摘要:

AbstractDeveloping amacrine and ganglion cells have been graphically reconstructed from a series of 567 consecutive thin sections of the E17 mouse retina on the first day when an obvious inner plexiform layer (IPL) is present and 2 days later than for our previous study of amacrine cell formation at E15 (Hinds and Hinds ('78). At E17 amacrine cells of the neuroblastic layer (normally placed amacrine cells), unlike those at E15, appear to develop directly from ventricular cells; intermediate elements are bipolar‐shaped cells with terminal arborization in the IPL. On the other hand, the development of displaced amacrine cells and some normally placed amacrine cells at E17 appears to closely resembles that described for all amacrine cells at E15: derivation from “ganglion cells” by loss of the axon and transformation of the cell. Three lines of evidence support this conclusion. (1) Cells have been found that resemble ganglion cells except that they have only an apparent axon remnant and have somata restricted to the IPL and the immediately adjacent portion of the ganglion cell layer (GCL); amacrine cells transitional between these cells and the smaller and darker, normally placed amacrine cells also occur in the IPL. (2) Axons of two ganglion cells have been found which appeared to be in the process of breaking up and degenerating. (3) The fraction of anaxonic cells with somata in the GCL (two out of 79, or 3%) or in the GCL plus IPL (ten out of 88 or 11%) is too small to account easily for the large fraction (probably at least 45%) of displaced amacrine cells found in the adult, even with conservative assumptions (P<0.05). A mathematical model suggests that approximately 40% of the ganglion cells present at E17 will lose their axon, and of these around half will migrate to the neuroblastic layer, while the other half will become displaced amacrine cells. The results suggest a natural explanation for the recent finding that wide field amacrine cells are found with somata on both sides of the IPL, while narrow field amacrine cells are never displaced: the former may be derived from ganglion cells by loss of the axon, while the latter may be formed directly from ventricular

ISSN:0092-7317    

DOI:10.1002/cne.902130102

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractRestricted injections either of horseradish peroxidase conjugated with wheat germ agglutinin, or of unconjugated horseradish peroxidase were made into hooded rats in order to distinguish subcortical sources of afferents to dorsal lateral geniculate nucleus from those to the adjacent visually responsive thalamic reticular nucleus, which modulates geniculate activity. Five “nonvisual” brainstem regions project to the dorsal lateral geniculate nucleus: mesencephalic reticular formation, dorsal raphe nucleus, periaqueductal gray matter, dorsal tegmental nucleus, and locus coeruleus. Projections are generally bilateral, but ipsilateral projections dominate. Of these regions, three also project ipsilaterally to the thalamic reticular nucleus: mesencephalic reticular formation, periaqueductal gray matter, and dorsal tegmental nucleus.Similar discrete injections of horseradish peroxidase into ventral lateral geniculate nucleus allowed a comparison of afferents to dorsal and ventral lateral geniculate nuclei. In addition to the five nonvisual brainstem regions which project to the dorsal division, the ventral lateral geniculate nucleus receives afferents from the perirubral reticular formation and the central gray matter at the thalamic level. The dorsal and ventral lateral geniculate nuclei receive substantially different afferents from subcortical visual centres. The dorsal division receives projections from superior colliculus, pretectum, and parabigeminal nucleus whereas the ventral division receives afferents from superior colliculus, additional pretectal nuclei, lateral terminal nucleus of the accessory optic system, and the contralateral ventral lateral geniculate nucl

ISSN:0092-7317    

DOI:10.1002/cne.902130103

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractRates of cerebral glucose utilization were measured by means of the autoradiographic 2‐deoxy‐D‐(l‐14C)glucose technique in normal rats under light halothane‐anesthesia. Three types of region‐specific metabolic alterations were elicited by inhalation of 0.5% halothane. The most striking effect observed was a significant increase of glucose consumption within the locus coeruleus, substantia nigra compacta and reticulata, interpeduncular nucleus, hippocampus, and fornix of the anesthetized animals in comparison to the corresponding brain areas of the conscious control rats. Halothane‐anesthesia was also associated with significant metabolic depression in 21 (out of the 74 examined) discrete regions of the rat brain, distributed within the pons, cerebellum, diencephalon, and cortex, and was more prevalent in thalamus and neocortex. However, halothane failed to alter consistently the rates of glucose utilization in the rest of the rat brain areas investigated. The present findings suggest that halothane specifically alters the regional cerebral glucose utilization, with some limbic system components and the basal ganglia displaying increased metabolism, in contrast to the sensori‐motor system which demonstrates significantly decreased met

ISSN:0092-7317    

DOI:10.1002/cne.902130104

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe energy metabolism of 74 anatomically discrete central nervous structures was investigated by means of the autoradiographic 2‐deoxy‐D‐(1‐14C) glucose method (14C‐DG) in conscious awake, as well as in halothane anesthetized rats, following unilateral substantia nigra (SN) electrical stimulation.All the basal ganglia structures displayed bilateral metabolic activation in conscious animals, with only the contralateral subthalamic nucleus being unaffected. In anesthetized rats only the SN reticulata, globus pallidus, and subthalamic nucleus were affected ipsilaterally whereas anesthesia masked the effects of SN stimulation in SN compacta and striatum ipsilaterally, as well as within‐all the above structures contralaterally. The entopeduncular nucleus was bilaterally activated no matter the state of consciousness. Unilateral SN stimulation also increased glucose utilization within several thalamic regions (ventromedial, ventrolateral, ventroanterior, intralaminar, ventrobasal, and mediodorsal nuclei), the habenular complex, a few mesencephalic, brainstem (locus coeruleus and dorsal raphe) and cerebellar structures, mostly bilaterally and independently of the state of consciousness.Some of the factors suggested to be responsible for the masking effects of halothane‐anesthesia on the metabolic activations elicited by unilateral SN stimulations are the following: (1) absence of movements in anesthetized rats, (2) halothane‐induced depression of polysynaptic pathways mostly mediated through the thalamus, and (3) the stimulatory effect of halothane‐anesthesia itself on metabolic activity in bot

ISSN:0092-7317    

DOI:10.1002/cne.902130105

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractCrayfish abdominal stretch receptor organs are innervated by inhibitory (GABA) and excitatory (glutamate) synapses. Previous studies with aldehyde fixation showed that synaptic vesicles in the inhibitory synapse are flat and small, whereas those in the excitatory synapse are rounder and larger. We have reexamined these inhibitory and excitatory synapses by using direct rapid‐freezing and freeze‐substitution in order to preserve synaptic structure closer to its living state. Fine details of synaptic structure appear to be better preserved by this method. Synaptic vesicles in inhibitory as well as excitatory synapses are round, so the conventional flattened shape of vesicles in the inhibitory synapse must depend on some aspect of aldehyde processing. However, the average size of vesicles in the inhibitory synapse is significantly smaller than that of vesicles in the excitatory synapse, so synaptic vesicle size is regarded as having functional significa

ISSN:0092-7317    

DOI:10.1002/cne.902130106

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe retinal ganglion cells projecting to the superior colliculus (SC) and dorsal lateral geniculate nucleus (LGNd) of the North American opossum(Didelphis virginiana)were studied by using the horseradish peroxidase (HRP). The four ganglion cell size groups recognized previously were found to project in systenatically different ways. After injections of HRP into the superior colliculus, labeled cells were seen in nasal retina contralateral to the injection and in temporal retina both ipsilateral anc contralateral to the injection. In contralateral nasal retina cells of all size classes were labeled, while in contralateeral temporal retina small (8–14 μm diameter), small‐medium small‐medium (15–19 μm diameter), and large (>24 μm diameter)cells were labeled but few, if any, large‐medium (20–24 μm diameter)cells were labeled. In ipsilateral temporal retina, soma size groups labeled included small‐medium, large‐medium, and large cells, but very few small cells. A nasal–temporal difference in the soma size of ganglion cells projecting to the SC was found: Labeled cells in temporal retina were 1.7–4.2 μm larger than their counterpats in nasal retina.Following injection of HRP into the LGNd, label was seen in contralateral nasal and ipsilateral temporal retina witn no label seen in contralateral temporal retina. The labeled cells were small‐medium, large‐medium, and large. No small ganglion cells were labeled from the LGNd. A small nasal‐temporal soma size difference in retinal ganglion cells projecting to the LGNd was seen: labeled cells in temporal retina were 1.0–2.1 μm larger than in nasal. It is concluded that all four ganglion cell size groups in the opossum project to the SC, but that only the

ISSN:0092-7317    

DOI:10.1002/cne.902130107

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractInjection of horseradish peroxidase solution (HRP) into the tracheosyringeal musculature and tongue of the domestic chick labeled their motorneuron somata inthe medulla. Those of tracheosyringeal motor neurons occupied the caudal portions of the nucleus nervi hypoglossi (n. XII), whereas those for motor neurons supplying the tongue occupied the rostral part. The rostrocaudal representations of tracheolateralis, sternotrachealis, and ypsilotrachealis muscles were roughly mapped by the rostrocaudal distribution of labeled somata inn. XII. Except for sparse labeling found in the caudal part of the dorsal vagal nucleus of a few animals, no labeled cells were found outside ofn XII. Most tracheosyringeal injections labeled contralateraln. XII, but section of the contralteral tracheosyringeal nerve high on the neck prior to HRP injection abolished this labeling.

ISSN:0092-7317    

DOI:10.1002/cne.902130108

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe pathways of selected optic axons were traced in representative urodele, anuran, teleost, reptile, and avian species by filling the fibers with HRP or by tracing, at the light and electron microscopic (EM) level, the degeneration caused by focal or optic nerve lesions.In all species it was shown that fibers retain retinotopic neighborhood relationships throughout their transit of the optic nerve. Additionally, inanurans, it was found that a subset of large diameter, myelinated fibers take up a random arrangement in the nerve. It is argued that retinotopic fiber organisation is a reflection fo contact guidance of axons during fiber outgrowth in the embryo and that this organisation could account for the arrival of fibers in orderly arrays at central nuclei during normal embryonic development.

ISSN:0092-7317    

DOI:10.1002/cne.902130109

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902130101

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY