bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of compensatory synaptic plasticity in inactive motor neurons of overwintering bullfrogs, Lithobates catesbeianus
Authors: Zubov Tanya , Santin Joseph M. 
Published: April 2020

Circuits must maintain stable electrophysiological function to produce behaviors. If neurons face a disturbance, such as changes in activity or environmental perturbations, they often compensate by altering synaptic and intrinsic properties to oppose the challenge, a type of plasticity termed “homeostatic plasticity.” Although homeostatic forms of plasticity are thought to maintain stability in the healthy nervous system, abnormal challenges using drugs, sensory deprivation, and injury have generated most of our mechanistic understanding of these processes. This has led to questions of how animals regulate these mechanisms physiologically in vivo. American bullfrogs, Lithobates catesbeianus, normally breathe often, but during months of aquatic overwintering the respiratory network is completely silent, representing a large and natural challenge to neuronal function. We recently showed that respiratory motor neurons use a classic type of synaptic homeostasis that compensates for inactivity during overwintering which regulates motor output from the network after months under water (Santin et al. 2017, eLife). Current models of homeostatic plasticity predict that neurons continuously increase synaptic strength during inactivity, but whether synaptic strength increases in a graded fashion or rises quickly and then plateaus during winter inactivity is unknown. To test this, we measured spontaneous postsynaptic AMPA receptor currents in respiratory motor neurons in brainstem slices that innervate the laryngeal dilator from frogs maintained at ~21°C (n=13) or those that had been cold (~1–2°C) and submerged for 2 (n=21) and 4 weeks (n=20). Consistent with our previous work, we found that cold submergence increased the postsynaptic amplitude and charge transfer (amplitude, p=0.004; charge transfer, p=0.0004; Kruskal‐Wallis test); however, increases in postsynaptic function did not differ between frogs cooled for 2 and 4 weeks (p>0.05 for amplitude and charge transfer; Dunn’s multiple comparisons test). Frequency of postsynaptic events did not differ between warm and cold‐submerged frogs, indicating that cold‐acclimation does not influence spontaneous and/or action potential‐driven transmitter release. Thus, postsynaptic strength increases relatively soon after entry into the overwintering environment and is likely maintained at a single, compensated level over long time scales. In contrast to theoretical work that suggests neurons may continue to compensate until they return to a homeostatic set point, our work shows that the amount of compensation may be tuned to meet future demands of the network (i.e., appropriate breathing) or constrained by limitations imposed by the environment.Support or Funding InformationThis work was funded by start‐up funds from UNC‐Greensboro to JS.
The Problem of Estimating Tissue Perfusion from Observations of Microvascular Flow
Authors: Secomb Timothy W. , Celaya-Alcala Jose T. , Boas David A. , Sakadžić Sava 
Published: April 2020

The perfusion of a tissue region is defined as the blood flow rate to the region divided by its volume. For a whole organ, this definition is unambiguous, but a problem arises for small tissue regions, with many microvessels crossing the boundaries. The total inflow rate is approximately proportional to the surface area of the region. If this inflow rate is used to estimate the perfusion, the result is approximately proportional to the surface‐area‐to‐volume ratio, and yields unrealistically high estimates for small regions. How, then, should tissue perfusion be estimated from observations or simulations of blood flow in small tissue regions? The discrepancy arises because any flow pathway that passes through a small tissue region also contributes to perfusion of regions upstream and/or downstream. Therefore, the flow on that pathway should be only partially attributed to the given region. Here, a method is proposed for estimating perfusion in a region of tissue. The blood flow on any pathway through the region is attributed to the region in proportion to the decline in blood oxygen content that occurs in the region, divided by the overall decline from arterial to venous oxygen content. If the chosen region is representative of the tissue with regard to oxygen consumption rate, then the local perfusion computed by this method is equal to the overall tissue perfusion. Implementation of this method requires simulation of oxygen transport in the microvascular network supplying the region, which can be done efficiently using a Green’s function method. In these simulations, boundary segments are classified as arterioles, capillaries and venules, and outflow oxygen levels in each category are used to define inflow oxygen boundary conditions. When applied to a network from the mouse cortex containing 4908 segments, this method yields estimates of perfusion consistent with whole‐organ values, resolving the discrepancy between microscale and macroscale estimates. Tissue perfusion is closely related to the oxygen extraction ratio, which is a key determinant of tissue oxygen levels. Therefore, the estimation of tissue perfusion is an important step towards realistic assessment of the effects of microvascular network structure and blood flow on tissue oxygenation.Support or Funding InformationSupported by NIH grant HL133362.
Glypican‐1 Plays a Cardiac Protective Effect During Heart Failure Induced by Pressure Overload
Authors: Cannon Marisa , Garcia Roxanne , Dull Randal O. , Carvalho-de-Souza Joao L. , Chignalia Andreia Z. 
Published: April 2020

About 1 in every 4 deaths is due to heart disease. Specifically, heart failure in its different forms impacts about 5.7 million people in the U.S. Hemodynamic pressure overload is a known cause for heart dysfunction and it may culminate in heart failure. Glypican‐1 (Gpc1) is a heparan sulfate proteoglycan that has mechanosensitive properties. Its role on heart function is not well understood but it may play a role on cardiac response to increased pressure. Herein we sought to investigate if deletion of Gpc1 contributes to cardiac dysfunction in a model of heart failure induced by pressure overload (Transverse Aortic Constriction, TAC). CD1 (wild type, WT) and Gpc1 knockout (Gpc1KO) mice were submitted to either a sham or TAC procedure. Heart function was assessed by echocardiography (ECHO) before (baseline), three and five weeks post‐surgery. The parameters analyzed by the ECHO were: stroke volume, cardiac output, left ventricle mass, left ventricle anterior wall during diastole (LVAWd), left ventricle posterior wall during diastole (LVPWd), left ventricle mean wall thickness (WTd), eccentricity, heart rate and ejection fraction. Baseline ejection fraction and heart rate was similar between WT and Gpc1KO. Baseline stroke volume, cardiac output and WTd were increased whereas eccentricity was decreased in Gpc1KO. Gpc1KO showed increased susceptibility to heart failure as evidenced by a faster and steep decrease in ejection fraction when compared to WT. In addition, Gpc1KO uniquely showed decreased stroke volume and cardiac output after 5 weeks of TAC. Left ventricle size was increased and eccentricity was decreased in the same time‐frame for both lines. Taken together, these results indicate that Gpc1 has a protective effect on cardiac function in a model of heart failure caused by pressure overload.Support or Funding InformationDepartment of Anesthesiology, College of Medicine, Tucson
Stimulation of AP evoke release of Ang II in the NTS detected by R‐GECO AT1R sniffer cells
Authors: Shimoura Caroline Gusson , Paundralingga Obed , Farmer George E. , Cunningham J. Thomas 
Published: April 2020

The renin angiotensin system (RAS) signaling in the brain plays an important role in cardiovascular control and body fluid homeostasis. Although systemic angiotensin II (Ang II) can access the brain through circumventricular organs such as the subfornical organ (SFO), organum vaculosum of the lamina terminalis (OVLT) and area postrema (AP), the existence of a brain RAS is still controversial. Our previous studies have used angiotensin sensitive sniffer cells to test whether angiotensin peptides are released from brain slices containing the SFO projections to the median preoptic nucleus. Sniffer cells were produced by transfecting Chinese Hamster Ovary cells with commercially available plasmids for the angiotensin type 1a (AT1a) receptor (Origene Tech.) and R‐GECO (Addgene #32462). These sniffer cells are sensitive to angiotensin II and III but not angiotensin 1–7, bradykinin, or neurotransmitters such as glutamate or acetylcholine. In these studies, we examined another pathway involving the AP and nucleus of tractus solitarius (NTS). The AP is angiotensin sensitive and projects to areas in the central nervous system such as the dorsal motor nucleus of the vagus, ventrolateral medulla, and NTS known to be important areas in autonomic regulation of cardiovascular function. The purpose of this study was to test for the release of angiotensin peptides in the NTS after stimulation of AP. Coronal brainstem slices (300 um) containing both the AP and NTS were prepared from adult male Sprague – Dawley rats that were anesthetized with isoflurane (2–3%). The slices were perfused with oxygenated artificial cerebrospinal fluid (containing containing (in mM): 126 NaCl, 3.0 KCl, 2.0 CaCl2, 2.0 MgSO4, 1.25 NaH2PO4, 26 NaHCO3, 10 and D‐Glucose; 300 mOsm, pH 7.4). Sniffer cells were placed on the NTS and imaged on an Olympus B51WI equipped with epifluorescence using CellSens Dimensions software (Olympus). Sniffer cell images were captured once every second. Changes in fluorescent intensity of sniffer cells in the NTS was determined following electric stimulation of the AP (100Hz, 10ms, 1mA). Electrical stimulation increased fluorescence intensity 134 ± 11%, n=13 of sniffer cells on the NTS with a mean response latency of 4 ± 0.7sec, n=13. Some cells demonstrated spontaneous changes in fluorescence intensity 2±0.1, n=28 that were not observed in cells located outside of the NTS. The results indicate that sniffer cells placed on the NTS demonstrated evidence of spontaneous and evoked release of angiotensin peptides.Support or Funding InformationP01 HL088052
PAWI‐2 Overcomes Tumor Stemness and Drug Resistance in Pancreatic Cancer Stem Cells
Authors: Cheng Jiongjia , Gomez-Galeno Jorge , Cashman John 
Published: April 2020

Today, pancreatic cancer (PC) remains a major health problem in the US and soon will be the second most common cause of mortality due to cancer. However, most of the front‐line PC chemotherapies cause serious side effects and a majority of patients with PC are often resistant to clinical therapies. The fact that cancer stem cells (CSCs) become enriched after anti‐cancer therapy implicates CSCs as key contributors to tumor dormancy, metastasis, and relapse in PC. Given the important role of human pancreatic cancer stem cells (hPCSCs) in PC, development of a novel treatment strategy that targets hPCSCs or their extrinsic and intrinsic regulators could be of great clinical utility to treat PC. Herein, we used a highly validated hPCSCs model (FGβ3 cells) to test a novel compound (PAWI‐2) to target CSCs. In this hPCSC model, integrin αvβ3 expression was shown to be a marker/functional contributor to CSC progression and drug resistance attributed to its ability to trigger anchorage‐independent cell survival and tumor metastasis. Specifically, integrin αvβ3 recruits KRAS and RalB to tumor cell plasma membranes to activate NF‐κB signaling that triggers dysregulated KRAS‐RalB‐NF‐κB pathways. This was shown to be a pharmacological target to reverse CSC‐like properties or re‐sensitize drug resistance (e.g., EGFR inhibitors, erlotinib) of established FGβ3 tumors. Compared to parental FG cells, PAWI‐2 showed greater potency to inhibit cell viability and self‐renewal capacity of FGβ3 cells. PAWI‐2 inhibited dysregulated integrin β3‐KRAS‐RalB‐NF‐κB signaling independent of KRAS and Ral. This is clinically relevant because >90% of KRAS is activated by mutations in PC and RAS or Ral inhibitors have not proven effective clinically. PAWI‐2 targeted downstream of KRAS signaling and was negatively regulated by other feedback mechanisms. This was further shown by genetic knockdown of key regulator and co‐treatment of specific inhibitors. PAWI‐2 overcomes erlotinib resistance in FGβ3 cells with greater potency than bortezomib. In the proposed mechanism of PAWI‐2 action, key regulators link the inhibition of KRAS signaling and cell cycle arrest (G2/M). The great utility and pharmacological potency of PAWI‐2 in FGβ3 cells (that possess stem‐like properties) compared to FG cells provide a basis for further development. PAWI‐2 as an efficient therapeutic to reverse tumor stemness and resensitize CSC tumors to drug inhibition.Support or Funding InformationThis work was supported by Inception Award from California Institute for Regenerative Medicine (CIRM) (DISC1‐10583; J.R. Cashman) and by funds from the Human BioMolecular Research Institute.
Visualizing the Unbalanced World of Domestic Dogs: An Interactive Examination of the Canid Vestibular System
Authors: Smith Christopher M. , Tang Cheuk Y. , Laitman Jeffrey T. 
Published: April 2020

The bony labyrinth (BL) of the petrous contains the organs responsible for balance (vestibular system) and hearing (cochlea). The vestibular system is comprised of three semicircular canals (which detect angular acceleration of the head) and two otolith organs (for detecting linear acceleration and static tilt). Studies in mammals have shown that semicircular canal morphology reflects sensitivity to angular acceleration, particularly canal orientations at right angles to one another (orthogonality). Due to their significant variation in craniofacial form while exhibiting similar locomotion, canids provide an excellent natural experiment to understand the influence of shape on vestibular morphology. This study expands upon our earlier analyses on relationships among BL size, cranial base length and semicircular canal morphology across dog breeds and creates an interactive three‐dimensional (3D) model of the canid cranium and BL to visualize relationships among variables. A portion of the sample is derived from the comprehensive study by Schweizer et al. on canid inner ear metrics (2017). Results show that orthogonality between the anterior and posterior semicircular canals is significantly correlated with BL size and cranial base length, suggesting their intimate association across dog breeds. Small, highly derived breeds, such as the short‐faced pug, had anterior and posterior semicircular canals that deviated the most from orthogonality. Similarly, due to their compressed cranial form, such highly bred domestic dogs may also be expected to exhibit altered vestibular function. Our interactive 3D model will allow visualization of statistically significant relationships among BL size, cranial base length and semicircular canal morphology among the breeds. The model will show predicted correlated change in the bony labyrinth based on cranial dimensions. In addition, the visualization will allow the prediction of intermediate and extreme semicircular canal morphologies by manipulating the dimensions of the model itself. By constructing such a model, we hope to lay the foundation for future research into visualizing the morphological integration of inner ear tissues and cranial architecture.Support or Funding InformationThis research was supported by The Graduate Center, City University of New York through a Graduate Center Fellowship; the New York Consortium in Evolutionary Primatology; and the Center for Anatomy and Functional Morphology, Icahn School of Medicine at Mount Sinai.
Sphingosine Kinase 1 Inhibitor, PF543, Blocks Inflammation and Airway Remodeling in a Murine Model of Allergic Asthma.
Authors: Ha Alison W. , Sudhadevi Tara , Ebenezer David L. , Fu Panfeng , Ackerman Steven J. , Natarajan Viswanathan , Harijith Anantha 
Published: April 2020

Asthma, a heterogeneous airway inflammatory disease, affects more than 300 million people worldwide, presenting a significant health and economic burden. Structural changes in the lung, known as airway remodeling (AWRM), as well as inflammation and airway hyperresponsiveness characterize the complex pathophysiology of severe asthma. Sphinogosine‐1‐phosphate (S1P), a bioactive sphingolipid metabolite, formed by the phosphorylation of sphingosine by either sphingosine kinase 1 or 2 (SPHK1/SPHK2) was found to be elevated in the BAL of patients with asthma. S1P signaling is involved in the pathogenesis of several lung conditions, including asthma, however, its role in the progression of the disease remains unclear.In our acute asthma model, sensitization of wild‐type C57BL/6 mice to Alum + a cocktail of allergens consisting of dust mite (D), Aspergillus (A), and ragweed (R), for 1 week, followed by challenge with DRA two weeks later, displayed an increase in inflammatory and eosinophil response, as well as goblet cell hyperplasia (Periodic acid‐Schiff staining) but no airway remodeling. In the chronic asthma model, mice were sensitized to DRA for 8 weeks, but no separate challenge was done. We observed increased pulmonary inflammation, in the absence of eosinophil response, as well as significant AWRM, as evidenced by increased subepithelial fibrosis (Masson’s trichrome staining) and smooth muscle hypertrophy (anti‐smooth muscle myosin heavy chain II staining). Furthermore, allergen challenged mice also showed increased airway hyper reactivity (AHR), as measured by methacholine challenge test. In the acute model, treatment with a specific SPHK1 inhibitor, PF543 (1 mg/kg), at 3 doses during allergen challenge, attenuated the inflammatory response, including eosinophil recruitment. In the chronic model, PF543 (1mg/kg) was administered twice weekly for three weeks after allergen challenge which reduced subepithelial fibrosis, and goblet cell hyperplasia. Decreased AHR was also observed following PF543 treatment. Together, these data suggest the significance of SPHK1/S1P signaling in the pathogenesis of asthma, as well as the therapeutic potential of PF543 in ameliorating inflammation and airway remodeling in allergic asthma.Support or Funding InformationThis work was supported by NIH/NICHD R01 HD090887 and AHA 18TPA34230095 to AH.
Human Carpal Evolution and its Implications for Hominin Locomotor Ancestry
Authors: Wuthrich Craig 
Published: April 2020

The ancestral locomotor repertoire from which hominin bipedalism emerged remains a subject of frequent debate, with multiple competing hypotheses maintaining support among active researchers. This study contributes to this ongoing debate by reconstructing the morphological and locomotor evolution of hominoids based on patterns of morphometric variation in the capitate, hamate, lunate, and triquetrum among extant and fossil anthropoids, including humans and fossil hominins. Aspects of carpal morphology found to consistently covary with locomotor behavior are used to reconstruct adaptive transitions within the anthropoid clade associated with locomotor behavior. The prevalence of different locomotor behaviors at the origin of nested clades within Hominoidea, including the one we share with Pan, are also estimated.While there is some inconsistency of morphological covariation with function and phylogeny among carpal elements, results are consistent in supporting frequent parallelism during hominoid locomotor evolution. This support is strongest as it applies to suspensory behaviors, with the last common ancestors of both apes and great apes predicted to have remained quite generalized relative to the clades’ extant representatives. The last common ancestor of humans and chimpanzees/bonobos is also estimated to have lacked adaptations in association with knuckle‐walking, providing further support for the hominin clade having descended from a relatively generalized ancestral morphotype that is not well modeled by any of the surviving hominoid lineages.
Optogenetic stimulation of Dbx1 neurons promote increase in sympathetic activity in vivo
Authors: Karlen-Amarante Marlusa , Huff Alyssa , Baertsch Nathan A , Colombari Debora S. A. , Ramirez Jan-Marino 
Published: April 2020

Under resting conditions, breathing is characterized by inspiration and postinspiration. Located in the ventrolateral medulla, the preBötzinger Complex (pre‐BötC) is critical for generating the inspiratory phase of breathing. This microcircuit contains glutamatergic neurons derived from progenitor cells that are characterized by the transcription factor “developing brain homeobox (Dbx1)”, and that are thought to be important for inspiratory rhythmogenesis. Located rostromedial of the preBötC is the so called postinspiratory complex (PiCo), which seems to be critical for the generation of the postinspiratory phase of breathing. Important for generating the postinspiratory phase are glutamateric‐cholinergic PiCo neurons. At resting conditions, sympathetic and parasympathetic activity is modulated by excitatory and inhibitory synaptic inputs from these respiratory networks. It is thought that changes in the respiratory‐sympathetic coupling contribute to imbalances that lead to hypertension, as demonstrated in various animal models of chronic intermittent hypoxia. Here we combine optogenetic and electrophysiological approaches in vivo and in vitro in order to investigate the respiratory‐sympathetic coupling. Spontaneously breathing Dbx1‐ERT2Cre/Ai32 and ChAT‐Cre/Ai32 (ChR2) adult mice were anaesthetized (Urethane 1.5mg/kg), and the ventral surface of their brainstem exposed in order to place an optical fiber bilaterally over the pre‐BötC and/or PiCo, while recording the hypoglossal (HN), cervical vagus (cVN) and cervical sympathetic nerves (cSN). Our preliminary data indicate that continuous light stimulation (10s) of pre‐BötC Dbx1 neurons (~ 9mV, 447nm) significantly increased the respiratory frequency, the amplitude of HN, cSN and cVN in relation to baseline. During the optogenetic stimulation of Dbx1 neurons the respiratory‐sympathetic coupling was enhanced. Using the in vivo approach as well as in vitro horizontal slices we are currently also characterizing the role of PiCo in regulating this coupling under control conditions and following CIH. Our preliminary data suggest that PiCo activity is enhanced following CIH exposure, which also contributes to the regulation of respiratory‐sympathetic coupling. Unraveling how the respiratory microcircuits regulate autonomic control will be critical to understand how CIH leads to increased sympathetic drive and hypertension.Support or Funding InformationFAPESP (2016/23513‐1; 2019/11969‐2), and the NIH: P01 HL090554, R01 HL144801 and R01 HL126523