bluuebunny/crossref_metadata_2025 huggingface dataset:
Sustained sensitivity modifications induced by brief length perturbations in the crayfish slowly adapting stretch receptor
Authors: Da Rocha A. F. , Buño W.
Published: January 2005

These experiments in the slowly adapting stretch receptor of crayfish test the effects of brief length perturbations (i.e., pulses) when presented in isolation at different constant elongations or superimposed on trapezoidal stretches of different amplitudes. Within “in vivo” lengths, during static responses, perturbations reduced firing rates to below control values and, in extreme cases, could silence the receptor. This effect, or “down‐step,” was sustained, occurred above a threshold pulse amplitude and background stretch, and increased with both stimulus characteristics, but was not present during dynamic responses. Beyond “in vivo” lengths, and in a few cases within those limits but close to the extremes, the receptor was silent but perturbations could restore activity. Lengthening pulses were more effective than shortening ones in generating after‐effects. Perturbations change, during indefinitively long periods, the receptor's length or static sensitivity acting as a negative feedback which tends to maintain the discharge rate within fixed values. Perturbations disclose marked nonlinerities, which suggest that the classical view of a proportional control in the reflex loop in which the receptor participates may not operate in natural conditions.
What is the correct value for Na, K‐ATPase activity in homogenates of cerebral cortex?
Authors: Křivánek J.
Published: January 2005

Activity of Na, K‐ATPase in homogenates of fresh cerebral cortex of rats was compared with that of cortex frozen under different conditions. Activity yields after rapid in situ freezing of the exposed cerebral cortex were twice, higher (26.1 U) than in homogenates of the fresh cortex (13.3 U). Fresh brain kept on ice for 60 and 300 s and subsequently frozen in liquid nitrogen yielded activities comparable to those of the tissue frozen in situ (24.1 U and 24.9 U for 60 s and 300 s periods, respectively). Inhibition of Na, K‐ATPase by 10−7 M vanadate was significantly stronger (38%) in homogenates of the fresh brain then in those of the cortex frozen in situ (28%). High Na, K‐ATPase activity (47.6 U) in suspensions of synaptosomal membranes (SM) prepared from fresh cortical homogenates was only slightly inhibited by 10−7 M vanadate (12%). Various treatments of homogenates or SM suspensions, like increase of piston rotation speed, repeated freezing and thawing procedure or vigorous shaking did not significantly affect the enzyme activity. Mg‐ATPase activity and its sensitivity to vanadate was also modified by tissue treatment but the effect was much less pronounced.
Cellular analyses of hormone influence on motoneuronal development and function
Authors: Breedlove S. Marc
Published: January 2005

The striated bulbocavernosus (BC) muscles of the rodent perineum are innervated by motoneurons in the spinal nucleus of the bulbocavernosus (SNB). In adulthood, the BC muscles are present in males only. However, newborn female rats have BC muscles, and SNB cells have made both anatomical and functional contact with them. Nevertheless, both motoneurons and muscles will degenerate unless androgens are administered perinatally. Such androgen treatment appears to be acting primarily on the BC muscles themselves, since the muscles are spared by androgen even after the loss of supraspinal neural afferents or even the entire lumbosacral spinal cord. Furthermore, androgen can spare SNB motoneurons that are themselves androgen insensitive. Perinatal steroid treatments can also alter the final spinal location of SNB cells as determined by retrograde tracing studies. Androgen continues to modify the morphology of the SNB system in adulthood, altering the size of both motoneurons and targets, which may be important for the reproductive function of BC muscles. Finally, the sexually dimorphic character of motoneuronal groups innervating perineal muscles seems to be common in mammals, since the homologue of the SNB, Onuf's nucleus, has more cells in males than in females in both dogs and humans.
The effects of trifluoperazine on fast and slow axonal transport in the rabbit vagus nerve
Authors: Ekström Per , Kanje Martin , McLean W. Graham
Published: January 2005

The effects of trifluoperazine (TFP) on fast and slow axonal transport (AXT) of labeled proteins were examined in the rabbit vagus nerve. Cuffs soaked in a 10 mM, but not 0.1 mM or 1 mM, concentration of TFP applied locally around the vagus nerve in vivo blocked both fast and slow AXT, as measured by the accumulation of 3H‐labeled proteins. In vitro, fast AXT was affected by 0.1 mM TFP. The TFP cuff treatment caused a reduction in the number of axonal microtubules (MT) whereas cuffs soaked in saline had no effect. The levels of ATP, ADP, and AMP were not significantly lowered by the TFP treatment. The results suggest that both fast and slow AXT are sensitive to TFP treatment, and that the axonal MT‐system may be the main target of the drug.
Multiple transmitter neurons in Tritonia. I. Biochemical studies
Authors: Lloyd Philip E. , Masinovsky Boris P. , Willows A. O. Dennis
Published: January 2005

The buccal ganglia of the marine mollusc Tritonia control a variety of movements associated with feeding, including gut motility. The buccal ganglia and gut contain a class of peptides termed small cardioactive peptides (SCPs). Cobalt backfilling of the nerve which innervates the gut stains several buccal neurons including two pairs of reidentifiable cells, B11 and B12. Both appear white under epiillumination, a characteristic of peptidergic neurons in gastropods. Enzymatic and biochemical analyses of extracts from microdissected B11 cell bodies demonstrate that this neuron contains two species of SCPs. Labeling in organ culture followed by dissection and extraction of cell bodies indicates that these peptides were synthesized in B11. One of these peptides appears to be identical to SCPB, one of two SCPs that have been sequenced. The other SCP present in these neurons is novel. Less extensive analyses of extracts of B12 somata suggest that it also contains the same SCPs. In addition to the peptides, B11 also contains large quantities of acetylcholine (ACh) as determined by a radioenzymatic assay of cell body extracts. B12 does not contain measureable ACh. The concentration of the two peptides and ACh in the B11 cytoplasm is approximately 1 mM. Neuron B11 appears to be an appropriate model system for studying the biochemical and physiological properties of multiple transmitter neurons.
Leptinotarsin‐D, a neurotoxic protein, evokes neurotransmitter release from, and calcium flux into, isolated electric organ nerve terminals
Authors: Miljanich George P. , Yeager Robert E. , Hsiao Ting H.
Published: January 2005

Previous work has demonstrated that the neurotoxin leptinotarsin elicits release of neurotransmitter from mammalian nerve terminals, and it has been suggested that the toxin may act either as a direct agonist of voltage‐sensitive calcium channels in these terminals (Crosland et al., 1984) or as a calcium ionophore (Madeddu et al., 1985a,b). Preliminary studies (Yeager et al., 1987) demonstrated that leptinotarsin also evokes transmitter release from isolated elasmobranch electric organ nerve terminals. We now report further investigations of the effects of leptinotarsin in this system. The action of the toxin is saturable, releasing about the same small fraction of total transmitter as that released by depolarization. An upper limit for the concentration for half maximal release is estimated to be 4 nM. Leptinotarsin‐evoked transmitter release exhibits behavior very similar to depolarization‐evoked release with respect to dependence on Ca2+, Ba2+, and Sr2+ and blockade by Co2+, Cd2+, and trifluoperazine. Leptinotarsin also promotes the uptake of calcium into synaptosomes to a degree similar to that caused by depolarization by K+. The binding of leptinotarsin to nerve terminals is probably Ca2+ dependent and receptor mediated. Taken together with the behavior of leptintoarsin‐evoked release in other preparations, these results are consistent with the hypothesis that this toxin acts by opening a presynaptic calcium channel. However, the possibility that leptinotarsin is a calcium ionophore cannot be excluded.
Synaptic competition and the elimination of polyneuronal innervation follwoing reinnervation of adult frog sartorius muscles
Authors: Werle Michael J. , Herrera Albert A.
Published: January 2005

The elimination of polyneuronal innervation (synapse elimination) that occurs following reinnervation was studied in sartorius muscles of adult Rana pipiens. The percentage of neuromuscular junctions that were polyneuronally innervated declined from 47% at 40–80 days after nerve crush to 22% at greater than 250 days after nerve crush. We measured the size, synaptic strength, and position of competing nerve terminals at identified dually innervated neuromuscular junctions at these two different periods of synapse elimination. Our goal was to determine if any of these parameters play a role in the competition between nerve terminals that ultimately results in the elimination of polyneuronal innervation. Our data support the hypothesis that polyneuronal innervation will persist if competing nerve terminals are of similar synaptic efficacies but will be eliminated if the competing terminals are of different synaptic efficacies. We also tested, but failed to find any evidence, that the spatial proximity of competing nerve terminals at the same synaptic site influences the elimination of polyneuronal innervation.
Wind‐activated thoracic interneurons of the cockroach: II. Patterns of connection from ventral giant interneurons
Authors: Ritzmann Roy E. , Pollack Alan J.
Published: January 2005

A number of thoracic interneurons (TIs) have been found to receive inputs from ventral giant interneurons (vGIs). Each of these cells responds to wind with short latency depolarizations. The previous paper described response properties of several TIs to wind stimuli, including those excited by vGIs. The data showed a correlation between the shape of the TI's wind fields and its morphology. The presence of ventral branches located near the midline of the ganglion predicts a strong response to wind on that side. These ventral median (VM) branches are in the proper location to permit overlap with processes from vGIs. Here we describe the patterns of connections between individual vGIs and 13 of the thoracic interneurons located in the meso‐ and metathoracic ganglia. A correlation was found between the presence of VM branches and excitation by vGIs. TIs were only excited by vGIs on the side(s) on which VM branches exist. However, presence of a VM branch does not imply that all vGIs on that side make connections with the TI.

Summation was found between various vGIs that excited each individual thoracic interneuron. In unilateral thoracic interneurons, no sign of inhibition was found from vGIs on the sides opposite that which contained excitatory vGI axons. Neither was there any evidence of inhibition from dorsal giant interneurons. In addition preliminary evidence indicated that left‐right homologues do not inhibit one another. Thus, the data suggest that directional wind fields are primarily the result of selective connection from specific vGIs.
Primary afferent responses of a crustacean mechanoreceptor are modulated by proctolin, octopamine, and serotonin
Authors: Pasztor Valerie M. , Bush Brian M. H.
Published: January 2005

Modulation of sensory responses recorded intracellularly in primary sensory afferents of a crustacean proprioceptor is described. The neuropeptide proctolin enhances the sensory response, whereas the bioamines octopamine and serotonin depress it.

The lobster oval organ of the second maxilla, a simple stretch receptor lacking centrifugal control, provides a useful model for studies on nonsynaptic modulation at peripheral sensory loci. Its three large afferents, X, Y, and Z, were prepared for intracellular recording and tested under five experimental conditions: (1) when fully rested, (2) when adapted to maintained stretch and firing tonically, (3) when showing reduced responses after habituation to repetitive stimulation, (4) not stretched but depolarized with current injections, (5) after TTX blockade.

The results, taken together, indicate that conductances contributing to the overall amplitude of the receptor potential are major targets for modulators. Thus proctolin increased receptor potential amplitudes with consequent augmentation of spiking, whereas serotonin and octopamine depressed the receptor potentials, often to subthreshold levels with loss of spiking. Octopamine was a less potent agent than serotonin and failed to act upon fibers under TTX blockade.

Fibers Y and Z consistently showed sensitivity to the modulators tested. The largest fiber, X, typically was resistant to proctolin, octopamine, and serotonin.

Threshold concentrations of 10−10−10−11 M determined in vitro are well below the circulating levels for serotonin and octopamine found in vivo. Proctolin, however, is usually not detectable in the hemolymph, and it is suggested that a significant site of proctolin release may be the oval organ itself.
Parallel processing and selection of the responses to serotonin during reinnervation of an identified leech neuron
Authors: Drapeau Pierre , Sanchez‐Armass Sergio
Published: January 2005

In an attempt to define the mechanism of synaptic specificity, we have been studying pairs of identified leech neurons isolated in tissue culture. The cultured neurons reform specific synapses when paired with appropriate partners in the absence of other cell types. In recent studies, we have examined in detail the reformation of a serotoninergic synapse between the Retzius cell and one of its targets, the pressure sensitive (P) cell. The P cell in vivo and its soma in vitro have two types of responses to serotonin (5‐HT). From voltage clamp analysis of cultured P cells, we demonstrated the parallel activation of chloride (gCls) and monovalent cation (gCations) channels coupled to distinct receptor subtypes and gated by separate second messengers. Only gCls was activated by 5‐HT released from the presynaptic Retzius cell both in vivo and in vitro. This demonstrates the remarkable specificity of the reformation of this synapse in culture since only the correct 5‐HT receptor subtype is activated.

An 80% reduction of gCations was observed in P cells that had failed to be innervated by Retzius cells in culture, suggesting that gCations may be lost prior to synapse formation. Retzius cells depleted of 5‐HT also reduced gCationss in the paired P cells and incubating single P cells in 5‐HT did not reduce gCations. In addition, aldehyde‐fixed Retzius cells were able to selectively reduce gCations when paired with P cells. We conclude that the loss of gCations was due to contact between the neurons. The early clearing of counter‐effective receptor subtypes may be a prelude to synapse formation.
Changes in contralateral protein metabolism following unilateral sciatic nerve section
Authors: Menéndez José A. , Cubas Susana C.
Published: January 2005

Changes in nerve biochemistry, anatomy, and function following injuries to the contralateral nerve have been repeatedly reported, though their significance is unknown. The most likely mechanisms for their development are either substances carried by axoplasmic flow or electrically transmitted signals. This study analyzes which mechanism underlies the development of a contralateral change in protein metabolism. The incorporation of labelled amino acids (AA) into proteins of both sciatic nerves was assessed by liquid scintillation after an unilateral section. AA were offered locally for 30 min to the distal stump of the sectioned nerves and at homologous levels of the intact contralateral nerves. At various times, from 1 to 24 h, both sciatic nerves were removed and the proteins extracted with trichloroacetic acid (TCA). An increase in incorporation was found in both nerves 14–24 h after section. No difference existed between sectioned and intact nerves, which is consistent with the contralateral effect. Lidocaine, but not colchicine, when applied previously to the nerves midway between the sectioning site and the spinal cord, inhibited the contralateral increase in AA incorporation. It is concluded that electrical signals, crossing through the spinal cord, are responsible for the development of the contralateral effect. Both the nature of the proteins and the significance of the contralateral effect are matters for speculation.
Development and survival of thoracic motoneurons and hindlimb musculature following transplantation of the thoracic neural tube to the lumbar region in the chick embryo: Anatomical aspects
Authors: O'Brien Michael K. , Oppenheim Ronald W.
Published: January 2005

Thoracic spinal cord transplanted to the lumbar region at the time of neural tube closure in the chick embryo survives and initially differentiates normally similar to in situ thoracic cord. Normal numbers of motoneurons are produced that innervate the host hindlimb musculature. In control thoracic cord approximately 70% of the motoneurons are lost by normal cell death between embryonic day (E) 6 and E11–E12. By contrast, the transplanted thoracic cord loses only about 30% of the motoneurons during this period. Transplantation of one hindlimb to the thoracic region also reduces the normal loss of in situ thoracic motoneurons. We conclude that some factor(s) associated with the increased target size provided by the hindlimbs promotes the survival of thoracic motoneurons. In contrast, by E16–E18 motoneuron numbers in the thoracic transplants decrease to below control levels. Dorsal root ganglion cells in the transplant were also initially increased (on E8) but later decreased to below control values. Hindlimb muscles innervated by thoracic motoneurons in the transplant also differentiated normally up to E10 to E12. Myotube size and numbers, muscle size and myotube types (fast versus slow) all developed normally in several thoracically‐innervated hindlimb muscles. However, beginning on E14 myotube numbers and muscle size were markedly decreased resulting in muscle atrophy. Injections of horse‐radish peroxidase (HRP) into the thoracic transplants labelled neurons in the host spinal cord and brainstem rostral to the transplant thereby indicating an anatomical continuity between host and transplant neural tube. Injections of HRP into specific thoracically innervated hindlimb muscles on E8 labelled distinct pools of motoneurons in the transplants. The location of the labelled motor pools were similar to the location of the motor pools serving these muscles in normal lumbar cord. For example, the sartorius motor pool, which is normally restricted to the first two segments of the lumbar cord, was located in the first two segments of the thoracic transplant. We conclude that thoracic neural tube transplanted to the lumbar region initially differentiates normally, innervates hindlimb muscles and that the thoracically innervated hindlimb muscles also differentiate normally. Subsequently, however, thoracic innervation of hindlimb muscles somehow becomes incompatible with normal development and the motoneurons and muscles eventually undergo regressive changes.
Conservation of antigen 3G6: A crystalline cone constitutent in the compound eye of arthropods
Authors: Edwards John S. , Meyer Mark R.
Published: January 2005

A monoclonal antibody (MAb), 3G6, highly selective for neuropil glia in the CNS of the house cricket Acheta domesticus, also demonstrates remarkable selectivity for the nonneuronal crystalline cone cells of the compound eye. MAb 3G6 labels cone cells in eucone eyes throughout Insecta, from ancestral forms such as the bristle tail to the more recent honeybee; eucone structures are also recognized in Crustacea. Analogous nonneural structures found in pseudocone or acone eyes also express detectable 3G6 immunoreactivity. Immunoblot analysis demonstrates that MAb 3G6 binds to similar Mr 85 kDa glycoproteins in the cricket CNS and retina, corresponding to the glial and crystalline cone forms of the antigen. Further, polypeptides of similar relative mass are also recognized in the eucone eye of the butterfly Pieris and the pseudocone eye of the fly Calliphora. The properties and function of glycoprotein 3G6 in the CNS and retina are yet to be explored. However, the finding that a unique antigen is highly conserved within the crystalline cone or analogous regions of the retina throughout the Arthropoda lends support at the molecular level to the notion that the arthropod compound eye has a monophyletic origin.
A developmental analysis of spontaneous and reflexive reversals in the nematode Caenorhabditis elegans
Authors: Chiba Catherine M. , Rankin Catharine H.
Published: January 2005

Reversals of forward locomotion in the nematode Caenorhabditis elegans are thought to be mediated by a common neural circuit, the touch withdrawal circuit. Despite substantial neuroanatomical changes over postembryonic development, one reversal behavior, the head‐touch withdrawal reflex, does not appear to change over development (Chalfie and Sulston, 1981). The experiments reported here indicate that two other reversal behaviors, spontaneous reversals and the tap reversal reflex to vibratory stimuli, show developmental changes. Young adult animals showed higher frequencies of spontaneous reversals than all other developmental stages, while larval stages differed from adults in their pattern of responses to tap. Although animals of all stages reversed in response to touch, taps elicited both reversals and accelerations of forward movement. In response to single taps, larval stages reversed on approximately half the occasions; young adult and 4‐day‐old adults almost always reversed. Increasing stimulus magnitudes increased the probability of accelerations at all developmental stages, but larval stages showed fewer reversals and more accelerations than adults. The behavioral changes observed coincide with known periods of neuroanatomical change in the touch withdrawal circuit. The addition of a late‐developing sensory neuron, AVM, is implicated in the behavioral differences between juveniles and adults.
Inhibition of protein synthesis prevents cell death in sensory and parasympathetic neurons deprived of neurotrophic factor in vitro
Authors: Scott Sheryl A. , Davies Alun M.
Published: January 2005

Shortly after neurons begin to innervate their targets in the developing vertebrate nervous system they become dependent on the supply of a neurotrophic factor, such as nerve growth factor (NGF) for survival. Recently, Martin et al. (1988) have shown that inhibiting protein synthesis prevents the death of NGF‐deprived sympathetic neurons, suggesting that NGF promotes neuronal survival by suppressing an active cell death program. To determine if other neurotrophic factors may regulate neuronal survival by a similar mechanism we examined the effects of inhibiting protein and RNA synthesis in other populations of embryonic neurons that require different neurotrophic factors, namely: (1) trigeminal mesencephalic neurons, a population of proprioceptive neurons that are supported by brain‐derived neurotrophic factor; (2) dorsomedial trigeminal ganglion neurons, a population of cutaneous sensory neurons that are supported by NGF; (3) and ciliary ganglion neurons, a population of parasympathetic neurons that are supported by ciliary neuronotrophic factor. Blocking either protein or RNA synthesis rescued all three populations of neurons from cell death induced by neurotrophic factor deprivation in vitro. Thus, at least three different neurotrophic factors appear to promote survival by a similar mechanism that may involve the suppression of an endogenous cell death program.
Cholinergic activation of the lobster cardiac ganglion
Authors: Sullivan Robert E. , Miller Mark W.
Published: January 2005

The frequency of rhythmic burst activity of the isolated lobster cardiac ganglion is increased by exogenously applied acetylcholine and muscarinic agonists. Responses of individual motor neurons isolated from the ganglion by transection consist of a slow depolarization and repetitive bursting. The pharmacological profile of the receptors mediating this response is similar to that of vertebrate neuronal muscarinic receptors. Isolated ganglia incubated in the presence of [3H]‐choline (18‐19 h) exhibited radiolabelled acetylcholine accumulation. It is suggested that ganglionic excitation may be accomplished by extrinsic or intrinsic activation of muscarinic receptors on the motor neurons.
Involvement of pedal peptide in locomotion in Aplysia: Modulation of foot muscle contractions
Authors: Hall Jon D. , Lloyd Philip E.
Published: January 2005

Pedal peptide (Pep) is a 15‐amino‐acid neuropeptide that is localized within the Aplysia central nervous system (CNS) predominantly to a broad band of neurons in each pedal ganglion. Pep‐neurons were identified by intracellular staining and immunocytology or by radioimmunoassay (RIA) of extracts from identified neurons. RIA reveals that 97% of all Pep‐like immunoreactivity (IR‐Pep) in pedal nerves is found in the three nerves that innervate the foot. Nearly every Pep‐neuron sends an axon out at least one of these three nerves. Application of Pep to foot muscle causes an increase in the amplitude and relaxation rate of contractions driven by nerve stimulation or intracellular stimulation of pedal motor neurons. The increase in relaxation rate was the predominant effect. Intracellular recording in “splitfoot” preparations reveals that Pep‐neurons increase their overall firing rates and fire in bursts with each step during locomotion. Recovery of IR‐Pep from foot perfusate following pedal nerve stimulation increases in a frequency‐dependent fashion. Thus it appears that one function of Pep‐neurons is to modulate foot muscle contractility during locomotion in Aplysia.
Activity‐driven sharpening of the regenerating retinotectal projection: Effects of blocking or synchronizing activity on the morphology of individual regenerating arbors
Authors: Schmidt John T. , Buzzard Marlene
Published: January 2005

Both blocking activity with intraocular tetrodotoxin (TTX) and synchronizing activity with a xenon strobe light (1 Hz) prevent retinotopic sharpening of regenerating optic projection in goldfish (Meyer, 1983; Schmidt, 1985; Cook and Rankin, 1986). In this study, we tested, in both normal and regenerating projections, the effects of these two treatments on individual optic arbors. Arbors were stained via anterograde transport of HRP, drawn in camera lucida from tectal whole mounts, and analyzed for spatial extent in the plane of the retinotopic map, order of branching, number of branch endings, depth of termination, and the caliber of the parent axon. In normal tectum, fine, medium, and coarse caliber axons gave rise to small, medium, and large arbors, which averaged 127 μm, 211 μm and 275 μm in horizontal extent, and terminated at characteristic depths. All three classes averaged roughly 21 branch endings. Optic arbors that regenerated with normal patterns of activity returned to a roughly normal appearance by 6–11 weeks postcrush: the same three calibers of axons gave rise to the same three sizes of arbors at the same depths, but they were much less stratified and were on average about 16% larger in horizontal extent. At this time point, arbors regenerated under TTX or strobe were on the average 71 and 119% larger, respectively, than the control‐regenerated arbors (larger in all classes), although they had approximately the same number of branch endings and were equally poorly stratified. Synapses formed under strobe were also normal in appearance. Thus the only significant effect of both strobe and TTX treatment was to enlarge the spatial extent of arbor branches. Arbors that were not regenerating were very slightly (but significantly) enlarged by TTX block of activity or strobe illumination. As previous staining showed that regenerating axons initially make widespread branches and later retract many of those branches (Schmidt, Turcotte, Buzzard, and Tieman, 1988; Stuermer, 1988), the present findings support the idea that blocking activity or synchronizing activity prevents retinotopic sharpening by interfering with the elimination of some of the errant branches.
The development of the lamprey pattern generator for locomotion
Authors: Cohen Avis H. , Dobrov Tamara A. , Li Guan , Kiemel Timothy , Baker Margaret T.
Published: January 2005

The life cycle of the lamprey includes a larval stage that can last for several years. The motor behavior of the larval lamprey, the ammocoete, has been only minimally studied and little is known of the neural correlates of that behavior. Comparison of known larval behavior to that of adults leaves unclear whether there are large or small changes in the spinal nervous system during transformation. The motor output of isolated larval and transforming spinal cords when stimulated to “swim” with d‐glutamate has some differences from that of comparable adult preparations, but shares many important features with adults. Primarily, the fictive swimming is less well regulated and less stable than adults of the same species. We propose that a major difference in the structure and organization of the central pattern generator for locomotion between adults and ammocoetes is a relative lack or immaturity of some cell types that participate in the coordination of the segments and the generation of the rhythm of the periodic bursting.
Constant topological organization of the coleopteran metamorphosing nervous system: Analysis of persistent elements in the nervous system of Tenebrio molitor
Authors: Breidbach Olaf
Published: January 2005

Evidence is provided that the topological organization of the larval neuropil is preserved during metamorphosis of Tenebrio molitor. Constancies in neuronal organization were due in part to persistence of individual neurons whose morphologies were individually followed. It appears that the phenomenologically static situation of the metamorphosing neuropil is achieved by stabilization and regulation due to cellular interactions. Comparisons are made with features of hemimetabolan postembryogenesis.
Topographical features of the substratum for growth of pioneering neurons in the manduca wing disc
Authors: Nardi James B. , Vernon Rebecca A.
Published: January 2005

The sensory neurons of the Manduca wing form a planar network nestled between the wing's upper and lower monolayers. The pioneering axons of this network grow in a distal‐to‐proximal direction over the basal surface of the upper epithelial monolayer. The basal surface of this monolayer has been examined ultrastructurally during the period of axonal outgrowth. The cellular terrain traversed by axons shows a graded distribution of epithelial processes, with the number of processes increasing in a proximal direction. Growth cones of axons, therefore, encounter increasing surface areas for contact with their substratum as they move toward the base of the wing. Because a basal lamina is laid down over these epithelial processes after axons have pioneered the neural pathways of the wing, axonal guidance cues apparently lie on surfaces of these basal processes. At branch points of the neural pathway examined in this study, axons avoid pathways in which the basal surfaces of cells in the upper wing monolayer interdigitate with basal surfaces of underlying tracheal cells. This interaction between wing epithelial cells and tracheal epithelial cells could act as a physical barrier to axonal outgrowth.
Neuroanatomical specificity in the co‐localization of aromatase and estrogen receptors
Authors: Balthazart Jacques , Foidart Agnes , Surlemont Chantal , Harada Nobuhiro
Published: January 2005

The relative distributions of aromatase and of estrogen receptors were studied in the brain of the Japanese quail by a double‐label immunocytochemical technique. Aromatase immunoreactive cells (ARO‐ir) were found in the medial preoptic nucleus, in the septal region, and in a large cell cluster extending from the dorso‐lateral aspect of the ventromedial nucleus of the hypothalamus to the tuber at the level of the nucleus inferioris hypothalami. Immunoreactive estrogen receptors (ER) were also found in each of these brain areas but their distribution was much broader and included larger parts of the preoptic, spetal, and tuberal regions. In the ventromedial and tuberal hypothalamus, the majority of the ARO‐ir cells (over 75%) also contained immunoreactive ER. By contrast, very few of the ARO‐ir cells were double‐labeled in the preoptic area and in the septum. More than 80% of the aromatase‐containing cells contained no ER in these regions. This suggests that the estrogens, which are formed centrally by aromatization of testosterone, might not exert their biological effects through binding with the classical nuclear ER. The fact that significant amounts of aromatase activity are found in synaptosomes purified by differential centrifugation and that aromatase immunoreactivity is observed at the electron microscope level in synaptic boutons suggests that aromatase might produce estrogens that act at the synaptic level as neurohomones or neuromodulators.
Ionic currents of the nodal membrane underlying the fastest saltory conduction in myelinated giant nerve fibers of the shrimp Penaeus japonicus
Authors: Terakawa Susumu , Hsu Ke
Published: January 2005

The myelinated giant nerve fiber of the shrimp, Penaeus japonicus, is known to have the fastest velocity of saltatory impulse conduction among all nerve fibers so far studied, owing to its long distances between nodal regions and large diameter. For a better understanding of the basis of this fast conduction, a medial giant fiber of the ventral nerve cord of the shrimp was isolated, and ionic currents of its presynaptic membrane (a functional node) were examined using the sucrose‐gap voltage‐clamp method. Inward currents induced by depolarizing voltage pulses had a maximum value of 0.5 μA and a reversal potential of 120 mV. These currents were completely suppressed by tetrodotoxin and greatly prolonged by scorpion toxin, suggesting that they are the Na current.

Both activation and inactivation kinetics of the Na current were unusually rapid in comparison with those of vertebrate nodes. According to a rough estimation of the excitable area, the density of Na current reached 500 mA/cm2. In many cases, the late outward currents were induced only by depolarizing pulses larger than 50 mV in amplitude. The slope conductance measured from late currents were mostly smaller than that measured from the Na current, suggesting a low density of K channels in the synaptic membrane. These characteristics are in good harmony with the fact that the presynaptic membrane plays a role as functional node in the fastest impulse conduction of this nerve fiber.
Synergistic interactions between transforming growth factor beta and fibroblast growth factor regulate Schwann cell mitosis
Authors: Schubert David
Published: January 2005

Cultured Schwann cells divide in response to a limited repertoire of mitogens. In addition to cyclic AMP analogs and reagents that raise intracellular cyclic AMP, the only purified mitogens for Schwann cells are transforming growth factor beta (TGFβ), acidic (a) and basic (b) fibroblast growth factor (FGF), and the BB and AB dimers of platelet‐derived growth factor (PDGF). Although individually each one of these growth factors is only weakly mitogenic, it is shown here that when TGFβ and bFGF are added to Schwann cell cultures together, they interact to produce a mitogenic response that is much greater than that produced by either growth factor alone. Both the absolute concentration of each protein and the molar ratio of TGFβ to bFGF determines the magnitude of the Schwann cell response.
Local regeneration in the retina of the goldfish
Authors: Hitchcock Peter F. , Myhr Karen J. Lindsey , Easter Stephen S. , Mangione‐Smith Rita , Jones Daphne Dwyer
Published: January 2005

We have studied regeneration of the retina in the goldfish as a model of regenerative neurogenesis in the central nervous system. Using a transsclearal surgical approach, we excised small patches of retina that were replaced over several weeks by regeneration. Lesioned retinas from three groups of animals were studied to characterize, respectively, the qualitative changes of the retina and surrounding tissues during regeneration, the concomitant cellular proliferation, and the quantitative relationship between regenerated and intact retina. The qualitative and quantitative analyses were done on retinas prepared using standard methods for light microscopy. The planimetric density of regenerated and intact retinal neurons was computed in a group of animals in which the normal planimetric density ranged from high to low. Cell proliferation was investigated by making intraocular injections of 5‐bromo‐2′‐deoxyuridine (BUdr) at various survival times to label proliferating cells and processing retinal sections for BUdr immunocytochemistry. The qualitative analysis showed that the surgery created a gap in the existing retina that was replaced with new retina over the subsequent weeks. The BUdr‐labeling experiments demonstrated that the excised retina was replaced by regeneration of new neurons. Neuroepithiallike cells clustered on the wound margin and migrated centripetally, appositionally adding new retina to the old. The quantitative analysis showed that the planimetric density of the regenerated neurons approximated that of the intact ones.
Immunocytochemical detection of the growth‐associated protein B‐50 by newly characterized monoclonal antibodies in human brain and muscle
Authors: Mercken Marc , Lübke Ursula , Vandermeeren Marc , Gheuens Jan , Oestreicher A. Beate
Published: January 2005

The growth‐associated protein B‐50 also termed GAP‐43, F1, pp46, P‐57 and neuromodulin is a nervous tissuespecific protein kinase C (PKC) substrate that is considered to play a major role in neurite formation, regeneration, and neuroplasticity. We describe the isolation of seven mouse monoclonal antibodies (Mabs) directed against B‐50. The Mabs are produced against the bovine B‐50, selected by ELISA for cross‐reactivity with its human counterpart, and evaluated on Western blots in comparison with the well‐characterized affinity‐purified rabbit polyclonal antibodies to rat‐B‐50. The Western blots show that the Mabs NM1, NM4, and NM6 recognize specifically the B‐50 of bovine, human, and rat brain extract and the purified PKC phosphorylated and unphosphorylated rat B‐50 isoforms. The Mabs NM2 and NM3 cross‐react with bovine B‐50 immunoreactive c‐kinase substrate (BICKS), a protein sharing a 17 amino acid sequence homology with B‐50. Two Mabs are useful for the detection of B‐50 immunoreactivity in formalin‐fixed human and rat brain tissues. In human specimen of the hippocampus, a characteristic neuropil distribution of B‐50 is detected by the Mabs. In human muscle, Mabs reveal B‐50 in nerve bundles and in axons at motor end plates. Thus, these Mabs are useful in investigating the function and localization of the B‐50 protein.
Demonstration of motoneuron‐12 sparing in cultured Manduca sexta ventral nerve cords
Authors: Choi Mikyung Kim , Fahrbach S. E.
Published: January 2005

The emergence of the adult Manduca sexta moth is accompained by the death of half of the neurons present in the pupal abdominal nervous system (Truman, 1983). This developmental neuronal death is highly selective, so that the same neurons die at the same time relative to emergence in every moth. In the case of the MN‐12 motoneurons, this cell death is regulated both by hemolymph concentrations of a steroid hormone, 20‐hydroxyecdysone, and by actions exerted by adjacent ganglia (Truman and Schwartz, 1984; Fahrbach and Truman, 1987). This latter effect, which has been previously described in isolated abdomens and in moths with transected ventral nerve cords, has now been reproduced under controlled culture conditions in which the selectivity and extent of postemergence neuronal death is comparable to that seen in vivo. With respect to the MN‐12 neurons found in the most anterior unfused abdominal ganglion, A3, the pterothoracic ganglion appears to be the source of a factor that permits these neurons to die according to their usual developmental schedule. © 1992 John Wiley & Sons, Inc.
Modifications of motoneuron development following transplantation of thoracic spinal cord to the lumbar region in the chick embryo: Evidence for target‐derived signals that regulate differentiation
Authors: Yin Qin‐Wei , Oppenheim Ronald W.
Published: January 2005

In order to examine the role of target cells in the development of spinal motoneurons, the neural tube from thoracic segments was transplanted to the lumbar region on embryonic day (E) 2, and allowed to innervate hindlimb muscles in the chick embryo. When examined at later stages of development, the proportion of white and gray matter in the thoracic transplant was altered to resemble normal lumbar cord. Many thoracic motoneurons were able to survive up to posthatching stages following transplantation. The branching and arborization of dendrites of thoracic motoneurons innervating hindlimb muscles, as well as motoneuron (soma) size, were also increased to an extent approximating that seen in normal lumbar motoneurons. In support of previous studies using a similar transplant model, we have also found that the peripheral (intramuscular) branching pattern of thoracic motoneuron axons innervating hindlimb muscles was similar to that of normal lumbar motoneurons. Axon size and the degree of myelination of transplanted thoracic motoneuron axons were also increased so that these parameters more closely resembled axons of normal lumbar than normal thoracic spinal motoneurons. Virtually all of the changes in motoneuron properties noted above were observed irrespective of whether or not the transplanted spinal cord had developed in anatomical continuity with the host rostral cord. Accordingly, it is unlikely that the changes in the development of transplanted thoracic motoneurons reported here are induced either entirely, or in part, by signals derived from the host central nervous system. Rather, these changes appear to be mediated by interactions between the transplanted motoneurons and the hindlimb. We favor the notion that retrograde trophic signals derived from the hindlimb act to modulate the development of innervating motoneurons. Whether this signal involves a diffusible trophic agent released from target cells, or acts by some other mechanism is presently unknown. © 1992 John Wiley & Sons, Inc.
Modulation of sprouting in organ culture after axotomy of an identified molluscan neuron
Authors: Berdan R. C. , Easaw J. C.
Published: January 2005

We examined a variety of factors that might modulate the initiation of neurite outgrowth in an attempt to identify means by which its initiation might be accelerated. We examined this initiatio from an identified molluscan neuron, Helisoma trivolvis buccal neuron B5 after axotomy, and determined whether the site of injury, temperature, ion channel blockers, pH, the second messenger cAMP, and protein synthesis affect the initiation of neurite outgrowth. Neurite outgrowth was assayed from axotomized neurons by filling the neurons intracellularly with Lucifer Yellow and examining the percentage of axons that extended (sprouted) new process after 9 or 24 h in organ culture. About one‐third (31%) of axotomized neurons sprouted from the site of injury after 9 h (n = 22), and 88% (n = 20) sprouted after 24 h in saline at 22°–24°C when the injury was located 800 μm from the soma. Elevating the temperature to 32°C or moving the lesion site to 400 or 1500 μm from the soma did not significantly alter the incidence of sprouting. Blocking sodium channels with tetrodotoxin [TTX (2 × 10−5 M)] did not significantly reduce the incidence of sprouting, whereas the sodium channel agonist, veratridine (10−5 M) did. The calcium channel blocker lanthanum (10−6–10−4 M), stimulated neurite outgrowth; however, the organic calcium channel blocker verapamil (10−3–10−5 M), and the calcium ionophore A23187 (10−5 M), had no effect on sprouting. Exposure of neurons to the potassium channel blocker tetraethylammonium [TEA (20 mM)], elevation of intracellular pH with NH4Cl (5 mM), or treatment with the adenylate cyclase activator forskolin (10−5 M) reduced the incidence of sprouting, whereas dideoxy‐forskolin (10−5 M) had no effect. Inhibition of protein synthesis with anisomycin (2 × 10−4 to 2 × 10−6 M) did not significantly suppress sprouting 24 h after axotomy. Both d and l isomers of glutamate (300 μM) stimulated sprouting. The present results suggest that the initiation of sprouting is regulated locally at or near the site of injury, and that blocking specific ion channels may either inhibit or enhance the initiation of neurite outgrowth.
Nonitegrin laminin receptors in the nervous system: Evidence for lack of a relationship to P40
Authors: Yang Guang , Douville Philippe , Gee Stephen , Carbonetto Salvatore
Published: January 2005

Laminins are extracellular matrix proteins that mediate their effects on cells through integrin and nonitegrin receptors. Two receptors of 67 and 110 kD that bind laminin with a high affinity (Kd ∼ nM) have been reported in neural cells. Here, we discuss these and other nonintegrin laminin receptors that have been implicated in neural function. In addition, we report studies characterizing a 43 kD protein, (P40), immunologically related to the 67 kD laminin receptor, which may be involved in retinal development.

In our studies, polyclonal antisera (anti‐P‐20‐A) to a synthetic peptide derived from the sequence of a cDNA for a putative high‐affinity laminin receptor (67 kD) detected a protein of 43 kD in immunoblots of adult rat retinas. Immunohistochemistry with this antiserum showed that the retinal immunoreactivity was predominantly localized in the ganglion cell layer of both adult chicken and rat retinas where it appeared to be intracellular. Retinal ganglion cells were shown to be immunoreactive by retrogradely labeling them from the superior colliculus with a lipophillic dye and subsequently with anti‐P‐20‐A antisera. Consistent with the preferential localization of the P‐20‐A immunoreactivity in ganglion cells, there was a substantial decrease in the amounts of P40 on Western blots following optic nerve section and resulting retinal ganglion cell death. Screening of a rat (PC12 cell) cDNA library with the anti‐P‐20‐A antiserum further confirmed the specificity of the antiserum for the rat homologue of P40. Rat P40 is 97% identical to the mouse and 87% identical to human P40 at the nucleic acid level and 98% at the protein level. Restriction mapping of the rather abundant positive clones in the library that cross‐hybridized with a human cDNA probe for P40 indicated that the full‐length cDNA of 1.2 kb was the major and perhaps the only cDNA in the library. In Northern blots of adult rat retina, these clones hybridized to a single 1.2‐kb transcript. Electroblots of retinal homogenates probed with radioiodinated laminin demon strated binding to a broad band at 110 kD, but none at 43 kD. Taken together these findings suggest that P40 may not be a laminin receptor and are in keeping with the hydrophillic composition of the protein, its intracellular localization, as well as other features predicted by its nucleic acid sequence. P40 copurifies with the protein synthesis initiation factor eIF‐4A, a finding consistent with recent data from other laboratories (G. Brawerman, personal communication), implicating P40 in the regulation of protein synthesis perhaps related to topographic specification of retinal ganglion cells. © 1992 John Wiley & Sons, Inc.