3,557 research outputs found
Production, Functional Characterization and Inhibition of Carbonic Anhydrases of Parasites
Hiilihappoanhydraasit (carbonic anhydrase, CA) ovat metalloentsyymejä, joita esiintyy kaikkialla elollisessa luonnossa. Niiden tehtävä on katalysoida elintärkeää käänteistä reaktiota: hiilidioksidin hydraatiota hiilihapoksi (CO2 + H2O ⇋ H2CO3 ⇋ HCO3- + H+). Reaktio on osana monissa fysiologisissa ja metabolisissa prosesseissa, kuten happo-emästasapainon säätelyssä, glukoneogeneesissa ja yhteyttämisessä. Hiilihappoanhydraasit jaetaan yhteensä kahdeksaan perheeseen, joista ihmisillä esiintyy vain ensimmäisenä löydettyä α-entsyymiperhettä. Monilla taudinaiheuttajilla, kuten bakteereilla ja loisilla, on myös muiden hiilihappoanhydraasiperheiden proteiineja.
Schistosoma mansoni on suolistotulehdusta aiheuttava halkiomato, jota esiintyy endeemisenä monilla trooppisilla ja subtrooppisilla seuduilla. Entamoeba histolytica ja Acanthamoeba castellanii ovat ihmisille infektioita aiheuttavia ameboja. E. histolytica aiheuttaa suolistotulehdusta ja A. castellanii pääasiassa sarveiskalvon tulehdusta, sekä immuunipuutteisille henkilöille myös syviä infektioita. Yhteistä näille loisille on, että niiden diagnostiikassa tai hoidossa on puutteita, ja ne ovat globaalisti erittäin yleisiä. Niiden aiheuttamat sairaudet voivat olla tappavia, ja aiheuttavat lievimmilläänkin merkittävää elämänlaadullista haittaa. Väitöskirjatutkimukseni tavoitteena on löytää nopeampi menetelmä tunnistaa A. castellanii biologisesta näytteestä sekä löytää uusia potentiaalisia lääkeainemolekyylejä näiden kolmen loisen aiheuttamien sairauksien tehokkaammaksi hoitamiseksi.
Väitöstutkimuksessani tuotin E. histolytican ja S. mansonin β-hiilihappoanhydraasit Escherichia coli -bakteereissa. Tutkimme hiilihappoanhydraasien inhibiittorien vaikutusta tuotettuihin entsyymeihin, ja löysimme useita lupaavia inhibiittoreita. Lisäksi kehitimme uuden nopean diagnostisen menetelmän A. castellaniin havaitsemiseksi näytteestä, sillä nykyinen ameban viljelyyn perustuva menetelmä on kliiniseen diagnostiikkaan liian hidas. Nykyiset A. castellaniin aiheuttamien infektioiden hoitoon käytetyt lääkkeet ovat vain kohtalaisen tehokkaita ja niihin liittyy useita haittavaikutuksia, joten kehitimme uuden menetelmän uusien lääkeaineiden etsimistä varten ja testasimme useita, jo kliinisessä käytössä olevia hiilihappoanhydraasin estäjiä menetelmällämme.
Havaitsimme, että dorsolamidi ja asetatsoliamidi ovat lupaavia uusia vaihtoehtoja akantamebakeratiitin hoitamiseksi. Niiden etuna on pitkään jatkunut käyttö ihmispotilaiden muiden sairauksien hoidossa, joten niiden haitta- ja sivuvaikutukset ovat tunnettuja. Valitettavasti asetatsoliamidi on vain kohtalaisen tehokas inhiboimaan E. histolytican ja S. mansonin β-hiilihappoanhydraaseja. Dorsolamidi on tehokas inbiittori S. mansonin β-hiilihappoanhydraasia vastaan, toisin kuin E. histolytican β-hiilihappoanhydraasia se inhiboi huonosti. Onneksi moni muu inhibiittori on tehokas estämään niiden molempien toimintaa.
Tämä väitöskirja lisää tietoa ja mahdollisuuksia hyödyntää hiilihappoanhydraaseja loisinfektioiden diagnostiikassa ja hoidossa.Carbonic anhydrases (CAs, EC 4.2.1.1) are metalloenzymes that can be found in almost all living organisms. They catalyze a vital chemical reaction: the reversible hydration of carbon dioxide (CO2 + H2O ⇋ H2CO3 ⇋ HCO3− + H+). It is part of multiple physiological and metabolic processes, such as p regulation, gluconeogenesis and photosynthesis. CAs are divided into eight families, from which the human genome only involves α-CAs. Many pathogens, such as bacteria and parasites, also have CA enzymes from other families.
Schistosoma mansoni is a parasitic blood fluke that causes intestinal infection in many tropical and subtropical areas. Entamoeba histolytica and Acanthamoeba castellanii are amoebae that cause different infections in humans. E. histolytica causes intestinal infection, and A. castellanii mainly infects the cornea but also causes invasive infections in immunocompromised people. The infections of these parasites are common globally, and unfortunately, the diagnosis and treatment are often delayed. The infections can be lethal, and at their mildest, they cause a significant reduction in the quality of life. My study aims to find a faster and more effective way to detect A. castellanii from a biological sample and discover new potential drug candidates to treat these parasitic infections.
In my thesis, I produced the β-CAs of E. histolytica and S. mansoni using Escherichia coli as a protein production organism. We studied the inhibitory effects of many known CA inhibitors and identified several promising candidates or potential leads for further development. In addition, we developed a novel rapid diagnostic method to detect A. castellanii from a biological sample. The novel method could replace the current gold standard, sample culture, which is slow in clinical diagnostics. We established a new method to investigate potential drug candidates for treating A. castellanii, as the current treatment options are only moderately effective and have many adverse side effects. By this method, we tested several clinically used CA inhibitors with interesting outcomes.
Dorzolamide and acetazolamide were found to be new promising options for
treating Acanthamoeba keratitis. The advantage of these drugs is also the long use history with human patients in treating other conditions, which has made the side effects and risks very familiar to medical staff. Unfortunately, acetazolamide was only moderately effective against the β-CAs of S. mansoni and E. histolytica, as was dorzolamide against the β-CA of E. histolytica. In contrast, dorzolamide was an effective inhibitor against the β-CA of S. mansoni. We also found many other effective inhibitors against the β-CAs of E. histolytica and S. mansoni.
This thesis increases the knowledge and options to use the CAs of parasites to diagnose and treat infections caused by parasites
Recommended from our members
Synaptic plasticity and memory addressing in biological and artificial neural networks
Biological brains are composed of neurons, interconnected by synapses to create large complex networks. Learning and memory occur, in large part, due to synaptic plasticity -- modifications in the efficacy of information transmission through these synaptic connections. Artificial neural networks model these with neural "units" which communicate through synaptic weights. Models of learning and memory propose synaptic plasticity rules that describe and predict the weight modifications. An equally important but under-evaluated question is the selection of \textit{which} synapses should be updated in response to a memory event. In this work, we attempt to separate the questions of synaptic plasticity from that of memory addressing.
Chapter 1 provides an overview of the problem of memory addressing and a summary of the solutions that have been considered in computational neuroscience and artificial intelligence, as well as those that may exist in biology. Chapter 2 presents in detail a solution to memory addressing and synaptic plasticity in the context of familiarity detection, suggesting strong feedforward weights and anti-Hebbian plasticity as the respective mechanisms. Chapter 3 proposes a model of recall, with storage performed by addressing through local third factors and neo-Hebbian plasticity, and retrieval by content-based addressing. In Chapter 4, we consider the problem of concurrent memory consolidation and memorization. Both storage and retrieval are performed by content-based addressing, but the plasticity rule itself is implemented by gradient descent, modulated according to whether an item should be stored in a distributed manner or memorized verbatim. However, the classical method for computing gradients in recurrent neural networks, backpropagation through time, is generally considered unbiological. In Chapter 5 we suggest a more realistic implementation through an approximation of recurrent backpropagation.
Taken together, these results propose a number of potential mechanisms for memory storage and retrieval, each of which separates the mechanism of synaptic updating -- plasticity -- from that of synapse selection -- addressing. Explicit studies of memory addressing may find applications not only in artificial intelligence but also in biology. In artificial networks, for example, selectively updating memories in large language models can help improve user privacy and security. In biological ones, understanding memory addressing can help with health outcomes and treating memory-based illnesses such as Alzheimers or PTSD
Spatiotemporal Control of Chemical Reaction Networks using Droplet Microfluidics
A number of cellular organisms, such as yeast, bacteria and slime moulds, exhibit dynamic behaviour, in particular switching and rhythms that are controlled by feedback mechanisms in enzyme-catalysed reactions. The mechanisms of these processes are well understood, and recently there has been a focus on generating similar reactions in synthetic biocatalytic systems to establish bioinspired analogues for applications in materials and medicine. In this context, compartmentalisation of biochemical reactions within synthetic cell models such as micelles, vesicles, and W/O/W-based double emulsions is attracting growing attention for applications in the field of therapeutics. In this respect, it is necessary to adopt easier-to-use stimuli-responsive (react to pH, temperature or light) biochemical reactions, to apply artificial cell models to the biomedical context, and regulate artificial cell communication in a spatiotemporal controlled way. As a first step, it is crucial to control the output of a chemical reaction that maybe exploited for applications in the field of programmable materials and biomedicine. Droplet emulsion and synthetic vesicle systems have been widely employed as bioinspired micro- or nanoreactors for production of materials such as hydrogels and ceramic particles. They also provide test platform for biomimetic cell like behaviour.
To address this, we have developed and fine-tuned a platform with synthetic bottom-up chemistry that has enabled us to systematically and thoroughly investigate the effects of entrapment on a feedback-driven enzymatic reaction. As a result of this process, we have revealed a system that is more intricate than originally thought. Firstly, taking advantage from pressure driven droplet microfluidics, we developed a system of enzyme-encapsulated (urea-urease) double emulsion (W/O/W) droplets to obtain a localised pH pulse, with a controllable induction time to program material properties. The urease-catalysed hydrolysis of urea (urea-urea reaction), has a feedback through the production of the base (NH3). This leads to a change from an acidic to a basic pH after an induction time (Tind), resulting in an environment with auto-changing pH conditions. Reaction was initiated by addition of urea and a pulse in base (ammonia) was observed in the droplets after a time lag of the order of minutes. The pH-time profile can be manipulated by the diffusion timescale of urea and ammonia through the oil layer, resulting in localised pH changes not accessible in bulk solutions.
Secondly, we performed a computational investigation of the nonlinear reaction chemistry (urea-urease) within the designed platform of the W/O/W-based reactor. A radially distributed reaction diffusion model is presented for a layered sphere mimicking a double emulsion. Here we have combined the experiments with simulations (shell-core model) to demonstrate the influence of urea transport triggered by the shell, the core and the external solution surrounding the cell model (µ-reactor) on the induction time/period (Tind) of urea-urease reaction.
Third, inspired from natural cellular systems (e.g. bacterial quorum sensing), we focus on the use of urea-urease reaction confined to double emulsions to investigate chemical communications. We observed a system that resulted in a system of microreactors acting as individual units with distinct induction periods (Tind) for the first time. We show that in contrast to other systems, the release of ammonia can accelerate the reaction in all the droplets but there is no evident synchronisation of activity characterised by a wide distribution of induction times across the population of micro-reactors. However, the investigation of behaviour of population/group of µ-reactors as a function of substrate urea concentration and the density of µ-reactors highlights the possibility of transitions to collective behaviours.
Finally, we aimed to use the double emulsion template for potential biomedical and therapeutic applications using the autocatalytic urea-urease reaction. We used the platform to produce thiol-acrylate gels in the form of double emulsion loaded gel films and spherical microcapsules for potential drug delivery applications. In addition, we employed the encapsulated double emulsion platform of the enzyme urease to study the inhibition of the enzyme itself; which is important in the development of anti-microbials for ureolytic bacteria.
By building this platform, we have not only learned how to control the kinetic output of the reaction (urea-urease), but have also demonstrated its potential in future applications
Planetary Hinterlands:Extraction, Abandonment and Care
This open access book considers the concept of the hinterland as a crucial tool for understanding the global and planetary present as a time defined by the lasting legacies of colonialism, increasing labor precarity under late capitalist regimes, and looming climate disasters. Traditionally seen to serve a (colonial) port or market town, the hinterland here becomes a lens to attend to the times and spaces shaped and experienced across the received categories of the urban, rural, wilderness or nature. In straddling these categories, the concept of the hinterland foregrounds the human and more-than-human lively processes and forms of care that go on even in sites defined by capitalist extraction and political abandonment. Bringing together scholars from the humanities and social sciences, the book rethinks hinterland materialities, affectivities, and ecologies across places and cultural imaginations, Global North and South, urban and rural, and land and water
Extreme multi-decadal trends in the North Atlantic Oscillation
Stochastic processes are shown to be useful tools for quantifying extreme trends in climate indices. The variance of the trend distribution is shown to generally increase with autocorrelation, with an increase in extreme trend exceedance probabilities. The winter North Atlantic Oscillation (NAO) index has weak autocorrelation which is underestimated in historical climate models and helps to explain the underestimation of extreme trends. The maximum observed 31-year NAO trend occurred in 1963-1993 and is estimated to have a 1 in 20 chance of being exceeded in the 144-year historical record using fitted stochastic models. Climate models and stochastic models without autocorrelation underestimate this probability as a 1 in 200 chance. The NAO trend in the 1963-1993 window was identified due to its unusual nature. If this window is wrongly treated as a randomly chosen single window, the exceedance probability is further reduced (a 1 in 1000 chance). Post-processing methods are proposed to increase the low autocorrelation in climate models and are shown to improve the simulation of extreme trends and also increase the variance of ensemble mean trends. Future projections show a small systematic increase in end-of-century NAO ensemble mean trends relative to the magnitude of the radiative forcing. The probability of a maximum 31-year trend greater than that observed is 3 7% in the next 75-years (under the higher “business as usual” radiative forcing scenario), which is similar to the historical model probability for the last 75-years. Near-term projections of the next 31 years (2024-2054) are relatively insensitive to the scenario, showing no forced trend in the models but a large ensemble range due to internal variability ( 7.41 to 7.68 hPa/decade) which could increase or decrease regional climate change signals in the Northern Hemisphere by magnitudes that are underestimated when using raw climate model output
Cooperative Pathways: Insights from Teacher Experiences on Improving Union and District Cooperation
This study involved an evaluation of teacher experiences within their districts, schools, and unions across the United States. The primary research question was: How are teachers currently experiencing the relationship between their unions, districts, and administrators and what opportunities exist to improve cooperation and shared ownership between those groups? The study used a mixed methods approach by gathering quantitative data in the form of a survey and qualitative data through open-ended responses on the survey as well as interviews with seven teachers. The results formed a general understanding of the current state of teacher experiences that was then applied to better understand Chicago as a case study and the at times contentious relationship between the teachers union and district. Finally, recommendations were made for policy and leadership to promote cooperation and shared ownership among teachers, unions, principals, and district leaders, including trust building strategies, engagement efforts, and fiscal sustainability
Doing Research. Wissenschaftspraktiken zwischen Positionierung und Suchanfrage
Forschung wird zunehmend aus Sicht ihrer Ergebnisse gedacht - nicht zuletzt aufgrund der Umwälzungen im System Wissensschaft. Der Band lenkt den Fokus jedoch auf diejenigen Prozesse, die Forschungsergebnisse erst ermöglichen und Wissenschaft konturieren. Dabei ist der Titel Doing Research als Verweis darauf zu verstehen, dass forschendes Handeln von spezifischen Positionierungen, partiellen Perspektiven und Suchbewegungen geformt ist. So knüpfen alle Beitragenden auf reflexive Weise an ihre jeweiligen Forschungspraktiken an. Ausgangspunkt sind Abkürzungen - die vermeintlich kleinsten Einheiten wissenschaftlicher Aushandlung und Verständigung. Der in den Erziehungs-, Sozial-, Medien- und Kunstwissenschaften verankerte Band zeichnet ein vieldimensionales Bild gegenwärtigen Forschens mit transdisziplinären Anknüpfungspunkten zwischen Digitalität und Bildung. (DIPF/Orig.
Influence of Behavioral Leadership Strategies on Employee Engagement in Hospital Departments
Lack of employee engagement as a result of deficient behavioral leadership strategies has the potential for adverse business outcomes on productivity, business mission, and strategy. As a result of this qualitative single case study, hospital department managers who apply behavioral leadership strategies are more likely to promote an environment conducive to employee engagement. Grounded in the employee engagement theory, the purpose of this qualitative single case study was to explore behavioral leadership strategies hospital department managers use to promote an environment conducive to employee engagement. The participants were five hospital department managers who had been successful with employee engagement. Data were collected using semistructured interviews, a review of organization employee handbooks, and employee meeting notes. Through thematic analysis, three themes were identified: (a) increased employee engagement with open communication, (b) empowering employee decision making, and (c) relationship development. A key recommendation is for business leaders to acknowledge the needs of their employees and continue to improve their behavioral leadership strategies. The implications for positive social change include the potential to retain valued employees and support the local community workforce through workers giving back their time
Accustomed to Obedience?
Many histories of Ancient Greece center their stories on Athens, but what would that history look like if they didn’t? There is another way to tell this story, one that situates Greek history in terms of the relationships between smaller Greek cities and in contact with the wider Mediterranean. In this book, author Joshua P. Nudell offers a new history of the period from the Persian wars to wars that followed the death of Alexander the Great, from the perspective of Ionia. While recent scholarship has increasingly treated Greece through the lenses of regional, polis, and local interaction, there has not yet been a dedicated study of Classical Ionia. This book fills this clear gap in the literature while offering Ionia as a prism through which to better understand Classical Greece.
This book offers a clear and accessible narrative of the period between the Persian Wars and the wars of the early Hellenistic period, two nominal liberations of the region. The volume complements existing histories of Classical Greece. Close inspection reveals that the Ionians were active partners in the imperial endeavor, even as imperial competition constrained local decision-making and exacerbated local and regional tensions. At the same time, the book offers interventions on critical issues related to Ionia such as the Athenian conquest of Samos, rhetoric about the freedom of the Greeks, the relationship between Ionian temple construction and economic activity, the status of the Panionion, Ionian poleis and their relationship with local communities beyond the circle of the dodecapolis, and the importance of historical memory to our understanding of ancient Greece. The result is a picture of an Aegean world that is more complex and less beholden narratives that give primacy to the imperial actors at the expense of local developments
- …