bluuebunny/crossref_metadata_2025 huggingface dataset:
ENDOCRINE DISRUPTORS: BISPHENOL A AND ITS RELATION WITH OBESITY
Authors: Sá Lucas Wanderley Rodrigues Gonçalves de S , Sousa Luciano Nunes de , Marques Thyciara Fontenele , Bernardo Gabriel Pereira , Bernardo Lorena Pereira , Parente Lucas Leimig Telles , Parente Rodrigo Emmanuel Leimig Telles , Telles Maria Valéria Leimig , Malheiro Djailson Ricardo
Published: April 2018

The prevalence of obesity is, worldwide, in wide intensification. This increase stimulates the search for new hypotheses that explain the genesis of the metabolic syndrome. This article seeks to clarify the obesogenic hypothesis of bisphenol A (BPA), based on its endocrine disrupting potential. Methodology: For the development of the present study, the Scopus and PubMed databases were used, from descriptors generated by the DeCS: Endocrine Disruptors; Foods; Obesity; Bisphenol A and its correspondents in English. Randomized and controlled trials were considered eligible, focusing on publications in English and Portuguese. The survey was conducted on April 11, 2017, with publications of the last five years being leaked. Based on this, 87 articles were obtained and, from the reading of the title and its abstracts, 26 publications were selected. After the complete reading of the 26 articles selected, 18 articles were obtained that served as a basis for this bibliographic review. Bisphenol A appears as an important agent that causes obesity in the contemporary world, interfering in the signaling mechanism of the endocrine system, being its high exposure linked to many of the habits present in the current context. Conclusion: Based on the possible consequences of bisphenol A, the reduction of human exposure to the compound should be considered. Based on this, alternatives to BPA in the production of industrial plastic polymers have to be considered since increased exposure to the endocrine disruptor is closely related to industrial production. Keywords: Endocrine Disruptors, Obesity, Bisphenol A
Effect of ozonized olive oil on oral levels of Candida spp. in patients with denture stomatitis
Authors: Crastechini Erica , Koga-Ito Cristiane Yumi , Machado Suzan de Fátima , Teodoro Guilherme Rodrigues , Back-Brito Graziella Nuernberg , Sangalli Jorgiana , Dias Almeida Janete
Published: April 2018

Objective: The aim of this study was to evaluate the effect of ozonized oil (OZ) on the oral levels of Candida spp. in patients with denture stomatitis. Material and Methods: In vitro tests were performed to validate antifungal activity and to standardize OZ conditions. Antifungal activity was screened against C. albicans and five non-albicans species (C. tropicalis, C. dubliniensis, C. krusei, C. guilliermondii, and C. parapsilosis). Also, the effects on C. albicans planktonic and biofilm were evaluated. After validation, OZ was included in a therapeutic protocol of denture stomatitis in vivo. Thirty patients used OZ and 20 used sodium bicarbonate (SB) for 14 days. After 7 and 14 days, clinical evaluation, isolation and identification of yeasts were performed. Isolates were identified by phenotypic and genotypic tests. Ozonized oil showed in vitro antifungal activity against all species of Candida. Ozonized oil reduced the number of viable cells in C. albicans biofilms. Oral candidal levels were lower in relation to baseline both after after 14 days of treatment with SB and OZ. Results: A total of 493 Candida spp. isolates was obtained and 80% were identified as C. albicans. Remission of denture stomatitis was observed in all patients after 7 days of treatment in both groups. Conclusion: Within the limits of the study we can conclude that ozonized olive oil can be a new alternative for the control of biofilm in patients with denture stomatitis. KeywordsOzone; Candida; Antifungal Agents; Stomatitis; Denture.
Evaluation of dimensional stability and details reproduction of alginate molds storage in different times and temperature
Authors: Penfold Rafael da Rocha Santos , Brandt William Cunha , Miranda Milton Edson , Vitti Rafael Pino
Published: April 2018

Objective: The aim of this study was to evaluate dimensional stability and detail reproduction in alginate molds stored at different times and temperatures. Material and Methods: Three different commercially available alginates (Cavex Color Change, Jeltrate Plus and Hydrogum 5) were tested at four different times (0 - control, 1, 3 and 5 days) and two temperatures (25ºC and 37ºC) (n=5). The alginates were handled following the manufacturer's instructions. The impression procedures occurred in an environment with controlled room temperature (25ºC) and relative humidity (50±5%). A metallic model (ISO 1563:1990) was used to perform the impressions. The tray containing alginate remained on the metallic model under constant pressure (2 kgf) until the alginate gelation process. The molds were stored (different times and temperatures) and analyzed in stereomicroscope at 30x magnification and 0.5 ?m accuracy (Olympus Measuring Microscope STM). The molds and the metallic model measurements were compared, and the data were statistically analyzed by Kolmogorov-Smirnov and three-way ANOVA tests, and the means were compared by Tukey test (5%). Results: The results showed no double interactions (p>0.05) and the different alginates presented statistically similar values of dimensional stability (p=0.102). However, 25ºC (temperature) and control group (time) showed the highest values of dimensional stability (p<0.05). Jeltrate Plus was the only material that presented inaccuracy in details reproduction. Conclusion: It is recommended that, for tested alginates, the stone casts should be poured immediately, even though the molds are dimensionally stable up to 5 days when stored at 25ºC. KeywordsDental impression materials; Dimensional measurement accuracy; Shrinkage.
Effects of intracanal medicaments and the remaining cavity wall on fracture strength of endodontically treated molars
Authors: Olcay Keziban , Coban Ata Nisa , Belli Sema
Published: April 2018

Objective: The aim of this study was to investigate the effects of the short-term intracanal application of two medicaments on the fracture strength of root-filled molar teeth with different levels of tooth structure loss. Material and Methods: Standard access cavities of totally 84 intact maxillary molar teeth were prepared in 72 teeth and were divided into 3 main groups. Standard access cavities were kept in the first group, while mesio-occlusal-distal cavities (MOD) were prepared in the second and third groups. One-half of the palatinal walls were removed in the third group. Twelve sound teeth were used in the fourth group as control. Each group was then assigned into two subgroups according to the medicament used (n=12): 2% chlorhexidine gel and calcium hydroxide. Samples were stored at 37°C and 100% humidity for 1 week. Then the teeth were inserted into a universal testing machine and vertically loaded (5 mm/min) from the occlusal surface. The data was recorded in Newtons and statistically evaluated using a Univariate ANOVA and a Tukey as post hoc test. Results: A significant difference was found among the test groups (p<0.01). No significant difference was found according to the medicament used (p>0.05), however the number of remaining walls significantly affected the fracture strength (p<0.01). The first group with access cavity showed mostly repairable fractures (60%–80%) whereas the others showed mostly non-repairable fracture patterns (60%–90%). Conclusion: In conclusion, the fracture strength of endodontically treated teeth is related to the structure loss rather than the intracanal medicament used. KeywordsEndodontically treated teeth; Fracture strength; Intracanal medicament; Remaining cavity wall; Root facture.
Prefabricated composite resin veneers: a clinical case report
Authors: De Araújo Amanda Oliveira , Manta Davi Farias , Lopes Mário José Pinto , Pedrosa Marlus da Silva , Da Silva Claudio Heliomar Vicente , Durão Márcia de Almeida
Published: April 2018

The authors present a complete clinical case report of functional and aesthetic rehabilitation of the smile harmony of a 23-year-old male patient through periodontal plastic surgery, tooth bleaching and prefabricated composite resin veneers, emphasizing the advantages, limitations and patient’s perceptions about the treatment.  After clinical and radiographic evaluations, extra and intra-oral photographs were taken, plaster study models were obtained, digital smile design and diagnostic wax-up were performed. The patient accepted and authorized the proposed dental procedures. The treatment proved to be effective, being a practical and safe approach, with aesthetic recovery of the smile harmony and patient satisfaction. KeywordsDental esthetics; Tooth bleaching; Dental veneers; Composite resin.
Antimicrobial and mechanical acrylic resin properties with silver particles obtained from Fusarium oxysporum
Authors: Sato Tabata Prado , Conjo Celio Ilidio , Rossoni Rodnei Dennis , Junqueira Juliana Campos , Melo Renata Marques de , Durán Nelson , Borges Alexandre Luiz Souto
Published: April 2018

Objective: This study evaluated the effects of the incorporation of silver nanoparticles (AgNPs) obtained from Fusarium oxysporum on heat-activated acrylic resin (HAAR) and their influence on resin’s surface roughness, hardness, color alteration and antimicrobial capacity against Candida albicans. Material and Methods: For this, 50 discs of HAAR (2x5 mm) were produced and divided into three groups, Control: HAAR; Ag1: HAAR plus 0.539 mg of AgNPs; and Ag2: HAAR plus 1.1 mg of AgNPs. Knopp hardness (HK), surface roughness (Ra and Rz) and color alteration according to the CIE Lab were measured. Specimens were then evaluated in vitro with regard to C. albicans biofilm formation through formed colony count (CFU/mL). Scanning Electron Microscopy (SEM) and Atomic force microscopy (AFM) analyses were performed. Results: The addition of AgNPs of both concentrations changed Ra, Rz and HK significantly. There was statistically significant difference for L (p=0.00); a*(p=0.00) and b*(p=0.00) parameters. There were no differences between Ag1 and Ag2 biofilm formation, but the comparison of both with the control group presented a significant reduction (p=0.0091) on biofilm formation. SEM and AFM images showed no signs of NPs clustering. Conclusion: It can be concluded tha AgNPs incorporation in HAAR was effective in reducing C. albicans activity, with a slight change in color and hardness of the material, being effective therefore, in regions such as the dental prostheses palate, which have lesser aesthetic appeal.KeywordsAcrylic resins; Silver; Antimicrobial agents.
Lie symmetry analysis for the solution of first-order linear and nonlinear fractional differential equations
Authors: Ilie Mousa , Biazar Jafar , Ayati Zainab
Published: April 2018

Obtaining analytical or numerical solution of fractional differential equations is one of the troublesome and challenging issues among mathematicians and engineers, specifically in recent years. The purpose of this paper is to solve linear and nonlinear fractional differential equations such as first order linear fractional equation, Bernoulli, and Riccati fractional equations by using Lie Symmetry method, based on conformable fractional derivative. For each equation, some numerical examples are presented to illustrate the proposed approach.Â Â
ANALISIS KELAYAKAN DAN STRATEGI PENGEMBANGAN WILAYAH DALAM WACANA PEMBENTUKAN DAERAH OTONOM BARU BOGOR TIMUR
Authors: Nurhasanah Aan , Juanda Bambang , Putri Eka Intan Kumala
Published: April 2018

ABSTRACTBogor District as one of large region and large number of population has any problems related to accesibility and equity welfare.  Regional proliferation considered as a way to overcome that problems.  The study used scoring method based on PP no. 78 2007 with descriptive analysis, location quotient analysis, and Klassen Tiphology. This study was aimed to analyzed feasibility of regional proliferation and to formulate regional development strategy based on economic potentials in eastern Bogor District region. In general the result showed that eastern Bogor District region appropriate to organize as an autonomous region.  High economic potential and fiscal cappacity of eastern Bogor region can be made as main factor to recommended eastern Bogor District region as an autonomous region.  Thus, the selected strategies are how to develop backward regions base on leading sector, support primary sector development such as agricultural. Goverment policy is important to optimize natural resources management, spread out infrastructure development mainly to support rural area development. The implication of policy directed base on each region characters such as social, culture, spatial, basic sector.   Furthermore regional development analysis can be set base on sub-district region.
A Dynamic Connectome Supports the Emergence of Stable Computational Function of Neural Circuits through Reward-Based Learning
Authors: Kappel David , Legenstein Robert , Habenschuss Stefan , Hsieh Michael , Maass Wolfgang
Published: April 2018

Synaptic connections between neurons in the brain are dynamic because of continuously ongoing spine dynamics, axonal sprouting, and other processes. In fact, it was recently shown that the spontaneous synapse-autonomous component of spine dynamics is at least as large as the component that depends on the history of pre- and postsynaptic neural activity. These data are inconsistent with common models for network plasticity and raise the following questions: how can neural circuits maintain a stable computational function in spite of these continuously ongoing processes, and what could be functional uses of these ongoing processes? Here, we present a rigorous theoretical framework for these seemingly stochastic spine dynamics and rewiring processes in the context of reward-based learning tasks. We show that spontaneous synapse-autonomous processes, in combination with reward signals such as dopamine, can explain the capability of networks of neurons in the brain to configure themselves for specific computational tasks, and to compensate automatically for later changes in the network or task. Furthermore, we show theoretically and through computer simulations that stable computational performance is compatible with continuously ongoing synapse-autonomous changes. After reaching good computational performance it causes primarily a slow drift of network architecture and dynamics in task-irrelevant dimensions, as observed for neural activity in motor cortex and other areas. On the more abstract level of reinforcement learning the resulting model gives rise to an understanding of reward-driven network plasticity as continuous sampling of network configurations.
The participation of a putative cell surface receptor for laminin and fibronectin in peripheral neurite extension
Authors: Bozyczko D , Horwitz AF
Published: April 2018

We have used the CSAT (cell substrate attachment) monoclonal antibody (Mab), which is directed against a putative laminin and fibronectin receptor, to examine its role in the adhesive phenomena of neurons. This antibody was previously found to disturb the adhesion of several classes of fibroblasts and muscle. Here we report its effects upon neuronal-substrate adhesion. Two sources of neurons were investigated-- the dorsal root and ciliary ganglia. Both responded similarly. Neurons plated in the presence of the CSAT Mab did not adhere to the substratum and process formation was inhibited completely for at least 24–48 hr. In explant cultures, when neurons were first allowed to extend processes prior to addition of the CSAT Mab, the results depended on the particular substrate. With some substrates, the neurites bundled and detached from the substratum; with others, they retracted and regrew to form large fascicles or bundles of processes. In dissociated cultures that already had extended processes, neurites fasciculated and cell bodies aggregated in response to the presence of the CSAT Mab. The magnitude of this response varied, depending upon the substrate. The antigen was localized, using immunofluorescence, on neuronal cell bodies, axons, and growth cones. This distribution correlated with its biological effects on all parts of the neuron. The antigen was isolated from neuronal cultures by immunoaffinity purification. It migrated in the molecular weight range of 140 kDa on reducing SDS-PAGE. This antigen is very similar to that isolated from fibroblasts, which is an integral membrane glycoprotein complex. The data presented implicate the participation of the CSAT antigen in neurite extension and fasciculation.
Fodrin degradation by calcium-activated neutral proteinase (CANP) in retinal ganglion cell neurons and optic glia: preferential localization of CANP activities in neurons
Authors: Nixon RA
Published: April 2018

The activity of calcium-activated neutral proteinases (CANPs) toward endogenous substrates was measured in axons of retinal ganglion cell (RGC) neurons and separately in adjacent optic glia under in vitro conditions that preserved the ultrastructure and anatomic relationships between these cellular elements. RGC neurons and optic glia both expressed CANP activity. In contrast to RGC axons, which contained at least two CANP activities with calcium requirements in the millimolar (CANP A) and micromolar (CANP B) range (Nixon et al., 1985), CANP activity in optic glia was detectable only at millimolar calcium concentrations. When maximally activated, CANP(s) in optic glia exhibited a broad specificity for endogenous proteins but degraded larger proteins at a faster rate. The cytoskeletal protein fodrin (brain spectrin) was among the most susceptible endogenous substrates in RGC axons or glia. The similar properties of fodrin in neurons and glia, including its susceptibility to a purified millimolar calcium- sensitive brain CANP (mCANP), provided the basis for using this protein as a substrate to compare the relative activity of neuronal and glial CANPs in situ. Fodrin degradation mediated by CANPs proceeded at least 6 X more rapidly in intact RGC axons than in optic glia. Comparable differences in the relative degradation rates of the total neuronal and glial protein pools were also observed. These results indicate that the potential activity of CANPs is substantially greater in RGC neurons than in glia. The enormous potential activity and preferential localization of multiple CANP activities in RGC neurons support previously hypothesized roles for CANPs in the processing of axonally transported proteins and in the regulation of neuronal cytoskeletal dynamics and geometry.(ABSTRACT TRUNCATED AT 250 WORDS)
Molecular specificity of defined types of amacrine synapse in cat retina
Authors: Sterling P , Lampson LA
Published: April 2018

The inner plexiform layer of cat retina contains synaptic structures belonging to 50 or more types of “identified” neurons. To learn whether there are antigens confined to subsets of these synaptic structures, we raised monoclonal antibodies to homogenates of neural retina. Binding patterns of these antibodies were visualized by the peroxidase- antiperoxidase method and studied in serial, ultrathin sections by electron microscopy. Four antibodies stained the synaptic varicosities of certain amacrine cells. Many of the stained varicosities formed reciprocal synapses with a rod bipolar axon terminal, but only about half of the reciprocal synapses associated with a rod bipolar were stained. Other stained varicosities formed synapses with cone bipolar axons, ganglion cell dendrites, and unstained amacrine processes. The patterns were essentially the same for each antibody and were not altered by staining with the antibodies two at a time; therefore, it is likely that all four antibodies stain the same subset of synaptic structures. These patterns would be accounted for if there were staining of all the synaptic varicosities of three of the four types of identified amacrine reciprocally connected to the rod bipolar (A6, A8, A13). This localization suggests that the antigen responsible for the binding pattern is not associated with synaptic transmission. Staining is present in the inner plexiform layer during the period of synaptogenesis and consequently the antibodies are serving as markers for following the development of identified synapses in an identified neural circuit.
Classical conditioning of Hermissenda: origin of a new response
Authors: Lederhendler II , Gart S , Alkon DL
Published: April 2018

Training of the marine snail Hermissenda crassicornis with paired light and rotation was previously shown to result in acquisition and retention of a behavioral change with many features characteristic of vertebrate associative learning. Here, this behavioral change is demonstrated to be classical, Pavlovian-like conditioning. A new response to light is formed (the CR) that is pairing-specific and resembles the unconditioned response (UCR) to rotation. The conditioned and unconditioned responses are relatively rapid, occurring within seconds of the onset of light or rotation stimuli, and correspond to pairing-specific reductions in speed during the same time period. Since the CR is independent of the presentation of rotation, and it is also expressed by the same effector system (the foot) responsible for the UCR, light stimulation has assumed some of the functional character of rotation.
Behavioral development in the absence of neural activity: effects of chronic immobilization on amphibian embryos
Authors: Haverkamp LJ , Oppenheim RW
Published: April 2018

Embryos of Xenopus laevis and Ambystoma mexicanum were continually immobilized from premotile stages of development to stages at which normally reared embryos were swimming well. Immobilization was achieved through exposure to solutions of chloretone, lidocaine, or alpha- bungarotoxin. At a number of stages after recovery from the drugs, spontaneous and stimulated behaviors were extensively quantified. Immobilization of Ambystoma embryos resulted in temporary defects in musculoskeletal development. In contrast, treated Xenopus embryos could not be distinguished from controls by simple visual observation within minutes to hours after removal from the drug solutions. Quantifications of behavior revealed, however, a transient period of 24–48 hr during which treated embryos exhibited consistently reduced measures of stimulated swimming, while showing an increase in frequency of spontaneous movements. Detailed behavioral testing could detect no permanent effects of chronic immobilization in either species after this initial period of recovery. The results are discussed in reference to the classic works of Harrison (1904), Carmichael (1926, 1927), and Matthews and Detwiler (1926).
The glycine receptor deficiency of the mutant mouse spastic: evidence for normal glycine receptor structure and localization
Authors: Becker CM , Hermans-Borgmeyer I , Schmitt B , Betz H
Published: April 2018

Homozygotes of the mutant mouse spastic exhibit reduced binding of 3H- strychnine to homogenates from various regions of the CNS compared with unaffected littermates (White and Heller, 1982). Here we report evidence that the spastic mutation coincides with a reduced concentration and an unaltered structure of the glycine receptor in spinal cord. Scatchard analysis of 3H-strychnine binding revealed a single binding site with a Bmax of 267 +/- 62 fmol/mg protein for spastic and of 864 +/- 220 fmol/mg protein for control mice; no difference was found for the corresponding KD values. Also Ki values of glycine for 3H-strychnine binding and displacement of 3H-strychnine by beta-alanine and taurine were indistinguishable for both preparations. Photoaffinity labeling of synaptic membranes with 3H-strychnine identified an Mr = 48,000 polypeptide in both control and spastic mouse membranes. Tryptic digestion of these membranes produced radiolabeled peptide fragments of identical molecular weights, suggesting that the proteolytic cleavage sites around the antagonist binding site are conserved in the mutant glycine receptor protein. Glycine receptors from both control and mutant mice were purified by affinity chromatography on aminostrychnine agarose. SDS/PAGE revealed three polypeptides of Mr = 48,000, 58,000, and 93,000 in both receptor preparations. Monoclonal antibodies directed against different subunits of the glycine receptor were applied to an enzyme-linked immunosorbent assay. The same pattern of immunoreactivity was obtained for glycine receptor from spinal cord of spastic homozygotes, control mice, and rats, suggesting conservation of the antigenic epitopes in the mutant receptor.(ABSTRACT TRUNCATED AT 250 WORDS)
A time-comparison circuit in the electric fish midbrain. II. Functional morphology
Authors: Carr CE , Maler L , Taylor B
Published: April 2018

The weakly electric fish Eigenmannia is able to detect temporal disparities as small as 400 nsec between two signals from different parts of the body surface (Carr et al., 1986). The elements of this time-comparison circuit have been identified by EM reconstruction of its component cells. Information about the timing of the zero-crossing of signals on each area of the body surface is coded in phase-coder receptors, a subset of tuberous electroreceptors. Electroreceptors on the body surface are innervated by primary afferents with their central termination on the spherical cells of the medullary electrosensory lateral line lobe. These cells project to lamina VI of the midbrain torus, a structure similar to the inferior colliculus. Afferents entering lamina VI form a very restricted terminal arbor in which they synapse on the three cell types of this lamina. Each afferent makes gap- junction synapses on one or two giant cell somata and morphologically mixed synapses on the distal dendrites of two types of small cell. The afferent terminals thus encode the timing of the electric signal on a local patch of the body surface, forming a somatotopic map of the body surface in lamina VI. The giant cells are adendritic and their axonal arbor is such as to distribute timing information originating from one part of the body surface throughout lamina VI, so that each region of lamina VI receives information about the timing of zero-crossings from the entire body surface from giant cells, as well as information from a local portion of the body surface from the afferent terminals. The giant cells terminate exclusively on the cell bodies of the small cells of lamina VI, shown to be sensitive to small temporal disparities by Heiligenberg and Rose (1985). Thus, each small cell receives a single synapse on its soma from a giant cell that conveys phase-coding information from some portion of the body surface and receives local phase-coding input onto its dendrites from spherical cell afferents. The sensitivity of the small cells to temporal disparities appears to be conferred by their segregation of inputs from two different parts of the body surface onto dendrites and soma, respectively. We propose that the dendritic input acts as a delay line, and the small cell fires maximally when the inputs from the dendrites and the giant cell input onto the soma coincide.
Intersegmental interneurons can control the gain of reflexes in adjacent segments of the locust by their action on nonspiking local interneurons
Authors: Laurent G , Burrows M
Published: April 2018

The gain of local reflexes of one leg of a locust can be altered by mechanosensory inputs generated by movements of or tactile inputs to an adjacent leg. Touching the mesothoracic tarsus, for example, increases the number of spikes that are produced by the metathoracic slow extensor tibiae motor neuron and enhances the depolarization of flexor tibiae motor neuron in response to imposed movements of the chordotonal organ in the ipsilateral hind femur. The sensory information from the middle leg is conveyed directly to nonspiking interneurons and motor neurons controlling the movements of the hindleg by a population of mesothoracic intersegmental interneurons (Laurent and Burrows, 1989). The metathoracic nonspiking interneurons receive direct inputs from receptors on a hindleg and are, therefore, a point of convergence for local and intersegmental inputs. We examine here the role of the connections between mesothoracic intersegmental interneurons and metathoracic nonspiking interneurons in controlling metathoracic local reflexes. The amplitude of synaptic potentials evoked in leg motor neurons by the stimulation of local afferents can be modulated by altering the membrane potential of an interposed nonspiking interneuron with current injected through an intracellular electrode. These imposed voltage changes mimic a mesothoracic input and show that the state of a nonspiking local interneuron is a determining factor in the expression of a local reflex. Inputs from mesothoracic intersegmental interneurons may cause large changes in the input conductance of nonspiking interneurons that can shunt a local afferent input. In some nonspiking interneurons, synaptic potentials caused by mesothoracic interneurons can be recorded, but no underlying conductance change can be detected at the recording site. Similarly, a particular nonspiking interneuron may receive synaptic inputs when two distinct regions of a middle leg are touched, but only one of these intersegmental inputs may be effective in reducing the amplitude of a synaptic potential caused by afferents from the hindleg. These results suggest that nonspiking local interneurons may be compartmentalized, with synaptic inputs and their associated conductance changes restricted to particular branches. In this way, an individual nonspiking neuron could contribute simultaneously to several local circuits. The inputs from different intersegmental interneurons could then modulate these pathways independently.
Synaptic plasticity and learning: selective impairment of learning rats and blockade of long-term potentiation in vivo by the N-methyl-D- aspartate receptor antagonist AP5
Authors: Morris RG
Published: April 2018

This paper reports a series of 5 experiments concerned with a possible role for N-methyl-D-aspartate (NMDA) receptors in certain types of learning. The results show that chronic intraventricular infusion of the NMDA receptor antagonist D,L-2-amino-5-phosphonopentanoic acid (D,L- AP5) caused an impairment of spatial but not of visual discrimination learning in rats. Such selectivity of the learning impairment occurred despite widespread distribution of the drug throughout the CNS. AP5 sometimes caused a disturbance of sensorimotor function during learning, but one experiment addressing whether this disturbance could be responsible for the spatial learning impairment established that it was statistically independent. Another experiment showed that AP5 did not affect the retention of previously acquired spatial information. These behavioral effects were all obtained with a concentration of AP5 that, in a final study, was found to be sufficient to block hippocampal long-term potentiation (LTP) in vivo without affecting normal synaptic transmission. Taken together, these observations (1) implicate NMDA receptors in certain types of learning, and (2) extend recent work showing that saturation of LTP causes an anterograde spatial amnesia (McNaughton et al., 1986). A preliminary report of parts of this work has been published (Morris et al., 1986a).
Operant conditioning of head-waving in Aplysia. I. Identified muscles involved in the operant response
Authors: Cook DG , Carew TJ
Published: April 2018

A basic goal in the neurosciences is to understand the cellular mechanisms underlying associative learning. The 2 major forms of associative learning are classical conditioning and operant conditioning. In recent years considerable progress has been made towards a cellular analysis of classical conditioning in a number of different preparations. In contrast, the cellular mechanisms underlying operant conditioning are poorly understood. Since the marine mollusc Aplysia has proved to be a powerful preparation for studying cellular and molecular mechanisms of a variety of forms of learning, including classical conditioning, we asked whether Aplysia might also be capable of exhibiting operant conditioning. In previous experiments we found that a naturally occurring behavior, the head-waving response of Aplysia, could be operantly conditioned (Cook and Carew, 1986). In the present paper we have carried out a quantitative analysis of the horizontal and vertical components of the head-waving response at the level of individual muscle groups. We have identified a discrete, bilateral band of neck muscles, the lateral columellar muscles (LCMs), whose electromyographic (EMG) activity is significantly correlated with the horizontal component of head-waving, the component modified by operant conditioning. Since head-waving is a complex behavioral response involving a variety of different muscle groups, using a restricted system such as the LCMs as an analog of the head-waving response will greatly facilitate a cellular analysis of operant conditioning in Aplysia.
Postsynaptic dorsal column pathway of the rat. III. Distribution of ascending afferent fibers
Authors: Cliffer KD , Giesler GJ
Published: April 2018

The distribution in the dorsal column nuclei (DCn) of post-synaptic dorsal column (PSDC) fibers was examined in rats following injections of Phaseolus vulgaris leucoagglutinin (PHA-L) in the spinal cord. Lemniscal neurons in the DCn were retrogradely labeled in the same animals by injecting the thalamus with Fluoro-Gold. In some experiments, primary afferent fibers were also labeled by injecting dorsal root ganglia with choleragenoid-conjugated HRP. Injections of PHA-L into the cervical enlargement labeled many fibers and varicosities throughout most of the ipsilateral cuneate nucleus. Labeled fibers were also present in the external cuneate and internal basilar nuclei. Injections of PHA-L into thoracic cord labeled fibers and varicosities in the medial cuneate and lateral gracile nuclei, as well as the external cuneate nucleus. Injections into the lumbar enlargement labeled fibers and varicosities throughout most of the gracile nucleus. Injections in sacral cord labeled fibers in the most medial part of the gracile nucleus. Dense labeling of PSDC fibers was found in areas with high densities of retrogradely labeled lemniscal neurons and areas with high densities of primary afferent fibers. In all regions of the DCn and in the external cuneate nucleus, fibers and varicosities labeled for PHA-L were seen in apposition to retrogradely labeled lemniscal cells. The distribution of postsynaptic afferent fibers in the DCn of the rat and its relationship to lemniscal neurons and primary afferent fibers contrast sharply with these features in cats.
Calcium current in cortical astrocytes: induction by cAMP and neurotransmitters and permissive effect of serum factors
Authors: Barres BA , Chun LL , Corey DP
Published: April 2018

Voltage-dependent L-type calcium channels were induced in highly purified, cultured, cortical astrocytes by exposure to substances known to increase their intracellular cAMP: 8-bromo-cAMP, forskolin, isoproterenol, and vasoactive intestinal peptide. In untreated control cultures, L-type calcium currents were entirely absent. The induction of this calcium current was specific to cortical astrocytes and a closely related astrocyte type in white matter and did not occur in meningeal cells or oligodendrocytes. The ability of forskolin to induce L-type calcium current in astrocytes depended on previous culture of these cells in a permissive lot of serum for at least 48 hr. In addition, certain lots of sera caused expression of a voltage-dependent T-type calcium channel in untreated control cultures. Several possible mechanisms of calcium channel induction by cAMP are consistent with our data: modification of a silent channel already present in the membrane, indirect effect of cytoskeletal alteration, or insertion of channels from submembrane stores. If the environment in vivo is permissive, regulation of glial ion channels may be under neuronal control.
Genesis and death of vocal control neurons during sexual differentiation in the zebra finch
Authors: Kirn JR , DeVoogd TJ
Published: April 2018

Several song-related regions in the adult zebra finch brain have substantially more neurons in males than in females. Such differences appear to arise from sex differences in circulating steroids during early posthatch life. In the present study, developmental mechanisms involved in the production of sex differences are explored by examinations of the normal time course of posthatch neurogenesis and cell death in vocal control circuits. As a first step toward determining whether rates of neuron production may be different in males and females, tritiated thymidine, a marker of cell division, was administered to zebra finches at various times during the first month after hatching. Birds were sacrificed at 60 d. The number of cells formed after hatching and present at 60 d was then evaluated in 3 vocal control regions--HVc (hyperstriatum ventralis pars caudalis) and its 2 principal targets, RA (robust nucleus of the archistriatum) and Area X. Cell death was quantified by counts of normal and pyknotic, degenerating cells made in these nuclei in additional, untreated birds of both sexes at 5 d intervals from 5 to 45 d of age. The combined results of these experiments suggest that differential cell death is a major factor in the development of sex differences in the song control system and provide the first direct evidence for sex differences in cell death in the developing telencephalon. Although developmental time tables differ among the 3 brain areas examined, at specific ages significantly higher numbers of pyknotic cells were observed in HVc, RA, and presumptive Area X in females compared to males. Peak levels of cell death in RA occur 4–6 weeks after hatching. This is about 3 weeks after the onset of sex differences in steroid levels that, in turn, lead to differential organization of song system nuclei. This pattern of results suggests that designation for death and actual cell loss are temporally dissociated in this system. Neuron proliferation for HVc and Area X, but not RA, continues throughout the first 30 d after hatching, and a significant sex difference was found in the number of cells present in HVc at 60 d that were formed after hatching. Comparisons of the timing of cell death and cell incorporation suggest that this difference may be best accounted for by differential survival of neurons formed after hatching rather than differential rates of neuron production. Neither differential neurogenesis nor differential neuron death can fully account for the apparent extreme sexual dimorphism in the number of neurons in Area X.(ABSTRACT TRUNCATED AT 400 WORDS)
Development of excitable membrane properties in mammalian sympathetic neurons
Authors: Nerbonne JM , Gurney AM
Published: April 2018

Using the whole-cell patch-clamp recording technique, resting membrane potentials (RPs), action potential (AP) waveforms, and the properties of voltage-activated inward Na+ (lNa) and Ca2+ (lCa) currents and outward K+ (lA,lK) currents were examined in embryonic and neonatal rat superior cervical ganglion (SCG) neurons as a function of time during development in vivo and in vitro. The passive and active membrane properties of neonatal SCG cells examined less than or equal to 24 hr after isolation were similar to those described previously for adult SCG neurons and for neonatal SCG cells maintained for several weeks in culture. Since recordings were obtained within hours of cell dissociations, it is assumed that the results reflect the membrane properties of neonatal SCG neurons in vivo at the time of isolation. When neonatal cells were examined as a function of time (up to approximately 2–3 weeks) in vitro, neither RPs nor AP waveforms varied measurably. Although absolute (inward and outward) current amplitudes increased in cells maintained in vitro, in parallel with increases in cell size, no changes in the time- or voltage-dependent properties of the currents were observed. Similar results were obtained for cells isolated on or after embryonic day 18.5 (greater than or equal to E 18.5). The membrane properties of E 14.5–16.5 SCG cells examined less than or equal to 24 hr after isolation, in contrast, were significantly different: mean lCa density was higher, and APs were broader than in greater than or equal to E 18.5 cells, and, in addition, lA was absent in these cells. When E 14.5–16.5 cells were examined after approximately 1 week in vitro, lCa densities and AP waveforms were indistinguishable from those in greater than or equal to E 18.5 SCG neurons, and lA was present. These studies reveal that rat SCG neurons are electrophysiologically mature early in development. Even lA, which seems to be the last voltage-gated current to develop, appears well before birth. As the appearance of lA correlates with decreased membrane excitability and AP shortening, it seems likely that the development of lA either reflects or regulates a marked change in the overall input and output properties of developing sympathetic neurons.
Identification of a cell-surface protein involved in PC12 cell- substratum adhesion and neurite outgrowth on laminin and collagen
Authors: Turner DC , Flier LA , Carbonetto S
Published: April 2018

On substrata coated with laminin or native collagen (Types I/III), PC12 cells employ an active adhesion mechanism (i.e., one inhibited at low temperature, by azide or in the absence of divalent cations) to attach and extend neurites; on substrata coated with wheat germ agglutinin (WGA) or polylysine, by contrast, PC12 cells attach via a passive mechanism and fail to extend neurites (Turner et al., 1987). This paper reports the isolation of 2 monoclonal antibodies (3A3 and 1B1) that promote retraction of neurites extended on laminin and collagen. In studies of initial cell attachment, 3A3 inhibited active attachment to laminin or collagen but not passive attachment to WGA or polylysine, whereas 1B1 inhibited both active and passive attachment. The more potent of the antibodies, 3A3, precipitates 2 radioactive protein bands (of approximately 185 and 125 kDa) from 1% Nonidet P-40 extracts of metabolically labeled PC12 cells. The properties of these proteins suggest that the antigen recognized by 3A3 is a member of the integrin family of matrix receptors. The other monoclonal antibody, 1B1, reacts with many PC12 proteins, including both bands precipitated by 3A3. The available data strongly suggest that an integrin with specificity for both laminin and collagen mediates PC12 adhesion to the substratum at both the cell body and the neurite growth cone.
The physiology of somatostatin in the rabbit retina
Authors: Zalutsky RA , Miller RF
Published: April 2018

The neuropeptide somatostatin (SS) has been localized to neurons of the rabbit retina by immunochemical and biochemical methods (Sagar et al., 1982, 1986; Marshak and Yamada 1984). We examined the effects of bath- applied SS on neurons of the rabbit retina, using intra- and extracellular electrophysiological techniques in an in vitro retina eyecup preparation. All commonly encountered ganglion cell receptive field types were affected by SS, and the effects were of 3 kinds: The first was a general excitation, occurring with a threshold concentration of about 100 nM; the onset of the excitation was too slow (seconds) for SS to participate in any rapid light-evoked responses. The second SS effect was an increase in the “signal-to-noise ratio,” defined here as the ratio of light-evoked to spontaneous spiking, which resulted from a decrease in spontaneous activity and, usually, a concomitant increase in light-evoked spiking. The third effect was a shift in center-surround balance towards a more dominant center. The signal-to-noise and center-surround effects were evident at concentrations as low as 0.5 nM; both were slow onset (tens of seconds) and long lasting (tens of minutes). SS acted at multiple levels within the retinal circuitry to produce the observed changes in ganglion cell output. These effects included direct actions on ganglion and amacrine cells, and a decrease in the efficiency with which horizontal cells could drive the retinal network. At least part of these SS actions on third-order neurons resulted from a decrease in conductance to ions with an equilibrium potential more positive than dark membrane potential. The degradation-resistant SS agonist SMS201–995 had effects qualitatively and quantitatively similar to those of SS, suggesting that SS may be degraded slowly enough to act at a distance from its sites of release. While no adequate SS antagonist is available, the greater sensitivity to exogenous SS, in retinas depleted of their SS content (with cysteamine), suggests a role for endogenous SS. The potency of SS also reinforces this view. The results of this study suggest that SS may be a neuromodulator in the rabbit retina, producing long-lasting changes in the “signal-to-noise” discharge pattern and center-surround balance of ganglion cells.
Adaptation and fatigue of a mechanosensory neuron in wild-type Drosophila and in memory mutants
Authors: Corfas G , Dudai Y
Published: April 2018

The mechanosensory neuron that innervates the anteronotopleural bristle of Drosophila melanogaster responds with a burst of action potentials to deflection of the bristle towards the body wall. The decay of the firing rate upon sustained deflection is typical of a slowly adapting mechanosensory neuron. Upon repeated monotonous stimulation, the response decreases and the kinetics of adaptation change; the response recovers after rest. This sensory fatigue depends on the duration of the stimuli and the rate of stimulation. Two mutants, rutabaga (rut) and dunce (dnc), which are defective in learning and in the activity of the cAMP cascade, show altered kinetics of sensory fatigue. In rut, which has a reduced cAMP synthesis, the mechanosensory neuron fatigues less rapidly, whereas in dnc, characterized by a reduced cAMP hydrolysis, the neuron fatigues more rapidly than in wild-type flies. The data suggest that the cAMP cascade plays a role in the mechanism of sensory fatigue. Our study shows, for the first time, the effect of memory mutations on functional properties of an identified neuron which subserves a modifiable behavior. The experimental system described here could also be useful for neurogenetic dissection of mechanosensory transduction.
Cell surface molecules containing N-acetylgalactosamine are associated with basket cells and neurogliaform cells in cat visual cortex
Authors: Naegele JR , Katz LC
Published: April 2018

In the cerebral cortex, the plant lectin Vicia villosa (VVA) selectively stains the surfaces of nonpyramidal neurons. This lectin binds specifically to alpha- and beta-linked N-acetylgalactosamine (GalNac). VVA-reactive carbohydrate is highly concentrated in layer 4 of the primary visual cortex of the cat, where it is associated exclusively with GABAergic local circuit neurons. We have studied this neuronal subset with intracellular electrophysiological recording and dye marking to identify the particular cell types expressing surface GalNac. Five different types of local circuit neurons were stained intracellularly (N = 45), but only 2 types, the columnar basket and large neurogliaform cells, were also labeled by the lectin (N = 19/45). Lectin negative types included small basket, chandelier, and large bitufted cells (26/45). Spiny stellate and pyramidal neurons were also lectin negative. Electrophysiological recordings revealed differences in the duration of action potentials in smooth versus spiny stellates but no differences between lectin-positive or -negative types. A biochemical analysis of cortical glycoproteins by SDS-PAGE and lectin blotting revealed multiple bands containing GalNac enriched in membrane fractions. These carbohydrate-containing molecules may be part of a biochemical mechanism for linking together cells with common functional properties.