bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrophysiological studies of the protozoan, Stentor coeruleus
Authors: Wood David C. 
Published: January 2005

AbstractTransmembrane potentials and membrane characteristics of Stentor coeruleus were studied by means of microelectrodes and standard electrophysiological techniques. Intracellular resting potentials were found to be variable and recordable for only a brief span of time owing to the encapsulation of the recording electrodes. During this brief time span of recorded resting potentials were anamolous in that they were generally of positive polarity.When an extended Stentor was stimulated to contract, a 10–60 mv negative‐going transient response was recorded from intracellular electrodes. After the electrodes had been encapsulated, a diphasic transient response was observed when the penetrated animal contracted. Simultaneous recordings from intracellular and encapsulated electrodes showed that the diphasic and negative‐going transient responses occurred simultaneously.Contractions of Stentor occurred in 7 to 8 msec following a 2 to 3 msec latent period after a suprathreshold shock. Records obtained by use of photomultiplier and microelectrodes indicated that the contractions began 1.8 msec after the onset of the diphasic response.Prepotentials were observed prior to mechanically stimulated responses.
Amino acid uptake in the peripheral nerve of the rat
Authors: Yamaguchi Masashi , Yanos Theodore , Yamaguchi Tomoko , Lajtha Abel 
Published: January 2005

AbstractWhen rat sciatic nerves were incubated with C14l‐lysine, l‐ or d‐glutamate, or d‐l γ‐aminoisobutyrate, the labeled compounds penetrated the nerve, and the level of lysine and leucine after 1 hr was higher in the nerve than in the medium. The level increased with time, and at 24 hr glutamate levels also were higher in the nerve than in the medium. Lowering the temperature strongly inhibited uptake, while other conditions such as absence of glucose, absence of sodium, or the presence of cyanide inhibited uptake by nerve less than uptake by brain slices. The uptake against a concentration gradient, and inhibitions of this uptake by metabolic inhibitors and by structural analogs, were interpreted as showing the presence of transport processes for amino acids in peripheral nerves with characteristics similar to such transport processes in the central nervous system.
Components of fast and slow axonal transport in the goldfish optic nerve
Authors: McEwen Bruce S. , Forman David S. , Grafstein Bernice 
Published: January 2005

AbstractThe composition of the fast and slow components of axonal transport in the goldfish optic nerve was investigated, using specific radioactive precursors injected into the eye. Tritiated glucosamine and fucose label macromolecules, presumably glycoproteins, which are rapidly transported from the eye to the optic tectum. Material labeled with these precursors is not evident in the slowly transported component. Glucosamine and fucose incorporation are blocked when a protein synthesis inhibitor, acetoxycycloheximide, is injected into the eye concurrently with the precursors. As well as labeling macromolecules, 3H‐glucosamine and 3H‐N‐acetylmannosamine ( a precursor of sialic acids) also label rapidly‐transported chloroform‐methanol‐extractable material which may contain transported glycolipids.Two procedures were used to show that the slow component of axonal transport contains tubulin, a protein characteristic of the microtubules:

Tracer doses of tritiated colchicine injected into the eye label a wave of radioactivity which moves 0.5 mm/day, the rate of slow axonal transport in the goldfish optic nerve. We believe this wave represents the movement of colchicine which is bound to colchicine‐binding protein moving in the slow component of axonal transport.
Tritiated proline labels a slowly transported protein which is precipitated by vinblastine and has a mobility on polyacrylamide gels comparable to authentic tubulin. These results indicate that the fast and slow components of axonal transport each provide specific chemical substances to the nerve endings.
Interrelation and dynamic activity of visceral muscle and nerve cells from insect embryos in long‐term cultures
Authors: Aloe L. , Levi‐Montalcini R. 
Published: January 2005

AbstractMultiple segments of esophagus dissected out from 16‐day cockroach embryos were cultured in vitro in a chemically defined medium in the presence of dissociated nerve cells from the same donors. A first migratory wave of cells took place from the explants between the first and fourth week of culture. The morphological characteristics of these cells suggest that they originate from tracheolar cells. Between the second and fifth month of culture, a second migratory wave of a different cell type replaces the first wave of short‐living cells. These cells migrate out only after nerve fibers from the ingluvial ganglion have branched into the medium. They form long cellular ribbons and exhibit spontaneous contractility. The characteristics of the contractile cycles were examined at the inverted microscope, with Nomarski optics, and in time‐lapse cinematography. The cells were identified as myocytes and their origin traced to the longitudinal and circular muscle layer of the explants. The contratile cell ribbons establish firm contact with nerve fibers from the ingluvial ganglion, which in turn exhibit a vibratory motion identical to that of the cells. The most plausible interpretation is that nerve fibers are pushed and pulled by contractile myocytes. The results of these in vitro experiments show a strong affinity of myocytes for nerve fibers and bring to light a new aspect of the relationship between these cells and the visceral fibers which provide for their innervation.
Axoplasmic transport: Differential inhibition by cytochalasin‐B
Authors: Fernandez Hugo L. , Samson Frederick E. 
Published: January 2005

AbstractSlow (1 mm/day) and fast (10mm/day) axoplasmic transport of labelled protein, shown by the movement of sharp peaks of radioactivity along the crayfish nerve cord, are blocked by cytochalasin‐B. Labelled proteins in the slow peak maintain their sharp distribution; however, those in the fast peak disperse over a broad area after the drug‐induced blockage.
Fast axonal transport in the C‐fibers of the garfish olfactory nerve
Authors: Gross Guenter W. , Beidler Lloyd M. 
Published: January 2005

AbstractThe application of aqueous solutions of tritiated L‐Leucine to the olfactory epithelium of the longnosed garfish (Lepisosteus osseus) results in a rapid sorption of the labeled precursor and the subsequent establishment along the nerve of a profile of labeled macromolecular constituents. This profile consists of a sharp wavefront, a peak and a saddle region. At 23°C, the wavefront enters the nerve 1.8 hr after the isotope application and moves away from the cell bodies at an average rate of 222 ± 2.4 mm/day. As the labeled material is propelled along the nerve fiber, its distribution undergoes several characteristic profile changes. The peak broadens and decreases in height and the slope of the wavefront becomes gradually less steep, while the area of the profile increases. These systematic, time‐dependent changes suggest a redistribution of some of the labeled axonal material during transport.
Experimental inhibition of myelination in spinal cord tissue cultures: Enzyme assays
Authors: Fry June M. , Lehrer Gerard M. , Bornstein Murray B. 
Published: January 2005

AbstractSeven specific enzyme activities were assayed in embryonic mouse spinal cord cultures during normal development and under conditions of myelination inhibition and disinhibition. Sulfatase A activity in the inhibited and disinhibited cultures was slightly lower than in the normal control cultures. No specific differences for glucose‐6‐phosphate dehydrogenase, β‐galactosidase, β‐glucuronidase, acid prosphatase, and NADP‐isocitrate dehydrogenase activities were found among these three experimental conditions. However 2′,3′‐cyclic nucleotide phosphohydrolase, an enzyme which has been specifically associated with myelin, showed identical patterns of inhibition and disinhibition as were previously observed for sulfatide synthesis.
Electrophysiological analysis of the actions of strychnine, bicuculline and picrotoxin on the axonal membrane
Authors: Freeman Alan R. 
Published: January 2005

AbstractStrychnine, bicuculline, and picrotoxin show similar effects on the membrane of the lobster giant axon. At concentrations above 5 × 10−5 M these compounds cause depolarization of the resting potential and a broadening of the action potential contour. Also occurring is an increase in excitability as defined by a decrease in stimulus threshold. Repetitive firing of action potentials is sometimes observed during the depolarizing process. Drug levels of 5 × 10−4 M and higher may secondarily induce depolarizing inactivation of the spike generating mechanism. The loss in resting potential is accounted for by a shift in relative membrane selectivity away from potassium and towards sodium. Associated with this alteration in selectivity is a marked fall in total conductance and abolition of delayed rectification. The results indicate that strychnine, bicuculline, and picrotoxin cause potassium inactivation and further that this effect is manifest in both the resting and active electrogenic state of the membrane.
The protein subunit of calf brain neurofilament
Authors: Davison Peter F. , Winslow Boyd 
Published: January 2005

AbstractA preparation of the protein subunits from calf neurofilaments has been obtained. Axon segments from an homogenate of calf brain white matter have been concentrated by a subcellular fractionation procedure. After further steps to achieve a complete elimination of unbound lipid, the neurofilament protein was dissolved in 4M guanidine hydrochloride solutions. The neurofilalment subunit was the major constituent of the guanidine hydrochloride extracts; other proteins of higher molecular weight were eliminated by agarose gel filtration in urea solutions. Dialysis to solutions of low ionic strength allowed the reformation of fibril aggregates, some of which, under electron microscopy, resembled the original neurofilaments in morphology.The physical characteristics of the neurofilament subunit protein are reported and a preliminary amino acid analysis is given. The neurofilament protein is clearly distinguishable from actin and tubulin on physical and chemical grounds.
The properties and connections of supernumerary sensory and motor nerve cells in the central nervous system of an abnormal leech
Authors: Kuffler Damien P. , Muller Kenneth J. 
Published: January 2005

AbstractThe characteristic features of individual neurons in leech ganglia are highly consistent from animal to animal. Hy chance a leech was dis‐ covered that had more cells to be seen than usual in many of its ganglia.In some segmental ganglia of the abnormal animal there were four or even five sensory cells responding independently to touch (T cells) instead of the usual complement of three on each side. Ganglia also contained three or four pressure sensitive cells (P cells) and three or four nociceptive cells (N cells) instead of two of each. The membrane properties, as well as the shapes, sizes, and positions, of all these cells were normal. Their axons reached the skin by the appropriate nerve bundles.Two sensory neurons of one modality, often independently innervated, overlay regions of skin that normally would be supplied by one cell. On the other hand, the areas innervated by some supernumerary cells were abnormal in their shape and position.In some ganglia instead of one motor neuron that raised the skin into bumps (the annulus erector, or AE cell) there were two, each of which could independently erect annuli. The regions innervated by the extra AE cells appeared normal and overlapped extensively.Normal synaptic interactions were found between supernumerary sensory cells and motor cells.The results with this animal indicate that two or more nerve cells can form effective connections with other neurons and with skin that normally would be innervated by a single cell.
Distribution of putrescine, spermidine, and spermine in rhesus monkey brain: Decrease in spermidine and spermine concentrations in motor cortex after electrical stimulation
Authors: Russell Diane H. , Gfeller Eduard , Marton Laurence J. , LeGendre Stephen M. 
Published: January 2005

AbstractPolyamine levels vary markedly throughout the brain of the rhesus monkey. In general, there is an inverse relationship between spermine and spermidine concentrations; i.e., areas with high spermine levels have low spermidine levels and vice versa. The ratio of spermidine to spermine is as high as 13 in the optic nerve, and as low as 1.2 in the vermis. The variability of this ratio suggests that the functions of the polyamines in the adult brain may be different from those in other tissues. For instance, the ratio of spermidine to spermine in adult rat liver and most other organs is approximately 1, and this ratio increases in growth‐stimulated systems. The precursor of spermidine, diaminobutane, is present in very low quantities in the brain. Electrical stimulation of the precentral gyrus was found to decrease the content of both spermidine and spermine, and these data provide further evidence for a separate brain function of the polyamines. Depletion of spermidine and spermine in the motor cortex by electrical stimulation suggests that these amines may be involved in transmission phenomena.
Changes in conduction velocity within a nerve net
Authors: Pickens Peter E. 
Published: January 2005

AbstractConduction velocity within the through‐conducting nerve net of the sea anemone Calamactis praelongus is altered as a result of the passage of one or more impulses. Facilitation of conduction velocity occurs when the second evoked impulse follows the first by less than 2 sec. The facilitating effect increases with decreasing interval between shocks until impulses are less than 0.5 sec apart and then it declines. Antifacilitation occurs when the nerve net is shocked at frequencies between one per 2 sec and one per 20 sec. It is seen also after the first two or three responses when shocks are applied at higher frequencies. Facilitation and antifacilitation increase with spread of excitation. Although the relationship of velocity changes to the behavior of Calamactis has not yet been determined, facilitation of conduction velocity in the net may produce greater synchronization of muscle contraction.
Seizure susceptibility in the developing mouse and its relationship to glutamate decarboxylase and pyridoxal phosphate in brain
Authors: Tapia Ricardo , Pasantes‐Morales Herminia , Taborda Efrain , de la Mora Miguel Pérez 
Published: January 2005

AbstractThe relationship between the susceptibility to convulsions, the content of pyridoxal 5′‐phosphate and the activity of pyridoxal kinase (EC 2.7.1.35) and glutamate decarboxylase (EC 4.1.1.15) in brain, was studied in the developing mouse. Seizures were induced by pyridoxal phosphate‐σ‐glutamyl hydrazone (PLPGH), a drug previously reported to reduce the levels of pyridoxal 5′‐phosphate and as a consequence to inhibit the activity of glutamate decarboxylase in brain of adult mice. It was found that the seizure pattern, as well as the time of appearance of convulsions, differed between 2‐ and 5‐day old mice and 10‐day old or older mice, indicating a progressive increase in seizure susceptibility during development. In brain, pyridoxal kinase activity and pyridoxal 5′‐phosphate levels were decreased by the administration of PLPGH at all ages studied, whereas glutamate decarboxylase activity was inhibited less than 25% in 2‐ and 5‐day old mice, and about 50% thereafter. Parallelly, the activation of glutamate decarboxylase by pyridoxal 5′‐phosphate added in vitro to control homogenates was less in 2‐ and 5‐day old mice than in older animals. It is concluded that the increase in the susceptibility to seizures induced by PLPGH during development is probably related to the increase observed in the sensitivity of glutamate decarboxylase in vivo to a decrease of pyridoxal 5′‐phosphate levels. The correlation between pyridoxal 5′‐phosphate, glutamate decarboxylase, and seizure susceptibility seems to be established at about 10 days of age.
Comparison of lipids in total brain tissue from five mouse genotypes
Authors: Sampugna J. , Clements Janice , Carter T. P. , Campagnoni A. T. 
Published: January 2005

AbstractBrain tissue from adult male and female mice of the C57BL/6J, C57BL/6J‐Aw—J, BALB/cJ, SJL/J, and DBA/2J genotypes was examined for brain weight, total protein, total lipid, cholesterol, phospholipid, plasmalogen, sulfatide, nonganglioside—glycolipid sphingosine, and ganglioside N‐acetyl neuraminic acid, fatty acid, and sphingosine. No significant differences were found between sexes for any of these constituents. When compared to the overall average obtained for other animals, the DBA/2J, C57BL/6J‐Aw−J, and BALB/cJ mice contained lower quantities of nonganglioside—glycolipid sphingosine. The DBA/2J and C57BL/6J‐Aw−J mice also contained lower quantities of plasmalogen and sulfatide compared to the overall averages obtained for the other genotypes. In addition, the sterol content in DBA/2J mice was significantly higher than the overall average value obtained for the other animals.
Physical and physiological properties of the crayfish antennal flagellum
Authors: Taylor Robert C. 
Published: January 2005

Abstract
Mechanoreceptors in the crayfish antennae are divided into four functional categories: vibration (13%), bidirectional displacement (19%), unidirectional displacement (45%), and position (23%) receptors. The distribution of receptors along the length of the flagellum follows a logarithmic progression, decreasing from about 40% at the base to less than 5% at the tip.
Vibratory stimulation of the antennae was found to induce a traveling wave. Because of an impedance gradient along the length of the flagellum, the traveling wave moves most efficiently from base to tip. The wave was observed to travel at an average velocity of 6.0 m/sec.
Large deflections of the tip are not uniformly transferred to the base, but decrease logarithmically. This is due to the existence of the impedance gradient.
Receptor output probability was found to be greatest when low frequency/high intensity stimulation was applied to the flagellar base.
Characteristics of large (2 cm) posterior‐going deflections of the flagellar tip that are effective in producing response differences are displacement: (a) amplitude, (b) velocity, and (c) acceleration.
Beating intraocular hearts: Light‐controlled rate by autonomic innervation from host iris
Authors: Olson Lars , Seiger Åke 
Published: January 2005

AbstractThe sympathetic adrenergic ground plexus of the rat iris is able to innervate whole embryonic hearts transplanted to the anterior eye chamber. The transplants beat continuously from the time of transplantation and for at least five months, initially at 150–200 beats/min, and later approximately 250 beats/min. From seven days postoperatively onwards increased light to the eye produced deceleration while decreased light produced acceleration of the transplants. The rate changes coincided with changes in pupil diameter. Topical atropine reduced the light dependent rate variations of the transplants, especially the dramatic decrease in rate at white light.Waking stress caused a large rate increase. The “waking‐effect” was strongly reduced by sympathetic decentralization and completely abolished by propranolol. The high rate seen in red light was decreased to the low rate of white light by decentralization. Isoprenaline restored red light rate levels in the decentralized transplant.The intraocular heart thus receives a dual functional autonomic input from the host iris and becomes a sensitive monitor of an autonomic nervous activity that can easily be varied at will in a physiological way by changing the light influx to the eye.
Anatomical basis for an apparent paradox concerning conduction velocities of two identified axons in Aplysia
Authors: Pinsker Harold , Feinstein Robert , Sawada Masashi , Coggeshall Richard 
Published: January 2005

AbstractLarger axons usually have faster conduction velocities, lower thresholds, and larger extracellular action potentials than smaller axons. However, it has been shown that the largest fiber, R2, in the right pleurovisceral connective of the marine mollusc, Aplysia, has a higher threshold and a slower conduction velocity than does the smaller axon of cell R1, even though the amplitude of R2's spike is larger than R1's spike. One explanation of this apparent paradox is that the two axons have different “intrinsic membrane and axoplasmic constants” (Goldman, L. (1961), J. Cell Comp. Physiol. 57: 185–191). However, the deep infolding of R2's axonal membrane suggested that differences in the shape of the two axons might also account for the paradox. Accordingly, we measured the conduction velocities of the two axons and then examined the same axons in the electron microscope in order to measure their volumes and surface areas. Our morphological observations indicate that the extensive infolding of surface membrane causes R2 to have a smaller volume to surface area ratio than R1. Thus, since conduction velocity is proportional to the square root of the volume to surface area ratio (Hodgkin, A. L. (1954), J. Physiol. 125: 221–224), it is predictable that the smaller axon would have a faster conduction velocity. The results suggest that the paradoxical conduction velocities can be explained largely as resulting from differences in the shapes of the two axons. However, certain discrepancies between the measured and the predicted values suggest that other factors are contributing as well.
The abdominal ganglion of Aplysia brasiliana: A comparative morphological and electrophysiological study, with notes on A. dactylomela
Authors: Blankenship J. E. , Coggeshall R. E. 
Published: January 2005

AbstractThe ultrastructure and electrophysiological properties of neurons in the abdominal (visceral) ganglion of the marine opisthobranch gastropod Aplysia brasiliana have been investigated to determine whether this preparation compares favorably with the well studied A. californica for neurobiological research. In general, the topography, morphology and physiological characteristics, including synaptic connections, of neurons in this ganglion are quite similar to those of A. californica. There is close correspondence between the two animals in terms of each of the identified cells or neuronal clusters in the ganglion, including the presence of the cell L10 (interneuron I) in A. brasiliana which makes synaptic connections comparable with those in A. californica. New follower cells of this interneuron have been found in A. brasiliana. This species offers some advantages in that the connective tissue surrounding the ganglion is thinner and more transparent, making cell identification and penetration easier. A. brasiliana appears to exhibit the behaviors of A. californica that have been used in previous functional analyses of neural circuits. In addition, this species swims and exhibits a „burrowing”︁ activity less commonly seen in A. californica. The rich repertoire of behaviors and accessibility of large identifiable and functionally interconnected neurons makes this species of Aplysia an excellent model preparation for future neurobiological studies. Similar, less thorough, investigations of the abdominal ganglion of A. dactylomela indicate that this species is also very similar to A. californica in terms of the identified cells in the abdominal ganglion.