Thesis (Ph.D.) in Biochemistry and Molecular Biology--University of Maine, 2006. / Includes vita. Includes bibliographical references (leaves 78-93).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographies. Also available via the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1954. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1954. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

"The induction phenomenon is a useful model for the study of mechanisms which regulate the synthesis of specific enzymes in mammalian tissue, as well as for the role of hormones in this process". The in vivo administration of hormone initiates a chain of reactions which culminate in the increase of protein synthesis. Many hepatic enzymes are thus affected resulting in an increase of their activity. Studies of the giant chromosomes in the salivary glands of Chironomus tentans provided the first indications that the earliest intracellular effects of hormone administration are at the genetic level. Injection of the insect moulting hormone, ecdysone, into last instar larvae of Chironomus tentans results in puff formation at specific loci of the chromosomes shortly after hormone administration. Since puffs are local and reversible alterations of the chromosome, formed at sites which are active in the synthesis of informational RNA, their formation shows a change in activity of particular gene loci in response to ecdysone.

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

Mémoire (M.Sc.)-- Université du Québec à Chicoutimi, 1992. / Ce mémoire a été réalisé à l'UQAC dans le cadre du programme de maîtrise en médecine expérimentale (génétique) extensionné de l'Université Laval à l'UQAC. CaQCU Bibliogr.: f. [1-5]. Document électronique également accessible en format PDF. CaQCU

This abstract sent to supervisor 5/4/12 Tyrosine hydroxylase is the enzyme which controls the ratelimiting step in the synthesis of noradrenaline. In order to discover whether the activity of tyrosine hydroxylase might serve as an indicator of noradrenergic function in the brain, two preparations for the direct measurement of TH activity in rat brain regions by a tritium-release method were employed: synaptosomal suspensions prepared from pinchedoff nerve terminals, and partially solubilised enzyme preparations prepared from frozen homogenates or synaptosomal suspensions and assayed at saturating concentrations of cofactor and tyrosine. There was evidence of an increase in tyrosine hydroxylase activity in hippocampal synaptosomes of rats killed immediately after a mild electrical footshock. Activation of synaptosomal enzyme activity was also found after single doses of clonidine and parachloroamphetamine, and after repeated handling; and single doses of morphine and of yohimbine appeared to lower tyrosine hydroxylase activity. Repeated administration of drugs such as clonidine, desipramine and 2-deoxyglucose, however, did not affect tyrosine hydroxylation rate. A preliminary finding , suggesting differences in synaptosomal tyrosine hydroxylase activity related to experience with different reinforcement schedules (continuous reward vs. partial reward) in a runway experiment, was not substantiated in later experiments; nor was there any difference between the synaptosomal tyrosine hydroxylase activity of naive controls and rats given repeated daily shocks for a week. The saturated TH assay performed on solubilised enzyme was, as predicted, unresponsive to the short term stimulation effects detected with the synaptosomal assay. However, other changes, such as a reduced maximal hydroxylation rate after repeated desipramine administration, and an increased rate several weeks after a course of electrical stimulation of the septal area, were established with the saturated assay. Although the changes in stimulated rats were associated with increased behavioural tolerance to stress, e.g. resistance to extinction of a running response in a runway, other experiments in which the behavioural stress-tolerance was induced by behavioural methods alone showed no accompanying changes in TH activity. Measures of synaptosomal and saturated soluble TH activity appear to constitute independent indicators of noradrenergic function. It seems that synaptosomal tyrosine hydroxylase activity is not, as anticipated, controlled by the firing rate of locus coeruleus neurones; but it may be subject to local regulation in noradrenergic terminals. The results are discussed in the context of theoretical aspects of the regulation of noradrenaline synthesis in the brain, and the mechanisms underlying physiological responses to stress and behavioural tolerance to stress.

Thèse (M.Sc.)--Université Laval, 2004. / Bibliogr.: f. 62-68. Publié aussi en version électronique.