Effect of oxygen on multidrug resistance in the first trimester human placenta.

INTRODUCTION: The multidrug resistance proteins, P-glycoprotein (P-gp, encoded by the ABCB1 gene) and breast cancer resistance protein (BCRP, encoded by ABCG2) are highly expressed in the first trimester placenta. These transporters protect the fetus from exposure to maternally derived toxins and xenobiotics. Since oxygen is a regulator of multidrug resistance in various tissues, we hypothesized that changes in oxygen tension alter placental ABCB1/P-gp and ABCG2/BCRP expression in the first trimester. METHODS: Placental specimens were collected from first (n = 7), second (n = 5) and term pregnancies (n = 5). First trimester placental villous explants were incubated (24 or 48 h) in different oxygen tension (3-20%). ABCB1, ABCG2 and VEGFA mRNA expression levels were assessed by RT-PCR and protein was localized by IHC. RESULTS: ABCB1 is expressed most highly in the first trimester placenta (p < 0.05), whereas ABCG2 expression does not change significantly over pregnancy. P-gp and BCRP staining is present in the syncytiotrophoblast and in cytotrophoblasts. ABCG2 mRNA is increased in hyperoxic (20%) conditions after 48 h (p < 0.05). In contrast, hypoxia (3%) did not change ABCB1 mRNA expression but significantly increased VEGFA mRNA (p < 0.05). Hypoxia resulted in increased BCRP staining in cytotrophoblasts and in the microvillous membrane of the syncytium. Whereas, hypoxia resulted in increased P-gp staining in proliferating cytotrophoblasts. CONCLUSION: We conclude that placental multidrug resistance expression, specifically ABCG2, is regulated by oxygen tension in the first trimester. It is possible that changes in placental oxygen supply are capable of altering fetal drug exposure especially during early pregnancy.

A model for sequential threading of alpha-cyclodextrin onto a guest: a complete thermodynamic and kinetic study in water.

The first variable-temperature and variable-pressure stopped-flow spectrophotometric study of the sequential threading of alpha-cyclodextrin (alpha-CD) onto the guest dye Mordant Orange 10, S, is reported. Complementary (1)H one-dimensional (1D) variable-temperature kinetic studies and two-dimensional (2D) rotating-frame nuclear Overhauser effect spectroscopy (ROESY) and EXSY NMR studies are also reported. In aqueous solution at 298.2 K, the first alpha-CD threads onto S to form a 1:1 complex S.alpha-CD with a forward rate constant k(1,f) = 15 200 +/- 200 M(-1) s(-1) and dethreads with a reverse rate constant k(1,r) = 4.4 +/- 0.3 s(-1). Subsequently, S.alpha-CD isomerizes to S.alpha-CD (k(3,f) = 0.158 +/- 0.006 s(-1), k(3,f) = 0.148 +/- 0.006 s(-1)). This process can be viewed as a thermodynamically controlled molecular shuttle. A second alpha-CD threads onto S.alpha-CD to form a 1:2 complex, S.(alpha-CD)(2), with k(2,f) = 98 +/- 2 M(-1) s(-1) and k(2,r) = 0.032 +/- 0.002 s(-1). A second alpha-CD also threads onto S.alpha-CD to form another 1:2 complex, S.(alpha-CD)(2), characterized by k(4,f) = 9640 +/- 1800 M(-1) s(-1) and k(4,r) = 61 +/- 6 s(-1). Direct interconvertion between S.(alpha-CD)(2) and S.(alpha-CD)(2) was not detected; instead, they interconvert by dethreading the second alpha-CD and through the isomerization equilibrium between S.alpha-CD and S.alpha-CD. The reaction volumes, DeltaV(0), were found to be negative for the first three equilibria and positive for the fourth equilibrium. For the first three forward and reverse reactions, the volumes of activation are substantially more negative, indicating a compression of the transition state in comparison with the ground states. These data were used in conjunction with DeltaH, DeltaH degrees, DeltaS, and DeltaS degrees data to deduce the dominant mechanistic threading processes, which appear to be largely controlled by changes in hydration and van der Waals interactions, and possibly by conformational changes in both S and alpha-CD. The structure of the four complexes were deduced from (1)H 2D ROESY NMR studies.

A pleasure to work with--an analysis of written comments on student evaluations.

OBJECTIVE: Studies assessing rating scales on student evaluations are available. However, there are no data related to the written comments on these evaluations. This study was designed to evaluate these comments. METHODS: A content analysis was performed on the narrative section of pediatric clerks' evaluations. Final evaluations were obtained from 10 outpatient clinical sites staffed by full-time faculty over 14 months. A coding dictionary containing 12 categories (7 linked to clinical skills) was used. RESULTS: One thousand seventeen comments on 227 evaluations were coded. The mean number of comments per evaluation was 4. Learner and personal characteristics were the largest categories. Normative comments, such as "good physical exam," as opposed to more specific comments, such as "complete presentation," predominated in all categories. CONCLUSIONS: Evaluation comments were infrequently related to basic clinical skills and were not often specific enough to lead to effective change in a student's performance. Faculty development is needed to make final evaluation comments more useful for students.

The search for effective and efficient ambulatory teaching methods through the literature.

OBJECTIVE: Education in ambulatory settings is characterized by the conflicting agendas of clinical efficiency and educational effectiveness. In recognition of the challenge to teach more effectively, this review was undertaken to identify literature-based teaching methods for ambulatory-based education. DESIGN: Literature search resources included electronic databases and relevant journal indices. After preliminary title/abstract review, final critical review using a coding sheet was undertaken to define the teaching behavior or characteristic in each article, and to evaluate empirical data related to effectiveness and/or efficiency. RESULTS: Our literature search and subsequent article analysis yielded 11 clinical teaching methods, but no agreed upon descriptor or key features for these methods. Synthesis of this literature lead to succinct descriptions of each method and a label. CONCLUSIONS: There is limited evidence regarding the effectiveness of ambulatory teaching methods in cited literature. By establishing a common nomenclature and descriptions for 11 methods, this review lays the foundation for investigators to systematically study the effectiveness and efficiency of ambulatory-focused clinical teaching methods both within and across specialties.

Advised follow-up after emergency treatment of adolescents with violence-related injuries.

OBJECTIVE: To compare the rate of advised medical follow-up for adolescents with violence-related, nonsuicidal injuries versus other complaints. DESIGN: Cross-sectional study. SETTING: Pediatric emergency department (ED). PATIENTS: All visits by adolescents, aged 13 to 18 years, during a one-week period from each season during 1992. MAIN OUTCOME MEASURES/RESULTS: Advised medical follow-up for patients sustaining violence-related injuries versus other complaints were compared. Four hundred twenty-six visits were reviewed; 351(82%) resulted in discharge from the ED. Sixty-eight (16%) were classified as violence-related, nonsuicidal. Male adolescents were more likely to sustain violence-related injuries (66% vs 34%, P < 0.01). There were no differences in admission rate or having a primary care provider (PCP) between the violence-related injury group and the group with other complaints. Adolescents with other complaints were twice as likely to have follow-up advised. Presence of PCP and older age were also positively associated with advised follow-up. CONCLUSION: Adolescents sustaining violence-related injuries were less likely to have follow-up advised at the time of their ED visit than were adolescents presenting with other complaints. Violently injured adolescents, at risk for recurrent violent injuries and psychosocial sequelae, were less likely to have follow-up advised at the time of their ED visit than were adolescents presenting with other complaints.

Do missed opportunities stay missed? A 6-month follow-up of missed vaccine opportunities in inner city Milwaukee children.

OBJECTIVES: To determine 1) the frequency of missed vaccine opportunities (VOs) in inner city children

Clinical teaching rounds. A case-oriented faculty development program.

OBJECTIVE: To improve clinical teaching with emphasis on improving provision of feedback through a faculty development series modeled on clinical rounds. METHOD: Seven 1-hour conferences were held for the pediatric faculty during the academic year 1994-1995. Clinical rounds were emulated, with a simulated learner functioning as the patient with a chief complaint of some instructional problem. The conferences progressed from discussion about teaching in a particular situation, to videotapes of clinical teaching, and finally to live clinical teaching. Evaluation of the conferences was assessed by attendance records, participants' evaluations of the conferences, and comparing student and resident evaluations of faculty who attended (i.e., those who attended > or = 2) with faculty who did not attend. Comparisons were made for the academic year before and after the conferences using paired t tests. RESULTS: Forty percent of the faculty attended 2 or more conferences. Mean conference ratings were 4.00 to 4.35, (1 is poor; 5, excellent). Faculty who attended had a significant improvement in ratings for feedback (P = .01) and overall teaching effectiveness (P = .04). Ratings for faculty who did not attend did not change. CONCLUSION: These conferences were well received by the faculty and are an effective way to improve clinical teaching.

Formation and properties of peroxynitrite as studied by laser flash photolysis, high-pressure stopped-flow technique, and pulse radiolysis.

Flash photolysis of alkaline peroxynitrite solutions results in the formation of nitrogen monoxide and superoxide. From the rate of recombination it is concluded that the rate constant of the reaction of nitrogen monoxide with superoxide is (1.9 +/- 0.2) x 10(10) M-1 s-1. The pKa of hydrogen oxoperoxonitrate is dependent on the medium. With the stopped-flow technique a value of 6.5 is found at millimolar phosphate concentrations, while at 0.5 M phosphate the value is 7.5. The kinetics of decay do not follow first-order kinetics when the pH is larger than the pKa, combined with a total peroxynitrite and peroxynitrous acid concentration that exceeds 0.1 mM. An adduct between ONOO- and ONOOH is formed with a stability constant of (1.0 +/- 0.1) x 10(4) M. The kinetics of the decay of hydrogen oxoperoxonitrate are not very pressure-dependent: from stopped-flow experiments up to 152 MPa, an activation volume of 1.7 +/- 1.0 cm3 mol-1 was calculated. This small value is not compatible with homolysis of the O-O bond to yield free nitrogen dioxide and the hydroxyl radical. Pulse radiolysis of alkaline peroxynitrite solutions indicates that the hydroxyl radical reacts with ONOO- to form [(HO)ONOO].- with a rate constant of 5.8 x 10(9) M-1 s-1. This radical absorbs with a maximum at 420 nm (epsilon = 1.8 x 10(3) M-1 cm-1) and decays by second-order kinetics, k = 3.4 x 10(6) M-1 s-1. Improvements to the biomimetic synthesis of peroxynitrite with solid potassium superoxide and gaseous nitrogen monoxide result in higher peroxynitrite to nitrite yields than in most other syntheses.

Adolescent health care in a pediatric emergency department.

STUDY OBJECTIVE: We examined the use of the pediatric emergency department of an urban children's hospital by adolescents. This study included visits by all adolescents aged 13 to 18 years in a 1-week period from each season during 1992. RESULTS: The ED saw 426 adolescents, representing approximately 15% of the total ED visits. Fifty percent of these patients were male. More than half of the patients were black; a few were members of other minority groups. Eighteen percent had emergency, 60% urgent, and 21% nonurgent conditions. Forty-three percent of the patients came to the ED between 3 PM and 11 PM. Injuries accounted for 47% of male visits and 42% of female visits. Approximately half of the injuries resulted from violent events. Twenty-seven percent of the visits were for exacerbation of a chronic illness such as asthma or diabetes. The most common reason for adolescent female visits was gynecologic problems. Injury was the most common reason for adolescent male visits. Only 27% of the adolescents lived in a two-parent home. In 16% of the cases, the adolescents were treated without consent. Nineteen percent of the adolescents were uninsured, and nearly 50% were publicly insured. CONCLUSION: Issues of violence, consent, and insurance present problems for many adolescents in the pediatric ED. Injuries, particularly those related to violent events, are cause for many adolescent visits. ED staff members should develop plans to care for the complex psychosocial and medical problems of adolescents.

Clinical impact of radiograph misinterpretation in a pediatric ED and the effect of physician training level.

Radiograph interpretation in the pediatric emergency department (ED) is commonly performed by pediatric emergency medicine (PEM) attendings or physicians-in-training. This study examines the effect of physician training level on radiograph interpretation and the clinical impact of false-negative radiograph interpretations. Data were collected on 1,471 radiographs of the chest, abdomen, extremity, lateral neck, and cervical spine interpreted by PEM attendings, one PEM fellow, one physician assistant, and emergency medicine, pediatric and family practice residents. Two hundred radiographs (14%) were misinterpreted, including 141 chest (16%), 24 extremity (8%), 20 abdomen (12%), 14 lateral neck (18%), and 1 cervical spine radiograph (2%). Physicians-in-training misinterpreted 16% of their radiographs versus 11% for PEM attendings (P = .01). Twenty (1.4%) radiographs had clinically significant (false-negative) misinterpretations, including 1.7% of physician-in-training and 0.8% of attending interpretations (P = 0.15). No morbidity resulted from the delay in correct interpretation. Radiograph misinterpretation by ED physicians occurs but is unlikely to result in significant morbidity.

Reliability of observation variables in distinguishing infectious outcome of febrile young infants.

We prospectively evaluated 7 observation variables (level of activity, level of alertness, respiratory status/effort, peripheral perfusion, muscle tone, affect, feeding pattern) which qualify patient clinical appearance in order to determine reliability in distinguishing the infectious outcome of 233 febrile infants ages 0 to 8 weeks. Each variable was graded either 1, 3, or 5, with a higher score indicative of a greater degree of compromise. All infants received physical examination and sepsis evaluation (lumbar puncture, complete blood count/blood culture, urinalysis/urine culture). The 3 outcome groups compared were 29 cases of serious bacterial infections, (+SBI; 10 with bacterial meningitis, 12 with bacteremia, 7 with urinary tract infection), 45 cases of aseptic meningitis (AM) and 159 cases culture-negative with normal cerebrospinal fluid (CN-NCSF). The mean score for each of the 7 variables was significantly greater in the +SBI group compared with both the AM and CN-NCSF groups (P < 0.05), whereas there was no significant difference in mean score for each of the 7 variables between the AM and CN-NCSF groups. Stepwise discriminant analysis identified 3 variables that best distinguished outcome: affect; respiratory status/effort; and peripheral perfusion, which constituted the Young Infant Observation Scale. The mean total Young Infant Observation Scale score generated from assessing these 3 variables was significantly greater (P = 0.0001) in the +SBI, group (9) compared with both the AM (5) and CN-NCSF (5) groups. A total Young Infant Observation Scale score > or = 7 had a sensitivity of 76%, specificity of 75% and negative-predictive value of 96% for outcome of +SBI.

Relationship of temperature pattern and serious bacterial infections in infants 4 to 8 weeks old 24 to 48 hours after antibiotic treatment.

STUDY OBJECTIVE: A new management approach to selected febrile infants 4 to 8 weeks old evaluated for possible sepsis is outpatient ceftriaxone therapy, with subsequent re-evaluation 24 to 48 hours after presentation. This study assessed whether the temperature profile of such infants during the 24- to 48-hour period after treatment distinguished those with from those without serious bacterial infections (SBIs). DESIGN: Prospective, descriptive clinical study. PARTICIPANTS: One hundred sixty-one febrile infants 4 to 8 weeks old. SETTING: An urban pediatric emergency department and hospital. MEASUREMENTS AND MAIN RESULTS: All infants underwent a sepsis evaluation (lumbar puncture, CBC/blood culture, and urinalysis/urine culture) and were hospitalized for at least 48 hours. Temperatures were measured on presentation and then every four hours during hospitalization. All infants received parenteral third-generation cephalosporin antibiotic therapy, and none received antipyretic medication unless fever was documented. Fever (rectal temperature of more than 38.0 C) was documented during the 24- to 48-hour period after presentation in 28 infants (17.6%)--one of a total of 18 infants (5.6%) with SBI and 27 of a total of 143 infants (19%) without SBI (alpha, more than .2: power .30). All bacterial isolates in cases of SBI were susceptible to third-generation cephalosporin antibiotics. All repeat blood and urine cultures that were performed in infants with bacteremia or urinary tract infections, respectively, were negative 24 hours after presentation. CONCLUSION: Infants 4 to 8 weeks old who remain febrile during the 24 to 48-hour period after presentation and initiation of parenteral antibiotic therapy are less likely to have SBI. This study did not have sufficient power for this difference to be statistically significant.