117 leaves : ill. ; 29 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1975

xi, 122 leaves : ill. ; 29 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1976

Indiana University-Purdue University Indianapolis (IUPUI) / Alzheimer disease (AD) results, in part, from the excess accumulation of the amyloid-β peptide (Aβ) as neuritic plaques in the brain. The short Aβ peptide is derived from a large transmembrane precursor protein, APP. Two different proteolytic enzymes, BACE1 and the gamma-secretase complex, are responsible for cleaving Aβ peptide from APP through an intricate processing pathway. Dysregulation of APP and BACE1 levels leading to excess Aβ deposition has been implicated in various forms of AD. Thus, a major goal in this dissertation was to discover novel regulatory pathways that control APP and BACE1 expression as a means to identify novel drug targets central to the Aβ-generating process. MicroRNAs (miRNA) are short, non-coding RNAs that act as post-transcriptional regulators of gene expression through specific interactions with target mRNAs. Global analyses predict that over sixty percent of human transcripts contain evolutionarily conserved miRNA target sites. Therefore, the specific hypothesis tested was that miRNA are relevant regulators of APP and BACE1 expression. In this work, several specific miRNA were identified that regulate APP protein expression (miR-101, miR-153 and miR-346) or BACE1 expression (miR-339-5p). These miRNAs mediated their post-transcriptional effects via interactions with specific target sites in the APP and BACE1 transcripts. Importantly, these miRNA also altered secretion of Aβ peptides in primary human fetal brain cultures. Surprisingly, miR-346 stimulated APP expression via target sites in the APP 5’-UTR. The mechanism of this effect appears to involve other RNA-binding proteins that bind to the APP 5’-UTR. Expression analyses demonstrated that these miRNAs are expressed to varying degrees in the human brain. Notably, miR-101, miR-153 and miR-339-5p are dysregulated in the AD brain at various stages of the disease. The work in this dissertation supports the hypothesis that miRNAs are important regulators of APP and BACE1 expression and are capable of altering Aβ homeostasis. Therefore, these miRNA may possibly serve as novel therapeutic targets for AD.

Indiana University-Purdue University Indianapolis (IUPUI) / To cope with the high metabolic demands of the body during pregnancy, the maternal liver adapts by increasing its mass and size. This increase is proportional to the increase in total body weight during the course of gestation. The pregnancy-induced maternal liver growth is a result of both hepatocyte hypertrophy and hyperplasia. Microarray analysis of pregnant maternal livers shows markedly different gene expression profiles when compared to a non-pregnant state. Most interesting was the 2,500-fold up-regulation in the mRNA expression of Ascl1, a transcription factor responsible for the differentiation of neural progenitor cells into various neuronal types, during the second half of pregnancy. Our investigation aimed at (1) characterizing the identity of maternal hepatic Ascl1-expressing cells and (2) tracing the fate of Ascl1-expressing cells in the maternal liver during pregnancy. Timed pregnancies were generated and non-pregnant (NP) and pregnant maternal livers were harvested and analysed. To identify the maternal hepatic Ascl1-expressing cells we used the Ascl1GFP/+ reporter mouse line. NP and gestation day 15 (D15) maternal livers were immunostained for green fluorescent protein (GFP). The result shows that GFP-positive, Ascl1-expressing cells are hepatocyte-like cells, which are present in D15 maternal livers, but absent in NP livers. The Rosa26floxstopLacZ/ floxstopLacZ;Ascl1CreERT2/+ mouse line was used to trace the fate of Ascl1-expressing cells during pregnancy. LacZ staining of gestation day 13 (D13) and 18 (D18) maternal livers demonstrates that D13 hepatic Ascl1-expressing cells (labeled with LacZ) undergo hyperplasia to repopulate a large portion of D18 maternal livers. Furthermore, LacZ and HNF4α co-staining of D13 and D18 maternal livers shows the presence of two populations of LacZ-expressing cells: HNF4α+ population and HNF4α- population. HNF4α+ LacZ-expressing cells represent hepatocyte lineage cells that are derived from Ascl1-expressing cells. We observe that, towards the end of pregnancy, a considerable portion of the maternal liver is comprised of hepatocytes derived from Ascl1-expressing cells. Taken together, our preliminary study suggests that pregnancy induces maternal liver turnover via Ascl1-expressing cells.

Indiana University-Purdue University Indianapolis (IUPUI) / Phytoestrogens that abound in soy products, legumes, and chickpeas can induce biologic responses in animals and humans due to structural similarity to 17β-estradiol. Although experimental studies suggest that phytoestrogen intake may alter the risk of cancer and cardiovascular disease, few epidemiologic studies have investigated this research question. This dissertation investigated the associations of intake of total and individual phytoestrogens and their urinary biomarkers with these chronic conditions using data previously collected from two US national cohort studies (NHANES and PLCO). Utilizing NHANES data with urinary phytoestrogen concentrations and follow-up mortality, Cox proportional hazards regression (HR; 95% CI) were performed to evaluate the association between total cancer, cardiovascular disease, and all-cause mortality and urinary phytoestrogens. After adjustment for confounders, it was found that higher concentrations of lignans were associated with a reduced risk of death from cardiovascular disease (0.48; 0.24-0.97), whereas higher concentrations of isoflavones (2.14; 1.03-4.47) and daidzein (2.05; 1.02-4.11) were associated with an increased risk. A reduction in all-cause mortality was observed for elevated concentrations of lignans (0.65; 0.43-0.96) and enterolactone (0.65; 0.44-0.97). Utilizing PLCO data and dietary phytoestrogens, Cox proportional hazards regression examined the associations between dietary phytoestrogens and the risk of prostate cancer incidence. After adjustment for confounders, a positive association was found between dietary intake of isoflavones (1.58; 1.11-2.24), genistein (1.42; 1.02-1.98), daidzein (1.62; 1.13-2.32), and glycitein (1.53; 1.09-2.15) and the risk of advanced prostate cancer. Conversely, an inverse association existed between dietary intake of genistein and the risk of non-advanced prostate cancer (0.88; 0.78-0.99) and total prostate cancer (0.90; 0.81-1.00). C-reactive protein (CRP) concentration levels rise in response to inflammation and higher levels are a risk factor for some cancers and cardiovascular disease reported in epidemiologic studies. Logistic regression performed on NHANES data evaluated the association between CRP and urinary phytoestrogen concentrations. Higher concentrations of total and individual phytoestrogens were associated with lower concentrations of CRP. In summary, dietary intake of some phytoestrogens significantly modulates prostate cancer risk and cardiovascular disease mortality. It is possible that these associations may be in part mediated through the influence of phytoestrogen intake on circulating levels of C-reactive protein.