A Golgi study on the olfactory bulb in the red stingray, Dasyatis akajei.

The intrinsic organization of the olfactory bulb (OB) was studied in the red stingray using the rapid Golgi method. The OB is horse shoe-shaped, surrounding the equator region of the nasal capsule. As seen in the sagittal sections, the OB is round with the long olfactory peduncle extending from the dorsocaudal region and the olfactory fibers in a thick bundle entering from the rostroventral aspect. Although not so distinct, the following areas are distinguished. A rostroventral ovoid area adjacent to the entrance of the olfactory fibers consists exclusively of the olfactory fibers running in various directions. Dorsocaudal to the olfactory fiber area is a wide crescent region containing thin bundles of olfactory fibers, olfactory glomeruli, mitral cells and a few disseminated granule cells. A narrow crescent area made up of scattered granule cells is located dorsocaudally to the above wide crescent area. The outermost region consists of a fiber layer encapsulating the dorsal to caudal aspect of the OB. Thus, while the major constituents of the vertebrate OB are recognized, the lamination is very obscure.     

A Golgi study on the neuronal organization of the habenular ganglion in the red stingray, Dasyatis akajei.

The neuronal organization of the habenular ganglion (HG) was studied in the red stingray using the rapid Golgi method. The HG was made up of the medial (MH) and lateral habenular nucleus (LH), and the former nucleus was further divided into a dorsal, intermediate and ventral subnucleus. Only one type of neurons were observed in the MH, while the LH was composed of two types of neurons. In the left HG cut at the rostrocaudal middle of the ganglion, the LH was located in the dorsolateral region, while the dorsal, intermediate and ventral subnuclei of the MH occupied the dorsomedial, intermediate and ventral portions of the ganglion, respectively. In contrast, the right ganglion seen at this level was composed exclusively of the MH, with the dorsal, intermediate and ventral subnuclei located in the dorsomedial, intermediate and ventral portions, respectively. In the caudal level of the left ganglion, each nucleus was seen almost in the same region as in the level of the rostrocaudal middle, however, three subnuclei of the MH fused with the same subnuclei of the opposite side. In the right ganglion at the caudal level, the LH appeared in the intermediate area. The right LH was far smaller and was located more ventrocaudally than the left LH. On account of the LH, the intermediate subnucleus of the MH was divided into a dorsal and ventral part. The dorsal and ventral subnuclei of the MH remained in the same region as in the rostral level. Thus, the HG of the red stingray exhibited a striking left-right asymmetry, the most remarkable aspect of which was considered to be differences of the size, form and location of the LH between the left and right HG.     

A Golgi study on the afferent fibers to the habenular ganglion in the red stingray, Dasyatis akajei.

Afferent fibers to the habenular ganglion (HG) were derived mainly from the stria medullaris thalami (SM), which was roughly divided into a dorsal and ventral bundle. In the left ganglion seen at the level of the rostrocaudal middle, the dorsal bundle gave off collaterals to the lateral habenular nucleus (LH) and dorsal subnucleus of the medial habenular nucleus (MH), while the ventral bundle innervated the intermediate and ventral subnuclei of the MH. On the other hand, in the right ganglion at the level of the rostrocaudal middle, the dorsal subnucleus of the MH was innervated by collaterals from the dorsal bundle of the SM, whereas in the intermediate and ventral subnucleus fibers from the ventral bundle were seen. In the left ganglion at the caudal level, the dorsal and ventral bundle extended medially and joined the same bundle of the opposite side to constitute a dorsal and intermediate component of the habenular commissure, respectively. A third component of the HC, a ventral component, was seen to run between the fasciculus retroflexus of both sides. As in the case of the rostral level, the dorsal bundle of the SM emitted collaterals to the LH and dorsal subnucleus of the MH, while the intermediate and ventral subnuclei of the MH were projected upon by collaterals from the ventral bundle of the SM. At the caudal level of the right ganglion, the dorsal bundle gave off collaterals to the dorsal subnucleus of the MH. In contrast, the LH and the intermediate and ventral subnuclei of the MH were innervated by fibers from the ventral bundle. With regard to terminal patterns of the SM, fibers to the MH gave off many short fine branchlets forming the glomerular structures, whereas those to the LH branched out into numerous terminals to form a dense fiber plexus. Thus, the afferent fibers to the HG in the red stingray exhibited a striking left-right asymmetry.     

A Golgi study on the red nucleus in the mouse.

The intrinsic organization of the red nucleus (RN) was studied in the mouse using the rapid Golgi method. Cytoarchitecturally, the RN was divided into the magnocellular (RNmc) and parvocellular parts (RNpc). The former occupied the caudal one-third and the latter formed the rostral two-thirds of the RN. Based primarily on the size of somata, the RN neurons were classified into four types: giant, large, medium-sized and small neurons. Of these, the former two types of neurons were distributed mainly in the RNmc, while the latter two types of neurons were seen mainly in the RNpc. Axons of the RN neurons, at least those of the former three types of neurons, ran medially or caudomedially. Some axons ran across the mesencephalic raphe region to be lost in the medial region of the contralateral tegmentum. Two groups of afferent fibers to the RN were distinguished. Group I afferents were fibers composing the superior cerebellar peduncle. After crossing in the decussation of the superior cerebellar peduncle, these fibers entered the RN from the caudomedial aspect, ran rostrally in the nucleus emitting numerous collaterals. Group II afferents reached the RN from the ventrolateral aspect and traveled mediodorsally to be distributed totally within this nucleus.     

Molecular cloning and characterization of CD9 cDNA from cartilaginous fish, red stingray, Dasyatis akajei

CD9 is a glycoprotein of the transmembrane 4 superfamily (TM4SF) and is involved in various cellular processes. In this study, we describe the isolation of the full-length cDNA encoding for CD9 molecule (daCD9) of red stingray, Dasyatis akajei. This 1252 bp cDNA was isolated from leukocyte cDNA library and contains 681 bp open reading frame encoding 226 amino acid residues. Amino acid sequences analysis and structure prediction display approximately 50% identity to higher vertebrates with the presence of conserved structures, including the four transmembrane domains and certain characteristic residues. Southern blot analysis shows that daCD9 exists as a single copy gene. Northern blot analysis reveals that daCD9 is highly expressed in gill and spleen although its expression can be found in other tissues suggesting daCD9 might play an important role in immune defense in this fish.     

Transsynaptic degeneration in the inferior olivary nucleus associated with pontine glioblastoma

A case of glioblastoma arising in the pons of a 14-year-old boy in whom transsynaptic degeneration was found in the inferior olivary nucleus is reported. The tumor occupied most of the pons including the tegmental tract and invaded into the midbrain, medulla oblongata, cerebellar peduncles, thalamus, basal ganglia, and meninges. The right inferior olivary nucleus was devoid of the tumorous lesion, but many neurons were severely vacuolated. An immunohistochemical study using glial fibrillary acidic protein (GFAP), neuron-specific enolase (NSE), and S-100 protein was performed. GFAP and S-100 protein were positive in the reactive glia of the nucleus and NSE gave a faint reaction in some degenerated neurons. These degenerative changes found in neurons of the inferior olivary nucleus were considered to be transsynaptic degeneration due to the destruction of the tegmental tract at the pons and of cerebellar peduncles by invasive pontine glioblastoma.     

The development of major projections to the inferior olivary nucleus

Summary We have employed degeneration techniques to study the ontogeny of major projections to the inferior olivary nucleus in the North American opossum, a species which is born 12 days after conception and which enjoys a protracted development in an external pouch. Subsequent to spinal lesions a small amount of axonal degeneration can be produced within the edge of the olive before subnuclei can be distinguished (7 days after birth, 24 mm, snout-rump length). Degenerating axons are present more deeply within the olive in animals operated 12 days after birth (30 mm, snout-rump length) and by at least day 16 (36 mm, snout-rump length), they are found in all of the regions they occupy in the adult animal. Subsequent to lesions which undercut all descending mesencephalic and diencephalic systems, a small amount of axonal degeneration is found at the dorsolateral edge of the olive by day 7 (23 mm, snout-rump length). Degenerating axons fill more of the olive, particularly caudally, after comparable lesions in older animals and by day 17 (38 mm, snout-rump length), degeneration is present in all of the olivary regions innervated by midbrain and thalamic axons in the adult opossum. There is some evidence that spinal, mesencephalic and diencephalic axons follow a caudal to rostral gradient in their intraolivary growth. Lesions which undercut neurites growing out of the cerebellum produce evidence for cerebello-olivary connections by day 17. Axons from the cerebral cortex reach their olivary targets considerably later than those from either the spinal cord, mesencephalon, diencephalon or cerebellum. It is not until approximately postnatal day 30 (55 mm, snout-rump length) that degenerating axons can be traced into the olive after lesions of the cortical mantle. These data indicate that the inferior olive receives major connections early in development and that there is an orderly sequence to their growth.This investigation was supported by U.S.P.H.S. Grants NS-07410 and NS-08798 and The West Virginia University Medical Corporation.     

The neural connectivity of the inferior olivary nucleus in the human brain: A diffusion tensor tractography study

Objectives

Many animal studies have reported on the neural connectivity of the inferior olivary nucleus (ION). However, the neural connectivity of the ION has not been clearly elucidated in the human brain. In this study, the neural connectivity of the ION in the human brain was investigated by diffusion tensor imaging (DTI).

Methods

Forty healthy subjects were recruited. DTIs were acquired using a sensitivity-encoding head coil at 1.5 T. Connectivity was defined as the incidence of connection between the ION and regions of interest (ROIs) in the brain.

Results

In these subjects, the ION showed higher connectivity to the reticular formation (100%), the posterior limb of internal capsule (100%), the red nucleus (93.75%), the cerebral peduncle of midbrain (91.25%), the primary motor cortex (86.25%), the primary somatosensory cortex (85%), the periaqueductal gray mater (81.25%), the globus pallidus (81.25%), the anterior limb of internal capsule (62.5%), the pontine basis (62.5%), and the posterior parietal cortex (60%).

Conclusions

The ION shows high connectivity with motor function-related areas, such as, the posterior limb of internal capsule, the red nucleus, the cerebral peduncle of midbrain, the primary motor cortex, and the pontine basis. These results indicate that the ION is closely related to motor function in the human brain.     

Light labeling of red nucleus neurons following an injection of peroxidase-conjugated wheat germ agglutinin into the inferior olivary nucleus of the rat

Since the rubro-olivary projection has not been demonstrated in the rat, unlike the monkey and cat (refs. in text). HRP or highly-concentrated wheat germ agglutinin-horseradish peroxidase (WGA-HRP) was injected into the inferior olivary nucleus using a ventral approach. After processing with a modified technique, sections were examined under high power. Three rats injected with WGA-HRP showed labelling in the red nucleus. In one of those rats with a well-confined injection, 583 neurons contained grains of HRP reaction product consistent with light retrograde labeling. This observation lends support to the existence of a rubro-olivary projection in the rat.     

An electron microscopic study of the direct spino-olivary projection to the inferior olivary nucleus in the rat

This study examines electrophysiologically the projection of neurons in the mesodiencephalic junction to the inferior rectus subdivision of the oculomotor nucleus, using cats anesthetized with pentobarbital sodium. Many of these neurons projected directly to the ipsilateral inferior rectus subdivision and some to both sides. The neurons appeared to distribute axon branches probably terminating within and near the subdivision. They were located in the medial region of the mesodiencephalic junction between A 6.5 and 8.0 histologically corresponding to the campus prerubralis.     

Electrotonic coupling in the inferior olivary nucleus revealed by simultaneous double patch recordings

Electrotonic coupling in the inferior olivary (IO) nucleus is assumed to play a crucial role in generating the subthreshold membrane potential oscillations in olivary neurons and in synchronizing climbing fiber input into the cerebellar cortex. We studied the strength and spatial distribution of the coupling by simultaneous double patch recordings from olivary neurons in the brain slice preparation. Electrotonic coupling was observed in 50% of the cell pairs. The coupling coefficient (CC), defined as the ratio between voltage responses of the post- and the prejunctional cell, varied between 0.002 and 0.17; most of the pairs were weakly coupled. In more than 75% of the pairs, the CC was <0.05. The coupling resistance varied between 0.7 to 19.8 G(Omega), and 68% of the values fell between 0.7 to 8 G(Omega). The difference between the coupling coefficient measured on stimulation of cell 1 or cell 2 of a coupled pair was 27 +/- 16%. Direct calculation of the coupling resistance revealed an asymmetry of 24 +/- 12%, suggesting a directional preference of coupling. The coupling was voltage independent, although depolarization of either the pre- or the postjunctional neuron reduced the CC. The chance of a cell pair being coupled was 80% in immediate neighboring cells, but dropped to about 30% at a distance of 40 microm. No coupled pairs were observed at distances larger than 70 microm. In 52% of staining experiments neurobiotin injection into an olivary neuron produced indirect labeling of 1-11 nearby cells with an average of 3.8 +/- 2.9. All indirectly labeled cells were found in, or immediately adjacent, to the dendritic field of the directly stained neuron. Two distinct morphological types of olivary neurons, "curly" and "straight" cells, were found. In each case all neurons stained indirectly by dye passage through gap junctions belonged to the same type. Using the physiological data we estimated that each olivary neuron is directly coupled to about 50 neurons. Since somatic recordings may not reveal coupling through remote dendrites, we conclude that each neuron is directly connected to > or =50 neurons forming two distinct networks of curly and straight cells.     

Spatial distribution and subunit composition of GABA(A) receptors in the inferior olivary nucleus

GABAergic inhibitory feedback from the cerebellum onto the inferior olivary (IO) nucleus plays an important role in olivo-cerebellar function. In this study we characterized the physiology, subunit composition, and spatial distribution of gamma-aminobutyric acid-A (GABA(A)) receptors in the IO nucleus. Using brain stem slices, we identified two types of IO neuron response to local pressure application of GABA, depending on the site of application: a slow desensitizing response at the soma and a fast desensitizing response at the dendrites. The dendritic response had a more negative reversal potential than did the somatic response, which confirmed their spatial origin. Both responses showed voltage dependence characterized by an abrupt decrease in conductance at negative potentials. Interestingly, this change in conductance occurred in the range of potentials wherein subthreshold membrane potential oscillations usually occur in IO neurons. Immunostaining IO sections with antibodies for GABA(A) receptor subunits alpha 1, alpha 2, alpha 3, alpha 5, beta 2/3, and gamma 2 and against the postsynaptic anchoring protein gephyrin complemented the electrophysiological observation by showing a differential distribution of GABA(A) receptor subtypes in IO neurons. A receptor complex containing alpha 2 beta 2/3 gamma 2 subunits is clustered with gephyrin at presumptive synaptic sites, predominantly on distal dendrites. In addition, diffuse alpha 3, beta 2/3, and gamma 2 subunit staining on somata and in the neuropil presumably represents extrasynaptic receptors. Combining electrophysiology with immunocytochemistry, we concluded that alpha 2 beta 2/3 gamma 2 synaptic receptors generated the fast desensitizing (dendritic) response at synaptic sites whereas the slow desensitizing (somatic) response was generated by extrasynaptic alpha 3 beta 2/3 gamma 2 receptors.     

The neural connectivity of the inferior olivary nucleus in the human brain: a diffusion tensor tractography study

Propofol is a rapidly acting water-insoluble non-barbiturate anesthetic agent that is widely used as an intravenous sedative-hypnotic agent. Anecdotal evidence indicates that propofol may be effective at terminating intractable migraine headache. Cortical spreading depression (CSD) is believed to be the neural correlate of migraine aura and may be a trigger for migraine pain. Agents that block the induction or slow the spread of CSD may be of utility in treating migraine. Here we examined the ability of propofol hemisuccinate (PHS), a water-soluble prodrug of propofol, to affect CSD in mice. For comparison, we examinined dizocilpine, an NMDA receptor antagonist, that is well recognized to inhibit CSD. When administered 15min prior to activation of CSD by KCl application to the cortex, intraperitoneal PHS at doses of 120 and 200mg/kg decreased the number of CSD deflections without an effect on CSD amplitude, and at 200mg/kg caused a 77% reduction in CSD velocity. The minimally-effective dose of PHS (120mg/kg) did not cause sedation or motor impairment and while some animals receiving 200mg/kg did demonstrate motor impariment none exhibited loss-of-righting reflex (anesthesia). Dizocilpine produced comparable inhibition of CSD at doses of 0.5 and 2.5mg/kg. We conclude that acute PHS treatment inhibits CSD. Our results indicate that propofol, or its prodrug PHS, are worthy of further investigation as a treatment for migraine.     

Colchicine injection in the inferior olivary nucleus increases the number of Purkinje cell dendritic spines

The number of Purkinje cell dendritic spines was evaluated in the cerebellum of rats after injection of colchicine into the inferior olivary nucleus. In these conditions, the spines situated in the proximal (inner) part of the molecular layer were increased as compared to lumicolchicine-injected or non-injected control animals. Most postsynaptic targets for climbing fibers are located in the inner molecular layer and the fact that spines in this region increased when axonal transport was blocked in the climbing fibers suggests that the latter play a role in the control of spine formation.     

Occurrence of lymphohaemopoietic tissue in the meninges of the stingray Dasyatis akajei (Elasmobranchii,Chondricthyes)

The cytoarchitecture of the lymphohaemopoietic masses occurring in the “meninx primitiva” of the stingray Dasyatis akajei (Elasmobranchii, Chondricthyes) has been analyzed by light and scanning and transmission electron microscopy. Lymphohaemopoietic aggregates showing similar morphologies occurred along all the central nervous system, but they were more frequent in the telencephalon, diencephalon, and mesencephalon. In each aggregate, the granulopoietic tissue appeared in a fibroblastic stroma surrounding the large blood vessels, and the lymphoid components were present in a reticular network. Developing and mature eosinophils and heterophils–as well as lymphocytes, monocytes, macrophages, and plasma cells–are the main free cells present in these meningeal aggregates. The remarkable intimate association between macrophages and lymphoid cells to form close cell clusters suggests some immunological capacity for the meningeal lymphohaemopoietic tissue. According to their capacities, presence of lymphoid tissue, and histological organization, the meningeal lymphuhemopoietic aggregates of Dasyatis akajei resemble other lymphomyeloid aggregates associated with cranium and choroid plexuses in Holocephali and Ganoidei. The phylogenetical relationships of these aggregates with mammalian bone marrow are discussed.     

A Golgi study of the lateral reticular nucleus in the rat

Summary The organization of the lateral reticular nucleus (LRN) of the rat was investigated by using the Golgi technique. Golgi-Cox preparations revealed neurons with shapes similar to those observed in Nissl-stained preparations. Fusiform cells possess rectilinear dendrites with secondary dendrites which are longer than the parent stem. The remaining cell types have short dendrites which branch for three or four generations and follow a tortuous course. These two types of neurons are similar to the isodendritic and allodendritic neurons which have been reported in the reticular formation. The neurons throughout the LRN form cell clusters. In Golgi preparations five to ten cells are seen in each cluster but counterstaining reveals that the clusters are made up of many more cells than the Golgi preparations suggest. Many cells lie in close apposition and the dendrites of the cells in each cluster intertwine to form dendritic plexuses. Dendritic input from both neighbouring and distant cell clusters also contributes to the plexus formations within each cell cluster. Under high magnification, the dendrites show irregularities in their contours, including warty excrescenses, bumps and an array of spines, some of which are pedunculated. The appendages are confined primarily to distal portions of the dendrites, with few spines observed on the somata and proximal dendrites. Varicosed dendrites are also in common occurrence throughout the nucleus.