Pattern conserving data structure and algorithms for computations on dendritic trees.

The linked list is offered as a pattern conserving data structure, useful for storing neuronal dendritic trees. A BASIC language algorithm is described. Modifications of this algorithm for building linked lists, graphing dendritic trees, and tarry ordering trees are presented. Brief mention is made of the last in first out stack as a alternative data structure for computations on dendritic trees.

Intracellular labeling of afferents to the lateral superior olive in the bat, Eptesicus fuscus.

An in vitro tissue slice preparation of the bat brain stem was used to label intracellularly individual axons projecting to the lateral superior olive from two different sources: the medial nucleus of the trapezoid body (MNTB) and the anteroventral cochlear nucleus (AVCN). The tracing of individually labeled MNTB axons into the lateral superior olive reaffirms the long accepted indirect route by which information from the contralateral ear reaches the lateral superior olive. While the MNTB appears to relay input from the contralateral AVCN, information from the ipsilateral ear reaches the lateral superior olive via a direct projection from the ipsilateral AVCN. Axons from the contralateral and ipsilateral pathways have different distribution patterns upon the fusiform cells of the lateral superior olive. Axon terminals of MNTB principal cells have a perisomatic and proximal dendritic distribution pattern. Axon terminal varicosities from the ipsilateral anteroventral cochlear nucleus are distributed primarily to more distal dendrites.

Reticulo-spinal neurons participating in the control of synergic eye and head movements during orienting in the cat. II. Morphological properties as revealed by intra-axonal injections of horseradish peroxidase.

Previously we described physiological properties of pontine reticulo-spinal neurons which generate bursts and decaying tonic discharges related to eye movements and neck muscle activity during ipsiversive gaze shifts (Grantyn and Berthoz 1987). Two of these "eye-neck reticulo-spinal neurons" (EN-RSN) were labeled by intra-axonal injections of HRP. The present report provides a detailed description of their morphology with an emphasis on the topography of axon collaterals, bouton numbers, and the structure of preterminal ramifications in different target areas. The cell bodies of labeled EN-RSNs were located rostro-ventrally to the abducens nucleus. Their descending axons issued 8 and 13 collaterals (left and right EN-RSN, respectively) at different rostro-caudal levels, between the abducens nucleus and the pyramidal decussation. On the basis of the size of their cell bodies, the isodendritic type of dendritic branching and their multiple collateralization, EN-RSNs correspond to the class of "generalized" reticular neurons, often referred to as The Scheibels' neurons. Collaterals of EN-RSNs terminated in the following structures: the abducens and facial nuclei, the medial and lateral vestibular nuclei, the nn. prepositus and intercalatus, and the bulbar reticular formation. As judged from bouton numbers, the strongest connection of both neurons was with the abducens nuclei. Terminations in the rostral part of the medial vestibular and prepositus nuclei indicate that EN-RSNs may also influence oculomotor output activity through these indirect routes. In the facial nucleus, a majority of terminations was found in its medial subdivision containing motoneurons of ear muscles. However, other subdivisions were also contacted by EN-RSNs. Most terminations in the rostral bulbar reticular formation are distributed to the dorsal, gigantocellular field. Within this field, there is a substantial contribution to the zone characterized by the highest density of reticulo-spinal neurons projecting directly to neck motoneurons. Other target areas which may participate in the modulation of spinal cord activity by EN-RSNs are the ventral reticular nucleus in the caudal medulla and the lateral vestibular nucleus. EN-RSNs also establish connections with precerebellar structures: the prepositus and the paramedian reticular nuclei. The numbers of boutons on collaterals issued within 6 mm of the injection site varied between 37 and 469. The occurrence of presumed axo-somatic contacts was low (0-8.2%) and not characteristic for any particular target area. Local accumulations of boutons in the form of small and large field clusters was a common observation.(ABSTRACT TRUNCATED AT 400 WORDS)

A Golgi study of the proximal portion of the human Purkinje cell axon.

The proximal portion of the Purkinje cell axon in normal cerebellum was investigated using the Golgi-Cox method. The axon emerging from the axon hillock tapered as it proceeded distally along the initial segment. The most distal portion of the initial segment was the narrowest (about 1 micron). Then the axon became thicker again in the probable myelinated portion. The length of the axon hillock plus the initial segment ranged from 21 micron to 52 micron, 35 +/- 6 micron on average +/- SD. The axon arose from any site of the soma and the primary dendrite of the Purkinje cell. Almost half of the axons emanated from a lateral surface of the soma. The dendritic arbores of the Purkinje cell with a torpedo were atrophic.

Direct observations on the contacts made between Ia afferent fibres and alpha-motoneurones in the cat's lumbosacral spinal cord.

1. The enzyme horseradish peroxidase was injected into identified lumbosacral alpha-motoneurones and Group Ia afferent fibres in cats anaesthetized with chloralose and paralysed with gallamine triethiodide. Subsequent histological examination allowed the determination of (a) the extent of the motoneuronal dendritic trees, (b) the number and location of Ia synapses upon the motoneurones. 2. alpha-motoneurones had seven to eighteen primary dendrites and each produced daughter branches up to the fourth to the sixth order. At dendritic bifurcations Rall's 3/2 Power Law was obeyed. There was little or no dendritic tapering up to about 800 micrometers from the soma. Beyond this distance, however, there was considerable tapering. 3. Horseradish peroxidase injections revealed that motoneuronal dendrites are much longer than previously thought. Individual dendrites could be traced for up to 1600 micrometers from the soma and dendritic trees were usually 2-3 mm from tip to tip. Nearly all the motoneurones had dendrites that entered the white matter of the cord. Dendrites could also reach as far dorsally as laminae V and VI. 4. Ia synapses upon motoneuronal somata were examined in cords counterstained with cresyl violet or methylene green. About 10% of Ia boutons in lamina IX were on somata and each Ia collateral terminated on 3.66 motoneuronal somata or the most proximal (30 micrometer) dendrites, with on average about two contacts per motoneurone. 5. Ten Ia afferent fibre-motoneurone pairs were injected with horseradish peroxidase. The following conclusions were drawn: (i) only one collateral of any given Ia axon makes contact with a motoneurone even though other collaterals from the same axon might pass through the dendritic tree, (ii) usually all contacts made between a Ia fibre and a motoneurone are at about the same geometrical distance from the soma, even when on different dendrites, (iii) between two and five contacts are made upon the dendritic tree (average 3.4) at distances of between 20 and 820 micrometers from the soma. 6. The results are discussed in relation to previous anatomical and electrophysiological work.

Localization and morphology of cat retractor bulbi motoneurons.

1. Motoneurons innervating the cat retractor bulbi muscle have been identified by retrograde axonal transport of horseradish peroxidase (HRP). Following injections of the four slips of the retractor bulbi muscle, labeled motoneurons were found in the abducens nucleus overlapping the distribution of lateral rectus motoneurons and in the oculomotor nucleus partially overlapping the distribution of medial rectus motoneurons. Retractor bulbi motoneurons also were found in the accessory abducens nucleus situated ventral and lateral to the abducens nucleus. 2. Retractor bulbi motoneurons varied considerably in shape and size, but in all instances contained similar cytoplasmic organelles. Quantitative analyses of mean soma diameter indicated that the average size of retractor bulbi motoneurons was larger than the average size of lateral rectus and medial rectus motoneurons. 3. Retractor bulbi motoneurons in the accessory abducens nucleus were identified electrophysically and stained by intracellular injection of HRP. Neuronal reconstructions demonstrated a dorsomedial axonal trajectory directed toward the abducens nucleus and elongated dendritic fields oriented in a dorsomedial-ventrolateral axis. Another major dendritic extension was directed toward the magnocellular division of the spinal trigeminal nucleus, a major source of excitatory input to these motoneurons. 4. Quantitative analyses of synaptic density indicated that the somata of retractor bulbi motoneurons were contacted by significantly fewer synaptic endings than the somata of motoneurons in the abducens nucleus. Retractor bulbi motoneurons in the abducens nucleus exhibited variations in synaptic density that were similar to the densities on lateral rectus motoneurons. 5. Given the morphological differences in location, size, and somadendritic extent between motoneurons in the accessory abducens, abducens and oculomotor nuclei, it is suggested that such features reflect functional differences between the motoneurons with respect to fiber composition of the muscles they innervate, and subsequently to the role each muscle plays in eye movement. 6. Since the morphological features of retractor bulbi motoneurons in the accessory abducens nucleus are quite different from those in either the abducens or oculomotor nuclei, it appears that each motoneuronal population may perform unique oculomotor functions.

Kitten ganglion cells: dendritic field size at 3 weeks of age and correlation with receptive field size.

A Golgi study of beta (brisk-X type) ganglion cells has been done to compare ganglion cells in the retina of 3-week-old and adult cats. An anatomical basis for the large receptive field centers found in the immature kitten retina was sought. Kitten beta-type ganglion cells have significantly smaller dendritic spreads than adult beta cells; the dendrites of the kitten cells must still grow to reach their final adult size. Therefore a synaptic basis for the large receptive field size of the immature cells is suggested.

Dendrite bundles, central programs and the olfactory bulb.

The long secondary dendrites of mitral cells in the olfactory bulb are well developed in the mammalian neonate and show a considerable degree of interweaving and coiling characteristic of dendrite bundles. In a number of other areas throughout the central nervous system, we have made a provisional correlation between the appearance of these bundles and the development of specific items of output performance characteristic of the aras involved. On this basis we have suggested that the dendrite bundles may serve as a repository for the central program shaping the response. This hypothesis is explored further in the case of the olfactory bulb. Mechanisms are suggested whereby rudimentary appetitive programs already encoded along facing dendrite membrane pairs within the specialized intrafascicular milieu, may trigger and control nipple search and suckling in the still blind and only primitively mobile neonate.

[Quantitative histological studies of the variability of Golgi-impregnated cortical neurons in rats and cats]. / Quantitativ-histologische Untersuchungen zur innerartlichen Variabilität GOLGI-imprägnierter corticaler Neurone der Ratte und Katze

Quantitative GOLGI-studies are executed about the layer V pyramidal neurons of the albino rat and the cat sensorimotor cortex. To this the length LP of the perikarya, the lenth LAD of the apical main dendrites, the spine-densities (spine-dendrite-quotients) DQ and the length NZ of the spineless ("nude") initial zone of the apical dendrites are measured in several male animals descending of the same litters. The neuronal signs are compared within the specimens of the same age. There are no statistical significant differences (level: 0,05) between these neuronal signs in all specimens of the same age and species. Relating to the examined marks of the cortical pyramids it is allowed to decline the hypothesis of variability between animals (rats or cats respectively) of the same age and sex. By this it is legal and sufficient to examine only one specimen (animal) for each stage of age in histological researches of ontogenetic series. This specimen is representative to this stage of evolution.

Dendritic-tree anatomy codes form-vision physiology in tadpole retina.

In tadpole frog retina, the development of four classes of visual form detectors matched the growth of four types of ganglion cell dendritic trees. From this correlation of electrophysiology and anatomy we concluded that the structure of retinal ganglion cell dendritic trees provides the code for detection of visual shapes.

Motoneuron morphology and synaptic contacts: determination by intracellular dye injection.

The structure and dendritic connections of an identified crustacean motoneuron were analyzed by intracellular injection of dye. Some processes of the neuron end in the ganglionic neuropil, but most terminate on axons which pass through the ganglion in specific, identifiable tracts. The former processes are ipsilateral to the soma, while the latter, as well as their connections, display bilateral symmetry. Structural and functional evidence suggests that the demonstrated contacts are synaptic junctions, and that the approach can therefore be used to study patterns of synaptic organization in complex neural networks.