bluuebunny/crossref_metadata_2025 huggingface dataset:
The neural basis of task-switching in working memory: Effects of performance and aging
Authors: Smith Edward E. , Geva Anat , Jonides John , Miller Andrea , Reuter-Lorenz Patricia , Koeppe Robert A.
Published: July 2002

We studied the performance of young and senior subjects on a
well known working memory task, the Operation Span. This is a dual-task
in which subjects perform a memory task while simultaneously verifying
simple equations. Positron-emission tomography scans were taken during
performance. Both young and senior subjects demonstrated a cost in
accuracy and latency in the Operation Span compared with performing
each component task alone (math verification or memory only). Senior
subjects were disproportionately impaired relative to young subjects on
the dual-task. When brain activation was examined for senior subjects,
we found regions in prefrontal cortex that were active in the
dual-task, but not in the component tasks. Similar results were
obtained for young subjects who performed relatively poorly on the
dual-task; however, for young subjects who performed relatively well in
the dual-task, we found no prefrontal regions that were active only in
the dual-task. Results are discussed as they relate to the executive
component of task switching.
Attentional distraction and time perception in children
Authors: Gautier Tatiana , Droit‐Volet Sylvie
Published: July 2002

The purpose of the present study was to test the effect of attentional distraction on temporal bisection performance in 5‐ and 8‐year‐old children. During a first learning phase, children were trained to discriminate on a temporal bisection task a short standard duration (2 sec) from a long one (8 sec), presented as visual stimuli. Later, in a second testing phase, intermediate durations (3, 4, 5, 6, 7 s), including the standard durations, were presented. Children's task still was to report if it was a short standard duration or a long one. In addition, during the non‐standard duration, a distracter either did or did not appear. Results showed increasing proportions of “it is the long standard duration” (response “long”) with increasing stimulus durations in both distracter and non‐distracter conditions. However, psychophysical functions were flatter in the 5‐year‐olds than in the 8‐year‐olds, revealing their lower sensibility to time. Nevertheless, the 5‐year‐olds' proportion of long responses was higher under the distracter than in the non‐distracter condition. Consequently, the point of subjective equality (PSE), corresponding to the stimulus duration to which the subject produced 50% of responses of “long” was lower under the distracter condition as compared to the non‐distracter condition. Conversely, for the 8‐year‐olds, the PSE was significantly higher in the distracter than in the non‐distracter condition. Five‐year old children overestimated the time in the presence of an attentional distracter, whereas 8‐year olds tended to underestimate it. The leftward shift and the rightward shift of the PSE in the 5‐ and the 8‐year‐olds, respectively, were accounted for by limited‐capacity attention in the five‐year olds.
The Governance of Interactive Learning within Innovation Systems
Authors: Antonelli Cristiano , Quere Michel
Published: July 2002

The generation of new technological knowledge is the result of a variety of interactions : market transactions are only a subset of a much wider flow of knowledge interactions and technological communication. Specific governance mechanisms are necessary to make technological interactions and technological communication possible. Dedicated governance mechanisms emerge under the influence of the types of knowledge, products, markets, organisation of firms and institutions involved. Geographical space plays a key role in such a context.
A New Phase of Urban Development in Western Europe? The Evidence for the 1980s
Authors: Cheshire Paul
Published: July 2002

This is the first report of patterns of population change during the 1980s in the major urban regions of the European Union (of 12), using the results of the 1990 census round (or registration data where no census was taken). There is evidence of a substantial breakup of the previous regular pattern of decentralisation, which had been spreading from northern to southern European cities and from the largest to the medium-sized cities. During the 1980s there was a significant degree of recentralisation in many northern European cities, with nearly half of all core cities gaining population. The evidence presented here is consistent with arguments advanced in an earlier paper which suggested that such a change of patterns should be anticipated. There does not appear to be a complete reversal of previous patterns, however. Some urban regions continue to decentralise and decline; others are declining but experiencing relative recentralisation. The pattern is that there is now a greater variation in patterns. Cities which are experiencing the most relative recentralisation show that they are not a random group. They have characteristics consistent with the causal analysis which is presented. The plausibility of general, rather than particularistic explanations, is made greater by the very similar change of trends recently reported for US cities.
Reconstructing Citizenship, the Re-scaling of the State and the New Authoritarianism: Closing the Belgian Mines
Authors: Swyngedouw Erik
Published: July 2002

The paper explores the contested re-configuration of the position of the national state as a result of the reworking of the scales of governance. It is argued that the intricate relationship between recent changes in the 'scaling' of the national state and the formation of new and differently 'scaled' institutional forms takes place in and through processes of urban/regional restructuring as part of an effort to 'produce' globally competitive spaces. The rise of 'glocal' forms of governance is paralleled by the formation of new elite coalitions on the one hand and the systematic exclusion or further disempowerment of politically and/or economically already weaker social groups on the other. Such exclusive homogenisation of regional spaces erodes diversity and difference in highly oppressive ways. The glocal 'entrepreneurial' or 'Schumpeterian workfare' state becomes an 'authoritarian' state. This new 'post-Fordist (?)' form of governance is unstable and re-enforces fragmentation and tension in civil society. This, in turn, not only jeopardises the potential success of the restructuring drive, but undermines social cohesion in an already fractured and fragmented regional social fabric. This thesis will be explored and documented through the analysis of the political economy of urban-regional socio-economic restructuring that paralleled the recent closure of Belgium's five remaining coal pits in the north-eastern Province of Limburg.
Modelling the Choice of Tenure and Building Type
Authors: Skaburskis Andrejs
Published: July 2002

A multinomial logistic (MNL) model and a naive nested logistic model are estimated to relate differences in household size, age, income and housing prices to differences in the choice of tenure and building type. The estimated models show that the demand for lower-density options decreases with a reduction in household size and increases with increasing age and real income. Higher rents increase the demand for owner-occupied single-family detached houses. Higher price levels for the ownership option shift demand toward all of the higher-density options, particularly toward high-rise rental apartments. The key assumption underlying the MNL model is examined and shown to not hold true. However, the differences in the predictions made by the two models are too small to matter in the study of the choices among the major building types. Issues regarding the choice of models are discussed in the conclusions.
Threads Intertwined: German National Egoism and Liberalism in Adolf fischhof's Vision for Austria
Authors: Reifowitz Ian
Published: July 2002

This article analyzes the ideas of Adolf Fischhof (1816–93) on the nationalities question in the Habsburg Monarchy. Throughout his career Fischhof argued that the survival of the multiethnic Habsburg polity required the strengthening of each nationality's separate consciousness as an ethno-cultural unit. In terms of the reform plan he espoused, he was perhaps more supportive of the rights of the non-German peoples of Austria than any other German liberal politician of the post-1848 era. Nevertheless, Fischhof's rationale for proposing such reforms, namely that they would lead the Monarchy's Slavs to reject the notion of ethnic kinship with Russia and instead join the civilized, European (read: German) side in its inevitable clash with barbarous Muscovite tyranny, revealed a clear belief in the supremacy of German Kultur and in a German-centered mission for the Austrian state.
Negotiation of conflict, communication patterns, and ego development in the family of adolescent daughters
Authors: von der Lippe Anna Louise , Møller Inger Ulrikke
Published: July 2002

Late-adolescent females ( N = 39) and their parents were studied, relating the quality of conflict negotiation in the family to their ego development and their dyadic communication patterns. Family communication was evaluated by the Constraining and Enabling Coding System (CECS; Hauser et al., 1985) from discussions in a revealed difference task. Each statement given by a person directed at another was coded and scores were aggregated. Quality of negotiation for the family as a unit was assessed from the discussions in molar codings guided by Stierlin’s (1974) model of individuated relationships and developed for this study. Ego development was measured by Loevinger’s Washington University Sentence Completion Test. Analyses showed that the adolescents’, but not the parents’, ego level predicted family negotiation scores. The results also suggested that the quality of family negotiations was enhanced by different patterns of dyadic communication between adolescent daughters and their parents. Negotiating skill was high when there was cognitive complementarity between parents and daughters such that the father was cognitively enabling toward the daughter (and she was not) and the daughter was cognitively enabling toward the mother (whereas this was not predictive of the mother), and there was affective symmetry between parents and daughters (both facilitative). Daughters contributed to negotiation skill in the family by being more attentive to the mother than to the father. Regression analyses indicated that affective factors were more predictive of the negotiation climate in the family than cognitive factors.
Peer acceptance in early childhood and subtypes of socially withdrawn behaviour in China, Russia, and the United States
Authors: Hart Craig H. , Yang Chongming , Nelson Larry J. , Robinson Clyde C. , Olsen Joseph A. , Nelson David A. , Porter Christin L. , Jin Shenghua , Olsen Susanne F. , Wu Peixia
Published: July 2002

To assess whether subtypes of withdrawal could be similarly identified by teachers and linked to peer group adjustment in mainland China, Russia, and the United States, 642 4- to 6-year-old children in these diverse cultural contexts were rated on items reflecting reticent, solitary-passive, solitary-active, and sociable behaviour (cf. Coplan & Rubin, 1998). Linkages of childhood withdrawal to peer group adjustment were also investigated using peer sociometric ratings. Findings, based on multisample confirmatory factor analysis, indicated that separate factors were required to represent the three withdrawn subtypes in each cultural setting. However, US and Russian teachers made finer discriminations between subtypes than did Chinese teachers. Controlling for other withdrawn subtypes, reticent behaviour was uniquely related to lower sociometric ratings in all three cultures. Sociability was associated with higher sociometric ratings in these diverse settings. Findings are interpreted in the light of cultural considerations.
Orthographic and phonological processing skills in reading and spelling in Persian/English bilinguals
Authors: Arab-Moghaddam Narges , Senechal Monique
Published: July 2002

The concurrent development of reading and spelling in English and Persian were examined in a sample of bilingual children. The objective was to compare how phonological and orthographic processing skills contribute to reading and spelling for two alphabetic languages that differ drastically. English orthography is characterised by both polyphony (i.e., a grapheme representing more than one phoneme) and polygraphy (i.e., a phoneme represented by more than one grapheme) which results in a complex script to read and write. In contrast, vowelised-Persian orthography is characterised by polygraphy only, which results in a simple script to read but more complex to write. Fifty-five Iranian children in grades 2 and 3, who had lived in English-speaking Canada for an average of 4 years, were tested on word reading and spelling in English and Persian. We found that the predictors of reading performance were similar across languages: Phonological and orthographic processing skills each predicted unique variance in word reading in English and in Persian once we had controlled for grade level, vocabulary, and reading experience. As expected, the predictors of spelling performance differed across language: Spelling in English was predicted similarly by phonological and orthographic processing skills, whereas spelling in Persian was predicted by orthographic processing skills only. It is possible that the nature of the Persian orthography encourages children to adopt different strategies when reading and spelling words. Spelling Persian words might be particularly conducive to using an analytic strategy which, in turn, promotes the development of and reliance on orthographic skills.
Preferences for collaborative and individual everyday problem solving in later adulthood
Authors: Strough JoNell , Cheng Suling , Swenson Lisa M.
Published: July 2002

Individual and contextual predictors of preferences for solving everyday problems alone and in collaboration with others were investigated in a sample community-dwelling older adults ( M age = 71.80 years, SD = 5.78, range = 56–87, 51 men, 56 women). Gender differences in problem-solving preferences were found in gender-stereotyped domains (e.g., meal-preparation; house repair). In several problem domains, more positive social comparisons of problem-solving ability were related to greater preferences for solving problems alone and lesser preferences for solving problems with others. Marital status, temporal comparisons of ability, and perceived health and control were related to problem-solving preferences in some problem domains. Results are discussed from a contextual perspective that focuses on the fit between individuals’ personal and social resources and their preferred approaches to solving everyday problems.
Reproductive Endocrinology and Toxicological Pathology over the Life Span of the Female Rodent
Authors: Davis Barbara J. , Travlos Gregory , McShane Teresa
Published: July 2002

Understanding the pathology of the female reproductive system with respect to toxicology requires a basic understanding of morphology and function of the system over time because the nature of the female reproductive system is cyclical. Thus, the morphology and the endocrinology is dependent on age and time, as form follows function and function follows form. The life span of the rodent is used as an outline to present an overview of key morphological and endocrinological events important for toxicologic pathologists to consider in study evaluations. Environmental and pharmaceutical compounds differentially impact the organs individually and/or the system in its entirety in a time- and dose-dependent way. Examples are used to illustrate the consequences of exposures at different times and with different outcomes.
Systemic Proliferative Changes and Clinical Signs in Cynomolgus Monkeys Administered a Recombinant Derivative of Human Epidermal Growth Factor
Authors: Reindel James F. , Gough Alexander W. , Pilcher Gary D. , Bobrowski Walter F. , Sobocinski Gregg P. , De La Iglesia Felix A.
Published: July 2002

Epidermal growth factor (EGF) effects have been explored extensively in vivo in rodents, but little is known about trophic responses in nonhuman primates. A previous publication reports the hyperplastic epithelial/parenchymal changes noted in the digestive tract (tongue, esophagus, stomach, intestine, liver, gallbladder, pancreas, and salivary glands) of adult cynomolgus monkeys treated with recombinant human EGF1-48 (rhEGF1-48). This report documents clinical findings and structural effects in the remaining epithelium-containing tissues of these animals. Two monkeys/sex/dose received rhEGF1-48 by intravenous bolus at 0 (vehicle), 10, 100, 500 (females only), or 1,000 μg/kg/day (males only) daily for up to 2 weeks. Treatment- and dose-related clinical findings included emesis, fecal alterations (soft feces and diarrhea), lacrimation, nasal discharge, hypoactivity, transient hypotension, and salivation after dosing. Male monkeys administered 1000 μg/kg became moribund after 5 days of treatment and were necropsied. All other monkeys completed the 2-week treatment period. Necropsy findings in nongastrointestinal tissues were: enlarged, pale kidneys at 100 μ g/kg and greater; small thymuses seen sporadically at all doses; and enlarged adrenals and small thyroids in males at 1,000 μg/kg. Respective organ-to-brain weight ratios at 500 and 1,000 μg/kg for kidneys were 1.5- and 2.6-fold greater and for heart were 1.7- and 1.3-fold greater than controls. Microscopically, pronounced dose-related epithelial hypertrophy and hyperplasia were evident in kidney, urinary bladder, skin (epidermis and adnexa), mammary gland, prostate, seminal vesicles, epididymis, uterus, cervix, vagina, thyroid, thymus, tonsillar crypts, cornea, trachea, and pulmonary airways. Epitheliotrophic effects were conspicuous in many tissues at 100 to 1,000 μg/kg. Changes to renal collecting ducts were present at 10 μg/kg, suggesting that kidneys were a relatively sensitive target. Proliferative alterations were not apparent in testes, intraocular structures, brain ependyma and choroid plexus at any dose. Aside from the noted exceptions, rhEGF1-48 was a pantrophic epithelial mitogen in cynomolgus monkeys when used intravenously at suprapharmacologic doses.
Regenerating Neighbourhoods: A Critical Look at the Role of Community Capacity Building
Authors: Banks Sarah , Shenton Felicity
Published: July 2002

This paper offers a critical analysis of the concept of ‘community capacity building’ identifying two approaches to practice: the strategic and developmental. Examples of these two approaches to the practice of capacity building by Groundwork Trusts in villages in South Yorkshire and County Durham are then discussed and some conclusions drawn as to the value of each.
Black teachers: curriculum and career
Authors: Pole Christopher
Published: July 2002

The influence of both the formal and hidden curriculum has been largely absent from studies of black and Asian teachers' lives and careers. This article seeks to address that absence by focusing on the successful career of one black teacher included in an ESRC‐funded life history study of black and Asian teachers (Pole, 1998, 1999). The article, which draws heavily on the words of the teacher, examines the way in which experience of both the formal and hidden curriculum was instrumental in eventually shaping a black identity and a positive sense of self for the teacher concerned. However, part of the journey towards this positive outcome involved coping with and overcoming different forms of racism manifest not only through the curriculum but also through pedagogy and school organization.
Unrecorded alcohol consumption in Ontario, Canada: estimation procedures and research implications
Authors: MACDONALD SCOTT , WELLS SAMANTHA , GIESBRECHT NORMAN
Published: July 2002

In 1975 the amount of alcohol consumed through unrecorded sources in Ontario was estimated to be between 4% and 6% of overall consumption of absolute alcohol. Population surveys and other data sources were used to produce more recent estimates of the amount of alcohol consumed through U‐brew and U‐vint production, home brewing, cross‐border shopping and illegal channels. Based on converging extimates, consumption of absolute alcohol from unrecorded sources is now estimated to be about 19.5%. Generally, the data provide more support for the substitution model rather than the additive model, as declines in official sales data appear to have coincided with increases in consumption from unrecorded sources. The implications of unrecorded consumption from a research and public health perspective are discussed.
The Role of Alcohol Use in Intimate Partner Femicide
Authors: Sharps Phyllis W. , Campbell Jacquelyn , Campbell Doris , Gary Fay , Webster Daniel
Published: July 2002

The purpose of this study was to examine alcohol use by victims and perpetrators as a risk factor for intimate partner violence and femicide. A case control design was used to describe alcohol use among Femicide/Attempted Femicide victims (n = 380,), Abused Controls (n = 384) and Non‐Abused Controls (n = 376), and their intimate partners. Telephone interviews of proxies (family members or friends) of femicide victims and actual survivors of attempted femicide were conducted in 10 cities. The purpose of the interviews was to gather information about relationship violence and alcohol use by femicide victims, attempted femicide survivors, and their perpetrators. Telephone interviews of controls, recruited from the same cities by random digit dialing, were also conducted. Perpetrator problem drinking was associated with an eight fold increase in partner abuse (eb = 8.24, p < .0001) and a two fold increased risk of femicide/attempted femicide (eb = 2.39, p = .001), controlling for demographic differences.
Nalbuphine Hydrochloride Dependence in Anabolic Steroid Users
Authors: Wines James D. , Gruber Amanda J. , Pope Harrison G. , Lukas Scott E.
Published: July 2002

Nalbuphine hydrochloride, a nonscheduled opioid agonist/antagonist analgesic, is currently approved for the treatment of pain. Recently, nalbuphine dependence was reported in three anabolic steroid users in Britain. To further document this phenomenon, we conducted interviews on eleven subjects who reported nalbuphine use. Eight subjects were clinically dependent on nalbuphine, and seven of the subjects who were asked about tolerance and withdrawal with nalbuphine acknowledged these symptoms. Eight subjects, who had never used drugs intravenously before, reported using nalbuphine by this route. Nalbuphine‐related morbidity was extensive and included medical complications and psychiatric symptoms. Nalbuphine users also exhibited a high rate of comorbid Axis I disorders, including other substance misuse. Virtually all subjects described widespread nalbuphine use in the gymnasiums they frequented. These observations, together with the recent increase in nalbuphine‐related articles in the lay press, suggest that nalbuphine may represent a new drug of abuse among athletes, especially those using anabolic steroids, and that nalbuphine's scheduling status may need to be re‐evaluated.
Teacher perceptions of communication impairment at screening stage in preschool children living in Patras, Greece
Authors: Okalidou Areti , Kampanaros Maria
Published: July 2002

The general aim was to obtain piloting data for a series of experiments about the prevalence of communication impairment in preschool children in Greece. At this screening stage of the overall project, teacher perceptions of communication impairment in 57 kindergartens servicing 1113 children were examined via a questionnaire distributed in the urban region of Patras. The specific research goals were (1) to screen for specific categories of communication impairment such as articulation/phonology, receptive language, expressive language and pragmatics, hearing, stuttering, and voice, as they appear in the mainstreamed kindergarten population and (2) to offer comparative information on sex differences in communication impairment(s). The information was gathered by administration of a Greek‐adapted version of the Communication Checklist for Pre‐school Teachers, which was administered three times to obtain validity and reliability measures. The results were analysed separately for two studies (original and follow‐up) and indicated teacher estimates of 14.4Þ18.7% for communication impairment in kindergarten children of the Patras region. Prevalence was higher for boys than for girls. Analysis of specific communication areas revealed that prevalence varies according to gender and category of communicative impairment. The limitations and follow‐up needs of this study are discussed.
Identification of Protein Transport Complexes in the Chloroplastic Envelope Membranes via Chemical Cross-Linking
Authors: Akita Mitsuru , Nielsen Erik , Keegstra Kenneth
Published: July 2002

Transport of cytoplasmically synthesized proteins into chloroplasts uses an import machinery present in the envelope membranes. To identify the components of this machinery and to begin to examine how these components interact during transport, chemical cross-linking was performed on intact chloroplasts containing precursor proteins trapped at a particular stage of transport by ATP limitation. Large crosslinked complexes were observed using three different reversible homobifunctional cross-linkers. Three outer envelope membrane proteins (OEP86, OEP75, and OEP34) and one inner envelope membrane protein (IEP110), previously reported to be involved in protein import, were identified as components of these complexes. In addition to these membrane proteins, a stromal member of the hsp100 family, ClpC, was also present in the complexes. We propose that ClpC functions as a molecular chaperone, cooperating with other components to accomplish the transport of precursor proteins into chloroplasts. We also propose that each envelope membrane contains distinct translocation complexes and that a portion of these interact to form contact sites even in the absence of precursor proteins.
Mannose 6-Phosphate Receptors Regulate the Formation of Clathrin-coated Vesicles in the TGN
Authors: Borgne Roland Le , Hoflack Bernard
Published: July 2002

The transport of the two mannose 6-phosphate receptors (MPRs) from the secretory pathway to the endocytic pathway is mediated by carrier vesicles coated with the AP-1 Golgi-specific assembly protein and clathrin. Using an in vitro assay that reconstitutes the ARF-1–dependent translocation of cytosolic AP-1 onto membranes of the TGN, we have previously reported that the MPRs are key components for the efficient recruitment of AP-1 (Le Borgne, R., G. Griffiths, and B. Hoflack. 1996. J. Biol. Chem. 271:2162–2170). Using a polyclonal antibody against the mouse γ-adaptin, we have now examined the steady state distribution of AP-1 after subcellular fractionation of mouse fibroblasts lacking both MPRs or reexpressing physiological levels of either MPR. We report that the amount of AP-1 bound to membranes and associated with clathrin-coated vesicles depends on the expression level of the MPRs and on the integrity of their cytoplasmic domains. Thus, these results indicate that the concentration of the MPRs, i.e., the major transmembrane proteins sorted toward the endosomes, determines the number of clathrin-coated vesicles formed in the TGN.
A Role for Mitogen-activated Protein Kinase in the Spindle Assembly Checkpoint in XTC Cells
Authors: Wang Xiao Min , Zhai Ye , Ferrell James E.
Published: July 2002

The spindle assembly checkpoint prevents cells whose spindles are defective or chromosomes are misaligned from initiating anaphase and leaving mitosis. Studies of Xenopus egg extracts have implicated the Erk2 mitogen-activated protein kinase (MAP kinase) in this checkpoint. Other studies have suggested that MAP kinases might be important for normal mitotic progression. Here we have investigated whether MAP kinase function is required for mitotic progression or the spindle assembly checkpoint in vivo in Xenopus tadpole cells (XTC). We determined that Erk1 and/or Erk2 are present in the mitotic spindle during prometaphase and metaphase, consistent with the idea that MAP kinase might regulate or monitor the status of the spindle. Next, we microinjected purified recombinant XCL100, a Xenopus MAP kinase phosphatase, into XTC cells in various stages of mitosis to interfere with MAP kinase activation. We found that mitotic progression was unaffected by the phosphatase. However, XCL100 rendered the cells unable to remain arrested in mitosis after treatment with nocodazole. Cells injected with phosphatase at prometaphase or metaphase exited mitosis in the presence of nocodazole—the chromosomes decondensed and the nuclear envelope re-formed—whereas cells injected with buffer or a catalytically inactive XCL100 mutant protein remained arrested in mitosis. Coinjection of constitutively active MAP kinase kinase-1, which opposes XCL100's effects on MAP kinase, antagonized the effects of XCL100. Since the only known targets of MAP kinase kinase-1 are Erk1 and Erk2, these findings argue that MAP kinase function is required for the spindle assembly checkpoint in XTC cells.
Interactions between Germ Cells and Extracellular Matrix Glycoproteins during Migration and Gonad Assembly in the Mouse Embryo
Authors: García-Castro Martín I. , Anderson Robert , Heasman Janet , Wylie Christopher
Published: July 2002

Cells are known to bind to individual extracellular matrix glycoproteins in a complex and poorly understood way. Overall strength of adhesion is thought to be mediated by a combinatorial mechanism, involving adhesion of a cell to a variety of binding sites on the target glycoproteins. During migration in embryos, cells must alter their overall adhesiveness to the substrate to allow locomotion. The mechanism by which this is accomplished is not well understood. During early development, the cells destined to form the gametes, the primordial germ cells (PGCs), migrate from the developing hind gut to the site where the gonad will form. We have used whole-mount immunocytochemistry to study the changing distribution of three extracellular matrix glycoproteins, collagen IV, fibronectin, and laminin, during PGC migration and correlated this with quantitative assays of adhesiveness of PGCs to each of these. We show that PGCs change their strength of adhesion to each glycoprotein differentially during these stages. Furthermore, we show that PGCs interact with a discrete tract of laminin at the end of migration. Closer analysis of the adhesion of PGCs to laminin revealed that PGCs adhere particularly strongly to the E3 domain of laminin, and blocking experiments in vitro suggest that they adhere to this domain using a cell surface proteoglycan.
An Activated Protein Kinase C α Gives a Differentiation Signal for Hematopoietic Progenitor Cells and Mimicks Macrophage Colony-stimulating Factor–stimulated Signaling Events
Authors: Pierce Andrew , Heyworth Clare M. , Nicholls Sian E. , Spooncer Elaine , Dexter T. Michael , Lord Janet M. , Owen-Lynch P. Jane , Wark Gwen , Whetton Anthony D.
Published: July 2002

Highly enriched, bipotent, hematopoietic granulocyte macrophage colony-forming cells (GM-CFC) require cytokines for their survival, proliferation, and development. GM-CFC will form neutrophils in the presence of the cytokines stem cell factor and granulocyte colony-stimulating factor, whereas macrophage colony-stimulating factor leads to macrophage formation. Previously, we have shown that the commitment to the macrophage lineage is associated with lipid hydrolysis and translocation of protein kinase C α (PKCα) to the nucleus. Here we have transfected freshly prepared GM-CFC with a constitutively activated form of PKCα, namely PKAC, in which the regulatory domain has been truncated. Greater than 95% of the transfected cells showed over a twofold increase in PKCα expression with the protein being located primarily within the nucleus. The expression of PKAC caused macrophage development even in the presence of stimuli that normally promote only neutrophilic development. Thus, M-CSF–stimulated translocation of PKCα to the nucleus is a signal associated with macrophage development in primary mammalian hematopoietic progenitor cells, and this signal can be mimicked by ectopic PKAC, which is also expressed in the nucleus.
Dual Roles for Ste24p in Yeast a-Factor Maturation: NH2-terminal Proteolysis and COOH-terminal CAAX Processing
Authors: Tam Amy , Nouvet Franklin J. , Fujimura-Kamada Konomi , Slunt Hilda , Sisodia Sangram S. , Michaelis Susan
Published: July 2002

Maturation of the Saccharomyces cerevisiae a-factor precursor involves COOH-terminal CAAX processing (prenylation, AAX tripeptide proteolysis, and carboxyl methylation) followed by cleavage of an NH2-terminal extension (two sequential proteolytic processing steps). The aim of this study is to clarify the precise role of Ste24p, a membrane-spanning zinc metalloprotease, in the proteolytic processing of the a-factor precursor. We demonstrated previously that Ste24p is necessary for the first NH2-terminal processing step by analysis of radiolabeled a-factor intermediates in vivo (Fujimura-Kamada, K., F.J. Nouvet, and S. Michaelis. 1997. J. Cell Biol. 136:271–285). In contrast, using an in vitro protease assay, others showed that Ste24p (Afc1p) and another gene product, Rce1p, share partial overlapping function as COOH-terminal CAAX proteases (Boyartchuk, V.L., M.N. Ashby, and J. Rine. 1997. Science. 275:1796–1800). Here we resolve these apparently conflicting results and provide compelling in vivo evidence that Ste24p indeed functions at two steps of a-factor maturation using two methods. First, direct analysis of a-factor biosynthetic intermediates in the double mutant (ste24Δ rce1Δ) reveals a previously undetected species (P0*) that fails to be COOH terminally processed, consistent with redundant roles for Ste24p and Rce1p in COOH-terminal CAAX processing. Whereas a-factor maturation appears relatively normal in the rce1Δ single mutant, the ste24Δ single mutant accumulates an intermediate that is correctly COOH terminally processed but is defective in cleavage of the NH2-terminal extension, demonstrating that Ste24p is also involved in NH2-terminal processing. Together, these data indicate dual roles for Ste24p and a single role for Rce1p in a-factor processing. Second, by using a novel set of ubiquitin–a-factor fusions to separate the NH2- and COOH-terminal processing events of a-factor maturation, we provide independent evidence for the dual roles of Ste24p. We also report here the isolation of the human (Hs) Ste24p homologue, representing the first human CAAX protease to be cloned. We show that Hs Ste24p complements the mating defect of the yeast double mutant (ste24Δ rce1Δ) strain, implying that like yeast Ste24p, Hs Ste24p can mediate multiple types of proteolytic events.
A Functional Role for Specific Spliced Variants of the α7β1 Integrin in Acetylcholine Receptor Clustering
Authors: Burkin Dean J. , Gu Maojian , Hodges Bradley L. , Campanelli James T. , Kaufman Stephen J.
Published: July 2002

The clustering of acetylcholine receptors (AChR) on skeletal muscle fibers is an early event in the formation of neuromuscular junctions. Recent studies show that laminin as well as agrin can induce AChR clustering. Since the α7β1 integrin is a major laminin receptor in skeletal muscle, we determined if this integrin participates in laminin and/or agrin-induced AChR clustering. The alternative cytoplasmic domain variants, α7A and α7B, and the extracellular spliced forms, α7X1 and α7X2, were studied for their ability to engage in AChR clustering. Immunofluorescence microscopy of C2C12 myofibers shows that the α7β1 integrin colocalizes with laminin-induced AChR clusters and to a much lesser extent with agrin-induced AChR clusters. However, together laminin and agrin promote a synergistic response and all AChR colocalize with the integrin. Laminin also induces the physical association of the integrin and AChR. High concentrations of anti-α7 antibodies inhibit colocalization of the integrin with AChR clusters as well as the enhanced response promoted by both laminin and agrin. Engaging the integrin with low concentrations of anti-α7 antibody initiates cluster formation in the absence of agrin or laminin. Whereas both the α7A and α7B cytoplasmic domain variants cluster with AChR, only those isoforms containing the α7X2 extracellular domain were active. These results demonstrate that the α7β1 integrin has a physiologic role in laminin-induced AChR clustering, that alternative splicing is integral to this function of the α7 chain, and that laminin, agrin, and the α7β1 integrin interact in a common or convergent pathway in the formation of neuromuscular junctions.
Matrix-dependent Tiam1/Rac Signaling in Epithelial Cells Promotes Either Cell–Cell Adhesion or Cell Migration and Is Regulated by Phosphatidylinositol 3-Kinase
Authors: Sander Eva E. , van Delft Sanne , ten Klooster Jean P. , Reid Tim , van der Kammen Rob A. , Michiels Frits , Collard John G.
Published: July 2002

We previously demonstrated that both Tiam1, an activator of Rac, and constitutively active V12Rac promote E-cadherin–mediated cell–cell adhesion in epithelial Madin Darby canine kidney (MDCK) cells. Moreover, Tiam1 and V12Rac inhibit invasion of Ras-transformed, fibroblastoid MDCK-f3 cells by restoring E-cadherin–mediated cell–cell adhesion. Here we show that the Tiam1/Rac-induced cellular response is dependent on the cell substrate. On fibronectin and laminin 1, Tiam1/Rac signaling inhibits migration of MDCK-f3 cells by restoring E-cadherin–mediated cell– cell adhesion. On different collagens, however, expression of Tiam1 and V12Rac promotes motile behavior, under conditions that prevent formation of E-cadherin adhesions. In nonmotile cells, Tiam1 is present in adherens junctions, whereas Tiam1 localizes to lamellae of migrating cells. The level of Rac activation by Tiam1, as determined by binding to a glutathione-S-transferase– PAK protein, is similar on fibronectin or collagen I, suggesting that rather the localization of the Tiam1/Rac signaling complex determines the substrate-dependent cellular responses. Rac activation by Tiam1 requires PI3-kinase activity. Moreover, Tiam1- but not V12Rac-induced migration as well as E-cadherin–mediated cell– cell adhesion are dependent on PI3-kinase, indicating that PI3-kinase acts upstream of Tiam1 and Rac.
AIR-2: An Aurora/Ipl1-related Protein Kinase Associated with Chromosomes and Midbody Microtubules Is Required for Polar Body Extrusion and Cytokinesis in Caenorhabditis elegans Embryos
Authors: Schumacher Jill M. , Golden Andy , Donovan Peter J.
Published: July 2002

An emerging family of kinases related to the Drosophila Aurora and budding yeast Ipl1 proteins has been implicated in chromosome segregation and mitotic spindle formation in a number of organisms. Unlike other Aurora/Ipl1-related kinases, the Caenorhabditis elegans orthologue, AIR-2, is associated with meiotic and mitotic chromosomes. AIR-2 is initially localized to the chromosomes of the most mature prophase I–arrested oocyte residing next to the spermatheca. This localization is dependent on the presence of sperm in the spermatheca. After fertilization, AIR-2 remains associated with chromosomes during each meiotic division. However, during both meiotic anaphases, AIR-2 is present between the separating chromosomes. AIR-2 also remains associated with both extruded polar bodies. In the embryo, AIR-2 is found on metaphase chromosomes, moves to midbody microtubules at anaphase, and then persists at the cytokinesis remnant. Disruption of AIR-2 expression by RNA- mediated interference produces entire broods of one-cell embryos that have executed multiple cell cycles in the complete absence of cytokinesis. The embryos accumulate large amounts of DNA and microtubule asters. Polar bodies are not extruded, but remain in the embryo where they continue to replicate. The cytokinesis defect appears to be late in the cell cycle because transient cleavage furrows initiate at the proper location, but regress before the division is complete. Additionally, staining with a marker of midbody microtubules revealed that at least some of the components of the midbody are not well localized in the absence of AIR-2 activity. Our results suggest that during each meiotic and mitotic division, AIR-2 may coordinate the congression of metaphase chromosomes with the subsequent events of polar body extrusion and cytokinesis.
Gap Junction–mediated Cell–Cell Communication Modulates Mouse Neural Crest Migration
Authors: Huang G.Y. , Cooper E.S. , Waldo K. , Kirby M.L. , Gilula N.B. , Lo C.W.
Published: July 2002

Previous studies showed that conotruncal heart malformations can arise with the increase or decrease in α1 connexin function in neural crest cells. To elucidate the possible basis for the quantitative requirement for α1 connexin gap junctions in cardiac development, a neural crest outgrowth culture system was used to examine migration of neural crest cells derived from CMV43 transgenic embryos overexpressing α1 connexins, and from α1 connexin knockout (KO) mice and FC transgenic mice expressing a dominant-negative α1 connexin fusion protein. These studies showed that the migration rate of cardiac neural crest was increased in the CMV43 embryos, but decreased in the FC transgenic and α1 connexin KO embryos. Migration changes occurred in step with connexin gene or transgene dosage in the homozygous vs. hemizygous α1 connexin KO and CMV43 embryos, respectively. Dye coupling analysis in neural crest cells in the outgrowth cultures and also in the living embryos showed an elevation of gap junction communication in the CMV43 transgenic mice, while a reduction was observed in the FC transgenic and α1 connexin KO mice. Further analysis using oleamide to downregulate gap junction communication in nontransgenic outgrowth cultures showed that this independent method of reducing gap junction communication in cardiac crest cells also resulted in a reduction in the rate of crest migration. To determine the possible relevance of these findings to neural crest migration in vivo, a lacZ transgene was used to visualize the distribution of cardiac neural crest cells in the outflow tract. These studies showed more lacZ-positive cells in the outflow septum in the CMV43 transgenic mice, while a reduction was observed in the α1 connexin KO mice. Surprisingly, this was accompanied by cell proliferation changes, not in the cardiac neural crest cells, but in the myocardium— an elevation in the CMV43 mice vs. a reduction in the α1 connexin KO mice. The latter observation suggests that cardiac neural crest cells may have a role in modulating growth and development of non–neural crest– derived tissues. Overall, these findings suggest that gap junction communication mediated by α1 connexins plays an important role in cardiac neural crest migration. Furthermore, they indicate that cardiac neural crest perturbation is the likely underlying cause for heart defects in mice with the gain or loss of α1 connexin function.
INCENP Centromere and Spindle Targeting: Identification of Essential Conserved Motifs and Involvement of Heterochromatin Protein HP1
Authors: Ainsztein Alexandra M. , Kandels-Lewis Stefanie E. , Mackay Alastair M. , Earnshaw William C.
Published: July 2002

The inner centromere protein (INCENP) has a modular organization, with domains required for chromosomal and cytoskeletal functions concentrated near the amino and carboxyl termini, respectively. In this study we have identified an autonomous centromere- and midbody-targeting module in the amino-terminal 68 amino acids of INCENP. Within this module, we have identified two evolutionarily conserved amino acid sequence motifs: a 13–amino acid motif that is required for targeting to centromeres and transfer to the spindle, and an 11–amino acid motif that is required for transfer to the spindle by molecules that have targeted previously to the centromere. To begin to understand the mechanisms of INCENP function in mitosis, we have performed a yeast two-hybrid screen for interacting proteins. These and subsequent in vitro binding experiments identify a physical interaction between INCENP and heterochromatin protein HP1Hsα. Surprisingly, this interaction does not appear to be involved in targeting INCENP to the centromeric heterochromatin, but may instead have a role in its transfer from the chromosomes to the anaphase spindle.
Visualization and Molecular Analysis of Actin Assembly in Living Cells
Authors: Schafer Dorothy A. , Welch Matthew D. , Machesky Laura M. , Bridgman Paul C. , Meyer Shelley M. , Cooper John A.
Published: July 2002

Actin filament assembly is critical for eukaryotic cell motility. Arp2/3 complex and capping protein (CP) regulate actin assembly in vitro. To understand how these proteins regulate the dynamics of actin filament assembly in a motile cell, we visualized their distribution in living fibroblasts using green flourescent protein (GFP) tagging. Both proteins were concentrated in motile regions at the cell periphery and at dynamic spots within the lamella. Actin assembly was required for the motility and dynamics of spots and for motility at the cell periphery. In permeabilized cells, rhodamine-actin assembled at the cell periphery and at spots, indicating that actin filament barbed ends were present at these locations. Inhibition of the Rho family GTPase rac1, and to a lesser extent cdc42 and RhoA, blocked motility at the cell periphery and the formation of spots. Increased expression of phosphatidylinositol 5-kinase promoted the movement of spots. Increased expression of LIM–kinase-1, which likely inactivates cofilin, decreased the frequency of moving spots and led to the formation of aggregates of GFP–CP. We conclude that spots, which appear as small projections on the surface by whole mount electron microscopy, represent sites of actin assembly where local and transient changes in the cortical actin cytoskeleton take place.
Molecular Organization of Sarcoglycan Complex in Mouse Myotubes in Culture
Authors: Chan Yiu-mo , Bönnemann Carsten G. , Lidov Hart G.W. , Kunkel Louis M.
Published: July 2002

The sarcoglycans are a complex of four transmembrane proteins (α, β, γ, and δ) which are primarily expressed in skeletal muscle and are closely associated with dystrophin and the dystroglycans in the muscle membrane. Mutations in the sarcoglycans are responsible for four autosomal recessive forms of muscular dystrophy. The function and the organization of the sarcoglycan complex are unknown. We have used coimmunoprecipitation and in vivo cross-linking techniques to analyze the sarcoglycan complex in cultured mouse myotubes. We demonstrate that the interaction between β- and δ-sarcoglycan is resistant to high concentrations of SDS and α-sarcoglycan is less tightly associated with other members of the complex. Cross-linking experiments show that β-, γ-, and δ-sarcoglycan are in close proximity to one another and that δ-sarcoglycan can be cross-linked to the dystroglycan complex. In addition, three of the sarcoglycans (β, γ, and δ) are shown to form intramolecular disulfide bonds. These studies further our knowledge of the structure of the sarcoglycan complex. Our proposed model of their interactions helps to explain some of the emerging data on the consequences of mutations in the individual sarcoglycans, their effect on the complex, and potentially the clinical course of muscular dystrophies.