bluuebunny/crossref_metadata_2025 huggingface dataset:
Exercise and postprandial lipid metabolism – an analysis of the current evidence
Authors: Gill Jason M. R.
Published: February 2004

Exaggerated levels of postprandial lipaemia are implicated in the atherosclerotic disease process and are a risk marker for cardiovascular disease. Postprandial lipaemia is reduced following an exercise session and the energy expended during exercise is an important determinant of the extent of triglyceride (TG) lowering. Interestingly, the TG‐lowering effect of an exercise session cannot be replicated by restricting energy intake to elicit a similar level of energy deficit. It seems likely that the low levels of postprandial lipaemia experienced by endurance‐trained individuals are largely due to the TG‐lowering effects of individual exercise sessions, rather than long‐term training adaptations, although trained individuals may also benefit from the hypotriglyceridaemic effects of having low levels of body fat. Increased lipoprotein lipase‐mediated TG clearance and reduced hepatic TG secretion are both likely to contribute to the TG reductions seen following an exercise session, but the relative importance of these two mechanisms is likely to depend on a number of factors including the energy expended during exercise and the training status of the exercising subject. Further study is needed to determine the effectiveness of exercise in reducing postprandial lipaemia in groups at increased risk for cardiovascular disease and to assess the impact of these lipoprotein changes on other aspects of cardiovascular risk.
Ability of GDNF to diminish free radical production leads to protection against kainate‐induced excitotoxicity in hippocampus
Authors: Cheng Henrich , Fu Yu‐Show , Guo Jiun‐Wen
Published: February 2004

The primary aim of this study is to explore the protective mechanisms of glial‐derived neurotrophic factor (GDNF) during excitotoxicity by kainate in the hippocampus. After a 15‐min microinjection with kainate, excitotoxicity was induced in the rat hippocampus. The protective effect of GDNF in the hippocampus was evaluated by administering GDNF 14 min after injection of kainate. The resulting hydroxyl free radicals were quantified by microdialysis of the hippocampus. The results show that GDNF can effectively suppress the production of kainate‐induced hydroxyl free radical production. In addition, histological observation indicated the ability of GDNF to decrease the damage level of pyramidal neurons in the CA3 and CA4 areas of the hippocampus. Superoxide dismutase (SOD) activity in the hippocampus was elevated significantly at 30 min and 7 days after kainate induction, while glutathione peroxidase (cGPx) activity did not increase significantly until the seventh day. With GDNF treatment, SOD and cGPx activity in the hippocampus was elevated significantly 7 days after kainate induction. We suggest that mechanisms including a decrease in free radical generation and scavenging of free radicals might be involved in GDNF protection against kainate‐induced excitotoxicity. © 2003 Wiley‐Liss, Inc.
Preserved anterograde and retrograde memory of rapidly acquired olfactory discrminations after neurotoxic hippocampal lesions
Authors: Jonasson Zachariah , Ballantyne John K. , Baxter Mark G.
Published: February 2004

A forced‐choice discrimination paradigm was used in two experiments, to evaluate retrograde and anterograde amnesia in rats after hippocampal ablation. In a within‐subjects design (Experiment 1), rats were trained on a set of 10 olfactory discriminations 4 weeks before surgery and on a separate set of 10 discriminations 1 week before surgery. In a mixed design (Experiment 2), rats were trained on olfactory discriminations in one of three conditions: condition 1 (10 discriminations at 4 weeks before surgery); condition 2 (10 discriminations at 1 week before surgery); or condition 3 (10 discriminations at 4 weeks before surgery and 10 discriminations at 1 week before surgery). Discriminations in both experiments were rapidly learned, requiring 7–10 trials to reach criterion. After training, half of the rats in each condition received bilateral neurotoxic lesions of the hippocampus, and the other half received sham surgery. One week after surgery, all rats were given a retention test, consisting of a single critical trial for each discrimination. In both experiments, rats with selective hippocampal lesions exhibited preserved retention of these olfactory discriminations with no observable retention gradient. A postoperative acquisition test for two new discriminations indicated that anterograde memory was also preserved, while a postoperative test of spatial learning in the Morris water maze confirmed that the hippocampal lesions impaired spatial learning. Together, these experiments refute the contention that the hippocampus is requisite for (nonspatial) olfactory memory consolidation, storage, or access, despite the condition that the information be rapidly acquired. © 2003 Wiley‐Liss, Inc.
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

c‐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

Experiments 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

Memory 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

There 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

We 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

The 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

Thyroid 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

AB/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

The 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

Neuroscientific 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

For 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

The 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

It 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

Suppose 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

We 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

Mader 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

Minocycline 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

We 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.
The phosphorylation state of neuronal processes determines growth cone formation after neuronal injury
Authors: Geddis Matthew S. , Rehder Vincent
Published: February 2004

Growth cones are essential for neuronal pathfinding during embryonic development and again after injury, when they aid in neuronal regeneration. This study was aimed at investigating the role of kinases in the earliest events in neuronal regeneration, namely, the formation of new growth cones from injured neuronal processes. Neurites of identified snail neurons grown in vitro were severed, and the formation of growth cones was observed from the ends of such transected processes. Under control conditions, all neurites formed a new growth cone within 45 min of transection. In contrast, growth cone formation in the presence of a general kinase inhibitor, K252a, was significantly inhibited. Moreover, decreasing the phosphorylation state of neurites by activating protein phosphatases with C2‐ceramide also reduced growth cone formation. Pharmacological analysis with specific kinase inhibitors suggested that targets of protein kinase C (PKC) and tyrosine kinase (PTK) phosphorylation control growth cone formation. Inhibition of PKC with calphostin C and cerebroside completely blocked growth cone formation, whereas the inhibition of PTK with erbstatin analog significantly reduced growth cone formation. In contrast, inhibitors of protein kinase A, protein kinase G, CaM‐kinase II, myosin light‐chain kinase, Rho kinase, and PI‐3 kinase had little or no effect 45 min after transection. These results suggest that the transformation underlying the formation of a growth cone from an injured (transected) neurite stump is highly sensitive to the phosphorylation state of key target proteins. Therefore, injury‐induced signaling events will determine the outcome of neuronal regeneration through their action on kinase and phosphatase activities. © 2003 Wiley‐Liss, Inc.
Lymphocyte regulation of neuropeptide gene expression after neuronal injury
Authors: Armstrong Brian D. , Hu Zhongting , Abad Catalina , Yamamoto Miya , Rodriguez Williams I. , Cheng Jennifer , Tam Jimmy , Gomariz Rosa P. , Patterson Paul H. , Waschek James A.
Published: February 2004

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylyl cyclase‐activating peptide (PACAP) are induced strongly in neurons after several types of injury, and exhibit neuroprotective actions in vitro and in vivo. It is thought that changes in expression of neuropeptides and other molecules in injured neurons are mediated by new factors produced in Schwann and immune cells at the injury site, a loss of target‐derived factors, or a combination of mediators. To begin to determine the role of the inflammatory mediators, we investigated axotomy‐induced changes in VIP and PACAP gene expression in the facial motor nucleus in severe combined immunodeficient (SCID) mice, and in mice with targeted mutations in specific cytokine genes. In normal mice, VIP and PACAP mRNA was induced strongly in facial motor neurons 4 days after axotomy. The increase in PACAP mRNA was blocked selectively in SCID mice, indicating that mechanisms responsible for VIP and PACAP gene induction are not identical. The loss of PACAP gene expression in SCID mice after axotomy was fully reversed by an infusion of normal splenocytes, suggesting that PACAP mRNA induction requires inflammatory mediators. PACAP and VIP mRNA inductions, however, were maintained in mice lacking leukemia inhibitory factor (LIF) and interleukin‐6 (IL‐6), and in mice lacking both receptors for tumor necrosis factor α (TNFα). The data suggest that an inflammatory response, most likely involving T lymphocytes, is necessary for the axotomy‐induced increase in PACAP but not in VIP. LIF, IL‐6, and TNFα, however, are not required for this response to injury. © 2003 Wiley‐Liss, Inc.
Presenilin 1 is involved in maturation and trafficking of N‐cadherin to the plasma membrane
Authors: Uemura Kengo , Kitagawa Naoyuki , Kohno Ryuichi , Kuzuya Akira , Kageyama Takashi , Chonabayashi Kazuhisa , Shibasaki Hiroshi , Shimohama Shun
Published: February 2004

One pathological characteristic of Alzheimer's disease (AD) is extensive synapse loss. Presenilin 1 (PS1) is linked to the pathogenesis of early onset familial Alzheimer's disease (FAD) and is localized at the synapse, where it binds N‐cadherin and modulates its adhesive activity. To elucidate the role of the PS1/N‐cadherin interaction in synaptic contact, we established SH‐SY5Y cells stably expressing wild‐type (wt) PS1 and dominant‐negative (D385A) PS1. We show that the formation of cadherin‐based cell–cell contact among SH‐SY5Y cells stably expressing D385A PS1 was suppressed. Conversely, wt PS1 cells exhibited enhanced cell–cell contact and colony formation. Suppression of cell–cell contact in D385A cells was accompanied by an alteration in N‐cadherin subcellular localization; N‐cadherin was retained mainly in the endoplasmic reticulum (ER) and cell surface expression was reduced. We conclude that PS1 is essential for efficient trafficking of N‐cadherin from the ER to the plasma membrane. PS1‐mediated delivery of N‐cadherin to the plasma membrane is important for N‐cadherin to exert its physiological function, and it may control the state of cell–cell contact. © 2003 Wiley‐Liss, Inc.
Fos‐B expression is required for polyamine‐induced increase in nuclear activator protein‐1 DNA binding in discrete structures of murine brain
Authors: Inoue Keiji , Kuramoto Nobuyuki , Sugiyama Chie , Taniura Hideo , Sakata Katsumi , Fujinami Yoshiaki , Ogita Kiyokazu , Yoneda Yukio
Published: February 2004

Spermidine (SPD) and spermine (SPN) have been shown to be endogenous agonists for N‐methyl‐D‐aspartate (NMDA) receptors that could lead to expression of the nuclear transcription factor activator protein‐1 (AP1) complex in the mammalian central nervous system both in vitro and in vivo. In nuclear extracts of murine whole brain, AP1 DNA binding increased significantly in a concentration‐dependent manner with the addition of either SPD or SPN at a concentration range of 50–500 μM. Similarly, the nuclear proteins histone and dephosphorylated casein, but not phosphorylated casein, significantly increased AP1 DNA binding alone but in the presence of either SPD or SPN did not increase further binding. By contrast, another endogenous polyamine, putrescine, significantly prevented AP1 DNA binding increases by histone and dephosphorylated casein, but did not by itself significantly alter binding. Invariably, SPD and SPN effected significantly increased AP1 DNA binding in neocortex, hippocampus, striatum, midbrain, hypothalamus and cerebellum, but not in medulla‐pons and spinal cord. Supershift and Western blotting analyses revealed relatively high constitutive expression of Fos‐B protein in neocortex and hippocampus, but not in medulla‐pons and spinal cord. Immunoprecipitation of Fos‐B led to complete abolition of the ability of SPN and SPD to increase AP1 DNA binding in neocortical and hippocampal nuclear extracts. These results suggest that expression of Fos‐B protein may be required for modulation of nuclear gene transcription by both SPD and SPN through stimulation DNA‐binding activity of AP1 complex in murine central structures. © 2003 Wiley‐Liss, Inc.
Blood‐spinal cord barrier after spinal cord injury: Relation to revascularization and wound healing
Authors: Whetstone William D. , Hsu Jung‐Yu C. , Eisenberg Manuel , Werb Zena , Noble‐Haeusslein Linda J.
Published: February 2004

Spinal cord injury produces prominent disruption of the blood‐spinal cord barrier. We have defined the blood‐spinal cord barrier breakdown to the protein luciferase (61 kDa) in the acutely injured murine spinal cord and during revascularization. We show that newly formed and regenerating blood vessels that have abnormal permeability exhibit differential expression of the glucose‐1 transporter (Glut‐1), and that its expression is dependent on astrocytes. There was overt extravasation of luciferase within the first hour after injury, a period that coincided with marked tissue disruption within the epicenter of the lesion. Although there was a significant reduction in the number of blood vessels relative to controls by 24 hr after injury, abnormal barrier permeability remained significantly elevated. A second peak of abnormal barrier permeability at 3–7 days postinjury coincided with prominent revascularization of the epicenter. The barrier to luciferase was restored by 21 days postinjury and vascularity was similar to that of controls. During wound‐healing process, the cord was reorganized into distinct domains. Between 14 and 21 days postinjury, each domain consisted primarily of nonneuronal cells, including macrophages. Astrocytes were limited characteristically to the perimeter of each domain. Only blood vessels affiliated closely with astrocytes in the perimeter expressed Glut‐1, whereas blood vessels within each domain of the repairing cord did not express it. Together, these data demonstrate that both injured and regenerating vessels exhibit abnormal permeability and suggest that Glut‐1 expression during revascularization is dependent on the presence of astrocytes. © 2003 Wiley‐Liss, Inc.
HIV‐1 Tat protein alters tight junction protein expression and distribution in cultured brain endothelial cells
Authors: András Ibolya E. , Pu Hong , Deli Mária A. , Nath Avindra , Hennig Bernhard , Toborek Michal
Published: February 2004

Disruption of the blood‐brain barrier (BBB) is widely believed to be the main route of human immunodeficiency virus (HIV) entry into the central nervous system (CNS). Although mechanisms of this process are not fully understood, alterations of tight junction protein expression can contribute, at least in part, to this phenomenon. Tight junctions are critical structural and functional elements of cerebral microvascular endothelial cells and the BBB. The aim of the present study was to examine the effects of HIV‐1 Tat protein on expression of tight junction proteins. Primary cultures of brain microvascular endothelial cells (BMEC) were employed in these experiments. A 24‐hr exposure of BMEC to Tat1–72 resulted in a decrease of claudin‐1, claudin‐5, and zonula occludens (ZO)‐2 expression, whereas total levels of occludin and ZO‐1 remained unchanged. In addition, a short (3‐hr) exposure of BMEC to Tat1–72 induced cellular redistribution of claudin‐5 immunoreactivity. Tat1–72‐induced alterations of claudin‐5 expression also were confirmed in vivo where Tat1–72 was injected into the right hippocampus of mice. These findings indicate that HIV‐1 Tat protein can markedly affect expression and distribution of specific tight junction proteins in brain endothelium. Alterations of only distinct tight junction proteins suggest a finely tuned effect of Tat1–72 on the BBB. Because tight junction proteins are critical for the barrier function of the BBB, such alterations can lead to disturbances of the BBB integrity and contribute to HIV trafficking into the brain. © 2003 Wiley‐Liss, Inc.
Involvement of Gas7 in nerve growth factor‐independent and dependent cell processes in PC12 cells
Authors: Chao Chuck C.‐K. , Su L.‐J. , Sun N.‐K. , Ju Y.‐T. , Lih Jason C.‐J. , Lin‐Chao Sue
Published: February 2004

Gas7, a growth arrest‐specific gene originally isolated from serum‐starved mouse fibroblast cells, is expressed in vivo predominantly in the brain and is required for neurite formation in cultured mouse cerebellar neurons (Ju et al. [ 1998] Proc. Natl. Acad. Sci. USA 95: 11423–11428). Here we report that Gas7 plays a key role in the morphological differentiation of PC12 preneuronal rat pheochromocytoma cells (PC12 cells). We found that overexpression of murine Gas7 in PC12 cells leads to an expanded cell morphology and promotes spike‐like cell processes that resemble the early stages of neurite formation. These processes undergo elongation upon addition of nerve growth factor (NGF). We also found that the addition of NGF induces the production of endogenous rat‐Gas7 (rGas7), which is transiently elevated prior to the appearance of NGF‐promoted neurite outgrowths. Furthermore, inhibition of endogenous rGas7 production by antisense nucleotides complimentary to the translation initiation region of a rGas7 cDNA (AJ131902) reduces the NGF‐promoted neurite outgrowths. Our results demonstrate that Gas7 by itself influences early cell morphological development and likely functions as an early‐stage intermediary in NGF‐induced neuronal differentiation of PC12 culture cells. © 2003 Wiley‐Liss, Inc.
Functional assay for human CD4+CD25+ Treg cells reveals an age‐dependent loss of suppressive activity
Authors: Tsaknaridis Laura , Spencer Leslie , Culbertson Nicole , Hicks Kevin , LaTocha Dorian , Chou Yuan K. , Whitham Ruth H. , Bakke Antony , Jones Richard E. , Offner Halina , Bourdette Dennis N. , Vandenbark Arthur A.
Published: February 2004

CD4+CD25+ regulatory T cells (Treg cells) prevent T cell‐mediated autoimmune diseases in rodents. To develop a functional Treg assay for human blood cells, we used FACS‐ or bead‐sorted CD4+CD25+ T cells from healthy donors to inhibit anti‐CD3/CD28 activation of CD4+CD25− indicator T cells. The data clearly demonstrated classical Treg suppression of CD4+CD25− indicator cells by both CD4+CD25+high and CD4+CD25+low T cells obtained by FACS or magnetic bead sorting. Suppressive activity was found in either CD45RO− (naive) or CD45RO+ (memory) subpopulations, was independent of the TCR signal strength, required cell–cell contact, and was reversible by interleukin‐2 (IL‐2). Of general interest is that a wider sampling of 27 healthy donors revealed an age‐ but not gender‐dependent loss of suppressive activity in the CD4+CD25+ population. The presence or absence of suppressive activity in CD4+CD25+ T cells from a given donor could be demonstrated consistently over time, and lack of suppression was not due to method of sorting, strength of signal, or sensitivity of indicator cells. Phenotypic markers did not differ on CD4+CD25+ T cells tested ex vivo from suppressive vs. nonsuppressive donors, although, upon activation in vitro, suppressive CD4+CD25+ T cells had significantly higher expression of both CTLA‐4 and GITR than CD4+CD25− T cells from the same donors. Moreover, antibody neutralization of CTLA‐4, GITR, IL‐10, or IL‐17 completely reversed Treg‐induced suppression. Our results are highly consistent with those reported for murine Treg cells and are the first to demonstrate that suppressive activity of human CD4+CD25+ T cells declines with age. Published 2003 Wiley‐Liss, Inc.
Patterned electrical activity modulates sodium channel expression in sensory neurons
Authors: Klein Joshua P. , Tendi Elisabetta A. , Dib‐Hajj Sulayman D. , Fields R. Douglas , Waxman Stephen G.
Published: February 2004

Peripheral nerve injury induces changes in the level of gene expression for sodium channels Nav1.3, Nav1.8, and Nav1.9 within dorsal root ganglion (DRG) neurons, which may contribute to the development of hyperexcitability, ectopic neuronal discharge, and neuropathic pain. The mechanism of this change in sodium channel expression is unclear. Decreased availability of neurotrophic factors following axotomy contributes to these changes in gene transcription, but the question of whether changes in intrinsic neuronal activity levels alone can trigger changes in the expression of these sodium channels has not been addressed. We examined the effect of electrical stimulation on the expression of Nav1.3, Nav1.8, and Nav1.9 by using cultured embryonic mouse sensory neurons under conditions in which nerve growth factor (NGF) was not limiting. Expression of Nav1.3 was not significantly changed following stimulation. In contrast, we observed activity‐dependent down‐regulation of Nav1.8 and Nav1.9 mRNA and protein levels after stimulation, as demonstrated by quantitative polymerase chain reaction and immunocytochemistry. These results show that a change in neuronal activity can alter the expression of sodium channel genes in a subtype‐specific manner, via a mechanism independent of NGF withdrawal. © 2003 Wiley‐Liss, Inc.
Hypoxia‐induced modification of the inositol triphosphate receptor in neuronal nuclei of newborn piglets: Role of nitric oxide
Authors: Mishra Om Prakash , Qayyum Imaran , Delivoria‐Papadopoulos Maria
Published: February 2004

Previous studies have shown that hypoxia results in increased Ca2+ influx in neuronal nuclei and generation of nitric oxide (NO) free radicals in the cerebral cortical tissue of newborn piglets. The present study tests the hypothesis that hypoxia results in modification of the inositol triphosphate (IP3) receptor characteristics in neuronal nuclei and that the hypoxia‐induced modification of the IP3 receptor is NO mediated. Studies were performed in piglets, 3–5 days old, divided into normoxic (n = 5), hypoxic (n = 5), and NO synthase (NOS) inhibitor N‐nitro‐L‐arginine (NNLA)‐treated hypoxic (n = 5) groups. The NNLA‐treated hypoxic group received an infusion of NNLA (40 mg/kg) over 1 hr prior to hypoxic exposure. The hypoxia was induced by lowering the FiO2 to 0.05–0.07 for 1 hr. Brain tissue hypoxia was documented biochemically by determining ATP and phosphocreatine (PCr) levels. Neuronal nuclei were isolated from the cerebral cortical tissue, and IP3 receptor binding was performed in a medium containing 50 mM HEPES (pH 8.0), 2 mM EDTA, 3H‐IP3 (7.5–100 nM), and 100 μg nuclear protein. Nonspecific binding was determined in the presence of 10 μM unlabelled IP3. The IP3 receptor characteristics Bmax (number of receptor sites) and Kd (dissociation constant) were determined. In normoxic, hypoxic, and NNLA‐hypoxic groups, ATP levels were 4.46 ± 0.35, 1.52 ± 0.10 (P < .05 vs. normoxic), and 1.96 ± 0.33 μmoles/g brain, respectively (P < .05 vs. normoxic). PCr levels were 3.75 ± 0.35, 0.87 ± 0.09 (P < .05 vs. normoxic), and 1.31 ± 0.10 μmoles/g brain, respectively (P < .05 vs. normoxic). IP3 receptor binding characteristics in normoxic nuclear membranes showed that the Bmax value was 150.0 ± 14.1 pmoles/mg protein compared with 239.3 ± 13.6 pmoles/mg protein in the hypoxic group (P < .05). In the NNLA‐treated hypoxic group, the Bmax value was 159.0 ± 42.6 pmoles/mg protein (P < .05 vs. hypoxic a, P = NS vs. normoxic). Similarly, the Kd was 25.2 ± 0.28 nM in the normoxic group, 44.6 ± 5.4 nM in the hypoxic group (P < .05), and 28.1 ± 6.4 nM in the NNLA‐treated hypoxic group. (P < .05 vs. hypoxic and P = NS vs. normoxic). The results show that hypoxia results in increased Bmax and Kd values for the IP3 receptor. Furthermore, the data demonstrate that administration of NNLA prior to hypoxia prevents the hypoxia‐induced modification of the IP3 receptor in neuronal nuclei of newborn piglets. Because NNLA inhibits NOS and prevents generation of NO, we conclude that the mechanism of hypoxia‐induced modification of the neuronal nuclear membrane IP3 receptor is NO mediated. We propose that NO‐mediated modification of the IP3 receptor during hypoxia may lead to increased intranuclear Ca2+, resulting in altered transcription of apoptotic genes and activation of cascades of hypoxia‐induced programmed neuronal death. © 2003 Wiley‐Liss, Inc.