bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cerebral energy reserves and glycolysis in neural tissue of 6‐aminonicotinamide‐treated mice
Authors: Kauffman F. C. , Johnson E. C. 
Published: January 2005

AbstractCerebral energy metabolism was studied in brains of mice treated with the nicotinamide analog, 6‐aminonicotinamide (6‐AN), which is converted to a potent inhibitor of 6‐phosphogluconate dehydrogenase in viro. Six hours after administration of 6‐AN, the level of cerebral 6‐phosphogluconate was increased at least 170‐fold, whereas substrates for other NADP +‐dependent dehydrogenases either did not change or increased only slightly. Large increases in 6‐phosphogluconate were observed in the cerebral cortex, three layers of the cerebellum, and the dorsal column and anterior horn regions of the spinal cord after administration of 6‐AN. Thus, glucose was metabolized via the oxidative enrymes of the pentose phosphate pathway in a wide variety of neuronal structures in vivo. Highest concentrations of 6‐phosphogluconate were observed in the cerebellar molecular layer.Energy use rates and glycolysis were studied by measuring the disappearance of the major energy reserves during periods of anoxic‐ischemia imposed on cerebral tissue of 6‐AN‐treated mice. Production of lactate and utilization of glycogen during anoxic‐ischemia were reduced in brain of 6‐AN‐treated mice, which is in accord with the suggestion that glycolysis is inhibited in cerebral tissue of 6‐AN‐treated animals. Levels and ratios of pyridine nucleotides in cerebral tissue were not altered by 6‐AN treatment. From changes in levels of ATP, phosphocreatine, glucose, and glycogen in brain during ischemia, the rate of energy use was calculated to be 21.7 mmol · kg wet tissue−1 · min−1, which was not significantly different from that observed in normal adult mouse brain. Therefore, despite an apparent slowing of hexose utilization in cerebral tissue 6‐AN‐treated mice, normal cerebral energy use was maintained during the initial period of anoxic‐ischemia.
Feedback cue and switching characteristics
Authors: Best Jay Boyd , Howell William , Riegel Virginia , Abelein Michal 
Published: January 2005

AbstractAsexual reproduction (fissioning) in planarians is controlled by group size; increased group size suppresses fissioning, isolation releases it. This effect is mediated through the brain; social stimulation from cohorts causes the brain to inhibit the segmental plexus fissioning system from initiating the events of fissioning. Experiments were conducted to elucidate (1) the stimulus cue conveying information regarding cohort number and (2) the switching characteristics of the control system. The results of these show that the social stimulus responsible for the effect involves neither vision nor discharge of pheromonal substances into the habitat; the sensory event apparently involves direct contact and chemoreceptive, as well as tactile, modalities. The switching characteristics (graduated response, long release time, short reinstatement time) found for the brain inhibitory system agree with those expected from the mathematical model derived for a simple neurohormonal control system in which it is postulated that social stimulation causes neurosecretory cells of the brain to release a fissioning inhibitory hormone (FIH) that inhibits the segmental plexus fissioning (SPF) system from initiating fissioning.
Alterations in the accumulation patterns of polyamines in brains of myelin‐deficient mice
Authors: Russell Diane H. , Meier Hans 
Published: January 2005

AbstractQuaking mutants and jimpy mutants of mice have known deficiencies of myelination of the central nervous system, as well as lesser involvement of the peripheral nervous system. Both mutants also have altered polyamine synthesis and accumulation, particularly in the hindbrain and spinal column. The ratio of spermidine/spermine, which generally is higher in tissues with high rates of biosynthetic activity, was significantly lower in the mutants as compared to their normal siblings. In quaking mutants, 5 months of age, the spermidine concentration of hindbrain and spinal column was 60% that of controls. In contrast, the decreased spermidine/spermine ratio in jimpy mutants resulted from a marked increase in the spermine concentration in both forebrain and hindbrain. Alterations in the spermidine/spermine ratio could lead to reductions in the biosynthetic potential of the brain during development.
Phenothiazine antagonism of the noradrenergic inhibition of cerebellar purkinje neurons
Authors: Freedman Robert , Hoffer Barry J. 
Published: January 2005

AbstractPhenothiazine derivatives were examined as potential antagonists of the inhibitory noradrenergic synapses from the nucleus locus coeruleus to rat cerebellar Purkinje cells. Fluphenazine, and its thioxanthine analogue, flupenthixol, antagonized the inhibitory action of norepinephrine, when iontrophoretically applied to single cells. Alpha‐flupenthixol was generally more active than the beta isomer. Fluphenazine had no appreciable effect on inhibitions induced by iontophoresis of GABA or cyclic AMP. Parenteral fluphenazine also blocked the inhibition of Purkinje cells produced by the stimulation of the noradrenergic pathway from locus coeruleus, but basket and stellate cell inhibitory inputs to Purkinje cells were unaffected. These data suggest that fluphenazine can specifically block a known central adrenergic inhibitory pathway.
Catechol‐O‐methyl transferase and monoamine oxidase activities in brains of mice susceptible and resistant to audiogenic seizures
Authors: Schlesinger Kurt , Harkins Jane , Deckard Betty S. , Paden Charles 
Published: January 2005

AbstractThe activities of catechol‐O‐methyl transferase (COMT), monoamine oxidase (MAO), and a methanol forming enzyme were studied in whole brain homogenates and in livers obtained from DBA/2J, C57B1/6J, and F1 hybrid mice. DBA/2J mice are extremely susceptible to audiogenic seizures, where as C57B1/6J mice are resistant to sound‐induced convulsions. C57B1/6J mice were found to have significantly higher brain levels of COMT, while MAO activities were not different in animals of these genotypes. No methanol forming activity was detected in animals of either strain. No differences were found in hepatic activities of either COMT or MAO. Pyrogallol was shown to protect DBA/2J animals against audiogenic seizures.
Further observations of the ultrastructure of synaptosomes separated from spinal cord and medulla, with especial emphasis on the postsynaptic membrane
Authors: Jones D. G. 
Published: January 2005

AbstractSynaptosomes from the rat medulla and spinal cord have been examined in an attempt to formulate morphological criteria for distinguishing between those found in two subfractions of P1 (nuclear fraction). The mean diameter of those in the lighter of the subfractions (P1C) is 0.6 μm, with a preponderance in the range 0.4–0.6 μm and a minor peak at 0.7–0.8 μm. Subjunctional bodies are associated with 60.2% of the junctional regions in this subfraction. By contrast, those in the heavy subfraction (P1D) have a larger overall diameter (0.7 μm), a greater percentage of them have visible junctional regions (68.1% opposed to 51.6%), but of the junctional regions a lower percentage have associated subjunctional bodies (36.2%).The subjunctional bodies consist of a central core with five spokes radiating from it. The tips of the spokes are connected by fine strands which connect individual bodies to neighboring ones, as well as to the postsynaptic thickening. The persistence of subjunctional bodies in synaptosomes highlights the strergth of the attachment between them and the postsynaptic thickening, and suggests that these bodies may be integral components of the “postsynaptic thickening complex.” They may also help in the formulation of criteria by which different populations of these synaptosomes may be separated from each other.
Movement of glycine across the blood‐brain barrier of the rabbit
Authors: Pollay Michael 
Published: January 2005

AbstractThe single pass clearance of glycine from the cerebral capillary bed was measured in the rabbit with the indicator diffusion method. It was shown that glycine was extracted to the same degree as fructose (ca. 07). The concentration of glycine injected into the carotid artery was varied some 700‐fold without significantly affecting the clearance of this amino acid in transit through the brain. Cross inhibition of the unidirectional movement of glycine was not demonstrable. These present results and most previous studies suggest that this putative neurotransmitter does not cross the blood‐brain barrier by a carrier mediated process.
The mechanism of β‐bungarotoxin action. I. Modification of transmitter release at the neuromuscular junction
Authors: Oberg Stephen G. , Kelly Regis B. 
Published: January 2005

AbstractThe protein, β‐bungarotoxin, a presynaptic neurotoxin isolated from the venom of the snake Bungarus multicinctus, is known to inhibit mitochondrial function. Within 30 min after adding the toxin to a rat diaphragmphrenic nerve preparation, the quantal content increased tenfold and the frequency of miniature endplate potentials increased fourfold. No increase in miniature endplate potential frequency was seen in the absence of extracellular calcium. Since mitochondria may be involved in regulating intracellular calcium levels, the rate at which the transmitter release is turned off was studied by measuring delayed release in the presence and absence of toxin. Delayed release is elevated about eightfold by the toxin. If delayed release is due to residual calcium, as has been hypothesized, these data may be explained if the toxin does not alter the amount of calcium which enters the terminal, but rather the rate at which that calcium is removed. Alternatively, a calcium‐dependent modification of the release process itself might be produced.The eventual reduction in transmitter output did not appear to result from depletion of the terminal of releaseable packets of transmitter, but does require extracellular calcium.
Cytophotometric identification of tetraploid purkinje cells in young and aged rats
Authors: Bohn Ronald C. , Mitchell Robert B. 
Published: January 2005

AbstractDNA content of cerebellar basket and Purkinje cells of four month, one year, and two year old albino rats was determined by Feulgen cytophotometry. DNA content per nucleus remained essentially constant during aging although there was a slight shift to lower Feulgen‐DNA values occurring in the one year age group. Purkinje cells of all three age groups were found to contain tetraploid amounts of DNA as compared to diploid basket cells.
Electrical properties and structure of the frog arachnoid membrane
Authors: Perez‐Gomez Jóse , Bindslev Niels , Orkand Paula M. , Wright Ernest M. 
Published: January 2005

AbstractWe have used an in vitro preparation of the frog arachnoid membrane to study the role of this membrane in the maintenance of the “blood‐cerebrospinal fluid (csf) barrier.” Electron microscopy showed that the membrane was made up of 10–15 layers of flat epithelial cells joined together by numerous cell junctions. The electrical resistance of the preparation was about 2000 ohms cm2. The steady‐state transmural potential difference (pd) ranged up to 45 mV, csf positive, and this was eliminated by either the addition of ouabain to the csf, or by replacing the NaCl with TEA Cl. The pd across the membrane increased when bicarbonate was added to the external bathing solutions. We conclude that this pd is due to the active transport of sodium from the subural fluid to the csf. In some preparations the transmural pd was reversed, i.e., csf negative, and this was also abolished by the addition of ouabain to the csf, or by replacing chloride with isethionate. We conclude that this pd is related to active chloride transport. These, and other experiments, lead us to the conclusion that the arachnoid membrane is involved in the production of the cerebrospinal fluid and the maintenance of the blood‐cerebrospinal fluid barrier.
A long‐lasting birefringence change recorded from a tetanically stimulated squid giant axon
Authors: Watanabe Akira , Terakawa Susumu 
Published: January 2005

AbstractA long‐lasting birefringence change (the delayed response) was found to be produced in a tetanically stimulated squid giant axon. The change was independent of the concurrent membrane potential change, summated on repetitive stimulation, and always had a sign representing a decrease in resting birefringence. The axon was placed between a polarizer and an analyzer with their polarizing axes crossed, making an angle of 45° with the longitudinal direction of the axon. The light beam that passed through the axon and the other optical elements was received by a photodiode. The change in light intensity evoked by repetitive stimulation was composed of brief initial responses, which took place in response to individual stimuli, and a delayed response, which developed gradually and lasted for several hundred msec. It was necessary to differentiate the effect of birefringence change from that of turbidity change. Formulas were derived on the assumption that the optical properties of the axon could be represented by a model of a uniaxial crystal that was not only birefringent but also dichroic, its extinction coefficients and the angle of retardation being changed independently on excitation. Calculations with them yielded the resting retardation, which agreed well with those obtained by the Sénarmont's method, and the change in birefringence, which agreed well with the other calculated value derived from experiments using a quarter‐wave plate. The results of the calculation confirmed the existence of the long‐lasting birefringence change in the tetanically stimulated axon.
Synaptic development in the crayfish opener muscle
Authors: Atwood H. L. , Kwan Irene 
Published: January 2005

AbstractNerve terminal regions in walking leg opener muscles of several crayfish of different ages (0 to 245 days after hatching) were examined by means of electron microscopy. This muscle is innervated by two axons (excitatory and inhibitory) and at maturity contains three classes of synapse: excitatory and inhibitory neuromuscular synapses, and inhibitory axo‐axonal synapses. The muscle itself is initially a syncytium, which gradually becomes subdivided into distinct “muscle fibers” as the animal matures. Innervation was not found in the opener muscle just before or just after hatching, but was present in restricted locations on the inner side of the muscle within a few days of hatching. As the muscle enlarged and became subdivided, innervation appeared in various other locations. Synaptic contacts were located in young stages soon after hatching, and in later stages. Morphological differences characteristic of excitatory and inhibitory nerve terminals could be found even at the earliest stages of innervation. Both excitatory and inhibitory synapses, but particularly the former, showed evidence of progressive enlargement to a final size within the first two months, and no evidence for further enlargement of existing synapses thereafter. Synaptic maturation also involved the appearance of presynaptic “dense bodies” thought to be regions at which transmitter substance is preferentially released. Nerve terminals at different levels of maturation were observed in opener muscles of young crayfish. Clear evidence for differential maturation of the three types of synapse present in this muscle was obtained. The inhibitory neuromuscular synapses attained their final average size and developed their dense bodies sooner than the excitatory neuromuscular synapses. The inhibitory axo‐axonal synapses were the last to appear and to mature.
A mutant of Paramecium with increased relative resting potassium permeability
Authors: Satow Youko , Kung Ching 
Published: January 2005

AbstractFast‐2, a membrane mutant of Paramecium aurelia, is due to a single‐gene mutation and has behavioral abnormalities. Intracellular recordings through changes of external solutions were made. The mutant membrane hyperpolarized when it encountered solutions with low K+ concentration. This hyperpolarization and other associated activities were best observed in Ca‐ or Na‐solutions devoid of K+. Membrane potential was plotted against the concentration of K+ (0.5 to 16 mM) in solutions of fixed Na+ or Ca++ concentration. The slopes of the curves for the mutant membrane were steeper than those for the wild type at the lower concentrations of K+. Inclusion of 2 mM tetraethylammonium chloride (TEA‐Cl) counteracted the mutational effects. Spontaneous action potentials in Ba‐solution and the electrically evoked action potentials in various solutions are normal in this mutant. We conclude that the resting permeability to K+ relative to the permeabilities to Na+ and Ca++ has been increased by the mutation.
Neuron culture from adult goldfish
Authors: De Boni U. , Seger M. , Scott J. W. , Crapper D. R. 
Published: January 2005

AbstractNeurons and gla from the central nervous system of the adult teleost Carassius auratus have been grown as explant cultures of minced brain tissue and as trypsin dissociated cells. These cultures exhibit extensive neurite growth from two neuronal types, have organotypic ultrastructure, and contain electrically active cells.Autoradiographic data indicate that these neurons do not divide in culture, and histological evidence suggests that some mature neurons survive explantation and regenerate processes. However, explantation of brain fragments not containing undifferentiated cells, localized in the ventricular and subventricular zones in the brains of fish, resulted in mesenchymal and glial cell cultures only. Therefore, a contribution to the population of cells in culture by undifferentiated cells must be considered.The cultured neurons remained viable for at least 19 weeks and ultrastructural and electrophysiological data indicate synaptic interaction between cells in explant cultures.
Effect of calcium removal on monoamine‐elicited depressions of cultured tuberal neurons
Authors: Geller Herbert M. , Hoffer Barry J. 
Published: January 2005

AbstractThe role of extracellular calcium in monoamine responses of central neurons was investigated using explant cultures of tuberal hypothalamus. The spontaneous activity of neurons in cultures was recorded in balanced salt and calcium‐deficient salt solutions. The firing rate was reversibly augmented during perfusion with calcium‐free salt solutions. This increased firing rate was counteracted by the addition of magnesium. Addition of magnesium also regularized the pattern of firing. Iontophoretic application of putative monoamine neurotransmitters reversibly decreased the rate of firing in both normal and calcium‐deficient salt solutions. These results suggest that monoamine inhibitions are not primarily mediated by transmembrane calcium fluxes.
Myelin subfractions isolated from mouse brain. Studies of normal mice during development, quaking mutants, and three brain regions
Authors: Sheads Linda D. , Eby Michael J. , Sampugna Joseph , Douglass Larry W. 
Published: January 2005

AbstractMyelin isolated from three areas of mouse brain, from whole brain at several ages in normal mice, and from whole brain of adult quaking mutant mice was separated into seven bands and a pellet on discontinuous density gradients using 0.32, 0.45, 0.55, 0.60, 0.70, 0.75, and 0.85 M sucrose. The distribution of myelin in the subfractions was independent of homogenization and shocking conditions employed to isolate the myelin preparations, but was related to the type of myelin applied to the gradient. Compared to myelin isolated from older animals, myelin isolated from 18–24 day old mice displayed a distribution pattern with greater proportions of material banding at lesser sucrose densities. Similarly, myelin obtained from hindbrain contained proportionately more material layering at lesser sucrose densities compared to myelin isolated from cerebral cortex. Myelin subfraction patterns observed for 8–12 day old control mice and quaking mutants were unlike each other or any other myelin preparation examined.In the 18–90 day old animals, the markers studied were not uniformly distributed among the myelin subfractions. The pellet and the layer banding at the 0.75/0.85 M sucrose interface contained the highest specific concentrations of sialic acid, nucleic acid, and total adenosine triphosphatase activity. In contrast, the specific activity of 2′,3′ ‐cyclicnucleotide‐3′‐phosphohydrolase was lowest in the pellet as well as the three bands obtained above 0.60 M sucrose and was highest in the fraction banding at the 0.65/0.70 M sucrose interface.The results obtained were not consistent with an artifactual origin of the myelin subfractions, but instead suggested that the subfractions have physiological significance. One explanation for the different banding patterns observed between young and mature myelin may be the different amount of myelin in various brain regions during development.
Inactivation of taste receptor cell function by two cationic protein modification reagents
Authors: Mooser Gregory , Lambuth Nancy 
Published: January 2005

AbstractTwo cationic protein modification reagents, 1‐cyclohexyl‐3‐(2‐morpholinylethyl) carbodiimide (CMCD) and dimethyl (2‐hydroxy‐5‐nitrobenzyl) sulfonium bromide (HNB‐dmS), inhibit taste receptor cell stimulation by NaCl, sucrose, and HCl. Modified inactive derivatives of the reagents under the same conditions are ineffective. Inactivation by HNB‐dmS is essentially irreversible. The effects of inactivation by CMCD are reversible after about 10–15 minutes of a water rinse, however, when applied in the presence of glycine methyl ester, the inhibited response is stabilized and only recovers after about 1.5–3 hours. Glycine methyl ester alone has no inhibitory properties. The kinetics of inactivation by both HNB‐dmS and CMCD are consistent with a second‐order reaction with rate constants of 0.041 ± 0.001 M−1 sec−1 and 0.121 ± 0.012 M−1 sec−1, respectively. The rate of inactivation by both compounds is independent of NaCl concentration as well as degree of receptor stimulation. This, together with the observation that the response to stimulation by all effectors examined is altered, suggests the inactivation occurs at an event which is common to the transduction of the response from all three stimuli. The ether:water partition coefficients, as well as previous results from inactivation by N–substituted maleimides, indicate that hydrophilic reagents do not cross the cell membrane in significant concentrations within the time period of application. This suggests the site of modification by the cationic protein modification reagents is at the surface of the cell membrane. Significant residual NaCl, sucrose, and HCl activity remains after total inactivation. To account for this, a two‐state membrane receptor system is postulated.