prospero is expressed in neuronal precursors and encodes a nuclear protein that is involved in the control of axonal outgrowth in Drosophila.

Neurogenesis in Drosophila begins with the formation of neuronal precursors, which give rise to neurons of individual identity. To find out whether there are genes that are expressed in most or all neuronal precursors and are involved in controlling particular aspects of neuronal differentiation, we used the enhancer-trap method to screen for such "neuronal precursor genes." One gene of this group is prospero. Our mutant analysis indicates that prospero regulates other neuronal precursor genes and is essential for the axonal outgrowth and pathfinding of numerous central and peripheral neurons. prospero encodes a large nuclear protein with multiple homopolymeric amino acid stretches and is expressed in neuronal precursors early during their formation. It is probably generally required for proper neuronal differentiation.     

Effects of high-fat diet on insulin receptor function in rat hippocampus and the level of neuronal corticosterone

AimChronic consumption of a high-fat (HF) diet contributes to peripheral insulin resistance and elevated plasma corticosterone. However, the effect of HF consumption on the neurofunctional insulin receptors and neuronal corticosterone level is unclear. We tested the hypothesis that HF consumption can lead to peripheral insulin resistance, elevated neuronal corticosterone, and impaired neuronal responses to insulin.Main methodsMale Wistar rats were fed with normal diet or HF diet for 4, 8 or 12 weeks. At the end of each dietary period, plasma was collected for investigating peripheral insulin resistance parameters and corticosterone. Brains were then rapidly removed for studying the function of neuronal insulin receptors (IRs) by extracellular recording in CA1 hippocampus, neuronal IR signaling by immunoblot technique and neuronal corticosterone.Key findingsElevated plasma corticosterone level was initially seen in 4-week HF-fed rats. Peripheral insulin resistance developed at 8-week HF-fed rats. However, the elevated neuronal corticosterone level was found at 12-week HF consumption. The neuronal IR response demonstrated by insulin-mediated long-term depression in CA1 hippocampus was diminished in 12-week HF-fed rats. The phosphorylation levels of neuronal IR, IR substrate 1 and Akt/PKB were decreased in 12-week HF-fed rats with no change in these proteins. There was a correlation among peripheral insulin resistance, neuronal stress (elevated neuronal corticosterone), and neuronal insulin resistance in HF group.SignificanceOur findings suggest that HF consumption can lead to the elevation of corticosterone and peripheral insulin resistance, which could contribute to neuronal insulin resistance and neuronal stress.     

The ultrastructure of the central nervous system neurons and synapses in the edible snail under a high concentration of potassium ions]

The morphometric and electron microscopic results on neuronal and synaptic ultrastructure of central nervous system of Helix pomatia snail, incubated in vitro in media with high potassium ion concentration are represented in the present paper. The activation of glial cells is revealed with its close attachment to neurons. The energization of neuronal mitochondria and signs of cytoplasmatic oedema are clearly visible. The penetration of glial endings in the large neuronal branches and the synaptic vesicles confluence in neuronal endings are found.     

Parvalbumin-immunoreactive structures in the hippocampus of the human adult

Summary Parvalbumin-immunoreactive structures in the fascia dentata and Ammon's horn of the adult human brain were studied using the avidin-biotin-peroxidase technique. Thin fibres (probably axons) were found to form dense networks throughout the cellular layers. Parvalbumin immunoreactivity is observed in even distal portions of nerve cell processes. The excellent quality of the immunoreaction renders the distinction of a large number of possible neuronal types. All parvalbumin-immunoreactive neurons belong to the class of non-granule cells in the fascia dentata and non-pyramidal neurons in Ammon's horn. The fascia dentata harbours four types of neurons in the molecular layer, one type within the granule cell layer and four types in the plexi-form layer. The frequently described basket cells are contained in the group of immunoreactive non-granule cells in the plexiform layer. In field CA4 two neuronal types can be distinguished. Field CA3 reveals a slender cell type in the stratum radiatum, three types in the pyramidal cell layer and three types in the stratum oriens. In field CA2 three neuronal types can be differentiated in the stratum pyramidale. The extended field CA1 is endowed with two types of nerve cells within the stratum moleculare, two types in the stratum radiatum, five neuronal types in the stratum pyramidale, and one spindle-shaped type in the stratum oriens. The morphological features of parvalbumin-immunoreactive neuronal types in the adult human brain are compared with those found in Golgi-studies of mostly young animals or in labelling experiments. This study serves as a basis for further analyzes involving specific diseases such as Alzheimer's disease or epilepsy, where it needs to be clarified to which extent certain neuronal types are afflicted.     

Enhanced neuronal expression in reaggregating cells of mouse cerebellum cultured in the presence of poly-L-lysine

Both neuronal and glial cell differentiation occur in reaggregating cell cultures of mouse cerebellums, as evidenced by electron microscopy and immunofluorescence to the glial fibrillary acidic protein (GFA). However, after the initial 10 days in culture a process occurs in which the neuronal cells degenerate while glial cells predominate. We have found that when poly-l-lysine is added to the culture medium either for the entire culture period or during the latter days of culture, i.e., Days 4 through 10, the neuronal character is stabilized, as evidenced by acetylcholin-esterase levels and electron microscopy, while the gliosis is inhibited. Culturing reaggregating cells in poly-l-lysine containing medium from Days 0 through 4 has no inhibitory influence on the gliosis observed on Day 10. Cerebellar cells cultured as monolayers on plastic surfaces coated with poly-l-lysine express an intense immunofluoresence with antisera to GFA as do cells grown on uncoated flasks. The data suggest that poly-l-lysine in reaggregating cell cultures stabilizes the neuronal cells by some unknown mechanism. It is postulated that a stable neuronal population reduces the trend toward gliosis in cerebellar aggregates.     

Selective self-synchronization of pulses in neuronal networks of the visual system

In the present study we have checked the hypothesis that the degree of pulse synchrony in neuronal pools is determined by the level of excitation of the neuronal network or its loci and that this relationship does not depend on the factor that causes the excitation. Pulse reactions of neurons in pools (2–4 cells) of cat lateral geniculate nucleus and visual cortex were registered. Neurons were excited using either visual stimuli or glutamic acid microinjections into neuronal pools. The increase of neural pool excitation level (No) regardless of the type of stimulus was shown to increase the pulse synchrony (Ns), with a correlation coefficient of 0.716 ± 0.217. One may suppose that the level of neuronal network excitation “governs” the synchrony of pulses generated by the network, i.e., neuronal networks function in compliance with the principle of self-synchronization.     

Expression of neuronal and glial markers in so-called oligodendroglial tumors induced by transplacental administration of ethyl-nitrosourea in the rat.

A series of 18 tumors with histological features of oligodendrogliomas, induced in the rat by means of transplacental ethyl-nitrosourea administration were studied for immunohistochemical demonstration of neuronal (synaptophysin and neurofilament protein) and glial (gliofibrillar acidic protein and vimentin) markers. Most of the tumors showed cells with strong positivity to synaptophysin and to a lesser degree, to neurofilament protein, suggesting the neuronal character of these neoplasms. In 10 tumors, cells with strong positivity to vimentin were found, and in three cases, tumoral cells expressed gliofibrillar acidic protein. The observation that ENU-induced oligodendroglial tumors express neuronal and, to a minor degree, glial markers, suggests their interpretation as primitive neuroectodermal tumors with clear neuronal differentiation.     

Development of neuron-capillary interrelationships in the nuclei of the anterior portion of the human hypothalamus during ontogenesis

Three periods in the formation of the spatial arrangement of the neuronal nuclei have been stated: 1) from the prenatal period, infancy including--pronounced decrease in the density of the neuronal cells arrangement; 2) from the childhood up to adolescence--relative stabilization in the hypothalamic cellular composition; 3) mature and old age--secondary decrease in the dencity of the neuronal cells arrangement. Certain peculiarities in the nuclear capillary composition and in their neuronal-capillary relationships have been revealed: during the prenatal ontogenesis, the dencity of the neuronal cells arrangement decreases and their size increases that is followed by decrease in their capillary loops. In postnatal ontogenesis no proportional relationship between the dencity of neuronal cells arrangement and that of capillary network in the nuclei of the anterior hypothalamus was noted.     

Role of melatonin in the dynamics of acute spinal cord injury in rats

Melatonin is well-documented to have the ability of reducing nerve inflammation and scavenging free radicals. However, the therapeutic effect of melatonin on spinal cord injury has not been fully described. In this study, we assessed the effect of melatonin on T9 spinal cord injury established by Allen method in rats. Melatonin deficiency significantly delayed the recovery of sensory and motor functions in SCI rats. Treatment with melatonin significantly alleviated neuronal apoptosis and accelerated the recovery of spinal cord function. These results suggest that melatonin is effective to ameliorate spinal cord injury through inhibition of neuronal apoptosis and promotion of neuronal repair.     

Atypical localization of myenteric neurons in the opossum lower esophageal sphincter

This study investigated sphincter-body differences in neuronal density and morphometry between the esophageal sphincter and body with a view to determining whether previously reported differences are authentic. The anatomical limits of the opossum lower esophageal sphincter were correlated with its physiological behavior by manometric demarcation. Following this, peeled whole mounts and paraffin and cryosections were used to study the morphology and morphometry of the esophageal myenteric plexus. Thirty animals were used and seven quantitated. The plexus of the esophageal body was located as usual in a plane between the longitudinal and circular muscle, which coincided with the plane of cleavage when these muscle layers were peeled apart for studying the plexus in whole mounts. In contrast, the plexus was located in several planes in the lower esophageal sphincter, which had no cleavage plane. Therefore, peeling the sphincter removes neurons and yields falsely low counts, making peel preparations of this region unsuitable for neuronal quantitation. In paraffin sections, the neuron density in the esophageal body 7 cm above the sphincter was 6,353 +/- 850/cm2, but decreased significantly to 2,254 +/- 353/cm2 at the 1-cm segment. In the lower esophageal sphincter, the neuronal count increased again to 8,530 +/- 1,606/cm2. Flash-frozen cryosections, which produced neuronal morphology similar to the in vivo condition, showed that there was no difference in neuronal size between esophageal body and sphincter. These studies show that atypical myenteric plexus localization causes spuriously low neuronal counts reported in the lower esophageal sphincter and that reported neuronal size differences are technique-dependent.     

Convergence of Signals and Reorganization of Neuronal Activity in a Model of Neuronal Network and in Striatum of the Monkey Brain

To elucidate principles of neuronal organization providing preservation of informational content of converging impulse flows in afferent impulsation of neurons, a comparison is performed of results obtained in the previously carried out experiments on a model of neuronal network and in a study of correlates of behavior in the neuronal network of the monkey brain neostriatum (putamen). This comparison has shown that responses of the neuronal network model to different ratio of input impulse flows and changes of the neostriatal neuronal activity, which accompany different behavioral actions, are seen the most clearly in reorganization of composition of the most active neurons. Each combination of input signals and each behavioral action of the animal correspond to a non-repeated mosaic of neuronal activity. The data obtained indicate that the neuronal network, both real and in the simplest model variant, is able to transform the converging input signals into the mosaic equivalent to their entire combination and thereby to transmit the result of generalization of the input signals of the network to the innervated brain structures.     

Recent advances in the study of electroreception.

Recent studies on electroreception in fish have focused on the structure and function of recurrent descending pathways, efference copy mechanisms, and multiple neuronal maps involved in the processing of sensory information. Studies on a neuronal oscillator have revealed that different neuronal inputs modulate the pattern of oscillations to produce different forms of behavioral output.     

Quantitative and morphometric parameters determining the development of the supraoptic nucleus in the albino rat

The principal part of the supraoptic nucleus (SON) of the rat presents specific developmental factors. The parameters selected for their evaluation were volume of the SON, neuronal number and neuronal density. White Wistar rats of the age of 18, 19, 20, 22 and 23 intrauterine days, 15 days and 1, 3, 6, 12, 18 and 30 months were chosen for this study. The rat brains were fixed, cut into 10-micron-thick sections and stained with hematoxylin-eosin. The different measurements were carried out with a semiautomatic IBAS I image analyzer. In all stages of the rat life, an increase in volume and a decrease in neuronal density per surface unit could be observed, but there was a difference in the dynamics of these changes depending on the stage in which the parameters were determined. There were two periods in the life of the rat in which neuronal death was very significant. The first was between the embryonic and juvenile stage and the second between the adult and senile stage. The increase in the volume influences predominantly the value of neuronal density.     

A Computational Model for the Loss of Neuronal Organization in Microcolumns

A population of neurons in the cerebral cortex of humans and other mammals organize themselves into vertical microcolumns perpendicular to the pial surface. Anatomical changes to these microcolumns have been correlated with neurological diseases and normal aging; in particular, in area 46 of the rhesus monkey brain, the strength of microcolumns was shown to decrease with age. These changes can be caused by alterations in the spatial distribution of the neurons in microcolumns and/or neuronal loss. Using a three-dimensional computational model of neuronal arrangements derived from thin tissue sections and validated in brain tissue from rhesus monkeys, we show that neuronal loss is inconsistent with the findings in aged individuals. In contrast, a model of simple random neuronal displacements, constrained in magnitude by restorative harmonic forces, is consistent with observed changes and provides mechanistic insights into the age-induced loss of microcolumnar structure. Connection of the model to normal aging and disease are discussed.     

A Computational Model for the Loss of Neuronal Organization in Microcolumns

A population of neurons in the cerebral cortex of humans and other mammals organize themselves into vertical microcolumns perpendicular to the pial surface. Anatomical changes to these microcolumns have been correlated with neurological diseases and normal aging; in particular, in area 46 of the rhesus monkey brain, the strength of microcolumns was shown to decrease with age. These changes can be caused by alterations in the spatial distribution of the neurons in microcolumns and/or neuronal loss. Using a three-dimensional computational model of neuronal arrangements derived from thin tissue sections and validated in brain tissue from rhesus monkeys, we show that neuronal loss is inconsistent with the findings in aged individuals. In contrast, a model of simple random neuronal displacements, constrained in magnitude by restorative harmonic forces, is consistent with observed changes and provides mechanistic insights into the age-induced loss of microcolumnar structure. Connection of the model to normal aging and disease are discussed.     

Role of blood vessels in the neuronal migration

The proper development and functioning of the vertebrate brain depends on the correct positioning of neuronal precursors which is achieved by the widespread and far-ranging migration of cells from their birthplaces. The vast majority of neuronal precursors use cellular substrates for their migration. Until very recently, it was assumed that these cellular substrates were either glial (glia-mediated or gliophilic migration) or neuronal (neuron-mediated or neurophilic migration) in nature. The widely studied examples of gliophilic and neurophilic migrations in the developing brain are displacement of neuronal precursors along the processes of radial glia in the developing cortex and migration of neurons expressing gonadotropin-releasing hormone (GnRH) along the vomeronasal axons, respectively. Recent data indicate, however, that neuronal precursors might also use blood vessels as a physical substrate for their migration. The vasculature-guided (vasophilic) migration of neuronal precursors has been observed not only under normal conditions, in the healthy brain, but also following strokes. The purpose of this review is to highlight emerging principles and delineate putative mechanisms of vasculature-guided neuronal migration under both normal and pathological conditions.     

Spike activity of neurons of the ventromedial hypothalamus of the rat during stress

In fixed Wistar line rats, neuronal activity of the ventromedial hypothalamus was studied in conditions of acute emotional stress elicited by electric stimulation of the ventromedial hypothalamus stochastically alternating with electrocutaneous stimuli. Distinctions were revealed in neuronal activity of the animals with different stress resistance. The pattern of neuronal impulse activity proved to be the most informative one.