bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrostatic steering and ionic tethering in enzyme–ligand binding: Insights from simulations
Authors: Wade Rebecca C. , Gabdoulline Razif R. , Lüdemann Susanna K. , Lounnas Valère
Published: July 2002

To bind at an enzyme’s active site, a ligand must diffuse or be
transported to the enzyme’s surface, and, if the binding site is
buried, the ligand must diffuse through the protein to reach it.
Although the driving force for ligand binding is often ascribed to the
hydrophobic effect, electrostatic interactions also influence the
binding process of both charged and nonpolar ligands. First,
electrostatic steering of charged substrates into enzyme active sites
is discussed. This is of particular relevance for diffusion-influenced
enzymes. By comparing the results of Brownian dynamics simulations and
electrostatic potential similarity analysis for triose-phosphate
isomerases, superoxide dismutases, and β-lactamases from different
species, we identify the conserved features responsible for the
electrostatic substrate-steering fields. The conserved potentials are
localized at the active sites and are the primary determinants of the
bimolecular association rates. Then we focus on a more subtle effect,
which we will refer to as “ionic tethering.” We explore, by means
of molecular and Brownian dynamics simulations and electrostatic
continuum calculations, how salt links can act as tethers between
structural elements of an enzyme that undergo conformational change
upon substrate binding, and thereby regulate or modulate substrate
binding. This is illustrated for the lipase and cytochrome P450
enzymes. Ionic tethering can provide a control mechanism for substrate
binding that is sensitive to the electrostatic properties of the
enzyme’s surroundings even when the substrate is nonpolar.
Biochemical basis of SOS-induced mutagenesis in
Escherichia coli
: Reconstitution of
in vitro
lesion bypass dependent on the UmuD′
2
C mutagenic complex and RecA protein
Authors: Tang Mengjia , Bruck Irina , Eritja Ramon , Turner Jennifer , Frank Ekaterina G. , Woodgate Roger , O’Donnell Mike , Goodman Myron F.
Published: July 2002

Damage-induced SOS mutagenesis requiring the UmuD′C proteins occurs as part of the cells’ global response to DNA damage.
In vitro
studies on the biochemical basis of SOS mutagenesis have been hampered by difficulties in obtaining biologically active UmuC protein, which, when overproduced, is insoluble in aqueous solution. We have circumvented this problem by purifying the UmuD′
2
C complex in soluble form and have used it to reconstitute an SOS lesion bypass system
in vitro
. Stimulated bypass of a site-directed model abasic lesion occurs in the presence of UmuD′
2
C, activated RecA protein (RecA*), β-sliding clamp, γ-clamp loading complex, single-stranded binding protein (SSB), and either DNA polymerases III or II. Synthesis in the presence of UmuD′
2
C is nonprocessive on damaged and undamaged DNA. No lesion bypass is observed when wild-type RecA is replaced with RecA1730, a mutant that is specifically defective for Umu-dependent mutagenesis. Perhaps the most noteworthy property of UmuD′
2
C resides in its ability to stimulate both nucleotide misincorporation and mismatch extension at aberrant and normal template sites. These observations provide a biochemical basis for the role of the Umu complex in SOS-targeted and SOS-untargeted mutagenesis.
Rapid polyether cleavage via extracellular one-electron oxidation by a brown-rot basidiomycete
Authors: Kerem Zohar , Bao Wuli , Hammel Kenneth E.
Published: July 2002

Fungi that cause brown rot of wood are essential biomass recyclers and also the principal agents of decay in wooden structures, but the extracellular mechanisms by which they degrade lignocellulose remain unknown. To test the hypothesis that brown-rot fungi use extracellular free radical oxidants as biodegradative tools,
Gloeophyllum trabeum
was examined for its ability to depolymerize an environmentally recalcitrant polyether, poly(ethylene oxide) (PEO), that cannot penetrate cell membranes. Analyses of degraded PEOs by gel permeation chromatography showed that the fungus cleaved PEO rapidly by an endo route.
13
C NMR analyses of unlabeled and perdeuterated PEOs recovered from
G. trabeum
cultures showed that a major route for depolymerization was oxidative C—C bond cleavage, a reaction diagnostic for hydrogen abstraction from a PEO methylene group by a radical oxidant. Fenton reagent (Fe(II)/H
2
O
2
) oxidized PEO by the same route
in vitro
and therefore might account for PEO biodegradation if it is produced by the fungus, but the data do not rule out involvement of less reactive radicals. The reactivity and extrahyphal location of this PEO-degrading system suggest that its natural function is to participate in the brown rot of wood and that it may enable brown-rot fungi to degrade recalcitrant organopollutants.
The thiazide-sensitive Na–Cl cotransporter is an aldosterone-induced protein
Authors: Kim Gheun-Ho , Masilamani Shyama , Turner Rachel , Mitchell Carter , Wade James B. , Knepper Mark A.
Published: July 2002

Although the collecting duct is regarded as the primary site at which mineralocorticoids regulate renal sodium transport in the kidney, recent evidence points to the distal convoluted tubule as a possible site of mineralocorticoid action. To investigate whether mineralocorticoids regulate the expression of the thiazide-sensitive Na–Cl cotransporter (TSC), the chief apical sodium entry pathway of distal convoluted tubule cells, we prepared an affinity-purified, peptide-directed antibody to TSC. On immunoblots, the antibody recognized a prominent 165-kDa band in membrane fractions from the renal cortex but not from the renal medulla. Immunofluorescence immunocytochemistry showed TSC labeling only in distal convoluted tubule cells. Semiquantitative immunoblotting studies demonstrated a large increase in TSC expression in the renal cortex of rats on a low-NaCl diet (207 ± 21% of control diet). Immunofluorescence localization in tissue sections confirmed the strong increase in TSC expression. Treatment of rats for 10 days with a continuous subcutaneous infusion of aldosterone also increased TSC expression (380 ± 58% of controls). Furthermore, 7-day treatment of rats with an orally administered mineralocorticoid, fludrocortisone, increased TSC expression (656 ± 114% of controls). We conclude that the distal convoluted tubule is an important site of action of the mineralocorticoid aldosterone, which strongly up-regulates the expression of TSC.
Pontin52, an interaction partner of β-catenin, binds to the TATA box binding protein
Authors: Bauer Andreas , Huber Otmar , Kemler Rolf
Published: July 2002

β-catenin, the vertebrate homolog of the
Drosophila
Armadillo protein, has been shown to have dual cellular functions, as a component of both the cadherin-catenin cell adhesion complex and the Wnt signaling pathway. At Wnt signaling, β-catenin becomes stabilized in the cytoplasm and subsequently available for interaction with transcription factors of the lymphocyte enhancer factor-1/T-cell factor family, resulting in a nuclear localization of β-catenin. Although β-catenin does not bind DNA directly, its carboxyl- and amino-terminal regions exhibit a transactivating activity still not well understood molecularly. Here we report the identification of an interaction partner of β-catenin, a nuclear protein designated Pontin52. Pontin52 binds β-catenin in the region of Armadillo repeats 2–5 and, more importantly, also binds the TATA box binding protein. We provide evidence for an
in vivo
multiprotein complex composed of Pontin52, β-catenin, and lymphocyte enhancer factor-1/T-cell factor. Our results suggest involvement of Pontin52 in the nuclear function of β-catenin.
The representation of the ipsilateral visual field in human cerebral cortex
Authors: Tootell Roger B. H. , Mendola Janine D. , Hadjikhani Nouchine K. , Liu Arthur K. , Dale Anders M.
Published: July 2002

Previous studies of cortical retinotopy focused on influences from
the contralateral visual field, because ascending inputs to cortex are
known to be crossed. Here, functional magnetic resonance imaging was
used to demonstrate and analyze an ipsilateral representation in human
visual cortex. Moving stimuli, in a range of ipsilateral visual field
locations, revealed activity: (
i
) along the vertical
meridian in retinotopic (presumably lower-tier) areas; and
(
ii
) in two large branches anterior to that, in
presumptive higher-tier areas. One branch shares the anterior vertical
meridian representation in human V3A, extending superiorly toward
parietal cortex. The second branch runs antero-posteriorly along
lateral visual cortex, overlying motion-selective area MT. Ipsilateral
stimuli sparing the region around the vertical meridian representation
also produced signal reductions (perhaps reflecting neural inhibition)
in areas showing contralaterally driven retinotopy. Systematic sampling
across a range of ipsilateral visual field extents revealed significant
increases in ipsilateral activation in V3A and V4v, compared with
immediately posterior areas V3 and VP. Finally, comparisons between
ipsilateral stimuli of different types but equal retinotopic extent
showed clear stimulus specificity, consistent with earlier suggestions
of a functional segregation of motion vs. form processing in parietal
vs. temporal cortex, respectively.
Long QT and ventricular arrhythmias in transgenic mice expressing the N terminus and first transmembrane segment of a voltage-gated potassium channel
Authors: London Barry , Jeron Andreas , Zhou Jun , Buckett Peter , Han Xingiang , Mitchell Gary F. , Koren Gideon
Published: July 2002

Voltage-gated potassium channels control cardiac repolarization, and mutations of K
+
channel genes recently have been shown to cause arrhythmias and sudden death in families with the congenital long QT syndrome. The precise mechanism by which the mutations lead to QT prolongation and arrhythmias is uncertain, however. We have shown previously that an N-terminal fragment including the first transmembrane segment of the rat delayed rectifier K
+
channel Kv1.1 (
Kv1.1N206Tag
) coassembles with other K
+
channels of the Kv1 subfamily
in vitro
, inhibits the currents encoded by Kv1.5 in a dominant-negative manner when coexpressed in
Xenopus
oocytes, and traps Kv1.5 polypeptide in the endoplasmic reticulum of GH3 cells. Here we report that transgenic mice overexpressing
Kv1.1N206Tag
in the heart have a prolonged QT interval and ventricular tachycardia. Cardiac myocytes from these mice have action potential prolongation caused by a significant reduction in the density of a rapidly activating, slowly inactivating, 4-aminopyridine sensitive outward K
+
current. These changes correlate with a marked decrease in the level of Kv1.5 polypeptide. Thus, overexpression of a truncated K
+
channel in the heart alters native K
+
channel expression and has profound effects on cardiac excitability.
Noninvasive measurement of the pH of the endoplasmic reticulum at rest and during calcium release
Authors: Kim Jae Hong , Johannes Ludger , Goud Bruno , Antony Claude , Lingwood Clifford A. , Daneman Richard , Grinstein Sergio
Published: July 2002

The pH within individual organelles of the secretory pathway is believed to be an important determinant of their biosynthetic activity. However, little is known about the determinants and regulation of the pH in the secretory organelles, which cannot be readily accessed by [H
+
]-sensitive probes. We devised a procedure for the dynamic, noninvasive measurement of pH in the lumen of the endoplasmic reticulum in intact mammalian cells. A recombinant form of the B subunit of Shiga toxin, previously modified to include a carboxyl-terminal KDEL sequence and a pH-sensitive fluorophore, was used for a two-stage delivery strategy. Retrograde traffic of endogenous lipids was harnessed to target this protein to the Golgi complex, followed by retrieval to the endoplasmic reticulum (ER) by KDEL receptors. Immunofluorescence and immunoelectron microscopy were used to verify the subcellular localization of the modified B fragment. Fluorescence ratio imaging and two independent calibration procedures were applied to determine the pH of the ER
in situ.
We found that the pH of the endoplasmic reticulum is near neutral and is unaffected during agonist-induced release of calcium. The ER was found to be highly permeable to H
+
(equivalents), so that the prevailing [H
+
] is susceptible to alterations in the cytosolic pH. Plasmalemmal acid-base transporters were shown to indirectly regulate the endoplasmic reticulum pH.
Antibody-mediated targeting of CD45 isoforms: A novel immunotherapeutic strategy
Authors: Basadonna G. P. , Auersvald L. , Khuong C. Q. , Zheng X. X. , Kashio N. , Zekzer D. , Minozzo M. , Qian H.-Y. , Visser L. , Diepstra A. , Lazarovits A. I. , Poppema S. , Strom T. B. , Rothstein D. M.
Published: July 2002

CD45 is a family of transmembrane protein tyrosine phosphatases exclusively expressed by hematopoietic cells and critically involved in the regulation of T cell activation signals. We now demonstrate that three 100-μg doses of anti-CD45RB mAb MB23G2 can induce long-term engraftment of islets into major histcompatibility complex-disparate chemically diabetic mice. Long-term graft survivors (>120 days) were tolerant to new islet allografts from the original donor strain. MB23G2 induced a temporary decrease in number circulating leukocytes but had no effect on leukocyte number in other lymphoid compartments. Histologic examination of allografts from treated and untreated recipients revealed a similar peri-islet infiltration on day 6. Eleven days after transplant, the peri-islet infiltrate in treated animals persisted, but in marked contrast to untreated control animals, there was no insulitis and islet integrity was preserved. The peri-islet infiltrate from treated animals showed a mild increase in CD4 cells, a decrease in CD8 cells, and decreased intensity of CD45RB expression. Treatment of naive animals with anti-CD45RB (MB23G2) resulted in a shift in CD45 isoform expression on T cells with a loss of higher molecular weight isoforms and increased expression of lower molecular weight (CD45R0) isoform. This shift in CD45 isoform expression from CD45RBHito CD45RBLowas associated with an increase in the intragraft expression of transcripts for interleukin (IL) 4 and IL-10, consistent with the expected activity of this distinct immunoregulatory T cell subset. Antibody-mediated targeting of CD45 may induce tolerance through novel mechanisms and have direct applicability to clinical transplantation in humans.
The accessory subunit of mtDNA polymerase shares structural homology with aminoacyl-tRNA synthetases: Implications for a dual role as a primer recognition factor and processivity clamp
Authors: Fan Li , Sanschagrin Paul C. , Kaguni Laurie S. , Kuhn Leslie A.
Published: July 2002

The accessory subunit of the heterodimeric mtDNA polymerase (polγ) from
Drosophila
embryos is required to maintain the structural integrity or catalytic efficiency of the holoenzyme. cDNAs for the accessory subunit from
Drosophila
, man, mouse, and rat have been identified, and comparative sequence alignment reveals that the C-terminal region of about 120 aa is the most conserved. Furthermore, we demonstrate that the accessory subunit of animal polγ has both sequence and structural similarity with class IIa aminoacyl-tRNA synthetases. Based on sequence similarity and fold recognition followed by homology modeling, we have developed a model of the three-dimensional structure of the C-terminal region of the accessory subunit of polγ. The model reveals a rare five-stranded β-sheet surrounded by four α-helices with structural homology to the anticodon-binding domain of class IIa aminoacyl-tRNA synthetases. We postulate that the accessory subunit plays a role in the recognition of RNA primers in mtDNA replication, to recruit polγ to the template–primer junction. A similar role is served by the γ-complex in
Escherichia coli
DNA polymerase III, and indeed our accessory subunit model shows structural similarity with the N-terminal domain of the δ′ subunit of the γ-complex. Structural similarity is also found with
E. coli
thioredoxin, the accessory subunit and processivity factor in bacteriophage T7 DNA polymerase. Thus, we propose that the accessory subunit of polγ is involved both in primer recognition and in processive DNA strand elongation.
c-Abl-induced apoptosis, but not cell cycle arrest, requires mitogen-activated protein kinase kinase 6 activation
Authors: Cong Feng , Goff Stephen P.
Published: July 2002

c-Abl is a ubiquitously expressed protein tyrosine kinase activated by DNA damage and implicated in two responses: cell cycle arrest and apoptosis. The downstream pathways by which c-Abl induces these responses remain unclear. We examined the effect of overexpression of c-Abl on the activation of mitogen-activated protein kinase pathways and found that overexpression of c-Abl selectively stimulated p38, while having no effect on c-Jun N-terminal kinase or on extracellular signal-regulated kinase. c-Abl-induced p38 activation was primarily mediated by mitogen-activated protein kinase kinase (MKK)6. A C-terminal truncation mutant of c-Abl showed no activity for stimulating p38 and MKK6, while a kinase-deficient c-Abl mutant still retained a residual activity. We tested different forms of c-Abl for their ability to induce apoptosis and found that apoptosis induction correlated with the activation of the MKK6-p38 kinase pathway. Importantly, dominant-negative MKK6, but not dominant-negative MKK3 or p38, blocked c-Abl-induced apoptosis. Because overexpression of p38 blocks cell cycle G
1
/S transition, we also tested whether the MKK6-p38 pathway is required for c-Abl-induced cell cycle arrest, and we found that neither MKK6 nor p38 dominant-negative mutants could relieve c-Abl-induced cell cycle arrest. Finally, DNA damage-induced MKK6 and p38 activation was diminished in c-Abl null fibroblasts. Our study suggests that c-Abl is required for DNA damage-induced MKK6 and p38 activation, and that activation of MKK6 by c-Abl is required for c-Abl-induced apoptosis but not c-Abl-induced cell cycle arrest.
Dopamine receptor subtypes modulate olfactory bulb γ-aminobutyric acid type A receptors
Authors: Brünig Ina , Sommer Michael , Hatt Hanns , Bormann Joachim
Published: July 2002

The γ-aminobutyric acid type A (GABA
A
) receptor is the predominant Cl
−
channel protein mediating inhibition in the olfactory bulb and elsewhere in the mammalian brain. The olfactory bulb is rich in neurons containing both GABA and dopamine. Dopamine D1 and D2 receptors are also highly expressed in this brain region with a distinct and complementary distribution pattern. This distribution suggests that dopamine may control the GABAergic inhibitory processing of odor signals, possibly via different signal-transduction mechanisms. We have observed that GABA
A
receptors in the rat olfactory bulb are differentially modulated by dopamine in a cell-specific manner. Dopamine reduced the currents through GABA-gated Cl- channels in the interneurons, presumably granule cells. This action was mediated via D1 receptors and involved phosphorylation of GABA
A
receptors by protein kinase A. Enhancement of GABA responses via activation of D2 dopamine receptors and phosphorylation of GABA
A
receptors by protein kinase C was observed in mitral/tufted cells. Decreasing or increasing the binding affinity for GABA appears to underlie the modulatory effects of dopamine via distinct receptor subtypes. This dual action of dopamine on inhibitory GABA
A
receptor function in the rat olfactory bulb could be instrumental in odor detection and discrimination, olfactory learning, and ultimately odotopic memory formation.
Characterization of complex mineral assemblages: Implications for contaminant transport and environmental remediation
Authors: Bertsch Paul M. , Seaman John C.
Published: July 2002

Surface reactive phases of soils and aquifers, comprised of
phyllosilicate and metal oxohydroxide minerals along with humic
substances, play a critical role in the regulation of contaminant fate
and transport. Much of our knowledge concerning contaminant-mineral
interactions at the molecular level, however, is derived from extensive
experimentation on model mineral systems. Although these investigations
have provided a foundation for understanding reactive surface
functional groups on individual mineral phases, the information cannot
be readily extrapolated to complex mineral assemblages in natural
systems. Recent studies have elucidated the role of less abundant
mineral and organic substrates as important surface chemical modifiers
and have demonstrated complex coupling of reactivity between
permanent-charge phyllosilicates and variable-charge Fe-oxohydroxide
phases. Surface chemical modifiers were observed to control colloid
generation and transport processes in surface and subsurface
environments as well as the transport of solutes and ionic tracers. The
surface charging mechanisms operative in the complex mineral
assemblages cannot be predicted based on bulk mineralogy or by
considering surface reactivity of less abundant mineral phases based on
results from model systems. The fragile nature of mineral assemblages
isolated from natural systems requires novel techniques and
experimental approaches for investigating their surface chemistry and
reactivity free of artifacts. A complete understanding of the surface
chemistry of complex mineral assemblages is prerequisite to accurately
assessing environmental and human health risks of contaminants or in
designing environmentally sound, cost-effective chemical and biological
remediation strategies.
Psychophysical isolation of a motion-processing deficit in schizophrenics and their relatives and its association with impaired smooth pursuit
Authors: Chen Yue , Nakayama Ken , Levy Deborah L. , Matthysse Steven , Holzman Philip S.
Published: July 2002

Schizophrenia patients and many of their relatives show impaired smooth pursuit eye tracking. The brain mechanisms underlying this impairment are not yet known, but because reduced open-loop acceleration and closed-loop gain accompany it, compromised perceptual processing of motion signals is implicated. A previous study showed that motion discrimination is impaired in schizophrenia patients. Motion discrimination can make use of position and contrast as well as velocity cues. Here, we report that the motion discrimination deficit, which occurs in both schizophrenic patients and in their first-degree relatives, involves a failure of velocity detection, which appears when judging intermediate target velocities. At slower and faster velocities, judgments of velocity discrimination seemed normal until we experimentally disentangled velocity cues from nonmotion cues. We further report that compromised velocity discrimination is associated with sluggish initiation of smooth pursuit. These findings point to specific central nervous system correlates of schizophrenic pathophysiology.
Local instrumental variables and latent variable models for identifying and bounding treatment effects
Authors: Heckman James J. , Vytlacil Edward J.
Published: July 2002

This paper examines the relationship between various treatment parameters within a latent variable model when the effects of treatment depend on the recipient’s observed and unobserved characteristics. We show how this relationship can be used to identify the treatment parameters when they are identified and to bound the parameters when they are not identified.
Epistatic and independent functions of Caspase-3 and Bcl-X
L
in developmental programmed cell death
Authors: Roth K. A. , Kuan C.-Y. , Haydar T. F. , D'Sa-Eipper C. , Shindler K. S. , Zheng T. S. , Kuida K. , Flavell R. A. , Rakic P.
Published: July 2002

The number of neurons in the mammalian brain is determined by a balance between cell proliferation and programmed cell death. Recent studies indicated that Bcl-X
L
prevents, whereas Caspase-3 mediates, cell death in the developing nervous system, but whether Bcl-X
L
directly blocks the apoptotic function of Caspase-3
in vivo
is not known. To examine this question, we generated
bcl-x
/
caspase-3
double mutants and found that
caspase-3
deficiency abrogated the increased apoptosis of postmitotic neurons but not the increased hematopoietic cell death and embryonic lethality caused by the
bcl-x
mutation. In contrast,
caspase-3
, but not
bcl-x
, deficiency changed the normal incidence of neuronal progenitor cell apoptosis, consistent with the lack of expression of Bcl-X
L
in the proliferative population of the embryonic cortex. Thus, although Caspase-3 is epistatically downstream to Bcl-X
L
in postmitotic neurons, it independently regulates apoptosis of neuronal founder cells. Taken together, these results establish a role of programmed cell death in regulating the size of progenitor population in the central nervous system, a function that is distinct from the classic role of cell death in matching postmitotic neuronal population with postsynaptic targets.
c-Abl is required for development and optimal cell proliferation in the context of p53 deficiency
Authors: Whang Young E. , Tran Chris , Henderson Cailin , Syljuasen Randi G. , Rozengurt Nora , McBride William H. , Sawyers Charles L.
Published: July 2002

The c-Abl tyrosine kinase and the p53 tumor suppressor protein interact functionally and biochemically in cellular genotoxic stress response pathways and are implicated as downstream mediators of ATM (ataxia-telangiectasia mutated). This fact led us to study genetic interactions
in vivo
between c-Abl and p53 by examining the phenotype of mice and cells deficient in both proteins. c-Abl-null mice show high neonatal mortality and decreased B lymphocytes, whereas p53-null mice are prone to tumor development. Surprisingly, mice doubly deficient in both c-Abl and p53 are not viable, suggesting that c-Abl and p53 together contribute to an essential function required for normal development. Fibroblasts lacking both c-Abl and p53 were similar to fibroblasts deficient in p53 alone, showing loss of the G
1
/S cell-cycle checkpoint and similar clonogenic survival after ionizing radiation. Fibroblasts deficient in both c-Abl and p53 show reduced growth in culture, as manifested by reduction in the rate of proliferation, saturation density, and colony formation, compared with fibroblasts lacking p53 alone. This defect could be restored by reconstitution of c-Abl expression. Taken together, these results indicate that the ATM phenotype cannot be explained solely by loss of c-Abl and p53 and that c-Abl contributes to enhanced proliferation of p53-deficient cells. Inhibition of c-Abl function may be a therapeutic strategy to target p53-deficient cells selectively.
Nutrient regulation of gene expression by the sterol regulatory element binding proteins: Increased recruitment of gene-specific coregulatory factors and selective hyperacetylation of histone H3
in vivo
Authors: Bennett Mary K. , Osborne Timothy F.
Published: July 2002

We have evaluated the mechanism for sterol-regulated gene expression by the sterol regulatory element binding proteins (SREBPs) in intact cells. We show that activation of SREBPs by sterol depletion results in the increased binding of Sp1 to a site adjacent to SREBP in the promoter for the low density lipoprotein (LDL) receptor gene
in vivo
. Similarly, sterol depletion resulted in the increased recruitment of two distinct SREBP coregulatory factors, NF-Y and CREB, to the promoter for hydroxymethyl glutaryl CoA reductase, another key gene of intracellular cholesterol homeostasis. Furthermore, increased acetylation of histone H3 but not H4 was also detected in chromatin from both promoters on SREBP activation. Thus, SREBP activation results in the similar selective recruitment of different coregulatory generic transcription factors to two separate cholesterol-regulated promoters. These studies demonstrate the utility of the chromatin immunoprecipitation technique for analyzing the differential action of low-abundance transcription factors in fundamental regulatory events in intact cells. Our results also provide key
in vivo
support for the mechanism proposed from cell-free experiments, where SREBP increased the binding of Sp1 to the LDL receptor promoter. Finally, our findings also indicate that subtle differences in the pattern of core histone acetylation play a role in selective gene activation.
The x-ray structure of
d
-amino acid oxidase at very high resolution identifies the chemical mechanism of flavin-dependent substrate dehydrogenation
Authors: Umhau Stephan , Pollegioni Loredano , Molla Gianluca , Diederichs Kay , Welte Wolfram , Pilone Mirella S. , Ghisla Sandro
Published: July 2002

Flavin is one of the most versatile redox cofactors in nature and
is used by many enzymes to perform a multitude of chemical reactions.
d
-Amino acid oxidase (DAAO), a member of the flavoprotein
oxidase family, is regarded as a key enzyme for the understanding of
the mechanism underlying flavin catalysis. The very high-resolution
structures of yeast DAAO complexed with
d
-alanine,
d
-trifluoroalanine, and
l
-lactate (1.20, 1.47,
and 1.72 Å) provide strong evidence for hydride transfer as the
mechanism of dehydrogenation. This is inconsistent with the alternative
carbanion mechanism originally favored for this type of enzymatic
reaction. The step of hydride transfer can proceed without involvement
of amino acid functional groups. These structures, together with
results from site-directed mutagenesis, point to orbital
orientation/steering as the major factor in catalysis. A diatomic
species, proposed to be a peroxide, is found at the active center and
on the
Re
-side of the flavin. These results are of
general relevance for the mechanisms of flavoproteins and lead to the
proposal of a common dehydrogenation mechanism for oxidases and
dehydrogenases.
Purification and kinetic analysis of recombinant CA XII, a membrane carbonic anhydrase overexpressed in certain cancers
Authors: Ulmasov Barbara , Waheed Abdul , Shah Gul N. , Grubb Jeffrey H. , Sly William S. , Tu Chingkuang , Silverman David N.
Published: July 2002

Carbonic anhydrase XII (CA XII) is a transmembrane glycoprotein
with an active extracellular CA domain that is overexpressed on cell
surfaces of certain cancers. Its expression has been linked to tumor
invasiveness. To characterize its catalytic properties, we purified
recombinant secretory forms of wild-type and mutant CA XIIs. The
catalytic properties of these enzymes in the hydration of
CO
2
were measured at steady state by stopped-flow
spectrophotometry and at chemical equilibrium by the exchange of
18
O between CO
2
and water determined by mass
spectrometry. The catalysis of CO
2
hydration by soluble CA
XII has a maximal value of
k
cat
/
K
m
at 34
μM
−1
⋅s
−1
, which is similar to those of
the membrane-associated CA IV and to soluble CA I. The pH profiles of
this catalysis and the catalyzed hydrolysis of 4-nitrophenylacetate
indicate that the pK
a
of the zinc-bound water in CA XII is
7.1. His64 in CA XII acts as a proton shuttle residue, as evidenced by
the reduced rate constant for proton transfer in the mutants containing
the replacements His64 → Ala and His64 → Arg, as well as by the
selective inhibition of the proton transfer step by cupric ions in
wild-type CA XII. The catalytic rate of CO
2
hydration by
the soluble form of CA XII is identical with that of the membrane-bound
enzyme. These observations suggest a role for CA XII in
CO
2
/HCO
3
−
homeostasis in cells in which
it is normally expressed. They are also compatible with a role for CA
XII in acidifying the microenvironment of cancer cells in which CA XII
is overexpressed, providing a mechanism for CA XII to augment tumor
invasiveness and suggesting CA XII as a potential target for
chemotherapeutic agents.
Brain size does not predict general cognitive ability within families
Authors: Schoenemann P. Thomas , Budinger Thomas F. , Sarich Vincent M. , Wang William S.-Y.
Published: July 2002

Hominid brain size increased dramatically in the face of apparently severe associated evolutionary costs. This suggests that increasing brain size must have provided some sort of counterbalancing adaptive benefit. Several recent studies using magnetic resonance imaging (MRI) have indicated that a substantial correlation (mean
r
= ≈0.4) exists between brain size and general cognitive performance, consistent with the hypothesis that the payoff for increasing brain size was greater general cognitive ability. However, these studies confound between-family environmental influences with direct genetic/biological influences. To address this problem, within-family (WF) sibling differences for several neuroanatomical measures were correlated to WF scores on a diverse battery of cognitive tests in a sample of 36 sibling pairs. WF correlations between neuroanatomy and general cognitive ability were essentially zero, although moderate correlations were found between prefrontal volumes and the Stroop test (known to involve prefrontal cortex). These findings suggest that nongenetic influences play a role in brain volume/cognitive ability associations. Actual direct genetic/biological associations may be quite small, and yet still may be strong enough to account for hominid brain evolution.
Alienation: A Symptomatic Reaction of Educated Unemployed Youth in India
Authors: Singh Lai Bahadur , Singh Arun Kumar , Rani Asha
Published: July 2002

A 21‐item 4‐point Alienation Scale (Kureshi & Dutt, 1979) in Hindi was administered to a randomly selected group of 400 educated youth equally divided into: (1) technically educated unemployed, (2) non‐technically educated unemployed, (3) technically educated employed, and (4) non‐technically educated employed. This scale aimed to ascertain in these subjects comparative degrees of feeling of alienation and its dimensions. Results of statistical comparison revealed that the technically and the non‐technically educated unemployed youth, as compared to their employed counterparts, evinced relatively a greater vulnerability to the feeling of alienation and its dimensions, though the latter were also moderately susceptible in this regard. Further, it was found that the technically educated unemployed youth were more prone to alienation and its dimensions and the non‐technically educated employed youth were the least affected, with the non‐technically educated unemployed and the technically educated employed youth in second and third places respectively. The study also indicated a close association between different dimensions of alienation, both with each other and with the total scale scores.
Mémoires exacte et inférentielle en arithmétique mentale
Authors: Fischer Jean‐Paul
Published: July 2002

Dans cette recherche, nous cherchons à éprouver la pertinence de la distinction de deux mémoires qualifiées d'exacte et d'inférentielle. Dans les deux expériences, sur 140 élèves de Cours Moyen et 456 étudiants respectivement, les sujets prennent d'abord connaissance d'un matériel numérique: un problème arithmétique ou un calcul mental (e.g. 86 + 47 + 93 + 52). Ensuite, ils sont interrogés à la fois sur des données exactes contenues dans ce matériel et sur des données susceptibles d'en ětre inférées.

La recherche ne confirme pas clairement une indépendance des deux types de mémoire. En revanche, elle apporte des évidences en faveur d'une moindre sensibilité à l'amorçage de la mémoire exacte. Elle suggère aussi que l'effet de distance peut, en calcul mental, ětre différencié suivant les opérations arithmétiques: les opérations additives y sont plus sensibles que les opérations multiplicatives.
Social Values and Relationships with Parents among American College Women of Chinese and European Descent
Authors: Wink Paul , Gao Beryl , Jones Stephanie , Chao Frances
Published: July 2002

This study compared social values and relationships with parents among American college women of Chinese and European descent. Chinese‐American women scored higher on a measure of practicality and pragmatism (mastery), hierarchy, and traditionality. The Euro‐American women showed a greater interest in voluntary prosocial behaviour and philanthropy. Both groups of women reported having a sense of self, autonomous of their parents. Within the Chinese‐American group, ethnic identification and religion, but not generation, moderated scores on a measure of traditionality of outlook regarding issues of law and order and social equality. We discuss the implications of our findings for recent debates in cross‐cultural psychology, including the growing challenge to the individualism‐collectivism dimension.
Retracing Estonia's Russians: Mikhail Kurchinskii and Interwar Cultural Autonomy
Authors: Smith David J.
Published: July 2002

In exploring the history of the Russian minority in Estonia during 1918–1940, one is inevitably drawn to the figure of Professor Mikhail Anatolevich Kurchinskii (1876–1939). An academic and journalist, Kurchinskii was also an important political actor devoted to the quest for a satisfactory resolution of the nationality question in Estonia and Europe. It is with good reason that Kurchinskii has been called “the most important theoretician and practical advocate of cultural autonomy amongst the [interwar] Russian minority in Estonia.” From 1927 he also served as a leading member of the Congress of European Minorities (CEM), which became the main promoter of the cultural autonomy concept on the wider European stage. During the same period he took a deep interest in the work of the Pan-Europe movement and the quest for a durable settlement of European affairs following the traumas of World War I. Until very recently, however, Kurchinskii has remained a neglected figure among historians, even within the narrow field of Baltic studies. This neglect is symptomatic of the lack of attention devoted to the political history of the Russian minority more generally. As the first group to implement Estonia's celebrated 1925 law on cultural autonomy, the interwar German minority has already formed the object of a number of studies. By contrast, Kurchinskii's failure to realize the autonomy project means that he—and, indeed, the Russian minority as a whole—barely receives a mention in most histories of Estonia. Just as Kurchinskii's aspirations regarding cultural autonomy were never realized during his lifetime, so his vision of building a “New Europe” faded against the background of economic depression and a retreat into inward-looking national particularism during the 1930s. The tragic fate that befell central and eastern Europe after 1939 has in turn tended to obscure many of the ideas and positive achievements of the interwar minorities movement. This article uses Kurchinskii's career to illuminate issues relating to the sociopolitical development of the Russian minority between the wars. In particular it compares Kurchinskii's thinking on minority issues with that of his rival Aleksei Janson (1866–1940), a socialist politician and pedagogical expert who served as Russian National Secretary in the Estonian Ministry of Education from 1922 to 1927. Finally, by linking Kurchinskii's quest for cultural autonomy to his broader thinking on the “New Europe,” the article assesses the relevance of these ideas to contemporary debates on the nationality question.
Traitors Everywhere! Political Trials in the late Habsburg Monarchy
Authors: Kelly T. Mills
Published: July 2002

On 4 March 1914 the Young Czech party newspaper Národní listy published the startling accusation that a prominent Czech politician, the National Socialist Karel Šviha, was a paid informant of the Habsburg imperial police. The paper alleged that for several years Šviha, who was the chairman of the National Socialist party's parliamentary club, had exchanged information on the activities of his colleagues for a police stipend. In the weeks that followed, the public was treated to a daily diet of charge and counter-charge in the Prague newspapers, a carnival of mutual recrimination that concluded with an elaborately staged public trial of Šviha in an attempt to settle once and for all whether he was truly an informant. During the proceedings leading figures of most of the main Czech political parties either sat in judgement of Šviha or testified for one side or the other, many of them displaying for all to see a level of personal animosity previously reserved for the Bohemian Germans or the Imperial government. As one observer (a National Socialist) put it, by the summer of 1914, “there was no nation in Europe as internally disorganized as were the Czechs” and according to another (a Young Czech), political life in Prague had reached a state where it was “everyone against everything.”
Scaffolding in low-income mother-child dyads: Relations with joint attention and dyadic reciprocity
Authors: Hustedt Jason T. , Raver C. Cybele
Published: July 2002

This study was conducted to further extend scaffolding research to low-income dyads because living in poverty may serve as a risk factor for experiencing difficulties in social and cognitive development during childhood. Scaffolding was examined in the context of mother-toddler dyads’ ( N = 56) performance of a routine feeding task that was difficult for 2-year-olds to complete independently. Both verbal and nonverbal behaviours were microanalytically coded in order to characterise the successive scaffolding strategies by mothers, and their children’s responses. Also, scaffolding data were compared to data on joint attention and dyadic reciprocity obtained from a free-play task. Results show that mothers’ use of constructive verbal strategies during the feeding task was positively associated with joint attention and mother-initiated dyadic reciprocity, both of which may be viewed as indices of maternal sensitivity. Thus, the provision of verbal assistance may be one mark of maternal sensitivity during scaffolding in low-income dyads.
Fathers’ and mothers’ distancing strategies towards toddlers
Authors: Labrell F. , Deleau M. , Juhel J.
Published: July 2002

Fathers’ and mothers’ distancing strategies towards preschoolers were studied in 30-month-old ( N = 13) and 42-month-old ( N = 15) parent-children dyads, using Sigel’s scheme. This coding scheme concerns either direct verbal requests (or denominations), or indirect demands about presented objects. Afree play situation included objects that allowed several activities, functional or not (doll, little cars, etc). The aim was twofold. First, distancing was linked to the child’s age and to the sex of parent with the assumption that fathers would be more challenging. Second, children’s symbolic activity was linked to parental distancing strategies at each age. Results showed that there was a significant effect of children’s age on the distancing measures as well as on children’s symbolic activity. The hypothesis of a more challenging father was not supported. The child’s symbolic activity was better predicted by mother’s distancing than by father’s. Such results indicate a need to consider more complex relationships between paternal interaction and children’s outcomes and to take into account extra-familial contributions.
Genetic and environmental influences on teacher ratings of the Child Behavior Checklist
Authors: Towers Hilary , Spotts Erica , Neiderhiser Jenae M. , Plomin Robert , Hetherington E. Mavis , Reiss David
Published: July 2002

The knowledge we have of childhood and adolescent behaviour is, to some extent, a function of the unique perspective of the rater. Although many behavioural genetics studies have used parent and child self-reports in their assessments of child and adolescent adjustment, few have included teacher ratings of behaviour. It is possible that genetic and environmental contributions to teacher reports are different from those using parent and self-reports. The present study examined genetic and environmental influences on six subscales of the Child Behavior Checklist Teacher Report Form (CBC-TRF) using a normative sample of adolescents. The sample consisted of 373 same-sex twin and sibling pairs of varying degrees of genetic relatedness participating in the Nonshared Environment in Adolescent project (NEAD). For all of the CBC subscales, except attention problems and social problems, nonshared environmental influence was the most important source of variance. Additive genetic factors were of moderate importance for externalising behaviours, whereas nonadditive genetic factors contributed to the anxious/depressed, attention problems, withdrawn, and social problems subscales. For none of the constructs was shared environment a significant influence. Three alternative models testing for contrast effects, differences in twin and nontwin siblings, and differences in nondivorced and stepfamilies were examined. In most cases, the best-fitting model was a model that did not include any of these effects, suggesting that these factors do not critically affect the basic model. However, some of the patterns of correlations and parameter estimates were unusual and may warrant future investigation.
Online Gambling: Challenges to National Sovereignty and Regulation
Authors: Mcmillen Jan
Published: July 2002

Online gambling utilises advanced telecommunications technology to provide access to gambling across national borders, presenting unprecedented opportunities for industry and new challenges for government regulation and national sovereignty. It also promises to revolutionise the way people gamble, raising critical issues about social and economic impacts. Nations have taken a variety of approaches to online gambling, ranging from unregulated legalisation to prohibition, creating a perplexing and uncertain legal environment. This paper will examine the development of Internet and interactive gambling, the responses by governments and industry, and the issues for policy-makers and regulators.
Environmental Management, Structure, Networks and Information Exchange: The Case of a Tasmanian Pulp and Paper Mill
Authors: Chadwick Samantha , Hanson Dallas
Published: July 2002

Pulp and paper is a major impact industry, in which environmental impacts can be seen to be complex, diverse and characterised by uncertainty and interdependence. A greening process within this industry requires wide ranging environmental knowledge. Also fundamental are effective networks for information exchange and greening is therefore dependent on changes to such networks. This study investigates the issue of how greening occurs, focusing on the process at the Fletcher Challenge New Zealand integrated pulp and paper mill situated in Tasmania, Australia. It was seen that effective greening within this industry relies on information processing capabilities to access external and internal knowledge and skills, and that this is fundamentally dependent on structural arrangements. Appropriate organisational structure and external networks are therefore essential for accessing information and facilitating its dissemination and integration, thereby enhancing the firm's ability to address environmental concerns. The study highlights interaction between the formal change process, one which sought limited change, and an informal change process that continued greening the company beyond the official aims. The reasons for this are located in the power of informal information exchange.
Gender and the Information Work Force: New Zealand Evidence and Issues
Authors: Engelbrecht Hans-Jürgen
Published: July 2002

This paper documents the growth and gender composition of New Zealand's information work force over the period 1976‐96. By 1996, about 55% of the female work force was employed in information occupations, compared to 40% of the male work force. The share of high-skilled information workers increased substantially over time, and faster for females than males. This suggests faster upskilling of the female information work force. The paper also briefly comments on some related, but much narrower, 'knowledge worker' concepts, and on some of the problems encountered if one wants to relate the work force measures to endogenous growth theory. The concluding comments provide a wish list of further research.