摘要:

AbstractThe biogenic amine octopamine is synthesized from both tyrosine and tyramine in the lateral, median, and ventral eyesof Limulus. The auto‐radiographic studies presented here were designed to locate the sites of octopamine synthesis in the ventral and lateral eyes. We found that efferent fibers, which project to ventral and lateral eyes from the central nervous system, became intesely and selectively labeled during in vitro incubationswith3H‐tyramine. In the ventral eye, more than 95% of the efferent fibers were labeled. Results of biochemical analyses suggested that most of the radioactive substance within these efferent fibers was newly synthesized octopamine.The selective labeline of efferent fibers during incubation with3H‐tyramine was used as anatomical tool to study me number ana distribution of efferent fibers within the ventral eye. Light microscopic (LM) reconstructions of the distribution of label in serial longitudinal sections through ventral optic nerves together with electron microscopic (EM) au‐toradiographic analyses revealed between 70 and 200 efferent axons. The results of these studies and of reconstructions of efferent innervation to photoreceptor somata suggest that each ventral photoreceptor cell or each small cluster of cells is innervated by a separate efferent fiber. Both LM reconstructions and EM analyses showed that efferent fibers ramify extensively and specifically in and near the internal rhabdom of ventral photo‐receptor cells.In EM autoradiographs of lateral eyes incubated with3H‐tyramine, the silver grains that were located over ommatidia were concentrated exclusively over efferent fibers. All of these efferent fibers, which lay near rhab‐doms and in partitions between retinular cells, were labeled.The results of our present studies support our hypothesis that octopamine is a neurotransmitter inLimulusretinal efferent fibers. This amine may modulate the biochemistry and physiology of ventral photoreceptor cells and may mediate many of the known effects of circadian efferent innervation to th

ISSN:0092-7317    

DOI:10.1002/cne.902190402

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractCorpus callosum connections of parietal and motor cortex were studied in New World owl monkeys(Aotus trivirgatus)and Old World macaque monkeys(Macaca fascicnlaris)after multiple injections of3H‐proline and horseradish peroxidase, HRP, into one cerebral hemisphere, and extensive microelectrode mapping of architectonic Areas 3b, 1, and 2 of the other hemisphere. Results were obtained both from parasagittal brain sections cut orthogonal to the brain surface and from sections from flattened brains cut parallel to the brain surface. Cortical fields varied in density of callosal connections, and the density of connections varied according to body part within sensory representations. Thus, Area 3b had few, Area 1 had more, and Area 2 had relatively dense callosal connections. Within each of these fields, connections were much less dense for the representations of the glabrous hand and foot and much more dense for the representations of the face and trunk. For the representation of the hand, retrogradely labeled cells were extremely sparse in Area 3b, moderately sparse in Area 1, and moderate in Area 2. There were less dense callosal connections in the hand representations of Areas 3b, 1, and 2 in macaque as compared to owl monkeys. Label in posterior parietal cortex was uneven with zones of extremely dense connections. A large region of very dense callosal connections was noted in motor cortex just medial to the probable location of the hand representation. In all regions, callosally projecting cells appeared to be more broadly distributed than callosal terminations. In no region was the discontinuous arrangement of callosal connections obviously organized into an extensive pattern of mediolateral or rostrocaudal bands or strip

ISSN:0092-7317    

DOI:10.1002/cne.902190403

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractRhodamine‐B‐isothiocyanate (RITC) is shown to be a convenient and advantageous fluorescence tracer both for anterograde staining of retinal ganglion cell axons on the tectum and for retrograde staining of ganglion cell bodies in the retina of chick embryos. After intravitreal injection the dye is taken up by ganglion cells of the retina from the extracellular space and is transported anterogradely at about 10 mm/day up to the axonal growth cones on the tectum. RITC can be taken up by growing axons on the tectum and it is transported retrogradely at about 5 mm/day to the cell bodies in the retina. Local staining can be achieved if RITC is applied in its crystalline form. RITC is nontoxic for the cells and their axons, is resistant to histologi‐cal fixation procedures, and allows quick observation in vivo and on dissected stained tissue.Local application of RITC to distinct retinal areas allows examination of the position of the corresponding stained fibers along the retinotectal pathway. Fibers which arise from the central temporal retina occupy deeper layers, whereas fibers from the peripheral temporal retina occupy more superficial layers in the optic tract and in thestratum opticumon the anterior tectum.The growth cones of early retinal fibers growing directly on the tectal surface show a different morphology to later growth cones growing on top of thestratum opticumon the t

ISSN:0092-7317    

DOI:10.1002/cne.902190404

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe histochemical and morphological maturation of the mediodorsal nucleus (MD) and its connections were compared in human and rhesus monkey using acetylthiocholine iodide and Nissl methods. Histochemical analysis in fetuses, neonates, and adults of both primate species revealed that MD passes through three major stages of cholinesterase (ChE) reactivity. In Stage I (up to about 16 fetal weeks in man; 9 fetal weeks in monkey), ChE staining gradually increases in the MD nucleus and is intense in axons directed toward the frontal lobe through the internal and external capsules. In Stage II (about 16‐28 fetal weeks in man; about 9‐14 weeks in monkey), ChE staining in MD reaches peak intensity so that reaction product in the neurons and neuropil blackens the entire nucleus in both species. In favorable planes of section, ChE‐positive fibers appear to connect MD and the basal forebrain both of which stain intensely. ChE‐positive fibers can also be traced from the lateral margins of MD to the subplate zone beneath the developing frontal cortical plate where they continue to accumulate before later invading the cortex with heaviest concentration in presumptive layers 3 and 5. In Stage III (after 28 weeks of gestation to 6 postnatal months in man; from about 14 fetal weeks until 2 postnatal months in monkey), except for scattered positive cells, ChE staining gradually disappears in MD and the formerly dense laminar pattern in the cortex begins to lighten. The dramatic but transient increase in ChE staining in MD during fetal development as well as the sequentially related changes in its projections indicate that this early appearing enzyme may play a role in the development of the frontal lobe by influencing the differentiation of thalamoprefrontal conn

ISSN:0092-7317    

DOI:10.1002/cne.902190405

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractTerminals of olfactory bulb afferent (OB) and association (ASSN) fiberswithin the piriform cortex were characterized ultrastructurally. Identification was by electron microscopic (EM) autoradiography following injections of tritiated amino acids into the olfactory bulb and anterior piriform cortex. The results show that terminals of both fiber systems contain round vesicles and make asymmetrical synaptic contacts predominantly onto dendriticspines. Profiles with pleomorphic vesicles do not appear to be labeled from either site. Since there is strong evidence that both fiber systems generate excitatory postsynaptic potentials (EPSPs) in pyramidal cells, these results provide additional examples in the mammalian CNS of terminals with round vesicles and asymmetrical contacts that mediate an excitatory effect.Percentage density analysis and quantitative study of a large number of heavily labeled terminals revealed that while OB and ASSN terminals are similar in terms of vesicle shape and contact type, they differ in many morphological details including pre‐and postsynaptic profile size, the packing density and distribution of synaptic vesicles, synaptic contact shape, and the presence of overlying neuroglial lamellae. However, large variations in appearance of different terminals of the same type are also present so that a small percentage of OB and ASSN terminals are indistinguishable morphologically in the absence of label.An important finding of the quantitative analysis is that spines contacted by lateral olfactory tract (LOT) terminals appear to be of two types based on a bimodal distribution in size and differences in morphology, while spines contacted by ASSN terminals appear to be of a single type. Comparison of these data with results from Golgi analysis indicates that ASSN terminals predominantly contact pyramidal cell spines while OB terminals contact both pyramidal and semilunar cell spines.Quantitative analysis of synaptic vesicles revealed that histograms of vesicle size for OB and ASSN terminals are virtually identical in shape, but peaks are slightly displaced (ASSN vesicles are 5% larger; significant withP<.002).An analysis of the laminar distribution of OB and ASSN synaptic terminals revealed that while moat OB terminals are segregated in layer Ia and most ASSN terminals in layer Ib, occasional OB terminals are observed up to approximately 50 μm deep to the Ia‐Ib boundary and occasional ASSN terminals up to approximately 50 μm superficial to this bou

ISSN:0092-7317    

DOI:10.1002/cne.902190406

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe anterior sensory ultrastructure of the C.elegansdauer larva was examined in several specimens and compared with that of the second‐stage (L2) larva, which immediately precedes the dauer stage. In some instances comparisons were made with L3, postdauer L4, and adult stages. Whereas sensory structures in different nondauer stages closely resemble each other, the dauer larva differs in certain chemosensory and mechanosensory organs, including the inner labial sensilla, amphids, and deirids. The relative positions of the afferent tips of the two types of inner labial neurons are reversed in the dauer stage compared to the L2 and postdauer L4 stages. Inner labial neuron 1 rather than neuron 2 is more anterior in each of the six sensilla, and neuron 1 has an enlarged tip. The neuron 2 cilia are only one‐third as long as those in the L2. Amphidial neurons c., d, g, and i and the amphidial sheath cell are altered in shape or position in the dauer stage. Neurons g and i are displaced posteriorly within the dauer amphidial channel. Neuron d has significantly more microvillar projections than do the d cells in L2, L3, or postdauer L4 larvae. Winglike processes of dauer neuron cform a 200°–240° are in transverse section, including extensive overlap of the two cells. The arc in an L2 seldom spans more than 100°, and overlap does not occur. While L2 larvae possess two separate bilateral amphidial sheath cells, the left and right sheath cells are often continuous in the dauer larva. Deirid sensory dendrites exhibit a dauer‐specific structure and orientation. The tip of each neuron is attached to the body wall cuticle by a substructure not observed in L2 or postdauer L4 stages, and the neurons are oriented parallel to the longitudinal axis of the dauer larva. The deirid sensory terminals are oriented perpendicular to the cuticle in other stages. Reversible alterations in neural structure are discussed in the context of dauer‐speci

ISSN:0092-7317    

DOI:10.1002/cne.902190407

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902190401

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY