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Neurons and glial cells were studied by computerized morphometry in segments of the ventral and dorsal areas of the compact zone of the substantia nigra (CZSN) of the brain in autopsy material obtained from six men and three women aged 52–87 years. Neuron body and nuclear sizes were found to be greater in segments of the ventral area of the CZSN than in segments of the dorsal area. Neuron and glial cell densities in the ventrolateral segment were higher than in segments of the dorsal area. The glial index in the ventromedial segment was lower than in segments of the dorsal area. These morphometric differences between CZSN segments need to be considered for assessment of morphological changes in the substantia nigra associated with both age-related involution and pathological processes.

The aim of the present work was to undertake a comparative study of the effects of prenatal alcoholization of the histological characteristics of neurons in the frontal cortex of the brains of rats of different ages. Experiments were performed on 175 mongrel white rats – the offspring of 25 females given 15% ethanol as drinking solution throughout pregnancy. The cerebral cortex was studied on postnatal days 2–90 using histological, histochemical, and morphometric methods. An increase (on days 2 and 5) followed by a decrease (on days 10 and 90) was seen in cortical thickness, with a decrease in neuron body size (on days 20–90), a decrease in the number of neurons in cortical layer V, a decrease in the number of normochromic cells, and increases in the numbers of hyperchromic shrunken neurons and ghost cells throughout the study period. Antenatal alcoholization in rats induced various histological changes in the frontal cortex, which were long-lasting and progressive during postnatal ontogeny.

The effects of rhythmic light stimulation on the postnatal development of the visual system were studied in relation to the formation of Meynert neurons in field 17 and the posteromedial area of the lateral suprasylvian sulcus (PMLS) in kittens reared with exposure to flashing light (frequency 15 Hz). Neuron body cross-sectional area and cytochrome oxidase (CO) activity levels were measured in the visual cortex of control (n = 6) and stimulated (n = 6) animals. Increases in the level of CO activity were seen in Meynert cells in field 17 and the PMLS area, by about 37%. There was also a decrease in the cross-sectional area of the bodies of Meynert neurons located in the PMLS, by 20% compared with normal. The existence of functional impairments of the Y conducting channel in stimulated animals and the possibility that binocular vision is suppressed are discussed.

In gypsy moth caterpillars exposed to a temperature of 35°C (for 1, 12 and 24 h and caterpillars that were exposed to elevated temperature for 12 h and were allowed to recover for 12 h at 23°C), changes in the brain protein profiles and morphometric characteristics of A1' medial and L2 lateral protocerebral neurosecretory neurons were analyzed. In all groups, protein bands with a molecular mass corresponding to that of members of heat-shock protein families were detected, indicating that acute exposure to this temperature likely induced the synthesis of HSP. Increased morphometric parameters of A1' neurons and the large amount of neurosecretory material in the neuron body implicate that the temperature of 35°C is not in the temperature range that exerts stimulatory effects on growth and survival. Changes in the morphometric characteristics of L2 neurosecretory neurons from the lateral part of the protocerebrum, and retention of neurosecretory material in their cytoplasm indicate a low level of secretion. Projekat ministarstva br. 173027

The aim of this paper is to investigate, by means of a numerical simulation, the effect of the half-life of cytoskeletal elements (CEs) on superposition of several waves representing concentrations of running, pausing, and off-track anterograde and retrograde CE populations. The waves can be induced by simultaneous microinjections of radiolabeled CEs in different locations in the vicinity of a neuron body; alternatively, the waves can be induced by microinjecting CEs at the same location several times, with a time interval between the injections. Since the waves spread out as they propagate downstream, unless their amplitude decreases too fast, they eventually superimpose. As a result of superposition and merging of several waves, for the case with a large half-life of CEs, a single wave is formed. For the case with a small half-life the waves vanish before they have enough time to merge.

Istituto di Scienze Fisiologiche, Universita` di Urbino, I-61029 Urbino, ItalyABSTRACTChanges in the number of satellite cells in neuron body sheaths indorsal root ganglia (DRGs) were studied from 1 to 5 months of age in controland in vitamin E-deficient rats; furthermore, the satellite cell proliferationrate was detected in the same groups of animals with immunohistochemis-try for 5-bromo-28-deoxyuridine (BrdU).ThenumberofsatellitecellsinsheathsofDRGneuronsincreasedintheperiod of life considered both in control and in vitamin E-deficient rats.Satellite cell proliferation was observed in both groups, but its rate wasfound to be higher in vitamin E-deficient rats.The results obtained in control rats confirm that mitotic ability isretained by satellite cells in adulthood and show that at least some ofnewborn satellite cells add to the pre-existing population.The results obtained in vitamin E-deficient rats suggest that a fasterturnover in satellite cell population takes place in these animals andsupport the idea that vitamin E could be an exogenous factor controlling cellproliferation.Anat Rec 256:109–115, 1999.

A basic neural-processing unit consists of a processing element (a neuron) and some connection weights (synapses). In a conventional linear-synapse model, which is the most widely used in the literature, the internal parameters of the neuron (stored as synaptic weight values) are multiplied by the inputs, and the corresponding weighted sum of the inputs constitutes the total input of the neuron body. This total input normally passes through a saturating (sigmoid) output function to provide the overall output of the neuron. The network learns by being exposed to sets of inputs (as training cases) while subjected to a process of gradual change in the weights as governed by a training algorithm. The training process tries to reduce the error observed at the output, namely the difference between the desired output values and the currently-existing ones.

Rall's idealized model of a dendritic tree is sufficiently simple so that an RCG cable analysis is feasible. When numerical values are substituted, further simplification occurs because it is assumed that the width of a postsynaptic potential (PSP) is the same as the shunt C/G time constant, 4 ms. The calculation shows that if a PSP having a peak amplitude of 100 mV is launched at the extreme end of the tree, it will arrive at the neuron body having a peak amplitude of 0.4625 mV and a width of 7.5 ms. The net stimulus arriving at the neuron body can be easily approximated, no matter how complex the set of input conditions, if dendritic potentials are replaced by their equivalent rectangular pulses.

UsingRana ridibunda Pall, total retinal preparations made by the Gross-Bilshovsky-Lavrentyev method the author investigated quantitative characteristics of the ganglionic layer neurons: dimensions of cell, nucleus, and dendrite field; number of dendrites leaving the neuron body, and number of arborization points; total length of dendrites, and distribution of their terminals in the internal synaptic layer, and others. Three hundred neurons of 28 frogs have been investigated. On the basis of morphometric analysis neurons are classified into five types that differ from each other by dimensions of perikaryon, dimensions and shape of dendrite field, and character of dendrite ramification. Dimensions of bodies and dendrite trees of all the five neuron types are found to increase with confidence from center to periphery of the retina. The proposed classification is compared with other concepts on neuron structures of frog retina ganglionic layer.