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41.
The characteristics of a tremor at rest in the left and right wrist joints were studied in 24 patients with Parkinson's disease using soft sensors, which insignificantly hampered the joint movements, and rigid sensors, which rigidly fixed the joint, thus approximating the experimental conditions to isometric. The fixation of the wrist joint appeared to decrease the amplitude of the tremor not only in this joint but also in the contralateral unfixed joint. Changes in the tremor frequency also occurred, but they were not so markedly pronounced. The nature of the tremor generators and their localization are discussed. 相似文献
42.
Safronov IV Drachkova IA Petruseva IO Khodyreva SN Dobrikov MI Ivanova TM Shishkin GV Lavrik OV 《Bioorganicheskaia khimiia》2001,27(5):372-382
ATP gamma-amides containing in gamma-N-position 1-methylpyrene, 9-methylanthracene, 10-chloro-9-methylanthracene, and 3-methylperylene residues were synthesized and characterized. These compounds were used as sensitizers of site-specific photomodification of the reconstituted elongating complex of the mammalian DNA polymerase beta. The photomodification was carried out with the use of photoaffine reagents, which were synthesized in situ by the 5'-(32)P-labeled primers extension with photoactive analogues of dCTP containing in the exo-N-position of cytosine various perfluoroarylazide groups. The effect of structures of the sensitizers and photoactive reagents on the efficiency and selectivity of photolinking of primers to the enzyme and template, as well as formation of a number of other photomodification products was studied. It was shown that the sensitizers containing 10-chloro-9-methylanthracene and 3-methylperylene residues allow preparation of photolinks in such irradiation conditions when photomodification in their absence is not essentially observed. 相似文献
43.
The ability of the soma of a spinal dorsal horn neuron, a spinal ventral horn neuron (presumably a motoneuron), and a hippocampal pyramidal neuron to generate action potentials was studied using patch-clamp recordings from rat spinal cord slices, the "entire soma isolation" method, and computer simulations. By comparing original recordings from an isolated soma of a dorsal horn neuron with simulated responses, it was shown that computer models can be adequate for the study of somatic excitability. The modeled somata of both spinal neurons were unable to generate action potentials, showing only passive and local responses to current injections. A four- to eightfold increase in the original density of Na(+) channels was necessary to make the modeled somata of both spinal neurons excitable. In contrast to spinal neurons, the modeled soma of the hippocampal pyramidal neuron generated spikes with an overshoot of +9 mV. It is concluded that the somata of spinal neurons cannot generate action potentials and seem to resist their propagation from the axon to dendrites. In contrast, the soma of the hippocampal pyramidal neuron is able to generate spikes. It cannot initiate action potentials in the intact neurons, but it can support their back-propagation from the axon initial segment to dendrites. 相似文献
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46.
P. A. Tolstoukhov D. A. Vikhlyaev D. S. Gavrilov A. G. Kakshin E. A. Loboda V. A. Lykov V. Yu. Politov A. V. Potapov V. A. Pronin V. N. Saprykin K. V. Safronov 《Plasma Physics Reports》2011,37(10):866-870
Results from experimental studies of bremsstrahlung and characteristic radiation spectra from laser targets irradiated with ultrashort laser pulses with intensities of up to ~1019 W/cm2 are presented. The continuous spectra of hard X-ray emission from Ta and Al targets and the line spectrum of copper were measured. The temperature of fast electrons was obtained from the measured hard X-ray spectra, and the Kα radiation yield from Ta was measured. The energy conversion efficiency of laser radiation into the copper characteristic radiation was obtained from the measured yield of Kα radiation. 相似文献
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48.
Dyrkheeva NS Khodyreva SN Sukhanova MV Safronov IV Dezhurov SV Lavrik OI 《Biochemistry. Biokhimii?a》2006,71(2):200-210
Human DNA apurinic/apyrimidinic (AP-) endonuclease 1 (APE1) is involved in the base excision repair (BER) pathway. The enzyme hydrolyzes DNA from the 5 side of the AP site. In addition to endonuclease activity, APE1 also possesses other slight activities including 3 -5 exonuclease activity. The latter is preferentially exhibited towards mispaired (non-canonical) nucleotides, this being the reason why APE1 is considered as a proofreading enzyme correcting the misincorporations introduced by DNA polymerase beta. We have studied 3 -5 exonuclease activity of APE1 towards dCMP and dTMP residues and modified dCMP analogs with photoreactive groups at the 3 end of the nicked DNA. Photoreactive dNMP residues were incorporated at the 3 end of the lesion using DNA polymerase beta and photoreactive dNTPs. The dependence of exonuclease activity on the "canonicity" of the base pair formed by dNMP flanking the nick at the 3 end, on the nature of the group flanking the nick at the 5 end, and on the reaction conditions has been determined. Optimal reaction conditions for the 3 -5 exonuclease hydrolysis reaction catalyzed by APE1 in vitro have been established, and conditions when photoreactive residues are not removed by APE1 have been chosen. These reaction conditions are suitable for using photoreactive nicked DNAs bearing 3 -photoreactive dNMP residues for photoaffinity labeling of proteins in cellular/nuclear extracts and model APE1-containing systems. We recommend using FAPdCTP for photoaffinity modification in APE1-containing systems because the FAPdCMP residue is less prone to exonuclease degradation, in contrast to FABOdCTP, which is not recommended. 相似文献
49.
Sónia F. A. Santos Liliana L. Luz Peter Szucs Deolinda Lima Victor A. Derkach Boris V. Safronov 《PloS one》2009,4(11)
Background
Substantia gelatinosa (SG, lamina II) is a spinal cord region where most unmyelinated primary afferents terminate and the central nociceptive processing begins. The glutamatergic excitatory interneurons (EINs) form the majority of the SG neuron population, but little is known about the mechanisms of signal processing in their synapses.Methodology
To describe the functional organization and properties of excitatory synapses formed by SG EINs, we did non-invasive recordings from 183 pairs of monosynaptically connected neurons. An intact presynaptic SG EIN was specifically stimulated through the cell-attached pipette while the evoked EPSCs/EPSPs were recorded through perforated-patch from a postsynaptic neuron (laminae I-III).Principal Findings
We found that the axon of an SG EIN forms multiple functional synapses on the dendrites of a postsynaptic neuron. In many cases, EPSPs evoked by stimulating an SG EIN were sufficient to elicit spikes in a postsynaptic neuron. EPSCs were carried through both Ca2+-permeable (CP) and Ca2+-impermeable (CI) AMPA receptors (AMPARs) and showed diverse forms of functional plasticity. The synaptic efficacy could be enhanced through both activation of silent synapses and strengthening of already active synapses. We have also found that a high input resistance (RIN, >0.5 GΩ) of the postsynaptic neuron is necessary for resolving distal dendritic EPSCs/EPSPs and correct estimation of their efficacy.Conclusions/Significance
We conclude that the multiple synapses formed by an SG EIN on a postsynaptic neuron increase synaptic excitation and provide basis for diverse forms of plasticity. This functional organization can be important for sensory, i.e. nociceptive, processing in the spinal cord. 相似文献50.
I. O. Petruseva I. S. Tikhanovich E. A. Maltseva I. V. Safronov O. I. Lavrik 《Biochemistry. Biokhimii?a》2009,74(5):491-501
Photoactivated DNA analogs of nucleotide excision repair (NER) substrates have been created that are 48-mer duplexes containing in internal positions pyrimidine nucleotides with bulky substituents imitating lesions. Fluorochloroazidopyridyl, anthracenyl, and pyrenyl groups introduced using spacer fragments at 4N and 5C positions of dCMP and dUMP were used as model damages. The gel retardation and photo-induced affinity modification techniques were used to study the interaction of modified DNA duplexes with proteins in HeLa cell extracts containing the main components of NER protein complexes. It is shown that the extract proteins selectively bind and form covalent adducts with the model DNA. The efficiency and selectivity of protein modification depend on the structure of used DNA duplex. Apparent molecular masses of extract proteins, undergoing modification, were estimated. Mutual influence of simultaneous presence of extract proteins and recombinant NER protein factors XPC-HR23B, XPA, and RPA on interaction with the model DNA was analyzed. The extract proteins and RPA competed for interaction with photoactive DNA, mutually decreasing the yield of modification products. In this case the presence of extract proteins at particular concentrations tripled the increase in yield of covalent adducts formed by XPC. It is supposed that the XPC subunit interaction with DNA is stimulated by endogenous HR23B present in the extract. Most likely, the mutual effect of XPA and extract proteins stimulating formation of covalent adducts with model DNA is due to the interaction of XPA with endogenous RPA of the extract. A technique based on the use of specific antibodies revealed that RPA present in the extract is a modification target for photoactive DNA imitating NER substrates. 相似文献