bluuebunny/crossref_metadata_2025_split huggingface dataset:
Limb blood flow and muscle oxygenation responses to rhythmic exercise below and above critical force
Authors: Hammer Shane M. , Alexander Andrew M. , Didier Kaylin D. , Huckaby Lillie M. , Barstow Thomas J. 
Published: April 2020

This study aimed to determine brachial artery blood flow (Q̇BA) and microvascular oxygen delivery responses to rhythmic exercise above and below critical force (CF; the isometric analog of critical power). We hypothesized that Q̇BA, deoxygenated‐heme (deoxy‐[heme]; an estimate of microvascular fractional oxygen extraction), and total‐heme concentrations (total‐[heme]; an estimate of changes in microvascular hematocrit) would demonstrate physiological maximums above CF despite increases in exercise intensity. 13 healthy subjects performed 1) a 5‐min rhythmic isometric‐handgrip maximal‐effort test (MET) to determine CF and 2) constant target‐force tests above (severe‐intensity; S1 and S2) and below (heavy‐intensity; H1 and H2) CF. CF was 189.3 ± 16.7 N (29.7 ± 1.6 %MVC). At end‐exercise, Q̇BA was greater during S1 (418 ± 147 mL/min) and S2 (403 ± 137 mL/min) than during H1 (287 ± 97 mL/min) and H2 (340 ± 116 mL/min; p < 0.05) but was not different between S1 and S2. Further, Q̇BA for S1 and S2 were not significantly different from the Q̇BA estimated for CF (392 ± 37 mL/min). At end‐exercise, deoxy‐[heme] was not different between S1 (150 ± 50 μM) and S2 (155 ± 57 μM), but was greater during S1 and S2 than during H1 (101 ± 24 μM) and H2 (111 ± 21 μM; p < 0.05). Total‐[heme] was not different between S1 (404 ± 58 μM) and S2 (397 ± 73 μM), but was greater during S1 and S2 than H1 (352 ± 58 μM; p < 0.01) but not H2 (371 ± 57 μM). These data suggest limb blood flow limitations and maximal levels of muscle microvascular oxygen delivery and extraction during exercise above, but not below, CF.End‐exercise brachial artery blood flow (Q̇BA) values. Q̇BA at end‐exercise below (● H1 and ○ H2) and above (▼ S1 and Δ S2) critical force (CF), and Q̇BA predicted at CF by linear regression (♦). * Significantly greater than Q̇BA at end‐exercise during H1 (p < 0.05). ** Significantly greater than Q̇BA at end‐exercise during H2 (p < 0.05). Note no differences among end‐exercise Q̇BA values at (estimated) and above CF, suggesting a maximal response in the severe‐intensity domain.Figure 1Frequency‐domain near‐infrared spectroscopy (FD‐NIRS) measurements of muscle oxygenation during exercise below (● H1 and ○ H2) and above (▼ S1 and Δ S2) critical force (CF). Dashed lines indicate average endexercise values of respective FD‐NIRS signals during the maximal‐effort test (MET). * Significantly different from end‐exercise during H1 and H2 (p < 0.05). ** Significantly greater than total‐[heme] at end‐exercise during H2 (p < 0.05).Figure 2
Characterizing the Functional Role of Tyrosine 381 in the Activity of E. coli Aminopeptidase N (PepN) Through Mutagenesis
Authors: Crawford Patrick , Rivard Ryan , Nelson Nicole , Butnik Kimberley 
Published: April 2020

Aminopeptidase N (PepN) from E. coli is an M1 class peptidase with broad specificity. PepN was over‐expressed, purified, and mechanistically characterized with L‐alanine‐p‐nitroanilide in an effort to understand the role of tyrosine 381. In an effort to characterize the functional roles of binding region components, this tyrosine was mutated to alanine, Y381A‐ PepN, and phenylalanine, Y381F‐ PepN. These mutants included a silent mutation, that is an addition or subtraction of an restriction enzyme site to easily identify successful mutagenesis. Successful mutants were over‐expressed, purified, and mechanistically characterized. Y381A‐PepN exhibited greater than 900‐fold loss of activity (kcat), while Y381F‐PepN maintained comparable activity, when compared to the wild‐type PepN. This suggests that Tyr381 has an essential mechanistic role in the function of PepN beyond the suggested role of hydrogen bond stabilization of substrate and product.Support or Funding InformationThis work was funded by Augustana College New Faculty Research Fund, Augustana College Research Foundation, and Augustana College Edwin Erickson Summer Research Award.Agarose gel showing silent mutation, addition of a NarI restriction site to Y381A‐PepN.Lanes from left to right: wild‐type, Y381A1‐PepN, Y381A2‐PepN. All samples were digested with NarI for 1 hour at 37°C. Y381A1 shows an unsuccessful mutation (lack of alteration to restriction digestion map). Y381A2 shows an successful mutation (an alteration to restriction digestion map). New restriction digest bands due to the silent mutation are below main band.Figure 1
Oxidized Hemoglobin Causes Human Lung Microvascular Endothelial Barrier Dysfunction
Authors: Meegan Jamie E. , Tomasek Toria , Ware Lorraine B. , Bastarache Julie A. 
Published: April 2020

Cell‐free hemoglobin is released into the circulation during conditions in which red blood cell lysis occurs such as hemolytic disorders and sepsis. In septic patients, increased levels of circulating cell‐free hemoglobin are independently associated with mortality and contribute to organ dysfunction, including acute respiratory distress syndrome (ARDS). Furthermore, during inflammatory conditions in which reactive oxygen species are high, cell‐free hemoglobin can be converted to higher oxidation states which enhances its damaging capacity. We previously showed that hemoglobin contributes to tissue edema in an ex vivo perfused human lung and microvascular endothelial barrier dysfunction in vitro; hemoprotein reductants (ascorbate and acetaminophen) protected against this phenomenon. Therefore, we hypothesized that higher oxidation states of hemoglobin are more injurious to the barrier function of lung microvascular endothelium. Utilizing primary human lung microvascular endothelial cells (HLMVEC), we found that stimulation with 0.5 mg/mL ferric (Hb3+; −380.2 Ω, p<0.001 vs. control) but not ferrous (Hb2+; +278.3 Ω, p=0.9893 vs. control) hemoglobin resulted in a drop in transendothelial electrical resistance (Figure
). The barrier‐disrupting effects of Hb3+ were reduced with haptoglobin (binds free hemoglobin; +208.5 Ω, p<0.0001 vs. Hb3+) and hemopexin (binds free heme), but not the iron chelator deferoxamine. The mechanism of Hb3+‐mediated microvascular endothelial barrier dysfunction involved disruption of adherens junction protein VE‐cadherin at cell‐cell borders and rearrangement of the actin cytoskeleton with intercellular gap formation. These data suggest that oxidized cell‐free hemoglobin causes microvascular endothelial barrier dysfunction to a greater degree than its non‐oxidized form.Support or Funding InformationThis work is funded by NIH HL135849, HL103836, and HL094296.Figure 1
Anatomical Variation of High Bilateral Brachial Artery Bifurcation: A Case Report
Authors: Gupta Rohun , Pham Luu , Hsia Charlene , Daboul Rania , Galen Benjamin , Gemechu Jickssa 
Published: April 2020

The brachial artery is a continuation of the axillary artery below the inferior border of the teres major muscle. It commonly bifurcates into the radial and ulnar artery low to the neck of the radius. Previous studies have documented variability for upper limb vasculature (9%–18.5%) and variability of brachial bifurcation in the middle of the arm (3–15%). However, there are a lack of cadaver studies that have discussed the effects of a brachial bifurcation in the proximal third of the arm, close to the teres major muscle. During routine anatomical dissections of 24 donors (11 males and 13 females) at Oakland University William Beaumont School of Medicine, it was found that only one donor (female) had a bilateral brachial artery bifurcation in the proximal third of the arm (4.17%). Both right and left arms were measured to be 21cm long, along with brachial artery bifurcation occurring 3cm from the teres major muscle. The bilateral bifurcation may be explained in terms of embryogenesis where there may be a persistence, unusual path, or obliteration of primitive vessels. The variance in the brachial artery bifurcation, especially in the proximal third of the arm, presents heavy clinical considerations. There is a potential that such bifurcations may affect the course of the median, radial, and ulnar nerves. Such variances may complicate surgeries in the brachial region, percutaneous brachial catheterization, and increase the likelihood of inaccurate readings of angiograms and other relevant radiological techniques. Brachial artery proximal bifurcation may also cause individuals to be vulnerable to laceration, which may result in hematomas. A proximal bifurcation of the brachial artery may affect the anastomosis of the ulnar artery with the superior and inferior ulnar collateral arteries and contribute to the excessive hematoma that was observed on the variant donor. The awareness of this clinically significant variation implicates the need for pre‐operative vessel mapping in order to decrease the possibility of iatrogenic injuriesBifurcation of brachial artery on the left arm.Figure 1Bifurcation of brachial artery on the right hand. The blood was determined to be pre‐mortem, leading to a conclusion of a hematoma.Figure 2
Diminished Expression of Na+/HCO3−cotransporter 1.2a (nbce1.2a) mRNA Accompanies Seawater Acclimation in Atlantic Salmon
Authors: Koltenyuk Victor , Nelson Nastasia , McKay Ian , Lema Sean , McCormick Stephen , Breves Jason 
Published: April 2020

The life history of anadromous Atlantic salmon (Salmo salar) entails an initial freshwater stage that precedes their migration to marine environments. The development of physiological systems that will ultimately support the survival of juvenile salmon upon their entry into marine habitats is termed parr‐smolt transformation. This springtime transformation (smoltification) includes the acquisition of seawater (SW) tolerance. Thus, the ability of smolts to successfully acclimate to SW is attained through the development of branchial pathways for ion‐secretion. In addition, the capacity to rapidly attenuate ion‐absorptive processes upon exposure to SW is a vital aspect of SW tolerance. In the current study, we investigated the branchial gene expression patterns of three Na+/HCO3−cotransporter 1 isoforms (nbce1.1, nbce1.2a, and nbce1.2b) during smoltification and following seawater challenges. Given the proposed roles of Nbce1s in the absorption of environmental Na+ by branchial ionocytes in other teleosts, we hypothesized that nbce1s would be downregulated in salmon undergoing smoltification and/or following SW exposure. In two separate years, we observed springtime increases in branchial Na+/K+‐ATPase activity, Na+/K+/2Cl−‐cotransporter 1 and cystic fibrosis transmembrane regulator 1 expression characteristic of smoltification, whereas there were no seasonal changes in the expression of nbce1 isoforms. On the other hand, we observed diminished nbce1.2a expression within 2 days after the transfer of parr and smolts to SW that remained low throughout the experiment (>2 weeks). Collectively, our results suggest that while there are no clear seasonal nbce1 dynamics during smoltification, the modulation of nbce1.2a expression upon exposure to SW may underlie the attenuation of environmental Na+ uptake.Support or Funding InformationSupported by the National Science Foundation (IOS‐1755131).
Qualitative Assessment of Carbon Nanotube Toxicity to Mouse Liver using Dark‐field Microscopy
Authors: Angtuaco Steven E. , Savenka Alena , Fite Todd , Liu Shijie , Khodakovskaya Mariya , Basnakian Alexei 
Published: April 2020

Broad use of nanomaterials may eventually lead to environmental poisoning, including the contamination of food. However, methods for the assessment of nanomaterial toxicity are not well developed. The goal of the current study was to develop a techniques to measure toxicity of multiwall carbon nanotubes (MWCNTs) in vivo. For this, male CD‐1 mice were fed by oral gavage with a water suspension of MWCNTs at varying doses up to 10 mg/kg/day. Twenty‐four hours later, blood chemistry testing showed elevation of aspartate aminotransferase (AST), a liver injury marker, at the highest used dose. The liver damage was confirmed by the terminal deoxynucleotidyl transferase dUTP nick‐end labeling (TUNEL) assay. Our further analysis included the application of dark‐field microscopy (DFM) for (a) the colocalization between MWCNTs and TUNEL‐positive cells and (b) development of a method to quantify MWCNTs burden in liver tissue. DFM clearly showed some elevation of particulate material in the liver with occasional association with TUNEL‐positive cells. DFM did not seem to allow precise quantification of nanoparticle aggregates due to low sensitivity of DFM at the concentration observed in the liver. However, we discovered that CNT gavage increased the percentage of nuclei colocalized with DF objects by systematically counting the number of liver cell nuclei in contact with dark‐field (DF) objects. TUNEL‐positive nuclei were photographed, analyzed at 100‐fold magnification and sorted by CNT treatment category. The process was repeated for DAPI nuclei to serve as a control. The percentage of nuclei with DF colocalization was recorded per group. Our results indicate that the rate of colocalization between dark‐field objects and nuclei appears to correlate directly with CNT‐gavage treatment. Another important observation, confirmed by an electron microscopy, was that there were many alive TUNEL‐negative cells containing MWCNTs. Overall, our data indicate that the DFM method designed for particle toxicology has only limited potential for measurement of nanoparticle toxicity, and that some mouse liver cells are capable of accumulating MWCNTs without inducing immediate cell death.Support or Funding InformationUAMS/ASPET Pharmacology/Toxicology Summer SURF Program USDA subcontract (Basnakian, PI) VA Merit Review grant (Basnakian, PI) COBRE grant (Hauer‐Jensen, PI)To study the effect of carbon nanotube (CNT) ingestion on mouse liver, we systematically counted the number of liver cell nuclei in contact with dark‐field (DF) objects. We found that CNT gavage increased the percentage of nuclei colocalized with DF objects at 100x. Of a total of 38 TUNEL cells recorded in gavage tissue, 22 were touching a DF‐positive object. Livers were extracted from male CD‐1 mice 72 hours after receiving a CNT gavage of 10mg CNT/kg mouse weight.Figure 1
Effects of Bambara Nut (Vigna subterranean) on Basal and Stimulated Gastric Acid Secretion due to Histamine, Pentagastrin and Carbachol in rats
Authors: Onwuchekwa Chinedu , Bassey Okon , Ajao Oluwatobi Sarah 
Published: April 2020

The seed extracts of V. subterranean (Bambara nuts) have many therapeutic applications in folkloric medicine owing to their effective secondary metabolites such as alkaloids, flavonoids, saponins, resins, and glycosides (Andzouana et al., 2014). The infusions and decoctions of the seeds are used to treat venereal diseases, diarrhoea, cataract, beriberi and polymenorrhea (Brink and Belay, 2006; Basu et al., 2007). The raw seeds are chewed to alleviate nausea and vomiting in pregnant women. V. Subterranea seed extracts have been shown to possess some biological properties such as antioxidant and hepatoprotective (Nyau et al., 2015; Iweala and Elekwa, 2001). In spite of multi‐functional properties of V. subterranea, its gastroprotective effect has not been fully explored. This study was carried out to examine the effects of V. Subterranea on basal and stimulated gastric acid secretion (GAS) in the Wistar rats. Each group of rats consisting of 5 rats (180–210g) was treated with aqueous extract of V. Subterranea (150 mg/kg, 250mg/kg and 400mg/kg) orally for 21 days. The animals were handled in accordance with guide for the care and use of laboratory animals (NIH, 2011). At the last day of the treatment, the rats were fasted for 24 hours, anaesthetized with ketamine. GAS (mEq/l) induced by histamine, carbachol and pentagastrin administration were assessed by the continuous perfusion technique using phenolphthalein as indicator. Data obtained were expressed as the Mean ± SEM) and analyzed using one way Analysis of Variance (ANOVA) and Graph Pad prism 5. The differences in mean were considered significant at p≤ 0.05. The aqueous extract of V. Subterranea significantly decreased (p<0.05) GAS induced by the histamine, carbachol and pentagastrin in a dose‐dependent manner over 80 minutes period in all the treated groups, although at varying rates. The gastroprotective action of V. Subterranea may be multifactorial that may include an anti‐secretory action.Support or Funding InformationWe wish to thank Usmanu Danfodiyo University, Sokoto, Nigeria for their support.Effect of Histamine on BambaraFigure 1Effect of Carbachol on BambaraFigure 2Effect of Pentagastrin on BambaraFigure 3
TRPM5 Activity is Potentiated with Glimepiride and Acts in Tandem with KATP Channels to Stimulate Glucose‐Induced Insulin Secretion
Authors: Philippaert Koenraad , Hubert Matt , Kerselaers Sara , Light Peter E. , Vennekens Rudi 
Published: April 2020

TRPM5 is a calcium‐activated monovalent cation channel expressed in the pancreatic beta‐cells where it is involved in the regulation of glucose‐induced insulin secretion. Screening of a large library of bioactive drug‐like compounds revealed that glimepiride displays TRPM5‐potentiating activity. Glimepiride is a third generation sulfolylurea drug and is used in clinical practice to stimulate insulin secretion in type II diabetic patients. It is an optimized sulfonylurea drug compound with improved pharmacological effects compared to earlier drugs in this class. One of the main advantages of glimepiride is the reduced observation of hypoglycemic events during treatment. The interaction of glimepiride with KATP channels, the bona fide target of sulfonylureas, cannot fully explain the differences in observed effects between glimepiride and earlier sulfonylureas as glyburide and tolbutamide. We used a series of in vitro and in vivo experiments to examine the interaction between glimepiride and TRPM5. We measured the TRPM5 currents evoked by glimepiride in a HEK‐cell overexpression system. In isolated pancreatic islets from WT, Trpm5−/− and KATP functional knockout mice, we measured the changes in intracellular calcium dynamics. Ultimately we observed the effects of glimepiride in vivo. Glimepiride increases TRPM5‐mediated currents in HEK cells. In isolated islets, we observe calcium activity in the presence of glimepiride in a lower concentration range compared to Trpm5−/− islets. Furthermore in islets isolated form KATP pore mutant mice, we observed increased calcium activity in the beta‐cells during application of glimepiride. Ultimately, in Trpm5−/− mice, glimepiride has less antihyperglycemic effects after a glucose injection compared to WT mice, indicating there is an important role for TRPM5 in the signal transduction of glimepiride in the beta‐cells. The action on TRPM5 is downstream of increases in [Ca2+]i, and therefore glucose‐dependent. Our data suggest an explanation for the reduced hypoglycemic effect of glimepiride. Taken together the promiscuity of glimepride leads to a synergetic action on KATP channels and TRPM5 channels to stimulate insulin secretion from pancreatic beta‐cells. This new information confirms the hypothesis that targeting TRPM5 is a valid approach to stimulate insulin secretion and in fact, is unknowingly already widely used.Support or Funding InformationKoenraad Philippaert is a FWO [PEGASUS]2 Marie Skłodowska‐Curie Fellow and received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska‐Curie grant agreement (665501) with the Research Foundation Flanders (FWO).
Computational and Structure‐Based Methods for the Prediction of Resistance Associated Mutations
Authors: Frey Kathleen M. , Segobia David , Boulos Monica 
Published: April 2020

Drug resistance is a major limitation of therapeutic agents used for the treatment of infectious diseases and cancer. For enzyme targets, mutations in drug binding sites often lead to amino acid changes that disrupt key drug‐target interactions. In the clinical setting, these resistance‐associated mutations (RAMs) are responsible for treatment failure. In order to aid drug design efforts, it would be efficient and cost effective to develop computational and structure‐based methods to pre‐evaluate resistance mutations for enzyme drug targets during preclinical design. Our main research objective is to use computational and structure‐based methods to pre‐evaluate RAMs for enzyme drug targets. As proof of concept, we evaluated 2 enzyme targets for this study: HIV reverse transcriptase (RT), an antiretroviral target, and Glutathione S‐transferase Pi (GSTP), an anticancer target. Our computational and structure‐based methods include molecular docking, residue scanning, comparative structure analysis, and molecular dynamics (MD) simulations. Computational predictions were further validated with experimental enzyme inhibition assays. Major results indicate that this approach can predict and elucidate the effects of clinically relevant RAMs. We believe that this approach may be useful in predicting RAMs for inhibitors in development.Support or Funding InformationProvost Seed Grant (FDU) 2019Computer‐based methods for predicting resistance‐associated mutationsFigure 1
Arterial baroreceptors sense blood pressure through decorated aortic claws
Authors: Min Soohong 
Published: April 2020

Mechanosensory neurons across physiological systems sense force using diverse terminal morphologies. Arterial baroreceptors are sensory neurons that monitor blood pressure for real‐time stabilization of cardiovascular output. Various aortic sensory terminals have been described, but those that sense blood pressure are unclear due to a lack of selective genetic tools. Here, we find that all baroreceptor neurons are marked in Piezo2‐ires‐Cre mice, and then use genetic approaches to visualize the architecture of mechanosensory endings. Cre‐guided ablation of vagal and glossopharyngeal PIEZO2 neurons eliminates the baroreceptor reflex, and aortic depressor nerve effects on blood pressure and heart rate. Genetic mapping reveals that PIEZO2 neurons form a distinctive mechanosensory structure: macroscopic claws that surround the aortic arch and exude fine end‐net endings. Other arterial sensory neurons that form flower spray terminals are dispensable for baroreception. Together, these findings provide structural insights into how blood pressure is sensed in the aortic vessel wall.Support or Funding InformationThis work was supported by NIH grants (DP1 AT009497, R01 HL132255, and OT2 OD023848) and, a Faculty Scholars Award from the Howard Hughes Medical Institute to Stephen D. Liberles. Stephen D. Liberles is an investigator of the Howard Hughes Medical Institute.Aortic depressor nerve innervate aortic arch with distinct sensory terminals.Figure 1PIEZO2 neurons form aortic claws surrounding the vessel wall.Figure 2