bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electroretinographic and ultrastructural study of the regenerated eye of the snail cryptomphallus aspersa
Authors: Flores D. Vladimir , Salas Pedro J. I. , Vedra Jorge Pecci Saa 
Published: January 2005

AbstractThe electroretinographic responses of regenerated eyes of snails (C. aspersa) were studied by means of suction electrodes and single or repetitive flash stimulation. The eyes were fixed and observed under light and electron microscopy. The results indicate that the electroretinographic response of regenerated eyes does not differ from control eyes after dark adaptation. However, the repetitive stimulation of the regenerated eyes induced an earlier fatigue of the response, evident after the fifth stimulus. This fatigue is a function of light intensity. Ultrastructural features of the regenerated eyes are similar to those of the control eyes but regenerated eyes show smaller rhabdomeres, fewer photic vesicles, and fewer paracrystalline bodies. It is suggested that the regenerated eye lability to the repetitive stimulation might be due to the decrease in the amount of photic vesicles and paracrystalline bodies, to the decrease in membrane surface of the rhabdomeres, or to some other metabolic failure not distinguished at electron microscopic level, like the membrane ionic regulation. The appearance of photic vesicles in the axon cones of regenerated and stimulated cells also suggests a possible failure in the mechanism of transport of vesicles.
Effects of c‐amp, caffeine, theophylline, and vinblastine on spontaneous transmitter release at locust nerve‐muscle junctions
Authors: Fahim M. A. , Usherwood P. N. R. 
Published: January 2005

AbstractThe effects of c‐AMP, phosphodiesterase inhibitors (caffeine and theophylline) and vinblastine on spontaneous transmitter release was investigated at locust neuromuscular junctions. c‐AMP, theophylline, caffeine, and vinblastine caused facilitation of transmitter release. None of these drugs had any effect on the amplitude of miniature excitatory postsynaptic potentials (min. E.P.S.P.'s), or on the resting membrane potential, but vinblastine increased the proportion of [large] min. E.P.S.P.'s The effect of theophylline (but not c‐AMP and caffeine) on min. E.P.S.P. frequency was found to be calcium dependent. The effects of these drugs on the locust glutamatergic synapse are compared with their actions at other synapses.
Axonal transport blockade and denervation have qualitatively different effects upon skeletal muscle metabolism
Authors: Ramírez Beatriz U. 
Published: January 2005

AbstractThe activity and isoenzyme pattern of muscle lactic dehydrogenase (LDH) was measured at different times after axonal transport blockade by colchicine or after denervation. After denervation, total LDH activity decreased and the isoenzyme pattern was altered, LDH‐1 being the most affected form. In contrast, after axonal transport blockade there was a decrease in LDH activity but the isoenzyme pattern was not modified. Denervation abolishes both nerve‐evoked muscle activity and the release of neuro trophic substances from the nerve whereas colchicine blocks axonal transport without affecting the nerve capacity to conduct action potentials or neuromuscular transmission. It is then concluded that nerve‐evoked muscle activity is the most important factor in the regulation of muscle LDH isoenzyme distribution. On the other hand, muscle metabolism can also be regulated by axonally transported molecules.The results presented here show that there is a qualitative difference between the effects of denervation and those of axonal transport blockade upon the muscle, since only denervation altered the isoenzyme pattern of muscle LDH.
Quantitative effects of a neurotoxin upon serotonin levels within tissue compartments of the medicinal leech
Authors: Lent Charles M. 
Published: January 2005

AbstractThe serotonin (5‐hydroxytryptamine, 5‐HT) content of tissue compartments in the medicinal leech, Hirudo medicinalis, was measured by means of highpressure liquid chromatography coupled with electrochemical detection (HPLC–EC). Each segmental ganglion contains 21.3 ± 2.9 (9) pmol 5‐HT [X ± SEM (N)]. The pharynx contains 7.1 ± 1.1 (9) pmol 5‐HT/mg wet weight; the salivary glands 3.2 ± 0.9 (10), ventral body wall 2.0 ± 0.2 (11), and vasofibrous tissue 1.2 ± 0.2 (11). The blood of hungry leeches contains 8.7 ± 1.9 (7) nM 5‐HT while that of well‐fed leeches is 2.2 ± 0.4 (6) nM.Leeches were injected with the cytotoxic analog of serotonin, 5,7‐dihydroxytryptamine (5,7‐DHT) producing selective lesions of the peripherally projecting serotonin‐containing neurons, and which in turn abolished their feeding behavior. The serotonin content of the pharynx and ganglia of these toxin‐treated leeches were lowered significantly. The serotonin levels within the body wall and salivary glands were not altered significantly by the toxin treatment, but the levels within the vasofibrous tissue and blood were elevated substantially.
Ring neuron control of columellar motor neurons during egg‐laying behavior in the pond snail
Authors: Jansen Rene F. , Ter Maat Andries 
Published: January 2005

AbstractEgg‐laying in Lymnaea is characterized by the stereotyped egg‐laying behavior (ELB), composed of foot contractions and shell movements. Egg‐laying can be induced by a clean water stimulus, that triggers a discharge of the neuroendocrine caudo‐dorsal cells (CDCs), which release the ovulation hormone into the blood. A part of the behavior is lost when egg‐laying is triggered by hormone injection, indicating that during natural stimulus‐induced or spontaneous egg‐laying this part (the first phase) may be controlled by neuronal events in the CNS triggered by (a) factor(s) not released to the blood. The authors have identified an unpaired neuron, the ring neuron, that is excited during an in vitro afterdischarge of the CDCs, and which, by its numerous axonal branches in the pedal ganglia, modulates motorneurons of the columellar muscle, which controls shell movements. These motorneurons, identified as such in reduced preparations by 1 for 1 muscle potentials and elements in the connecting nerve, all receive either excitatory or inhibitory input from the ring neuron, as well as from an unknown neuron which has common input of the ring neuron and the motorneurons. The action of the CDCs on the ring neuron cannot be mimicked by the ovulation hormone, and we therefore conclude that the first part of the ELB is probably caused by a nonhormonal local action of the CDCs on the ring neuron and possibly the common input neuron.
Triple innervation of the crayfish opener muscle: The astacuran common inhibitor
Authors: Wiens Theodore J. 
Published: January 2005

AbstractPart of the much‐studied crayfish opener muscle receives a second inhibitory input in addition to its well known specific excitatory and inhibitory innervation. This second inhibitor, formerly thought to innervate only four of the seven peripheral leg muscles, is in fact a common inhibitor of all seven. This has significance both for previous findings in this muscle and for the role of the common inhibitor in decapods.
The central morphology of mechanoreceptor afferents in the metathoracic leg of the cockroach, Periplaneta americana (insecta)
Authors: Collin Shaun P. 
Published: January 2005

AbstractThe sensory arborizations of the femoral chordotonal organ (FECO), trochanteral campaniform sensilla (CS) and the trochanteral hairplate (THP) are restricted to the ipsilateral hemiganglion and possess large dendritic fields in the dorsal and ventral neuropiles. The efferent projections of the fast (Df) and the slow (Ds) depressor motoneurons project into the same areas.Three groups of trichoid sensilla located on the coxal and trochanteral cuticular walls have central contralateral projections and in one case intersegmental projections. All sensory projections terminate either just lateral of or in the Ventral Association Centre (VAC).Comparisons with the mechanoreceptors of other insects reveal similar projection patterns for some proprioceptors and non‐homologous central configurations for others.
Serotonin immunoreactivity in the nervous system of the dragonfly nymph
Authors: Longley Alison J. , Longley Roger D. 
Published: January 2005

AbstractSerotonin‐like immunoreactivity was mapped using an antiserotonin antibody in wholemounts of the ventral nerve cord from dragonfly nymphs (Epitheca sp. and Pachydiplax logipennis). In both species, an immunoreactive cell ventral to each connective tract and an immunoreactive median cell cluster on the ganglion ventral surface were found in the unfused abdominal ganglia. Axon(s) from the median cell cluster branch in the anterior unpaired median nerve. Posterolaterally, in all of the ganglia examined, two or more intensely immunoreactive, bilaterally symmetric pairs of neurons were seen. Comparison of these posterolateral neurons, which appear to be serially homologous, with similar antiserotonin immunoreactive neurons described in other insects suggests that these neruron pairs may have cross‐species homology as well.
Early differences between alternate n blast cells in leech embryo
Authors: Bissen Shirley T. , Weisblat David A. 
Published: January 2005

AbstractSegmentally interated tissues of the mature leech comprise five distinct sets of definitive progeny that arise from chains of blast cells (m, n, o, p, and q bandlets) produced by five bilateral pairs of stem cells (M, N, O/P, O/P, and Q teloblasts). In each n and q bandlet, two blast cells are needed to generate one set of hemisegmental progeny, and two alternating classes of blast cells (nf and ns, qf and qs) can be distinguished after their first divisions. Furthermore, two distinct subsets of definitive N and Q progeny exist within each hemisegment. Here we first show that there is a fixed correspondence between the class of blast cell and the subset of final progeny: ns cells contribute mainly anteior ganglionic neurons and epidermal cells; nf cells contribute mainly posterior ganglionic neurons, peripheral neurons and neuropil glia; qs cells contribute both ventral and dorsal progeny; and qf cells contribute only dorsal progeny. Second, ablation studies indicate that the two classes of n blast cells do not behave as an equivalence group in the germinal band. Finally, we show that the cycles giving rise to nf and ns blast cells differ. These data suggest that cellular interactions within the germinal band may not be critical in establishing the distinct nf and ns cell fates and that, conversely, differences between the two classes of n blast cells may be established at birth.
Isolation of the heparan sulfate proteoglycans from the extracellular matrix of rat skeletal muscle
Authors: Brandan Enrique , Inestrosa Nibaldo C. 
Published: January 2005

AbstractWe have previously shown that asymmetric collagen‐tailed acetylcholinesterase (AChE) is anchored to the extracellular matrix (ECM) by heparan sulfate proteoglycans (HSPGs). Here we present our studies on the characterization of such PGs from the ECM of rat skeletal muscles. After radiolabling with 35SO4 for 24 h, PGs were extracted from the muscle ECM with 4.0 M guanidine‐HCl containing protease inhibitors. PGs were subsequently isolated using sequential DEAE‐Sephacel chromatography, digestion with chondroitinase ABC, and Sepharose CL‐4B. Two different hydrodynamic size species of HSPGs were found. One type had a Mr of 4–6 × 105 (Kav = 0.25) as estimated by gel chromatography in the presence of 1% SDS and accounted for 75% of the total HSPGs. The other HSPG had a Mr 1.5–2.5 × 105 (Kav = 0.41). The glycosaminoglycan (GAG) side chains (Mr 20,000 and 12,000) were found composed only of heparan sulfate as determined by nitrous acid oxidation and heparitinase treatment. The large‐sized HSPG, which is concentrated in synaptic regions, contains only GAG chains of Mr 20,000, suggesting that each HSPG contains only one kind of heparan sulfate chain in its structure. Our results definitively establish by biochemical criteria that the basement membrane of mammalian skeletal muscle contains HSPGs, the likely matrix receptor for the immobilization of the asymmetric collagen‐tailed AChE at the neuromuscular junction.
Regulation of synaptic frequency: Comparison of the effects of hypoinnervation with those of hyperinnervation in the fly's compound eye
Authors: Fröhlich A. , Meinertzhagen I. A. 
Published: January 2005

AbstractAt the anterior rim of the first optic neuropile, or lamina, of the housefly's (Musca domestica) compound eye, the terminals of photoreceptors (R) innervate postsynaptic neurons in variable numbers to provide a continuous range of natural hypo‐and hyperinnervations. Frequencies of photoreceptor synapses have been measured from quantitative electron microscopy on single sections of the lamina's unit synaptic modules, called cartridges. These are normally innervated by six photoreceptor terminals (6R cartridges). At the lamina's edge hypoinnervated cartridges (2R–5R) are found, whereas hyperinnervated cartridges (7R, 8R) are located at the equator between dorsal and ventral eye halves. In 2R cartridges each presynaptic terminal forms up to 1.5 times the normal, 6R cartridge number of synapses, thereby offsetting the reduced number of terminals and partially conserving the input upon the postsynaptic neurons. Thus the terminals have a reserve synaptogenic capacity never normally revealed. By comparison, terminals in 8R cartridges form about the same numbers of synapses as in “normal” eye regions, so that their postsynaptic neurons have a synaptic input increased by the extra number of terminals. The number of synapses formed between input terminals and target neurons is therefore not fixed but changes as a function of the total receptor terminal complement. The size of a photoreceptor terminal covaries to a certain extent with the number of its presynaptic sites; the spacing density of presynaptic sites over the terminals' surface in a 2R cartridge compared with an 8R cartridge increases far less (only 17%) than the increase in the number of sites (43%). The pair of postsynaptic cell interneurons in each 2R cartridge also shows a decrease in axonal diameter compared with those in 8R cartridges. Thus both the pre‐ and postsynaptic cells show size changes correlated with changes in their synaptic engagement.
Possible interactions of a steroid hormone and neural inputs in controlling the death of an identified neuron in the moth Manduca sexta
Authors: Fahrbach S. E. , Truman J. W. 
Published: January 2005

AbstractThe emergence of the adult Manduca sexta moth is followed by the loss of almost half of this insect's abdominal motoneurons and interneurons (Truman, 1983). This programmed cell death completes the transformation of the nervous system of the caterpillar into that of the moth. The death of these neurons has been previously shown to be a response to an endocrine signal: the decline in ecdysteroids that occurs at the end of metamorphosis (Truman and Schwartz, 1984). Our current research is focussed on the regulation of the fate of a pair of identified motoneurons, the MN‐12 cells, in the third abdominal ganglion. Isolation of this ganglion from anterior parts of the nervous system can prevent the death of these cells at the time when they would normally die in response to the decline in ecdysteroids. Transection of the ventral nerve cord at various levels revealed that the source of this regulatory „death signal”︁ is the fused pterothoracic ganglion and that it is transmitted via the interganglionic connectives. We hypothesize that the factors mediating this effect may act in concert with the ecdysteroid decline to specify the exact time of death for individual neurons.
Compression and expansion without impulse activity in the retinotectal projection of goldfish
Authors: Meyer Ronald L. , Wolcott Leslie L. 
Published: January 2005

AbstractThe capacity of regenerating optic fibers to undergo retinotopic compression and expansion in the absence of impulse activity was tested by eliminating activity with periodic intraocular injections of tetrodotoxin (TTX) during regeneration. To test for compression, the posterior half of tectum was removed and the optic nerve crushed. For expansion, the temporal half of retina was ablated and the nerve also crushed. The projection was then subsequently examined with electrophysiological mapping and autoradiographic tracing.Like electrically active fibers, silent fibers formed a retinotopically ordered projection that was compressed onto the anterior half tectum. Similarly, TTX‐treated fibers from a nasal half retina formed a retinotopic projection that was expanded across the entire tectum. Except for some enlargement of receptive fields produced by the TTX, the topography was equivalent to that formed by active fibers.Thus, fibers can apparently maintain relative positions irrespective of absolute tectal position without the benefit of activity‐dependent ordering. This implies the existence of an activity‐independent mechanism for relative positioning that may operate across larger distances than the activity‐dependent ordering responsible for fine topography and ocular dominance columns.
An identified cell is required for the formation of a major nerve during embryogenesis in the leech
Authors: Jellies John , Kristan William B. 
Published: January 2005

AbstractInvestigations of the cues by which axonal growth cones navigate long distances to their targets have revealed the use of a rich and complex diversity of cellular and extracellular information. In the present study we describe one of the most conceptually simple pathfinding cues: a single identified cell in the leech, Hirudo medicinalis, that may guide axons several hundred micrometers to innervate a particular target. One of the stereotyped nerves of H. medicinalis is a “sex nerve” thatprojects from the anterior root of ganglion 6 [SNA (6)] tothe male reproductive structures in the adjacent anterior segment. The pathway for SNA (6) is completely underlainbya single peripheral cell, here called the axonal runway cell (ARC), before axons enter the pathway. The ARC is apparently a nonneuronal cell that stains with a monoclonalantibody that recognizes leech muscle cells. The importance ofthe ARC for establishing SNA (6) was tested by ablating itbefore axons entered the pathway. When the ARC was killed either by physical disruption with a microelectrode, or byphotoablation after filling it with the fluorescent dye Lucifer yellow, SNA(6) always failed to form, whereas all other nerves formed normally. Killing other peripheral cellsin proximity to the ARC did not interfere with SNA(6) formation. Ablation of possible “pioneer neurons” for SNA(6) also did not prevent its formation. These results show that formation of a particular nerve requires onlya single cell to serve as a guide for outgrowingprocesses.
Overlaping taste and tactile maps of the oropharynx in the vagal lobe of the channel catfish, Ictalurus punctatus
Authors: Kanwal Jagmeet S. , Caprio John 
Published: January 2005

AbstractMicroelectrode mapping experiments indicate an ipsilateral representation of the oropharynx and a well‐defined, bilateral input from the proximal portion of the maxillary barbels and snout region within the vagal lobe of channel catfish. The map of the oropharyngeal epithelium is distorted so that the gill arches are rotated through an angle of 90° along the transverse plane, and the dorsally mapped region of the gill rakers is tilted posteriorly in the sagittal plane of the vagal lobe. Multiunit recording studies fail to provide definitive boundaries of adjacently mapped domains of oropharyngeal structures. Gustatory receptive fields of neurons in the vagal lobe correspond to their location on the topological map obtained by tactile stimulation of the oropharyngeal epithelium. A few single unit recordings indicate restricted receptive fields and different response patterns of taste, tactile, and proprioceptive neurons in the vagal lobe of catfish.
Regeneration restores some of the altered electrical properties of axotomized bullfrog B‐cells
Authors: Kelly M. E. M. , Bisby M. A. , Lukowiak Ken 
Published: January 2005

AbstractIn bullfrog B‐type sympathetic neurones axon injury produces substantial changes in somal membrane properties. These include a shortening of action potential afterhyperpolarization (AHP) and an increase in action potential (AP) duration. In the present experiments we compared two injury situations: nerve crush, which was followed by regeneration, and nerve cut, after which regeneration to the original target was prevented, to investigate whether these electrophysiological changes were related to axon regeneration. Both crush and cut injuries produced a similar maximum decrease in AHP duration (to 33 and 30%) by 14 days after axotomy. After nerve crush, AHP duration recovered to within control values by 42 days, while after cut it remained depressed. AHP amplitude decreased to the same extent after nerve crush or cut (to 62 and 58%), but the rate of decrease was slower following crush when compared with cut, and following both types of injury it still remained depressed at 42 and 49 days. Changes in AP duration also took longer to occur following nerve crush, reaching maximal values at 35–42 days, at which time AHP duration had returned to within the normal range. The early reduction in AHP duration and its rapid recovery in regenerating neurones suggests that the current underlying this membrane property is regulated by events associated with axon outgrowth and peripheral reconnection. In contrast, changes in AHP amplitude and AP repolarization appeared to be independent of the occurrence of axon regeneration and remained abnormal at 49 days despite the recovery of AHP duration. These results imply that the electrophysiological changes seen in B‐cells following injury are differentially regulated during subsequent regeneration.
Activation of DUM cell interneurons by ventral giant interneurons in the cockroach, periplaneta americana
Authors: Pollack Alan J. , Ritzmann Roy E. , Westin Joanne 
Published: January 2005

AbstractDorsal unpaired median (DUM) cells in orthopteran insects are known to contain the neuromodulatory substance octopamine, and DUM cells with peripheral axons augment synaptic activity at neuromuscular junctions. One of the most studied systems in the cockroach is the giant interneuron (GI) system which controls the initial movements of a wind‐ mediated escape response. Our data demonstrate that DUM cells that are restricted to the central nervous system (DUM interneurons) receive inputs from ventral giant interneurons (vGIs) but not from dorsal giant interneurons (dGIs). In contrast, DUM cells that have peripheral axons consistently fail to be excited by any giant intereurons. The DUM interneurons are excited by vGIs on both sides of the CNS and, when the vGIs are excited in pairs, summation occurs. Wind fields that have been generated for two of the DUM interneurons are omnidirectional. These data, taken along with the known association of DUM cells with the neuromodulatory substance octopamine, suggest that the DUM interneurons may act to modulate central synapses.