bluuebunny/crossref_metadata_2025 huggingface dataset:
Auditory Cortical Images of Cochlear-Implant Stimuli: Coding of Stimulus Channel and Current Level
Authors: Middlebrooks John C. , Bierer Julie Arenberg
Published: May 2017

This study quantified the accuracy with which populations of neurons in the auditory cortex can represent aspects of electrical cochlear stimuli presented through a cochlear implant. We tested the accuracy of coding of the place of stimulation (i.e., identification of the active stimulation channel) and of the stimulus current level. Physiological data came from the companion study, which recorded spike activity of neurons simultaneously from 16 sites along the tonotopic axis of the guinea pig's auditory cortex. In that study, cochlear electrical stimuli were presented to acutely deafened animals through a 6-electrode animal version of the 22-electrode Nucleus banded electrode array (Cochlear). Cochlear electrode configurations consisted of monopolar (MP), bipolar (BP + N) with N inactive electrodes between the active and return electrodes (0 ≤ N ≤ 3), tripolar (TP) with one active electrode and two flanking return electrodes, and common ground (CG) with one active electrode and as many as five return electrodes. In the present analysis, an artificial neural network was trained to recognize spatiotemporal patterns of cortical activity in response to single presentations of particular stimuli and, thereby, to identify those stimuli. The accuracy of pair-wise discrimination of stimulation channels or of current levels was represented by the discrimination index, d′, where d′ = 1 was taken as threshold. In many cases, the threshold for discrimination of place of cochlear stimulation was <0.75 mm, and the threshold for discrimination of current levels was <1 dB. Cochlear electrode configurations varied in the accuracy with which they signaled to the auditory cortex the place of cochlear stimulation. The BP + N and TP configurations provided considerably greater sensitivity to place of stimulation than did the MP configuration. The TP configuration maintained accurate signaling of place of stimulation up to the highest current levels, whereas sensitivity was degraded at high current levels in BP + N configurations. Electrode configurations also varied in the dynamic range over which they signaled stimulus current level. Dynamic ranges were widest for the BP + 0 configuration and narrowest for the TP configuration. That is, the configuration that showed the most accurate signaling of cochlear place of stimulation (TP) showed the most restricted dynamic range for signaling of current level. These results suggest that the choice of the optimal electrode configuration for use by human cochlear-prosthesis users would depend on the particular demands of the speech-processing strategy that is to be employed.
Auditory Cortical Images of Cochlear-Implant Stimuli: Dependence on Electrode Configuration
Authors: Bierer Julie Arenberg , Middlebrooks John C.
Published: May 2017

This study examines patterns of auditory cortical activity elicited by single-pulse cochlear implant stimuli that vary in electrode configuration, cochlear place of stimulation, and stimulus level. Recordings were made from the primary auditory cortex (area A1) of ketamine-anesthetized guinea pigs. The spatiotemporal pattern of neural spike activity was measured simultaneously across 16 cortical locations spanning approximately 2–3 octaves of the tonotopic axis. Such a pattern, averaged over 40 presentations of any particular stimulus, was defined as the “cortical image” of that stimulus. Acutely deafened guinea pigs were implanted with a 6-electrode animal version of the 22-electrode Nucleus banded electrode array (Cochlear). Cochlear electrode configurations consisted of monopolar (MP), bipolar (BP + N) with N inactive electrodes between the active and return electrodes (0 ≤ N ≤ 4), tripolar (TP) with one active electrode and two flanking return electrodes, and common ground (CG) with one active electrode and as many as five return electrodes. Cortical images typically showed a focus of maximum spike probability and minimum latency. Spike probabilities tended to decrease, and latencies tended to increase, with increasing cortical distance from that focus. Cortical images of TP stimuli were the most spatially compact, followed by BP + N images, and then MP images, which were the broadest. Images of CG stimuli were rather variable across animals and stimulus channels. The locations of cortical images shifted systematically from caudal to rostral as the cochlear place of stimulation changed from basal to apical. At the most sensitive cortical site for each condition, the dynamic ranges over which spike rates increased with increased current level were restricted to about 1–2 dB, regardless of configuration. Dynamic ranges tended to increase with increasing cortical distance from the most sensitive site. Electrode configurations that produced compact cortical images (e.g., TP and BP + 0) showed the greatest range of thresholds within each cortical image and the largest dynamic range at cortical sites removed from the most sensitive site.
Multisecond Periodicities in Basal Ganglia Firing Rates Correlate With Theta Bursts in Transcortical and Hippocampal EEG
Authors: Allers Kelly A. , Ruskin David N. , Bergstrom Debra A. , Freeman Lauren E. , Ghazi Leyla J. , Tierney Patrick L. , Walters Judith R.
Published: May 2017

Multisecond oscillations in firing rate with periods in the range of 2–60 s (mean, 20–35 s) are present in 50–90% of spike trains from basal ganglia neurons recorded from locally anesthetized, immobilized rats. To determine whether these periodic oscillations are associated with similar periodicities in cortical activity, transcortical electroencephalographic (EEG) activity was recorded in conjunction with single- or dual-unit neuronal activity in the subthalamic nucleus (STN) or the globus pallidus (GP), and the data were analyzed with spectral and wavelet analyses. Multisecond oscillations in firing rates of 31% of the STN neurons and 46% of the GP neurons with periodicities significantly correlated with bursts of theta (4–7 Hz) activity in transcortical EEG. Further recordings of localized field potentials in the hippocampus and frontal or parietal cortices simultaneously with GP unit activity showed field potentials from the hippocampus, but not from the frontal or parietal cortices, exhibited bursts of theta rhythm that were correlated with GP firing rate oscillations. These results demonstrate a functional connectivity between basal ganglia neuronal activity and theta band activity in the hippocampus.
Coding of Temporal Information by Activity-Dependent Synapses
Authors: Fuhrmann Galit , Segev Idan , Markram Henry , Tsodyks Misha
Published: May 2017

Synaptic transmission in the neocortex is dynamic, such that the magnitude of the postsynaptic response changes with the history of the presynaptic activity. Therefore each response carries information about the temporal structure of the preceding presynaptic input spike train. We quantitatively analyze the information about previous interspike intervals, contained in single responses of dynamic synapses, using methods from information theory applied to experimentally based deterministic and probabilistic phenomenological models of depressing and facilitating synapses. We show that for any given dynamic synapse, there exists an optimal frequency of presynaptic spike firing for which the information content is maximal; simple relations between this optimal frequency and the synaptic parameters are derived. Depressing neocortical synapses are optimized for coding temporal information at low firing rates of 0.5–5 Hz, typical to the spontaneous activity of cortical neurons, and carry significant information about the timing of up to four preceding presynaptic spikes. Facilitating synapses, however, are optimized to code information at higher presynaptic rates of 9–70 Hz and can represent the timing of over eight presynaptic spikes.
Excitation and Adaptation in the Detection of Hydrogen Ions by Taste Receptor Cells: A Role for cAMP and Ca2+
Authors: Lyall Vijay , Alam Rammy I. , Phan Tam-Hao T. , Phan Duy Q. , Heck Gerard L. , DeSimone John A.
Published: May 2017

The role of intracellular cAMP and Ca2+ in the excitation and adaptation of taste responses by HCl was investigated by direct measurement of intracellular pH (pHi) in polarized taste receptor cells (TRCs) and by chorda tympani (CT) nerve recordings. Stimulating the tongue with HCl concentrations between 1 and 30 mM caused a dose-dependent increase in CT responses that were insensitive to voltage clamp of the lingual receptive field and to amiloride. At a fixed HCl concentration (20 mM) topical lingual application of 8-chlorophenylthio(CPT)-cAMP increased the magnitude of HCl-induced CT response by twofold under zero current clamp. The magnitude of the CT response increased further at −60 mV and decreased at +60 mV lingual voltage clamp but remained amiloride insensitive. In untreated polarized TRCs, apical stimulation with HCl concentrations between 1 and 30 mM HCl induced sustained decreases in TRC pHi. The magnitude of pHidecrease increased with increasing HCl concentration. Following treatment of the basolateral membrane with 8-CPT-cAMP the decrease in pHi due to apical 1 mM HCl application was significantly increased. Treatment with cAMP alone decreased resting TRC pHi and inhibited the recovery of pHi from a basolateral NH4Cl pulse by 46%. Topical lingual application of ionomycin, a Ca2+ ionophore, did not affect the initial CT response to 20 mM HCl +10 mM CaCl2, but the response declined rapidly to 50% of its initial level within 2 min. In polarized TRCs, basolateral exposure to ionomycin increased TRC pHi and activated pHi recovery from NH4Cl pulse by 388%. Apical HCl stimulation induced a transient decrease in resting TRC pHifollowed by spontaneous recovery. The data suggest that cAMP enhances the sour taste of strong acids by activating a Ca2+- and amiloride-insensitive H+ conductance and inhibiting pHi recovery in TRCs. However, an increase in [Ca2+]i stimulates pHi recovery, which, in turn, increases sensory adaptation to acids.
Electrical Coupling Can Prevent Expression of Adult-Like Properties in an Embryonic Neural Circuit
Authors: Bem Tiaza , Le Feuvre Yves , Simmers John , Meyrand Pierre
Published: May 2017

Electrical coupling is widespread in developing nervous systems and plays a major role in circuit formation and patterning of activity. In most reported cases, such coupling between rhythmogenic neurons tends to synchronize and enhance their oscillatory behavior, thereby producing monophasic rhythmic output. However, in many adult networks, such as those responsible for rhythmic motor behavior, oscillatory neurons are linked by synaptic inhibition to produce rhythmic output with multiple phases. The question then arises whether such networks are still able to generate multiphasic output in the early stage of development when electrical coupling is abundant. A suitable model for addressing this issue is the lobster stomatogastric nervous system (STNS). In the adult animal, the STNS consists of three discrete neural networks that are comprised of oscillatory neurons interconnected by reciprocal inhibition. These networks generate three distinct rhythmic motor patterns with large amplitude neuronal oscillations. By contrast, in the embryo the same neuronal population expresses a single multiphasic rhythm with small-amplitude oscillations. Recent findings have revealed that adult-like network properties are already present early in the embryonic system but are masked by an as yet unknown mechanism. Here we use computer simulation to test whether extensive electrical coupling may be involved in masking adult-like properties in the embryonic STNS. Our basic model consists of three different adult-like STNS networks that are built of relaxation oscillators interconnected by reciprocal synaptic inhibition. Individual model cells generate slow membrane potential oscillations without action potentials. The introduction of widespread electrical coupling between members of these networks dampens oscillation amplitudes and, at moderate coupling strengths, may coordinate neuronal activity into a single rhythm with different phases, which is strongly reminiscent of embryonic STNS output. With a further increase in coupling strength, the system reaches one of two final states depending on the relative contribution of inhibition and inherent oscillatory properties within the networks: either fully synchronized and dampened oscillations, or a complete collapse of activity. Our simulations indicate that, beginning from either of these two states, the emergence of distinct adult networks during maturation may arise from a developmental decrease in electrical coupling that unmasks preexisting adult-like network properties.
Probable Corticospinal Tract Control of Spinal Cord Plasticity in the Rat
Authors: Chen Xiang Yang , Wolpaw Jonathan R.
Published: May 2017

Descending activity from the brain shapes spinal cord reflex function throughout life, yet the mechanisms responsible for this spinal cord plasticity are poorly understood. Operant conditioning of the H-reflex, the electrical analogue of the spinal stretch reflex, is a simple model for investigating these mechanisms. An earlier study in the Sprague-Dawley rat showed that acquisition of an operantly conditioned decrease in the soleus H-reflex is not prevented by mid-thoracic transection of the ipsilateral lateral column (LC), which contains the rubrospinal, reticulospinal, and vestibulospinal tracts, and is prevented by transection of the dorsal column, which contains the main corticospinal tract (CST) and the dorsal column ascending tract (DA). The present study explored the effects of CST or DA transection on acquisition of an H-reflex decrease, and the effects of LC, CST, or DA transection on maintenance of an established decrease. CST transection prior to conditioning prevented acquisition of H-reflex decrease, while DA transection did not do so. CST transection after H-reflex decrease had been acquired led to gradual loss of the decrease over 10 days, and resulted in an H-reflex that was significantly larger than the original, naive H-reflex. In contrast, LC or DA transection after H-reflex decrease had been acquired did not affect maintenance of the decrease. These results, in combination with the earlier study, strongly imply that in the rat the corticospinal tract (CST) is essential for acquisition and maintenance of operantly conditioned decrease in the H-reflex and that other major spinal cord pathways are not essential. This previously unrecognized aspect of CST function gives insight into the processes underlying acquisition and maintenance of motor skills and could lead to novel methods for inducing, guiding, and assessing recovery of function after spinal cord injury.
Giant Miniature EPSCs at the Hippocampal Mossy Fiber to CA3 Pyramidal Cell Synapse Are Monoquantal
Authors: Henze Darrell A. , McMahon David B. T. , Harris Kristen M. , Barrionuevo German
Published: May 2017

The mechanisms generating giant miniature excitatory postsynaptic currents (mEPSCs) were investigated at the hippocampal mossy fiber (MF) to CA3 pyramidal cell synapse in vitro. These giant mEPSCs have peak amplitudes as large as 1,700 pA (13.6 nS) with a mean maximal mEPSC amplitude of 366 ± 20 pA (mean ± SD; 5 nS; n = 25 cells). This is compared with maximal mEPSC amplitudes of <100 pA typically observed at other cortical synapses. We tested the hypothesis that giant mEPSCs are due to synchronized release of multiple vesicles across the release sites of single MF boutons by directly inducing vesicular release using secretagogues. If giant mEPSCs result from simultaneous multivesicular release, then secretagogues should increase the frequency of small mEPSCs selectively. We found that hypertonic sucrose and spermine increased the frequency of both small and giant mEPSCs. The peptide toxin secretagogues alpha-latrotoxin and pardaxin failed to increase the frequency of giant mEPSCs, but the possible lack of tissue penetration of the toxins make these results equivocal. Because a multiquantal release mechanism is likely to be mediated by a spontaneous increase in presynaptic calcium concentration, a monoquantal mechanism is further supported by results that giant mEPSCs were not affected by manipulations of extracellular or intracellular calcium concentrations. In addition, reducing the temperature of the bath to 15°C failed to desynchronize the rising phases of giant mEPSCs. Together these data suggest that the giant mEPSCs are generated via a monovesicular mechanism. Three-dimensional analysis through serial electron microscopy of the MF boutons revealed large clear vesicles (50 to 160 nm diam) docked presynaptically at the MF synapse in sufficient numbers to account for the amplitude and frequency of giant mEPSCs recorded electrophysiologically. It is concluded that release of the contents of a single large clear vesicle generates giant mEPSCs at the MF to CA3 pyramidal cell synapse.
Principles of Linear and Angular Vestibuloocular Reflex Organization in the Frog
Authors: Rohregger M. , Dieringer N.
Published: May 2017

We compared the spatial organization patterns of linear and angular vestibuloocular reflexes in frogs by recording the multiunit spike activity from cranial nerve branches innervating the lateral rectus, the inferior rectus, or the inferior obliquus eye muscles. Responses were evoked by linear horizontal and/or vertical accelerations on a sled or by angular accelerations about an earth-vertical axis on a turntable. Before each sinusoidal oscillation test in darkness, the static head position was systematically altered to determine those directions of horizontal linear acceleration and those planes of angular head oscillation that were associated with minimal response amplitudes. Inhibitory response components during angular accelerations were clearly present, whereas inhibitory response components during linear accelerations were absent. Likewise was no contribution from the vertical otolith organs (i.e., lagena and saccule) observed during vertical linear acceleration. Horizontal linear acceleration evoked responses that originated from eye muscle–specific sectors on the contralateral utricular macula. The sectors of the inferior obliquus and lateral rectus muscles on the utricle had an opening angle of 45 and 60°, respectively and overlapped to a large extent in the laterorostral part of the utricle. Both sectors were coplanar with the horizontal semicircular canals. The sector of the inferior rectus muscle was narrow (opening 5°), laterocaudally oriented, and slightly pitched up by 6°. Angular acceleration evoked maximal responses in the inferior obliquus muscle nerve that originated from the ipsilateral horizontal and the contralateral anterior vertical canals in a ratio of 50:50. Lateral rectus excitation originated from the contralateral horizontal and anterior vertical semicircular canals in a ratio of 80:20. The excitatory responses of the inferior rectus muscle nerve originated exclusively from the contralateral posterior vertical canal. Measured data and known semicircular canal plane vectors were used to calculate the spatial orientation of maximum sensitivity vectors for the investigated eye muscle nerves in semicircular canal coordinates. Comparison of the directions of maximal sensitivity vectors of responses evoked by linear or angular accelerations in a given eye muscle nerve showed that the two vector directions were oriented about orthogonally with respect to each other. With this arrangement the linear and the angular vestibuloocular reflex can support each other dynamically whenever they are co-activated without a change in the spatial response characteristics. The mutual adaptation of angular and linear vestibuloocular reflexes as well as the differences in their organization described here for frogs may represent a basic feature common for vertebrates in general.
Neural Processing of Gravitoinertial Cues in Humans. III. Modeling Tilt and Translation Responses
Authors: Merfeld D. M. , Zupan L. H.
Published: May 2017

All linear accelerometers measure gravitoinertial force, which is the sum of gravitational force (tilt) and inertial force due to linear acceleration (translation). Neural strategies must exist to elicit tilt and translation responses from this ambiguous cue. To investigate these neural processes, we developed a model of human responses and simulated a number of motion paradigms used to investigate this tilt/translation ambiguity. In this model, the separation of GIF into neural estimates of gravity and linear acceleration is accomplished via an internal model made up of three principal components: 1) the influence of rotational cues (e.g., semicircular canals) on the neural representation of gravity, 2) the resolution of gravitoinertial force into neural representations of gravity and linear acceleration, and 3) the neural representation of the dynamics of the semicircular canals. By combining these simple hypotheses within the internal model framework, the model mimics human responses to a number of different paradigms, ranging from simple paradigms, like roll tilt, to complex paradigms, like postrotational tilt and centrifugation. It is important to note that the exact same mechanisms can explain responses induced by simple movements as well as by more complex paradigms; no additional elements or hypotheses are needed to match the data obtained during more complex paradigms. Therefore these modeled response characteristics are consistent with available data and with the hypothesis that the nervous system uses internal models to estimate tilt and translation in the presence of ambiguous sensory cues.
Temporal Properties of the Mouse Cone Electroretinogram
Authors: Krishna Vivek R. , Alexander Kenneth R. , Peachey Neal S.
Published: May 2017

To determine the temporal response characteristics of the mouse cone electroretinogram (ERG), we recorded responses to high contrast sinusoidal stimuli ranging from 2 to 52 Hz. The largest response amplitudes obtained from wild-type (WT) mice occurred at stimulus frequencies below 10 Hz, and cone ERG amplitude declined progressively with increasing stimulus frequency above that level. In comparison, human responses recorded under the same stimulus and recording conditions displayed maximal responses to stimulus frequencies near 4 and 40 Hz, and a pronounced dip at 12 Hz. Responses were also obtained from nob ( no b-wave) mice, which lack ERG contributions from depolarizing bipolar cells (DBCs). At low temporal frequencies, nob cone ERGs were smaller than those of WT mice and had a different waveform. As temporal frequency increased, nob and WT responses became more similar and came into register at the highest temporal frequencies. To evaluate the contribution of the DBC pathway to the mouse cone ERG, nobresponses were vector-subtracted from those of WT mice. The derived DBC response was maximal at low stimulus frequencies and fell sharply as stimulus frequency increased. These results indicate that the mouse cone ERG is more linear than the primate response and that the temporal response of the mouse outer retina is tuned to much lower frequencies than that of primate.
Corticostriatal Combinatorics: The Implications of Corticostriatal Axonal Arborizations
Authors: Zheng T. , Wilson C. J.
Published: May 2017

The complete striatal axonal arborizations of 16 juxtacellularly stained cortical pyramidal cells were analyzed. Corticostriatal neurons were located in the medial agranular or anterior cingulate cortex of rats. All axons were of the extended type and formed synaptic contacts in both the striosomal and matrix compartments as determined by counterstaining for the mu-opiate receptor. Six axonal arborizations were from collaterals of brain stem-projecting cells and the other 10 from bilaterally projecting cells with no brain stem projections. The distribution of synaptic boutons along the axons were convolved with the average dendritic tree volume of spiny projection neurons to obtain an axonal innervation volume and innervation density map for each axon. Innervation volumes varied widely, with single axons occupying between 0.4 and 14.2% of the striatum (average = 4%). The total number of boutons formed by individual axons ranged from 25 to 2,900 (average = 879). Within the innervation volume, the density of innervation was extremely sparse but inhomogeneous. The pattern of innervation resembled matrisomes, as defined by bulk labeling and functional mapping experiments, superimposed on a low background innervation. Using this sample as representative of all corticostriatal axons, the total number of corticostriatal neurons was estimated to be 17 million, about 10 times the number of striatal projection neurons.
Modulation of Gasp Frequency by Activation of Pre-Bötzinger Complex In Vivo
Authors: Solomon Irene C.
Published: May 2017

Under hyperoxic conditions, both chemical stimulation of neurons and focal hypoxia in the pre-Bötzinger complex (pre-BötC) in vivo modify the eupneic pattern of inspiratory motor output by eliciting changes in the patterning and timing of phrenic bursts, which includes both phasic and tonic excitation. The influence of this region on the gasping pattern of phrenic motor output produced during severe brain hypoxia is unknown. We therefore examined the effects of chemical stimulation of neurons (dl-homocysteic acid; DLH; 10 mM; ≤20 nl) and focal hypoxia (sodium cyanide; NaCN; 1 mM; ≤20 nl) in the pre-BötC on hypoxia-induced gasping in chloralose-anesthetized, vagotomized, mechanically ventilated cats. Unilateral microinjection of DLH into the pre-BötC during hypoxia-induced gasping increased phrenic burst frequency by ∼630% ( P < 0.01) over baseline frequency due predominantly to a reduction in T E (from 28.9 ± 6.2 to 5.2 ± 1.8 s; mean ± SE; P < 0.01). No significant changes in T I or rate of rise between hypoxia-induced gasps and the DLH-induced bursts were observed; the effects on peak amplitude of integrated phrenic nerve discharge were variable. Similar responses were evoked by unilateral microinjection of NaCN into the pre-BötC. These findings demonstrate that both activation of pre-BötC neurons and focal hypoxia in the pre-BötC not only influence the eupneic pattern of phrenic motor output but also modify the expression of hypoxia-induced gasping in vivo. These findings also provide additional support to the concept of intrinsic hypoxic chemosensitivity of the pre-BötC.
Tonic and Phasic Discharge Patterns in Toe Flexor γ-Motoneurons During Locomotion in the Decerebrate Cat
Authors: Murphy P. R.
Published: May 2017

To investigate the specificity of fusimotor (γ) drive during locomotion, γ-efferents were recorded from the flexor digitorum longus (FDL) and flexor hallucis longus (FHL) nerves in a decerebrate cat preparation. These nerves innervate hindlimb muscles that differ in some aspects of their mechanical action. For both FHL and FDL two stereotyped patterns of γ activity were distinguished. Tonic units fired throughout the step cycle and had less modulation, but higher minimum rates, than phasic units, which were mainly recruited with ankle extensor [soleus (SOL)] electromyogram (EMG) activity. Differences in the relative timing of these patterns were apparent. In FHL the activity of phasic and most tonic neurons peaked after EMG onset. With FDL, tonic units generally reached maximum rate before, while phasic units peaked after, the beginning of EMG activity. During locomotion FHL and FDL α activity were rhythmically recruited with SOL. However, consistent with previous reports, FHL and FDL differed in their patterns of α activity. FHL was stereotyped while FDL was variable. Both FHL and FDL had activity related to ankle extensor EMG, but only FDL exhibited a peak around the end of this phase. No corresponding γ activity was observed in FDL. In conclusion, 1) FHL and FDL received tonic and phasic fusimotor drive; 2) there was no α/γ linkage for the late FDL α burst; 3) phasic γ-efferents in both muscles received similar inputs, linked to plantar flexor α activity; and 4) tonic γ-efferents differed, to the extent that they were modulated at all. The FHL units peaked with the plantar flexor alphas. The FDL neurons generally peaked before α activity even began.
Long-Term Potentiation in Direct Perforant Path Projections to the Hippocampal CA3 Region In Vivo
Authors: Do Viet H. , Martinez Carlo O. , Martinez Joe L. , Derrick Brian E.
Published: May 2017

The perforant path constitutes the primary projection system relaying information from the neocortex to the hippocampal formation. Long-term synaptic potentiation (LTP) in the perforant path projections to the dentate gyrus is well characterized. However, surprisingly few studies have addressed the mechanisms underlying LTP induction in the direct perforant path projections to the hippocampus. Here we investigate the role of N-methyl-d-aspartate (NMDA) and opioid receptors in the induction of LTP in monosynaptic medial and lateral perforant path projections to the CA3 region in adult pentobarbital sodium–anesthetized rats. Similar to LTP observed at the medial perforant path–dentate gyrus synapse, medial perforant path–CA3 synapses display LTP that is blocked by both local and systemic administration of the competitive NMDA receptor antagonist (±)-3-(2-carboxypiperazin-4-yl) propyl-1-phosphonic acid [(±)-CPP]. By contrast, LTP induced at the lateral perforant path–CA3 synapses is not blocked by either local or systemic administration of this NMDA receptor antagonist. The induction of LTP at lateral perforant path–CA3 synapses, which is blocked by the opioid receptor antagonist naloxone, is also blocked by the selective mu (μ) opioid receptor antagonist Cys2-Tyr3-Orn5-Pen7-amide (CTOP), but not the selective delta (δ) opioid receptor antagonist naltrindole (NTI). CTOP was without effect on the induction of medial perforant path–CA3 LTP. The selective sensitivity of lateral perforant path–CA3 LTP to μ-opioid receptor antagonists corresponds with the distribution of μ-opioid receptors within the stratum lacunosum-moleculare of area CA3 where perforant path projections to CA3 terminate. These data indicate that both lateral and medial perforant path projections to the CA3 region display LTP, and that LTP induction in medial and lateral perforant path–CA3 synapses are differentially sensitive to NMDA receptor and μ-opioid receptor antagonists. This suggests a role for opioid, but not NMDA receptors in the induction of LTP at lateral perforant path projections to the hippocampal formation.
Targeting FBW7 as a Strategy to Overcome Resistance to Targeted Therapy in Non–Small Cell Lung Cancer
Authors: Ye Mingxiang , Zhang Yong , Zhang Xinxin , Zhang Jianbin , Jing Pengyu , Cao Liang , Li Nan , Li Xia , Yao Libo , Zhang Jian , Zhang Jian
Published: May 2017

Inhibition of EGFR and anaplastic lymphoma kinase (ALK) signaling is highly effective in a subgroup of non–small cell lung cancer (NSCLC) patients with distinct clinicopathologic features. However, resistance to EGFR and ALK inhibitors inevitably occurs, and the molecular mechanism underlying resistance is not fully understood. In this study, we report a PI3K/Akt- and MEK/ERK–independent resistance mechanism by which loss of the E3 ubiquitin ligase F-box and WD repeat domain containing 7 (FBW7α) leads to targeted therapy resistance via stabilization of antiapoptotic protein MCL-1. Using a panel of in vitro and in vivo studies, we showed that the regulatory machinery responsible for MCL-1 protein degradation was a step-wise event involving phosphorylation and nucleus translocation. ERK cooperated with GSKβ to phosphorylate MCL-1 Ser159 residue, which enabled MCL-1 to translocate into the nucleus and bind FBW7. Defects in this sequence impaired MCL-1 degradation and cell apoptosis, recapitulating phenotypes observed in FBW7 deficiency. Downregulation of FBW7 was found in EGFR inhibitor–resistant human NSCLC specimens and correlated with increased MCL-1 protein expression. Reactivation of FBW7 sensitized resistant cells to targeted therapy and facilitated MCL-1 degradation. Overall, our study provides proof-of-principle insight into a PI3K/Akt- and MEK/ERK–independent resistant model and suggests that targeting FBW7 can overcome resistance to targeted therapy. Cancer Res; 77(13); 3527–39. ©2017 AACR.
Mismatch Repair Proteins Initiate Epigenetic Alterations during Inflammation-Driven Tumorigenesis
Authors: Maiuri Ashley R. , Peng Michael , Podicheti Ram , Sriramkumar Shruthi , Kamplain Caitlin M. , Rusch Douglas B. , DeStefano Shields Christina E. , Sears Cynthia L. , O'Hagan Heather M.
Published: May 2017

Aberrant silencing of genes by DNA methylation contributes to cancer, yet how this process is initiated remains unclear. Using a murine model of inflammation-induced tumorigenesis, we tested the hypothesis that inflammation promotes recruitment of epigenetic proteins to chromatin, initiating methylation and gene silencing in tumors. Compared with normal epithelium and noninflammation-induced tumors, inflammation-induced tumors gained DNA methylation at CpG islands, some of which are associated with putative tumor suppressor genes. Hypermethylated genes exhibited enrichment of repressive chromatin marks and reduced expression prior to tumorigenesis, at a time point coinciding with peak levels of inflammation-associated DNA damage. Loss of MutS homolog 2 (MSH2), a mismatch repair (MMR) protein, abrogated early inflammation-induced epigenetic alterations and DNA hypermethylation alterations observed in inflammation-induced tumors. These results indicate that early epigenetic alterations initiated by inflammation and MMR proteins lead to gene silencing during tumorigenesis, revealing a novel mechanism of epigenetic alterations in inflammation-driven cancer. Understanding such mechanisms will inform development of pharmacotherapies to reduce carcinogenesis. Cancer Res; 77(13); 3467–78. ©2017 AACR.
SMAD4 Loss Is Associated with Cetuximab Resistance and Induction of MAPK/JNK Activation in Head and Neck Cancer Cells
Authors: Ozawa Hiroyuki , Ranaweera Ruchira S. , Izumchenko Evgeny , Makarev Eugene , Zhavoronkov Alex , Fertig Elana J. , Howard Jason D. , Markovic Ana , Bedi Atul , Ravi Rajani , Perez Jimena , Le Quynh-Thu , Kong Christina S. , Jordan Richard C. , Wang Hao , Kang Hyunseok , Quon Harry , Sidransky David , Chung Christine H.
Published: May 2017

Purpose: We previously demonstrated an association between decreased SMAD4 expression and cetuximab resistance in head and neck squamous cell carcinoma (HNSCC). The purpose of this study was to further elucidate the clinical relevance of SMAD4 loss in HNSCC.

Experimental Design: SMAD4 expression was assessed by IHC in 130 newly diagnosed and 43 patients with recurrent HNSCC. Correlative statistical analysis with clinicopathologic data was also performed. OncoFinder, a bioinformatics tool, was used to analyze molecular signaling in TCGA tumors with low or high SMAD4 mRNA levels. The role of SMAD4 was investigated by shRNA knockdown and gene reconstitution of HPV-negative HNSCC cell lines in vitro and in vivo.

Results: Our analysis revealed that SMAD4 loss was associated with an aggressive, HPV-negative, cetuximab-resistant phenotype. We found a signature of prosurvival and antiapoptotic pathways that were commonly dysregulated in SMAD4-low cases derived from TCGA-HNSCC dataset and an independent oral cavity squamous cell carcinoma (OSCC) cohort obtained from GEO. We show that SMAD4 depletion in an HNSCC cell line induces cetuximab resistance and results in worse survival in an orthotopic mouse model in vivo. We implicate JNK and MAPK activation as mediators of cetuximab resistance and provide the foundation for the concomitant EGFR and JNK/MAPK inhibition as a potential strategy for overcoming cetuximab resistance in HNSCCs with SMAD4 loss.

Conclusions: Our study demonstrates that loss of SMAD4 expression is a signature characterizing the cetuximab-resistant phenotype and suggests that SMAD4 expression may be a determinant of sensitivity/resistance to EGFR/MAPK or EGFR/JNK inhibition in HPV-negative HNSCC tumors. Clin Cancer Res; 23(17); 5162–75. ©2017 AACR.
Antitumor Synergism and Enhanced Survival with a Tumor Vasculature–Targeted Enzyme Prodrug System, Rapamycin, and Cyclophosphamide
Authors: Krais John J. , Virani Needa , McKernan Patrick H. , Nguyen Quang , Fung Kar-Ming , Sikavitsas Vassilios I. , Kurkjian Carla , Harrison Roger G.
Published: May 2017

Mutant cystathionine gamma-lyase was targeted to phosphatidylserine exposed on tumor vasculature through fusion with Annexin A1 or Annexin A5. Cystathionine gamma-lyase E58N, R118L, and E338N mutations impart nonnative methionine gamma-lyase activity, resulting in tumor-localized generation of highly toxic methylselenol upon systemic administration of nontoxic selenomethionine. The described therapeutic system circumvents systemic toxicity issues using a novel drug delivery/generation approach and avoids the administration of nonnative proteins and/or DNA required with other enzyme prodrug systems. The enzyme fusion exhibits strong and stable in vitro binding with dissociation constants in the nanomolar range for both human and mouse breast cancer cells and in a cell model of tumor vascular endothelium. Daily administration of the therapy suppressed growth of highly aggressive triple-negative murine 4T1 mammary tumors in immunocompetent BALB/cJ mice and MDA-MB-231 tumors in SCID mice. Treatment did not result in the occurrence of negative side effects or the elicitation of neutralizing antibodies. On the basis of the vasculature-targeted nature of the therapy, combinations with rapamycin and cyclophosphamide were evaluated. Rapamycin, an mTOR inhibitor, reduces the prosurvival signaling of cells in a hypoxic environment potentially exacerbated by a vasculature-targeted therapy. IHC revealed, unsurprisingly, a significant hypoxic response (increase in hypoxia-inducible factor 1 α subunit, HIF1A) in the enzyme prodrug–treated tumors and a dramatic reduction of HIF1A upon rapamycin treatment. Cyclophosphamide, an immunomodulator at low doses, was combined with the enzyme prodrug therapy and rapamycin; this combination synergistically reduced tumor volumes, inhibited metastatic progression, and enhanced survival. Mol Cancer Ther; 16(9); 1855–65. ©2017 AACR.
Fifteen-Year-Old Male with Type 2 Autoimmune Pancreatitis: An Argument for Endoscopy
Authors: Kolasinski Nathan T. , Johannsen Marc T. , Hollon Justin R.
Published: May 2017

Type 2 autoimmune pancreatitis, an increasingly recognized etiology of pancreatitis in patients less than 20 years old, has characteristically been diagnosed with the histological finding of duct-centric pancreatitis in a patient who lacks elevated serum immunoglobulin G4. We present the case of a nonobese 15-year-old male, without any chronic medical conditions, who presented with the chief complaint of abdominal pain. The laboratory study results were remarkable for a lipase level of 5,419 U/L and a γ-glutamyl transferase level of 373 U/L. Magnetic resonance cholangiopancreatography revealed delayed contrast enhancement of the pancreas, diffuse parenchymal enlargement, and lack of normal lobulation. The patient’s serum immunoglobulin G4 level was found to be 66 mg/dL, which was within normal limits and supportive of a diagnosis of type 2 autoimmune pancreatitis. Despite the absence of intestinal complaints, the patient underwent subsequent endoscopy due to the correlation of type 2 autoimmune pancreatitis with inflammatory bowel disease that has been described in recent literature. Pan-colonic mild colitis was visualized, and the patient began treatment with steroids, to which he quickly responded. Performing endoscopy on this patient allowed for confident initiation of early therapy for both autoimmune pancreatitis and inflammatory bowel disease, and may have limited further surgical intervention and disease progression. For these reasons, this case highlights the utility of endoscopy in pediatric patients with suspected type 2 autoimmune pancreatitis, even in the absence of intestinal symptoms.
Three-Quarters Adrenalectomy for Infantile-Onset Cushing Syndrome due to Bilateral Adrenal Hyperplasia in McCune-Albright Syndrome
Authors: Itonaga Tomoyo , Goto Hironori , Toujigamori Manabu , Ohno Yasuharu , Korematsu Seigo , Izumi Tatsuro , Narumi Satoshi , Hasegawa Tomonobu , Ihara Kenji
Published: May 2017

Background: Bilateral adrenalectomy is performed in cases with infantile-onset Cushing syndrome due to bilateral adrenal hyperplasia in McCune-Albright syndrome (MAS) because severe Cushing syndrome with heart failure and liver dysfunction can have a lethal outcome. This procedure can completely ameliorate hypercortisolism, although lifetime steroid replacement therapy and steps to prevent adrenal crisis are necessary. Recently, the efficacy of unilateral adrenalectomy has been reported in adult cases of bilateral macronodular adrenal hyperplasia, but there is no consensus regarding the appropriate surgical treatment for bilateral adrenal hyperplasia in MAS. Objective: A 6-month-old girl presented with café-au-lait spots, short stature, central obesity, a moon face, and hypertension. Endocrinological tests and imaging studies led to the diagnosis of ACTH-independent Cushing syndrome due to bilateral adrenal hyperplasia induced by MAS. “Three-quarters adrenalectomy”, namely right-sided total adrenalectomy and left-sided half adrenalectomy, was carried out. An activating mutation of the GNAS1 gene (p.Arg201Cys) was identified in the adrenal tissues. Since the operation, our patient has been in a state of clinical remission for more than 2 years. Conclusion: Our original surgical intervention, three-quarters adrenalectomy, may be a new treatment option for Cushing syndrome associated with MAS.
Molecular Diagnosis of Tubercular Lymphadenopathy from Fine-Needle Aspirates in Pediatric Patients
Authors: Gupta Vivek , Bhake Arvind
Published: May 2017

Objectives: The diagnosis of peripheral tubercular lymphadenopathy (TBLN) in pediatric patients is often a challenge because features evident on fine-needle aspiration cytology (FNAC) or tissue biopsy can be deceptive for the reason that they result from an immunological response. This study aimed to evaluate polymerase chain reaction (PCR) for Mycobacterium tuberculosis complex (MTBC) in pediatric patients under clinical suspicion for TBLN and to assess its role in the evaluation of cases cytodiagnosed as reactive lymphoid hyperplasia. Methods: This was a cross-sectional study conducted on 45 pediatric patients clinically suspected and unsuspected for TBLN. FNAC, culture on Löwenstein-Jensen medium, and real-time PCR were performed. Comparative values with reference to the culture were calculated. Results: Cytology had a sensitivity and specificity of 38.5 and 87.5%, respectively. Real-time PCR had a sensitivity and specificity of 84.6 and 81.3%, respectively. Of the 32 cases with a cytodiagnosis of reactive lymphoid hyperplasia, 53% were positive both on PCR and culture for M. tuberculosis; the φ value of 0.93 demonstrated a strong association between these 2 methods. Conclusion: Real-time PCR is useful in detecting MTBC in pediatric patients, and it also helps in the diagnosis of cases missed on FNAC.
Synergistic Effect of Dofetilide and Mexiletine on Prevention of Atrial Fibrillation
Authors: Liu Guizhi , Xue Xiaolin , Gao Chuanyu , Huang Jiaqi , Qi Datun , Zhang Yanzhou , Dong Jian‐Zeng , Ma Chang‐Sheng , Yan Gan‐Xin
Published: May 2017

Background

Although atrial fibrillation (
AF
) is the most common abnormal heart rhythm and its prevalence continues to rise, there is a marked paucity of effective and safe antiarrhythmic drugs for
AF
. This study was done to test whether combined use of dofetilide and mexiletine exhibits not only a synergistic effect on
AF
suppression but also a safer profile in drug‐induced ventricular proarrhythmias.

Methods and Results

The effects of dofetilide plus mexiletine on atrial effective refractory period (
ERP
),
AF
inducibility,
QT
, and
QT
‐related ventricular arrhythmias were studied using the isolated arterially perfused rabbit atrial and ventricular wedge preparations. Dofetilide or mexiletine alone mildly to moderately prolonged atrial
ERP
, but their combined use produced a markedly rate‐dependent increase in atrial
ERP
. Dofetilide (3 nmol/L) plus mexiletine (10 μmol/L) increased the
ERP
by 28.2% from 72.2±5.7 to 92.8±5.9 ms (n=9,
P
<0.01) at a pacing rate of 0.5 Hz and by 94.5% from 91.7±5.2 to 178.3±12.0 ms (n=9,
P
<0.01) at 3.3 Hz. Dofetilide plus mexiletine strongly suppressed
AF
inducibility. On the other hand, dofetilide at 10 nmol/L produced marked
QT
and T
p‐e
prolongation, steeper
QT
‐
BCL
and T
p‐e
‐
BCL
slopes, and induced early afterdepolarizations and torsade de pointes in the ventricular wedges. Mexiletine at 10 μmol/L reduced dofetilide‐induced
QT
and T
p‐e
prolongation,
QT
‐
BCL
and T
p‐e
‐
BCL
slopes, and abolished early afterdepolarizations and torsade de pointes.

Conclusions

In rabbits, combined use of dofetilide and mexiletine not only synergistically increases atrial
ERP
and effectively suppresses
AF
inducibility, but also markedly reduces
QT
liability and torsade de pointes risk posed by dofetilide alone.
Gerard Manley Hopkins’s Incarnational Ecology
Authors: Cochran James M.
Published: May 2017

This essay examines Hopkins’s “Binsey Poplars” from an incarnational theological lens. Such a reading negotiates seemingly incongruent arguments put forth by Post, who argues that Hopkins’s ecological world is “other,” and Day, who argues that Hopkins makes the ecological world comprehensible. Incarnational theology allows for a middle ground by preserving beings’ uniqueness yet unifying them in a collective body. Additionally, reading the poem from an incarnational theological lens continues recent critical work that sees religious dimensions in the poem. Finally, this essay suggests that Hopkins’s incarnational theology anticipates and speaks to contemporary ecological and ecocritical issues. As such, this essay reads contemporary and emerging ecocritical voices alongside Hopkins’s poem to demonstrate the harmony between the theological and theoretical voices.
Staging Resistance from the Clergy During the Holocaust
Authors: Plunka Gene A.
Published: May 2017

The resistance to the Holocaust from Catholic and Protestant clergymen came in myriad forms. A few clergy willingly gave up their lives, thus becoming martyrs for refusing to be judged by Nazi law, surrendering instead to divine justice. Such noble and heroic decisions in which a humble person surrenders life in defiance of a totalitarian regime opposed to Christian humanism is a subject most worthy of study. This essay focuses exclusively on stage representations of the extreme sacrifices the clergy made during the Holocaust as reflected by martyrdom in Arthur Giron’s Edith Stein and David Gooderson’s Kolbe’s Gift. The protagonists of these two plays, Edith Stein and Maximilian Kolbe, died and suffered greatly to uphold the moral position of the Church.
Language contact, borrowing and code switching
Authors: Alvanoudi Angeliki
Published: May 2017

The present study is an in-depth investigation of the Greek language spoken by immigrants in Far North Queensland, Australia. The study focuses on contact-induced changes in the language, such as borrowing of lexemes and discourse patterns, and on code switching. The data analyzed derive from participant observation and some 23 hours of audio and video-recorded conversations with first- and second-generation Greek immigrants that were collected during fieldwork in 2013 in Far North Queensland. The study contributes to the investigation of the structure and use of Greek in the diaspora by integrating perspectives from contact linguistics and interactional approaches to code switching.