摘要:

AbstractA study of goldfish optic tectum was performed with conventional electron microscopy and with the Golgi‐EM technique described by Fairén et al. (1977). Five types of tectal afferents, three types of interneurons and three types of efferent neurons were investigated.Afferents from the torus longitudinalis, which terminate in the marginal layer, contain round synaptic vesicles with a mean diameter of 43 nm. Optic afferents, which terminate in the superficial gray and plexiform layer, are characterized by pale mitochondria with dilated cristae and round vesicles with a mean diameter of 49 nm. Afferents of unknown origin, terminating in several tectal layers, can be subdivided in three types; one containing round vesicles and two containing pleomorphic vesicles with different degrees of ellipticity.The three types of interneurons studied (type I, III and XIV, of Meek and Schellart, 1978) were selected on basis of their high frequency of occurrence. The apical dendrites of type I neurons make many synaptic contacts with the marginal axons. All three types have dendrites in the superficial gray and plexiform layer making contacts with optic nerve terminals. In addition, their dendrites and cell bodies make synaptic contacts with several types of unidentified presynaptic elements. The axon terminals of type I and of type XIV contain round vesicles with a mean diameter of 45 and 46 nm respectively.Three of the four types of efferent neurons present in the goldfish tectum were studied (type VI, XII and XIII). Two of them make contact with optic terminals (type VI and XII) and two make contact with tectal afferents of unknown origin in the central white layer or in the lower part of the central gray layer (type XII and XIII). The axons of all three types become myelinated at some distance from their origin. Their intial unmyelinated parts are covered with a so‐called “outer surface coating”, have no collaterals and are occasionally (type VI and XII) or frequently (type XIII1) postsynaptic to other elements. The archiform axons of type XIII1, and to a lesser extent also the shepherds‐crook shaped axons of type XII, have a close apposition to looping and narrowing dendrites in the inner plexiform layer.The present results concerning neuronal circuitry of the goldfish optic tectum are summarized in a tentat

ISSN:0092-7317    

DOI:10.1002/cne.901990202

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe size, density, and number of the synaptic contacts of three types of interneurons (types I, III, and XIV of Meek and Schellart, 1978) and three types of efferent neurons (types VI, XII, and XIII) of the goldfish optic tectum were quantified by means of a quantitative stereological study of Golgi‐EM serial sections. Furthermore, an estimation was made of the percentage of optic terminals on these six cell types and of the ratio between terminals with pleomorphic and terminals with round vesicles.The mean density of contacts per receptive component (i.e. the cell body and the different parts of the dendritic tree) varies from 0 to 100 per 100/μm2surface, corresponding to 0‐8% receptive surface. Each cell type has a characteristic average density as well as a characteristic density distribution along the distinct components. This suggests that the receptive components of the tectal cell types investigated have a predetermined density and that a morphological classification of tectal cells has functional relevance.The mean length of the contact zones in the ultrathin sections varies from 213 to 332 nm for identified postsynaptic elements and from 188 to 293 nm for identified presynaptic elements. The size of the contacts on the distinct receptive components appears to be primarily related to the tectal lamination pattern. Distinct types of axons, however, have characteristic mean sizes of contacts. This might suggest that the size of the contacts, contrary to their density, is primarily determined by the presynaptic elements.The mean number of synaptic contacts calculated per cell type is as follows: type XIV, 200; type III, 450; type VI, 1,400; type I, 2,100; type XII, 4,200; and type XIII1, 5,400. Multiplication of these numbers with the number of cells per tectal half shows that the population of type XIV cells has by far the most synaptic contacts, since their low number of synaptic contacts is clearly overruled by their high frequency of occurrence.Optic terminals, identified by their characteristic mitochondria and large round vesicles, appear to contribute to about 10–20% of the contacts on identified postsynaptic elements in layer 5. The ratio between presynaptic elements with pleomorphic vesicles and those with round vesicles shows a slight tendency to increase when the distance to the origin of the axon decreases.It is concluded that a combination of the Golgi‐EM technique with quantitative stereological methods appears well suited to the study of the synaptic organization of brain centers, and that combination of quantitative Golgi‐EM with neuronal tracing methods (degeneration, HRP, autoradiography) offers good prospects for detailed investigations of neuronal co

ISSN:0092-7317    

DOI:10.1002/cne.901990203

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe organization and structure of dendrites penetrating into the white matter of upper cervical spinal segments have been examined by means of Golgi staining techniques, intracellular horseradish peroxidase (HRP) injections, and ultrastructural studies. The Golgi studies established that several groups of neurons located in intermediate and ventral laminae of the upper cervical spinal cord have a substantial part of their dendritic tree extending into adjacent ventral and lateral funiculi. Most dendrites in white matter showed irregular varicosities along their length. They were devoid of spines and followed relatively direct paths. In contrast, grey matter dendrites were occasionally observed with spines and complex appendages and frequently followed tortuous paths. The size and location of some Golgi stained neurons suggested that white matter dendrites might originate from neck muscle motoneurons. This possibility was confirmed using intracellular HRP injections. These studies also showed that the distribution of white matter dendrites of neck muscle motoneurons depended on the location of the motoneuron soma. White matter dendrites of neck muscle motoneurons located deep in the ventral horn projected into all regions of white matter surrounding the ventral horn. Other neck muscle motoneurons, located in the spinal accessory nucleus, had white matter dendrites largely confined to the lateral funiculus. White matter dendrites of motoneurons in the commissural nucleus were found to project across the ventral commissure into the contralateral spinal cord.Light microscopic studies of semi‐thin sections stained with toluidine blue and electron microscopic studies of thin sections revealed that white matter dendrites were confined to special regions of the white matter. These regions resembled the grey matter neuropil and contained dendrites and unmyelinated and small diameter myelinated axons. Axon terminals were also found in white matter. These terminals contained either flattened or spherical vesicles and formed synaptic contacts on white matter dendrites.White matter dendrites, by virtue of their frequency of occurrence, distribution, and type of synaptic contacts may represent a means by which descending or ascending spinal systems can influence spinal neurons without recourse to axon collaterals which terminate in grey matte

ISSN:0092-7317    

DOI:10.1002/cne.901990204

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe corticostriate projections of temporal areas TA, TE, TF, TG, 35, and 28 were studied in the rhesus monkey with the use of autoradiography. Widespread projections were observed to rostral as well as caudal parts of the striatum for all areas except area 28. For example, areas TA and TG have sizable projections to the medial or periventricular part of the head of the caudate nucleus, as well as to the medial part of the tail of this structure and the dorsally adjacent putamen. Areas TE and TF also were observed to send strong projections to the head of the caudate nucleus. In addition, they project to the rostral putamen. Both have projections to the tail of the caudate nucleus and caudal putamen.The widespread distribution of temporostriate axons to the rostral striatum suggests strongly that previous silver impregnation studies have not only underestimated the strength of the temporal cortical contribution to the corticostriate system, but also failed to identify the major projection zone of temporostriate axon terminals. For example, while all temporal cortical areas contribute projections to an organized topography in the tail of the caudate nucleus and the ventrocaudal putamen, they were observed consistently to have larger projections to the head of the caudate nucleus and rostral putamen.These results add to a growing body of evidence which demonstrates the existence of widespread nonmotor cortical input to the basal ganglia, and an organization of this input far greater in complexity than that demonstrated by earlier suppressive silver impregnation methods.

ISSN:0092-7317    

DOI:10.1002/cne.901990205

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe distribution of hormone‐concentrating cells in the brains of South African clawed frogs,Xenopus laevis, was examined autoradiographically after the administration of3H‐dihydrotestosterone. Hormone‐accumulating cells were found in cranial nerve nucleus IX‐X and adjacent smaller cells, a presumed medullary vestibular nucleus, a presumed sensory nucleus of cranial nerve V, dorsal tegmental area of the medulla, laminar nucleus of the torus semicircularis, ventral thalamus, and anterior pituitary.The pattern of dihydrotestosterone‐labelled cells differs from previously reported results following testosterone or estradiol administration. Unlike these latter hormones, dihydrotestosterone does not accumulate in anterior preoptic or ventral infundibular nuclei. Both androgens but not estradiol label medullary motor neurons; limbic telencephalic nuclei appear to concentrate only estradiol. Hormone‐concentrating brain nuclei inX. laevishave been implicated in neuroendocrine regulation and the control of male and female reproductiv

ISSN:0092-7317    

DOI:10.1002/cne.901990206

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe immunocytochemical localization of tyrosine hydroxylase is examined during ontogeny in the fetal rat brain in order to determine the age of first detection and subsequent cellular localization of the enzyme and the developmental characteristics of the immature catecholaminergic neurons. Fetal atlases of the tyrosine hydroxylase‐labeled neurons are presented at embryonic day (E) 12.5, 13.5, and 14.5.Tyrosine hydroxylase is first detected immunocytochemically at E 12.5. At this stage, the labeled neurons have completed final mitosis, but are still migrating and are cytologically immature. Tyrosine hydroxylase can also be detected in axons and axonal growth cones at this stage of development. The age of first immunocytochemical detection of the enzyme precedes the demonstration of catecholamine fluorescence by 1 to 2 days in certain nuclear groups.At later stages of development (E 13.5 and E 14.5), the major groups of perikarya and processes labeled for tyrosine hydroxylase have a distribution similar to that previously described by catecholamine fluorescence. At E 14.5, the perikarya undergo considerable changes in their cytology and exhibit the first dendrites immunocytochemically labeled for the enzyme. The first terminal fields are also detected in the rudimentary caudate‐putamen at this st

ISSN:0092-7317    

DOI:10.1002/cne.901990207

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe immunocytochemical localization of tyrosine hydroxylase is examined at embryonic (E) days 18 and 21 in rat brain in order to determine changes in the distribution and cytology of neurons showing immunoreactivity for the enzyme during late prenatal developmnt. As compared with earlier stages of development, the distribution and morphology of the tyrosine hydroxylasecontaining neurons at E18 and E21 more closely resemble catecholaminergic neurons in the adult brain. The changes occuring from the early to the late prenatal stages of development appear to be the result of an increase in number of cells and continued aggregation and migration of the labeled neurons.The major differences in the distribution of labeled perikarya between E18 and E21 are in the olfactory bulb and cerebral cortex. In the olfactory bulb, tyrosine hydroxylase‐containing neurons are not detected until E21. In contrast in the cerebral cortex, a few neurons are transiently labeled for the enzyme at E18, but are not detected at E21 and have not been reported in the adult brain.The most striking change in the tyrosine‐hydroxylase labeled structures in the late prenatal period is the increase in detectable immunoreactivity in bundles of axons and in terminal aborizations. The orderly appearance of tyrosine hydroxylase‐labeled axons in the neostriatum and cortex are discussed in relation to the formation of these two contrasting regions innervated by catecholaminergic ne

ISSN:0092-7317    

DOI:10.1002/cne.901990208

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

年代:1981

数据来源: WILEY

摘要:

AbstractWhen the sciatic and saphenous nerves are cut and ligated in adult cats, the immediate effect is the production of a completely anesthetic foot and a region in medial lumbar dorsal horn where almost all cells have lost their natural receptive fields (RFs). Beginning at about 1 week and maturing by 4 weeks, some 40% of cells in the medial dorsal horn gain a novel RF on proximal skin, that is, upper and lower leg, thigh, lower back, or perineum. This new RF is supplied by intact proximal nerves and not by sciatic and saphenous nerve fibers that sprouted in the periphery. During the period of switching of RFs from distal to proximal skin there was no gross atrophy of dorsal horn grey matter and no Fink‐Heimer stainable degeneration of central arbors and terminals of peripherally axotomized afferents. In intact animals medial dorsal horn cells showed no sing of response to mechanical stimulation of proximal skin. RFs of some of the cells had spontaneous variations in size and sensitivity, but these were not nearly sufficient to explain the large shifts observed after chronic nerve section. Tetanic electrical stimulation of skin or peripheral nerves often caused RFs to shrink, but never to expand. Although natural stimuli of proximal skin would not excite medial dorsal horn cells in intact or acutely deafferented animals, it was found that electrical stimulation of proximal nerves did excite many of these cells, often at short latencies. In the discussion we justify our working hypothesis that the appearance of novel RFs is due to the strengthening or unmasking of normally present but ineffective afferent terminals, rather than to long‐distance sprouting of new afferent arbors within the spinal c

ISSN:0092-7317    

DOI:10.1002/cne.901990209

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

年代:1981

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901990201

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

年代:1981

数据来源: WILEY