bluuebunny/crossref_metadata_2025 huggingface dataset:
Regional distribution of type II Ca2+/calmodulin-dependent protein kinase in rat brain
Authors: Erondu NE , Kennedy MB
Published: March 2018

The distribution of type II Ca2+/calmodulin-dependent protein kinase has been mapped in rat brain by immunochemical and immunohistochemical methods using an antibody against its alpha-subunit. The concentration of the kinase, measured by radioimmunoassay, varies markedly in different brain regions. It is most highly concentrated in the telencephalon where it comprises approximately 2% of the total hippocampal protein, 1.3% of cortical protein, and 0.7% of striatal protein. It is less concentrated in lower brain structures, ranging from about 0.3% of hypothalamic protein to 0.1% of protein in the pons/medulla. The gradient of staining intensity observed in brain sections by immunohistochemistry corroborates this distribution. Neurons and neuropil of the hippocampus are densely stained, whereas little staining is observed in lower brain regions such as the superior colliculus. Within the diencephalon and midbrain, dense staining is observed only in thalamic nuclei and the substantia nigra. The skewed distribution of alpha-subunit appears to be due in part to the occurrence in the cerebellum and pons/medulla of forms of the kinase with a high ratio of beta- to alpha-subunits. However, most of the variation is due to the extremely high concentration of the kinase in particular neurons, especially those of the hippocampus, cortex and striatum. The unusually high expression of the kinase in these neurons is likely to confer upon them specialized responses to calcium ion that are different from those of neurons in lower brain regions.
The influence of neural tube-derived factors on differentiation of neural crest cells in vitro. I. Histochemical study on the appearance of adrenergic cells
Authors: Howard MJ , Bronner-Fraser M
Published: March 2018

The neural crest gives rise to numerous derivatives including adrenergic and cholinergic neurons, supportive cells of the nervous system, and melanocytes. In tissue culture, neural crest cells explanted from both cranial and trunk regions were found to differentiate into adrenergic neuroblasts or into pigmented cells when grown in medium containing 10% chick embryo extract. When the embryo extract concentration was lowered to 2%, no catecholamine-containing cells (as assayed by formaldehyde-induced fluorescence) were detected, although pigment cells were observed. These results suggest the presence of a factor(s) in embryo extract that promotes or supports adrenergic differentiation. To examine the possible tissue sources of this factor(s), neural tube, notochord, or somite cells were used to condition medium containing 2% embryo extract. When neural crest cells were grown in medium conditioned by neural tube cells, adrenergic neuroblasts were observed in all cultures. However, somite- and notochord conditioned medium did not support adrenergic differentiation. In addition, medium supplemented with extracts derived from central nervous system components did support adrenergic expression, whereas medium supplemented with embryo extract from which the neural tissue was removed did not. Direct contact with neural tube cell ghost membranes was unable to substitute for high embryo extract concentrations or for neural tube-conditioned medium. These results suggest that the neural tube makes a diffusible factor(s) that will support adrenergic differentiation of neural crest cells.
Molecular forms and subunit structure of the acetylcholine receptor in the central nervous system of insects
Authors: Breer H , Kleene R , Hinz G
Published: March 2018

The nicotinic acetylcholine receptor as probed by alpha-bungarotoxin binding has been isolated from detergent-solubilized ganglionic membrane preparations from the insect, Locusta migratoria. The isolation and characterization of the receptor protein was achieved by preparation of membrane fragments, extraction by sodium deoxycholate, centrifugation on sucrose density gradient, affinity chromatography, gel electrophoresis, and immunoblotting. The purified receptor protein migrated as a single band on polyacrylamide when native (Mr = 250,000 to 300,000) but also under denaturing conditions (Mr = 65,000) and cross-reacted with some monoclonal antibodies against the Torpedo receptor. In immunohistochemical approaches using polyclonal antibodies the acetylcholine receptor antigenic sites could topochemically be identified at very distinct zones in the neuropil of locust ganglia. The results suggest that the acetylcholine receptor in the central nervous system of insects represents an oligomeric complex composed of four identical or very similar subunits and thus may represent a prototype of the recently proposed homo-oligomeric ancestral acetylcholine receptor.
A functional organization of ON and OFF pathways in the rabbit retina
Authors: Bloomfield SA , Miller RF
Published: March 2018

Intracellular electrophysiological recordings were obtained from amacrine and ganglion cells in an isolated, superfused retina-eyecup preparation of the rabbit. Cells were characterized physiologically, after which cell-staining was accomplished by intracellular iontophoresis of HRP. A computer-assisted image-processing system was used to study the dendritic stratification pattern of HRP-labeled neurons within the inner plexiform layer (IPL). Our results support the concept that the IPL is functionally divided into a distal OFF region and proximal ON layer. ON and OFF ganglion and amacrine cells show dendritic arborizations consistent with this division and ON-OFF ganglion cells have processes in both portions of the IPL. It appears that these functional subdivisions of the IPL reflect excitatory, but not necessarily inhibitory, inputs. Thus, the pattern of dendritic arborization of a cell appears to predict its physiological response polarity, regardless of the type of inhibition it receives.
Noradrenergic hyperinnervation of the motor trigeminal nucleus: alterations in membrane properties and responses to synaptic input
Authors: Vornov JJ , Sutin J
Published: March 2018

The physiological consequences of the noradrenergic (NE) hyperinnervation of the rat brain stem produced by neonatal administration of 6-hydroxydopamine (6-OHDA) was studied in the motor trigeminal nucleus. Stimulation of the region of the lateral lemniscus, the source of the noradrenergic innervation of the nucleus, facilitated the masseteric reflex for up to 200 msec in both normal and hyperinnervated animals. The peak facilitation was 71% larger in the NE hyperinnervated animals and was reduced by systemically administered alpha- and beta-adrenergic receptor antagonists. Intracellular recordings revealed that the mean resting potential of NE hyperinnervated trigeminal motoneurons was 3 mV more hyperpolarized than that of normal cells. The mean input resistance of NE hyperinnervated motoneurons was reduced from 1.83 +/- 0.15 to 1.22 +/- 0.19 M Omega. NE hyperinnervation increased the amplitude of the monosynaptic EPSP evoked by stimulation of primary afferent cell bodies in the mesencephalic trigeminal nucleus (MesV) by 65%. The mean rise time of the EPSP was increased in NE hyperinnervated motoneurons while the mean half-width was unchanged, suggesting a shift in the distribution of primary afferent terminals away from the motoneuron soma. Stimulation of the lateral lemniscus region produced a predominantly depolarizing PSP with a time course similar to that of the reflex facilitation. The amplitude of the depolarization in NE hyperinnervated motoneurons was not significantly different from that of controls. During this lateral lemniscus region-evoked PSP, stimulation of MesV produced an EPSP of increased amplitude, associated with a decrease or no change in input resistance.(ABSTRACT TRUNCATED AT 250 WORDS)
Differentiation of astrocytes and oligodendrocytes from germinal matrix cells in primary culture
Authors: Goldman JE , Geier SS , Hirano M
Published: March 2018

Primary cultures derived from neonatal rat forebrain grow almost entirely as glial cultures, with a large astrocytic preponderance and smaller numbers of oligodendrocytic cells. Although both astrocytic and oligodendrocytic characteristics are acquired in vitro, the origins of both types of glia in primary cultures have not been determined. We tested the hypothesis that glia differentiate in vitro from immature neuroectodermal cells by following the fate of germinal zone cells in primary cultures. A monoclonal antibody that binds GD3 ganglioside was used as a marker for cells of the subventricular zone (SVZ), since antibody binding in newborn rat forebrain could be detected by immunofluorescence only in the SVZ of newborn rats (Goldman et al., 1984). We followed the expression of glial fibrillary acidic protein (GFAP), an astrocytic marker; galactocerebroside (GC), an oligodendrocytic marker; and GD3 during the first several weeks of culture. Both GFAP and GC expression were first detected in cells that bound the GD3 antibody. Astrocytes developed during the first week in vitro; eventually, they lost the ability to bind the GD3 antibody and most became GD3-/GFAP+ cells. In high-density cultures, a population of small cells that resided on top of the astrocytic monolayer retained GD3 expression. GC-antibody binding was first observed in these cells of the upper layer, although it was not readily apparent until the second week of culture. Few GC+ cells were seen in cultures grown at low density, however.(ABSTRACT TRUNCATED AT 250 WORDS)
Endogenous dopamine can modulate inhibition of substantia nigra pars reticulata neurons elicited by GABA iontophoresis or striatal stimulation
Authors: Waszczak BL , Walters JR
Published: March 2018

Previous reports from this laboratory have described an ability of iontophoretically applied dopamine to attenuate the inhibitory effects of iontophoresed GABA on neurons of the substantia nigra pars reticulata. This finding raised the question of whether endogenous dopamine, released from dendrites of neighboring pars compacta dopamine neurons, might act as a neuromodulator which diminishes the inhibition of pars reticulata neurons evoked by either GABA iontophoresis or electrical stimulation of the striatonigral GABAergic pathway. Extracellular, single-unit activity of pars reticulata neurons was recorded in male rats anesthetized with chloral hydrate. In one set of studies, d-amphetamine, a drug reported to release dopamine from nigral dendrites, was administered intravenously (1.6 mg/kg) during regular, intermittent iontophoretic pulses of GABA. As had been previously observed with iontophoresed dopamine, i.v. amphetamine significantly lessened the inhibition of reticulata neurons produced by GABA application. This change was reflected by a decrease in GABA's inhibitory potency by 22% relative to the control level of inhibition achieved prior to amphetamine administration. Amphetamine caused no decreases in GABA's effectiveness, however, in animals that had previously received treatments that depleted or destroyed nigral dopamine stores, i.e., in rats pretreated with reserpine and alpha- methyl-p-tyrosine, or in rats with 6-hydroxydopamine lesions of the nigrostriatal dopamine pathway. In a second set of experiments, amphetamine or dopamine was delivered iontophoretically while monitoring the GABA-mediated (bicuculline-reversible) inhibition of reticulata neurons that can be elicited by striatal stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
Integration of direction signals of image motion in the superior temporal sulcus of the macaque monkey
Authors: Saito H , Yukie M , Tanaka K , Hikosaka K , Fukada Y , Iwai E
Published: March 2018

Using anesthetized and paralyzed monkeys, we have studied the visual response properties of neurons in the cortical area surrounding the middle temporal area (MT) in the superior temporal sulcus (STS). Systematic electrode penetrations revealed that there is a functionally distinct region where three classes of directionally selective cells with large receptive fields cluster. This region is anteriorly adjoined to the dorsal two-thirds of MT, has a width of 4–5 mm mediolaterally, and therefore may correspond to the dorsal part of the medial superior temporal area (MST), which was previously defined as a MT-recipient zone. One class of cells responded to a straight movement of patterns in the frontoparallel plane with directional selectivity (D cells: 217/422, 51.4%). The second class of cells selectively responded to an expanding or contracting size change of patterns (S cells: 66/422, 15.7%). These cells responded neither to a change in width of a slit of any orientation or any length, nor to a change in brightness. The third class of cells responded only to a rotation of patterns in one direction (R cells: 58/422, 13.7%). A majority of these cells (41/58) responded to the clockwise or counterclockwise rotation of patterns in the frontoparallel plane (Rf cells), while the rest responded to a rotation of patterns in depth (Rd cells). We will suggest that these cells acquire the ability to discover whole events of visual motion-- i.e., unidirectional straight movement, size change (radial movement), and rotation--by integrating elemental motion information extracted by MT cells. The receptive fields of D, S, and Rf cells can be constructed by converging signals of MT cells, the preferred directions of which are arranged in parallel (D cells), radially (S cells), and circularly (Rf cells). The receptive fields of Rd cells can be constructed, in turn, by the convergence of signals of S cells.
Relation of animal size to convergence, divergence, and neuronal number in peripheral sympathetic pathways
Authors: Purves D , Rubin E , Snider WD , Lichtman J
Published: March 2018

The enormous range of animal size raises a fundamental problem: How do larger animals maintain adequate control of peripheral structures that are many times more massive and extensive than the homologous structures in smaller animals? To explore this question, we have determined neuronal number, the number of axons that innervate each neuron (convergence) and the number of neurons innervated by each axon (divergence), in a peripheral sympathetic pathway of several mammals (mouse, hamster, rat, guinea pig, and rabbit). The average adult weights of these species vary over approximately a 65-fold range. However, the number of superior cervical ganglion cells increases by only a factor of 4 between the smallest of these animals (mice; about 25 gm) and the largest (rabbits; about 1700 gm); the number of spinal preganglionic neurons that innervate the ganglion increases by only a factor of 2. Thus, the number of nerve cells in the sympathetic system does not increase in proportion to animal size. On the other hand, our results indicate that there are systematic differences across these species in the number of axons that innervate each ganglion cell and in the number of ganglion cells innervated by each axon. We suggest that modulation of convergence and divergence in sympathetic ganglia allows this part of the nervous system to effectively activate homologous peripheral targets over a wide range of animal size.
Prenatal development of retinal ganglion cell axons: segregation into eye-specific layers within the cat's lateral geniculate nucleus
Authors: Sretavan DW , Shatz CJ
Published: March 2018

The morphological changes in individual retinal ganglion cell axons associated with the formation of the eye-specific layers in the dorsal lateral geniculate nucleus (LGN) were studied during the prenatal development of the cat's visual system. Previous work has shown that the pattern of segregated eye inputs found in the adult arises from an immature state in which inputs from the two eyes are intermixed within the nucleus (Shatz, 1983). Here, this developmental process is examined at its fundamental unit of connectivity--the individual retinal ganglion cell axon. To do so, an in vitro method was used to label fetal cat optic tract axons with HRP at various times during development between embryonic day 38 (E38) and postnatal day 2 (P2) (gestation = 65 d). The results presented here are based on reconstructions of 172 axons. During the initial period of intermixing (E38–43), axons are relatively simple in morphology. Many axons studied at the earliest ages (E38) end in growth cones and have very few branches along the main axon trunk as they traverse the nucleus. By E43, the number of side branches given off along the main axon trunk has increased and most axons also have a simple terminal arbor. Over the next 2 weeks (E43–55), the majority of axons are studded with side branches and the terminal arbor is well defined. Then, between E55 and birth, axons lose their side branches and the eye-specific layers appear. By birth, nearly all axons have a smooth trunk and an elaborate terminal arbor restricted to the LGN layer appropriate to the eye of axon origin. When the number of side branches per axon was quantified, the time course of appearance and subsequent loss of side branches was found to parallel the time course of the initial intermixing of inputs and subsequent reduction in territory shared by the two eyes as determined from previous intraocular injection experiments. Our results also showed that the side branches along each axon were located primarily within LGN territory destined to be occupied by the other eye. Thus, the side branches are likely to represent a morphological substrate for the intermixing of inputs from the two eyes. These observations suggest that the segregation of eye input to the LGN involves two fundamental and simultaneous events. One event is the remodeling of the branching pattern along the length of the main axon trunk so that the side branches present early on are eliminated and the main axon trunk becomes smooth.(ABSTRACT TRUNCATED AT 400 WORDS)
Regeneration of a distinctive set of axosomatic contacts in the leech central nervous system
Authors: French KA , Muller KJ
Published: March 2018

The nociceptive sensory neurons (N cells) in the leech Hirudo medicinalis contact other neurons through conventional synapses in the neuropile and through baskets of processes that wrap the somata of particular cells. These axosomatic contacts are made with the pressure (P) and N sensory neurons in the adjacent segmental ganglia, but not with cells within the same ganglion as the wrapping cell. Physiological evidence indicates that these contacts may be synaptic, although conventional synapses have not been observed with electron microscopy. After they have been injured, lateral N cell processes can grow into the anterior adjacent ganglion and regenerate somatic contacts. In general, regenerated N cell processes wrap the same somata as do intact N cells, but they often wrap fewer somata. However, six of 14 regenerated N cells also wrapped the soma of a small posterior cell that was contacted in only one of 120 normal ganglia examined. It thus appears that the growing processes of an injured N cell select certain cell somata to wrap, but that the selection is somewhat broader than that in the embryonic leech.
The rod pathway in the rabbit retina: a depolarizing bipolar and amacrine cell
Authors: Dacheux RF , Raviola E
Published: March 2018

Anatomical and electrophysiological techniques were combined to study the morphology, synaptic connections, and response properties of two neurons in the rod pathway of the rabbit retina: the rod bipolar cell and the narrow-field, bistratified (NFB) amacrine cell. Rod bipolars receive synaptic input from rod cells in the outer plexiform layer (OPL), where their dendrites end as central elements in the invaginating synapse of rod spherules. Their main synaptic output in the inner plexiform layer (IPL) is onto NFB amacrine cells and at least one other type of amacrine, which in turn feeds a reciprocal synapse back onto the bipolar endings. Rod bipolars, or a variety of them, respond to diffuse, white light stimulation with a transient-sustained depolarization dominated by rods; with high-intensity flashes, they generate a secondary depolarization at off, which is homologous to the rod aftereffect of horizontal cells, although opposite in polarity. NFB amacrine cells receive synaptic input from rod bipolars, cone bipolars, and other types of amacrine cells; they are presynaptic to ganglion cell dendrites and communicate via gap junctions with other processes, whose parent neuron has not yet been identified. They respond to light with a triphasic potential, characterized by a depolarizing transient at on, followed by a sustained plateau phase, and finally by a hyperpolarizing transient at off. Threshold of their responses is the same as in the depolarizing rod bipolars and saturation is reached with nearly the same stimulus intensity in both neurons. Furthermore, NFB amacrine cells exhibit a depolarizing rod aftereffect at the termination of high-intensity flashes. Thus, this amacrine cell type is inserted in series along the rod pathway in the rabbit retina and modulates the transfer of scotopic signals from rod bipolars to ganglion cells.
Development of ultrastructural specializations during the formation of acetylcholine receptor aggregates on cultured myotubes
Authors: Olek AJ , Ling A , Daniels MP
Published: March 2018

The ultrastructure of cultured rat myotubes was examined at stages in the initial assembly of acetylcholine receptor (AChR) aggregates in order to elucidate the role of cell-surface specializations in aggregate formation. Within 4–6 hr, embryonic brain extract (EBX) induces the formation of sites of AChR density elevated 5–9 X above that of surrounding regions, and the appearance of these aggregates is preceded by the formation of clouds of punctate microaggregates (Olek et al., 1983). A video image-intensification system was used to monitor this redistribution of fluorescently labeled AChR, and sites of aggregation were mapped on identified myotubes. After processing the cultures for electron microscopy, thin sections were taken through identified aggregate sites at various stages in assembly. Specializations, including a basal lamina, mound-shaped plasma membrane contours with occasional deep infoldings, and a subjacent dense cytoskeletal specialization, which tended to exclude other cytoplasmic organelles, were associated with newly formed aggregates found 4–6 hr after adding EBX to the cultures. Analysis of random thin sections through EBX-treated and untreated myotubes showed that the extent of specializations of the basal lamina and cytoplasm was approximately threefold greater in cells exposed to EBX for 4 hr, suggesting a concurrent, and possibly interdependent, organization of such specializations with AChR aggregate assembly. Examination of sections through clouds of microaggregates, which formed within 90 min, revealed mound-shaped plasma membrane contours and underlying cytoplasm depleted of organelles but relatively little basal lamina and submembrane cytoskeletal density. These results suggest that the initial stage of AChR aggregate assembly involves relatively subtle changes in the structure of the cell cortex and that the evolution of microaggregates to aggregates may require the formation of additional cytoskeletal and extracellular matrix structures.
Gain control in the electrosensory system mediated by descending inputs to the electrosensory lateral line lobe
Authors: Bastian J
Published: March 2018

The electrosensory lateral line lobe (ELLL) of weakly electric fish, the primary electrosensory processing station, receives a large descending input from the midbrain in addition to the input from the electroreceptor afferents. The role of a major component of this descending input in determining the properties of ELLL output neurons was investigated. The descending input was reduced or eliminated by microinjections of the local anesthetic lidocaine or by small lesions. This treatment increased the responses of the ELLL output neurons to suprathreshold stimuli by about 300% and also increased the size of the neurons' receptive fields for moving electrolocation targets and the resolution with which they encode target distance. The neurons' threshold sensitivity and tuning to amplitude modulation frequency were unchanged by removal of the descending input. The results of this study show that this portion of the descending input to the ELLL normally mediates an inhibition that controls the responsiveness of ELLL output neurons. This descending input could function as a gain control mechanism, allowing the animal to modulate the sensitivity of the electrosensory system in response to changing environmental conditions.
Stimulation of the lateral habenula inhibits dopamine-containing neurons in the substantia nigra and ventral tegmental area of the rat
Authors: Christoph GR , Leonzio RJ , Wilcox KS
Published: March 2018

Neurons in the lateral habenula (LHb) of rats have efferent projections that terminate in the substantia nigra pars compacta (SNC) and ventral tegmental area (VTA), where cell bodies of dopamine-containing neurons are located. In order to study the influence of the habenula on dopaminergic activity, single-cell electrophysiological techniques were used to record unit discharge of dopamine-containing neurons in the SNC and VTA during electrical stimulation of the LHb or adjacent structures. Dopamine-containing neurons in the SNC and VTA were identified by their characteristic spike duration (greater than 2 msec), discharge rate (2–8 spikes/sec), and irregular firing pattern. Analysis of peristimulus time histograms showed that 85% of SNC cells and 91% of VTA neurons were inhibited after single pulse stimulation (0.25 mA, 0.1 msec) of the LHb. The mean time between stimulation and onset of inhibition was 11 msec (range, 2–22 msec) and mean duration of maximal suppression was 76 msec (range, 20–250 msec). Stimulation of structures adjacent to the LHb (hippocampus, lateral thalamus, medial dorsal thalamus, medial habenula) had little or no effect. Destruction of the fasciculus retroflexus, the fiber pathway that contains most habenular efferents, blocked the stimulation effects on dopamine- containing neurons. Destruction of the stria medullaris, which contains most habenular afferents, did not alter the inhibitory effect of habenular stimulation. Injection of a cytotoxin, kainic acid, in the LHb 1 week before recording sessions blocked the inhibitory consequences of habenular stimulation. These experiments show that activation of neuronal perikarya in the LHb causes orthodromic inhibition of dopamine-containing neurons in SNC and VTA via the fasciculus retroflexus.
Decline in calcium cooperativity as the basis of facilitation at the squid giant synapse
Authors: Stanley EF
Published: March 2018

The role of Ca in transmitter release and facilitation has been examined at the squid giant synapse by evaluating the effect of changes in the external concentration of Ca on the excitatory postsynaptic potential (EPSP). Changes in Ca were achieved by means of an arterial perfusion technique, circumventing the diffusion barrier that exists between the synapse and the bathing medium. Transmitter release was found to follow a high power (n) of the external Ca at low nonsaturating Ca concentrations and low stimulus frequencies: 4.0 +/- 0.1 (mean +/- SE) in 22 experiments. The value of n was not fixed, however, but declined at stimulus frequencies above 0.3 Hz to 2.9 at Hz, 2.3 at 10 Hz, 1.7 at 50 Hz, and 1.1 at 80 Hz. This decline in n was due to a greater proportional facilitation of the EPSP at lower Ca levels. In a separate experiment, facilitation was determined at a fixed low Ca level over a wide range of stimulus frequencies. A plot of the maximum percentage increase in the EPSP against the stimulus frequency described three “steps,” with plateaus occurring at 0.3–10 Hz, 10–50 Hz, and over 80 Hz. The timing of these steps corresponds to the stimulus frequencies at which the cooperativity declines. The results of this study indicate that the cooperative action of four Ca ions are required to trigger the transmitter release mechanism, and that the phenomenon of facilitation involves a reduction in Ca cooperativity. It is proposed that Ca ions can bind up to four receptors on the release site and that binding results in the opening of “gates.” The opening of all four gates triggers transmitter release.(ABSTRACT TRUNCATED AT 250 WORDS)
Novel monoclonal antibodies provide evidence for the in situ existence of a nonphosphorylated form of the largest neurofilament subunit
Authors: Lee VM , Carden MJ , Trojanowski JQ
Published: March 2018

We have obtained five monoclonal antibodies to the Mr 200,000 neurofilament component (NF200) after immunization with polypeptides purified from enzymatically dephosphorylated bovine neurofilaments. In immunoblots of untreated neurofilament protein and protein from filaments exposed to phosphatase, these antibodies recognize nonphosphorylated or dephosphorylated, but not phosphorylated, forms of NF200. The epitopes recognized by these new monoclonal antibodies reside in the carboxyterminal domain of the NF200 polypeptide as defined by immunoreaction with limited chymotryptic fragments. Immunohistochemical studies of bovine cerebellum, spinal cord, trigeminal ganglion, and trigeminal nerve with these new monoclonal antibodies demonstrate immunoreactivity primarily in neuronal perikarya; axons and dendrites are weakly or infrequently immunostained. After enzymatic dephosphorylation of these tissues, a more extensive distribution of immunoreactivity is seen, especially in axons and dendrites. Immunostaining of cultured rat sympathetic neurons is restricted to cell bodies. These data provide evidence for the in situ existence of NF200 epitopes that are not phosphorylated in some classes of neurons or regions of a neuron, but are modified by phosphorylation in other neurons or neuronal domains. These new monoclonal antibodies are distinctly different from those in a large library (over 100) raised to, and specific for, phosphorylated neurofilament proteins. They are novel tools for probing neurofilament distribution, metabolism, structure, and possibly function.
Microcircuitry of beta ganglion cells in cat retina
Authors: McGuire BA , Stevens JK , Sterling P
Published: March 2018

We reconstructed from electron micrographs of 189 serial ultrathin sections a major portion of the dendritic tree of an on-beta ganglion cell through its sixth order of branching. One hundred three contacts from three cone bipolar cells were identified. Forty-seven contacts were from a single CBb1 cone bipolar. These were distributed widely over the dendritic tree but were frequently found on the slender “basal tuft” dendrites. Twenty-two additional contacts from a second CBb1 cell were found but not studied in detail. Thirty-four contacts were from a single CBb2 cone bipolar; these also were distributed widely but were primarily on the branches of the main dendritic arborization. A major portion of the dendritic tree of an off-beta cell was also reconstructed through its seventh order of branching. Thirty-five contacts from two cone bipolar cells were identified. Twenty-three contacts were from a single CBa1 cone bipolar and 12 widely distributed over the off-beta cell dendritic tree. We propose that the photopic receptive field center of a beta cell corresponds to the envelope of the receptive fields of the bipolar cells that connect it to the cones. The center response of a beta cell may be generated by a “push-pull” mechanism. For the on-beta cell there would be excitation at light on from CBb1 and disinhibition from CBb2 and the reverse at light off. For the off-beta cell there would be inhibition at light on from CBa2 and withdrawal of excitation from CBa1. Should the bipolars have antagonistic surrounds (so far reported only for CBb1), the beta cell surrounds as well as their centers might be generated by this push-pull mechanism.
Prenatal development of cat retinogeniculate axon arbors in the absence of binocular interactions
Authors: Sretavan DW , Shatz CJ
Published: March 2018

During prenatal development of the cat's retinogeniculate projection, inputs from the ganglion cell axons of the two eyes are initially intermixed with each other within the lateral geniculate nucleus (LGN). As development proceeds, the inputs sort out to give rise to the eye- specific layers characteristic of the adult. During this sorting out process, individual axons undergo a stereotyped sequence of morphological changes that ultimately produce the characteristic pattern of arborization in which axon arbors are restricted in extent only to those layers of the LGN appropriate for the eye of origin (Sretavan and Shatz, 1984, 1986). Here, we examine whether binocular interactions between retinal ganglion cell axons from the two eyes are required for the formation of this restricted pattern of terminal arborization. To examine this question, one eye was removed at embryonic day 23 (E23), when ganglion cell axons have not yet reached the optic chiasm, and the ganglion cell axons from the remaining eye were allowed to develop in the complete absence of binocular interactions. At E59, when segregation into eye-specific layers is normally almost complete, the retinogeniculate projection from the remaining eye was then examined both by anterograde transport following intraocular injections of 3H-leucine and by the in vitro filling of individual ganglion cell axons with HRP. Results from the intraocular injections showed that in the absence of one eye, the remaining eye is still capable of forming both ipsilateral and contralateral optic tracts; however, the projection was distributed diffusely throughout each LGN, rather than being confined to normal eye-specific territories. When individual HRP-filled axons were reconstructed and examined, it was remarkable to find that the pattern of terminal arborization was virtually indistinguishable from normal axons. As usual, arbors were restricted to the distal portion of each axon trunk, and measurements showed that the total linear length of axon contributing to each arbor was within the normal range (enucleated, 2310 +/- 920 microns; normal, 2520 +/- 810 microns). Furthermore, the terminal arborizations of axons appeared to be organized into a series of tiers within the LGN in a pattern surprisingly similar to the pattern of eye-specific layers normally present by E59. Also unchanged was the normally occurring loss of axons from the remaining optic nerve: Counts at E59 showed that about 2.3 X 10(5) axons were present in enucleated animals as compared to 2.5 X 10(5) axons in controls.(ABSTRACT TRUNCATED AT 400 WORDS)
Synaptic functions in rat sympathetic neurons in microcultures. I. Secretion of norepinephrine and acetylcholine
Authors: Furshpan EJ , Landis SC , Matsumoto SG , Potter DD
Published: March 2018

This is the first of a series of four papers that describes the use of a sensitive “microculture” procedure for examining the neurotransmitter profile of a neuron by assaying the transmitter(s) it releases. Sympathetic principal neurons isolated from the superior cervical ganglia of neonatal or adult rats were grown for 10 d to several months on small islands of cardiac myocytes (island diameter, ca. 0.5 mm). To assay transmitter status a neuron and a myocyte in the same microculture were impaled with microelectrodes, the neuron was stimulated and the pharmacology of the effect(s) on the group of electrically coupled myocytes, and on the neuron itself, was investigated. Because the growing axonal processes were confined to the island, the innervation of the myocytes became dense; transmission from neuron to myocytes occurred reliably and was often intense. Most experiments were done on islands containing only a single neuron so that the observed effect(s) on the myocytes could be confidently assigned to that neuron. After the physiological assay, the fine structure or cytochemistry of the neuron was often examined. With single-neuron microcultures the physiology and anatomy of the neuron, including the fine structure of its synaptic endings and varicosities, could be correlated unambiguously. During the course of this work, we have observed five pharmacologically distinct effects exerted on the myocytes by either neonate- or adult-derived neurons. Three of these effects, one exerted at least in large part by adenosine and the others by agents still under study (one appears to be 5-HT), are described by Furshpan et al. (1986), Matsumoto et al. (in press), and D. Sah and S. G. Matsumoto (unpublished observations). This paper is concerned with evidence for secretion by these neurons of norepinephrine (NE) and acetylcholine (ACh). The physiological effects of the secretion of these two substances onto the myocytes (excitation and inhibition, respectively) were generally similar to those reported in vivo. The minimal latencies of the responses were short, probably due to the high density of innervation. ACh secreted by a neuron onto itself, at autapses, evoked fast nicotinic EPSPs. We have not detected autaptic effects attributable to the secretion of NE. A minority of the neurons were detectably only adrenergic or only cholinergic. The incidence of these transmitter states was strongly dependent on culture age and culture conditions; in a heterogeneous group of about 300 reasonably well-characterized neurons about 17% (12% of neonate-derived) were apparently purely adrenergic and about 10% (13% of neonate-derived) were apparently purely cholinergic.(ABSTRACT TRUNCATED AT 400 WORDS)
Regional properties of calcium entry in barnacle neurons determined with Arsenazo III and a photodiode array
Authors: Ross WN , Stockbridge LL , Stockbridge NL
Published: March 2018

Calcium changes were simultaneously measured at many positions on individual neurons from the supraesophageal ganglion of the barnacle by detecting absorbance changes of the indicator dye Arsenazo III with a 10 X 10 photodiode array. These changes were correlated with positions on the stimulated cell determined from Lucifer yellow injections. Absorbance signals were found at all locations on the cells, demonstrating that calcium channels were distributed on the somata, axons, and neuropil processes. By comparing the amplitude of the signal with the membrane area in each region, we could measure the calcium entry per impulse per unit of surface in each part of the cell. Assuming that the properties of the calcium channels are the same in all regions, we determined that calcium channels were distributed uniformly along the commissural axon of one cell and were found at higher density in the neuropil. Because significant calcium changes are only detected when cells are depolarized above about -20 mV, the presence of absorbance signals indicates membrane depolarization above this level. We used this fact to show that calcium spikes propagate along the axon and into the neuropil of one cell, along the axon of another, and not at all in a third. Differences in time course of calcium transients were observed in different regions of cells. The recovery time course was faster at the edge of the cell body than in the center and faster in the neuropil than in the axon or soma. During trains of action potentials or during wide action potentials in tetraethylammonium (TEA) saline, the calcium signal reached a plateau in the neuropil while continuing to rise in the axon and soma.
Relationships between horizontal interactions and functional architecture in cat striate cortex as revealed by cross-correlation analysis
Authors: Ts'o DY , Gilbert CD , Wiesel TN
Published: March 2018

Anatomical studies in the visual cortex have shown the presence of long- range horizontal connections with clustered axonal collaterals, suggesting interactions over distances of several millimeters. We used cross-correlation analysis in cat striate cortex to detect interactions between cells over comparable distances. Using one cell as a reference, we recorded from other cells with a second electrode at varying distances and looked for correlated firing between the two recording sites. This technique allowed us to combine a physiological measure of the strength and type of connection between cells with a characterization of their receptive field properties. The observed interactions were excitatory, and extended over horizontal distances of several millimeters. Furthermore, the interactions were between orientation columns of like specificity, resulting in a waxing and waning in the strength of interaction as the electrodes passed through different orientation columns. We studied relationships between strength of correlation and other receptive field properties and found a tendency for facilitatory interactions between cells sharing the same eye preference. A large proportion of our correlations was due to common input. This feature, and the similarity of interactions between cells in the same column with the reference cell, suggest a high degree of interconnectivity between and within the columns. As the distance between the two electrodes increased, the overlap of the receptive fields of the cells participating in the interactions gradually diminished. At the furthest distances recorded, the cell pairs had nonoverlapping receptive fields separated by several degrees. The distribution and range of these interactions corresponded to the clustering and extent of the horizontal connections observed anatomically.
Cyclic AMP regulates somatostatin mRNA accumulation in primary diencephalic cultures and in transfected fibroblast cells
Authors: Montminy MR , Low MJ , Tapia-Arancibia L , Reichlin S , Mandel G , Goodman RH
Published: March 2018

Although the factors controlling the secretion of the neuropeptide somatostatin have been extensively studied, little is known about the mechanisms that control somatostatin biosynthesis. Somatostatin secretion is regulated by numerous agents that increase intracellular levels of cAMP. We sought to determine whether cAMP also regulates somatostatin mRNA accumulation. We found that forskolin elicited an increase in somatostatin secretion and mRNA levels in primary cultures of rat diencephalic cells. Another secretagogue, KCl, was as effective as forskolin in causing somatostatin secretion but had no effect on mRNA accumulation. Somatostatin expression in fibroblast cells transfected with the somatostatin gene was also regulated by forskolin. These results demonstrate that somatostatin mRNA accumulation can be regulated through a cAMP-dependent pathway, that this pathway is operative in heterologous cells transfected with the somatostatin gene, and that stimulation of somatostatin secretion and mRNA accumulation can be uncoupled from one another.
Diversity in the axonal transport of structural proteins: major differences between optic and spinal axons in the rat
Authors: McQuarrie IG , Brady ST , Lasek RJ
Published: March 2018

Investigations of slow axonal transport reveal variation in both protein composition and the rate of movement. However, these studies involve a variety of nerve preparations in different species, and most lack the resolution needed to determine the kinetics of identified proteins. We have compared the axonal transport of slow-transported proteins in retinal ganglion cells and spinal motor neurons of young rats. Nine proteins that contribute to axonal structures were examined: the neurofilament triplet (NFT), alpha and beta tubulin, actin, fodrin, calmodulin, and clathrin. Axonally transported proteins were pulse- labeled by intraocular or intracord injections of 35S-methionine. After allowing sufficient time for labeled slow-component proteins to enter the spinal or optic nerves, consecutive 2–3 mm nerve segments were subjected to SDS-PAGE. Fluorographs were used as templates for locating the gel regions containing the above polypeptides, and the radioactivity in these regions was measured by liquid-scintillation spectrometry. In retinal ganglion cells, the peak of tubulin labeling advanced at 0.36 mm/d in association with the NFT and fodrin. The cotransport of tubulin and the NFT identified this complex as the slower subcomponent of slow transport, termed slow component a (SCa) and representing the movement of the microtubule-neurofilament network. The peaks of actin and calmodulin labeling were cotransported at 2.3 mm/d in near-register with peaks of fodrin and clathrin labeling. These 4 proteins, moving ahead of the NFT, identified this complex as SCb-- the faster subcomponent of slow transport, which represents the movement of the cytoplasmic matrix and microtrabecular lattice. Both subcomponents had the same composition and rate as that reported for the optic axons of guinea pigs and rabbits, establishing a basic mammalian pattern. In spinal motor axons, the SCa tubulin peak advanced at 1.3 mm/d, and the SCb actin and calmodulin peaks were cotransported at 3.1 mm/d. Unlike optic axons, SCa in motor axons was more heavily labeled than SCb, and included labeled peaks of actin, clathrin, and calmodulin moving in register with the SCa tubulin peak. Actin was the most heavily labeled of these SCb proteins moving with SCa, and it left a higher plateau of radioactivity behind the advancing SCa peak. The SDS-PAGE labeling pattern for SCb did not differ from that seen in optic axons, except that some tubulin was found to form a peak that advanced in register with the actin and calmodulin peaks.(ABSTRACT TRUNCATED AT 400 WORDS)
Consequences of partial axotomy for production of neurotransmitter vesicles and routing of rapidly transported membrane glycoproteins in the axonal tree
Authors: Goldberg DJ , Ambron RT
Published: March 2018

It was found previously that transection of one branch of the bifurcate axon of a giant serotonergic neuron of Aplysia causes a proportionate decrease in the export of transmitter storage vesicles from the cell body, despite the ability of the remaining branch to transport all of the vesicles normally exported (Aletta and Goldberg, 1982). We report here evidence that this down-regulation is achieved by a decrease in the production of vesicles, rather than a slowing of the processing of vesicles for export from the cell body. Counts of serotonergic vesicles in the cell body show that the size of the somal pool of vesicles is not increased at a time when their rate of export has been halved. Also, transection of one or both branches of the axon decreases the amount of 3H-fucose incorporated during a short period into a putative vesicle membrane glycoprotein but not into other glycoproteins. The results indicate that axotomy should be a useful technique for studying the mechanism of regulation of the synthesis of a secretory organelle. It was also previously shown that transection of one branch of the axon far from the cell body does not impair the ability of the injured branch to transport serotonergic vesicles, yet the majority of vesicles that would normally enter that branch are nevertheless rerouted into the uninjured branch. We have studied quantitatively the partitioning between the 2 branches, after one has been transected distally, of 6 fucosyl glycoproteins, including the putative vesicle glycoprotein and a glycoprotein whose transport moderately increases after transection.(ABSTRACT TRUNCATED AT 250 WORDS)