Thesis (Ph.D.)--Kent State University, 2009. / Title from PDF t.p. (viewed Apr. 15, 2010). Advisor: J. David Glass. Keywords: Suprachiasmatic nucleus; serotonin; nonphotic; arginine vasopressin; hamster. Includes bibliographical references (p. 91-111).

Thesis (Ph. D.)--University of California, San Diego, 1997. / Vita. Includes bibliographical references (leaves 108-111).

Thesis (Ph. D.)--Virginia Commonwealth University, 2010. / Prepared for: Dept. of Human Genetics. Title from title-page of electronic thesis. Includes bibliographical references . Record unavailable until 5/13/2015.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed June 11, 2007). PDF text: viii, 133 p. : ill. UMI publication number: AAT 3239364. Includes bibliographical references. Also available in microfilm and microfiche formats.

No description available.

Circadian rhythms are known to be entrained to the 24 hour day through interactions between endogenous mechanisms and a number exogenous factors that include the light-dark cycle and social interaction. Intensive care patients are thought to be prone to disturbances in their circadian rhythms due to isolation from environmental changes and sensory deprivation as a result of sedation and sleep disturbance. The main aim of this thesis was to determine whether circadian rhythms in critically ill patients are desynchronised from the environment in comparison with those observed in healthy individuals, using urinary aMT6s excretion, plasma melatonin and core body temperature as markers of the endogenous clock. Patients in the Intensive Care Unit (ICU) at the Royal Free Hospital, London, who were stable, inotrope-free, not undergoing haemodiafiltration and with an ICU stay of more than three days were studied. Cosinor analysis of retrospective core body temperature data taken from nursing charts showed that a statistically significant rhythm with a period of 24h was present in 49.5% of the patient days studied. The position of acrophase showed abnormalities within individuals and between individuals. Prospective core body temperature studies confirmed the findings of abnormal circadian rhythmicity but suggested that the rhythms were influenced by fever associated with infection. Urinary 6-sulphatoxymelatonin (aMT6s) excretion data detected rhythmic activity and allowed for the identification of four patterns of excretion rate over 24h: normal rhythmicity, phase shifted rhythms, abnormal with frequent fluctuations and abnormal but arrhythmic. Urinary aMT6s excretion rate measured on two or three occasions at weekly intervals identified changes associated with the normalisation of circadian rhythmicity, namely an increase in the amplitude in some patients and the development of significant diurnal changes from grossly abnormal patterns of urinary aMT6s excretion in others. This trend was seen in patients that were improving clinically, but could not be associated with disease severity as determined by APACHE II scoring. Studies on the circadian rhythms of urine volume and creatinine clearance suggested that renal function in the absence of acute renal failure was still impaired or possibly influenced by treatment medication and could modify urinary aMT6s excretion. Measurements of plasma melatonin identified circadian rhythmicity in 7 out of 9 patients of which 5 were significant by cosinor analysis. These 5 patients had plasma melatonin rhythms that were either normal or phase shifted. The circadian rhythms of plasma cortisol, plasma prolactin and plasma TSH in most ICU patients were also abnormal and showed poor correlations with plasma melatonin. Overall this thesis provides evidence of abnormal circadian rhythmicity in critically ill patients and identifies this group of patients as one that might benefit from light or melatonin treatment to help resynchronise rhythms.

No description available.

Choline is an essential nutrient, in the liver it is a precursor necessary for the synthesis of phosphatidylcholine (PC) and is also required as a methyl donor towards the synthesis of betaine and later regeneration of S-adenomethionine (SAM). Choline deficiency is known to trigger the development of non-alcoholic fatty liver disease and affect mitochondrial homeostasis along with a myriad of methylation related regulatory mechanisms. Because of its importance in maintaining liver lipid and mitochondrial homeostasis, choline metabolism has been well characterized with the exception of its transport. The identification of choline transporters has only been recently discovered and because of this, relatively little is known about their expression and regulation. This study has established that choline transporter like proteins 1-5 (CTL1-5) is an intermediate affinity transport system responsible for ~80% of hepatic choline uptake with a smaller percentage accomplished through the low affinity organic cation transporter 1-3/N1-2 (OCT1-3/N1-2) transporters. SLC44A1 expression and choline incorporation have been shown to follow a 24 hour rhythmic trend suggesting the presence of a circadian regulatory mechanism. This finding is supported by the significant decrease in choline expression and aberrant pattern of choline incorporation discovered among rhythmic deficient BMAL-/- mice and through a bioinformatics analysis which revealed the existence of four REV-ERBα consensus sequences. Hepatic SLC44A1 expression and choline incorporation have also been shown to decrease with the onset of obesity. Choline uptake was also shown to decrease following treatment with the free fatty acid oleate. This work increases our knowledge of hepatic choline transport and demonstrates a link between the circadian rhythm and obesity with the hepatic CTL1 transporter.

Circadian rhythms have been implicated in severity and outcome of infection and disease. Commonly, LPS and bacterial infection have been used to identify the mechanisms behind the difference in immune responses depending on the time of day of the challenge. In this thesis, the colon dwelling nematode parasite Trichuris muris, which elicits a Th2 immune response in resistant mice, was used to identify if circadian rhythms influence infection outcome 3 weeks post infection. C57BL/6 mice infected with 200 eggs of T. muris at ZT0 (7am, lights on) expelled the parasite more efficiently than mice infected at ZT12 (7pm, lights off), which expelled with a delay of several days compared to ZT0 infected mice. Analysis of cell infiltration into the colon during the first days of infection suggested that there was no visible difference in the local immune response. There also were no differences in macrophage and dendritic cell numbers in colon tissue of naïve mice at ZT0 or ZT12. Further experiments examined immunomodulation of the immune response to T. muris by pushing the immune response towards a Th1, by low dose infection, or a Th2 response, by vaccination with excretory/secretory antigen. In both cases any circadian influence was overwritten. Mice infected at ZT0 or ZT12 with only 40 eggs of T. muris were equally susceptible to infection and mice infected at ZT3 10 days after vaccination at ZT0 or ZT12 were equally resistant to infection. Mice food restricted to mid-light phase and infected at ZT0 were not significantly delayed in their worm expulsion or polarised more towards a Th1 immune response compared to ZT0 infected mice fed during the dark phase. Therefore it is unlikely that feeding behaviour during the first days of infection is able to polarise towards a Th1 response and lead to delayed worm expulsion. Transgenic mice were used to dissect the mechanism underlying the delay in worm expulsion in ZT12 infected mice. mPer2::luc mice were used to confirm rhythmic Per2 expression in colon tissue and dendritic cells. Infection of mPer2::luc mice at ZT0 or ZT12 with T. muris showed similar worm expulsion, antibody and cytokine production when infected at ZT0 or ZT12. Bmal1floxLysMcre mice, which lack rhythmic clock gene expression in macrophages and granulocytes, produced a stronger Th2 antibody response in a primary infection at ZT3 than wild-type littermate controls. Newly generated mPer2::lucBmal1floxCD11ccre mice showed the no difference in worm burden and parasite specific antibody production between ZT0 and ZT12 infected mice. Only IL-10 and IL-6 levels were significantly lower in ZT12 infected mPer2::LucBmal1floxCD11ccre mice compared to ZT12 infected wild-type littermates. Confirmation of removal of exon 8 of the Bmal1 gene was not achieved; therefore it is not clear if circadian rhythm in dendritic cells has any impact on the immune response to T. muris or if the mPer2::LucBmal1floxCD11ccre mice and littermate controls both contain circadian rhythm in dendritic cells and therefore cannot be used to identify the role of the dendritic cell clock in the time of day differences in infection outcome. This thesis shows that time of day of the infection impacts on the outcome of infection with Trichuris muris.

Circadian rhythms are the outward manifestation of an internal timing system that measures time in 24-hr increments. The mammalian circadian system is hierarchical, with a pacemaker in the suprachiasmatic nucleus (SCN) synchronizing cell-autonomous oscillators in peripheral tissues. Much of what we know about rhythmicity in peripheral tissues comes from studies monitoring bioluminescence rhythms in PERIOD2::LUCIFERASE knock-in mice. A limitation with this model is that rhythmicity cannot be monitored in specific cells due to widespread reporter expression. To address this shortcoming, we generated a mouse that expresses luciferase from the Dbp locus only after Cre-mediated recombination. I validated this conditional mouse to provide a tool for monitoring circadian rhythms in a tissue/cell-specific manner. Crossing the conditional reporter mice with mice expressing Cre recombinase in various cell types allowed detection of rhythmic bioluminescence in the expected tissues, in vivo and ex vivo, as well as in slice cultures containing the SCN. The phase of bioluminescence rhythms from explants of mouse peripheral tissues indicated that DbpLuc/+ bioluminescence rhythms have an earlier phase than PER2::LUC/+ rhythms. Importantly, we confirmed that editing of the Dbp locus did not alter the period of circadian locomotor activity rhythms and did not alter liver Dbp RNA rhythms. Finally, the reporter mouse allows for monitoring rhythms in specific tissues in ambulatory mice. Thus, this mouse line is useful for studying circadian rhythms in a tissue/cell-type specific manner, which can be used to better monitor phase relationships between tissues at baseline and after environmental perturbations that disrupt circadian rhythms.