bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphological and enzyme histochemical studies of dissociated chick neural tube cultured in vitro
Authors: Kim Seung U. , Wenger Eleanor L. 
Published: January 2005

AbstractNeural 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

AbstractIntact 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

AbstractThe 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

AbstractCockroach 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

AbstractA 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

AbstractThe 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

AbstractOptomotor 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

Abstract1) 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

AbstractMemory 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

AbstractThe 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

AbstractThe 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

AbstractCable 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

AbstractThe 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

AbstractThe 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

AbstractFive 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

AbstractIn 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.