Climate Change and Regions at Risk: A Look at Central America

Climate change has been a security issue for mankind since Homo sapiens first emerged on the planet, driving him to find new and better food, water, shelter, and basic resources for survival and the advancement of civilization. Only recently, however, has the rate of climate change coupled with man’s knowledge of his own role in that change accelerated, perhaps profoundly, changing the security paradigm. If we take a ―decades‖ look at the security issue, we see competition for natural resources giving way to Cold War ideological containment and deterrence, itself giving way to non-state terrorism and extremism. While we continue to defend against these threats, we are faced with even greater security challenges that inextricably tie economic, food and human security together and where the flash points may not provide clearly discernable causes, as they will be intrinsically tied to climate change. Several scientific reports have revealed that the modest development gains that can be realized by some regions could be reversed by climate change. This means that climate change is not just a long-term environmental threat as was widely believed, but an economic and developmental disaster that is unfolding. As such, addressing climate change has become central to the development and poverty reduction by the World Bank and other financial institutions. In Latin America, poorer countries and communities, such as those found in Central America, will suffer the hardest because of weaker resilience and greater reliance on climatesensitive sectors such as agriculture. The US should attempt to deliver capability to assist these states to deal with the effects of climate change.

Toward an understanding of how individuals overcome challenges to development: A phenomenological study of an inner -city student's attitude toward academic orientation and life

The purpose of this qualitative case study was to gain an understanding of the phenomenon of academic orientation by seeking the insights into an inner-city Haitian-American middle school student's attitudes and world view toward education and life. A phenomenological approach was used in order to explore the way in which Cindy, a minority student, gives meaning to her lived-experiences in terms of her desire to meet academic expectations and her ability to overcome social adversity and/or other risk factors.^ The study attempted to answer the following two research questions: (1) What provides the focus for Cindy's (the subject's) approach to her school work and/or life? (2) What are the processes that give meaning and direction to academic orientation and life for Cindy? In-depth interviewing was the primary method of data collection. In addition, journal and sketchbook entries and school district records were used and classroom observations made.^ The nature of the study to understand lived-experience facilitated the use of the case study method and a phenomenological method of description. Data analysis was conducted by means of an adapted form of the constant comparative approach. Patterns in the data which emerged were coded and categorized according to underlying generative themes. Phenomenological reflection and analysis were used to grasp the experiential structures of Cindy's experience. The following textural themes were identified and confirmed to be essential themes to Cindy's experience: personal challenge to do her best, personal challenge to want to learn, having a sense of determination, being able to think for self, having a disposition to like self, achieving self-respect through performance, seeing a need to help others, being intrinsically motivated, being an independent learner, attending more to academic pressure and less to peer pressure, having motivational catalysts in her life, learning and support opportunities, and having a self-culture. Using Mahrer's humanistic theory of experiencing, Cindy's development was interpreted in terms of her progression through a sequence of developmental plateaus: externalized self, internalized self, and integrating and actualizing self.^ The findings of this study were that Cindy's desire to meet academic expectations is guided by a meaning construction internal frame of reference. High expectations of self in conjunction with other protective factors found in Cindy's home and school environments were also found to be linked to her educational resilience and success. Cindy's lived-experiences were also found to be related to Mahrer's theory of human development. In addition, it was concluded that "minority" students do not all fit into social categories and labels. ^

Synthetic Approaches to Flexible Fluorescent Conjugated Polymers

Conjugated polymers (CPs) are intrinsically fluorescent materials that have been used for various biological applications including imaging, sensing, and delivery of biologically active substances. The synthetic control over flexibility and biodegradability of these materials aids the understanding of the structure-function relationships among the photophysical properties, the self-assembly behaviors of the corresponding conjugated polymer nanoparticles (CPNs), and the cellular behaviors of CPNs, such as toxicity, cellular uptake mechanisms, and sub-cellular localization patterns. Synthetic approaches towards two classes of flexible CPs with well-preserved fluorescent properties are described. The synthesis of flexible poly(p-phenylenebutadiynylene)s (PPBs) uses competing Sonogashira and Glaser coupling reactions and the differences in monomer reactivity to incorporate a small amount (~10%) of flexible, non-conjugated linkers into the backbone. The reaction conditions provide limited control over the proportion of flexible monomer incorporation. Improved synthetic control was achieved in a series of flexible poly(p-phenyleneethynylene)s (PPEs) using modified Sonogashira conditions. In addition to controlling the degree of flexibility, the linker provides disruption of backbone conjugation that offers control of the length of conjugated segments within the polymer chain. Therefore, such control also results in the modulation of the photophysical properties of the materials. CPNs fabricated from flexible PPBs are non-toxic to cells, and exhibit subcellular localization patterns clearly different from those observed with non-flexible PPE CPNs. The subcellular localization patterns of the flexible PPEs have not yet been determined, due to the toxicity of the materials, most likely related to the side-chain structure used in this series. The study of the effect of CP flexibility on self-assembly reorganization upon polyanion complexation is presented. Owing to its high rigidity and hydrophobicity, the PPB backbone undergoes reorganization more readily than PPE. The effects are enhanced in the presence of the flexible linker, which enables more efficient π-π stacking of the aromatic backbone segments. Flexibility has minimal effects on the self-assembly of PPEs. Understanding the role of flexibility on the biophysical behaviors of CPNs is key to the successful development of novel efficient fluorescent therapeutic delivery vehicles.

Characterization of the poxAB Operon Encoding a Class D Carbapenemase in Pseudomonas aeruginosa,

Pseudomonas aeruginosa is a dreaded opportunistic pathogen that causes severe and often intractable infections in immunocompromised and critically ill patients. This bacterium is also the primary cause of fatal lung infections in patients with cystic fibrosis and a leading nosocomial pathogen responsible for nearly 10% of all hospital-acquired infections. P. aeruginosa is intrinsically recalcitrant to most classes of antibiotics and has the ability to acquire additional resistance during treatment. In particular, resistance to the widely used β-lactam antibiotics is frequently mediated by the expression of AmpC, a chromosomally encoded β-lactamase that is ubiquitously found in P. aeruginosa strains. This dissertation delved into the role of a recently reported chromosomal β-lactamase in P. aeruginosa called PoxB. To date, no detailed studies have addressed the regulation of poxB expression and its contribution to β-lactam resistance in P. aeruginosa. In an effort to better understand the role of this β-lactamase, poxB was deleted from the chromosome and expressed in trans from an IPTG-inducible promoter. The loss of poxB did not affect susceptibility. However, expression in trans in the absence of ampC rendered strains more resistant to the carbapenem β-lactams. The carbapenem-hydrolyzing phenotype was enhanced, reaching intermediate and resistant clinical breakpoints, in the absence of the carbapenem-specific outer membrane porin OprD. As observed for most class D β-lactamases, PoxB was only weakly inhibited by the currently available β-lactamase inhibitors. Moreover, poxB was shown to form an operon with the upstream located poxA, whose expression in trans decreased pox promoter (Ppox) activity suggesting autoregulation. The transcriptional regulator AmpR negatively controlled Ppox activity, however no direct interaction could be demonstrated. A mariner transposon library identified genes involved in the transport of polyamines as potential regulators of pox expression. Unexpectedly, polyamines themselves were able induce resistance to carbapenems. In summary, P. aeruginosa carries a chromosomal-encoded β-lactamase PoxB that can provide resistance against the clinically relevant carbapenems despite its narrow spectrum of hydrolysis and whose activity in vivo may be regulated by polyamines.

Ecologia de comunidades e comportamento reprodutivo de anfíbios anuros em savana amazônica

The Amazon savannas occur as isolated patches throughout extensive areas of forest in the states of Amapá, Amazonas, Pará, and Roraima. There is a considerable variation in the composition of anuran assemblages in the localities and phytophysiognomies of Amazon savannas and given the absence of studies on reproductive behavior, a systematic and geographically wide sampling has been carried out in the Amapá savanna, located in the Eastern Amazon. The study was conducted in a savanna area in the state of Amapá to examine the composition, ecology, and reproductive behavior of anuran amphibians. We carried out 24 field trips in each phytophysiognomy (gramineous-woody savana, gramineous-herbaceous-woody savana, park savana, and arboreal savanna); for analysis of reproductive behavior observations were made during the period January to December 2013, lasting four consecutive days. Samples were collected by active and acoustic search along 20 plots of 100x50 meters. Twenty-one anuran species were recorded, of which four are new records for the state of Amapá: Dendropsophus walfordi, Scinax fuscomarginatus, Pseudopaludicola boliviana e Elachistocleis helianneae. The KruskalWallis ANOVA revealed significant differences between richness and species diversity in the phytophysiognomies (p < 0.05). The Bray-Curtis similarity coefficient divided the phytophysiognomies into three groups: arboreal savana, gramineous-woody savanna and gramineous-herbaceous-woody savanna, and park savanna. According to the non-metric multidimensional scaling, the structure of the anuran community resulted in a separation into three phytophysiognomies, with significant differences in the structure of communities (ANOSIM, R = 0.823; p < 0.001). In the study of community ecology, the results obtained for spatial, temporal, and trophic niche breadth suggest that the assemblage of anurans of the Amapá savanna is not composed of predominantly generalist species. Also, the presence of other specialist anurans may explain the processes of speciation associated with the isolation of habitats, resulting in heterogeneity and spatial discontinuity in the phytophysiognomies with open formations. The null model analysis revealed that the community is structured based on temporal and trophic niche, indicating a significant influence of contemporary ecological factors on the assemblage. The absence of structure based on spatial niche might be explained by the spatial segregation in the distribution and occupation of anurans in the different phytophysiognomies of the Amapá savanna. Regarding the reproductive behavior of anurans, 11 species were classified as having a long breeding season, intrinsically associated with the rainy season and the reproductive mode of most species that lay egg clutches in lentic water bodies. Six reproductive modes were recorded and parental care was observed in Leptodactylus macrosternum and L. podicipinus, whose reproductive mode is characterized by foam nests. Regarding behavioral reproductive strategies, calling males were observed in all species of anurans, satellite males were recorded only for D. walfordi, Hypsiboas multifasciatus, S. nebulosus and S. fuscomarginatus; active search for females was observed for Phyllomedusa hypochondrialis and L. fuscus, and male displacement was recorded only for Rhinella major and R. margaritifera. Of the reproductive behaviors observed, throat and vocal sac display is associated with courtship and territorial behavior exhibited by males. In addition to courtship behavior, visual signals associated with courtship strategies were recorded for the anurans of the Amapá savanna.

Efeitos da nicotina no complexo do septo medial na via septo hipocampal em camundongos anestesiados por Ketamina

Nicotine administration in humans and rodents enhances memory and attention, and also has a positive effect in Alzheimer's Disease. The Medial Septum / Diagonal Band of Broca complex (MS/DBB) – a main cholinergic system – massively projects to the hippocampus through the fimbria-fornix, and this pathway is called the septohippocampal pathway. It has been demonstrated that the MS/DBB acts directly on the local field potential (LFP) rhythmic organization of the hippocampus, especially in the rhythmogenesis of Theta (4-8Hz) – an oscillation intrinsically linked to hippocampus mnemonic function. In vitro experiments gave evidence that nicotine applied to the MS/DBB generates a local network Theta rhythm within the MS/DBB. Thus, the present study proposes to elucidate the function of nicotine in the MS/DBB on the septo-hippocampal pathway. In vivo experiments compared the effect of MS/DBB microinfusion of saline (n=5) and nicotine (n=8) on Ketamine/Xylazine anaesthetized mice. We observed power spectrum density in the Gamma range (35 to 55 Hz) increasing in both structures (Wilcoxon Rank-Sum test, p=0.038) but with no change in coherence between these structures in the same range (Wilcoxon Rank-Sum test, p=0.60). There was also a decrease in power of the ketamineinduced Delta oscillation (1 to 3 Hz). We also performed in vitro experiments on the effect of nicotine on membrane voltage and action potential. We patch-clamped 22 neurons in current-clamp mode; 12 neurons were responsive to nicotine, half of them increased firing rate and other 6 decreased, and they significantly differed in action potential threshold (-47.3±0.9 mV vs. -41±1.9 mV, respectively, p=0.007) and halfwidth time (1.6±0.08 ms vs. 2±0.12 ms, respectively, p=0.01). Furthermore, we performed another set of in vitro experiments concerning the connectivity of the three major neuronal populations of MS/DBB that use acetylcholine, GABA or glutamate as neurotransmitter. Paired patch-clamp recordings found that glutamatergic and GABAergic neurons realize intra-septal connections that produce sizable currents in MS/DBB postsynaptic neurons. The probability of connectivity between different neuronal populations gave rise to a MS/DBB topology that was implemented in a realistic model, which corroborates that the network is highly sensitive to the generation of Gamma rhythm. Together, the data available in the full set of experiments suggests that nicotine may act as a cognitive enhancer, by inducing gamma oscillation in the local circuitry of the MS/DBB.

Development of calix[4]arene-functionalized microcantilever array sensing system for the rapid, sensitive and simultaneous detection of metal ions in aqueous solutions

The work described in this thesis was conducted with the aim of: 1) investigating the binding capabilities of calix[4]arene-functionalized microcantilevers towards specific metal ions and 2) developing a new16-microcantilever array sensing system for the rapid, and simultaneous detection of metal ions in fresh water. Part I of this thesis reports on the use of three new bimodal calix[4]arenes (methoxy, ethoxy and crown) as potential host/guest sensing layers for detecting selected ions in dilute aqueous solutions using single microcantilever experimental system. In this work it was shown that modifying the upper rim of the calix[4]arenes with a thioacetate end group allow calix[4]arenes to self-assemble on Au(111) forming complete highly ordered monolayers. It was also found that incubating the microcantilevers coated with 5 nm of Inconel and 40 nm of Au for 1 h in a 1.0 M solution of calix[4]arene produced the highest sensitivity. Methoxy-functionalized microcantilevers showed a definite preference for Ca²⁺ ions over other cationic guests and were able to detect trace concentration as low as 10⁻¹² M in aqueous solutions. Microcantilevers modified with ethoxy calix[4]arene displayed their highest sensitivity towards Sr²⁺ and to a lesser extent Ca²⁺ ions. Crown calix[4]arene-modified microcantilevers were however found to bind selectively towards Cs⁺ ions. In addition, the counter anion was also found to contribute to the deflection. For example methoxy calix[4]arene-modified microcantilever was found to be more sensitive to CaCl₂ over other water-soluble calcium salts such as Ca(NO₃)₂ , CaBr₂ and CaI₂. These findings suggest that the response of calix[4]arene-modified microcantilevers should be attributed to the target ionic species as a whole instead of only considering the specific cation and/or anion. Part II presents the development of a 16-microcantilever sensor setup. The implementation of this system involved the creation of data analysis software that incorporates data from the motorized actuator and a two-axis photosensitive detector to obtain the deflection signal originating from each individual microcantilever in the array. The system was shown to be capable of simultaneous measurements of multiple microcantilevers with different coatings. A functionalization unit was also developed that allows four microcantilevers in the array to be coated with an individual sensing layer one at the time. Because of the variability of the spring constants of different cantilevers within the array, results presented were quoted in units of surface stress unit in order to compare values between the microcantilevers in the array.

(Table 1) Salinity and dissolved organic carbon concentration of marine water (ANT-XIX/2) and mangrove porewater (Brazil)

The chemical structure of refractory marine dissolved organic matter (DOM) is still largely unknown. Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS) was used to resolve the complex mixtures of DOM and provide valuable information on elemental compositions on a molecular scale. We characterized and compared DOM from two sharply contrasting aquatic environments, algal-derived DOM from the Weddell Sea (Antarctica) and terrigenous DOM from pore water of a tropical mangrove area in northern Brazil. Several thousand molecular formulas in the mass range of 300-600 Da were identified and reproduced in element ratio plots. On the basis of molecular elemental composition and double-bond equivalents (DBE) we calculated an average composition for marine DOM. O/C ratios in the marine samples were lower (0.36 ± 0.01) than in the mangrove pore-water sample (0.42). A small proportion of chemical formulas with higher molecular mass in the marine samples were characterized by very low O/C and H/C ratios probably reflecting amphiphilic properties. The average number of unsaturations in the marine samples was surprisingly high (DBE = 9.9; mangrove pore water: DBE = 9.4) most likely due to a significant contribution of carbonyl carbon. There was no significant difference in elemental composition between surface and deep-water DOM in the Weddell Sea. Although there were some molecules with unique marine elemental composition, there was a conspicuous degree of similarity between the terrigenous and algal-derived end members. Approximately one third of the molecular formulas were present in all marine as well as in the mangrove samples. We infer that different forms of microbial degradation ultimately lead to similar structural features that are intrinsically refractory, independent of the source of the organic matter and the environmental conditions where degradation took place.

A dinâmica geográfica da construção de um território para moradias sociais: estudo testemunhal do empreendimento Vitória Brasil em Uberlândia (MG)

This work describes and analyzes the situation planned with the current, according to the housing development project style of social interest (Gleba 9), named Victory Brazil at Shopping Park II neighborhood, located in the southern sector of Uberlândia (MG), built with Program resources Minha Casa, Minha Vida (PMCMV). The specific objectives are: to present the housing policy of social interest directed to the Minha Casa, Minha Vida in the city of Uberlândia, from its history to its current information; trace the environmental characterization of the housing Vitoria Brazil through the development of thematic maps; identify the impacts generated by the housing projects of social interest; and show through interviews with 25 residents of Vitoria Brazil, the structural problems of the houses. Therefore, the research became quali-quantitative with descriptive approach and use of semi- structured interviews to collect data. In addition, the iconographic sources, ie photographs of the problems raised by the residents of the whole Victory Brazil and maps of the study area, enlarged the qualitative and dialogic nature of this study, as there is opportunity to contextualize specific way what was reported the residents interviewed. We understand that the city is intrinsically related to the design of agglomeration, characterized by the production of the possessor market capitalism a public administration system that is guided by the ideals of consumption and utilization of space, and its inhabitants are high class with the construction of equipment and adequate social services. One of the important biases to solving the problems of urbanization is by the intervention of the government through public policies through the master plan so that would allow prospects to enable the population of low-income housing in locations that offer housing and decent urbanization conditions.

Cidades saudáveis e qualidade de vida em Uberlândia (MG): aportes metodológicos para um processo em construção

The current study includes theoretical and methodological reflections on the quality of life in the city of Uberlândia, Minas Gerais. It started from the thought that the quality of life is multifactorial and is permanently under construction and the main objective of analyzing it as one of the componets of Healthy Cities's moviment. The theoretical research focused on the concepts of healthy cities, quality of life, health, sustainability, well-being, happiness, indexes and indicators. From the use of multiple search strategies, documentary and on field of quantitative and qualitative character, this research of exploratory descriptive nature can offers a contribution to the studies on the quality of life in cities. It is proposed that the studies startes to work with some concept, like some notions os life quality adequated for some paticular reality, whose notions can approach concepts already established as health. This step is important on the exploratory researches. The studies may include aspects of objective analysis, subjective or both. The objective dimension, which is most common approach, are traditionally considered variables and indicators related to: the urban infrastructure (health, education, leisure, security, mobility), dwelling (quantitative and qualitative dwlling deficit), the urban structure (density and mix uses), socioeconomic characteristics (age, income, education), urban infrastructure (sanitation, communication), governance (social mobilization and participation). To focus on the subjective dimension, most recent and unusual, it is proposed to consider the (dis)satisfaction, the personal assessment in relation to the objective aspects. In conclusion, being intrinsically related to the health, the quality of life also has a number of determinants, and the ideal of the reach of quality of life depends on the action of all citizens based on the recognition of networks and territories, in a interescalar perspective and intersectoral. Therefore, emphasis in given on the potential of tools, such as the observatories, to monitor and intervent in reality, aiming in a building process of healthy cities.

Percepção ambiental como ferramenta diagnóstica para o processo de integração entre uma unidade de conservação e a comunidade do entorno

It is remarkable the current planet’s situation of degradation and modification of natural assets and the considerable loss of the recovery power inherent to the ecosystems. Concomitant with this, all communities and species are suffering the consequences of these changes without planning. The creation of conservation units (UCs) through the National System of Conservation Units (SNUC) was a concrete action on the deliberateness of halting these processes, which, on the other hand, generated socio-environmental, geo-economical and cultural-political conflict of interests between traditional communities in the vicinity of these units, institutions, governmental entities and society in general. The country’s National Program of Environmental Education (ProNEA) provides the integration of the communities and UCs’ managers in a co-participative administration to solve these conflicts. The principles of Environmental Education (EA) leads the methodology found to change the socio-educational paradigms of traditional teaching, still existing in our society and intrinsically related to environmental problems, which are contrary to the dialogic pedagogy from Paulo Freire, that valorize popular knowledge, pro-active citizenship, as well as contrary to Ecopedagogy, that re-integrate human being on its natural environment, the Earth. One of the tools for starting environmental sensitization is the diagnosis by environmental perception of individuals. In this context, the objective of our work was to identify the environmental perception of Tenda do Moreno community located nearby Pau Furado State Park (PEPF) in Uberlândia – MG. To reach this objective, the research sought, in a first moment, to evaluate the environmental perception of residents of this community through semi-structured interviews applied in their homes and, in a second moment, we evaluated the environmental perception of community’ school students and made Environmental Education intervention activities with the intention to make children aware of the importance of conservation and function of PEPF. Using the Content analysis methodology, we found in nearly 60% of the 118 residents a systemic perception of nature, while approximately 32% expressed an anthropocentric perception. Mixed perceptions were found in 21%. A considerable part of the residents (47 individuals) indicated not knowing the park, although many of them recognize its importance. Among the 46 interviewed students, half expressed an anthropocentric perception of nature, while almost 36% had a systemic view. Seventeen children said they did not know the park and almost half of the students recognize some aspect of the importance of its existence. During the intervention activities, we had huge participation and dedication of students, beyond the massive expression of their personal views and daily experiences. In relation to the ten students that subjected the second evaluation about their environmental perception after the intervention, 80% showed systemic perception and emphasized the importance of conservation and of park. We believe that the continuity of the intervention activities could generate positive perspectives of socio-environmental effective changes in the daily school. Activities lead by Ecopedagogy and that encourage the citizen leadership in the young students are fundamental, while in the community, closer ties and dialog by UC’s managers would be important elements to generate effective change.

WEBJORNALISMO COLABORATIVO - A PRESENÇA DOS USUÁRIOS NO CONTEÚDO INFORMATIVO DO PORTAL R7

Este estudo procura verificar como ocorre a colaboração dos usuários no conteúdo informativo do Portal R7, a partir da nova configuração da internet, a web 2.0, criada em 2004. O termo web 2.0 surgiu para qualificar uma segunda geração de comunidades e serviços, em um ambiente de interação e participação que engloba diversas linguagens. Com o crescimento da adesão à tecnologia digital, algumas barreiras que limitavam a colaboração nos conteúdos informativos foram superadas e o ambiente comunicacional tornou-se um espaço de intercâmbio para experiências e práticas do cotidiano. Nesse cenário, os internautas passam a ter uma relação mais aproximativa nos processos midiáticos presentes no suporte digital, no qual o cidadão pode se expressar, ter maior visibilidade e se relacionar a partir do momento em que ele produz, publica e compartilha qualquer tipo de conteúdo, seja de caráter informativo ou de entretenimento. A revisão bibliográfica abrangeu autores como Ciro Marcondes Filho, José Marques de Melo, Nelson Traquina, Alex Primo, Ana Brambilla, Marcelo Träsel, Raquel Recuero, Polyana Ferrari, Squirra, entre outros. O método de investigação utilizado é o qualitativo, por meio de uma pesquisa exploratória descritiva, do tipo estudo de caso. Os instrumentos para a investigação foram a observação direta assistemática e a entrevista semiestruturada (ou semiaberta). O principal resultado obtido é que o webjornalismo colaborativo no Portal R7 é prioritariamente induzido pelas redes sociais, especialmente o Facebook e o Twitter, inspirado no “call for action”, como estratégia para chamar à colaboração. As práticas jornalísticas estão intrinsicamente dependentes da ação do usuário, sendo que o jornalista agrega às práticas de checagem uma nova etapa, a de relacionamento com o usuário do Portal, para agregar e fidelizar a audiência, valorizando a colaboração em todas as etapas de produção.

A Sting in the Tail : The N-Terminal Domain of the Androgen Receptor as a Drug Target

AEM was supported by a BBSRC-CASE studentship award. Research in the IJM laboratory is currently supported by the Chief Scientist's Office of the Scottish Government and the charity Friends of Anchor.

Stimulus Integration and Parsing in the Primate Auditory Midbrain

Integrating information from multiple sources is a crucial function of the brain. Examples of such integration include multiple stimuli of different modalties, such as visual and auditory, multiple stimuli of the same modality, such as auditory and auditory, and integrating stimuli from the sensory organs (i.e. ears) with stimuli delivered from brain-machine interfaces.

The overall aim of this body of work is to empirically examine stimulus integration in these three domains to inform our broader understanding of how and when the brain combines information from multiple sources.

First, I examine visually-guided auditory, a problem with implications for the general problem in learning of how the brain determines what lesson to learn (and what lessons not to learn). For example, sound localization is a behavior that is partially learned with the aid of vision. This process requires correctly matching a visual location to that of a sound. This is an intrinsically circular problem when sound location is itself uncertain and the visual scene is rife with possible visual matches. Here, we develop a simple paradigm using visual guidance of sound localization to gain insight into how the brain confronts this type of circularity. We tested two competing hypotheses. 1: The brain guides sound location learning based on the synchrony or simultaneity of auditory-visual stimuli, potentially involving a Hebbian associative mechanism. 2: The brain uses a ‘guess and check’ heuristic in which visual feedback that is obtained after an eye movement to a sound alters future performance, perhaps by recruiting the brain’s reward-related circuitry. We assessed the effects of exposure to visual stimuli spatially mismatched from sounds on performance of an interleaved auditory-only saccade task. We found that when humans and monkeys were provided the visual stimulus asynchronously with the sound but as feedback to an auditory-guided saccade, they shifted their subsequent auditory-only performance toward the direction of the visual cue by 1.3-1.7 degrees, or 22-28% of the original 6 degree visual-auditory mismatch. In contrast when the visual stimulus was presented synchronously with the sound but extinguished too quickly to provide this feedback, there was little change in subsequent auditory-only performance. Our results suggest that the outcome of our own actions is vital to localizing sounds correctly. Contrary to previous expectations, visual calibration of auditory space does not appear to require visual-auditory associations based on synchrony/simultaneity.

My next line of research examines how electrical stimulation of the inferior colliculus influences perception of sounds in a nonhuman primate. The central nucleus of the inferior colliculus is the major ascending relay of auditory information before it reaches the forebrain, and thus an ideal target for understanding low-level information processing prior to the forebrain, as almost all auditory signals pass through the central nucleus of the inferior colliculus before reaching the forebrain. Thus, the inferior colliculus is the ideal structure to examine to understand the format of the inputs into the forebrain and, by extension, the processing of auditory scenes that occurs in the brainstem. Therefore, the inferior colliculus was an attractive target for understanding stimulus integration in the ascending auditory pathway.

Moreover, understanding the relationship between the auditory selectivity of neurons and their contribution to perception is critical to the design of effective auditory brain prosthetics. These prosthetics seek to mimic natural activity patterns to achieve desired perceptual outcomes. We measured the contribution of inferior colliculus (IC) sites to perception using combined recording and electrical stimulation. Monkeys performed a frequency-based discrimination task, reporting whether a probe sound was higher or lower in frequency than a reference sound. Stimulation pulses were paired with the probe sound on 50% of trials (0.5-80 µA, 100-300 Hz, n=172 IC locations in 3 rhesus monkeys). Electrical stimulation tended to bias the animals’ judgments in a fashion that was coarsely but significantly correlated with the best frequency of the stimulation site in comparison to the reference frequency employed in the task. Although there was considerable variability in the effects of stimulation (including impairments in performance and shifts in performance away from the direction predicted based on the site’s response properties), the results indicate that stimulation of the IC can evoke percepts correlated with the frequency tuning properties of the IC. Consistent with the implications of recent human studies, the main avenue for improvement for the auditory midbrain implant suggested by our findings is to increase the number and spatial extent of electrodes, to increase the size of the region that can be electrically activated and provide a greater range of evoked percepts.

My next line of research employs a frequency-tagging approach to examine the extent to which multiple sound sources are combined (or segregated) in the nonhuman primate inferior colliculus. In the single-sound case, most inferior colliculus neurons respond and entrain to sounds in a very broad region of space, and many are entirely spatially insensitive, so it is unknown how the neurons will respond to a situation with more than one sound. I use multiple AM stimuli of different frequencies, which the inferior colliculus represents using a spike timing code. This allows me to measure spike timing in the inferior colliculus to determine which sound source is responsible for neural activity in an auditory scene containing multiple sounds. Using this approach, I find that the same neurons that are tuned to broad regions of space in the single sound condition become dramatically more selective in the dual sound condition, preferentially entraining spikes to stimuli from a smaller region of space. I will examine the possibility that there may be a conceptual linkage between this finding and the finding of receptive field shifts in the visual system.

In chapter 5, I will comment on these findings more generally, compare them to existing theoretical models, and discuss what these results tell us about processing in the central nervous system in a multi-stimulus situation. My results suggest that the brain is flexible in its processing and can adapt its integration schema to fit the available cues and the demands of the task.

Investigating the Structure of FtsZ to Understand its Functional Role in Bacterial Cell Division

FtsZ, a bacterial tubulin homologue, is a cytoskeleton protein that plays key roles in cytokinesis of almost all prokaryotes. FtsZ assembles into protofilaments (pfs), one subunit thick, and these pfs assemble further to form a “Z ring” at the center of prokaryotic cells. The Z ring generates a constriction force on the inner membrane, and also serves as a scaffold to recruit cell-wall remodeling proteins for complete cell division in vivo. FtsZ can be subdivided into 3 main functional regions: globular domain, C terminal (Ct) linker, and Ct peptide. The globular domain binds GTP to assembles the pfs. The extreme Ct peptide binds membrane proteins to allow cytoplasmic FtsZ to function at the inner membrane. The Ct linker connects the globular domain and Ct peptide. In the present studies, we used genetic and structural approaches to investigate the function of Escherichia coli (E. coli) FtsZ. We sought to examine three questions: (1) Are lateral bonds between pfs essential for the Z ring? (2) Can we improve direct visualization of FtsZ in vivo by engineering an FtsZ-FP fusion that can function as the sole source of FtsZ for cell division? (3) Is the divergent Ct linker of FtsZ an intrinsically disordered peptide (IDP)?

One model of the Z ring proposes that pfs associate via lateral bonds to form ribbons; however, lateral bonds are still only hypothetical. To explore potential lateral bonding sites, we probed the surface of E. coli FtsZ by inserting either small peptides or whole FPs. Of the four lateral surfaces on FtsZ pfs, we obtained inserts on the front and back surfaces that were functional for cell division. We concluded that these faces are not sites of essential interactions. Inserts at two sites, G124 and R174 located on the left and right surfaces, completely blocked function, and were identified as possible sites for essential lateral interactions. Another goal was to find a location within FtsZ that supported fusion of FP reporter proteins, while allowing the FtsZ-FP to function as the sole source of FtsZ. We discovered one internal site, G55-Q56, where several different FPs could be inserted without impairing function. These FtsZ-FPs may provide advances for imaging Z-ring structure by super-resolution techniques.

The Ct linker is the most divergent region of FtsZ in both sequence and length. In E. coli FtsZ the Ct linker is 50 amino acids (aa), but for other FtsZ it can be as short as 37 aa or as long as 250 aa. The Ct linker has been hypothesized to be an IDP. In the present study, circular dichroism confirmed that isolated Ct linkers of E. coli (50 aa) and C. crescentus (175 aa) are IDPs. Limited trypsin proteolysis followed by mass spectrometry (LC-MS/MS) confirmed Ct linkers of E. coli (50 aa) and B. subtilis (47 aa) as IDPs even when still attached to the globular domain. In addition, we made chimeras, swapping the E. coli Ct linker for other peptides and proteins. Most chimeras allowed for normal cell division in E. coli, suggesting that IDPs with a length of 43 to 95 aa are tolerated, sequence has little importance, and electrostatic charge is unimportant. Several chimeras were purified to confirm the effect they had on pf assembly. We concluded that the Ct linker functions as a flexible tether allowing for force to be transferred from the FtsZ pf to the membrane to constrict the septum for division.