bluuebunny/crossref_metadata_2025_split huggingface dataset:
Velocity measurements of particulate neuroplasmic flow in organized mammalian CNS tissue cultures
Authors: Leestma Jan E. 
Published: January 2005

AbstractThe movements of spherical particles in the range of 0.3 to 0.8 μm diameter within neurities of cultured embryonic mouse spinal cord fragments were observed and recorded by means of Nomarski optics and time‐lapse photocinematography at high power. Particulate movements were measured by projecting the motion pictures onto a calibrated screen and recording the distances moved with time of linearly moving particles and making note of the direction (toward or away from the neuron soma) of movement. In all, 128 particles were measured in six cultures. These measurements were taken away from the neuron soma near the periphery of the neurites. Eighty‐three particles were noted to be moving toward the neuron at a mean velocity of 1.03 ± 0.38 (SD) μm/sec while 45 anterograde moving particles were noted to move at 1.07 ± 0.62 (SD) μm/sec. Statistical analysis of these velocities revealed no significant difference between them. Particles which were elongated and probably represented mitochondria moved more sluggishly and could not be measured accurately by the techniques employed. It appeared the spherical particles moving in a retrograde direction originated at the neurite tip apparently by pinocytosis. There was a suggestion that anterograde flow and retrograde flow may have been affected unequally by factors which develop in the observation chamber over a period of 2 hr or more. The most likely factor responsible was probably hypoxia.
Chloride conductance of denervated gastrocnemius fibers from normal goats
Authors: Bryant S. H. , Camerino D. 
Published: January 2005

AbstractMembrane potentials, cable parameters, and component resting ionic conductances of gastrocnemius fibers from normal goats were measured in vitro at six to 32 days following denervation by section of the tibial nerve.Denervated fibers were depolarized an average of 11.6 ± 1.5 mV (six preparations) from the control mean of 62.1 ± 1.0 mV (124 fibers) over the period studied. Fibrillation, tetrodotoxin‐resistant action potentials, and anodebreak excitation were present in the denervated preparations after 13 days. The control cable parameters from 124 fibers (13 preparations) were membrane resistance, 1052 ± 70 ω·cm2 and membrane capacitance, 6.2 μF/cm2. In denervated fibers membrane resistance increased two to three times in the 13 to 32 day period; membrane capacitance increased about 50% in normal solution at eight to nine, 27–28, and 32 days. Myoplasmic resistivity was assumed to be 112 Ωcm. Measurements were made at 38°C.Component resting conductances were determined from the cable parameters in normal and chloride‐free solution. Mean chloride conductance GCl and mean potassium conductance GK of control fibers were 776 ± 49 μmhos/cm2 and 175 ± 15 μmhos/cm2 (92 fibers), respectively. Following denervation GCl increased slightly at six to nine days then fell to low values at 16 to 32 days that were close to or indistinguishable from zero. GK increased significantly to 372 ± 40 μmhos/cm2 and 499 ± 90 μmhos/cm2 at 16 to 20 and 32 days, respectively.It was concluded from these findings that GCl and GK of mammalian skeletal muscle are controlled by factors from the nerve and/or muscle action potentials. Goat muscle is different from frog muscle in which GCl does not change and GK decreases during denervation.
A regional study of developing rat brain: The accumulation and distribution of proteolipid proteins
Authors: Campagnoni Anthony T. , Campagnoni Celia W. , Dutton Gary R. , Cohen James 
Published: January 2005

AbstractThe accumulation and distribution of proteolipid proteins in rat brain and selected brain regions (cerebellum, cerebral cortex, basal ganglia, and hippocampus) were studied during early postnatal development. In whole brain an eightfold increase of proteolipid was observed between ten and 33 days after birth. This was reflected in the separate regions examined where the proteolipid protein content increased six‐ to ten‐fold during the same period. The basal ganglia and cerebral cortex contributed the greatest amount to the total proteolipid present. However, at 28–33 days the greatest concentration (mg/g tissue) was observed in the basal ganglia and hippocampus.When the proteolipid protein preparations were examined by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis, distinctive, heterogeneous patterns for each brain region were obtained. Proteolipid from basal ganglia (the region richest in white matter) consisted primarily of two major protein bands with apparent molecular weights of approximately 21,500 and 26,000. Both of these bands dramatically increased in quantity during myelination, and the larger protein coelectrophoresed with isolated myelin proteolipid protein. Both bands were also found present in proteolipid preparations from the other brain regions but in varying amounts relative to the total. The data suggest that the increase in proteolipid observed during this developmental period was due in large measure to the accumulation of myelin‐specific proteolipids, but also that a significant proportion of the increase was due to the accumulation of nonmyelin components.
Magnesium‐resistant excitatory synaptic potentials in the leech retzius cell
Authors: Kleinhaus Anna L. , Prichard James W. 
Published: January 2005

AbstractPostsynaptic potentials (PSPs) recorded from leech Retzius cells in response to stimulation of interganglionic connective could not be reversed by soma depolarization or abolished by 40 mM Mg ion, nor could input resistance changes be detected during them. Alteration of external Cl and K over a tenfold range provided no clear evidence that the PSPs involved a conductance change to either ion. The method of extrapolation yielded an apparent PSP equilibrium potential of about −20 mV. The steep portion of the relationship between Retzius cell action potential amplitude and membrane potential extrapolated to an apparent reversal potential of −13 mV. It is likely that the connective‐to‐Retzius cell PSPs were principally electrical events. Their apparent reversal potentials could have been in the range associated with chemical synapses because they traversed an electrical synapse with a variable coupling resistance, or because the polarizing currents, passing “backwards” across electrical synapses, changed the amplitude of the presynaptic action potentials.
N‐substituted maleimide inactivation of the response to taste cell stimulation
Authors: Mooser Gregory 
Published: January 2005

AbstractN‐Ethylmaleimide (NEM) irreversibly inactivates the response of gustatory cells to stimulation by NaCl, sucrose and hydrogen ions. The rate of inactivation can be measured by monitoring the decay of NaCl‐stimulated summated electrophysiological activity at the chorda tympani nerve in the presence of NEM. The observed pseudo first‐order rate constants are linear with NEM concentration, and the second‐order rate constant is 0.38 M−1 sec−1. Other N‐substituted maleimides, such as N‐methylmaleimide and N‐butylmaleimide, which have ether:water partition coefficients similar to NEM, inactivate the NaCl‐stimulated response at rates comparable to NEM. However, the hydrophobic derivative, 4‐(N‐maleimido)phenyltrimethylammonium has a significantly lower ether:water partition coefficient and is essentially ineffective as an inactivator of the NaCl response. These results, together with the observation that the inactivation rate is independent of pH between 4.5 and 7.0, indicate the inactivation site is either intracellular or buried within the cell membrane at a locus inaccessible to most extracellular fluids. The rate of inactivation of the sucrose and HCl responses were measured indirectly and found to be comparable to the NaCl‐stimulated inactivation rate, indicating the inhibited event is common to the transduction of the response for all of the stimuli examined. Possible sites of inactivation by N‐Substituted maleimides are considered in the context of the results. This kinetic approach should have application in searching for and characterizing receptor‐specific as well as other classes of taste cell inhibitors.
Genetic and physiological evidence concerning the development of chemically sensitive voltage‐dependent ionophores in L6 cells
Authors: Gartner T. Kent , Land Bruce , Podleski T. R. 
Published: January 2005

AbstractThe electrophysiological properties of a tissue culture muscle line, L6, and a K+ resistant mutant (MK1) derived from L6 were determined to elucidate certain aspects of membrane differentiation and function. MK1 was selected as a clone of myoblasts resistant to the toxic effects of 55 mM K+. The resting potentials of L6 and MK1 myoblasts and myotubes were K+ dependent and equal. The amplitudes of the action potentials were equal in normal medium, but 27.7 mM K+ interfered with or eliminated the ability of L6 myotubes to produce action potentials. MK1 myotubes produced nearly normal action potentials under these conditions. Thus, the K+ resistant myoblasts differentiate into myotubes which have an action potential generating mechanism much less sensitive to K+ than the normal mechanism. Also, both d‐tubocurarine and α‐bungarotoxin enhance the amplitude of the action potentials produced by L6 myotubes in the presence of 27.7 mM K+; these compounds do not enhance the amplitude of the action potentials produced by MK1 myotubes under the same conditions. It is proposed that as a consequence of differentiation a type of ionophore present in myoblasts becomes a voltage‐dependent ionophore in myotubes. Furthermore, these voltage‐dependent ionophores can be chemically sensitive.
A comparative statistical study of hippocampal neuronal spontaneous spike activity in situ and in vitro
Authors: Shtark M. B. , Stratievsky V. I. , Ratushnjak A. S. , Voskresenskaja L. V. , Karasev N. P. 
Published: January 2005

AbstractThe statistical characteristics of the spontaneous spike activity of rat hippocampal neurons in fields CA1−2 were compared in situ and in tissue culture. Statistical analyses have shown strong similarities in estimators of basic numerical characteristics of interspike interval (ISI) distributions.These similarities may serve as evidence of maintenance of normal functional properties and an “organotypic arrangement” of neurons in tissue culture, and they are also indicative of an intrahippocampal origin of the spontaneous impulse activity in the hippocampus.On the other hand, some differences are noted in the tests of firing patterns. Interpretation of these results leads to some assumptions about mechanisms of the phenomenon under study.
Fast axonal transport: Effect of antimitotic drugs and inhibitors of energy metabolism on the rate and amount of transported protein in frog sciatic nerves
Authors: Hanson Mats , Edström Anders 
Published: January 2005

AbstractMitosis inhibitors, drugs affecting the energy metabolism, heavy water and ouabain were used to partially inhibit fast axonal transport in frog sciatic nerves. Effects on the rate and on the amount of pulse labeled protein could be separated. The pulse of labeled protein, released after a cold‐block, rapidly reached a maximum height which indicated that the transport system was saturated in the nerve segment occupied by the pulse.Both the rate and the amount were reduced by the mitosis inhibitors colchicine, vinblastine, and griseofulvin. Colchicine had a differential effect and reduced the rate of material migrating in the advancing front of the pulse less than the rate of that moving in the peak. Preincubation at low temperature potentiated the effects of colchicine.Two inhibitors of energy metabolism, NaCN and IAA, reduced the amount of labeled material in the pulse. The slope of the pulse was markedly reduced and multiple peaks appeared. The distance covered by the migrating pulse was largely unaffected, but some retardation of late components might have occurred. In contrast, 2.4‐DNP reduced the rate without any effects on the amount of migrating material.Heavy water uniformly reduced the rate of the migrating pulse, whereas the main effect of ouabain was a diminished amount and multiple peaks as with NaCN and IAA.All drugs were tested for their effects on the electrical activity of sciatic nerves. The compound action potential was not affected by the mitosis inhibitors and heavy water, but was depressed by the inhibitors of energy metabolism and abolished by ouabain.The results indicate that the effects of various transport inhibitory drugs can be differentiated if both the rate and the amount are considered.
The long‐term fate of neurons in allografts of ganglia in AG‐B‐compatible normal and immunologically tolerant rats
Authors: Zalewski Andrew A. , Silvers Willys K. 
Published: January 2005

AbstractNeurons in Ag‐B‐incompatible allografts of ganglia are acutely rejected while those in Ag‐B‐compatible grafts are able to survive the immune reaction directed against them. The present study was undertaken to determine the long‐term fate of neurons in allografts of ganglia in Ag‐B‐compatible rats. Isogenic strains of Ag‐B‐compatible adult Lewis (LE) and Fischer (FR) rats were used. The sensory nodose ganglia were reciprocally exchanged between normal LE and FR and between LE and FR animals rendered immunologically tolerant of each other's histocompatibity antigens. The findings were similar in both rat strains and revealed that although neurons and glial cells (i.e., satellite and Schwann cells) could survive for prolonged periods they were nevertheless eventually rejected by normal (nonimmunosuppressed) recipients. On the other hand, neurons and glial cells survived indefinitely in allografts in tolerant rats. Moreover, these neurons were functional because they regenerated nerve fibers into cotransplanted isografts of tongue and exerted the neurotrophic influence of inducing taste bud regeneration. The results demonstrate that, unlike kidney and heart, neurons in ganglia allografts cannot survive indefinitely without immunosuppression in Ag‐B‐compatible animals. Nevertheless, the permanent survival and function of neurons in Ag‐B‐compatible grafts can be achieved, as it is in Ag‐B‐incompatible ganglia grafts, by rendering the recipient immunologically tolerant.
A histofluorescence study of events accompanying accumulation and migration of norepinephrine within locally cooled nerves
Authors: Brimijoin Stephen 
Published: January 2005

AbstractGlyoxylic acid was used to induce fluorescence in sections of rabbit sciatic nerve. In fresh nerves treated with this agent there were scattered finely beaded axons with a weak blue‐green fluorescence. During local cooling, blue—green fluorescence accumulated steadily at the proximal boundary of the cooled region but never at its distal boundary. This accumulation gave rise to dilated axons that often swelled into brilliantly fluorescent balloon‐like structures up to 10 μm in diameter. Axonal fluorescence was probably specific for norepinephrine, being enhanced by inhibition of the metabolism and diminished by inhibition of the synthesis or storage of this neurotransmitter. After local cooling of nerves for 1.5 hr, specific fluorescence was confined within 0.8 mm of the cooled region. Rewarming led to rapid removal of fluorescence from the cooled region and to disappearance of most of the balloon‐like swellings. Simultaneously, rewarming caused brightly fluorescent fibers that were neither dilated nor swollen to appear in distal regions of nerve. As this wave of fluorescence migrated distally with increasing duration of rewarming, it was spread over increasingly broad regions of nerve, which suggests that axonal transport of norepinephrine may involve some kind of dispersive process.
Effects of methylazoxymethanol given at different stages of postnatal life on development of the rat brain. Comparison with those of thyroid deficiency
Authors: Rabié Alain , Selme‐Matrat Maryse , Clavel Marie‐Claude , Clos Jean , Legrand Jacques 
Published: January 2005

AbstractNewborn rats were treated at different stages of their development with low doses of methylazoxymethanol acetate. The postnatal increase of the DNA content of the cerebrum did not differ from that of controls. In the cerebellum, the DNA content was transitorily reduced, but later, the external granular layer became thicker and DNA deposition increased in comparison with controls; finally, the cerebellar DNA returned to a normal value. Morphological abnormalities of the cerebellum, abnormal orientation of migrating cells, scattering of Purkinje cell bodies within the internal granule cells and specially striking abnormalities of the morphology and orientation of Purkinje cell dendrites were noted in rats treated with MAM from birth to day 3. The effects on the Purkinje cell morphogenesis persisted but were much less marked when MAM was given from 4 to 7 or from 8 to 11 days. Neonatal thyroid deficiency, as MAM‐treatment between days 0 and 3, leads to an abnormal position of Purkinje cell bodies within the cerebellar cortex; it also leads to morphological abnormalities of their dendritic arborization which closely resemble those observed after MAM‐treatment during the second postnatal week. It also alters the cell formation in the cerebellum. Thyroid deficiency probably exerts its effect on cell formation earlier than previous biochemical studies have shown. On another hand, the morphological abnormalities of Purkinje cell arborizations in the thyroid‐deficient animals may be partly due to the perturbations of cell formation which persist later in the cerebellum.
Rapid axonal transport in vitro. Effects of derivatives of cyclic AMP and other agents acting on the cyclic AMP system
Authors: Edström Anders 
Published: January 2005

AbstractThe effects of agents known to affect the cyclic AMP (cAMP) system in nervous tissue have been studied on the rapid axonal transport in vitro of [3H]leucine‐labeled proteins in the frog sciatic nerve. The transport was inhibited by 3 different cAMP analogues; dibutyryl cAMP (1 mM), zeatin (0.5 mM), and zeatin riboside (0.5 mM), whereas another N6‐substituted adenine derivative, N6‐, isopentyl‐adenine (DMA) (0.5 mM), and also dibutyryl cyclic GMP (1 mM), lacked effects. Two inhibitors of cAMP phosphodiesterases, papaverine and RO 207222, increased the level of cAMP in the nerve and arrested the transport. Papaverine was very potent and caused a reversible transport block at 0.05 mM. Adenosine (3 mM) increased the cAMP content about 16 times, much more than any of the other drugs tested, but only inhibited the transport by about 50%. Veratridine, a depolarizing agent, irreversibly blocked the transport at a low concentration (0.01 mM), which did not change the cAMP level.Transport inhibitory effects by another depolarizing substance, ouabain, and tricyclic psychotropic agent, chlorpromazine, have been described earlier. Ouabain (0.1 mM), in contrast to chlorpromazine (0.1 mM), caused a small increase in the cAMP content.The present results do not suggest the existence of a close relationship between rapid axonal transport and the cAMP system. Transport inhibitory effects due to disturbed energy metabolism will be discussed.
Effects of denervation on the permeability of acetylcholine‐activated channels to organic cations
Authors: Guy H. Robert , Dekin Michael S. , Morello Robert 
Published: January 2005

AbstractExperiments were performed on chronically denervated frog sartorius muscles to determine the permeability of the acetylcholine‐activated channels to organic cations. The membrane voltage response to bath‐applied acetylcholine was measured with the moving electrode when the muscles were bathed in normal Ringer and in Ringer in which all of the Na+ had been replaced with an organic cation. The magnitude of the maximum voltage response was used to estimate the permeability of the channel to the organic cation. These results were compared with those which have been reported for innervated frog sartorius muscles (Maeno, Edwards, and Anraku, 1977). It is concluded that the permeability to a wide range of organic cations is virtually identical for the extrajunctional channels which develop following denervation and the channels which are localized at the junctional region of innervated muscles.
Physiological properties of the penis retractor muscle of Aplysia
Authors: Blankenship J. E. , Rock M. K. , Hill J. 
Published: January 2005

AbstractThe properties of the penis retractor muscle of Aplysia have been studied using intracellular, sucrose gap and tension recording. The fibers are of the invertebrate smooth muscle type and exhibit slow contractions which occur spontaneously or in response to stretch in isolated preparations. Individual muscle fibers are innervated by excitatory and inhibitory axons. A variety of sizes of excitatory and inhibitory junctional potentials can be recorded from them. The innervation is probably diffuse and functionally polyneuronal. The fibers are electrically coupled, permeable to potassium and chloride at rest, and exhibit no overshooting active responses. The muscle shows graded responses of depolarization and contraction proportional to strength of nerve stimulation. Facilitation and depression of junctional potentials are seen with various frequencies of nerve stimulation. Post‐tetanic potentiation occurs with nerve stimulation at frequencies from 2 to 50 Hz and is suppressed in the presence of increased extracellular calcium concentrations.
Penis‐retractor muscle of Aplysia: Excitatory motor neurons
Authors: Rock M. K. , Blankenship J. E. , Lebeda F. J. 
Published: January 2005

AbstractCobalt axonal iontophoresis and intracellular recordings were used to identify a cluster of several motor neurons innervating the penis‐retractor muscle of Aplysia. Intracellularly recorded motor neuron action potentials elicited direct, one‐for‐one, constant latency excitatory junctional potentials (ejps) in individual muscle fibers. The axons of motor neurons could be recorded extracellularly in the penis‐retractor nerve and stimulation of the nerve backfired the motor neurons. Perfusion of the ganglion, the muscle, or both with solutions of either increased Mg++/decreased Ca++ or increased Ca++ sea water indicated that the presumed motor neuron impaled was not a sensory cell and that interneurons were not intercalated in the pathway. Innervation of muscle fibers was found to be functionally polyneuronal and diffuse. The ejps were found to undergo marked facilitation with repetitive motor‐neuron stimulation. The motor neurons were isolated in a distinct cluster in the right pedal ganglion. Their electrical activity was characterized by spontaneous irregular action potentials and a moderate input of postsynaptic potentials.