Body plethysmography - additional information on exercise capacity in patients with congenital heart disease?

AIMS

In each cardiopulmonary exercise test (CPET), resting spirometry is performed in advance. In patients with a congenital heart defect (CHD), lung volumes are often impaired. This study investigates correlations between lung volumes and CPET parameters and determines, whether body plethysmography provides substantial additional information for these patients.

METHODS

Data from 102 patients (23.8 ± 10.4 years of age, 39 female) with various forms of CHD were examined from April 2018 to October 2022. All patients underwent spirometry (measuring forced vital capacity, FVC and forced expiratory volume in 1 s, FEV1), body plethysmography (measuring total lung capacity, TLC) and an exhausting CPET. Data is presented as the median and interquartile range (z-scores) and correlated with Spearman's rho.

RESULTS

Fifty-five% of all patients had normal results in lung function and 45% had normal peak oxygen uptake (≥ 80% predicted in peak VO2). Patients with impaired lung function were significantly more likely to have low exercise capacity (Fisher's exact test: p = 0.028). FVC z-values and %predicted peak VO2 (r = 0.365, p < 0.001) correlated significantly as well as FEV1_z and %predicted peak VO2 (r = 0.320, p = 0.001), and TLC z-values and %predicted peak VO2 (r = 0.249, p = 0.012). No correlation was found between FEV1/FVC z-values and %predicted peak VO2 (r = -0.043, p = 0.670).

CONCLUSION

Spirometry and exercise capacity positively correlate, also in CHD patients. However, body plethysmography does not provide additional or improved prediction and is therefore only recommended in noteworthy results in spirometry to exclude further lung co-morbidities.

Reference Values of Cardiopulmonary Exercise Test Parameters in the Contemporary Paediatric Population

BACKGROUND

The evaluation of health status by cardiopulmonary exercise test (CPET) has shown increasing interest in the paediatric population. Our group recently established reference Z-score values for paediatric cycle ergometer VO_2max, applicable to normal and extreme weights, from a cohort of 1141 healthy children. There are currently no validated reference values for the other CPET parameters in the paediatric population. This study aimed to establish, from the same cohort, reference Z-score values for the main paediatric cycle ergometer CPET parameters, apart from VO_2max.

RESULTS

In this cross-sectional study, 909 healthy children aged 5-18 years old underwent a CPET. Linear, quadratic, and polynomial mathematical regression equations were applied to identify the best CPET parameters Z-scores, according to anthropometric parameters (sex, age, height, weight, and BMI). This study provided Z-scores for maximal CPET parameters (heart rate, respiratory exchange ratio, workload, and oxygen pulse), submaximal CPET parameters (ventilatory anaerobic threshold, VE/VCO₂ slope, and oxygen uptake efficiency slope), and maximum ventilatory CPET parameters (tidal volume, respiratory rate, breathing reserve, and ventilatory equivalent for CO₂ and O₂).

CONCLUSIONS

This study defined paediatric reference Z-score values for the main cycle ergometer CPET parameters, in addition to the existing reference values for VO_2max, applicable to children of normal and extreme weights. Providing Z-scores for CPET parameters in the paediatric population should be useful in the follow-up of children with various chronic diseases. Thus, new paediatric research fields are opening up, such as prognostic studies and clinical trials using cardiopulmonary fitness outcomes. Trial registration NCT04876209-Registered 6 May 2021-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04876209 .

Reference values of aerobic fitness in the contemporary paediatric population

AIMS

There has been a growing interest in the use of markers of aerobic physical fitness (VO2max assessed by cardiopulmonary exercise testing (CPET)) in the follow-up of paediatric chronic diseases. The dissemination of CPET in paediatrics requires valid paediatric VO2max reference values to define the upper and lower normal limits. This study aimed to establish VO2max reference Z-scores values, from a large cohort of children representative of the contemporary paediatric population, including those with extreme weights.

METHODS AND RESULTS

In this cross-sectional study, 909 children aged 5 to 18-years-old from the general French population (development cohort), and 232 children from the general German and US populations (validation cohort) underwent a CPET, following the guidelines on high-quality CPET assessment. Linear, quadratic, and polynomial mathematical regression equations were applied to identify the best VO2max Z-score model. Predicted and observed VO2max values using the VO2maxZ-score model, and the existing linear equations were compared, in both development and validation cohorts. For both sexes, the mathematical model using natural logarithms of VO2max, height, and BMI was the best fit for the data. This Z-score model could be applied to normal and extreme weights and was more reliable than the existing linear equations, in both internal and external validity analyses (https://play.google.com/store/apps/details?id=com.d2l.zscore).

CONCLUSION

This study established reference Z-score values for paediatric cycloergometer VO2max using a logarithmic function of VO2max, height and BMI, applicable to normal and extreme weights. Providing Z-scores to assess aerobic fitness in the paediatric population should be useful in the follow-up of children with chronic diseases.

Peak Oxygen Uptake on Cardiopulmonary Exercise Test Is a Predictor for Severe Arrhythmic Events during Three-Year Follow-Up in Patients with Complex Congenital Heart Disease

Patients with congenital heart disease (CHD) are at increased risk for severe arrhythmia and sudden cardiac death (SCD). Although implantable cardioverter defibrillators (ICD) effectively prevent SCD, risk stratification for primary prophylaxis in patients with CHD remains challenging. Patients with complex CHD undergoing CPET were included in this single-center study. Univariable and backwards stepwise multivariable logistic regression models were used to identify variables associated with the endpoint of severe arrhythmic event during three years of follow-up. Cut-off values were established with receiver operating characteristic (ROC) curve analysis. Survival analysis was conducted via Kaplan–Meier plots. Severe Arrhythmia was documented in 97 of 1194 patients (8.1%/3 years). Independent risk factors for severe arrhythmia during follow-up were old age and a low peak oxygen uptake (V.O2peak) on multivariable analysis. Patients with more advanced age and with V.O2peak values of less than 24.9 mL/min/kg were at significantly increased risk for the occurrence of severe arrhythmias during follow-up. The combined analysis of both risk factors yielded an additional benefit for risk assessment. Age at CPET and V.O2peak predict the risk for severe arrhythmic events and should be considered for risk stratification of SCD in patients with complex CHD.

How well can wearables in children and adolescents with congenital heart disease represent their exercise capacity?

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): Stiftung KinderHerz

Background

Wearables enjoy great popularity in children and adolescents. They suggest objectively measuring subjects’ physical activity (PA) or at least give a hint of how it is. But is there a correlation between step-count, moderate to vigorous physical activity (MVPA), and peak oxygen uptake (peakV’O2)?

Purpose

This study investigates this question in children with various congenital heart diseases (CHD).

Methods

From September 2017 to September 2021 sixty-six patients (13 ± 3 years, 20 girls) measured their daily step-count and MVPA via Garmin fit jr. over one week and underwent a cardiopulmonary exercise test (CPET) to quantify their peakV’O2. CHD severity was complex in 50%, moderate in 39%, and simple in 11%. The distribution consisted of 18% with a left heart defect, 50% with a right heart defect, 5% with a Fontan circulation, 9% with an isolated shunt, and 18% with transposition of the great arteries. The correlation was performed via first Spearman’s correlation and secondly partial correlation, adjusted for age, sex height, and weight. Results are presented in median [IQR25;IQR75].

Results

Median steps on a weekly average were 7,576 [6,100;10,888] and MVPA 68 [52;95] minutes. PeakV’O2 was 33 [28;39] ml/min/kg, represented as 77 [68;91] % of predicted, which corresponds to slight impairment. Step-counts slightly correlates with peakV’O2 (r=0.277, p=0.024). However, correlation vanished after adjusting for anthropometrics (step-count: r=0.244, p=0.056). MVPA and peakV’O2 did not correlate at all.

Conclusions

Objectively measured PA and exercise capacity are poorly associated. Since both are independent constructs, it is necessary to assess both in a clinical setting - PA in the context of cardiovascular prevention and peakV’O2 as the strongest predictor for morbidity and mortality.

Are there correlations between lung volume and exercise capacity in children and adolescents with native Ebstein's anomaly?

Funding Acknowledgements

Type of funding sources: None.

Background

Patients with Ebstein’s Anomaly (EA) represent a wide clinical range with patients needing surgery in infancy and others needing no surgery throughout life. Exercise capacity in EA is often impaired. However, lung function is rarely investigated.

Purpose

This study examines lung volumes in native EA and their correlation with exercise capacity.

Methods

This retrospective study investigated 35 children with native EA (14 ± 4 years, 17 female), who underwent a cardiopulmonary exercise test (CPET) including spirometry to examine peak oxygen uptake (peakV’O2), forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1) and its ratio (FEV/FVC). Percentage in peakV’O2 &lt;80% represents a reduced exercise capacity, and values &lt;60% are defined as impaired. Z-scores below -1.64 categorize restrictive (FVC) or obstructive (FEV1/FVC) patterns. To analyse correlations between CPET and lung volumes Spearman’s rank test was performed.

Results

Reduced exercise capacity was found in 17 children (47%), and further seven (20%) children showed impaired exercise capacity. Seven patients (20%) had a restrictive lung volume pattern and three patients (9%) showed obstructive patterns. One patient showed both. Eleven (92%) patients with an impaired lung function had at least a reduced exercise capacity with a median of 64 [53;73] %predicted. Lung volumes correlate significantly with %peakV’O2 (z-FVC: r=0.500, p=0.002 and z-FEV1: r=0.443, p=0.008).

Conclusions

Most young patients with native EA have impaired results in exercise capacity and a third has reduced lung volumes. Low lung volumes correlate with worse exercise capacity. Thus, the lung function should also be taken into consideration when looking at the performance of these and medical aftercare.

Cardiovascular Function and Exercise Capacity in Childhood Cancer Survivors

Introduction: Childhood cancer survivors (CCS) might be at high risk of additional chronic diseases due to cardiotoxic side effects. The aim of this study was to analyze long-term side effects of cancer therapy on vascular structure/function, cardiac biomarkers and on physical activity. Methods: In total, 68 asymptomatic patients aged 16–30 years with childhood cancer (diagnosed 10.6 ± 3.9 years ago) were examined from 2015–2020. (Central) blood pressure and pulse wave velocity were registered via the oscillometric method, while carotid intima-media thickness (cIMT) was measured non-invasively by ultrasound. cIMT values of patients were compared to healthy controls (n = 68; aged 22.3 ± 3.5 years). Patients’ exercise capacity was recorded. The plasma N-terminal pro-brain natriuretic protein (NTproBNP) and troponin levels were measured as cardiac biomarkers. CCS were categorized in groups with low, moderate and high anthracyclines. Results: No differences were found in cIMT between patients and controls as well as between patients with various anthracycline dosage. Patients with high dose anthracyclines showed a significant lower performance versus patients with moderate dose anthracyclines (84.4% of predicted VO₂peak; p = 0.017). A total of 11.6% of CCS had abnormal NTproBNP values which correlated with received anthracycline dosage (p = 0.024; r = 0.343). Conclusion: NTproBNP levels and exercise capacity might be early markers for cardiovascular dysfunction in CCS and should be included in a follow-up protocol, while cIMT and troponin seem not to be adequate parameters.

Breathing training improves exercise capacity in patients with tetralogy of Fallot: a randomised trial

OBJECTIVE

Patients with tetralogy of Fallot (ToF) have limited pulmonary blood flow before corrective surgery and ongoing dysfunction of the pulmonary valve and right ventricle throughout life leading to lower exercise capacity and lung volumes in many patients. Inhalation training can increase lung volumes, improve pulmonary blood flow and consequently exercise capacity. This study tests whether home-based daily breathing training improves exercise capacity and lung volumes.

METHODS

From February 2017 to November 2018, 60 patients (14.7±4.8 years, 39% female) underwent spirometry (forced vital capacity (FVC); forced expiratory volume in 1 s (FEV1)), cardiopulmonary exercise testing (peak oxygen uptake (peak [Formula: see text]O2)) and breathing excursion measurement. They were randomised into immediate breathing exercise or control group (CG) and re-examined after 6 months. The CG started their training afterwards and were re-examined after further 6 months. Patients trained with an inspiratory volume-oriented breathing device and were encouraged to exercise daily. The primary endpoint of this study was the change in peak [Formula: see text]O2. Results are expressed as mean±SEM (multiple imputations).

RESULTS

In the first 6 months (intention to treat analysis), the training group showed a more favourable change in peak [Formula: see text]O2 (Δ0.5±0.6 vs -2.3±0.9 mL/min/kg, p=0.011), FVC (Δ0.18±0.03 vs 0.08±0.03 L, p=0.036) and FEV1 (Δ0.14±0.03 vs -0.00±0.04 L, p=0.007). Including the delayed training data from the CG (n=54), this change in peak [Formula: see text]O2 correlated with self-reported weekly training days (r=0.282, p=0.039).

CONCLUSIONS

Daily inspiratory volume-oriented breathing training increases dynamic lung volumes and slows down deconditioning in peak [Formula: see text]O2 in young patients with repaired ToF.

Sportmedizinische Aspekte bei EMAH-Patienten

Immer mehr Patienten mit angeborenem Herzfehler erreichen das Erwachsenenalter. Neben der allgemeinen medizinischen Untersuchung (Elektrokardiogramm, Echokardiografie, Laborparameter etc.) findet auch die Funktionsdiagnostik immer mehr an Bedeutung. Zu dieser zählen sowohl die Lungenfunktion (Spirometrie, Bodyplethysmografie) als auch die Bestimmung der Leistungsfähigkeit (6-Minuten-Gehtest, Spiroergometrie). Wann jedoch eine solche Untersuchung sinnvoll ist, scheint oftmals unklar. Dieser Artikel soll sowohl das standardisierte Vorgehen dieser Untersuchungen aufzeigen als auch die Vor- und Nachteile unterschiedlicher Untersuchungen je nach Fragestellung aufzeigen.

Wichtig hierbei ist, dass eine vollständige sportmedizinische Untersuchung bei Patienten mit angeborenem Herzfehler immer zusammen mit einer kardiologischen Untersuchung stattfinden muss. Nur dann kann eine sichere Untersuchung durch das geschulte Personal gewährleistet werden.

Comparison of the Stanford ECG Left Atrial Criteria With the International ECG Criteria for Sports Screening

OBJECTIVE

Because the International left atrial enlargement electrocardiographic (ECG) screening criteria (ECG-LAE) for athletes are rarely fulfilled in young athletes, we compared it with evidence-based criteria from a recent clinical outcome study of ECG left atrial abnormality (ECG-LAA).

DESIGN

Retrospective analyses.

SETTING

Routine preparticipation ECG screening in California.

PARTICIPANTS

Four thousand four hundred thirty-eight young individuals (18.5 ± 5.4 years, 40% women).

ASSESSMENT OF RISK FACTORS

The International criteria for ECG-LAE were applied: prolonged P wave duration of ≥120 ms in leads I or II AND negative portion of ≥1 mm in depth in lead V1. This was compared with Stanford criteria for ECG-LAA: prolonged P wave duration of ≥140 ms odds ratio (OR) negative portion in V1 and V2 greater than 1 mm.

MAIN OUTCOME MEASURES

Differences in the classification of abnormal ECGs between the 2 criteria applied to the same population of young athletes.

RESULTS

Only 33 (0.7%) of our subjects fulfilled the International criteria for ECG-LAE while 110 (2.5%) fulfilled the ECG-LAA criteria. Adding our new ECG-LAA criterion and considering it a major criterion raised the abnormal ECG prevalence and athletes referred for further evaluation from 2.9% to 4.4%.

CONCLUSIONS

The Stanford evidence-based criterion for ECG-LAA incorporating V2 and replacing "or" for "and" regarding P wave duration increased the yield of abnormal classification for P waves. Future follow-up studies are needed to confirm that this new criterion should be included in future ECG screening consensus documents.

Exercise capacity in patients with repaired Tetralogy of Fallot aged 6 to 63 years

OBJECTIVES

This study aimed to provide a perspective for the interpretation of exercise capacity (peakVO₂) in patients with repaired Tetralogy of Fallot (patients with rTOF) by describing the course of peakVO₂ from patients aged 6-63 years.

METHODS

A retrospective study was performed between September 2001 and December 2016 in the German Heart Centre Munich, Germany, and in the University Medical Centre Groningen, the Netherlands. A total of 1175 cardiopulmonary exercise tests (CPETs) were collected from 586 patients with rTOF, 46% female. Maximal exertion was verified using a respiratory exchange ratio ≥1.00. PeakVO₂ was modelled using time-dependent multilevel models for repeated measurements (n=889 in 300 patients), and compared with subject-specific reference values calculated by the models of Bongers et al and Mylius et al. RESULTS: The peakVO₂ of patients with rTOF was reduced at all ages. At the age of 6, the peakVO₂ was 614 mL/min (70% of predicted (95% CI 67 to 73)). The reduced increase in peakVO₂ during adolescence resulted in a significant lower maximum peakVO₂ of 1209 mL/min at 25 years (65% predicted, p<0.001). A linear decline after 25 years was observed in patients and references, although patients showed an accelerated decline, with a -0.24% point of predicted (95% CI 0.11 to 0.38) per year without differences between sexes (p=0.263).

CONCLUSIONS

This study provides a context for peakVO₂ across ages in patients with rTOF under contemporary treatment strategies. It showed that the reduction in peakVO₂ originates from childhood and declines over time. Sex differences in patients with rTOF were similar to natural existing sex differences.

Tetralogy of Fallot or Pulmonary Atresia with Ventricular Septal Defect after the Age of 40 Years: A Single Center Study

Background: The population of adults with tetralogy of Fallot (TOF) or pulmonary atresia with ventricular septal defect (PA/VSD) is growing and aging. Data regarding older patients are scarce. Prognostic outcome parameters in adults with TOF or PA/VSD ≥ 40 years were studied. Methods: This was a retrospective study of patients ≥ 40 years of age during the study period (January 2005–March 2018). Major adverse cardiac events (MACE) were a combined primary endpoint including death from any cause, prevented sudden cardiac death, pacemaker implantation, arrhythmia, and new-onset heart failure. Additionally, MACE II (secondary endpoint) was a combination of death from any cause and prevented sudden cardiac death. Results: 184 (58.7% female, mean age 45.3 ± 7.2 years) patients were included (159 (86.4%) TOF and 25 (13.6%) PA/VSD). During a median follow-up of 3.1 years (IQR: 0.6–6.5), MACE occurred in 35 and MACE II in 13 patients. On multivariable analysis, New York Heart Association class [HR: 2.1, 95% CI: 1.2–3.6, p = 0.009] emerged as an independent predictor for MACE, and age at corrective surgery [HR: 13.2, 95% CI: 1.6–107.1, p = 0.016] for MACE II. Conclusions: Adults with TOF or PA/VSD ≥ 40 years are burdened with significant morbidity and mortality. New York Heart Association class and age at corrective surgery were independent predictors of outcome.

Children with Congenital Heart Disease Are Active but Need to Keep Moving: A Cross-Sectional Study Using Wrist-Worn Physical Activity Trackers

OBJECTIVE

To compare daily physical activity of children with congenital heart disease (CHD) with healthy peers measured using wearables bracelets in a large cohort. Additionally, subjectively estimated and objectively measured physical activity was compared.

STUDY DESIGN

From September 2017 to May 2019, 162 children (11.8 ± 3.2 years; 60 girls) with various CHD participated in a self-estimated and wearable-based physical activity assessment. Step-count and moderate-to-vigorous physical activity were recorded with the Garmin vivofit jr. for 7 consecutive days and compared with a reference cohort (RC) of 96 healthy children (10.9 ± 3.8 years; 49 girls).

RESULTS

Children with CHD were active and 123 (75.9%) achieved 60 minutes physical activity on a weekly average according to the World Health Organization criteria as 81 (84.3%) of the healthy peers did (P = .217). After correction for age, sex, and seasonal effects, only slightly lower step count (CHD: 10 206 ± 3178 steps vs RC: 11 142 ± 3136 steps; P = .040) but no lower moderate-to-vigorous physical activity (CHD: 80.5 ± 25.6 minutes/day vs RC: 81.5 ± 25.3 minutes/day; P = .767) occurred comparing CHD with RC. In children with CHD higher age (P = .004), overweight or obesity (P = .016), complex severity (P = .046), and total cavopulmonary connection (P = .027) were associated with not meeting World Health Organization criteria. Subjective estimation of daily moderate-to-vigorous physical activity was fairly correct in half of all children with CHD.

CONCLUSIONS

Even though the majority is sufficiently active, physical activity needs to be promoted in overweight or obese patients, patients with complex CHD severity, and in particular in those with total cavopulmonary connection.

Functional outcome in contemporary children and young adults with tetralogy of Fallot after repair

OBJECTIVE

Functional outcome measures are of growing importance in the aftercare of patients with congenital heart disease. This study addresses the functional status with regard to exercise capacity, health-related physical fitness (HRPF) and arterial stiffness in a recent cohort of children, adolescents and young adults with tetralogy of Fallot (ToF) after repair.

DESIGN

Single-centre, uncontrolled and prospective cohort study.

SETTING

Outpatient department of the German Heart Centre Munich; July 2014-January 2018.

PATIENTS

One hundred and six patients with ToF after repair (13.5±3.7 years, 40 females) were included. Data were compared with a recent cohort of healthy controls (HCs) (n=1700, 12.8±2.6 years, 833 females).

MAIN OUTCOME MEASURES

Patients underwent a symptom-limited cardiopulmonary exercise test, performed an HRPF test (FitnessGram) and had an assessment of their arterial stiffness (Mobil-O-Graph).

RESULTS

Compared with HC, patients with ToF showed lower predicted [Formula: see text]O₂ peak (ToF: 80.4% ± 16.8% vs HC: 102.6% ± 18.1%, p<0.001), impaired ventilatory efficiency (ToF: 29.6 ± 3.6 vs HC: 27.4 ± 2.9, p<0.001), chronotropic incompetence (ToF: 167 ± 17 bpm vs HC: 190 ± 17 bpm, p<0.001) and reduced HRPF (ToF z-score: -0.65 ± 0.87 vs HC z-score: 0.03 ± 0.65, p<0.001). Surrogates of arterial stiffness, central and peripheral systolic blood pressure, did not differ between the two groups.

CONCLUSIONS

Contemporary children, adolescents and young adults with ToF still have functional limitations. How impaired HRPF and limited exercise capacity interact and how they can be modified needs to be evaluated in further intervention studies.

Electrocardiographic left atrial abnormalities predict cardiovascular mortality

OBJECTIVE

Clinical utilization of electrocardiography for diagnosis of left atrial abnormalities is hampered by variable P-wave morphologies, multiple empiric criteria, and lack of an imaging "gold standard". Our aim was to determine the prevalence of P-wave patterns and demonstrate which components have associations with cardiovascular death (CVD).

METHODS

This is a retrospective analysis of 20,827 veterans <56 years of age who underwent electrocardiograms at a Veteran's Affairs Medical Center from 1987 to 1999, followed for a median duration of 17.8 years for CVD. Receiver Operating Characteristic, Kaplan-Meier and Cox Hazard analyses were applied, the latter with adjustment for age, gender and electrocardiography abnormalities.

RESULTS

The mean age was 43.3 ± 8 years, and 888 CVD (4.3%) occurred. A single positive deflection of the P-wave (Pattern 1) was present in 29% for V1 and 81% for V2. A singular negative P-wave (Pattern 2) was present in 4.6% for V1 and 1.6% in V2. A P-wave with an upward component followed by downward component (Pattern 3) was present in 64.5% for V1 and 17.5% for V2. When the downward component in Patterns 2 and/or 3 is at least -100 μV, a significant association is observed with CVD (adjusted hazard ratios [HRs] 2.9-4.1, P < 0.001). Total P-wave duration ≥140 ms was also associated with CVD (adjusted HR 2.2, P < 0.001).

CONCLUSIONS

A negative P-wave in V1 or V2 ≤-100 μV, and P-wave with a duration of ≥140 ms, all have independent and significant associations with CVD, with HRs comparable to other electrocardiography abnormalities.

Health-related quality of life in children and adolescents: Current normative data, determinants and reliability on proxy-report

AIM

Health-related quality of life (HrQoL) is a multidimensional concept including self-reported measures of physical and mental health. Throughout the last decades, HrQoL has become a more and more important outcome measure not only in clinical conditions. This study evaluates current HrQoL of healthy children and adolescents, determinants of HrQoL, and the agreement between self- and proxy-report.

METHODS

From April 2012 to July 2013, we prospectively examined 530 healthy children (13.2 ± 2.1 years, 236 girls) and their parents on their childrens HrQoL using the KINDL-R self-report questionnaire and the parent's proxy-report. Data was compared to the established reference value from 2007 and the agreement of self- and parent's proxy-report was assessed by calculation of intraclass correlation coefficient (ICC).

RESULTS

In general, the HrQoL improved compared to references in both children's (104.5 ± 12.6 % of predicted reference value, P < .001) and parent's proxy-report (104.3 ± 12.3 % of predicted reference value, P < .001). HrQoL declined with proceeding age (r = -.247, P < .001) but was not associated with BMI (r = -.035, P = .420). There was good accordance between children's reported HrQoL and the parent's proxy-report (ICC: .774). Only in the domains 'self-esteem' (ICC: .558) and 'Emotional well-being' (ICC: .612) the agreements were moderate.

CONCLUSIONS

HrQoL perception has increased throughout the past 10 years and worsens with increasing age. Moreover, the parent's proxy-report of the KINDL-R questionnaire is a good supplementary method to provide additional information regarding to children's HrQoL.

Operational Head-on Beam-Beam Compensation with Electron Lenses in the Relativistic Heavy Ion Collider

Head-on beam-beam compensation has been implemented in the Relativistic Heavy Ion Collider in order to increase the luminosity delivered to the experiments. We discuss the principle of combining a lattice for resonance driving term compensation and an electron lens for tune spread compensation. We describe the electron lens technology and its operational use. To date, the implemented compensation scheme approximately doubled the peak and average luminosities.

Osteoblast intracellular localization of Nmp4 proteins

Nmp4 proteins are transcription factors that contribute to the expression of type I collagen and many of the matrix metalloproteinase genes. Numerous Nmp4 isoforms have been identified. These proteins, all derived from a single gene, have from five to eight Cys(2)His(2) zinc fingers, the arrangement of which directs specific isoforms to nuclear matrix subdomains. Nmp4 isoforms also have an SH3 binding domain, typical of cytoplasmic docking proteins. Although recent evidence indicates that Nmp4 proteins also reside in the osteoblast cytoplasm, whether they localize to specific organelles or structures is not well defined. The intracellular localization of a protein is a determinant of its function and provides insights into its mechanism of action. As a first step toward determining the functional relationship between the cytoplasmic and nuclear Nmp4 compartments, we mapped their location in the osteoblast cytoplasm. Immunocytochemical analysis of osteoblasts demonstrated that Nmp4 antibodies labeled the mitochondria, colocalized with Golgi protein 58K, and lightly stained the cytoplasm. Western analysis using Nmp4 antibodies revealed a complex profile of protein bands in the nuclear, mitochondrial, and cytosolic fractions. Several of these proteins were specific to defined intracellular domains. Consistent with the western analyses, reverse transcription-polymerase chain reaction (RT-PCR) analysis detected previously uncharacterized Nmp4 isoforms. These data necessarily enlarge the known Nmp4 family from nuclear matrix transcription factors to a more widely extended class of intracellular proteins.

Cloning and functional analysis of a family of nuclear matrix transcription factors (NP/NMP4) that regulate type I collagen expression in osteoblasts

Collagen expression is coupled to cell structure in connective tissue. We propose that nuclear matrix architectural transcription factors link cell shape with collagen promoter geometry and activity. We previously indicated that nuclear matrix proteins (NP/NMP4) interact with the rat type I collagen alpha1(I) polypeptide chain (COL1A1) promoter at two poly(dT) sequences (sites A and B) and bend the DNA. Here, our objective was to determine whether NP/NMP4-COL1A1 binding influences promoter activity and to clone NP/NMP4. Promoter-reporter constructs containing 3.5 kilobases (kb) of COL1A1 5' flanking sequence were fused to a reporter gene. Mutation of site A or site B increased promoter activity in rat UMR-106 osteoblast-like cells. Several full-length complementary DNAs (cDNAs) were isolated from an expression library using site B as a probe. These clones expressed proteins with molecular weights and COLIA1 binding activity similar to NP/NMP4. Antibodies to these proteins disrupted native NP/NMP4-COL1A1 binding activity. Overexpression of specific clones in UMR-106 cells repressed COL1A1 promoter activity. The isolated cDNAs encode isoforms of Cys2His2 zinc finger proteins that contain an AT-hook, a motif found in architectural transcription factors. Some of these isoforms recently have been identified as Cas-interacting zinc finger proteins (CIZ) that localize to fibroblast focal adhesions and enhance metalloproteinase gene expression. We observed NP/NMP4/CIZ expression in osteocytes, osteoblasts, and chondrocytes in rat bone. We conclude that NP/NMP4/CIZ is a novel family of nuclear matrix transcription factors that may be part of a general mechanical pathway that couples cell structure and function during extracellular matrix remodeling.

Assessment of maintenance therapy with reduced doses of PTH(1-34) in combination with a raloxifene analogue (LY117018) following anabolic therapy in the ovariectomized rat

This experiment was designed to evaluate the ability of a raloxifene analogue (RA), LY117018, with or without reduced dosing of human parathyroid hormone (hPTH)(1-34) to maintain gains in bone mass after a fully anabolic treatment regimen given to aging osteopenic rats. Six-month-old rats were ovariectomized (ovx) or sham-operated (sham). After 1 month, ovx rats were treated with an anabolic regimen consisting of subcutaneous hPTH(1-34) 80 microg/kg/day and oral raloxifene 3 mg/kg/day, each given 5 days/week for 3 months. Thereafter, the treated ovx rats went on to an 8 week maintenance phase of treatment with either RA alone at the same dose, hPTH(1-34) at a reduced dosing interval (twice a week), or a combination of the two. Bone mineral density (BMD) was measured ex vivo at four skeletal sites, lumbar spine (L2-4), proximal hemipelvis, whole femur, and tibia, by dual-energy X-ray densitometry. All four sites showed a similar pattern of response. After the 3 month anabolic phase, the sham group had significantly higher BMD values than ovx rats at all skeletal sites (p < or = 0.002). The ovx rats treated with PTH + RA during the anabolic phase of the protocol had significantly higher BMD than the sham group in the femur, tibia, and spine (p < or = 0.02) and higher but not significantly different values in the pelvis. Following the 2 month maintenance phase, comparisons were made with the PTH-RA group at the end of the anabolic phase. Decrements in BMD were seen in all three maintenance therapy groups, but they were not statistically significant in the RA plus reduced PTH dose group. However, reduced hPTH(1-34) dosing and RA alone resulted in significant reductions of bone mass measurements at several skeletal sites during the maintenance phase. We conclude that the raloxifene analogue LY117018 may be useful in maintaining bone mass in aging ovx rats following anabolic therapy with hPTH(1-34) and raloxifene analogue, but that this strategy only allows for dose reduction of hPTH(1-34) rather than its discontinuation.

The addition of a raloxifene analog (LY117018) allows for reduced PTH(1-34) dosing during reversal of osteopenia in ovariectomized rats

To test the hypothesis that an antiresorptive agent might reduce the dosing requirement for an anabolic drug during reversal of osteopenia due to estrogen deficiency, the following experiment was conducted in 6-month-old female rats. Ovariectomy or sham surgery was performed and the following six experimental groups were studied. Untreated (SHAM) or ovariectomized (OVX) animals served as control groups. Four weeks post-OVX, osteopenic rats (now 7 months old), were treated in one of four experimental protocols: human parathyroid hormone (hPTH(1-34)), 80 microg/kg/day, given by subcutaneous injection 5 days/week; a selective estrogen receptor modulator (SERM), raloxifene analog LY117018 (RA), 3 mg/kg/day, given by gavage 5 days/week; and two combinations of LY117018 at the same dose and frequency with hPTH(1-34) (same dose, 5 times/week) and a reduced dosing interval of hPTH(1-34) (same dose, 2 times/week). After 12 weeks of treatment, the four experimental groups were sacrificed at age 10 months. SHAM and OVX controls were also studied at 7 and 10 months of age. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry at four skeletal sites: two mixed cortical/trabecular sites (femur and tibia) and two predominantly trabecular sites (lumbar spine and pelvis). The differences in BMD were consistent at all four sites. RA alone maintained BMD at all skeletal sites, but the results were not significantly improved over OVX controls, at age 10 months. hPTH(1-34) injections given 5 days/week resulted in BMD increments significantly higher than in either OVX or SHAM controls (p < 0.001). While the RA did not enhance the anabolic effects of full doses of hPTH(1-34), the addition of RA treatment to twice-weekly hPTH(1-34) dosing resulted in BMD increments at all four skeletal sites that were similar to the more intensive anabolic regimen of hPTH(1-34) therapy given 5 times/week. Therefore, an antiresorptive agent such as SERMs may potentially reduce the pharmacologic doses of PTH needed to reverse estrogen deficiency-induced osteopenia.

Parathyroid hormone regulates the expression of fibroblast growth factor-2 mRNA and fibroblast growth factor receptor mRNA in osteoblastic cells

We examined the effect of parathyroid hormone (PTH) on basic fibroblast growth factor-2 (FGF-2) and FGF receptor (FGFR) expression in osteoblastic MC3T3-E1 cells and in neonatal mouse calvariae. Treatment of MC3T3-E1 cells with PTH(1-34) (10-8M) or forskolin (FSK; 10-5M) transiently increased a 7 kb FGF-2 transcript with a peak at 2 h. The PTH increase in FGF-2 mRNA was maintained in the presence of cycloheximide. PTH also increased FGFR-1 mRNA at 2 h and transiently increased FGFR-2 mRNA at 1 h. FGFR-3 and FGFR-4 mRNA transcripts were not detected in MC3T3-E1 cells. In cells transiently transfected with an 1800-bp FGF-2 promoter-luciferase reporter, PTH and FSK increased luciferase activity at 2 h and 4 h. Immunohistochemistry showed that PTH and FSK increased FGF-2 protein labeling in the nuclei of MC3T3-E1 cells. PTH also increased FGF-2 mRNA, and FGFR-1 and FGFR-2 mRNA levels within 30 minutes in neonatal mouse calvarial organ cultures. We conclude that PTH and cAMP stimulate FGF-2 mRNA abundance in part through a transcriptional mechanism. PTH also regulated FGFR gene expression. We hypothesize that some effects of PTH on bone remodeling may be mediated by regulation of FGF-2 and FGFR expression in osteoblastic cells.

PTH-responsive osteoblast nuclear matrix architectural transcription factor binds to the rat type I collagen promoter

In connective tissue, cell structure contributes to type I collagen expression. Differences in osteoblast microarchitecture may account for the two distinct cis elements regulating basal expression, in vivo and in vitro, of the rat type I collagen alpha1(I) polypeptide chain (COL1A1). The COL1A1 promoter conformation may be the penultimate culmination of osteoblast structure. Architectural transcription factors bind to the minor groove of AT-rich DNA and bend it, altering interactions between other trans-acting proteins. Similarly, nuclear matrix (NM) proteins bind to the minor groove of AT-rich matrix-attachment regions, regulating transcription by altering DNA structure. We propose that osteoblast NM architectural transcription factors link cell structure to promoter geometry and COL1A1 transcription. Our objective was to identify potential osteoblast NM architectural transcription factors near the in vitro and in vivo regulatory regions of the rat COL1A1 promoter. Nuclear protein-promoter interactions were analyzed by gel shift analysis and related techniques. NM extracts were derived from rat osteosarcoma cells and from rat bone. The NM protein, NMP4, and a soluble nuclear protein, NP, both bound to two homologous poly(dT) elements within the COL1A1 in vitro regulatory region and proximal to the in vivo regulatory element. These proteins bound within the minor groove and bent the DNA. Parathyroid hormone increased NP/NMP4 binding to both poly(dT) elements and decreased COL1A1 mRNA in the osteosarcoma cells. NP/NMP4-COL1A1 promoter interactions may represent a molecular pathway by which osteoblast structure is coupled to COL1A1 expression.

Parathyroid hormone regulates the expression of the nuclear mitotic apparatus protein in the osteoblast-like cells, ROS 17/2.8

The parathyroid hormone (PTH) signaling pathways that effect changes in osteoblast gene expression also alter the organization of the cytoskeletal proteins. PTH regulates the expression of nucleoskeletal proteins, such as nuclear mitotic apparatus protein (NuMA) and topoisomerase II-alpha. NuMA is a structural component of the interphase nucleus and organizes the microtubules of the mitotic spindle during mitogenesis. We propose that PTH-induced alterations in osteoblast cytoarchitecture are accompanied by changes in osteoblast nuclear structure that contribute to changes in gene expression. We used immunofluorescence and confocal microscopy to determine the effect of PTH on the expression and nuclear distribution of NuMA in the rat osteosarcoma cell line, ROS 17/2.8. Cells were treated with PTH or vehicle, then fixed and stained with NuMA antibody. Optical sections of interphase naive cells revealed a diffuse distribution of NuMA, interspersed with speckles, in the central nuclear planes but not in nucleoli. During the metaphase and anaphase, NuMA localized at the mitotic spindle apparatus. The percentage of NuMA-immunopositive ROS 17/2.8 cells decreased with increasing confluence, but serum starvation did not attenuate NuMA expression. Cell density-dependent changes in cytoskeletal organization were observed in these cells. PTH treatment induced changes in cytoskeletal organization and increased the percentage of NuMA-immunopositive ROS 17/2.8 cells. These data suggest that PTH effects changes in osteoblast nuclear architecture by regulating NuMA, and that these alterations may be coupled to cytoskeletal organization.

Immunohistochemical demonstration of enzymatically modified human LDL and its colocalization with the terminal complement complex in the early atherosclerotic lesion

Treatment of low density lipoprotein (LDL) with degrading enzymes transforms the molecule to a moiety that is micromorphologically indistinguishable from lipoproteinaceous particles that are present in atherosclerotic plaques, and enzymatically modified LDL (E-LDL), but not oxidized LDL (ox-LDL), spontaneously activates the alternative complement pathway, as do lesion lipoprotein derivatives. Furthermore, because E-LDL is a potent inducer of macrophage foam cell formation, we propose that enzymatic degradation may be the key process that renders LDL atherogenic. In this article, we report the production of two murine monoclonal antibodies recognizing cryptic epitopes in human apolipoprotein B that become exposed after enzymatic attack on LDL. One antibody reacted with LDL after single treatment with trypsin, whereas recognition by the second antibody required combined treatment of LDL with trypsin and cholesterol esterase. In ELISAs, both antibodies reacted with E-LDL produced in vitro and with lesion complement activator derived from human atherosclerotic plaques, but they were unreactive with native LDL or ox-LDL. The antibodies stained E-LDL, but not native LDL or ox-LDL, that had been artificially injected into arterial vessel walls. With the use of these antibodies, we have demonstrated that early human atherosclerotic coronary lesions obtained at autopsy as well as lesions examined in freshly explanted hearts always contain extensive extracellular deposits of E-LDL. Terminal complement complexes, detected with a monoclonal antibody specific for a C5b-9 neoepitope, colocalized with E-LDL within the intima, which is compatible with the proposal that subendothelially deposited LDL is enzymatically transformed to a complement activator at the earliest stages in lesion development.

Analysis of differential gene expression in rat tibia after an osteogenic stimulus in vivo: mechanical loading regulates osteopontin and myeloperoxidase

The skeleton has the ability to alter its mass, geometry, and strength in response to mechanical stress. In order to elucidate the molecular mechanisms underlying this phenomenon, differential display reverse transcriptase-polymerase chain reaction (DDRT-PCR) was used to analyze gene expression in endocortical bone of mature female rats. Female Sprague-Dawley rats, approximately 8 months old, received either a sham or bending load using a four-point loading apparatus on the right tibia. RNA was collected at 1 h and 24 h after load was applied, reverse-transcribed into cDNA, and used in DDRT-PCR. Parallel display of samples from sham and loaded bones on a sequencing gel showed several regulated bands. Further analysis of seven of these bands allowed us to isolate two genes that are regulated in response to a loading stimulus. Nucleotide analysis showed that one of the differentially expressed bands shares 99% sequence identity with rat osteopontin (OPN), a noncollagenous bone matrix protein. Northern blot analysis confirms that OPN mRNA expression is increased by nearly 4-fold, at 6 h and 24 h after loading. The second band shares 90% homology with mouse myeloperoxidase (MPO), a bactericidal enzyme found primarily in neutrophils and monocytes. Semiquantitative PCR confirms that MPO expression is decreased 4- to 10-fold, at 1 h and 24 h after loading. Tissue distribution analysis confirmed MPO expression in bone but not in other tissues examined. In vitro analysis showed that MPO expression was not detectable in total RNA from UMR 106 osteoblastic cells or in confluent primary cultures of osteoblasts derived from either rat primary spongiosa or diaphyseal marrow. Database analysis suggests that MPO is expressed by osteocytes. These findings reinforce the association of OPN expression to bone turnover and describes for the first time, decreased expression of MPO during load-induced bone formation. These results suggest a role for both OPN and MPO expression in bone cell function.

Nuclear matrix proteins and osteoblast gene expression

The molecular mechanisms that couple osteoblast structure and gene expression are emerging from recent studies on the bone extracellular matrix, integrins, the cytoskeleton, and the nucleoskeleton (nuclear matrix). These proteins form a dynamic structural network, the tissue matrix, that physically links the genes with the substructure of the cell and its substrate. The molecular analog of cell structure is the geometry of the promoter. The degree of supercoiling and bending of promoter DNA can regulate transcriptional activity. Nuclear matrix proteins may render a change in cytoskeletal organization into a bend or twist in the promoter of target genes. We review the role of nuclear matrix proteins in the regulation of gene expression with special emphasis on osseous tissue. Nuclear matrix proteins bind to the osteocalcin and type I collagen promoters in osteoblasts. One such protein is Cbfa1, a recently described transcriptional activator of osteoblast differentiation. Although their mechanisms of action are unknown, some nuclear matrix proteins may act as "architectural" transcription factors, regulating gene expression by bending the promoter and altering the interactions between other trans-acting proteins. The osteoblast nuclear matrix is comprised of cell- and phenotype-specific proteins including proteins common to all cells. Nuclear matrix proteins specific to the osteoblast developmental stage and proteins that distinguish osteosarcoma from the osteoblast have been identified. Recent studies indicating that nuclear matrix proteins mediate bone cell response to parathyroid hormone and vitamin D are discussed.

Tissue matrix protein expression in human osteoblasts, osteosarcoma tumors, and osteosarcoma cell lines

Treatment for osteosarcoma is problematic because there are no prognostic markers. Diagnosis is primarily limited to cytologic grading. Oncogenesis alters cell structure therefore osteoblast tissue matrix proteins (extracellular matrix, cytoskeletal, intermediate filament, and nuclear matrix proteins), components of the cell substructure, are candidates for osteosarcoma markers. Structural proteins of the extracellular matrix, e.g. the collagens, are useful for diagnosis but not for tumors that produce little osteoid. To identify principal cellular tissue matrix proteins that distinguish normal from transformed human osteoblasts, their expression in normal osteoblasts, two osteosarcoma cell lines, and three primary osteosarcoma tumors were compared. The tumors were graded as (i) intermediate, (ii) high, and (iii) high grade recurrent. The 1-D SDS/PAGE profiles of the major components of the nuclear matrix and intermediate filament fractions from normal osteoblasts did not vary with biopsy site, age, or sex of patients. These profiles included known cytoskeletal proteins and OB250, a approximately 250 kD protein(s) observed in the intermediate filament fraction. A loss of protein bands, including OB250, was observed in the osteosarcoma cell lines and tumors. The intermediate and high grade tumors exhibited nearly identical protein profiles including potential tumor-specific proteins and collagen, consistent with the presence of intracellular collagen fibers in osteosarcoma. A microsequence was obtained for OT25, a novel low molecular weight protein observed in osteosarcoma cell lines. Fibrinogen gamma-chain, a protein that mediates cell adhesion was recovered from the high grade recurrent tumor.

Rat osteoblast and osteosarcoma nuclear matrix proteins bind with sequence specificity to the rat type I collagen promoter

The nuclear matrix mediates the 3-dimensional organization of DNA and supports DNA replication and its transcription. We hypothesize that the osteoblast nuclear matrix contributes to the transcriptional control of type I collagen (COL1A1) expression. Cis-regulatory elements of the rat COL1A1 promoter that control osteoblast expression in vivo are between -2.3 and -1.67 kilobase pairs (kb) but lie within -3.5 and -2.3 kb in cultured bone cells. This may result from differences in cell architecture between osteoblasts in tissue and those in vitro. Our aim was to identify osteoblast nuclear matrix proteins (NMPs) that associated with sequence-specificity to the COL1A1 promoter. We used osteoblasts from the rat metaphyseal femur and the rat osteosarcoma cells, ROS 17/2.8. Nuclear matrix and soluble nuclear proteins were obtained as separate subfractions. Gel mobility shift analysis, using fragments of the COL1A1 promoter, was used to identify DNA-binding proteins in the nuclear subfractions. A NMP-DNA interaction, NMP3, was observed between -2149 and -2106 nucleotide in both osteoblasts and osteosarcoma cells. NMP4 was detected between -3518 to -3406 nucleotide. Therefore, osteoblast NMPs recognize sequences in regulatory regions of the COL1A1 promoter and may link cell structure and the transcriptional regulation of this protein.

Parathyroid hormone regulates the expression of rat osteoblast and osteosarcoma nuclear matrix proteins

Parathyroid hormone (PTH) alters osteoblast morphology. How these changes in cell shape modify nuclear structure and ultimately gene expression is not known. Chronic exposure to rat PTH (1-34) [10 nM] attenuated the expression of 200, 190, and 160 kD proteins in the nuclear matrix-intermediate filament subfraction of the rat osteosarcoma cells, ROS 17/2.8 [Bidwell et al. (1994b): Endocrinology 134:1738-1744]. Here, we determined that these same PTH-responsive proteins were expressed in rat metaphyseal osteoblasts. We identified the 200 kD protein as a non-muscle myosin. Although the molecular weights, subcellular distribution, and half-lives of the 190 and 160 kD proteins were similar to topoisomerase II-alpha and -beta, nuclear matrix enzymes that mediate DNA topology, the 190 and 160 kD proteins did not interact with topoisomerase antibodies. Nevertheless, the expression of topoisomerase II-alpha, and NuMA, a component of the nuclear core filaments, was also regulated by PTH in the osteosarcoma cells. The 190 kD protein was selectively expressed in bone cells as it was not observed in OK opossum kidney cells, H4 hepatoma cells, or NIH3T3 cells. PTH attenuated mRNA expression of the PTH receptor in our cell preparations. These results demonstrate that PTH selectively alters the expression of osteoblast membrane, cytoskeletal, and nucleoskeletal proteins. Topoisomerase II-alpha, NuMA, and the 190 and 160 kD proteins may direct the nuclear PTH signalling pathways to the target genes and play a structural role in osteoblast gene expression.

Quantification of hemostatic proteins and activation products in synovial fluids from arthritic joints prior to and after induction of chemical synoviorthesis

Synovial fluids drawn from joints of patients suffering from rheumatoid arthritis were investigated for their concentrations of proteins and activation markers of the complement, coagulation and fibrinolytic systems. A broad spectrum of plasmatic inhibitors and other hemostatic proteins were detectable by immunologic assays. Compared to normal plasma concentration ranges, levels of alpha 2-antiplasmin, antithrombin III, heparin-cofactor II, factor H, alpha 2-macroglobulin, inter-alpha-trypsin inhibitor, fibrinogen and particularly high molecular weight kininogen were found to be decreased when corrected for total protein content. However, highly elevated levels of C-reactive protein, factor XIII, PMN-elastase, prothrombin fragment F1+2, thrombin-antithrombin III, plasmin-antiplasmin and terminal complement-complexes as well as C5a were determined. Eight and 24 hours after induction of chemical synoviorthesis, a general increase in most of the parameters was observed. Statistically significant alterations were found for C1-inhibitor, factor H, alpha 1-antitrypsin, inter-alpha-trypsin inhibitor, factor XIII, protein C, thrombin-antithrombin III complexes and C5a.

Mapping of the high molecular weight kininogen binding site of prekallikrein. Evidence for a discontinuous epitope formed by distinct segments of the prekallikrein heavy chain

Prekallikrein, a glycoprotein involved in contact phase activation, circulates in plasma in the form of a binary complex with high molecular weight kininogen (H-kininogen). The binding to H-kininogen is mediated by the prekallikrein heavy chain consisting of four repetitive domains, A1-A4. To define more precisely the region(s) involved in kininogen binding, we have employed an affinity cross-linking strategy with a synthetic peptide of 31 residues which mimics the prekallikrein binding site of H-kininogen. Cross-linking of the radiolabeled peptide to (pre)kallikrein revealed a binding segment in the NH2-terminal portion of the prekallikrein heavy chain; another binding segment was located in the COOH-terminal part of the heavy chain. The latter binding segment is harbored by a previously identified fragment of the kallikrein heavy chain involved in H-kininogen binding (Page, J.D., and Colman, R.W. (1991) J. Biol. Chem. 266, 8143-8148). Chemical cleavage of the heavy chain cross-linked with the radiolabeled peptide mapped the NH2-terminal binding segment to 60 residues (positions 53-112) of A1. Synthesis of a peptide (positions 56-86) and development of specific antibodies to this peptide narrowed down the kininogen binding segment to 31 residues of the center portion of A1. This NH2-terminal segment is equivalent to a kininogen binding site previously identified in factor XI (Baglia, F.A., Jameson, B.A., and Walsh, P.N. (1992) J. Biol. Chem. 267, 4247-4252). We conclude that prekallikrein exposes at least two segments on its heavy chain portion which form a continuous surface thereby facilitating the intimate binding of the zymogen to its nonenzymatic cofactor, H-kininogen.

A G protein-linked receptor for parathyroid hormone and parathyroid hormone-related peptide

The complementary DNA encoding a 585-amino acid parathyroid hormone-parathyroid hormone-related peptide (PTH-PTHrP) receptor with seven potential membrane-spanning domains was cloned by COS-7 expression using an opossum kidney cell complementary DNA (cDNA) library. The expressed receptor binds PTH and PTHrP with equal affinity, and both ligands equivalently stimulate adenylate cyclase. Striking homology with the calcitonin receptor and lack of homology with other G protein-linked receptors indicate that receptors for these calcium-regulating hormones are related and represent a new family.

High molecular weight kininogen-binding site of prekallikrein probed by monoclonal antibodies

A panel of monoclonal antibodies against human prekallikrein was raised in mice and characterized with respect to the major antigenic epitopes. Of 18 antibodies, nine were directed against the light chain portion performing the proteolytic function of activated kallikrein, and nine recognized the heavy chain mediating the binding of prekallikrein to high molecular weight (H-)kininogen. Among the anti-heavy chain antibodies, one (PK6) interfered with the procoagulant activity of prekallikrein, and prolonged in a concentration-dependent manner the activated partial thromboplastin time of reconstituted prekallikrein-deficient plasma (Fletcher type). Antibody PK6 was subtyped IgG1,k and had an apparent Kass of 6.8 +/- 0.44.10(8) M-1 for prekallikrein. Functional analyses revealed that PK6 does not interfere with prekallikrein activation by activated Hageman factor (beta-F XIIa), and has no effect on the kininogenase function of activated kallikrein. Monoclonal antibody PK6 but none of the other anti-heavy chain antibodies completely prevented complex formation of prekallikrein with H-kininogen, and readily dissociated preformed complexes of prekallikrein and H-kininogen. Likewise, Fab' and F(ab')2 fragments of PK6 blocked H-kininogen binding to prekallikrein. A synthetic peptide of 31 amino acid residues encompassing the entire prekallikrein binding region of H-kininogen effectively competed with PK6 for prekallikrein binding indicating that the target epitope of PK6 is juxtaposed to, if not incorporated in the H-kininogen-binding site of prekallikrein. Extensive cross-reactivity of PK6 with another H-kininogen-binding protein of human plasma, i.e. factor XI, suggested that the structure of the target epitope of PK6 is well conserved among prekallikrein and factor XI, as would be expected for the kininogen-binding site shared by the two proteins. It is anticipated that monoclonal antibody PK6 will be an important tool for the precise mapping of the hitherto unknown kininogen-binding site of prekallikrein.

Blood and urine fluoride concentrations associated with topical fluoride applications on dog gingiva

The circulatory uptake and urinary excretion of topical fluoride were investigated by applying a sodium fluoride solution containing 18F for six min to healthy gingiva of four adult dogs. Blood and urine samples were taken a regular intervals. Maximal fluoride in blood represented 0.02-0.05% of the applied dose and occurred four min after completion of the application. By 6.0 h, 0.02-0.06% of the applied dose had been excreted in urine. Preliminary data showed that this represented about 8.8% of the fluoride absorbed through the gingiva.

Clinical study to compare the effect of stannous fluoride and chlorhexidine mouthrinses on plaque formation

A clinical study was conducted on four adults to compare the relative efficacy of 0.2% chlorhexidine digluconate and 0.1% stannous fluoride (SnF2). Using a crossover experimental design, subjects rinsed twice daily for 5 days with SnF2 and then, after a 2-day interim recovery period, for 5 days with chlorhexidine. Statistically significant differences (P less than 0.05) in the relative efficacy of the two agents were found. Chlorhexidine was more effective in reducing Gingival and Plaque Indices, plaque wet weight and bacterial Colony Forming Units, calculated both per subject and per group.

Effect of stannous fluoride mouthrinse on dental plaque formation

A double-blind, crossover design study was performed on 29 young adults to test the effectiveness of 0.1% SnF2 mouthrinse (250 ppmF-) on plaque formation using clinical and microbiological criteria. Participants were assigned to either a placebo or SnF2 rinse which was used twice daily for 5 days. After an interim recovery period of 2 days, the participants used the alternate rinse in a similar manner for another 5 days. Clinical data collected at the end of each experimental period included Gingival Index (GI), and plaque scores. Supragingival plaque removed from each subject at the end of the experimental periods was weighed and then microbial enumeration was performed. Results showed that after SnF2 rinses, there were statistically significant reductions (P < 0.01) in plaque wet weight, number of bacteria per milligram plaque (CFU/mg), and total number of bacteria per sample (Total CFU). Visual plaque scores (PS) showed a significant (P < 0.05) but small reduction as a result of SnF2 rinse. No significant difference in gingival inflammation was noted. It is apparent from this study that, besides the well-documented ability of SnF2 to increase the resistance of teeth to demineralization, this agent is capable of reducing plaque formation. Long-term studies are indicated to examine usefulness of SnF2 in the control of early periodontal disease.