Morphological and electrophysiological peculiarities of sensory bush-like receptors of the frog urinary bladder.

Results of synchronous morpho-electrophysiological experiments conducted on living bush-like receptors of the urinary bladder of a frog (Rana temporaria) and results of their ultrastructural and cytochemical studies are presented in this article. It is demonstrated that these endings are mechanical receptors reacting to tactile stimuli. Rapidly and slowly adapting units are registered. The slowly adapting receptors prevail (94%). Morpho-topographic peculiarities of the rapidly and slowly adapting forms are recorded at the light (optic) level. Different variants of sediment deposits at Ranvier nodes of the myelinated afferent fibers are demonstrated by means of a ferri-ferricyanide technique. In this connection a hypothesis is discussed concerning the existence in bush-like receptors of several generators of impulses converging on to a solitary fiber. The ultrastructure of receptor terminals is demonstrated. Their connection with tissue elements of the organ wall is realized with the help of collagen fibrils braiding the terminals with a dense irregular net. No connections are discovered between terminals and cells with the help of desmosomes. It is supposed that this very interrelation of the receptor terminals with the surrounding tissues ensures a predominance of the slowly adapting forms among them.

Ultrastructural changes in receptor terminals on prolonged action by local anesthetics.

We have studied ultrastructural changes in the terminal plates of the bushy receptors in the frog urinary bladder after exposure for two hours to 0.05% novocaine solution and for one hour to 0.05 dicaine and trimecaine solution. During these periods a steady blockage of the receptor impulse activity develops. The local anesthetics essentially change the ultramicroscopical structure of the terminals. The reaction to the anesthetics investigated shows some common features and certain peculiarities. For each effect three types of change can be determined characterized by various degrees of rearrangement in the neurolemma, neuroplasma, and organelles. Each type of change is assumed to reflect a certain phase of the plate reactive response. Specific features of the reaction to novocaine include slight changes in mitochondria, accumulation of glycogen granules, and deformation and decrease in numbers of vesicles. Under the action of dicaine the mitochondria do not change and the number of vesicles increases without change in their shape, while under the action of trimecaine marked changes can be observed in mitochondria. Changes observed in the terminal plates are regarded as adaptive. The action of the local anesthetics on the receptors is not limited to the blockage of the sodium channels of the afferent fibers, while the biochemical processes occurring in the cytosol of the terminals also change. Their morphological manifestations reflect the ultrastructural changes observed.

Computerized morphometric analysis of the dendrites of Dogiel type II neurons.

Silver nitrate impregnation by the Bil'shovskii-Gros method was used to study the dendrites of Dogiel type II cells in the cat large intestine (local receptors) by computerized morphometric analysis. The following parameters were measured: the areas of the receptive field of the dendrite, the total area of all receptor elements, the total length of all branches of the receptor. There was significant individual variation in all these measures: the ratios of maximum to minimum values were 41, 29, and 45 respectively. There were no correlations between these three measures. It is suggested that this morphological heterogeneity of dendrites may underlie functional differences in Dogiel type II cells.

[The effect of weak electromagnetic fields and ionizing radiation on the regeneration of the murine sciatic nerve]. / Vliianie slabykh élektromagnitnykh polei i ioniziruiushchei radiatsii na regeneratsiiu sedalishchnogo nerva myshei.

The influence of X-ray impulses (dose 0.003 cGy, longitudity 10 ns) and EM impulses (induction 0.003 mT) on sciatic nerve regeneration in mice after crush lesion was studied. Limb jerk amplitude at electric stimulation of nerve and postural reflex in thin rod in X + EM and EM groups were restored within 13th days after lesion, in control group within 15 days (p < 0.05). The beginning of repairing of postural reflex was early in X + EM group than on EM group, rehabilitation of limb jerk amplitude--in EM group. Histological examination demonstrated that myelin degenerated in EM group more rapidly as compared with X + EM and control groups. This data suppose different effects of EM and X + EM impulses on nerve-regenerating processes.

[The use of several types of metal cations--a new approach to the study of the metallophilia of Ranvier's nodes of nerve fibers]. / Primenenie neskol'kikh vidov kationov metallov--novyi podkhod k izucheniiu metallofilii perekhvatov Ranv'e nervnykh volokon.

Mechanisms of metal affinity of Ranvier's nodes of myelinated nerve fibers in the peripheral nerve system have been investigated. It is indicated that Fe(3+)-ions are able to reduce to Fe(2+)-ions. Ag(+)-ions compete with Fe(3+)-ions for places of adsorption in a gap [correction of chick] between myelinated segments of Ranvier's node. It is demonstrated that Fe(3+)- and Fe(2+)-ions are adsorbed in the gap [correction of chink], while Ag(+)-ions are adsorbed in the gap [correction of chink] and axon in the bulbs of the node. One can increase ferrocyanide of ferrous sediment by several times by ferricyanide of ferrous sediment as well as by ferrocyanide of silver and of metal silver ones. A possibility to use several kinds of metal ions for demonstration of cytochemical heterogeneity of nerve fibre membrane is discussed.

[Electron microscopic study of the interrelations of the bush-like receptor terminals with the tissue]. / Elektronno-mikroskopicheskoe issledovanie vzaimootnoshenii terminalei kustikovidnogo retseptora s tkan'iu.

A study was made of the ultrastructure of elements linking the bush-like receptors with tissues of the frog bladder. It is demonstrated that the connection is realized mainly by collagen fibres, whose dense and irregular net is branching the nervous terminals. Besides, a dense contact has been found between the terminals and epithelial cells without any layer of collagen fibres. No desmosomal connection between terminals and tissue elements was found. It is suggested that the above peculiarities of the connections may influence considerably the functional-adaptational characteristics of the receptors.

[Morphological and functional changes of tissue receptors of an organ plexus under the effect of blockers of cytoskeleton assembly]. / Morfofunktsional'nye izmeneniia tkanevykh retseptorov organnogo spleteniia pod vliianiem blokatorov sborki tsitoskeleta.

Colchicine and cytochalasine C exert modifying action on tissue receptors of urinary bladder of the frog. Under the effect of cytochalasine the period of vital staining of receptors were changed. Latent period of decoloration grew 37-56% longer while the period of staining accumulation grows 18% shorter. The forming of granules was also altered 2 types of terminal plaques were distinguished according to this sign in the course of treatment with colchicine and 3 types in the experiment with cytochalasine. Modifying action of cytochalasine was greater. Cytochalasin caused mass appearance of round intensely stained plaque the appearance of which was obviously connected with microtubules destruction. Mean area of terminals profile field also increased. Spontaneous impulse activity of receptors was significantly suppressed. Specificity of responses to colchicine and cytochalasine was probably conditioned by their effect on different elements of cytoskeleton.

[Morphological and functional changes of free sensory receptors of the frog urinary bladder during regeneration]. / Morfologicheskie i funktsional'nye izmeneniia svobodnykh sensornykh okonchanii mochevogo puzyria liagushki v protsesse regeneratsii.

Dynamics of morphological and functional changes of bush-like sensory receptors including free visceroreceptors of the frog urinary bladder were investigated. For this purpose surgical operation was performed to intersect the ischiococcygeal plexus. It was demonstrated that 1) receptors can generate spontaneous impulse activity up to 18th postoperative day. In this stage one part of afferent fibres was left undamaged, although the others demonstrated the Wallerian degeneration features; 2) regeneration of fibres began after a postoperative month 3) first remyelinated fibres were registered in nerve bundles following 2-3 months; at the same time non myelinated distal regions left bundles and form non myelinated arbors in the surrounding tissues. The receptor impulse activity was registered simultaneously; 4) morphological features of growing bush-like receptors at light optic level differed from those in native state; 5) maturation of regenerating receptors was finished a year later.

[Dynamics of terminal plaque structure during changes in the impulse activity of sensory endings in the process of their regeneration]. / Dinamika terminal'nykh bliashek pri izmenenii impul'snoi aktivnosti sensornykh okonchanii v protsesse ikh regeneratsii.

The dynamics of changes in terminal plates of frog's urinary bladder sensory free visceroceptors during their posttraumatic regeneration was studied. It was shown that during the time period from two months to one year the terminal plate number in receptor bush increased, while their average dimensions decreased and their shape changed. No correlations between the changes of afferent impulse activity and these morphological transformations were found. The data obtained suggest that terminal plates do not seem to participate in the generation of bioelectric activity, but rather appear to be the growth cones of non-myelinated terminal and thus are involved in repair processes.

[The morphophysiological mechanisms in the adaptation of mechanoreceptors]. / Morfofiziologicheskie mekhanizmy adaptatsii mekhanoretseptorov.

The review was dedicated to the analysis of mechanisms mediating mechanostimuli transformation into bioelectric process in sensory nerve endings Influence of viscous-elastic properties of nerve ending and of the surrounding tissues as well as neuromembrane ion channels on adaptive process in mechanoreceptors were examined in detail on the basis of recent research. Special attention was drawn to consideration of morphophysiological features of similarity and differences of various mechanoreceptor types (both free and non-free).

[Computer morphometric analysis of dendrites of the type II Dogiel neurons]. / Komp'iuternyi morfometricheskii analiz dendritov neironov Gogelia II tipa.

Dendrites of type II Dogiel neurons (the local receptors) stained with silver nitrate impregnation by Bilschovsky-Gross method, were analyzed with computer morphometry in cat large intestine. The following parameters have been measured: an area of dendritic receptor field, total area of all receptor elements and total length of all receptor branches. Significant individual variability was noted in the values of these parameters: the maximum value exceeded the minimum one by a factor of 41, 29 and 45, respectively. No correlation between these three parameters has been found. It is suggested that the morphological diversity of dendrites found in this study may serve as a basis of the functional variability of type II Dogiel neurons.

[Metallophilia in the Ranvier's nodes of nerve fibers in rats of different strains (histochemical study)]. / Metallofiliia uzlovykh perekhvatov nervnykh volokon u krys razlichnykh linii (gistokhimicheskoe issledovanie)

Myelinated nerve fibers formed by the processes of LV spinal ganglion neurons were studied in two lines of rats selected according to high and low thresholds of nerve system excitability to electric current. Before ultrastructural study the fibres have been treated with potassium pyroantimonate. It was demonstrated that specific dense precipitate was deposited in the nodes of Ranvier of the nerve fibers of rats with low excitability thresholds; this precipitate was not found in the fibers of rats with high thresholds. It is suggested that deposition of precipitate is indicative of a high density of sodium channels in neurilemma, i.e. of high functional activity of nerve fibers.

[Changes in the redox system of the terminal boutons of bush receptors in different functional states]. / Izmenenie redoks-sistem terminal'nykh bliashek kustikovidnogo retseptora pri ego razlichnykh funktsional'nykh sostoianiiakh.

Live cytophotometry with simultaneous recording of spikes in response to mechanical stimulus and increased NaCl concentration revealed the dependence between the level of functional activity of the frog bladder's bush receptors and the changes in activity of the terminal buttons' redox-systems checked by means of the pattern of transition of oxygenated (coloured) form of the methylene blue into the leucoform. Heterogenous character of the terminal buttons was revealed with the aid of the transition parameter of these forms of the live staining, as well as the 2- and 4-phasic character of the pattern of changes in the buttons' redox-systems.

[Characteristics of the vital morphology and bioelectrical activity of a single bushy receptor]. / Nekotorye osobennosti vital'noi morfologii i bioélektricheskoi aktivnosti odinochnogo kustikovidnogo retseptora.

Synchronous morpho-electrophysiological experiment in the frog bladder's single bushy receptor revealed that the receptor vitally stained with methylene blue preserves high functional activity and responded adequately to mechanical square stimuli. The intensity of staining, at that, is related to the spike activity level. The dependence is not linear but has rather a character of inverse proportion. Fast- and slow-adapting terminals were revealed as well as some of their morpho-topographical differences. The slow-adapting receptors were shown to prevail (94%).

[Changes in the redox systems of preterminals and the partition plateau of the bush receptor in different functional states]. / Izmenenie redoks-sistem preterminalei i ploshchadok deleniia kustikovidnogo retseptora pri ego razlichnykh funktsional'nykh sostoianiiakh.

Effects of mechanical stimulation and high concentration of sodium chloride on recuperative equivalents of preterminals and partition plateau of the frog bladder bush-receptors, were studied. Changes of levels of different parts of the interoceptor were shown to be similar and to consist of the phases as follows: initial increase of the level followed by its decrease and the rerminal increase of the recuperative equivalents level. Specifics of the pattern in these parts of the receptor involves different obviousness of phases and their duration. This specifics seems to be associated with different roles played by different parts of the receptor in generation of the bioelectrical activity.

[The structural dynamics of the afferent flow in the action on the receptor field of a low-intensity stimulant]. / Dinamika struktury afferentnogo potoka pri vozdeistvii na retseptornoe pole razdrazhitelia nizkoi intensivnosti.

The pattern of changes in afferent flow from a uniform isolated receptor field (3-5 mechanoreceptor units) under the effect of unspecific external stimulus of low intensity, was studied. A diverse dynamics of the afferent flow was observed: the firing rate, relative distribution of discharges in time, the amplitude and the form of spikes, are altered. The changes occur simultaneously, as a rule, which renders the idea of afferent flow's structure rather uncertain. The growth in amplitude and the change in the form of discharges seem to be based on a synchronizing of receptor units excitation. The latter can serve as a premise for actualization of the mechanism of sensory information compression by means of involvement of parallel afferent fibres in the excitation.

[Heterogeneity of the morpho-functional organization of bushy interoceptors as one of the factors of their resistance]. / Geterogennost' morfo-funktsional'noi organizatsii kustikovidnykh interotseptorov kak odin iz faktorov ikh rezistentnosti.

Bush interoceptors reveal their obvious heterogeneity of morphofunctional organization through non-standard responses of their units and elements to adequate and extreme irritants, the responses involving different degree of receptor resistance upon change of ionic power and in anoxia, and non-standard spikes of biopotentials. The morpho-functional heterogeneity of bush receptors seems to enlarge considerably the scope of adequate responses of reflexogenic areas to stimuli, thus raising the functional resistance of sensory system in unfavourable conditions.