摘要:

AbstractNineteen physiologically identified group Ia and five group Ib fibers at the L3 and L4 levels of the spinal cord originating from various hind‐limb muscles were intraaxonally injected with horseradish peroxidase (HRP). The trajectories of the stained axons were reconstructed. They extended for distances of 8.6 mm–18.0 mm rostrocaudally.Ascending axons ran in various regions of the dorsal funiculus: The ascending axon from a toe muscle (3 μm in diameter) ran in the ventralmost part of the paramedian region; those from shank muscles (3.0–5.0 μm) in both dorsal and ventral paramedian regions; those from thigh muscles (5.0–7.0 μm) in both the paramedian and the more lateral regions; and those from hip muscles (6.0–7.0 μm) in the lateral region. Main collaterals arising from the parent fiber were given off at intervals of 0.5–6.2 mm (mean 2.4 mm). Collaterals of a fiber from a toe muscle (1.0 μm in diameter) entered Clarke's column from the dorsomedial side and ramified mostly in the dorsomedial one‐third of the column. Collaterals of fibers from shank muscles (1.0–2.0 μm) entered Clarke's column from the dorsal side and terminated in its middle parts as well as in laminae V–VII. Collaterals of fibers from thigh muscles (1.0–2.5 μm) passed lateral to or through the lateral part of Clarke's column and terminated in its ventrolateral part and in laminae V–VIII. Collaterals of fibers from hip muscles (1.5–2.5 μm) passed lateral to Clarke's column and ramified mostly in laminae VII–IX. As the muscle of origin became more proximal, the proportion of termination outside of Clarke's column progressively increased. Thus, the trajectory of group I fibers was somatotopically organized both in the dorsal funiculus and in the gray matter.The long axis of boutons ranged from 0.5 to 17 μm in Ia fibers and from 0.5 to 8 μm in Ib fibers. “Giant” Ia boutons (above 7 μm) were f

ISSN:0092-7317    

DOI:10.1002/cne.902620202

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractAge‐related changes in ampullary and tuberous receptor organ morphology were studied in six species of gymnotiform weakly electric fish. Cheek skin was silver‐stained, whole‐mounted, and viewed under Nomarski differential interference contrast optics. The ampullary receptor units of all species show an increasing number of receptor organs per afferent fiber with fish size, presumably the result of addition of newly formed receptor organs. Ampullary units composing over a dozen organs were observed in large specimens of a few species. Receptor cells were also added in the tuberous receptor system of all species, but in different ways. As previously reported forSternopygus, small specimens ofEigenmanniahad only a single tuberous receptor organ per afferent. Fish of increasing size retained a population of afferents that innervated only a single receptor organ and, in addition, had a population of afferents that innervated a cluster of receptor organs. The mean number of receptor organs per cluster increased in fish of increasing size. In addition, the mean number of sensory receptor cells per organ increased. New organs presumably derive from older ones, which divide under the stimulus of continued addition of new receptor cells.Apteronotus, Adontosternarchus, andHypopomusall added more receptor cells to their tuberous organs. In these species, every afferent innervated only a single tuberous organ and there was no indication of division of receptor organs.GymnorhamphichthysandGymnotuswere intermediate in that they added new receptor cells to each receptor organ, and, in larger fish, these were segregated into discrete patches within a single receptor organ. It is likely that the additon of new receptor cells aids in increasing sensitivity of both ampullary and tuberous receptors as fish

ISSN:0092-7317    

DOI:10.1002/cne.902620203

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractBrainstem and forebrain projections to major subdivisions of the rat inferior colliculus were studied by using retrograde and anterograde transport of horseradish peroxidase. Retrograde label from injection into the external cortex of the inferior colliculus appears bilaterally in cells of the inferior colliculus, as well as in other brainstem auditory groups including the ipsilateral dorsal nucleus of the lateral lemniscus and contralateral dorsal cochlear nucleus. The external cortex is the only collicular subdivision where an injection labels cells in the contralateral cuneate nucleus, gracile nucleus, and spinal trigeminal nucleus. Other projecting cells to the external cortex are found in the lateral nucleus of substantia nigra, the parabrachial region, the deep superior colliculus, the midbrain central gray, the periventricular nucleus, and area 39 of auditory cortex. Injection of the dorsal cortex of inferior colliculus heavily labels pyramidal cells of areas 41, 20, and 36 of the ipsilateral neocortex. Anterograde label from a large injection of auditory cortex is densely distributed in the dorsal cortex, lesser so in the external cortex., and only slightly in the central nucleus. Labelled cells appear in the central nucleus, dorsal cortex, and external cortex, primarily ipsilaterally, following dorsal cortex injection. Relatively few cells from other brainstem auditory groups show projections to the dorsal cortex. Injection of the central nucleus of the inferior colliculus results in robust labelling of nuclei of the ascending auditory pathway including the anteroventral, posteroventral, and dorsal cochlear nuclei (mainly contralaterally), and bilaterally the lateral superior olive, lateral nucleus of the trapezoid body, dorsal nucleus of the lateral lemniscus, and the central nucleus, dorsal cortex, and external cortex of the colliculus. The medial superior olive, superior paraolivary nucleus, and ventral nucleus of the trapezoid body essentially show ipsilateral projections to the central nucleus. The differential distribution of afferents to the inferior colliculus provides a substrate for functional parcellation of collicular subdivisions.

ISSN:0092-7317    

DOI:10.1002/cne.902620204

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractInbred BALB/c mice are genetically the same, yet less than half of adults show absent or small corpus callosum. Is this because only a minority has prenatal defects of the sling at the telencephalic midline, or do most fetuses have a defective sling but some are able to form a corpus callosum via some other substrate pathway? This question was addressed by comparing large samples of BALB/c fetuses at 17, 18, and 19 days after conception with a series of normal C57BL/6 and hybrid fetuses matched for body size.At 17 days postconception almost all BALB/c fetuses show an unusual widening or bulge in the interhemispheric fissure anterior to the hippocampal commissure. Furthermore, formation of the hippocampal commissure is greatly retarded, although it eventually attains a normal size in adult mice. At 17 days, when mice of normal strains all have a corpus callosum at midplane, almost every BALB/c fetus lacks the structure, but 1 day later 67% of fetuses show delayed formation of this structure and by 19 days all but 7% of fetuses have some callosal axons crossing the midsagittal plane. Many BALB/c fetuses are able to form a corpus callosum without the benefit of a normal sling. The degree of delay of axon crossing is strongly correlated with the severity of sling defects. An unusually small adult corpus callosum occurs because fetal axons are able to follow unusual pathways and actively compensate for absence of the sling, not because of arrested midline development.

ISSN:0092-7317    

DOI:10.1002/cne.902620205

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractSynaptic organization of the intermediolateral nucleus of the guinea pig thoracic spinal cord was examined with particular focus on monoamine‐ and peptide‐containing nerve terminals. Axon varicosities having flat synaptic vesicles constituted 17% of all axons in the nucleus and formed exclusively symmetric synapses. Enkephalin‐, substance P‐, somatostatin‐, 5‐hydroxytryptamine‐, and catecholamine‐immunoreactive nerve terminals were densely distributed, while neurotensin‐, vasoactive intestinal polypeptide‐, oxytocin‐, and cholecystokinin‐8‐immunoreactive nerves were sparse in the nucleus. Coexistence of 5‐hydroxytryptamine and enkephalin was demonstrated, and coexistence of somatostatin and enkephalin as well as somatostatin and 5‐hydroxytryptamine in the same axons was also shown by serial semithin sections. Catecholamine axons labelled by 5‐hydroxydopamine formed axodendritic and axosomatic synapses and made direct synaptic contacts on the preganglionic sympathetic neurons identified by retrograde transport of horseradish peroxidase. Direct synaptic contacts from enkephalin‐ and substance P‐immunoreactive axons to preganglionic sympathetic neurons were also revealed. Enkephalin‐, substance P‐, and 5‐hydroxytryptamine‐imunoreactive axons formed axodendritic and axosomatic synapses. Catecholamine axon varicosities constituted 19% of all axon varicosities in the nucleus and 30% of them showed synaptic specializations in a sectional plane. Axon varicosities immunoreactive to enkephalin, 5‐hydroxytryptamine, and substance P constituted approximately 35, 19, and 13% of all axon varicosities, respectively, while those with synaptic contacts made up 27, 30, and 26%, respectively, in a sectional plane. Enkephalin‐, 5‐hydroxytryptamine‐, and noradrenaline‐immunorea

ISSN:0092-7317    

DOI:10.1002/cne.902620206

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe cytoarchitecture and thalamic afferents of cingulate cortex were evaluated in the rhesus monkey (Macaca mulatto). Area 24 has three divisions of which area 24a is adjacent to the callosal sulcus and has the least laminar differentiation. Area 24b has more clearly defined layers II, III, and Va, and area 24c, which forms the lower bank of the anterior cingulate sulcus, has a particularly dense layer III. Area 23 also has three divisions, each of which has a distinct layer IV. Area 23a is adjacent to the callosal sulcus and has the thinnest layers II–IV, which have the same cell density as layers V and VI. Area 23b has the largest pyramids in layers IIIc and Va, and area 23c, in the depths of the posterior cingulate sulcus, has the broadest external and thinnest internal pyramidal layers. Finally, areas 29 and 30 are located in the posterior depths of the callosal sulcus. Two divisions of area 29 are apparent: one with a granular layer directly adjacent to layer I (area 29a–c) and another with differentiation of layers III and IV (area 29d). Area 30 has a dysgranular layer IV.Injections of the retrograde tracer horseradish peroxidase (HRP) were made into subdivisions of cingulate cortex in the monkey. Area 25 received thalamic input mainly from the midline parataenial (Pt), central densocellular (Cdc), and reuniens nuclei as well as from the dorsal parvicellular division of the mediodorsal nucleus (MDpc). A less dense projection also originated in the intralaminar parafascicular (Pf), central superior, and limitans (Li) nuclei as well as the medial division of the anterior nuclei (AM).Areas 24a and 24b received most thalamic afferents from fusiform and multipolar cells in the Cdc and Pf nuclei with fewer from the ventral anterior (VA) and MDpc and MD densocellular (MDdc) nuclei and only minor input from AM. Most input to premotor cingulate area 24c appeared to originate in VA, MDdc, and Li.Area 29 received the most dense input from nuclei traditionally associated with limbic cortex including the anteroventral (AV), anterodorsal (AD), and laterodorsal (LD) nuclei. Areas 23a and 23b, in contrast, did not receive AV, AD, or LD input, but the greatest proportion of their thalamic afferents arose in AM. Less‐pronounced input also came from the lateroposterior (LP), medial pulvinar, and MDdc nuclei. This latter nucleus projected more to area 23b than to areas 30 or 23a.Anterior medial nucleus efferents to cingulate cortex were of particular note for two reasons. First, AM projected primarily to posterior cingulate areas with area 23 receiving its principal thalamic input from AM. Second, projections to areas 30, 23a, and 23b were topographically organized with ventral areas 30 and 23a receiving from the central core of AM. While the more dorsally located area 23b received input from peripheral and medial.In light of the extensive projections of Cds, Csl, and Pf to anterior cingulate cortex, it is proposed that the midline and intralaminar thalamic nuclie be classified as part of limbic thalamus along with the anterior, LD, and MD nuclei. Furthermore, although AM projects mainly to posterior cingulate cortex, it also has light projections to area 25 and minor input to area 24. As suhc, AM is the only limbic thalamic nucleus that has such widespread projections to cingulate cortex. Finally, visually evoked activity in area 23 may be the result of projections from the LP and medial pul

ISSN:0092-7317    

DOI:10.1002/cne.902620207

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractCortical projections to subdivisions of the cingulate cortex in the rhesus monkey were analyzed with horseradish peroxidase and tritiated amino acid tracers. These projections were evaluated in terms of an expanded cytoarchitectural scheme in which areas 24 and 23 were divided into three ventrodorsal parts, i.e., areas 24a–c and 23a–c.Most cortical input to area 25 originated in the frontal lobe in lateral areas 46 and 9 and orbitofrontal areas 11 and 14. Area 25 also received afferents from cingulate areas 24b, 24c, and 23b, from rostral auditory association areas TS2 and TS3, from the subiculum and CA1 sector of the hippocampus, and from the lateral and accessory basal nuclei of the amygdala (LB and AB, respectively).Areas 24a and 24b received afferents from areas 25 and 23b of cingulate cortex, but most were from frontal and temporal cortices. These included the following areas: frontal areas 9, 11, 12, 13, and 46; temporal polar area TG as well as LB and AB; superior temporal sulcus area TPO; agranular insular cortex; posterior parahippocampal cortex including areas TF, TL, and TH and the subiculum. Autoradiographic cases indicated that area 24c received input from the insula, parietal areas PG and PGm, area TG of the temporal pole, and frontal areas 12 and 46, Additionally, caudal area 24 was the recipient of area PG input but not amygdalar afferents. It was also the primary site of areas TF, TL, and TH projections.The following projections were observed both to and within posterior cingulate cortex. Area 29a–c received inputs from area 46 of the frontal lobe and the subiculum and in turn it projected to area 30. Area 30 had afferents from the posterior parietal cortex (area Opt) and temporal area TF. Areas 23a and 23b received inputs mainly from frontal areas 46, 9, 11, and 14, parietal areas Opt and PGm, area TPO of superior temporal cortex, and areas TH, TL, and TF. Anterior cingulate areas 24a and 24b and posterior areas 29d and 30 projected to area 23. Finally, a rostromedial part of visual association area 19 also projected to area 23.The origin and termination of these connections were expressed in a number of different laminar patterns. Most corticocortical connections arose in layer III and to a lesser extent layer V, while others, e.g., those from the cortex of the superior temporal sulcus, had an equal density of cells in both layers III and V. In one instance projections to area 24 arose almost entirely from layer V of areas TH, TL, and TF. Furthermore, although most projections terminated in layers I–III of cingulate cortex, those of the amygdala to rostral area 24 terminated in deep layer I and layer II while area Opt projections to area 23 terminated mainly in layers I, II, and IV.Four classes of cortical connections have been characterized and each may play a role in the sensorimotor functions of cingulate cortex. These include connections with sensory association and multimodal areas, projections to and from premotor area 24c, subicular termination in areas 25, 24, and 29, and intracingulate connections that may transmit sensory input to areas 24 and 23 into a

ISSN:0092-7317    

DOI:10.1002/cne.902620208

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe inner plexiform layer (IPL) of the retina provides a useful model for ultrastructural analysis of synaptic development. In primates, the IPL consists of numerous combinations of neuronal contacts that assume the morphological configuration of either conventional or ribbon synapses. We have determined the sequential development of these combinations by analyzing serial electron microscopic sections from fetal rhesus monkeys. Our analysis reveals an orderly emergence of various pre‐ and postsynaptic elements: (1) patches of dense filamentous membrane first appear on the dendrites of ganglion (G) cells; (2) membrane densities on ganglion cell dendrites then become apposed to amacrine (A) cell processes still lacking their own membrane densities and synaptic vesicles; (3) amacrine cell processes acquire membrane specializations associated with vesicles at the sites apposing ganglion cell dendrites, thereby establishing the first morphologically complete, A → G subtype of conventional synapse; (4) pairs of amacrine cell processes form A → A subtypes of conventional synapses; (5) next, monad ribbon synapses are established between bipolar (B) and ganglion or amacrine cell processes (B → G; B → A); (6) the three subclasses of dyad ribbon synapses (B → GG; B → GA; B → AA) are subsequently formed by the introduction of additional amacrine or ganglion cell processes in the dyad synapse; (7) concurrently, processes of some amacrine and interplexiform (I) cells form a feedback circuit with bipolar cell axons (A → B; I → B), thereby completing the synaptic microcircuitry of the IPL.Present findings provide evidence that the sequence of synaptic differentiation in the IPL proceeds from the postsynaptic to the presynaptic site. Furthermore, lateral interactions (A → G and A → A) are established prior to the formation of the “straight signal” pathway from photoreceptors (P) via bipolar cells to ganglion cells (P → B → G). Observed developmental events provide new insight into the order of establishment of local neuronal

ISSN:0092-7317    

DOI:10.1002/cne.902620209

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902620210

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902620201

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY