bluuebunny/crossref_metadata_2025 huggingface dataset:
Pharmacology of the vestibular hair cell-afferent fiber synapse in the frog
Authors: Annoni JM , Cochran SL , Precht W
Published: March 2018

The isolated, intact, membranous labyrinth of the frog (Rana temporaria) has been investigated electrophysiologically in vitro to determine the nature of the transmitter substance at the synapse between the vestibular hair cells and afferent fibers. Spontaneous synaptic activity can be monitored with intra-axonal recordings from the afferents. Increased K+ in the bath results in an increase in frequency of presynaptic release, as indicated by an increased frequency of spontaneous synaptic potentials. Adding Mg2+ and lowering Ca2+ results in a decrease in synaptic potential frequency (often to zero) with no change in their mean amplitude, indicating pre-synaptic blockade. Extracellular recordings from individual vestibular afferents indicate that bath-applied glutamate and related acidic amino acids consistently increase the firing rates of these afferents in a dose- dependent manner with no evidence of desensitization. In the presence of presynaptic blockade (high Mg2+/low Ca2+), bath application of glutamate and its agonists results in a reversible depolarization of vestibular afferents, suggesting a postsynaptic action of these substances. 2-Amino-5-phosphonovaleric acid, kynurenic acid, and other acidic amino acid antagonists reversibly decrease the amplitudes of spontaneously occurring synaptic potentials without affecting their frequency, indicating subsynaptic blockade. These antagonists also block the postsynaptic depolarizations due to glutamate and its agonists. GABA and its agonists and antagonists have no consistent effect upon afferent activity. These findings suggest that glutamate, aspartate, or a related compound is the transmitter at this synapse. However, the antagonists used, or the receptors themselves, are not selective enough to discriminate adequately between the agonists. Therefore, which of these glutamate agonists are actually involved in synaptic transmission remains to be determined.
Quantitative autoradiographic distribution of L-[3H]glutamate-binding sites in rat central nervous system
Authors: Greenamyre JT , Young AB , Penney JB
Published: March 2018

Quantitative autoradiography was used to determine the distribution of L-[3H]glutamate-binding sites in the rat central nervous system. Autoradiography was carried out in the presence of Cl- and Ca2+ ions. Scatchard plots and Hill coefficients of glutamate binding suggested that glutamate was interacting with a single population of sites having a K-D of about 300 nM and a capacity of 14.5 pmol/mg of protein. In displacement studies, ibotenate also appeared to bind to a single class of non-interacting sites with a KI of 28 microM. However, quisqualate displacement of [3H]glutamate binding revealed two well-resolved sites with KIS of 12 nM and 114 microM in striatum. These sites were unevenly distributed, representing different proportions of specific glutamate binding in different brain regions. The distribution of glutamate- binding sites correlated very well with the projection areas of putative glutamatergic pathways. This technique provides an extremely sensitive assay which can be used to gather detailed pharmacological and anatomical information about L-[3H]glutamate binding in the central nervous system.
Immunocytochemical localization of the mammalian voltage-dependent sodium channel using polyclonal antibodies against the purified protein
Authors: Haimovich B , Bonilla E , Casadei J , Barchi R
Published: March 2018

Antibodies were raised in rabbits against the purified voltage- dependent sodium channel from rat skeletal muscle sarcolemma. The resultant antiserum reacted with the purified channel in a solid-phase radioimmunoassay and precipitated the sodium channel from a crude mixture of solubilized membrane proteins. Crude membrane proteins separated according to size under nondenaturing conditions by chromatography on Sepharose CL-6B contained a single peak of immunoreactivity that coincided with the native channel. On immunoblots of sarcolemmal membrane proteins, the antiserum reacted predominantly with a diffuse high molecular weight band that was comparable in migratory characteristics to the large glycoprotein subunit of the purified channel. Using immunocytochemical techniques, binding of this polyclonal antiserum was localized to the surface membrane of rat skeletal muscle. This staining was specifically blocked by pre- incubation of the antiserum with the purified channel protein. The antiserum also stained the surface membrane of rat cardiac muscle and the nodes of Ranvier in rat peripheral nerve. Species cross-reactivity was seen with mouse, human, and guinea pig skeletal muscle while chicken, rabbit, and frog muscle was not stained. The antiserum also reacted with the surface membranes of fetal rat muscle in tissue culture. These results indicate that sodium channels in adult mammalian skeletal muscle, cardiac muscle, and peripheral nerve and in fetal muscle in culture all share common antigenic determinants. The antiserum should prove useful for topographical studies of sodium channel distribution in these tissues.
Redistribution of acetylcholine receptors on developing rat myotubes
Authors: Ziskind-Conhaim L , Geffen I , Hall ZW
Published: March 2018

The mechanism of formation of acetylcholine receptor (AChR) clusters at developing mammalian endplates was investigated in vitro, using intercostal muscles from embryonic rats. The muscles were explanted in organ culture with the spinal cord attached, as described previously (Ziskind-Conhaim, L., and M. J. Dennis (1981) Dev. Biol. 85: 243–251). AChRs on the myofibers were labeled with [125I]-alpha-bungarotoxin shortly before clusters appeared and subsequently were cultured in unlabeled toxin for 1 day. Autoradiography of the cultured fibers demonstrated the presence of labeled clusters of AChRs indicating that the AChRs in the newly formed clusters arise from AChRs that had previously been uniformly distributed on the muscle surface.
The role of feedback from the vocal organ. I. Maintenance of stereotypical vocalizations by adult zebra finches
Authors: Bottjer SW , Arnold AP
Published: March 2018

The stereotypical vocal patterns of adult male zebra finches (Poephila guttata) were examined before and after elimination of auditory feedback and/or feedback from the vocal organ (the syrinx). Elimination of auditory feedback was accomplished via bilateral removal of the cochleae, whereas feedback from the syrinx was eliminated by cutting hypoglossal afferent fibers while leaving hypoglossal efferents intact. Very little or no disruption of song was observed in birds which underwent deafening as well as unilateral deafferentation of the syrinx. Control experiments showed that the minor deficits observed were not attributable to lesion of pulmonary fibers in the descending branch of the vagus. There was also little deficit in song behavior of birds that were deafened and subjected to bilateral deafferentation of the syrinx. These results are consistent with the hypothesis that stable song patterns in adult passerine birds are not dependent on peripheral sources of feedback, but may be governed by a learned central control program.
Spatial contrast sensitivity of dark-reared cats with striate cortex lesions
Authors: Lehmkuhle S , Sherman SM , Kratz KE
Published: March 2018

We measured the spatial contrast sensitivity of two dark-reared cats before and after bilateral ablations of area 17 and parts of area 18. These lesions produced large deficits in the contrast sensitivity of both cats at intermediate and high spatial frequencies. This postoperative reduction in contrast sensitivity in dark-reared cats is relatively similar to the sensitivity deficits produced by the same cortical lesions in normally reared cats. However, both pre- and postoperatively, the normally reared cats exhibited contrast sensitivity that is clearly superior to that of the dark-reared cats. The results demonstrate both that striate cortex is significantly involved in the spatial contrast sensitivity of dark-reared cats and that dark rearing produces widespread deficits, independent of those in striate cortex, through much of the visual system.
The postnatal reduction of the uncrossed projection from the nasal retina in the cat
Authors: Jacobs DS , Perry VH , Hawken MJ
Published: March 2018

We have investigated the postnatal reduction of the uncrossed projection from the nasal retina in the cat by injecting horseradish peroxidase into one optic tract of kittens and cats and retrogradely labeling the cells in the ipsilateral retina that have an uncrossed projection to the brain. The newborn kitten has over 600 uncrossed cells in the nasal retina. The number is reduced to about one-quarter of that value by postnatal day 10. The two adult cats examined had 75 and 100 of these ipsilaterally projecting nasal cells. They are distributed all across the nasal retina, and most have the morphology characteristic of gamma cells. A lesion in one optic tract in the newborn kitten results in an increase in the number of cells from the nasal retina with an ipsilateral projection at maturity. There are more of these cells in the region that has been depleted of ganglion cells by the lesion. This excess consists mostly of gamma and epsilon cells. These findings indicate that competitive factors play a role in the elimination of inappropriate ganglion cell projections in the cat, and that this process contributes to the precision of the nasotemporal division of the retina.
Dorsal root ganglia development in chicks following partial ablation of the neural crest
Authors: Carr VM
Published: March 2018

To assess the effects of reduced competition for peripheral targets on developing brachial dorsal root ganglia (DRG), chick embryos were subjected to partial ablations of the brachial neural crest at stages 13 or 14 (Hamburger, V., and H.L. Hamilton (1951) J. Morphol. 88: 49– 92), using an ophthalmological cauterization unit. In the initial studies reported here, ganglia developing from the remaining crest material were examined for ganglionic volume and neuronal size, neuronal number, and degenerative activity at stage 35. Results showed that the lesion procedure resulted in the reduction or absence of one or two ganglia on each side at the level of DRG 15 to DRG 17. Hypertrophies occurred in other ganglia remaining at these and at more rostral levels and ranged up to 220%. These hypertrophies were most pronounced, however, not in the ganglia adjacent to those lesioned but rather in more remote ganglia, including those at cervical levels. Accompanying these ganglionic changes were significant alterations in all three neuronal parameters examined. The findings clearly demonstrate a responsiveness of chick brachial DRG to reduced competition resulting from neural crest ablations and that such responsiveness occurs along several axial segments.
Recovery of the ipsilateral oculotectal projection following nerve crush in the frog: evidence that retinal afferents make synapses at abnormal tectal locations
Authors: Adamson J , Burke J , Grobstein P
Published: March 2018

The ipsilateral oculotectal projection in the frog is a topographic mapping of the binocular part of the visual field of one eye on the ipsilateral tectal lobe. The underlying neuronal circuitry consists of the topographic, crossed retinotectal projection and an intertectal pathway which relays information from a given point in one tectal lobe to the visually corresponding point in the other. During optic nerve regeneration, there is a period when the terminals of retinotectal afferents are found at abnormal locations in the opposite tectal lobe. Whether they form functional synapses at this time is not known. If so, one would expect to observe correlated abnormalities in the ipsilateral oculotectal projection. To determine whether such abnormalities exist, we have made parallel electrophysiological studies of the recovery of the retinotectal and ipsilateral oculotectal projections following crush of one optic nerve. The earliest stage of recovery was characterized by a lack of significant topographic order in the retinotectal projection and by the absence of a physiologically observable ipsilateral projection. Within a short time, the retinotectal projection became topographically organized and a similarly organized ipsilateral projection appeared. While topographic, the retinotectal projection at intermediate times was abnormal in that the multiunit receptive fields recorded at individual tectal loci were greatly enlarged. Multiunit receptive fields were similarly enlarged in the ipsilateral projection. In addition, some ipsilateral fields included areas of visual space not normally represented in the projection. The abnormalities in both projections subsequently disappeared over the same time course. Throughout recovery there was a high correlation between multiunit receptive field sizes in the contralateral tectal lobe and those at visually corresponding points in the ipsilateral tectal lobe. Enlarged multiunit receptive fields in the contralateral tectal lobe could not be accounted for in terms of optical or retinal abnormalities since single unit receptive field sizes were normal. Nor could they be accounted for in terms of changes in recording characteristics since simultaneously recorded fields activated by the undisturbed eye were normally sized. We conclude that the enlarged fields in the contralateral tectal lobe indicate the presence at individual tectal loci of afferents from wider than normal retinal regions. Similar considerations ruled out optical, retinal, and recording abnormalities as the explanation for the enlarged multiunit receptive fields in the ipsilateral tectal lobe.(ABSTRACT TRUNCATED AT 400 WORDS)
The distribution and chromatographic characterization of PHI (peptide histidine isoleucine amide)-27-like peptides in rat and porcine brain
Authors: Beinfeld MC , Korchak DM , Roth BL , O'Donohue TL
Published: March 2018

This study was initiated to characterize PHI (peptide histidine isoleucine amide)-27-like peptides (PLPs) in rat and porcine brain in comparison with other members of the vasoactive intestinal polypeptide (VIP) family and to investigate their distribution by radioimmunoassay. The peptidic nature of the rat brain PLP was indicated by its trypsin sensitivity. On Sephadex chromatography rat brain PLP has the same molecular weight as synthetic (porcine intestinal) PHI-27. High pressure liquid chromatographic separations revealed that PLP in rat and porcine brain extracts elutes as a single peak distinct from VIP or secretin. Porcine brain PLP elutes in the same position as synthetic PHI-27, whereas rat brain PLP immunoreactivity consistently separates from synthetic PHI-27. This suggests that porcine brain PLP is identical to synthetic PHI-27, in agreement with the reported sequence of Tatemoto et al. (Tatemoto, K., M. Carlquist, T. McDonald, and V. Mutt (1983) FEBS Lett. 153: 248–252), whereas PLP may have a different amino acid sequence (or may be post-translationally modified). Using specific PHI and VIP radioimmunoassays, the distribution of PLP was found to parallel that of VIP in rat and porcine brain, being highest in cerebral cortex, amygdala, and hippocampus. PLP, like VIP, is abundant in rat retina and can be included in the growing list of retinal peptides. This highly correlated distribution of VIP and PLP may be explained by the recent discovery that they are derived from the same precursor (Itoh, N., K. Obata, N. Yanaihara, and H. Okamoto (1983) Nature 304: 547–549).(ABSTRACT TRUNCATED AT 250 WORDS)
Glial repair in an insect central nervous system: effects of surgical lesioning
Authors: Treherne JE , Harrison JB , Treherne JM , Lane NJ
Published: March 2018

Surgical lesioning of central nervous connectives in the cockroach (Periplaneta americana (L.], although causing only local glial damage, resulted in complex and prolonged cellular changes. An early response to mechanical disruption was the appearance of granule-containing cells within the damaged perineurium, among adjacent, undamaged, perineurial cells, and between glial processes deep within the connectives. These cells, which were strikingly similar to hemocytes, were clearly involved in phagocytic activity and persisted in the damaged regions for more than a month after lesioning. There was only a slow restoration of organized perineurial glia and re-establishment of the blood-brain barrier, as indicated by the exclusion of an extracellular tracer, ionic lanthanum. These observations contrast with the speedy, ordered repair of the neuroglia observed following selective glial disruption and suggest that undamaged axons and/or the extracellular matrix exert a profound influence on the mechanisms of glial repair.
Calmodulin stimulates adenylate cyclase activity and increases dopamine activation in bovine retina
Authors: Gnegy ME , Muirhead N , Roberts-Lewis JM , Treisman G
Published: March 2018

Adenylate cyclase activity in bovine retina is highly responsive to Ca2+ and the endogenous Ca2+-binding protein, calmodulin (CaM). CaM stimulated adenylate cyclase activity in washed particulate fractions of bovine retina by 6.6-fold in a Ca2+-dependent manner. Activation of adenylate cyclase activity by CaM was maximal at 0.12 microM free Ca2+. The apparent Ka for calmodulin stimulation of adenylate cyclase was 67 nM and the apparent Vmax was 116 pmol/min/mg of protein above basal activity. Adenylate cyclase activity in bovine retina was stimulated approximately 50% by guanosine 5′-triphosphate (GTP), but the nonhydrolyzable GTP analogue, guanosine-5′-(beta, gamma- imido)triphosphate (Gpp(NH)p), was able to activate the enzyme nearly 5- fold. CaM and Gpp(NH)p appeared to be partially competitive activators of adenylate cyclase in the retina particulate fraction. Dopamine stimulated adenylate cyclase activity in the presence of GTP with an apparent Ka of 1.0 microM and an apparent Vmax of 66 pmol/min/mg of protein. Ca2+ and CaM increased the apparent Vmax of the dopamine- stimulated adenylate cyclase activity more than 2-fold to a level of 146 pmol/min/mg of protein but did not alter the apparent Ka. This suggests that CaM is an endogenous modulator of dopamine-stimulated adenylate cyclase activity in the retina. CaM-stimulated adenylate cyclase activity may be a common component to retina since we found this activity in retinas from rabbit, rat, and goldfish as well as cow.
The spatial control of ganglionic neurite growth by the substrate- associated material from conditioned medium: an experimental model of haptotaxis
Authors: Collins F , Lee MR
Published: March 2018

Techniques are described for forming on the culture substrate a narrow pathway of material derived from medium conditioned by embryonic non- neuronal cells. There is a precise correlation between the known location of the pathway and the spatial distribution of neurites extended from whole ciliary ganglia or dissociated neurons grown on the patterned substrate. When individual growth cones moving on the pathway contact one of its edges, they turn sharply so as to remain on the pathway. This turning response is not simply due to a physical barrier to movement across the edge, since growth cones can cross onto the pathway when entering from the adjacent untreated substrate. The strong preference for neurites to maintain contact with the pathway also is not simply a result of their inability to survive or elongate outside of the pathway, since neurites from whole ganglia elongate readily on other regions of the substrate, although their growth is then undirected. Direct contact with the pathway is required for these directive effects, and there is no indication that the material bound to the substrate diffuses off and exerts its effects at a distance. The neurite-guiding activity is found in partially purified fractions of conditioned medium which also contain a substrate-bound inducer of neurite outgrowth. It is possible that both activities may be due to the same components of conditioned medium. These results suggest that ciliary ganglion growth cones are able to detect specific components of conditioned medium on the substrate and respond to their presence by changing their direction of movement so as to remain in contact with these components.(ABSTRACT TRUNCATED AT 250 WORDS)
The discharge characteristics of vagal cardiac neurons during classically conditioned heart rate change
Authors: Gold MR , Cohen DH
Published: March 2018

Classically conditioned heart rate change in the pigeon has been developed as a vertebrate model system for cellular analysis of associative learning. One aspect of this development involved characterizing in detail the “final common path” for the conditioned response, the “cardiac motoneurons.” With this as a foundation it has been possible to investigate the discharge properties of these motoneurons during acquisition of the conditioned heart rate response, and in this paper we report such data for the vagal (parasympathetic) component of the conditioned response. The activity of single neurons was recorded in the intermediate zone of the dorsal motor nucleus of the vagus of the pigeon. Antidromic activation confirmed that these cells gave rise to efferent axons in the vagus nerve and allowed their classification on the basis of conduction velocity into three groups: A, B1 (cardiac), and B2 units. B1 and B2 units had low levels of irregularly maintained activity, whereas A units discharged more regularly at higher frequency. B1 units had a weak cardiac rhythm, no respiratory rhythm, and showed decreased discharge in response to visual stimulation or foot-shock. These stimulus-evoked decreases in the activity of cardiac cells were accompanied by increases in heart rate. B2 units were unresponsive to both visual stimulation and foot- shock, whereas A units were unresponsive to visual stimulation but possibly responsive to foot-shock. The activity of vagal cardiac neurons was recorded during or after classical conditioning (paired lights and foot-shocks) or sensitization (unpaired lights and foot- shocks) to characterize discharge changes associated with conditioned cardioacceleration.(ABSTRACT TRUNCATED AT 250 WORDS)
Localization, chromatographic characterization, and development of somatostatin-like immunoreactivity in the guinea pig retina
Authors: Spira AW , Shimizu Y , Rorstad OP
Published: March 2018

We have studied the anatomical localization, chromatographic properties, and development of somatostatin-like immunoreactivity (SLI) in the guinea pig retina. The majority of guinea pig retinal SLI in the adult and fetus eluted similarly to somatostatin-28 by gel filtration and high pressure liquid chromatography. This represents a higher ratio of somatostatin-28-like material to total SLI than had been observed in retinal extracts from most other animal species. Somatostatin-like- immunoreactive cells and fibers were localized using two antisera in cryostat-sectioned and flat mounted retinae. Distribution of cells and fibers differed uniquely from that in other species previously reported. Reactive perikarya were located only in the far peripheral region: in the innermost layer of the inner nuclear layer (INL), in the inner plexiform layer (IPL), and in the ganglion cell layer. Reactive fibers were prominent in the IPL and nerve fiber layer (NFL) in both the peripheral and central retina. Less frequently, processes were observed between the NFL and IPL, between the IPL and INL, and, rarely, in the outer plexiform layer and outer nuclear layer. Small numbers of reactive fibers were found in the optic nerve and disc. These observations suggest that processes of intrinsic (amacrine or associational ganglion cells) and projection neurons (true ganglion cells or efferent fibers) containing SLI are intermingled in the guinea pig retina. SLI, quantified by radioimmunoassay, was present in the developing retina as early as the 6th week of gestation (full term is 10 weeks). Immunohistochemically detected somatostatin-like- immunoreactive elements were seen first at 2 weeks before birth, coincident with the onset of the period of most rapid increase in levels of assayed SLI. Somatostatin-like-immunoreactive peptides reached two-thirds of adult levels by birth.
Localization of spectrin in mammalian brain
Authors: Zagon IS , McLaughlin PJ , Goodman SR
Published: March 2018

Spectrin is a major skeletal component of the erythrocyte membrane and is essential in controlling cell shape and structural stability. The brain has also been found to be rich in an immunoreactive and structural analogue of spectrin. In the present study, spectrin was localized in the mouse brain by indirect immunofluorescence using an antibody to erythrocyte spectrin that cross-reacts specifically with the alpha and beta subunits of brain spectrin. Spectrin antigens were concentrated in neuronal perikarya and cell processes. Synaptic structures and axons were observed to have little detectable spectrin antigen by immunofluorescence methodology. The cell bodies of glia had a less intense immunoreactivity in contrast to neurons, and glial processes and myelin were unstained. Cell nuclei of neural cells were not fluorescent. These results show that (a) spectrin is found in all regions of mammalian brain and its intensity corresponds to neural cell density, (b) different neural cell types contain variable spectrin content, and (c) within a single neural cell, the regional disposition of spectrin varies.
Cell-cell interactions of isolated and cultured oligodendrocytes: formation of linear occluding junctions and expression of peculiar intramembrane particles
Authors: Massa PT , Szuchet S , Mugnaini E
Published: March 2018

Oligodendrocytes were isolated from lamb brain. Freshly isolated cells and cultured cells, either 1- to 4-day-old unattached or 1- to 5-week- old attached, were examined by thin section and freeze-fracture electron microscopy. Freeze-fracture of freshly isolated oligodendrocytes showed globular and elongated intramembrane particles similar to those previously described in oligodendrocytes in situ. Enrichment of these particles was seen at sites of inter- oligodendrocyte contact. Numerous gap junctions and scattered linear tight junctional arrays were apparent. Gap junctions were connected to blebs of astrocytic plasma membrane sheared off during isolation, whereas tight junctions were facing extracellular space or blebs of oligodendrocytic plasma membrane. Thin sections of cultured, unattached oligodendrocytes showed rounded cell bodies touching one another at points without forming specialized cell junctions. Cells plated on polylysine-coated aclar dishes attached, emanated numerous, pleomorphic processes, and expressed galactocerebroside and myelin basic protein, characteristic markers for oligodendrocytes. Thin sections showed typical oligodendrocyte ultrastructure but also intermediate filaments not present in unattached cultures. Freeze-fracture showed intramembrane particles similar to but more numerous, and with a different fracture face repartition, than those seen in oligodendrocytes, freshly isolated or in situ. Gap junctions were small and rare. Apposed oligodendrocyte plasma membrane formed linear tight junctions which became more numerous with time in culture. Thus, cultured oligodendrocytes isolated from ovine brains develop and maintain features characteristic of mature oligodendrocytes in situ and can be used to explore formation and maintenance of tight junctions and possibly other classes of cell-cell interactions important in the process of myelination.
Neural mechanisms of motor program switching in the mollusc Pleurobranchaea. I. Central motor programs underlying ingestion, egestion, and the "neutral" rhythm(s)
Authors: Croll RP , Davis WJ , Kovac MP
Published: March 2018

The buccal musculature of the carnivorous gastropod Pleurobranchaea is used in three cyclic patterns of coordination underlying, respectively, ingestion, egestion, and a third, unknown behavior(s) (Croll, R. P., and W. J. Davis (1981) J. Comp. Physiol. 145: 277–287; Croll, R. P., and W. J. Davis (1982) J. Comp. Physiol. 147: 143–154). The corresponding three motor programs can be identified and distinguished in the intact animal (Croll, R. P., and W. J. Davis (1981) J. Comp. Physiol. 145: 277–287), the reduced preparation (Croll, R. P., and W. J. Davis (1982) J. Comp. Physiol. 147: 143–154, and the present paper), and the isolated CNS (present paper), on the basis of several qualitative and quantitative criteria. Distinguishing parameters developed here include: the activity of the salivary duct, which bursts in phase with protraction during ingestion, is silent during egestion, and usually bursts biphasically and in antiphase with protraction during the third (“neutral”) rhythm(s); and the protractor duty cycle, which is generally 33 to 50% during ingestion, greater than 50% during egestion, and less than 33% during the neutral rhythm(s). Retractor duty cycles did not differ significantly between the three motor programs. The neutral rhythm(s) may be a low-intensity version of the ingestion motor program, with which it shares most features. The three buccal motor programs can be elicited in the reduced preparation (sensory feedback intact) and in the isolated, deafferented CNS. Therefore, multiple motor programs in this metastable motor system are each endogenous to the CNS; i.e., they can each be generated by a central pattern generator(s) in the absence of sensory feedback.(ABSTRACT TRUNCATED AT 250 WORDS)
Distribution of serotonin-immunoreactive cell bodies and processes in the abdominal ganglion of mature Aplysia
Authors: Kistler HB , Hawkins RD , Koester J , Steinbusch HW , Kandel ER , Schwartz JH
Published: March 2018

Sensitization of the gill withdrawal reflex in Aplysia californica is an elementary form of learning, in part resulting from presynaptic facilitation of the LE mechanoreceptor neurons of the abdominal ganglion. It has previously been established that either application of serotonin or direct stimulation of a group of facilitatory neurons, the L29 cells of the abdominal ganglion, can simulate the effect of physiological stimulation in producing presynaptic facilitation. Because the evidence that serotonin serves as a facilitatory transmitter was indirect, we examined the distribution of serotonin- immunoreactive fibers and cell bodies in the abdominal ganglion in order to answer two questions: (1) do the sensory neurons receive serotonergic innervation and (2) are the L29 cells serotonergic? We observed two distinctive patterns of serotonergic innervation within the ganglion, sparse and dense. The sparse pattern is correlated with a serotonin-stimulated increase in cAMP in identified target cells, while the dense innervation is not. We found a sparse distribution of serotonin-immunoreactive fibers with varicosities close to both cell bodies and processes of identified LE sensory cells. It therefore is likely that the sensory neurons do receive serotonergic innervation. We also mapped the population of serotonergic neuronal cell bodies in the ganglion, and found five clusters of neurons. Cells in one of these clusters, the identified RB neurons, had previously been shown to synthesize serotonin from tryptophan and to contain the neurotransmitter in high concentration. Identified L29 facilitator cells marked by injection with Lucifer Yellow do not contain serotonin immunoreactivity and therefore evidently are not a source of serotonergic input onto sensory cells.
Rapid recovery of pineal function after partial denervation: a possible role for heteroneuronal uptake of transmitter in modulating synaptic efficacy
Authors: Zigmond RE , Baldwin C , Bowers CW
Published: March 2018

The pineal gland is innervated by sympathetic neurons whose cell bodies are located in the two superior cervical ganglia and whose axons reach the gland via the two internal carotid nerves (ICNs). Bilateral decentralization of the superior cervical ganglia, produced by lesioning both cervical sympathetic trunks (CSTs), abolishes the circadian rhythm in the activity of the pineal enzyme serotonin N- acetyltransferase (NAT). We have examined the effects on NAT activity of unilaterally cutting the ICN or the CST. During the first night after either operation, nocturnal NAT activity was reduced by 75% compared to controls. However, during the second night after unilaterally cutting the ICN, NAT activity was restored to control values, and normal enzyme activity was seen in these lesioned animals for up to 1 month after this operation. On the other hand, following unilateral decentralization of one superior cervical ganglion, enzyme activity was reduced for at least 5 months. The high enzyme activity in animals with one ICN cut was abolished by cutting the contralateral CST, indicating that the recovery of NAT activity depended on the remaining intact sympathetic neurons. Electrical stimulation of the intact ICN during the daytime in animals in which the contralateral ICN was cut produced an increase in pineal NAT activity which was greater than the increase seen when similar stimulation was performed in sham- operated animals or in animals in which the contralateral superior cervical ganglion had been decentralized. The time course of the recovery of nocturnal NAT activity after unilateral denervation of the pineal gland was similar to the time course of the decrease in norepinephrine uptake sites in the gland.(ABSTRACT TRUNCATED AT 250 WORDS)
Inhibition of choline acetyltransferase by monoclonal antibodies
Authors: Strauss WL , Nirenberg M
Published: March 2018

Four monoclonal antibodies were obtained to rat brain choline acetyltransferase (CAT). The enzyme was purified 95,000-fold from rat brain by precipitation with acetic acid at pH 4.5, fractionation with 40 to 60% (NH4)2SO4, CM-Sephadex chromatography, and affinity column chromatography on agarose-hexane-coenzyme A. The enzyme preparation was applied to the affinity column in the presence of 10 mM acetylcholine to increase the affinity of CAT for coenzyme A; the enzyme then was eluted with 10 mM acetyl coenzyme A. Fusion of P3X63 Ag8 myeloma cells with spleen cells isolated from a BALB/c mouse that had been immunized with affinity-purified CAT with a specific activity of 29.4 mumol of ACh synthesized/min/mg of protein resulted in the isolation of four hybridomas synthesizing antibodies to CAT that inhibit the activity of the enzyme. Anti-CAT 1 or 2 inhibits CAT activity 100%. At the highest antibody concentration tested, anti-CAT 3 inhibited acetylcholine synthesis 80%. Hybridoma antibody-dependent inhibition of CAT activity was reversed by dissociation of immune complexes via dilution, demonstrating that antibody binding does not irreversibly alter the structure of the enzyme. When bound to [rabbit anti-mouse IgG . protein A Staphylococcus aureus] complexes, anti-CAT 1, 3, and 4 each were effective reagents for the precipitation of CAT activity from solution. Thirty-one to 53% of the precipitated enzyme was recovered following the dissociation of immune complexes. Anti-CAT 1, 2, and 3 inhibit CAT from 18-day chick embryo brain, NS20-Y mouse neuroblastoma cells, and rat brain.
Conditioned modification of phototactic behavior in Hermissenda. I. Analysis of light intensity
Authors: Crow T
Published: March 2018

Psychophysical experiments examined the control of phototactic behavior by light intensity in the nudibranch mollusk Hermissenda by measuring the time that Hermissenda remained in an illuminated area. This measure of phototactic behavior exhibits a closer correspondence to changes in test light intensity than other previously examined measures of phototaxis. Changing the intensity of a test light in a series of increasing steps resulted in a graded increase in positive phototactic behavior. Behavioral responses to different light intensities were examined in conditioned and control animals. Conditioning resulted in a significant suppression of phototactic behavior at all light intensities examined. Random control procedures did not produce suppression of phototactic responding. These behavioral results provide a data base to examine how well neural correlates produced during conditioning fit the behavior.
Androgen and estrogen receptors in perinatal ferret brain
Authors: Vito CC , Baum MJ , Bloom C , Fox TO
Published: March 2018

Using DNA-cellulose affinity chromatography and either 3H-labeled dihydrotestosterone, testosterone, or estradiol, we qualitatively and quantitatively analyzed the androgen- and estrogen-binding activities present in four regions of male and female ferret brain at prenatal, early and late neonatal, and adult ages. The cytosolic androgen- and estrogen-binding activities in ferret brain at all ages studied were qualitatively similar in both sexes and in all brain regions and exhibited characteristics which resemble those of androgen and estrogen receptors from other species, including rodents and nonhuman primates. A developmental analysis indicated that high levels of both androgen and estrogen receptors were present in the hypothalamus-preoptic area as early as 5 days before birth. A significant, transient decline in concentrations of estrogen receptors (approximately 5-fold) occurred in anterior hypothalamus-preoptic area and mediobasal hypothalamus at 12 days of age in both males and females; this phenomenon has not been observed in any other species studied to date. The observed ontogeny of androgen receptors correlates with the known ability of testosterone, acting over postnatal days 5 to 20, to cause coital masculinization in ferrets, whereas the observed postnatal dip in estradiol receptor concentrations correlates with the inability of estradiol to cause coital masculinization or defeminization of receptive behavior in this species.
Identification of a cell surface glycoprotein family of olfactory receptor neurons with a monoclonal antibody
Authors: Allen WK , Akeson R
Published: March 2018

A monoclonal antibody (Mab) has been developed which recognizes a family of cell surface glycoproteins found in high levels of rat olfactory receptor neurons. This Mab, designated 2B8, was produced by the fusion of X63-Ag8.653 myeloma cells and spleen cells of a mouse immunized with PC12 rat pheochromocytoma cells. Immunofluorescence analyses of cryostat sections of neonatal olfactory epithelium show prominent 2B8 binding to receptor neurons. Within the olfactory bulb only the glomerular and olfactory nerve layers show 2B8 binding. All other neural structures in the main olfactory bulb have background levels of reactivity. Analyses of 2B8 binding to particulate protein preparations from several central and peripheral nervous system components demonstrated highest 2B8 antigen specific activity in olfactory bulb and epithelium and detectable levels in dorsal root ganglia (DRG), whole cerebrum, cerebellum, and brainstem. However, 2B8 antigen could not be detected in non-olfactory structures by immunofluorescence. Some non-neural tissues also had the ability to bind 2B8 Mab in the particulate protein radioimmunoassay. In order to compare the 2B8-reactive molecules found in each tissue, Mab was applied to polyacrylamide gels of unlabeled membrane proteins. A family of molecules with diverse molecular weights was found. Some were unique to individual tissues whereas others were shared among tissues. Olfactory bulb and epithelium had a unique band with Mr = 215,000 and another band with Mr = 142,000. The 142,000-dalton band was also found with PC12 cells. PC12 cells also had several bands of lesser molecular weight, including 51,000 and 43,000. Testes membranes had immunoreactive bands only at Mr = 46,000 and 43,000. Bone marrow, perinatal liver, and DRG each expressed a single 2B8-reactive band with Mr = approximately 114,000. Salivary gland had four reactive bands, two common to it and only PC12 cells, the 114,000-dalton band which is similar to that found in adult rat bone marrow and DRG, and a unique band at Mr = 152,000. 2B8 immunoprecipitates of olfactory bulb and epithelium were analyzed for glycosyl groups by lectin reactivity. Wheat germ agglutinin and Ricinus communus agglutinin I bound the 2B8 antigens using two distinct assay methods. This suggests that the 2B8 antigens recognized in the olfactory system are glycoproteins having sialic acid and D-galactosyl components.(ABSTRACT TRUNCATED AT 400 WORDS)
alpha-Bungarotoxin receptors on neurons isolated from turtle retina: molecular heterogeneity of bipolar cells
Authors: James WM , Klein WL
Published: March 2018

We studied localization of specific [125I]-alpha-bungarotoxin (alpha- BTX) receptors on neurons dissociated from the adult turtle retina. Cells isolated from papain-treated retinas retained complex morphologies and were readily identifiable with cell classes (photoreceptors, Muller cells, multipolar and bipolar cells). Levels of alpha-BTX receptors, measured by filtration assays, averaged 120 fmol/mg of protein whether or not retinas were treated with papain. Light microscope autoradiographs of isolated cells showed that only bipolar neurons had receptors for alpha-BTX. In the presence of d- tubocurarine, no cells were labeled above background. Receptors were localized both close to and far from known sites of synaptic contacts. Highly labeled bipolar cells had grains over Landolt clubs, cell bodies, and axons as well as over dendrites, but lightly labeled cells had few grains over axons and cell bodies. Overall, most receptors occurred on dendrites, suggesting the activity of cellular mechanisms capable of directing receptor molecules to specific subcellular positions. The receptor phenotype was not expressed all or none, as autoradiographs of individual bipolar cells showed a wide spectrum of receptor levels. A maximum level of about 30,000 receptors/cell was seen. Unlabeled bipolar cells also were prevalent (70%), and this group included virtually all “displaced” type bipolar cells. The data show molecular heterogeneity both between and within retina cell classes.
Neuron-specific interactions with two neurite-promoting fragments of fibronectin
Authors: Rogers SL , McCarthy JB , Palm SL , Furcht LT , Letourneau PC
Published: March 2018

Proteolytic fragments of fibronectin were used to identify regions of the molecule that support neurite extension and to investigate further the differential behavior of central and peripheral nervous system neurons in response to fibronectin (Rogers, S. L., P. C. Letourneau, S. L. Palm, J. B. McCarthy, and L. T. Furcht (1983) Dev. Biol. 98: 212–2220). Fibronectin fragments with differing biological activities were produced by proteolytic digestion with trypsin and cathepsin D and sequential affinity chromatography on gelatin-agarose and heparin- Sepharose. The resulting fragments (described by Smith, D. E., D. F. Mosher, R. B. Johnson, and L. T. Furcht (1982) J. Biol. Chem. 257: 5831– 5838; Smith, D. E., and L. T. Furcht (1982) J. Biol. Chem. 257: 6518– 6523 included an NH2-terminal 27,000-dalton peptide that weakly binds heparin, a 46,000-dalton gelatin-binding fragment, a series of fragments (80,000 to 125,000 daltons) from the center of the molecule containing previously described cell-binding activity, two major peptides of Mr = 33,000 and 66,000 that bind heparin strongly and are thought to originate from the A and B chains, respectively, of plasma fibronectin, and a 31,000-dalton COOH-terminal peptide containing a free sulfhydryl from the A chain of the molecule. Tissue culture dishes were treated with these proteolytic preparations, and dissociated embryonic chick peripheral (PNS) and central nervous system (CNS) cells were cultured on each experimental substratum in serum-free medium. The fibronectin fragments were evaluated for ability to promote cell attachment, neurite initiation, and maintenance of neurite growth. The 27,000–, 46,000-, and 31,000-dalton preparations did not promote cell attachment or neurite extension. Both PNS and CNS neurons attached to and extended stable neurites upon the COOH-terminal heparin-binding preparation containing the 33,000- and 66,000-dalton peptides. A differential response of the neurons to the 80,000- to 125,000-dalton “cell-binding” peptides was observed: whereas PNS neurons maintained neuritic growth on this preparation for at least 48 hr, CNS neurons extended neurites during the first 24 hr of culture but, by 48 hr, withdrew these neurites and became increasingly clumped. On the basis of (1) the observed neuronal responses to the heparin binding and “cell binding” regions, and (2) the different ligand-binding properties of these regions, we propose that cell attachment and neurite extension can be mediated and/or modulated by two separate regions of fibronectin and that cellular response to the intact molecule may involve multivalent interactions.
Age-dependent long-term adaptation of crayfish phasic motor axon synapses to altered activity
Authors: Lnenicka GA , Atwood HL
Published: March 2018

Crustacean tonic and phasic motoneurons have neuromuscular synaptic properties corresponding with their functional requirements. Phasic axon synapses produce large excitatory postsynaptic potentials (EPSPs) which depress rapidly during repetitive activation. Tonic axon synapses generally produce smaller EPSPs which are more resistant to fatigue. To test whether nerve impulse activity of the motoneuron plays a role in the establishment of these synaptic properties, a phasic axon was tonically stimulated in vivo. The “fast” closer excitor of the crayfish claw, which normally fires few impulses, was stimulated for 2 hr/day at 5 Hz, through implanted electrodes. In young crayfish, this stimulation produced an 11-fold decrease in synaptic fatigue at the fast axon's neuromuscular synapses, as determined from measurements of EPSPs during 5 Hz stimulation of the fast axon for 30 min. In comparison with EPSPs of the contralateral control claw, the initial EPSP amplitude was 44% smaller and the final EPSP amplitude was 4.3 times larger for the chronically stimulated fast axon. These changes in EPSP amplitude are due to changes in transmitter release. This long-term adaptation of the fast axon to imposed tonic activity persists for at least 10 days after the effect has been established. The same chronic stimulation regimen produces significant, although less dramatic, results in adult crayfish. Compared to the contralateral control, the chronically stimulated fast axon showed no change in initial EPSP amplitude and only a 2-fold increase in the EPSP amplitude after 30 min of stimulation at 5 Hz. Thus, the decrease in synaptic fatigue was only 2- to 3-fold, much less than in young crayfish.(ABSTRACT TRUNCATED AT 250 WORDS)