Coping strategies in response to peer victimization: Comparing adolescents in the United States and Korea

We examined cultural specificity in how adolescents' coping strategies in response to peer victimization are associated with adjustment with a sample of 7th-8th graders from the United States (n = 292, 60% female, Mage  = 13.6, SD = 0.65) and South Korea (n = 462, 50.2% female, Mage  = 13.7, SD = 0.58). Participants read scenarios describing victimization and rated the likelihood of utilizing different coping strategies. US adolescents rated conflict resolution, cognitive distancing, and revenge higher than Korean adolescents, while Korean adolescents endorsed social support seeking more than US adolescents. Social support seeking was positively associated with global self-worth in both countries; however, social support seeking was negatively related to depression and social anxiety only for Korean youth.

Youth Aggression and Peer Victimization as Predictors of Adolescent Alcohol and Marijuana Use: A Longitudinal Analysis of Youth with Aggressive Behavior Problems

Youth who are behaviorally aggressive and victimized by their peers comprise a significant population with specific risks and vulnerabilities relative to substance use. The goals of the current study were to examine the roles that youth aggression and peer victimization play in determining the timing of alcohol and marijuana use initiation and the frequency of use 5-years later in a sample of at-risk, aggressive youth. 360 youth (Mage= 10.17 years; 65% boys, 35% girls; 78.1% African American, 20.3% Caucasian, 1.4% Hispanic, and 0.3% other) recruited for a prevention program for at-risk youth were followed for 5 years (4th - 9th grade). Cox PH regressions were conducted to predict timing of alcohol and marijuana use initiation. Zero-inflated negative binomial regressions were used to predict frequency of alcohol and marijuana use 5 years later. Results showed that peer victimization inferred decreased risk of alcohol use initiation. However, this effect was only observed for youth with relatively moderate, and low levels of aggression. Findings suggest that differences in youth aggression and victimization interact to predict distinct outcomes, suggesting the need for a more comprehensive approach when working with aggressive youth who have experienced peer victimization.

A Prospective Study of Co-Rumination in Parent-Adolescent Conversations Several Years After a Devastating Tornado

OBJECTIVE

This study examined the association between youth post-disaster stress responses and co-rumination in conversations with a parent several years after a devastating tornado.

METHOD

Adolescents (N = 200) drawn from an ongoing study for aggressive youth (ages 13 to 17; 80% African American) and their parents experienced an EF-4 tornado in 2011 and then provided joint recollections about their tornado experiences approximately 5 years later. Recollections were coded for the four components of co-rumination: rehashing problems, dwelling on negative affect, mutual encouragement of problem talk, and speculating about problems. Parent-rated post-traumatic stress symptoms (PTSS) and youth resting respiratory sinus arrhythmia (RSA) were measured approximately 6-months and 1-year post-tornado, respectively.

RESULTS

Results indicated that co-rumination could be identified, and reliably measured, in the tornado conversations. Resting RSA moderated the association between post-disaster PTSS and the co-rumination component dwelling on negative affect, such that youth PTSS was associated with higher levels of dwelling on negative affect but only at lower levels of resting RSA (an index of physiological dysregulation). There was no association between youth PTSS and dwelling on negative affect at high resting RSA (an index of better physiological regulation). Youth PTSS and resting RSA were unrelated to the other three co-rumination components. No gender differences were found.

CONCLUSIONS

Results provide preliminary evidence establishing the co-rumination coding scheme in a sample of disaster-exposed parents and adolescents. Results also indicated that PTSS and resting RSA are important youth-level factors that relate to how parents and adolescents discuss their disaster experiences even years post-exposure.

Interpretations and revenge goals in response to peer provocations: Comparing adolescents in the United States and Pakistan

This study examined cultural specificity in how interpretations about peer provocation are associated with revenge goals and aggression. The sample consisted of young adolescents from the United States (369 seventh-graders; 54.7% male; 77.2% identified as White) and from Pakistan (358 seventh-graders; 39.2% male). Participants rated their interpretations and revenge goals in response to six peer provocation vignettes and completed peer nominations of aggressive behavior. Multi-group SEM models indicated cultural specificity in how interpretations were related to revenge goals. Interpretations that a friendship with the provocateur was unlikely were uniquely related to revenge goals for Pakistani adolescents. For U.S adolescents positive interpretations were negatively related to revenge but self-blame interpretations were positively related to vengeance goals. Revenge goals were related to aggression similarly across groups.

Disaster Exposure and Temperament as Predictors of Adolescent Substance Use

OBJECTIVE

Children who have been exposed to a natural disaster in their lifetime comprise a significant population with specific risks and vulnerabilities, particularly for at-risk youth. The goal of the current study was to examine the role that severity of disaster exposure plays in determining the timing of alcohol and marijuana use initiation and the frequency of use four years later in a sample of at-risk, aggressive youth exposed to a devastating tornado. Of further interest was the examination of the moderating effect of temperamental fear and inhibitory control.

METHOD

Three hundred and forty-six youth (Mage = 11.33; 65% boys; 77.5% African-Americans, 18.3% Caucasian, 1.7% Hispanic) initially recruited for a prevention program for at-risk youth were followed for 4 years after a tornado. Cox PH regressions were conducted to predict timing of alcohol and marijuana use initiation. Zero-inflated negative binomial regressions were used to predict frequency of alcohol and marijuana use 4 years after the tornado.

RESULTS

Disaster exposure severity was predictive of frequency of marijuana use four years after the tornado, but exposure alone was not predictive of initiation. Exposure severity predicted increases in risk for alcohol use initiation only for youth high in fear. Additionally, greater levels of inhibitory control protected youth from earlier alcohol use initiation.

CONCLUSIONS

Findings highlight a need to research the initiation and frequency of use for substances individually, while also assessing the needs of youth exposed to natural disasters with both their degree of disaster exposure and specific temperamental characteristics in mind.

"I Felt Like a Hero:" Adolescents' Understanding of Resolution-Promoting and Vengeful Actions on Behalf of Their Peers

Bystander intervention on behalf of victims of peer aggression is credited with reducing victimization, yet little is known about how bystanders evaluate their intervention efforts. African-, European-, Mexican-, and Native-American adolescents (N = 266) between 13 and 18 years (M_age = 15.0, 54% female) recounted vengeful and peaceful responses to a peer's victimization. For comparison, they also described acts of personal revenge. Youth's explanations of how they evaluated each action were coded for goals and outcomes. Befitting its moral complexity, self-evaluative rationales for third-party revenge cited more goals than the other two conditions. References to benevolence and lack thereof were more frequent after third-party revenge compared to personal revenge. Concerns that security was compromised and that actions contradicted self-direction were high after both types of revenge. Third-party resolution promoted benevolence, competence, self-direction, and security more than third-party revenge. Epistemic network analyses and thematic excerpts revealed the centrality of benevolence goals in adolescents' self-evaluative thinking. Self-focused and identity-relevant goals were cited in concert with benevolence after third-party intervention.

Co-reminiscing with a caregiver about a devastating tornado: Association with adolescent anxiety symptoms

This study explores the association between caregivers' style of co-reminiscing with their adolescents about an EF4 tornado and youth anxiety symptoms several years following the disaster. Caregiver reward of their children's emotional expression, defined as attending to and validating emotionally salient content, is generally associated with adaptive youth psychosocial outcomes. However, caregiver reward of youth recollections that are centered around the youth's negative emotional expression could be an indicator that both caregivers and adolescents are engaged in co-rumination regarding negative emotional experiences. This process may contribute to relatively higher levels of anxiety over time. Adolescents (N = 169) drawn from an ongoing study for aggressive youth (ages 12 to 17; 82% African American) provided individual recollections about their experiences during a devastating tornado 4 to 5 years following the disaster. Caregivers and youth then co-reminisced about their tornado-related experiences. Individual youth recollections were coded for negative personal impact and use of negative emotion words; caregiver-adolescent conversations were coded for caregiver reward of negative emotional expression. Youth who noted more negative personal impacts and used more negative emotion words were higher in parent-rated youth anxiety, and these associations were moderated by caregiver reward of negative emotional expression. The associations between youth recollection qualities and anxiety emerged only when caregivers exhibited high levels of reward of negative emotional expression. These patterns were generally stronger for girls compared to boys. Findings suggest that excessively discussing and rehashing negative experiences, especially several years after the disaster, may be a risk factor for anxiety among disaster-exposed adolescents. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Validation of the Arabic and Hebrew versions of the Utrecht-Management of Identity Commitments Scale (U-MICS)

INTRODUCTION

The Utrecht-Management of Identity Commitments Scale (U-MICS; Crocetti, Rubini, & Meeus, 2008) is a self-report scale that can be applied to measure three identity processes (commitment, in-depth exploration, and reconsideration of commitment) in specific domains. The current study was aimed at testing the applicability of the U-MICS in two new languages: Arabic and Hebrew. Specifically, we (a) tested the fit of the three-factor structure; (b) examined measurement invariance of the Arabic and Hebrew versions; and (c) investigated convergent validity by relating the identity processes (commitment, in-depth exploration, and reconsideration of commitment) to multiple indicators of psychosocial adjustment (self-esteem, prosocial behaviors, and delinquency).

METHODS

Participants were 314 Arab and 386 Jewish adolescents living in Israel (N = 770; 54.7% girls; M_age = 13.79, SD_age = 0.51, age-range = 12-15). Assessments of identity processes, self-esteem, and delinquency were collected using self-report measures, while prosocial behaviors were measured through peer nominations.

RESULTS

The results highlighted that (a) the three-factor model fit the data excellently in the total sample as well as in Arab and Jewish samples; (b) hierarchical levels of measurement invariance (configural, metric, and scalar), as well as invariance of covariances, could be clearly established; and (c) convergent validity was demonstrated by showing meaningful associations between identity processes and indicators of psychosocial functioning.

CONCLUSIONS

This study indicates that the U-MICS is a reliable instrument for assessing identity processes in Arabic and Hebrew-speaking adolescents.

Trajectories of tornado-related posttraumatic stress symptoms and pre-exposure predictors in a sample of at-risk youth

OBJECTIVE

The current study examined how severity of disaster exposure and predisaster individual and family characteristics predicted trajectories of disaster-related posttraumatic stress symptoms (PTSS) in children over 4 years following a devastating EF-4 tornado.

METHOD

Participants (n = 346; 65% male; 77.5% African American) were 4th-6th-graders and their caregivers, from predominantly low-income households, who were already participating in a longitudinal study of indicated prevention effects for externalizing outcomes when the tornado occurred in 2011. Latent class trajectory analyses were used to identify disaster-related PTSS trajectory groups across the 4-year postdisaster period.

RESULTS

Three groups were identified: (1) a group that declined (recovery) in PTSS over time (15.90%); (2) a group that was stable and low in PTSS over time (76.87%); and (3) a group that was stable and high (chronic) in PTSS over time (7.23%). Multinomial logistic regression analyses revealed that greater tornado exposure predicted membership in the declining trajectory group relative to the low-stable group. Positive parenting and pretornado caregiver trauma exposure also moderated how disaster exposure, particularly perceived life threat, predicted PTSS trajectories.

CONCLUSIONS

Some youth reported elevated disaster-related PTSS repeatedly for 4 years following a devastating tornado. Consistent with the concept of equifinality, results suggest that there are several pre-exposure risk factors that may increase risk for a chronic PTSS trajectory following disaster exposure. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Identifying and Distinguishing Value Profiles in American and Israeli Adolescents

Although research has examined how values are correlated with behavior, little has examined how the system of values predicts behavior. In a cross-cultural sample of American (109 European American; 216 African American) and Israeli (318 Arab Israeli; 216 Jewish Israeli) adolescents, the present study used latent profile analysis to identify groups which reflected the theoretical structure of values across both cultures. Four profiles were found: self-focused, anxiety-free, other-focused, and undifferentiated. Results indicated that Self-Focused adolescents were the most aggressive and viewed as leaders by their peers compared to the other groups. Self-Focused and anxiety-free youth reported more delinquency than their peers. Few differences between cultural groups emerged, suggesting that this approach is a promising avenue for understanding heterogeneity in behavior.

Pacifists and Revenge-Seekers in Response to Unambiguous Peer Provocation

In order to better understand why some children retaliate when they feel provoked and others do not, the present study identified "pacifistically-oriented" children who made negative interpretations in response to unambiguous provocations, yet did not endorse revenge goals, and compared them to "revenge-seeking" children who also made negative interpretations but did endorse revenge goals. Groups were identified based on seventh graders' (N = 367; 54.77% male; 22.89% racial/ethnic minority) responses to hypothetical situations in which a peer excluded and insulted them. Comparing these groups revealed that Pacifists endorsed relationship-maintaining goals and emotion regulation goals more highly than Revenge-Seekers. Revenge-Seekers reported more anger and endorsed beliefs about negative reciprocity and aggression being legitimate more highly than Pacifists. Additionally, Revenge-Seekers were more disrespect sensitive than were Pacifists, based on a measure of vigilance for signs of disrespect and expectations that others would disrespect them. Together these findings point to social-cognitive and emotion-related processes that may inhibit revenge-seeking in unambiguous provocation situations, even when children interpret the peer's behavior quite negatively.

Sources and Implications of Maternal Accuracy About Young Adolescents' Vulnerability to Friendship Jealousy

To assist effectively with social difficulties, parents must accurately understand the peer situations that are difficult for their child. Mothers' insight into their young adolescent's vulnerability to friendship jealousy was assessed by posing identical vignettes to 72 young adolescents and their mothers and matching their responses. Mothers and children also completed questionnaires on their relationship and the child's adjustment. Mothers as a group were poor judges of their child's jealousy, but considerable variability existed. Accuracy was greater when mother-child pairs were closer. Polynomial regression and response surface analyses indicated that maternal accuracy could dampen the friendship and aggression risks otherwise associated with being vulnerable to jealousy.

Racially diverse classrooms: effects of classroom racial composition on interracial peer relationships

The purpose of this study was to examine the interactive effects that a child's race and the racial composition of a classroom have on a variety of sociometric measures. Sociometric nominations were collected from 872 fifth-grade students (48% male, 48% Black) who were in classrooms that ranged from nearly all Black to nearly all White students. Hierarchical Linear Modeling analyses indicated that the race of the child, the race of the rater, and the classroom race composition each impacted sociometric nominations. Results suggest that schools that are more balanced in the distribution of Black and White students might promote more positive interracial peer relationships. However, opportunities to be highly liked and to be perceived as a leader might be greatest in a school in which the child is in the clear racial majority.

Interleukins in glioblastoma pathophysiology: implications for therapy

Despite considerable amount of research, the poor prognosis of patients diagnosed with glioblastoma multiforme (GBM) critically needs new drug development to improve clinical outcomes. The development of an inflammatory microenvironment has long been considered important in the initiation and progression of glioblastoma; however, the success of developing therapeutic approaches to target inflammation for GBM therapy has yet been limited. Here, we summarize the accumulating evidence supporting a role for inflammation in the pathogenesis of glioblastoma, discuss anti-inflammatory targets that could be relevant for GBM treatment and provide a perspective on the challenges faced in the development of drugs that target GBM inflammation. In particular, we will review the function of IL-1β, IL-6 and IL-8 as well as the potential of kinase inhibitors targeting key players in inflammatory cell signalling cascades such as JAK, JNK and p38 MAPK.

The T genotype of the MGMT C>T (rs16906252) enhancer single-nucleotide polymorphism (SNP) is associated with promoter methylation and longer survival in glioblastoma patients

Clinical studies in patients with newly diagnosed glioblastoma treated with temozolomide have shown that the methylation status of the O(6)-methylguanine-DNA methyltransferase (MGMT) gene is both predictive and prognostic of outcome. Methylation of the promoter region of MGMT is the most clinically relevant measure of MGMT expression and its assessment has become integral in current and planned clinical trials in glioblastoma. Our study confirmed that MGMT methylation, assessed by pyrosequencing, is associated with a significant survival benefit in glioblastoma patients treated with temozolomide (either concurrently with radiotherapy or sequential treatment). More interestingly, our study demonstrated that a promoter variant, the c.-56C>T (rs16906252) single nucleotide polymorphism (SNP) located within a cis-acting enhancer element at the proximal end of MGMT, is associated with the presence of MGMT promoter methylation in de novo glioblastoma. Furthermore, we show that the overall survival of patients carrying both the SNP and MGMT methylation showed a strong survival benefit when compared to either molecular event on their own. Promoter reporter experiments in MGMT methylated glioblastoma cell lines showed the T allele conferred a ∼30% reduction in normalised MGMT promoter activity compared to the wild-type haplotype. This might account for the propensity of the T allele to undergo promoter methylation, and in turn, the improved survival observed in carriers of the T allele. An independent validation on larger cohorts is required to confirm the prognostic and predictive value of individuals carrying the T allele.

Peer Rejection as a Social Antecedent to Rejection Sensitivity in Youth: The Role of Relational Valuation

Although much is known about the consequences of rejection sensitivity (RS), less is known about its social antecedents, particularly during development. Despite research demonstrating the role of peer rejection in the development and maintenance of problematic social schema like RS, little is known about why some youth are more susceptible to these negative consequences than others. We examined how relational valuation might moderate the effects of peer rejection on RS in a sample of 294 youth (138 boys) who made the transition from middle to high school. Results from path analysis revealed that 8^th grade peer rejection was most highly associated with 9^th grade RS for youth who held high regard for social relationships. Findings demonstrate the importance of examining cognitive moderators in the links between negative social experiences and problematic social schema, and highlight the need to move beyond simple main effects models for understanding the heterogeneity of rejection.

College Students' Revenge Goals Across Friend, Romantic Partner, and Roommate Contexts: The Role of Interpretations and Emotions

Residential college environments provide young people with distinctive relationship opportunities and challenges. A major purpose of the present study was to learn whether college students respond differently to conflict-of-interest vignettes in three different relationship contexts. Students were more likely to make negative interpretations about their romantic partner's behavior than they did about their friend's or roommate's behavior. They were also more likely to feel angry and hurt and to endorse hostile goals and strategies with romantic partners. A second major purpose was to learn about the types of interpretations and emotions associated with revenge goals in conflict-of-interest situations. Results indicated that interpreting the other person's actions as disrespectful and as rejecting was related to revenge goals and also predicted to revenge goals beyond the contributions of anger and hurt feelings.

Freeze substitution in 3 hours or less

Freeze substitution is a process for low temperature dehydration and fixation of rapidly frozen cells that usually takes days to complete. New methods for freeze substitution have been developed that require only basic laboratory tools: a platform shaker, liquid nitrogen, a metal block with holes for cryotubes and an insulated container such as an ice bucket. With this equipment, excellent freeze substitution results can be obtained in as little as 90 min for cells of small volume such as bacteria and tissue culture cells. For cells of greater volume or that have significant diffusion barriers such as cuticles or thick cell walls, one can extend the time to 3 h or more with dry ice. The 3-h method works well for all manner of specimens, including plants and Caenorhabditis elegans as well as smaller samples. Here, we present the basics of the techniques and some results from Nicotiana leaves, C. elegans adult worms, Escherichia coli and baby hamster kidney tissue culture cells.

A review of high-pressure freezing preparation techniques for correlative light and electron microscopy of the same cells and tissues

In this paper, we review some published studies using correlative light and electron microscopy methods. We further refined our criteria to include only those studies using live cells for light microscope and where high-pressure freezing was the method of specimen preparation for electron microscopy. High-pressure freezing is especially important for some difficult-to-fix samples, and for optimal preservation of ultrastructure in samples larger than a few micrometres. How the light microscope observations are done is completely sample dependent, but the choice of high-pressure freezer depends on the speed required to capture (freeze) the biological event of interest. For events requiring high time resolution (in the 4-5 s range) the Leica EM PACT2 with rapid transfer system works well. For correlative work on structures of interest that are either non-motile or moving slowly (minutes rather than seconds), any make of high-pressure freezer will work. We also report on some efforts to improve the capabilities of the Leica EM PACT2 rapid transfer system.

Microarray gene expression and immunohistochemistry analyses of adrenocortical tumors identify IGF2 and Ki-67 as useful in differentiating carcinomas from adenomas

The management of adrenocortical tumors (ACTs) is complex. The Weiss score is the present most widely used system for ACT diagnosis. An ACT is scored from 0 to 9, with a higher score correlating with increased malignancy. However, ACTs with a score of 3 can be phenotypically benign or malignant. Our objective is to use microarray profiling of a cohort of adrenocortical carcinomas (ACCs) and adrenocortical adenomas (ACAs) to identify discriminatory genes that could be used as an adjunct to the Weiss score. A cohort of Weiss score defined ACCs and ACAs were profiled using Affymetrix HGU133plus2.0 genechips. Genes with high-discriminatory power were identified by univariate and multivariate analyses and confirmed by quantitative real-time reverse transcription PCR and immunohistochemistry (IHC). The expression of IGF2, MAD2L1, and CCNB1 were significantly higher in ACCs compared with ACAs while ABLIM1, NAV3, SEPT4, and RPRM were significantly lower. Several proteins, including IGF2, MAD2L1, CCNB1, and Ki-67 had high-diagnostic accuracy in differentiating ACCs from ACAs. The best results, however, were obtained with a combination of IGF2 and Ki-67, with 96% sensitivity and 100% specificity in diagnosing ACCs. Microarray gene expression profiling accurately differentiates ACCs from ACAs. The combination of IGF2 and Ki-67 IHC is also highly accurate in distinguishing between the two groups and is particularly helpful in ACTs with Weiss score of 3.

Controlled microaspiration for high-pressure freezing: a new method for ultrastructural preservation of fragile and sparse tissues for TEM and electron tomography

High-pressure freezing is the preferred method to prepare thick biological specimens for ultrastructural studies. However, the advantages obtained by this method often prove unattainable for samples that are difficult to handle during the freezing and substitution protocols. Delicate and sparse samples are difficult to manipulate and maintain intact throughout the sequence of freezing, infiltration, embedding and final orientation for sectioning and subsequent transmission electron microscopy. An established approach to surmount these difficulties is the use of cellulose microdialysis tubing to transport the sample. With an inner diameter of 200 microm, the tubing protects small and fragile samples within the thickness constraints of high-pressure freezing, and the tube ends can be sealed to avoid loss of sample. Importantly, the transparency of the tubing allows optical study of the specimen at different steps in the process. Here, we describe the use of a micromanipulator and microinjection apparatus to handle and position delicate specimens within the tubing. We report two biologically significant examples that benefit from this approach, 3D cultures of mammary epithelial cells and cochlear outer hair cells. We illustrate the potential for correlative light and electron microscopy as well as electron tomography.

Direct attachment of cell suspensions to high-pressure freezing specimen planchettes

We describe a procedure for high-pressure freezing (HPF) of cultured cells using the HPF aluminium planchettes as a substrate. Cells are either grown directly on planchettes covered with Matrigel or allowed to attach to poly-l-lysine-coated planchettes. This method allows for rapid transfer of the cells into the HPF and minimizes physical and physiological trauma to the cells. Furthermore, the yield of well-frozen cells approaches 100% for every cell type we have tried so far. In this report, we show well-preserved ultrastructure in mitotic and interphase HeLa cells, isolated gastric parietal cells and isolated gastric glands. Immunogold labelling of H+/K+-ATPase is shown in parietal cells of isolated gastric glands embedded in LR White resin. The aluminium planchettes appear to have little effect on cell physiology, as demonstrated by the fact that parietal cells cultured for 24-28 h on the planchettes retain their responsiveness to stimulation with histamine.

A new approach for high-pressure freezing of primary culture cells: the fine structure and stimulation-associated transformation of cultured rabbit gastric parietal cells

A newly designated procedure for high-pressure freezing of primary culture cells provided excellent ultrastructure of rabbit gastric parietal cells. The isolated parietal cells were cultivated on Matrigel-coated aluminium plates for conventional subsequential cryoimmobilization by high-pressure freezing. The ultrastructure of different organelles (Golgi apparatus, mitochondria, multivesicular bodies, etc.) was well preserved compared to conventional chemical fixation. In detail, actin filaments were clearly shown within the microvilli and the subapical cytoplasm. Another striking finding on the cytoskeleton system is the abundance of microtubules among the tubulovesicles. Interestingly, some microtubules appeared to be associating with tubulovesicles. A large number of electron-dense coated pits and vesicles were observed around the apical membrane vacuoles in cimetidine-treated resting parietal cells, consistent with an active membrane uptake in the resting state. Immunogold labelling of H+/K+-ATPase was seen on the tubulovesicular membranes. When stimulated with histamine, the cultured parietal cells undergo morphological transformation, resulting in great expansion of apical membrane vacuoles. Immunogold labelling of H+/K+-ATPase was present not only on the microvilli of expanded apical plasma membrane vacuoles but also in the electron-dense coated pits. The present findings provide a clue to vesicular membrane trafficking in cultured gastric parietal cells, and assure the utility of the new procedure for high-pressure freezing of primary culture cells.

Dynamic localization of the Swe1 regulator Hsl7 during the Saccharomyces cerevisiae cell cycle

In Saccharomyces cerevisiae, entry into mitosis requires activation of the cyclin-dependent kinase Cdc28 in its cyclin B (Clb)-associated form. Clb-bound Cdc28 is susceptible to inhibitory tyrosine phosphorylation by Swe1 protein kinase. Swe1 is itself negatively regulated by Hsl1, a Nim1-related protein kinase, and by Hsl7, a presumptive protein-arginine methyltransferase. In vivo all three proteins localize to the bud neck in a septin-dependent manner, consistent with our previous proposal that formation of Hsl1-Hsl7-Swe1 complexes constitutes a checkpoint that monitors septin assembly. We show here that Hsl7 is phosphorylated by Hsl1 in immune-complex kinase assays and can physically associate in vitro with either Hsl1 or Swe1 in the absence of any other yeast proteins. With the use of both the two-hybrid method and in vitro binding assays, we found that Hsl7 contains distinct binding sites for Hsl1 and Swe1. A differential interaction trap approach was used to isolate four single-site substitution mutations in Hsl7, which cluster within a discrete region of its N-terminal domain, that are specifically defective in binding Hsl1. When expressed in hsl7Delta cells, each of these Hsl7 point mutants is unable to localize at the bud neck and cannot mediate down-regulation of Swe1, but retains other functions of Hsl7, including oligomerization and association with Swe1. GFP-fusions of these Hsl1-binding defective Hsl7 proteins localize as a bright perinuclear dot, but never localize to the bud neck; likewise, in hsl1Delta cells, a GFP-fusion to wild-type Hsl7 or native Hsl7 localizes to this dot. Cell synchronization studies showed that, normally, Hsl7 localizes to the dot, but only in cells in the G1 phase of the cell cycle. Immunofluorescence analysis and immunoelectron microscopy established that the dot corresponds to the outer plaque of the spindle pole body (SPB). These data demonstrate that association between Hsl1 and Hsl7 at the bud neck is required to alleviate Swe1-imposed G2-M delay. Hsl7 localization at the SPB during G1 may play some additional role in fine-tuning the coordination between nuclear and cortical events before mitosis.

Age-related changes in detecting a mistuned harmonic

The effects of age on discriminating simultaneous sounds were investigated by comparing the hearing threshold in detecting a mistuned harmonic in young, middle-aged, and older adults. The stimuli were complex sounds containing multiple harmonics, one of which could be "mistuned" so that it was no longer an integer multiple of the fundamental. Older adults had higher thresholds than middle-aged or young adults. The effect of age was greater for short than for long duration sounds and remained even after controlling for hearing sensitivity. The results are consistent with an age-related decline in parsing simultaneous auditory events, which may contribute to the speech perception difficulties in the elderly.

Clathrin in gastric acid secretory (parietal) cells: biochemical characterization and subcellular localization

Clathrin from H-K-ATPase-rich membranes derived from the tubulovesicular compartment of rabbit and hog gastric acid secretory (parietal) cells was characterized biochemically, and the subcellular localization of membrane-associated clathrin in parietal cells was characterized by immunofluorescence, electron microscopy, and immunoelectron microscopy. Clathrin from H-K- ATPase-rich membranes was determined to be comprised of conventional clathrin heavy chain and a predominance of clathrin light chain A. Clathrin and adaptors could be induced to polymerize quantitatively in vitro, forming 120-nm-diameter basketlike structures. In digitonin-permeabilized resting parietal cells, the intracellular distribution of immunofluorescently labeled clathrin was suggestive of labeling of the tubulovesicular compartment. Clathrin was also unexpectedly localized to canalicular (apical) membranes, as were alpha-adaptin and dynamin, suggesting that this membrane domain of resting parietal cells is endocytotically active. At the ultrastructural level, clathrin was immunolocalized to canalicular and tubulovesicular membranes. H-K-ATPase was immunolocalized to the same membrane domains as clathrin but did not appear to be enriched at the specific subdomains that were enriched in clathrin. Finally, in immunofluorescently labeled primary cultures of parietal cells, in contrast to the H-K-ATPase, intracellular clathrin was found not to translocate to the apical membrane on secretagogue stimulation. Taken together, these biochemical and morphological data provide a framework for characterizing the role of clathrin in the regulation of membrane trafficking from tubulovesicles and at the canalicular membrane in parietal cells.

The coronin-like protein POD-1 is required for anterior-posterior axis formation and cellular architecture in the nematode caenorhabditis elegans

Establishment of anterior-posterior (a-p) polarity in the Caenorhabditis elegans embryo depends on filamentous (F-) actin. Previously, we isolated an F-actin-binding protein that was enriched in the anterior cortex of the one-cell embryo and was hypothesized to link developmental polarity to the actin cytoskeleton. Here, we identify this protein, POD-1, as a new member of the coronin family of actin-binding proteins. We have generated a deletion within the pod-1 gene. Elimination of POD-1 from early embryos results in a loss of physical and molecular asymmetries along the a-p axis. For example, PAR-1 and PAR-3, which themselves are polarized and required for a-p polarity, are delocalized in pod-1 mutant embryos. However, unlike loss of PAR proteins, loss of POD-1 gives rise to the formation of abnormal cellular structures, namely large vesicles of endocytic origin, membrane protrusions, unstable cell divisions, a defective eggshell, and deposition of extracellular material. We conclude that, analogous to coronin, POD-1 plays an important role in intracellular trafficking and organizing specific aspects of the actin cytoskeleton. We propose models to explain how the role of POD-1 in basic cellular processes could be linked to the generation of polarity along the embryonic a-p axis.

The bipolar kinesin, KLP61F, cross-links microtubules within interpolar microtubule bundles of Drosophila embryonic mitotic spindles

Previous genetic and biochemical studies have led to the hypothesis that the essential mitotic bipolar kinesin, KLP61F, cross-links and slides microtubules (MTs) during spindle assembly and function. Here, we have tested this hypothesis by immunofluorescence and immunoelectron microscopy (immunoEM). We show that Drosophila embryonic spindles at metaphase and anaphase contain abundant bundles of MTs running between the spindle poles. These interpolar MT bundles are parallel near the poles and antiparallel in the midzone. We have observed that KLP61F motors, phosphorylated at a cdk1/cyclin B consensus domain within the BimC box (BCB), localize along the length of these interpolar MT bundles, being concentrated in the midzone region. Nonphosphorylated KLP61F motors, in contrast, are excluded from the spindle and display a cytoplasmic localization. Immunoelectron microscopy further suggested that phospho-KLP61F motors form cross-links between MTs within interpolar MT bundles. These bipolar KLP61F MT-MT cross-links should be capable of organizing parallel MTs into bundles within half spindles and sliding antiparallel MTs apart in the spindle midzone. Thus we propose that bipolar kinesin motors and MTs interact by a "sliding filament mechanism" during the formation and function of the mitotic spindle.

Saccharomyces cerevisiae Duo1p and Dam1p, novel proteins involved in mitotic spindle function

In this paper, we describe the identification and characterization of two novel and essential mitotic spindle proteins, Duo1p and Dam1p. Duo1p was isolated because its overexpression caused defects in mitosis and a mitotic arrest. Duo1p was localized by immunofluorescence, by immunoelectron microscopy, and by tagging with green fluorescent protein (GFP), to intranuclear spindle microtubules and spindle pole bodies. Temperature-sensitive duo1 mutants arrest with short spindles. This arrest is dependent on the mitotic checkpoint. Dam1p was identified by two-hybrid analysis as a protein that binds to Duo1p. By expressing a GFP-Dam1p fusion protein in yeast, Dam1p was also shown to be associated with intranuclear spindle microtubules and spindle pole bodies in vivo. As with Duo1p, overproduction of Dam1p caused mitotic defects. Biochemical experiments demonstrated that Dam1p binds directly to microtubules with micromolar affinity. We suggest that Dam1p might localize Duo1p to intranuclear microtubules and spindle pole bodies to provide a previously unrecognized function (or functions) required for mitosis.

The rim sign in hepatic abscess: case report and review of the literature

We studied a previously healthy patient who presented with a 3-wk history of fever, flu-like symptoms and abdominal pain.

METHODS

Blood cultures were positive for Escherichia coli. A computed tomography (CT) scan revealed a 2-cm low-density focus in the right hepatic lobe. A technetium-99m-mebrofenin scan showed a photopenic area in the right hepatic lobe surrounded by a rim of activity greater than the adjacent parenchymal activity.

RESULTS

Gallbladder visualization was normal and the diagnosis of hepatic abscess was made. CT-guided percutaneous drainage of the lesion yielded six cc of pus, the culture of which grew E. coli, Prevotella and Bacteroides fragilis. Drainage and a 6-wk course of intravenous antibiotics were followed by clinical improvement and resolution of the abscess by CT.

CONCLUSION

The rim sign and its possible mechanism of causation in hepatic abscess are discussed in this report, together with a review of the literature.

Three-dimensional ultrastructural analysis of the Saccharomyces cerevisiae mitotic spindle

The three dimensional organization of microtubules in mitotic spindles of the yeast Saccharomyces cerevisiae has been determined by computer-aided reconstruction from electron micrographs of serially cross-sectioned spindles. Fifteen spindles ranging in length from 0.6-9.4 microns have been analyzed. Ordered microtubule packing is absent in spindles up to 0.8 micron, but the total number of microtubules is sufficient to allow one microtubule per kinetochore with a few additional microtubules that may form an interpolar spindle. An obvious bundle of about eight interpolar microtubules was found in spindles 1.3-1.6 microns long, and we suggest that the approximately 32 remaining microtubules act as kinetochore fibers. The relative lengths of the microtubules in these spindles suggest that they may be in an early stage of anaphase, even though these spindles are all situated in the mother cell, not in the isthmus between mother and bud. None of the reconstructed spindles exhibited the uniform populations of kinetochore microtubules characteristic of metaphase. Long spindles (2.7-9.4 microns), presumably in anaphase B, contained short remnants of a few presumed kinetochore microtubules clustered near the poles and a few long microtubules extending from each pole toward the spindle midplane, where they interdigitated with their counterparts from the other pole. Interpretation of these reconstructed spindles offers some insights into the mechanisms of mitosis in this yeast.

Interpolar spindle microtubules in PTK cells

Spindle microtubules (MTs) in PtK1 cells, fixed at stages from metaphase to telophase, have been reconstructed using serial sections, electron microscopy, and computer image processing. We have studied the class of MTs that form an interdigitating system connecting the two spindle poles (interpolar MTs or ipMTs) and their relationship to the spindle MTs that attach to kinetochores (kMTs). Viewed in cross section, the ipMTs cluster with antiparallel near neighbors throughout mitosis; this bundling becomes much more pronounced as anaphase proceeds. While the minus ends of most kMTs are near the poles, those of the ipMTs are spread over half of the spindle length, with at least 50% lying > 1.5 microns from the poles. Longitudinal views of the ipMT bundles demonstrate a major rearrangement of their plus ends between mid- and late anaphase B. However, the minus ends of these MTs do not move appreciably farther from the spindle midplane, suggesting that sliding of these MTs contributes little to anaphase B. The minus ends of ipMTs are markedly clustered in the bundles of kMTs throughout anaphase A. These ends lie close to kMTs much more frequently than would be expected by chance, suggesting a specific interaction. As sister kinetochores separate and kMTs shorten, the minus ends of the kMTs remain associated with the spindle poles, but the minus ends of many ipMTs are released from the kMT bundles, allowing the spindle pole and the kMTs to move away from the ipMTs as the spindle elongates.

Three-dimensional reconstruction and analysis of mitotic spindles from the yeast, Schizosaccharomyces pombe

Mitotic spindles of Schizosaccharomyces pombe have been studied by EM, using serial cross sections to reconstruct 12 spindles from cells that were ultrarapidly frozen and fixed by freeze substitution. The resulting distributions of microtubules (MTs) have been analyzed by computer. Short spindles contain two kinds of MTs: continuous ones that run from pole to pole and MTs that originate at one pole and end in the body of the spindle. Among the latter there are three pairs of MT bundles that end on fibrous, darkly staining structures that we interpret as kinetochores. The number of MTs ending at each putative kinetochore ranges from two to four; all kinetochore-associated MTs disappear as the spindle elongates from 3-6 microns. At this and greater spindle lengths, there are no continuous MTs, only polar MTs that interdigitate at the spindle midzone, but the spindle continues to elongate. An analysis of the density of neighboring MTs at the midzone of long spindles shows that their most common spacing is approximately 40 nm, center to center, and that there is a preferred angular separation of 90 degrees. Only hints of such square-packing are found at the midzone of short spindles, and near the poles there is no apparent order at any mitotic stage. Our data suggest that the kinetochore MTs (KMTs) do not interact directly with nonkinetochore MTs, but that interdigitating MTs from the two spindle poles do interact to form a mechanically stable bundle that connects the poles. As the spindle elongates, the number of MTs decreases while the mean length of the MTs that remain increases. We conclude that the chromosomes of S. pombe become attached to the spindle by kinetochore MTs, that these MTs disappear as the chromosomes segregate, that increased separation of daughter nuclei is accompanied by a sliding apart of anti-parallel MTs, and that the mitotic processes of S. pombe are much like those in other eukaryotic cells.

Arrangement of inner dynein arms in wild-type and mutant flagella of Chlamydomonas

We have used computer averaging of electron micrographs from longitudinal and cross-sections of wild-type and mutant axonemes to determine the arrangement of the inner dynein arms in Chlamydomonas reinhardtii. Based on biochemical and morphological data, the inner arms have previously been described as consisting of three distinct subspecies, I1, I2, and I3. Our longitudinal averages revealed 10 distinguishable lobes of density per 96-nm repeating unit in the inner row of dynein arms. These lobes occurred predominantly but not exclusively in two parallel rows. We have analyzed mutant strains that are missing I1 and I2 subspecies. Cross-sectional averages of pf9 axonemes, which are missing the I1 subspecies, showed a loss of density in both the inner and outer portions of the inner arm. Averages from longitudinal images showed that three distinct lobes were missing from a single region; two of the lobes were near the outer arms but one was more inward. Serial 24-nm cross-sections of pf9 axonemes showed a complete gap at the proximal end of the repeating unit, confirming that the I1 subunit spans both inner and outer portions of the inner arm region. Examination of pf23 axonemes, which are missing both I1 and I2 subspecies, showed an additional loss almost exclusively in the inner portion of the inner arm. In longitudinal view, this additional loss occurred in three separate locations and consisted of three inwardly placed lobes, one adjacent to each of the two radial spokes and the third at the distal end of the repeating unit. These same lobes were absent ida4 axonemes, which lack only the I2 subspecies. The I2 subspecies thus does not consist of a single dynein arm subunit in the middle of the repeating unit. The radial spoke suppressor mutation, pf2, is missing four polypeptides of previously unknown location. Averages of these axonemes were missing a portion of the structures remaining in pf23 axonemes. This result suggests that polypeptides of the radial spoke control system are close to the inner dynein arms.

Kinetochore microtubules in PTK cells

We have analyzed the fine structure of 10 chromosomal fibers from mitotic spindles of PtK1 cells in metaphase and anaphase, using electron microscopy of serial thin sections and computer image processing to follow the trajectories of the component microtubules (MTs) in three dimensions. Most of the kinetochore MTs ran from their kinetochore to the vicinity of the pole, retaining a clustered arrangement over their entire length. This MT bundle was invaded by large numbers of other MTs that were not associated with kinetochores. The invading MTs frequently came close to the kinetochore MTs, but a two-dimensional analysis of neighbor density failed to identify any characteristic spacing between the two MT classes. Unlike the results from neighbor density analyses of interzone MTs, the distributions of spacings between kinetochore MTs and other spindle MTs revealed no evidence for strong MT-MT interactions. A three-dimensional analysis of distances of closest approach between kinetochore MTs and other spindle MTs has, however, shown that the most common distances of closest approach were 30-50 nm, suggesting a weak interaction between kinetochore MTs and their neighbors. The data support the ideas that kinetochore MTs form a mechanical connection between the kinetochore and the pericentriolar material that defines the pole, but that the mechanical interactions between kinetochore MTs and other spindle MTs are weak.

Two types of genetic interaction implicate the whirligig gene of Drosophila melanogaster in microtubule organization in the flagellar axoneme

The mutant nc4 allele of whirligig (3-54.4) of Drosophila melanogaster fails to complement mutations in an alpha-tubulin locus, alpha 1t, mutations in a beta-tubulin locus, B2t, or a mutation in the haywire locus. However, wrl fails to map to any of the known alpha- or beta-tubulin genes. The extragenic failure to complement could indicate that the wrl product participates in structural interactions with microtubule proteins. The whirligig locus appears to be haploinsufficient for male fertility. Both a deficiency of wrl and possible loss of function alleles obtained by reverting the failure to complement between wrlnc4 and B2tn are dominant male sterile in a genetic background wild type for tubulin. The dominant male sterility of the revertant alleles is suppressed if the flies are also heterozygous for B2tn, for a deficiency of alpha 1t, or for the haync2 allele. These results suggest that it is not the absolute level of wrl gene product but its level relative to tubulin or microtubule function that is important for normal spermatogenesis. The phenotype of homozygous wrl mutants suggests that the whirligig product plays a role in postmeiotic spermatid differentiation, possibly in organizing the microtubules of the sperm flagellar axoneme. Flies homozygous for either wrlnc4 or revertant alleles are viable and female fertile but male sterile. Premeiotic and meiotic stages of spermatogenesis appear normal. However, in post-meiotic stages, flagellar axonemes show loss of the accessory microtubule on the B-subfiber of outer doublet microtubules, outer triplet instead of outer doublet microtubules, and missing central pair microtubules.

The mechanism of anaphase spindle elongation: uncoupling of tubulin incorporation and microtubule sliding during in vitro spindle reactivation

To study tubulin polymerization and microtubule sliding during spindle elongation in vitro, we developed a method of uncoupling the two processes. When isolated diatom spindles were incubated with biotinylated tubulin (biot-tb) without ATP, biot-tb was incorporated into two regions flanking the zone of microtubule overlap, but the spindles did not elongate. After biot-tb was removed, spindle elongation was initiated by addition of ATP. The incorporated biot-tb was found in the midzone between the original half-spindles. The extent and rate of elongation were increased by preincubation in biot-tb. Serial section reconstruction of spindles elongating in tubulin and ATP showed that the average length of half-spindle microtubules increased due to growth of microtubules from the ends of native microtubules. The characteristic packing pattern between antiparallel microtubules was retained even in the "new" overlap region. Our results suggest that the forces required for spindle elongation are generated by enzymes in the overlap zone that mediate the sliding apart of antiparallel microtubules, and that tubulin polymerization does not contribute to force generation. Changes in the extent of microtubule overlap during spindle elongation were affected by tubulin and ATP concentration in the incubation medium. Spindles continued to elongate even after the overlap zone was composed entirely of newly polymerized microtubules, suggesting that the enzyme responsible for microtubule translocation either is bound to a matrix in the spindle midzone, or else can move on one microtubule toward the spindle midzone and push another microtubule of opposite polarity toward the pole.

Technetium-99m RBC scintigraphy in the evaluation of small bowel leiomyoma

Hypervascularity and persistent uptake were demonstrated in a small bowel leiomyoma not actively bleeding at the time of Tc-99m RBC scintigraphy. The potential value of Tc-99m RBC scanning in the evaluation of benign small bowel tumors is discussed.

Sonographic and scintigraphic evaluation of gallbladder duplication

The incidence of unilobar or bilobar pathology is disproportionately high in patients with duplication of the gallbladder. The results of ultrasound and Tc-99m DISIDA studies in one case of gallbladder duplication are presented. An awareness of gallbladder anomalies may improve the accuracy of hepatobiliary imaging by eliminating some false-negative results.