bluuebunny/crossref_metadata_2025_split huggingface dataset:
Social Change Affects Vocal Structure in a Callitrichid Primate (Callithrix kuhlii)
Authors: Rukstalis Michael , Fite Jeffrey E. , French Jeffrey A. 
Published: December 2004

AbstractVocal plasticity in the face of changing social context is well‐documented in passerine birds, but the degree to which changes in social environment affect the vocal structure of non‐human primates is a topic which has remained largely unexplored. We assessed whether modification of social environments, in this case the presence of marmosets in neighboring cages, influenced the vocal morphology of phee calls, which possess ‘signature’‐like features, in Wied's black tufted‐ear marmosets (Callithrix kuhlii). Individual phee calls were obtained over a period of 8 wk from 11 animals maintained in rooms with stable social environments. After this baseline phase, seven marmosets were housed for an additional 8 wk in rooms that contained cages with unfamiliar marmosets, while four marmosets maintained the same neighbors as the first phase. Calls were digitized and both frequency and temporal parameters were measured. Multivariate discriminant function analyses (DFA) generated from vocalizations collected in the first phase produced functions that accurately classified calls to the correct individual, showing that calls had significant individual distinctiveness. DFAs generated from vocalizations in the first phase of the study continued to show high classification accuracy for marmosets in a stable social environment, but DFAs from the first phase were significantly less likely to correctly classify vocalizations in marmosets that were housed next to novel conspecifics. These data show that phee calls, which have signature‐like properties in marmosets, can be modified by changes in social context. The results suggest a degree of plasticity in vocal signals that is rare among non‐human primates.
The Causes of Resource Monopolization: Interaction Between Resource Dispersion and Mode of Competition
Authors: Weir Laura K. , Grant James W. A. 
Published: December 2004

AbstractThe degree of monopolization of resources is thought to be higher in groups that compete by interference than by exploitation. However, the monopolization of resources will presumably depend on (1) whether the dispersion of resources is economically defendable, and (2) whether some competitors have the ability to defend these resource distributions and hence capitalize on this potential. We tested for an interaction between the effects of temporal resource dispersion and aggressiveness on the degree of resource monopolization in a foraging system. Two species of fish differing markedly in aggressiveness (high: convict cichlids, Archocentrus nigrofasciatus; low: goldfish, Carrasius auratus) were allowed to compete intra‐specifically in groups of four for food that was either potentially defendable (arrived asynchronously) or not (arrived synchronously). As predicted, the monopolization of food, measured as the coefficient of variation of food eaten within groups, was significantly higher in the defendable than in the undefendable treatment for convict cichlids but not for goldfish. However, the monopolization of food was higher in the non‐aggressive goldfish than in the aggressive convict cichlids. Future studies should quantify and compare the monopolization in species that compete primarily via scramble competition to those that use primarily resource defence.
Beyond the 12 lead: Review of the use of additional leads for the early electrocardiographic diagnosis of acute myocardial infarction
Authors: Carley Simon D 
Published: December 2004

AbstractDespite known limitations, the standard 12 lead ECG is the principal risk stratification device for patients presenting with chest pain to the ED. However, it has a sensitivity of less than 60% for MI. One reason for this is that the standard placement of chest leads fails to interrogate many areas of the myocardium. Various workers have addressed this problem through the use of additional leads or body surface mapping. Additional leads on the posterior and right thoracic surface have been shown to give additional information, which may be important to the emergency physician. This review demonstrates the need for additional leads in the acute setting and makes recommendations about the utility of using additional leads in the ED.
Ultrasound for primary confirmation of mechanical capture in emergency transcutaneous pacing
Authors: Tam Michael MK 
Published: December 2004

AbstractClinical confirmation of mechanical capture in emergency transcutaneous pacing is sometimes difficult because of weak pulse volume or interference from skeletal muscle contractions. This report is of a case of using bedside ultrasound for primary confirmation of emergency transcutaneous pacemaker capture, and for differentiating between causes of persistent hypotension despite successful pacing. The technique of ultrasound‐guided transcutaneous pacing is described.
Topography of cocaine‐induced gene regulation in the rat striatum: relationship to cortical inputs and role of behavioural context
Authors: Willuhn Ingo , Sun Weiwen , Steiner Heinz 
Published: December 2004

AbstractPsychostimulants alter gene expression in projection neurons of the striatum, and such neuroplasticity is implicated in drug addiction and dependence. Evidence indicates that excitatory inputs from the cortex and thalamus are critical for these molecular changes. In the present study, we determined the topography of cocaine‐induced changes in gene expression in the rat striatum and investigated whether these molecular alterations are associated with particular cortical inputs. Acute induction of c‐fos (by 25 mg/kg of cocaine), and the c‐fos response and dynorphin expression after repeated cocaine treatment (25 mg/kg, 4 days) were assessed as examples for short‐term and longer‐term molecular changes, respectively. In addition, we examined whether these molecular effects were influenced by the behaviour performed during cocaine action (running‐wheel training vs. open field). Our results demonstrate that the overall topography of cocaine‐induced gene regulation in the striatum is remarkably stable. Both acute and longer‐term molecular changes were maximal in caudal dorsal striatal sectors that receive convergent inputs from the medial agranular and the sensorimotor cortex. In contrast, relatively minor or no effects were found in rostral and ventral striatal sectors. However, running‐wheel training under the influence of cocaine enhanced the c‐fos response to a subsequent cocaine challenge selectively in parts of the caudal sensorimotor striatum. These results indicate that cocaine produces molecular adaptations preferentially in cortico‐basal ganglia circuits through the sensorimotor striatum, and that some of these neuronal changes are influenced by the behaviour performed during drug exposure.
Mechanisms underlying the noradrenergic modulation of longitudinal coordination during swimming in Xenopus laevis tadpoles
Authors: Merrywest Simon D. , McDearmid Jonathan R. , Kjaerulff Ole , Kiehn Ole , Sillar Keith T. 
Published: December 2004

AbstractNoradrenaline (NA) is a potent modulator of locomotion in many vertebrate nervous systems. When Xenopus tadpoles swim, waves of motor neuron activity alternate across the body and propagate along it with a brief rostro–caudal delay (RC‐delay) between segments. We have now investigated the mechanisms underlying the reduction of RC‐delay s by NA. When recording from motor neurons caudal to the twelfth postotic cleft, the mid‐cycle inhibition was weak and sometimes absent, compared to more rostral locations. NA enhanced and even unmasked inhibition in these caudal neurons and enhanced inhibition in rostral neurons, but to a lesser extent. Consequently, the relative increase in the amplitude of the inhibition was greater in caudal neurons, thus reducing the RC‐inhibitory gradient. We next investigated whether NA might affect the electrical properties of neurons, such that enhanced inhibition under NA might promote postinhibitory rebound firing. The synaptic inputs during swimming were simulated using a sustained positive current, superimposed upon which were brief negative currents. When these conditions were held constant NA enhanced the probability of rebound firing – indicating a direct effect on membrane properties – in addition to any indirect effect of enhanced inhibition. We propose that NA preferentially enhances weak caudal inhibition, reducing the inhibitory gradient along the cord. This effect on inhibitory synaptic transmission, comprising parallel pre‐ and postsynaptic components, will preferentially facilitate rebound firing in caudal neurons, advancing their firing relative to more rostral neurons, whilst additionally increasing the networks ability to sustain the longer cycle periods under NA.
Regulation of RGS proteins by chronic morphine in rat locus coeruleus
Authors: Gold Stephen J. , Han Ming‐Hu , Herman Amy E. , Ni Yan G. , Pudiak Cindy M. , Aghajanian George K. , Liu Rong‐Jian , Potts Bryan W. , Mumby Susanne M. , Nestler Eric J. 
Published: December 2004

AbstractThe present study explored a possible role for RGS (regulators of G protein signalling) proteins in the long term actions of morphine in the locus coeruleus (LC), a brainstem region implicated in opiate physical dependence and withdrawal. Morphine influences LC neurons through activation of µ‐opioid receptors, which, being Gi/o‐linked, would be expected to be modulated by RGS proteins. We focused on several RGS subtypes that are known to be expressed in this brain region. Levels of mRNAs encoding RGS2, ‐3, ‐4, ‐5, ‐7, ‐8 and ‐11 are unchanged following chronic morphine, but RGS2 and −4 mRNA levels are increased 2–3‐fold 6 h following precipitation of opiate withdrawal. The increases in RGS2 and −4 mRNA peak after 6 h of withdrawal and return to control levels by 24 h. Immunoblot analysis of RGS4 revealed a striking divergence between mRNA and protein responses in LC: protein levels are elevated twofold following chronic morphine and decrease to control values by 6 h of withdrawal. In contrast, levels of RGS7 and −11 proteins, the only other subtypes for which antibodies are available, were not altered by these treatments. Intracellular application of wild‐type RGS4, but not a GTPase accelerating‐deficient mutant of RGS4, into LC neurons diminished electrophysiological responses to morphine. The observed subtype‐ and time‐specific regulation of RGS4 protein and mRNA, and the diminished morphine‐induced currents in the presence of elevated RGS4 protein levels, indicate that morphine induction of RGS4 could contribute to aspects of opiate tolerance and dependence displayed by LC neurons.
Somatic and visceral afferents to the ‘vasodepressor region’ of the caudal midline medulla in the rat
Authors: Potas Jason R. , Keay Kevin A. , Henderson Luke A. , Bandler Richard 
Published: December 2004

AbstractPrevious research has found that the integrity of a restricted region of the caudal midline medulla (including caudal portions of nucleus raphé obscurus and nucleus raphé pallidus) was critical for vasodepression (hypotension, bradycardia, decreased cardiac contractility) evoked either by haemorrhage or deep pain. In this anatomical tracing study we found that the vasodepressor part of the caudal midline medulla (CMM) receives inputs arising from spinal cord, spinal trigeminal nucleus (SpV) and nucleus of the solitary tract (NTS). Specifically: (i) a spinal–CMM projection arises from neurons of the deep dorsal horn, medial ventral horn and lamina X at all spinal segmental levels, with approximately 60% of the projection originating from the upper cervical spinal cord (C1–C4); (ii) a SpV–CMM projection arises primarily from neurons at the transition between subnucleus caudalis and subnucleus interpolaris; (iii) a NTS–CMM projection arises primarily from neurons in ventrolateral and medial subnuclei. In combination, the specific spinal, SpV and NTS regions which project to the CMM receive the complete range of somatic and visceral afferents known to trigger vasodepression. The role(s) of each specific projection is discussed.
Syntaxin I modulation of presynaptic calcium channel inactivation revealed by botulinum toxin C1
Authors: Stanley Elise F. 
Published: December 2004

AbstractThe chick ciliary ganglion calyx‐type nerve terminal was used to examine voltage‐sensitive inactivation of presynaptic N‐type Ca2+ channels and to test if this inactivation is modulated by the transmitter release‐associated protein syntaxin I. We tested the role of this protein with botulinum toxin C1 (BtC1) which cleaves syntaxin I close to its membrane anchor. The presynaptic Ca2+ current inactivated as two distinct populations with ∼75% inactivating at a depolarized potential, V1/2∼−15 mV, with the remainder inactivating at ∼−75 mV. BtC1 had no detectable effect on the latter component but resulted in a ∼7 mV positive shift in the V1/2 of the −15 mV inactivating component. These results confirm that the bulk of presynaptic N‐type Ca2+ channels are in general resistant to voltage dependent inactivation and provide the first direct evidence that the physiological properties of presynaptic nerve terminal Ca2+ channels are subject to modulation by release site‐associated proteins.
Postnatal development of serotonin 1B, 2 A and 2C receptors in brainstem motoneurons
Authors: Volgin Denys V. , Fay Richard , Kubin Leszek 
Published: December 2004

AbstractThe effects of serotonin (5‐HT) on motoneurons are mediated via multiple receptor subtypes. In hypoglossal (XII) motoneurons, the prototypic brainstem motoneurons whose functions change during the postnatal period, 5‐HT effects evolve from inhibitory to excitatory, probably in association with changes in receptor expression. We studied 5‐HT1B, 5‐HT2A and 5‐HT2C receptor mRNA in 414 dissociated XII motoneurons and 5‐HT2A protein in the XII, facial and spinal cervical (C2‐3) motor nuclei. The percentage of motoneurons expressing distinct mRNAs varied with the postnatal age (P3‐33 days) and receptor subtype. Initially, 5‐HT1B mRNA was present in 50–85% of cells, but on P14 its expression transiently decreased below 35%. 5‐HT2A mRNA was present in nearly all cells after P6, but in less than 65% on P3‐5. Normal and/or short splice variants of the 5‐HT2C mRNA were expressed in less than 20% of motoneurons on P3‐9, and in ∼ 35% thereafter. 5‐HT1B and 5‐HT2A mRNAs often were expressed in different cells during early and intermediate postnatal periods, whereas 5‐HT2C mRNA never occurred alone. The 5‐HT2A receptor protein level gradually increased through P15 in the XII and facial nuclei, with dendritic labelling appearing in XII motoneurons only after P12. In spinal motoneurons, both somatic and dendritic labelling was strongest on P5 and then decreased. The development of 5‐HT receptors in XII motoneurons may be related to changes in feeding behaviour, whereas different cues regulate 5‐HT receptor expression in upper spinal motoneurons.
‘One‐trial sensitization’ to the anxiolytic‐like effects of cannabinoid receptor antagonist SR141716A in the mouse elevated plus‐maze
Authors: Rodgers R. J. , Haller J. , Halasz J. , Mikics E. 
Published: December 2004

AbstractSignificant variability in the effects of cannabinoid CB1 receptor ligands on emotional reactivity in animals and humans suggests that the endocannabinoid system may selectively modulate certain types of anxiety. In view of substantial evidence for qualitative differences in the nature of anxiety elicited on initial and subsequent exposures to the elevated plus‐maze, the present studies contrasted the behavioural effects of the selective CB1 receptor antagonist SR141716A (0.1–10.0 mg/kg) and the reference benzodiazepine chlordiazepoxide (CDP, 15 mg/kg) both in maze‐naive mice (trial 1) and in mice that had been given a single undrugged exposure to the maze 24 h prior to testing (trial 2). Results confirmed the anxioselective effect of CDP on trial 1 but a complete absence of such activity on trial 2 (i.e. one trial tolerance). In marked contrast, SR141716A had no behavioural effects in maze‐naive mice but, at doses of 1.0–3.0 mg/kg (effect maximal at 1.0 mg/kg), significantly reduced anxiety‐like responses in maze‐experienced animals. Like the effect of CDP on trial 1, the antianxiety profile of SR141716A on plus‐maze trial 2 was observed in the absence of any change in general activity levels. The apparent experientially induced ‘sensitization’ to the anxiolytic‐like effects of SR141716A in the plus‐maze contrasts markedly with the widely reported loss of benzodiazepine efficacy in test‐experienced animals. Data are discussed in relation to the recently described phenotypes of CB1 receptor knockout mice and, in particular, to mounting evidence for the existence of a novel SR141716A‐sensitive neuronal cannabinoid receptor.
Modulation of the ability of clozapine to facilitate NMDA‐ and electrically evoked responses in pyramidal cells of the rat medial prefrontal cortex by dopamine: pharmacological evidence
Authors: Ninan Ipe , Wang Rex Y. 
Published: December 2004

AbstractPrevious studies have shown that dopamine (DA) may play an important role in mediating or modulating the facilitating action of clozapine in glutamatergic transmission. This possibility was tested further in the present study by pharmacological manipulation of the DA system. When rats were pretreated with reserpine (which blocks storage of biogenic amines) and alpha‐methyl para‐tyrosine (AMPT, which inhibits tyrosine hydroxylase, the rate‐limiting enzyme for the DA synthesis), the ability of clozapine to augment glutamatergic transmission in pyramidal cells of the medial prefrontal cortex (mPFC) was totally abolished. Furthermore, the application of l‐dihydroxyphenylalanine (L‐DOPA, the immediate precursor of DA which bypasses the synthesis step inhibited by AMPT) reversed the effect produced by reserpine plus AMPT and re‐instated the facilitating action of clozapine, whereas administration of 5‐hydroxytryptophan (5‐HTP), the immediate precursor of 5‐HT, was ineffective. In addition, DA D1 receptor antagonist SCH 23390 also completely prevented clozapine‐induced facilitating action in the mPFC pyramidal cells. The present results demonstrate that newly synthesized DA and DA D1 receptors are required for clozapine to elicit its facilitating action on glutamatergic neurotransmission in the mPFC.
The large conductance Ca2+‐activated potassium channel (pSlo) of the cockroach Periplaneta americana: structure, localization in neurons and electrophysiology
Authors: Derst C. , Messutat S. , Walther C. , Eckert M. , Heinemann S. H. , Wicher D. 
Published: December 2004

AbstractVoltage‐activated, Ca2+‐sensitive K+ channels (BK or maxi K,Ca channels) play a major role in the control of neuronal excitability. We have cloned pSlo, the BK channel α subunit of the cockroach Periplaneta americana. The amino acid sequence of pSlo shows 88% identity to dSlo from Drosophila. There are five alternatively spliced positions in pSlo showing differential expression in various tissues. A pSlo‐specific antibody prominently stained the octopaminergic dorsal unpaired median (DUM) neurons and peptidergic midline neurons in Periplaneta abdominal ganglia. HEK293 cells expressing pSlo exhibit K+ channels of 170 pS conductance. They have a tendency for brief closures, exhibit subconductance states and show slight inward rectification. Activation kinetics and voltage dependence are controlled by cytoplasmic [Ca2+]. In contrast to dSlo, pSlo channels are sensitive to charybdotoxin and iberiotoxin. Mutagenesis at two positions (E254 and Q285) changed blocking efficacy of charybdotoxin. In contrast to pSlo expressed in HEK293 cells, native IbTx‐sensitive K,Ca currents in DUM and in peptidergic neurons, exhibited rapid, partial inactivation. The fast component of the K,Ca current partly accounts for the repolarization and the early after‐hyperpolarization of the action potential. By means of Ca2+‐induced repolarization, BK channels may reduce the risk of Ca2+ overload in cockroach neurons. Interestingly, the neurons expressing pSlo were also found to express taurine, a messenger that is likely to limit overexcitation by an autocrine mechanism in mammalian central neurons.
The pyramidal neuron in occipital, temporal and prefrontal cortex of the owl monkey (Aotus trivirgatus): regional specialization in cell structure
Authors: Elston Guy N. 
Published: December 2004

AbstractRecent studies have revealed marked regional variation in pyramidal cell morphology in primate cortex. In particular, pyramidal cells in human and macaque prefrontal cortex (PFC) are considerably more spinous than those in other cortical regions. PFC pyramidal cells in the New World marmoset monkey, however, are less spinous than those in man and macaques. Taken together, these data suggest that the pyramidal cell has become more branched and more spinous during the evolution of PFC in only some primate lineages. This specialization may be of fundamental importance in determining the cognitive styles of the different species. However, these data are preliminary, with only one New World and two Old World species having been studied. Moreover, the marmoset data were obtained from different cases. In the present study we investigated PFC pyramidal cells in another New World monkey, the owl monkey, to extend the basis for comparison. As in the New World marmoset monkey, prefrontal pyramidal cells in owl monkeys have relatively few spines. These species differences appear to reflect variation in the extent to which PFC circuitry has become specialized during evolution. Highly complex pyramidal cells in PFC appear not to have been a feature of a common prosimian ancestor, but have evolved with the dramatic expansion of PFC in some anthropoid lineages.
Bidirectional modulation of visual plasticity by cholinergic receptor subtypes in the frog optic tectum
Authors: Yu Chuan‐Jiang , Butt Christopher M. , Debski Elizabeth A. 
Published: December 2004

AbstractCholinergic input to the optic tectum is necessary for visual map maintenance. To understand why, we examined the effects of activation of the different cholinergic receptor subtypes in tectal brain slices and determined whether the retinotectal map was affected by manipulations of their activity in vivo. Both α‐bungarotoxin sensitive and insensitive nicotinic receptor agonists increased spontaneous postsynaptic currents (sPSCs) in a subpopulation of patch‐clamped tectal cells; application of subtype selective receptor antagonists reduced nicotine‐induced increases in sPSCs. Activation of α‐bungarotoxin insensitive nicotinic receptors also induced substantial inward current in some cells. Muscarinic receptor mediated outward current responses were blocked by the M2‐like muscarinic receptor antagonists himbacine or AF‐DX 384 and mimicked by application of the M2‐like agonist oxotremorine. A less frequently observed muscarinic response involving a change in sPSC frequency appeared to be mediated by M1‐like muscarinic receptors. In separate experiments, pharmacological manipulation of cholinergic receptor subtype activation led to changes in the activity‐dependent visual map created in the tectum by retinal ganglion cell terminals. Chronic exposure of the tectum to either α‐bungarotoxin insensitive, α‐bungarotoxin sensitive or M1‐like receptor antagonists resulted in map disruption. However, treatment with the M2‐like receptor antagonist, AF‐DX 384, compressed the map. We conclude that nicotinic or M1‐like muscarinic receptors control input to tectal cells while α‐bungarotoxin insensitive nicotinic receptors and M2‐like muscarinic receptors change tectal cell responses to that input. Blockade of the different cholinergic receptor subtypes can have opposing effects on map topography that are consistent with expected effects on tectal cell activity levels.