Technique for Rapidly Forming Networks of Microvessel-Like Structures

Modeling organ-blood barriers through the inclusion of microvessel networks within in vitro tissue models could lead to more physiologically accurate results, especially since organ-blood barriers are crucial to the normal function, drug transport, and disease states of vascularized organs. Microvessel networks are difficult to form, since they push the practical limits of most fabrication methods, and it is difficult to coax vascular cells to self-assemble into structures larger than capillaries. Here, we present a method for rapidly forming networks of microvessel-like structures using sacrificial alginate structures. Specifically, we encapsulated endothelial cells within short alginate threads, and then embedded them in collagen gel. Following enzymatic degradation of the alginate, the collagen gel contained a network of hollow channels seeded with cells, all surrounding a perfusable central channel. This method uses a 3D-printed coaxial extruder and syringe pumps to generate short threads in a way that is repeatable and easily transferrable to other labs. The cell-laden, sacrificial alginate threads can be frozen after fabrication and thawed before embedding without significant loss of cell viability. The ability to freeze the threads enables future scale-up and ease of use. Within millifluidic devices that restrict access to media, the threads enhance cell survival under static conditions. These results indicate the potential for use of this method in a range of tissue engineering applications.

Technique for rapidly forming networks of microvessel-like structures

Modelling organ-blood barriers through the inclusion of microvessel networks within in vitro tissue models could lead to more physiologically accurate results, especially since organ-blood barriers are crucial to the normal function, drug transport, and disease states of vascularized organs. Microvessel networks are difficult to form, since they push the practical limit of most fabrication methods, and it is difficult to coax vascular cells to self-assemble into structures larger than capillaries. Here we present a method for rapidly forming networks of microvessel-like structures using sacrificial, alginate structures. Specifically, we encapsulated endothelial cells within short alginate threads, then embedded them in collagen gel. Following enzymatic degradation of the alginate, the collagen gel contained a network of hollow channels seeded with cells, all surrounding a perfusable central channel. This method uses a 3D printed coaxial extruder and syringe pumps to generate short threads in a way that is repeatable and easily transferrable to other labs. The cell-laden, sacrificial alginate threads can be frozen after fabrication and thawed before embedding without significant loss of cell viability. The ability to freeze the threads enables future scale up and ease of use. Within millifluidic devices that restrict access to media, the threads enhance cell survival under static conditions. These results indicate the potential for use of this method in a range of tissue engineering applications.

Isolation and Characterization of Porcine Endocardial Endothelial Cells

The heart contains diverse endothelial cell types. We sought to characterize the endocardial endothelial cells (EECs), which line the chambers of the heart. EECs are relatively understudied, yet their dysregulation can lead to various cardiac pathologies. Due to the lack of commercial availability of these cells, we reported our protocol for isolating EECs from porcine hearts and for establishing an EEC population through cell sorting. In addition, we compared the EEC phenotype and fundamental behaviors to a well-studied endothelial cell line, human umbilical vein endothelial cells (HUVECs). The EECs stained positively for classic phenotypic markers such as CD31, von Willebrand Factor, and vascular endothelial (VE) cadherin. The EECs proliferated more quickly than HUVECs at 48 h (1310 ± 251 cells vs. 597 ± 130 cells, p = 0.0361) and at 96 h (2873 ± 257 cells vs. 1714 ± 342 cells, p = 0.0002). Yet EECs migrated more slowly than HUVECs to cover a scratch wound at 4 h (5% ± 1% wound closure vs. 25% ± 3% wound closure, p < 0.0001), 8 h (15% ± 4% wound closure vs. 51% ± 12% wound closure, p < 0.0001), and 24 h (70% ± 11% wound closure vs. 90% ± 3% wound closure, p < 0.0001). Finally, the EECs maintained their endothelial phenotype by positive expression of CD31 through more than a dozen passages (three populations of EECs showing 97% ± 1% CD31+ cells in over 14 passages). In contrast, the HUVECs showed significantly reduced CD31 expression over high passages (80% ± 11% CD31+ cells over 14 passages). These important phenotypic differences between EECs and HUVECs highlight the need for researchers to utilize the most relevant cell types when studying or modeling diseases of interest.

Dantrolene inhibits lysophosphatidylcholine-induced valve interstitial cell calcific nodule formation via blockade of the ryanodine receptor

Calcific aortic valve disease (CAVD), a fibrocalcific thickening of the aortic valve leaflets causing obstruction of the left ventricular outflow tract, affects nearly 10 million people worldwide. For those who reach end-stage CAVD, the only treatment is highly invasive valve replacement. The development of pharmaceutical treatments that can slow or reverse the progression in those affected by CAVD would greatly advance the treatment of this disease. The principal cell type responsible for the fibrocalcific thickening of the valve leaflets in CAVD is valvular interstitial cells (VICs). The cellular processes mediating this calcification are complex, but calcium second messenger signaling, regulated in part by the ryanodine receptor (RyR), has been shown to play a role in a number of other fibrocalcific diseases. We sought to determine if the blockade of calcium signaling in VICs could ameliorate calcification in an in vitro model. We previously found that VICs express RyR isotype 3 and that its modulation could prevent VIC calcific nodule formation in vitro. We sought to expand upon these results by further investigating the effects of calcium signaling blockade on VIC gene expression and behavior using dantrolene, an FDA-approved pan-RyR inhibitor. We found that dantrolene also prevented calcific nodule formation in VICs due to cholesterol-derived lysophosphatidylcholine (LPC). This protective effect corresponded with decreases in intracellular calcium flux, apoptosis, and ACTA2 expression but not reactive oxygen species formation caused by LPC. Interestingly, dantrolene increased the expression of the regulator genes RUNX2 and SOX9, indicating complex gene regulation changes. Further investigation via RNA sequencing revealed that dantrolene induced several cytoprotective genes that are likely also responsible for its attenuation of LPC-induced calcification. These results suggest that RyR3 is a viable therapeutic target for the treatment of CAVD. Further studies of the effects of RyR3 inhibition on CAVD are warranted.

Differential proteome profile, biological pathways, and network relationships of osteogenic proteins in calcified human aortic valves

Calcific aortic valve disease (CAVD) is the most common heart valve disease requiring intervention. Most research on CAVD has focused on inflammation, ossification, and cellular phenotype transformation. To gain a broader picture into the wide range of cellular and molecular mechanisms involved in this disease, we compared the total protein profiles between calcified and non-calcified areas from 5 human valves resected during surgery. The 1413 positively identified proteins were filtered down to 248 proteins present in both calcified and non-calcified segments of at least 3 of the 5 valves, which were then analyzed using Ingenuity Pathway Analysis. Concurrently, the top 40 differentially abundant proteins were grouped according to their biological functions and shown in interactive networks. Finally, the abundance of selected osteogenic proteins (osteopontin, osteonectin, osteocalcin, osteoprotegerin, and RANK) was quantified using ELISA and/or immunohistochemistry. The top pathways identified were complement system, acute phase response signaling, metabolism, LXR/RXR and FXR/RXR activation, actin cytoskeleton, mineral binding, nucleic acid interaction, structural extracellular matrix (ECM), and angiogenesis. There was a greater abundance of osteopontin, osteonectin, osteocalcin, osteoprotegerin, and RANK in the calcified regions than the non-calcified ones. The osteogenic proteins also formed key connections between the biological signaling pathways in the network model. In conclusion, this proteomic analysis demonstrated the involvement of multiple signaling pathways in CAVD. The interconnectedness of these pathways provides new insights for the treatment of this disease.

Congenital Heart Disease: An Immunological Perspective

Congenital heart disease (CHD) poses a significant global health and economic burden-despite advances in treating CHD reducing the mortality risk, globally CHD accounts for approximately 300,000 deaths yearly. Children with CHD experience both acute and chronic cardiac complications, and though treatment options have improved, some remain extremely invasive. A challenge in addressing these morbidity and mortality risks is that little is known regarding the cause of many CHDs and current evidence suggests a multifactorial etiology. Some studies implicate an immune contribution to CHD development; however, the role of the immune system is not well-understood. Defining the role of the immune and inflammatory responses in CHD therefore holds promise in elucidating mechanisms underlying these disorders and improving upon current diagnostic and treatment options. In this review, we address the current knowledge coinciding CHDs with immune and inflammatory associations, emphasizing conditions where this understanding would provide clinical benefit, and challenges in studying these mechanisms.

The Immune and Inflammatory Basis of Acquired Pediatric Cardiac Disease

Children with acquired heart disease face significant health challenges, including a lifetime of strict medical management, multiple cardiac surgeries, and a high mortality risk. Though the presentation of these conditions is diverse, a unifying factor is the role of immune and inflammatory responses in their development and/or progression. For example, infectious agents have been linked to pediatric cardiovascular disease, leading to a large health burden that disproportionately affects low-income areas. Other implicated mechanisms include antibody targeting of cardiac proteins, infection of cardiac cells, and inflammation-mediated damage to cardiac structures. These changes can alter blood flow patterns, change extracellular matrix composition, and induce cardiac remodeling. Therefore, understanding the relationship between the immune system and cardiovascular disease can inform targeted diagnostic and treatment approaches. In this review, we discuss the current understanding of pediatric immune-associated cardiac diseases, challenges in the field, and areas of research with potential for clinical benefit.

Tumor necrosis factor alpha and interleukin 1 beta suppress myofibroblast activation via nuclear factor kappa B signaling in 3D-cultured mitral valve interstitial cells

Mitral valve disease is a major cause of cardiovascular morbidity throughout the world. Many different mitral valve pathologies feature fibrotic remodeling, often accompanied by an inflammatory state. Mitral valve fibrosis is mediated by valvular interstitial cells (VICs), which reside in the valve leaflets and often differentiate into myofibroblast-like cells during disease conditions. In this study, we investigated the effects of tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) on mitral VICs, since these pro-inflammatory cytokines have been shown to exert pleiotropic effects on various cell types in other fibrotic disorders. Using biomimetic three-dimensional culture systems, we demonstrated that TNF-α and IL-1β suppress myofibroblast differentiation in mitral VICs, as evidenced by gene and protein expression of alpha smooth muscle actin and smooth muscle 22 alpha. Addition of TNF-α and IL-1β also inhibited mitral VIC-mediated contraction of collagen gels. Furthermore, inhibition of NF-κB, which is downstream of TNF-α and IL-1β, reversed these effects. These results reveal targetable pathways for potential development of pharmaceutical treatments for alleviating fibrosis during mitral valve disease. STATEMENT OF SIGNIFICANCE: Mitral valve disease is a common cardiovascular condition that is often accompanied by fibrotic tissue remodeling. Valvular interstitial cells (VICs), the fibroblast-like cells that reside in heart valve leaflets, are thought to drive fibrosis during valve disease by differentiating into activated myofibroblasts. However, the signaling pathways that regulate this process in the mitral valve are not fully understood. In the present study, we cultured mitral VICs in collagen and poly(ethylene glycol) scaffolds designed to mimic the heart valve microenvironment and treated the cell-seeded scaffolds with cytokines. Using these 3D culture models, we found that the pro-inflammatory cytokines TNF-α and IL-1β downregulate myofibroblast and fibrosis markers in mitral VICs via the canonical NF-κB signaling pathway.

Poly(ethylene glycol)-Based Coatings for Bioprosthetic Valve Tissues: Toward Restoration of Physiological Behavior

Bioprosthetic valves (BPVs) have a limited lifespan in the body necessitating repeated surgeries to replace the failed implant. Early failure of these implants has been linked to various surface properties of the valve. Surface properties of BPVs are significantly different from physiological valves because of the fixation process used when processing the xenograft tissue. To improve the longevity of BPVs, efforts need to be taken to improve the surface properties and shield the implant from the bodily interactions that degrade it. Toward this goal, we evaluated the use of hydrogel coatings to attach to the BPV tissue and impart surface properties that are close to physiological. Hydrogels are well characterized for their biocompatibility and highly tunable surface characteristics. Using a previously published coating method, we deposited hydrogel coatings of poly(ethylene glycol)diacrylate (PEGDA) and poly(ethylene glycol)diacrylamide (PEGDAA) atop BPV samples. Coated samples were evaluated against the physiological tissue and uncoated glutaraldehyde-fixed tissue for deposition of hydrogel, surface adherence, mechanical properties, and fixation properties. Results showed both PEGDA- and PEGDAA-deposited coatings were nearly continuous across the valve leaflet surface. Further, the PEGDA- and PEGDAA-coated samples showed restoration of physiological levels of protein adhesion and mechanical stiffness. Interestingly, the coating process rather than the coating itself altered the material behavior yet did not alter the cross-linking from fixation. These results show that the PEG-based coatings for BPVs can successfully alter surface properties of BPVs and help promote physiological characteristics without interfering with the necessary fixation.

Interfacial Coating Method for Amine-Rich Surfaces using Poly(ethylene glycol) Diacrylate Applied to Bioprosthetic Valve Tissue Models

Bioprosthetic heart valve implants are beset by calcification and failure due to the interactions between the body and the transplant. Hydrogels can be used as biological blank slates that may help to shield implants from these interactions; however, traditional light-based hydrogel polymerization is impeded by tissue opacity and topography. Therefore, new methods must be created to bind hydrogel to implant tissues. To address these complications, a two-step surface-coating method for bioprosthetic valves was developed. A previously developed bioprosthetic valve model (VM) was used to investigate and optimize the coating method. Generally, this coating is achieved by first reacting surface amine groups with an NHS-PEG-acrylate while also allowing glucose to absorb into the bulk. Then, glucose oxidase, poly(ethylene glycol) diacrylate (PEGDA), and iron ions are added to the system to initiate free-radical polymerization that bonds the PEGDA hydrogel to the acrylates sites on the surface. Results showed a thin (∼8 μm), continuous coating on VM samples that is capable of repelling protein adhesion (2% surface fouling versus 20% on uncoated samples) and does not significantly affect the surface mechanical properties. Based on this success, the coating method was translated to glutaraldehyde-fixed valve tissue samples. Results showed noncontinuous but evident coating on the surface, which was further improved by adjusting the coating solution. These results demonstrate the feasibility of the proposed two-step surface coating method for modifying the surface of bioprosthetic valve replacements.

Monitoring Oxygen Levels within Large, Tissue-Engineered Constructs Using Porphyin-Hydrogel Microparticles

A major barrier to the creation of engineered organs is the limited diffusion of oxygen through biological tissues. Advances in biofabrication bring us increasingly closer to complex vascular networks capable of supplying oxygen to large cellularized scaffolds. However, technologies for monitoring oxygen levels in engineered tissues do not accommodate imaging depths of more than a few dozen micrometers. Here, we report the creation of fluorescent porphyrin-hydrogel microparticles that can be used at depths of 2 mm into artificial tissues. By combining an oxygen-responsive porphyrin dye with a reference dye, the microparticles generate a ratiometric signal that is photostable, unaffected by attenuation from biological material, and responsive to physiological change in oxygen concentration. These microparticles can measure long-distance oxygen gradients within 3D, cellularized constructs and accurately report cellular oxygen consumption rates. Furthermore, they are compatible with a number of hydrogel polymerization chemistries and cell types, including primary human cells. We believe this technology will significantly advance efforts to visualize oxygen gradients in cellularized constructs and inform efforts to tissue engineer solid organs.

Knockout of hyaluronan synthase 1, but not 3, impairs formation of the retrocalcaneal bursa

Hyaluronan (HA), a high molecular weight non-sulfated glycosaminoglycan, is an integral component of the extracellular matrix of developing and mature connective tissues including tendon. There are few published reports quantifying HA content during tendon growth and maturation, or detailing its effects on the mechanical properties of the tendon extracellular matrix. Therefore, the goal of the current study was to examine the role of HA synthesis during post-natal skeletal growth and maturation, and its influence on tendon structure and biomechanical function. For this purpose, the morphological, biochemical, and mechanical properties of Achilles tendons from wild type (WT) and hyaluronan synthase 1 and 3 deficient mouse strains (Has1-/- (Has1KO), Has3-/- (Has3KO), and Has1-/- 3-/- (Has1/3KO)) were determined at 4, 8, and 12 weeks of age. Overall, HAS-deficient mice did not show any marked differences from WT mice in Achilles tendon morphology or in the HA and chondroitin/dermatan sulfate (CS/DS) contents. However, HAS1-deficiency (in the single or Has1/3 double KO) impeded post-natal formation of the retrocalcaneal bursa, implicating HAS1 in regulating HA metabolism by cells lining the bursal cavity. Together, these data suggest that HA metabolism via HAS1 and HAS3 does not markedly influence the extracellular matrix structure or function of the tendon body, but plays a role in the formation/maintenance of peritendinous bursa. Additional studies are warranted to elucidate the relationship of HA and CS/DS metabolism to tendon healing and repair in vivo. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2622-2632, 2018.

Left-Ventricular Assist Device Impact on Aortic Valve Mechanics, Proteomics and Ultrastructure

BACKGROUND

Aortic regurgitation is a prevalent, detrimental complication of left ventricular assist devices (LVADs). The altered hemodynamics of LVADs results in aortic valves (AVs) having distinct mechanical stimulation. Our hypothesis was that the altered AV hemodynamics modulates the valve cells and matrix, resulting in changes in valvular mechanical properties that then can lead to regurgitation.

METHODS

AVs were collected from 16 LVAD and 6 non-LVAD patients at time of heart transplant. Standard demographic and preoperative data were collected and comparisons between the two groups were calculated using standard statistical methods. Samples were analyzed using biaxial mechanical tensile testing, mass spectrometry-based proteomics, and transmission electron microscopy to assess ultrastructure.

RESULTS

The maximum circumferential leaflet strain in LVAD patients was less than in non-LVAD patients (0.35 ± 0.10MPa versus 0.52 ± 0.18 MPa, p = 0.03) with a trend of reduced radial strain (p = 0.06) and a tendency for the radial strain to decrease with increasing LVAD duration (p = 0.063). Numerous proteins associated with actin and myosin, immune signaling and oxidative stress, and transforming growth factor β were increased in LVAD patients. Ultrastructural analysis showed a trend of increased fiber diameter in LVAD patients (46.2 ± 7.2 nm versus 45.1 ± 6.9 nm, p = 0.10), but no difference in fiber density.

CONCLUSIONS

AVs in LVAD patients showed decreased compliance and increased expression of numerous proteins related to valve activation and injury compared to non-LVAD patients. Further knowledge of AV changes leading to regurgitation in LVAD patients and the pathways by which they occur may provide an opportunity for interventions to prevent and/or reverse this detrimental complication.

Therapeutic Transdifferentiation: A Novel Approach for Ischemic Syndromes

The technological development of induced pluripotent stem cells (iPSCs) has overcome many of the limitations of adult and embryonic stem cells. We have found that activation of innate immunity signaling is necessary for this process, as it facilitates epigenetic plasticity in cells by a process called transflammation. More recently, we have discovered that transflammation also facilitates the transdifferentiation of cells directly from one somatic cell type to another. This insight may lead to a promising therapeutic pathway that avoids reverting cells all the way back to pluripotency before achieving a cell type of interest. While there is much therapeutic promise to transflammation and transdifferentiation, there is also evidence that transdifferentiation plays a role in some pathological conditions, including atherosclerosis. Ultimately, better understanding of transflammation will facilitate the development of regenerative therapies.

Extracellular matrix remodeling in wound healing of critical size defects in the mitral valve leaflet

The details of valvular leaflet healing following valvuloplasty and leaflet perforation from endocarditis are poorly understood. In this study, the synthesis and turnover of valvular extracellular matrix due to healing of a critical sized wound was investigated. Twenty-nine sheep were randomized to either CTRL (n = 11) or HOLE (n = 18), in which a 2.8-4.8 mm diameter hole was punched in the posterior mitral leaflet. After 12 weeks, posterior leaflets were harvested and histologically stained to localize extracellular matrix components. Immunohistochemistry was also performed to assess matrix components and markers of matrix turnover. A semi-quantitative grading scale was used to quantify differences between HOLE and CTRL. After 12 weeks, the hole diameter was reduced by 71.3 ± 1.4 % (p < 0.001). Areas of remodeling surrounding the hole contained more activated cells, greater expression of proteoglycans, and markers of matrix turnover (prolyl 4-hydroxylase, metalloproteases, and lysyl oxidase, each p ≤ 0.025), along with fibrin accumulation. Two distinct remodeling regions were evident surrounding the hole, one directly bordering the hole rich in versican and hyaluronan and a second adjacent region with abundant collagen and elastic fiber turnover. The remodeling also caused reduced delineation between valve layers (p = 0.002), more diffuse staining of matrix components and markers of matrix turnover (p < 0.001), and disruption of the collagenous fibrosa. In conclusion, acute valve injury elicited distinct, heterogeneous alterations in valvular matrix composition and structure, resulting in partial wound closure. Because these changes could also affect leaflet mechanics and valve function, it will be important to determine their impact on healing wounds.

Individual differences and the development of perceived control

Research on individual differences demonstrates that children's perceived control exerts a strong effect on their academic achievement and that, in turn, children's actual school performance influences their sense of control. At the same time, developmental research shows systematic age-graded changes in the processes that children use to regulate and interpret control experiences. Drawing on both these perspectives, the current study examines (1) age differences in the operation of beliefs-performance cycles and (2) the effects of these cycles on the development of children's perceived control and classroom engagement from the third to the seventh grade. Longitudinal data on about 1,600 children were collected six times (every fall and spring) over 3 consecutive school years, including children's reports of their perceived control and individual interactions with teachers; teachers' reports of each student's engagement in class; and, for a subset of students, grades and achievement tests. Analyses of individual differences and individual growth curves (estimated using hierarchical linear modeling procedures) were consistent, not only with a cyclic model of context, self, action, and outcomes, but also with predictors of individual development over 5 years from grade 3 to grade 7. Children who experienced teachers as warm and contingent were more likely to develop optimal profiles of control; these beliefs supported more active engagement in the classroom, resulting in better academic performance; success in turn predicted the maintenance of optimistic beliefs about the effectiveness of effort. In contrast, children who experienced teachers as unsupportive were more likely to develop beliefs that emphasized external causes; these profiles of control predicted escalating classroom disaffection and lower scholastic achievement; in turn, these poor performances led children to increasingly doubt their own capacities and to believe even more strongly in the power of luck and unknown causes. Systematic age differences in analyses suggested that the aspects of control around which these cycles are organized change with development. The beliefs that regulated engagement shifted from effort to ability and from beliefs about the causes of school performance (strategy beliefs) to beliefs about the self's capacities. The feedback loop from individual performance to subsequent perceived control also became more pronounced and more focused on ability. These relatively linear developmental changes may have contributed to an abrupt decline in children's classroom engagement as they negotiated the transition to middle school and experienced losses in teacher support. Implications are discussed for future study of individual differences and development, especially the role of changing school contexts, mechanisms of influence, and developmentally appropriate interventions to optimize children's perceived control and engagement.

Emotion regulation in two-year-olds: strategies and emotional expression in four contexts

A descriptive study of the modulation of negative emotion in the toddler period was conducted by examining expressions of negative emotion and the strategies used to reduce or change these expressions. 6 strategies were identified and evaluated in terms of their frequency of use in different situations, relations with emotional expressiveness, and cross-situational consistency. 37 2-year-olds were seen in 2 laboratory contexts (delay and separation) each with 2 variants. Emotion regulation strategies and emotional expressiveness were coded from videotapes of children's behavior in these 4 situations. Findings suggest that active engagement was most commonly used and most negatively associated with child distress. Use of strategies varied by context, and there was more cross-situational consistency in use of strategies that were more negatively or positively associated with distress within a given context than in use of particular strategies without consideration of their within-context significance.

Educational risk and resilience in African-American youth: context, self, action, and outcomes in school

This study examined the empirical validity of a model of human motivation as it applies to school success and failure in 3 independent samples of 10- to 16-year-old African-American youth. Specifically, we assessed how indicators of context, self, and action relate to measures of risk and resilient outcomes in school in 3 different samples, using 3 different measurement strategies. Correlational and path analyses on the 3 data sets supported the empirical validity of the model. African-American youth's experience of their parents' school involvement predicted a composite of self-system processes, which in turn predicted the subjects' reports of their engagement in school. Engagement then predicted school performance and adjustment. The data supported a reciprocal path from action to context, suggesting that youth who show more disaffected patterns of behavior and emotion in school experience less support from their families than those reporting more engaged patterns of action. Implications for program and policy decisions are discussed.

What motivates children's behavior and emotion? Joint effects of perceived control and autonomy in the academic domain

This study examined the contribution of perceived control and autonomy to children's self-reported behavior and emotion in the classroom (N = 246 children ages 8-10 years). Multiple regression analyses revealed unique effects of autonomy over and above the strong effects of perceived control. In addition, both sets of perceptions (and their interaction) were found to distinguish children who were active but emotionally disaffected from those who were active and emotionally positive. Specific predictions were also tested regarding the effects of (a) control attributions to 5 causes and (b) 4 reasons for task involvement that differed in degree of autonomy on children's active (vs. passive) behavior and 4 kinds of emotions: boredom, distress, anger, and positive emotions. Implications of the findings for theories of children's motivation are discussed, as well as for diagnostic strategies to identify children at risk for motivational problems

What motivates children's behavior and emotion? Joint effects of perceived control and autonomy in the academic domain

This study examined the contribution of perceived control and autonomy to children's self-reported behavior and emotion in the classroom (N = 246 children ages 8-10 years). Multiple regression analyses revealed unique effects of autonomy over and above the strong effects of perceived control. In addition, both sets of perceptions (and their interaction) were found to distinguish children who were active but emotionally disaffected from those who were active and emotionally positive. Specific predictions were also tested regarding the effects of (a) control attributions to 5 causes and (b) 4 reasons for task involvement that differed in degree of autonomy on children's active (vs. passive) behavior and 4 kinds of emotions: boredom, distress, anger, and positive emotions. Implications of the findings for theories of children's motivation are discussed, as well as for diagnostic strategies to identify children at risk for motivational problems

Requirement for ICR-like sequences in the replication of brome mosaic virus genomic RNA

Previous studies using a brome mosaic virus (BMV) RNA-2 deletion mutant (pRNA-2 M/S) and additional derivatives as reporters established that viral sequences resembling internal control regions (ICRs) 1 and 2 of tRNA gene promoters are vital to (+)-strand replication in protoplasts. Transfer of these mutations to genomic RNA-2 and functional analysis in protoplast, local lesion, and systemic infections revealed a sequence-specific requirement for bases within the ICR2-like motif. Despite the low (generally less than 20% of wild-type) and sometimes undetectable levels of replication of these RNA-2 mutants, sufficient p2a protein was produced to support at least modest levels of RNA-1, -3 and -4 replication in protoplasts. However, only those RNA-2 ICR2 mutants supporting substantial replication of the viral genome in protoplasts were capable of establishing local lesions in Chenopodium hybridum and systemic infections in barley, further establishing the essential role of the ICR-like sequences in viral infectivity. Upon passage through a second set of barley plants, accumulation patterns for progeny from inocula containing certain RNA-2 mutants paralleled those from wild-type inocula, indicating repair of the introduced mutations. RNA stability and translatability were shown to be unaffected by the introduced mutations. BMV RNA-3 contains several ICR-like sequences, each of which was individually deleted. Whereas deletion of the 5'-terminal ICR2-like motif had little effect on RNA-3 accumulation in protoplasts or local lesion formation, it debilitated systemic spread in barley. Deletion of an internal ICR2-like motif at position 1100 decreased (+):(-) strand asymmetry from greater than 100:1 to 14:1, reduced RNA-3 replication in protoplasts to less than 15% of wild-type, and abolished local lesion and systemic infectivity.

Non-replicating deletion mutants of brome mosaic virus RNA-2 interfere with viral replication

Naturally occurring defective interfering RNAs (DI-RNAs) and satellite RNAs greatly reduce the accumulation of their helper virus in vivo, but often modulate symptom expression in an unpredictable manner. Deletion mutants Nc/S, Na/M and Sa/Nc + M/S, derived from brome mosaic virus (BMV) RNA-2, failed to replicate when co-inoculated with BMV RNAs-1 and -2 to barley protoplasts. However, the inoculum RNA corresponding to these deletion mutants was extremely stable and could have been mistaken for plus-strand progeny had minus-strand progeny analysis been omitted. These results accentuate the need for such tests in evaluating the ability of mutant viral sequences to replicate. One of the mutants, Nc/S, effectively interfered with the accumulation of BMV RNAs-1 and -2 in barley protoplasts. This non-replicating interfering RNA was termed NRI RNA-2 Nc/S. When present with RNAs-1 and -2 at low inoculum amounts (1 microgram), NRI RNA-2 Nc/S reduced replication of RNA-2, the parental RNA, by 63% and preferentially interfered with minus-strand RNA accumulation. At higher levels (4 micrograms), it completely displaced replication of both RNAs-1 and -2. Mutations eliminating translation of a truncated p2a protein from NRI RNA-2 Nc/S did not alleviate the interference effect, demonstrating that a defective replicase protein was not responsible for the decreased accumulation of genomic RNA. At an NRI RNA: genomic RNA inoculum molar ratio of 1:1, NRI RNA-2 Nc/S reduced the accumulation of all helper virus RNAs by 55%. Since this reduction was seen for both wild-type RNA-3 and delta SGP RNA-3, a deletion mutant of RNA-3 that lacks the subgenomic promoter necessary for coat protein expression, it was evident that the effective interference mediated by NRI RNA-2 Nc/S was not mitigated by encapsidation. The ability of the NRI RNAs to mimic satellite DI RNAs in depressing helper virus replication suggests that their expression in transgenic plants may provide a new and widely applicable approach for inducing resistance to viral infection.

Artificial defective interfering RNAs derived from brome mosaic virus

Naturally occurring defective interfering RNAs (DI-RNAs) greatly reduce the accumulation of their helper virus in vivo, but are rarely associated with plant positive-strand RNA viruses. Deletion mutants pRNA-2 M/S and pRNA-2 E/S, derived from brome mosaic virus (BMV) genomic RNA-2, replicated in a manner dependent on BMV RNA-1 and -2, and effectively interfered with their accumulation in barley protoplasts. Based on their mode of replication, these mutant RNAs have been termed parasitic RNAs (pRNAs). When present with RNA-1 and -2 at low inoculum amounts, pRNA-2 M/S and pRNA-2 E/S reduced the level of replication of RNA-2, the parental RNA, by 37% and 64%, respectively. Greater amounts of pRNA in the inoculum completely eliminated the replication of both RNA-1 and -2. Mutations that prevented translation of truncated proteins from the pRNAs did not affect interference, but those that reduced pRNA replication decreased their ability to interfere with genomic RNA replication. At a molar pRNA: genomic RNA inoculum ratio of 1.5:1, pRNA-2 E/S reduced the accumulation of all helper virus RNAs by greater than 60%. This occurred in the presence of wild-type RNA-3 or delta SGP RNA-3, a deletion mutant of RNA-3 that lacks the subgenomic promoter necessary for coat protein expression, demonstrating that the interference mediated by the pRNAs was not effected by encapsidation. These data indicate that the expression of pRNAs that function as artificial DI-RNAs in transgenic plants may be an approach for inducing resistance to virus infection which is applicable to a wide range of plant viruses.

Regulation of (+):(-)-strand asymmetry in replication of brome mosaic virus RNA

Transfection of barley protoplasts with brome mosaic virus (BMV) RNAs 1 + 2 in the absence of RNA-3 yielded a molar ratio for (+):(-)-strand progeny at 24 hr postinoculation near unity, whereas over 100-fold more (+)- than (-)-strand progeny accumulated in its presence. The presence of RNA-3 enhanced total (+)-strand RNA production 205-fold and that of RNAs 1 + 2 by 29-fold. In contrast, total (-)-strand RNA accumulation decreased by 68% and that for (-)RNAs 1 + 2 by 79% in the presence of RNA-3. Transfections containing an RNA-3 mutant (Gsgi----U RNA-3) that is incapable of yielding RNA-4 as a result of a single nucleotide substitution at the subgenomic RNA initiation site yielded only 66% of the (+):(-) asymmetry seen in the presence of wild-type RNA-3. Only 1.8-fold excess of (+)-over (-)-strand production was obtained for transfections that included delta SGP RNA-3, a deletion that includes the subgenomic promoter core and extends 43 nt into the RNA-4 sequence. Transfections containing RNA-3 mutants bearing frameshifts or deletions in the coat protein cistron yielded levels of asymmetry similar to those seen for Gsgi----U RNA-3. These findings implicate the subgenomic promoter and other sequences in the intercistronic region of RNA-3 as the primary determinants of asymmetric replication, although the coat protein may be an additional factor enhancing the accumulation of (+)-strand RNA.

Perceived locus of causality and internalization: examining reasons for acting in two domains

Theories of internalization typically suggest that self-perceptions of the "causes" of (i.e. reasons for) behavior are differentiated along a continuum of autonomy that contains identifiable gradations. A model of perceived locus of causality (PLOC) is developed, using children's self-reported reasons for acting. In Project 1, external, introjected, identified, and intrinsic types of reasons for achievement-related behaviors are shown to conform to a simplex-like (ordered correlation) structure in four samples. These reason categories are then related to existing measures of PLOC and to motivation. A second project examines 3 reason categories (external, introject, and identification) within the domain of prosocial behavior. Relations with measures of empathy, moral judgement and positive interpersonal relatedness are presented. Finally, the proposed model and conceptualization of PLOC are discussed with regard to intrapersonal versus interpersonal perception, internalization, cause-reason distinctions, and the significance of perceived autonomy in human behavior.

Gender and sex-role influences on children's self-esteem

This study examined direct and moderating influences of gender and sex-role orientations on children's general self-esteem. Moderating influences of these variables on the prediction of self-esteem were examined with respect to two sets of competence beliefs regarding school achievement: perceived capacities and perceived strategies for doing well in school. One hundred nineteen fourth-, fifth-, and sixth-grade children were assessed using the Perceived Competence Scale for Children (Harter, 1982), the Multidimensional Measure of Children's Perceptions of Control (Connell, 1985), and the Children's Personal Attributes Questionnaire (Hall & Halberstadt, 1980). Correlational and hierarchical multiple regression analyses indicated that upper elementary schoolchildren's general self-esteem is (a) marginally related to biological gender, with boys showing a slight advantage; (b) significantly related to masculinity and androgyny; and (c) predicted more strongly by perceived capacities to do schoolwork in girls than in boys, and by perceived (lack of) strategies for academic success in nontraditionally sex-typed children than in traditionally sex-typed children. Of the two nontraditionally sex-typed groups, androgynous children were found to have more positive school competence beliefs than were undifferentiated children.

Perceived locus of causality and internalization: Examining reasons for acting in two domains

Theories of internalization typically suggest that self-perceptions of the "causes" of (i.e. reasons for) behavior are differentiated along a continuum of autonomy that contains identifiable gradations. A model of perceived locus of causality (PLOC) is developed, using children's self-reported reasons for acting. In Project 1, external, introjected, identified, and intrinsic types of reasons for achievement-related behaviors are shown to conform to a simplex-like (ordered correlation) structure in four samples. These reason categories are then related to existing measures of PLOC and to motivation. A second project examines 3 reason categories (external, introject, and identification) within the domain of prosocial behavior. Relations with measures of empathy, moral judgement and positive interpersonal relatedness are presented. Finally, the proposed model and conceptualization of PLOC are discussed with regard to intrapersonal versus interpersonal perception, internalization, cause-reason distinctions, and the significance of perceived autonomy in human behavior.

Comparison of methods for enumeration of selected coliforms exposed to ozone

mT7 medium performed no better than m-Endo medium in enumerating cells of Escherichia coli and Citrobacter freundii exposed to ozone. Also, there was no difference in the plate count of heterotrophic bacteria in ozonated raw water determined on modified Henrici agar or R2A agar. Statistically significant differences were seen between bacteria and the type of water in which they were suspended during ozonation.

Temperament, emotion, and social interactive behavior in the strange situation: a component process analysis of attachment system functioning

This study examines the contributions of temperamentally and nontemperamentally based emotional reactions to the organization of social interactive behavior within the Strange Situation to better understand the emotional underpinnings of attachment system functioning. At 12 1/2 and 19 1/2 months, temperamental fear (assessed via maternal report) was related to independent per-episode dimensions of social interactive and distress behavior. Fear was moderately correlated with both distress and interactive dimensions at each age. Path-analytic models revealed that temperamental fear had direct effects on interactive behavior and also indirect effects mediated by preceding distress reactions. However, residualized measures of "context-specific" distress (with temperamental variance removed) were still highly consistent across Strange Situation episodes and also significantly predicted subsequent social interactive behavior; furthermore, stable distress reactions from 12 1/2 to 19 1/2 months significantly predicted concurrent stability in social interactive behavior. We discuss likely sources of "context-specific" emotional influences on Strange Situation behavior and also age-related differences in these findings.

Self-system concomitants of discrepancies between children's and teacher's evaluations of academic competence

The purpose of this study was to elucidate the psychological concomitants of discrepancies between fourth- to sixth-grade children's perceptions of academic competence and 2 measures of their "actual" competence in this domain: teacher ratings and achievement test scores. Over-, under-, and congruent child raters were identified on the basis of the 2 external standards and then compared on child and teacher ratings of self-esteem, self-regulatory style, and coping with perceived failure. 6 teachers and 121 lower- to upper-middle-class suburban students participated. As predicted, no differences were obtained between congruent and distorted (combined over- and under-) raters on these self-system variables. Consistent with previous research, overrating children showed higher self-esteem on self- and teacher ratings than underraters. After controlling for level of perceived competence, overraters scored higher on anxiety, and, when overrating occurred against the teacher standard, these children were rated by teachers as having lower self-esteem, poorer coping strategies, and less internalized self-regulatory styles. Comparing the 2 standards, self-reported difficulties were associated with underrating against the teacher's standard but not the achievement standard. Teacher reported difficulties were associated with the opposite pattern of underrating against the 2 standards. Motivational factors contributing to patterns of discrepancies are discussed, as are the educational implications of mismatches between teacher and student perceptions of objective and intrapsychic aspects of school experience.

Pea chloroplast glutathione reductase: purification and characterization

Glutathione reductase (EC 1.6.4.2) was purified from intact pea (Pisum sativum) chloroplasts by a method which includes affinity chromatography on ADP-agarose. Fractions from the affinity column which had glutathione reductase activity consisted of polypeptides of 60 and 32 kilodaltons. Separation of the proteins by electrophoresis on native gels showed that glutathione reductase activity was associated with 60 kilodalton polypeptides and not with the 32 kilodalton polypeptides. Antibodies to spinach whole leaf glutathione reductase (60 kilodaltons) cross-react with the chloroplast 60 kilodalton glutathione reductase but not the 32 kilodalton polypeptides. In the absence of dithiothreitol the 60 kilodalton polypeptides showed a shift in apparent molecular weight on sodium dodecyl sulfate gels to 72 kilodaltons. Dithiothreitol did not alter the activity of the chloroplast enzyme. Chloroplast glutathione reductase is relatively insensitive to NADPH.

A new multidimensional measure of children's perceptions of control

Perceived control plays a central role in many motivational and cognitive accounts of behavior. In this study, a new 48-item self-report instrument, the Multidimensional Measure of Children's Perceptions of Control, is described. Perceptions of control are defined as children's understanding of the locus of the sufficient cause for success and failure outcomes. 3 dimensions of third- through ninth-grade children's perceptions of control are independently assessed: internal, powerful others, and unknown. Each of these sources of control is assessed within 3 behavioral domains: cognitive, social, and physical. General items are also included. Perceptions of control over success outcomes and failure outcomes are assessed separately. The psychometric properties of the new measure's subscales are presented. Correlations of the new measure with measures of perceived and actual competence and findings demonstrating the sensitivity of the new measure to developmental, gender, and environmental influences are reported. It is argued that the new measure is an advance over existing measures of internal versus external locus of control in children because it provides domain-specific assessments of 3 separate dimensions of locus of control, including the previously untapped dimension of unknown control.