bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional reorganization in somatosensory cortical areas 3b and 1 of adult monkeys after median nerve repair: possible relationships to sensory recovery in humans
Authors: Wall JT , Kaas JH , Sur M , Nelson RJ , Felleman DJ , Merzenich MM
Published: March 2018

Previous studies have shown that the primary somatosensory cortex of adult mammals undergoes somatotopic reorganization in response to peripheral nerve transection. The present study assesses how cortical organization is affected when a transected nerve subsequently regenerates. The median nerve to one hand of adult owl monkeys was transected and repaired. Following nerve regeneration, the representations of the hand in cortical areas 3b and 1 were studied with neurophysiological mapping methods. The major results were as follows: Peripherally, median nerve transection, repair, and regeneration resulted in reinnervation of the median nerve skin territory. Centrally, both the initial loss and subsequent regeneration of median nerve inputs caused reorganizational changes in cortex. Reorganizational changes were specifically restricted to regions of the hand cortex where inputs from the median nerve were normally represented. The functional features of cortical regions that recovered tactile responsiveness from reinnervated skin regions were abnormal in several respects. Most notably, these regions contained recording sites with abnormally located or multiple cutaneous receptive fields, and contained major topographical changes, such as reestablishment of palmar pad or digit representations in small, discontinuous patches of cortex. Normal organizational features were reestablished to a more limited extent. These features included recovery of delimited, discrete receptive fields and reestablishment of topographic representations for localized skin areas. Different transformations in topographical organization were seen in areas 3b and 1 of the same monkey. These results suggest that nerve regeneration reestablishes the cortical capacity to process tactile information from reinnervated skin via a prolonged reorganizational process that appears dependent on peripheral and central factors. Cortical recovery mechanisms clearly appear to have limitations, since preinjury patterns of cortical organization are not widely recovered even almost 1 year after repair. We suggest possible relationships between cortical reorganizational changes in these primates, and postrepair sensory changes in humans.
Analysis of FMRF-amide effects on Aplysia bursting neurons
Authors: Ruben P , Johnson JW , Thompson S
Published: March 2018

The peptide L-phenylalanyl-L-methionyl-L-arginyl-L-phenylalaninamide (FMRF-amide) was pressure-applied onto the somata of bursting neurons L4 and L6 in the Aplysia abdominal ganglion. FMRF-amide causes a biphasic response, first depolarizing and then hyperpolarizing the neuron. In voltage-clamp experiments, FMRF-amide induces an inward current that begins 100–200 msec after applying the peptide and peaks in 2–10 sec. This is followed by an outward current that begins with a latency of 2–5 sec and peaks in 15–65 sec. The entire response lasts 1– 5 min. Experiments were done to separate the two currents induced by FMRF-amide on the basis of ion selectivity and kinetics and to determine their I(V) relationships. The currents were studied using a method to quickly measure I(V) curves. The inward current is caused by a conductance increase and has a reversal potential of approximately +18 mV. This current depends on the concentration of extracellular Na ions but not Ca, Cl, or K ions and is insensitive to tetrodotoxin, hexamethonium, and curare. The outward current is caused by a conductance increase and has a reversal potential of approximately -61 mV, which is similar to the reversal potential of the fast, transient K current (IA) in the same cells. This current is sensitive to changes in the external K ion concentration but not to changes in Cl, Ca, or Na concentration. The outward current is partially blocked by 1 mM 4- aminopyridine but not TEA or curare. Neither current is significantly voltage dependent within the range from -70 to -40 mV.(ABSTRACT TRUNCATED AT 250 WORDS)
Doses of 6-hydroxydopamine sufficient to deplete norepinephrine are not sufficient to decrease plasticity in the visual cortex
Authors: Trombley P , Allen EE , Soyke J , Blaha CD , Lane RF , Gordon B
Published: March 2018

These experiments were designed to test Kasamatsu and Pettigrew's (1979, 1983, and see below) hypothesis that plasticity in the visual cortex requires cortical norepinephrine (NE). Kittens were treated with various doses of intraventricular 6-hydroxydopamine (6-OHDA) or vehicle solution. Cortical NE content was measured with high-performance liquid chromatography with electrochemical detection. We sutured the right eyes of some kittens approximately 6 weeks of age for 1 week and recorded from the left visual cortex of these kittens at the end of the week of suture. We measured the ability of the deprived eye to drive cortical cells in animals that received either 0.2 or 4.8 mg of 6-OHDA, and also in control animals that received only vehicle solution. We concluded that a particular dose of 6-OHDA decreased plasticity if it increased (relative to controls) the ability of the deprived eye to drive cortical cells. Doses of 6-OHDA as small as 0.2 mg were sufficient to produce approximately maximal depletion of NE but did not decrease cortical plasticity. Doses of 4.8 mg or more did decrease cortical plasticity, although not as much as was reported by Kasamatsu and Pettigrew. We conclude that 6-OHDA can alter cortical plasticity but the decrease in plasticity does not result from NE depletion.
Organization of choline acetyltransferase-containing structures in the forebrain of the rat
Authors: Ichikawa T , Hirata Y
Published: March 2018

The cholinergic structures in the forebrain of the rat were studied immunohistochemically with a monoclonal antibody to choline acetyltransferase (ChAT) which has proven to be particularly suited to reveal the trajectory of ChAT-positive fibers and their terminations. The habenulo-interpeduncular tract contained the most distinctly ChAT- positive fibers. Here, ChAT-positivity was demonstrated in the perikarya, fibers and terminal field. From the basal forebrain, ChAT- positive fiber bundles could be followed rostrally to the olfactory bulb, dorsomedially to the neocortex and hippocampus, and dorsocaudally to the hippocampus. Terminations of ChAT-positive fibers in these regions were either boutons terminaux (in the interpeduncular nucleus), finely granular (in the hippocampus) or a network of varicose fibers (in the olfactory bulb and neocortex). Cholinergic terminal fields were also demonstrated in the following regions: the nucleus of the lateral olfactory tract, the olfactory tubercle, the pyriform cortex, the lateral nucleus and part of the basal nucleus of the amygdala, the caudate-putamen, the nucleus accumbens, some thalamic nuclei, and the suprachiasmatic nucleus of the hypothalamus. In most of these regions, ChAT-positivity appeared as either fine granules or a meshwork of varicose fibers.
Pioneer growth cone morphologies reveal proximal increases in substrate affinity within leg segments of grasshopper embryos
Authors: Caudy M , Bentley D
Published: March 2018

We have compared the morphologies of approximately 5000 antibody- labeled afferent pioneer growth cones fixed at various stages of growth along their characteristic path over the epithelium in the legs of grasshopper embryos, and have used growth cone morphology as an indicator of differences in the affinity of the epithelial substrate for pioneer growth cones in vivo. Growth cone morphologies differ markedly between different locations in limb buds, and also in the same location in limbs at different stages of differentiation. Growth cones characteristically extend branches and lamellae circumferentially along segment boundaries, and filopodia and lamellae are retained (or extended) longer there. Where they contact a relatively well- differentiated segment boundary, the growth cones also abruptly reorient circumferentially. In the proximal regions of limb segments, growth cones consistently have a high degree of branching and lamellae; previously formed axons also extend secondary branches and spread there as development progresses. Low incidence of these morphologies is observed at all stages in the distal regions of limb segments. Thus, neuronal morphologies correlate both spatially and temporally with the differentiation of limb segmentation. These results suggest the following: Detailed growth cone morphology is a reliable indicator of differences in extrinsic guidance cues. The affinity of the epithelial substrate for afferent pioneer growth cones increases proximally within segments, with a peak at the segment boundary. (This affinity could be based on surface density of adhesion molecules or on nonadhesive molecules that actively regulate growth cone extension.) Increasing epithelial affinity within segments appears to act as a proximal guidance cue for afferent pioneer growth cones. Pioneer growth cones are observed to navigate proximally in circumstances where proximally located guidepost cells differentiate too late to guide them.
Differentiation of NTERA-2 clonal human embryonal carcinoma cells into neurons involves the induction of all three neurofilament proteins
Authors: Lee VM , Andrews PW
Published: March 2018

Monoclonal antibodies were used in indirect immunofluorescence and immunoblot studies to examine the expression of four different classes of intermediate filaments, namely, neurofilaments, glial filaments, cytokeratin, and vimentin, in NTERA-2 cl.D1 (NT2/D1) pluripotent human embryonal carcinoma (EC) cells, and in the neurons derived from these cells by differentiation induced with retinoic acid. In the EC cell cultures, grown in the absence of retinoic acid, cytokeratin was the predominant intermediate filament detected by immunofluorescence; only a few cells expressed vimentin, and none expressed glial filament protein or any of the three neurofilament proteins (NF195, NF170, and NF70). Immunoblot analyses of cytoskeletal extracts of these cells supported these data. Two days after exposure to retinoic acid, all three neurofilament subunits were detected in a few cells with a non- neuronal morphology and, by double indirect immunofluorescence, were observed to colocalize with cytokeratin. The number of neurofilament- positive cells increased with time after initial exposure to retinoic acid, and although 95% of these cells contained cytokeratin initially, less than 5% of the neurofilament-positive cells retained cytokeratin 2 weeks later. By this time, many of the cells expressing all three neurofilaments but no cytokeratin exhibited a neuronal morphology. Vimentin was evident in a large number of cells in the cultures, but it was not detected in the neurofilament-positive cells. Also, many of the neurofilament-negative cells continued to express cytokeratin. No cells expressing glial filament proteins were found. Immunoblot analysis of the differentiated cultures also revealed all three neurofilament subunits, and vimentin and cytokeratin, but no glial filament protein.(ABSTRACT TRUNCATED AT 250 WORDS)
Neurite outgrowth patterns in cerebellar microexplant cultures are affected by antibodies to the cell surface glycoprotein L1
Authors: Fischer G , Kunemund V , Schachner M
Published: March 2018

To probe for the role of the L1 cell surface glycoprotein during neurite outgrowth and fasciculation in the early postnatal mouse cerebellar cortex, a microexplant culture system was used. Fasciculation of neurites was reduced in the presence of antigen- binding fragments (Fab) of poly- and monoclonal L1 antibodies, as compared to untreated controls. In addition, speed of neurite outgrowth was enhanced in the presence of antibodies. Migration of cell bodies of small neurons was also significantly increased. Very similar effects on these outgrowth parameters were observed with Fab fragments from poly- and monoclonal neural cell adhesion molecule (N-CAM) antibodies. Antibodies from preimmune sera had no effect. These findings suggest that L1 antigen not only plays a role in adhesion of isolated neural cell bodies and migration of granule cell neurons in the early postnatal mouse cerebellar cortex (Lindner et al., 1983; Rathjen and Schachner, 1984), but also in neurite outgrowth and fasciculation.
L-glutamate: a neurotransmitter candidate for cone photoreceptors in the monkey retina
Authors: Sarthy PV , Hendrickson AE , Wu JY
Published: March 2018

In order to examine whether L-aspartate and L-glutamate are photoreceptor transmitters in monkey retina, we have carried out two different studies: an autoradiographic localization of the high- affinity uptake sites for aspartate (Asp) and glutamate (Glu), and an immunocytochemical localization of the biosynthetic enzyme, L-aspartate aminotransferase (AAT). Our results show that L-Glu is taken up by a sodium-dependent, high-affinity uptake system with a Km = 8 +/- 3.5 X 10(-6) M and a Vmax = 48 +/- 14 X 10(-12) mol/min/mg protein; 3H-L-Glu or 3H-L- and D-Asp are taken up and accumulated by rod somata and inner segments in retinas incubated at 37 degrees C or at ambient temperature; cones accumulate 3H-L-Glu at ambient temperature but not at 37 degrees C. Neither 3H-L-Asp nor D-Asp is accumulated by cones at either temperature; rods and cones show the same labeling pattern irrespective of whether they are located in the central or peripheral retina; and antiserum to AAT preferentially stains the cone somata, inner segments, and synaptic pedicles, while the outer segments are negative. Both foveal and peripheral cones are strongly reactive, but rods show little reactivity. These findings point to the existence of major differences between rods and cones in the uptake and metabolism of L-Asp and L-Glu and are consistent with L-Glu being a cone transmitter in the monkey retina.
Expression of neurofilament subunits in neurons of the central and peripheral nervous system: an immunohistochemical study with monoclonal antibodies
Authors: Trojanowski JQ , Walkenstein N , Lee VM
Published: March 2018

The extent to which all neurofilament (NF) subunits (NF68, NF150, NF200) are expressed by different populations of mature CNS and PNS neurons is controversial. We addressed this issue in immunohistochemical studies of mature bovine tissues using monoclonal antibodies specific for each bovine NF subunit. All three NF subunits were detected in the perikarya and neurites of both CNS and PNS neurons; they were seen in nearly all PNS neuronal perikarya, and in all identifiable CNS and PNS axons. Most, but not all, CNS neuronal perikarya contained each of these NF antigens. CNS neurons devoid of immunodetectable NF antigens were generally small. The presence of low levels of NF antigens in neurons with scant perikaryal cytoplasm may account for the apparent absence of NF immunoreactivity in some classes of neurons, although other explanations, such as microheterogeneity among NF proteins, could account for this finding. NF antigens were also seen in some cells of the diffuse neuroendocrine system (adrenal chromaffin cells and cells of the pars distalis and pars intermedia), but not in other cell types. We suggest that the expression of all three NF subunits is a common feature of CNS and PNS neurons and their processes, and of some cells of the diffuse neuroendocrine system. These findings have implications for hypotheses concerning the structure and function of the intermediate filaments of neurons, and for hypotheses concerning neurodegenerative diseases involving NF proteins.
Loss of acetylcholine receptor clusters induced by treatment of cultured rat myotubes with carbachol
Authors: Bloch RJ
Published: March 2018

Prolonged exposure to carbachol disrupts the acetylcholine receptor (AChR) clusters of cultured rat myotubes without causing myotube loss. The effect is reversible, and is dependent on temperature. Half-maximal cluster loss is achieved at 3 microM carbachol. Cluster loss is also caused by other agonists of the AChR and is blocked by receptor antagonists. QX314 (a lidocaine derivative), meproadifen, and fluphenazine also completely block cluster loss caused by carbachol. These results are consistent with the idea that cluster loss caused by carbachol and other receptor agonists results from their interaction with the AChR, and the consequent influx of cations into the myotubes. Several experiments suggest that extracellular Na+ and Ca2+ are required, and that at least Na+ must permeate the AChR ion channel for full cluster loss to occur in the presence of carbachol. Depolarization alone is not sufficient to cause cluster loss, however. Ca2+-activated proteases do not play a significant role in carbachol-induced cluster loss.
Characterization of inhibition of the spinal nociceptive tail-flick reflex in the rat from the medullary lateral reticular nucleus
Authors: Gebhart GF , Ossipov MH
Published: March 2018

Inhibition of the spinal nociceptive tail-flick (TF) reflex by focal electrical stimulation in the caudal medulla was examined and characterized in lightly pentobarbital-anesthetized rats. Systematic mapping studies revealed that inhibition of the TF reflex was produced at low intensities of stimulation (12.5–25 microA) only from the lateral reticular nucleus (LRN). Areas dorsal and medial to the LRN required higher intensities of stimulation to produce descending inhibition of the TF reflex, likely reflecting spread of current to the LRN at these higher intensities of stimulation (50–100 microA). At threshold inhibitory intensities of stimulation in the LRN, changes in blood pressure were not produced. Strength-duration characterization of stimulation and the microinjection of glutamate into the LRN at the same site where focal electrical stimulation was effective suggest that the descending inhibition produced arises from activation of cell bodies in the LRN. The intrathecal administration of a variety of pharmacological antagonists revealed the descending inhibition produced by stimulation in the LRN to be mediated at least in part by spinal alpha 2-adrenoceptors. These findings, together with previous observations, suggest a role for the LRN in the centrifugal modulation of spinal nociceptive transmission.
Estrogen establishes sex differences in androgen accumulation in zebra finch brain
Authors: Nordeen KW , Nordeen EJ , Arnold AP
Published: March 2018

In zebra finches, androgens stimulate the production of a learned courtship song in males but not in females. Corresponding to this behavioral dimorphism, neural regions controlling the learning and production of song are much larger in males than in females. In two of these song-related brain regions, magnocellular nucleus of the anterior neostriatum (MAN) and hyperstriatum ventrale pars caudale (HVc), males have a larger percentage of androgen-accumulating cells than females. Since sex differences in the capacity for song and in the size of songrelated nuclei are established by gonadal hormones shortly after hatching, we determined whether the early hormonal environment also establishes sex differences in androgen accumulation within MAN and HVc. Newly hatched female zebra finches received either estradiol (E2) or cholesterol (Ch). Three to six months later, E2-females, Ch-females, and normal adult males were gonadectomized and injected 24 hr later with 3H-dihydrotestosterone. Autoradiograms were prepared, and the incidence of androgen-labeled cells was determined for MAN, HVc, and a control region, the lateral septal nucleus (SL). In females, early E2 exposure dramatically increases the percentage of androgen-accumulating cells in MAN and HVc, without influencing androgen accumulation in SL. In MAN and HVc, the percentage of androgen-concentrating cells in E2- females approximates that observed in normal adult males. Cells also tended to be more densely labeled in E2-females than in Ch-females. Since early E2 exposure renders the female song system neuroanatomically and functionally responsive to androgens, we suggest that E2 establishes this responsiveness by regulating the number of androgen target neurons within MAN and HVc.
Differential distribution of cell adhesion molecules during histogenesis of the chick nervous system
Authors: Daniloff JK , Chuong CM , Levi G , Edelman GM
Published: March 2018

We have compared the expression of the neural cell adhesion molecule (N- CAM) and the neuron-glial cell adhesion molecule (Ng-CAM) during histogenesis of the chick nervous system. Data from immunohistochemistry and photometry were combined to construct maps of the overall distribution and dynamics of CAM appearance and disappearance. Each CAM appeared in a characteristic spatial and temporal pattern in various areas during cell movement, fiber outgrowth, tract formation, and myelination. N-CAM was more uniformly distributed than Ng-CAM and was present on all neural cell bodies and processes of the CNS and PNS. In the adult, the staining pattern of N- CAM remained similar to that in the embryo, although the staining intensity was diminished. During embryonic development, Ng-CAM was expressed on extending neurites and migrating neurons. The appearance Ng-CAM in the CNS was correlated particularly with times of cell migration in spinal cord and cerebellum, and in regions undergoing neurite extension, such as the developing white matter of the spinal cord, the optic nerve, and the medial longitudinal fasciculus. Cell bodies not undergoing migration were negative for Ng-CAM. In the adult CNS, Ng-CAM was markedly decreased in myelinated fiber tracts like the white matter of the spinal cord but persisted in unmyelinated regions such as the olfactory bulb. In contrast, in the PNS (for example, the dorsal root ganglion and sciatic nerve), Ng-CAM appeared early on both cell bodies and neurites, and it continued to be present on both in the adult, even in the presence of myelin. Maps comparing the relative distribution of Ng-CAM and N-CAM showed dynamic reversals as the nervous system developed and, as a result, the pattern of CAM expression was markedly different in embryos and adults. This difference appears to reflect changes in the roles of selective adhesion and of the two neuronal CAMs at different times of development.
Synaptic plasticity in vitro: cell culture of identified Aplysia neurons mediating short-term habituation and sensitization
Authors: Rayport SG , Schacher S
Published: March 2018

The gill withdrawal reflex of the marine mollusk, Aplysia californica, shows habituation and sensitization, two simple forms of learning. In order to extend the cellular studies on synaptic plasticity underlying the changes in the reflex behavior, and to explore further the development of synaptic plasticity during synapse formation, we have sought to establish the neural circuit of the gill withdrawal reflex in vitro. We report here the reconstruction of the elementary gill withdrawal circuit in cell culture and find that the cells show short- term homosynaptic depression and heterosynaptic facilitation, the cellular mechanisms of habituation and sensitization, respectively.
Variation in content and function of non-neuronal cells in the outgrowth of sympathetic ganglia from embryos of differing age
Authors: Roufa D , Bunge MB , Johnson MI , Cornbrooks CJ
Published: March 2018

Studies on cellular interactions in the developing nervous system are greatly facilitated by the availability of tissue culture preparations that contain single or combined populations of neurons and non-neuronal cells (NNCs). Using superior cervical ganglia (SCG) from early E15 rats on air-dried collagen, we were able to prepare cultures containing neurons along with Schwann cells (SCs) as the only NNC type present without the use of antimitotic treatment and cultures containing only neurons, following brief antimitotic treatment. Light-microscopic observation of E15 outgrowth showed a uniform population of flattened cells, unlike that of E20 cultures, which contained a mixture of spindle-shaped and flattened cells. Autoradiograms following [3H]thymidine administration to E15 cultures revealed a striking gradient of nuclear labeling: Only a few cells were labeled near the explant and nearly all cells were labeled at the growth front. This was in marked contrast to E20 cultures, in which nuclei were labeled throughout the outgrowth. The conclusion that the labeling gradient is explained by the presence of SCs without other NNC types in E15 cultures was confirmed by immunocytochemical studies. Anti-laminin antibodies stain only those extracellular matrix components related to the SC surface, whereas anti-fibronectin antibodies stain fibroblast- related components (Cornbrooks et al., 1983a). Anti-laminin antibodies stained cell surfaces in both E15 and E20 outgrowth. E15 outgrowth did not stain with anti-fibronectin antibodies although marked staining was obtained in E20 cultures. Electron microscopy confirmed the presence of only SCs in E15, and of both SCs and fibroblasts in E20 outgrowth. Thus, it appears that there is a narrow developmental window in which the ganglia contain neurons and SCs but relatively few fibroblast components; cultures prepared from ganglia at this stage form outgrowth containing only neurites and SCs without antimitotic treatment. Surprisingly, neither SC ensheathment nor SC basal lamina formation was normal in E15 and E20 outgrowth. When either E15 or E20 SCG SCs were transplanted onto dorsal root ganglion neurons free of endogenous SCs, however, the sensory neurites were typically ensheathed or myelinated and basal lamina appeared 9 d later, identifying the SCG NNCs as functionally competent SCs.(ABSTRACT TRUNCATED AT 400 WORDS)
The bag cells of Aplysia as a multitransmitter system: identification of alpha bag cell peptide as a second neurotransmitter
Authors: Sigvardt KA , Rothman BS , Brown RO , Mayeri E
Published: March 2018

The bag cell neurons of the marine mollusk, Aplysia, are a putative multitransmitter system that utilizes two or more peptide transmitters derived from a common precursor protein. Two putative transmitters are egg-laying hormone (ELH), a 36 amino acid peptide that induces egg laying and mediates bag cell-induced excitatory effects on certain abdominal ganglion neurons, and alpha-bag cell peptide (alpha BCP), which mimics bag cell-induced inhibition of the left upper quadrant (LUQ) neurons and the depolarization of the bag cells that occurs during the bag cell burst discharge. Alpha BCP was previously purified from bag cell extracts in three neuroactive forms: alpha BCP(1–9), a nine amino acid peptide encoded on the ELH/BCP precursor protein, and two NH2-terminal fragments, alpha BCP(1–8) and alpha BCP(1–7). Analyzing bag cell-induced inhibition of LUQ neurons, we report here that alpha BCP fulfills the main criteria for transmitter identification: stimulation of individual bag cells produces inhibition of the neurons; inhibitory activity is present in releasate collected following an elicited bag cell burst discharge in the presence of protease inhibitors; alpha BCP(1–9) and alpha BCP(1–8) are detected in the releasate in the presence of protease inhibitors; alpha BCP is rapidly inactivated after release, as indicated by the lack of detectable alpha BCP or inhibitory activity in the releasate in the absence of protease inhibitors, and by the increase in potency of the arterially perfused peptide in the presence of protease inhibitors; alpha BCP and the endogenously released transmitter produce apparently identical changes in membrane conductance; bag cell-induced inhibition is reduced or abolished following desensitization of the inhibitory response by long-term application of high concentrations of alpha BCP. The results provide additional evidence that the bag cells are a multitransmitter system and also suggest that many of the physiological properties of alpha BCP-mediated neurotransmission differ from those of ELH. First, unlike ELH, alpha BCP is rapidly inactivated after release. Second, alpha BCP(1–9) may be activated by carboxypeptidase cleavage since alpha BCP(1–8) and alpha BCP(1–7) are 30 and 10X as potent, respectively, as alpha BCP(1–9). Third, the inhibitory action of alpha BCP on its targets has a more rapid onset and a shorter time course than the excitatory actions of ELH. Thus, alpha BCP may diffuse to less distant targets than ELH and serve to regulate the more rapidly occurring neural events underlying egg-laying behavior.
Retinal constraints on orientation specificity in cat visual cortex
Authors: Schall JD , Vitek DJ , Leventhal AG
Published: March 2018

Most retinal ganglion cells (Levick and Thibos, 1982) and cortical cells (Leventhal, 1983; Leventhal et al., 1984) subserving peripheral vision respond best to stimuli that are oriented radially, i.e., like the spokes of a wheel with the area centralis at the hub. We have extended this work by comparing directly the distributions of orientations represented in topographically corresponding regions of retina and visual cortex. Both central and peripheral regions were studied. The relations between the orientations of neighboring ganglion cells and the manner in which the overrepresentation of radial orientations is accommodated in the functional architecture of visual cortex were also studied. Our results are based on an analysis of the orientations of the dendritic fields of 1296 ganglion cells throughout the retina and the preferred orientations of 1389 cells located in retinotopically corresponding regions of cortical areas 17, 18, and 19 in the cat. We find that horizontal and vertical orientations are overrepresented in regions of both retina and visual cortex subserving the central 5 degrees of vision. The distributions of the orientations of retinal ganglion cells and cortical cells subserving the horizontal, vertical, and diagonal meridians outside the area centralis differ significantly. The distribution of the preferred orientations of the S (simple) cells in areas 17, 18 and 19 subserving a given part of the retina corresponds to the distribution of the dendritic field orientations of the ganglion cells in that part of retina. The distribution of the preferred orientations of C (complex) cells with narrow receptive fields in area 17 but not C cells with wide receptive fields in areas 17, 18, or 19 subserving a given part of the retina matches the distribution of the orientations of the ganglion cells in that part of retina. The orientations of all of the alpha-cells in 5–9 mm2 patches of retina along the horizontal, vertical, and oblique meridians were determined. A comparison of the orientations of neighboring cells indicates that other than a mutual tendency to be oriented radially, ganglion cells with similar orientations are not clustered in the retina. Reconstructions of electrode penetrations into regions of visual cortex representing peripheral retina indicate that columns subserving radial orientations are wider than those subserving nonradial orientations. Our results provide evidence that the distribution of the preferred orientations of simple cells in visual cortex subserving any region of the visual field matches the distribution of the orientations of the ganglion cells subserving the same region of the visual field.(ABSTRACT TRUNCATED AT 400 WORDS)
Characterization of pro-ACTH/endorphin-derived peptides in rat hypothalamus
Authors: Emeson RB , Eipper BA
Published: March 2018

The proteolytic processing pattern of pro-ACTH/endorphin in rat hypothalamus is similar to the pattern in the pars intermedia; peptides the size of beta-endorphin, gamma-lipotropin (gamma-LPH), corticotropin- like intermediate lobe peptide (CLIP), alpha-melanotropin (gamma-MSH), joining peptide, and glycosylated gamma 3-MSH all represent predominant end products. Equimolar amounts of beta-endorphin-, alpha-MSH-, CLIP-, gamma-LPH-, and joining peptide-related immunoreactivity are found in hypothalamic extracts (approximately 3 pmol per hypothalamus). Although the proteolytic processing pattern in the hypothalamus is similar to that in the pars intermedia, a tissue-specific posttranslational processing pattern was detected. Ion-exchange analysis of beta- endorphin-sized immunoreactive material from hypothalamic extracts resolves three major forms, corresponding to beta-endorphin(1–31), beta- endorphin(1–27), and beta-endorphin(1–26). The alpha-N-acetylated forms of endorphin represent less than 10% of the total beta-endorphin immunoreactivity. Analyses of hypothalamic alpha-MSH-sized molecules with acetyl- and amide-directed alpha-MSH antisera suggest that hypothalamic alpha-MSH is fully amidated, but largely not alpha-N- acetylated. Fractionation by reverse-phase high-performance liquid chromatography (HPLC) confirms that greater than 85% of the alpha-MSH immunoreactivity corresponds to ACTH(1–13)NH2 or its sulfoxide, and less than 10% corresponds to alpha-MSH [alpha-N-acetyl-ACTH(1–13)NH2] or its sulfoxide. Isoelectric focusing demonstrates that 83–93% of hypothalamic CLIP is phosphorylated. Isoelectric focusing suggests that the majority of the hypothalamic gamma-LPH-sized immunoreactive material is indistinguishable from gamma-LPH synthesized by pituitary melanotropes. The minor extent of alpha-N-acetylation of alpha-MSH and beta-endorphin, the limited carboxyl-terminal proteolysis of beta- endorphin, and the extensive phosphorylation of CLIP represent major differences between the posttranslational processing patterns of pro- ACTH/endorphin in the hypothalamus and pars intermedia.
Uniformity of metabolic enzymes within individual motor units
Authors: Nemeth PM , Solanki L , Gordon DA , Hamm TM , Reinking RM , Stuart DG
Published: March 2018

Individual muscle fibers of 10 motor units from the tibialis posterior muscle of cat were identified by glycogen depletion techniques, characterized for histochemical type, diameter, and intramuscular locations, and analyzed by quantitative biochemical methods. Four enzymes, representing different energy-yielding pathways, were quantitatively assayed in muscle fibers belonging to motor units selected from each of the three major physiological types. All four enzymes demonstrated identical activities among fibers within a motor unit, while showing up to 11-fold differences among fibers belonging to different motor units. Moreover, fibers within a single motor unit, but of substantially different diameters, were nevertheless homogeneous in specific enzyme activities.
Expression and regulation of catecholaminergic traits in primary sensory neurons: relationship to target innervation in vivo
Authors: Katz DM , Black IB
Published: March 2018

Catecholaminergic (CA) phenotypic characteristics have recently been detected in adult sensory neurons, demonstrating that CA expression in the periphery extends beyond the sympathoadrenal axis. Consequently, we may now determine whether common principles underlie CA phenotypic organization in functionally and embryologically diverse populations of peripheral neurons. To begin defining sensory transmitter regulation, the present study examined the relationship of CA expression to sensory target innervation in cranial nerve ganglion cells of the adult rat. Retrograde labeling combined with tyrosine hydroxylase (TH) immunocytochemistry indicated that 80–90% of CA sensory neurons in the glossopharyngeal petrosal ganglion project peripherally in the carotid sinus nerve (CSN). Most of these cells innervate a single target, the carotid body, revealing a striking correlation between CA expression and the pattern of sensory target innervation. Furthermore, CSN transection resulted in a transient marked decrease in TH catalytic activity and immunoreactivity within 1 week. Activities returned to normal by 3 weeks. Thus, axotomy reversibly decreased sensory TH, reproducing effects observed with central CA neurons (Ross et al., 1975), but differing in certain aspects from observations with sympathetic CA neurons (Cheah and Geffen, 1973; Kessler and Black, 1979). To determine whether disruption of axonal transport itself decreased TH in petrosal neurons, colchicine cuffs were placed around the intact CSN. Colchicine blockade reproduced the effects of axotomy, suggesting that deranged transport, and not axonal damage per se, altered TH. Finally, we studied the role of sensory projections to the CNS by examining petrosal TH after glossopharyngeal nerve rhizotomy. In contrast to sequelae of peripheral axotomy, rhizotomy did not alter TH, suggesting that projections to the periphery predominate in regulation of sensory TH.(ABSTRACT TRUNCATED AT 250 WORDS)
Sensitization of the crayfish lateral giant escape reaction
Authors: Krasne FB , Glanzman DL
Published: March 2018

Most behavioral reactions that habituate can also be dishabituated by strong stimuli. In the best studied cases, dishabituation seems to be the result of an independent “sensitization” of the behavioral reaction that compensates for habituation without necessarily abolishing it. Crayfish lateral giant (LG) neuron-mediated escape reactions are one of the most fully analyzed behavioral reactions that are prone to habituation; however, sensitization/dishabituation of LG escape has not previously been reported. Here, the effect of strong AC shocks to head or abdomen on the ability of 0.1 msec “test” shocks to sensory roots innervating the tailfan to elicit an LG escape response was examined. Following single AC shocks, test shock threshold for eliciting LG escape reliably fell 5–80% and recovered over 15 min to 1 hr. When AC shocks and test shocks alternated at 90 sec intervals, test shock threshold rapidly dropped to an asymptote that was maintained as long as AC shocks were given (up to 2 hr); following such repeated AC shocks, recovery often required a number of hours but was complete within 24. Comparable sensitization is seen in the response of interneuron A, the largest of a set of sensory interneurons that links afferents to LGs. AC shocks (to either head or tail) no longer sensitize abdominal LG reflex circuitry if the nerve cord is severed between thorax and abdomen. Thus, sensitization appears to depend on a neurally conducted influence that arises in the rostral half of the animal. Pharmacological evidence suggests that octopamine may mediate the sensitization.
Synaptic functions in rat sympathetic neurons in microcultures. II. Adrenergic/cholinergic dual status and plasticity
Authors: Potter DD , Landis SC , Matsumoto SG , Furshpan EJ
Published: March 2018

This is the second in a series of papers that describes the use of a sensitive microculture procedure to investigate the transmitter status of sympathetic neurons. Cultured immature principal neurons, dissociated from the superior cervical ganglia of newborn rats, are known to be plastic with respect to transmitter status; under certain culture conditions, populations of neurons that display (at least) adrenergic properties at the outset can be induced to display a variety of cholinergic properties, including the formation of functional neuron- neuron cholinergic synapses, as adrenergic properties decline. With the microculture procedure described in the preceding paper (Furshpan et al., 1986a), we have examined the transmitter status of individual neonate-derived neurons during this transition. Many such neurons secreted both norepinephrine and ACh (adrenergic/cholinergic dual function); examination of such neurons with the EM revealed a mixed population of synaptic vesicles. Direct evidence for a transition via this dual status was obtained by serial physiological assays of 14 neurons. The neonate-derived neurons were markedly heterogeneous in the rate of change of transmitter status. Principal neurons derived from adult superior cervical ganglia also displayed dual status, but the incidence was lower than in neonate-derived neurons cultured for similar periods. In preliminary serial assays of adult-derived neurons, many of the neurons did not acquire detectable cholinergic function, but in two cases evidence consistent with plasticity was obtained. While it is known that several types of neurons will form functional junctions in the presence of agents that block electrical activity, sympathetic principal neurons have apparently not been tested. In microculture, neuron-neuron synapses and junctions with cardiac myocytes were formed by sympathetic neurons grown chronically in the presence of blocking concentrations of TTX and hexamethonium.
Purification of a human red blood cell protein supporting the survival of cultured CNS neurons, and its identification as catalase
Authors: Walicke P , Varon S , Manthrope M
Published: March 2018

We have previously reported that red blood cells contain high levels of a protein that supports the survival of a variety of CNS neurons in vitro for 24 hr. Here we report the isolation of this trophic activity from human red blood cells. The active material, purified over 1000- fold by ion-exchange chromatography and isoelectric point, subunit molecular weight, and ability to degrade hydrogen peroxide. Commercially produced bovine liver catalase, lactoperoxidase, HRP, and vitamin E all mimic the ability of the purified human protein to support neuronal survival in vitro. Pharmacological inhibitors of peroxidase activity inhibit the trophic effects of both commercial catalase and the purified blood-derived protein. These results suggest that peroxidase activity mediates the neuronotrophic activity of these agents. The bioassay culture medium itself generates peroxides in the absence of cells. Removal of this toxic material may be the basis for the trophic effects of catalase.
Response properties of horizontal cells in the isolated retina of wild- type and pearl mutant mice
Authors: Suzuki H , Pinto LH
Published: March 2018

Intracellular recordings were made from axon bearing horizontal cells in isolated retinas (with retinal pigment epithelium removed) of normal and pearl mutant mice superfused with mammalian Ringer's solution. Cells were injected with Lucifer yellow and identified by their morphology and their response wave-forms. On impalement, we measured a dark, resting voltage of 25–35 mV. All cells had similar spectral sensitivities that were consistent with the CIE scotopic relative spectral luminosity function. For stimuli of high irradiance, two types of responses could be distinguished, based on their waveform at stimulus offset. One consisted of a rapid and wavelength-dependent repolarization followed by a small, slow hyperpolarization. The other consisted of a large, long-lived, and wavelength-independent after- hyperpolarization. The former were recorded from the somatic end and the latter from the axon terminal arborization. The spatial distribution of sensitivity was measured in over 100 locations within the receptive field using small stimuli. The area within which sensitivity of the soma was within 0.1 log unit of the maximal sensitivity was larger than that of the soma dendritic field, but the sizes were nearly equal for the terminal arborization. No secondary maximum of sensitivity was noted over the dendritic field of the unimpaled part of the cell. For the terminal arborization, the half- saturating irradiance for diffuse 502 nm stimuli was about 180 photons micron-2 sec-1, about one-tenth that for the soma. These values are in good agreement with those for cat and rabbit.(ABSTRACT TRUNCATED AT 250 WORDS)
The representation of peripheral nerve inputs in the S-I hindpaw cortex of rats raised with incompletely innervated hindpaws
Authors: Wall JT , Cusick CG
Published: March 2018

The hindpaws of 1-d-old rats were partially denervated by transection and ligation of the sciatic nerve. Following growth to adulthood, the topographical organization of the hindpaw representation in primary somatosensory (S-I) cortex was studied with neurophysiological mapping techniques and compared to the organization of previously studied normal adult rats and adult rats that had sciatic transection. The goals were (1) to determine how the topographical organization of the hindpaw representation is affected when development occurs with an incomplete set of peripheral inputs, and (2) to identify possible differences in the capacity of neonatal and adult CNSs to adjust to loss of inputs. The rat hindpaw is relatively immature on the day of birth. Neonatal transection and ligation of the sciatic nerve stunted gross development of the hindpaw and resulted in a permanent loss of low-threshold mechanoreceptor inputs from hindpaw zones normally innervated by the sciatic nerve. A comparison of the cortical representations of neonatally denervated and normal rats indicated that early loss of sciatic inputs caused several changes in the topographical organization of the hindpaw cortex, including (1) a loss of the representation of hindpaw skin areas innervated by the sciatic nerve, (2) a limited infringement of cutaneous inputs from the hindquarter into the cortical zone deprived of sciatic hindpaw inputs, (3) increased variability in the topographical relationships of the hindpaw and hindquarter representations, and (4) a decrease in the size of the cortical area responsive to cutaneous inputs. A comparison of the cortical representations of neonatal and adult denervates indicated that the general cortical reaction to sciatic injury at both ages was similar: Neurons in some parts of the deprived hindpaw cortex were activated by cutaneous inputs from uninjured nerves, whereas neurons in other parts of this cortex were unresponsive to cutaneous stimulation. The topographical organization and size of projection zones of uninjured peripheral inputs were different, however, after denervation in neonatal and adult rats. From these findings we suggest that (1) development of a normal, topographically organized hindpaw representation requires integration of hindpaw inputs in a spatially specific manner, (2) more than one pattern of cortical adjustment occurs after sciatic injury, and age is an important determinant of the pattern that is established.(ABSTRACT TRUNCATED AT 400 WORDS)
Demonstration of thyrotropin-releasing hormone immunoreactivity in neurons of the mouse spinal dorsal horn
Authors: Coffield JA , Miletic V , Zimmermann E , Hoffert MJ , Brooks BR
Published: March 2018

Thyrotropin-releasing hormone-like immunoreactivity was demonstrated in neurons within the superficial laminae (I, II, III) of the mouse spinal dorsal horn by light-microscopic peroxidase immunocytochemistry. The immunoreactivity was distributed in a narrow dorsoventral band that enclosed the substantia gelatinosa (lamina II), with a higher concentration along the lamina II/III border. At present, the functional significance of these neurons is unknown. Their existence within the substantia gelatinosa suggests a role in sensory information processing.