bluuebunny/crossref_metadata_2025 huggingface dataset:
Evoked potentials in the central auditory system of alert porpoises to their own and artificial sounds
Authors: Bullock Theodore H. , Ridgway Sam H.
Published: January 2005

A series of 8 experiments is reported in which arrays of 7 or more electrodes on an axis were implanted stereotaxically in Tursiops truncatus. From 1 to 3 of the electrodes were in or near the inferior colliculus or lateral lemniscus.

A total of 39 electrodes out of 130 proved to be responsive to suitable acoustic stimuli. Nine of these lay above the tentorium, 30 in the midbrain above the ventral tegmentum.

The typical midbrain evoked potential is specialized for ultrasonic, ultrabrief, fast rising, closely spaced sounds like the echolocating clicks. It has a short latency and the main deflection is less than 1 ms wide. No potential is evoked if the frequency is below 5 kHz or the rise time above 5 ms.

The typical midbrain evoked potential is specialized for ultrasonic, ultrabrief, fast rising, closely spaced sounds like the echolocating clicks. It has a short latency and the main deflection is less than 1 ms wide. No potential is evoked if the frequency is below 5 kHz or the rise time above 5 ms.

At several cerebral loci a different response was found: long latency, long duration, slowly recovering potentials evoked by frequencies below 5 kHz whether fast or slowly rising. The cerebral “whistle” sensitive loci are probably in the posterolateral temporal cortex.

A few loci at about the tentorial level, probably rostral and lateral to the inferior colliculus gave intermediate or mixed response with some features of each of the previous 2 types.

Implanted, cooperating porpoises were trained to give series of clicks of echolocating types. These evoked potentials like those to artificial tone bursts. Often the highest intensity voluntary clicks evoked quite modest potentials and a much weaker form of click gave maximal potentials. Important differences in click composition are inferred.

Artificial echoes show more rapid recovery following the porpoise's own click than following an artificial conditioning tone burst of equal evoking power.

It has proven practicable to place electrodes with reasonable accuracy, to combine computerized electrophysiological analysis with trained behavior and to maintain chronic implants for at least a month in porpoises. Opportunities for improvements in technique are emphasized.
Transport of radioactivity derived from labeled N‐acetylglucosamine in mammalian motor axons
Authors: Held Irene , Young I. James
Published: January 2005

The distribution of radioactivity in L7 ventral roots after microinjection of N‐acetyl‐3H‐glucosamine into the L7 segment of the feline neuraxis was examined under several conditions; i.e., the isotope was injected before and after ligation of the roots and various periods were allowed for uptake. The results indicated a transport of radiolabeled macromolecular material in both slow and fast components of axoplasmic flow.

Further characterization of the nature of the transported, macromolecular material revealed that more than half of the radioactivity was non‐ultrafilterable even after pronase digestion, only 2% of this activity was incorporated into acidic glycosaminoglycans and the remaining activity was probably derived from glycoproteins.
Zonal centrifugation and flotation– fractionation of MSD mutant mouse brain
Authors: Day Eugene D. , Mickey Don D. , Rigsbee Lewis C. , Meier Hans
Published: January 2005

Zonal centrifuge and flotation–fractionation profile analysis of neonatal mouse brain homogenates in iso‐osmotic Ficoll–sucrose density–gradients demonstrates the presence of four light density fractions. In msd neurological mutant mice with a myelin‐synthesizing deficiency syndrome, the bands appear to be relatively normal until after the 10th day of postnatal brain development. With the onset of visible neurological symptoms after the 11th day, the four density bands begin to disappear from the zonal profiles and are all but absent at the time of death at about the 21st postnatal day. In normal littermates of the mutants, the bands persist with age and intensify. Although their identities remain unknown, the top three identify by their density with adult myelin and the fourth with the lighter of two adult synaptosome fractions. Mixtures of brain homogenates between mutant and normal littermates give rise to zonal and banding profiles intermediate between the separate profiles but somewhat less than their average in intensity.
Characterization of fast and slow transported proteins in dorsal root and sciatic nerve of cat
Authors: Sabri M. I. , Ochs S.
Published: January 2005

Labeled components, carried by axoplasmic transport into the cat dorsal roots and sciatic nerves following injection of 3H‐leucine into the lumbar seventh (L7) dorsal root ganglia, were studied. The pattern of activity present in the subcellular fractions was similar for the two branches of the ganglion neurons entering the nerve and the dorsal root.

Fractionation of the proteins present in the high speed supernatant fraction shows that slow transport carries a major proportion of high molecular weight soluble proteins. Further fractination of the soluble proteins with Sephadex G‐200 showed labeled activity present in three peaks: Ia, proteins of 480,000 M. W., lb, proteins of 60,000–120,000 M. W. containing colchicine binding (microtubular) protein, and peak II polypeptides, 5,000–10,000 M. W.

Isoelectrofocusing of la proteins gave three peaks at pl 4.0, 4.05, and 4.15, and of lb proteins gave peaks at pl 4.0, 4.45, and 4.8 with several minor peaks also present. A gradual shift in pl values of the labeled proteins from acidic to neutral pH was seen from 3 hr to 7 days after the injections.

A small amount of soluble proteins and some free leucine is carried down by fast transport, which is characterized by a high amount of activity in the particulate component. A comparison of the distribution of labeled incorporation in the crest and plateau region of fast transported materials showed a somewhat smaller percentage of activity in the small particulate fraction in the plateau, with more labeling of the soluble fraction and with no free leucine present.

The results are in conformity with the concept of a compartmentalization of incorporated proteins in the cell body from which materials of somewhat different compositions later enter the axon for transport.
Neural mechanisms underlying behavior in the locust Schistocerca gregaria III. Topography of limb motorneurons in the metathoracic ganglion
Authors: Burrows Malcolm , Hoyle Graham
Published: January 2005

Somata of 26 of the motorneurons situated on the right side of the metathoracis ganglion of the locust S. gregaria were identified by correlating their electrical activity with extracellularly or intracellularly recorded muscle potentials evoked either reflexly or by direct elctrical stimulation of the somata through the recording microelectrode. The neurons identified included most of those innervating the major leg muscles. Each neuron occupies a relatively fixed site on the ventral surface of the ganglion. The identified neurons were filled with procion yellow, the ganglia fixed and photographed as whole mounts, and then serially sectioned to determine the three dimensional topography of the major dendrites and the pathway of the axons through the neuropil. The topographical features of individual motorneurons were sufficiently characteristic to permit identification, Nevertheless, it was not found possible to classify the neurons on the basis of branching pattern. There is no relation between location in the ganglion and the muscle innervated, but locomotor motorneurons are clustered togethers in anterior, ventral, and lateral pockets.
The neuronal basis of behavior in Tritonia. I. Functional organization of the central nervous system
Authors: Willows A. O. D. , Dorsett D. A. , Hoyle G.
Published: January 2005

An account is presented of the brain (paired cerebral, pleural, and pedal ganglia) of the nudibranch mollusc Tritonia diomedia. The major efferent nerve fibers are related to their nerve cell bodies and their functional roles identified as far as possible. The channels of sesory input relating to some of these neurons are given so as to provide an overall view of the organization of the brain.

A standardized system of abbreviation and notation for the central ganglia, nerve trunks, and gaint somata is proposed. The system of references is intended to provide a guide to the location in the ganglia of many of the smaller neurons of which the functional attributes are known, but which cannot be consistently recognized on visual criteria alone. A system of rectangular coordinates is proposed which is applied to the natural outline of the ganglia. In addition, a system of cell notation is described which is independent of the co‐ordinates used to define the position of the cell on the grid. Cell which by reason of their size, pigmentation, characteristic location and physiological attributes are consistently recognizable from animal to animal are numbered. Two principles were followed in numbering cells; (i) the series begins at unity in each ganglion; (ii) cell homologues in opposite ganglia are given the same number, but distinguished by prefixing the abbreviation for the ganglion in which they occur. It is considered that the system will facilitate the exchange of information between workers on the same species, and also benefit the comparison of neural organization of behavior in closely related forms.

The brain is organized in an almost exactly bilaterally symmetrical manner. There are a few bilateral neural pathways, but the major functional routes are ipsilateral. A few motorneurons, which are uniquely identifiable anatomically, cause unique, discrete movements. Others are in small groups sharing overlapping or similar functions.
Transport of sulfate in the rabbit's brain
Authors: Hollingsworth Jillian G. , Davson H.
Published: January 2005

The possibility that, in the rabbit, sulfate is actively transported across the choroid plexuses was investigated by ventriculo‐cisternal perfusion in the absence and presence of carrier. No evidence for this could be found.

Penetration of sulfate from blood to brain and CSF was measured in the intact animal equilibration was very slow, indicating the presence of high barriers for this solute, but the low steady‐state level in the brain, approached in these experiments, was quite consistent with slow passive permeability aacross the barriers, with free exchange between extracellular fluid and CSF. The clearance of another slowly penetrating solute, creatinine, from the perfusion fluid during ventriculo‐cisternal perfusion was comparabl with that of sulfate.
Neurite development in vitro: II. The role of microfilaments and microtubules in dibutyryl adenosine 3′,5′‐cyclic monophosphate and nerve growth factor stimulated maturation
Authors: Roisen Fred J. , Murphy Richard A.
Published: January 2005

Dibutyryl cyclic AMP (DBC) and Nerve Growth Factor (NGF) have both been shown to enhance in vitro neuronal maturation in embryonic sensory ganglia. Since microfilaments and microtubules are known to be involved in neurite elongation, embryonic chick dorsal root ganglia have been treated with cytochalasin B and colcemid in the presence of these growth promoters (DBC or NGF). Established 48‐hr cultures show drastic neurite retraction when treated with either inhibitor. The treatment of cultures with DBC or NGF in the presence of colcemid reverses the inhibitive effects and normal elongation occurs. The growth stimulators, however, are unable to effectively reverse the action of cytochalasin B. These data suggest that increased microtubule assembly is involved in DBC and NGF stimulation of neurite elongation, and hence provide further support for the suggestion that cyclic AMP mediates some of the actions of NGF.
Morphological and enzyme histochemical studies of dissociated chick neural tube cultured in vitro
Authors: Kim Seung U. , Wenger Eleanor L.
Published: January 2005

Neural tubes from Hamburger‐Hamilton Stage 14–18 (50–68 hr incubation) chick embryos were dissociated by exposure to trypsin and cultured in Maximow double coverslip assemblies for up to 155 days. Undifferentiated neural tube cells continued to differentiate into large multipolar neurons with the features characteristic of mature neurons.

Choline acetyltransferase and acetylcholinesterase activity, enzymes responsible for synthesizing and catabolizing acetylcholine transmitter in neurons, were demonstrated histochemically in neurons differentiated from early neural tube cells, indicating the development of these cells into biochemically mature neurons.

It is concluded that the disruption of the tissue integrity of the neural tube does not interfere with the morphological and biochemical differentiation potencies of the neural tube cells in tissue culture.
Isolation and ultrastructure of human synaptic complexes
Authors: Wannamaker Braxton B. , Kornguth Steven E. , Scott Grayson , Dudley Alden W. , Kelly Alma
Published: January 2005

Intact synaptic complexes were isolated from five human cerebral cortices obtained 4–20 hr after death. Synaptic complexes had a common isopycnic banding density of 1.17–1.20 in CsCl. Their banding densities and ultrastructural features were similar to those of complexes isolated from a variety of other mammalian species. The ultrastructure of the synaptic complexes isolated from different aged subjects (2, 3, 28, 76, and 78 years old) were similar.
Histology and histochemistry of the peripheral neural plexus in the Aplysia gill
Authors: Peretz Bertram , Estes Jane
Published: January 2005

The neural plexus in the Aplysia gill is comprised of monopolar, bipolar, and multipolar neurons. Histochemical procedures reveal acetycholinesterase (AChE), serotonin (5HT), and possibly dopamine present in plexus neurons. The three cell morphologies in the plexus are found in specific regions of the gill. Monopolar cells singly and in clusters lie along branches of the branchial and ctenidial nerves. The largest cluster, the gill ganglion, is located on the branchial nerve; ganglion neurons show a marked similarity to neurons in the central nervous system. AChE is present in monopolar neurons; its presence was demonstrated using acetylthiocholine as a substrate with inhibitors specific for esterases other than AChE. Monoamines are also contained in monopolar cells; yellow and green fluorescence, resulting from exposure to paraformaldehyde vapor, indicated that 5HT and catecholamines, respectively, are present in the cells. Bipolar neurons, containing AChE, are located beneath the ciliated epithelium in the pinnule. Multipolar, monopolar, and bipolar cells are found in the gill musculature. Single neurons appear to innervate at least two muscle bundles. Evidence is also presented suggesting that cells containing different neurotransmitters can terminate in the same muscle. Acetylcholine, 5HT, and dopamine, when infused in the gill, elicited discernable movements for each agent. The plexus, with its apparent hierarchy of neurons, has a number of properties ascribed to the central nervous system. The hierarchy is discussed in relation to the physiology of plexus neurons and to the behavior manifested by the gill.
After effects of spikes in cockroach giant axons
Authors: Dagan D. , Parnas I.
Published: January 2005

Cockroach abdominal giant axons (AGF) demonstrate a period of hyperexcitability following a spike; namely, an ineffective, subthreshold stimulus becomes effective if it occurs 5 to 100 msec after a spike. This phenomenon appears not to be synaptically mediated since it is not affected by high Mg2+ low Ca2+. It is likely that the normally subthreshold pulses summate with the negative after potential of a preceding spike. Hyperexcitability was found in the fine terminals of the AGF in the head and in the last abdominal and thoracic ganglia. It does not occur in the five smaller abdominal ganglia or connectives. The hyperexcitability of the AGF may be functional. Sensory inputs from one cercal nerve, when activating the AGF, increase the sensitivity to following inputs from the same or the second cercal nerve for periods much longer than the EPSP (100–120 msec).
Biochemical and physiological properties of a purified snake venom neurotoxin which acts presynaptically
Authors: Kelly Regis B. , Brown Frank R.
Published: January 2005

A highly toxic protein has been isolated from the venom of the snake Bungarus multicinctus. No major contaminants were detected on isoelectric focusing, gel filtration, or gel electrophoresis. The molecular weight calculated from its amino acid composition (21,800) agreed well with that calculated from gel filtration and equilibrium sedimentation data. Gel electrophoresis showed that the toxin consisted of two subunits of molecular weight 8,800 and 12,400 held together by disulfide bonds. Both the structure, determined by circular dichroism, and the biological activity, determined by toxicity assay, were remarkably resistant to heating.

In the rat phrenic nerve‐diaphragm preparation, the toxin caused a failure of neuromuscular transmission, after which subthreshold endplate potentials could be detected. The frequency of spontaneous miniature potentials was altered only to a very slight extent. The toxin appeared to have no postsynaptic activity. Similarities between the properties of this neurotoxin and that described by Lee and Chang (1966) suggest that it is identical to β‐bungarotoxin.
Intracellular generated potentials during excitation‐contraction coupling in muscle
Authors: Strickholm Alfred
Published: January 2005

The initiation of frog muscle contraction by surface membrane depolarization was investigated by the local passive voltage clamp technique. Contractions are locally confined to the region below the excited surface membrane and ordinarily involve the entire sarcomere diameter in summer fast fibers. In contrast, fibers of winter hibernating frogs show graded contractions with limited inward spread. The depolarization strength‐duration relation for contraction initiation appears hyperbolic and has a contraction threshold around –50 mV membrane potential. When rapid local muscle contraction is initiated, an intracellular generated potential (IGP) of several millivolts is observed which starts after surface membrane excitation and initiates before contraction. The time course of the IGP parallels the time course of contraction in summer fast fibers and has three components; a pre‐potential, an early and a lite depolarization. These intracellular potential changes are interpreted as resulting from excitation of the transverse tubular structures and the sarcoplasmic reticulum.
Memory evoked optomotor responses in crustaceans
Authors: Wiersma C. A. G. , Hirsh Richard
Published: January 2005

Optomotor memory in crustaceans was studied by recording the activity of optomotor neurons. Animals were placed in a stationary striped drum, which was subsequently turned in the dark to a new position. Upon reillumination the eye movements of the animals follow the apparent movement of the stripes. It can be inferred that the position of the stripes after movement is compared with the remembered position of the stripes before movement.

The size and sign of the memory response of the optomotor neurons are functions of the apparent movement. Changes as small as 0.1° can be detected. Memory starts forming almost immediately upon exposure of a position and develops as a function of viewing time. While a new memory is forming, the old one, though declining, is still present for 30 sec. In the dark a memory declines gradually, lasting for more than 8 min. In certain circumstances the set point of memory is adjusted for the effects of eye movements.

The possibilities that memory involves a peripheral afterimage or stabilization of a particular part of the eye upon a particular feature of the surroundings are considered.
The in vitro polymerization of tubulin from beef brain
Authors: Lee Young C. , Samson Frederick E. , Houston L. L. , Himes Richard H.
Published: January 2005

The conditions for the in vitro polymerization of beef brain tubulin have been examined using turbidity and electron microscopic examination as methods of following the reaction. The optimal conditions are 37°, pH 6.0‐‐6.4, and an ionic strength of approximately 0.08 to 0.1 μ. The ionic strength is particularly critical, at 0.25 μ the polymerization does not occur and increasing the ionic strength of a solution contaning microtubules to this value causes the tubules to depolymerize. GTP and Mg2+ are required. After an initial lag period the rate of polymerization appears to follow first‐order kinetics. Although colchicine inhibits the polymerization reaction it does not cause the tubules formed in vitro to depolymerize. Binding studies show that colchicine binds to free tubulin better than to tubules. Calcium also inhibits polymerization and causes the depolymerization of tubules.
Gel filtration of myelin using 2,2,2‐trichloroethanol as the solvent
Authors: Wolfgram Frederick , Myers Lawrence
Published: January 2005

The use of 2, 2, 2‐trichloroethanol as a solvent for myelin from both the central and peripheral nervous systems is described. Concentrated, optically clear solutions of lyophilized myelin in this solvent are stable for weeks. The preparation of highly concentrated myelin proteins by gel filtration in trichloroethanol is described.
Functional characterization of types of plasma membranes in cerebral cortex
Authors: Malhotra S. K. , Tewari J. P. , Tu J. C.
Published: January 2005

The cerebral cortex of normal oxygenated and of asphyxiated mice has been studied by freeze‐fracturing technique with a twofold purpose. First, to investigate changes, if any, in the molecular organization of the plasma membrane of any specific cell type(s) that could be correlated with permeability changes thought to take place as a consequence of asphyxiation. Secondly, to attempt characterization of plasma membranes on the basis of the organization of their fractured faces. The decrease in the extracellular material in asphyxiated cerebral cortex seen in electron micrographs of thin sections could not be correlated with change(s), if any, in the molecular organization of the plasma membrane of any particular cell type. Plasma membranes of various types could be characterized on the basis of the arrangement of particles on the fractured faces. Some of these types correspond to identifiable cell processes, while others have not yet been identified with certainty. Fusion of synaptic vesicles with the presynaptic membrane is mediated through clustering of 100–150 Å membrane‐associated particles.
Low temperature slowing and cold‐block of fast axoplasmic transport in mammalian nerves in vitro
Authors: Ochs S. , Smith Carolyn
Published: January 2005

1) Fast axoplasmic transport in mammalian nerve in vitro was studied using an isotope labeling technique. The rate of outflow in cat sciatic nerve fibers of 410 mm/day in vitro was reduced at temperatures below 38°C with a Q10 of 2.0 in the range 38–18°C and a Q10 of 2.3 at 38–13°C. 2) At a temperature of 11°C a partial failure of transport occurred. At temperatures below 11°C a complete block of fast axoplasmic transport occurred, a phenomenon termed “cold‐block.” No transport at all was seen over the temperature range of 10–0°C for times lasting up to 48 hr. 3) Transport was resumed after a period of cold‐block lasting up to 22 hr when the nerves were brought back to a temperature of 38°C. Some deleterious effects due to cold‐block were seen in the recovery phase as indicated by a reduction in crest amplitude, change in its form, and slowed rate. 4) The ∼P level (combined ATP and creatine phosphate) remained near control level in nerves kept at low or cold‐block temperatures for times as long as 64 hr. The reduction in fast axoplasmic transport rate seen at low temperatures for times up to 22 hr was therefore considered due to a decrease in the utilization of ATP, a concept in accord with the “transport filament” model proposed to account for fast axoplasmic transport. 5) The sloping of the front of the crest over the temperature range of 18–13°C suggests an additonal factor at the lower temperatures. A disassembly of microtubules is discussed as a possible explanation of the cold‐block phenomenon.
On the organization of memory in the optomotor system of the crab pachygrapsus crassipes
Authors: Wiersma C. A. G. , Hirsh Richard
Published: January 2005

Memory responses of the optomotor system to rotations of various stripe patterns were studied. The separate elements of the visual background are individually remembered in terms of the parts of the eye on which their images fell. A visual illusion resulting from this property is described.

All parts of the retina have an equal capacity to contribute to memory. The memory response results from the summation of contributions from individual elements rather than the maintenance of a fixation upon any particular feature of the situation. Both the separation between background elements for angles from 6° up to 60° and the number of elements present affect the size of the memory evoked response.
Viability of some metabolic processes in the isolated toad brain adapted to two osmotic environments
Authors: Shank R. P. , Whiten J. T. , Baxter C. F.
Published: January 2005

The viability of the isolated toad brain in an aerated Ringer‐like medium has been evaluated by the following criteria: 1) amino acid content before and after incubation; 2) accumulation of amino acids in the incubation medium; 3) a comparison of glucose utilization and [U‐14C]glucose metabolism with that occurring in vivo; 4) tissue swelling; and 5) tissue lactate content.

On the basis of these criteria, the isolated toad brain, from toads adapted to a fresh‐water or a salt‐water environment, retains considerable metabolic integrity for at least 2 hr of incubation at 25° C. Specifically, there was no swelling of the tissue, no apparent accumulation of lactate in the tissue, glucose appeared to be utilized at a rate not too different from that calculated for the toad brain in vivo, and the distribution of label from [U‐14C]glucose had an overall pattern which resembled that observed in vivo.

The tissue levels of amino acids were generally stable in vitro; however, there was a marked decline in the content of aspartate. The accumulation of amino acids in the medium varied considerably from one amino acid to another. Thus, there was very little net efflux of aspartate, GABA, and glutamate from the tissue but considerable net efflux of glutamine. This efflux of amino acids was greater from brains of hyperosmotically adapted toads than from the brains of toads adapted to fresh water by amounts proportional to their initial tissue contents.
Habituation and dishabituation mediated by the peripheral and central neural circuits of the siphon of aplysia
Authors: Lukowiak Kenneth , Jacklet Jon
Published: January 2005

The siphon withdrawal response evoked by a weak tactile (water drop) or light stimulus is mediated primarily by neurons in the siphon. Central neurons (abdominal ganglion) contribute very little since the response amplitude and latency are not changed following removal of the abdominal ganglion. Similarly, habituation and dishabituation of this withdrawal response are not different after removal of the abdominal ganglion, indicating that the peripheral neural circuit in the isolated siphon can mediate habituation itself, and thus has many of the properties attributed to central neurons. Responses evoked by electrical stimulation of the siphon nerve habituate, depending upon the stimulus intensity and interval. These habituated responses may be dishabituated by tactile or light stimulation of the siphon. These results show that each neural system, peripheral and central, has an excitatory modulatory influence on the other. Normally adaptive siphon responses must be shaped by the integrated activity of both of these neural systems.
Electrophysiological properties of biventer cervicis muscle fibers of normal and roller pigeons
Authors: Entrikin Richard K. , Bryant S. H.
Published: January 2005

Cable parameters, excitability characteristics, and contractile response to acetylcholine were measured in biventer cervicis muscles from Helmet pigeons, Racing Homer pigeons and Parlor (nonflying) Roller pigeons. Cable parameters for the three strains, were respectively: calculated diameter, 30.1, 42.5, and 37.3 m̈m; membrane resistance, 450, 556, and 386 ω · cm2; membrane capacitance, 4.2, 3.9, and 4.5 m̈F/cm2, and myoplasmic resistivity, 79, 185, and 116 ω · cm. Significant differences between excitability characteristics of Homer pigeon and Roller pigeon fibers were a 17% shorter maximal latency for spike initiation (P < 0.025) and 24% lower rheobasic current (P < 0.05) in Roller fibers. Doseresponse curves of isolated biventer cervicis to acetylcholine revealed slight, but significant, differences between Helmets and Rollers.

These are the first electrophysiological data from pigeon skeletal muscle and the first from any avian biventer cervicis. The biventer muscles of chickens contain mainly “slow” fibers, but our results show that pigeon biventer fibers have properties similar to the “fast” PLD fibers of the chicken. Furthermore, the existence of different myoplasmic resistivities for each strain of pigeons used in this study suggests the need for more careful determination of this parameter in electrophysiological investigations.

Although our results show that Roller pigeon fibers differ from those of nonrolling pigeons in the respects described above, these differences are minor in comparison to the severe behavioral abnormalities of Roller pigeons. Some yet untested component of neuromuscular transmission may be directly involved in the rolling phenomenon, but the differences we report may simply be due to strain differences, muscle hypertrophy, or a more severe defect elsewhere in the nervous system.
Ultrastructural correlates of interneuronal function in the abdominal ganglion of Aplysia californica
Authors: Gillette Rhanor , Pomeranz Bruce
Published: January 2005

The synaptic inputs and outputs of the major interneuron L10 of the abdominal ganglion of Aplysia were studied using an intracellular staining technique for the electron microscope. The sites of both the chemical synaptic input and output of L10 are localized to the dendritic arborizations that arise from the axon in the ganglion neuropil. Thus, the interneuronal functions are mediated at the dendritic processes and could occur in the absence of spiking in the axon and cell body. The sites of L10 synaptic output are presumed to be at. aggregations of vesicles and mitochondria in the dendrites. The synaptic vesicle content of L10, a cholinergic neuron, with many large dense vesicles resembles that described for serotonergic cells in Aplysia, making distinction of synaptic pharmacology by ultrastructure difficult. Focal membrane specializations with a clear synaptic cleft were not observed between L10 and its large population of postsynaptic cells. In contrast, clear focal input sites were frequently found on L10. Gap junctions, sites of probable electrical coupling between L10 and other neurons, were also found. These observations are discussed as evidence that many synapses do not have focal specializations.
Spontaneous bioelectric activity of cultured purkinje cells during exposure to glutamate, glycine, and strychnine
Authors: Gäuhwiler B. H.
Published: January 2005

The addition of glutamate to the bathing medium increased the average firing rate of cerebellar rat Purkinje cells in vitro. At concentrations lower than 10−6 M, there was no deviation from controls in the firing pattern or rate that was detectable. At 10−3 M glutamate, the amplitude of the action potentials was gradually decreased until all activity was abolished. The action of glutamate was rapid in onset and reversible. Glycine produced sustained depression of firing at concentrations higher than 10−3 M. This inhibition was strychnine‐insensitive and considered nonspecific. Strychnine, on the other hand, exerted an excitatory influence on Purkinje cells when applied at low concentrations (10−8 to 10−6 M). The firing became more irregular and complex discharges appeared. Higher concentrations of strychnine (>10−5 M) inhibited the spontaneous activity. The effect of strychnine was partly reversible. The data suggest that low concentrations of strychnine lower the threshold for inputs at excitatory as well as inhibitory synapses.
The metabolism of adenine derivatives in different parts of the brain of the rat, and their release from hypothalamic preparations on excitation
Authors: Sun Man‐Chi , McIlwain Henry , Pull Ian
Published: January 2005

Five enzymes concerned with the metabolism of adenine derivatives were assayed in seven regions of the rat brain. A region which included the hypothalamus had the highest AMP deaminase and adenosine deaminase activities, while its 5'‐nucleotidase activities were relatively low. The enzymes named and also the uptake of [14C]adenine by incubated tissue samples were more active with hypothalamic than with neocortical tissues. On superfusion with glucose‐bicarbonate saline after assimilating [14C]adenine, the hypothalamic tissues released about 0.2% of their 14C content per minute. This release was increased fourfold with electrical excitation but the presence of 0.25 μUM tetrodotoxin prevented most of this increase. The compounds released during superfusion and electrical stimulation were preponderantly hypoxanthine, inosine, and adenosine, with only small amounts of adenine nucleotides. The output of all these compounds increased during the period of stimulation and also the proportion of adenine nucleotides increased when stimulation was carried out in the presence of tetrodotoxin. The output of the nucleotides and adenosine increased more promptly when stimulated than did that of the other compounds named. The results are discussed in terms of the metabolic roles of the enzymes concerned, and in relation to whether the enzymes are acting on intracellular or extracellular substrates.
Membrane marker movement on sympathetic axons in tissue culture
Authors: Koda L. Y. , Partlow L. M.
Published: January 2005

In cultures of dissociated chick sympathetic ganglia, retrograde (somatopetal) movement of concanavalin A receptors in the axolemma can be observed directly. Such movement was visualized by using concanavalin A coated red blood cells (ConA‐RBCs) as membrane markers. Forty‐eight percent of all ConA‐RBCs which bound to sympathetic nerve fibers moved somatopetally at rates ranging from 11‐84 μ/hr with a mean and standard error of 49 ± 6 μ/hr (n = 18). On nongrowing nerve fibers, the ConA‐ RBCs within 60 μ of the cell body showed retrograde movement, while on elongating neurites only those markers within 30 μ showed such movement. The rate of retrograde ConA‐RBC movement appeared to increase with distance from the cell soma. The binding of ConA‐RBCs to sympathetic neurites was specific for concanavalin A receptors since pretreatment with either concanavalin A or α‐methylglucopyranoside prevented this binding. Untreated polystyrene beads (1.1 μ) which bound nonspecifically to the neurite membrane also showed retrograde movement. These beads moved somatopetally at rates similar to those of the ConA‐RBCs but did so regardless of their initial distance from the soma. These data suggest that retrograde movement of surface elements might be a general property of cultured sympathetic nerve fibers.
Velocity measurements of particulate neuroplasmic flow in organized mammalian CNS tissue cultures
Authors: Leestma Jan E.
Published: January 2005

The 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

Membrane 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

The 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

Postsynaptic 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

N‐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

The 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

The 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

Mitosis 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.