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A M Petrov

Publications and source records attributed to A M Petrov.

16 recordsLinked to original sources
PubMed2006

[The intracellular calcium and mechanisms of endocytosis of synaptic vesicles at the frog nerve ending].

In the experiments on frog motor nerve endings of cutaneous pectoris muscle, made by extracellular recording of synaptic signals, it has been shown that the increase in intracellular calcium ion concentration in the nerve ending (by enhance of extracellular potassium ion concentration, or by addition of caffeine) leads to an increase in the miniature end-plate potential frequency, which is preserved over the whole period (about 10 min) of action of these substrates. The rhythmic stimulation of motor nerve (20 or 100 imp/s) quickly leads to a decrease in the end plate potentials amplitude. It has been shown by fluorescent microscopy with the use of endocytotic marker FM 1-43 that in the course of a short time exposition (5 min) in a high potassium solution (40 mM) or caffeine (5 mM), light spots appeared in the nerve ending. This shows that synaptic vesicles undergo intensive processes of endocytosis. During a longer exposition (30 min) no light spots were revealed, whereas the nerve ending width increased. This data allowed to propose that the process of endocytosis was blocked. In the presence of even lower concentrations of potassium ions and caffeine, and during a long rhythmic stimulation (20 or 100 imp/s) no blocking of endocytosis was revealed. It is concluded that high concentrations of intracellular calcium in the frog motor nerve ending leads to a reversible block of endocytosis, while exocytosis in synaptic vesicles is proceeding.

Animals↗
PubMed2006

[Clinical and radiological (PET, MRI) correlations depending on disease progression in patients with multiple sclerosis].

The aim of the study was to investigate the structural-functional changes in the cerebral gray matter (cortical and subcortical areas) of patients with multiple sclerosis (MS) depending on the disease severity. One hundred and seven patients (107) with definite diagnosis of MS (Mc Donald's criteria), aged 16-60 years, illness duration 1-30 years, and 21 healthy age-matched controls have been studied. Neurological assessment including Kurtzke and EDSS scales (range 0-8) was performed in all the patients. The patients and controls underwent MRI with a 1,5 imager and PET using 18F-flurodeoxyglucose (FDG). A type of the disease course was determined as remitting in 63 patients, primarily-progressive in 8, remitting progressive in 6 and secondary-progressive in 30. To analyze pathogenesis of the disease progression, the patients were divided into 3 clinical groups: (1) remitting (RRMS, n=63); (2) progressive (PRMS) with EDSS < or =6 (n=34); 3) PRMS with EDSS >6 (n=11). Along with the progression of MS from RRMS to PRMS and increasing of EDSS, the rCMRglu reduction of the cerebral gray matter developed from the supplementary motor cortex of a dominant hemisphere to the marked global reduction of cerebral metabolic rate in the PRMS group (EDSS >6). In the PRMS group with EDSS56, there was functional reorganization of cortical and subcortical areas compensatorily developing with the disease progression. In the PRMS group with EDSS >6, the data obtained did not support the evidence for the regional compensatory increase of rCMRglu in the same brain areas. Decompensation of the functional cortical reorganization in the PRMS group with EDSS >6 correlated with diffuse brain atrophy as well as with atrophy of the gray matter of the regional basal ganglia, first of all of the thalamus.

Adolescent↗
PubMed2005

Reactive oxygen species contribute to the presynaptic action of extracellular ATP at the frog neuromuscular junction.

During normal cell metabolism the production of intracellular ATP is associated with the generation of reactive oxygen species (ROS), which appear to be important signalling molecules. Both ATP and ROS can be released extracellularly by skeletal muscle during intense activity. Using voltage clamp recording combined with imaging and biochemical assay of ROS, we tested the hypothesis that at the neuromuscular junction extracellular ATP generates ROS to inhibit transmitter release from motor nerve endings. We found that ATP produced the presynaptic inhibitory action on multiquantal end-plate currents. The inhibitory action of ATP (but not that of adenosine) was significantly reduced by several antioxidants or extracellular catalase, which breaks down H2O2. Consistent with these data, the depressant effect of ATP was dramatically potentiated by the pro-oxidant Fe2+. Exogenous H2O2 reproduced the depressant effects of ATP and showed similar sensitivity to anti- and pro-oxidants. While NO also inhibited synaptic transmission, inhibitors of the NO-producing cascade did not prevent the depressant action of ATP. The ferrous oxidation in xylenol orange assay showed the increase of ROS production by ATP and 2-MeSADP but not by adenosine. Suramin, a non-selective antagonist of P2 receptors, and pertussis toxin prevented the action of ATP on ROS production. Likewise, imaging with the ROS-sensitive dye carboxy-2',7'-dichlorodihydrofluorescein revealed increased production of ROS in the muscle treated with ATP or ADP while UTP or adenosine had no effect. Thus, generation of ROS contributed to the ATP-mediated negative feedback mechanism controlling quantal secretion of ACh from the motor nerve endings.

Acetylcholine↗
PubMed2003

[Analysis of living motor nerve ending of a frog by endocytotic fluorescent marker FM 1-43].

In our experiments on motor nerve endings of the frog cutaneous pectoris muscle, using fluorescent marker FM 1-43, the intensity and topography of endocytosis were investigated after the initiation of massive exocytosis of synaptic vesicles by increasing the extracellular potassium concentration. Using FM 1-43, fluorescent spots were shown to appear, looking as accumulations of synaptic vesicles in the active zone region. The forms and sizes of luminous spots and the distances between them were analysed. Considerable variations in brightness and total areas of fluorescent spots per a length unit in different regions of the nerve ending were revealed in addition to a proximal-distal gradient of these parameters along the nerve terminal. Peculiarities of topography and intensities of luminescence in the most terminal regions of the nerve ending are described. The obtained data are discussed in terms of the exo- and endocytosis cycle of synaptic vesicles in the active zone region, and from the point of view of the plasticity of the motor nerve ending and active zones. The factors involved in the transmitter release nonuniformity are analysed.

Animals↗
PubMed1980

[Factors that influence the late treatment results in ovarian cancer].

Retrospectively, clinico-morphological data on 411 patients with primary malignant epithelial ovarian tumors were examined. All patients were followed up for 5 years and over. Based on the analysis of the data obtained some prognostic factors definitely correlating with the patients' survival were singled out: 1) at all stages; 2) mainly at late stages.

Adult↗