Debunking Myths of Gender Informed Care: What Every Pediatric Surgeon Should Know

As the transgender population in the United States grows, gender-affirming care is becoming increasingly relevant to the practice of pediatric surgery. Medical care for the transgender and gender diverse population is a politically charged topic with significant complexity and opportunities for clarification. It is important for providers to better understand this population's unique health and social needs. This review aims to debunk long-standing myths regarding gender-affirming care and highlight the current therapeutic and legislative landscapes within the scope of pediatric surgical practice. LEVEL OF EVIDENCE: IV.

Minimally invasive surgery of the pancreas: a narrative review of current practice

Minimally invasive surgery has moved from the fringe of pediatric surgery to the mainstream to address a variety of problems. Pancreatic pathology, though uncommon and complex, is frequently amenable to laparoscopic intervention. Indications for pediatric pancreatic operative intervention includes trauma, congenital hyperinsulinemia and neoplasm. Children may require distal pancreatectomy, subtotal pancreatectomy, enucleation, lateral pancreaticojejunostomy and pancreaticoduodenectomy. Of these operations, all but pancreaticoduodenectomy have been successfully described in children using a minimally invasive approach. Traumatic transection of the main pancreatic duct may require operative intervention if endoscopic techniques are unsuccessful. Distal pancreatectomy has been successfully utilized in this circumstance. Additionally, near total pancreatectomy may also be performed laparoscopically although successful reports are limited. Enucleation, especially with the use of intraoperative ultrasound may avoid a large laparotomy for isolated benign masses. Finally, chronic pancreatitis resulting in a dilated main pancreatic duct may benefit from a lateral pancreaticojejunostomy. This operation has also successfully been performed in children. Included is a review of pediatric pancreatic minimally invasive operations paired with corresponding pathology.

Pediatric gastric adenocarcinoma: A National Cancer Data Base review

PURPOSE

We sought to compare the presentation, management, and outcomes in gastric adenocarcinoma cancer for pediatric and adult patients.

METHODS

Using the 2004 to 2014 National Cancer Database (NCDB), patients ≤21 years (pediatric) were retrospectively compared to >21 years (adult). Chi-squared tests were used to compare categorical variables, and Cox regression was used to estimate hazard ratios (HR) for survival differences.

RESULTS

Of the 129,024 gastric adenocarcinoma cases identified, 129 (0.10%) occurred in pediatric patients. Pediatric cases presented with more advanced disease, including poorly differentiated tumors (81% vs 65%, p = 0.006) and stage 4 disease (56% vs 41%, p = 0.002). Signet ring adenocarcinoma comprised 45% of cases in the pediatric group as compared to 20% of cases in the adults (P < 0.001). Similar proportions in both groups underwent surgery. However, near-total gastrectomy was more common in the pediatric group (16% vs 6%, p < 0.001). The proportions of patients with negative margins, nodal examination, and presence of positive nodes were similar. There was no overall survival difference between the two age groups (HR 0.92, 95% Confidence interval 0.73-1.15).

CONCLUSION

While gastric adenocarcinoma in pediatric patients present with a more advanced stage and poorly differentiated tumors compared to adults, survival appears to be comparable.

TYPE OF STUDY

Retrospective cohort study.

LEVEL OF EVIDENCE

III.

Health outcomes and the healthcare and societal cost of optimizing pediatric surgical care in the United States

BACKGROUND

There is a movement to ensure that pediatric patients are treated in appropriately resourced hospitals through the ACS Children's Surgery Verification (CSV) program. The objective of this study was to assess the potential difference in care provision, health outcomes and healthcare and societal costs after implementation of the CSV program.

METHODS

All 2011 inpatient admissions for selected complex pediatric patients warranting treatment at a hospital with Level I resources were evaluated across 6 states. Multivariate regressions were used to analyze differences in healthcare outcomes (postoperative complications including death, length of stay, readmissions and ED visits within 30 days) and costs by CSV level. Recycled predictions were used to estimate differences between the base case scenario, where children actually received care, and the optimized scenario, where all children were theoretically treated at Level I centers.

RESULTS

8,006 children (mean age 3.06 years, SD 4.49) met inclusion criteria, with 45% treated at Level I hospitals, 30% at Level II and 25% at Level III. No statistically significant differences were observed in healthcare outcomes. Readmissions within 30 days were higher at Level II compared to Level I centers (adjusted IRR 1.61; 95% CI 1.11, 2.34), with an estimated 24 avoidable readmissions per 1000 children if treatment were shifted from Level II to Level I centers. Overall, costs per child were not significantly different between the base case and the optimized scenario.

CONCLUSION

Many complex surgical procedures are being performed at Level II/III centers. This study found no statistically significant increase in healthcare or societal costs if these were performed instead at Level I centers under the optimized scenario. Ongoing evaluation of efforts to match institutional resources with individual patient needs is needed to optimize children's surgical care in the United States.

LEVEL OF EVIDENCE

II.

Partial Nephrectomy for Nephroblastoma: A National Cancer Data Base Review

Standard of care for unilateral nephroblastoma includes total nephrectomy (TN) with nodal sampling. We sought to compare the outcomes of TN and partial nephrectomy (PN). We performed a retrospective cohort study of TN and PN for nephroblastoma using the National Cancer Data Base. The outcomes included nodal sampling frequency, margin status, and survival. Categorical and continuous data were evaluated with χ2 and t tests, respectively ( P < 0.05). Generalized linear models evaluated nodal sampling and margin status. Cox regression compared survival. In total, 235 patients underwent PN and 3572 had TN. TN patients were 50 per cent more likely to undergo nodal sampling (RR: 1.47, 95% CI 1.30–1.66). There was no difference in margin status (RR: 0.91, 95% CI 0.65–1.28) or overall survival (HR 1.57; 95% CI 0.78–3.19). This study reports the largest review of patients with PN for unilateral nephroblastoma. PN patients had less nodal sampling but similar margin involvement and overall survival.

Partial Nephrectomy for Nephroblastoma: A National Cancer Data Base Review

Standard of care for unilateral nephroblastoma includes total nephrectomy (TN) with nodal sampling. We sought to compare the outcomes of TN and partial nephrectomy (PN). We performed a retrospective cohort study of TN and PN for nephroblastoma using the National Cancer Data Base. The outcomes included nodal sampling frequency, margin status, and survival. Categorical and continuous data were evaluated with χ2 and t tests, respectively (P < 0.05). Generalized linear models evaluated nodal sampling and margin status. Cox regression compared survival. In total, 235 patients underwent PN and 3572 had TN. TN patients were 50 per cent more likely to undergo nodal sampling (RR: 1.47, 95% CI 1.30-1.66). There was no difference in margin status (RR: 0.91, 95% CI 0.65-1.28) or overall survival (HR 1.57; 95% CI 0.78-3.19). This study reports the largest review of patients with PN for unilateral nephroblastoma. PN patients had less nodal sampling but similar margin involvement and overall survival.

The association between nephroblastoma-specific outcomes and high versus low volume treatment centers

BACKGROUND

Though the volume-outcome relationship has been well-established in adults, low mortality rates and small sample sizes have precluded definitive demonstration in children. This study compares treatment-specific factors for children with nephroblastoma at high (HVC) versus low volume centers (LVC).

METHODS

We performed a retrospective cohort study comparing patients ≤18years with unilateral nephroblastoma treated at HVCs and LVCs using the National Cancer Data Base (1998-2012). Definitions of HVCs included performing above the median, the upper two quartiles, and the highest decile of nephroblastoma resections. Outcomes included nodal sampling, margin status, time to chemotherapy and radiation, and survival. Statistical analyses included χ², t-tests, generalized linear, and Cox regression models (p<0.05).

RESULTS

Of 2911 patients from 210 centers, 1443 (49.6%) were treated at HVCs. There was no difference in frequency of preoperative biopsy or days to radiation (p>0.05). High volume centers were more likely to perform nodal sampling (RR 1.04, 95%CI 1.01-1.08) and had fewer days to chemotherapy (RR 0.80, 95%CI 0.69-0.93). Five-year survival was similar (HVC: 0.93, 95%CI 0.92-0.94; LVC: 0.93, 95%CI 0.91-0.94).

CONCLUSIONS

HVCs were more likely to perform nodal sampling and had fewer days to chemotherapy. There was no difference in days to radiation or survival between centers.

LEVEL OF EVIDENCE

Level II (retrospective prognosis study).

Establishing Equipoise: National Survey of the Treatment of Pediatric Para-Pneumonic Effusion and Empyema

BACKGROUND

Despite six randomized trials of various treatments for pediatric para-pneumonic effusion (PPE), management approaches differ. The purpose of this study was to gain insight into opinions on PPE treatment with the goal of designing a definitive trial to generate consensus intervention guidelines.

METHODS

To evaluate physician opinions regarding PPE management, we developed a survey based on input from a nationwide, multi-disciplinary advisory group that established content validity. The survey was disseminated broadly to six pediatric medicine and interventional radiology groups. Descriptive and χ² statistics were calculated.

RESULTS

There were 741 respondents (response rate 13.1%), of whom 52.2% were surgeons, 15.2% hospitalists, 14.2% pulmonologists, 12.4% intensivists, and 6.0% interventional radiologists. Nearly all respondents (97.3%) reported caring primarily for pediatric patients. Eighty percent reported no written institutional treatment guidelines. Nearly all (90.3%) agreed that patients require antibiotics, but there was disagreement regarding their duration. Respondents also were split as to how often PPE required drainage. There were multiple absolute indications for drainage, including mediastinal shift on chest radiograph (67.2%) and loculations on imaging (47.7%). There were substantial differences in the preferred first-line methods of drainage based on the treating physician's specialty, with surgeons preferring tube thoracostomy and a fibrinolytic agent (42.0%) or video-assisted thoracoscopic surgery (41.6%), whereas interventional radiologists preferred either a tube thoracostomy (46.4%) or a tube thoracostomy with a fibrinolytic agent (39.3%) (p < 0.001). A large majority (75.3%) believed that the published evidence does not identify the optimal intervention.

CONCLUSIONS

There is a lack of consensus regarding the optimal treatment of PPE. Respondents believed the published evidence is inconclusive and were willing to participate in a prospective trial. These findings will help inform the design of a randomized, pragmatic clinical trial to optimize PPE management.

Factors Associated With Mortality in Pediatric vs Adult Nasopharyngeal Carcinoma

IMPORTANCE

Nasopharyngeal carcinoma (NPC) is endemic in some Asian regions but is uncommon in the United States. Little is known about the racial, demographic, and biological characteristics of the disease in pediatric patients.

OBJECTIVES

To improve understanding of the differences between pediatric and adult NPC and to determine whether race conferred a survival difference among pediatric patients with NPC.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study included all 17 317 patients with a primary diagnosis of NCP in the National Cancer Data Base from January 1, 1998, to December 31, 2011. Of these, 699 patients were 21 years or younger (pediatric); 16 618 patients, older than 21 years (adult). Data were analyzed after data collection.

EXPOSURE

Pediatric age at diagnosis of NPC.

MAIN OUTCOMES AND MEASURES

Demographic, tumor, and treatment characteristics of pediatric patients with NPC were compared with those of adults using the χ2 test for categorical variables. An adjusted Cox proportional hazards regression model was used to examine survival differences in pediatric patients relative to adult patients. In addition, the risk for pediatric mortality by race was estimated.

RESULTS

Of the 17 317 patients, a total of 699 pediatric and 16 618 adult patients were identified with a primary diagnosis of NPC (female, 239 pediatric patients [34.2%] and 5153 adult patients [32.4%]). Pediatric patients were most commonly black (299 of 686 [43.6%]), whereas adults were most likely to be non-Hispanic white (9839 of 16 504 [60.0%]; P < .001). Pediatric patients were less likely to be Asian (39 of 686 [5.7%]) than were adults (3226 of 16 405 [19.7%]; P < .001). Pediatric patients were more likely to have regional nodal evaluation and to present with stage IV disease (227 of 643 [35.3%] and 330 of 565 [58.4%], respectively) than were adult patients (3748 of 15 631 [24.0%] and 6553 of 13 721 [47.8%], respectively; P < .001 for both comparisons). Pediatric patients had a lower risk for mortality relative to adults (hazard ratio, 0.37; 95% CI, 0.25-0.56). No difference in mortality by racial group was found among pediatric patients (hazard ratio, 1.10; 95% CI, 0.82-1.40).

CONCLUSIONS AND RELEVANCE

Pediatric patients with NPC were more commonly black and presented more frequently with stage IV disease. Pediatric patients had a decreased mortality risk relative to adults, even after adjusting for covariables. Asian race was not associated with increased mortality in pediatric patients with NPC. Racial differences are not associated with an increased risk for mortality among pediatric patients.

Efficacy and cost of robotic hepatectomy: is the robot cost-prohibitive?

Robotic technology is being utilized in multiple hepatobiliary procedures, including hepatic resections. The benefits of minimally invasive surgical approaches have been well documented; however, there is some concern that robotic liver surgery may be prohibitively costly and therefore should be limited on this basis. A single-institution, retrospective cohort study was performed of robotic and open liver resections performed for benign and malignant pathologies. Clinical and cost outcomes were analyzed using adjusted generalized linear regression models. Clinical and cost data for 71 robotic (RH) and 88 open (OH) hepatectomies were analyzed. Operative time was significantly longer in the RH group (303 vs. 253 min; p = 0.004). Length of stay was more than 2 days shorter in the RH group (4.2 vs. 6.5 days; p < 0.001). RH perioperative costs were higher ($6026 vs. $5479; p = 0.047); however, postoperative costs were significantly lower, resulting in lower total hospital direct costs compared with OH controls ($14,754 vs. $18,998; p = 0.001). Robotic assistance is safe and effective while performing major and minor liver resections. Despite increased perioperative costs, overall RH direct costs are not greater than OH, the current standard of care.

Primary cesarean section and adverse delivery outcomes among women of very advanced maternal age

OBJECTIVE

To assess associations between primary cesarean delivery and adverse delivery outcomes with very advanced maternal age.

STUDY DESIGN

We conducted a population-based cohort study including 78,880 births to mothers 25 years and older with singleton births from 2003 to 2012 using Washington State birth certificates and hospital discharge data, excluding births to women with a prior cesarean section. The primary outcome was mode of delivery. Secondary outcomes included maternal transfusion, chorioamnionitis, severe perineal lacerations and prolonged length of stay. Outcomes of births to women of advanced maternal age (35 to 39, 40 to 44) and very advanced maternal age (45 to 49, ⩾50) were compared with referent births among women aged 25 to 34 years. General linear models with a log-link function were used to calculate unadjusted and adjusted relative risks and 95% confidence intervals (CIs).

RESULT

Proportions and risks of primary cesarean section increased with age (25 to 34 years, referent: 20.0%; 35 to 39 years: 25.9%, relative risk (RR)=1.25 (95% CI=1.20 to 1.29); 40 to 44 years: 30.9%, RR=1.45 (95% CI=1.40 to 1.50); 45 to 49 years: 35.7%, RR=1.59 (95% CI=1.45 to 1.75); and ⩾50 years: 60.7%, RR=2.44 (95% CI=1.95 to 3.05); P-trend <0.001). Associations did not differ between primiparous and multiparous women. No differences were noted for measures of maternal morbidity, except there was a trend of increasing risk of prolonged length of stay among births to older women (P-trend <0.001).

CONCLUSION

Primary cesarean delivery risk continues to increase above age 35 regardless of prior vaginal birth, with the highest risk among women aged 50 years and older.

Factors associated with 30-day unplanned pediatric surgical readmission

BACKGROUND

Unplanned readmissions are costly to family satisfaction and negatively associated with quality of care. We hypothesized that patient, operative, and hospital factors would be associated with pediatric readmission.

METHODS

All patients with an inpatient operation from 10/1/2008 to 7/28/2014 at a freestanding children's hospital were included. A retrospective cohort study using multivariable forward stepwise logistic regression determined factors associated with unplanned readmission within 30 days of discharge.

RESULTS

Among 20,785 patients with an operation there were 26,978 encounters and 3,092 readmissions (11.5%). Thirteen of 33 candidate variables considered in the stepwise regression were significantly associated with readmission. Patients with an emergency department visit within 365 days of operation, American Society of Anesthesiologists class 4 or greater, Hispanic ethnicity and late-day or holiday/weekend discharges were more likely to have an unplanned readmission (odds ratio [OR] = 1.96; 95% confidence interval [CI] = 1.76 to 2.19, OR = 2.00; 95% CI = 1.58 to 2.53, OR = 1.16; 95% CI = 1.04 to 1.29, OR = 2.27; 95% CI = 1.55 to 3.63. respectively).

CONCLUSIONS

Patient and hospital factors may be associated with readmission. Day and time of discharge represent variability of care and are important targets for hospital initiatives to decrease unplanned readmission.

Patient-centered care and quality: Activating the system and the patient

Patient-centered care is an expectation in our current environment, yet it is only one of the six domains that the Institute of Medicine has described as critical in redesigning the architecture of a medical system. Patients requiring long-term feeding tube access represent a particularly complex group of patients who stress the mechanisms placed within a healthcare system to optimize quality and safety. We describe the implementation of a new approach to this patient population that serves as an example of redesigning a system of care to optimize safety using the principles of patient-centered care while delivering safe, effective, timely, efficient, and equitable care.

A national review of the frequency of minimally invasive surgery among general surgery residents: assessment of ACGME case logs during 2 decades of general surgery resident training

IMPORTANCE

Minimally invasive surgery (MIS) has created a shift in how many surgical diseases are treated. Examining the effect on resident operative experience provides valuable insight into trends that may be useful for restructuring the requirements of resident training.

OBJECTIVE

To evaluate changes in general surgery resident operative experience regarding MIS.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective review of the frequency of MIS relative to open operations among general surgery residents using the Accreditation Council for Graduate Medical Education case logs for academic years 1993-1994 through 2011-2012.

EXPOSURES

General surgery residency training among accredited programs in the United States.

MAIN OUTCOMES AND MEASURES

We analyzed the difference in the mean number of MIS techniques and corresponding open procedures across training periods using 2-tailed t tests with statistical significance set at P < .05.

RESULTS

Of 6,467,708 operations with the option of MIS, 2,393,030 (37.0%) were performed with the MIS approach. Of all MIS operations performed, the 5 most common were cholecystectomy (48.5%), appendectomy (16.2%), groin hernia repair (10.0%), abdominal exploration (nontrauma) (4.4%), and antireflux procedures (3.6%). During the study period, there was a transition from a predominantly open to MIS approach for appendectomy, antireflux procedures, thoracic wedge resection, and partial gastric resection. Cholecystectomy is the only procedure for which MIS was more common than the open technique throughout the study period (P < .001). The open approach is more common for all other procedures, including splenectomy (0.7% MIS), common bile duct exploration (24.9% MIS), gastrostomy (25.9% MIS), abdominal exploration (33.1% MIS), hernia (20.3% MIS), lung resection (22.3% MIS), partial or total colectomy (39.1%), enterolysis (19.0% MIS), ileostomy (9.0% MIS), enterectomy (5.2% MIS), vagotomy (1.8% MIS), and pediatric antireflux procedures (35.9% MIS); P < .001.

CONCLUSIONS AND RELEVANCE

Minimally invasive surgery has an increasingly prominent role in contemporary surgical therapy for many common diseases. The open approach, however, still predominates in all but 5 procedures. Residents today must become efficient at performing multiple techniques for a single procedure, which demands a broader skill set than in the past.

Use and accuracy of diagnostic imaging in the evaluation of pediatric appendicitis

BACKGROUND

There are safety concerns about the use of radiation-based imaging (computed tomography [CT]) to diagnose appendicitis in children. Factors associated with CT use remain to be determined.

METHODS

For patients ≤18 years old undergoing appendectomy, we evaluated diagnostic imaging performed, patient characteristics, hospital type, and imaging/pathology concordance (2008-2012) using data from Washington State's Surgical Care and Outcomes Assessment Program.

RESULTS

Among 2538 children, 99.7% underwent pre-operative imaging. 52.7% had a CT scan as their first study. After adjustment, age >10 years (OR 2.9 (95% CI 2.2-4.0), Hispanic ethnicity (OR 1.7, 95% CI 1.5-1.9), and being obese (OR 1.7, 95% CI 1.4-2.1) were associated with CT use first. Evaluation at a non-children's hospital was associated with higher odds of CT use (OR 7.9, 95% CI 7.5-8.4). Ultrasound concordance with pathology was higher for males (72.3 vs. 66.4%, p=.03), in perforated appendicitis (75.9 vs. 67.5%, p=.009), and at children's hospitals compared to general adult hospitals (77.3 vs. 62.2%, p<.001). CT use has decreased yearly statewide.

CONCLUSIONS

Over 50% of children with appendicitis had radiation-based imaging. Understanding factors associated with CT use should allow for more specific QI interventions to reduce radiation exposure. Site of care remains a significant factor in radiation exposure for children.

Improving ultrasound quality to reduce computed tomography use in pediatric appendicitis: the Safe and Sound campaign

BACKGROUND

Safety concerns about the use of radiation-based imaging such as computed tomography (CT) in children have resulted in national recommendations to use ultrasound (US) for the diagnosis of appendicitis when possible. We evaluated the trends in CT and US use in a statewide sample and the accuracy of these modalities.

METHODS

Patients less than or equal to 18 years undergoing appendectomy in Washington State from 2008 to 2013 were evaluated for preoperative US/CT use, as well as imaging/pathology concordance using data from the Surgical Care and Outcomes Assessment Program.

RESULTS

Among 3,353 children, 98.3% underwent preoperative imaging. There was a significant increase in the use of US first over the study period (P < .001). The use of CT at any time during the evaluation decreased. Despite this, in 2013, over 40% of the children still underwent CT imaging. Concordance between US imaging and pathology varied between 40% and 75% at hospitals performing greater than or equal to 10 appendectomies in 2013. Over one third (34.9%) of CT scans performed in the evaluation of children with appendicitis were performed after an indeterminate US.

CONCLUSIONS

Although the use of US as the first imaging modality to diagnose pediatric appendicitis has increased over the past 5 years, over 40% of children still undergo a CT scan during their preoperative evaluation. Causality for this persistence of CT use is unclear, but could include variability in US accuracy, lack of training, and lack of awareness of the risks of radiation-based imaging. Developing a campaign to focus on continued reduction in CT and increased use of high-quality US should be pursued.

Technetium-99m sestamibi imaging: are the results dependent on the reviewer?

BACKGROUND

Minimally invasive parathyroidectomy (MIP) is dependent upon accurate preoperative parathyroid localization. We hypothesized that surgeon recognition of subtle differences in radiotracer accumulation would increase the sensitivity of technetium-99m sestamibi imaging and result in more frequent use of MIP.

METHODS

Technetium-99m sestamibi scans completed at our institution for patients who underwent resection of a solitary parathyroid adenoma were reviewed by a surgeon and a radiologist who were blinded to patient identifying information, prior scan interpretation, and results of the operation. For each scan, the reviewer determined whether there was abnormal radiotracer accumulation and documented its location. Results were correlated with outcome of operation and final pathology. Blinded interpretations of the surgeon and radiologist were compared to each other and to the original radiologic interpretation.

RESULTS

From 1994 to 2009, 274 patients with primary hyperparathyroidism (HPT) had sestamibi imaging prior to parathyroidectomy; 149 patients with a single adenoma underwent curative parathyroidectomy and had scans available for review. Seventeen radiologists who reviewed an average of 11 ± 14 scans (range = 1-61) completed the original interpretations of the sestamibi imaging. Sensitivity of sestamibi imaging was 86% for the blinded surgeon compared to 75% for the blinded radiologist and 69% for the original radiologists (P < 0.05). There was no difference in the false positive rates (blinded surgeon = 5%, blinded radiologist = 5%, original radiologists = 5%, P > 0.05).

CONCLUSION

Radiologists were less likely to call a scan positive. Surgeon recognition of subtle anatomic asymmetry increases the sensitivity of sestamibi imaging and successful completion of MIP.

Stunting is associated with overweight in children of four nations that are undergoing the nutrition transition

A higher risk of obesity in stunted children has been described in Hispanic-American, Jamaican and Andean populations, but little systematic exploration has been done concerning this area in nutrition. This paper examines the relationship between stunting and overweight status for children aged 3-6 and 7-9 y in nationally representative surveys in Russia, Brazil, and the Republic of South Africa and a large nationwide survey in China. Using identical cut-offs for body mass index, the prevalence of child overweight in these countries ranges from 10.5 to 25.6% (based on the 85th percentile); recent NHANES III results indicate that this prevalence is around 22% in the U.S. Stunting is also common in the surveyed countries affecting 9.2-30.6% of all children. Our results showed a significant association between stunting and overweight status in children of all countries. The income-adjusted risk ratios of being overweight for a stunted child ranged from 1.7 to 7.8. Clearly, there is an important association between stunting and high weight-for-height in a variety of ethnic environmental and social backgrounds. Although the underlying mechanisms remain unexplored, this association has serious public health implications particularly for lower income countries. As these countries enter the nutrition transition experiencing large changes in dietary and activity patterns, they may face, among other problems, additional difficulties in their fight against obesity.

Characterization of C415 mutants of neuronal nitric oxide synthase

Nitric oxide synthase (NOS) catalyzes the oxidation of L-arginine to citrulline and nitric oxide. C415H and C415A mutants of the neuronal isoform of NOS (nNOS) were expressed in a baculovirus system and purified to homogeneity for spectral analysis and activity measurements. UV-visible spectra of each mutant lacked an observable Soret peak, suggesting that neither mutant contained heme. When reduced in the presence of CO, however, a small Soret centered at 417 nm could be detected for the C415H mutant, further supporting the assignment of C415 as the axial ligand to the heme. In addition to a deficiency in bound heme, neither mutant had any detectable bound tetrahydrobiopterin, as compared to wild-type enzyme, which had a ratio of 0.84 mol of bound pteridine:1 mol of nNOS 160 kDa subunit. The C415H mutant contained bound FAD and FMN at levels of 1.0 +/- 0.1 and 0.9 +/- 0.1 mol/mol of nNOS subunit, respectively. UV-visible spectra of both nNOS mutants retained the distinctive absorbance due to tightly associated oxidized flavin prosthetic groups. Further, the spectra suggested the presence of a neutral flavin semiquinone. Ferricyanide oxidation of the C415A mutant yielded a spectrum that was essentially that of oxidized flavin. Ferricyanide titration showed that the C415A mutant contained approximately 1 reducing equiv. Circular dichroism spectra suggested that each mutant was folded properly, in that both spectra were found to be essentially identical to the spectrum of wild-type nNOS. Neither mutant could synthesize nitric oxide, and neither mutant had the ability to oxidize NADPH unless an exogenous electron acceptor was added. The rate of cytochrome c reduction by each mutant was found to be slightly less, but very similar to the rate (approximately 20 mumol mg-1 min-1) observed with wild-type nNOS. In all cases, the rate of cytochrome c reduction increased approximately 15-fold with the addition of calmodulin. Overall, these spectral and activity data suggest that C415 is the axial heme ligand and that a point mutation at C415 prevents binding of heme and tetrahydrobiopterin without interfering with the global folding or the reductase function of nNOS.

Lung sources and cytokine requirements for in vivo expression of inducible nitric oxide synthase

Products of inducible nitric oxide synthase (iNOS) are known to be involved in lung injury following intrapulmonary deposition of immunoglobulin G immune complexes (IgG-ICx). In the current studies rat alveolar macrophages stimulated in vitro with murine interferon gamma (IFN-gamma), tumor necrosis factor alpha, interleukin 1 alpha, (IL-1 alpha), lipopolysaccharide (LPS), or IgG-ICx immunostained for iNOS and produced nitrite/nitrate- (NO2-/NO3-) in a dose- and time-dependent manner requiring availability of L-arginine. Under the same conditions, IL-4 and IL-10 reduced NO2-/NO3- generation. Type II alveolar epithelial cells, which were obtained from normal rat lungs and stimulated in vitro with IgG-ICx, LPS, or IFN-gamma, also immunostained for iNOS and generated NO2-/NO3-. Special techniques of bronchoalveolar lavage (BAL) were used to retrieve alveolar macrophages and type II alveolar epithelial cells. Under these conditions, intrapulmonary deposition of LPS yielded BAL fluids containing increased amounts of NO2-/NO3- and macrophages that spontaneously released NO2-/NO3- and stained for iNOS. After intrapulmonary deposition of IgG both macrophages as well as type II cells (retrieved by BAL) spontaneously produced NO2-/NO3- and both cell types immunostained for iNOS (approximately 20% of all type II cells and 35% of all alveolar macrophages). Using dual fluorescence staining for cell identification, frozen sections of lung tissue after IgG immune complex deposition revealed iNOS in both alveolar macrophages and type II cells. Finally, in the immune complex model of alveolitis, the appearance of iNOS in macrophages as well as macrophage production in vitro of NO2-/NO3- was dependent on the in vivo availability of tumor necrosis factor alpha, IL-1, and IFN-gamma. These studies suggest a dual cell source for nitric oxide in inflamed lungs and the requirements for iNOS of several cytokines.

Characterization of neuronal nitric oxide synthase and a C415H mutant, purified from a baculovirus overexpression system

Nitric oxide synthase (NOS) catalyzes the conversion of L-arginine to citrulline and nitric oxide (.NO). A baculovirus overexpression system has been developed for a constitutive NOS isoform, cloned originally from rat cerebellum (B-NOS). Recombinant virus was used at a multiplicity of infection of 5 to infect Spodoptera frugiperda cells in culture, and NOS was expressed to 10% of the total soluble protein at 48 h postinfection. In order to express catalytically active enzyme, it was necessary to supplement the culture media with hemin. This increased the activity of the enzyme 7-fold. A two column affinity purification was developed for the recombinant enzyme, which gave homogeneous protein that migrated at 150 kDa on a denaturing polyacrylamide gel. A Km for L-arginine was determined to be 2.0 +/- 0.4 microM. As isolated, recombinant B-NOS exhibited a Soret maximum at 402 nm, which shifted to 394 nm in the presence of L-arginine. The Soret maximum of the reduced enzyme in the presence of CO was 444 nm. Initial rate steady-state kinetic analysis of the recombinant B-NOS showed evidence of substrate inhibition by L-arginine, which could also be seen in a partially purified preparation of B-NOS from rat cerebella. This substrate inhibition was not observed with the inducible isoform of NOS, purified from immunostimulated murine macrophages. A C415H mutant was overexpressed and purified using the same conditions established for the wild-type recombinant B-NOS. This C415H mutant exhibited no activity and did not bind heme, providing the first experimental evidence to support previously reported primary amino acid comparisons which suggest that C415 provides the coordinating thiolate to the heme moiety in B-NOS.

Inactivation of macrophage nitric oxide synthase activity by NG-methyl-L-arginine

.N = O synthase catalyzes the oxidation of one of the two chemically equivalent guanido nitrogens of L-arginine to nitric oxide (.N = O). NG-Methyl-L-arginine has been previously characterized as a potent competitive inhibitor of both major types of .N = O synthases. Initial rate kinetics were performed with a spectrophotometric assay based on the oxidation of oxy- to methemoglobin by .N = O. NG-Methyl-L-arginine was a competitive inhibitor of .N = O synthase activity derived from activated murine macrophages with a Ki of 6.2 microM. When the enzyme was pre-incubated in the presence of the required cofactors NADPH and tetrahydrobiopterin, time- and concentration-dependent irreversible inactivation of the activity was observed. At 37 degrees C the kinact was 0.050 min-1. This inactivation process exhibited substrate protection, saturation kinetics and required the cofactors necessary for enzymatic turnover. These data indicate that NG-methyl-L-arginine acts as a mechanism-based enzyme inactivator of murine macrophage .N = O synthase.

Novel avermectins produced by mutational biosynthesis

Avermectins with a wide range of novel C-25 substituents have been prepared by feeding carboxylic acids or their biosynthetic precursors to a Streptomyces avermitilis mutant strain ATCC 53568. This organism lacks the ability to form isobutyric and S-2-methylbutyric acids from their 2-oxo acid precursors and thus is unable to produce natural avermectins unless supplied with these acids. The novel avermectins produced by mutational biosynthesis possess broad-spectrum antiparasitic activity.

Rapid analysis of glycolipid anchors in amphiphilic dimers of acetylcholinesterases

1. We describe two simple procedures for the rapid identification of certain structural features of glycolipid anchors in acetylcholinesterases (AChEs). 2. Treatment with alkaline hydroxylamine (that cleaves ester-linked acyl chains but not ether-linked alkyl chains) converts molecules possessing a diacylglycerol, but not those with an alkylacylglycerol, into hydrophilic derivatives. AChEs in human and bovine erythrocytes possess an alkylacylglycerol (Roberts et al., J. Biol. Chem. 263:18766-18775, 1988; Biochem. Biophys. Res. Commun. 150:271-277, 1988) and are not converted to hydrophilic dimers by alkaline hydroxylamine. Amphiphilic dimers of AChE from Drosophila, from mouse erythrocytes, and from the human erythroleukaemia cell line K562 also resist the treatment with hydroxylamine and likely possess a terminal alkylacylglycerol. This indicates that the cellular pool of free glycolipids used as precursors of protein anchors is distinct from the pool of membrane phosphatidylinositols (which contain diacylglycerols). 3. Pretreatment with alkaline hydroxylamine is required to render the amphiphilic AChE from human erythrocytes susceptible to digestion by Bacillus thuringiensis phosphatidylinositol-specific phospholipase C (PI-PLC) (Toutant et al., Eur. J. Biochem. 180:503-508, 1989). We show here that this is also the case for the AChE from mouse erythrocytes, which therefore likely possesses an additional acyl chain in the anchor that prevents the action of PI-PLC. 4. In two sublines of K562 cells (48 and 243), we observed that AChE either was directly susceptible to PI-PLC (243) or required a prior deacylation by alkaline hydroxylamine (48). This suggests that glycolipid anchors in AChE of K562-48 cells, but not those in AChE of K562-243 cells, contain the additional acylation demonstrated in AChE from human erythrocytes. These observations illustrate the cell specificity (and the lack of species-specificity) of the structure of glycolipid anchors.

The immune response to myelin proteolipid protein in the Lewis rat: identification of the immunodominant B cell epitope

The polyclonal antibody response of the Lewis rat to bovine myelin proteolipid protein (PLP) has been investigated following immunisation with either the purified protein or bovine central nervous system myelin. In both situations, the carboxyl-terminal sequence of PLP was identified as the immunodominant domain of this protein and epitope mapping demonstrated that the carboxyl-terminal amino acid, phenylalanine276, was a critical requirement for antibody recognition of this epitope. This single epitope accounted for approximately 78% and 56% of the antibody response to PLP in rats immunised with PLP or bovine myelin, respectively. Polyclonal rat antibodies specific for this carboxyl terminal epitope of PLP were also obtained following immunisation with a synthetic 20 amino acid oligopeptide analogue of the carboxyl-terminal sequence of PLP. Western blotting demonstrated this antibody response was specific for the PLP and DM-20 components of mammalian central nervous system myelin. In contrast, no major PLP epitopes were detected within the PLP amino acid sequences 35-58 and 91-150, the other major hydrophilic domains of this protein.

Molecular forms of acetylcholinesterase in two sublines of human erythroleukemia K562 cells. Sensitivity or resistance to phosphatidylinositol-specific phospholipase C and biosynthesis

Acetylcholinesterase (AChE) in K562 cells exists in two molecular forms. The major form, an amphiphilic dimer (G2a) which sediments at 5.3 S, and the minor form, an amphiphilic monomer (G1a) which sediments at 3.5 S. Extraction in the presence of the sulfhydryl alkylating agent N-ethylmaleimide was required to preserve the G2a form. In Triton X-100 extracts of the subline K562-243, phosphatidylinositol-specific phospholipase C (PtdIns-PLC) from Bacillus thuringiensis converted most of the G2a AChE into a hydrophilic dimer (G2h), indicating that the G2a form possessed a hydrophobic glycoinositol phospholipid that mediated its attachment to the membrane. Treatment of intact K562-243 cells with PtdIns-PLC released approximately 60% of the total AChE activity and provided an estimate of the externally exposed AChE. The direct conversion from an amphiphilic to a hydrophilic dimeric form by PtdIns-PLC was not obtained in extracts or intact cells of the subline K562-48. Instead, pretreatment with alkaline hydroxylamine was necessary to render the amphiphilic G2 form of this subline susceptible to digestion by the phospholipase. In this respect, the amphiphilic dimer of K562-48 AChE resembles the G2a form of human erythrocyte AChE, which is resistant to PtdIns-PLC because of the direct palmitoylation of an inositol hydroxyl group in the anchor [Roberts et al. (1988) J. Biol. Chem. 263, 18766-18775]. Release of this acyl chain by hydroxylamine renders the enzyme susceptible to PtdIns-PLC [Toutant et al. (1989) Eur. J. Biochem. 180, 503-508]. In both K562 sublines, sialidase decreased the migration of the G2a form but not of the G1a form of AChE. G1a forms thus appear to represent an intracellular pool of newly synthesized molecules residing in a compartment proximal to the trans-Golgi apparatus. The sialidase-resistant G1a molecules were also resistant to PtdIns-PLC digestion; possible explanations for this resistance are presented.