A previously completed study in the field of concrete block construction by Ahmed and Feldman (2012) indicated that, on average, the reinforcing bars in non-contact lap splices, where the lapped bars are located in adjacent cells, only develop 71% of the tensile resistance of spliced bars which are in contact. An experimental program was therefore initiated to design and evaluate remedial measures which can potentially increase the tensile resistance of non-contact lap splices to that of contact lap splice of the same lap length. Implementation of the proposed measures in various field situations was also analyzed. Six unique remedial splice details, along with standard contact and unaltered non-contact lap splices were evaluated and compared. The mitigative details included providing additional confinement, installing knock-out webs, placing splice reinforcement between the lapped bars, and combinations of these aforementioned details. Three replicates of each splice detail were constructed for a total of 24 wall splice specimens. Each wall splice specimen was reinforced with No. 15 Grade 400 deformed steel reinforcing bars with 200 mm lap splice lengths at located the midspan. The specimens were tested in a horizontal position under a monotonic, four-point loading geometry. Load and deflection data were collected throughout testing and were subsequently used in an iterative moment-curvature analysis to calculate the maximum tensile resistance of the spliced reinforcement. This was then used to compare the structural performance of each remedial splice detail to the standard contact and non-contact lap splices. The wall splice specimens which contained non-contact lap splices with knock-out webs, s-shaped, and transverse reinforcement in the splice region achieved similar tensile capacities as the wall splice specimens with standard contact lap splices. Industry professionals have indicated that the installation of the remedial measures evaluated in this study would not affect the constructability of masonry assemblages in field situations. The splice detail with knock-out webs confined within the lap splice length was determined to be the most viable procedure as it can be installed to increase the resistance of non-contact lap splices in almost all construction situations. This remedial procedure was able to improve the tensile resistance of the lapped reinforcement by 63% compared to the wall splice specimens with standard non-contact lap splices.

The proprotein convertase subtilisin/kexin type 9, PCSK9, belongs to the proprotein convertase (PC) family. Human mutations in the gene encoding PCSK9 lead to either familial hyper- or hypocholesterolemia, resulting from a gain or loss of function, respectively. Mice lacking PCSK9 are viable and show a 42% decrease in plasma cholesterol levels. The enzyme triggers the degradation of the low density lipoprotein receptor (LDLR) through a partially unknown mechanism. / PCSK9 is very abundant in the liver and intestine during development and adulthood. Hepatocytes have a capacity to reproduce themselves and, upon injury, can repopulate the liver. For a better understanding of the role of PCSK9 in the liver, partial hepatectomy was performed on Pcsk9 +/+, Pcsk9+/- and Pcsk9-/- mice. The absence of PCSK9 resulted in defective liver regeneration, while wild type (WT) and heterozygous mice had no phenotype. Regeneration defects could be prevented by a high cholesterol diet. PCSK9 deficiency, by contributing to maintaining low circulating cholesterol levels may thus hamper liver regeneration. This knowledge is critical for the analysis of future PCSK9 inhibitors expected to be developed in the near future. / Key words. Proprotein convertase subtilisin/kexin 9 (PCSK9), a familial hyper- or hypocholesterolemia, low density lipoprotein receptor, knockout mouse model, partial hepatectomy.

Mammals are well adapted to respond to changes in ambient oxygen concentration (O2) by activating homeostatic physiological and cellular responses which maintain cell function and survival. Although anemia has been associated with increased mortality in a number of clinical settings, surprisingly little is known about how anemia affects tissue PO2 and hypoxia signaling. Because nitric oxide synthases (NOSs) figure prominently in the cellular response to acute hypoxia, we define the effects of NOS deficiency in acute anemia. Unlike wildtype (WT), endothelial NOS (eNOS) and inducible NOS (iNOS) deficient mice, only neuronal NOS (nNOS) deficient mice (nNOS-/-) demonstrated increased mortality during acute anemia. With respect to global tissue O2 delivery, anemia did not increase cardiac output (CO) or reduce systemic vascular resistance (SVR) in nNOS -/- mice. At the cellular level, anemia increased expression of HIF-1α and HIF-responsive mRNA levels (EPO, VEGF, GLUT1, PDK) in the brain of WT, but not nNOS-/- mice. These date suggest that nNOS contributed to cardiovascular and cellular mechanisms which maintain oxygen homeostasis in anemia. To confirm the physiological relevance of these findings in a whole animal model of anemia, we utilized transgenic animals which express a reporter HIF-α(ODD)-luciferase chimeric protein. Using this model, we confirmed that nNOS is essential for anemia-induced increases in HIF-α protein stability in vivo in real-time whole animal images and brain tissue. With respect to the mechanism, nNOS-derived NO is known to affect S-nitrosylation of specific proteins, which may interfere with HIF-α and von Hippal Lindau protein (pVHL) interaction. Utilizing the biotin switch assay, we demonstrated that anemia caused a time-dependent increase in S-nitrosylation of pVHL in brain tissue from WT but not nNOS-/- mice. In addition, anemia also leads to a decrease in S-nitrosoglutathione (GSNO) reductase protein expression, an important enzyme responsible for de-nitrosylation of proteins. The combination of increased nNOS expression and decreased GSNO reductase expression would favor prolonged S-nitrosylation of proteins during anemia. These findings identify nNOS effects on the HIF/pVHL signaling pathway as critically important in the physiological responses to anemia in vivo. By contrast, after exposure to acute hypoxia, nNOS-/- mice survived longer, retained the ability to regulate CO and SVR, and increased brain HIF-α protein levels and HIF-responsive mRNA transcripts. This comparative assessment provided essential mechanistic insight into the unexpected and striking difference between anemia and hypoxia. Understanding the adaptive responses to acute anemia will help to define novel therapeutic strategies for anemic patients.

The purpose of this study was to examine the expression of GABAergic proteins in Fmr1 knockout mice during brain maturation and to assess behavioural changes potentially linked to perturbations in the GABAergic system. Quantitative western blotting of the forebrain revealed that compared to wild-type mice, the GABAA receptor α1, β2, and δ subunits, and the GABA catabolic enzymes GABA transaminase and SSADH were down-regulated during postnatal development, while GAD65 was up-regulated in the adult knockout mouse forebrain. In tests of locomotor activity, the suppressive effect on motor activity of the GABAA β2/3 subunit-selective drug loreclezole was impaired in the mutant mice. In addition, sleep time induced by the GABAA β2/3-selective anaesthetic drug etomidate was decreased in the knockout mice. Our results indicate that disruptions in the GABAergic system in the developing brain may result in behavioural consequences in adults with fragile X syndrome.

Mammals are well adapted to respond to changes in ambient oxygen concentration (O2) by activating homeostatic physiological and cellular responses which maintain cell function and survival. Although anemia has been associated with increased mortality in a number of clinical settings, surprisingly little is known about how anemia affects tissue PO2 and hypoxia signaling. Because nitric oxide synthases (NOSs) figure prominently in the cellular response to acute hypoxia, we define the effects of NOS deficiency in acute anemia. Unlike wildtype (WT), endothelial NOS (eNOS) and inducible NOS (iNOS) deficient mice, only neuronal NOS (nNOS) deficient mice (nNOS-/-) demonstrated increased mortality during acute anemia. With respect to global tissue O2 delivery, anemia did not increase cardiac output (CO) or reduce systemic vascular resistance (SVR) in nNOS -/- mice. At the cellular level, anemia increased expression of HIF-1α and HIF-responsive mRNA levels (EPO, VEGF, GLUT1, PDK) in the brain of WT, but not nNOS-/- mice. These date suggest that nNOS contributed to cardiovascular and cellular mechanisms which maintain oxygen homeostasis in anemia. To confirm the physiological relevance of these findings in a whole animal model of anemia, we utilized transgenic animals which express a reporter HIF-α(ODD)-luciferase chimeric protein. Using this model, we confirmed that nNOS is essential for anemia-induced increases in HIF-α protein stability in vivo in real-time whole animal images and brain tissue. With respect to the mechanism, nNOS-derived NO is known to affect S-nitrosylation of specific proteins, which may interfere with HIF-α and von Hippal Lindau protein (pVHL) interaction. Utilizing the biotin switch assay, we demonstrated that anemia caused a time-dependent increase in S-nitrosylation of pVHL in brain tissue from WT but not nNOS-/- mice. In addition, anemia also leads to a decrease in S-nitrosoglutathione (GSNO) reductase protein expression, an important enzyme responsible for de-nitrosylation of proteins. The combination of increased nNOS expression and decreased GSNO reductase expression would favor prolonged S-nitrosylation of proteins during anemia. These findings identify nNOS effects on the HIF/pVHL signaling pathway as critically important in the physiological responses to anemia in vivo. By contrast, after exposure to acute hypoxia, nNOS-/- mice survived longer, retained the ability to regulate CO and SVR, and increased brain HIF-α protein levels and HIF-responsive mRNA transcripts. This comparative assessment provided essential mechanistic insight into the unexpected and striking difference between anemia and hypoxia. Understanding the adaptive responses to acute anemia will help to define novel therapeutic strategies for anemic patients.

The purpose of this study was to examine the expression of GABAergic proteins in Fmr1 knockout mice during brain maturation and to assess behavioural changes potentially linked to perturbations in the GABAergic system. Quantitative western blotting of the forebrain revealed that compared to wild-type mice, the GABAA receptor α1, β2, and δ subunits, and the GABA catabolic enzymes GABA transaminase and SSADH were down-regulated during postnatal development, while GAD65 was up-regulated in the adult knockout mouse forebrain. In tests of locomotor activity, the suppressive effect on motor activity of the GABAA β2/3 subunit-selective drug loreclezole was impaired in the mutant mice. In addition, sleep time induced by the GABAA β2/3-selective anaesthetic drug etomidate was decreased in the knockout mice. Our results indicate that disruptions in the GABAergic system in the developing brain may result in behavioural consequences in adults with fragile X syndrome.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2008. / Title from first page of PDF file (viewed Feb. 13, 2009). Includes bibliographical references.

Thesis (Ph.D.)--University of Alabama at Birmingham, 2009. / Title from first page of PDF file (viewed on June 8, 2009). Includes bibliographical references.

Dissertation (Ph.D.)--University of South Florida, 2008. / Title from PDF of title page. Document formatted into pages; contains 140 pages. Includes vita. Includes bibliographical references.

Thesis--University of Oklahoma. / Bibliography: leaves 53-55.