When exposed to either abiotic or biotic stressors, plants release chemical compounds that can serve as defense mechanisms. For example, plants of the mustard and cabbage family produce a class of anti-herbivory compounds called glucosinolates. In the model mustard plant Arabidopsis thaliana, some glucosinolates are produced from the amino acid tryptophan and are called indole glucosinolates (IGs). Expression of IG synthesis genes is positively regulated by the partially redundant transcription factors, MYB34 and MYB51. Recent studies have shown that these two transcription factors have distinct roles in regulating IG production in different tissues and in mediating responses to different environmental cues. To understand the distinct roles of these transcription factors at a more detailed temporal and spatial level, reporters for CYP79B2, a transcriptional target of both MYB34 and MYB51, were used. CYP79B2-GFP and CYP79B2-GUS reporter expression was analyzed in wild-type and MYB34 and MYB51 mutant plants in response to increased ambient temperature, increased light intensity, ATP exposure, and chitin exposure. Reverse-phase HPLC quantification of IGs was also performed to determine how these transcription factors are mediating the synthesis of IGs in response stressors. Overall, it was found that MYB51 is responsible for the temperature induction of IG production, while increased light intensity has no impact on IG synthesis. Furthermore, ATP appears to induce IG production independently of both MYB34 and MYB51, while chitin does not increase IG synthesis. Taken together, these studies allow us to better understand how plants respond to and defend themselves from different abiotic and biotic stress / 2025-02-26T00:00:00Z

Mesotrione is under evaluation for registration in turfgrass for weed control, but often requires repeat treatments. Previous research in agricultural crops indicates tank mixtures with mesotrione may improve weed control. Three field trials were conducted in 2005 and 2006 in Blacksburg, VA on smooth crabgrass in perennial ryegrass and tall fescue. Data indicate mesotrione applied in combination with bentazon, bromoxynil, or carfentrazone, controlled smooth crabgrass better than any of these herbicides applied alone at all sites. Adding mesotrione to MSMA and quinclorac improved smooth crabgrass on of three sites. Sequential mesotrione applications improved long term weed control. / Master of Science

Relationships between macroinvertebrate assemblages and environmental stressors were assessed from fall 2002 through spring 2004 in five small streams that represented a study design that involved a gradient of increasing stress (increased cattle density). Macroinvertebrate assemblages were related to environmental factors that were quantified at the sample scale. Environmental factors and macroinvertebrates were concurrently collected so that assemblage structure could be directly related to environmental variables and so that the relative importance of stressors associated with cattle grazing in structuring assemblages could be assessed. Macroinvertebrate metrics showed significant and strong responses to cattle density during most sampling periods. The majority of metrics responded negatively to the grazing gradient, while a few (total taxa richness, number of sensitive taxa, and % collector filterers) increased along the gradient before declining at the most heavily grazed sites. Total number of sensitive taxa and % Coleoptera had the strongest relationship with cattle density throughout the study period. Based on sample-scale, quantitative measures of environmental variables, measures of physical habitat (% fines and substrate homogeneity) were most important in structuring assemblages. Detrital food variables (coarse benthic and fine benthic organic matter) were secondarily important while autochthonous food variables (chlorophyll a and epilithic biomass) were not as important in influencing assemblage structure. Based on a comparative analysis of reach-scale habitat measures and estimates, quantitative measures of % fines, collected from within an enclosed sampler concurrently with macroinvertebrates, were the best predictor of macroinvertebrate assemblages. Quantitative measures and visual estimates of riparian and channel characteristics had strong relationships with macroinvertebrate metrics but the relationships were never as strong as those detected with instream measurements of % fines. The channel characteristic, bank height, was the best predictor of % fines. / Ph. D.

É comum, em problemas de inferência bayesiana, deparar-se com uma distribuição a priori para o parâmetro de interesse, theta, que seja intratável analítica ou computacionalmente. Como a priori é uma escolha do pesquisador, tal situação ocorre por conta da intratabilidade da função de verossimilhança. Por meio de algoritmos ABC, é possível simular-se uma amostra da distribuição a posteriori, sem a utilização da verossimilhança. Neste trabalho, aplica-se o ABC no contexto de Environmental Stress Screening - ESS. ESS é um procedimento de estresse, em um processo de produção industrial, que visa evitar que peças de qualidade inferior sejam utilizadas no produto final. A partir de uma abordagem bayesiana do ESS, depara-se com uma verossimilhança (e, consequentemente, uma posteriori) intratável para o vetor de parâmetros de interesse. Utiliza-se, então, o ABC para obtenção de uma amostra da posteriori e calcula-se o tempo ótimo de duração de um futuro procedimento de estresse a partir da simulação feita. É também proposta uma generalização do problema de ESS para a situação em que existem k tipos de peças no processo de produção. Quantifica-se o problema e, novamente, aplica-se um algoritmo ABC para a obtenção de uma simulação da posteriori, bem como calcula-se o tempo ótimo de duração de um futuro teste de estresse. / In Bayesian inference problems, it is common to obtain a posterior distribution for the parameter of interest, theta, which is analytically or computationally intractable. Since the priori is chosen by the researcher, this situation arises from the intractability of the likelihood function. Through ABC algorithms it is possible to simulate a sample from the posterior distribution, without the analytical use of the likelihood function. In this work ABC is applied in the context of Environmental Stress Screening - ESS. ESS is a stress procedure, in an industrial production process, which aims to avoid low quality parts to be used in the final product. Under a Bayesian approach to ESS, an intractable likelihood (consequently, a posterior) is obtained for the paramater of interest. ABC is used to simulate a sample from the posterior and the optimal duration for a next stress procedure is calculated afterwards. A generalization of the ESS is also proposed considering that there are k types of parts in the production process. Again, ABC is used to simulate a sample from the posterior, and it is calculated the optimal duration for a next stress procedure.

É comum, em problemas de inferência bayesiana, deparar-se com uma distribuição a priori para o parâmetro de interesse, theta, que seja intratável analítica ou computacionalmente. Como a priori é uma escolha do pesquisador, tal situação ocorre por conta da intratabilidade da função de verossimilhança. Por meio de algoritmos ABC, é possível simular-se uma amostra da distribuição a posteriori, sem a utilização da verossimilhança. Neste trabalho, aplica-se o ABC no contexto de Environmental Stress Screening - ESS. ESS é um procedimento de estresse, em um processo de produção industrial, que visa evitar que peças de qualidade inferior sejam utilizadas no produto final. A partir de uma abordagem bayesiana do ESS, depara-se com uma verossimilhança (e, consequentemente, uma posteriori) intratável para o vetor de parâmetros de interesse. Utiliza-se, então, o ABC para obtenção de uma amostra da posteriori e calcula-se o tempo ótimo de duração de um futuro procedimento de estresse a partir da simulação feita. É também proposta uma generalização do problema de ESS para a situação em que existem k tipos de peças no processo de produção. Quantifica-se o problema e, novamente, aplica-se um algoritmo ABC para a obtenção de uma simulação da posteriori, bem como calcula-se o tempo ótimo de duração de um futuro teste de estresse. / In Bayesian inference problems, it is common to obtain a posterior distribution for the parameter of interest, theta, which is analytically or computationally intractable. Since the priori is chosen by the researcher, this situation arises from the intractability of the likelihood function. Through ABC algorithms it is possible to simulate a sample from the posterior distribution, without the analytical use of the likelihood function. In this work ABC is applied in the context of Environmental Stress Screening - ESS. ESS is a stress procedure, in an industrial production process, which aims to avoid low quality parts to be used in the final product. Under a Bayesian approach to ESS, an intractable likelihood (consequently, a posterior) is obtained for the paramater of interest. ABC is used to simulate a sample from the posterior and the optimal duration for a next stress procedure is calculated afterwards. A generalization of the ESS is also proposed considering that there are k types of parts in the production process. Again, ABC is used to simulate a sample from the posterior, and it is calculated the optimal duration for a next stress procedure.

Alterations in energy metabolism due to factors including cellular stress from the hostile tumour micro-environment are a emerging cancer hallmark. Distinct hypoxic and quiescent cell populations develop, which are resistant to chemotherapy due to lack of proliferation, drug inactivity in the altered redox status of the cell and enhanced drug biotransformation. The present study characterises the metabolic strategies employed by these distinct populations of cancer cells. The in vitro 3-dimensional tumour spheroid model, which reflects tumour architecture and behaviour, cultured under different micro-environmental conditions was utilized in this study. Metabolic enzyme activity and expression, overall metabolic flux rates for nutrients, metabolomics profiles of specific pathways and tissue status were assessed. Metabolic adaptations consistent with the Warburg effect were observed in fully oxygenated, proliferative tumour spheroids, with glucose being metabolised to produce lactate. Additionally, metabolomics investigations determined glucose was metabolised by the pentose phosphate pathway, demonstrated by high enrichment of glucose-derived carbon in 6-phophogluconate. The extraction of 39.7 ± 7.6 μ moles (mg protein) ^-1 glutamine from the medium over 24 hours was observed in these spheroids, consistent with glutaminolysis pathway activity. A 2-fold higher rate of glycolytic flux (measured by production of 3h2O from 5-³H-glucose) was measured in hypoxic tumour spheroids, despite reduced levels of glycolytic enzymes being determined. Surprisingly, although lower rates of glycolysis (2.6-fold) were measured in quiescent spheroids, increased glycolytic enzyme activities (HK 1.9 fold, PK 2 fold and LDH 1.8 fold), glucose (1.9 fold over 24 hours) and glutamine uptake (5.5 fold over 12 hours) as well as lactate production (1.8 fold) were measured, relative to their proliferating counterparts. This study demonstrates that metabolic strategies employed by tumour spheroids differ upon exposure to distinct micro-environmental stresses, additionally identifying hexokinase as a potential therapeutic target for the inhibition of glycolysis under all micro-environmental stress conditions analysed.

The use of biomarkers is considered a promising alternative, or complement, to traditional ecotoxicological assays. Toxic effects are often initially manifested at the molecular or biochemical level, biomarkers are therefore used as sensitive indicators of toxic exposure. Ideally, biomarkers would also indicate reduced fitness and possible later effects at the individual or population levels. However, implementing biomarkers in ecotoxicology is challenging and few biomarkers have an established connection to reduced individual fitness. The aim of this thesis was to increase the value and improve the interpretation of biomarker responses in ecotoxicological studies by examining the impact of confounding factors and the relationship between oxidative biomarkers and reproductive effects in crustaceans. The sensitivity of biomarkers was confirmed in paper I as toxic effects of pharmaceuticals with conserved drug target orthologs were observed at the molecular and biochemical levels both earlier and at lower concentrations than effects on mortality and reproduction. No toxic effects were observed for the pharmaceutical without identified drug target orthologs, thus stressing the importance of considering toxic mechanisms and being aware of the most likely target when evaluating toxic effects also in non-target species. Many xenobiotics and environmental stressors interfere with oxidative processes, making oxidative biomarkers interesting to study in ecotoxicology and stress ecology. Still, feeding rate was identified as a confounding factor for antioxidant capacity (assayed as oxygen radical absorbance capacity, ORAC) and lipid peroxidation in ecotoxicological studies (paper II). However, ORAC normalized to protein was independent of altered feeding rates, hence it can be applied as a suitable exposure biomarker without considering alterations and effects of feeding rate. The connection between reproduction and oxidative stress is dual, as reproduction both can be inhibited by oxidative stress and induce pro-oxidative processes. Further, a positive association was found between ORAC and the occurrence of embryo aberrations in the benthic amphipod Monoporeia affinis (paper III). An association between antioxidant defense and reproduction was also observed for Daphnia magna (paper IV). Threshold values for identification of exposed individuals and prediction of possible later reproductive effects were established for ORAC. This thesis has contributed to diminishing some of the knowledge gaps limiting the use of oxidative biomarkers in ecotoxicology, by contributing to increased understanding of how oxidative biomarkers relate to important life-traits. Moreover, ORAC has been identified as a suitable biomarker of not only exposure, but also reproductive effects. Future research should continue to establish connections between biomarker responses and effects at higher levels, and focus on providing defined threshold values to enable predictions about later effects. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>

A model for optimizing the differential cost between a preventive maintenance program and a traditional run-to-failure program on managing assets under uncertainty is developed to assist electric power utilities in decision-making. The assets studied, though not necessarily critical to power delivery, are so numerous in number that the failures of thousands of them result in millions of dollars in instantaneous replacement cost to the utility. The ages of some of the assets are approaching an excess of one hundred years, the age of commercial electricity in the United States. The developed model includes the economics of inspections and replacements as random variables, where the cost of corrective replacements could significantly exceed the cost of planned or preventive replacements. The model also relies on uncertainties in annual failures and inaccuracy of diagnostics that drive planned replacements. Age-specific fragilities of the assets under environmental stress are assessed, and the likelihood of failures of the assets was found to increase significantly as they approached one hundred years, past some initial age of failures that are comparable to new assets. This finding led to the development of an improved geographical inspection scheme, where only components past that initial age are recommended for diagnostic evaluation. The optimization results suggest that the present net benefit/cost of preventive replacement programs of the electric power utility to the unpopular run-to-failure program can be improved on. This, by using the developed models and adopting the frameworks presented in the research work. Implications for future research are also discussed.

Οι ανησυχητικές διαστάσεις που έχει λάβει τα τελευταία χρόνια η περιβαλλοντική ρύπανση και ιδιαίτερα η ρύπανση του θαλάσσιου περιβάλλοντος, καθιστούν επιτακτική την ανάγκη εύρεσης και εγκαθίδρυσης νέων βιοδεικτών που μπορούν να συμβάλουν δραστικά στην έγκαιρη αναγνώριση της κατάστασης της υγείας του θαλάσσιου οικοσυστήματος και συνεπώς στη λήψη βελτιωτικών μέτρων για την αποκατάστασή του. Κυρίαρχο ρόλο ανάμεσα στους θαλάσσιους ρύπους κατέχουν τα βαρέα μέταλλα, τα οποία λόγω της ικανότητάς τους να επάγουν ή να προκαλούν οξειδωτικό στρες μπορούν να προκαλέσουν σημαντικές, ακόμη και θανατογόνες βλάβες στους θαλάσσιους οργανισμούς. Η έκθεση σε μέταλλα προκαλεί την απορρύθμιση πολλών κυτταρικών διαδικασιών και κυρίως αυτών που διεξάγονται από μακρομοριακά σύμπλοκα, όπως η μεταφραστική μηχανή, τα οποία είναι ιδιαίτερα ευαίσθητα σε συνθήκες stress. Οι αλλαγές που προκαλούνται από το κυτταρικό stress στη διαδικασία της μετάφρασης καλύπτουν ένα ευρύ φάσμα αποκρίσεων, που μπορεί να περιλαμβάνει μείωση της ολικής μετάφρασης ή αύξηση της μετάφρασης ειδικών mRNAs. Ένας αποτελεσματικός τρόπος εκτίμησης των μεταφραστικών αποκρίσεων ενός οργανισμού στο περιβαλλοντικό stress είναι ο προσδιορισμός του μεταφραστικά ενεργού ριβοσωματικού κλάσματος των πολυσωμάτων. Επίσης, καθώς ρυθμιστικά γεγονότα μπορεί να συμβούν σε οποιοδήποτε βήμα της μετάφρασης, έγινε μία σειρά πειραμάτων, που αφορούν στον έλεγχο της μεταφραστικής λειτουργίας του μυδιού Mytilus galloprovincialis, οργανισμού που χρησιμοποιείται συχνά ως βιομάρτυρας, σε εργαστηριακές συνθήκες, υπό την επίδραση τριών μετάλλων, του υδραργύρου, του χαλκού και του καδμίου. Για την εκτίμηση της κατάστασης της υγείας των εκτεθειμένων μυδιών έγινε προσδιορισμός ορισμένων κλασικών, ευρέως χρησιμοποιούμενων βιοδεικτών, καθώς και βιοδεικτών οξειδωτικού στρες. Ο έλεγχος των μεταφραστικών αποκρίσεων των εκτεθειμένων μυδιών περιλάμβανε εκτίμηση του ποσοστού πολυσωμάτων και προσδιορισμό της επίδρασης των μετάλλων τόσο στο προπαρασκευαστικό στάδιο της μετάφρασης, δηλαδή την αμινοακυλίωση των υποστρωμάτων, όσο και στα τρία κύρια στάδια της μετάφρασης, δηλαδή την έναρξη, την επιμήκυνση και τον τερματισμό. Τα δεδομένα της μελέτης αυτής αποκαλύπτουν ότι τόσο ο υδράργυρος, όσο και ο χαλκός προκαλούν το ίδιο πρότυπο αλλαγών στη μεταφραστική λειτουργία των εκτεθειμένων μυδιών, οδηγώντας σε απορρύθμιση όλων των σταδίων και των ενδιάμεσων βημάτων της πρωτεϊνοσύνθεσης. Οι διαταραχές αυτές οφείλονται στο οξειδωτικό στρες που προκαλείται από τα μέταλλα αυτά και στην παράλληλη αδυναμία του συστήματος αντιοξειδωτικής άμυνας των κυττάρων να το αντιμετωπίσει. Η στατιστική επεξεργασία των αποτελεσμάτων επιβεβαιώνει την αρνητική επίδραση του οξειδωτικού στρες που προκαλείται από τα μέταλλα στη μετάφραση, με μία στατιστικά σημαντική συσχέτιση το ποσοστού πολυσωμάτων με τους βιοδείκτες οξειδωτικού στρες. Από την άλλη, τα αποτελέσματα της έκθεσης των μυδιών στο κάδμιο διαφοροποιούνται σημαντικά. Αρχικά, η έκθεση των μυδιών στο μέταλλο αυτό προκαλεί μία έντονη διαταραχή στην πρωτεϊνοσυνθετική διαδικασία, οφειλόμενη στην πρόκληση οξειδωτικού στρες. Με την πάροδο όμως το χρόνου, τα κύτταρα καταφέρνουν να διεγείρουν τους αντιοξειδωτικούς μηχανισμούς, που σε αυτή την περίπτωση αντιπροσωπεύονται κυρίως από τις μεταλλοθειονίνες, με αποτέλεσμα να καταφέρνουν να ανταπεξέλθουν στη δύσκολες συνθήκες και να αναχαιτίσουν την αρνητική επίδραση του καδμίου, γεγονός που οδηγεί σε ανάκαμψη της μεταφραστικής ικανότητας των μυδιών αυτών, στο τέλος της περιόδου έκθεσης. Το διφασικό προφίλ της επίδρασης του καδμίου αντανακλάται στην έλειψη συσχέτισης μεταξύ του ποσοστού πολυσωμάτων των εκτεθειμένων στο κάδμιο μυδιών και των βιοδεικτών οξειδωτικού στρες αλλά και των λοιπών βιοδεικτών. / The alarming levels of the environmental and especially the marine pollution in recent years constitute an urgent need of finding and establishing new biomarkers which may contribute to the early detection of the health status of the marine ecosystem leading to ameliorating measures towards its restoration. Heavy metals, which are capable of causing severe or even leathal defects to marine organisms, through their ability to induce or produce oxidative stress, posess a leading role among the marine pollutants. Exporure to heavy metals may cause the deregulation of many cellular processeses, mainly of those that are carried out by macromolecular complexes, such as the translational machinery, which are particularly sensitive to stress conditions. The alterations induced by the cellular stress in the translation may cover a broad range of responses, including a decline of the global translation or an increase of the translation of certain mRNAs. An effective way to reveal translational responses of an organism to environmetal stress is the evaluation of the translationally active ribosomal fraction of polysomes. Moreover, considering the fact that regulatory events may occur at any step of the translational process, a set of experiments was carried out, concerning the examination of the translational function of the mussel Mytilus galloprovindialis, which is commonly used as a bioindicator, in laboratory conditions, under the influence of three metals, mercury, copper and cadmium. In order to evaluate the health condition of the exposed mussels, a battery of standard biomarkers was applied, including biomarkers of oxidative stress. The determination of the translational responses of the treated mussels included measurement of the polysome content and assessment of the metal effect on the preparative stage of protein synthesis, the aminacylation of the substrates, as well as on the three main stages of translation, that is the initiation, the elongation and the termination. The data of the study reveal that mercury as well as copper cause the same patern of alterations in the translational function of the exposed mussels, leading to a deregulation of every stage and intermediate step of protein synthesis. These perturbations are a consequence of the metal induced oxidative stress, followed by a failure of the antioxidant defense system to confront it. Statistical analysis of the results confirms the negative effect of the metals on the translation, with a statistically important correlation of the polysome content with the oxidative stress biomarkers. On the other hand, the results of the cadmium exposed mussels follow a different pattern. First, the exposure of mussels to the metal causes a severe perturbation of the translational process, due to the oxidative stress induction. Finally, cells stimulate antioxidant mechanisms, in this case represented by metallotheioneins, managing to cope with the difficult conditions and to block the negative effect of cadmium, which leads to a restoration of the translational capacity of the mussels, at the end of the exposure period.The two-phase profile of the cadmium effect is reflected on the absence of statistical correlation between the polysomal content and biomarkers of oxidative stress, as well as other biomarkers.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20422号 / 農博第2207号 / 新制||農||1047(附属図書館) / 学位論文||H29||N5043(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 天野 洋, 教授 田中 千尋, 准教授 刑部 正博 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM