Long-term stimulation and recording with a penetrating microelectrode array in cat sciatic nerve

Journal ArticleWe studied the consequences of long-term implantation of a penetrating microelectrode array in peripheral nerve over the time course of 4-6 mo. Electrode arrays without lead wires were implanted to test the ability of different containment systems to protect the array and nerve during contractions of surrounding muscles. Treadmill walking was monitored and the animals showed no functional deficits as a result of implantation. In a different set of experiments, electrodes with lead wires were implanted for up to 7 mo and the animals were tested at 2-4 week intervals at which time stimulation thresholds and recorded sensory activity were monitored for every electrode. It was shown that surgical technique highly affected the long-term stimulation results. Results between measurement sessions were compared, and in the best case, the stimulation properties stabilized in 80% of the electrodes over the course of the experiment (162 days). The recorded sensory signals, however, were not stable over time. A histological analysis performed on all implanted tissues indicated that the morphology and fiber density of the nerve around the electrodes were normal

Coding of position by simultaneously recorded sensory neurones in the cat dorsal root ganglion

Journal ArticleMuscle, cutaneous and joint afferents continuously signal information about the position and movement of individual joints. How does the nervous system extract more global information, for example about the position of the foot in space? To study this question we used microelectrode arrays to record impulses simultaneously from up to 100 discriminable nerve cells in the L6 and L7 dorsal root ganglia (DRG) of the anaesthetized cat. When the hindlimb was displaced passively with a random trajectory, the firing rate of the neurones could be predicted from a linear sum of positions and velocities in Cartesian (x, y), polar or joint angular coordinates. The process could also be reversed to predict the kinematics of the limb from the firing rates of the neurones with an accuracy of 1-2 cm. Predictions of position and velocity could be combined to give an improved fit to limb position. Decoders trained using random movements successfully predicted cyclic movements and movements in which the limb was displaced from a central point to various positions in the periphery. A small number of highly informative neurones (6-8) could account for over 80% of the variance in position and a similar result was obtained in a realistic limb model. In conclusion, this work illustrates how populations of sensory receptors may encode a sense of limb position and how the firing of even a small number of neurones can be used to decode the position of the limb in space

Encoding mechanisms for sensory neurons studied with a multielectrode array in the cat dorsal root ganglion

Journal ArticleRecent advances in microelectrode array technology now permit a direct examination of the way populations of sensory neurons encode information about a limb's position in space. To address this issue, we recorded nerve impulses from about 100 single units simultaneously in the L6 and L7 dorsal root ganglia (DRG) of the anesthetized cat. Movement sensors, placed near the hip, knee, ankle, and foot, recorded passive movements of the cat's limb while it was moved pseudo-randomly. The firing rate of the neurons was correlated with the position of the limb in various coordinate systems. The firing rates were less correlated to the position of the foot in Cartesian coordinates (x, y) than in joint angular coordinates (hip, knee, ankle), or in polar coordinates. A model was developed in which position and its derivatives are encoded linearly, followed by a nonlinear spike-generating process. Adding the nonlinear portion significantly increased the correlations in all coordinate systems, and the full models were able to accurately predict the firing rates of various types of sensory neurons. The observed residual variability is captured by a simple stochastic model. Our results suggest that compact encoding models for primary afferents recorded at the DRG are well represented in polar coordinates, as has previously been suggested for the cortical and spinal representation of movement. This study illustrates how sensory receptors encode a sense of limb position, and it provides a general framework for modeling sensory encoding by populations of neurons

Gauged Q-balls

Classical non-topological soliton configurations are considered within the theory of a complex scalar field with a gauged U symmetry. Their existence and stability against dispersion are demonstrated and some of their properties are investigated analytically and numerically. The soliton configuration is such that inside the soliton the local U symmetry is broken, the gauge field becomes massive and for a range of values of the coupling constants the soliton becomes a superconductor pushing the charge to the surface. Furthermore, because of the repulsive Coulomb force, there is a maximum size for these objects, making impossible the existence of Q-matter in bulk form. Also briefly discussed are solitons with fermions in a U gauge theory

Insights into the evolution of the ErbB receptor family and their ligands from sequence analysis

BACKGROUND: In the time since we presented the first molecular evolutionary study of the ErbB family of receptors and the EGF family of ligands, there has been a dramatic increase in genomic sequences available. We have utilized this greatly expanded data set in this study of the ErbB family of receptors and their ligands. RESULTS: In our previous analysis we postulated that EGF family ligands could be characterized by the presence of a splice site in the coding region between the fourth and fifth cysteines of the EGF module and the placement of that module near the transmembrane domain. The recent identification of several new ligands for the ErbB receptors supports this characterization of an ErbB ligand; further, applying this characterization to available sequences suggests additional potential ligands for these receptors, the EGF modules from previously identified proteins: interphotoreceptor matrix proteoglycan-2, the alpha and beta subunit of meprin A, and mucins 3, 4, 12, and 17. The newly available sequences have caused some reorganizations of relationships among the ErbB ligand family, but they add support to the previous conclusion that three gene duplication events gave rise to the present family of four ErbB receptors among the tetrapods. CONCLUSION: This study provides strong support for the hypothesis that the presence of an easily identifiable sequence motif can distinguish EGF family ligands from other EGF-like modules and reveals several potential new EGF family ligands. It also raises interesting questions about the evolution of ErbB2 and ErbB3: Does ErbB2 in teleosts function differently from ErbB2 in tetrapods in terms of ligand binding and intramolecular tethering? When did ErbB3 lose kinase activity, and what is the functional significance of the divergence of its kinase domain among teleosts

A new Cambrian arthropod, Emeraldella brutoni, from Utah

Emeraldella is a rare arthropod of relatively large body size that belongs with the trilobite-like arthropods, Artiopoda. E. brutoni n. sp. from the Wheeler Formation of west-central Utah is the second species described and marks the first confirmed occurrence of Emeraldella outside the Burgess Shale of British Columbia. An articulated, flagelliform telson, similar to that of the Burgess Shale taxon Molaria, is recognized in Emeraldella. Evidence for the presence of lamellae on the exopods of Molaria is presented, supporting affinity of that taxon with Artiopoda. A close relationship between Emeraldella and Molaria is tentatively suggested, based on the morphology of tergites and telson

From ACE2 to COVID-19: A Multiorgan Endothelial Disease

Editoria

Effects of the Novel NMDA Receptor Antagonist Gacyclidine on Recovery From Medial Frontal Cortex Contusion Injury in Rats

Gacyclidine, a novel, noncompetitive NMDA receptor antagonist, was injected (i.v.) into rats at three different doses to determine if the drug could promote behavioral recovery and reduce the behavioral and anatomical impairments that occur after bilateral contusions of the medial frontal cortex (MFC). In the Morris water maze,contused rats treated with gacyciidine at a dosage of 0.1 mg/kg performed better than their vehicle-treated conspecifics. Rats given gacyclidine at either 0,3 or 0.03 mg/kg performed better than brain-injured controls, but not as well as those treated with 0.1 mg/kg. Counts of surviving neurons in the nucleus basalis magnoceilularis (NBM) and the medial dorsal nucleus (MDN) of the thalamus were used to determine whether gacyclidine treatment attenuated secondary cell death. In both the NBM and the MDN, the counts revealed fewer surviving neurons in untreated contused rats than in gacyclidine-treated rats. Increases in the size and number of microglia and astrocytes were observed in the striatum of gacyclidinetreated contused brains. Although most consequences of MFC contusions were attenuated, we still observed increases in ventricle dilation and thinning of the cortex. In fact, the ventricles of rats treated with 0.1 mg/kg of gacyclidine were larger than those of their vehicle treated counterparts, although we observed no behavioral impairment