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Öğe Can hypo/hypernatremic conditions be a factor for na ion channel kinetics: model study(Turkish Neurosurgical Soc, 2018) Ayaz, Murat; Karabagli, Hakan; Yanardag, Sirma BasakAIM: Dysnatremic cases are frequently faced in clinical practice. Its macroscopic effects and consequences are well known, but microscopic effects are not well defined. The aim of this study was to reveal the effects of dysnatremia at the cellular level. MATERIAL and METHODS: By using an action potential simulation, the effects of extracellular sodium (Na) concentration on the Na ion channel kinetics were studied. The experimental sets were chosen to mimic hypo/hypernatremic conditions and, in both cases, the degree of the severity was varied. RESULTS: Hyponatremic situations through modifying the axonal Na+ channels kinetics result in the rundown of the sodium current (INa). The degree of the hyponatremia-dependent effect seen in the Na ion channel is severity dependent, which is more effective in the recovery phase of the ion channel. Hypernatremic conditions, on the other hand, have also affected the Na ion channel activity through modifying the kinetics of the channel. Unlike hyponatremia, the effect seen in hypernatremic conditions was through decreasing the response time of the channel. The degree of the significance of the effect seen on the Na ion channel in the case of the hypernatremia was found to be less destructive compared to the hyponatremic condition. CONCLUSION: The Na channels are susceptible to the changes of the extracellular Na concentrations. Thus, the underestimation of hypo/hypernatremic conditions can put patients in danger and close monitoring of serum Na level might be required.Öğe Comparative Effects of Alpha Lipoic Acid and Melatonin on Cisplatin-İnduced Neurotoxicity(Taylor & Francis Ltd, 2010) Tuncer, Seçkin; Dalkılıç, Nizamettin; Dunbar, Mehmet Akif; Keleş, BaharCisplatin is a carcinogenic agent having important cytotoxic effects. Cisplatin treatment increases the levels of free oxygen radicals in neurologic tissues. We investigated the effects of alpha lipoic acid (ALA) and melatonin (MEL) on the electrophysiological parameters and on activities of nerve fibers having different conduction properties on cisplatin neurotoxicity. Neurotoxicity was induced by a single injection of 10 mg/kg intraperitoneal (ip) cisplatin. Supplementation was started 1 day before cisplatin injection with either 100 mg/kg/day ip ALA or 4 mg/kg/day ip MEL for 7 days. Compound action potentials were recorded from isolated sciatic nerves in vitro, and numerical analyses were conducted. Cisplatin-induced neurotoxicity resulted in a significant decrease (p <.05) in maximum depolarization (mV), areas (mV.ms), and maximum and minimum upstroke velocity values (mV/ms). Although these decrements were restored by ALA and MEL, ALA was found to be more effective. Conventional conduction velocity measurements and conduction velocity distribution histograms have shown that ALA supplementation can recover the effects of cisplatin while MEL cannot. The conduction velocity distribution histograms have shown that antioxidant supplementation results in a restoration on contribution of fast-conducting fibers (51.8-77.7 m/s), which is deteriorated by cisplatin. Consequently, ALA has more potential to make up for the deleterious effects of cisplatin-induced neurotoxicity.Öğe Somatosensory Conduction Velocity Distribution of Median Nerve Middle Palmar Digital Component(2004) Dalkılıç, Nizamettin; Yürüten, Betigül; İlhan, BarkınCollision technique is one of the methods used to obtain the relative number of fibers in a nerve bundle. In 25 normal subjects, the right median nerve has been concurrently stimulated at proximal (elbow) and distal (wrist) locations, and the resultant compound action potentials (CAP) were recorded at the middle finger via ring electrodes. The delay between the two stimuli (Inter Stimulus Interval; ISI), beginning from 7 ms, has been decreased in 0.1 ms steps, until the CAPs, elicited by proximal stimulation, totally disappeared. The obtained data have been transferred to computer medium for further analysis. In this procedure, areas under proximal CAPs have been obtained for each ISI value. Using these areas, the relative numbers of fibers (%) belonging to the middle proper palmar digital (MPPD) component of sensory median nerve have been derived. The mean conduction velocities in MPPD component of sensory median nerve ranged from 40 m/s to 68 m/s. In the histogram, a large amount of heaping of the relative number of fibers has been observed in 48-59 m/s conduction velocity interval with the ratio of 64%, although there has been a 21% group having 43-47 ms conduction velocity. These results can be a guide to future studies concerning basic and clinical nerve conduction studies.Öğe Does Collagenase Affect the Electrophysiological Parameters of Nerve Trunk?(PHARMACEUTICAL SOC JAPAN, 2003) Dalkilic, Nizamettin; Kiziltan, Erhan; Pehlivan, Ferit; Kose, KenanCollegenase is widely used in the process of teasing a nerve in order to perform single fiber action potential (SFAP) recordings. In this study, the effects of collagenase on nerve conduction parameters were investigated. To accomplish this, normal compound action potentials (nCAPs) were recorded from isolated frog sciatic nerve at various distances using the suction technique. Then, the same nerve was treated with collagenased Ringer's solution (3.5 mg/ml, Sigma Type XI) for 90 minutes and action potentials (cCAPs) were recorded again. Numerical analysis of these records was performed and the results were compared. Using the nCAP and cCAP recordings, the conduction velocity distributions (CVD) of the individual nerve trunks were determined by a method that we have previously described. Statistical results indicated significant differences (p<0.05) between the nCAP and cCAP CVD data. From these findings it is concluded that, when used for teasing the nerve fibers, collagenase may affect the nerve trunk conduction parameters. Specifically, a significant amount of decrease has been observed in conduction velocities of myelinated fibers having diameters smaller than 8 mum.Öğe Comparison of Fiber Diameter Distributions Deduced by Modeling Compound Action Potentials Recorded by Extracellular and Suction Techniques(TAYLOR & FRANCIS LTD, 2002) Dalkılıç, Nizamettin; Pehlivan, FeritIn this study, the extracellular and suction techniques, used widely to record compound action Potentials (CAP), were compared in respect to their ability to deduce fiber diameter distribution (FDD). Fiber. diameter distribution derived by applying the deconvolution model to CAP depends not only on the modeling but also on the recording techniques. The FDDs determined by these two techniques were compared with that predicted by histological means. In our model study, a waveform for single fiber action potential (SFAP) was defined as f(t) = Asin(t/tau(01)) . exp(-t/tau(02)) where the parameters tau(1) and tau(2) were taken from the literature and given for the SFAP of each fiber diameter between d = 3-22 mum, and A Was chosen to normalize the amplitude of SFAP to 1. We substituted the measured CAPs into our model and calculated the histograms related with the fiber diameter distribution of the sciatic nerve trunk. We sail, that the FDD as predicted from the CAP, recorded by the extracellular techniques, coincides better with that of the histologically determined FDD than that predicted by suction techniques.Öğe A Correction Procedure for the Volume Conductor Effect in the Compound Action Potential Recorded From Isolated Nerve Trunk(Taylor & Francis Ltd, 2002) Dalkılıç, Nizamettin; Pehlivan, FeritThe shape and magnitude of the compound action potential (CAP), which is the linear summation of the single fiber action potentials, depend strongly on the recording conditions. Volume conductor effect should be eliminated or corrected in order to get reliable information about the functional state of the nerve trunk. In the case of nronophasic extracellular recordings, the integral of CAP recorded extracellularly tends to decrease with the distance, because the extracellular resistance between the stimulating and recording electrodes changes. To compensate for this effect, we took into account the spatial deviation of the integral of CAP versus distance and defined a spatial correcting factor, g(x). By applying g(x) to all CAPS, we get corrected CAP (cCAP) data for further evaluations. It is well known that the slope of the maximum derivative of CAP versus distance curve would be a measure of conduction velocity distribution for the fast conducting nerves in a nerve trunk. The slopes of these curves for extracellular and suction techniques on the same nerves are compared; we concluded that the difference between the two techniques was not important for the correction procedure on extracellular records.
