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Dramatic Loss (dramatic + loss)
Selected AbstractsTargeted cell-ablation in Xenopus embryos using the conditional, toxic viral protein M2(H37A)DEVELOPMENTAL DYNAMICS, Issue 8 2007Stuart J. Smith Abstract Harnessing toxic proteins to destroy selective cells in an embryo is an attractive method for exploring details of cell fate and cell,cell interdependency. However, no existing "suicide gene" system has proved suitable for aquatic vertebrates. We use the M2(H37A) toxic ion channel of the influenza-A virus to induce cell-ablations in Xenopus laevis. M2(H37A) RNA injected into blastomeres of early stage embryos causes death of their progeny by late-blastula stages. Moreover, M2(H37A) toxicity can be controlled using the M2 inhibitor rimantadine. We have tested the ablation system using transgenesis to target M2(H37A) expression to selected cells in the embryo. Using the myocardial MLC2 promoter, M2(H37A)-mediated cell death causes dramatic loss of cardiac structure and function by stage 39. With the LURP1 promoter, we induce cell-ablations of macrophages. These experiments demonstrate the effectiveness of M2(H37A)-ablation in Xenopus and its utility in monitoring the progression of developmental abnormalities during targeted cell death experiments. Developmental Dynamics 236:2159,2171, 2007. © 2007 Wiley-Liss, Inc. [source] Campylobacter and IFN, interact to cause a rapid loss of epithelial barrier integrityINFLAMMATORY BOWEL DISEASES, Issue 3 2008Louisa E.N. Rees PhD Abstract Background: The intestinal epithelium is a single layer of polarized cells and is the primary barrier separating foreign antigen and underlying lymphoid tissue. IFN, alters epithelial barrier function during inflammation by disrupting tight cell junctions and facilitating the paracellular transport of luminal antigens. The aim of this work was to determine whether Campylobacter infection of cells exposed to IFN, would lead to greater disruption of cell monolayers and hence increased bacterial translocation. Methods: Monolayers were polarized on Transwell polycarbonate membranes for 14 days and then cultured in the presence or absence of 100 U/mL IFN,. Campylobacter was added to the apical side of the monolayer at an MOI of 30. Transepithelial electrical resistance (TEER) was recorded and bacteria in the basal well counted every 2 hours. Cells were stained for occludin, actin, and nuclear DNA, and cell viability determined by measurement of apoptosis. Results: In the presence of IFN,, TEER dropped significantly after 18 hours, indicating a reduction in barrier function. A further significant decrease was seen in the presence of both IFN, and Campylobacter, indicating a synergistic effect, and cellular morphology and viability were affected. Bacterial translocation across the monolayer was also significantly greater in the presence of IFN,. Conclusions: These combined effects indicate that Campylobacter infection concomitant with intestinal inflammation would result in a rapid and dramatic loss of epithelial barrier integrity, which may be a key event in the pathogenesis of Campylobacter -mediated colitis and the development of bloody diarrhea. (Inflamm Bowel Dis 2007) [source] Hot air dehydration of figs (Ficus carica L.): drying kinetics and quality lossINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2004Antonio Piga Summary The dehydration of fruit from fig trees is normally achieved by sun drying. There is concern about the safety of the end product, mainly because there is a risk of the development of aflatoxins. These concerns can be overcome by artificial drying (oven dehydration). Fig fruits of a local cultivar, which were either pre-treated by blanching or blanching plus sulphuring or not treated at all, underwent hot air dehydration under mild processing conditions in a pilot airflow cabinet dryer. Sampling was carried out at regular intervals to calculate the rate of dehydration and assess quality changes. Microbiological counts and nonenzymatic browning were also monitored. Pretreatments resulted in a shorter processing time, compared with control fruits. In general, a falling dehydration rate period was observed. A dramatic loss of ascorbic acid was recorded, while an informal sensorial assay of the dried fruits gave a positive assessment. [source] Acellular dermal matrix allograft used to gain attached gingiva in a case of epidermolysis bullosaJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 11 2003Eralp Buduneli Abstract Background: Epidermolysis bullosa (EB) is an acquired disease or inherited as either autosomal dominant or recessive with an incidence of 1/50,000. The prominent clinical characteristic of the disease is the development of bullae or vesicles in mucosa or skin in response to minor trauma. Aim: A female patient with a dystrophic type of EB had been put in a maintenance regimen after completion of the initial phase of periodontal therapy and followed for 7 years. The purpose of this report is to document acellular dermal matrix allograft application to increase the width of the attached gingiva in this patient experiencing difficulty in chewing and performing plaque control due to the dramatic loss of attached gingiva after 7 years of supportive periodontal therapy. Methods: Under local anaesthesia and antibiotic coverage, the acellular dermal matrix allograft was applied in the anterior region of the upper jaw in order to increase the width of attached gingiva, thereby improving patient comfort. Results: The healing was uneventful and a significant gain in attached gingiva dimensions was observed 9 months after the periodontal surgery. The procedure avoided a second surgical site, provided satisfactory results from an aesthetic point of view, and improved patient comfort. Conclusion: Acellular dermal matrix allograft may be regarded as an alternative in the treatment of EB cases to increase the width of attached gingiva and facilitate maintenance of the dentition. Zusammenfassung Hintergrund: Die Epidermolysis bullosa (EB) ist eine erworbene oder eine autosomal dominant oder rezessiv vererbte Krankheit mit einer Incidenz von 1:50,000. Die hervorstechenden klinischen Symptome dieser Erkrankung sind die Entwicklung von Blasen oder Vesikeln in der Mukosa oder in der Haut auf geringste Traumen. Ziel: Eine Frau mit dem dystrophischen Typ von EB wurde in der Erhaltungsphase seit 7 Jahren geführt, nachdem die initiale Phase der parodontalen Therapie beendet worden war. Der Zweck dieser Studie ist die Dokumentation der Applikation eines azellulären Hautmatrixtransplantats für die Verbreiterung der fest angewachsenen Gingiva bei dieser Patientin, die nach 7 Jahren der erhaltenden parodontalen Therapie Probleme beim Kauen und bei der Durchführung der Plaquekontrolle durch einen starken Verlust an fest angewachsener Gingiva hatte. Methoden: Unter lokaler Anästhesie und antibiotischer Abschirmung wurde das azelluläre Hautmatrixtransplantat in die anteriore Region des Oberkiefers appliziert, um die Breite der fest angewachsenen Gingiva zu vergrößern und so das Befinden der Patientin zu verbessern. Ergebnisse: Die Heilung war komplikationslos, und ein signifikanter Gewinn an fest angewachsener Gingiva 9 Monate nach der parodontalen Operation wurde beobachtet. Die Methode vermied eine zweite chirurgische Region, erbrachte zufriedenstellende Ergebnisse aus ästhetischer Sicht und verbesserte das Befinden der Patientin. Schlussfolgerung: Das azelluläre Hautmatrixtransplantat kann als eine Alternative in der Behandlung von EB betrachtet werden, um die Breite der fest angewachsenen Gingiva zu vergrößern und zur Möglichkeit der Erhaltung der Dentition beizutragen. Résumé La bullose épidermolysie (EB) est une maladie contractée ou héritée qui peut être aussi bien autosomale dominante que récessive avec une fréquence de 1/50,000. La caractéristique clinique importante de la maladie est le développement de bulles ou de vésicules au niveau de la muqueuse ou de la peau comme réponse à un traumatisme mineur. Une femme avec un type dystrophique de EB a été placée dans un régime de maintenance après la fin de la phase initiale du traitement parodontal et suivie durant sept années. Le but de ce rapport est de documenter le placement d'un allographe de la matrice dermique acellulaire visant à augmenter la largeur de la gencive attachée chez cette patiente qui avait des problèmes aux niveaux masticatoire et du contrôle de la plaque dentaire vu la perte dramatique de la gencive attachée après sept années de maintenance parodontale. Sous anesthésie locale et sous couverture antibiotique, l'allographe de la matrice dermique acellulaire a été placé dans la région antérieure de la mâchoire supérieure pour augmenter la largeur de la gencive attachée afin d'améliorer le confort de la patiente. La guérison s'est déroulée sans problème et un gain significatif de gencive attachée a été observé neuf mois après la chirurgie parodontale. Ce processus chirurgical élimine la nécessité d'avoir un site donneur, apporte des résultats satisfaisants du point de vue esthétique et améliore le confort du patient. L'allographe de la matrice dermique acellulaire peut donc être considéré comme une alternative dans le traitement des cas de EB afin d'augmenter la largeur de la gencive attachée et faciliter le maintien de la dentition. [source] Developing bifunctional , -lactamase molecules with built-in target-recognizing module for prodrug therapy: identification of Enterobacter Cloacae P99 cephalosporinase loops suitable for randomization and phage-display selectionJOURNAL OF MOLECULAR RECOGNITION, Issue 6 2009Girja S. Shukla Abstract This study was focused on developing catalytically active , -lactamase enzyme molecules that have target-recognizing sites built within their scaffold. Using phage-display approach, nine libraries were constructed by inserting the randomized linear or cysteine-constrained heptapeptides in the five different loops on the outer surface of P99 , -lactamase molecule. The pIII signal peptide of Sec-pathway was employed for a periplasmic translocation of the , -lactamase fusion protein, which we found more efficient than the DsbA signal peptide of SRP-pathway. The randomized heptapeptide loops replaced native amino acids between positions 34Y- 37K, 238M- 246A, 275N- 280A, 305A- 311S, or 329I- 334I of the P99 , -lactamase molecules for generating the loop-1 to -5 libraries, respectively. The diversity of each loop library was judged by counting the primary and , -lactamase-active clones. The linear peptide inserts in the loop-2 library showed the maximum number of the , -lactamase-active clones, followed by the loop-5, loop-3, and loop-4. The insertion of the cysteine-constrained loops exhibited a dramatic loss of the enzyme-active , -lactamase clones. The complexity of the loop-2 linear library, as determined by the frequency and diversity of amino acid distributions in the randomized region, appears consistent with the standards of other types of phage display library systems. The selection of the loop-2 linear library on streptavidin protein as a test target identified several , -lactamase clones that specifically bound to streptavidin. In conclusion, this study identified the suitability of the loop-2 of P99 , -lactamase for constructing a phage-display library of the , -lactamase enzyme-active molecules that can be selected against a target. This is an enabling step in our long-term goal of developing bifunctional , -lactamase molecules against cancer-specific targets for enzyme prodrug therapy of cancer. Copyright © 2009 John Wiley & Sons, Ltd. [source] Dejerine-Sottas Neuropathy with Multiple Nerve Roots Enlargement and Hypomyelination Associated with a Missense Mutation of the Transmembrane Domain of MPZ/P0JOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2003A Simonati In a patient affected with a slowly progressive, severe form of Dejerine-Sottas syndrome, symmetric enlargement of cranial nerves and focal hypertrophy of cervical and caudal roots were detected following MRI. Neuropathological features of the sural nerve disclosed a dramatic loss of myelinated fibres, with skewed-to-the-left, unimodal distribution of the few residual fibres, consistent with the diagnosis of congenital hypomyelination neuropathy. Genetic analysis revealed this condition to be associated with a heterozygous G to A transition at codon 167 in the exon 4 of the MPZ/P0 gene causing a Gly138Arg substitution in the transmembrane domain of the mature MPZ/P0 protein. Focal enlargement of the nerve trunks in demyelinating, hereditary motor and sensory neuropathies (HMSN) was previously reported in both asymptomatic and symptomatic cases with root compression, but peculiar to this case is the diffuse involvement of both cranial and spinal nerves. We believe that the relevance of nerve trunk hypertrophy in HMSN is probably underevaluated: therefore MRI investigation of the head and spine should be included in the diagnostic study of selected HMSN patients. Molecular analysis of peripheral myelin genes will help to rule out misdiagnosed cases. [source] Use of a lactic acid bacteria starter culture during green olive (Olea europaea L cv Ascolana tenera) processingJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 7 2005Vincenzo Marsilio Abstract Among the Italian olive germplasm, ,Ascolana tenera' is one of the best varieties for table olive production. This research addressed the impact of different processing types (Greek-style and Spanish-style) on the fermentation and phenolic composition of olive fruit. In particular, the effects of a lactic acid bacteria (LAB) starter culture on the fermentation of naturally green olives processed according to the traditional Greek method were studied. Results revealed that Spanish-style processing produced a dramatic loss of total phenolics, while natural olive processing favoured a higher retention of biophenols. Oleoside 11-methylester, a phenol-related compound, and hydroxytyrosol, tyrosol, vanillic acid, 3,4-dihydroxyphenylglycol, oleuropein and oleuropein aglycons, as the main phenols, were detected in olive fruit. More interestingly, this research indicated that inoculation with LAB affected the pH, total acidity, microbial profile and palatability of olives. Olives fermented with the LAB starter culture were perceived by panellists to be less bitter and more aromatic than those spontaneously fermented. Thus the use of LAB inoculants during olive fermentation could be applied with the currently available technology. Copyright © 2005 Society of Chemical Industry [source] Impacts of global change on plant diversity and vice versa: Old and new challenges for vegetation scientistsJOURNAL OF VEGETATION SCIENCE, Issue 6 2005Frank Berendse Abstract. The desire to stop the current dramatic loss of biodiversity has been a major stimulus for many vegetation ecologists to unravel the mechanisms responsible for the coexistence of species. After the Rio Janeiro Convention many ecologists were convinced that nature conservation would gain strong societal support if they could prove that the loss of species would have important negative effects on the ecosystem functions that are relevant to society. I conclude that in order to understand such possible effects, it is necessary to analyse the effects of individual species on those ecosystem processes that we consider to be relevant in the context of specific questions. The great challenge for the near future is to scale the effects of plant species on their local environment up to the level of the whole planet, so that we learn about possible feedbacks that might regulate or destabilize those characteristics of the globe that are essential to our society. [source] Community-level changes in Australian subalpine vegetation following invasion by the non-native shrub Cytisus scopariusJOURNAL OF VEGETATION SCIENCE, Issue 5 2004Lynise J. Wearne Abstract: Question: What are the changes associated with the recent invasion by the non-native legume, Cytisus scoparius? Location: Subalpine vegetation (1500 m a.s.l.) in Australia. Methods: We used multivariate techniques and regression analyses to assess vegetation and environmental changes across six study sites. Vegetation and environmental variables were investigated at three different stages of invasion: (1) recent invasion (8,10 yr), (2) mature invasion (15,16 yr) and (3) long-term invasion (25 yr). Results: Substantial changes in floristic composition and species richness were evident after 15 yr and these changes became more pronounced after 25 yr. Changes due to invasion were associated with a dramatic loss of native species or a reduction in their abundance. No ,new species' were evident under invaded stands. Forbs were most affected by the establishment of C. scoparius, although all growth forms responded negatively. Dense canopy shading and an increasingly dense, homogeneous litter layer in the understorey as a result of C. scoparius were strong environmental drivers of vegetation change. Greenhouse studies confirmed the importance of these processes on the germination and growth of two native species. Conclusions: This study highlights the potential for C. scoparius to alter both vegetation and environmental processes in the subalpine region. [source] Inferring the past to predict the future: climate modelling predictions and phylogeography for the freshwater gastropod Radix balthica (Pulmonata, Basommatophora)MOLECULAR ECOLOGY, Issue 3 2009M. CORDELLIER Abstract Understanding the impact of past climatic events on species may facilitate predictions of how species will respond to future climate change. To this end, we sampled populations of the common pond snail Radix balthica over the entire species range (northwestern Europe). Using a recently developed analytical framework that employs ecological niche modelling to obtain hypotheses that are subsequently tested with statistical phylogeography, we inferred the range dynamics of R. balthica over time. A Maxent modelling for present-day conditions was performed to infer the climate envelope for the species, and the modelled niche was used to hindcast climatically suitable range at the last glacial maximum (LGM) c. 21 000 years ago. Ecological niche modelling predicted two suitable areas at the LGM within the present species range. Phylogeographic model selection on a COI mitochondrial DNA data set confirmed that R. balthica most likely spread from these two disjunct refuges after the LGM. The match observed between the potential range of the species at the LGM given its present climatic requirements and the phylogeographically inferred refugial areas was a clear argument in favour of niche conservatism in R. balthica, thus allowing to predict the future range. The subsequent projection of the potential range under a global change scenario predicts a moderate pole-ward shift of the northern range limits, but a dramatic loss of areas currently occupied in France, western Great Britain and southern Germany. [source] Are cattle, sheep, and goats endangered species?MOLECULAR ECOLOGY, Issue 1 2008P. TABERLET Abstract For about 10 000 years, farmers have been managing cattle, sheep, and goats in a sustainable way, leading to animals that are well adapted to the local conditions. About 200 years ago, the situation started to change dramatically, with the rise of the concept of breed. All animals from the same breed began to be selected for the same phenotypic characteristics, and reproduction among breeds was seriously reduced. This corresponded to a strong fragmentation of the initial populations. A few decades ago, the selection pressures were increased again in order to further improve productivity, without enough emphasis on the preservation of the overall genetic diversity. The efficiency of modern selection methods successfully increased the production, but with a dramatic loss of genetic variability. Many industrial breeds now suffer from inbreeding, with effective population sizes falling below 50. With the development of these industrial breeds came economic pressure on farmers to abandon their traditional breeds, and many of these have recently become extinct as a result. This means that genetic resources in cattle, sheep, and goats are highly endangered, particularly in developed countries. It is therefore important to take measures that promote a sustainable management of these genetic resources; first, by in situ preservation of endangered breeds; second, by using selection programmes to restore the genetic diversity of industrial breeds; and finally, by protecting the wild relatives that might provide useful genetic resources. [source] A comprehensive set of simulations studying the influence of gas expulsion on star cluster evolutionMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007H. Baumgardt ABSTRACT We have carried out a large set of N -body simulations studying the effect of residual-gas expulsion on the survival rate, and final properties of star clusters. We have varied the star formation efficiency (SFE), gas expulsion time-scale and strength of the external tidal field, obtaining a three-dimensional grid of models which can be used to predict the evolution of individual star clusters or whole star cluster systems by interpolating between our runs. The complete data of these simulations are made available on the internet. Our simulations show that cluster sizes, bound mass fraction and velocity profile are strongly influenced by the details of the gas expulsion. Although star clusters can survive SFEs as low as 10 per cent if the tidal field is weak and the gas is removed only slowly, our simulations indicate that most star clusters are destroyed or suffer dramatic loss of stars during the gas removal phase. Surviving clusters have typically expanded by a factor of 3 or 4 due to gas removal, implying that star clusters formed more concentrated than as we see them today. Maximum expansion factors seen in our runs are around 10. If gas is removed on time-scales smaller than the initial crossing time, star clusters acquire strongly radially anisotropic velocity dispersions outside their half-mass radii. Observed velocity profiles of star clusters can therefore be used as a constraint on the physics of cluster formation. [source] Not All Injury-induced Muscle Proteolysis Is Due to Increased Activity of the Ubiquitin/Proteasome System: Evidence for Up-Regulation of Macrophage-associated Lysosomal Proteolysis in a Model of Local TraumaNUTRITION REVIEWS, Issue 1 2003Article first published online: 16 SEP 200 A characteristic response to injury is a dramatic loss of skeletal muscle protein owing to increased muscle protein breakdown. Over the past decade, numerous studies have indicated that up-regulaton of the ubiquitin-proteasome system is a common mechanism underlying such injury-induced muscle proteolysis. However, a recent study using a single-impact trauma to the gastrocnemius muscle found that, although the rate of muscle proteolysis was dramatically increased, the ubiquitin-proteasome system was not involved. Rather, an increase in lysosomal activity, through infiltration of the damaged tissue by mononuclear macrophages, is responsible for the high rates of protein breakdown. [source] Photoinactivation of Sindbis Virus Infectivity Without Inhibition of Membrane FusionPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2009Wor Thongthai Photoinactivation of enveloped viruses is commonly associated with damage to fusion proteins and inhibition of membrane fusion capacity. Here we show that photobleaching of Sindbis virus labeled with the membrane localized dye, R18 (octadecyl rhodamine B) causes a dramatic loss of infectivity without observable changes in low-pH triggered membrane fusion to liposomes. Sindbis labeled with DiI (1,1,-dioctadecyl-3,3,3,,3,-tetramethylindocarbocyanine perchlorate) also maintains low-pH triggered membrane fusion capacity, but in contrast to R18, extensive photobleaching of DiI-labeled virus has little effect on infectivity. Electrophoretic gel analysis suggests no cross-linking of viral fusion proteins following photobleaching of dye-labeled Sindbis. These observations have implications for live-cell, single particle tracking studies of dye-labeled Sindbis virus. Our observations suggest that R18 and DiI have different propensities for spontaneous flip-flop in lipid bilayers. [source] A Question of GuiltRATIO JURIS, Issue 3 2006JENS MEIERHENRICH The focus is on the relationship between collective violence and collective memory in countries that have experienced cultural trauma, defined as a dramatic loss of identity and meaning, a tear in the social fabric. Analyzing the dynamics,the mechanisms and processes,of remembering and forgetting such trauma, I argue that the idea of collective guilt is essential for making sense of collective violence and collective memory. Specifically, I show that collective violence requires collective action; that collective action produces collective guilt; that collective violence generates perceptions,and misperceptions,of collective guilt; and that collective memory is formed, deformed, and transformed by perceptions,and misperceptions,of collective guilt. The article uses illustrative data from a variety of cases to illuminate these dynamics. It concludes by explaining why understanding these dynamics is imperative for responding to historic injustice in the twenty-first century. Flash-backs falsify the Past: they forget the remembering Present. (Auden 1976, 841) [source] The accumulation of intracellular ITEGE and DIPEN neoepitopes in bovine articular chondrocytes is mediated by CD44 internalization of hyaluronanARTHRITIS & RHEUMATISM, Issue 2 2006Jennifer J. Embry Flory Objective A dramatic loss of aggrecan proteoglycan from cartilage is associated with osteoarthritis. The fate of residual G1 domains of aggrecan is unknown, but inefficient turnover of these domains may impede subsequent repair and retention of newly synthesized aggrecan. Thus, the objective of this study was to determine whether ITEGE- and DIPEN-containing G1 domains, generated in situ, are internalized by articular chondrocytes, and whether these events are dependent on hyaluronan (HA) and its receptor, CD44. Methods ITEGE and DIPEN neoepitopes were detected by immunofluorescence staining of bovine articular cartilage chondrocytes treated with or without interleukin-1, (IL-1,). Additionally, purified ITEGE- or DIPEN-containing G1 domains were aggregated with HA and then added to articular chondrocytes, articular chondrocytes transfected with CD44,67, or COS-7 cells transfected with or without full-length CD44. Internalized epitopes were distinguished by their resistance to extensive trypsinization of the cell surface. Results Both ITEGE and DIPEN were visualized within the extracellular cell-associated matrix of chondrocytes as well as within intracellular vesicles. Following trypsinization, the intracellular accumulation of both epitopes was clearly visible. IL-1 treatment increased extracellular as well as intracellular ITEGE epitope accumulation. Once internalized, the ITEGE neoepitope became localized within the nucleus and displayed little colocalization with HA, DIPEN, or other G1 domain epitopes. The internalization of both ITEGE and DIPEN G1 domains was dependent on the presence of HA and CD44. Conclusion One important mechanism for the elimination of residual G1 domains following extracellular degradation of aggrecan is CD44-mediated co-internalization with HA. [source] Critical catalytic functional groups in the mechanism of aspartate-,-semialdehyde dehydrogenaseACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2004Julio Blanco Aspartate-,-semialdehyde dehydrogenase (ASADH) catalyzes the reductive dephosphorylation of ,-aspartyl phosphate to l -aspartate-,-semialdehyde in the aspartate biosynthetic pathway. This pathway is not found in humans or other eukaryotic organisms, yet is required for the production of threonine, isoleucine, methionine and lysine in most microorganisms. The mechanism of this enzyme has been examined through the structures of two active-site mutants of ASADH from Haemophilus influenzae. Replacement of the enzyme active-site cysteine with serine (C136S) leads to a dramatic loss of catalytic activity caused by the expected decrease in nucleophilicity, but also by a change in the orientation of the serine hydroxyl group relative to the cysteine thiolate. In contrast, in the H277N active-site mutant the introduced amide is oriented in virtually the same position as that of the histidine imidazole ring. However, a shift in the position of the bound reaction intermediate to accommodate this shorter asparagine side chain, coupled with the inability of this introduced amide to serve as a proton acceptor, results in a 100-fold decrease in the catalytic efficiency of H277N relative to the native enzyme. These mutant enzymes have the same overall fold and high structural identity to native ASADH. However, small perturbations in the positioning of essential catalytic groups or reactive intermediates have dramatic effects on catalytic efficiency. [source] Water-soluble vitamins in fish ontogenyAQUACULTURE RESEARCH, Issue 5 2010Rune Waagbø Abstract Studies on vitamin requirement at early stages are difficult and vary in quality, both due to the scientific approach and vitamin analysis. Focus has been on water-soluble vitamins that cause dramatic losses of the offspring in practical farming situations or in wild life, like vitamin C and thiamine deficiencies respectively. Practical solutions including vitamin administration through brood stock and larvae diets have confirmed and corrected the vitamin deficiencies. For the other water-soluble vitamins, the situation is not so obvious. Descriptive studies of folate and vitamin B6 during fish ontogeny have shown a net loss of vitamin during endogenous feeding and a steady transfer of vitamin from the yolk sac into the body compartment, and finally, dramatic increases in body vitamin levels after the start of feeding. The kinetics of mass transfer with ontogeny appears, however, to differ between vitamins. Start of feeding of fish larvae with live or formulated feeds includes several challenges with respect to water-soluble vitamins, including aspects of live feed enrichment and stability, micro-diet leaching, variable feed intakes, immature gastrointestinal tract, variable bioavailability of vitamins and larvae vitamin storage capacity. Consequently, the exact minimum requirements are difficult to estimate and vitamin recommendations need to consider such conditions. [source] Auswirkungen der Matrixzusammensetzung auf die Dauerhaftigkeit von Betonen mit textilen Bewehrungen aus AR-GlasBETON- UND STAHLBETONBAU, Issue 8 2009Marko Butler Dipl.-Ing. Baustoffe; Bewehrung; Versuche Abstract Verbundmaterialien aus Feinbetonen mit textiler Bewehrung aus alkaliresistentem Glas (AR-Glas) können ausgeprägten zeitabhängigen Veränderungen hinsichtlich des mechanischen Leistungsvermögens unterliegen. Für eine zielsichere Anwendung solcher Werkstoffe im Bauwesen sind genaue Kenntnisse über die Höhe und die Ursachen dieser Leistungsverluste unabdingbar. In diesem Artikel werden anhand von Ergebnissen aktueller Untersuchungen entscheidende Mechanismen für die Alterungsprozesse dargestellt, die aus der Zusammensetzung der Feinbetone resultieren. Dazu wurden aus verschiedenen Betonzusammensetzungen, die sich maßgeblich in ihrer Hydratationskinetik und Alkalität unterschieden, textilbewehrte Dehnkörper hergestellt und nach beschleunigter Alterung geprüft. Dehnkörper aus Feinbeton mit hoher Alkalität (das Bindemittel bestand nur aus CEM I) zeigten dramatische Einbußen bei Zugfestigkeit und Bruchdehnung. Das Leistungsvermögen von Proben aus Feinbetonen mit puzzolanisch abgepufferter Bindemittelzusammensetzung und gleichzeitig reduziertem Portlandzementklinkeranteil zeigte sich dagegen weitgehend unbeeinflusst von Alterungsprozessen. Mit Hilfe von beidseitigen Garnauszugversuchen an beschleunigt gealterten Feinbetonproben wurden die für das unterschiedliche Materialverhalten verantwortlichen Degradationsmechanismen aufgeklärt. Neben der mechanischen Prüfung wurde dazu auch die Interphase zwischen Fasern und umgebendem Feinbeton mit bildgebenden und analytischen Verfahren charakterisiert. Die festgestellten Einbußen im Leistungsvermögen des Garn-Matrix-Verbundes konnten überwiegend auf die Neubildung von ungünstig strukturierten Hydratationsprodukten in der Interphase Filament-Matrix bzw. in Filamentzwischenräumen zurückgeführt werden. Die Morphologie dieser Phase wird maßgeblich von der Bindemittelzusammensetzung bestimmt. Korrosion des AR-Glases als Schadensursache kann unter ungünstigen Umständen auch eine große Rolle spielen, ist aber bei geeigneter Matrixformulierung von untergeordneter Bedeutung. Effect of Matrix Composition on the Durability of Concretes Reinforced with Glass Fibre Fabric The mechanical performance of composites made of finegrained concrete and textile reinforcement can worsen markedly with increasing age if alkali-resistant glass (AR-glass) is used as the reinforcing material. For reliable practical applications of textile-reinforced concrete, precise knowledge as to the extent and causes of such degradation is indispensable. This paper discusses important aging mechanisms resulting from the composition of fine-grained concrete. Tensile tests on composites made of different concrete compositions distinguished from one another by their hydration kinetics and alkalinity were performed before and after accelerated aging. Composites made of concrete with high alkalinity showed dramatic losses of tensile strength and strain capacity. In contrast the mechanical performance of composites whose binders had reduced Portland cement clinker content plus added puzzolana was hardly affected by the accelerated aging. To clarify the mechanisms of degradation, yarn pullout tests were performed on specimens of equal matrix composition and age. Additionally, the morphology of the interphase between matrix and fibre was characterised using direct microscopic examination and analytical methods. The new formation of unfavourably structured products of hydration in the filament-matrix interphase and/or in the empty spaces between filaments was found to be the main reason for the performance losses observed. The morphology of these hydration products is determined to a great extent by the binder composition. Under unfavourable conditions corrosion of AR-glass can occur as well and lead to distinct composite damage. However, if the formulation of the binder is proper, bulk glass corrosion is of minor importance. 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