bluuebunny/crossref_metadata_2025 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

Cerebral 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

Asexual 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

Quaking 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

Phenothiazine 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

The 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

Synaptosomes 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

The 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

The 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

DNA 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

We 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

A 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

Nerve 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

Fast‐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

Neurons 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

The 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

Myelin 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

Two 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.
Role of calcium in the initiation of fast axonal transport of protein: Effects of divalent cations
Authors: Hammerschlag Richard , Bakhit Charles , Chiu Arlene Y. , Dravid Anant R.
Published: January 2005

Fast axonal transport of [3H]protein has been examined in bullfrog primary afferent neurons incubated in media supplemented with divalent cations that can act as agonists or antagonists of calcium ions. Incubation in calcium‐free medium (CFM) had no effect on the rate of transport, but reduced the amount of transported [3H]protein by 40–60% relative to transport in the contralateral preparation maintained in normal medium. Preparations incubated in CFM supplemented with 1.8 mM SrCl2 (equimolar to the CaCl2 concentration in normal medium) carried out transport at control levels. Incubation conditions in which primary afferent somata were exposed to the Sr2+‐medium while nerve trunks were maintained in CFM also supported normal transport. By contrast, selective exposure of nerve trunks to Sr2+‐medium, and somata to CFM resulted in a reduced level of transport similar to that observed when the whole preparation was incubated in CFM. The depression of transport resulting from incubation in CFM was shown to be reversible when preparations were transferred from CFM to either Sr2+‐supplemented CFM or to normal medium. By contrast to the effects of Sr2+, Ba2+ (up to 18 mM) did not substitute for Ca2+ in the transport process. When normal medium was supplemented with calciumantagonist cations, the amount of transport was depressed (Co2+ > Mn2+ >> Mg2+), with no concomitant effect on the rate of transport. Results of studies with Co2+, as well as those with Sr2+, suggest that a major locus of action of these cations is within the neuronal soma at a step subsequent to protein synthesis, and prior to the onset of protein translocation via the transport system. Thus, it is inferred that these divalent cations affect a calcium‐dependent step that occurs during the initiation phase of fast axonal transport.
Computer‐assisted analysis of particulate axoplasmic flow in organized CNS tissue cultures
Authors: Leestma Jan E. , Freeman Stephennie S.
Published: January 2005

Using organized nervous system tissue cultures of embryonic mouse spinal cord, time‐lapse motion pictures of intra‐axonal particle movements were made using Nomarski optics. The paths of 272 particles were followed and analyzed using digital computer methods. Particles had a bidirectional saltatory motility with net anterograde and retrograde velocities which were shown to be the same (about 1 micron per second). When anterograde moving and retrograde moving particles were analyzed separately for anterograde and retrograde saltations, the velocities of saltations in the direction of net movement were found to be 1.5 times greater than saltations against the direction of net movement. These differences were statistically significant. In addition, it was shown that there were regions within the axon where variations in particle motion were similar from particle to particle as they passed, and that more disturbed motion was found to occur near intra‐axonal objects which were judged to be mitochondria. No decrease of particle velocity was noted in regions away from mitochondria nor was an increase in velocity noted near them. Computer‐drawn particle plots illustrate the various facets of particle motion.
Distribution of 45Ca in the superior cervical ganglion of the cat
Authors: Robinson Joseph D. , Kabela Emilio
Published: January 2005

Superior cervical ganglia isolated from immature cats accumulated 0.9 ng atoms of 45Ca per mg wet weight during 10‐min incubations at 37°C; when expressed as an equivalent volume of medium the accumulation was four times the uptake of 3H‐inulin. Orthodromic stimulation of the ganglia doubled 45Ca accumulation, whereas excitation with 50 mM KCl, 5 mM glutamate, or antidromic stimulation increased accumulation by one‐half. Hexamethonium reduced the increment in 45Ca accumulation due to orthodromic stimulation only, but another ganglionic blocking agent, tetraethylammonium, did not reduce accumulation in any case. Both agents blocked ganglionic transmission monitored electrophysiologically. To resolve this discrepancy, and to approach the localization of 45Ca within the ganglia, the efflux of previously accumulated 45Ca was examined. The data could be fitted by an equation incorporating the sum of three exponentials, representing a rapidly exchanging compartment plus two more slowly exchanging ones. The latter two appeared to reflect the pre‐ and postganglionic elements in the ganglia: 45Ca content of the “preganglionic” compartment was increased by orthodromic but not by antidromic stimulation, and was not decreased by either blocking agent; conversely, 45Ca content of the “postganglionic” compartment was increased by both orthodromic and antidromic stimulation, and was decreased by both blocking agents after orthodromic stimulation. The lack of effect of tetraethylammonium on the whole ganglion resulted from an increase in “preganglionic” accumulation that offset the “postganglionic” decrease. After preganglionic denervation, the 45Ca content of the “preganglionic” compartment was reduced by two‐thirds, while the 45Ca content of the “postganglionic” compartment was unchanged. Chemical stimulation increased 45Ca accumulation in both compartments. Diphenylhydantoin, 0.1 mM, decreased the increment in 45Ca accumulation due to electrical stimulation and to 50 mM KCl; this inhibition occurred in the “preganglionic” compartment (and perhaps also in the “postganglionic”), and was accompanied by an increased efflux of 45Ca.
Protein composition of cockroach muscles: Identification of candidate recognition macromolecules
Authors: Denburg Jeffrey L.
Published: January 2005

The protein composition of each of the coxal depressor muscles from the leg of the cockroach, Periplaneta americana, was analyzed by SDS polyacrylamide gel electrophoresis. The proteins from each muscle were fractionated according to their extractability in Ringer's solution, 1% Triton X‐100 and 1% SDS. The gel protein patterns of the fractionated muscles revealed some biochemical differences that could be correlated with mechanical and ultrastructural differences observed among the muscles. In addition, proteins were detected that were considered to be candidate recognition macromolecules that are responsible for the intercellular recognition process that enables regenerating motor neurons to specifically recognize and make stable, functional connections only with the muscles to which they were originally connected. The major evidence for this identification of candidate recognition macromolecules was that their presence in the muscle could best be correlated with innervation by an identified motor neuron. In addition, these proteins remain present in denervated muscles for at least as long as it takes for the original innervation pattern to be reformed by the regenerating motor neurons.
Uptake of radiolabeled glucose analogues by organotypic cerebellar cultures
Authors: Renkawek K. , Spatz M. , Murray M. R. , Klatzo I.
Published: January 2005

Permeability of brain cells to radiolabeled glucose analogues with sucrose or inulin or L‐glucose was studied in the living, intact state of the organotypic cerebellar cultures. In vitro uptake of 3H 3‐O‐methyl D‐glucose and 3H 2‐deoxy‐D‐glucose exhibited saturation kinetics with increasing substrate concentrations. Each of the labeled sugars uptake could be self‐inhibited in the presence of unlabeled (cold) substrate and cross‐inhibited with cold glucose or xylose or phlorizin present in the incubating medium. The uptake was Na‐independent and stereo‐specific for D‐form.
Anoxic block and recovery of axoplasmic transport and electrical excitability of nerve
Authors: Leone J. , Ochs S.
Published: January 2005

Axoplasmic transport of cat sciatic nerves was studied in vitro in a chamber in which maximal α action potentials could also be elicited. After initiation of N2 anoxia, electrical responses fell to zero at an average time of 22 min. A shorter time to zero of 11 min was seen during a second period of anoxia.

A good recovery of both action potential responses and axoplasmic transport occurs after a period of anoxia lasting 1–1.5 hr. An apparent failure of recovery of axoplasmic transport was seen after 2 hr of anoxia with a good recovery of electrical responses. Axoplasmic transport tended to return toward normal when more time was allowed for recovery after anoxia. An adequate supply of ∼P was shown to be present by measurement of ATP and creatine phosphate levels. The delay in recovery of transport thus signifies a failure of utilization of ∼P by the transport mechanism.

Longer periods of anoxia and recovery were limited in vitro and for this reason, ischemic anoxia was produced in vivo. Blood pressure cuffs were placed on the upper thigh of cats and maintained for times of 1–8 hr at pressures of 300–310 mm Hg. Then, recovery times up to 7 days were allowed. It was shown that axoplasmic transport could gradually recovery after an anoxia lasting up to 6–7 hr if sufficient recovery times were allowed.

A possible explanation for the delay in the recovery of axoplasmic transport and the disassociation in the earlier recovery of electrical responses as against the recovery of transport was discussed.
Synaptic connections and functional organization in Aplysia buccal ganglia
Authors: Fiore L. , Meunier J.‐M.
Published: January 2005

The buccal ganglion of Aplysia contains three morpho‐functional groups (A, B, and C) of large cells and two groups (s1 and s2) of small cells. The A cells evoke monosynaptic IPSPs in the B cells. We found that s1 cells can evoke large EPSPs in the A cells, IEPSPs in the B cells, and EIIPSPs in the C cells; several s1 cells are able to evoke all three types of responses. Many s2 cells can evoke these same responses, but only in the A and B cells. Furthermore, the s cells can evoke depolarizing PSPs in other s cells; this relation is often reciprocal. All these responses may also be contralateral. Their monosynaptic nature is shown by the consistent 1:1 relationship with the presynaptic spike, and also by the effects of intracellular tetraethylammonium and of high Mg2+ concentration in the bathing medium. D‐tubocurarine reversibly suppresses the I phase of the IEPSP evoked by the s cells in the B cells. All the responses evoked by the s cells undergo depression with repetition.

The network formed by all these relations is outlined, and a double relationship proposed between s cells and B cells. By electrophysiological tracing of axonal pathways it is shown that the A cells send axons into the 3rd buccal nerve, the B cells into the 2nd and/or 3rd buccal nerve and in two cases into the redular nerve, and the C cells into the gastro‐oesophageal nerve. Spontaneous synaptic activity of the buccal neurons appears to be formed mostly by the described PSPs. Spontaneous firing inside the isolated ganglion corresponds well to the alternate pattern of muscular contractions of the buccal mass.
The structure and function of serially homologous leg motor neurons in the locust. I. Anatomy
Authors: Wilson John A.
Published: January 2005

Twenty‐one prothoracic and 17 mesothoracic motor neurons innervating leg muscles have been identified physiologically and subsequently injected with dye from a microelectrode. A tract containing the primary neurites of motor neurons innervating the retractor unquis, levator and depressor tarsus, flexor tibiae, and reductor femora is described. All motor neurons studied have regions in which their dendritic branches overlap with those of other leg motor neurons. Identified, serially homologous motor neurons in the three thoracic ganglia were found to have: (1) cell bodies at similar locations and morphologically similar primary neurites (e.g., flexor tibiae motor neurons), (2) cell bodies at different locations in each ganglion and morphologically different primary neurites in each ganglion (e.g., fast retractor unguis motor neurons), or (3) cell bodies at similar locations and morphologically similar primary neurites but with a functional switch in one ganglion relative to the function of the neurons in the other two ganglia. As an example of the latter, the morphology of the metathoracic slow extensor tibiae (SETi) motor neurons was similar to that of pro‐and mesothoracic fast extensortibiae (FETi) motor neurons. Similarly the metathoracic FETi bears a striking resemblance to the pro‐ and the mesothoracic SETi. It is proposed that in the metathoracic ganglion the two extensor tibiae motor neurons have switched functions while retaining similar morphologies relative to the structure and function of their pro‐ and mesothoracic serial homologues.
The intra‐axonal transport of acetylcholine and cholinergic enzymes in rat sciatic nerve during regeneration after various types of axonal trauma
Authors: Heiwall P.‐O. , Dahlström A. , Larsson P.‐A. , Bööj S.
Published: January 2005

The proximo‐distal intra‐axonal transport of acetylcholine (ACh) and cholinergic enzymes (choline acetyltransferase, CAT, and ACh‐esterase, AChE) in rat regenerating sciatic nerve was studied by accumulation technique. Four types of axonal trauma were performed: freezing with solid CO2, crushing, ligating the nerve with remaining tight silk ligature, and cutting the nerve. Normal and sham‐operated rats were used as controls. One to twenty‐nine days later, the nerves were crushed about 15 mm proximal to the trauma. The nerve segment proximal to this crush was dissected out 12 hr later and assayed for ACh‐content and enzyme activities. The increase in this segment 12 hr after crushing was taken as an indication of proximo‐distal transport in the regenerating nerves. ACh transport did not seem to vary during regeneration as compared to controls. In contrast, the transport of both CAT and AChE was initially markedly depressed. Towards the end of the observation period (29 days), a recovery of CAT‐transport occurred in all groups. Recovery of AChE‐transport was marked in the freeze and crush groups. In the cut group no recovery was seen and in the ligated group only a small recovery occurred. Thus, in the nerves where regeneration was facilitated by the presence of intact connective tissue sheaths (freezing and crushing) recovery of transport occurred earlier than in cut or ligated nerves.
Dopamine β‐hydroxylase distribution in density gradients: Physiological and artefactual implications
Authors: Klein Richard L. , Thureson‐Klein Åsa K. , Yen Shu‐Hui Chen , Baggett Jack McC. , Gasparis Milton S. , Kirksey Donny F.
Published: January 2005

Knowledge of the vesicular origin of circulating dopamine β‐hydroxylase (DβH) is indispensable for any attempts to explain the parallelism or lack of it between circulating enzyme and catecholamines as they may relate to physiological stress, forms of hypertension, neurological disorders, and the response to pharmacological agents. The present study represents an effort to evaluate and to place in proper perspective data based on the DβH activity found in the region of the light vesicle peak of noradrenaline (NA), which is used as a quantitative measure of a population of small terminal vesicles.

Distributions of vesicles and subvesicular components are compared with DβH and NA in sucrose‐D2O density gradients used to prepare relatively pure fractions of large dense cored vesicles (LDV) from bovine splenic nerve. Although NA in sedimentable particles of the light vesicle peak is likely to be a valid measure of a small vesicle population, the following is demonstrated: (1) A substantial fraction (25%–37%) of the total sedimentable DβH acitivity can be proven to distribute in the region of the light vesicle peak from a tissue with an insignificant small vesicle population. Based on studies of vesicles from sequential nerve segments, this enzyme activity probably corresponds to a population of “immature” LDV which are undergoing axoplasmic transport and have not synthesized their full complement of transmitter. (2) Physical lysis which depletes the matrix of LDV causes redistribution of DβH activity from the heavy vesicle peak into the region of the light vesicle peak. Analogously, DβH associated with exocytosed LDV and retrograde transport particles is also likely to contaminate the region of the light vesicle peak. (3) Based on available data, it can be calculated that each small dense cored vesicle could contain only 0.1–0.5 molecules of DβH and that a contamination of only 0.016% LDV can account for all of the DβH reported to occur in the light vesicle peak of normal rat vas deferens preparations.
The morphology and coupling of Aplysia bag cells within the abdominal ganglion and in cell culture
Authors: Kaczmarek L. K. , Finbow M. , Revel J. P. , Strumwasser F.
Published: January 2005

The bag cells in the abdominal ganglion of Aplysia californica control egglaying behavior by releasing a polypeptide (ELH) during an afterdischarge of synchronous action potentials. We have used intracellular injection of Lucifer Yellow to study the morphology and interconnections of the bag cells. These neurosecretory cells are typically multipolar and their processes extend in all directions out from the bag cell clusters into the surrounding connective tissue, where they branch in a complex manner. In some of the dye injection experiments, dye transfer from the injected cell to neighboring cells was observed. Freeze fracture of the bag cell clusters and their surrounding connective tissue revealed numerous gap junctions on bag cell processes within the clusters as well as on more distal processes. We have also examined the morphology and coupling between bag cells in primary culture. As in the intact ganglion, bag cells in culture were found to be multipolar. All pairs of bag cells whose somata or processes had formed contacts in culture were electrically coupled. The strongest coupling was observed between pairs of cells whose somata appeared closely apposed. In these cases transfer of Lucifer Yellow between cells could also be observed. It is therefore likely that the synchrony of bag cell action potentials during a bag cell afterdischarge is a result of coupling between individual cells in the bag cell cluster.
Electrical and dye coupling in an identified group of neurons in a coelenterate
Authors: Spencer Andrew N. , Satterlie Richard A.
Published: January 2005

A compressed network of “giant” neurons, lying within the inner nerve‐ring of the hydrozoan jellyfish Polyorchis, functions as the overall pattern generator and the motor neuron system for the subumbrellar swimming musculature. The neurons that form the network are all electrically coupled. The coupling is tight, so that action potentials and slow membrane‐potential oscillations are synchronous throughout the network. The fluorescent dye Lucifer Yellow CH passes throughout the network following iontophoretic injection into a single neuron. The sites of both current and dye passage are presumably the numerous gap junctions which are found where the giants run together. Based on the morphological identification of the giant network from the dye injections and ultrastructural studies, the electrophysiological data on the firing pattern and input–output relations of the network, and its position relative to other neurons in the inner nerve‐ring, the giant network can be considered an identified neuronal group.
The deutocerebrum of the cockroach Blaberus craniifer burm. Spatial organization of the sensory glomeruli
Authors: Chambille Irène , Masson Claudine , Rospars Jean Pierre
Published: January 2005

The objective of this work is to describe the glomerular organization of the deutocerebrum in Blaberus craniifer and to test the hypothesis that the glomeruli are identifiable. The problem is studied using the techniques of analytical geometry, i.e., by measuring the location of the glomeruli in cartesian coordinate systems. Computerized geometrical and statistical techniques are described for the three‐dimensional reconstruction and quantitative study of these brain structures. The invariance of the glomerular organization, and consequently the identifiability of the glomeruli, is based on three criteria: (1) the number of glomeruli per hemideutocerebrum (hDTC) is a constant (109); (2) the position of the glomeruli is symmetrical in the two sides of one individual and identical in the same side of two individuals, except for small local variations, (3) the dimensions of two positionally homologous glomeruli are statistically equal in the same and in different individuals, except for a macroglomerulus which is found only in the male. The causes of variability, from experimental and biological origin, are discussed and quantitatively evaluated. The interindividual biological variability, not ascribable to differences in size between brains, expressed as a 95% interval, is estimated to be 27 μm for the location of glomeruli and 12 μm for the diameter of glomeruli.
Characteristics of tetanic and post‐tetanic potentiation in the septohippocampal and hippocampal commissural systems in the acute rabbit
Authors: Stanley James C. , DeFrance Jon F. , Marchand James E.
Published: January 2005

The frequency characteristics of tetanic and post‐tetanic potentiation of the septohippocampal and hippocampal commissural systems were studied in the acute rabbit preparation. Glass micropipettes were employed to stimulate the medial septal (MSR) and contralateral CA1 (cCA1) regions. Extracellular postsynaptic potentials were recorded in the stratum radiatum and stratum oriens layers of dorsal CA1. Low frequencies of stimulation (2–12 Hz) and brief stimulus trains (7 or 16 stimuli) ensured that only short‐term effects appeared in the data. With MSR and cCA1 stimulation, tetanic potentiation became pronounced at 4 Hz, and plateaued at 6–8 Hz. Thus potentiation was found to be pronounced within the range of the rabbit hippocampal theta rhythm. No differences were found in the characteristics of potentiation evoked by stimulation of MSR and cCA1. Post‐tetanic potentiation lasting 6–12 sec was found. Again, potentiation characteristics did not depend on stimulus site, suggesting a common mechanism for the pathways studied. A two‐factor mechanism was proposed to account for the post‐tetanic potentiation data.
Slice preparation of rat medulla and pons maintained for five hours in vitro
Authors: Hinrichsen C. F. L.
Published: January 2005

Slices of rat medulla and pons were incubated in bicarbonate‐buffered medium and their electrical activity was monitored for five hours with microelectrodes. The morphology of these slices was compared with that of the same region of rats of the same age using prior perfusion or immersion in fixatives before incubation. Many neurons in incubated slices show shrinkage necrosis (apoptosis) but not dilatation of the endoplasmic reticulum seen in most neurons fixed immediately after slicing. In incubated slices, some processes but not somata of glia appeared swollen: to a lesser extent some dendritic and axonal processes were swollen. Glia showed no cytoplasmic reaction after five hours to indicate that they might phagocytose damaged tissue components. Synapses appeared morphologically normal after the period of incubation and there was an apparent increase in numbers of profiles resembling growth cones.
Connectivity changes in an isolated molluscan ganglion during in vivo culture
Authors: Bulloch A. G. M. , Kater S. B. , Murphy A. D.
Published: January 2005

The stability of neuronal connections in the isolated buccal ganglia of Helisoma trivolvis was examined during in vivo culture for periods up to one month. After 4–8 days the characteristic IPSP input to protractor motoneurons (PMNs) was either abolished or reduced in efficacy. This is apparently due to reduced efficacy of chemical synapses, since the input resistance and resting potential of the motoneurons is unchanged and a fraction of spike‐evoked IPSPs from premotor neurons (cyberchrons) onto PMNs was absent. PMNs lacking IPSP input nevertheless exhibit vigorous cyclical bursts of action potentials driven by electrical EPSPs. The IPSP of PMNs showed partial or full restoration after 14–32 days of culture despite the lack of reinnervation of normal targets. Existing electrical synapses were apparently more stable during culture, but electrical connections between cyberchrons and PMNs were strengthened. Probably because of the reinforcement of these electrical synapses, regenerative cycles of activity in both cyberchrons and PMNs may often be initiated by brief stimulation of a single PMN in cultured ganglia. This is in marked contrast to normal ganglia in which PMNs possess a limited ability to generate such activity. It is concluded that isolation of the buccal ganglia results in a predictable, functional alteration of its neuronal circuitry. Such a perturbation of connectivity indicates that a significant degree of plasticity can be exhibited by adult molluscan neurons.
Stimulation is necessary for the development of tolerance to a neuronal effect of ethanol
Authors: Traynor Alexis E. , Schlapfer Werner T. , Barondes Samuel J.
Published: January 2005

Ethanol accelerates the decay of post‐tetanic potentiation at an identified synapse in Aplysia. We have previously shown that with repeated exposures the ethanol effect diminishes, a development termed “tolerance.” Here we present evidence that the establishment of tolerance depends on adequate stimulation of the presynaptic terminal in the presence of ethanol. Elevated magnesium in the perfusion medium prevents tolerance, whereas elevated calcium in the perfusion medium reduces the amount of stimulation required for tolerance to develop.