bluuebunny/crossref_metadata_2025 huggingface dataset:
CONSTRUÇÃO DE DIAGRAMAS UNIFILARES DA REDE HIDROMETEOROLÓGICA NACIONAL E DE APROVEITAMENTOS HIDRELÉTRICOS DAS SUB-BACIAS 85 A 88, NA BACIA HIDROGRÁFICA DO ATLÂNTICO – TRECHO SUDESTE / SINGLE-LINE DIAGRAM DEVELOPMENT OF NATIONAL HYDROMETEOROLOGICAL NETWORK AND OF HYDROPOWER DAMS IN SUB-BASINS 85 TO 88 IN THE ATLANTIC WATHERSHED – SOUTHESTERN PORTION
Authors: Mendoza Guimarães Guilherme , Santos Finck Juliano , Noronha Marcuzzo Francisco Fernando
Published: April 2018

Diagramas unifilares são métodos de organização sistemáticos que consistem na construção de esquemas de dados em cursos d’água, nos quais são locados tanto as estações em operação, as desativadas e os barramentos na bacia, visando um mais claro entendimento de informações de estações da rede hidrometeorológica e de barramentos disponíveis em uma bacia hidrográfica. O objetivo deste trabalho foi propor um modelo de diagrama unifilar, utilizando o mapeamento das informações de interesse hidrológico das sub-bacias 85, 86, 87 e a porção brasileira da sub-bacia 88 (Bacia Hidrográfica do Atlântico – Trecho Sudeste), englobando parte do estado do Rio Grande do Sul. Assim, colocaram-se as principais informações de interesse para estudos sobre recursos hídricos. O estudo foi descritivo a fim de fornecer informações do organograma básico de funcionamento dos principais rios através de SIG, servindo como base para diversos tipos de estudo, como a regionalização de vazões. Entre os principais rios das sub-bacias estão: Rio Piratini, Rio Camaquã, Rio Jaguarão, Rio dos Sinos, Rio Gravataí. Confeccionaram-se 14 partes de diagramas unifilares para a sub-bacia 85; 10 partes para sub-bacia 86; 16 partes para a sub-bacia 87; e 5 partes para a sub-bacia 88.Abstract:Single-line diagrams are systematic methods of organization that consist of the development of data schemes for streams, in which the hydropower dams and hydrological stations, both in operation and deactivated, are located, aiming for a better knowledge of information from the national hydrometeorological network and hydropower dams available in a watershed. The aim of this paper was to propose a single-line diagram model using digital mapping information of hydrological interest for the sub-basins 85, 86, 87 and on the Brazilian section of sub-basin 88 (Atlantic watershed, or basin 8, – southeast section), encompassing the state of Rio Grande do Sul, managing the synthesis of major information of hydrological interest for studies on water resources. This study was descriptive in order to provide basic chart information of the dynamic of main rivers and it is the foundation for many types of studies using GIS, such as regionalization of flow rates. Among the majors rivers of the sub-basins are: Piratini River, Camaquã River, Jaguarão River, Gravataí River. The sub-basin 85 has fourteen pieces of single-line diagram; the sub-basin 86 has ten; the sub-basin 87 has sixteen; and the sub-basin 88 has five pieces of single-line diagram.Keywords: Single-Line Diagrams; National Hydrometeorological Network; Data Consistency; Geographic Information System; South Atlantic Watershed.
LAS PLANTAS BALLENERAS EN CHILE: historias de abandono - el Caso de la Planta de San Carlos de Corral, Valdivia
Authors: Quiroz Daniel , Carreño Gastón
Published: April 2018

En Chile se construyeron siete plantas balleneras entre Iquique y Punta Arenas en el marco de la caza moderna de ballenas. En 1905 se construyó la primera y en 1956 la última. Desde 1983 ninguna de las plantas se encuentra activa. En este trabajo queremos contar la historia de una de las plantas balleneras más antiguas en el país, que funcionó durante 30 años (1906-1936): la de San Carlos de Corral, situada cerca de Valdivia. La historia de cada planta ballenera en Chile es una “historia de abandono”, de desmantelamiento, de olvido.
O TECER DE UMA REDE SUL AMERICANA DE ANTROPOLOGIA MARÍTIMO-COSTEIRA: relato de uma experiencia em andamento
Authors: Adomilli Gianpaolo Knoller , D’Ambrosio Camarero Letícia , Quiroz Daniel
Published: April 2018

Neste trabalho, apresentamos algumas iniciativas para construção e consolidação de uma rede sul-americana de estudos em antropologia marítimo-costeira, bem como introduzir brevemente esta temática de estudos. Assim, buscamos relatar um percurso que vem sendo realizado nos últimos anos entre um grupo de pesquisadores do Chile, Uruguai, Argentina e Brasil, através da organização e participação de encontros científicos, onde vem sendo realizadas interlocuções e debates em torno de perspectivas teórico-metodológicas para esta temática de estudos, sobretudo a partir de etnografias e demais experiências junto a comunidades pesqueiras e sua relação com o ambiente aquático. Neste percurso, também acompanha a criação/desenvolvimento de dois núcleos de estudos e de projetos de pesquisa, objetivando proporcionar espaços para discussão e realização de pesquisas de caráter teórico/etnográfico e interdisciplinar em torno desta temática, bem como alguns esforços em ampliar o que convencionalmente é chamado de antropologia marítima e/ou da pesca.
Kinetics of the receptor current in bullfrog saccular hair cells
Authors: Corey DP , Hudspeth AJ
Published: April 2018

The receptor current of hair cells from the bullfrog's sacculus was measured by voltage clamp recording across the isolated sensory epithelium. Several hundred hair cells were stimulated en masse by moving the overlying otolithic membrane with a piezoelectrically activated probe. As measured by optical recording of otolithic membrane motion, the step displacement stimuli reached their final amplitudes of up to 1 micrometer within 100 microseconds. The relationship between displacement and steady-state receptor current is an asymmetric, sigmoidal curve about 0.5 micrometer in extent. The time constant of the approach to steady state depends upon the magnitude of the hair bundle displacement and ranges from 100 to 500 microseconds at 4 degrees C; the time course is faster with larger displacements or at higher temperatures. Both the displacement-response curve and the kinetics of the response are changed by alterations in the Ca2+ concentration at the apical surface of the cells. The characteristics of the response are not consistent with simple models for the transduction process that involve enzymatic regulation of channel proteins or diffusible second messengers. Mechanical stimulation is instead posited to act directly by altering the free energy difference between the open and closed forms of the transduction channel, thereby inducing a redistribution between these states. The dependences of the response kinetics on displacement and on temperature suggest that the thermal interconversion between open and closed transduction channels is limited by an enthalpy of activation of about 12 kcal/mol.
Effects of perturbations on accuracy of arm movements
Authors: Sanes JN , Evarts EV
Published: April 2018

This study was carried out to test the hypothesis that the magnitude of perturbation-induced disruption of active movement depends upon the size of the active movement, with small movements being more disrupted than large ones. Human subjects performed pronating or supinating arm movements of 3 degrees, 10 degrees, and 30 degrees in a discrete visual tracking task. When the movements were briefly stopped or reversed, the resultant errors in trajectory and static position (expressed relative to the movement size) were greater for small as compared to large movements. These findings demonstrate that peripheral kinesthetic disturbances modify movement trajectory and end point error, with small movements being more affected than large movements.
Development of sodium channels during differentiation of chick skeletal muscle in culture. I. Binding studies
Authors: Baumgold J , Parent JB , Spector I
Published: April 2018

[125I]Scorpion toxin and [3H]saxitoxin, two neurotoxins that bind specifically to different sites on sodium channels, were used to monitor the development of sodium channels during synchronous differentiation of chick skeletal muscle in culture. [3H]Saxitoxin- binding sites are not detectable in myoblasts. They appear only after myoblasts fuse to form myotubes and increase gradually to reach a maximal value of 58 fmol/mg of protein by 8 days in culture. In contrast, [125I]scorpion toxin-binding sites are first detected during the period of cell fusion and increase after fusion to reach a maximum by 4 days in culture, well before either the maximal value of the [3H]saxitoxin binding or the appearance of fully developed sodium action potentials. Neither [3H]saxitoxin binding nor [125I] scorpion toxin binding affinity changes during development; they have values of 1.4 and 62 nM, respectively. These data, and data described in the companion paper (Baumgold, J., J. B. Parent, and I. Spector (1983) J. Neurosci. 3: 1004–1013), suggest that sodium channel development involves two sequential steps: incorporation into the cell membrane of an immature form of the sodium channel capable of binding scorpion toxin alone, followed by the acquisition of the ability to bind saxitoxin and thus to become a mature and functional channel.
Enkephalin reduces calcium action potentials in Rohon-Beard neurons in vivo
Authors: Bixby JL , Spitzer NC
Published: April 2018

Rohon-Beard neurons of the Xenopus spinal cord develop somatic Ca++- dependent action potentials at early embryonic stages. Because many Ca++-dependent events are blocked or reduced by enkephalin in other neuronal systems, we tested the effect of met-enkephalin on the Ca++ spikes of Rohon-Beard cells. Our results indicate that met-enkephalin, which has no effect on the resting membrane potential or conductance in these cells, reversibly and specifically shortens their Ca++ action potentials, probably by decreasing the Ca++ conductance. Enkephalin has a similar effect on Xenopus dorsal root ganglion cells in vivo. Examination of Rohon-Beard cells at various stages of development shows that enkephalin shortens Ca++ spikes from the earliest times that the spikes appear (approximately 21 hr after fertilization) to the latest times they are detectable (7 to 9 days). This very early response suggests either that enkephalin binds directly to the Ca++ channels or that an “enkephalin receptor” is among the earliest neuronal phenotypes to appear in these cells.
Acoustic parameters underlying the responses of song-specific neurons in the white-crowned sparrow
Authors: Margoliash D
Published: April 2018

Songbirds such as the white-crowned sparrow memorize the song of conspecific adults during a critical period early in life and later in life develop song by utilizing auditory feedback. Neurons in one of the telencephalic nuclei controlling song have recently been shown to respond to acoustic stimuli. I investigated the auditory response properties of units in this nucleus using a technique that permitted great flexibility in manipulating complex stimuli such as song. A few of the units exhibited considerable selectivity for the individual's own song. In wild-caught birds, song-specific units exhibited intradialect selectivity. In those birds that sang abnormal songs due to laboratory manipulation of song exposure during the critical period for song learning, units were selective for the abnormal songs. By systematic modification of a song, and by construction of complex synthetic sounds mimicking song, the acoustic parameters responsible for the response selectivity were identified. Song-specific units responded to sequences of two song parts but not to the parts in isolation. Modification of the frequencies of either part of the sequence, or increasing the interval between the parts, varied the strength of the response. Thus, temporal as well as spectral parameters were important for the response. When sequences of synthetic sounds mimicking song were effective in evoking an excitatory response, the response was sensitive to the aforementioned manipulations. Wih these techniques it was possible to elucidate the acoustic parameters required to excite song-specific units. All songs of the repertoire eliciting a strong excitatory response contained the appropriate parameters, which were missing from all weakly effective, ineffective, or inhibitory songs.
Postembryonic growth of the optic tectum in goldfish. I. Location of germinal cells and numbers of neurons produced
Authors: Raymond PA , Easter SS
Published: April 2018

The growth and morphology of the optic tectum of adult goldfish were studied with light and electron microscopy and with thymidine radioautography. The tectum is roughly hemispheric in shape, with a smaller radius of curvature rostrally than caudally. A narrow region containing proliferating cells (the germinal zone) is found along two- thirds of the rim of the tectal hemisphere but is absent rostrally, adjacent to the tectal region which receives input from the rostral visual field. New cells generated in the germinal zone are added to the tectum appositionally in crescent-shaped increments; these was no evidence of migration of new cells into the rostral region which lacks a germinal zone. Some of the new cells added to the adult tectum were shown to be neurons on the basis of cytological and ultrastructural features. Counts of tectal neurons likewise demonstrated that new cells were added with growth of the tectum; large goldfish (25 cm long) had 27% more tectal neurons than did small fish (4 cm long). Spreading apart of existing cells also contributed to overall growth of the tectum. These results confirm and extend those of R. L. Meyer ((1978) Exp. Neurol. 59: 99–111). The topological dissimilarity of the patterns of growth of retina (which adds cells appositionally around its entire perimeter) and tectum supports the suggestion that retinotectal terminals must continually move (Gaze R. M., M. J. Keating, A. Ostberg, and S. H. Chung (1979) J. Embryol. Exp. Morphol. 53: 103–143). Our estimates of cell numbers and tectal areas lead to predictions about the directions and magnitudes of these displacements.
Synaptic contacts between physiologically identified neurons in the visual system of the barnacle
Authors: Schnapp BJ , Stuart AE
Published: April 2018

Neurons in the median visual system of the barnacle were injected with horseradish peroxidase (HRP) and their processes traced in serial thick (3 micrometers) and thin (100 nm) sections with light and electron microscopy. The anatomy confirms that the I-cells identified by Oertel and Stuart (Oertel, D., and A. E. Stuart (1981) J. Physiol. (Lond.) 311: 127–146) are second-order neurons in the median visual pathway. The terminal branches of the photoreceptor axons are associated in each half of the supraesophageal ganglion with a region of neuropil that extends for 30 to 40 micrometers along the commissure; this photoreceptor-associated neuropil is continuous with but much simpler than the main mass of neuropil in the core of each hemiganglion. The photoreceptor-associated neuropil consists of a small number of different neuronal elements, each with distinctive cytological features. The photoreceptor terminal processes dominate the neuropil; in addition, one finds there the most medial processes of the arborizations of the ipsilateral and contralateral I-cells and the processes of an axon or class of axons of unknown origin referred to as the “RL” fibers. These RL processes associate and branch with the receptor axons and constitute the only major neuronal element in this region of neuropil besides the median photoreceptors and the I-cells. In preparations with an HRP-filled I-cell, the photoreceptors were shown to be presynaptic to I-cell processes at synapses which are characterized by a pair of closely apposed postsynaptic profiles referred to as a dyad. The filled I-cell constituted only one element of the dyad. Receptor endings were also presynaptic to dyads where both postsynaptic elements were unfilled. The RL processes were presynaptic to the photoreceptor terminals at nondyadic synapses, and the receptor endings made specialized junctions, possibly synaptic, with the RL processes. Lateral to the region occupied by the photoreceptor arborization, varicosities of the I-cell are juxtaposed to processes of the A-cell; thus, these sites of the I-cell, where it is most likely to be presynaptic to the A-cell, are segregated from the sites at which it is postsynaptic to the photoreceptors. The I-cell is postsynaptic to photoreceptors and has varicosities juxtaposed to A-cell processes in both hemiganglia.
Localization of dopamine D2 receptor mRNA and D1 and D2 receptor binding in the rat brain and pituitary: an in situ hybridization- receptor autoradiographic analysis
Authors: Mansour A , Meador-Woodruff JH , Bunzow JR , Civelli O , Akil H , Watson SJ
Published: April 2018

Several lines of evidence suggest the existence of multiple dopamine receptor subtypes, referred to as D1 and D2. The present study examines the distribution of these dopamine binding sites in the rat brain and pituitary in relation to the distribution of D2 receptor mRNA using a combination of in vitro receptor autoradiographic and in situ hybridization techniques. 3H-Raclopride and 3H-SCH23390 (in the presence of 1 microM ketanserin) were used to label D2 and D1 receptor binding sites, respectively, while a 495 bp cRNA probe synthesized from the Sac I-Bgl II fragment of a rat D2 receptor cDNA was used to visualize the D2 receptor mRNA. Analysis of adjacent tissue sections in which receptor autoradiography and in situ hybridization had been performed revealed several brain regions where the D2 binding site and corresponding mRNA appear to be similarly distributed, including the caudate-putamen, nucleus accumbens, olfactory tubercle, globus pallidus, substantia nigra, and ventral tegmental area. In the pituitary gland, D2 binding sites and mRNA appear to be codistributed with very dense levels in the intermediate lobe and individually labeled cells in the anterior lobe. Brain regions demonstrating a lack of correspondence between the distribution of the D2 binding site and D2 receptor mRNA include the olfactory bulb, neocortex, paleocortex, hippocampus, and zona incerta. Several hypotheses are discussed to explain the lack of correspondence in certain brain regions; these include the localization of receptor binding sites on both fibers and cell bodies and receptor transport. These studies provide a better understanding of the anatomical distribution of the D2 receptor and serve as a framework for future regulatory and anatomical mapping studies. By focusing on specific brain regions, such as the nigrostriatal system, hippocampus, and olfactory bulb, they provide insights into D2 receptor synthesis, transport, and insertion into cell membranes.
Muscle tone suppression and stepping produced by stimulation of midbrain and rostral pontine reticular formation
Authors: Lai YY , Siegel JM
Published: April 2018

Stimulation of the midbrain retrorubral (RRN), ventral paralemniscal tegmental field (vFTP), reticular tegmental (TRN), and pedunculopontine tegmental (PPN) nuclei was found to produce bilateral suppression of muscle tone in the unanesthetized, decerebrate animal. The RRN is the most rostral area shown to produce such suppression. This muscle tone suppression was frequency- and intensity-dependent. At low stimulus intensities, bilateral suppression was produced at these sites. At higher current and frequency levels, 2 types of muscle responses were found, excitation in PPN and RRN and initial suppression followed by excitation in TRN and vFTP. The mean latency to muscle tone suppression was not significantly different in TRN (36.8 msec) and RRN (36.5 msec). However, muscle tone suppression latency was significantly shorter in vFTP (31 msec) and PPN (27.1 msec). In addition to muscle tone suppression, stepping-like activity could be elicited at the same points by consecutive train stimulations in PPN and single train stimulation in TRN and vFTP. Thus, systems producing atonia are colocalized with those producing locomotion. We hypothesize that the midbrain atonia regions control more caudal regions producing muscle tone suppression in REM sleep, and that the locomotor and atonia eliciting regions are normally coactivated during REM sleep.
Resetting the circadian clock in cultured Xenopus eyecups: regulation of retinal melatonin rhythms by light and D2 dopamine receptors
Authors: Cahill GM , Besharse JC
Published: April 2018

A circadian oscillator is located within the eye of Xenopus laevis. This oscillator regulates retinal melatonin synthesis, stimulating it at night. The primary goal of the studies reported here was to define input pathways to this circadian oscillator as a step toward identification of circadian clock mechanisms. A flow-through superfusion culture system was developed to monitor circadian rhythms of melatonin release from individual eyecups. This system was used to determine the effects of light and dopaminergic agents on melatonin production and on the phase of the circadian oscillator. Six hour light pulses suppressed melatonin production and reset the phase of the free- running melatonin rhythm. Light pulses caused phase delays when applied during the early subjective night, phase advances when applied during the late subjective night, and no phase shift when applied during the subjective day. Dopamine receptor agonists mimicked light in suppressing melatonin release and resetting the phase of the circadian rhythm. The phase-response relationship for phase shifts induced by quinpirole, a D2 dopamine receptor agonist, was similar to that for phase shifts induced by light. Pharmacological analysis with selective catecholamine receptor agonists and antagonists indicated that there are pathways to the melatonin-generating system and the circadian oscillator that include D2 dopamine receptors. A D2 receptor antagonist, eticlopride, completely blocked the effects of dopamine on melatonin release and on circadian phase. However, eticlopride did not alter similar effects induced by light, indicating that dopamine- independent pathways exist for light input to these systems. The effects of light and quinpirole on melatonin release and circadian phase were not additive, indicating that the pathways converge. These pathways to the circadian oscillator in the retina present new avenues for pursuit of cellular circadian clock mechanisms.
Target-dependent hormonal control of neuron size in the rat spinal nucleus of the bulbocavernosus
Authors: Araki I , Harada Y , Kuno M
Published: April 2018

The spinal nucleus of the bulbocavernosus (SNB) in the rat is a cluster of sexually dimorphic motoneurons that innervate perineal muscles. In adult male rats, the size of SNB neurons is reduced following castration, and this effect is reversed by treatment with testosterone. However, androgen receptors are present in the perineal muscles as well as in SNB neurons. Therefore, it is not clear whether the neuronal size is regulated by direct action of the hormone on SNB neurons or by a target-derived factor that may be controlled via hormonal action on the innervated muscle. To address this question, the peripheral (pudendal) nerve of SNB neurons on one side was cut and united to the grafted soleus muscle, which lacks androgen sensitivity. On the control side, the pudendal nerve was similarly cut but was allowed to reinnervate the perineal muscles. The size of SNB neurons was measured on both sides after a postoperative period of 10 weeks, during which the animal had been castrated or treated with testosterone after castration. The size of SNB neurons that had reinnervated perineal muscles was reduced following castration and enlarged by testosterone treatment. In contrast, the size of SNB neurons that had innervated the soleus muscle remained unaltered in response to testosterone manipulation. It is concluded that hormonal regulation of the size of SNB neurons in adult rats is mediated by their target muscles.
Characterization of single calcium channels in Drosophila embryonic nerve and muscle cells
Authors: Leung HT , Byerly L
Published: April 2018

Voltage-activated Ca channels play a central role in synaptic transmission, control of cell excitability, and many other cellular processes. It is now clear that there are multiple types of Ca channels with various modes of modulation. Drosophila offers exceptional advantages for studying the molecular basis of the diversity and modulation of Ca channels. As a step in this study, we have characterized the single-channel Ba currents recorded from cell- attached patches on cultured embryonic Drosophila nerve and muscle cells. The voltage dependence and selectivity of the channels carrying these Ba currents identify them as Ca channels. All Ca channels found in Drosophila neurons appear to have the same voltage dependence of activation and similar single-channel conductance, 12–17 pS (100 mM Ba2+). However, the kinetic properties of individual Ca channels vary greatly. The mean open time of individual channels ranges from 2 msec to less than 0.2 msec. Some channels completely inactivate during the first half of a 90 msec depolarization, while others are more active in the second half. Many channels open during almost every depolarization, while others open in less than 20% of the depolarizations. Channels with longer open times tend to inactivate and open during a small fraction of depolarizations. When these kinetic properties were quantified, a continuum of values was found, instead of the clustering of values that might be expected for discrete types of channels. Muscle Ca channels form a more homogeneous class than do the neuronal Ca channels. The muscle Ca channel conductance is 18 pS. These channels do not inactivate during 90 msec depolarizations and open during a majority of depolarizations applied. Muscle Ca channels are similar to a subset of neuronal Ca channels. When a purified toxin from the spider Hololena curta is applied to neurons, the number of active Ca channels is reduced, and those channels still active open in a small fraction of depolarization. Since channels that open in a small fraction of depolarizations tend to inactivate, these data support the hypothesis that this toxin selectively blocks noninactivating neuronal Ca channels. This differential toxin sensitivity and the much larger variability observed in kinetic properties of neuronal, compared to muscle, Ca channels suggest that there are at least two types of neuronal Ca channels in Drosophila.
Ciliary neurotrophic factor enhances neuronal survival in embryonic rat hippocampal cultures
Authors: Ip NY , Li YP , van de Stadt I , Panayotatos N , Alderson RF , Lindsay RM
Published: April 2018

First described as a survival factor for chick ciliary ganglion neurons, ciliary neurotrophic factor (CNTF) has recently been shown to promote survival of chick embryo motor neurons. We now report neurotrophic effects of CNTF toward three populations of rat hippocampal neurons, the first demonstration of effects of CNTF upon rodent CNS neurons in culture. CNTF elicited an increase in the neurofilament content of hippocampal cultures prepared from embryonic day 18 (E18) rat brain. This was accompanied by increases of 2-, 28-, and 3-fold in the number of GABAergic, cholinergic, and calbindin- immunopositive cells, respectively. CNTF totally prevented the 67% loss of GABAergic neurons that occurred in control cultures over 8 d. CNTF also increased high-affinity GABA uptake and glutamic acid decarboxylase activity. Effects of CNTF were in all cases dose dependent, with maximal stimulation at approximately 100 pg/ml. When addition was delayed for 3 d, CNTF failed to elicit increases either in the number of cholinergic neurons or in GABA uptake.
Exposure to high-pH medium increases the incidence and extent of dye coupling between rat hippocampal CA1 pyramidal neurons in vitro
Authors: Church J , Baimbridge KG
Published: April 2018

Previous studies have demonstrated that dye coupling between neurons can be reduced by maneuvers that reduce intracellular pH. However, it is apparent that marked extracellular alkaline- as well as acid-going pH shifts can occur in the mammalian CNS. In light of the fact that an applied change in extracellular pH may produce a damped change in intracellular pH in the same direction, in this study we have examined the effects of exposure to high extracellular pH (achieved by raising [HCO3-] at a constant PCO2) on the incidence of Lucifer yellow dye coupling between CA1 pyramidal neurons in the rat hippocampal slice. Under standard conditions (pH 7.4), 44% of CA1 pyramidal neurons were dye-coupled, and the mean number of neurons stained per injection was 1.62. A marked increase in the incidence (88%) and extent (mean number of neurons stained per injection, 3.25) of dye coupling was observed during exposure to high-pH medium (pH 7.9). Under both standard and high-pH conditions, dye coupling was associated with the ability of CA1 pyramidal neurons to generate bursts of action potentials in response to intracellularly applied depolarizing current pulses. The results provide additional evidence that dye coupling between hippocampal pyramidal neurons may be modulated dynamically and may have implications for the genesis of synchronized epileptiform activity under alkalotic conditions.
Skeletal muscle-derived trophic factors prevent motoneurons from entering an active cell death program in vitro
Authors: Comella JX , Sanz-Rodriguez C , Aldea M , Esquerda JE
Published: April 2018

The purpose of the experiments reported here is to provide evidence that motoneurons (MTNs) isolated from chick embryo spinal cords go through an active process of cell death when deprived of trophic support in vitro. In order to analyze and characterize this process, MTNs were isolated with a metrizamide gradient technique and cultured in the presence of saturating concentrations of soluble muscle extract. When muscle extract was washed off from the cultures, MTNs entered a process of cell death that could be blocked with inhibitors of mRNA and protein synthesis. Two other additional criteria were used to define this process as an active one. First, ultrastructural analysis of MTNs dying as a consequence of muscle extract deprivation showed that some, but not all, of the MTNs displayed clear signs of apoptotic cell death. Those included cytoplasm condensation, fragmentation of chromatin, and preservation of cytoplasmic organelles. Second, internucleosomal degradation of DNA was detected in MTNs deprived of muscle extract. When DNA was analyzed by Southern hybridization techniques using digoxigenin-labeled genomic probes, a clear ladder pattern could be identified on muscle extract-deprived MTNs. The degradation of DNA upon trophic deprivation could be prevented by cycloheximide (CHX). In an attempt to characterize further the process of active cell death in MTNs, we found a time point of commitment to cell death of approximately 10 hr by using three different approaches: muscle extract deprivation plus readdition of muscle extract, muscle extract deprivation plus addition of CHX, and muscle extract deprivation plus addition of actinomycin D. Moreover, we show that MTNs deprived of trophic support from muscle extract but maintained alive with CHX could not be rescued from cell death by reading muscle extract if CHX was washed off the cultures within the first 15 hr of muscle extract deprivation. However, muscle extract alone was able to rescue MTNs that had been kept alive with CHX for periods of time longer than 24 hr after muscle extract deprivation. From these results we postulate that the activation of the cell death program after trophic deprivation is transient.
Time course of recovery of extracellular dopamine following partial damage to the nigrostriatal dopamine system
Authors: Robinson TE , Mocsary Z , Camp DM , Whishaw IQ
Published: April 2018

Partial damage to the nigrostriatal dopamine (DA) system can produce severe behavioral deficits, from which animals gradually recover. Although the compensatory neuroadaptations that contribute to recovery of function have received considerable attention, the exact role of presynaptic versus postsynaptic contributions remains unclear. For example, it has been suggested that presynaptic adaptations may not be sufficient to account for recovery of function, because compensatory increases in DA biosynthesis, metabolism, and release are maximal within 3 d following a unilateral 6-hydroxydopamine (6-OHDA) lesion, before behavioral recovery is complete. The purpose of this study was to examine another presynaptic adaptation, the normalization of extracellular DA. If this is also complete within 3 d postlesion, it, too, would be insufficient to account for the protracted time course of behavioral recovery. But if the normalization of extracellular DA proceeds more gradually, it could potentially account for the time course behavioral recovery. To address this issue, the extracellular concentration of striatal DA ipsilateral and contralateral to a unilateral 6-OHDA lesion was estimated with microdialysis, either 4 d or 3–4 weeks following the lesion. After estimating the basal extracellular concentration of DA, the ability to increase DA release further was assessed by administering an amphetamine challenge. It was found that in animals with a 6-OHDA lesion, the concentration of DA in dialysate was higher than would be predicted by the extent of DA denervation. Furthermore, in groups matched for lesion size, extracellular DA was significantly higher 3–4 weeks following a 6-OHDA lesion than 4 d following the lesion. These findings suggest that the normalization of extracellular DA may be a relatively gradual process, and therefore may be sufficient to account for the protracted time course of behavioral recovery.
Kainate-induced status epilepticus alters glutamate and GABAA receptor gene expression in adult rat hippocampus: an in situ hybridization study
Authors: Friedman LK , Pellegrini-Giampietro DE , Sperber EF , Bennett MV , Moshe SL , Zukin RS
Published: April 2018

In adult rats, intraperitoneal administration of kainic acid, a glutamic acid analog and potent neurotoxin, induces persistent seizure activity that results in electrographic alterations and neuropathology that closely resemble human temporal lobe epilepsy. We used in situ hybridization to identify regions of altered glutamate and GABAA receptor gene expression following kainate-induced status epilepticus. In the CA3/CA4 area, the hippocampal region most vulnerable to neurodegeneration after kainate acid treatment, expression of GluR2 (the AMPA/kainate receptor subunit that limits Ca2+ permeability) and GluR3 was decreased markedly at 12 and 24 hr, times preceding neurodegeneration. These findings raise the possibility that increased formation of Ca(2+)-permeable AMPA/kainate receptors in the CA3/CA4 area may enhance glutamate pathogenicity. Expression of the GABAA alpha 1, subunit was also reduced, indicating a possible decrease in inhibitory transmission, which would also enhance excitotoxicity. GluR1 and NR1 expression was not significantly changed. In the dentate gyrus, a region resistant to neurodegeneration, concomitant increases in GluR2 and GluR3 expression were observed; GluR1, NR1, and GABAA alpha 1 mRNAs were not detectably altered. Analysis of emulsion-dipped sections revealed that the changes in GluR2, GluR3, and GABAA alpha 1 expression represented changes in mRNA content per neuron and were specific to pyramidal cells of the CA3/CA4 area and to granule cells of the dentate gyrus. These findings indicate that kainate seizures modify hippocampal glutamate and GABAA receptor expression in a cell-specific manner. Timing of the changes in glutamate and GABAA receptor mRNAs indicates that these changes may play a causal role in hippocampal neuronal cell loss following kainate-induced seizures.
Corticosterone circadian secretion differentially facilitates dopamine- mediated psychomotor effect of cocaine and morphine
Authors: Marinelli M , Piazza PV , Deroche V , Maccari S , Le Moal M , Simon H
Published: April 2018

Studies of intravenous self-administration and psychomotor effects of drugs have recently suggested that stress-induced corticosterone secretion may be an important factor determining vulnerability to drugs of abuse. In this report, we studied if basal physiological corticosterone secretion modulates sensitivity to cocaine and morphine, and if changes in the reactivity of mesolimbic dopaminergic (DA) neurons, one of the principal substrates of drug-reinforcing effects, are involved. For this purpose we determined the psychomotor effects of these drugs in animals in which corticosterone secretion was suppressed by adrenalectomy and in adrenalectomized animals submitted to different corticosterone replacement therapies designed to mimic (1) only the diurnal levels of the hormone, obtained by the subcutaneous implantation of 50 mg corticosterone pellets; (2) only the nocturnal levels, obtained by adding corticosterone (50 micrograms/ml) to the drinking solution during the dark period; and (3) the entire circadian fluctuation, obtained by combining the two previous treatments. Locomotor response to cocaine and morphine was studied after both systemic and central injections, into the nucleus accumbens for cocaine and into the ventral tegmental area for morphine. These sites were chosen because stimulant effects of cocaine and morphine injected in these structures are dopamine dependent. Our results show that suppression of corticosterone by adrenalectomy reduced the locomotor response to cocaine and morphine, injected both systemically and centrally. The reinstatement of diurnal levels of corticosterone totally reversed adrenalectomy's effects on the behavioral response to cocaine, whereas the reestablishment of the entire corticosterone circadian fluctuation (diurnal plus nocturnal levels) was necessary to reverse the response to morphine.(ABSTRACT TRUNCATED AT 250 WORDS)
The neurosteroid 3 alpha-hydroxy-5 alpha-pregnan-20-one induces cytoarchitectural regression in cultured fetal hippocampal neurons
Authors: Brinton RD
Published: April 2018

The neurosteroid 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha, 5 alpha-THP) acts as a potent allosteric modulator and a direct activator of the GABA-chloride channel complex. This neurosteroid has also been found to protect against seizures that arise from blockade of the GABA- chloride channel complex. Because 3 alpha,5 alpha-THP protects against excitotoxin-induced seizure activity and because seizure activity has been found to be associated with aberrant hippocampal nerve cell growth, the rapid effect of the neurosteroid 3 alpha,5 alpha-THP upon nerve cell growth was investigated using videomicroscopy of hippocampal neurons in culture. Within 40 min of exposure 3 alpha,5 alpha-THP induced a significant decrease in the area and length of neurites. A concomitant decrement in the number and length of filopodia decorating neuritic extensions also occurred within the 40 min of 3 alpha,5 alpha- THP exposure. Both rapid and slow retrograde movement of intracellular organelles was observed in 3 alpha,5 alpha-THP-treated neurons. 3 alpha,5 alpha-THP-induced regression of neuritic extensions occurred only in nerve cells that had not yet established contact with other nerve or glial cells in culture. Established structural connections between neurons or glia did not erode during 3 alpha,5 alpha-THP exposure. Neither the inactive stereoisomer 3 beta-hydroxy-5 beta- pregnan-20-one nor progesterone had a significant effect upon any of the morphological parameters assessed. In approximately 25% of the cells in which 3 alpha,5 alpha-THP had induced regression, subsequent exposure to 17 beta-estradiol induced profuse filopodial growth within 60 sec of exposure. In cultures similar in age to those used in the morphological studies, 3 alpha,5 alpha-THP induced a significant increase in 36Cl- uptake within 10 sec. The magnitude of 36Cl- uptake was comparable to that induced by exposure to 100 microM GABA. In older, more mature cultures in which the nerve cells had established structural connections, 3 alpha,5 alpha-THP protected cells from picrotoxin-induced nerve cell death. These results demonstrate that 3 alpha,5 alpha-THP can induce regression of neuronal morphology within a relatively rapid time frame. 3 alpha,5 alpha-THP induction of 36Cl- uptake within 10 sec suggests that activation of neurosteroid-regulated chloride channels is an initial step in the biochemical mechanism underlying the retraction induced by this progesterone metabolite steroid. In select instances, 17 beta-estradiol induced an extremely rapid reversal of the filopodial regression produced by 3 alpha,5 alpha- THP.(ABSTRACT TRUNCATED AT 400 WORDS)
Omega-conotoxin sensitivity and presynaptic inhibition of glutamatergic sensory neurotransmission in vitro
Authors: Gruner W , Silva LR
Published: April 2018

Synaptic transmission between embryonic chick dorsal root ganglion (DRG) neurons and spinal cord neurons was studied in dissociated cell culture. Stimulation of DRG neurons evoked monosynaptic and polysynaptic excitatory responses in the spinal neurons. These responses could be reversibly blocked by application of 6-cyano-7- nitroquinoxaline-2,3-dione (a selective non-NMDA receptor antagonist) and irreversibly eliminated through the presynaptic action of omega- conotoxin GVIA (a selective N-type calcium channel antagonist). As N- type calcium channels in DRG neuron somata are targets for modulation via GABAB receptors, we tested the role of these receptors as regulators of synaptic transmission. Baclofen (a selective GABAB receptor agonist) reversibly inhibited synaptic transmission via a presynaptic, pertussis toxin-sensitive mechanism; CGP 35348 (a selective GABAB receptor antagonist) blocked the actions of baclofen. Taken together, these results demonstrate that N-type calcium channels play a dominant role in glutamatergic sensory neurotransmission. They suggest, in addition, that modulation of N-channel activity may underlie, at least in part, presynaptic inhibition of synaptic transmission between DRG neurons and their targets in the intact spinal cord.
Block of Ca channels in rat central neurons by the spider toxin omega- Aga-IIIA
Authors: Mintz IM
Published: April 2018

The effects of the spider toxin omega-Aga-IIIA were studied on Ca channel currents in rat central neurons. In hippocampal CA1 pyramidal neurons, omega-Aga-IIIA blocked approximately 70% of the high-threshold Ca currents and had no effect on low-threshold T-type current. Occlusion experiments with blockers of L-, N-, and P-type Ca currents showed that omega-Aga-IIIA abolished dihydropyridine-sensitive L-type current and blocked a substantial fraction of the omega-conotoxin (CgTX)-sensitive N-type and omega-Aga-IVA-sensitive P-type Ca currents. The high-threshold current remaining with saturating concentrations of nimodipine, CgTX, and omega-Aga-IVA was also partially blocked by omega- Aga-IIIA in a variety of central neurons. Block of P-type current by omega-Aga-IIIA was investigated in more detail in cerebellar Purkinje neurons. Block was potent (Kd approximately 0.5 nM), but incomplete and voltage dependent. Tail current activation curves showed that channel gating is shifted in the depolarizing direction by approximately 7 mV. The instantaneous current-voltage curve for P-type current was also altered; the toxin reduced Ba-carried inward currents by approximately 40% and had little effect on Cs-carried outward currents. The partial, voltage-dependent reduction of P-type Ca current can be accounted for by a combination of toxin effects on channel permeation and gating.
Functional plasticity of regenerated and intact taste receptors in adult rats unmasked by dietary sodium restriction
Authors: Hill DL , Phillips LM
Published: April 2018

Unilateral chorda tympani nerve sectioning was combined with institution of a sodium-restricted diet in adult rats to determine the role that environment has on the functional properties of regenerating taste receptor cells. Rats receiving chorda tympani sectioning but no dietary manipulation (cut controls) and rats receiving only the dietary manipulation (diet controls) had normal responses to a concentration series of NaCl, sodium acetate (NaAc), and NH4Cl. However, responses from the regenerated nerve in NaCl-restricted rats (40–120 d postsectioning) to NaCl and NaAc were reduced by as much as 30% compared to controls, indicating that regenerating taste receptors are influenced by environmental (dietary) factors. Responses to NH4Cl were normal; therefore, the effect appears specific to sodium salts. Surprisingly, in the same rats, NaCl responses from the contralateral, intact chorda tympani were up to 40% greater than controls. Thus, in the same rat, there was over a twofold difference in sodium responses between the right and left chorda tympani nerves. A study of the time course of the functional alterations in the intact nerve revealed that responses to NaCl were extremely low immediately following sectioning (about 20% of the normal response), and then increased monotonically during the following 50 d until relative response magnitudes became supersensitive. This function occurred even when the cut chorda tympani was prevented from reinnervating lingual epithelia, demonstrating that events related to regeneration do not play a role in the functional properties of the contralateral side of the tongue.(ABSTRACT TRUNCATED AT 250 WORDS)
The differential control of c-jun expression in regenerating sensory neurons and their associated glial cells
Authors: De Felipe C , Hunt SP
Published: April 2018

Damage to the axons of adult sensory neurons results in massively increased expression of the protooncogene c-jun both in neurons and in the associated Schwann cells. The role of growth factors and axon contact in mediating this expression was investigated in dissociated cultures of adult sensory neurons and glial cells that expressed c-jun within 24 hr of plating. Trk, trkB, and trkC growth factor receptor genes were expressed in discrete subpopulations of sensory neurons but addition of NGF or brain-derived neurotrophic factor (BDNF) did not inhibit the expression of c-jun. Similarly, axon contact was not sufficient to decrease c-jun expression in glial cells. However, c-jun expression could be downregulated in glial cells, but not neurons, by treatment with cAMP or forskolin and increased by raising intracellular calcium levels. The results suggest that c-jun levels are differentially regulated in neurons and glial cells but that NGF or BDNF do not regulate c-jun expression in damaged neurons.