The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Carleric Aubin - One of the best experts on this subject based on the ideXlab platform.
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cyclically controlled vertebral body tethering for scoliosis an in vivo verification in a pig model of the Pressure exerted on vertebral end plates
Spine deformity, 2020Co-Authors: Viviane Lalande, Isabelle Villemure, Manuel Vonthron, Stefan Parent, Carleric AubinAbstract:Study design Experimental in vivo study of the Pressure exerted on the spine of a pig by a new cyclic anterior vertebral body tethering (AVBT) prototype. Objectives To evaluate the relationship between the tether Tension and the Pressures transmitted onto the vertebral end plates by a cyclic AVBT prototype. AVBT is a recent surgical technique for the treatment of pediatric scoliosis that compresses the convex side of the spine with a sustained Tension, to modulate the growth to progressively correct the deformity over time. Previous studies demonstrated that cyclic compression has similar growth modulation capacity but with less detrimental effects on the integrity of the discs and growth plates. Methods A 3-month-old healthy Duroc pig was anesthetized and a lateral thoracotomy was performed. The T7-T10 segment was instrumented and compressed during 50 s with the load oscillating (0.2 Hz) from + 30 to - 30% of the following mean Tensions: 29, 35, 40, 44, and 49 N. The Pressure exerted on T9 superior vertebral end plate was monitored during the cyclic loading. Three repetitions of each test were performed. Results The resulting mean Pressure exerted on the vertebral end plate was linearly correlated with the mean tether Tension (r2 = 0.86). Each cycle translated in a hysteresis profile of the measured Pressure and Tension, with amplitudes varying between ± 11.5 and ± 29.9%. Conclusions This experimental study documented the relationship between the tether Tension and the Pressure. This study confirmed the feasibility of cyclic AVBT principle to transfer varying Pressures on the vertebral end plates, which is intended to control vertebral growth, while keeping the spine flexibility and preserving the health of soft tissues such as the intervertebral discs and the growth plate but remained to be further verified. Level of evidence Level IV.
David R Jones - One of the best experts on this subject based on the ideXlab platform.
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form and function of the bulbus arteriosus in yellowfin tuna thunnus albacares bigeye tuna thunnus obesus and blue marlin makaira nigricans static properties
The Journal of Experimental Biology, 2003Co-Authors: Marvin H Braun, Richard W Brill, John M Gosline, David R JonesAbstract:SUMMARY The juxtaposition of heart and gills in teleost fish means that the Windkessel function characteristic of the whole mammalian arterial tree has to be subserved by the extremely short ventral aorta and bulbus arteriosus. Over the functional Pressure range, arteries from blue marlin ( Makaira nigricans ) and yellowfin tuna ( Thunnus albacares ) have J-shaped Pressure-volume (P-V) loops, while bulbi from the same species have r-shaped P-V loops, with a steep initial rise followed by a compliant plateau phase. The steep initial rise in Pressure is due to the geometry of the lumen. The interactions between radius, Pressure and Tension require a large initial Pressure to open the bulbar lumen for flow. The plateau is due to the unique organization of the bulbar wall. The large elastin:collagen ratio, limited amount of collagen arranged cirumferentially, lack of elastin lamellae and low hydrophobicity of the elastin itself all combine to lower stiffness, increase extensibility and allow efficient recoil. Even though the modulus of bulbus material is much lower than that of an artery, at large volumes the overall stiffness of the bulbus increases rapidly. The morphological features that give rise to the special inflation characteristics of the bulbus help to extend flow and maintain Pressure during diastole.
Marcos A Trevisan - One of the best experts on this subject based on the ideXlab platform.
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Exploring the anatomical encoding of voice with a mathematical model of the vocal system.
NeuroImage, 2016Co-Authors: M Florencia Assaneo, Jacobo Sitt, Gaël Varoquaux, Mariano Sigman, Laurent Cohen, Marcos A TrevisanAbstract:The faculty of language depends on the interplay between the production and perception of speech sounds. A relevant open question is whether the dimensions that organize voice perception in the brain are acoustical or depend on properties of the vocal system that produced it. One of the main empirical difficulties in answering this question is to generate sounds that vary along a continuum according to the anatomical properties the vocal apparatus that produced them. Here we use a mathematical model that offers the unique possibility of synthesizing vocal sounds by controlling a small set of anatomically based parameters. In a first stage the quality of the synthetic voice was evaluated. Using specific time traces for sub-glottal Pressure and Tension of the vocal folds, the synthetic voices generated perceptual responses, which are indistinguishable from those of real speech. The synthesizer was then used to investigate how the auditory cortex responds to the perception of voice depending on the anatomy of the vocal apparatus. Our fMRI results show that sounds are perceived as human vocalizations when produced by a vocal system that follows a simple relationship between the size of the vocal folds and the vocal tract. We found that these anatomical parameters encode the perceptual vocal identity (male, female, child) and show that the brain areas that respond to human speech also encode vocal identity. On the basis of these results, we propose that this low-dimensional model of the vocal system is capable of generating realistic voices and represents a novel tool to explore the voice perception with a precise control of the anatomical variables that generate speech. Furthermore, the model provides an explanation of how auditory cortices encode voices in terms of the anatomical parameters of the vocal system.
Christian Kirschneck - One of the best experts on this subject based on the ideXlab platform.
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Effects of Compressive and Tensile Strain on Macrophages during Simulated Orthodontic Tooth Movement.
Mediators of inflammation, 2020Co-Authors: Agnes Schröder, Paul Käppler, Ute Nazet, Jonathan Jantsch, Peter Proff, Fabian Cieplik, James Deschner, Christian KirschneckAbstract:During orthodontic tooth movement (OTM) to therapeutically correct the position of misaligned teeth, thus improving oral health and quality of life, fibroblasts, macrophages, and other immune cells within the periodontal ligament (PDL), which connects a tooth to its surrounding bone, are exposed to compressive and tensile strain. While it is known that PDL fibroblasts are critically involved in the biological regulation of OTM by a mechanotransductively triggered release of cytokines, it is unclear whether macrophages also react to Pressure and Tension in a similar manner thus impacting on or mediating OTM. RAW264.7 macrophages were seeded onto conventional 6-well cell culture plates for Pressure or on Bioflex plates for Tension assays and preincubated for 24 h. For in vitro simulation of physiological orthodontic compressive or tensile strain for 2 h, 4 h, 24 h, and 48 h, glass discs (2 g/cm2) were placed or adherent macrophages isotropically stretched for 16%, respectively. We determined cell number, cytotoxicity, and gene/protein expression of Vegf-a/VEGF-A (macrophage-mediated angiogenesis), Mmp-8/9 (extracellular matrix reorganization), and Cox-2/PG-E2, Il-6/IL-6, and Tnf-α/TNF-α (proinflammatory mediators) by RT-qPCR and ELISA. Compressive but not tensile strain resulted in a significant reduction in cell number after only 2 h. Mmp-8 and Mmp-9 expression was significantly enhanced within 24 h of compressive and in part tensile strain. Significantly increased Vegf-a/VEGF-A expression was detected within 4 h of Pressure, but not during application of tensile strain. Expression of proinflammatory mediators Cox-2/PG-E2, Il-6/IL-6, and Tnf-α/TNF-α was significantly increased as early as 2-4 h after application of compressive or tensile strain. Our results indicate that macrophages respond early on to compressive and tensile strain occurring during OTM with an enhanced gene expression of proinflammatory cytokines, which could affect PDL fibroblasts, osteoblasts, and immune cells triggering or enhancing the biological mechanisms and osteoclastogenesis underlying OTM.
Asbjørn Mohr Drewes - One of the best experts on this subject based on the ideXlab platform.
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Differences Between Male and Female Responses to Painful Thermal and Mechanical Stimulation of the Human Esophagus
Digestive Diseases and Sciences, 2004Co-Authors: Jan Pedersen, Lars Arendt-nielsen, Hans Gregersen, Hariprasad Reddy, Peter Funch-jensen, Asbjørn Mohr DrewesAbstract:It is uncertain to what degree sensation and pain relating to the gut are influenced by sex. The aim of the study was to explore sex differences to experimental multimodal stimulation of the esophagus in 22 age-matched males and females. A probe was positioned in the lower part of the esophagus. Mechanical stimuli were applied as disTensions with a bag using an impedance planimetric method. The disTensions were done before and after relaxation of the smooth muscle. Thermal stimulation was done with recirculating water at 1 and 60°C in the bag. The sensory intensities were assessed during the stimulations, and the referred pain area was drawn at maximum pain intensities. An increased sensation to mechanical stimuli was found in the males for volume, Pressure, and Tension ( P =0.003, P =0.02, P =0.005), whereas cross-sectional area and strain showed no sex difference ( P =0.06, P =0.9). Sex differences were not found for the cold and warmth stimulations ( P =0.6, P =0.1). The mean size of the referred pain areas to the different stimuli was 23.6 cm^2 in males and 48.7 cm^2 in females ( P =0.002). As strain is believed to be the major determinant for the sensory response to mechanical stimulation of the gut, we conclude that no robust sex differences were observed in the assessments of the multimodal stimulations. However, the larger referred pain area in females reflects sex differences in central pain processing, which may explain the female preponderance in functional disorders relating to the gut.
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Pain intensity and biomechanical responses during ramp-controlled disTension of the human rectum.
Digestive diseases and sciences, 2003Co-Authors: P. Petersen, Chunwen Gao, Lars Arendt-nielsen, Hans Gregersen, Asbjørn Mohr DrewesAbstract:The current study aimed to refine the conventional disTension model in the human rectum by measuring the cross-sectional area with a ramp-controlled impedance planimetric system. After preconditioning, the rectum in seven volunteers was distended 56 times with infusion rates of 50, 100 and 200 ml/min and at 100 ml/min during relaxation of the smooth muscle with glucagon. The pump was reversed at maximal tolerated pain. The subjects tolerated a higher volume and Pressure with a more reliable sensory rating after preconditioning of the tissue. The three disTension rates resulted in different Pressure and Tension at the maximal pain intensity (P < 0.02 and P < 0.05) with a decrease after relaxation of the smooth muscle with glucagon (P < 0.05). On the other hand, the cross-sectional area and volume were robust, did not show strain-rate dependency, and were not affected by muscle relaxation. Since the cross-sectional area is directly related to the deformation of the gut wall and hence to the strain, the study supports the idea that, independent of the muscular function, the mechano sensitive nociceptors in the human rectum depend directly on circumferential wall strain rather than on Pressure and Tension.