bluuebunny/crossref_metadata_2025 huggingface dataset:
Tamoxifen fails to block estradiol accumulation, yet is weakly accumulated by the juvenile zebra finch anterior hypothalamus: An autoradiographic study
Authors: Mathews Greta A. , Arnold Arthur P.
Published: May 2005

In experiment 1, we used autoradiographic procedures to examine whether tamoxifen could displace 3H‐estradiol labeling in the anterior hypothalamus and the caudal nucleus of the ventral hyperstriatum (HVc) of ovariectomized 20‐day‐old female zebra finches. There was no significant reduction in labeling of cells by 3H‐estradiol in birds preinjected with unlabeled tamoxifen. In experiment 2, we found that injections of 3H‐tamoxifen causedweak labeling of cells in the anterior hypothalamus of 20‐day‐old male and female zebra finches. These results are compatible with the idea that tamoxifen does not block the action of estradiol in the brain of zebra finches, and suggest that the effects of early tamoxifen treatment on the morphology of the song system may reflect central action of tamoxifen.
Hormonally mediated plasticity of motoneuron morphology in the adult rat spinal cord: A cholera toxin‐HRP study
Authors: Kurz E. M. , Brewer R. G. , Sengelaub D. R.
Published: May 2005

The dorsolateral nucleus (DLN) and the spinal nucleus of the bulbocavernosus (SNB) of the rat lumbar spinal cord are sexually dimorphic groups of motoneurons that innervate striated perineal muscles involved in male copulatory behavior. Androgens control the development of these motoneurons and their target muscles, and continue to influence the system in adulthood. Given that several features of SNB motoneuron morphology have been shown to be androgen sensitive in adult male rats, we examined the effects of androgen manipulations on the morphology of motoneurons in the DLN in adult rats. Adult male rats were castrated and implanted with testosterone‐filled or blank implants, or were subjected to a sham‐castration procedure. Six weeks after treatment, motoneurons in the DLN were retrogradely labeled with cholera toxin‐horseradish peroxidase (HRP) after injection into the ischiocavernosus (IC) muscle and their morphology assessed. Measures of the radial extent and coverage of the dendritic arbor of DLN motoneurons projecting to the IC (DLN‐IC motoneurons) were similar across the groups, indicating comparable degrees of HRP transport. However, DLN‐IC motoneurons in castrates with blank implants possessed both shorter dendritic lengths and smaller somas than those of castrates treated with testosterone. Castrates with testosterone implants had DLN‐IC motoneurons that were significantly larger than those of sham castrates in dendritic length and soma area. These results suggest that motoneurons in the DLN, like those in the SNB, possess a significant degree of structural plasticity in adulthood which is influenced by androgens.
Androgen locally regulates rat bulbocavernosus and levator ani size
Authors: Rand Mark N. , Breedlove S. Marc
Published: May 2005

Adult male rats were gonadectomized, and small Silastic capsules filled with hormone were sutured to each bulbocavernosus and levator ani muscle complex (BC/LA). In the first experiment, one capsule contained testoster one (T), while the capsule on the contralateral muscles contained the antiandrogen hydroxyflutamide (hFI). The intent of this treatment was to provide a focus of androgenic stimulation to the muscles on the muscles on one side. After 30 days, animals were sacrificed, and the BC / LA muscle pairs were removed, weighed, and compared. BC/LAs receiving T treatment were heavier than those receiving hFl treatment (p <0.0001), with an average weight difference of 12%. Muscle fibers from T‐treated BCs were significantly larger in diameter than those from contralateral, hFl‐treated BCs. These results indicate that androgen exerts its anabolic effect by acting locally upon a cell population within or near the BC/LA. When hFl and blank capsules were implanted in castrated males, the hFl‐treated muscles were significantly heavier (by 9%), demonstrating an anabolic effect of hFl in the absence of androgen, and refuting the idea that hFl may have caused local toxic effects in the first experiment. Gonadectomized animals given T versus blank capsules had T‐treated muscles that were 8% heavier than the blank treated side. Muscle weights were also compared in animals receiving bilateral denervation of the BC/LA at the time of T and hFl capsule implantation and gonadectomy; local testosterone treatment failed to affect BC/LA weights in these denervated muscles.
Connections of the forewing tegulae in the locust flight system and their modification following partial deafferentation
Authors: Büschges Ansgar , Ramirez Jan‐Marino , Driesang Robert , Pearson Keir G.
Published: May 2005

The flight motor pattern of the adult locust (Locusta migratoria L.) is able to recover from the loss of the hindwing tegulae. This recovery is due to a functional substitution of the hindwing tegulae by the forewing tegulae (Büschges, Ramirez, and Pearson, 1992). To assess changes in the pathways from the forewing tegulae in the flight system, we investigated the pathways of the forewing tegula in intact locusts and in animals 2 weeks after hindwing tegula removal. The following physiological alterations in these pathways were found to be associated with the recovery: (1) In the intact locusts, the connections of forewing tegula afferents to flight interneurons are variable but this variability did not occur in recovered animals, and (2) larger numbers of forewing tegula afferents connect to interneurons that excite elevator motoneurons (interneurons 566 and 567) and to an interneuron that inhibits depressor motoneurons (interneuron 511). The size of unitary excitatory postsynaptic potentials (EPSPs) evoked by single forewing tegula afferents was found not to be altered in recovered animals. The changes in connectivity of forewing tegula afferents are correlated with morphological alterations in the structure of the terminal processes of the afferents and with sprouting of some branches of interneurons receiving input from these afferents.
Monoclonal M6 antibody interferes with neurite extension of cultured neurons
Authors: Lagenaur Carl , Kunemund Volker , Fischer Gunther , Fushiki Shinji , Schachner Melitta
Published: May 2005

Monoclonal M6 antibody binds to the surface of murine central nervous system neurons as well as to apical surfaces of epithelial cells in the choroid plexus and proximal tubules of the kidney. M6 antigen is expressed in the central nervous system as early as embryonic day 10, most strongly in the marginal zone of the neural tube, and remains detectable in adulthood. IgG or Fab fragments of M6 antibody interfere with the extension of neurites by cultured cerebellar neurons. Effects of the antibody on neurite extension are readily detectable after 24 h. No reduction of cell viability is detected during the first 3 days of antibody treatment. Cultures maintained in the presence of antibody for longer than 5 days exhibit reduced viability of neurons. This reduction in long‐term viability in the presence of M6 antibody is largely avoided when 25 mM KCl is included in the culture medium. The antibody‐mediated perturbation of neurite outgrowth is not blocked by the presence of elevated KCl. The unusually short and flattened appearance of neurites in these cultures suggests that the M6 antibody selectively affects neurite extension. Time‐lapse cinematography of anti‐M6‐treated neurons reveals no apparent effect on movement of lamellipodia and filopdia of growth cones. Only the overall extension of the neurite appears to be inhibited. M6 antigen is a 35 kD glycoprotein that can be isolated from a deoxycholate‐ (DOC) solubilized membrane fraction from adult mouse brain.
Neuron death in the developing avian isthmo–optic nucleus, and its relation to the establishment of functional circuitry
Authors: Clarke P. G. H.
Published: May 2005

The present review covers all the published data on neuron death in the developing avian isthmo–optic nucleus (ION), which provides a particularly convenient situation for studying the causes and consequences of neuron death in the development of the vertebrate central nervous system. The main conclusions are as follows: The naturally occurring neuron death in the ION is related both temporally and causally to the ION's formation of afferent and efferent connections. The ION neurons need to obtain both anterograde and retrograde survival signals in order to survive during a critical period in embryogenesis. They may compete, at least for the retrograde signals, but the nature of the competition is still unclear. The retrograde signals are modified by action potentials. Neurons dying from a lack of anterograde survival signals can be distinguished morphologically from ones dying from a lack of retrograde signals. The neuron death refines circuitry by selectively eliminating neurons with “aberrant” axons projecting to the “wrong” (i.e., ipsilateral) retina or to the “wrong” (topographically inappropriate) part of the contralateral retina. © 1992 John Wiley & Sons, Inc.
Biochemical characterization of programmed cell death in NGF‐deprived sympathetic neurons
Authors: Martin David P. , Ito Akira , Horigome Kazuhiko , Lampe Patricia A. , Johnson Eugene M.
Published: May 2005

Young sympathetic neurons die when deprived of nerve growth factor (NGF). Under such circumstances, cell death is appropriate to the developing nervous system and requires RNA and protein synthesis. We have hypothesized the existence of an endogenous death program within neurons that is suppressed by trophic factors. The extent and timing of required changes in the synthetic events that comprise the death program are unknown. In an effort to characterize the biochemical events that mediate the death program further, we performed several experiments on embryonic rat sympathetic neurons in vitro. The death program was blocked with cycloheximide when total protein synthesis was inhibited ≥80%. When protein synthesis was inhibited within 22 ± 4 h of NGF deprivation, death was prevented in half the neurons. Hence, we define the commitment point for protein synthesis to be 22 ± 4 h. Analogously, the commitment point for RNA synthesis was 26 ± 4 h and that for NGF rescue, 24 ± 4 h. We tested the ability of a wide variety of chemicals to interfere with the death program. Most compounds tested were unable to prevent neuronal death. Some treatments, however, did save NGF‐deprived neurons and were subsequently characterized. These included ultraviolet light and agents that raise intracellular concentrations of cAMP. Finally, we looked for the neuronal expression in vitro and in vivo of genes that have been associated with programmed death in other cell types, including TRPM‐2/SGP‐2, polyubiquitin, TGFβ‐1, c‐fos, and c‐myc. None of these genes showed significant activation associated with neuronal death. © 1992 John Wiley & Sons, Inc.
Cell death in the oligodendrocyte lineage
Authors: Barres B. A. , Hart I. K. , Coles H. S. R. , Burne J. F. , Voyvodic J. T. , Richardson W. D. , Raff M. C.
Published: May 2005

We have recently found that about 50% of newly formed oligodendrocytes normally die in the developing rat optic nerve. When purified oligodendrocytes or their precursors are cultured in the absence of serum or added signalling molecules, they die rapidly with the characteristics of programmed cell death. This death is prevented either by the addition of medium conditioned by cultures of their normal neighboring cells in the developing optic nerve, or by the addition of platelet‐derived growth factor (PDGF) or insulin‐like growth factors (IGFs). Increasing PDGF in the developing optic nerve decreases normal oligodendrocyte death by up to 90% and doubles the number of oligodendrocytes, suggesting that this normally occurring glial cell death might result from a competition for limiting amounts of survival signals. These results suggest that competition for limiting amounts of survival factors is not confined to developing neurons, and raise the possibility that a similar mechanism may be responsible for some naturally occurring cell deaths in nonneural tissues. © 1992 John Wiley & Sons, Inc.
Insect muscle as a model for programmed cell death
Authors: Schwartz Lawrence M.
Published: May 2005

Programmed cell death (PCD) is a fundamental component of development in virtually all animals. Despite the ubiquity of this phenomenon, little is known about what tells a cell to die, and less still about the physiological and molecular mechanisms that bring about death. One system that has proven to be very amenable for the study of PCD is the intersegmental muscle (ISM) of the tobacco hawkmoth Manduca sexta. These giant muscle cells are used during the eclosion (emergence) behavior of the adult moth, and then die during the subsequent 30 h. This review uses the ISMs as a model system to address questions that are basic to any cell death system, including the following: (1) how do cells know when to die; (2) what physiological changes accompany death; (3) what are the molecular mechanisms that mediate death; and (4) do all cells die by the same process? For the ISMs, the trigger for PCD is a decline in the circulating titer of the insect molting hormone, 20‐hydroxyecdysone (20‐HE). During cell death there are rapid decreases in both the myofibrillar sensitivity to intracellular calcium and the resulting force of fiber contraction. The ability of the ISMs to under go PCD requires the repression and activation of specific genes. Two of the repressed genes encode actin and myosin. One of the upregulated presumptive cell‐death genes encodes polyubiquitin, which appears to play a critical role in the rapid proteolysis that accompanies ISM death. One curious aspect of ISM death is that these cells display none of the features that are characteristic of apoptosis, suggesting that they may die by a fundamentally different mechanism. © 1992 John Wiley & Sons, Inc.
History of developmental neuroethology: Early contributions from ethology
Authors: Fentress John C.
Published: May 2005

Ethology has its roots in the natural history of animal behavior. Questions of causation and function have historically been complementary, and each has rested upon a prior appreciation of the behavior of animals in nature. It is thus difficult to place a single time or place where ethology was born. Early evolutionary interests hinted at developmental constraints that continue to guide much research. It has only been relatively recently, however, that the explicit analysis of neural mechanisms in behavior has received the attention it deserves in developmental analyses. A mature developmental neuroethology will require a synthesis of the broad insights of ethology with refined neurobiological technique. Fundamental, however, is the primary focus upon behavior as it normally occurs. © 1992 John Wiley & Sons, Inc.
Pathways in the emergence of developmental neuroethology: Antecedents to current views of neurobehavioral ontogeny
Authors: Oppenheim Ronald W.
Published: May 2005

The historical forces that have contributed to our current views of neurobehavioral development (and thus to the fields of developmental psychobiology and neuroethology) are many and varied. Although similar statements might be made about almost any field of science, it is in particular true of this field, which represents a kind of mongrel discipline derived from at least three major sources (psychology, embryology, and neuroscience) and several more minor ones (including developmental psychology and psychiatry, psychoanalysis, education, zoology, ethology, and sociology). Although I attempt to demonstrate here how each of these sources may have influenced the emergence of a unified field of developmental psychobiology or developmental neuroethology, because the present article represents the first attempt of which I am aware to trace the history of these fields I am certain that there is considerable room for improvement, correction, and revision of the views expressed here. Accordingly, I consider this inaugural effort a kind of reconnaissance intended to trace a necessarily imperfect historic path for others to follow and improve upon. In the final analysis, I will be satisfied if this article only serves to underscore two related points: first is the value derived from historical studies of contemporary issues in development, and the second concerns the extent to which our current ideas and concepts about neurobehavioral development, ideas often considered new and contemporary, were already well known to those who came before us. The first point underscores the arguments expressed in the Introduction that the present must always be reconciled with the past, for the past is never entirely past. The second point returns full circle to an important thought expressed in the opening quotation to this article, namely, that even though our historic predecessors lacked much of the empirical facts available to us they were nonetheless able to attain a surprisingly deep understanding of neurobehavioral ontogeny. © 1992 John Wiley & Sons, Inc.
Developmental neuroethology of insect metamorphosis
Authors: Truman James W.
Published: May 2005

During metamorphosis, the insect nervous system must change to accomodate alterations in body form and behavior. Studies primarily on moths have shown that these changes involve the death of some larval neurons, the conservation and remodeling of others, and the maturation of new, adult‐specific cells. The motor and sensory sides of the adult CNS vary in this regard with the former being constructed primarily from remodeled larval components, whereas the latter arises primarily from new neurons.

Neuronal remodeling has received considerable attention. Larval‐specific dendritic fields are pruned back during the larval–pupal transition, followed by the sprouting of adult‐specific dendrites. Simple reflexes have been used to correlate these neuronal changes with the acquisition or loss of particular behaviors. The loss of the proleg retraction reflex is associated with the regression of the dendritic arbors of the proleg motoneurons. By contrast, expansion of axon arbors of the gin‐trap afferents is necessary, but not sufficient, for the assembly of the gin‐trap reflex in the pupal stage. The stretch receptor reflex provides a third example in which a new dendritic field in the adult form of a neuron is associated with new adult‐specific connections. Interestingly, these connections are masked by persisting larval contacts until the emergence of the adult moth. For the metamorphosis of more complex behavioral circuits, some, such as that for flight behavior, seem to be assembled de novo, whereas others, like that for adult ecdysis behavior, show conservation of some circuit elements from the larval stage but with the superposition of some adult‐specific components. © 1992 John Wiley & Sons, Inc.
Resealing of the proximal and distal cut ends of transected axons: Electrophysiological and ultrastructural analysis
Authors: Spira Micha E. , Benbassat Dorit , Dormann Ada
Published: May 2005

The fates of the proximal and distal segments of transected axons differ. Whereas the proximal segment usually recovers from injury and regenerates, the distal segment degenerates. In the present report we studied the kinetics of the recovery processes of both proximal and distal axonal segment following axotomy and its temporal relations to the alterations in the cytoarchitecture of the injured neuron. The experiments were performed on primary cultured metacerebral neurons (MCn) isolated from Aplysia. We transected axons while monitoring the changes in transmembrane potential and input resistance (Rn) by inserting intracellular microelectrodes into the soma and axon. Correlation between the electrophysiological status of the injured axon and its ultrastructure was provided by rapid fixation of the neuron at selected times postaxotomy. Axotomy leads to membrane depolarization from a mean of −55.7 S.D. 12.8 mV to −12.7 S.D. 3.3 mV and decreased Rn from tens of MΩ to 1–3 MΩ. The transected axons remained depolarized for a period of 10–260 s for as long as the axoplasm was in direct contact with the bathing solution. Rapid repolarization and partial recovery of Rn was associated with the formation of a membrane seal over the cut ends by the constriction and subsequent fusion of the axolema. Prior to the formation of a membraneous barrier, electron‐dense deposits aggregate at the tip of the cut axon and appear to form an axoplasmic “plug.” Electrophysiological analysis revealed that this “plug” does not provide resistance for current flow and that the axoplasmic resistance is homogenously distributed. The kinetics of injury and recovery processes as well as the ultrastructural changes of the proximal and distal segments are cannot be attributed to differences in the immediated response of the segments to axotomy. © 1993 John Wiley & Sons, Inc.
Brachially innervated ectopic hindlimbs in the chick embryo. II. The role of supraspinal input in the loss of limb motility
Authors: Kitchener P. D. , Laing N. G.
Published: May 2005

Brachially innervated grafted hindlimbs display a progressive loss of motility as development proceeds. However, the virtually immobile grafted hindlimbs of E20 embryos exhibited strong, synchronous contractions of gastrocnemius and tibialis muscles upon intraperitoneal injection of strychnine nitrate (20 μg). This result indicated that the marked behavioral deficit was not due to an inability of the motoneurons that innervate the immobile grafted hindlimbs to initiate and propagate action potentials, but was probably the result of an effective loss of motoneuron excitation. To examine the hypothesis that interaction with the supraspinal nervous system is involved in the reduction of grafted hindlimb activity, the normal forelimb and grafted hindlimb movements of chronic spinal embryos were examined. The normal forelimbs of chronic spinal embryos exhibited the same number of movements as normal embryos at all stages examined. Thus the deficit in grafted hindlimb motility is not comparable to the behavior of the normal forelimb in chronic spinal embryos and is, therefore, unlikely to be due to a lack of excitation from the supraspinal nervous system. The possibility of an inhibitory influence via supraspinal projections was examined in chronic spinal embryos that had brachially innervated grafted hindlimbs. After E12, the grafted hindlimbs of chronic spinal embryos displayed significantly fewer movements than the normal forelimbs of chronic spinal embryos but significantly more movements than the brachial hindlimb of embryos with intact spinal cords. By E18, however, both spinal and nonspinal brachial hindlimbs were equally dysfunctional. Thus prevention of supraspinal communication transiently reduces but does not prevent the emergence of motor dysfunction in the brachially innervated hindlimbs, which appears to be due to motoneurons not receiving sufficient net excitation, from spinal circuits, to propagate action potentials to the muscles. © 1993 John Wiley & Sons, Inc.
Acceleration of axonal outgrowth in rat sciatic nerve at one week after axotomy
Authors: Jacob Jane M. , McQuarrie Irvine G.
Published: May 2005

Following injury of sciatic motor axons in the rat, the rate of axonal outgrowth is faster if there has been a prior “conditioning” axotomy. The acceleration of outgrowth is due to an acceleration of SCb, the rate [slow (SC)] component of axonal transport that carries cytomatrix proteins; this occurs throughout the axon by 7 days after the conditioning axotomy (Jacob and McQuarrie, 1991a, J. Neurobiol. 22:570–583). To further characterize the conditioning lesion effect (CLE), it is important to know (1) the minimum effective conditioning interval (time between conditioning and testing lesions), (2) whether the cell body reaction is required, and (3) whether outgrowth accelerates after a single axotomy. Outgrowth distances were measured by radiolabeling all newly synthesized neuronal proteins and detecting those carried to growth cones by fast axonal transport. When the conditioning and testing lesions were made simultaneously (0 day conditioning interval), there was no CLE. With a conditioning interval of 3 days, there was a shortening of the initial delay (before the onset of outgrowth) without a change in outgrowth rate. With conditioning intervals of 7, 14, and 21 days, the rates of outgrowth were increased by 8%, 22%, and 11%, respectively. To determine whether the cell body reaction to axotomy is necessary for the CLE, a nonaxotomizing stimulus to axonal growth (partial denervation) was used in place of a conditioning axotomy. This had no effect on the rate of outgrowth from a testing lesion made 14 days later. Finally, we examined the possibility that outgrowth accelerates after a single lesion. Outgrowth was faster at 6–9 days after axotomy than at 3–6 days (p < 0.001), and accelerated further at 9–12 days (p < 0.001). We conclude that (1) the shortest effective conditioning interval is 3 days; (2) the cell body reaction is necessary for the CLE; (3) axonal outgrowth from a single axotomy accelerates in concert with the anabolic phase of the cell body reaction. The SCb motor is, in turn, upregulated by this reaction. This suggests that the SCb motor responds to a fast‐transported signal that is a product of the cell body reaction. © 1993 John Wiley & Sons, Inc.
Song‐selective auditory input to a forebrain vocal control nucleus in the zebra finch
Authors: Vicario David S. , Yohay Kaleb H.
Published: May 2005

Neurons in nuclei on the motor pathway for vocalizations in songbirds are known to responses in one such nucleus, robustus archistriatalis (RA), were characterized by making multi‐unit recordings in awake and anesthetized adult male zebra finches and in birds that had received lesions of the input to RA from the lateral part of the magnocellular nucleus of the anterior neostriatum (LMAN) or the Higher Vocal Center (HVC). In awake birds, RA neurons have a high level of spontaneous activity and vigorous auditory responses to song stimuli. Significantly greater responses are seen to the bird's own song (BOS) than to BOS played in reverse (REV) or to the songs of conspecifics (CON). Under ketamine‐xylazine anesthesia, spontaneous activity is reduced, response latency increases and responses to BOS, REV and CON are indistinguishable. Responses obtained under urethane anesthesia are similar to those seen in awake birds. Thus, the pattern and selectivity of auditory responses in RA depend on the animal's state. Auditory responses in RA are qualitatively unchanged following lesion of the input to RA from LMAN, indicating that this pathway is not required for the sensory processing that underlies the preference for BOS on the vocal production pathway. Our results show that an input other than that from LMAN must be primarily responsible for auditory responses in RA. The direct projection form HVC is the most likely pathway by which song selective auditory information arrives in RA, since lesioning HVC abolished auditory responses in RA. © 1993 John Wiley & Sons, Inc.
Expression of JUN, KROX, and CREB transcription factors in goldfish and rat retinal ganglion cells following optic nerve lesion is related to axonal sprouting
Authors: Herdegen Thomas , Bastmeyer Martin , Bähr Mathias , Stuermer Claudia , Bravo Rodrigo , Zimmermann Manfred
Published: May 2005

Goldfish and rat optic nerves were cut and crushed, respectively, and the expression of the transcription factor proteins c‐JUN, JUN B, JUN D, c‐FOS, FOS B, KROX‐24, and CREB was investigated in retinal ganglion cells (RGCs) by immunocytochemistry. Immunoreactivities (IRs) were followed up to 350 days in the goldfish and upto 22 days in the rat. In RGCs of untreated goldfish and rats, all JUN, FOS, and KROX proteins were absent whereas CREB was constitutively expressed. After optic nerve cut in goldfish, a JUN‐like immunoreactivity (JUN‐IR) appeared in a small number of RGCs of central retina after 24 h, reached a maximum within 5 days, declined after 30 days, and was on a half‐maximal level after 50 days. Between 100 and 200 days, JUN‐IR was only visible in a few RGCs and was completely absent after 350 days. Specific antibodies against c‐JUN, JUN B, and JUN D gave no distinct immunoreactive signal. Thus, we could not determine which member of the JUN family contributed to the JUN‐IR. The expression of CREB declined after 5 days. The number of CREB‐labeled RGCs was reduced (not significant) and the intensity of labeling faded out. After 50 days, CREB‐IR had returned to basal level. c‐FOS, FOS B, and KROX‐24 could not be detected in goldfish RGCs following optic nerve cut. After optic nerve crush in the rat, c‐JUN, JUN D, and KROX‐24 appeared in a substantial number of RGCs after 24 h, had a maximal expression after 5 days, and strongly declined after 8 days. c‐JUN and KROX‐24 were completely absent after 22 days whereas JUN D was still present in a few rat RGCs. The number of CREB‐labeled RGCs decreased after 5 days and had declined by 50% after 22 days. Expression of JUN B, c‐FOS, FOS B could not be detected in rat RGCs after optic nerve crush. Our data demonstrate that the decrease of CREB and the increase of JUN and KROX‐24 transcription factors precedes and parallels both the alteration of de novo protein synthesis and the axonal sprouting, which are long lasting in goldfish and transient in rat. © 1993 John Wiley & Sons, Inc.
Target determination of neurotransmitter phenotype in sympathetic neurons
Authors: Schotzinger Robert , Yin Xinghuan , Landis Story
Published: May 2005

While the majority of sympathetic neurons are noradrenergic, a minority population are cholinergic. At least one population of cholinergic sympathetic neurons arises during development by a target‐dependent conversion from an initial noradrenergic phenotype. Evidence for retrograde specification has been obtained from transplantation studies in which sympathetic neurons that normally express a noradrenergic phenotype throughout life were induced to innervate sweat glands, a target normally innervated by cholinergic sympathetic neurons. This was accomplished by transplanting footpad skin containing sweat gland primordia from early postnatal donor rats to the hairy skin region of host rats. The sympathetic neurons innervating the novel target decreased their expression of noradrenergif traints and developed choline acetyltransferase (ChAT) activity. In addition, many sweat gland‐associated fibers acquired acetylcholinesterase (AChE) staining and VIP immunoreactivity. These studies indicated that sympathetic neurons in vivo alter their neurotransmitter phenotype in response to novel envronmental signals and that sweat glands play a critical role in the cholinergic and peptidergic differentiation of the sympathetic neurons that innervate them. The sweat gland‐derived cholinergic differentiation factor is distinct from leukemia inhibitory factor and ciliary neurotrophic factor, two well‐characterized cytokines that alter the neurotransmitter properties of cultured sympathetic neurons in a similar fashion. Recent studies indicate that anterograde signalling is also important for the establishment of functional synapses in this system. We have found that the production of cholinergic differentiation activity by sweat glands required sympathetic innervation, and the acquisition and maintenance of secretory competence by sweat glands depends upon functional cholinergic innervation. 1994 John Wiley & Sons, Inc.
Cell‐cell interactions that modulate neuronal development in the leech
Authors: French Kathleen A. , Kristan William B.
Published: May 2005

Mitotic lineage has been found to determine the cellular identity of leech neurons (reviewed in Stent et al., 1992), Int. Rev. Neurobiol. 33:109–133. However, the details of the adult phenotype of many neurons in the central nervous system of the leech have been shown to be shaped by interactions either with other neurons or with non‐neuronal tissues in the environment. Four effects of cell‐cell interactions will be considered in this article: stimulation of mitosis that generates new neurons, modulation of cell death or axonal retraction, modification of neurotransmitter metabolism, and modification of other physiological properties. In all cases, the interactons that modify development are thought to occur at a location distant from the soma, requiring that signals be transmitted a significant distance from the site of interaction to the metabolic machinery in the soma. 1994 John Wiley & Sons, Inc.
Retrograde determination of motoneuron properties and their synaptic input
Authors: Mendell Lorne M. , Collins William F. , Munson John B.
Published: May 2005

Both motoneurons and the muscle fibers that they innervate can vary widely in their properties. The finding that these properties are highly correlated indicates that these cells are not specified independently, but rather interact in some manner to achieve the observed coherence. The direction of the interaction, i.e., whether orthograde or retrograde, required analysis beyond the simple observation of these correlated properties. Evidence, largely from experiments involving reinnervation of muscle by the original or a foreign motor nerve, suggests the action of retrogradely transported factors from the muscle as well as orthograde ones. Various possible factors, specifically neurotrophins, are advanced as possible candidates for retrograde specification. In addition, synaptic input to motoneurons also varies in a coordianted fashion in a manner that suggests a retrograde determination from the muscle. However, motoneuron properties and their synaptic input change after peipheral nerve manipulations such that they are no longer in register. This indicates some independence in retrograde specification of motoneurons and their synaptic input. 1994 John Wiley & Sons, Inc.
Retrograde signaling in the formation and maintenance of the neuromuscular junction
Authors: Connor Elizabeth A. , Smith Martin A.
Published: May 2005

The neuromuscular junction is characterized by precise alignment between the nerve terminal an the postsynaptic apparatus formed by the muscle fiber. Organization of the neuromuscular junction during embryonic development, growth, and maintenance is coordinated by signals exchanged between motor neurons and their target muscel fibers. Identification of proteins such as agrin, likely to represent neuronal agents that direct the organization of the postsynaptic apparatus, has focused attention on characterization of proteins that mediate retrograde signals that regualte the organization and function of the nerve terminal. The results of these studies implicate a role for both adhesive and diffusible signal in coordinating the development, maturation, and maintenance of the motor nerve terminal. The diversity of molecules identified to date that appear to play a role in these processes implies a considerable level of redundancy in the transduction pathway. However, studies of early nerve‐muscle interactions suggest that a common feature of many of these retrograde agents is activation of a protein kinase coupled with and increase in cytosolic Ca2+ concentration. While the molecular signals that regulate growth and maintenance of neuromuscular junctions are less well understood it seems likely that similar adhesive and diffusible factor will be involved. 1994 John Wiley & Sons, Inc.
Changes in retinal arbors in compressed projections to half tecta in goldfish
Authors: Schmidt John , Coen Timothy
Published: May 2005

In adult goldfish, electrophysiological studies have shown that the retinotectal projection reorganizes, following removal of half of the tectum, to form a complete but compressed projection over the remaining half tectum. As a result, each fiber terminates more rostrally than normal. Electron microscopic studies suggest a competition between retinal fibers for a fixed number of synaptic sites. The current study examines whether retinal arbors in the compressed projection are smaller than normal in extent or branching and whether the fiber paths in the tectum show the rostral movements and the search strategy that the retinal fibers use. The caudal half tectum was removed without cutting retinal fibers except those at the cut edge. At 3 to 19 months afterward, retinal fibers were labeled with horseradish peroxidase. In whole‐mounted tecta, fibers and terminals were drawn under camera lucida and compared with normal arbors. The axonal paths were also traced across the tectum to their termination sites. At 3 to 6 months (early stages of compression), the arbors were rather normal in appearance, although they were actually significantly larger (23%) than normal in linear extent, arborized somewhat deeper and had fewer branches (18%). The fibers normally terminating in the rostral tectum followed normal stereotyped paths, whereas those cut at the edge had grown back and forth loops (apparent searching behavior) with little branching. By 10 months when compression is complete, arbors were significantly smaller than normal (19%), were arborizing significantly deeper, and had significantly fewer branches (19%). The differences were more pronounced in arbors of coarse and medium caliber than in fine caliber axons. The axons still ran in stereotyped fascicles, but included an extrafascicular portion that, unlike any axons in normals, turned back in a rostral direction before branching. This striking effect, present even in far rostral tectum, indicated that arbors had been forced to move rostrally to accomodate those from the ablated half. The small effect on arbor extent suggests that this is influenced by factors other than the magnification factor of the map, perhaps postsynaptic dendritic extent. The increased depth of termination is consistent with the increased thickness of the retinal terminal layer. The decreased number of branches is consistent with the conclusion that the remaining fixed number of synaptic sites shared among the full complement of retinal fibers should result in fewer synapses per retinal fiber. © 1995 John Wiley & Sons, Inc.
Acetylcholine receptor clustering in C2 muscle cells requires chondroitin sulfate
Authors: Mook‐Jung Inhee , Gordon Herman
Published: May 2005

Proteoglycans have been implicated in the clustering of acetylcholine receptors (AChRs) on cultured myotubes and at the neuromuscular junction. We report that the presence of chondroitin sulfate is associated with the ability of cultured myotubes to form spontaneous clusters of AChRs. Three experimental manipulations of wild type C2 cells in culture were found to affect both glycosaminoglycans (GAGs) and AChR clustering in concert. Chlorate was found to have dose‐dependent negative effects both on GAG sulfation and on the frequency of AChR clusters. When extracellular calcium was raised from 1.8 to 6.8 mM in cultures of wild‐type C2 myotubes, increases were observed both in the level of cell layer‐associated chondroitin sulfate and in the frequency of AChR clusters. Culture of wild‐type C2 myotubes in the presence of chondroitinase ABC eliminated cell layer‐associated chondroitin sulfate while leaving heparan sulfate intact and simultaneously prevented the formation of AChR clusters. Treatment with either chlorate or chondroitinase inhibited AChR clustering only if begun prior to the spontaneous formation of clusters. We propose that chondroitin sulfate plays an essential role in the initiation of AChR clustering and in the early events of synapse formation on muscle. © 1995 John Wiley & Sons, Inc.
Sexual differentiation and hormonal regulation of the laryngeal synapse in Xenopus laevis
Authors: Tobias Martha L. , Kelley Darcy B.
Published: May 2005

In Xenopus laevis frogs, sex differences in adult laryngeal synapses contribute to sex differences in vocal behavior. This study explores the development of sex differences in types of neuromuscular synapses and the development and hormone regulation of sex differences in transmitter release. Synapses in the juvenile larynx have characteristics not found in adults: juvenile muscle fibers can produce subthreshold or suprathreshold potentials in response to the same strength of nerve stimulation and can also produce multiple spikes to a single nerve stimulus. Juvenile laryngeal muscle also contains the same synapse types (I, II, and III) as are found in adult laryngeal muscle. The distribution of laryngeal synapse types in juveniles is less sexually dimorphic than the distribution in adults. Analysis of quantal content indicates that laryngeal synapses characteristically release low amounts of transmitter prior to sexual differentiation. Quantal content values from male and female juveniles are similar to values for adult males and are lower than values for adult females. When juveniles are gonadectomized and treated with exogenous estrogen, quantal content values increase significantly, suggesting that this hormone may increase transmitter release at laryngeal synapses during development. Gonadectomy alone does not affect quantal content of laryngeal synapses in either sex. Androgen treatment decreases quantal content in juvenile females but not males; the effect is opposite to and smaller than that of estrogen. Thus, muscle fiber responses to nerve stimulation and transmitter release are not sexually dimorphic in juvenile larynges. Transmitter release is strengthened, or feminized, by the administration of estradiol, an ovarian steroid hormone. © 1995 John Wiley & Sons, Inc.
A general survey of the proton spin–lattice relaxation rates of steroids
Authors: Colebrook Lawrence D. , Hall Laurance D.
Published: May 2005

The spin‐lattice relaxation rates of the aromatic, alkene, hydroxyl, methine and methyl protons of 19 steroid derivatives have been measured using the null point method. A simple procedure is described whereby the R1 values of molecules which have different motional tumbling rates can be directly inter‐compared, and it is shown that such ‘normalized’ relaxation data can provide novel insight concerning both the geometry and the local molecular motion of these substances in solution.
1H NMR parameters of the N‐terminal 13‐residue C‐peptide of ribonuclease in aqueous solution
Authors: Rico M. , Nieto J. L. , Santoro J. , Bermejo F. J. , Herranz J.
Published: May 2005

The 1H NMR chemical shifts and the spin‐spin coupling constants of the non‐exchangeable protons of the N‐terminal 13‐residue C‐peptide of ribonuclease A, obtained by cleavage of the enzyme with cyanogen bromide, have been measured in a 5 mM solution in D2O (pH 3.0, 24°C) at 360 MHz. The titration parameters for end groups (Lys‐1 and homo‐Ser‐13) and side chains (Lys‐1, Glu‐2, Lys‐7, Glu‐9 and His‐12) have been determined. The chemical shifts, their temperature coefficients and the vicinal coupling constants, 3J(HNCH‐α), for the exchangeable NH protons have been measured in a 5 mM solution in D2O/H2O (1:9 v/v) at pH 3.0. An assignment of observed signals to individual residue protons based on characteristic shifts, standard double resonance experiments, spectral simulations and titration shifts is proposed. All experimental evidence indicates that under the conditions studied the C‐peptide is in a random coil form.
1H dynamic nuclear magnetic resonance study of hindered rotations in N‐aryl‐N‐benzyl alkyl carbamates
Authors: Julià S. , Ginebreda A. , Sala P. , Sancho M. , Annunziata R. , Cozzi F.
Published: May 2005

The NMR variable temperature behaviour of a series of N‐aryl‐N‐benzyl alkyl carbamates was investigated. The barrier to rotation about the N‐aryl bond was determined for all the compounds studied. The values obtained, which are in good agreement with those found for structurally related N‐aryl‐N‐benzylamides, are in the range ΔG≠ = 60.7‐89.6kJ mol−1. For some carbamates another conformational phenomenon has been observed, namely the hindered rotation about the carbonyl carbon–nitrogen bond, with a barrier to rotation corresponding to reported values for similar systems.
Heteroatom migration upon electron‐impact
Authors: Williams L. R.
Published: May 2005

Migration of the heteroatom substituent is an important feature in the mass spectra of β‐chloro‐ and β‐hydroxy‐ethyl aryl sulphones. In these compounds the migratory aptitude of the heteroatoms appears to be greater than that of the hydrogen atoms.
Massenspektren von sekundären Vinylcarbinolen
Authors: Kraft Manfred , Spiteller Gerhard
Published: May 2005

Die Massenspektren sekundärer des Typs RCH(OH)CHCH2 zeigen die gleichen Bruchstücke wie die der isomeren Äthylketone RCOC2H5. Dies ist auf eine Umlagerung der Molekülionen der Vinylcarbinole in solche der Äthylktone vor Eintritt der Bruchstückbildung zurückzuführen. Die Massenspektren beider Verbindungsklassen unterscheiden sich nur geringfügig in den Intensitätswerten.
The fragmentation of organic molecules under electron‐IMPACT—II. The mass spectra of tetronic acid and some of its derivatives
Authors: Haynes L. J. , Kirkien‐Konasiewicz Alicja , Loudon A. G. , Maccoll Allan
Published: May 2005

The mass spectra of tetronic acid and of a number of its derivatives are recorded and discussed. Where necessary, the composition of the fragment ions has been checked by high resolution mass measurements. Fragmentation of the molecular ion is explained in terms of the rupture of a bond attached to C‐4, and the predominant routes for many of the compounds can be explained on the basis of two schemes, the first involving preliminary ketonisation of the molecular ion, followed by elimination of carbon monoxide, the second involving rupture of the C‐4R3 bond prior to elimination of carbon monoxide. Special structural features, however, provide alternative routes.
The fragmentation of tetronic acids and related compounds under electron‐impact
Authors: Ballantine J. A. , Fenwick R. G. , Ferrito V.
Published: May 2005

The mass spectra of two fungal metabolites, aspertetronin A and B, have been examined in conjunction with a series of tetronic acids and related compounds, and as a result the major modes of fragmentation of the tetronic acid ring system have been determined. Several substituent dependent rearrangements have also been recognised during this investigation which should prove useful in the structural elucidation of unknown compounds.
Etude Des Spectres de Masse Des Constituants Amers Des Simarubacées
Authors: Fourrey Jean‐Louis , Das Bhupesh C. , Polonsky Judith
Published: May 2005

The bitter compounds isolated from the species Simaroubaceae represent a new family of degraded triterpenoids. Ailanthone, glaucarubolone and chaparrinone having a C20 skeleton belong to this family and their structures were previously determined. Mass spectra of these compounds and some of their derivatives have now been studied in detail and the results obtained are discussed in this communication. The observed fragmentation pattern is characteristic of the structural features of this group of compounds.
Pyrolysis and mass spectra of some aromatic‐imides
Authors: Cotter J. L. , Dine‐Hart R. A.
Published: May 2005

The electron‐impact induced loss of CO2 from phthalanil and 4‐phthalimidobiphenyl is paralleled by the formation of large amounts of CO2 on pyrolysis. CO is also a major pyrolysis product, but the loss of CO from these compounds under electron‐impact is not an important fragmentation process.

The mass spectra of meta and para‐chlorophthalanils show prominent [M  CO2] peaks but the corresponding peak for the ortho isomer is of relatively low intensity. CO and CO2 are the principal gaseous products of the thermal decomposition of o‐chlorophthalanil.