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Essential
Kinds of Essential Terms modified by Essential Selected AbstractsCharacterization and functional analysis of the ,-1,3-glucanosyltransferase 3 of the human pathogenic fungus Paracoccidioides brasiliensisFEMS YEAST RESEARCH, Issue 1 2009Nadya Da Silva Castro Abstract The fungus Paracoccidioides brasiliensis causes paracoccidioidomycosis, a systemic granulomatous mycosis prevalent in Latin America. In an effort to elucidate the molecular mechanisms involved in fungus cell wall assembly and morphogenesis, ,-1,3-glucanosyltransferase 3 (PbGel3p) is presented here. PbGel3p presented functional similarity to the glucan-elongating/glycophospholipid-anchored surface/pH-regulated /essential for pseudohyphal development protein families, which are involved in fungal cell wall biosynthesis and morphogenesis. The full-length cDNA and gene were obtained. Southern blot and in silico analysis suggested that there is one copy of the gene in P. brasiliensis. The recombinant PbGel3p was overexpressed in Escherichia coli, and a polyclonal antibody was obtained. The PbGEL3 mRNA, as well as the protein, was detected at the highest level in the mycelium phase. The protein was immunolocalized at the surface in both the mycelium and the yeast phases. We addressed the potential role of PbGel3p in cell wall biosynthesis and morphogenesis by assessing its ability to rescue the phenotype of the Saccharomyces cerevisiae gas1, mutant. The results indicated that PbGel3p is a cell wall-associated protein that probably works as a ,-1,3-glucan elongase capable of mediating fungal cell wall integrity. [source] THE ESSENTIAL AND THE ACCIDENTALRATIO, Issue 3 2005Michael Gorman The distinction between the essential and the accidental is nearly always understood in modal terms. After criticizing some recent writings by Kit Fine that question that understanding, I develop a theory according to which whether a given feature of a thing is essential turns on whether it is explained by other features of that thing. The theory differs from the modal view by leaving room for features that are accidental even though their bearers cannot exist without them. The theory has the additional advantage of being open to the results of scientific theory. [source] ESSENTIALS OF PLASTIC SURGERYDERMATOLOGIC SURGERY, Issue 9 2007R. EDWARD NEWSOME MD No abstract is available for this article. [source] Hole Injection in a Model Fluorene,Triarylamine CopolymerADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Hon Hang Fong Abstract Recent developments in synthesis and purification have yielded conjugated polymers with hole mobilities exceeding 0.01,cm2 V,1 s,1. Essential to harvesting the potential of these materials in organic light emitting diodes (OLEDs) is the identification of suitable ohmic contacts. Using a model fluorene copolymer that shows high-mobility, non-dispersive hole transport, it is demonstrated that electrodes commonly used as anodes in OLEDs are very poor hole injectors. Injection from Au and indium tin oxide anodes is limited by energy barriers of 0.75 and 0.65,eV, respectively, and the injected current is found to be temperature independent,a prediction that was not reproduced by the leading injection model for disordered organic semiconductors. Injection from a poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) anode, on the other hand, is found to become less efficient with electric field, a behavior which is currently not understood. In thinner poly[(9,9,-dioctylfluorenyl-2,7-diyl)- co -(4,4,-(N -(4- sec -butyl))diphenylamine)] films, which are of relevance to OLEDs, ohmic losses on the PEDOT:PSS layer are found to limit the flow of current. These results illustrate the opportunity to further improve the performance of OLEDs as well as the challenge posed by high mobility conjugated polymers for the design of hole injection layers. [source] Climate dynamics of atmosphere and ocean in the equatorial zone: a synthesisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2004Stefan Hastenrath Abstract A synopsis is offered of circulation mechanisms in the oceanic regions of the equatorial zone. Over the eastern Atlantic and Pacific, and especially in boreal summer, cross-equatorial flow from the Southern Hemisphere is strong and induces a tongue of cold surface waters, centred to the south of the equator. Upon crossing the equator in these sectors, owing to the Coriolis effect and a kinetic energy imbalance, the airstream speeds up and divergence develops, producing the Intertropical Divergence Zone (ITDZ). Once these processes result in the wind recurving from southeasterly to southwesterly, the flow slows down and becomes convergent, manifest in the Intertropical Convergence Zone, with a maximum to the south of the wind confluence. By contrast, over the western Atlantic and central Pacific and especially in boreal winter, winds in the equatorial band are predominantly from the east, upper-ocean Ekman transport is directed away from the equator, and the upwelling and cold tongue are centred on the equator. Cross-equatorial flow is insufficient to produce recurvature, the ITDZ is narrower and weaker, the divergence maximum is at the equator rather than in low northern latitudes, and the convergence maximum straddles the wind confluence. Over the Indian Ocean, the wind field is dominated by the alternation between the predominantly meridional flow of the winter and summer monsoons. Equatorial westerlies are limited to the short monsoon transition seasons. Essential for their origin is an eastward pressure gradient along the equator and weak southern trade winds, allowing recurvature somewhat south of the equator. Because the zonal pressure gradient is strongest in boreal summer and the southern trade winds are weakest in austral summer, the equatorial westerlies peak in spring and autumn. The boreal autumn equatorial westerlies are the surface manifestation of a powerful zonal,vertical circulation cell along the Indian Ocean equator. Equatorial zonal,vertical circulation cells require well-developed zonal flow in the lower troposphere along the equator and, therefore, appear confined to the oceanic longitudes and certain seasons. Thus, they are found over the Atlantic only in boreal winter and over the Indian Ocean only in boreal autumn, whereas over the Pacific they prevail all year round. Copyright © 2004 Royal Meteorological Society [source] Cyclo-Oxygenase 2 Function Is Essential for Bone Fracture Healing,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 6 2002Ann Marie Simon Abstract Despite the molecular and histological similarities between fetal bone development and fracture healing, inflammation is an early phase of fracture healing that does not occur during development. Cyclo-oxygenase 2 (COX-2) is induced at inflammation sites and produces proinflammatory prostaglandins. To determine if COX-2 functions in fracture healing, rats were treated with COX-2-selective nonsteroidal anti-inflammatory drugs (NSAIDs) to stop COX-2-dependent prostaglandin production. Radiographic, histological, and mechanical testing determined that fracture healing failed in rats treated with COX-2-selective NSAIDs (celecoxib and rofecoxib). Normal fracture healing also failed in mice homozygous for a null mutation in the COX-2 gene. This shows that COX-2 activity is necessary for normal fracture healing and confirms that the effects of COX-2-selective NSAIDs on fracture healing is caused by inhibition of COX-2 activity and not from a drug side effect. Histological observations suggest that COX-2 is required for normal endochondral ossification during fracture healing. Because mice lacking Cox2 form normal skeletons, our observations indicate that fetal bone development and fracture healing are different and that COX-2 function is specifically essential for fracture healing. [source] Insulin-Like Growth Factor I Production Is Essential for Anabolic Effects of Thyroid Hormone in Osteoblasts,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2000Bill K. Huang Abstract Thyroid hormone (T3) and insulin-like growth factor I (IGF-I) are critical regulators of skeletal function. T3 increases IGF-I production in bone. To assess the potential role of IGF-I as a mediator of T3 actions, we characterized phenotypic markers of osteoblast activity in two osteoblast models, normal mouse osteoblasts and MC3T3-E1 cells, exposed to T3 alone or under conditions that interfere with IGF-I actions. T3 significantly increased osteoblast 3H-proline incorporation, alkaline phosphatase (ALP), and osteocalcin. Both ,IR3, a neutralizing monoclonal antibody to the IGF-I receptor, and JB1, an IGF-I analogue antagonist, attenuated the stimulatory effects of T3. T3 effects also were decreased in cells transfected with antisense oligonucleotide (AS-ODN) to the IGF-I receptor gene. Both IGF-I and T3 had mitogenic effects that were inhibited by the antagonists. IGF-I by itself did not stimulate 3H-proline incorporation, ALP, and osteocalcin in the models used, revealing that although IGF-I is essential for the anabolic effects of T3, it acts in concert with other factors to elicit these phenotypic responses. (J Bone Miner Res 2000;15:188,197) [source] Modeling Judgments in the Angoff and Contrasting-Groups Method of Standard SettingJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 1 2008Daniël Van Nijlen Essential for the validity of the judgments in a standard-setting study is that they follow the implicit task assumptions. In the Angoff method, judgments are assumed to be inversely related to the difficulty of the items; contrasting-groups judgments are assumed to be positively related to the ability of the students. In the present study, judgments from both procedures were modeled with a random-effects probit regression model. The Angoff judgments showed a weaker link with the position of the items on the latent scale than the contrasting-groups judgments with the position of the students. Hence, in the specific context of the study, the contrasting-groups judgments were more aligned with the underlying assumptions of the method than the Angoff judgments. [source] Oestrogen Receptor , is Essential for Female-Directed Chemo-Investigatory Behaviour but is not Required for the Pheromone-Induced Luteinizing Hormone Surge in Male MiceJOURNAL OF NEUROENDOCRINOLOGY, Issue 2 2000S. R. Wersinger The expression of normal masculine sexual behaviour requires testosterone. Testosterone can bind to androgen receptors, either in its native form, or after reduction to other androgen metabolites. In addition, testosterone can be aromatized to oestrogen, and bind to oestrogen receptor , and/or ,. Male copulatory behaviour is deficient in mice lacking functional oestrogen receptor , gene (ER,KO mice). We sought to determine which aspect(s) of masculine sexual behaviour is compromised in the ER,KOs. Specifically, we asked whether ER,KO males have reduced motivation and/or an inability to recognize oestrous females. We found significant differences between mice of different genotypes in the amount of chemo-investigatory behaviour displayed and in the target of their investigation. Wild-type males spent more time investigating ovariectomized, oestradiol-treated females, than either males, or ovariectomized females that had not received hormone priming. ER,KO males spent little time investigating any of the stimulus mice and showed no preferences. To test the hypothesis that this lack of chemo-investigatory behaviour is due to the inability of ER,KO males to detect and respond to female pheromones, we exposed males to chemosensory cues (soiled bedding) from females. Males resided in clean, or female-soiled, cage bedding for 60 min. Next, blood was collected and plasma luteinizing hormone (LH) assayed. We also assessed Fos-like immunoreactivity (Fos-ir) in several neural regions involved in processing chemosensory cues. Despite the fact that male ER,KOs spend little time engaged in chemo-investigation of females, their neuroendocrine responses to female-soiled bedding were similar to those seen in wild-type males. Our data suggest that the normal coupling between the neuroendocrine response to females and the generation of sexual behaviour is disrupted in ER,KO mice. Responses to female pheromones do not require ER,. However, normal male sexual performance requires the ER, gene. [source] Proopiomelanocortin Peptides Are Not Essential for Development of Ethanol-Induced Behavioral SensitizationALCOHOLISM, Issue 7 2009Amanda L. Sharpe Background:, Behavioral sensitization is a result of neuroadaptation to repeated drug administration and is hypothesized to reflect an increased susceptibility to drug abuse. Proopiomelanocortin (POMC) derived peptides including ,-endorphin and ,-melanocyte stimulating hormone have been implicated in development of behavioral sensitization and the reinforcing effects of alcohol and other drugs of abuse. This study used a genetically engineered mouse strain that is deficient for neural POMC to directly determine if any POMC peptides are necessary for the development of ethanol-induced locomotor sensitization. Methods:, Adult female mice deficient for POMC in neurons only (Pomc,/,Tg/Tg, KO) and wildtype (Pomc+/+Tg/Tg, WT) littermates were injected once daily with either saline or ethanol (i.p.) for 12 to 13 days. On ethanol test day (day 13 or 14) all mice from both treatment groups received an i.p. injection of ethanol immediately before a 15-minute analysis of locomotor activity. Blood ethanol concentration (BEC) was measured on ethanol test day immediately following the test session. Baseline locomotor activity was measured for 15 minutes after a saline injection 2 days later in both groups. Results:, There was no significant difference in BEC between genotypes (WT = 2.11 ± 0.06; KO = 2.03 ± 0.08 mg/ml). Both WT and nPOMC-deficient mice treated repeatedly with ethanol demonstrated a significant increase in locomotor activity on test day when compared to repeated saline-treated counterparts. In addition, mice of both genotypes in the repeated saline groups showed a significant locomotor stimulant response to acute ethanol injection. Conclusions:, Central POMC peptides are not required for either the acute locomotor stimulatory effect of ethanol or the development of ethanol-induced locomotor sensitization. While these peptides may modulate other ethanol-associated behaviors, they are not essential for development of behavioral sensitization. [source] Adolescent Obesity: Current Trends in Identification and ManagementJOURNAL OF THE AMERICAN ACADEMY OF NURSE PRACTITIONERS, Issue 11 2004M. Anette Hagarty RN Purpose To discuss the prevalence, identification, and clinical manifestations of adolescent obesity for the advanced practice nurse in primary care. Data Sources Selected research and clinical articles. Conclusions Adolescent obesity has been historically attributed to inappropriate diet and exercise; however, recent research also attributes adolescent obesity to genetic factors and metabolic dysfunction. If left untreated, adolescent obesity may result in the metabolic complications of dyslipidemia, hypertension, cardiovascular disease, and early onset of type 2 diabetes. Implications for Practice Practitioners should focus on using the new body mass index (BMI) national guidelines for early identification of obesity. Essential to the management of this condition are education, parental involvement, behavior modification, and psychological support. [source] Surface Enthalpy, Enthalpy of Water Adsorption, and Phase Stability in Nanocrystalline Monoclinic ZirconiaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2009A. V. Radha A fundamental issue that remains to be solved when approaching the nanoscale is how the size induces transformation among different polymorphic structures. Understanding the size-induced transformation among the different polymorphic structures is essential for widespread use of nanostructured materials in technological applications. Herein, we report water adsorption and high-temperature solution calorimetry experiments on a set of samples of single-phase monoclinic zirconia with different surface areas. Essential to the success of the study has been the use of a new ternary water-in-oil/water liquid solvothermal method that allows the preparation of monoclinic zirconia nanoparticles with a broad range of (BET) Brunauer,Emmett,Teller surface area values. Thus, the surface enthalpy for anhydrous monoclinic zirconia is reported for the first time, while that for the hydrous surface is a significant improvement over the previously reported value. Combining these data with previously published surface enthalpy for nanocrystalline tetragonal zirconia, we have calculated the stability crossovers between monoclinic and tetragonal phases to take place at a particle size of 28 ± 6 nm for hydrous zirconia and 34 ± 5 nm for anhydrous zirconia. Below these particle sizes, tetragonal hydrous and anhydrous phases of zirconia become thermodynamically stable. These results are within the margin of the theoretical estimation and confirm the importance of the presence of water vapor on the transformation of nanostructured materials. [source] Apolipoprotein(a) inhibits the conversion of Glu-plasminogen to Lys-plasminogen: a novel mechanism for lipoprotein(a)-mediated inhibition of plasminogen activationJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2008N. T. FERIC Summary.,Background:,Elevated plasma concentrations of lipoprotein(a) [Lp(a)] are associated with an increased risk for thrombotic disorders. Lp(a) is a unique lipoprotein consisting of a low-density lipoprotein-like moiety covalently linked to apolipoprotein(a) [apo(a)], a homologue of the fibrinolytic proenzyme plasminogen. Several in vitro and in vivo studies have shown that Lp(a)/apo(a) can inhibit tissue-type plasminogen activator-mediated plasminogen activation on fibrin surfaces, although the mechanism of inhibition by apo(a) remains controversial. Essential to fibrin clot lysis are a number of plasmin-dependent positive feedback reactions that enhance the efficiency of plasminogen activation, including the plasmin-mediated conversion of Glu-plasminogen to Lys-plasminogen. Objective:,Using acid,urea gel electrophoresis to resolve the two forms of radiolabeled plasminogen, we determined whether apo(a) is able to inhibit Glu-plasminogen to Lys-plasminogen conversion. Methods:,The assays were performed in the absence or presence of different recombinant apo(a) species, including point mutants, deletion mutants and variants that represent greater than 90% of the known apo(a) isoform sizes. Results:,Apo(a) substantially suppressed Glu-plasminogen conversion. Critical roles were identified for the kringle IV types 5,9 and kringle V; contributory roles for sequences within the amino-terminal half of the molecule were also observed. Additionally, with the exception of the smallest naturally-occurring isoform of apo(a), isoform size was found not to contribute to the inhibitory capacity of apo(a). Conclusion:,These findings underscore a novel contribution to the understanding of Lp(a)/apo(a)-mediated inhibition of plasminogen activation: the ability of the apo(a) component of Lp(a) to inhibit the key positive feedback step of plasmin-mediated Glu-plasminogen to Lys-plasminogen conversion. [source] Trans Fatty Acids, Insulin Resistance, and Type 2 DiabetesNUTRITION REVIEWS, Issue 8 2006Andrew O. Odegaard BA Type 2 diabetes, a growing global health problem, has a complex etiology involving many interactions between genetic and environmental factors. Essential to the development of the disease is insulin resistance of the peripheral tissues. Insulin resistance may be partly modified by the specific types of dietary fatty acids. Trans fatty acids (TFAs), created through the transformation of polyunsaturated fatty acids from their natural cis form to the trans form, are abundant in the Western diet. TFAs take on similar properties as saturated fats, and appear to be more atherogenic. High intakes of saturated fats may promote insulin resistance. It is therefore reasonable to hypothesize that high intakes of TFAs would have similar, or stronger, effects. In this review, all current evidence on the topic of TFAs, insulin resistance, and type 2 diabetes is summarized and interpreted. Although there is some support from observational and experimental studies for the hypothesis that high intakes of TFAs may increase the risk for type 2 diabetes, inconsistencies across studies and methodological problems make it premature to draw definitive conclusions at this time. More experimental research in humans is needed to further address this question. [source] Insulin Is Essential for the Recovery from Allodynia Induced by Complete Freund's AdjuvantPAIN MEDICINE, Issue 9 2010Gregory P. Casey PhD Abstract Objective., To determine the effect of streptozotocin (STZ)-induced diabetes on the development and recovery of thermal and mechanical hyperalgesia associated with inflammation induced by subcutaneous injection of complete Freund's adjuvant (CFA). Background., The response to nociceptive injury in diabetes differs from that seen in normal individuals in that diabetic patients have increased susceptibility to infections and recover slowly or incompletely from infections and tissue injury due to an abnormal inflammatory response. We have chosen to examine the effect of STZ-induced hypoinsulinemia on the hyperalgesia associated with the enhanced inflammatory state that is induced by the subcutaneous injection of CFA to delineate the potential role of insulin in the development of chronic pain. Methods., STZ- and vehicle-treated Sprague-Dawley rats were tested using thermal and mechanical stimulation after subcutaneous injection of CFA. The behavioral response was compared with that similarly determined in non-diabetic controls and insulin-depleted rats that received insulin replacement. Results., Recovery of the thermal hyperalgesic response to baseline levels occurred over a period of 9,14 days, but the allodynic response to mechanical stimulation persisted for the duration of the study in STZ-treated rats. Insulin replacement prevented the delay in recovery of mechanical allodynia, but had no obvious effect on nociception in uninflamed tissue. Conclusions., Normal insulin function is essential for recovery from mechanical allodynia associated with inflammation induced by CFA. Altered insulin metabolism may selectively influence fiber-type specific mechanisms related to mechanical allodynia associated with inflammation and wound healing. [source] Essential versus reactive thrombocythemia in children: Retrospective analyses of 12 casesPEDIATRIC BLOOD & CANCER, Issue 1 2007Abeer Abd El-Moneim Abstract Background Essential thrombocythemia (ET) rarely occurs in the pediatric population and little is known about the clinical course and the molecular characteristics. Procedure In this retrospective multi-institutional study we examine the clinical, hematological, and molecular features of 12 children aged 5,16 years with thrombocytosis and a suspected diagnosis of ET. Results Median follow-up was 59 months (range 10,72). Seven patients presented with clinical symptoms potentially related to thrombocytosis. The remaining five patients were diagnosed incidentally. Median platelet count at diagnosis was 1,325,×,109/L (range 600,3,050). In 11 out of 12 cases bone marrow morphology was consistent with ET, the remaining patient had chronic idiopathic myelofibrosis. Cytogenetic analyses were normal in all studied cases and only one out of nine analyzed cases harbored a JAKV617F allele. Within 6 months after initial presentation one patient who was initially asymptomatic developed thrombosis and another patient had mild bleeding. Eight patients were treated with acetylsalicylic acid, one patient received hydroxyurea, and two patients received anagrelide. At last follow-up, all patients were alive and none had developed leukemia. Five patients experienced hematological remission. Two children had not received any therapy. During the course of their disease, nine patients developed symptoms possibly attributable to an elevated platelet count. Conclusions In JAK2 mutation negative cases, long-term follow-up is helpful to distinguish between primary and secondary thrombocytosis. Secondary cases are not associated with organomegaly but may present with unspecific symptoms. Indications for treatment in children remain unclear. Pediatr Blood Cancer 2007;49:52,55. © 2006 Wiley-Liss, Inc. [source] The Glycine Decarboxylase Complex is not Essential for the Cyanobacterium Synechocystis sp.PLANT BIOLOGY, Issue 1 2005Strain PCC 680 Abstract: In order to investigate the metabolic importance of glycine decarboxylase (GDC) in cyanobacteria, mutants were generated defective in the genes encoding GDC subunits and the serine hydroxymethyl-transferase (SHMT). It was possible to mutate the genes for GDC subunits P, T, or H protein in the cyanobacterial model strain Synechocystis sp. PCC 6803, indicating that GDC is not necessary for cell viability under standard conditions. In contrast, the SHMT coding gene was found to be essential. Almost no changes in growth, pigmentation, or photosynthesis were detected in the GDC subunit mutants, regardless of whether or not they were cultivated at ambient or high CO2 concentrations. The mutation of GDC led to an increased glycine/serine ratio in the mutant cells. Furthermore, supplementation of the medium with low glycine concentrations was toxic for the mutants but not for wild type cells. Conditions stimulating photorespiration in plants, such as low CO2 concentrations, did not induce but decrease the expression of the GDC and SHMT genes in Synechocystis. It appears that, in contrast to heterotrophic bacteria and plants, GDC is dispensable for Synechocystis and possibly other cyanobacteria. [source] On a numerical scheme for curved crack propagation based on configurational forces and maximum dissipationPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008Henning Schütte A numerical scheme is presented to predict crack trajectories in two dimensional components. First a relation between the curvature in mixed,mode crack propagation and the corresponding configurational forces is derived, based on the principle of maximum dissipation. With the help of this, a numerical scheme is presented which is based on a predictor,corrector method using the configurational forces acting on the crack together with their derivatives along real and test paths. With the help of this scheme it is possible to take bigger than usual propagation steps, represented by splines. Essential for this approach is the correct numerical determination of the configurational forces acting on the crack tip. The methods used by other authors are shortly reviewed and an approach valid for arbitrary non,homogenous and non,linear materials with mixed,mode cracks is presented. Numerical examples show, that the method is a able to predict the crack paths in components with holes, stiffeners etc. with good accuracy. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Affinity reagent resources for human proteome detection: Initiatives and perspectivesPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 16 2007Oda Stoevesandt Abstract Essential to the ambition of characterising fully the human proteome are systematic and comprehensive collections of specific affinity reagents directed against all human proteins, including splice variants and modifications. Although a large number of affinity reagents are available commercially, their quality is often questionable and only a fraction of the proteome is covered. In order for more targets to be examined, there is a need for broad availability of panels of affinity reagents, including binders against proteins of unknown functions. The most familiar affinity reagents are antibodies and their fragments, but engineered forms of protein scaffolds and nucleic acid aptamers with similar diversity and binding properties are becoming viable alternatives. Recent initiatives in Europe and the USA have been established to improve both the availability and quality of reagents for affinity proteomics, with the ultimate aim of creating standardised collections of well-validated binding molecules for proteome analysis. As well as coordinating affinity reagent production through existing resources and technology providers, these projects aim to benchmark key molecular entities, tools, and applications, and establish the bioinformatics framework and databases needed. The benefits of such reagent resources will be seen in basic research, medicine and the biotechnology and pharmaceutical industries. [source] Testing for Interaction in Binary Logit and Probit Models: Is a Product Term Essential?AMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 1 2010William D. Berry Political scientists presenting binary dependent variable (BDV) models often hypothesize that variables interact to influence the probability of an event, Pr(Y). The current typical approach to testing such hypotheses is (1) estimate a logit or probit model with a product term, (2) test the hypothesis by determining whether the coefficient for this term is statistically significant, and (3) characterize the nature of any interaction detected by describing how the estimated effect of one variable on Pr(Y) varies with the value of another. This approach makes a statistically significant product term necessary to support the interaction hypothesis. We show that a statistically significant product term is neither necessary nor sufficient for variables to interact meaningfully in influencing Pr(Y). Indeed, even when a logit or probit model contains no product term, the effect of one variable on Pr(Y) may be strongly related to the value of another. We present a strategy for testing for interaction in a BDV model, including guidance on when to include a product term. [source] Hypothesis: Research in Otolaryngology Is Essential for Continued Improvement in Health Care,THE LARYNGOSCOPE, Issue 6 2002Robert H. Mathog MD Abstract The present report, in the form of a research proposal, is based on the hypothesis that research in otolaryngology is essential for continued improvement in health care. Examples of advances in otolaryngology as a result of research are noted, but for continued success, otolaryngology must maintain and find better ways to train clinically directed researchers. Traditional methods of training such as hands-on experience, courses in the basic principles of research, protected time, and mentoring are discussed and evaluated. Barriers to success such as age, time, and debt are noted. Potential solutions are presented with an emphasis on integration of the research and clinical training. Success of faculty will continue to depend on laboratory and financial support, technical assistance, protected time, salary equivalent to other faculty, and accessibility of research funds. For research to gain support and enthusiasm and to keep it strong and productive, cost-effectiveness and value must be recognized. [source] Decay Accelerating Factor is Essential for Successful Corneal EngraftmentAMERICAN JOURNAL OF TRANSPLANTATION, Issue 3 2010A. Esposito In contrast to immune restrictions that pertain for solid organ transplants, the tolerogenic milieu of the eye permits successful corneal transplantation without systemic immunosuppression, even across a fully MHC disparate barrier. Here we show that recipient and donor expression of decay accelerating factor (DAF or CD55), a cell surface C3/C5 convertase regulator recently shown to modulate T-cell responses, is essential to sustain successful corneal engraftment. Whereas wild-type (WT) corneas transplanted into multiple minor histocompatibility antigen (mH), or HY disparate WT recipients were accepted, DAF's absence on either the donor cornea or in the recipient bed induced rapid rejection. Donor or recipient DAF deficiency led to expansion of donor-reactive IFN-, producing CD4+ and CD8+ T cells, as well as inhibited antigen-induced IL-10 and TGF-,, together demonstrating that DAF deficiency precludes immune tolerance. In addition to demonstrating a requisite role for DAF in conferring ocular immune privilege, these results raise the possibility that augmenting DAF levels on donor corneal endothelium and/or the recipient bed could have therapeutic value for transplants that clinically are at high risk for rejection. [source] Detailed Outcomes Analyses Are Essential for Optimizing Kidney Utilization StrategiesAMERICAN JOURNAL OF TRANSPLANTATION, Issue 12 2009R. P. Pelletier The optimal surgical approach for transplanting pediatric donor kidneys must pit the need to obtain the greatest number of recipients against that of obtaining the best possible outcomes. See article by Kayler et al on page 2745. [source] Is Tryptophan ,more' Essential than Other Essential Aminoacids in Development?ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2009A Morphologic Study Summary An ontogenetic study was designed on developing rats in uterus of mothers tryptophan deprived at day 1 (exp. 1) and day 14.5 (exp. 2) of conception to verify the supposed determining role of the serotoninergic system (SS) in sexual differentiation in mammals. Tryptophan-free feeding was pursued uninterruptedly in the litter after birth, during lactation and post-natal development. Tryptophan-free pregnant rats were obtained by exclusion of tryptophan sources from chow. In both exp. 1 and exp. 2, the litter showed at birth a significant physical under evolution that worsened, during post-natal development, to a much more marked dwarfism in exp. 1 pups. Growth hormone concentrations in both sexes of dwarf rats were lower than that in the control rats. At 30 days post-natal age, whereas exp. 1 female rats showed a right-timed onset of puberty, no descensus of testes could be observed in male rats of same experiment. Dwarf male rats showed an evident hypotrophy of the whole reproductive apparatus. In histological examination of testes, neither spermatogenesis nor Leydig cells have been observed. Moreover, dwarf female rats showed a pronounced hypotrophy of reproductive organs, but a normal puberal status pattern was evident. In exp. 2, litters showed a less pronounced dwarfism, but a normal right-timed onset of puberty in both male and female rats. Data indicate that role of tryptophan in physical and sexual maturation in both male and female rats is essential. [source] Diagnosis And Treatment Planning Are Essential Prior To Commencing Endodontic Treatment: Discuss This Statement As It Relates To Clinical Endodontic ManagementAUSTRALIAN ENDODONTIC JOURNAL, Issue 1 2005Ms Trudy Stewart Diagnosis and treatment planning are essential to the practice of endodontics. Diagnosis aims to determine whether pathological involvement of the dental pulp has or is occurring. Treatment planning meanwhile, involves appropriately selecting cases, determining how difficult the treatment may be to perform on a specific individual and sequencing treatment procedures to achieve a healthy and functional dentition. In endodontic management, this may involve establishing whether the tooth is restorable and periodontally sound, the patient is able to tolerate the treatments and the clinician has the skills to perform the required treatment procedures. Careful consideration of these issues must be given prior to commencing treatment. [source] Windows of operation for bioreactor design for the controlled formation of tissue-engineered arteriesBIOTECHNOLOGY PROGRESS, Issue 3 2009Spyridon Gerontas Abstract The availability of large numbers of units of artificial arteries would offer significant benefits to the clinical management of bypass surgery. Tissue engineering offers the potential of providing vessels that can mimic the morphology, function, and physiological environment of native vessels. Ideally this would involve culturing stem cells in vitro within a biodegradable tubular scaffold so as to construct tissue for implantation. Essential to establishing a robust process for the production of tissue-engineered arteries is the understanding of the impact of changes in the operating conditions and bioreactor design on the construct formation. In this article, models of transport phenomena were developed to predict the critical flow rates and mass transfer requirements of a prototype bioreactor for the formation of tissue-engineered arteries. The impact of the cell concentration, tube geometry, oxygen effective diffusivity in alginate, substrate and metabolite concentration levels, feed rate, and recycle rate on the design of the bioreactor was visualized using windows of operation and contour plots. The result of this analysis determined the best configuration of the bioreactor that meets the cellular transport requirements as well as being reliable in performance while seeking to reduce the amount of nutrients to be used. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Ras and Signal Transducer and Activator of Transcription (STAT) Are Essential and Sufficient Downstream Components of Janus Kinases in Cell ProliferationCANCER SCIENCE, Issue 5 2000Rumiko Mizuguchi Cytokines exert their activities in cell growth and differentiation by binding specific cell membrane receptors. Janus kinases (JAKs) are cytoplasmic protein tyrosine kinases that physically interact with intracellular domains of the cytokine receptors and they play crucial roles in transducing signals triggered by the cytokine-receptor interaction. We have previously shown that conditional activation of JAK through membrane-proximal dimerization confers cytokine-independence on interleukin-3 (IL-3)-dependent Ba/F3 lymphoid cells and that the cytokine-independent proliferation is completely inhibited by dominant negative Ras. In this work, we demonstrate that ectopic expression of a dominant negative form of Stat5, a major signal transducer and activator of transcription (STAT) expressed in Ba/F3 cells, also inhibits JAK-triggered mitogenesis. In contrast, overexpression of constitutively active Ras or conditional activation of Stat5 by chemical dimerization fails to confer cytokine-independence. However, concomitant activation of ectopic Ras and Stat5 molecules in Ba/F3 cells suffices for cell proliferation in the absence of IL-3. Our results indicate that Ras and STAT are essential and sufficient components of JAK-triggered mitogenesis. Our findings further indicate that the cytokine signal bifurcates into Ras and STAT pathways following JAK activation. [source] A Salmonella type III secretion effector interacts with the mammalian serine/threonine protein kinase PKN1CELLULAR MICROBIOLOGY, Issue 5 2006Andrea Haraga Summary Essential to salmonellae pathogenesis is an export device called the type III secretion system (TTSS), which mediates the transfer of bacterial effector proteins from the bacterial cell into the host cell cytoplasm. Once inside the host cell, these effectors are then capable of altering a variety of host cellular functions in order to promote bacterial survival and colonization. SspH1 is a Salmonella enterica serovar Typhimurium TTSS effector that localizes to the mammalian nucleus and down-modulates production of proinflammatory cytokines by inhibiting nuclear factor (NF)-,B-dependent gene expression. To identify mammalian binding partners of SspH1 a yeast two-hybrid screen against a human spleen cDNA library was performed. It yielded a serine/threonine protein kinase called protein kinase N 1 (PKN1). The leucine-rich repeat domain of SspH1 was demonstrated to mediate this interaction and also inhibition of NF-,B-dependent gene expression. This suggested that PKN1 may play a role in modulation of the NF-,B signalling pathway. Indeed, we found that expression of constitutively active PKN1 in mammalian cells results in a decrease, while depletion of PKN1 by RNA interference causes an increase in NF-,B-dependent reporter gene expression. These data indicate that SspH1 may inhibit the host's inflammatory response by interacting with PKN1. [source] Proline-40 is Essential to Maintaining Cytochrome b5, s Stability and Its Electron Transfer with Cytochrome cCHINESE JOURNAL OF CHEMISTRY, Issue 11 2002Zhi-Qian Wang Abstract In order to illustrate the roles played by Pro40 in the structure, properties and functions of Cytochrome b5, three mutated genes, P40V, P40Y, P40G were constructed in this work. Only the P40V gene was successfully expressed into holoprotein in E. coli JM83. According to the results of X-ray crystallographic analysis and various kinds of spectroscopy studies, it is evident that substituting valine for Pro40 does not result in significant alterations in the protein,s overall structure; however, local conformational perturbations in the proximity of the heme do occur. The redox potential of the P40V mutant is 40 mV lower than that of the wild type protein. Its stability towards heat, urea, acid and ethanol were significantly decreased. The mutation leads to a decrease in the hydrophobicity of the heme pocket, which is probably the major factor contributing to the above changes. Binding constants and electron transfer rates between cytochrome bs and cytochrome c were determined using UV-visible spectroscopy and stopped-flow techniques for both the wild type and the mutant. The results showed that the substitution of Pro40 by valine does not influence the binding constant of cytochrome b5 to cytochrome c; however, the electron transfer rate between them decreased significantly. This indicates that proline-40 is essential to maintaining cytochrome bss stability and its electron transfer with cytochrome c. These studies also provided a good example that property and functional changes of a protein do not necessarily require large overall structural alterations; in most cases, only perturbations on the local conformations are sufficient to induce significant changes in protein,s properties and functions. [source] Activation Of ,1 -Adrenoceptors Is Not Essential For The Mediation Of Ischaemic Preconditioning In Rat HeartCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1-2 2002E Vasara SUMMARY 1. The aim of the present study was to clarify the role of ,1 -adrenoceptors in the mechanism of ischaemic preconditioning (IP). 2. Rat isolated perfused hearts were either non- preconditioned, preconditioned with 5 min ischaemia or treated for 5 min with ,1 -adrenoceptor agonists (50 ,mol/L phenylephrine; 0.1, 0.5 and 1 ,mol/L methoxamine) before being subjected to 45 min of sustained ischaemia followed by 60 min reperfusion. 3. Within each of the above protocols, hearts were divided into groups to which ,1 -adrenoceptor antagonists (prazosin, 5,-methyl urapidil and chloroethylclonidine (CEC)) were administered. Functional recovery and infarct size were used as indices of the effects of ischaemia. Ischaemic contracture characteristics and maximal diastolic pressure during reflow were also assessed. 4. Blockade of ,1 -adrenoceptors with prazosin or the subtype-selective antagonists 5,-methyl urapidil and CEC did not abolish the protective effect of IP with respect to both functional recovery and infarct size reduction. 5. Protection afforded by phenylephrine was attenuated in hearts treated with prazosin or the ,1B -adrenoceptor- selective antagonist CEC, but not in those treated with the ,1A -adrenoceptor-selective antagonist 5,-methyl urapidil. 6. Treatment with low concentrations of methoxamine, considered to be ,1A -adrenoceptor selective, did not confer any protection to the ischaemic myocardium. 7. A close relationship between accelerated ischaemic contracture and enhanced cardioprotection was observed. 8. The results suggest that ,1 -adrenoceptor stimulation mimics IP, but it is not an essential component in the mechanism behind the protective effect of IP in rat heart. In addition, the present study demonstrates that stimulation of the ,1B - but not the ,1A -adrenoceptor subtype is responsible for the catecholamine-induced protection of ischaemic myocardium in rat. [source] | |||||||||||||||||||||||||||||||||||||||||||