bluuebunny/crossref_metadata_2025 huggingface dataset:
Motor dynamics of song production by mimic thrushes
Authors: Suthers Roderick A. , Goller Franz , Hartley Rebecca S.
Published: January 2005

In 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

Song 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.
Kinase requirement for retinal growth cone motility
Authors: Jian X. , Hidaka H. , Schmidt J. T.
Published: January 2005

Since cytoplasmic Ca2+ levels are reported to regulate neurite elongation, we tested whether calcium‐activated kinases might be necessary for growth cone motility and neurite elongation in explant cultures of goldfish retina. Kinase inhibitors and activators were locally applied by micropipette to retinal growth cones and the responses were observed via phase‐contrast videomicroscopy. In some cases, growth rates were also quantifed over several hours after general application in the medium. The selective inhibitors of protein kinase C, calphostin C (0.1–1 μM) and chelerythrin (up to 50 μM), caused no obvious changes in growth cones or neurite elongation, and activators of PKC (phorbols, arachidonic acid, and diacylglycerol) also were generally without effects, although phorbols slowed the growth rate. Inhibitors of protein kinase A and tyrosine kinases also produced no obvious effects. The calmodulin antagonists, calmidazolium (0.1 μM), trifluoperazine (100 μM), and CGS9343B (50 μM), however, caused a reversible growth cone arrest with loss of filopodia and lamellipodia. The growth cone became a club‐shaped swelling which sometimes moved a short distance back the shaft, leaving evacuated filaments at points of strong filopodial attachments. A similar reversible growth cone arrest occurred with the general kinase inhibitors: H7 at 200 but not at 100 μM, and staurosporine at 100 but not 10 nM, suggesting possible involvement of a calmodulin‐dependent kinase (camK) rather than PKC. The selective inhibitor of camKII, KN‐62 (tested up to 50 μM), produced no effects but the specific myosin light‐chain kinase (MLCK) inhibitors ML‐7 (3–5 μM) and ML‐9 (5–10 μM) reversibly reproduced the effect, suggesting that MLCK rather than camKII is necessary for growth cone motility. The MLCK inhibitors' effects both on growth cone morphology and on F‐actin filaments (rhodamine‐phalloidin staining) were similar to those caused by cytochalasin D (5 μM), and are discussed in light of findings that inhibiting MLCK disrupts actin filaments in astrocytes and fibroblasts. 1994 John Wiley & Sons, Inc.
Neurotrophic factor therapy for nervous system degenerative diseases
Authors: Hefti Franz
Published: January 2005

The ability of neurotrophic factors to regulate developmental neuronal survival and adult nervous system planticity suggests the use of these molecuales to treat neurodegeneration associated with human diseases. Solid rationales exist for the use of NGF and neurotrophin‐3 in the treatment of neuropathies of the peripheral sensory system, insulin‐like growth factor and ciliary neurotrophic factor in motor neuron atrophy, and NGF in Alzheimer's disease. Growth factors have been identified for neurons affected in Parkinson's disease, Huntington's disease, and acute brain and spinal cord injury. Various strategies are actively pursued to deliver neurotrophic factors to the brain, and develop therapeutically useful molecules that mimic neurotrophic factor actions or stimulate their production or receptor mechanisms. 1994 John Wiley & Sons, Inc.
Target specificity and size of avian sensory neurons supported in vitro by nerve growth factor, brain‐derived neurotrophic factor, and neurotrophin‐3
Authors: Lopresti Patrizia , Scottt Sheryl A.
Published: January 2005

To obtain insight into which subpopulations of sensory neurons in dorsal root ganglia are supported by different neurotrophins, we retrogradely labeled cutaneous and muscle afferents in embryonic day 9 chick embryos and followed their survival in neuron‐enriched cultures supplemented with either nerve growth factor (NGF), brain‐derived neurotrophic factor (BDNF), or neurotrophin‐3 (NT‐3). We found that NGF is a wide survival factor for subpopulations of both cutaneous and muscle afferents, whereas the survival effects of BDNF and NT‐3 are restricted primarily to muscle afferents. We also measured soma size in each neurotrophic factor. These new data show that BDNF‐ and NT‐3–dependent cells appear to be a mixture of two populations of neurons: one small diameter and the other large diameter. In contrast, based on size alone, NGF‐dependent cells appear to be a single population of only small‐diameter neurons. Thus, BDNF and NT‐3 may have some new, previously unreported effects on small‐diameter afferent neurons. © 1994 John Wiley & Sons, Inc. 1994 John Wiley & Sons, Inc.
Androgen directs sexual differentiation of laryngeal innervation in developing Xenopus laevis
Authors: Robertson John C. , Watson James T. , Kelley Darcy B.
Published: January 2005

In adult Xenopus laevis, innervation of the vocal organ is more robust in males than in females. This sex difference originates during tadpole development; at stage 56, when the gonads first differentiate, the number of axons entering the larynx is the same in the sexes, but by stage 62, innervation is greater in males. To determine if androgen secretion establishes sex differences in axon number, we treated tadpoles with antiandrogen or androgen beginning at stage 48 or 54 and counted laryngeal nerve axons at stage 62 using electron microscopy. When male tadpoles were treated with the antiandrogen hydroxyflutamide, axon numbers were reduced to female‐typical values; axon numbers in females were unaffected by antiandrogen treatment. When female tadpoles were treated with the androgen DHT (dihydrotestosterone), axon numbers were increased to male‐like values. These findings suggest that endogenous androgen secretion during late tadpole stages in males is required for the sexual differentiation of laryngeal innervation observed from stage 62 on. Because androgen treatment and laryngeal innervation affect myogenesis in postmetamorphic frogs, numbers of laryngeal dilator muscle fibers were determined for hormonally manipulated tadpoles. At stage 62, vehicle‐treated males had more laryngeal axons than females; laryngeal muscle fiber numbers did not, however, differ in the sexes. Both male and female tadpoles, treated from stage 54 with DHT, had more muscle fibers at stage 62 than vehicle‐treated controls. Thus, while endogenous androgen secretion during late tadpole stages is subthreshold for the establishment of masculinized muscle fiber numbers, laryngeal myogenesis is androgen sensitive at this time and can be increased by suprathreshold provision of exogenous DHT. A subgroup of tadpoles, DHT treated from stage 54 to 62, was allowed to survive, untreated, until postmetamorphic stage 2 (PM2: 5 months after metamorphosis is complete). Androgen treatment between tadpole stages 54 and 62 does not prevent the ontogenetic decrease in axon numbers characteristic of laryngeal development. In addition, the elevation in stage 62 axon numbers produced by DHT‐treatment at late tadpole stages was not associated with elevated numbers of laryngeal muscle fibers at PM2. Juvenile males normally maintain elevated axon numbers (relative to final adult values) through PM2 and the presence of these additional axons may result from‐rather than contribute directly to—laryngeal muscle fiber addition. 1994 John Wiley & Sons, Inc.
Dual pathways for tactile sensory information to thoracic interneurons in the cockroach
Authors: Pollack Alan J. , Ritzmann Roy E. , Watson James T.
Published: January 2005

The escape system of the American cockroach is both fast and directional. In response to wind stimulation both of these characteristics are largely due to the properties of the ventral giant interneurons (vGIs), which conduct sensory information from the cerci on the rear of the animal to type A thoracic interneurons (TIAs) in the thoracic ganglia. The cockroach also escapes from tactile stimuli, and although vGIs are not involved in tactile‐mediated escapes, the same thoracic interneurons process tactile sensory information. The response of TIAs to tactile information is typically biphasic. A rapid initial depolarization is followed by a longer latency depolarization that encodes most if not all of the directional information in the tactile stimulus. We report here that the biphasic response of TIAs to tactile stimulation is caused by two separate conducting pathways from the point of stimulation to the thoracic ganglia. Phase 1 is generated by mechanical conduction along the animal's body cuticle or other physical structures. It cannot be eliminated by complete lesion of the nerve cord, and it is not evoked in response to electrical stimulation of abdominal nerves that contain the axons of sensory receptors in abdominal segments. However, it can be eliminated by lesioning the abdominal nerve cord and nerve 7 of the metathoracic ganglion together, suggesting that the relevant sensory structures send axons in nerve 7 and abdominal nerves of anterior abdominal ganglia. Phase 2 of the TIAs tactile response is generated by a typical neural pathway that includes mechanoreceptors in each abdominal segment, which project to interneurons with axons in either abdominal connective. Those interneurons with inputs from receptors that are ipsilateral to their axon have a greater influence on TIAs than those that receive inputs from the contralateral side. The phase 1 response has an important role in reducing initiation time for the escape response. Animals in which the phase 2 pathway has been eliminated by lesion of the abdominal nerve cord are still capable of generating a partial startle response with a typically short latency even when stimulated posterior to the lesion. © 1995 John Wiley & Sons, Inc.
Lamina‐specific synaptic connections of hippocampal neurons in vitro
Authors: Frotscher M. , Heimrich B.
Published: January 2005

By using slice cultures as a model, we demonstrate here that different target selectivities exist among the various afferent fibers to the hippocampus. As in intact animals, septohippocampal cholinergic fibers, provided by a slice culture of septum, innervate a co‐cultured slice of hippocampus diffusely, that is, without forming distinct layers of termination. As in vivo, the septal cholinergic fibers establish synapses with a variety of target cells. Conversely, fibers from an entorhinal slice co‐cultured to a hippocampal slice display their normal laminar specificity. They preferentially terminate in the outer molecular layer of the fascia dentata, thereby selectively contacting peripheral dendrites of the granule cells. This preferential termination on peripheral dendritic segments is remarkable, since these fibers do not have to compete with commissural fibers, hypothalamic fibers, and septal afferents for dendritic space under these culture conditions. Moreover, in triplet cultures in which first two hippocampal slices were co‐cultured and then, with a delay of 5 days, an entorhinal slice was added, the fibers from the entorhinal slice and those from the hippocampal culture terminated in their appropriate layers in the hippocampal target culture. However, in this approach the normal sequence of ingrowth of these two afferents was reversed. In normal ontogenetic development, entorhinal afferents arrive in the hippocampus before the commissural fibers. The results show that there are different degrees of target selectivity of hippocampal afferents and that the characteristic lamination of certain afferent fibers in the hippocampus is not determined by their sequential ingrowth during development. © 1995 John Wiley & Sons, Inc.
Fos: An immediate‐early transcription factor in neurons
Authors: Curran Tom , Morgan James I.
Published: January 2005

In the past several years a great deal of evidence has accumulated linking neuronal activation events to the regulation of gene expression. We have pursued an analysis of c‐fos regulation in the nervous system to elucidate the molecular mechanisms involved in stimulus‐transcription coupling. The c‐fos gene can be viewed as an archetype of the set of cellular immediate‐early genes encoding transcription factors. These genes are believed to function in coupling short‐term signals elicited by extracellular to long‐term changes in cellular phenotype by orchestrating alterations in target gene expression. Several animal seizure models have been used to demonstrate the activation of gene expression in specific populations of neurons. Using a transgenic mouse approach, based on a foslacZ fusion gene, we now demonstrate an association between c‐fos expression and cell death in the nervous system. A delayed and protracted induction was observed following surgical lesion and in response to neurotoxin exposure. This system allows us to determine, for the first time, the DNA regulatory sequences that are responsible for the induction of gene expression in neurons in vivo. Furthermore, foslacZ transgenic mice provide a unique resource for identifying cell populations that respond to specific stimuli or that are susceptible to particular toxins. © 1995 John Wiley & Sons, Inc.
Plasticity in cultured carotid body chemoreceptors: Environmental modulation of GAP‐43 and neurofilament
Authors: Jackson Adele , Nurse Colin
Published: January 2005

In this study we use dissociated cell cultures of the rat carotid body to investigate the adaptive capabilities of endogenous oxygen chemoreceptors, following chronic stimulation by various environmental factors. These oxygen chemoreceptors are catecholamine‐containing glomus cells, which derive from the neural crest and resemble adrenal medullary chromaffin cells. Using double‐label immunofluorescence, we found that chronic exposure of carotid body cultures to hypoxia (2% to 10% oxygen) caused a significant fraction of tyrosine hydroxylase‐positive (TH+) glomus cells to acquire detectable immunoreactivity for growth‐associated protein gap‐43. The effect was dose‐dependent and peaked around an oxygen tension of 6%, where approximately 30% of glomus cells were GAP‐43 positive. Treatment with agents that elevate intracellular cyclic adenosine monophosphate (cAMP) (i.e., dibutyryl cAMP or forskolin) also markedly stimulated GAP‐43 expression. Since hypoxia is known to increase cAMP levels in glomus cells, it is possible that the effect of hypoxia on GAP‐43 expression was mediated, at least in part, by a cAMP‐dependent pathway. Unlike hypoxia, however, cAMP analogs also stimulated neurofilament (NF 68 or NF 160 kD) expression and neurite outgrowth in glomus cells, and these properties were enhanced by retinoic acid. Nerve growth factor, which promotes neuronal differentiation in related crest‐derived endocrine cells, and dibutyryl cGMP were ineffective. Thus, it appears that postnatal glomus cells are plastic and can express neuronal traits in vitro. However, since hypoxia stimulated GAP‐43 expression, without promoting neurite outgrowth, it appears that the two processes can be uncoupled. We suggest that stimulation of GAP‐43 by hypoxia may be important for other physiological processes, e.g., enhancing neurotransmitter release or sensitization of G‐protein–coupled receptor transduction. © 1995 John Wiley & Sons, Inc.
Proliferating hair cell precursors in the ear of a postembryonic fish are replaced after elimination by cytosine arabinoside
Authors: Presson Joelle C. , Smith Tamara , Mentz Lynn
Published: January 2005

Identified, proliferating S‐phase cells in the postembryonic fish ear are known to be the precursors to new hair cells. It is not known, however, whether the ability to proliferate is restricted to a small population of cells. The ability of cells that are not normally in the cell cycle to enter S‐phase was examined using the antimitotic drug cytosine arabinoside (ara‐C). The normal population of S‐phase cells in the saccule was destroyed by a single large dose of ara‐C. Two weeks later, the prsence of S‐phase cells was evaluated using the S‐phase marker bromodeoxyuridine. The results strikingly demonstrate that S‐phase cells are replaced, since S‐phase cells returned to the saccule in the same number as found in normal fish. The data are interpreted to suggest that a large number of nonsensory support cells are capable of entering the cell cycle and that some mechanism must regulate which of these are actually cycling at any given time. © 1995 John Wiley & Sons, Inc.
Distribution of androgen receptor immunoreactivity in the spinal cord of wild‐type, androgen‐insensitive and gonadectomized male rats
Authors: Freeman Louise M. , Padgett Barbara A. , Prins Gail S. , Breedlove S. Marc
Published: January 2005

The polyclonal antiserum PG21 was used to detect androgen receptor (AR) protein in three motoneuronal pools of the male rat lumbar spinal cord. In gonadally intact, wild‐type males, the spinal nucleus of the bulbocavernosus (SNB), dorsolateral nucleus (DLN), and retrodorsolateral nucleus (RDLN) all displayed immunolabeling of cell nuclei. The percentage of motoneurons displaying such labeling was highest in the SNB and lowest in the RDLN. This pattern of AR immunocytochemical labeling agrees well with previous steroid autoradiographic studies of androgen accumulation in the rat spinal cord. In contrast, virtually no motoneurons in any of the three pools displayed nuclear AR immunostaining in long‐term gonadectomized males or in gonadally intact males carrying the Tfm mutation, which renders the AR incompetent. In gonadectomized males, labeling was restored in the SNB and DLN, but not the RDLN, 30 min after an injection of replacement testosterone. Eight hours of testosterone exposure restored immunolabeling in all three motor nuclei. Apparent cytoplasmic staining was seen in SNB motoneurons of untreated castrates and Tfm rats, but not intact rats, suggesting that AR residing in the cytoplasm translocates to the nucleus on binding to androgen in these motoneurons. © 1995 John Wiley & Sons, Inc.
Imaging of caffeine‐inducible release of intracellular calcium in cultured embryonic mouse telencephalic neurons
Authors: Tsai Ti Dao , Barish Michael E.
Published: January 2005

To gain a better understanding of Ca2+‐induced Ca2+ release in central neurons, we have studied the increase in intracellular Ca2+ concentration ([Ca2+]i) induced by application of caffeine to cells cultured from embryonic mouse telencephalon (hippocampus or cortex). The magnitudes and distributions of changes in [Ca2+]i in neuron somata were measured by quantitative video microscopy. We observed that application of caffeine to pyramidally shaped neurons typically initiated an increase in [Ca2+]i in the cytoplasmic region between the nucleus and the base of a major dendrite. [Ca2+] in this region increased over a period of 3 to 6 s and was followed by, with a slight delay, a surge of Ca2+ that moved across the soma and into or over the nucleus. Similar Ca2+ that moved across the soma and into or over the nucleus. Similar Ca2+ responses to caffeine were observed in Ca2+‐containing and nominally Ca2+‐free external solutions, suggesting that caffeine was inducing Ca2+ release from intracellular stores. Ca2+ responses to caffeine were potentiated by inducing a tonic Ca2+ influx through N‐methyl‐D‐aspartate (NMDA)‐type glutamate receptors activated by 0.3 μM glutamate and multiple responses to caffeine could be elicited by using this Ca2+ influx to refill the intracellular stores. Ryanodine inhibition of caffeine‐induced Ca2+ release was use‐ and concentration‐dependent; the median effective concentration EC50 for ryanodine declined from 22 μM for the first application of caffeine to 20 nM for the fourth. We conclude, based on these responses to caffeine, that ryanodine‐sensitive mechanisms of intracellular Ca2+ release are active in hippocampal and cortical neurons and may be involved in generation of directed Ca2+ waves that engulf the nucleus. © 1995 John Wiley & Sons, Inc.
Multiple strategies for directed growth cone extension and navigation of peripheral neurons
Authors: Jellies John , Johansen Jørgen
Published: January 2005

Leeches have a diverse constellation of peripheral neural elements that are challenged to extend growth cones in highly specific ways in a constantly changing embryonic environment. Two major systems are reviewed here. In one, peripheral afferents extend growth cones toward the central nervous system (CNS), forming common pathways, and then segregate into particular tracts within the CNS. A majority of these afferents depend on CNS‐derived guidance cues and projections from the CNS to guide their way. However, not all of the nerves are established this way and at least one of the peripheral nerves is likely to be pioneered by sensillar sensory afferents. The distribution of particular antigens (such as the lan3–2 antigen) suggests the identity of molecules involved in homophilic adhesion along common pathways, whereas others (such as the lan4–2 and 3–6 antigens) are candidates for mediating specific pathway choices. In the second system, the myo‐organizing Comb cell (C cell) projects multiple growth cones simultaneously along oblique trajectories not influenced by segmental or midline boundaries. Its parallel growth cones exhibit space‐filling as well as directional growth and are guided by local cues to extend in discrete phases that are coordinated with the development of the environment. Both systems exhibit highly directed outgrowth orchestrated by a hierarchy of cues, establish patterns of neurites used to direct later migrating cells, and seem to be regulated temporally and spatially by interactions with the embryonic environment. These systems illustrate the strengths of examining neural development in vivo across several levels of analysis. © 1995 John Wiley & Sons, Inc.
Sequential steps in axonal targeting are mediated by carbohydrate markers
Authors: Zipser Birgit
Published: January 2005

Mannose and hybrid/complex‐type oligosaccharides serve as markers for both the full set of peripheral sensory afferent neurons in the leech and also for disjoint subsets of these neurons. We have shown that these various surface carbohydrates play crucial roles in the multistep process by which afferents meet their synaptic parterns in the central nervous system (CNS). The carbohydrate marker common to all these afferents allows their projections (which are fasciculated as they enter the CNS) to disperse and search out target regions. Carbohydrate markers specific for subsets of these afferents subsequently allow each subset to consolidate the position of its projections in appropriate regions of the CNS where it contacts its synaptic partners. ‐ 1995 John Wiley & Sons, Inc.
Cell–cell interactions define the innervation patterns of central leech neurons during development
Authors: Wolszon Laura
Published: January 2005

In the last 20 years, the nervous system of the developing leech has been used to great advantage to study the processes by which neurons seek and finally innervate their targets. This review summarizes what is presently known about how neurons of the CNS interact with each other and with their targets during embryogenesis. ‐ 1995 John Wiley & Sons, Inc.
Heartbeat control in the medicinal leech: A model system for understanding the origin, coordination, and modulation of rhythmic motor patterns
Authors: Calabrese Ronald L. , Nadim Farzan , Olsen Øystein H.
Published: January 2005

We have analyzed in detail the neuronal network that generates heartbeat in the leech. Reciprocally inhibitory pairs of heart interneurons form oscillators that pace the heartbeat rhythm. Other heart interneurons coordinate these oscillators. These coordinating interneurons, along with the oscillator interneurons, form an eight‐cell timing oscillator network for heartbeat. Still other interneurons, along with the oscillator interneurons, inhibit heart motor neurons, sculpting their activity into rhythmic bursts. Critical switch interneurons interface between the oscillator interneurons and the other premotor interneurons to produce two alternating coordination states of the motor neurons. The periods of the oscillator interneurons are modulated by endogenous RFamide neuropeptides. We have explored the ionic currents and graded and spike‐mediated synaptic transmission that promote oscillation in the oscillator interneurons and have incorporated these data into a conductance‐based computer model. This model has been of considerable predictive value and has led to new insights into how reciprocally inhibitory neurons produce oscillation. We are now in a strong position to expand this model upward, to encompass the entire heartbeat network, horizontally, to elucidate the mechanisms of FMRFamide modulation, and downward, to incorporate cellular morphology. By studying the mechanisms of motor pattern formation in the leech, using modeling studies in conjunction with parallel physiological experiments, we can contribute to a deeper understanding of how rhythmic motor acts are generated, coordinated, modulated, and reconfigured at the level of networks, cells, ionic currents, and synapses. © 1995 John Wiley & Sons, Inc.
Naturally occurring motoneuron cell death in rat upper respiratory tract motor nuclei: A histological, fast Dil and immunocytochemical study in the hypoglossal nucleus
Authors: Friedland David R. , Eden Avrim R. , Laitman Jeffrey T.
Published: January 2005

We have previously reported on our investigation of motoneuron cell death (MCD) in the rat nucleus ambiguus (NA). This article focuses on the other major upper respiratory tract motor nucleus: the hypoglossal. The hypoglossal nucleus (XII) contains motoneurons to the tongue and, as such, plays a critical role in defining patterns of respiration, deglutition, and vocalization. Motoneuron counts were made in XII in a developmental series of rats. In addition, the neural tracer fast DiI was used to ensure that all hypoglossal motoneurons had migrated into the nucleus at the time cell death was assessed. Furthermore, an antibody to γ‐aminobutyric acid (GABA) was used to determine the potential effect of inadvertently counting large interneurons on motoneuron counts. Cell death in XII was shown to occur entirely prenatally with a loss of 35% of cells between embryonic day 16 (E16) and birth. Fast DiI tracings of the prenatal hypoglossal nerve indicated that all motoneurons were present in a well‐defined nucleus by E15. Immunocytochemical staining for GABA demonstrated considerably fewer interneurons than motoneurons in XII. These findings in XII, in comparison with those previously reported for NA, demonstrate differences in the timing and amount of cell death between upper respiratory tract motor nuclei. These differences establish periods during which one nucleus may be preferentially insulted by environmental or teratogenic factors. Preferential insults may underlie some of the upper respiratory tract incoordination pathologies seen in the newborn such as the sudden infant death syndrome (SIDS). © 1995 John Wiley & Sons, Inc.
Brain‐derived proteins that rescue spinal motoneurons from cell death in the chick embryo: Comparisons with target‐derived and recombinant factors
Authors: Johnson James E. , Qin‐Wei Yin , Prevette David , Oppenheim Ronald W.
Published: January 2005

Spinal motoneurons that normally die during early development can be rescued by a variety of purified growth or neurotrophic factors and target tissue extracts. There is also indirect evidence that brain or supraspinal afferent input may influence lumbar motoneuron survival during development and that this effect may be mediated by central nervous system–derived trophic agents. This report examines the biological and biochemical properties of motoneuron survival activity obtained from extracts of the embryonic chick brain. Treatment with an ammonium sulfate (25% to 75%) fraction of embryonic day 16 (E16) or E10 brain extracts rescued many spinal motoneurons that otherwise die during the normal period of cell death in vivo (E6 to E10). The same fractions also enhanced lumbar motoneuron survival following deafferentation. There were both similarities and differences between the active fractions derived from brain extracts (BEX) when compared with extracts derived from target muscles (MEX) or with purified neurotrophic factors. Survival activity from E10 BEX was as effective in promoting motoneuron survival as E10 MEX and more effective than astrocyte‐conditioned media. Unlike MEX, the active fractions from BEX also rescued placode‐derived nodose ganglion cells. In addition, unlike nerve growth factor and brain‐derived neurotrophic factor, active BEX fractions did not rescue neural crest‐derived dorsal root ganglion cells or sympathetic ganglion neurons. Interestingly, among many cranial motor and other brainstem nuclei examined, only the survival of motoneurons from the abducens nucleus was enhanced by BEX. Active proteins obtained from BEX were further separated by gel filtration chromatography and by preparative isolelectric focusing techniques. Activity was recovered in a basic (pI8) and an acidic (pI5) small molecular weight protein fraction (20 kD or less). The specific activity of the basic fraction was increased ×66 when compared with the specific activity of crude BEX, and the basic fraction had a slightly higher specific activity than the acidic fraction. The biological and biochemical properties of these fractions are discussed in the context of known neurotrophic factors and their effects on normal and lesion‐induced motoneuron death during development. © 1995 John Wiley & Sons, Inc.
Hu protein as an early marker of neuronal phenotypic differentiation by subependymal zone cells of the adult songbird forebrain
Authors: Barami Kaveh , Iversen Kristin , Furneaux Henry , Goldman Steven A.
Published: January 2005

The avian forebrain exhibits neurogenesis in adulthood, with neuronal production from ependymal/subependymal zone (SZ) precursor cells. To follow the commitment of newborn cells to neuronal lineage, we used their expression of the Hu family of neuronal RNA‐binding proteins to identify them before their migration from the SZ. Adult canaries were injected with [3H]thymidine as a marker of DNA replication, sacrificed after varying intervals, stained for Hu, and autoradiographed. We found that Hu was not expressed by premitotic precursor cells, but rather appeared within hours in their neuronal progeny, which did not embark on parenchymal migration until 4 to 7 days later. Hu was expressed by all neurons, but not glia, both in vivo and in vitro, as determined by ultrastructural analysis as well as co‐localization of Hu and cell‐type selective antigens. In addition, co‐staining for Hu and N‐cadherin, whose expression is down‐regulated on neuronal emigration from the SZ, revealed their initial co‐expression by neuronal daughter cells still within the SZ. These results suggest that Hu expression may be used as a very early indicator of neuronal differentiation by SZ cells. Furthermore, the data indicate that in the adult avian brain, neuronal phenotype is established within hours of precursor mitosis, even though the neuronal daughter cells do not initiate parenchymal migration for at least 4 days thereafter, following their down‐regulation of N‐cadherin. © 1995 John Wiley & Sons, Inc.
Distinct adhesive properties of ciliary and choroid neurons from the avian ciliary ganglion
Authors: Porter Brenda E. , Sanes Joshua R.
Published: January 2005

The avian ciliary ganglion (CG) contains two populations of neurons: ciliary neurons, which innervate striated muscle, and choroid neurons, which innervate vascular smooth muscle. We used cell size (ciliary cells are larger) and somatostatin immunoreactivity (which is restricted to choroid cells) as markers to compare the adhesive properties of these two neuronal types. Similar numbers of freshly dissociated embryonic chick ciliary and choroid neurons adhered to laminin (laminin 1) and polylysine, consistent with the fact that each population comprises about half of the ganglionic neurons. In contrast, severalfold more ciliary neurons than choroid neurons adhered to a recombinant fragment of a synapse‐specific basal lamina protein, s‐laminin/laminin β2. Moreover, severalfold more ciliary neurons than choroid neurons adhered to a plastic surface when assayed by the method of Needels et al. in serum‐free medium. Adhesion to s‐laminin and plastic appears to be mediated by different cell surface components, as adhesion to recombinant s‐laminin is inhibited by the tripeptide, LRE, and by Ca2+ions, but not by heparin, whereas adhesion to plastic is LRE and Ca2+ insensitive but heparin sensitive. Both adhesive differences are apparent at embryonic day 8, soon after the ciliary and choroid neurons have begun to form synapses. Thus, two sets of neurons in the CG that send axons through different nerves and innervate different targets also show distinct adhesive behaviors. © 1995 John Wiley & Sons, Inc.
Preparation and characterization of chitosan‐based dispersions
Authors: da Trindade Neto Cypriano G , Fernandes Ana LP , Santos Ana IB , Morais Waldenice A , Navarro Marcos VM , Dantas Tereza NC , Pereira Márcia R , Fonseca José LC
Published: January 2005

Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry
Rheological properties and thermal transitions in millable polyurethane fluoroelastomers
Authors: Turri Stefano , Levi Marinella , Cristini Marco , Sanguineti Aldo
Published: January 2005

A series of segmented polyurethane fluoroelastomers based on dimethylol‐terminated perfluoropolyethers (PFPEs), aliphatic diisocyanates and allyl functionality is presented. Depending on the type of diisocyanate monomer used, it was found that quite different prepolymer molecular weights were achieved. Thermal analysis by differential scanning calorimetry showed formation of polyphasic copolymers, either amorphous or semi‐crystalline depending on the monomer structure. Rheological measurements showed that much higher zero‐shear viscosity, a shorter Newtonian plateau and more marked shear thinning behaviour were achieved with polyurethanes based on hexamethylene diisocyanate (HDI) or H12‐MDI monomers. Isothermal viscosity curves were fitted with either three‐ or two‐parameter empirical models, and relaxation times of the structures were estimated at the temperature of 120 °C. Copyright © 2004 Society of Chemical Industry
Preparation and evaluation of polyaniline and polypyrrole modified water‐dispersible conducting nanocomposites of polyacrylonitrile with silica
Authors: Maity Arjun , Biswas Mukul
Published: January 2005

Water‐dispersible conducting nanocomposites were prepared by precipitating polyaniline (PANI)/polypyrrole (PPY) in an aqueous suspension of polyacrylonitrile–SiO2 (PAN–SiO2) via K2CrO4–NaAsO2 redox polymerization. Incorporation of PANI and PPY in the composites was confirmed by the FTIR spectrum. Scanning electron microscopic analyses for the PANI–(PAN–SiO2) and PPY–(PAN–SiO2) composites indicated formation of lumpy aggregates with irregular sizes. TEM analyses revealed formation of spherical particles with size ranging between 80 and 150 nm for PANI–(PAN–SiO2) nanocomposite and 75–150 nm for PPY‐(PAN‐SiO2) nanocomposites, respectively. Thermal stabilities of the PANI–(PAN–SiO2) and PPY–(PAN–SiO2) nanocomposites were higher than those of the individual base polymers. Conductivity values of PANI–(PAN–SiO2) nanocomposite (10−3 S cm−1) and PPY–(PAN–SiO2) nanocomposite (10−4 S cm−1) were remarkably improved relative to that for PAN homopolymer (>10−11 S cm−1). Both of these composites produced a permanently stable aqueous suspension when the polymerization was conducted in presence of nanodimensional SiO2 as a particulate dispersant. Copyright © 2004 Society of Chemical Industry
Analysis of the cytosolic proteome of Halobacterium salinarum and its implication for genome annotation
Authors: Tebbe Andreas , Klein Christian , Bisle Birgit , Siedler Frank , Scheffer Beatrix , Garcia‐Rizo Carolina , Wolfertz Jan , Hickmann Volker , Pfeiffer Friedhelm , Oesterhelt Dieter
Published: January 2005

The halophilic archaeon Halobacterium salinarum (strain R1, DSM 671) contains 2784 protein‐coding genes as derived from the genome sequence. The cytosolic proteome containing 2042 proteins was separated by two‐dimensional gel electrophoresis (2‐DE) and systematically analyzed by a semi‐automatic procedure. A reference map was established taking into account the narrow isoelectric point (pI) distribution of halophilic proteins between 3.5 and 5.5. Proteins were separated on overlapping gels covering the essential areas of pI and molecular weight. Every silver‐stained spot was analyzed resulting in 661 identified proteins out of about 1800 different protein spots using matrix‐assisted laser desorption/ionization time of flight mass spectrometry (MALDI‐TOF MS) peptide mass fingerprinting (PMF). There were 94 proteins that were found in multiple spots, indicating post‐translational modification. An additional 141 soluble proteins were identified on 2‐D gels not corresponding to the reference map. Thus about 40% of the cytosolic proteome was identified. In addition to the 2784 protein‐coding genes, the H. salinarum genome contains more than 6000 spurious open reading frames longer than 100 codons. Proteomic information permitted an improvement in genome annotation by validating and correcting gene assignments. The correlation between theoretical pI and gel position is exceedingly good and was used as a tool to improve start codon assignments. The fraction of identified chromosomal proteins was much higher than that of those encoded on the plasmids. In combination with analysis of the GC content this observation permitted an unambiguous identification of an episomal insert of 60 kbp (“AT‐rich island”) in the chromosome, as well as a 70 kbp region from the chromosome that has integrated into one of the megaplasmids and carries a series of essential genes. About 63% of the chromosomally encoded proteins larger than 25 kDa were identified, proving the efficacy of 2‐DE MALDI‐TOF MS PMF technology. The analysis of the integral membrane proteome by tandem mass spectrometric techniques added another 141 identified proteins not identified by the 2‐DE approach (see following paper).
A novel GABAA antagonist [3H]SR 95531: Microscopic analysis of binding in the rat brain and allosteric modulation by several benzodiazepine and barbiturate receptor ligands
Authors: McCabe R. Tyler , Wamsley James K. , Yezuita James P. , Olsen Richard W.
Published: January 2005

Recent reports have demonstrated that the synthetic gamma‐aminobutyric acid (GABA)‐derivative, SR 95531 [2‐(3′‐carbethoxy‐2′‐propyl)‐3‐amino‐6‐paramethoxy‐phenyl‐pyridazini‐um bromide], possesses selective GABAA sites, this agent has been used to identify GABAA receptors. In the present investigation, we studied the binding of [3H]SR 95531 to tissue sections of rat brain using microscopic analysis of receptor localization. The appropriate binding conditions for defining GABAA receptors with this radioligand were obtained by determining the dissociation and association kinetics, and performing saturation and displacement studies. Using membrane preparations from whole rat brain (or brain regions representing cortex, striatum, hippocampus, midbrainthalamus, medulla‐pons and cerebellum), saturation and displacement studies were analyzed, and allosteric modulation of [3H]SR 95531 binding was examined by including several benzodiazepine and barbiturate receptor ligands in the incubation media. To assess the stereoselective properties of [3H]SR 95531 binding in rat membranes, numerous barbiturates were added during the incubation. The binding of [3H]SR 95531 was demonstrated to be saturable, specific and to bind with relatively high affinity to low‐affinity GABAA sites. Scatchard analysis performed on saturation data of binding to tissue sections showed a dissociation constant (KD) of 42.4 nM and a maximum number of binding sites (Bmax) of 105.8 fmol/mg tissue. Microscopic analysis showed that intermediate to high densities of [3H]SR 95531 binding occurred in brain regions containing intermediate to high densities of low‐affinity GABAA sites. Results from competition studies demonstrated that [3H]SR 95531 is displaceable by GABAA agents and displaced preferentially by GABAA antagonists. Scatchard analysis of saturation experiments from membrane preparations indicated that the KD and Bmax from the centrifugation assay was 53.0 nM and 4.26 pmol/mg protein, respectively. Using the filtration assay, binding to membranes yielded a KD value of 45.6 nM and a Bmax of 0.77 pmol/mg protein. The allosteric modulation data demonstrated that numerous benzodiazepine and barbiturate agents inhibited [3H]SR 95531 binding and this varied according to brain region. Several barbiturates included in the incubation media exhibited a stereoselective inhibition of [3H]SR 95531 binding to whole rat brain membranes. In summary, [3H]SR 95531 identifies the antagonist conformation of GABAA receptors in the rat brain and binds preferentially to the low‐affinity site. The data collected in the present study show that [3H]SR 95531 is an excellent probe to recognize the GABAA receptor subtype and allows for the identification of the interactions of subcomponents of the macromolecular GABA receptor complex.
(D‐Phe12) bombesin and substance P analogues function as central bombesin receptor antagonists
Authors: Merali Zul , Merchant Carol A. , Crawley Jacqueline N. , Coy David H. , Heinz‐Erian Peter , Jensen Robert T. , Moody Terry W.
Published: January 2005

The potency of synthetic bombesin (BN) analogues with D‐Phe12 substitutions and substance P analogues was investigated in the rat CNS. (D‐Phe12, Leu14)BN, (D‐Phe12)BN and (Tyr4,D‐Phe12)BN inhibited binding to rat brain slices with IC50 values of approximately 2 μM. Similarly, spantide inhibited binding to rat brain slices with an IC50 value of 1.5 μM. Spantide inhibited specific (125I‐Tyr4)BN binding as a result of decreased rate of association, whereas the rate of dissociation was unaffected. Neither the (D‐Phe12)BN analogues nor the substance P analogues inhibited specific binding of 125I‐VIP to rat brain slices. Central administration of BN (0.5 μg) induced grooming and suppressed feeding and resting. (Tyr4, D‐Phe12)BN (5 μg) antagonized the behavioral effects of BN. Although spantide (2 μg) also antagonized many of the BN effects, it had intrinsic effects and hence the behavioral antagonism was not specific. These data suggest that although both (D‐Phe12)BN and substance P analogues may function as central BN receptor antagonists, the (D‐Phe12)BN analogues may be functionally the more useful class of antagonists.
Ultrastructure of stratum lacunosum moleculare interneurons of hippocampal CA1 region
Authors: Kunkel Dennis D. , Lacaille Jean‐Claude , Schwartzkroin Philip A.
Published: January 2005

Intracellular recordings were obtained from nonpyramidal neurons (interneurons) in stratum lacunosum‐moleculare (L‐M) of the CA1 region of guinea pig hippocampal slices. These interneurons had response characteristics that distinguish them from pyramidal cells and other interneuron types: the L‐M neurons had relatively broad action potentials with large spike afterhyperpolarizations, high input resistance and little spike‐firing adaptation, and low spontaneous activity. Lucifer Yellow (LY) and horseradish peroxidase (HRP) were injected intracellularly into physiologically identified L‐M interneurons, and the cells were characterized morphologically using light and electron microscopy.

L‐M somata were fusiform‐shaped (15 × 25 μm), had multiple processes, and were located at the border between stratum (str.) lacunosum‐moleculare and str. radiatum. L‐M dendrites coursed through str. lacunosum‐moleculare and projected into str. radiatum. L‐M axons made axodendritic synaptic contacts primarily in str. lacunosum‐moleculare and str. radiatum, but also in str. moleculare of the dentate gyrus. These axodendritic synaptic contacts were made onto spiny dendritic processes (presumably pyramidal cell and granule cell dendrites) and onto aspinous dendrites (presumably interneuron dendrites), and appeared to be of the symmetric type (type 2), characteristic of inhibitory synapses.

In separate groups of animals, selective lesions were made of afferents to the CA1 and dentate regions of hippocampus, and subsequent degeneration of contacts onto L‐M interneuron somata and dendrites was examined at the ultrastructural level. Fibers originating from contralateral and ipsilateral CA3 region, and from ipsilateral entorhinal cortex, were found to make synaptic contact onto presumed L‐M interneurons. Degenerating terminals appeared to be of the asymmetric type (type 1), characteristic of excitatory synapses. These morphological data are consistent with electrophysiological results showing that L‐M interneurons can mediate feedforward inhibition of CA1 pyramidal cells.