Robot-assisted thoracoscopic repair of tracheal gunshot wound.

A 23-year-old man suffered two gunshot wounds and upon arrival to the emergency room was found on imaging to have a large pneumothorax with considerable subcutaneous emphysema. Intubation and placement of bilateral chest tubes did not improve the patient's oxygenation; bronchoscopy revealed a 1 cm tracheal defect in the membranous wall 4 cm proximal to the carina. The patient underwent robot-assisted primary repair of the tracheal injury with a #3-0 PDS Stratafix barbed suture buttressed with an intercostal muscle flap. The patient was discharged in good condition on post-operative day 17, with follow-up bronchoscopy showing complete healing of the trachea.

Early impairment of cortical circuit plasticity and connectivity in the 5XFAD Alzheimer's disease mouse model.

Genetic risk factors for neurodegenerative disorders, such as Alzheimer's disease (AD), are expressed throughout the life span. How these risk factors affect early brain development and function remain largely unclear. Analysis of animal models with high constructive validity for AD, such as the 5xFAD mouse model, may provide insights on potential early neurodevelopmental effects that impinge on adult brain function and age-dependent degeneration. The 5XFAD mouse model over-expresses human amyloid precursor protein (APP) and presenilin 1 (PS1) harboring five familial AD mutations. It is unclear how the expression of these mutant proteins affects early developing brain circuits. We found that the prefrontal cortex (PFC) layer 5 (L5) neurons in 5XFAD mice exhibit transgenic APP overloading at an early post-weaning age. Impaired synaptic plasticity (long-term potentiation, LTP) was seen at 6-8 weeks age in L5 PFC circuit, which was correlated with increased intracellular APP. APP overloading was also seen in L5 pyramidal neurons in the primary visual cortex (V1) during the critical period of plasticity (4-5 weeks age). Whole-cell patch clamp recording in V1 brain slices revealed reduced intrinsic excitability of L5 neurons in 5XFAD mice, along with decreased spontaneous miniature excitatory and inhibitory inputs. Functional circuit mapping using laser scanning photostimulation (LSPS) combined with glutamate uncaging uncovered reduced excitatory synaptic connectivity onto L5 neurons in V1, and a more pronounced reduction in inhibitory connectivity, indicative of altered excitation and inhibition during VC critical period. Lastly, in vivo single-unit recording in V1 confirmed that monocular visual deprivation-induced ocular dominance plasticity during critical period was impaired in 5XFAD mice. Our study reveals plasticity deficits across multiple cortical regions and indicates altered early cortical circuit developmental trajectory as a result of mutant APP/PS1 over-expression.

Reduced HGF/MET Signaling May Contribute to the Synaptic Pathology in an Alzheimer's Disease Mouse Model.

Alzheimer's disease (AD) is a neurodegenerative disorder strongly associates with aging. While amyloid plagues and neurofibrillary tangles are pathological hallmarks of AD, recent evidence suggests synaptic dysfunction and physical loss may be the key mechanisms that determine the clinical syndrome and dementia onset. Currently, no effective therapy prevents neuropathological changes and cognitive decline. Neurotrophic factors and their receptors represent novel therapeutic targets to treat AD and dementia. Recent clinical literature revealed that MET receptor tyrosine kinase protein is reduced in AD patient's brain. Activation of MET by its ligand hepatocyte growth factor (HGF) initiates pleiotropic signaling in the developing brain that promotes neurogenesis, survival, synaptogenesis, and plasticity. We hypothesize that if reduced MET signaling plays a role in AD pathogenesis, this might be reflected in the AD mouse models and as such provides opportunities for mechanistic studies on the role of HGF/MET in AD. Examining the 5XFAD mouse model revealed that MET protein exhibits age-dependent progressive reduction prior to overt neuronal pathology, which cannot be explained by indiscriminate loss of total synaptic proteins. In addition, genetic ablation of MET protein in cortical excitatory neurons exacerbates amyloid-related neuropathology in 5XFAD mice. We further found that HGF enhances prefrontal layer 5 neuron synaptic plasticity measured by long-term potentiation (LTP). However, the degree of LTP enhancement is significantly reduced in 5XFAD mice brain slices. Taken together, our study revealed that early reduction of HGF/MET signaling may contribute to the synaptic pathology observed in AD.

Combination therapy of insulin-like growth factor I and BTP-2 markedly improves lipopolysaccharide-induced liver injury in mice.

Acute liver injury is a common disease without effective therapy in humans. We sought to evaluate a combination therapy of insulin-like growth factor 1 (IGF-I) and BTP-2 in a mouse liver injury model induced by lipopolysaccharide (LPS). We chose this model because LPS is known to increase the expression of the transcription factors related to systemic inflammation (i.e., NFκB, CREB, AP1, IRF 3, and NFAT), which depends on calcium signaling. Notably, these transcription factors all have pleiotropic effects and account for the other observed changes in tissue damage parameters. Additionally, LPS is also known to increase the genes associated with a tissue injury (e.g., NGAL, SOD, caspase 3, and type 1 collagen) and systemic expression of pro-inflammatory cytokines. Finally, LPS compromises vascular integrity. Accordingly, IGF-I was selected because its serum levels were shown to decrease during systemic inflammation. BTP-2 was chosen because it was known to decrease cytosolic calcium, which is increased by LPS. This current study showed that IGF-I, BTP-2, or a combination therapy significantly altered and normalized all of the aforementioned LPS-induced gene changes. Additionally, our therapies reduced the vascular leakage caused by LPS, as evidenced by the Evans blue dye technique. Furthermore, histopathologic studies showed that IGF-I decreased the proportion of hepatocytes with ballooning degeneration. Finally, IGF-I also increased the expression of the hepatic growth factor (HGF) and the receptor for the epidermal growth factor (EGFR), markers of liver regeneration. Collectively, our data suggest that a combination of IGF-I and BTP-2 is a promising therapy for acute liver injury.

Calcium released by osteoclastic resorption stimulates autocrine/paracrine activities in local osteogenic cells to promote coupled bone formation.

A major cause of osteoporosis is impaired coupled bone formation. Mechanistically, both osteoclast-derived and bone-derived growth factors have been previously implicated. Here, we hypothesize that the release of bone calcium during osteoclastic bone resorption is essential for coupled bone formation. Osteoclastic resorption increases interstitial fluid calcium locally from the normal 1.8 mM up to 5 mM. MC3T3-E1 osteoprogenitor cells, cultured in a 3.6 mM calcium medium, demonstrated that calcium signaling stimulated osteogenic cell proliferation, differentiation, and migration. Calcium channel knockdown studies implicated calcium channels, Cav1.2, store-operated calcium entry (SOCE), and calcium-sensing receptor (CaSR) in regulating bone cell anabolic activities. MC3T3-E1 cells cultured in a 3.6 mM calcium medium expressed increased gene expression of Wnt signaling and growth factors platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), and bone morphogenic protein-2 (BMP 2). Our coupling model of bone formation, the receptor activator of nuclear factor-κΒ ligand (RANKL)-treated mouse calvaria, confirmed the role of calcium signaling in coupled bone formation by exhibiting increased gene expression for osterix and osteocalcin. Critically, dual immunocytochemistry showed that RANKL treatment increased osterix-positive cells and increased fluorescence intensity of Cav1.2 and CaSR protein expression per osterix-positive cell. The above data established that calcium released by osteoclasts contributed to the regulation of coupled bone formation. CRISPR/Cas-9 knockout of Cav1.2 in osteoprogenitor cells cultured in basal calcium medium caused a >80% decrease in the expression of downstream osteogenic genes, emphasizing the large magnitude of the effect of calcium signaling. Thus, calcium signaling is a major regulator of coupled bone formation.

Disrupted Timing of MET Signaling Derails the Developmental Maturation of Cortical Circuits and Leads to Altered Behavior in Mice.

The molecular regulation of the temporal dynamics of circuit maturation is a key contributor to the emergence of normal structure-function relations. Developmental control of cortical MET receptor tyrosine kinase, expressed early postnatally in subpopulations of excitatory neurons, has a pronounced impact on the timing of glutamatergic synapse maturation and critical period plasticity. Here, we show that using a controllable overexpression (cto-Met) transgenic mouse, extending the duration of MET signaling after endogenous Met is switched off leads to altered molecular constitution of synaptic proteins, persistent activation of small GTPases Cdc42 and Rac1, and sustained inhibitory phosphorylation of cofilin. These molecular changes are accompanied by an increase in the density of immature dendritic spines, impaired cortical circuit maturation of prefrontal cortex layer 5 projection neurons, and altered laminar excitatory connectivity. Two photon in vivo imaging of dendritic spines reveals that cto-Met enhances de novo spine formation while inhibiting spine elimination. Extending MET signaling for two weeks in developing cortical circuits leads to pronounced repetitive activity and impaired social interactions in adult mice. Collectively, our data revealed that temporally controlled MET signaling as a critical mechanism for controlling cortical circuit development and emergence of normal behavior.

Transcriptional repression by FEZF2 restricts alternative identities of cortical projection neurons.

Projection neuron subtype identities in the cerebral cortex are established by expressing pan-cortical and subtype-specific effector genes that execute terminal differentiation programs bestowing neurons with a glutamatergic neuron phenotype and subtype-specific morphology, physiology, and axonal projections. Whether pan-cortical glutamatergic and subtype-specific characteristics are regulated by the same genes or controlled by distinct programs remains largely unknown. Here, we show that FEZF2 functions as a transcriptional repressor, and it regulates subtype-specific identities of both corticothalamic and subcerebral neurons by selectively repressing expression of genes inappropriate for each neuronal subtype. We report that TLE4, specifically expressed in layer 6 corticothalamic neurons, is recruited by FEZF2 to inhibit layer 5 subcerebral neuronal genes. Together with previous studies, our results indicate that a cortical glutamatergic identity is specified by multiple parallel pathways active in progenitor cells, whereas projection neuron subtype-specific identity is achieved through selectively repressing genes associated with alternate identities in differentiating neurons.

Conditional knockout of MET receptor tyrosine kinase in cortical excitatory neurons leads to enhanced learning and memory in young adult mice but early cognitive decline in older adult mice.

Human genetic studies established MET gene as a risk factor for autism spectrum disorders. We have previously shown that signaling mediated by MET receptor tyrosine kinase, expressed in early postnatal developing forebrain circuits, controls glutamatergic neuron morphological development, synapse maturation, and cortical critical period plasticity. Here we investigated how MET signaling affects synaptic plasticity, learning and memory behavior, and whether these effects are age-dependent. We found that in young adult (postnatal 2-3 months) Met conditional knockout (Metfx/fx:emx1cre, cKO) mice, the hippocampus exhibits elevated plasticity, measured by increased magnitude of long-term potentiation (LTP) and depression (LTD) in hippocampal slices. Surprisingly, in older adult cKO mice (10-12 months), LTP and LTD magnitudes were diminished. We further conducted a battery of behavioral tests to assess learning and memory function in cKO mice and littermate controls. Consistent with age-dependent LTP/LTD findings, we observed enhanced spatial memory learning in 2-3 months old young adult mice, assessed by hippocampus-dependent Morris water maze test, but impaired spatial learning in 10-12 months mice. Contextual and cued learning were further assessed using a Pavlovian fear conditioning test, which also revealed enhanced associative fear acquisition and extinction in young adult mice, but impaired fear learning in older adult mice. Lastly, young cKO mice also exhibited enhanced motor learning. Our results suggest that a shift in the window of synaptic plasticity and an age-dependent early cognitive decline may be novel circuit pathophysiology for a well-established autism genetic risk factor.

Time-delimited signaling of MET receptor tyrosine kinase regulates cortical circuit development and critical period plasticity.

Normal development of cortical circuits, including experience-dependent cortical maturation and plasticity, requires precise temporal regulation of gene expression and molecular signaling. Such regulation, and the concomitant impact on plasticity and critical periods, is hypothesized to be disrupted in neurodevelopmental disorders. A protein that may serve such a function is the MET receptor tyrosine kinase, which is tightly regulated developmentally in rodents and primates, and exhibits reduced cortical expression in autism spectrum disorder and Rett Syndrome. We found that the peak of MET expression in developing mouse cortex coincides with the heightened period of synaptogenesis, but is precipitously downregulated prior to extensive synapse pruning and certain peak periods of cortical plasticity. These results reflect a potential on-off regulatory synaptic mechanism for specific glutamatergic cortical circuits in which MET is enriched. In order to address the functional significance of the 'off' component of the proposed mechanism, we created a controllable transgenic mouse line that sustains cortical MET signaling. Continued MET expression in cortical excitatory neurons disrupted synaptic protein profiles, altered neuronal morphology, and impaired visual cortex circuit maturation and connectivity. Remarkably, sustained MET signaling eliminates monocular deprivation-induced ocular dominance plasticity during the normal cortical critical period; while ablating MET signaling leads to early closure of critical period plasticity. The results demonstrate a novel mechanism in which temporal regulation of a pleiotropic signaling protein underlies cortical circuit maturation and timing of cortical critical period, features that may be disrupted in neurodevelopmental disorders.

Depletion of microglia in developing cortical circuits reveals its critical role in glutamatergic synapse development, functional connectivity, and critical period plasticity.

Microglia populate the early developing brain and mediate pruning of the central synapses. Yet, little is known on their functional significance in shaping the developing cortical circuits. We hypothesize that the developing cortical circuits require microglia for proper circuit maturation and connectivity, and as such, ablation of microglia during the cortical critical period may result in a long-lasting circuit abnormality. We administered PLX3397, a colony-stimulating factor 1 receptor inhibitor, to mice starting at postnatal day 14 and through P28, which depletes >75% of microglia in the visual cortex (VC). This treatment largely covers the critical period (P19-32) of VC maturation and plasticity. Patch clamp recording in VC layer 2/3 (L2/3) and L5 neurons revealed increased mEPSC frequency and reduced amplitude, and decreased AMPA/NMDA current ratio, indicative of altered synapse maturation. Increased spine density was observed in these neurons, potentially reflecting impaired synapse pruning. In addition, VC intracortical circuit functional connectivity, assessed by laser scanning photostimulation combined with glutamate uncaging, was dramatically altered. Using two photon longitudinal dendritic spine imaging, we confirmed that spine elimination/pruning was diminished during VC critical period when microglia were depleted. Reduced spine pruning thus may account for increased spine density and disrupted connectivity of VC circuits. Lastly, using single-unit recording combined with monocular deprivation, we found that ocular dominance plasticity in the VC was obliterated during the critical period as a result of microglia depletion. These data establish a critical role of microglia in developmental cortical synapse pruning, maturation, functional connectivity, and critical period plasticity.

Intramasseteric Schwanoma mimicking an isolated cheek mass: Case report and review of literature.

INTRODUCTION: Schwannoma is a benign well circumscribed tumor of the nerve sheath and it is mostly localized in the head and neck. Intramasseteric schwannoma represents a very rare entity and a few cases have been described in the literature. PRESENTATION OF CASE: We present a case of an isolated, asymptomatic and slowly progressive right cheek tumor in a middle aged man. Although multiple investigations, including neck scanner and fine needle aspiration, were done, the diagnosis was obscure and difficult before definite surgical resection. Surgery showed an isolated and well-defined tumor inside the masseter muscle which was completely resected. Histopathologic finding confirmed the diagnosis of schwannoma with the characteristic Antoni A and Antoni B cells. DISCUSSION: Among benign tumors of the peripheral nerves, schwannoma is a specific type that originates from Schwann cells. It is typically slowly growing, neoplasm that is displacing neural structures without direct invasion. History, physical examination, fine needle aspiration, and magnetic resonance imaging are used as diagnostic modalities, however definitive diagnosis and identification of the affected nerve are often difficult up to the time of surgery. CONCLUSION: Herby we describe a very rare localization of schwannoma arising from masseter muscle in a 30 year old man who presents with painless neck mass. This rare entity should be considered in the differential diagnosis in any patient presented with cheek mass.

Measures of the electrically evoked compound action potential threshold and slope in HiRes 90K(TM) users.

OBJECTIVES: To investigate electrically evoked compound action potentials (eCAPs) measured with the neural response imaging (NRI) 'SmartNRI' algorithm. NRI thresholds and slopes were examined according to three aspects: (1) site along the cochlea, (2) development of responses over time, and (3) influence of age/duration of deafness. METHODS: Thirty-four individuals implanted with the Advanced Bionics HiRes 90K(TM) device were included. The eCAP recordings were made from four electrodes along the array at first fitting and at frequent intervals up to at least 2 years. Slope and threshold (tNRI) of the amplitude growth function were measured and a range of explanatory variables were tested for significant effects on these measures using multi-factorial analysis of variance. RESULTS: Electrode position emerged as a significant effect for the tNRI measure, with lowest thresholds at the apical end of the array. Mean slope was greatest for the most apical electrode, but not significantly. Slope was significantly influenced by onset of deafness, with congenital hearing loss associated with steeper slopes than acquired hearing loss. There was also a highly significant effect of duration of device use, with a gradual increase in slope over the 2 years following device activation. DISCUSSION: The observed effects of electrode position are consistent with a model in which eCAP threshold is governed primarily by an effect of distance between electrode and neural interface (which is shorter towards the apex of the cochlea) and in which slope is governed primarily by density of surviving neural elements.

Metastatic parotid myoepithelial carcinoma in a 7-year-old boy.

Myoepithelial carcinoma is a rare malignancy of the parotid gland that is usually seen in adults. We report the first case in children of myoepithelial carcinoma of the parotid gland with massive invasion of the facial nerve and metastasis to cervical lymph nodes. Due to its rarity, the treatment and the clinical course of this tumor are not well defined yet. We performed a total parotidectomy, a modified neck dissection, and a postoperative radiotherapy in 7-year-old boy. Sparing of the facial nerve was impossible; it was sacrificed and grafted with a sural nerve. Histopathology confirmed the diagnosis of a parotid gland carcinoma and immunohistochemical markers showed that the tumor cells express cytokeratin, epithelial membrane antigen, cytokeratin 7, smooth muscle actin, P63, CEA, and S100. This pattern of immunostaining is consistent with the diagnosis of myoepithelial carcinoma. On the postoperative tenth month he presented with a pulmonary and lumbar vertebra metastasis.

Inflammatory chronic otitis media and the anterior epitympanic recess.

OBJECTIVE: To demonstrate the important role of the anterior epitympanic recess (AER) in the surgery of noncholesteatomateous chronic inflammatory middle ear disorders. To establish selective criteria as to the indication of surgical intervention on the AER, aiming to create a permanent anterior aeration pathway for the attic. In addition, to point out the mandatory role of preoperative temporal bone computed tomography (CT) demonstrating whether the AER is involved and thus contributing, within the clinical context, to the indication for this surgery and its appropriate approach. STUDY DESIGN: Prospective study on patients with persistent or recurring chronic inflammatory middle ear disease for at least 3 years, after failure of conventional medical or surgical treatments. SETTING: Tertiary referral university centre. PATIENTS: Between November 2002 and July 2003, every patient presenting with clinical findings suggestive of an AER pathology was included in this study. SURGERY: Surgical approach of the AER during a mastoatticotomy and tympanoplasty with excision of the Cog and the tensor tympani fold, preserving the ossicular chain in almost all cases. OUTCOME MEASURES: Absence of postoperative otorrhea, satisfactory otoscopic examination, and improvement in the air-bone gap postoperatively in case the presurgery hearing level was abnormal and not due to an ossicular chain abnormality. RESULTS: Eight patients were included in the study. The preoperative CT scan showed AER opacities in all patients that were either isolated or associated with a diseased meso- or hypotympanum or the mastoid cavity. The measurement of the relevant transverse diameter of the AER is proposed to evaluate preoperatively the distance between the Cog laterally and the facial nerve canal medially to minimize the risk of a perioperative injury. During the operation, we found granulation tissue and adhesions in the AER in all cases A clinical follow-up 3 months after the intervention showed good local control in all patients, absence of otorrhea, and almost complete closure of the air-bone gap at audiometric evaluation. The last clinical follow-up in August 2004, a mean of 18 months after our intervention, did not reveal any relapse of symptoms in any case. CT control could be obtained in five of eight cases, within 13 to 21 months after the intervention, showing a reaerated tympanic cavity and AER. CONCLUSION: The AER plays a major role in sustaining some noncholesteatomateous chronic or recurrent inflammatory middle ear disorders that do not respond to conventional medical treatment. Definitive control of this pathology will be obtained by approaching the AER through an excision of the Cog and the tensor tympani fold, exenterating the inflammatory tissues, and creating a sufficient and permanent anterior atticomesotympanic communication. The indication for such a surgical approach is highly dependent on clinical findings correlated to temporal bone CT. Familiarity with the AER and its critical role should become part of every resident's training program in otology.