28 NICUs participating in a quality improvement collaborative targeting early-onset sepsis antibiotic use

OBJECTIVE

There is widespread overuse of antibiotics in neonatal intensive care units (NICUs). The objective of this study was to safely reduce antibiotic use in participating NICUs by targeting early-onset sepsis (EOS) management.

STUDY DESIGN

Twenty-eight NICUs participated in this statewide multicenter antibiotic stewardship quality improvement collaborative. The primary aim was to reduce the total monthly mean antibiotic utilization rate (AUR) by 25% in participant NICUs.

RESULT

Aggregate AUR was reduced by 15.3% (p < 0.001). There was a wide range in improvement among participant NICUs. There were no increases in EOS rates or nosocomial infection rates related to the intervention.

CONCLUSION

Participation in this multicenter NICU antibiotic stewardship collaborative targeting EOS was associated with an aggregate reduction in antibiotic use. This study informs efforts aimed at sustaining improvements in NICU AURs.

Cohort selection and the estimation of racial disparity in mortality of extremely preterm neonates

BACKGROUND

Racial disparities in preterm neonatal mortality are long-standing. We aimed to assess how cohort selection influences mortality rates and racial disparity estimates.

METHODS

With 2014-2018 California data, we compared neonatal mortality rates among Black and non-Hispanic White very low birth weight (VLBW, <1500 g) or very preterm infants (22-29 weeks gestational age). Relative risks were estimated by different cohort selection criteria. Blinder-Oaxaca decomposition quantified factors contributing to mortality differential.

RESULTS

Depending upon standard selection criteria, mortality ranged from 6.2% (VLBW infants excluding first 12-h deaths) to 16.0% (22-29 weeks' gestation including all deaths). Black observed neonatal mortality was higher than White infants only for delivery room deaths in VLBW infants (5.6 vs 4.2%). With risk adjustment accounting for higher rate of low gestational age, low Apgar score and other factors, White infant mortality increased from 15.9 to 16.6%, while Black infant mortality decreased from 16.7 to 13.7% in the 22-29 weeks cohort. Across varying cohort selection, risk adjusted survival advantage among Black infants ranged from 0.70 (CL 0.61-0.80) to 0.84 (CL 0.76-0.93).

CONCLUSIONS

Standard cohort selection can give markedly different mortality estimates. It is necessary to reduce prematurity rates and perinatal morbidity to improve outcomes for Black infants.

IMPACT

In this population-based observational cohort study that encompassed very low birth weight infant hospitalizations in California, varying standard methods of cohort selection resulted in neonatal mortality ranges from 6.2 to 16.0%. Across all cohorts, the only significant observed Black-White disparity was for delivery room deaths in Very Low Birth Weight births (5.6 vs 4.2%). Across all cohorts, we found a 16-30% survival advantage for Black infants. Cohort selection can result in an almost three-fold difference in estimated mortality but did not have a meaningful impact on observed or adjusted differences in neonatal mortality outcomes by race and ethnicity.

Early childhood outcomes of NICU graduates with cytomegalovirus infection in California

BACKGROUND

To assess demographics and outcomes up to 3 years of age among children with cytomegalovirus (CMV) infection in California neonatal intensive care units (NICUs) during 2010-2021.

METHODS

The California Perinatal Quality Care Collaborative (CPQCC) collects data on all very low birth weight (VLBW, birth weight ≤ 1500 g) and acutely ill infants with birth weight > 1500 g across 92% of NICUs in California. VLBW infants and those with neurological conditions are referred to a statewide high-risk infant follow-up (HRIF) program. CMV infection was defined as a positive culture or PCR identified during the NICU hospitalization.

RESULTS

During 2010-2021, CMV reporting rates averaged 3.5/1000 VLBW infants (n = 205) and 1.1/1000 infants >1500 g (n = 128). Among all 333 infants with CMV, 314 (94%) were discharged home alive, 271 (86%) were referred for HRIF and 205 (65%) had ≥1 visit. Whereas infants born to mothers <20 years of age had highest CMV reporting rates and those born to Hispanic mothers comprised 49% of all infected infants, they had the highest loss of follow-up. At the 12-month visit (n = 152), 19 (13%) infants with CMV had bilateral blindness and 18 (12%) had hearing loss. At the 24-month visit, 5 (5%) of 103 had severe cerebral palsy.

CONCLUSIONS

Among infants admitted to the NICU, those with CMV diagnoses may over represent infants with more severe CMV disease and outcomes. The CPQCC and HRIF program findings may help inform implementation of surveillance for congenital CMV infection in other U.S. states and guide strategies to reduce disparities in access to services.

Vignettes Identify Variation in Antibiotic Use for Suspected Early Onset Sepsis

BACKGROUND AND OBJECTIVES

There is widespread unwarranted antibiotic use and large individual provider variation in antibiotic use in NICUs. Vignette-based research methodology offers a unique method of studying variation in individual provider decisions. The objective with this study was to use a vignette-based survey to identify specific areas of provider antibiotic use variation in newborns being evaluated for early onset sepsis.

METHODS

This study was undertaken as part of a statewide multicenter neonatal antibiotic stewardship quality improvement project led by a perinatal quality improvement collaborative. A web-based vignette survey was administered to identify variation in decisions to start and discontinue antibiotics in cases of early onset sepsis.

RESULTS

The largest variation was noted in 3 of the 6 vignette cases. These cases highlighted variation in (1) decisions to start antibiotics in a case describing a well-appearing newborn with risk factors and an elevated C-reactive protein, (2) decisions to start antibiotics in the case of a newborn with risk factors plus mild respiratory signs at birth, and (3) decisions to stop antibiotics in the case of the newborn with a history of sepsis risk factors and mild clinical respiratory signs that resolved after 72 hours.

CONCLUSIONS

Clinical vignette assessment identified specific areas of variation in individual provider antibiotic use decisions in cases of suspected early onset sepsis. Vignettes are a valuable method of describing individual provider variation and highlighting antibiotic stewardship improvement opportunities in NICUs.

Designing a bed-side system for predicting length of stay in a neonatal intensive care unit

Increased length of stay (LOS) in intensive care units is directly associated with the financial burden, anxiety, and increased mortality risks. In the current study, we have incorporated the association of day-to-day nutrition and medication data of the patient during its stay in hospital with its predicted LOS. To demonstrate the same, we developed a model to predict the LOS using risk factors (a) perinatal and antenatal details, (b) deviation of nutrition and medication dosage from guidelines, and (c) clinical diagnoses encountered during NICU stay. Data of 836 patient records (12 months) from two NICU sites were used and validated on 211 patient records (4 months). A bedside user interface integrated with EMR has been designed to display the model performance results on the validation dataset. The study shows that each gestation age group of patients has unique and independent risk factors associated with the LOS. The gestation is a significant risk factor for neonates < 34 weeks, nutrition deviation for < 32 weeks, and clinical diagnosis (sepsis) for ≥ 32 weeks. Patients on medications had considerable extra LOS for ≥ 32 weeks’ gestation. The presented LOS model is tailored for each patient, and deviations from the recommended nutrition and medication guidelines were significantly associated with the predicted LOS.

Maternal and Infant Adverse Outcomes Associated with Mild and Severe Preeclampsia during the First Year after Delivery in the United States

OBJECTIVE

The burden of preeclampsia severity on the health of mothers and infants during the first year after delivery is unclear, given the lack of population-based longitudinal studies in the United States.

STUDY DESIGN

We assessed maternal and infant adverse outcomes during the first year after delivery using population-based hospital discharge information merged with vital statistics and birth certificates of 2,021,013 linked maternal-infant births in California. We calculated sampling weights using the National Center for Health Statistics data to adjust for observed differences in maternal characteristics between California and the rest of the United States. Separately, we estimated the association between preeclampsia and gestational age and examined collider bias in models of preeclampsia and maternal and infant adverse outcomes.

RESULTS

Compared with women without preeclampsia, women with mild and severe preeclampsia delivered 0.66 weeks (95% confidence interval [CI]: 0.64, 0.68) and 2.74 weeks (95% CI: 2.72, 2.77) earlier, respectively. Mild preeclampsia was associated with an increased risk of having any maternal adverse outcome (relative risk [RR] = 1.95; 95% CI: 1.93, 1.97), as was severe preeclampsia (RR = 2.80; 95% CI: 2.78, 2.82). The risk of an infant adverse outcome was increased for severe preeclampsia (RR = 2.15; 95% CI: 2.14, 2.17) but only marginally for mild preeclampsia (RR = 0.99; 95% CI: 0.98, 1). Collider bias produced an inverse association for mild preeclampsia and attenuated the association for severe preeclampsia in models for any infant adverse outcome.

CONCLUSION

Using multiple datasets, we estimated that severe preeclampsia is associated with a higher risk of maternal and infant adverse outcomes compared with mild preeclampsia, including an earlier preterm delivery.

Hospitalization costs associated with bronchopulmonary dysplasia in the first year of life

OBJECTIVE

To determine costs of hospitalization associated with bronchopulmonary dysplasia (BPD) during the first year in very low birth weight infants.

STUDY DESIGN

Retrospective cohort study of California births from 2008 to 2011 linking birth certificate, discharge records, and clinical data from California Perinatal Quality Care Collaborative. Inclusion: birth weight 401-1500 g, gestational age < 30 weeks, inborn or transferred within 2 days, alive at 36 weeks corrected, and without major congenital anomalies. Outcomes included cost and length of stay of initial hospitalization and rehospitalizations.

RESULT

Out of 7998 eligible infants, 2696 (33.7%) developed BPD. Median hospitalization cost in the first year was $377,871 per infant with BPD compared with $175,836 per infant without BPD (adjusted cost ratio 1.54, 95% confidence interval (CI) 1.49-1.59). Infants with BPD also had longer length of stay and a higher likelihood of rehospitalization.

CONCLUSION

BPD is associated with substantial resource utilization. Prevention strategies could help conserve healthcare resources.

Newborn Antibiotic Exposures and Association With Proven Bloodstream Infection

OBJECTIVES

To estimate the percentage of hospital births receiving antibiotics before being discharged from the hospital and efficiency diagnosing proven bloodstream infection.

METHODS

We conducted a cross-sectional study of 326 845 live births in 2017, with a 69% sample of all California births involving 121 California hospitals with a NICU, of which 116 routinely served inborn neonates. Exposure included intravenous or intramuscular antibiotic administered anywhere in the hospital during inpatient stay associated with maternal delivery. The main outcomes were the percent of newborns with antibiotic exposure and counts of exposed newborns per proven bloodstream infection. Units of observation and analysis were the individual hospitals. Correlation analyses included infection rates, surgical case volume, NICU inborn admission rates, and mortality rates.

RESULTS

The percent of newborns with antibiotic exposure varied from 1.6% to 42.5% (mean 8.5%; SD 6.3%; median 7.3%). Across hospitals, 11.4 to 335.7 infants received antibiotics per proven early-onset sepsis case (mean 95.1; SD 71.1; median 69.5), and 2 to 164 infants received antibiotics per proven late-onset sepsis case (mean 19.6; SD 24.0; median 12.2). The percent of newborns with antibiotic exposure correlated neither with proven bloodstream infection nor with the percent of patient-days entailing antibiotic exposure.

CONCLUSIONS

The percent of newborns with antibiotic exposure varies widely and is unexplained by proven bloodstream infection. Identification of sepsis, particularly early onset, often is extremely inefficient. Knowledge of the numbers of newborns receiving antibiotics complements evaluations anchored in days of exposure because these are uncorrelated measures.

Cytomegalovirus Infection among Infants in Neonatal Intensive Care Units, California, 2005 to 2016

AIM

The main purpose of this article is to assess trends in cytomegalovirus (CMV) infection reported among infants in California neonatal intensive care units (NICUs) during 2005 to 2016.

STUDY DESIGN

The California Perinatal Quality Care Collaborative collects data on all very low birth weight (VLBW, birth weight ≤ 1,500 g) and acutely ill infants > 1,500 g, representing 92% of NICUs in California. We compared clinical characteristics and length of hospital stay among infants with and without reported CMV infection (CMV-positive viral culture or polymerase chain reaction).

RESULTS

During 2005 to 2016, CMV infection was reported in 174 VLBW infants and 145 infants > 1,500 g, or 2.7 (range: 1.5-4.7) and 1.2 (range: 0.8-1.7) per 1,000 infants, respectively (no significant annual trend). Among infants > 1,500 g, 12 (8%) versus 4,928 (4%) of those reported with versus without CMV infection died (p < 0.05). The median hospital stay was significantly longer among infants reported with versus without CMV infection for both VLBW infants (98 vs. 46 days) and infants > 1,500 g (61 vs. 14 days) (p < 0.001).

CONCLUSION

Reports of CMV infection remained stable over a 12-year period. Although we were not able to assess whether infection was congenital or postnatal, CMV infection among infants > 1,500 g was associated with increased mortality.

Covariation of Neonatal Intensive Care Unit-Level Patent Ductus Arteriosus Management and In-Neonatal Intensive Care Unit Outcomes Following Preterm Birth

OBJECTIVE

To test the hypothesis that neonatal intensive care unit (NICU)-specific changes in patent ductus arteriosus (PDA) management are associated with changes in local outcomes in preterm infants.

STUDY DESIGN

This retrospective repeated-measures study of aggregated data included infants born 400-1499 g admitted within 2 days of delivery to NICUs participating in the California Perinatal Quality Care Collaborative. The period 2008-2015 was divided into four 2-year epochs. For each epoch and NICU, we calculated proportions of infants receiving cyclooxygenase inhibitor (COXI) or PDA ligation and determined NICU-specific changes in these therapies between consecutive epochs. Generalized estimating equations were used to examine adjusted relationships between NICU-specific changes in PDA management and contemporaneous changes in local outcomes.

RESULTS

We included 642 observations of interepoch change at 119 hospitals summarizing 32 094 infants. NICU-specific changes in COXI use and ligation showed significant dose-response associations with contemporaneous changes in adjusted local outcomes. Each percentage point decrease in NICU-specific proportion treated with either COXI or ligation was associated with a 0.21 percentage point contemporaneous increase in adjusted local in-hospital mortality (95% CI 0.06, 0.33; P = .005) among infants born 400-749 g. In contrast, decreasing NICU-specific ligation rate among infants 1000-1499 g was associated with decreasing adjusted local bronchopulmonary dysplasia (P = .009) and death or bronchopulmonary dysplasia (P = .01).

CONCLUSIONS

NICU-specific outcomes of preterm birth co-vary with local PDA management. Treatment for PDA closure may benefit some infants born 400-749 g. Decreasing NICU-specific rates of COXI use or ligation were not associated with increases in local adjusted rates of examined adverse outcomes in larger preterm infants.

Population-based trends and underlying risk factors for infant respiratory syncytial virus and bronchiolitis hospitalizations

OBJECTIVE

Respiratory syncytial virus (RSV) is a common pathogen during infancy, with the potential to cause serious disease and mortality in high-risk groups. The objective of this study was to characterize trends of RSV and bronchiolitis hospitalizations in the first year in a population-based cohort and assess differences in trends according to risk status.

METHODS

Using an observational retrospective cohort design, we examined a California population-based dataset of vital statistics linked to hospital discharge data for up to 1 year after birth from 1997-2011. Infants were categorized by medical condition and then by gestational age. Medical conditions of interest included chronic lung disease, certain congenital heart diseases, or others known to affect risk for developing severe bronchiolitis. The primary outcome was hospitalization due to RSV; secondary outcome was hospitalization for unspecified bronchiolitis (UB) not coded as RSV. Annual person-year rates were calculated for infants <12 months of age during January to December of each year.

RESULTS

Of 7,298,401 infants born during the study period, 121,230 (1.7%) had a medical condition associated with risk; these infants experienced 6853 RSV and 6568 UB hospitalizations in the first year. In infants without medical conditions, 96,694 RSV and 69,886 UB hospitalizations occurred. All-cause infant hospitalizations declined over time from 12.2 to 9.3 per 100 person-years. RSV hospitalization rates for infants with medical conditions decreased from 7.6 to 3.4 per 100 person-years, with the largest relative decline in infants with chronic lung disease (12.0 to 5.0 per 100 person-years). For infants without medical conditions, RSV hospitalizations declined from 1.4 to 0.8 per 100 person-years, with greater decreases among preterm infants with earlier gestational age. UB hospitalization rates remained relatively stable across the study years, from 6.2 to 5.4 and 1.0 to 0.8 per 100 person-years for infants with and without medical conditions.

CONCLUSIONS

Various interventions may have contributed to observed decreases in RSV hospitalizations from 1998-2011, which were greater in high-risk populations recommended for RSV immunoprophylaxis and not observed with UB. Further efforts to promote evidence-based practice and optimal targeting of appropriate interventions will ensure continued improvement in care for vulnerable infants.

Variations in Neonatal Antibiotic Use

OBJECTIVES

We sought to identify whether and how the NICU antibiotic use rate (AUR), clinical correlates, and practice variation changed between 2013 and 2016 and attempted to identify AUR ranges that are consistent with objectively determined bacterial and/or fungal disease burdens.

METHODS

In a retrospective cohort study of >54 000 neonates annually at >130 California NICUs from 2013 to 2016, we computed nonparametric linear correlation and compared AURs among years using a 2-sample test of proportions. We stratified by level of NICU care and participation in externally organized stewardship efforts.

RESULTS

By 2016, the overall AUR declined 21.9% (95% confidence interval [CI] 21.9%-22.0%), reflecting 42 960 fewer antibiotic days. Among NICUs in externally organized antibiotic stewardship efforts, the AUR declined 28.7% (95% CI 28.6%-28.8%) compared with 16.2% (95% CI 16.1%-16.2%) among others. The intermediate NICU AUR range narrowed, but the distribution of values did not shift toward lower values as it did for other levels of care. The 2016 AUR correlated neither with proven infection nor necrotizing enterocolitis. The 2016 regional NICU AUR correlated with surgical volume (ρ = 0.53; P = .01), mortality rate (ρ = 0.57; P = .004), and average length of stay (ρ = 0.62; P = .002) and was driven by 3 NICUs with the highest AUR values (30%-57%).

CONCLUSIONS

Unexplained antibiotic use has declined but continues. Currently measured clinical correlates generally do not help explain AUR values that are above the lowest quartile cutpoint of 14.4%.

Comparison of Collaborative Versus Single-Site Quality Improvement to Reduce NICU Length of Stay

BACKGROUND

There is unexplained variation in length of stay (LOS) across NICUs, suggesting that there may be practices that can optimize LOS.

METHODS

Three groups of NICUs in the California Perinatal Quality Care Collaborative were followed: (1) collaborative centers participating in an 18-month collaborative quality improvement project to optimize LOS for preterm infants; (2) individual centers aiming to optimize LOS; and (3) nonparticipants. Our aim in the collaborative project was to decrease postmenstrual age (PMA) at discharge for infants born between 27 + 0 and <32 weeks' gestational age by 3 days. A secondary outcome was "early discharge," the proportion of infants discharged from the hospital before 36 + 5 weeks' PMA. The balancing measure of readmissions within 72 hours was tracked for the collaborative group.

RESULTS

From 2013 to 2015, 8917 infants were cared for in 20 collaborative NICUs, 19 individual project NICUs, and 71 nonparticipants. In the collaborative group, the PMA at discharge decreased from 37.8 to 37.5 weeks (P = .02), and early discharge increased from 31.6% to 41.9% (P = .006). The individual project group had no significant change. Nonparticipants had a decrease in PMA from 37.5 to 37.3 weeks (P = .01) but no significant change in early discharge (39.8% to 43.6%; P = .24). There was no significant change in readmissions over time in the collaborative group.

CONCLUSIONS

A structured collaborative project that was focused on optimizing LOS led to a 3-day decrease in LOS and was more effective than individualized quality improvement efforts.

Association Between Neonatal Intensive Care Unit Admission Rates and Illness Acuity

IMPORTANCE

Most neonates admitted to a neonatal intensive care unit (NICU) are born at gestational age (GA) of 34 weeks or more. The degree of uniformity of admission criteria for these infants is unclear, particularly at the low-acuity end of the range of conditions warranting admission.

OBJECTIVES

To describe variation in NICU admission rates for neonates born at GA of 34 weeks or more and examine whether such variation is associated with high illness acuity or designated facility level of care.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional study of 35 921 NICU inborn admissions of GA at 34 weeks or more during calendar year 2015, using a population database of inborn NICU admissions at 130 of the 149 hospitals in California with a NICU. The aggregate service population comprised 358 453 live births. The individual NICU was the unit of observation and analysis. The analysis was stratified by designated facility level of care and correlations with the percentage admissions with high illness acuity were explored. The hypothesis at the outset of the study was that inborn admission rates would correlate positively with the percentage of admissions with high illness acuity.

EXPOSURES

Live birth at GA of 34 weeks or more.

MAIN OUTCOMES AND MEASURES

Inborn NICU admission rate.

RESULTS

Of the total of 358 453 live births at GA of 34 weeks or more, 35 921 infants were admitted to a NICU and accounted for 79.2% of all inborn NICU admissions; 4260 (11.9%) of these admissions met high illness acuity criteria. Inborn admission rates varied 34-fold, from 1.1% to 37.7% of births (median, 9.7%; mean [SD], 10.6% [5.8%]). Percentage with high illness acuity varied 40-fold, from 2.4% to 95% (median, 11.3%; mean, 13.2% [9.9%]). Inborn admission rate correlated inversely with percentage of admissions with high illness acuity (Spearman ρ = -0.3034, P < .001). Among regional NICUs capable of caring for patients with the highest degree of illness and support needs, inborn admission rate did not significantly correlate with percentage of admissions with high illness acuity (Spearman ρ = -0.21, P = .41).

CONCLUSIONS AND RELEVANCE

Percentage of admissions with high illness acuity does not explain 34-fold variation in NICU inborn admission rates for neonates born at GA of 34 weeks or more. The findings are consistent with a supply-sensitive care component and invite future investigation to clarify the lower-acuity end of the range of conditions considered to warrant neonatal intensive care.

Variation in quality report viewing by providers and correlation with NICU quality metrics

BACKGROUND

To examine variation in quality report viewing and assess correlation between provider report viewing and neonatal intensive care unit (NICU) quality.

METHODS

Variation in report viewing sessions for 129 California Perinatal Quality Care Collaborative NICUs was examined. NICUs were stratified into tertiles based on their antenatal steroid (ANS) use and hospital-acquired infection (HAI) rates to compare report viewing session counts.

RESULTS

The number of report viewing sessions initiated by providers varied widely over a 2-year period (median=11; mean=25.5; s.d.=45.19 sessions). Report viewing was not associated with differences in ANS use. Facilities with low HAI rates had less frequent report viewing. Facilities with high report views had significant improvements in HAI rates over time.

CONCLUSIONS

Available audit and feedback reports are utilized inconsistently across California NICUs despite evidence that report viewing is associated with improvements in quality of care delivery. Further studies are needed for reports to reach their theoretical potential.

Effects of delivery room quality improvement on premature infant outcomes

OBJECTIVE

Delivery room management interventions have been successfully implemented via collaborative quality improvement (QI) projects. However, it is unknown whether these successes translate to reductions in neonatal morbidity and mortality.

STUDY DESIGN

This was a prospective pre-post intervention study of three nonrandomized hospital groups within the California Perinatal Quality Care Collaborative. A collaborative QI model (Collaborative QI) was compared with a single-site QI model (NICU QI) and a non-participant population when implementing evidence-based delivery room practices. The intervention period was between June 2011 and May 2012. Infants born with gestational age between 22 weeks 0 days and 29 weeks 6 days and birth weight ⩽1500 g were included. Outcomes were mortality and select morbidities (bronchopulmonary dysplasia (BPD), intraventricular hemorrhage (IVH), retinopathy of prematurity (ROP) and necrotizing enterocolitis (NEC)). Outcomes were compared between the baseline (January 2010 to May 2011) and post-intervention period (June 2012 to May 2013) within each comparison group.

RESULTS

Ninety-five hospitals were included with 4222 infants in the baseline period and 4186 infants in the post-intervention period. The Collaborative QI group had significantly reduced odds of developing BPD post-intervention (odds ratio (OR) 0.8, 95% confidence interval (CI) 0.65 to 0.99) or composite BPD-death (OR 0.83, 95% CI 0.69 to 1.00). In both the Collaborative QI and non-participants there were also reductions in IVH, severe IVH, composite severe IVH-death, severe ROP and composite severe ROP-death.

CONCLUSION

Hospitals dedicated to improving delivery room practices can impact neonatal outcomes.

Implementing Delivery Room Checklists and Communication Standards in a Multi-Neonatal ICU Quality Improvement Collaborative

BACKGROUND

The 2015 American Academy of Pediatrics Neonatal Resuscitation Program (NRP) and International Liaison Committee on Resuscitation (ILCOR) resuscitation guidelines state, "It is still suggested that briefing and debriefing techniques be used whenever possible for neonatal resuscitation." Effective communication and reliable delivery of evidence-based best practices are critical aspects of the 2015 NRP guidelines. To promote optimal communication and best practice-focused checklists use during active neonatal resuscitation, the Readiness Bundle (RB) was integrated within the larger change package deployed in the California Perinatal Quality Care Collaborative's (CPQCC) 12-month Delivery Room Management Quality Improvement Collaborative.

METHODS

The RB consisted of (1) a checklist for high-risk neonatal resuscitations and (2) briefings and debriefings to improve teamwork and communication in the delivery room (DR). Implementation of the RB was encouraged, compliance with the RB was tracked monthly up through 6 months after the completion of the collaborative, and satisfaction with the RB was evaluated.

RESULTS

Twenty-four neonatal intensive care units (NICUs) participated in the CPQCCDR collaborative. Before the initiation of the collaborative, the elements of the RB were complied with in 0 of 740 reported deliveries (0%). During the 12-month collaborative, compliance with the RB improved to a median of 71%, which was surpassed in the 6-month period after the collaborative ended (80%). One-hundred percent of responding NICUs would recommend the RB to other NICUs working on improving DR management.

CONCLUSIONS

The RB was rapidly adopted, with compliance sustained for 6 months after completion of the collaborative. Inclusion of the RB in the next generation of the NRP guidelines is encouraged.

Estimating Length of Stay by Patient Type in the Neonatal Intensive Care Unit

Objective Develop length of stay prediction models for neonatal intensive care unit patients. Study Design We used data from 2008 to 2010 to construct length of stay models for neonates admitted within 1 day of age to neonatal intensive care units and surviving to discharge home. Results Our sample included 23,551 patients. Median length of stay was 79 days when birth weight was < 1,000 g, 46 days for 1,000 to 1,500 g, 21 days for 1,500 to 2,500 g, and 8 days for ≥2,500 g. Risk factors for longer length of stay varied by weight. Units with shorter length of stay for one weight group had shorter lengths of stay for other groups. Conclusion Risk models for comparative assessments of length of stay need to appropriately account for weight, particularly considering the cutoff of 1,500 g. Refining prediction may benefit counseling of families and health care systems to efficiently allocate resources.

Neonatal intensive care unit antibiotic use

BACKGROUND AND OBJECTIVES

Treatment of suspected infection is a mainstay of the daily work in the NICU. We hypothesized that NICU antibiotic prescribing practice variation correlates with rates of proven infection, necrotizing enterocolitis (NEC), mortality, inborn admission, and with NICU surgical volume and average length of stay.

METHODS

In a retrospective cohort study of 52,061 infants in 127 NICUs across California during 2013, we compared sample means and explored linear and nonparametric correlations, stratified by NICU level of care and lowest/highest antibiotic use rate quartiles.

RESULTS

Overall antibiotic use varied 40-fold, from 2.4% to 97.1% of patient-days; median = 24.5%. At all levels of care, it was independent of proven infection, NEC, surgical volume, or mortality. Fifty percent of intermediate level NICUs were in the highest antibiotic use quartile, yet most of these units reported infection rates of zero. Regional NICUs in the highest antibiotic quartile reported inborn admission rate 218% higher (0.24 vs 0.11, P = .03), and length of stay 35% longer (90.2 days vs 66.9 days, P = .03) than regional NICUs in the lowest quartile.

CONCLUSIONS

Forty-fold variation in NICU antibiotic prescribing practice across 127 NICUs with similar burdens of proven infection, NEC, surgical volume, and mortality indicates that a considerable portion of antibiotic use lacks clear warrant; in some NICUs, antibiotics are overused. Additional study is needed to establish appropriate use ranges and elucidate the determinants and directionality of relationships between antibiotic and other resource use.

Implementation methods for delivery room management: a quality improvement comparison study

BACKGROUND

There is little evidence to compare the effectiveness of large collaborative quality improvement versus individual local projects.

METHODS

This was a prospective pre-post intervention study of neonatal resuscitation practice, comparing 3 groups of nonrandomized hospitals in the California Perinatal Quality Care Collaborative: (1) collaborative, hospitals working together through face-to-face meetings, webcasts, electronic mailing list, and data sharing; (2) individual, hospitals working independently; and (3) nonparticipant hospitals. The collaborative and individual arms participated in improvement activities, focusing on reducing hypothermia and invasive ventilatory support.

RESULTS

There were 20 collaborative, 31 individual, and 44 nonparticipant hospitals caring for 12,528 eligible infants. Each group had reduced hypothermia from baseline to postintervention. The collaborative group had the most significant decrease in hypothermia, from 39% to 21%, compared with individual hospital efforts of 38% to 33%, and nonparticipants of 42% to 34%. After risk adjustment, the collaborative group had twice the magnitude of decrease in rates of newborns with hypothermia compared with the other groups. Collaborative improvement also led to greater decreases in delivery room intubation (53% to 40%) and surfactant administration (37% to 20%).

CONCLUSIONS

Collaborative efforts resulted in larger improvements in delivery room outcomes and processes than individual efforts or nonparticipation. These findings have implications for planning quality improvement projects for implementation of evidence-based practices.

Cytomegalovirus infection among infants in California neonatal intensive care units, 2005-2010

AIM

To assess the burden of congenital and perinatal cytomegalovirus (CMV) disease among infants hospitalized in neonatal intensive care units (NICUs).

METHODS

CMV infection was defined as a report of positive CMV viral culture or polymerase chain reaction at any time since birth in an infant hospitalized in a NICU reporting to California Perinatal Quality Care Collaborative during 2005-2010.

RESULTS

One hundred and fifty-six (1.7 per 1000) infants were reported with CMV infection, representing an estimated 5% of the expected number of live births with symptomatic CMV disease. Prevalence was higher among infants with younger gestational ages and lower birth weights. Infants with CMV infection had significantly longer hospital stays and 14 (9%) died.

CONCLUSIONS

Reported prevalence of CMV infection in NICUs represents a fraction of total expected disease burden from CMV in the newborn period, likely resulting from underdiagnosis and milder symptomatic cases that do not require NICU care. More complete ascertainment of infants with congenital CMV infection that would benefit from antiviral treatment may reduce the burden of CMV disease in this population.

Accounting for variation in length of NICU stay for extremely low birth weight infants

OBJECTIVE

To develop a length of stay (LOS) model for extremely low birth weight (ELBW) infants.

STUDY DESIGN

We included infants from the California Perinatal Quality Care Collaborative with birth weight 401 to 1000 g who were discharged to home. Exclusion criteria were congenital anomalies, surgery and death. LOS was defined as days from admission to discharge. As patients who died or were transferred to lower level of care were excluded, we assessed correlation of hospital mortality rates and transfers to risk-adjusted LOS.

RESULTS

There were 2012 infants with median LOS 79 days (range 23 to 219). Lower birth weight, lack of antenatal steroids and lower Apgar score were associated with longer LOS. There was negligible correlation between risk-adjusted LOS and hospital mortality rates (r=0.0207) and transfer-out rates (r=0.121).

CONCLUSION

Particularly because ELBW infants have extended hospital stays, identification of unbiased and informative risk-adjusted LOS for these infants is an important step in benchmarking best practice and improving efficiency in care.

Dual manganese-enhanced and delayed gadolinium-enhanced MRI detects myocardial border zone injury in a pig ischemia-reperfusion model

BACKGROUND

Gadolinium (Gd)-based delayed-enhancement MRI (DEMRI) identifies nonviable myocardium but is nonspecific and may overestimate nonviable territory. Manganese (Mn(2+))-enhanced MRI (MEMRI) denotes specific Mn(2+) uptake into viable cardiomyocytes. We performed a dual-contrast myocardial assessment in a porcine ischemia-reperfusion (IR) model to test the hypothesis that combined DEMRI and MEMRI identifies viable infarct border zone (BZ) myocardium in vivo.

METHODS AND RESULTS

Sixty-minute left anterior descending coronary artery IR injury was induced in 13 adult swine. Twenty-one days post-IR, 3-T cardiac MRI was performed. MEMRI was obtained after injection of 0.7 mL/kg Mn(2+) contrast agent. DEMRI was then acquired after injection of 0.2 mmol/kg Gd. Left ventricular (LV) mass, infarct, and function were analyzed. Subtraction of MEMRI defect from DEMRI signal identified injured BZ myocardium. Explanted hearts were analyzed by 2,3,5-triphenyltetrazolium chloride stain and tissue electron microscopy to compare infarct, BZ, and remote myocardium. Average LV ejection fraction was reduced (30±7%). MEMRI and DEMRI infarct volumes correlated with 2,3,5-triphenyltetrazolium chloride stain analysis (MEMRI, r=0.78; DEMRI, r=0.75; P<0.004). MEMRI infarct volume percentage was significantly lower than that of DEMRI (14±4% versus 23±4%; P<0.05). BZ MEMRI signal-to-noise ratio (SNR) was intermediate to remote and core infarct SNR (7.5±2.8 versus 13.2±3.4 and 2.9±1.6; P<0.0001), and DEMRI BZ SNR tended to be intermediate to remote and core infarct SNR (8.4±5.4 versus 3.3±0.6 and 14.3±6.6; P>0.05). Tissue electron microscopy analysis exhibited preserved cell structure in BZ cardiomyocytes despite transmural DEMRI enhancement.

CONCLUSIONS

The dual-contrast MEMRI-DEMRI detects BZ viability within DEMRI infarct zones. This approach may identify injured, at-risk myocardium in ischemic cardiomyopathy.

Quantitative tissue characterization of infarct core and border zone in patients with ischemic cardiomyopathy by magnetic resonance is associated with future cardiovascular events

OBJECTIVES

This study evaluates how characterization of tissue heterogeneity of myocardial infarction by cardiovascular magnetic resonance (CMR) is associated with cardiovascular events (CVE) in patients with ischemic cardiomyopathy (ICM).

BACKGROUND

Prior studies demonstrated that the quantification of myocardial scar volume by CMR is superior to left ventricular end-diastolic volume, left ventricular end-systolic volume, and left ventricular ejection fraction (LVEF) in predicting future CVE in ICM patients. Evaluation of infarct heterogeneity by measuring infarct core and border zones through CMR might have a higher association with CVE.

METHODS

Seventy patients (mean LVEF: 25 +/- 11%) considered for revascularization or medical management +/- implantable cardiac defibrillator were enrolled. A 1.5-T GE MRI (Signa, GE Healthcare, Milwaukee, Wisconsin) was used to acquire cine and delayed enhancement images. The patients' core and border zones of infarcted myocardium were analyzed and followed for CVE.

RESULTS

Larger infarct border zone and its percentage of myocardium were found in the 29 patients (41%) who had CVE (median 13.3 g [interquartile range (IQR) 8.4 to 25.1 g] vs. 8.0 g [IQR 3.0 to 14.5 g], p = 0.02 and 7.8% [IQR 4.9% to 17.0%] vs. 4.1% [IQR 1.9% to 9.3%], p = 0.02, respectively). The core infarct zone and its percentage of myocardium, left ventricular end-diastolic volume, left ventricular end-systolic volume, and LVEF were not statistically significant. Sub-analysis of the medical management and revascularization patients with CVE demonstrated that the medically managed patients had a larger border zone, whereas there was no difference between border and core zones in the revascularization group (p < 0.05).

CONCLUSIONS

Quantification of core and border zones and their percentages of myocardium through CMR is associated with future CVE and might assist in the management of patients with ICM.

The Electrophysiology of Electric Organs of Marine Electric Fishes : I. Properties of electroplaques of Torpedo nobiliana

Single electroplaques of Torpedo nobiliana have been studied with microelectrode recording. Direct evidence is presented that the only electrogenically reactive membrane of the cells is on the innervated surface and that this membrane is electrically inexcitable. Responses are not evoked by depolarizing currents applied to this membrane, but only by stimulating the innervating nerve fibers. The responses arise after a latency of 1 to 3 msec. This latency is not affected by large depolarizing or hyperpolarizing changes in membrane potential. Various properties that have been theoretically associated with electrically inexcitable responses have been also demonstrated to occur in the electroplaques. The neurally evoked response is not propagated actively in the membrane and may have different amplitudes and forms in closely adjacent regions. The maximal responses frequently are slightly larger than the recorded resting potential but the apparent small overshoot may be due to difficulty in recording the full resting potential. The responses are subject to electrochemical gradation and appear inverted in sign on applying strong outward currents across the innervated membrane. This membrane is cholinoceptive and shows marked desensitization. The membrane of the uninnervated surface has a very low resistance, a factor that aids maximum output of current during the discharge of the electric organ.

The Electrophysiology of Electric Organs of Marine Electric Fishes : III. The electroplaques of the stargazer, Astroscopus y-graecum

The electroplaques of Astroscopus y-graecum were studied in situ with microelectrode recordings. Despite the distant taxonomic relations and the different origins of the organs, their properties in the teleost and torpedine marine electric fishes are remarkably similar. Only the innervated membrane (the dorsal) is electrogenically reactive in Astroscopus, and it, too, does not respond to electrical stimuli. As in the torpedine fishes, the uninnervated membrane of the electroplaques offers a very low resistance to the discharge of the innervated membrane. Additional direct evidence for electrical inexcitability of the reactive surface was obtained by denervating one of the bilateral organs. The denervated one did not respond to strong electrical stimuli which evoked responses in the opposite, innervated organ. The denervated electroplaques had a normal resting potential and were depolarized by acetylcholine and carbamylcholine similarly to normal cells. Other properties related to electrical inexcitability were also demonstrated. A pharmacological finding of considerable theoretical significance is that desensitization occurred on depolarizing cells with acetylcholine but was absent on depolarizing them with carbamylcholine.

The Electrophysiology of Electric Organs of Marine Electric Fishes : II. The electroplaques of main and acccessory organs of Narcine brasiliensis

Studies on the electric organs of Narcine brasiliensis and particularly of the responses of the electroplaques of the accessory organ confirm and amplify data obtained on the electroplaques of Torpedo nobiliana. Only the innervated surface is electrogenically reactive and the uninnervated surface has a low resistance, as in Torpedo electroplaques. However, in the accessory organ of Narcine the innervated surface is the dorsal, rather than the ventral, and it has a different pattern of innervation. The responses of single cells of the accessory organ exhibit marked facilitation on repetitive stimulation. The facilitated responses, like the individual responses of Torpedo and of the main organ of Narcine, are electrochemically graded on changing the membrane potential with applied currents, and are inverted in sign when outward currents through the innervated face are very strong.

Global ischemia-induced increases in the gap junctional proteins connexin 32 (Cx32) and Cx36 in hippocampus and enhanced vulnerability of Cx32 knock-out mice

Gap junctions are conductive channels that connect the interiors of coupled cells. In the hippocampus, GABA-containing hippocampal interneurons are interconnected by gap junctions, which mediate electrical coupling and synchronous firing and thereby promote inhibitory transmission. The present study was undertaken to examine the hypothesis that the gap junctional proteins connexin 32 (Cx32; expressed by oligodendrocytes, interneurons, or both), Cx36 (expressed by interneurons), and Cx43 (expressed by astrocytes) play a role in defining cell-specific patterns of neuronal death in hippocampus after global ischemia in mice. Global ischemia did not significantly alter Cx32 and Cx36 mRNA expression and slightly increased Cx43 mRNA expression in the vulnerable CA1, as assessed by Northern blot analysis and in situ hybridization. Global ischemia induced a selective increase in Cx32 and Cx36 but not Cx43 protein abundance in CA1 before onset of neuronal death, as assessed by Western blot analysis. The increase in Cx32 and Cx36 expression was intense and specific to parvalbumin-positive inhibitory interneurons of CA1, as assessed by double immunofluorescence. Protein abundance was unchanged in CA3 and dentate gyrus. The finding of increase in connexin protein without increase in mRNA suggests regulation of Cx32 and Cx36 expression at the translational or post-translational level. Cx32(Y/-) null mice exhibited enhanced vulnerability to brief ischemic insults, consistent with a role for Cx32 gap junctions in neuronal survival. These findings suggest that Cx32 and Cx36 gap junctions may contribute to the survival and resistance of GABAergic interneurons, thereby defining cell-specific patterns of global ischemia-induced neuronal death.

Expanded Prussian blue analogues incorporating [Re6Se8(CN)6](3-/4-) clusters: adjusting porosity via charge balance

Face-capped octahedral [Re(6)Se(8)(CN)(6)](3-/4-) clusters are used in place of octahedral [M(CN)(6)](3-/4-) complexes for the synthesis of microporous Prussian blue type solids with adjustable porosity. The reaction between [Fe(H(2)O)(6)](3+) and [Re(6)Se(8)(CN)(6)](4-) in aqueous solution yields, upon heating, Fe(4)[Re(6)Se(8)(CN)(6)](3).36H(2)O (4). A single-crystal X-ray analysis confirms the structure of 4 to be a direct expansion of Prussian blue (Fe(4)[Fe(CN)(6)](3).14H(2)O), with [Re(6)Se(8)(CN)(6)](4-) clusters connected through octahedral Fe(3+) ions in a cubic three-dimensional framework. As in Prussian blue, one out of every four hexacyanide units is missing from the structure, creating sizable, water-filled cavities within the neutral framework. Oxidation of (Bu(4)N)(4)[Re(6)Se(8)(CN)(6)] (1) with iodine in methanol produces (Bu(4)N)(3)[Re(6)Se(8)(CN)(6)] (2), which is then metathesized to give the water-soluble salt Na(3)[Re(6)Se(8)(CN)(6)] (3). Reaction of [Co(H(2)O)(6)](2+) or [Ni(H(2)O)(6)](2+) with 3 in aqueous solution affords Co(3)[Re(6)Se(8)(CN)(6)](2).25H(2)O (5) or Ni(3)[Re(6)Se(8)(CN)(6)](2).33H(2)O (6). Powder X-ray diffraction data show these compounds to adopt structures based on the same cubic framework present in 4, but with one out of every three cluster hexacyanide units missing as a consequence of charge balance. In contrast, reaction of [Ga(H(2)O)(6)](3+) with 3 gives Ga[Re(6)Se(8)(CN)(6)].6H(2)O (7), wherein charge balance dictates a fully occupied cubic framework enclosing much smaller cavities. The expanded Prussian blue analogues 4-7 can be fully dehydrated, and retain their crystallinity with extended heating at 250 degrees C. Consistent with the trend in the frequency of framework vacancies, dinitrogen sorption isotherms show porosity to increase along the series of representative compounds 7, Ga(4)[Re(6)Se(8)(CN)(6)](3).38H(2)O, and 6. Furthermore, all of these phases display a significantly higher sorption capacity and surface area than observed in dehydrated Prussian blue. Despite incorporating paramagnetic [Re(6)Se(8)(CN)(6)](3-) clusters, no evidence for magnetic ordering in compound 6 is apparent at temperatures down to 5 K. Reactions related to those employed in preparing compounds 4-6, but carried out at lower pH, produce the isostructural phases H[cis-M(H(2)O)(2)][Re(6)Se(8)(CN)(6)].2H(2)O (M = Fe (8), Co (9), Ni (10)). The crystal structure of 8 reveals a densely packed three-dimensional framework in which [Re(6)Se(8)(CN)(6)](4-) clusters are interlinked through a combination of protons and Fe(3+) ions.

Activation of metabotropic glutamate receptor 1 accelerates NMDA receptor trafficking

Regulation of neuronal NMDA receptors (NMDARs) by group I metabotropic glutamate receptors (mGluRs) is known to play a critical role in synaptic transmission. The molecular mechanisms underlying mGluR1-mediated potentiation of NMDARs are as yet unclear. The present study shows that in Xenopus oocytes expressing recombinant receptors, activation of mGluR1 potentiates NMDA channel activity by recruitment of new channels to the plasma membrane via regulated exocytosis. Activation of mGluR1alpha induced (1) an increase in channel number times channel open probability, with no change in mean open time, unitary conductance, or reversal potential; (2) an increase in charge transfer in the presence of NMDA and the open channel blocker MK-801, indicating an increased number of functional NMDARs in the cell membrane; and (3) increased NR1 surface expression, as indicated by cell surface Western blots and immunofluorescence. Botulinum neurotoxin A or expression of a dominant negative mutant of synaptosomal associated protein of 25 kDa molelcular mass (SNAP-25) greatly reduced mGluR1alpha-mediated potentiation, indicating that receptor trafficking occurs via a SNAP-25-mediated form of soluble N-ethylmaleimide sensitive fusion protein attachment protein receptor-dependent exocytosis. Because group I mGluRs are localized to the perisynaptic region in juxtaposition to synaptic NMDARs at glutamatergic synapses in the hippocampus, mGluR-mediated insertion of NMDARs may play a role in synaptic transmission and plasticity, including long-term potentiation.

mGluR1-mediated potentiation of NMDA receptors involves a rise in intracellular calcium and activation of protein kinase C

Potentiation of ionotropic glutamate receptor activity by metabotropic glutamate receptors (mGluRs) is thought to modulate activity at glutamatergic synapses in the hippocampus. However, the precise pathway by which this modulation occurs is not well understood. The present study tests the hypothesis that mGluR1-mediated potentiation of N-methyl-D-aspartate receptors (NMDARs) occurs via a phospholipase C (PLC)-initiated cascade. NMDAR functional activity was examined by whole-cell recording from Xenopus oocytes expressing recombinant NMDARs and mGluR1alpha. The mGluR1 agonist (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylic acid (ACPD) significantly potentiated NMDA-elicited currents. mGluR1alpha-mediated potentiation of NMDA responses was eliminated by the PLC inhibitor U-73122. Buffering of intracellular Ca2+ by BAPTA-AM or depletion of intracellular Ca2+ by the Ca2+/ATPase inhibitor thapsigargin greatly reduced ACPD potentiation. ACPD potentiation was reduced by the specific protein kinase C (PKC) inhibitor Ro-32-0432 and eliminated by the broad spectrum kinase inhibitor staurosporine. ACPD produced no further potentiation after potentiation of NMDARs by the PKC-activating phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA). Thus, Group I mGluRs potentiate NMDA responses via activation of PLC; at least part of the potentiation is due to rise in intracellular Ca2+ and stimulation of PKC. Cytochalasin D, which disrupts the actin cytoskeleton, blocked ACPD-elicited chloride currents and ACPD-induced potentiation of NMDAR currents, consistent with a role for cytoskeletal protein(s) in the signaling pathway. As Group I mGluRs are localized to the perisynaptic region in juxtaposition to NMDARs at glutamatergic synapses, mGluR-mediated potentiation of NMDAR activity may play a role in synaptic transmission and plasticity including LTP.

Gating properties of gap junction channels assembled from connexin43 and connexin43 fused with green fluorescent protein

We used cell lines expressing wild-type connexin43 (Cx43) and Cx43 fused with enhanced green fluorescent protein (Cx43-EGFP) to examine mechanisms of gap junction channel gating. Previously it was suggested that each hemichannel in a cell-cell channel possesses two gates, a fast gate that closes channels to a nonzero conductance or residual state via fast (< approximately 2 ms) transitions and a slow gate that fully closes channels via slow transitions (> approximately 10 ms). Here we demonstrate that transjunctional voltage (V(j)) regulates both gates and that they are operating in series and in a contingent manner in which the state of one gate affects gating of the other. Cx43-EGFP channels lack fast V(j) gating to a residual state but show slow V(j) gating. Both Cx43 and Cx43-EGFP channels exhibit slow gating by chemical uncouplers such as CO(2) and alkanols. Chemical uncouplers do not induce obvious changes in Cx43-EGFP junctional plaques, indicating that uncoupling is not caused by dispersion or internalization of junctional plaques. Similarity of gating transitions during chemical gating and slow V(j) gating suggests that both gating mechanisms share common structural elements. Cx43/Cx43-EGFP heterotypic channels showed asymmetrical V(j) gating with fast transitions between open and residual states only when the Cx43 side was relatively negative. This result indicates that the fast V(j) gate of Cx43 hemichannels closes for relative negativity at its cytoplasmic end.

Functional alterations in gap junction channels formed by mutant forms of connexin 32: evidence for loss of function as a pathogenic mechanism in the X-linked form of Charcot-Marie-Tooth disease

CMTX, the X-linked form of Charcot-Marie-Tooth disease, is an inherited peripheral neuropathy arising in patients with mutations in the gene encoding the gap junction protein connexin 32 (Cx32). In this communication, we describe the expression levels and biophysical parameters of seven mutant forms of Cx32 associated with CMTX, when expressed in paired Xenopus oocytes. Paired oocytes expressing the R15Q and H94Q mutants show junctional conductances not statistically different from that determined for Cx32WT, though both show a trend toward reduced levels. The S85C and G12S mutants induce reduced levels of junctional conductance. Three other mutants (R15W, H94Y and V139M) induce no conductance above baseline when expressed in paired oocytes. Analysis of the conductance voltage relations for these mutants shows that the reduced levels of conductance are entirely (H94Y and V139M) or partly (S85C and R15W) explicable by a reduced open probability of the mutant hemichannels. The R15Q and H94Q mutations also show alterations in the conductance voltage relations that would be expected to minimally (H94Q) or moderately (R15Q) reduce the available gap junction communication pathway. The reduction in G12S induced conductance cannot be explained by alterations in hemichannel open probability and are more likely due to reduced junction formation. These results demonstrate that many CMTX mutations lead to loss of function of Cx32. For these mutations, the loss of function model is likely to explain the pathogenesis of CMTX.

Protein kinase C modulates NMDA receptor trafficking and gating

Regulation of neuronal N-methyl-D-aspartate receptors (NMDARs) by protein kinases is critical in synaptic transmission. However, the molecular mechanisms underlying protein kinase C (PKC) potentiation of NMDARs are uncertain. Here we demonstrate that PKC increases NMDA channel opening rate and delivers new NMDA channels to the plasma membrane through regulated exocytosis. PKC induced a rapid delivery of functional NMDARs to the cell surface and increased surface NR1 immunofluorescence in Xenopus oocytes expressing NMDARs. PKC potentiation was inhibited by botulinum neurotoxin A and a dominant negative mutant of soluble NSF-associated protein (SNAP-25), suggesting that receptor trafficking occurs via SNARE-dependent exocytosis. In neurons, PKC induced a rapid delivery of functional NMDARs, assessed by electrophysiology, and an increase in NMDAR clusters on the surface of dendrites and dendritic spines, as indicated by immunofluorescence. Thus, PKC regulates NMDAR channel gating and trafficking in recombinant systems and in neurons, mechanisms that may be relevant to synaptic plasticity.

Microglia at brain stab wounds express connexin 43 and in vitro form functional gap junctions after treatment with interferon-gamma and tumor necrosis factor-alpha

Gap junctional communication between microglia was investigated at rat brain stab wounds and in primary cultures of rat and mouse cells. Under resting conditions, rat microglia (FITC-isolectin-B4-reactive cells) were sparsely distributed in the neocortex, and most (95%) were not immunoreactive for Cx43, a gap junction protein subunit. At brain stab wounds, microglia progressively accumulated over several days and formed aggregates that frequently showed Cx43 immunoreactivity at interfaces between cells. In primary culture, microglia showed low levels of Cx43 determined by Western blotting, diffuse intracellular Cx43 immunoreactivity, and a low incidence of dye coupling. Treatment with the immunostimulant bacterial lipopolysaccharide (LPS) or the cytokines interferon-gamma (INF-gamma) or tumor necrosis factor-alpha (TNF-alpha) one at a time did not increase the incidence of dye coupling. However, microglia treated with INF-gamma plus LPS showed a dramatic increase in dye coupling that was prevented by coapplication of an anti-TNF-alpha antibody, suggesting the release and autocrine action of TNF-alpha. Treatment with INF-gamma plus TNF-alpha also greatly increased the incidence of dye coupling and the Cx43 levels with translocation of Cx43 to cell-cell contacts. The cytokine-induced dye coupling was reversibly inhibited by 18 alpha-glycyrrhetinic acid, a gap junction blocker. Cultured mouse microglia also expressed Cx43 and developed dye coupling upon treatment with cytokines, but microglia from homozygous Cx43-deficient mice did not develop significant dye coupling after treatment with either INF-gamma plus LPS or INF-gamma plus TNF-alpha. This report demonstrates that microglia can communicate with each other through gap junctions that are induced by inflammatory cytokines, a process that may be important in the elaboration of the inflammatory response.

Insulin promotes rapid delivery of N-methyl-D- aspartate receptors to the cell surface by exocytosis

Insulin potentiates N-methyl-d-aspartate receptors (NMDARs) in neurons and Xenopus oocytes expressing recombinant NMDARs. The present study shows that insulin induced (i) an increase in channel number times open probability (nP(o)) in outside-out patches excised from Xenopus oocytes, with no change in mean open time, unitary conductance, or reversal potential, indicating an increase in n and/or P(o); (ii) an increase in charge transfer during block of NMDA-elicited currents by the open channel blocker MK-801, indicating increased number of functional NMDARs in the cell membrane with no change in P(o); and (iii) increased NR1 surface expression, as indicated by Western blot analysis of surface proteins. Botulinum neurotoxin A greatly reduced insulin potentiation, indicating that insertion of new receptors occurs via SNARE-dependent exocytosis. Thus, insulin potentiation occurs via delivery of new channels to the plasma membrane. NMDARs assembled from mutant subunits lacking all known sites of tyrosine and serine/threonine phosphorylation in their carboxyl-terminal tails exhibited robust insulin potentiation, suggesting that insulin potentiation does not require direct phosphorylation of NMDAR subunits. Because insulin and insulin receptors are localized to glutamatergic synapses in the hippocampus, insulin-regulated trafficking of NMDARs may play a role in synaptic transmission and plasticity, including long-term potentiation.

Molecular determinants of membrane potential dependence in vertebrate gap junction channels

The conductance, g(j), of many gap junctions depends on voltage between the coupled cells (transjunctional voltage, V(j)) with little effect of the absolute membrane potential (V(m)) in the two cells; others show combined V(j) and V(m) dependence. We examined the molecular determinants of V(m) dependence by using rat connexin 43 expressed in paired Xenopus oocytes. These junctions have, in addition to V(j) dependence, V(m) dependence such that equal depolarization of both cells decreases g(j). The dependence of g(j) on V(m) was abolished by truncation of the C-terminal domain (CT) at residue 242 but not at 257. There are two charged residues between 242 and 257. In full-length Cx43, mutations neutralizing either one of these charges, Arg243Gln and Asp245Gln, decreased and increased V(m) dependence, respectively, suggesting that these residues are part of the V(m) sensor. Mutating both residues together abolished V(m) dependence, although there is no net change in charge. The neutralizing mutations, together or separately, had no effect on V(j) dependence. Thus, the voltage sensors must differ. However, V(j) gating was somewhat modulated by V(m), and V(m) gating was reduced when the V(j) gate was closed. These data suggest that the two forms of voltage dependence are mediated by separate but interacting domains.

The AMPAR subunit GluR2: still front and center-stage

Abnormal influx of Ca(2+) through AMPA-type glutamate receptors (AMPARs) is thought to contribute to the neuronal death associated with a number of brain disorders. AMPARs exist as both Ca(2+)-impermeable and Ca(2+)-permeable channels. AMPARs are encoded by four genes designated GluR1 (GluR-A) through GluR4 (GluR-D). The presence of the GluR2 subunit renders heteromeric AMPA receptor assemblies Ca(2+)-impermeable. Molecular diversity of AMPARs under physiological and pathological conditions is generated by differential spatio-temporal patterns of GluR expression, by alternative RNA splicing and editing and by targeting and trafficking of receptor subunits at dendritic spines. The GluR2 gene is under transcriptional control by the RE1 element specific transcription factor, a gene silencing factor which renders it neuron-specific. GluR2 transcripts are edited by ADAR2 (double-stranded RNA-specific editase 1). AMPAR targeting and trafficking to spines are regulated by synaptic activity and are critical to synaptic plasticity. Recent studies involving animal models of transient forebrain ischemia and epilepsy show that GluR2 mRNA and GluR2 subunit expression are downregulated in vulnerable neurons prior to cell death. Ca(2+) imaging and electrical recording from individual pyramidal neurons in hippocampal slices reveal changes in AMPAR functional properties after ischemia. In slices from post-ischemia animals, CA1 neurons with robust action potentials exhibit greatly enhanced AMPA-elicited rises in intracellular Ca(2+). Excitatory postsynaptic currents in post-ischemic CA1 exhibit an enhanced Ca(2+)-dependent component that appears to be mediated by Ca(2+)-permeable AMPARs. These studies provide evidence for Ca(2+) influx through AMPARs in neurons destined to die. To examine whether acute GluR2 downregulation, even in the absence of a neurological insult, can induce neuronal death, we performed knockdown experiments in rats and gerbils with antisense oligonucleotides targeted to GluR2 mRNA. GluR2 antisense oligonucleotide induced neuronal cell death of pyramidal neurons and enhanced pathogenicity of brief ischemic episodes. These observations provide evidence for Ca(2+) influx through AMPARs in neurons destined to die and implicate Ca(2+)-permeable AMPARs in the pathogenesis of ischemia-induced neuronal death.

Remodeling of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor subunit composition in hippocampal neurons after global ischemia

Transient global ischemia induces selective delayed cell death, primarily of principal neurons in the hippocampal CA1. However, the molecular mechanisms underlying ischemia-induced cell death are as yet unclear. The present study shows that global ischemia triggers a pronounced and cell-specific reduction in GluR2 [the subunit that limits Ca(2+) permeability of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors] in vulnerable CA1 neurons, as evidenced by immunofluorescence of brain sections and Western blot analysis of microdissected hippocampal subfields. At 72 h after ischemia (a time before cell death), virtually all CA1 pyramidal neurons exhibited greatly reduced GluR2 immunolabeling throughout their somata and dendritic processes. GluR2 immunolabeling was unchanged in pyramidal cells of the CA3 and granule cells of the dentate gyrus, regions resistant to ischemia-induced damage. Immunolabeling of the AMPA receptor subunit GluR1 was unchanged in CA1, CA3, and dentate gyrus. Western analysis indicated that GluR2 subunit abundance was markedly reduced in CA1 at 60 and 72 h after the ischemic insult; GluR1 abundance was unchanged in all subfields at all times examined. These findings, together with the previous observation of enhanced AMPA-elicited Ca(2+) influx in postischemic CA1 neurons, show that functional GluR2-lacking, Ca(2+)-permeable AMPA receptors are expressed in vulnerable neurons before cell death. Thus, the present study provides an important link in the postulated causal chain between global ischemia and delayed death of CA1 pyramidal neurons.

Connexin43 null mice reveal that astrocytes express multiple connexins

The gap junction protein connexin43 (Cx43) is the primary component of intercellular channels in cardiac tissue and in astrocytes, the most abundant type of glial cells in the brain. Mice in which the gene for Cx43 is deleted by homologous recombination die at birth, due to profound hypertrophy of the ventricular outflow tract and stenosis of the pulmonary artery. Despite this significant cardiovascular abnormality, brains of connexin43 null [Cx43 (-/-)] animals are shown to be macroscopically normal and to display a pattern of cortical lamination that is not detectably different from wildtype siblings. Presence of Cx40 and Cx45 in brains and astrocytes cultured from both Cx43 (-/-) mice and wildtype littermates was confirmed by RT-PCR, Northern blot analyses and by immunostaining; Cx46 was detected by RT-PCR and Northern blot analyses. Presence of Cx26 in astrocyte cultures was indicated by RT-PCR and by Western blot analysis, although we were unable to resolve whether it was contributed by contaminating cells; Cx30 mRNA was detected by Northern blot in long term (2 weeks) but not fresh cultures of astrocytes. These studies thus reveal that astrocyte gap junctions may be formed of multiple connexins. Presumably, the metabolic and ionic coupling provided by these diverse gap junction types may functionally compensate for the absence of the major astrocyte gap junction protein in Cx43 (-/-) mice, providing whatever intercellular signaling is necessary for brain development and cortical lamination.

Electrical synapses, a personal perspective (or history)

Gap junctions are the morphological substrate of one class of electrical synapse. This memoir records the author's involvement in the development of our knowledge of the physiology and ultrastructure of electrical synapses. The answer to whether neurotransmission is electrical or chemical is either. One lesson is that Occam's razor sometimes cut too deep; the nervous system does its operations in a number of different ways and a unitarian approach can lead one astray [M.V.L. Bennett, Nicked by Occam's razor: unitarianism in the investigation of synaptic transmission, Biol. Bull. 168 (1985) 159-167]. Electrical synapses can do many things that chemical synapses can do, and do them just as slowly. The new molecular, cellular and physiological techniques will clarify where gap junctions and electrical coupling do and do not occur and permit experimental manipulation with high specificity.

Status epilepticus decreases glutamate receptor 2 mRNA and protein expression in hippocampal pyramidal cells before neuronal death

Kainic acid (KA)-induced status epilepticus in adult rats leads to delayed, selective death of pyramidal neurons in the hippocampal CA1 and CA3. Death is preceded by down-regulation of glutamate receptor 2 (GluR2) mRNA and protein [the subunit that limits Ca(2+) permeability of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors] in CA1 and CA3, as indicated by in situ hybridization, immunolabeling, and quantitative Western blotting. GluR1 mRNA and protein are unchanged or slightly increased before cell death. These changes could lead to formation of GluR2-lacking, Ca(2+)-permeable AMPA receptors and increased toxicity of endogenous glutamate. GluR2 immunolabeling is unchanged in granule cells of the dentate gyrus, which are resistant to seizure-induced death. Thus, formation of Ca(2+)-permeable AMPA receptors may be a critical mediator of delayed neurodegeneration after status epilepticus.

Clustering of connexin 43-enhanced green fluorescent protein gap junction channels and functional coupling in living cells

Communication-incompetent cell lines were transfected with connexin (Cx) 43 fused with enhanced green fluorescent protein (EGFP) to examine the relation between Cx distribution determined by fluorescence microscopy and electrical coupling measured at single-channel resolution in living cell pairs. Cx43-EGFP channel properties were like those of wild-type Cx43 except for reduced sensitivity to transjunctional voltage. Cx43-EGFP clustered into plaques at locations of cell-cell contact. Coupling was always absent in the absence of plaques and even in the presence of small plaques. Plaques exceeding several hundred channels always conferred coupling, but only a small fraction of channels were functional. These data indicate that clustering may be a requirement for opening of gap junction channels.

Seeing is relieving: electrical synapses between visualized neurons

Two reports of electrical synapses between identified inhibitory neurons in the neocortex suggest that many neuron types known to communicate chemically may also be electrically coupled.

Protein kinase C potentiation of N-methyl-D-aspartate receptor activity is not mediated by phosphorylation of N-methyl-D-aspartate receptor subunits

N-methyl-D-aspartate receptors (NMDARs) are Ca(2+)-permeable glutamate-gated ion channels whose physiological properties in neurons are modulated by protein kinase C (PKC). The present study was undertaken to determine the role in PKC-induced potentiation of the NR1 and NR2A C-terminal tails, which serve as targets of PKC phosphorylation [Tingley, W. G., Ehlers, M. D., Kameyama, K., Doherty, C., Ptak, J. B., Riley, C. T. & Huganir, R. L. (1997) J. Biol. Chem. 272, 5157-5166]. Serine residue 890 in the C1 cassette is a primary target of PKC phosphorylation and a critical residue in receptor clustering at the membrane. We report herein that the presence of the C1 cassette reduces PKC potentiation and that mutation of Ser-890 significantly restores PKC potentiation. Splicing out or deletion of other C-terminal cassettes singly or in combination had little or no effect on PKC potentiation. Moreover, experiments involving truncation mutants reveal the unexpected finding that NMDARs assembled from subunits lacking all known sites of PKC phosphorylation can show PKC potentiation. These results indicate that PKC-induced potentiation of NMDAR activity does not occur by direct phosphorylation of the receptor protein but rather of associated targeting, anchoring, or signaling protein(s). PKC potentiation of NMDAR function is likely to be an important mode of NMDAR regulation in vivo and may play a role in NMDA-dependent long-term potentiation.

Knockdown of AMPA receptor GluR2 expression causes delayed neurodegeneration and increases damage by sublethal ischemia in hippocampal CA1 and CA3 neurons

Considerable evidence suggests that Ca(2+)-permeable AMPA receptors are critical mediators of the delayed, selective neuronal death associated with transient global ischemia and sustained seizures. Global ischemia suppresses mRNA and protein expression of the glutamate receptor subunit GluR2 and increases AMPA receptor-mediated Ca(2+) influx into vulnerable neurons of the hippocampal CA1 before the onset of neurodegeneration. Status epilepticus suppresses GluR2 mRNA and protein in CA3 before neurodegeneration in this region. To examine whether acute downregulation of the GluR2 subunit, even in the absence of a neurological insult, can cause neuronal cell death, we performed GluR2 "knockdown" experiments. Intracerebral injection of antisense oligodeoxynucleotides targeted to GluR2 mRNA induced delayed death of pyramidal neurons in CA1 and CA3. Antisense-induced neurodegeneration was preceded by a reduction in GluR2 mRNA, as indicated by in situ hybridization, and in GluR2 protein, as indicated by Western blot analysis. GluR2 antisense suppressed GluR2 mRNA in the dentate gyrus but did not cause cell death. The AMPA receptor antagonist 6-cyano-7-nitroquinoxiline-2,3-dione (CNQX) and the Ca(2+)-permeable AMPA receptor channel blocker 1-naphthyl acetyl spermine protected against antisense-induced cell death. This result indicates that antisense-induced cell death is mediated by Ca(2+)-permeable AMPA receptors. GluR2 antisense and brief sublethal global ischemia acted synergistically to cause degeneration of pyramidal neurons, consistent with action by a common mechanism. These findings demonstrate that downregulation of GluR2 is sufficient to induce delayed death of specific neuronal populations.

Mutation of structural determinants lining the N-methyl-D-aspartate receptor channel differentially affects phencyclidine block and spermine potentiation and block

Spermine and other endogenous polyamines potentiate, block and permeate the N-methyl-D-aspartate receptor channel. To identify structural determinants of the N-methyl-D-aspartate channel that mediate spermine's actions, we generated mutant receptors with asparagine (N) to glutamine (Q) or arginine (R) substitutions in the selectivity filter of the channel. We demonstrate that mutation of the three critical asparagines in this domain differentially affects block by phencyclidine and both potentiation and block by spermine. N-to-Q and N-to-R mutations in the N site of the NR1 subunit (N598 in NR1(011), N619 in NR1(100)) and N-to-Q mutations in the N and N + 1 sites (N595 and N596 in NR2A, respectively) of the NR2 subunit (Q/NN, R/NN, N/QN, N/NQ, Q/QN and Q/NQ receptors) reduced affinity for phencyclidine. The Q/NN receptor showed markedly reduced potentiation by spermine, with little or no change in spermine block. The R/NN receptor showed markedly reduced spermine potentiation and affinity for spermine at its block site. The N/QN, N/NQ and Q/QN mutant receptors showed somewhat enhanced spermine block, while the Q/ NQ double mutant exhibited significantly more enhanced spermine block. Thus, the asparagine residues critical to Ca2+ permeability and Mg2+ block of N-methyl-D-aspartate channels are also critical to block by spermine and phencyclidine. To examine the interaction of spermine and phencyclidine within the channel, we performed competition studies. Spermine appeared to compete with phencyclidine for binding to the receptor; however, blocks by phencyclidine and by spermine were not additive. The findings suggest that spermine can bind to a site in the external vestibule of the channel to impede phencyclidine binding, but allow Na+ influx.

Spermine and arcaine block and permeate N-methyl-D-aspartate receptor channels

Polyamines such as spermine are thought to be endogenous regulators of NMDA (N-methyl-D-aspartate)-type glutamate receptors. Polyamine block of NMDA receptors was studied in excised outside-out patches from rat hippocampal neurons and Xenopus oocytes expressing recombinant receptors. Extracellular spermine and arcaine reduced NMDA single-channel conductance in a voltage-dependent manner, with partial relief of block evident at large inside negative membrane potentials. Reducing extracellular Na+ concentration increased the apparent affinities for spermine and arcaine, indicating strong interaction between spermine and permeant ions. Internal spermine also blocked NMDA channels in a voltage-dependent manner, with relief of block evident at large inside positive potentials. The Woodhull model of channel block by an impermeant ion adequately described the actions of external spermine from -60 to +60 mV, but failed for more negative potentials. Eyring rate theory for a permeable blocker with two barriers and one binding site adequately described the voltage-dependent block and relief from block by both external and internal spermine over the range of -120 to +60 mV. These findings indicate that polyamines block and permeate neuronal NMDA receptor channels from the extracellular and intracellular sides, although sensitivity to internal spermine is probably too low to be physiologically relevant.