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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Retrograde axonal transport of cholera toxin B subunit (CTB) was used to compare the development of intracortical and thalamocortical connections in normal rats with those in rats in which all of the whiskers were trimmed continuously from birth. In normal animals, injections of CTB into a single barrel column resulted in an asymmetrical labeling of cells that were distributed preferentially within columns related to the same row in which the injection was placed. This anisotropy in the patterns of intracortical connections was not observed in whisker-clipped animals. In these animals, there was a significant reduction in the mean number of labeled cells in the infragranular layers, and labeled cells were distributed symmetrically around the injection site. The same injections of CTB also labeled thalamocortical neurons in the ventrobasal thalamus. Analysis of the distribution of these cells revealed that, in both control and experimental animals, the vast majority of labeled cells were restricted to a homologous (i.e., corresponding to the injected cortical barrel) thalamic barreloid. These findings indicate that manipulations of sensory experience alter patterns of intracortical, but not thalamocortical, connections.
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PMID:Neonatal whisker clipping alters intracortical, but not thalamocortical projections, in rat barrel cortex. 1044 Jul 11

Previous light microscopical studies have indicated that fibres from the ventrolateral thalamic nucleus (VL) establish direct axo-somatic and axo-dendritic presumed contacts with layers III and V neurones of the intact frontal cortex projecting to the striatum. Additional experiments provided evidence that this thalamo-fronto-striate pathway could be partly reconstructed by transplantation of embryonic frontal tissue into the damaged cortex. The present study was undertaken to validate these results at the ultrastructural level. Several months after the transplantation of fetal frontal tissue into the damaged frontal cortex of newborn rats, a retrograde neurotracer (subunit b of the cholera toxin) was used to label the grafted neurones projecting to the striatum whereas an anterograde neurotracer (Phaseolus vulgaris leuco-agglutinin) was used to label within the transplant, axons and terminations arising from the VL. The same injection procedures were applied to intact adult rats (control). The distribution of retrograde and anterograde labellings within the intact cortex and within the graft was examined at light and electron microscopic levels to identify the synaptic contacts. Our findings showed that labelled contacts were less numerous within the transplant than within the intact cortex but their synaptic organization was similar: asymmetrical synaptic axo-dendritic and axo-somatic contacts. This synaptic articulation is probably supplied by a thalamic excitatory input. These results provide ultrastructural evidence of the capacity of a frontal cortical transplant placed in damaged frontal cortex of newborn rats to help reconstruction of appropriate synaptic integration within the thalamo-fronto-striate system.
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PMID:The thalamo-fronto-striate system: ultrastructural evidence of appropriate synaptic integration of embryonic neurones grafted within the frontal cortex of newborn rats. 1063 30

It is generally known that the nucleus of the optic tract (NOT) subserves visuomotor relations between the retina and preoculomotor structures as the only subcortical pathway mediating optokinetic responses (OKR) in mammals. We have examined the projections from the retina and visual cortical areas (areas 17, 18a and 18b) to NOT using tracers (wheat germ agglutinin-conjugated horseradish peroxidase, WGA-HRP and cholera toxin B subunit, CTB) in order to clarify how these two different functional inputs to OKR are organized. CTB injection into the vitreous body resulted in anterograde label almost exclusively in the contralateral NOT. Ultrastructually, the size of the retinal axon terminals was small (up to 0.7 micron in diameter), contained round synaptic vesicles and pale mitochondria, and made asymmetrical synaptic contacts with both GABA-positive and GABA-negative NOT neurons. Visual cortical area 17 and the transitional area between area 17 and 18a, or between area 17 and 18b projected their axons to the ipsilateral NOT. Ultrastructually, the size of the cortical axon terminals was small (up to 0.5 micron in diameter), contained round synaptic vesicles, and made asymmetrical synaptic contacts only with GABAnegative NOT neurons. With light and electron microscopical observation, there was a considerable overlap in the cortico-NOT and retino-NOT projection pattern: GABA-negative (presumably NOT projection) neurons simultaneously receive input from both cortical and retinal terminals. From these results, it seems reasonable to postulate that inputs from visual cortical areas in the pigmented rat cooperate with those from the retina in controlling OKR.
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PMID:A light and electron microscopic analysis of the convergent retinal and visual cortical projections to the nucleus of the optic tract (NOT) in the pigmented rat. 1089 5

The nucleus retroambiguus (NRA) consists of premotor neurons in the caudal medulla. It is involved in expiration, vomiting, vocalization, and probably reproductive behavior by means of projections to distinct motoneuronal cell groups. Because no information is available about the NRA and its efferent pathways in primates, the present study examines NRA projections to the lumbosacral spinal cord in female rhesus monkeys. To identify the NRA, wheat germ agglutinin-horseradish peroxidase (WGA-HRP) was injected into the lumbosacral cord in three monkeys. To study the distribution of NRA axons in the lumbosacral cord, WGA-HRP injections were made into the NRA in seven monkeys. To identify motoneuronal cell groups receiving input from the NRA, the same seven monkeys also received cholera toxin subunit b (CTb) injections into different hindlimb, axial, and pelvic floor muscles. The results show that NRA neurons projecting to the lumbosacral cord are mainly located between 1 to 4 mm caudal to the obex. They send numerous axons to external oblique and pelvic floor motoneurons, whereas projections to iliopsoas and axial motoneurons are less numerous. The projections are bilateral, but show a clear contralateral predominance in the iliopsoas, axial, and pelvic floor motoneuronal cell groups. At the ultrastructural level, NRA-terminal profiles make asymmetrical contacts with labeled and unlabeled dendrites in these motoneuronal cell groups and contain large amounts of spherical and a few dense core vesicles. It is concluded that the NRA is well developed in the monkey and that there exists a direct pathway from the NRA to lumbosacral motoneurons in this species. The finding that the NRA projects to a somewhat different set of motoneuronal cell groups compared with other species fits the concept that it is not only involved in expiration-related activities but also in species specific receptive and submissive behavior.
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PMID:Monosynaptic projections from the nucleus retroambiguus to motoneurons supplying the abdominal wall, axial, hindlimb, and pelvic floor muscles in the female rhesus monkey. 1090

The periaqueductal gray (PAG) is known to be essential for vocalization and reproductive behavior. The PAG controls components of these behaviors by means of projections to the nucleus retroambiguus (NRA), a group of premotor neurons in the caudal medulla oblongata. In the accompanying study (VanderHorst et al., 2000 [accompanying study]), the NRA and its lumbosacral projections have been identified in the rhesus monkey. The present light and electron microscopical tracing study describes the PAG-NRA pathway in primates. To locate midbrain neurons projecting to the NRA, wheat germ agglutinin horseradish peroxidase (WGA-HRP) was injected into the NRA in six monkeys. To determine the distribution pattern of PAG axons in the medulla oblongata, WGA-HRP was injected into the PAG and adjacent tegmentum in three additional monkeys. In one of these three monkeys, biotinylated dextran amine and cholera toxin subunit b were injected into the lumbosacral cord to retrogradely identify NRA neurons. The results show that a compact group of neurons in the medial part of the lateral PAG at the intercollicular level sends a dense projection to the NRA. The projection is bilateral with a clear ipsilateral predominance. At the ultrastructural level, there are monosynaptic contacts between PAG fibers and NRA neurons, including NRA neurons that project to the lumbosacral cord. The synaptic contacts were primarily asymmetrical and the labeled terminal profiles contained spherical and dense core vesicles. It is concluded that there exists a strong and direct PAG-NRA pathway in the rhesus monkey. Because NRA neurons projecting to the lower lumbar cord are included, the PAG-NRA projection is likely to be involved not only in vocalization but also in other behaviors, such as receptive posture.
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PMID:Monosynaptic projections from the lateral periaqueductal gray to the nucleus retroambiguus in the rhesus monkey: implications for vocalization and reproductive behavior. 1090 1

The synaptic architecture of spinal afferents of the dorsal portion (DRtd) of the medullary dorsal reticular nucleus (DRt) is studied. After iontophoretic injections of cholera toxin subunit B (CTb) into the superficial (laminae I-II), deep (laminae IV-V) or entire (laminae I-V) dorso-ventral extent of the spinal dorsal horn at the cervico-thoracic or lumbo-sacral levels, axonal boutons of two distinct types were labelled in the DRtd. Type A boutons (82% after cervico-thoracic injections and 92% after lumbo-sacral injections) were roundish, small and presented few mitochondria and small, round synaptic vesicles. Type B boutons (18% after cervico-thoracic injections and 8% after lumbo-sacral injections) were elongated, two to three times larger, and exhibited numerous mitochondria and larger round vesicles. Both types of bouton established asymmetrical synaptic contacts with small dendritic profiles and, less frequently, with dendritic trunks and perikarya. Retrograde labelling occurred in the postsynaptic profile of 15-18% type A boutons labelled from any injection site. Taken together with previous data on DRt-spinal synaptic contacts at the superficial dorsal horn, the present results point to the occurrence of a reciprocal excitatory loop connecting the dorsal DRt and lamina I, which may be at the basis of the DRt-mediated pain-facilitating effects described recently.
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PMID:Reciprocal connections between the medullary dorsal reticular nucleus and the spinal dorsal horn in the rat. 1112 10

The curved, comma, or bent shape of Vibrio cholerae is attributed to, and explained by, the normal helical growth of the cell. The comma-like shape of V. cholerae is not due to an asymmetrical positioning of peptidoglycan such that some chains of peptidoglycan are placed so they are more spread out on one side of the cell and squeezed together on the other side.
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PMID:Helical growth and the curved shape of Vibrio cholerae. 1143 Apr 1

Vocalization and straining-related activities require the activation of laryngeal muscles. The control of laryngeal muscles during these activities is thought to be mediated by a pathway from the periaqueductal gray via premotor neurons in the nucleus retroambiguus to laryngeal motoneurons in the nucleus ambiguus. However, direct contacts between the nucleus retroambiguus and laryngeal motoneurons have never been demonstrated anatomically. Moreover, data in primates about the nucleus retroambiguus-nucleus ambiguus pathway are lacking. Therefore, the present study examines the projection from the nucleus retroambiguus region to laryngeal motoneurons in the rhesus monkey at the light and electron microscopic levels. Injections with wheat germ agglutinin-horseradish peroxidase were made into the nucleus retroambiguus in five rhesus monkeys to anterogradely label fibers in the nucleus ambiguus. In two of these animals, the cricothyroid muscle was injected with cholera toxin subunit b to identify the motoneurons that supply it. The results show that the nucleus retroambiguus region most densely projects to the compact formation of the nucleus ambiguus, whereas cricothyroid motoneurons, which surround the compact formation, receive a moderate projection. The projections are bilateral, with a contralateral predominance. Ultrastructurally, anterogradely labeled terminal profiles from the nucleus retroambiguus contact cholera toxin subunit b-labeled dendrites of cricothyroid motoneurons. The terminal profiles contain primarily spherical vesicles and form asymmetrical contacts with cricothyroid motoneurons. This study demonstrates that the nucleus retroambiguus region projects to the nucleus ambiguus in the primate. Some of these projections include monosynaptic connections to laryngeal motoneurons. This pathway is important for the control of the vocal folds during vocalization and straining-related activities.
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PMID:Monosynaptic projections from the nucleus retroambiguus region to laryngeal motoneurons in the rhesus monkey. 1174 52

Vocalization can be elicited by stimulation in the periaqueductal gray (PAG). Light-microscopical tracing and physiological studies have revealed that the PAG uses the nucleus retroambiguus (NRA) as a relay to excite the vocalization muscle motoneurons. Direct NRA projections have been demonstrated to pharyngeal and abdominal wall muscle motoneurons, but not to laryngeal motoneurons. In two cats 0.1% cholera toxin subunit b was injected in the cricothyroid muscle of the larynx to retrogradely label its motoneurons, and 2.5% wheat germ agglutinin-horseradish peroxidase was injected into the NRA to anterogradely label its fibers. The electronmicroscopical results indicate that the NRA fibers make monosynaptic contacts with cricothyroid motoneuronal dendrites. Almost all NRA terminal profiles had asymmetrical synapses and contained mostly round or pleiomorphic vesicles, which strongly suggests that the NRA-cricothyroid motoneuronal projection is an excitatory pathway.
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PMID:Direct projections from the nucleus retroambiguus to cricothyroid motoneurons in the cat. 1181 40

We investigated whether direct, cortico-motoneuronal connections are present in the rat, using both light microscopic and electron microscopic techniques. Corticospinal fibres were labelled using the anterograde tracer, biotinylated dextran-amine (BDA), which was injected into forelimb sensorimotor cortex. Motoneurons were retrogradely labelled after injection of cholera toxin subunit B (CTB) into forelimb muscles, contralateral to the injected hemisphere. Terminals of peripheral afferent fibres, which were also labelled by CTB, were easily distinguishable from, and much larger than, BDA-labelled corticospinal terminals. At the light microscope level, corticospinal terminals were found in all laminae contralateral to the injection site, most extensively in laminae VI and VII of cervical segments C5-C8. Although labelling in the ventral horn (lamina IX) was present, it was extremely sparse. A total of 47 corticospinal synapses were studied at the electron microscope level; most of these were in lamina VII and the majority (35/47; 74%) made axo-dendritic contacts with asymmetrical synapses; one made an axo-somatic synapse, and in the remaining 11 cases no postsynaptic structure could be identified. All corticospinal terminals contained spherical boutons. Serial sectioning of eight BDA-labelled corticospinal boutons in lamina IX revealed that most (seven out of eight) did not make synaptic contacts with any neuronal structure, and none made any contact with adjacent dendrites of CTB-labelled motoneurons. Thus these results provide no positive ultrastructural evidence for direct cortico-motoneuronal synaptic connections within lamina IX between corticospinal axon boutons and the proximal dendrites of forelimb motoneurons. The results confirm other lines of evidence suggesting that such connections are not present in the rat.
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PMID:An electron microscopic examination of the corticospinal projection to the cervical spinal cord in the rat: lack of evidence for cortico-motoneuronal synapses. 1267 26


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