摘要:

AbstractA study of the regions of myelination of spiral ganglion cell bodies at birth in the kitten revealed that the first signs of myelination occurred before birth. A quantitative analysis of myelinated versus unmyelinated cells, and the distribution of myelin lamellae of the ganglion cell sheath reflect the kinetics of the later stages of cochlear maturation. The onset of the final maturation process begins in the basal region of the first turn, which is 20% of the length of the spiral lamina measured from the basal extremity of the cochlea. This maturation proceeds in an orderly manner from the lower half of the first turn to the apex, but also develops to a smaller degree toward the hook region. Results are compared with previous findings.

ISSN:0092-7317    

DOI:10.1002/cne.902040102

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe intercollicular pathway of the hamster was studied by means of a combination of horseradish peroxidase (HRP), autoradiographic, and double‐labeling (nuclear yellow‐HRP) techniques. Small deposits of HRP marked significant numbers of cells in the contralateral colliculus only when the injection site included the laminae ventral to thestratum opticum.Anterior deposits labeled many more neurons than injections into the caudal part of the tectum. Of the cells labeled by our injections, 18.2% were located in the superficial collicular laminae(stratum griseum superficialeandstratum opticum), and the remainder (81.8%) were in the deep layers. A wide variety of morphological cell types contributed axons to the intercollicular projection, and in a given animal the loci of the labeled neurons were generally symmetrical with the injection site.Small deposits of [3H]‐leucine resulted in contralateral labeling only when the injection included the deep collicular laminae. The transported label was most dense in thestratum griseum intermedialeandstratum griseum profundum, and its location was generally homotopic with the injection site.Experiments in which collicular HRP deposits were combined with large cervical spinal or pontine reticular injections of Nuclear Yellow indicated that intertectal neurons did not, in most cases, contribute axon branches to the spinal or pontine reticular projections of the colliculus.Receptive field data obtained at the time of the HRP and/or [3H]‐leucine deposits demonstrated that the collicular representations of the ipsilateral and at least 45° of the contralateral hemifields were encompassed by intercollicular connections. This was also true for the somatosensory representation of the entire head and a portion of

ISSN:0092-7317    

DOI:10.1002/cne.902040103

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

年代:1982

数据来源: WILEY

摘要:

AbstractLocal nonspiking interneurons have been implicated in the control of behavior. We have characterized the physiology of two local nonspiking interneurons in the locust and subsequently examined the neurons in the light and electron microscopes. Physiologically the two interneurons have opposite effects upon antagonistic motor neurons and are tonically releasing transmitter at their “resting potentials.” This combination of tonic release and reciprocal driving of antagonistic motor neurons by single interneurons provides a hitherto undescribed means of controlling posture. One interneuron (DCVII, 4) excites flexor tibiae and inhibits the slow extensor tibiae motor neurons when depolarized. The other interneuron (DCVII, 5) inhibits the flexor tibiae and excites the slow extensor tibiae motor neurons when depolarized. In both cases, when the interneurons are hyperpolarized, they have the opposite effects upon the same motor neurons. Intracellular staining of these neurons confirms that they are local interneurons. Furthermore, an examination of sectioned material shows that the neurons are unique and can be identified as such in a population of locust neurons. Ultrastructurally, we find synapses only on the smaller (less than 2 μm) branches. These neurons may form the presynaptic element in either of two configurations, these being the discrete density (one presynaptic, one postsynaptic) and the dense bar (one presynaptic, two postsynaptic) type of configurations. The functional implications of these findings for neurons controlling posture are discu

ISSN:0092-7317    

DOI:10.1002/cne.902040104

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe arachnoid membrane of chick embryos was prepared for electron microscopic study by means of thin sections and freeze‐fracture replicas. Particular attention was given to the relationships among junctional complexes during arachnoid maturation. By 14 days of incubation, the arachnoid had differentiated into morphologically distinct inner and outer zones. Both desmosomes and gap junctions were present among the cells of both layers at this time. Desmosomes were most numerous in the inner arachnoid layer and their structure remained constant. Gap junctions showed a great variation in structure. The large gap junctions contained a particle packing pattern in which rows of intramembranous particles were separated by particle‐free zones. Arched gap junctions were also present. Smaller arrays of gap junctions exhibited a variety of configurations on the membrane P‐face. The first tight‐junctional strands clearly identifiable in freeze‐fractured preparations appeared at 15–17 days. These were closely associated with the particles of gap junctions and consisted of single strands on the P‐face. By hatching age (21 days) a “mature” pattern of tight‐junctional strands was interwoven in several layers. In the interim, more complex arrangements of tight‐junctional strands were in intimate relati

ISSN:0092-7317    

DOI:10.1002/cne.902040105

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe projections from the pontine nuclei and the nucleus reticularis tegmenti pontis (N.r.t.) onto the flocculus, uvula, and the paramedian lobule were studied with retrograde transport of horseradish peroxidase in the rhesus monkey. The main findings are as follows:There is a conspicuous tendency for labeled cells to occur in numerous discrete clusters in the pontine nuclei after injections of these parts of the cerebellum.There appears to be very limited overlap between pontine cell groups projecting to the flocculus, the uvula, and the paramedian lobule, respectively.Theflocculusappears to receive a substantial projection from the pontine nuclei. The projection is almost totally crossed (3% ipsilateral), and arises mainly laterally in the rostral half of the pons, but in addition from a minor group dorsomedially. The flocculus receives a bilateral projection (slight contralateral preponderance) from medial and dorsomedial parts of the NRT. The number of labeled cells in the NRT was 13% of the number in the pontine nuclei.Theuvulais amply supplied from the pontine nuclei. The projection takes origin throughout the rostrocaudal extent of the pons, from one medial and one dorsolateral region. Labeled cells are found in greatest number dorsolaterally in the rostral half of the pons. In the caudal N.r.t., one medial and one lateral cell group were labeled after injection of the uvula. The number of labeled cells in the N.r.t. was only 4% of the number in the pontine nuclei.Findings with regard to theparamedian lobuleconfirm and extend earlier observations in the monkey (Brodal, '79, '80).The present results are discussed in relation to HRP studies of the pontocerebellar projection in lower animals. Several possible species differences are noted—for example, with regard to projections to the flocculus. There is some evidence that the pontocerebellar projection is more precisely organized in the monkey than in lower animal

ISSN:0092-7317    

DOI:10.1002/cne.902040106

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

年代:1982

数据来源: WILEY

摘要:

AbstractAfferent neurones that provide proprioceptive innervation of extraocular muscles of the cat have been identified by means of retrograde axonal transport of horseradish peroxidase (HRP). Discrete injections of HRP into the medial rectus, lateral rectus, or retractor bulbi muscles labeled pseudounipolar neurones that were localized exclusively to the ipsilateral semilunar ganglion. The distribution of labeled neurones within the ganglion was consistent with its somatotopic organization with the majority found within the ophthalmic subdivision. Cell counts indicating approximately 90 labeled neurones per horizontal rectus muscle correlated well with earlier quantitative observations regarding the percentage of afferent fibers in oculomotor nerves and the number of proprioceptive terminals in the extraocular muscles. Neither the trigeminal mesencephalic nucleus nor the contralateral semilunar ganglion contained labeled neurones following injections of HRP into extraocular muscles.Consistent with other studies of spinal and cranial ganglia the contingent of pseudounipolar neurones present in the cat semilunar ganglion included both light and dark cell types. Light and electron microscope analysis of HRP‐labeled neurones in combination with acetylcholinesterase (AChE) histochemistry revealed that only one of the two neuronal types, the light cell, subserves extraocular muscle proprioception. Our data support the hypothesis that ganglion neurone type and, more specifically, soma diameter, are important determinants of functional statu

ISSN:0092-7317    

DOI:10.1002/cne.902040107

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe hypothalamic arcuate nuclei of several hundred rats were studied with several types of Golgi impregnations in young and adult animals. In addition to qualitative observations, a computer‐assisted quantitative analysis of dendritic arbors and axonal trajectories in coronal and horizontal sections was performed on 1,702 neurons in young rats. With data on large numbers of neurons, and using a product‐moment analysis of dendritic trees, we found statistically reliable differences in the mean size, shape, center of mass, skewness, and orientation of dendritic trees of neurons in different parts of the arcuate nucleus. Despite differences within the nucleus, neurons of the arcuate nucleus characterized as a group were different from neurons of the hypothalamic ventromedial nucleus.Generally two or three, but sometimes one or four, primary dendrites arise from somata in the arcuate nucleus. The total dendritic tree is usually fairly small. Some dendrites are covered with spines, while others appear to have smooth surfaces. Medially located neurons often have dendritic trees oriented in a dorsoventral direction, while more lateral cells, especially at the ventral surface of the hypothalamus, have mediolaterally oriented dendritic arbors; a graded transition of orientation occurs between the two extremes. Dendrites originating in the arcuate nucleus may enter the cellpoor zone between the ventromedial and the arcuate nucleus, and therefore may share afferents with dendrites of the ventromedial nucleus projecting into the cell‐poor zone. The mean center of mass for dendritic trees in all parts of the arcuate nucleus in coronal and horizontal sections was situated lateral, and, in most areas, ventral to the cell body. Dendritic fields tend to be elongated; if an elliptical shape is fitted to the dendritic arbors with the product‐moment analysis, the major axis of the ellipse is four to five times greater than the minor axis. The orientation of dendritic trees in horizontal sections is generally in a rostrocaudal direction; this is less pronounced laterally than medially. Near the third ventricle in a horizontal plane, dendrites tend to run orthogonal to the tanycytes; tanycytes, as studied with Golgi impregnations and scanning electron microscopy, constitute a large percentage of total tissue volume medially. Tanycyte distal processes run in a very orderly progression through the arcuate nucleus.Axons originate from either the perikaryon or a proximal dendrite. Some axons arising in the arcuate nucleus also terminate within the nucleus. Axons of arcuate nucleus origin may bifurcate, with one branch leaving the nucleus and the other terminating within it. Axons entering the median eminence are more likely to divide into collaterals within the median eminence rather than before entering it. The trajectory of axons in single thick coronal sections originating from arcuate neurons is more often ventral than dorsal. In the medial arcuate nucleus in horizontal sections, axons of intrinsic origin generally run in a rostrocaudal direction. Taken together, the data in the present study indicate intrinsic regional variation of dendritic structure and a complex level of internal organization of the arcuate

ISSN:0092-7317    

DOI:10.1002/cne.902040108

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

年代:1982

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902040109

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

年代:1982

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902040101

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

年代:1982

数据来源: WILEY