Medicine and Health Sciences Commons^™

Conditioned Place Avoidance Is Associated With A Distinct Hippocampal Phenotype, Partly Preserved Pattern Separation, And Reduced Reactive Oxygen Species Production After Stress, D. Parker Kelley, Lucas Albrechet-Souza, Shealan Cruise, Rajani Maiya, Aspasia Destouni, Siva S.V.P. Sakamuri, Alexander Duplooy, Meghan Hibicke, Charles Nichols, Prasad V.G. Katakam, Nicholas W. Gilpin, Joseph Francis

School of Medicine Faculty Publications

Stress is associated with contextual memory deficits, which may mediate avoidance of trauma-associated contexts in posttraumatic stress disorder. These deficits may emerge from impaired pattern separation, the independent representation of similar experiences by the dentate gyrus-Cornu Ammonis 3 (DG-CA3) circuit of the dorsal hippocampus, which allows for appropriate behavioral responses to specific environmental stimuli. Neurogenesis in the DG is controlled by mitochondrial reactive oxygen species (ROS) production, and may contribute to pattern separation. In Experiment 1, we performed RNA sequencing of the dorsal hippocampus 16 days after stress in rats that either develop conditioned place avoidance to a predator urine-associated …

Acute Oxygen-Sensing Via Mitochondria-Generated Temperature Transients In Rat Carotid Body Type I Cells, Ryan J. Rakoczy, Clay M. Schiebrel, Christopher N. Wyatt

Neuroscience, Cell Biology & Physiology Faculty Publications

The Carotid Bodies (CB) are peripheral chemoreceptors that detect changes in arterial oxygenation and, via afferent inputs to the brainstem, correct the pattern of breathing to restore blood gas homeostasis. Herein, preliminary evidence is presented supporting a novel oxygen-sensing hypothesis which suggests CB Type I cell “hypoxic signaling” may in part be mediated by mitochondria-generated thermal transients in TASK-channel-containing microdomains. Distances were measured between antibody-labeled mitochondria and TASK-potassium channels in primary rat CB Type I cells. Sub-micron distance measurements (TASK-1: 0.33 ± 0.04 µm, n = 47 vs TASK-3: 0.32 ± 0.03 µm, n = …

Ethanol And Opioids Do Not Act Synergistically To Depress Excitation In Carotid Body Type I Cells, Ryan J. Rakoczy, Kajal Kamra, Yoon-Jae Yi, Christopher N. Wyatt

Neuroscience, Cell Biology & Physiology Faculty Publications

The combination of opioids and ethanol can synergistically depress breathing and the acute ventilatory response to hypoxia. Multiple studies have shown that the underlying mechanisms for this may involve calcium channel inhibition in central neurons. But we have previously identified opioid receptors in the carotid bodies and shown that their activation inhibits calcium influx into the chemosensitive cells. Given that the carotid bodies contribute to the drive to breathe and underpin the acute hypoxic ventilatory response, we hypothesized that ethanol and opioids may act synergistically in these peripheral sensory organs to further inhibit calcium influx and therefore inhibit ventilation.

Methods …

Microrna-148a Regulates Low-Density Lipoprotein Metabolism By Repressing The (Pro)Renin Receptor, Na Wang, Lishu He, Hui Lin, Lunbo Tan, Yuan Sun, Xiaoying Zhang, A. H. Jan Danser, Hong S. Lu, Yongcheng He, Xifeng Lu

Saha Cardiovascular Research Center Faculty Publications

High plasma LDL cholesterol (LDL-c) concentration is a major risk factor for atherosclerosis. Hepatic LDL receptor (LDLR) regulates LDL metabolism, and thereby plasma LDL-c concentration. Recently, we have identified the (pro)renin receptor [(P)RR] as a novel regulator of LDL metabolism, which regulates LDLR degradation and hence its protein abundance and activity. In silico analysis suggests that the (P)RR is a target of miR-148a. In this study we determined whether miR-148a could regulate LDL metabolism by regulating (P)RR expression in HepG2 and Huh7 cells. We found that miR-148a suppressed (P)RR expression by binding to the 3’-untranslated regions (3’-UTR) of the (P)RR …

On The Origin Of Superoxide Dismutase: An Evolutionary Perspective Of Superoxide-Mediated Redox Signaling., Adam J. Case

Journal Articles: Cellular & Integrative Physiology

The field of free radical biology originated with the discovery of superoxide dismutase (SOD) in 1969. Over the last 5 decades, a plethora of research has been performed in species ranging from bacteria to mammals that has elucidated the molecular reaction, subcellular location, and specific isoforms of SOD. However, while humans have only begun to study this class of enzymes over the past 50 years, it has been estimated that these enzymes have existed for billions of years, and may be some of the original enzymes found in primitive life. As life evolved over this expanse of time, these enzymes …

Optimal Bone Strength And Mineralization Requires The Type 2 Iodothyronine Deiodinase In Osteoblasts, J. H. D. Bassett, Alan Boyde, Peter G. T. Howell, Richard H. Bassett, Thomas M. Galliford, Marta Archanco, Holly Evans, Michelle A. Lawson, Peter Croucher, Donald L. St. Germain, Valerie A. Galton, Graham R. Williams

Dartmouth Scholarship

Hypothyroidism and thyrotoxicosis are each associated with an increased risk of fracture. Although thyroxine (T4) is the predominant circulating thyroid hormone, target cell responses are determined by local intracellular availability of the active hormone 3,5,3'-L-triiodothyronine (T3), which is generated from T4 by the type 2 deiodinase enzyme (D2). To investigate the role of locally produced T3 in bone, we characterized mice deficient in D2 (D2KO) in which the serum T3 level is normal. Bones from adult D2KO mice have reduced toughness and are brittle, displaying an increased susceptibility to fracture. This phenotype is characterized by a 50% reduction in bone …

Corr4a And Vrt325 Do Not Reduce The Inflammatory Response To P. Aeruginosa In Human Cystic Fibrosis Airway Epithelial Cells, Laleh Talebian, Bonita Coutermarsh, Jacqueline Y. Channon, Bruce A. Stanton

Dartmouth Scholarship

P. aeruginosa chronically colonizes the lung in CF patients and elicits a proinflammatory response. Excessive secretion of IL-6 and IL-8 by CF airway cells in response to P. aeruginosa infection in the CF airway is though to contribute to lung injury. Accordingly, the goal of this study was to test the hypothesis that Corr4a and VRT325, investigational compounds that increase ΔF508-CFTR mediated Cl⁻ secretion in human CF airway cells, reduce the pro-inflammatory response to P. aeruginosa.

The Synthetic Triterpenoid Cddo-Methyl Ester Modulates Microglial Activities, Inhibits Tnf Production, And Provides Dopaminergic Neuroprotection, Thi A. Tran, Melissa K. Mccoy, Michael B. Sporn, Malú G. Tansey

Dartmouth Scholarship

Recent animal and human studies implicate chronic activation of microglia in the progressive loss of CNS neurons. The inflammatory mechanisms that have neurotoxic effects and contribute to neurodegeneration need to be elucidated and specifically targeted without interfering with the neuroprotective effects of glial activities. Synthetic triterpenoid analogs of oleanolic acid, such as methyl-2-cyano-3,12-dioxooleana-1,9-dien-28-oate (CDDO-Me, RTA 402) have potent anti-proliferative and differentiating effects on tumor cells, and anti-inflammatory activities on activated macrophages. We hypothesized that CDDO-Me may be able to suppress neurotoxic microglial activities while enhancing those that promote neuronal survival. Therefore, the aims of our study were to identify specific …

A Developmental Cycle Masks Output From The Circadian Oscillator Under Conditions Of Choline Deficiency In Neurospora, Mi Shi, Luis F. Larrondo, Jennifer J. Loros, Jay C. Dunlap

Dartmouth Scholarship

In Neurospora, metabolic oscillators coexist with the circadian transcriptional/translational feedback loop governed by the FRQ (Frequency) and WC (White Collar) proteins. One of these, a choline deficiency oscillator (CDO) observed in chol-1 mutants grown under choline starvation, drives an uncompensated long-period developmental cycle ( approximately 60-120 h). To assess possible contributions of this metabolic oscillator to the circadian system, molecular and physiological rhythms were followed in liquid culture under choline starvation, but these only confirmed that an oscillator with a normal circadian period length can run under choline starvation. This finding suggested that long-period developmental cycles elicited by nutritional stress …

The Flagellum Of Pseudomonas Aeruginosa Is Required For Resistance To Clearance By Surfactant Protein A, Shiping Zhang, Francis X. Mccormack, Roger C. Levesque, George A. O'Toole, Gee W. Lau

Dartmouth Scholarship

Surfactant protein A (SP-A) is an important lung innate immune protein that kills microbial pathogens by opsonization and membrane permeabilization. We investigated the basis of SP-A-mediated pulmonary clearance of Pseudomonas aeruginosa using genetically-engineered SP-A mice and a library of signature-tagged P. aeruginosa mutants. A mutant with an insertion into flgE, the gene that encodes flagellar hook protein, was preferentially cleared by the SP-A(+/+) mice, but survived in the SP-A(-/-) mice. Opsonization by SP-A did not play a role in flgE clearance. However, exposure to SP-A directly permeabilized and killed the flgE mutant, but not the wild-type parental strain. P. aeruginosa …

Cardiac-Specific Elevations In Thyroid Hormone Enhance Contractility And Prevent Pressure Overload-Induced Cardiac Dysfunction, Maria G. Trivieri, Gavin Y. Oudit, Rajan Sah, Benoit-Giles Kerfant, Hui Sun, Anthony O. Gramolini, Yan Pan, Alan D. Wickenden, Walburga Croteau

Dartmouth Scholarship

Thyroid hormone (TH) is critical for cardiac development and heart function. In heart disease, TH metabolism is abnormal, and many biochemical and functional alterations mirror hypothyroidism. Although TH therapy has been advocated for treating heart disease, a clear benefit of TH has yet to be established, possibly because of peripheral actions of TH. To assess the potential efficacy of TH in treating heart disease, type 2 deiodinase (D2), which converts the prohormone thyroxine to active triiodothyronine (T3), was expressed transiently in mouse hearts by using the tetracycline transactivator system. Increased cardiac D2 activity led to elevated cardiac T3 levels and …

A Drosophila Deg/Enac Channel Subunit Is Required For Male Response To Female Pheromones, Heping Lin, Kevin J. Mann, Elena Starostina, Ronald D. Kinser, Claudio W. Pikielny

Dartmouth Scholarship

Odorants and pheromones as well as sweet- and bitter-tasting small molecules are perceived through activation of G protein-coupled chemosensory receptors. In contrast, gustatory detection of salty and sour tastes may involve direct gating of sodium channels of the DEG/ENaC family by sodium and hydrogen ions, respectively. We have found that ppk25, a Drosophila melanogaster gene encoding a DEG/ENaC channel subunit, is expressed at highest levels in the male appendages responsible for gustatory and olfactory detection of female pheromones: the legs, wings, and antennae. Mutations in the ppk25 gene reduce or even abolish male courtship response to females in the dark, …

Hearing Loss And Retarded Cochlear Development In Mice Lacking Type 2 Iodothyronine Deiodinase, Lily Ng, Richard J. Goodyear, Chad A. Woods, Mark J. Schneider

Dartmouth Scholarship

The later stages of cochlear differentiation and the developmental onset of hearing require thyroid hormone. Although thyroid hormone receptors (TRs) are a prerequisite for this process, it is likely that other factors modify TR activity during cochlear development. The mouse cochlea expresses type 2 deiodinase (D2), an enzyme that converts thyroxine, the main form of thyroid hormone in the circulation, into 3,5,3'-triiodothyronine (T3) the major ligand for TRs. Here, we show that D2-deficient mice have circulating thyroid hormone levels that would normally be adequate to allow hearing to develop but they exhibit an auditory phenotype similar to that caused by …

Interpreting Hemoglobin And Water Concentration, Oxygen Saturation, And Scattering Measured In Vivo By Near-Infrared Breast Tomography, Subhadra Srinivasan, Brian W. Pogue, Shudong Jiang, Hamid Dehghani, Christine Kogel, Sandra Soho, Jennifer J. Gibson, Tor D. Tosteson, Steven P. Poplack, Keith D. Paulsen

Dartmouth Scholarship

Near-infrared spectroscopic tomography was used to measure the properties of 24 mammographically normal breasts to quantify whole-breast absorption and scattering spectra and to evaluate which tissue composition characteristics can be determined from these spectra. The absorption spectrum of breast tissue allows quantification of (i) total hemoglobin concentration, (ii) hemoglobin oxygen saturation, and (iii) water concentration, whereas the scattering spectrum provides information about the size and number density of cellular components and structural matrix elements. These property data were tested for correlation to demographic information, including subject age, body mass index, breast size, and radiographic …

Circadian Clock-Specific Roles For The Light Response Protein White Collar-2, Michael A. Collett, Jay C. Dunlap, Jennifer J. Loros

Dartmouth Scholarship

To understand the role of white collar-2 in theNeurospora circadian clock, we examined alleles ofwc-2 thought to encode partially functional proteins. We found that wc-2 allele ER24 contained a conservative mutation in the zinc finger. This mutation results in reduced levels of circadian rhythm-critical clock gene products, frq mRNA and FRQ protein, and in a lengthened period of the circadian clock. In addition, this mutation altered a second canonical property of the clock, temperature compensation: as temperature increased, period length decreased substantially. This temperature compensation defect correlated with a temperature-dependent increase in overall FRQ protein levels, with the …

Differentiation Of Renal Beta-Intercalated Cells To Alpha-Intercalated And Principal Cells In Culture., Geza Fejes-Tóth, Aniko Náray-Fejes-Tóth

Dartmouth Scholarship

The renal collecting duct is a heterogenous epithelium consisting of intercalated cells (ICC) and principal cells (PC). The origin of this cellular heterogeneity is not clear. To test the hypothesis that the two cell types might originate from one another, pure populations of ICC (beta subtype) and PC were isolated by fluorescence-activated cell sorting and grown on permeable supports. After the monolayers reached confluence, the expression of ICC- and PC-specific functions and antigens was monitored. Cultures of sorted beta-ICC, in addition to expressing ICC-specific functions (such as an electrogenic H+ secretion) and antigens, progressively acquired PC functions (amiloride-sensitive Na+ transport …