Thesis (M.S.)--University of Michigan, 1986.

Thesis (M.S.)--University of Michigan, 1969.

Thesis (M.S.)--University of Michigan, 1986.

Thesis (M.S.)--University of Michigan, 1985.

The mismatching of alveolar ventilation and perfusion (VA/Q) is the major determinant of impaired gas exchange. The gold standard for analyzing VA/Q distribution is the multiple inert gas elimination technique (MIGET), conventionally based on gas chromatography (GC), and, although simple in principle, a technically demanding procedure limiting its use. A new technique based on micropore membrane inlet mass spectrometry (MMIMS) combined MIGET with mass spectrometry, simplifying the sample handling process, and potentially providing VA/Q distributions for a general clinical approach. The kinetics of volatile anesthetics are well known in patients with healthy lungs. The uptake and distribution of inhaled anesthetics have usually been modeled by physiologic models. However, these models have limitations, and they do not consider ventilation/perfusion matching. Respiratory diseases account for a large part of morbidity and mortality and are associated with pulmonary VA/Q mismatch that may affect uptake and elimination of volatile anesthetics. The objectives of the studies were firstly to investigate assessment of VA/Q mismatch by MMIMS and secondly to investigate the effects of asthma-like VA/Q mismatch on the kinetics of volatile anesthetics in an experimental porcine model. Anesthetized and mechanically ventilated piglets were studied. In study I, a direct comparison of MIGET by MMIMS with the conventional MIGET by GC in three animal models that covered a wide range of VA/Q distributions was preformed. The two methods agreed well, and parameters derived from both methods showed good agreement with externally measured references. In studies II–IV, a stable method of inducing and maintaining asthma-like VA/Q mismatch with methacholine (MCh) administration was established, and the effect of VA/Q mismatch on the pharmacokinetics of desflurane and isoflurane was investigated. The present model of bronchoconstriction demonstrates a delay in volatile anesthetic uptake and elimination, related to the heterogeneity of MCh-inhalation induced ventilation. The difference in solubility of volatile anesthetics has a significant influence on their uptake and elimination under VA/Q mismatch. The higher blood soluble isoflurane is affected to a lesser degree than the fairly insoluble desflurane.

Mice with human immune systems, generated by transplanting human CD34+ cells into immunodeficient mice, are essential tools for studying phenomena unique to the human immune system or poorly reproduced in existing mouse models. Human immune tolerance induction, function and autoimmunity have been poorly modeled in conventional murine models, which often have poor predictive value for preclinical development. Models that allow the study of human immune cells with the reproducibility and flexibility of small animal models are required. In our lab, humanized mouse models have been used to study preclinical protocols for human xenotolerance induction and to better understand the immunological underpinnings of human autoimmunity. These are each areas of critical unmet medical need. Xenotolerance-inducing protocols may be necessary to allow long-term survival of a transplanted pig organ in a human patient, and, with more than 113,000 Americans currently waiting for a life-saving organ, the need to expand the pool available for transplantation is urgent. Additionally, clinical options for patients with autoimmune diseases are limited. Currently, most patients with autoimmunity are only diagnosed after significant immune damage of target organs. Predicting who will develop autoimmunity – and who will not – before damage occurs would be very useful but is currently very difficult. Small animal models that can better help us understand how human autoimmunity develops could help us develop protocols for early detection and even prevention. We have developed a personalized immune model to study the development of an individual patient’s immune system in a transplanted mice to better understand immune abnormalities that underlie autoimmunity. We have used existing humanized mouse models to answer important questions related to human xenotolerance induction and autoimmunity, but in the studies described here we have worked to extend our capacity to use these models to study human T cell development and peripheral function. We would like to be able to study both the initial selection of T cell receptors (TCRs) in the thymus based on their ability to recognize antigen in the context of presenting MHC without reacting unduly to self-antigen, as well as in the periphery, where T cells interact with peripheral antigen-presenting cells (APCs) to maintain homeostasis and respond to antigen. First, we have incorporated TCR transgenesis into our humanized mouse models to allow greater precision in studying thymic selection in our humanized mice. Developing a system for this would allow us to study in greater detail mechanisms of human xenotolerance induction, including confirming that a swine thymus can support positive selection of T cells with human-restricted TCRs to allow a future xenotransplantation patient to maintain immune competence, while also robustly tolerizing human T cells expressing pig-reactive TCRs. We will also expand this system to study the thymic selection of human T cells with autoreactive TCRs to better understand mechanisms of central tolerance and understand how they fail in autoimmunity. Finally, while processes of thymic selection are critical for human T cell development and function, peripheral interactions also have a large impact on human T cell function and homeostasis and may contribute to the development of autoimmunity. For these interactions to occur appropriately requires robust engraftment and reconstitution of APCs, especially of myeloid and B cell lineages, in transplanted immunodeficient mice. APC reconstitution tends to be suboptimal in humanized mice and is even more so in mice transplanted with patient-derived CD34+ cells. Better characterization of human APC populations and their progenitors could allow us to develop approaches to improve long-term human APC reconstitution in patient-derived humanized mice, allowing us to more fully model patient peripheral T cell function.

Frequency selectivity is one of the most important functions of the mammalian hearing organ – the cochlea. The interaction of fluid mass and organ of Corti compliance sets a traveling wave along the basilar membrane (BM), which is longitudinally tuned to different frequencies. Beyond this passive tuning process, cochlear amplification locally enhances the vibration of the best frequency peak by factors of hundreds to boost the frequency selectivity and sensitivity of the cochlea. This amplification is achieved by a positive feedback loop between BM motion and outer hair cell (OHC) electrical-mechanical response. However, this active mechanism is vulnerable to damage and cannot be fully recovered in vivo. As the instruments of cochlear amplification, the frequency response of BM and OHCs are of great importance to understand cochlear tuning process. This thesis used animal models, aimed to understand cochlear tuning and investigate possibilities to manipulate the cochlear amplifier, by testing the cochlear amplifier’s sensitivity to operating conditions. The first project tested whether the cochlear amplification can adjust to a lower endocochlear potential (EP), which controls OHC electromechanical force by providing part of the voltage source to drive OHC transduction current. To investigate this possibility, we use intraperitoneal (IP) and intravenous (IV) injection of furosemide to reversibly reduce EP, while monitoring the EP and cochlear amplification simultaneously. Cochlear amplification was monitored by measuring the local cochlear microphonic (LCM) and distortion product emission (DPOAE). With IV injection, the cochlear amplification observed in LCM could attain nearly full or even full recovery with reduced EP. This showed the cochlea has an ability to adjust to diminished operating condition. Furthermore, the cochlear amplifier and EP recovered with different time courses: cochlear amplification just started to recover after the EP was nearly fully recovered and stabilized. Using a Boltzmann model and the 2nd harmonic of the LCM to estimate the mechanoelectric transducer channel operating point, we found that the recovery of cochlear amplification occurred with re-centering of the operating point. The second project studied the physiological and anatomical effects of perfusing the cochlea with a viscous fluid, for better understanding cochlear fluid mechanics. Perilymphatic perfusion was applied with artificial perilymph and viscous sodium hyaluronate (Healon, HA) in four different concentrations. Using compound action potential (CAP) thresholds as an indicator of cochlear condition, our results and analysis indicated that the cochlea can sustain, without a significant CAP threshold shift, up to a 1.5 Pa shear stress. Histology of the cochleae perfused with higher shear stress showed the Reissner's membrane was torn. These data also indicated that the cochlea mechanics remains normal within increased perilymphatic fluid viscosity up to an increase of a factor of 50. Beside these findings, a temporary CAP threshold shift was observed, perhaps due to the presence and then clearance of viscous fluid within the cochlea, or to a temporary position shift of the organ of Corti. The last project was to test the effect of OHC intracellular Cl- concentration on cochlear amplification. Chloride is known to enable the electromotility of the OHC by binding its motor protein, prestin. By locally perfusing high chloride perilymph and the chloride ionophore tributyltin, this study investigated whether increasing intracellular chloride concentration can restore cochlear sensitivity in a cochlea that was slightly damaged. This had been shown by others in guinea pig. However, we did not observe recovery in several attempts in gerbil.

It is a major challenge to understand functional neuronal circuits across the whole brain. Existing methods for observing neuronal activity represent a major bottleneck in addressing biological problems. In our lab, we developed Swept Confocally Aligned Planar Excitation (SCAPE) microscopy, which offers the ability to image a large 3D volume (e.g. 1000x800x250um) at speeds exceeding 10 volumes per second. Used with different genetically encoded fluorescent indicators, SCAPE enables us to observe neuronal activity across the whole brain of different small animal models, or a much larger volume of intact cortex/tissue compared to traditional approaches. The unique single objective design and flexible system layout of SCAPE makes it simple to image different samples without complex sample preparation and restraint. During this thesis work, I collaborated with biology and neuroscience labs to develop and optimize a range of novel in-vivo/in-vitro neuroimaging applications using SCAPE microscopy. In particular, my research has focused on using SCAPE to image freely crawling Drosophila Melanogaster larvae, intact mouse olfactory epithelium, head fixed behaving adult Drosophila, larval zebrafish brain and beating heart, and the neuronal system of behaving C. elegans, all in collaboration with experts in these models from Columbia University and other research institutions. I also developed and optimized different sample preparations and experimental procedures to take full advantage of the high-speed 3D imaging capabilities and flexibility of SCAPE microscopy. Finally, I optimized computational and image analysis techniques for large scale 5D SCAPE imaging datasets, including 3D cell tracking, large scale 3D data motion correction/registration, and cellular level neuronal activity extraction with different dimensionality reduction methods. The experiments I have performed in different animal models have enriched the long-term development of SCAPE by providing valuable feedback for system improvement and dissemination, and pushing the SCAPE design towards a more interchangeable platform with diverse capabilities suitable for routine uses by our collaborators and the wider neuroscience community.

No description available.

The following research paper was concerned with five basic objectives:(1) outlining the major theoretical and methodological approaches used in the reconstruction of early hominid social behavior/social structure as a context in which to view Richard Wrangham's and Michael Ghiglieri's phylogenetic models of stem-hominid social structure.(2) examining Wrangham's and Ghiglieri's models of stem-hominid and chimpanzee social structure.(3) indicating how theoretical and methodological aspects of structure essentially represent an extension of the theoretical and methodological approaches the same researchers applied to their models of chimpanzee social structure.(4) addressing the theoretical and methodological deficiences of Wrangham's and Ghiglieri's models of chimpanzee social structure.(5) providing suggestions for improved phylogenetic models of early hominid social structure.The first objective was achieved by: (a) reviewing Tooby and Devore's (1986) and Wrangham's (1986) evaluations of the major theoretical approaches and methodologies used in the reconstruction of hominid social behavior/structure (b) defining, classifying and evaluating Wrangham's and Ghiglieri's phylogenetic approaches within this context.The second objective was accomplished by outlining, analyzing, and comparing/contrasting Wrangham's and Ghiglieri's phylogenetic models of stem-hominid social structure (i.e.Wrangham 1986; Ghiglieri 1987, 1989) and Wrangham's and Ghiglieri's models of chimpanzee social structure (i.e. Wrangham 1975, 1979; Ghiglieri 1984, 1985, 1987, 1989).The third objective was achieved by recognizing how Wrangham and Ghiglieri used/stressed principles and concepts derived from evolutionary biology and/or behavioral ecology to develop their models of stem-hominid and chimpanzee social structure. This analysis showed that Wrangham's models of social structure were more favorably inclined toward the method of behavioral ecology than Ghiglieri's models, which favored a sociobiological paradigm. Furthermore, although neither researcher relied exclusively on the above theoretical approaches, the main thrust of their argument often centered around it. For instance, Wrangham's analysis of chimpanzee social structure (Wrangham 1975, 1979) indicated that the ultimate cause of that structure was ecological i.e., patchy food distribution leads to wide female dispersal for optimal foraging efficiency, which in turn favors a male kin breeding group that can maintain a territority that includes several individual female ranges. In contrast, Wrangham's phylogenetic model of the social structure of the stem-hominid (Wrangham, 1986) suggested that phylogenetic inertia may be partially responsible for the shared social features found among African Hominoidea. However, in the same work, Wrangham also suggested that further socioecological analysis of African apes may indicate whether food distribution and its effects on female dispersion/association may partially explain conservative African ape social features.Ghiglieri's phylogenetic model of the stem-hominid (1987, 1989), on the other hand, explained the conservative social features of bonobos, common chimpanzees, and hominids to be primarily a product of phylogenetic inertia and sexual selection. Furthermore, for Ghiglieri the most important sexual selection variable was a male communal reproductive strategy. This, according to Ghiglieri, is the ultimate cause of social structure. Notably, Ghiglieri (1984, 1985) had earlier stressed the overiding importance of a male communal reproductive strategy but was less dogmatic in his insistence that chimpanzees had essentially solved their ecological problems (e.g. that they had solved the food distribution problem by fusion-fission sociality; predators were never a real problem). Nevertheless, Ghiglieri's earlier position similarily expressed the idea that a communal reproductive strategy constituted the ultimate cause of social structure.The fourth objective was accomplished by presentation of an alternative model of chimpanzee social behavior which suggested that structure; the effect of phylogenetic inertia on social structure; chimpanzee social structure is the combined product of ecological and sexual selection forces: female optimal foraging, male mating strategies, and predator pressure. The model was considered by the author to be unique in that it integrated essential aspects of both Wrangham's and Ghiglieri's models and, in addition, provided support for Alexander's (1974) contention that predation pressure is an ultimate cause of ape social structure. The model also outlined scenarios for the evolution of chimpanzee group._ extensibility (fusion-fission sociality) and the capacity for warfare among chimpanzees.The last objective was achieved by a discussion of the implications that the author's model had for phylogenetic models of stem-hominid social structure. In this discussion the author reviewed the following issues as they related to the phylogenetic reconstruction of hominid social structure: the role of phylogeny and/or ecology in the causation of social encountered when using a phylogenetic referential model for the personal biases that enter into phylogenetic econstructions; pitfalls reconstruction of early hominid social evolution; the significance of chimpanzee models of social structure.The importance of the preceding study lay in its ability to stimulate improved conceptual models of African hominoid social structure. / Department of Anthropology