Oncospheral hook morphogenesis in the davaineid cestode Inermicapsifer madagascariensis (Davaine, 1870) Baer, 1956

The fine structural characteristics of oncospheral hook morphogenesis in the davaineid cestode Inermicapsifer madagascariensis are described. The primordia of the hooks appear in the oncoblasts of embryos in the advanced stage of development, in which there is a greatly reduced number of blastomeres that exhibit a bilaterally symmetrical pattern in their organization.

The hook primordium, adjacent to the invaginated part of the nuclear envelope, is surrounded by an abundance of free ribosomes, mitochondrial aggregations and extended Golgi regions. Simultaneously with its elongation and transformation into a blade, the hook primordium material becomes differentiated to form an electron dense cortex and a less dense, inner, crystal-like core. At the beginning of shank formation, the blade of the hook protrudes outside the oncoblast. The membrane-enclosed point of exit of the blade is surrounded by a cytoplasmic sheath which later forms a circular, septate desmosome.

With oncoblast degeneration, muscle fibres attach directly to the collar and the base of the hook.     

Assessment of SAR and thermal changes near a cochlear implant system for mobile phone type exposures

A cochlear implant system is a device used to enable hearing in people with severe hearing loss and consists of an internal implant and external speech processor. This study considers the effect of scattered radiofrequency fields when these persons are subject to mobile phone type exposure. A worst-case scenario is considered where the antenna is operating at nominal full power, the speech processor is situated behind the ear using a metallic hook, and the antenna is adjacent to the hook and the internal ball electrode. The resultant energy deposition and thermal changes were determined through numerical modelling. With a 900 MHz half-wave dipole antenna producing continuous-wave (CW) 250 mW power, the maximum 10 g averaged SAR was 1.31 W/kg which occurred in the vicinity of the hook and the ball electrode. The maximum temperature increase was 0.33 degrees C in skin adjacent to the hook. For the 1800 MHz antenna, operating at 125 mW, the maximum 10 g averaged SAR was 0.93 W/kg in the pinna whilst the maximum temperature change was 0.16 degrees C. The analysis predicts that the wearer complies with the radiofrequency safety limits specified by the International Commission on Non-Ionizing Radiation Protection (ICNIRP), the Institute of Electrical and Electronics Engineers (IEEE), and the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) for 900 and 1800 MHz mobile phone type exposure and thus raises no cause for concern. The resultant temperature increase is well below the maximum rise of 1 degrees C recommended by ICNIRP. Effects in the cochlea were insignificant.     

Phase-dependent coordination of two motor programs in the buccal ganglion of a pteropod mollusk

Rhythmic activities of two feeding structures of the pteropod mollusk Clione limacina, redula and hooks, controlled by the neural networks in the buccal ganglia must be coordinated in order to produce a meaningful feeding response. Optical recording from the buccal ganglia, which allows the simultaneous activities of numerous neurons to be traced, revealed that such coordination exists in a phase-dependent manner. Instead of recording four theoretically possible phases of neuronal rhythmic activity, we always recorded only two phases, even after the electrical stimulation of the cerebro-buccal connective, which triggers both radula and hook rhythmic movements in the preparation.     

Action potentials resulting from mechanical stimulation of pea epicotyls

Summary Non-propagating, asynchronous action potentials may be detected with an extracellular electrode placed on the hook of the pea epicotyl following mechanical stimulation. These may well mediate the release of ethylene which has previously been shown to control the diameter of mechanically stressed shoots.     

PTFOS: Flexible and Absorbable Intracranial Electrodes for Magnetic Resonance Imaging

Intracranial electrocortical recording and stimulation can provide unique knowledge about functional brain anatomy in patients undergoing brain surgery. This approach is commonly used in the treatment of medically refractory epilepsy. However, it can be very difficult to integrate the results of cortical recordings with other brain mapping modalities, particularly functional magnetic resonance imaging (fMRI). The ability to integrate imaging and electrophysiological information with simultaneous subdural electrocortical recording/stimulation and fMRI could offer significant insight for cognitive and systems neuroscience as well as for clinical neurology, particularly for patients with epilepsy or functional disorders. However, standard subdural electrodes cause significant artifact in MRI images, and concerns about risks such as cortical heating have generally precluded obtaining MRI in patients with implanted electrodes. We propose an electrode set based on polymer thick film organic substrate (PTFOS), an organic absorbable, flexible and stretchable electrode grid for intracranial use. These new types of MRI transparent intracranial electrodes are based on nano-particle ink technology that builds on our earlier development of an EEG/fMRI electrode set for scalp recording. The development of MRI-compatible recording/stimulation electrodes with a very thin profile could allow functional mapping at the individual subject level of the underlying feedback and feed forward networks. The thin flexible substrate would allow the electrodes to optimally contact the convoluted brain surface. Performance properties of the PTFOS were assessed by MRI measurements, finite difference time domain (FDTD) simulations, micro-volt recording, and injecting currents using standard electrocortical stimulation in phantoms. In contrast to the large artifacts exhibited with standard electrode sets, the PTFOS exhibited no artifact due to the reduced amount of metal and conductivity of the electrode/trace ink and had similar electrical properties to a standard subdural electrode set. The enhanced image quality could enable routine MRI exams of patients with intracranial electrode implantation and could also lead to chronic implantation solutions.     

Listening for bats: the hearing range of the bushcricket Phaneroptera falcata for bat echolocation calls measured in the field

The hearing range of the tettigoniid Phaneropterafalcata for the echolocation calls of freely flying mouseeared bats (Myotis myotis) was determined in the field. The hearing of the insect was monitored using hook electrode recordings from an auditory interneuron, which is as sensitive as the hearing organ for frequencies above 16 kHz. The flight path of the bat relative to the insect's position was tracked by recording the echolocation calls with two microphone arrays, and calculating the bat's position from the arrival time differences of the calls at each microphone. The hearing distances ranged from 13 to 30 m. The large variability appeared both between different insects and between different bat approaches to an individual insect. The escape time of the bushcricket, calculated from the detection distance of the insect and the instantaneous flight speed of the bat, ranged from 1.5 to more than 4s. The hearing ranges of bushcrickets suggest that the insect hears the approaching bat long before the bat can detect an echo from the flying insect.     

Click-evoked responses from the exposed intracranial portion of the eight nerve during vestibular nerve section: bipolar and monopolar recordings

We compare the click-evoked compound action potentials from the exposed intracranial portion of the eight nerve using bipolar and monopolar recording electrodes in patients undergoing vestibular nerve section. It is assumed that a bipolar recording electrode will only record propagated neural activity in the auditory nerve, whereas a monopolar recording electrode may in addition record electrical activity that is conducted passively to the recording site. The results of the present study confirm that the earliest detectable propagated neural activity in the intracranial portion of the auditory nerve occurs with a latency that is close to that of peak II of the brain-stem auditory evoked potentials, and the results also confirm that the late components in the click-evoked compound action potentials that have been demonstrated previously using the monopolar recording technique represent propagated neural activity in the auditory nerve. The results also indicate that the responses that are recorded by a bipolar recording electrode, when the small tips of which are placed on the eight nerve when it is relatively dry, represent only small populations of nerve fibers. Even when an attempt is made to align the two tips of a bipolar electrode with the course of the auditory nerve, this type of electrode may record from different populations of nerve fibers.     

Electrode for selective recording of electromyograms from intercostal muscles

An electromyogram-recording electrode is described that makes it possible to record separately the electrical signals generated within two closely approximated muscle layers. The device consists of two bipolar wire hook electrodes embedded in opposite faces of a thin laminated plastic wafer. The middle lamina of the wafer is a sheet of metal foil that shields the electrical field on one side of the wafer from the bipolar electrode on the other side. The device was tested by inserting it from the inside of the chest wall between the internal and external intercostal muscle layers. Signals from the two muscle layers were clearly separated. Single motor unit spikes were attenuated by factors ranging from 41 to 2.4. The device can be implanted with minimal trauma to surrounding muscles and is suitable for chronic animal experiments.     

Computer interface and algorithm determines bioelectrode impedance

A computer system for measurement of electrode impedance was developed which permits periodic and automatic determination of proper electrode contact during long-term recording sessions. In addition, the voltage gain of the entire recording system was obtained for subsequent calibration of records. The computer could then record the impedance for documentation or signal the operator for necessary electrode adjustment.     

Simple techniques suitable for student use to record action potentials from the frog heart

Demonstrating action potentials during class experiments is very educational for science students. It is not easy, however, to obtain a stable intracellular recording of action potentials from the conventionally used skeletal muscle cells, because the tip of a glass microelectrode often comes out or breaks due to muscle contraction. Here, I present a much simpler recording method using a flexible polyethylene electrode with a wide orifice (approximately 1 mm) for a bullfrog heart beating on automaticity. Extracellular recordings of action potentials (electrocardiogram) can be obtained by placing an electrode on the cardiac surface, and transmembrane potentials can be obtained by rupturing the membrane with negative pressure, i.e., whole cell configuration. Once attached to the heart by suction, the polyethylene electrode does not easily come off during contraction of the heart. Perfusion of the heart via the postcaval vein offers us opportunities for observing the effects of either changing ionic compositions of solutions or applying drugs. The techniques shown here provide a simple and convenient way to perform a variety of class experiments.     

The enhancement of neural growth by amino-functionalization on carbon nanotubes as a neural electrode

This paper reports the success of amino-functionalization on multi-walled carbon nanotubes (MWCNTs) to promote neuronal cells growth on MWCNT electrode for extracellular recording, attributed to the formation of positive charge of NH(2) molecules on their surfaces. Besides, the surface of MWCNT electrode becomes hydrophilic after amino-functionalization (AF-MWCNTs) which can enhance electrical conductivity because of lower MWCNT/electrolyte interfacial impedance and higher interfacial capacitance. Durability tests show that electrical characteristics of the MWCNTs treated by 2 wt% 1,4-diaminobutane solution (2 wt%-AF-MWCNTs) can last for at least six months in air ambient. The neural recording of crayfish shows that 2 wt%-AF-MWCNTs can provide better capability on detecting action potentials of caudal photoreceptor (CPR) interneuron compared to suction glass pipette from the evidence of a higher S/N ratio (126 versus 23). The amino-functionalized MWCNT electrode is feasible for long-term recording application according to the results of biocompatibility tests. As the MWCNTs were directly synthesized on Si-based substrates by catalyst-assisted thermal chemical vapor deposition (CVD) at a low temperature (400 °C), these self-aligned MWCNT electrodes could be friendly implemented in integrated circuits fabrications.     

微丝电极阵列的参考电极内置与外置的对比研究*

目的: 通过对比内置和外置参考电极的微丝电极阵列在记录大鼠脑神经元放电过程中的优缺点,优化微丝电极阵列的制作与埋置,为多通道电生理实时记录系统提供更加实惠、优异的媒介工具。方法: 采用镍铬合金丝、电路板、电极引脚和地线(银线)制作16通道的微丝电极阵列,通过内置(参考电极与电极阵列并列排布)或外置(参考电极与地线分别焊接在电极一侧的两端)微丝电极阵列的参考电极,观察对比两种电极在记录大鼠ACC脑区神经元放电中的区别。实验大鼠分为内置组(8只)和外置组(9只),检测指标有信噪比(n=8)、放电幅度(n=380)和放电频率(n=54)。结果: 内置与外置参考电极的微丝电极阵列均可顺利记录出大鼠ACC脑区神经元的电信号;与外置组相比,内置组的神经元电信号具有信噪比高(P＜0.05)、背景信号幅度小、受噪音干扰小,和放电幅度大(P＜0.05)的优点;锋电位放电频率没有显著差异(P＞0.05)。结论: 在记录大鼠ACC脑区神经元电活动时,内置参考电极的微丝电极阵列记录到更高信噪比、更大放电幅度的电信号,为多通道电生理技术提供更加可靠的工具。     

Theoretical Analysis of the Local Field Potential in Deep Brain Stimulation Applications

Deep brain stimulation (DBS) is a common therapy for treating movement disorders, such as Parkinson’s disease (PD), and provides a unique opportunity to study the neural activity of various subcortical structures in human patients. Local field potential (LFP) recordings are often performed with either intraoperative microelectrodes or DBS leads and reflect oscillatory activity within nuclei of the basal ganglia. These LFP recordings have numerous clinical implications and might someday be used to optimize DBS outcomes in closed-loop systems. However, the origin of the recorded LFP is poorly understood. Therefore, the goal of this study was to theoretically analyze LFP recordings within the context of clinical DBS applications. This goal was achieved with a detailed recording model of beta oscillations (∼20 Hz) in the subthalamic nucleus. The recording model consisted of finite element models of intraoperative microelectrodes and DBS macroelectrodes implanted in the brain along with multi-compartment cable models of STN projection neurons. Model analysis permitted systematic investigation into a number of variables that can affect the composition of the recorded LFP (e.g. electrode size, electrode impedance, recording configuration, and filtering effects of the brain, electrode-electrolyte interface, and recording electronics). The results of the study suggest that the spatial reach of the LFP can extend several millimeters. Model analysis also showed that variables such as electrode geometry and recording configuration can have a significant effect on LFP amplitude and spatial reach, while the effects of other variables, such as electrode impedance, are often negligible. The results of this study provide insight into the origin of the LFP and identify variables that need to be considered when analyzing LFP recordings in clinical DBS applications.     

Molecular Characterization of the Flagellar Hook in Bacillus subtilis

The structure of the Gram-positive flagellum is poorly understood, and Bacillus subtilis encodes three proteins homologous to the flagellar hook protein from Salmonella enterica. Here we generated a modified B. subtilis hook protein that could be fluorescently stained using a cysteine-reactive dye. We used the fluorescently labeled hook to demonstrate that FlgE is the hook structural protein and that FliK regulated hook length. We further demonstrate that two proteins of unknown function, FlhO and FlhP, and the putative hook cap, FlgD, were required for hook assembly, such that when flhO, flhP, or flgD was mutated, hook protein was secreted into the supernatant. All mutants defective in hook completion resulted in homogeneously reduced σ(D)-dependent gene expression due to the action of the anti-sigma factor FlgM.     

A technique for the long-term application of surface electrodes

A technique is reported for the long-term application of surface electrodes for ambulatory electromyographic (EMG) recording. Prior to electrode application the surrounding skin is lightly painted with tincture of benzoin. This treatment improves adherence to the skin of disposable electrodes and electrode attachment collars, reduces skin trauma associated with electrode removal, and minimizes sensitivity to electrode adhesives.     

Morphological study of the innervation pattern of the rabbit sinoatrial node

The pattern of nerves, ganglia, and fine nerve processes in the adult rabbit sinoatrial node, identified by microelectrode recording, was defined by staining histochemically for cholinesterase followed by silver impregnation. A generalized repeatable pattern of innervation was recognized, including 1) a large ganglionic complex inferior to the sinoatrial node; 2) two or three moderately large nerves traversing the sinoatrial node parallel to the crista terminalis; 3) nerves entering the region from the atrial septum, the superior vena cava, and the inferior vena cava; and 4) a fine network of nerve processes, particularly extensive in the morphologically dense small-cell part of the sinoatrial node. When the site of initial depolarization in the node was located and marked by a broken-off electrode tip, it was found, after cholinesterase staining, to be characterized by a cluster of cells enclosed in a nest or basket of fine nerves. Similar nested cell clusters were observed elsewhere in the sinoatrial node in this same preparation and in other hearts. A complex interweaving of atrial muscle fibers was observed medial and inferomedial to the sinoatrial node, which may form the anatomical basis for the lack of conduction through this region. The morphological pattern of nerves, ganglia, and myocardial cells described in this study emphasizes the complexity of innervation of the sinoatrial node, including its intrinsic neural elements. Cholinesterase/silver staining can be useful in the definition and comparison of electrophysiologically identified sites within the sinoatrial node.     

Use of micromachined probes for the recording of cardiac electrograms in isolated heart tissues

Micromachined probes, with iridium (Ir) microelectrodes on silicon shanks, were evaluated to assess their suitability for cardiac electrogram recording. The electrochemical activation (anodic oxidation) procedure for the circular Ir microelectrode was investigated using the square wave potential according to the electrode size, number of cycles, and cathodic-anodic potential level of the square wave. Increase in the charge storage capacity was pronounced either in smaller electrodes or with higher potential level of the square wave. The electrode impedance reduced in a similar manner with increasing number of cycle irrespective of the electrode size. With either lower potential level (-0.70/+0.60 V) or smaller number of cycle (200 cycles) than those for the activation of stimulating electrode, the likelihood of overactivation of the recording microelectrode can be minimized. These anodic IrOx film (AIROF) microelectrodes were used for the recording of extracellular electrograms in two different ex vivo cardiac tissue preparations. A single-shank microprobe was applied to the left ventricle of a mouse heart. Both the spontaneous and paced transmural responses propagating between epicardium and endocardium were obtained. Longitudinal cardiac wavefronts propagating along the rabbit papillary muscle were also recorded with a unique multiple-shank design. The measured mean amplitude and the propagation velocity of the extracellular voltage were 12.2 +/- 1.8 mV and 58.9 +/- 2.2 cm/s, respectively (n = 27). These microprobes with precisely defined electrode spacing make a useful tool for the spatial and temporal mapping of electrical properties in isolated heart tissues ex vivo.     

Interactions of light and ethylene in hypocotyl hook maintenance in Arabidopsis thaliana seedlings

Etiolated seedlings frequently display a hypocotyl or epicotyl hook which opens on exposure to light. Ethylene has been shown to be necessary for maintenance of the hook in a number of plants in darkness. We investigated the interaction of ethylene and light in the regulation of hypocotyl hook opening in Arabidopsis thaliana . We found that hooks of Arabidopsis open in response to continuous red, far-red or blue light in the presence of up to 100 μl l⁻¹ ethylene. Thus a change in sensitivity to ethylene is likely to be responsible for hook opening in Arabidopsis, rather than a decrease in ethylene production in hook tissues. We used photomorphogenic mutants of Arabidopsis to demonstrate the involvement of both blue light and phytochrome photosensory systems in light-induced hook opening in the presence of ethylene. In addition we used ethylene mutants and inhibitors of ethylene action to investigate the role of ethylene in hook maintenance in seedlings grown in light and darkness.     

Spiral nerve cuff electrode for recordings of respiratory output

Sahin, Mesut, Musa A. Haxhiu, Dominique M. Durand, andIsmail A. Dreshaj. Spiral nerve cuff electrode for recordings ofrespiratory output. J. Appl. Physiol.83(1): 317-322, 1997.The feasibility of using the spiral nervecuff electrode design for recordings of respiratory output from thehypoglossal (HG) and phrenic nerves is demonstrated in anesthetized,paralyzed, and artificially ventilated cats. Raw neural discharges ofthe HG nerve were analyzed in terms of signal-to-noise ratios andfrequency spectra. The rectified and integrated moving average activity of the HG nerve had a peak value of 1.74 ± 0.21 µV and a baseline value of 0.72 ± 0.11 µV at elevated respiratory drive induced byincreases in CO₂ or oxygendeprivation when recorded with 10-mm-long cuffs. The frequency contentof the HG electroneurogram extended from several hundred hertz to 6 kHz. Spiral nerve cuff recordings without desheathing of the nerveprovided large enough signal-to-noise ratios that allowed them to beused as a measure of respiratory output and had much wider frequencybandwidths than the hook electrode preparations. A major advantage ofthe cuff electrode over the hook electrode was its mechanicalstability, which significantly improved the reproducibility of therecordings both in terms of signal amplitudes and frequency contents.

     

Micromolded PDMS planar electrode allows patch clamp electrical recordings from cells

The patch clamp method measures membrane currents at very high resolution when a high-resistance 'gigaseal' is established between the glass microelectrode and the cell membrane (Pflugers Arch. 391 (1981) 85; Neuron 8 (1992) 605). Here we describe the first use of the silicone elastomer, poly(dimethylsiloxane) (PDMS), for patch clamp electrodes. PDMS is an attractive material for patch clamp recordings. It has low dielectric loss and can be micromolded (Annu. Rev. Mat. Sci. 28 (1998) 153) into a shape that mimics the tip of the glass micropipette. Also, the surface chemistry of PDMS may be altered to mimic the hydrophilic nature of glass (J. Appl. Polym. Sci. 14 (1970) 2499; Annu. Rev. Mat. Sci. 28 (1998) 153), thereby allowing a high-resistance seal to a cell membrane. We present a planar electrode geometry consisting of a PDMS partition with a small aperture sealed between electrode and bath chambers. We demonstrate that a planar PDMS patch electrode, after oxidation of the elastomeric surface, permits patch clamp recording on Xenopus oocytes. Our results indicate the potential for high-throughput patch clamp recording with a planar array of PDMS electrodes.