Real-time refinement of subthalamic nucleus targeting using Bayesian decision-making on the root mean square measure.

The subthalamic nucleus (STN) is a major target for treatment of advanced Parkinson's disease patients undergoing deep brain stimulation surgery. Microelectrode recording (MER) is used in many cases to identify the target nucleus. A real-time procedure for identifying the entry and exit points of the STN would improve the outcome of this targeting procedure. We used the normalized root mean square (NRMS) of a short (5 seconds) MER sampled signal and the estimated anatomical distance to target (EDT) as the basis for this procedure. Electrode tip location was defined intraoperatively by an expert neurophysiologist to be before, within, or after the STN. Data from 46 trajectories of 27 patients were used to calculate the Bayesian posterior probability of being in each of these locations, given RMS-EDT pair values. We tested our predictions on each trajectory using a bootstrapping technique, with the rest of the trajectories serving as a training set and found the error in predicting the STN entry to be (mean +/- SD) 0.18 +/- 0.84, and 0.50 +/- 0.59 mm for STN exit point, which yields a 0.30 +/- 0.28 mm deviation from the expert's target center. The simplicity and computational ease of RMS calculation, its spike sorting-independent nature and tolerance to electrode parameters of this Bayesian predictor, can lead directly to the development of a fully automated intraoperative physiological procedure for the refinement of imaging estimates of STN borders.     

Electrophysiologic target localization in posteroventral pallidotomy

Summary The current interest in stereotactic posteroventral pallidotomy (PVP) for treating Parkinson's disease and the variability of published results have raised questions regarding techniques for target localization. In our technique the probe is guided to the optimum target at the most ventral pallidum and ansa lenticularis by macroelectrode stimulation of the internal capsule and optic tract from within the globus pallidus, with the thresholds providing a relative measure of the electrode proximity to these structures. We have characterized these localizing macroelectrode stimulation parameters in 57 posteroventral pallidotomies with consistent anatomic lesion placement, excellent outcome, and no complications.Using a 1.8 × 2.0 mm radiofrequency electrode for macroelectrode stimulation (RFG-3C, Radionics Inc.), minimum voltages (thresholds) to activate motor (at a frequency of 2 Hz) or visual (at a frequency of 100 Hz) responses as well as impedance measurements were obtained at the final target (Tf) and at distances proximal to Tf along the electrode trajectory. The visual and motor threshold voltages at Tf via our standard approach angles (50 ° above base plane, 20 ° from the sagittal plane), had a range of 1.0 to 1.5 V, and 2.0 to 3.5 V respectively. We also found that as the probe approaches Tf there is a significant decrease in voltage thresholds for motor (P<.0001) and visual (P<.0001) responses in an individual patient indicating that the probe is converging on these structures. Increases in impedance between Tf, 2–3 mm, and 4–5 mm proximal to Tf were also statistically significant (P<.0001). Microelectrode recording of electrophysiological neuronal activity at various points along the trajectory towards the target showed distinct firing patters providing identification of the globus pallidus externus and internus, ansa lenticularis, and optic tract.Macroelectrode electrophysiological stimulation within the target volume, inducing threshold responses in the internal capsule and optic tract, provides for accurate localization of the most effective PVP target in the ansa lenticularis. In unresponsive patients, the utilization of microelectrode recording for the identification of the pallidal borders and the optic tract improves safety.     

东莨菪碱对大鼠体感区皮层神经元单位放电的影响

目的观察东莨菪碱对大鼠体感区皮层自发放电和诱发放电的影响。方法用玻璃微电极在大鼠体感区皮层记录神经元单位放电。结果实验记录了３５个单位放电，其中对触压后肢应答放电的有２２个，前肢９个；触前肢兴奋，后肢抑制的１个；触前肢抑制，后肢兴奋的１个；触毛及皮肤呈汇聚反应的２个。静注东莨菪碱后有２３个呈增频反应，１２个为减频反应。增频单位多分布在Ⅰ～Ⅳ层，减频单位则在Ⅴ～Ⅵ层。结论东莨菪碱对皮层体感区Ａｃｈ兴奋神经元或Ａｃｈ抑制神经元均有阻断作用。     

Effects of Vagal and Sympathetic Nerves on Transmembrane Potential of Cardiac Ventricular Cells of Toad

The effects of vagal and sympathetic nerves on the transmembranepotentials of cardiac cells of toad were observed by means of microelectrodetechnique.The vagal nerve was stimulated there would be an increase in restingpotential and acceleration in repolarization of action potential(AP).However,ifatropine was used before stimulation the above-mentioned phenomena woulddisappear.When the sympathetic nerve was stimulated the AP amplitudeincreased,but resting potential(RP)remained the same.The increase of APresulted from the increases of overshoot.When the sympathetic nerve wasstimulated although the heart rate increased and the duration of AP wasshortened,the plateau phase of AP was prolonged.These results suggest that theeffects of vagal and sympathetic nerves on the transmembrane potential of cardiacventricular cells are coordinated and the normal characteritics of transmembranepotential are maintained by both the vagal and sympathetic nerves.     

A slim needle-shaped multiwire microelectrode for intracerebral recording

The construction of a needle-shaped multiwire microelectrode is described. It can be made with simple mechanical tools. The presented electrode assembly consists of 12 insulated nichrome wires (core diameter 25 μm) which are embedded in epoxylite resin. The straight-cut wire tips are aligned lengthwise and have a relative spacing of 150 μm. Outer dimensions vary from 100 × 180 μm at the level of the 1st electrode channel, to 100 × 100 μm at the level of the 12th channel at the tip. The configuration of this electrode was determined by its application: the laminar analysis of evoked potentials in the cortex of the rat. However, the number of channels, the diameter of the (nichrome) wire which determines the surface area of these channels, and the channel spacing can be easily adjusted during construction to meet other experimental requirements, such as the recording of single-unit activity. The electrode which is composed of biocompatible materials is suited for the study of field potentials and multiple-unit activity, in both acute and chronic experiments, and can be used repeatedly. To demonstrate the performance of the electrode assembly, a depth profile of field potentials is presented, accompanied by the corresponding current source density distribution. The potentials were recorded in the somatosensory cortex of the rat following stimulation of the median nerve under ketamine anesthesia.     

Effects of intra- and extracellular H+ and Na+ concentrations on Na+-H+ antiport activity in the lacrimal gland acinar cells

Kinetic properties of the Na⁺-H⁺ antiport in the acinar cells of the isolated, superfused mouse lacrimal gland were studied by measuring intracellular pH (pH_i) and Na⁺ activity (aNa_i) with the aid of double-barreled H⁺- and Na⁺-selective microelectrodes, respectively. Bicarbonate-free solutions were used throughout. Under untreated control conditions, pH_i was 7.12±0.01 and aNa_i was 6.7±0.6 mmol/l. The cells were acid-loaded by exposure to an NH ₄ ⁺ solution followed by an Na⁺-free N-methyl-d-glucamine (NMDG⁺) solution. Intracellular Na⁺ and H⁺ concentrations were manipulated by changing the duration of exposure to the above solutions. Subsequent addition of the standard Na⁺ solution rapidly increased pH_i. This Na⁺-induced increase in pH_i was almost completely inhibited by 0.5 mmol/l amiloride and was associated with a rapid, amiloride-sensitive increase in aNa_i. The rate of pH_i recovery induced by the standard Na⁺ solution increased in a saturable manner as pH_i decreased, and was negligible at pH_i 7.2–7.3, indicating an inactivation of the Na⁺-H⁺ antiport. The apparent K _m for intracellular H⁺ concentration was 105 nmol/l (pH 6.98). The rate of acid extrusion from the acid-loaded cells increased proportionally to the increase in extracellular pH. Depletion of aNa_i to less than 1 mmol/l by prolonged exposure to NMDG⁺ solution significantly increased the rate of Na⁺-dependent acid extrusion. The rate of acid extrusion increased as the extracellular Na⁺ concentration increased following Michaelis-Menten kinetics (V _max was 0.55 pH/min and the apparent K _m was 75 mmol/l at pH_i 6.88). The results clearly showed that the Na⁺-H⁺ antiport activity is dependent on the chemical potential gradient of both Na⁺ and H⁺ ions across the basolateral membrane, and that the antiporter is asymmetric with respect to the substrate affinity of the transport site. The data agree with the current model of activation and inactivation of the antiporter by an intracellular site through changes in the intracellular Na⁺ and H⁺ concentrations.     

Exocrine ductalpCO2 in the rabbit pancreas

An improvedpCO₂ microelectrode has been evaluated and used to investigate whether a significant barrier to diffusion of CO₂ exists in the rabbit pancreas. The results of this study show the improved Carter and CaflischpCO₂ microelectrode to be an accurate and reliable tool for measuring pancreatic venous and ductalpCO₂. The similarities betweenpCO₂ values from the pancreatic ducts and small pancreatic veins suggest that there is no barrier to CO₂ diffusion between small veins and exocrine ducts in the rabbit pancreas, and that ductalpCO₂ is probably strongly influenced by the CO₂ tension of the small pancreatic blood vessels.     

隔核内注射吗啡对海马痛单位的影响

目的：探讨隔核内阿片主相应的受体在隔核影响海马单位中的作用。方法：参照Ｓａｗｙｅｒ兔脑图谱,用ＳＮ－２型推进器以２μｍ／ｓ速度将玻璃微电极插入海马Ｐ２．５,Ｌ３－６,Ｈ６－９处引导神经元自发放电;在Ａ３Ｒ１Ｈ２（外侧隔核）处插入钨比有,人和刺激隔核用;在Ａ２Ｒ１Ｈ２及中脑导水管周围灰质（ＰＡＧ）Ｐ９．５Ｒ１Ｈ１．５）处分别埋不锈钢微量注射套管,用牙托水配牙托粉固定,作脑室注射用。结果：共引导８５个     

Acidified seawater impacts sea urchin larvae pH regulatory systems relevant for calcification

Calcifying echinoid larvae respond to changes in seawater carbonate chemistry with reduced growth and developmental delay. To date, no information exists on how ocean acidification acts on pH homeostasis in echinoderm larvae. Understanding acid–base regulatory capacities is important because intracellular formation and maintenance of the calcium carbonate skeleton is dependent on pH homeostasis. Using H⁺-selective microelectrodes and the pH-sensitive fluorescent dye BCECF, we conducted in vivo measurements of extracellular and intracellular pH (pH_e and pH_i) in echinoderm larvae. We exposed pluteus larvae to a range of seawater CO₂ conditions and demonstrated that the extracellular compartment surrounding the calcifying primary mesenchyme cells (PMCs) conforms to the surrounding seawater with respect to pH during exposure to elevated seawater pCO₂. Using FITC dextran conjugates, we demonstrate that sea urchin larvae have a leaky integument. PMCs and spicules are therefore directly exposed to strong changes in pH_e whenever seawater pH changes. However, measurements of pH_i demonstrated that PMCs are able to fully compensate an induced intracellular acidosis. This was highly dependent on Na⁺ and HCO₃⁻, suggesting a bicarbonate buffer mechanism involving secondary active Na⁺-dependent membrane transport proteins. We suggest that, under ocean acidification, maintained pH_i enables calcification to proceed despite decreased pH_e. However, this probably causes enhanced costs. Increased costs for calcification or cellular homeostasis can be one of the main factors leading to modifications in energy partitioning, which then impacts growth and, ultimately, results in increased mortality of echinoid larvae during the pelagic life stage.     

Assessment of multidrug resistance on cell coculture patterns using scanning electrochemical microscopy

The emergence of resistance to multiple unrelated chemotherapeutic drugs impedes the treatment of several cancers. Although the involvement of ATP-binding cassette transporters has long been known, there is no in situ method capable of tracking this transporter-related resistance at the single-cell level without interfering with the cell’s environment or metabolism. Here, we demonstrate that scanning electrochemical microscopy (SECM) can quantitatively and noninvasively track multidrug resistance-related protein 1–dependent multidrug resistance in patterned adenocarcinoma cervical cancer cells. Nonresistant human cancer cells and their multidrug resistant variants are arranged in a side-by-side format using a stencil-based patterning scheme, allowing for precise positioning of target cells underneath the SECM sensor. SECM measurements of the patterned cells, performed with ferrocenemethanol and [Ru(NH₃)₆]³⁺ serving as electrochemical indicators, are used to establish a kinetic “map” of constant-height SECM scans, free of topography contributions. The concept underlying the work described herein may help evaluate the effectiveness of treatment administration strategies targeting reduced drug efflux.