Medical Cell Biology Commons^™

Signaling Switches And Bistability Arising From Multisite Phosphorylation In Protein Kinase Cascades., Nick I Markevich, Jan B. Hoek, Boris N. Kholodenko

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Mitogen-activated protein kinase (MAPK) cascades can operate as bistable switches residing in either of two different stable states. MAPK cascades are often embedded in positive feedback loops, which are considered to be a prerequisite for bistable behavior. Here we demonstrate that in the absence of any imposed feedback regulation, bistability and hysteresis can arise solely from a distributive kinetic mechanism of the two-site MAPK phosphorylation and dephosphorylation. Importantly, the reported kinetic properties of the kinase (MEK) and phosphatase (MKP3) of extracellular signal-regulated kinase (ERK) fulfill the essential requirements for generating a bistable switch at a single MAPK cascade level. Likewise, …

Stretch-Induced Calcium Release In Smooth Muscle., Guangju Ji, Robert J Barsotti, Morris E Feldman, Michael I Kotlikoff

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Smooth muscle cells undergo substantial increases in length, passively stretching during increases in intraluminal pressure in vessels and hollow organs. Active contractile responses to counteract increased transmural pressure were first described almost a century ago (Bayliss, 1902) and several mechanisms have been advanced to explain this phenomenon. We report here that elongation of smooth muscle cells results in ryanodine receptor-mediated Ca(2+) release in individual myocytes. Mechanical elongation of isolated, single urinary bladder myocytes to approximately 120% of slack length (DeltaL = 20) evoked Ca(2+) release from intracellular stores in the form of single Ca(2+) sparks and propagated Ca(2+) waves. Ca(2+) …

Vdac-Dependent Permeabilization Of The Outer Mitochondrial Membrane By Superoxide Induces Rapid And Massive Cytochrome C Release., M Madesh, György Hajnóczky

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Enhanced formation of reactive oxygen species (ROS), superoxide (O2*-), and hydrogen peroxide (H2O2) may result in either apoptosis or other forms of cell death. Here, we studied the mechanisms underlying activation of the apoptotic machinery by ROS. Exposure of permeabilized HepG2 cells to O2*- elicited rapid and massive cytochrome c release (CCR), whereas H2O2 failed to induce any release. Both O2*- and H2O2 promoted activation of the mitochondrial permeability transition pore by Ca2+, but Ca2+-dependent pore opening was not required for O2*--induced CCR. Furthermore, O2*- alone evoked CCR without damage of the inner mitochondrial membrane barrier, as mitochondrial membrane potential …

Eliciting The Low-Activity Aldehyde Dehydrogenase Asian Phenotype By An Antisense Mechanism Results In An Aversion To Ethanol., E Garver, Tu Gc, Q N Cao, M Aini, F Zhou, Y Israel

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

A mutation in the gene encoding for the liver mitochondrial aldehyde dehydrogenase (ALDH2-2), present in some Asian populations, lowers or abolishes the activity of this enzyme and results in elevations in blood acetaldehyde upon ethanol consumption, a phenotype that greatly protects against alcohol abuse and alcoholism. We have determined whether the administration of antisense phosphorothioate oligonucleotides (ASOs) can mimic the low-activity ALDH2-2 Asian phenotype. Rat hepatoma cells incubated for 24 h with an antisense oligonucleotide (ASO-9) showed reductions in ALDH2 mRNA levels of 85% and ALDH2 (half-life of 22 h) activity of 55% equivalent to a >90% inhibition in ALDH2 …

Acidification-Induced Sensitization To Thermoradiotherapy In Breast Cancer, Dennis B. Leeper, L T. Komarnicky

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Hyperthermia is an extensively studied cytotoxic agent, with strong radio- and chemosensitizing potential. Recent positive clinical trials combining superficial or deep heating techniques with radiation therapy strongly support a role for hyperthermia as an adjuvant to radiation. Many in vitro and in vivo studies have shown that acute extracellular acidification will compromise fundamental protective cellular responses and enhance tumor response to hyperthermia and chemotherapy.

Breast cancers, like most other tumors, exhibit elevated levels of lactate production that provides a basis for selective acidification. A phase I/II clinical trial is underway to test the hypothesis that hyperglycemia-induced acute acidification will sensitize …

In Vivo Spectroscopic And Imaging Studies Of Photosensitizer In Photodynamic Therapy, Y. Liu, Roger M. Hawk, R. K. Pandey, A. H. Fowler, S. Ramaprasad

Journal of the Arkansas Academy of Science

Photodynamic Therapy (PDT) has emerged as a useful cancer treatment modality which utilizes a tumor localizing dye and activating light to selectively destroy neoplastic tissue. In an effort to understand the newly synthesized photosensitizers, we are studying them in a mouse tumor model grown on the dorsal side of the foot by in vivo magnetic resonance techniques. We have synthesized several photosensitizers which are specifically labeled with fluorine. Several coils appropriate for the tumor study by 19F NMR were designed and constructed for this project. The solenoid coil tunable to both 1Hand 19F nuclei was used to monitor the 19F …

The Influence Of Antimicrobial Use On Bacterial Resistance, James T. Griffith

Walden Dissertations and Doctoral Studies

Antimicrobial resistance is becoming an increasingly serious problem accompanied by relatively few studies examining the relationship between use and resistance. The present study undertakes a twenty year analysis of antimicrobial production and factors affecting antimicrobial use for a particular microorganism (Stp. faecalis)/antimicrobial agent (Cephalothin) combination. The period is inclusive of the market introduction of the agent and considerate of prescribing practices to the present time. The accumulated data reveal that there is indeed a relationship between total drug availability (medicinal, agricultural) and increased antimicrobial resistance. The data also suggest that national (or global) use changes would likely have a long …