bluuebunny/crossref_metadata_2025_split huggingface dataset:
c‐fos is induced in the hippocampus during consolidation of sexual imprinting in the zebra finch (Taeniopygia guttata)
Authors: Sadananda Monika , Bischof Hans‐Joachim 
Published: February 2004

Abstractc‐fos was used to mark regions of enhanced neuronal activity during sexual imprinting, an early learning process by which information about the prospective sexual partner is acquired and consolidated. In the present study, we demonstrate that the hippocampus, already known for its specialized spatial memory capacities in navigating pigeons and in food‐storing birds, depicts a selective differential c‐fos induction in a situation shown to lead to sexual imprinting, that is, exposing previously isolated male birds to a female for 1 h. c‐fos induction is lateralized, the left hippocampus showing more c‐fos activity than the right. Our results would indicate a role for the hippocampus in the consolidation process of imprinting, probably in the transfer of information to the other telencephalic areas that show alterations in synaptic connectivity as a result of consolidation of sexual imprinting. © 2003 Wiley‐Liss, Inc.
Comparison of spontaneous and septally driven hippocampal theta field and theta‐related cellular activity
Authors: Scarlett Darren , Dypvik Audny T. , Bland Brian H. 
Published: February 2004

AbstractExperiments were carried out for the purpose of comparing the electrophysiological properties of spontaneously occurring hippocampal theta field activity with those of theta‐like field activity elicited by 5‐Hz and 7‐Hz electrical stimulation of the medial septum in urethane‐anesthetized rats. Experiment 1 compared the amplitude and phase depth profiles for the three conditions of spontaneously occurring theta, theta elicited by 5‐Hz medial septal stimulation, and theta elicited by 7‐Hz medial septal stimulation. The results supported the conclusion that septally elicited theta field activity exhibited characteristics similar to those of spontaneously occurring theta field activity. Experiment 2 compared the discharge properties of hippocampal theta‐related cellular discharges during spontaneous and septally elicited theta field activity. In contrast to the results of Experiment 1, the findings of Experiment 2 supported the conclusion that electrical stimulation of medial septal nuclei did not produce typical responses of hippocampal theta‐related cellular activity. During spontaneously occurring field conditions, HPC theta‐ON cells increased their discharge rates during spontaneous theta field activity, relative to LIA, and theta‐OFF cells decreased (often to zero) their discharge rates during theta field activity relative to LIA. During septally elicited theta‐like activity, phasic and tonic theta‐ON cells decreased their discharge rates (some were totally inhibited), and most tonic theta‐OFF cells increased their discharge rates (although two were totally inhibited). In addition, the discharges (albeit reduced) of the majority of both phasic and tonic theta‐ON cells during septal driving became entrained to the stimulation pulses and thus exhibited rhythmicity and strong phase relations with the field activity. Furthermore, both cell types discharged near the positive peak of the septally elicited theta field activity during 5‐Hz stimulation and near the negative peak during 7‐Hz stimulation. The discharges of most tonic theta‐OFF cells also became entrained to the stimulation pulses and exhibited similar phase relations to theta‐ON cells during the 5‐Hz and 7‐Hz driving frequencies. Thus, based on cellular evidence, electrical stimulation of the medial septum activates the hippocampal neural circuitry involved in the generation of theta field activity in a nonphysiological manner. The findings of the present paper provide an explanation for why electrical stimulation of the medial septum in freely moving rats elicits a theta‐like field activity that is dissociated from the normal behavioral correlates, in contrast to those elicited by stimulation of the posterior nucleus of the hypothalamus (Bland and Oddie. 2001. Behav Brain Res 127:119–136). © 2003 Wiley‐Liss, Inc.
Hippocampal protein‐protein interactions in spatial memory
Authors: Nelson Thomas J. , Backlund Peter S. , Alkon Daniel L. 
Published: February 2004

AbstractMemory consolidation in mammalian brain is accompanied by widespread reorganization of synaptic contacts and dendritic structure. Understanding of the protein‐protein interactions that underlie these structural changes has been hampered by the difficulty of studying protein‐protein interactions produced in vivo by signaling, learning, and other physiological responses using current methodologies. Using a novel technique that separates interacting proteins from noninteracting proteins on the basis of their protein‐target affinity, we identified 16 proteins for which protein‐target binding is altered in vivo by spatial learning, including stathmin, complexin I, 14‐3‐3, and several structural proteins including F‐actin capping protein, tubulin, GFAP, and actin. Interactions between complexin and its targets (p25α and Drac1‐like protein) and the interaction between CapZ and tubulin were calcium‐dependent. The preponderance of structural proteins and proteins involved in synapse formation and reorganization of growth cones among proteins undergoing memory‐specific changes in protein‐protein interactions suggests that synaptic structural reorganization is a predominant feature of the consolidation phase of memory. © 2004 Wiley‐Liss, Inc.
Detection of novelty, but not memory of spatial habituation, is associated with an increase in phosphorylated cAMP response element‐binding protein levels in the hippocampus
Authors: Winograd Milena , Viola Haydée 
Published: February 2004

AbstractThere is a growing body of evidence showing that the formation of associative memories is associated with an increase in phosphorylated cAMP response element‐binding protein (pCREB) levels. We recently reported increased pCREB levels in the rat hippocampus after an exploration to a novel environment. In the present work, we studied whether this increment in CREB activation is associated with the formation of memory of habituation to a novel environment or with the detection of novelty. Rats were submitted to consecutive open field sessions at 3‐h intervals. Measurement of the hippocampal pCREB level, carried out 1 h after each training session, showed that (1) it did not increase when rats explored a familiar environment; (2) it did not increase after a reexposure that improves the memory of habituation; (3) it increased after a brief novel exploration unable to form memory of habituation; and (4) it increased in amnesic rats for spatial habituation. Taken as a whole, our results suggest that the elevated pCREB level after a single open field exploration is not associated with the memory formation of habituation. It is indeed associated with the detection of a novel environment. © 2003 Wiley‐Liss, Inc.
Effects of age and alcohol exposure during early life on pyramidal cell numbers in the CA1‐CA3 region of the rat hippocampus
Authors: Miki Takanori , Harris Simon J. , Wilce Peter A. , Takeuchi Yoshiki , Bedi Kuldip S. 
Published: February 2004

AbstractWe have previously shown that exposing rats to a relatively high dose of ethanol during early postnatal life can result in an alteration in spatial learning ability. The hippocampal formation is known to be involved in the control of this ability. The purpose of the present study was to determine whether exposure of rats to ethanol during early postnatal life had either immediate or delayed effects on the numbers of pyramidal cells in the CA1‐CA3 subregion of the hippocampus. Wistar rats were exposed to a relatively high daily dose of ethanol at postnatal day 10–15 by placing them for 3 h/day in a chamber containing ethanol vapor. Groups of ethanol‐treated (ET), separation control (SC), and mother‐reared control (MRC) rats were anesthetized and killed at 16 and 30 days of age by perfusion with phosphate‐buffered 2.5% glutaraldehyde. The Cavalieri principle was used to determine the volumes of the CA1 and CA2+CA3 regions. The physical disector method was used to estimate the numerical density of neurons in each of the subdivisions. The total number of pyramidal cells was calculated by multiplying the appropriate estimates of the numerical density by the volume. There were significant age‐related reductions in the total numbers of pyramidal cells at 16–30 days of age irrespective of the groups examined. Ethanol treated rats were found to have slightly but significantly fewer pyramidal cell neurons than either the MRC or SC groups. These observations indicate that pyramidal cells in the hippocampus may be vulnerable to a relatively high dose of ethanol exposure during this short period of early postnatal life. © 2003 Wiley‐Liss, Inc.
Trace eyeblink conditioning is hippocampally dependent in mice
Authors: Tseng W. , Guan R. , Disterhoft J.F. , Weiss C. 
Published: February 2004

AbstractThe goal of this study was to determine whether trace eyeblink conditioning is a hippocampally dependent associative learning task in the mouse. First, we examined trace intervals of 0, 250, and 500 ms to determine a relatively long trace interval that would support eyeblink conditioning in young adult C57BL/6 mice. Mice rapidly acquired conditioned responses (CRs) with a 0‐ms trace interval, acquired CRs with a 250‐ms trace interval in ∼2 days (2 sessions per day), and showed little acquisition with a 500‐ms trace interval. Control mice were presented randomly unpaired stimuli and failed to show conditioning. We then determined the effect of lesioning dorsal hippocampal neurons on trace eyeblink conditioning. The hippocampus was injected bilaterally with vehicle (phosphate‐buffered saline), 0.1% ibotenic acid, or 1% ibotenic acid. The vehicle group showed >60% CRs. The 0.1% group showed significantly fewer CRs (35–45%). The 1% group showed a level of CRs similar to that of the control mice. All the lesioned mice exhibited >60% CRs when subsequently trained with a 0‐ms trace interval. A regression analysis indicated that the volume of area CA1 lesioned was more predictive of the behavioral impairment than the lesion volume of either CA3 or dentate gyrus, or even the total lesion volume. We conclude that dorsal hippocampal neurons play a critical role in eyeblink conditioning when a 250‐ms trace interval is used with the C57BL/6 mouse, and that this paradigm will be useful for studying behavior and the in vivo and in vitro electrophysiology of hippocampal neurons in normal and transgenic or knockout mice. © 2003 Wiley‐Liss, Inc.
Hypothyroidism impairs late LTP in CA1 region but not in dentate gyrus of the intact rat hippocampus: MAPK involvement
Authors: Gerges Nashaat Z. , Alkadhi Karim A. 
Published: February 2004

AbstractThyroid hormone activates extracellular signal‐regulated kinases (ERK1 and ERK2), which are important in late long‐term potentiation (L‐LTP). The aim of this study was to determine the possible mechanism underlying the impairment of L‐LTP as a result of hypothyroidism. We investigated the effect of hypothyroidism on L‐LTP of the two associative pathways in the hippocampus: the Schaffer collateral synapses and the perforant path synapses. We also examined the effect of hypothyroidism on ERK1 and ERK2 levels in both the CA1 and dentate gyrus (DG) regions of the hippocampus. Electrophysiological recordings from hippocampi of anesthetized rats show that hypothyroidism impairs L‐LTP in CA1 region, but not in the DG. Western blot analysis of the CA1 region shows that hypothyroidism decreases phosphorylated ERK1 and ERK2 levels without affecting their total levels. In the DG of the hypothyroid rat, however, there was no significant change in the levels of phosphorylated or total ERKs. The correlation between the effect of hypothyroidism on L‐LTP and enzyme levels suggests that hypothyroidism‐induced impairment of L‐LTP in CA1 may be due to decreased levels of phosphorylated ERK1 and ERK2. © 2003 Wiley‐Liss, Inc.
Exploration, emotionality, and hippocampal mossy fibers in nonaggressive AB/Gat and congenic highly aggressive mice
Authors: Prior Helmut , Schwegler Herbert , Marashi Vera , Sachser Norbert 
Published: February 2004

AbstractAB/Gat mice and congenic mice bred for high aggressiveness (CS/ag) were tested for exploratory behavior in novel situations and anxiety‐related behavior, using an open‐field test and the elevated plus‐maze test. Subsequently, the size of hippocampal mossy fiber terminal fields was evaluated. Considerably higher exploratory activity was found in nonaggressive mice, whereas aggressive mice exhibited more anxiety‐related behavior. Larger intra‐ and infrapyramidal mossy fiber terminal fields (IIP‐MF) and a larger hilus were found in the highly aggressive strain. Within the nonaggressive AB/Gat strain, larger IIP‐MF were correlated with higher exploratory behavior and lower anxiety in the plus‐maze test. Within the aggressive strain, no individual correlations between hippocampal morphometry and behavior were found. The results corroborate the “ecotype hypothesis,” which suggests that mice of subpopulations with highly aggressive males tend to display reduced exploratory behavior. The findings support the view that genetic factors involved in aggressive behavior also affect hippocampal connectivity. However, our results do not support the hypothesis that a higher level of aggressiveness is necessarily related to smaller IIP‐MF. © 2003 Wiley‐Liss, Inc.
Encoding versus retrieval of spatial memory: Double dissociation between the dentate gyrus and the perforant path inputs into CA3 in the dorsal hippocampus
Authors: Lee Inah , Kesner Raymond P. 
Published: February 2004

AbstractThe hippocampus is an essential neural structure for spatial memory. Computational models suggest that the CA3 subregion of the hippocampus plays an essential role in encoding and retrieval of spatial memory. The perforant path (PPCA3) and dentate gyrus (DG)‐mediated mossy fibers (MFs) compose major afferent inputs into CA3. A possible functional dissociation between these afferent inputs was attempted using a simple navigation test (i.e., the modified Hebb‐Williams maze). Behavioral testing was combined with electrolytic lesions of PPCA3 or neurotoxic lesions of the DG, to eliminate each afferent input into CA3. Lesions in either afferent input into CA3 affected learning of an effective navigational path on the maze. The contributions of the two CA3 afferent inputs, however, were different regarding encoding and retrieval of memory measured based on indices operationally defined for the behavioral paradigm (i.e., encoding, the number of errors reduced within a day; retrieval, the number of errors reduced between days). The DG‐lesioned animals exhibited deficits regarding the encoding index, but not the retrieval index, whereas the PPCA3‐lesioned rats displayed deficits regarding the retrieval index, but not the encoding index. The results suggest that the two major afferent inputs of CA3 may contribute differentially to encoding and retrieval of spatial memory. © 2004 Wiley‐Liss, Inc.
A critical role for the anterior hippocampus in relational memory: Evidence from an fMRI study comparing associative and item recognition
Authors: Sullivan Giovanello Kelly , Schnyer David M. , Verfaellie Mieke 
Published: February 2004

AbstractNeuroscientific research has established that the hippocampal formation, a structure within the medial temporal lobe (MTL), plays a critical role in memory for facts and events (declarative memory) (Milner et al., 1998). However, its precise role remains unclear. According to one view, the hippocampus has a special role in relating or binding together previously unrelated pieces of information, while another view proposes that the hippocampus is equally involved in all forms of declarative memory, regardless of their demands on relational processing. Using functional magnetic resonance imaging (fMRI), we show that hippocampal activation is modulated by the extent to which a retrieval task depends on relational processing. © 2003 Wiley‐Liss, Inc.
On the irregularity strength of trees
Authors: Bohman Tom , Kravitz David 
Published: February 2004

AbstractFor any graph G, let ni be the number of vertices of degree i, and $\lambda (G)={max} _{i\le j}\{ {n_i+\cdots +n_j+i-1\over j}\}$. This is a general lower bound on the irregularity strength of graph G. All known facts suggest that for connected graphs, this is the actual irregularity strength up to an additive constant. In fact, this was conjectured to be the truth for regular graphs and for trees. Here we find an infinite sequence of trees with λ(T) = n1 but strength converging to ${11-\sqrt 5\over 8} n_1$. © 2004 Wiley Periodicals, Inc. J Graph Theory 45: 241–254, 2004
Complexity of approximating the oriented diameter of chordal graphs
Authors: Fomin Fedor V. , Matamala Martín , Rapaport Ivan 
Published: February 2004

AbstractThe oriented diameter of a bridgeless connected undirected (bcu) graph G is the smallest diameter among all the diameters of strongly connected orientations of G. We study algorithmic aspects of determining the oriented diameter of a chordal graph. We (a) construct a linear‐time approximation algorithm that, for a given chordal bcu graph G, finds a strongly connected orientation of G with diameter at most one plus twice the oriented diameter of G; (b) prove that, for every k ≥ 2 and k # 3, to decide whether a chordal (split for k = 2) bcu graph G admits an orientation of diameter k is NP‐complete; (c) show that, unless P = NP, there is neither a polynomial‐time absolute approximation algorithm nor an α‐approximation algorithm that computes the oriented diameter of a bcu chordal graph for α < ${3\over2}$. © 2004 Wiley Periodicals, Inc. J Graph Theory 45: 255–269, 2004
Subdivisions of large complete bipartite graphs and long induced paths in k‐connected graphs
Authors: Böhme Thomas , Mohar Bojan , Škrekovski Riste , Stiebitz Michael 
Published: February 2004

AbstractIt is proved that for every positive integers k, r and s there exists an integer n = n(k,r,s) such that every k‐connected graph of order at least n contains either an induced path of length s or a subdivision of the complete bipartite graph Kk,r. © 2004 Wiley Periodicals, Inc. J Graph Theory 45: 270–274, 2004
Spanning 2‐trails from degree sum conditions
Authors: Ellingham M. N. , Zha Xiaoya , Zhang Yi 
Published: February 2004

AbstractSuppose G is a simple connected n‐vertex graph. Let σ3(G) denote the minimum degree sum of three independent vertices in G (which is ∞ if G has no set of three independent vertices). A 2‐trail is a trail that uses every vertex at most twice. Spanning 2‐trails generalize hamilton paths and cycles. We prove three main results. First, if σ3G)≥ n ‐ 1, then G has a spanning 2‐trail, unless G ≅ K1,3. Second, if σ3(G) ≥ n, then G has either a hamilton path or a closed spanning 2‐trail. Third, if G is 2‐edge‐connected and σ3(G) ≥ n, then G has a closed spanning 2‐trail, unless G ≅ K2,3 or K (the 6‐vertex graph obtained from K2,3 by subdividing one edge). All three results are sharp. These results are related to the study of connected and 2‐edge‐connected factors, spanning k‐walks, even factors, and supereulerian graphs. In particular, a closed spanning 2‐trail may be regarded as a connected (and 2‐edge‐connected) even [2,4]‐factor. © 2004 Wiley Periodicals, Inc. J Graph Theory 45: 298–319, 2004
Tutte's spring theorem
Authors: Thomassen Carsten 
Published: February 2004

AbstractWe present a short proof of the theorem of Tutte that every planar 3‐connected graph has a drawing in the plane such that every vertex which is not on the outer cycle is the barycenter of its neighbors. Moreover, this holds for any prescribed representation of the outer cycle. © 2004 Wiley Periodicals, Inc. J Graph Theory 45: 275–280, 2004
Proof of Mader's conjecture on k‐critical n‐connected graphs
Authors: Jianji Su 
Published: February 2004

AbstractMader conjectured that every k‐critical n‐connected noncomplete graph G has 2k + 2 pairwise disjoint fragments. The author in 9 proved that the conjecture holds if the order of G is greater than (k + 2)n. Now we settle this conjecture completely. © 2004 Wiley Periodicals, Inc. J Graph Theory 45: 281–297, 2004
Minocycline enhances MPTP toxicity to dopaminergic neurons
Authors: Yang Lichuan , Sugama Shuei , Chirichigno Jason W. , Gregorio Jason , Lorenzl Stefan , Shin Dong H. , Browne Susan E. , Shimizu Yoshinori , Joh Tong H. , Beal M. Flint , Albers David S. 
Published: February 2004

AbstractMinocycline has been shown previously to have beneficial effects against ischemia in rats as well as neuroprotective properties against excitotoxic damage in vitro, nigral cell loss via 6‐hydroxydopamine, and to prolong the life‐span of transgenic mouse models of Huntington's disease (HD) and amyotrophic lateral sclerosis (ALS). We investigated whether minocycline would protect against toxic effects of 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP), a toxin that selectively destroys nigrostriatal dopaminergic (DA) neurons and produces a clinical state similar to Parkinson's disease (PD) in rodents and primates. We found that although minocycline inhibited microglial activation, it significantly exacerbated MPTP‐induced damage to DA neurons. We present evidence suggesting that this effect may be due to inhibition of DA and 1‐methyl‐4‐phenylpridium (MPP+) uptake into striatal vesicles. © 2003 Wiley‐Liss, Inc.
Neurotrophic factors expressed in both cortex and spinal cord induce axonal plasticity after spinal cord injury
Authors: Zhou Lijun , Shine H. David 
Published: February 2004

AbstractWe reported recently that overexpression of neurotrophin‐3 (NT‐3) by motoneurons in the spinal cord of rats will induce sprouting of corticospinal tract (CST) axons (Zhou et al. [2003] J. Neurosci. 23:1424–1431). We now report that overexpression of brain‐derived neurotrophic factor (BDNF) or glial cell‐derived neurotrophic factor (GDNF) in the rat sensorimotor cortex near the CST neuronal cell bodies together with overexpression of NT‐3 in the lumbar spinal cord significantly increases axonal sprouting compared to that induced by NT‐3 alone. Two weeks after unilaterally lesioning the CST at the level of the pyramids, we injected rats with saline or adenoviral vectors (Adv) carrying genes coding for BDNF (Adv.BDNF), GDNF (Adv.GDNF) or enhanced green fluorescent protein (Adv.EGFP) at six sites in the sensorimotor cortex, while delivering Adv.NT3 to motoneurons in each of these four groups on the lesioned side of the spinal cord by retrograde transport from the sciatic nerve. Four days later, biotinylated dextran amine (BDA) was injected into the sensorimotor cortex on the unlesioned side to mark CST axons in the spinal cord. Morphometric analysis of axonal sprouting 3 weeks after BDA injection showed that the number of CST axons crossing the midline in rats treated with Adv.BDNF or Adv.GDNF were 46% and 52% greater, respectively, than in rats treated with Adv.EGFP or PBS (P < 0.05). These data demonstrate that sustained local expression of neurotrophic factors in the sensorimotor cortex and spinal cord will promote increased axonal sprouting after spinal cord injury, providing a basis for continued development of neurotrophic factor therapy for central nervous system damage. © 2003 Wiley‐Liss, Inc.