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Characterization of the hemodynamic response function in white matter tracts for event-related fMRI.
Li M, Newton AT, Anderson AW, Ding Z, Gore JC
(2019) Nat Commun 10: 1140
MeSH Terms: Adult, Cerebral Cortex, Cerebrovascular Circulation, Female, Gray Matter, Healthy Volunteers, Hemodynamics, Hemoglobins, Humans, Magnetic Resonance Imaging, Male, Nerve Net, Oxygen, Pattern Recognition, Visual, Stroop Test, White Matter
Show Abstract · Added March 26, 2019
Accurate estimates of the BOLD hemodynamic response function (HRF) are crucial for the interpretation and analysis of event-related functional MRI data. To date, however, there have been no comprehensive measurements of the HRF in white matter (WM) despite increasing evidence that BOLD signals in WM change after a stimulus. We performed an event-related cognitive task (Stroop color-word interference) to measure the HRF in selected human WM pathways. The task was chosen in order to produce robust, distributed centers of activity throughout the cortex. To measure the HRF in WM, fiber tracts were reconstructed between each pair of activated cortical areas. We observed clear task-specific HRFs with reduced magnitudes, delayed onsets and prolonged initial dips in WM tracts compared with activated grey matter, thus calling for significant changes to current standard models for accurately characterizing the HRFs in WM and for modifications of standard methods of analysis of functional imaging data.
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16 MeSH Terms
Glutamate-oxaloacetate transaminase activity promotes palmitate lipotoxicity in rat hepatocytes by enhancing anaplerosis and citric acid cycle flux.
Egnatchik RA, Leamy AK, Sacco SA, Cheah YE, Shiota M, Young JD
(2019) J Biol Chem 294: 3081-3090
MeSH Terms: Animals, Aspartate Aminotransferases, Cell Death, Cell Line, Citric Acid Cycle, Extracellular Space, Glutamine, Hepatocytes, Ketoglutaric Acids, Male, Oxidative Stress, Oxygen, Palmitates, Rats, Rats, Sprague-Dawley
Show Abstract · Added March 28, 2019
Hepatocyte lipotoxicity is characterized by aberrant mitochondrial metabolism, which predisposes cells to oxidative stress and apoptosis. Previously, we reported that translocation of calcium from the endoplasmic reticulum to mitochondria of palmitate-treated hepatocytes activates anaplerotic flux from glutamine to α-ketoglutarate (αKG), which subsequently enters the citric acid cycle (CAC) for oxidation. We hypothesized that increased glutamine anaplerosis fuels elevations in CAC flux and oxidative stress following palmitate treatment. To test this hypothesis, primary rat hepatocytes or immortalized H4IIEC3 rat hepatoma cells were treated with lipotoxic levels of palmitate while modulating anaplerotic pathways leading to αKG. We found that culture media supplemented with glutamine, glutamate, or dimethyl-αKG increased palmitate lipotoxicity compared with media that lacked these anaplerotic substrates. Knockdown of glutamate-oxaloacetate transaminase activity significantly reduced the lipotoxic effects of palmitate, whereas knockdown of glutamate dehydrogenase (Glud1) had no effect on palmitate lipotoxicity. C flux analysis of H4IIEC3 cells co-treated with palmitate and the pan-transaminase inhibitor aminooxyacetic acid confirmed that reductions in lipotoxic markers were associated with decreases in anaplerosis, CAC flux, and oxygen consumption. Taken together, these results demonstrate that lipotoxic palmitate treatments enhance anaplerosis in cultured rat hepatocytes, causing a shift to aberrant transaminase metabolism that fuels CAC dysregulation and oxidative stress.
© 2019 Egnatchik et al.
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15 MeSH Terms
The Structure of the Bifunctional Everninomicin Biosynthetic Enzyme EvdMO1 Suggests Independent Activity of the Fused Methyltransferase-Oxidase Domains.
Starbird CA, Perry NA, Chen Q, Berndt S, Yamakawa I, Loukachevitch LV, Limbrick EM, Bachmann BO, Iverson TM, McCulloch KM
(2018) Biochemistry 57: 6827-6837
MeSH Terms: Amino Acid Sequence, Aminoglycosides, Bacterial Proteins, Biosynthetic Pathways, Catalytic Domain, Conserved Sequence, Crystallography, X-Ray, Gene Fusion, Genes, Bacterial, Methyltransferases, Micromonospora, Models, Molecular, Oxygenases, Protein Interaction Domains and Motifs, Sequence Homology, Amino Acid
Show Abstract · Added April 1, 2019
Members of the orthosomycin family of natural products are decorated polysaccharides with potent antibiotic activity and complex biosynthetic pathways. The defining feature of the orthosomycins is an orthoester linkage between carbohydrate moieties that is necessary for antibiotic activity and is likely formed by a family of conserved oxygenases. Everninomicins are octasaccharide orthosomycins produced by Micromonospora carbonacea that have two orthoester linkages and a methylenedioxy bridge, three features whose formation logically requires oxidative chemistry. Correspondingly, the evd gene cluster encoding everninomicin D encodes two monofunctional nonheme iron, α-ketoglutarate-dependent oxygenases and one bifunctional enzyme with an N-terminal methyltransferase domain and a C-terminal oxygenase domain. To investigate whether the activities of these domains are linked in the bifunctional enzyme EvdMO1, we determined the structure of the N-terminal methyltransferase domain to 1.1 Å and that of the full-length protein to 3.35 Å resolution. Both domains of EvdMO1 adopt the canonical folds of their respective superfamilies and are connected by a short linker. Each domain's active site is oriented such that it faces away from the other domain, and there is no evidence of a channel connecting the two. Our results support EvdMO1 working as a bifunctional enzyme with independent catalytic activities.
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15 MeSH Terms
Renal Medullary Interstitial COX-2 (Cyclooxygenase-2) Is Essential in Preventing Salt-Sensitive Hypertension and Maintaining Renal Inner Medulla/Papilla Structural Integrity.
Zhang MZ, Wang S, Wang Y, Zhang Y, Ming Hao C, Harris RC
(2018) Hypertension 72: 1172-1179
MeSH Terms: Animals, Apoptosis, Aquaporin 2, Blood Pressure, Cyclooxygenase 2, Epithelial Sodium Channels, Hypertension, Kidney Medulla, Mice, Mice, Transgenic
Show Abstract · Added November 8, 2018
COX (cyclooxygenase)-derived prostaglandins regulate renal hemodynamics and salt and water homeostasis. Inhibition of COX activity causes blood pressure elevation. In addition, chronic analgesic abuse can induce renal injury, including papillary necrosis. COX-2 is highly expressed in the kidney papilla in renal medullary interstitial cells (RMICs). However, its role in blood pressure and papillary integrity in vivo has not been definitively studied. In mice with selective, inducible RMIC COX-2 deletion, a high-salt diet led to an increase in blood pressure that peaked at 4 to 5 weeks and was associated with increased papillary expression of AQP2 (aquaporin 2) and ENac (epithelial sodium channel) and decreased expression of cystic fibrosis transmembrane conductance regulator. With continued high-salt feeding, the mice with RMIC COX-2 deletion had progressive decreases in blood pressure from its peak. After return to a normal-salt diet for 3 weeks, blood pressure remained low and was associated with a persistent urinary concentrating defect. Within 2 weeks of institution of a high-salt diet, increased apoptotic RMICs and collecting duct cells could be detected in papillae with RMIC deletion of COX-2, and by 9 weeks of high salt, there was a striking loss of the papillae. Therefore, RMIC COX-2 expression plays a crucial role in renal handling water and sodium homeostasis, preventing salt-sensitive hypertension and maintaining structural integrity of papilla.
1 Communities
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10 MeSH Terms
Light-activatable cannabinoid prodrug for combined and target-specific photodynamic and cannabinoid therapy.
Ling X, Zhang S, Liu Y, Bai M
(2018) J Biomed Opt 23: 1-9
MeSH Terms: Animals, Antineoplastic Agents, Cannabinoids, Cell Line, Tumor, Cell Survival, HEK293 Cells, Humans, Indoles, Mice, Organosilicon Compounds, Photochemotherapy, Photosensitizing Agents, Prodrugs, Reactive Oxygen Species
Show Abstract · Added April 2, 2019
Cannabinoids are emerging as promising antitumor drugs. However, complete tumor eradication solely by cannabinoid therapy remains challenging. In this study, we developed a far-red light activatable cannabinoid prodrug, which allows for tumor-specific and combinatory cannabinoid and photodynamic therapy. This prodrug consists of a phthalocyanine photosensitizer (PS), reactive oxygen species (ROS)-sensitive linker, and cannabinoid. It targets the type-2 cannabinoid receptor (CB2R) overexpressed in various types of cancers. Upon the 690-nm light irradiation, the PS produces cytotoxic ROS, which simultaneously cleaves the ROS-sensitive linker and subsequently releases the cannabinoid drug. We found that this unique multifunctional prodrug design offered dramatically improved therapeutic efficacy, and therefore provided a new strategy for targeted, controlled, and effective antitumor cannabinoid therapy.
(2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).
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14 MeSH Terms
Bid maintains mitochondrial cristae structure and function and protects against cardiac disease in an integrative genomics study.
Salisbury-Ruf CT, Bertram CC, Vergeade A, Lark DS, Shi Q, Heberling ML, Fortune NL, Okoye GD, Jerome WG, Wells QS, Fessel J, Moslehi J, Chen H, Roberts LJ, Boutaud O, Gamazon ER, Zinkel SS
(2018) Elife 7:
MeSH Terms: Animals, Apoptosis, BH3 Interacting Domain Death Agonist Protein, Beclin-1, Cell Respiration, Fibrosis, Gene Expression Regulation, Genome-Wide Association Study, Genomics, Heart Diseases, Heart Ventricles, Humans, Mice, Inbred C57BL, Mitochondria, Mitochondrial Proton-Translocating ATPases, Mutation, Myeloid Progenitor Cells, Myocardial Infarction, Myocytes, Cardiac, Polymorphism, Single Nucleotide, Protein Multimerization, Protein Structure, Secondary, Protein Subunits, Reactive Oxygen Species, Reproducibility of Results, Up-Regulation
Show Abstract · Added December 11, 2018
Bcl-2 family proteins reorganize mitochondrial membranes during apoptosis, to form pores and rearrange cristae. In vitro and in vivo analysis integrated with human genetics reveals a novel homeostatic mitochondrial function for Bcl-2 family protein Bid. Loss of full-length Bid results in apoptosis-independent, irregular cristae with decreased respiration. mice display stress-induced myocardial dysfunction and damage. A gene-based approach applied to a biobank, validated in two independent GWAS studies, reveals that decreased genetically determined BID expression associates with myocardial infarction (MI) susceptibility. Patients in the bottom 5% of the expression distribution exhibit >4 fold increased MI risk. Carrier status with nonsynonymous variation in Bid's membrane binding domain, Bid, associates with MI predisposition. Furthermore, Bid but not Bid associates with Mcl-1, previously implicated in cristae stability; decreased MCL-1 expression associates with MI. Our results identify a role for Bid in homeostatic mitochondrial cristae reorganization, that we link to human cardiac disease.
© 2018, Salisbury-Ruf et al.
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26 MeSH Terms
Combined CB2 receptor agonist and photodynamic therapy synergistically inhibit tumor growth in triple negative breast cancer.
Zhang J, Zhang S, Liu Y, Su M, Ling X, Liu F, Ge Y, Bai M
(2018) Photodiagnosis Photodyn Ther 24: 185-191
MeSH Terms: Acetamides, Animals, Apoptosis, Cell Line, Tumor, Cell Proliferation, Cell Survival, Combined Modality Therapy, Female, Gene Expression Regulation, Neoplastic, Humans, Indoles, Mice, Neoplasm Recurrence, Local, Phenyl Ethers, Photochemotherapy, Photosensitizing Agents, Quality of Life, Receptor, Cannabinoid, CB2, Receptors, GABA, Singlet Oxygen, Triple Negative Breast Neoplasms, Xenograft Model Antitumor Assays
Show Abstract · Added April 2, 2019
Triple negative breast cancer (TNBC) is the deadliest form of breast cancer because it is more aggressive, diagnosed at later stage and more likely to develop local and systemic recurrence. Many patients do not experience adequate tumor control after current clinical treatments involving surgical removal, chemotherapy and/or radiotherapy, leading to disease progression and significantly decreased quality of life. Here we report a new combinatory therapy strategy involving cannabinoid-based medicine and photodynamic therapy (PDT) for the treatment of TNBC. This combinatory therapy targets two proteins upregulated in TNBC: the cannabinoid CB2 receptor (CBR, a G-protein coupled receptor) and translocator protein (TSPO, a mitochondria membrane receptor). We found that the combined CBR agonist and TSPO-PDT treatment resulted in synergistic inhibition in TNBC cell and tumor growth. This combinatory therapy approach provides new opportunities to treat TNBC with high efficacy. In addition, this study provides new evidence on the therapeutic potential of CBR agonists for cancer.
Copyright © 2018 Elsevier B.V. All rights reserved.
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22 MeSH Terms
Adrenal serotonin derives from accumulation by the antidepressant-sensitive serotonin transporter.
Brindley RL, Bauer MB, Walker LA, Quinlan MA, Carneiro AMD, Sze JY, Blakely RD, Currie KPM
(2019) Pharmacol Res 140: 56-66
MeSH Terms: Adrenal Glands, Animals, Antidepressive Agents, Female, Male, Mesencephalon, Mice, Transgenic, Models, Animal, Rhombencephalon, Serotonin, Serotonin Plasma Membrane Transport Proteins, Spinal Cord, Tyrosine 3-Monooxygenase
Show Abstract · Added August 8, 2018
Adrenal chromaffin cells comprise the neuroendocrine arm of the sympathetic nervous system and secrete catecholamines to coordinate the appropriate stress response. Deletion of the serotonin (5-HT) transporter (SERT) gene in mice (SERT mice) or pharmacological block of SERT function in rodents and humans augments this sympathoadrenal stress response (epinephrine secretion). The prevailing assumption is that loss of CNS SERT alters central drive to the peripheral sympathetic nervous system. Adrenal chromaffin cells also prominently express SERT where it might coordinate accumulation of 5-HT for reuse in the autocrine control of stress-evoked catecholamine secretion. To help test this hypothesis, we have generated a novel mouse model with selective excision of SERT in the peripheral sympathetic nervous system (SERT), generated by crossing floxed SERT mice with tyrosine hydroxylase Cre driver mice. SERT expression, assessed by western blot, was abolished in the adrenal gland but not perturbed in the CNS of SERT mice. SERT-mediated [H] 5-HT uptake was unaltered in midbrain, hindbrain, and spinal cord synaptosomes, confirming transporter function was intact in the CNS. Endogenous midbrain and whole blood 5-HT homeostasis was unperturbed in SERT mice, contrasting with the depleted 5-HT content in SERT mice. Selective SERT excision reduced adrenal gland 5-HT content by ≈ 50% in SERT mice but had no effect on adrenal catecholamine content. This novel model confirms that SERT expressed in adrenal chromaffin cells is essential for maintaining wild-type levels of 5-HT and provides a powerful tool to help dissect the role of SERT in the sympathetic stress response.
Copyright © 2018 Elsevier Ltd. All rights reserved.
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13 MeSH Terms
Relating structural and functional brainstem connectivity to disease measures in epilepsy.
Englot DJ, Gonzalez HFJ, Reynolds BB, Konrad PE, Jacobs ML, Gore JC, Landman BA, Morgan VL
(2018) Neurology 91: e67-e77
MeSH Terms: Adult, Brain Stem, Case-Control Studies, Cognition Disorders, Epilepsy, Female, Humans, Image Processing, Computer-Assisted, Magnetic Resonance Imaging, Male, Middle Aged, Nerve Net, Neuropsychological Tests, Oxygen, Retrospective Studies
Show Abstract · Added September 25, 2018
OBJECTIVE - While epilepsy studies rarely examine brainstem, we sought to examine the hypothesis that temporal lobe epilepsy (TLE) leads to subcortical arousal center dysfunction, contributing to neocortical connectivity and neurocognitive disturbances.
METHODS - In this case-control study of 26 adult patients with TLE and 26 controls, we used MRI to measure structural and functional connectivity of the cuneiform/subcuneiform nuclei (CSC), pedunculopontine nucleus, and ventral tegmental area. Ascending reticular activating system connectivity patterns were related to neuropsychological and disease measures.
RESULTS - Compared to controls, patients with TLE demonstrated reductions in ascending reticular activating system structural and functional connectivity, most prominently to neocortical regions ( < 0.05, unpaired tests, corrected). While reduced CSC structural connectivity was related to impaired performance IQ and visuospatial memory, diminished CSC functional connectivity was associated with impaired verbal IQ and language abilities ( < 0.05, Spearman ρ, tests). Finally, CSC structural connectivity decreases were quantitatively associated with consciousness-impairing seizure frequency ( < 0.05, Spearman ρ) and the presence of generalized seizures ( < 0.05, unpaired test), suggesting a relationship to disease severity.
CONCLUSIONS - Connectivity perturbations in brainstem arousal centers are present in TLE and may contribute to neurocognitive problems. These studies demonstrate the underappreciated role of brainstem networks in epilepsy and may lead to novel neuromodulation targets to treat or prevent deleterious brain network effects of seizures in TLE.
© 2018 American Academy of Neurology.
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15 MeSH Terms
Individual differences in dopamine D receptor availability correlate with reward valuation.
Dang LC, Samanez-Larkin GR, Castrellon JJ, Perkins SF, Cowan RL, Zald DH
(2018) Cogn Affect Behav Neurosci 18: 739-747
MeSH Terms: Adult, Anticipation, Psychological, Benzamides, Brain, Brain Mapping, Cerebrovascular Circulation, Female, Fluorine Radioisotopes, Humans, Individuality, Magnetic Resonance Imaging, Male, Oxygen, Positron-Emission Tomography, Radiopharmaceuticals, Receptors, Dopamine D2, Reward
Show Abstract · Added April 15, 2019
Reward valuation, which underlies all value-based decision-making, has been associated with dopamine function in many studies of nonhuman animals, but there is relatively less direct evidence for an association in humans. Here, we measured dopamine D receptor (DRD2) availability in vivo in humans to examine relations between individual differences in dopamine receptor availability and neural activity associated with a measure of reward valuation, expected value (i.e., the product of reward magnitude and the probability of obtaining the reward). Fourteen healthy adult subjects underwent PET with [F]fallypride, a radiotracer with strong affinity for DRD2, and fMRI (on a separate day) while performing a reward valuation task. [F]fallypride binding potential, reflecting DRD2 availability, in the midbrain correlated positively with neural activity associated with expected value, specifically in the left ventral striatum/caudate. The present results provide in vivo evidence from humans showing midbrain dopamine characteristics are associated with reward valuation.
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17 MeSH Terms