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Main Obstacles (main + obstacle)
Selected AbstractsRelationship between legitimation, competition and organizational death: current state of the artINTERNATIONAL JOURNAL OF MANAGEMENT REVIEWS, Issue 1 2004Manuel Núñez Nickel There is agreement among ecology researchers that the concepts of legitimation and competition are partly responsible for organizational selection. Finding adequate measures to represent these concepts, however, has been elusive and has been the main obstacle to the development of this stream of investigation. On the basis of the germinal density dependence model, we identify two lines of research, which have generated seven distinct models. This survey shows that there has been a general tendency to use only three variables to measure legitimation and competition, which are often measured together. However, we argue that fruitful results have emerged when efforts have been made to separate both concepts and that there is some potential in using new measures (mass or concentration) which have so far only found limited application in the field of population demography. These findings, together with the inconclusive results of this stream of research, allow us to identify the existing gaps in the literature and comment on directions for future research. [source] Vesicle amine transport protein-1 (VAT-1) is upregulated in glioblastomas and promotes migrationNEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 4 2009S. Mertsch Aim:,Diffuse invasion of single-glioma cells is the main obstacle to successful therapy of these tumours. After identifying vesicle amine transport protein-1 (VAT-1) as being upregulated in invasive human gliomas, we study its possible function in glioblastoma cell migration. Methods:,Based on data obtained from previous oligonucleotide arrays, we investigated expression of VAT-1 in glioblastoma tissue and cell lines on mRNA levels using reverse transcriptase PCR. Furthermore, we examined the amount and localization of VAT-1 protein using immunoblotting and immunohistochemistry. Using small interfering RNA technology we repressed VAT-1 expression in human glioma cell lines and analysed their migration using wound healing and transwell migration assays. Results:,Increased VAT-1 mRNA and protein levels were found in glioblastoma tissues and cell lines compared with normal human brain. Small interfering RNA-mediated VAT-1 knockdown led to significantly reduced migration of human glioma cells. Conclusions:,VAT-1 is overexpressed in glioblastomas and functionally involved in glioma cell migration, representing a new component involved in glioma invasion. [source] Upgrading Patients with Chronic Defibrillator Leads to a Biventricular System and Reducing Patient Risk: Contralateral LV Lead PlacementPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2006DAVID J. FOX Increasing numbers of patients with indwelling single- or dual- chamber internal cardioverter defibrillators (ICDs) will require upgrading of an existing system to a biventricular ICD providing cardiac resynchronization with back-up defibrillation. Upgrading, usually by the addition of a new left ventricular (LV) lead, can be technically challenging with central venous occlusion or stenosis often being the main obstacle to a successful procedure. We report a new technique of implanting a LV lead from the contralateral side to the existing ICD system to minimize the peri- and postoperative risk to the patient. [source] YB-1 is upregulated during prostate cancer tumor progression and increases P-glycoprotein activityTHE PROSTATE, Issue 3 2004Pepita Giménez-Bonafé Abstract BACKGROUND Currently, the main obstacle to curing advanced prostate cancer is development of androgen independence (AI), where malignant cells acquire the ability to survive in the absence of androgens. Our initial experimental approach used cDNA microarrays to characterize changes in gene expression in the LNCaP human prostate tumor model during progression to AI. The transcription factor Y-box binding protein (YB-1) was shown to be one of the genes upregulated. We focused on increased YB-1 expression during progression in clinical specimens, and further examined one of its downstream targets, P-glycoprotein (P-gp). METHODS Northern blot analysis was performed on LNCaP tumor series, as well as immunohistochemical analyses of human prostate cancer tissue samples. YB-1 was transiently transfected and transport analysis were performed to analyze P-gp efflux activity. RESULTS YB-1 expression is markedly increased during benign to malignant transformation and further following androgen ablation. In addition, increased YB-1 expression after castration in the LNCaP model is linked to upregulation of P-gp. We demonstrate that YB-1 upregulates P-gp activity resulting in a 40% intracellular decrease in the P-gp substrate vinblastine. We have also found that P-gp increases the efflux of the endogenous androgen, dihydrotestosterone (DHT), from prostate cells and leads to decreased androgen regulated gene expression. CONCLUSIONS We hypothesize that early in prostate cancer progression, increased expression of YB-1 may increase P-gp activity which may in turn lower androgen levels in the prostate tumor cells. Suppression of androgen levels may activate cell survival pathways and lead to an adaptive survival advantage of androgen independent prostate cancer cells following androgen ablation therapy. © 2004 Wiley-Liss, Inc. [source] A double-screening method to identify reliable candidate non-synonymous SNPs from chicken EST dataANIMAL GENETICS, Issue 4 2003H. Kim Summary Discovery of non-synonymous single nucleotide polymorphisms (nsSNP), which cause amino acid substitutions, is important because they are more likely to alter protein function than synonymous SNPs (sSNP) or those SNPs that do not result in amino acid changes. By changing the coding sequences, nsSNP may play a role in heritable differences between individual organisms. In the chicken and many other vertebrates, the main obstacle for identifying nsSNP is that there is insufficient protein and mRNA sequence information for self-species referencing and thus, determination of the correct reading frame for expressed sequence tags (ESTs) is difficult. Therefore, in order to estimate the correct reading frame at nsSNP in chicken ESTs, a double-screening approach was designed using self- or cross-species protein referencing, in addition to the ESTScan coding region estimation programme. Starting with 23 427 chicken ESTs, 1210 potential SNPs were discovered using a phred/phrap/polyphred/consed pipeline process and among these, 108 candidate nsSNP were identified with the double screening method. A searchable SNP database (chicksnps) for the candidate chicken SNPs, including both nsSNPs and sSNPs is available at http://chicksnps.afs.udel.edu. The chicken SNP data described in this paper have been submitted to the data base SNP under National Center for Biotechnology Information assay ID ss4387050-ss4388259. [source] Migration and Policies in the European Union: Highly Skilled Mobility, Free Movement of Labour and Recognition of DiplomasINTERNATIONAL MIGRATION, Issue 1 2001João Peixoto This article evaluates the relationship between highly skilled mobility (especially by individuals with university-level degrees) and migration policies. Data from the European Union (EU) and Portugal (in particular) provide the empirical basis of the research. EU policies regarding the free circulation of individuals which aim to build the "common market" for economic factors (including labour) are reviewed, as are the more specific recognition of diplomas policies for professional and academic purposes, and recent levels of international mobility in both the EU and Portugal. The article also enumerates the main obstacles that, from a political and legal or social and cultural perspective, explain the low mobility revealed by those figures. Obstacles include the broad denial of citizenship rights; the necessity of assuring a means of sustenance; linguistic and technical exigencies for diploma recognition; the social attributes of work (more explicit in the service sector); and the institutional nature of national skilled labour markets. The main exception to the low mobility rule , movements of cadres in the internal labour markets of transnational corporations , together with flows in other multinational organizations, are also reviewed. In these, migrations are relatively exempt from political constraints and, significantly, avoid the recognition procedures adopted by the EU. In other words, it seems that the entry of highly skilled individuals in a transnational corporation, and not their citizenship in a Europe without frontiers, is what enables them to achieve effective mobility. [source] Properties of cell penetrating peptides (CPPs)IUBMB LIFE, Issue 1 2006Alexandre Kerkis Abstract Different approaches have been developed for the introduction of macromolecules, proteins and DNA into target cells. Viral (retroviruses, lentiviruses, etc.) and nonviral (liposomes, bioballistics etc.) vectors as well as lipid particles have been tested as DNA delivery systems. However, all of them share several undesirable effects that are difficult to overcome, such as unwanted immunoresponse and limited cell targeting. The discovery of the cell penetrating peptides (CPPs) showing properties of macromolecules carriers and enhancers of viral vectors, opened new opportunities for the delivery of biologically active cargos, including therapeutically relevant genes into various cells and tissues. This review summarizes recent data about the best characterized CPPs as well as those sharing cell-penetrating and cargo delivery properties despite differing in the primary sequence. The putative mechanisms of CPPs penetration into cells and interaction with intracellular structures such as chromosomes, cytoskeleton and centrioles are addressed. We further discuss recent developments in overcoming the lack of cells specificity, one of the main obstacles for CPPs application in gene therapy. In particular, we review a newly discovered affinity of CPPs to actively proliferating cells. IUBMB Life, 58: 7 - 13, 2006 [source] The Challenge of asthma in adolescencePEDIATRIC PULMONOLOGY, Issue 8 2007Diletta de Benedictis MD Abstract The adolescents with asthma are a distinct group of patients with different problems and needs compared to children and adults. Specific issues of asthma in adolescence are the variability of the clinical spectrum, the presence of particular risk factors for the persistence of symptoms, underdiagnosis and undertreatment of the disease. Refusal of the sick role, denial of symptoms, carelessness about dangerous inhalation exposure, erratic self-medication, overexertion without taking precautions against exercise-induced asthma, and a poor relationship between patients, their families, and often doctors are the main obstacles to successful management of asthma in this critical age. There are also major problems of compliance for these patients. The goal of optimal quality of life will be achieved only if the physician thoroughly understands the adolescent's needs and provides optimal care. Pediatr Pulmonol. 2007, 42:683,692. © 2007 Wiley-Liss, Inc. [source] Localization of arginine decarboxylase in tobacco plantsPHYSIOLOGIA PLANTARUM, Issue 1 2004Cristina Bortolotti The lack of knowledge about the tissue and subcellular distribution of polyamines (PAs) and the enzymes involved in their metabolism remains one of the main obstacles in our understanding of the biological role of PAs in plants. Arginine decarboxylase (ADC; EC 4.1.1.9) is a key enzyme in polyamine biosynthesis in plants. We have characterized a cDNA coding for ADC from Nicotiana tabacum L. cv. Petit Havana SR1. The deduced ADC polypeptide had 721 amino acids and a molecular mass of 77 kDa. The ADC cDNA was overexpressed in Escherichia coli, and the ADC fusion protein obtained was used to produce polyclonal antibodies. Using immunological methods, we demonstrate the presence of the ADC protein in all plant organs analysed: flowers, seeds, stems, leaves and roots. Moreover, depending on the tissue, the protein is localized in two different subcellular compartments, the nucleus and the chloroplast. In photosynthetic tissues, ADC is located mainly in chloroplasts, whereas in non-photosynthetic tissues the protein appears to be located in nuclei. The different compartmentation of ADC may be related to distinct functions of the protein in different cell types. [source] INLINE RADIOFREQUENCY ABLATION-ASSISTED LAPAROSCOPIC LIVER RESECTION: FIRST EXPERIMENT WITH STAPLING DEVICEANZ JOURNAL OF SURGERY, Issue 6 2007Peng Yao Background: In liver surgery, the increase in advancement of laparoscopic equipment has allowed the feasibility and safety of complex laparoscopic liver resection. However, blood loss and the potential risk of gas embolism seem to be the main obstacles. In this study, we successfully used the InLine radiofrquency ablation (RFA) device to carry out laparoscopic hand-assisted liver resection in pigs. Methods: Under general anaesthesia with tracheal intubation, pigs underwent InLine RFA-assisted laparoscopic liver resection. After installation of Hand Port and trocars, the InLine RFA device was introduced through Hand Port system and inserted into the premarked resection line. Then the generator was turned on and the power was applied according to the power setting. The resection was finally carried out using diathermy or stapler. For the control group, resection was simply carried out by diathermy or stapler. Results: Eight Landrace pigs underwent 23 liver resections. Blood loss was reduced significantly in the InLine group (P < 0.001) when compared with control group in both surgical methods (diathermy and stapler). Conclusion: In this study, we successfully carried out InLine RFA-assisted laparoscopic liver resection in both stapled and diathermy group. We showed that there was a highly significant difference between InLine and other liver resection techniques laparoscopically. [source] Novel Strategy to Engineer Trachea Cartilage Graft With Marrow Mesenchymal Stem Cell Macroaggregate and Hydrolyzable ScaffoldARTIFICIAL ORGANS, Issue 5 2010Liangqi Liu Abstract Limited donor sites of cartilage and dedifferentiation of chondrocytes during expansion, low tissue reconstruction efficiency, and uncontrollable immune reactions to foreign materials are the main obstacles to overcome before cartilage tissue engineering can be widely used in the clinic. In the current study, we developed a novel strategy to fabricate tissue-engineered trachea cartilage grafts using marrow mesenchymal stem cell (MSC) macroaggregates and hydrolyzable scaffold of polylactic acid,polyglycolic acid copolymer (PLGA). Rabbit MSCs were continuously cultured to prepare macroaggregates in sheet form. The macroaggregates were studied for their potential for chondrogenesis. The macroaggregates were wrapped against the PLGA scaffold to make a tubular composite. The composites were incubated in spinner flasks for 4 weeks to fabricate trachea cartilage grafts. Histological observation and polymerase chain reaction array showed that MSC macroaggregates could obtain the optimal chondrogenic capacity under the induction of transforming growth factor-,. Engineered trachea cartilage consisted of evenly spaced lacunae embedded in a matrix rich in proteoglycans. PLGA scaffold degraded totally during in vitro incubation and the engineered cartilage graft was composed of autologous tissue. Based on this novel, MSC macroaggregate and hydrolyzable scaffold composite strategy, ready-to-implant autologous trachea cartilage grafts could be successfully fabricated. The strategy also had the advantages of high efficiency in cell seeding and tissue regeneration, and could possibly be used in future in vivo experiments. [source] In Vivo Preclinical Anticoagulation Regimens After Implantation of Ventricular Assist DevicesARTIFICIAL ORGANS, Issue 7 2009Diyar Saeed Abstract Ventricular assist devices (VADs) have demonstrated successfully their ability to treat failing circulation of patients with end-stage heart failure. Among the main obstacles with these VADs is thromboembolic events that increase device-related morbidity and mortality. Prior to the clinical application of any newly developed VAD, the feasibility of the device is tested on animal models. Animal species have different hemostatic properties than human patients, and this factor creates a margin of error when comparing the occurrence of VAD-induced thrombosis in an animal versus a human. This detailed literature review provides a thorough documentation of various preclinical anticoagulation protocols used to date, including their outcomes and recommendations for future anticoagulation management strategies. In summary, the outcomes favor a sheep or pig model over other animal models, and discourage the application of a single anticoagulative agent to improve outcomes with any of the currently available devices. [source] Bioreactor strategies for improving production yield and functionality of a recombinant human protein in transgenic tobacco cell culturesBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Ting-Kuo Huang Abstract Plant cell culture production of recombinant products offers a number of advantages over traditional eukaryotic expression systems, particularly if the product can be targeted to and purified from the cell culture broth. However, one of the main obstacles is product degradation by proteases that are produced during cell culture, and/or the loss of biological activity of secreted (extracellular) products as a result of alteration in the protein conformation. Because proteolysis activity and target protein stability can be significantly influenced by culture conditions, it is important to evaluate bioprocess conditions that minimize these effects. In this study, a bioreactor strategy using a protocol involving pH adjustment and medium exchange during plant cell culture is proposed for improving the production of functional recombinant ,1 -antitrypsin (rAAT), a human blood protein, produced using several alternative expression systems, including a Cauliflower mosaic virus (CaMV) 35S constitutive promoter expression system, a chemically inducible, estrogen receptor-based promoter (XVE) expression system, and a novel Cucumber mosaic virus (CMV) inducible viral amplicon (CMViva) expression system developed by our group. We have demonstrated that higher medium pH help reduce protease activity derived from cell cultures and improve the inherent stability of human AAT protein as well. This strategy resulted in a fourfold increase in the productivity of extracellular functional rAAT (100 µg/L) and a twofold increase in the ratio of functional rAAT to total rAAT (48%) in transgenic N. benthamiana cell cultures using a chemically inducible viral amplicon expression system. Biotechnol. Bioeng. 2009;102: 508,520. © 2008 Wiley Periodicals, Inc. [source] | |||||||||||||