Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [64]-71).

Thesis (Ph. D.)--University of Chicago, 1931. / Lithoprinted. "Private edition, distributed by the University of Chicago libraries, Chicago, Illinois."

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliography.

Thesis (Ph. D.)--University of Chicago, Dept. of Pharmacological and Physiological Sciences, August 1999. / Includes bibliographical references. Also available on the Internet.

Th. 3e cycle--Physico-chim. des matér.--Toulouse--I.N.P., 1982. N°: 122.

L’étude des silicates fondus présente un intérêt dans divers domaines de recherche comme la géologie ou la fabrication des verres avec des applications technologiques importantes telles que par exemple, le confinement des déchets nucléaires. Ces recherches demandent des informations fondamentales sur la structure et la dynamique de ces liquides au niveau microscopique mais l’acquisition des données est très souvent limitée par les températures de fusion élevées des composés étudiés. Notre travail s’est donc basé sur l’utilisation de techniques sans contact afin de s’affranchir de cette difficulté. Dans le cadre de cette thèse, nous nous sommes intéressés à l’étude des propriétés structurales et dynamiques de divers aluminosilicates de calcium (CAS) fondus. Pour cela, nous avons développé un dispositif utilisant la lévitation aérodynamique afin d’effectuer des expériences de diffusion quasi-élastique des neutrons. En combinant ces mesures avec la diffusion inélastique des rayons X, nous avons pu obtenir des résultats sur la dynamique microscopique des CAS à l’état liquide ainsi que dans le régime de surfusion. En particulier, nous avons pu déterminer l’évolution de la viscosité avec la température et les coefficients de diffusion cohérents. Nous avons pu aussi étudier l’évolution de la dynamique de ces verres en fonction de l’augmentation de la quantité de silice dans la composition. En parallèle de nos travaux sur la dynamique, nous avons aussi réalisé des expériences de diffraction de neutrons et de rayons X sur les mêmes compositions et températures afin d’examiner l’ordre atomique local et essayer de le corréler aux propriétés dynamiques observées. / Because of their interesting properties as glass-forming systems, molten silicates play an important role in the geology of the Earth’s crust and mantle and are also of industrial interest for nuclear waste treatment. Research in these areas requires fundamental information on the microscopic structure and dynamics of silicate melts, but such measurements are hampered by the very high melting points of these systems. By extending the technique of aerodynamic levitation to inelastic neutron scattering, and also making use of inelastic synchrotron x-ray scattering, we have obtained results on the microscopic dynamics of silicates both above the melting point and in the supercooled regime. In particular, we have determined the temperature evolution of the viscosity and diffusion coefficient of calcium aluminosilicates, and thereby quantified the decrease in fragility of this glass-forming system as a function of increasing silica content. In parallel with our dynamical studies, we have performed x-ray and neutron diffraction experiments on the same compositions and temperatures in order to examine the local chemical order pertinent to the observed dynamical properties.

The calcination of calcium carbonate in a cement or a lime kiln uses approximately two to four times the theoretical quantity of energy predicted from thermodynamic calculation depending upon the type of the kiln used (1.4 x 10^6 Btu/ton theoretical to 6 x 10^6 Btu/ton actual). The objective of this research was to attempt to reduce the energy required for the calcination by 1. decreasing the calcination temperature of calcium carbonate, and/or 2. increasing the rate of calcination at a specific temperature. Assuming a catalytic enhancement of 20 percent in the industrial applications, an energy savings of 300 million dollars annually in the United States could be reached in the cement and lime industries. Three classes of compounds to date have shown a positive catalytic effect on the calcination of calcium carbonate. These include alkali halides, phospho- and silico-molybdate complexes, and the fused carbonates system.

Les pathologies du nœud sino-atrial provoquent un dysfonctionnement intrinsèque de l'automaticité de ce tissu. La maladie, l'âge ou une anomalie génétique peuvent être la cause d'un dérèglement de la fréquence cardiaque associé à la bradycardie ou la dysfonction atrio-ventriculire. Sans intervention médicale cette pathologie peut conduire à l'arrêt cardiaque. Les pathologies touchant le sinus sont fréquentes, avec une occurrence accrue dans la population âgée. Ainsi, avec le vieillissement des populations occidentales il devient primordial de mieux comprendre les mécanismes générant l'activité automatique du cœur. Les nombreuses études déjà réalisées dans ce domaine ont conduit à une forte controverse entre deux modèles explicatifs des mécanismes pacemaker. Dans ce contexte, j'ai étudié au cours de cette thèse le rôle joué par les canaux calciques Cav1.3 dans la génération de l'activité pacemaker. Afin de distinguer et expliquer le rôle des différents canaux ioniques impliqués dans le mécanisme pacemaker nous avons utilisé une combinaison d'outils pharmacologiques et plusieurs souches de souris transgéniques dont les gènes impliqués dans l'activité pacemaker étaient inactivés ou leur fonction modifiée. Dans le but de constituer un nouveau cadre d'interprétation du mécanisme pacemaker, plusieurs approches expérimentales ont été utilisées. L'activité pacemaker a été étudié dans 3 systèmes au niveau de complexité croissant: des cellules sino-atriales isolées, des tissus sino-atriales entiers et des animaux vivants. Ces différentes approches ont permis d'obtenir des résultats probants et ouvrent la voie à une meilleure compréhension de l'automaticité. En conclusion de cette thèse, nous proposons un cadre intégratif des modèles préexistants, dans lequel les canaux de la membrane cytoplasmique et les libérations de calcium interagissent pour générer un mécanisme pacemaker complexe. / The “sick sinus syndrome” has been defined as an intrinsic dysfunction of the heart Sino-atrial node to perform its pacemaking function. Disease, ageing, or gene defects may cause sinus dysfunctions, ranging from rhythm disturbance to bradycardia, sinus pauses, sinus arrest, and arrhythmias. Without medical intervention these dysfunctions can result in heart block. Sick sinus syndrome is a common pathology, with an increased penetration in the elder population. In the light of the actual increase of elderly in western population, a better comprehension of the mechanism generating spontaneous automaticity appears fundamental. Several investigations have been already carried out in the field of automaticity, leading to a heated controversy between two models of the pacemaker mechanism. In the light this controversy, we investigated the role of Ca2+ channels in generating pacemaker activity. In order to discern and explain the roles of different ion channel actors already implicated in the complex pacemaker machinery we used a combination of pharmacological tools and a variety of transgenic mice. These mice present genetic inactivation or modification in genes involved in pacemaker activity. Furthermore, to provide a new framework for interpreting the pacemaker mechanism, different experimental approaches have been employed. Pacemaker activity was studied in three systems with increasing complexity: isolated sino-atrial cells, intact sino-atrial tissues and in freely-moving animals. These systems led us to consistent conclusions and will pave the way to a better understanding of pacemaking. In particular, we propose an integrative framework for bridging current models in a common mechanism where both, membrane channels and Ca2+ release interact generating a complex pacemaker machinery.

The regulation of calcium (Ca²⁺) was examined during long-term changes of neuronal excitability in the mammalian CNS. The preparations under investigation included the kindling model of epilepsy, a genetic form of epilepsy and long-term potentiation (LTP) of neuronal activity. The study also includes a discussion of the possible roles of a neuron-specific calcium-binding protein (CaBP). The findings are summarized as follows: 1) The distribution of CaBP was determined in cortical areas of the rat using a specific radioimmunoassay. The protein was found to have an unequal distribution in various cortical areas with preponderence in ventral structures. 2) Extending previous studies on the role of CaBP in kindling-induced epilepsy, its decline was correlated to the number of evoked afterdischarges (AD's) during the process of kindling. 3) Marked changes in CaBP levels were also found in the brains of the epileptic strain of mice (El). The hippocampal formation and the dorsal occipital cortex contained significantly lower CaBP than the control (CF-1) strain. The induction of seizures further decreased the levels of CaBP in the El mice. These findings are indicative of a possible genetic impairment of neuronal Ca²⁺ homeostasis in the El strain. 4) The levels of total hippocampal Ca²⁺ and Zn²⁺ were measured by atomic absorption spectrophotometry in control and commissural-kindled animals. While no change was found in the total Ca²⁺ content of the region, hippocampal Zn²⁺ of kindled preparations was found to be significantly elevated. 5) To measure Ca²⁺ -homeostasis, the kinetic analysis of ⁴⁵Ca uptake curves was undertaken in the in vitro hippocampus. This technique was found to be a valid method for assessment of Ca²⁺-regulation in the CNS under both physiological and pathophysiological conditions. The effect of various extracellular Ca²⁺ concentrations, 2,3-dinitrophenol (DNP), calcitonin, nifedipine and 3-isobutyl-1-methylxanthine (IBMX) on ⁴⁵Ca uptake curves was examined in order to identify the two exchangeable Ca²⁺ pools derived through kinetic analysis. 6) The kinetic analysis of ⁴⁵Ca uptake curves revealed that Ca²⁺-regulation of the hippocampus is impaired following amygdala- and commissural kindling. The changes reflect an enhancement of a Ca²⁺ pool that includes free cytosolic Ca²⁺ and a concomitant decrease in the amount of buffered calcium probably as a result in the decrease of hippocampal CaBP levels. 7) A novel form of long-term potentiation (LTP) of neuronal activity in the CA1 region of the hippocampus is described. Perfusion of 100 uM of IBMX in the hippocampal slice preparation induced a long lasting increase in the amplitude of the stratum radiatum evoked population spike and EPSP responses with changes in synaptic efficacy as indicated by the altered input/output relationships. Intracellular correlates of IBMX-induced LTP included lowering of synaptic threshold and enhancement of the rate of rise of the EPSP with no alterations in the passive membrane characteristics of CA1 pyramidal neurons. The fact that IBMX was able to exert its effect even in the presence of the calcium-blocker cation Co²⁺, taken together with the drug's action on hippocampal exchangeable Ca²⁺, raises the possibility that the Ca²⁺ necessary for induction of LTP may be derived from an intraneuronal storage site. These studies indicate the significance of intracellular Ca²⁺ -regulatory mechanisms in long-term changes of neuronal excitability which occur in experimental models of epilepsy and long-term potentiation. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

The sarcoplasmic reticulum (SR) is an intracellular membrane system dedicated to the active regulation of cytosolic calcium in muscle. The opening of Ca²⁺ channels in the SR results in a rapid increase in the myoplasmic Ca²⁺ concentration and the initiation of contraction. Closure of these channels allows the SR to re-accumulate the released Ca²⁺ which results in muscle relaxation. While it is known that a muscle fiber is stimulated to contract by the depolarization of the sarcolemma, it is not understood how this signal is communicated to the SR. The focus of this dissertation is twofold. The first objective is to gain an understanding of the mechanism of Ca²⁺ release from the SR. To this end, three studies have been performed which indicate that Ca²⁺ release is mediated by an oxidation reaction. The second goal is to gain insight into the function of the Ca²⁺ release channel. This is addressed by a fourth study which characterizes the effect of the plant alkaloid, ryanodine on channel operation. The anthraquinones mitoxantrone , doxorubicin, daunorubicin, and rubidazone are shown to be potent stimulators of Ca²⁺ release from SR vesicles. Anthraquinoneinduced Ca²⁺ release is shown to be via a specific interaction with the Ca²⁺ release system of the SR. In addition, a strong interaction between anthraquinone and caffeine binding sites on the Ca²⁺ release channel is observed when monitoring Ca²⁺ fluxes across the SR. It is shown that Ca²⁺ release stimulated by anthraquinones is inhibited by preincubating the quinone with dithionite, a strong reducing agent. Spectrophotometric measurements show that the dithionite treated quinone is in a reduced state. Previous work in this lab has shown that the photooxidizing xanthene dye rose bengal stimulates rapid Ca²⁺ release from skeletal muscle SR vesicles. In this thesis, it is shown that following fusion of vesicles to a bilayer lipid membrane (BLM), Ca²⁺ channel activity is stimulated by nanomolar concentrations of rose bengal in the presence of a broad-spectrum light source. This stimulation is shown to be independent of the Ca²⁺ concentration but is inhibited by μM ruthenium red. The photooxidation of rose bengal is shown to not affect either the K+ or Cl- channels which are present in the SR. Exposure of the Ca²⁺ release channel to 500 nM rose bengal in the presence of light is shown to reverse the modification to the channel induced by μM ryanodine. This apparent displacement of bound ryanodine by nanomolar concentrations of rose bengal is directly observed upon measurement of [³H]ryanodine binding to TSR vesicles. Evidence is presented which suggests that Ca²⁺ release is mediated by singlet oxygen. Micromolar concentrations of the porphyrin meso-Tetra(4-N-methylpyridyl)porphine tetraiodide (TMPyP) is shown to induce the rapid release of Ca²⁺ from skeletal muscle SR vesicles. Porphyrin-induced Ca²⁺ release is stimulated by adenine nucleotides and μM Ca²⁺, and is inhibited by mM Mg²⁺ and μM ruthenium red. High-affinity [³H]ryanodine binding is also enhanced in the presence of the porphyrin. The presence of 1 mM Mg²⁺ in the assay medium sensitizes ryanodine binding to activation by ca²⁺. Porphyrin stimulated single channel activity is also sensitized to activation by Ca²⁺ in the presence of Mg²⁺. Reduction of the porphyrin by dithionite, a strong reducing agent, prior to exposure to the Ca²⁺ release channel inhibited the ability of TMPyP to stimulate Ca²⁺ release. These observations indicate that anthraquinones, rose bengal , and porphyrins induce a stimulation of the Ca²⁺ release protein from skeletal muscle SR by interacting with the ryanodine binding site. In addition, the mechanism of interaction for these compounds appears to be via an oxidation reaction. Nanomolar to micromolar concentrations of ryanodine are shown to alter the gating kinetics of the Ca²⁺ release channel from skeletal muscle SR fused with bilayer lipid membranes. In the presence of asymmetric CsCl, 5 to 40 nM concentrations of ryanodine are shown to activate the channel by increasing the open probability (P₀) without changing the conductance. Statistical analysis of gating kinetics reveal that the open and closed dwell times exhibit bi-exponential distributions that are significantly modified by nM ryanodine. The altered channel gating kinetics seen with low nM ryanodine is reversible and is shown to correlate with the binding kinetics of [³H]ryanodine with its highest affinity site under identical ionic conditions. Ryanodine concentrations between 20 and 50 nM are observed to induce occasional 1/2 conductance fluctuations while ryanodine concentrations greater than 50 nM stabilize the channel into a ½ conductance state which is not reversible. These results are shown to correlate with [³H]ryanodine binding to a second site having lower affinity than the first site. Ryanodine at concentrations greater than 70 μM from the 1/2 to a 1/4 conductance fluctuation , whereas ryanodine concentrations greater than 200 μM cause complete closure of the channel. The concentration of ryanodine required to stabilize either the 1/4 conductance transitions or channel closure do not directly correlate with the measured [³H]ryanodine equilibrium binding constants. However, these results can be explained by considering the association kinetics of ryanodine concentrations greater than 200 nM in the presence of 500 mM CsCl. These results indicate that ryanodine stabilizes four discrete states of the SR release channel and supports the existence of multiple interacting ryanodine binding sites on the channel protein.