bluuebunny/crossref_metadata_2025 huggingface dataset:
Ontogeny, compartmentation, and turnover of spectrin isoforms in rat central neurons
Authors: Siman R , Ahdoot M , Lynch G
Published: March 2018

A variant of a principal structural protein of erythrocytes, spectrin, is a major neuronal protein. Here we have examined the subcellular and regional distributions, subunit composition, ontogeny, and metabolism of spectrin in rat CNS. While all subcellular fractions, except the mitochondrial, expressed the previously characterized brain form of spectrin (fodrin, or alpha gamma-spectrin), limited brain regions contained, in cytoplasm, a second isoform immunologically related to erythrocyte alpha beta-spectrin. Both alpha gamma- and alpha beta- spectrin are primarily neuronal, as evidenced by immunocytochemistry. The spectrins are distributed between 2 distinct subneuronal compartments: a membrane-associated domain containing alpha gamma- spectrin in relatively constant amounts across brain regions, and a cytoplasmic domain containing both the alpha gamma and alpha beta isoforms in widely varying amounts across brain regions. Although forebrain has considerable alpha beta-spectrin, the diencephalon, mesencephalon, and brain stem are devoid of this isoform. Further evidence for spectrin compartmentation comes from its ontogeny. Membrane-associated alpha gamma-spectrin is present at birth at its adult levels, but cytoplasmic alpha beta-spectrin is expressed only following the second postnatal week. Similarly, the 4-fold difference in cytoplasmic alpha gamma-spectrin content across brain regions develops during the third postnatal week. In this compartment, both spectrin forms may be metabolized in vivo, at least in part, by calcium- activated proteolysis. The presence in mammalian neurons of 2 spectrin isoforms and their compartmentation into distinct domains suggests multiple functions for neuronal spectrin, one of which may be in the stabilization or maturation of forebrain neurons.
A model of chronic pain in the rat: functional correlates of alterations in the activity of opioid systems
Authors: Millan MJ , Czlonkowski A , Pilcher CW , Almeida OF , Millan MH , Colpaert FC , Herz A
Published: March 2018

Intradermal inoculation of rats at the tail base with Mycobacterium butyricum led to the gradual development of an arthritic swelling of the limbs which peaked at 3 weeks and subsided thereafter. Arthritic rats displayed a loss of body weight, hypophagia, and hypodipsia in addition to a disruption of the diurnal rhythms of ingestive behavior and of core temperature. The activity of adenohypophyseal beta- endorphin-(beta-EP) secreting corticotrophs, in contrast to prolactin- (PRL) secreting lactotrophs, was increased in arthritic rats. Indeed, hypertrophy of the adrenal glands was seen. Arthritic rats also showed an elevation in spinal cord levels of immunoreactive dynorphin (DYN), an endogenous ligand of the kappa-opioid receptor. The paws and tail of arthritic rats showed lower thresholds in response to noxious pressure (hyperalgesia), higher thresholds in response to noxious heat (hypoalgesia), and no change in their response to noxious electrical stimulation. Neither naloxone nor ICI-154, 129 (a preferential delta- receptor antagonist) modified the responses of the paw or tail to pressure. However, MR 2266 (an antagonist with higher activity at kappa- receptors) decreased thresholds to pressure in arthritic, but not control, rats; that is, it potentiated the hyperalgesia. This action was stereospecific. None of the antagonists modified the response to heat. MR 2266 did not affect the response to pressure in rats with acute inflammation produced by yeast. Thus, the potentiation of pressure hyperalgesia by MR 2266 in chronic arthritic rats is highly selective. Arthritic rats showed a reduced response to the analgesic effect of a kappa-agonist (U-50,488H), whereas the response to a mu- agonist (morphine) was enhanced. These effects were specific to nociception in that their influence upon endocrine secretion (PRL and beta-EP) was otherwise changed. The secretion of beta-EP and PRL was stimulated by both morphine and U-50,488H, and the influence of U- 50,488H upon the release of beta-EP (from the adenohypophysis) was enhanced in arthritic rats. It is suggested that polyarthritis is a complex condition entailing many changes, both behavioral and endocrinological. Further, arthritic rats cannot simply be described as “hyperalgesic”: of critical importance is the nature of the nociceptive stimulus applied. The parallel alterations in spinal cord pools of DYN and kappa-receptors (see also Millan et al., 1986) and the changes in the influence on nociception of kappa-agonists and kappa-antagonists suggest an increased activity of spinal DYN. Thus, spinal kappa- receptors may play a role in the modulation of nociception under chronic pain.(ABSTRACT TRUNCATED AT 400 WORDS)
Ionic channels in mouse astrocytes in culture
Authors: Nowak L , Ascher P , Berwald-Netter Y
Published: March 2018

We observed Na, K, and Cl voltage-dependent currents in a patch-clamp study of mouse brain astrocytes. In whole-cell recordings, depolarizations activated inward currents that were identified as Na currents since they were blocked by TTX, although complete block required high concentrations (greater than 1 microM). The corresponding single-channel Na currents were observed in outside-out patches. The channels were opened by a depolarizing pulse applied from a holding potential identical to the resting potential (-70 to -80 mV). Therefore, they may be considered functional Na channels. After addition of veratridine and an alpha-scorpion toxin, the decay of Na currents in whole-cell recordings was slower than observed under control conditions. At the single-channel level, the channels appeared to open in bursts. Depolarization did not increase the duration of the bursts, but inside each burst, increased the time spent in the open state. The K currents observed in the whole-cell recording mode were separated into inactivating and noninactivating currents. The inactivating current resembled the A current in its kinetics, its insensitivity to tetraethylammonium, and its sensitivity to 4- aminopyridine. At the single-channel level, at least 3 classes of K channels were observed at steady depolarized potentials. They resembled the K channels found in chromaffin cells by Marty and Neher (1985). Large conductance channels (385 pS) activated around 0 mV were identified as Cl channels.
Functional properties of parietal visual neurons: mechanisms of directionality along a single axis
Authors: Motter BC , Steinmetz MA , Duffy CJ , Mountcastle VB
Published: March 2018

The directional properties of parietal visual neurons (PVNs) were examined using the method of single-neuron analysis in waking monkeys. PVN properties were determined with passive visual stimuli as the animal executed a simple detection task. Parietal area PG was studied in 10 hemispheres of 6 male Macaca mulatta. Each class of parietal neurons was identified in PG: the fixation, projection, visual, and oculomotor neurons; 613 PVNs were identified, 323 were studied quantitatively, and 188 were studied with one or more of the protocols described. The receptive fields of PVNs are commonly large and bilateral, and at the limit some may fill the visual field; for many, the central zone of the visual field is spared when the fields are determined by stimuli that enter from the periphery and transit meridians. The receptive fields vary with the behavioral state, the angle of gaze, and the parameters of the stimuli used to determine them. PVNs are sensitive to stimulus movement but relatively insensitive to stimulus speed; many respond over a speed range of 5 degrees-500 degrees/sec. Stimulus-response relations may be incremental or decremental with increasing speed or show maxima or minima in the midrange of speed, but the response variation over the full range is rarely greater than 2:1. The directional preferences of PVNs with bilateral receptive fields are opponently organized; the preferred directions point either inward toward or outward away from the central line of gaze along the 4 meridians tested, which were equally spaced in the circular dimension of the visual field. The mechanism of the axis directionality of PVNs was studied using conditioning-test paradigms. They revealed a feed-forward inhibition preceding a stimulus, an effect that extends from the leading edge of the stimulus for 10 degrees-20 degrees in front of the moving stimulus and lasts for several hundred milliseconds. A double-Gaussian model of superimposed but unequal excitatory and inhibitory effects suffices to explain the present observations. It places demand upon the projection of functional properties from the contralateral hemisphere or from the ipsilateral prestriate areas that project upon PG over multistaged pathways and minimal demands upon intracortical processing mechanisms.
Collapse of growth cone structure on contact with specific neurites in culture
Authors: Kapfhammer JP , Raper JA
Published: March 2018

We have studied the morphology of embryonic chick retinal and sympathetic growth cones as they meet retinal and sympathetic neurites grown in culture. Growth cones preserve their normal morphology and ability to locomote when retinal growth cones contact retinal neurites or when sympathetic growth cones contact sympathetic neurites. Growth cones collapse and their motility ceases when retinal growth cones contact sympathetic neurites or when sympathetic growth cones contact retinal neurites. Collapse was never observed before a growth cone touched a neurite. As a growth cone collapses, the neurite it leads retracts. After a brief pause, a new growth cone is organized and extension recommences. These results suggest that contact-mediated inhibition of locomotion could play a role in growth cone guidance.
Preservation of motoneuron electrotonic characteristics during postembryonic growth
Authors: Hochner B , Spira ME
Published: March 2018

The postembryonic developmental period of the nervous system involves, among other processes, an increase in the dimensions of individual neurons. In the present study we examine whether the characteristic electronic parameters that underlie the integrative properties of the neuron (L, the electrotonic length; rho, dendritic to somatic conductance ratio; and tau m, the membrane time constant) are established before, during, or after the neurons reach their final adult size. A second aspect that we analyze are the mechanisms by which the neurons adjust their electrotonic parameters during the growth period. The dimensions of the soma and dendrites of the phallic motoneurons (Ph.m.n.) of the cockroach, Periplaneta americana, increase during the last postembryonic developmental stages and metamorphosis to adult by a factor of 1.75 and 1.5, respectively. This increase is not associated with major changes in the morphological outline of the neuron but is associated with a significant decrease in the input resistance (Rin) by a factor of 6 (from 120 to 20 M omega). The dendritic to somatic conductance ratio (rho) is maintained constant. Morphological analysis of cobalt-filled neurons reveals that the neurons can be represented by an equivalent cylinder (Rall, 1969). Calculations of the electrotonic length (L) of the equivalent cylinder from measurements of the time constants tau m and tau 1 (Rall, 1969) revealed that L is constant throughout the period of neuronal growth (1.29 +/- 0.24 lambda in adult, and 1.13 +/- 0.28 lambda in nymph). The mechanism by which the electrotonic parameters are maintained in spite of growth is continuous adjustment of the diameter and length of the various neuronal segments, rather than by changes in the biophysical properties of the neuron. Several implications in relation to mechanisms of integration and input-output relations during growth and development of neurons are discussed in view of our findings.
Distribution of cAMP and cAMP-dependent protein kinases in Aplysia sensory neurons
Authors: Greenberg SM , Bernier L , Schwartz JH
Published: March 2018

Sensitization of the gill- and siphon-withdrawal reflex in Aplysia is considered a simple form of learning. Previous work has provided physiological and pharmacological evidence that cAMP-dependent protein phosphorylation within identified sensory neurons of the abdominal ganglion underlies the short-term form of this behavioral modification. Our main goal in this paper is to determine the subcellular distribution of cAMP and to measure the amounts and properties of the 2 types of subunits (regulatory and catalytic) that constitute the cAMP- dependent protein kinase. Do these biochemical parameters differ in sensory cells from those in other parts of nervous tissue? We found that the increased cAMP synthesized under conditions of sensitization is distributed in 3 compartments in the neuron: most of it is free in the cytoplasm; the remainder is bound either to cytoplasmic or to particulate proteins, which are believed to be regulatory subunits of the cAMP-dependent protein kinase. Binding of cAMP within the neurons is a measure of activation of the kinase. At rest, 17% of the binding sites in sensory cells were occupied. After brief electrical stimulation of the connective, which released endogenous transmitter, occupancy increased to 34%. This treatment increased the amount of cAMP bound to the various binding proteins differentially. The biochemical characteristics of cAMP binding were found to be the same in sensory neurons as in the rest of the nervous system but different from those in muscle. Thus, memory and learning are likely to be mediated by enzymes that are shared by other nerve cells. We found that sensory neurons have greater cAMP-dependent protein kinase activity than other neurons, however, and as a result may be more sensitive to small increases of cAMP.
Stimulation of adenylate cyclase in relation to dopamine-induced long- term enhancement (LTE) of muscarinic depolarization in the rabbit superior cervical ganglion
Authors: Mochida S , Kobayashi H , Libet B
Published: March 2018

Dopamine (DA) induction of the long-term enhancement (LTE) of the slow muscarinic depolarizing response to methacholine (MCh), equivalent to the slow EPSP (S-EPSP), was previously found to be mimicked by exogenous cyclic AMP (cAMP) in the rabbit superior cervical ganglion (SCG). DA-induced LTE of the S-EPSP was shown to be depressed by some DA antagonists. We now show that DA (15 microM), its analog, 2-amino- 6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (ADTN), and a D2 receptor antagonist, metoclopramide, each can induce both LTE of MCh depolarization and an increase in ganglionic cAMP. Conversely, antagonists of DA-induced LTE also depress DA-induced rises in cAMP; these antagonists include haloperidol (1 microM), both (+) and (-) enantiomers of butaclamol (0.7–7 microM), flupenthixol (1 microM), and (+)-R-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepine-7- o l (SCH-23390) (7 microM). The selective D2 antagonists sulpiride (10 microM) and domperidone (10 microM) affect neither DA action. Alpha-2 adrenergic agonists (alpha-methyl-norepinephrine and clonidine) produce no LTE; alpha-antagonist dihydroergotamine (35 microM) does not affect either DA action, although it can completely block the hyperpolarizing response to DA or other catecholamines. Beta-antagonist propranolol (5 microM) partially depresses DA-induced rises in cAMP but has no effect on the DA-induced LTE. (Butaclamol and propranolol in combination can completely block the cAMP rise induced by DA.) Beta-agonist isoproterenol can induce appreciable LTE of MCh depolarization, but this LTE is not depressed by propranolol (10 microM). Isoproterenol can elicit a substantial rise in cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)
Functional subdivisions of the temporal lobe neocortex
Authors: Baylis GC , Rolls ET , Leonard CM
Published: March 2018

In order to gather evidence on functional subdivisions of the temporal lobe neocortex of the primate, the activity of more than 2600 single neurons was recorded in 10 myelo- and cytoarchitecturally defined subdivisions of the cortex in the superior temporal sulcus (STS) and inferior temporal gyrus of the anterior part of the temporal lobe of 5 hemispheres of 3 macaque monkeys. First, convergence of different modalities into each area was investigated. Areas TS and TAa, in the upper part of this region, were found to receive visual as well as auditory inputs. Areas TPO, PGa, and IPa, in the depths of the STS, received visual, auditory, and somatosensory inputs. Areas TEa, TEm, TE3, TE2, and TE1, which extend from the ventral bank of the STS through the inferior temporal gyrus, were primarily unimodal visual areas. Second, of the cells with visual responses, it was found that some neurons in areas TS-IPa could be activated only by moving visual stimuli, whereas the great majority of neurons in areas TEa-TE1 could be activated by stationary visual stimuli. Third, it was found that there were few sharply discriminating visual neurons in areas TS and TAa; of the sharply discriminating visual neurons in other areas, however, neurons that responded primarily to faces were found predominantly in areas TPO, TEa, and TEm (in which they represented 20% of the neurons with visual responses); neurons that were tuned to relatively simple visual stimuli such as sine-wave gratings, color, or simple shapes were relatively common in areas TEa, TEm, and TE3; and neurons that responded only to complex visual stimuli were common in areas IPa, TEa, TEm, and TE3. These findings show inter alia that areas TPO, PGa, and IPa are multimodal, that the inferior temporal gyrus areas are primarily unimodal, that there are areas in the cortex in the anterior and dorsal part of the STS that are specialized for the analysis of moving visual stimuli, that neurons responsive primarily to faces are found predominantly in areas TPO, TEa, and TEm, and that architectural subdivisions of the temporal lobe cortex are related to neuronal response properties.
Voltage-dependent gating of single sodium channels from mammalian neuroblastoma cells
Authors: Aldrich RW , Stevens CF
Published: March 2018

Single sodium channel currents have been studied in cell-attached patches from the mouse neuroblastoma cell line N1E115. Distributions of open duration, latency until first opening, and the average probability of a channel being open after a voltage step, p(t), were analyzed and compared to predicted distributions from various kinetic models for voltage-dependent gating. It was found that, over most of the voltage range under which channel gating occurs, the slow steps in gating are opening transitions and that inactivation of open channels is significantly faster than the decline in p(t) (tau h). This view of gating is confirmed by comparison of the kinetics of ensemble averages of single-channel currents obtained from step- and tail-current records at the same voltage. The probability of a channel reopening after having closed was calculated by comparing p(t) with the convolution of the first-latency probability density and the conditional probability of remaining open t milliseconds after opening. This reopening probability is small but slightly voltage dependent over the voltage range where the mean open duration remains constant and tau h changes considerably. The voltage dependence of open channel inactivation and deactivation were calculated from the probability of reopening and the mean open duration. The equivalent gating charge for the inactivation rate is a few tenths of an electronic charge, whereas the equivalent charge for the closing rate is 2.5–3.5 electronic charges.
Cytotypic differences in the protein composition of the axonally transported cytoskeleton in mammalian neurons
Authors: Oblinger MM , Brady ST , McQuarrie IG , Lasek RJ
Published: March 2018

Many of the structural and functional differences between axons are thought to reflect underlying differences in the biochemical composition and dynamic aspects of the axonal cytoskeleton and cytomatrix. In this study we investigated how the composition of the 2 slow components of axonal transport, SCa and SCb, which convey the cytoskeleton and cytomatrix, differs in axons that are structurally and functionally distinct. For this comparison we analyzed axons of retinal ganglion cells in the optic nerve (ON), axons of dorsal root ganglion (DRG) cells, and axons of ventral motor neurons (VMN) in adult rats. 35S-Methionine-labeled proteins transported with the peak of SCa and SCb were analyzed using high-resolution 2-dimensional polyacrylamide gels (2D-PAGE) and fluorography, and the amounts of major SCa and SCb proteins were quantified. The polypeptide composition of both SCa and SCb was found to be largely similar in DRG and VMN axons, but major qualitative as well as quantitative differences between these axons and ON axons were found. Notable among these were higher ratios of neurofilament protein to tubulin in SCa in DRG and VMN axons compared to ON axons, and significantly larger amounts of 2 microtubule- associated proteins relative to tubulin in SCa of ON axons than in both VMN and DRG axons. Tubulin was the major SCb protein in VMN and DRG axons, but it was not present in SCb in ON axons. Additionally, relatively larger amounts of 2 metabolic enzymes, creatine phosphokinase and nerve-specific enolase, were present in SCb in ON axons than in DRG or VMN axons. The results indicate that significant biochemical heterogeneity among different types of axons can be identified by examining the slow components of axonal transport.
Solubilization of the apamin receptor associated with a calcium- activated potassium channel from rat brain
Authors: Seagar MJ , Marqueze B , Couraud F
Published: March 2018

The apamin binding protein was solubilized from rat brain synaptic membranes using sodium cholate. Receptor yield and stability depended closely on the detergent/protein ratio. In optimum conditions the receptor retained high affinity for mono 125I-iodoapamin with Kd = 40 pM at pH 7.5 and 1 degree C and a binding capacity of 17 fmol/mg protein. 125I-apamin binding was stimulated by K+ ions with a K0.5 = 0.6 mM, demonstrating that the regulatory K+ site is also part of the soluble complex. Other ions could be substituted for K+ with an affinity sequence Tl+ = K+ = Rb+ greater than Cs+ greater than NH4+ greater than Li+ or Na+. Binding was inhibited by the neuromuscular blockers gallamine and tubocurarine and by the K+ channel blockers quinidine and tetraethylammonium chloride but not by 4-aminopyridine, in agreement with known pharmacological profile for inhibition of apamin-sensitive K+ permeability. Increasing the K+ concentration did not reverse inhibition by tetraethylammonium ions demonstrating that it does not bind competitively to the regulatory cationic site. Analysis of the covalently labeled apamin binding protein/sodium cholate complex by density gradient centrifugation indicated a high molecular weight with S20,w = 20 S.
Retinotopic organization of human visual cortex mapped with positron- emission tomography
Authors: Fox PT , Miezin FM , Allman JM , Van Essen DC , Raichle ME
Published: March 2018

The retinotopic organization of primary visual cortex was mapped in normal human volunteers. Positron-emission tomographic measurements of regional cerebral blood flow were employed to detect focal functional brain activation. Oxygen-15-labeled water, delivered by intravenous bolus, was used as the blood flow tracer to allow multiple stimulated- state (n = 5) and control-state (n = 3) measurements to be acquired for each of 7 subjects. Responses were identified by applying a maximum- detection algorithm to subtraction-format images of the stimulus- induced change in cerebral blood flow. Response locales were described using a standardized system of stereotactic coordinates. Changes in stimulus location (macular, perimacular, peripheral, upper-field, lower- field) caused systematic, highly significant changes in response locale within visual cortex. Discrete extrastriate visual responses were also observed.
Postnatal development of the rat dorsal funiculus
Authors: Chung KS , Coggeshall RE
Published: March 2018

The present study shows that there are approximately 21,000 axons in the neonatal rat dorsal funiculus, as compared to 26,000 in 2-week-old animals. We attribute this increase primarily to arriving corticospinal fibers. In adult animals, however, there are approximately 15,000 axons. This is a decline of 58% from the 2 week level, and the decrease is proportionately similar in the corticospinal area and the dorsal funiculus proper. Thus, axon numbers decline in later postnatal development, and since the decline seems to be well past the time of the histogenetic death of the cells that give rise to these axons, we propose that the loss is not caused by the death of neurons. This is further evidence that a reduction in axon numbers not accompanied by cell death is a widespread phenomenon in mammalian postnatal neural development. We infer that the mechanism of axon loss is a reduction in axon branching and that its function is to sharpen synaptic connections.
The response of suprachiasmatic neurons of the rat hypothalamus to photic and nicotinic stimuli
Authors: Miller JD , Murakami DM , Fuller CA
Published: March 2018

Single neurons in the suprachiasmatic nucleus (SCN) and surrounding hypothalamic nuclei of the rat were characterized functionally and pharmacologically. Photically responsive neurons of the SCN typically exhibited a similar response to intravenous nicotine. The response to nicotine was antagonized by the nicotinic blocker, mecamylamine. Nicotinic blockade either eliminated or even reversed the sign of the photic response during subsequent photic stimulation. This constellation of results was not seen in neurons of adjacent hypothalamic regions.
Evidence for transient perinatal glutamatergic innervation of globus pallidus
Authors: Greenamyre T , Penney JB , Young AB , Hudson C , Silverstein FS , Johnston MV
Published: March 2018

There is no known glutamatergic innervation of globus pallidus (GP) in adult mammals, but we report that during postnatal development of the GP there are large, transient increases in both presynaptic high- affinity glutamate uptake and postsynaptic Na+-independent glutamate receptor binding. These glutamatergic markers increase rapidly in rat GP after birth and then decrease to adult levels over a period of weeks. A similar developmental pattern of pallidal glutamate binding was found in human brains. In contrast, binding in rat caudate-putamen (CPu) increases after birth, reaches a peak, and remains constant into adulthood. The results suggest that a glutamatergic pathway transiently innervates the globus pallidus during the perinatal period. Because glutamate is an excitotoxin, this pathway may account, in part, for the basal ganglia damage seen in some forms of cerebral palsy after perinatal hypoxia/ischemia.
Visualization of endogenous glycine in cat retina: an immunocytochemical study with Fab fragments
Authors: Pourcho RG , Goebel DJ
Published: March 2018

Fab fragments of a glycine antiserum were prepared and used for immunocytochemical visualization of glycine in the cat retina. The use of Fab fragments in conjunction with Fab-specific secondary and tertiary antisera improved tissue penetration and made it possible to identify a number of the immunoreactive neurons. Staining was observed in several subpopulations of amacrine cells, including the A7(AII) rod amacrine. Multiple subpopulations of cone bipolar cells were also seen to be immunoreactive. Many neurons exhibited no detectable immunostaining, indicating that general metabolic levels of glycine do not interfere with the visualization of those cells that contain large amounts of endogenous glycine. The distribution of immunostaining appears to parallel the pattern of glycine labeling seen previously with autoradiographic techniques and implicates these cells in glycine- mediated neurotransmission.
Fluorescent probes that stain living nerve terminals
Authors: Magrassi L , Purves D , Lichtman JW
Published: March 2018

We have evaluated the efficacy of 18 cationic mitochondrial dyes that, as a class, show some ability to stain living nerve terminals. Several of these agents provide excellent staining of neuromuscular junctions in a wide range of species. More detailed studies of the most effective of these dyes--4-(4-diethylaminostyryl)-N-methylpyridinium iodide (4-Di- 2-ASP)--indicate that it has no lasting effect on the structure or function of motor nerve terminals. As demonstrated in the accompanying paper (Lichtman et al., 1987; see also Lichtman et al., 1986), 4-Di-2- ASP can therefore be used to follow the configuration of identified motor terminals over arbitrarily long intervals.
Visualization of neuromuscular junctions over periods of several months in living mice
Authors: Lichtman JW , Magrassi L , Purves D
Published: March 2018

Identified neuromuscular junctions were followed in the sternomastoid muscle of living mice for several months by repeated staining with the fluorescent dye 4-(4-diethylaminostyryl)-N-methylpyridinium iodide (4- Di-2-ASP; Magrassi et al., 1987). Overall terminal growth occurred at many endplates; however, the branching pattern of presynaptic arbors was largely unchanged, even after several months. The absence of significant remodeling over time was not a result of dye-staining, since sprouting was readily induced at residual motor endings by partial denervation. We conclude that--apart from overall growth--most neuromuscular junctions in the adult mouse are stable over intervals that represent a significant fraction of the animal's lifetime.
Molecular markers of neuronal subpopulations in layers 4, 5, and 6 of cat primary visual cortex
Authors: Arimatsu Y , Naegele JR , Barnstable CJ
Published: March 2018

Cat primary visual cortex has been used as an immunogen to produce monoclonal antibodies that detect subpopulations of neurons. When tested by immunofluorescence on tissue sections of areas 17 and 18, 2 of these antibodies, VC1.1 and VC5.1, outlined a rare subpopulation of neurons located mainly in layer 4 but also in layers 5 and 6. Double- labeling immunofluorescence experiments in area 17 revealed that all VC1.1-reactive cells were also VC5.1-reactive and 83% of VC5.1-reactive cells were VC1.1-reactive, suggesting that the antibodies were reacting with the same subpopulation of cells. Both antibodies labeled similar or identical subpopulations of cells in other areas of the cat CNS, including the superior colliculus, parts of hippocampus, cerebellar deep nuclei, and rostral spinal cord. Neither antibody labeled cell bodies in the lateral geniculate nucleus. In the retina, VC1.1 labeled cell bodies and processes of some horizontal and amacrine cells, whereas VC5.1 labeled only ganglion cell axons. In the cerebellar cortex, the most prominent labeling of VC1.1 was of Purkinje cells, whereas that of VC5.1 was of Lugaro cells. Immunoblotting analyses of cat cortical homogenates demonstrated that VC1.1 recognized a major polypeptide band of Mr 95,000–105,000 and additional bands of Mr 145,000 and Mr 170,000. VC5.1 recognized bands of Mr 97,000 and Mr 150,000. Subcellular fractionation and extraction studies showed that the VC1.1 antigens were integral membrane proteins preferentially located in a synaptosomal plasma membrane fraction. The VC5.1 antigens were preferentially located in a soluble cytoplasmic or extracellular fraction. The results indicate that antibodies VC1.1 and VC5.1 recognize unique epitopes in the cat CNS and define a previously unrecognized subpopulation of cells in cat visual cortex.
Effects of early unilateral blur on the macaque's visual system. II. Anatomical observations
Authors: Hendrickson AE , Movshon JA , Eggers HM , Gizzi MS , Boothe RG , Kiorpes L
Published: March 2018

We studied the effects of early unilateral blur on the anatomical organization of the visual pathways in 8 macaque monkeys. Blur was induced in one eye, beginning 2–14 d after birth, by 0.5% atropine twice a day. Atropinization was stopped at 6–8 months of age, and the animals were studied for anatomy 3–24 months later. The retina and all other eye tissues showed normal histology. In the dorsal lateral geniculate nucleus (LGN), cells in parvocellular layers receiving input from the atropine-treated eye were 9–32% smaller and were more lightly stained than those in layers innervated by the untreated eye. These changes were generally larger in the LGN ipsilateral to the treated eye. LGN cell size changes were absent or much smaller in the magnocellular layers. In the striate cortex, the distribution of the oxidative enzyme cytochrome oxidase (CO) was markedly altered in layer 4C beta. Layer 4C beta is uniformly stained in normal animals, but showed a distinct pattern of alternating high and low CO bands in the atropine-treated animals; the bands of higher CO activity were narrower than the bands of lower activity and had a 857–1050 micron repeat. Fainter banding was seen in layers 4A, 4C alpha, and 6, but the density of the rows of dark CO-stained dots in layer 3 was unaffected. Double- labeling revealed that the narrow dark CO bands were associated with the centers of the ocular dominance columns devoted to the atropine- treated eye. The distribution of 14C-2-deoxyglucose uptake in visual cortex produced by 4.5–9 c/deg spatial frequency stimulation was strongly biased toward the untreated eye. The treated eye could, however, elicit reasonably strong uptake when stimulated with patterns containing lower spatial frequencies. These results suggest that unilateral neonatal blur preferentially affects the parvocellular layers of the LGN and layer 4C beta of striate cortex, which are the portions of the central visual system associated with the processing of information concerning fine spatial detail. These anatomical changes are consistent with the high spatial frequency loss of vision demonstrated behaviorally and electrophysiologically in the atropine eye-driven visual system of these same animals.
Effects of early unilateral blur on the macaque's visual system. III. Physiological observations
Authors: Movshon JA , Eggers HM , Gizzi MS , Hendrickson AE , Kiorpes L , Boothe RG
Published: March 2018

We studied the properties of visual cortical and lateral geniculate neurons in 5 macaque monkeys raised with the vision of one eye blurred by daily instillation of atropine. This rearing reduced the degree of binocular interaction in striate cortical neurons and caused a modest shift in eye dominance away from the atropine-treated eye. It also led to a difference in the spatial properties of neurons driven by the 2 eyes: neurons driven by the treated eye tended to have lower optimal spatial frequencies, poorer spatial resolution, and lower contrast sensitivity than neurons driven by the untreated eye. Some of the few binocularly driven neurons had receptive fields with sharply different spatial properties in the 2 eyes, with the treated eye's receptive field always having poorer spatial resolution. In striate cortex, the effects on neuronal spatial properties were less marked in layer 4 than in more superficial or deeper layers; there was no difference in the spatial properties of lateral geniculate neurons driven by the 2 eyes. A small sample of extrastriate cortical neurons from a single animal showed effects similar to those seen in striate cortex. The striate cortical changes varied consistently from animal to animal: The less affected animals had no discernible eye dominance shift and relatively small differences in spatial properties between the eyes; the more affected animals had substantial eye dominance shifts and larger interocular spatial differences. These variations were also reflected in, and consistent with, behavioral and anatomical measurements performed in the same monkeys.
Functional topography in cat area 18
Authors: Cynader MS , Swindale NV , Matsubara JA
Published: March 2018

Using closely spaced microelectrode penetrations, we have mapped the representation of the visual field and of several functional response properties on the surface of cat area 18. The representation of the visual field was anisotropic, with the magnification factor for vertical visual space being about 2–5 times greater than that for horizontal. The topographic anisotropy was paralleled by an anisotropy in the cortical point-spread function, a measure of the distribution in the cortex of cells with overlapping receptive-field centers. The spread of this distribution (measured as twice the standard deviation) was positively correlated with the magnification factor anisotropy, averaging about 0.6 mm along the mediolateral (M-L) axis and 1.2 mm along the anteroposterior (A-P) axis. Units with similar response properties were clustered across the cortical surface, but different response features were laid out in different ways. For units with orientations within a 90 degrees range, the clusters took the form of branching bands, with a center to center spacing of 1.25 +/- 0.13 mm. These bands ran from postero-medial to anterolateral across the cortical surface, roughly perpendicular to the 17/18 border. Units with similar preferred eye input were laid out in patches without a well- defined direction of elongation, and with a less well-defined periodicity that averaged 1.86 +/- 0.75 mm. Local correlations in direction preference extending over distances of 300 micron were found, together with frequent 180 degrees differences in the direction preferences of units close together. The organization of the map of orientation preference, and the way in which direction selectivity is overlaid on this map, is discussed in more detail in the accompanying paper (Swindale et al., 1987). No obvious structural relationships between the ocular dominance patches and the pattern of iso-orientation domains were observed. There were, however, obvious interrelationships between the topographic map and other functional response properties. The iso-orientation bands ran approximately perpendicular to the direction in which both the point-spread function and magnification factor were elongated. This will have the effect of maximizing the allocation of a full range of orientations by the cortex to each location in visual space.
The molecular structure of microtubule-associated protein 1A (MAP1A) in vivo and in vitro. An immunoelectron microscopy and quick-freeze, deep- etch study
Authors: Shiomura Y , Hirokawa N
Published: March 2018

We studied the distribution of microtubule-associated protein 1A (MAP1A) in Purkinje cell dendrites by means of electronmicroscopic immunocytochemistry, using a monoclonal antibody (McAb) against MAP1A; this was combined with the observation of the 3-dimensional cytoskeletal ultrastructure in dendrites via the quick-freeze, deep- etch technique (QF-DE). We prepared a McAb against rat brain MAP1. This McAb recognized MAP1A on a nitrocellulose filter through use of the immunoblotting method, and stained immunofluorescently Purkinje cell perikarya, dendrites, and axons. Using the McAb, we labeled rat cerebellum extracted with Triton X-100 and simultaneously fixed with aldehyde, followed by gold-labeled rabbit anti-mouse IgG. Gold particles were attached to the filamentous, fuzzy materials, mostly those connected to microtubules (MTs), but were hardly localized on those attached to neurofilaments (NFs). The 3-dimensional cytoskeletal ultrastructure of fresh Purkinje cell dendrites was revealed by QF-DE. In Purkinje cell dendrites, MT was a predominant cytoskeletal element, whereas only a few NFs were found. Fine, elaborate cross-bridges filled up the interstices among MTs, and between MTs and other cellular components. Cross-bridges linking MTs to one another were composed mainly of a fine filamentous structure, frequently branching and anastomosing at several sites, and appeared somewhat granular. We ensured that the cross-bridges observed in saponin-extracted tissues were not a result of artifactual condensations or precipitations of soluble proteins during deep etching. The molecular structure of MAP1A was further investigated by the rotary shadowing technique. The affinity-purified MAP1A was a long, thin, filamentous, and very flexible molecule.(ABSTRACT TRUNCATED AT 250 WORDS)
Differential recovery rates of rat D2 dopamine receptors as a function of aging and chronic reserpine treatment following irreversible modification: a key to receptor regulatory mechanisms
Authors: Norman AB , Battaglia G , Creese I
Published: March 2018

The density of D2 dopamine receptors identified by 3H-spiperone binding was significantly lower in the striatum of senescent (28-month-old) than in mature (4-month-old) Fischer 344 rats. The time course of recovery of 3H-spiperone binding to D2 dopamine receptors following irreversible receptor modification by a single injection of N- ethoxycarbonyl–2-ethoxy-1,2-dihydroquinoline (EEDQ) was significantly slower in senescent than in mature rats. The kinetics of D2 dopamine receptor repopulation could be adequately described by a model assuming a constant rate of receptor production and a rate of degradation that was dependent on receptor concentration. Both the production rate and degradation rate constant of D2 dopamine receptors were lower in the senescent rats compared to mature rats. The changes in receptor density that occur as a function of development and aging are the result of changes in both the receptor production rate and receptor degradation rate constant, which, while both are reduced, tend to maintain receptor density. That is, receptor density decreased by 26% from 4 to 28 months of age, although the receptor production rate and degradation rate constant decreased by 40–50%. Chronic treatment of rats with reserpine produced a 21% increase in the density of striatal D2 dopamine receptors of mature, but not senescent, rats, accompanied by an increase in the initial recovery rate of 3H-spiperone binding sites following EEDQ treatment. It might have been expected that the reduced formation of agonist-bound receptors would have lead to a decrease in the receptor degradation rate constant.(ABSTRACT TRUNCATED AT 250 WORDS)
Monoclonal antibodies against rat brain protein kinase C and their application to immunocytochemistry in nervous tissues
Authors: Kitano T , Hashimoto T , Kikkawa U , Ase K , Saito N , Tanaka C , Ichimori Y , Tsukamoto K , Nishizuka Y
Published: March 2018

Three monoclonal antibodies were prepared against rat brain soluble protein kinase C. Two of the antibodies, CKI-97 (IgG2b subclass) and CKII-90 (IgG1 subclass), showed weak binding to native protein kinase C. The third antibody, CKI-33 (IgG2b subclass), showed no binding. However, the mixture of CKI-97, CKII-90, and CKI-33 exhibited much stronger binding activity to this protein kinase than any of the antibodies alone. Although none of these antibodies showed protein kinase C-neutralizing activity, Western blot analysis indicated that these antibodies reacted specifically with protein kinase C, presumably its subspecies, that is present predominantly in nervous tissues. Immunocytochemical studies shows that these antibodies can be used for identification of this enzyme in nervous tissues. In rat Purkinje cells, the immunoreactive material was present throughout the cytoplasm, including dendrites and axons, but was poorly represented in the cell nucleus. In cerebellum, the localization of protein kinase C appears to be very similar to that of cGMP-dependent protein kinase.
A second opsin gene expressed in the ultraviolet-sensitive R7 photoreceptor cells of Drosophila melanogaster
Authors: Montell C , Jones K , Zuker C , Rubin G
Published: March 2018

We have identified a second Drosophila opsin gene, Rh4, which is expressed specifically in the ultraviolet-sensitive R7 photoreceptor cells. The two R7 opsins, Rh3 and Rh4, are expressed in nonoverlapping subsets of R7 cells. The Rh4 opsin shares 72% amino acid identity with Rh3, but is only about 35% homologous with the other 2 Drosophila opsins, ninaE and Rh2. Twenty-eight amino acids are conserved among all 4 invertebrate and 5 vertebrate opsin genes thus far sequenced, suggesting that these residues play an important role in rhodopsin function.
Tactile discrimination of shape: responses of slowly adapting mechanoreceptor afferents to a step stroked across the monkey fingerpad
Authors: LaMotte RH , Srinivasan MA
Published: March 2018

The representation of shape in the responses of slowly adapting mechanoreceptive afferent fibers (SAs) in monkeys was investigated. A series of flat plates was used, each having an increase in thickness (a step) in the middle so that one-half of the plate was thicker than the other. The cross-sectional shape of the step approximated that of a half-cycle of a sinusoid. The height of the step was fixed at 0.5 mm, while its width (half-cycle wavelength) was varied from 0 to 3.13 mm, resulting in step shapes that varied in steepness and curvature. The steps fell into 2 categories, characterized as “steep” and “gradual.” A servocontrolled mechanical stimulator stroked each step across the distal fingerpad from the high to the low side of the step and back, while maintaining the contact force at 20 gm wt. Evoked action potentials in single SAs innervating the fingerpads of anesthetized monkeys were recorded. Each SA's response to a step provided a spatial response profile (discharge rate as a function of step position) that reflected the distribution of curvature across the step shape. All the major features of the SA response could be consistently explained as being due to the sensitivity of the SA to the amount and rate of change in skin curvature. The response profile was altered by changes in stroke direction, step shape, and stroke velocity. Differences in stroke direction (back and forth) were indicated by differences in pattern of response: a “burst-pause-burst” for strokes from high to low, and a “pause-burst-pause” for strokes from low to high; a greater discharge rate in response to the step for low to high strokes, and for some SAs, the reduction or absence of basal discharge in one of the directions. The discharge rate during the burst for either direction of stroking was greater for steep than for gradual steps, and increased, for a given step shape, with increases in stroke velocity. Regardless of differences in stroke velocity, steep steps were distinguished from gradual steps by having narrower burst widths for low-to-high strokes and narrower pause widths for high-to-low strokes. The same stimuli were delivered to the human fingerpad, and the capacities of humans to discriminate between the steps were measured. It was concluded that the spatial features of SA responses, representing the widths of regions of active and inactive SA populations, as well as the intensive feature of discharge rate, accounted for the gross sensory discriminations of shape.(ABSTRACT TRUNCATED AT 400 WORDS)
The dendritic complexity and innervation of submandibular neurons in five species of mammals
Authors: Snider WD
Published: March 2018

I have compared the dendritic complexity and innervation of homologous parasympathetic ganglion cells in several closely related species of mammals. In the smaller of these species (mouse, hamster, and rat), submandibular ganglion cells generally lack dendrites altogether and are innervated by a single axon. In the guinea pig, a somewhat larger species, these neurons possess rudimentary dendritic arbors and are innervated by 2 axons, on average. In the largest species investigated, the rabbit, submandibular ganglion cells have moderately complex dendritic arbors and receive innervation from several axons. These findings, together with a previous study of sympathetic ganglion cells in these same species (Purves and Lichtman, 1985a), indicate that relationships among neuronal morphology, convergent innervation, and animal size are widespread in the autonomic nervous system of mammals.