摘要:

AbstractThis study mapped the histamine‐immunoreactive neuronal system in the brain of the tree shrew (Tupaia belangeri) and compared its structure with that of the rat and guinea pig. The histamine‐containing cell bodies lay in the posterior ventral hypothalamus in the tuberomammillary complex, as in the rodents. The morphology of this complex resembled that of the rat. The histaminergic axons projected to nearly all parts of the brain. The main ascending bundle ran ventromedially: the densest innervation was found in the ventral hypothalamus, preoptic area, septum, medial part of nucleus accumbens, and bed nucleus of the stria terminalis. High fiber densities were present in the amygdaloid nuclei and claustrum. Another pathway ran dorsomedially along the periventricular hypothalamus and sent fibers to all parts of the diencephalon. Part of these fibers followed the central gray to the midbrain and spread laterally below the inferior colliculus. Another descending pathway ran through the interfascicular and medial raphe nuclei to meet the pontine central gray. The densest fiber networks were seen in the dorsal tegmental and parabrachial nuclei, and around the locus coeruleus. Also the substantia nigra, interpeduncular and mesencephalic reticular nuclei, colliculi, and vestibular and raphe nuclei received a dense histaminergic innervation.The organization of the fibers in the tree shrew brain resembled more that in the guinea pig than that in the rat. As compared with the guinea pig, more fibers were present, particularly in the globus pallidus, central thalamus, and deep cerebellar nuclei. No fibers were seen in the outer layer of the piriform cortex. InTupaia, a laminar organization of the fibers was evident in the hippocampus, in contrast to the rodents. Also, a dense periventricular fiber plexus was promin

ISSN:0092-7317    

DOI:10.1002/cne.902860302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe retrograde and anterograde transport of horseradish peroxidase conjugated to wheat germ agglutinin (WGA‐HRP) has been used to trace afferent connections of the rat mamillary body (MB) at the light and electron microscopic levels. Injections of WGA‐HRP into different parts of the MB resulted in heavy retrograde labeling in the subicular complex, medial prefrontal cortex, and dorsal and ventral tegmental nuclei. Injections of WGA‐HRP into each of these brain regions, respectively, resulted in anterograde labeling with specific distributions and characteristic synaptic organizations in the MB. Projections from the rostrodorsal and caudoventral subiculum terminated in a topographically organized laminar fashion in the medial mamillary nucleus bilaterally, whereas afferent projections from the presubiculum and parasubiculum terminated only in the lateral mamillary nucleus. Labeled axon terminals which originated from the subicular complex were characterized by round vesicles and formed asymmetric synaptic junctions with small‐diameter dendrites and dendritic spines in the medial and lateral mamillary nuclei. Projections from the prefrontal cortex originated mainly in the infralimbic area and to a lesser degree in the prelimbic and anterior cingulate areas. Injections of tracer into these brain regions gave rise to dense labeling of axon terminals in the medial mamillary nucleus, pars medianus, and in the anterior dorsomedial portion of the pars medialis. The labeled terminals were characterized by round vesicles and formed asymmetric synaptic junctions with small‐diameter dendrites and dendritic spines. Projections from the dorsal tegmental nucleus terminated in the ipsilateral lateral mamillary nucleus, whereas afferent projections from the anterior and posterior subnuclei of the ventral tegmental nucleus terminated topographically in the medial mamillary nucleus. The ventral tegmental nucleus, pars anterior projected to the midline region of the medial nucleus and the dorsolateral and ventromedial subdivisions of the pars posterior projected to medial and lateral parts of the medial nucleus, respectively. In contrast to the synaptic morphology of subicular complex and medial prefrontal cortex axon terminals in the MB, labeled axon terminals in the MB which originated from the midbrain tegmentum were characterized by pleomorphic vesicles and formed symmetric synaptic junctions with neuronal somata and proximal dendrites as well as distal dendrites and dendritic spines. The morphological differences among axon terminals of afferent projections from the subicular complex and the medial prefrontal cortex compared to those from the midbrain tegmentum suggest that the inputs differ in terms of excitatory or inhibitory effects on MB neurons. It is proposed that cortical, subcortical, and brainstem connections of the MB form three distinct neural circuits which may represent anatomical substrates for different functional a

ISSN:0092-7317    

DOI:10.1002/cne.902860303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractObservations have been made on the peripheral nerves of shiverer (shi/shi) mice in comparison with control animals. Although this mutant lacks P1myelin basic protein in peripheral and central myelin, myelin is defective only in the central nervous system. No ultrastructural abnormalities were observed in the shiverer nerves. Myelin spacing was normal. The density and distribution of intramembranous particles on the E and P faces of myelin and in the axolemma of myelinated and unmyelinated axons did not differ between the shiverer and control mice. Morphometric studies showed that external myelinated fiber diameter was significantly less and that myelin thickness was slightly but significantly greater in relation to axon diameter in the shiverer mice, suggesting a minor degree of axonal atrophy. It is concluded that P1protein is not necessary for the formation and maintenance of the normal structure of peripheral myelin. The failure to detect differences in intramembranous particle density in myelin between shiverer and control mice indicates that P1protein is not detected in freeze‐fracture preparation

ISSN:0092-7317    

DOI:10.1002/cne.902860304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractTo test recent ideas on the origin of retinal astrocytes, we have studied the spread of astrocytes in the developing retina of the albino rat. Astrocytes were identified with antibodies to their intermediate filaments, glial fibrillary acidic protein (GFAP). Astrocytes were first detected at E(embryonic day)18, forming a corona of processes around the optic disc. Over subsequent days, astrocytes extended over the retina, covering approximately 35% of the retina at birth (typically E21–22) and reaching the edge of the retina by P(postnatal day)8. As they spread, astrocytes were closely associated with the developing vasculature, spreading ahead of patent vessels by a small but distinct margin. The most peripheral astrocytes assumed a bipolar morphology and extended processes towards the margin of the retina. Astrocytes nearer the optic disc showed the stellate shape characteristic of mature cells. The appearance of astrocytes at the optic disc at E18, 2 days after the appearance of type‐1 astrocytes in the optic nerve (Miller et al.:Dev. Biol. 11135–41, '85), suggests that retinal astrocytes may be type‐1 astrocytes generated in the optic nerve. Watanabe and Raff (Nature 332:834–837, '88) have recently reported an independent study supporting the same co

ISSN:0092-7317    

DOI:10.1002/cne.902860305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractAn investigation of the architectonic organization and intrinsic connections of the prefrontal cortex was conducted in rhesus monkeys. Cytoarchitectonic analysis indicates that in the prefrontal cortex there are two trends of gradual change in laminar characteristics that can be traced from limbic periallocortex towards isocortical areas. The stepwise change in laminar features is characterized by the emergence and gradual increase in the width of granular layer IV, by an increase in the size of pyramidal cells in layers III and V, and by a higher cell‐packing density in the supragranular layers. Myeloarchitectonic analysis reveals that the limbic areas are poorly myelinated, adjacent areas have a diffuse myelin content confined to the deep layers, and in isocortices the myelinated fibers are distributed in organized horizontal bands (of Baillarger) and a vertical plexus. Using the above architectonic criteria, we observed that one of the architectonic trends takes a radial basoventral course from the periallocortex in the caudal orbitofrontal region to the adjacent proisocortex and then to area 13. The next stage of architectonic regions includes orbital areas 12, 11, and 14, which is followed by area 10, lateral area 12, and the rostral part of ventral area 46. The last group includes the caudal part of ventral area 46 and ventral area 8. The other trend takes a mediodorsal course from the periallocortex around the rostral portion of the corpus callosum to the adjacent proisocortical areas 24, 25, and 32 and then to the medially situated isocortical areas 9, 10, and 14. The next stage includes lateral areas 10 and 9 and the rostral part of dorsal area 46. The last group includes the caudal part of dorsal area 46 and dorsal area 8.The interconnections of subdivisions of the basoventral and mediodorsal cortices were studied with the aid of anterograde and retrograde tracers. Within each trend a given area projects in two directions: to adjoining regions belonging to succeeding architectonic stages on the one hand, and to nearby regions from the preceding architectonic stage on the other. In each direction there is more than one region involved in this projection system, paralleling the radial nature of architectonic change. Periallo‐ and proisocortices have widespread intrinsic connections, whereas isocortices situated at a distance from limbic areas, such as area 8, have restricted connections. Most interconnections are limited to areas within the same architectonic trend. However, there are links between cortices from the two trends, and these seem to occur between areas that are at a similar stage of architectonic differentiation.The results suggest that there are two architectonically, and perhaps functionally, distinct axes within the prefrontal cortex. The earliest stages within each axis, which have widespread connections, may have a global role in neural processing. On the other hand, the latest stages, which have restricted connections, may have a more specific role in processes associated with the frontal l

ISSN:0092-7317    

DOI:10.1002/cne.902860306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractTo label the spinal motoneurons innervating the forelimb muscles of the Japanese toad, horseradish peroxidase (HRP) was injected into these muscles or applied to the cut end of the branchial nerves (N. radialis and N. ulnaris). Spatial distribution of the HRP‐labeled motoneurons was reconstructed from serial frontal sections of the spinal cord and their location was examined.Motoneurons innervating forelimb muscles were distributed in the lateral cell column from segment 3 to segment 5 of the ipsilateral brachial spinal cord. In the transverse plane of the spinal cord, motoneurons innervating the medial forearm muscles (innervated by N. ulnaris) were located in the more medial part of the lateral cell column, whereas those innervating the lateral forearm muscles and the upper arm muscle (innervated by N. radialis) were located in the more lateral part of the lateral cell column. Along the longitudinal axis of the spinal cord, motoneurons innervating the more anterior (flexor side) forearm muscles were located in the more rostral part of the spinal cord, whereas those innervating the more posterior (extensor side) forearm muscles were located in the more caudal part of the spinal cord.Thus, motoneurons innervating forearm muscles were well organized somatotopically not only in the transverse plane, but also along the longitudinal axis of the spinal cord. Such a somatotopic organization of motoneurons along the longitudinal axis could also be regarded as a functional one; the flexor motoneurons were located rostrally to the extensor motoneuron

ISSN:0092-7317    

DOI:10.1002/cne.902860307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe primary objectives of this study were to determine (1) if quantitative axon‐myelin relationships are similar for large‐ and for small‐fibre classes within individual nerves and (2) if the same axon‐myelin relationships hold for equivalent fibre classes in closely similar nerves. The oculomotor, trochlear, and abducent nerves of the rat were examined since they each contain distinct large‐ and small‐fibre classes and are similar in a wide range of anatomical and developmental respects. Accordingly, morphometric analyses of axon‐myelin relationships were performed separately on large and small fibres of each of the three nerves.Withineach nerve, the setting of the relationship between the two parameters was found to be different for the two fibre classes: Scatterplots relating sheath thickness to axon perimeter for large fibres were shifted upwards relative to those for small fibres. These differences were also reflected in the positions of the regression lines fitted to the plots and in the g‐ratios.Significant differences were foundbetweennerves in relation to their large fibres: Those of the abducent nerve had significantly thicker sheaths, those of the oculomotor nerve had significantly smaller axon perimeters, and the myelin sheath–axon perimeter relationship of the abducent nerve differed significantly from that of the other two.This study therefore shows that morphometric axon‐myelin relationships may differ significantly between equivalent fibre classes of nerves that are closely similar in respect of morphological class, central origin, peripheral distribution, developmental enviro

ISSN:0092-7317    

DOI:10.1002/cne.902860308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractMormyromast electroreceptor organs are the most numerous type of electroreceptor organs in mormyrid electric fish and provide the sensory information necessary for active electrolocation. Mormyromast organs and their primary afferent fibers have not been studied very extensively. Both morphological and physiological questions remain to be answered before the neural basis of active electrolocation in mormyrids can be understood. This paper examines four different aspects of the morphology of mormyromast organs and afferent fibers: (1)Mormyromast organs in the skin.The innervation patterns for the two types of separately innervated sensory cells in the mormyromast organ are described on the basis of silver‐stained whole mounts of skin. The number of sensory cells per mormyromast organ increases linearly with fish growth for both types of sensory cells. (2)Relation between peripheral sensory cell innervated and central zone of termination for mormyromast afferent fibers.The afferent fibers arising from the two types of sensory cell in the mormyromast organ project to separate zones of the electrosensory lateral line lobe, as shown by using retrograde labeling with horseradish peroxidase. (3)Central trajectories and terminal arbors of mormyromast afferent fibers.These aspects of mormyromast fibers are described by using intracellular staining of individual fibers as well as whole nerve staining of an electrosensory nerve. (4)Fine structure of mormyromast afferent terminals in the electrosensory lateral line lobe.Afferent fibers make various synaptic contacts, including contacts of a mixed type, gap junction‐chemical, onto a restricted class of granule cells. The fine structure is described based on electron microscopy of horseradish‐peroxidase‐labeled fibers.The results provide an anatomical base for current physiological studies on mormyromast afferent

ISSN:0092-7317    

DOI:10.1002/cne.902860309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902860301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY