bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microelectrode procedures for the determination of silicate and phosphate in waters – fundamental studies
Authors: Carpenter Neil G. , Hodgson Alexia W. E. , Pletcher Derek 
Published: May 2005

AbstractThe voltammetry of the molybdosilicate and molybdophosphate complexes, formed by the addition of hexafluorosilicate and phosphate to anacidic sodium molybdate solution, have been defined at gold microdisk electrodes. It is shown that the reaction conditions influence both the kinetics of formation of the complexes and their voltammetry. It is possible to find conditions where the steady state amperometric response of the Au microdisk electrodes allows a rapid and convenient method for the determination of silicate and phosphate at concentrations in the range 1–1000 μM.
Microdialysis‐bioreactor for on‐line monitoring of glucose in food samples
Authors: Mannino Saverio , Brenna O. , Buratti S. , Cosio M. S. 
Published: May 2005

AbstractA new microsystem, integrating microdialysis sampling and glucose oxidase immobilized on a tungsten wire inserted into the lumen of the microdialysis probe, has been developed. The microsystem, coupled with amperometric detection, has proved to be viable for glucose determination in food samples. The immobilization procedure, based on the formation of an insoluble net formed by the enzyme with a polyanhydride (in the presence of polyethyleneimine), yielded a very stable enzyme layer that maintained about 75% of its initial activity after one month of daily use. Complex sample matrices (milk, juices) were successfully analyzed with little or no sample pretreatment using the fully automated flow system.
Electrocatalysis of ascorbic acid on the glassy carbon electrode chemically modified with polyaniline films
Authors: Casella Innocenzo G. , Guascito Maria R. 
Published: May 2005

AbstractChemically modified electrodes prepared by electropolymerization of aniline on glassy carbon electrodes, exhibited good electrocatalytic properties towards ascorbic acid oxidation. The electrocatalytic response was evaluated by cyclic voltammetry with regard to pH, film thickness, ascorbic acid concentration, scan rate, electrolyte composition, rotation speeds of the electrode, and other variables. The location of the reactions taking place was discussed with experimental evidence that the cross‐exchange reaction is the rate‐determining step. Experiments in flowing streams were performed to characterize the electrode as an amperometric sensor for the determination of ascorbic acid. The electrode stability, precision, limit of detection and linear range were evaluated at a constant potential of 0.350 V (vs. Ag/AgCl). The limit of detection was 1.0 μM (i.e., 1.76 ng injected), and the calibration plot was linear in the range 1.0 μM–0.7 mM (correlation coefficient 0.999). The resulting modified electrode was found to retain 80% of its initial response in flowing streams for 8 h of operating time.
Activated pulsed amperometric detection of cysteine at platinum electrodes in acidic media
Authors: Johll Matthew E. , Williams Douglas G. , Johnson Dennis C. 
Published: May 2005

AbstractAnodic voltammetric detection of sulfhydryl compounds, represented here by cysteine, at Pt electrodes in acidic media occurs concomitantly with anodic generation of surface oxide. It is speculated that the adsorbed hydroxyl species (PtOH), proposed to be the intermediate product in formation of the inert oxide (PtO), is the source of O‐atoms transferred to the sulfonic acid produced by oxidation of the sulfhydryl moiety. However, as a consequence of this electrocatalytic response mechanism, application of the traditional three‐step waveform for pulsed amperometric detection (PAD) of sulfhydryl compounds is accompanied by a large background signal resulting from PtO formation. To diminish the background signal, the traditional three‐step PAD waveform has been modified by insertion of a brief (100 ms) anodization step prior to the detection step to activate the Ptsurface by the generation of PtOH with minimal conversion to PtO. The subsequent negative step from the activation potential (Eact) to the detection detection potential (Edet < Eact) permits the PtOH to be harvested within the detection mechanism without significant background signal.
Voltammetric determination of hydrazine based on catalytic reaction in the presence of 4‐hydroxy‐2,2,6,6‐tetramethyl‐piperdinyloxy (TEMPOL) radical
Authors: Xia He , Li Hulin , Yang Dequan 
Published: May 2005

AbstractA rapid, simple and highly sensitive voltammetric method was developed for the determination of hydrazine based on the electrochemical oxidation of hydrazine catalyzed by TEMPOL at a glassy carbon electrode at neutral medium. A linear calibration plot was obtained over the range of 1 × 10−6 M‐5 × 10−4 M. The detection limit was 1 × 10−6 M. The method was applied successfully to the determination of hydrazine in waste and river water.
The electrophysiology of the olfactory–hippocampal circuit in the isolated and perfused adult mammalian brain in vitro
Authors: de Curtis Marco , Paré Denis , Lliás Rodolfo R. 
Published: May 2005

AbstractThe viability and general electrophysiological properties of the limbic system in the adult mammalian brain isolated and maintained in vitro by arterial perfusion are described. The isolated brain preparation combines the advantages of intact synaptic connectivity and accessibility of different areas of the encephalic mass with those of the in vitro approach, i.e., stability and control of the ionic environment. Extracellular field potential as well as intracellular recordings were performed at different levels in the limbic system of isolated adult guinea pig brains. The results demonstrate that in the piriform, entorhinal, and hippocampal cortices, the intrinsic electrical properties of individual cells as well as the spontaneous and evoked electrical activity in the neuronal ensembles they comprise, were virtually identical to those observed in vivo. The properties of the limbic system loop were determined.
Electrophysiological characterization of associational pathway terminating on dentate gyrus granule cells in the rat
Authors: Bekenstein Jonathan W. , Lothman Eric W. 
Published: May 2005

AbstractThe functional topography and parameters of excitation and inhibition were determined in the in situ associational pathway of the rat dentate gyrus. The functional topography was found to be consistent with previous anatomical studies. The greatest amplitude population spikes and the strongest paired‐pulse inhibition were generated with the stimulating electrode placed in the hilus at least 1.5 mm caudal to the ipsilateral dentate gyrus recording electrode. With this standard electrode configuration, neither long‐term potentiation of the population spike nor of the population excitatory postsynaptic potential occurred. Hilar associational pathway activation of dentate gyrus granule cells elicited paired‐pulse responses similar to those produced in granule cells by perforant path stimulation. Thus, the associational pathway provides another way to assess dentate granule cell function electrophysiologically.
Organization of CA1 projections to the subiculum: A PHA‐L analysis in the rat
Authors: Amaral David G. , Dolorfo Cynthia , Alvarez‐Royo Pablo 
Published: May 2005

AbstractThe organization of CA1 projections to the rat subiculum was investigated with the anterograde tracer, Phaseolus vulgaris leucoagglutinin (PHA‐L). Discrete iontophoretic injections of PHA‐L were placed into various transverse positions of the CA1 field at different septotemporal levels of the hippocampus. The distribution of CA1 projections was observed in dissected and extended hippocampal preparations. CA1 cells located proximally in the field, i.e., close to the CA2 field, gave rise to projections that terminated in the distal third of the subiculum, i.e., close to the presubiculum. CA1 cells located distally in the field, i.e., close to the subiculum, gave rise to projections that terminated proximally in the subiculum, i.e., just across the CA1/subiculum border. CA1 cells in the middle of the field projected to a midtransverse portion of the subiculum. The same general pattern of projections was observed at all septotemporal levels of the hippocampus. Varicose fibers from the CA1 neurons terminated among the basal dendrites of the subicular pyramidal cells, within the pyramidal cell layer, and in the deep portion of the molecular layer. In addition to the CA1 to subiculum projections, the discrete PHA‐L injections provided the opportunity of examining the extent of local and associational connections within CA1. In general, associational connections in CA1 are far less extensive than in CA3. CA1 is not entirely without local connections, however. CA1 cells located close to the subicular border, for example, originated axons that first innervated the proximal subiculum and then reentered the CA1 field at the interface between stratum radiatum and stratum lacunosum‐moleculare. In most of the experimental cases, there were collaterals located in stratum oriens of CA1 that branched from the fibers directed toward the subiculum. Thus, the basal dendrites of CA1 cells may receive associational inputs. The organization of the CA1 projections to the subiculum is discussed in relation to the organization of CA3 projections to CA1 and the differential output of transverse regions of the subiculum. The possibility is raised that information may be “channeled” through the hippocampal formation via the transverse organization of these connections and ultimately distributed to different recipients of hippocampal efferent projections.
Connections between the retrosplenial cortex and the hippocampal formation in the rat: A review
Authors: Wyass J. Michael , Van Groen Thomas 
Published: May 2005

AbstractThe retrosplenial cortex is situated at the crossroads between the hippocampal formation and many areas of the neocortex, but few studies have examined the connections between the hippocampal formation and the retrosplenial cortex in detail. Each subdivision of the retrosplenial cortex projects to a discrete terminal field in the hippocampal formation. The retrosplenial dysgranular cortex (Rdg) projects to the postsubiculum, caudal parts of parasubiculum, caudal and lateral parts of the entorhinal cortex, and the perirhinal cortex. The retrosplenial granular b cortex (Rgb) projects only to the postsubiculum, but the retrosplenial granular a cortex (Rga) projects to the postsubiculum, rostral presubiculum, parasubiculum, and caudal medial entorhinal cortex. Reciprocating projections from the hippocampal formation to Rdg originate in septal parts of CA1, postsubiculum, and caudal parts of the entorhinal cortex, but these are only sparse projections. In contrast, Rgb and Rga receive dense projections from the hippocampal formation. The hippocampal projection to Rgb originates in area CA1, dorsal (septal) subiculum, and postsubiculum. Conversely, Rga is innervated by ventral (temporal) subiculum and postsubiculum. Further, the connections between the retrosplenial cortex and the hippocampal formation are topographically organized. Rostral retrosplenial cortex is connected primarily to the septal (rostrodorsal) hippocampal formation, while caudal parts of the retrosplenial cortex are connected with temporal (caudoventral) areas of the hippocampal formation. Together, the elaborate connections between the retrosplenial cortex and the hippocampal formation suggest that this projection provides an important pathway by which the hippocampus affects learning, memory, and emotional behavior.
Evidence for commissurally projecting parvalbumin‐immunoreactive basket cells in the dentate gyrus of the rat
Authors: Goodman Jeffrey H. , Sloviter Robert S. 
Published: May 2005

AbstractThe fluorescent retrograde tracer, fluorogold, was used to identify commissurally projecting neurons in the hippocampus and dentate gyrus. After injection of fluorogold into the hippocampus, the contralateral hippocampus was evaluated for fluorogold‐immunoreactive or fluorescent neurons. In addition to observing labeled hilar neurons and CA3 pyramidal cells that previously have been reported to send commissurally projecting axons to the contralateral hippocampus, the authors unexpectedly found a population of fluorogold‐labeled cells in the granule cell layer with the morphology and location of GABA‐immunoreactive basket cells. Immunocytochemical staining revealed that all fluorogold‐labeled cells of the granule cell layer were immunoreactive for parvalbumin. However, not all parvalbumin cells, shown previously to be a subset of GABA neurons, were fluorogold‐labeled. The association between fluorogold transport and parvalbumin immunoreactivity was unique for these cells of the granule cell layer. In the adjacent hilus, relatively few of the many fluorogold‐labeled cells were parvalbumin‐ or GABA‐immunoreactive. These results (1) identify a population of presumed inhibitory neurons that apparently form commissural projections; (2) document that all of these cells contain the calcium‐binding protein parvalbumin; and (3) indicate that the vast majority of commissurally projecting hilar neurons are neither parvalbumin‐ nor GABA‐immunoreactive.
Evidence for NMDA receptor involvement in environmentally induced dentate gyrus plasticity
Authors: Croll Susan D. , Sharp Patricia E. , Bostock Elizabeth 
Published: May 2005

AbstractResearch has demonstrated environmentally induced plasticity of hippocampal dentate gyrusevoked potentials. Other research has shown a role of the NMDA receptor in dentate gyrus long‐term potentiation (LTP). The authors tested the role of the NMDA receptor in one form of environmentally induced plasticity, in which transferring animals from their home cages to another environment results in significant excitatory postsynaptic potential (EPSP) enhancement and concomitant depression of the population spike. Rats were chronically implanted with stimulating electrodes in the perforant path and recording electrodes in the dentate gyrus bilaterally. Evoked potentials were recorded from freely behaving rats for four 20‐minute sessions (1/wk), which took place immediately following an environmental transfer. Rats received 0.00, 0.05, 0.08, or 0.10 mg/kg MK‐801 s. c. 30 minutes prior to recording sessions in either an ascending‐ or descending‐dose series. Results showed that MK‐801 produced a reduction of the EPSP enhancement, which takes place over the 20‐minute session. The effects of MK‐801 on spike depression varied as a function of dose series and time within a session, suggesting a long‐term effect of MK‐801 on spike depression. There was no detected effect of MK‐801 on behavior. Results suggest a role of the NMDA receptor in this form of environmentally induced plasticity with different effects of NMDA receptor antagonism on EPSP enhancement and spike depression.
Effects of chronic alcohol consumption and withdrawal on the somatostatin‐immunoreactive neurons of the rat hippocampal dentate hilus
Authors: Andrade José P. , Fernando Paulo M. , Madeira Maria D. , Paula‐Barbosa Manuel M. , Cadete‐Leite António , Zimmer Jens 
Published: May 2005

AbstractPrevious studies have demonstrated that the dentate granule and the CA3 pyramidal cells of the rat hippocampal formation are neuronal populations vulnerable to the toxic effects of ethanol. It also has been shown that the resulting alterations do not end after withdrawal from ethanol. As the neurons in the dentate hilus are heavily interconnected with the dentate granule cells, the authors decided to examine the fate of the hilar neurons after chronic alcohol consumption and withdrawal, inasmuch as the hilar somatostatin‐immunoreactive (SS‐I) neurons were found to be sensitive to cerebral ischemia and to seizures.The following groups of adult rats were studied: (1) alcohol‐fed for 6 and 12 months; (2) alcoholfed for 6 months and then switched to water for a further 6 months; (3) pair‐fed controls; and (4) controls fed ad libitum. The authors determined the numerical density of hilar neurons and the number of its SS‐I subpopulation. These were found to be significantly reduced in both the alcohol‐fed and withdrawal groups when compared with the respective age‐matched controls. The consequent loss of the integrative action of the hilar neurons, including the SS‐Is, could explain some of the alcohol‐related functional deficits as well as their persistence after withdrawal.
Time course and distribution of neuronal degeneration in the dentate gyrus of rat after adrenalectomy: A silver impregnation study
Authors: Jaarsma Dick , Postema Folkert , Korf Jakob 
Published: May 2005

AbstractRecently, Sloviter et al. reported that adrenalectomy (ADX) of young adult rats after 3 months led to a selective loss of granule neurons in the dentate gyrus (DG) and that this loss could be prevented by low doses of corticosterone. In the present study, the ADX‐induced neuronal degeneration was investigated in Wistar rats, using a silver impregnation method for degenerating neurons. To examine the time course and distribution of the ADX‐induced degeneration, young adult male rats were allowed to survive 2, 3, and 5 days and 1, 2, and 3 weeks after ADX. Argyrophilic neurons were present in the dentate granule cell layer on the second day following ADX. Three days after ADX, the number of argyrophilic granule neurons was much more abundant, and it increased gradually with longer post‐ADX survival times. Argyrophilia was specifically confined to dentate granule cells and was accompanied by the occurrence of pyknotic nuclei as observed in adjacent cresyl violet‐stained section. There were significant differences between individual rats in quantity of argyrophilia. About one fifth of the ADX rats showed sporadic or no argyrophilia, in spite of plasma corticosterone levels below the detection limit (10 ng/mL). Sham‐operated rats and ADX rats receiving corticosterone (10 mg/L) or dexamethasone (15 mg/L) in their drinking water did not display any argyrophilic neurons in the dentate gyrus. The distribution of the argyrophilia within the DG was highly characteristic with the highest number of degenerating cells in the hidden blade of the middle and the temporal thirds of the DG. There was a strong crest‐to‐tip and deep (hilar)‐to‐superficial increase in density of degenerating neurons. Along the entire septotemporal axis of the free blade and at the septal pole of the hidden blade, the number of argyrophilic cells was low. Wistar rats of different sex and aged 1–6 months all showed dentate granule cell degeneration 1 week following ADX. The distribution of the degeneration was identical to that of the young adult male group.In order to examine whether the absence of corticosteroids affects dentate granule cells directly or through other mechanisms induced by ADX, low doses of dexamethasone were infused with a microdialysis probe directly into the hippocampus on one side of ADX rats. As a result, the ADX‐induced neuronal degeneration was selectively prevented at the treated side.
Navigation by fragment fitting: A theory of hippocampal function
Authors: Worden Robert 
Published: May 2005

AbstractThis paper describes a computational theory of spatial learning and navigation and its possible realization in the hippocampus. In the theory, mammals store memories of their geographical environment as a large number of independentfragments. A typical fragment denotes a few prominent landmarks in some region, their geometric relations, and their nongemetric properties, such as smells and visual cues. Navigation involves piecing together current sense data and relevant fragments to form a local map of the animal's surroundings; this is like solving a jigsaw puzzle. This computational model has been implemented in a computer program, whose performance is broadly consistent with observed levels of animal performance, and laboratory results, in spatial learning.Possible realizations of the model in animal brains are discussed. Unlike some neural net models of spatial learning, the model is strongly geometric, and uses special neural structures to store and manipulate two‐dimensional vectors and bearings. A possible neural architecture is described in which the hippocampus performs the geometric operatios; this has a long‐term memory for fragments (somewhere in the neocortex), which can associatively recall fragments into a number of parallelfragment fitters, in the dentate gyrus and CA3 regions. These vary the positions and orientations of their fragments, to optimize the fit of the fragments to each other and to the animal's recent sense data. A local map of the animal's surroundings is stored in CA1 and subicular regions, where matching of fragment positions and attributes takes place. Mismatches are passed back via the entorhinal cortex to improve the fit during the next hippocampal theta cycle.The model offers the potential for understading current data on spatial learning, on the neuroanatomy of the hippocampus and on place cells in a coherent framework, as well as understanding the role of the hippocampus in nonpositional memory tasks. Comparisons with experimental data are given.
Computational constraints suggest the need for two distinct input systems to the hippocampal CA3 network
Authors: Treves Alessandro , Rolls Edmund T. 
Published: May 2005

AbstractThe CA3 network in the hippocampus may operate as an autoassociator, in which declarative memories, known to be dependent on hippocampal processing, could be stored, and subsequently retrieved, using modifiable synaptic efficacies in the CA3 recurrent collateral system. On the basis of this hypothesis, the authors explore the computational relevance of the extrinsic afferents to the CA3 network. A quantitative statistical analysis of the information that may be relayed by such afferent connections reveals the need for two distinct systems of input synapses. The synapses of the first system need to be strong(but not associatively modifiable) in order to force, during learning, the CA3 cells into a pattern of activity relatively independent of any inputs being received from the recurrent collaterals, and which thus reflects sizable amounts of new information. It is proposed that the mossy fiber system performs this function. A second system, with a large number of associatively modifiable synapses on each receiving cell, is needed in order to relay a signal specific enough to initiate the retrieval process. This may be identified, we propose, with the perforant path input to CA3.