Abridgement of thesis (doctoral)--Kyoto University, 1977. / "Translation of Doctoral Dissertation in Japanese."

Thesis (Ph. D.)--University of Chicago, Dept. of Neurobiology, Pharmacology and Physiology, August 2003. / Includes bibliographical references. Also available on the Internet.

Activation of a5??1 integrin potentiates L-type calcium current in vascular smooth muscle, which is partly mediated by tyrosine phoshorylation of the a1c channel subunit. Expressed rabbit VSM and neuronal isoforms are also potentiated by a5??1 integrin activation and require dual phosphorylation of a1c by PKA and c-Src. To explore common mechanisms of regulation by a5??1 integrin, whole cell patch clamp experiments were used to investigate the effects of a5??1 integrin antibody on expressed cardiac calcium channels. In HEK cells transfected with a1c, ??2a and a2-d1 subunits alone, currents increased 1.8 ?? 2.0 fold on application of a5??1 antibody. The potentiation was almost completely abolished on the application of PKI, a highly specific Protein Kinase A (PKA) inhibitor. The expressed currents increased 2.0 ?? 2.2 fold on application of PKA activator 8-Br-cAMP, and abolished by PKI. Our results suggest that regulation of L-type calcium channels by a5??1 integrin is a general mechanism shared by VSM, neuronal and cardiac channels. However, in the cardiac isoform, only PKA phosphorylation is involved.

We investigate the creation of linear block codes using Hadamard matrices for block fading channels. The aforementioned codes are very easy to find and have bounded cross correlation spectrum. The optimality is with respect to the metric-spectrum which gives a performance for the codes very close to optimal codes. Also, we can transform these codes according to different characteristics of the channel and can use selective transmission methods.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 128-138). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Chicago, Dept. of Neurobiology, Pharmacology and Physiology, August 2003. / Includes bibliographical references. Also available on the Internet.

CO₂ sequestration aims for the most efficient utilization of reservoir pore volume and for maximizing security of storage. For typical field conditions and injection rates, buoyancy and capillary forces grow dominant over viscous forces within hundreds of meters of the injection wells as the pressure gradient from injection becomes less influential on flow processes. Flow regimes ranging from compact flow to capillary channel flow or secondary accumulation beneath a seal are possible through time as the CO₂ plume travels through the storage reservoir. Here we model the range of possible migration behavior in the capillary channel regime in small-scale domains whose heterogeneity has been resolved at depositional (sub-millimeter) scale. Two types of model domains have been studied in this work: domains with depositional fabric from real, naturally-occurring geologic samples and geostatistically generated synthetic model fabrics. The real domains come from quasi-2D physical geologic samples (peel # 1: ~1 m × 0.5 m sample and peel # 2: ~0.4 m × 0.6 m sample) that are vertically oriented relief peels of fluvial sediment extracted from the Brazos River, Texas. Peel # 1 is oriented perpendicular to dominant depositional flow while peel # 2 is a flow-parallel specimen. The various depositional fabrics represent definite correlation lengths of threshold pressures in the horizontal and vertical directions which can be extracted. High-resolution (~2 million element model) laser scanning of the samples provided detailed topography which is the result of nearly linear corresponding changes in measured grain size (normal distribution) and sorting. We model the basic physics of buoyant migration in heterogeneous domain using commercial software which applies the principle of invasion percolation (IP). The criterion for governing drainage at the pore scale is that the capillary pressure of the fluid needs to be greater than or equal to the threshold pressure of the pore throat it is trying to enter for the interface to advance into the pore. Here we employ the extension of this concept to flows at larger scales, which replaces the pore throat with a volume of rock with a characteristic value of capillary entry pressure. The fluid capillary pressure is proportional to the height of continuous column of the buoyant phase. The effects of (i) threshold pressure range, i.e. difference between the maximum and minimum threshold pressures in the domain; and (ii) the density difference between CO₂ and connate water on capillary channels of CO₂ were studied on the various sedimentologic fabrics. As the rock and fluid properties varied for different model domains, ₂ migration patterns varied between predominantly fingering and predominantly back-filling structures. Sufficiently heterogeneous media (threshold pressures varying by a factor of 10 or more) and media with depositional fabrics having high ratios of horizontal and vertical correlation lengths of capillary entry pressures in the domain yield back-filling pattern, resulting in a significantly large storage capacity. Invasion percolation simulation models give qualitatively similar CO₂ migration patterns compared to full-physics simulators in small-scale but high resolution domains which are sufficiently heterogeneous. On the other hand, we find the invasion percolation simulations predicting disperse capillary fingering pattern in relatively homogeneous media (threshold pressures varying by less than a factor of 10) while the full-physics simulations reveal a very compact CO₂ front in the same media. This stark difference needs to be investigated to understand the governing flow physics in these domains. Fingering flow pattern in the capillary channel regime would clearly result in the estimated storage capacity being much less than the nominal value (the pore volume of the rock) as the rock-fluid contact is minimal. The importance of this work lies in the verification that a relatively simple model (invasion percolation), which runs in a very small fraction of the time required by full-physics simulators, can be used to study buoyant migration in rocks at the micro-scale. Understanding migration behavior at the small-scale can help us approach the problem of upscaling better and hence define the complex plume dynamics at the reservoir scale more realistically. Knowledge of the correlation structure of the sedimentologic fabric (ratio of correlation lengths of threshold pressures in horizontal and vertical directions) and the threshold pressure distribution (permeability distribution) for any given reservoir rock could help evaluate amount of CO₂ that can be stored per unit volume of rock (storage potential) for a reservoir in the migration phase of sequestration. The possibility of predictive ability for expected capillary channel flow patterns kindles the prospect of enabling an engineered storage strategy that drives the behavior toward the desired flow patterns in the subsurface. / text

Transient receptor potential (TRP) channels play important roles in cellular physiology and biology. The present PhD project investigated the functional expression of TRPV and TRPM channels in human preadipocytes and cardiac c-kit+ progenitor cells and their roles in regulating cell proliferation, adipogenic differentiation or migration. In addition, the role of store-operated Ca2+ entry (SOCE) channels in regulating cell proliferation and migration was also studied in human cardiac c-kit+ progenitor cells using multiple approaches including whole-cell patch voltage-clamp, confocal microscope, molecular biology, etc. We found that TRPV2, TRPV4 and TRPM7 channels were abundantly expressed in human preadipocytes. Activation of TRPV2 channels by probenecid caused a long-lasting intracellular Ca2+ transient, while activation of TRPV4 channels by 4-PDD induced Ca2+ oscillations. TRPM7 current was recorded with a Mg2+-free pipette solution, and inhibited by 2-aminoethyl diphenyl borate (2-APB). Silence of TRPV2 or TRPM7, but not TRPV4, with the specific shRNA, reduced cell proliferation via inhibiting cyclin D1, cyclin E, and p-ERK1/2. Individually silencing these three channels decreased adipogenic differentiation by reducing p-Akt kinase. The results indicate that TRPV2, TRPV4 and TRPM7 are involved in adipogenesis, while TRPV2 and TRPM7, but not TRPV4, regulate cell proliferation in human preadipocytes. In second part of the thesis, abundant expression of TRPV2, TRPV4, and TRPM7 channels was demonstrated in human cardiac c-kit+ progenitor cells. Similar to human preadipocytes, probenecid and 4-PDD activated Ca2+ signaling, and TRPM7 current recorded with a Mg2+-free pipette solution was inhibited by 2-APB. Silencing TRPV2 or TRPM7, but not TRPV4, inhibited cell proliferation by arresting cells at G0/G1 phase with a reduced cyclin D, cyclin E, and p-ERK1/2. Cell migration was decreased with silence of TRPV2, TRV4 or TRPM7 via inhibiting p-Akt kinase. The results show that TRPV2, TRPV4 and TRPM7 mediate cell migration, while TRPV2 and TRPM7, but not TRPV4 channels, participate in regulating cell proliferation. In third part of the thesis, we demonstrated that SOCE channels were composed of TRPC1, STIM1 and Orai1 by protein-protein interaction. Silence of TRPC1, STIM1, or Orai1 with specific siRNA reduced Ca2+ influx through SOCE channels, decreased cell proliferation by inhibiting cyclin D1 and cyclin E, and slowed down cell migration via reducing p-Akt kinase. These results suggest that TRPC1, STIM1 and Orai1 are the major components of SOCE channels in human cardiac c-kit+ cells. SOCE channels play an essential role in regulating cell proliferation and migration. Collectively, this PhD project has demonstrated for the first time that 1) TRPV2, TRPV4, and TRPM7 are abundantly expressed in human preadipocytes and cardiac c-kit+ progenitor cells. 2) These TRP channels regulate adipogenic differentiation in preadipocytes and migration in cardiac c-kit+ progenitor cells. 3) TRPV2 and TRPM7, but not TRPV4, are involved in cell proliferation of human preadipocytes and cardiac c-kit+ progenitor cells. 4) TRPC1, STIM1 and Orai1 are interacted to form SOCE channels and regulate cell proliferation and migration in human cardiac c-kit+ cells. 5) All the above physiological roles of TRPV2, TRPV4, TRPM7, and SOCE channels are mediated by cyclin D1, cyclin E, p-ERK1/2, and/or p-Akt. / published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

abstract / Chemistry / Doctoral / Doctor of Philosophy

Autophagy is a major catabolic pathway for maintaining cell homeostasis through degradation and recycle of macromolecules and organelles. Autophagy can be activated under environmental stress conditions, including reactive oxygen species (ROS). TRPM2, a non-selective trans-membrane calcium channel, can be activated by ROS that, in turn, leads to intracellular 〖Ca〗^(2+) increase through 〖Ca〗^(2+) influx. It is well known that ROS regulates autophagy, and vice versa. Yet, the molecular mechanisms underlying the interplay between ROS and autophagy remain elusive. Here we studied the role of TRPM2-mediated 〖Ca〗^(2+) influx in interplay between ROS and autophagy. From our study, we found that ROS activated TRPM2 for 〖Ca〗^(2+) influx via ADPR to inhibit early autophagy induction, which ultimately led to apoptosis in TRPM2 expressing cancer cell lines. On the other hand, ROS induced autophagy, not apoptosis, for cell survival in cancer cell lines which do not express TRPM2, and autophagy inhibition, either by ATG5 knockdown or by treating cells with bafilomycin A1 (an autophagy inhibitor), converted cells to apoptosis upon ROS treatment. In addition, ROS dramatically changed mitochondrial morphology, increased mitochondrial 〖Ca〗^(2+) content, and abolished mitochondrial membrane potential in TRPM2 expressing cells. Moreover, we found that ROS-induced Ca2+ influx via TRPM2 actually activated calmodulin-dependent protein kinase II (CaMKII) to phosphorylate Ser295 on Beclin1. Phosphorylated Beclin1, in turn, decreased the association between Beclin1 and VPS34, but induced the binding between Beclin1 and BCL-2. In summary, our data demonstrated that the TRPM2/〖Ca〗^(2+)/CaMKII/ Beclin1 cascade is the molecular switch between autophagy and apoptosis in response to ROS. Since dysregulation of ROS and autophagy has been associated with a variety of human diseases, e.g. cancer, neurological disorders, heart diseases, and liver diseases, manipulating the TRPM2/〖Ca〗^(2+)/CaMKII/ Beclin1 cascade should provide novel treatment option for these diseases. / published_or_final_version / Physiology / Doctoral / Doctor of Philosophy