bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions between spinal cord stimulation and activity blockade in the regulation of synaptogenesis and motoneuron survival in the chick embryo
Authors: Le Ray C. Fournier , Prevette D. , Oppenheim R. W. , Fontaine‐Perus J.
Published: January 2005

The present study investigated the effects of spinal cord stimulation, neuromuscular blockade, or a combination of the two on neuromuscular development both during and after the period of naturally occurring motoneuron death in the chick embryo. Electrical stimulation of the spinal cord was without effect on motoneuron survival, synaptogenesis, or muscle properties. By contrast, activity blockade rescued motoneurons from cell death and altered synaptogenesis. A combination of spinal cord stimulation and activity blockade resulted in a marked increase in motoneuron death, and also altered synaptogenesis similar to that seen with activity blockade alone. Perturbation of normal nerve–muscle interactions by activity blockade may increase the vulnerability of developing motoneurons to excessive excitatory afferent input (spinal cord stimulation) resulting in excitotoxic‐induced cell death. © 1993 John Wiley & Sons, Inc.
Members of the Dlx‐and NKx2‐gene families are regionally expressed in the developing forebrain
Authors: Price Melanie
Published: January 2005

Members of the vertebrate Dlx‐ and NKx2‐homeobox‐containing gene families exhibit closely related, comple‐mentary areas of gene expression in the developing forebrain. The expression domains and onset of gene transcription indicate that these genes may play a role in forebrain patterning, particularly in the diencephalon. In some cases, gene expression borders coincide with mor‐phological boundaries separating functional and anatomical regions of the forebrain suggesting that the rostral region of the neural tube may indeed arise from a segmented structure. © 1993 John Wiley & Sons, Inc.
Touch receptor development and function in Caenorhabditis elegans
Authors: Chalfie Martin
Published: January 2005

Mutations causing a touch‐insensitive phenotype in the nematode Caenorhabditis elegans have been the basis of studies on the specification of neuronal cell fate, inherited neurodegeneration, and the molecular nature of mechanosensory transduction. © 1993 John Wiley & Sons, Inc.
Local intracerebral implants of estrogen masculinize some aspects of the zebra finch song system
Authors: Grisham William , Mathews Greta A. , Arnold Arthur P.
Published: January 2005

The song system of zebra finches is sexually dimorphic: the volumes of the song control nuclei and the neurons within these nuclei are larger in males. The song system of hatching female zebra finches is masculinized by systemic treatment with estrogen. We investigated the locus of this estrogen action by using microimplants of estradiol benzoate (EB). We implanted female zebra finch nestlings 10–13 days old with Silastic pellets containing approximately 2 μg EB at one of several sites: near the higher vocal center (HVC), in the brain distant from HVC, or in the periphery either under the skin of the breast or in the peritoneal cavity. Controls were either unimplanted or implanted near HVC with Silastic pellets without hormone. The brains were fixed by perfusion at 60 days, and the volumes of the song control regions as well as the sizes of individual neurons were measured. Neurons in HVC were lerger (more masculine) in the HVC‐implanted group than in other groups, which did not differ among themselves. The size of neurons in the robust nucleus of the archistriatum (RA) and the lateral magnocellular nucleus ofthe neostriatum (lMAN) were inversely correlated with the distance of the EB pellet to HVC; neurons in RA and lMAN were larger when the EB pellets were closer to HVC. This result suggests that implants near HVC were at or near a site of estrogen action. To our knowledge, this is the first demonstration that localized brain implants of estrogen cause morphological masculinization in any species. 1994 John Wiley & Sons, Inc.
Dynamics and metamorphosis of an identifiable peptidergic neuron in an insect
Authors: Riddiford Lynn M. , Hewes Randall S. , Truman James W.
Published: January 2005

Eclosion hormone (EH) is a 7000 Da peptide that triggers ecdysis behavior in insects. In the moth, Manduca sexta, EH is found in two pairs of ventromedial (VM) cells in the brain which send their axons down the ventral nerve cord to a neurohemal site in the proctodeal nerve in the larva and pupa. During adult development, these cells send axon collaterals to the corpora cardiaca where they form a new release site used for adult eclosion. Studies of bioassayable peptide during the 5th larval instar and the larval‐pupal transformation revealed that after depletion at ecdysis, the VM cells showed a transient increase in EH found in their cell bodies and axons. By contrast, their terminals in the proctodeal nerve showed a gradual accumulation of peptide followed by a release of over 90% of the stored material at pupal ecdysis. In situ hybridization analysis on whole mounts of the brains showed that the VM cells always contained EH mRNA with increased accumulation during the larval and pupal molting periods with a slight decline just before ecdysis. High levels of EH mRNA were found in brains of diapausing pupae. During the first two‐thirds of adult development, mRNA accumulated to high levels, then slowly declined until ecdysis. EH mRNA levels up to 3 days after adult eclosion. At no time was EH mRNA found in the lateral neurosecretory cell cluster previously reported to produce EH for adult eclosion. 1994 John Wiley & Sons, Inc.
Effects of testosterone on a sexually dimorphic frog muscle: Repeated in vivo observations and androgen receptor distribution
Authors: Dorlöchter Marlies , Astrow Stephanie H. , Herreta Albert A.
Published: January 2005

In the present study the sexually dimorphic, androgen‐sensitive flexor carpi radialis muscle (FCR) in male Xenopus laevis was viewed repeatedly in vivo to assess the influence of testosterone on muscle fiber size over a period of up to 12 weeks. Regions of the muscle innervated by different spinal nerves responded differently to testosterone treatment. Muscle fibers innervated by spinal nerve 2 (SN2) hypertrophied within 7 days in frogs that had been castrated and given testosterone‐filled implants. This initial hypertrophy was followed by a return to normal fiber size a week late, after which fiber size slowly increased again. In castrated males with empty implants, muscle fibers innervated by SN2 gradually atrophied. Fibers innervated by spinal nerve 3 (SN3) were not affected by androgen replacement or withdrawal. The sartorius, a control muscle that is neither sexually dimorphic nor particularly androgen sensitive, was also unaffected.

The in vivo observations were confirmed by measurements of muscle fiber cross‐sectional areas in frozen sections of whole forelimbs. At 8 and 12 weeks after castration, cross‐sectional areas of fibers innervated by SN2 were significantly larger in frogs provided with testosterone than in castrates without testosterone. No difference was found in the SN2 region or in the anconeus caput scapulare (triceps), another control muscle.

Immunocytochemistry employing an antibody against the androgen receptor (AR) indicated that the receptor is present in myonuclei of all muscles of the forelimb. While no difference in labeling intensity was detected, the number of AR‐containing nuclei per muscle fiber cross‐section was higher in fibers innervated by SN2 than in those innervated by SN3, and was yet lower in the triceps. This suggests that regulation of androgen sensitivity may occur via muscle fiber. ARs, although an influence of the nerve may also contribute. 1994 John Wiley & Sons, Inc.
Regulation of SC1/DM‐GRASP during the migration of motor neurons in the chick embryo brain stem
Authors: Simon Horst , Guthrie Sarah , Lumsden Andrew
Published: January 2005

The hindbrain of the chick embryo contains three classes of motor neurons: somatic, visceral, and branchial motor. During development, somata of neurons in the last two classes undergo a laterally directed migration within the neuroepithelium; somata translocate towards the nerve exit points, through which motor axons are beginning to extend into the periphery. All classes of motor neuron are immunopositive for the SC1/DM‐GRASP cell surface glycoprotein. We have examined the relationship between patterns of motor neuron migration, axon outgrowth, and expression of the SC1/DM‐GRASP mRNA and protein, using anterograde or retrograde axonal tracing, immunohistochemistry, and in situ hybridization. We find that as motor neurons migrate laterally, SC1/DM‐GRASP is down‐regulated, both on neuronal somata and axonal surfaces. Within individual motor nuclei, these lateral, more mature neurons are found to possess longer axons than the young, medial cells of the population. Labelling of sensory or motor axons growing into the second branchial arch also shows that motor axons reach the muscle plate first, and that SC1/DM‐GRASP is expressed on the muscle at the time growth cones arrive. 1994 John Wiley & Sons, Inc.
Muscarinic acetylcholine responses in the early embryonic chic retina
Authors: Yamashita Masayuki , Yoshimoto Yukiko , Fukada Yutaka
Published: January 2005

The action of acetylcholine on cytoplasmic Ca2+ concentration ([Ca2+]i) was studied in early embryonic chick retinae. Whole neural retinae were isolated from embryonic day 3 (E3) chicks and loaded with a Ca2+‐sensitive fluorescent dye (Fura‐2). Increases in [Ca2+]i were evoked by the puff application of acetylcholine at concentration than 0.1 μM. The Ca2+ response became larger in dose–dependant manner up to 10 μM of acetylcholine applied. The rise in [Ca2+]i was not due to the influx of Ca+2 through calcium channels, but to the release of Ca2+ from internal stores. A calcium channel antagonist, nifedipine, which completely blocks the Ca2+ rise caused by depolarization with 100 mM K+, had no effects on the acetylcholine response and the Ca2+ response to acetylcholine occurred even in a Ca2+‐free medium. The Ca2+ response to acetylcholine was mediated by muscarinic receptors. Atropine of 1 μM abolished the response to 10 μM acetylcholine, whereas d‐tubocurarine of 100 μM had no effects. Two muscarinic agonists, muscarine and carbamylcholine (100 μM each), evoked comparable responses with that to 10 μM acetylcholine. The developmental change of the muscarinic response was examined from E3 to E13. The Ca2+ response to 100 μM carbamylcholine was intense at E3‐E5, then rapidly declined until E8. The muscarinic Ca2+ mobilization we found in the early embryonic chick retina may be regarded as a part of the “embryonic muscarinic system” proposed by Drew's group, which appears transiently and ubiquitously at early embryonic stages in relation to organogenesis. 1994 John Wiley & Sons, Inc.
Structure–function relationships in the neurotrophin family
Authors: Ibáñez Carlos F.
Published: January 2005

The study of structure–function relationships in the neurotrophin family has in recent years increased our understanding of several important aspects of neurotrophin function. Site‐directed mutagenesis studies have localized amino acid residues important for binding to the low‐affinity (p75LNGFR), as well as to the members of the Trk family of tyrosine kinase receptors. A cluster of positively charged residues has been shown to form a surface for binding to p75LNGFR in all four neurotrophins. Differences in the spatial distribution of these charges among the different neurotrophins may explain some of their distinct binding properties. Elimination of these positive charges drastically reduces binding to P75LNGFR but not to the Trk family members, and it does not impair the biological properties of the neurotrophins in vitro, arguing that binding to and activation of Trk receptors is sufficient to mediate the biological responses of neurotrophins. In contrast. the binding sites to Trk receptors appear to be formed by discontinuous stretches of amino acid residues distributed throughout the primary sequence of the molecule. These include the N‐terminus, some of the variable loop regions and a β‐strand. Despite their apparent distribution, when viewed in the three‐dimensional structure of NGF, these residues appear grouped on one side of the neurotrophin dimer, delineating a continuous surface extending approximately parallel to the twofold symmetry axis of the molecule. Two symmetrical surfaces are formed along the axis of the neurotrophin dimer providing a model for ligand‐mediated receptor dimerization. In the neurotrophin family, co‐evolution of cognate ligands and Trk receptors has developed specific contacts through different residues in the same variable regions of the neurotrophins. Thus, binding specificity is determined by the cooperation of distinct active and inhibitory binding determinants that restrict ligand‐receptors interactions. Binding determinants to the Trk receptors can be manipulated independently in a rational fashion to create neurotrophin analogues with novel ligand‐binding properties. In this way, second‐generation chimeric neurotrophins with multiple specificities (pan‐neurotrophins) have been engineered which may have valuable applications in the treatment of neurodegeneration and nerve damage. 1994 John Wiley & Sons, Inc.
The Trk family of neurotrophin receptors
Authors: Barbacid Mariano
Published: January 2005

Accumulating evidence indicates that the Trk family of tyrosine protein kinase receptors, Trk (also known as TrkA), TrkB, and TrkC, are responsible for mediating the trophic effects of the NGF family of neurotrophins. Nerve growth factor (NGF) specifically recognizes Trk, a receptor indentified in all major NGF targets, including sympathetic, trigeminal, and dorsal root ganglia as well as in cholinergic neurons of the basal forebrain and the striatum. Brain‐derived neurotropic factor (BDNF) and neurotrophin‐4 (NT‐4) specifically activate the TrkB tyrosine kinase receptor. trkB transcripts encoding this receptor are found throughout multiple structure of the central and peripheral nervous system. Neurotrophin‐3 (NT‐3) primarily activates the TrkC tyrosine protein kinases, four related isoforns encoded by alternative splicing of trkC, a gene also wildely expressed throughtout the mammalian nervous system. Unlike the other neurotrophins, NT‐3 appears to be somewhat promiscuous since it can activate Trk and TrkB kinase receptors, at least in certain cell systems. The trkB and trkC genes also encode noncatalytic neurotrophin receptor isoforms of an as yet, unknown function. Recently, strains of mice lacking each of these tyrosine kinase receptors have been generated. Preliminary characterization of these mutant mice has provided significant information regarding the role of these receptors in the ontogeny of the mammlian nervous system. For instance, mice deficient for Trk receptors lack most sympathetic neurons and do not display nociceptive and temperature sensations, two defects likely to result from severe neuronal cell loss in their trigeminal and dorsal root ganglia. Mice lacking TrkB tyrosine kinase receptors die postnatally due to their inability to intake food. Neuron cell loss in their trigeminal, nodose and pretrosal sensory ganglia as well as in the facial motor nucleus are likely to contribute to this phenotype. Finally, TrkC‐deficient mice display strikingly abnormal movements consistent with loss of proprioception, a defect likely to be a consequence of the complete loss of Ia muscle afferents observed in this mutant mice. 1994 John Wiley & Sons, Inc.
Activity‐dependent regulation of dendritic spine density on cortical pyramidal neurons in organotypic slice cultures
Authors: Annis Casey M. , K. O'Dowd Diane , Robertson Richard T.
Published: January 2005

In order to examine the effects of activity on spine production and/or maintenance in the cerebral cortex, we have compared the number of dendritic spines on pyramidal neurons in slices of PO mouse somatosensory cortex maintained in organotypic slice cultures under conditions that altered basal levels of spontaneous electrical activity. Cultures chronically exposed to 100 μM picrotoxin (PTX) for 14 days exhibited significantly elevated levels of electrical activity when compared to neurons in control cultures. Pyramidal neurons raised in the presence of PTX showed significantly densities of dendritic spines on primary apical, secondary apical, and secondary basal dendrites when compared to control cultures. The PTX‐induced increase in spine density was dose dependent and appeared to saturate at 100 μM. Cultures exhibiting little or no spontaneous activity, as a result of growth in a combination of PTX and tetrodotoxin (TTx), showed significantly fewer dendritic spines compared to cultures maintained in PTX alone. These results demonstrate that the density of spines on layers V and VI pyramidal neurons can be modulated by growth conditions that alter the levels of spontaneous electrical activity. 1994 John Wiley & Sons, Inc.
Effects of experience and juvenile hormone on the organization of the mushroom bodies of honey bees
Authors: Withers G. S. , Fahrbach S. E. , Robinson G. E.
Published: January 2005

There is an age‐related division of labor in the honey bee colony that is regulated by juvenile hormone. After completing metamorphosis, young workers have low titers of juvenile hormone and spend the first several weeks of their adult lives performing tasks within the hive. Older workers, approximately 3 weeks of age, have high titers of juvenile hormone and forage outside the hive for nectar and pollen. We have previously reported that changes in the volume of the mushroom bodies of the honey bee brain are temporally associated with the performance of foraging. The neuropil of the mushroom bodies is increased in volume, whereas the volume occupied by the somata of the Kenyon cells is significantly decreased in foragers relative to younger workers. To study the effect of flight experience and juvenile hormone on these changes within the mushroom bodies, young worker bees were treated with the juvenile hormone analog methoprene but a subset was prevented from foraging (big back bees). Stereological volume estimates revealed that, regardless of foraging experience, bees treated with methoprene had a significantly larger volume of neuropil in the mushroom bodies and a significantly smaller Kenyon cell somal region volume than did 1‐day‐old bees. The bees treated with methoprene did not differ on these volume estimates from untreated foragers (presumed to have high endogenous levels of juvenile hormone) of the same age sampled from the same colony. Bees prevented from flying and foraging nonetheless received visual stimulation as they gathered at the hive entrance. These results, coupled with a subregional analysis of the neuropil, suggest a potentially important role of visual stimulation, possibly interacting with juvenile hormone, as an organizer of the mushroom bodies. In an independent study, the brains of worker bees in which the transition to foraging was delayed (overaged nurse bees) were also studied. The mushroom bodies of overaged nurse bees had a Kenyon cell somal region volume typical of normal aged nurse bees. However, they displayed a significantly expanded neuropil relative to normal aged nurse bees. Analysis of the big back bees demonstrates that certain aspects of adult brain plasticity associated with foraging can be displayed by worker bees treated with methoprene independent of foraging experience. Analysis of the over‐aged nurse bees suggests that the post‐metamorphic expansion of the neuropil of the mushroom bodies of worker honey bees is not a result of foraging experience. © 1995 John Wiley & Sons, Inc.
A direct comparison of the masculinizing effects of testosterone, androstenedione, estrogen, and progesterone on the development of the zebra finch song system
Authors: Grisham William , Arnold Arthur P.
Published: January 2005

To assess which hormones are capable of masculinizing the neural song system of zebra finch hatchlings, we implanted female hatchlings with estrogen (estradiol [E2], 75 μg, n = 9), testosterone (T, 75–88 μg, n = 13), androstenedione (AE, 75 μg, n = 7), progesterone (P, 117 μg, n = 10), or nothing (Blanks, n = 10) and compared these to unimplanted males (n = 7). Implants, consisting of a hormone and Silastic mixture encased in polyethylene tubing, were placed under the skin of the breast on the day of hatching. Birds were killed when they were subadult (58 to 68 days old). We measured volumes of area X, the higher vocal center (HVC), and the robust nucleus of the archistriatum (RA); measured soma sizes in the lateral magnocellular nucleus of the neostriatum (IMAN), HVC, and RA: and counted RA neurons. E2 masculinized all measures in the song system and nearly sex‐reversed the size of RA neurons. T masculinized volumes of nuclei and soma sizes but not the number or spacing of RA neurons. E2 was always at least as effective as T in masculinizing measures of the song system and was usually more effective. AE and P did not significantly masculinize any measure. These data suggest that E2 is more potent than aromatizable androgens or P in masculinizing the female song system in development and that the action of E2 alone may be sufficient to masculinize the volume of song control nuclei and the size and number of neurons. © 1995 John Wiley & Sons, Inc.
Calcium‐activated proteolysis of neurofilament proteins in goldfish Mauthner axons
Authors: Raabe Tim D. , Nguyen Tri , Bittner George D.
Published: January 2005

We have examined the proteolytic breakdown of neurofilament proteins (NFPs) in isolated Mauthner axoplasm (M‐axoplasm). Documentation of proteolytic breakdown of NFPs in M‐axoplasm is important because NFPs are not degraded in distal segments of severed Mauthner axons (M‐axons) maintained in vivo for up to 62 days at 20°C. By incubating M‐axoplasm with 2 mM calcium in vitro, we have demonstrated that M‐axoplasm contains an endogenous calcium‐activated neutral protease that degrades NFPs. This calcium‐activated proteolysis of M‐axoplasm NFPs produced novel bands on silver‐stained gels. These novel bands were presumed to be NFP breakdown products because they reacted with antibodies to the α‐intermediate filament antigen (anti‐IFA) on immunoblots from these gels. Incubations of M‐axoplasm with 2 mM calcium plus exogenous calpain produced novel bands similar to those observed for M‐axoplasm incubated with 2 mM calcium. Incubations of M‐axoplasm with 2m M calcium plus calpain inhibitors did not produce these novel bands. These in vitro data indicate that M‐axoplasm contains calpain that degrades NFPs and produces novel bands similar to those observed from distal segments of severed M‐axons maintained in vivo longer than 62 days postseverance. Factors that affect the activity of calpain or affect the ability of calpain to degrade NFPs could account for the delayed degradation of NFPs in distal segments of severed M‐axons maintained in vivo. © 1995 John Wiley & Sons, Inc.
Electric field‐directed growth and branching of cultured frog nerves: Effects of aminoglycosides and polycations
Authors: Erskine L. , Stewart R. , McCaig C. D.
Published: January 2005

The direction and rate of earliest nerve growth are critical determinants of neuronal architecture. One extrinsic cue that influences these parameters is a small direct current electric field, although the underlying mechanisms are unclear. We have studied the orientation, rate of growth, and branching behavior of embryonic Xenopus spinal neurites exposed to aminoglycoside antibiotics, to raised external cations, to applied direct current electric fields, and to combinations of these treatments. Field‐induced cathodal turning and cathodal branching of neurites were blocked by the aminoglycosides, by raised extracellular calcium ([Ca2+]0) and by raised extracellular magnesium ([Mg2+]0). Neomycin together with high external Ca2+, by contrast, induced a reversal in the polarity of turning and branching, with neurites reorienting and branching more frequently anodally. Aminoglycosides decreased neurite growth rates, and for neomycin this was partially reversed by high external Ca2+. Raised [Ca2+]0 alone but not raised [Mg2+]0 altered growth rates in a field‐strength dependent manner. Modulation of membrane surface charge may underlie altered galvanotropic orientation and branching. Such an effect is insufficient to explain the changes in growth rates, which may result from additional perturbations to Ca2+ influx and inositol phospholipid metabolism. © 1995 John Wiley & Sons, Inc.
Number and dendritic morphology of retinal ganglion cells that survived after axotomy in adult cats
Authors: Watanabe Masami , Sawai Hajime , Fukuda Yutaka
Published: January 2005

Retinal ganglion cells (RGCs) of adult cats were labeled by injection of diI into the proximal stump of completely transected optic nerves. Approximately 2% to 5% of the RGC population appeared viable 2 months after these axotomies, based on diI retention. The morphological type and dendritic arbor of these surviving RGCs were examined after intracellular injections of Lucifer Yellow into diI‐labeled RGCs. Postaxotomy survival rate was much higher for α‐like cells than for β‐like cells. However, in one of four retinas examined, a large number of RGCs seemed to survive axotomy, and among these, β cells survived at an unusually high rate. Dendritic arbors of surviving RGCs were also examined after intracellular injection of horseradish peroxidase. Some dendrites of these RGCs lacked branches and were thin in caliber. Other dendrites displayed many spiny processes and bulbous swellings. Essentially, these results confirm the previous suggestion that α cells survive axotomy longer than β cells. The ability of α cells to regenerate axons may thus be attributable to their relatively high resistance to axotomy. The atypical dendritic profiles seen after optic nerve transection may reflect either degeneration or regrowth of dendrites. © 1995 John Wiley & Sons, Inc.
Using reflexive behaviors of the medicinal leech to study information processing
Authors: Kristan William B. , Lockery Shawn R. , Lewis John E.
Published: January 2005

The interneuronal network that produces local bending in the leech is distributed, in the sense that most of the interneurons involved are activated in all forms of local bending, even those in which their outputs would produce inappropriate movements. Such networks have been found to control a number of different behaviors in a variety of animals. This article reviews three issues: the physiological and modeling observations that led to the conclusion that local bending in leeches is controlled by a distributed system; what distributed processing means for this and other behaviors; and why the leech interneuronal network may have evolved to be distributed in the first place. © 1995 John Wiley & Sons, Inc.
Diversity and modulation of ionic conductances in leech neurons
Authors: Kleinhaus Anna L. , Angstadt James D.
Published: January 2005

A complete understanding of animal behavior at the cellular level requires detailed information on the intrinsic biophysical properties of neurons, muscles, and the synaptic connections they make. In the past 10 to 15 years, electrophysiological studies of leech neurons have revealed a diverse array of voltage‐gated ionic conductances distinguished by their pharmacological sensitivity to classic ion channel blockers. Voltage‐clamp studies have provided new information about the kinetics and voltage‐dependence of Na+ conductances, several K+ currents, including IA, IK and IK(Ca.)' and high‐ and low‐voltage‐gated Ca2+ conductances. These studies showed that the action potentials of most leech neurons result from the usual sequence of permeability changes to Na+, K+, and Ca2+ ions. They also added insight as to the role played by particular combinations of conductances in providing individual neurons with electrical properties appropriate for the particular information they encode. Evidence is accumulating on the modulatory actions of endogenous neurotransmitters such as FMRFamide, serotonin, and octopamine on motor behaviors in the animal. Parallel studies suggest that changes in behavior can be explained, at least in part, by the alteration of firing patterns of selected neurons and muscles resulting form modulation of multiple ion conductances. This makes the leech exceptionally attractive for neuroethological studies because it is one of the simplest organisms in which the methods of psychology and neurobiology can be combined. Information gathered from this animal will therefore increase our understanding regarding general principles underlying the cellular basis of behavior. © 1995 John Wiley & Sons, Inc.
Lack of a synergistic effect between estradiol and dihydrotestosterone in the masculinization of the zebra finch song system
Authors: Jacobs Erin C. , Grisham William , Arnold Arthur P.
Published: January 2005

Previous studies have suggested that both major active metabolites of testosterone, estradiol (E2) and dihydrotestosterone (DHT), are needed for complete masculinization of the brain regions that control song in passerine birds. However, DHT treatment of hatchling female zebra finches has only small masculinizing effects on the song system. To assess whether E2 and DHT have a synergistic effect on the masculinization of the zebra finch song system, female zebra finches were given Silastic implants of E2 on the day of hatching (day 1) either without any additional hormone treatment or in combination with DHT on days 1, 14, or 70. At 105 to 110 days of age, we measured the volumes of Area X, higher vocal center (HVC), robust nucleus of the archistriatum (RA), soma sizes in HVC, RA, and the lateral magnocellular nucleus of the neostriatum (lMAN), and neuron density and number in RA. E2 masculinized all of the measures in the song system with the exception of the number of neurons in RA. DHT did not synergize with E2 to produce any additional masculinization of the attributes measured. These data demonstrate that the combination of E2 and DHT did not result in the complete masculinization of the song control nuclei and argue against the importance of androgen in sexual differentiation of the song system. © 1995 John Wiley & Sons, Inc.
Seasonal changes in song nuclei and song behavior in Gambel's white‐crowned sparrows
Authors: Troy Smith G. , Brenowitz Eliot A. , Wingfield John C. , Baptista Luis F.
Published: January 2005

In males of several songbird species, the morphology of forebrain nuclei that control song changes seasonally. The only seasonally breeding songbird in which seasonal changes in the structure of song control nuclei have been reported not to occur is the nonmigratory Nuttall's subspecies of white‐crowned sparrow. In the present study, we manipulated photoperiod and plasma testosterone concentrations in captive male white‐crowned sparrows of the migratory Gambel's subspeices. Males exposed to photoperiods and plasma testosterone concentrations typical of those experienced by wild breeding males had larger song control nuclei than males held on a winter photoperiod. We also found seasonal change in stereotypy of spectral and temporal parameters of song in wild Gambel's white‐crowned sparrows. We hypothesize that seasonal changes in song control nuclei may correlate with seasonal changes in song stereotypy. © 1995 John Wiley & Sons, Inc.
Fate of the anterior neural ridge and the morphogenesis of the xenopus forebrain
Authors: Eagleson Gerald , Ferreiro Beatriz , Harris William A.
Published: January 2005

The fate of the anterior neural ridge was studied by following the relative movements of simultaneous spot applications of DiI and DiO from stage 15 through stage 45. These dye movements were mapped onto the neuroepithelium of the developing brain whose shape was gleaned from whole‐mount in situs to neural cell adhesion molecule and dissections of the developing nervous system. The result is a model of the cell movements that drive the morphogenesis of the forebrain. The midanterior ridge moves inside and drops down along the most anterior wall of the neural tube. It then pushes forward a bit, rotates ventrally during forebrain flexing, and gives rise to the chiasmatic ridge and anterior hypothalamus. The midanterior plate drops, forming the floor of the forebrain ventricle, and, keeping its place behind the ridge, it gives rise to the posterior hypothalamus or infundibulum. The midlateral anterior ridge slides into the lateral anterior wall of the neural tube and stretches laterally into the optic stalk and retina, and then rotates into a ventral position. The lateral anterior ridge converges to the most anterior part of the dorsal midline during neural tube closure, then rotates anteriorly, and gives rise to telencephalic structures. Whole‐mount bromodeoxyuridine labeling at these stages showed that cell division is widespread and relatively uniform throughout the brain during the late neurula and early tailbud stages, but that during late tailbud stages cell division becomes restricted to specific proliferative zones. We conclude that the early morphogenesis of the brain is carried out largely by choreographed cell movements and that later morphogenesis depends on spatially restricted patterns of cell division. © 1995 John Wiley & Sons, Inc.
Human schwann cells in vitro. II. Myelination of sensory axons following extensive purification and heregulin‐induced expansion
Authors: Morrissey T. K. , Kleitman N. , Bunge R. P.
Published: January 2005

Co‐culture conditions are well established in which Schwann cells (SCs) derived from immature or adult rats proliferate and form myelin in response to contact with sensory axons. In a companion article, we report that populations of adult‐derived human Schwann cells (HASCs) fail to function under these co‐culture conditions. Furthermore, we report progressive atrophy of neurons in co‐cultures containing populations of either human fibroblasts. Two factors that might account for the insufficiency of the co‐culture system to support HASC differentiation are the failure of many HASCs to proliferate and the influence of contaminating fibroblasts. To minimize fibroblast contamination of neuron‐HASC co‐cultures, we used fluorescence‐activated cell sorting to highly purify HASC populations (to more than 99.8%). To stimulate expansion of the HASC population, a mitogenic mixture of heregulin (HRGβ1 amino acid residues 177‐244; 10 nM), cholera toxin (100 ng/mL), and forskolin (1 μM) was used. When these purified and expanded HASCs were co‐cultured with embryo‐derived rat sensory neurons, neuronal shrinkage did not occur and after 4 to 6 weeks some myelin segments were seen in living co‐cultures. This myelin was positively identified as human by immunostaining with a monoclonal antibody specific to the human peripheral myelin protein P0 (antibody 592). Although this is the first reported observation of myelination by HASCs in tissue culture, it should be noted that myelination occurred more slowly and in much less abundance than in comparable cultures containing adult rat‐derived SCs. We anticipate that further refinements of the HASC co‐culture system that enhance myelin formation will provide insights into important aspects of human SC biology and provide new opportunities for studies of human peripheral neuropathies. © 1995 John Wiley & Sons, Inc.
Development of an identified serotonergic neuron in the antennal lobe of the moth and effects of reduction in serotonin during construction of olfactory glomeruli
Authors: Oland Lynne A. , Kirschenbaum Sheila R. , Pott Wendy M. , Mercer Alison R. , Tolbert Leslie P.
Published: January 2005

Each olfactory (antennal) lobe of the moth Manduca sexta contains a single serotonin (5‐HT) immunoreactive neuron whose processes form tufted arbors in the olfactory glomeruli. To extend our present understanding of the intercellular interactions involved in glomerulus development to the level of an individual, identified antennal lobe neuron, we first studied the morphological development of the 5‐HT neuron in the presence and absence of receptor axons. Development of the neuron's glomerular tufts depends, as it does in the case of other multiglomerular neurons, on the presence of receptor axons. Processes of the 5‐HT neuron are excluded from the region in which the initial steps of glomerulus construction occur and thus cannot provide a physical scaffolding on which the array of glomeruli is organized. Because the neuron's processes are present in the antennal lobe neuropil throughout postembryonic development, 5‐HT could provide signals that influence the pattern of development in the lobe. By surgically producing 5‐HT‐depleted antennal lobes, we also tested the importance of 5‐HT in the construction of olfactory glomeruli. Even in the apparent absence of 5‐HT, the glomerular array initiated by the receptor axons was histologically normal, glial cells migrated to form glomerular borders, and receptor axons formed terminal branches in their normal region within each glomerulus. In some cases, 5‐HT‐immunoreactive processes from abnormal sources entered the lobe and formed the tufted intraglomerular branches typical of most antennal lobe neurons, suggesting that local cues strongly influence the branching patterns of developing antennal lobe neurons. © 1995 John Wiley & Sons, Inc.
Establishment of neuronal connectivity during development of the Drosophila larval visual system
Authors: Campos Ana Regina , Lee Kevin J. , Steller Hermann
Published: January 2005

We used confocal microscopy in conjunction with specific antibodies and enhancer trap strains to investigate the development of specific neuronal connections in a simple model system, the larval visual system of Drosophila. We find that the establishment of axonal projections from the larval photoreceptor neurons to their central nervous system targets involves a series of discrete steps. During embryogenesis, the larval optic nerve contacts several different cell types, including optic lobe pioneer (OLP) neurons and a number of glial cells. We demonstrate that OLP neurons are present and project normally in glass (gl) mutant embryos in which the larval optic nerve fails to develop, suggesting that they do not depend on interactions with the larval optic nerve for differentiation and proper axonal projection. The OLPs fail to differentiate properly in disconnected (disco) mutant embryos, where appropriate connections between the larval optic nerve and its targets in the brain are not formed. The disco gene is expressed in the OLPs and may therefore act autonomously to direct the differentiation of these cells. Taken together, our results suggest that the OLPs act as an intermediate target required for the establishment of normal optic nerve projection and connectivity. © 1995 John Wiley & Sons, Inc.
Characterization of resol resins modified by the addition of PVC plastisols
Authors: Manfredi LB , Jiménez A , Vázquez A
Published: January 2005

Plastisols, which are a blend of poly(vinyl chloride) resin and a plasticizer (DEHP), were used as a toughening agent of a resol resin in order to improve the mechanical properties. It was not possible to formulate resol blends by adding more than 10 % of plastisol owing to a lack of apparent homogeneity in the systems, which also showed many air bubbles. The relationship between dynamic mechanical, mechanical and thermal properties and the amount of plastisol added was studied. It was determined from the infrared spectroscopy and dynamic mechanical results that the resol–plastisol blends seem to be formed by a reaction between the phenol and PVC giving a higher crosslinked structure. An improvement in the thermal resistance of the blends at lower temperatures was observed with an increase in the percentage of plastisol. Flexural analysis showed the elastic behaviour of the systems. However, it was not possible to observe the effect of the plasticizer (DEHP) owing to the low quantity of plastisol that was added to the resol. Copyright © 2004 Society of Chemical Industry
Conducting composites of polythiophene and polyfuran with acetylene black
Authors: Ballav Nirmalya , Biswas Mukul
Published: January 2005

Conducting composites of polythiophene (PTP) and polyfuran (PF) with acetylene black (AB) were prepared via chemical oxidative polymerization of thiophene and furan in a suspension of AB in CHCl3 at room temperature using anhydrous FeCl3 as the oxidant. Formation of PTP and PF and their subsequent incorporation in PTP–AB and PF–AB composite systems were confirmed by FTIR analysis. Scanning electron microscope analysis showed the presence of compact clusters of particles in both composites. Transmission electron micrographs of PTP–AB and PF–AB composites showed formation of globular polymer encapsulated AB particles with average diameters of the order of ∼100 nm in both systems. Thermogravimetric analysis revealed that the overall thermal stability varied in the order: AB > PTP–AB > PTP and AB > PF–AB > PF. DC conductivity values for the PTP–AB and PF–AB composites were of the order of 10−2 and 10−3 S cm−1, respectively. Copyright © 2004 Society of Chemical Industry
Differential protein expression by Porphyromonas gingivalis in response to secreted epithelial cell components
Authors: Zhang Yi , Wang Tiansong , Chen Weibin , Yilmaz Özlem , Park Yoonsuk , Jung Il‐Young , Hackett Murray , Lamont Richard J.
Published: January 2005

The human oral pathogen Porphyromonas gingivalis colonizes the gingival crevice and invades gingival epithelial cells. Multidimensional capillary high‐performance liquid chromatography coupled with tandem mass spectrometry and two‐dimensional gel electrophoresis were used to analyze the proteome of P. gingivalis as it adapts to a set of experimental conditions designed to reflect important features of an epithelial cell environment. 1014 proteins (46% of the total theoretical proteome) were identified in four independent analyses; 479 of these proteins showed evidence of differential expression after exposure of P. gingivalis to either conditioned epithelial cell growth medium or control conditions: i.e., they were only detected under one set of conditions. Moreover, 276 genes annotated as hypothetical were found to encode expressed proteins. Among the proteins up‐regulated in the presence of epithelial cell components were a homolog of the internalin proteins of Listeria monocytogenes and subunits of the ATP‐dependent Clp protease complex. Insertional inactivation of clpP, encoding the Clp proteolytic subunit, resulted in approximately a 50% reduction in invasion of P. gingivalis. These results suggest that adaptation to an epithelial cell environment induces a major shift in the expressed proteome of the organism. Furthermore, ClpP, that is up‐regulated in this environment, is required for optimal invasive activity of P. gingivalis.
Polymerization of styrene with tetramethylthiuram disulfide as an initiator in the presence of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy
Authors: Xu Wenjian , Zhu Xiulin , Cheng Zhenping , Chen Gaojian , Zhu Jian
Published: January 2005

The bulk polymerization of styrene was investigated with tetramethylthiuram disulfide (TMTD) as an initiator in the presence of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) at 123 °C. The polymerization proceeded in a controlled/living way; that is, the polymerization rate was first‐order with respect to the monomer concentration, and the molecular weight increased linearly with conversion. The molecular weights of the polymers obtained were close to the theoretical values, and the molecular weight distributions were relatively low (weight‐average molecular weight/number‐average molecular weight = 1.1–1.3). The rate of polymerization with TMTD as an initiator was faster than that with benzoyl peroxide, and the rate was independent of the initial concentration of TMTD in the presence of TEMPO. The obtained polystyrene was functionalized with ultraviolet‐light‐sensitive SC(S)N(CH3)2 groups, which was characterized with 1H NMR spectroscopy. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 543–551, 2005
Enantiomer (+)physostigmine prevents organophosphate‐induced subjunctional damage at the neuromuscular synapse by a mechanism not related to cholinesterase carbamylation
Authors: Kawabuchi M. , Boyne A. F. , Deshpande S. S. , Cintra W. M. , Brossi A. , Albuquerque E. X.
Published: January 2005

The natural alkaloid (‐)PHY is a reversible anticholinesterase carbamate, but in contrast, its optical isomer (+)PHY, is a very weak anticholinesterase. We have shown that treatment of rats with atropine and (‐)PHY prior to injections of a lethal dose of the irreversible organophosphate sarin (0.13 mg/kg) not only protected 100% of the animals from lethality but also reduced the size of the subneural lesions of the nicotinic synapses of skeletal muscle. Similar protection against lethality is provided by pretreatment with (+)PHY. At the concentration used (0.3 mg/kg), there was no detectable inhibition of AChE activity. We have examined the protection afforded by (+)PHY or (‐)PHY against lethality and myopathy due to organophosphate agents such as sarin. The major alterations in the soleus motor endplates 1 hr after drug treatment were as follows: (1) A single sublethal dose of sarin (0.08 mg/kg) produced enlarged, blistered, and severely disrupted subjunctional regions, with muscle damage extendig beyond the endplate to include myofiber necrosis and subsequent phagocytosis; (2) (+)PHY (0.3 mg/kg) produced no obvious damage in the postjunctional region; (3) (‐)PHY (0.1 mg/kg) had a selective effect in inducing irregularities of the subjunctional sarcomere band patterns without any gross vacuolization; (4) light microscopic data indicated that the combination of atropine and (+)PHY, or of atropine and (‐)PHY (0.1 mg/kg), 30 min prior to a lethal dose of sarin, offered dramatic reduction in the average dimension of lesions. Lesions were detectable in most endplates but recognizable changes were markedly less severe than those seen in sarin myopathy. Few instances of extensive muscle damage and myofiber necrosis were visible.

In each of the 3 experimental groups examined, the extrajunctional myopathy was reversible with substantial recovery being observed on days 5 and 10 after drug treatment.

In addition to its anticholinesterase activity, (‐)PHY is also a powerful ion channel blocker of the nicotinic acetylcholine receptor. As for (+)PHY, its protective effect almost certainly does not depend at inhibition of acetylcholinesterase, but as with (‐)PHY, it my depend on a direct blockade at the nicotinic‐acetylcholine receptor and its ion channel.