The dynamics of the activity parameters of the neuronal populations in the dorsal hyperstriatum of hens depending on the afferent input in ontogeny]

Studies have been made on the properties of neuronal populations of the dorsal hyperstriatum of the forebrain in hens beginning from the 18th day incubation up to the 7th day after hatching, which were incubated and kept either in darkness or under periodic illumination. Among the investigated parameters of multicellular activity, mean frequency of the discharge activity was found to be most susceptible to the level of external light afferentation in ontogenesis. The discharge activity was more intense in the left hemisphere of chick embryos and chicks from illuminated group, which may be associated with asymmetrical visual afferentation resulting from embryonic position within the egg, and its modulating effect on synchronization processes in the adjacent neurones of the given structure.     

The isoenzyme composition of liver pyruvate kinase from hens in ontogeny]

Only one isozyme M2 of pyruvate kinase was found in the liver of hens at all stages of embryonic and postembryonic development. No analogue to isozyme L from the liver of mammals was found. During embryogenesis and postnatal life, isozyme M2 is presented by two forms which differ in pI values. Throughout embryonic and postembryonic development, pyruvate kinase is presented by two forms which differ in their substrate affinity.     

Development of the cerebellar glomeruli in the ontogeny of hens

By means of light and electron microscopy development of the cerebellar glomeruli has been studied in the hen ontogenesis. Two successive stages have been revealed: protoglomerular (the 16th-18th days of incubation) and glomerular (the 19th day of incubation--the end of the 3d week after hatching). Specific peculiarities of their structural organization are presented. A suggestion is made on an inductive effect of the afferent mossy fibers on processes of morphological formation of the cerebellar glomeruli.     

The organization of capsaicin-sensitive visceral afferent systems

It has become clear that a number of neuropeptides are found in sensory nerves, some of which have been identified in visceral afferents. The best studied peptide is substance P, which has been localized in a population of capsaicin-sensitive visceral afferents. It has been established that there are a varied proportion of substance P-containing afferents in different visceral structures. In general, the peripheral termination of these nerves is around blood vessels. The central terminations of visceral afferents are in laminae I and V in the dorsal horn of the spinal cord. Substance P has been localized in these laminae and appears to be capsaicin-sensitive and therefore of sensory origin. Recently, substance K, which is derived from the same gene as substance P, has been found in visceral structures. Calcitonin gene-related peptide has been found in certain viscera to be contained in capsaicin-sensitive nerves. The contribution that other peptides make to visceral afferent innervation is not known.     

The quantitative morphological characteristics of the spinal neurons in the kitten developing under conditions of limited afferent input]

Golgi preparations of cervical part of the spinal cord were used to study sparely and densely branching neurons of lamina VII, sparely and densely branching neurons of lamina VIII and large densely branching motor neurons of lamina IX in 30-day kittens developing under the conditions of limited reticulospinal input. Limitation was induced by electrocoagulation of bulbar magnocellular nucleus and caudal reticular pontine nucleus performed at the 7th day. Computerized morphometry revealed that partial deafferentation affects the geometry in all studied cell types except densely branching neurons of lamina VIII. Adaptive nature of structural reorganization of spinal neurons and possible relationship between morphological properties and functional profile of cells are discussed.     

The stochastic properties of input spike trains control neuronal arithmetic

In the nervous system, the representation of signals is based predominantly on the rate and timing of neuronal discharges. In most everyday tasks, the brain has to carry out a variety of mathematical operations on the discharge patterns. Recent findings show that even single neurons are capable of performing basic arithmetic on the sequences of spikes. However, the interaction of the two spike trains, and thus the resulting arithmetic operation may be influenced by the stochastic properties of the interacting spike trains. If we represent the individual discharges as events of a random point process, then an arithmetical operation is given by the interaction of two point processes. Employing a probabilistic model based on detection of coincidence of random events and complementary computer simulations, we show that the point process statistics control the arithmetical operation being performed and, particularly, that it is possible to switch from subtraction to division solely by changing the distribution of the inter-event intervals of the processes. Consequences of the model for evaluation of binaural information in the auditory brainstem are demonstrated. The results accentuate the importance of the stochastic properties of neuronal discharge patterns for information processing in the brain; further studies related to neuronal arithmetic should therefore consider the statistics of the interacting spike trains.     

Various principles of the organization of preterminal and terminal branches of afferent conductors in neuropil of the snail dorsal ganglia

Character of ramifications in the preterminal and terminal axonal parts in the neuropil of the dorsal ganglia have been studied in 16 edible snails (Halix pomatia). The nervous tissue is impregnated with silver nitrate after Golgifast method. Serial sections are made in two projections: horizontal and vertical. The analysis of peculiarities of the spatial distribution of the afferent fibers (AF) demonstrates their several forms that are united into the following types: dominant, probable and transitional. Comparison of the edible snail AF with those in the higher vertebrata makes it possible to conclude that the character of ramification of their preterminal and terminal parts and principle of organizational connections of the AF with the postsynaptical structures are principally similar.     

Cortical modulations of the fine temporal structures of impulse trains in the dorsal lateral geniculate body in cats]

In response to a visual stimulation, "replicated triplets" of impulses may appear in many spike trains recorded from the cat dorsal lateral geniculate nucleus (dLGN). The number and the temporal structure of these triplets depend upon the general organization of the geniculate impulse trains. In this study, we show that a pharmacological blockade of the corticothalamic activity, obtained through microinjection of GABA into area 17, affects the replicated triplet production and leads to an increase in the dispersal of their structure. These results suggest that the corticothalamic pathway closely influences the fine temporal organization of the geniculate messages.     

Organization of the afferent input in the rabbit superior colliculus

The organization of the afferent input into the superior colliculus was investigated in unanesthetized curarized rabbits. The afferent signal reaches the rabbit superior colliculus via at least two groups of fibers with mean conduction velocities of 3 and 6 m/sec. The components C₁ and C₂ of the evoked potential reflect postsynaptic unit activity arising after the arrival of impulses along these groups of fibers. This is confirmed by investigation of the shape of the evoked potential after stimulation of different points of the afferent pathway, data on conduction velocities, and comparison of single unit activity with the phases of evoked potential. The presence of components of this potential with short latent periods is evidence of predominance of the direct retinotectal input in the rabbit, a fact which may be connected with the lissencephalic type of brain development.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 9, No. 3, pp. 281–289, May–June, 1977.     

Response of a pacemaker neuron model to stochastic pulse trains

 We investigated the response of a pacemaker neuron model to trains of inhibitory stochastic impulsive perturbations. The model captures the essential aspect of the dynamics of pacemaker neurons. Especially, the model reproduces linearization by stochastic pulse trains, that is, the disappearance of the paradoxical segments in which the output firing rate of pacemaker neurons increases with inhibition rate, as the coefficient of variation of the input pulse train increases. To study the response of the model to stochastic pulse trains, we use a Markov operator governing the phase transition. We show how linearization occurs based on the spectral analysis of the Markov operator. Moreover, using Lyapunov exponents, we show that variable inputs evoke reliable firing, even in situations where periodic stimulation with the same mean rate does not. Received: 30 April 2001 / Accepted in revised form: 19 September 2001     

Succession in the morphological organization in human postnatal ontogeny

Preserving morphological organization succession in the human postnatal ontogenesis is studied in the growth processes in 7-17 years old boys. Canonical variables are separated by canonical correlation method, which are those maximally correlated morphological structures relating to each other hierarchically: body--head, body trunk--limbs, brain--face. It is shown that morphological organization succession is provided by preserving the stable level of interdependence between morphological structures, which are under relatively independent genetical control. The stability of this interdependence in disturbed only during the "critical phase" of adolescent spurt, which is characterized by maximal rate of morphofunctional development. After this phase initial level of the interdependence is restored.     

Injury in relation to cell organization

When a part of a Nitella cell, A, is covered with water and the rest of the cell, B, is in contact with a toxic solution there is an escape of solutes at B. This is followed by the escape of solutes at A which causes the death of A. Water enters at A, flows along inside the cell, and escapes at B carrying solutes with it. When this is prevented by covering A with mineral oil the escape of solutes at A is delayed and the life of A is correspondingly prolonged. It is remarkable that this occurs in spite of the fact that the hydrostatic pressure inside the cell (turgor) drops from 6.4 atmospheres to zero. It would seem that A might not be affected by the death of B if the escape of solutes could be prevented.     

Chromatin organization in relation to the nuclear periphery

In the limited space of the nucleus, chromatin is organized in a dynamic and non-random manner. Three ways of chromatin organization are compaction, formation of loops and localization within the nucleus. To study chromatin localization it is most convenient to use the nuclear envelope as a fixed viewpoint. Peripheral chromatin has both been described as silent chromatin, interacting with the nuclear lamina, and active chromatin, interacting with nuclear pore proteins. Current data indicate that the nuclear envelope is a reader as well as a writer of chromatin state, and that its influence is not limited to the nuclear periphery.     

Role of afferent input in muscle atrophy.

It is well known that soleus muscle of rat atrophies following spaceflight or hindlimb suspension (Ohira et al., 1992). It is, further, reported that the electromyogram (EMG) of soleus muscle disappears immediately in response to unloading by exposure to actual micro-g environment (Kawano et al., 2002; Leterme and Falempin, 1998) and by hindlimb suspension of rats (Alford et al., 1987; Ohira et al., 2000). However, the EMG level is increased gradually to the control level following 7-10 days of continuous hindlimb suspension (Alford et al., 1987; Ohira, 2000), while muscle atrophy is progressing (Winiarski et al., 1987). We previously reported that reduction of the EMG level of rat soleus in response to actual micro-g environment, created by a parabolic flight of a jet airplane, was closely associated with a decrease of the afferent input recorded at the L5 segmental level of spinal cord (Kawano et al., 2002). However, it is still unclear how the EMG level of soleus muscle adapts to unloading condition. The current study was performed to investigate the responses of soleus EMG and both afferent and efferent neurogram at the L5 segmental level of spinal cord to acute (20 seconds) and chronic (14 days) unloading.