bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructural differentiation during drosophila neurogenesis in vitro
Authors: Gerson Ines , Seecof Robert L. , Teplitz Raymond L. 
Published: January 2005

AbstractDrosophila melanogaster neuroblasts differentiate in vitro, and each gives rise to a cluster of about 18 daughter neurons. Electron microscopic observations of single clusters show that axons from daughter neurons form a neuropile within the cluster of cell bodies. The neuropile increases in size and complexity for several hours, during which time chemical, and probably electrotonic, synapses form between neurites. Clear vesicles with diameters of about 35 nm and dense core vesicles with diameters of about 60 and 160 nm were detected. The development of the neuropile indicates that the prerequisite cell recognition phenomena were manifested during differentiation in vitro, and the complexity of the neuropile suggests it may have attained the capacity to process information.
Characterization of the postnatal development of superior laryngeal nerve fibers in the postnatal kitten
Authors: Miller Arthur J. , Dunmire Carole R. 
Published: January 2005

AbstractA combined electron microscopic and electrophysiological study of the superior laryngeal nerve (SLN) was undertaken in postnatal kittens ranging in age from 1–63 days. The superior laryngeal nerve is predominantly a sensory nerve innervating the upper respiratory tract, and could play a potential role in the modulation of respiration, particularly in the infant animal. Distribution of fibers in the developing SLN indicates that within the first postnatal month, 75% of the fibers are unmyelinated, and by 42 days, the myelinated fibers increase in number to approximately 50%. Of the myelinated fibers present in the one day old kitten, 3–4% of those exceeded 4 μm in total diameter, which is the minimum diameter for normal conduction velocity of action potentials. The distribution of the diameter sizes of the myelinated fibers is bell‐shaped within the first 45 days after which the curve becomes skewed to the right (43–61 days; mean 2.6 μm, range 0.5–8.0 μm) to resemble the adult distribution of myelinated fibers (mean 4.2 μm, range 1.6–13.0 μm). Two variable plots of myelin width to axon diameter suggest a steeper slope for developing fibers as compared to that of the adult fibers. Electrical stimulation of the sectioned SLN indicates that evoked potentials could be recorded from the recurrent laryngeal nerve innervating the laryngeal intrinsic muscles and from the hypoglossal nerve to the tongue musculature in the youngest kittens tested (i.e., age 9 days). Stimulation at selected frequencies of 3 and 30/sec readily evoked apnea in the youngest kitten studied (i.e., age 5 days), while swallowing was more readily evoked at 28–30 days when using electrical stimulation.
Regional differences of respiration in the bullfrog brain based on cell density
Authors: Potter Richard L. 
Published: January 2005

AbstractThe comparison of analogous and homologous regions of the anuran and mammalian brains, according to their rate of oxygen uptake per unit weight of DNA, has revealed a lack of correspondence between the respective brain regions. This discrepancy between corresponding regions was observed during incubation either in low‐potassium or in high‐potassium Ringer. Per unit weight of DNA, the rate of cellular respiration in the amphibian hindbrain exceeded that of the thalamus‐midbrain, and cells in the latter region exceeded those in the telencephalon. Hindbrain values were only higher if based on unit weight of DNA, and were actually lower on a wet weight basis. This pattern contrasted with a uniform rate of oxygen consumption for the homologous regions of the mammalian brain. Such inequalities between the regional brain metabolism of two different classes of vertebrates clearly illustrate the unique evolutionary history of both forms.The intensity of potassium‐stimulated oxygen uptake in the three brain regions of the amphibian was interpreted as probably being proportional to the number of glial cells in each area. The smallest percentage of stimulation in the hindbrain may signify fewer glia, and the highest percentage of stimulation in the mid‐ and forebrain may indicate more numerous glia. Histological descriptions of ependymal glia in consecutive regions of the anuran brain appear to confirm this distribution of non‐neuronal cells.
Primitive nervous systems: Peripheral habituation in decerebrate polyclad flatworms
Authors: Bernardo K. , Stone G. C. , Koopowitz H. 
Published: January 2005

AbstractThe response to a vibration stimulus recorded from the cords of the ventral submuscular plexus of the polyclad flatworm, Notoplana acticola, consists of a burst of action potentials. The response can be abolished by the application of MgCl2 to the sea water bathing the preparation. With repeated application of the stimulus, decreasing numbers of action potentials can be measured. This waning responsiveness can be dishabituated by applying a more intense vibration stimulus or with electrical shocks applied directly to the ventral nerve plexus. With electrical stimuli a number of shocks have to be applied before the response can be dishabituated. Changes in responsiveness can be measured simultaneously in a number of sites in the plexus even after the nerves between recording sites have been severed. With different interstimulus intervals the extent of habituation changes. As interstimulus intervals increase from 1 to 5 sec, there appears to be a decrease in responsiveness which recovers when interstimulus intervals become longer than 5 sec.
The presence of transfer RNA in the axoplasm of the squid giant axon
Authors: Black M. M. , Lasek R. J. 
Published: January 2005

AbstractPrevious work has revealed that 4S RNA is the primary species of RNA in the axoplasm from the giant axons of the squid and Myxicola. This study shows that axoplasmic 4S RNA from the squid giant axon has the functional properties of tRNA. Axoplasmic RNA was charged with amino acids by aminoacyl‐tRNA synthetases prepared from squid brain. The aminoacylation was prevented by incubating the RNA with RNase prior to running the reaction. The amino acid‐RNA complex was labile at pH 9, which is characteristic of the acyl linkage between an amino acid and its tRNA. Aminoacyl‐tRNA synthetase activity was also present in the axoplasm, primarily in the soluble fraction.
Direct comparison of the rapid axonal transport of norepinephrine and dopamine‐β‐hydroxylase activity
Authors: Brimijoin Stephen , Wiermaa Mary Jo 
Published: January 2005

AbstractStop‐flow techniques were used to examine the rapid axonal transport of norepinephrine in rabbit sciatic nerves. When the midpoint of a nerve incubated in vitro was cooled to 2°C while the remainder was kept at 37°C, norepinephrine accumulated proximal to the cooled region at a rate corresponding to an average transport velocity between 5 and 6 mm/hr in a distal direction. Since only about half of the norepinephrine appeared to be free to move, the mean velocity of the moving fraction was probably twice as great. No norepinephrine accumulated distal to a broad cooled region under conditions in which there would have been a significant accumulation of dopamine‐β‐hydroxylase activity. Therefore, unlike dopamine‐β‐hydroxylase, norepinephrine may not be subject to rapid retrograde transport. When nerves that had been locally cooled for 1.5 hr were rewarmed uniformly to 37°C, a wave of norepinephrine moved exclusively in a distal direction. The peak of this wave moved at a velocity of 12.2 ± 0.5 mm/hr or 293 ± 12 mm/day; the front of the wave moved at about 18 mm/hr. or 430 mm/day; and the tail probably moved faster than 6 mm/hr. This spectrum of velocities was virtually identical to the one displayed by the wave of dopamine‐β‐hydroxylase activity that was generated under the same conditions. Our results are consistent with the conclusion that all axonal structures containing norepinephrine also contain dopamine‐β‐hydroxylase, but they are not consistent with the converse.
Release of acetylcholinesterase by cultured spinal cord cells
Authors: Oh Tae H. , Chyu Juliana Y. , Max Stephen R. 
Published: January 2005

AbstractThe release of acetylcholinesterase from neurons was studied using cultured chick‐embryo spinal‐cord cells. Cells dissociated from 12‐day‐old chick‐embryo spinal cords were grown in culture for 10–12 days. Numerous well differentiated spinal neurons were found after 7–10 days in culture. Acetylcholinesterase activity per dish increased by 60‐fold from days 2–12. Acetylcholinesterase was released into the surrounding media by the cells when they were incubated either in the standard culture medium or the serum‐free medium. Acetylcholinesterase release was significantly reduced when protein synthesis and microtubules were disrupted by cycloheximide and colchicine, respectively. Histochemical localization of acetylcholinesterase indicated that the synthesis and release of acetylcholinesterase are attributable to neurons. Cultured chick‐embryo brain and neuroblastoma cells also released acetylcholinesterase into the media. These results are discussed with regard to possible physiological roles for acetylcholinesterase secretion from neurons.
Thermosensitivity of single units in the hypothalamus of the conscious pekin duck
Authors: Simon E. , Hammel H. T. , Oksche A. 
Published: January 2005

AbstractAdult Pekin ducks were chronically equipped with a thermode device which allowed local thermal stimulation and simultaneous single‐unit recording in the hypothalamus of the conscious animals during a period of up to three months. In two animals the activities of 29 single units were recorded extracellularly for sufficient time to measure static firing rates as a function of local temperature ranging from 32° to 42°C. Eleven units could be classified as warm sensitive, five units as cold sensitive, five neurons were insensitive to repeated local cooling and heating, and eight were variably active but not correlated with local temperature. The results indicate that the percentage of thermosensitive neurons in the hypothalamus of the two ducks may have been higher than the percentage found in several cats, rabbits, and dogs. The warm sensitive units recorded in the two ducks and additional 6 hypothalamic warm units found in three other ducks exhibited Q10 values between 2 and 17 with a mean of 4.8 · 4.3 s.d., i.e., their sensitivities were equal to those of warm‐sensitive neurons recorded in the hypothalamus of mammals. Thermoreceptivity has been attributed to the thermosensitive neurons in the rostral brainstem of mammals, since heating this tissue increases the rate of heat loss whereas cooling the same tissue reduces the rate of heat loss and increases the rate of heat production. In ducks, and penguins as well, cooling the rostral brainstem does not induce shivering or vasoconstriction but only inhibits metabolism and vasoconstriction. Thermosensitivity of a neuron in the rostral brainstem is not a sufficient criterion for presuming a thermoreceptive role for it in the duck, and probably not in a mammal either.
Nonhomogeneous excitatory synapses of a crab stomach muscle
Authors: Atwood H. L. , Govind C. K. , Kwan I. 
Published: January 2005

AbstractNeuromuscular synapses of pyloric muscle P1 in the blue crab Callinectes sapidus were examined using electrophysiological and electron microscopic methods. The muscle is innervated by a single excitatory axon of the stomatogastric ganglion. Excitatory postsynaptic potentials show striking facilitation at very low frequencies of stimulation, indicating very slow decay of the facilitation process after a single nerve impulse. Quantal content of transmitter release at a low frequency of stimulation averaged 1.5. Evidence was obtained that not all synapses on a muscle fiber are equivalent. This was particularly evident at the morphological level in serially sectioned nerve terminals. On each nerve terminal examined, a wide range of synapse sizes was found. Synaptic contact areas ranged from less than 0.5 μm2 to almost 10 μm2; the latter value is large compared with those obtained for other crustacean neuromuscular synapses. Most of the smaller synapses lacked the presynaptic dense bodies which are putative release sites for the transmitter substance. The larger synapses all had presynaptic dense bodies, and some showed evidence of splitting apart into smaller subunits. It is postulated that about half the morphologically identified synapses are relatively inactive.
Brain reaggregate cultures: Biochemical evidence for myelin membrane synthesis
Authors: Sheppard J. R. , Brus David , Wehner Jeanne M. 
Published: January 2005

AbstractMyelin membrane synthesis was studied using mechanically dissociated fetal rodent CNS which formed spherical reaggregates while being maintained in rotating culture flasks. These reaggregate cultures exhibited myelinogenesis in vitro after precisely the same period of time needed for myelin synthesis to commence in vivo. The myelin membrane related enzymes, 2′,3′ cyclic nucleotide phosphohydrolase (CNP) and cerebroside sulfotransferase (CST), appear similar in their specific activities and follow the same developmental patterns that these enzymes exhibit in vivo. In addition, phosphorylation of myelin basic protein occurs by the third week in vitro which agrees with previously published in vivo studies. These experiments indicate that this nerve‐cell culture system may be an appropriate model for studying the biological regulation of myelinogenesis as well as a variety of other nervous‐system functions.
The caudal ganglion of the leech, with particular reference to homologues of segmental touch receptors
Authors: Rubin Eric 
Published: January 2005

AbstractThe caudal ganglion of the leech, which provides sensory and motor innervation to the posterior sucker, represents the fusion of seven embryonic segmental ganglia. Although fused, each of the seven contributing ganglia (“subganglia”) of the caudal ganglion can be distinguished morphologically and functionally. The roots from each subganglion carry the axons of mechanoreceptors homologous to “touch” cells found in the segmental ganglia and the subesophageal compound ganglion. The receptive fields supplied by the touch cells of the caudal ganglion are uniquely arranged and reveal the modified segmentation of the circular posterior sucker. Extensive overlap of sensory innervation occurs between adjacent segments of the sucker, beyond the overlap characteristic of the homologous cells of body segments. It thus appears that the touch receptors of the caudal ganglion are less restricted than receptors of the segmental ganglia with regard to their territories of innervation. The caudal ganglion has additional unique properties that establish it as a distinct integrative center of the leech CNS.
Lack of limb motor asymmetry in the neonate
Authors: Korczyn Amo S. D. , Sage J. I. , Karplus M. 
Published: January 2005

AbstractNeonates were examined for evidence of lateralization of motor function. The stepping test was done and the foot that moved first was recorded. The reaction of both arms to avoid an obstacle was also tested. No evidence for lateralization was found. Previous studies in the neonate have shown asymmetry of anatomical structures subserving language, and functional asymmetry of auditory functions and head position. However, the development of limb handedness occurs only at a later age.
The brain‐specific S‐100 protein on neuronal cell membranes
Authors: Hydén Holger , Rönnbäck Lars 
Published: January 2005

AbstractThe S‐100 protein has been localized to the neuronal plasma membranes of isolated Deiters' neurons by fluorescence microscopy using fluorescein‐conjugated antiserum to the protein and by immunoelectron microscopy using peroxidase‐conjugated anti‐S‐100 antiserum. In the present study this is shown also by incubating neurons with Sepharose 4B or methylacrylate spherules to which were coupled anti‐S‐100 antibodies. The specificity of the antiserum is discussed in the text. The technique described can be used to study the topography of antigenic characteristics of nerve cells by using antisera insolubilized on spherules of suitable size.
Neurobiology of Polyorchis. II. Structure of effector systems
Authors: Spencer A. N. 
Published: January 2005

AbstractThe gross and fine morphology of the major effector systems in the anthomedusan, Polyorchis penicillatus, is described and discussed in relation to the known physiological and behavioral properties of these systems. Swimming is controlled by an anastomosing network of giant neurons within the inner nerve ring and radial nerves. Although these neurons may be coupled by gap junctions it is likely that they form a syncytium. The photosensitivity of the “giants” is attributed to reflexive membranes within the cytoplasm. Giant neurons act as both the pre‐ and postsynaptic cell when forming synapses with other neurons of the inner nerve ring. Neuromuscular synapses between “giants” and the striated swimming muscle are found around the margin and along the radii. Swimming muscle cells are connected laterally by gap junctions and end‐to‐end by desmosomes which are sometimes elaborated with extra‐thick filaments. Unstriated sphincter and radial muscles, the major muscles associated with crumpling, are both greatly folded over mesogloeal ridges and have processes that cross the mesogloea to contact the ring and radial canals, respectively. Synapses or other sites that might be responsible for exciting these muscles during crumpling have not been found. The ability of the endodermal lamella and canals to propagate action potentials can be accounted for by the numerous gap junctions that are seen in these tissues. The precise location where excitation is transferred to the nervous system to initiate crumpling is not known but epithelial bridges crossing the mesogloea are likely routes. Synapses between neurons originating in the outer nerve ring and tentacle longitudinal muscle can account for the control of tentacle length. Neurons of the outer nerve ring also synapse onto velar, radial fibers and the sphincter muscle. The inner and outer nerve rings have nervous connections. The organisation of the outer nerve ring and the arrangement of nerves within the endodermal plexus is described. A diagram showing the major connections and interactions of components of the effector systems is presented.
Retrograde axonal transport of specific macromolecules as a tool for characterizing nerve terminal membranes
Authors: Dumas M. , Schwab M. E. , Thoenen H. 
Published: January 2005

AbstractThe uptake of macromolecules by nerve terminals which is followed by retrograde axonal transport seems to occur by two different mechanisms, a specific and a nonspecific one. The nonspecific uptake depends on the presence of macromolecules (e.g., horseradish peroxidase) in the vicinity of the nerve terminals at very high concentrations and is enhanced by neuronal activity. In contrast, the specific uptake and subsequent retrograde axonal transport becomes apparent at much lower concentrations of the appropriate macromolecules, depends on the affinity of these ligands for specific binding sites on the surface of the neuronal membrane, and is independent of neuronal activity. The fact that lectins and some bacterial toxins bind to specific membrane glycoproteins or glycolipids allows conclusions to be drawn regarding qualitative and even quantitative aspects of the composition of the plasma membrane of the nerve terminals.125I‐labelled nerve growth factor (NGF), tetanus toxin, cholera toxin, wheat germ agglutinin (WGA), ricin II, phytohemagglutinin (PHA), and concanavalin A (ConA) were injected into the anterior eye chamber of rats where they were taken up by adrenergic nerve terminals and transported retrogradely to the superior cervical ganglion. The saturation of the uptake‐transport found for NGF, WGA, choleragenoid and an atoxic binding‐fragment of tetanus toxin indicates that limited numbers of binding sites, which showed also different affinites, are present for each ligand on the membrane of the nerve terminals. Competition experiments showed that the binding sites for the ligands investigated are largely independent. Two different classes of binding sites (high affinity‐low capacity and intermediate affinity‐intermediate capacity) seem to be involved in the saturable retrograde axonal transport of NGF. In contrast, WGA seems to have only a single class of binding‐uptake sites with high capacity and relatively low affinity. Strong evidence for positive cooperativity was obtained for the uptake and subsequent transport of the tetanus toxin fragment.
L9 modulation of gill withdrawal reflex habituation in Aplysia
Authors: Lukowiak Ken 
Published: January 2005

AbstractRepeated tactile stimulation of the siphon in Aplysia normally results in habituation of the gill withdrawal reflex and a concomitant decrease in the amplitude of the excitatory synaptic input to gill motor neurons in the abdominal ganglion. It was found, however, that induced low‐level tonic activity in motor neuron L9, which does not itself elicit a gill withdrawal movement, prevented habituation of the reflex from occurring. Further, in preparations already habituated, this tonic low‐level activity brought about a reversal of habituation. Although tonic L9 activity prevented the occurrence of habituation or brought about its reversal, it did not interfere with the synaptic decremental process which normally accompanies gill reflex habituation. Motor neurons L7 and LDG1 were found not to possess this ability of L9 to modulate gill reflex habituation. Evidence suggests that L9's modulatory effect is mediated in the periphery, in the gill and not centrally in the abdominal ganglion.
Effects of L‐proline and some of its analogs on retinal spreading depression
Authors: Van Harreveld A. 
Published: January 2005

AbstractL‐Protine inhibits glumate‐based spreading depressions (SDs) at low concentrations (2–2.5mM) and promotes K+‐based SDs at higher concentrations (5 mM). The inhibition of glutamate‐based SDs was postulate receptors on somatic and dendritic plasma membranes. The binding of proline to glutamate receptors was furthermore postulated to result in a result in a release of K+ from the intracellular compartment, enhancing the extracellular K+ concentration sufficiently to promote K+ based SDs. A proline analog, L‐baikiain, containing a double bond and one more based A atom in the ring structure than proline had similar affects as the latter amino acid, but an analog, L‐azetidine‐2‐hydroxylic acid, with one less C atom in the ring had little effect on SD in the retina.
Functional characterization of the neurodepressing hormone in the crayfish
Authors: Aréchiga Hugo , Cabrera‐Peralta Casimiro , Huberman Alberto 
Published: January 2005

AbstractThe effect of the neurodepressing hormone (NDH) was studied on different identified motoneurons in the abdominal ganglia of the crayfish Procambarus bouvieri (Ortmann). Although differences in sensitivity were apparent, all the neurons tested responded to NDH with a reduction in spontaneous firing rate, which lasted as long as NDH was present, and, depending on the concentration and time od action of the hormone, for even longer periods. NDH activity was determined in the various parts of the central nervous system of the crayfish, being highest in the eyestalk, gradually diminishing away from the eyestalk, with a cephalo‐caudal gradient, being lowest in the abdominal ganglia. High levels of NDH activity were detected in the blood. After eyestalk ablation, NDH concentrations steadily diminishes, in the blood and central nervous systems, until virtually disappearing after 4 days; from day 5 onwards, the activity is recovered up to its original levels. NDH synthesis takes place with a time constant of approximately 3 hr in cultured segments of central nervous system, being highest in the eyestalk.