bluuebunny/crossref_metadata_2025 huggingface dataset:
The co-occurrence of a substance P-like peptide and cholecystokinin-8 in a fiber system of turtle cortex
Authors: Reiner A , Eldred WD , Beinfeld MC , Krause JE
Published: March 2018

Single-label and double-label immunohistochemical techniques were used to demonstrate the coexistence of substance P-like immunoreactivity (SPLI) and cholecystokinin-8-like immunoreactivity (CCK-8-LI) in an extensive fiber system within the telencephalic cortex of turtle. All SPLI-containing fibers and terminals of this system contain CCK-8-LI and vice versa. The fibers of this system course from more medial cortical regions to more lateral ones, originating either from neurons in the more medial cortices or from extracortical neurons, the axons of which ascend the medial wall of the cortex. The precise location of the neurons that give rise to this cortical projection system is uncertain, but a hypothalamic location seems most likely at present. The fibers and terminals of this system are found throughout the entire mediolateral and rostrocaudal extent of the telencephalic cortex of turtle and are largely confined to the cell body layer of the cortex. Fewer SPLI/CCK-8-LI-containing fibers are found in pyriform (olfactory) cortex than in the other cortices. Ultrastructural studies indicate that SPLI/CCK-8-LI-containing terminals make asymmetric synapses on cell bodies or their proximal dendrites. Both SPLI and CCK-8-LI are found in large dense core vesicles in these labeled terminals. Labeled terminals also contained numerous small, round, unlabeled vesicles clustered near synaptic release sites and a number of unlabeled large dense core vesicles. Quantification of the percentage of the large dense core vesicles that were labeled in SP-labeled terminals, in CCK-8- labeled terminals, and in terminals labeled for both SP and CCK-8 provided suggestive evidence that SPLI and CCK-8-LI must be contained within the same large dense core vesicles. Radioimmunoassay indicated that the SP/CCK-8-containing system of turtle cortex contains 0.93 +/- 0.090 pg of SP/microgram of cortical tissue protein and 0.31 +/- 0.11 pg of CCK-8/micrograms of cortical tissue protein. The CCK-8-like material in turtle cortex coelutes with CCK-8-sulfate, using gradient elution high pressure liquid chromatography (HPLC). The SP-like material, although immunologically highly similar to undecapeptide SP (Reiner, A., J. E. Krause, K. T. Keyser, W. D. Eldred, and J. F. McKelvy (1984) J. Comp. Neurol. 226: 50–75), does not coelute with undecapeptide SP using gradient elution HPLC.
Ontogeny of brain nuclei controlling song learning and behavior in zebra finches
Authors: Bottjer SW , Glaessner SL , Arnold AP
Published: March 2018

An anatomically discrete system of interconnected brain nuclei controls production of learned song patterns in adult male zebra finches (Poephila guttata). The corresponding nuclei in females, who do not sing, are greatly reduced in volume. Cells in some telencephalic song- control nuclei accumulate androgens, and male nuclei contain a much higher proportion of hormone-concentrating cells than do female nuclei. The main purpose of this experiment was to examine the normal ontogeny of the total volume of various telencephalic nuclei that have been directly or indirectly implicated in song learning and behavior in male zebra finches. In addition, the corresponding nuclei of age-matched females were examined. The major findings were as follows: the volumes of the caudal nucleus of the ventral hyperstriatum (HVc), the robust nucleus of the archistriatum (RA), and area X increased sharply in males between 12 and 53 days of age, whereas brain regions not involved with song control increased much less. Increases in the size of HVc occurred prior to those in RA and area X. Previous studies have shown that males are learning the auditory and motor characteristics of song during this time. In contrast, the volume of the magnocellular nucleus of the anterior neostriatum (MAN) decreased precipitously in males between 25 and 53 days. Measurements of neuron density and soma size demonstrated that this decreased volume is attributable to a loss of greater than 50% of the neurons in MAN. We have previously shown that lesions of MAN during this time completely disrupt song development. The volumes of HVc and RA were smaller in females than in males at all ages studied. Between 12 and 25 days the volumes of female HVc and RA increased less than brain regions not involved with song control. Female HVc and RA decreased slightly in volume between 25 and 53 days.
Membrane potential and response changes in mammalian cochlear hair cells during intracellular recording
Authors: Dallos P
Published: March 2018

In the preceding paper (Dallos, P. (1985) J. Neurosci. 5: 1591–1608) some fundamental properties of cochlear inner and outer hair cells were considered. On the basis of intracellular recording from the low frequency region of the guinea pig cochlea, such measures as membrane potentials, the dependence of AC and DC receptor potential magnitude on stimulus level and frequency, and tuning characteristics relative to gross responses were discussed. During prolonged recording various changes in membrane and receptor potentials were observed. In the present paper the relationship between these variations is described and evaluated in the context of a simple hair cell model.
Properties of visual inputs that initiate horizontal smooth pursuit eye movements in monkeys
Authors: Lisberger SG , Westbrook LE
Published: March 2018

Smooth pursuit eye movements allow primates to fixate and track small, slowly moving objects. Pursuit usually requires visual targets; our aim was to determine the properties of the visual signals transmitted to the pursuit motor system. Rhesus monkeys were rewarded for tracking spots of light that underwent discreet changes in velocity under a variety of visual conditions. We measured the resulting smooth eye acceleration in a 100-msec interval that began with the initiation of pursuit and ended before there had been time for visual feedback. This approach allowed us to vary the parameters of visual stimulation and measure eye movement responses in a way that provides estimates of the properties of signals transmitted by visual pathways. The initiation of pursuit showed different properties early and late in the interval we studied. In the first 20 msec of pursuit, eye acceleration was in the correct direction, but was independent of the initial position of the moving images, the velocity of the stimulus, or the presence or absence of background illumination. Thereafter, the initiation of pursuit depended strongly on all of the above parameters. Eye acceleration was highest when the moving images fell close to the fovea and decreased sharply as eccentricity was increased up to 21 degrees. When the background was diffusely illuminated, eye acceleration showed velocity selectivity; it was highest for a middle range of velocities (30 to 60 degrees/sec) and decreased for higher velocities. When the background was dark, eye acceleration increased as a function of target velocity up to 150 degrees/sec. We conclude that the initiation of pursuit has at least 2 visual components. The two components have different latencies and show quite different relationships to the visual properties of the stimulus, suggesting two cell populations that could provide the visual inputs for pursuit.
Development of neuromuscular specificity in the grasshopper embryo: guidance of motoneuron growth cones by muscle pioneers
Authors: Ball EE , Ho RK , Goodman CS
Published: March 2018

In the grasshopper embryo, neuromuscular specificity develops between individual identified motoneurons whose cell bodies are located in the central nervous system, and specific skeletal muscles in the periphery. We previously reported on a class of large mesodermal cells, called muscle pioneers (MPs), that arise early in development (Ho, R. K., E. E. Ball, and C. S. Goodman (1983) Nature 301: 66–69). We suggested that the MPs might be involved in orchestrating the coordinated development of nerve and muscle. In this paper, we describe the development of the MP for coxal muscle 133a in the metathoracic limb bud, and its innervation by two excitatory motoneurons (fast, Df, and slow, Ds). Although many motoneuron growth cones extend out of nerve 5 and quite likely come in contact with the 133a MP between 35% and 45% of development, only Df and Ds display a high affinity for its surface; the other motoneurons innervate more distal leg muscles. When the 133a MP is ablated before arrival of motoneurons in the limb bud, the Df growth cone extends past the location where it normally gets off nerve 5 and continues to extend distally along the same pathway taken by its sibling motoneuron. Although there is a mass of small mesodermal cells in the area where the differentiated coxal muscle 133a normally forms, evidently it does not provide the necessary guidance cue for the Df growth cone. These results indicate the important role played by MPs in the specific guidance of motoneuron growth cones in the grasshopper embryo.
Immunopurification and characterization of a neuronal heparan sulfate proteoglycan
Authors: Matthew WD , Greenspan RJ , Lander AD , Reichardt LF
Published: March 2018

We have identified a unique heparan sulfate (HeS) proteoglycan synthesized by the neuronal-like cell line PC12. The proteoglycan, purified with monoclonal antibodies from medium conditioned by PC12 cells, has an apparent molecular weight of 350,000, and it contains a Mr 80,000 core protein and HeS side chains of Mr 15,000 each. The purified molecule has the same apparent size and density as it has in conditioned medium. HeS proteoglycans that are indistinguishable antigenically but very difficult to solubilize are found on the external surface and in the interior of PC12 cells and neurons. Mild proteolysis converts the surface proteoglycan into a molecule closely resembling that found in the medium. The same surface antigens are also present on a subpopulation of T-cells and on a non-neuronal accessory cell found in dorsal root ganglion cultures. The PC12 cell line and the non-neuronal dorsal root ganglion cells secrete a factor into medium that, after adsorption to polylysine-coated surfaces, induces rapid neurite out-growth by primary sympathetic neurons. The monoclonal antibodies used to purify the neuronal HeS proteoglycan from PC12 cells are capable of depleting this conditioned medium of its neurite- promoting activity. These studies suggest that a HeS proteoglycan synthesized and secreted by neurons and certain accessory cells plays a role in regulating neurite outgrowth.
Optical mapping of electrical activity in rat somatosensory and visual cortex
Authors: Orbach HS , Cohen LB , Grinvald A
Published: March 2018

We have investigated the use of optical methods for monitoring neuron activity in mammalian cortex. The cortex was stained with a voltage- sensitive dye and fluorescence was simultaneously measured from 124 areas using a photodiode array. Optical signals were detected in rat somatosensory cortex in response to small whisker movements and in visual cortex in response to light flashes to the eye. Relatively large signals were obtained during focal interictal epileptiform discharges induced by bicuculline. The measuring system had a time resolution of milliseconds and a spatial resolution of a few hundred micrometers. Simultaneous, multi-site optical recordings of activity may provide a new and potentially powerful method for studying function and dysfunction in mammalian cortex.
Characterization of GABAergic neurons in cerebellar primary cultures and selective neurotoxic effects of a serum fraction
Authors: Aloisi F , Ciotti MT , Levi G
Published: March 2018

The morphological and functional differentiation of GABAergic interneurons present in cerebellar primary cultures has been examined by means of [3H]gamma-aminobutyric acid (GABA) autoradiography and [3H]GABA depolarization-evoked release. At 2 days in vitro these neurons showed scarce accumulation of radioactivity and no Ca2+- dependent K+-evoked or veratridine-induced release of [3H]GABA. At 5 days in vitro GABAergic interneurons appeared more intensely labeled and had grown out long and often branched neuritic processes; a large Ca2+-dependent release of [3H] GABA could be evoked by high K+. At later stages the progressive increase in labeling and branching of the neuritic processes was paralleled by a further increase in the amount and Ca2+ dependence of [3H]GABA release; a tetrodotoxin-sensitive, veratridine-stimulated release was also demonstrated. The [3H]GABA- accumulating stellate astrocytes present in the culture were not responsible for the observed release of the amino acid. GABAergic neurons were also identified by indirect immunofluorescence, using antibodies to the specific marker glutamic acid decarboxylase. Total renewal of the culture medium at 7 days in vitro caused a drastic (90%) reduction in the number of GABAergic neurons and a concomitant decrease in the amount of [3H]GABA uptake and release in the cultures. The disappearance of GABAergic neurons was caused by a low molecular weight (Mr less than 1000) fraction of the serum used to supplement the basal culture medium. This serum component did not significantly influence the survival of the major neuronal population of the culture (the granule cells) and appeared to be selectively toxic for GABAergic neurons only after they had reached a quite advanced degree of morphological and functional differentiation in vitro. The toxic activity was no longer present in neuronal or glial conditioned media.
Effects of elimination of activity on contractile and histochemical properties of rat soleus muscle
Authors: Spector SA
Published: March 2018

Morphological, contractile, and histochemical properties of rat soleus muscle were studied after 2 or 4 weeks of complete elimination of neuromuscular activity. Inactivity was induced by chronic perfusion of tetrodotoxin (TTX) to the sciatic nerve. Significant reductions in muscle mass and fiber size were found after 2 or 4 weeks of disuse. Correspondingly, the percentage of dark-staining alkaline myosin ATPase fibers was increased from about 20% to 40% after 4 weeks of treatment. The capacity of soleus to generate tension when stimulated through the nerve was significantly impaired at frequencies greater than 20 Hz. Nevertheless, when the curarized muscle was stimulated directly, tension developed at frequencies above 20 Hz relative to peak tension was similar to control values. Absolute tetanic tension was significantly reduced after 2 or 4 weeks of treatment. These reductions could be only partly explained by muscle atrophy, resulting in specific tensions or approximately 55% of control after 2 or 4 weeks of treatment. Measures of the time course of the isometric twitch were found not to be reliable indicators of the contractile speed in TTX- treated soleus. Significant increases in the rate of tetanic tension development, expressed relative to peak tension, and the velocity of unloaded shortening, were seen after 4 weeks of disuse. These results reveal the extent to which virtually complete neuromuscular inactivity leads to chronic deficits in neuromuscular transmission and changes in both the net amount and quality of contractile proteins of rat soleus muscle.
Astrocytes in culture synthesize and secrete a variant form of fibronectin
Authors: Price J , Hynes RO
Published: March 2018

Astrocytes in culture have very little cell surface fibronectin as detected by iodination or immunocytochemistry. Nonetheless, they synthesize and secrete this glycoprotein in amounts comparable with the production by fibroblasts. Astrocyte fibronectin has properties in common with other forms of the protein. It binds to gelatin- and heparin-coupled Sepharose and it is recognized by specific anti- fibronectin sera. It also exists as a dimer under non-reducing conditions. However, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), astrocyte fibronectin appears larger, under both reduced and non-reduced conditions, than other cellular fibronectins. This apparent size difference is not the result of post- translational modifications. If the cultures are treated with tunicamycin, the astrocytes produce fibronectin that is unglycosylated, as shown by [3H]glucosamine labeling, and is neither sulfated nor phosphorylated as indicated by [35S]O4 and [32P]O4 labeling studies. This astrocyte-derived, carbohydrate-free fibronectin resolves on SDS- PAGE as four bands, of which the heavier ones predominate. Fibroblasts produce a similar set of four bands, but in this form of fibronectin the less heavy bands predominate. Thus, we conclude that fibronectin is a major secreted protein of astrocytes in vitro and that these cells produce a variant form of the protein which is enriched in the higher molecular weight subunits.
The morphology of physiologically identified GABAergic neurons in the somatic sensory part of the thalamic reticular nucleus in the cat
Authors: Yen CT , Conley M , Hendry SH , Jones EG
Published: March 2018

Neurons with somatic sensory receptive fields were examined electrophysiologically in the thalamic reticular nucleus of the cat. All cells had receptive fields much larger than those of neurons in the ventral posterior nucleus and were driven by less readily defined somesthetic stimuli. Response latencies to peripheral or medial lemniscal stimulation were, on average, longer than in the ventral posterior nucleus and suggested activation of the reticular nucleus cells by collaterals of thalamocortical relay cell axons arising in the ventral posterior nucleus. When injected intracellularly with horseradish peroxidase, reticular nucleus cells displayed thin axons with intrareticular collaterals and diffuse branches through much of the ventral posterior and posterior thalamic nuclei. Dendrites ended in processes resembling synaptic terminals. Electron microscopic immunocytochemistry of the same part of the reticular nucleus revealed processes immunoreactive for glutamic acid decarboxylase and identifiable as both collateral axon terminals and presynaptic dendrites of GABAergic reticular nucleus cells. These synaptically linked reticular nucleus cells and, in addition, immunoreactive somata and presynaptic dendrites received synapses from at least three varieties of nonimmunoreactive profiles.
Structure and function of electrosensory neurons in the torus semicircularis of Eigenmannia: morphological correlates of phase and amplitude sensitivity
Authors: Rose G , Heiligenberg W
Published: March 2018

Structure-function relations in the electrosensory system of Eigenmannia were examined by labeling physiologically characterized neurons of the dorsal torus semicircularis. The sensitivity of cells to modulations in amplitude (AMs) and modulations in differential phase was determined. Approximately half of the 48 cell types defined by Golgi studies (Carr, C.E., and L. Maler (1985) J. Comp. Neurol. 235: 207–240) were identified in this manner. The majority of the neurons located in laminae (8a, b, c, and d, and 9 exhibited sensitivity to differential phase. In laminae 5 and 7, however, in addition to neurons which were sensitive to differential phase, many cells were found that were purely AM sensitive. Differential phase sensitivity originates in the small cells of lamina 6 (Heiligenberg, W., and G. Rose (1985) J. Neurosci. 5: 515–531), the exclusive termination site of phase-coding afferents from the electrosensory lateral line lobe. Cells that had dendritic extensions into the neuropil of lamina 6 exhibited sensitivity to differential phase, whereas neurons lacking dendrites in this lamina were only excited by AMs. These findings support the notion of a relationship between the morphology and laminar position of a neuron and its function.
Multiple marker analysis in the avian optic tectum reveals three classes of neuroglia and carbonic anhydrase-containing neurons
Authors: Linser PJ
Published: March 2018

The distribution and biochemical diversity of neuroglial cells in the avian optic tectum were analyzed using immunohistochemical techniques. Polyclonal and monoclonal antibodies were employed to define the distributions and localizations of four proteins that are considered to be glial-specific in the mammalian central nervous system: glutamine synthetase, carbonic anhydrase-C, glial fibrillary acidic protein, and S-100 protein. The results showed the presence of at least three distinguishable populations of glia: glutamine synthetase/glial fibrillary acidic protein-positive fibrous astrocytes, glutamine synthetase/carbonic anhydrase-C-positive protoplasmic astrocytes, and S- 100-positive oligodendroglia. In addition, a distinct population of neurons was observed that showed very intense immunostaining for the presence of carbonic anhydrase-C. The results suggest that the segregation of biochemical functions in the major categories of brain neuroglial cells (oligodendroglia and astroglia) varies significantly between vertebrate species. This observation raises the possibility of using comparative studies to refine our understanding of the roles that glial cells play in nervous tissue.
Dissociated neurons regenerate into sciatic but not optic nerve explants in culture irrespective of neurotrophic factors
Authors: Schwab ME , Thoenen H
Published: March 2018

Explants of adult or 10-day-old rat sciatic and optic nerves were implanted as “bridges” through a silicon grease seal in a three- compartment chamber culture system, leading from a narrow center chamber to two adjacent side chambers. Dissociated newborn rat sympathetic or sensory neurons were plated into the center chamber and grown in the presence of optimal concentrations of nerve growth factor (NGF). By light microscopy, nerve fibers were seen to grow out of the sciatic nerve explants in the side chambers after 2 to 3 weeks. Electron microscopy showed large numbers of axons present inside the sciatic nerves, irrespective of the presence and number of living Schwann cells. Besides their tendency to fasciculate, axons grew with high preference on Schwann cell membranes and the Schwann cell side of the basal lamina, a situation identical to in vivo regeneration. In contrast to the sciatic nerves, no axons could be found under any condition in the optic nerves. This result points to the existence of extremely poor, non-permissive substrate conditions in the differentiated optic nerves which cannot be overcome by the strong fiber outgrowth-promoting effects of NGF.
Local order among the dendrites of an amacrine cell population
Authors: Tauchi M , Masland RH
Published: March 2018

The cholinergic amacrine cells of the rabbit retina branch within a narrow stratum of the retina's inner synaptic layer, and their dendritic fields overlap as much as 70-fold. Because each cell's dendrites have many branches, the overlap must create a dense meshwork of cholinergic dendrites. To learn how the overlapping dendrites are positioned with respect to each other, we filled the dendrites of groups of neighboring cells with Lucifer Yellow CH. The cholinergic amacrine cells were selectively stained by intraocular injection of the fluorescent molecule 4,6-diamidino-2-phenylindole. The retinas were then fixed with 2% paraformaldehyde and 0.01% glutaraldehyde. The stained cells were penetrated under visual control by Lucifer Yellow- filled micropipettes. A systematic arrangement of the dendrites was observed. When a pair of cells was injected, their dendrites were often seen to lie alongside each other. In the terminal dendritic region, there are virtually no dendrites that do not end in apposition to a dendrite of a neighboring cholinergic amacrine cell. When small clusters of nearby cells were injected, an ordered microstructure appeared. The dendrites of the cells join together to form curving bundles, which enclose spaces that rarely contain any cholinergic dendrites: the appearance of the dendritic mosaic is that of a lattice with a repeating unit roughly 10 microns in diameter. The significance of this ordering is not certain, but it is possible that the repeating structural unit participates in a modular functional arrangement.
Immunoblot analysis of horseradish peroxidase conjugates of wheat germ agglutinin before and after retrograde transport in the rat peripheral nervous system
Authors: Schmidt ML , Trojanowski JQ
Published: March 2018

Immunoblot studies were performed on tissue extracts of rats injected with horseradish peroxidase (HRP) conjugates of wheat germ agglutinin (WGA) using anti-HRP and anti-WGA antisera. Immunoblots of uninjected, purified conjugates (WGA-HRP) demonstrated a 62-kilodalton (kd) conjugate (monomeric WGA conjugated to HRP). Other prominent immunobands included HRP (40 kd), monomeric WGA (22 kd), and 15- to 30- kd HRP breakdown products. Following injections of WGA-HRP into the submandibular gland of rats which survived 16 hr to 8 days, immunoblots were performed on homogenates of injected submandibular glands and of superior cervical ganglia containing neurons retrogradely labeled with WGA-HRP. The anti-HRP antiserum detected unconjugated, 40-kd HRP and a 62-kd immunoband corresponding to WGA-HRP in the superior cervical ganglia and submandibular glands. No immunobands were detected with the antiserum to WGA in superior cervical ganglia homogenates. Blots of submandibular gland homogenates harvested 24 hr after a WGA-HRP injection, but not at later time points, contained an immunoband reactive with the anti-WGA antiserum; it corresponded to monomeric WGA. These studies analyze for the first time the molecular composition of WGA-HRP conjugates before and after retrograde transport; they provide a novel approach for probing the intraneuronal transport and degradation of proteins. We conclude that morphologically defined endocytic pathways using protein markers reflect the endocytosis and transport of immunochemically altered and unaltered forms of the markers.
Proteins rapidly transported to the synapses of a single identified neuron of Aplysia californica
Authors: Ambron RT , Schacher S , Rayport SG
Published: March 2018

The cell body of R2, a giant cholinergic neuron of Aplysia californica, resides in the abdominal ganglion, whereas its synapses are on thousands of unicellular mucus glands located in the skin. Due to the great spatial separation between the site of macromolecular synthesis and the presynaptic terminals, rapid axonal transport can be used to segregate synaptic proteins from those to be used elsewhere in the cell. The proteins of R2 were labeled by incubating the abdominal ganglion in [35S]methionine for 5 hr in a chamber separated from the rest of the isolated central nervous system. After 50 hr, 28 radiolabeled proteins were reproducibly found by one- and two- dimensional polyacrylamide gel electrophoresis to be transported to the distal regions of peripheral nerves P6, P7, and P8 that innervate the parapodia and middle body wall. We are sure that R2 is the source of these proteins since radioautography of sections taken throughout the nervous system, complemented by cobalt tracings, showed that R2 is the only neuron in the abdominal ganglion with axons in these nerves. Nine of the 28 transported proteins are glycoproteins since they were also labeled after injecting R2's cell body with [3H]-L-fucose. There is evidence that the proteins and glycoproteins are destined for R2's presynaptic terminals. For example, in experiments in which the body wall and parapodium remained attached to the nerves, the proteins were transported to the skin region that contains the glands. Moreover, analyses of the distribution of the rapidly transported proteins by qualitative radioautography and by extrusion of axoplasm indicated that none are constituents of the axolemma.(ABSTRACT TRUNCATED AT 250 WORDS)
Responses to odors mapped in snail tentacle and brain by [14C]-2- deoxyglucose autoradiography
Authors: Chase R
Published: March 2018

The method of 2-deoxyglucose (2-DG) autoradiography has been widely used to map functional neuronal systems in vertebrates, but in invertebrate species, where morphological dimensions favor its use, the applications have been minimal. This study uses [14C]-2-DG to map the olfactory system of a terrestrial snail, Achatina fulica. The olfactory organ in the snail's tentacles bears a striking resemblance to the vertebrate olfactory mucosa. There are also complex neural structures in the tentacle and brain that are devoted to subsequent processing. These facts make the molluscan olfactory system a suitable complement to the traditional vertebrate and insect models in olfaction. The experiments utilized intact snails in which one tentacle was exposed to a controlled odor environment while the contralateral tentacle was held in a retracted position. The dose of [14C]-2-DG (2 microCi/gm) was injected into the hemocele. Tissue processing involved freeze- substitution with acetone, dry sectioning, and the preparation of liquid film autoradiographs. Optical density measurements permitted quantitative comparisons between experimental conditions. The natural odors of conspecific snails and of carrots elicited significantly more uptake of 2-DG in the exposed tentacle than in the unexposed tentacle and, in the exposed tentacle, significantly more label over the axons of the primary sensory neurons than was elicited by exposure to clean air. Amyl acetate and octanol were less effective. A small number of superficially placed sensory neurons were labeled in all stimulus conditions, including clean air, and may represent the mechanosensors. Stimulus-dependent labeling in the brain was limited to the procerebrum and included both neuropilar and cellular parts. In contrast to vertebrate and insect olfactory systems, there was no evidence of spatial coding for odor quality.
Regular alternation of fiber types in the transversus abdominis muscle of the garter snake
Authors: Wilkinson RS , Lichtman JW
Published: March 2018

The snake transversus abdominis muscle is an extremely simple segmentally repeating muscle containing 80 to 100 muscle fibers in a single-fiber-thick sheet. This muscle exhibits a striking pattern of muscle fiber types: twitch fibers alternate with tonic fibers and, among the twitch fibers, slower and faster contracting subtypes also alternate. Thus, in many regions of the muscle the pattern of fiber types is: faster twitch, tonic, slower twitch, tonic, faster twitch, tonic, and so on. The existence of a spatial pattern of fiber types, perhaps discernible in this muscle because of the muscle's extreme geometrical simplicity, provides good evidence for an intrinsic component to muscle fiber differentiation.
Experience alters the spatial tuning of auditory units in the optic tectum during a sensitive period in the barn owl
Authors: Knudsen EI
Published: March 2018

The auditory spatial tuning of bimodal (auditory-visual) units in the optic tectum of the barn owl was altered by raising animals with one ear occluded. Changes in spatial tuning were assessed by comparing the location of a unit's auditory best area with that of its visual receptive field. As shown previously, auditory best areas are aligned with visual receptive fields in the tecta of normal birds (Knudsen, E. I. (1982) J. Neurosci. 2: 1177–1194). It was demonstrated in this study that, when birds were raised with one ear occluded, best areas and visual receptive fields were aligned only as long as the earplug was in place. When the earplug was removed, best areas and visual receptive fields became misaligned, indicating that a change in auditory spatial tuning had taken place during the period of occlusion. However, in a bird that received an earplug as an adult, no such alterations in auditory spatial tuning were observed; even after 1 year of monaural occlusion, auditory best areas and visual receptive fields were misaligned so long as the earplug was in place, and were aligned when the earplug was removed. These results suggest that exposure to abnormal localization cues modifies the auditory spatial tuning of tectal units only during a restricted, sensitive period early in development. After the earplug was removed from a juvenile bird that had been raised with an occluded ear, the initial misalignment between auditory best areas and visual receptive fields decreased gradually over a period of weeks. In contrast, when earplugs were removed from two adult birds that had been raised with monaural occlusions, auditory- visual misalignments persisted for as long as measurements were made, which was up to 1 year after earplug removal. These data indicate that auditory cues become permanently associated with locations in visual space during a critical period which draws to a close at about the age when the animal reaches adulthood. Horseradish peroxidase was injected into two optic tecta (in a single animal) that contained units with permanently altered auditory spatial tuning. The positions of retrogradely labeled cells in the external nucleus of the inferior colliculus (ICX) were the same as those observed in control birds (Knudsen, E. I., and P. F. Knudsen (1983) J. Comp. Neurol. 218: 187–196). Thus, the changes in spatial tuning were not due to a shift in the topographic projection from the ICX to the optic tectum.(ABSTRACT TRUNCATED AT 400 WORDS)
125I-lysergic acid diethylamide binds to a novel serotonergic site on rat choroid plexus epithelial cells
Authors: Yagaloff KA , Hartig PR
Published: March 2018

125I-Lysergic acid diethylamide (125I-LSD) binds with high affinity to serotonergic sites on rat choroid plexus. These sites were localized to choroid plexus epithelial cells by use of a novel high resolution stripping film technique for light microscopic autoradiography. In membrane preparations from rat choroid plexus, the serotonergic site density was 3100 fmol/mg of protein, which is 10-fold higher than the density of any other serotonergic site in brain homogenates. The choroid plexus site exhibits a novel pharmacology that does not match the properties of 5-hydroxytryptamine-1a (5-HT1a), 5-HT1b, or 5-HT2 serotonergic sites. 125I-LSD binding to the choroid plexus site is potently inhibited by mianserin, serotonin, and (+)-LSD. Other serotonergic, dopaminergic, and adrenergic agonists and antagonists exhibit moderate to weak affinities for this site. The rat choroid plexus 125I-LSD binding site appears to represent a new type of serotonergic site which is located on non-neuronal cells in this tissue.
Intrinsic connections of macaque striate cortex: axonal projections of cells outside lamina 4C
Authors: Blasdel GG , Lund JS , Fitzpatrick D
Published: March 2018

We have exploited a technique for making small injections of horseradish peroxidase into single cortical laminae in order to study axonal projections in macaque striate cortex. In the preceding paper (Fitzpatrick, D., J. S. Lund, and G. G. Blasdel (1985) J. Neurosci. 5: 3329–3349) we examined the projections of cells in lamina 4C--cells that receive most of their input from the lateral geniculate nucleus. The present paper deals with the projections of neurons that lie outside of lamina 4C. Among our findings are several projections that previously had not been described in the monkey. These include: a strong and precise (point-to-point) projection from lamina 4B to lamina 2/3A, a reciprocal projection from 2/3A back to 4B, a definite projection from lamina 4B to 5B, as well as a prominent input to lamina 6 from 5B. In many cases, we find it possible to trace the flow of visual information through several “circuits” in striate cortex that have, as their output, projections to extrastriate cortex or to the brainstem. Our results offer additional insights in this regard since we are able, in many cases, to compare the lateral spreads of particular projections. These vary and can be separated into at least three categories: those that terminate in a precise, point-to-point, fashion, those that spread widely, and those that terminate in a laterally periodic fashion. In several cases we find evidence for a correlation between specific patterns of projection and known physiological differences between the topographies of laminae that are connected. In cases where two laminae possess similar topographies (for example, where both contain orderly maps for orientation) their interconnections appear precise, with little diffuse spread. In cases where two laminae are characterized by strikingly different topographies (where, for example, one contains an orderly map for orientation and the other a precise map for retinotopic position, but no specificity for orientation), the connections appear more diffuse.
Coexistence of adenosine deaminase, histidine decarboxylase, and glutamate decarboxylase in hypothalamic neurons of the rat
Authors: Senba E , Daddona PE , Watanabe T , Wu JY , Nagy JI
Published: March 2018

Neurons immunoreactive for the enzyme adenosine deaminase (ADA) in the posterior basal hypothalamus of the rat have a distribution pattern similar to those immunoreactive for histidine decarboxylase (HDC) and are particularly numerous in the tuberal (TM), caudal (CM) and postmammillary caudal (PCM) hypothalamic magnocellular nuclei which harbor neurons containing glutamic acid decarboxylase (GAD). The extent to which these enzymes coexist within neurons of these hypothalamic regions was examined using either serial sections or simultaneous immunostaining for ADA and HDC or GAD in the same section. Analysis of serial sections revealed neuronal coexistence of ADA with HDC or GAD in both TM and CM. In addition some neurons in CM, the only area examined for triple coexistence, were found to contain all three enzymes. In sections processed for ADA simultaneously with HDC or GAD, nearly all ADA-immunoreactive neurons in TM, CM, and PCM as well as those scattered between these nuclei were found to contain HDC, and nearly all contained GAD. Exceptions to this, however, were small cells located lateral to the posterior arcuate nucleus, which appeared to contain ADA but not HDC, and large neurons located at the anterior extreme of TM, which appeared to contain ADA but not GAD. The relatively few ADA- compared with GAD-containing neural systems in brain, together with the presence of ADA in GAD-containing hypothalamic magnocellular neurons, which appear to have widespread projections throughout the brain, indicate that ADA may be a convenient immunohistochemical marker for anatomical investigations of these projections.(ABSTRACT TRUNCATED AT 250 WORDS)
Co-localization and characterization of immunoreactive peptides derived from two opioid precursors in guinea pig adrenal glands
Authors: Evans CJ , Erdelyi E , Hunter J , Barchas JD
Published: March 2018

Peptides derived from both proenkephalin and prodynorphin have been identified in guinea pig adrenal medulla. In extracts of whole adrenal glands radioimmunoassays directed to the prodynorphin-derived peptides alpha-neoendorphin, dynorphin A, and dynorphin B detected high concentrations of immunoreactive material ranging from 113 to 216 pmol/gm. The concentrations measured by radioimmunoassays directed to the proenkephalin products met-enkephalin-Arg-Gly-Leu and met- enkephalin-Arg-Phe were 878 and 484 pmol/gm, respectively. No metorphamide or dynorphin(1–8) could be detected in the adrenals. Leucine-enkephalin immunoreactivity which can be generated from either prodynorphin or proenkephalin could also be measured in the extracts. Gel filtration showed the immunoreactive material, with the exception of that measured by the alpha-neoendorphin radioimmunoassay, to be predominantly of high molecular weight ranging from Mr = 3,000 to 12,000. Immunocytochemistry, using well characterized antisera to alpha- neoendorphin and met-enkephalin-Arg-Gly-Leu, demonstrated that the prodynorphin and proenkephalin products were present in the same cells in the medulla region of the gland. The results show that two opioid peptide precursors can be localized in the same cells and exhibit some common features in their processing. As a relatively homogeneous, localized system, the guinea pig adrenal gland should prove a valuable, in vivo model for the study of co-localized opioid precursors.
Regulation of the circadian clock in the Aplysia eye: mimicry of neural action by serotonin
Authors: Nadakavukaren JJ , Lickey ME , Jordan WP
Published: March 2018

In Aplysia, activity of efferent fibers in the optic nerve can influence the circadian clock in the eye. In addition, serotonin (5-HT) is present in the eye and influences the function of the clock. Accordingly, we hypothesized that 5-HT is the transmitter of the optic efferents, and tested the prediction that exogenous 5-HT would mimic the action of the optic efferents on the clock. We also tested the prediction that the action of the efferents would be prevented by blocking synaptic secretions with high Mg2+, low Ca2+ (HMLC). Activity of the optic efferents enhances clock resetting in response to the onset of darkness. We used this neural enhancement as a measure of neural action on the eye clock. We found that HMLC blocked neural enhancement. Serotonin enhanced resetting to the same extent as efferent activity. Enhancement by 5-HT did not summate with neural enhancement. High concentrations of 5-HT ([5-HT] greater than or equal to 6 X 10(-4) did not cause enhancement. High concentrations of 5-HT also blocked neural enhancement. Enhancement by 5-HT depended on the phase of drug application, much as neural enhancement depends on the phase of neural activity. Enhancement by 5-HT depended on day length in a manner similar to the enhancement by neural activity. HMLC did not block the facilitatory action of 5-HT. Several other transmitters that may be active in the eye did not enhance resetting.(ABSTRACT TRUNCATED AT 250 WORDS)
Localization of a filamin-like protein in glia of the chick central nervous system
Authors: Lemmon V
Published: March 2018

Monoclonal antibody 5E10 binds to Muller cells in the chick retina and radial glia in the optic tectum. Biochemical and immunohistochemical experiments indicate that the 5E10 antigen is related to, but may not be identical to, filamin, a high-molecular-weight, actin-binding protein. Developmental studies show that the 5E10 antigen is present in all neuroepithelial cells very early in development, but disappears by about Embryonic Day 10. These results suggest that neurons developmentally regulate not only the type of intermediate filament proteins they express, switching from vimentin to neurofilaments, but also the type of actin-binding proteins.
NIF (neurite-inducing factor): a novel peptide inducing neurite formation in PC12 cells
Authors: Wagner JA
Published: March 2018

Neurite-inducing factor (NIF) is a novel protein that has been partially purified from mouse submaxillary glands. NIF induces neurite formation in PC12 pheochromocytoma cells, and the NIF-induced neurites are indistinguishable from NGF-induced neurites in both their morphology and the time course of their formation. Neurite-inducing activity can be recovered at a position corresponding to a molecular weight of 20,000 Da after fractionation of partially purified preparations via SDS-PAGE. Partially purified preparations of NIF are about half as potent as pure beta NGF, and since the neurite-inducing activity does not correspond to any of the major proteins in this fraction, specific activity of purified NIF will probably be significantly greater than the 60 ng/ml found for our partially purified material. NIF is distinct from beta NGF by four criteria: (1) antibodies to beta NGF can block the activity of beta NGF, but not the activity of NIF; (2) beta NGF can induce ornithine decarboxylase (ODC) in PC12 cells at concentrations significantly below those required to induce neurites, while NIF induces ODC only at concentrations greatly in excess of those required to induce neurite formation; (3) by the criterion of SDS-PAGE, there is insufficient beta NGF in our partially purified preparations of NIF to explain the biological activity of this fraction; and (4) the biological activity of NIF has a molecular weight (20,000 Da) that is distinct from beta NGF (13,000 Da). We conclude that NIF is probably a novel peptide that is very active in promoting morphological differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)
Reticularis thalami neurons revisited: activity changes during shifts in states of vigilance
Authors: Steriade M , Domich L , Oakson G
Published: March 2018

This study tested the hypothesis that inhibitory actions are exerted by reticularis thalami (RE) neurons upon thalamocortical neurons. The RE neurons were recorded in the rostral pole and lateral districts of the nucleus, and were activated monosynaptically by cortical volleys. Thalamocortical neurons were identified antidromically in intralaminar and ventrolateral nuclei. During sleep with EEG synchronization, prolonged spike barrages of RE neurons extended over the whole spindle sequences. This result suggests that RE neurons are depolarized throughout spindle oscillations, whereas thalamocortical neurons show, simultaneously, long hyperpolarizations and short rebounds. During waking, parallelism rather than reciprocity was found between RE and thalamocortical neurons. Spontaneous discharge rates almost doubled in RE neurons on arousal from sleep, and the probability of cortically evoked short-latency discharges increased. The increase in spontaneous firing rates of RE neurons during natural arousal is consistent with their short-latency synaptic excitation by stimulating the rostral brain stem reticular formation after chronic degeneration of passing fibers. We suggest that RE cells inhibit GABAergic local-circuit cells, in addition to inhibiting thalamocortical neurons, and that different ratios of inhibitory effects are exerted by RE neurons upon these two cell classes during waking and sleep. We further suggest that, upon arousal, disinhibition of thalamocortical neurons (via the local- circuit neurons) outweighs direct inhibition of the thalamocortical neurons.
Autoradiographic localization of tryptamine binding sites in the rat and dog central nervous system
Authors: McCormack JK , Beitz AJ , Larson AA
Published: March 2018

Tryptamine, an endogenous trace amine, is currently postulated to be a neuromodulator or neurotransmitter in the mammalian CNS. High-affinity binding sites have been described for tryptamine in rat brain homogenate preparations. The present study further characterizes tryptamine binding throughout the CNS and delineates its distribution using in vitro receptor binding in conjunction with autoradiographic techniques. Saturation studies on 20-micron-thick brain sections suggest a single class of binding sites (Hill coefficient = 0.97 +/- 0.04) with a high affinity (KD = 4.79 +/- 1.55 nM). In competition studies, kynuramine and tetrahydrobetacarboline significantly inhibited H3-tryptamine binding while serotonin, dopamine, and phenylethylamine failed to significantly inhibit it. The most potent inhibitor of H3- tryptamine binding was tryptamine (KI = 4.19 +/- 2.13 nM). In rat brain sections processed for in vitro autoradiography, highest binding occurred in the following limbic structures: the accumbens nucleus, the amygdalohippocampal area, the lateral septal nucleus, the entorhinal cortex, and the anterior olfactory nucleus. At diencephalic levels, the highest binding was observed in the reuniens thalamic nucleus, the paraventricular thalamic nucleus, the medial habenular nucleus, the central medial thalamic nucleus, and the arcuate hypothalamic nucleus. In the midbrain of the rat, binding was most notable in the interpeduncular nucleus, the superficial layer of the superior colliculus, the periaqueductal gray, and the paranigral nucleus. In the lower brain stem of the dog, binding was evident in the external cuneate nucleus, the spinal trigeminal nucleus, and in the region of the solitary nucleus. Binding was also present in both the ventral and dorsal horns of the canine spinal cord.(ABSTRACT TRUNCATED AT 250 WORDS)