bluuebunny/crossref_metadata_2025 huggingface dataset:
Distinct ligand binding sites in integrin α3β1 regulate matrix adhesion and cell–cell contact
Authors: Zhang Feng , Tom Clifford C. , Kugler Matthias C. , Ching Tsui-Ting , Kreidberg Jordan A. , Wei Ying , Chapman Harold A.
Published: October 2003

The integrin α3β1 mediates cellular adhesion to the matrix ligand laminin-5. A second integrin ligand, the urokinase receptor (uPAR), associates with α3β1 via a surface loop within the α3 β-propeller (residues 242–246) but outside the laminin binding region, suggesting that uPAR–integrin interactions could signal differently from matrix engagement. To explore this, α3−/− epithelial cells were reconstituted with wild-type (wt) α3 or α3 with Ala mutations within the uPAR-interacting loop (H245A or R244A). Wt or mutant-bearing cells showed comparable expression and adhesion to laminin-5. Cells expressing wt α3 and uPAR dissociated in culture, with increased Src activity, up-regulation of SLUG, and down-regulation of E-cadherin and γ-catenin. Src kinase inhibition or expression of Src 1–251 restored the epithelial phenotype. The H245A and R244A mutants were unaffected by coexpression of uPAR. We conclude that α3β1 regulates both cell–cell contact and matrix adhesion, but through distinct protein interaction sites within its β-propeller. These studies reveal an integrin- and Src-dependent pathway for SLUG expression and mesenchymal transition.
AIP is a mitochondrial import mediator that binds to both import receptor Tom20 and preproteins
Authors: Yano Masato , Terada Kazutoyo , Mori Masataka
Published: October 2003

Most mitochondrial preproteins are maintained in a loosely folded import-competent conformation by cytosolic chaperones, and are imported into mitochondria by translocator complexes containing a preprotein receptor, termed translocase of the outer membrane of mitochondria (Tom) 20. Using two-hybrid screening, we identified arylhydrocarbon receptor–interacting protein (AIP), an FK506-binding protein homologue, interacting with Tom20. The extreme COOH-terminal acidic segment of Tom20 was required for interaction with tetratricopeptide repeats of AIP. An in vitro import assay indicated that AIP prevents preornithine transcarbamylase from the loss of import competency. In cultured cells, overexpression of AIP enhanced preornithine transcarbamylase import, and depletion of AIP by RNA interference impaired the import. An in vitro binding assay revealed that AIP specifically binds to mitochondrial preproteins. Formation of a ternary complex of Tom20, AIP, and preprotein was observed. Hsc70 was also found to bind to AIP. An aggregation suppression assay indicated that AIP has a chaperone-like activity to prevent substrate proteins from aggregation. These results suggest that AIP functions as a cytosolic factor that mediates preprotein import into mitochondria.
Huntingtin forms toxic NH2-terminal fragment complexes that are promoted by the age-dependent decrease in proteasome activity
Authors: Zhou Hui , Cao Fengli , Wang Zhishan , Yu Zhao-Xue , Nguyen Huu-Phuc , Evans Joy , Li Shi-Hua , Li Xiao-Jiang
Published: October 2003

Although NH2-terminal mutant huntingtin (htt) fragments cause neurological disorders in Huntington's disease (HD), it is unclear how toxic htt fragments are generated and contribute to the disease process. Here, we report that complex NH2-terminal mutant htt fragments smaller than the first 508 amino acids were generated in htt-transfected cells and HD knockin mouse brains. These fragments constituted neuronal nuclear inclusions and appeared before neurological symptoms. The accumulation and aggregation of these htt fragments were associated with an age-dependent decrease in proteasome activity and were promoted by inhibition of proteasome activity. These results suggest that decreased proteasome activity contributes to late onset htt toxicity and that restoring the ability to remove NH2-terminal fragments will provide a more effective therapy for HD than inhibiting their production.
A role for Yip1p in COPII vesicle biogenesis
Authors: Heidtman Matthew , Chen Catherine Z. , Collins Ruth N. , Barlowe Charles
Published: October 2003

Yeast Ypt1p-interacting protein (Yip1p) belongs to a conserved family of transmembrane proteins that interact with Rab GTPases. We encountered Yip1p as a constituent of ER-derived transport vesicles, leading us to hypothesize a direct role for this protein in transport through the early secretory pathway. Using a cell-free assay that recapitulates protein transport from the ER to the Golgi complex, we find that affinity-purified antibodies directed against the hydrophilic amino terminus of Yip1p potently inhibit transport. Surprisingly, inhibition is specific to the COPII-dependent budding stage. In support of this in vitro observation, strains bearing the temperature-sensitive yip1-4 allele accumulate ER membranes at a nonpermissive temperature, with no apparent accumulation of vesicle intermediates. Genetic interaction analyses of the yip1-4 mutation corroborate a function in ER budding. Finally, ordering experiments show that preincubation of ER membranes with COPII proteins decreases sensitivity to anti-Yip1p antibodies, indicating an early requirement for Yip1p in vesicle formation. We propose that Yip1p has a previously unappreciated role in COPII vesicle biogenesis.
Cdc48p is required for the cell cycle commitment point at Start via degradation of the G1-CDK inhibitor Far1p
Authors: Fu Xinrong , Ng Christine , Feng Daorong , Liang Chun
Published: October 2003

The budding yeast Cdc48p and its mammalian homologue p97 are involved in many important cellular activities. Because previous cdc48 mutants have exclusive G2/M arrest, Cdc48p was thought to play an essential role only during mitosis. We found that Cdc48p is required for the execution of Start (a yeast cell cycle commitment point equivalent to the restriction point in mammalian cells) in both a normal mitotic cell cycle and cell cycle reentry after mating pheromone withdrawal through degradation of the G1–cyclin-dependent kinase inhibitor Far1p. Our work is the first to uncover novel roles of Cdc48p as a critical cell cycle regulator in G1, and to shed new light on cell cycle regulation of Far1p, which is the first cyclin-dependent kinase inhibitor shown to be a substrate of an essential proteolysis event mediated by Cdc48p.
The distribution of prime ideals of imaginary quadratic fields
Authors: Harman G. , Kumchev A. , Lewis P.
Published: October 2003

Let

Q
(
x
,
y
)

Q(x, y)

be a primitive positive definite quadratic form with integer coefficients. Then, for all

(
s
,
t
)
∈

R

2

(s, t)\in \mathbb R^2

there exist

(
m
,
n
)
∈

Z

2

(m, n) \in \mathbb Z^2

such that

Q
(
m
,
n
)

Q(m, n)

is prime and
\[

Q
(
m
−
s
,
n
−
t
)
≪
Q
(
s
,
t

)

0.53

+
1.

Q(m - s, n - t) \ll Q(s, t)^{0.53} + 1.

\]
This is deduced from another result giving an estimate for the number of prime ideals in an ideal class of an imaginary quadratic number field that fall in a given sector and whose norm lies in a short interval.
Asymptotic relations among Fourier coefficients of automorphic eigenfunctions
Authors: Wolpert Scott
Published: October 2003

A detailed stationary phase analysis is presented for noncompact parameter ranges of the family of elementary eigenfunctions on the hyperbolic plane

K

(
z
)
=

y

1

/

2

K

i
r

(
2
π
m
y
)

e

2
π
i
m
x

\mathcal {K}(z)=y^{1/2}K_{ir}(2\pi my)e^{2\pi im x}

,

z
=
x
+
i
y

z=x+iy

,

λ
=

1
4

+

r
2

\lambda =\frac 14+r^2

the eigenvalue,

s
=
2
π
m

λ

−
1

/

2

s=2\pi m\lambda ^{-1/2}

and

K

i
r

K_{ir}

the Macdonald-Bessel function. The phase velocity of

K

\mathcal {K}

on

{

|

s

|

I
m
z
≤
1
}

\{|s|Im z\le 1\}

is a double-valued vector field, the tangent field to the pencil of geodesics

G

\mathcal {G}

tangent to the horocycle

{

|

s

|

I
m
z
=
1
}

\{|s|Im z =1 \}

. For

A
∈
S
L
(
2
;

R

)

A\in SL(2;\mathbb {R})

a multi-term stationary phase expansion is presented in

λ
\lambda

for

K

(
A
z
)

e

2
π
i
n

R
e
z

\mathcal {K}(Az)e^{2\pi in\,Re z}

uniform in parameters. An application is made to find an asymptotic relation for the Fourier coefficients of a family of automorphic eigenfunctions. In particular, for

ψ
\psi

automorphic with coefficients

{

a
n

}

\{a_n\}

and eigenvalue

λ
\lambda

it is shown for the special range

n
∼

λ

1

/

2

n\sim \lambda ^{1/2}

that

a
n

a_n

is

O
(

λ

1

/

4

e

π

λ

1

/

2

/

2

)

O(\lambda ^{1/4}\,e^{\pi \lambda ^{1/2}/2})

for

λ
\lambda

large, improving by an order of magnitude for this special range upon the estimate from the general Hecke bound

O
(

|

n

|

1

/

2

λ

1

/

4

e

π

λ

1

/

2

/

2

)

O(|n|^{1/2}\lambda ^{1/4}\,e^{\pi \lambda ^{1/2}/2})

. An exposition of the WKB asymptotics of the Macdonald-Bessel functions is presented.
Some Picard theorems for minimal surfaces
Authors: López Francisco
Published: October 2003

This paper deals with the study of those closed subsets

F
⊂

R

3

F \subset \mathbb {R}^3

for which the following statement holds: If

S
S

is a properly immersed minimal surface in

R

3

\mathbb {R}^3

of finite topology that is eventually disjoint from

F
,

F,

then

S
S

has finite total curvature. The same question is also considered when the conclusion is finite type or parabolicity.
Symmetrization, symmetric stable processes, and Riesz capacities
Authors: Betsakos Dimitrios
Published: October 2003

Let

X

t

\texttt {X}_t

be a symmetric

α
\alpha

-stable process killed on exiting an open subset

D
D

of

R

n

\mathbb R^n

. We prove a theorem that describes the behavior of its transition probabilities under polarization. We show that this result implies that the probability of hitting a given set

B
B

in the complement of

D
D

in the first exit moment from

D
D

increases when

D
D

and

B
B

are polarized. It can also lead to symmetrization theorems for hitting probabilities, Green functions, and Riesz capacities. One such theorem is the following: Among all compact sets

K
K

in

R

n

\mathbb R^n

with given volume, the balls have the least

α
\alpha

-capacity (

0
>
α
>
2

0>\alpha >2

).
The geometry of profinite graphs with applications to free groups and finite monoids
Authors: Auinger K. , Steinberg B.
Published: October 2003

We initiate the study of the class of profinite graphsΓ\Gammadefined by the following geometric property: for any two verticesvvandwwofΓ\Gamma, there is a (unique) smallest connected profinite subgraph ofΓ\Gammacontaining them; such graphs are calledtree-like. Profinite trees in the sense of Gildenhuys and Ribes are tree-like, but the converse is not true. A profinite group is then said to bedendralif it has a tree-like Cayley graph with respect to some generating set; a Bass-Serre type characterization of dendral groups is provided. Also, such groups (including free profinite groups) are shown to enjoy a certain small cancellation condition. We define a pseudovariety of groupsH\mathbf {H}to bearboreousif all finitely generated free pro-H\mathbf {H}groups are dendral (with respect to a free generating set). Our motivation for studying such pseudovarieties of groups is to answer several open questions in the theory of profinite topologies and the theory of finite monoids. We prove, for arboreous pseudovarietiesH\mathbf {H}, a pro-H\mathbf {H}analog of the Ribes and Zalesskiĭ product theorem for the profinite topology on a free group. Also, arboreous pseudovarieties are characterized as precisely the solutionsH\mathbf {H}to the much studied pseudovariety equation\mathbf {J}\ast \mathbf {H}= \mathbf {J} \text {\textcircled {m}} \mathbf {H}.
On a conjecture of Whittaker concerning uniformization of hyperelliptic curves
Authors: Girondo Ernesto , González-Diez Gabino
Published: October 2003

This article concerns an old conjecture due to E. T. Whittaker, aiming to describe the group uniformizing an arbitrary hyperelliptic Riemann surface

y
2

=

∏

i
=
1

2
g
+
2

(
x
−

a
i

)

y^2=\prod _{i=1}^{2g+2}(x-a_i)

as an index two subgroup of the monodromy group of an explicit second order linear differential equation with singularities at the values

a
i

a_i

. Whittaker and collaborators in the thirties, and R. Rankin some twenty years later, were able to prove the conjecture for several families of hyperelliptic surfaces, characterized by the fact that they admit a large group of symmetries. However, general results of the analytic theory of moduli of Riemann surfaces, developed later, imply that Whittaker’s conjecture cannot be true in its full generality. Recently, numerical computations have shown that Whittaker’s prediction is incorrect for random surfaces, and in fact it has been conjectured that it only holds for the known cases of surfaces with a large group of automorphisms. The main goal of this paper is to prove that having many automorphisms is not a necessary condition for a surface to satisfy Whittaker’s conjecture.
Truncated second main theorem with moving targets
Authors: Ru Min , Wang Julie
Published: October 2003

We prove a truncated Second Main Theorem for holomorphic curves intersecting a finite set of moving or fixed hyperplanes. The set of hyperplanes is assumed to be non-degenerate. Previously only general position or subgeneral position was considered.
Revealing Preferences: Empirical Estimation of a Crisis Bargaining Game with Incomplete Information
Authors: Lewis Jeffrey B. , Schultz Kenneth A.
Published: October 2003

We develop an empirical estimator directly from an extensive-form crisis bargaining game with incomplete information and discuss its features and limitations. The estimator makes it possible to draw inferences about states' payoffs from observational data on crisis outcomes while remaining faithful to the theorized strategic and informational structure. We compare this estimator to one based on a symmetric information version of the same game, using the quantal response equilibrium proposed in this context by Signorino (1999,American Political Science Review93:279–298). We then address issues of identification that arise in trying to learn about actors' utilities by observing their play of a strategic game. In general, a number of identifying restrictions are needed in order to pin down the distribution of payoffs and the effects of covariates on those payoffs.
Strategic Interaction and Candidate Competition in U.S. House Elections: Empirical Applications of Probit and Strategic Probit Models
Authors: Carson Jamie L.
Published: October 2003

In recent work, Signorino (American Political Science Review 93:279–297, 1999; International Interactions 28:93–115, 2002) has sought to test statistical models derived from extensive-form games in the context of international relations research focusing on conflict and interstate bargaining. When two or more actors interact with one another under conditions of uncertainty, Signorino demonstrates that it is necessary to incorporate such strategic interaction into the underlying model to avoid potential threats to statistical inference. Outside the realm of international relations research, however, there have been limited applications of Signorino's strategic probit model in understanding strategic interaction. In this article, I present an empirical comparison of probit and strategic probit models in the context of candidate competition in House elections during the 1990s. I show that incumbent spending deters challenger entry and factors such as minority party affiliation and redistricting significantly affect incumbent career decisions, findings that run counter to those reported in the nonstrategic model. Overall, the results illustrate that failing to account for strategic interaction can lead to biased and inaccurate estimates related to challenger and incumbent entry decisions.
Valuing Policy Alternatives: A Generalization
Authors: Dietz Nathan , Rothenberg Lawrence S.
Published: October 2003

Those interested in political phenomena such as voting have found random utility models, originally developed for decisions such as transportation choice, especially attractive, as the underlying model can yield a statistical model with a few simple, realistic assumptions. Unfortunately, such models have proven difficult to apply to situations with more than two votes and three alternatives or an unknown cutpoint. Additionally, as we show, standard applications of such models to voting, while producing consistent parameter estimates, yield standard errors that are too small and, due to a failure to employ all relevant theoretical information, biased ideal point estimates. We specify a general model applicable to any number of votes and alternatives, with correct standard errors and unbiased ideal point estimates. We apply this model to a number of cases studied by previous scholars involving legislative voting over the minimum wage: (1) when there are two votes and two known cutpoints (K. Krehbiel and D. Rivers, American Journal of Political Science, 1988, 32, 1151–1174); (2) when there are three votes and three known cutpoints (J. Wilkerson, American Journal of Political Science, 1991, 35, 613–623); and (3) when there are three votes but where one cutpoint is unknown given a lack of knowledge about the impact of a policy (J. Wilkerson, American Journal of Political Science, 1991, 35, 613–623) or the possibility of sophisticated voting (C. Volden, Journal of Politics, 1998, 60, 149–173). We show that in various contexts our analysis improves on existing methods, yielding consistent and efficient ideal point estimates and a better-fitting model with improved predictive accuracy.
Multiple Hands on the Wheel: Empirically Modeling Partial Delegation and Shared Policy Control in the Open and Institutionalized Economy
Authors: Franzese Robert J.
Published: October 2003

The causal arguments of modern, positive political science often imply complex interactions among multiple explanatory factors. In one example from comparative and international political economy (C&IPE), sharing of monetary-policymaking control between partially autonomous central banks and politically responsive governments yields inflation as a convex combination of the rates that would have held under full-government and full-central-bank policy control. The anti-inflationary effect of central bank independence (autonomy plus conservatism: CBA) therefore depends on all political—economic variables to which central banks and governments respond differently, and, vice versa, CBA mutes the inflation effects of all such factors. Extending that logic of shared policy control to open political economies: insofar as domestic monetary authorities fix exchange rates, they effectively delegate inflation control to foreign (peg-currency) authorities, and policymakers in small and financially exposed economies must match domestic inflation to foreign (global) rates to avoid massive exchange-rate pressures. Thus, analogously, the domestic-inflation effects of fixed exchange rates and of monetary exposure depend on each other and on many other institutional and structural aspects of the domestic and foreign political economies, and, vice versa, the effects of all domestic and foreign political—economic conditions depend on degrees of exchange-rate fixity and financial openness at home and abroad. This article shows how to model such complexly interactive hypotheses empirically compactly and substantively meaningfully, and demonstrates the postwar inflation records of 21 developed democracies to favor such specifications decidedly over standard linear-additive or linear-interactive alternatives. The concluding sections discuss specific results and implications and then suggest several more potential applications of this general approach to further instances of shared policy control and other substantive contexts that induce the multiple, complex interactions characteristic of modern, positive political science in general and C&IPE especially.
Enhanced Retention in the Passive-Avoidance Task By 5-HT1A
Receptor Blockade Is Not Associated With Increased Activity of the Central
Nucleus of the Amygdala
Authors: Schneider Allen M. , Wilkins Emily , Firestone Aaron , Everbach E. Carr , Naylor Jennifer C. , Simson Peter E.
Published: October 2003

The effect of blockade of 5-HT1A receptors was investigated on
(1) retention in a mildly aversive passive-avoidance task, and (2) spontaneous
single-unit activity of central nucleus of the amygdala (CeA) neurons, a brain
site implicated in modulation of retention. Systemic administration of the
selective 5-HT1A antagonist NAN-190 immediately after training
markedly—and dose-dependently—facilitated retention in the
passive-avoidance task; enhanced retention was time-dependent and was not
attributable to variations in wattages of shock received by animals. Systemic
administration of NAN-190 had mixed effects on spontaneous single-unit
activity of CeA neurons recorded extracellularly in vivo; microiontophoretic
application of 5-HT, in contrast, consistently and potently suppressed CeA
activity. The present findings—that 5-HT1A receptor blockade
by NAN-190 (1) enhances retention in the passive-avoidance task, and (2) does
not consistently increase spontaneous neuronal activity of the
CeA—provide evidence that a serotonergic system tonically inhibits
modulation of retention in the passive-avoidance task through activation of
the 5-HT1A receptor subtype at brain sites located outside the
CeA.
Improvements in Hippocampal-Dependent Learning and Decremental Attention in 5-HT3Receptor Overexpressing Mice
Authors: Harrell Amber V. , Allan Andrea M.
Published: October 2003

The 5-HT3receptor for serotonin is expressed within limbic structures and is known to modulate neurotransmitter release, suggesting that this receptor may influence learning and memory. Perturbations in serotonergic neurotransmission lead to changes in the ability to attend, learn, and remember. To examine the role of 5-HT3receptors in learning, memory, and attention, 5-HT3receptor overexpressing (5-HT3-OE) transgenic mice and their wild-type littermates (WT) were tested in Pavlovian contextual and cued fear conditioning, fear extinction, and latent inhibition (LI) paradigms. Prepulse inhibition (PPI) was assessed to reveal changes in sensorimotor gating. Additionally, anxious behaviors, shock sensitivity, and reactions to novel stimuli were evaluated. 5-HT3-OE mice displayed enhanced contextual conditioning, whereas cued conditioning remained the same as that of WT mice. 5-HT3-OE mice did not differ from WT in extinction rates to either the context or cue. LI was enhanced for 5-HT3-OE mice compared to WT. PPI remained unchanged. No differences in sensitivity to footshock or startle were found. However, 5-HT3-OE mice demonstrated heightened exploratory behavior in response to novel environmental stimuli and decreased anxiety as measured in the elevated plus-maze. Results indicate that overexpression of the 5-HT3receptor in mouse forebrain results in enhanced hippocampal-dependent learning and attention. Enhanced inspective behavior in response to novelty may contribute to the observed improvements in learning, memory, and attention due to 5-HT3receptor overexpression.
Hemispheric Dissociation of the Involvement of NOS Isoforms in Memory for Discriminated Avoidance in the Chick
Authors: Rickard Nikki S. , Gibbs Marie E.
Published: October 2003

Previous research has indicated a role for both the neuronal (nNOS) and
endothelial (eNOS) nitric oxide isoforms in memory formation. In addition, two
distinct periods of activity of nitric oxide activity, dissociated by
hemispheric localization, are implicated following passive avoidance training
in the chick. In the present study, we trained black Australorp-white Leghorn
chicks on a color discrimination avoidance task. Diphenyleneiodonium chloride
(1 μM) or N-propyl-l-arginine (50 μM) was
administered into either the left or right hemisphere of the chick brain in an
attempt to differentiate the effects of inhibiting eNOS or nNOS, respectively.
The memory loss previously observed following administration of
diphenyleneiodonium chloride between 10 and 20 min posttraining was found to
be lateralized to the right hemisphere, although administration of this agent
into the left hemisphere around the time of training was also amnestic. In
contrast, N-propyl-l-arginine caused memory loss only when
administered to the left hemisphere around the time of training. These
findings suggest that activation of both eNOS and nNOS isoforms may be
essential for long-term memory consolidation of this task. Further, these two
periods of activity are defined temporally and by hemisphere localization,
although confirmation with more selective inhibitors when they become
available is advised.
Delay-Dependent Working Memory Impairment in Young-Adult and Aged 5-HT1BKO Mice as Assessed in a Radial-Arm Water Maze
Authors: Wolff Mathieu , Benhassine Narimane , Costet Pierre , Hen René , Segu Louis , Buhot Marie-Christine
Published: October 2003

Serotonin (5-HT) plays a modulatory role in mnemonic functions, especially by interacting with the cholinergic system. The 5-HT1B receptor is a key target of this interaction. The 5-HT1B receptor knockout mice were found previously to exhibit a facilitation in hippocampal-dependent spatial reference memory learning. In the present study, we submitted mice to a delayed spatial working memory task, allowing the introduction of various delays between an exposure trial and a test trial. The 5-HT1BKO and wild-type mice learned the task in a radial-arm water maze (returning to the most recent presented arm containing the escape platform), and exhibited a high level of performance at delays of 0 and 5 min. However, at the delay of 60 min, only 5-HT1BKO mice exhibited an impairment. At a delay of 90 min, all mice were impaired. Treatment by scopolamine (0.8 mg/kg) induced the same pattern of performance in wild type as did the mutation for short (5 min, no impairment) and long (60 min, impairment) delays. The 22-month-old wild-type and knockout mice exhibited an impairment at short delays (5 and 15 min). The effect of the mutation affected both young-adult and aged mice at delays of 15, 30, and 60 min. Neurobiological data show that stimulation of the 5-HT1B receptor inhibits the release of acetylcholine in the hippocampus, but stimulates this in the frontal cortex. This dual function might, at least in part, explain the opposite effect of the mutation on reference memory (facilitation) and delay-dependent working memory (impairment). These results support the idea that cholinergic-serotonergic interactions play an important role in memory processes.
A Pharmacological Analysis of an Associative Learning Task: 5-HT1to 5-HT7Receptor Subtypes Function on a Pavlovian/Instrumental Autoshaped Memory
Authors: Meneses Alfredo
Published: October 2003

Recent studies using both invertebrates and mammals have revealed that endogenous serotonin (5-hydroxytryptamine [5-HT]) modulates plasticity processes, including learning and memory. However, little is currently known about the mechanisms, loci, or time window of the actions of 5-HT. The aim of this review is to discuss some recent results on the effects of systemic administration of selective agonists and antagonists of 5-HT on associative learning in a Pavlovian/instrumental autoshaping (P/I-A) task in rats. The results indicate that pharmacological manipulation of 5-HT1-7receptors or 5-HT reuptake sites might modulate memory consolidation, which is consistent with the emerging notion that 5-HT plays a key role in memory formation.
Role of the Serotonin 5-HT2AReceptor in Learning
Authors: Harvey John A.
Published: October 2003

This study reviews the role of the serotonin 5-HT2Areceptor in learning as measured by the acquisition of the rabbit's classically conditioning nictitating membrane response, a component of the eyeblink response. Agonists at the 5-HT2Areceptor including LSD (d-lysergic acid diethylamide) enhanced associative learning at doses that produce cognitive effects in humans. Some antagonists such as BOL (d-bromolysergic acid diethylamide), LY53,857, and ketanserin acted as neutral antagonists in that they had no effect on learning, whereas others (MDL11,939, ritanserin, and mianserin) acted as inverse agonists in that they retarded learning through an action at the 5-HT2Areceptor. These results were placed in the context of what is known concerning the anatomical distribution and electrophysiological effects of 5-HT2Areceptor activation in frontal cortex and hippocampus, as well as the role of cortical 5-HT2Areceptors in schizophrenia. It was concluded that the 5-HT2Areceptor demonstrates constitutive activity, and that variations in this activity can produce profound alterations in cognitive states.
Desensitization of Postsynaptic Glutamate Receptors Contributes to
High-Frequency Homosynaptic Depression of Aplysia Sensorimotor
Connections
Authors: Antzoulatos Evangelos G. , Cleary Leonard J. , Eskin Arnold , Baxter Douglas A. , Byrne John H.
Published: October 2003

Withdrawal reflexes of Aplysia are mediated in part by a
monosynaptic circuit of sensory (SN) and motor (MN) neurons. A brief
high-frequency burst of spikes in the SN produces excitatory postsynaptic
potentials (EPSPs) that rapidly decrease in amplitude during the burst of
activity. It is generally believed that this and other (i.e., low-frequency)
forms of homosynaptic depression are entirely caused by presynaptic mechanisms
(e.g., depletion of releasable transmitter). The present study examines the
contribution that desensitization of postsynaptic glutamate receptors makes to
homosynaptic depression. Bath application of cyclothiazide, an agent that
reduces desensitization of non-NMDA glutamate receptors, reduced high-, but
not low-frequency synaptic depression. Thus, a postsynaptic mechanism,
desensitization of glutamate receptors, can also contribute to homosynaptic
depression of sensorimotor synapses.
A Specific Role for the Human Amygdala in Olfactory Memory
Authors: Buchanan Tony W. , Tranel Daniel , Adolphs Ralph
Published: October 2003

The medial temporal lobe is known to play a role in the processing of olfaction and memory. The specific contribution of the human amygdala to memory for odors has not been addressed, however. The role of this region in memory for odors was assessed in patients with unilateral amygdala damage due to temporal lobectomy (n= 20; 11 left, 9 right), one patient with selective bilateral amygdala damage, and in 20 age-matched normal controls. Fifteen odors were presented, followed 1 h later by an odor–name matching test and an odor–odor recognition test. Signal detection analyses showed that both unilateral groups were impaired in their memory for matching odors with names, these patients were not significantly impaired on odor–odor recognition. Bilateral amygdala damage resulted in severe impairment in both odor–name matching as well as in odor–odor recognition memory. Importantly, none of the patients were impaired on an auditory verbal learning task, suggesting that these findings reflect a specific impairment in olfactory memory, and not merely a more general memory deficit. Taken together, the data provide neuropsychological evidence that the human amygdala is essential for olfactory memory.
Emotion-Induced Amnesia in Rats: Working Memory-Specific Impairment, Corticosterone-Memory Correlation, and Fear Versus Arousal Effects on Memory
Authors: Woodson James C. , Macintosh Deric , Fleshner Monika , Diamond David M.
Published: October 2003

We have shown previously that psychological stress (predator exposure) impairs spatial memory in rats. We have extended that finding here to show that predator stress selectively impaired recently acquired (hippocampal-dependent) spatial working memory without affecting long-term (hippocampal-independent) spatial reference memory. We also investigated why predator exposure impairs memory. Was spatial memory impaired because of the fear-provoking aspects of predator exposure or only because the cat was a novel and arousing stimulus? If the latter possibility was correct, then any novel and arousing stimulus, independent of its emotional valence (i.e., aversive or appetitive), would impair memory. We found that spatial working memory was not impaired when the male rats were exposed to a sexually receptive female rat, a stimulus that was novel and arousing to them, but not aversive. We also found that there was an equivalent increase in serum corticosterone levels in male rats exposed to either a cat or a female rat, but only the cat-exposed rats exhibited a significant correlation between corticosterone levels and impaired memory. Overall, this series of experiments demonstrates that (1) predator stress selectively impaired working (hippocampal-dependent), but not reference (hippocampal-independent), memory; (2) a fear-provoking stimulus, and not merely novelty and increased arousal, impaired spatial memory; and (3) increased corticosterone levels correlated withimpaired spatial working memory only under predator exposure, that is, fear-provoking conditions.
Developmental Changes in Eyeblink Conditioning and Neuronal Activity in the Pontine Nuclei
Authors: Freeman John H. , Muckler Adam S.
Published: October 2003

Neuronal activity was recorded in the pontine nuclei of developing rats
during eyeblink conditioning on postnatal days 17–18 (P17–P18) or
P24–P25. A pretraining session consisted of unpaired presentations of a
300-msec tone conditioned stimulus (CS) and a 10-msec periorbital shock
unconditioned stimulus (US). Five paired training sessions followed the
unpaired session, consisting of 100 trials of the CS paired with the US. The
rats trained on P24–P25 exhibited significantly more conditioned
responses (CRs) than the rats trained on P17–P18, although both groups
produced CRs by the end of training. Ontogenetic increases in pre-CS and
stimulus-elicited activity in the pontine nuclei were observed during the
pretraining session and after paired training. The activity of pontine units
was greater on trials with CRs relative to trials without CRs in rats trained
on P24–P25, but almost no CR-related modulation was observed in the
pontine units of rats trained on P17–P18. The findings indicate that
pontine neuronal responses to the CS and modulation of pontine activity by the
cerebellum and red nucleus undergo substantial postnatal maturation. The
developmental changes in pontine neuronal activity might play a significant
role in the ontogeny of eyeblink conditioning.
Quantitation of Contacts Among Sensory, Motor, and Serotonergic Neurons
in the Pedal Ganglion of Aplysia
Authors: Zhang Han , Wainwright Marcy , Byrne John H. , Cleary Leonard J.
Published: October 2003

Present models of long-term sensitization in Aplysia californica
indicate that the enhanced behavioral response is due, at least in part, to
outgrowth of sensory neurons mediating defensive withdrawal reflexes.
Presumably, this outgrowth strengthens pre-existing connections by formation
of newsynapses with follower neurons. However, the relationship between the
number of sensorimotor contacts and the physiological strength of the
connection has never been examined in intact ganglia. As a first step in
addressing this issue, we used confocal microscopy to examine sites of contact
between sensory and motor neurons in naive animals. Our results revealed
relatively fewcontacts between physiologically connected cells. In addition,
the number of contact sites was proportional to the amplitude of the EPSP
elicited in the follower motor neuron by direct stimulation of the sensory
neuron. This is the first time such a correlation has been observed in the
central nervous system. Serotonin is the neurotransmitter most closely
examined for its role in modulating synaptic strength at the sensorimotor
synapse. However, the structural relationship of serotonergic processes and
sensorimotor synapses has never been examined. Surprisingly, serotonergic
processes usually made contact with sensory and motor neurons at sites located
relatively distant from the sensorimotor synapse. This result implies that
heterosynaptic regulation is due to nondirected release of serotonin into the
neuropil.
Multiple Serotonergic Mechanisms Contributing to Sensitization in
Aplysia: Evidence of Diverse Serotonin Receptor Subtypes
Authors: Barbas Demian , DesGroseillers Luc , Castellucci Vincent F. , Carew Thomas J. , Marinesco Stéphane
Published: October 2003

The neurotransmitter serotonin (5-HT) plays an important role in memory
encoding in Aplysia. Early evidence showed that during sensitization,
5-HT activates a cyclic AMP-protein kinase A (cAMP-PKA)-dependent pathway
within specific sensory neurons (SNs), which increases their excitability and
facilitates synaptic transmission onto their follower motor neurons (MNs).
However, recent data suggest that serotonergic modulation during sensitization
is more complex and diverse. The neuronal circuits mediating defensive
reflexes contain a number of interneurons that respond to 5-HT in ways
opposite to those of the SNs, showing a decrease in excitability and/or
synaptic depression. Moreover, in addition to acting through a cAMP-PKA
pathway within SNs, 5-HT is also capable of activating a variety of other
protein kinases such as protein kinase C, extracellular signal-regulated
kinases, and tyrosine kinases. This diversity of 5-HT responses during
sensitization suggests the presence of multiple 5-HT receptor subtypes within
the Aplysia central nervous system. Four 5-HT receptors have been
cloned and characterized to date. Although several others probably remain to
be characterized in molecular terms, especially the Gs-coupled 5-HT receptor
capable of activating cAMP-PKA pathways, the multiplicity of serotonergic
mechanisms recruited into action during learning in Aplysia can now
be addressed from a molecular point of view.
Stimulus Generalization of Conditioned Eyelid Responses Produced Without Cerebellar Cortex: Implications for Plasticity in the Cerebellar Nuclei
Authors: Ohyama Tatsuya , Nores William L. , Mauk Michael D.
Published: October 2003

In Pavlovian eyelid conditioningand adaptation of the vestibulo-ocular reflex, cerebellar cortex lesions fail to completely abolish previously acquired learning, indicating an additional site of plasticity in the deep cerebellar or vestibular nucleus. Three forms of plasticity are known to occur in the deep cerebellar nuclei: formation of new synapses, plasticity at existingsynapses, and changes in intrinsic excitability. Only a cell-wide increase in excitability predicts that learningshould generalize broadly from a trainingstimulus to other stimuli capable of supporting learning, whereas the alternatives predict that learning should be relatively specific to the trainingstimulus. Here we show that deep nucleus plasticity, as assessed by conditioned eyelid responses produced without input from the cerebellar cortex, is relatively specific to the trainingconditioned stimulus (CS). We trained rabbits to a tone or light CS with periorbital stimulation as the unconditioned stimulus (US), and pharmacologically disconnected the cerebellar cortex duringa posttraininggeneralization test. The short-latency conditioned responses unmasked by this treatment showed strongdecrement alongthe dimension of auditory frequency and did not generalize across stimulus modalities. These results cannot be explained solely by a cell-wide increase in the excitability of deep nucleus neurons, and imply that an input-specific mechanism in the deep cerebellar nucleus operates as well.
Acquisition, Retention, and Recall of Memory After Injection of RS67333, a 5-HT4 Receptor Agonist, Into the Nucleus Basalis Magnocellularis of the Rat
Authors: Orsetti Marco , Dellarole Anna , Ferri Simona , Ghi Piera
Published: October 2003

The serotonin 5-HT4 subtype receptor is predominantly localized into
anatomical structures linked to memory and cognition. A few experimental
studies report that the acute systemic administration of selective 5-HT4
agonists has ameliorative effects on memory performance, and that these
effects are reversed by contemporary administration of 5-HT4 receptor
antagonists. To verify whether this procognitive action occurs via the
activation of the cholinergic nucleus basalis magnocellularis (NBM)-cortical
pathways, we examined the effects of RS67333, a selective partial agonist of
the 5-HT4 receptor, on rat performance in a place recognition task upon local
administration of the drug into the NBM area. The intra-NBM administration of
RS67333 enhances the acquisition (200–500 ng/0.5 μL) and the
consolidation (40–200 ng/0.5 μL) of the place recognition memory.
These effects are reversed by pretreatment with the selective 5-HT4 receptor
antagonist RS39604 (300 ng/0.5μL). Conversely, the recall of memory is not
affected by the 5-HT4 agonist. Our results indicate that 5-HT4 receptors
located within the NBM may play a role in spatial memory and that the
procognitive effect of RS67333 is due, at least in part, to the potentiation
of the activity of cholinergic NBM-cortical pathways.
Corrosion inhibition of steel by 1‐phenyl 5‐mercapto 1,2,3,4‐ tetrazole in acidic environments (0.5 M H2SO4 and 1/3 M H3PO4)
Authors: Bensajjay F. , Alehyen S. , El Achouri M. , Kertit S.
Published: October 2003

1‐phenyl 5‐mercarpto 1,2,3,4‐tetrazole (PMT) was tested as an inhibitor for the corrosion of steel in 0.5 M H2SO4 and 1/3 M H3PO4 by weight‐loss and electrochemical methods. Results obtained showed that the inhibition efficiency of PMT increased with the increase of inhibitor concentration and reached an optimum value (98 per cent) at 10−3 M in H2SO4 and H3PO4 solutions. The effect of the temperature on the kinetic parameters of corrosion of steel in the aqueous solutions of H2SO4 and H3PO4 with and without addition of PMT has been studied and the associated parameters were determined.
Inhibition of CO2 corrosion of carbon steel by rosin amide
Authors: Guomin Li
Published: October 2003

The inhibition of sweet gas corrosion of carbon steel in high pressure CO2 saturated brine by rosin amine has been studied by weight‐loss, electrochemical polarisation and electrochemical impedance spectrum measurements. The results obtained revealed that rosin amine compound is a good inhibitor. The inhibition efficiency increased with the increase of inhibitor concentration. Rosin amine acts mainly as a adsorptive mixed‐type inhibitor. The adsorption of the inhibitor on the metal surface in high pressure CO2 saturated brine obey Langmuir isotherm. The adsorption mechanism of inhibitor was both electrostatic‐adsorption and chemisorption.
Studies on the inhibition of aluminium corrosion by 2‐acetylphenothiazine in chloroacetic acids
Authors: Ebenso E.E. , Okafor P.C. , Ekpe U.J.
Published: October 2003

The inhibition of corrosion of aluminium in chloroacetic acids, namely monochloroacetic acid (MCA), dichloroacetic acid (DCA) and trichloroacetic acid (TCA) solutions, using 2‐acetylphenothiazine (2APTZ) at 30 and 40°C, at concentrations of 1×10−3M, 1×10−4M, 7.5×10−5M, 5×10−5M and 1×10−5M, was studied using the weight loss and hydrogen evolution techniques. At the highest concentration studied, using the hydrogen evolution technique, an inhibition efficiency of 86.16 per cent was obtained. The investigation revealed that 2APTZ inhibited the corrosion reaction. A physical adsorption mechanism is proposed on the basis of the obtained average Ea values of 76.05 kJ/mol for MCA, 70.75 kJ/mol for DCA and 68.52 kJ/mol for TCA. 2APTZ was confirmed to obey the Freundlish adsorption isotherm equation at the concentration studied. The two techniques employed revealed a first‐order kinetics.
Inhibition of the corrosion of low carbon steel in acidic solution by selected polyelectrolytes and polymers
Authors: Bereket G. , Yurt A. , Türk H.
Published: October 2003

The inhibiting effects of 2,6‐ionen and 2,10‐ionen type polyvinylbenzyltrimethylammonium chloride, and latex, on low carbon steel in hydrochloric acid solution was investigated by potentiodynamic polarisation measurements and impedance measurement techniques over the temperature range of 20‐60°C at different inhibitor concentrations. It was found that the inhibition efficiencies increased with increasing inhibitor concentration. The degree of shift in Ecorr values, together with the change in anodic and cathodic Tafel slopes (βa, βc), revealed that the studied inhibitors behaved as anodic inhibitors. Thermodynamic and kinetic parameters for dissolution and adsorption were also calculated.
The dissolution mechanism of steel in inorganic acids
Authors: Abdel‐Gaber A.M. , Khalil N. , Abou El‐Fetouh A.
Published: October 2003

The dissolution behaviour of steel in 1 N solutions of HCl, H2SO4 and HClO4 acid containing 10 per cent (v/v) ethanol was investigated at 30‐60°C using gas volume measurements, polarisation and electrochemical impedance spectroscopy techniques. The data revealed that the rate of corrosion decreased in the order Cl−>SO42−>ClO4−. The corrosion mechanism of the acid dissolution for steel at low pH was found to be dependent on the counter ion present. The mechanism was discussed on the basis that the acid anion is first adsorbed on the steel surface, followed by the formation of a surface complex in the anodic process and finally the complex was desorbed from the surface. In general, if the adsorbed anion or the surface complex was stable, the corrosion of steel was suppressed. The calculated values of the activation energy for the steel in different acid indicated that the dissolution process proceeded via similar mechanisms.
Staff development and training in the digital library environment
Authors: Joint Nick
Published: October 2003

Traditional approaches to library training flourished in the period of hard copy collection building, when certain common generic skills, such as those of cataloguing and indexing, formed the bedrock of knowledge for many LIS professionals. The skills required in the digital library context are more heterogeneous, fluid and fast‐changing. They require a different training philosophy, one more closely identified with a “constructivist” approach to teaching and learning. This article attempts to flesh out these ideas by relating them to past and present practice, and sketches possible paths along which digital library training might evolve.
The Instruction Commons: an information literacy initiative at Iowa State University
Authors: Gregory David , Nixon William J.
Published: October 2003

The Instruction Commons information literacy initiative at Iowa State University provides users with both an information literacy program and a virtual space in which students, librarians, and members of the teaching faculty at Iowa State can explore new ways of integrating electronic resources and library research instruction into teaching and learning. Furthermore, the concept of a “commons” implies not just a collaborative information space for students, faculty and librarians, but also an area in which an information literacy program can subsist with learning materials which promote IT literacy. The following paper describes the institutional background of the Instruction Commons, its history, funding, and organization while also providing a description and tour of the Commons. Future directions are also anticipated, including the need for effective program assessment with a view to extracting useful planning and management information. With regard to functionality, we anticipate the integration of more interactive features, including increased use of learner‐controlled paths and quizzes to provide immediate feedback. Finally, the paper offers a useful summary of some other related projects in the USA.