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A G Nikonenko

Publications and source records attributed to A G Nikonenko.

7 recordsLinked to original sources
PubMed2000

Computer simulation approach to the quantification of immunogold labelling on plasma membrane of cultured neurons.

Cell culture is a convenient model system to study the expression of plasma membrane-bound proteins in nerve cells. Analysing it with an ultrastructural detail researchers often apply transmission electron microscopy together with immunogold labelling. Plasma membrane profiles are one-dimensional (1D) and provide little information about the topography of membrane-bound proteins. In order to convert 1D estimates of spatial arrangement for preembedding immunogold labelled proteins into two-dimensional (2D) quantities, namely the 2D pattern and density of labelling, this paper presents a simple computer simulation technique. This technique is based on a mathematical model permitting a simulated immunogold labelled membrane to be sampled in a way similar to microtome sectioning. An interlabel distance (ILD) estimate is used to define the position of immunogold particles in membrane profiles. In order to interpret experimental ILD measurements the simulated distribution best fit to the experimental data is selected and the corresponding 2D density and pattern of particle scattering are considered to explain the real situation. Various parameters including a cell section thickness, immunogold particle size etc can be adjusted to suit the demands of a particular experiment. The technique was applied to quantify the NCAM preembedding immunogold labelling in the plasma membrane of cultured rat hippocampal neurons.

Animals↗
PubMed1998

Computer simulation as a tool in evaluating intracellular spatial arrangement of an organelle using random section data.

A random profile of a cell gives a highly biased presentation of the location of various organelles within an intracellular space. The technique combining mathematical modeling and computer simulation presented here is aimed to overcome this bias and interpret intracellular spatial arrangement of an organelle using two-dimensional (2-D) observations from random sections. It allows to simulate random sectioning of a cell whose shape approximates to an ellipsoid of rotation, and to obtain the coordinates for the center of an organelle profile located within a cell profile. The pilot study was performed to investigate the influence of different three-dimensional (3-D) scattering patterns of an organelle on the coordinates of an organelle profile's center. Computer tests were carried out on a personal computer using the original software written in Pascal. It was ascertained that statistical properties of a sample of organelle profile's center coordinates allow for a quantitative estimation of some 3-D features, including the position of an organelle with respect to a cell center and specific characteristics of an organelle position (e.g., its fixity or randomness).

Cells↗
PubMed1996

The cell sectioning model. Nuclear/cytoplasmic ratio studied by computer simulation.

OBJECTIVE: Stereologic analysis can be supported using methods of modeling and simulation. To illustrate the use of a mathematical cell sectioning model (CSM) in predicting two-dimensional (2-D) measurement characteristics of sectioned cells by means of computer-assisted simulation, the present study was performed. STUDY DESIGN: Computer software based on the CSM was developed to simulate 2-D nuclear/cytoplasmic (N/C) ratio distributions and to test the sensitivity of the parameter to several factors. Simulations were performed with the following feature set for cells of simulated populations: (1) size, shape (approximated by an ellipsoid of rotation) and orientation of the cell, and (2) size, shape and intracellular position of the nucleus. RESULTS: The computer tests showed that the value of the 2-D N/C ratio depends upon many factors; the real three-dimensional N/C ratio is only one. Statistical characteristics of a 2-D N/C ratio sample were found to be sensitive to changes in (1) the nuclear position inside the cell, (2) cell shape, and (3) orientation of the asymmetric cell with respect to a cutting plane. CONCLUSION: CSM tests demonstrated the model validity of and potentials for using it as an algorithm for morphometry software. Taking into account the sensitivity of the 2-D N/C ratio parameter to various factors, great care must be used in interpreting its observations.

Animals↗
PubMedDate not supplied

[Neurocyte reaction of the anterior and mediobasal hypothalamic nuclei in birds to testosterone propionate].

Some magnocellular and parvocellular hypothalamic nuclei of cockerel were studied for their reactivity to testosterone-propionate (TP). It has been ascertained that injections of 1 or 5 micrograms/100 g doses of TP activate the neurocytes of preoptic periventricular and tuberal nuclei. This effect is manifested between 45th and 60th day of life and may be regarded as an early event of sexual maturation.

Aging↗
PubMedDate not supplied

[The prenatal dynamics of erythropoiesis in the liver of the guinea pig].

Erythroid cell kinetics in the liver of guinea pig embryo was investigated on the semithin epon sections with stereologic and morphometrical methods. It was shown that from 20 to 60 days of prenatal development the volume density (VD) of proerythroblasts decreased 15 times. A decrease in the VD of another erythroblasts was less pronounced. These changes coincided with the liver parenchyma reconstruction. It was concluded that the main influence on erythroid cell kinetics was determined by a surpassing disappearance of the precursor cells from the prenatal liver and, also, that stability of some morphological parameters of hemopoietic stroma was important for realization of the liver hemopoietic activity.

Animals↗