bluuebunny/crossref_metadata_2025_split huggingface dataset:
Habituation of mechanoreceptive interneurons in the crayfish
Authors: Aréchiga H. , Barrera‐Mera B. , Fuentes‐Pardo B. 
Published: January 2005

AbstractThe effect of repetition of sensory stimuli was studied on the responses of mechanoreceptive interneurons in the optic tract of the crayfish (Procambarus bouvieri (Ortmann)). The number of spikes recorded from a given unit gradually decreased during a train of stimuli. The decrease showed a negative exponential time course, with a curvature dependent upon the frequency of stimulation, the intensity of stimuli, and the hour of the day. Habituation is selective for the intensity and rate of stimulation, and the particular spot of receptive field stimulated. Locomotor excitation results in a dimminution of the rate of decay. The effect of a single train of stimuli when leading to pronounced habituation may persist for periods longer than 24 hr.
Differences in some properties of newborn and adult brain glutamate decarboxylase
Authors: Tapia Ricardo , Meza‐Ruíz Graciela 
Published: January 2005

AbstractSome properties of glutamate decarboxylase (EC 4.1.1.15) activity in brain of newborn and adult mouse were studied comparatively. It was found that glutamate decarboxylase of the newborn brain was strongly inactivated by homogenization in hypotonic medium, centrifugation of isotonic sucrose homogenates, preincubation at 37°C or the addition of Triton‐X‐100, whereas the adult brain enzyme was practically unaffected by any of these conditions. It was also found that the newborn glutamate decarboxylase was less activated by pyridoxal 5′‐phosphate and less inhibited by pyridoxal 5′‐phosphate oxime‐O‐acetic acid, than the adult enzyme. These differences do not exist for brain dihydroxyphenylalanine decarboxylase (EC 4.1.1.26) and are not due to the release of inhibitors from the newborn brain. On the basis of the results obtained it is postulated that two forms of glutamate decarboxylase exist in brain: a newborn form, which is unstable and has high affinity for pyridoxal 5′‐phosphate, and an adult form, which is much more stable and has low affinity for pyridoxal 5′‐phosphate. The possible implications of these findings in the establishment of the σ‐aminobutyric acid dependent synaptic inhibitory mechanisms during development are discussed.
A quantitative analysis of isotope concentration profiles and rapid transport velocities in the C‐fibers of the garfish olfactory nerve
Authors: Gross Guenter W. , Beidler Lloyd M. 
Published: January 2005

AbstractIn the olfactory nerve of the long‐nosed garfish (Lepisosteus osseus), unusually well‐defined isotope concentration distributions can be established with the rapid transport process. Transport velocities of two profile loci can be accurately described and a quantitative profile analysis is possible after profile normalization. Results from such studies indicate that: (1) peak amplitudes decrease exponentially as a function of distance from the olfactory mucosa according to the equation p = 2130 exp (– 0.109x); (2) the wavefront base and the peak apex loci move at rates of 221 ± 2 and 201 ± 4 mm/day, respectively (at 23°C), revealing a peak dispersion or broadening during transport; (3) the broadening is asymmetric with material shifting to the rear of the peak; (4) plateau regions are established behind the peak with material deposited by the peak; (5) only 20% of the total radioactivity in a cut nerve reaches the nerve terminals in the rapid transport peak while 80% is deposited along the axon; (6) profile areas from cut nerves decrease and lose 15% of their activity in 20 hr, while intact nerve profiles increase 10% in 16 hr due to continued somal contribution to the profile; (7) the displacement of the wavefront base (WFB) and peak apex (PA) profile loci can be described by the functions

(8) transport velocities are linear functions of temperature between 10 and 25°C and increase 370% in that range. A linear extrapolation of the WFB and PA functions to 37°C yields 410 and 377 mm/day, respectively.
Effect of aromatic acids on protein synthesis in subcellular preparations from the rat brain
Authors: Lähdesmäki P. , Oja S. S. 
Published: January 2005

AbstractThe incorporation of [3H]phenylalanine, [3H]tyrosine, and [3H]tryptophan into protein and amino acyl–tRNA was studied in cell‐free preparations from rat brain. Tyrosine and tryptophan inhibited the incorporation of phenylalanine into protein, and tyrosine inhibited the incorporation of phenylalanine and tryptophan into amino acyl–tRNAs. In most cases, homogentisate, phenylpyruvate, and phenyllactate inhibited the incorporation of phenylalanine, tyrosine, and tryptophan into protein and amino acyl–tRNAs, and the incorporation of phenylalanine into polyphenylalanine. All other protein amino acids, and phenylacetate, salicylate, and benzoate were wholly ineffectual. The results suggest that the formation of amino acyl–tRNAs may have been the step which was affected most by the inhibitors. The incorporation data at different concentrations of the aromatic amino acids were fitted to the simple Michaelis equation. Homogentisate and phenylpyruvate generally tended to reduce both Km and V in the incorporation of aromatic amino acids into protein and amino acyl‐tRNAs, even if V decreased more than Km.
Neuromuscular junctions in the buccal mass of Aplysia: Fine structure and electrophysiology of excitatory transmission
Authors: Orkand P. M. , Orkand R. K. 
Published: January 2005

AbstractThe lower extrinsic protractor muscle in the buccal mass of Aplysia consists of bundles of muscle fibers 4–12 m̈ in diameter, containing thick and thin filaments that are not arranged in a transversely striated pattern. Individual fibers come close to one another and form specialized junctional regions. Electrophysiological evidence indicates that the muscle fibers form an electrical syncytium. Muscle bundles are innervated by more than one excitatory axon at a number of points along their length. The presynaptic terminals contain spherical electron‐lucent vesicles and a few larger electron‐dense vesicles. There are no obvious structural postsynaptic specializations. Graded contraction can result from summation of excitatory junctional potentials in separate axons or from summation and facilitation of junctional potentials from a single axon. The buildup of facilitation during a train of stimuli results from the linear summation of facilitation remaining from preceding impulses.
Isolation from bovine brain of a fraction containing capillaries and a fraction containing membrane fragments of the choroid plexus
Authors: Sessa Grazia , Orlowski Marian , Green Jack Peter 
Published: January 2005

AbstractCombined differential and density gradient centrifugation was used for the isolation of a capillary‐rich fraction from the cerebral cortex and a brush border containing fraction from the bovine choroid plexus.The activities of γ‐glutamyl transpeptidase and several other marker enzymes were monitored during the fractionation procedure. Electron microscopic examination showed a membrane‐rich fraction in the choroid plexus high in γ‐glutamyl transpeptidase and 5'‐nucleotidase activities. From the brain cortex, a capillary‐rich fraction was obtained which was high in γ‐glutamyl transpeptidase and alkaline phosphatase activities. A histochemical examination showed γ‐glutamyl transpeptidase activity localized in the capillary walls.
Ionic mechanism of 5‐hydroxytryptamine induced hyperpolarization and inhibitory junctional potential in body wall muscle cells of Hirudo medicinalis
Authors: Sawada Masashi , Coggeshall Richard E. 
Published: January 2005

AbstractFive‐hydroxy tryptamine (5‐HT) causes a hyperpolarization and increased conductance of the leech body wall muscle cell membrane. If 5‐HT is applied in the absence of the Cl−ion, the response appears as a depolarization, whereas if 5‐HT is applied in the absence of the K+ion, the response is a hyperpolarization. In both cases, the conductance of the muscle cell membrane is increased. Stimulation of the peripheral nerve to the body wall muscle produces a complex junctional potential in muscle cells. Exposing the muscle to d‐tubocurarine (d‐TC) eliminates the excitatory component (EJP) of the complex potential. The inhibitory potential (IJP) that remains has an equilibrium potential at approximately 65 m V. Furthermore, this IJP appears as a depolarization when the nerve is stimulated in the presence of d‐TC and low CL−, whereas this is not the case if the nerve is stimulated in the presence of d‐TC and low K+. The drugs BOL‐148 and cyproheptadine block the IJP's in the body wall muscle. These data are interpreted as indicating that 5'HT acts on leech body wall muscle cells by increasing the conductance to the Cl−ion and that the IJP's caused by nerve stimulation are probably the result of 5‐HT release at nerve terminals.As a final point, it has been shown that the inhibition by 5‐HT of the spontaneous EJP's that occur on the leech body wall muscle results from an inhibition of central neurons and not from any direct effect on the muscle cell or on peripheral synapses.
Effects of different ions on resting polarization and on the mass receptor potential of carotid body chemosensors
Authors: Eyzaguirre C. , Nishi K. 
Published: January 2005

AbstractThe carotid body and its own nerve were removed from cats anesthetized with sodium pentobarbital and placed in an air gap system; the carotid body was bathed in modified Locke's solution equilibrated with 50% O2 in N2, pH 7.43 at 35°C. The sensory discharges, changes in “resting” receptor polarization and the mass receptor potential evoked by ACh or NaCN were recorded with nonpolarizable electrodes placed across the gap.Receptor potentials and sensory discharges evoked by ACh showed an appreciable increase in amplitude and frequency when the preparation was bathed in eserinized Locke. Eserine did not change appreciably the responses evoked by NaCN. Excessive depolarization elicited by either ACh or NaCN was accompanied by sensory discharge block.Removal of K+ ions from the bathing solution induced receptor hyperpolarization and an increase in the amplitude of the evoked receptor potentials. An increase of K+ concentration had the opposite effect.Reduction of Na+ or NaCl to one half, or total removal of this salt, induced an initial reduction and later disappearance of the sensory discharges, some receptor hyperpolarization and a reduction in the amplitude of the evoked receptor potentials.Reduction or removal of Ca++ produced receptor depolarization, a marked depression of the evoked receptor potentials, an increase in the frequency of the sensory discharges and a reduction in the amplitude of the nerve action potentials.High Ca++ or Mg++ had little or no effect on action potential amplitude or resting polarization, but decreased sensory discharge frequency and the evoked receptor potentials.Total or partial replacement of Ca++ with Mg++ induced complex effects: (1) receptor depolarization which occurred in low Ca++, was prevented by addition of Mg++ ions; (2) the amplitude of the evoked receptor potentials was depressed; (3) the nerve discharge frequency was reduced as it was in high Mg++ solutions; and (4) the amplitude of the nerve action potentials was reduced as it was in low Ca++ solutions.Temperature had a marked effect on the chemoreceptors since a t high temperatures the receptors were depolarized and the discharge frequency increased. The baseline discharge and responses evoked by ACh or NaCN were depressed at low temperatures.The results are discussed in terms of possible receptor mechanisms influenced by the different ions.
Muscle insensitivity to tetrodotoxin: Induction by α‐bungarotoxin and removal by submechanical threshold stimulation
Authors: Gruener Raphael , Baumbach Neal 
Published: January 2005

AbstractIntramuscular injection of alpha‐bungarotoxin (αBGT) into rat extensor digitorum longus muscles produced pharmacological blockade of neuromuscular transmission and resulted in denervation‐like changes (Berg, D. and Hall, Z. (1975), J. Physiol. (London) 244:659–676). More than 80% of fibers from αBGT‐injected muscles produced action potentials (ap's) in the presence of tetrodotoxin (TTX, 1 × 10−6 M). Chronic electrical stimulation of these muscles, below the level necessary to elicit a contraction, resulted in a marked return toward normal of sarcolemmal sensitivity to TTX. After 4 days of submechanical threshold stimulation, less than 45% of αBGT‐injected fibers produced ap' in the presence of TTX, whereas more than 80% of unstimulated fibers from contralateral control muscles exhibited resistance to TTX. These findings indicate that in addition to sarcolemmal sensitivity to acetylcholine, sensitivity of the sodium conductance mechanism to TTX is also directly influenced by muscle activity independent of contraction.
Intracellular calcium and extra‐retinal photoreception in Aplysia giant neurons
Authors: Brown A. M. , Brodwick M. S. , Eaton D. C. 
Published: January 2005

AbstractThe early or “instantaneous” current‐voltage relationship for the light‐activated potassium current in Aplysia giant neurons was linear during the first second of illumination. However, the light current was greatly reduced or abolished by prolonged hyperpolarization. It was also greatly reduced by the injection of calcium EGTA buffers having calcium activities of 5.6 × 10−8 M and simulated by injecting buffers with calcium activities of 2.8–5.6 × 10−7 M. Removal of calcium from the extracellular fluid had no effect. Both the light‐and calcium‐activated outward potassium currents were reduced by tetra‐ethylammonium (TEA) ions. The light current was not affected by substituting rubidium for potassium nor by substituting either lithium or Tris for sodium. The calcium‐activated potassium current persisted when the neuron was cooled to 5°C. However, the light response could no longer be elicited. Light hyperpolarizes Aplysia neurons probably by increasing intracellular calcium activity two‐to six‐fold which activates a membrane potassium conductance. Calcium levels appear to be restored within the cell and are energy dependent. The light‐activated release of calcium is inhibited by cooling. The body wall of Aplysia transmits enough visible or 500‐nm light to hyperpolarize some Aplysia giant neurons under ambient conditions. These neurons may be involved in the extraretinal light entrainment that occurs in Aplysia.
Neurotrophic control of cyclic nucleotide levels during muscle differentiation in cell culture
Authors: Festoff B. W. , Oh T. H. 
Published: January 2005

AbstractThe effects of chick brain–spinal cord extract on morphological development and cyclic nucleotide levels of cultured chick embryo skeletal muscle cells were determined. It had previously been shown that the extract stimulated morphological differentation, protein synthesis, and cholinesterase activity of muscle cells. Myoblasts fused earlier and an increase in number as well as diameter of myotubes were seen in the extract treated cultures. Cyclic nucleotides levels were higher (almost twice the controls for both adenosine 3′, 5′ ‐cyclic monophosphate and guanosine 3′, 5′ ‐cyclic monophosphate) and preceded their occurence in the control cultures. It was suggested that factor(s) in the extract interact with membrane receptor(s) to alter nucleotide levels which, in turn, allow the effects to be expressed.
Effect of curare on responses to different putative neurotransmitters in Aplysia neurons
Authors: Carpenter D. O. , Swann J. W. , Yarowsky P. J. 
Published: January 2005

AbstractWe have studied the effects of curare on responses resulting from iontophoretic application of several putative neurotransmitters onto Aplysia neurons. These neurons have specific receptors for acetylcholine (ACh), dopamine, octopamine, phenylethanolamine, histamine, γ‐aminobutyric acid (GABA), aspartic acid, and glutamic acid. Each of these substances may on different specific neurons elicit at least three types of response, caused by a fast depolarizing Na+, a fast hyperpolarizing Cl−, or a slow hyperpolarizing K+ conductance increase. All responses resulting from either Na+ or Cl− conductance increases, irrespective of which putative transmitter activated the response, were sensitive to curare. Most were totally blocked by ≤ 10−4 M curare. GABA responses were less sensitive and were often only depressed by 10−3 M curare. K+ conductance responses, irrespective of the transmitter, were not curare sensitive. These results are consistent with a model of receptor organization in which one neurotransmitter receptor may be associated with any of at least three ionophores, mediating conductance increase responses to Na+, Cl−, and K+, respectively. In Aplysia nervous tissue, curare appears not to be a specific antagonist for the nicotinic ACh receptor, but rather to be a specific blocking agent for a class of receptor‐activated Na+ and Cl− responses.
Similar polypeptide composition of fast‐transported proteins in rat motor and sensory axons
Authors: Bisby M. A. 
Published: January 2005

AbstractSDS‐polyacrylamide gel electrophoresis was used to characterize labeled proteins transported in rat motor and sensory axons after application of 3H‐leucine to the neuron cell bodies. Two types of experiments were performed: first, transported protein accumulating proximal to a ligature placed on the sciatic nerve was analyzed; second, the segment of sciatic nerve nearest to the “lwavecrest” of transported protein travelling down the nerve was analyzed. In both cases, no significant differences in peak position or amplitude were found in gels containing labeled proteins from motor or sensory axons. This may mean that the majority of fast‐transported protein is involved in an axonal function common to the two types of neuron.
Excitatory effects of cholinergic, adrenergic and glutaminergic agonists on a buccal muscle of Aplysia
Authors: Taraskevich P. S. , Gibbs D. , Schmued L. , Orkand R. K. 
Published: January 2005

AbstractThe anterior extrinsic protractors in the buccal mass of Aplysia are symmetrical sheets of branching bundles of muscle fibers which form an electrical syncytium. The addition of potassium or cholinergic, adrenergic, and glutaminergic agonists to the sea water bathing medium produces contracture of the muscle.Strychnine and cholinergic or adrenergic antagonists all block contractures produced by cholinergic and adrenergic agonists but not those produced by potassium or glutamate.Iontophoretic application through microelectrodes of acetylcholine or dopamine anywhere on the muscle surface produced a graded depolarization of the membrane. By contrast, glutamate produces depolarization only at discrete membrane sites. Endogeneous contractions often appeared spontaneously or could be induced by drug exposure. ATP inhibits endogeneous contractions.
A prolonged, voltage‐dependent calcium permeability revealed by tetraethylammonium in the soma and axon of Aplysia giant neuron
Authors: Horn Richard , Miller Jeffrey J. 
Published: January 2005

AbstractThe soma but not the axon of the giant neuron, R2, of Aplysia can generate an all‐or‐none Ca spike in Na‐free or TTX‐containing medium (Junge and Miller, 1974). Extracellular axonal recordings made at several distances from the soma provide evidence that the transition in ability to fire a spike in Na‐free medium occurs within the first 250 μm of the axon. Application of 25 mM TEA‐Br to the bathing medium causes a more than tenfold increase in the duration of the somatic action potential. The duration of the axonal action potential in TEA decreases with distance from the soma. At distances greater than 3 mm from the soma this concentration of TEA causes little or no increase in the duration of the axon spike. The effect of 25 mM TEA on both the soma and proximal axon is blocked reversibly by 30 mM CoCl2 or 1 mM CdCl2. The duration of the somatic action potential in TEA increases with an increase in Ca concentration of the bath. At a constant concentration of Na, the voltage level of the somatic plateau increases with Ca concentration in the manner predicted for a Ca electrode. In the presence of 11 mM Ca2+ the potential of the plateau is relatively insensitive to Na concentration. The TEA plateau in R2 reveals a prolonged voltage‐dependent permeability to Ca. The duration of the plateau may indicate the degree of Ca activation during a spike.
The role of the electrosensory system in postural control of the weakly electric fish Eigenmannia virescens
Authors: Feng Albert S. 
Published: January 2005

AbstractThe role of the electrosensory inputs in postural control was examined in the weakly electric fish Eigenmannia virescens. These fish exhibit tonic postural tilt in response to a tilted plexiglas substrate in both transverse and longitudinal planes (rolling and head‐up pitching responses, respectively), but not to electrically “transparent” agar substrate. The fish's pitching and rolling responses were abolished when the electrosensory inputs from the trunk were bilaterally eliminated even though the fish's visual and mechanosensory lateral‐line systems remained intact. Unilateral lesion abolished the rolling response but not the pitching response. These results demonstrate the functional role of the electrosensory system in postural control, in addition to its known role in social communication and in object location, and the underlying neuronal mechanism is discussed.
Hypothermic decrease in microtubule density and birefringence in unmyelinated axons
Authors: Rome‐Talbot D. , Andre D. , Chalazonitis N. 
Published: January 2005

AbstractThe density of microtubules, T.D. (number of tubules/unit area) is highest in small crab nerve axons. After cooling of the nerve at 0°C, the tubule density tends to zero (T.D. 2% of the normothermic value). Once the cooled nerves are returned in normothermia, the reconstitution of the microtubules is evidenced (T.D. = 90% of the initial normothermic value). Therefore cooling “depolymerizes” the tubules, whereas rewarming leads to their “repolymerization.” These results definitely improve the interpretation of the birefringence decrease by cooling: as tubules and filaments contribute to the positive fraction of the total positive birefringence, their depolymerization by cooling explains to a large extent the decrease in total birefringence.
A difference between the proteins conveyed in the fast component of axonal transport in guinea pig hypoglossal and vagus motor neurons
Authors: Black Mark M. , Lasek Raymond J. 
Published: January 2005

AbstractWe compared the proteins transported in the fast component of guinea pig hypoglossal motor neurons with those of guinea pig vagus (preganglionic parasympathetic) neurons. The fast component proteins of hypoglossal and vagus neurons were radioactively labeled by injecting 3H‐amino acids into the hypoglossal and vagus motor nuclei. The radioactive fast component proteins obtained from each system were then compared with each other by SDS‐polyacrylamide slab gel electrophoresis and fluorography. These analyses revealed at least twenty polypeptides which appear common to the fast component of each neuronal system. In addition, we identified one difference between the proteins comprising the fast component of these neuronal systems. A polypeptide, molecular weight 50,000 daltons, present in the fast component of vagus neurons was not detected in the fast component of hypoglossal motor neurons. These observations are discussed with regard to the similarities and differences between these neuronal systems.