH similarly coupled these overexpressed receptors to both signaling pathways. In contrast, we discovered that α‐MSH significantly increased primary rat osteoblast proliferation while for desacetyl‐α‐MSH there was only a trend to do the same. Osteoblast cells expressing very low levels of endogenous melanocortin receptors, in contrast with transfected HEK293 cells overexpressing a single melanocortin receptor, may provide an in vitro model for differentiating between α‐MSH and desacetyl‐α‐MSH signaling.
MT‐II Induces Penile Erection via Brain and Spinal Mechanisms
Authors: WESSELLS HUNTER , HRUBY VICTOR J. , HACKETT JOHN , HAN GUOXIA , BALSE‐SRINIVASAN PREETI , VANDERAH TODD W.
Published: July 2009

Abstract: α‐Melanocyte‐stimulating hormone induces penile erection via melanocortin (MC) receptors in areas surrounding the third ventricle, but spinal and peripheral mechanisms have not been demonstrated. We used pharmacological strategies to localize the site of the proerectile action of the melanocortin receptor agonist MT‐II. We administered MT‐II intracerebroventribularly (i.c.v.), intrathecally (i.th.), and intravenously (i.v.) and scored penile erection and yawning for 90 min in awake male rats. In some animals i.c.v. or i.th. SHU‐9119 was injected 10 minutes before i.c.v. and i.th. MT‐II to confirm the MC receptor action of the agonist and to distinguish spinal from supraspinal effects. To exclude a site of action in the penis, we recorded intracorporal pressure responses to intracavernosal injection of MT‐II in the anesthetized rat. MT‐II induced penile erections in a dose‐dependent fashion, with optimal response at 1 μg for both i.c.v. and i.th. routes. Supraspinal MT‐II‐induced erections were completely suppressed by 1 μg SHU‐9119 i.c.v. Yawning was observed with i.c.v. and i.v. MT‐II, whereas spinal injection did not produce this behavior. SHU‐9119 blocked the erectile responses to i.th. MT‐II when injected i.th. but not i.c.v. Intracavernosal MT‐II neither increased intracorporal pressure nor augmented neurostimulated erectile responses. The lumbosacral spinal cord contains MC receptors that can initiate penile erection independent of higher centers. We confirmed the supraspinal proerectile action of MT‐II. These results provide insight into the central melanocortinergic pathways that mediate penile erection and may allow for more efficacious melanotropin‐based therapy for erectile dysfunction.
Body Weight Regulation by Selective MC4 Receptor Agonists and Antagonists
Authors: FOSTER ALAN C. , JOPPA MARGARET , MARKISON STACY , GOGAS KATHY R. , FLECK BETH A. , MURPHY BRIAN J. , WOLFF MEIRA , CISMOWSKI MARY J. , LING NICHOLAS , GOODFELLOW VAL S. , CHEN CHEN , SAUNDERS JOHN , CONLON PAUL J.
Published: July 2009

Abstract: There has been great interest in melanocortin (MC) receptors as targets for the design of novel therapeutics to treat disorders of body weight, such as obesity and cachexia. Both genetic and pharmacological evidence points toward central MC4 receptors as the principal target. Using highly selective peptide tools for the MC4 receptor, which have become available recently, we have provided pharmacological confirmation that central MC4 receptors are the prime mediators of the anorexic and orexigenic effects reported for melanocortin agonists and antagonists, respectively. The current progress with receptor‐selective small molecule agonist and antagonist drugs should enable the therapeutic potential of MC4 receptor activation and inhibition to be assessed in the clinic in the near future.
Expression, Desensitization, and Internalization of the ACTH Receptor (MC2R)
Authors: CLARK ADRIAN J.L. , BAIG ASMA H. , NOON LUKE , SWORDS FRANCESCA M. , HUNYADY LASZLO , KING PETER J.
Published: July 2009

Abstract: Research into the functions and mechanisms of action of the melanocortin 2 receptor (MC2R) has been severely hampered by difficulties in expressing this gene in heterologous cells. This probably arises because of the need for a cofactor for cell surface expression. Using either the Y1 cell line that expresses endogenous MC2R or the Y6 cell line that expresses this putative expression factor, we have explored the mechanisms of desensitization and internalization after agonist stimulation. Protein kinase A dependence of desensitization has been demonstrated, although internalization is apparently independent of this kinase and dependent on a G protein receptor kinase. Possible underlying reasons for this paradox are discussed.
A Polymorphic Form of Steroidogenic Factor 1 Associated with ACTH Receptor Deficiency in Mouse Adrenal Cell Mutants
Authors: SCHIMMER BERNARD P. , CORDOVA MARTHA , TSAO JENNIVINE , FRIGERI CLAUDIA
Published: July 2009

Abstract: We have described a family of adrenocortical tumor cell mutants (including clones OS3, Y6, and 10r9) that are resistant to ACTH because they fail to express the gene encoding the ACTH receptor (MC2R). The MC2R deficiency results from a mutation that impairs the activity of the nuclear receptor steroidogenic factor 1 (SF1) at the MC2R promoter. In this report, we show that ACTH resistance in the mutant clones is associated with a Sf1 gene that has Ser at codon 172 instead of Ala. In two of the three mutant clones, this Sf1 allele is amplified together with flanking DNA from chromosome 2 that includes the genes encoding germ cell nuclear factor and the beta‐type proteosome subunit Psmb7. SF1A172 and SF1S172 exhibit little or no difference in transcriptional activity in SF1‐dependent reporter gene assays, suggesting that SF1S172 per se is not directly responsible for the loss of MC2R expression. Instead, the Sf1S172 allele appears to be a marker of ACTH resistance in this family of adrenocortical tumor cell mutants, possibly reflecting the activity of a neighboring gene.
Lack of Proopiomelanocortin Peptides Results in Obesity and Defective Adrenal Function but Normal Melanocyte Pigmentation in the Murine C57BL/6 Genetic Background
Authors: SMART JAMES L. , LOW MALCOLM J.
Published: July 2009

Abstract: Mice deficient in proopiomelanocortin peptides (Pomc−/−) generated on a 129 (Aw/ Aw) genetic background were back‐crossed onto the C57BL/6 (a/a) genetic background. These mice exhibited most of the phenotypic characteristics previously reported on the 129 genetic background (Yaswen et al. 1999. Nat. Med. 5: 1066–1070). Adult mice became obese, their adrenals were atrophied, and they had undetectable plasma corticosterone in basal and stressed states. The partial perinatal lethality previously reported was also present on the C57BL/6 background. In addition, we found that both male and female homozygote (−/−) adults were fertile, but when homozygous males were intercrossed with homozygous females, all the pups died in the perinatal period. Attempts to rescue the perinatal lethality of pups from homozygous breeder pairs by supplementing the mother's drinking water with glucocorticoids were unsuccessful. Furthermore, failure to stimulate adrenal development and corticosterone production/release with daily exogenous adreno‐corticotropin‐stimulating hormone (ACTH) injections indicates an adrenal dependence on POMC peptides for normal development and function. While the original Pomc−/− mice, bred on a mixed white‐bellied agouti (Aw/ Aw) 129 genetic background, had patchy alternations in their coat color, they clearly were not a uniform yellow like the lethal yellow (Ay/a) mice. Our Pomc−/− mice bred onto the C57BL/6 (a/a) genetic background had a black coat color indistinguishable from that of the wild‐type C57BL/6 mice, further suggesting that the POMC peptide melanocyte‐stimulating hormone (α‐MSH) is not essential for the production of eumelanin (black/brown) pigmentation.
Putative Targets of CNS Melanocortin Receptor Activity
Authors: LAMAR CLIFFORD R. , GARDNER WENDI , BRAZDA AMY , KESTERSON ROBERT A.
Published: July 2009

Abstract: Chronic antagonism of hypothalamic melanocortin receptors, primarily melanocortin‐4 receptor (MC4R), is the molecular basis for “agouti obesity syndrome,” whereas suppression of MC4R gene activity due to genetic mutations induces obesity in both rodents and humans. However, little is known about the neurocircuitry of MC4R‐mediated control of energy balance, the regulation of MC4R gene expression, or how suppression of MC4R activity leads to differential expression of potential downstream central nervous system (CNS) targets or effectors of melanocortin signaling. This paper focuses on strategies for mapping CNS melanocortin circuits using transgenic mouse models for conditional expression of MC4R and MC3R as well as progress in characterizing the murine MC4R promoter. Additionally, preliminary studies that focus on putative targets of melanocortinergic signaling will include a discussion of CD81, a gene identified using the polymerase chain reaction‐based method of suppression subtractive hybridization. CD81, first described as TAPA‐1 (target of antiproliferative antibody), is a member of the tetraspanin family of cell surface proteins believed to function in cell‐cell adhesion, signal transduction, and possibly neuronal plasticity. Elevated expression of CD81 mRNA in hypothalamic regions of obese yellow mice suggests that loss of MC4R activity may lead to altered neuronal function via modulation of the cell surface protein CD81.
The Central Melanocortin System and Fever
Authors: TATRO JEFFREY B. , SINHA PARTHA S.
Published: July 2009

Abstract: Fever is a phylogenetically ancient response that is mounted upon exposure of the host to pathogens or inflammatory agents. Melanocortin agonists act centrally to inhibit fever by acting at receptors, including the melanocortin‐4 receptor, which is prominently expressed in key hypothalamic thermoregulatory centers. Furthermore, endogenous melanocortins act centrally as physiological modulators of fever, recruited during the febrile response to restrain its intensity. Functionally, these actions lie at the interface between the anti‐inflammatory effects of melanocortins, which involve suppression of the synthesis and actions of proinflammatory cytokines, and the central control of thermoregulation. Considering the extensive neuroanatomic and functional overlaps between central pathways and peripheral effectors involved in thermoregulation and energy balance, it is not surprising that melanocortins have been found to influence the metabolic economy profoundly in pathological as well as normal states. For example, despite suppressing endotoxin‐induced fever, endogenous melanocortins appear to mediate the associated anorexia, a classic component of the “illness syndrome” accompanying acute infections, and promote a negative energy balance. The thermoregulatory actions of melanocortins are in several respects functionally opposed, and are remarkably dependent on physiological state, indicating that responsiveness to melanocortins is a physiologically modulated variable. Elucidating the anti‐inflammatory and thermoregulatory roles of central melanocortin receptors during inflammatory states may lead to novel pharmacotherapeutic targets based on selective targeting of melanocortin receptor subtypes, for clinical benefit in human disease states involving neuroinflammatory components and metabolic wasting.
Sequence Characterization of Teleost Fish Melanocortin Receptors
Authors: LOGAN DARREN W. , BRYSON‐RICHARDSON ROBERT J. , TAYLOR MARTIN S. , CURRIE PETER , JACKSON IAN J.
Published: July 2009

Abstract: Zebrafish are an excellent model system for studying the function of melanocortins in developmental and physiological processes, not least because there are a considerable number of mutant lines in which pigment patterns are affected. The behavior of fish melanophores is influenced by α‐melanocyte‐stimulating hormone (α‐MSH) and melanin‐concentrating hormone (MCH). We have used a rapid assay for α‐MSH and MCH function using melanophores present on single zebrafish scales. By in silico analysis, we have identified the full complement of melanocortin receptors in both zebrafish and the pufferfish, Fugu. Mammals have five such receptors. Zebrafish have six melanocortin receptors, including two MC5R orthologues, whereas Fugu, lacking MC3R, has only four. We have confirmed the sequences of these 10 genes and show the comparison of the amino acid sequences of the encoded proteins with the orthologous receptor in other vertebrates.
Significance of the Melanocortin 1 Receptor in Regulating Human Melanocyte Pigmentation, Proliferation, and Survival
Authors: KADEKARO ANA LUISA , KANTO HIROMI , KAVANAGH RENNY , ABDEL‐MALEK ZALFA A.
Published: July 2009

Abstract: The characterization of the melanocortin 1 receptor (MC1R) expressed on human melanocytes and the findings that certain mutations in the POMC gene or the MC1R gene result in red hair phenotype underscore the significance of melanocortins and MC1R in regulating human pigmentation. We demonstrated that human melanocytes respond to α‐melanocortin (α‐MSH) or ACTH with increased proliferation and melanogenesis, and to agouti signaling protein by abrogation of these effects. α‐MSH and ACTH were equipotent and more potent than β‐MSH, and γ‐MSH was the least potent in activating the MC1R and stimulating melanogenesis and proliferation of human melanocytes. We characterized the MC1R genotype in a panel of human melanocyte cultures and identified three cultures that were homozygous for Arg160Trp, heterozygous for Arg151Cys and Asp294His, and heterozygous for Arg160Trp and Asp294His substitutions, respectively. Those cultures failed to respond to α‐MSH with increase in cAMP levels, tyrosinase activity, or proliferation and had an exaggerated response to the cytotoxic effect of ultraviolet (UV) radiation. These loss‐of‐function mutations have been associated with red hair phenotype and increased risk for skin cancer. Melanocytes homozygous for Val29Met substitution in MC1R responded normally to α‐MSH and UVB, suggesting that this variant is a polymorphism. We observed that α‐MSH promotes human melanocyte survival by inhibiting the UV‐induced apoptosis independently of melanin synthesis. This effect was absent in human melanocytes with loss of function MC1R mutations. We predict that the survival effect of α‐MSH is caused by reduction of UV‐induced DNA damage and contributes to the prevention of melanoma.
The Roles of Activin in Cytoprotection and Tissue Repair
Authors: WANKELL MIRIAM , WERNER SILKE , ALZHEIMER CHRISTIAN , WERNER SABINE
Published: July 2009

Abstract: Activin is a member of the transforming growth factor beta family of growth and differentiation factors. Initially discovered as a protein that stimulates release of follicle‐stimulating hormone, it is now well accepted as an important regulator of cell growth and differentiation. Most interestingly, a series of previous studies have revealed novel roles of activin in inflammation and repair. Our own results have provided evidence for an important function of activin in cutaneous wound repair as well as in neuroprotection, and these data will be summarized and discussed in this chapter.
Tissue Growth and Remodeling of the Embryonic and Adult Adrenal Gland
Authors: BLAND MICHELLE L. , DESCLOZEAUX MARION , INGRAHAM HOLLY A.
Published: July 2009

Abstract: The adrenal gland provides a model system for the study of tissue remodeling in endocrine physiology. For example, proper adrenal development requires proliferation of the adrenogonadal primordia, separation of adrenal and gonadal precursors, and cell migration that unites the adrenal cortex and adrenal medulla. In the adult, normal adrenal function is assured by the adrenal gland's unique capacity for growth in response to both tissue injury and physiological demand. Identification of the molecular and genetic programs underlying tissue remodeling in the adrenal is important for understanding basic aspects of development and regeneration, as well as adrenal disease. Here, we will highlight the roles that nuclear receptors and pituitary hormones play in regulating fetal adrenal development and adult adrenal growth. In addition, we will review the most current data on how extracellular signaling pathways are coupled to the function of these important regulators of adrenal development and function.