Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (leaves 73-76).

Previous models of the pulmonary microvascular exchange system (28,29) have been restricted to the study of fluid and solute exchange between the pulmonary microcirculation, interstitial tissue space, and lymphatics. In severe pulmonary edema the capacities of the lymphatics and tissue space are exceeded. The fluid and solutes entering the interstitium from the circulation will, then, be transported Into the air space. The accumulation of fluid in the air space impairs the diffusion of gas (oxygen and carbon dioxide) between the air space and blood circulation; if this fluid accumulation is excessive a patient's health may be compromised. In this thesis severe pulmonary edema is studied by including the air space as a fourth compartment into the interstitial model developed by Bert and Pinder (29). A computer simulation of the four compartment (alveolar) model was developed on a digital computer. Tests of the model were made to study the effect of the parameters which were introduced into the alveolar model. These parameters include: a filtration coefficient that describes the alveolar membrane fluid conductivity, an extravascular fluid volume that represents the point at which fluid enters the air space, the alveolar fluid pressure at the onset of fluid flow into the air space, and the rate of alveolar fluid pressure change relative to an alveolar fluid volume change. For each case the dynamic response of the exchange system was recorded. In addition, two types of pulmonary edema were simulated: 1) hydrostatically induced edema, and 2) edema induced by changes to the fluid and solute permeability of the porous membrane separating the circulatory and interstitial compartments. Due to the limited data available on the interaction of the air space with the other three compartments of the pulmonary microvascular exchange system, only partial verification of the appropriate range of values of the alveolar model parameters and the predictions of the simulations was possible. The alveolar model developed in this thesis is an initial approximation but appears to provide a satisfactory approach for the inclusion of the air space in the pulmonary microvascular exchange system. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.

Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisor: Ajay K. Prasad, Dept. of Mechanical Engineering. Includes bibliographical references.

Francisella tularensis is a facultative intracellular pathogen and is the etiological agent of tularemia. One key aspect to the success of Francisella as a pathogen is ability of the organism to establish infection with a low inoculum, as few as 10 colony forming units (cfu). Essential to this process is the Francisella pathogenicity island (FPI). Several studies have been performed to understand how the FPI is regulated; however, the working model is not complete, as the signals important for regulation are unknown. Additionally, the mechanisms of the proteins MigR, TrmE, and CphA, which are important for activation of the FPI, are unknown. I initiated the study of this regulatory system by measuring the ability of various cellular stresses to activate an iglA-lacZ reporter. I identified that amino acid starvation and growth in basic pH activated expression of the reporter in both LVS and Schu S4. By combining these two stresses I was able to induce iglA-lacZ reporter expression in an additive manner. As it was previously demonstrated that ppGpp is important for stabilization of the regulatory complex that transcribes FPI genes, I demonstrated by TLC that both amino acid starvation and basic pH effected iglA-lacZ expression by increasing ppGpp. Due to the importance of ppGpp in FPI expression and because MigR, TrmE, and CphA each appear to be involved in a metabolic process: fatty acid metabolism (migR) t-RNA modification (trmE) and amino acid storage (cphA), I had hypothesized that the effect on these mutations were due to decreased levels of the small alarmone ppGpp. I compared ppGpp accumulation of LVS mutants in migR, trmE, and cphA to the parent strain and observed that loss of these genes resulted in reduced ppGpp. To better understand the importance of ppGpp synthesis in F. tularensis pathogenesis, I compared the phenotypes of these strains in primary human macrophages and two immortalized epithelial cell lines. These experiments demonstrated that although each of these strains had reduced ppGpp, there were cell line specific growth phenotypes. Mice infected with these strains survived suggesting tight regulation of the FPI is required for virulence. When similar mutations were characterized in the Schu S4 background these mutations retained their regulatory role; however, mutation of migR did not significantly decrease virulence in mice. As my data demonstrated that there are different challenges that Francisella must overcome to successfully replicate within cells, I developed an in vitro model to study the interactions of F. tularensis with human alveolar type II cells (AT-II). Interestingly, Schu S4 internalizes and replicates in these recently immortalized human AT-II cells whereas, LVS internalizes, but replicates poorly within these cells. Finally, to better understand the role of AT-II cells in vivo, I performed Transmission Electron Microscopy (TEM) of infected mice. These data confirmed that Schu S4 infected both alveolar macrophages and AT-II cells. Together, this work contributes to the understanding of how Francisella adapts to various environments by modulating virulence gene expression and highlights differences between virulent Schu S4 and LVS, which may partially contribute to virulence differences observed between strains.

The spontaneous tumoricidal ability of pulmonary alveolar macrophages (PAM) isolated from C57B1/6 mice bearing either a metastatic or a nonmetastatic cloned variant of Lewis lung carcinoma (LLC) was examined in vitro. During the early weeks of tumor development the cytotoxicity mediated by macrophages was enhanced in the tumor-bearing mice, especially in the metastatic tumor bearers. Later in tumor progress (week 4) the spontaneous cytotoxicity of both groups typically declined to levels less than those of normal macrophages. Experiments were performed to determine if macrophages could be activated further in vitro by incubation in a mixture of lymphokine and lipopolysaccha ride. The macrophages from the metastatic tumor bearers were consistently activated in vitro. However, macrophages isolated from mice bearing large tumors and whose spontaneous cytotoxicity was suppressed could not be activated.The secretion of prostaglandin E2 (PGE2) by macrophages at different times during tumor development was measured to determine if PGE2 levels corresponded with the ability or inability of macrophages to kill tumor cells. Secretion of PGE2 typically corresponded with the capacity to kill rather than with an inability to kill target cells. Similarly, the production of PGE2 by macrophages was not responsible for the decline in the ability of macrophages to kill tumor cells.These results suggest that PAM are activated to be cytotoxic during the period when pulmonary metastases are developing. The successful establishment of these metastases does not appear to depend on the capacity of the tumor to suppress alveolar macrophage cytotoxicity. / Department of Biology

This research develops a detailed, anatomically-based model of the human pulmonary circulatory system from the large scale arterial and venous vessels, to the microcirculatory alveolar-capillary unit. Flow is modelled through these networks enabling structure-function simulations to be conducted to increase our understanding of this complex system.Voronoi meshing is applied in a novel technique to represent the three-dimensional structure of the alveoli, and the corresponding capillary plexus intimately wrapped over the alveolar surface. This technique is used to create the alveolar-capillary structure of a single alveolar sac, closely representing the geometry measured in anatomical studies.A Poiseuille type flow solution technique is implemented within the capillary geometry. The solution procedure incorporates calculations of red and white blood cell transit time frequencies. Novel predictions of regional microcirculatory blood cell transit in the anatomically-realistic alveolar-capillary model compare well with experimental measures.An anatomically-based finite element model of the arterial and venous vessels, down to the level of their accompanying respiratory bronchioles, is created using a combination of imaging and computational algorithms, which includes generation of supernumerary vessels. Large arterial and venous vessels and lobar geometries are derived from multi-detector row x-ray computed tomography (MDCT) scans. From these MDCT vessel end points a volume-filling branching algorithm is used to generate the remaining blood vessels that accompany the airways into the MDCT-derived host volume. An empirically-based algorithm generates supernumerary blood vessels - unaccompanied by airways that branch to supply the closest parenchymal tissue. This new approach produces a model of pulmonary vascular geometry that is far more anatomically-realistic than previous models in the literature.A reduced form of the Navier-Stokes equations are solved within the vascular geometries to yield pressure, radius, and velocity distributions. Inclusion of a gravitational term in the governing equations allows application of the model in investigating the relative effects of gravity, structure, and posture on regional perfusion.Gravity is shown to have a lesser influence on blood flow distribution than suggested by earlier experimental studies, and by comparison between different model solutions the magnitude of the gravitational flow gradient is predicted. This study clearly demonstrates the significant role that symmetric vascular branching has in determining the distribution of blood flow. The influence of branching geometry is revealed by solution in symmetric, human, and ovine vascular models.

This research develops a detailed, anatomically-based model of the human pulmonary circulatory system from the large scale arterial and venous vessels, to the microcirculatory alveolar-capillary unit. Flow is modelled through these networks enabling structure-function simulations to be conducted to increase our understanding of this complex system.Voronoi meshing is applied in a novel technique to represent the three-dimensional structure of the alveoli, and the corresponding capillary plexus intimately wrapped over the alveolar surface. This technique is used to create the alveolar-capillary structure of a single alveolar sac, closely representing the geometry measured in anatomical studies.A Poiseuille type flow solution technique is implemented within the capillary geometry. The solution procedure incorporates calculations of red and white blood cell transit time frequencies. Novel predictions of regional microcirculatory blood cell transit in the anatomically-realistic alveolar-capillary model compare well with experimental measures.An anatomically-based finite element model of the arterial and venous vessels, down to the level of their accompanying respiratory bronchioles, is created using a combination of imaging and computational algorithms, which includes generation of supernumerary vessels. Large arterial and venous vessels and lobar geometries are derived from multi-detector row x-ray computed tomography (MDCT) scans. From these MDCT vessel end points a volume-filling branching algorithm is used to generate the remaining blood vessels that accompany the airways into the MDCT-derived host volume. An empirically-based algorithm generates supernumerary blood vessels - unaccompanied by airways that branch to supply the closest parenchymal tissue. This new approach produces a model of pulmonary vascular geometry that is far more anatomically-realistic than previous models in the literature.A reduced form of the Navier-Stokes equations are solved within the vascular geometries to yield pressure, radius, and velocity distributions. Inclusion of a gravitational term in the governing equations allows application of the model in investigating the relative effects of gravity, structure, and posture on regional perfusion.Gravity is shown to have a lesser influence on blood flow distribution than suggested by earlier experimental studies, and by comparison between different model solutions the magnitude of the gravitational flow gradient is predicted. This study clearly demonstrates the significant role that symmetric vascular branching has in determining the distribution of blood flow. The influence of branching geometry is revealed by solution in symmetric, human, and ovine vascular models.

This research develops a detailed, anatomically-based model of the human pulmonary circulatory system from the large scale arterial and venous vessels, to the microcirculatory alveolar-capillary unit. Flow is modelled through these networks enabling structure-function simulations to be conducted to increase our understanding of this complex system.Voronoi meshing is applied in a novel technique to represent the three-dimensional structure of the alveoli, and the corresponding capillary plexus intimately wrapped over the alveolar surface. This technique is used to create the alveolar-capillary structure of a single alveolar sac, closely representing the geometry measured in anatomical studies.A Poiseuille type flow solution technique is implemented within the capillary geometry. The solution procedure incorporates calculations of red and white blood cell transit time frequencies. Novel predictions of regional microcirculatory blood cell transit in the anatomically-realistic alveolar-capillary model compare well with experimental measures.An anatomically-based finite element model of the arterial and venous vessels, down to the level of their accompanying respiratory bronchioles, is created using a combination of imaging and computational algorithms, which includes generation of supernumerary vessels. Large arterial and venous vessels and lobar geometries are derived from multi-detector row x-ray computed tomography (MDCT) scans. From these MDCT vessel end points a volume-filling branching algorithm is used to generate the remaining blood vessels that accompany the airways into the MDCT-derived host volume. An empirically-based algorithm generates supernumerary blood vessels - unaccompanied by airways that branch to supply the closest parenchymal tissue. This new approach produces a model of pulmonary vascular geometry that is far more anatomically-realistic than previous models in the literature.A reduced form of the Navier-Stokes equations are solved within the vascular geometries to yield pressure, radius, and velocity distributions. Inclusion of a gravitational term in the governing equations allows application of the model in investigating the relative effects of gravity, structure, and posture on regional perfusion.Gravity is shown to have a lesser influence on blood flow distribution than suggested by earlier experimental studies, and by comparison between different model solutions the magnitude of the gravitational flow gradient is predicted. This study clearly demonstrates the significant role that symmetric vascular branching has in determining the distribution of blood flow. The influence of branching geometry is revealed by solution in symmetric, human, and ovine vascular models.