bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of brainstem and cerebellar projections to the diencephalon with notes on thalamocortical projections: Studies in the north american opossum
Authors: Martin G. F. , Cabana T. , Hazlett J. C. , Ho R. , Waltzer R.
Published: January 2005

The North American opossum is born in a very immature state, 12 days after conception, and climbs into an external pouch where it remains attached to a nipple for an extended period of time. We have taken advantage of the opossum's embryology to study the development of brainstem and cerebellar projections to the diencephalon as well as the timing of diencephalic projections to somatosensory motor areas of neocortex. The techniques employed included immunocytochemistry for serotonin, the retrograde and orthograde transport of wheat germ agglutinin conjugated to horseradish peroxidase, and the selective impregnation of degenerating axons. Our results suggest that serotoninergic axons, presumably from the dorsal raphe and superior central nuclei, are present in the diencephalon at birth. Axons from the bulbar reticular formation, the vestibular complex, the trigeminal sensory nuclei, and the dorsal column nuclei reach at least mesencephalic (and probably diencephalic) levels by postnatal day (PND) 3, whereas those from the cerebellar nuclei may not grow into comparable levels until PND 5. The dorsal column and cerebellar nuclei innervate the ventral nuclei of the thalamus by estimated postnatal day (EPND) 17 and all of the diencephalic nuclei supplied in the adult animal by EPND 26. Diencephalic axons enter ventrolateral (face) areas of presumptive somatosensory motor cortex by PND 12, but do not reach dorsomedial (limb) regions until EPND 21. At both ages, diencephalic axons are limited to the cortical subplate and marginal zone; they do not innervate an identifiable internal granular layer until considerably later. Our results suggest that axons from the brainstem and cerebellum grow into the diencephalon early in development, but that they do not influence the cerebral cortex until relatively late. When the results of the present study are compared with those reported previously on the development of ascending spinal (Martin et al., '83) and corticofugal (Martin et al., '80; Cabana and Martin, '85b, c) projections, it appears that specific components of major somatosensory and motor circuits develop according to different timetables.
Somatotopic alignment between climbing fiber input and nuclear output of the cat intermediate cerebellum
Authors: Gibson A. R. , Robinson F. R. , Alam J. , Houk J. C.
Published: January 2005

The rostral dorsal accessory olive (rDAO) contains a detailed somatosensory map of the entire contralateral body surface. The rDAO projects to the anterior interpositus nucleus (NIA) directly as well as indirectly by way of Purkinje cells in cerebellar cortex. NIA maintains a topographic relation to different levels of the spinal cord through a relay in the magnocellular red nucleus (RNm) and, thus, contains a motor somatotopy. By using bidirectional transport of WGA‐HRP, we demonstrate that the sensory somatotopy of rDAO aligns with the motor somatotopy of NIA. It is likely that rDAO information supplied to the cerebellum from a specific part of the body is used to influence movements restricted to that same body part.
Short axon cells of the rat olfactory bulb display NADPH‐diaphorase activity, neuropeptide Y‐like immunoreactivity, and somatostatin‐like immunoreactivity
Authors: Scott John W. , McDonald John K. , Pemberton Janice L.
Published: January 2005

Several types of short axon cells of the mammalian olfactory bulb have been described after Golgi impregnation. Two of these types have been observed in our material after treatment with the NADPH‐diaphorase procedure or after immunohistochemistry for neuropeptide‐Y (NPY). The cells stained by the two procedures have similar morphologies and distributions. A less extensive series of observations confirms that similar cells also display somatostatin (SS)‐like immunoreactivity. One of these cell types corresponds to the superficial short axon cell of Golgi and electron microscopic studies. The dendrites of this cell lie within the periglomerular region and in the superficial external plexiform layer (EPL), generally lying parallel to the glomerular layer. In some cases the axon has been traced across the EPL into the granule cell layer (GCL). This cell may provide another route of interaction between the periglomerular region and the granule cells in addition to the influences conducted by basal dendrites and axon collaterals of some mitral and tufted cells. A type of deep short axon cell is also visible with these two procedures. It lies deep in the granule cell layer, frequently near the ventricular layer and its dendrites lie parallel to that layer. This deep short axon cell is stained with much greater frequency by the NADPH‐diaphorase and NPY procedures than is the superficial short axon cell. It corresponds most closely to the Blanes or Golgi cells of the Golgi impregnation literature, but it appears to differ from these cells in the position and orientation of its dendrites. No spines have been observed on either the superficial or deep cells in this series. Many glomeruli are also stained by the NADPH‐diaphorase procedure, but are not NPY or SS immunoreactive. This may provide additional evidence for functional differences between glomeruli in local regions of the olfactory bulb.
Morphological properties of respiratory intercostal motoneurons in cats as revealed by intracellular injection of horseradish peroxidase
Authors: Lipski J. , Martin‐body R. L.
Published: January 2005

This study was undertaken to describe details of the location and cellular morphology of functionally identified (inspiratory or expiratory) external and internal intercostal motoneurons on the basis of intracellular injection of horseradish peroxidase (HRP). Sixty HRP‐labeled motoneurons were examined; 44 in transverse, 16 in sagittal sections. In the upper thoracic segments ( T3T4), there was only a small overlap in the location of inspiratory external and internal intercostal motoneurons; the inspiratory external motoneurons were generally found more ventromedially within the ventral horn than either inspiratory or expiratory internal intercostal motoneurons. No major morphological differences were observed between the types of motoneurons studied. The number of primary dendrites ranged from 6 to 10. The dendrites projected mainly along the medial or the lateral border of the ventral horn, and rostrocaudally up to 1,760 μm from the cell body. The paths taken by dendrites to fill the territory occupied by the dendritic trees appeared to depend upon location of the cell body. Few dendrites penetrated the white matter. Axon diameters varied from 1.1 to 6.7 μm (mean 3.6 ± 1.3 μm, n = 55). Collateral branches were identified in 78% of axons. The number of branches arising from a given axon varied from 1 to 4. It is concluded that the respiratory intercostal motoneurons form a morphologically homogeneous population, in spite of their functional differences.
Early development of photoreceptors in the ventral retina of the zebrafish embryo
Authors: Kljavin Ivar J.
Published: January 2005

The first photoreceptor outer segments in the retina of the zebrafish Brachydanio rerio appear in the embryo 2.5 days after fertilization, as revealed by scanning and transmission electron microscopy. These outer segments arise in a small region ventral to the exit of the optic nerve. Ultrastructural features of the developing photoreceptor cells, especially those that distinguish the rods and cones, are described. By 3 days after fertilization, the time of hatching, photoreceptor outer segments are widespread in the retina. However, at this time and in the young larva the early developing ventral region remains distinctive because of its conspicuous population of rods.
Immunohistochemical localization of substance P and enkephalin in the nucleus tractus solitarii of the rhesus monkey, Macaca mulatta
Authors: Maley Bruce E. , Newton Bruce W. , Howes Kimberly A. , Herman Linda M. , Oloff Clarence M. , Smith Katherine C. , Elbe Robert P.
Published: January 2005

The nucleus tractus solitarii in the monkey Macaca mulatta was found to have several subdivisions based upon cytoarchitectonics and immunohistochemistry. Subdivisions that could be identified included commissural, medial, parvicellular, dorsolateral, ventrolateral, intermediate, and interstitial. Substance P and enkephalin immunoreactivity was localized within discrete regions of the nucleus tractus solitarii, by means of the peroxidase‐antiperoxidase technique. Substance P immunoreactivity occurred most frequently in the interstitial subdivision of the nucleus tractus solitarii. Moderate accumulations of substance P immunoreactivity were present in the commissural, medial, parvicellular, dorsolateral, and intermediate subdivisions, but very little was present in the ventrolateral subdivision. Enkephalin immunoreactivity followed the staining patterns of substance P; however, the amounts of enkephalin immunoreactivity were less than amounts for substance P. Following colchicine treatment, large numbers of enkephalin‐immunoreactive neurons were distributed throughout all subdivisions, many being located in the parvicellular and medial subdivisions. The few substance P‐immunoreactive neurons found were restricted to the parvicellular subdivision. The distribution of substance P and enkephalin immunoreactivity in M. mulatta is very similar to that described in the cat and rat. In addition, the extensive overlap of the distribution of these two putative neurotransmitters provides morphological evidence for their possible participation in the autonomic regulation within the nucleus tractus solitarii.
Convergence of ascending pathways at the inferior colliculus of the mustache bat, pteronotus parnellii
Authors: Zook J. M. , Casseday J. H.
Published: January 2005

To compare patterns of projections to the inferior colliculus from different sources, injections of [3H]‐leucine were placed in the cochlear nuclei, superior olivary complex, and nuclei of the lateral lemniscus of Pteronotusc parnellii. The results show that the target of the anteroventral cochlear nucleus (AVCN) is the ventral and lateral two thirds of the central nucleus of the inferior colliculus. The binaural pathways from the medial and lateral superior olives (MSO and LSO) project to the same target. The dorsal cochlear nucleus (DCN) projects to the entire central nucleus of the inferior colliculus and does so in a more diffuse manner than does the AVCN. The DCN also sends sparse projections beyond the central nucleus into dorsal parts of the pericentral area. The intermediate (INLL) and ventral (VNLL) nuclei of the lateral lemniscus are relays in pathways that originate in the cochlear nucleus and terminate in the contralateral inferior colliculus. These nuclei also receive indirect input from the contralateral AVCN via the medial nucleus of the trapezoid body. Although nuclei of the lateral lemniscus project most densely to those areas of the inferior colliculus that are also the targets of the AVCN, MSO, and LSO, the nuclei of the lateral lemniscus also send spare projections outside these areas. Many of the pathways just described project in bands, a finding that raises the possibility that the projections parallel the orientation of disk‐shaped cells in the inferior colliculus and raises the question of whether the bands from one source overlap or interdigitate with the bands from another source.
Mapping study of serotoninergic input to diencephalic‐projecting dorsal column neurons in the rat
Authors: Willcockson H. H. , Carlton S. M. , Willis W. D.
Published: January 2005

Several lines of evidence indicate that the processing of somatosensory information in the dorsal column nuclei (DCN) is subject to descending controls. Anatomical experiments have demonstrated projections to the DCN from the sensorimotor cerebral cortex and the reticular formation. Physiological studies have shown that the activity of DCN neurons can be altered following stimulation of the cerebral cortex, reticular formation, periaqueductal gray, or raphe nuclei. Recent biochemical and electrophysiological evidence suggests a serotoninergic modulation of DCN neurons. The present study identifies serotonin‐containing contacts on cells in the DCN that project to the thalamus in the rat. Retrograde labeling of brainstem neurons by horseradish peroxidase demonstrated projections to the DCN from the nucleus reticularis paragigantocellularis lateralis and from several raphe nuclei, including nuclei raphe obscurus (RO), pallidus (RP), and magnus (RM). Double labeling with horseradish peroxidase and antibody for serotonin indicated that the RO, RP and RM are likely to be the sources of the serotoninergic projections to the DCN. Thus, the role of the serotoninergic output from the raphe nuclei includes modulation of activity in the DCN.
Ultrastructure of apical specializations of taste cells in the mudpuppy, Necturus maculosus
Authors: Cummings T. A. , Delay R. J. , Roper S. D.
Published: January 2005

The first interaction of taste stimuli with lingual chemoreceptors occurs on the apical membrane of taste cells, since only that portion is exposed to the oral cavity. To gain better insight into this interaction, we examined the pore region of taste buds in Necturus maculosus with scanning electron microscopy (SEM), transmission electron microscopy, and high‐voltage electron microscopy. SEM of the pore reveals a patchwork distribution of three morphologically distinct types of apical specializations: long and branched (LB) microvilli, short and unbranched (SU) microvilli, and bundles of sterocilia. As demonstrated in thin and thick sections, LB microvilli are specializations of dark cells, SU microvilli are the apical specializations of light cells, and stereocilia arise from a cell that has the cytoplasmic markers characteristic of light cells. When left in place, the pore mucus completely covers the SU microvilli and partially covers the LB microvilli. However, stereocilia project above the surface and thus are highly exposed to taste stimuli in the oral cavity. These three morphologically distinct types of apical specializations may reveal functional differences among taste cells. The initial interaction between chemical stimulus and taste cell, and possibly chemoreceptor specificity itself, may be influenced by the morphology of the apical ending.
Developmental and other factors affecting regeneration of crayfish CNS axons
Authors: Seshan Kalpathi R. , Bittner George D.
Published: January 2005

According to histological and ultrastructural criteria, nongiant CNS axons in newly hatched crayfish regenerate more rapidly and with greater frequency than do similar axons in adult crayfish.

Regenerative ability is greater in one species (Procambarus clarkii) than in another species (Procambarus simulans), is greater at 20–25°C than at 15–16°C, and is greater in nongiant axons than in giant axons. In contrast to axonal regeneration, nerve cell bodies do not regenerate in newly hatched or adult crayfish of either species. While the ability to regenerate CNS axons differs between newly hatched and adult crayfish, the ultrastructural appearance of the CNS is very similar at any age it is examined.
Immunohistochemical localization of calcium‐binding proteins, parvalbumin and calbindin‐D 28K, in the adult and developing visual cortex of cats: A light and electron microscopic study
Authors: Stichel C. C. , Singer W. , Heizmann C. W. , Norman A. W.
Published: January 2005

In the cat primary visual cortex, we investigated with immunohistochemical techniques the developmental changes in the cellular and subcellular localization of the Ca2+‐binding proteins parvalbumin (PV) and calbindin‐D 28K (CBP), in order to determine whether there is a correlation between the expression of Ca2+‐dependent processes and the time course of the critical period for use‐dependent plasticity.

On the 54th day of gestation and at 1 week postnatally, both calcium‐binding proteins were present only in a subpopulation of neurons in layers V and VI. During subsequent maturation, the number of PV(+) and CBP(+) neurons increased significantly and labeled cells were detected in more superficial layers. Moreover, the homogeneous labeling of some CBP(+) neurons in layers IV to VI decreased and changed to a punctate pattern. In adult cats PV(+) neurons were evenly distributed throughout layers II to VI, whereas CBP(+) neurons were concentrated in layers II/III. Only a few immunoreactive cells had morphological features characteristic of pyramidal cells; the large majority were nonpyramidal.

Electron microscopy confirmed the presence of PV‐ and CBP‐reaction product within the perikarya, axons, and dendrites of labeled cells. It was associated preferentially with microtubules, postsynaptic densities, and intracellular membranes. Immunoreactive neurons received immunonegative asymmetric synapses on their dendritic shafts and made symmetric synaptic contacts with labeled and unlabeled somata and with unlabeled dendritic shafts.

The large number and widespread distribution of immunoreactive neurons implies that PV and CBP play an important role in the regulation of calcium‐dependent processes in the visual cortex. Furthermore, the developmental redistribution of PV and CBP points to changes in the organization of Ca2+‐dependent processes during maturation.
Localization of tyrosine hydroxylase immunoreactive neurons in the cat hypothalamus, with special reference to fluorescence histochemistry
Authors: Kitahama Kunio , Luppi Pierre‐Herve , Berod Anne , Goldstein Menek , Jouvet Michel
Published: January 2005

The present study examines the distribution and morphological characteristics of neurons containing immunoreactivity of tyrosine hydroxylase in the cat hypothalamus. We used the indirect immunoperoxidase technique on vibratome sections. Tyrosine hydroxylase immunoreactive cell bodies were widely distributed in discrete regions of the cat hypothalamus. Several principal cell groups were identified. They were seen in the posterior and dorsal hypothalamic areas, zona incerta, dorsomedial and lateral hypothalamic areas, arcuate nucleus, periventricular nucleus, paraventricular nucleus, and an area of the tuber cinereum and preoptic area. These cells presented two different morphological characteristics; small with two to three short processes and medium to large, multipolar with three to five long dendritic trees. The atlas is presented in twelve cross‐sectional drawings of the cat hypothalamus from the level A8.5 to A15 of the Horsley‐Clarke stereotaxic planes. We also examined the distribution of hypothalamic catecholamine fluorescent neurons by using the aqueous aldehyde method in combination with glyoxylic acid applied to vibratome sectioned tissues, which improves sensitivity. Comments are made on the relative localizations of the tyrosine hydroxylase‐immunoreactive and aldehyde‐induced histofluorescent cells, as well as on species differences between the cat, rat, and mouse.
Movement of newly synthesized membrane by fast transport along the axon of an identified aplysia neuron
Authors: Cleary Leonard J. , Schwartz James H.
Published: January 2005

In order to ascertain the form in which newly synthesized membrane is moved by fast axonal transport, we examined the distribution of label along an axon of the identified giant, serotoninergic neuron (GCN) in the cerebral ganglion of Aplysia, californica. Membrane glycoproteins were labeled by intrasomatic injection of 3H‐fucose, and segments of GCN's axon in the posterior lip nerve containing the transported organelles were examined at 1, 5, 15, and 24 hours by quantitative electron‐microscopic autoradiography. To show that membrane which is rapidly transported is contained only in discrete organelles rather than in continuous shoots of axoplasmic reticulum, we systematically varied conditions of fixation. We found that we could distinguish vesicles from axoplasmic reticulum most reliably in axons fixed with 2% formaldehyde and 2% glutaraldehyde in cacodylate buffer. At short times after intrasomatic injection of 3H‐fucose, dense‐cored vesicles and multivesicular tubules were the only axonal organelles labeled.
Frontal projections to the region of the oculomotor complex in the rat: A retrograde and anterograde HRP study
Authors: Leichnetz G. R. , Hardy S. G. P. , Carruth M. K.
Published: January 2005

The retrograde and anterograde capabilities of the horseradish peroxidase (HRP) technique were employed to study frontal projections to the perioculomotor region in the rat. Following HRP microinjections or trans‐cannular HRP gel implants into the oculomotor complex (OMC), the majority of retrogradely labeled pyramidal cells were located in lamina V of the dorsomedial frontal shoulder cortex, i.e., medial precentral and anterior cingulate (PrCm/AC) cortices, the proposed frontal eye field (FEF) in the rat. A smaller number of labeled cells were present in the frontal polar cortex, agranular insular (AI), and lateral precentral (PrCl) cortices. Following HRP gel implants into the PrCM/Ac, anterogradely labeled projections were observed to the dorsal medial subthalamic region (nucleus campi Foreli, NCF) and medial accessory nucleus of Bechterew (MAB), and to other subcortical nuclei known to receive inputs from cortical area 8 in the monkey. These results, taken together with previous anatomical and physiological studies, support the conclusion that the PrCm/AC cortex contains the rat FEF. Its homo logy with the primate FEF is discussed.
Motoneuronal death during human fetal development
Authors: Forger Nancy G. , Breedlove S. Marc
Published: January 2005

The total number of ventral horn motoneurons throughout the spinal cord was determined for 19 human fetuses ranging in age from 11 to 32 menstrual weeks. There was a significant (∽35%) decline in motoneuron number between wks 11 and 25 of gestation, but no further decline from wks 25–32. Counts of pyknotic cells indicated a peak of motoneuronal degeneration between about wks 12 and 16 of age. The normal period of motoneuronal death observed here overlaps with the initiation of functional neuromuscular contact as well as the period of androgen production by the human fetal testes. As in rats, androgen may influence final motoneuron number in the human spinal cord by attenuating cell death in sexually dimorphic motor nuclei.
Central projections of the glossopharyngeal and vagal nerves in the channel catfish, Ictalurus punctatus: Clues to differential processing of visceral inputs
Authors: Kanwal Jagmeet S. , Caprio John
Published: January 2005

Transganglionic transport of horseradish peroxidase was used to trace the pattern of medullary terminations of the glossopharyngeal and vagal nerve complex in the channel catfish, Ictalurus punctatus. The glossopharyngeal root terminates centrally in the anterior end of the vagal lobe except for two fascicles that terminate in separate regions of the nucleus intermedius of the facial lobe. Vagal nerve branches innervating regions of the oropharynx terminate in an overlapping, segmental fashion throughout the ipsilateral vagal lobe and the nucleus intermedius of the vagal lobe. The descending branch of the vagus, innervating the abdominal viscera, terminates in the general visceral nucleus and in the nucleus intermedius of the vagal lobe. In addition, abdominal visceral fibers decussate through the commissural nucleus of Cajal and terminate in the general visceral nucleus of the contralateral side. Efferents included in the oropharyngeal and abdominal branches of the vagus also originate from two morphologically separable populations of motor neurons.
Differential localization of alkaline phosphatase in barrier tissues of the frog and rat nervous systems: A cytochemical and biochemical study
Authors: Latker Carole H. , Shinowara Nancy L. , Miller Joseph C. , Rapoport Stanley I.
Published: January 2005

We investigated the localization of alkaline phosphatase (AP) in the peripheral and central nervous systems of the frog (Rana pipiens) and rat. In the frog sciatic nerve, AP reaction product was seen as a precipitate within caveolae and vesicular profiles of perineurial cells, and frequently filled the extracellular space. In the rat peripheral nerve, AP reaction product appeared as small tufts on the cell surfaces and within vesicular profiles of endoneurial blood vessels. AP reaction product was not detected in the rat perineurium or in endoneurial blood vessels of the frog. In the frog central nervous system, AP reaction product was detected in the arachnoid membrane adjacent to the subarachnoid space, but not in the cerebral or pial vessels, whereas in the rat it was detected in the outer arachnoid membrane and in the cerebral and pial blood vessels. Biochemical analysis indicated a sevenfold higher AP activity in the frog perineurium over the endoneurium, whereas in the rat, threefold more activity was measured in the endoneurium over the perineurium. Levamisole, an AP inhibitor, decreased the enzyme activity by 95% in rat tissues, and by 70% in frog tissues and in plasma from both animals. Similar decrements were observed cytochemically.

This study suggests that: (1) the distribution of AP varies between species, but that it is always present in at least one component of the blood‐brain and blood‐nerve barriers, (2) because barrier tissues of the nervous system have enzymatic activity, they may biochemically modify the adjacent environment, (3) vesicular profiles and caveolae in the blood vessels and perineurium may function as microenvironments for enzymatic activity, and (4) in the rat and frog, different isozymes of AP may be present.
The entorhinal cortex of the monkey: III. Subcortical afferents
Authors: Insausti R. , Amaral D. G. , Cowan W. M.
Published: January 2005

The subcortical afferent connections of the entorhinal cortex of the Macaca fascicularis monkey were investigated by the placement of small injections of the retrograde tracer wheat germ agglutinin conjugated to horseradish peroxidase into each of its subdivisions. Retrogradely labeled cells were observed in several subcortical regions including the amygdaloid complex, claustrum, basal forebrain, thalamus, hypothalamus, and brainstem. In the amygdala, labeled cells were observed principally in the lateral nucleus, the accessory basal nucleus, the deep or paralaminar portion of the basal nucleus, and the periamygdaloid cortex. Additional retrogradely labeled cells were found in the endopiriform nucleus, the anterior amygdaloid area, and the cortical nuclei. Retrogradely labeled cells were observed throughout much of the rostrocaudal extent of the claustrum and tended to be located in its ventral half. In the basal forebrain, retrogradely labeled cells were observed in the medial septal nucleus, the nucleus of the diagonal band, and to a lesser extent within the substantia innominata. Several of the cells in the latter region were large and located within the densely packed neuronal clusters of the basal nucleus of Meynert. Most of the labeled cells in the thalamus were located in the midline nuclei. Many were found in nucleus reuniens, but even greater numbers were located in the centralis complex. Additional labeled cells were located in the paraventricular and parataenial nuclei. In all cases, numerous retrogradely labeled cells were observed in the medial pulvinar. In the hypothalamus, most of the retrogradely labeled cells were located in the supramamillary area, though scattered cells were also observed in the perifornical region and in the lateral hypothalamic area. Caudal to the mamillary nuclei there were labeled cells in the ventral tegmental area. There were relatively few labeled cells in the brainstem and these were invariably located either in the raphe nuclei or locus coeruleus.
Anatomical and physiological characteristics of vestibular neurons mediating the vertical vestibulo‐ocular reflexes of the squirrel monkey
Authors: McCrea R. A. , Strassman A. , Highstein S. M.
Published: January 2005

The morphology of 35 vestibular neurons whose firing rate was related to vertical eye movements was studied by injection of horseradish peroxidase intracellularly into physiologically identified vestibular axons in alert squirrel monkeys. The intracellularly injected cells were readily classified into four main groups. One group of cells, down position‐vestibular‐pause neurons (down PVPs; N = 12), increased their firing rate during downward eye positions, paused during saccades, and were located in the medial vestibular nucleus (MV) and the adjacent ventrolateral vestibular nucleus (VLV). They had axons that crossed the midline and ascended in the medial longitudinal fasciculus (MLF) to terminate in the trochlear nucleus, the lateral aspect of the caudal oculomotor nucleus, and the dorsal aspect of the rostral oculomotor nucleus. A second group of cells (N = 15) were also located in the MV and VLV, but increased their firing rate during upward eye positions, and paused during saccades. These cells had axons that crossed the midline and ascended in the contralateral MLF to terminate in the medial aspect of the oculomotor nucleus. A third group of cells (N = 4) were located in the superior vestibular nucleus, generated bursts of spikes during upward saccades, and increased their tonic firing rate during upward eye positions. These cells had axons that ascended laterally to the ipsilateral MLF to terminate in regions of the trochlear and oculomotor nuclei similar to those in which down PVPs terminated. A fourth group of cells (N = 4), located in the VLV, had axons that projected to the spinal cord, although they had firing rates that were significantly correlated with vertical eye position. Electrical stimulation of the vestibular nerve evoked spikes at monosynaptic latencies in each of the above classses of cells, six of which were injected with horseradish peroxidase.

Each group of cells had collateral projections to other areas of the brainstem. Some of the neurons that projected to the contralateral trochlear and oculomotor nuclei had collaterals that crossed the midline to terminate in the oculomotor nucleus ipsilateral to the soma, and some gave rise to small collaterals that terminated in the abducens nucleus. Other areas of the brainstem that received collateral inputs from neurons projecting to oculomotor and trochlear nuclei included the interstitial nucleus of Cajal, the caudal part of the dorsal raphe nucleus, the nucleus raphe obscurus, Roller's nucleus, the intermediate and caudal interstital nuclei of the MLF, and the nucleus prepositus.
Ultrastructural analyses of afferent terminals in the subthalamic nucleus of the cat with a combined degeneration and horseradish peroxidase tracing method
Authors: Moriizumi Tetsuji , Nakamura Yasuhisa , Kitao Yasuko , Kudo Motoi
Published: January 2005

The synaptic organization of the feline subthalamic nucleus (STN) was studied electron microscopically. Following horseradish peroxidase (HRP) injections into the globus pallidus (GP) and electrolytic lesions of the nucleus tegmenti pedunculopontinus pars compacta (TPC) in the same cat, both degenerating and HRP‐labeled terminals were found in the STN with abundant retrogradely HRP‐labeled neurons. Degenerating terminals of TPC origin were medium‐sized and characterized by asymmetric synaptic contacts. They synapsed widely on the STN neuronal surface, including the somata, dendrites of varying dimensions, dendritic spines and vesicle‐containing processes. They formed 25.1%, 65.1%, 4.7%, and 4.7%, respectively, of all TPC efferent terminals. Some of the postsynaptic components were labeled with HRP. Occasionally both degenerating terminals and HRP‐labeled terminals were in synaptic contact with the same HRP‐labeled neuron: therefore, afferents of TPC and GP converge on the same STN projection neuron.

In order to discover the origin of these HRP‐labeled terminals, a mixed solution containing HRP and kainic acid was injected into the GP. Numerous degenerating terminals were observed to synapse with HRP‐labeled STN neurons, but no HRP‐labeled terminal was observed. These degenerating terminals were similar in appearance to the above‐mentioned HRP‐labeled terminals. They were characterized by their relatively large size, predominantly symmetric synapses, and preferential distribution on the somata and large or medium‐sized dendrites. They formed 39.6%, 20.1%, and 31.1%, respectively, of all GP efferent terminals. Therefore, it became clear that both the HRP‐labeled terminals of the first experiment and the degenerating terminals of the second experiment originated from the GP.

Following surgical ablations of the primary sensorimotor cortex (Cx), some axon terminals in the STN showed degeneration. These degenerating terminals were small and formed asymmetric synapses mainly with dendritic spines, small dendrites and vesicle‐containing processes. They formed 48.0%, 28.0%, and 12.0%, respectively, of all Cx efferent terminals.

These electron microscopic investigations reveal the convergence of TPC and GP afferents and that STN projection neurons relay the TPC and pallidal inputs directly to the GP.
Electron microscopic analysis of the synaptic organization of the globus pallidus in the cat
Authors: Okoyama Shigeo , Nakamura Yasuhisa , Moriizumi Tetsuji , Kitao Yasuko
Published: January 2005

The synaptic organization of the feline globus pallidus (GP) was studied electron microscopically. The axon terminals were classified into five types on the basis of the size and shape of synaptic vesicles and the type of postsynaptic differentiations. Type I and II axon terminals were characterized by large, pleomorphic vesicles and by a symmetric and an asymmetric synaptic contact, respectively. Type III and IV axon terminals were characterized by small, pleomorphic vesicles and by a symmetric and an asymmetric synaptic contact, respectively. Type V axon terminals were characterized by elongated and large round vesicles and by a symmetric synaptic contact.

The origins of these terminals were determined by a combined degeneration and HRP tracing technique. Following injections of HRP into the caudate nucleus or electrolytic lesions in this nucleus, type I terminals were anterogradely labeled with HRP or degenerated, respectively. Although type III, IV, and V terminals were labeled with HRP after HRP injections into the subthalamic nuclear region, only type IV and V terminals degenerated after lesions in that area. Type II terminals did not show any alterations following such treatment. These results suggest that type I terminals originate from the caudate nucleus, that type IV and V terminals come from the subthalamic nucleus or caudal to it, and that type III terminals are the terminals of intrinsic axon collaterals of GP neurons which send axons to the subthalamic nucleus.

Occasionally convergence of different kinds of axon terminals on the same GP neuron was also observed. These terminals originated from the caudate nucleus and the subthalamic nucleus or caudal to it. The similarity between the synaptic organization of the GP and the entopeduncular nucleus is briefly discussed.
Proctolin‐like immunoreactive neurons in the blowfly central nervous system
Authors: Nässel Dick R. , O'shea Michael
Published: January 2005

The pentapeptide proctolin (H‐Arg‐Tyr‐Leu‐Pro‐Thr‐OH) is a well‐studied bioactive substance in insects. With an antiserum against proctolin we have mapped proctolinlike‐immunoreactive (PLI) neurons in the nervous system of the blowfly Calliphora erythrocephala. In the brain, including the suboesophageal ganglia, 80–90 neurons were found to be PLI. A further 200–250 PLI neurons innervate the lobula of the optic lobe. The thoracic ganglia contain 100–130, and the abdominal ca. 60 PLI neurons. In the brain and ventral ganglia the immunoreactive neurons are of different types: interneurons, efferents (possibly some motorneurons), and neurosecretory cells. Some of these neurons are individually identifiable; others can be identified collectively as clusters. Identifiable neurons innervate protocerebral neuropil associated with the pars intercerebralis and the β‐lobes of the mushroom bodies as well as tritocerebral neuropil. Some of the prominent clusters innervate the central body of the protocerebrum, tritocerebrum, and possibly leg motor neurons. One abdominal cluster is of special interest because it consists of efferent neurons with processes in the lateral abdominal nerves. Some of these processes are located in the neural sheath in neurohaemal regions, and electron microscopy demonstrates that their terminals are outside the blood‐brain barrier. The PLI processes in the proto‐cerebrum contain large granular vesicles and form chemical synapses with different kinds of nonimmunoreactive neural elements. Thus, in Calliphora the proctolinlike substance may be used as a central transmitter/modulator, a neuromuscular transmitter, and a neurohormone released into the circulation.
Distribution and morphological characteristics of efferent neurons innervating end organs in the ear and lateral line of the european eel
Authors: Meredith G. E. , Roberts B. L.
Published: January 2005

Neurons that provide the efferent innervation to the labyrinthine and lateral line sense organs of the eel were located by applying horseradish peroxidase to branches of the appropriate cranial nerves. Retrogradely labeled neurons were found in a single median column, the octavolateralis efferent nucleus (OEN), located immediately rostral to and overlapping with the facial nucleus of the branchiomotor column. We estimate that on each side of the brain the efferent nucleus contains about 60–70 neurons, most of which supply the ear and the lateral line system of the head. Most neurons (∼90%) are ipsilateral to the targets they innervate. There is no crisp topographical order within the nucleus because neurons supplying different end organs intermingle. However, the head lateral line is supplied by rostrally located neurons, and the body system by more caudal neurons.

There are no marked differences in cell form between neurons supplying different targets. Most are multipolar, relatively uniform in size, and have extensive dendrites. The dendrites of some cells extend to the contralateral side of the brain. Efferent axons are of small diameter (∼3 μm). Two neurons are sufficiently constant in size and location that they can be consistently recognized from fish to fish. Their axons branch to supply more than one target. Nearly all efferent neurons stain for acetylcholinesterase and some, bordering the midline, consistently stain weakly.
Identification of motor neurons that contain a FMRFamidelike peptide and the effects of FMRFamide on longitudinal muscle in the medicinal leech, Hirudo medicinalis
Authors: Norris Brian J. , Calabrese Ronald L.
Published: January 2005

Excitatory motor neurons in the leech are cholinergic. By using a combination of intracellular Lucifer yellow injection and indirect immunofluorescence, we localized FMRFamidelike immunoreactivity to a number of the motor neurons innervating longitudinal and dorsoventral muscle in the leech. All excitatory motor neurons innervating longitudinal muscle (cells 3, 4, 5, 6, 8, L, 106, 107, 108) were labeled with an antiserum to FMRFamide, while the inhibitory motor neurons innervating longitudinal muscle (cells 1, 2, 7, 9, 102) were not. The excitatory motor neuron innervating medial dorsoventral muscle (cell 117) was labeled, while the excitatory motor neuron innervating lateral dorsoventral muscle (cell 109) was not. The inhibitory motor neuron innervating dorsoventral muscle (cell 101) was also labeled. Nerve terminals along dorsoventral muscle were also labeled with the antiserum.

FMRFamide was bath applied to strips of longitudinal muscle while recording tension, and the muscle's response was compared to its response to the previously identified neuromuscular transmitter ACh. Brief applications of FMRFamide caused a contraction approximately one‐tenth as large as that caused by an equimolar amount of ACh. The muscle response to FMRFamide was unaffected by curare. During extended exposures, FMRFamide caused a maintained contraction in longitudinal muscle without any apparent desensitization of the FMRFamide receptors and occasionally triggered an irregular myogenic rhythm. This extended exposure to FMRFamide caused a post‐exposure potentiation of the longitudinal muscle's response to ACh that shorter applications of FMRFamide did not. Thus FMRFamide may act as a transmitter or modulator in cholinergic motor neurons innervating longitudinal and dorsoventral muscles in the leech.
Topographic organization of the middle temporal visual area in the macaque monkey: Representational biases and the relationship to callosal connections and myeloarchitectonic boundaries
Authors: Maunsell John H. R. , van Essen David C.
Published: January 2005

We have used physiological and anatomical techniques to address three general issues concerning the topographic organization of the middle temporal visual area (MT) of the macaque monkey. First, we carried out a quantitative analysis of irregularities and asymmetries in the visual representation in MT. This analysis revealed a striking overemphasis on a restricted portion of the visual field that runs obliquely through the inferior contralateral quadrant and largely avoids both the horizontal meridian and the inferior vertical meridian. This corresponds to the portion of the visual field that would be maximally stimulated during visually guided hand movements. Second, the physiologically determined topographic organization of MT was compared to the pattern of callosal inputs in the same hemisphere, which are known to be distributed irregularly within MT. Callosal inputs tended to be densest near the representation of the vertical meridian, but there were numerous exceptions to this trend. Thus, topographic irregularities account for only part of the irregularities in callosal inputs to MT. Finally, comparison of these data with previous reports shows a strong correlation between body weight and the average size of MT. The representation in myeloarchitectonically defined MT was found to include much of the visual periphery, although it is unclear from our data whether this representation is invariably complete.
Metamorphosis of identified neurons innervating thoracic neurohemal organs in the blowfly: Transformation of cholecystokininlike immunoreactive neurons
Authors: Nässel Dick R. , Ohlsson Lennart G. , Cantera Rafael
Published: January 2005

With antisera to gastrin/cholecystokinin, we studied the postembryonic development of neurons in the thoracic ganglia of the blowfly Calliphora erythrocephala. There are some changes in the population of thoracico‐abdominal neurons displaying gastrin/CCK‐like immunoreactivity (CCKLI): some CCKLI neurons cannot be found after pupariation; other neurons become immunoreactive during metamorphosis. Six large thoracic CCKLI neurons could, however, be followed through metamorphosis. These CCKLI neurons innervate neuropil in thoracic ganglia and segmental neurohemal organs in the larva. In the adult insect the same neurons innervate many regions of thoracic neuropil and extensive neurohemal areas dorsally in the fused thoracico‐abdominal ganglia. The immunoreactive terminals are located in the neural sheath, and electron microscopy shows that only an extracellular basal lamina separates them from the circulating hemolymph. On the basis of the location of their terminals, it can be suggested that the six CCKLI neurons have functions as neurosecretory cells both in the larva and in the adult. In both developmental stages the neurons can interact with large portions of the thoracic nervous system and release bioactive substance into the circulation. A CCK‐like substance may be used both as a transmitter/neuromodulator and as a neurohormone by the same neuron. The larval neurohemal organs are described here for the first time. They show characteristics of thoracic perisympathetic organs known to exist in more primitive insects. The adult neurohemal regions on the other hand are typical of higher insects. Since the neurohemal areas are continuously (during development) innervated by the six large CCKLI neurons, we conclude that the larval neurohemal organs metamorphose into the adult neurohemal area in the neural sheath.
Glycoconjugate boundaries during early postnatal development of the neostriatal mosaic
Authors: Steindler Dennis A. , O'brien Thomas F. , Cooper Nigel G. F.
Published: January 2005

The dispositions of galactosyl‐containing glycoconjugates were studied during postnatal development of the caudate putamen in mice. The binding of the lectin peanut agglutinin, which has an affinity for galactosyl B‐1,3 N‐acetylgalactosamine residues, was compared to acetylcholinesterase staining and tyrosine hydroxylase immunoreactivity in the immature and adult neostriatum.

The binding of peanut agglutinin conjugated to horseradish peroxidase, in sections that were processed for peroxidase histochemistry, was extremely pronounced in the neostriatum through the first postnatal week and constituted ringlike or polygonally shaped structures, which, overall, produced a variegated mosaic, These structures consist of outer rims of dense lectin‐associated reaction product surrounding lightly labeled centers. Lectin delineations of the neostriatal mosaic are no longer visible in the second postnatal week. When adjacent sections were processed for lectin binding or acetylcholinesterase histochemistry, the dense lectin binding sites represented borders of acetylcholinesterase‐rich and ‐poor zones. The distribution of dense patches of tyrosine hydroxylase immunoreactive fibers and terminals also coincides with the acetylcholinesterase‐rich zones during the same times, and thus the glycoconjugate‐delineated boundaries can also be directly compared with the distribution of nigrostriatal dopaminergic projections.

The findings presented here represent the first demonstration of a probe that recognizes apparent borders of neostriatal compartments during a limited period of development. They are consistent with previous observations made on transient glycoconjugate “hidden boundaries” during development of other central nervous system structures, including the somatosensory cortical barrel field, and thalamic and brainstem nuclei (Cooper and Steindler, '86a, b; Steindler and Cooper, in press). In those studies, glia were shown to be the major source of glycoconjugate‐associated patterns, and thus, glia and glycoconjugates that they synthesize during pattern formation events may be involved in the formation and stabilization of neurochemically distinct components of the neostriatal mosaic.