bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interhemispheric functional differences in prefrontal cortex of monkeys
Authors: Stamm J. S. , Gadotti A. , Rosen S. C. 
Published: January 2005

AbstractMonkeys had nonpolarizable electrodes implanted bilaterally in prefrontal (principal sulcus), precentral, and occipital cortex. They were trained on a spatial delayed‐response (DR) task (8‐sec intratrial delay), while cortical potentials were recorded. Three groups of monkeys were trained to 90% criterion: (A) 4 monkeys with only the right hand (the left wrist was attached to the testing chair); (B) 2 monkeys with only the left hand; and (C) 2 monkeys with the left and right hands on alternate sessions. Intermanual transfer tests were then given.Averaged steady potential (SP) shifts of several seconds duration were found in prefrontal cortex during cue presentation and the early portion of the intratrial delay and from the precentral area during the choice response. Evaluations of these SP shift magnitudes indicated: (1) Training with only one hand resulted in substantially larger SP shifts in the prefrontal and precentral areas contralateral to the responding hand; (2) alternate hand training resulted in somewhat larger prefrontal SP shifts in the right hemisphere; (3) intermanual transfer had marked effects on the precentral SP shifts, with larger magnitudes in the hemisphere contralateral to the responding hand, but had little effect on the magnitudes of both prefrontal SP shifts. (4) Subsequent training of Group C monkeys with only one hand resulted in greater SP shifts in the prefrontal area contralateral to the responding hand and in decreased SP shifts in the ipsilateral prefrontal area; and (5) additional intermanual transfer tests had no effects on SP shift magnitudes from both prefrontal areas. These findings indicate a dissociation in interhemispheric functions between the precentral and prefrontal cortical areas, with the former implicated in motor organization for the contralateral limb, and the latter in mediation of mnemonic processes, primarily in one hemisphere. This hemispheric specialization is affected by the hand‐training procedure, but other endogenous or experiential factors may be involved.
Content of amino acids in axons from the CNS of the lobster
Authors: McBride W. J. , Freeman A. R. , Graham L. T. , Aprison M. H. 
Published: January 2005

AbstractThe contents of alanine, proline, glycine, GABA, glutamate, and aspartate were measured in four bundles of axons (designated areas A through D) from the circumesophageal connective of the lobster (Homarus americanus). The contents of these amino acids were also determined in individual axons within specific bundles and in the external sheath covering the circumesophageal connective. Within the nerve bundles the levels of aspartate were highest of the amino acids measured, ranging from 1.95 ± 0.12 m̈mol/mg protein in area C to 7.55 ± 0.54 m̈mol/mg protein in area B. On the other hand, GABA had the lowest value in the four bundles; its highest level was found in area C (0.083 ± 0.006 m̈mol/mg protein) and the lowest in area B (none detected). The content of glycine ranged from 1.63 ± 0.14 (area C) to 2.52 ± 0.32 m̈mol/mg protein in area A; that for glutamate ranged from 0.390 ± 0.019 (area C) to 1.01 ± 0.103 (area B). The contents of alanine and proline changed relatively little from bundle‐to‐bundle. The content of aspartate was the highest of any of the amino acids assayed in individual axons (with diameters in the range of 40 to 65 m̈) dissected from areas B and C. Glycine had the next highest content followed in order by glutamate, proline, and alanine. GABA was not detected in these axons. With the exception of GABA (which could not be detected), aspartate had the lowest level (0.066 ± 0.017) and glycine had the highest level (2.00 ± 0.498 m̈mol/mg protein) in the external sheath covering the the circumesophageal connective.
Effects of thiamine antagonists on nerve conduction. II. Voltage clamp experiments with antimetabolites
Authors: Goldberg Daniel J. , Begenisich Ted B. , Cooper Jack R. 
Published: January 2005

AbstractThiamine antimetabolites were externally applied to voltage clamped squid giant axons to investigate the possible role of thiamine in nerve conduction. Phenylthiazinothiamine, in concentrations as low as 250 m̈M, reduced peak early current and steady‐state current, with the depression of the former being two to five times greater than that of the latter. Peak transient and steady‐state conductances were about equally depressed by thiamine tert‐butyl disulfide (2 mM) and L‐586944‐00P07 (5–10 mM). None of the antimetabolites produced an appreciable change in the kinetics of Na+ activation, K+ activation, or Na+ inactivation. Thiamine itself, applied externally up to 30 mM, had no appreciable effect on either the magnitude or time course of the ionic currents. Although these data are consistent with the hypothesis that thiamine may be involved in nerve conduction, they probably reflect a nonspecific stabilizing interaction of this class of compound with the axon membrane. Taken in this light, the hypothesis that thiamine plays a direct role in Na+ channel permeability changes must be reevaluated.
Agonistic and antagonistic activity of glutamate analogs on neuromuscular excitation in the walking limbs of lobsters
Authors: Shank R. P. , Freeman A. R. 
Published: January 2005

AbstractForty‐six analogs of L‐glutamate were tested for activity on muscle fibers in the walking limbs of lobsters. Effects on the membrane potential, input resistance, and amplitude of neurally evoked EPSPs and IPSPs were studied as well as effects on applied L‐glutamate. Seventeen of the compounds studied depolarized the muscle fibers in a manner indicative of an agonistic action on receptors in the neuromuscular excitatory membrane. Six analogs selectively reduced the amplitude of evoked EPSPs, and at least three of these (kainic acid, D‐glutamate, and D‐aspartate) antagonized the excitatory action of applied L‐glutamate. Kainic acid was the most potent of the blockers of neuromuscular excitation, but even it was relatively weak since a concentration of 1 mM was required for an apparent effect. Generally those analogs in the l‐configuration which possessed activity, had agonistic actions, whereas those in the d‐configuration were usually antagonistic.These observations provide pharmacological evidence for the concept that L‐glutamate is the transmitter agent which mediates neuromuscular excitation in the walking limbs of lobsters. In addition, our results are consistent with recent studies which indicate that l‐aspartate may also function in this neuromuscular excitatory process.
Alteration of protein metabolism in individual, identified neurons from Aplysia
Authors: Wilson David L. 
Published: January 2005

AbstractA search for control mechanisms governing protein metabolism in neurons from Aplysia californica has uncovered two examples of altered patterns of newly synthesized proteins: (1) The pattern of newly synthesized proteins in the R2 neuron is altered when protein synthesis occurs at elevated temperatures (22–30°C as compared with 13–15°C). (2) The processing of newly synthesized 12,000 dalton (12k) material to 6–9,000 dalton (6–9k) size in the R15 neuron (Strumwasser, F. and Wilson, D. F. [1976], J. Gen. Physiol., in press) can be blocked by certain ion replacements. If acetate replaces chloride in the incubation medium during the synthesis of 12k material, an early step in the processing, prior to the actual breakdown of 12k material, is blocked.Experiments with RNA‐synthesis inhibitors indicate that none of the mRNAs which code for abundantly synthesized protein species in the R2 or R15 neurons have short (less than 4 hr) half‐lives. This result has implications for an earlier report of regulation of protein synthesis in the R15 neuron.
Characterization of proteins transported at different rates by axoplasmic flow in the dorsal root afferents of rats
Authors: White F. P. , White S. R. 
Published: January 2005

AbstractProteins synthesized by soma located in L4 dorsal root ganglia and supplied to the axonal branches extending centrally in the dorsal root and peripherally towards the sciatic nerve were analyzed for radioactivity following injections of [3H] leucine into the L4 dorsal root ganglia. All proteins located in the dorsal root and sciatic nerve were analyzed by SDS acrylamide gel electrophoresis at various times post injection. The differences in radioactivity between the dorsal root and sciatic nerve proteins were mainly quantitative and not qualitative, with many proteins of various molecular weight ranges being transported into both segments. Generally, it appears that in both axonal branches the high molecular weight proteins are transported at the highest rate, medium weights slower and low molecular weight proteins slowest. More proteins of high and low molecular weights are transported into the dorsal root whereas more of those of medium molecular weight are transported towards the sciatic nerve.
Short‐lasting memory in lower nervous centers in Octopus
Authors: Young J. Z. 
Published: January 2005

AbstractOctopuses with the supraesophageal lobes split and the subesophageal centers isolated by cutting the cerebrobrachial connective on one or both sides were trained by food and shock rewards to discriminate between rough and smooth balls. Because there is a greater tendency to take the rough ball, training was done with the smooth ball positive for half the animals, and the rough ball positive for the others. In the animals with the cerebrobrachial connective cut only on one side, the subesophageal lobes showed no capacity to use the information gained by their opposite, intact, half‐brains, which learned well. In animals with isolated subesophageal lobes, there was a decrease during each training session in the tendency to take both types of ball; however, this decrease did not persist from day to day. During each training session there were signs of discrimination between the balls by animals with isolated subesophageal lobes, but these also did not survive from day to day. In a series of training sessions spread over seven weeks, there was no change in results in animals with isolated subesophageal lobes when the smooth ball was positive. When the rough was positive the discrimination in its favor was slightly increased at later sessions.
Physiological properties of afferents and synaptic reorganization in the rat cerebellum degranulated by postnatal x‐irradiation
Authors: Puro Donald G. , Woodward Donald J. 
Published: January 2005

AbstractElimination of most granule, basket, and stellate interneurons in the rat cerebellum was achieved by repeated doses of low level x‐irradiation applied during the first two weeks of postnatal life. Electrical stimulation of the brain stem and peripheral limbs was employed to investigate the properties of afferent cerebellar pathways and the nature of the reorganized neuronal synaptic circuitry in the degranulated cerebellum of the adult. Direct contacts of mossy fibers on Purkinje cells were indicated by short latency, single spike responses: 1.9 msec from the lateral reticular nucleus of brain stem and 5.4 msec from ipsilateral forlimb. These were shorter than in normal rats by 0.9 and 2.1 msec, respectively. The topography of projections from peripheral stimulation was approximately normal. Mossy fiber responses followed stimulation at up to 20/sec, whereas climbing fiber pathways fatigued at 10/sec. The latency of climbing fiber input to peripheral limb stimulation in x‐irradiated cerebellum was 23 ± 8 (SD) msec. In x‐irradiated rats, the climbing fiber pathways evoked highly variable extracellular burst responses and intracellular EPSPs of different, discrete sizes. These variable responses suggest that multiple climbing fibers contact single Purkinje cells.We conclude that each type of afferent retains identifying characteristics of transmission. However, rules for synaptic specification appear to break down so that: (1) abnormal classes of neurons develop synaptic connections, i.e., mossy fibers to Purkinje cells; (2) incorrect numbers of neurons share postsynaptic targets, i.e., more than one climbing fiber to a Purkinje cell; and (3) inhibitory synaptic actions may be carried out in the absence of the major inhibitory interneurons, i.e., Purkinje cell collaterals may be effective in lieu of basket and stellate cells.
Postsynaptic potentials in pacemaker cells: A correlate of behavior in command cells of an electric fish
Authors: Feng Albert S. , Bullock Theodore H. 
Published: January 2005

AbstractIntracellular recordings were made from pacemaker‐command cells of the electric organ discharge (EOD) of the weakly electric fish Eigenmannia virescens. The fish was immobilized with gallamine triethiodide (Flaxedil) which silenced the EOD. A simulated EOD of this fish (ca. 300 Hz) and a sine wave simulating a neighbor, a few Hz higher (+ΔF) or lower (‐ΔF) were introduced into the bath to elicit the “jamming avoidance response” (JAR), monitored through the pacemaker potential. We observed that accompanying the JAR there is a minute hyperpolarizing postsynaptic potential (hpsp) superimposed on the pacemaker potential. A shift in the phase of the hpsp occurs with a change in the sign of ΔF, and therefore of the JAR. Assuming that the behaviorally correlated hpsp is inhibitory, it suggests that mutual inhibition may play a role in regulating the synchronous firing frequency of command neurons, which are electrically coupled with one‐another. Scheich and Bullock (1974) proposed a neuronal scheme for the JAR in which they suggest that two systems (P and T) operate together in the nervous system. The T system affects the pacemaker cells at a precise, variable phase of the pacemaker cycle. Although the present results indeed reveal a shift in the hpsp with a change in the sign of ΔF, the actual significance of this shift remains to be evaluated. The unexpected direction of the shift suggests either that the hpsp is excitatory at the phases when it occurs, or that effectiveness of inhibition decreases at later phases in this case instead of increasing as in other cases, or that the hpsp opposes the JAR. The parallel P system is probably more important in explaining the JAR, acting by a DC level control rather than a phase control.
Biosynthesis and processing of presumed neurosecretory proteins in single identified neurons of Aplysia californica
Authors: Aswad Dana W. 
Published: January 2005

AbstractThe biosynthesis and processing of low molecular weight protein (presumed neurosecretory protein) in cells R15, R14 and L11 of Aplysia californica was studied at high resolution by polyacrylamide slab gel electrophoresis in sodium dodecylsulfate. The number of low molecular weight proteins detected in each cell ranges from 3 in R14 and L11 to 5 or 6 in R15. In each of the cells studied, the low molecular weight protein consists of a primary precursor of ca. 12,000 daltons, and its proteolytic processing products. In each cell, the smallest protein, or in the case of R14, one of the two smallest proteins, accumulates to a significant extent, suggesting that it might correspond to a final processed neurohormone. In cell R15, the biosynthesis of the primary precursor and its subsequent processing to smaller peptides is largely unaffected by removal of extracellular calcium, by replacement of calcium with cobalt or by inhibition of spontaneous bursting via stimulation of the brachial nerve.
Developmental abnormalities of identifiable neurons in the crayfish Procambarus simulans
Authors: Ballinger Martis L. , Bittner George D. 
Published: January 2005

AbstractWe report anomalies of lateral giant neurons in field‐caught animals. In one case, both lateral giant neurons arising from the fifth abdominal ganglion did not terminate in the next‐most anterior ganglion, but rather continued to the third abdominal ganglion. In another case, an additional large neuron arising in the fifth abdominal ganglion coursed in a posterior direction. All other CNS structures appeared normal in animals having either anomaly.
Serial synapses in Aplysia
Authors: Graubard Katherine 
Published: January 2005

AbstractSerial synapses occur between small profiles in the neuropil of Aplysia abdominal ganglion. Material was fixed in phosphate buffered OsO4, embedded in epon, and sections were stained with uranyl acetate and lead citrate. A class of synapses had the following characteristics: (1) synaptic vesicles clustered against the presynaptic membrane, (2) a widened extracellular space of about 20 nm containing electron‐dense material, (3) straightening of the pre‐ and postsynaptic membranes, and (4) no postsynaptic membrane specialization. Some density between the presynaptic membrane and the adjacent synaptic vesicles was occasionally observed. Synapses occurred between small profiles in the neuropil (typical profile diameters were 1–3 m̈m).In this sample of approximately 100 synapses, four serial synapses were identified. The serial synaptic profiles were all small. In addition to the finding of serial synapses, 40% of the postsynaptic profiles contained vesicles similar to the synaptic vesicles seen in presynaptic profile. Serial synapses may be the anatomical substrate of presynaptic inhibition and facilitation and of dishabituation.
Effect of experimental colchicine encephalopathy on brain protein synthesis and tubulin metabolism
Authors: McMartin Donald N. , Schedlbauer Lewis M. 
Published: January 2005

AbstractColchicine blocks axoplasmic flow and produces neurofibrillary degeneration. Brain slices from mice injected intracerebrally with colchicine incorporated more [14C]leucine into protein and had a decreased uptake of [14C]leucine into the perchloric acid‐soluble pool than did their controls. Brain RNA content was decreased and free leucine increased by colchicine‐induced encephalopathy. The specific activities of proteins from subcellular fractions of colchicine‐injected brain were increased in the nuclear fraction, the 100,000‐g supernatant, and its vinblastine‐precipitable tubulin. The ratio of the specific activity of the crude mitochondrial fraction to that of the total homogenate was decreased, as would consistent with impaired movement of newly labeled protein into synaptosomes. Colchicine‐injected brain extracts contained one or more cytosol fractions that stimulated ribosomal incorporation of [14C]leucine into protein in a cell‐free system. Colchicine‐binding‐activity measurements indicated loss of soluble and particulate tubulin in colchicine‐injected brains; the decrease of soluble tubulin was verified by its selective precipitation with vinblastine. Colchicine encephalopathy did not affect the rate of spontaneous breakdown of in vitro colchicine binding activity. Similarities of colchicine encephalopathy to the neuron's response to axonal damage suggest that colchicine‐induced increase in protein synthesis may, in part, reflect a neuronal response to blockage of neuroplasmic transport.
Taurine in the developing rabbit visual system: Changes in concentration and axonal transport including a comparison with axonally transported proteins
Authors: Sturman John A. 
Published: January 2005

Abstract[35S]Taurine injected intravitreally into rabbits was transported axonally to the optic nerve terminals. Considerably more [35S]taurine was transported in young rabbits than in mature rabbits. The time course of taurine transport did not parallel that of proteins labeled with [3H]proline in the same system. The concentration of taurine in all components of the visual system, except retina, was greater in young animals than in mature animals, and was especially high in optic nerve. The possible functions of the high concentrations of taurine and the greater amount of axonally transported taurine in developing mammalian CNS are discussed.
Central inhibition of an identified mechanosensory interneuron in the crayfish
Authors: Wilkens Lon A. , Marzelli George A. 
Published: January 2005

AbstractInhibitory input from crayfish mechanoreceptors is mediated polysynaptically to sensory interneurons. An identifiable sensory interneuron, the caudal photoreceptor (CPR), has been used as a model system to characterize inhibitory intermediate cells. A survey of the abdominal connectives, by antidromic stimulation, has identified eleven inhibitory cells, some of which also function as ascending sensory interneurons. These results indicate that lateral interactions within networks of mechanosensory interneurons form an integral part of the information processing mechanisms.
Cobalt mapping of the nervous system: Evidence that cobalt can cross a neuronal membrane
Authors: Fredman Steven M. , Jahan‐Parwar Behrus 
Published: January 2005

AbstractExposing intact nerves of Aplysia to exogenous CoCl2 was sufficient to fill neurons by axonal iontophoresis. There were no significant differences between filling intact nerves and nerves whose ends had been cut. Nonneuronal elements were not filled appreciably. These results show that Co2+ can cross intact axonal membranes and suggest that in tracing neuronal pathways Co2+ may not remain confined to neurons whose interiors are directly exposed to it.
Electric membrane properties of adult mouse DRG neurons and the effect of culture duration
Authors: Scott Brian S. , Edwards Beverley A. V. 
Published: January 2005

AbstractThe electrical membrane properties (EMP) of adult mouse dorsal root ganglion (DRG) neurons were characterized by an extensive electrophysiological investigation of 450 cells. The neurons were divided into two types: an M‐type having an action potential with monophasic falling phase and a B‐type with a more complex biphasic or triphasic falling phase. Compared to M‐type, B‐type were “slow” neurons with a higher specific membrane resistance (Rm), and a longer time constant (τ), duration of action potential (Δt), and absolute refractory period (ARP). B‐type also had a larger amplitude action potential, afterhyperpolarization and positive overshoot. The action potential of the M‐type neuron had only a Na+ component while that of the B‐type had both a Na+ and a Ca2+ component. After two days in culture, M‐type neurons exhibited phase bright cytoplasmic granules, which were seldom observed for B‐type neurons. Although neuron survival remained constant during the first six days in culture (DIV), the relative frequency of occurrence of the M‐type decreased from 82 to 50%. Thereafter, it decreased more gradually to a final value of approximately 20% after 40 DIV. It was concluded that at least during the first 6 DIV and possibly through to 40 DIV, M‐type neurons transformed into B‐type. Both M‐ and B‐type neurons showed significant and similar changes in their EMP with increasing DIV (up to 40 DIV). For M‐ and B‐types combined, Rm increased approximately 142%, τ by 204%, and no significant change in specific membrane capacitance was observed. Rheobasic threshold depolarization decreased 58%, while the resting membrane potential decreased by only 19%. These changes in the EMP of adult neurons are strikingly similar to changes in EMP observed in adult denervated muscle and in cultures of either embryonic nerve or muscle. This similarity suggested that the adult DRG neurons in cell culture undergo progressive dedifferentiation because of isolation from their usual trophic interactions. Determination of neuronal membrane electrical characteristics provides a new method for evaluating the effects of various possible trophic agents, e.g., hormones and tissue extracts, on the state of differentiation of neurons in cell culture.