An ultrastructural study of the craniocaudal continuation of the glycogen body

An ultrastructural analysis of the chicken glycogen body and its craniocaudal continuation areas shows a continuum of astroglial cell types. Characteristic glycogen body astroglia are confined to the classically defined body located in the chicken lumbosacral spinal cord. These are large cells which have an eccentric dark nucleus surrounded by a rim of dense cytoplasm which contains the usual complement of organelles. The remainder of the cell volume is occupied by alpha and beta glycogen particles interspersed with a flocculo-granular material continuous with the main cytoplasmic mass. Astroglial cells of continuation areas usually have a light cytoplasm and a centrally placed nucleus. They contain beta glycogen particles of varying sizes, but like the glycogen body cells, may have beta particles as large as 45 nm. Such particles, which resemble four leaf clovers in shape, are suggestive of an ordered substructure. Gliofilaments are not always conspicuous in astroglial perikarya, but large numbers of them are present in the processes. Although the continuation areas are mostly confined to gray matter regions, the contained astroglial processes exhibit circular, triangular, or cylindrical shapes and form an unpatterned mosaic. Astrocytic processes forming the glia limitans on the anterior and posterior margins of the cord often contain conspicuous amounts of glycogen. The ultrastructural identification of such large amounts of glycogen within the chicken nervous system suggests that it plays a major role in avian neural metabolism.     

Development of the glycogen body of the Japanese quail, Coturnix japonica. I. Light microscopy of early development

The glycogen body is a functionally enigmatic structure located in lumbosacral region of the spinal cord in birds. This tissue is unique to birds, and, although it is believed to be present in all species, studies on the glycogen body to date have been confined largely to the domestic chicken. The present study is the first to describe the glycogen body of the Japanese quail (Coturnix japonica) during incubation and at hatching. Light microscopy and histochemistry were used to identify the glycogen body in the spinal cord of the developing quail beginning at 7 days of incubation and to ascertain the presence of nerve fibers in that tissue at hatching.     

A brachial glycogen body in the spinal cord of the domestic chicken.

When cervical segments 14 to 15 of the chicken spinal cord are cut transversely and studied by routine histological and histochemical methods, an onion-shaped region, filled with thread-like fibers, is seen to surround the ependymal cells of the central canal and to be bounded laterally by the neural elements of the spinal gray matter. This area is negative for succinic dehydrogenase, beta-hydroxybutyrate dehydrogenase and cholinesterase activity, but very strongly periodic acid-Schiff positive. Diastase controls show the positive material to be glycogen. Parasagittal sections through this cervical region and into the upper thoracic cord, show the glycogen-rich region to extend longitudinally throughout the region. Because of its location and histochemical characterization, which are similar to that of the ventral portion of the glycogen body, the term brachial glycogen body is proposed for this structure.     

Histochemistry of the glycogen body of the turkey spinal cord

Summary Enzyme histochemical studies of the glycogen body of the turkey showed very little activity of suocinic dehydrogenase and cytochrome oxidase in the glycogen body cells, and marked activity of lactic dehydrogenase, NAD-diaphorase and the hexosemonophosphate shunt enzymes. Gradients of histochemical staining intensity for lactic and succinic dehydrogenase in the glycogen body and spinal cord were confirmed by biochemical assays of homogenates of these tissues. It was concluded that glycogen body metabolism is predominantly glycolytic. Alkaline phosphatase activity was weak; acid phosphatase activity was moderate. There was no acetyl cholinesterase or nonspecific cholinesterase activity in the glycogen body.This investigation was supported by U. S. Public Health Grant B 3250.Submitted in partial fulfillment of Masters' degree requirements.     

Neurohistologische und fluoreszenzmikroskopische Untersuchungen über die Innervation des Glykogenkörpers der Vögel

Zusammenfassung Mit Versilberung und mit der fluoreszenzmikroskopischen Technik von Falck-Hillarp wurden im Glykogenkörper des Vogelrückenmarks Nervenfasern dargestellt. Diese Nervenfasern stammen aus Kerngebieten, die den Glykogenkörper flankieren. Die stärkste Fluoreszenz dieser lumbalen Kernareale findet sich an den beiden Polen des Glykogenkörpers. Es wird angenommen, daß das beschriebene aminerge Neuronensystem einen funktionellen Einfluß auf den Glykogenkörper ausübt. Der Glykogenkörper der Vögel wird mit anderen zentralnervösen Glykogendepots verglichen.

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Neurohistological and fluorescence microscopic investigations of the innervation of the avian glycogen body

Summary Nerve fibers were demonstrated in the glycogen body of the avian lumbar spinal cord by using silver-impregnation and fluorescence microscopic (Falck-Hillarp) techniques. These nerve fibers originated from nuclear areas in lateral juxtaposition with the glycogen body. The fluorescence of the nuclear area was strongest near the polar regions of the glycogen body. It was suggested that the aminergic neurons of the avian lumbar spinal cord may influence the glycogen body. The avian glycogen body was compared with other storage sites of glycogen within the central nervous system.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Immunohistochemical mapping of perineuronal nets containing chondroitin unsulfate proteoglycan in the rat central nervous system

Subsets of neurons ensheathed by perineuronal nets containing chondroitin unsulfate proteoglycan have been immunohistochemically mapped throughout the rat central nervous system from the olfactory bulb to the spinal cord. A variable proportion of neurons were outlined by immunoreactivity for the monoclonal antibody (Mab 1B5), but only after chondroitinase ABC digestion. In forebrain cortical structures the only immunoreactive nets were around interneurons; in contrast, throughout the brainstem and spinal cord a large proportion of projection neurons were surrounded by intense immunoreactivity. Immunoreactivity was ordinarily found in the neuropil between neurons surrounded by an immunopositive net. By contrast, within the pyriform cortex the neuropil of the plexiform layer was intensely immunoreactive even though no perineuronal net could be found. The presence of perineuronal nets could not be correlated with any single class of neurons; however a few functionally related groups (e.g., motor and motor-related structures: motor neurons both in the spinal cord and in the efferent somatic nuclei of the brainstem, deep cerebellar nuclei, vestibular nuclei; red nucleus, reticular formation; central auditory pathway: ventral cochlear nucleus, trapezoid body, superior olive, nucleus of the lateral lemniscus, inferior colliculus, medial geniculate body) were the main components of the neuronal subpopulation displaying chondroitin unsulfate proteoglycans in the surrounding extracellular matrix. The immunodecorated neurons found in the present study and those shown by different monoclonal antibodies or by lectin cytochemisty, revealed consistent overlapping of their distribution patterns.     

The Sense Organs and Ventral Ganglion of Sagitta (Chaetognatha)

This paper describes some features of the chaetognath nervous system from ultrastructural observations and observations on material stained with specific techniques for nervous tissue, and from records of the activity of the locomotor muscles and ventral ganglion. Sensory cells grouped on the ventral surface of the head bear ciliary processes (some with multiple tubules), and are probably in connexion with the central nervous system by their own axons, unlike the sensory cells of the hair fan vibration receptors of head and body. The ventral ganglion is motor to the locomotor muscles of the body, and controls the rhythmic locomotor activity of the animal. Electrical events associated with contraction of these muscles are compound non-overshooting spike-like potentials. The ventral ganglion contains several large nerve fibres constant in position and connexions in different individuals. Some of these arise from cells in the ganglia of the head, and pass to the ventral ganglion, others from cells within the ventral ganglion, and probably supply the ciliary hair fan receptors of the body, whilst the motor axons issuing from the ventral ganglion are smaller in diameter. The ganglion is arranged on a ladder-like plan, and axons of the lateral cell bodies cross the central neuropil transversely before they contribute to the longitudinal tracts or pass out in the radial nerves. Synapses in the neuropil contain 30–40 nm electron lucent vesicles; the transmitter is unknown, but is unlikely to be either acetylcholine or l -glutamate. Occasional larger electron dense vesicles up to 70 nm in diameter are also found within nerve fibres of the neuropil. It is concluded that the arrangement of the peripheral nervous system is unlike that of several groups which have been suggested as related to chaetognaths.     

Formation of the peripheral nervous system during tail regeneration in urodele amphibians: ultrastructural and immunohistochemical studies of the origin of the cells.

In the regenerating newt tail, epimorphic regeneration--which recapitulates morphologically normal embryonic development--proceeds along a rostrocaudal differentiation gradient. Innervation of the new myomeres results from the spinal roots of segments rostral to the amputation plane and from ventral roots emerging from the lateroventral region of the regenerating spinal cord, in which motor neurons are differentiating. Electron microscopy and an indirect immunofluorescence study with anti-glial fibrillary acid protein (GFAP) confirm that the ventrolateral part of the regenerated ependymal tube gives rise to cells of the ventral root sheath and the spinal ganglia. Anti-GFAP and anti-neurofilament antibodies showed that ependymoglial cells and Schwann cells may play a role in neuronal pathfinding by helping guide and stabilize pioneering axons as they extend toward the myomeres. The carbohydrate epitope NC-1 is expressed in the spinal cord, in sheath cells of the spinal ganglia and in the non-myelin-forming Schwann cells of the peripheral nervous system. L1, a Ca++ independent neural cell adhesion molecule, was detected in the axonal compartments of the regenerating spinal cord, on immature and/or non-myelin-forming Schwann cells within the peripheral nervous system (PNS), and on nerve fibers within the regenerate. These immunohistochemical observations collectively support the hypothesis that Schwann cells already present in the blastema could be involved in organizing neural pathways.     

Ontogeny of the collar cord: Neurulation in the hemichordate Saccoglossus kowalevskii

The chordate body plan is characterized by a central notochord, a pharynx perforated by gill pores, and a dorsal central nervous system. Despite progress in recent years, the evolutionary origin of each of theses characters remains controversial. In the case of the nervous system, two contradictory hypotheses exist. In the first, the chordate nervous system is derived directly from a diffuse nerve net; whereas, the second proposes that a centralized nervous system is found in hemichordates and, therefore, predates chordate evolution. Here, we document the ontogeny of the collar cord of the enteropneust Saccoglossus kowalevskii using transmission electron microscopy and 3D‐reconstruction based on completely serially sectioned stages. We demonstrate that the collar cord develops from a middorsal neural plate that is closed in a posterior to anterior direction. Transversely oriented ependymal cells possessing myofilaments mediate this morphogenetic process and surround the remnants of the neural canal in juveniles. A mid‐dorsal glandular complex is present in the collar. The collar cord in juveniles is clearly separated into a dorsal saddle‐like region of somata and a ventral neuropil. We characterize two cell types in the somata region, giant neurons and ependymal cells. Giant neurons connect via a peculiar cell junction that seems to function in intercellular communication. Synaptic junctions containing different vesicle types are present in the neuropil. These findings support the hypotheses that the collar cord constitutes a centralized element of the nervous system and that the morphogenetic process in the ontogeny of the collar cord is homologous to neurulation in chordates. Moreover, we suggest that these similarities are indicative of a close phylogenetic relationship between enteropneusts and chordates. J. Morphol., 2010. ©2010 Wiley‐Liss, Inc.     

Immunocytochemical localization of glycogen phosphorylase isozymes in rat nervous tissues by using isozyme-specific antibodies

Isozyme-specific antibodies were raised against peptides from the low-homology regions of the sequences of rat glycogen phosphorylase BB and MM isozymes by immunization of rabbits and guinea pigs. Immunocytochemical double-labelling experiments on frozen sections of rat nervous tissues were performed to investigate the isozyme localization pattern. Astrocytes throughout the brain and spinal cord expressed both isozymes in perfect co-localization. Ependymal cells only expressed the BB isozyme. Most neurones were not immunoreactive. The rare neurones that contained glycogen phosphorylase only expressed the BB isozyme. Nearly all of these neurones formed part of the afferent somatosensory system. These findings stress the general importance of glycogen in neural energy metabolism and indicate a special role for the glycogen phosphorylase BB isozyme in neurones in the somatosensory system.     

Autoradiographic localization of estrogen target cells in the spinal cord of the armadillo and baboon: a comparative study

The uptake and retention of radiolabeled estradiol by the spinal cord were examined in the baboon and the armadillo and compared to previous observations in the rat. Four females of each species were injected intracardially with 1.0-1.4 micrograms/kg body weight of 3H-estradiol and two females, one baboon and one armadillo, were injected with both labeled and 100-140 micrograms/kg body weight of unlabeled estradiol. One hour after the injections, the animals were killed and segments from the cervical, thoracic, lumbar and sacral cord were removed and processed for autoradiography. In the armadillo, labeling of neuronal nuclei were noted in laminae I & II and in alpha motor neurons. In addition, nuclei of the ependymal cells of the ventral portion of the central canal in the cervical cord concentrated radioactivity. In contrast, the baboon demonstrated only sporadic labeling of neurons in lamina II in all levels of the spinal cord. The comparison of our observations with that of the rat suggest that estrogen mediated sensations are probably coordinated at higher brain centers in the primate as opposed to the more primitive mammals.     

Distribution of tachykinin-related neuropeptide in the developing central nervous system of the moth Spodoptera litura

Neuropeptides with similarities to vertebrate tachykinins, designated tachykinin-related peptides (TRPs), have been identified in several insect species. In this investigation we have utilized an antiserum raised to one of the locust TRPs, locustatachykinin-I (LomTK-I), to determine the distribution pattern of LomTK-like immunoreactive (LTKLI) neurons in the developing nervous system of the moth Spodoptera litura. A number of LTKLI neurons could be followed from the larval to the adult nervous system: a set of median neurosecretory cells (MNCs) in the brain, a pair of brain descending neurons and a few sets on neurons in the ventral nerve cord. The distribution of LTKLI neurons in the adult brain is very similar to that seen in other insect species with prominent arborizations in the central body, antennal lobes, mushroom body calyces, optic lobe neuropils and other distinct neuropil areas in the protocerebrum and tritocerebrum. A new finding is the presence of LTKLI neurosecretory cells with axon terminals in the anterior aorta and corpora cardiaca, suggesting for the first time a neurohormonal role of tachykinin-related peptide(s) in insects. During postembryonic development the number of LTKLI neurons in the ventral nerve cord decreases somewhat, whereas the number increases in the brain. Thus the functional roles of TRPs may change to some extent during development.     

Mechanism of stem cells in the central nervous system

Injury to the central nervous system (CNS) can result in severe functional impairment. The brain and spinal cord, which constitute the CNS, have been viewed for decades as having a very limited capacity for regeneration. However, over the last several years, the body of evidence supporting the concept of regeneration and continuous renewal of neurons in specific regions of the CNS has increased. This evidence has significantly altered our perception of the CNS and has offered new hope for possible cell therapy strategies to repair lost function. Transplantation of stem cells or the recruitment of endogenous stem cells to repair specific regions of the brain or spinal cord is the next exciting research challenge. However, our understanding of the existing stem cell pool in the adult CNS remains limited. This review will discuss the identification and characterization of CNS stem cells in the adult brain and spinal cord.     

Immunocytochemical localization of glycogen phosphorylase in primary sensory ganglia of the peripheral nervous system of the rat

Neuronal localization was investigated of glycogen phosphorylase (GP) in ganglia of the peripheral nervous system of the rat. Immunofluorescence and immunoenzymatic procedures were applied with a monoclonal anti-bovine brain GP antibody on paraformaldehyde-fixed, paraffin-embedded tissues. Immunoreactivity was only present in the somatic neurons of the mesencephalic trigeminal nucleus in the brain stem and in dorsal root ganglia (DRG), but not in the autonomic neurons of the superior cervical ganglia or in the sensory nuclei of the spinal cord. GP immunoreactivity was present as early as day 1 after birth. In the adult rat, staining was present in neurons of different sizes, and to varying intensities. No relationship was apparent between the staining intensities and morphologically distinguishable types of neurons. In DRG, the type of reactivity was the same from cervical to sacral ganglia. The selected occurrence of GP in specific neurons of the peripheral nervous system in contrast to the ubiquitous occurrence in all astrocytes of the central nervous system may indicate a different role of neuronal glycogen compared to astrocytic glycogen.     

Changes in the blood vessels, spinal cord neurocytes, pia mater and spinal ganglia in chronic stimulation of the sympathetic trunks

Taking into account the data concerning disturbances in blood supply of the spinal cord as a response to irritation of the sympathetic trunks, the experimental morphological investigation has been performed on rabbits. By means of the injection technique and staining of neurocytes, changes in the spinal cord, in the spinal nodes and in the pia mater have been studied at chronic irritation of the lumbar nodes of the sympathetic trunk. Certain degenerative changes have been revealed in nervous cells and also phenomena of the spinal cord ischemia, decreasing contacts between the nervous cells and the capillaries surrounding them. As the authors believe, these data can be used by clinicians for revealing pathological mechanisms of the spinal cord ischemia as a result of chronic irritation of the sympathetic trunk.     

Requirement of N-myc protein down-regulation for neuronal differentiation in the spinal cord

Previous work has indicated that N-myc expression occurs widely in the developing central nervous system, but its level changes dynamically with region- and stage-specificities. We show in the present report that in the developing spinal cord of the mouse, N-myc protein expression takes place in the ventricular zone and reaches its maximum at the outermost layer, but is extinct in the intermediate zone, indicating that N-myc protein is not expressed in mature neurons. We examined the effect of forced, persistent N-myc expression in development of the spinal cord in order to understand the functional significance of N-myc down-regulation. We made embryonic stem (ES) cell lines that constitutively expressed N-myc at a high level, then produced mouse embryo chimeras with a high contribution of the ES cells. The majority of the chimeras developed to day 12 with normal gross morphology, but in these chimeras neuronal differentiation in the spinal cord was perturbed at the histological level. Intermediate zones and ventral horns were formed, but the expression of N-CAM and neurofilaments was diminished. Chimeras using β-galactosidase-expressing recipient embryos indicated that inhibition of the neuronal differentiation was a cell-autonomous effect of persistent N-myc expression. These observations indicate that N-myc down-regulation in individual cells is required for full differentiation of neurons.     

Acid phosphatase localization in individual neurons by a quantitative histochemical method

—By an adaptation of the fluorometric method of Campbell and Moss (1961), the activity of α-naphthyl acid phosphatase was measured in individual neurons of monkey and human spinal cord and found to be many times higher in nerve cell bodies than in the surrounding neuropil. It was also measured in cerebellar cortex and found most concentrated in the granular (neuronal) layer. As this distribution is distinctive and paralleled by two other acid hydrolases, β-galactosidase and β-glucuronidase, it is considered to offer additional support for the lysosomal concept in nervous tissue and to indicate that nerve cell perikarya are much richer in lysosomes than are axons, dendrites or glial cells.     

Differential distribution of G-protein beta-subunits in brain: an immunocytochemical analysis.

Heterotrimeric G proteins play central roles in signal transduction of neurons and other cells. The variety of their alpha-, beta-, and gamma-subunits allows numerous combinations thereby confering specificity to receptor-G-protein-effector interactions. Using antisera against individual G-protein beta-subunits we here present a regional and subcellular distribution of Gbeta1, Gbeta2, and Gbeta5 in rat brain. Immunocytochemical specificity of the subtype-specific antisera is revealed in Sf9 cells infected with various G-protein beta-subunits. Since Gbeta-subunits together with a G-protein gamma-subunit affect signal cascades we include a distribution of the neuron-specific Ggamma2- and Ggamma3-subunits in selected brain areas. Gbeta1, Gbeta2, and Gbeta5 are preferentially distributed in the neuropil of hippocampus, cerebellum and spinal cord. Gbeta2 is highly concentrated in the mossy fibres of dentate gyrus neurons ending in the stratum lucidum of hippocampal CA3-area. High amounts of Gbeta2 also occur in interneurons innervating spinal cord alpha-motoneurons. Gbeta5 is differentially distributed in all brain areas studied. It is found in the pyramidal cells of hippocampal CA1-CA3 as well as in the granule cell layer of dentate gyrus and in some interneurons. In the spinal cord Gbeta5 in contrast to Gbeta2 concentrates around alpha-motoneurons. In cultivated mouse hippocampal and hypothalamic neurons Gbeta2 and Gbeta5 are found in different subcellular compartments. Whereas Gbeta5 is restricted to the perikarya, Gbeta2 is also found in processes and synaptic contacts where it partially colocalizes with the synaptic vesicle protein synaptobrevin. An antiserum recognizing Ggamma2 and Ggamma3 reveals that these subunits are less expressed in hippocampus and cerebellum. Presumably this antiserum specifically recognizes Ggamma2 and Ggamma3 in combinations with certain G alphas and/or Gbetas. The widespread but regionally and cellularly rather different distribution of Gbeta- and Ggamma2/3-subunits suggests that region-specific combinations of G-protein subunits mediate signal transduction in the central nervous system. The different subcellular distribution of Gbeta-subunits in cultivated neurons reflects that observed in tissue where Gbeta5 and Gbeta2 associate preferentially with the perikarya and the neuropil, respectively, and suggests an additional association of Gbeta2 with secretory vesicles.     

How do genes regulate simple behaviours? Understanding how different neurons in the vertebrate spinal cord are genetically specified

Understanding how the vertebrate central nervous system develops and functions is a major goal of a large body of biological research. This research is driven both by intellectual curiosity about this amazing organ that coordinates our conscious and unconscious bodily processes, perceptions and actions and by the practical desire to develop effective treatments for people with spinal cord injuries or neurological diseases. In recent years, we have learnt an impressive amount about how the nerve cells that communicate with muscles, motoneurons, are made in a developing embryo and this knowledge has enabled researchers to grow motoneurons from stem cells. Building on the success of these studies, researchers have now started to unravel how most of the other nerve cells in the spinal cord are made and function. This review will describe what we currently know about spinal cord nerve cell development, concentrating on the largest category of nerve cells, which are called interneurons. I will then discuss how we can build and expand upon this knowledge base to elucidate the complete genetic programme that determines how different spinal cord nerve cells are made and connected up into neural circuits with particular functions.