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Schooling SR, Klinger K, Korenevski A, Glasauer S. Reduction of antibiotic-induced biofilm accumulation of Pseudomonas aeruginosa by quaternized phytoglycogen. Lett Appl Microbiol 2021; 73:544-552. [PMID: 34398504 DOI: 10.1111/lam.13554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 07/19/2021] [Accepted: 07/21/2021] [Indexed: 11/28/2022]
Abstract
Biofilms are oft cited as a factor in the unwanted persistence and recalcitrance of microbial life and a strong research initiative exists to identify, understand, and target vulnerabilities. Phytoglycogen is a biodegradable nanoparticulate biomaterial that is purified from crop plants. Importantly, the highly branched glucan structure provides a scaffold on which to construct novel polymers. Functionalized phytoglycogen (FP) was synthesized using green chemistry principles. Screening of several molecules identified a form of quaternized phytoglycogen which reduced biofilm formation and accretion by Pseudomonas aeruginosa. Exposing P. aeruginosa to modified phytoglycogen and antibiotic in combination not only substantively reduced biofilms, but also prevented increased biofilm formation, a biological response to suboptimal antibiotic concentrations. Treatment of pregrown biofilms with sub-minimum inhibitory concentration antibiotic alone also led to increased proliferation, whereas FP-antibiotic combinations prevented or reduced the extent of this. Swimming, swarming and twitching motility, all critical for biofilm development, were negatively affected by FP. This work supports phytoglycogen as a promising foundational molecule for novel polymers, including those with anti-biofilm function. Critically, in addition to published reports on how suboptimal antibiotic concentrations promote biofilm formation, we demonstrated a similar effect upon pre-existing biofilms, indicating a further route for the failure of antibiotic therapies.
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Affiliation(s)
- S R Schooling
- School of Environmental Sciences, University of Guelph, Guelph, ON, Canada
| | - K Klinger
- Mirexus Biotechnologies Incorporated, Guelph, ON, Canada
| | - A Korenevski
- Mirexus Biotechnologies Incorporated, Guelph, ON, Canada
| | - S Glasauer
- School of Environmental Sciences, University of Guelph, Guelph, ON, Canada
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Dietrich H, Heidger F, Schniepp R, MacNeilage P, Glasauer S, Wuehr M. P85 Head motion predictability explains phase- and speed-dependent suppression of vestibular balance control during walking. Clin Neurophysiol 2020. [DOI: 10.1016/j.clinph.2019.12.083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Dietrich H, Heidger F, Schniepp R, MacNeilage PR, Glasauer S, Wuehr M. Head motion predictability explains activity-dependent suppression of vestibular balance control. Sci Rep 2020; 10:668. [PMID: 31959778 PMCID: PMC6971007 DOI: 10.1038/s41598-019-57400-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 12/21/2019] [Indexed: 11/25/2022] Open
Abstract
Vestibular balance control is dynamically weighted during locomotion. This might result from a selective suppression of vestibular inputs in favor of a feed-forward balance regulation based on locomotor efference copies. The feasibility of such a feed-forward mechanism should however critically depend on the predictability of head movements (HMP) during locomotion. To test this, we studied in 10 healthy subjects the differential impact of a stochastic vestibular stimulation (SVS) on body sway (center-of-pressure, COP) during standing and walking at different speeds and compared it to activity-dependent changes in HMP. SVS-COP coupling was determined by correlation analysis in frequency and time domains. HMP was quantified as the proportion of head motion variance that can be explained by the average head trajectory across the locomotor cycle. SVS-COP coupling decreased from standing to walking and further dropped with faster locomotion. Correspondingly, HMP increased with faster locomotion. Furthermore, SVS-COP coupling depended on the gait-cycle-phase with peaks corresponding to periods of least HMP. These findings support the assumption that during stereotyped human self-motion, locomotor efference copies selectively replace vestibular cues, similar to what was previously observed in animal models.
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Affiliation(s)
- H Dietrich
- German Center for Vertigo and Balance Disorders, University Hospital, LMU, Munich, Germany
| | - F Heidger
- Department of Neurology, University Hospital, LMU, Munich, Germany
| | - R Schniepp
- German Center for Vertigo and Balance Disorders, University Hospital, LMU, Munich, Germany
- Department of Neurology, University Hospital, LMU, Munich, Germany
| | - P R MacNeilage
- German Center for Vertigo and Balance Disorders, University Hospital, LMU, Munich, Germany
- Department of Psychology, Cognitive and Brain Sciences, University of Nevada, Nevada, USA
| | - S Glasauer
- German Center for Vertigo and Balance Disorders, University Hospital, LMU, Munich, Germany
- Institute of Medical Technology, Brandenburg University of Technology Cottbus-Senftenberg, Senftenberg, Germany
| | - M Wuehr
- German Center for Vertigo and Balance Disorders, University Hospital, LMU, Munich, Germany.
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Lehnen N, Henningsen P, Ramaioli C, Glasauer S. An experimental litmus test of the emerging hypothesis that persistent physical symptoms can be explained as perceptual dysregulation. J Psychosom Res 2018; 114:15-17. [PMID: 30314573 DOI: 10.1016/j.jpsychores.2018.08.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 08/16/2018] [Indexed: 12/20/2022]
Affiliation(s)
- N Lehnen
- Technical University of Munich, University Hospital rechts der Isar, Department of Psychosomatic Medicine and Psychotherapy & Brandenburg Technical University, Institute of Medical Technology, Germany.
| | - P Henningsen
- Technical University of Munich, University Hospital rechts der Isar, Department of Psychosomatic Medicine and Psychotherapy, Germany
| | - C Ramaioli
- Brandenburg Technical University, Institute of Medical Technology & Technical University of Munich, University Hospital rechts der Isar, Department of Psychosomatic Medicine and Psychotherapy, Germany
| | - S Glasauer
- Brandenburg Technical University, Institute of Medical Technology, Germany
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Glasauer S, Dieterich M, Brandt T. Neuronal network-based mathematical modeling of perceived verticality in acute unilateral vestibular lesions: from nerve to thalamus and cortex. J Neurol 2018; 265:101-112. [PMID: 29845378 DOI: 10.1007/s00415-018-8909-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 05/14/2018] [Accepted: 05/16/2018] [Indexed: 11/29/2022]
Abstract
Acute unilateral lesions of vestibular graviceptive pathways from the otolith organs and semicircular canals via vestibular nuclei and the thalamus to the parieto-insular vestibular cortex regularly cause deviations of perceived verticality in the frontal roll plane. These tilts are ipsilateral in peripheral and in ponto-medullary lesions and contralateral in ponto-mesencephalic lesions. Unilateral lesions of the vestibular thalamus or cortex cause smaller tilts of the perceived vertical, which may be either ipsilateral or contralateral. Using a neural network model, we previously explained why unilateral vestibular midbrain lesions rarely manifest with rotational vertigo. We here extend this approach, focussing on the direction-specific deviations of perceived verticality in the roll plane caused by acute unilateral vestibular lesions from the labyrinth to the cortex. Traditionally, the effect of unilateral peripheral lesions on perceived verticality has been attributed to a lesion-based bias of the otolith system. We here suggest, on the basis of a comparison of model simulations with patient data, that perceived visual tilt after peripheral lesions is caused by the effect of a torsional semicircular canal bias on the central gravity estimator. We further argue that the change of gravity coding from a peripheral/brainstem vectorial representation in otolith coordinates to a distributed population coding at thalamic and cortical levels can explain why unilateral thalamic and cortical lesions have a variable effect on perceived verticality. Finally, we propose how the population-coding network for gravity direction might implement the elements required for the well-known perceptual underestimation of the subjective visual vertical in tilted body positions.
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Affiliation(s)
- S Glasauer
- Department of Neurology, University Hospital, Ludwig-Maximilians-University, Munich, Germany. .,German Center for Vertigo and Balance Disorders, Ludwig-Maximilians-University, Munich, Germany.
| | - M Dieterich
- Department of Neurology, University Hospital, Ludwig-Maximilians-University, Munich, Germany.,German Center for Vertigo and Balance Disorders, Ludwig-Maximilians-University, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - T Brandt
- German Center for Vertigo and Balance Disorders, Ludwig-Maximilians-University, Munich, Germany.,Clinical Neuroscience, Ludwig-Maximilians-University, Munich, Germany
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Saglam M, Glasauer S, Lehnen N. Über die Feedforward Kontrolle der Blickstabilisierung während Auge-Kopf-Bewegungen. KLIN NEUROPHYSIOL 2013. [DOI: 10.1055/s-0033-1337286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Schneider E, Lehnen N, Bartl K, Bardins S, Kohlbecher S, Glasauer S, Jahn K. Zentral oder peripher? Schwindelursachen auf der Spur mit dem video-basierten Kopfimpulstest. KLIN NEUROPHYSIOL 2012. [DOI: 10.1055/s-0032-1301511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Lehnen N, Bartl K, Bardins S, Kohlbecher S, Glasauer S, Jahn K, Schneider E. Der video-basierte Kopfimpulstest zur Quantifizierung peripher-vestibulärer Funktion bei Kindern und Jugendlichen. KLIN NEUROPHYSIOL 2011. [DOI: 10.1055/s-0031-1272766] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Schwarzkopf R, Valdeolivas I, Wutte M, Zwergal A, Glasauer S, Jahn K. Path integration ability in humans: establishing a new diagnostic tool. KLIN NEUROPHYSIOL 2011. [DOI: 10.1055/s-0031-1272759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Spiegel R, Kalla R, Rettinger N, Schneider E, Straumann D, Marti S, Glasauer S, Brandt T, Strupp M. Head position during resting modifies spontaneous daytime decrease of downbeat nystagmus. Neurology 2011; 75:1928-32. [PMID: 21098408 DOI: 10.1212/wnl.0b013e3181feb22f] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND The intensity of downbeat nystagmus (DBN) decreases during the daytime when the head is in upright position. OBJECTIVE This prospective study investigated whether resting in different head positions (upright, supine, prone) modulates the intensity of DBN after resting. METHODS Eye movements of 9 patients with DBN due to cerebellar (n = 2) or unknown etiology (n = 7) were recorded with video-oculography. Mean slow-phase velocities (SPV) of DBN were determined in the upright position before resting at 9 am and then after 2 hours (11 am) and after 4 hours (1 pm) of resting. Whole-body positions during resting were upright, supine, or prone. The effects of all 3 resting positions were assessed on 3 separate days in each patient. RESULTS Before resting (9 am), the average SPV ranged from 3.05 °/s to 3.6 °/s on the separate days of measurement. After resting in an upright position, the average SPV at 11 am and 1 pm was 0.65 °/sec, which was less (p < 0.05) than after resting in supine (2.1 °/sec) or prone (2.22 °/sec) positions. CONCLUSION DBN measured during the daytime in an upright position becomes minimal after the patient has rested upright. The spontaneous decrease of DBN is less pronounced when patients lie down to rest. This indicates a modulation by otolithic input. We recommend that patients with DBN rest in an upright position during the daytime. CLASSIFICATION OF EVIDENCE This study provides Class II evidence that for patients with DBN 2 hours of rest in the upright position decreases nystagmus more than 2 hours of rest in the supine or prone positions (relative improvement 79% upright, 33% supine, and 38% prone: p < 0.05).
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Affiliation(s)
- R Spiegel
- Department of Neurology and IFB, Ludwig-Maximilians-University, Campus Grosshadern, Marchioninistr. 15, 81377 Munich, Germany
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Schneider KD, van Straaten P, de Orduña RM, Glasauer S, Trevors J, Fallow D, Smith PS. Comparing phosphorus mobilization strategies using Aspergillus niger for the mineral dissolution of three phosphate rocks. J Appl Microbiol 2010; 108:366-74. [PMID: 19709342 DOI: 10.1111/j.1365-2672.2009.04489.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phosphorus deficiencies are limiting crop production in agricultural soils worldwide. Locally available sources of raw phosphate rock (PR) are being recognized for their potential role in soil fertility improvement. Phosphorus bioavailability is essential for the efficiency of PRs and can be increased by acid treatments. The utilization of organic acid producing micro-organisms, notably Aspergillus niger, presents a sustainable alternative to the use of strong inorganic acids, but acid production of A. niger strongly depends on the mineral content of the growth media. This study compared the phosphorus mobilization efficiency of two biological treatments, namely addition of acidic cell-free supernatants from A. niger cultivations to PRs and the direct cultivation of A. niger with PRs. The results show that addition of PR to cultivations leads to significant differences in the profile of organic acids produced by A. niger. Additions of PR, especially igneous rocks containing high amounts of iron and manganese, lead to reduced citric acid concentrations. In spite of these differences, phosphorus mobilization was similar between treatments, suggesting that the simpler direct cultivation method was not inferior. In addition to citric acid, it is suggested that oxalic acid contributes to PR solubilization in direct cultivations with A. niger, which would benefit farmers in developing countries where conventional fertilizers are not adequately accessible.
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Affiliation(s)
- K D Schneider
- Department of Land Resource Science, University of Guelph, Guelph, ON, Canada N1G 2W1.
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Hüfner K, Stephan T, Flanagin V, Deutschländer A, Dera T, Karch C, Linn J, Glasauer S, Dieterich M, Strupp M, Brandt T. Cerebellar and Visual Gray Matter Brain Volume Increases in Congenital Nystagmus. KLIN NEUROPHYSIOL 2010. [DOI: 10.1055/s-0030-1250968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Spiegel R, Kalla R, Rettinger N, Schneider E, Straumann D, Claassen J, Glasauer S, Marti S, Brandt T, Strupp M. The influence of resting in light or darkness on the spontaneous decrease of downbeat nystagmus. KLIN NEUROPHYSIOL 2010. [DOI: 10.1055/s-0030-1250845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Spiegel R, Kalla R, Rettinger N, Schneider E, Straumann D, Marti S, Claassen J, Glasauer S, Brandt T, Strupp M. The influence of positional effects on the spontaneous decrease of downbeat nystagmus in the course of the day. KLIN NEUROPHYSIOL 2010. [DOI: 10.1055/s-0030-1250844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Deutschländer A, Hüfner K, Stephan T, Flanagin V, Glasauer S, Dera T, Jahn K, Fesl G, Dieterich M, Strupp M, Brandt T. Does the oculomotor vermis generate congenital nystagmus? KLIN NEUROPHYSIOL 2010. [DOI: 10.1055/s-0030-1250859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Kremmyda O, Rettinger N, Strupp M, Buttner U, Glasauer S. Teaching Video NeuroImages: Unilateral RIMLF lesion: Pathologic eye movement torsion indicates lesion side and site. Neurology 2009; 73:e92-3. [DOI: 10.1212/wnl.0b013e3181c04654] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Flanagin V, Guenther A, Bardins S, Brandt T, Glasauer S. Dual task interference during linear distance estimation: an fMRI study. Neuroimage 2009. [DOI: 10.1016/s1053-8119(09)71010-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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Kalla R, Spiegel R, Rettinger N, Glasauer S, Strupp M. Therapy of downbeat nystagmus: 4-aminopridine versus 3,4-diaminopyridine. KLIN NEUROPHYSIOL 2009. [DOI: 10.1055/s-0029-1216151] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Hüfner K, Stephan T, Flanagin V, Kalla R, Deutschländer A, Glasauer S, Fesl G, Strupp M, Brandt T. The resting brain in blind subjects – an fMRI study with eyes open and closed in darkness. KLIN NEUROPHYSIOL 2009. [DOI: 10.1055/s-0029-1216235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Nuding U, Kalla R, Muggleton NG, Buttner U, Walsh V, Glasauer S. TMS Evidence for Smooth Pursuit Gain Control by the Frontal Eye Fields. Cereb Cortex 2008; 19:1144-50. [DOI: 10.1093/cercor/bhn162] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kremmyda O, Wagner J, Büttner U, Glasauer S. P06. Holmes tremor of the head caused by a left midbrain astrocytoma. Clin Neurophysiol 2007. [DOI: 10.1016/j.clinph.2007.09.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Hüfner K, Stephan T, Kalla R, Deutschländer A, Wagner J, Holtmannspötter M, Schulte-Altedorneburg G, Strupp M, Brandt T, Glasauer S. Structural and functional MRIs disclose cerebellar pathologies in idiopathic downbeat nystagmus. Neurology 2007; 69:1128-35. [PMID: 17846412 DOI: 10.1212/01.wnl.0000276953.00969.48] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Neurologic disorders in which the etiology and pathogenesis are not yet understood are termed idiopathic. Downbeat nystagmus (DBN) is a frequent eye movement disorder that clinically manifests with oscillopsia and postural instability. Forty percent of patients with DBN are classified as having idiopathic DBN, because no underlying pathology can be demonstrated by conventional MRI or laboratory tests. METHODS We evaluated gray matter brain volumes of 11 patients with idiopathic DBN and compared them to those of healthy controls using voxel-based morphometry. In a second, functional MRI experiment, patients and controls performed downward smooth pursuit eye movements (DOWN), which were then compared with straight-ahead fixation of a stationary target (MID). RESULTS Small areas of localized gray matter atrophy were detected in the lateral cerebellar hemispheres (lobule VI) and ocular motor vermis of patients with idiopathic DBN, but not in the flocculus and paraflocculus. The functional imaging data, however, revealed reduced activation in the parafloccular lobule and in the ponto-medullary brainstem of the patients when they performed smooth pursuit eye movements downwards. CONCLUSIONS The applied specialized imaging and data analysis techniques disclosed pathologies in an idiopathic eye movement disorder. The focal atrophy found in the vermal and lateral cerebellar regions in downbeat nystagmus (DBN) may lead to deficits in smooth pursuit eye movement initiation, which in turn causes hypofunction of the parafloccular lobe, associated with DBN. Our data are in line with experiments in primates showing that ablation of the floccular and parafloccular lobes disrupts smooth pursuit and causes DBN.
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Affiliation(s)
- K Hüfner
- Department of Neurology, Klinikum Grosshadern, Neurologisches Forschungshaus, Munich, Germany.
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Glasauer S, Marti S, Nuding U, Straumann D, Büttner U. Ein mathematisches Modell vertikaler Augenbewegungen zur Simulation von Downbeat-Nystagmus. KLIN NEUROPHYSIOL 2007. [DOI: 10.1055/s-2007-976397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Jahn K, Stein A, Brandt T, Glasauer S. Entfernungsschätzung durch „Path integration“ bei Ameise und Mensch. KLIN NEUROPHYSIOL 2007. [DOI: 10.1055/s-2007-976315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Nuding U, Glasauer S, Eggert T, Büttner U. Modellierung und Analyse der Verstärkungsregelung von Augenfolgebewegungen. KLIN NEUROPHYSIOL 2007. [DOI: 10.1055/s-2007-976401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Stephan T, Kupferberg A, Stein A, Dera T, Bardins S, Brandt T, Glasauer S. Subjektiver visueller Zenit – funktionelle MRT der Schwerkraftwahrnehmung. KLIN NEUROPHYSIOL 2007. [DOI: 10.1055/s-2007-976352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Hüfner K, Kalla R, Hamilton D, Stephan T, Glasauer S, Ma J, Brüning R, Markowitsch H, Labudda K, Schichor C, Strupp M, Brandt T. Räumliches Gedächtnis und Navigation bei Patienten mit einseitiger vestibulärer Deafferentierung. KLIN NEUROPHYSIOL 2007. [DOI: 10.1055/s-2007-976353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Lehnen N, Büttner U, Glasauer S. Vestibuläre Kontrolle von Willkürbewegungen – Systemanalyse und Modellbildung. KLIN NEUROPHYSIOL 2007. [DOI: 10.1055/s-2007-976398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Lehnen N, Büttner U, Glasauer S. Willkürbewegung des Kopfes: vestibuläre Rückkopplung und Kleinhirn. Akt Neurol 2007. [DOI: 10.1055/s-2007-987459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Wagner J, Lehnen N, Rettinger N, Karch C, Büttner U, Glasauer S, Brandt T, Strupp M. Downbeat nystagmus caused by a paramedian ponto-medullary lesion. Akt Neurol 2007. [DOI: 10.1055/s-2007-988062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Glasauer S, Langley S, Boyanov M, Lai B, Kemner K, Beveridge TJ. Mixed-valence cytoplasmic iron granules are linked to anaerobic respiration. Appl Environ Microbiol 2006; 73:993-6. [PMID: 17142380 PMCID: PMC1800766 DOI: 10.1128/aem.01492-06] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Intracellular granules containing ferric and ferrous iron formed in Shewanella putrefaciens CN32 during dissimilatory reduction of solid-phase ferric iron. It is the first in situ detection at high resolution (150 nm) of a mixed-valence metal particle residing within a prokaryotic cell. The relationship of the internal particles to Fe(III) reduction may indicate a respiratory role.
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Affiliation(s)
- S Glasauer
- Department of Land Resource Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
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Wright WG, Glasauer S. Subjective somatosensory vertical during dynamic tilt is dependent on task, inertial condition, and multisensory concordance. Exp Brain Res 2006; 172:310-21. [PMID: 16463151 DOI: 10.1007/s00221-006-0347-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2004] [Accepted: 12/12/2005] [Indexed: 11/24/2022]
Abstract
To investigate how visual and vestibular cues are integrated for the perception of gravity during passive self-motion, we measured the ability to maintain a handheld object vertical relative to gravity without visual feedback during sinusoidal roll-tilt stimulation. Visual input, either concordant or discordant with actual dynamic roll-tilt, was delivered by a head-mounted display showing the laboratory. The four visual conditions were darkness, visual-vestibular concordance, stationary visual scene, and a visual scene 180 degrees phase-shifted relative to actual tilt. Tilt-indication performance using a solid, cylindrical joystick was better in the presence of concordant visual input relative to the other visual conditions. In addition, we compared performance when indicating the vertical by the joystick or a full glass of water. Subjects indicated the direction of gravity significantly better when holding the full glass of water than the joystick. Matching the inertial characteristics, including fluid properties, of the handheld object to the glass of water did not improve performance. There was no effect of visual input on tilt performance when using the glass of water to indicate gravitational vertical. The gain of object tilt motion did not change with roll-tilt amplitude and frequency (+/-7.5 degrees at 0.25 Hz, +/-10 degrees at 0.16 Hz, and +/-20 degrees at 0.08 Hz), however, the phase of object tilt relative to subject tilt showed significant phase-leads at the highest frequency tested (0.25 Hz). Comparison of the object and visual effects observed suggest that the task-dependent behavior change may be due to an attentional shift and/or shift in strategy.
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Affiliation(s)
- W G Wright
- Department of Neurology and Center for Sensorimotor Research, Klinikum Grosshadern, Ludwig-Maximilians University, 81377, Munich, Germany.
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Abstract
The authors evaluated floccular activity with fMRI during the performance of vertical smooth pursuit eye movements in four patients with downbeat nystagmus (DBN) due to cerebellar degeneration and in 16 healthy controls. Region of interest analysis revealed a significantly diminished activation of both floccular lobes during downward but not upward pursuit in DBN. These imaging data support the view that a functional deficiency of the flocculi in downward pursuit causes DBN.
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Affiliation(s)
- R Kalla
- Department of Neurology, University of Munich, Germany
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Kalla R, Glasauer S, Büttner U, Brandt T, Strupp M. 4-Aminopyridine restores neural integrator function in downbeat nystagmus. Akt Neurol 2006. [DOI: 10.1055/s-2006-953052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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36
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Zingler V, Krivoshey D, Schneider E, Glasauer S, Brandt T, Strupp M. Comparison of static ocular counter-roll induced by active and passive head tilt and whole body roll. Akt Neurol 2005. [DOI: 10.1055/s-2005-919324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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37
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Abstract
The increased postural sway of patients with disorders of the vestibular system improves with vision. The suppression of pathologic nystagmus also reduces sway. Because the latter effect cannot be attributed to retinal slip as a relevant feedback for postural control, the authors investigated how eye movements rather than retinal slip affect balance. They found that slow eye movements increase sway, possibly by an efference copy, which explains why spontaneous nystagmus causes postural imbalance.
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Affiliation(s)
- S Glasauer
- Department of Neurology, Ludwig-Maximilians University, Munich, Germany.
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Abstract
The effect of the potassium channel blocker 4-aminopyridine (4-AP) on spontaneous upbeat nystagmus (UBN) was investigated with the search coil technique during fixation in different gaze positions and smooth pursuit in a patient before and after ingestion of 10 mg 4-AP. UBN was reduced from 8.6 deg/s to 2.0 deg/s by 4-AP causing subjective relief from distressing oscillopsia, and impaired upward smooth pursuit was restored (gains: before medication 0.38; after medication 0.86). In the dark, UBN was slightly stronger and not affected by 4-AP. We propose that 4-AP improved the function of cerebellar pathways that mediate gaze holding and smooth pursuit by intensifying the excitability of cerebellar Purkinje cells.
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Affiliation(s)
- S Glasauer
- Department of Neurology, Klinikum Grosshadern, Marchioninistrasse 23, 81377 Munich, Germany.
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39
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Abstract
BACKGROUND In a recent study, the authors found that blinks in healthy volunteers always triggered ocular torsion quick phases during dynamic roll movements of the head. On the basis of this observation, they hypothesized that blinks in patients with a vestibular tone imbalance would also trigger torsional quick phases. METHODS Using video-oculography with a fixation target, the authors recorded the ocular torsion position of the left eye of 37 participants while they made voluntary blinks once every 6 to 10 seconds. The participants were recruited from four groups: two age groups of healthy volunteers with a mean +/- SD age of 32 +/- 4 (n = 9) and 65 +/- 11 y (n = 9); patients with a unilateral vestibular disorder in an acute state (n = 12, 53 +/- 17 y); and those in a persisting state in which spontaneous nystagmus had already faded (n = 9, 65 +/- 13 y). RESULTS In the control groups of healthy volunteers, blinks triggered no or only small quick phases on the order of 0.1 deg. In both patient groups blinks always triggered quick phases with significantly higher amplitudes of 1.85 +/- 1.02 deg and were followed by exponentially decaying slow-phases with time constants on the order of 1 to 2 seconds. Patients in the persisting state clearly differed from patients in the acute state in that their torsional spontaneous nystagmus had already vanished due to vestibular compensation. But surprisingly, these two groups did not show a large difference in terms of the effect of blinks on ocular torsion. The authors always observed torsional quick phases with the upper pole of the eye beating away from the side of the lesion. CONCLUSIONS Blinks are able to trigger torsional quick phases in patients with both acute and persisting vestibular disorders. The side of the impairment can be determined from the direction in which the eye is rotated after a blink. Thus, ocular torsion recordings during blinks can be used as a simple clinical test for a vestibular tone imbalance, particularly during a persisting failure in which spontaneous nystagmus has resolved and can therefore no longer be used for diagnosis.
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Affiliation(s)
- E Schneider
- Department of Neurology, University Hospital of Munich-Grosshadern, Marchioninistr. 23, D-81377 Munich, Germany.
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Abstract
Patients with episodic ataxia type 2 (EA2) can often be successfully treated with acetazolamide. The authors report three patients with EA2 (two with proven mutations in the CACNA1A gene) whose attacks were prevented with the potassium channel blocker 4-aminopyridine (4-AP; 5 mg tid). Attacks recurred after treatment was stopped; subsequent treatment alleviated the symptoms (mean follow-up time 6 months). These effects might be due to an improvement of the impaired functioning of Purkinje cells.
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Affiliation(s)
- M Strupp
- Department of Neurology, University of Munich, Germany.
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Kalla R, Glasauer S, Strupp M, Büttner U, Brandt T. Effect of 4-Aminopyridine on Upbeat and Downbeat Nystagmus Elucidates the Mechanism of Downbeat Nystagmus. KLIN NEUROPHYSIOL 2004. [DOI: 10.1055/s-2004-832036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Affiliation(s)
- R Kalla
- Department of Neurology, University of Munich, Germany
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Büttner U, Glasauer S, Glonti L, Guan Y, Kipiani E, Kleine J, Siebold C, Tchelidze T, Wilden A. Multimodal signal integration in vestibular neurons of the primate fastigial nucleus. Ann N Y Acad Sci 2004; 1004:241-51. [PMID: 14662463 DOI: 10.1196/annals.1303.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The rostral fastigial nucleus contains vestibular neurons, which presumably are involved in spinal mechanisms (neck, gait, posture) and which are not modulated with individual eye movements. Single-unit recordings in the alert behaving monkey during natural stimulus conditions reveal that virtually all neurons demonstrate integration of several sensory inputs. This applies not only for canal-canal and canal-otolith interaction, but also for otolith-otolith interaction. There is also some evidence that most neurons receive not only an utriculus but also a sacculus input. Furthermore, most neurons also respond to large-field optokinetic stimulation, reflecting visual-vestibular interaction. Neurons are also affected by the head on trunk position, which would allow these neurons to operate in a body-centered rather than a head-centered reference frame. These complex, multisensory features could permit fastigial nucleus neurons to rather specifically affect spinal motor functions.
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Affiliation(s)
- U Büttner
- Department of Neurology, Ludwig-Maximilians University, 81377 Munich, Germany.
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Schneider E, Glasauer S, Brandt T, Dieterich M. Nonlinear nystagmus processing causes torsional VOR nonlinearity. Ann N Y Acad Sci 2003; 1004:500-5. [PMID: 14662504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
The eye movement component that rotates around the line of sight, i.e., the ocular torsion, is in many aspects different from horizontal and vertical eye movements. While ocular torsion is mediated only by reflexive pathways like the torsional vestibulo-ocular and optokinetic reflexes (TVOR and OKN, respectively), horizontal and vertical components are also subject to intentional control mechanisms that are mediated by the saccadic and the pursuit systems. Dynamic properties of torsional eye movements are also very distinct. While horizontal and vertical VOR components show a gain close to unity and a small neural integration leakage with a time constant around pi=30 s, the TVOR shows a smaller gain of 0.4 and also a greater leakage with pi=2 s. During slow head rotations in roll, the TVOR is even less compensatory. At small stimulation levels the gain drops to a value of 0.2 and proves thus to be nonlinear, i.e., to depend on the stimulus magnitude. In a recent study, we hypothesized that this nonlinearity might be the result of a nonlinear processing of nystagmus quick phases rather than a nonlinearity in direct or integrator TVOR pathways. In the present study, we experimentally tested this hypothesis by measuring ocular torsion responses at different head rotation speeds. In addition to the conventional approach of analyzing slow-phase velocity (SPV) gains, we also analyzed properties of nystagmus quick phases. This method proved to be suitable for determining whether nonlinear processing of nystagmus frequency is responsible for the TVOR nonlinearity.
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Affiliation(s)
- E Schneider
- Ludwig-Maximilians University, Department of Neurology and Center for Sensorimotor Research, Munich, Germany.
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Strupp M, Glasauer S, Schneider E, Eggert T, Glaser M, Jahn K, Brandt T. Anterior canal failure: ocular torsion without perceptual tilt due to preserved otolith function. J Neurol Neurosurg Psychiatry 2003; 74:1336-8. [PMID: 12933952 PMCID: PMC1738659 DOI: 10.1136/jnnp.74.9.1336] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
A patient with anterior semicircular canal dehiscence syndrome underwent surgical patching that caused an isolated dysfunction of the left anterior semicircular canal postoperatively. He exhibited significant ocular torsion toward the side of the affected labyrinth (17 degrees excyclotropia of the ipsilateral eye), but no displacement of the subjective visual vertical. This dissociation suggests that an isolated ocular torsion may occur after an anterior semicircular canal lesion. A combined ocular torsion and subjective visual vertical tilt, which is usually seen with vestibular lesions, requires an associated otolith dysfunction.
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Affiliation(s)
- M Strupp
- Department of Neurology, Klinikum Grosshadern, Ludwig-Maximilians University, Munich, Germany.
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Glasauer S, Hoshi M, Kempermann U, Eggert T, Büttner U. Three-dimensional eye position and slow phase velocity in humans with downbeat nystagmus. J Neurophysiol 2003; 89:338-54. [PMID: 12522184 DOI: 10.1152/jn.00297.2002] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Downbeat nystagmus (DN), a fixation nystagmus with the fast phases directed downward, is usually caused by cerebellar lesions, but the precise etiology is not known. A disorder of the smooth-pursuit system or of central vestibular pathways has been proposed. However, both hypotheses fail to explain why DN is usually accompanied by gaze-holding nystagmus, which implies a leaky neural velocity-to-position integrator. Because three-dimensional (3-D) analysis of nystagmus slow phases provides an excellent means for testing both hypotheses, we examined 19 patients with DN during a fixation task and compared them with healthy subjects. We show that the presentation of DN patients is not uniform; they can be grouped according to their deficits: DN with vertical integrator leakage, DN with vertical and horizontal integrator leakage, and DN without integrator leakage. The 3-D analysis of the slow phases of DN patients revealed that DN is most likely neither caused by damage to central vestibular pathways carrying semicircular canal information nor by a smooth pursuit imbalance. We propose that the observed effects can be explained by partial damage of a brain stem-cerebellar loop that augments the time constant of the neural velocity to position integrators in the brain stem and neurally adjusts the orientation of Listing's plane.
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Affiliation(s)
- S Glasauer
- Department of Neurology with Center for Sensorimotor Research, Klinikum Grosshadern, Ludwig-Maximilians-University, 81377 Munich, Germany.
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Glasauer S, Amorim MA, Viaud-Delmon I, Berthoz A. Differential effects of labyrinthine dysfunction on distance and direction during blindfolded walking of a triangular path. Exp Brain Res 2002; 145:489-97. [PMID: 12172660 DOI: 10.1007/s00221-002-1146-1] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2001] [Accepted: 04/30/2002] [Indexed: 11/30/2022]
Abstract
While we walk through the environment, we constantly receive inputs from different sensory systems. For us to accomplish a given task, for example to reach a target location, the sensory information has to be integrated to update our knowledge of self-position and self-orientation with respect to the target so that we can correctly plan and perform the remaining trajectory. As has been shown previously, vestibular information plays a minor role in the performance of linear goal-directed locomotion when walking blindfolded toward a previously seen target within a few meters. The present study extends the question of whether vestibular information is a requirement for goal-directed locomotion by studying a more complex task that also involves rotation: walking a triangular path. Furthermore, studying this task provides information about how we walk a given trajectory, how we move around corners, and whether we are able to return to the starting point. Seven young male, five labyrinthine-defective (LD) and five age- and gender-matched control subjects were asked to walk a previously seen triangular path, which was marked on the ground, first without vision (EC) and then with vision (EO). Each subject performed three clockwise (CW) and three counterclockwise (CCW) walks under the EC condition and one CW and CCW walk under the EO condition. The movement of the subjects was recorded by means of a 3D motion analysis system. Analysis of the data showed that LD subjects had, in the EC condition, a significantly larger final arrival error, which was due to increased directional errors during the turns. However, there was no difference between the groups as regards the overall path length walked. This shows that LD subjects were able to plan and execute the given trajectory without vision, but failed to turn correctly around the corners. Hence, the results demonstrate that vestibular information enhances the ability to perform a planned trajectory incorporating whole body rotations when no visual feedback is available.
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Affiliation(s)
- S Glasauer
- Department of Neurology, Center for Sensorimotor Research, Ludwig-Maximilians University Munich, Klinikum Grosshadern - NRO, Marchioninistr. 23, 81377 Munich, Germany.
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Glasauer S, Dieterich M, Brandt T. Modeling the role of the interstitial nucleus of Cajal in otolithic control of static eye position. Acta Otolaryngol Suppl 2002; 545:105-7. [PMID: 11677720 DOI: 10.1080/000164801750388243] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Previous models of ocular counterroll assumed that static eye position was controlled by direct brainstem pathways from the vestibular nuclei via the ocular motor nuclei to the extraocular eye muscles. However, recent experimental evidence has shown that the interstitial nucleus of Cajal (INC), known as the vertical-torsional velocity-to-position integrator, plays a crucial role in torsional otolith-dependent eye position, i.e. for the modification of Listing's plane by static head tilts. To evaluate possible mechanisms by which otolithic input may influence eye position via the INC, we constructed a 3D mathematical model of saccade and nystagmus generation. The model includes the burst generators located in the rostral interstitial nucleus of the medial longitudinal fasciculus (MLF) and paramedian pontine reticular formation and the velocity-to-position integrators located in the INC and prepositus hypoglossi. The model simulations suggest that otolith pathways to the neural integrator that adjust Listing's plane may involve the cerebellum.
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Affiliation(s)
- S Glasauer
- Department of Neurology, Klinikum Grosshadern, Ludwig-Maximilians University, Munich, Germany
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Glasauer S, Langley S, Beveridge TJ. Sorption of Fe (hydr)oxides to the surface of Shewanella putrefaciens: cell-bound fine-grained minerals are not always formed de novo. Appl Environ Microbiol 2001; 67:5544-50. [PMID: 11722905 PMCID: PMC93342 DOI: 10.1128/aem.67.12.5544-5550.2001] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Shewanella putrefaciens, a gram-negative, facultative anaerobe, is active in the cycling of iron through its interaction with Fe (hydr)oxides in natural environments. Fine-grained Fe precipitates that are attached to the outer membranes of many gram-negative bacteria have most often been attributed to precipitation and growth of the mineral at the cell surface. Our study of the sorption of nonbiogenic Fe (hydr)oxides revealed, however, that large quantities of nanometer-scale ferrihydrite (hydrous ferric oxide), goethite (alpha-FeOOH), and hematite (alpha-Fe(2)O(3)) adhered to the cell surface. Attempts to separate suspensions of cells and minerals with an 80% glycerin cushion proved that the sorbed minerals were tightly attached to the bacteria. The interaction between minerals and cells resulted in the formation of mineral-cell aggregates, which increased biomass density and provided better sedimentation of mineral Fe compared to suspensions of minerals alone. Transmission electron microscopy observations of cells prepared by whole-mount, conventional embedding, and freeze-substitution methods confirmed the close association between cells and minerals and suggested that in some instances, the mineral crystals had even penetrated the outer membrane and peptidoglycan layers. Given the abundance of these mineral types in natural environments, the data suggest that not all naturally occurring cell surface-associated minerals are necessarily formed de novo on the cell wall.
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Affiliation(s)
- S Glasauer
- Department of Microbiology, College of Biological Sciences, University of Guelph, Ontario, Canada.
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Glasauer S, Dieterich M, Brandt T. Central positional nystagmus simulated by a mathematical ocular motor model of otolith-dependent modification of Listing's plane. J Neurophysiol 2001; 86:1546-54. [PMID: 11600619 DOI: 10.1152/jn.2001.86.4.1546] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To find an explanation of the mechanisms of central positional nystagmus in neurological patients with posterior fossa lesions, we developed a three-dimensional (3-D) mathematical model to simulate head position-dependent changes in eye position control relative to gravity. This required a model implementation of saccadic burst generation, of the neural velocity to eye position integrator, which includes the experimentally demonstrated leakage in the torsional component, and of otolith-dependent neural control of Listing's plane. The validity of the model was first tested by simulating saccadic eye movements in different head positions. Then the model was used to simulate central positional nystagmus in off-vertical head positions. The model simulated lesions of assumed otolith inputs to the burst generator or the neural integrator, both of which resulted in different types of torsional-vertical nystagmus that only occurred during head tilt in roll plane. The model data qualitatively fit clinical observations of central positional nystagmus. Quantitative comparison with patient data were not possible, since no 3-D analyses of eye movements in various head positions have been reported in the literature on patients with positional nystagmus. The present model, prompted by an open clinical question, proposes a new hypothesis about the generation of pathological nystagmus and about neural control of Listing's plane.
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Affiliation(s)
- S Glasauer
- Department of Neurology and Center for Sensorimotor Research, Klinikum Grosshadern, Ludwig-Maximilians University, 81377 Munich, Germany.
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