bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neurobiology of Stomotoca. I. Action systems
Authors: Mackie G. O. , Singla C. L. 
Published: May 2005

AbstractThe layout of nerves, muscles, and conducting epithelia is described for the simple hydrozoan medusa Stomotoca. Comparisons are drawn with Sarsia and other recently studied forms. The major action systems are those responsible for swimming, crumpling (protective involution), tentacle posture, pointing (unilateral reciprocal flexions of the manubrium and margin), and visceral movements (barely mentioned). Crumpling is a simple summating response in this species. Crumpling and pointing are considered to use the same effectors but different conduction pathways.New histological results include the demonstration of a nerve plexus running through the endodermal canal system and a nerve plexus in the ectoderm encircling the peduncle. Special attention is given to the distribution of synapses and gap junctions, as possible trasmission pathways in behavioral responses. Some details are included on organization within the marginal nerve rings.
Stop‐flow: A new technique for measuring axonal transport, and its application to the transport of dopamine‐β‐hydroxylase
Authors: Brimijoin Stephen 
Published: May 2005

AbstractAn apparatus was devised which utilizes local cooling to reversibly interrupt the axonal transport of dopamine‐β‐hydroxylase (DBH) in rabbit sciatic nerves in vitro. Lowering the temperature of a short region of nerve to between 1 and 3°C, while keeping the remainder at 37°C, caused DBH activity to accumulate in and proximal to the cooled region. This accumulation was evident after 0.5 hr of cooling and increased in a nearly linear fashion with time for about 3 hr. The cooling‐induced interruption in transport was rapidly reversed when nerves were rewarmed to 37°C. Upon rewarming after local cooling for 1.5 hr, a peak of accumulated DBH activity migrated toward the distal end of the nerve at a velocity of 300 ± 17 mm/day. This velocity was maintained for as long as the peak could be followed and was four times greater than the average velocity estimated from the rate of accumulation of DBH activity above a ligature at the distal end of these same nerves. It is concluded that ligation experiments grossly underestimate the true velocity of axonal transport of DBH and that the present technique offers great advantages in permitting direct study of the migration of separate axonal compartments of transported materials.
The tail flattening reflex in Lumbricus: Reconstitution after tail amputation and modifications in segmental nerve roots
Authors: Gras Heribert 
Published: May 2005

AbstractOn stimulation of the head, the caudal 20–30 segments of intact earthworms exhibit a marked dorso‐ventral flattening reflex which is an element of the escape response. When the tail is removed this reflex is reconstituted gradually in segments anterior to the amputation level without regeneration of new tail segments. It takes longer to reestablish the flattening if larger parts of the body are cut off, but after 60 days p.o. all animals regained the full response independent of the number of segments amputated.Extirpation of three consecutive ganglia from the ventral nerve cord also suffices to develop flattening anterior to the operated segments, but the reaction is less pronounced and appears later than after tail amputation. Moreover, it vanishes at the same time the normal tail flattening is observed again, presumably after regeneration across the gap in the cord.In different regions of the body, area and perimeter distributions of transversely sectioned axons in the three pairs of segmental nerves (SN I–III) of the cord were measured. Characteristic changes along the length of the animal were found for SN I and SN III. In tail segments the axonal size distributions are more variable than in “typical” segments. The flattening reflex is mediated by axons in SN III (Pallas and Drewes, 1981). In body segments having reconstituted behavioral characteristics of the lost tail segments, the area of the largest axons and the general size distribution in SN III approximate those found in normal tail segments.
Conduction block in a branching axon innervating two muscles under physiological conditions
Authors: Baranes‐Shahrabany O. , Grossman Y. , Parnas I. 
Published: May 2005

AbstractThe escape reflex of the lobster consists of a series of tail flips resulting from alternating activity of the abdominal flexor and extensor muscles. Electromyographic (EMG) activity was recorded from the medial (DEAM) and the lateral (DEAL1) deep abdominal extensor muscles during free swimming. During the escape response, the muscles were active either synchronously or separately, at frequencies of 100–120 Hz. This activity pattern could be generated either by central programming, or by a peripheral mechanism such as frequency‐dependent differential conduction block into one of the two branches of the common excitor axon (C.Ex) innervating these muscles.In order to explore the latter possibility in a living animal, we left the DEAM and DEAL1 muscles innervated only by the C.Ex from the tested segment. This was accomplished by manually cutting all other axons in the nerve under visual control. During escape responses in six successfully dissected animals, we found 27 sudden failures of the DEAM responses and only three in DEAL1. The failures were usually preceded by an increase in the delay of the response. These findings strongly suggest that conduction block occurs in the M branch innervating the DEAM under physiological conditions.
Octopamine and chlordimeform enhance sensory responsiveness and production of the flight motor pattern in developing and adult moths
Authors: Kinnamon Sue C. , Klaassen Leland W. , Kammer Ann E. , Claassen Dale 
Published: May 2005

AbstractOctopamine and an agonist, chlordimeform, increase the responsiveness of adult and pharate adult Manduca sexta to gentle mechanical stimulation of the wing. Higher doses of chlordimeform elicit almost continuous production of the flight motor pattern in both adults and pharate adults, and the effect persists for more than 24 h. The dose of chlordimeform necessary for this effect increases with age. Mechanical stimulation of the wing of pharate adults elicits several cycles of flight motor pattern, but with repeated stimulation the animal habituates. Habituation is slower in chlordimeform‐treated animals than in controls. Injection of octopamine (1–8 × 10−8 mol) or chlordimeform (3 × 10−9 mol) into the mesothoracic ganglion elicits the flight motor pattern. The excitatory actions of both compounds can be blocked by cyproheptidine. Chlordimeform (5 × 10−8 mol) in acetone applied to the wing does not cause a noticeably greater increase in the electrical activity of sensory neurons than does acetone applied alone; this result suggests that chlordimeform does not act on these peripheral sites or on axonal membranes in general. We suggest that chlordimeform and octapamine act on the thoracic ganglia to alter the level of excitation on reffectiveness of synaptic transmission among central neurons, including those involved in producing the flight motor pattern.
Comparison of differential pavlovian conditioning in whole animals and physiological preparations of Pleurobranchaea: Implications of motor pattern variability
Authors: Mpitsos George J. , Cohan Christopher S. 
Published: May 2005

AbstractThe present study compares differential Pavlovian conditioning in whole animals with the behavior of the same animals during electrophysiological recording. Untrained specimens of the sea slug Pleurobranchaea did not discriminate between two appetitive stimuli, one derived from an extract of beer (Sbr) and the other from a homogenate of squid muscle (Ssq). When animals received Sbr as the CS+ and Ssq as the CS− in a single day of five‐trial, differential Pavlovian conditioning they learned to avoid selectively the Sbr but continued to exhibit appetitive responses to Ssq. Quantitative measures show that there was over a 1000‐fold increase in the thresholds of the proboscis extension and bite‐strike responses, many animals ceased all feeding behavior, and exhibited withdrawal responses to Sbr. We examined the behavior of the same trained animals immediately before preparing them for physiological recording and during the recording session. There was a close one‐to‐one relationship between these behavioral observations, showing that the qualitative and quantitative features of whole‐animal Pavlovian conditioning persist into the physiological preparations. Unexpectedly, motor patterns from untrained preparations showed considerable variability both within the same preparation at different times and between preparations; conditioning appeared to increase such variability. Thus, it was not possible to state unequivocally the behavior of the animal by examining the electromyogram recording alone. Many of the trained preparations not only exhibited suppressed feeding behavior and withdrawal responses to Sbr, but, as a consequence of the multifunctional nature of the Pleurobranchaea buccal‐oral system, also regurgitated previously ingested Ssq or squid meat when they were stimulated with Sbr. We discuss the findings with respect to self‐organizing mechanisms that may establish motor patterns in multifunctional systems, and suggest that such mechanisms may lead to the generation of behaviors that are not specifically encoded by the conditioned cellular changes.
Auditory and hormonal stimulation interact to produce neural growth in adult canaries
Authors: Bottjer Sarah W. , Schoonmaker Judith N. , Arnold Arthur P. 
Published: May 2005

AbstractGonadal hormones can produce striking behavioral and neural plasticity in adult organisms. For example, systemic administration of testosterone to adult female canaries induces the development of male‐typical song behavior and results in a striking increase in the size of brain nuclei that are known to be involved with song control. The mechanism whereby androgens produce such neural plasticity is not known, although it has seemed likely that growth‐promoting effects of androgens are due to a direct induction of protein synthesis in cells containing hormone receptors (following activation of specific genes by the hormone‐receptor complex). In this experiment we have examined the trophic effect of testosterone in the song‐control nucleus HVc (caudal nucleus of the ventral hyperstriatum), which has been shown to contain androgen‐concentrating cells as well as neurons that are especially responsive to conspecific song. We report here that testosterone administration increases the volume of HVc in hearing adult female canaries only; testosterone‐induced growth of HVc is greatly attenuated in birds that are deprived of auditory stimulation via deafening. Thus, testosterone treatment alone is not a sufficient stimulus for neural growth in HVc. This result suggests that testosterone does not stimulate growth solely via a direct action on hormone receptors in HVc, but rather that testosterone and sensory stimulation can act synergistically to produce structural plasticity in the adult brain.
Autoradiographic identification of ecdysteroid‐binding cells in the nervous system of the moth Manduca sexta
Authors: Fahrbach S. E. , Truman J. W. 
Published: May 2005

AbstractThe steroid hormone 20‐hydroxyecdysone regulates many aspects of nervous system development in the moth Manduca sexta, including stage‐specific neuronal morphology and stage‐specific neuronal death. We have used steroid hormone autoradiography to study the distribution of cells that cocentrate ecdysteroids in the ventral nervous system of this insect. The ligand was [3H]‐ponasterone A, a bioactive phytoecdysone. Tissue was examined from three stages of development: the end of larval life (first day of wandering), the end of metamorphosis (pharate adult), and 4‐day‐old adults. In the abdominal ganglia of wandering larvae and pharate adults, a subset of neurons including both motoneurons and interneurons exhibited a nuclear concentration of radiolabeled hormone. The pattern of binding was reproducible but stage‐specific, with a greater proportion of neurons showing binding in the larvae than in pharate adults. No labeled neurons were found in abdominal ganglia from mature (4‐day‐old) adults. In the case of the pharate adult ganglia, the ecdysteroid receptor content of specific, identified motoneurons was determined. These results are discussed in light of the responses of these neurons to physiological changes in levels of circulating ecdysteroids.
Regeneration of an identifiable motoneuron in the crayfish. II. Patterns of reconnection and synaptic strength established in the presence of an extra nerve
Authors: Hunt William P. , Vélez Samuel J. 
Published: May 2005

AbstractThe regeneration of neuromuscular connections to the superficial flexor muscle system in the crayfish has been studied under a variety of experimental manipulations. These have provided insight into the factors that can influence the regeneration program of neurons. In this work the regeneration of the largest excitor motoneuron was studied under two different conditions: (1) when the original neuron and a transplanted neuron were growing simultaneously into a denervated target, and (2) when a transplanted neuron was growing into a target that had its original nerve supply intact. In condition 1 both the transplanted and the original neuron formed normal patterns of connectivity and synaptic strength in comparable periods of time. In condition 2 the rate of growth of the transplanted neuron is significantly reduced and does not extend into the lateral fibers of the muscle. It is concluded that the regeneration program of this neuron is not affected by the presence of other neurons growing at the same time into a denervated muscle. Since regeneration is seriously affected if growth occurs into a fully innervated target area, it is suggested that lack of growth stimuli from the target or competitive interactions between established and growing synaptic terminals could influence the regeneration program of this neuron.
Competitive interactions between retinal ganglion cells during prenatal development
Authors: Shatz Carla J. 
Published: May 2005

AbstractIn the mammalian visual system, retinal ganglion cell axons terminate within the LGN in a series of alternating eye‐specific layers. These layers are not present initially during development. In the cat they emerge secondarily following a prenatal period in which originally intermixed inputs from the two eyes gradually segregate from each other to give rise to the characteristic set of layers by birth. Many lines of evidence suggest that activity‐dependent competitive interactions between ganglion cell axons from the two eyes for LGN neurons play an important role in the final patterning of retinogeniculate connections. Studies of the branching patterns of individual ganglion cell axons suggest that during the period when inputs from the two eyes are intermixed, axons from one eye send side branches into territory later occupied exclusively by axons from the other eye. Ultrastructural studies indicate that these branches in fact are sites of synaptic contacts, which are later eliminated since the side branches disappear as axons form their mature terminal arbors in appropriate territory. In vitro microelectrode recordings from LGN neurons indicate that they can receive convergent synaptic excitation from electrical stimulation of the optic nerves before but not after the eye‐specific layers form, suggesting that at least some of the synaptic contacts seen at the ultrastructural level are functonal. Finally, experiments in which tetrodotoxin was infused intracranially during the two week period during which the eye‐specific layers normally form demonstrate that it is possible to prevent, or at least delay, the formation of the layers. Accordingly, individual axons fail to develop their restricted terminal arbor branching pattern and instead branch widely throughout the LGN. These results indicate that all of the machinery necessary for synaptic function and competition is present during fetal life. Moreover, it is highly likely that neuronal activity is required for the formation of the eye‐specific layers. If so, then activity would have to be present in the form of spontaneously generated action potentials, since vision is not possible at these early ages. Thus, the functioning of the retinogeniculate system many weeks before it is put to the use for which it is ultimately designed may contribute to the final patterning of connections present in the adult.
Down‐regulation of progestin receptors in guinea pig brain: New findings using an immunocytochemical technique
Authors: Blaustein Jaffery D. , Turcotte Joanne C. 
Published: May 2005

AbstractProgesterone injection in estradiol‐primed, ovariectomized guinea pigs results in down‐regulation of hypothalamic progestin receptors determined by in vitro binding assays. In order to determine if progesterone also decreases immunostaining of progestin receptors and if progestin receptors are down‐regulated preferentially in particular neuroanatomical areas, ovariectomized guinea pigs were injected with doses of estradiol benzoate (10 μg at 42 h before progesterone injection) and progesterone (500 μg at 4, 12, or 24 h before perfusion) that reliably induce the expression of lordosis and subsequent behavioral refractoriness to progesterone. Progestin receptor‐immunoreactive cells were counted in sections from discrete parts of the preoptic area and hypothalamus. As expected, estradiol dramatically increased cell nuclear, and, to a lesser extent, cytoplasmic, immunostaining in defined regions of the preoptic area and hypothalamus. By 12 h after progesterone injection, the number of progestin receptor‐immunoreactive cells had decreased in some areas, but not others. The rostral and caudal aspects of the ventrolateral hypothalamus were particularly responsive showing a substantial decrease in progestin receptor‐immunoreactivity by 12 h after injection. No decreases in the progestin receptor‐immunoreactive cell number were observed in any of the preoptic regions examined, although obvious decreases in immunostaining intensity were seen. The results of these immunocytochemical experiments extend earlier findings from in vitro progestin binding experiments and demonstrate that as with progestin binding, progestin receptor‐immunoreactivity decreases when progesterone is injected in a behavioral desensitization procedure. Furthermore, they point to the ventrolateral hypothalamus as one site in which the down‐regulation of progestin receptors may be particularly responsive to progesterone.
Sex differences in hormonal responses of vasopressin pathways in the rat brain
Authors: De Vries Geert J. , Al‐Shamma Hussien Ali 
Published: May 2005

AbstractVasopressin (AVP) immunoreactivity in cells and projections of the bed nucleus of the stria terminalis (BST) and medial amygdaloid nucleus (MA) depends on gonadal steroids. In addition, the AVP projections from the BST show denser fiber staining in males than in females. To study whether these differences depend on different hormone levels in adulthood, male and female rats were gonadectomized and similarly treated with testosterone for 4 weeks prior to sacrifice. Immunocytochemistry showed that males had significantly more AVP‐immunoreactive (AVP‐IR) cells in the BST and significantly denser AVP‐IR projections from this nucleus to the lateral septum, lateral habenular nucleus, and periaqueductal central gray than did females. The number of AVP‐IR cells in the MA nucleus was not statistically different, but denser AVP‐IR fiber networks were found in the MA and ventral hippocampus, which receives its input from the MA. No differences were found in the anteroventral portion of the periventricular nucleus and the dorsomedial nucleus of the hypothalamus that receive their AVP innervation from the suprachiasmatic nucleus. These results indicate that the sex difference in the steroid‐sensitive AVP pathways depends on other factors besides circulating hormone levels in adulthood.
Immunohistochemical localization of cholecystokinin in the medial preoptic area and anterior hypothalamus of the Brazilian gray short‐tailed opossum: A sex difference
Authors: Fox Charles A. , Adam Diane E. , Watson Robert , Hoffman Gloria E. , Jacobson Carol D. 
Published: May 2005

AbstractWe have studied the anatomical localization of cholecystokinin‐like immunoreactivity (CCK IR) in somata and fibers in the medial preoptic area (MPA) and anterior hypothalamus (AH) of the Brazilian gray shorttailed opossum, (Monodelphis domestica). With the aid of an avidin‐biotin, nickel‐enhanced, immunohistochemical technique, CCK IR neuronal elements were found within the MPA and AH. A large number of CCK IR cell bodies were located in the MPA of colchicine‐treated opossums. The MPA also contained a CCK IR fiber plexus. Quantitative image analysis revealed that the periventricular preoptic area of noncolchicine‐treated male opossums had a significantly higher percent of blocked light measurements than that of the noncolchicine‐treated females, indicating a higher density of CCK IR neuronal elements in the males. Neuronal fibers and somata containing CCK IR were also found within the periventricular hypothalamic nucleus (Pe), and the suprachiasmatic nucleus (SCh). These results show that CCK IR neuronal elements are found within the MPA and AH of the Brazilian short‐tailed opossum. Furthermore, there is a sexually dimorphic distribution of CCK IR elements within the MPA of this small marsupial.
Are separable aromatase systems involved in hormonal regulation of the male brain?
Authors: Hutchison J. B. , Schumacher M. , Steimer Th. , Gahr M. 
Published: May 2005

AbstractIn vitro study of testosterone (T) metabolism shows that formation of estradiol‐17β (E2) is regionally specific within the preoptic area (POA) of the male ring dove. The POA is known to be involved in the formation of E2 required for specific components of male sexual behavior. Two sub‐areas of high aromatase activity, anterior (aPOA) and posterior preoptic (pPOA) areas, have been identified. Aromatase activity is higher in aPOA than in pPOA. The aromatase activity within the aPOA is also more sensitive to the inductive effects of low circulating T, derived from subcutaneous silastic implants, than the enzyme activity in pPOA. Kinetic analysis of preoptic fractions indicates that a similar high‐affinity enzyme occurs in both areas (apparent Km < 14nM), but the Vmax of aPOA enzyme activity is higher than pPOA. Cells containing estrogen receptors (ER) are localized in areas of high aromatase activity. There is overlap between immunostained cells in the aPOA and in samples containing inducible aromatase activity measured in vitro. Within the aPOA there is a higher density of ER cells in the nucleus preopticus medialis. The pPOA area also contains ER, notably in the nucleus interstitialis, but at a lower density. We conclude that the hormonal regulation of the male preoptic‐anterior hypothalamic region, which is a target for the behavioral action of T, involves at least two inducible aromatase systems with associated estrogen receptor cells.