Prenatally Diagnosed Large Lung Lesions: Timing of Resection and Perinatal Outcomes

INTRODUCTION

Fetuses with large lung lesions including congenital cystic adenomatoid malformations (CCAMs) are at risk for cardiopulmonary compromise. Prenatal maternal betamethasone and cyst drainage for micro- and macrocystic lesions respectively have improved outcomes yet some lesions remain large and require resection before birth (open fetal surgery, OFS), at delivery via an Ex Utero Intrapartum Treatment (EXIT), or immediately post cesarean section (section-to-resection, STR). We sought to compare prenatal characteristics and outcomes in fetuses undergoing OFS, EXIT, or STR to inform decision-making and prenatal counseling.

METHODS

A single institution retrospective review was conducted evaluating patients undergoing OFS, EXIT, or STR for prenatally diagnosed lung lesions from 2000 to 2021. Specimens were reviewed by an anatomic pathologist. Lesions were divided into "CCAMs" (the largest pathology group) and "all lung lesions" since pathologic diagnosis is not possible during prenatal evaluation when care decisions are made. Prenatal variables included initial, greatest, and final CCAM volume-ratio (CVR), betamethasone use/frequency, cyst drainage, and the presence of hydrops. Outcomes included survival, ECMO utilization, NICU length of stay (LOS), postnatal nitric oxide use, and ventilator days.

RESULTS

Sixty-nine percent (59 of 85 patients) of lung lesions undergoing resection were CCAMs. Among patients with pathologic diagnosis of CCAM, the initial, largest, and final CVRs were greatest in OFS followed by EXIT and STR patients. Similarly, the incidence of hydrops was significantly greater and the rate of hydrops resolution was lower in the OFS group. Although the rate of cyst drainage did not differ between groups, maternal betamethasone use varied significantly (OFS 60.0%, EXIT 100.0%, STR 74.3%; p = 0.0378). Notably, all OFS took place prior to 2014. There was no difference in survival, ventilator days, nitric oxide, NICU LOS, or ECMO between groups. In multiple variable logistic modeling, determinants of survival to NICU discharge among patients undergoing resection with a pathologic diagnosis of CCAM included initial CVR <3.5 and need for <3 maternal betamethasone doses.

CONCLUSION

For CCAMs that remain large despite maternal betamethasone or cyst drainage, surgical resection via OFS, EXIT, or STR are viable options with favorable and comparable survival between groups. In the modern era there has been a shift from OFS and EXIT procedures to STR for fetuses with persistently large lung lesions. This shift has been fueled by the increased use of maternal betamethasone and introduction of a Special Delivery Unit during the study period and the appreciation of similar fetal and neonatal outcomes for STR vs. EXIT and OFS with reduced maternal morbidity associated with a STR. Accordingly, efforts to optimize multidisciplinary perinatal care for fetuses with large lung lesions are important to inform patient selection criteria and promote STR as the preferred surgical approach in the modern era.

LEVEL OF EVIDENCE

Level IV.

Effect of Smoking on Motor Recovery After Cervical American Spinal Injury Association Grade D Traumatic Spinal Cord Injury

BACKGROUND

Smoking is a known neurotoxin that has been shown to negatively impact neurological function and recovery in multiple animal studies. Patients who smoke have been shown to have decreased rates of motor improvement, fusion, and overall successful outcomes after elective spinal surgery, but the effect of smoking on outcomes after traumatic spinal cord injury (TSCI) has not been demonstrated in prior literature. This study aims to investigate how smoking effects motor recovery after TSCI.

METHODS

Using the National Spinal Cord Injury Statistical Center database, patients who underwent surgical management of American Spinal Injury Association grade D cervical TSCI between 2009 and 2016 were included. Patients were grouped by smoking or nonsmoking status. Overall total motor score and change in motor scores at rehabilitation admission, rehabilitation discharge, and 1-year follow-up visits were compared between groups. Multiple linear regression analysis was completed, including any possible confounding demographic or injury variables.

RESULTS

A total of 152 patients (121 smokers and 31 nonsmokers) completed their 1-year follow-up interview and physical examination and were included in the study. There were no differences in motor score between groups at rehabilitation admission or discharge. Smokers had worse improvement in motor score at 1 year (7.99 nonsmokers vs 4.61 smokers; P = 0.019 on multivariate analysis) and worse overall total motor score at 1 year (94.0 nonsmokers vs 90.0 smokers; P = 0.018 on multivariate analysis) after controlling for confounders.

CONCLUSIONS

These results indicate diminished motor recovery in patients who continue to smoke after TSCI. These patients should be targeted for aggressive smoking cessation and require intervention from providers and peers in order to maximize recovery after injury.

CLINICAL RELEVANCE

This study demonstrates that smoking cessation may be beneficial for patients with cervical ASIA grade D spinal cord injury and may be a focus for providers of these patients.

LEVEL OF EVIDENCE: 3

Do Patients With Chronic Diabetes Have Worse Motor Outcomes After Cervical ASIA C Traumatic Spinal Cord Injury?

STUDY DESIGN

This was a level IV retrospective prognostic study.

OBJECTIVE

The objective of this study was to determine if patients with chronic diabetes have worse functional outcomes and motor recovery after cervical traumatic spinal cord injury (TSCI).

SUMMARY OF BACKGROUND DATA

Diabetes mellitus has multiple deleterious neurological effects and has been shown to worsen elective cervical spine surgery outcomes. Prior literature has scarcely characterized the impact of chronic diabetes on motor and functional outcomes after TSCI.

METHODS

The National Spinal Cord Injury Statistical Center (NSCISC) database was utilized to retrospectively collect data on cervical American Spinal Injury Association (ASIA) C TSCI between 2011 and 2016. Patients were divided into diabetes and nondiabetes groups. Primary outcomes included wheelchair requirement and ambulatory status 1 year after injury. Secondary outcomes were motor score collected at the time of rehab admission, rehab discharge, and 1-year follow-up. All outcome variables were analyzed using univariate and multivariate regression to assess for differences between diabetes and nondiabetes groups and possible confounders.

RESULTS

A total of 219 patients met the inclusion criteria for the study: 193 without diabetes and 26 with diabetes (12.0%). After controlling for confounders, patients with diabetes had had significantly increased wheelchair requirement (83.3% vs. 51.8%, relative risk=1.63, 95% confidence interval: 1.20-1.83, P =0.009 multivariate) and decreased ambulatory rates (50% vs. 67.9%, relative risk=0.55, 95% confidence interval: 0.25-0.98, P =0.042 multivariate) at 1 year. They also had no difference in average total motor scores at rehab admission but significantly worse total motor scores at rehab discharge (50.6±23.3 vs. 60.3±21.4, P =0.033 univariate, P =0.002 multivariate).

CONCLUSIONS

Patients with diabetes have increased wheelchair requirement and decreased ambulatory ability at 1 year after the injury as well as diminished recovery in motor scores after motor-incomplete cervical TSCI. These patients may be targets for aggressive diabetic screening and intervention to minimize negative outcomes.

Pediatric cervical spine injury in the United States: Defining the burden of injury, need for operative intervention, and disparities in imaging across trauma centers

BACKGROUND

Pediatric cervical spine injury (PCSI) in children is rare. Incidence of PCSI requiring intervention is not known, and imaging practices for screening in United States trauma centers are not well described.

METHODS

The 2016 NTDB was queried for patients younger than 15 years with PCSI. Incidence of PCSI, operative interventions, and imaging rates were analyzed by age and ACS accreditation status.

RESULTS

Of 84,554 children, 873 (1.03%) had PCSI. Patients <4 years were less likely to have PCSI (0.68% vs. 1.1%, RR 0.59, p < 0.001). 165 children (0.20%) required an intervention for PCSI. 12.8% of all children were screened for PCSI with imaging, 9.3% with CT, and 3.2% with plain X-rays. In spite of similar injury and intervention rates, stand-alone pediatric trauma centers were less likely than others to image patients without PCSI (11% vs. 13% p < 0.001), less likely to utilize CT scan (5.8% vs. 10.6% p < 0.001) and more likely to utilize plain films (5.2% vs. 2.4% p < 0.001).

CONCLUSION

Despite exceedingly low rates of PSCI requiring intervention (0.2%), imaging rates for screening are significant. Stand-alone pediatric trauma centers outperform others in limiting unnecessary imaging.

LEVEL OF EVIDENCE

IV.

Spondylolysis and End Plate Arthrosis at L5-S1: A Cadaveric Study

This study examined the effect of bilateral and unilateral L5 pars defects on the degree of disk degeneration at the L5-S1 level in cadaveric specimens. An observational study was performed of 690 cadaveric specimens selected at random. These specimens represent individuals who died between 1893 and 1938. The study included 558 male and 132 female cadavers. Of the 120 specimens with L5 spondylolysis, 95 cases were bilateral and 25 were unilateral. The remaining 544 specimens were used as the control cohort. Degenerative disk disease was measured by the classification of Eubanks et al. According to this classification, degenerative disk disease was graded from no arthrosis (grade 0) to complete ankylosis (grade IV). Linear regression analysis corrected for age, sex, and race showed that subjects with bilateral spondylolysis at L5 had a statistically significant increase in the amount of disk degeneration (P=.02) compared with those with unilateral lesions. Student's t tests showed significant differences (P<.001 and P=.002, respectively) in the amount of degeneration seen with both bilateral and unilateral spondylolysis above what would be predicted in the normal control population. A positive correlation was found between the number of pars defects at L5 and the degree of disk degeneration at L5-S1. These results support the idea that individuals with spondylolysis at these levels may be at increased risk for development of low back pain and reduced quality of life. [Orthopedics. 2017; 40(1):e59-e64.].

Calcaneocuboid Joint Arthritis of the Midfoot Precedes Tibiotalar Joint Arthritis

Surgical models have best shown the relationship between ankle and mid-foot osteoarthritis, although findings regarding the calcaneocuboid joint have varied. To the authors' knowledge, no studies have evaluated the relationship between degenerative changes across the tibiotalar and calcaneocuboid joints. The goal of this study was to determine whether such a relationship exists and which joint degenerates first. A single examiner evaluated 694 tibiotalar and calcaneocuboid joints to determine the presence of osteoarthritis. Multiple linear regression analysis was conducted with a standard P value cutoff (P<.05) and 95% confidence interval. The average incidence of tibiotalar and calcaneocuboid osteoarthritis in specimens older than 40 years was compared with the incidence in those 40 years and younger. A positive correlation between tibiotalar and calcaneocuboid osteoarthritis was noted. African-American subjects were less likely than white subjects to have tibiotalar osteoarthritis. The finding of right and left tibiotalar and calcaneocuboid osteoarthritis in subjects 40 years and younger showed that midfoot arthritis was significantly more common than arthritis of the ankle. The prevalence of calcaneocuboid osteoarthritis remains stable after 40 years of age, and the prevalence of tibiotalar osteoarthritis approaches that of calcaneocuboid osteoarthritis. Calcaneocuboid osteoarthritis precedes tibiotalar osteoarthritis. Altered biomechanics involved in calcaneocuboid osteoarthritis are transferred to the tibiotalar joint, leading to tibiotalar osteoarthritis as the subject ages. Early education, surveillance, physical therapy, shoe adjustment, and orthotics may help to reduce the forces across the midfoot and prevent ankle arthritis in the long term. [Orthopedics. 2016; 39(6):e1112-e1116.].

Robotic Single- and Multisite Cholecystectomy in Children

BACKGROUND

Elective cholecystectomy is a high-volume, simple procedure, well suited for the development of a pediatric robotic surgery program. Surgical robot software, by "reversing" the surgeon's hands, simplifies single-site cholecystectomy through a single incision at the umbilicus.

MATERIALS AND METHODS

Data were reviewed on the first nine children who had robotic cholecystectomy, with the Da Vinci® Surgical System (Intuitive Surgical Inc., Sunnyvale, CA) device, at our institution. All cases were performed by a single surgeon, proctored by an experienced robotic general surgeon.

RESULTS

There were 9 patients: the first 4 patients had robotic multiport cholecystectomy, and the last 5 had robotic single-site cholecystectomy. Eight were girls. They were 10-18 years of age (median, 14 years). Diagnoses were biliary dyskinesia (n = 5) and symptomatic cholelithiasis (n = 4). Median body mass index was 24.9 (range, 20.2-43.8) kg/m(2). Median anesthesia time for multiport cholecystectomy was 139 (range, 120-162) minutes; median anesthesia time for single-site cholecystectomy was 169 (range 122-180) minutes. Median console time for multiport cholecystectomy was 47 (range, 44-58) minutes; median console time for single-site cholecystectomy was 69 (range, 66-86) minutes. Eight of the 9 patients went home on the day of surgery, and 1 stayed overnight. Patients were seen at 13-20 days after surgery (median, 14 days). There were no complications. There were no conversions to open surgery and none from single-site to multiport surgery.

CONCLUSIONS

Robotic cholecystectomy is safe and efficacious and is a suitable introductory procedure for pediatric surgeons considering a robotic surgery program. Single-site robotic cholecystectomy is a cosmetically attractive option but takes longer than multiport robotic cholecystectomy.

The influence of obesity and ambient temperature on physiological and oxidative responses to submaximal exercise

This study investigated the effects of obesity and ambient temperature on physiological responses and markers of oxidative stress to submaximal exercise in obese and lean people. Sixteen healthy males were divided into an obese group (n=8, %fat: 27.00±3.00%) and a lean group (n=8, %fat: 13.85±2.45%). Study variables were measured during a 60 min submaximal exercise test at 60% VO2max in a neutral (21±1°C) and a cold (4±1°C) environment. Heart rate, blood lactate, rectal temperature, serum levels of malondialdehyde (MDA) and superoxide dismutase (SOD) were measured at rest, during exercise and in recovery. Heart rate of both groups was significantly lower (P<0.05) in the cold than the warm environment, but there were no significant differences between the two groups. Serum SOD activity increased to a significantly greater extent (P<0.05) in the cold than the neutral environment, and remained elevated for longer during exercise in the obese group than the lean group. Serum MDA level during submaximal exercise was not significantly different between conditions or groups. Cold stress in exercise may challenge antioxidant defence mechanisms in obese subjects, but lipid peroxidation remains unchanged.

Physiological and leukocyte subset responses to exercise and cold exposure in cold-acclimatized skaters

We investigated physiological responses and changes in circulating immune cells following exercise in cold and thermoneutral conditions. Participants were short track skaters (n=9) who were acclimatized to cold conditions, and inline skaters (n=10) who were not acclimatized. All skaters were young, and skating at a recreational level three days per week for at least one year. Using a cross-over design, study variables were measured during 60 min of submaximal cycling (65% V.O₂max) in cold (ambient temperature: 5±1°C, relative humidity: 41±9%) and thermoneutral conditions (ambient temperature: 21±1°C, relative humidity: 35±5%). Heart rate, blood lactate and tympanic temperature were measured at rest, during exercise and recovery. Plasma cortisol, calprotectin and circulating blood cell numbers were measured before and after 60 min of cold or thermoneutral conditions, and during recovery from exercise. Heart rate was lower in both groups during exercise in cold versus thermoneutral conditions (P<0.05). The increase in total leukocytes during recovery was primarily due to an increase in neutrophils in both groups. The cold-acclimatized group activated neutrophils after exercise in cold exposure, whereas the non-acclimatized group activated lymphocyte and cortisol after exercise in cold exposure. Lymphocyte subsets significantly changed in both groups over time during recovery as compared to rest. Immediately after exercise in both groups, CD16+ and CD69+ cells were elevated compared to rest or before exercise in both conditions. Acclimatization to exercise in the cold does not appear to influence exercise-induced immune changes in cold conditions, with the possible exception of neutrophils, lymphocytes and cortisol concentration.

Trabecular microfracture precedes cortical shell failure in the rat caudal vertebra under cyclic overloading

Microscopic tissue damage has been observed in otherwise healthy cancellous bone in humans and is believed to contribute to bone fragility and increased fracture risk. Animal models to study microscopic tissue damage and repair in cancellous bone would be useful, but it is currently not clear how loads applied to a whole animal bone are related to the amount and type of resulting microdamage in cancellous bone. In the current study we determine the relationship between applied cyclic compressive overloading and the resulting amount of microdamage in isolated rat tail vertebrae, a bone that has been used previously for in vivo loading experiments. Rat caudal vertebrae (C7-C9, n = 22) were potted in bone cement and subjected to cyclic compressive loading from 0 to 260 N. Loading was terminated in the secondary and tertiary phases of the creep-fatigue curve using custom data-monitoring software. In cancellous bone, trabecular microfracture was the primary form of microdamage observed with few microcracks. Trabecular microfracture prevalence increased with the amount of cyclic loading and occurred in nine out of 10 specimens loaded into the tertiary phase. Only small amounts of microdamage were observed in the cortical shell of the vertebrae, demonstrating that, under axial cyclic loading, damage occurs primarily in regions of cancellous bone before overt fracture of the bone (macroscopic cracks in the cortical shell). These experiments in isolated rat tail vertebrae suggest that it may be possible to use an animal model to study the generation and repair of microscopic tissue damage in cancellous bone.

Cross-cascade activation of ERKs and ternary complex factors by Rho family proteins

Mitogens promote cell growth through integrated signal transduction networks that alter cellular metabolism, gene expression and cytoskeletal organization. Many such signals are propagated through activation of MAP kinase cascades partly regulated by upstream small GTP-binding proteins. Interactions among cascades are suspected but not defined. Here we show that Rho family small G proteins such as Rac1 and Cdc42hs, which activate the JNK/SAPK pathway, cooperate with Raf-1 to activate the ERK pathway. This causes activation of ternary complex factors (TCFs), which regulate c-fos gene expression through the serum response element. Examination of ERK pathway kinases shows that neither MEK1 nor Ras will synergize with Rho-type proteins, and that only MEK1 is fully activated, indicating that MEKs are a focal point for cross-cascade regulation. Rho family proteins utilize PAKs for this effect, as expression of an active PAK1 mutant can substitute for Rho family small G proteins, and expression of an interfering PAK1 mutant blocks Rho-type protein stimulation of ERKs. PAK1 phosphorylates MEK1 on Ser298, a site important for binding of Raf-1 to MEK1 in vivo. Expression of interfering PAK1 also reduces stimulation of TCF function by serum growth factors, while expression of active PAK1 enhances EGF-stimulated MEK1 activity. This demonstrates interaction among MAP kinase pathway elements not previously recognized and suggests an explanation for the cooperative effect of Raf-1 and Rho family proteins on cellular transformation.

Mitogen-activated protein kinase activation is not necessary for, but antagonizes, 3T3-L1 adipocytic differentiation

In 3T3-L1 fibroblasts, Ras proteins mediate both insulin-induced differentiation to adipocytes and its activation of cytosolic serine/threonine kinases, including Raf-1 kinase, mitogen-activated protein kinase (MAPK), and Rsk. Here, we report that insulin- and Ras-induced activation of MAPK is not required for the differentiation process and in fact antagonizes it. The treatment of 3T3-L1 preadipocytes with MEK-specific inhibitor PD98059 blocked insulin- and Ras-induced MAPK activation but had no effect on or slightly enhanced adipocytic differentiation. Tumor necrosis factor alpha (TNF-alpha), an inhibitor of insulin-stimulated adipogenesis, activated MAPK in 3T3-L1 cells. PD98059 treatment blocked MAPK activation by TNF-alpha and reversed the blockade of adipogenesis mediated by low (1 ng/ml) TNF-alpha concentrations. 3T3-L1 transfectants containing hyperactivated MEK1 or overexpressed MAPK displayed impaired adipocytic differentiation. PD98059 treatment also reversed the blockade of differentiation in MEK1 transfectants. These results indicate that MAPK does not promote but can contribute to inhibition of the process of adipocytic differentiation of 3T3-L1 cells.

Contributions of the mitogen-activated protein (MAP) kinase backbone and phosphorylation loop to MEK specificity

To examine the specificity of MEKs for MAP kinase family members, we determined the abilities of several MEK isoforms to phosphorylate mutants of the MAP kinase ERK2 and the related kinase ERK3 which are modified in the phosphorylation loop. The ERK2 mutants included mutations of the two phosphorylation sites, mutations of the acidic residue between these two sites, and mutations that shorten the length of this loop. All mutants were tested for phosphorylation by six mammalian MEKs and compared with several wild type MAP kinases. MEK1 and MEK2 phosphorylate a majority of the ERK2 mutants. MEK2 but not MEK1 will phosphorylate ERK3. Alteration of the residue between the two phosphorylation sites neither dramatically affected the activity of MEK1 and MEK2 toward ERK2 nor conferred recognition by other MEKs. Likewise, reduction of the length of the phosphorylation loop only partially reduces recognition by MEK1 and MEK2 but does not promote recognition by other MEKs. Thus other yet to be identified factors must contribute to the specificity of MEK recognition of MAP kinases.

Mos/mitogen-activated protein kinase can induce early meiotic phenotypes in the absence of maturation-promoting factor: a novel system for analyzing spindle formation during meiosis I

Mitogen-activated protein kinase (MAPK) is selectively activated by injecting either mos or MAPK kinase (mek) RNA into immature mouse oocytes maintained in the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX). IBMX arrests oocyte maturation, but Mos (or MEK) overexpression overrides this block. Under these conditions, meiosis I is significantly prolonged, and MAPK becomes fully activated in the absence of p34cdc2 kinase or maturation-promoting factor. In these oocytes, large openings form in the germinal vesicle adjacent to condensing chromatin, and microtubule arrays, which stain for both MAPK and centrosomal proteins, nucleate from these regions. Maturation-promoting factor activation occurs later, concomitant with germinal vesicle breakdown, the contraction of the microtubule arrays into a precursor of the spindle, and the redistribution of the centrosomal proteins into the newly forming spindle poles. These studies define important new functions for the Mos/MAPK cascade in mouse oocyte maturation and, under these conditions, reveal novel detail of the early stages of oocyte meiosis I.

Developmental regulation of various annexins in the embryonic palate of the mouse: dexamethasone affects expression of annexin-1

The annexins are a group of structurally related proteins implicated in a number of cellular processes, including growth, membrane fusion, and the effects of glucocorticoids on cellular physiology, signal transduction, and regulation of activities of phospholipase A2. Though their exact role in cellular physiology is not clear, their properties make them candidate proteins for signal transduction pathways by which growth factors and glucocorticoids modulate development of the palate. We have determined the exact cellular location and development expression of various annexins in the embryonic murine palate as a first step in assessing their developmental function. Western blot analysis revealed an increased accumulation of selected annexins in elevated palates compared to vertical (unelevated) ones. This was particularly striking for lipocortin I1 (annexin I), whose mRNA accumulated as well. Lipocortin I was expressed primarily in the apical portion of the palatal epithelium at early stages of development, but throughout the epithelium at later stages. Also, there was increased immunoreactivity for lipocortin I in the mesenchyme as development proceeded. Immunoreactivity for the endonexins (annexins IV and V) was found in the palatal epithelium and mesenchyme, whereas immunoreactivity for the 67-kDa calelectrin (annexin VI) was found only in the mesenchyme. Treatment of pregnant A/J strain mice with a cleft-palate inducing regimen of dexamethasone stimulated accumulation of lipocortin I protein and mRNA, but not lipocortin II (annexin II) protein. In contrast, the same regimen of dexamethasone did not affect levels of lipocortin I protein in palates of the glucocorticoid-less sensitive C57BL/6J strain mouse embryo. These data permit the suggestion that lipocortin I plays some critical, but as yet undefined, role in modulating ontogeny of the murine palate.

Thyrotropin-induced mitogenesis is Ras dependent but appears to bypass the Raf-dependent cytoplasmic kinase cascade

Cellular growth control requires the coordination and integration of multiple signaling pathways which are likely to be activated concomitantly. Mitogenic signaling initiated by thyrotropin (TSH) in thyroid cells seems to require two distinct signaling pathways, a cyclic AMP (cAMP)-dependent signaling pathway and a Ras-dependent pathway. This is a paradox, since activated cAMP-dependent protein kinase disrupts Ras-dependent signaling induced by growth factors such as epidermal growth factor and platelet-derived growth factor. This inhibition may occur by preventing Raf-1 protein kinase from binding to Ras, an event thought to be necessary for the activation of Raf-1 and the subsequent activation of the mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinases (MEKs) and MAP kinase (MAPK)/ERKs. Here we report that serum-stimulated hyperphosphorylation of Raf-1 was inhibited by TSH treatment of Wistar rat thyroid cells, indicating that in this cell line, as in other cell types, increases in intracellular cAMP levels inhibit activation of downstream kinases targeted by Ras. Ras-stimulated expression of genes containing AP-1 promoter elements was similarly inhibited by TSH. On the other hand, stimulation of thyroid cells with TSH resulted in stimulation of DNA synthesis which was Ras dependent but both Raf-1 and MEK independent. We also show that Ras-stimulated DNA synthesis required the use of this kinase cascade in untreated quiescent cells but not in TSH-treated cells. These data suggest that in TSH-treated thyroid cells, Ras might be able to signal through effectors other than the well-studied cytoplasmic kinase cascade.

Teenage childbearing and high school completion: accounting for individual heterogeneity

Estimates from the National Longitudinal Survey of Youth (1979-1987) indicate that differences in high school completion rates between women who have a teenage birth and those who do not are affected by the birth itself, family background characteristics and individual heterogeneity. Merely having a teenage birth leads to a 50% reduction in the likelihood of high school completion, compared with not having a teenage birth. Individual heterogeneity accounts for a 42% reduction in the likelihood of finishing high school among those who have a birth before age 17, and a 30% reduction among those who have a birth between ages 17 and 19, compared with those who do not have a teenage birth. However, individual heterogeneity accounts for less than 30% of the difference in the likelihood that black teenage mothers will complete school, compared with more than 50% among Hispanics and whites. Family background variables, such as maternal education and parental marital stability, also have positive effects on school completion.

Changes in the determinants of fertility in Korea: analyses of pregnancy intervals and outcomes

Korea completed the whole process of what is called the demographic transition to a low fertility and mortality level with the successful implementation of the national family planning program in 1962, and this has been accompanied by rapid socioeconomic development. Most of the fertility decline was due to a rising age at marriage and to lower marital fertility. The national family planning program, combined with the widespread practice of induced abortion, has placed an important role in reducing marital fertility, particularly among older women. This paper aims, therefore, to examine the determinants of fertility and their changes over time in an effort to suggest future population policy directions for Korea. The analysis is divided into 2 parts-estimation of pregnancy intervals by applying the proportional hazards model, and estimation of the determinants of fertility by adopting the logistic regression model to find out whether a pregnancy terminates in a live birth or in an abortion. In both analyses, the sex was included as the main explanatory variable. A woman's education has been shown to have a significant effect on delaying the timing or on the wife's age at first pregnancy, but its effect on the pace of subsequent pregnancies is much smaller and often positive. On the other hand, the woman's education has a consistently positive effect on the probability of a pregnancy ending in an abortion although the effect shows a steady decline over time. Form first parity, the sex composition of previous children stands out consistently as the most important factor in deciding both the pace of pregnancy and its outcome. The pregnancy risks of the women with sons are reduced by almost 50% at the second and third parities. The probability of a pregnancy ending in an abortion also increases substantially when parents already have a son. The decline of the desired family size but the sustained strong son preference has made the sex of children a more important factor in the determination of Korean fertility. The woman's education, on the other hand, has become a less important factor.

Computerized detection of pulmonary nodules in digital chest images: use of morphological filters in reducing false-positive detections

Currently, radiologists can fail to detect lung nodules in up to 30% of actually positive cases. If a computerized scheme could alert the radiologist to locations of suspected nodules, then potentially the number of missed nodules could be reduced. We are developing such a computerized scheme that involves a difference-image approach and various feature-extraction techniques. In this paper, we describe our use of digital morphological processing in the reduction of computer-identified false-positive detections. A feature-extraction technique, which includes the sequential application of nonlinear filters of erosion and dilation, is employed to reduce the camouflaging effect of ribs and vessels on nodule detection. This additional feature-extraction technique reduced the true-positive rate of the computerized scheme by 13% and the false-positive rate by 50%. In a comparison of the scheme with and without the additional feature-extraction technique, inclusion of the additional technique increased the detection sensitivity by about half at the level of three to four false-positive detections per chest image.

Mechanism of modulation of dopamine beta-monooxygenase by pH and fumarate as deduced from initial rate and primary deuterium isotope effect studies

Dopamine beta-monooxygenase catalyzes a reaction in which 2 mol of protons are consumed for each turnover of substrate. Studies of the pH dependence of initial rate parameters (Vmax and Vmax/Km) and their primary hydrogen isotope effects show that at least two ionizable residues are involved in catalysis. One residue (B1, pK = 5.6-5.8) must be protonated prior to the carbon-hydrogen bond cleavage step, implying a role for general-acid catalysis in substrate activation. A second protonated residue (B2, pK = 5.2-5.4) facilitates, but is not required for, product release. Recent measurement of the intrinsic isotope effect for dopamine beta-monoxygenase [Miller, S. M., & Klinman, J. P. (1983) Biochemistry (preceding paper in this issue)] allows an analysis of the pH dependence of rate constant ratios and in selected instances individual rate constants. We demonstrate large changes in the rate-determining step as well as an unprecedented inversion in the kinetic order of substrate release from ternary complex over an interval of 2 pH units. Previously, fumarate has been used in dopamine beta-monooxygenase assays because of its property of enzyme activation. Studies of the pH behavior in the presence of saturating concentrations of fumarate have shown two causes of the activation: (i) fumarate perturbs the pK of B1 to pK = 6.6-6.8 such that the residue remains protonated and the enzyme optimally active over a wider pH range; (ii) fumarate decreases the rate of dopamine release from the ternary enzyme-substrate complex, increasing the equilibrium association constant for dopamine binding. Both effects are consistent with a simple electrostatic stabilization of bound cationic charges by the dianionic form of fumarate.