Cell and Developmental Biology Commons^™

The Effects Of Nesting Environment On Neonatal Hypoxic-Ischemic Injury, Laura Grace Rollins

Graduate Masters Theses

Term neonates with hypoxic-ischemic (HI) injury are at risk for devastating neurological sequelae. The objective of this study is to determine if altering the early environment for maternal care-taking impacts the immediate and long-term sequelae of HI offspring. The Rice-Vannucci model was used to induce HI in postnatal day (PND) 7 Long-Evans pups. Litters were assigned to a closed nest (CN) or normal standard housing (SH) condition. Neurobehavioral development, cognitive ability, and stress response were assessed to establish any benefits of the CN condition. Finally, postmortem brain tissue was analyzed for morphometric markers of injury.

Evaluation Of Higher Plant Virus Resistance Genes In The Green Alga, Chlorella Variabilis Nc64a, During The Early Phase Of Infection With Paramecium Bursaria Chlorella Virus-1, Janet M. Rowe, David D. Dunigan, Guillaume Blanc, James R. Gurnon, Yuannan Xia, James L. Van Etten

David D Dunigan Ph. D.

With growing industrial interest in algae plus their critical roles in aquatic systems, the need to understand the effects of algal pathogens is increasing. We examined a model algal host–virus system, Chlorella variabilis NC64A and virus, PBCV-1. C. variabilis encodes 375 homologs to genes involved in RNA silencing and in response to virus infection in higher plants. Illumina RNA-Seq data showed that 325 of these homologs were expressed in healthy and early PBCV-1 infected (≤60 min) cells. For each of the RNA silencing genes to which homologs were found, mRNA transcripts were detected in healthy and infected cells. C. variabilis, …

Welcome To The Journal Of Evolution And Health, Aaron Blaisdell, Paul Jaminet, David C. Pendergrass

Aaron P Blaisdell

Welcome to the first issue of the Journal of Evolution and Health! The Journal of Evolution and Health is the peer-reviewed, open-access journal of the Ancestral Health Society, a community of scientists, healthcare professionals, and laypersons who collaborate to understand health challenges from an evolutionary perspective.

Small Molecule Antagonists Of Melanopsin-Mediated Phototransduction, Kenneth A. Jones, Megumi Hatori, Ludovic S. Mure, Jayne R. Bramley, Roman Artymyshyn, Sang-Phyo Hong, Mohammad Marzabadi, Huailing Zhong, Jeffrey Sprouse, Quansheng Zhu, Andrew T. E. Hartwick, Patricia J. Sollars, Gary E. Pickard, Satchidananda Panda

School of Veterinary and Biomedical Sciences: Faculty Publications

Melanopsin, expressed in a subset of retinal ganglion cells, mediates behavioral adaptation to ambient light and other non-image forming photic responses. This has raised the possibility that pharmacological manipulation of melanopsin can modulate several CNS responses including photophobia, sleep, circadian rhythms and neuroendocrine function. Here we describe the identification of a potent synthetic melanopsin antagonist with in vivo activity. Novel sulfonamide compounds inhibiting melanopsin (opsinamides) compete with retinal binding to melanopsin and inhibit its function without affecting rod/cone mediated responses. In vivo administration of opsinamides to mice specifically and reversibly modified melanopsin-dependent light responses including the pupillary light reflex and …

Synthesis And Antiproliferative Activities Of Quebecol And Its Analogs, Kasiviswanadharaju Pericherla, Amir Nasrolahi Shirazi, V. Kameshwara Rao, Rakesh Tiwari, Nicholas Dasilva, Kellen Mccaffrey, Yousef A. Beni, Antonio González- Sarrías, Navindra P. Seeram, Keykavous Parang, Anil Kumar

Pharmacy Faculty Articles and Research

Simple and efficient synthesis of quebecol and a number of its analogs was accomplished in five steps. The synthesized compounds were evaluated for antiproliferative activities against human cervix adenocarcinoma (HeLa), human ovarian carcinoma (SK-OV-3), human colon carcinoma (HT-29), and human breast adenocarcinoma (MCF-7) cancer cell lines. Among all the compounds, 7c, 7d, 7f, and 8f exhibited antiproliferative activities against four tested cell lines with inhibition over 80% at 75 mu M after 72 h, whereas, compound 7b and 7g were more selective towards MCF-7 cell line. The IC50 values for compounds 7c, 7d, and 7f were 85.1 mu M, 78.7 …

Osmotic Stress, Not Aldose Reductase Activity, Directly Induces Growth Factors And Mapk Signaling Changes During Sugar Cataract Formation, Peng Zhang, Kuiyi Xing, James Randazzo, Karen Blessing, Marjorie F. Lou, Peter Kador

School of Veterinary and Biomedical Sciences: Faculty Publications

In sugar cataract formation in rats, aldose reductase (AR) actitvity is not only linked to lenticular sorbitol (diabetic) or galactitol (galactosemic) formation but also to signal transduction changes, cytotoxic signals and activation of apoptosis. Using both in vitro and in vivo techniques, the interrelationship between AR activity, polyol (sorbitol and galactitol) formation, osmotic stress, growth factor induction, and cell signaling changes have been investigated. For in vitro studies, lenses from Sprague Dawley rats were cultured for up to 48 hrs in TC-199-bicarbonate media containing either 30 mM fructose (control), or 30 mM glucose or galctose with/without the aldose reductase inhibitors …

Modulation Of Bax/Bak Dependent Apoptosis By Sirtuin 3 And Mitochondrial Permeability Transition By Sirtuin 4, Manish Verma

Graduate School of Biomedical Sciences Theses and Dissertations

Mitochondria are dynamic organelles that regulate a myriad of cellular functions, including energy production and metabolic regulation. Mitochondria are also a critical regulator of cell death signaling cascades modulating both apoptotic and necrotic cell death. However, what determines which cell death pathway is activated is still unclear. The mitochondrial/intrinsic pathway of apoptosis is dependent on the activation of pro-apoptotic proteins, Bax and Bak, which induce mitochondrial outer membrane permeabilization (MOMP). Once the integrity of outer mitochondrial membrane (OMM) is compromised, pro-apoptotic intermembrane space proteins like cytochrome c, Smac/Diablo, Omi/HtrA2 and AIF are released into the cytoplasm, which activates the post-mitochondrial …

T-Cell Treatments For Solid And Hematological Tumors, Drew C. Deniger

Dissertations & Theses (Open Access)

Cell-based therapies have demonstrated potency and efficacy as cancer treatment modalities. T cells can be dichotomized by their T cell receptor (TCR) complexes where alpha/beta T cells (95% of T cells) and gamma/delta T cells (+T cells proliferated to clinically significant numbers and ROR1⁺ tumor cells were effectively targeted and killed by both ROR1-specific CAR⁺ T cell populations, although ROR1RCD137 were superior to ROR1RCD28 in clearance of leukemia xenografts in vivo. The second specific aim focused on generating bi-specific CD19-specific CAR⁺ gamma/delta T cells with polyclonal TCRgamma/delta repertoire on CD19⁺ artificial antigen presenting cells (aAPC). …

Oncogenic Transformation Of Mammary Epithelial Cells By Transforming Growth Factor Beta Independent Of Mammary Stem Cell Regulation, Karen A. Dunphy, Jae-Hong Seo, Daniel J. Kim, Amy L. Roberts, James Direnzo, Amanda Balboni

Dartmouth Scholarship

BackgroundTransforming growth factor beta (TGFβ) is transiently increased in the mammary gland during involution and by radiation. While TGFβ normally has a tumour suppressor role, prolonged exposure to TGFβ can induce an oncogenic epithelial to mesenchymal transition (EMT) program in permissive cells and initiate the generation of cancer stem cells. Our objective is to mimic the transient exposure to TGFβ during involution to determine the persistent effects on premalignant mammary epithelium.

Heterogeneous Nuclear Ribonucleoprotein K Supports Vesicular Stomatitis Virus Replication By Regulating Cell Survival And Cellular Gene Expression, Phat X. Dinh, Anshuman Das, Rodrigo Franco, Asit K. Pattnaik

School of Veterinary and Biomedical Sciences: Faculty Publications

The heterogeneous nuclear ribonucleoprotein K (hnRNP K) is a member of the family of hnRNPs and was recently shown in a genome-wide small interfering RNA (siRNA) screen to support vesicular stomatitis virus (VSV) growth. To decipher the role of hnRNP K in VSV infection, we conducted studies which suggest that the protein is required for VSV spreading. Virus binding to cells, entry, and nucleocapsid uncoating steps were not adversely affected in the absence of hnRNP K, whereas viral genome transcription and replication were reduced slightly. These results indicate that hnRNP K is likely involved in virus assembly and/or release from …

Truncation Of Type Iv Pilin Induces Mucoidy In Pseudomonas Aeruginosa Strain Pao579, T. Ryan Withers, F. Heath Damron, Yeshi Yin, Hongwei D. Yu

Biochemistry and Microbiology

Pseudomonas aeruginosa is a Gram negative, opportunistic pathogen that uses the overproduction of alginate, a surface polysaccharide, to form biofilms in vivo. Overproduction of alginate, also known as mucoidy, affords the bacterium protection from the host's defenses and facilitates the establishment of chronic lung infections in individuals with cystic fibrosis. Expression of the alginate biosynthetic operon is primarily controlled by the alternative sigma factor AlgU (AlgT/σ²²). In a nonmucoid strain, AlgU is sequestered by the transmembrane antisigma factor MucA to the cytoplasmic membrane. AlgU can be released from MucA via regulated intramembrane proteolysis by proteases AlgW and MucP …

Associations Between Alcohol Consumption And Fasting Blood Glucose In Young Adults, Julie Ann Lucca

Master's Theses

Current research shows moderate alcohol consumption is associated with decreased risk of diabetes and excessive consumption or binge drinking can cause insulin resistance and diabetes. In 2010, diabetes was the seventh leading cause of death in the United Statesand was responsible for significant health complications: blindness, kidney failure, and limb amputations, and is a large national economic burden. Fasting blood glucose (FBG) is a tool used to help diagnose diabetes. Abnormally high FBG, ≥100 mg/dl, is indicative of diabetes and pre-diabetes. Few studies have observed diabetic prevalence among young adults or college students. Studying young adults can help provide added …

A Novel Mechanism For Mechanosensing By Endothelial Cells, Jennifer Macdowell

Honors College

The formation of new vasculature is an essential process, but can also be utilized by cancerous cells. Angiogenesis requires the directed migration of the endothelial cells lining the nascent blood vessels. This process is largely mediated by integrin, which plays a key role in the interplay between sensing a force in the extracellular matrix (ECM) and transducing this signal, a process termed mechanotransduction. Through cell-ECM focal adhesions, integrin mediates the signaling both into and out of the cell, promoting growth of focal adhesions and subsequent cell spreading and migration. In order to study focal adhesion dynamics related to force, we …

Characterization Of Differentiation And Prognostic Biomarkers On Cd8+ Tumor-Infiltrating Lymphocytes In Metastatic Melanoma, Richard C. Wu

Dissertations & Theses (Open Access)

CD8⁺ cytotoxic T lymphocytes (CTL) frequently infiltrate tumors, yet most melanoma patients fail to undergo tumor regression. We studied the differentiation of the CD8⁺ tumor-infiltrating lymphocytes (TIL) from 44 metastatic melanoma patients using known T-cell differentiation markers. We also compared CD8⁺ TIL against the T cells from matched melanoma patients’ peripheral blood. We discovered a novel subset of CD8⁺ TIL co-expressing early-differentiation markers, CD27, CD28, and a late/senescent CTL differentiation marker, CD57. This CD8⁺CD57⁺ TIL expressed a cytolytic enzyme, granzyme B (GB), yet did not express another cytolytic pore-forming molecule, perforin (Perf). In …

Oxidative Stress For An Acute Bout Of Bikram Yoga In Healthy, Trained Adults, Kimberly Anne Trocio

UNLV Theses, Dissertations, Professional Papers, and Capstones

BACKGROUND:Generation of free radicals resulting in oxidative damage has been linked to cellular damage, aging, and human disease. Many studies have reported that physical exercise can contribute to oxidative stress. Further, exercise in a hyperthermic environment can promote additional oxidative stress. It is important to consider that practices in yoga may be beneficial in reducing oxidative stress according to some studies. The compound effects of exercise and hyperthermic exposure are experienced in the practice of Bikram yoga, the original "hot" yoga. Because Bikram yoga and other hot exercise classes are an increasingly growing fitness trend, it is necessary to investigate …

Flash4 Dark Reference Images, George Mcnamara

George McNamara

Hamamatsu FLASH4.0 dark reference images, acquired with 10 second exposure times, no light to camera. Camera offset (set by Hamamatsu( is ~100 (the average intensity of the first image is always ~1 intensity level higher - an odd feature, but trivial in practice for a 16-bit camera).

George McNamara, Ph.D.

Single Cells Analyst at L.J.N. Cooper Lab

University of Texas M.D. Anderson Cancer Center

Cellular Life Beyond An Individual’S Death, Emily Schmitt

CAHSS Intellectual Conversations

One of the most famous examples of cell lines surviving long after a person has died comes from a tumor found in the body of Henrietta Lacks, who died of cervical cancer in 1950. The study of approximately 50 million tons of her cells, which would conservatively equal the amount of cells in one billion people, has resulted in nearly 11,000 patents, including the polio vaccine. These cells have become a focus of public attention since Rebecca Skloot’s 2010 book, The Immortal Life of Henrietta Lacks. This talk will discuss what happens to cells once they leave our bodies, …

Video Codec Performance (Excel Spreadsheet), George Mcnamara

George McNamara

Video codec performance (Excel spreadsheet). Movie was made in 2005-2006 when I worked at City of Hope National Medical Center. VTLF refers to Video Timelapse Light Facility. Videos were outputted from MetaMorph as AVI files. Personally, I always recommend uncompressed video files fro scientific uses. I also encourage posting the original scientific data format (ex. .lsm, .zvi, .lif, .stk).

Pubspectra Tattletales, George Mcnamara

George McNamara

Tattletales for Multiplex Fluorescent Reporters in Single Cells for Metabolomics

George McNamara

As of April 2013: L.J.N. Cooper & D.A. Lee Cellular Immunotherapy Lab, University of Texas M.D. Anderson Cancer Center, Houston, TX

Email: gtmcnamara@mdanderson.org, geomcnamara@earthlink.net

Tattletales is my concept for spatial multiplexing many fluorescent protein (FP) biosensors in the same live cell. For example, there are excellent FP biosensors to Ca++ ions, pH, glucose, ribose, glutamine, glutamate, ATP, redox, ROS, pyruvate, cAMP, cGMP, IP3, PI(3,4,5)P3, cell cycle indicators (Fucci2), PKA, PKC, photsphatases, caspase(s) [1, 2]. However, these are typically used one biosensor per experiment, due in part to flooding …

The Herpesvirus Vp1/2 Protein Is An Effector Of Dynein-Mediated Capsid Transport And Neuroinvasion, Sofia V. Zaichick, Kevin P. Bohannon, Ami Hughes, Patricia J. Sollars, Gary E. Pickard, Gregory A. Smith

School of Veterinary and Biomedical Sciences: Faculty Publications

Microtubule transport of herpesvirus capsids from the cell periphery to the nucleus is imperative for viral replication and, in the case of many alphaherpesviruses, transmission into the nervous system. Using the neuroinvasive herpesvirus, pseudorabies virus (PRV), we show that the viral protein 1/2 (VP1/2) tegument protein associates with the dynein/dynactin microtubule motor complex and promotes retrograde microtubule transport of PRV capsids. Functional activation of VP1/2 requires binding to the capsid protein pUL25 or removal of the capsid-binding domain. A proline-rich sequence within VP1/2 is required for the efficient interaction with the dynein/ dynactin microtubule motor complex as well as for …

Pathology In Practice, Timothy L. Cushing, David J. Steffen, Gerald E. Duhamel

School of Veterinary and Biomedical Sciences: Faculty Publications

A 1.5-year-old second-parity Large Black X Tamworth cross sow from a well-managed 20-sow, unvaccinated, pasture-raised herd of pigs in upstate New York aborted a litter of 7 variably mummified near-term fetuses and stillborn piglets. This sow had no signs of ill health other than abortion; it was housed in a group with 4 other sows and a 2-year-old Gloucestershire Old Spot boar. One of the stillborn piglets from this litter was submitted to the New York State Animal Health Diagnostic Center for necropsy; no placental tissue was submitted with the piglet. A second sow from this group had aborted a …

Development And Evaluation Of A Replicon Particle Vaccine Expressing The E2 Glycoprotein Of Bovine Viral Diarrhea Virus (Bvdv) In Cattle, John Dustin Loy, Jill Gander, Mark Mogler, Ryan Vander Veen, Julia Ridpath, Delbert Hank Harris, Kurt Kamrud

School of Veterinary and Biomedical Sciences: Faculty Publications

Background: Bovine viral diarrhea virus is one of the most significant and costly viral pathogens of cattle worldwide. Alphavirus-derived replicon particles have been shown to be safe and highly effective vaccine vectors against a variety of human and veterinary pathogens. Replicon particles are non-propagating, DIVA compatible, and can induce both humoral and cell mediated immune responses. This is the first experiment to demonstrate that Alphavirus-based replicon particles can be utilized in a standard prime/boost vaccination strategy in calves against a commercially significant bovine pathogen.

Findings: Replicon particles that express bovine viral diarrhea virus sub-genotype 1b E2 glycoprotein were …

A Dysfunctional Tricarboxylic Acid Cycle Enhances Fitness Of Staphylococcus Epidermidis During Β-Lactam Stress, Vinai Chittenzham Thomas, Lauren Kinkhead, Ashley Janssen, Carolyn Schaeffer, Keith Woods, Jill Lindgren, Johnathan Peaster, Sujata Chaudhari, Marat Sadykov, Joselyn Jones, Sameh Mohamadi Abdelghani, Matthew Zimmerman, Kenneth W. Bayles, Greg Somerville, Paul Fey

School of Veterinary and Biomedical Sciences: Faculty Publications

A recent controversial hypothesis suggested that the bactericidal action of antibiotics is due to the generation of endogenous reactive oxygen species (ROS), a process requiring the citric acid cycle (tricarboxylic acid [TCA] cycle). To test this hypothesis, we assessed the ability of oxacillin to induce ROS production and cell death in Staphylococcus epidermidis strain 1457 and an isogenic citric acid cycle mutant. Our results confirm a contributory role for TCA-dependent ROS in enhancing susceptibility of S. epidermidis toward β-lactam antibiotics and also revealed a propensity for clinical isolates to accumulate TCA cycle dysfunctions presumably as a way to tolerate these …

Rhodotorula Minuta Fungemia In A Ewe Lamb, C. G. Chitko-Mckown, K. A. Leymaster, M. P. Heaton, D. D. Griffin, J. K. Veatch, S. A. Jones, M. L. Clawson

School of Veterinary and Biomedical Sciences: Faculty Publications

An 8-month-old crossbred ewe, normal upon physical examination, was humanely euthanized for tissue collection. After approximately 3 weeks in tissue culture, fungi began budding out of cells obtained from the choroid plexus. After an additional 3 weeks, budding was observed in kidney cell cultures and eventually in monocyte cultures as well. Serum from the lamb was submitted to the Veterinary Diagnostic Laboratory at Colorado State University for fungal diagnosis and was found negative for Aspergillus, Blastomyces, Coccidioidomycosis and Histoplasmosis. DNA was isolated from fungi collected from tissue culture supernatants and used in a set of pan-fungal PCR assays with …

Sequence-Optimized And Targeted Double-Stranded Rna As A Therapeutic Antiviral Treatment Against Infectious Myonecrosis Virus In Litopenaeus Vannamei, J. Dustin Loy, Duan S. Loy, Mark A. Mogler, Bruce Janke, Kurt Kamrud, D. L. Hank Harris, Lyric C. Bartholomay

School of Veterinary and Biomedical Sciences: Faculty Publications

Infectious myonecrosis virus (IMNV) is a significant and emerging pathogen that has a tremendous impact on the culture of the Pacific white shrimp Litopenaeus vannamei. IMNV first emerged in Brazil in 2002 and subsequently spread to Indonesia, causing large economic losses in both countries. No existing therapeutic treatments or effective interventions currently exist for IMNV. RNA interference (RNAi) is an effective technique for preventing viral disease in shrimp. Here, we describe the efficacy of a double-stranded RNA (dsRNA) applied as an antiviral therapeutic following virus challenge. The antiviral molecule is an optimized dsRNA construct that targets an IMNV sequence …

Global Neuroaids Roundtable, Jeymohan Joseph, Cristian L. Achim, Michael J. Boivin, Bruce J. Brew, David B. Clifford, Deborah A. Colosi, Ronald J. Ellis, Robert K. Heaton, Amadou Gallo-Diop, Igor Grant, Georgette D. Kanmogne, Mahendra Kumar, Scott Letendre, Thomas D. Marcotte, Avindra Nath, Carlos A. Pardo, Robert H. Paul, Lynn Pulliam, Kevin Robertson, Walter Royal Iii, Ned Sacktor, Pasiri Sithinamsuwan, Davey M. Smith, Victor Valcour, Brian Wigdahl, Charles Wood

Nebraska Center for Virology: Faculty Publications

In May 2012, the Division of AIDS Research at the National Institute of Mental Health (NIMH) organized the “Global NeuroAIDS Roundtable” in conjunction with the 11th International Symposium on Neurovirology and the 2012 Conference on HIV in the Nervous System. The meeting was held in New York, NY, USA and brought together NIMH-funded investigators who are currently working on projects related to the neurological complications of AIDS (NeuroAIDS) in Africa, Asia, Eastern Europe, and Latin America in order to provide an opportunity to share their recent findings and discuss the challenges encountered within each country. The major goals of the …

Interferon Inducible Protein Ifi35 Negatively Regulates Rig-I Antiviral Signaling And Supports Vesicular Stomatitis Virus Replication, Anshuman Das, Phat X. Dinh, Debasis Panda, Asit K. Pattnaik

School of Veterinary and Biomedical Sciences: Faculty Publications

In a genome-wide siRNA screen, we recently identified the interferon (IFN) inducible protein 35 (IFI35, also known as IFP35) as a factor required for VSV infection. Studies reported here were conducted to further understand the role and requirement of IFI35 in VSV infection. Consistent with the siRNA screening data, we found that depletion of IFI35 led to reduced VSV replication at the level of viral gene expression. Although no direct interaction of IFI35 with the viral replication machinery was observed, we found that IFI35 negatively regulated the host innate immune response and rescued poly(I:C)-induced inhibition of VSV replication. Promoter-driven reporter …

Trex1 Regulates Lysosomal Biogenesis And Interferon-Independent Activation Of Antiviral Genes, Maroof Hasan, James Koch, Dinesh Rakheja, Asit K. Pattnaik, James Brugarolas, Igor Dozmorov, Beth Levine, Edward K. Wakeland, Min Ae Lee-Kirsch, Nan Yan

School of Veterinary and Biomedical Sciences: Faculty Publications

Innate immune sensing of viral nucleic acids triggers type I interferon (IFN) production, which activates interferon-stimulated genes (ISGs) and directs a multifaceted antiviral response. ISGs can also be activated through IFN-independent pathways, although the precise mechanisms remain elusive. Here we found that the cytosolic exonuclease Trex1 regulates the activation of a subset of ISGs independently of IFN. Both Trex1−/− mouse and TREX1-mutant human cells express high levels of antiviral genes and are refractory to viral infections. The IFN-independent activation of antiviral genes in Trex1−/− cells requires STING, TBK1 and IRF3 and IRF7. We also found that Trex1-deficient cells display expanded …

Glutaredoxin-2 Is Required To Control Proton Leak Through Uncoupling Protein-3, Ryan J. Mailloux, Jian Ying Xuan, Brittany Beauchamp, Marjorie F. Lou, Mary-Ellen Harper

School of Veterinary and Biomedical Sciences: Faculty Publications

Glutathionylation has emerged as a key modification required for controlling protein function in response to changes in cell redox status. Recently, we showed that the glutathionylation state of uncoupling protein-3 (UCP3) modulates the leak of protons back into the mitochondrial matrix, thus controlling reactive oxygen species production. However, whether or not UCP3 glutathionylation is mediated enzymatically has remained unknown because previous work relied on the use of pharmacological agents, such as diamide, to alter the UCP3 glutathionylation state. Here, we demonstrate that glutaredoxin-2 (Grx2), a matrix oxidoreductase, is required to glutathionylate and inhibit UCP3. Analysis of bioenergetics in skeletal muscle …

Molecular Architecture Of The Uncleaved Hiv-1 Envelope Glycoprotein Trimer, Youdong Mao, Luis Castillo-Menendez, Liping Wang, Christopher Gu, Alon Herschhorn, Anik Désormeaux, Andrés Finzi, Shi-Hua Xiang, Joseph Sodroski

Nebraska Center for Virology: Faculty Publications

The human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) trimer, a membrane-fusing machine, mediates virus entry into host cells and is the sole virusspecific target for neutralizing antibodies. Binding the receptors, CD4 and CCR5/CXCR4, triggers Env conformational changes from the metastable unliganded state to the fusion-active state. We used cryo-electron microscopy to obtain a 6-Å structure of the membranebound, heavily glycosylated HIV-1 Env trimer in its uncleaved and unliganded state. The spatial organization of secondary structure elements reveals that the unliganded conformations of both gp120 and gp41 subunits differ from those induced by receptor binding. The gp120 trimer association domains, which …