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Molina JM, Capitant C, Spire B, Pialoux G, Cotte L, Charreau I, Tremblay C, Le Gall JM, Cua E, Pasquet A, Raffi F, Pintado C, Chidiac C, Chas J, Charbonneau P, Delaugerre C, Suzan-Monti M, Loze B, Fonsart J, Peytavin G, Cheret A, Timsit J, Girard G, Lorente N, Préau M, Rooney JF, Wainberg MA, Thompson D, Rozenbaum W, Doré V, Marchand L, Simon MC, Etien N, Aboulker JP, Meyer L, Delfraissy JF. On-Demand Preexposure Prophylaxis in Men at High Risk for HIV-1 Infection. N Engl J Med 2015; 373:2237-46. [PMID: 26624850 DOI: 10.1056/nejmoa1506273] [Citation(s) in RCA: 1201] [Impact Index Per Article: 120.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Antiretroviral preexposure prophylaxis has been shown to reduce the risk of human immunodeficiency virus type 1 (HIV-1) infection in some studies, but conflicting results have been reported among studies, probably due to challenges of adherence to a daily regimen. METHODS We conducted a double-blind, randomized trial of antiretroviral therapy for preexposure HIV-1 prophylaxis among men who have unprotected anal sex with men. Participants were randomly assigned to take a combination of tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) or placebo before and after sexual activity. All participants received risk-reduction counseling and condoms and were regularly tested for HIV-1 and HIV-2 and other sexually transmitted infections. RESULTS Of the 414 participants who underwent randomization, 400 who did not have HIV infection were enrolled (199 in the TDF-FTC group and 201 in the placebo group). All participants were followed for a median of 9.3 months (interquartile range, 4.9 to 20.6). A total of 16 HIV-1 infections occurred during follow-up, 2 in the TDF-FTC group (incidence, 0.91 per 100 person-years) and 14 in the placebo group (incidence, 6.60 per 100 person-years), a relative reduction in the TDF-FTC group of 86% (95% confidence interval, 40 to 98; P=0.002). Participants took a median of 15 pills of TDF-FTC or placebo per month (P=0.57). The rates of serious adverse events were similar in the two study groups. In the TDF-FTC group, as compared with the placebo group, there were higher rates of gastrointestinal adverse events (14% vs. 5%, P=0.002) and renal adverse events (18% vs. 10%, P=0.03). CONCLUSIONS The use of TDF-FTC before and after sexual activity provided protection against HIV-1 infection in men who have sex with men. The treatment was associated with increased rates of gastrointestinal and renal adverse events. (Funded by the National Agency of Research on AIDS and Viral Hepatitis [ANRS] and others; ClinicalTrials.gov number, NCT01473472.).
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Multicenter Study |
10 |
1201 |
2
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Maier-Hein KH, Neher PF, Houde JC, Côté MA, Garyfallidis E, Zhong J, Chamberland M, Yeh FC, Lin YC, Ji Q, Reddick WE, Glass JO, Chen DQ, Feng Y, Gao C, Wu Y, Ma J, He R, Li Q, Westin CF, Deslauriers-Gauthier S, González JOO, Paquette M, St-Jean S, Girard G, Rheault F, Sidhu J, Tax CMW, Guo F, Mesri HY, Dávid S, Froeling M, Heemskerk AM, Leemans A, Boré A, Pinsard B, Bedetti C, Desrosiers M, Brambati S, Doyon J, Sarica A, Vasta R, Cerasa A, Quattrone A, Yeatman J, Khan AR, Hodges W, Alexander S, Romascano D, Barakovic M, Auría A, Esteban O, Lemkaddem A, Thiran JP, Cetingul HE, Odry BL, Mailhe B, Nadar MS, Pizzagalli F, Prasad G, Villalon-Reina JE, Galvis J, Thompson PM, Requejo FDS, Laguna PL, Lacerda LM, Barrett R, Dell'Acqua F, Catani M, Petit L, Caruyer E, Daducci A, Dyrby TB, Holland-Letz T, Hilgetag CC, Stieltjes B, Descoteaux M. The challenge of mapping the human connectome based on diffusion tractography. Nat Commun 2017; 8:1349. [PMID: 29116093 PMCID: PMC5677006 DOI: 10.1038/s41467-017-01285-x] [Citation(s) in RCA: 791] [Impact Index Per Article: 98.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 09/01/2017] [Indexed: 01/14/2023] Open
Abstract
Tractography based on non-invasive diffusion imaging is central to the study of human brain connectivity. To date, the approach has not been systematically validated in ground truth studies. Based on a simulated human brain data set with ground truth tracts, we organized an open international tractography challenge, which resulted in 96 distinct submissions from 20 research groups. Here, we report the encouraging finding that most state-of-the-art algorithms produce tractograms containing 90% of the ground truth bundles (to at least some extent). However, the same tractograms contain many more invalid than valid bundles, and half of these invalid bundles occur systematically across research groups. Taken together, our results demonstrate and confirm fundamental ambiguities inherent in tract reconstruction based on orientation information alone, which need to be considered when interpreting tractography and connectivity results. Our approach provides a novel framework for estimating reliability of tractography and encourages innovation to address its current limitations. Though tractography is widely used, it has not been systematically validated. Here, authors report results from 20 groups showing that many tractography algorithms produce both valid and invalid bundles.
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Research Support, Non-U.S. Gov't |
8 |
791 |
3
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Ghaziri J, Tucholka A, Girard G, Houde JC, Boucher O, Gilbert G, Descoteaux M, Lippé S, Rainville P, Nguyen DK. The Corticocortical Structural Connectivity of the Human Insula. Cereb Cortex 2018; 27:1216-1228. [PMID: 26683170 DOI: 10.1093/cercor/bhv308] [Citation(s) in RCA: 195] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The insula is a complex structure involved in a wide range of functions. Tracing studies on nonhuman primates reveal a wide array of cortical connections in the frontal (orbitofrontal and prefrontal cortices, cingulate areas and supplementary motor area), parietal (primary and secondary somatosensory cortices) and temporal (temporal pole, auditory, prorhinal and entorhinal cortices) lobes. However, recent human tractography studies have not observed connections between the insula and the cingulate cortices, although these structures are thought to be functionally intimately connected. In this work, we try to unravel the structural connectivity between these regions and other known functionally connected structures, benefiting from a higher number of subjects and the latest state-of-the-art high angular resolution diffusion imaging (HARDI) tractography algorithms with anatomical priors. By performing an HARDI tractography analysis on 46 young normal adults, our study reveals a wide array of connections between the insula and the frontal, temporal, parietal and occipital lobes as well as limbic regions, with a rostro-caudal organization in line with tracing studies in macaques. Notably, we reveal for the first time in humans a clear structural connectivity between the insula and the cingulate, parahippocampal, supramarginal and angular gyri as well as the precuneus and occipital regions.
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Research Support, Non-U.S. Gov't |
7 |
195 |
4
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Girard G, Whittingstall K, Deriche R, Descoteaux M. Towards quantitative connectivity analysis: reducing tractography biases. Neuroimage 2014; 98:266-78. [PMID: 24816531 DOI: 10.1016/j.neuroimage.2014.04.074] [Citation(s) in RCA: 194] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 04/23/2014] [Accepted: 04/28/2014] [Indexed: 11/18/2022] Open
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11 |
194 |
5
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Schilling KG, Nath V, Hansen C, Parvathaneni P, Blaber J, Gao Y, Neher P, Aydogan DB, Shi Y, Ocampo-Pineda M, Schiavi S, Daducci A, Girard G, Barakovic M, Rafael-Patino J, Romascano D, Rensonnet G, Pizzolato M, Bates A, Fischi E, Thiran JP, Canales-Rodríguez EJ, Huang C, Zhu H, Zhong L, Cabeen R, Toga AW, Rheault F, Theaud G, Houde JC, Sidhu J, Chamberland M, Westin CF, Dyrby TB, Verma R, Rathi Y, Irfanoglu MO, Thomas C, Pierpaoli C, Descoteaux M, Anderson AW, Landman BA. Limits to anatomical accuracy of diffusion tractography using modern approaches. Neuroimage 2018; 185:1-11. [PMID: 30317017 DOI: 10.1016/j.neuroimage.2018.10.029] [Citation(s) in RCA: 152] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 09/14/2018] [Accepted: 10/09/2018] [Indexed: 12/12/2022] Open
Abstract
Diffusion MRI fiber tractography is widely used to probe the structural connectivity of the brain, with a range of applications in both clinical and basic neuroscience. Despite widespread use, tractography has well-known pitfalls that limits the anatomical accuracy of this technique. Numerous modern methods have been developed to address these shortcomings through advances in acquisition, modeling, and computation. To test whether these advances improve tractography accuracy, we organized the 3-D Validation of Tractography with Experimental MRI (3D-VoTEM) challenge at the ISBI 2018 conference. We made available three unique independent tractography validation datasets - a physical phantom and two ex vivo brain specimens - resulting in 176 distinct submissions from 9 research groups. By comparing results over a wide range of fiber complexities and algorithmic strategies, this challenge provides a more comprehensive assessment of tractography's inherent limitations than has been reported previously. The central results were consistent across all sub-challenges in that, despite advances in tractography methods, the anatomical accuracy of tractography has not dramatically improved in recent years. Taken together, our results independently confirm findings from decades of tractography validation studies, demonstrate inherent limitations in reconstructing white matter pathways using diffusion MRI data alone, and highlight the need for alternative or combinatorial strategies to accurately map the fiber pathways of the brain.
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Research Support, Non-U.S. Gov't |
7 |
152 |
6
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Côté MA, Girard G, Boré A, Garyfallidis E, Houde JC, Descoteaux M. Tractometer: Towards validation of tractography pipelines. Med Image Anal 2013; 17:844-57. [PMID: 23706753 DOI: 10.1016/j.media.2013.03.009] [Citation(s) in RCA: 140] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 03/04/2013] [Accepted: 03/28/2013] [Indexed: 12/13/2022]
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12 |
140 |
7
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Ghaziri J, Tucholka A, Girard G, Boucher O, Houde JC, Descoteaux M, Obaid S, Gilbert G, Rouleau I, Nguyen DK. Subcortical structural connectivity of insular subregions. Sci Rep 2018; 8:8596. [PMID: 29872212 PMCID: PMC5988839 DOI: 10.1038/s41598-018-26995-0] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 05/18/2018] [Indexed: 12/19/2022] Open
Abstract
Hidden beneath the Sylvian fissure and sometimes considered as the fifth lobe of the brain, the insula plays a multi-modal role from its strategic location. Previous structural studies have reported cortico-cortical connections with the frontal, temporal, parietal and occipital lobes, but only a few have looked at its connections with subcortical structures. The insular cortex plays a role in a wide range of functions including processing of visceral and somatosensory inputs, olfaction, audition, language, motivation, craving, addiction and emotions such as pain, empathy and disgust. These functions implicate numerous subcortical structures, as suggested by various functional studies. Based on these premises, we explored the structural connectivity of insular ROIs with the thalamus, amygdala, hippocampus, putamen, globus pallidus, caudate nucleus and nucleus accumbens. More precisely, we were interested in unraveling the specific areas of the insula connected to these subcortical structures. By using state-of-the-art HARDI tractography algorithm, we explored here the subcortical connectivity of the insula.
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Research Support, Non-U.S. Gov't |
7 |
119 |
8
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Butterworth RF, Girard G, Giguère JF. Regional differences in the capacity for ammonia removal by brain following portocaval anastomosis. J Neurochem 1988; 51:486-90. [PMID: 3392540 DOI: 10.1111/j.1471-4159.1988.tb01064.x] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Portocaval anastomosis (PCA) in the rat leads, within 4 weeks, to severe liver atrophy, sustained hyperammonemia, and increased brain ammonia. Because brain is not equipped with an effective urea cycle, removal of ammonia involves glutamine synthesis and PCA results in significantly increased brain glutamine. Glutamine synthetase activities, however, are decreased by 15% in cerebral cortex and are unchanged in brainstem of shunted rats. Administration of ammonium acetate to rats following PCA results in severe encephalopathy (loss of righting reflex and, ultimately, coma). Glutamine concentrations in brainstem of comatose rats are increased a further two-fold, whereas those of cerebral cortex are unchanged. Consequently, ammonia levels in cerebral cortex reach disproportionately high levels (of the order of 5 mM). These findings suggest a limitation in the capacity of cerebral cortex to remove additional blood-borne ammonia by glutamine formation following PCA. Such mechanisms may explain the hypersensitivity of rats with PCA and of patients with portal-systemic shunting to small increases of blood ammonia. Disproportionately high levels of brain ammonia in certain regions, such as cerebral cortex, may then result in alterations of inhibitory neurotransmission and, ultimately, loss of cellular (astrocytic) integrity.
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9
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Schilling KG, Rheault F, Petit L, Hansen CB, Nath V, Yeh FC, Girard G, Barakovic M, Rafael-Patino J, Yu T, Fischi-Gomez E, Pizzolato M, Ocampo-Pineda M, Schiavi S, Canales-Rodríguez EJ, Daducci A, Granziera C, Innocenti G, Thiran JP, Mancini L, Wastling S, Cocozza S, Petracca M, Pontillo G, Mancini M, Vos SB, Vakharia VN, Duncan JS, Melero H, Manzanedo L, Sanz-Morales E, Peña-Melián Á, Calamante F, Attyé A, Cabeen RP, Korobova L, Toga AW, Vijayakumari AA, Parker D, Verma R, Radwan A, Sunaert S, Emsell L, De Luca A, Leemans A, Bajada CJ, Haroon H, Azadbakht H, Chamberland M, Genc S, Tax CMW, Yeh PH, Srikanchana R, Mcknight CD, Yang JYM, Chen J, Kelly CE, Yeh CH, Cochereau J, Maller JJ, Welton T, Almairac F, Seunarine KK, Clark CA, Zhang F, Makris N, Golby A, Rathi Y, O'Donnell LJ, Xia Y, Aydogan DB, Shi Y, Fernandes FG, Raemaekers M, Warrington S, Michielse S, Ramírez-Manzanares A, Concha L, Aranda R, Meraz MR, Lerma-Usabiaga G, Roitman L, Fekonja LS, Calarco N, Joseph M, Nakua H, Voineskos AN, Karan P, Grenier G, Legarreta JH, Adluru N, Nair VA, Prabhakaran V, Alexander AL, Kamagata K, Saito Y, Uchida W, Andica C, Abe M, Bayrak RG, Wheeler-Kingshott CAMG, D'Angelo E, Palesi F, Savini G, Rolandi N, Guevara P, Houenou J, López-López N, Mangin JF, Poupon C, Román C, Vázquez A, Maffei C, Arantes M, Andrade JP, Silva SM, Calhoun VD, Caverzasi E, Sacco S, Lauricella M, Pestilli F, Bullock D, Zhan Y, Brignoni-Perez E, Lebel C, Reynolds JE, Nestrasil I, Labounek R, Lenglet C, Paulson A, Aulicka S, Heilbronner SR, Heuer K, Chandio BQ, Guaje J, Tang W, Garyfallidis E, Raja R, Anderson AW, Landman BA, Descoteaux M. Tractography dissection variability: What happens when 42 groups dissect 14 white matter bundles on the same dataset? Neuroimage 2021; 243:118502. [PMID: 34433094 PMCID: PMC8855321 DOI: 10.1016/j.neuroimage.2021.118502] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 08/10/2021] [Accepted: 08/21/2021] [Indexed: 10/20/2022] Open
Abstract
White matter bundle segmentation using diffusion MRI fiber tractography has become the method of choice to identify white matter fiber pathways in vivo in human brains. However, like other analyses of complex data, there is considerable variability in segmentation protocols and techniques. This can result in different reconstructions of the same intended white matter pathways, which directly affects tractography results, quantification, and interpretation. In this study, we aim to evaluate and quantify the variability that arises from different protocols for bundle segmentation. Through an open call to users of fiber tractography, including anatomists, clinicians, and algorithm developers, 42 independent teams were given processed sets of human whole-brain streamlines and asked to segment 14 white matter fascicles on six subjects. In total, we received 57 different bundle segmentation protocols, which enabled detailed volume-based and streamline-based analyses of agreement and disagreement among protocols for each fiber pathway. Results show that even when given the exact same sets of underlying streamlines, the variability across protocols for bundle segmentation is greater than all other sources of variability in the virtual dissection process, including variability within protocols and variability across subjects. In order to foster the use of tractography bundle dissection in routine clinical settings, and as a fundamental analytical tool, future endeavors must aim to resolve and reduce this heterogeneity. Although external validation is needed to verify the anatomical accuracy of bundle dissections, reducing heterogeneity is a step towards reproducible research and may be achieved through the use of standard nomenclature and definitions of white matter bundles and well-chosen constraints and decisions in the dissection process.
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Research Support, N.I.H., Extramural |
4 |
83 |
10
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Sirois P, Borgeat P, Jeanson A, Roy S, Girard G. The action of leukotriene B4 (LTB4) on the lung. PROSTAGLANDINS AND MEDICINE 1980; 5:429-44. [PMID: 6258182 DOI: 10.1016/0161-4630(80)90067-1] [Citation(s) in RCA: 78] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The actions of leukotriene B4 (LTB4), a member of a newly discovered pathway of metabolism of arachidonic acid, were investigated both on the guinea-pig perfused lung preparation and on the parenchymal strip and compared to histamine and Slow Reacting Substance of Anaphylaxis (SRS-A). LTB was prepared from human polymorphonuclear leukocytes, extracted and purified by chromatography (Silicic acid and HPLC) and its purity was determined by gas chromatography and mass spectrometry. LTB4 is three times more potent than histamine (molar concentration) to contract the parenchymal strips and the contraction to LTB4 as well as to SRS-A lasted longer. The contraction to LTB4 is blocked by indomethacin (20 micrograms/ml), reduced by polyphloretin phosphate (50 micrograms/ml) and unaffected by FPL-55712 (1 micrograms/ml). Following its injection in the pulmonary artery of a perfused lung, LTB4 (1 microgram) induced the release of RCS (Rabbit Aorta Contracting Substance: a mixture of prostaglandins and thromboxanes) which can be abolished by indomethacin (1 microgram/ml). These findings suggest (a) that in the lung, LTB4 is a myotropic agent three times more powerful than histamine (b) that LTB4 stimulated a receptor which is different of histamine of SRS-A receptors, and (c) that its contractile action in the lung is mediated by prostaglandins and thromboxanes.
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Comparative Study |
45 |
78 |
11
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Hau J, Sarubbo S, Houde JC, Corsini F, Girard G, Deledalle C, Crivello F, Zago L, Mellet E, Jobard G, Joliot M, Mazoyer B, Tzourio-Mazoyer N, Descoteaux M, Petit L. Revisiting the human uncinate fasciculus, its subcomponents and asymmetries with stem-based tractography and microdissection validation. Brain Struct Funct 2016; 222:1645-1662. [PMID: 27581617 DOI: 10.1007/s00429-016-1298-6] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 08/22/2016] [Indexed: 12/29/2022]
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9 |
71 |
12
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Devroede G, Girard G, Bouchoucha M, Roy T, Black R, Camerlain M, Pinard G, Schang JC, Arhan P. Idiopathic constipation by colonic dysfunction. Relationship with personality and anxiety. Dig Dis Sci 1989; 34:1428-33. [PMID: 2527735 DOI: 10.1007/bf01538081] [Citation(s) in RCA: 68] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The personality of two groups of constipated women (by delayed colonic transit or by colonic inertia) was compared to that of two control groups of arthritic patients (rheumatoid or degenerative disease) with the Minnesota Multiphasic Personality Inventory (MMPI). All subjects suffered from chronic pain. Constipated women were found to have significantly higher scores on the hypochondria, hysteria, control, and low back pain scales and a lower score on the masculinity-femininity scale. Discriminant analysis permitted us to sort out constipated from arthritic patients in 83% of the cases, on the basis of only the personality data. In women with constipation by delayed colonic transit, multiple regression analysis demonstrated a close link (r = 0.90; P less than 0.001) between transit time in the ascending colon and levels of anxiety. It is concluded that women with constipation of colonic origin have a different pattern of personality than arthritic women and that severe constipation may play the role of a defense mechanism, where psychophysiologic responses to life stresses replace normal emotional reactions.
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36 |
68 |
13
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Labrie F, Archer DF, Bouchard C, Fortier M, Cusan L, Gomez JL, Girard G, Baron M, Ayotte N, Moreau M, Dubé R, Côté I, Labrie C, Lavoie L, Berger L, Gilbert L, Martel C, Balser J. Intravaginal dehydroepiandrosterone (prasterone), a highly efficient treatment of dyspareunia. Climacteric 2011; 14:282-8. [DOI: 10.3109/13697137.2010.535226] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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14 |
66 |
14
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Zhang Z, Descoteaux M, Zhang J, Girard G, Chamberland M, Dunson D, Srivastava A, Zhu H. Mapping population-based structural connectomes. Neuroimage 2018; 172:130-145. [PMID: 29355769 PMCID: PMC5910206 DOI: 10.1016/j.neuroimage.2017.12.064] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 11/09/2017] [Accepted: 12/20/2017] [Indexed: 11/23/2022] Open
Abstract
Advances in understanding the structural connectomes of human brain require improved approaches for the construction, comparison and integration of high-dimensional whole-brain tractography data from a large number of individuals. This article develops a population-based structural connectome (PSC) mapping framework to address these challenges. PSC simultaneously characterizes a large number of white matter bundles within and across different subjects by registering different subjects' brains based on coarse cortical parcellations, compressing the bundles of each connection, and extracting novel connection weights. A robust tractography algorithm and streamline post-processing techniques, including dilation of gray matter regions, streamline cutting, and outlier streamline removal are applied to improve the robustness of the extracted structural connectomes. The developed PSC framework can be used to reproducibly extract binary networks, weighted networks and streamline-based brain connectomes. We apply the PSC to Human Connectome Project data to illustrate its application in characterizing normal variations and heritability of structural connectomes in healthy subjects.
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Research Support, N.I.H., Extramural |
7 |
55 |
15
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Rheault F, De Benedictis A, Daducci A, Maffei C, Tax CMW, Romascano D, Caverzasi E, Morency FC, Corrivetti F, Pestilli F, Girard G, Theaud G, Zemmoura I, Hau J, Glavin K, Jordan KM, Pomiecko K, Chamberland M, Barakovic M, Goyette N, Poulin P, Chenot Q, Panesar SS, Sarubbo S, Petit L, Descoteaux M. Tractostorm: The what, why, and how of tractography dissection reproducibility. Hum Brain Mapp 2020; 41:1859-1874. [PMID: 31925871 PMCID: PMC7267902 DOI: 10.1002/hbm.24917] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 11/23/2019] [Accepted: 12/16/2019] [Indexed: 12/19/2022] Open
Abstract
Investigative studies of white matter (WM) brain structures using diffusion MRI (dMRI) tractography frequently require manual WM bundle segmentation, often called "virtual dissection." Human errors and personal decisions make these manual segmentations hard to reproduce, which have not yet been quantified by the dMRI community. It is our opinion that if the field of dMRI tractography wants to be taken seriously as a widespread clinical tool, it is imperative to harmonize WM bundle segmentations and develop protocols aimed to be used in clinical settings. The EADC-ADNI Harmonized Hippocampal Protocol achieved such standardization through a series of steps that must be reproduced for every WM bundle. This article is an observation of the problematic. A specific bundle segmentation protocol was used in order to provide a real-life example, but the contribution of this article is to discuss the need for reproducibility and standardized protocol, as for any measurement tool. This study required the participation of 11 experts and 13 nonexperts in neuroanatomy and "virtual dissection" across various laboratories and hospitals. Intra-rater agreement (Dice score) was approximately 0.77, while inter-rater was approximately 0.65. The protocol provided to participants was not necessarily optimal, but its design mimics, in essence, what will be required in future protocols. Reporting tractometry results such as average fractional anisotropy, volume or streamline count of a particular bundle without a sufficient reproducibility score could make the analysis and interpretations more difficult. Coordinated efforts by the diffusion MRI tractography community are needed to quantify and account for reproducibility of WM bundle extraction protocols in this era of open and collaborative science.
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Review |
5 |
53 |
16
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St-Onge E, Daducci A, Girard G, Descoteaux M. Surface-enhanced tractography (SET). Neuroimage 2018; 169:524-539. [DOI: 10.1016/j.neuroimage.2017.12.036] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 11/27/2017] [Accepted: 12/13/2017] [Indexed: 12/31/2022] Open
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52 |
17
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Girard G, Butterworth RF. Effect of portacaval anastomosis on glutamine synthetase activities in liver, brain, and skeletal muscle. Dig Dis Sci 1992; 37:1121-6. [PMID: 1352200 DOI: 10.1007/bf01300297] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
Glutamine synthetase is responsible for the ATP-dependent amidation of glutamate to glutamine. In liver the enzyme is highly localized in perivenous hepatocytes; in brain the enzyme is localized in astrocytes. Portacaval anastomosis resulted in liver atrophy, hyperammonemia, and up to 90% loss of glutamine synthetase activity in liver homogenates. This effect, which appears to be irreversible, probably reflects the selective loss of perivenous hepatocytes following portacaval anastomosis. Glutamine synthetase activities in brain were unaffected by portacaval anastomosis of up to 12 weeks' duration. Enzyme activities in homogenates of skeletal muscle, on the other hand, were significantly increased at one and four weeks after shunt surgery. These effects were not the result of decreased food intake in shunted animals. These findings suggest fundamentally different regulatory mechanisms for glutamine synthetase in these tissues. Skeletal muscle may thus provide an important alternative site for ammonia detoxification after portal-systemic shunting.
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Girard G, Daducci A, Petit L, Thiran JP, Whittingstall K, Deriche R, Wassermann D, Descoteaux M. AxTract: Toward microstructure informed tractography. Hum Brain Mapp 2017; 38:5485-5500. [PMID: 28766853 DOI: 10.1002/hbm.23741] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 07/13/2017] [Accepted: 07/13/2017] [Indexed: 12/13/2022] Open
Abstract
Diffusion-weighted (DW) magnetic resonance imaging (MRI) tractography has become the tool of choice to probe the human brain's white matter in vivo. However, tractography algorithms produce a large number of erroneous streamlines (false positives), largely due to complex ambiguous tissue configurations. Moreover, the relationship between the resulting streamlines and the underlying white matter microstructure characteristics remains poorly understood. In this work, we introduce a new approach to simultaneously reconstruct white matter fascicles and characterize the apparent distribution of axon diameters within fascicles. To achieve this, our method, AxTract, takes full advantage of the recent development DW-MRI microstructure acquisition, modeling, and reconstruction techniques. This enables AxTract to separate parallel fascicles with different microstructure characteristics, hence reducing ambiguities in areas of complex tissue configuration. We report a decrease in the incidence of erroneous streamlines compared to the conventional deterministic tractography algorithms on simulated data. We also report an average increase in streamline density over 15 known fascicles of the 34 healthy subjects. Our results suggest that microstructure information improves tractography in crossing areas of the white matter. Moreover, AxTract provides additional microstructure information along the fascicle that can be studied alongside other streamline-based indices. Overall, AxTract provides the means to distinguish and follow white matter fascicles using their microstructure characteristics, bringing new insights into the white matter organization. This is a step forward in microstructure informed tractography, paving the way to a new generation of algorithms able to deal with intricate configurations of white matter fibers and providing quantitative brain connectivity analysis. Hum Brain Mapp 38:5485-5500, 2017. © 2017 Wiley Periodicals, Inc.
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Research Support, Non-U.S. Gov't |
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Girard G, Giguère JF, Butterworth RF. Region-selective reductions in activities of glutamine synthetase in rat brain following portacaval anastomosis. Metab Brain Dis 1993; 8:207-15. [PMID: 7910653 DOI: 10.1007/bf01001062] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Portacaval anastomosis in the rat results in liver atrophy, sustained hyperammonemia and mild encephalopathy. Previous studies have demonstrated region-selective alterations of glutamine and other ammonia-related amino acids in brain following portacaval anastomosis. Ammonia removal by brain relies on glutamine synthesis and the enzyme responsible, glutamine synthetase, has an almost exclusively astrocytic localization. Glutamine synthetase activities were measured using a radioenzymatic assay in homogenates of seven brain regions of rats four weeks after end-to-side portacaval anastomosis. Enzyme activities were significantly reduced in hippocampus (by 25%, p < 0.01), in cerebellum (by 29%, p < 0.01) and in cerebral cortex (by 14%, p < 0.05). Enzyme activities in other brain regions were within normal limits. Region-selective reductions of glutamine synthetase following portacaval anastomosis could result in disruption of neuron-glial metabolic interactions and in a deficit of glutamatergic synaptic regulation. Similar mechanisms could be implicated in the pathogenesis of hepatic encephalopathy accompanying chronic liver disease in humans.
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Girard G, Caminiti R, Battaglia-Mayer A, St-Onge E, Ambrosen KS, Eskildsen SF, Krug K, Dyrby TB, Descoteaux M, Thiran JP, Innocenti GM. On the cortical connectivity in the macaque brain: A comparison of diffusion tractography and histological tracing data. Neuroimage 2020; 221:117201. [PMID: 32739552 DOI: 10.1016/j.neuroimage.2020.117201] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 07/17/2020] [Accepted: 07/22/2020] [Indexed: 12/22/2022] Open
Abstract
Diffusion-weighted magnetic resonance imaging (DW-MRI) tractography is a non-invasive tool to probe neural connections and the structure of the white matter. It has been applied successfully in studies of neurological disorders and normal connectivity. Recent work has revealed that tractography produces a high incidence of false-positive connections, often from "bottleneck" white matter configurations. The rich literature in histological connectivity analysis studies in the macaque monkey enables quantitative evaluation of the performance of tractography algorithms. In this study, we use the intricate connections of frontal, cingulate, and parietal areas, well established by the anatomical literature, to derive a symmetrical histological connectivity matrix composed of 59 cortical areas. We evaluate the performance of fifteen diffusion tractography algorithms, including global, deterministic, and probabilistic state-of-the-art methods for the connectivity predictions of 1711 distinct pairs of areas, among which 680 are reported connected by the literature. The diffusion connectivity analysis was performed on a different ex-vivo macaque brain, acquired using multi-shell DW-MRI protocol, at high spatial and angular resolutions. Across all tested algorithms, the true-positive and true-negative connections were dominant over false-positive and false-negative connections, respectively. Moreover, three-quarters of streamlines had endpoints location in agreement with histological data, on average. Furthermore, probabilistic streamline tractography algorithms show the best performances in predicting which areas are connected. Altogether, we propose a method for quantitative evaluation of tractography algorithms, which aims at improving the sensitivity and the specificity of diffusion-based connectivity analysis. Overall, those results confirm the usefulness of tractography in predicting connectivity, although errors are produced. Many of the errors result from bottleneck white matter configurations near the cortical grey matter and should be the target of future implementation of methods.
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Research Support, Non-U.S. Gov't |
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39 |
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Koch PJ, Park CH, Girard G, Beanato E, Egger P, Evangelista GG, Lee J, Wessel MJ, Morishita T, Koch G, Thiran JP, Guggisberg AG, Rosso C, Kim YH, Hummel FC. The structural connectome and motor recovery after stroke: predicting natural recovery. Brain 2021; 144:2107-2119. [PMID: 34237143 PMCID: PMC8370413 DOI: 10.1093/brain/awab082] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 11/11/2020] [Accepted: 12/14/2020] [Indexed: 11/20/2022] Open
Abstract
Stroke patients vary considerably in terms of outcomes: some patients present 'natural' recovery proportional to their initial impairment (fitters), while others do not (non-fitters). Thus, a key challenge in stroke rehabilitation is to identify individual recovery potential to make personalized decisions for neuro-rehabilitation, obviating the 'one-size-fits-all' approach. This goal requires (i) the prediction of individual courses of recovery in the acute stage; and (ii) an understanding of underlying neuronal network mechanisms. 'Natural' recovery is especially variable in severely impaired patients, underscoring the special clinical importance of prediction for this subgroup. Fractional anisotropy connectomes based on individual tractography of 92 patients were analysed 2 weeks after stroke (TA) and their changes to 3 months after stroke (TC - TA). Motor impairment was assessed using the Fugl-Meyer Upper Extremity (FMUE) scale. Support vector machine classifiers were trained to separate patients with natural recovery from patients without natural recovery based on their whole-brain structural connectomes and to define their respective underlying network patterns, focusing on severely impaired patients (FMUE < 20). Prediction accuracies were cross-validated internally, in one independent dataset and generalized in two independent datasets. The initial connectome 2 weeks after stroke was capable of segregating fitters from non-fitters, most importantly among severely impaired patients (TA: accuracy = 0.92, precision = 0.93). Secondary analyses studying recovery-relevant network characteristics based on the selected features revealed (i) relevant differences between networks contributing to recovery at 2 weeks and network changes over time (TC - TA); and (ii) network properties specific to severely impaired patients. Important features included the parietofrontal motor network including the intraparietal sulcus, premotor and primary motor cortices and beyond them also attentional, somatosensory or multimodal areas (e.g. the insula), strongly underscoring the importance of whole-brain connectome analyses for better predicting and understanding recovery from stroke. Computational approaches based on structural connectomes allowed the individual prediction of natural recovery 2 weeks after stroke onset, especially in the difficult to predict group of severely impaired patients, and identified the relevant underlying neuronal networks. This information will permit patients to be stratified into different recovery groups in clinical settings and will pave the way towards personalized precision neurorehabilitative treatment.
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van Meerten D, Girard G, van Duin J. Translational control by delayed RNA folding: identification of the kinetic trap. RNA (NEW YORK, N.Y.) 2001; 7:483-494. [PMID: 11333027 PMCID: PMC1370103 DOI: 10.1017/s1355838201001984] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The maturation or A-protein gene of single-stranded RNA phage MS2 is preceded by a 130-nt long untranslated leader. When MS2 RNA folding is at equilibrium, the gene is untranslatable because the leader adopts a well-defined cloverleaf structure in which the Shine-Dalgarno (SD) sequence of the maturation gene is taken up in long-distance base pairing with an upstream complementary sequence (UCS). Synthesis of the A-protein takes place transiently while the RNA is synthesized from the minus strand. This requires that formation of the inhibitory cloverleaf is slow. In vitro, the folding delay was on the order of minutes. Here, we present evidence that this postponed folding is caused by the formation of a metastable intermediate. This intermediate is a small local hairpin that contains the UCS in its loop, thereby preventing or slowing down its pairing with the SD sequence. Mutants in which the small hairpin could not be formed made no detectable amounts of A-protein and were barely viable. Apparently, here the cloverleaf formed quicker than ribosomes could bind. On the other hand, mutants in which the small intermediary hairpin was stabilized produced more A-protein than wild type and were viable. One hardly growing mutant that could not form the metastable hairpin and did not make detectable amounts of A-protein was evolved. The emerging pseudo-revertant had selected two second site repressor mutations that allowed reconstruction of a variant of the metastable intermediate. The pseudo-revertant had also regained the capacity to produce the A-protein.
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Bernard-Bonnin AC, Stachtchenko S, Girard G, Rousseau E. Hospital practices and breastfeeding duration: a meta-analysis of controlled trials. Birth 1989; 16:64-6. [PMID: 2547392 DOI: 10.1111/j.1523-536x.1989.tb00863.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Controlled clinical trials studying the influence of hospital practices on breastfeeding duration were combined using meta-analysis. Nine studies were selected. Supplementation demonstrated a negative clinical effect on breastfeeding duration that was not significant. Nursing support demonstrated a positive clinical effect on breastfeeding duration that was not statistically significant if there was no telephone follow-up, but was significant if there was telephone follow-up. Early contact revealed a positive clinical effect that was significant. We conclude that early contact and nursing support with telephone follow-up appear as enhancing factors of breastfeeding duration.
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Rensonnet G, Scherrer B, Girard G, Jankovski A, Warfield SK, Macq B, Thiran JP, Taquet M. Towards microstructure fingerprinting: Estimation of tissue properties from a dictionary of Monte Carlo diffusion MRI simulations. Neuroimage 2019; 184:964-980. [PMID: 30282007 PMCID: PMC6230496 DOI: 10.1016/j.neuroimage.2018.09.076] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 09/18/2018] [Accepted: 09/25/2018] [Indexed: 12/12/2022] Open
Abstract
Many closed-form analytical models have been proposed to relate the diffusion-weighted magnetic resonance imaging (DW-MRI) signal to microstructural features of white matter tissues. These models generally make assumptions about the tissue and the diffusion processes which often depart from the biophysical reality, limiting their reliability and interpretability in practice. Monte Carlo simulations of the random walk of water molecules are widely recognized to provide near groundtruth for DW-MRI signals. However, they have mostly been limited to the validation of simpler models rather than used for the estimation of microstructural properties. This work proposes a general framework which leverages Monte Carlo simulations for the estimation of physically interpretable microstructural parameters, both in single and in crossing fascicles of axons. Monte Carlo simulations of DW-MRI signals, or fingerprints, are pre-computed for a large collection of microstructural configurations. At every voxel, the microstructural parameters are estimated by optimizing a sparse combination of these fingerprints. Extensive synthetic experiments showed that our approach achieves accurate and robust estimates in the presence of noise and uncertainties over fixed or input parameters. In an in vivo rat model of spinal cord injury, our approach provided microstructural parameters that showed better correspondence with histology than five closed-form models of the diffusion signal: MMWMD, NODDI, DIAMOND, WMTI and MAPL. On whole-brain in vivo data from the human connectome project (HCP), our method exhibited spatial distributions of apparent axonal radius and axonal density indices in keeping with ex vivo studies. This work paves the way for microstructure fingerprinting with Monte Carlo simulations used directly at the modeling stage and not only as a validation tool.
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Research Support, N.I.H., Extramural |
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Grolla A, Jones S, Kobinger G, Sprecher A, Girard G, Yao M, Roth C, Artsob H, Feldmann H, Strong JE. Flexibility of mobile laboratory unit in support of patient management during the 2007 Ebola-Zaire outbreak in the Democratic Republic of Congo. Zoonoses Public Health 2013; 59 Suppl 2:151-7. [PMID: 22958259 DOI: 10.1111/j.1863-2378.2012.01477.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mobile laboratory provides a safe, rapid and flexible platform to provide effective diagnosis of Ebola virus as well as additional differential diagnostic agents in remote settings of equatorial Africa. During the 2007 Democratic Republic of Congo outbreak of Ebola-Zaire, the mobile laboratory was set up in two different locations by two separate teams within a day of equipment arriving in each location. The first location was in Mweka where our laboratory took over the diagnostic laboratory space of the local hospital, whereas the second location, approximately 50 km south near Kampungu at the epicentre of the outbreak, required local labour to fabricate a tent structure as a suitable pre-existing structure was not available. In both settings, the laboratory was able to quickly set up, providing accurate and efficient molecular diagnostics (within 3 h of receiving samples) for 67 individuals, including four cases of Ebola, seven cases of Shigella and 13 cases of malaria. This rapid turn-around time provides an important role in the support of patient management and epidemiological surveillance.
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Journal Article |
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