Ethanol induces MAP2 changes in organotypic hippocampal slice cultures

Microtubule-associated protein 2 (MAP2) and neuron-specific protein (NeuN) immunostains were used to demonstrate neurotoxic effects in mature hippocampal slice cultures exposed to ethanol (50, 100, 200 mM) for 4 weeks. At the low dose the density of MAP2 immunostaining in the dentate molecular layer was 118% of the control cultures, with no detectable changes in CA1 and CA3. At 100 mM no changes were detected, while 200 mM ethanol significantly reduced the MAP2 density in both dentate (19%) and hippocampal dendritic fields (CA3, 52%; CA1, 55%). At this dose NeuN staining showed considerable loss of CA3 pyramidal cells and moderate loss of dentate granule cells, as seen in vivo. The results indicate that brain slice cultures combined with immunostaining for cytoskeleton and neuronal markers can be used for studies of ethanol and organic solvent neurotoxicity.

Increased hippocampal AMPA and NMDA receptor subunit immunoreactivity in temporal lobe epilepsy patients

This study determined if hippocampal AMPA and NMDA subunit immunoreactivity (IR) in temporal lobe epilepsy patients was increased compared with nonseizure autopsies. Hippocampi from hippocampal sclerosis patients (HS; n = 26) and nonsclerosis cases (non-HS: n = 12) were compared with autopsies (n = 6) and studied for GluR1, GluR2/3, NMDAR1, and NMDAR2 IR gray values (GV) along with fascia dentata and Ammon's horn neuron densities. Compared with autopsies, non-HS cases with similar neuron densities and HS patients with decreased neuron densities showed: (a) Increased GluR1 GVs in the fascia dentata molecular layer: (b) increased NMDAR1 GVs in the CA3-1 stratum radiatum and greater IR within pyramids; and (c) increased GluR2/3 and NMDAR2 GVs throughout all hippocampal subfields. Furthermore, HS patients showed that relative to the outer molecular layer: (a) GluR1 GV differences were decreased in the CA4/hilar region and CA1 stratum radiatum compared with autopsies; and (b) NMDAR2 GV differences were increased in the inner molecular layer compared with non-HS cases. In temporal lobe seizure patients, these results indicate that AMPA and NMDA receptor subunit IR was increased in HS and non-HS hippocampi compared with nonseizure autopsies. In humans, these findings support the hypothesis that glutamate receptor subunits are increased in association with chronic temporal lobe seizures, which may enhance excitatory neurotransmission and seizure susceptibility.

Functional injury of cholinergic, GABAergic and dopaminergic systems in the basal ganglia of adult rat with kaolin-induced hydrocephalus

Structural and/or functional injury of the basal ganglia can lead to motor functional disabilities, abnormal gait and posture, and intellectual/emotional impairment, disorders also frequently seen in hydrocephalus. Previous reports have documented changes in dopamine levels in the neostriatum in experimental hydrocephalus. The present study was designed to investigate possible functional injury of cholinergic, GABAergic and dopaminergic systems in the basal ganglia immunohistochemically in a model of kaolin-induced hydrocephalus. Hydrocephalus was induced in 12 Wistar rats by intracisternal injection of 0.05 ml volume of 25% kaolin solution under microscopic guidance. Four controls received an equal volume of sterile saline. The animals were killed at 2, 4 and 8 weeks after injection. The numbers of choline acetyltransferase (ChAT)- and glutamic acid decarboxylase (GAD)-immunoreactive (IR) neostriatal neurons and tyrosine hydroxylase (TH)-IR nigral neurons, were counted in 60-micron thick representative sections and the IR cellular densities (counted cell number/neostriatal area) were calculated in the neostriatum. The number of total neostriatal neurons was also counted in 15-micron thick sections stained by cresyl violet (Nissl staining) to calculate the cellular density. The number and cellular density of neostriatal ChAT-IR neurons were significantly reduced at 2, 4, and 8 weeks after injection (P < 0.05), while those of GAD-IR neurons decreased at 4 and 8 weeks (P < 0.05). There was a linear correlation between degree of ventricular enlargement, and reduction in number of ChAT- and GAD-IR neurons (P < 0.001) as well as in the cellular density (P < 0.001). However, Nissl staining revealed no reduction in the cellular density of total neostriatal neurons (P < 0.001). TH immunoreactivity was reduced in neostriatal axons and in nigral compacta neurons, particularly in the medial portion of the dopaminergic nigrostriatal pathway. These findings suggest that progressive hydrocephalus results in functional injuries of cholinergic and GABAergic neurons in the neostriatum and dopaminergic neurons in the substantia nigra compacta by mechanical distortion. The disturbance in balance of these neurotransmitter systems in the basal ganglia may explain some of motor functional disabilities in hydrocephalus.

Increased 3-nitrotyrosine in both sporadic and familial amyotrophic lateral sclerosis

The pathogenesis of neuronal degeneration in both sporadic and familial amyotrophic lateral sclerosis (ALS) associated with mutations in superoxide dismutase may involve oxidative stress. A leading candidate as a mediator of oxidative stress is peroxynitrite, which is formed by the reaction of superoxide with nitric oxide. 3-Nitrotyrosine is a relatively specific marker for oxidative damage mediated by peroxynitrite. In the present study, biochemical measurements showed increased concentrations of 3-nitrotyrosine and 3-nitro-4-hydroxyphenylacetic acid in the lumbar and thoracic spinal cord of ALS patients. Increased 3-nitrotyrosine immunoreactivity was observed in motor neurons of both sporadic and familial ALS patients. Neurologic control patients with cerebral ischemia also showed increased 3-nitrotyrosine immunoreactivity. These findings suggest that peroxynitrite-mediated oxidative damage may play a role in the pathogenesis of both sporadic and familial ALS.

AN ELECTRON MICROSCOPE STUDY OF CULTURED RAT SPINAL CORD

Explants prepared from 17- to 18-day fetal rat spinal cord were allowed to mature in culture; such preparations have been shown to differentiate and myelinate in vitro (61) and to be capable of complex bioelectric activity (14–16). At 23, 35, or 76 days, the cultures were fixed (without removal from the coverslip) in buffered OsO₄, embedded in Epon, sectioned, and stained for light and electron microscopy. These mature explants generally are composed of several strata of neurons with an overlying zone of neuropil. The remarkable cytological similarity between in vivo and in vitro nervous tissues is established by the following observations. Cells and processes in the central culture mass are generally closely packed together with little intervening space. Neurons exhibit well developed Nissl bodies, elaborate Golgi regions, and subsurface cisternae. Axosomatic and axodendritic synapses, including synaptic junctions between axons and dendritic spines, are present. Typical synaptic vesicles and increased membrane densities are seen at the terminals. Variations in synaptic fine structure (Type 1 and Type 2 synapses of Gray) are visible. Some characteristics of the cultured spinal cord resemble infrequently observed specializations of in vivo central nervous tissue. Neuronal somas may display minute synapse-bearing projections. Occasionally, synaptic vesicles are grouped in a crystal-like array. A variety of glial cells, many apparently at intermediate stages of differentiation, are found throughout the otherwise mature explant. There is ultrastructural evidence of extensive glycogen deposits in some glial processes and scattered glycogen particles in neuronal terminals. This is the first description of the ultrastructure of cultured spinal cord. Where possible, correlation is made between the ultrastructural data and the known physiological properties of these cultures.

Transplantation of polymer-encapsulated fetal hippocampal cells into ischemic lesions of adult rat hippocampus

In a previous study we demonstrated that fetal hippocampal cells, when transplanted into ischemic lesions of the adult rat hippocampus, can survive in large numbers in the host brain and show the innervation of the transplants by cholinergic fibers originated from the host brain. The present study was undertaken in an attempt to elucidate the hypothesis that the fiber connections forming synapses between the transplanted fetal neurons and the host brain play an important role in the survival of the transplanted cells. We transplanted the polymer-encapsulated fetal hippocampal cells prepared from E17-18 rat fetuses into the ischemic lesions in the adult rat hippocampus at which the CA1 pyramidal cells selectively died, and examined both histochemically or immunohistochemically for their survival and the expression of the synaptic vesicle protein, synaptophysin, and dendritic cytoskeltal protein, microtubule-associated protein 2 (MAP 2) within them. In addition, the cholinergic fibers originated from the host brain were examined by acetylcholine esterase (AChE) histochemistry. The results demonstrated that the polymer-encapsulated hippocampal cells could survive in the brain; however, the number of surviving cells markedly decreased following the transplantation, whereas no host-derived cholinergic fibers penetrated the polymer membrane of the capsules following the transplantation. In the cluster of surviving cells, only slight synaptophysin expression and no extensive growth of the dendrites were detected. The present results indicate that the direct contact between the host brain tissue and the transplant play an important role in the survival of such allografted neurons.

Contrasting effects of fetal CA1 and CA3 hippocampal grafts on deficits in spatial learning and working memory induced by global cerebral ischaemia in rats

Functional effects of fetal hippocampal field grafts were assessed in rats with spatial learning and memory impairments following global cerebral ischaemia. Experiment 1 examined effects of grafts dissected from fields CA1 and CA3 at embryonic day 19 and from the dentate gyrus at postnatal day 1. Cell suspensions (15,000 cells/site) were implanted bilaterally at two points above the dorsal CA1 area two weeks after four-vessel occlusion (electrocoagulation of the vertebral arteries followed the 24 h later by occlusion of the carotid arteries for 15 min). Histological examination showed that CA1 neuronal loss (60-70%) was equivalent in all ischaemic groups and that 80% of CA1 and 60% of CA3 grafts survived and were sited appropriately in the alveus or corpus callosum above the area of ischaemic CA1 damage in the host, but there was no survival of dentate grafts. Results from rats with poor pyramidal cell graft survival were excluded, but those from rats with non-surviving dentate grafts were retained as an additional control group. Acquisition in the water maze was examined nine and 25 weeks after transplantation, and spatial working memory was assessed in three-door runway and water maze matching-to-position tasks 19 and 28 weeks after grafting, respectively. For water maze acquisition rats were trained with two trails/day and a 10 min inter-trial interval for 10-12 days to locate a submerged platform. Ischaemic rats with CA1 grafts learned the platform position as rapidly as non-ischaemic controls, searched appropriately in the training quadrant and were accurate in heading towards the platform, but were initially impaired on recall of the precise platform position on probe trials with the platform removed. Performance of ischaemic controls and groups with CA3 and non-surviving dentate graft groups was significantly impaired relative to controls and to the CA1 grafted group. The CA1 grafted group was also as successful as controls in matching-to-position in the water maze and substantially superior to the other ischaemic groups, assessed using three trials/day, with a 30-s inter-trial interval and a different platform position on each day. In a more complex matching-to-position task in the three-door runway, the performance of the CA1 grafted group was significantly impaired relative to controls, although superior to that of the other ischaemic control and graft groups. Functional recovery with CA1, but not CA3, grafts in ischaemic rats was replicated in a second experiment which assessed water maze acquisition and working memory at 10 and 14 weeks after transplantation, in rats with 90% graft survival. These results indicate that long-lasting, task-dependent improvements can be seen in ischaemic rats with CA1 fetal grafts in both aversively and appetitively motivated spatial learning tasks. The findings suggest that functional recovery requires homotypic replacement of CA1 cells damaged by ischaemia, rather than provision of structurally similar glutamate-releasing CA3 pyramidal cells.

Cytoarchitecture of the abducens nucleus of man: a Nissl and Golgi study

The abducens nucleus is a pontine nucleus directly involved in oculomotion through its connections with the lateral rectus muscle of the eye. The aim of the present study was to investigate the cytoarchitectural organization of the abducens nucleus in man. The data obtained showed that the nerve cell bodies were small, medium and large in size and polygonal, oval, round or spindle shaped. The cytoplasm of all neurons appeared basophilic due to clearly evident scattered Nissl granules. On the basis of the characteristics of the dendritic arborization, multipolar and fusiform cells were identified. The multipolar neurons showed four to eight primary dendrites which gave off a wide secondary ramification. The fusiform neurons showed two dendrites emerging from the opposite poles of the elongated nerve cell body. The dendrites of all the neurons were largely confined within the boundaries of the nucleus. This finding would suggest that the neuronal relationships of the abducens nucleus supplied by the afferent fibers which pass through or end within it take place almost completely inside the nucleus. The wider dendritic arborization shown by the multipolar cells would indicate the latter as the principal target fields for the afferent inputs.

Cajal-Retzius neurons in human cerebral cortex at midgestation show immunoreactivity for neurofilament and calcium-binding proteins

Along with subplate neurons, Cajal-Retzius cells (CRc) are the first neurons to be generated in the cortical anlage. Studies of their chemical content, such as neurofilament and calcium-binding proteins, might give indications on their role in cortical development at midgestation in human fetuses (20-24 gestation weeks), when the CRc are morphologically mature. Cajal-Retzius cells were immunolabeled with antibodies to subunits of neurofilament proteins SMI31 and SMI32. The SMI32 antibodies (directed against the nonphosphorylated epitope) specifically labeled the CR cell bodies, dendrites, and proximal axons in a Golgilike fashion. Specific acetylcholinesterase activity is known to be typical of all the CRc, and double labeling for SMI32 immunoreactivity and acetylcholinesterase histochemistry demonstrated that all the CRc exhibited SMI32 immunoreactivity. The SMI31 antibodies (directed against the phosphorylated epitope) exclusively labeled the CRc axons, forming a dense positive network in the deep one-half of layer 1. This plexus was much denser than the one described with the Golgi method (Marin-Padilla, 1990: J. Comp Neurol 239:89-105). Calbindin D28k, parvalbumin, and calretinin immunoreactivities were visualized in the CRc. Double-labeling experiments showed that most of the CRc contained both calbindin and calretinin and sometimes parvalbumin. These colocalizations revealed a chemical heterogeneity within the CRc population even though they were described as morphologically homogeneous. These colocalizations of calcium-binding proteins in the CRc differed from the other nonpyramidal cortical neurons where calbindin, calretinin, and parvalbumin are contained in different (mutually exclusive) neuronal populations. Based on the morphological features and differential chemical contents described for the CRc, different hypotheses on their possible role and fate are discussed.

Retinohypothalamic projections and immunocytochemical analysis of the suprachiasmatic region of the desert iguana Dipsosaurus dorsalis

Two separate and distinct retinal projections to the hypothalamus in the iguanid lizard Dipsosaurus dorsalis were described using horseradish peroxidase and cobalt-filling techniques. Both of the projections were unilateral and completely crossed; one terminated in the supraoptic nucleus and the other in the suprachiasmatic nucleus. Immunocytochemical analysis showed that the supraoptic nucleus contained cell bodies and fibers that cross-react with antibodies raised against arginine vasopressin, while the suprachiasmatic nucleus contained arginine vasopressin-like immunoreactive fibers emanating from cells in the nearby paraventricular nucleus. The suprachiasmatic nucleus contained a dense plexus of fibers that cross-reacted with neuropeptide-Y antibody. Antiserum against vasoactive intestinal polypeptide showed no reactivity in any part of the forebrain, while antiserum against serotonin showed sparse and uniform reactivity throughout the forebrain, including the suprachiasmatic nucleus. These results, together with other data, indicate that the suprachiasmatic nucleus of D. dorsalis is homologous to the suprachiasmatic nuclei of rodents, structures known to contain circadian pacemakers. We suggest that the suprachiasmatic nucleus may play a similar role in the circadian system of D. dorsalis.

[Relationship between neuronal size and axonal length in chick propriospinal neurons]

In order to investigate the relationship between neuronal size and axonal length, we compared the size of chick propriospinal neurons in several segmental levels. As the index of neuron size, the cross sectional areas of somata were measured. After unilateral implantation of solidified HRP into the lumbar enlargement (2 cases) or the cervical enlargement (1 case) in the 2-4 day post-hatch chick under Nembutal anesthesia, propriospinal neurons projecting to the enlargement were visualized by TMB method. Labeled cells found in complete serial transverse sections were all traced onto tracing papers put on photomicrographs under examination with the microscope (Fig. 2). In several successive sections in the cervical cord, the cervical enlargement, the lumbar and the sacral cord, the cross sectional areas of their 3601 somata were measured on traced drawings of final magnification X243 by means of a computer system graphic analyzer (Cosmo Zone, Nikon) (Fig. 1). As a control case, cross sectional areas of somata were also measured in Nissl preparations in laminae V-VIII, where vast majority of propriospinal neurons are located, and also lamina IX. In Nissl preparations, the cross sectional areas of neurons in laminae V-VIII had a wide range distribution from 50 to 1600 micron 2. Over 90% of them were distributed from 50 to 600 micron 2. Among them, the neurons with somata of 150-250 micron 2 were most numerous. The distribution pattern was almost the same in all segments examined. The cross sectional areas of neurons in lamina IX were also distributed in a wide range from 150 to 1600 micron 2 (Fig. 3).(ABSTRACT TRUNCATED AT 250 WORDS)

Opiate receptors in the human spinal cord: a detailed anatomical study comparing the autoradiographic localization of [3H]diprenorphine binding sites with the laminar pattern of substance P, myelin and nissl staining

The anatomical localization of opiate receptors in the human spinal cord has been examined in six cases aged 7-41 years using quantitative autoradiographic methods following the incubation of fresh, unfixed cryostat sections with [3H]diprenorphine. In order to precisely localize the distribution of receptors in the spinal cord, the laminar anatomy of the spinal grey was demonstrated at each spinal level examined using 50-microns sections stained for myelin, Nissl substance and substance P. In all cases, autoradiograms demonstrated that opiate receptors were distributed in a similar fashion in the grey matter of the cervical, thoracic, lumbar, sacral and coccygeal regions of the human spinal cord. At all 25 spinal levels examined, opiate receptors were mainly localized within the upper laminae of the dorsal horn (laminae I-III) and within the tract of Lissauer. The highest density of opiate receptors was localized within the inner segment of lamina II where the receptors formed a very dense band lying immediately dorsal to lamina III. The density of receptors in this inner region of lamina II (33 +/- 2 fmol/mg) was more than two-and-one-half times greater than that in the remaining upper laminae which showed moderate receptor densities: lamina I (12 +/- 4 fmol/mg) and outer lamina II (13 +/- 3 fmol/mg) both showed similar receptor densities which were higher than those in lamina III (10 +/- 3 fmol/mg) The tract of Lissauer (11 +/- 2 fmol/mg) also showed a moderate density of opiate receptors which was intermediate between the densities in laminae I/IIo and the density of lamina III. The density of receptors in the remaining laminae of the spinal cord varied from moderately low to virtually zero. Moderately low densities of receptors were found in laminae V, VI, VIII, IX and X with very low levels within laminae IV and VII. In particular, in lamina VII opiate receptors were unable to be detected above normal background levels in the dorsal nucleus of Clarke. These results show that, as in other mammalian species, opiate receptors in the human spinal cord are mainly concentrated in the upper laminae of the dorsal horn and in the tract of Lissauer. The possible role of these receptors in modulating spinal nociceptive information is discussed with respect to previous findings on the relationship of opiate receptors to primary afferent fibres in the spinal cord.

Localisation of the spinal nucleus of the accessory nerve in the rabbit

The spinal nucleus of the accessory nerve (SNA) was localised in eight adult rabbits by a retrograde degeneration technique using thionine as a stain for the Nissl substance. The SNA was found to extend from the caudal one fifth of the medulla oblongata to the cranial one fourth of the sixth cervical segment. In the caudal part of the medulla oblongata, the SNA was located in the dorsal part of the detached ventral grey column. In the first cervical segment, the SNA was dorsolateral to the dorsomedial column and dorsal to the ventromedial column of the ventral grey column. In the cranial part of the second cervical segment, the SNA shifted laterally to the lateral margin of the ventral grey column. After this lateral shift, the SNA was located in the lateral part of the ventral grey column of the second, third and fourth cervical segments. In the fifth and cranial one fourth of the sixth cervical segments, the SNA was not a well defined column of cells but was represented by isolated cells scattered in the ventral part of the ventral grey column between the phrenic nucleus and the ventral border of the grey matter. The total number of chromatolysed cells found in the SNA of the right experimental side varied from 2723 to 3210.

Amyotrophic lateral sclerosis. Lack of central chromatolytic response of motor neurocytons corresponding to active axonal degeneration

Ventral spinal roots and anterior horn cells in the lateral nuclear group of the fourth lumbar segment from 21 patients with amyotrophic lateral sclerosis (ALS) and 23 control patients were morphometrically analyzed. The number of large myelinated fibers was remarkably decreased, while small myelinated fibers were well preserved. The population of large myelinated fibers significantly correlated with the population of anterior horn cells. Numerous axonal degenerations were observed in the ventral spinal roots of patients with ALS, even in patients with severe loss of neurons and axons. In spite of this high frequency of active axonal degeneration, the incidence of central chromatolysis of anterior horn cells remained at the control level.

Ganglion cell distribution in the retina of the mouse

The distribution of ganglion cells in the mouse retina was studied with the use of Nissl criteria for distinguishing cell types in the ganglion cell layer. Retrograde filling with horseradish peroxidase (HRP) from the optic fiber tract helped to validate Nissl criteria and served to identify displaced ganglion cells. We estimated a total of 117,000 nonvascular cells in the ganglion cell layer; of these, 70,000 were probably ganglion cells, and 47,000 could not be classified. The density of the presumed ganglion cells was highest-more than 8000 cells/mm2-just temporal to the optic disk, and lowest-less than 2000 cells/mm2-in the most dorsal retina. The retinal region with highest ganglion cell density was slightly elongated in a nasotemporal direction. About 2% of all HRP-filled ganglion cells had their cell bodies in the inner nuclear layer. These displaced cells differed in topographical distribution from the normally positioned ganglion cells: although occurring throughout the retina, they were more common along the retinal periphery. Measurements of ganglion cell areas showed a tendency toward larger size with eccentricity. At no retinal location did cell-size histograms reveal clearly separate size classes.

The nature of dendritic cells of the epidermis of the white guinea pig

The melanocytes, the intermediate cells of Billingham and Medawar and the Langerhans' cells of the epidermis of the white guinea pig were found to be positive to Bielschowsky's silver and Gomori's acetylcholinesterase reactions. The melanocytes were full of Nissl substance. On these evidences, supported by other morphological and histochemical characteristics, the dendritic cells of the epidermis were considered to be nervous structures.

Morphological characteristics of dendrite bundles in the lumbar spinal cord of the rat

The finding of motoneuron dendrites organized into small compact bundles in cats, monkeys and pigs suggested that a study of this phenomenon in rats should be undertaken. An analysis was performed with electron microscopy, light microscopy and Golgi methods. An extensive dendrite bundle organization was found in the sixth lumbar segment of the spinal cord. Two discrete bundles were localized bilaterally: a lateral bundle in the ventrolateral gray substance, and a medial bundle in the ventral funiculus. The lateral bundle was found to consist of longitudinally oriented dendrites, neurocytons, glial cells and capillaries. As many as 1678 closely packed dendrites were observed in the lateral bundle. The medial bundle contained dendrites directed across the midline and also longitudinally oriented dendrites. Neurocytons in the medial dendrite bundle were found singly or in clusters, and many radiating bundles of dendrites were observed projecting toward the lateral bundle. Golgi analysis confirmed that neurons in the lateral bundle had most of their dendrites oriented longitudinally. It was possible to trace several dendrites into the lateral bundle from dorsally and medially lying neurons. Electron microscopy substantiated the fact that the bundles were composed of dendrites. It also revealed numerous dendrodendritic and dendrosomatic contacts which were desmosomal in type as well as an abundance of small unidentified processes. Various functions which have been attributed to the dendrite bundles are discussed.

A histochemical investigation on mucopolysaccharides in the dog sympathetic ganglia

A histochemical study in the dog Superior Cervical ganglion and in the Cervicothoracic or Stellate ganglion is reported. The mucopolysaccharide composition of these ganglia are studied by means of five histochemical techniques. The different histochemical composition between the neurons of these ganglia is investigated. In the sections stained with the PAS technique some neurons appeared more intensely stained than the others. With Thionin or Toluidine blue some neurones appeared more metachromatic than others. A peculiar distribution of the Nissl bodies, related with metachromasia, is reported. In sections stained with the Colloidal Iron method yellow neurons like those presented in the dorsal root ganglia were not found in the sympathetic ganglia. This fact suggests that the yellow neurons might be a different type of neuron. The possibility that the staining variations associated to the distribution of the Nissl bodies perhaps correspond to different functional states of the same type of neurons is also suggested.

Neurofilament and glycogen changes during cold acclimation in the trochlear nucleus of lizards (Sceloporus undulatus)

In lizards (Sceloporus undulatus), long term (13 or 19 weeks) acclimation to an environment of 6 degrees C produces a striking increase in the argyrophilic neurofibrillar network in most large perikarya of the trochlear nucleus. In electron micrographs the cells contain numerous bundles of 10-30 regularly-spaced 90 A neurofilaments. In the cells from warm acclimated animals, a plexus of neurofibrils is seen by light microscopy. The electron micrographs show scattered neurofilaments and fewer, thinner bundles than in the cold. Within the cell bodies of the cold animals, glycogen particles are organized in regional accumulations from which other organelles are excluded except for the bundles of neurofilaments which are distributed throughout the cytoplasm. The aggregations of rough endoplasmic reticulum (RER) are also penetrated by the neurofilament bundles. The increased neurofilamentous network in the cold is not accompanied by obvious changes in the amount or distribution of RER or of microtubules which are present in limited numbers in both conditions. The dendrites of trochlear cells and axon terminals within the nucleus also show a cold induced increase in neurofilaments, as well as in the distinctive accumulations of glycogen particles.

A quantitative study of subsurface cisterns and their relationships in normal and axotomized hypoglossal neurones

A quantitative ultrastructural survey was made of subsurface cisterns and their association with overlying structures in the left hypoglossal nucleus of normal rats, and rats which had received left hypoglossal axotomies 7-84 days previously. Subsurface cisterns in normal rats occurred in some hypoglossal neurones, and, sporadically, in proximal dendrites. They were mostly subsynaptic, and often associated with Nissl substance; From 7-14 days postoperatively, when many somatic boutons temporarily lost contact with the perikaryal surface, and were replaced by a microglial sheath, the percentage of perikaryon with underlying cistern was significantly reduced. The Nissl substance was also dispersed at this stage, and not restored until 28 days postoperatively. At 21 days normal percentages of subsurface cistern were restored, but the cisterns were now mostly subastrocytic, an astrocytic sheath having replaced the microglial sheath. From 63 days onwards the cisterns were mostly subsynaptic again as boutons returned to the regenerating perikarya and the temporary astrocytic sheath disappeared. It is suggested that subsurface cisterns might alter the overlying perikaryal surface in some way during neuronal regeneration, causing certain boutons to adhere there.