bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transport of proteins and sulfated mucopolysaccharides in the goldfish visual system
Authors: Elam John S. , Agranoff Bernard W. 
Published: January 2005

Abstract3H‐Proline, 3H‐asparagine and Na235SO4 have been found to be highly specific markers for axonal transport in the goldfish visual system. The amino acids label both rapidly and slowly transported proteins while the 35S is recovered mainly with the rapidly transported materials, including protein‐bound mucopolysaccharides. These precursors have been used to study the rate of transport, the subcellular distribution and the rate of turnover of transported proteins in the nerve terminals.
Preparative resolution and identification of synaptic components of rat neocortex
Authors: Garey Richard , Harper Jon , Best Jay Boyd , Goodman Alan B. 
Published: January 2005

AbstractA varity of density gradient centrifugation techniques have been used with varying degrees of success, for the preparative resolution of pinched off nerve endings, i.e. “synaptosomes,” and synaptic components from brain homogenates. The physics of such gradients was critically considered from the standpoint of improving the degree of resolution of particulate classes and preserving morphological integrity. A procedure, using continuous linear Ficoll gradients, is presented which yields improved particulate resolution with good preservation of ultrastructural morphology. Further purification of the membraneous fraction yielded relatively high purity preparations of PSM particulates. The PSM particulates were identified as dissociated postsynaptic membranes by three kinds of electron microscope studies. Broad field electron micrographs, which permit assessment of fraction homogeneity, are presented for all fractions.
Comparison of tertiary and quaternary amine local anesthetics in their ability to depress membrane ionic conductances
Authors: Narahashi Toshio , Frazier Donald T. , Moore John W. 
Published: January 2005

AbstractTertiary and quaternary amine local anesthetics have been studied to determine their effect on membrane ionic conductances in squid giant axons. The tertiary compounds 6211 and 6603 (10mM), both lidocaine derivatives, suppressed both peak transient and steady‐state currents from either side of the nerve membrane. The time for the transient current to reach its peak was not appreciably affected. When applied internally, two quaternary compounds, QX‐314 and hemicholinium‐3 (1mM), were effective in suppressing both components of the membrane currents. However, when applied externally, they had no effect on the membrane currents even at a concentration of 10mM. The time to peak current was slightly prolonged when QX‐314 was applied internally. Another quaternary compound QX‐572 suppressed both currents from outside, but was more effective from the inside, 1mM externally being roughly equipotent to 0.1mM internally. The tertiary and quaternary compounds used in the present study block the nerve conduction by essentially the same mechanism as that previously reported for other local anesthetics.
Superfused cerebral tissues in hypoxia: Neurotransmitter and amino acid retention; labile constituents and response to excitation
Authors: Pull I. , Jones D. A. , McIlwain H. 
Published: January 2005

AbstractHypoxic conditions have been imposed on incubating superfused neocortical tissues. Their lactate production increased and K and phosphocreatine content fell moderately; under these conditions the release of amino acid and putative neurotransmitters into the superfusing medium was studied. During the hypoxia, total free amino acids increased, the major increase being in the quantity found in the superfusing medium. With [3H] leucine introduced in vitro however, hypoxia caused a significant diminution of efflux from tissue to medium. Electrical stimulation under hypoxia increased the efflux of total amino acid, but not that of leucine. Retention of norepinephrine and serotonin by the tissue, and their release into the superfusing medium during electrical stimulation, were found to persist during hypoxia.
Neural mechanisms underlying behavior in the locust Schistocerca gregaria. II. Integrative activity in metathoracic neurons
Authors: Hoyle Graham , Burrows Malcolm 
Published: January 2005

AbstractPreliminary studies are reported on the roles of some interneurons and motorneurons in generating simple behavior patterns in the locust Schistocerca gregaria. The neurons were penetrated by intracellular electrodes singly, or in pairs, whilst a variety of reflexes and spontaneous movements was observed. For example: large oscillations of membrane potential occurring at characteristic flight frequency were observed in flight motorneurons after blowing on the head. The pattern of impulses was directly determined by the amplitude and period of the oscillations. Similar oscillations were observed to occur spontaneously in leg motorneurons, where they caused bursts of impulses which closely resembled those occurring during walking.Both sensory‐integrating and pre‐motor interneurons were encountered, but none with the function of “commanding” motor output. Much of the input to leg motorneurons is already in programmed form.
Neuronal circuit reorganization in mammalian agranular cerebellar cortex
Authors: Llinás R. , Hillman D. E. , Precht W. 
Published: January 2005

AbstractMorphological and electrophysiological studies of the agranular cerebellar cortex of ferret after infection with panleukopenia virus have led to the following conclusions:
At light microscopic level this agranular cerebellar cortex is shown to be totally disorganized when compared to its normal lamination.
From an ultrastructural point of view, Purkinje cells are present throughout the thickness of the cerebellar cortex, demonstrating dendritic branches studded with unwed spines.
Purkinje cells receive four different types of inputs‐climbing fibers, mossy fibers, stellate cell terminals, and Purkinje cell axon collateral terminals. The mossy fiber contacts which are generally not present in mammals are made in some cases to elongated, “dolichoderic” spines.
Stellate, basket, and Golgi cell interneurons are present, and receive inputs from mossy and climbing fiber terminals, and probably from axon collaterals of Purkinje cells. The mossy fiber input to these neurons represents a true reorganization of the cerebellar circuit, since it has never been observed in any other vertebrate.
Stellate and basket cells terminate in contact with dendrites and somata from Purkinje cells, while the Golgi cell terminals seem to be restricted to somata and dendrites of other Golgi cells.
Electrophysiologically, Purkinje cells can show normal excitability following antidromic invasion, and may be activated by the mossy and climbing fiber afferent systems. Intra‐and extracellular recording from Purkinje cells demonstrates that the mossy fiber afferent system activates Purkinje cells with a latency of approximately 1 msec and its excitatory action is graded with relation to the amplitude of the white matter stimulation. Following an initial excitation, this input generates a longlasting inhibition (50 msec), which is attributed to mossy and climbing fiber activation of inhibitory interneurons.
Climbing fiber activation generates the typical all‐or‐none burst response in Purkinje cells extracellularly. Intracellularly, large unitary EPSPs characteristic of this form of activation may be recorded with a latency of 1.5 to 3 msec. This large unitary EPSP seems to behave in the usual one‐to‐one relation (one climbing fiber to one Purkinje cell).
Double climbing fiber activation reveals that a conditioning white matter stimulation produces a total inhibition of a climbing fiber burst at 15 msec interval, which indicates a rather strong inhibitory action on Purkinje cells following this form of activation.
Climbing fiber activation is followed in most cases by a so‐called climbing fiber reflex, suggesting that the inferior olive in this agranular condition is functioning in a normal manner.
Finally, some of the neurobiological implications of these findings are considered in the discussion.
Neuronal basis of behavior in Tritonia. II. Relationship of muscular contraction to nerve impulse pattern
Authors: Hoyle G. , Willows A. O. D. 
Published: January 2005

AbstractRecordings were made of the movements elicited in the body of Tritonia diomedia by direct intracellular stimulation of identified brain neurons, which have a motor command function. It was shown that the latency of a movement response decreases as the frequency of stimulation is increased in the range 1 Hz to 20 Hz. Over the same range, the speed of the response increases. The extent, and also the speed, of a movement are proportional to the total number of stimuli, but response speeds and magnitudes vary greatly at different times. The minimum latency, after deduction of conduction time, is 160 ms at 11 °C.It is concluded that the identified brain cells, which cause discrete movements, do so indirectly, by activating a peripheral nerve net which in turn excites the muscle fibers. The nerve net is the site of independent excitatory, inhibitory, and local reflex action.
Five classes of visual interneurons in the optic nerve of the hermit crab
Authors: Glantz Raymon M. 
Published: January 2005

AbstractResponse characteristics and trigger features are described for five operational classes of visual interneurons in the optic nerve of the hermit crab. The units were initially segregated on the basis of response sign (“on”, “off”, “on‐off”) and duration (phasic, tonic). Tonic “on” and tonic “off” units were observed to be indistinguishable from the previously described sustaining and dimming fibers of other decapod crustacea. Phasic “off” units closely resemble either jittery motion or novelty detectors also previously documented. Phasic “on” units are characterized by an excitable antagonistic surround, a slow rate of habituation, and a sustained low level discharge during periods of increasing luminous flux at any point within their receptive fields. Highly sensitive to moving contours, they occasionally revealed a directional preference. The phasic “on” units are also capable of following brief stimuli at rates of up to 20/sec. Phasic “on‐off” units were characterized by coextensive receptive fields for “on” and “off” responses and movement sensitivity independent of contrast.
Restorative effects of cyclic AMP on complex bioelectric activities of cultured fetal rodent CNS tissues after acute CA++‐deprivation
Authors: Crain Stanley M. , Pollack Emanuel D. 
Published: January 2005

AbstractExplants of fetal mouse spinal cord and cerebral cortex generate organotypic slow‐wave and repetitive‐spike discharges in vitro which can be abolished by agents which reduce the concentration of Ca++ available to the tissue. Synaptically mediated discharges are rapidly blocked in Ca++‐free balanced salt solution (BSS), or in regular BSS after addition of 10−3 M EGTA, 5–10 × 10−3 M Mg++, or 10−4 M xylocaine, but simple spike potentials can still propagate. When low concentrations of cyclic AMP or dibutyryl cyclic AMP (2 × 10−6 M) are added to the Ca ++‐free BSS or Ca++‐antagonist‐BSS, a temporary (1–20 min) restoration of characteristic complex bioelectric activities occurs (or the onset of depression is delayed if cyclic AMP is initially added). Phosphodiesterase inhibitors, e.g. 10−3 M caffeine, are also effective in restoring these blockades, whereas 5′AMP and ATP are not. Application of 10−6 M cyclic AMP or 10−3 M caffeine in regular BSS greatly enhances excitability of some CNS explants, resembling convulsive effects observed in CNS in situ.The data suggest that cyclic AMP can mobilize Ca++ from membranebound Ca pools within neurons in CNS explants so as to permit Ca++‐dependent release of neurotransmitter during Ca++ deficits. Thus, it may also be that under normal conditions, cyclic AMP can regulate the availability of Ca++ for synaptic transmission in the central nervous system, thereby modulating the efficacy of synaptic functions.
Effects of axonal injury on norepinephrine, tyrosine hydroxylase and monoamine oxidase levels in sympathetic ganglia
Authors: Cheah T. B. , Geffen L. B. 
Published: January 2005

AbstractA combined morphological and biochemical study was made of the responses of lumbar sympathetic ganglion cells to ligation of their axons in the sciatic nerve of the rat. There was a progressive accumulation of norepinephrine proximal to the ligature for the first few days without detectable changes in the ganglion cells. However, three days after ligation there was a decrease in the axoplasmic accumulation of norepinephrine, accompanied by pronounced falls in ganglion norepinephrine, tyrosine hydroxylase, and monoamine oxidase. These changes, that coincided with the development of signs of chromatolysis in the light and electron microscope, were fully developed one week after ligation and by one month were almost reversed. Proteolysis and death of chromatolytic cells may have made some contribution to the observed changes, but there were no significant changes in the soluble protein content of the lumbar ganglia, presumably because of the counter‐balancing increase in protein synthesis known to occur during chromatolysis and regeneration. It is suggested that axotomy caused a reordering of the priorities of protein synthesis in sympathetic neurones to favor the production of proteins necessary for regenerative rather than transmitter functions.
Dopaminergic neurons in explants of substantia nigra in culture
Authors: Coyle Joseph T. , Jacobowitz David , Klein David , Axelrod Julius 
Published: January 2005

AbstractExplants of substantia nigra and corpus striatum obtained from newborn rats were maintained in tissue culture for up to six days. Explants of substantia nigra exhibited a net increase in the ability to take up H3‐dopamine, a process associated with the dopaminergic neurons; in contrast, the explants of corpus striatum showed a rapid loss in this ability to accumulate H3‐dopamine. After three days in culture, the specific activity of tyrosine hydroxylase and monoamine oxidase had decreased 50% in explants of substantia nigra. A medium including fetal calf serum and chick embryo extracts was necessary for the increase in H3‐dopamine uptake, and nerve growth factor had an inhibitory effect. Histofluorescent examination of nigral explants cultured for three days indicated morphologically normal dopaminergic neurons.
Intracortical impedance changes during spreading depression
Authors: Hoffman Clifford J. , Clark Francis J. , Ochs Sidney 
Published: January 2005

AbstractSpecific impedance at various depths in the cerebral cortex of the rat was measured using a newly developed thin film coaxial microelectrode. This novel electrode has the advantage of measuring specific impedance of extremely small volumes of tissue, and thus of making highly localized measurements.The resting level of cortical impedance in the rat was found to be stable, but to vary for different sites and animals from 200–700 ohm‐cm. During spreading depression, loop‐shaped impedance loci were consistently observed in the complex impedance plane with peak magnitude 2–3 times resting level. These unusual loop‐shaped loci are thought to represent distinct process differences during development and recovery phases of spreading depression.This preliminary investigation has demonstrated the feasibility of a technique for making highly localized impedance measurements in nervous tissue. Such measurements are useful for in vivo studies of such tissue parameters as extracellular space.
Control of habituation of the withdrawal reflex by the gill ganglion in Aplysia
Authors: Peretz Bertram , Moller Robert 
Published: January 2005

AbstractThe regions of the gill neural plexus responsible for habituation of the withdrawal reflex were studied using surgical and electrophysiological techniques. Waterdrops were applied to the gill pinnule, and testing for habituation was carried out in each preparation before and after ganglionectomy of the large ganglion in the gill and pinnule isolation. Three parameters of habituation, response decrement, spontaneous recovery, and dishabituation, were used to evaluate the function of the ganglion and the plexus in the pinnule in habituation of the reflex. Disruption of response decrement, of spontaneous recovery, and of dishabituation were caused by either isolating the stimulated pinnule from the gill ganglion by severing the branchial nerve, or by extirpating the gill ganglion. We conclude that: (a) the gill ganglion is necessary for the withdrawal reflex to exhibit the three parameters which characterize hibituation; and (b) the plexus in the pinnule mediates the withdrawal reflex. Extracellular recordings from the pinnule showed that sensory adaptation cannot be contributing to habituation of the reflex since the apparent sensory activity evoked by waterdrops in the pinnule was unaltered by repeated stimulation. In gill ganglion neurons, biphasic potentials were evoked by waterdrops and consisted of an initial depolarization followed by a longer lasting hyperpolarization whose duration was increased with repeated stimulation. In three spontaneously active neurons the rate of activity decreased with repeated stimulation. It is felt that the decreased rate is brought about by potentiation of the hyperpolarization. The rate of spike activity is considered to control the reflex amplitude since the increased rate with intracellular stimulation, in one neuron, resulted in an increased amplitude and since the absence of spontaneous discharge, after ganglionectomy, resulted in a reduced amplitude. A neural network mediating habituation of the withdrawal reflex is proposed.
Specific protein metabolism in identifiable neurons of Aplysia californica
Authors: Gainer Harold , Wollberg Zvi 
Published: January 2005

AbstractThe patterns of protein metabolism of identified cholinergic (R2, L10, and L11) and neurosecretory (R3–13, R14, and Bag cells) cells were analyzed with the use of SDS‐polyacrylamide gel electrophoresis and isoelectric focusing. L11 was unique amongst the three cholinergic neurons in its relatively high rate of incorporation of labeled leucine into proteins at 12,000 daltons. All the neurosecretory cells incorporated relatively large quantities of 3H‐leucine into small proteins (<12,000 daltons), which were concentrated in putative neurosecretory granule fractions of these cells. R3–13 and R14 synthesized a distinct basic protein which appeared specifically in the branchial nerve which contains the axons of these cells. The combination of these two analytical electrophoretic techniques allowed for the characterization of protein specificity in single nerve cells.
Comparative effects of nerve growth factor and ganglionic nonneuronal cells on purified mouse ganglionic neurons in culture
Authors: Varon Silvio , Raiborn Charles , Burnham Patricia 
Published: January 2005

AbstractPurified neuronal fractions from dissociated mouse dorsal root ganglia were cultured in the presence of variable amounts of homologous ganglionic nonneuronal cells, and with or without addition of variable amounts of exogenous Nerve Growth Factor in the culture medium. The ability of the nonneurons to support long‐term neuronal survival in the absence of exogenous Nerve Growth Factor increased linearly with their numbers and maximal neuronal performance was achieved with a 4:1 ratio of non‐neurons to neurons; however, neuronal attachment was elicited maximally as soon as that ratio reached or slightly exceeded a value of one. Besides this Nerve Growth Factor‐like function, the nonneurons were also involved in determining whether and to what extent the factor was capable of supporting neuronal performance. In the absence of non‐neurons, even high concentrations of the factor failed to elicit neuronal attachment. As more nonneuronal cells were made available, Nerve Growth Factor progressively raised neuronal performance and did so at sharply declining requirement levels: with 12,000 nonneurons/dish maximal performance required only 10−2 biological unit/ml of the factor. Further increases of the nonneurons reduced the scope of a neuronal response to Nerve Growth Factor between the maximal performance of the culture system and the increasing performance elicited without the factor. The results indicate that, given a minimal level of nonneurons, the performance in culture of these ganglionic neurons could be promoted in very similar patterns by either increasing the exogenous Nerve Growth Factor in the medium or increasing the ganglionic nonneurons on the culture floors, with an approximate and fixed ratio of 10−7 biological unit per nonneuron. Possibilities are discussed of a common mechanism underlying the supportive properties of the two agents.
Incorporation of [14C] ethanolamine and [3H] Methionine into phospholipids of rat brain and liver in vivo and in vitro
Authors: Morganstern Roberta D. , Abdel‐Latif Ata A. 
Published: January 2005

AbstractComparative studies were undertaken on the in vivo and in vitro incorporation of [14C] ethanolamine, [3H] methionine and [14C] S‐adenosyl‐methionine into phosphatidylethanolamine (PhE) and phosphatidylcholine (PhC) of rat liver and brain. It was observed that brain can synthesize de novo PhC from PhE via the transmethylation pathway, however synthesis rates were (1) markedly lower than those of liver and (2) decreased significantly with age. In the choline‐containing lipids more than 95% of the radioactivity was found in PhC. Studies on the localization of the radioactivity in PhC following the intracranial injection of [3H] methionine or [14C] ethanolamine revealed that both precursors are incorporated almost exclusively into the choline moiety of this phospholipid. There was significant labeling of PhC only when the precursors were administered intracranially and much less incorporation was observed with the systemic routes. Thus following the intravenous administration of [14C] ethanolamine, the specific radioactivities of liver PhE and PhC were up to 75 times as high as those of brain and 4 to 5 times as high in the organs of the 20‐day old as those of the adult. In contrast, when this precursor was administered intracranially the specific radioactivities of both phospholipids in liver were only twice as high as those of brain. Although the short‐and long‐term time‐course studies on the in vivo incorporation of [14C] ethanolamine and [3H] methionine into PhC of both organs could suggest a precursor‐product relationship between the biosynthesis of this phospholipid in liver and brain, this apparent relationship could also be due to the high turnover of PhE in liver, with half‐life of 2.87 hr, and its low turnover in brain, with half‐life of 10.7 days. The present findings on the low rate of formation of PhC from PhE in brain coupled with the fact that this conversion declines sharply with age, especially when the isotopes are administered systemically, could explain the observation of previous investigators that the brain cannot synthesize its own choline and thus it must derive its choline from exogenous sources such as lipid‐choline. It was concluded that the brain can synthesize its own choline; however it remains also dependent on liver and dietary choline which are probably transported into the brain as free choline.