The effect of group status on children's hierarchy-reinforcing beliefs

Members of advantaged groups are more likely than members of disadvantaged groups to think, feel, and behave in ways that reinforce their group's position within the hierarchy. This study examined how children's status within a group-based hierarchy shapes their beliefs about the hierarchy and the groups that comprise it in ways that reinforce the hierarchy. To do this, we randomly assigned children (4-8 years; N = 123; 75 female, 48 male; 21 Asian, 9 Black, 21 Latino/a, 1 Middle-Eastern/North-African, 14 multiracial, 41 White, 16 not-specified) to novel groups that differed in social status (advantaged, disadvantaged, neutral third-party) and assessed their beliefs about the hierarchy. Across five separate assessments, advantaged-group children were more likely to judge the hierarchy to be fair, generalizable, and wrong to challenge and were more likely to hold biased intergroup attitudes and exclude disadvantaged group members. In addition, with age, children in both the advantaged- and disadvantaged-groups became more likely to see membership in their own group as inherited, while at the same time expecting group-relevant behaviors to be determined more by the environment. With age, children also judged the hierarchy to be more unfair and expected the hierarchy to generalize across contexts. These findings provide novel insights into how children's position within hierarchies can contribute to the formation of hierarchy-reinforcing beliefs. RESEARCH HIGHLIGHTS: A total of 123 4-8-year-olds were assigned to advantaged, disadvantaged, and third-party groups within a hierarchy and were assessed on seven hierarchy-reinforcing beliefs about the hierarchy. Advantaged children were more likely to say the hierarchy was fair, generalizable, and wrong to challenge and to hold intergroup biases favoring advantaged group members. With age, advantaged- and disadvantaged-group children held more essentialist beliefs about membership in their own group, but not the behaviors associated with their group. Results suggest that advantaged group status can shape how children perceive and respond to the hierarchies they are embedded within.

Does racial diversity affect White children's racial bias and reasoning? Depends on where they live and how their social world is structured

By 4 years of age, White children from across the United States begin to exhibit an awareness of racial inequalities, along with in-group preferences for other White children. The present study explored how the size and racial diversity of White children's social network (e.g., friends, family, and classmates) and neighborhood (zip code) are related to variation in their explanations for racial disparities and anti-Black bias among a sample of 395 White children (ages = 4-11 years old; Mage = 6.6 years) from 263 unique zip codes across the United States. White children in neighborhoods with low diversity were more likely to endorse an extrinsic explanation for racial inequality as their network diversity increased, whereas network diversity did not relate to children's choices for those who lived in neighborhoods with high diversity. These findings held even after controlling for parents' beliefs about diversity, which were themselves positively correlated with children's network and neighborhood diversity. An exploratory analysis revealed that for White children in small networks only, as the number of children of color in their network increased, they were more likely to choose to play with a Black child. Results demonstrate how the diversity of children's social networks and neighborhoods relates to children's developing racial beliefs in contextually dependent ways. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Preschoolers selectively trust and selectively share with others based on their past accuracy and intentions

This study investigated whether preschool-age children consider both an individual's past accuracy and intentions when deciding whether to trust and share with that individual. The participants, 3- to 5-year-olds (N = 168), played a searching game with partners who varied in both accuracy (accurate or inaccurate) and intentions (prosocial or antisocial). Children received advice from partners about where to look for a hidden object, earning prizes for correct guesses. Then they were given an opportunity to share their prizes with their partner. Results indicated that children trusted sources who provided accurate advice (regardless of intentions) and shared with sources who provided accurate advice or demonstrated prosocial intentions. These findings suggest that children attend to both an individual's accuracy and intentions when deciding how to interact with social partners and may weigh this information differently to make different social decisions.

Developmental origins of anti-Black bias in White children in the United States: Exposure to and beliefs about racial inequality

Anti-Black racism remains a pervasive crisis in the United States. Racist social systems reinforce racial inequalities and perpetuate prejudicial beliefs. These beliefs emerge in childhood, are difficult to change once entrenched in adolescence and adulthood, and lead people to support policies that further reinforce racist systems. Therefore, it is important to identify what leads children to form prejudicial beliefs and biases and what steps can be taken to preempt their development. This study examined how children's exposure to and beliefs about racial inequalities predicted anti-Black biases in a sample of 646 White children (4 to 8 years) living across the United States. We found that for children with more exposure to racial inequality in their daily lives, those who believed that racial inequalities were caused by intrinsic differences between people were more likely to hold racial biases, whereas those who recognized the extrinsic factors underlying racial inequalities held more egalitarian attitudes. Grounded in constructivist theories in developmental science, these results are consistent with the possibility that racial biases emerge in part from the explanatory beliefs that children construct to understand the racial inequalities they see in the world around them.

Testing the effectiveness of the Developing Inclusive Youth program: A multisite randomized control trial

The Developing Inclusive Youth program is a classroom‐based, individually administered video tool that depicts peer‐based social and racial exclusion, combined with teacher‐led discussions. A multisite randomized control trial was implemented with 983 participants (502 females; 58.5% White, 41.5% Ethnic/racial minority; M_age = 9.64 years) in 48 third‐, fourth‐, and fifth‐grade classrooms across six schools. Children in the program were more likely to view interracial and same‐race peer exclusion as wrong, associate positive traits with peers of different racial, ethnic, and gender backgrounds, and report play with peers from diverse backgrounds than were children in the control group. Many approaches are necessary to achieve antiracism in schools. This intervention is one component of this goal for developmental science.

Desire to play with counterstereotypical peers is related to gender stereotypes and playmate experiences

This study investigated the role of children's gender stereotypes and peer playmate experiences in shaping their desire to play with peers who hold counterstereotypical preferences (e.g., a boy who likes dolls or a girl who likes trucks). Children (N = 95; 46 girls, 49 boys; 67% White, 18% Black, 8% Latinx, 4% Asian, 3% other; median household income = $US97,810) who were 4 to 8 years old (M = 6.11 years old, SD = 1.34) were interviewed about their gender stereotypes about toy preferences, how often they engage in counterstereotypical playmate experiences, and their desire to play with peers who hold counterstereotypical toy preferences. Children with less gender stereotype-consistent expectations reported more playmate experiences with children who played with toys that were gender counterstereotypical compared to children with more gender stereotype-consistent expectations. Additionally, children with less gender stereotype-consistent expectations reported a greater desire to play with peers who held counterstereotypical toy preferences compared to children with more gender stereotype-consistent expectations. Younger children's reported playmate experiences with peers who liked toys that were gender counterstereotypical and their desire to play with these peers were strongly related to their gender stereotypical expectations (and more so than for older children). Together, these findings indicate that children's gender stereotypes and peer playmate experiences are related to their desire to play with peers who hold counterstereotypical toy preferences, highlighting the importance of facilitating diverse friendships for promoting inclusive orientations in childhood. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Beliefs about social norms and racial inequalities predict variation in the early development of racial bias

Racism remains a pervasive force around the world with widespread and well documented harmful consequences for members of marginalized racial groups. The psychological biases that maintain structural and interpersonal racism begin to emerge in early childhood, but with considerable individual variation-some children develop more racial bias than others. The present study (N = 116; 4-year-old children) provides novel insights into the developmental mechanisms underlying the emergence of racial bias by longitudinally documenting how two psychological processes-normative beliefs about interracial friendships and explanatory beliefs about racial inequalities-developmentally predict the emergence of pro-White/anti-Black racial bias during early childhood. In a 6-month, three-wave, longitudinal study, we found that 4-year-old children's beliefs that their parents and peers do not value interracial friendships predicted increased racial bias in and across time and that children's endorsement of essentialist over extrinsic explanations for racial inequalities predicted the developmental trajectory of racial bias over time. These findings suggest that children's foundational beliefs about the social world developmentally predict the emergence of racial bias in early childhood and speak to the importance of early and persistent intervention efforts targeting children's normative beliefs about interracial friendships and explanatory beliefs about racial inequalities.

Children's evaluations of individually and structurally based inequalities: The role of status

Social inequalities limit important opportunities and resources for members of marginalized and disadvantaged groups. Understanding the origins of how children construct their understanding of social inequalities in the context of their everyday peer interactions has the potential to yield novel insights into when-and how-individuals respond to different types of social inequalities. The present study examined whether children (N = 176; 3- to 8-years-old; 52% female, 48% male; 70% European American, 16% African American, 10% Latinx, and 4% Asian American; middle-income backgrounds) differentiate between structurally based inequalities (e.g., based on gender) and individually based inequalities (e.g., based on merit). Children were randomly assigned to a group that received more (advantaged) or fewer (disadvantaged) resources than another group due to either their groups' meritorious performance on a task or the gender biases of the peer in charge of allocating resources. Overall, children evaluated structurally based inequalities to be more unfair and worthy of rectification than individually based inequalities, and disadvantaged children were more likely to view inequalities to be wrong and act to rectify them compared to advantaged children. With age, advantaged children became more likely to rectify the inequalities and judge perpetuating allocations to be unfair. Yet, the majority of children allocated equally in response to both types of inequality. The findings generated novel evidence regarding how children evaluate and respond to individually and structurally based inequalities, and how children's own status within the inequality informs these responses. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

A Developmental Science Perspective on Social Inequality

Many people believe in equality of opportunity, but overlook and minimize the structural factors that shape social inequalities in the United States and around the world, such as systematic exclusion (e.g., educational, occupational) based on group membership (e.g., gender, race, socioeconomic status). As a result, social inequalities persist, and place marginalized social groups at elevated risk for negative emotional, learning, and health outcomes. Where do the beliefs and behaviors that underlie social inequalities originate? Recent evidence from developmental science indicates that an awareness of social inequalities begins in childhood, and that children seek to explain the underlying causes of the disparities that they observe and experience. Moreover, children and adolescents show early capacities for understanding and rectifying inequalities when regulating access to resources in peer contexts. Drawing on a social reasoning developmental framework, this paper synthesizes what is currently known about children's and adolescents' awareness, beliefs, and behavior concerning social inequalities, and highlights promising avenues by which developmental science can help reduce harmful assumptions and foster a more just society.

Advancing Developmental Science via Unmoderated Remote Research with Children

This article introduces an accessible approach to implementing unmoderated remote research in developmental science-research in which children and families participate in studies remotely and independently, without directly interacting with researchers. Unmoderated remote research has the potential to strengthen developmental science by: (1) facilitating the implementation of studies that are easily replicable, (2) allowing for new approaches to longitudinal studies and studies of parent-child interaction, and (3) including families from more diverse backgrounds and children growing up in more diverse environments in research. We describe an approach we have used to design and implement unmoderated remote research that is accessible to researchers with limited programming expertise, and we describe the resources we have made available on a new website (discoveriesonline.org) to help researchers get started with implementing this approach. We discuss the potential of this method for developmental science and highlight some challenges still to be overcome to harness the power of unmoderated remote research for advancing the field.

Expectations for Cross-Ethnic Inclusion by Asian America Children and Adolescents

Asian American youth’s inclusion decisions were investigated in cross-ethnic peer contexts (Asian and non-Asian). Ten-, 13-, and 16-year-old participants ( N = 134), enrolled in U.S. schools, decided whether to include a same-ethnic peer with different interests or a different-ethnic peer with similar interests. Findings showed that with age, participants more frequently included a peer who shared interests even when this peer was not of the same ethnicity. Participants expected their peer groups to be equally inclusive of others of both ethnic backgrounds, and expected that in-group parents would be less inclusive of cross-ethnic peers. In addition, adolescents expected parents to have prejudicial attitudes about ethnic out-group members. Views about peer group and in-group parents’ inclusivity diverged from adolescents’ own inclusivity. These findings point to areas for intervention regarding the promotion of cross-group friendships and the reduction of prejudice.

Lying, negligence, or lack of knowledge? Children's intention-based moral reasoning about resource claims

In a hidden inequality context, resource allocators and resource recipients are unaware that an unknowingly advantaged recipient possesses resources. The present study presented children aged 3-13 years (N = 121) with a hidden inequality vignette involving an accidental transgression in which one resource claimant, who unknowingly possessed more resources than another claimant, made an "unintentional false claim" to resources. This unintentional false claim resulted in depriving another recipient of needed resources. Results revealed that children's ability to accurately identify the claimant's intentions was related to how they evaluated and reasoned about resource claims, a previously understudied aspect of resource allocation contexts. Children's attributions of intentions to the accidental transgressor mediated the relationship between age and evaluations of the accidental transgression and the relationship between age and assignment of punishment to the accidental transgressor. With age, children who negatively evaluated the unintentional false claim shifted from reasoning about lying to a focus on negligence on the part of the unintentional false claimant. This shift reflects an increasing understanding of the accidental transgressor's benign intentions. These findings highlight how mental state knowledge and moral reasoning inform children's comprehension of resource allocation contexts. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The Role of Competitive and Cooperative Norms in the Development of Deviant Evaluations

The present study examined how peer group norms influence children's evaluations of deviant ingroup members. Following the manipulation of competitive or cooperative norms, participants (children, M_age  = 8.69; adolescents, M_age  = 13.81; adults, M_age  = 20.89; n = 263) evaluated deviant ingroup members from their own and the group's perspective. Children rated cooperative deviancy positively and believed their group would do the same. Adolescents and adults believed that their group would negatively evaluate cooperative deviancy when their group supported a competitive allocation strategy. Reasoning varied based on norm and participants' agreement with deviancy. Understanding an ingroup may not be favorable toward a cooperative deviant in a competitive context is a developmental challenge requiring the coordination of social and moral norms.

Theory of mind is related to children's resource allocations in gender stereotypic contexts

The present study investigated the relations between 4- to 6-year-old children's (N = 67) gender stereotypes, resource allocations, and mental state knowledge in gender-stereotypic contexts. Participants were told vignettes about female and male characters completing gender-stereotyped activities (making dolls or trucks). Children held stereotypic expectations regarding doll- and truck-making abilities, and these expectations predicted the degree of bias in their allocations of resources to the characters. Critically, children's performance on a Theory of Mind (ToM) Scale (Diverse Desires [DD], Contents False-Belief [FB], Belief-Emotion [BE]) was significantly related to their allocations of resources to individuals whose effort did not fit existing gender stereotypes (e.g., a boy who was good at making dolls). With increasing ToM competence, children allocated resources based on merit (even when the character's effort did not fit existing gender stereotypes) rather than based on stereotypes. The present results provide novel information regarding the emergence of gender stereotypes about abilities, the influence of stereotypes on children's resource allocations, and the role of ToM in children's ability to challenge gender stereotypes when allocating resources. (PsycINFO Database Record

Children's recognition of fairness and others' welfare in a resource allocation task: Age related changes

The present study investigated age-related changes regarding children's (N = 136) conceptions of fairness and others' welfare in a merit-based resource allocation paradigm. To test whether children at 3- to 5-years-old and 6- to 8-years-old took others' welfare into account when dividing resources, in addition to merit and equality concerns, children were asked to allocate, judge, and reason about allocations of necessary (needed to avoid harm) and luxury (enjoyable to have) resources to a hardworking and a lazy character. While 3- to 5-year-olds did not differentiate between distributing luxury and necessary resources, 6- to 8-year-olds allocated luxury resources more meritoriously than necessary resources. Further, children based their allocations of necessary resources on concerns for others' welfare, rather than merit, even when one character was described as working harder. The findings revealed that, with age, children incorporated the concerns for others' welfare and merit into their conceptions of fairness in a resource allocation context, and prioritized these concerns differently depending on whether they were allocating luxury or necessary resources. Further, with age, children weighed multiple moral concerns including equality, merit, and others' welfare, when determining the fair allocation of resources. (PsycINFO Database Record

Young children's inclusion decisions in moral and social-conventional group norm contexts

Being a member of a peer group involves making decisions about whom to include in or exclude from the group. Sometimes these decisions are related to whether members of the group support or challenge the norms of the group. To examine how young children weigh concerns for group norms and group membership in both moral and social-conventional norm contexts, children (3- to 6-year-olds; N=73) were asked to decide between including an ingroup member who challenged the group's norm or an outgroup member who supported the norm. Groups held either moral (equal or unequal resource allocation) or social-conventional (traditional or nontraditional) norms. In the moral contexts, children were more likely to include the peer who advocated for the moral concern for equality regardless of the peer's group membership or their group's specific norm. In the social-conventional contexts, however, children were more likely to include the peer who advocated for the conventional concern for maintaining traditions but only at the group-specific level. Furthermore, with age children increasingly based their inclusion decisions on normative concerns, rather than on group membership concerns, and differed in their inclusion decisions for ingroups and outgroups. Finally, children reasoned about their decisions by referencing concerns for fairness, group norms, and group membership, suggesting that preschool children weigh multiple concerns when deciding whom to include in their groups. Overall, the current study revealed differences in how preschool children weigh moral and social-conventional concerns in intergroup contexts.

Theory of Mind and Resource Allocation in the Context of Hidden Inequality

In many situations, children evaluate straightforward resource inequalities as unfair. It remains unclear, however, how children interpret hidden inequalities (i.e., inequalities that are unknown to allocators and/or recipients). Children 3-9-years-old (N = 87) evaluated and attributed intentions to a naïve resource allocator who, while unaware of a hidden inequality, made three hypothetical resource allocations: 1) an unknowingly equitable allocation (which rectified the inequality), 2) an inequitable allocation (which perpetuated the inequality), and 3) an equal allocation (which maintained the inequality). Children without false belief morally-relevant theory of mind (FB MoToM) attributed more positive intentions to the unknowingly equitable allocation than to the inequitable allocation. Children with FB MoToM, however, did not differ in their attributions of intentions to the unknowingly equitable and inequitable allocations, reflecting their knowledge that the naïve allocator was not aware of the hidden inequality. Further, children's attributions of intentions were related to their evaluations of the allocations. These findings underscore the importance of children's social cognitive inferences to their evaluations of resource allocation decisions.

Rectifying social inequalities in a resource allocation task

To investigate whether children rectify social inequalities in a resource allocation task, participants (N=185 African-American and European-American 5-6year-olds and 10-11year-olds) witnessed an inequality of school supplies between peers of different racial backgrounds. Assessments were conducted on how children judged the wrongfulness of the inequality, allocated new resources to racial ingroup and outgroup recipients, evaluated alternative allocation strategies, and reasoned about their decisions. Younger children showed ingroup favorability; their responses differed depending on whether they had witnessed their ingroup or an outgroup at a disadvantage. With age, children increasingly reasoned about the importance of equal access to school supplies and correcting past disparities. Older children judged the resource inequality negatively, allocated more resources to the disadvantaged group, and positively evaluated the actions of others who did the same, regardless of whether they had seen their racial ingroup or an outgroup at a disadvantage. Thus, balancing moral and social group concerns enabled individuals to rectify inequalities and ensure fair access to important resources regardless of racial group membership.

Children's understanding of equity in the context of inequality

In the context of a pre-existing resource inequality, the concerns for strict equality (allocating the same number of resources to all recipients) conflict with the concerns for equity (allocating resources to rectify the inequality). This study demonstrated age-related changes in children's (3-8 years old, N = 133) ability to simultaneously weigh the concerns for equality and equity through the analysis of children's judgements, allocations, and reasoning in the context of a pre-existing inequality. Three- to 4-year-olds took equity into account in their judgements of allocations, but allocated resources equally in a behavioural task. In contrast, 5- to 6-year-olds rectified the inequality in their allocations, but judged both equitable and equal allocations to be fair. It was not until 7-8 years old that children focused on rectifying the inequality in their allocations and judgements, as well as judged equal allocations less positively than equitable allocations, thereby demonstrating a more complete understanding of the necessity of rectifying inequalities. The novel findings revealed age-related changes from 3 to 8 years old regarding how the concerns for equity and equality develop, and how children's judgements, allocations, and reasoning are coordinated when making allocation decisions.

When and Why Parents Prompt Their Children to Apologize: The Roles of Transgression Type and Parenting Style

Young children are sensitive to the importance of apologies, yet little is known about when and why parents prompt apologies from children. We examined these issues with parents of 3-10-year-old children (N = 483). Parents judged it to be important for children to apologize following both intentional and accidental morally-relevant transgressions, and they anticipated prompting apologies in both contexts, showing an 'outcome bias' (i.e., a concern for the outcomes of children's transgressions rather than for their underlying intentions). Parents viewed apologies as less important after children's breaches of social convention; parents recognized differences between social domains in their responses to children's transgressions. Irrespective of parenting style, parents were influenced in similar fashion by particular combinations of transgressions and victims, though permissive parents were least likely to anticipate prompting apologies. Parents endorsed different reasons for prompting apologies as a function of transgression type, suggesting that they attend to key features of their children's transgressions when deciding when to prompt apologies.

Challenging gender stereotypes: Theory of mind and peer group dynamics

To investigate the social cognitive skills related to challenging gender stereotypes, children (N = 61, 3-6 years) evaluated a peer who challenged gender stereotypic norms held by the peer's group. Participants with false belief theory of mind (FB ToM) competence were more likely than participants who did not have FB ToM to expect a peer to challenge the group's stereotypes and propose that the group engage in a non-stereotypic activity. Further, participants with FB ToM rated challenging the peer group more positively. Participants without FB ToM did not differentiate between their own and the group's evaluation of challenges to the group's stereotypic norms, but those with ToM competence asserted that they would be more supportive of challenging the group norm than would the peer group. Results reveal the importance of social-cognitive competencies for recognizing the legitimacy of challenging stereotypes, and for understanding one's own and other group perspectives.

Morality, Intentionality, and Intergroup Attitudes

Morality is at the core of what it means to be social. Moral judgments require the recognition of intentionality, that is, an attribution of the target's intentions towards another. Most research on the origins of morality has focused on intragroup morality, which involves applying morality to individuals in one's own group. Yet, increasingly, there has been new evidence that beginning early in development, children are able to apply moral concepts to members of an outgroup as well, and that this ability appears to be complex. The challenges associated with applying moral judgments to members of outgroups includes understanding group dynamics, the intentions of others who are different from the self, and having the capacity to challenge stereotypic expectations of others who are different from the ingroup. Research with children provides a window into the complexities of moral judgment and raises new questions, which are ripe for investigations into the evolutionary basis of morality.

Therapeutic implications of disorders of cell death signalling: membranes, micro-environment, and eicosanoid and docosanoid metabolism

Disruptions of cell death signalling occur in pathological processes, such as cancer and degenerative disease. Increased knowledge of cell death signalling has opened new areas of therapeutic research, and identifying key mediators of cell death has become increasingly important. Early triggering events in cell death may provide potential therapeutic targets, whereas agents affecting later signals may be more palliative in nature. A group of primary mediators are derivatives of the highly unsaturated fatty acids (HUFAs), particularly oxygenated metabolites such as prostaglandins. HUFAs, esterified in cell membranes, act as critical signalling molecules in many pathological processes. Currently, agents affecting HUFA metabolism are widely prescribed in diseases involving disordered cell death signalling. However, partly due to rapid metabolism, their role in cell death signalling pathways is poorly characterized. Recently, HUFA-derived mediators, the resolvins/protectins and endocannabinoids, have added opportunities to target selective signals and pathways. This review will focus on the control of cell death by HUFA, eicosanoid (C20 fatty acid metabolites) and docosanoid (C22 metabolites), HUFA-derived lipid mediators, signalling elements in the micro-environment and their potential therapeutic applications. Further therapeutic approaches will involve cell and molecular biology, the multiple hit theory of disease progression and analysis of system plasticity. Advances in the cell biology of eicosanoid and docosanoid metabolism, together with structure/function analysis of HUFA-derived mediators, will be useful in developing therapeutic agents in pathologies characterized by alterations in cell death signalling.

Calcium-sensitive mitochondrial membrane potential in human platelets and intrinsic signals of cell death

The mechanisms involved in storage-induced damage in platelets are not well understood, but membrane signalling via Ca2+ ion flux may affect mitochondrial H+ gradients and metabolism and the intrinsic pathways of cell death, platelet survival and function. In this study, the effects of blood bank storage conditions, including reduced plasma concentration and interrupted agitation, were evaluated in platelets from 136 healthy donors. Mitochondrial membrane potential (DeltaPsim), an indicator of intrinsic cell death, and its sensitivity to Ca2+ ionophore A23187, were monitored using JC-1 by flow cytometry and fluorescence microscopy. Platelet survival was examined using lactate dehydrogenase release, annexin V binding and caspase-3/7 activity. Decreased plasma concentration and interrupted agitation affected DeltaPsim and caspase-3/7. Over 7 days in 30% plasma DeltaPsim showed a significant reduction (86.3 +/- 1.1% platelets with polarised mitochondria day 1; 79.9 +/- 2.1% day 5; 75.1 +/- 3.8% day 7, P = 0.01 day 1 vs. day 7). Whilst DeltaPsim in agitated platelets in 100% plasma was unchanged up to day 7, interruption of agitation was associated with a 44% reduction in the proportion of platelets with polarised mitochondria after 5 days (56 +/- 11%). The Ca2+ sensitivity of DeltaPsim changed earlier: 5 microM A23187 caused a 20-30% change in the fraction of platelets with polarised mitochondria by day 5. Ca2+ sensitivity also increased during interrupted agitation and reduced plasma concentration. DeltaPsim also correlated with indicators of platelet death, caspase-3 activity and annexin V binding (correlation coefficients of 0.8). In conclusion, changes in Ca2+-sensitive DeltaPsim are involved in the initiation of storage-induced cell death signals that influence platelet count and function in vivo.

Antitumour and pro-apoptotic actions of highly unsaturated fatty acids in glioma

The highly unsaturated fatty acids (HUFA) of the n-6 and n-3 series are involved in cell signalling in normal and transformed cells and have recently been associated with pathways leading to tumour cell death. The antitumour activity of three HUFA (arachidonic acid, gamma linolenic acid and eicosapentaenoic acid) were studied in glioma cells and tissue. Using five glioma models, including primary cell suspensions prepared from 46 human glioma samples and an in vivo rat C6 glioma model, we obtained evidence that, following exposure to HUFA, either administered into the medium surrounding human glioma cells or in 16 preparations of multicellular spheroids derived from human and rodent glioma cell lines (C6, MOG, U87, U373) or administered intra-tumourally by infusion using osmotic mini-pumps in 48 rats, glioma regression and apoptosis were detected. Additionally, synergy between gamma irradiation and HUFA administration was observed in 13 experiments analyzing C6 glioma cell apoptosis in vitro. These pro-apoptotic and antiproliferative activities were observed using both C18 and C20 fatty acids of the n-6 and n-3 series, but not when saturated and monounsaturated C18 and C20 fatty acid preparations were used. In the glioma infusion model, in addition to the apoptosis detected in glioma tissue infused with HUFA for 3-7 days, preservation of normal neural tissue and vasculature in adjacent brain was observed. Also, there was little evidence of acute inflammatory infiltration in regressing tumours. Our findings suggest that intraparenchymal infusion of HUFA may be effective in stimulating glioma regression.

Secreted phospholipase A(2) induces vascular endothelial cell migration

Secreted phospholipase A(2) (sPLA(2)) regulates a variety of cellular functions. The present investigation was undertaken to elucidate the potential role of sPLA(2) in endothelial cell (EC) migration. Bovine aortic endothelial cells (BAECs) exposed to sPLA(2) placed in the lower compartment of a modified Boyden chamber displayed increased migration compared to cells exposed to vehicle. The effect of sPLA(2) on EC migration was time and dose dependent. Migration of BAECs was observed at 30 minutes, increased over 1 to 2 hours, and declined thereafter. At 2 hours of stimulation, sPLA(2) (0.01-2 micromol/L) induced 1.2- to 3-fold increased cell migration compared with media alone. Among the different sPLA(2)s tested, bee venom, Naja naja, and porcine and human pancreatic PLA(2)s all evoked a migratory response in ECs. Moreover, human synovial fluid, obtained from patients with arthritis and containing sPLA(2) activity, induced EC migration. Migration of ECs was significantly reduced after exposure to a catalytic site mutant of pancreatic sPLA(2) with decreased lipolytic activity as compared to wild-type sPLA(2). Similarly, pretreatment of human synovial fluid with p-bromophenacyl bromide, an irreversible inhibitor of sPLA(2), markedly decreased the ability of human synovial fluid to stimulate EC migration. Moreover, migration of ECs was stimulated on exposure to hydrolytic products of sPLA(2) activity including arachidonic acid, lysophosphatidic acid, and lysophosphatidylcholine. These findings suggest that sPLA(2) plays a physiologic role in induction of EC migration. Moreover, the effects of sPLA(2) on EC migration are mediated, at least in part, by its catalytic activity. (Blood. 2000;96:3809-3815)

Arachidonic acid induces endothelin-1 gene expression in vascular endothelial cells

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide synthesized and secreted by vascular endothelial cells. Regulation of ET-1 production occurs at the level of gene transcription. We previously demonstrated a role for arachidonic acid as an intracellular mediator in the regulation of gene expression. This study investigated the role of arachidonic acid in induction of ET-1 production in endothelial cells. Challenge of bovine aortic endothelial cells (BAECs) with arachidonic acid induced a dose- and time-dependent increase in the amount of immunoreactive ET-1 in the supernatant. The maximum effect was observed at concentrations of 20 microM. Release of ET-1 by arachidonic acid was preceded by induction of ET-1 gene expression. Arachidonic acid increased ET-1 gene expression by increasing transcription of the ET-1 gene. The effect of arachidonic acid was mimicked by other polyunsaturated fatty acids, whereas saturated fatty acids had no effect. Moreover, inhibitors of the lipoxygenase pathway blocked arachidonic acid-induced release of ET-1. These results suggest that arachidonic acid stimulated the production of ET-1 in BAECs by inducing ET-1 gene transcription. Arachidonic acid-induced production of ET-1 is dependent on lipoxygenase products of arachidonate metabolism.

Induction of apoptosis by arachidonic acid in chronic myeloid leukemia cells

The hallmark of chronic myeloid leukemia (CML) is the presence of the bcr-abl oncogene, which is associated with transforming ability and an intrinsic resistance to induction of apoptosis by genotoxic agents. Arachidonic acid (AA), a biologically active fatty acid, plays a crucial role as a mediator of signaling pathways involved in cell proliferation and survival. In this study, we investigated the potential role of AA as a proapoptotic agent in CML. Pretreatment of human CML isolated progenitor cells with AA (100 microM for 18 h) induced 71-75% inhibition of in vitro colony formation of granulocyte-macrophage colony-forming units, multilineage colony-forming units, and erythroid burst-forming units. This inhibition was significantly greater than the effect on normal progenitor cells (19-39% growth inhibition of erythroid burst-forming units, multilineage colony-forming units, and granulocyte-macrophage colony-forming units). AA also inhibited growth of the bcr-abl-transformed cell line H7.bcr-abl A54. In contrast, a minimal effect of AA on inhibition of cell growth was observed in the parental nontransformed NSF/N1.H7 cell line. The antiproliferative effect of AA was associated with apoptosis. Gamma-linolenic acid, a precursor of AA, also inhibited cell growth, whereas other unsaturated and saturated fatty acids had no effect. Pharmacological inhibition of cyclooxygenase, lipooxygenase, and cytochrome P450 monooxygenase enzymes prior to exposure to AA did not rescue cells from the inhibitory effect of AA. Moreover, 5,8,11,14-eicosatetraynoic acid, a nonmetabolizable arachidonate analogue, also inhibited cell growth, suggesting that the effect of AA did not require further metabolism. Treatment with antioxidants prior to stimulation with AA was also ineffective in preventing its antiproliferative effect. Thus, AA inhibited proliferation of CML cells by inducing apoptotic cell death. The signaling mechanisms of AA-induced inhibition of cell growth appeared to be independent of its conversion into eicosanoids or free radical generation.

Arachidonic acid induces mobilization of calcium stores and c-jun gene expression: evidence that intracellular calcium release is associated with c-jun activation

Arachidonic acid (AA) plays a signaling role in the induction of several genes. We previously demonstrated that AA induces c-jun gene expression in the stromal cell line +/+.1 LDA 11 by a signaling pathway involving activation of the c-jun amino-terminal kinase (JNK). This study investigated the role of calcium in AA signaling of c-jun activation in +/+.1 LDA 11 cells. AA (10-50 microM) caused a rapid dose-dependent rise in cytosolic calcium. AA-induced calcium mobilization involved both influx of extracellular calcium and the release of intracellular calcium. The importance of calcium was investigated by variation of the extracellular calcium concentration, chelation of intracellular calcium and by calcium ionophore-induced influx of extracellular calcium. AA-induced c-jun gene expression and increased luciferase activity of a construct containing the high affinity AP-1 binding site was decreased in cells preincubated with the intracellular calcium chelator 1,2-bis(o-aminophenoxy)-eThane-N,N,N',N',-tetraacetic acid tetra(aceToxymethyl-esTer) (BAPTA-AM, 10 microM) prior to stimulation with AA. Similarly, chelation of intracellular calcium decreased AA-induced JNK activation. On the contrary, changes in the extracellular calcium concentration had no effect. Also, ionophore A23187 failed to induce c-jun and JNK activation either alone than in combination with AA. These results suggested that calcium was required for AA-dependent activation of c-jun, but that calcium alone was insufficient to induce activation of c-jun. Thus, release of calcium from intracellular stores is implicated in the signaling pathway of AA-induced c-jun activation in stromal cells.

Lineage commitment of HLA-DR/CD38-defined progenitor cell subpopulations in bone marrow and mobilized peripheral blood assessed by four-color immunofluorescence

We used four-color fluorescence analysis to compare lineage antigen expression in relationship to CD38 and HLA-DR on CD34+ progenitor cells in adult human bone marrow and mobilized peripheral blood. Each of four progenitor cell subpopulations defined by HLA-DR and CD38 intensity (CD38-/HLA-DR-, CD38-/HLA-DR+, CD38+/HLA-DR+, and CD38+/HLA-DR-) were present in both progenitor cell sources in similar ratios. The most prevalent subpopulation consisted of cells that expressed both CD38 and HLA-DR. Virtually all progenitor cells that lacked CD38 also lacked lineage antigens regardless of their HLA-DR expression. In contrast, the majority of the cells within both CD38+ progenitor cell subpopulations possessed either lineage antigens or the proliferation-associated antigen, CD71. Furthermore, CD71 was expressed on three times the number of CD38+/HLA-DR- cells when compared with the CD38-/HLA-DR- subpopulation. Within CD34+ progenitor cell subpopulations defined by the expression of CD38 and HLA-DR, the CD38+/HLA-DR- component appears to be the most mature, based on the expression of CD71 and various lineage-associated antigens, including representative markers characterizing early lymphoid, myeloid, and erythroid precursors. Thus, selection of the most immature CD34+ progenitor cells based solely on the lack of HLA-DR expression results in isolation of two distinct cell populations with markedly different maturation status and resultant growth characteristics.

Arachidonic acid mediates interleukin-1 and tumor necrosis factor-alpha-induced activation of the c-jun amino-terminal kinases in stromal cells

We have previously shown that arachidonic acid mediates interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha)-induced transcription of c-jun. The signaling pathway of arachidonic acid-induced c-jun transcription was independent of protein kinase C activation and involved a tyrosine kinase-dependent process. The present study was undertaken to further elucidate the signal transduction pathway of arachidonate-induced c-jun transcription. We used a glutathione-S-transferase-c-jun fusion protein containing the aminoterminal domain of c-jun (residues 5 to 89) to explore the hypothesis that arachidonic acid stimulates c-jun amino-terminal kinase (JNK) activity in the murine stromal cell line +/+.1 LDA 11. Extracts from arachidonic acid-treated cells catalyzed phosphorylation of the c-jun fusion protein, indicating stimulation of JNK activity. Similar results were obtained when cells were challenged with IL-1 and TNF-alpha. The effect of arachidonic acid was specific, because extracts from stimulated cells failed to phosphorylate a mutated fusion protein in which serine 63 and 73 of c-jun were each substituted with leucine. Arachidonic acid induced JNK activation in a time- and dose-dependent manner that was not mimicked by saturated fatty acids such as palmitic acid or other unsaturated fatty acids from the n-3, n-6, or n-9 series. Furthermore, other lipids, such as diacylglycerol, phosphatidic acid, and C2-ceramide, failed to induce a significant increase in JNK activity. Treatment of stromal cells with propyl gallate, a dual inhibitor of lipoxygenase and cyclooxygenase enzymes, did not affect the ability of arachidonic acid to induce JNK activation. Moreover, ETYA (5,8,11,14-eicosate-traynoic acid), a nonmetabolizable arachidonate analogue, also induced JNK activation. These results are consistent with the hypothesis that the signal transduction pathway by which arachidonate stimulates c-jun transcription involves activation of the JNK cascade. Furthermore, arachidonic acid itself and not its cyclooxygenase or lipoxygenase metabolites is involved in stimulating JNK activity. Thus, arachidonic acid may act as a second messenger in mediating the effects of IL-1 and TNF-alpha in the activation of c-jun.

Selection of myeloid progenitors lacking BCR/ABL mRNA in chronic myelogenous leukemia patients after in vitro treatment with the tyrosine kinase inhibitor genistein

Chronic myelogenous leukemia (CML) is a clonal disorder of the hematopoietic stem cell characterized by a chimeric BCR/ABL gene giving rise to a 210-kD fusion protein with dysregulated tyrosine kinase activity. We investigated the effect of genistein, a protein tyrosine kinase inhibitor, on the in vitro growth of CML and normal marrow-derived multi-potent (colony-forming unit-mix [CFU-Mix]), erythroid (burst-forming unit-erythroid [BFU-E]), and granulocyte-macrophage (colony-forming unit-granulocyte-macrophage [CFU-GM]) hematopoietic progenitors. Continuous exposure of CML and normal marrow to genistein induced a statistically significant and dose-dependent suppression of colony formation. Genistein doses causing 50% inhibition of CML and normal progenitors were not significantly different for CFU-Mix (27 mumol/L v 23 mumol/L), BFU-E (31 mumol/L v 29 mumol/L), and CFU-GM (40 mumol/L v 32 mumol/L v 32 mumol/L). Preincubation of CML and normal marrow with genistein (200 mumol/ L for 1 to 18 hours) induced a time-dependent suppression of progenitor cell growth, while sparing a substantial proportion of long-term culture-initiating cells (LTC-IC) from CML (range, 91% +/- 9% to 32% +/- 3%) and normal marrow (range, 85% +/- 8% to 38% +/- 9%). Analysis of individual CML colonies for the presence of the hybrid BCR/ABL mRNA by reverse transcription-polymerase chain reaction (RT-PCR) showed that genistein treatment significantly reduced the mean +/- SD percentage of marrow BCR/ABL+ progenitors both by continuous exposure (76% +/- 18% v 24% +/- 12%, P < or = .004) or preincubation (75% +/- 16% v 21% +/- 10%, P < or = .002) experiments. Preincubation with genistein reduced the percentage of leukemic LTC-IC from 87% +/- 12% to 37% +/- 12% (P < or = .003). Analysis of individual colonies by cytogenetics and RT-PCR confirmed that genistein-induced increase in the percentage of nonleukemic progenitors was not due to suppression of BCR/ABL transcription. Analysis of nuclear DNA fragmentation by DNA gel electrophoresis and terminal deoxynucleotidyl transferase assay showed that preincubation of CML mononuclear and CD34+ cells with genistein induced significant evidence of apoptosis. These observations show that genistein is capable of (1) exerting a strong antiproliferative effect on CFU-Mix, BFU-E, and CFU-GM while sparing the more primitive LTC-IC and (2) selecting benign hematopoietic progenitors from CML marrow, probably through an apoptotic mechanism.

Effect of the protein tyrosine kinase inhibitor genistein on normal and leukaemic haemopoietic progenitor cells

Receptor and nonreceptor protein tyrosine kinases (PTKs) play a key role in the control of normal and neoplastic cell growth. The availability of PTK inhibitors prompted us to evaluate the effects of genistein, a natural inhibitor of PTKs, on in vitro colony formation by normal multilineage colony-forming units (CFU-Mix), erythroid bursts (BFU-E), granulocyte-macrophage colony-forming units (CFU-GM), long-term culture-initiating cells (LTC-IC) and acute myelogenous leukaemia colony-forming units (CFU-AML). Continuous exposure of normal marrow and blood mononuclear non-adherent cells, blood CD34+CD45RA- cells, and leukaemic blasts to increasing doses of genistein (1-100 microM) resulted in a statistically significant (P < or = 0.05) dose-dependent suppression of CFU-Mix, BFU-E, CFU-GM and CFU-AML growth. Regression analysis showed that growth inhibition was linearly related to genistein concentration. Genistein dose causing 50% inhibition (ID50) of CFU-AML was significantly lower compared to CFU-GM ID50 for marrow (19 v 32 microM, P < or = 0.017), unseparated blood (19 v 44 microM, P < or = 0.028) or CD34+CD45RA- blood (19 v 36, P < or = 0.04). Preincubation of leukaemic blasts with genistein (200 microM) for 1-2h confirmed that CFU-AML were significantly more sensitive than normal marrow and blood CFU-GM to genistein. Preincubation conditions which maximally suppressed leukaemic and normal colony growth spared a substantial percentage of marrow (29 +/- 4%) and blood (40 +/- 3%) LTC-IC. In conclusion, our data demonstrate that: (a) genistein strongly inhibits the growth of normal and leukaemic haemopoietic progenitors; (b) growth inhibition is dose- and time-dependent; (c) leukaemic progenitors are more sensitive than normal progenitors to genistein-induced growth inhibition; (d) genistein exerts a direct toxic effect on haemopoietic cells while sparing a substantial proportion of LTC-IC. The potent CFU-AML growth inhibition associated with the relative resistance of normal LTC-IC strongly supports the use of genistein for marrow purging.

Arachidonic acid induces c-jun gene expression in stromal cells stimulated by interleukin-1 and tumor necrosis factor-alpha: evidence for a tyrosine-kinase-dependent process

We have previously shown that granulocyte-macrophage colony-stimulating factor (GM-CSF) gene expression induced by interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) in the murine stromal cell line +/+.1-LDA 11 involves activation of phospholipase A2 (PLA2). Furthermore, induction of GM-CSF gene expression due to release of arachidonic acid as a result of PLA2 activation was mediated by the transcriptional factor c-jun. In the present study, we have investigated the potential mechanism involved in the induction of c-jun gene expression by arachidonic acid. Arachidonic acid induced transcription of c-jun mRNA. Downregulation of protein kinase C (PKC) by chronic exposure of stromal cells to the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA; 400 nmol/L) did not effect c-jun expression induced by arachidonate. Moreover, pretreatment of cells with the PKC inhibitor, calphostin C (1 mumol/L), caused a marked decrease of c-jun expression induced by TPA, but had no influence on c-jun expression induced by arachidonate. To explore the hypothesis that a tyrosine kinase signalling pathway, independent of PKC activation, was involved in arachidonate-induced c-jun expression, stromal cells were pretreated with the protein tyrosine kinase inhibitor, genistein, before challenge with arachidonic acid. Arachidonate 50 mumol/L)-induced c-jun expression was inhibited, in a dose- and time-dependent manner, by genistein. Genistein similarly inhibited c-jun expression in stromal cells exposed to IL-1 (500 U/mL) plus TNF-alpha (500 U/mL). The potential role of a tyrosine kinase pathway in arachidonate-mediated c-jun expression was further investigated by assaying the tyrosine kinase activity of cells challenged with arachidonic acid, IL-1, and TNF-alpha. Exposure of stromal cells to arachidonic acid induced a 2.1-fold increase in intracellular tyrosine kinase activity determined by phosphorylation of the synthetic peptide, raytide, in the presence of [gamma-32P]-ATP. Similarly, IL-1 and TNF-alpha induced 1.7- and 2.4-fold increases in tyrosine protein kinase activity, respectively. The effect of arachidonic acid on tyrosine kinase activity was inhibited by genistein and was enhanced by sodium vanadate. The increase of protein tyrosine kinase activity detected in arachidonate-stimulated cells was associated, in a dose- and time-dependent fashion, with tyrosine phosphorylation of 240-, 40-, and 29-kD substrates. These results are consistent with the hypothesis that a tyrosine phosphorylation process is triggered by arachidonate as an early event in the signalling pathway that leads to increased expression of c-jun.(ABSTRACT TRUNCATED AT 400 WORDS)

1-Phosphatidylinositol 4-kinase: an enzyme linked with proliferation and malignancy

The activity of 1-phosphatidylinositol 4-kinase (EC 2.7.1.67), the first committed ATP-utilizing enzyme of inositol 1,4,5-trisphosphate and diacylglycerol biosynthesis, was determined in a spectrum of rat hepatomas of different growth rates, in sarcoma, and in normal tissues of high cell renewal rates which include differentiating and regenerating liver. A standard isotopic method was developed to measure the enzymic activity in crude particulate extracts. In this assay, the enzyme activity was linear with time for 2 min and proportional with protein concentrations over a range of 0.1 to 1.0 mg per 0.1 ml reaction mixture. The optimum pH for both liver and hepatoma enzyme was 7.4. The apparent Km values of the kinase for ATP, Mg2+, and the substrate phosphatidylinositol in normal liver were 0.03, 10, and 0.2 mM, respectively, and in rapidly growing hepatoma 3924A 0.01, 0.1, and 5.3 mM. The kinase activity in adult rat livers was 0.3 to 0.5 +/- 0.01 nmol/h/mg protein. In hepatomas of slow and intermediate growth rates, kinase activity increased 5.3- to 7.6-fold, and in rapidly proliferating hepatoma 3924A, it was elevated 28.5-fold over that of normal liver. In rat sarcoma, kinase activity was 13.2-fold higher than in normal muscle. To clarify further the linkage between kinase activity and proliferation, enzymic activity was determined in rapidly growing rat tissues. The kinase activity in rat thymus, bone marrow, spleen, and testis increased 8.4-, 7.6-, 5.6- and 5.6-fold, respectively, over the values of normal rat liver; by contrast, in skeletal muscle, liver, heart, and renal cortex, the activities were low. In the rapidly growing neonatal rat liver and in 24-h regenerating liver, activities were 3.4- and 3.0-fold higher than in the adult resting liver. From this study, the relationship of 1-phosphatidylinositol 4-kinase activity with transformation and cell proliferation is clearly apparent in the markedly increased activity in transplantable hepatomas of different growth rates and in sarcoma and is further emphasized by the high activity observed in newborn and regenerating liver and in thymus, bone marrow, spleen, and testis. Since the kinase activity is linked with proliferation and malignancy, it may well be a sensitive target for chemotherapy.

Regulation of interleukin-1 and tumor necrosis factor-alpha induced granulocyte-macrophage colony-stimulating factor gene expression: potential involvement of arachidonic acid metabolism

Signal transduction pathways evoked by interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) to stimulate expression of other cytokines in mesenchymal cells are not clearly understood. Stimulation of the murine bone marrow stromal cell line +/(+)-1.LDA 11 with IL-1 (500 U/ml) in combination with TNF-alpha (500 U/ml) (IL-1 plus TNF-alpha) induced expression of c-jun mRNA as well as granulocyte-macrophage colony stimulating factor (GM-CSF) mRNA. We investigated the possibility that arachidonic acid metabolites, acting through protein kinase C (PKC) and perhaps also through the PKC-responsive transcription factor c-jun/AP-1, may be responsible for regulating GM-CSF transcription in these stromal cells. Expression of GM-CSF mRNA was preceded by IL-1 plus TNF-alpha induced arachidonate release (assayed using the 3H-derivative). Pretreatment of cells with the phospholipase A2 inhibitor quinacrine (20 microM) inhibited accumulation of both c-jun and GM-CSF mRNA but had no influence on expression of other genes induced by IL-1 and TNF-alpha, including leukemia inhibitory factor (LIF). In addition, quinacrine partially blocked IL-1 plus TNF-alpha induced 3H-arachidonic acid release from prelabeled stromal cells. Furthermore, exogenous arachidonate (10 to 50 microM) induced expression of c-jun. To investigate the role of arachidonate in GM-CSF transcription, we used a reporter vector consisting of the murine GM-CSF promoter linked to firefly luciferase. Transfection efficiency was monitored by assessing expression of a constitutively active gene, RSV-beta galactosidase. In this system, quinacrine significantly inhibited IL-1 plus TNF-alpha induced GM-CSF transcription assayed with the reporter construct. Exogenous arachidonic acid alone (10 microM) increased activity of GM-CSF reporter vector 1.5-fold over control. These results are consistent with the hypothesis that arachidonate metabolites are involved in the signaling pathway that leads to IL-1 plus TNF-alpha induced GM-CSF gene expression. Thus, transcriptional activation of GM-CSF gene is mediated, in part, by the arachidonate cascade.

Gp-regulated phosphoinositide hydrolysis in turkey and human erythrocytes exposed to fluoride ion: relationship to calcium influx

Previous studies have demonstrated that although both mammalian and avian erythrocytes express an inducible inositol bisphosphate-specific phospholipase C, only the latter possess the guanine nucleotide-binding protein (Gp) that regulates this activity. In confirmation of previous reports, turkey erythrocyte plasma membranes responded to guanosine 5'-0-(3-thio)triphosphate (GTP-gamma-S) and fluoroaluminates with hydrolysis of phosphoinositides, release of inositol phosphates, and generation of diacylglycerol, whereas human erythrocyte plasma membranes exhibited no such changes when incubated with known activators of guanine nucleotide regulatory proteins. We next contrasted responses of intact turkey and human erythrocytes to fluoroaluminates to develop a model to investigate the cellular effects of Gp activation. When turkey erythrocytes were exposed to fluoroaluminates, cellular levels of diacylglycerol and phosphatidic acid rapidly increased as phosphoinositides were hydrolyzed. The alterations in the lipid composition of turkey erythrocytes effected by fluoroaluminates were remarkable; phosphatidic acid levels increased over 30-fold, whereas levels of polyphosphoinositides were decreased to less than 10% of those present before stimulation. In contrast, fluoroaluminates caused only minor alterations in the diacylglycerol and phospholipid content of intact human erythrocytes. To define the role of inositol-specific phospholipase C activation in the transmembrane conveyance of extracellular Ca++, we compared the influx of extracellular Ca++ in human and turkey erythrocytes exposed to fluoroaluminates. Fluoroaluminates initiated a sustained influx of extracellular 45Ca++ into turkey, but not human, erythrocytes. These results provide strong support for the hypothesis that Gp activation results in an influx of calcium into stimulated cells. Moreover, the data demonstrate that comparison of responses of human and turkey erythrocytes to fluoroaluminates provides a well-defined method for investigating the mechanisms and consequences of Gp activation in intact cells.

In vitro bone marrow cell culture and cytogenetic analysis in a case of myelodysplasia

A case of refractory anemia with sideroblastosis and a number of bone-marrow blasts slightly over the limit which separates the I/II and III FAB-subtypes of myelodysplastic syndromes is described. The leukemic-like type of in vitro growth and the multiple karyotypic changes observed in the bone-marrow cells at presentation were both indicators of the malignant nature of the disorder and underlined the importance of these studies in assessing diagnosis and prognosis in patients with preleukemic disorders. The role that the chromosome aberrations, del(11)(q14) and del(18)(q21), both found in 100% of the bone-marrow metaphases examined, may play in the pathogenesis of the disease is also discussed.

Expression of val-12 mutant ras p21 in an IL-3-dependent murine myeloid cell line is associated with loss of serum-dependence and increases in membrane PIP2-specific phospholipase C activity

We previously showed that the proliferative response of a serum- and interleukin-3 (IL-3)-dependent murine myeloid cell line, NFS/N1-H7, was partially inhibited by pertussis toxin as a result of toxin-induced increased adenylate cyclase activity. In the present studies, we examined the role of the phosphoinositide cycle in the proliferative response of these cells and demonstrated that there was no change in PIP (phosphatidylinositol bisphosphate)-specific phospholipase C activity in response to IL-3 alone. However, serum caused a pertussis toxin-insensitive increase in PIP2-specific phospholipase C activity as reflected by decreased cellular levels of 32P-labelled PIP2. Proliferation of a subline selected from val-12-mutant H-ras-transfected NFS-H7 cells, clone E5, was insensitive to pertussis toxin, occurred in the absence of serum but remained serum-stimulatable and absolutely dependent on IL-3. This val-12 mutant ras-expressing cell line showed an increase in 32P-labelled PIP (phosphatidylinositol phosphate) in response to serum whereas the parent cell line did not. Membrane fractions from 32P-labelled ras-transfected cells displayed higher GTP gamma S-, GTP-, or F(-)-stimulated PIP2-specific phospholipase C activity compared to membranes from the parent cell line. Thus serum-dependence and adenylate cyclase-mediated pertussis toxin-sensitivity of the parent cell line was bypassed by val-12 mutant ras p21, possibly as a result of increased PIP2-specific phospholipase C activity.

Inosine monophosphate dehydrogenase inhibitors. Probes for investigations of the functions of guanine nucleotide binding proteins in intact cells

Taken together, the above reports indicate that the IMP dehydrogenase inhibitors are valuable probes for investigation of the biological functions of guanine nucleotides in intact cells. While these agents have minor effects on levels of other nucleotides and enzymes, non-specific effects can be monitored by addition of guanine or guanosine to provide substrates for the salvage pathway of guanine nucleotide synthesis. The most important question yet to be resolved in employing these agents is why incomplete depletion of intracellular guanine nucleotides results in such dramatic effects on G-protein function. Since the level of GTP in resting cells is approximately 0.5 mM, even a 90% reduction in GTP levels should leave enough nucleotide to adequately activate most known G-proteins, as the latter display high binding affinities for guanine nucleotides in cell free systems. Several explanations have been proposed to account for this disparity. Much of the intracellular guanine nucleotide may be bound or compartmentalized and therefore unable to interact with certain G-proteins. Possibly, G-proteins in the intracellular environment possess a much lower affinity for GTP that they do in cell free system. It may be to the cells' advantage that relatively minor fluctuations in levels of GTP result in pronounced alterations in the biological function of G-proteins as this effect may provide a physiologically important mechanism for the regulation of G-proteins in vivo. Further studies are necessary to clarify the mechanisms involved in the regulation of the biological function of G-proteins and oncogene products by guanine nucleotides in intact cells.

[Whole blood filterability in chronic cerebrovascular disorders: effects of the use of buflomedil hydrochloride]

Buflomedil chlorhydrate is a newly synthesized molecule with a notable effect of vasodilatation even on cerebral blood vessels. It is effective in the treatment of Chronic Cerebrovascular Disorders (CCVD) as it reduces membrane rigidity in red blood cells. Since, however, new techniques for the evaluation of this haemorheological parameter suggest it may no longer be considered the sole expression of whole blood filterability we decided to monitor the haemorheological effect of Buflomedil once again. The aim of this random blind vs. Placebo study was to monitor whole blood filterability (Reid and coll., 1976) and its main determinants (hematocrit, leucocyte count, fibrinogen levels, plasma viscosity and red blood cell deformability) in 20 (10 male and 10 female) CCVD patients (Ad Hoc Committee, Paris, 1980), aged between 66 and 75 years of age before and after intravenous injection in bolus of 150 mg Buflomedil chlorhydrate. Our results showed a significant increase in whole blood filterability, confirming those of recent studies on other molecules with a known effect on the haemorheological pattern but not only on the plasticity of red blood cells. Further studies are therefore necessary to define the rheological activity of this drug more precisely.

Involvement of guanine nucleotides in superoxide release by fluoride-treated neutrophils. Implications for a role of a guanine nucleotide regulatory protein

Previous studies demonstrating hydrolysis of phosphatidylinositol bisphosphate (PIP2) and generation of inositol phosphates in neutrophils exposed to 20.0 mM NaF provide indirect evidence that activation of phospholipase-associated guanine nucleotide regulatory protein, a guanine nucleotide binding protein which regulates the activation of a membrane inositol-specific phospholipase C, is an early event in the neutrophil stimulus-response pathway triggered by fluoride. Consistent with this hypothesis, exposure of a plasma membrane rich preparation isolated from 32P labeled neutrophils to 20.0 mM NaF resulted in hydrolysis of labeled PIP2. Levels of other phospholipids were not affected. Inositol bisphosphate and inositol trisphosphate were detected in extracts of neutrophil plasma membranes exposed to fluoride. To further explore the involvement of guanine nucleotides in functional responses of intact neutrophils triggered by fluoride, we preincubated cells with 2-beta-D-ribofuranosylthiazole-4-carboxamide (tiazofurin), a selective inhibitor of inosine monophosphate dehydrogenase, to diminish guanine nucleotide synthesis and then compared superoxide generation induced by FMLP, PMA, digitonin, and 20.0 mM NaF to intracellular levels of guanine nucleotides. Preincubation of neutrophils for 2.5 h at 37 degrees C with tiazofurin resulted in dose-dependent depletion of GTP and GDP. Maximal depletion of guanine nucleotides required relatively high levels of tiazofurin (200 to 400 microM) and resulted in a 55 to 60% reduction of GTP and GDP. The effects of tiazofurin on guanine nucleotides levels were not observed when neutrophils were preincubated at 4 degrees C. AT 37 degrees C, tiazofurin also decreased intracellular ATP and ADP levels but adenine nucleotide depletion was less pronounced than guanine nucleotide depletion for each concentration of tiazofurin used. When tiazofurin was removed by washing cells after incubation, adenine nucleotide quickly returned to preincubation values but guanine nucleotide levels remained depressed. Addition of exogenous guanosine (200 microM) prevented tiazofurin-dependent depletion of guanine nucleotides but had no influence on adenine nucleotide depletion. Superoxide released triggered by FMLP and F- was inhibited to an extent similar to that of guanine nucleotide depletion under different conditions of preincubation. Inhibition of superoxide release was not observed if cells were preincubated at 4 degrees C, was not rapidly reversible, and was not observed when guanosine was added with tiazofurin.(ABSTRACT TRUNCATED AT 400 WORDS)

Involvement of guanine nucleotides in superoxide release by fluoride-treated neutrophils. Implications for a role of a guanine nucleotide regulatory protein

Previous studies demonstrating hydrolysis of phosphatidylinositol bisphosphate (PIP2) and generation of inositol phosphates in neutrophils exposed to 20.0 mM NaF provide indirect evidence that activation of phospholipase-associated guanine nucleotide regulatory protein, a guanine nucleotide binding protein which regulates the activation of a membrane inositol-specific phospholipase C, is an early event in the neutrophil stimulus-response pathway triggered by fluoride. Consistent with this hypothesis, exposure of a plasma membrane rich preparation isolated from 32P labeled neutrophils to 20.0 mM NaF resulted in hydrolysis of labeled PIP2. Levels of other phospholipids were not affected. Inositol bisphosphate and inositol trisphosphate were detected in extracts of neutrophil plasma membranes exposed to fluoride. To further explore the involvement of guanine nucleotides in functional responses of intact neutrophils triggered by fluoride, we preincubated cells with 2-beta-D-ribofuranosylthiazole-4-carboxamide (tiazofurin), a selective inhibitor of inosine monophosphate dehydrogenase, to diminish guanine nucleotide synthesis and then compared superoxide generation induced by FMLP, PMA, digitonin, and 20.0 mM NaF to intracellular levels of guanine nucleotides. Preincubation of neutrophils for 2.5 h at 37 degrees C with tiazofurin resulted in dose-dependent depletion of GTP and GDP. Maximal depletion of guanine nucleotides required relatively high levels of tiazofurin (200 to 400 microM) and resulted in a 55 to 60% reduction of GTP and GDP. The effects of tiazofurin on guanine nucleotides levels were not observed when neutrophils were preincubated at 4 degrees C. AT 37 degrees C, tiazofurin also decreased intracellular ATP and ADP levels but adenine nucleotide depletion was less pronounced than guanine nucleotide depletion for each concentration of tiazofurin used. When tiazofurin was removed by washing cells after incubation, adenine nucleotide quickly returned to preincubation values but guanine nucleotide levels remained depressed. Addition of exogenous guanosine (200 microM) prevented tiazofurin-dependent depletion of guanine nucleotides but had no influence on adenine nucleotide depletion. Superoxide released triggered by FMLP and F- was inhibited to an extent similar to that of guanine nucleotide depletion under different conditions of preincubation. Inhibition of superoxide release was not observed if cells were preincubated at 4 degrees C, was not rapidly reversible, and was not observed when guanosine was added with tiazofurin.(ABSTRACT TRUNCATED AT 400 WORDS)

Leucocyte rheology in the early stages of ischaemic stroke

Within 5 hours of the onset of ischaemic stroke the filterability patterns and the counts of the granulocyte, monocyte and lymphocyte subfractions were monitored. The results were compared to those of a healthy matched control group and to those of a matched group with cardiovascular risk factors. The granulocyte filterability rate was significantly impaired in the group at risk and even more so in the stroke group suggesting alterations in it may be a sign of latent ischaemia.