摘要:

AbstractThe aim of this study was to define the overall distribution pattern of the axon collaterals of single inferior olive (IO) neurons in relation to the multiple somatotopic maps defined by the climbing fiber (CF) input through the cerebellar cortex.In a previous study (Rosina and Provini:Brain Res. 289:45–63, '83), it was shown that the IO neurons supply interlobar collaterals to pairs of somatotopically related areas in the intermediate part of the anterior lobe (PIAL), in the paramedian lobule (PML), in crus II, and in the simple lobule, within strips C1 to D2. The residual branches then could either distribute within single folia or to adjacent folia within each somatotopically defined cerebellar area or both. We studied whether or not the IO axons branch over neighboring folia of the face‐forelimb (FL) areas of PIAL and PML and how this interfolial branching relates to the interlobar collateralization by using the multiple fluorescent retrograde tracing technique.The main results of the study were as follows: (1) the axons from neurons in IO subdivisions that are related to strips C1–C3 give off two interfolial branches in the FL area of PIAL and practically no interfolial collaterals are given in the FL area of PML; and (2) the neurons that give off interfolial collaterals also give interlobar branches.From these data we have inferred the general branching pattern of the IO neurons that convey FL information to PIAL and PML. Each neuron gives off two interlobar collaterals: the branch directed to PIAL splits again into two interfolial collaterals, while each of these three collaterals should give off about three branches within each target folium to account for the ten collaterals estimated to be present in the cat.The distribution pattern of IO axon collaterals proposed here suggests that the same CF‐relayed information may interact, at the Purkinje cell level, with different sets of mossy fiber inputs. The effect of this interaction would be to modulate the motor commands forwarded to specific muscle groups in relation to the different conditions under which a given movement is e

ISSN:0092-7317    

DOI:10.1002/cne.902560302

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe present study provides a description of the distribution patterns of enkephalin, substance P and dopamine immunoreactivity, and acetylcholinesterase activity in the striatum, nucleus accumbens, globus pallidus, and ventral pallidum of theGekko gecko.The pallidal structures were identified on the basis of characteristic enkephalin and substance P immunoreactive Plexus. The globus pallidus contains a very dense enkephalin immunoreactive wooly fiber plexus and a light and less extensive substance P immune‐reactive plexus. The ventral pallidum is characterized by substance P and enkephalin immunoreactive woolly fiber plexus, which show a dense and moderate staining, respectively. The striatum and the nucleus accumbens were found to be inhomogeneous with respect to staining intensities for all four makers. Except for the enkephalin immunoreactivity distribution pattern in the striatum, the compartments that can be distinguished in material stained for these markers appear to coincide quite wel

ISSN:0092-7317    

DOI:10.1002/cne.902560303

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractTwo types of large neurons are described in the caudal one‐third of the spinal cord of larval lampreys (26‐day, 13‐mm),Lampetra japonica.Rohon‐Beard cells (RB cells) are large neurons (8–14 m̈m in diameter) consistently positioned superficially in the dorsolateral part of the medullary wall and separated from the extramedullary space only by a basal lamina and a thin glia limitans and from the central canal lumen by the ependyma. The RB cell contains an extensive Golgi apparatus and granular endoplasmic reticulum. Its two processes arise from the basal part of the perikaryon and join the dorsolateral tract (DLT) to extend rostrally and caudally within the DLT, which is formed exclusively by contribution of RB cell processes at least in the caudal one‐third of the tail spinal cord. RB cells receive no synaptic nerve endings on their surfaces. The early developing RB cell exhibits an apical process that reaches the luminal surface of the central canal.Interneurons (15–19 m̈m in diameter) lie in the lateral region of the cord between the DLT and ependyma and receive from the DLT many synaptic nerve endings that contain aggregates of small, clear vesicles. They contribute axonal processes to the ventrolateral tract (VLT). Some developing interneurons have an apical process that contains abundant free ribosomes and granular ER.A presumptive model of how these cell classes are interconnected within the co

ISSN:0092-7317    

DOI:10.1002/cne.902560304

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractDuring a series of studies on the development of spinal nerves in the tail of larval lampreys (13 mm, 26 days),Lampetra japonica, we observed outflows of cytoplasmic processes (cytoplasmic outflow) or whole cell bodies (cellular outflow) from the neural tube or from the cord. Three types were distinguished according to their site of exit from the surface of the neuraxis.Thedorsal outflow(DO) is the cellular outflow seen on the midsagittal surface of the dorsal wall of the caudalmost region of the neural tube, just rostral or caudal to the opening in the dorsal tube wall. It is hypothesized that the cells from the dorsal neural tube become polymorphous cells scattered in the extramedullar space.Thedorsolateral outflow(DLO) is the cytoplasmic outflow emerging from the dorsolateral aspect of the spinal cord at the intermyotome level. DLO fibers are non‐myelinated fibers arising from the dorsolateral tract (DLT) and, after piercing the basal lamina and the glia limitans, run in the myosepta laterally to spread along the deep surface of the dermis. DLO fibers terminate in two different ways: those of one group pierce the dermis and the basal lamina to end as intraepidermal free endings that contain aggregates of clear vesicles, and those of the other group form varicosities that lie within depressions on the lateral cell surface of myotomes. DLO fibers in the extramedullary space characteristically lack any sheaths, including the basal lamina.Theventrolateral outflow(VLO) represents primitive ventral roots consisting of both the cytoplasmic and the cellular outflows: the former shows the axonal outgrowth from primitive somatomotor neurons, and the latter is represented by elongated cells derived from the glia limitans, extending along the axonal processes to form the Schwann cell sheath around the proximal portion of the ventral root axons. The basal lamina covering the cord does not extend along the VLO fibers. The developing ventral root contains axons at different stages of differentiation. Some axons end on the medial surface of the myotome at the midsegmental level to form neuromuscular junctions. However, axonal processes of primitive motoneurons form close contacts with muscle cells by means of small cytoplasmic projections that contain no synaptic vesicles and lack the basal lamina interposed between them.The proposed sequence of development, based on stages in caudal to rostral sections, is the DO, the DLO, and then the VLO. We observed no DLO or DLO fibers on the surface of the spinal cord and subunits of the myotome in 21‐mm larval lampreys: the typical DLO and DLO fibers have disappeared by this developmental st

ISSN:0092-7317    

DOI:10.1002/cne.902560305

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractSerial sections of the trunk and tail of 26‐day (13 mm) larval lampreys were examined by light and electron microscopy.Trunk region: Spinal ganglia and ventral nerves are seen alternately along the spinal cord and the notochord in the trunk. Spinal ganglia are located medially in intermyotome spaces with intersegmental blood vessels and send “dorsal nerves” ventrally along the vessels. “Ventral nerves” are seen on the midmedial surface of each myotome. Fibers containing densecored vesicles occur in the dorsal root but not in the ventral root.Caudal region: In the caudal one‐third of the tail the ventral nerves are formed earlier than spinal ganglia and dorsal nerves. The most caudal (primitive) ventral nerve (root) develops at the 12th myotome from the caudal end of the series of myotomes, the caudalmost ganglion being formed between the 15th and the 14th myotome in a 13‐mm larval lamprey. The intimate association of dorsolateral outflow (DLO) fibers (Nakao and Ishizawa:J. Comp. Neural256:356–368, '87b) with neural crest cells (DO cells of Nakao and Ishizawa; ibid.) strongly suggested that these fibers play an important role as the substrate for guiding the cells to form compact cell masses as primitive spinal ganglia. Two types of cell groups are progressively distinguished in primitive spinal ganglia during development. One of them has a light round nucleus with a prominent nucleolus and a large amount of the perinuclear cytoplasm that contains abundant free ribosomes, rough endoplasmic reticulum (ER), numerous Golgi apparatuses, and dense bodies. Cells of the other type are characterized by a dense, flattened nucleus with a small amount of perinuclear cytoplasm that extends as a thin cytoplasmic sheet to surround cells of the other type as a whole, the basal lamina surrounding the whole cell mass. The former type is interpreted as neural cells and the latter satellite cells of the ganglion. Central processes of ganglionic neural cells are assumed to enter the spinal cord along DLO fibers by using them as a substrate to establish the dorsal root. Intersegmental blood vessels develop later than spinal ganglia and peripheral processes extend al

ISSN:0092-7317    

DOI:10.1002/cne.902560306

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractSpinal nerve roots of 21‐mm larval and adult lampreys were electron microscopically studied. In 21‐mm larval lampreys, each ventral and dorsal rootlet contains axons of various diameters enclosed together as groups in individual troughs of a Schwann cell cytoplasm, lying in direct contact with one another, and is further ensheathed entirely by a basal lamina. Dorsal roots possess visceral axons, while ventral roots lack them. In adult lampreys the ventral and dorsal roots possess individual sheaths for larger somatic axons, each being surrounded by a single Schwann cell and the basal lamina and separated from one another by a considerable amount of connective tissue. Visceral fibers are present in both the dorsal and ventral roots of adult lampreys. They aggregate to form fascicles that lie among somatic axons, being separated from them.Two layers of the meningeal tissue invaginate to form a root sheath around the distal portion of individual dorsal and ventral roots of 21‐mm larval lampreys. In adult lampreys the sheath is similarly formed but extends over most of the dorsal and ventral roots. The perineurium is not developed in 21‐mm larval lampreys, but is present and ensheaths only the proximal portion of spinal nerve trunks outside the meninges in adult lampreys: it is completely absent along most of the length of peripheral nerves. In both larval and adult lampreys, the outer cell layer of the root sheath is open‐ended near the middle of nerve roots with respect to the extramedullary connective tissue space. Similar loosening of the cellular barrier is seen along blood vessels. Thus, the outer meningeal fibrous layer is directly continuous with the extra medullary connective tissue space by way of the inner fibrous layer of the ro

ISSN:0092-7317    

DOI:10.1002/cne.902560307

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractAnterograde transport of either HRP or wheat germ agglutinin‐conjugated HRP was used to study the posthatching development of the retinotectal connection in the pigeon. The functional maturation of the retinotectal system was also investigated by recording electroretinographic (ERG) and tectal evoked (TEP) responses to either flash or pattern stimuli. Two main morphological changes occurred in the retinotectal system during the first 6 days after hatching: (1) an ipsilateral retinofugal component that was present at hatching disappeared and (2) the outer tectal layers were progressively invaded by the contralateral retinofugal axons, which at hatching were limited to thestratum griseum et fibrosum superficialeof the dorsolateral tectal quadrant. During the early posthatching period, at the same developmental stage at which an ERG to unpatterned or patterned stimulation could first be recorded, a visually evoked response could be elicited in the contralateral optic tectum. Therefore, the retina and optic tectum seem to start functioning simultaneously, the limiting factor being the late maturation of photosensitive lamellae in the outer segments of the developing photoreceptors. During the first 20 days posthatching, the retinotectal system undergoes extensive development as revealed by latency and amplitude changes of the visually evoked potentials. We suggest that the pigeon visual system serves as a useful model for studies concerning visual development and plasticit

ISSN:0092-7317    

DOI:10.1002/cne.902560308

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractA population of intersegmental interneurones with axons extending from the meso‐ to the metathoracic ganglion of the locust is described. They receive specific mechanosensory inputs from one mesothoracic leg. Their cell bodies are in group at the posterior of the mesothoracic ganglion, lying over the lateral base of each connective, and their primary neurites emerge in one of four bundles. Their mesothoracic branches are ipsilateral to the cell bodies and the leg from which they receive inputs. Each interneurone has two to six mesothoracic secondary neurites that divide and form a dense field of arborizations in specific regions of the neuropil so that each individual interneurone has a characteristic shape that is an elaboration of a basic and common plan.An interneurone excited by tibial campaniform sensilla and tarsal hair afferents branches in the intermediate neuropil and the ventral association center where the afferents from these receptors also project. An interneurone excited by proprioceptive inputs from the tarsus arborizes in the dorsal and intermediate neuropils, lateral to the ventral intermediate and ventral median tracts, in the same area as the proprioceptors afferents. An interneurone inhibited by proprioceptive inputs from the tibia (and wing) arborizes only in the dorsal neuropil, where there are no afferent projections.Some interneurones have one to three axonal branches with sparse and varicose side branches in the mesothoracic ganglion, which resemble the metathoracic axonal branches.The metathoracic axonal branches are mostly restricted to the dorsal neuropil and the dorsal part of the intermediate neuropil where local non‐spiking interneurones and motor neurones controlling movements of the hind leg also project.The overlap between the branches of the sensory afferents and the intersegmental interneurones in the mesothoracic ganglion and between those of the nonspiking local interneurones or motor neurones and intersegmental interneurones in the metathoracic ganglion suggest that these interneurones are responsible for transferring information about the action of one leg to an adjacent

ISSN:0092-7317    

DOI:10.1002/cne.902560309

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe axon terminals of cone horizontal cells in the goldfish retina form typical chemical synaptic contacts in the middle of the inner nuclear layer. Approximately 60% of the identified postsynaptic elements were perikarya, axons and dendrites of bipolar cells. The other identified postsynaptic elements were perikarya and processes of interplexiform cells. We propose that the horizontal cell axon terminals contribute to the antagonistic surround responses of the bipolar cells and that they modulate inputs to the outer plexiform layer conveyed by interplexiform cells. Output synapses from horizontal cell axons to unidentified neuronal processes as well as occasional input synapses to the axons from interplexiform cell processes and unidentified perikarya were also observed in the same region of the inner nuclear layer.

ISSN:0092-7317    

DOI:10.1002/cne.902560310

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractRats whose right eyes were enucleated on day 1 after birth and nonenucleated rats were raised in either “light” or “dark” (red light) conditions from birth until 39 days of age. This resulted in 4 groups of animals: light‐reared nonenucleated, light‐reared enucleated, dark‐reared nonenucleated, and dark‐reared enucleated. At 39 days of age, the animals were killed by perfusion with 2.5% sodium cacodylate buffered glutaraldehyde. The superior colliculi were dissected out and processed for embedding in resin. Stereological procedures at the light and electron microscopical levels were used to estimate the synapse‐to‐neuron ratios in the superficial layers of these colliculi.Light‐reared, nonenucleated rats had about 1,850 synapses‐per‐neuron in both the right and left superior colliculi. Rearing nonenucleated rats in the dark reduced this value to about 1,200.Enucleated rats reared in the light showed a differential response in the 2 colliculi. Thus, the contralateral (to the enucleated eye) colliculi showed a decrease, whereas the ipsilateral colliculi showed an increase in the synapse‐to‐neuron ratio compared with light‐reared, nonenucleated rats.When enucleated rats were reared in the red light, there was a decrease in the ratio in both colliculi, although the extent of this decrease was more marked in the contralateral than the ipsilateral colliculi. However, the decrease in the contralateral colliculi was not significantly greater than that observed in the corresponding colliculi from dark‐reared, nonenucleated rats.These results provide useful information on the combined and separate effects of unilateral enucleation at around birth and dark (red light) rearing during early life on the interneuronal connectivity of both the ipsi‐ and contralateral superior colliculi of rats. They also show the vast importance of visual stimulation for the normal developmen

ISSN:0092-7317    

DOI:10.1002/cne.902560311

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY