bluuebunny/crossref_metadata_2025_split huggingface dataset:
Leg position learning by an insect: II. Motor strategies underlying learned leg extension
Authors: Forman Robin R. , Zill Sasha N. 
Published: January 2005

AbstractThe patterns of myographic activity in the flexor and extensor tibiae muscles of the locust which accompany learned tibial extension were examined. Three distinct motor strategies were identified: (1) repeated flexion‐extension movements, each of which resulted in a momentary excursion beyond the required, pre‐set joint angle (demand angle) and in sum met the criterion for learning; (2) changes in basic muscle tonus, which resulted in maintained shifts in tibial position without discernible myographic activity; (3) tonic activity in the single slow excitatory motoneuron of the extensor tibiae (SETi) which produced maintained tibial extension. These strategies were selectively employed depending on the particular range of joint angle required. These strategies were compared and their effectiveness evaluated using a variety of behavioral criteria. Neuronal mechanisms which might underlie each of these strategies are discussed.
The nature of the chick's magnesium‐sensitive retinal spreading depression
Authors: van Harreveld A. 
Published: January 2005

AbstractSpreading depression (SD) in the chick retina is completely suppressed by 10 mM MgCl2 in the bathing solution (Mg‐sensitive SD). However, after increasing the KCl concentration in the Mg solution to values between 10 and 20 mM the retina can again exhibit SDs (Mg‐insensitive SD). It has been postulated that the Mg‐sensitive SD is a glutamatergic phenomenon. This is supported by the effect of four gl(utamate)‐antagonists—L‐proline, glutamic acid diethyl ester (GDEE), D‐α‐aminoadipate (D‐AA), and 2‐amino‐4‐phosphonobutyrate (APB)—which all suppressed this type of SD. It was suggested that this effect is due to competitive binding of glutamate involved in the Mg‐sensitive SD and the gl‐antagonist to glutamate receptors. The suppression of SD could be reversed by washing the preparation in a physiologic salt solution. The gl‐antagonists in relatively high concentrations had a cytotoxic effect which, when severe, suppressed SD and prevented the recovery of this phenomenon by washing the compound out of the tissue.The compounds examined had, in addition to their gl‐antagonistic properties, a gl‐agonistic effect, which was postulated to enhance the Na+ permeability of neural membranes resulting in a release of K+ into the extracellular space. In preparations bathed in 10 mM MgCl2 (which suppresses Mg‐sensitive SDs) the four compounds investigated promoted Mg‐insensitive SDs supposedly when the extracellular K+ concentration reached values between 10 and 20 mequiv.
Dorsal unpaired median neurons, and ventral bilaterally paired neurons, project to a visceral muscle in an insect
Authors: Lange Angela B. , Orchard Ian 
Published: January 2005

AbstractCobalt backfilling, Lucifer yellow injection and neurophysiological recordings have been used to identify the neurons, in particular dorsal unpaired median neurons, which contribute axons to the oviducal muscles of the locust Locusta migratoria. A total of eight neurons within the VIIth abdominal ganglion have axons passing to the oviducts. Three pairs of bilaterally symmetrical neurons have ventrally located cell bodies. One neuron from each pair projects to the left side of the oviducts and the other the right side of the oviducts. These cells lie ipsilateral to the nerve root through which they exit. The neuropilar branches are intraganglionic and lie mainly in the ipsilateral neuropile, however one of the neurons from each side possesses a giant process, reaching 10 μm in diameter, which passes dorsally to the contralateral side of the ganglion.The other two neurons are dorsal unpaired median neurons, and have large cell bodies which lie at the posterior end of the ganglion. Lucifer yellow injection into these two dorsal unpaired median neurons reveals a single neurite passing anteriorly from the cell body which bifurcates into two bilaterally symmetrical processes which exit to the oviducts through both the left and right sternal roots. Similar to other identified dorsal unpaired median neurons, the cell bodies stain with neutral red and can support overshooting action potentials. The possibility that these two cells contain octopamine is discussed.
Morphology of two pairs of identified peptidergic neurons in the Buccal ganglia of the mollusc Tritonia diomedea
Authors: Masinovsky Boris , Lloyd Philip E. , Willows A. O. Dennis 
Published: January 2005

AbstractThe morphology of two pairs of identified peptidergic neurons (B11 and B12) located in the buccal ganglia of Tritonia diomedea was described. Both pairs of neurons contained a large quantity of a small cardioactive peptide (SCP) in their somata. One of the pairs (B11), the large dorsal white cells, contained ACh in their somata along with SCP.Both pairs of cells appeared white in live preparations under epi‐illumination. Each B11 and B12 was a unipolar neuron and sent its major axonal branch through the ipsilateral gastro‐esophageal nerve to the gut. In addition, B12 sent a small branch to the contralateral buccal ganglion.A characteristic feature of both neuron pairs was their vesicular content. Three types of vesicles were observed in B11. Vesicles with electron‐lucent core (LCV) and electron‐dense core (DCV) were found in the somata. The axon hillock and the beginning of axon contained vesicles with variable electron dense core (VDCV) in addition to LCV and DCV. The ratio of DCV: LCV: VDCV changed from 5:95:0 for the perinuclear cytoplasm to 8:55:37 for the beginning of axon. The average maximum diameters were 97 ± 23 nm for DCV, 103 ± 32 nm for LCV and 106 ± 29 nm for VDCV.B12 somata contained DCV (average maximum diameter 100 ± 26 nm), LCV (109 ± 23 nm) and elliptical vesicles with eccentric electron‐opaque core (115 ± 20 nm).
Evidence for octopaminergic modulation of an insect visceral muscle
Authors: Orchard Ian , Lange Angela B. 
Published: January 2005

AbstractTwo dorsal unpaired median neurons (DUMOV1 and DUMOV2) lying in the posterior region of the VIIth abdominal ganglion of Locusta migratoria have axons which project to the muscles of the oviducts. This study reports the presence of octopamine within isolated DUMOV cell bodies, as well as in the oviducal nerve and innervated oviducal muscle. Individual cell bodies were pooled and found to contain about 0.34 pmol of octopamine per cell body giving an approximate value of 1.27 mM octopamine. Octopamine is concentrated within the area of oviducal muscle which receives DUMOV axons.Pharmacological studies reveal that the amplitude of neurally‐evoked contractions of the oviducal muscle is reduced in a dose‐dependent manner by octopamine, with threshold lying between 5 × 10−10 M and 7 × 10−9M. The receptors for this response show a specificity for octopamine and synephrine, with an order of potency being octopamine = synephrine > metanephrine > tyramine > dopamine.The presence of octopamine throughout this neural pathway, coupled with the demonstration of octopaminergic modulation of muscular contraction, supports the hypothesis that octopamine serves a physiological role in this visceral system.
Donor‐recipient interconnections between giant nerve fibers in transplanted ventral nerve cords of earthworms
Authors: Vining E. P. , Drewes C. D. 
Published: January 2005

AbstractTwelve segments of ventral nerve cord (VNC) from donor earthworms, Eisenia foetida, were transplanted into recipient worms from which a comparable length of VNC had been removed. Within the first few days after transplantation, bud‐like formations, containing outgrowths of the giant nerve fibers, were evident at the ends of transplanted and recipient VNC. Morphological and electrophysiological evidence indicated that by 4–10 days after transplantation, medial (MGF) and lateral (LGF) giant fibers within the transplanted VNC formed cell‐specific connections with their counterparts in the recipient VNC. Although the diameters of the giant fiber connections in the transplant‐recipient junctions were often larger than normal, spike conduction across the junction was initially slow (approximately 1.0 m/s) but gradually increased over the next 2–3 weeks. Within the transplant, giant fibers were initially normal in appearance, but spike conduction was slow (1–2 m/s). During the next few weeks velocities increased by as much as fourfold and then stabilized for the next several months. However, by 4–5 weeks after transplantation, giant fiber morphology within the transplant was altered significantly, as indicated by the formation of numerous branch‐like extensions along the length of each giant fiber. By 9–10 months there were further morphological changes in the transplant, as indicated by decreased branching of the giant fibers and altered neuropile. Despite these morphological changes, through‐conduction of giant fiber spikes remained reliable.
Innervation of the limb accessory flexor muscle in several decapod crustaceans. I. Anatomy
Authors: Govind C. K. , Wiens T. J. 
Published: January 2005

AbstractThe innervation of the accessory flexor muscle of the limbs of several decapod crustaceans was studied by means of vital staining, with methylene blue and electron microscopy. Three patterns of innervation were found. In the first pattern, the distal (DAFM) and proximal (PAFM) heads of the accessory flexor muscle were supplied by two axons (a thick and a thin) which travel in a private nerve along the length of the merus. This pattern was found in the crab (Cancer) and the lobster (Homarus), and conforms to the classical pattern established in the literature. In the second pattern, the nerve to the DAFM is made up of conjoined branches of the flexor and accessory flexor nerves. Consequently, the DAFM receives at least five axons in the portunid crabs, Carcinus, Callinectes, and Ovalipes, and occasionally six axons in Ovalipes. The PAFM in those portunids receives the usual two axons. In the third pattern, based on preliminary observations on the grapsid crab, Pachygrapsus, “super‐innervation” of the accessory flexor muscle appears to include not only five axons to the DAFM but also at least three to the PAFM. In all species, methylene blue staining of the axon terminations revealed a regular pattern of blebs which are thought to correspond to synaptic terminals as revealed by electron microscopy.
Dietary choline augments associative memory function in Limax maximus
Authors: Sahley C. L. , Barry S. R. , Gelperin A. 
Published: January 2005

AbstractPrevious clinical and experimental work has shown that increased dietary intake of choline elevates blood choline and brain acetylcholine levels. This change in neuronal acetylcholine concentration may augment learning and memory functions. We tested this prediction using the mollusc Limax maximus, an animal which can be readily conditioned to avoid food odors. In our experiments, initial learning of a food avoidance task was not augmented by the high choline diet. However, the duration of memory retention was prolonged. In previous studies, we have shown that intake of the choline enriched diet significantly increases blood choline and amplifies transmission at an identified cholinergic synapse in Limax. Together, these results support the involvement of cholinergic synapses in the memory retention mechanism.
Control of the development of the ipsilateral retinothalamic projection in Xenopus laevis by thyroxine: Results and speculation
Authors: Hoskins Sally G. 
Published: January 2005

AbstractThe ipsilateral retinothalamic projection of the frog Xenopus laevis is formed by the axons of a subset of retinal ganglion cells which are found throughout peripheral and non‐nasodorsal retina. Unlike the crossed retinotectal and retinothalamic projections, which begin to form during early embryonic stages, the ipsilateral projection does not begin to develop until late in tadpole life, at stages when thyroxine first becomes detectable in the circulation. Blocking the production of thyroid hormone in tadpoles prevents the development of the ipsilateral projection, in a reversible manner. Intraocular injection of thyroxine can “rescue” the development of the projection in tadpoles which otherwise remain premetamorphic. In addition, the projection from one eye of a metamorphically‐blocked tadpole can be induced to form by an intraocular injection of thyroxine at a dose which has no detectable effect on retinal development in the other, untreated eye. These results indicate that the development of the ipsilateral retinothalamic projection is dependent upon thyroxine, and strongly suggest that the hormone acts at the level of the eye, rather than at the optic chiasm or thalamic target, to bring about the development of a new pathway. A number of ways in which thyroxine might act in the system are discussed.
A model of pattern generation of cockroach walking reconsidered
Authors: Zill Sasha N. 
Published: January 2005

AbstractCockroaches that have been decapitated or that have cut thoracic connectives can show rhythmic bursting in motoneurons to intrinsic leg muscles. These preparations have been studied as models for walking and to evaluate the functions of leg proprioceptors. The present study demonstrates that (1) headless cockroaches walk extremely poorly and slowly with considerable discoordination of motoneuronal activity, (2) these preparations show rhythmic motoneuron bursting that is similar to righting responses (attempts to turn upright) of intact animals when placed on their backs, and (3) bursting is inhibited when a headless animal is turned or turns itself upright. Thus, rhythmic motoneuron activity of these preparations is most probably attempted righting rather than walking. It is concluded that the headless cockroach is useful for understanding the motor mechanisms underlying righting and walking but is not of value in assessing the functions of proprioceptive feedback.
A genetic analysis of glutamaterigic function in Drosophila
Authors: Chase Bruce A. , Kankel Douglas R. 
Published: January 2005

AbstractNeurotransmitters are essential for communication between neurons and hence are vital in the overall integrative functioning of the nervous system. Previous work on acetylcholine metabolism in the fruit fly, Drosophila melanogaster, has also raised the possibility that transmitter metabolism may play a prominent role in either the achievement or maintenance of the normal structure of the central nervous system in this species. Unfortunately, acetylcholine is rather poorly characterized as a neurotransmitter in Drosophila; consequently, we have begun an analysis of the role of glutamate (probably the best characterized transmitter in this organism) in the formation and/or maintenance of nervous system structure. We present here the results of a series of preliminary analyses. (1) To suggest where glutamatergic function may be localized, an examination of the spatial distribution of high affinity [3H]‐glutamate binding sites are presented. (2) We present the results of an analysis of the spatial and temporal distribution of enzymatic activities thought to be important in the regulation of transmitter‐glutamate pools (i.e., glutamate oxaloacetic transaminase, glutaminase, and glutamate dehydrogenase). (3) To begin to examine whether mutations in any of these functions are capable of affecting glutamaterigic activity, we present the results of an initial genetic analysis of one enzymatic function, glutamate oxaloacetic transaminase (GOT), chosen because of its differential distribution within the adult central nervous system and musculature.
Ontogenetic changes in the pattern of androgen accumulation in song‐control nuclei of male zebra finches
Authors: Bottjer Sarah W. 
Published: January 2005

AbstractThe present study examines the development of androgen accumulation in cells of two brain nuclei that are involved in controlling vocal behavior in zebra finches (Poephila guttata). HVc (caudal nucleus of the ventral hyperstriatum) is involved with vocal production in adult birds, and MAN (magnocellular nucleus of the anterior neostriatum) is involved with the initial ability to learn song. In both of these nuclei there is an increase in the proportion of cells that are labeled by systemic injections of tritiated dihydrotestosterone in juvenile male zebra finches during the time when production of song is becoming stereotyped (25–60 days). Within MAN there is an overall loss of cells during this time, such that the absolute number of androgen target cells in MAN remains at a constant level. However, it does not appear to be the case that unlabeled cells are selectively lost from MAN (see the text). Rather it appears that both labeled and unlabeled cells are lost, and the absolute number of labeled cells is maintained at a constant level via recruitment of additional labeled cells from the unlabeled population (i.e., some MAN cells that are unlabeled in young birds become labeled in older birds). In line with this hypothesis, there is a large increase in the density of labeling in individual MAN cells, indicating that these cells have an enhanced ability to concentrate androgen. In contrast to the situation in MAN, there is an increase in the overall number of cells within HVc during this time; this increase in total cell number combines with the increased proportion of labeled cells such that the absolute number of androgen target cells in HVc increases threefold. The ability of individual HVc cells to accumulate androgen remains constant. The relationship of these changes in the pattern of androgen accumulation to other aspects of neural and behavioral development related to song in zebra finches are discussed.
Synaptic competition and the persistence of polyneuronal innervation at frog neuromuscular junctions
Authors: Werle Michael J. , Herrera Albert A. 
Published: January 2005

AbstractMechanisms governing the elimination of polyneuronal innervation were examined by correlating the morphology and physiology of competing nerve terminals at identified dually innervated neuromuscular junctions in sartorius muscles of adult frogs (Rana pipiens). Synaptic efficacy (endplate potential amplitude per unit nerve terminal length) was presumed to reflect the ability of a terminal to compete for synaptic space. The synaptic efficacies of two terminals at the same synaptic site were found to be surprisingly equal, with a median difference of 33%. Much more variation would be expected if dually innervated junctions were randomly innervated by pairs of terminals having the same range of synaptic efficacy as that found at singly innervated junctions in the same muscle. This finding supports the hypothesis that the weaker input is elimianted from dually innervated junctions when there is a large discrepancy in competitive efficacy, and that both inputs may persist if competitive efficacies are relatively equal. We also tested but failed to find support for the hypothesis that spatial proximity between competing terminals intensifies competition for synaptic space during synapse elimination.
A novel serotonin‐immunoreactive neuron in the antennal lobe of the sphinx moth Manduca sexta persists throughout postembryonic life
Authors: Kent Karla S. , Hoskins Sally G. , Hildebrand John G. 
Published: January 2005

AbstractA single serotonin‐immunoreactive neuron in the antennal lobe (AL) of the brain of the sphinx moth Manduca sexta is present in larval, pupal, and adult stages. This neuron has a neurite that extends to the contralateral AL, where it forms sparse arborizations in each glomerulus. Other neurites from this neuron project into the ipsilateral and contralateral protocerebrum. This cell is morphologically very different from other neurons previously characterized in the adult AL. The neuron maintains the same basic profile in the adult as in the larva, although fine processes such as the arborizations within the AL neuropil appear to be restructured to conform to the larger, more anatomically diffentiated regions of the adult brain.
Regeneration studies on a crayfish neuromuscular system. I. Connectivity changes after intersegmental nerve transplants
Authors: Worden Mary Kate , Hwang Ji‐Chuu , Vélez Samuel J. 
Published: January 2005

AbstractThe superficial flexor muscles of the crayfish are a neuromuscular system of a few muscle cells innervated by six neurons in a precise position‐dependent pattern. The neurons are capable of regenerating their normal connectivity patterns within a short span of time when conditions are favorable. The superficial flexor muscles of the second and third segments, despite their similarities in neuronal and muscle cell size and number, have distinctive connectivity patterns; some homologous neurons form similar patterns but other homologous neurons form patterns that are reversed between segments. We transplanted each segment's nerve into each other's muscle in order to observe regeneration of the nerves into a target area that differed in connectivity patterns from their original muscle. During the first weeks of regeneration all neurons formed a connectivity pattern with more connections medially and declining connections laterally, a pattern determined bythe medial location of the nerve transplant. This pattern is maintained for most of the neurons, but for some there is an eventual reduction in medial connections as maximum synapse formation shifts to the lateral muscle fibers. Three of the eight neurons studied were able to regenerate connectivity patterns that corresponded to their segment of origin and not to their host muscle. This suggests that intersegmental muscle differences are not influencing the formation of these connectivity patterns, so the neurons will follow their inherent synaptogenesis program.
Regeneration studies on a crayfish neuromuscular system. II. Effect of changing the nerve entry point into the muscle field on the gradient of innervation
Authors: Goransson Leslie G. , Hunt William P. , Vélez Samuel J. 
Published: January 2005

AbstractThe superficial flexor muscle of the crayfish is a neuromuscular system in which the neurons form position‐dependent connectivity patterns with the muscle fibers. This system could be formed with the help of a single medial‐to‐lateral gradient during development that embodies positional information. To test this gradient hypothesis we changed the nerve's normal medial entrypoint into the muscle by transplanting it to the middle ofthe muscle sheet. When all the muscle fibers were present in the target area, most of the neurons studied passed through a stage during regeneration in which they showed preference for either medial or lateral synapse formation. Those neurons that in normal animals innervated preferentially the medial fibers showed a medial preference for new contacts; the neuron that normally innervated the lateral fibers showed a lateral preference for new contacts; the neuron that normally innervated everywhere regenerated equallywell into both medial and lateral fibers. Therefore, theseneurons are able to detect information regarding their position within the muscle mass and respond to it by preferential synapse formation. The effect of a positional gradient could not be detected when half of the target field was removed prior to regeneration. In this instance, the neuron that innervated the missing target area now regenerated to almost all the available fibers. It is suggested that the interplay of positional cues with other factors at different points in time could determine the final connectivity patterns formed by these cells.