bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intracellular partitioning of androgen receptor immunoreactivity in the brain of the male syrian hamster: Effects of castration and steroid replacement
Authors: Wood R. I. , Newman S. W. 
Published: January 2005

AbstractThe effect of castration and steroid replacement on the intracellular partitioning of the androgen receptor in the brain of the male Syrian hamster was determined using immunocytochemistry. Androgen receptors were visualized using the PG‐21 antibody (G. S. Prins) on 40‐μm coronal brain sections from hamsters perfused with 4% paraformaldehyde with or without 0.4% glutaraldehyde. Control studies confirmed antibody specificity in gonad‐intact and castrate males. In the normal adult male, androgen receptor immunocytochemistry reveals intense staining confined to the cell nucleus. Castration caused a gradual increase in cytoplasmic labelling within 2 weeks, accompanied by a reduction in nuclear staining intensity in androgen receptor‐containing neurons throughout the brain. Cytoplasmic androgen receptor staining was eliminated after treatment of orchidectomized males for only 8 h with exogenous testosterone. Likewise, long‐term exposure to testosterone and dihydrotestosterone, a nonaromatizable androgen, maintained nuclear androgen receptor immunoreactivity. However, exposure to low physiologic concentrations of estrogen was not effective in this regard. In addition, we determined that nuclear androgen receptor immunoreactivity decreases in response to inhibitory short‐day photoperiod, but without an increase in cytoplasmic immunostaining. This appears to be due to the decrease in androgen production by the testis, rather than a direct photoperiodic effect, because testosterone supplementation to short‐day males restored the intensity of nuclear androgen receptor immuno‐reactivity to levels comparable to those in the intact male. These findings are compatible with a new model for the intracellular localization of androgen receptors, in which a subset of unoccupied receptors is located in the cell cytoplasm in the absence of ligand. They further demonstrate the repartitioning of such cytoplasmic receptors, thereby confirming and extending previous observations using biochemical techniques on the regulation of neuronal androgen receptors. © 1993 John Wiley & Sons, Inc.
Ultrastructure of neuromuscular junctions in Drosophilal: Comparison of wild type and mutants with increased excitability
Authors: Jia Xi‐Xi , Gorczyca Michael , Budnik Vivian 
Published: January 2005

AbstractThe ventral longitudinal muscles of the Drosphila larval body wall are innervated by at least four types of synaptic terminals that can be distinguished on morphological grounds at the light microscopical level. The innervation of these muscles has been previously shown to be regulated by neuronal activity. In this report we investigate the ultrastructural basis for synaptic bouton differences by using serial sections, and examine the structure of synaptic terminals in mutants with increased excitability. We report that individual identifiable muscle fibers are innervated by terminals containing two to three types of synaptic boutons that can be distinguished in terms of synaptic vesicle population, presynaptic and postsynaptic specialization, and general shape. We propose a model to account for the bouton types observed at the light microscopical level. We find that in the hyperexcitable mutant eag Sh, there are dramatic ultrastructural alterations at synaptic boutons. These alterations include a partial depletion of two types of synaptic vesicles and a change in appearance of a third type, changes in number and appearance of synaptic densities, and the presence of multivesicular bodies. Our results show that an increase in neuronal excitability produces profound effects in synaptic terminal structure. © 1993 John Wiley & Sons, Inc.
The quantitative relationship between olfactory axons and mitral/tufted cells in developing Xenopus with partially deafferented olfactory bulbs
Authors: Byrd Christine A. , Burd Gail D. 
Published: January 2005

AbstractPartial deafferentation of the olfactory bulb in Xenopus embryos was performed to analyze the effects of afferent innervation on the development of the central olfactory structure. In an attempt to analyze a possible early inductive role of the olfactory axons, one olfactory placode was removed before differentiation of the neural tube began (stages 26–31). A morphological and quantitative analysis was performed on larvae at the onset of metamorphic climax (stage 58). When the single olfactory nerve innervated one side of the rostral telencephalon, a single olfactory bulb developed on that side and no olfactory bulb formed on the contralateral side. When the nerve innervated the midline of the rostral telencephalon, a smaller‐than‐normal, fused olfactory bulb developed. Partial deafferentation at these early stages resulted in a significant reduction in the number of olfactory axons (to approximately one‐half of control values) and a corresponding decrease in the number of mitral/tufted cells (output neurons of the olfactory bulb). To control for possible damage to the neural tube during olfactory‐placode removal, a portion of the neural tube directly beneath one of the olfactory placodes was removed in embryos. In these animals, the neural tube regenerated within 24 h and formed a normal olfactory bulb; olfactory axon and mitral/tufted‐cell numbers were not significantly different from controls. In conclusion, olfactory‐afferent innervation was critical for differentiation of the olfactory bulb, and decreasing the number of olfactory axons resulted in a reduction in the number of output neurons of the olfactory bulb. © 1993 John Wiley & Sons, Inc.
Insulin‐like growth factors: Putative muscle‐derived trophic agents that promote motoneuron survival
Authors: Neff Nicola T. , Prevette David , Houenou Lucien J. , Lewis Michael E. , Glicksman Marcie A. , Yin Qin‐Wei , Oppenheim Ronald W. 
Published: January 2005

AbstractTreatment of chick embryos in ovo with IGF‐I during the period of normal, developmentally regulated neuronal death (embryonic days 5–10) resulted in a dose‐dependent rescue of a significant number of lumbar motoneurons from degeneration and death. IGF‐II and two variants of IGF‐I with reduced affinity for IGF binding proteins, des(1‐3) IGF‐I and long R3 IGF‐I, also elicited enhanced survival of motoneurons equal to that seen in IGF‐I‐treated embryos. IGF‐I did not enhance mitogenic activity in motoneuronal populations when applied to embryos during the period of normal neuronal proliferation (E2‐5). Treatment of embryos with IGF‐I also reduced two types of injury‐induced neuronal death. Following either deafferentation or axotomy, treatment of embryos with IGF‐I rescued approximately 75% and 50%, respectively, of the motoneurons that die in control embryos as a result of these procedures. Consistent with the survival‐promoting activity on motoneurons in ovo, IGF‐I, ‐II, and des(1‐3) IGF‐I elevated choline acetyltransferase activity in embryonic rat spinal cord cultures, with des (1‐3) IGF‐I demonstrating 2.5 times greater potency than did IGF‐I. A single addition of IGF‐I at culture initiation resulted in the maintenance of 80% of the initial ChAT activity for up to 5 days, during which time ChAT activity in untreated control cultures fell to 9%. In summary, these results demonstrate clear motoneuronal trophic activity for the IGFs. These findings, together with previous reports that IGFs are synthesized in muscle and may participate in motoneuron axonal regeneration and sprouting, indicate that these growth factors may have an important role in motoneuron development, maintenance, and recovery from injury. © 1993 John Wiley & Sons, Inc.
Calcium channels and GABA receptors in the early embryonic chick retina
Authors: Yamashita Masayuki , Fukuda Yutaka 
Published: January 2005

AbstractThe properties of calcium channels were studied at the period of neurogenesis in the early embryonic chick retina. The whole neural retina was isolated from embryonic day 3 (E3) chick and loaded with a Ca2+‐sensitive fluorescent dye (Fura‐2). The retinal cells were depolarized by puff application of high‐K+ solutions. Increases in intracellular Ca2+ concentrations were evoked by the depolarization through calcium channels. The type of calcium channel was identified as l‐type by the sensitivity to dihydropyridines. The Ca2+ response was completely blocked by 10 μM nifedipine, whereas it was remarkably enhanced by 5 μM Bay K 8644. Then we sought a factor to activate the calcium channel and found that GABA could activate it by membrane depolarization at the E3 chick retina. Puff application of 100 μM GABA raised intracellular Ca2+ concentrations, and this Ca2+ response to GABA was also sensitive to the two dihydropyridines. Intracellular potential recordings verified clear depolarization by bath‐applied 100 μM GABA. The Ca2+ response to GABA was mediated by GABAA receptors, since the GABA response was blocked by 10 μgM bicuculline or 50 μM picrotoxin, and mimicked by muscimol but not by baclofen. Neither glutamate, kainate, nor glycine evoked any Ca2+ response. We conclude that l‐type calcium channels and GABAA receptors are already are already expressed before differentiation of retinal cells and synapse formation in the chick retina. A possibility is proposed that GABA might act as a trophic factor by activating l‐type calcium channels via GABAA receptors during the early period of retinal neurogenesis. © 1993 John Wiley & Sons, Inc.
Laryngeal muscle and motor neuron plasticity in Xenopus laevis: Testicular masculinization of a developing neuromuscular system
Authors: Watson James T. , Robertson John , Sachdev Ulka , Kelley Darcy B. 
Published: January 2005

AbstractIn Xenopus laevis, the sexual differentiation of the neuromuscular system responsible for courtship song is controlled by testicular androgen secretion. To explore the sensitivity of this system to androgenic stimulation, male and female frogs were gonadectectomized and given testis transplants at seven different developmental stages between the end of metamorphosis and adulthood, grown to sexual maturity, and the laryngeal muscle fibers and motor axons were counted. Muscle fiber and axon numbers in males were not affected by the testicular transplant at any stage. In females, testicular transplants at all developmental stages increased muscle fiber numbers in adulthood. Values attained were, however, significantly less than those of adult intact or testis‐transplanted males. Testis transplantation increased laryngeal axon numbers in females to levels equivalent to those of intact males; this effect was obtained at every stage of postmetamorphic development including adulthood. To further explore androgen regulation in adults, males and females were gonadectomized and implanted with silicone tubes containing testosterone propionate for 1.5–3 years and laryngeal muscle fibers and axon numbers compared to those of gonadectomized or sham‐operated adult controls. Neither treatment with exogenous androgen nor gonadectomy had any effect on laryngeal muscle fiber or axon number in either males or females; values did not differ from those of sham‐operated controls. We conclude that testicular secretions can induce laryngeal muscle fiber and axon addition in females throughout postmetamorphic life. This degree of plasticity, exhibited after the period when adult values are normally attained, stands in contrast to the effects of administration of synthetic androgen and suggests that the degree of plasticity in adult females may be underestimated if exogenous hormones rather than testicular transplants are provided. © 1993 John Wiley & Sons, Inc.
Axonal outgrowth within the abnormal scaffold of brain tracts in a zebrafish mutant
Authors: Patel Chetan K. , Rodriguez Luis C. , Kuwada John Y. 
Published: January 2005

AbstractThe role of specific axonal tracts for the guidance of growth cones was investigated by examining axonal outgrowth within the abnormal brain tracts of zebrafish cyclops mutants. Normally, the earliest differentiating neurons in the zebrafish brain establish a simple scaffold of axonal tracts. Later‐developing axons follow cell‐specific pathways within this axonal scaffold. In Cyclops embryos, this scaffold is perturbed due to the deletion of some ventromedial neurons that establish parts of the axonal scaffold and the development of an abnormal crease in the brain. In these mutant embryos, the growth cones projected by the neurons of the nucleus of the posterior commissure (nur PC) are deprived of the two tracts of axons that they sequentially follow to first extend ventrally, then posteriorly. These growth cones respond to the abnormal scaffold in several interesting ways. First, nuc PC growth cones initially always extend ventrally as in wild‐type embryos. This suggests that for the first portion of their pathway the axons they normally follow are not required for proper navigation. Second, approximately half of the nuc PC growth cones follow aberrant longitudinal pathways after the first portion of their pathway. This suggests that for the longitudinal portion of the pathway, specific growth cone/axon interactions are important for guiding growth cones. Third, although approximately half of the nuc PC growth cones follow aberrant longitudinal pathways, the rest follow normal pathways despite the absence of the axons that they normally follow. This suggests that cues independent of these axons may be capable of guiding nuc PC growth cones as well. These results suggest that different guidance cues or combinations of cues guide specific growth cones along different portions of their pathway. 1994 John Wiley & Sons, Inc.
Proposed pathways for vocal self‐stimulation: Met‐enkephalinergic projections linking the mibrain vocal nucleus, auditory‐responsive thalamic vocal nucleus, auditory‐responsive thalamic regions and neurosecretory hypothalamus
Authors: Cheng Mei‐Fang , Zuo Mingxue 
Published: January 2005

AbstractIn this study, we have investigated the neuroanatomical pathways that may underlie the influence of a female bird's vocal behavior upon her own reproductive endocrine response. We traced the ascending efferent projections of the midbrain vocal control nucleus, the intercollicularis (ICo), using an anterograde tracer, PHAL, delivered by iontophoretic application. We found labelled terminal fields in the anterior regions of the hypothalamus that contained luteinizing hormone releasing hormone‐ (LHRH) immunoreactive neurons. We injected into the LHRH‐rich anterior medial hypothalamus (AM) the retrograde tracer, fluorogold, to verify the results of PHAL anterograde tracing and exmine whether retrogradely labelled neurons in the ICo can be stained with met‐enkephalin antiserum by the immunohistochemical method. Of the retrogradely labelled neurons in the medial division of ICo (mICo), between 5% and 15% were found to be met‐enkephalin‐immunoreactive positive perikarya. Our data suggest that axonal projections into the anterior medial hypothalamus may arise in part from enkephalin‐immunoreactive neurons in the medial ICo. The mICo neurons distributed along the medial border of the midbrain auditory nucleus give rise to projections into the posterior medial hypothalamus (PMH) via synapses within the shell region of thalamic auditory nucleus, ovoidalis (Ov).We conclude that in the ring dove, the medial division of the vocal control nucleus, by virtue of its connection with the auditory thalamus and neurosecretory hypothalamus, is in a position to exert influence on endocrine response partly through enkephalinergic systems. Implications of similar connections in other species are discussed. 1994 John Wiley & Sons, Inc.
Neurotrophic regulation of mouse muscle β‐amyloid protein precursor and α1‐antichymotrypsin as revealed by axotomy
Authors: Akaaboune Mohammed , Ma Jianxin , Festoff Barry W. , Greenberg Barry D. , Hantaï Daniel 
Published: January 2005

AbstractKunitz‐inhibitor containing forms of the β‐amyloid precursor protein (βAPP), known also as protease nexin II (PNII), and α1‐antichymotrypsin (α1‐ACT), a serpin, are important components of the serine protease and inhibitor balance in many tissues. In the nervous system, this balance may have trophic or growth factor activity at different stages of development, after injury and in disease states. In the current study, using immunocytochemistry and Western blotting with antibodies against the human homologues, we analyzed whether denervation affected the localization of βAPP and α1‐ACT in adult mouse muscle following axotomy. In mouse muscle, antitive band and anti‐human βAPP antibody a band at 92 kD in both normal and denervated extracts. βAPP was present in normal mouse muscle at both neuromuscular junctions and within intramuscular nerves. α1‐ACT was also detected at neuromuscular junctions, on the perineruim and endothelial cell surfaces. Following axotomy, both βAPP and α1‐ACT disappeared from intramuscular nerves simultaneously. However, at the neuromuscular junction, α1‐ACT decreased more rapidly with βAPP lingering before disappearing. Since both α1‐ACT as well as βAPP are present within senile plaques in Alzheimer's disease brains such experiments with the nicotinic, cholinergic neuromuscular synapse in denervated muscle may help to focus experiments on the mechanism of synapse loss as well as plaque deposition in this disease. © 1994 John Wiley & Sons, Inc.
Growth behavior of retinotectal axons in live zebrafish embryos under TTX‐induced neural impulse blockade
Authors: Kaethner Rolf J. , Stuermer Claud A. O. 
Published: January 2005

AbstractThe growth dynamics of individual DiO‐labeled retinal axons deprived of normal neural impulse activity by TTXZ was monitored in the tectum of living zebrafish embryos with time‐lapse video microscopy and compared with normal active axons. Growth cones of TTX‐blocked axons advance intermittently with an average velocity similar to normal axons. While exploring their local environment, they are broadened and bear ruffling lamellipodia and filopodia, but become streamlined when advancing. The activity‐deprived axons grow directly towards their retinotopic target sites in the tectum as do their normal counterparts and very rarely extend branches en route. Much like normal axons, TTX‐blocked axons begin to branch and develop their terminal arbors only at their retinotopic target area. They emit and retract numerous short side branches over a period of several hours. Thearea they contact (the “exploration field”) is of similar dimension as that of active axons, covering from 1% to 7.4% of the tectal neuropil surface, but the final arbor, cover an area only one‐half to one‐sixth as large. TTX arbors are as small as arbors of normal active axons and retinotopically correct. Thus, the typical exploratory growth behavior of developing retinal axons in the tectum, the dynamics of terminal arbor formation at retinotopically correct sites, the dimension of the exploration field, and the shaping of the arbors in zebrafish embryos are unaffected by TTX‐induced neural impulse blockade. 1994 John Wiley & Sons, Inc.
Motor dynamics of song production by mimic thrushes
Authors: Suthers Roderick A. , Goller Franz , Hartley Rebecca S. 
Published: January 2005

AbstractIn brown thrashers (Toxostoma rufum) and grey catbirds (Dumetella carolinensis) neither side of the syrinx has a consistently dominant role in song production. During song, the two sides operate independently, but in close cooperation with each other and with the respiratory muscles which are capable of adjusting expiratory effort to maintain a constant rate of syringeal airflow despite sudden changes in syringeal resistance. Phonation is frequently switched from one side of the syrinx to the other, both between syllables and within a syllable. When both sides of the syrinx produce sound simultaneously, their respective contributions are seldom harmonically related. The resulting “two‐voice” syllables sometimes contain difference tones with prominent sinusoidal amplitude modulation (AM). Rarely, both sides simultaneously produce the same sound. In general, however, the frequency range of sound contributed by the right syrinx is higher than that of the left syrinx. The right syrinx is also primarily responsible for producing a rapid cyclical amplitude modulation which is a characteristic feature of some syllables. This kind of AM is generated by either repetitive brief bursts of sound from the right side that modulate the amplitude of a continuous sound arising on the left side or cyclically opening the right syrinx, allowing unmodulated expiratory air to bypass the phonating left side. 1994 John Wiley & Sons, Inc.
Lateralization and motor stereotype of song production in the brown‐headed cowbird
Authors: Allan Susan E. , Suthers Roderick A. 
Published: January 2005

AbstractSong production in adult brown‐headed cowbirds(Molothrus ater ater) is lateralized, with a slight right syringeal dominance. The left size of the syrinx produces low‐frequency (200–2000 Hz) notes within the introductory note clusters, while the right side produces the higher‐frequency (1500–6000 Hz) introductory notes, the interphrase unit (10–12 kHz), and the final high‐frequency whistle (5–13 kHz). Cross‐correlation analyses reveal that individual cowbirds produce each of their four to seven song types with a distinct stereotyped motor pattern–as judged by the patterns of syringeal airflow and subsyringeal pressure. The acoustic differences across song types are reflected in the differences in the bronchial airflow and air sac pressure patterns associated with song production. These motor differences are particularly striking within the second and third introductory note clusters where there is a rapid switching back and forth between the two sides of the syrinx in the production of notes. These motor skills may be especially important in producing behaviorally effective song. 1994 John Wiley & Sons, Inc.