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Biomedical subjects

S V Lebedev

Publications and source records attributed to S V Lebedev.

At least 37 records · Page 2Linked to original sources
PubMed2002

Use of linearity of the Sokoloff model to improve performance of non-linear search.

The three-parameter Sokoloff equation is used to measure the rates of glucose consumption in the brain in vivo. This equation depends linearly on one of its parameters, k1, which is responsible for the glucose transport from plasma to tissue. By equating to zero the first derivative of the minimization function with respect to k1, it is possible to express this parameter as a function of the other two and reduce the non-linear search from three to two dimensions. This approach was examined by the Nelder-Mead simplex method and the Levenberg-Marquardt algorithm. In both cases the process of convergence was more robust and required fewer iterations to achieve a given accuracy than the direct three-parameter non-linear search.

Algorithms↗
PubMed2001

Immunoenzyme assay of glial fibrillary acidic protein for evaluation of functional activity of cell grafts from embryonic ventral mesencephalon in rats with experimental hemiparkinsonism.

The relationship between the release of glial fibrillary acidic protein (GFAP) into systemic circulation and the efficacy of transplantation of embryonic nervous tissue was studied on rats with 6-OHDA-induced hemiparkinsonism. It was found that intrastriatal transplantation of cell preparations from embryonic ventral mesencephalon significantly attenuated apomorphine-induced rotation, which points to functional recovery of the dopaminergic nigrostriatal system. The degree of this recovery depends on reactive astrogliosis around the graft and survival of dopaminergic neurons. Analysis of GFAP concentration revealed significant elimination of this antigen into the circulation 7 and 14 days after transplantation. In rats with good consolidation of the graft without pronounced reactive gliosis, the concentration of GFAP reached 253.99+/-79.30 ng/ml on week 4 after transplantation and decreased to 8.2+/-3.3 ng/ml 8-12 weeks after transplantation. In rats with poor graft consolidation associated with death of transplanted neurons and gliosis in the graft and surrounding tissue the concentration GFAP increased to 476.4+/-111.0 ng/ml within 4 weeks after transplantation and remained elevated (235.0+/-44.8 ng/ml) for 12 weeks. Thus, monitoring of serum GFAP concentrations allows in vivo evaluation of the functional state of intracerebral graft and the level of reactive gliosis. This test can be used for the prognosis of transplantation efficacy.

Animals↗
PubMed2000

Catecholamines and their metabolites in the brain and urine of rats with experimental Parkinson's disease.

The content of catecholamines and their metabolites in the brain and the relationship between cerebral catecholamine levels and their urinary excretion were studied in rats with 6-OHDA-induced hemiparkinsonism. 6-OHDA reduced brain concentrations of dopamine, DOPAC, and homovanilic acid and urinary excretion of dopamine, dioxyphenilalanine, and DOPAC by more than 90%. A positive correlation was found between the concentrations of these metabolites in the urine and striatum. Measurement of urinary catecholamines and their metabolites is a perspective test for evaluating the status of the dopaminergic nigrosostriate system of the brain in experimental parkinsonism.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2000

Complex analysis of efficiency of transplantation of embryonic nerve tissue to rats with hemiparkinsonism.

Effect of transplantation of embryonic ventral mesencephalon preparation containing dopaminergic neurons on repair of the dopaminergic nigrostriatal system was studied in rats with hemiparkinsonism induced by 6-hydroxydopamine. Transplantation of embryonic ventral mesencephalon into denervated striatum led to a more than 50% decrease in apomorphine-induced rotation, recovery of dopamine and DOPAC levels in the brain, and to an increase in DOPAC excretion and the DOPAC-dopamine ratio in daily urine of rats with hemiparkinsonism. Dopaminergic neurons of the transplant survived, forming a network of tyrosine hydroxylase-positive processes growing beyond the transplant and reinnervating the adjacent compartments of the striatum. A positive correlation between urinary excretion of DOPAC and brain concentration of dopamine was revealed in denervated rats after transplantation of ventral mesencephalon. Intrastriatal transplantation of cell preparations of embryonic striatum containing no dopaminergic neurons and isolated local injury to the striatum did not affect regeneration of the denervated nigrostratal system.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1998

[Reaction of melanocytes in vertebrate retina to the exposure to constant magnetic field].

The influence of a constant magnetic field (strain 40 kA/m) on retina pigmentary cells of grass frog (Rana temporaria) and grey pigeon (Columba livia) eyes was investigated. Changes in the number and length of melanocytes appendixes were noticed accompanied by formation of thickenings in which melanosomes sized from 0.1 to 0.5 micron are moving. It is established that magnetic properties of eye retina pigmentary cells depend on the presence of Fe3+ in melanin. A theoretical model of paramagnetic receptor has been elaborated, according to which the induction of a magnetic field, formed by melanocyte, makes of the order 100 pT1. This value well compares with the size of magnetic field of a nervous impulse (120 pT1), extending throughout a nervous fibre of the frog sciatic nerve (Wikswo et al., 1980). This allows to suggest a possible unsynaptic way of transferring the information about the perceived magnetic field.

Animals↗
PubMed1989

[Hygienic evaluation of substrata of contamination of ventilation and air conditioning systems].

Modern ventilation and air conditioning systems are complex technological objects in environment which can be sources of health-hazardous factors, including biological ones. Ventilation and air conditioning contact systems with water and partial air recirculation have construction prerequisites for environmental accumulation and dispersal of organic substances of microorganism and anthropogenic origin. Pollution substrates of inner surfaces of the above systems contain specific antigens causing immune response in persons working in air-conditioned premises.

Air Conditioning↗
PubMed1988

[Humidifier fever].

Pollution of air ventilation and conditioning systems by microorganisms and products of their activity can lead to the development of infectious (legionnaires' disease) and allergic (humidifier fever) diseases. Clinical, immunological and hygienic investigations under natural conditions of 72 persons working in offices helped to study a respiratory disease which was similar to humidifier fever. The removal of dust and mud from the system and thorough cleaning of all conditioned rooms put an end to this disease.

Acute Disease↗