bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium-promoted translocation of protein kinase C to synaptic membranes: relation to the phosphorylation of an endogenous substrate (protein F1) involved in synaptic plasticity
Authors: Akers RF , Routtenberg A
Published: March 2018

The translocation of protein kinase C between membrane and cytosol has been implicated in several cellular processes (Kraft and Anderson, 1983; Wooten and Wrenn, 1984; Akers et al., 1985, 1986; Hirota et al., 1985; Wolf et al., 1986). We desired to identify potential trigger mechanisms underlying the translocation of protein kinase C activity to neural membranes following the synaptic plasticity observed after long- term potentiation (LTP; Akers et al., 1986). Takai et al. (1979) have suggested an important role for calcium in protein kinase C translocation; we have therefore studied the effects of Ca2+ on both the translocation of protein kinase C activity and the in vitro phosphorylation of its endogenous substrate, protein F1, in rat hippocampal synaptosomes. Since identical free Ca2+ levels were maintained in subsequent assays of synaptosomal membranes (SPM) and cytosol preparations, alterations in endogenous enzyme activity and in vitro phosphorylation were due to the Ca2+ present during treatment of synaptosomes, and not to the Ca2+ present during assays of enzymatic activity. This afforded the opportunity to relate directly such enzyme translocation to endogenous substrate phosphorylation. The major findings were as follows: 1. Following treatment of synaptosomes with Ca2+, protein kinase C activity in synaptic membrane and protein F1 in vitro phosphorylation were elevated in a dose-dependent manner. 2. The greatest increment in membrane protein kinase C activity and protein F1 in vitro phosphorylation occurred when Ca2+ was increased from 0.1 to 1.0 microM. Maximal levels of enzyme activity were seen following treatment with 10 microM Ca2+, and minimum levels were observed following treatment with EGTA.
Structurally different neuronal nicotinic acetylcholine receptor subtypes purified and characterized using monoclonal antibodies
Authors: Whiting PJ , Liu R , Morley BJ , Lindstrom JM
Published: March 2018

Acetylcholine receptors that bind nicotine with high affinity but do not bind alpha-bungarotoxin have recently been immunoaffinity purified from brains of chickens and rats (Whiting and Lindstrom, 1986a, b; Whiting and Lindstrom, 1987a). Antisera to these receptors bind to the nicotinic receptors that regulate cation channel opening on chick ciliary ganglion neurons (Stollberg et al., 1986) and rat PC12 cells (Whiting et al., 1987c). Here we report the preparation and characterization of monoclonal antibodies to chicken brain acetylcholine receptors. These monoclonal antibodies are used to identify 2 nicotinic receptor subtypes in the chicken brain. The 2 subtypes have very similar affinities for nicotine and other cholinergic agonists and antagonists. However, they are structurally distinct, having very similar or identical alpha subunits (Mr 49,000), but different beta subunits (Mr 59,000, or for beta' subunit, Mr 75,000). Evidence is presented that suggests that the subunit stoichiometry of these neuronal nicotinic acetylcholine receptors is alpha n = 2 - 3 beta n = 2 - 3. Different levels of receptor subtype expression were detected in embryonic, compared to adult, chicken brain.
Intracellular regulators of neuronal sprouting: II. Phosphorylation reactions in isolated growth cones
Authors: Hyman C , Pfenninger KH
Published: March 2018

Mechanisms potentially involved in the regulation of neurite growth were investigated. Since both the phosphatidylinositol (PI) pathway and protein kinase C have been implicated in transmembrane signal transduction, protein and lipid phosphorylation reactions were examined in intact growth cone particles (GCPs) isolated from fetal rat brain. Three major substrates of Ca2+-dependent phosphorylation were observed: proteins of 40 and 46 kDa and an acidic 80 kDa species separated in 2D PAGE (pp40, pp46, and pp80ac). The pp40 and pp80ac substrates had similar rates of 32P incorporation, whereas that of pp46 was more rapid. The importance of protein kinase C in growth cone function is indicated by the enhancement of phosphorylation of the 3 major substrates by the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA). An examination of the Ca2+-dependent 32P incorporation into pp40 and pp46 revealed serine to be the only amino acid phosphorylated under these conditions. A rapidly metabolized pool of phosphoinositides was observed in GCPs. This suggests the presence of the Pl pathway's enzymes in this fraction. Inositol trisphosphate (IP3) was found to stimulate the phosphorylation of pp40 and pp80ac, indicating a possible link between the activation of the PI pathway and protein phosphorylation. Our findings demonstrate the prominence of the PI pathway and of Ca2+-dependent protein phosphorylation in the growth cone and may suggest the involvement of these mechanisms in growth- factor signal transduction.
Dentate granule cells are essential for kainic acid-induced wet dog shakes but not for seizures
Authors: Grimes L , McGinty J , McLain P , Mitchell C , Tilson H , Hong J
Published: March 2018

The purpose of this study was to determine the role that dentate granule cells play in wet dog shakes (WDS), behavioral seizures, and hippocampal cell loss caused by systemic administration of kainic acid (KA). Rats were given bilateral injections of colchicine (COL) into the hippocampal formation to selectively lesion dentate granule cells. Two weeks later, they were injected subcutaneously with KA and were observed for WDS and seizures. Seizures were terminated with pentobarbital 2.5 hr after KA injection, and the rats were killed 48 hr later. The integrity of hippocampal cell populations and projections to the hippocampal formation from entorhinal cortex was assessed with radioimmunoassay and immunostaining for methionine-enkephalin (ME) and dynorphin (DYN) A, as well as with Timm and Nissl staining. Results indicate that COL injections eliminated KA-induced WDS, did not affect the latency to onset of seizures, and potentiated KA-induced cell loss in the CA3 region of hippocampus. COL lesions eliminated ME and DYN immunostaining of granule cells, but not ME immunostaining of entorhinal afferents to the dentate gyrus or Ammon's horn. These findings indicate that granule cells are an essential neuronal link in the expression of KA-induced WDS, but that seizures propagate along other pathways in the limbic system.
Effect of partial denervation and terminal field expansion on neuromuscular transmitter release and nerve terminal structure
Authors: Rochel S , Robbins N
Published: March 2018

The efficacy of evoked ACh release by intact and newly sprouted terminals in response to partial denervation and expansion of the motor neuron terminal field was studied in mouse soleus muscle after section of the L-5 spinal root. From 2 to 4 d after partial denervation until 90 d later, only 3–7 motor units of the normal 21 remained. Regeneration of the dissected nerve was prevented while the remaining motor units were sprouting. The indirect twitch, which was only 20% of direct twitch tension 2–4 d after nerve section, recovered between 28 and 50 d postoperatively. However, the depression of twitch in low Ca/high Mg solution, which was equal to control 2–3 d postoperatively, was 2–3 times more depressed than control by 50 d and remained so up to 90 d. This indicated persistent reduction of the safety factor in sprouted motor units. Intracellular measurement of quantal content in 0.4 mM Ca, 2.75 mM Mg revealed 2 groups of nerve terminals in partially denervated muscle. The quantal content of the first group was greater than contralateral control at earlier times (28–50 d) and only slightly greater than control later (74 and 90 d). This group consisted of the original undenervated terminals, since it was associated with normal miniature endplate potential (MEPP) frequency and end-plate potential (EPP) latency, and presumably with the class of fibers with normal (zinc iodide osmium-stained) nerve terminal morphology and occasional large myelinated preterminal axons.
Anatomical distribution of the growth-associated protein GAP-43/B-50 in the adult rat brain
Authors: Benowitz LI , Apostolides PJ , Perrone-Bizzozero N , Finklestein SP , Zwiers H
Published: March 2018

GAP-43 (B-50,F1,pp46) is a neuron-specific phosphoprotein that has been implicated in the development and modulation of synaptic relationships. Although most neurons cease expressing high levels of GAP-43 after the completion of synaptogenesis (Jacobson et al., 1986), certain brain regions continue to have considerable amounts of the protein throughout life (Oestreicher et al., 1986); in at least one such area, the phosphorylation of the protein has been linked with the events that underlie synaptic potentiation (Lovinger et al., 1985). In this study, we used the indirect immunoperoxidase method to map the distribution of GAP-43/B-50 in the brains of 8 adult rats with 2 different antibodies: a monospecific, polyclonal antibody prepared in sheep against the purified protein and an affinity-purified IgG prepared in rabbits. Specific immunoreactivity was found primarily in the neuropil and followed a generally increasing caudal-to-rostral gradient along the neuraxis. Densest staining occurred in layer I of the cortex, the CA1 field of the hippocampus, and in a continuum of subcortical structures that included the caudate-putamen, olfactory tubercle, nucleus accumbens, bed nucleus of the stria terminalis, amygdala, and medial preoptic area-hypothalamus. In the brain stem, staining was seen in the central gray and in ascending visceral relay nuclei, but was essentially absent in areas related to ascending somatosensory information (e.g., the cochlear nuclei or vestibular complex) and motor control (e.g., nucleus ruber or the motor nuclei of the cranial nerves). Staining in dorsal thalamus was likewise modest in most somatosensory and somatomotor relay nuclei, but dark in certain other structures (e.g., mediodorsal nucleus, lateral complex). This distributional pattern raises the question of whether synapses in all areas containing high levels of GAP-43/B-50 are capable of undergoing functional plasticity, or whether the protein may function in some of these areas in some other capacity (e.g., general signal transduction).
Corticotropin-releasing factor in cerebellar afferent systems: a combined immunohistochemistry and retrograde transport study
Authors: Cummings S , Sharp B , Elde R
Published: March 2018

The flocculus and paraflocculus of cat and sheep cerebellum were studied with immunohistochemical methods, using antisera to corticotropin-releasing factor (CRF). CRF immunoreactivity was present within 3 populations of varicose nerve fibers. One population of CRF- immunoreactive (CRF-IR) fibers appeared to appose Purkinje cell somata and to follow their dendrites into the molecular layer. This arrangement suggested they were climbing fibers. A second group of CRF- IR profiles reminiscent of mossy fibers was widely distributed throughout the granule cell layer. A third population of CRF-IR fibers was present as a beaded plexus lying parallel to the pial surface, above and subadjacent to the Purkinje cell layer. The fibers of this plexus extended into the Purkinje cell layer and surrounded these somata. The source of some of the CRF-IR fibers within the flocculus and paraflocculus was determined by a retrograde axonal transport study utilizing the fluorescent tracer Fast blue (FB) in combination with the immunohistochemical localization of CRF. It was determined that CRF-IR perikarya within the inferior olivary nucleus gave rise to a population of climbing fibers within those lobules. Furthermore, all divisions of the inferior olive were found to contain CRF-IR somata. This latter finding suggests the potential for CRF-IR climbing fiber projections from the inferior olive to other regions of the cerebellar cortex. The existence of CRF-IR mossy fibers and fibers within the ganglionic plexus suggests the possibility of CRF-IR afferent projections from other regions of the brain stem to the flocculus and paraflocculus.
Development and survival of neurons in dissociated fetal mesencephalic serum-free cell cultures: II. Modulatory effects of gangliosides
Authors: Leon A , Dal Toso R , Presti D , Benvegnu D , Facci L , Kirschner G , Tettamanti G , Toffano G
Published: March 2018

This paper analyzes the effects of exogenously supplied GM1 on the development, i.e., specific neurotransmitter uptake capability and survival, of the dopaminergic neurons present in fetal mouse- dissociated mesencephalic cells. Exogenous GM1, but not asialo-GM1, sialic acid, or the oligosaccharide chain of GM1, enhances in a time- and concentration-dependent manner the specific 3H-dopamine uptake (increase of the apparent Vmax and decrease of the apparent Km value) and the long-term survival of the dopaminergic neurons. The GM1 effects on the behavior of the dopaminergic neurons require the presence of cell-derived neuronotrophic influences present within the culture system and are associated with an increase in the response of the cells to the trophic influences. GM1 effects are not limited to dopaminergic neurons, and depend on the stable association of the ganglioside molecule with the cells. It is suggested that GM1 is not a trophic agent per se, but rather potentiates neuronotrophic activities and/or exerts independent influences to which neurons respond only if appropriately supported.
Optokinetic nystagmus: modeling the velocity storage mechanism
Authors: Maioli C
Published: March 2018

To account for the oscillatory behavior of the optokinetic after- nystagmus (OKAN), a nonlinear model of the optokinetic system is proposed here that includes 2 first-order storage elements interconnected in a negative feedback loop. The adequacy of the model is tested by comparing its predictions with experimental data available in the literature. In addition, the question of the contribution of the storage element responsible for secondary OKAN (OKAN II) to the dynamic properties of the optokinetic nystagmus (OKN) is addressed. The results show that the model is compatible with all modifications of the OKAN time course observed under various experimental situations. By comparing computer simulations and experimental data, it is inferred that (1) the dynamic properties of the optokinetic system during OKN and during OKAN are different; (2) the switching in velocity storage dynamics is not determined by the light-dark transition, but is induced whenever nystagmic slow phase velocity (SPV) is not sustained by an appropriate retinal slip error signal; (3) although no signs of adaptation are seen during OKN, the storage element responsible for OKAN II becomes charged during optokinetic stimulation; and (4) the time constants of the integrators are affected by the parameters of the preceding optokinetic stimulation.
Recovery of tactile function after damage to primary or secondary somatic sensory cortex in infant Macaca mulatta
Authors: Carlson M , Burton H
Published: March 2018

These studies were designed to determine the basis for recovery of tactile function after the removal of primary (SI) or secondary (SII) cortex in infant Macaca mulatta. From previous studies we know that although removal of SI or SII in the adult macaque produces severe and irreversible impairment on a variety of tactile tasks, normal function can be obtained after partial or total SI lesions in the infant. From the present studies we have found that, as with SI, neither unilateral nor bilateral removals of SII in infants significantly affected the acquisition of or the performance on size tasks, but did cause a temporary delay in acquisition of texture tasks. Performance on texture threshold tasks was normal. The removal of the remaining SI in a juvenile animal that had received a unilateral SI lesion in infancy did not disrupt the recovered function, indicating that recovery is not mediated by the intact SI. However, when SI and SII were removed together from the same hemisphere in an infant, either sequentially or simultaneously, major impairment in the acquisition of texture tasks followed. These results suggest that although SI and SII are necessary for normal tactile function in the adult macaque, they show an equipotentiality for mediating normal tactile function after damage to either area in infants.
Redistribution and internalization of antibodies to galactocerebroside by oligodendroglia
Authors: Dyer CA , Benjamins JA
Published: March 2018

Glial cultures from mouse brain were used to examine the direct interaction between oligodendroglia and antibodies to galactocerebroside (GalC). The external surface of oligodendroglial membrane sheets showed large GalC+ patches separated by a GalC- network after exposure to anti-GalC and fluoresceinated second antibody at 37 degrees C. However, the membrane sheets were evenly stained when cultures were fixed prior to staining or stained at 0 degrees C. Further, exposure to second antibody at 0 degrees C or to Fab fragments of second antibody at 37 degrees C also gave even staining. These results indicate that GalC is normally distributed evenly on the surface of oligodendroglial membrane sheets, but that redistribution or patching of GalC:anti-GalC complexes occurs by cross-linking with second antibody at 37 degrees C. Antibodies to GalC are internalized rapidly and specifically by oligodendroglia. This process is temperature-dependent, and, in contrast to patching, does not require the presence of second antibody. Internalized antibodies are seen within 1 min throughout oligodendroglial membrane sheets, then aggregate in the sheets and in large vein-like structures leading to the cell body. By 1 hr, the cell body is densely packed with vesicles containing anti-GalC. By 24 hr after a 10 min exposure to anti-GalC, internal antibody has disappeared. Anti-GalC is recycled to the cell surface within 5 min after exposure, and continues to appear on the surface for at least 4 hr after the pulse.
Developmental changes in Ca2+/calmodulin-dependent protein kinase II in cultures of hippocampal pyramidal neurons and astrocytes
Authors: Scholz WK , Baitinger C , Schulman H , Kelly PT
Published: March 2018

We have analyzed Ca2+/calmodulin-dependent protein kinase II (CaM- kinase II) localization, activity, and endogenous protein substrates during differentiation and synaptogenesis in cultured hippocampal neurons. Primary cultures from hippocampi from 18 d embryonic rats are composed primarily of pyramidal neurons, with minimal contamination by nonneuronal cells. We have used monoclonal (Mab) and affinity-purified polyclonal antibodies that recognize either or both of the subunits of CaM-kinase II in order to localize the enzyme at progressive stages of neuronal differentiation. Diffuse but specific binding, determined by indirect immunofluorescence analyses, was first detected in cell bodies and growth cones of pyramidal neurons after 4 d in culture. Immunoreactivity increased during the next 3 d of culture, at which time fluorescent, labeling was patchy along neuritic processes. By 10 d, intensely fluorescent, discrete spots were observed along processes and on cell bodies. Astrocyte cultures prepared from newborn rat cortex showed no detectable immunofluorescence with anti-CaM-kinase II antibodies. Cytosolic and particulate fractions from cultured pyramidal neurons and astrocytes were analyzed using immunoblot, in vitro phosphorylation, 2-dimensional gel electrophoresis, and phosphopeptide mapping techniques. Although pure astrocyte cultures contained low levels of Ca2+/CaM-stimulated protein kinase activity, they did not display detectable levels of immunoreactive 50 kDa subunit nor 50 and 60 kDa phosphoproteins analogous to the autophosphorylated subunits of CaM-kinase II. Immunoblot analysis detected the 60 kDa kinase subunit in particulate and cytosolic fractions from 2 d neurons. By contrast, the 50 kDa subunit of CaM-kinase II was not detected in cytosolic or particulate fractions of pyramidal neurons before 4 d in culture. In 2 d pyramidal neuron cultures, only low levels of Ca2+/CaM-stimulated protein phosphorylation were observed. Ca2+/CaM-dependent phosphorylation of 10 d pyramidal cell proteins was 3–5-fold greater than that of 2 d cultures, and included major phosphoproteins of 48, 50, 56, 58/60, 80–86, 90, 120, 138, 175, and 190 kDa. Phosphopeptide maps of 58/60 and 50 kDa phosphoproteins gave patterns very similar to those of the autophosphorylated 60 and 50 kDa subunits, respectively, of purified CaM-kinase II. A phosphoprotein doublet of 83 kDa was identified as synapsin I. Developmental changes in Ca2+/CaM-dependent phosphorylation in pyramidal neuron cultures were very similar to those previously described in subcellular fractions from postnatal rat forebrain.
Autoradiographic localization and biochemical characteristics of M1 and M2 muscarinic binding sites in the striatum of the cat, monkey, and human
Authors: Nastuk MA , Graybiel AM
Published: March 2018

The autoradiographic distribution of M1 and M2 muscarinic cholinergic binding sites was studied in the striatum of the cat, monkey, and human, and concurrent binding assays were carried out on striatal tissue sections from the cat. M1 sites were directly labeled with 3H- pirenzepine; M2 sites were labeled as a consequence of binding competition between pirenzepine and 3H-N-methylscopolamine. Serial section analysis with autoradiograms and stained tissue sections allowed for comparisons among M1 and M2 binding distributions and AChE staining patterns. The 2 subtypes of binding sites demonstrated distinct striatal distributions. M2 sites were virtually homogeneous except in the ventral striatum, where zones of sparse and especially dense binding were observed. Striatal M1 sites were generally more abundant than M2 sites and showed similar heterogeneity in the ventral striatum. Dorsally, however, patches of dense M1 binding were found, and proved to correspond with AChE-poor striosomes, hallmarks of striatal compartmentalization. The finding of differing distributions for the 2 subtypes of muscarinic cholinergic binding sites suggests a mechanism for the intrinsic spatial segregation of striatal cholinergic function. Further, the striosomal patterning of M1 binding indicates that certain aspects of cholinergic function in the striatum may be constrained and thus regulated by the compartmental ordering characteristic of this region of the basal ganglia.
Proliferation and differentiation of rat neuroepithelial precursor cells in vivo
Authors: Frederiksen K , McKay RD
Published: March 2018

Important features of adult neuronal number, location, and type are a consequence of early embryonic events that occur before neurons have differentiated. We have measured cell number during embryogenesis of the rat CNS. Markers that are expressed in the proliferating neuronal precursor are required to study the mechanisms controlling their proliferation and differentiation. By applying immunohistochemistry, fluorescence-activated cell sorting, and 3H-thymidine auto-radiography to dissociated rat CNS cells, we show that the monoclonal antibody Rat 401 recognizes a cell population with proliferative, temporal, and quantitative features expected of neuronal precursors.
Can oligodendrocytes attached to myelin proliferate?
Authors: Ludwin SK , Bakker DA
Published: March 2018

The uptake of thymidine by oligodendrocytes in the brains of adult mice was examined after the induction of cortical traumatic lesions in an attempt to determine whether mature oligodendrocytes actively attached to myelin sheaths were capable of proliferating. In view of the great difficulty in visualizing the connection between a given oligodendrocyte and a myelin sheath even in the normal adult animal, the neuropil was made edematous in the traumatized animals in order to separate out the components and to study the oligodendrocyte processes. Uptake of tritiated thymidine was found in oligodendrocytes, as well as in endothelial cells, astrocytes, and microglia. The percentage of labeled oligodendrocytes appeared low in relation to the total number of the oligodendrocytes. In addition, in a few labeled cells, cytoplasmic processes could be seen extending to and apparently forming the myelin sheath. The possibility that a differentiated cell still attached to myelin may at the same time be able to proliferate is of great significance in understanding the potential for remyelination and recovery, in the adult, because it would imply that any oligodendrocyte is a candidate for proliferation, rather than only uncommitted or immature glial cells, which may be limited in the mature brain.
The central projections of the stretch receptor neurons of crayfish: segmental gradients of synaptic probability and strength
Authors: Bastiani MJ , Mulloney B
Published: March 2018

The 20 stretch receptor neurons (SRs) of the crayfish abdomen send axons into the CNS that then project both to the brain and to the last abdominal ganglion, G6 (Bastiani and Mulloney, 1988). In G6, we recorded intracellularly from different kinds of neurons postsynaptic to SR axons. In a sample of 100 postsynaptic neurons, 59 synapsed with both SR1 and SR2 axons, 19 synapsed only with SR1 axons, and 22 synapsed only with SR2 axons. Most monosynaptic connections in G6 were excitatory and behaved like typical chemical synapses. The EPSPs showed moderate facilitation but could be depressed about 50% by protracted stimulation at 20 Hz or more. In individual postsynaptic neurons, comparisons of synapses made by SRs that originated from different abdominal segments and from each side of the abdomen revealed gradients of probability of synaptic connection and of relative sizes of EPSPs; SRs originating in anterior segments were less likely to synapse with most postsynaptic neurons than were SRs originating in posterior segments, and the EPSPs caused by these anterior SRs tended to be smaller. Similarly, SRs contralateral to the postsynaptic neuron were less likely to make a connection, and the EPSPs they caused tended to be smaller than those caused by ipsilateral SRs. Some local interneurons in G6 had reversed anterior-posterior gradients in EPSP amplitude. Calculations of shape indices for PSPs from SRs originating in different segments and measurements of the maximum shunting by preceding PSPs from other SR axons indicated that neither electrotonic decrement in the postsynaptic neurons nor shunting could account fully for the observed gradients in PSP strength.
Functional anatomy of macaque striate cortex. III. Color
Authors: Tootell RB , Silverman MS , Hamilton SL , De Valois RL , Switkes E
Published: March 2018

Using spatially diffuse stimuli (or sinusoidal gratings of very low spatial frequency), levels of 14C-2-deoxy-d-glucose (DG) uptake produced by color-varying stimuli are much greater than those produced by luminance-varying stimuli in macaque striate cortex. Such a difference in DG results is consistent with previous psychophysical and electrophysiological results from man and monkey. In DG experiments with color-varying gratings of low and middle spatial frequencies, or with spatially diffuse color variations, DG uptake was highest in the cytochrome oxidase blobs, as was also seen with low-spatial-frequency luminance gratings. High-spatial-frequency, color-varying uptake patterns were shifted to cover both blob and interblob regions in a manner similar to that of the patterns obtained with middle-spatial- frequency luminance stimuli. However, in no instance did chromatic gratings produce uptake restricted to the interblob regions, as with the pattern seen with the highest-spatial-frequency luminance gratings. Thus, DG uptake is relatively higher in the interblob regions when comparing luminance with color-varying gratings that are otherwise similar. It was also possible to show DG evidence for receptive-field double-opponency in the upper-layer blobs, but color sensitivity in layer 4Cb appears single-opponent. The DG results suggest that color sensitivity is also high in the lower-layer (layers 5 + 6) blobs, and that many layer 5 receptive fields are double-opponent. Striate layers 4Ca and 4B-appeared color-insensitive in a wide variety of DG tests; this supports the idea of a color-insensitive stream running from the magnocellular LGN layers through striate layers 4Ca and 4B to extrastriate areas MT and V3. There was also a major effect due to wavelength: long and short wavelengths produced much more uptake than did middle wavelengths, even when all colors were equated for luminance and saturation. No variation with eccentricity was seen in cortical color sensitivity, at least between 0 degrees and 10 degrees.
The intermediolateral cell column of the thoracic spinal cord is comprised of target-specific subnuclei: evidence from retrograde transport studies and immunohistochemistry
Authors: Appel NM , Elde RP
Published: March 2018

In this study we examined the hypothesis that the intermediolateral cell column (IML) of the thoracic spinal cord, the nucleus from which preganglionic sympathetic neurons originate, provides an anatomical substrate through which selective regulation of sympathetic nervous system targets is accomplished. Preganglionic sympathetic neurons of rats were retrogradely labeled by the simultaneous exposure of the cervical sympathetic trunk (CST) and the adrenal medulla to Fluoro-Gold and True blue, contrasting fluorescent dyes. Retrograde labeling from these sites revealed 2 populations of sympathetic preganglionic neurons in IML whose distribution overlapped between segments T1 and T4. In regions where these 2 groups of retrogradely labeled neurons overlapped, sympathoadrenal preganglionic (SAP) neurons occupied the most lateral aspect of the nucleus. It was also determined whether individual retrogradely labeled neurons within these two groups sent axon collaterals to both the CST and adrenal medulla. Diamidino yellow, a fluorescent retrograde tracer dye that labels only nuclei, was substituted for Fluoro-Gold and used in combination with True blue to simultaneously label preganglionic sympathetic neurons projecting to either the CST or adrenal medulla. No double-labeled cell bodies were observed in spinal cords of rats treated in this manner. Thus it appeared that the efferent projections of these 2 cell populations in IML were target-specific. Immunohistochemical analysis of the relationship between nerve fibers in the IML and preganglionic sympathetic neurons was also undertaken in an attempt to classify further these 2 populations of sympathetic preganglionic neurons. Equal proportions of identified CST and SAP neurons appeared to be apposed by varicosities immunoreactive for either somatostatin or serotonin. On the other hand, when the comparison was based on whether oxytocin- immunoreactive varicosities appeared to appose these 2 populations of retrogradely labeled sympathetic neurons, a highly significant difference was revealed. That is, oxytocin-immunoreactive fibers and terminals appeared to avoid SAP neurons. Thus these data support the hypothesis that an anatomical substrate exists in spinal cord IML whereby selective regulation of sympathetic nervous system targets may be mediated. Moreover, the lack of oxytocin-immunoreactive varicosities apposing SAP neurons in IML suggests that if the paraventricular nucleus innervates SAP neurons in IML, it does so via a population of neurons that do not use oxytocin as a neurotransmitter.
Thalamic connections of two functional subdivisions of the somatosensory forepaw cerebral cortex of the raccoon
Authors: Doetsch GS , Standage GP , Johnston KW , Lin CS
Published: March 2018

The purpose of this study was to compare the thalamic interconnectivities of 2 functionally distinct subdivisions of the somatosensory (Sml) forepaw cortex of the raccoon--the somatotopic subdivision representing the glabrous skin of the digits and the more heterogeneous subdivision representing the hairy skin and claws. Injections of HRP were made into one or the other functional subdivision of a specific digit subgyrus of Sml cortex in 10 adult raccoons. The distribution of HRP-labeled neurons and axon terminals in the thalamus revealed that the 2 sectors have different patterns of thalamic projections. The glabrous skin region of each cortical digit zone was interconnected with a specific crescent-shaped lamella of neurons that extended rostrocaudally through the ventral posterior lateral (VPL) nucleus and typically was separated from adjacent lamellae by small bundles of myelinated fibers. The VPL lamellae constituted relatively distinct digit subnuclei that were connected somatotopically with the glabrous subdivisions of the corresponding cortical digit areas. The projections were dense, topographic, and reciprocal; labeled neurons and axon terminals within a particular lamella overlapped considerably and tended to be arranged in clusters. In contrast, the heterogeneous region of each cortical digit zone was reciprocally connected with the somatotopically appropriate VPL digit subnucleus and with adjoining subnuclei as well. The projections were comparatively sparse, less topographic, and more widely distributed than those of the glabrous skin sectors; groups of HRP-positive neurons and terminals in VPL tended to straddle the borders of the appropriate lamella and extended into adjacent lamellae. Furthermore, small clusters of labeling were found in the dorsal, presumed kinesthetic region of VPL and in portions of the ventral posterior inferior nucleus and the posterior nucleus. These results indicate that the glabrous cortical subdivisions have precise, somatotopically organized connections with specific VPL subnuclei, whereas the heterogeneous cortical subdivisions have more diffuse and scattered connections with several subregions of VPL and other thalamic nuclei as well. These 2 thalamocortical projection patterns may account for many of the differing functional properties of neurons residing within the 2 cortical sectors. Finally, the convergent thalamic projections to the heterogeneous cortical regions could contribute, at least indirectly, to the functional reactivation that occurs within Sml cortex of the raccoon following peripheral nerve transection (Kelahan and Doetsch, 1984).
Intracortical connections of two functional subdivisions of the somatosensory forepaw cerebral cortex of the raccoon
Authors: Doetsch GS , Standage GP , Johnston KW , Lin CS
Published: March 2018

The aim of this study was to compare the intrinsic intracortical connectivities of 2 functionally distinct subdivisions of the somatosensory (Sml) forepaw cortex of the raccoon--the somatotopic glabrous skin representation and the more heterogeneous, hairy skin and claw representation of the digits. HRP was injected into one or the other functional subdivision of a particular digit subgyrus of Sml cortex in 10 adult raccoons. The distribution of HRP-labeled neurons and axon terminals in the cortex showed that intrinsic “horizontal” connections exist within and between individual cortical digit zones; the labeling tended to have an oval-shaped configuration that was longer in the mediolateral than in the anteroposterior curvilinear plane. The 2 cortical sectors were found to have different patterns of intracortical projections. The connections of the glabrous skin region of each cortical digit zone were primarily local and confined to that same digit representation. HRP-filled neurons were concentrated near the injection site and decreased in density within the banks and fundi demarcating the injected digit subgyrus; few labeled cells were found in adjoining digit zones. Longer projections to the glabrous subdivision of a particular digit area typically originated from neurons in the heterogeneous subdivision of that same digit area. In contrast, the connections of the heterogeneous region of each digit zone were much more extensive and usually included projections from nonadjacent, as well as neighboring digit zones. The density of HRP- positive neurons declined more gradually with distance from the injection site, and considerable labeling was present in the heterogeneous sectors of adjacent digit zones. The intracortical projections of both functional subdivisions were often, but not always, reciprocal, and the cells of origin tended to be distributed in clusters. The laminar distributions of labeled neurons were similar for both sectors; HRP-filled cells were concentrated more in the supragranular layers, especially in layer III; fewer were found in the infragranular layers, mainly in layer VI and rarely in layer V. These results show that the intrinsic connections of the glabrous cortical subdivisions are fairly localized, whereas those of the heterogeneous cortical subdivisions are more diffuse and highly convergent. The differing intracortical connectional patterns of the 2 sectors are consistent with their contrasting thalamocortical projection patterns and may contribute to the unique functional properties of neurons located within each sector.(ABSTRACT TRUNCATED AT 400 WORDS)
Experimental induction of an abnormal ipsilateral visual field representation in the geniculocortical pathway of normally pigmented cats
Authors: Schall JD , Ault SJ , Vitek DJ , Leventhal AG
Published: March 2018

In the normally pigmented neonatal cat, many ganglion cells in temporal retina project to the contralateral dorsal lateral geniculate nucleus (LGNd) and medial interlaminar nucleus (MIN). Most of these cells are eliminated during postnatal development. If one optic tract is sectioned at birth, much of this exuberant projection from the contralateral temporal retina is stabilized (Leventhal et al., 1988b). To determine how the abnormal projection from the contralateral temporal retina is accommodated in the central visual pathways, neuronal activity was recorded in the visual thalamus and cortex of adult cats whose optic tracts were sectioned as neonates. The recordings showed that up to 20 degrees of the ipsilateral hemifield is represented in the LGNd and MIN. Recordings from areas 17 and 18 of the intact visual cortex showed that up to 20 degrees of the ipsilateral visual field is also represented and that the ipsilateral representation is organized as in a Boston Siamese cat (Hubel and Wiesel, 1971; Shatz, 1977; Cooper and Blasdel, 1980) or a heterozygous albino cat (Leventhal et al., 1985b). The extent of the ipsilateral visual field representation was greater in area 18 than in area 17; the extent of the ipsilateral hemifield representation in areas 17 and 18 varied with elevation, increasing with distance from the horizontal meridian. The receptive fields of cells in the LGNd and visual cortex subserving contralateral temporal retina were abnormally large. Otherwise, their receptive field properties seemed normal. In the same animals studied physiologically, HRP was injected into the ipsilateral hemifield representation in the LGNd and MIN of the intact hemisphere. The topographic distribution of the alpha and beta cells, respectively, labeled by these injections correlated with the elevation-related changes in the ipsilateral visual field representation in areas 18 and 17. Our results indicate that the retinotopic organization of the mature geniculocortical pathway reflects the abnormal pattern of central projections of ganglion cells in neonatally optic tract sectioned cats. Thus, if they do not die, retinal ganglion cells normally eliminated during development are capable of making seemingly normal, functional connections. The finding that an albino-like representation of the ipsilateral hemifield can be induced in the visual cortex of normally pigmented cats suggests that the well- documented defects in the geniculocortical pathways of albinos are secondary to the initial misrouting of ganglion cells at the optic chiasm (Kliot and Shatz, 1985) and not a result of albinism per se.
Characterization and regional distribution of glutamatergic and cholinergic ligand binding sites in goldfish brain
Authors: Henley JM , Oswald RE
Published: March 2018

The binding of several ligands that selectively interact with glutamate receptor subtypes was characterized in extensively washed synaptosomal membrane preparations from goldfish brain. The binding affinity (Kd), an estimate of the number of sites (Bmax), the rank-order potency of glutamatergic ligands at inhibiting binding, and the regional localization of binding sites were determined. In whole brain preparations, 3H-kainate had a Kd of 136 nM and a Bmax of 63 pmol/mg protein, 3H-AMPA had a Kd of 26 nM and a Bmax of 0.4 pmol/mg protein, and 3H-L-glutamate bound with an apparent affinity of 323 nM and a Bmax of 5 pmol/mg protein. Most of the binding sites for each of the glutamate analogs were present in the cortex and the fewest were in the cerebellum, except for 3H-kainate binding sites, which were most prevalent in the cerebellum and least abundant in the cortex. The proposed neuronal nicotinic acetylcholine receptor (nAChR) ligands 3H-(- )nicotine and 125I-alpha-Bgt were also investigated. 125I-alpha-Bgt had a Kd of 0.08 nM and a Bmax of 132 fmol/mg protein. 3H-(-)nicotine did not bind to the extensively washed membrane preparations, so a less stringently washed P2 tissue fraction was used. In this tissue preparation, 3H-(-)nicotine had a Kd of 9 nM and a Bmax of 84 fmol/mg protein. Eye removal resulted in a time-dependent decrease in the number of 3H-(-)nicotine and 125I-alpha-Bgt binding sites in the contralateral optic tectum, but no reduction in the number of binding sites for any of the glutamatergic ligands. The results suggest that both 3H-(-)nicotine and 125I-alpha-Bgt binding sites are similarly regulated in the optic tectum, which supports previously reported data indicating that the binding sites are located on closely related proteins or may, at least partially, be colocalized on the same protein (Henley and Oswald, 1987).(ABSTRACT TRUNCATED AT 250 WORDS)
Distribution of growth cones and synapses in developing laminar and interlaminar regions of the dorsal lateral geniculate nucleus
Authors: Brunso-Bechtold JK , Vinsant SL
Published: March 2018

In the present study, we quantified the distribution of growth cones and synapses in 2 developing layers, as well as in the intervening interlaminar space of the dorsal lateral geniculate nucleus (dLGN) in tree shrews. Our goal was to gain insight into mechanisms involved in the segregation of dLGN cells into layers during development. We sacrificed tree shrews before (P0), during (P4 and P7), and after (P15) laminar segregation as well as at maturity (P90). The dLGN from each animal was sectioned horizontally, and all tissue for analysis was blocked from the middle third of the nucleus along the dorsoventral axis. Each micrograph was coded and blindly scored for the number of growth cones and synapses in layers 4 and 5 and the intervening interlaminar space. We also measured each growth cone and classified synapse type. Statistical analyses of these data reveal that neither growth cones nor synapses are significantly more common in the interlaminar space early in the period of laminar segregation (P4). By nearly a week after the interlaminar space can first be distinguished (P7), there are more growth cones in the interlaminar space than in the layers, but this difference is no longer present at (P15). These results suggest that, although neuropil development at the laminar borders may not play a role in the onset of laminar segregation, it may contribute to the widening of the interlaminar spaces once this process has begun. In addition, growth cones continuously decrease in number and become less bulbous and more linear in shape with development. Synapses, on the other hand, continuously increase in number with age and pass through a transient period characterized by heavy spinous terminations.
Cellular interrelationships during laminar segregation in the dorsal lateral geniculate nucleus
Authors: Brunso-Bechtold JK , Vinsant SL
Published: March 2018

In order to gain insight into the mechanisms involved in the formation of groupings of functionally similar cells in the developing nervous system, we have studied the formation of cell layers in the developing dorsal lateral geniculate nucleus (dLGN). To examine the possibility that a higher affinity or adhesion between cells in individual layers may play a role in laminar segregation, we studied cellular interrelationships in the dLGN of tree shrews before (P0), during (P4 and P7), and just after (P15) laminar segregation has taken place. We compared our observations at these stages of development with similar observations in the adult. In none of the cases do we see evidence of gap junctions either between adjacent neurons or between neurons and processes in the surrounding neuropil. However, we frequently observe the presence of puncta adherentes between adjacent neurons at all stages of development. These profiles are also present between neurons and cellular processes in the neuropil. We also see subsurface cisternae in all of our cases, although these are more pronounced before and during interlaminar space formation. As with the puncta adherentes, these are found both between adjacent neurons as well as between neurons and other elements in the neuropil. We also see some evidence of what appear to be cytoplasmic bridges between adjacent neurons; these are quite rare but appear to be present only before and during laminar segregation. Finally, we frequently see cytoplasmic processes interdigitated between otherwise immediately adjacent cells. These processes also are often found oriented along other portions of the neuronal plasmalemma. Whether these processes are portions of neuronal growth cones or glial processes is impossible to determine at this time. Because of the potential role glial processes may play in the formation and maintenance of laminar cell groupings during layer formation, we have also made a preliminary survey of whether glial cells can be distinguished ultrastructurally at the stages we have studied.
Mapping of radial glia and of a new cell type in adult canary brain
Authors: Alvarez-Buylla A , Theelen M , Nottebohm F
Published: March 2018

Frontal and coronal sections of adult male and female canary brain were stained with a monoclonal antibody to vimentin using an immunoperoxidase technique; some sections were counterstained with cresyl violet. The position of radial glia cells was mapped using a computer-linked microscope. The telencephalon was found to have a rich set of radial glia. The long processes of these radial glia showed a mediolateral orientation, and were much more abundant in some parts of the telencephalon (e.g., hyperstriatum, caudal neostriatum, and lobus parolfactorius) than in others (e.g., anterior neostriatum, archistriatum, and septum), which had few or no radial glia fibers. A small, elongated cell type not previously described in adult avian brain was frequently seen to be associated with the long processes of the radial glia, oriented in the same direction and often in close apposition. The position of these cells was also systematically mapped, and they were found to be virtually absent outside of the telencephalon. The relation between radial glia fibers and the small, elongated cells was most commonly seen close to the lateral ventricle of the forebrain, where the radial glia cells have their cell bodies. The above observations suggest that there may be a functional relation between radial glia and the small, elongated cells. We hypothesize that the latter cells are young migrating neurons. This hypothesis is tested in a separate publication (A. Alvarez-Buylla and F. Nottebohm, unpublished observations).