The ability to selectively stimulate A[alpha], A[beta]-fibers and A[delta]-fibers in an isolated rat sciatic nerve (SNR) was assessed. The stimulus used was a current, biphasic pulse with a quasitrapezoidal cathodic phase and rectangular anodic phase where parameters were systematically varied: intensity of the cathodic phase (ic); width of the cathodic phase (tc); width of the cathodic exponential decay (texp) and time constant of the exponential decay ([tau]exp). A SNR was stimulated using a pair of hook electrodes while conduction velocity (CV) and compound action potentials (CAP) were measured at two sites along the SNR using another two pairs of electrodes. Results showed that the highest CAP1 (8.5-9 mV), shall be expected when parameters of the stimulus were within the following range: ic=3.8-4 mA, tc=350-400 [micro]s and texp=330-440 [micro]s. Results also showed that with ascending tc and texp, CV of the corresponding superficial region of the SNR was reduced in both, conduction velocity of CAP1 and conduction velocity of CAP2. It was concluded that action potentials (APs) were activated in the A[beta]-fibers and A[delta]-fibers along with a slight AP inhibition in the A[beta]-fibers. The obtained results, could serve as a tool for developing multi-electrode systems that potentially enable fiber-type selective stimulation of nerve fibers.
COBISS.SI-ID: 32523481
The purpose of this article is to investigate the electrochemical performance of platinum stimulating nerve electrodes (WE1 and WE2) with different surface structures to define which one is able to produce a higher neural activation function during nerve stimulation than that achieved by conventional electrodes. The purpose is also to present a method that enables the electrochemical scanning of stimulating electrode surfaces. The surface of WE1 was modified using rough sand paper, while the surface of WE2 was modified using fine sand paper. The potential at the different roughened surfaces in the sodium phosphate mixture, when excited with specific current pulses, was measured against a Ag/AgCl reference electrode. Voltage transients were recorded to determine the polarization across the electrode-electrolyte interface. The results indicate that the surface of WE1 could deliver more current to the nerve tissue and more activation for a fixed input voltage than WE2. Namely, it is shown that the mean |Zpol| of WE1 was lower than that for WE2 (237.1 vs. 251 ). Accordingly, the platinum electrode that was superficially modified using rough sand paper is more suitable for safe and efficient nerve stimulation than the electrode that was superficially modified using fine sand paper.
COBISS.SI-ID: 33560025
Synaptotagmin 7 (SYT7) is ubiquitously expressed calcium sensor, involved in neuronal membrane trafficking. Immunoprecipitation experiments demonstrated that SYT7 interacts with Synaptotagmin-binding, cytoplasmic RNA-interacting protein (SYNCRIP). SYNCRIP is a component of mRNA granules, which are transported to dendrites and are prerequisite for synaptic plasticity. Given the potential significance of SYT7 regulation in processes of neurodegeneration, which are characterized by high level of synaptic vulnerability, we aimed to analyse and compare the distribution of SYT7 and SYNCRIP proteins in the adult rat striatum, hippocampus, cerebral and cerebellar cortex. We investigated the degree of SYT7-SYNCRIP co-localization in order to examine possible functional interaction of these two proteins. We found that SYT7 is abundantly distributed in neuropil of all examined anatomical areas of the brain, most prominently in axons. On the contrary, SYNCRIP had cytoplasmic somatodendritic pattern of expression, which was most prominent in the hippocampus and cerebellum. In the striatum, hippocampus and cerebral cortex SYT7 and SYNCRIP immunofluorescent signals were mutually excluded, thus diminishing the probability for their physiological interaction. In somata of Purkinje neurons in the cerebellar cortex, both SYT7 and SYNCRIP were expressed and partially co-localized suggesting possible functional connection between SYT7 and SYNCRIP proteins in Purkinje neurons.
COBISS.SI-ID: 4079951
Deposition of aggregates of hyperphosphorylated tau protein is a hallmark of tauopathies like Alzheimer and many other neurodegenerative diseases. A sensitive and selective method of in vivo detection of tau-aggregate presence and distribution could provide the means of an early diagnosis of tau-associated diseases. Furthermore, the use of selective molecular probes that enable histochemical differentiation of protein aggregates post-mortem would be advantageous for the insight into the properties of tau protein aggregates. We chose to design new molecular probes based on the structure of 2-(1-(6-((2-[18F]fluoroethyl)(methyl)amino)-2-naphthyl)ethylidene)malononitrile to investigate their likelihood of fitting into VQIVYK tau protein binding channel model. In a modular approach, using cross-coupling reactions, we synthesized a series of candidates, radiolabeled them with fluorine-18 radioisotope, and determined their physicochemical and in vitro binding properties. Herein we report the synthesis of a series of molecular probes capable of detection of tau protein deposits in vitro.
COBISS.SI-ID: 1537632707