bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphorylating DNA with DNA
Authors: Li Yingfu , Breaker Ronald R.
Published: July 2002

Nearly 50 individual DNAs with polynucleotide kinase-like activity were isolated from a random-sequence pool by using
in vitro
selection. Each self-phosphorylating deoxyribozyme makes use of one or more of the eight standard NTPs or dNTPs as a source of activated phosphate. Although most prototypic deoxyribozymes poorly differentiate between the ribose and deoxyribose moieties, further optimization by
in vitro
selection produced variants that display up to 100-fold discrimination between related NTP and dNTP substrates. An optimized ATP-dependent deoxyribozyme uses ATP >40,000-fold more efficiently than CTP, GTP, or UTP. This enzyme operates with a rate enhancement of nearly one billion-fold over the uncatalyzed rate of ATP hydrolysis. A bimolecular version of the ATP-dependent deoxyribozyme was further engineered to phosphorylate specific target DNAs with multiple turnover. The substrate-recognition patterns and rate enhancements intrinsic to these DNAs are characteristic of naturally occurring RNA and protein enzymes, supporting the hypothesis that DNA has sufficient catalytic potential to function as an enzyme in biological systems.
Designing conditions for
in vitro
formation of amyloid protofilaments and fibrils
Authors: Chiti Fabrizio , Webster Paul , Taddei Niccolò , Clark Anne , Stefani Massimo , Ramponi Giampietro , Dobson Christopher M.
Published: July 2002

We have been able to convert a small α/β protein, acylphosphatase, from its soluble and native form into insoluble amyloid fibrils of the type observed in a range of pathological conditions. This was achieved by allowing slow growth in a solution containing moderate concentrations of trifluoroethanol. When analyzed with electron microscopy, the protein aggregate present in the sample after long incubation times consisted of extended, unbranched filaments of 30–50 Å in width that assemble subsequently into higher order structures. This fibrillar material possesses extensive β-sheet structure as revealed by far-UV CD and IR spectroscopy. Furthermore, the fibrils exhibit Congo red birefringence, increased fluorescence with thioflavine T and cause a red-shift of the Congo red absorption spectrum. All of these characteristics are typical of amyloid fibrils. The results indicate that formation of amyloid occurs when the native fold of a protein is destabilized under conditions in which noncovalent interactions, and in particular hydrogen bonding, within the polypeptide chain remain favorable. We suggest that amyloid formation is not restricted to a small number of protein sequences but is a property common to many, if not all, natural polypeptide chains under appropriate conditions.
The β
2
-adrenergic receptor/βarrestin complex recruits the clathrin adaptor AP-2 during endocytosis
Authors: Laporte Stéphane A. , Oakley Robert H. , Zhang Jie , Holt Jason A. , Ferguson Stephen S. G. , Caron Marc G. , Barak Larry S.
Published: July 2002

βarrestins mediate the desensitization of the β
2
-adrenergic receptor (β
2
AR) and many other G protein-coupled receptors (GPCRs). Additionally, βarrestins initiate the endocytosis of these receptors via clathrin coated-pits and interact directly with clathrin. Consequently, it has been proposed that βarrestins serve as clathrin adaptors for the GPCR family by linking these receptors to clathrin lattices. AP-2, the heterotetrameric clathrin adaptor protein, has been demonstrated to mediate the internalization of many types of plasma membrane proteins other than GPCRs. AP-2 interacts with the clathrin heavy chain and cytoplasmic domains of receptors such as those for epidermal growth factor and transferrin. In the present study we demonstrate the formation of an agonist-induced multimeric complex containing a GPCR, βarrestin 2, and the β2-adaptin subunit of AP-2. β2-Adaptin binds βarrestin 2 in a yeast two-hybrid assay and coimmunoprecipitates with βarrestins and β
2
AR in an agonist-dependent manner in HEK-293 cells. Moreover, β2-adaptin translocates from the cytosol to the plasma membrane in response to the β
2
AR agonist isoproterenol and colocalizes with β
2
AR in clathrin-coated pits. Finally, expression of βarrestin 2 minigene constructs containing the β2-adaptin interacting region inhibits β
2
AR endocytosis. These findings point to a role for AP-2 in GPCR endocytosis, and they suggest that AP-2 functions as a clathrin adaptor for the endocytosis of diverse classes of membrane receptors.
Self-assembly of polyglutamine-containing huntingtin fragments into amyloid-like fibrils: Implications for Huntington’s disease pathology
Authors: Scherzinger Eberhard , Sittler Annie , Schweiger Katja , Heiser Volker , Lurz Rudi , Hasenbank Renate , Bates Gillian P. , Lehrach Hans , Wanker Erich E.
Published: July 2002

Huntington’s disease is a progressive neurodegenerative disorder caused by a polyglutamine [poly(Q)] repeat expansion in the first exon of the huntingtin protein. Previously, we showed that N-terminal huntingtin peptides with poly(Q) tracts in the pathological range (51–122 glutamines), but not with poly(Q) tracts in the normal range (20 and 30 glutamines), form high molecular weight protein aggregates with a fibrillar or ribbon-like morphology, reminiscent of scrapie prion rods and β-amyloid fibrils in Alzheimer’s disease. Here we report that the formation of amyloid-like huntingtin aggregates
in vitro
not only depends on poly(Q) repeat length but also critically depends on protein concentration and time. Furthermore, the
in vitro
aggregation of huntingtin can be seeded by preformed fibrils. Together, these results suggest that amyloid fibrillogenesis in Huntington’s disease, like in Alzheimer’s disease, is a nucleation-dependent polymerization.
Assembly of τ protein into Alzheimer paired helical filaments depends on a local sequence motif (
306
VQIVYK
311
) forming β structure
Authors: von Bergen M. , Friedhoff P. , Biernat J. , Heberle J. , Mandelkow E.-M. , Mandelkow E.
Published: July 2002

We have searched for a minimal interaction motif in τ protein that supports the aggregation into Alzheimer-like paired helical filaments. Digestion of the repeat domain with different proteases yields a GluC-induced fragment comprising 43 residues (termed PHF43), which represents the third repeat of τ plus some flanking residues. This fragment self assembles readily into thin filaments without a paired helical appearance, but these filaments are highly competent to nucleate bona fide PHFs from full-length τ. Probing the interactions of PHF43 with overlapping peptides derived from the full τ sequence yields a minimal hexapeptide interaction motif of
306
VQIVYK
311
at the beginning of the third internal repeat. This motif coincides with the highest predicted β-structure potential in τ. CD and Fourier transform infrared spectroscopy shows that PHF43 acquires pronounced β structure in conditions of self assembly. Point mutations in the hexapeptide region by proline-scanning mutagenesis prevent the aggregation. The data indicate that PHF assembly is initiated by a short fragment containing the minimal interaction motif forming a local β structure embedded in a largely random-coil protein.
Hybridization as a stimulus for the evolution of invasiveness in plants?
Authors: Ellstrand Norman C. , Schierenbeck Kristina A.
Published: July 2002

Invasive species are of great interest to evolutionary biologists and ecologists because they represent historical examples of dramatic evolutionary and ecological change. Likewise, they are increasingly important economically and environmentally as pests. Obtaining generalizations about the tiny fraction of immigrant taxa that become successful invaders has been frustrated by two enigmatic phenomena. Many of those species that become successful only do so (i) after an unusually long lag time after initial arrival, and/or (ii) after multiple introductions. We propose an evolutionary mechanism that may account for these observations. Hybridization between species or between disparate source populations may serve as a stimulus for the evolution of invasiveness. We present and review a remarkable number of cases in which hybridization preceded the emergence of successful invasive populations. Progeny with a history of hybridization may enjoy one or more potential genetic benefits relative to their progenitors. The observed lag times and multiple introductions that seem a prerequisite for certain species to evolve invasiveness may be a correlate of the time necessary for previously isolated populations to come into contact and for hybridization to occur. Our examples demonstrate that invasiveness can evolve. Our model does not represent theonlyevolutionary pathway to invasiveness, but is clearly an underappreciated mechanism worthy of more consideration in explaining the evolution of invasiveness in plants.
In vitro
cultivation of human islets from expanded ductal tissue
Authors: Bonner-Weir Susan , Taneja Monica , Weir Gordon C. , Tatarkiewicz Krystyna , Song Ki-Ho , Sharma Arun , O'Neil John J.
Published: July 2002

A major obstacle to successful islet transplantation for both type 1 and 2 diabetes is an inadequate supply of insulin-producing tissue. This need for transplantable human islets has stimulated efforts to expand existing pancreatic islets and/or grow new ones. To test the hypothesis that human adult duct tissue could be expanded and differentiated
in vitro
to form islet cells, digested pancreatic tissue that is normally discarded from eight human islet isolations was cultured under conditions that allowed expansion of the ductal cells as a monolayer whereupon the cells were overlaid with a thin layer of Matrigel. With this manipulation, the monolayer of epithelial cells formed three-dimensional structures of ductal cysts from which 50-to 150-μm diameter islet-like clusters of pancreatic endocrine cells budded. Over 3–4 weeks culture the insulin content per flask increased 10- to 15-fold as the DNA content increased up to 7-fold. The cultivated human islet buds were shown by immunofluorescence to consist of cytokeratin 19-positive duct cells and hormone-positive islet cells. Double staining of insulin and non-β cell hormones in occasional cells indicated immature cells still in the process of differentiation. Insulin secretion studies were done over 24 h in culture. Compared with their basal secretion at 5 mM glucose, cysts/cultivated human islet buds exposed to stimulatory 20 mM glucose had a 2.3-fold increase in secreted insulin. Thus, duct tissue from human pancreas can be expanded in culture and then be directed to differentiate into glucose responsive islet tissue
in vitro
. This approach may provide a potential new source of pancreatic islet cells for transplantation.
Nitric oxide and salicylic acid signaling in plant defense
Authors: Klessig Daniel F. , Durner Jörg , Noad Robert , Navarre Duroy A. , Wendehenne David , Kumar Dhirendra , Zhou Jun Ma , Shah Jyoti , Zhang Shuqun , Kachroo Pradeep , Trifa Youssef , Pontier Dominique , Lam Eric , Silva Herman
Published: July 2002

Salicylic acid (SA) plays a critical signaling role in the
activation of plant defense responses after pathogen attack. We have
identified several potential components of the SA signaling pathway,
including (
i
) the
H
2
O
2
-scavenging enzymes catalase and ascorbate
peroxidase, (
ii
) a high affinity SA-binding protein
(SABP2), (
iii
) a SA-inducible protein kinase (SIPK),
(
iv
) NPR1, an ankyrin repeat-containing protein that
exhibits limited homology to IκBα and is required for SA signaling,
and (
v
) members of the TGA/OBF family of bZIP
transcription factors. These bZIP factors physically interact with NPR1
and bind the SA-responsive element in promoters of several defense
genes, such as the pathogenesis-related 1 gene (
PR-1
).
Recent studies have demonstrated that nitric oxide (NO) is another
signal that activates defense responses after pathogen attack. NO has
been shown to play a critical role in the activation of innate immune
and inflammatory responses in animals. Increases in NO synthase
(NOS)-like activity occurred in resistant but not susceptible tobacco
after infection with tobacco mosaic virus. Here we demonstrate that
this increase in activity participates in
PR-1
gene
induction. Two signaling molecules, cGMP and cyclic ADP ribose (cADPR),
which function downstream of NO in animals, also appear to mediate
plant defense gene activation (e.g.,
PR-1
).
Additionally, NO may activate
PR-1
expression via an
NO-dependent, cADPR-independent pathway. Several targets of NO in
animals, including guanylate cyclase, aconitase, and mitogen-activated
protein kinases (e.g., SIPK), are also modulated by NO in plants. Thus,
at least portions of NO signaling pathways appear to be shared between
plants and animals.
The TACC domain identifies a family of centrosomal proteins that can interact with microtubules
Authors: Gergely Fanni , Karlsson Christina , Still Ivan , Cowell John , Kilmartin John , Raff Jordan W.
Published: July 2002

We recently showed that the
Drosophila
transforming
acidic coiled-coil (D-TACC) protein is located in the centrosome,
interacts with microtubules, and is required for mitosis in the
Drosophila
embryo. There are three known human TACC
proteins that share a conserved, C-terminal, coiled-coil region with
D-TACC. These proteins have all been implicated in cancer, but their
normal functions are unknown. We show that all three human TACC
proteins are concentrated at centrosomes, but with very different
characteristics: TACC1 is weakly concentrated at centrosomes during
mitosis; TACC2 is strongly concentrated at centrosomes throughout the
cell cycle; and TACC3 is strongly concentrated in a more diffuse region
around centrosomes during mitosis. When the C-terminal TACC domain is
overexpressed in HeLa cells, it forms large polymers in the cytoplasm
that can interact with both microtubules and tubulin. The full-length
TACC proteins form similar polymers when overexpressed, but their
interaction with microtubules and tubulin is regulated during the cell
cycle. At least one of the human TACC proteins appears to increase the
number and/or stability of centrosomal microtubules when
overexpressed during mitosis. Thus, the TACC domain identifies a family
of centrosomal proteins that can interact with microtubules. This may
explain the link between the TACC genes and cancer.
Glucocorticoids repress NF-κB-driven genes by disturbing the interaction of p65 with the basal transcription machinery, irrespective of coactivator levels in the cell
Authors: De Bosscher Karolien , Vanden Berghe Wim , Vermeulen Linda , Plaisance Stéphane , Boone Elke , Haegeman Guy
Published: July 2002

Glucocorticoids (GCs) are used to combat inflammatory diseases. Their beneficial effect relies mainly on the inhibition of NF-κB- and/or AP-1-driven proinflammatory gene expression. Previously, we have shown that GCs repress tumor necrosis factor-induced IL-6 gene expression by an NF-κB-dependent nuclear mechanism without changing the DNA-binding capacity of NF-κB or the expression levels of the cytoplasmic inhibitor of NF-κB (IκB-α). In the present work, we investigate the effect of GC repression on different natural and/or recombinant NF-κB-driven reporter gene constructs in the presence of increasing amounts of various coactivator molecules, such as CREB-binding protein (CBP), p300, and SRC-1. We found that GCs maintain their repressive capacities, irrespective of the amount of cofactor present in the cell. Similar results were obtained for the reciprocal transrepression of a GC receptor (GR) element-driven reporter gene by p65. We demonstrate that neither the expression levels of p65 and CBP nor their physical association are affected by activated GR. Using Gal4 chimeras, we show that repression by GCs is specific for p65-mediated transactivation, ruling out competition for limiting nuclear factors as the major underlying mechanism of gene repression. In addition, the transactivation potential of a point-mutated Gal4-p65 variant with a decreased CBP interaction capability is still repressed by GR. Finally, we present evidence that the specificity of GC repression on p65-driven gene expression is codetermined by the TATA box context.
Uncovering the [2Fe2S] domain movement in cytochrome
bc
1
and its implications for energy conversion
Authors: Darrouzet Elisabeth , Valkova-Valchanova Maria , Moser Christopher C. , Dutton P. Leslie , Daldal Fevzi
Published: July 2002

In crystals of the key respiratory and photosynthetic electron transfer protein called ubihydroquinone:cytochrome (cyt)
c
oxidoreductase or cyt
bc
1
, the extrinsic [2Fe2S] cluster domain of its Fe-S subunit assumes several conformations, suggesting that it may move during catalysis. Herein, using
Rhodobacter capsulatus
mutants that have modifications in the hinge region of this subunit, we were able to reveal this motion kinetically. Thus, the
bc
1
complex (and possibly the homologous
b
6
f
complex in chloroplasts) employs the [2Fe2S] cluster domain as a device to shuttle electrons from ubihydroquinone to cyt
c
1
(or cyt
f
). We demonstrate that this domain movement is essential for cyt
bc
1
function, because a mutant enzyme with a nonmoving Fe-S subunit has no catalytic activity, and one with a slower movement has lower activity. This motion is apparently designed with a natural frequency slow enough to assure productive Q
o
site charge separation but fast enough not to be rate limiting. These findings add the unprecedented function of intracomplex electron shuttling to large-scale domain motions in proteins and may well provide a target for cyt
bc
1
antibiotics.
A family of tissue-specific resistin-like molecules
Authors: Steppan Claire M. , Brown Elizabeth J. , Wright Christopher M. , Bhat Savitha , Banerjee Ronadip R. , Dai Charlotte Y. , Enders Gregory H. , Silberg Debra G. , Wen Xiaoming , Wu Gary D. , Lazar Mitchell A.
Published: July 2002

We have identified a family of resistin-like molecules (RELMs) in rodents and humans. Resistin is a hormone produced by fat cells. RELMα is a secreted protein that has a restricted tissue distribution with highest levels in adipose tissue. Another family member, RELMβ, is a secreted protein expressed only in the gastrointestinal tract, particularly the colon, in both mouse and human. RELMβ gene expression is highest in proliferative epithelial cells and is markedly increased in tumors, suggesting a role in intestinal proliferation. Resistin and the RELMs share a cysteine composition and other signature features. Thus, the RELMs together with resistin comprise a class of tissue-specific signaling molecules.
Molecular clocks
Authors: Robinson Noah E. , Robinson Arthur B.
Published: July 2002

A convenient and precise mass spectrometric method for measurement
of the deamidation rates of glutaminyl and asparaginyl residues in
peptides and proteins has been developed; the rates of deamidation of
306 asparaginyl sequences in model peptides at pH 7.4, 37.0°C, 0.15 M
Tris⋅HCl buffer have been determined; a library of 913
amide-containing peptides for use by other investigators in similar
studies has been established; and, by means of simultaneous deamidation
rate measurements of rabbit muscle aldolase and appropriate model
peptides in the same solutions, the use of this method for quantitative
measurement of the relative effects of primary, secondary, tertiary,
and quaternary protein structure on deamidation rates has been
demonstrated. The measured rates are discussed with respect to the
hypothesis that glutaminyl and asparaginyl residues serve, through
deamidation, as molecular timers of biological events.
CoREST is an integral component of the CoREST- human histone deacetylase complex
Authors: You Angie , Tong Jeffrey K. , Grozinger Christina M. , Schreiber Stuart L.
Published: July 2002

Here we describe the components of a histone deacetylase (HDAC)
complex that we term the CoREST-HDAC complex. CoREST-HDAC is composed
of polypeptides distinct from previously characterized
HDAC1/2-containing complexes such as the mSin3 and nucleosome
remodeling and deacetylating (NRD, also named NURD, NuRD) complex.
Interestingly, we do not observe RbAp46 and RbAp48 in this complex,
although these proteins have been observed in all previously identified
complexes and are thought to be part of an HDAC1/2 core. We identify
the transcriptional corepressor CoREST and a protein with homology to
polyamine oxidases as components of CoREST-HDAC. The
HDAC1/2-interacting region of CoREST is mapped to a 179-aa region
containing a SANT domain, a domain found in other HDAC1/2-interacting
proteins such as NCoR, MTA1, and MTA2. Furthermore, we demonstrate that
the corepressor function of CoREST depends on this region. Although
CoREST initially was cloned as a corepressor to REST (RE1 silencing
transcription factor/neural restrictive silencing factor), we find no
evidence for the existence of the eight-zinc finger REST transcription
factor as an interacting partner in this complex; however, we do find
evidence for association of the putative oncogene ZNF 217 that
contains eight zinc fingers.
Does the Chinese construct of guan export to the West?
Authors: Stewart Sunita Mahtani , Bond Michael H. , Kennard Betsy D. , Ho L.M. , Zaman Riffat Moazam
Published: July 2002

This study reverses the usual process of assessing universality by examining whether a construct originating in non‐western cultures has functional relevance in the West. The construct of guan or “training” was proposed by Chao (1994) as reflecting important Chinese parenting practices also shared by other Confucian cultures. She proposed that this construct is more relevant to the understanding of outcomes among Asian‐American youth than constructs that have been developed in the West, such as “authoritative” parenting. The association among the behaviours incorporated in this construct and other “universal” parenting styles such as parental warmth has not been previously reported. Nor has there been a previous report of the prevalence and perceived desirability of guan behaviours from Western individuals. Participants in the present study were US (N = 118), Hong Kong (N = 171) and Pakistani (N = 98) nursing students. In all three cultures, guan items had adequate internal consistency (Cronbach's alphas ranging from .69 to .76), associated positively with parental warmth (Pearsons' r ranging from .37 to .52), and were seen as attributes of ideal parents. Mothers in all three cultures were perceived as showing more guan than fathers show. The associations between parental guan and the outcomes of perceived health, relationship harmony and life satisfaction were significant for the Asian participants. Tests of guan's functional relevance in the West had equivocal results with weak associations to positive outcomes in the West compared to Asia. However, the differences between cultures did not reach statistical significance. When the cultures were merged, parental training perceptions predicted a significant proportion of the variance in outcomes. Mothers' guan predicted self‐esteem in their children, whereas fathers' guan predicted life satisfaction. Although guan may have emerged from a Chinese cultural context, it appears to function similarly in many cultural systems, and may represent the Asian face of authoritative parenting.
Diversity and Specialisation in Cities: Why, Where and When Does it Matter?
Authors: Duranton Gilles , Puga Diego
Published: July 2002

Why are some cities specialised and others diversified? What are the advantages and disadvantages of urban specialisation and diversity? To what extent do the structure of cities and the activities of firms and people in them change over time? How does the sectoral composition of cities influence their evolution? To answer these and related questions, we first distil some key stylised facts from the empirical literature on cities and the composition of their activities. We then turn to a review of different theories looking at such issues, and study the extent to which these theories contribute to the understanding of the empirical regularities.
Network Cities: Creative Urban Agglomerations for the 21st Century
Authors: Batten David F.
Published: July 2002

The global economy is nurturing an innovative class of polycentric urban configurations: network cities. A network city evolves when two or more previously independent cities, potentially complementary in function, strive to cooperate and achieve significant scope economies aided by fast and reliable corridors of transport and communications infrastructure. Creative network cities place a higher priority on knowledge-based activities like research, education and the creative arts. The cooperative mechanisms may resemble those of inter-firm networks in the sense that each urban player stands to benefit from the synergies of interactive growth via reciprocity, knowledge exchange and unexpected creativity. Two case studies are discussed briefly—Randstad Holland and Kansai, Japan. Since much of their future dynamism may rely upon transnational human resources, it is foreseen that more network cities will transcend national borders during the next millennium.
The Jobs-Housing Balance and Urban Commuting
Authors: Peng Zhong-Ren
Published: July 2002

This paper applies geographical information system (GIS) techniques and a piece-wise, non-linear model-spline functions—to analyse empirically the relationship between the jobs-housing ratio and urban commuting patterns in terms of vehicle miles travelled (VMT) and trip length. A dynamic buffering process in GIS is developed to measure the jobs-housing ratio within floating catchment areas of a 5-7 mile (8.05-11.27 km) radius as opposed to pre-defined and arbitrary jurisdictional boundaries. This study found a non-linear relationship between the jobs-housing ratio and VMT and trip length in the Portland, Oregon, metropolitan area. Only when the jobs-housing ratio is less than 1.2 or larger than 2.8 do VMT vary noticeably as the jobs-housing ratio changes. Marginal changes in VMT are small when the jobs-housing ratio is between 1.2 and 2.8. Since most areas in the study region have a job-household ratio between 1.2 and 2.8, any changes in the jobs-housing ratio will have little impact on VMT. Consequently, hardly any land use policy changes could affect the jobs-housing ratio enough to produce a significant change in VMT per capita, and jobs-housing policy will have limited impact on VMT at the regional level.
Developing Formative Assessment in the Classroom: Using action research to explore and modify theory
Authors: Torrance Harry , Pryor John
Published: July 2002

Abstract This article reports the outcomes of a research project designed to investigate and develop formative classroom assessment in primary schools. The project was a collaborative one, involving two university‐based researchers and a team of teacher‐researchers. The aims were to build on basic research already carried out by the university researchers by investigating the issues from a more practical and applied perspective; consider how a collaborative action research approach to the professional development of teachers might be used to bring about changes in classroom assessment practices; and provide a basis for the further development and refinement of theory on formative assessment. The article reports on changes in classroom practice, particularly involving the clarification and communication of assessment criteria to pupils, and on the processes by which this came about.
A Market in Love? Choosing Pre‐school Childcare
Authors: Vincent Carol , Ball Stephen J.
Published: July 2002

Abstract The article is an initial consideration of data collected for a project exploring working parents' choices of care for their pre‐school children. First, the policy developments in this area are reviewed. However, the heart of the article is an analysis of the ways in which the sample of mainly white middle‐class mothers operates within the childcare market. The impact of class and gender upon their choices is considered, and the strategies the women use to personalise the market are mapped. The authors conclude that despite their relatively advantaged position as consumers, the women's control of the market‐based relations that develop remains imperfect and incomplete as they negotiate the tensions between work and domestic responsibilities.
A comparative-longitudinal study of action-control beliefs and school performance: On the role of context
Authors: Little Todd D. , Lopez David F. , Oettingen Gabriele , Baltes Paul B.
Published: July 2002

In a previous cross-sectional study comparing East and West Berlin children (Oettingen, Little, Lindenburger, & Baltes, 1994), we found that children in West Berlin had higher beliefs in their own performance potential than in East Berlin, but that the correlation between these personal agency beliefs and actual school performance was stronger in East Berlin than in West Berlin. In this study, we report on a three-wave longitudinal follow-up of the original samples wherein we examined the impact of change in the East Berlin education system, which adopted the West Berlin system between the second and third measurement occasions. As expected, we found that the context change did not affect the East Berlin children’s (grades 2-5, n = 198) lower mean levels of agency beliefs; however, the changes did reduce the correlations between the beliefs and performance to the levels observed in West Berlin (n = 381).
Gauging Children’s Understanding of Artificially Intelligent Objects: A Presentation of “Counterfactuals”
Authors: Van Duuren Mike , Dossett Barbara , Robinson Dawn
Published: July 2002

Children aged 5 to 11 years and a comparison group of adults were presented with two instances where the behaviour of a computational object was contrary to what might normally be expected of such a device. In both instances findings are discussed with regard to children’s understanding of a computer program and resulting computational behaviour generally. In the first study, children viewed a ”lm featuring a number of robots either acting as traditionally programmed devices or, alternatively, with apparent intentionality. We examine to what extent, if at all, children were aware of this difference. Findings indicated that although the younger children mentioned other alleged differences between the robots, the issue of different loci of control was not a salient one. In the second study, children were encouraged to type two kinds of questions into a computer. The first kind (simple maths questions) required a general solution procedure commonly accessible to a computational object. The second (details of a biographical nature) did not. With respect to the first as well as the second kind of questions the computer was seen to provide apparently correct answers. Findings showed that although with increasing age children were better at articulating the difference between rote- and rule-generated solutions generally, this was not generally accompanied by an accurate assessment of the kinds of problems that could normally be expected to be solved by a computer.
Pathogenesis of Male Reproductive Toxicity
Authors: Creasy Dianne M.
Published: July 2002

Toxicologic disturbance of male reproductive function can occur at many sites and produce a range of effects, some primary and some secondary to the initial insult. The challenge to the toxicological pathologist is to identify the primary site of damage and provide an insight into the pathogenesis of the morphologic lesion or functional defi cit. Target sites include the testis, the epididymis, the mature sperm, and the hormonal regulatory system. Detection of effects at these varied sites requires the measurement of multiple endpoints only 1 of which is histopathology, but once identifi ed, careful microscopic examination of the early changes in lesion development can provide essential information on the probable target cell and possible mechanisms of toxicity. Chemicals that affect different cell types or specifi ccellular functions generally elicit predictable patterns of pathological changes that can be readily recognized. Understanding the pathogenesis, the likely reversibility and the significance of reproductive tract lesions is aided by a sound knowledge of the physiology of the testis and epididymis and, in particular, an understanding of the timing of sperm production and transport. and transport.
Dissociable Lexical and Phonological Influences on Serial Recognition and Serial Recall
Authors: Gathercole Susan E. , Pickering Susan J. , Hall Melanie , Peaker Sarah M.
Published: July 2002

The impact of the lexicality of memory items on memory performance was compared in two paradigms, serial recall and serial recognition. Experiments 1 to 3 tested 7- and 8-year-old children. Memory accuracy was only mildly impaired in lists containing nonwords compared with words in a serial recognition task involving judgements of whether the items in two sequences were in the same order (Experiment 1), although a substantial advantage for word over nonword items from the same stimulus pool was found in serial recall (Experiment 2). A stronger influence of lexicality on serial recall than serial recognition was further demonstrated in Experiments 3A and 3B, and in 4A and 4B using adult participants. These experiments also established comparable degrees of sensitivity to the phonological similarity of the memory sequences in the two paradigms. The phonological similarity effect in serial recall was found to arise from increased phoneme order errors, whereas the lexicality effect was due principally to the greater frequency of phoneme identity errors for nonwords. It is proposed that the lexicality effect originates in the redintegration of item information just prior to recall, and that this process is largely bypassed in serial recognition.
Controlling youth access to tobacco: a review of the literature and reflections on the New Zealand programme of controlled purchasing operations
Authors: BLEWDEN MICHAEL B. , SPINOLA CARLA
Published: July 2002

A literature review on the active enforcement of youth tobacco access laws was undertaken as part of an evaluation of two public health services involved in the delivery of the New Zealand programme of active enforcement. The current paper summarizes the reviewed literature and discusses the programme in light of the literature findings. It is concluded that a more comprehensive programme may increase the likelihood of successful and sustained programme outcomes. It is suggested that programme enhancements may be possible through the more strategic use of educational interventions, a greater balance between co‐operative and punitive strategies, attention to contextual influences on illegal sales, greater community participation, the licensing of tobacco retailers and the use of civil penalties for non‐compliance. The literature highlights that active enforcement alone will not reduce youth smoking and care should be taken to ensure that active enforcement strategies do not divert resources away from other strategies known to reduce youth smoking. It is hoped that the current paper will encourage further discussion about the future direction of the New Zealand programme.
Outcomes of Naltrexone Maintenance Following Ultra Rapid Opiate Detoxification Versus Intensive Inpatient Detoxification
Authors: Rabinowitz Jonathan , Cohen Hagit , Atias Shmuel
Published: July 2002

Relapse rates of 30 opiate‐addicted social service clients who were given a 9‐month course of naltrexone after being rapidly detoxified using naltrexone + clonidine under anesthesia were compared to 33 similar clients detoxified in a 30‐day intensive inpatient detoxification but not given naltrexone. Both groups had the same counseling aftercare. Telephone follow‐up of 26 of the intensive inpatient detoxification clients and 24 of the rapidly detoxified clients found no significant differences (p = .62) in relapse rates, with 34% of respondents returning to regular opiate use 13.4 (± 3.8) months after detoxification. Naltrexone maintenance and counseling following rapid detoxification may be as effective as intensive inpatient detoxification and counseling.
The Subchronic Oral Toxicity of Ethane, 1,2-Bis(pentabromophenyl) (Saytex 8010) in Rats
Authors: Hardy M. L. , Margitich D. , Ackerman L. , Smith R. L.
Published: July 2002

Ethane, 1,2-bis(pentabromophenyl) (EBP; CAS no. 8452–53–9) dose levels of 0, 100, 320 and 1000 mg/kg/day administered to rats by gavage in corn oil for 90 consecutive days produced no compound-related clinical signs of systemic toxicity, ocular lesions, or alterations in urinalysis, clinical chemistry, and hematology values in the treated or recovery groups. No biologically or toxicologically significant differences were observed in body weights, body weight gains, and food consumption. Statistically significant differences were found between control and high-dose animals in mean absolute or relative liver weights. Histomorphological evaluation showed in male rats low-grade liver changes consisting of minimal to slight hepatocellular vacuolation (high-dose males) and minimal to slight centrilobular hepatocytomegaly (high- and possibly mid-dose males). These changes had resolved by the end of the 28-day recovery period. No treatment-related changes were found in the livers of female rats. No treatment-related histomorphologic changes were present in any of the other tissues examined in either sex, except for evidence of aspirated test article in individual rats. The 90-day EBP no-adverse-effect level in the rat was 1000 mg/kg/day, and was consistent with that of the preceding 28-day study (no-effect level 1250 mg/kg/day). EBP's lack of toxicity is likely related to poor bioavailability due to its high molecular weight and low solubility.
An α-Helical Signal in the Cytosolic Domain of the Interleukin 2 Receptor β Chain Mediates Sorting Towards Degradation after Endocytosis
Authors: Subtil Agathe , Delepierre Muriel , Dautry-Varsat Alice
Published: July 2002

High-affinity IL2 receptors consist of three components, the α, β, and γ chains that are associated in a noncovalent manner. Both the β and γ chains belong to the cytokine receptor superfamily. Interleukin 2 (IL2) binds to high-affinity receptors on the cell surface and IL2-receptor complexes are internalized. After endocytosis, the components of this multimolecular receptor have different intracellular fates: one of the chains, α, recycles to the plasma membrane, while the others, β and γ, are routed towards late endocytic compartments and are degraded. We show here that the cytosolic domain of the β chain contains a 10–amino acid sequence which codes for a sorting signal. When transferred to a normally recycling receptor, this sequence diverts it from recycling. The structure of a 17–amino acid segment of the β chain including this sequence has been studied by nuclear magnetic resonance and circular dichroism spectroscopy, which revealed that the 10 amino acids corresponding to the sorting signal form an amphipathic α helix. This work thus describes a novel, highly structured signal, which is sufficient for sorting towards degradation compartments after endocytosis.
Myosin I Overexpression Impairs Cell Migration
Authors: Novak Kristine D. , Titus Margaret A.
Published: July 2002

Dictyostelium myoB, a member of the myosin I family of motor proteins, is important for controlling the formation and retraction of membrane projections by the cell's actin cortex (Novak, K.D., M.D. Peterson, M.C. Reedy, and M.A. Titus. 1995. J. Cell Biol. 131:1205–1221). Mutants that express a three- to sevenfold excess of myoB (myoB+ cells) were generated to further analyze the role of myosin I in these processes. The myoB+ cells move with an instantaneous velocity that is 35% of the wild-type rate and exhibit a 6–8-h delay in initiation of aggregation when placed under starvation conditions. The myoB+ cells complete the developmental cycle after an extended period of time, but they form fewer fruiting bodies that appear to be small and abnormal. The myoB+ cells are also deficient in their ability both to form distinct F-actin filled projections such as crowns and to become elongate and polarized. This defect can be attributed to the presence of at least threefold more myoB at the cortex of the myoB+ cells. In contrast, threefold overexpression of a truncated myoB that lacks the src homology 3 (SH3) domain (myoB/SH3− cells) or myoB in which the consensus heavy chain phosphorylation site was mutated to an alanine (S332A-myoB) does not disturb normal cellular function. However, there is an increased concentration of myoB in the cortex of the myoB/SH3− and S332A-myoB cells comparable to that found in the myoB+ cells. These results suggest that excess full-length cortical myoB prevents the formation of the actin-filled extensions required for locomotion by increasing the tension of the F-actin cytoskeleton and/ or retracting projections before they can fully extend. They also demonstrate a role for the phosphorylation site and SH3 domain in mediating the in vivo activity of myosin I.
Lysosomes Behave as Ca2+-regulated Exocytic Vesicles in Fibroblasts and Epithelial Cells
Authors: Rodríguez Ana , Webster Paul , Ortego Javier , Andrews Norma W.
Published: July 2002

Lysosomes are considered to be a terminal degradative compartment of the endocytic pathway, into which transport is mostly unidirectional. However, specialized secretory vesicles regulated by Ca2+, such as neutrophil azurophil granules, mast cell–specific granules, and cytotoxic lymphocyte lytic granules, share characteristics with lysosomes that may reflect a common biogenesis. In addition, the involvement of Ca2+ transients in the invasion mechanism of the parasite Trypanosoma cruzi, which occurs by fusion of lysosomes with the plasma membrane, suggested that lysosome exocytosis might be a generalized process present in most cell types.

Here we demonstrate that elevation in the intracellular free Ca2+ concentration of normal rat kidney (NRK) fibroblasts induces fusion of lysosomes with the plasma membrane. This was verified by measuring the release of the lysosomal enzyme β-hexosaminidase, the appearance on the plasma membrane of the lysosomal glycoprotein lgp120, the release of fluid-phase tracers previously loaded into lysosomes, and the release of the lysosomally processed form of cathepsin D. Exposure to the Ca2+ ionophore ionomycin or addition of Ca2+containing buffers to streptolysin O–permeabilized cells induced exocytosis of ∼10% of the total lysosomes of NRK cells. The process was also detected in other cell types such as epithelial cells and myoblasts. Lysosomal exocytosis was found to require micromolar levels of Ca2+ and to be temperature and ATP dependent, similar to Ca2+-regulated secretory mechanisms in specialized cells.

These findings highlight a novel role for lysosomes in cellular membrane traffic and suggest that fusion of lysosomes with the plasma membrane may be an ubiquitous form of Ca2+-regulated exocytosis.
Partitioning of the Golgi Apparatus during Mitosis in Living HeLa Cells
Authors: Shima David T. , Haldar Kasturi , Pepperkok Rainer , Watson Rose , Warren Graham
Published: July 2002

The Golgi apparatus of HeLa cells was fluorescently tagged with a green fluorescent protein (GFP), localized by attachment to the NH2-terminal retention signal of N-acetylglucosaminyltransferase I (NAGT I). The location was confirmed by immunogold and immunofluorescence microscopy using a variety of Golgi markers. The behavior of the fluorescent Golgi marker was observed in fixed and living mitotic cells using confocal microscopy. By metaphase, cells contained a constant number of Golgi fragments dispersed throughout the cytoplasm. Conventional and cryoimmunoelectron microscopy showed that the NAGT I–GFP chimera (NAGFP)-positive fragments were tubulo-vesicular mitotic Golgi clusters. Mitotic conversion of Golgi stacks into mitotic clusters had surprisingly little effect on the polarity of Golgi membrane markers at the level of fluorescence microscopy. In living cells, there was little self-directed movement of the clusters in the period from metaphase to early telophase. In late telophase, the Golgi ribbon began to be reformed by a dynamic process of congregation and tubulation of the newly inherited Golgi fragments. The accuracy of partitioning the NAGFP-tagged Golgi was found to exceed that expected for a stochastic partitioning process. The results provide direct evidence for mitotic clusters as the unit of partitioning and suggest that precise regulation of the number, position, and compartmentation of mitotic membranes is a critical feature for the ordered inheritance of the Golgi apparatus.
Amphiphysin II (SH3P9; BIN1), a Member of the Amphiphysin/Rvs Family, Is Concentrated in the Cortical Cytomatrix of Axon Initial Segments and Nodes of Ranvier in Brain and around T Tubules in Skeletal Muscle
Authors: Butler Margaret Husta , David Carol , Ochoa Gian-Carlo , Freyberg Zachary , Daniell Laurie , Grabs Detlev , Cremona Ottavio , Camilli Pietro De
Published: July 2002

Amphiphysin (amphiphysin I), a dominant autoantigen in paraneoplastic Stiff-man syndrome, is a neuronal protein highly concentrated in nerve terminals, where it has a putative role in endocytosis. The yeast homologue of amphiphysin, Rvs167, has pleiotropic functions, including a role in endocytosis and in actin dynamics, suggesting that amphiphysin may also be implicated in the function of the presynaptic actin cytoskeleton. We report here the characterization of a second mammalian amphiphysin gene, amphiphysin II (SH3P9; BIN1), which encodes products primarily expressed in skeletal muscle and brain, as differentially spliced isoforms. In skeletal muscle, amphiphysin II is concentrated around T tubules, while in brain it is concentrated in the cytomatrix beneath the plasmamembrane of axon initial segments and nodes of Ranvier. In both these locations, amphiphysin II is colocalized with splice variants of ankyrin3 (ankyrinG), a component of the actin cytomatrix. In the same regions, the presence of clathrin has been reported. These findings support the hypothesis that, even in mammalian cells, amphiphysin/Rvs family members have a role both in endocytosis and in actin function and suggest that distinct amphiphysin isoforms contribute to define distinct domains of the cortical cytoplasm. Since amphiphysin II (BIN1) was reported to interact with Myc, it may also be implicated in a signaling pathway linking the cortical cytoplasm to nuclear function.