Rationale and design of the Nephrotic Syndrome Study Network (NEPTUNE) Match in glomerular diseases: designing the right trial for the right patient, today

Glomerular diseases are classified using a descriptive taxonomy that is not reflective of the heterogeneous underlying molecular drivers. This limits not only diagnostic and therapeutic patient management, but also impacts clinical trials evaluating targeted interventions. The Nephrotic Syndrome Study Network (NEPTUNE) is poised to address these challenges. The study has enrolled >850 pediatric and adult patients with proteinuric glomerular diseases who have contributed to deep clinical, histologic, genetic, and molecular profiles linked to long-term outcomes. The NEPTUNE Knowledge Network, comprising combined, multiscalar data sets, captures each participant's molecular disease processes at the time of kidney biopsy. In this editorial, we describe the design and implementation of NEPTUNE Match, which bridges a basic science discovery pipeline with targeted clinical trials. Noninvasive biomarkers have been developed for real-time pathway analyses. A Molecular Nephrology Board reviews the pathway maps together with clinical, laboratory, and histopathologic data assembled for each patient to compile a Match report that estimates the fit between the specific molecular disease pathway(s) identified in an individual patient and proposed clinical trials. The NEPTUNE Match report is communicated using established protocols to the patient and the attending nephrologist for use in their selection of available clinical trials. NEPTUNE Match represents the first application of precision medicine in nephrology with the aim of developing targeted therapies and providing the right medication for each patient with primary glomerular disease.

Tissue-resident memory T cell maintenance during antigen persistence requires both cognate antigen and interleukin-15

Our understanding of tissue-resident memory T (TRM) cell biology has been largely developed from acute infection models in which antigen is cleared and sterilizing immunity is achieved. Less is known about TRM cells in the context of chronic antigen persistence and inflammation. We investigated factors that underlie TRM maintenance in a kidney transplantation model in which TRM cells drive rejection. In contrast to acute infection, we found that TRM cells declined markedly in the absence of cognate antigen, antigen presentation, or antigen sensing by the T cells. Depletion of graft-infiltrating dendritic cells or interruption of antigen presentation after TRM cells were established was sufficient to disrupt TRM maintenance and reduce allograft pathology. Likewise, removal of IL-15 transpresentation or of the IL-15 receptor on T cells during TRM maintenance led to a decline in TRM cells, and IL-15 receptor blockade prevented chronic rejection. Therefore, antigen and IL-15 presented by dendritic cells play nonredundant key roles in CD8 TRM cell maintenance in settings of antigen persistence and inflammation. These findings provide insights that could lead to improved treatment of chronic transplant rejection and autoimmunity.

Attracting Diverse Students to Field Experiences Requires Adequate Pay, Flexibility, and Inclusion

Access to field experiences can increase participation of diverse groups in the environmental and natural resources (ENR) workforce. Despite a growing interest among the ENR community to attract and retain diverse students, minimal data exist on what factors undergraduate students prioritize when applying for field experiences. Using a nationwide survey of US undergraduate ENR students, we show that attracting most students to field experiences—especially racial or ethnic minority students—will require pay above minimum wage. However, the concurrent landscape of pay in ENR fell short of meeting many students’ pay needs. Aside from pay, ENR students valued training in technical field skills and analytical or research skills, working with their desired study species or taxa, and working near school or family. Additional barriers beyond limited pay included incompatible schedules and noninclusive work environments. Our findings provide important insights for attracting a diverse workforce to this critical stage in career advancement for students in ENR.

Resident memory T cells form during persistent antigen exposure leading to allograft rejection

Tissue-resident memory T cells (T_RM) contained at sites of previous infection provide local protection against reinfection. Whether they form and function in organ transplants where cognate antigen persists is unclear. This is a key question in transplantation as T cells are detected long term in allografts, but it is not known whether they are exhausted or are functional memory T cells. Using a mouse model of kidney transplantation, we showed that antigen-specific and polyclonal effector T cells differentiated in the graft into T_RM and subsequently caused allograft rejection. T_RM identity was established by surface phenotype, transcriptional profile, and inability to recirculate in parabiosis and retransplantation experiments. Graft T_RM proliferated locally, produced interferon-γ upon restimulation, and their in vivo depletion attenuated rejection. The vast majority of antigen-specific and polyclonal T_RM lacked phenotypic and transcriptional exhaustion markers. Single-cell analysis of graft T cells early and late after transplantation identified a transcriptional program associated with transition to the tissue-resident state that could serve as a platform for the discovery of therapeutic targets. Thus, recipient effector T cells differentiate into functional graft T_RM that maintain rejection locally. Targeting these T_RM could improve renal transplant outcomes.

Cross-dressed dendritic cells sustain effector T cell responses in islet and kidney allografts

Activation of host T cells that mediate allograft rejection is a 2-step process. The first occurs in secondary lymphoid organs where T cells encounter alloantigens presented by host DCs and differentiate to effectors. Antigen presentation at these sites occurs principally via transfer of intact, donor MHC-peptide complexes from graft cells to host DCs (cross-dressing) or by uptake and processing of donor antigens into allopeptides bound to self-MHC molecules (indirect presentation). The second step takes place in the graft, where effector T cells reengage with host DCs before causing rejection. How host DCs present alloantigens to T cells in the graft is not known. Using mouse islet and kidney transplantation models, imaging cytometry, and 2-photon intravital microscopy, we demonstrate extensive cross-dressing of intragraft host DCs with donor MHC-peptide complexes that occurred early after transplantation, whereas host DCs presenting donor antigen via the indirect pathway were rare. Cross-dressed DCs stably engaged TCR-transgenic effector CD8+ T cells that recognized donor antigen and were sufficient for sustaining acute rejection. In the chronic kidney rejection model, cross-dressing declined over time but was still conspicuous 8 weeks after transplantation. We conclude that cross-dressing of host DCs with donor MHC molecules is a major antigen presentation pathway driving effector T cell responses within allografts.

PIRs mediate innate myeloid cell memory to nonself MHC molecules

Immunological memory specific to previously encountered antigens is a cardinal feature of adaptive lymphoid cells. However, it is unknown whether innate myeloid cells retain memory of prior antigenic stimulation and respond to it more vigorously on subsequent encounters. In this work, we show that murine monocytes and macrophages acquire memory specific to major histocompatibility complex I (MHC-I) antigens, and we identify A-type paired immunoglobulin-like receptors (PIR-As) as the MHC-I receptors necessary for the memory response. We demonstrate that deleting PIR-A in the recipient or blocking PIR-A binding to donor MHC-I molecules blocks memory and attenuates kidney and heart allograft rejection. Thus, innate myeloid cells acquire alloantigen-specific memory that can be targeted to improve transplant outcomes.

A Latent Profile Analysis of Young Adult Lifestyle Behaviors

Objective: The aim of this study was to identify lifestyle profiles of young adult males and females based on their alcohol, diet, and exercise behaviors and then link these profiles with health. Method: We used the nationally representative 2017 Behavioral Risk Factor Surveillance System (BRFSS; N = 17,286; 47% female; M_age = 23.22; SD = 3.16; 65% white) to examine profiles of alcohol use, daily fruit and vegetable intake, fried potato intake, and exercise per week using latent profile analysis. Participants also reported the days their general, physical, and mental health were poor and BMI. Results: Five distinct profiles for both males and females were identified: Healthy Eaters/Exercisers, Moderates, Unhealthy Eaters, Medium Drinkers, and Heavy Drinkers. Heavy Drinkers and Unhealthy Eaters reported the most days of poor mental and physical health. Conclusions: Heavy drinkers and unhealthy eaters had the highest number of days of poor health, which also places them at risk for a host of health adversities throughout adulthood. Examining motivations behind young adults' patterns of consumption and activity is an important future direction to identify mechanisms for healthy lifestyle promotion during the transition to adulthood.

Using Latent Class Growth Modeling to Examine Longitudinal Patterns of Body Mass Index Change from Adolescence to Adulthood

BACKGROUND

Few studies use longitudinal designs to assess patterns of body mass index (BMI) change from adolescence to adulthood or incorporate severe obesity as a unique subgroup.

OBJECTIVE

To examine patterns of BMI trajectories from adolescence to adulthood and identify demographic characteristics associated with each BMI trajectory pattern.

DESIGN

Height, weight, and demographic characteristics were drawn from Waves I to V of the nationally representative school-based sample of the National Longitudinal Study of Adolescent to Adult Health (Add Health) conducted from 1994 to 2018 (data collection is ongoing).

PARTICIPANTS/SETTING

Participants included 3,315 (55.5% female) subjects responding to in-home interviews across all five Waves of Add Health.

MAIN OUTCOME MEASURES

BMI at each wave modeled over time.

STATISTICAL ANALYSES

Latent class growth modeling and logistic regression analysis using population sample weights.

RESULTS

Five classes of weight patterns best fit the sample. Twenty-nine percent of the sample had an always healthy BMI (class 1) and 34.9% changed from healthy weight to overweight (class 2). Moving from healthy weight to obese comprised 21.8% of the sample (class 3). BMI patterns increasing from overweight to obese (class 4) and from obese to severely obese (class 5) comprised 7.6% and 7.1% of the sample, respectively. Weight change was similar for males and females with some racial or ethnic minority participants more likely to be severely obese in adulthood.

CONCLUSIONS

Results emphasize the importance of tracking weight longitudinally and point to a nationally representative trend of increasing BMI during the transition to adulthood. There was no substantive decreasing trend identified in the sample. Findings highlight the need for effective early and ongoing intervention and prevention strategies and can aid in identification of vulnerable youth who are at the highest risk for moving to problematic weight categories.

Donor SIRPα polymorphism modulates the innate immune response to allogeneic grafts

Mice devoid of T, B, and natural killer (NK) cells distinguish between self and allogeneic nonself despite the absence of an adaptive immune system. When challenged with an allograft, they mount an innate response characterized by accumulation of mature, monocyte-derived dendritic cells (DCs) that produce interleukin-12 and present antigen to T cells. However, the molecular mechanisms by which the innate immune system detects allogeneic nonself to generate these DCs are not known. To address this question, we studied the innate response of Rag2^-/- γc^-/- mice, which lack T, B, and NK cells, to grafts from allogeneic donors. By positional cloning, we identified that donor polymorphism in the gene encoding signal regulatory protein α (SIRPα) is a key modulator of the recipient's innate allorecognition response. Donors that differed from the recipient in one or both Sirpa alleles elicited an innate alloresponse. The response was mediated by binding of donor SIRPα to recipient CD47 and was modulated by the strength of the SIRPα-CD47 interaction. Therefore, sensing SIRPα polymorphism by CD47 provides a molecular mechanism by which the innate immune system distinguishes between self and allogeneic nonself independently of T, B, and NK cells.

Graft-infiltrating host dendritic cells play a key role in organ transplant rejection

Successful engraftment of organ transplants has traditionally relied on preventing the activation of recipient (host) T cells. Once T-cell activation has occurred, however, stalling the rejection process becomes increasingly difficult, leading to graft failure. Here we demonstrate that graft-infiltrating, recipient (host) dendritic cells (DCs) play a key role in driving the rejection of transplanted organs by activated (effector) T cells. We show that donor DCs that accompany heart or kidney grafts are rapidly replaced by recipient DCs. The DCs originate from non-classical monocytes and form stable, cognate interactions with effector T cells in the graft. Eliminating recipient DCs reduces the proliferation and survival of graft-infiltrating T cells and abrogates ongoing rejection or rejection mediated by transferred effector T cells. Therefore, host DCs that infiltrate transplanted organs sustain the alloimmune response after T-cell activation has already occurred. Targeting these cells provides a means for preventing or treating rejection.

CD8+ Effector T Cell Migration to Pancreatic Islet Grafts Is Dependent on Cognate Antigen Presentation by Donor Graft Cells

Pancreatic islet transplantation is a promising therapy for diabetes, but acute rejection of the islets by host effector T cells has hindered clinical application. In this study, we addressed the mechanisms of CD8(+) effector T cell migration to islet grafts because interrupting this step is key to preventing rejection. We found that effector T cell migration to revascularized islet transplants in mice is dependent on non-self Ag recognition rather than signaling via Gαi-coupled chemokine receptors. Presentation of non-self Ag by donor cells was necessary for migration, whereas Ag presentation by recipient cells was dispensable. We also observed that deficiency of SKAP1, an immune cell adaptor downstream of the TCR and important for integrin activation, prolongs allograft survival but does not reduce effector T cell migration to the graft. Therefore, effector T cell migration to transplanted islets is Ag driven, not chemokine driven, but SKAP1 does not play a critical role in this process.

Antigen presentation via intravascular extensions of renal DC is necessary for antigen-specific T Cell migration into the kidney

We have previously shown that CX3CR1+ renal DC sample antigen via intravascular processes in the context of systemic infection and immune complex disease. Here, we investigated the role of intravascular DC processes in antigen presentation and effector T cell migration to the kidney.

To investigate T cell migration, CFP-OVA E. coli and CD8+ DsRed+ OT-I effector T cells, pretreated with Pertussis toxin (PTX), were i.v. injected into CX3CR1gfp/+ mice 24h before 2P intravital microscopy (2PIM) of the kidney was performed.

OT-I T cells migrated into the kidney, with 2PIM showing prolonged (30 min) DC-T cell interactions. OT-I migration was significantly higher (2-fold) when OVA was present (CFP-OVA E. coli vs WT E.coli), demonstrating that migration of effector T cells was antigen-specific. To test if antigen presentation by DC was necessary to mediate migration of T cells, we used CD11c-YFP Kb−/− bone marrow chimeric recipients (hematopoietic cells lack H-2k(b), parenchymal cells express H-2k(b)). CFP-OVA E. coli injection into a CD11c YFP Kb−/− bone marrow chimeric mouse abrogated effector OT-I T cell migration into the renal tissue.

Our data demonstrate that migration of effector T cells in the setting of systemic infection is antigen-specific. In addition, antigen presentation by hematopoietic cells, most likely DC, is necessary to mediate antigen-specific effector T cell migration. H-2k(b) expression on parenchymal and endothelial cells does not mediate antigen-specific effector T cell migration. Our findings show that renal DC have two roles: immune surveillance by sampling and presenting antigen via intravascular processes, and guiding effector T cells to the site of antigen.

Body mass index, self-esteem and weight contentment from adolescence to young adulthood and women's risk for sexually transmitted disease

Background Women's risk for sexually transmitted diseases (STDs) were examined in terms of adolescent and young adult weight status, self-esteem trajectories and weight contentment using two waves of a nationally representative dataset.

METHODS

Using Waves 1 and 3 of the National Longitudinal Study of Adolescent Health, body mass index (BMI), self-esteem and weight contentment were examined during adolescence and young adulthood to assess the likelihood of STDs among 4000 young adult single women.

RESULTS

Change in BMI, specifically weight loss between adolescence and young adulthood, significantly increased women's risk for STDs. Continuously low self-esteem during adolescence and young adulthood significantly increased women's risk for STDs. When women's contentment with their weight decreased from adolescence to young adulthood, women's risk for STDs was greater. Regardless of other variables, Black women were more likely to have an STD.

CONCLUSIONS

RESULTS suggest that women's self-perception is important in reducing sexual risk; specifically, patterns of self-esteem, BMI and weight contentment across developmental periods should be a critical focus of research and practice related to adolescent and young adult sexual health. There are many known benefits to fostering self-esteem during adolescence and findings from this study add STD prevention among young women to this list. RESULTS emphasise the needed prevention during adolescence to address self-perspective and self-esteem for the long-term sexual well-being of young women.

Non-self recognition by monocytes initiates allograft rejection

Maturation of T cell-activating APCs directly links innate and adaptive immunity and is typically triggered by microbial infection. Transplantation of allografts, which are sterile, generates strong T cell responses; however, it is unclear how grafts induce APC maturation in the absence of microbial-derived signals. A widely accepted hypothesis is that dying cells in the graft release "danger" molecules that induce APC maturation and initiate the adaptive alloimmune response. Here, we demonstrated that danger signals associated with dying cells are not sufficient to initiate alloimmunity, but that recognition of allogeneic non-self by the innate immune system is required. In WT as well as in T cell-, B cell-, and innate lymphoid cell-deficient mice, allogeneic grafts elicited persistent differentiation of monocytes into mature DCs that expressed IL-12 and stimulated T cell proliferation and IFN-γ production. In contrast, syngeneic grafts in the same mice elicited transient and less pronounced differentiation of monocytes into DCs, which neither expressed IL-12 nor stimulated IFN-γ production. In a model in which T cell recognition is restricted to a single foreign antigen on the graft, rejection occurred only if the allogeneic non-self signal was also sensed by the host's innate immune system. These findings underscore the importance of innate recognition of allogeneic non-self by monocytes in initiating graft rejection.

Cognate antigen directs CD8+ T cell migration to vascularized transplants

The migration of effector or memory T cells to the graft is a critical event in the rejection of transplanted organs. The prevailing view is that the key steps involved in T cell migration - integrin-mediated firm adhesion followed by transendothelial migration - are dependent on the activation of Gαi-coupled chemokine receptors on T cells. In contrast to this view, we demonstrated in vivo that cognate antigen was necessary for the firm adhesion and transendothelial migration of CD8+ effector T cells specific to graft antigens and that both steps occurred independent of Gαi signaling. Presentation of cognate antigen by either graft endothelial cells or bone marrow-derived APCs that extend into the capillary lumen was sufficient for T cell migration. The adhesion and transmigration of antigen-nonspecific (bystander) effector T cells, on the other hand, remained dependent on Gαi, but required the presence of antigen-specific effector T cells. These findings underscore the primary role of cognate antigen presented by either endothelial cells or bone marrow-derived APCs in the migration of T cells across endothelial barriers and have important implications for the prevention and treatment of graft rejection.

Allograft outcomes in outbred mice

Inbreeding depression and lack of genetic diversity in inbred mice could mask unappreciated causes of graft failure or remove barriers to tolerance induction. To test these possibilities, we performed heart transplantation between outbred or inbred mice. Unlike untreated inbred mice in which all allografts were rejected acutely (6-16 days posttransplantation), untreated outbred mice had heterogeneous outcomes, with grafts failing early (<4 days posttransplantation), acutely (6-24 days) or undergoing chronic rejection (>75 days). Blocking T cell costimulation induced long-term graft acceptance in both inbred and outbred mice, but did not prevent the early graft failure observed in the latter. Further investigation of this early phenotype established that it is dependent on the donor, and not the recipient, being outbred and that it is characterized by hemorrhagic necrosis and neutrophilic vasculitis in the graft without preformed, high titer antidonor antibodies in the recipient. Complement or neutrophil depletion prevented early failure of outbred grafts, whereas transplanting CD73-deficient inbred hearts, which are highly susceptible to ischemia-reperfusion injury, recapitulated the early phenotype. Therefore, outbred mice could provide broader insight into donor and recipient determinants of allograft outcomes but their hybrid vigor and genetic diversity do not constitute a uniform barrier to tolerance induction.

Teamwork behaviours and errors during neonatal resuscitation

OBJECTIVE

To describe relationships between teamwork behaviours and errors during neonatal resuscitation.

METHODS

Trained observers viewed video recordings of neonatal resuscitations (n = 12) for the occurrence of teamwork behaviours and errors. Teamwork state behaviours (such as vigilance and workload management, which extend for some duration) were assessed as the percentage of each resuscitation that the behaviour was observed and correlated with the percentage of observed errors. Teamwork event behaviours (such as information sharing, inquiry and assertion, which occur at specific times) were counted in 20-s intervals before and after resuscitation steps, and a generalised linear mixed model was calculated to evaluate relationships between these behaviours and errors.

RESULTS

Resuscitation teams who were more vigilant committed fewer errors (Spearman's rho for vigilance and errors = -0.62, 95% CI -0.07 to -0.87, p = 0.031). Assertions were more likely to occur before errors than correct steps (OR = 1.44, 95% CI 1.10 to 1.89, p = 0.008) and teaching/advising occurred less frequently after errors (OR = 0.59, 95% CI 0.37 to 0.94, p = 0.028). Though not statistically significant, there was less information sharing before errors (OR = 0.90, 95% CI 0.77 to 1.05, p = 0.172).

CONCLUSIONS

Vigilance is an important behaviour for error management. Assertion may have caused errors, or perhaps was an indicator for some other factor that caused errors. Teams may have preferred to resolve errors directly, rather than using errors as opportunities to teach their teammates. These observations raise important questions about the appropriate use of some teamwork behaviours and how to include them in team training programmes.

Prisoner health and valuation of life, loneliness, and depressed mood

OBJECTIVE

To examine valuation of life, loneliness, and depressed mood as mediating the association between age and race/ethnicity and health outcomes among older adult male prisoners.

METHODS

Survey of 261 male prisoners ages 45-80 from 8 Oklahoma correctional facilities.

RESULTS

African American prisoners report fewer health conditions than White prisoners - a finding mediated by significantly greater valuation of life, less loneliness, and lower depressed mood among African American prisoners. Older prisoners reported more health conditions than younger prisoners independent of other study variables.

CONCLUSION

Results suggest improving inmates' internal states will reduce incidence of illness and disease among older male offenders and associated healthcare costs.

Innate immunity alone is not sufficient for chronic rejection but predisposes healed allografts to T cell-mediated pathology

BACKGROUND

Acute allograft rejection is dependent on adaptive immunity, but it is unclear whether the same is true for chronic rejection. Here we asked whether innate immunity alone is sufficient for causing chronic rejection of mouse cardiac allografts.

METHODS

We transplanted primarily vascularized cardiac grafts to recombinase activating gene-knockout (RAG(-/-)) mice that lack T and B cells but have an intact innate immune system. Recipients were left unmanipulated, received adjuvants that stimulate innate immunity, or were reconstituted with B-1 lymphocytes to generate natural IgM antibodies. In a second model, we transplanted cardiac allografts to mice that lack secondary lymphoid tissues (splenectomized aly/aly recipients) and studied the effect of NK cell inactivation on T cell-mediated chronic rejection.

RESULTS

Acute cardiac allograft rejection was not observed in any of the recipients. Histological analysis of allografts harvested 50 to 90 days after transplantation to RAG(-/-) mice failed to identify chronic vascular or parenchymal changes beyond those observed in control syngeneic grafts. Chronic rejection of cardiac allografts parked in splenectomized aly/aly mice was observed only after the transfer of exogenously activated T cells. NK inactivation throughout the experiment, or during the parking period alone, reduced the severity of T cell-dependent chronic rejection.

CONCLUSIONS

The innate immune system alone is not sufficient for causing chronic rejection. NK cells predispose healed allografts to T cell-dependent chronic rejection and may contribute to chronic allograft pathology.

Modeling community asbestos exposure near a vermiculite processing facility: Impact of human activities on cumulative exposure

Contaminated vermiculite ore from Libby, Montana was processed in northeast Minneapolis from 1936 to 1989 in a densely populated urban residential neighborhood, resulting in non-occupational exposure scenarios from plant stack and fugitive emissions as well as from activity-based scenarios associated with use of the waste rock in the surrounding community. The objective of this analysis was to estimate potential cumulative asbestos exposure for all non-occupationally exposed members of this community. Questionnaire data from a neighborhood-exposure assessment ascertained frequency of potential contact with vermiculite processing waste. Monte Carlo simulation was used to develop exposure estimates based on activity-based concentration estimates and contact durations for four scenarios: S1, moved asbestos-contaminated waste; S2, used waste at home, on lawn or garden; S3, installed/removed vermiculite insulation; S4, played in or around waste piles at the plant. The simulation outputs were combined with air-dispersion model results to provide total cumulative asbestos exposure estimates for the cohort. Fiber emissions from the plant were the largest source of exposure for the majority of the cohort, with geometric mean cumulative exposures of 0.02 fibers/cc × month. The addition of S1, S2 and S3 did not significantly increase total cumulative exposure above background exposure estimates obtained from dispersion modeling. Activity-based exposures were a substantial contributor to the upper end of the exposure distribution: 90th percentile S4 exposure estimates are ∼10 times higher than exposures from plant emissions. Pile playing is the strongest source of asbestos exposure in this cohort, with other activity scenarios contributing less than from plant emissions.

Type I interferons are not critical for skin allograft rejection or the generation of donor-specific CD8+ memory T cells

Type I interferons (IFN-I) link innate to adaptive immunity in microbial infection, autoimmune disease and tumor immunity. It is not known whether IFN-I have an equally central role in alloimmunity. Here we tested this possibility by studying skin allograft survival and donor-specific CD8+ T-cell responses in mice that lack the IFN-I receptor (IFN-IR-/-). We found that IFN-IR-/- mice reject fully allogeneic wild-type skin grafts at the same rate as wild-type recipients. Similarly, allograft rejection was not delayed if IFN-IR-/- male skin was transplanted to syngeneic IFN-IR-/- female mice. Quantitation of the male (H-Y)-specific CD8+ T-cell response in these mice revealed normal generation of donor-specific CD8+ effector T cells but fourfold reduction in CD8+ memory T cells. Memory CD8+ T cells generated in the absence of IFN-IR had normal phenotype and recall function, assessed by ex vivo cytokine production and the ability of IFN-IR-/- mice to mount second set rejection. Finally, these memory T cells were maintained at a constant number despite their inability to respond to IFN-1. Our findings indicate that IFN-I cytokines are not critical for acute allograft rejection or for the expansion and differentiation of donor-specific CD8+ T cells into long-lived, functional memory T cells.

A randomized clinical trial evaluating silicone earplugs for very low birth weight newborns in intensive care

OBJECTIVE

To determine whether very low birth weight (VLBW) newborns (<1500 g) wearing silicone earplugs grow larger and perform better on developmental exams than controls.

STUDY DESIGN

VLBW newborns (n=34) were randomized to wearing earplugs or not. Hospital outcomes were abstracted from medical charts by research staff masked to intervention status. Fourteen extremely low birth weight (ELBW) newborns (<1000 g) were also evaluated at 18 to 22 months.

RESULT

After adjusting for birth weight, 11 surviving newborns in the earplug group were 225 g (95% CI: 45, 405) heavier at 34 weeks post menstrual age than the 13 controls. Six ELBW earplug infants scored 15.53 points (95% CI: 3.03, 28.02) higher than six controls on the Bayley Mental Development Index. Their head circumferences were 2.59 cm (95% CI: 0.97, 4.21) larger.

CONCLUSION

Earplugs may facilitate weight gain in VLBW newborns. Better outcomes may persist at 18 to 22 months at least in ELBW infants.

Adolescents' Online Social Networking Following the Death of a Peer

The purpose of this study was to examine how online social networking facilitates adolescent grieving following the sudden death of a peer. Researchers reviewed 20 profiles authored by adolescents who had died between 2005 and 2007 collecting information from commentary posted to the profiles posthumously. Observed themes included adolescent Internet users directing comments to the deceased, posting memorial sentiments, indicators of coping strategies, current events and memories, comments about the act of commenting, cause of death, comments from distal or unknown peers, religious beliefs, and attending the funeral. In addition to prolonging an attachment with the deceased, online social networking also facilitates teenagers' coping in a way that grants unlimited freedom and opportunity to reflect back over their relationship with the deceased.

A review of online social networking profiles by adolescents: implications for future research and intervention

This study explored content posted and interactions taking place on adolescent online social networking profiles. Although "blogging" continues to soar in popularity, with over half of teenagers online participating in some form, little research has comprehensively explored blog communication within the context of adolescent development. Content was qualitatively coded from 100 randomly selected profiles authored by adolescents between the ages of 16 and 18. Rich thematic elements were identified including family and social issues, risk behaviors, disclosure of personally identifiable information, and frequent peer interaction. Results indicate adolescent blogs frequently contain appropriate images, positive comments about parents and peers, athletics, a variety of risk behaviors, and sexual and profane language. In addition, school type was examined (public versus private, religious) as a potential factor in understanding the differences in content posted by adolescents; however, no significant differences were found. Implications for parental monitoring and intervention are discussed as well as direction for future research. Adolescents' online profiles contain a wealth of intimate, candid, and publicly available information on a wide range of social issues pertinent to adolescence that contribute to the understanding of adolescent development and well-being.

Teaching teamwork during the Neonatal Resuscitation Program: a randomized trial

OBJECTIVE

To add a team training and human error curriculum to the Neonatal Resuscitation Program (NRP) and measure its effect on teamwork. We hypothesized that teams that received the new course would exhibit more teamwork behaviors than those in the standard NRP course.

STUDY DESIGN

Interns were randomized to receive NRP with team training or standard NRP, then video recorded when they performed simulated resuscitations at the end of the day-long course. Outcomes were assessed by observers blinded to study arm allocation and included the frequency or duration of six team behaviors: inquiry, information sharing, assertion, evaluation of plans, workload management and vigilance.

RESULT

The interns in the NRP with team training group exhibited more frequent team behaviors (number of episodes per minute (95% CI)) than interns in the control group: information sharing 1.06 (0.24, 1.17) vs 0.13 (0.00, 0.43); inquiry 0.35 (0.11, 0.42) vs 0.09 (0.00, 0.10); assertion 1.80 (1.21, 2.25) vs 0.64 (0.26, 0.91); and any team behavior 3.34 (2.26, 4.11) vs 1.03 (0.48, 1.30) (P-values <0.008 for all comparisons). Vigilance and workload management were practiced throughout the entire simulated code by nearly all the teams in the NRP with team training group (100% for vigilance and 88% for workload management) vs only 53 and 20% of the teams in the standard NRP. No difference was detected in the frequency of evaluation of plans.

CONCLUSION

Compared with the standard NRP, NRP with a teamwork and human error curriculum led interns to exhibit more team behaviors during simulated resuscitations.

Mathematical model of manganese ion catalyzed microwave deactivation of Enterococcus faecalis, Staphylococcus aureus and Escherichia coli

Enterococcus faecalis, Staphylococcus aureus and Escherichia coli survival was investigated using microwave irradiation (power 130 W) both in a water control and in the presence of a 1 microM manganese ion solution. Measured survival dependencies had "bell" shape form with maximum bacterial viability between 1-2 min of microwave heating. Additional heating revealed bacteria survival decreasing up to 3 min of microwave heating when viability became insignificantly small. The total deactivation time of bacteria in the presence of manganese ions was significantly smaller then that of bacteria irradiated in the microwave without manganese ions present (4-5 min). One possible explanation for the rapid reduction of bacterial survival during microwave irradiation in the presence of manganese ions is that increasing manganese ion penetration into bacteria along with microwave irradiation related to an increase of kinetic energy of ions, and damaging of bacteria by metal ions. The proposed mathematical model for microwave heating took into account "growth" and "death" factors of bacteria. It assumes that rates of bacterial growth and decay are linear functions of water temperature, and rate of bacterial decay that relates with metal concentration into water is also linear, which influenced the differential equation for the dependence between number of survival bacteria and temperature water. By using proportionality between the time of microwave heating and water temperature we derived the differential equation, between bacterial viability and time of microwave irradiation which was used as mathematical model for microwave heating in the presence of metal ions. This model had forms of second-degree polynomial functions. We received good relationships (with coefficient of correlation 0.92-0.99) between proposed mathematical model and experimental data for all bacterial deactivation.

In vitro reconstitution of legumin (11S) mRNA and binding proteins as related to post-transcriptional regulation of protein synthesis in developing alfalfa embryos

There is undetectable transcription of 11S storage protein (medicagin) mRNA by nuclei isolated from pre-cotyledonary-stage somatic embryos of alfalfa (Medicago sativa L). However, this message exists at steady-state levels in the embryos at this stage of development without concomitant synthesis of the storage protein. At the pre-cotyledonary stage, therefore, the transcriptional rate for 11S mRNA is low; what message is transcribed is sequestered in the form of mRNP complexes and is not recruited into polysomes in vivo (33). Both transcription (in vivo and in isolated nuclei) and translation of the 11S mRNA are evident at the onset of cotyledon development in somatic and zygotic embryos, reaching a maximum during expansion of the cotyledons and then declining as the embryos mature. Pre-cotyledonary-stage somatic embryos which do not utilize the 11S-mRNA in polysomes lack certain mRNA-binding proteins (32, 36 and 38 kD) which are present at later stages of development. These mRNA-binding proteins may be responsible for the initiation of large polysome formation since they were exclusively present in the translational extracts of cotyledonary somatic and zygotic embryos in which there was no repression of storage protein synthesis. In contrast, the pre-cotyledonary somatic embryos contained a different set of 11S-mRNA-binding proteins (28, 50, 55, and 62 kD) whose presence in the cotyledonary stage embryos was very rare or non-existent; these could be responsible for preventing translation.

Mathematical models for conventional and microwave thermal deactivation of Enterococcus faecalis, Staphylococcus aureus and Escherichia coli

Temperature dependencies of survival fecal coliforms such as Enterococcus faecalis, Staphylococcus aureus and Escherichia coli in water were investigated between 25-65 degrees C. Measured dependencies had "bell" shaped form with maximum bacterial viability at 35-45 degrees C. The rates of growth and decay of bacterial viability depend on specific forms of bacteria. At temperatures of 60-65 degrees C the number of viable bacteria decreased in one hundred times in comparison with the maximum value. Similar "bell" shape forms were found for dependencies between bacterial viability and time of microwave (dielectric) heating of water. The dependencies had maximum value at 1-2 min of microwave heating. Then, the number of viable bacteria decreased, and at 4-5 min of microwave heating, became insignificantly small. The proposed mathematical models for conventional and microwave heating took into account "growth" and "death" factors of bacteria, and had forms of second degree polynomial functions. The results showed good relationships (with coefficient correlation 0.84-0.99) between the proposed mathematical models and experimental data for both conventional and microwave heating.

Effect of Cnidoscolus aconitifolius leaf extract on the blood glucose and insulin levels of inbred type 2 diabetic mice

The effects of Cnidoscolus aconitifolius (CA) leaf extract and chlorpropamide on blood glucose and insulin levels in the inbred type 2 diabetic mice are reported. After treatment with CA, the glucose levels were measured at 0 and 2-hour intervals in experimental groups and controls. Group I received no treatment and served as control; Group II was the reference and it received chlorpropamide; Groups I-III were moderately diabetic, 100-300 mg/dL blood glucose levels while Group IV were severely diabetic (> 300 mg/dL). Groups III and IV received CA and served as test groups. There was no significant difference between the blood glucose levels at 0 and 2 hours for the control group, (P>0.23) but there were statistically significant differences for Group II (P<0.0002); Group III (P<0.002) and Group IV (P<0.0001). For moderately diabetic mice, CA and chlorpropamide decreased the glucose levels by 25.6% and 16.3% respectively while for the severely diabetic mice CA decreased the blood glucose by 43.7%. It is proposed that CA has an insulinogenic property that possibly stimulated dormant beta-cells to secrete insulin. The histopathology of several organs in the treated animals was found to differ from the expected. The islets of Langerhans for example were found to be preserved in the time frame examined. Also the liver and kidney were found to display milder pathology in the treated groups.

Sensitivity to optic flow in human cortical areas MT and MST

The macaque V5/MT complex comprises several sub-regions but little is known of their human homologues. We examined human V5/MT with fMRI in terms of specificity to optic flow stimuli, a key characteristic of macaque MST. Stimuli were large fields of moving dots, forming coherent global flow patterns. Random motion was used as a control. Retinotopic mapping was also conducted. The previously suggested existence of at least two distinct sub-regions, MT and MST, within the V5/MT complex was confirmed. Human MT is activated about equally by all moving dot patterns, including random motion, suggesting that it has little sensitivity to global flow structure. As previously described, this region shows strong signs of retinotopic organization and is only weakly activated by stimuli confined to the ipsilateral hemifield. In human MST, located immediately anterior to MT and strongly driven by ipsilateral stimuli, activation varies markedly with optic flow structure. The strongest activation is produced by complex flow that contains multiple flow components (expansion, contraction and rotation). Single components produce rather less response, while rigid translation and random motion produce less still. The results suggest that human MST is strongly specialized for encoding global flow properties, while human MT is less so.

Endogenous protein kinase-C activity and phosphorylated proteins in messenger ribonucleoprotein complexes of developing embryos of alfalfa

Developing somatic and zygotic embryos of alfalfa (Medicago sativa L.) exhibited endogenous protein kinase activity and protein acceptors of phosphate groups using both cell-free translational extracts and oligo(dT)-cellulose-column-purified mRNPs. The cell-free-translation extracts from pre-cotyledonary-stage somatic embryos had approximately 50- and 100-fold more protein kinase activity than cotyledonary-stage somatic and zygotic embryos. Several polypeptides were phosphorylated; some of them were unique to the early stage and some to the late-stage developing embryos. A 65 kDa protein was phosphorylated heavily in pre-cotyledonary-stage somatic embryos. This phosphorylated protein was comprised of three main components, two of which were phosphorylated heavily. Heat-shock treated-embryos lost their exitant kinase activity and at the same time another form of protein kinase activity was activated which phosphorylated a novel 28 kDa protein. Endogenous protein kinase activity was also observed within the mRNPs of polysomal and non-polysomal fractions of developing embryos, and this phosphorylated only 65, 43 and 30 kDa proteins within these fractions. A 30 kDa protein from the pre-cotyledonary-stage somatic embryos showed a higher affinity for accepting phosphate groups than the proteins from cotyledonary-stage somatic or zygotic embryos. The activity of protein kinase was largely c-AMP-independent, but was dependent on Ca2+, phospholipid and phorbol ester. The enzyme belongs to the protein kinase-C family; the 65 kDa protein cross-reacts with antibodies made against protein kinase-C (alpha- and beta-isoforms) and it may be an autophosphorylated protein.

Differential responses to measures of gait performance among healthy and neurologically impaired individuals11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated

OBJECTIVES

To compare gait during a 5-minute walk among healthy individuals, persons with spinal cord injury (SCI), and stroke survivors and to investigate whether simultaneous measures of oxygen consumption enhance information about performance.

DESIGN

Descriptive study.

SETTING

Veterans Affairs medical center.

PARTICIPANTS

Thirty-nine healthy individuals, 10 persons with SCI, and 20 stroke survivors.

INTERVENTIONS

Participants were fitted with a portable gas analyzer and walked on a 5-m walkway for 5 minutes.

MAIN OUTCOME MEASURES

Measures of walk distance, gait speed, gait energy expenditure (GEE), and gait cost were obtained, along with measures of ventilation (.Ve), ventilation and carbon dioxide production slope (.Ve . .VCo2), oxygen pulse, and heart rate.

RESULTS

The SCI group (127.65+/-81.74m) walked less than the stroke survivors (148.80+/-64.3m) or the healthy group (268.90+/-35.01m) but had higher energy demands, as shown by GEE (SCI group, 13.28+/-3.23mL.kg(-1).min(-1); stroke group, 10.18+/-2.14mL.kg(-1).min(-1); healthy group, 9.61+/-1.90mL.kg(-1).min(-1)) and by gait cost (SCI group,.57+/-.40 mL.kg(-1).m(-1); stroke group,.40+/-.52mL.kg(-1).m(-1); healthy group,.18+/-.02mL.kg(-1).m(-1)). Compared with the healthy group, the stroke group had higher .Ve (stroke group, 22.34+/-5.20L/min vs healthy group, 16.11+/-3.22L/min) and .Ve . .VCo2 slope (24.22+/-8.80 vs 18.73+/-5.44, respectively).

CONCLUSION

Use of metabolic assessment during the 5-minute walk was feasible and provided further information for evaluating gait performance with the subjects studied.

Systemic infection, interleukin 1beta, and cognitive decline in Alzheimer's disease

Activated microglia, the resident macrophages of the brain, are a feature of Alzheimer's disease. Animal models suggest that when activated microglia are further activated by a subsequent systemic infection this results in significantly raised levels of interleukin 1beta within the CNS, which may in turn potentiate neurodegeneration. This prospective pilot study in Alzheimer's disease subjects showed that cognitive function can be impaired for at least two months after the resolution of a systemic infection and that cognitive impairment is preceded by raised serum levels of interleukin 1beta. These relations were not confounded by the presence of any subsequent systemic infection or by baseline cognitive scores. Further research is needed to determine whether recurrent systemic infections drive cognitive decline in Alzheimer's disease subjects through a cytokine mediated pathway.

Conformation of the hexasaccharide repeating subunit from the Vibrio cholerae O139 capsular polysaccharide

In the past decade, several outbreaks of cholera have been reported to be caused by Vibrio cholerae O139, a strain which differs from the more common O1 strain in that the former is encapsulated. The hexasaccharide repeating subunit has been isolated from the V. cholerae O139 capsular polysaccharide by digestion with a recently discovered polysaccharide lyase derived from a bacteriophage specific for this serogroup. It specifically cleaves at a single position of the 4-linked galacturonic acid producing an unsaturated sugar product in quantities for conformational studies by (1)H and (13)C NMR spectroscopy. We report conformational studies on this oligosaccharide by molecular modeling and NMR spectroscopy including nuclear Overhauser effects and residual dipolar coupling of a sample weakly oriented in liquid crystalline solution. The structure contains a tetrasaccharide epitope homologous to the human Lewis(b) blood group antigen, which adopts a relatively well-defined single conformation. Comparison of these results with those of a previously published study of the intact capsular polysaccharide indicates that the conformations of the epitope in the two cases are identical or at least closely similar. Thus, this epitope, which may be essential for the pathogenicity of this V. cholerae strain, is not a "conformational epitope" requiring a certain critical size for antigenicity as has been reported for several other bacterial capsular antigens.

Estimating receptive field size from fMRI data in human striate and extrastriate visual cortex

Functional magnetic resonance imaging (fMRI) was used to estimate the average receptive field sizes of neurons in each of several striate and extrastriate visual areas of the human cerebral cortex. The boundaries of the visual areas were determined by retinotopic mapping procedures and were visualized on flattened representations of the occipital cortex. Estimates of receptive field size were derived from the temporal duration of the functional activation at each cortical location as a visual stimulus passed through the receptive fields represented at that location. Receptive fields are smallest in the primary visual cortex (V1). They are larger in V2, larger again in V3/VP and largest of all in areas V3A and V4. In all these areas, receptive fields increase in size with increasing stimulus eccentricity. The results are qualitatively in line with those obtained by others in macaque monkeys using neurophysiological methods.

A canine model to assess the biochemical stress response to laparoscopic and open surgery

PURPOSE

To develop an animal model to assess the stress response to open and laparoscopic surgery. Such a model would allow objective physiologic assessment of the putative benefits of laparoscopy and provide a framework in which to compare modifications in operative and anesthetic technique that might decrease the stress of surgery.

MATERIALS AND METHODS

Mongrel dogs underwent laparoscopic (N = 12) or open surgical (N = 12) left nephrectomy. In 11 control animals, after induction of anesthesia and line placement, the animal underwent either no intervention (open surgery sham; N = 6) or pneumoperitoneum only (laparoscopic sham; N = 5). Serum glucose and cortisol were measured preoperatively, at skin closure, and at 4, 8, and 24 hours postoperatively. Values at each time point were compared in the laparoscopic and open surgical nephrectomy groups and in each of the two nephrectomy groups and their respective shams.

RESULTS

Compared with baseline, there was a sharp rise in serum cortisol at the time of skin closure, with a gradual decline to baseline values by 24 hours, in all experimental animals. Significantly lower serum cortisol concentrations were seen at 4 and 8 hours postoperatively in the laparoscopic group than in the open surgery group. Cortisol was significantly higher in the open group than in the sham-open group at all time points, whereas cortisol was greater in the laparoscopic group than in the pneumoperitoneum-only group only at the 4-hour time point. No differences were seen in serum glucose between groups.

CONCLUSIONS

The serum cortisol concentration appears to be a good measure of surgical stress in the canine model. The rapid decline in serum cortisol after laparoscopy compared with open surgery may indicate a lesser degree, or quicker resolution, of surgical stress in the former. Furthermore, the similarity in cortisol curves between laparoscopy and pneumoperitoneum only suggests that surgical stress in laparoscopic surgery may be attributable mainly to the effects of pneumoperitoneum.

Model studies toward the total synthesis of the Lycopodium alkaloid spirolucidine

[reaction: see text] A strategy for the synthesis of the spirocyclic core of spirolucidine was explored through a model study. The diene 4a was prepared and photolyzed to give the desired [2 + 2] photoadduct 17 containing the correct relative stereochemistry corresponding to spirolucidine.

Evidence of a critical leucite particle size for microcracking in dental porcelains

The leucite particles in dental porcelains are often partially encircled by microcracks that are the result of the thermal expansion mismatch between leucite and the surrounding glass matrix. Although the magnitude of the stress at the particle-matrix interface is independent of the particle size (Selsing, 1961), Davidge and Green (1968) showed experimentally that there is a critical particle size below which microcracking is absent. The critical particle size is explained by a Griffith-type energy balance criterion: Below the critical size, the stress magnitude may be sufficient to cause cracking, but there is insufficient strain energy for the creation of the new surfaces of the microcrack. The purpose of the present study was to determine whether the mean leucite particle size of a dental porcelain influences the degree of microcracking in the porcelain. Microcrack density, leucite particle surface area per unit volume, and leucite mean volume-surface diameter, D3,2, were determined by quantitative stereology on 10 specimens each of 6 dental porcelains and Component No. 1 of the Weinstein et al. patent (US Patent 3,052,982, 1962). The fraction of leucite particles with microcracks around them, f(mc), was estimated for each porcelain from the microcrack density and the leucite surface area. Using the equations of Selsing (1961) and Davidge and Green (1968), we calculated the critical particle diameter, Dc, for leucite to be 4 microm. The porcelains were partitioned according to whether their mean leucite particle diameters, D3,2, fell above or below Dc, and their values of f(mc) were analyzed by a permutation test with random re-sampling. The porcelains with mean leucite particle diameters below Dc had a significantly lower fraction of cracked particles compared with the porcelains with mean leucite particle diameters above Dc (p < 0.05). This study provides evidence that microcracking in dental porcelain can be minimized by a reduction of the mean leucite particle diameter to less than 4 microm.

Functional effects of unilateral laser papillectomy in the pig

OBJECTIVES

To evaluate the use of endoscopic laser papillectomy in a multi-papillary animal model to unilaterally impair concentrating ability and increase the urinary flow rate.

METHODS

Domestic pigs underwent unilateral retrograde flexible nephroscopy. With a holmium:yttrium-aluminum-garnet laser, varying numbers of papillae were ablated. Four weeks after the procedure, renal function studies were performed during hydropenia and after hydration, the animals were killed, and the kidneys were examined histologically.

RESULTS

The urine flow rate per 100 mL creatinine clearance was significantly increased in the papillectomized kidney compared with the control kidney during hydropenia (1.50 versus 0.94, P <0.01). The papillectomized kidneys were unable to concentrate the urine as well as the control kidneys during both hydropenia (urine osmolarity 430 versus 534 mOsm/L, P <0.01) and after hydration (329 versus 362 mOsm/L, P = 0.02). The free water reabsorption per 100 mL creatinine clearance was impaired in the papillectomized kidneys compared with the control kidneys (0.48 versus 1.00, P = 0.02) after hydration. A significant correlation existed between the percentage of papillae ablated and the difference in osmolarity between the operated and control kidneys (r(2) = 0.50, P = 0.015). Histologic examination demonstrated transitional re-epithelialization with moderate collecting duct dilation and medullary fibrosis underlying the ablated papillae early in the series; however, the histologic features normalized and the creatinine clearance was less impaired with a more proficient technique later in the series.

CONCLUSIONS

Endoscopic laser papillectomy results in increased urine flow and impaired urinary concentrating ability. This surgical technique should be investigated further for its role in the prevention of nephrolithiasis.

Comparison of 2-octyl cyanoacrylate adhesive, fibrin glue, and suturing for wound closure in the porcine urinary tract

OBJECTIVES

To evaluate 2-octyl cyanoacrylate glue (OCG) for wound closure in the urinary tract and compare the ability of OCG, fibrin glue (FG), and suture to withstand physiologic and supraphysiologic stress, because the use of tissue adhesives such as OCG or FG might simplify laparoscopic surgery.

METHODS

Female domestic pigs (n = 22) underwent a 7.5-cm cystotomy. Of these, 8 had closure with OCG and 8 with FG (6 open and 2 laparoscopic in each group). The controls were closed with suture (n = 4) or not at all (n = 2). Postoperative catheter drainage was not used. At 2 days or 4 weeks postoperatively, the bladders were filled with saline to 200 mm Hg pressure and the cystotomy scars inspected for leakage. The excised scars were also examined histologically.

RESULTS

The 2 OCG and 2 FG pigs tested on postoperative day 2 leaked at less than 200 mm Hg. None of the 6 OCG pigs tested at 4 weeks leaked at less than 200 mm Hg, including the 2 closed laparoscopically. Of the 6 FG pigs intended for study at 4 weeks, 3 (including the 2 closed laparoscopically) died from a massive urine leak, 1 tested at 4 weeks leaked, and 2 did not leak. Thus, 4 of 6 FG pigs leaked by 4 weeks compared with none in the OCG group (P = 0.06). The histologic examination was similar in the two groups.

CONCLUSIONS

Preliminary results suggest that OCG provides enough strength to hold together a large bladder wound. In the same model, FG did not consistently provide adequate closure.

Growth dynamics of the developing lateral geniculate nucleus

Segregated binocular maps in the lateral geniculate nucleus (LGN) develop from stages where they initially completely overlap. Here, we show that segregation occurs at different rates across the depth of the nucleus and that the volume of the ipsilateral projection does not decrease significantly during this period, rather LGN volume expands markedly and its shape changes. Hence, we have examined the differential growth of the ferret LGN during the process of segregation by using novel shape modelling techniques. These have facilitated quantification of its three-dimensional structure at successive developmental stages as well as the definition of growth vectors which illustrate shape change. This has been undertaken in direct representations of the LGN and those normalised for size and orientation. Spatiotemporal aspects of shape change have then been compared with different measurements of its cellular population. Initial stages of segregation are associated with a large expansion of the rostrocaudal axis of the nucleus along which segregation takes place, and an expansion of caudal regions that will eventually contain the binocular representation. Later stages are associated with dorsoventral expansions and a consolidation of the rostrocaudal axis. The pace of shape change peaks toward the end of the period of segregation when the nucleus has adopted approximately 50% of its adult shape. After segregation, nuclear growth is mainly isotropic. The mature shape of the nucleus is achieved before it reaches its full size and while cell density and cell sizes are still changing.

Subunit structure of a mammalian ER/Golgi SNARE complex

SNAP receptor (SNARE) complexes bridge opposing membranes to promote membrane fusion within the secretory and endosomal pathways. Because only the exocytic SNARE complexes have been characterized in detail, the structural features shared by SNARE complexes from different fusion steps are not known. We now describe the subunit structure, assembly, and regulation of a quaternary SNARE complex, which appears to mediate an early step in endoplasmic reticulum (ER) to Golgi transport. Purified recombinant syntaxin 5, membrin, and rbet1, three Q-SNAREs, assemble cooperatively to create a high affinity binding site for sec22b, an R-SNARE. The syntaxin 5 amino-terminal domain potently inhibits SNARE complex assembly. The ER/Golgi quaternary complex is remarkably similar to the synaptic complex, suggesting that a common pattern is followed at all transport steps, where three Q-helices assemble to form a high affinity binding site for a fourth R-helix on an opposing membrane. Interestingly, although sec22b binds to the combination of syntaxin 5, membrin, and rbet1, it can only bind if it is present while the others assemble; sec22b cannot bind to a pre-assembled ternary complex of syntaxin 5, membrin, and rbet1. Finally, we demonstrate that the quaternary complex containing sec22b is not an in vitro entity only, but is a bona fide species in living cells.

Water-enhanced crystallization of leucite in dental porcelain

OBJECTIVE

The purpose of this study was to determine whether long-term exposure of dental porcelain to saliva during temporary cementation of a porcelain-fused-to-metal (PFM) restoration could enhance leucite crystallization if the restoration is refired. Such water-enhanced leucite crystallization in dental porcelains could lead to porcelain-metal thermal incompatibility problems.

METHODS

Six commercial dental body porcelains and the Component No. 1 (leucite-containing) frit of the Weinstein et al. [13] patent were studied. For each porcelain, 30 coupon specimens were randomly assigned to a treatment group. Ten specimens were placed in artificial saliva, 10 in distilled water, and 10 in a desiccator and were stored for six months. At the end of the six months, an additional 10 coupons of each porcelain were prepared to serve as a control. All 40 specimens of each porcelain were randomized and subjected to one additional firing. Leucite weight fraction was determined by quantitative X-ray powder diffraction analysis via an internal standard technique.

RESULTS

Comparisons among the treatments via the least-squares-means test-adjusting for porcelain showed that the saliva group mean leucite weight fraction was significantly higher than that of the other groups. The change in porcelain thermal expansion that would be associated with a leucite change in this range would be between 0.2 x 10(-6) K-1 and 0.3 x 10(-6) K-1.

SIGNIFICANCE

The results of this work constitute the first demonstration that moisture absorbed by a porcelain can act as a glass modifier and enhance the crystallization of the glass during subsequent firing. The effect was sufficiently large to generate thermal expansion changes that would exceed the maximum safe mismatch between porcelain and metal.

High-temperature X-ray diffraction measurement of sanidine thermal expansion

Dental porcelains that are designed to be fused to PFM (porcelain-fused-to-metal) alloys are formulated by their manufacturers to be closely matched in thermal expansion to these alloys. The high thermal expansion of the mineral leucite has been exploited to regulate porcelain expansion. Leucite, however, has been observed to convert to the sanidine polymorph of feldspar during certain heat treatments within the normal firing range of dental porcelain. The effects of this conversion on porcelain thermal expansion and porcelain-metal thermal compatibility have been uncertain, due to the paucity of published data on the thermal expansion of sanidine. The purpose of this study was to measure the thermal expansion of sanidine by high-temperature X-ray diffraction over the temperature range in which thermal mismatch stresses can develop in porcelain-fused-to-metal restorations, i.e., from room temperature to 700 degrees C. The lattice parameters a, b, c, and beta were determined from the d-spacings and hkl values of multiple reflections by means of a least-squares iteration. The dependence of each lattice parameter on temperature was determined via analysis of variance, and the coefficient of thermal expansion, alpha, was obtained from this analysis. The lattice parameters of sanidine at room temperature were determined to be: a = 0.8524 +/- 0.0015 nm, b = 1.3020 +/- 0.0004 nm, c = 0.7165 +/- 0.0002 nm, and beta = 116.02 degrees +/- 0.01 degree (mean +/- 95% confidence interval). The linear thermal expansion coefficient, a, over the range from room temperature to 700 degrees C was determined to be 4.1 x 10(-6) K(-1) +/- 0.6 x 10(6) K(-1) (mean +/- 95% confidence interval). Because the coefficient of thermal expansion for sanidine is substantially lower than that of leucite (the effective linear thermal coefficient of thermal expansion of leucite over the range of 25 degrees to 700 degrees C is 28 x 10(-6) K(-1)), the conversion of leucite to sanidine during porcelain heat treatments would produce a detrimental lowering of the porcelain thermal expansion.