Somatic polyploidy in neurons of the gastropod molluscs. II. Dynamics of DNA synthesis in the process of postnatal growth of CNS neurons in Succineid snail

A study was made of the age dynamics of polyploidization and dynamics of DNA synthesis in neuron cell nuclei during the postnatal growth of the gastropod pulmonate snail Succinea lauta. According to cytophotometrical results, the degree of polyploidization in neuron nuclei increases from young to adult individuals, varying from 2c to 16,384c. In the visceral complex, the maximum and medium ploidy values of the neuron nuclei are higher by almost 4-8 times than those in cerebral and pedal ganglia. The medium level of ploidy in adult snails increases by 5.7 times in the visceral complex of ganglia and by 4.1-4.2 times in the pedal and cerebral ganglia. According to 3H-thymidine autoradiography, DNA synthesis in neuron nuclei occurs during the whole life of the snail. In young individuals the neurons have the highest activity of DNA synthesis--the index of labeled nuclei of neurons making in total 50.2%. In older age, a steady decrease in the index of labeled nuclei is observed--in total to 35.8% and 7.0% in small and large adult snails, respectively. The state of summer hibernation completely stops DNA syntheses in neurons, but emergency from hibernation is accompanied by restoration of DNA syntheses.     

Study of the hypothalamus of neonatally castrated rats by the karyometric method]

The sensitivity of different hypothalamic regions to the effect of androgens has been studied during the period of the brain sex differentiation. The castration of animals during the first week of life was shown to result in the marked increase of size of the neuron nuclei in the preoptic, suprachiasmatic, arcuate and ventromedial nuclei of the hypothalamus; the size of neuron nuclei in the dorsomedial nucleus suffered no changes. The dynamics of size of the cell nuclei was followed in different hypothalamic regions with respect to the time of castration.     

Cerebellar Nuclear Neurons Use Time and Rate Coding to Transmit Purkinje Neuron Pauses

Neurons of the cerebellar nuclei convey the final output of the cerebellum to their targets in various parts of the brain. Within the cerebellum their direct upstream connections originate from inhibitory Purkinje neurons. Purkinje neurons have a complex firing pattern of regular spikes interrupted by intermittent pauses of variable length. How can the cerebellar nucleus process this complex input pattern? In this modeling study, we investigate different forms of Purkinje neuron simple spike pause synchrony and its influence on candidate coding strategies in the cerebellar nuclei. That is, we investigate how different alignments of synchronous pauses in synthetic Purkinje neuron spike trains affect either time-locking or rate-changes in the downstream nuclei. We find that Purkinje neuron synchrony is mainly represented by changes in the firing rate of cerebellar nuclei neurons. Pause beginning synchronization produced a unique effect on nuclei neuron firing, while the effect of pause ending and pause overlapping synchronization could not be distinguished from each other. Pause beginning synchronization produced better time-locking of nuclear neurons for short length pauses. We also characterize the effect of pause length and spike jitter on the nuclear neuron firing. Additionally, we find that the rate of rebound responses in nuclear neurons after a synchronous pause is controlled by the firing rate of Purkinje neurons preceding it.     

Effect of prenatal emotional-pain stress on the status of interphase chromatin in neurons of the rat developing brain with various excitation of the nervous system

A short-term emotional-painful stress, experienced by pregnant rat females differing in threshold of excitability of their nervous system, was used to assess the state of interphase condensed chromatin and C-heterochromatin of neuron nuclei in developing brains of 16-17 day old embryos. To reveal relationships between the genetically determined excitability of rats and the state of interphase chromatin in their neuron nuclei a computer information system has been used that enabled us to classify the neuronal nuclei according to their specific DNA image cytometry features. The results indicate an obvious relationship between excitability of the nervous system and structural-functional state of the neuronal interphase chromatin.     

Androgen receptors in cranial nerve motor nuclei of male and female rats

This study compared AR proteins in four cranial nerve motor nuclei among male and female rats that were intact, gonadectomized, or gonadectomized and given TP by immunohistochemistry. AR-immunoreactive (ir) neurons were found, in descending order of abundance, in the nucleus ambiguus, hypoglossal nucleus, and the facial and trigeminal motor nuclei of both males and females of intact and gonadectomized plus TP rats. Virtually every neuron of the nucleus ambiguus was AR-ir. In contrast, AR-ir neurons were either restricted to a specific area of the hypoglossal nucleus, or randomly distributed in the facial and trigeminal motor nuclei. The predominant AR-ir site shifted from cell nuclei to the cytoplasm, depending upon the presence or absence of ligand. Sex differences in the amount and staining intensity of AR-ir neurons were discernable in all four motor nuclei of intact rats, and these differences were maintained in gonadectomized plus TP rats, with the exception of the nucleus ambiguus. The immunostaining results were complemented by results from AR binding studies. Cytosolic AR binding values for the hypoglossal and facial motor nuclei of females were only approximately 50% of those of males despite the absence of a sex difference in neuron number. These results indicate that intrinsic sex differences in AR levels and androgenic regulation of AR exist in cranial nerve motor nuclei, and that there are differences in the abundance and distribution pattern of AR responsive neurons in cranial nerve motor nuclei. These results are consistent with the idea that sex differences in AR could account for sex differences observed in nerve regeneration and neuron loss following cranial nerve injury.     

Quantitative study of cellular and volumetric growth of magnocellular and laminar auditory nuclei in developing chick brainstem

Development of the second and third order auditory nuclei—nucleus magnoscellularis (NM) and nucleus laminaris (NL) respectively—was studied using Nissl stained serial sections from brain specimens between 8 day of incubation and posthatch day 1, at every two day interval. Reconstruction of these nuclei from three incubation ages showed progressive growth of both nuclei in a rostrocaudal direction. The volume, total neuron, dead cell and glial cell numbers were estimated using stereological quantitation methods. Both nuclei, while undergoing an overall gradual increase in volume up to 20 days registered a transient drop in volume; earlier for NM at 10 days and later for NL at 18 days. From day 20 the two nuclei showed accelerated growth in volume. The total neuron count rapidly declined up to 12 days with 43% loss of neurons in NM followed by a rise and later stabilization within a certain range. The NL, however, showed a continuous fall in neuron numbers throughout the incubation period with 20% cell loss by day 12 and an overall loss of 52%. Cell death in both nuclei was maximal at 16 days and spanned the entire period of incubation. Glia showed a biphasic increase with peak at 14 days for both NM and NL followed by a subsequent rise at day 20 for both nuclei. These data would help in planning further experimental studies of auditory manipulation.     

Study of some neurohistologic objects by the method of scanning microscopy]

With the aid of a scanning measuring microscope (R. E. Bykov et al., 1972) different biological microobjects were measured in particular the nuclei of neurons and gliocytes at differnt levels of the spinal cord under normal and experimental conditions. The nuclei of the rabbit hypothalamus were stimulated by graded electrical current in order to induce neurogenic visceral dystrophies. Investigation of the square surfaces of cross sections of the neuron and gliocyte nuclie in different terms permitted establishment of progressing diminishing of the size of the square surface of the neuron nuclei against the background of a relatively steady state of steady state of wquare surfaces of the cross section of the nuclei of the adjacent glial cells. The obtained data are of interest not only for studying transneuronal changes in disturbed trophical function of the nervous system, but may be taken into consideration in clinical practice when elaborationg prerequistites for purposeful neurovegetative blocade in neurogenic dystrophies of the central genesis.     

Sexually dimorphic neuron number in lumbosacral dorsal root ganglia of the rat: Development and steroid regulation

Rats possess a sexually dimorphic neuromuscular system that controls penile reflexes critical for copulation. This system includes two motor nuclei in the lumbar cord and their target musculature in the perineum. The spinal nucleus of the bulbocavernosus (SNB) and the dorsolateral nucleus (DLN) motoneuron populations and their target perineal muscles are much larger in males than in females. The sex difference in motoneuron number develops via androgen-regulated differential cell death during the perinatal period; androgen also regulates retention of the target muscles. The developmental pattern and steroid sensitivity of peripheral afferents to the SNB/DLN motor nuclei were previously unknown. In order to characterize the peripheral sensory component of the dimorphic SNB/DLN system, the neurons of the relevant dorsal root ganglia (DRGs) were quantified in terms of number, size, and androgen sensitivity at various perinatal ages. DRG neuron number is greatest prenatally, then decreases in both sexes after birth; the timing and pattern of neuron number development are similar to those seen in the SNB and DLN. Postnatally, males have more DRG neurons than females, as a result of greater neuron death in the DRGs of females. Females treated with testosterone propionate during the perinatal period exhibit masculine development of DRG neuron number. Thus, the normal development of DRG neuron number parallels that of the SNB/DLN motor nuclei and target muscles in pattern and timing, is sexually dimorphic, and is regulated by androgen. © 1993 John Wiley & Sons, Inc.     

RIBONUCLEASE ACTIVITIES IN VARIOUS CLASSES OF NUCLEI FROM BOVINE CEREBRUM

Abstract— Nuclei of adult bovine cerebrum were separated by dissection of grey matter from white matter and discontinuous sucrose gradient centrifugation, into neuron, astrocyte-enriched and oligodendrocyte fractions. The activities of alkaline and acidic RNAses were determined in the different nuclei types. The acidic and alkaline RNAse activities of the neuronal nuclei were much higher than those of the glial nuclei. In each type of nuclei the acidic RNAse activity was lower than the measured alkaline RNAse activity.     

Non-traditional large neurons in the granular layer of the cerebellar cortex

The granular layer of the cerebellar cortex is composed of two groups of neurons, the granule neurons and the so-called large neurons. These latter include the neuron of Golgi and a number of other, lesser known neuron types, generically indicated as non-traditional large neurons. In the last few years, owing to the development of improved histological and histochemical techniques for studying morphological and chemical features of these neurons, some non-traditional large neurons have been morphologically well characterized, namely the neuron of Lugaro, the synarmotic neuron, the unipolar brush neuron, the candelabrum neuron and the perivascular neuron. Some types of non-traditional large neurons may be involved in the modulation of cortical intrinsic circuits, establishing connections among neurons distributed throughout the cortex, and acting as inhibitory interneurons (i.e., Lugaro and candelabrum neurons) or as excitatory ones (i.e., unipolar brush neuron). On the other hand, the synarmotic neuron could be involved in extrinsic circuits, projecting to deep cerebellar nuclei or to another cortex regions in the same or in a different folium. Finally, the perivascular neuron may intervene in the intrinsic regulation of the cortex microcirculation.     

Addition of song-related neurons in swamp sparrows coincides with memorization, not production, of learned songs

During song learning in birds, neurons are added to some song nuclei and lost from others. Previous studies have been unable to distinguish whether these neural changes are uniquely associated with memorizing a song model (sensory acquisition) or vocal practice (sensorimotor learning). In this study we measured changes in neuron number within song nuclei of swamp sparrows, a species in which the two phases of song learning are nonoverlapping. Male swamp sparrows were collected as hatchlings and tape-tutored from approximately 22 to 62 days of age. Swamp sparrows memorize about 60% of their song material during this period, but do not begin practicing this learned material until approximately 275 days of age. Birds were sacrificed at 23, 41, 61, 71, 274, or 340 days of age. During sensory acquisition, neuron number increased drastically in both the caudal nucleus of the ventral hyperstriatum (HVc) and Area X. The period of sensorimotor learning was not associated with any further changes in neuron number within these regions. We were unable to detect any significant changes in neuron number within the magnocellular nucleus of the neostriatum or the robust nucleus of the archistriatum during either stage of song learning. These results raise the possibility that ongoing addition of HVc and Area X neurons may encourage, and thereby temporally restrict, song acquisition.     

Somatic polyploidy in neurons of the gastropod mollusca. III. Mitosis and endomitosis in the postnatal development of neurons in the Succinea snail central nervous system

General morphology of chromatin, the number of chromosomes and chromocenters in normal condition and at the increase of bivalent cation (Ca2+, Mg2+) concentration were studied with the purpose to reveal mechanisms of polyploidization of neuron nuclei in the snail Succinea lauta (Gastropoda, Pulmonata). The morphology of nuclei was studied on squashed preparations. Normal diploid mitoses are described in the cerebral ganglia. A possibility is supposed that part of neurons or neuroblasts in the central nervous system (CNS) of succineid snail may divide mitotically. It has been shown that the basic mechanism of neuron postnatal growth is endomitotic polyploidization of nuclei. The transition from ordinary mitosis to polyploid cycles occurs via restitutional (polyploidizing) mitosis (4c2n-->4c4n). The next endocycles are carried out by means of classic endomitosis up to reaching the highest ploidy levels--4096n--16,384n. The study of general morphology of chromatin and chromocenters at normal condition and at artificial compactization enabled us to exclude any probability of polyteny in the CNS of lauta.     

The cochlear nuclei in Colubrid and boid snakes: A qualitative and quantitative study

The cochlear nuclear complex was investigated in snakes of the advanced family Colubridae and the primitive family Boidae. This study was undertaken in an attempt to correlate the elaboration of the cochlear nuclei with behavior and phylogeny and to elucidate the relative effects of these factors on the evolution of the cochlear nuclear complex. Fifty-five brains, of 14 colubrid species and three boid species, were examined to collect data on neuron diameter, neuron population, nuclear volume, and neuronal density of the cochlear nuclear complex and of its component nuclei (nucleus angularis and nucleus magnocellularis). Intraspecific and interspecific comparisons of the data were performed by nested analysis of variance. The species were grouped by cluster analysis and ranked on the basis of the morphometric parameters. Interspecific comparisons indicate that the elaboration of the cochlear nuclei is related, first, to prey preference and, second, to habitat preference. The most elaborate cochlear nuclei occur in species with a preference for vertebrate prey. Burrowing species that prey on vertebrates exhibit the highest degree of elaboration of the cochlear nuclei. In some burrowing species, the nucleus magnocellularis is differentiated into medial and lateral subdivisions. The primitive boid snakes show greater elaboration of the cochlear nuclei than do most of the advanced colubrid snakes. The elaboration of the cochlear nuclear complex in snakes seems to reflect the influence of both behavior and phylogeny. Further investigation of primitive snakes of varied behaviors is needed to establish more clearly the influence of phylogeny on the evolution of the cochlear nuclear complex.     

A multivariate phenetic approach to neuronal nuclei resemblances across species, with examples from three regions of cerebral cortex of a mammal, a bird and a reptile

In order to test the assumed homology between three examples of cortical cerebral architecture corresponding to three species of mammals, birds and reptiles respectively, a method arising from the quantitative standpoint of the concept of homology has been utilized. For this purpose, data corresponding to randomly selected neurons were analysed by means of multivariate techniques such as principal component, principal co-ordinates and hierarchical cluster analyses since on each neuron a set of nineteen variables, chosen as a definition of its dendritic morphology, was measured. This method has made it possible both to discern the neuron forms which are responsible for the discrimination between the three cortical nuclei studied and to show by setting up a discriminant index, the degree of overall similarity between such nuclei. These two findings provide evidence against both the fibrous connection criterion with which some modern neurobiologists ascertain homologs and the categorical concept of homology.     

Degeneration of the laminated corpuscles (of Vater--Pacini) following colchicine application to a nerve]

Laminated pacinian corpuscles from the cat mesentery have been studied morphologically and morphometrically after nerve section and colchicine application to the nerve and the results obtained are represented. Similar interventions in the nerve produce changes in the receptors resembling those of wallerian type degeneration, degeneration rate after sectioning being higher than after colchicine application. At early stages after colchicine application the internal cone and its nuclei increase in size. The data obtained suggest the nuclei of the internal cone to be under neurotrophic control of the sensory neuron that might be realized via axoplasmic transport of substances.     

中华绒螯蟹神经细胞和胶质细胞的光镜及电镜观察

中华绒螯蟹神经节存在神经细胞和胶质细胞两类细胞。神经细胞膜为３层,细胞质由内质网和核蛋白体的聚合体的所构成的尼氏体,高尔基体,线粒体,液泡等细胞器组成,核膜双层,核仁明显,胶质细胞内含有似神经细胞的细胞器结构,根据细胞核的形态及核内染色质的分布情况,可把胶质细胞分成３类：星形胶质细胞核最大,卵圆形,少突胶质细胞核较小,圆形;小胶质细胞核最小,呈三角形或卵圆形,神经细胞的数量与附肢的生理活动强弱有一     

Dichotomous organization of the external globus pallidus

Different striatal projection neurons are the origin of?a?dual organization essential for basal ganglia function. We have defined an analogous division of labor in the external globus pallidus (GPe) of Parkinsonian rats, showing that the distinct temporal activities of two populations of GPe neuron in?vivo are?underpinned by distinct molecular profiles and axonal connectivities. A first population of prototypic GABAergic GPe neurons fire antiphase to subthalamic nucleus (STN) neurons, often express parvalbumin, and target downstream basal ganglia nuclei, including STN. In contrast, a second population (arkypallidal neurons) fire in-phase with STN neurons, express preproenkephalin, and only innervate the striatum. This novel cell type provides the largest extrinsic GABAergic innervation of striatum, targeting both projection neurons and interneurons. We conclude that GPe exhibits several core components of?a dichotomous organization as fundamental as?that in striatum. Thus, two populations of GPe neuron?together orchestrate activities across all basal ganglia nuclei in a cell-type-specific manner.     

Objective criteria for determining the degree of radiation injury of nerve cells in a cerebral syndrome

The automatized morphometric technique was used to estimate the degree of injury to spinal nervous cells of rats exposed to 360 Gy radiation. It was shown that the compression coefficient and the volume of neuron nuclei considerably diminished as the CNS-syndrome developed, and the geometrical dimensions of the nervous cells themselves underwent phase changes.     

Effect of neonatal androgenization on the septal neurons of the brain in female rats in early postnatal ontogeny

Newborn female rats were androgenized, and the reaction of neurons of brain septum on excessive quantity of exogenous androgens, introduced during so-called "crucial" period of formation of centers of gonadotropic regulation of sexual cycles, has been studied in 3, 5, 7, 10, 20, 30, and 60 days old animals. Morphometry of brain septum cell nuclei revealed that most neuron nuclei shrink after androgenization. Monoamine content was significantly increased in septum nuclei of experimental animals. Neonatal androgenization led to the increased capacity of septal complex neurons to bind 3H-estradiol and to the decreased 3H-testosterone binding. The data obtained suggest that the brain septum neurons of female rats depend on sex steroids, particularly during "crucial" period of development.     

Kismet Positively Regulates Glutamate Receptor Localization and Synaptic Transmission at the Drosophila Neuromuscular Junction

The Drosophila neuromuscular junction (NMJ) is a glutamatergic synapse that is structurally and functionally similar to mammalian glutamatergic synapses. These synapses can, as a result of changes in activity, alter the strength of their connections via processes that require chromatin remodeling and changes in gene expression. The chromodomain helicase DNA binding (CHD) protein, Kismet (Kis), is expressed in both motor neuron nuclei and postsynaptic muscle nuclei of the Drosophila larvae. Here, we show that Kis is important for motor neuron synaptic morphology, the localization and clustering of postsynaptic glutamate receptors, larval motor behavior, and synaptic transmission. Our data suggest that Kis is part of the machinery that modulates the development and function of the NMJ. Kis is the homolog to human CHD7, which is mutated in CHARGE syndrome. Thus, our data suggest novel avenues of investigation for synaptic defects associated with CHARGE syndrome.