摘要:

AbstractPurkinje cells in the intermediate cortex of the anterior lobe and paramedian lobule of the cat cerebellum were intracellularly injected with horseradish peroxidase. Light microcopic analysis of the distribution paterns of the local collaterals arising from the axons of Purkinje cells in these two cortical areas was carried out. These data suggest that the distribution of the axon collaterals is different in these two areas of the cerebellar cortex. Collaterals arising from the axons of Purkinje cells in the anterior lobe form a highly branched, densely beaded plexus which is restricted to the immediate area of the cell of origin. The axonal ramification is located primarily along the Purkinje cell layer, although a few branches extend into the deep to middle molecular layer. In contrast, collaterals derived from Purkinje cells in the paramedian lobule branch infrequently, and give rise to only a few beaded chains. They extend for great distances, up to 1 mm from the cell of origin. In some cases, collateral branches of paramedian lobule Purkinje cells course into the subcortical white matter to the opposite side of their folium of origin or extend to adjacent folia. These data suggest that the distribution pattern of recurrent collaterals within the cerebellar cortex may not be uniform. In addition, differences in distribution may be correlated with differences in the afferent and efferent organization of the two areas in the cerebellar cortex.

ISSN:0092-7317    

DOI:10.1002/cne.902100102

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

年代:1982

数据来源: WILEY

摘要:

AbstractDo structres exist within the embryonic central nervous system that guide axons across the midline during development of the great cerebral commissures (corpus callosum, anterior commissure)? With the use of serial section and reconstructive computer graphic techniques we have found that during normal ontogeny of the mouse forebrain and before the arrival of the pioneer fibers of the corpus callosum at the midline, a population of primitive glial cells migrates medially (through the fused walls of the dorsal septum) from the ependymal zones of each hemisphere. At the midline, and well rostral to the lamina terminalis, these cells unite to form a bridgelike structure of “sling” suspended below the longitudinal cerebral fissure. The first callosal axons grow along the surface of this cellular bridge as they travel toward the contralateral side of the brain. The “sling” disappears neonatally. The fibers of the anterior commissure grow within the lamina terminalis along a different type of preformed glial structure. Movement of these axons occurs through an aligned system of glial processes separated by wide extracellular spaces.Do these transient glial tissues actually provide guidance cues to the commissural axons? Analyses of three situations in which the glial “sling” is genetically or surgically impaired or nonexistent indicate that this structure does, indeed, play an essential role in the development of the corpus callosum. We have analyzed (1) the embryonic stages of a congenitally acallosal mouse mutant (strain BALB/cCF), (2) several pouch stages of a primitive acallosal marsupial,Didelphys virginiana(opossum), and (3) animals in which the “sling” had been lesioned surgically through the uterine wall in the normal embryo (strain C57BL/6J).In the acallosal mouse mutant fusion of the septal midline is delayed by about 72 hours and the “sling” does not form. Although the would‐be callosal axons approach the midline on schedule, they do not cross. Instead, the callosal fibers whirl into a pair of large neuromas adjacent to the longitudinal fissure. Similarly, in the opossum, fusion of the medial septal walls and formation of the glial “sling” are also lacking. However, in this species, instead of traveling dorsally, the “callosal” axons turn ventrally and pass contralaterally by way of the anterior commissure pathway. Surgical disunion of the glial “sling” also resulted in acallosal individuals. The callosal pathology in these affected animals mimicked exactly that of the genetically lesioned mutant. Our observations suggest that many different types of oriented glial tissues exist within the embryonic neural anlage. We propose that such tissues have the ability to influence the directionality of axonal movements and, thereby, play a crucial role in establishing orderly fiber projections within the

ISSN:0092-7317    

DOI:10.1002/cne.902100103

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe organization of the lateral reticulocerebellar projection to the pyramis and copula pyramidis in the rat was studied with the use of microinjections of horseradish peroxidase (HRP). These injections were mae in different mediolateral positoins along the width of this lobule. The objective was to determine whether reticulocerebellar parasagittal zones (Chan‐Palay et al., 1977) receive differential inputs from the lateral reticular nucleus (LRN). This material has previously been used to analyze the olivo and pontocerebellar projection to this same cortical region of the rat cerebellum (Eisenman, 1981a,b). The results do not support a clear‐cut topographic organization in this projection system to the pyramis and copula pyramidis in the rat. There is some suggestion, however, of a difference in emphasis in the region of the LRN projecting to different mediolateral positions in this lobule. Injections in medial and lateral parts of this lobule result in the labeling of cells in the subtrigeminal and ventral parts of the parvicellular and magnocellular divisions. Injections in intermediate parts of this lobule result in the labeling of cells primarily in the subtrigeminal division. However, cells in each of the divisons (primarly the subtrigeminal and parvicellular) are labeled in each experiment. These results are discussed with reference to electrophysiological and other anatomical studies of the topography of the reticulocerebellar projection in the

ISSN:0092-7317    

DOI:10.1002/cne.902100104

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe retinal projections of the juvenile and adult channel catfish,Ictalurus (Ameiurus) punctatus, were studied by using horseradish peroxidase (HRP) and autoradiography. The contralateral optic tract sends fibers to the suprachiasmatic nucleus (SCN) and divides into lateral (LOT) and medial optic tracts (MOT). In the adult fish, the former is thicker than the latter, whereas in the juvenile form, the reverse is true. The MOT curves laterally and divides into eight to 15 medial fascicles of the optic tract (MFOT). The contralateral optic fibers project to the nucleus opticus dorsolateralis, nucleus of the posterior commissure, nucleus geniculatus lateralis, pretectal nuclear complex, nucleus corticalis, stratum fibrosum et griseum superficiale (SFGS), and a few optic fibers extend into the stratum griseum centrale. The tractus opticus accessorius arises from the postero‐dorsal margin of the LOT and extends ventromedially to project to the nucleus opticus accessorius. At the optic chiasm a few fibers do not decussate, and these fibers project to almost all ipsilateral sites similar to those of the contralateral side, including the optic tectum. The autoradiographic observations substantiated the analysis of optic fiber projections provided by the HRP techniqu

ISSN:0092-7317    

DOI:10.1002/cne.902100105

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe fiber compositio of the left major splanchnic nerve was studed in cats by electron microscopy. Comparisons were made between normal and partically degenerated nerve specimens following ventral rhizotomy (T3‐L1), or spinal nerve division (T3‐L1). Normal, major splanchnic nerves contained 2,500–4,000 myelinated and 10,000–15,000 unmyelinated fibers. Preganglionic fibers included approximately 90% of the finely myelinated (1–7μm) and over 50% of the unmyelinated fibers. Removal of the sensory and preganglionic components by spinal nerve division revealed a third, postganglionic fiber category. This included 13–38 small myelinated (1–5μm) and 1,645‐7,619 unmyelinated fibers. Finally, a comparison of normal and partially degenerated nerve specimens of both groups (ventral rhizotomy and spinal nerve cut) indicated that splanchnic afferents are made up of virtually all of the 120–350 large myelinated (8‐14μm) and 10% of the small myelinated (1–7μm) fibers. A preliminary estimate indicated that about 10–20% of the unmyelinated fibers were sensory. The implications of t

ISSN:0092-7317    

DOI:10.1002/cne.902100106

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

年代:1982

数据来源: WILEY

摘要:

AbstractMale rats undernourished from the 18th day of gestation until 100 days of age were nutritionally rehabilitated until 200 days of age. Six control and six experimental rats at each of 100 and 200 days of age were killed by perfusion with buffered 2.5% glutaraldehyde. Pieces of visual cortex from each rat were postfixed in osmium tetroxide and embedded in resin. Stereological procedures at the light and electron microscope levels were used to estimate the synapse‐to‐neuron ratios in cortical layers II to IV.Rats undernourished until 100 days of age had a mean ± S.E. of 10,350 ± 470 synapses associated with each neuron. This represented a 13% deficit (P<0.05) when compared to the control value of 11,950 ± 530.Following nutritional rehabilitation till 200 days of age it was found that the previously undernourished rats had about 23% more (P<0.05) synapses‐per‐neuron than their age‐matched controls. This was due almost entirely to a substantial increase in the ratio in the previously undernourished animals; the value of controls did not alter significantly between the two age groups.It appears that the deficit in the synapse‐to‐neuron ratio seen after a lengthy period of undernutrition is not permanent, at least in rats subsequently allowed nutritional rehabilitation. In fact, such animals seem to be capable of not only “catching‐up” but “overshooting” the values fou

ISSN:0092-7317    

DOI:10.1002/cne.902100107

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe utilization of dopamine in the adult human retina was examined by using high‐affinity uptake, localization, synthesis, and release as neurotransmitter‐specific physiological probes. Autoradiographic and histochemical studies have shown that dopamine‐accumulating and dopamine‐containing cells of the human retina belong to a population of neurons whose somata are located in the proximal regions of the inner nuclear layer. Some of these are amacrine cells which are pre‐and postsynaptic to other amacrine cells exclusively in the inner plexiform layer. However, evidence is presented which indicates the existence of interplexiform dopaminergic neurons which send processes to both plexiform layers of the retina. These neurons contain a high concentration of dopamine, take up3H‐dopamine by a high‐affinity mechanism, and release endogenous or accumulated dopamine by a Ca2+‐dependent mechanism upon depolarization with high extracellular K+. An endogenous level of about 20 pmoles dopamine per mg protein was measured in freshly isolated retina using high‐pressure liquid chromatography with electrochemical detection. These results demonstrate that mechanisms for dopaminergic neurotransmission are present in

ISSN:0092-7317    

DOI:10.1002/cne.902100108

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe onset of responsiveness to eighth nerve stimulation was examined in n. magnocellularis and n. laminaris, (second‐ and third‐order neurons) of the chick brainstem auditory system. Extracellular microelectrode mapping techniques were used to examine postsynaptic responses inin vitrobrainstem preparations. Two specific questions were addressed. First, what is the earliest time at which postsynaptic action potentials can be evoked in n. magnocellularis and n. laminaris by eighth nerve stimulation? Second, does responsiveness to eighth nerve stimulation develop along a spatial gradient in n. magnocellularis and, if so, how does this gradient compare with other developmental events observed in the chick auditory system?Postsynaptic responses in n. magnocellularis were first recorded at 11 days of incubation. Nucleus laminaris responses to direct stimulation of n. magnocellularis were also first recorded at 11 days, although n. laminaris responses to eighth nerve stimulation were not seen until 12 days of incubation.A gradient of response development within n. magnocellularis was indicated by mapping of responsive sites on days 11–13. At 11 days, responses to eighth nerve stimulation were restricted to the most anteromedial portion of n. magnocellularis. Between 11 and 13 days, cells in increasingly more posterolateral portions of n. magnocellularis became responsive. This is anteromedial‐to‐posterolateral gradient in n. magnocellularis is correlated with the basal‐to‐apical gradient of morphogenesis observed in the basilar papilla and morphogenetic gradients previously observed in n. magnocellularis and

ISSN:0092-7317    

DOI:10.1002/cne.902100109

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe origin and terminations of thalamic inputs to the striate cortex and the occipital cortex of the rabbit were studied using both anterograde autoradiographic techniques and retrograde transport of horseradish peroxidase (HRP). After injections of [3H]‐leucine into the dorsal lateral geniculate nucleus (DLGN) the transport of radiolabeled material was demonstrated in separate loci in both the striate and the occipital cortex. In both these cortical areas, the principal site of geniculocortical termination was in lamina IV with some diminished input spreading into laminae II‐III and a light termination in layer I overlying the lamina IV termination. Layer VI of striate cortex received a substantial projection from DLGN while infragranular laminae of occipital cortex received a similar although lighter and more diffuse projection. The lateral posterior nucleus (LPN) was similarly demonstrated to project to both striate and occipital cortices, the projection terminating principally in lamina IV of occipital cortex, lamina V of striate cortex, and layer I over a large, continuous area of the posterior pole of the cortex. Moreover, a projection from LPN to the retrosplenial cortex medial to the striate area was consistently seen.The autoradiographic demonstration of a projection from DLGN and LPN to both striate cortex and occipital cortex was corroborated by the retrograde studies. Following the injection of HRP into either the striate or occipital cortex, columns of retrogradely filled somata were identified in both the DLGN and LPN. The location of the column of labeled neurons within each nucleus varied predictably with the location of the injection in either the striate or the occipital cor

ISSN:0092-7317    

DOI:10.1002/cne.902100110

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe present study determined the effect of the housing condition experienced by old adult male rats on the appearance and number of dendritic spines. Specifically, 20‐month‐old rats were killed following 6 months of living in either a social environment (three to a cage) or living alone. The total number of dendritic spines per unit length was examined along segments of oblique, basal, and apical dendritic branches of pyramidal cells from layers II, III, Va, and Vb of the visual cortex. In addition to determining the total spine number, the spines were differentiated into two topographical categories: those with a lollipop configuration (type L) and those with a nubbin configuration (type N). Out results show that neither the total spine density nor the type L spine density were generally influenced by the two housing conditions. However, the density of type N spines was almost always greater on neurons from rats which had been living alone irrespective of the cortical layer or the dendritic segment counted.Some differences in total spine density and type L spine density were noted when neurons from the same environment but different cortical layers were compared, and these findings are discussed. However, the major focus of this paper was to extend our previous report of a selective increase in type N spines with age. We now show that in addition to increasing with age, type N spine density is also selectively increased by the condition of social deprivat

ISSN:0092-7317    

DOI:10.1002/cne.902100111

出版商:Alan R. Liss, Inc.    

年代:1982

数据来源: WILEY