The Experts below are selected from a list of 138 Experts worldwide ranked by ideXlab platform
Matthew R. Hayes - One of the best experts on this subject based on the ideXlab platform.
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The nucleus tractus solitarius: a portal for visceral Afferent Signal processing, energy status assessment and integration of their combined effects on food intake
International Journal of Obesity, 2009Co-Authors: Harvey J. Grill, Matthew R. HayesAbstract:The nucleus tractus solitarius: a portal for visceral Afferent Signal processing, energy status assessment and integration of their combined effects on food intake
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the nucleus tractus solitarius a portal for visceral Afferent Signal processing energy status assessment and integration of their combined effects on food intake
International Journal of Obesity, 2009Co-Authors: Harvey J. Grill, Matthew R. HayesAbstract:For humans and animal models alike there is general agreement that the central nervous system processing of gastrointestinal (GI) Signals arising from ingested food provides the principal determinant of the size of meals and their frequency. Despite this, relatively few studies are aimed at delineating the brain circuits, neurochemical pathways and intracellular Signals that mediate GI-stimulation-induced intake inhibition. Two additional motivations to pursue these circuits and Signals have recently arisen. First, the success of gastric-bypass surgery in obesity treatment is highlighting roles for GI Signals such as glucagon-like peptide-1 (GLP-1) in intake and energy balance control. Second, accumulating data suggest that the intake-reducing effects of leptin may be mediated through an amplification of the intake-inhibitory effects of GI Signals. Experiments reviewed show that: (1) the intake-suppressive effects of a peripherally administered GLP-1 receptor agonist is mediated by caudal brainstem neurons and that forebrain-hypothalamic neural processing is not necessary for this effect; (2) a population of medial nucleus tractus solitarius (NTS) neurons that are responsive to gastric distention is also driven by leptin; (3) caudal brainstem-targeted leptin amplifies the food-intake-inhibitory effects of gastric distention and intestinal nutrient stimulation; (4) adenosine monophosphate-activated protein kinase (AMPK) activity in NTS-enriched brain lysates is elevated by food deprivation and reduced by refeeding and (5) the intake-suppressive effect of hindbrain-directed leptin is reversed by elevating hindbrain AMPK activity. Overall, data support the view that the NTS and circuits within the hindbrain mediate the intake inhibition of GI Signals, and that the effects of leptin on food intake result from the amplification of GI Signal processing.
Jungwon Yoon - One of the best experts on this subject based on the ideXlab platform.
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Identifying the effects of using integrated haptic feedback for gait rehabilitation of stroke patients
2017 International Conference on Rehabilitation Robotics (ICORR), 2017Co-Authors: Muhammad Raheel Afzal, Min-kyun Oh, Young Sook Park, Jungwon YoonAbstract:This paper evaluates the prospects of using a novel Integrated Haptic Feedback (IHF) system. IHF can provide over-ground gait training regimens for post-stroke ambulatory subjects. IHF system combines the use of a portable cane for kinesthetic feedback and a wearable vibrotactor array for tactile feedback. Continuous somatosensory input is aiforded to the users at the handle of cane; it serves the purpose of balance assurance at higher gait speeds. Besides, restricted use of upper limb for weight-bearing inspires the users to involve the paretic lower limbs more actively. Furthermore, tactile feedback contributes in enhancing the gait symmetry through Afferent Signal of vibration. Six post-stroke ambulatory individuals participated in walking trials to identity the effects of IHF system. Results indicate that while walking faster patients' body sway was not disturbed. Statistically significant increase was observed in temporal stance symmetry (p-value=0.02) and in paretic muscle (vastus medialis obliquus and semitendinosus) activation during stance phase (p-value
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Haptic based gait rehabilitation system for stroke patients
2016 IEEE RSJ International Conference on Intelligent Robots and Systems (IROS), 2016Co-Authors: Muhammad Raheel Afzal, Min-kyun Oh, Young Sook Park, Jungwon YoonAbstract:Among most existing gait rehabilitation robots, it is difficult to find adequate devices for gait rehabilitation of chronic stroke patients who can already stand and move but still need to rehabilitate the affected lower limb through simple, compact, and easy-to use devices. This paper presents a novel haptic based gait rehabilitation system (HGRS) which has the potential to provide over-ground gait training regimens for post-stroke ambulatory subjects. It consists of a portable cane for kinesthetic sensing and a wearable vibrotactor array for tactile biofeedback. Contact of user with the handle provides light grip force, it serves the purpose of balance assurance and increased muscle activity through light touch concept and vibrotactors contribute in enhancing the gait modification through Afferent Signal of vibration. Walking trials conducted with stroke patients indicate increased muscle activation and balance, and improved temporal symmetry with use of HGRS. HGRS is capable of assisting physical therapists in training individuals with stroke suffering from gait abnormalities. In addition, it is easy to use and low-cost which makes it reachable to a vast domain of subjects suffering from gait abnormalities.
Mark V Sauer - One of the best experts on this subject based on the ideXlab platform.
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prolonged inhibition of presynaptic catecholamine synthesis does not alter leptin secretion in normal weight men and women
Human Reproduction, 1998Co-Authors: Ralf C. Zimmermann, Lois Elaine Krahn, Nooria Rahmanie, Mark V SauerAbstract:: Leptin has been called a hormone of reproduction, and seems to link fat and fertility. It has been speculated that the neurotransmitter norepinephrine (NE) (noradrenaline), possibly via the sympathetic nervous system, may represent the Afferent Signal which modulates leptin release from adipocytes. The purpose of this study was to produce a state of decreased sympathetic output by using the catecholamine synthesis inhibitor alpha-methyl-para-tyrosine (AMPT), in order to study the effect of this compound on the secretion of leptin from fat cells. Ten subjects (five women and five men) received a total of 5 x 1 g doses of AMPT or 5 x 50 mg promethazine (active placebo) over a 26 h period, separated by 4-6 weeks using a randomized, double-blind, placebo-controlled, cross-over design. Blood samples for hormone measurements were obtained over 24 h (18 time points) on day 2 of each experiment. Urinary measurement of the NE metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) on study day 2 served as a marker of the effectiveness of AMPT as an inhibitor of NE synthesis. The daily excretion of this metabolite decreased from 1.56 +/- 0.22 mg in the placebo experiment to 0.53 +/- 0.1 mg in the active experiment (P < 0.05). Plasma leptin concentrations measured in the control group in women and men were similar to those reported previously in lean subjects with a body mass index < 27.5 kg/m2. Leptin concentrations in women were 3-fold higher than in men. Leptin is secreted in a circadian rhythm in both sexes with an increase of nocturnal concentrations by approximately 50%. Two-way analysis of variance reveals no significant difference in leptin secretion between the control and active groups in women and men. In summary, preliminary results do not support the hypothesis that NE represents the Afferent Signal from the central nervous system which modulates leptin release from adipocytes in the human. Further studies are needed to define the role of the sympathetic nervous system as well as NE in the regulation of leptin secretion and its involvement in obesity and reproduction.
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Prolonged inhibition of presynaptic catecholamine synthesis does not alter leptin secretion in normal-weight men and women.
Human Reproduction, 1998Co-Authors: Ralf C. Zimmermann, Lois Elaine Krahn, Nooria Rahmanie, Mark V SauerAbstract:Leptin has been called a hormone of reproduction, and seems to link fat and fertility. It has been speculated that the neurotransmitter norepinephrine (NE) (noradrenaline), possibly via the sympathetic nervous system, may represent the Afferent Signal which modulates leptin release from adipocytes. The purpose of this study was to produce a state of decreased sympathetic output by using the catecholamine synthesis inhibitor alpha-methyl-para-tyrosine (AMPT), in order to study the effect of this compound on the secretion of leptin from fat cells. Ten subjects (five women and five men) received a total of 5 x 1 g doses of AMPT or 5 x 50 mg promethazine (active placebo) over a 26 h period, separated by 4-6 weeks using a randomized, double-blind, placebo-controlled, cross-over design. Blood samples for hormone measurements were obtained over 24 h (18 time points) on day 2 of each experiment, Urinary measurement of the NE metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) on study day 2 served as a marker of the effectiveness of AMPT as an inhibitor of NE synthesis. The daily excretion of this metabolite decreased from 1.56 ± 0.22 mg in the placebo experiment to 0.53 ± 0.1 mg in the active experiment (P < 0.05). Plasma leptin concentrations measured in the control group in women and men were similar to those reported previously in lean subjects with a body mass index < 27.5 kg/m 2 . Leptin concentrations in women were 3-fold higher than in men. Leptin is secreted in a circadian rhythm in both sexes with an increase of nocturnal concentrations by ∼50%. Two-way analysis of variance reveals no significant difference in leptin secretion between the control and active groups in women and men. In summary, preliminary results do not support the hypothesis that NE represents the Afferent Signal from the central nervous system which modulates leptin release from adipocytes in the human. Further studies are needed to define the role of the sympathetic nervous system as well as NE in the regulation of leptin secretion and its involvement in obesity and reproduction.
Norman F. Capra - One of the best experts on this subject based on the ideXlab platform.
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modulation of jaw muscle spindle Afferent activity following intramuscular injections with hypertonic saline
Pain, 2001Co-Authors: Jin Y. Ro, Norman F. CapraAbstract:Abstract Transient noxious chemical stimulation of small diameter muscle Afferents modulates jaw movement-related responses of caudal brainstem neurons. While it is likely that the effect is mediated from the spindle Afferents in the mesencephalic nucleus (Vmes) via the caudally projecting Probst's tract, the mechanisms of pain induced modulations of jaw muscle spindle Afferents is not known. In the present study, we tested the hypothesis that jaw muscle nociceptors gain access to muscle spindle Afferents in the same muscle via central mechanisms and alter their sensitivity. Thirty-five neurons recorded from the Vmes were characterized as muscle spindle Afferents based on their responses to passive jaw movements, muscle palpation, and electrical stimulation of the masseter nerve. Each cell was tested by injecting a small volume (250 μl) of either 5% hypertonic and/or isotonic saline into the receptor-bearing muscle. Twenty-nine units were tested with 5% hypertonic saline, of which 79% (23/29) showed significant modulation of mean firing rates (MFRs) during one or more phases of ramp-and-hold movements. Among the muscle spindle primary-like units ( n =12), MFRs of 4 units were facilitated, five reduced, two showed mixed responses and one unchanged. In secondary-like units ( n =17), MFRs of 9 were facilitated, three reduced and five unchanged. Thirteen units were tested with isotonic saline, of which 77% showed no significant changes of MFRs. Further analysis revealed that the hypertonic saline not only affected the overall output of muscle spindle Afferents, but also increased the variability of firing and altered the relationship between Afferent Signal and muscle length. These results demonstrated that activation of muscle nociceptors significantly affects proprioceptive properties of jaw muscle spindles via central neural mechanisms. The changes can have deleterious effects on oral motor function as well as kinesthetic sensibility.
David Grundy - One of the best experts on this subject based on the ideXlab platform.
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sensitivity of vagal mucosal Afferents to cholecystokinin and its role in Afferent Signal transduction in the rat
The Journal of Physiology, 1996Co-Authors: W Richards, K Hillsley, C Eastwood, David GrundyAbstract:1. Extracellular recordings from rat mesenteric paravascular nerve bundles were made in order to characterize the responses of different populations of Afferents supplying the small intestine to intravenous cholecystokinin (CCK; in the form of sulphated CCK8). 2. Approximately 70% of mesenteric nerve bundles contained CCK-sensitive Afferent fibres. Responsive Afferents had low spontaneous discharge (1.6 +/- 0.3 impulses s-1) and showed a 14-fold increase in firing at the peak of the response to 50 pmol CCK with the overall response lasting several minutes. The onset of the response occurred after a latency of (3.9 +/- 0.1 s) following i.v. administration of CCK, which corresponds largely to the circulation delay in these animals. The threshold dose of CCK was < 5 pmol. 3. The response to 100 pmol CCK was completely abolished by devazepide (0.5 mg kg-1) and by chronic subdiaphragmatic vagotomy performed 10-14 days prior to experimentation, indicating that CCK sensitivity was via CCKA receptors and exclusively mediated via vagal Afferents rather than splanchnic or enteric Afferents. 4. Evidence that CCK-sensitive Afferents had mucosal receptive fields was indicated by the lack of any response to luminal distension and the sensitivity of the CCK response to luminal anaesthesia. Furthermore, CCK-sensitive Afferents responded to luminal hydrochloric acid (50 mM) in a slowly adapting manner. The response to acid was significantly reduced (P < 0.005), but not abolished, by devazepide at a time when the response to exogenous CCK had been completely eliminated. 5. The exquisite sensitivity of some vagal mucosal Afferents to CCK suggests that they may play a physiological role in the reflex and behavioural consequences of CCK release from the small intestine, possibly acting in a paracrine fashion. However, this sensitivity to CCK represents only one aspect of the broad chemosensitivity of these mucosal Afferents and is not an obligatory component of the Signal transduction pathway.
