摘要:

AbstractLocus coeruleus of the rat was studied in material prepared by aldehyde‐osmium fixation. Cell bodies of locus coeruleus neurons possess large nuclei with a prominent nucleolus, a homogeneous karyoplasm of moderate density, and occasional indentations of the nuclear membrane. The cytoplasm is rich in organelles, including an extensive network of endoplasmic reticulum which forms well organized Nissl bodies. The highly developed Golgi apparatus surrounds the nucleus and extends into large dendritic trunks. In coronal section, cell bodies appear elongated along an approximate dorso‐ventral axis, and most dendrites as well as axons appear in cross‐section. In parasagittal sections the cells are very elongate, with dendrites and axons in the neuropil mostly cut longitudinally. Thus, locus coeruleus neurons possess disc‐shaped dendritic fields parallel to the anterior‐posterior axis of the brainstem, with predominantly longitudinal axo‐dendritic synaptic configurations.Presynaptic profiles in locus coeruleus neuropil were classified according to the characteristics of their vesicle populations and other features. The most frequently encountered synaptic ending was characterized by small, round, densely packed synaptic vesicles, and comprised approximately 41% of the total sample of 775 synapses. Another group having large, rounded synaptic vesicles, which could be traced in a number of instances to large myelinated axons, accounted for 20% of the sample. Synaptic endings having large, flattened vesicles were also numerous, comprising 23% of the total. Another category of presynaptic endings was identified as those possessing numerous, small, flattened vesicles and comprising about 11% of the sample. Presynaptic endings having many vesicles of mixed sizes accounted for 2% of the total, and another group of the same proportion having small, rounded synaptic vesicles but also an unusually large number of larger, dense‐cored vesicles was also present. Two other categories of synaptic endings were encountered, each comprising less than 1% of the total. One of these was derived from small, unmyelinated axons and contained clusters of pleomorphic synaptic vesicles. The other consisted of dendro‐dendritic synapses between locus coeruleus neurons and also displayed small clusters of pleomorphic synaptic vesicles near the zone of synaptic apposition. Quantitative analysis revealed that most afferents to the nucleus synapse onto dendrites ranging between 0.5 and 2.5 micrometers in diameter and onto spine‐like appendages derived from somata and dendrites. There were no significant differences between different categories of afferent terminals and their spatial distribution onto various postsynaptic targets of locus

ISSN:0092-7317    

DOI:10.1002/cne.901930402

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

年代:1980

数据来源: WILEY

摘要:

AbstractLocus coeruleus was studied in rats pretreated with intraventricularly administered 5‐hydroxydopamine ½ to 3 hours prior to conventional aldehydeosmium fixation. Presynaptic profiles in locus coeruleus neuropil were classified according to the characteristics of their vesicle populations and other features, as in our previous report. Similar categories of endings were observed, and the sites of postsynaptic innervation were identical to those described previously, that is, a majority of synapses were made with dendrites between 0.5 and 2.5 micrometers in cross‐sectional diameter, a significant proportion was seen ending onto somatic and dendritic spines, with a relative paucity of synapses made with spine‐free membrane of somata and large dendritic trunks. There were no significant differences between different morphological categories of afferent terminals and their spatial distribution onto various postsynaptic targets on locus coeruleus neurons.In addition to various membrane‐bound compartments of the cytoplasm, three categories of synaptic endings were labelled by the synaptic marker, while all others were unlabelled. One of these was identified previously as containing small, rounded synaptic vesicles and an unusually large number of large, dense core vesicles. The synaptic vesicles were lightly labelled with scattered, small, eccentrically placed opaque cores inside the synaptic vesicles, apparently randomly distributed throughout the terminal. This terminal is thought to be serotonergic. A second category of labelled synapse has been previously identified as that derived from small, unmyelinated axons having clusters of pleomorphic synaptic vesicles in which the vesicles are heavily labelled by 5‐hydroxydopamine. These are believed to represent catecholaminergic synaptic endings derived from recurrent collaterals as well as extrinsic catecholaminergic innervation of locus coeruleus. A final category of heavily labelled profile was identified as presynaptic dendrites, which, along with recurrent catecholaminergic axon collaterals, probably play an important part in the intrinsic regulation of nucleus locus coeruleus. When 59 labelled synapses were examined in adjacent serial sections, every vesiclecontaining profile was associated with a synaptic contact having characteristic membrane specializations. A similar result was obtained when 132 other unlabelled terminals of different categories were examined in seria

ISSN:0092-7317    

DOI:10.1002/cne.901930403

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

年代:1980

数据来源: WILEY

摘要:

AbstractMale rats undernourished from birth to 30 days of age were nutritionally rehabilitated till 160 days of age. Quantitative stereological procedures at the light microscope level were used to estimate, among other things, the numerical densities of cerebellar granule and Purkinje cells on a “per unit volume of cortex” basis. These were subsequently used to calculate granule‐to‐Purkinje cell ratios.The 30‐day‐old undernourished rats had a mean ± S.E. of 290 ± 27 granule cells for every Purkinje cell present, compared to 395 ± 34 for the controls. This was a deficit of about 27% (p<0.05). At 160 days of age, the previously undernourished rats still showed a persisting deficit of about 25% (p<0.05) in this ratio, despite the lengthy nutritional rehabilitation. There were no statistically significant age‐related changes in this ratio.The numerical density of Purkinje cells but not that of granule cells, was significantly greater in the previously undernourished rats than in controls, for both age groups. Increasing age caused a fall in the numerical density of both cell types.Granule and Purkinje cell nuclear diameters were unaffected by nutrition. However, Purkinje cell nuclei decreased in size by between 7%–13% with increasing age.These results indicate that undernutrition during early life can cause a permanent distortion of the relative number of the various cell types

ISSN:0092-7317    

DOI:10.1002/cne.901930404

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe cells of origin, course and site of termination of long propriospinal fibers interconnecting the intumescences have been studied with the aid of the horseradish peroxidase technique, as well as with anterograde degeneration techniques, in some quadrupedal reptiles (the lizardsTupinambis nigropunctatusandVaranus exanthematicus, and the turtlesTestudo hermanniandPseudemys scripta elegans). The anterograde degeneration findings suggest that long descending propriospinal fibers from the cervical intumescence are distributed bilaterally to the ventral gray of the lumbar enlargement, including the lateral motoneuron column. Long ascending fibers from the lumbar to the cervical intumescence are distributed, also bilaterally, to the ventromedial part of area VII–VIII. The cells of origin of long descending propriospinal fibers were found in the medial part of area VII–VIII in the cervical intumescence, particularly contralateral to the injection side. The cells of origin of long ascending propriospinal fibers were found in the lumbar intumescence, also particularly contralateral to the injection side, in the ventromedial part of area VII–VIII. It seems likely that in the reptiles studied the long propriospinal fibers interconnecting the spinal enlargements are in large part organized as crossed connections.The demonstration of long propriospinal fibers in lizards and turtles—i.e. quadrupedal reptiles that move their limbs in a particular diagonal pattern—suggests that these pathways are of great importance for the coordination of forelimb and hindlimb

ISSN:0092-7317    

DOI:10.1002/cne.901930405

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

年代:1980

数据来源: WILEY

摘要:

AbstractA projection from the subiculum to the retrosplenial cortex (area 29a and b) was studied by autoradiographic tracing of anterogradely transported proteins following injections of radioactive amino acids into ventral and dorsal parts of the subiculum. Only the dorsal parts of the subiculum projected to the retrosplenial cortex. The projection was exclusively ipsilateral, and topographically arranged along both the longitudinal septotemporal axis and the transverse plane of the subiculum. The termination in the retrosplenial cortex was confined to the relatively cell free superficial layer (lamina 1) and the underlying cell‐rich layers (laminae 3–4). Between these two terminations a narrow zone (lamina 2) was only weakly labeled. The projection constitutes an output route for hippocampal activity in addition to the fimbria‐fornix system and the subicular projections to the parahippocampal

ISSN:0092-7317    

DOI:10.1002/cne.901930406

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

年代:1980

数据来源: WILEY

摘要:

AbstractFrom the extracellular recording of single units in the monkey striate cortex and electrical stimulation at two selected sites in the optic radiations it was possible to estimate (1) the ordinal position of striate neurons (i.e., whether they received a monosynaptic, disynaptic or polysynaptic input from the thalamus) and (2) the nature of the afferent input to these neurons (i.e., whether it came from the magnocellular or parvocellular subdivision of the lateral geniculate nucleus (LGN)). Based on receptive field properties six major classes of striate neuron were identified—three which lacked orientation specificity (the ON‐center, the OFF‐center, and the ON/OFF or nonoriented (N‐0) receptive fields) and three with orientation specific responses (the S, the C, and the B categories of receptive field). Units lacking orientation specificity were concentrated in laminae 4A, 4Cβ and 6 while, for the cells with orientation specificity, C cells were found in laminae 4B and 6, B cells in 2/3 and 5, and S cells predominantly in laminae 2/3, 4Cα, and 5.The results of electrical stimulation indicated that cell‐to‐cell transmission time in the monkey striate cortex is 1.5 msec, and latency measures showed that cells with a monosynaptic drive from the thalamus were confined to laminae 4 and 6 while disynaptically driven cells were found principally in upper lamina 4 (4A and 4B). No cell class was identified exclusively with a given ordinal position and there were many types of potential first‐order neurons.The conduction time from one stimulating electrode to the next in the optic radiation was used to identify the afferent input to each striate neuron. The input to color‐coded neurones was found to come exclusively from parvocellular layers while the C cells and two subclasses of the S cell (S2and S3) were driven predominantly by the magnocellular subdivision. For other cell types (those with ON‐center, N‐0, and S1receptive fields) the input came from either type of LGN neuron.The laminar distribution of neurons receiving a direct input from the magnocellular and parvocellular streams is in accord with the results of anatomical studies into the site of termination of the LGN input. The cell types receiving these direct inputs vary in the two streams so that the parvocellular input terminates on cells with ON‐center and N‐0 receptive fields in lamina 4Cβ while the magnocellular input goes to cells with S, ON‐center, N‐0, and C receptive fields in lamina 4Cα and the lower part of 4B.Consideration is given to the influence of these results on models for neural processing in monkey striate cortex and a comparison is drawn with the result

ISSN:0092-7317    

DOI:10.1002/cne.901930407

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe subcortical inputs to several distinct subdivisions of the cat's visual cortex were examined using retrograde transport of horseradish peroxidase (HRP) with particular reference to the topography of the thalamic projections. Injections along the border between cortical areas 17 and 18 (a representation of the vertical meridian) lead to thalamic labelling in: (1) each lamina of the dorsal division of the lateral geniculate nucleus (LGNd), (2) the medial intralaminar nucleus (NIM), (3) the lateral, medial, and inferior pulvinar nuclei, and (4) the paracentral and central lateral nuclei. A topographic organization was observed in the projections of both the geniculate and pulvinar complexes. The spatial transformations in each system can be characterized as “point‐to‐line” representations, where points in the visual field are represented by columns (lines) of projection cells.Strikingly similar patterns of retrograde labelling were observed following injections in the medial bank of the middle suprasylvian sulcus (e.g., the Clare‐Bishop area, or the posteromedial lateral suprasylvian area (PMLS) of Palmer et al., '78). The thalamic afferents to PMLS differ from those to the 17–18 border, however, in that: (1) the magnocellular laminae of the LGNd (lamina A and A1) do not project to the suprasylvian sulcus, and (2) the suprasylvian projection of the C laminae appears much weaker than their striate‐peristriate counterpart. Taken together, the results support the interpretation of Updyke ('77), who, based on observations of the thalamic projections of areas 17, 18, and 19, suggested that the lateral pulvinar and the adjacent striate‐recipient zone of the medial pulvinar contain mirror‐symmetric representations of the visual field.It is further demonstrated that, the colliculorecipient zone of the medial pulvinar (adjacent to the medial border of the striate‐recipient zone) projects to a newly discovered visual area located on the lateral bank of the middle suprasylvian sulcus (i.e., the posterolateral lateral suprasylvian area (PLLS) of Palmer et al., '78), and to area 7, an association area located on the convexity of the middle suprasylvian gyrus. Despite the fact that labelled cells in the colliculorecipient zone frequently were distributed in the characteristic columnar pattern, these data failed to demonstrate a topographic organization in this projection.Finally, several extrathalamic afferent sources were also observed. Brainstem afferents to the 17–18 border were identified in one fortuitous case involving a particularly large injection. These reticulocortical projections originate bilaterally from: (1) locus coeruleus, (2) nucleus subcoeruleus, and (3) the dorsal tegmental nucleus. A few additional labelled cells were found in the central superior nucleus and nucleus linearis, both of which lie close to the midline and are part of the raphe system. In addition, labelled cells were consistently foundbilaterallyin the claustrum, regardless of the site of injection.The possibility that some of these diverse subcortical afferent sources exert nonvisual influences over the visua

ISSN:0092-7317    

DOI:10.1002/cne.901930408

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

年代:1980

数据来源: WILEY

摘要:

AbstractRats were undernourished by halving the mother's food intake from the sixth day of pregnancy onwards and through lactation. At weaning, the young rats were restricted to half the normal weight of food. A combination of light and electron microscopic techniques was used to study the effects of this regime on gliogenesis and glial maturation in the corpus callosum of animals aged between 15 and 48 days.A disturbance of neuroglial proliferation was suggested by the finding of an increased proportion of astroglia relative to oligodendroglia in the 15‐day‐old undernourished rats, indicating a delay in the acquisition of cells produced relatively late in development. Impaired differentiation of oligodendroglia was suggested by the finding in treated animals of increased light oligodendrocytes at 15 days and a deficit of dark oligodendrocytes at 48 days, relative to controls. The previously observed retardation in myelin acquisition seems thus to be related to a dealy in the differentiation of oligodendroglia, although it seems likely that the proliferation of these cells is also disturbed in undernutrit

ISSN:0092-7317    

DOI:10.1002/cne.901930409

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

年代:1980

数据来源: WILEY

摘要:

AbstractRats were undernourished by halving the mother's food intake from the sixth day of pregnancy onwards and through lactation. Subsequently, the young animals were maintained up to 48 days on half the normal diet. The effects of this regime of treatment on myelination in the corpus callosum were investigated by light and electron microscopy.In comparison with controls, the percentage of axons myelinated at 15, 21, and 48 days was reduced in undernourished rats. The number of lamellae constituting the myelin sheath was also reduced at 15 and 21 days, but at 48 days no difference was seen between control and treated rats, suggesting that a catch‐up in myelination had occured. A linear relationship between myelin sheath thickness and axonal diameter was observed in both groups of animals. However, a long‐term effect on axonal growth was suggested by findings in the 48‐day undernourished animals; in comparison with controls, axonal diameter was reduced, relative to myelin sheath thic

ISSN:0092-7317    

DOI:10.1002/cne.901930410

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

年代:1980

数据来源: WILEY

摘要:

AbstractIn cats anesthetized with urethane, all‐or‐nothing, synaptically evoked recordings were made from 80 separate units in the descending spinal tract of the trigeminal nerve above the left trigeminal nucleus caudalis, at depths not exceeding 50 μm from the surface of the medulla. The units were excited by the left upper (21), left lower (25), either (28), or only on simultaneous stimulation of both (six) canine tooth pulps. There was no somototopic distribution.The latency of responses ranged from 4 to 82 msec. For the group of 28 units excited by upper and lower tooth pulps, there was close matching of response latencies from the two teeth.An abrupt decrease in latency upon increasing stimulation strength (“jumping”), and a gradual increase in latency during repetitive stimulation at a frequency between 1 and 20 Hz (“drifting”) was characteristic of most, but not all, responses. Units evoked by stimulation of the inferior dental or infraorbital nerves had similar characteristics.Stimulation of a tooth pulp at threshold for a particular unit was used to test the excitability of that unit after suprathreshold stimulation of the same or a different canine tooth pulp. Stimulation of the upper left canine tooth pulp was generally only facilitatory, while stimulation of the lower left canine tooth pulp was initially facilitatory and later inhibitory. Stimulation of the upper or lower right canine tooth pulps did not excite but could inhibit units excited by the left canine tooth pulps.There was a significant correlation between the frequency at which a unit would follow repetitive stimulation and the duration of the inhibition generated by the first of a pair of stimuli. Long inhibition was associated with poor frequen

ISSN:0092-7317    

DOI:10.1002/cne.901930411

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

年代:1980

数据来源: WILEY