bluuebunny/crossref_metadata_2025 huggingface dataset:
Safety Assessments and Public Concern for Genetically Modified Food Products: The American View
Authors: Harlander Susan K.
Published: July 2002

In the relatively short time since their commercial introduction in 1996, genetically modified (GM) crops have been rapidly adopted in the United States GM crops are regulated through a coordinated framework developed in 1992 and administered by three agencies—the US Department of Agriculture (USDA) that ensures the products are safe to grow, the Environmental Protection Agency (EPA) that ensures the products are safe for the environment, and the Food and Drug Administration (FDA) that ensures the products are safe to eat. Rigorous food and environmental safety assessments must be completed before GM crops can be commercialized. Fifty-one products have been reviewed by the FDA, including several varieties of corn, soybeans, canola, cotton, rice, sugar beets, potatoes, tomatoes, squash, papaya, and flax. Because FDA considers these crops “substantially equivalent” to their conventional counterparts, no special labeling is required for GM crops in the United States and they are managed as commodities with no segregation or identity preservation. GM crops have thus made their way through commodity distribution channels into thousands of ingredients used in processed foods. It has been estimated that 70% to 85% of processed foods on supermarket shelves in the United States today contain one or more ingredients potentially derived from GM crops. The food industry and retail industry have been monitoring the opinions of their consumers on the GM issue for the past several years. Numerous independent groups have also surveyed consumer concerns about GM foods. The results of these surveys are shared and discussed here.
Managing Change or Coping with Conflict? - Mapping the Experience of a Local Regeneration Partnership
Authors: Diamond John
Published: July 2002

Post May 1997 the conventional approaches to regeneration strategies in Britain have focused upon establishing local partnerships between - not only service providers an d potential employers - but also local community-based groups. Neighbourhoods or ‘localities’ are now seen as the arenas within which coalitions of local interest groups meet to identify needs, to allocate resources and to engage with local communities. This paper will examine the assumptions behind such approaches and will explore the sites of conflict an d the ways in which local managers attempt to reconcile differing aspirations and expectations. The paper draws upon a series of interviews with participants in regeneration initiatives in Manchester, and will suggest that regeneration managers occupy a significant place in arbitrating between different interest groups. In particular, the role of multi-agency working will be explored an d the ways in which professionals (from a variety of occupations) seek to negotiate common terms of reference and understanding.
Can Actions Affect Perceptual Processing?
Authors: Müsseler Jochen , Steininger Silke , Wühr Peter
Published: July 2002

Previous studies reported impairments in a perceptual task performed during the selection and execution of an action. These findings, however, always raise the question of whether the impairment actually reflects a reduction in perceptual sensitivity or whether it results only from an unspecific reduction in attentiveness given the perceptual task. Recent studies by the authors indicate that actions can also have a specific impact on perception in a dual-task situation. The identification of a left or right arrow is impaired when it appears during the execution of a compatible left or right keypress. In three experiments Signal Detection Theory is applied to test whether this impairment is also found in the sensitivity measure d′ or whether it originates only from a response tendency. The results revealed a general lower d′ for the identification of arrows that were compatible to simultaneously executed keypresses than for arrows that were incompatible. The bias measure c was small and/or did not differ between conditions. Additional analyses revealed that the impairment is due to a higher mean perceptual degradation of stimuli in the compatible condition and that it is restricted to the point in time when the central movement command is generated. Thus, actions actually seem able to affect perceptual processing.
Location and Attention
Authors: Newby Ethan A. , Rock Irvin
Published: July 2002

A discrepancy exists in the literature concerning attention and visual localization accuracy. Prinzmetal, Amiri, Allen, and Edwards (1998), and Tsal and Bareket (1999a) found that localization accuracy increases with attention. Using an inattention paradigm, Rock, Linnett, Grant, and Mack (1992) found no difference between localization accuracy in three attention conditions: inattention, divided attention, and control. Using a similar inattention paradigm, the current study addressed this discrepancy. Subjects were instructed to perform a line judgement task, and attention for an additional location task was manipulated. In Experiment 1, location accuracy was worse in the inattention condition than in either the divided attention or the control condition. There was no difference between the divided-attention and control conditions. Experiment 2 controlled for the possibility that improved location accuracy in the divided and control conditions was due to the expectation of performing a location response, rather than the manipulation of attention. Our results are in agreement with previous findings (Prinzmetal et al., 1998; Tsal & Bareket, 1999a) and suggest that the apparent discrepancy is due to coarse coding of the location responses in the study by Rock et al. (1992).
The Attentional Blink is Immune to Masking-Induced Data Limits
Authors: McLaughlin Elizabeth N. , Shore David I. , Klein Raymond M.
Published: July 2002

The attentional blink is the robust finding that processing a masked item (T1) hinders the subsequent identification of a backwards masked second item (T2), which follows soon after the first one. There has been some debate about the theoretically important relation between the difficulty of T1 processing and the ensuing blink. In Experiment 1 we manipulated the difficulty of T1 in such a way as to affect the quality of data without altering the amount of resources allocated to its identification. We found no relation between the accuracy of T1 identification and the blink. In Experiment 2, the same difficulty manipulation was applied to T2, and we observed an additive pattern with the blink. Together, this pattern of results indicates that a data-limited difficulty manipulation does not affect the blink, whether applied to T1 or T2. In Experiment 3 we used an individual differences methodology to show that performance in the traditional “stream”-like presentation (rapid serial visual presentation) was highly correlated with performance in our modified “target mask, target mask” paradigm, thus allowing for comparisons beyond the present methodology to much of the previous literature that has used the stream paradigm.
Central Tendencies, Extreme Points, and Prototype Enhancement Effects in Ill-Defined Perceptual Categorization
Authors: Palmeri Thomas J. , Nosofsky Robert M.
Published: July 2002

In three perceptual classification experiments involving ill-defined category structures, extreme prototype enhancement effects were observed in which prototypes were classified more accurately than other category instances. Such empirical findings can prove theoretically challenging to exemplar-based models of categorization if prototypes are psychological central tendencies of category instances. We found instead that category prototypes were sometimes better characterized as psychological extreme points relative to contrast categories. Extending a classic and widely cited study (Posner & Keele, 1968), participants learned categories created from distortions of dot patterns arranged in familiar shapes. Participants then made pairwise similarity judgements of the patterns. Multidimensional scaling (MDS) analyses of the similarity data revealed the prototypes to be psychological extreme points, not central tendencies. Evidence for extreme point representations was also found for novel prototype patterns displaying a symmetry structure and for prototypes of grid patterns used in recent studies by McLaren and colleagues (McLaren, Bennet, Guttman-Nahir, Kim, & Mackintosh, 1995). When used in combination with the derived M DS solutions, an exemplar-based model of categorization, the Generalized Context Model (Nosofsky, 1986), provided good fits to the observed categorization data in all three experiments.
Accessing Source Information in Analogical Problem-Solving
Authors: Anolli Luigi , Antonietti Alessandro , Crisafulli Laura , Cantoia Manuela
Published: July 2002

Several studies showed that people presented with source information fail to apply it to an analogous target problem unless they are instructed to use the source. Seven experiments were carried out to assess whether such a lack of spontaneous transfer occurs because individuals do not activate the source during the target task or because they do not realize the source-target relationship. Experiment 1 compared a condition in which the source was activated with no cue about the source-target connection to conditions in which subjects were informed about this connection. Results suggested that the lack of spontaneous transfer does not depend on failure in activating source information. Experiments 2, 3, and 4 were devised to falsify this finding by activating the source closer and closer to the target and by focusing participants’ attention toward the relevant aspects of the source. Experiments 5, 6, and 7 were aimed at stressing source-target correspondences by introducing surface similarities. All experiments showed that the mere activation of the source does not facilitate analogical transfer. Results suggested that two processes should be distinguished in the access phase of analogical problem-solving: Source retrieval and identification of the source-target connection.
Collecting information: Optimizing outcomes, screening options, or facilitating discrimination?
Authors: Harvey Nigel , Bolger Fergus
Published: July 2002

Collection of information prior to a decision may be integrated into a compensatory choice process; if it is, the information packet that is collected should be the one that produces the highest net gain. Alternatively, information may be collected in order to screen out options that fail to meet minimum standards; if this is the case, people should not choose options on which they have not collected available information. We tested these and other predictions from the two approaches in four experiments. Participants were given specific information about three attributes of each choice option but only probabilistic information about a fourth one. They rated attractiveness of options, decided whether to collect specific information about the fourth attribute of each one, rated options again, and then selected one of them. Data were consistent with neither of the above approaches. Instead they suggested that people collect information in order to facilitate their ability to discriminate between the attractiveness of options.
Modality-specific auditory and visual temporal processing deficits
Authors: Soto-Faraco Salvador , Spence Charles
Published: July 2002

We studied the attentional blink (AB) and the repetition blindness (RB) effects using an audio-visual presentation procedure designed to overcome several potential methodological confounds in previous cross-modal research. In Experiment 1, two target digits were embedded amongst letter distractors in two concurrent streams (one visual and the other auditory) presented from the same spatial location. Targets appeared in either modality unpredictably at different temporal lags, and the participants’ task was to recall the digits at the end of the trial. We evaluated both AB and RB for pairs of targets presented in either the same or different modalities. Under these conditions both AB and RB were observed in vision, AB but not RB was observed in audition, and there was no evidence of AB or RB cross-modally from audition to vision or vice versa. In Experiment 2, we further investigated the AB by including Lag 1 items and observed Lag 1 sparing, thus ruling out the possibility that the observed effects were due to perceptual and/or conceptual masking. Our results support a distinction between a modality-specific interference at the attentional selection stage and a modality-independent interference at later processing stages. They also provide a new dissociation between the AB and RB.
Influences of metamemory on performance predictions for text
Authors: Rawson Katherine A. , Dunlosky John , McDonald Susan L.
Published: July 2002

When predicting future performance on tests over text material, do individuals estimate retention in addition to assessing comprehension? In Experiment 1, participants either rated their comprehension or predicted performance for each text, with lower ratings indicating lower confidence either in comprehension or in eventual performance. Judgement magnitude was significantly lower for performance predictions than for comprehension ratings, suggesting that predictions were based partly on retention estimates. In Experiment 2, predictions varied with anticipated test delay (15 min or 2 weeks) whereas comprehension ratings did not, providing further evidence that individuals estimate retention when predicting performance. Analyses of individual differences suggest that both good and poor performers incorporate retention estimates when predicting performance, but better performers do so in a more discriminative manner. Implications for theory of metacognitive judgements are discussed.
Attentional cueing effect in the identification of words and pseudowords of different length
Authors: Auclair Laurent , Siéroff Eric
Published: July 2002

Three experiments studied the influence of spatial attention on familiar and unfamiliar letter string identification. Siéroff and Posner's (1988) cueing procedure was used: A cue indicated in advance either the beginning (left) or the end (right) of a foveally presented letter string that participants were instructed to read aloud. Results showed that the precue had a stronger influence on pseudoword than on word identification. Similar results were obtained when participants were instructed to report the identity of the cue or not. For pseudowords, a cueing effect was obtained regardless of length (6, 8, and 10 letters), whereas only 10-letter words showed such an effect, though to a lesser degree than pseudowords of the same length. However, results showed that shorter words were also influenced by the cue location when the exposure duration was reduced. Results are compatible with an early role of spatial attention in letter string processing, but they also suggest that the lexical status of a letter string can directly influence the distribution of attention before the identification process is completely achieved. Although orienting of spatial attention seems heavily involved in a pseudoword identification, some spatial attention mechanism could also take place in the case of familiar words. The results are discussed within two theoretical frameworks concerning the involvement of spatial attention in word identification: The “replacement” theory and the “redistribution” theory.
A Simon effect for stimulus-response duration
Authors: Kunde Wilfried , Stöcker Christian
Published: July 2002

A non-spatial variant of the Simon effect for the stimulus-response (S-R) feature of duration is reported. In Experiment 1 subjects were required to press a single response key either briefly or longer in response to the colour of a visual stimulus that varied in its presentation duration. Short keypresses were initiated faster with short than with long stimulus duration whereas the inverse was observed with long keypresses. In Experiment 2 subjects were required to press a left or right key (according to stimulus form) either briefly or longer (according to stimulus colour). The stimuli concurrently varied in their location (left or right) and duration (short or long), which were both task irrelevant. Approximately additive correspondence effects for S-R location and S-R duration were observed. To summarize, the results suggest that the irrelevant stimulus features of location and duration are processed automatically and prime corresponding responses in an independent manner.
Spoken language planning and the initiation of articulation
Authors: Roelofs Ardi
Published: July 2002

Minimalist theories of spoken language planning hold that articulation starts when the first speech segment has been planned, whereas non-minimalist theories assume larger units (e.g., Levelt, Roelofs, & Meyer, 1999a). Three experiments are reported, which were designed to distinguish between these views using a new hybrid task that factorially manipulated preparation and auditory priming of spoken language production. Minimalist theories predict no effect from priming of non-initial segments when the initial segment of an utterance is already prepared; observing such a priming effect would support non-minimalist theories. In all three experiments, preparation and priming yielded main effects, and together their effects were additive. Preparation of initial segments does not eliminate priming effects for later segments. These results challenge the minimalist view. The findings are simulated by WEAVER++ (Roelofs, 1997b), which employs the phonological word as the lower limit for articulation initiation.
Is the word length effect in STM entirely attributable to output delay? Evidence from serial recognition
Authors: Baddeley Alan , Chincotta Dino , Stafford Lorenzo , Turk David
Published: July 2002

Although it is generally accepted that the word length effect in short-term memory operates through output delay or interference, there is less agreement on whether it also influences performance through its impact on rehearsal. We investigated this issue by studying the effect of word length on recall and on a recognition task in which output delay was controlled. Word sequences were repeated exactly, or with one pair of words reversed. Two experiments using auditory presentation showed clear word length effects for both recall and serial recognition, although the magnitude of the effect tended to be less for recognition. A third experiment using visual presentation studied the effect of articulatory suppression during the recognition test; again we found a clear word length effect. It is concluded that the word length effect can influence retention through both rehearsal and output factors, as proposed by the phonological loop hypothesis.
I Recognize Your Face, But I Can't Remember Your Name: A Grown up Explanation
Authors: Lesley C. Scanlan , Johnston Robert A.
Published: July 2002

Contemporary models of face recognition explain everyday difficulties in name retrieval by proposing that name information can only be accessed after semantic information (e.g. Bruce & Young, 1986) or by proposing an architecture which puts name retrieval at a disadvantage (e.g. Burton& Bruce,1992). Experiments reported here examined the time required to access name and semantic details by adult and child subjects. In Experiment 1 adult subjects took more time to match familiar faces to names than to other semantic details (e.g. occupation), a finding consistent with all the previous literature on name retrieval. Experiment 2, however, showed that the youngest subjects were significantly faster in matching familiar faces to names than to semantic details. Experiment 3 also showed that children were faster at accessing names than occupations when giving vocal responses to presentations of familiar faces. These findings are not predicted by rigidly sequential models of face recognition and are discussed with specific reference to the ontogenesis of models based on a more flexible connectionist architecture.
Contextual Dependencies in a Stimulus Equivalence Paradigm
Authors: Dibbets P. , Maes J.H.R. , Vossen J.M.H.
Published: July 2002

Two experiments with human subjects assessed contextual dependencies in a stimulus equivalence paradigm. Subjects learned to form two sets of stimuli in a matching-to-sample training procedure. Each set was presented against one of two different background colours, the contextual cues. At test, the influence of a context change—that is, presenting each set against the other context—was measured on baseline, symmetry, and equivalence trials. These three trial types reflect a difference in task complexity. It was predicted that the magnitude of context-dependent effects would be a positive function of task complexity. In Experiment 1, the context change was realized by switching the stimulus set at test while keeping the background colour constant. In Experiment 2, the stimulus set remained constant, and the background colour was switched. In both experiments, a change in context only resulted in an increase in response latency on equivalence trials; no effect was seen on symmetry and baseline trials. Results were discussed in the framework of switch costs, habituation to contextual stimuli, and a model based on Shea and Wright (1995) that explains the differential influence of a context switch on easy versus difficult tasks.
High prevalence of drink‐driving in Thailand
Authors: Chongsuvivatwong Virasakdi , Ritsmitchai Skulrat , Suriyawongpaisal Paibul , Chariyalertsak Suwat , Kosuwan Weerachai , Punyaratabandhu Porapan , Sutiwipakorn Wiwat
Published: July 2002

This study was conducted to measure the prevalence of drivers with a blood alcohol concentration (BAC) over 50 mg/dl and to identify predictors for such an outcome. A cross‐sectional study was conducted during March to August 1995 in eight provinces in Thailand. In each province, with the collaboration of the police, one checkpoint in a suburban area and one on a highway were used to collect data on drivers of 20 motorcycles, 20 4‐wheel and 20 6+‐wheel motor vehicles, during 1300‐1500h, 1700‐1900h and 2200‐2400h. For each subject, a breath test for alcohol was undertaken using standard breath testing instruments. Four thousand, six hundred and seventy‐five male drivers were tested. The crude prevalence of high BAC was 12.6% (range 4.5‐23.7%). The differences in prevalence between the suburban area (8.7%) and the highway (8.4%) and between drivers tested on weekdays (9.8%) and on holidays (7.5%) were not statistically significant. The crude prevalences were 3.4‐3.8% and 3.8‐3.9% at 1300‐1500h and 1700‐1900h, respectively. During 2200‐2400h the prevalence rose to 19.2%, 16.0% and 11.9% among the motorcyclists, the 4‐wheel vehicle drivers and the 6+‐wheel vehicle drivers, respectively. High BAC among Thai drivers in the study period was very common, especially at night. Efforts should be focused on these high‐risk groups and this time period.
Mobile telephone use in Italy in the 1990s: interpretative models
Authors: Colombo Fausto
Published: July 2002

The spread of mobile telephones in Italy is examined as a typical technological phenomenon and is contextualized in the theoretical literature on technological change. A brief introduction is followed by a historical account of the growth of mobile telephony and then by an examination of its current spread and likely future development. After this, two interpretative models are put forward which, it is suggested, may be used both in this particular case and for any form of technologically mediated communication (TMC): the butterfly paradigm (applied to the spread of a technology), and the circuit synergy paradigm (applied to the relative importance of individual factors in the process of diffusion).
SIV infection of macaques: a model for studying AIDS and drug abuse
Authors: CHUANG LINDA F. , KILLAM KEITH F. , CHUANG RONALD Y.
Published: July 2002

Abstract Rhesus monkeys (Macaca mulatta) and the simian immunodeficiency virus (SIV) were used as an animal model system to evaluate longitudinally the effects of opioid dependence on the development of AIDS. Results have shown that in addition to weakening the host's T cell and PMN functions, chronic opioid treatment of SIVmac239‐infected animals caused (a) an increased virus replication rate, (b) an increased rate of viral mutation, (c) a nascent humoral (antibody) response against mutated autologous strains of virus, (d) an alteration of CD8 + cell‐mediated immunity toward the mutant virus, (e) an increased tolerance of AZT among the infectious virus and (f) a shorter life span for the infected animals. These results suggest that chronic administration of opioids alters general fundamental aspects of the AIDS viremia.
CLASS CLEAVAGES IN PARTY PREFERENCES IN THE NEW DEMOCRACIES IN EASTERN EUROPE: A comparison with Western democracies
Authors: Gijsberts Mérove , Nieuwbeerta Paul
Published: July 2002

Since 1989 the political systems in Eastern European societies have changed radically, from totalitarian regimes towards democratic regimes with free general elections and multi-party systems similar to early democracies. This paper examines whether in these new democracies the same class cleavages have become important as in longstanding Western democracies. The relation between social class, attitudes towards economic justice and voting behavior is investigated in five new democracies and compared with those in nine longstanding democracies. The data used are from various cross-nationally comparable and nationally representative surveys held in the 1990s (total N = 20,270). Results show that social class has clear effects on economic justice attitudes and voting behavior in Western democracies. In the post-communist societies, members of different social classes consistently differ in their attitudes towards income inequality and social security, but hardly differ in their voting behavior. Owing to the politically unstable situation in the emerging democracies in Eastern Europe, people in different classes are probably unable to translate their policy preferences into party preferences.
THE BATTLEGROUNDS OF EUROPEAN IDENTITY1
Authors: Kohli Martin
Published: July 2002

The study of European identity cannot take its clues from national identity, neither in form nor in substance. I begin with an examination of the general sociological concept of identity in order to uncover its resources for a more complex understanding of European identity. I then ask to what extent Europe really needs a European identity, and on what levels an identity may be found: in the received cultural ‘idea’ of Europe, in the cultural practices of celebration and ritualization, and in the consciousness if its citizens. In the next section, I present some of the basic descriptive evidence on the individual sense of European identity as routinely surveyed by Eurobarometer. In the final part I sketch some of the current battlegrounds of European identity: its relation to national identity, the challenge posed to it by globalization, and the shifts towards new identity mixes or hybrid identities. I conclude that there is indeed a potential for hybridity, that there are carrier groups for it (e.g. border populations or migrants), but that its development depends on the old social question now taken to the new European level-finding a viable social contract.
ECONOMISTS AND THE ECONOMIC ORDER: The field of economists and the field of power in France
Authors: Lebaron Frédéric
Published: July 2002

Economic beliefs play a central role in the social construction of economic reality. It is necessary to include in the programme of a new economic sociology the active contribution of the main producers of economic beliefs, namely the economists. The role of economists in the reproduction of the social order can, to a certain extent, be described as the function of a central bank of economic beliefs. Economists are the producers of economic beliefs that are received, interpreted, used by various kinds of social actors in everyday life. In a situation of crisis like the one the French government faced in December 1995, it seems more and more obvious that they are becoming the ultimate reference, the lender of last resort for most contemporary social actors - economic leaders, technocrats, politicians, unionists, intellectuals, etc. To understand this particular position, one needs to consider economists as members of a specific social field, which has its own laws, regularities and structure. The social characteristics (especially the distribution of their kinds of capital, and the relative dispositions of economists) define their positions in this social space. It is then necessary to determine the relative autonomy of this field and its interdependence with other social spaces (for example, the field of enterprises, the bureaucratic, political and media fields, etc.).

The main hypothesis developed here is the idea that the field of economists is less autonomous than it is usually thought to be, at least by many economists, and its structure is very similar to that of the field of power (and, among others, the opposition between economic and intellectual powers). In the general interdependence and homologies between social fields, the logic of the field of economists is a key contribution to the production of the symbolic economic order. The word ‘science’ applied to economics refers not only to an epistemological issue but also to the symbolic aspect of the order we refer to when we talk about economic reality, economic argument, economic constraints, etc.
MODIFICATIONS IN THE RELIGIOUS FIELD OF CENTRAL AND EASTERN EUROPE
Authors: Pollack Detlef
Published: July 2002

The aim of this paper is to analyse the current situation of religion in Central and Eastern Europe. The main question is whether the transformation processes in the former Communist countries are following lines of development comparable to those in the West, or whether completely new patterns of development will emerge in these countries. In order to show how church and religion developed in Central and Eastern Europe different religious dimensions are separated and the interconnections between them examined. The four religious dimensions distinguished are personal religiousness, personal church adherence, impersonal church adherence and occultism . The author concludes that the situation of church and religion in Central and Eastern Europe has undergone a dramatic change since the end of the Soviet Empire. At this point of time it cannot be said whether or not processes of a growing differentiation between the distinguished religious dimensions are taking place as they are doing in Western Europe.
A Transfected Sialyltransferase That Is Elevated in Breast Cancer and Localizes to the medial/trans-Golgi Apparatus Inhibits the Development of core-2–based O-Glycans
Authors: Whitehouse Caroline , Burchell Joy , Gschmeissner Stephen , Brockhausen Inka , Lloyd Kenneth O. , Taylor-Papadimitriou Joyce
Published: July 2002

The α2,3 sialyltransferase, α2,3 SAT (O), catalyzes the transfer of sialic acid to Galβ1,3 N-acetyld-galactosamine (GalNAc) (core-1) in mucin type O-glycosylation, and thus terminates chain extension. A Core-2 branch can also be formed from core-1 by the core-2 β1,6 N-acetyl-d-glucosamine transferase (β1,6 GlcNAc T) that leads to chain extension. Increased levels of the α2,3 SAT (O) and decreased levels of the core-2 β1,6 GlcNAc T are seen in breast cancer cells and correlate with differences in the structure of the O-glycans synthesized (Brockhausen et al., 1995; Lloyd et al., 1996). Since in mucin type O-glycosylation sugars are added individually and sequentially in the Golgi apparatus, the position of the transferases, as well as their activity, can determine the final structure of the O-glycans synthesized. A cDNA coding for the human α2,3 SAT (O) tagged with an immunoreactive epitope from the myc gene has been used to map the position of the glycosyltransferase in nontumorigenic (MTSV1-7) and malignant (T47D) breast epithelial cell lines. Transfectants were analyzed for expression of the enzyme at the level of message and protein, as well as for enzymic activity. In T47D cells, which do not express core-2 β1,6 GlcNAc T, the increased activity of the sialyltransferase correlated with increased sialylation of core-1 O-glycans on the epithelial mucin MUC1. Furthermore, in MTSV1-7 cells, which do express core-2 β1,6 GlcNAc T, an increase in sialylated core-1 structures is accompanied by a reduction in the ratio of GlcNAc: GalNAc in the O-glycans attached to MUC1, implying a decrease in branching. Using quantitative immunoelectron microscopy, the sialyltransferase was mapped to the medial- and trans-Golgi cisternae, with some being present in the TGN. The data represent the first fine mapping of a sialyltransferase specifically active in O-glycosylation and demonstrate that the structure of O-glycans synthesized by a cell can be manipulated by transfecting with recombinant glycosyltransferases.
Specific Localization of Serine 19 Phosphorylated Myosin II during Cell Locomotion and Mitosis of Cultured Cells
Authors: Matsumura Fumio , Ono Shoichiro , Yamakita Yoshihiko , Totsukawa Go , Yamashiro Shigeko
Published: July 2002

Phosphorylation of the regulatory light chain of myosin II (RMLC) at Serine 19 by a specific enzyme, MLC kinase, is believed to control the contractility of actomyosin in smooth muscle and vertebrate nonmuscle cells. To examine how such phosphorylation is regulated in space and time within cells during coordinated cell movements, including cell locomotion and cell division, we generated a phosphorylation-specific antibody.

Motile fibroblasts with a polarized cell shape exhibit a bimodal distribution of phosphorylated myosin along the direction of cell movement. The level of myosin phosphorylation is high in an anterior region near membrane ruffles, as well as in a posterior region containing the nucleus, suggesting that the contractility of both ends is involved in cell locomotion. Phosphorylated myosin is also concentrated in cortical microfilament bundles, indicating that cortical filaments are under tension. The enrichment of phosphorylated myosin in the moving edge is shared with an epithelial cell sheet; peripheral microfilament bundles at the leading edge contain a higher level of phosphorylated myosin. On the other hand, the phosphorylation level of circumferential microfilament bundles in cell–cell contacts is low. These observations suggest that peripheral microfilaments at the edge are involved in force production to drive the cell margin forward while microfilaments in cell–cell contacts play a structural role. During cell division, both fibroblastic and epithelial cells exhibit an increased level of myosin phosphorylation upon cytokinesis, which is consistent with our previous biochemical study (Yamakita, Y., S. Yamashiro, and F. Matsumura. 1994. J. Cell Biol. 124:129–137). In the case of the NRK epithelial cells, phosphorylated myosin first appears in the midzones of the separating chromosomes during late anaphase, but apparently before the formation of cleavage furrows, suggesting that phosphorylation of RMLC is an initial signal for cytokinesis.
Stimulation of the p38 Mitogen-activated Protein Kinase Pathway in Neonatal Rat Ventricular Myocytes by the G Protein–coupled Receptor Agonists, Endothelin-1 and Phenylephrine: A Role in Cardiac Myocyte Hypertrophy?
Authors: Clerk Angela , Michael Ashour , Sugden Peter H.
Published: July 2002

We examined the activation of the p38 mitogen-activated protein kinase (p38-MAPK) pathway by the G protein–coupled receptor agonists, endothelin-1 and phenylephrine in primary cultures of cardiac myocytes from neonatal rat hearts. Both agonists increased the phosphorylation (activation) of p38-MAPK by ∼12-fold. A p38-MAPK substrate, MAPK-activated protein kinase 2 (MAPKAPK2), was activated approximately fourfold and 10 μM SB203580, a p38-MAPK inhibitor, abolished this activation. Phosphorylation of the MAPKAPK2 substrate, heat shock protein 25/27, was also increased. Using selective inhibitors, activation of the p38-MAPK pathway by endothelin-1 was shown to involve protein kinase C but not Gi/Go nor the extracellularly responsive kinase (ERK) pathway. SB203580 failed to inhibit the morphological changes associated with cardiac myocyte hypertrophy induced by endothelin-1 or phenylephrine between 4 and 24 h. However, it decreased the myofibrillar organization and cell profile at 48 h. In contrast, inhibition of the ERK cascade with PD98059 prevented the increase in myofibrillar organization but not cell profile. These data are not consistent with a role for the p38-MAPK pathway in the immediate induction of the morphological changes of hypertrophy but suggest that it may be necessary over a longer period to maintain the response.
Electrospray Ionization Tandem Mass Spectrometry (Esi-Ms/Ms) Analysis of the Lipid Molecular Species Composition of Yeast Subcellular Membranes Reveals Acyl Chain-Based Sorting/Remodeling of Distinct Molecular Species En Route to the Plasma Membrane
Authors: Schneiter Roger , Brügger Britta , Sandhoff Roger , Zellnig Günther , Leber Andrea , Lampl Manfred , Athenstaedt Karin , Hrastnik Claudia , Eder Sandra , Daum Günther , Paltauf Fritz , Wieland Felix T. , Kohlwein Sepp D.
Published: July 2002

Nano-electrospray ionization tandem mass spectrometry (nano-ESI-MS/MS) was employed to determine qualitative differences in the lipid molecular species composition of a comprehensive set of organellar membranes, isolated from a single culture of Saccharomyces cerevisiae cells. Remarkable differences in the acyl chain composition of biosynthetically related phospholipid classes were observed. Acyl chain saturation was lowest in phosphatidylcholine (15.4%) and phosphatidylethanolamine (PE; 16.2%), followed by phosphatidylserine (PS; 29.4%), and highest in phosphatidylinositol (53.1%). The lipid molecular species profiles of the various membranes were generally similar, with a deviation from a calculated average profile of ∼± 20%. Nevertheless, clear distinctions between the molecular species profiles of different membranes were observed, suggesting that lipid sorting mechanisms are operating at the level of individual molecular species to maintain the specific lipid composition of a given membrane. Most notably, the plasma membrane is enriched in saturated species of PS and PE. The nature of the sorting mechanism that determines the lipid composition of the plasma membrane was investigated further. The accumulation of monounsaturated species of PS at the expense of diunsaturated species in the plasma membrane of wild-type cells was reversed in elo3Δ mutant cells, which synthesize C24 fatty acid-substituted sphingolipids instead of the normal C26 fatty acid-substituted species. This observation suggests that acyl chain-based sorting and/or remodeling mechanisms are operating to maintain the specific lipid molecular species composition of the yeast plasma membrane.
The Maize tha4 Gene Functions in Sec-Independent Protein Transport in Chloroplasts and Is Related to hcf106, tatA, and tatB
Authors: Walker Macie B. , Roy Laura M. , Coleman Eric , Voelker Rodger , Barkan Alice
Published: July 2002

Proteins are translocated across the chloroplast thylakoid membrane by a variety of mechanisms. Some proteins engage a translocation machinery that is derived from the bacterial Sec export system and require an interaction with a chloroplast-localized SecA homologue. Other proteins engage a machinery that is SecA-independent, but requires a transmembrane pH gradient. Recently, a counterpart to this Δ pH mechanism was discovered in bacteria. Genetic studies revealed that one maize protein involved in this mechanism, HCF106, is related in both structure and function to the bacterial tatA and tatB gene products. We describe here the mutant phenotype and molecular cloning of a second maize gene that functions in the Δ pH mechanism. This gene, thylakoid assembly 4 (tha4), is required specifically for the translocation of proteins that engage the Δ pH pathway. The sequence of the tha4 gene product resembles those of the maize hcf106 gene and the bacterial tatA and tatB genes. Sequence comparisons suggest that tha4 more closely resembles tatA, and hcf106 more closely resembles tatB. These findings support the notion that this sec-independent translocation mechanism has been highly conserved during the evolution of eucaryotic organelles from bacterial endosymbionts.
Division versus Fusion: Dnm1p and Fzo1p Antagonistically Regulate Mitochondrial Shape
Authors: Sesaki Hiromi , Jensen Robert E.
Published: July 2002

In yeast, mitochondrial division and fusion are highly regulated during growth, mating and sporulation, yet the mechanisms controlling these activities are unknown. Using a novel screen, we isolated mutants in which mitochondria lose their normal structure, and instead form a large network of interconnected tubules. These mutants, which appear defective in mitochondrial division, all carried mutations in DNM1, a dynamin-related protein that localizes to mitochondria. We also isolated mutants containing numerous mitochondrial fragments. These mutants were defective in FZO1, a gene previously shown to be required for mitochondrial fusion. Surprisingly, we found that in dnm1 fzo1 double mutants, normal mitochondrial shape is restored. Induction of Dnm1p expression in dnm1 fzo1 cells caused rapid fragmentation of mitochondria. We propose that dnm1 mutants are defective in the mitochondrial division, an activity antagonistic to fusion. Our results thus suggest that mitochondrial shape is normally controlled by a balance between division and fusion which requires Dnm1p and Fzo1p, respectively.
Conservation of a Gliding Motility and Cell Invasion Machinery in Apicomplexan Parasites
Authors: Kappe Stefan , Bruderer Thomas , Gantt Soren , Fujioka Hisashi , Nussenzweig Victor , Ménard Robert
Published: July 2002

Most Apicomplexan parasites, including the human pathogens Plasmodium, Toxoplasma, and Cryptosporidium, actively invade host cells and display gliding motility, both actions powered by parasite microfilaments. In Plasmodium sporozoites, thrombospondin-related anonymous protein (TRAP), a member of a group of Apicomplexan transmembrane proteins that have common adhesion domains, is necessary for gliding motility and infection of the vertebrate host. Here, we provide genetic evidence that TRAP is directly involved in a capping process that drives both sporozoite gliding and cell invasion. We also demonstrate that TRAP-related proteins in other Apicomplexa fulfill the same function and that their cytoplasmic tails interact with homologous partners in the respective parasite. Therefore, a mechanism of surface redistribution of TRAP-related proteins driving gliding locomotion and cell invasion is conserved among Apicomplexan parasites.
Dynein, Dynactin, and Kinesin II's Interaction with Microtubules Is Regulated during Bidirectional Organelle Transport
Authors: Reese Eric L. , Haimo Leah T.
Published: July 2002

The microtubule motors, cytoplasmic dynein and kinesin II, drive pigmented organelles in opposite directions in Xenopus melanophores, but the mechanism by which these or other motors are regulated to control the direction of organelle transport has not been previously elucidated. We find that cytoplasmic dynein, dynactin, and kinesin II remain on pigment granules during aggregation and dispersion in melanophores, indicating that control of direction is not mediated by a cyclic association of motors with these organelles. However, the ability of dynein, dynactin, and kinesin II to bind to microtubules varies as a function of the state of aggregation or dispersion of the pigment in the cells from which these molecules are isolated. Dynein and dynactin bind to microtubules when obtained from cells with aggregated pigment, whereas kinesin II binds to microtubules when obtained from cells with dispersed pigment. Moreover, the microtubule binding activity of these motors/dynactin can be reversed in vitro by the kinases and phosphatase that regulate the direction of pigment granule transport in vivo. These findings suggest that phosphorylation controls the direction of pigment granule transport by altering the ability of dynein, dynactin, and kinesin II to interact with microtubules.
Vitamin D3 promotes the differentiation of colon carcinoma cells by the induction of E-cadherin and the inhibition of β-catenin signaling
Authors: Pálmer Héctor G. , González-Sancho José Manuel , Espada Jesús , Berciano María T. , Puig Isabel , Baulida Josep , Quintanilla Miguel , Cano Amparo , de Herreros Antonio García , Lafarga Miguel , Muñoz Alberto
Published: July 2002

The β-catenin signaling pathway is deregulated in nearly all colon cancers. Nonhypercalcemic vitamin D3 (1α,25-dehydroxyvitamin D3) analogues are candidate drugs to treat this neoplasia. We show that these compounds promote the differentiation of human colon carcinoma SW480 cells expressing vitamin D receptors (VDRs) (SW480-ADH) but not that of a malignant subline (SW480-R) or metastasic derivative (SW620) cells lacking VDR. 1α,25(OH)2D3 induced the expression of E-cadherin and other adhesion proteins (occludin, Zonula occludens [ZO]-1, ZO-2, vinculin) and promoted the translocation of β-catenin, plakoglobin, and ZO-1 from the nucleus to the plasma membrane. Ligand-activated VDR competed with T cell transcription factor (TCF)-4 for β-catenin binding. Accordingly, 1α,25(OH)2D3 repressed β-catenin–TCF-4 transcriptional activity. Moreover, VDR activity was enhanced by ectopic β-catenin and reduced by TCF-4. Also, 1α,25(OH)2D3 inhibited expression of β-catenin–TCF-4-responsive genes, c-myc, peroxisome proliferator-activated receptor δ, Tcf-1, and CD44, whereas it induced expression of ZO-1. Our results show that 1α,25(OH)2D3 induces E-cadherin and modulates β-catenin–TCF-4 target genes in a manner opposite to that of β-catenin, promoting the differentiation of colon carcinoma cells.
Clathrin exchange during clathrin-mediated endocytosis
Authors: Wu Xufeng , Zhao Xiaohong , Baylor Lauren , Kaushal Shivani , Eisenberg Evan , Greene Lois E.
Published: July 2002

During clathrin-mediated endocytosis, clathrin-coated pits invaginate to form clathrin-coated vesicles (CVs). Since clathrin-coated pits are planar structures, whereas CVs are spherical, there must be a structural rearrangement of clathrin as invagination occurs. This could occur through simple addition of clathrin triskelions to the edges of growing clathrin-coated pits with very little exchange occurring between clathrin in the pits and free clathrin in the cytosol, or it could occur through large scale exchange of free and bound clathrin. In the present study, we investigated this question by studying clathrin exchange both in vitro and in vivo. We found that in vitro clathrin in CVs and clathrin baskets do not exchange with free clathrin even in the presence of Hsc70 and ATP where partial uncoating occurs. However, surprisingly FRAP studies on clathrin-coated pits labeled with green fluorescent protein–clathrin light chains in HeLa cells show that even when endocytosis is blocked by expression of a dynamin mutant or depletion of cholesterol from the membrane, replacement of photobleached clathrin in coated pits on the membrane occurs at almost the same rate and magnitude as when endocytosis is occurring. Furthermore, very little of this replacement is due to dissolution of old pits and reformation of new ones; rather, it is caused by a rapid ATP-dependent exchange of clathrin in the pits with free clathrin in the cytosol. On the other hand, consistent with the in vitro data both potassium depletion and hypertonic sucrose, which have been reported to transform clathrin-coated pits into clathrin cages just below the surface of the plasma membrane, not only block endocytosis but also block exchange of clathrin. Taken together, these data show that ATP-dependent exchange of free and bound clathrin is a fundamental property of clathrin-coated pits, but not clathrin baskets, and may be involved in a structural rearrangement of clathrin as clathrin-coated pits invaginate.