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Distinct Forms (distinct + form)
Selected AbstractsRGS7 Is Palmitoylated and Exists as Biochemically Distinct FormsJOURNAL OF NEUROCHEMISTRY, Issue 5 2000Jeremy J. Rose Abstract:Regulator of G protein signaling (RGS) proteins are GTPase-activating proteins that modulate neurotransmitter and G protein signaling. RGS7 and its binding partners G, and G,5 are enriched in brain, but biochemical mechanisms governing RGS7/G,/G,5 interactions and membrane association are poorly defined. We report that RGS7 exists as one cytosolic and three biochemically distinct membrane-bound fractions (salt-extractable, detergent-extractable, and detergent-insensitive) in brain. To define factors that determine RGS7 membrane attachment, we examined the biochemical properties of recombinant RGS7 and G,5 synthesized in Spodoptera frugiperda insect cells. We have found that membrane-bound but not cytosolic RGS7 is covalently modified by the fatty acid palmitate. G,5 is not palmitoylated. Both unmodified (cytosolic) and palmitoylated (membrane-derived) forms of RGS7, when complexed with G,5, are equally effective stimulators of G,o GTPase activity, suggesting that palmitoylation does not prevent RGS7/G,o interactions. The isolated core RGS domain of RGS7 selectively binds activated G,i/o in brain extracts and is an effective stimulator of both G,o and G,i1 GTPase activities in vitro. In contrast, the RGS7/G,5 complex selectively interacts with G,o only, suggesting that features outside the RGS domain and/or G,5 association dictate RGS7-G, interactions. These findings define previously unrecognized biochemical properties of RGS7, including the first demonstration that RGS7 is palmitoylated. [source] Cutaneous T-cell lymphomaJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 2 2003EA Kotz ABSTRACT Cutaneous T-cell lymphoma (CTCL) is a neoplasm of helper T cells whose first manifestations usually appear in the skin. The various forms of CTCL are distinguished by both clinical features and histopathology. Early on, the diagnosis may be difficult to establish because of its numerous, and often non-specific, clinical presentations. Further, the pathological findings of early lesions may lack the diagnostic features observed in well-developed or advanced disease. The diagnosis of CTCL must be considered in any patient with a chronic, therapy-resistant condition of the skin. In patients with non-specific histological findings, a high index of suspicion and multiple biopsies may eventually lead to a diagnosis of CTCL. Once the diagnosis of CTCL is established, accurate staging is essential both for its effect on treatment decisions and for its prognostic value. In general, CTCL is a chronic, slowly progressive disease with a long evolution. The development of tumours is a poor prognostic sign, as is erythroderma. The Sezary syndrome is a distinct form of erythrodermic CTCL that is characterized by exfoliative erythroderma, lymphadenopathy, lymphocytosis, intense pruritus, and circulating large, abnormal lymphocytes (Sezary cells). When death does occur, it is most often due to septicemia. Treatment of CTCL must be tailored to the individual patient. The most commonly employed treatment options are photochemotherapy and topical chemotherapy. [source] Disorders of carnitine transport and the carnitine cycle,AMERICAN JOURNAL OF MEDICAL GENETICS, Issue 2 2006Nicola Longo Abstract Carnitine plays an essential role in the transfer of long-chain fatty acids across the inner mitochondrial membrane. This transfer requires enzymes and transporters that accumulate carnitine within the cell (OCTN2 carnitine transporter), conjugate it with long chain fatty acids (carnitine palmitoyl transferase 1, CPT1), transfer the acylcarnitine across the inner plasma membrane (carnitine-acylcarnitine translocase, CACT), and conjugate the fatty acid back to Coenzyme A for subsequent beta oxidation (carnitine palmitoyl transferase 2, CPT2). Deficiency of the OCTN2 carnitine transporter causes primary carnitine deficiency, characterized by increased losses of carnitine in the urine and decreased carnitine accumulation in tissues. Patients can present with hypoketotic hypoglycemia and hepatic encephalopathy, or with skeletal and cardiac myopathy. This disease responds to carnitine supplementation. Defects in the liver isoform of CPT1 present with recurrent attacks of fasting hypoketotic hypoglycemia. The heart and the muscle, which express a genetically distinct form of CPT1, are usually unaffected. These patients can have elevated levels of plasma carnitine. CACT deficiency presents in most cases in the neonatal period with hypoglycemia, hyperammonemia, and cardiomyopathy with arrhythmia leading to cardiac arrest. Plasma carnitine levels are extremely low. Deficiency of CPT2 present more frequently in adults with rhabdomyolysis triggered by prolonged exercise. More severe variants of CPT2 deficiency present in the neonatal period similarly to CACT deficiency associated or not with multiple congenital anomalies. Treatment for deficiency of CPT1, CPT2, and CACT consists in a low-fat diet supplemented with medium chain triglycerides that can be metabolized by mitochondria independently from carnitine, carnitine supplements, and avoidance of fasting and sustained exercise. © 2006 Wiley-Liss, Inc. [source] The Effects of Supraoptimal Temperatures on Population Growth and Cortical Patterning in Tetrahymena pyriformis and Tetrahymena thermophila: A ComparisonTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2001JOSEPH FRANKEL ABSTRACT. In this investigation, we compare the multiplication rates and morphogenetic responses of the two most studied Tetrahymena species, T. pyriformis and T. thermophila, at supraoptimal temperatures. Although the upper temperature limits differ greatly in the two species, the pattern of growth responses to high temperature is for the most part similar, with some differences in detail. The transient recovery of cell division at the highest temperature that allows cell division, characteristic of T. pyriformis, is observed in a less distinct form in T. thermophila. Moreover, there is a remarkable difference in developmental response, with drastic abnormalities in patterning of oral structures during the transient recovery of cell division in T. pyriformis, and far more limited abnormalities under similar conditions in T. thermophila. The abnormalities result from spatial disorder in the alignment and orientation of basal body pairs within the early oral primordium, followed by failures in the realignment that normally occurs as oral structures (membranelles and undulating membrane) mature. Both the initial spatial disorder and the failures in realignment are far more severe in T. pyriformis than in T. thermophila. [source] Chronic Recurrent Rhinosinusitis: Disease Severity and Clinical CharacterizationTHE LARYNGOSCOPE, Issue 2 2005Neil Bhattacharyya MD Objectives/Hypothesis: The objective was to clinically characterize and determine disease severity parameters for chronic recurrent rhinosinusitis (CRRS). Study Design: Prospective. Methods: A consecutive series of adult patients undergoing evaluation for CRRS was prospectively evaluated. Patients with four or more acute rhinosinusitis episodes in the previous calendar year with an absence of symptoms between episodes were considered as manifesting CRRS. Symptom severity and disease data from the Rhinosinusitis Symptom Inventory was obtained, as well as Lund staging information from the paranasal sinus CT scan. The Lund staging scores for patients with CRRS were compared with a control group of patients without CRRS. Symptom domain scores and disease severity parameters were compared between the CRRS group and a third group of patients with chronic persistent rhinosinusitis. Results: In all, 30 patients met inclusion criteria for the diagnosis of CRRS. Mean age was 40.9 years with a 3:1 female preponderance. The mean Lund score for patients with CRRS was 3.79. Patients with CRRS failed to demonstrate a statistically different Lund score from control patients (mean Lund score, 4.26 [P = .538]). Symptom severity scores according to Rhinosinusitis Symptom Inventory domains were largely similar for the nasal, facial, and total symptom domains between patients with CRRS versus chronic persistent rhinosinusitis. However, patients with CRRS demonstrated statistically significant increases in oropharyngeal and systemic symptom domain scores. Patients with CRRS also had significant increases in number of antibiotic courses (4.8 vs. 2.9 [P < .001]) and number of missed workdays (8.8 vs. 4.6 d [P = .046]) attributable to rhinosinusitis. Conclusion: Chronic recurrent rhinosinusitis is a distinct form of chronic rhinosinusitis differing somewhat from chronic persistent rhinosinusitis. However, patients with CRRS still experience significant symptoms associated with this diagnosis, which results in significant medication usage and workplace impact. [source] Patterns of Compliance with the German Corporate Governance CodeCORPORATE GOVERNANCE, Issue 4 2008Till Talaulicar ABSTRACT Manuscript Type: Empirical Research Question/Issue: This study investigates whether the form of compliance with the recommendations of the German Corporate Governance Code (GCGC) appears to be idiosyncratic to a specific company or features similarities across firms. The major aim of this research is thus to explore the ability of a classification of compliance patterns to account for the similarities and differences between firms regarding their conformity with the GCGC. Research Findings/Insights: Based on seven dimensions of code compliance, cluster analysis is used to identify discrete groups of companies with similar patterns of code observance. We determine eight patterns of compliance which are characterized by distinct forms of code conformity. Theoretical Academic Implications: The identified cluster solution does not merely reflect the number of rejected code recommendations. Rather, companies with very similar rates of overall compliance with the GCGC are assigned to different clusters because they feature, at the same time, different patterns of code conformity. These findings imply that governance prediction and governance performance studies have to overcome overly aggregated measures of code compliance which only incorporate the number of rejected code recommendations. Practitioner/Policy Implications: This study provides evidence to practitioners and policy makers that firms can be classified regarding their compliance with the code recommendations. In-depth analyses of the identified patterns of compliance furthermore reveal that some patterns may indicate less well substantiated deviations from the code and partly even decouplings of the declared compliance practices. [source] Two distinct forms of minor neurological dysfunction: perspectives emerging from a review of data of the Groningen Perinatal ProjectDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 8 2002Mijna Hadders-Algra MD PhD First page of article [source] Understanding the impact of painful diabetic neuropathyDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue S1 2003Cristian Quattrini Abstract Painful neuropathy is a common and often distressing complication of diabetes. It has considerable impact on the social and psychological well-being of affected individuals. There are two distinct forms of painful neuropathy: an acute and self-limiting form that resolves within a year or a chronic form that can go on for years. There are now a number of drugs available for the treatment of neuropathic pain. However, some may fail to respond to these drugs or may have unacceptable adverse side effects. When this is the case, the patient's quality of life can be severely affected. Health care professionals need to assess the full impact of painful neuropathy. In this article we review a number of instruments that are used to assess the severity of painful neuropathy and its impact on the quality of life. Copyright © 2003 John Wiley & Sons, Ltd. [source] Principles and Practices of Knowledge Creation: On the Organization of "Buzz" and "Pipelines" in Life Science CommunitiesECONOMIC GEOGRAPHY, Issue 4 2008Jerker Moodysson abstract This article links up with the debate in economic geography on "local buzz" and "global pipelines" as two distinct forms of interactive knowledge creation among firms and related actors and argues for a rethinking of the way social scientists should approach interactive knowledge creation. It highlights the importance of combining the insights from studies of clusters and innovation systems with an activity-oriented approach in which more attention is paid to the specific characteristics of the innovation processes and the conditions underpinning their organization. To illustrate the applicability and added value of such an alternative approach, the notion of embeddedness is linked with some basic ideas adopted from the literature on knowledge communities. The framework is then applied to a study of innovation activities conducted by firms and academic research groups working with biotechnology-related applications in the Swedish part of the Medicon Valley life science region. The findings reveal that local buzz is largely absent in these types of activities. Most interactive knowledge creation, which appears to be spontaneous and unregulated, is, on closer examination, found safely embedded in globally configured professional knowledge communities and attainable only by those who qualify. [source] Alternative splicing generates a family of putative secreted and membrane-associated MUC4 mucinsFEBS JOURNAL, Issue 14 2000Nicolas Moniaux The MUC4 mucin gene encodes a putative membrane-anchored mucin with predicted size of 930 kDa, for its 26.5-kb allele. It is composed of two regions, the 850-kDa mucin-type subunit MUC4, and the 80-kDa membrane-associated subunit MUC4,. In this study, we cloned and characterized unique MUC4 cDNA sequences that differ from the originally published sequence. Eight alternative splice events located downstream of the central large tandem repeat array generated eight new, distinct cDNAs. The deduced sequences of these MUC4 cDNAs (sv1- MUC4 to sv8- MUC4, the full length cDNA being called sv0- MUC4) provided seven distinct variants, five secreted forms and two membrane-associated forms. Furthermore, two other alternative splicing events located on both sides of the tandem repeat array created two variants, MUC4/Y and MUC4/X, both lacking the central tandem repeat. Therefore, MUC4 can be expressed in three distinct forms, one membrane-bound, one secreted, and one lacking the hallmark feature of mucin, the tandem repeat array. Although no specific function has yet been discovered for the family of proteins putatively produced from the unique MUC4 gene, we suspect that the MUC4 proteins may be implicated in the integrity and renewal of the epithelium. [source] Surface T-cell antigen receptor expression and availability for long-term antigenic signalingIMMUNOLOGICAL REVIEWS, Issue 1 2003Adam G. Schrum Summary:, It is important to understand how T-cell antigen receptor (TCR) engagement and signaling are regulated throughout an immune response. This review examines the dynamics of surface TCR expression and signaling capacity during thymic and effector T-cell development. Although the TCR can undergo vast changes in surface expression, T cells remain capable of sustaining TCR engagement for long periods of time. This may be achieved by a combination of mechanisms that involve (a) controlling the quantity of surface TCR available for ligand interaction and (b) controlling the quality of surface TCR expression during T-cell activation. TCR signaling itself appears to be one of the main quantitative modulators of surface TCR expression, and it can cause both downregulation and upregulation at different times of T-cell activation. Recent studies indicate that the degree of upregulation is tunable by the strength of antigenic stimulation. There is evidence that qualitatively distinct forms of the TCR exist, and their potential role in sustained antigenic signaling is also discussed. A goal of future studies will be to better characterize these modulations in surface TCR expression and to clarify their impact on the regulation of immune responses. [source] What do mothers attune to during interactions with their infants?INFANT AND CHILD DEVELOPMENT, Issue 4 2006Carl-Otto Jonsson Abstract There has been considerable theoretical interest in the developmental importance of affect mirroring and attunement, but little empirical attention has been directed toward the topic. The present study systematically explored the sorts of infant behaviour that elicit affect attunement in mothers. Written descriptions of video-recorded sequences of interaction in 27 mother,infant dyads were used to examine 141 instances of affect attunement in samples from Sweden and the former Yugoslavia. Infants were aged between 2 and 12 months. Behaviour that elicited affect attunement from mothers was rated in terms of 10 behavioural themes, which were used to cluster episodes of affect attunement. Cluster analysis suggested that mothers attuned to six distinct forms of infant behaviour: pleasurable motoric behaviour, effect initiation, focusing, loss of balance, uncontrolled behaviour and displeasure. Incidents of affect attunement elicited by categorical affects comprised only 20% of the instances examined. Most importantly, affect attunement was often elicited by infant exploration and play in relation to the non-social world. Affect attunement may function to reinforce and regulate on-going behaviour that is largely explorative in nature. How mothers respond to the infant's interaction with the external, non-social world may be more important for intrapsychic development than previously thought. Copyright © 2006 John Wiley & Sons, Ltd. [source] Digital Disaster, Cyber Security, and the Copenhagen SchoolINTERNATIONAL STUDIES QUARTERLY, Issue 4 2009Lene Hansen This article is devoted to an analysis of cyber security, a concept that arrived on the post-Cold War agenda in response to a mixture of technological innovations and changing geopolitical conditions. Adopting the framework of securitization theory, the article theorizes cyber security as a distinct sector with a particular constellation of threats and referent objects. It is held that "network security" and "individual security" are significant referent objects, but that their political importance arises from connections to the collective referent objects of "the state,""society,""the nation," and "the economy." These referent objects are articulated as threatened through three distinct forms of securitizations: hypersecuritization, everyday security practices, and technifications. The applicability of the theoretical framework is then shown through a case-study of what has been labeled the first war in cyber space against Estonian public and commercial institutions in 2007. [source] New concepts in radiation-induced apoptosis: ,premitotic apoptosis' and ,postmitotic apoptosis'JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 3 2001N. ShinomiyaArticle first published online: 1 MAY 200 Abstract Formerly, the mechanisms responsible for the killing of cells by ionizing radiation were regarded as being divided into two distinct forms, interphase death and reproductive death. Since they were defined based on the classical radiobiological concepts using a clonogenic cell survival assay, biochemical and molecular biological mechanisms involved in the induction of radiation-induced cell death were not fully understood in relation to the modes of cell death. Recent multidisciplinary approaches to cell death mechanism have revealed that radiation-induced cell death is divided into several distinct pathways by the time course and cell-cycle position, and that apoptotic cell death plays a key role in almost every mode of cell death. This review discusses the mechanisms of radiation-induced apoptosis in relation to cellcycle progression and highlights a new concept of the mode of cell death: ,premitotic apoptosis' and ,postmitotic apoptosis'. The former is a rapid apoptotic cell death associated with a prompt activation of caspase-3, a key enzyme of intracellular signaling of apoptosis. Arapid execution of cell killing in premitotic apoptosis is presumably due to the prompt activation of a set of pre-existed molecules following DNA damages. In contrast, the latter is a delayed apoptotic cell death after cell division, and unlike premitotic apoptosis, it neither requires a rapid activation of caspase-3 nor is inhibited by a specific inhibitor, Ac-DEVD-CHO. A downregulation of anti-apoptotic genes such as MAPK and Bcl-2 may play a key role in this mode of cell death. Characterization of these two types of apoptotic cell death regarding the cell cycle regulation and intrcellular signaling will greatly help to understand the mechanisms of radiation-induced apoptosis. [source] The standard of neutrality: still flapping in the breeze?JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 7 2010S. R. PROULX Abstract Neutrality plays an important role as a null model in evolutionary biology. Recent theoretical advances suggest that neutrality is not a unitary concept, and we identify three distinct forms of neutrality. Eu-neutrality means that types do not differ in any measurable way and is thus the idealized form of neutrality. However, individuals or species that do differ in important ways can behave neutrally under some circumstances, both broadening and complicating the applicability of the concept of neutrality. Our second two types of neutrality address two quite different forms of context-dependent neutrality. Circum-neutrality means that two character states have the same direct effect on fitness but do not evolve neutrally because of differences in their circumstances. Iso-neutrality means that two types are equivalent in some population or ecological contexts but not in others, producing an isocline. Confounding of these different definitions has created significant confusion about which models are truly neutral, why some models behave neutrally even when there are large differences in reproductive outputs, and what these different views of neutrality mean to practicing biologists. These complications call into question the acceptance of neutral models as null models and suggest that a better approach is to compare the predictions of models that differ in sources of stochasticity and degree of selection. [source] Satellite species in lampreys: a worldwide trend for ecological speciation in sympatry?JOURNAL OF FISH BIOLOGY, Issue 2 2003V. Salewski Amongst several theories of speciation, sympatric speciation has been the most controversial but it is now widely accepted that populations can become reproductively isolated without being separated geographically. One problem with the acceptance of the theory of sympatric speciation, however, has been the lack of supporting empirical data and it is still believed that geographical isolation is responsible for the majority of speciation events. Here the example of species pairs in lampreys suggests that sympatric speciation in a whole taxonomic group could occur throughout its worldwide range. Lampreys occur in two ecologically distinct forms: parasitic mostly anadromous species that forage on tissue and body fluids of host fishes, and non-parasitic forms that, apart from a short adult life when they cease feeding, spend their entire life as filter feeders in the substratum of stream beds. Both forms occur in sympatric species pairs throughout the range of lampreys that occur in Eurasia, North America and Australia and it is widely acknowledged that non-parasitic forms derive from parasitic forms. The larvae of both forms can be distinguished by their potential fecundity and therefore, it is argued that the mode of life is not a consequence of different ecological conditions. Furthermore, as lampreys prefer to choose mates of similar sizes and fertilization success decreases with increasing difference in body size, there is a strong disruptive selection between the two forms and they are therefore reproductively isolated. Besides theoretical aspects, the similarity of the species pairs, together with their occurrence in sympatry, the occurrence of forms with intermediate characteristics, and examples where speciation might be in progress, hints at the possibility that speciation also occurred in sympatry. The difference between lampreys and other examples of sympatric speciation is that there seems to be a trend towards sympatric speciation events throughout the worldwide range of lampreys which is neither restricted to relatively small localities nor caused by human disturbance. Species pairs in lampreys therefore offer a unique possibility of studying the process of sympatric speciation on a large scale. [source] Professional Competence as Ways of Being: An Existential Ontological PerspectiveJOURNAL OF MANAGEMENT STUDIES, Issue 7 2009Jörgen Sandberg abstract Current theories propose that professional competence is primarily constituted by scientific and tacit knowledge, knowing-in-action, understanding of work or practice. While providing valuable insights we contend that they present a fragmented understanding of professional competence. In particular, they do not adequately explain how central aspects of practice such as knowledge and understanding are integrated into a specific professional competence in work performance. An existential ontological perspective is proposed as offering a more comprehensive and integrative analysis of professional competence. It is explored through an empirical study of corporate lawyers and the findings suggest that professional competence should be understood as ways of being. The results show that different ways of practising corporate law distinguish and integrate a specific understanding of work, a particular self-understanding, other people, and tools into distinct forms of competence in corporate law. [source] GENETIC DIVERGENCE CORRELATES WITH MORPHOLOGICAL AND ECOLOGICAL SUBDIVISION IN THE DEEP-WATER ELK KELP, PELAGOPHYCUS PORRA (PHAEOPHYCEAE)JOURNAL OF PHYCOLOGY, Issue 5 2000Kathy Ann Miller Pelagophycus porra (Leman) Setchell has a narrow distribution confined to deep water from the Channel Islands off the southern California coast to central Baja California, Mexico. Distinct morphotypes are consistently correlated with distinctive habitats, that is, windward exposures characterized by strong water motion and rocky substrates, and sheltered areas with soft substrates found on the lee sides of the islands. We tested the hypothesis that morphologically and ecologically distinct forms reflect genetically distinct stands. Individuals representing populations from three islands and the mainland were compared using RFLP analyses of the nuclear rDNA internal transcribed spacers (ITS1 and ITS2), chloroplast trnL (UAA) intron sequences, and random amplified polymorphic DNA (RAPDs). No variation was found in a survey of 20 restriction sites of ITS1 (ca. 320 base pair [bp]) and ITS2 (ca. 360 bp) among individuals from six populations. Likewise, comparisons of trnL intron (241 bp) sequences among nine individuals from seven populations were identical with the exception of a CATAGT insert in two adjacent stands. A RAPD analysis of 24 individuals from nine populations (4 windward and 5 leeward) using 16 primers generated 166 bands. Thirty-eight percent of the bands did not vary, 16% were unique to a given individual, and 46% were variable. Neighbor joining analysis produced a well-resolved tree with moderately high bootstrap support in which windward and leeward populations were easily distinguished. The lack of divergence in both the fast evolving nuclear rDNA-ITS and the chloroplast trnL intron does not support the morphotypes as different species. However, the compartmentalized differentiation shown in the RAPD data clearly points to isolation. This, and previous ecological studies that demonstrate habitat specificity suggest that leeward stands probably comprise a species in statu nascendi. [source] Failure to Update: An Institutional Perspective on Noncompliance With the Family and Medical Leave ActLAW & SOCIETY REVIEW, Issue 1 2010Erin L. Kelly At least one-quarter of covered workplaces violated the parental leave requirements of the Family and Medical Leave Act of 1993 (FMLA) when surveyed in 1997. What explains this noncompliance? Using a survey of 389 U.S. workplaces and qualitative interviews with managers in 40 organizations, I demonstrate that noncompliance comes in distinct forms. Some forms of noncompliance result from a failure to update institutionalized,and gendered,policies, practices, and norms. This form of noncompliance (indicated by illegally short leaves) is better explained by the institutional perspective, while outright noncompliance (as evidenced by a lack of leaves) is best explained by rational choice and deviant culture theories. [source] The Physiology of Endothelial Xanthine Oxidase: From Urate Catabolism to Reperfusion Injury to Inflammatory Signal TransductionMICROCIRCULATION, Issue 3 2002AVEDIS MENESHIAN ABSTRACT Xanthine oxidoreductase (XOR) is a ubiquitous metalloflavoprotein that appears in two interconvertible yet functionally distinct forms: xanthine dehydrogenase (XD), which is constitutively expressed in vivo; and xanthine oxidase (XO), which is generated by the posttranslational modification of XD, either through the reversible, incremental thiol oxidation of sulfhydryl residues on XD or the irreversible proteolytic cleavage of a segment of XD, which occurs at low oxygen tension and in the presence of several proinflammatory mediators. Functionally, both XD and XO catalyze the oxidation of purines to urate. However, whereas XD requires NAD+ as an electron acceptor for these redox reactions, thereby generating the stable product NADH, XO is unable to use NAD+ as an electron acceptor, requiring instead the reduction of molecular oxygen for this purine oxidation and generating the highly reactive superoxide free radical. Nearly 100 years of study has documented the physiologic role of XD in urate catabolism. However, the rapid, posttranslational conversion of XD to the oxidantgenerating form XO provides a possible physiologic mechanism for rapid, posttranslational, oxidant-mediated signaling. XO-generated reactive oxygen species (ROS) have been implicated in various clinicopathologic entities, including ischemia/reperfusion injury and multisystem organ failure. More recently, the concept of physiologic signal transduction mediated by ROS has been proposed, and the possibility of XD to XO conversion, with subsequent ROS generation, serving as the trigger of the microvascular inflammatory response in vivo has been hypothesized. This review presents the evidence and basis for this hypothesis. [source] Individual chitin synthase enzymes synthesize microfibrils of differing structure at specific locations in the Candida albicans cell wallMOLECULAR MICROBIOLOGY, Issue 5 2007Megan D. Lenardon Summary The shape and integrity of fungal cells is dependent on the skeletal polysaccharides in their cell walls of which ,(1,3)-glucan and chitin are of principle importance. The human pathogenic fungus Candida albicans has four genes, CHS1, CHS2, CHS3 and CHS8, which encode chitin synthase isoenzymes with different biochemical properties and physiological functions. Analysis of the morphology of chitin in cell wall ghosts revealed two distinct forms of chitin microfibrils: short microcrystalline rodlets that comprised the bulk of the cell wall; and a network of longer interlaced microfibrils in the bud scars and primary septa. Analysis of chitin ghosts of chs mutant strains by shadow-cast transmission electron microscopy showed that the long-chitin microfibrils were absent in chs8 mutants and the short-chitin rodlets were absent in chs3 mutants. The inferred site of chitin microfibril synthesis of these Chs enzymes was corroborated by their localization determined in Chsp,YFP-expressing strains. These results suggest that Chs8p synthesizes the long-chitin microfibrils, and Chs3p synthesizes the short-chitin rodlets at the same cellular location. Therefore the architecture of the chitin skeleton of C. albicans is shaped by the action of more than one chitin synthase at the site of cell wall synthesis. [source] Heterochromatin-mediated control of virulence gene expressionMOLECULAR MICROBIOLOGY, Issue 3 2006Catherine J. Merrick Summary In recent years, the sequencing and annotation of complete genomes, together with the development of genetic and proteomic techniques to study previously intractable eukaryotic microbes, has revealed interesting new themes in the control of virulence gene expression. Families of variantly expressed genes are found adjacent to telomeres in the genomes of both pathogenic and non-pathogenic organisms. This subtelomeric DNA is normally heterochromatic and higher-order chromatin structure has now come to be recognized as an important factor controlling both the evolution and expression dynamics of these multigene families. In eukaryotic cells, higher-order chromatin structure plays a central role in many DNA processes including the control of chromosome integrity and recombination, DNA partitioning during cell division, and transcriptional control. DNA can be packaged in two distinct forms: euchromatin is relatively accessible to DNA binding proteins and generally contains active genes, while heterochromatin is densely packaged, relatively inaccessible and usually transcriptionally silent. These features of chromatin are epigenetically inherited from cell cycle to cell cycle. This review will focus on the epigenetic mechanisms used to control expression of virulence genes in medically important microbial pathogens. Examples of such control have now been reported in several evolutionarily distant species, revealing what may be a common strategy used to regulate many very different families of genes. [source] Maintaining a healthy SPANC balance through regulatory and mutational adaptationMOLECULAR MICROBIOLOGY, Issue 1 2005Thomas Ferenci Summary Stress protection is an important but costly contributor to bacterial survival. Two distinct forms of environmental protection share a common cost and a significant species-wide variability. Porin-mediated outer membrane permeability and the RpoS-controlled general stress response both involve a trade-off between self- preservation and nutritional competence, called the SPANC balance. Interestingly, different Escherichia coli strains exhibit distinct settings of the SPANC balance. It is tilted towards high stress resistance and a restricted diet in some isolates whereas others have broader nutritional capability and better nutrient affinity but lower levels of resistance. Growth- or stress-related selective pressures working in opposite directions (antagonistic pleiotropy) result in polymorphisms affecting porins and RpoS. Consequently, these important cellular components are present at distinct concentrations in different isolates. A generalized hypothesis to explain bacterial adaptation, based on the SPANC investigations, is offered. A holistic approach to bacterial adaptation, involving a gamut of regulation and mutation, is likely to be the norm in broadening the capabilities of a species. Indeed, there is unlikely to be a standard regulatory setting typical for all members of a species. Gene regulation provides a limited fine control for maintaining the right level of adaptation in a particular niche but mutational changes provide the coarse control for adaptation between the species-wide environments of free-living bacteria. [source] Amplification of Hot DNA segments in Escherichia coliMOLECULAR MICROBIOLOGY, Issue 6 2002Ken-ichi Kodama Summary In Escherichia coli, a replication fork blocking event at a DNA replication terminus (Ter) enhances homologous recombination at the nearby sister chromosomal region, converting the region into a recombination hotspot, Hot, site. Using a RNaseH negative (rnhA,) mutant, we identified eight kinds of Hot DNAs (HotA,H). Among these, enhanced recombination of three kinds of Hot DNAs (HotA,C) was dependent on fork blocking events at Ter sites. In the present study, we examined whether HotA DNAs are amplified when circular DNA (HotA plus a drug-resistance DNA) is inserted into the homologous region on the chromosome of a rnhA, mutant. The resulting HotA DNA transformants were analysed using pulsed-field gel electrophoresis, fluorescence in situ hybridization and DNA microarray technique. The following results were obtained: (i) HotA DNA is amplified by about 40-fold on average; (ii) whereas 90% of the cells contain about 6,10 copies of HotA DNA, the remaining 10% of cells have as many as several hundred HotA copies; and (iii) amplification is detected in all other Hot DNAs, among which HotB and HotG DNAs are amplified to the same level as HotA. Furthermore, HotL DNA, which is activated by blocking the clockwise oriC -starting replication fork at the artificially inserted TerL site in the fork-blocked strain with a rnhA+ background, is also amplified, but is not amplified in the non-blocked strain. From these data, we propose a model that can explain production of three distinct forms of Hot DNA molecules by the following three recombination pathways: (i) unequal intersister recombination; (ii) intrasister recombination, followed by rolling-circle replication; and (iii) intrasister recombination, producing circular DNA molecules. [source] Functional redundancy in the Arabidopsis Cathepsin B gene family contributes to basal defence, the hypersensitive response and senescenceNEW PHYTOLOGIST, Issue 2 2009Hazel McLellan Summary ,,Cysteine proteases are required for programmed cell death (PCD) in animals. Recent work in Nicotiana benthamiana has implicated cathepsin B-like cysteine proteases in the hypersensitive response (HR) in plants, a form of PCD involved in disease resistance. Here, we investigate the function and regulation of Cathepsin B (CathB) genes in plant defence, and in both pathogen-inducible and developmental forms of PCD. ,,Single, double and triple knockout mutants were isolated for the three Arabidopsis thaliana AtCathB genes. ,,AtCathB genes were redundantly required for full basal resistance against the virulent bacterial pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. By contrast, AtCathB genes were not required for R gene-mediated resistance to Pst DC3000 expressing AvrB or AvrRps4. Neither did they contribute to PCD triggered by AvrRps4, although they were crucial for the full development of PCD during HR triggered by AvrB. Cathepsin B has also been proposed to play a positive regulatory role in senescence. Atcathb triple mutants showed a delay in senescence and a seven-fold decrease in accumulation of senescence marker gene SAG12. ,,Our results demonstrate a redundant function for AtCathB genes in basal defence as well as a potential regulatory role in distinct forms of plant PCD. [source] Viruses in periodontal disease , a reviewORAL DISEASES, Issue 4 2005I Cappuyns The purpose of this review was to evaluate the evidence supporting the hypothesis that viral infection plays a role in the development of periodontitis. An involvement in periodontal diseases has been suspected specifically for human immunodeficiency virus (HIV) and herpes viruses. An association has been demonstrated between HIV infection and some distinct forms of periodontal infection, i.e. necrotizing lesions. Furthermore, reports of increased prevalence and severity of chronic periodontitis in HIV-positive subjects suggests that HIV infection predispose to chronic periodontitis. Several studies, most of them from the same research group, have demonstrated an association of herpesviruses with periodontal disease. Viral DNA have been detected in gingival tissue, gingival cervicular fluid (GCF) and subgingival plaque from periodontaly diseased sites. In addition markers of herpesviral activation have been demonstrated in the GCF from periodontal lesions. Active human cytomegalovirus (HCMV) replication in periodontal sites may suggest that HCMV re-activation triggers periodontal disease activity. Concerns regarding sampling, methods and interpretation cast doubts on the role of viruses as causes of periodontal disease. [source] Variation and context of yawns in captive chimpanzees (Pan troglodytes)AMERICAN JOURNAL OF PRIMATOLOGY, Issue 3 2010Sarah-Jane Vick Abstract Primate yawns are usually categorized according to context (e.g. as a threat, anxious, or rest yawn), but there has been little consideration of whether these yawns are best regarded as a unitary behavior that only differs with respect to the context in which it is observed. This study examined the context and precise morphology of yawns in a group of 11 captive chimpanzees. Focal video sampling was used to describe the morphology and intensity of 124 yawns using ChimpFACS, a system for coding facial movements. Two distinct forms of yawn were identified, a full yawn and a yawn which is modified by additional actions that reduce the mouth aperture. These modified yawns may indicate some degree of voluntary control over facial movement in chimpanzees and, consequently, multiple functions of yawning according to context. To assess context effects, mean activity levels (resting, locomotion, and grooming) and scratching rates were compared one minute before and after each yawn. Locomotion was significantly increased following both types of yawn, whereas scratching rates significantly increased following modified yawns but decreased following full yawns. In terms of individual differences, males did not yawn more than females, although male yawns were of higher intensity, both in the degree of mouth opening and in the amount of associated head movement. These data indicate that yawning is associated with a change in activity levels in chimpanzees, but only modified yawns may be related to increased arousal. Different types of yawn can therefore be differentiated at the morphological level as well as context level. Am. J. Primatol. 72:262,269, 2010. © 2009 Wiley-Liss, Inc. [source] Art, dreams and active imagination: A post-Jungian approach to transference and the imageTHE JOURNAL OF ANALYTICAL PSYCHOLOGY, Issue 2 2005Joy Schaverien Abstract:, The term active imagination is sometimes applied rather uncritically to describe all forms of creative activity that take place in depth psychology. Whilst there are many forms of expression that evoke or are evoked by active imagination, they cannot automatically be classed as active imagination. In this article investigation of visualized mental imagery, dreams and art reveals three distinct forms of image-based psychological activity. Integrated and mediated within the transference and countertransference dynamic, it is proposed that the engagement in active imagination reflects and is influenced by the transference. Distinctions between sign and symbol, simple and big dreams as well as diagrammatic and embodied imagery clarify the differences. Examples from clinical practice demonstrate each mode in action within the analytic frame. [source] Effect of the Disruption of RNA Pol II on the Transcription by RNA Pol l by Trypanosoma bruceiTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005S. DEVAUX Trypanosomes exist in two major distinct forms: the procyclic form in insects in which the surface molecule is procyclin and the bloodstream form in mammals in which the surface molecule is VSG. The promoter of these locus recruits RNA Pol I. Despite the use of this polymerase, the transcripts are spliced and polyadenylated exactly as the mRNAs synthesised by RNA Pol II. The fact that mRNA production from these sites must involve a concerted action between RNA Pol I and a "RNA factory" normally linked to RNA Pol II, led to the proposal that the control of these Pol I transcription units would involve a limiting component bridging RNA Pol I and an elongation/processing complex normally associated with RNA Pol II. To study the effects of the disruption of RNA Pol II on VSG expression level, we cloned the T. brucei homologue of the rpb9 subunit of RNA Pol II, which plays a role in RNA elongation in other eukaryotic cells. In PF, disruption of Tbrpb9 by conditional RNAi led to a strong transcriptional stimulation in the beginning of the ESs. This effect was linked to the inhibition of procyclin transcription. Thus, the disruption of RNA Pol II abolished the stage-specific regulation of the transcription units for the two major surface antigens, both of which recruit RNA Pol I. [source] Expression, purification and preliminary X-ray diffraction analysis of the catalytic module of a ,-agarase from the flavobacterium Zobellia galactanivoransACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 4 2010Jan-Hendrik Hehemann Marine bacteria secrete specific glycoside hydrolases such as agarases to access polysaccharides from algal cell walls as a carbon and energy source. In an attempt to identify agarases with variable degradation patterns, a novel family GH16 ,-agarase from the marine bacterium Zobellia galactanivorans was expressed, purified and crystallized. The purified enzyme crystallized in two distinct forms that were grown by the hanging-drop vapour-diffusion method using polyethylene glycol as a precipitant. Hexagonal crystals belonging to space group P3121 diffracted to 2.2,Å resolution, whereas orthorhombic crystals belonging to space group P212121 diffracted to 1.5,Å resolution. [source] | ||||||||||||||||||||||||||||