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Biomedical subjects

Ia A Bedrov

Publications and source records attributed to Ia A Bedrov.

18 recordsLinked to original sources
PubMed2005

[The vasomotion characteristics in isolated segment of the tail artery under conditions of slow constant increase of the perfusion pressure].

In vitro, the Wistar rat tail artery segments were perfused with the Crebs-Henselite solution. Under the conditions of perfusion pressure increasing from 0 to 110 mm Hg with the velocity of 5 mm Hg/min, the "diameter-pressure" curves were obtained. Changes in the vessel diameter during increase of pressure in the vessel were accompanied by vasomotions. For the first time, a regularity of the vasomotion direction changes as determined by an increase or decrease of the vessel diameter was established. The increase of the vessel diameter was accompanied by a sequence of its spike-formed decreases, whereas decrease of the vessel diameter was accompanied by a sequence of its spike-formed increases.

Animals↗
PubMed2004

[Responses of isolated arterial segment to a slow changing of perfusion pressure in it].

In in vitro experiments, segments of the Wistar rat tail artery's segments were perfused with the Krebs-Henselite solution. Increase of the perfusion pressure with the velocity of 5 mm Hg/min from 0 to 110 mm Hg with its subsequent drop with the same velocity down to zero showed that, within the limits of the above interval of values of the intravascular pressure, existed a range where two values of the artery diameter corresponded to each established value of the pressure. The data obtained prompt a further deciphering of mechanisms of the mechanogenic regulation of the blood vessels.

Animals↗
PubMed1979

[Certain quantitative patterns in the control of cutaneous blood flow during thermoregulatory reactions].

The total blood flow of rabbit's ear was inversely proportional to ambient temperature when the hypothalamic temperature was by 1 +/- 1.5 degrees C higher than normal due to ambient temperature raise from 15 degrees to 35 degrees C. The data obtained corroborate the viewpoint that the blood flow regulation not only controls heat loss by the rabbit ear, but also stabilizes the temperature of venous blood flow in the ear, when the ambient temperature varies in wide range.

Animals↗
PubMed1976

[Mechanism of inhibition of erythropoiesis during post-transfusion polycythemia].

In mouse with posttransfusion polycytemia, depression of erythropoiesis suggests that, in response to erythrocytes transfusion, not only the differentiation of erythropoietin-sensitive cells is interrupted (cessation of inflow of the labelled erythrocytes into the circulation on the 8th day), but the proligeration of differentiated erythroid precursors is also inhibited (fall of amount of labelled erythrocytes during first days). This was corroborated by analysis of the experimental data with the aid of mathematical model of erythropoiesis. The model revealed that, in posttransfusion polycytemia, division of 40 percent of all divisionable erythroid precursors was halted.

Animals↗
PubMed1976

[Several statistical patterns in the control of vascular thermoregulatory reactions].

In intact rabbits, in near to natural conditions with ambient temperature changing from 15 to 40 degrees C, switching on (off) of the thermoregulatory vascular response in the ear occurs at the moments when the suspended temperature of the hypothalamus, the temperature of the back skin, and speed of changes in the skin temperature attain (drop to) some extreme value. Quantitative estimates of the weight for this summation, were obtained.

Animals↗
PubMed1976

[Analysis of the imperative stimulus restricting voluntary breath holding].

In 5 healthy young men, the maximal voluntary breath holding--was studied under conditions of different initial values of PACO2--after oxygen inhalation at ordinary minute volume of respiration or at hyperventilation, or after breathing with oxygen mixtures with 2, 4, 6, 8 or 10% CO2. PACO2 was recorded at the moment of resuming of the intercostal muscles electric activity and at the point of breaking up the apnoea. A mathematical model was constructed. The hypothesis of participation of two independent factors (chemo- and mechanoreceptive) in genesis of the imperative stimulus for breathing was checked. The data obtained suggest that, in fact, the only factor restricting the duration of voluntary breath holding--is the summed up in time chemoreceptive stimulation. The involuntary contractions of respiratory muscles observed during apnoea are, apparently, a connecting link in formation of the imperative stimulus which breaks up the cessation of breathing.

Adult↗
PubMed1975

[Use of a mathematical model to assess cutaneous blood flow and heat loss during a thermoregulatory reaction].

The general blood flow and heat loss were determined in the rabbit ear with the aid of a mathematical model and on the basis of measurements of ambient, hypothalamic, and the ear temperatures, while the ambient temperature changed from--10 degrees C to + 40 degrees C. A static dependence of ear's heat loss on the blood flow intensity at different ambient temperatures, was quantitatively determined.

Animals↗
PubMedDate not supplied

[Receptive field types in the lateral geniculate body and their frequency characteristics].

Time amplitude -- frequency characteristics of the I and II types of receptive fields (RF) of lateral geniculate and their dependence on the contrast and spatial parameters of the light stimulus were studied. It is shown that the frequency characteristics of the RF I type depends on the contrast and area of the light stimulus, the higher being the contrast at a small area the smaller are the low frequencies. However at a large area of the stimulus the inhibition of low frequencies is greater at a small contrast. The transmitting band of frequency characteristics of RF II type does not depend on the contrast at a small area of the stimulus, at a large area a fall of low frequencies takes place at high contrasts of the stimulus. Such different behaviour of the receptive fields is explained by the models, which take into account RF spatial characteristics.

Animals↗
PubMedDate not supplied

[Characteristics of the pressure center movement under upright posture regulation].

The hypothesis was put forward that, along with the regulation of mass center projection, the system of upright posture control stabilizes the deviation of pressure center from the position of the mass center projection. The regularities in the behavior of the trajectories of pressure center and mass center projection were analysed. Experimental evidence was obtained supporting the validity of the hypothesis. The structure of the control system that corresponds to the new understanding of the variables being regulated during the maintenance of vertical posture was considered.

Algorithms↗
PubMedDate not supplied

[Learning characteristics and long-term memory in rhesus macaques].

The use of entropy of choices distribution in studying the processes of learning and long-term memory in rhesus monkeys during differentiation of periodic and non-periodic visual stimuli, showed that the transition from the unlearned state to the learned one proceeds not gradually but in two stages; the first stage--the accumulation of information and externally random behaviour, the second stage--rapid transition to the learned behaviour. For "filters" selective to spatial frequency, the change of stimuli orientation leads to an increase of the behaviour entropy. For "filters" selective to the bar width, the entropy practically does not change. During prolonged storage of acquired information, in the long-term memory, its partial loss takes place leading to an increase of the behaviour entropy. The difference between the entropy determined directly after the learning and that determined again after a prolonged storage of the memorized habit characterizes the quantity of information lost during the storage period.

Animals↗
PubMedDate not supplied

[Model of the formation of nystagmic reactions to a set of caloric tests].

The model can furnish additional information about the vestibulary system, when evaluating caloric tests. The model has been built with certain assumptions being made. The nystagmus intensity (the slow component rate during maximum intensity) is assumed to be proportional to the difference between energy levels (EL) of the right and left vestibular nuclear complexes (NC). El of each NC is equal to the afferent flow (AF) plus its inherent activity (IA). During caloric (two warm and two cold) tests IA remains constant. AF at rest is equal to spontaneous activity of receptors and during stimulation it increases or decreases in a linear fashion. Parameters of the model are: difference between intensities of reactions to warm and cold tests, difference between EL of two (right and left) unstimulated NC, and ratio of nystagmus intensity to the stimulus for each labyrinth. The behavior of the model during vestibular dysfunctions of various origin (changes in one of AF characteristics or changes in IA of one NC) is discussed. The diagnostic application of the model is illustrated by the discussion of nystagmometric data. The conclusion about vestibular dysfunction and its etiology can be made on the basis of statistic analysis of parameters of the model in the norm.

Caloric Tests↗