A Systematic Scoping Review of Comparative Effectiveness Studies in Kidney Stone Disease

OBJECTIVE

To review the status of comparative effectiveness studies for kidney stone disease with focus on study outcome, type, population, time trends, and patient-centered approaches.

METHODS

A systematic scoping review was performed for articles published between January 1, 2005, and March 30, 2021, using keywords relevant to kidney stone disease. Studies published in English that compared two or more alternative methods for prevention, diagnosis, treatment, monitoring, or care delivery were included. Two reviewers independently reviewed abstracts and an arbitrator resolved discrepancies. Nine reviewers abstracted information from full-length studies. Descriptive statistics were summarized, and linear regression was performed to evaluate temporal trends of study characteristics.

RESULTS

We reviewed 1773 abstracts and 707 full-length manuscripts focused on surgical intervention (440); medical expulsive therapy (MET) (152); analgesic control (80); and homeopathic, diagnostics, and/or prophylaxis (84). Randomized controlled trials were common across all outcome categories, including surgery (41.6%), MET (60.2%), analgesic control (81.3%), homeopathic (41.2%), diagnostic (47.6%), and prophylaxis (49.1%). Patient-reported outcomes were utilized in 71.7% and 95% of MET and analgesic control studies, respectively, but in the minority of all other study themes. Over time, meta-analyses and multicenter studies increased [P < .001].

CONCLUSION

Surgical and MET themes dominate published comparative literature in kidney stone disease. There is substantial variation in use of patient-reported outcomes across surgical themes. Multicentered studies and those generating higher level evidence have increased over time but opportunities exist to improve collaborative, high-quality, and patient-centered research in kidney stone disease.

Robot-assisted Laparoscopic Pyeloplasty: Experience of a Single Pediatric Institution, Including Long-term and Safety Outcomes

OBJECTIVE

To evaluate the efficacy and safety of robot-assisted laparoscopic pyeloplasty (RALP) and describe the short and long-term outcomes of pediatric RALP.

METHODS

We retrospectively reviewed all patients ..±21 years old who underwent primary RALP from 7/2007 through 12/2019. Patients were excluded from postoperative analysis if follow-up data after stent removal was not available. The primary outcome was surgical success, defined as radiographic improvement of hydronephrosis without need for reoperation. Secondary outcomes were time to reoperation and 90-day complication rate.

RESULTS

A total of 356 patients underwent primary repair of ureteropelvic junction obstruction during the study period; 29.ßpatients were limited to intraoperative data due to lack of follow-up imaging. Radiographic improvement at latest follow-up was seen in 308/327 (94.2%). Ten of 327 patients (3.1%) underwent reoperation: 7 were identified within 1 year of RALP and 3 were identified over 1 year after RALP. The median time to reoperation was 13.0 months (IQR 9.3-21.7). We defined long-term as>3 years after pyeloplasty. Over one-third (122/327, 37.3%) of the cohort had>3 years of follow-up, none of whom developed evidence of recurrent obstruction requiring reoperation beyond 3 years. Complications occurred within 90 days of surgery in 20/327 (6.1%).

CONCLUSION

This largest single-institution series confirms short- and long-term surgical effectiveness and safety of RALP. Our data also indicate that most patients who needed reoperation were identified within 1 year, and reoperation more than 3 years after RALP is rare.

Septin-mediated RhoA activation engages the exocyst complex to recruit the cilium transition zone

Septins are filamentous GTPases that play important but poorly characterized roles in ciliogenesis. Here, we show that SEPTIN9 regulates RhoA signaling at the base of cilia by binding and activating the RhoA guanine nucleotide exchange factor, ARHGEF18. GTP-RhoA is known to activate the membrane targeting exocyst complex, and suppression of SEPTIN9 causes disruption of ciliogenesis and mislocalization of an exocyst subunit, SEC8. Using basal body-targeted proteins, we show that upregulating RhoA signaling at the cilium can rescue ciliary defects and mislocalization of SEC8 caused by global SEPTIN9 depletion. Moreover, we demonstrate that the transition zone components, RPGRIP1L and TCTN2, fail to accumulate at the transition zone in cells lacking SEPTIN9 or depleted of the exocyst complex. Thus, SEPTIN9 regulates the recruitment of transition zone proteins on Golgi-derived vesicles by activating the exocyst via RhoA to allow the formation of primary cilia.

Prospective evaluation of a pediatric urodynamics protocol before and after limiting urine cultures

PURPOSE

While our institution has historically obtained a urine culture (UCx) from every child at the time of urodynamics (UDS), no consensus exists on UDS UCx utility, and practice varies widely. This study aims to prospectively study our symptomatic post-UDS UTI rate before and after implementing a targeted UCx protocol.

MATERIALS AND METHODS

A 2-part prospective study of patients undergoing UDS at one pediatric hospital was undertaken, divided into Phase 1 (7/2016-6/2017) with routine UCx at the time of UDS and Phase 2 (7/2019-6/2020) after implementation of a protocol limiting UCx at the time of UDS to only a targeted subset of patients. The primary outcome was symptomatic post-UDS UTI, defined as positive UCx ≥10ˆ4 CFU/mL and fever ≥38.5 °C or new urinary symptoms within seven days of UDS.

RESULTS

A total of 1,154 UDS were included: 553 in 483 unique patients during Phase 1 and 601 in 533 unique patients during Phase 2. Age, sex, race, ethnicity, and bladder management did not differ significantly between phases. All 553 UDS in Phase 1 had UCx at the time of UDS, compared to 34% (204/601) in Phase 2. The rate of positive UCx decreased from 39% in Phase 1-35% in Phase 2. Three patients developed symptomatic post-UDS UTI in each study period, resulting in a stable post-UDS UTI rate of 0.5% (3/553) in Phase 1 and 0.5% (3/601) in Phase 2. These patients varied in age, sex, UDS indication, and bladder management. Four of the six (67%) patients had positive UCx at the time of UDS, one had a negative UCx, and one had no UCx under the targeted UCx protocol. Predictors of symptomatic post-UDS UTI could not be evaluated.

DISCUSSION

In the largest prospective study to date, we found that symptomatic post-UDS UTI was <1% and that UCx at the time of UDS can safely be limited at our hospital. This reduction has important implications for cost containment and antibiotic stewardship. We will continue iterative modifications to our protocol, which may eventually include the elimination of UCx at the time of UDS in all groups.

CONCLUSIONS

This 2-part prospective evaluation at one pediatric hospital determined that the symptomatic post-UDS UTI rate remained <1% with no identifiable predictors after limiting previously universal UCx at the time of UDS to only a targeted subset of patients.

Variation in care between pediatric and adult patients presenting with nephrolithiasis to tertiary care pediatric emergency departments in the United States (2009-2020)

BACKGROUND

Individuals with nephrolithiasis frequently present to the Emergency Department (ED). Safety and quality principles are often applied in pediatric EDs to children presenting with nephrolithiasis, such as limiting ionizing radiation exposure and opioid analgesics. However, it is unknown whether pediatric EDs apply these same principles to adult patients who present with nephrolithiasis. We hypothesized that adult patients would be associated with higher use of radiation-based imaging and opioid analgesics.

OBJECTIVE

To assess variations in diagnostic and treatment interventions and hospital utilization between pediatric and adult patients presenting to the pediatric ED with nephrolithiasis.

STUDY DESIGN

A retrospective cohort study was conducted, examining outcomes for pediatric (<18-years-old) versus adult (≥18-years-old) patients in 42 pediatric EDs from 2009 to 2020 using the Pediatric Health Information System (PHIS) database. Patients with an ICD-9/10 principal diagnosis code of nephrolithiasis with no nephrolithiasis-related visits within the prior 6 months were included. Primary outcomes were imaging, medications, and surgical interventions. Secondary outcomes were hospital admissions, 90-day ED revisits, and 90-day readmissions. Generalized linear mixed models with random effects were used to adjust for confounding and clustering.

RESULTS

In total, 16,117 patients with 17,837 encounters were included. Most hospitals were academic (95.2%), and a plurality were located in the South (38.1%). Most patients were <18-years-old (84.4%, median (interquartile range): 15 (12-17)-years-old), female (57.9%), and White (76.3%), and 17.1% were Hispanic/Latino. Most had no complex chronic conditions (89.2%) and no chronic disease per pediatric medical complexity algorithm (51.5%). For the primary outcome, adults, relative to pediatric patients, who presented to the pediatric ED with nephrolithiasis had higher adjusted odds of receiving computerized tomography (CT) scans (Odds Ratio [OR] 1.43 [95% Confidence Interval [CI] 1.29-1.59]) and opioid analgesics (OR 1.45 [95%CI 1.33-1.58]) (Summary Figure). Secondary outcomes showed that adults, relative to pediatric patients, had lower adjusted odds of hospital admissions, 90-day ED revisits, and 90-day readmissions.

DISCUSSION

Our results suggest that certain pediatric safety and quality principles, such as limiting ionizing radiation exposure and opioid analgesic prescriptions, are not being equally applied to pediatric and adult patients who present to pediatric EDs with nephrolithiasis. The mechanism of these findings remains to be elucidated.

CONCLUSIONS

Variations in care for individuals with nephrolithiasis reflect an opportunity for quality improvement in pediatric EDs and inform work exploring optimal care pathways for all patients presenting to the pediatric ED with nephrolithiasis.

Can diagnostic and imaging recommendations from the 2011 AAP UTI guidelines be applied to infants <2 months of age?

INTRODUCTION

In 2011, the American Academy of Pediatrics (AAP) published guidelines regarding diagnosis and management of children 2-to-24-months-old with initial febrile urinary tract infection (fUTI). Available data were insufficient to determine whether evidence from studies of 2-to-24-month-olds applies to those <2-months-old, so they were excluded.

OBJECTIVE

This study aimed to 1) compare demographic, clinical, imaging and outcomes between patients <2-months-old and those 2-to-24-months-old hospitalized with fUTI, and 2) assess whether diagnostic and imaging recommendations of the AAP 2011 guidelines apply to those <2-months-old.

STUDY DESIGN

A cohort study of patients ≤24-months-old hospitalized at a children's hospital with fUTI from 2016 to 2018 was conducted. Data were collected via a prospectively generated electronic medical record note template, supplemented with retrospective chart review. Primary outcomes included differences in demographics, clinical presentation, urine culture results, and imaging utilization/results by age group. Secondary outcomes included surgical procedures, UTI recurrence, and 90-day all-cause readmissions and emergency department (ED) revisits. Univariate and bivariate statistics were utilized to compare age groups.

RESULTS

Overall, 137 patients were included (median age 70 days, 55.5% male [92.1% uncircumcised], 53.3% Hispanic/Latino, 89.8% 1st fUTI). There were no demographic differences between groups, except children <2-months-old were more frequently male (71.2 vs 43.6%, p = 0.002). The Summary Table compares clinical factors and imaging utilization by age. There were no differences in urinalysis or urine culture results between groups. Patients <2-months-old had shorter fever duration, lower maximum temperature, and lower white blood cell counts. Voiding cystourethrograms (VCUGs) were recommended and obtained more frequently in patients <2-months-old, but there were no differences in renal and bladder ultrasound (RBUS) or VCUG results between age groups. There were no differences in UTI recurrence (13.6% of <2-months-old vs 14.1% of 2-to-24-months-old, p = 1.00) or fUTI recurrence (13.6 vs 7.7%, p = 0.40) within 1 year, 90-day readmission (6.8 vs 6.4%, p = 1.00), or 90-day ED revisit (22.0 vs 20.5%, p = 1.00).

DISCUSSION

There were minimal differences between the <2-months-old and 2-to-24-months-old age groups in demographics, laboratory (including microbial) or imaging results, or clinical outcomes. Patients <2-months-old were more frequently male and less ill. These data support applying urinalysis and urine culture diagnostic criteria, and universal RBUS, from the AAP guidelines to patients <2-months-old. Given utilization differences, applicability of VCUG guideline recommendations requires further clarification for patients <2-months-old.

CONCLUSION

Laboratory testing and RBUS recommendations from the AAP guidelines may be safely applied to infants <2-months-old. Further studies are needed to clarify optimal VCUG recommendations.

Developing and testing a case-management intervention to support the return to work of health care workers with common mental health disorders

BACKGROUND

To assess the feasibility and acceptability of conducting a trial of the clinical effectiveness and cost-effectiveness of a new case-management intervention to facilitate the return to work of health care workers, on sick leave, having a common mental disorder (CMD).

METHODS

A mixed methods feasibility study.

RESULTS

Systematic review examined 40 articles and 2 guidelines. Forty-nine National Health Service Occupational Health (OH) providers completed a usual care survey. We trained six OH nurses as case managers and established six recruitment sites. Forty-two out of 1938 staff on sick leave with a CMD were screened for eligibility, and 24 participants were recruited. Out of them, 94% were female. Eleven participants received the intervention and 13 received usual care. Engagement with most intervention components was excellent. Return-to-work self-efficacy improved more in the intervention group than in the usual care group. Qualitative feedback showed the intervention was acceptable.

CONCLUSIONS

The intervention was acceptable, feasible and low cost to deliver, but it was not considered feasible to recommend a large-scale effectiveness trial unless an effective method could be devised to improve the early OH referral of staff sick with CMD. Alternatively, the intervention could be trialled as a new stand-alone OH intervention initiated at the time of usual OH referral.

Randomized trial of prophylactic antibiotics vs. placebo after midshaft-to-distal hypospadias repair: the PROPHY Study

BACKGROUND

Use of prophylactic antibiotics after stented hypospadias repair is very common, but most research has not identified any clinical benefits of this practice. Only one study has found that postoperative prophylaxis reduces symptomatic urinary tract infections (UTIs). Data from the same trial suggested that prophylaxis may also reduce urethroplasty complications. No studies on this subject have been placebo-controlled.

OBJECTIVE

We performed a randomized, double-blind, placebo-controlled study to evaluate the effect of postoperative prophylactic antibiotics on the incidence of infection or urethroplasty complications after stented repair of midshaft-to-distal hypospadias.

STUDY DESIGN

Boys were eligible for this multicenter trial if they had a primary, single-stage repair of mid-to-distal hypospadias with placement of an open-drainage urethral stent for an intended duration of 5-10 days. Participants were randomized in a double-blind fashion to receive oral trimethoprim-sulfamethoxazole or placebo twice daily for 10 days postoperatively. The primary outcome was a composite of symptomatic UTI, surgical site infection (SSI), and urethroplasty complications, including urethrocutaneous fistula, meatal stenosis, and dehiscence. Secondary outcomes included each component of the primary outcome as well as acute adverse drug reactions (ADRs) and C. difficile colitis.

RESULTS

Infection or urethroplasty complications occurred in 10 of 45 boys (22%) assigned to receive antibiotic prophylaxis as compared with 5 of 48 (10%) who received placebo (relative risk [RR], 2.1; 95% confidence interval [CI], 0.8 to 5.8; p = 0.16). There were no significant differences between groups in symptomatic UTIs, SSIs, or any urethroplasty complications. Mild ADRs occurred in 3 of 45 boys (7%) assigned to antibiotics as compared with 5 of 48 (10%) given placebo (RR, 0.6; 95% CI, 0.2 to 2.5; p = 0.72). There were no moderate-to-severe ADRs, and no patients developed C. difficile colitis.

CONCLUSIONS

In this placebo-controlled trial of 93 patients, prophylactic antibiotics were not found to reduce infection or urethroplasty complications after stented mid-to-distal hypospadias repair. The study did not reach its desired sample size and was therefore underpowered to independently support a conclusion that prophylaxis is not beneficial. However, the result is consistent with most prior research on this subject.

GOV IDENTIFIER

NCT02096159.

The complex web of canonical and non-canonical Hedgehog signaling

Hedgehog (Hh) signaling is a widely studied signaling pathway because of its critical roles during development and in cell homeostasis. Vertebrate canonical and non-canonical Hh signaling are typically assumed to be distinct and occur in different cellular compartments. While research has primarily focused on the canonical form of Hh signaling and its dependency on primary cilia - microtubule-based signaling hubs - an extensive list of crucial functions mediated by non-canonical Hh signaling has emerged. Moreover, amounting evidence indicates that canonical and non-canonical modes of Hh signaling are interlinked, and that they can overlap spatially, and in many cases interact functionally. Here, we discuss some of the many cellular effects of non-canonical signaling and discuss new evidence indicating inter-relationships with canonical signaling. We discuss how Smoothened (Smo), a key component of the Hh pathway, might coordinate such diverse downstream effects. Collectively, pursuit of questions such as those proposed here will aid in elucidating the full extent of Smo function in development and advance its use as a target for cancer therapeutics.

Robot-assisted laparoscopic urologic surgery in infants weighing ≤10 kg: A weight stratified analysis

INTRODUCTION

Robot-assisted laparoscopic (RAL) urologic surgery is widely used in pediatric patients, though less commonly in infants. There are small series demonstrating safety and efficacy in infants, however, stratification by infant size has rarely been reported. Whether a cut-off weight, below which RAL surgery is not technically feasible, safe, or efficacious has not be determined.

OBJECTIVE

To assess safety and efficacy of RAL urologic procedures in infants <1 year of age, weighing ≤10 kg.

STUDY DESIGN

A single-institution retrospective cohort study of patients <1 year of age, and ≤10 kg undergoing RAL pyeloplasty (RALP) or RAL ipsilateral ureteroureterostomy (RALUU) between January 2011 and September 2020 was performed. Demographic, operative, and post-operative data were extracted from the medical record. Patients were stratified by post-hoc weight quartiles. Outcomes, including operative time, total OR time, estimated blood loss (EBL), post-operative length of stay (LOS), post-operative radiographic improvement, and 30-day complications were assessed by weight quartile for each procedure. The Kruskal-Wallis rank test was used to assess differences in continuous outcomes between weight quartiles and Pearson's Chi-squared test was used for categorical outcomes.

RESULTS

Of 696 RAL urologic surgeries performed, 101 met eligibility criteria. Median (IQR) age of patients was 7.2 (6.0-9.2) months with median weight of 8.0 (7.2-8.9) kg. The lowest weight was 5.5 kg. Procedures performed included 79 RALPs (78.2%), 22 RALUUs (21.8%). We identified 97 patients (94%) with post-operative imaging, with radiographic improvement in 92%. When stratified by weight quartile, there was no difference between groups in median operative time, total OR time, LOS, EBL, or post-operative radiographic improvement for both RALP and RALUU. Post-operative complications were assessed based on Clavien-Dindo classification with the majority of complications (9/12, 75%) in the >50th percentile weight groups.

DISCUSSION

To our knowledge, this is the largest published series of infant RAL urologic procedures, with similar rates of radiographic improvement and post-operative complications to prior published series. There are few prior series of RALP and RALUU in infants ≤10 kg, and we show comparable outcomes regardless of patient weight. Our study is limited by the inherent biases of retrospective studies.

CONCLUSION

RAL urologic surgery is technically feasible, safe, and efficacious in infants ≤10 kg, without worse outcomes as weight decrease. A cut-off weight, below which RAL surgery should not be performed has yet to be identified.

Association between intra-operative meatal mismatch and urethrocutaneous fistula development in hypospadias repair

INTRODUCTION

The Glans-Meatus-Shaft (GMS) Score is a pre-operative phenotypic scoring system used to assess hypospadias severity and risk for post-operative complications. The 'M' component is based on pre-operative meatal location, but meatal location sometimes changes after penile degloving, resulting in 'meatal mismatch.'

OBJECTIVE

To identify: 1) the incidence and clinical predictors of meatal mismatch, and 2) the association of meatal mismatch with post-operative urethrocutaneous fistula development.

STUDY DESIGN

We performed a retrospective cohort study on patients who underwent primary hypospadias repair at a single center from 2011 to 2018. Meatal mismatch was defined as: upstaging (meatus moving more proximally after degloving), downstaging (moving more distally after degloving), or none. Covariates included: pre-degloving meatal location, chordee severity, penoscrotal anatomy, pre-operative testosterone, and number of stages for repair. To test the association between meatal mismatch and fistula development, we constructed two, nested, multivariable Cox proportional hazards regression models with and without meatal mismatch and compared them with the likelihood ratio test. A sensitivity analysis excluded patients with <6 months of follow-up.

RESULTS

Of 485 patients, 99 (20%) exhibited meatal mismatch, including 75 (15%) with upstaging and 24 (5%) patients with downstaging (Figure). Meatal mismatch was significantly associated with penoscrotal webbing, number of stages for repair, and pre-degloving meatal location, with downstaging being associated with more proximal meatal location. Over a median follow-up of 7.3 months (interquartile range 2.0-20.9), fistulae developed in 56 (12%) patients. On multivariable analysis, meatal upstaging was associated with a 3-fold increased risk of fistula development (Hazards Ratio [HR]: 3.04, 95% Confidence Interval [CI]: 1.44-6.45) compared to no mismatch. Meatal downstaging had similar risk of fistula development compared to no mismatch (HR: 0.99, 95% CI: 0.29-3.35). Multi-stage compared to single-stage repair was associated with reduced risk of fistula development (HR: 0.24, 95% CI: 0.09-0.66). The likelihood ratio test favored the model that included meatal mismatch. The sensitivity analysis showed similar findings.

DISCUSSION

Our short-term results suggest that meatal mismatch may be an important additional consideration to the GMS score as a tool to assess hypospadias severity, counsel families, and predict outcomes. Longer-term studies are needed to enhance the precision of risk stratification in hypospadias.

CONCLUSIONS

Meatal mismatch occurred in 20% of patients undergoing hypospadias repair. Among this cohort, meatal upstaging was associated with a 3-fold increased risk of post-operative urethrocutaneous fistula development.

Frequency and Variability of Advice Given to Parents on Care of the Uncircumcised Penis by Pediatric Residents: A Need to Improve Education

OBJECTIVE

To understand the extent to which pediatricians are providing advice on care of the uncircumcised penis and the advice they are providing. We hypothesized that pediatric residents lack preparedness to offer parents advice on caring for the uncircumcised penis and as such are unlikely to offer such advice.

METHODS

An IRB approved, anonymous survey was administered to 244 pediatric residents in 5 urban training programs (Appendix). Descriptive statistics were used for clinical and demographic data and Fisher's exact and Kruskal-Wallis tests were used for comparative analysis.

RESULTS

Eighty-three residents completed the survey for a response rate of 34%. Less than half (45%) of the residents surveyed were likely, or extremely likely to voluntarily offer advice to parents on care of the uncircumcised penis. On a scale of 0-100, the median confidence level in offering advice was 48 (interquartile range [IQR] 30-52). Forty-nine percent of residents reported never being taught care of the uncircumcised penis. Of those who received education, 72% reported learning informally from a senior resident or attending and only 9% learned from a formal lecture. Pediatric residents varied greatly on advice given to parents in regards to the frequency of retraction and 40% offered no advice.

CONCLUSION

This study demonstrates that pediatric residents currently lack confidence in providing parents advice on preputial care and are unlikely to offer such advice. When offered, the advice given is highly variable. This study emphasizes the need for improved education of pediatric residents.

Advising on the care of the uncircumcised penis: A survey of pediatric urologists in the United States

BACKGROUND

Parents of uncircumcised boys often report confusion regarding the proper care and hygiene practices for the uncircumcised penis. The lack of guidance from healthcare providers may be due to a lack of consensus on the proper care of the prepuce.

OBJECTIVE

The aim of this study was to determine whether or not there exists consensus among pediatric urologists on the care of the uncircumcised penis and on the advice they provide to parents.

METHODS

An electronic survey was delivered to 514 members of the Society for Pediatric Urology (SPU). The survey contained demographical and clinical questions which were analyzed using descriptive statistics.

RESULTS

Of 261 SPU members who opened the e-mail invitation, a total of 204 responses were received for a response rate of 78% (overall response rate 40%). Nine responses were excluded for members practicing outside of the United States or whose locations were not disclosed for a final number of responses of 195. Overall, pediatric urologists reported a high level of confidence in providing advice to parents with a median confidence score of 10 (scale 1-10, IQR 9-10). Only 66% reported providing advice to parents on when to begin retracting the foreskin, with 48% basing their advice on the patient's age and 19% on the patient's toilet training status (Figure). Respondents who based their advice on age, advised beginning retraction at 2-5 years (61%), 6-11 years (17%), less than 2 years (12%), and greater than 12 years (10%). For frequency of retraction before toilet training, 50% recommended no retraction, 25% with cleaning or baths, 10% with each diaper change, and 13% provided no advice. After toilet training, 48% of respondents recommended retracting the foreskin with cleaning or baths, 41% with each void, and 19% recommended no retraction. The majority of respondents agreed that problems with voiding (77%), infection (74%), and hygiene (64%) were indications for treatment of phimosis. In asymptomatic cases, 47% believed that phimosis required treatment if persisting beyond a specific age, the most common being greater than 12 years of age (40%).

CONCLUSIONS

Although pediatric urologists reported being highly confident in advising parents on the care of the uncircumcised penis, there is not a clear consensus among these subspecialists on when to begin and how often to retract the foreskin, or when phimosis requires treatment. These findings offer insight into current practice patterns to better inform primary care providers and parents.

Eine probabilistische Kosteneffektivitätsanalyse einer azellulären synthetischen Matrix (ASM) als Ergänzung zur Standardversorgung venöser und gemischter Ulzera cruris in Deutschland auf Basis eines Discrete-Event-Simulations-Modells

Ziel Das vorliegende gesundheitsökonomische Modell wurde entwickelt, um in Deutschland standardmäßig Therapien im Bereich chronische Wunden systematisch und vergleichend zu analysieren. In der zugrunde liegenden Analyse wurden die gesundheitsökonomischen Parameter von Patienten mit einem Ulcus cruris venosum/mixtum, die zusätzlich zur Standardversorgung (SV) mit einer azellulären synthetischen Matrix (ASM) behandelt wurden, berechnet und mit denen von Patienten verglichen, die nur eine Standardversorgung erhalten haben.

Methodik Zunächst wurde in den (Standard-)Literaturdatenbanken systematisch nach einem gesundheitsökonomischen Modell gesucht. Die Ergebnisse dieser Literatursuche werden in einer anderen Publikation zur Methodik und Modellbeschreibung ausführlich diskutiert. Angesichts des Fehlens eines publizierten, akzeptierten und für Deutschland adäquaten Modells wurde in Form eines Discrete-Event-Simulations-Modells (DES-Modell) ein neues gesundheitsökonomisches Modell für den Bereich chronische Wunden entwickelt. Auf Basis des DES-Modells wurde eine Kosteneffektivitätsanalyse aus Sicht der Gesetzlichen Krankenversicherung (GKV) durchgeführt. Für die Kostendaten wurden GKV-Routinedaten genutzt. Patienten aus dem Deutschen Register chronischer Wunden (DRCW), die nur mit der SV behandelt wurden und ähnliche Patientencharakteristika aufwiesen, wurden mit Patienten aus einer einarmigen multizentrischen Phase-II-Studie einer azellulären synthetischen Matrix (ASM) verglichen. Die Wirksamkeit der Behandlung (1-Jahres-Vorhersage) wurde mittels Kaplan-Meier-Kurven für die 12-Wochen-Heilungszeit der SV + ASM im Vergleich zur alleinigen Behandlung mit der SV berechnet. Die Modellergebnisse wurden mittels einer probabilistischen Sensitivitätsanalyse für ulzerationsfreie Tage validiert und die Ergebnisse jeweils in einem Scatterplot der geschätzten gemeinsamen Dichte der inkrementellen Kosten und der inkrementellen Effekte der SV versus der SV + ASM sowie in einer Kosteneffektivitäts-Akzeptanz-Kurve dargestellt.

Ergebnisse Die Kosteneffektivitätsanalyse zeigte, dass eine auf SV + ASM basierende Therapie gemäß dem Modell effektiver (0,008 inkrementeller Effekt ambulant; −0,045 inkrementeller Effekt stationär) und kostensparender (−321,14 €) ist und somit aus gesundheitsökonomischer Sicht als dominant gegenüber der SV angesehen werden kann. Zusätzlich zeigten sich die Therapien in der Versorgungssäule Facharzt gegenüber denen in der Versorgungssäule Hausarzt als zumindest gleich effektiv und kosteneinsparend und somit dominant. Bei Berücksichtigung der ambulanten Pflege in Verbindung mit dem jeweiligen Arzt war die hausärztliche Versorgung zwar gleich effektiv, aber kostensparender (129,40 € vs. 187,20 € = −57,80 €) als die fachärztliche Versorgung und somit dominant. Die Dominanz nach Hausarzt und Facharzt sowie mit ambulanter Pflege war konsistent zu der, die sich aus der Kosteneffektivität ergibt.

Schlussfolgerung Die azelluläre synthetische Matrix (ASM) bestätigte in einer klinischen Studie ihre signifikanten Heilungschancen, die in das gesundheitsökonomische Modell zur chronischen Wunde eingeflossen sind. Unter den zugrunde liegenden Modellannahmen bekräftigt das Modell angesichts von Kosteneinsparungen in allen Behandlungspfaden eines Ulcus cruris venosum/mixtum die Wirtschaftlichkeit einer möglichen Verordnung der ASM im deutschen Kontext.

Blind ending vessels on diagnostic laparoscopy for nonpalpable testis: Is a nubbin present?

INTRODUCTION

The traditional management paradigm for nonpalpable testis (NPT) has been that inguinal or scrotal exploration for a nubbin may be omitted when blind ending vessels are observed during diagnostic laparoscopy. Our aim was to examine whether blind ending vessels excluded the presence of a nubbin in a series of boys who underwent exploration in this setting.

MATERIALS AND METHODS

Using a surgical database and chart review, pre-pubertal boys (≤12 years) with the diagnosis of undescended or atrophic testis who underwent a diagnostic laparoscopy for unilateral NPT between 2000 and 2015 were retrospectively identified. Physical exam, procedural and pathologic findings were confirmed by chart review.

RESULTS

595 boys underwent diagnostic laparoscopy for NPT by 11 surgeons. Of these, 318 had an intra-abdominal testis and 18 underwent diagnostic laparoscopy alone. Of the remaining 259, 32 had an open internal ring and inguinal or scrotal exploration was performed. The remaining 227 with a closed ring comprised the cohort for our analysis, of whom 188 had vessels entering the ring, 36 had blind ending vessels, and in three the vessel status was unavailable. In the 188 boys with vessels entering the ring, 164 (87%) had a nubbin excised during inguinal or scrotal exploration, of which 93% were grossly identified as an atrophic testis. Pathology confirmed the presence of hemosiderin in 44% and calcifications in 54%. In the 36 boys with blind ending vessels, 26 (72%) had a nubbin excised during inguinal or scrotal exploration, of which 96% were grossly identified as an atrophic testis. Pathology confirmed hemosiderin in 54% and calcifications in 58%. All seven cases with both blind ending vas and vessels had an atrophic testis grossly identified. Of all 207 excised remnants in this series, nubbins with viable testicular elements (seminiferous tubules in 11, germ cells in two) were only excised during cases that reported a non-atretic vas or any vessels entering the internal ring.

CONCLUSION

In this large multi-institutional series, blind ending vessels were associated with a nubbin noted during inguinal or scrotal exploration in the majority of cases. Based on this series if the surgeon's goal is to remove all nubbins, exploration is necessary regardless of vessel appearance. However, viable testicular elements were rarely identified and only when either a non-atretic vas or any vessels were observed to enter the ring.

Urinary tract infection after voiding cystourethrogram

BACKGROUND

Reported rates of post-procedural urinary tract infection (ppUTI) after voiding cystourethrogram (VCUG) are highly variable (0-42%).

OBJECTIVE

This study aimed to determine the risk of ppUTI after cystogram, and evaluate predictors of ppUTI.

STUDY DESIGN

A retrospective cohort study of children undergoing VCUG or radionuclide cystogram (henceforth 'cystogram') was conducted. Children with neurogenic bladder who underwent cystogram in the operating room and without follow-up at the study institution were excluded. Incidence of symptomatic ppUTI within 7 days after cystogram was recorded. Predictors of ppUTI were evaluated using univariate statistics.

RESULTS

A total of 1108 children (54% female, median age 1.1 years) underwent 1203 cystograms: 51% were on periprocedural antibiotics, 75% had a pre-existing urologic diagnosis (i.e., vesicoureteral reflux (VUR) or hydronephrosis; not UTI alone), and 18% had a clinical UTI within 30 days before cystogram. Of the cystograms, 41% had an abnormal cystogram and findings included VUR (82%), ureterocele (6%), and diverticula (6%). Twelve children had a ppUTI (1.0%; four girls, five uncircumcised boys, three circumcised boys; median age 0.9 years). Factors significantly associated with diagnosis of a ppUTI (Summary fig.) included: pre-existing urologic diagnosis prior to cystogram (12/12, 100% of patients with ppUTI), abnormal cystogram results (11/12, 92%), and use of periprocedural antibiotics (11/12, 92%). All 11 children with an abnormal cystogram had VUR ≥ Grade III. However, among all children with VUR ≥ Grade III, 4% (11/254) had a ppUTI.

DISCUSSION

This is the largest study to date that has examined incidence and risk factors for ppUTI after cystogram. The retrospective nature of the study limited capture of some clinical details. This study demonstrated that the risk of ppUTI after a cystogram is very low (1.0% in this cohort). Having a pre-existing urologic diagnosis such as VUR or hydronephrosis was associated with ppUTI; therefore, children with moderate or high-grade VUR on cystogram may be at highest risk. Development of ppUTI after cystogram also highlighted the potential for a delay in diagnosis or oversight of a healthcare-associated infection due to several factors: 1) cystograms may be ordered, performed/interpreted, and followed up by multiple different providers; and 2) such infections are not captured by traditional healthcare-associated infection surveillance strategies.

CONCLUSIONS

The risk of ppUTI after a cystogram is very low. Only children with pre-existing urologic diagnoses developed ppUTI in this study. This study's findings suggest that children undergoing a cystogram should not be given peri-procedural antibiotic prophylaxis for the sole purpose of ppUTI prevention.

Social dimensions of science-humanitarian collaboration: lessons from Padang, Sumatra, Indonesia

This paper contains a critical exploration of the social dimensions of the science-humanitarian relationship. Drawing on literature on the social role of science and on the social dimensions of humanitarian practice, it analyses a science-humanitarian partnership for disaster risk reduction (DRR) in Padang, Sumatra, Indonesia, an area threatened by tsunamigenic earthquakes. The paper draws on findings from case study research that was conducted between 2010 and 2011. The case study illustrates the social processes that enabled and hindered collaboration between the two spheres, including the informal partnership of local people and scientists that led to the co-production of earthquake and tsunami DRR and limited organisational capacity and support in relation to knowledge exchange. The paper reflects on the implications of these findings for science-humanitarian partnering in general, and it assesses the value of using a social dimensions approach to understand scientific and humanitarian dialogue.

Discharge Identity of Medullary Inspiratory Neurons is Altered during Repetitive Fictive Cough

This study investigated the stability of the discharge identity of inspiratory decrementing (I-Dec) and augmenting (I-Aug) neurons in the caudal (cVRC) and rostral (rVRC) ventral respiratory column during repetitive fictive cough in the cat. Inspiratory neurons in the cVRC (n = 23) and rVRC (n = 17) were recorded with microelectrodes. Fictive cough was elicited by mechanical stimulation of the intrathoracic trachea. Approximately 43% (10 of 23) of I-Dec neurons shifted to an augmenting discharge pattern during the first cough cycle (C1). By the second cough cycle (C2), half of these returned to a decrementing pattern. Approximately 94% (16 of 17) of I-Aug neurons retained an augmenting pattern during C1 of a multi-cough response episode. Phrenic burst amplitude and inspiratory duration increased during C1, but decreased with each subsequent cough in a series of repetitive coughs. As a step in evaluating the model-driven hypothesis that VRC I-Dec neurons contribute to the augmentation of inspiratory drive during cough via inhibition of VRC tonic expiratory neurons that inhibit premotor inspiratory neurons, cross-correlation analysis was used to assess relationships of tonic expiratory cells with simultaneously recorded inspiratory neurons. Our results suggest that reconfiguration of inspiratory-related sub-networks of the respiratory pattern generator occurs on a cycle-by-cycle basis during repetitive coughing.

Respiratory and Mayer wave-related discharge patterns of raphé and pontine neurons change with vagotomy

Previous models have attributed changes in respiratory modulation of pontine neurons after vagotomy to a loss of pulmonary stretch receptor "gating" of an efference copy of inspiratory drive. Recently, our group confirmed that pontine neurons change firing patterns and become more respiratory modulated after vagotomy, although average peak and mean firing rates of the sample did not increase (Dick et al., J Physiol 586: 4265-4282, 2008). Because raphé neurons are also elements of the brain stem respiratory network, we tested the hypotheses that after vagotomy raphé neurons have increased respiratory modulation and that alterations in their firing patterns are similar to those seen for pontine neurons during withheld lung inflation. Raphé and pontine neurons were recorded simultaneously before and after vagotomy in decerebrated cats. Before vagotomy, 14% of 95 raphé neurons had increased activity during single respiratory cycles prolonged by withholding lung inflation; 13% exhibited decreased activity. After vagotomy, the average index of respiratory modulation (eta(2)) increased (0.05 +/- 0.10 to 0.12 +/- 0.18 SD; Student's paired t-test, P < 0.01). Time series and frequency domain analyses identified pontine and raphé neuron firing rate modulations with a 0.1-Hz rhythm coherent with blood pressure Mayer waves. These "Mayer wave-related oscillations" (MWROs) were coupled with central respiratory drive and became synchronized with the central respiratory rhythm after vagotomy (7 of 10 animals). Cross-correlation analysis identified functional connectivity in 52 of 360 pairs of neurons with MWROs. Collectively, the results suggest that a distributed network participates in the generation of MWROs and in the coordination of respiratory and vasomotor rhythms.

Reconfiguration of the pontomedullary respiratory network: a computational modeling study with coordinated in vivo experiments

A large body of data suggests that the pontine respiratory group (PRG) is involved in respiratory phase-switching and the reconfiguration of the brain stem respiratory network. However, connectivity between the PRG and ventral respiratory column (VRC) in computational models has been largely ad hoc. We developed a network model with PRG-VRC connectivity inferred from coordinated in vivo experiments. Neurons were modeled in the "integrate-and-fire" style; some neurons had pacemaker properties derived from the model of Breen et al. We recapitulated earlier modeling results, including reproduction of activity profiles of different respiratory neurons and motor outputs, and their changes under different conditions (vagotomy, pontine lesions, etc.). The model also reproduced characteristic changes in neuronal and motor patterns observed in vivo during fictive cough and during hypoxia in non-rapid eye movement sleep. Our simulations suggested possible mechanisms for respiratory pattern reorganization during these behaviors. The model predicted that network- and pacemaker-generated rhythms could be co-expressed during the transition from gasping to eupnea, producing a combined "burst-ramp" pattern of phrenic discharges. To test this prediction, phrenic activity and multiple single neuron spike trains were monitored in vagotomized, decerebrate, immobilized, thoracotomized, and artificially ventilated cats during hypoxia and recovery. In most experiments, phrenic discharge patterns during recovery from hypoxia were similar to those predicted by the model. We conclude that under certain conditions, e.g., during recovery from severe brain hypoxia, components of a distributed network activity present during eupnea can be co-expressed with gasp patterns generated by a distinct, functionally "simplified" mechanism.

Viral and host correlates of serum resistin in simian AIDS

Resistin is an adipocytokine with a proposed dual role in metabolism and inflammation. In light of the ability to promote inflammatory responses, adipocytokines may prove key factors in modulating the host response to HIV. This study utilizes the simian immunodeficiency virus (SIV) model of HIV/AIDS to investigate changes in serum resistin levels following dietary intervention and SIV infection and determine associations with measures of body composition and disease severity. Resistin levels, body composition (n = 34), and insulin resistance (n = 16) were determined in healthy rhesus macaques. A subset of animals (n = 8) was placed on an atherogenic diet (AD) and subsequently inoculated with SIVmac239. Longitudinal measures of serum resistin, cytokines, viral load, lymphocyte subsets, and body composition were obtained. In healthy macaques consuming a standard diet, resistin levels correlated positively with total fat mass (r = 0.49; p < 0.01) and tissue fat percent (r = 0.53; p < 0.01) but failed to associate with measures of insulin resistance. In contrast, a negative correlation was noted between these measures of adiposity and resistin following SIV inoculation (r = -0.27; p < 0.05 and r = -0.24; p < 0.05, respectively). Viral load correlated positively with serum resistin (r = 0.32; p < 0.01). Serum levels of MCP-1 and sTNF RII demonstrated no correlation with resistin in normal animals on a standard diet, while a significant positive correlation was observed following SIV infection (r = 0.52; p < 0.0001 and r = 0.59; p < 0.0001, respectively). Findings indicate a fundamental difference in the relationship between resistin and body composition following SIV infection and suggest that elevations in resistin parallel measures of disease severity including loss of body fat and viral replication.

Participation in prenatal care in the Paso del Norte border region: the influence of acculturation

Women who resided on the El Paso, Texas/Juarez, Mexico border (the Paso del Norte region) were surveyed to determine the barriers and facilitators to receiving early and adequate prenatal care. Postpartum interviews and medical chart abstractions were conducted among 493 Hispanic women. Primary facilitators were all factors that made prenatal care services more accessible to women and a priority among other issues competing for time and resources. The factors reported by these women as barriers to timely entry and sustaining enrollment in prenatal care were related to the availability of social support networks and affiliation with the Mexican/Hispanic culture (acculturation).

Production of reflex cough by brainstem respiratory networks

Delineation of neural mechanisms involved in reflex cough is essential for understanding its many physiological and clinical complexities, and the development of more desirable antitussive agents. Brainstem networks that generate and modulate the breathing pattern are also involved in producing the motor patterns during reflex cough. Neurones of the ventrolateral medulla respiratory pattern generator mutually interact with neural networks in the pons, medulla and cerebellum to form a larger dynamic network. This paper discusses evidence from our laboratory and others supporting the involvement of the nucleus tractus solitarii, midline raphe nuclei and lateral tegmental field in the medulla, and the pontine respiratory group and cerebellum in the production of reflex cough. Gaps in our knowledge are identified to stimulate further research on this complicated issue.

Prenatal care in the Paso del Norte border region

OBJECTIVES

The impact of a Medicaid-managed care system on access to prenatal care was investigated.

STUDY DESIGN

Postpartum interviews and medical chart abstractions were conducted among 493 Hispanic women who reside on the El Paso Texas/Juarez Mexico border (the Paso del Norte region). Descriptive analysis identified barriers and facilitators to prenatal care. Logistic regression identified the impact of social and demographic characteristics on selected maternal and infant outcomes.

RESULTS

The factors reported by these women as barriers to timely entry and sustaining enrollment in prenatal care were related to the availability of social support networks and affiliation with the Mexican/Hispanic culture (acculturation). Having Medicaid-managed care or other insurance was associated with receiving more adequate levels of prenatal care. Women who crossed the border to seek perinatal services were more likely to have infants who received higher levels of neonatal care (odds ratio 0.500; 95% CI [0.264, 0.946]).

CONCLUSIONS

The promotion of preconceptional, prenatal, and family planning services is strongly recommended as a strategic, regional, public health intervention.

Invited review: Neural network plasticity in respiratory control

Respiratory network plasticity is a modification in respiratory control that persists longer than the stimuli that evoke it or that changes the behavior produced by the network. Different durations and patterns of hypoxia can induce different types of respiratory memories. Lateral pontine neurons are required for decreases in respiratory frequency that follow brief hypoxia. Changes in synchrony and firing rates of ventrolateral and midline medullary neurons may contribute to the long-term facilitation of breathing after brief intermittent hypoxia. Long-term changes in central respiratory motor control may occur after spinal cord injury, and the brain stem network implicated in the production of the respiratory rhythm could be reconfigured to produce the cough motor pattern. Preliminary analysis suggests that elements of brain stem respiratory neural networks respond differently to hypoxia and hypercapnia and interact with areas involved in cardiovascular control. Plasticity or alterations in these networks may contribute to the chronic upregulation of sympathetic nerve activity and hypertension in sleep apnea syndrome and may also be involved in sudden infant death syndrome.

Medullary respiratory neurones and control of laryngeal motoneurones during fictive eupnoea and cough in the cat

1. This study addressed the hypothesis that ventrolateral medullary respiratory neurones participate in the control of laryngeal motoneurones during both eupnoea and coughing. 2. Data were obtained from 28 mid-collicular decerebrated, artificially ventilated cats. Cough-like motor patterns (fictive cough) in phrenic, lumbar and recurrent laryngeal nerves were elicited by mechanical stimulation of the intrathoracic trachea. Microelectrode arrays were used to monitor simultaneously several neurones in the ventral respiratory group, including the Bötzinger and pre-Bötzinger complexes. Spike trains were evaluated for responses during fictive cough and evidence of functional connectivity with spike-triggered averages of efferent recurrent laryngeal nerve activity. 3. Primary features were observed in averages triggered by 94 of 332 (28 %) neurones. An offset biphasic wave with a positive time lag was present in the unrectified average for 10 inspiratory and 13 expiratory neurones. These trigger neurones were respectively identified as inspiratory laryngeal motoneurones with augmenting, decrementing, plateau and "other" discharge patterns, and expiratory laryngeal motoneurones with decrementing firing patterns. 4. Rectified averages triggered by inspiratory neurones included 37 offset peaks, 11 central peaks and one offset trough. Averages triggered by expiratory neurones had 12 offset peaks, six central peaks and four offset troughs. Relationships inferred from these features included premotor actions of inspiratory neurones with augmenting, decrementing, plateau and "other" patterns on inspiratory laryngeal motoneurones, and premotor actions of decrementing and "other" expiratory neurones on expiratory laryngeal motoneurones. Corresponding changes in neuronal firing patterns during fictive cough supported these inferences. 5. The data confirm and extend previous results on the control of laryngeal motoneurones during eupnoea and support the hypothesis that the same premotor neurones help to shape motoneurone firing patterns during both eupnoea and coughing.

Changes in cat medullary neurone firing rates and synchrony following induction of respiratory long-term facilitation

1. Long-term facilitation is a respiratory memory expressed as an increase in motor output lasting more than an hour. This change is induced by repeated hypoxia, stimulation of carotid chemoreceptors, or electrical stimulation of the carotid sinus nerve or brainstem mid-line. The present work addressed the hypothesis that persistent changes in medullary respiratory neural networks contribute to long-term facilitation. 2. Carotid chemoreceptors were stimulated by close arterial injection of CO(2)-saturated saline solution. Phrenic nerve efferent activity and up to 30 single medullary neurones were recorded simultaneously in nucleus tractus solitarii (NTS) including the dorsal respiratory group (DRG), Botzinger-ventral respiratory group (Böt-VRG), and nucleus raphe obscurus of nine adult cats, anaesthetized, injected with a neuromuscular blocking agent, vagotomized and artificially ventilated. 3. The firing rates of 87 of 105 neurones (83 %) changed following induction of long-term facilitation. Nine of eleven DRG and Böt-VRG putative premotor inspiratory neurones had increased firing rates with long-term facilitation. Fourteen of twenty-one raphe obscurus neurones with control firing rates less than 4 Hz had significant long-term increases in activity. 4. Cross-correlogram analysis suggested that there were changes in effective connectivity of neuron pairs with long-term facilitation. Joint peristimulus time histograms and pattern detection methods used with 'gravity' analysis also detected changes in short time scale correlations associated with long-term facilitation. 5. The results suggest that changes in firing rates and synchrony of VRG and DRG premotor neurones and altered effective connectivity among other functionally antecedent elements of the medullary respiratory network contribute to the expression of long-term facilitation.

The treatment of Wilms' tumour: results of the United Kingdom Children's cancer study group (UKCCSG) second Wilms' tumour study

The aims of the UKW2 study were: (1) to further refine treatment for stage I and II favourable histology (FH) patients; (2) to consolidate the UKW1 results for stage III FH patients; (3) to improve the outlook for patients with inoperable primary tumours and those patients with stage IV and unfavourable histology disease. Treatment consisted of primary nephrectomy, wherever possible, followed by chemotherapy and radiotherapy, as dictated by stage and histology. Treatment was refined successfully for stage I and II FH patients. The 4-year event-free survival for these two groups was 94% and 91%, respectively. Stage III FH patients had a 4-year event free survival of 84%. The outlook for patients with clear cell sarcoma of the kidney is as good as for patients with favourable histology, whilst that for patients with anaplastic or rhabdoid variants remains poor. The outlook for the majority of children with Wilms' tumour is now excellent.

Repeated sequences of interspike intervals in baroresponsive respiratory related neuronal assemblies of the cat brain stem

Many neurons exhibit spontaneous activity in the absence of any specific experimental perturbation. Patterns of distributed synchrony embedded in such activity have been detected in the brain stem, suggesting that it represents more than "baseline" firing rates subject only to being regulated up or down. This work tested the hypothesis that nonrandom sequences of impulses recur in baroresponsive respiratory-related brain stem neurons that are elements of correlational neuronal assemblies. In 15 Dial-urethan anesthetized vagotomized adult cats, neuronal impulses were monitored with microelectrode arrays in the ventral respiratory group, nucleus tractus solitarius, and medullary raphe nuclei. Efferent phrenic nerve activity was recorded. Spike trains were analyzed with cycle-triggered histograms and tested for respiratory-modulated firing rates. Baroreceptors were stimulated by unilateral pressure changes in the carotid sinus or occlusion of the descending aorta; changes in firing rates were assessed with peristimulus time and cumulative sum histograms. Cross-correlation analysis was used to test for nonrandom temporal relationships between spike trains. Favored patterns of interspike interval sequences were detected in 31 of 58 single spike trains; 18 of the neurons with significant sequences also had short-time scale correlations with other simultaneously recorded cells. The number of distributed patterns exceeded that expected under the null hypothesis in 12 of 14 data sets composed of 4-11 simultaneously recorded spike trains. The data support the hypothesis that baroresponsive brain stem neurons operate in transiently configured coordinated assemblies and suggest that single neuron patterns may be fragments of distributed impulse sequences. The results further encourage the search for coding functions of spike patterns in the respiratory network.

Respiratory neuronal assemblies

This review describes results from in vivo experiments on brain stem network mechanisms that control breathing. Multi-array recording technology and computational methods were used to test predictions derived from simulations of respiratory network models. This highly efficient approach has the advantage that many simultaneously recorded neurons are subject to shared stimulus, history, and state-dependent conditions. Our results have provided evidence for concurrent or parallel network interactions in the generation and modulation of the respiratory motor pattern. Recent data suggest that baroreceptors, chemoreceptors, nociceptors, and airway cough receptors shape the respiratory motor pattern, at least in part, through a system of shared coordinated 'multifunctional' neurons distributed in the brain stem. The 'gravity method' for the analysis and representation of multi-neuron data has demonstrated respiratory phase-dependent impulse synchrony among neurons with no respiratory modulation of their individual firing rates. The detection of this emergent property motivated the development of pattern detection methods that subsequently identified repeated transient configurations of these 'correlational assemblies'. These results support the view that information can be 'coded' in the nervous system by spike timing relationships, in addition to firing rate changes that traditionally have been measured by neurophysiologists.

Respiratory neural activity during long-term facilitation

Intermittent hypoxia results in a long-term facilitation (LTF) of respiratory efferent activity. The studies reviewed here presented data from both anesthetized and decerebrate, paralyzed, vagotomized, artificially ventilated adult cats. Multiple arrays of tungsten microelectrodes were used to record the concurrent responses of brain stem neurons that contribute to respiratory motor pattern generation. Spike trains were analyzed with firing rate histograms, peristimulus time histograms, cycle triggered histograms, spike triggered averages with multiunit phrenic efferent activity, cross correlation histograms, joint peristimulus time histograms and the gravity method. These studies addressed several hypotheses. (1) There is parallel processing of input from carotid chemoreceptors to the brain stem. (2) Respiratory related midline neurons are involved in the induction and maintenance of LTF. (3) There is a change in effective connectivity of brain stem neurons with LTF. (4) Neural networks involved in the induction and maintenance of LTF have patterns of synchrony that recur with a frequency greater than expected by chance.

Recombinant human bone morphogenetic protein-2 and collagen for bone regeneration

The study reported describes a combination of recombinant human bone morphogenetic protein-2 (rhBMP-2) and collagen (C) to regenerate bone. Unilateral critical-sized defects (CSDs) were prepared in radii of 32 skeletally mature New Zealand white rabbits. Rabbits were divided evenly among four treatments: autograft, absorbable C (Helistat), 35 microg of rhBMP-2 combined with absorbable C (rhBMP-2/C), and untreated CSDs. The two euthanasia periods were 4 and 8 weeks. Radiographs were taken the day of surgery, every 2 weeks, and at term and the percent of radiopacity was measured. Data analysis revealed a time-dependent increase in the percent radiopacity with rhBMP-2/C. Histological examination revealed the rhBMP-2/C treatment regenerated osseous contour by 8 weeks. According to quantitative histomorphometry, the CSD and C groups had significantly less new bone than either autograft or rhBMP-2/C (p < or = 0.05). The results suggest that rhBMP-2/C could be an effective therapy to restore segmental bone defects.

Transient configurations of baroresponsive respiratory-related brainstem neuronal assemblies in the cat

The regulation of gas exchange requires coordination of the respiratory and cardiovascular systems. Previous work suggested that medullary raphe neurones transform and transmit information from baroreceptors to neurones in the ventral respiratory group. This study tested the hypothesis that distributed brainstem neuronal assemblies are transiently reconfigured during the respiratory cycle and baroreceptor stimulation. Blood pressure was perturbed by intravenous injection of an alpha1-adrenergic receptor agonist, unilateral pressure changes in the carotid sinus, or occlusion of the descending aorta in 14 Dial-urethane anaesthetized, vagotomized, paralysed, artificially ventilated cats. Neurones were monitored simultaneously with microelectrode arrays in two or more of the following sites: n. raphe obscurus, n. raphe magnus, rostral and caudal ventrolateral medulla, and the nucleus tractus solitarii. Transient configurations of baroresponsive assemblies were detected with joint pericycle-triggered histograms, the gravitational representation, and related pattern detection methods. Data were also analysed with cycle-triggered histograms, peristimulus-time and cumulative sum histograms, cross-correlograms, spike-triggered averages of efferent phrenic activity, and joint impulse configuration scatter diagrams (snowflakes). Five to nine simultaneously recorded spike trains from control expiratory phases were compared with data from interleaved equal-duration time blocks from control inspiratory phases. In each of seven animals, significant impulse synchrony detected by gravity analysis was confined to one phase of the respiratory cycle. Repeated patterns of distributed synchrony confined to periods of altered baroreceptor activity were detected and involved neurones that individually did not change firing rates during stimulation. Snowflakes and logical cross-correlation analysis provided evidence for the cooperative actions of impulses in concurrently active parallel channels. In 12 of 17 pairs of neurones with at least one baroresponsive cell, joint pericycle-triggered histograms detected synchrony indicative of shared inputs or functional excitatory interactions that varied as a function of time in the respiratory cycle. Neurones in four of the pairs had no respiratory modulation of their individual firing rates. Data from eight other pairs were indicative of fluctuations in inhibition during the respiratory cycle. The results demonstrate repeated transient configurations of baroresponsive neuronal assemblies during the respiratory cycle, without concomitant firing rate changes in the constituent neurones, and suggest distributed network mechanisms for the modulation of baroreceptor-mediated reflexes.