bluuebunny/crossref_metadata_2025_split huggingface dataset:
Embryonic and larval development of the sonic motor nucleus in the oyster toadfish
Authors: Galeo Anthony J. , Fine Michael L. , Stevenson James A. 
Published: January 2005

AbstractThe sonic motor nucleus (SMN), a likely homologue of the hypoglossal nucleus, provideds the final common pathway for sound production in the oyster toadfish (Opsanus tau). SMN neurons increase in size and number for 7–8 years postnatally, and the swimbladder‐sonic muscle complex grows throughout life. This study describes the normal embryonic and larval development of the SMN from its initial differentiation on about day 19 through day 40, when the yolk sac is resorbed and the fish is free swimming.In contrast to the rapid development of CNS nuclei in mammals, the SMN gradually increased in maturity with more active growth at the beginning and end of the observation period and a relatively static period in the middle. Consistent with a hypoglossal homology, the SMN differentiated within the spinal cord, added cells rostrally, and eventually extended into the medulla. Immature neurons appeared to originate from precursor cells in the ventral portion of the ventricular zone of the central canal. Such cells were initially round with little cytoplasmic development and later added processes and Nissl substance. The number of neurons increased 10‐fold from a median of 35 to 322 cells, and no evidence of cell death was observed. Soma area approximately doubled from 20.6 to 41.2 m̈m2, and cell nucleus area followed a similar pattern. [3H]‐thymidine autoradiography demonstrated that neurons were added continuously throughout the nucleus during embryonic and larval development.
Differences in surface molecules of motor axon terminals correlated with cell–cell recognition
Authors: Denburg Jeffrey L. , Caldwell Robert T. , Marner Joyce M. 
Published: January 2005

AbstractThe cell–cell interactions leading to the formation of synaptic connections among cells in the nervous system may be mediated by cell surface macromolecules. In the cockroach the specific reformation of the original innervation pattern of a set of leg muscles during axonal regeneration indicates a significant contribution from cell–cell recognition. Macromolecules mediating such a process would be expected to be distributed differentially among the axon terminals of the various motor neurons. Monoclonal antibodies have been isolated that selectively bind to the surfaces of axon terminals of some motor neurons and not others. Preliminary biochemical characterization indicates that these antigens are glycoproteins and are good candidates for consideration as recognition macromolecules.
Mechanism for amine modulation of the neurogenic Limulus heart: Evidence for involvement of cAMP
Authors: Groome James R. , Watson Winsor H. 
Published: January 2005

AbstractThe role of cyclic nucleotides as intracellular second messengers mediating the excitatory chronotropic and inotropic actions of octopamine (OCT) and dopamine (DA) on the neurogenic Limulus heart was investigated. Tissue levels of cAMP, but not cGMP, were significantly increased in isolated cardiac ganglia and cardiac muscle following 10 min exposure to 10−5 M OCT or 10−5M DA. In both tissues, OCT elicited larger increases in cAMP than did DA. Amine‐induced cAMP accumulation in the cardiac ganglion and in the cardiac muscle was prevented by the alpha‐adrenergic blocker phentolamine. The adenylate cyclase activator forskolin and the phosphodiesterase inhibitor IBMX produced amine‐like chronotropic and inotropic effects when applied to the isolated heart preparation. However, the kinetics of the responses differed for the two agents. Additional pharmacological agents (RO‐20‐1724, papaverine, SQ 20,009, and 8‐parachloro‐phenylthio cAMP) also had amine‐like effects but to a lesser extent. The chronotropic, but not inotropic, effects of OCT and DA were potentiated in the presence of IBMX. These data suggest that a cAMP‐dependent mechanism underlies the excitatory effects of the neuromodulators OCT and DA on the Limulus heart.
Multiple transmitter neurons in Tritonia. III. Modulation of central pattern generator controlling feeding
Authors: Willows A. O. Dennis , Lloyd Philip E. , Masinovsky Boris P. 
Published: January 2005

AbstractFeeding behavior in the gastropod mollusc Tritonia diomedea is controlled by a central pattern generator (CPG) in the buccal ganglia. The medially located, large dorsal white cells (B11) have been shown to contain two small cardioactive peptides (SCPs). A smaller nearby neuron (B12) also appears to contain the SCPs. B11's have also been shown to contain acetycholine (ACh), whereas B12's do not.We have shown earlier that intracellular stimulation of B11's drives contractions of the foregut. Here we show that intracellular electrical stimulation of B11's also elicits excitation of neurons B5 and stimulates the patterned motor output of the CPG. We showed earlier that B12's also stimulate contractions in the foregut, but they are in the opposite direction from those elicited by B11. We show here that electrical stimulation of B12's inhibits the output of the CPG.We showed earlier that superfusion of the isolated gut with SCPB enhances peristalsis, and here we report that superfusion of the buccal ganglion with SCPB elicits enhanced coordinated motor output from the CPG. The peptide has two effects on the bursting output of motor neurons. It produces an increase in (1) the rate of bursting and (2) the spike frequency during each burst. On the other hand, we reported earlier that ACh applied directly to isolated foregut inhibits ongoing peristalsis. Here we demonstrate that ACh superfusion of the buccal ganglion also inhibits the CPG output.Our evidence supports the view that in addition to stimulating foregut contractility, B11's modulate the output of the swallowing CPG by releasing a peptide from central terminals. We suggest roles for B11, B12, the SCPs, and ACh in controlling both central and peripheral aspects of feeding behavior.
Connections between the nucleus isthmi and the tectum in larval and post‐metamorphic axolotls
Authors: Fisher Mark D. , Udin Susan B. 
Published: January 2005

AbstractThe nucleus isthmi (NI) is the primary relay for the frog's ipsilateral visuotectal projection. Using electrophysiological methods, ipsilateral visuotectal activity has been recorded in thyroxine‐treated, postmetamorphic axolotls but not in larval axolotls. In order to determine whether changes in isthmotectal projections are responsible for this change in electrophysiological responsiveness, we have investigated the connections between the tectum and the NI using horseradish peroxidase. Our results indicate that the axolotl's isthmotectal pathways are strikingly similar to those of the frog NI, and that the NI sends bilateral projections to the tecta in both larval and thyroxine‐treated, postmetamorphic axolotls. Thus, the anatomical connections underlying the ipsilateral visuotectal projection are present during larval stages, despite the lack of electrophysiological evidence for the larval ipsilateral visuotectal projection. We hypothesize that thyroxine‐induced metamorphosis produces changes in the terminal arborizations of the crossed isthmotectal projection which allow them to be detected by presynaptic electrophysiological techniques.
Intersegmental modulation of abdominal postural responses initiated by mechanostimulation of the swimmeret in lobster
Authors: Kotak Vibhakar C. , Page Charles H. , Abenante Frank 
Published: January 2005

AbstractIn a multiganglionic preparation of the lobster abdominal nerve cord, composed of the first through fifth ganglia (A1–A5) and attached second swimmeret, tactile stimulation of the cuticular surface of the swimmeret initiates a postural motor program in A2 for abdominal extension, whereas deflection of feathered hair sensilla that fringe the swimmeret rami does not affect postural motor activity recorded from A2 (Kotak and Page, 1986a). This report demonstrates that partial isolation of A2 from adjacent abdominal ganglia by sectioning the A1–A2 or the A2–A3 connectives both increases the strength of the extension response evoked by cuticular stimulation and disinhibits a postural flexion inhibition response initiated by feathered hair stimulation. Complete isolation of A2, by cutting the A1–A2 and the A2–A3 connectives, further increases the strength of these postural responses. Intersegmental inhibition of these responses originates in the ganglia adjacent to A2, since mechanoresponsiveness of A2 is not affected by resection of a more distant connective (A3–A4). These results provide evidence for the presence in adjacent abdominal ganglia of intersegmental interneurons that regulate the access of swimmeret sensory activity to the postural motor neurons in A2.
Disruption of muscle reorganization by lesions of the peripheral nerve in transforming claws of snapping shrimps
Authors: Mellon DeForest , Quigley Michael M. 
Published: January 2005

AbstractWe have performed surgical transections on nerves in the transforming claws of snapping shrimps. In normal transformation muscle restructuring occurs, involving degeneration of some fibers and biochemical changes in others. Surgical section of the entire second limb nerve root or of its distal, dorsal branch—both of which contain the motor axons to the closer muscle—prevents muscle restructuring, even though transformation of external claw morphology proceeds. Furthermore, nerve lesions must be performed within a specific time period after transformation has been triggered in order for the effects to be observed. We suggest that transformation involves an early sensitization of the targeted muscle and that this process depends upon an intact nervous pathway within the second nerve root.
Anatomical specificity of regenerated muscle sensory afferents in the spinal cord of the bullfrog
Authors: Peng Yan‐Yi , Frank Eric 
Published: January 2005

AbstractThe specificity of central projections made by regenerated muscle sensory fibers in the brachial spinal cord was studied with anatomical tracing methods. Sensory fibers were interrupted by freezing dorsal roots in postmetamorphic bullfrogs. After several months, regenerated sensory fibers were labeled with horseradish peroxidase applied to the triceps brachii muscle nerve, and their arborizations within the spinal cord were reconstructed from serial cross sections.Most of the regenerated projections from triceps muscle sensory afferents ended in or near their normal terminal field. A few branched and appeared to terminate more dorsally than normal, however, sometimes within the region where cutaneous afferents normally terminate. In contrast to the normal pathway followed by muscle afferents within the spinal cord, many regenerated afferents grew along the circumference of the spinal cord, just under the pial surface, and then turned abruptly toward the midline and into their appropriate terminal region. This suggests that regenerating afferents may actively seek out their appropriate targets and are not simply passively guided to them.
Mosaic Drosophila wings reveal regional heterogeneity in the guidance of ectopic axons
Authors: Blair Seth S. , Palka John 
Published: January 2005

AbstractIn most studies of axon guidance in the peripheral tissues of insects, the ability of experimentally pertubed axons to pathfind was examined only along their normal pathways. This means that regions normally devoid of axons have not been sampled for their ability to influence axonal trajectories. To examine this question, we have induced the formation of single sensory neurons in a variety of abnormal locations in the developing wing of Drosophila and have examined the course taken by their axons. The axons of such ectopic neurons have a regionally varying tendency to grow in the normal, proximal direction. This proximal bias approaches 100% for neurons located in the distal part of vein L2 and 70% in distal vein L4 but falls to chance (50%) along vein L5. Thus, neurons forming in ectopic regions of the wing, especially those found near the normal axon pathways (veins L1 and L3), have a high probability of growing axons in the correct direction. We conclude that information relevant to axon outgrowth is not restricted to the normal pathways. Whether this information is intrinsic or extrinsic to the neurons, and why its strength shows such conspicuous regional variation, awaits further study.
Central projections of a homoeotic regenerate, antennapedia, in a stick insect, Carausius morosus (Phasmida)
Authors: Edwards John S. , Reddy G. R. , Rani M. U. 
Published: January 2005

AbstractHomoeotic appendages provide a system for the analysis of neuronal pathfinding in which the appendage is mismatched with its segmented ganglion. Central projections of sensory neurons from homoeotic antennapedia regenerates induced by antennal amputation in the stick insect, Carausius morosus, are described. The majority of afferent axons project to the olfactory lobe as in the normal antennal nerve, but they do not give rise to compact glomeruli. Nor does the form of the projection resemble that of leg sensory nerves in thoracic ganglia. The projection of antennapedia regenerate neurons in Carausius resembles the antennapedia mutant of Drosophila except that some primary afferents bypass the olfactory lobe and take several courses through the brain, sometimes reaching distant contralateral areas. It appears that these wandering fibers, having bypassed the olfactory lobe, tend to follow established tracts and to arborize or to deviate at circumscribed synaptic areas. The behavioral evidence for sensory input from antennapedia regenerates is equivocal.
Sensitivity of ocellar interneurons of the honeybee to constant and temporally modulated light
Authors: Baader A. 
Published: January 2005

AbstractSinusoidally modulated and discrete light pulses, the parameters of which approximated natural light conditions, were used to determine the response characteristics of ocellar first‐order interneurons of the worker honeybee (Apis mellifera carnica). Large ocellar interneurons which terminate within the brain (LB neurons) were recorded from intracellularly and were identified visually after dye injection.Absolute sensitivity of LB neurons to light flashes ranges from 4 × 109 quanta/cm2s (Q) for MOC1,7 neurons to 1 × 1012 Q for MOC3,4. The slope of the response‐intensity (R/I) functions, which were calculated for intensities between 2 × 109 and 4 × 1013 Q, varies in different types of LB neurons. The strongest response is given by one group of median ocellar neurons. With constant light around 1013 Q, most LB neurons exhibit oscillatory hyperpolarizations which, upon increasing the stimulus to even higher intensities (1014–1015 Q), gradually evolve to a hyperpolarized plateau. The frequency of these oscillatory voltage fluctuations increases with the rate of modulation of the stimulating light and reaches maximum values at 5–15 Hz modulation frequency. Two groups of MOC neurons follow sinusoidally modulated light up to 32 ± 8 Hz (n = 5) and 29 ± 6 Hz (n = 3), respectively, whereas lateral ocellar neurons cut off at 17 ± 5 Hz (n = 4).The possible role of LB neurons is discussed. They may be inactivated when the bee is flying in bright sunlight.
Respecification of larval proleg motoneurons during metamorphosis of the tobacco hornworm, Manduca sexta: Segmental dependence and hormonal regulation
Authors: Weeks Janis C. , Ernst‐Utzschneider Kristina 
Published: January 2005

AbstractThe principal locomotory appendages of the Manduca sexta caterpillar, the prolegs, are present on the third through sixth abdominal segments (anal prolegs located on the terminal segment were not included in this study). Previous studies have characterized some of the proleg retractor muscles and their motoneurons. In the present study we identified additional proleg motoneurons and their putative homologs in the non‐proleg‐bearing segments. One of the motoneurons present in the proleg‐bearing segments is absent in the non‐proleg‐bearing segments. At pupation the prolegs are lost, their muscles degenerate, and some of their motoneurons regress structurally. Subsequently, subsets of the proleg motoneurons and their homologs in other segments die in a segment‐specific pattern. This is the first report of segment‐specific motoneurons, and of segment‐specific death of identified motoneurons, in Manduca. During adult development the surviving proleg motoneurons innervate the tergosternal muscle (TSM) and grow bilateral dendritic arbors. Dendritic growth is completed by about the 12th of the 18 days of adult development. Following adult emergence all but one of the respecified proleg motoneurons dies. The hormonal dependence of dendritic outgrowth was tested by isolating abdomens to eliminate the ecdysteroid‐secreting glands in the thorax. Between the second and fifth days after pupation the motoneurons became progressively more competent to undergo dendritic outgrowth following abdomen isolation. The extent of dendritic outgrowth paralleled the degree of morphological development attained by isolated abdomens. It is concluded that ecdysteroids are required for motoneuron outgrowth, but our findings suggest that, unless an abdominal source of ecdysteroids exists in pupae, a relatively small exposure may be sufficient.
Cell death during development of a forebrain nucleus involved with vocal learning in zebra finches
Authors: Bottjer Sarah W. , Sengelaub Dale R. 
Published: January 2005

AbstractLateral MAN (magnocellular nucleus of the anterior neostriatum) is a forebrain nucleus that is known to be importantly involved with vocal learning in juvenile male zebra finches only during a restricted period of the learning process: lesions of lMAN completely disrupt song behavior in zebra finches prior to 50 days of age but have little or no effect in older juvenile or adult birds. The development of lMAN, as of other song‐control regions, is delayed until the time that song behavior is being learned. Lateral MAN undergoes a substantial loss of neurons between 25 and 55 days of age, a time that encompasses initial stages of vocal production as well as the interval during which lMAN lesions become ineffective. In this study, we measured both the time course of neuronal loss and the incidence of pyknotic cells within lMAN during the period of cell loss. There is a pronounced loss of neurons from lMAN between 20 and 35 days, after which the adult number of neurons is established. The incidence of pyknosis is greatest at 20 days, around the time when the loss of live cells is also most pronounced, suggesting that the loss of neurons from lMAN is attributable to cell death. The loss of neurons occurs well before lesions of lMAN become ineffective in disrupting vocal behavior. Thus the neurons remaining in lMAN after the period of cell loss apparently undergo a substantial change in function at the time lesions lose effectiveness (about 55–60 days).
A temporal analysis of testosterone‐induced changes in electric organs and electric organ discharges of mormyrid fishes
Authors: Freedman E. G. , Olyarchuk J. , Marchaterre M. A. , Bass A. H. 
Published: January 2005

AbstractThe electric organ discharge (EOD) of several species of mormyrid fishes within the genus Brienomyrus is sexually dimorphic during the breeding season: the duration of the male's EOD is much longer than the duration of the female's (for a review see Hopkins, 1986). The mormyrid used here, Brienomyrus sp., exhibits similar alterations in the duration of the triphasic EOD after treatment with testosterone, as do other members of this genus (for reviews see Bass, 1986a,b). In this experiment, animals were intraperitoneally implanted with pellets of either 11‐ketotestosterone or 17 a‐methyltestosterone, and the time course of the changes in the duration of each of the three phases of the EOD were quantified. Additionally, the time course of changes in the morphology of the electric organ, after testosterone treatment, was also quantified using electron microscopic techniques. The results suggest that the change in the duration of the first phase of the EOD is due exclusively to the change in the thickness of the electrocyte body: this is consistent with a model proposed by Bennett and Grundfest (1961) for the electrogenesis of a triphasic EOD. Changes in the duration of the second and third phases of the EOD are highly correlated with changes in the surface area of the posterior and anterior faces of the electrocyte, respectively. The results support the hypothesis that gonadal steroid hormone‐induced changes in the EOD are due to structural changes in the electrocyte's membranes, and that all of the observed changes in the discharge of this system can be explained by the action of steroid hormones on the peripheral target cells (electrocytes).
Ocular dominance stripe formation by regenerated isogenic double temporal retina in Xenopus laevis
Authors: Coletti Steven M. , Ide Charles F. , Blankenau Andrew J. , Meyer Ronald L. 
Published: January 2005

AbstractIn lower vertebrates such as frogs and fish, long ocular dominance stripes with anterior‐posterior (A‐P) orientation can be produced by causing both eyes to innervate one optic tectum during the course of development. Similar experiments on adult animals usually produce patches rather than stripes. During development, new retinal fibers from the nasal retina segregate into appropriate stripes at the growing edge of the posterior (P) tectum while new temporal fibers segregate at the nongrowing anterior (A) tectal edge. Fiber segregation into long A‐P oriented stripes might depend upon a template produced by new nasal fibers initiating stripe orientation in the vicinity of new tectal cells; new nasal fibers would orient to the nascent (posterior) edge of the template while temporal fibers would orient to the anterior (nongrowing) end of the template. To test the dependence of stripe formation on the matching of nascent retinal cells with nascent tectal cells, we compared stripe orientation in animals with isogenic double nasal innervation and isogenic double temporal innervation of the tectum. In double nasal innervation, the oldest retinal cells innervate the anterior tectum; new fibers from the entire retinal periphery always innervate the newest tectal cells at the posterior tectum. Stripes are oriented A‐P, consistent with a maturation front model. In contrast, the oldest retinal cells innervate the newest (posterior) tectal cells in double temporal innervation of the tectum; the growing retinal periphery innervates the non‐growing anterior tectum. Stripes are also oriented A‐P, indicating that the production of long stripes does not depend upon maturation front matching of nascent retinal fibers and nascent tectal cells.