bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of the rat superior cervical ganglion: initial stages of synapse formation
Authors: Rubin E
Published: March 2018

Synapse formation in the rat superior cervical ganglion has been investigated electrophysiologically and at the ultrastructural level. Preganglionic axons first enter the superior cervical ganglion between days 12 and 13 of gestation (E12 to E13), and on E13 a postganglionic response can be evoked by preganglionic stimulation. The susceptibility of this response to fatigue and to blocking agents indicates that it is mediated by cholinergic synapses. On E14, the overall strength of ganglionic innervation arising from different spinal segments already varies in a pattern resembling that found in maturity. However, the distribution of synapses on individual target cells gradually changes in the prenatal period. Transmission begins prior to the elaboration of ganglion cell dendrites; therefore, the first contacts to form are largely axosomatic. As dendrites appear (beginning on E14), ultrastructural evidence shows that synaptogenesis becomes focused upon these processes. The significance of these findings is discussed in relation to possible mechanisms for the formation of appropriate synaptic connections.
Developmental arborization of sensory neurons in the leech Haementeria ghilianii. I. Origin of natural variations in the branching pattern
Authors: Kramer AP , Goldman JR , Stent GS
Published: March 2018

The overall sizes, contours, and positions of the receptive fields maintained by different individual cells of the T, P, and N types of mechanosensory neurons in the segmental skin of the leech Haementeria ghilianii are not subject to wide variation. However, the locations and contours of the boundaries which separate the various compartments of the sensory field, namely, the major and minor fields, as well as their component subfields, do vary significantly. These variations are reflected in differences in the detailed pattern of arborization of the mechanosensory axon branches that innervate different parts of the receptive field. The appreciable variation in the kinetics of embryonic outgrowth of sensory axon branches, in conjunction with a mechanism of neuronal self-avoidance, is a probable source of this variability in adult receptive field structure. Thus, establishment of these sensory field components would seem to entail a first-come-first-served territorial exclusion between different axon branches extended by the same neuron.
Developmental arborization of sensory neurons in the leech Haementeria ghilianii. II. Experimentally induced variations in the branching pattern
Authors: Kramer AP , Stent GS
Published: March 2018

The sharp, nonoverlapping boundaries of the major and minor receptive fields of the mechanosensory neuron Pv of the leech, as well as the mutual exclusion during embryonic development of growing axon branches belonging to the same Pv cell, have suggested that peripheral axon arborization of these neurons is constrained by a process of neuronal self-avoidance. To provide a direct experimental test of this proposal, the development of the major and minor receptive fields of the Pv neuron was studied in embryos of the leech, Haementeria ghilianii, after surgically preventing or delaying the outgrowth of the axon branches which establish only a minor or only the major field of that neuron. As predicted by the proposal of self-avoidance, interference with the outgrowth of a minor field axon branch resulted in the spread of the major field axon branch into what is normally minor field territory. Conversely, similar interference with the establishment of the major field resulted in the spread of the minor field axon branches into what is normally major field territory. The findings presented here indicate that neuronal self-avoidance does play a significant role in the development of mechanosensory receptive field structure but suggest also that the detailed pattern of arborization of the sensory axons is guided by prespecified pathways of only ephemeral availability or recognizability.
Choline acetyltransferase and acetylcholine levels in Drosophila melanogaster: a study using two temperature-sensitive mutants
Authors: Salvaterra PM , McCaman RE
Published: March 2018

Choline acetyltransferase (ChAT, acetyl-CoA-choline-O- acetyltransferase, EC 2.3.1.6) activity was measured in homogenates prepared from wild type (Canton S) and two temperature-sensitive presumed ChAT structural gene mutants (Chats1 and Chats2; originally described by Greenspan, R. (1980) J. Comp. Physiol. 137: 83–92) of Drosophila melanogaster. Wild type flies grown at 32 degrees C for 12 or 24 hr showed increased ChAT activity, whereas Chats1 and Chats2 flies showed a progressive decrease in enzyme activity at 32 degrees C (restrictive temperature) when compared to flies reared at 18 degrees C (permissive temperature). Acetylcholine (ACh) and choline levels were determined in formic acid-acetone extracts of individual fly heads, and the ACh levels showed the same variation with time at 32 degrees C as did the ChAT activity. In contrast, choline levels did not vary in any regular pattern. Acetylcholinesterase (EC 3.1.1.7) activity did not vary during heat treatment (except for Chatts2 flies held at 32 degrees C for 24 hr, where a decrease was observed) indicating that this treatment may be specific for ChAT. We conclude that ChAT activity is strongly correlated with ACh levels in Drosophila heads and may thus have an important regulatory role in determining the levels of ACh available for physiological function. We also report on the preliminary characterization of ChAT in both Chats mutants and compare the biochemical properties to those of wild type enzyme. Isoelectric focusing profiles of ChAT from both Chats mutants revealed enzymes with altered patterns compared to wild type, indicating that the mutations are most probably in the structural gene.
Development of the ipsilateral retinothalamic projection in the frog Xenopus laevis. II. Ingrowth of optic nerve fibers and production of ipsilaterally projecting retinal ganglion cells
Authors: Hoskins SG , Grobstein P
Published: March 2018

We have studied the development of the ipsilateral retinothalamic projection in the frog Xenopus laevis by analyzing patterns of histochemical reaction product resulting from anterograde transport of horseradish peroxidase (HRP) applied to cut optic nerves in animals of various ages. We have also determined the stages during which ipsilaterally projecting ganglion cells are born using a combination of [3H] thymidine autoradiography and retrograde marking of ganglion cells following injection of HRP into the thalamus. Projections to ipsilateral thalamic terminal zones were first detectable beginning at about larval stage 54. There was a clear asynchrony in innervation, with projections to some terminal zones appearing before projections to others; projections to all terminal zones were present by late metamorphic stages. Within individual terminal zones there were progressive increases in the density of the projections as well as changes in their distribution. By these criteria, development of the ipsilateral projection was not complete at the end of metamorphosis but continued for some months thereafter. Our birth dating studies show that ipsilaterally projecting cells are produced relatively late in development and that, like the development of the projection, the production of ipsilaterally projecting ganglion cells continues postmetamorphically. The vast majority of ipsilaterally projecting cells are born over a period beginning at stage 54/55, when the projection first appears. This stage is significant, since it is at approximately this time that thyroxine-dependent metamorphic events begin. In the following paper (Hoskins, S.G., and P. Grobstein (1985) J. Neurosci. 5: 930–940) we report studies on the involvement of thyroxine in the development of the ipsilateral retinothalamic projection.
Recovery of acetylcholinesterase at intact neuromuscular junctions after in vivo inactivation with di-isopropylfluorophosphate
Authors: Kasprzak H , Salpeter MM
Published: March 2018

Recovery of acetylcholinesterase (AChE) at endplates of mouse sternomastoid muscle was studied after inactivation with di- isopropylfluorophosphate in vivo. A short incubation with alpha- bungarotoxin was used to prevent muscle necrosis which usually occurs after esterase inactivation. Under these conditions there was no delay in AChE recovery, unlike what we had previously seen in necrotic muscle. However, even in non-necrotic muscle, the overall recovery of AChE at the postjunctional membrane was very slow, with a half-life of about 20 days. The fact that, at adult neuromuscular junctions, both esterases and receptors turn over about 10 times slower than they do in embryonic muscle suggests a similar regulation of these two molecules by the nerve.
The acquisition and expression of a peptidergic phenotype in the grasshopper embryo
Authors: Keshishian H , O'Shea M
Published: March 2018

We have examined the developmental acquisition and regional expression of the neurotransmitter proctolin in neurons of the grasshopper embryo, using both assay and immunocytochemistry. There are four stages in the acquisition and accumulation of proctolin in the embryo. The first stage (50 to 60% embryogenesis) consists of a slow accumulation of proctolin prior to the onset of central nervous system (CNS) staining. During the second stage proctolin levels increase at a 5-fold faster rate. During this stage, which ends at 70% of development, a stable pattern of staining is established in the ganglia. The third stage (70 to 95% embryogenesis) consists of a rapid accumulation of peripheral proctolin levels that occurs principally in motor endings, without a significant increase in the CNS. This stage also correlates with the onset of peripheral staining. During the fourth stage, over the final 5% of embryogenesis, there is a 20% loss of proctolin in the periphery. We have attempted to relate these changes to developmental events occurring in identified clusters of neurons, by examining the development of neuromuscular connections made by embryonic terminal ganglion motoneurons to the intrinsic muscles of the hindgut. Of the 30 hindgut motoneurons, only six anterior medial (AM) efferents are proctolin immunoreactive in the embryo. Their axons establish a dense proctolin-staining arborization over the intrinsic muscles. The peptide accumulates in the endings as staining appears in the terminal ganglion. Hindgut proctolin levels increase substantially and then decline in a manner similar to that found for total peripheral proctolin. By the end of embryogenesis the endings will release proctolin, in a calcium-dependent manner, when depolarized. The six proctolin-staining AM neurons constitute a simple model system for studying the determination and expression of neurotransmitters in identified embryonic cells.
Membrane assembly in retinal photoreceptors. II. Immunocytochemical analysis of freeze-fractured rod photoreceptor membranes using anti- opsin antibodies
Authors: Defoe DM , Besharse JC
Published: March 2018

We have used a cytochemical technique for labeling freeze-fractured tissues (Pinto da Silva, P., C. Parkison, and N. Dwyer (1981) Proc. Natl. Acad. Sci. U.S.A. 78: 343–347) to examine the distribution of immunoreactive opsin in rod photoreceptor membranes. Aldehyde-fixed retinas of African clawed frogs (Xenopus laevis) embedded in a cross- linked protein matrix were frozen and fractured at -196 degrees C, then thawed and labeled with biotinylated sheep anti-cow opsin IgG followed by avidin-ferritin. In thin sections of plastic-embedded retinas, rod outer segment (ROS) disc membranes exposed by fracturing bound specific antibody intensely and relatively uniformly. However, they differed from membranes of the inner segment as well as those of erythrocytes in that protoplasmic face leaflets did not assume an interrupted bilayer appearance and disc exoplasmic face leaflets were apparently lost during thawing. The disposition of opsin immunoreactivity in the cell membrane was highly asymmetric. Although ROS plasma membranes from which discs are elaborated labeled heavily with anti-opsin after cleavage, fractures passing along inner segment plasma membranes bound very little antibody. In cross-fractures exposing inner segment cytoplasm, we found specific labeling of Golgi complex elements, as well as both perimitochondrial and periciliary vesicles. The latter are presumed to be the vehicle shuttling newly synthesized membrane to the ROS for disc assembly. These results suggest that opsin-containing membrane is sorted out within the cell, being transported from synthetic sites to the immediate periciliary zone where localized insertion into the cell membrane takes place. Furthermore, the close correspondence of the present immunocytochemical analysis with the distribution of opsin deduced from prior quantitative freeze-fracture analysis (Besharse, J. C., and K. H. Pfenninger (1980) J. Cell Biol. 87: 451–463) offers the possibility that fracture-label may be generally useful for study of patterned membrane topography in neuronal cells.
Membrane assembly in retinal photoreceptors. III. Distinct membrane domains of the connecting cilium of developing rods
Authors: Besharse JC , Forestner DM , Defoe DM
Published: March 2018

To investigate the putative role of the photoreceptor connecting cilium in the delivery of opsin to forming discs and in the maintenance of membrane domains (Besharse, J. C., and K. H. Pfenninger (1980) J. Cell Biol. 87: 451–463), we have studied developing photoreceptors of neonatal rats during the period of initial disc formation using conventional freeze-fracture, immunocytochemistry, and lectin cytochemistry. Specific anti-opsin-binding sites were localized in the distal cilium, the developing outer segment plasma membrane, and at focal sites on the inner segment plasma membrane at all developmental stages examined, including the period prior to the onset of disc morphogenesis. The proximal ciliary shaft generally lacked anti-opsin- binding sites or exhibited them in extremely low density. The distribution of anti-opsin-binding sites corresponded in a general way to the distribution of large intramembranous particles (IMPs) in freeze- fracture replicas like those seen in the rod outer segment (ROS). The proximal zone corresponded in freeze-fracture images to a zone of consecutive horizontal rows of intramembrane particles (ciliary necklaces) and axoneme-membrane cross-linkers. Although protoplasmic face leaflet IMPs similar to those of the distal cilium and outer segment were less abundant in the inner segment and proximal cilium than in the distal cilium and ROS, they were detected in these zones at low frequency. Cytochemistry with concanavalin A and wheatgerm agglutinin revealed the presence of a well developed glycocalyx in the proximal zone. Although opsin binds both lectins, the results suggest heterogeneity among the glycoconjugates of the three membrane domains. Our data define distinct membrane domains of the developing photoreceptor cilium that have important implications for the mechanisms for delivering and sequestering opsin in the outer segment. They also establish that the mechanism of opsin delivery to the distal zone occurs well in advance of the period of disc morphogenesis.
Studies of the earliest generated cells of the cat's visual cortex: cogeneration of subplate and marginal zones
Authors: Luskin MB , Shatz CJ
Published: March 2018

The earliest generated cells of the cat's telencephalon that may play a role in the formation of the primary visual cortex are the subject of this study. Using [3H]thymidine autoradiography, we have found that these cells are generated between embryonic day 24 (E24) and E30 (gestation is 65 days) and that they are present in very low numbers in the white matter of the adult brain. These cells are rarely labeled by injections made after E30, when the cells destined for the cortical layers are generated. Examination of the labeling pattern in the fetal brain 10 days or more after administration of [3H]thymidine between E24 and E30 revealed a bistratified distribution of these early generated cells. Labeled cells were found in large numbers in two embryonic zones flanking the developing cortical plate: above in the marginal zone and below in the subplate. (Some if not all of the marginal zone cells constitute the population of Cajal-Retzius cells of the cat's telencephalon.). These experiments indicate that cells of the subplate and marginal zones are cogenerated in time during the days just preceding the genesis of the cortical plate. We also examined the distribution of the early generated cells shortly after their genesis-- on E30, a time when cells of the cortical plate are just being generated at the ventricular zone. In this case, the labeling pattern at the occipital pole was not bistratified. Rather, labeled cells were situated within a single zone extending from the pial surface inward to the border of the ventricular zone. This finding indicates that the cells of the subplate and marginal zones are generated as a contiguous population that is subsequently split apart by the insertion of cells forming the cortical plate. A comparison between the number of early generated cells found in fetal and newborn brains with that found in adult brains suggests that these cells are generated initially in substantial numbers but then largely disappear during early postnatal life, since injections of [3H]thymidine between E24 and E30 yielded large numbers of labeled cells in the white matter and layer 1 at birth, but very few at 2 months postnatal. This significant loss contrasted with the results from injections made just a few days later (E33) that resulted in large numbers of labeled cells in cortical layer 6 not only at birth but also in adulthood.
Attentional influences on noxious and innocuous cutaneous heat detection in humans and monkeys
Authors: Bushnell MC , Duncan GH , Dubner R , Jones RL , Maixner W
Published: March 2018

This study examines whether selective attention can influence sensory- discriminative aspects of nociception in humans and monkeys trained to detect innocuous and noxious thermal stimuli. Human subjects had two contact thermodes positioned bilaterally above the upper lip. Upon trial initiation both thermodes heated to either 39 degrees C, an innocuous warm temperature, or 45 degrees C, a slightly noxious temperature. After 4 to 9 sec, the temperature of one thermode increased an additional step of less than 1 degree C. Subjects released a button when they detected this second temperature increase (T2). Three types of trials were presented in order to assess the effects of spatially selective attention on thermal detection. On 40% of the trials a light correctly signaled the location of the thermode on which T2 would occur. On 10% of trials a light incorrectly signaled the location of T2. No signal was presented on the remaining trials. From the 45 degrees C base line, detection latencies were shortest in the correct signal condition, longest in the incorrect signal condition, and intermediate in the unsignaled condition. The percent of undetected T2s was greatest in the incorrect signal condition and least in the correct signal condition. From the 39 degree C base line, the detection latency in the incorrect signal condition was greater than in the unsignaled condition, but the latter latency was not different from the correct signal latency. In addition, the percent of undetected T2s was the same on all three types of trials.
Development of chemosensitivity of an identified insect interneurone
Authors: Blagburn JM , Beadle DJ , Sattelle DB
Published: March 2018

Characteristic features of cockroach embryos (Periplaneta americana) are determined for different stages in development. Morphological changes in giant interneurone 2 (GI 2) in the terminal abdominal ganglion during embryogenesis are described based on cobalt injections. A sequential proliferation of branches preceded by filopodial extension is observed between 45 and 80% embryogenesis, by which time the characteristic arborization of the first instar cell is established. The cholinergic agonist carbamylcholine was ionophoretically applied to the cell body and dendritic region of GI 2 at various stages in development, and the responses were recorded intracellularly. Chemosensitivity of GI 2 appears at 40 to 45% embryogenesis, to a similar degree in both cell body and dendrites. The sensitivity of these areas subsequently diverges, and after the 60 to 65% stage, the dendrites are approximately 1000 times more sensitive than the cell body. At 80 to 85% embryogenesis, there is a temporary peak in dendritic sensitivity, and cell body sensitivity increases during postembryonic development. The changes in sensitivity take place before synaptogenesis, and the decline in dendritic sensitivity after the 80% stage may be related to synaptic maturation.
Selective reinnervation of intercostal muscles transplanted from different segmental levels to a common site
Authors: Wigston DJ , Sanes JR
Published: March 2018

We transplanted external intercostal muscles from one of several thoracic (T) levels to the neck of adult rats. The cervical sympathetic trunk, which innervates the superior cervical ganglion, was cut, and its proximal end was apposed to the muscle. Preganglionic axons in the trunk reinnervated muscle fibers in the transplants. We determined the segmental origin of synaptic inputs to transplanted muscles by recording intracellularly from muscle fibers while stimulating individual ventral roots which supply axons to the trunk. In one series of experiments, T2 or T8 muscles were transplanted from the thorax to the neck of the same rat. While T2 and T8 muscles were reinnervated to a similar extent, they differed in the segmental origin of the innervation they received: T2 muscles received more inputs from rostral segments (T1 and T2) than did T8 muscles, and T8 muscles received more inputs from caudal segments (T4 to T6) than did T2 muscles. This difference between reinnervation of T2 and T8 muscles was detected both 2 to 4 weeks and 10 to 14 weeks after surgery. In a separate series, using rats of an inbred strain, T3, T4, or T5 muscles were transplanted from one rat to a separate host. Again, the average segmental origin of inputs to transplants from different levels differed systematically: it was most rostral to T3 muscles, intermediate to T4 muscles, and most caudal to T5 muscles. Finally, T3 and T5 muscles were soaked in a myotoxin, Marcaine, before reimplantation. This treatment kills muscle fibers but not myoblastic satellite cells; therefore, muscle fibers were replaced by regeneration. Marcaine-treated T3 and T5 muscles were successfully reinnervated but did not differ significantly in the segmental origin of their inputs. Our results show that adult mammalian muscles can be selectively reinnervated, and they raise the possibility that the selectivity is based on some positional quality that matches axons and muscles from corresponding segments. However, while differences among muscles survive denervation and transplantation, their expression or accessibility may change during regeneration.
Comparison of labeled heat shock proteins in neuronal and non-neuronal cells of Aplysia californica
Authors: Greenberg SG , Lasek RJ
Published: March 2018

Aplysia californica has been used to study the protein synthetic response of nervous tissue to stress induced by elevated temperatures. The abdominal and pleural ganglia as well as associated connectives were exposed to various temperatures for 30 min, labeled with [33S]methionine at room temperature, and then analyzed by sodium dodecyl sulfate gel electrophoresis. All cells examined responded to temperatures of greater than 31 degrees C by a reduction in levels of labeled actin, as well as by the enhanced labeling of proteins with apparent Mr of 70,000 and 110,000. Two-dimensional electrophoresis indicated that the molecular weight and isoelectric focusing properties are similar to the heat shock proteins (HSPs) observed in other systems. In addition to these major HSPs, heat-induced proteins with molecular weights ranging from 70,000 to 90,000 were highly labeled in the neurosecretory bag cells. Further cell type-specific differences in the protein synthetic response to elevated temperatures were revealed by quantitation of the major HSPs. Levels of labeled HSPs were significantly lower in ganglion cells as compared to the non-neuronal connective cells. In addition, the decrease in actin levels appeared to be less dramatic in the ganglion cells. Analysis of the cellular compartmentalization of HSPs suggests that both neurons and glia are capable of HSP synthesis. Studies in the squid have demonstrated that HSPs are transferred from adaxonal glia into the axoplasm (Tytell, M., S. G. Greenberg, and R. J. Lasek, unpublished observation).
Synaptic connectivity between cricket auditory interneurons as studied by selective photoinactivation
Authors: Selverston AI , Kleindienst HU , Huber F
Published: March 2018

Sound detection and localization are important for crickets. Interneurons located in the prothoracic ganglion play a crucial role in the initial processing of the auditory inputs. Two of the most readily recorded and dye-marked auditory interneurons in the prothoracic ganglion of the cricket are the omega cells (ON/1) and the ascenders (AN/2). By using a new photoinactivation technique to selectively inactivate these cells, the synaptic relationship between them could be studied. Our results indicate that the ON/1 cells are connected to each other with reciprocal inhibitory synapses. An ON/1 cell responds to contralateral stimulation with strong inhibition mediated by the other ON/1 cell. When one cell is killed, this inhibition is removed, and a weak excitatory response is unmasked. Unlike the ON/1 cell, AN/2 produces an inhibitory response when stimulated ipsilaterally to the cell body side, and this response is also removed when the ipsilateral ON/1 cell is killed, providing strong evidence that ON/1 is the source of the inhibition. As with the ON/1, the inhibition is replaced by weak excitation.
A description of the GABAergic neurons and axon terminals in the motor nuclei of the cat thalamus
Authors: Kultas-Ilinsky K , Ribak CE , Peterson GM , Oertel WH
Published: March 2018

The GABA neurons and their processes in the cat motor thalamic nuclei were identified and studied with glutamic acid decarboxylase (GAD) immunocytochemistry at both the light and electron microscopic levels. The three nuclei that comprise the motor thalamus, ventral anterior (VA), ventral medial (VM), and ventral lateral (VL), each displayed a characteristic distribution pattern of GAD-positive structures that was consistent with their afferent and intrinsic neuronal organization. All three thalamic nuclei displayed a population of small, GAD-positive cells the dendrites of which contained synaptic vesicles and participated in complex synaptic arrays such as serial synapses, triads, and glomeruli. Based on their ultrastructural features, these GAD-containing cells were identified as local circuit neurons. In contrast, the larger, GAD-negative cells were presumed to be the thalamocortical projection neurons. The axons of GAD-positive local circuit neurons could not be identified in these preparations. The number of GAD-positive dendrites in the neuropil was different for the three thalamic nuclei. In the VA and VM, the GAD-positive dendrites were numerous and formed symmetric synapses with dendrites of GAD- negative cells, mainly in association with corticothalamic boutons. Within VL, the GAD-containing dendrites were more numerous than in VA and VM and formed synapses at influential locations on presumed thalamocortical projection neurons, such as bases of primary dendrites, and bifurcation sites of primary and secondary dendrites. The VA and anterolateral VM nuclei that receive inhibitory GABAergic afferents from the entopeduncular nucleus and substantia nigra contained the highest concentration of large GAD-positive axon terminals. These boutons contained pleomorphic vesicles and numerous mitochondria and formed symmetric synapses and multiple puncta adherentes with dendrites and somata of presumed thalamocortical projection neurons. The size, ultrastructural features, and distribution of these GAD-positive boutons were similar to those features described for basal ganglia terminals in the motor thalamus of the cat. In addition, similar large- size GAD-positive boutons were observed in the medial VM, which receives basal ganglia afferents exclusively from the substantia nigra. The concentration of these terminals in medial VM along the dendrites of thalamocortical projection neurons was much less than that in VA and anterolateral VM. The VL nucleus which lacks basal ganglia input did not contain any large GAD-positive boutons.
The influence of retinal afferents upon the development of layers in the dorsal lateral geniculate nucleus of mustelids
Authors: Guillery RW , LaMantia AS , Robson JA , Huang K
Published: March 2018

The extent to which the development of a normal laminated lateral geniculate nucleus depends upon retinal afferents has been studied in normal and albino ferrets and in mink. Removal of all retinal afferents before they invade the nucleus (28 days in utero) or before they establish distinct monocular terminal fields (newborn, approximately 41 days post-conception) produces a nucleus that is smaller than normal and poorly separated from the adjacent perigeniculate and medial interlaminar nuclei. However, the nucleus is wedge-shaped, resembling a normal adult nucleus, in which a broad medial binocular segment is distinguishable from a narrower lateral monocular segment. There is a normal mediolateral gradient of cell sizes and some signs of a laminar differentiation, cells next to the optic tract being morphologically distinguishable from cells near the optic radiation, but no cell-free interlaminar zones are formed. The development of a monocularly innervated nucleus depends on the size of the surviving retinal input. In normally pigmented ferrets or mink the crossed retinofugal component is larger than the uncrossed component. In the monocular animals one sees essentially a monocular set of geniculate layers on each side, with an appropriate asymmetry. Each nucleus can be regarded as representing the survival of those layers which would have been innervated by the good eye, together with some additional geniculate territory that appears to be added to the surviving layers as retinogeniculate axons occupy territory normally innervated by the other eye. The crossed component of an albino ferret is abnormally large and the monocularly innervated contralateral nucleus is almost like that of a normal albino. There is a full complement of geniculate layers and interlaminar zones, which appears to develop without any binocular interactions. The ipsilateral retinogeniculate component of albinos is extremely small. In the monocular albino animals it forms discontinuous terminal patches, leaving sectors of the poorly differentiated nucleus uninnervated. These results show that in geniculate development there is a limited interaction between the two sets of retinal afferents. Each set plays a well defined and distinctive role, and one can replace the other to a limited extent only.
Nerve growth cones isolated from fetal rat brain. III. Calcium- dependent protein phosphorylation
Authors: Katz F , Ellis L , Pfenninger KH
Published: March 2018

Calcium-dependent protein kinase activities have been studied in nerve growth cone particles (GCPs) and compared with those of synaptosomes. GCPs contain a set of phosphoproteins qualitatively similar to that of synaptic nerve terminals. However, major quantitative differences appear to exist: whereas synapsin I phosphorylation is relatively weak, the major kinase substrates of GCPs are a 46,000-dalton membrane protein (calcium/calmodulin dependent) and two acidic proteins of 80,000 and 40,000 daltons, phosphorylated by a calcium/phospholipid- dependent protein kinase. The presence of synaptic kinase activities in GCPs is consistent with their neuronal origin. The role of these kinases in GCPs is not understood at present. They may be involved in growth-related functions and/or may prepare the sprouting neuron for synaptic function.
Afferent perturbations during "monopodal" swimming movements in the turtle: phase-dependent cutaneous modulation and proprioceptive resetting of the locomotor rhythm
Authors: Lennard PR
Published: March 2018

Locomotion consists of a repeating series of movement cycles (locomotor rhythm) with an orderly activation of musculature during each movement cycle (intracycle motor pattern). The effects of sensory stimulation, on both the intracycle motor pattern and the locomotor rhythm, were examined during electrically elicited swimming movements of a single turtle hindlimb. The resulting “monopodal” swimming was not subject to movement-related reflexes from other limbs or postural constraints, and provided a sensitive system for analyzing the effects of transient sensory perturbations. During “monopodal” swimming, cutaneous and extensor muscle-nerve stimulation (single 0.1- to 0.3-msec electrical pulse) had similar phase-dependent effects on the swim cycle in progress. Stimuli delivered during the powerstroke (limb retracting) shortened the period of the cycle. Stimulation during the returnstroke prolonged the cycle. Changes in cycle period were accompanied by in- phase adjustments of the EMG burst duration or interburst interval which was being expressed at the time of stimulus delivery. The in- phase adjustment of each muscle served to maintain the timing relationships between muscles, and resulted in the preservation of the intracycle motor pattern. Cutaneous and muscle-nerve stimulation had dramatically different effects on the locomotor rhythm. Cutaneous nerve stimulation produced period changes in poststimulus cycles which led to a temporary phase shift of the swimming rhythm. This temporary modulation suggests that cutaneous afferents do not have direct access to the timing circuitry of the central nervous system locomotor network. Muscle-nerve stimulation only altered the period of the cycle in progress at the time of stimulus delivery, and thus permanently reset the locomotor rhythm. This permanent phase shift suggests that muscle afferents have direct access to a central timing network which controls the locomotor rhythm.
Thalamic projections to areas 5a and 5b of the parietal cortex in the cat: a retrograde horseradish peroxidase study
Authors: Avendano C , Rausell E , Reinoso-Suarez F
Published: March 2018

The cytoarchitecture of areas 5a and 5b of the cat's parietal cortex was re-examined and the afferent connections from the thalamus were investigated using the horseradish peroxidase (HRP) retrograde transport technique. Single or multiple small injections of the enzyme were made in different points of these areas in the rostral sectors of the lateral and middle suprasylvian gyri. The cytoarchitecture of the cortical region affected by the injections was carefully assessed in each case, and the labeled neurons found in the thalamus were plotted on projection drawings of each histological section. A prominent projection to area 5a arises from the posterior (Po) and ventral lateral (VL) complexes; less substantial projections originate in the ventral anterior nucleus (VA), the lateral intermediate complex (LI), and the central lateral nucleus (CL). Projections to area 5b (and to the laterally adjacent area suprasylviana anterior) mainly arise from LI, the dorsal part of VL, and the caudodorsal part of VA and CL; a moderate projection was also found from Po, the pulvinar, and the lateral dorsal complex. The main conclusions of this study are as follows. The shape and extent of areas 5a and 5b show notable variations when only their projection on the convoluted cortical surface is considered; however, they are relatively constant when plotted on unfolded cortical maps. The thalamic neurons projecting to areas 5a and 5b are organized according to a loose topographic plan, particularly noticeable in Po, VL and LI. In general, the rostral portion of this cortex (5a) receives projections from more ventral regions of the thalamus (mainly Po and VL), whereas the caudal part (5b) has connections from more dorsal regions (mainly LI and VA-VL). Moreover, the medial portions of these areas receive projections from lateral and ventral parts of the thalamic nuclei, whereas more dorsal and medial sectors of the thalamus project to the lateral portions of areas 5a and 5b. When labeled thalamic cell populations resulting from cases with single injections in neighboring cortical loci were compared, no abrupt changes of labeling were observed; rather, we generally observed gradual transitions and overlaps, even across nuclear boundaries. When only layers I and II of the cortex received the HRP, the number of labeled neurons and the intensity of their labeling decreased, their location in the thalamus was more restricted, and the mean size of the labeled cells was significantly smaller than that of the neurons labeled in the same regions after deep HRP injections.
Compensatory changes in contralateral sympathetic neurons of the superior cervical ganglion and in their terminals in the pineal gland following unilateral ganglionectomy
Authors: Dornay M , Gilad VH , Gilad GM
Published: March 2018

The sympathetic noradrenergic neurons of the rat superior cervical ganglia (SCGs) provide the major source of innervation to the pineal gland. The present study sought to determine if this sympathetic innervation can undergo collateral sprouting following partial denervation of the pineal by unilateral removal of the SCG (ganglionectomy), and whether such growth of axon terminals is associated with biochemical changes in the contralateral SCG. In the pineal gland following partial denervation, residual noradrenergic terminals underwent compensatory changes indicative of collateral sprouting, as evidenced by: a rapid reduction in tyrosine hydroxylase (TH) activity and in [3H]norepinephrine (NE) uptake, to about 50% of control by 2 days, which was followed by a gradual but sustained increase to levels of approximately 80% of control by 10 days and a reduction in the intensity and density but not in the distribution of fibers containing NE-induced fluorescence by 2 days, which was followed by a sustained increase. In the contralateral SCG, choline acetyltransferase (CAT) activity, a marker of cholinergic preganglionic terminals, was transiently increased to about 115% of control by 4 days and returned to control levels by 14 days after unilateral ganglionectomy; later, TH activity in noradrenergic cell bodies was gradually increased to about 140% of control by 10 days where it remained for up to 52 days. Unilteral ganglionectomy combined with decentralization of the contralateral SCG by preganglionic nerve cut prevented the compensatory changes in noradrenergic nerve terminals within the pineal.
High-affinity binding of [3H]acetylcholine to muscarinic cholinergic receptors
Authors: Kellar KJ , Martino AM , Hall DP , Schwartz RD , Taylor RL
Published: March 2018

High-affinity binding of [3H]acetylcholine to muscarinic cholinergic sites in rat CNS and peripheral tissues was measured in the presence of cytisin, which occupies nicotinic cholinergic receptors. The muscarinic sites were characterized with regard to binding kinetics, pharmacology, anatomical distribution, and regulation by guanyl nucleotides. These binding sites have characteristics of high-affinity muscarinic cholinergic receptors with a Kd of approximately 30 nM. Most of the muscarinic agonist and antagonist drugs tested have high affinity for the [3H]acetylcholine binding site, but pirenzepine, an antagonist which is selective for M-1 receptors, has relatively low affinity. The ratio of high-affinity [3H]acetylcholine binding sites to total muscarinic binding sites labeled by [3H]quinuclidinyl benzilate varies from 9 to 90% in different tissues, with the highest ratios in the pons, medulla, and heart atrium. In the presence of guanyl nucleotides, [3H] acetylcholine binding is decreased, but the extent of decrease varies from 40 to 90% in different tissues, with the largest decreases being found in the pons, medulla, cerebellum, and heart atrium. The results indicate that [3H]acetylcholine binds to high-affinity M-1 and M-2 muscarinic receptors, and they suggest that most M-2 sites have high affinity for acetylcholine but that only a small fraction of M-1 sites have such high affinity.
Calcium dependence of membrane sealing at the cut end of the cockroach giant axon
Authors: Yawo H , Kuno M
Published: March 2018

Following transection of a nerve fiber, the ruptured membrane must be resealed before regeneration from the proximal cut end. However, it is not certain how fast the cut end is resealed or how it is resealed. We have examined the membrane sealing process following transection of the cockroach giant axon, using recovery of decreased membrane potential and input resistance as criteria. The cable analysis and the injury current profile measured under voltage clamp suggested that the injured site is resealed by a structure with high electrical resistances 5 to 30 min after the transection. This recovery of membrane properties roughly coincided in time with the appearance of a partition-like structure formed near the cut end. The membrane resealing process was highly dependent upon temperature and extracellular Ca2+. Substitution of Ca2+ by equimolar Mg2+, Mn2+, or Sr2+ failed to induce the membrane sealing following transection. However, even in a Ca2+-free solution, the membrane resealing occurred if Ca2+ was injected into the axoplasm near the cut end. Thus, the membrane resealing appears to require Ca2+ entry into the axoplasm. The resealing process was not affected by colchicine or cytochalasin. However, the resealing was prevented by the application of phospholipase A2 inhibitors. These results suggest that the membrane resealing is triggered by phospholipase A2, which is activated by excess Ca2+ entering the axoplasm at the injured site.
Autoradiographic localization and characterization of spinal cord substance P binding sites: high densities in sensory, autonomic, phrenic, and Onuf's motor nuclei
Authors: Charlton CG , Helke CJ
Published: March 2018

The presence of the neurotransmitter or neuromodulator, substance P (SP), in the spinal cord implies that a discrete localization of SP receptors also occurs. To map the distribution of and to characterize SP binding sites in the spinal cord, light microscopic autoradiography was used. SP binding sites occurred in the dorsal horn, intermediolateral cell column (IML) and lamina X-region. In the ventral horn, the phrenic, Onuf's and sacral ventromedial motor nuclei were densely labeled. Other regions of the ventral horn were moderately labeled for SP binding sites. The localization of binding sites parallels the regional distribution of SP-containing nerve fibers in the spinal cord. A close correlation between the binding sites for SP and the presence of cholinesterase-stained neurons occurred, and suggest that the SP receptors are located on or proximal to cholinergic neurons. The density of the binding sites in the dorsal horn was highest in the sacral section, followed by the lumbar, thoracic and cervical section. In the lamina X region, however, the density was highest in the thoracic followed by the sacral, lumbar and cervical sections. The high density binding of 125I-Bolton-Hunter reagent labeled SP was inhibited, in a dose-dependent manner, by unlabeled SP. Quantification of the dose-dependent inhibition binding, using computer densitometry, showed differences in the inhibition curves for the cervical lamina X-region and the IML as compared with the other loci containing high density binding sites. The differential sensitivity of the SP receptors to unlabeled SP suggests that there are heterogeneous receptors for SP in the spinal cord, which may be relevant to the role of SP in different spinal cord functions. The binding to specific motor nuclei in the ventral horn also suggest that SP may play a role in the function of specialized striated muscles.
Potassium-stimulated purine release by cultured sympathetic neurons
Authors: Wolinsky EJ , Patterson PH
Published: March 2018

Environmental factors can influence cultured sympathetic neurons to acquire several different neurotransmitter phenotypes. Cholinergic and noradrenergic transmitter status can be influenced by heart cell conditioned medium, chronic depolarization (Patterson, P. H. (1978) Annu. Rev. Neurosci. 1:1–17), and rat serum (Wolinsky, E. J., and P. H. Patterson, (1985) J. Neurosci. 5:1509–1512); formation of electrical synapses can be induced by insulin (Wolinsky, E. J., H. Patterson, and A. L. Willard (1985) J. Neurosci., 5:1675–1679). Purine release has also been proposed as a possible transmission mode for sympathetic neurons (Potter, D. D., E. J. Furshpan, and S. C. Landis (1983) Fred. Proc. 42:1626–1632), and as such, it is another candidate for environmental modulation. In this report, we assess the ability of sympathetic neuron cultures grown with and without serum to release metabolically labeled tritriated purine compounds in response to depolarization. Exposure to 54 mM potassium stimulated release of adenosine, inosine, and hypoxanthine from both serum-supplemented and defined-medium cultures. However, depolarization-stimulated release of adenine nucleotides was observed only from serum-supplemented cultures and not from serum-free cultures. The release of adenine nucleotides from serum-containing cultures is affected by divalent cations in the manner expected for a neurosecretory process. The failure of serum-free cultures to release detectable adenine nucleotides raises the possibility that they do not share with, or that they differ from, serum-supplemented cultures in the purinergic aspect of the multiple transmission modes available to sympathetic neurons, and that this difference may be due to effects of the culture medium.