bluuebunny/crossref_metadata_2025 huggingface dataset:
Neurotrophic agents prevent motoneuron death following sciatic nerve section in the neonatal mouse
Authors: Li Linxi , Openheim Ronald W. , Lei Ming , Houenou Lucien J.
Published: January 2005

We have examined the ability of different neurotrophic and growth factors to prevent axotomy‐induced motoneuron cell death in the developing mouse spinal cord. After postnatal unilateral section of the mouse sciatic nerve, most motoneuron (MN) loss occurs in the lateral motor column of the fourth lumbar segment (L4). Significant axotomy‐induced cell death occurred after surgery performed on or before postnatal day (PN) 5. In contrast, no significant cell loss was found when axotomy was performed after PN10. Axotomy on PN2 or PN5 resulted in a 44% loss of L4 motoneurons by 7 days, and a 66% loss of motoneurons by 10 days postsurgery. Implantation of gelfoam presoaked in various neurotrophic factors at the lesion site rescued axotomized motoneurons. Nerve growth factor (NGF), nedurotrophin‐4/5 (NT‐4/5) and ciliary neurotrophic factor (CNTF) rescued 20%–30% of motoneurons, whereas brain‐derived neurotrophic factor (BDNF), neurotrophin‐3 (NT‐3), and insulin‐like growth factor 1 (IGF‐1) rescued virtually all motoneurons from axotomy‐induced death. By contrast, platelet‐derived growth factor (PDGF)‐AA, PDGF‐AB, basic fibroblast growth factor (bFGF), and interleukin (IL‐6) were ineffective on motoneuron survival following axotomy. NGF, BDNF, NT‐3, IGF‐1, and CNTF also prevented axotomy‐induced atrophy of surviving motoneurons. These data show that mouse lumbar motoneurons continue to be vulnerable to axotomy up to about 1 week after birth and that a number of trophic agents, including the neurotrophins, CNTF, and IGF‐1, can prevent the death of these neurons following axotomy. Our studies confirm and extend previous reports on the time course of axotomy‐induced mouse motoneuron death and the survival promoting effects of neurotrophic factors. 1994 John Wiley & Sons, Inc.
Motoneurons deprived of trophic support in vitro require new gene expression to undergo programmed cell death
Authors: Milligan C. E. , Oppenheim R. W. , Schwartz L. M.
Published: January 2005

During normal development, large numbers of neurons die by programmed cell death. This phenomena has been extensively studied in the lateral motor column of chick embryos, where approximately 50% of the motoneurons that are initially produced, subsequently die due in part to competition for a limited supply of target‐derived trophic support. Inhibitors of RNA and protein synthesis block this cell loss in vivo, indicating a requirement for new gene expression (Oppenheim et al., 1990). Prior to their commitment to death, motoneurons can be isolated as a relatively pure population from chick spinal cord for in vitro study. Cells plated with muscle extract, a potent source of target‐derived trophic support, survive, and have large, phase‐bright cell bodies and extensive neurite outgrowth. In contrast, motoneurons cultured in the absence of muscle extract die within 48 h. This death can be blocked by the RNA synthesis inhibitor actinomycin D, at the time when the cells become committed to die, suggesting that new gene expression is required for cell death. DNA fragmentation and nuclear condensation indicate that some of these cells die by apoptosis. Therefore, it appears that many aspects of motoneuron development observed in vivo can be reconstituted in vitro. These cultures can be used as a model system for studying neuronal death and may contribute to an understanding of the molecular mechanisms that mediate programmed cell death during neuronal development. 1994 John Wiley & Sons, Inc.
Specific pathway selection by the early projections of individual peripheral sensory neurons in the embryonic medicinal leech
Authors: Jellies John , Johansen Kristen , Johansen Jørgen
Published: January 2005

In leech, the central annulus of each midbody segment possesses seven pairs of sensilla, which are mixed clusters of primary peripheral sensory neurons that extend their axons into the CNS where they segregate into distinct fascicles. Pathway selection by individual afferent growth cones of sensillar neurons was examined by double labeling using intracellular dye‐filling with anitobody labeling in early Hirudo medicinalis embryos. The monoclonal antibody Lan3–2 was used because sensillar neuronal tracts are specifically labeled by this antibody. Examining 68 individually filled neurons we found that sensillar neuron growth cones bifurcate within the CNS, that they project long filopodia capable to sampling the local environment, and that all of them appeared to choose a single particular CNS fascicle without apparent retraction or realignment of growth cones. Furthermore, each side of the bifurcating afferent growth cones always chose the same fascicle, implying a specific choice of a distinct labeled pathway. By dye‐filling individual central neurons (P‐cells), we show that there are centrally projecting axons present at the time sensillar afferents enter the ganglionic primordia and select a particular fascicle, and we confirm that at least the dorsal peripheral nerve is likely to be pioneered by central neurons, not by the peripheral afferent. In the sensillum studied here, we sound examples of sensory neurons extending axons into one of all the avilable fascicles. Thus, an individual embryonic sensillum possesses a heterogeneous population of afferents with respect to the central fascicle chosen. This is consistent with the idea that segregation into distinct axon fascicles may be based upon functional differences between individual afferent neurons. Our findings argue strongly in favor of specific pathway selection by afferents in this system and are consistent with previous suggestions that there exists a hierarchy of cues, including surface glycoconjugates that mediate navigation of the sensillar growth cones and the fasciculation of their axons. 1994 John Wiley & Sons, Inc.
Maturation of neurites in mixed cultures of spinal cord neurons and muscle cells from Xenopus laevis embryos followed with antibodies to neurofilament proteins
Authors: Lin Weichun , Szaro Ben G.
Published: January 2005

Dissociated cell cultures of Xeopus laevis embryonic spinal cord have proved useful for studying the differentiation of neuronal ionic channel and membrane properties and for examining the dynamics of microtubules in developing neurons. To examine their usefulness for studying neurofilaments in developing neurites, we prepared similar cultures from stage 22 embryos. Between 3 and 55 h after plating, these cultures were fixed and immunostained with antibodies directed against various epitopes of neurofilament proteins from X. Laevis. These antibodies were specific for nonphosphorylated epitopes of the two low molecular weight Xenopus neurofilament proteins (Xenopus NF‐L and the Xenopus neuronal intermediate filament protein, XNIF), both phosphorylated and nonphosphorylated epitopes of the Xenopus middle molecular weight neurofilament protein (NF‐M), and a nonphosphorylated epitope of the Xenopus high molecular weight neurofilament protein (NF‐H). The emergence of these neurofilament proteins in culture was compared to the time course previously reported for them in Xenopus spinal cord neurons in situ. To facilitate the comparison of times in culture to developmental stages, the age of cultured neurons was converted to an equivalent Nieuwkoop and Faber normal stage using data presented here on the effect of changing temperature on developmental rates of X. laevis. With the exception of the nonphosphorylated epitope of NF‐H, which is indicative of the most mature axons found in situ. the emergence of the other neurofilament protein antibody epitopes closely paralleled that previously reported for these antibodies in situ. Thus, with respect to XNIF, NF‐M, and NF‐L, the neurities of cultured neurons were typical of young embryonic Xenopus laevis spinal cord axons. This system should prove useful for studying both the function of these neurofilament proteins during the early stages of axonal development and the dynamics of their transport. 1994 John Wiley & Sons, Inc.
Influence of factors released from sciatic nerve on adult dorsal root ganglion neurons
Authors: Dobretsov Maxim , Dobretsov Anna , Kuffler Damien P.
Published: January 2005

Previous experiments have shown that medium conditioned (CM) by denervated peripheral nerve contains a process outgrowth promoting factor (s) for cultured adult frog dorsal root ganglion (DRG) neurons. The present experiments further characterize the influences of these factors on DRG neurons. The growth factors increases average process length by threefold, restricts the number of processes extended from four to two while simultaneously altering the morphology of those processes. Neurons with preexisting processes respond to the factors by significantly increasing the length of 35% of these processes. Only the newly elongated portions of preexisting processes have morphology typical of factor‐induced processes, while the previously extended portions retain their original morphology. The number of processes of these neurons remains unchanged. Although composed of two population according to size, neurons in both populations are similarly influenced, suggesting that the factors influence neurons of all sensory modalities. To look at other possible influences of the nerve‐released factors, a novel simple culture system has been developed in which concentration gradients of these factors can be established and maintained. The front of the outgrowth‐promoting influence in these cultures could be followed over time (up to 9 days) as it affected the process length and morphology of neurons at increasing distances (up to 8 mm) from the source of the factors. The trophic factors may play important roles during regeneration in vivo by influencing the cytoskeletal organization in the cell body and growth cones to bring about a stabilization and consolidation of growth cone membrane of only a limited number of processes resulting in increasing the rate of process elongation. The factors may also serve to direct process outgrowth, which can be examined using the new culture system. 1994 John Wiley & Sons, Inc.
The p75 neurotrophin receptor
Authors: Chao Moses V.
Published: January 2005

The low‐affinity p75 molecule and trk tyrosine kinases serve as receptors for target‐derived neurotrophins. While the mechanism by which receptor tyrosine kinases impart intracellular signaling has become well understood, the precise roles of the p75 receptor are not fully defined. The p75 neurotrophin receptor belongs to a family of transmembrane molecules which also serve as receptors for the tumor necrosis factor family of cytokines. Each receptor shares a common extracellular structure highlighted by conserved cysteine‐rich repeats. Because NGF, BDNF, NT‐3, and NT‐4/5 bind to p75 with similar affinity, p75 may either act as a common subunit in a neurotrophin receptor complex with trk family members, or act by independent mechanisms to mediate biological actions of each neurotrophin. 1994 John Wiley & Sons, Inc.
Expression of trk and neurotrophin mRNA in dorsal root and sympathetic ganglia of the quail during development
Authors: Zhang Damin , Yao Lihua , Bernd Paulette
Published: January 2005

The nerve growth factor (NGF) family of neurotrophins exerts effects by binding to products of the trk family of proto‐oncogenes. We examined the expression of both trk and neurotrophin mRNA during the entire range of development of quail dorsal root ganglia (DRG) and sympathetic ganglia (SG) using in situ hybridization and reverse transcriptase‐polymerase chain reaction (RT‐PCR). TrkC mRNA was present in neurons or their precursors from the time of formation of DRG (stage 18, embryonic day 2.5 [E2.5]) and throughout development. The number of labeled cells changes, however, from a majority to a minority at later developmental stages. Expression of trkA mRNA was not detected in DRG until stage 30 (E6) by in situ hybridization, although results with RT‐PCR were positive at stage 23 (E3.5). Labeling was always detected on majority of neurons or their precursors. SG exhibited low level of trkC mRNA during the later stages of development, whereas trdA mRNA was present from stage 34 onward in most neurons. We have also shown that NGF, neurotrophin‐3 (NT‐3), and brain‐derived neurotrophic factor (BDNF) mRNA were present at all stages examined (stages 23 through 45 for DRG, stages 35–36 and 45 for SG). In DRG, NGF mRNA expression was limited to support cells, whereas NT‐3 and BDNF mRNA were detected in both neurons and support cells. These results suggest that neurotrophins could serve a local function in developing ganglia, which can be correlated with the presence of their respective receptors. 1994 John Wiley & Sons, Inc.
Birth times of neurons in labellar taste sensilla of the blowfly Phormia regina
Authors: Pollack Gerald S. , Lakes‐Harlan Reinhard
Published: January 2005

We studied the birth times of neurons of labellar taste sensilla in blowflies using incorporation of the thymidine analogue 5‐bromodeoxyuridine (BrdU) as an indicator of birth time. We found that one of the two main sensillum types, the taste papillae, arise according to a clear spatial gradient of birth times, whereas the other sensillum type, taste hairs, arise without any apparent spatial ordering. Within each sensillum type, there was a strong tendency for either all or none of the neurons to have incorporated BrdU. Among those rare sensilla in which only some of the neurons incorporated BrdU, there were clear patterns of the distribution of labeled and unlabeled neurons per sensillum. These results suggest that subsets of the neurons of a sensillum are siblings, and thus argue against the possibility that the several neurons of a sensillum arise from a single stem cell precursor through repeated asymmetrical divisions. © 1995 John Wiley & Sons, Inc.
Ethanol influences on the chick embryo spinal cord motor system: Analyses of motoneuron cell death, motility, and target trophic factor activity and in vitro analyses of neurotoxicity and trophic factor neuroprotection
Authors: Heaton Marieta B. , Bradley Douglas M.
Published: January 2005

A series of in vivo and in vitro experiments were conducted to determine the influence of prenatally administered ethanol on several aspects of the developing chick embryo spinal cord motor system. Specifically, we examined: (1) the effect of chronic ethanol administration during the natural cell death period on spinal cord motoneuron numbers; (2) the influence of ethanol on ongoing embryonic motility; (3) the effect of ethanol exposure on neurotrophic activity in motoneuron target tissue (limbbud); and (4) the responsiveness of cultured spinal cord neurons to ethanol, and the potential of target‐derived neurotrophic factors to ameliorate ethanol neurotoxicity. These studies revealed the following: Chronic prenatal ethanol exposure reduces the number of motoneurons present in the lateral motor column after the cell death period [embryonic day 12 (E12)]. Ethanol tends to inhibit embryonic motility, particularly during the later stages viewed (E9‐E11). Chronic ethanol exposure reduces the neurotrophic activity contained in target muscle tissue. Such diminished support could contribute to the observed motoneuron loss. Direct exposure of spinal cord neurons to ethanol decreases neuronal survival and process outgrowth in a dose‐dependent manner, but the addition of target muscle extract to ethanol‐containing cultures can ameliorate this ethanol neurotoxicity. These studies demonstrate ethanol toxicity in a population not previously viewed in this regard and suggest a mechanism that may be related to this cell loss (i.e., decreased neurotrophic support). © 1995 John Wiley & Sons, Inc.
Telencephalic and diencephalic origin of radial glial processes in the developing preoptic area/anterior hypothalamus
Authors: Tobet Stuart A. , Paredes Raul G. , Chickering Troy W. , Baum Michael J.
Published: January 2005

Neuronal birth‐dating sudies using [3H]thymidine have indicated that neurons in the preoptic area/anterior hypothalamus (POA/AH) are derived primarily from progenitors in proliferative zones surrounding the third ventricle. Radial glial processes are potential guides for neuronal migration, and their presence and orientation during development may provide further information about the origin of cells in the POA/AH. In addition to determining the orientation of radial glial fibers, we examined the relationship of neurons with identified birth dates to radial glial processes in the developing POA/AH of ferrets. Neuronal birth dates were determined by injecting ferret fetuses with bromodeoxyuridine (BrdU) at several different gestational ages; brains were taken from ferret kits at subsequent prenatal ages. Sections were processed for immunocytochemistry to reveal vimentin or glial fibrillary acidic protein in radial glia, or BrdU‐labeled cell nuclei. Numerous radial glial processes extended from the lateral ventricles through ventral portions of the septal region to the pial surface of the POA/AH. These fibers both encapsulated and coursed ventrally through and around the anterior commissure of ferret, rat, and mouse fetuses. These ventrally directed fibers were less evident at older ages. In double‐labeled sections from ferrets, BrdU‐labeled cells in the dorsal POA/AH were often aligned in the same dorsal‐ventral orientation as adjacent radial glial fibers. We suggest that a subset of neurons, originating in telencephalic proliferative zones, migrates ventrally along radial glial guides into the dorsal POA/AH. © 1995 John Wiley & Sons, Inc.
The canary androgen receptor mRNA is localized in the song control nuclei of the brain and is rapidly regulated by testosterone
Authors: Nastiuk Kent L. , Clayton David F.
Published: January 2005

Singing in canaries is an androgen‐inducible behavior, under the control of an identified motor pathway, which includes several discrete “song nuclei” in the telencephalon. To determine whether the mRNA for the canary androgen receptor (cAR) is expressed in these song control nuclei, we synthesized probes from the recently cloned cAR cDNA and used in situ hybridization to examine spring male canary brain sections. Concentrations of cAR mRNA are detectable in several of the song control nuclei of the forebrain, including high vocal center (HVC), lateral magnocellular nucleus of the anterior neostriatum and robust nucleus of the archistriatum. In addition, we also show that testosterone treatment rapidly induces a significant reduction of cAR mRNA levels in nucleus HVC of females. Since the effects of androgen on singing behavior occur much more slowly, the behavioral effects are probably a secondary or independent result of androgen's primary and immediate action on target gene transcription. © 1995 John Wiley & Sons, Inc.
Collagen synthesis inhibition reduces clustering of heparan sulfate proteoglycan and acetylcholine receptors but not agrin or p65, at neuromuscular contacts in vitro
Authors: Bixby John L.
Published: January 2005

We have studied presynaptic and postsynaptic differentiation at neuromuscular junctions in vitro by examining the localization of synapse‐specific proteins. In nerve–muscle co‐cultures, the synaptic vesicle protein synaptotagmin (p65) accumulated in the nerve terminal overlying myotubes in association with postsynaptic cluster of acetylcholine receptors (AChRs), heparan sulfate proteoglycan (HSPG), laminin, and agrin. Inhibition of collagen synthesis with cis‐hydroxyproline decreased the nerve‐induced clustering of AChRs in muscle cells as well as that caused by exogenous agrin in muscle‐only cultures. Moreover, accumulation of HSPG at contacts was also inhibited in cis‐hydroxyproline–treated cultures. However, accumulation of p65 in nerve fibers at sites of muscle contact, a sign of presynaptic differentiation, was unaffected by cis‐hydroxyproline treatment. In addition, even in cis‐hydroxyproline–inhibited cultures, agrin was evident at more than 90% of contacts showing accumulation of p65 in the nerve terminal. Therefore, a mechanism exists to maintain agrin concentrations at nerve–muscle contacts, even when at least some extracellular matrix (ECM) proteins are disrupted. Our results suggest that HSPG is not required for the induction of nerve terminal differentiation but are consistent with the idea that HSPG or other ECM proteins are important in both nerve‐and agrin‐induced AChR clustering. In particular, agrin accumulation at sites of nerve–muscle contact is not sufficient to induce AChR clusters when the ECM at these contacts is disrupted. © 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 nucleus ambiguus
Authors: Friedland David R. , Eden Avrim R. , Laitman Jeffrey T.
Published: January 2005

The mammalian upper respiratory tract (URT) serves as the common modality for aspects of respiration, deglutition, and vocalization. Although these actions are dependent on coordinated and specific neuromuscular control, little is known about the development of URT control centers. As such, this study investigated the occurrence of naturally occurring motoneuron cell death (MCD) in the nucleus ambiguus (NA) of a developmental series of rats. Standard histological techniques were used to count motoneurons in the ventrolateral brainstem where the mature NA is found. In addition, the neural tracer, fast Dil, was used to determine whether motoneurons were still migrating into the region of the NA during the period that cell counts were first taken. Furthermore, to elucidate the potential effect of inadvertently counting large interneurons on the assessment of motoneuron numbers, an antibody to γ‐aminobutyric acid (GABA) was used. The results of this study have, for the first time, demonstrated that MCD occurs in a URT‐related motor nucleus. Approximately a 50% cell death was observed during the prenatal development of NA, with no further loss seen postnatally. The fast DiI studies showed that by embryonic day 17, NA was fully formed, suggesting that motoneuron migration from the basal plate was complete. In addition, use of the GABA antibody showed a lack of inhibitory interneurons within the NA. The finding of MCD in the NA helps define a critical period in the formation of URT neuromuscular control. As the course of MCD is modifiable by epigenetic signals, insult to the organism during this prenatal period may compromise future URT control. © 1995 John Wiley & Sons, Inc.
Calcium transients in growth cones and axons of cultured Helisoma neurons in response to conditioning factors
Authors: Williams Diana K. , Cohan Christopher S.
Published: January 2005

Accumulating evidence indicates that cytosolic calcium levels regulate growth cone motility and neurite extension. The purpose of this study was to determine if intracellular calcium levels also influence the initiation of neurite extension induced by growth‐promoting factors. An in vitro preparation of axotomized neurons that can be maintained in the absence of growth‐promoting factors was utilized. The distal axons of cultured Helisoma neurons plated into defined medium do not extend neurites until they are exposed to Helisoma brain‐conditioned medium. This provided the opportunity to study the intracellular changes associated with neurite extension. Cytosolic calcium levels were monitored with the calcium‐sensitive dye fura 2 at the distal axon. In control medium calcium levels in the distal axon were constant. However, transient elevations in cytosolic calcium in the axonal growth cone occurred after addition of conditioned medium and coincident with the initiation of neurite extension. Application of calcium channel blockers showed that the transients resulted from calcium influx across the neuronal membrane. The transients, however, were not required for neurite extension, although they did influence the rate and extent of neurite outgrowth. Simultaneous extracellular patch recordings demonstrated that the calcium transients were correlated temporally with an increase in rhythmic spontaneous electrical activity of cells, suggesting that conditioned medium influences ionic membrane properties of these neurons. © 1995 John Wiley & Sons, Inc.
Early isolation from conspecific song does not affect the normal developmental decline of N‐methyl‐D‐aspartate receptor binding in an avian song nucleus
Authors: Aamodt Sandra M. , Nordeen Ernest J. , Nordeen Kathy W.
Published: January 2005

Early effects of experience on synaptic reorganization and behavior often involve activation of N‐methyl‐D‐aspartate (NMDA) receptors. We have begun to explore the role of this glutamate‐receptor subtype in the development of learned birdsong. Song learning in zebra finches occurs during a restricted period that coincides with extensive synaptic reorganization within neural regions controlling song behavior. In one brain region necessary for song learning, the lateral magnocellular nucleus of the anterior neostriatum (lMAN), NMDA receptor binding is twice as high at the onset of song learning as in adulthood. In the present study, we used quantitative autoradiography with the noncompetitive NMDA antagonist [3H]MK‐801 to examine more closely the developmental decline in NMDA receptor binding within lMAN and found that it occurred gradually over the period of song learning and was not associated with a particular stage of the learning process. In addition, early isolation from conspecific song did not affect [3H]MK‐801 binding in lMAN at 30, 60, or 80 days. Since behavioral studies confirmed that our isolate rearing conditions extended the sensitive period for song learning, we conclude that the normal developmental decline in overall NMDA receptor binding within lMAN does not terminate the capacity for song learning. Finally, early deafening, which prevents both stages of song learning, also did not affect [3H]MK‐801 binding in lMAN at 80 days, indicating that the decline in NMDA receptor binding occurs in the absence of auditory experiences associated with song development. © 1995 John Wiley & Sons, Inc.
Regeneration of neuromuscular connections in crayfish allotransplanted neurons
Authors: Krause Kristin M. , Vélez Samuel J.
Published: January 2005

Transplantation of whole ganglia was used to study the regeneration of four of the neurons that innervate the superficial flexor muscles of the crayfish Procambarus clarkii. The isolated ganglia containing the somas of these neurons were successfully transplanted from one crayfish to another. Reinnervation proceeded across the muscle surface and by 8 to 10 weeks connections were detected across the entire target field. At different time periods after the transplant, junction potentials (JPs) produced in phase with spontaneous neuronal spikes were recorded. The distribution of JP sizes and their decay times were examined. JPs from transplanted preparations were smaller than JPs from control or normal regeneration animals. These JPs also failed to facilitate when stimulated at 1 and 10 Hz. These are normal characteristics of immature terminals, but in the transplant preparations, once established, they remained stable for the duration of the study. Thus, synaptogenesis appears to be arrested at a stage before synaptic efficacy is established in the allotransplants. In addition, connectivity maps were plotted for each axon over the muscle surface. Some muscle fibers did not receive any contacts, and overall innervation leveled off at around 60% of the muscle fibers, remaining stable for the duration of this study. Despite the incomplete physiological innervation, however, three of the four neurons showed the same medial/lateral preferences observed in control animals, regenerating their original patterns of connectivity across the muscle surface. © 1995 John Wiley & Sons, Inc.
Filarin, a novel invertebrate intermediate filament protein present in axons and perikarya of developing and mature leech neurons
Authors: Johansen Kristen M. , Johansen Jørgen
Published: January 2005

The lan 3–8 monoclonal antibody recognizes a 63 kD antigen that is associated with the cytoskeleton in leech neurons. We have used this antibody to clone a novel invertebrate neuronal intermediate filament protein, filarin, by screening an expression vector library. A full‐length clone of 2.2 kb identified by the antibody was isolated and sequenced. The protein contains a coiled‐coil rod domain typical of the superfamily of intermediate filament proteins flanked by unique N‐ and C‐terminal domains. The highest homology of filarin is to the alternatively spliced squid brain intermediate filament protein (Szaro et al., 1991, J. Biol. Chem. 266:15035–15041), the only other invertebrate neuronal intermediate filament in the data bank. However, apart from extensive homology in the two end regions of the rod domain, the similarity of the two proteins is limited to the general coiled‐coil structure of intermediate filaments. Thus, filarin may represent a novel type of invertebrate neuronal intermediate filament protein. Filarin contains the extra 6 heptads characteristic of lamins and of all cytoplasmic invertebrate intermediate filaments analyzed so far. By Northern analysis, it appears that filarin is not alternatively spliced, since only a single transcript of 2.2 kb is recognized by the clone. Using the lan 3–8 antibody to follow its developmental expression, we found that filarin is present in all known neurons in the central and peripheral nervous system. © 1995 John Wiley & Sons, Inc.
Repair of the central nervous system: Lessons from lesions in leeches
Authors: von Bernhardi Rommy , Muller Kenneth J.
Published: January 2005

In contrast to the limited repair observed in the mammalian central nervous system (CNS), injured neurons in the leech reliably regenerate synapses and restore function with remarkable accuracy at the level of individual neurons. New and recent results reveal important roles for microglial cells and extracellular matrix components, including laminin, in repair. Tissue culture experiments have permitted isolation of neurons and manipulation of their environment, providing insights into the influence of substrate, electrical activity, and other cells, including microglia, on axon growth and synapse formation. The results account for distinctive features of successful repair in the adult leech, where axonal sprouting and target selection can be influenced by unequal competition between neurons. Differences between the formation of connections during embryonic development and repair in the adult include dissimilarities in the roles of glia and microglia in adults and embryos, suggesting that axon growth during regeneration in the CNS is not simply a recapitulation of processes observed during embryonic development. It may be possible in the future to improve mammalian CNS regeneration by recruiting cells whose counterparts in the leech have been identified as instrumental in repair. © 1995 John Wiley & Sons, Inc.
Estrogens and non‐estrogenic ovarian influences combine to promote the recruitment and decrease the turnover of new neurons in the adult female canary brain
Authors: Hidalgo Andrea , Barami Kaveh , Iversen Kristin , Goldman Steven A.
Published: January 2005

The higher vocal center (HVC) of the songbird forebrain exhibits persistent neurogenesis in adulthood, particularly in a region of the mediocaudal neostriatum that is associated with a subventricular layer of estrogen receptive cells. We asked whether estrogens might influence adult neurogenesis, by assessing the effect of ovariectomy on HVC neuronal production in the adult female canary. Fifteen 1‐year‐old females were separated into groups of ovariectomized, estradiol‐replaced ovariectomized, and gonadally intact birds. To label dividing cells and their progency, the birds were given [3H]thymidine for 8 days, killed 32 days later, and their brains autoradiographed. A significant rise was noted in the number of HVC neurons per section in estradiol‐treated birds relative to the untreated control birds. The number of [3H]‐thymidine‐labeled HVC neurons was also higher in the estrogen‐treated birds; however, the neuronal labeling index (LI) did not vary as a function of estradiol replacement, as the total number of HVC neurons rose in parallel with the added new neurons. In contrast, the neuronal LI did rise as a result of ovariectomy, and this ovariectomy‐associated increase in the LI was not reversed by estradiol. Among non‐neuronal cell types, the endothelial LI was higher in estrogen‐treated birds than in their untreated counterparts, suggesting estrogen‐associated angiogenesis. Radioimmunoassay confirmed that serum estradiol was reduced in the castrated birds. Since estrogen appeared to promote the survival of [3H]thymidine+ neurons, we next sought to determine whether estrogen acted directly on the newly generated neurons, or rather indirectly through an intermediary cell population. To this end, we asked whether the new neurons or their precursors expressed estrogen receptor immunoreactivity (ER‐IR). Five adult male canaries were given [3H]thymidine for periods ranging from 2 to 28 days, killed at varying times up to 3 weeks therafter, then probed for ER‐IR and autoradiographed. [3H]thymidine+ cells displayed no detectable ER‐IR within their first 4 weeks of postmitotic life. Rather, during migration from the ventricular zone (VZ), the new neurons traversed a layer of mitotically quiescent, ER+ subventricular cells. Double labeling for ER‐IR and cell‐type selective antigens confirmed that these ER+ cells were neurons. These results indicate that the early survival of new neurons in the adult songbird HVC is promoted by estrogen, and may be mediated by the estrogen‐stimulated paracrine release of neurotrophic agents by ER‐IR subventricular neurons. Our data suggest that estrogen's promotion of neuronal survival may operate concurrently with an estrogen‐independent ovarian suppression of neuronal mitogenesis.
Leukemia inhibitory factor influences the timing of programmed synapse withdrawal from neonatal muscles
Authors: Kwon Young W. , Abbondanzo Susan J. , Stewart Colin L. , Gurney Mark E.
Published: January 2005

We show that leukemia inhibitory factor (LIF) plays a physiological role in the programmed withdrawal of synapses form neonatal muscles. First, LIF mRNA is present in embryonic skeletal muscle and is developmentally regulated. We detect high levels of LIF mRNA at embryonic day 17 (E17) in mouse hind leg muscles. The content of LIF mRNA falls 10‐fold between E17 and birth and then remains low in the neonate and adult. The decrease in LIF mRNA in skeletal muscle coincides with the end of secondary myogenesis and the completion of the adult number of myofibers. Second, treatment of the mouse tensor fascia latae (TFL), a superficial muscle of the hind leg, with LIF from birth (100 ng/day), transiently delays the withdrawal of excess inputs from polyneuronally innervated myofibers by approximately 3 days. The midpoint of the process is shifted from 7.5 ± 0.5 to 10.2 ± 0.6 days of age. LIF treatment delays synapse withdrawal by altering its timing without an appreciable effect on its rate. Third, in mice homozygous for a distruption of the LIF gene, the midpoint in the reduction of multiply innervated TFL myofibers occurs 1 day earlier, at 6.5 ± 0.5 days of age. Muscle fiber number is unchanged in LIF null mice. Treatment with LIF does not alter the rate of neonatal growth, the number of muscle fibers in the TFL, or the reappearance of inputs that have been eliminated. Instead, LIF appears to delay maturation of the motor unit by transiently delaying the onset of synapse withdrawal. We hypothesize that this is a necessary component of a selective process that will operate simultaneously and equally on multiple, competing motor units. © 1995 John Wiley & Sons, Inc.
Pharmacological analysis of heartbeat in Drosophila
Authors: Gu Gang‐Guo , Singh Satpal
Published: January 2005

Analysis of the mechanisms underlying cardiac excitability can be faciliated greatly by mutations that disrupt ion channels and receptors involved in this excitability. With an extensive repertoire of such mutations, Drosophila provides the best available genetic model for these studies. However, the use of Drosophila for this purpose has been severely handicapped by lack of a suitable preparation of heart and a complete lack of knowledge about the ionic currents that underlie its excitability. We describe a simple preparation to measure heartbeat in Drosophila. This preparation was used to ask if heartbeat in Drosophila is myogenic in origin, and to determine the types of ion channels involved in influencing the heart rate. Tetrodotoxin, even at a high concentration of 40 μM, did not affect heart rate, indicating that heartbeat may be myogenic in origin and that it may not be determined by Na+ channels. Heart rate was affected by PN200–110, verapamil, and diltiazem, which block vertebrate L‐type Ca2+ channels. Thus, L‐type channels, which contribute to the prolonged plateau of action potentials in vertebrate heart, may play a role in Drosophila cardiac excitability. It also suggests that Drosophila heart is subject to a similar intervention by organic Ca2+ channel blockers as the vertebrate heart. A role for K+ currents in the function of Drosophila heart was suggested by an effect of tetraethylammonium, which blocks all the four identified K+ currents in the larval body wall muscles, and quinidine, which blocks the delayed rectifier K+ current in these muscles. The preparation described here also provides an extremely simple method for identifying mutations that affect heart rate. Such mutations and pharmacological agents will be very useful for analyzing molecular components of cardiac excitability in Drosophila. © 1995 John Wiley & Sons, Inc.
Projection pattern of sensory neurons in the central nervous system of a homeotic mutation of the moth Manduca sexta
Authors: Booker Ronald , Miles Carol I.
Published: January 2005

Octopod (Octo) is a mutation of the moth Manduca sexta, which transforms the first abdominal segment (A1) in the anterior direction. Mutant animals are characterized by the appearance of homeotic thoracic‐like legs on A1. We exploited this mutation to determine what rules might be used in specifying the fates of sensory neurons located on the body surface of larval Manduca. Mechanical stimulation of homeotic leg sensilla did not cause reflexive movements of the homeotic legs, but elicited responses similar to those observed following stimulation of ventral A1 body wall hairs. Intracellular recordings demonstrated that several of the motoneurons in the A1 ganglion received inputs from the homeotic sensory hairs. The responses of these motoneurons to stimulation of homeotic sensilla resembled their responses to stimulation of ventral body wall sensilla. Cobalt fills revealed that the mutation transformed the segmental projection pattern of only the sensory neurons located on the ventral surface of A1, resulting in a greater number with intersegmental projection patterns typical of sensory neurons found on the thoracic body wall. Many of the sensory neurons on the homeotic legs had intersegmental projection patterns typical of abdominal sensory neurons: an anteriorly directed projection terminating in the third thoracic ganglion (T3). Once this projection reached T3, however, it mimicked the projections of the thoracic leg sensory neurons. These results demonstrate that the same rules are not used in the establishment of the intersegmental and leg‐specific projection patterns. Segmental identity influences the intersegmental projection pattern of the sensory neurons of Manduca, whereas the leg‐specific projections are consistent with a role for positional information in determining their pattern. © 1995 John Wiley & Sons, Inc.
Ciliary neurotrophic factor arrests muscle and motoneuron degeneration in androgen‐insensitive rats
Authors: Forger Nancy G. , Wong Vivien , Marc Breedlove S.
Published: January 2005

Steroid hormones and neurotrophic factors exert profound and widespread effects on the developing nervous system, including regulation of the size, connectivity, and survival of neurons. Androgenic control of the survival of motoneurons in the spinal nucleus of the bulbocavernosus (SNB) of rats has been well documented. We previously found that ciliary neurotrophic factor (CNTF) mimics many effects of androgen on the developing SNB. Whether effects of CNTF depend on the presence of a functional androgen receptor was evaluated in the present study. Androgen‐insensitive male rats bearing the testicular feminization mutation, Tfm, and female littermates were treated with CNTF or with vehicle alone from embryonic day 22 through postnatal day 3. On postnatal day 4 SNB cell number was elevated in both groups receiving CNTF. Volumes of the bulbocavernosus (BC) and levator ani (LA) muscles, targets of SNB motoneurons, were also markedly increased by CNTF. Since the BC appears to degenerate completely in untreated females, these results indicate that CNTF can delay or prevent muscle fiber death. The relative sparing of muscles and motoneurons did not differ for Tfm males and females, demonstrating that effects of CNTF on the SNB neuromuscular system do not require functional androgen receptors. © 1995 John Wiley & Sons, Inc.
Chemical alteration of poly(tetrafluoroethylene) Teflon induced by exposure to vacuum ultraviolet radiation and comparison with exposure to hyperthermal atomic oxygen
Authors: Everett Michael L. , Hoflund Gar B.
Published: January 2005

The chemical alteration of poly(tetrafluoroethylene) Teflon by vacuum ultraviolet radiation (VUV) (115–400 nm) has been examined with X‐ray photoelectron spectroscopy (XPS). The initial F/C atom ratio of 1.98 decreases to 1.65 after a 2‐h exposure. The F/C atom ratio is further reduced to a steady‐state value of 1.60 after a 74‐h exposure. The high‐resolution XPS C1s data indicate that new chemical states of carbon form as F is removed and that the relative amounts of these states depend on the F content of the near‐surface region. The states are most likely due to C bonded only to one F atom, C bonded only to other C atoms, and C that has lost a pair of electrons through the emission of F−. The exposure of the VUV‐damaged surface to research‐grade O2 results in the chemisorption of a very small amount of O, and this indicates that large quantities of reactive sites are not formed during the chemical erosion by VUV. Further exposure to VUV removes this chemisorbed oxygen. A comparison of the XPS data indicates that the mechanisms of chemical alteration by VUV radiation and hyperthermal (∼5 eV) atomic oxygen are different, as expected, because the excitation sources are quite different. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 552–561, 2005
Cyanoxyl‐mediated free‐radical polymerization of acrylic acid: Its scope and limitations
Authors: Grande Daniel , Guerrero Ramiro , Gnanou Yves
Published: January 2005

This work examines the scope and limitations of the cyanoxyl (·OCN)‐mediated free‐radical polymerization of acrylic acid (AA) with respect to the criteria of livingness. Cyanoxyl persistent radicals were generated in situ through the reaction between arenediazonium salts (XC6H4NN⊕BF, where X is H, OCH3, Cl, or NO2) and sodium cyanate (NaOCN). This article thoroughly discusses the role played by such oxygen‐centered radicals in the polymerization process; it particularly focuses on the influence of the concentration and nature of the diazonium salt, the solvent, and the temperature on features such as the variations of ln([M]0/[M]) versus time (where [M]0 is the initial monomer concentration and [M] is the monomer concentration), the number‐average molar mass versus conversion, and the polydispersity versus conversion in cyanoxyl‐mediated free‐radical polymerizations of AA. Cyanoxyl‐terminated samples were used as macroinitiators for the polymerization of methyl methacrylate to generate poly(acrylic acid)‐b‐poly(methyl methacrylate) block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 519–533, 2005
Identification of motor neurons for accessory muscles of inspiration and expiration, pectoralis, trapezius and external oblique: Comparison with non‐respiratory skeletal muscle
Authors: Charlton Clivel G. , Crowell Bernard , Benson Richard
Published: January 2005

The motor neurons for the accessory muscles of respiration, pectoralis, trapezius, external oblique, and the rectus abdominis were studied in the spinal cord. The objective was to determine if the localization and morphology of the motor neurons for these muscles bear any distinct relationship to the specialized function of these muscles, serving both as supportive skeletal muscles and as accessory respiratory muscles. In addition, it was of interest to know if the inspiratory role of the pectoralis and trapezius muscles and the expiratory role of the external oblique and rectus abdominis are related to the spatial organization of the motor neurons; this knowledge may be important in the discrimination of influences from afferent connections. The motor neurons for these muscles were retrogradely labeled with true blue and were compared with the triceps motor neurons. All neurons occurred ipsilateral and most labeling occurred in C6–7. The motor neurons for the accessory muscles were mainly confined to the ventrolateral tip of the ventral gray matter. The triceps neurons were dorsolateral to the respiratory related neurons in C6–7. Within the confines of the ventrolateral area, the majority of neurons for the pectoralis were localized medial to ventromedial, those for the trapezius were ventrolateral, and those for the external oblique were in the extreme ventrolateral to ventral sections of C7. No neurons were observed in C2 to T2 for the rectus abdominis. A second neuronal column occurred medioventrally in the ventral gray of C4–6 for the trapezius, and is distinct and separated from the C6–7 cell column. The motor neurons for the accessory muscles were oval in shape and of medium size (≈︁ 35 microns). Those for the triceps were small to large 18–45 microns, elongated in shape with distinctly labeled processes and well defined perimeter. The neurons within each column often occurred in clumps and are probably separated by densely packed dendrites that may cause the insulation of one cellular column from another to achieve discriminatory afferent influences to individual neuronal columns. The localization of the motor neurons for the accessory respiratory muscles in C7 superimposed the localization of a high density of substance P receptors (Charlton and Helke, 1986) that also occurred in the phrenic nucleus. The overlapping of the substance P receptors with the motor neurons for the accessory respiratory muscles is supportive of a role for substance P in respiratory control. Finally, the accesory respiratory muscles were innervated by dorsal root sensory neurons that occurred throughout the cervical segments and the first and second thoracic segments. This was in contrast to the innervation of the triceps by sensory neurons located in just one or two segments from its motor neurons of innervation.
Asymptomatic striatal dopamine depletion: PET scans in unilateral MPTP monkeys
Authors: Guttman M. , Yong V. W. , Kim S. U. , Calne D. B. , Martin W. R. W. , Adam M. J. , Ruth T. J.
Published: January 2005

In cynomolgus monkeys, 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MRTP) produces irreversible clinical, chemical, and pathological alterations that are similar to those found in Parkinson's disease. Unilateral carotid injections of this toxin produce ipsilateral nigrostriatal dopamine depletion while sparing the contralateral dopaminergic pathways. In order to study the damage to the nigrostriatal dopamine system in asymptomatic animals after unilateral MPTP administration, positron emission tomography (PET) scans were performed with [18F]fluoro‐L‐dopa (6‐FD). This study demonstrates that clinically asymptomatic MPTP lesions may be assessed in vivo using 6‐FD and PET.