摘要:

AbstractPrimary afferent fibers in the lumbar, sacral, and caudal spinal segments of several mammals (rat, cat, monkey) were stained by applying horseradish peroxidase to the proximal part of cut dorsal rootlets and reacting the tissue histochemically after several hours of survival. The stained fibers' pattern of termination in the dorsal horn was similar in all three species, with many bouton‐like enlargements in the ipsilateral marginal zone, substantia gelatinosa, and nucleus proprius, as well as a few projections at each level to the dorsal commissure and contralaterally to the ventral border of the nucleus proprius. Partial lesions of dorsal rootlets in monkey revealed that the thin fibers comprising the lateral division end principally in the marginal zone and substantia gelatinosa, while the thick fibers of the medial division terminate in the nucleus proprius and deeper regions, contributing little to the substantia gelatinosa and marginal zone. On the basis of the termination patterns observed for whole and partly sectioned rootlets, the superficial dorsal horn can be divided into at least four regions. (1) The marginal zone (lamina I of cat) appears to receive terminations from intermediate (smaller myelinated) fibers; (2) the outer substantia gelatinosa (outer lamina II) receives many terminations from the very finest afferent fibers; (3) the inner substantia gelatinosa (inner lamina II) receives endings from some of the finest fibers and also from intermediate (smaller myelinated) fibers; and (4) the superficial part of the nucleus proprius (lamina III) receives endings from intermediate and large diameter dorsal root fiber

ISSN:0092-7317    

DOI:10.1002/cne.901860202

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

年代:1979

数据来源: WILEY

摘要:

AbstractSingle primary afferent myelinated fibers from cutaneous receptors of cat and monkey were functionally identified by recording from the spinal cord with micropipettes filled with horseradish peroxidase (HRP). Relatively slowly conducting fibers (<40 m/sec) from high threshold mechanoreceptors (mechanical nociceptors) and two types of low threshold mechanoreceptor (D‐hair and field) were selected for staining. Iontophoresis of the HRP and subsequent histochemical reaction stained the axons recorded from and their collaterals, including terminations, for several millimeters. The termination patterns in the two species proved essentially identical. Ipsilaterally, the mechanical nociceptor fibers terminated principally in the dorsal horn's marginal zone and in the ventral parts of the nucleus proprius (lamina V in the cat). Some of these nociceptors also had terminals in the midline just dorsal to the central canal, contralaterally in the marginal zone, and at the base of the opposite nucleus proprius. In contrast, the D‐hair primary afferent axons terminated in the dorsal part of the nucleus proprius overlapping into the innermost portion of the substantia gelatinosa. The field receptor fibers terminated predominantly in the middle part of the nucleus proprius. These results suggest that there is a highly specialized central projection of primary afferent endings which is related to sensory function and not to fiber diameter. The marginal zone and most dorsal parts of the substantia gelatinosa receive direct projections from cutaneous nociceptors but do not have direct input from cutaneous receptors transmitting activity initiated by innocuous stimulat

ISSN:0092-7317    

DOI:10.1002/cne.901860203

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

年代:1979

数据来源: WILEY

摘要:

AbstractFunctional characteristics of spinal neurons located in the marginal zone (lamina I) and substantia gelatinosa (lamina II) were compared to their structural features by intracellularly staining the source of unitary potentials with horseradish peroxidase (HRP) in unanesthetized, spinal cats. The responses of postsynaptic units to graded electrical volleys in intact dorsal roots and to physiological stimulation revealed that the peripheral excitatory input to neurons of the region is dominated by slowly conducting afferent fibers; often, the input to a given element is largely from a particular class of receptors. One type commonly seen received its principal peripheral excitation from low threshold mechanoreceptors with Aδ or C afferent fibers. Mechanoreceptive elements often exhibited a marked, prolonged habituation and many were not excited by afferent volleys. Other units were predominantly excited by nociceptors with myelinated or unmyelinated fibers, or by thermoreceptors with unmyelinated fibers. A few units (principally the thermoreceptive) showed substantial ongoing activity which was modulated by sensory stimulation, but most had little or none.The HRP staining revealed neuronal morphology in fine detail. No relationship between neuronal configuration and physiological response was discerned. Soma location was not always linked to afferent input, although the cell bodies of nonciceptive and thermoreceptive neurons tended to be in lamina I or outer lamina II (SGo) while those of the inocuous mechanoreceptive neurons tended to be in inner lamina II (SGi). The locus of a neuron's major dendritic arborization was more closely related to the source(s) of peripheral excitation. Cells excited by nociceptors with myelinated fibers had major dendritic projections in the marginal zone. Cells excited by nociceptors or thermoreceptors with unmyelinated fibers had important dendritic branching in the SGo. Innocuous mechanoreceptive neurons had primary dendritic aranching in the SGo. Innocuous mechanoreceptive neurons had primary dendritic arborization in the SGi when the input derived from unmyelinated fibers, or in the SGi and extending into the outer nucleus proprius (lamina III) when the afferent drive came from Aδ fibers.These findings support the concept that laminae I and II constitute a major termination region for thin primary afferent fibers, myelinated fibers from nociceptors ending principally in lamina I and unmyelinated fibers from nociceptors, thermoreceptors, and mechanoreceptors terminating predominantly in lamina II. Substantial integrative and distributive functions can be expected of such an afferent termination zon

ISSN:0092-7317    

DOI:10.1002/cne.901860204

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

年代:1979

数据来源: WILEY

摘要:

AbstractIntracellular microelectrodes filled with either Lucifer Yellow CH, a highly florescent dye, or horseradish peroxidase (HRP) were used to electrophysiolgically characterize and mark cells in the cerebral cortex of cat. Fifty‐eight cells, characterized electrophysiologically as glia, were marked with Lucifer Yellow CH. All were identified as protoplasmic astrocytes, and included cells in the glia limitans of the molecular layer. An additional 54 cells, similarly characterized as glia, were labeled with HRP. The results were the same; only protoplasmic astrocytes were labeled. The “staining quality” of the glia labeled with HRP was superior to that of cells injected with Lucifer Yellow; greater lengths of individual processes were revealed, and they could often be followed to blood vessels where they ended on the walls of vessels with expanded perivascular end‐feet. The observations indicate that the many previously reported studies on presumed glial cells in the cat cerebral cortex have characterized the behavior of protoplasmic astrocytes.Neurons were also marked during these experiments. The “staining” quality of the Lucifer Yellow filled neurons was excellent; dendritic spines, axons, and axon collaterals were clearly visible. These fine neuronal details were not as well revealed after HRP labeling. High resting membrane potentials (RMPs) were not a prerequisite for obtaining well‐marked neurons (mean RMP of Lucifer Yellow filled neurons was −33.6 mV; mean RMP of HRP filled neurons was 42.3 mV). In contrast, the mean RMPs of Lucifer Yellow and HRP marked glia was −68 Mv and −75 mV respectively, and the quality of “staining” appeared to be more clo

ISSN:0092-7317    

DOI:10.1002/cne.901860205

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

年代:1979

数据来源: WILEY

摘要:

AbstractA reconstruction was made of the intramedullary trajectory of 23 physiologically identified Ia afferents from cat hind limb muscles (medial gastrocnemius, soleus, plantaris, flexor digitorum‐hallucis longus, and hamstring). The afferents were stained by intra‐axonally injected HRP. The axons of these afferents were traced over distances of 5.8 mm to 15.7 mm rostrocaudally. In the dorsal funiculus fibers from all the muscles showed a similar course and similarly bifurcated into an ascending and a descending branch. The mean diameters of stem axons, ascending branches, and descending branches were 6.6 μm, 5.8 μm, and 3.0 μm, respectively. Within the analyzed lengths of the spinal cord five to eleven collaterals were given off from the two branches. The distances between adjacent collaterals of the ascending and descending branches averaged 1200 μm and 790 μm, respectively.The collaterals as a rule passed through the medial half of the dorsal horn before they entered the deeper parts of the gray matter. The terminal distribution areas common to all Ia collaterals were: (1) the medial half of the base of the dorsal horn, mainly lamina VI; (2) lamina VII; and (3) lamina IX. The numbers of terminals were largest in lamina IX and smallest in lamina VII. The density of terminals in lamina IX was highest in the homonymous motor cell column. The terminal distribution areas of adjacent collaterals showed no overlap in the sagittal plane. Terminal branches carried onebouton terminaland up to sixboutons en passagewith an average of 1.8 terminals per terminal branch. Apparent axosomatic and axodendritic contacts were seen on small‐sized and medium‐sized neurons in laminae V–VI, medium‐sized neurons in lamina VII, and large neurons in lamina IX. One motoneuron was contacted by an average of 3.3 terminals.In addition to the common features, Ia collaterals of various muscles of origin showed some differences in their trajectories in the ventral horn, and in their terminations in

ISSN:0092-7317    

DOI:10.1002/cne.901860206

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

年代:1979

数据来源: WILEY

摘要:

AbstractNucleus laminaris (NL) is a third‐order auditory nucleus in the avian brain stem which received spatially‐segregated binaural inputs from the second‐order magnocellular nuclei. The organization of dendritic structure in NL was examined in Golgi‐impregnated brains from hatchling chickens. Quantitative analyses of dendritic size and number were made from camera lucida drawings of 135 neurons sampled from throughout the nucleus.The most significant results of this study may be summarized as follows:(1)The preponderant neuron in n. laminaris may be characterized as having a cylindrical‐to‐ovoid cell body, about 20 μm in diameter. The neurons comprising NL were found to be nearly completely homogeneous in issuing their dendrites in a bipolar fashion: one group of dendrites is clustered on the dorsal surface of the cells, the other group on the ventral. The dendrites of NL are contained within the glia‐free neuropil surrounding the nucleus. From the rostromedial to the caudolateral poles of NL there is a gradient of increasing extension of the dendrites, increasing number of tertiary and higher‐order dendrites, and increasing distance from the somata of the occurrence of branching.(2)The total dendritic size (sum of the dorsal and ventral dendritic lengths of the cells) increases 3‐fold from the rostromedial to the caudolateral poles of NL. About 50% of the variance in dendritic size is accounted for by the position of the cells in NL, and the gradient of dendritic size increase has the same orientation across NL as the tonotopic gradient of decreasing characteristic frequency in NL.(3)From the rostromedial pole to the caudolateral pole of NL there is an 11‐fold decrease in the number of primary dendrites along a gradient coinciding with the length and frequency gradients. Sixty‐six percent of the variance in dendrite number is accounted for by position in the nucleus.(4)The correlation of dorsal and ventral dendritic size on a cell‐by‐cell basis is not high (r = 0.47), indicating a fair amount of variability on the single‐cell level. On the other hand, the average dorsal dendritic length within an isofrequency band in NL correlates very highly with the average ventral dendritic length. Thus, on an areal basis, the amount of dendritic surface area offered to the dorsal and ventral afferents is tightly regulated.(5)The dorsal and ventral dendrites have separate gradients of increasing length and number across NL. The dorsal gradients are skewed toward the rostrocaudal axis, while the ventral dendritic gradients are skewed mediolaterally.(6)There was no correlation between either dendritic size or number of primary dendrites and the size of the somata in NL, which remains relatively constant throughout the nucleus.Several hypotheses about the ontogenetic control of dendritic structure are examined in light of the above data. Of these, the hypotheses that the ontogeny of dendritic size and number is largely under afferent control receives a great de

ISSN:0092-7317    

DOI:10.1002/cne.901860207

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe development of the retinal projections to the roof of the midbrain was studied in Syrian hamsters after right superior colliculus (SC) lesions on the day of birth, using both autoradiographic and degeneration techniques. The dead tissue resulting from the heat lesion is not completely removed until the eighth day after birth. Normally the midline of the SC is defined by a pia‐lined fissure separating the left and right colliculi, but in the animals with early unilateral lesions, the pia at the midline is damaged. When it regrows, together with vascular and other meningeal tissues, it forms a flat tissue bridge across the midline as early as two days after the lesion.When the axons from the left eye reach the right SC, they encounter the dead tissue and separate into two bundles. One bundle courses over the surface of the dead tissue and one grows underneath it. It is not until the third to fourth day that axons in the dorsal bundle cross the midline, via the tissue bridge, to terminate anomalously in the medial wall of the left SC. When the quantity of such recrossing axons is small, they overlap extensively with the optic tract fibers from the other (right) eye which normally have innervated the entire SC by day 3. However, it appears that as the density of the recrossing axons increases they displace the axons originating in the other eye from the medial wall of the left SC. Thus, eventually fibers from both eyes terminate in the left SC, occupying separate territories with little, if any, overlap.Axons in the ventral bundle begin to innervate the deep layers of the right SC on day 2. These axons were never observed to recross the midline.These results indicate that mechanical guidance and axonal segregation dependent on relative densities are two processes that govern the development of retinotectal projections after early SC lesions in hamster

ISSN:0092-7317    

DOI:10.1002/cne.901860208

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

年代:1979

数据来源: WILEY

摘要:

AbstractA modified Golgi method (Vaisamruat and Hess, '53) was found to give satisfactory impregnation of cell bodies and dendrites, but not of dendritic spines and axons, in adult human material fixed by immersion in formalin. Examination of the motor columns in the spinal cord intumescences and of the third and twelfth cranial nerve nuclei revealed four neuron types, based on dendritic field size and dendritic branching pattern. Two of these were recognized as alpha‐motoneurons; one of them was seen only in the medial motor column of the spinal ventral horn, while the other was observed in the cranial motor nuclei as well as the spinal lateral motor column. Differences in somadendritic dimensions in this neuron type were thought to reflect motor unit size, and thus terminal axon field dimensions. Of the two types of gamma‐motoneurons recognized in the spinal cord and oculomotor nucleus, one was a miniature version of the commoner type of alpha‐motoneuron. On this basis, it is proposed that it may give rise to fusimotor axons with plate endings. The second type of gamma‐motoneuron does not resemble any of the other motoneuron types, and its axons may therefore be thought to terminate in trail

ISSN:0092-7317    

DOI:10.1002/cne.901860209

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe pattern of projection of the retina to the pretectal region and its retinotopic organization were investigated in the rat by autoradiographic and silver impregnation techniques for axonal pathways. The endings of retinal axons form three terminal fields in the pretectum in:1, olivary pretectal nucleus (PO), bilaterally;2, posterior pretectal nucleus (PP), bilaterally; and3, nucleus of the optic tract (NTO), contralaterally. The following retinotopic pattern was observed in rats surviving peripheral retinal lesions and injections of 3H‐proline in the same eye, when the positions occupied by terminal degeneration in Fink‐Heimer stained sections were matched with the corresponding areas deficient in radiolable in adjacent autoradiographic sections showing the surviving parts of the terminal fields. The nasal periphery of the retina maps along the adjoining edges of PO and PP, both of which extend obliquely, in a posterolateral direction, through the entire extent of the pretectum. Both nuclei map the line of representation of the anterior midline (in the temporal retina) along their opposite edges (anterolaterally, in PO; posteromedially, in PP). This mirror‐image symmetry is completed by the representation of the ventral peripheral retina separately in the rostral poles and the dorsal peripheral retina separately in the caudal poles of both nuclei. The map in NTO is vertically oriented, with the temporal retina, dorsally, the nasal retina, ventrally, the ventral retina, rostrally, and the dorsal retina caudally represented. The binocular area of the terminal field in PO is subdivided by a terminal‐free zone into two parts that may process separately events in the central and lateral visua

ISSN:0092-7317    

DOI:10.1002/cne.901860210

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

年代:1979

数据来源: WILEY

摘要:

AbstractCytophotometric analyses of Feulgen‐stained nuclei present in homogenates of vertical and subseophageal lobes of octopus brain have shown that the latter region contains larger nuclei with up to several times the amount of DNA present in vertical nuclei. No obvious relationship was found between DNA content and nuclear size. Except for a rather small minority, nuclei of the vertical lobe have a uniform size and the expected diploid amount of DNA. These parameters are not substantially dependent on body weight. In contrast, the DNA content of subesophageal nuclei increases progressively with body weight. The amount of DNA found in subesophageal nuclei does not seem to be a simple multiple of the diploid or haploid valu

ISSN:0092-7317    

DOI:10.1002/cne.901860211

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

年代:1979

数据来源: WILEY