bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elucidating the molecular interactions of the L‐nucleotide analogs with the Complex of HIV‐1 Reverse Transcriptase and DNA and the mechanism of drug resistance conferred by the M184V mutation
Authors: Suo Zucai 
Published: April 2020

Emtricitabine (FTC) and lamivudine (3TC) are widely used nucleoside reverse transcriptase inhibitors (NRTIs) in antiretroviral therapy for HIV. They contain an oxathiolane ring with unnatural (−)‐stereochemistry as a mimic of the ribose ring found in natural deoxynucleotides (L‐nucleoside). Treatment with FTC or 3TC primarily selects for the HIV‐1 reverse transcriptase (RT) M184V/I resistance mutants that are characterized by a marked decrease of incorporation of these NRTIs. Pre‐steady state kinetic data and crystal structures of both (−) and (+) oxathiolane analog triphosphates were determined in wild‐type and M184V HIV‐1 RT to elucidate the structural features of RT that recognize these substrates and gain insight into how M184V confers resistance. The pre‐steady state kinetic data reveal that (−)‐FTC‐TP and (−)‐3TC‐TP have higher binding affinities (1/Kd) for WT RT than dCTP however they have a slower rate of incorporation (kp). The crystal structures corroborate these results revealing that the oxathiolane sulfur orients toward the DNA primer terminus and two different triphosphate orientations are observed which would reduce the rate of incorporation. The structure of (+)‐FTC‐TP shows a close match to that of the natural substrate dCTP illustrating how the oxathiolane D‐isomers adopt a triphosphate orientation conducive for incorporation. The M184V mutation displays significantly greater (>200‐fold) Kd for the L isomers and moderately higher (>9‐fold) Kd for the D‐isomers compared to dCTP. The structure of M184V RT illustrates how the mutation repositions the oxathiolane ring, inducing a shift of the triphosphates into a conformation that hinders nucleotide incorporation. This combined study provides a comprehensive kinetic and structural basis for inhibiting WT HIV‐1 RT by the active metabolites of 3TC and FTC and the mechanism of M184V resistance.Support or Funding InformationThis work was supported by a grant from the National Science Foundation (grant number MCB‐1716168).
Putative Sympathetic Oscillator in the Thoracic Spinal Cord of the Bullfrog
Authors: Herrington Brittney , Braun Connor , Wilson Richard 
Published: April 2020

BACKGROUNDCardiorespiratory control is essential for survival of all vertebrates, yet our understanding of the neuronal circuitry involved is rudimentary ‐‐ in part because there is little data beyond mammals to guide us. Neuronal oscillators are discrete neural circuits located within the central nervous system that are capable of generating rhythmic outputs without phasic input. These circuits are found throughout the animal kingdom and are often critical for regulating overt rhythmic behaviours such breathing. Previously, we found three oscillators in the frog brainstem that control ventilation: one for buccal ventilation, two for lung. Three respiratory oscillators have subsequently been found in mammals. Central neuronal oscillators within the sympathetic nervous system of frogs and mammals have also been suspected, but these oscillators have yet to be precisely located.FINDINGSUsing extracellular recording and transection techniques in the frog superfused, isolated brainstem and spinal cord preparation, we discovered a robust, yet previously unreported buccal‐like rhythm in the third spinal nerve (SNIII). Unlike the ventilatory rhythms we normally study, the SNIII rhythm demonstrates poor bilateral synchrony. Our data also suggest that this rhythm is: (a) not coupled to ventilatory rhythms recorded in cranial nerves; (b) has distinct responses to pharmacological stimulation compared to ventilatory rhythms; (c) does not require the brainstem; and (d) persists in a chunk of spinal cord centered around SNIII. These data suggest an additional neuronal oscillator in the frog spinal cord located at the level of SNIII. However, removing the brainstem alters the frequency, increases variability and degrades left‐right synchrony of the rhythm, suggesting brainstem connections are important for normal function.SIGNIFICANCEThe literature has long debated the existence of central neuronal oscillators that modulate sympathetic nervous system activity in vertebrates. We propose that the bursting activity recorded from the SNIII in frog is the output of such an oscillator, discovery of which could prove critical in shaping our current understanding of the function and evolution of the sympathetic nervous system.Support or Funding InformationNSERC and HBI.
The effect of acetylation on isocitrate dehydrogenase 1 regulation
Authors: Strom Alexandra , Widjaja Vinnie , Weeks Joi , Alexander Sati , Pucher Dahra , Nguyen Tin Duc , Luna Lucas , Matteo Diego Avellaneda , Hoang An , Sohl Christal D. 
Published: April 2020

Isocitrate dehydrogenase 1 (IDH1) is a metabolic enzyme responsible for catalysis of isocitrate to α‐ketoglutarate using NADP+ as a cofactor. Cancerous mutations of IDH1 yield the neomorphic conversion of α‐ketoglutarate to D‐2‐hydroxyglutarate, a proposed oncometabolite. Various cancers such as gliomas, glioblastomas, acute myeloid leukemias, and bone cancers, are driven by IDH1 mutations. Although it has been established that IDH1 is an enzymatic driver of disease, more research is necessary to elucidate the molecular mechanisms of its regulation. Post‐translational modifications (PTMs), such as acetylation, serve as effective methods of protein regulation. Here, we hypothesize that acetylation may have a significant impact on IDH1 efficiency. To investigate this, we treated wild type IDH1 with acetyl group donors and generated wild type IDH1 mutants (K81Q, K224Q, K321Q) to mimic acetylation in a physiologically relevant setting. We then employed steady state enzyme kinetics to measure the rate of the normal reaction yielding α‐ketoglutarate. We report that acetylation has a notable effect on IDH1 catalytic efficiency in both the acetylation mimics and acetyl‐treated IDH1. Our data suggests that acetylation may be an essential post‐translational modification for regulating IDH1 catalytic efficiency, thus helping us understand pathways relevant to IDH1 activity.Support or Funding InformationThis work was funded by a Research Scholar Grant, RSG‐19‐075‐01‐TBE, from the American Cancer Society (C.D.S.), National Institutes of Health R00 CA187594 (C.D.S.), U54CA132384 (SDSU) & U54CA132379 (UC San Diego), MARC 5T34GM008303 (SDSU), and IMSD 5R25GM058906 (SDSU), as well as the California Metabolic Research Foundation (SDSU).
Chirality of novel bitopic agonists determine unique pharmacology at the dopamine 2 and 3 receptors
Authors: Adhikari Pramisha , Yano Hideaki , Bonifazi Alessandro , Battiti Francisco O. , Newman Amy Hauck , Shi Lei 
Published: April 2020

The dopamine 2 and 3 receptors (D2R and D3R) are well‐characterized targets for neuropsychiatric disorders. D2R/D3R agonists are used as add‐on therapies for Parkinson’s disease (PD) and have been studied for other motor‐associated disorders. Selectively targeting D3R over D2R is attractive for two reasons: i) restricted tissue distribution of D3R compared to D2R exhibits potential for lesser side‐effects; ii) there is evidence for dominant role of D3R over D2R for neuroprotective and neurorestorative actions of dopaminergic agonists used for the treatment of PD. However, lack of highly selective D3R agonists has made it difficult to separate the D3R vs. D2R physiological effects. Indeed, the development of highly selective D3R agonists has remained a challenge due to their 78% sequence identity in the transmembrane domain. To improve the outlook of D3R agonist‐based medication development, based on a potent D3R‐selective agonist PF592,379, we have designed, synthesized, and pharmacologically characterized bitopic ligands with a secondary pharmacophore tethered to the PF592,379 primary pharmacophore by a linker.Using BRET based functional assays that measure G‐protein activation and β‐arrestin recruitment, we characterized these bitopic ligands at both D3R and D2R. We found that the addition of secondary pharmacophore to the PF592,379 scaffold improved potency at D3R in G‐protein activation with maximal efficacy similar or higher than that of the parent compound. In contrast, the potencies at D3R in recruitment of β‐arrestin remained the same. Some of these compounds also showed modest D3R over D2R selectivity. Interestingly, certain combinations of secondary pharmacophores and linkers resulted in G‐protein signaling bias at either D3R or D2R but not both, resulting in receptor‐selective bias. We also found that given the same ligand structure, chirality can confer subtype selectivity and promote G‐protein bias. Together, our novel bitopic D3R agonists based on PF592,379 scaffold provide novel tools to further probe unique pharmacology at D3R and evaluate the therapeutic potential of targeting D3R vs. D2R for PD.Support or Funding InformationNational Institute on Drug Abuse – Intramural Research Program, National Institutes of Health
The Brain Atlas Glow Up: Utilizing Autofluorescence to Enhance Contrast Between White and Gray Matter
Authors: Shearer Jake , Stabio Maureen , Spitzer Victor 
Published: April 2020

Myelin stained brain atlases are essential tools used to develop an understanding of brain organization and wiring. However, in a medical setting, accurate diagnoses require providers to be able to mentally translate the information gained from atlases to their patient’s MRI data. Myelin stained atlases provide excellent contrast and detail but are routinely constructed with a centimeter or more between images. This poor volumetric resolution poses a challenge when comparing anatomy from myelin stained atlases to MRI datasets as there are often significant gaps of data between subsequent images. Students must learn how to interpolate the missing data between the myelin stained sections. This study was designed to test the hypothesis that an ultrahigh‐resolution, high‐contrast, volumetric atlas of the brain could be re‐constructed from images obtained from blockface milling of whole brains while taking advantage of the autofluorescent properties of myelin to enhance contrast. Using custom‐built 470nm LED panels in conjunction with a 511/20nm bandpass gel filter, we were able to capture images with enhanced contrast between white and gray matter with sufficient detail to identify individual nuclei of the brain. Formalin‐fixed brains were cryopreserved, frozen, and serially imaged at 50μm intervals. At each interval, we imaged the brain using both full color and fluorescent photography, then converted the data into image volumes. The high volumetric resolution of the visual data allows any viewing plane to be generated and directly compared with the equivalent plane in an MRI volume. The volumes were then coregistered and efficiently segmented using the high contrast between white and gray matter to generate full‐color, 3D models of gray matter nuclei and white matter fiber tracts. We also created an accompanying 2D atlas using traditional atlas sections. This atlas will enhance the literacy of MRI anatomy by allowing both students and providers to visualize the information gaps in current myelin stained atlases.Support or Funding InformationUniversity of Colorado: Modern Human Anatomy Program, Touch of Life Technologies, Colorado State Anatomical Board, Inworks
PPARγ Regulates the Inflammatory Response to Ozone‐Induced Lung Injury in Mice
Authors: Malcolm Callum , Smith Ley Cody , Gow Andrew J. , Laskin Debra 
Published: April 2020

Ozone is an urban air pollutant that is highly reactive causing tissue damage and inflammation in the lung. Long term exposure is linked to various health complications and increased mortality due to respiratory diseases. The inflammatory response to ozone is regulated by distinct populations of macrophages, which consist of M1/pro‐inflammatory and M2/anti‐inflammatory subsets; these cells are involved in the acute response to injury and long term resolution of tissue damage, respectively. Previous studies from our laboratory demonstrated that exposure of mice to ozone caused significant downregulation of PPARγ, a transcription factor important in anti‐inflammatory signaling in macrophages, phagocytosis of apoptotic neutrophils (efferocytosis), and the resolution of inflammation. We hypothesized that administration of a pharmacological agonist of PPARγ would reduce ozone‐induced lung injury by altering macrophage phenotype. Female C57BL/6J mice were exposed to air or ozone (0.8 ppm, 3 hr) and treated with vehicle control or rosiglitazone, a PPARγ agonist, daily via intraperitoneal injection beginning 24 hr prior to ozone exposure; mice were euthanized 24, 48, and 72 hr post ozone. Bronchoalveolar lavage fluid (BAL) was collected and analyzed for total protein and phospholipid content. BAL was enriched for alveolar macrophages by gentle lung massage and isolated cells analyzed by flow cytometry and qPCR. Ozone caused increases in total protein and phospholipid content, consistent with lung injury. In rosiglitazone‐treated animals, there was a trend towards reduced BAL protein levels at 48 hr and significant reduction in phospholipid content at 72 hr, suggesting accelerated injury resolution. Flow cytometric analysis showed increases in both pro‐ and anti‐inflammatory macrophages in the lungs of ozone‐exposed animals throughout the time‐course; a trend towards reduced numbers of these cells was observed in rosiglitazone‐treated animals at 72 hr. These results were consistent with reduced mRNA expression of pro‐ and anti‐inflammatory markers Ptgs2 and Arg1, respectively, at 72 hr. mRNA expression of Caveolin 1, a downstream target of PPARγ involved in lipid catabolism, was reduced in response to ozone but maintained in rosiglitazone‐treated animals. Collectively, these results suggest that PPARγ may modulate ozone‐induced lung injury by regulating inflammatory signaling and lipid metabolism in alveolar macrophages.Support or Funding InformationSupported by NIH Grants ES004738, ES005022, ES029254, ES007148, ES030984.
Study Preferences of Generation Z Students Admitted to Medical School
Authors: Addae Jonas , Ettarh Rajunor , Crowley Jason 
Published: April 2020

Persons born between 1995 and 2012 have been described as belonging to Generation Z (iGen), a group that follows on Generation Y, the millennials. Generation Z individuals have been described as being technologically sophisticated, dependent on mobile devices, love the internet, have short attention span, dislike reading printed material, prefer collaborative activities and learning in teams. In an effort to understand how students will adjust to a medical school’s curriculum, we asked the question: To what extent did students exhibit the characteristics of Generation Z just before they started a medical programme?We examined the study habits of students at the School of Medicine at the University of the West Indies, St. Augustine Campus in Trinidad & Tobago. We administered a paper questionnaire during the orientation week to students admitted in August, 2019. The total number of students admitted was 236 of which 223 students belonged to the category of Generation Z.The mean age of the Generation Z group was 19.5 years (range 17 – 24) with 63% females and 37% males. The average time a student took to study before his/her mind began to wander was 48.7 minutes (CI: 44.0, 53.4). There was no significant correlation between age and attention span with r = .061 (p=.388). The number of students who preferred studying alone was 193 (86.5%); those who preferred group study totally or partially (i.e. both alone and in groups) was 30 (13.5%). Most students, 156 (70.0%), preferred studying from textbooks and other printed materials. In contrast, 67 (30.0%) preferred using online materials only or in combination with printed materials. Overall, chi‐square analysis demonstrated a significant difference between student preferences regarding materials used and studying alone or in groups (χ2 (1) = 8.945, p=0.003). Compared to students who preferred group study, students who preferred studying alone significantly preferred printed materials over online material, odds ratio 3.18 [1.45, 6.98]ConclusionThe majority of students admitted into the medical programme fit in the demographic of Generation Z. This study shows that, on admission, the vast majority of the Generation Z students preferred studying alone using printed material, and not in groups or using online material. Thus, the students’ preferred study habits (regarding studying in groups or using online materials) did not fit the expected characteristics of Generation Z. These results are similar to those of previous studies obtained for Millennials who were admitted to medical schools in Kuwait and Canada, and provide guidance to how we may think of adjusting the curriculum to facilitate learning by Generations Z & Y students.
Use of a Water‐soaked Garment, with and without an Electric Fan, to Mitigate Thermal Strain in Older Individuals under Heat Wave Conditions
Authors: Huang Mu , Cramer Matthew N. , Moralez Gilbert , Crandall Craig G. 
Published: April 2020

As average global surface temperatures are projected to rise, and heat waves are expected to increase in frequency, duration, and intensity, exposure to high levels of heat stress will occur with greater regularity. Older individuals are particularly vulnerable to heat stress, evidenced by excess hospitalizations and mortality among individuals aged >60 years. With the continue rise of electricity costs coupled with vulnerable regions that do not have easy access to air conditioning, it is imperative to find alternative cooling strategies that are cost‐effective and accessible for older individuals. The present study evaluated whether wearing a water‐soaked t‐shirt, with and without electric fan use, mitigates thermal and cardiovascular strain under heat wave conditions. Nine healthy older individuals (68 ± 4 years; five females) completed three, 120‐min heat exposures (42.4 ± 0.2°C, 34.2 ± 0.9% relative humidity) on separate occasions while wearing either a dry t‐shirt (CON), a t‐shirt soaked with 500 ml of tap water (WET), or a t‐shirt soaked with 500 ml of tap water while facing an electric fan forcing air at 2.4 ± 0.4 m/s (WET+FAN). Measurements included core and mean skin temperatures, evaporative mass loss, heart rate, and blood pressure. The rise in core temperature was attenuated by ~0.3°C in WET compared to DRY and WET+FAN during the first hour of heat stress (P < 0.01). At 120 min, the rise in core temperature remained attenuated by ~0.2 °C in WET compared to DRY (P=0.0016), while other comparisons were not different. After the 120‐min heat exposure, changes in body mass, which largely reflect evaporation of sweat and moisture trapped in clothing, were greatest in WET+FAN, followed by WET, and then DRY (P < 0.01). However, sweat losses were lowest in WET, followed by DRY, and then WET+FAN (P < 0.01). Heart rate was lower during the first hour in WET vs. DRY, and at 30 min only in WET vs. WET+FAN (P < 0.01). No differences in mean arterial pressure were found (P = 0.51). In conclusion, simply wearing a water‐soaked t‐shirt is an effective heat management strategy to mitigate thermal and cardiovascular strain and lower sweat losses in older people exposed to heat wave conditions. Conversely, the cooling benefits of a water‐soaked t‐shirt are eliminated when used in combination with a fan.Support or Funding InformationFunding: National Institutes of Health (R01GM068865) and Department of Defense – US Army (W81XWH‐15‐1‐0647)
Fatty Acid Amide Hydrolase (FAAH) Inhibition in the Dorsal Periaqueductal Gray Improves Chronic Neuropathic Pain in Rats
Authors: Dean Caron , Hillard Cecilia J. , Hopp Frances A. , Sherman Katherine , Cao Freddy , Hogan Quinn 
Published: April 2020

Neuropathic pain is a critical treatment challenge that accompanies many injury and disease states in which peripheral nerves are damaged. The periaqueductal gray (PAG) in the midbrain is an integrative region that receives sensory input and, in turn, mediates descending sensory inhibition producing antinociception. Increased endocannabinoid concentrations in the dorsal PAG (dPAG) are associated with analgesic effects in neuropathy, and recent data from our lab reveal reduced content of the endocannabinoid anandamide and upregulation of its catabolic enzyme fatty acid amide hydrolase (FAAH) in the dPAG of rats with chronic neuropathic pain, suggesting that maladaptive changes in endocannabinoid signaling in the dPAG could contribute to chronic pain. Therefore, the present study was undertaken to determine the therapeutic potential of FAAH inhibitors in the dPAG for the treatment of chronic neuropathic pain.Male and female rats (230–300 gm) underwent ligation of the tibial and peroneal branches of the sciatic nerve, leaving the sural nerve intact. Guide cannulae were implanted bilaterally targeting the dPAG in a sub‐group of injured rats. Hyperalgesia (sustained lifting/shaking/grooming after plantar pin touch) was tested prior to surgery, and on days 1,3,7,10,18 and 21 post injury. Twothirds of injured rats demonstrated a hyperalgesia response rate >20% to noxious mechanical stimulation of the hindpaw on day 21 and were considered to have developed chronic hyperalgesia. In these rats, hyperalgesia testing was performed prior to, and 3hr after, administration of a FAAH inhibitor (PF‐3845 as either 2mg/kg i.p., or 0.6ng intra‐dPAG) or vehicle on days 21, 22 and 23. Values for hyperalgesia response rate at 21 days were considered as baseline prior to drug administration. Systemic administration of the FAAH inhibitor reduced the hyperalgesia response rate in both male and female rats. In males, a reduction of 50% was maintained after PF‐3845 administered i.p., while female rats demonstrated a similar consistent response with a 40% reduction in hyperalgesia behavior. A progressive decrease in hyperalgesia response rate up to 80% in males and 50% in females was observed after direct administration of PF‐3845 into the dPAG over the 3d test period. However, the analgesia subsided in the 24hr period between drug administrations for both sexes. These data suggest that A) dysregulation of the endocannabinoid system in the dPAG may contribute to chronic neuropathic pain, and B) that inhibition of the catabolic enzyme FAAH in the dPAG could have therapeutic potential by enhancing endocannabinoid signaling.Support or Funding InformationSupported by Merit Review Award # RX002747 from the U.S. Department of Veterans Affairs Rehabilitation, Research and Development Program.