bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional mapping of neural pathways in rodent brain in vivo using manganese‐enhanced three‐dimensional magnetic resonance imaging
Authors: Watanabe Takashi , Frahm Jens , Michaelis Thomas 
Published: January 2005

AbstractThis work presents three‐dimensional MRI studies of rodent brain in vivo after focal and systemic administration of MnCl2. Particular emphasis is paid to the morphology and dynamics of Mn2+‐induced MRI signal enhancements, and the physiological mechanisms underlying cerebral Mn2+ uptake and distribution. It turns out that intravitreal and intrahippocampal injections of MnCl2 emerge as useful tools for a delineation of major axonal connections in the intact central nervous system. Subcutaneous administrations may be exploited to highlight regions involved in fundamental brain functions such as the olfactory bulb, inferior colliculus, cerebellum and hippocampal formation. Specific insights into the processes supporting cerebral Mn2+ accumulation may be obtained by intraventricular MnCl2 injection as well as by pharmacologic modulation of, for example, hippocampal function. Taken together, Mn2+‐enhanced MRI opens new ways for mapping functioning pathways in animal brain in vivo with applications ranging from assessments of transgenic animals to follow‐up studies of animal models of human brain disorders. Copyright © 2004 John Wiley & Sons, Ltd.
Anesthetic blocking of nerve membrane conductances by internal and external applications
Authors: Narahashi Toshio , Moore John W. , Poston Robin N. 
Published: January 2005

AbstractDibucaine hydrochloride, pentobarbital sodium, tropine p‐tolyl acetate hydrochloride (tertiary form), and tropine p‐tolyl acetate methiodide (quaternary form) reversibly blocked both peak transient and steadystate components of conductance changes from either side of the squid nerve membrane. With external and internal applications of dibucaine and with internal application of the tertiary topine, the steady‐state current declined somewhat, leaving a “hump.” The time to the early peak transient current was unaffected by either external or internal application of dibucaine, but prolonged by either external or internal application of pentobarbital. The curve relating the peak transient conductance to the membrane potential was shifted along the potential axis in the direction of depolarization by external or internal application of pentobarbital. It is suggested that the mechanism of blockage of the peak transient conductance by these anesthetic agents is different from that by tetrodotoxin or by uncharged lipid‐soluble chemicals.
Circadian rhythm of responsiveness in crayfish visual units
Authors: Aréchiga Hugo , Wiersma C. A. G. 
Published: January 2005

AbstractMetal microelectrodes were implanted in the optic nerve of the crayfish, Procambarus clarki, and the activity of the sustaining fibers (units which react tonically to changes in illumination) was continuously recorded over periods up to 8 weeks. In animals kept in darkness, the response to periodic test light pulses was found to vary in a circadian manner. The duration of the cycles varied between 22 24 hr, with a phase of high responsiveness during the subjective night, which abruptly changed to one of low responsiveness at subjective dawn. The phase, amplitude, and shape of the cycles were modifiable by light pulses. The spontaneous activity of these units in darkness showed a similar fluctuation, and so did the electroretinogram amplitude, the spontaneous motor activity of the animal, as indicated by records from mechanoreceptive and activity fibers (units which are activated, directly or indirectly by body movements), and the motor responsiveness to light. The time course of these cycles suggests that they are driven by a common “clock,” through humoral mechanisms.
The effect of prolonged cortical spreading depression on learning and memory in rats
Authors: Burešová Olga , Bureš Jan 
Published: January 2005

AbstractMemory impairment evoked by prolonged cortical spreading depression (PCSD) was examined in 387 rats. PCSD was maintained for 5 hrs by repeated applications of 25% KCl to the exposed cortical surface. Behavioral tests were performed 24 or more hours after PCSD. Whereas a single application of 25% KCl does not affect subsequent learning, acquisition of a simple T‐maze avoidance reaction is slower and exploration of a novel environment is impaired during 3–5 days following PCSD. The effect of CSD on the memory depends on the total duration of the depression. While a single KCl application has a negligible amnesic effect, PCSD prevents later retrieval of moderately overlearned (to‐criterion learning on 3 consecutive days) T‐maze habit but does not affect markedly overlearned behavior (to‐criterion learning on 12 consecutive days). Similarly PCSD impairs the exploration of a novel but not of a familiar environment. Even moderately overlearned habits remain unaffected by PCSD applied 7–12 days after completion of learning. The amnesic effects of PCSD are not permanent, retrieval of the impaired experience improves over 7–14 days to control level. Since spontaneous EEG and evoked responses are more or less normal 24 hr after PCSD, it is proposed that PCSD interferes with the metabolic phase of engram formation. The relative significance of the components of the PCSD effect affecting learning and memory is discussed.
Glutamate release from the retina during spreading depression
Authors: Van Harreveld A. , Fifková Eva 
Published: January 2005

AbstractThe retina was charged with 14C labled glutamate in a near isotonic KCl solution containing, in addition to the label, 25 mM unlabeled glutamate. In extracts of retinas thus charged most of the label was present as glutamate, an appreciable amount as glutamine, and some as aspartate, γ‐aminobutyric acid and other, probably non‐aminated, metabolites of glutamate.The charged retinas, superfused in a chamber, were stimulated either chemically with unlabeled glutamate or KCl solutions, or electrically with direct current. These stimuli caused a transient increase in the transparency of the retina, indicative of spreading depression. Only minute portions of the superfusion solution were collected, and subjected to paper electrophoresis. The radioactivity of the labeled spots was determined with a strip counter. When not stimulated the retina released mostly glutamine, but during and after the various modes of stimulation the release of glutamate increased markedly. Repeated stimulation with short current pulses did not cause a transparency increase and did not enhance the glutamate release. During spontaneous spreading depressions a slight increase in glutamate release was observed. The possibility that glutamate release is the primary mechanism in spreading depression is discussed.
Retinular and eccentric cell morphology in the neural plexus of Limulus lateral eye
Authors: Schwartz E. A. 
Published: January 2005

AbstractRetinular and eccentric cells of Limulus lateral eye are stained by intracellular iontophoretic injection of Procion M4R. Eccentric cell branching can be divided into multiple neuropile, long lateral branches and distal collaterals. Retinular cells possess only short axon spines. This morphology is discussed in relation to the known physiology of cell interactions.
Characterization of the fast and slow components of axonal transport in retinal ganglion cells
Authors: Karlsson J. O. , Sjöstrand J. 
Published: January 2005

AbstractThe constituent proteins of the fast (110–150 mm/day) and slow (1.5–2 mm/day) components of axonal transport in the retinal ganglion cells of the rabbit were investigated. The fast and slow components were labelled by intraocular injection of (3H)‐ and (14C)‐leucine, respectively.Subcellular fractionation of the optic nerve and tract and subsequent gel electrophoresis of the fractions showed that most of the soluble proteins moved with the slow phase of axonal transport, whereas only some of the soluble proteins were transported with the rapid phase.Extraction of the microsomal fraction with triton X‐100 resulted in the solubilization of highly labelled proteins belonging to the rapid phase. These proteins showed a relatively low electrophoretic mobility.
Effect of the convulsant methionine sulfoximine on the in vivo uptake and metabolism of d‐methionine in rat brain
Authors: Ghittoni Nora E. , Sellinger Otto Z. 
Published: January 2005

AbstractD‐methionine was administered intraperitoneally to rats in tracer (2–2.5 μmoles/kg) and large doses (4.7 mmoles/kg) and the brain levels of total (D + L) methionine, as well as of cysteine (+cystine) and glutathione were determined. The effect of co‐administering the convulsant agent, L‐methionine‐DL‐sulfoximine (MSO) was also examined. The administration of tracer doses of C12‐D‐methionine resulted in a doubling of total brain methionine within 4 hours post‐injection, but only in a moderate increase of the levels of cysteine. When C14‐D‐methionine was used as tracer, the peak increase of the isotopic methionine pool and a peak accumulation of 0.35% of the injected radioactivity were noted in the brain within 1.5 hours. When 4.7 mmoles/kg of D‐methionine were administered, total brain methionine and cysteine increased by 4‐ and 3‐fold respectively, the former peaking at 1.5 hr and the latter at 2.5 hr post‐injection. The administration of MSO retarded the attainment of these peaks. It could also be shown that while about 65% of the total brain methionine existed as the D‐isomer 1.5 hr after its administration, only 46% was still present as the D‐isomer 0.5 hr later. When MSO was administered simultaneously with D‐methionine, the corresponding percentage values stood at 70% at 1.5 and at 2 hr. The results, therefore, suggest that even though D‐methionine reaches the brain largely unchanged, its uptake and its conversion to the natural L‐isomer may be inhibited by MSO under certain conditions and hence its conversion to cysteine retarded.
Serotonin metabolism in the brains of mice sensitive or resistant to audiogenic seizures
Authors: Kellogg Carol 
Published: January 2005

AbstractProperties involved in the maintenance of the steady‐state level of serotonin were studied in the brains of mice showing a genetically determined susceptibility or resistance to audiogenic seizures. Animals susceptible to sezures appear to possess an inefficient 5‐HT system which stimulates a compensatory increase in neuronal activity resulting in decreased 5‐HT levels and increased 5‐HT turnover. Biochemical mechanisms that could be responsible for such an inefficiency are discussed.
The movement of sulfate and thiosulfate into in vivo choroid plexus
Authors: Pollay Michael , Kaplan Ralph J. 
Published: January 2005

AbstractThe accumulation of sulfate (SO4) and thiosulfate (S2O3) in the choroid plexus, brain, and cerebrospinal fluid (CSF) of the rat was measured at various plasma levels of these anions. Increasing the plasma SO4  or S2O3  concentration levels 40‐ and 580‐fold, respectively, resulted in a linear increase in CSF, brain and choroid plexus concentration of these ions. The relationship between the concentration of these ions in CSF and choroid plexus was also approximately linear over a wide CSF concentration range. In addition, S2O3 did not appear to influence the relation between the concentration of SO4 in choroid plexus and CSF. The results seem to indicate that there is no saturation of the mechanism responsible for maintaining the low SO4 or S2O3 concentration in CSF nor does there appear to be competition between these anions for clearance from the CSF. These findings are in conflict with data supporting the active transport of SO4 and S2O3 from the CSF across the CSF‐blood barrier (choroid plexus).
The flow of mitochondria in chicken sciatic nerve
Authors: Jeffrey P. L. , James K. A. C. , Kidman A. D. , Richards A. M. , Austin L. 
Published: January 2005

AbstractMitochondrial flow in chicken sciatic nerve has been followed using [59Fe] as a marker for mitochondrial cytochromes.Radioactively labelled iron was injected into the ventral horn of the chicken spinal cord in the region of the cell bodies of the motor neurons, whose axons pass into the sciatic nerve. Protein‐bound [59Fe] was found to move at a slow rate (1–4 mm/day) in the sciatic nerve. The total protein bound [59Fe] in the nerve reached a maximum at 9 days and then gradually diminished.The percentage of label in the mitochondria (expressed both as total and protein bound radioactivity) as compared to the total homogenate of the spinal cord increased up to 14 days and then showed a gradual levelling off.Subcellular fractionation of both spinal cord and sciatic nerve revealed that the mitochondrial fraction obtained by discontinuous gradient centrifugation had the highest specific activity of the fractions isolated. The major portion of this label is present in cytochromes a and b, localized in the mitochondria.Colchicine which has been shown to inhibit both rapid and slow axonal protein flow, markedly reduced the amount of protein bound [59Fe] in the sciatic nerve.
Synaptic stimulation of RNA metabolism in the giant neuron of Aplysia californica
Authors: Berry R. W. , Cohen M. J. 
Published: January 2005

AbstractWe have monitored the incorporation of tritiated uridine into RNA by the giant neuron of the Aplysia abdominal ganglion. Synaptic stimulation evoking a mean of 3,000 impulses in the neuron increased incorporation by about 67%. Incorporation was proportional to the number of stimuli given and to the number of synaptically evoked action potentials produced in the stimulated neuron. Stimulation did not alter uridine uptake or the percentage of intracellular label appearing in UTP. The effect of stimulation cannot be accounted for by glial incorporation.
Regeneration of ventral root axons into dorsal roots as shown by increased acetylcholinesterase activity
Authors: Ranish N. , Ochs S. , Barnes C. D. 
Published: January 2005

AbstractRegeneration of ventral root axons of the lumbar seventh (L7) segment into the dorsal L7 roots on the opposite side of cat spinal cord was shown by changes in the levels of acetylcholinesterase (AChE) and pseudocholinesterase (PsChE). Low levels of AChE and PsChE were found in control dorsal roots, but when regenerating ventral root fibers entered the dorsal roots, there was a doubling of AChE activity within 2 weeks. Growth appears to start some time after the first week; this is in accord with earlier evidence based on axoplasmic flow of isotope labeled protein in this experimental preparation.The level of AChE activity in the reinnervated dorsal roots increased continually for about 100 days before reaching a plateau at approximately 20 × control levels. The gradual increase and the plateau of AChE activity is in accord with a maturation of the ventral root fibers which had regenerated into the dorsal roots. PsChE in the dorsal roots changes in parallel with AChE in a ratio of 1:10, suggesting that PsChE may in part be localized in the regenerating axons.
The effect of synaptic stimulation on RNA and protein metabolism in the R2 soma of Aplysia
Authors: Wilson David L. , Berry Robert W. 
Published: January 2005

AbstractExcitatory synaptic stimulation of the R2 neuron in the abdominal ganglion of Aplysia californica causes an increased incorporation of 3Huridine into RNA. However, this could be the result of a change in precursor specific activity rather than an increase in RNA synthesis. We find that at low external uridine concentrations (1.5 μM) there is no increase in 3H‐uridine incorporation correlated with synaptic stimulation. In addition, no change in incorporation of 3H‐leucine into total protein or in the pattern of newly‐synthesized proteins, resolved by electrophoresis on SDS‐polyacrylamide gels, was detected with stimulation. Since the R2 neuron can be stimulated without a detectable change in RNA or protein synthesis, we conclude that the increase in incorporation observed at high external uridine concentrations (100 μM) could be caused by increased specific activity in a precursor pool rather than by an RNA synthesis change.
Slow accumulation of choline acetyltransferase in crushed sciatic nerves of the rat
Authors: Saunders N. R. , Dziegielewska K. , Häggendal C. J. , Dahlström A. B. 
Published: January 2005

AbstractCholine Acetyltransferase (CHAc) activity has been estimated using a microradiochemical method in short segments of rat sciatic nerve at different times after crushing the nerve once or with a second crush 2 cm distal to the first. Above a single or proximal crush, the CHAc levels rose slowly in the 5 mm immediately above the crush to reach about 1 1/2 times control at 24 hr. Distal to a single crush and between two crushes no change was detected in CH‐Ac‐activity up to 18–24 hr. The results are discussed in relation to the rapid accumulation of acetylcholine (ACH) above a crush, and redistribution between two crushes which have previously been demonstrated in the same preparation. It is concluded that the rate of transport of CHAc is probably much slower than that of ACH, and that their mechanismes of transport are not the same.
The neuronal basis of behavior in Tritonia. IV. The central origin of a fixed action pattern demonstrated in the isolated brain
Authors: Dorsett D. A. , Willows A. O. D. , Hoyle G. 
Published: January 2005

AbstractThe mechanisms which initiate and integrate the patterned sequence of activity in the interacting cell groups responsible for the swimming behavior of Tritonia remain operative after complete isolation of the brain from the periphery. Following isolation, a short electrical stimulus applied to a nerve from the oral veil leads to patterned bursting in the flexion neurons of the pedal ganglia, which is identical to that occurring in the same cells during the swimming escape response.Direct evidence of cell‐cell interaction in the form of unitary postsynaptic potentials was not obtained, but the close synchronization of burst patterning in both ipsilateral and contralateral synergists infers the existence of positive feed back between many neurons of the group. Alternating bursts of impulses in functional antagonists are associated with reciprocal inhibition between the two networks. As all possibility of proprioceptive feedback has been excluded in the isolated brain, it is evident that the motor output pattern for the escape‐swimming response has been generated by a central mechanism without reference to sensory input, which serves only to trigger the action.
Genetic manipulation of motor output in shaker mutants of Drosophila
Authors: Trout W. E. , Kaplan W. D. 
Published: January 2005

AbstractHk1, Hk2, Sh5, and Eag are sex‐linked behavior mutants of Drosophila which shake their legs vigorously when etherized. The shaking rate increases with age to a plateau by five days after eclosion; it is decreased by increasing ether concentrations. Eag is temperature sensitive, shaking vigorously at 30°C but not at all below 20°C. Hk1 and Hk2 have cyclic shaking patterns consisting of three to six periods of shaking per minute. Hk1 stakes more, and has longer shaking periods than Hk2; the heterozygote Hk1/Hk2 is intermediate. When heterozygous with a deletion for the locus, both Hk1 and Hk2 shake more, the pattern of Hk2 resembling that of Hk1. Therefore, these alleles may differ only quantitatively. The shaking pattern of Sh5 is distinctly different, consisting of short bursts of shaking two or three times a second. Flies with both Hk and Sh5 mutations in different combinations can have a pattern which is Hk‐type, Sh5‐type, or both simultaneously, depending upon the geno‐type. The shaking of Hk1 is known to be a consequence of abnormally firing neurons in the thoracic ganglion. Therefore, the interactions between Hk and Sh5 are probably between two different mutant effects upon the motor system, both subject to genetic manipulation.
Levels of glutamate decarboxylase, choline acetyltransferase and acetylcholinesterase in identified motorneurons of the locust
Authors: Emson P. C. , Burrows M. , Fonnum F. 
Published: January 2005

AbstractIsolated somata of identified motorneurons in the metathoracic ganglion of the locust were analyzed for glutamate decarboxylase (GAD), choline acetyltransferase (ChAc), acetylcholinesterase (AChE), and aromatic amino acid decarboxylase (AAD). Isolated inhibitory motorneuron somata have GAD activity but those of excitatory motorneurons do not. Since this enzyme is responsible for the synthesis of gamma amino butyric acid there is a metabolic basis for these motorneurons to accumulate GABA. In contrast to the specific localization of GAD in inhibitory motorneurons, AChE was found in large amounts in all motorneurons tested. The specific activity of ChAc and AAD in both inhibitory and excitatory motorneurons were similar or lower than the specific activity of the whole ganglion. Degeneration experiments suggest that ChAc is mainly localized in the sensory neurons.
Effects of fluorodeoxyuridine on growth and choline acetyltransferase activity in fetal rat brain cells in surface culture
Authors: Schrier Bruce K. , Shapiro Donald L. 
Published: January 2005

AbstractInhibition of DNA synthesis by 5‐fluoro‐2‐deoxyuridine in cultures of rapidly growing fetal rat brain cells resulted in a marked decrease in the development of total activity and a stimulation of specific activity (pmoles\min\μg DNA) of the enzyme choline acetyltransferase, a putative neuronal marker. Similar treatment of higher density, less rapidly dividing cultures of the same age resulted in no change in total activity development, although an increment in specific activity was again found. The findings appeared to be the result of inhibition of DNA synthesis by fluorodeoxyuridine, rather than secondary effects of the drug, and indicate either that the nucleotide analog specifically inhibited choline acetyltransferase gene expression in rapidly growing, but not in stationary cultures, or that cells capable of producing the enzyme activity were able to proliferate in culture. If the latter were true and if cells producing the enzyme were, in fact, neurons, it may be possible to clone untransformed neurons for in‐depth study in a culture system.
Biochemical and cytochemical studies of the development of choline acetyltransferase and acetylcholinesterase in organotypic cultures of chick neural tube
Authors: Kim Seung U. , Oh Tae H. , Wenger Eleanor L. 
Published: January 2005

AbstractCholine acetyltransferase (ChAc) and acetylcholinesterase (AChE) activities have been studied in organotypic cultures of early chick neural tube. During the first week in culture the ChAc activity remains extremely low at which time it can not be demonstrated histochemically in early neurons. It increases rapidly during the second and third weeks in culture, as demonstrated biochemically and histochemically. AChE activity rises rapidly during the first week, and then more gradually for the remainder of the culture period; it can be demonstrated histochemically in early neurons and well differentiated multipolar neurons throughout this period. In our culture system biochemical differentiation (ChAc and AChE activity) occurs concomitantly with morphological differentiation.