Home About us Contact
|
Home About us Contact | ||
|
|
||
Many Types (many + type)
Selected AbstractsSpeciation via species interactions: the divergence of mating traits within speciesECOLOGY LETTERS, Issue 4 2010Conrad J. Hoskin Ecology Letters (2010) 13: 409,420 Abstract A species may overlap with a mosaic of species across its geographic range. Many types of species interaction cause selection on mating traits, but their role in generating within-species divergence has been neglected. The pattern of reproductive character displacement (RCD) has been classically attributed to reinforcement, a process driven by selection against hybridisation. Recent reinforcement research shows that sexual isolation can result between displaced and non-displaced populations. We argue that RCD (and hence potentially speciation) among populations can be generated by a variety of fundamental species interactions beyond reinforcement. We unify these interactions under one process of mating trait divergence and speciation (,RCD speciation'). This process can occur in many geographic settings. Because selection is acting directly on mating traits, rapid speciation can result involving little differentiation in other traits. This pattern of diversification is seen in many groups and regions, and has previously been attributed to sexual selection alone. [source] Quorum-sensing in Gram-negative bacteriaFEMS MICROBIOLOGY REVIEWS, Issue 4 2001Neil A Whitehead Abstract It has become increasingly and widely recognised that bacteria do not exist as solitary cells, but are colonial organisms that exploit elaborate systems of intercellular communication to facilitate their adaptation to changing environmental conditions. The languages by which bacteria communicate take the form of chemical signals, excreted from the cells, which can elicit profound physiological changes. Many types of signalling molecules, which regulate diverse phenotypes across distant genera, have been described. The most common signalling molecules found in Gram-negative bacteria are N -acyl derivatives of homoserine lactone (acyl HSLs). Modulation of the physiological processes controlled by acyl HSLs (and, indeed, many of the non-acyl HSL-mediated systems) occurs in a cell density- and growth phase-dependent manner. Therefore, the term ,quorum-sensing' has been coined to describe this ability of bacteria to monitor cell density before expressing a phenotype. In this paper, we review the current state of research concerning acyl HSL-mediated quorum-sensing. We also describe two non-acyl HSL-based systems utilised by the phytopathogens Ralstonia solanacearum and Xanthomonas campestris. [source] Impaired efflux of cholesterol from aged cells and its molecular mechanism: A basis for age-related enhancement of atherosclerosisGERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 3 2007Shizuya Yamashita Aging is one of the risk factors for atherosclerotic cardiovascular diseases, however, its molecular mechanism is currently unknown. Many types of cells in the atherosclerotic lesions are considered to have various biological abnormalities such as impaired lipid homeostasis and slow cell proliferation, which may be related to senescence at cellular levels. One of the common characteristics of senescent cells in vitro is the alteration of actin cytoskeletons, which were reported to be involved in the intracellular transport of lipids. Cholesterol efflux from the cells is the initial step of reverse cholesterol transport, a major protective system against atherosclerosis. Recently, we demonstrated that Cdc42, a member of the Rho -GTPase family, might be crucial for cellular lipid transport and cholesterol efflux based upon studies of Tangier cells that are deficient in ABCA1 gene. In the current review, we also indicate that the expression of Cdc42 is decreased in the cells from aged subjects in close association with the retarded intracellular lipid transport. Furthermore, the Cdc42 expression is reduced by culturing fibroblasts in vitro for a long duration. Werner syndrome (WS) is characterized by the early onset of senescent phenotypes including premature atherosclerotic cardiovascular diseases, although the underlying molecular mechanism for the enhanced atherosclerosis has not been fully understood yet. We examined the intracellular lipid transport and cholesterol efflux and the expression levels of cholesterol efflux-related molecules in skin fibroblasts obtained from patients with WS. Cholesterol efflux was markedly reduced in the WS fibroblasts in association with an increased cellular cholesterol content. Fluorescent recovery after photobleaching technique revealed that intracellular lipid transport around Golgi apparatus was markedly reduced when using a C6-NBD-ceramide as a tracer. Cdc42 protein and its guanosine 5,-triphosphate-bound active form were markedly reduced in the WS fibroblasts. The adenovirus-mediated complementation of wild-type Cdc42 corrected the impaired cholesterol efflux, intracellular lipid transport and cellular cholesterol levels in the WS fibroblasts. These data indicate that the reduced expression of Cdc42 might be responsible for the abnormal lipid transport, which in turn might be related to the accelerated cardiovascular manifestations in WS patients. The current review focuses on the impaired efflux of cholesterol from aged cells and its molecular mechanism as a basis for age-related enhancement of atherosclerosis. [source] Pathology of lymphoma progressionHISTOPATHOLOGY, Issue 4 2001H K Müller-Hermelink Reflecting the stepwise process of oncogenesis, lymphomas may cumulatively develop a more aggressive phenotype during the course of disease, a process referred to as lymphoma progression. Although morphological, clinical and biological aspects of lymphoma progression do not always overlap, changes in lymphoma morphology frequently indicate alterations in the clinical and biological behaviour of the disease. Indolent and aggressive lymphomas in disease progression can either be clonally related or represent clonally unrelated neoplasms. We propose to use the term ,lymphoma progression' in a biological sense denoting only clonal development of and within a lymphoma entity. The term ,composite lymphoma' should be used as a merely descriptive morphological designation for different lymphoma entities in one individual irrespective of clonal relationship. Many types of aggressive B-cell non-Hodgkin's lymphomas and Hodgkin's lymphomas are reported to secondarily develop in lymphoma progression. Genetic changes associated with lymphoma progression frequently abrogate the differentiating effects of alterations occurring in indolent lymphomas, leading to increased cell proliferation. Within different lymphoma entities, high-risk disease variants mimicking lymphoma progression exist. [source] Auxiliary functions for molecular integrals with Slater-type orbitals.INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 9 2006Abstract Many types of molecular integrals involving Slater functions can be expressed, with the ,-function method in terms of sets of one-dimensional auxiliary integrals whose integrands contain two-range functions. After reviewing the properties of these functions (including recurrence relations, derivatives, integral representations, and series expansions), we carry out a detailed study of the auxiliary integrals aimed to facilitate both the formal and computational applications of the ,-function method. The usefulness of this study in formal applications is illustrated with an example. The high performance in numerical applications is proved by the development of a very efficient program for the calculation of two-center integrals with Slater functions corresponding to electrostatic potential, electric field, and electric field gradient. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Subnuclear targeting of Runx1 Is required for synergistic activation of the myeloid specific M-CSF receptor promoter by PU.1,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 4 2005Xiangen Li Abstract Many types of acute myelogenous leukemia involve chromosomal translocations that target the C-terminus of Runx1/AML1 transcription factor, a master regulator of hematopoiesis. The C-terminus of Runx1/AML1 that includes the nuclear matrix targeting signal (NMTS) is essential for embryonic development, hematopoiesis, and target gene regulation. During the onset and normal progression of hematopoiesis, several lineage-specific factors such as C/EBP, and PU.1 interact with Runx1 to regulate transcription combinatorially. Here we addressed the functional interplay between subnuclear targeting of Runx1 and gene activation during hematopoiesis. Point mutations were generated in the NMTS of the human Runx1 protein and tested for their effect on transcriptional cooperativity with C/EBP, and PU.1 at myeloid-specific promoters. We characterized five mutants that do not alter nuclear import, DNA binding or C/EBP,-dependent synergistic activation of the target gene promoters. However a critical tyrosine in the NMTS is required for subnuclear targeting and activation of the granulocyte-macrophage colony stimulating factor (GM-CSF) promoter. Furthermore, this point mutation is defective for transcriptional synergism with PU.1 on the macrophage colony stimulating factor (MCSF) receptor c-FMS promoter. Our results indicate that the NMTS region of Runx1 is required for functional interactions with PU.1. Taken together, our findings establish that subnuclear targeting of Runx1 is a critical component of myeloid-specific transcriptional control. © 2005 Wiley-Liss, Inc. [source] How does the USA PATRIOT Act affect international business?JOURNAL OF CORPORATE ACCOUNTING & FINANCE, Issue 6 2002Enger McCartney-Smith Congress passed the USA PATRIOT Act to combat terrorist money laundering. But the law isn't confined just to banks, say the attorney authors of this article. Many types of U.S. companies can be affected. However, many companies,both domestic and foreign,are reluctant to reveal security breaches or questionable transactions, fearing public disclosure. Are these fears justified? And what about the USA PATRIOT Act's expansion of the federal government's power to investigate foreign businesses? © 2002 Wiley Periodicals, Inc. [source] The ZiReal Post: A New Ceramic Implant AbutmentJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 1 2003URS BRODBECK DMD ABSTRACT Restorations in the anterior esthetic zone present significant challenges in both the surgical and prosthetic phases of implant dentistry. Titanium has been established as the material of choice for endosseous implants, resulting in a high degree of predictability. Many types of implants require transmucosal abutments to retain implant restorations. Ceramics may be the ideal material to replace natural teeth, but most transmucosal abutments are made of titanium. However, ceramics may also be used as abutments in implant restorations. This combination of ceramics for abutment and crown provides better translucency for the implant restoration than is available with metal abutments and porcelain-fused-to-metal crowns. Ceramic abutments and implant restorations also minimize the gray color associated with metal components that is transmitted through the peri-implant tissues. Customized emergence profiles also may be obtained with ceramic abutments; this generally improves the predictability and consistency of the esthetics obtainable in implant restorations. Zirconia as a ceramic material offers not only outstanding material properties but also a well-documented biocompatibility. CLINICAL SIGNIFICANCE This article discusses the clinical and laboratory features of a new ceramic abutment, ZiRealÔ Post (Implant Innovations, Inc., Palm Beach Gardens, Florida). [source] Transitions in function at low Reynolds number: hair-bearing animal appendagesMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 17-18 2001M. A. R. Koehl Abstract Many types of animals use appendages bearing arrays of hair-like structures to capture molecules (e.g. olfactory antennae, gills) or particles (e.g. suspension-feeding appendages) from the surrounding water or air, and to locomote or move fluid past themselves. The performance of these functions depends on how much of the fluid encountered by the array of hairs flows through the gaps between the hairs rather than around the perimeter of the whole array. By modelling such arrays of hairs as rows of finite width of cylinders operating at low Reynolds numbers, the fluid velocity fields with respect to the hairs were calculated. Such models revealed a transition from non-leaky to leaky behaviour as Re was increased. The purpose of this paper is to provide a brief review of the features of this transition as revealed by models, and then to describe examples of how animals use the transition in fluid flow to perform particular functions: rejection of captured material by copepods, and sniffing by lobsters. Copyright © 2001 John Wiley & Sons, Ltd. [source] Regulation of Blood,Brain Barrier PermeabilityMICROCIRCULATION, Issue 2 2001WILLIAM G. MAYHAN ABSTRACT The blood-brain barrier minimizes the entry of molecules into brain tissue. This restriction arises by the presence of tight junctions (zonulae occludens) between adjacent endothelial cells and a relative paucity of pinocytotic vesicles within endothelium of cerebral arterioles, capillaries, and venules. Many types of stimuli can alter the permeability characteristics of the blood-brain barrier. Acute increases in arterial blood pressure beyond the autoregulatory capacity of cerebral blood vessels, application of hyperosmolar solutions, application of various inflammatory mediators known to be elevated during brain injury, and/or activation of blood-borne elements such as leukocytes can produce changes in permeability of the blood-brain barrier. The second messenger systems that account for increases in permeability of the blood-brain barrier during pathophysiologic conditions, however, remain poorly defined. This review will summarize studies that have examined factors that influence disruption of the blood-brain barrier, and will discuss the contribution of various cellular second messenger pathways in disruption of the blood-brain barrier during pathophysiologic conditions. [source] Interactive visualization of quantum-chemistry dataACTA CRYSTALLOGRAPHICA SECTION A, Issue 5 2010Yun Jang Simulation and computation in chemistry studies have improved as computational power has increased over recent decades. Many types of chemistry simulation results are available, from atomic level bonding to volumetric representations of electron density. However, tools for the visualization of the results from quantum-chemistry computations are still limited to showing atomic bonds and isosurfaces or isocontours corresponding to certain isovalues. In this work, we study the volumetric representations of the results from quantum-chemistry computations, and evaluate and visualize the representations directly on a modern graphics processing unit without resampling the result in grid structures. Our visualization tool handles the direct evaluation of the approximated wavefunctions described as a combination of Gaussian-like primitive basis functions. For visualizations, we use a slice-based volume-rendering technique with a two-dimensional transfer function, volume clipping and illustrative rendering in order to reveal and enhance the quantum-chemistry structure. Since there is no need to resample the volume from the functional representations for the volume rendering, two issues, data transfer and resampling resolution, can be ignored; therefore, it is possible to explore interactively a large amount of different information in the computation results. [source] Population-based study of non-infectious rhinitis in relation to occupational exposure, age, sex, and smokingAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 1 2002Johan Hellgren MD Abstract Background Many types of occupational exposure are associated with the risk of non-infectious rhinitis. We investigate the risk factors for this association. Methods A random population of 2,044 subjects (aged 21,51) answered a questionnaire that was comprised of detailed questions on occupational exposure, nasal complaints, and smoking. NIR was defined as the sensation of nasal blockage and/or attacks of sneezing without having a cold. The incidence rates for NIR among exposed and unexposed were calculated. In the different exposed groups, only NIR with onset after the start of exposure was regarded as exposed. If a subject reported NIR before the relevant exposure started, he/she was excluded from that analysis. Relative risks (RR) were calculated as incidence rate ratios. Odds ratios controlling for smoking, age, and atopy were also calculated. Results The incidence rate for NIR was 13.5/1,000 person-years. Males exposed to fire fumes (RR 2.5, 95% confidence interval (CI) 1.5,4.1), women exposed to paper dust (RR 2.0, 95% CI 1.5,2.9), and male cleaners (RR 3.1, 95% CI 1.9,5.1) displayed an increased risk of developing NIR. Smoking was associated with an increased risk of NIR for both sexes. Conclusion Exposure to several occupational irritants is associated with a higher risk of developing NIR. Am. J. Ind. Med. 42:23,28, 2002. © 2002 Wiley-Liss, Inc. [source] SYMPOSIUM REVIEW: Lipid microdomains and the regulation of ion channel functionTHE JOURNAL OF PHYSIOLOGY, Issue 17 2010Caroline Dart Many types of ion channel localize to cholesterol and sphingolipid-enriched regions of the plasma membrane known as lipid microdomains or ,rafts'. The precise physiological role of these unique lipid microenvironments remains elusive due largely to difficulties associated with studying these potentially extremely small and dynamic domains. Nevertheless, increasing evidence suggests that membrane rafts regulate channel function in a number of different ways. Raft-enriched lipids such as cholesterol and sphingolipids exert effects on channel activity either through direct protein,lipid interactions or by influencing the physical properties of the bilayer. Rafts also appear to selectively recruit interacting signalling molecules to generate subcellular compartments that may be important for efficient and selective signal transduction. Direct interaction with raft-associated scaffold proteins such as caveolin can also influence channel function by altering gating kinetics or by affecting trafficking and surface expression. Selective association of ion channels with specific lipid microenvironments within the membrane is thus likely to be an important and fundamental regulatory aspect of channel physiology. This brief review highlights some of the existing evidence for raft modulation of channel function. [source] Outline of the International Organization for Standardization Standard for Circulatory Support Devices (ISO 14708-5)ARTIFICIAL ORGANS, Issue 9 2010Kou Imachi Abstract The rapid progress of artificial heart and circulatory support devices enables us to apply them to severe heart failure patients. Many types of circulatory support devices have been developed in the United States, Europe, and Japan. This situation urged the establishment of an International Organization for Standardization (ISO) Standard for the circulatory support devices. A new work, "Cardiac Ventricular Assist Devices," was proposed to the ISO/TC150/SC6 (TC150: Technical Committee of Implants for Surgery, SC6: Sub-committee of Active Implants) in 2000, and the work was finalized for publication at a 2009 meeting of the ISO/TC150 in Kyoto. In this article, the authors would like to introduce the ISO system and the outline of the ISO Standard for Circulatory Support Devices. [source] Index Pteridophytorum Guadalupensium or a revised checklist to the ferns and club mosses of Guadeloupe (French West Indies)BOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2009MAARTEN J. M. CHRISTENHUSZ Recent revision of the fern diversity of the French Caribbean island of Guadeloupe and its dependencies (Marie Galante, Les Saintes and La Désirade) resulted in the listing of 292 native ferns and club mosses in 28 families and 88 genera, of which eight ferns are endemic to Guadeloupe and 20 taxa are only recorded from the Lesser Antilles. Additionally, 21 species have recently been found to be naturalized. Nineteen new combinations are made and a new hybrid is described. Many types from the Fée collection have been reassessed and a number of names are lecto- or neotypified. Studied specimens are cited and localities are provided. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161, 213,277. [source] Basic principles of radiotherapy in ophtalmic oncologyACTA OPHTHALMOLOGICA, Issue 2009R DENDALE Ophtalmologic Radiation Oncology concerns intra ocular tumors, orbital tumors and eyelid tumors. In these locations, tumors are often close to normal critical tissues, increasing the risk of radiation toxicities. Basic principles of ophthalmic radiotherapy are not really different from radiotherapy of others organs. They are based on a precise description of the tumor volume, knowledge of potential tumor local or regional extension, knowledge of tissue biological radiosensitivity for tumors and the surrounding normal tissues. Based on these features, treatment modalities (radiation treatment length and fractionation) are determined to fulfill the aims of medical curative intents: good local control with acceptable toxicities or the aims of medical palliative intents: to relief with minimal toxicities. Many types of radiation therapy can be used for ophthalmic tumors: brachytherapy, orthovoltage radiotherapy, conformal therapy with photons and electrons including intensity modulated radiation therapy, protontherapy, and the use of specific devices such as CyberKnife and Tomotherapy. All of these techniques have their advantages and their disadvantages, leading the radiation oncologist to make a choice depending on the tumor site and characteristics. [source] Finding stale-value errors in concurrent programsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 12 2004Michael Burrows Abstract Concurrent programs can suffer from many types of errors, not just the well-studied problems of deadlocks and simple race conditions on variables. This paper addresses a kind of race condition that arises from reading a variable whose value is possibly out of date. The paper introduces a simple technique for detecting such stale values, and reports on the encouraging experience with a compile-time checker that uses the technique. Copyright © 2004 John Wiley & Sons, Ltd. [source] Role of orexin in the regulation of glucose homeostasisACTA PHYSIOLOGICA, Issue 3 2010H. Tsuneki Abstract Orexin-A (hypocretin-1) and orexin-B (hypocretin-2) are hypothalamic neuropeptides that play key roles in the regulation of wakefulness, feeding, reward, autonomic functions and energy homeostasis. To control these functions indispensable for survival, orexin-expressing neurones integrate peripheral metabolic signals, interact with many types of neurones in the brain and modulate their activities via the activation of orexin-1 receptor or orexin-2 receptor. In addition, a new functional role of orexin is emerging in the regulation of insulin and leptin sensitivities responsible for whole-body glucose metabolism. Recent evidence indicates that orexin efficiently protects against the development of peripheral insulin resistance induced by ageing or high-fat feeding in mice. In particular, the orexin receptor-2 signalling appears to confer resistance to diet-induced obesity and insulin insensitivity by improving leptin sensitivity. In fact, the expression of orexin gene is known to be down-regulated by hyperglycaemia in the rodent model of diabetes, such as ob/ob and db/db mice. Moreover, the levels of orexin receptor-2 mRNA have been shown to decline in the brain of mice along with ageing. These suggest that hyperglycaemia due to insulin insensitivity during ageing or by habitual consumption of a high-fat diet leads to the reduction in orexin expression in the hypothalamus, thereby further exacerbating peripheral insulin resistance. Therefore, orexin receptor controlling hypothalamic insulin/leptin actions may be a new target for possible future treatment of hyperglycaemia in patients with type 2 diabetes. [source] The Measurement of Daily Surge and Its Relevance to Disaster PreparednessACADEMIC EMERGENCY MEDICINE, Issue 11 2006Melissa L. McCarthy MS This article reviews what is known about daily emergency department (ED) surge and ED surge capacity and illustrates its potential relevance during a catastrophic event. Daily ED surge is a sudden increase in the demand for ED services. There is no well-accepted, objective measure of daily ED surge. The authors propose that daily and catastrophic ED surge can be measured by the magnitude of the surge, as well as by the nature and severity of the illnesses and injuries that patients present with during the surge. The magnitude of an ED surge can be measured by the patient arrival rate per hour. The nature and severity of the surge can be measured by the type (e.g., trauma vs. infection vs. biohazard) and acuity (e.g., triage level) of the surge. Surge capacity is defined as the extent to which a system can respond to a rapid and sizeable increase in the demand for resources. ED surge capacity includes multiple dimensions, such as systems, space, staffing, and supplies. A multidimensional measure is needed that reflects both the core components and their relative contribution to ED surge capacity. Although many types of factors may influence ED surge capacity, relatively little formal research has been conducted in this area. A better understanding of daily ED surge capacity and influencing factors will improve our ability to simulate the potential impact that different types of catastrophic events may have on the surge capacity of hospital EDs nationwide. [source] Directional change produced by perpendicularly-oriented microgrooves is microtubule-dependent for fibroblasts and epitheliumCYTOSKELETON, Issue 5 2009Douglas W. Hamilton Abstract Anisotropic substrata such as micromachined grooves can control cell shape, orientation, and the direction of cell movement, a phenomena termed topographic guidance. Although many types of cells exhibit topographic guidance, little is known regarding cell responses to conflicting topographic cues. We employed a substratum with intersecting grooves in order to present fibroblasts and epithelial cells with conflicting topographic cues. Using time-lapse and confocal microscopy, we examined cell behavior at groove intersections. Migrating fibroblasts and epithelial cells typically extended a cell process into the intersection ahead of the cell body. After travelling along the "X" groove to enter the intersection, the leading lamellipodia of the cell body encountered the perpendicular "Y" groove, and spread latterly along the "Y" groove. The formation of lateral lamellipodia resulted in cells forming "T" or "L" morphologies, which were characterized by the formation of phosphotyrosine-rich focal adhesions at the leading edges. The "Y" groove did not prove an absolute barrier to cell migration, particularly for epithelial cells. Analysis of cytoskeletal distribution revealed that F-actin bundles did not adapt closely to the groove patterns, but typically did align to either the "X" or "Y" grooves. In contrast microtubules (MT) adapted closely to the walls. Inhibition of microtubule nucleation attenuated fibroblast and epithelial cell orientation within the intersection of the perpendicular grooves. We conclude that MT may be the prime determinant of fibroblast and epithelial cell conformation to conflicting topographies. Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source] Debridement and wound bed preparationDERMATOLOGIC THERAPY, Issue 6 2006Anna F. Falabella ABSTRACT:, Debridement can play a vital role in wound bed preparation and the removal of barriers that impair wound healing. In accordance with the TIME principles, debridement can help remove nonviable tissue, control inflammation or infection, decrease excess moisture, and stimulate a nonadvancing wound edge. There are many types of debridement, each with a set of advantages and disadvantages that must be clearly understood by the healthcare team. Failure to use the correct debridement method for a given type of wound may lead to further delays in healing, increase patient suffering, and unnecessarily increase the cost of care. This review article discusses the various methods of debridement, describes currently available debriding agents, evaluates the clinical data regarding their efficacy and safety, and describes strategies for the management of problematic nonhealing wounds. [source] Design Thinking to Make Organization Change and Development More ResponsiveDESIGN MANAGEMENT REVIEW, Issue 2 2010Steve Sato There are many types of organization change and development (OC&D) approaches, from John Kotter's Leading Change methodology to Robert Schaffer's Rapid Results technique. No matter which you use, success depends on how well it can be adapted to the situation at hand. At Hewlett-Packard, design thinking turned out to be the glue that held everything together. [source] Multiple sites of L-histidine decarboxylase expression in mouse suggest novel developmental functions for histamineDEVELOPMENTAL DYNAMICS, Issue 1 2001Kaj Karlstedt Abstract Histamine mediates many types of physiologic signals in multicellular organisms. To clarify the developmental role of histamine, we have examined the developmental expression of L-histidine decarboxylase (HDC) mRNA and the production of histamine during mouse development. The predominant expression of HDC in mouse development was seen in mast cells. The HDC expression was evident from embryonal day 13 (Ed13) until birth, and the mast cells were seen in most peripheral tissues. Several novel sites with a prominent HDC mRNA expression were revealed. In the brain, the choroid plexus showed HDC expression at Ed14 and the raphe neurons at Ed15. Close to the parturition, at Ed19, the neurons in the tuberomammillary (TM) area and the ventricular neuroepithelia also displayed a clear HDC mRNA expression and histamine immunoreactivity (HA-ir). From Ed14 until birth, the olfactory and nasopharyngeal epithelia showed an intense HDC mRNA expression and HA-ir. In the olfactory epithelia, the olfactory receptor neurons (ORN) were shown to have very prominent histamine immunoreactivity. The bipolar nerve cells in the epithelium extended both to the epithelial surface and into the subepithelial layers to be collected into thick nerve bundles extending caudally toward the olfactory bulbs. Also, in the nasopharynx, an extensive subepithelial network of histamine-immunoreactive nerve fibers were seen. Furthermore, in the peripheral tissues, the degenerating mesonephros (Ed14) and the convoluted tubules in the developing kidneys (Ed15) showed HDC expression, as did the prostate gland (Ed15). In adult mouse brain, the HDC expression resembled the neuronal pattern observed in rat brain. The expression was restricted to the TM area in the ventral hypothalamus, with the main expression in the five TM subgroups called E1,E5. A distinct mouse HDC mRNA expression was also seen in the ependymal wall of the third ventricle, which has not been reported in the rat. The tissue- and cell-specific expression patterns of HDC and histamine presented in this work indicate that histamine could have cell guidance or regulatory roles in development. © 2001 Wiley-Liss, Inc. [source] HEMODYNAMIC MECHANISM OF ESOPHAGEAL VARICESDIGESTIVE ENDOSCOPY, Issue 1 2006Katsutoshi Obara We investigated the correlation between the collaterals around the esophagus and recurrence of esophageal varices in patients with portal hypertension who had undergone endoscopic injection sclerotherapy (EIS). In patients with portal hypertension, many types of collaterals around the esophagus were visualized by endoscopic ultrasonography (EUS). The collaterals outside the esophageal wall detected by EUS were divided into two groups according to the location of the veins: peri-esophageal collateral veins (peri-ECV) and para-esophageal collateral veins (para-ECV) Perforating veins are those that have penetrated the esophageal wall and have connected with either peri-ECV or para-ECV. We demonstrated that severe peri-ECV and large perforating veins play an important role in the development of esophageal varices in untreated patients with portal hypertension. The results of our investigation have shown that detection of peri-ECV and perforating veins by EUS and treatment of them by EIS appears to be important for the treatment of esophageal varices. The disappearance of peri-ECV by EIS is essential for reducing the recurrence rate of esophageal varices. To prevent variceal recurrence, a mucosal fibrosing method using argon plasma coagulation has been widely performed in Japan. If EUS abnormalities are associated with variceal recurrence, we recommend the use of the mucosal fibrosing method. In conclusion, the presence of severe peri-ECV and large perforating veins in the esophageal wall strongly correlate with the recurrence of esophageal varices in patients with portal hypertension. An understanding of these EUS abnormalities on the basis of hemodynamics around the esophagus is important for the management of esophageal varices in patients with portal hypertension. [source] Role of mitogen-activated protein kinase cascades in P2Y receptor-mediated trophic activation of astroglial cells ,DRUG DEVELOPMENT RESEARCH, Issue 2-3 2001Joseph T. Neary Abstract The trophic actions of extracellular nucleotides and nucleosides on astroglial cells in the central nervous system may be important in development as well as injury and repair. Here we summarize recent findings on the signal transduction mechanisms and gene expression that mediate the trophic effects of extracellular ATP on astrocyte cultures, with a particular emphasis on mitogenesis. Activation of ATP/P2Y receptors leads to the stimulation of mitogen-activated protein kinase (MAPK) cascades, which play a crucial role in cellular proliferation, differentiation, and survival. Inhibition of ERK and p38, members of two distinct MAPK cascades, interferes with the ability of extracellular ATP to stimulate astrocyte proliferation, thereby indicating their importance in mitogenic signaling by P2Y receptors. Signaling from P2Y receptors to ERK involves phospholipase D and a calcium-independent protein kinase C isoform, PKC; this pathway is independent of the phosphatidylinositol-phospholipase C / calcium pathway which is also coupled to P2Y receptors. Pharmacological studies suggest that astrocytes may express an as-yet uncloned P2Y receptor that recruits a novel MEK activator in the ERK cascade. Extracellular ATP can also potentiate fibroblast growth factor (FGF)-2-induced proliferation, and studies on interactions between ATP and FGF-2 signaling pathways have revealed that although ATP does not activate cRaf-1, the first protein kinase in the ERK cascade, it can reduce cRaf-1 activation by FGF-2. As intermediate levels of Raf activity stimulate the cell cycle, the partial inhibition of FGF-induced Raf activity by ATP may contribute to the enhancing effect of ATP on FGF-2-induced astrocyte proliferation. Activation of P2Y receptors also leads to nuclear signaling, and the use of DNA arrays has shown that treatment of astrocytes with extracellular ATP results in the up- and downregulation of a number of genes; studies to determine which of these genes are regulated by MAPKs are now in progress. Elucidation of the components of MAPK pathways linked to P2Y receptors and subsequent changes in gene expression may provide targets for a new avenue of drug development aimed at the management of astrogliosis which occurs in many types of neurological disorders and neurodegeneration. Drug Dev. Res. 53:158,165, 2001. Published 2001 Wiley-Liss, Inc. [source] Feeding by Hessian fly [Mayetiola destructor (Say)] larvae does not induce plant indirect defencesECOLOGICAL ENTOMOLOGY, Issue 2 2007JOHN F. TOOKER Abstract 1.,Recent research has addressed the function of herbivore-induced plant volatiles in attracting natural enemies of feeding herbivores. While many types of insect herbivory appear to elicit volatile responses, those triggered by gall insects have received little attention. Previous work indicates that at least one gall insect species induces changes in host-plant volatiles, but no other studies appear to have addressed whether gall insects trigger plant indirect defences. 2.,The volatile responses of wheat to feeding by larvae of the Hessian fly Mayetiola destructor (Say) (Diptera: Cecidomyiidae) were studied to further explore indirect responses of plants to feeding by gall insects. This specialist gall midge species did not elicit a detectable volatile response from wheat plants, whereas a generalist caterpillar triggered volatile release. Moreover, Hessian fly feeding altered volatile responses to subsequent caterpillar herbivory. 3.,These results suggest that Hessian fly larvae exert a degree of control over the defensive responses of their host plants and offer insight into plant-gall insect interactions. Also, the failure of Hessian fly larvae to elicit an indirect defensive response from their host plants may help explain why natural enemies, which often rely on induced volatile cues, fail to inflict significant mortality on M. destructor populations in the field. [source] Bayesian hierarchical models in ecological studies of health,environment effectsENVIRONMETRICS, Issue 2 2003Sylvia Richardson Abstract We describe Bayesian hierarchical models and illustrate their use in epidemiological studies of the effects of environment on health. The framework of Bayesian hierarchical models refers to a generic model building strategy in which unobserved quantities (e.g. statistical parameters, missing or mismeasured data, random effects, etc.) are organized into a small number of discrete levels with logically distinct and scientifically interpretable functions, and probabilistic relationships between them that capture inherent features of the data. It has proved to be successful for analysing many types of complex epidemiological and biomedical data. The general applicability of Bayesian hierarchical models has been enhanced by advances in computational algorithms, notably those belonging to the family of stochastic algorithms based on Markov chain Monte Carlo techniques. In this article, we review different types of design commonly used in studies of environment and health, give details on how to incorporate the hierarchical structure into the different components of the model (baseline risk, exposure) and discuss the model specification at the different levels of the hierarchy with particular attention to the problem of aggregation (ecological) bias. Copyright © 2003 John Wiley & Sons, Ltd. [source] How does intergroup contact reduce prejudice?EUROPEAN JOURNAL OF SOCIAL PSYCHOLOGY, Issue 6 2008Meta-analytic tests of three mediators Recent years have witnessed a renewal of interest in intergroup contact theory. A meta-analysis of more than 500 studies established the theory's basic contention that intergroup contact typically reduces prejudices of many types. This paper addresses the issue of process: just how does contact diminish prejudice? We test meta-analytically the three most studied mediators: contact reduces prejudice by (1) enhancing knowledge about the outgroup, (2) reducing anxiety about intergroup contact, and (3) increasing empathy and perspective taking. Our tests reveal mediational effects for all three of these mediators. However, the mediational value of increased knowledge appears less strong than anxiety reduction and empathy. Limitations of the study and implications of the results are discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source] EVOLUTION O ANTIBIOTIC RESISTANCE BY HUMAN AND BACTERIAL NECHE CONSTRUCTIONEVOLUTION, Issue 3 2005Maciej F. Boni Abstract Antibiotic treatment by humans generates strong viability selection for antibiotic-resistant bacterial strains. The frequency of host antibiotic use often determines the strength of this selection, and changing patterns of antibiotic use can generate many types of behaviors in the population dynamics of resistant and sensitive bacterial populations. In this paper, we present a simple model of hosts dimorphic for their tendency to use/avoid antibiotics and bacterial pathogens dimorphic in their resistance/sensitivity to antibiotic treatment. When a constant fraction of hosts uses antibiotics, the two bacterial strain populations can coexist unless host use-frequency is above a critical value; this critical value is derived as the ratio of the fitness cost of resistance to the fitness cost of undergoing treatment. When strain frequencies can affect host behavior, the dynamics may be analyzed in the light of niche construction. We consider three models underlying changing host behavior: conformism, the avoidance of long infections, and adherence to the advice of public health officials. In the latter two, we find that the pathogen can have quite a strong effect on host behavior. In particular, if antibiotic use is discouraged when resistance levels are high, we observe a classic niche-construction phenomenon of maintaining strain polymorphism even in parameter regions where it would not be expected. [source] Exploring the mast cell enigma: a personal reflection of what remains to be doneEXPERIMENTAL DERMATOLOGY, Issue 2 2008Beate M. Henz Abstract: Mast cells are traditionally viewed as effector cells of allergic reactions and parasitic diseases, but their importance in host defense against bacteria, in tissue remodelling, their bone marrow and stem cell origin and a central role of the stem cell factor (SCF) as mast cell growth and chemotactic factor has been worked out only in recent years. Despite this, major aspects about the nature of the cells and their role in disease remain unclear. This holds in particular for the identification of mast cell precursors and the role of growth factors that stimulate specific mast cell commitment from stem cells, such as nerve growth factor, neutrotrophin-3 and certain interleukins, alone and during interaction with SCF. Early data suggesting also an involvement of specific transcription factors need to be expanded in this process. Furthermore, although mast cell proliferative disease (mastocytosis) has been shown to be often associated with SCF receptor c-kit mutations, reasons for the development of this disease remain unclear. This holds also for mast cell release mechanisms in many types of mast cell-dependent urticaria. Exciting new insights are emerging regarding the role of mast cells in bacterial infections, in defense against tumors, in wound healing and in the interplay with the nervous system, with hormones, and in the neurohormonal network. The aim of this reflection is to delineate the many known and unknown aspects of mast cells, with a special focus on their development, and to discuss in detail two mast cell-related diseases, namely mastocytosis and urticaria. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||