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Biomedical subjects

A D Nozdrachev

Publications and source records attributed to A D Nozdrachev.

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

[The influence of pineal peptides on in vitro immunoglobulin secretion by Peyer's patches in rats].

The influence of the pineal peptides (1 mcg/ml) on immunoglobulin secretion by rat's Peyer's patches isolated from nonimmunized rats and from orally immunized by ovalbumin during 40 min incubation, was investigated. Using alpha- and beta-adrenoblockers--phentolamine hydrochloride (0.02 mg/ml) and anaprilin (0.6 mg/ml), respectively--the possibility of pineal peptides' effect on the gut secondary lymphoid organ' adrenoreceptors, was evaluated. Basic levels of immunized rats' control Peyer's patches secretory activity were 2.4--fold (p < 0.01) higher than those of non-immunized rats. The effect of pineal peptides on antibody-producing cells' secretory activity depended on Peyer's patches' functional condition. Application of pineal peptides led to a 35% (p < 0.05) increasing of immunoglobulin secretion by non-immunized rat Peyer's patches and to a 25% (p < 0.05) decreasing of antibody production by immunized rats lymphoid organs. These data suggest that the pineal peptides activation influence on Peyer's patches antibody-producing cells of nonimmunized rats connected with alpha-adrenoreceptors, and inhibiting action of these peptides on immunized rats lymphoid organs immunoglobulin secretion are not mediated through adrenoreceptors.

Adrenergic Antagonists↗
PubMed2001

Development of the evoked potentials in the thalamus and cerebral cortex after stimulation of the stellate ganglion afferents in kittens.

The primary evoked potentials (EP) were studied in newborn, 10-, 20-day-old, 1-month-old kittens in the thalamus and cerebral cortex after stimulation of the stellate ganglion (SG) afferents. The nerves were irritated with single square-wave pulses with an amplitude of 1.2-1.3 threshold for EP appearance. In all kittens, EP were registered in the same zones as in adult animals. In the thalamus, this zone was represented by the centromedial part of the ventralis posterior lateralis (n. VPL), contralaterally to the stimulation place. In the cerebral cortex, the EP were observed in the cerebral cortex, specifically in the somatosensory zones S1 and S2 also contralaterally to the stimulation place. In postnatal ontogenesis, the latency of evoked potentials decreases, amplitude increases and the form of these potentials transforms from negative in newborn kittens to positive-negative wave in 1-month-old animals. Maturation of the SG afferent pathways exists in parallel with the somatosensory ones and does not finish at 1 month of life.

Afferent Pathways↗
PubMed2001

How is bursting mode maintained under the action of exo- and endogenous factors?

The investigation is concerned with slow oscillations of the intracellular calcium concentration, fast oscillations of the membrane potential, and their interactions during bursting generation. The question associated with functioning of the bursting mode is considered: how is the condition of simultaneous existence of the slow and fast membrane potential oscillations (necessary for the bursting mode) realized under exo- and endogenous actions that result in changes in the neuron membrane parameters? To answer the question the regions of existence of fast, slow and bursting oscillations have been constructed on different parameter planes. The study has revealed that in spite of the fact the regions of the existence of the slow and fast oscillations are sensitive to parameter variations, the condition of the bursting mode existence remains due to invariance of the spatial vicinity of these regions. Furthermore, it has been demonstrated that there exists the possibility to enhance the maximal conductances of the calcium-dependent currents simultaneously such that even strong variations of their values do not induce changes of the oscillations mode (i.e. it remains bursting).

Action Potentials↗
PubMed2001

[Capsaicin-sensitive afferents in the vagus nerve].

Vanilloids were shown to interact with over 70% of vagal C-afferents first causing an excitation followed by desensitisation and a lasting destruction of nerve fibres. Capsaicin induces a secretion of some neuropeptides from 10-30% of vagal sensory terminals and therefore serves as a pharmacological tool for testing local "effector function" of primary afferents. Vagal afferents seem to have their own subtype of vanilloid receptors (VR), not completely identical with the VR receptors in the dorsal root ganglia. Considering potentiation of the capsaicin receptors sensitivity by some factors such as local heating, pH, free oxygen radicals, a possible role of the VRs as integrators of chemical and physical components of nociceptive stimuli, is discussed.

Afferent Pathways↗
PubMed2001

[Participation of the dopaminergic brain system in effects of glucocorticoid hormones].

Following the conditioning with dexamethasone, a dose-dependent place preference in non-preferred compartment was observed on the second test day in male Wistar rats. Amphetamine in subthreshold dose exerted no effect if administered alone and induced a place preference in an unbiased paradigm after pre-treatment with dexamethasone. Administration of D2-dopamine receptors' antagonist sulpiride 30 min prior to dexamethasone conditioning completely blocked the acquisition of the place preference. The D1-dopamine receptors' antagonist SCH23390 exerted no effect on the place conditioning. The findings suggest that the D2-dopamine receptors take part in conditioned place preference with dexamethasone.

Animals↗
PubMed2000

Morphological features of neurons innervating different viscera in the cat stellate ganglion in postnatal ontogenesis.

Retrograde axonal transport of horseradish peroxidase (HRP) was used in this study to determine morphological parameters in the stellate ganglion (SG) in newborn, 10-, 20-day- and 1-month-old kittens. Neurons with the largest average size participated in innervation of the heart in newborn kittens and in innervation of the sternocleidomastoid muscle in other animals. The number of neurons sending their axons to target-organs also changed in postnatal ontogenesis. Regardless of the site of HRP injection at animals of all ages labeled neurons in the SG were located in certain zones on a topographical basis. Thus, it is concluded that in postnatal ontogenesis the neuronal organization of the SG changes in parallel to the increase of neuronal sizes and ganglion cross section area and practically finishes at 1 month of age.

Animals↗
PubMed2000

Age-dependent changes of electrophysiologic characteristics of the stellate ganglion conducting pathways in kittens.

The conducting pathways of the cat stellate ganglia were examined in newborn, 10- and 20-day-old kittens by recording the evoked responses in the branches of the ganglion following electrical stimulation of its other branches. In the course of postnatal ontogenesis, the average conduction velocity of excitation and the average amplitude of the responses was increased. In newborn and 10-day-old kittens, all fibers on their conduction velocities belong to C-fibers. In 20-day-old kittens, Adelta- and B-fibers also appeared. In this age-group, two subgroups among fibers of the C group were determined according to their conduction velocity of excitation. From 10 days of age, the axon reflex was recorded in the anastomosis and the inferior cardiac nerve following stimulation of the cranial and caudal branches of the subclavian loop. All branches of the stellate ganglia of 20-day-old kittens contain both continuous and synaptically switched fibers.

Action Potentials↗
PubMed2000

Method for constructing the boundary of the bursting oscillations region in the neuron model.

We examine the problem of constructing the boundary of bursting oscillations on a parameter plane for the system of equations describing the electrical behaviour of the membrane neuron arising from the interaction of fast oscillations of the cytoplasma membrane potential and slow oscillations of the intracellular calcium concentration. As the boundary point on the parameter plane we consider the values at which the limit cycle of the slow subsystem is tangent to the Hopf bifurcation curve of the fast subsystem. The method suggested for determining the boundary is based on the dissection of the system variables into slow and fast. The strong point of the method is that it requires the integration of the slow subsystem only. An example of the application of the method for the stomatogastric neuron model [Guckenheimer J, Gueron S, Harris-Warrick RM (1993) Philos Trans R Soc Lond B 341: 345-359] is given.

Calcium↗
PubMed2000

Activity of foot skin mechanoreceptors and afferent nerve fibres in the adult rat sciatic nerve are altered after central axotomy of sensory neurons.

The functional properties of skin mechanoreceptors were examined in the hind foot of normal rats in comparison with animals subjected to dorsal rhizotomy. Evoked nerve impulses were recorded from afferent nerve fibres of the tibial nerve. The decentralized mechanoreceptors displayed evidence of autonomous functioning, but with several abnormalities as compared to normal animals. There was a decreased sensitivity to mechanical stimulation and a lower adaptive capacity as a consequence of rhizotomy. The underlying mechanism is suggested to be a loss of central trophic support because of the interrupted link between the central nervous system and the sensory ganglion cell periphery. The findings indicate that mechanical receptors continue functioning under conditions when sensory impulses flow cannot reach postsynaptic target neurons in the central nervous system, but stop at the level of the primary sensory neuron.

Adaptation, Physiological↗
PubMed2000

[Neurochemical organization of the brain reinforcing systems].

Modern concepts of neurophysiological mechanisms of the brain reinforcing systems are reviewed from A.A. Ukhtomsky's concept of dominanta. The brain mesocorticolimbic system was shown to play a key role in functioning of the brain reinforcing systems. Morphological and neurochemical organisation of this system determining the emotional sphere, was studied. The dopamine system was found to be the main neurochemical tool of the mesocorticolimbic system. Other transmitters, neuromodulators, and hormones play a regulatory role in the latter. The data obtained corroborate the authors' concept of fluctuating emotional gradient.

Animals↗
PubMed2000

[Pinealocyte functioning in stress during daytime in rats].

Several types of unit activity were detected in the rat pineal gland during a 48-hour water and food deprivation. The unit activity rate in stress was higher by 4-6 times than in intact rats (due to an increase in the "fast" cells number and switching of some cells from regular to a burst type of activity). Electrical stimulation of olfactory epithelium decreased the unit activity rate in the most active pinealocytes. The daytime increase in the pineal electrical activity reflects an intensification of secretion of the protein/peptide substances and, probably, serotonin but not the melatonin. Blocking exocytosis with colchicin revealed a close relation of the pinealocytes secretion with their electrical activity. Existence of central (olfactory in particular) mechanisms limiting the pineal activation, was shown.

Animals↗
PubMed2000

[Putative molecular mechanism of defensin interaction with the membrane of the sensory neuron].

NP-1 defensin decreased effective charge transfer in the activation gating system of TTX-resistant (slow) sodium channels in a dose-dependent manner. The dissociation constant and Hill coefficient values were KD = 2 pM and X--0.9. Geometry of the NP-1 defensin molecule was built using its primary structure with three S-S briges and fully optimised in the framework of molecular mechanics method. The data obtained explain experimental results of stechiometry 1:1 due to ligand-receptor interaction by the only outward directed carboxyl group of Glu 14 which might form a hydrogen bond with a single binding site of non-identified defensin membrane receptor.

Animals↗
PubMed1999

Changes in afferent impulse activity of small intestine mesenteric nerves in response to antigen challenge.

Sprague-Dawley rats (weight 130-150 g) were sensitized by an intraperitoneal injection of 1 mg chicken egg albumin with 0.25 ml Freund's adjuvant to stimulate immunoglobulin E antibody production. Leukocyte migration inhibitory factor was used as an indicator of animal sensitization. In acute electrophysiological experiments on sensitized animals, an intra-arterial or intraluminal chicken egg albumin (100 microg) challenge evoked a 10% enhancement of the activity of mesenteric nerves of the small intestine, regardless of the injection site chosen. Afferent nerve activity in control animals was not changed during the chicken egg albumin challenge. Morphometry at the light microscope level showed activation of mast cell degranulation after the antigen challenge to presensitized rats. Intraluminal injections of a stimulator of mast cell degranulation, compound 48/80 (20-30 mg), were found to increase afferent discharges in intact rats. An antagonist of H1 histamine receptors, clemastine, reduced the effect of compound 48/80. The results obtained provide direct evidence for the stimulation of sensory nerve endings by mast cell mediators released during mast cell degranulation.

Afferent Pathways↗