bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simultaneous assessment of left‐ventricular infarction size, function and tissue viability in a murine model of myocardial infarction by cardiac manganese‐enhanced magnetic resonance imaging (MEMRI)
Authors: Hu Tom C.‐C. , Bao Weike , Lenhard Stephen C. , Schaeffer Thomas R. , Yue Tian‐li , Willette Robert N. , Jucker Beat M. 
Published: January 2005

AbstractOwing to its signal‐enhancing characteristics in viable well‐perfused tissue, divalent manganese (Mn2+) has been used as a myocardial imaging contrast agent. Because Mn2+ can enter excitable cells through the voltage‐gated L‐type calcium channels, manganese‐enhanced MRI (MEMRI) has been used to determine the viability and the inotropic state of the heart. In this study, we examined the correlation between left ventricular infarction zone as assessed by cardiac MEMRI and function in mice with permanent coronary artery occlusion. At an Mn2+ infusion dose of 1.72±0.47 nmol/min/g body weight, the steady‐state signal intensity (SI) enhancement 20–26 min post‐Mn2+ infusion of the normal septum and left‐ventricular wall during diastole was 128.2±14.4 and 127.9±26.5%, respectively, whereas the infarction zone was 56.0±7.1%. During systole, the SI enhancement was 144.6±33.0, 116.0±18.7 and 48.3±20.0% for the normal septum, left‐ventricular wall and infarction zone, respectively. A good correlation was obtained between the MEMRI determined infarction volume and conventional histological TTC staining (r = 0.9582, p<0.01). There was also a strong negative correlation between MEMRI determined infarction percentage (compared with whole left ventricle) and ejection fraction (r = −0.94, p<0.05). These data suggest that the Mn2+ concentration at steady state in the heart may reflect altered tissue viability in the infarcted tissue as well as surrounding region following myocardial infarction. In conclusion, in vivo cardiac MEMRI offers a manner in which functional, pathologic and viability data may be obtained simultaneously in myocardial tissue. Copyright © 2004 John Wiley & Sons, Ltd.
Manganese‐enhanced magnetic resonance imaging (MEMRI) of brain activity and applications to early detection of brain ischemia
Authors: Aoki Ichio , Naruse Shoji , Tanaka Chuzo 
Published: January 2005

AbstractDivalent manganese ion (Mn2+) has been reported to be a useful contrast agent for functional MRI, through a technique named activity‐induced manganese‐dependent MRI (AIM). In AIM, signal enhancement is related to functional increases in calcium influx, and therefore AIM is, thus far, the only MRI method able to map brain activation in vivo independently of the surrogate hemodynamic changes used in functional MRI. Because of its high signal‐to‐noise ratio (SNR) and high sensitivity, AIM allows the use of multi‐slice or three‐dimensional MRI techniques to map functional activity at high spatial resolution. In the present review, we define AIM as a functional MRI tool based on the administration of divalent ionized manganese through an open or disrupted blood–brain barrier (BBB). The adequacy and efficacy of AIM in detecting neural activation is described in light of supporting experiments on inhibition of calcium channels, FOS expression, and on direct comparison to BOLD‐ and perfusion‐based functional MRI. Two main applications of AIM, mapping brain activation in rat somatosensory cortex, as well stroke research based on the well‐established middle cerebral artery occlusion model, are described in detail. Methodological problems associated with a strong dependence on anesthetic conditions, potential corruption due to disruption of the BBB, and unspecific increase of the baseline signal due to acoustical noise are discussed. Finally, recommended preparation methods and experimental protocols for AIM are introduced. Copyright © 2004 John Wiley & Sons, Ltd.
Manganese‐enhanced magnetic resonance imaging (MEMRI): methodological and practical considerations
Authors: Silva Afonso C. , Lee Jung Hee , Aoki Ichio , Koretsky Alan P. 
Published: January 2005

AbstractManganese‐enhanced MRI (MEMRI) is being increasingly used for MRI in animals due to the unique T1 contrast that is sensitive to a number of biological processes. Three specific uses of MEMRI have been demonstrated: to visualize activity in the brain and the heart; to trace neuronal specific connections in the brain; and to enhance the brain cytoarchitecture after a systemic dose. Based on an ever‐growing number of applications, MEMRI is proving useful as a new molecular imaging method to visualize functional neural circuits and anatomy as well as function in the brain in vivo. Paramount to the successful application of MEMRI is the ability to deliver Mn2+ to the site of interest at an appropriate dose and in a time‐efficient manner. A major drawback to the use of Mn2+ as a contrast agent is its cellular toxicity. Therefore, it is critical to use as low a dose as possible. In the present work the different approaches to MEMRI are reviewed from a practical standpoint. Emphasis is given to the experimental methodology of how to achieve significant, yet safe, amounts of Mn2+ to the target areas of interest. Copyright © 2004 John Wiley & Sons, Ltd.
The effect of motor activity on the reactivity of single visual units in the crayfish
Authors: Aréchiga Hugo , Wiersma C. A. G. 
Published: January 2005

AbstractMetal microelectrodes were chronically implanted in the optic nerve and circumesophageal commissure of the crayfish. The activity from single units was recorded in freely moving animals, and responsiveness to visual stimuli was found correlated with motor activity of the animal. The lowest firing rate corresponded to states of quietness and the highest to fighting reactions. The two types of visual units studied showed a different degree of modulation. The sustaining fibers, which signal the intensity of illumination, were facilitated at all levels of motor excitation. The movement fibers, which are phasic units, reacted to great enhancements of motor activity by an increased number of spikes in each response to movement, and by a lowering in the rate of “habituation.” This facilitatory influence is neural in origin, presumably conveyed by the “activity” fibers, which run efferently in the optic nerve, carrying information about movement of the various body parts.
Retrograde amnesia: Time dependent effects of rhinencephalic lesions
Authors: Hudspeth William J. , Wilsoncroft William E. 
Published: January 2005

AbstractRetrograde amnesia (RA) produced by post‐trial lesions of mouse anterior limbic field was found to be inversely related to trial‐lesion intervals. Control experiments demonstrated that the RA was not due to response bias, seizures, spreading depression, or generalized electrical stimulation. Damage of the motor cortex failed to produce RA. The results support the contention that small lesions of the anterior limbic field selectively interfere with memory storage processes without disrupting retieval of memory.
Studies on the mechanism of axoplasmic transport in the crayfish cord
Authors: Fernandez H. L. , Huneeus F. C. , Davison P. F. 
Published: January 2005

AbstractFollowing the injection of 3H‐leucine into a crayfish ganglion, tritiumlabeled proteins were detected remaining in the ganglion and moving at a slow linear rate caudad along the nerve cord. The rate of movement increased linearly with temperature between 5 and 20°C, but ceased at 3° C. The movement was also blocked for a distance around a colchicine‐injected ganglion. Both of these observations would be compatible with the involvement of microtubules in slow axoplasmic transport. However, in both instances normal‐appearing microtubules were observed by electron microscopy. Gel electropherograms of the denatured labeled proteins showed that the transported proteins are complex and may correspond to most of the axoplasmic proteins including the microtubules.
Influence of ionic environment on the relationship between pre‐ and postsynaptic potentials
Authors: Kusano Kiyoshi 
Published: January 2005

AbstractThe effects of various ions on the relationship between pre‐ and postsynaptic potentials were studied using untreated squid giant synapses, or those injected presynaptically with tetraethylammonium ions (TEA) in the presence of 10−6 g/ml tetrodotoxin (TTX). The synaptic transfer function was, in general, augmented by increasing [Ca2+]0 or by reducing [Mg2+]0. Opposite results were found by lowering either [Na+]0 or [Ca2+]0, or by increasing [K+]0 or [Mg2+]0. When [Ca2+]0 was removed, presynaptically applied depolarizations failed to produce both “On‐” and “Off‐PSP's.” Electrophoretically injected Ca2+ into the presynaptic terminal reduced synaptic transmission.The minimal level of presynaptic membrane potential produced by an applied outward current pulse, which suppressed On‐PSP completely, averaged 106 mV inside positive (ranging between 52–205 mV from 12 preparations). The potential level was shifted more negatively on lowering [Ca2+]0 and more positively in high [Ca2+]0‐media. However, altering the [Na+]0 did not change the suppression level appreciably. Under these ionic circumstances the maximum amplitude of On‐PSP, as well as Off‐PSP, was markedly changed, but the level of the presynaptic depolarization required to evoke a maximum On‐PSP appeared to be unchanged, and the average value was 50 mV from the resting membrane potential level. Although the data are only qualitative, they appear to support the “Ca hypothesis” for the transmitter release and its shut‐off mechanism. Replacement of 423 mM Cl− by Br− or with isethionate did not affect synaptic transmission.
Stimulus generalization in the tactile system of octopus
Authors: Wells M. J. , Young J. Z. 
Published: January 2005

AbstractAfter training octopuses to discriminate between spheres with markedly different numbers of grooves, unrewarded transfer tests with spheres other than those used in training showed a greater number of takes of the previously positive sphere than any other, the previously negative sphere being taken least. However, when the spheres used for training were nearly similar the maximum tendency to take in transfer tests was displaced from the sphere used in positive training in a direction away from the negative one. Conversely, the minimum showed a post‐discrimination gradient in a direction away from the positive. These gradients must be due either to some form of interaction between systems that classify for different degrees of roughness or to the fact that the systems are imperfectly tuned so that each is influenced by a range of frequencies. In either case it is likely that the center contains a linear array of units responding to specific patterns of nerve impulses. This center must lie in the posterior buccal lobe and may be subdivided into eight subsets for the individual arms.The transfer tests showed that octopuses can detect fine differences in numbers of grooves. A sphere of 3 cm diameter with 6 grooves (10% of surface cut away) was treated differently from one with 7 grooves (11.3% cut away).After removal of the vertical lobes learning was slowed, but the transfer gradients were similar to those in normal animals. This confirms that although these lobes assist in the setting up of representations elsewhere in the brain they do not themselves contain the cells responsible for classifying the stimulus.
Facilitation of cortical cell activity during spreading depression
Authors: Muñoz‐Martínez Emilio J. 
Published: January 2005

AbstractThe steady potential changes which develops together with spreading depression of the cat sensoriomotor cortex were recorded at several cortical depths and related with concomitant modifications in cell firing rates.In most cases, it was found that the slow negative wave which spreads on the cortical surface does not invade the deep cortical layers. In these cases only a slow positive wave was recorded at the deep layers.At each layer the cell firing rates modification of PT and non‐identified neurons consisted of an initial acceleration followed by a depression. The deeper the recorded cells, the more prolonged the acceleration and shorter lasting the depression. At layers invaded by the slow negative wave, acceleration occurred during a part or all the temporal course of such wave. At layers not invaded by the slow negative wave, acceleration occurred coinciding with the slow positive wave.Acceleration of cell firing is believed to result from an adequate “local” active or “remote” passive depolarization of the cortical cells. Depression could result from excessive depolarization of the cortical cells. Depression could result from excessive depolarization of cortical neurons and presynaptic fibers.
Isolated dorsal root ganglion neurons in culture: Cytological maturation and extension of electrically active processes
Authors: Okun Lawrence M. 
Published: January 2005

AbstractDissociated chick embryo dorsal root ganglion cells were maintained in vitro for long periods (up to 7 weeks) in cultures essentially free of nonneuronal cells. The cultured neurons attained an advanced stage of cytological maturity and extended long, highly branched processes which formed elaborate networks. Electrical activity was evoked and recorded extracellularly from these processes. Responses obtained from the processes of young (19–20 hr), fully isolated cells indicate that the ability to propagate action potentials is present very early in newly extended fibers and can be developed by neurons deprived of contact with any other cells. Complex responses evoked by single stimulus pulses suggest that many processes, especially in older cultures, contained more than a single active fiber.
Aromatic acid decarboxylase and choline acetylase activities in a single identified 5‐HT containing cell of the leech
Authors: Coggeshall Richard E. , Dewhurst Susan A. , Weinreich Daniel , McCaman Richard E. 
Published: January 2005

AbstractThe two largest cells (Retzius cells) in a typical ganglion of the leech nervous system have been shown previously to contain a high concentration of 5‐hydroxytryptamine (5‐HT). The present study demonstrates that the isolated Retzius cell somata contain approximately 40% of the total aromatic acid decarboxylase activity of a single ganglion. A single Retzius cell has approximately 70 times more enzyme activity than adjacent “control” cells. Since this enzyme activity subserves the synthesis of 5‐HT, a metabolic basis is provided for the cell‐specific accumulation of the amine in the Retzius cells. Further indication of the specificity of the above metabolic relationship was obtained from the study of the distribution of choline acetylase, the enzyme responsible for the synthesis of acetylcholine. The specific activity (enzyme activity per unit of protein) of the acetylase in the “control” cells is nearly 8 times greater than that in the Retzius cell.
Neural mechanisms underlying behavior in the locust Schistocerca gregaria I. Physiology of identified motorneurons in the metathoracic ganglion
Authors: Hoyle Graham , Burrows Malcolm 
Published: January 2005

AbstractA preparation of the desert locust, Schistocera gregaria, has been developed, in which it was possible to work with identified neurons while still allowing some behavior. A total of 26 motorneurons to the hind leg were studied singly, and in various pairs, both by direct stimulation, and by recording during spontaneous activity and various reflex actions. Motorneurons were identified by passing current into their somata and correlating the evoked somata spikes with extracellularly or intracellularly recorded events in the muscles. Tension of the muscle was also recorded and motor axons were stimulated to evoke antidromic spikes in the somata. Both epsp's and ipsp's can be seen clearly in recordings from the somata; spikes appear as electrotonically conducted remnants only. Somata exhibited little or no electrogenesis. It is inferred that impulses are initiated in a zone tentatively identified with the region of emergence of the motor axon from the neuropil. Integration occurs in the neuropilar segment, with the soma serving as a parallel RC element. Data was obtained on the central mechanisms of coordination of synergistic and antagonistic motorneurons and on the modes of excitation of slow and fast neurons to the same muscles.
Mechanisms involved in spreading depression
Authors: Van Harreveld A. , Fifková Eva 
Published: January 2005

AbstractApplication of unlabelled glutamate to the isolated chicken retina caused an increase in the tissue transparency and a release of labelled glutamate with which the retina had previously been charged. The threshold for both responses was about 0.2 mM. Stimulation with KCI and direct current elicited transparency changes at a threshold of 8 mM and 4–6 V, respectively, and a release of the label at higher KCl concentrations (75 mM) and potentials (15 V). The transparency change caused by glutamate stimulation was severely depressed by MgC12 (10–15 mM) in contrast to the changes elicited by KC1 and direct current which were little affected by Mg ions. It was postulated that glutamate causes transparency changes by acting on neuronal elements. KC1 would act on glia and would only in high concentrations affect neurons. It was furthermore suggested that the propagation of spreading depression is dependent both on the release of glutamate from the intracellular compartment and on the depolarization of neuronal elements resulting from this release.
Some physiological and biochemical features of striated muscles reinnervated by preganglionic sympathetic fibers
Authors: Ramirez Beatriz , Luco J. V. 
Published: January 2005

AbstractSkeletal muscle fibers can be reinnervated by motor cholinergic fibers, that is, functional connection can be achieved. However, functional connection implies not only the capacity of the nerve impulse to elicit a contractile response but also the capability of the reinnervating neurons to evoke particular modifications of the physiological and biological features of the muscles.In order to search for some of the modifications due to reinnervation by preganglionic sympathetic fibers, muscle contraction time was studied in three different preparations of adult cats: a) cricothyroid muscle reinnervated by preganglionic fibers; b) cricothyroideus reinnervated by its own nerve; and c) the corresponding normal neuromuscular preparation. The activities of malic dehydrogenase, of aldolase and pyruvic kinase were studied in these three preparations as well as in the denervated cricothyroid muscles.Reinnervation by preganglionic fibers prolonged the twich contraction time, whereas, self‐reinnervation did not alter it. On the other hand, the activities of the three enzymes decreased as a result of denervation. In contrast, the muscle reinnervated with sympathetic preganglionic fibers partially recovered the normal level of malic dehydrogenase and the aldolase activities; but showed no modification in the level of pyruvic kinase activity. Conversely, in the muscle fibers reinnervated by their own nerve, the activity of the three enzymes returned to normal levels. The shortening of contraction time of the preganglionic reinnervated muscle correlates well with the features of the enzymic activities found in these muscles. It can be concluded: a) preganglionic sympathetic axons are able to achieve functional connections with striated muscles and b) considering the trophic effect, preganglionic fibers resemble the motor nerve supplying slow muscles.
Histofluorescence study of chromaffin cells in dissociated cell cultures of chick embryo sympathetic ganglia
Authors: Jacobowitz David M. , Greene Lloyd A. 
Published: January 2005

AbstractChromaffin cells were studied by fluorescence microscopy in long‐term cell cultures of dissociated chick embryo sympathetic ganglia. These cells were distinguishable in culture from the sympathetic ganglionic neurons by their small size, relative infrequency of occurrence, intense fluorescence and survival in the absence of nerve growth factor (NGF). By several weeks in culture, with or without NGF in the medium, the chromaffin cells produced extensive ramifications of fluorescent varicose processes. It is suggested that at least part of the intraganglionic system of adrenergic varicose terminals arises from chromaffin cells. This capability with regard to fiber production lends credence to the suggestion that chromaffin cells may play an active role in ganglionic function.
Optimum topographical conditions for reverberating cortical spreading depression in rats
Authors: Shibata M. , Bureš J. 
Published: January 2005

AbstractReverberation of cortical spreading depression (RCSD) around circular cortical lesions was studied in anesthetized rats. Reverberation was started by KCl injection into an area recovering from a first CSD wave in a narrow region between the lesion and the sagittal sulcus. Frontal lesions 3.3 mm in diameter yielded less reliable reverberation than lesions 5.2 mm in diameter. With continuing reverberation the spreading rate of CSD gradually decreased. Reverberation stopped when the CSD relocity dropped below 2.2 mm/min. With large lesions (5.2 mm in diameter) RCSD lasted longer with frontal (12.2 ± 2.0 cycles) than with parietal (4.0 ± 0.4) and occipital (4.4 ± 0.9) obstacles. Application of 10± KCl on the cortical area between the lesion and the sagittal sulcus could also elicit RCSD because the CSD waves spreading in the rostral and caudal directions were not generated simultaneously and some of them went round the obstacle without being intercepted by the opposite wave. The experimental data agree with the mathematical model of excitation spreading in simply connected sheets of excitable tissue and indicate regional differences in CSD susceptibility in the rat.
Localization and identification of the receptors by electron micrographic and ablation studies
Authors: Pigon Andrew , Morita Michio , Best Jay Boyd 
Published: January 2005

AbstractAsexual reproduction (fissioning) in the planarian Dugesia dorotocephala is socially controlled through a cephalic mechanism; isolation releases fissioning, grouping inhibits it; decapitation releases it even in grouped subjects. Experiments were performed to confirm previous indications that direct contact is involved in the sensing of cohorts; the partial release of fissioning in grouped planarians by introduction of a chemically inert lubricant (0.1% purified agar) into the habitat water further confirms the necessity of intimate contact between the sensors and bodily surfaces of the sensed cohorts. Further experiments, correlating electron microscopic observations with the release of fissioning by various selected surgical ablations, reveal the pertinent sensors to be clumps of neural cilia concentrated in the cephalic margins. Comparable structures occur in the chemoreceptors of catfish, lamprey, and honey bee as well as in the olfactory epithelium of mammals.