- Baltimore, Maryland, United States
- brain monitoring and therapeutic hypothermia, peripheral nerve injury and regeneration, translational therapeutic mod... morebrain monitoring and therapeutic hypothermia, peripheral nerve injury and regeneration, translational therapeutic model for neurological injuries, development and characterization of biomaterials for bone and peripheral nerve regenerationedit
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Reliable prognostic methods for cerebral functional outcome of post cardiac-arrest (CA) patients are necessary, especially since therapeutic hypothermia (TH) as a standard treatment. Traditional neurophysiological prognostic indicators,... more
Reliable prognostic methods for cerebral functional outcome of post cardiac-arrest (CA) patients are necessary, especially since therapeutic hypothermia (TH) as a standard treatment. Traditional neurophysiological prognostic indicators, such as clinical examination and chemical biomarkers, may result in indecisive outcome predictions and do not directly reflect neuronal activity, though they have remained the mainstay of clinical prognosis. The most recent advances in electrophysiological methods-electroencephalography (EEG) pattern, evoked potential (EP) and cellular electrophysiological measurement-were developed to complement these deficiencies, and will be examined in this review article. EEG pattern (reactivity and continuity) provides real-time and accurate information for early-stage (particularly in the first 24 h) hypoxic-ischemic (HI) brain injury patients with high sensitivity. However, the signal is easily affected by external stimuli, thus the measurements of EP should ...
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Brain recovery after cardiac arrest (CA) is sensitive to temperature. Yet the effect of temperature management on different EEG frequency bands has not been elucidated. A novel quantitative EEG algorithm, sub-band information quantity... more
Brain recovery after cardiac arrest (CA) is sensitive to temperature. Yet the effect of temperature management on different EEG frequency bands has not been elucidated. A novel quantitative EEG algorithm, sub-band information quantity (SIQ), was applied to evaluate EEG recovery and outcomes after CA. Twenty-four Wistar rats undergoing 7-min CA were randomly assigned to immediate hypothermia (32-34 °C), normothermia (36.5-37.5 °C), or hyperthermia (38.5-39.5 °C) (n = 8). EEG was recorded continuously for the first 8 h and then for serial 30-min epochs daily. The neurologic deficit score (NDS) at 72-h was the primary functional outcome. Another four rats without brain injury were added as a control. Better recovery of gamma-band SIQ was found in the hypothermia group (0.60 ± 0.03) compared with the normothermia group (0.40 ± 0.03) (p < 0.01) and in the normothermia group compared with the hyperthermia group (0.34 ± 0.03) (p < 0.05). The NDS was also improved in the lower temperature groups: hypothermia [median (25th, 75th), 74 (61, 74)] versus normothermia [49 (47, 61)] versus hyperthermia [43 (0, 50)] (p < 0.01). Throughout the 72-h experiment, the gamma-band SIQ showed the strongest correlation at every time point (ranging 0.520-0.788 from 30-min to 72-h post-resuscitation, all p < 0.05) whereas the delta-band SIQ had poor correlation with the 72-h NDS. No significant difference of sub-band EEG was found with temperature manipulation alone. Recovery of gamma-band SIQ-qEEG was strongly associated with functional outcomes after CA. Induced hypothermia was associated with faster recovery of gamma-band SIQ and improved functional outcomes. Targeted temperature management primarily affected gamma frequency oscillations but not delta rhythm.
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By detection and analysis of neuro-information from amputee in experiments, a research on the correlations of three main nerves (median nerve, radial nerve and ulnar nerve), on the patterns for discharging information, and on the... more
By detection and analysis of neuro-information from amputee in experiments, a research on the correlations of three main nerves (median nerve, radial nerve and ulnar nerve), on the patterns for discharging information, and on the mechanics about how neuro-information dominates movements was performed. These researches would contribute to the development of neuroprosthesis.
Research Interests: Radial Nerve, Humans, Movement, Male, Arm, and 7 moreAmputation, Microelectrodes, Amputees, Adult, Artificial Limbs, Median Nerve, and Ulnar Nerve
The term "burst-suppression" is used to describe the electroencephalogram (EEG) pattern characterized by theta or delta waves, at times intermixed with faster waves, and intervening periods of relative quiescence.... more
The term "burst-suppression" is used to describe the electroencephalogram (EEG) pattern characterized by theta or delta waves, at times intermixed with faster waves, and intervening periods of relative quiescence. Burst-suppression pattern can reflect the seriously suppressed brain activity under deep anesthesia. To investigate the relationship between burst-suppression features and anesthetic concentration, we adopted four straightforward indexes, i. e., burst-suppression ratio (BSR), burst frequency, burst amplitude and suppression amplitude, and used them to analyze the EEG recordings in ten isoflurane-anesthetized rats. It was found that all the four burst-suppression indexes changed along with anesthetic concentration, that BSR and burst amplitude increased with higher concentration of isoflurane while burst frequency and suppression amplitude decreased, and that BSR was the most sensitive and consistent measurement to indicate isoflurane concentration so it constitut...
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Beneficial effects of hypothermia on subjects with neuro-pathologies have been well demonstrated in both animal studies and clinical trials. Although it is known that temperature significantly impacts neurological injuries, the underlying... more
Beneficial effects of hypothermia on subjects with neuro-pathologies have been well demonstrated in both animal studies and clinical trials. Although it is known that temperature significantly impacts neurological injuries, the underlying mechanism remains unclear. We studied the effect of temperature modulation on neural signals in the cortex and the thalamus in uninjured brains of anesthetized rats. Six rats were divided into a hypothermic (32 to 34 °C, n=3) and a hyperthermic group (38.5 to 39.5 °C, n=3). EEG, and extracellular signals from somatosensory cortex and the ventral posterolateral nucleus of thalamus were recorded at different temperature phases (normothermia (36.5 to 37.5 °C) and hypothermia or hyperthermia). During hypothermia, similar burst suppression (BS) patterns were observed in cortical and thalamic signals as in EEG, but thalamic activity was not completely under suppression when both EEG and cortical signals were electrically silent. In addition, our results showed that hypothermia significantly increased the burst suppression ratio (BSR) in EEG, cortical and thalamic signals by 3.42, 3.25, 7.29 times respectively (P<0.01), and prolonged the latency of neuronal response in cortex to median nerve stimulation from 9 ms to 16 ms (P<0.01). Furthermore, during normothermia, the correlation coefficient between thalamic and cortical signals was 0.35±0.02 while during hypothermia, it decreased to 0.16±0.03 with statistical significance (P<0.01). These results can potentially assist in better understanding the effects of hypothermia.
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In this paper we provide a quantitative electroencephalogram (EEG) analysis to study the effect of hypothermia on the neurological recovery of brain after cardiac arrest. We hypothesize that the brain injury results in a reduction in... more
In this paper we provide a quantitative electroencephalogram (EEG) analysis to study the effect of hypothermia on the neurological recovery of brain after cardiac arrest. We hypothesize that the brain injury results in a reduction in information of the brain rhythm. To measure the information content of the EEG a new measure called information quantity (IQ), which is the Shannon entropy of decorrelated EEG signals, is developed. For decorrelating EEG signals, we use the discrete wavelet transform (DWT) which is known to have good decorrelating properties and to show a good match to the standard clinical bands in EEG. In simulation for measuring the amount of information, the IQ shows better tracking capability for dynamic amplitude change and frequency component change than conventional entropy-based measures. Experiments are carried out in rodents to monitor the neurological recovery after cardiac arrest. In addition, EEG signal recovery under normothermic (37 degrees C) and hypothermic (33 degrees C) resuscitation following 5, 7 and 9 minutes of cardiac arrest is recorded and analyzed. Experimental results show that the IQ is higher for hypothermic than normothermic rats. The results quantitatively support the hypothesis that hypothermia accelerates the recovery of brain injury after cardiac arrest.
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Cardiac Arrest (CA) leads to a global hypoxic-ischemic injury in the brain leading to a poor neurological outcome. Understanding the mechanisms of functional disruption in various regions of the brain may be essential for the development... more
Cardiac Arrest (CA) leads to a global hypoxic-ischemic injury in the brain leading to a poor neurological outcome. Understanding the mechanisms of functional disruption in various regions of the brain may be essential for the development of improved diagnostic and therapeutic solutions. Using controlled laboratory experiment with animal models of CA, our primary focus here is on understanding the functional changes in the thalamus and the cortex, associated with the injury and acute recovery upon resuscitation. Specifically, to study the changes in thalamocortical synchrony through these periods, we acquired local field potentials (LFPs) from the ventroposterior lateral (VPL) nucleus of the thalamus and the forelimb somatosensory cortex (S1FL) in rats after asphyxial CA. Band-specific relative Hilbert phases were used to analyze synchrony between the LFPs. We observed that the CA induced global ischemia changes the local phase-relationships by introducing a phase-lag in both the tha...
Research Interests: Thalamus, Anoxia, Animals, Male, Microelectrodes, and 3 moreSomatosensory Cortex, Rats, and Wistar Rats
Neuroprotective effects of hypothermia are well documented in many injuries of the central nervous system in animal models as well as clinical studies. However, the underlying mechanisms are not fully understood. An important yet... more
Neuroprotective effects of hypothermia are well documented in many injuries of the central nervous system in animal models as well as clinical studies. However, the underlying mechanisms are not fully understood. An important yet unexplored background issue is the effect of hypothermic cooling on the regional functionality of the healthy CNS. In a pilot study with the rat model, we seek to characterize the effect of moderate bodily cooling on the thalamo-cortical (T-C) function. Multiunit activity (MUA) and local field potentials (LFPs) were recorded from the thalamus (VPL nucleus) and the somatosensory cortex (S1) for normothermic, mild hypothermic and mild hyperthermic conditions in healthy rats and the thalamo-cortical dynamics was characterized with Granger Causal Interaction (GCI). The GCI indicated that the thalamic driving of the cortical activity significantly increases in strength with bodily cooling and weakens with mild heating. These results could have important implicat...
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The paper studies the distributional characteristics, sources and enrichment factors of arsenic in groundwater in Yinchuan Plain, and gives some suggestions for improvement of water quality for prevention and control of endemic diseases.... more
The paper studies the distributional characteristics, sources and enrichment factors of arsenic in groundwater in Yinchuan Plain, and gives some suggestions for improvement of water quality for prevention and control of endemic diseases. 1) There is distinct zonal distribution in anomalous arsenic regions of groundwater in Yinchuan plain. The content of arsenic is increasing from the front of prolusion inclined plain before mountain to the center of alluvial lacustrine plain. High arsenic groundwater has shown points distribution from the south to the north-east, and overall zonary located in lacustrine plain areas; high arsenic groundwater is mainly enriched between 0 and 40m depths of the aquifer; 2)The coal stratums enriched arsenic of Helan Mountains are main sources of arsenic in groundwater. 3) The specific paleogeographic environment, reducing environment, slow groundwater runoff and arid-semiarid climate are the major enrichment factors of Arsenic in groundwater. 4) In futur...
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The residual motor pathways after amputation have not been fully elucidated. We sampled potentials from peripheral nerve stumps with intrafascicular electrodes to study residual motor transmission and explore the feasibility of nerve... more
The residual motor pathways after amputation have not been fully elucidated. We sampled potentials from peripheral nerve stumps with intrafascicular electrodes to study residual motor transmission and explore the feasibility of nerve signal-controlled artificial limbs. Six intrafascicular electrodes were inserted into the ulnar, radial, and median nerves in the stump of an amputee. An electrode was placed outside the fascicle as a reference. Potentials from 4 of the 6 electrodes per trial were monitored using a 4-channel electromyogram machine, and 32 groups of electrophysiologic tests were conducted under volitional control. Actions included finger extension and flexion, forearm pronation and supination, and wrist extension and flexion. Each action was carried out with light, intermediate, and full efforts. Then, 2 of 6 electrodes randomly chosen per trial were interfaced to a nerve signal-controlled artificial limb. Finger extension and flexion of the prosthesis were tested under volitional control. The volitional motor nerve potentials uniquely associated with the missing limb were recorded successfully with intrafascicular electrodes. The signal amplitude from the radial nerve was 5.5 microV +/- 0.8 (mean +/- SD), which was greater than the amplitudes from the ulnar (2.5 microV +/- 0.4) and median (2.2 microV +/- 0.3) nerves. Under volitional control of the subject, finger extension of the artificial limb was triggered by the radial nerve signal, but the remaining actions were unsuccessful. The long-term amputee was able to generate motor neuron activity related to phantom limb movement. Intrafascicular electrodes can be used to monitor residual motor nerve activity in the stump, and the amplitude may predict successful control of artificial limbs.
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Assessment of network connectivity across multiple brain regions is critical to understanding the mechanisms underlying various neurological disorders. Conventional methods for assessing dynamic interactions include cross-correlation and... more
Assessment of network connectivity across multiple brain regions is critical to understanding the mechanisms underlying various neurological disorders. Conventional methods for assessing dynamic interactions include cross-correlation and coherence analysis. However, these methods do not reveal the direction of information flow, which is important for studying the highly directional neurological system. Granger causality (GC) analysis can characterize the directional influences between two systems. We tested GC analysis for its capability to capture directional interactions within both simulated and in vivo neural networks. The simulated networks consisted of Hindmarsh-Rose neurons; GC analysis was used to estimate the causal influences between two model networks. Our analysis successfully detected asymmetrical interactions between these networks ( , t -test). Next, we characterized the relationship between the "electrical synaptic strength" in the model networks and interactions estimated by GC analysis. We demonstrated the novel application of GC to monitor interactions between thalamic and cortical neurons following ischemia induced brain injury in a rat model of cardiac arrest (CA). We observed that during the post-CA acute period the GC interactions from the thalamus to the cortex were consistently higher than those from the cortex to the thalamus ( 1.983±0.278 times higher, p = 0.021). In addition, the dynamics of GC interactions between the thalamus and the cortex were frequency dependent. Our study demonstrated the feasibility of GC to monitor the dynamics of thalamocortical interactions after a global nervous system injury such as CA-induced ischemia, and offers preferred alternative applications in characterizing other inter-regional interactions in an injured brain.
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Research Interests: Algorithms, Biomedical Engineering, Electroencephalography, Treatment Outcome, Sparse Signal Recovery, and 12 moreComa, Cardiac arrest, Animals, Electroencephalogram, Brain injury, Information Content, Rats, Discrete wavelet transform, Wistar Rats, Shannon entropy, Electrical And Electronic Engineering, and Confidence Interval
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Research Interests: Mechanical Engineering, Rheology, Brain, Lasers, Photometry, and 16 moreAnimals, Skull, Light, Imaging spectroscopy, Fluorescence Imaging, Contrast-Enhanced Ultrasound, Applied Optics, Optical physics, High Resolution, Rats, Time Factors, Cerebral Blood Flow, Field of View, Blood Flow Velocity, Electrical And Electronic Engineering, and Contrast Media
Wolters Kluwer Health may email you for journal alerts and information, but is committed to maintaining your privacy and will not share your personal information without your express consent. For more information, please refer to our... more
Wolters Kluwer Health may email you for journal alerts and information, but is committed to maintaining your privacy and will not share your personal information without your express consent. For more information, please refer to our Privacy Policy. ... Skip Navigation Links Home > December 2012 - Volume 40 - Issue 12 > 553: Novel Transnasal Cooling Using High Flow Air for Brain... ... Introduction: Therapeutic hypothermia (32-34[degrees]C) after cardiac arrest improves survival and functional outcomes. However, the methods of inducing rapid hypothermia continue ...
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The innate immune response following bone injury plays an important role in promoting cellular recruitment, revascularization, and other repair mechanisms. Tumor necrosis factor-α (TNF) is a prominent pro-inflammatory cytokine in this... more
The innate immune response following bone injury plays an important role in promoting cellular recruitment, revascularization, and other repair mechanisms. Tumor necrosis factor-α (TNF) is a prominent pro-inflammatory cytokine in this cascade, and has been previously shown to improve bone formation and angiogenesis in a dose- and timing-dependent manner. This ability to positively impact both osteogenesis and vascular growth may benefit bone tissue engineering, as vasculature is essential to maintaining cell viability in large grafts after implantation. Here, we investigated the effects of exogenous TNF on the induction of adipose-derived stem/stromal cells (ASCs) to engineer pre-vascularized osteogenic tissue in vitro with respect to dose, timing, and co-stimulation with other inflammatory mediators. We found that acute (2-day), low-dose exposure to TNF promoted vascularization, whereas higher doses and continuous exposure inhibited vascular growth. Co-stimulation with platelet-der...
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Previous research has shown that hypothermia immediately after Cardiac Arrest (CA) improves neurological outcomes. In order to study how hypothermia affects neural spiking, cortical and subcortical neural activity was recorded from... more
Previous research has shown that hypothermia immediately after Cardiac Arrest (CA) improves neurological outcomes. In order to study how hypothermia affects neural spiking, cortical and subcortical neural activity was recorded from rodents. Consistent with previous findings, preliminary results show that the firing rate is proportional to the temperature. We also studied the information coded in the spike-timing information of individual neurons and observed that information content varies with temperature. Furthermore, there is an increased dependence between the cortex and sub-cortical structures such as the Thalamus during hypothermia. The latter is most likely an indicator of coupling between these highly connected structures in response to temperature manipulation leading to arousal after global cerebral ischemia.
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Cardiac arrest (CA) can produce complex changes in somatosensory evoked potentials (SSEPs). Somatosensory evoked potentials (SSEPs) indicate the intactness of somatosensory pathways and are commonly used for brain function monitoring... more
Cardiac arrest (CA) can produce complex changes in somatosensory evoked potentials (SSEPs). Somatosensory evoked potentials (SSEPs) indicate the intactness of somatosensory pathways and are commonly used for brain function monitoring during surgeries. Multiresolution biorthogonal wavelet analysis was applied to SSEPs recorded during established CA experiments and post-CA long-term recovery periods in rats. Our results showed that during the first 4 hours after CA, the amplitudes of SSEP, defined here as the difference between the amplitudes of P23 and N20, decreased greatly while the inter-peak latencies between N20 and P23 increased greatly. In the long-term recovery period (within 72 hours), both the amplitudes of SSEPs and the interpeak latencies returned to the baseline. Our results suggest that the changes of SSEPs may represent the post-CA neurological injuries and recovery in the somatosensory afferent pathways. The results here lay ground work for establishing the relationship between SSEPs and post-CA neurological injuries and functional outcomes as well as deploying SSEP in clinical settings to monitor patients resuscitated from CA in the future.
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Previous research has shown that a characteristic burst-suppression (BS) pattern appears in EEG during the early recovery period following cardiac arrest (CA). To study cortical and subcortical neural activity underlying BS, extracellular... more
Previous research has shown that a characteristic burst-suppression (BS) pattern appears in EEG during the early recovery period following cardiac arrest (CA). To study cortical and subcortical neural activity underlying BS, extracellular activity in the parietal cortex and the centromedian nucleus of the thalamus and extradural EEG were recorded in a rodent CA model. Preliminary results show that during the BS, the cortical firing rate is extraordinarily high, and that bursts in EEG correlate to dense spikes in cortical neurons. An unexpected and novel observation is that 1) thalamic activity reappears earlier than cortical activity following CA, and 2) the correlation coefficient of cortical and thalamic activity rises during BS period. These results will help elucidate the mechanism of brain recovery after CA injury.
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Abstract Induced hypothermia is known as an efficient neuro-protectant, while rapid posthypothermic rewarming has harmful effects on neural system and worsens cerebral injury. This study investigated burst suppression (BS) pattern in EEG... more
Abstract Induced hypothermia is known as an efficient neuro-protectant, while rapid posthypothermic rewarming has harmful effects on neural system and worsens cerebral injury. This study investigated burst suppression (BS) pattern in EEG during moderate hypothermia and rapid rewarming in 9 isoflurane-anesthetized rats. Temperature-induced changes were observed in BS features throughout the experiment: maximum BS ratio and burst amplitude, and minimum suppression amplitude appeared at the lowest temperature ...
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Somatosensory evoked potentials (SSEPs) have been established as an electrophysiological tool for the prognostication of neurological outcome in patients with hypoxic-ischemic brain injury. The early and late responses in SSEPs reflect... more
Somatosensory evoked potentials (SSEPs) have been established as an electrophysiological tool for the prognostication of neurological outcome in patients with hypoxic-ischemic brain injury. The early and late responses in SSEPs reflect the sequential activation of neural structures along the somatosensory pathway. This study reports that the SSEP can be separated into early (short-latency, SL) and late (long-latency, LL) responses using independent component analysis (ICA), based on the assumption that these components are generated from different neural sources. Moreover, this source separation into the SL and LL components allows analysis of electrophysiological response to brain injury, even when the SSEPs are severely distorted and SL and LL components get mixed. With the help of ICA decomposition and corrected peak estimation, the latency of LL-SSEP is shown to be predictive of long-term neurological outcome. Further, it is shown that the recovery processes of SL- and LL-SSEPs follow different dynamics, with the SL-SSEP restored earlier than LL-SSEP. We predict that the SL- and LL-SSEPs reflect the timing of the progression of evoked response through the thalamocortical pathway and as such respond differently depending upon injury and recovery of the thalamic and cortical regions, respectively.
Research Interests: Psychology, Cognitive Science, Principal Component Analysis, Independent Component Analysis, Blood Pressure, and 13 moreAnimals, Male, Brain Ischemia, Brain injury, Somatosensory Cortex, Rats, Wistar Rats, Source Separation, Neural pathways, Rat Model, Blood gas analysis, Neurosciences, and Nervous System Diseases
Abstract Asphyxial cardiac arrest (CA) introduces a global hypoxic-ischemic insult to the brain and disturbs the neural networks. We analyzed the thalamocortical interactions in a rat model of asphyxial CA, using the local field... more
Abstract Asphyxial cardiac arrest (CA) introduces a global hypoxic-ischemic insult to the brain and disturbs the neural networks. We analyzed the thalamocortical interactions in a rat model of asphyxial CA, using the local field potentials recorded from the thalamus and cortex during CA and the recovery periods. The direct Directed Transfer Function (dDTF) and Directed Information Flow (DIF) were applied to characterize the causal coherence and causal mutual information of the network, respectively. Key results from dDTF and DIF ...
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In this paper, we present a novel method to study the effect of induced mild hypothermia on cerebral vascular responses. To measure cerebral vascular responses, a minimally invasive imaging method, temporal laser speckle imaging, was... more
In this paper, we present a novel method to study the effect of induced mild hypothermia on cerebral vascular responses. To measure cerebral vascular responses, a minimally invasive imaging method, temporal laser speckle imaging, was developed and adapted for induced-hypothermia rat model. Experiments were carried out in rats under anesthesia. Laser speckle images were acquired at different temperature points, normothermia (37 °Q and mild therapeutic hypothermia (34 °Q. We extracted multiple hemodynamic responses simultaneously from the images, including blood flow, vessel size and deoxy-hemoglobin saturation. A wide-field view of the cerebral vascular response distribution was studied, which showed an inhomogeneous response map across the region of interest. A comparison between responses in arterioles and venules was carried out (blood flow decreased by 58 ± 9 % vs. 27 ± 8 %). The global decrease of blood flow, dilatation in arterioles and decrease of deoxy-hemoglobin saturation in veins at mild hypothermia suggests a beneficial role of circulatory and oxygenation changes in therapeutic hypothermia. The results reported provide a circulatory explanation for the hypothermia therapeutic effects and mechanism.
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Previous studies have implicated the abnormal activation of the trigeminal system to be a factor in the pathogenesis of migraine. The relationship between vascular changes and migraine, however, is under considerable debate. In this... more
Previous studies have implicated the abnormal activation of the trigeminal system to be a factor in the pathogenesis of migraine. The relationship between vascular changes and migraine, however, is under considerable debate. In this study, temporal laser speckle contrast imaging is combined with ridge tracking based vessel detection to obtain high resolution (6.7μm×6.7μm), high contrast images of cerebral vascular structure.
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Upon secretion, transforming growth factor β (TGFβ) is maintained in a sequestered state in extracellular matrix as a latent form. The latent TGFβ is considered as a molecular sensor that releases active TGFβ in response to the... more
Upon secretion, transforming growth factor β (TGFβ) is maintained in a sequestered state in extracellular matrix as a latent form. The latent TGFβ is considered as a molecular sensor that releases active TGFβ in response to the perturbations of the extracellular matrix at the situations of mechanical stress, wound repair, tissue injury, and inflammation. The biological implication of the temporal discontinuity of TGFβ storage in the matrix and its activation is obscure. Here, using several animal models in which latent TGFβ is activated in vascular matrix in response to injury of arteries, we show that active TGFβ controls the mobilization and recruitment of mesenchymal stem cells (MSCs) to participate in tissue repair and remodeling. MSCs were mobilized into the peripheral blood in response to vascular injury and recruited to the injured sites where they gave rise to both endothelial cells for re-endothelialization and myofibroblastic cells to form thick neointima. TGFβs were activated in the vascular matrix in both rat and mouse models of mechanical injury of arteries. Importantly, the active TGFβ released from the injured vessels is essential to induce the migration of MSCs, and cascade expression of monocyte chemotactic protein-1 stimulated by TGFβ amplifies the signal for migration. Moreover, sustained high levels of active TGFβ were observed in peripheral blood, and at the same time points following injury, Sca1+ CD29+ CD11b- CD45- MSCs, in which 91% are nestin+ cells, were mobilized to peripheral blood and recruited to the remodeling arteries. Intravenously injection of recombinant active TGFβ1 in uninjured mice rapidly mobilized MSCs into circulation. Furthermore, inhibitor of TGFβ type I receptor blocked the mobilization and recruitment of MSCs to the injured arteries. Thus, TGFβ is an injury-activated messenger essential for the mobilization and recruitment of MSCs to participate in tissue repair/remodeling.
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In the evaluation of the painful shoulder, especially in the overhead athlete, diagnosing superior labrum anterior and posterior (SLAP) lesions continues to challenge the clinician because of 1) the lack of specificity of examination... more
In the evaluation of the painful shoulder, especially in the overhead athlete, diagnosing superior labrum anterior and posterior (SLAP) lesions continues to challenge the clinician because of 1) the lack of specificity of examination tests for SLAP; 2) a paucity of well-controlled studies of those tests; and 3) the presence of coexisting confounding abnormalities. Some evidence indicates that multiple positive tests increase the likelihood that a SLAP lesion is present, but no one physical examination finding conclusively makes that diagnosis. The goals of this article were to review the physical examination techniques for making the diagnosis of SLAP lesions, to evaluate the clinical usefulness of those examinations, and to review the role of magnetic resonance imaging in making the diagnosis.
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Temperature fluctuations significantly impact neurological injuries in intensive care units. As the benefits of therapeutic hypothermia continue to unfold, many of these discoveries are generated by studies in animal models undergoing... more
Temperature fluctuations significantly impact neurological injuries in intensive care units. As the benefits of therapeutic hypothermia continue to unfold, many of these discoveries are generated by studies in animal models undergoing experimental procedures under the influence of anesthetics. We studied the effect of induced hypothermia on neural electrophysiological signals of an uninjured brain in a rodent model while under isoflurane. Fourteen rats were divided into 2 groups (n=7 each), on the basis of electrode placement at either frontal-occipital or primary somatosensory cortical locations. Neural signals were recorded during normothermia (T=36.5 to 37.5°C), mild hypothermia (T=32 to 34°C), and hyperthermia (T=38.5 to 39.5°C). The burst-suppression ratio was used to evaluate electroencephalography (EEG), and amplitude-latency analysis was used to assess somatosensory-evoked potentials (SSEPs). Hypothermia was characterized by an increased burst-suppression ratio (mean±SD) of 0.58±0.06 in hypothermia versus 0.16±0.13 in normothermia, P<0.001 in frontal-occipital; and 0.30±0.13 in hypothermia versus 0.04±0.04 in normothermia, P=0.006 in somatosensory. There was potentiation of SSEP (2.89±1.24 times the normothermic baseline in hypothermia, P=0.02) and prolonged peak latency (N10: 10.8±0.4 ms in hypothermia vs. 9.1±0.3 ms in normothermia; P15: 16.2±0.8 ms in hypothermia vs. 13.7±0.6 ms in normothermia; P<0.001), whereas hyperthermia was primarily marked by shorter peak latencies (N10: 8.6±0.2 ms, P15: 12.6±0.4 m; P<0.001). In the absence of brain injury in a rodent model, hypothermia induces significant increase to the SSEP amplitude while increasing SSEP latency. Hypothermia also suppressed EEGs at different regions of the brain by different degrees. The changes to SSEP and EEG are both reversible with subsequent rewarming.
Research Interests: Neuroscience, Psychology, EEG, Electroencephalography, Brain, and 5 moreAnimals, Male, Clinical Sciences, Rats, and Wistar Rats
Research Interests: Biomedical Engineering, Electrophysiology, Polymers, Neurophysiology, Biodegradable, and 22 moreFilms, Neuroprosthetics, Animals, Peripheral Nervous System, Plastics, Fabrication, Microelectrodes, Interface, Impedance, Temperature measurement, Next Generation, Peripheral Nerve, Molecular weight, prosthesis Design, Rabbits, Electrodes, Electrode, Biocompatible Materials, Mechanical Processes, Electrical And Electronic Engineering, Electric Impedance, and Tyrosine
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The shoulder is one of the most complex joints in the human body and, as such, presents an evaluation and diagnostic challenge. The first steps in its evaluation are obtaining an accurate history and physical examination and evaluating... more
The shoulder is one of the most complex joints in the human body and, as such, presents an evaluation and diagnostic challenge. The first steps in its evaluation are obtaining an accurate history and physical examination and evaluating conventional radiography. The use of other imaging modalities (eg, ultrasound, magnetic resonance imaging and computed tomography) should be based on the type of additional information needed. The goals of this study were to review the current limitations of evidence-based medicine with regard to shoulder examination and to assess the rationale for and against the use of diagnostic physical examination tests.