Aberrant Long-Chain Fatty Acid Metabolism Associated with Evolving Systemic Sclerosis-Associated Pulmonary Arterial Hypertension

We sought to investigate differential metabolism in patients with systemic sclerosis (SSc) who develop pulmonary arterial hypertension (PAH) versus those who do not, as a method of identifying potential disease biomarkers. In a nested case-control design, serum metabolites were assayed in SSc subjects who developed right heart catheterization-confirmed PAH (n=22) while under surveillance in a longitudinal cohort from Johns Hopkins, then compared to metabolites assayed in matched SSc patients who did not develop PAH (n=22). Serum samples were collected at "proximate" (within 12 months) and "distant" (within 1-5 years) time points relative to PAH diagnosis. Metabolites were identified using liquid chromatography-mass spectroscopy (LC-MS). An LC-MS dataset from SSc subjects with either mildly elevated pulmonary pressures or overt PAH from the University of Michigan was compared. Differentially abundant metabolites were tested as predictors of PAH in two additional validation SSc cohorts. Long-chain fatty acid metabolism (LCFA) consistently differed in SSc-PAH versus SSc without PH. LCFA metabolites discriminated SSc-PAH patients with mildly elevated pressures in the Michigan cohort and predicted SSc-PAH up to two years prior to clinical diagnosis in the Hopkins cohort. Acylcholines containing LCFA residues and linoleic acid metabolites were most important for discriminating SSc-PAH. Combinations of acylcholines and linoleic acid metabolites provided good discrimination of SSc-PAH across cohorts. Aberrant lipid metabolism is observed throughout the evolution of PAH in SSc. Lipidomic signatures of abnormal LCFA metabolism distinguish SSc-PAH patients from those without PH, including prior to clinical diagnosis and in mild disease.

Fatty acid metabolism promotes TRPV4 activity in lung microvascular endothelial cells in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a morbid disease characterized by significant lung endothelial cell (EC) dysfunction. Prior work has shown that microvascular endothelial cells (MVECs) isolated from animals with experimental PAH and patients with PAH exhibit significant abnormalities in metabolism and calcium signaling. With regards to metabolism, we and others have shown evidence of increased aerobic glycolysis and evidence of increased utilization of alternate fuel sources (such as fatty acids) in PAH EC. In the realm of calcium signaling, our prior work linked increased activity of the transient receptor potential vanilloid-4 (TRPV4) channel to increased proliferation of MVECs isolated from the Sugen/Hypoxia rat model of PAH (SuHx-MVECs). However, the relationship between metabolic shifts and calcium abnormalities was not clear. Specifically, whether shifts in metabolism were responsible for increasing TRPV4 channel activity in SuHx-MVECs was not known. In this study, using human data, serum samples from SuHx rats, and SuHx-MVECs, we describe the consequences of increased MVEC fatty acid oxidation in PAH. In human samples, we observed an increase in long-chain fatty acid levels that was associated with PAH severity. Next, using SuHx rats and SuHx-MVECs, we observed increased intracellular levels of lipids. We also show that increasing intracellular lipid content increases TRPV4 activity, whereas inhibiting fatty acid oxidation normalizes basal calcium levels in SuHx-MVECs. By exploring the fate of fatty acid-derived carbons, we observed that the metabolite linking increased intracellular lipids to TRPV4 activity was β-hydroxybutyrate (BOHB), a product of fatty acid oxidation. Finally, we show that BOHB supplementation alone is sufficient to sensitize the TRPV4 channel in rat and mouse MVECs. Returning to humans, we observe a transpulmonary BOHB gradient in human patients with PAH. Thus, we establish a link between fatty acid oxidation, BOHB production, and TRPV4 activity in MVECs in PAH. These data provide new insight into metabolic regulation of calcium signaling in lung MVECs in PAH.NEW & NOTEWORTHY In this paper, we explore the link between metabolism and intracellular calcium levels in microvascular endothelial cells (MVECs) in pulmonary arterial hypertension (PAH). We show that fatty acid oxidation promotes sensitivity of the transient receptor potential vanilloid-4 (TRPV4) calcium channel in MVECs isolated from a rodent model of PAH.

Metabolomic Differences in Connective Tissue Disease-Associated Versus Idiopathic Pulmonary Arterial Hypertension in the PVDOMICS Cohort

OBJECTIVE

Patients with connective tissue disease-associated pulmonary arterial hypertension (CTD-PAH) experience worse survival and derive less benefit from pulmonary vasodilator therapies than patients with idiopathic PAH (IPAH). We sought to identify differential metabolism in patients with CTD-PAH versus patients with IPAH that might underlie these observed clinical differences.

METHODS

Adult participants with CTD-PAH (n = 141) and IPAH (n = 165) from the Pulmonary Vascular Disease Phenomics (PVDOMICS) study were included. Detailed clinical phenotyping was performed at cohort enrollment, including broad-based global metabolomic profiling of plasma samples. Participants were followed prospectively for ascertainment of outcomes. Supervised and unsupervised machine learning algorithms and regression models were used to compare CTD-PAH versus IPAH metabolomic profiles and to measure metabolite-phenotype associations and interactions. Gradients across the pulmonary circulation were assessed using paired mixed venous and wedged samples in a subset of 115 participants.

RESULTS

Metabolomic profiles distinguished CTD-PAH from IPAH, with patients with CTD-PAH demonstrating aberrant lipid metabolism with lower circulating levels of sex steroid hormones and higher free fatty acids (FAs) and FA intermediates. Acylcholines were taken up by the right ventricular-pulmonary vascular (RV-PV) circulation, particularly in CTD-PAH, while free FAs and acylcarnitines were released. In both PAH subtypes, dysregulated lipid metabolites, among others, were associated with hemodynamic and RV measurements and with transplant-free survival.

CONCLUSIONS

CTD-PAH is characterized by aberrant lipid metabolism that may signal shifted metabolic substrate utilization. Abnormalities in RV-PV FA metabolism may imply a reduced capacity for mitochondrial beta oxidation within the diseased pulmonary circulation.

Kynurenine pathway metabolism evolves with development of preclinical and scleroderma-associated pulmonary arterial hypertension

Understanding metabolic evolution underlying pulmonary arterial hypertension (PAH) development may clarify pathobiology and reveal disease-specific biomarkers. Patients with systemic sclerosis (SSc) are regularly surveilled for PAH, presenting an opportunity to examine metabolic change as disease develops in an at-risk cohort. We performed mass spectrometry-based metabolomics on longitudinal serum samples collected before and near SSc-PAH diagnosis, compared with time-matched SSc subjects without PAH, in a SSc surveillance cohort. We validated metabolic differences in a second cohort and determined metabolite-phenotype relationships. In parallel, we performed serial metabolomic and hemodynamic assessments as the disease developed in a preclinical model. For differentially expressed metabolites, we investigated corresponding gene expression in human and rodent PAH lungs. Kynurenine and its ratio to tryptophan (kyn/trp) increased over the surveillance period in patients with SSc who developed PAH. Higher kyn/trp measured two years before diagnostic right heart catheterization increased the odds of SSc-PAH diagnosis (OR 1.57, 95% CI 1.05-2.36, P = 0.028). The slope of kyn/trp rise during SSc surveillance predicted PAH development and mortality. In both clinical and experimental PAH, higher kynurenine pathway metabolites correlated with adverse pulmonary vascular and RV measurements. In human and rodent PAH lungs, expression of TDO2, which encodes tryptophan 2,3 dioxygenase (TDO), a protein that catalyzes tryptophan conversion to kynurenine, was significantly upregulated and tightly correlated with pulmonary hypertensive features. Upregulated kynurenine pathway metabolism occurs early in PAH, localizes to the lung, and may be modulated by TDO2. Kynurenine pathway metabolites may be candidate PAH biomarkers and TDO warrants exploration as a potential novel therapeutic target.NEW & NOTEWORTHY Our study shows an early increase in kynurenine pathway metabolism in at-risk subjects with systemic sclerosis who develop pulmonary arterial hypertension (PAH). We show that kynurenine pathway upregulation precedes clinical diagnosis and that this metabolic shift is associated with increased disease severity and shorter survival times. We also show that gene expression of TDO2, an enzyme that generates kynurenine from tryptophan, rises with PAH development.

Spatial and temporal resolution of metabolic dysregulation in the Sugen hypoxia model of pulmonary hypertension

Although PAH is partially attributed to disordered metabolism, previous human studies have mostly examined circulating metabolites at a single time point, potentially overlooking crucial disease biology. Current knowledge gaps include an understanding of temporal changes that occur within and across relevant tissues, and whether observed metabolic changes might contribute to disease pathobiology. We utilized targeted tissue metabolomics in the Sugen hypoxia (SuHx) rodent model to investigate tissue-specific metabolic relationships with pulmonary hypertensive features over time using regression modeling and time-series analysis. Our hypotheses were that some metabolic changes would precede phenotypic changes, and that examining metabolic interactions across heart, lung, and liver tissues would yield insight into interconnected metabolic mechanisms. To support the relevance of our findings, we sought to establish links between SuHx tissue metabolomics and human PAH -omics data using bioinformatic predictions. Metabolic differences between and within tissue types were evident by Day 7 postinduction, demonstrating distinct tissue-specific metabolism in experimental pulmonary hypertension. Various metabolites demonstrated significant tissue-specific associations with hemodynamics and RV remodeling. Individual metabolite profiles were dynamic, and some metabolic shifts temporally preceded the emergence of overt pulmonary hypertension and RV remodeling. Metabolic interactions were observed such that abundance of several liver metabolites modulated lung and RV metabolite-phenotype relationships. Taken all together, regression analyses, pathway analyses and time-series analyses implicated aspartate and glutamate signaling and transport, glycine homeostasis, lung nucleotide abundance, and oxidative stress as relevant to early PAH pathobiology. These findings offer valuable insights into potential targets for early intervention in PAH.

Low-affinity insulin-like growth factor binding protein 7 and its association with pulmonary arterial hypertension severity and survival

Insulin-like growth factor (IGF) binding proteins (IGFBPs) are a family of growth factor modifiers, some of which are known to be independently associated with pulmonary arterial hypertension (PAH) survival. IGF factor binding protein 7 (IGFBP7) is a unique low-affinity IGFBP that, independent of IGF, stimulates prostacyclin production. This study proposed to establish associations between IGFBP7 and PAH severity and survival, using enrollment and longitudinal samples. Serum IGFBP7 levels were significantly elevated in patients with PAH compared to controls. After adjusting for age and sex, logarithmic increases in IGFBP7 were associated with a 20 m shorter six-minute walk distance (6MWD; p < 0.001), a 2-3 mmHg higher mean right atrial pressure (p < 0.001 and 0.02), and a higher likelihood of a greater REVEAL 2.0 risk category placement (p < 0.001). Kaplan-Meier analysis demonstrated significantly decreased survival with IGFBP7 above the median and Cox multivariable analysis adjusted for age and sex, demonstrated higher serum IGFBP7 was an independent predictor of survival. Though the exact mechanism is still unknown, given IGFBP7's role as a prostacyclin stimulant, it has potential use as a therapeutic target for disease modulation.

Metabolic profiling of in vivo right ventricular function and exercise performance in pulmonary arterial hypertension

Right ventricular (RV) adaptation is the principal determinant of outcomes in pulmonary arterial hypertension (PAH), however, RV function is challenging to assess. RV responses to hemodynamic stressors are particularly difficult to interrogate without invasive testing. This study sought to identify metabolomic markers of in vivo right ventricular function and exercise performance in PAH. Consecutive subjects with PAH (n = 23) underwent rest and exercise right heart catheterization with multibeat pressure volume loop analysis. Pulmonary arterial blood was collected at rest and during exercise. Mass spectrometry-based targeted metabolomics were performed, and metabolic associations with hemodynamics and comprehensive measures of RV function were determined using sparse partial least squares regression. Metabolite profiles were compared with N-terminal prohormone of B-type natriuretic peptide (NT-proBNP) measurements for accuracy in modeling ventriculo-arterial parameters. Thirteen metabolites changed in abundance with exercise, including metabolites reflecting increased arginine bioavailability, precursors of catecholamine and nucleotide synthesis, and branched-chain amino acids. Higher resting arginine bioavailability predicted more favorable exercise hemodynamics and pressure-flow relationships. Subjects with more severe PAH augmented arginine bioavailability with exercise to a greater extent than subjects with less severe PAH. We identified relationships between kynurenine pathway metabolism and impaired ventriculo-arterial coupling, worse RV diastolic function, lower RV contractility, diminished RV contractility with exercise, and RV dilation with exercise. Metabolite profiles outperformed NT-proBNP in modeling RV contractility, diastolic function, and exercise performance. Specific metabolite profiles correspond to RV functional measurements only obtainable via invasive pressure-volume loop analysis and predict RV responses to exercise. Metabolic profiling may inform discovery of RV functional biomarkers.NEW & NOTEWORTHY In this cohort of patients with pulmonary arterial hypertension (PAH), we investigate metabolomic associations with comprehensive right ventricular (RV) functional measurements derived from multibeat RV pressure-volume loop analysis. Our results show that tryptophan metabolism, particularly the kynurenine pathway, is linked to intrinsic RV function and PAH pathobiology. Findings also highlight the importance of arginine bioavailability in the cardiopulmonary system's response to exercise stress. Metabolite profiles selected via unbiased analysis outperformed N-terminal prohormone of B-type natriuretic peptide (NT-proBNP) in predicting load-independent measures of RV function at rest and cardiopulmonary system performance under stress. Overall, this work suggests the potential for select metabolites to function as disease-specific biomarkers, offers insights into PAH pathobiology, and informs discovery of potentially targetable RV-centric pathways.

Insulin-like growth factor binding Protein-4: A novel indicator of pulmonary arterial hypertension severity and survival

Proteomic analysis of patients with pulmonary arterial hypertension (PAH) has demonstrated significant abnormalities in the insulin-like growth factor axis (IGF). This study proposed to establish associations between a specific binding protein, insulin-like growth factor binding protein 4 (IGFBP4), and PAH severity as well as survival across varying study cohorts. In all cohorts studied, serum IGFBP4 levels were significantly elevated in PAH compared to controls (p < 0.0001). IGFBP4 concentration was also highest in the connective tissue-associated PAH (CTD-PAH) and idiopathic PAH subtypes (876 and 784 ng/mL, median, respectively). After adjustment for age and sex, IGFBP4 was significantly associated with worse PAH severity as defined by a decreased 6-min walk distance (6MWD), New York heart association functional class (NYHA-FC), REVEAL 2.0 score and higher right atrial pressures. In longitudinal analysis provided by one of the study cohorts, IGFBP4 was prospectively significantly associated with a shorter 6MWD, worse NYHA-FC classification, and decreased survival. Cox multivariable analysis demonstrated higher serum IGFBP4 as an independent predictor of survival in the overall PAHB cohort. Therefore, this study established that higher circulating IGFBP4 levels were significantly associated with worse PAH severity, decreased survival and disease progression. Dysregulation of IGF metabolism/growth axis may play a significant role in PAH cardio-pulmonary pathobiology.

Improved Survival for Patients with Systemic Sclerosis-associated Pulmonary Arterial Hypertension: The Johns Hopkins Registry

Rationale: To date, it remains unclear whether recent changes in the management of patients with systemic sclerosis-associated pulmonary hypertension (SSc-PH) have improved survival. Objectives: To describe a cohort of patients with SSc-PH and compare their characteristics and survival between the last two decades. Methods: Patients with SSc-PH prospectively enrolled in the Johns Hopkins Pulmonary Hypertension Center Registry were grouped into two cohorts based on the date of diagnostic right heart catheterization: cohort A included patients whose disease was diagnosed between 1999 and 2010, and cohort B included those whose disease was diagnosed between 2010 and 2021. Patients' characteristics were compared between the two cohorts. Measurements and Main Results: Of 504 patients with SSc-PH distributed almost equally between the two cohorts, 308 (61%) had World Symposium on Pulmonary Hypertension group 1, 43 (9%) had group 2, and 151 (30%) had group 3 disease. Patients with group 1 disease in cohort B had significantly better clinical and hemodynamic characteristics at diagnosis, were more likely to receive upfront combination pulmonary arterial hypertension therapy, and had a nearly 4-year increase in median transplant-free survival in univariable analysis than those in cohort A (P < 0.01). Improved transplant-free survival was still observed after adjusting for patients' baseline characteristics. In contrast, for group 2 or 3 patients with SSc-PH, there were no differences in baseline clinical, hemodynamic, or survival characteristics between the two cohorts. Conclusions: This is the largest single-center study that compares clinical characteristics of patients with SSc-PH between the last two decades. Transplant-free survival has improved significantly for those with group 1 disease over the last decade, possibly secondary to earlier detection and better therapeutic management. Conversely, those with group 2 or 3 disease continue to have dismal prognosis.

Pregnancy Considerations in the Multidisciplinary Care of Patients with Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a vasoconstrictive disease of the distal pulmonary vasculature resulting in adverse right heart remodeling. Pregnancy in PAH patients is associated with high maternal morbidity and mortality as well as neonatal and fetal complications. Pregnancy-associated changes in the cardiovascular, pulmonary, hormonal, and thrombotic systems challenge the complex PAH physiology. Due to the high risks, patients with PAH are currently counseled against pregnancy based on international consensus guidelines, but there are promising signs of improving outcomes, particularly for patients with mild disease. For patients who become pregnant, multidisciplinary care at a PAH specialist center is needed for peripartum monitoring, medication management, delivery, postpartum care, and complication management. Patients with PAH also require disease-specific counseling on contraception and breastfeeding. In this review, we detail the considerations for reproductive planning, pregnancy, and delivery for the multidisciplinary care of a patient with PAH.

Risk Stratification of Patients with Pulmonary Arterial Hypertension: The Role of Echocardiography

Background: Given the morbidity and mortality associated with pulmonary arterial hypertension (PAH), risk stratification approaches that guide therapeutic management have been previously employed. However, most patients remain in the intermediate-risk category despite initial therapy. Herein, we sought to determine whether echocardiographic parameters could improve the risk stratification of intermediate-risk patients. Methods: Prevalent PAH patients previously enrolled in observational studies at 3 pulmonary hypertension centers were included in this study. A validated PAH risk stratification approach was used to stratify patients into low-, intermediate-, and high-risk groups. Right ventricular echocardiographic parameters were used to further stratify intermediate-risk patients into intermediate-low- and intermediate-high-risk groups based on transplant-free survival. Results: From a total of 146 patients included in our study, 38 patients died over a median follow-up of 2.5 years. Patients with intermediate-/high-risk had worse echocardiographic parameters. Tricuspid annular plane systolic excursion (TAPSE) and the degree of tricuspid regurgitation (TR) were highly associated with survival (p < 0.01, p = 0.04, respectively) and were subsequently used to further stratify intermediate-risk patients. Among intermediate-risk patients, survival was worse for patients with TAPSE < 19 mm compared to those with TAPSE ≥ 19 mm (estimated one-year survival 74% vs. 96%, p < 0.01) and for patients with moderate/severe TR compared to those with no/trace/mild TR (estimated one-year survival 70% vs. 93%, p < 0.01). Furthermore, among intermediate-risk patients, those with both TAPSE < 19 mm and moderate/severe TR had an estimated one-year survival (56%) similar to that of high-risk patients (56%), and those with both TAPSE ≥ 19 mm and no/trace/mild TR had an estimated one-year survival (97%) similar to that of low-risk patients (95%). Conclusions: Echocardiography, a routinely performed, non-invasive imaging modality, plays a pivotal role in discriminating distinct survival phenotypes among prevalent intermediate-risk PAH patients using TAPSE and degree of TR. This can potentially help guide subsequent therapy.

Defining minimal detectable difference in echocardiographic measures of right ventricular function in systemic sclerosis

BACKGROUND

Echocardiography (2DE) is integral for screening and longitudinal evaluation of pulmonary arterial hypertension (PAH) in systemic sclerosis (SSc). In the present study, we sought to establish the reliability, repeatability, and reproducibility of 2DE parameters in SSc patients with and without PAH and to define the minimal detectable difference (MDD), the smallest change detected beyond measurement error.

METHODS

SSc patients without known PAH and with invasively confirmed PAH on stable therapies underwent 2DE with strain at two time points. Analysis of variance (ANOVA) and coefficients of variation (CV) were calculated to assess for repeatability, reliability, and reproducibility. Intra- and inter-observer agreement were assessed using intraclass correlation. Bland-Altman analysis explored the level of agreement between evaluations. MDD was calculated using the standard error of measurement for each parameter by cohort.

RESULTS

ANOVA demonstrated few significant differences between evaluations across groups. Global right ventricular longitudinal systolic strain (GRVLSS, 9.7%) and fractional area change (FAC, 21.3%) had the largest CV, while tricuspid annular plane excursion (TAPSE), S' wave, and right ventricular outflow track velocity time integral (RVOT VTI) were 0.87%, 3.2%, and 6.0%, respectively. Intra- and inter-observer agreement was excellent. MDD for TAPSE, FAC, S' wave, RVOT VTI, GRVLSS, and RVSP were 0.11 cm, 0.03%, 1.27 cm/s, 0.81 cm, 1.14%, and 6.5 mmHg, respectively.

CONCLUSIONS

We demonstrate minimal measurement error in clinically important 2DE-based measures in SSc patients with and without PAH. Defining the MDD in this population has important implications for PAH screening, assessment of therapeutic response, and sample size calculations for future clinical trials.

COL18A1 genotypic associations with endostatin levels and clinical features in pulmonary arterial hypertension: a quantitative trait association study

Endostatin (ES) is a circulating peptide derived from collagen XVIII alpha 1 (COL18A1) known to inhibit angiogenesis [1, 2]. Decreased angiogenesis is a feature of pulmonary arterial hypertension (PAH) in animal models [3] and human subjects [4]. Our group has reported strong associations between circulating ES levels and haemodynamics and survival in PAH [5–7]. We have also reported that a missense variant in COL18A1, which encodes ES, confers lower ES and longer survival, suggesting that variation within the gene contributes to circulating levels [5]. In the current study, we assessed COL18A1 variant associations with clinical phenotypes and outcomes, including COL18A1 associations with circulating ES levels, in a large, multicentre PAH cohort in which we previously investigated ES as a prognostic biomarker [6].

Variation around the COL18A1 gene, which encodes the angiostatic peptide endostatin, may influence disease heterogeneity in pulmonary arterial hypertensionhttps://bit.ly/3shXrNR

Causes and outcomes of ICU hospitalisations in patients with pulmonary arterial hypertension

Rationale

Pulmonary arterial hypertension (PAH) is a rare disease characterised by limited survival despite remarkable improvements in therapy. The causes, clinical burden and outcomes of patients admitted to the intensive care unit (ICU) remain poorly characterised. The aim of this study was to describe patient characteristics, causes of ICU hospitalisation, and risk factors for ICU and 1-year mortality.

Methods

Data from patients enrolled in the Johns Hopkins Pulmonary Hypertension Registry were analysed for the period between January 2010 and December 2020. Clinical, functional, haemodynamic and laboratory data were collected.

Measurements and main results

102 adult patients with 155 consecutive ICU hospitalisations were included. The leading causes for admission were right heart failure (RHF, 53.3%), infection (17.4%) and arrhythmia (11.0%). ICU mortality was 27.1%. Mortality risk factors included Na <136 mEq·mL-1 (OR: 3.10, 95% CI: 1.41-6.82), elevated pro-B-type natriuretic peptide (proBNP) (OR: 1.75, 95% CI: 1.03-2.98), hyperbilirubinaemia (OR: 1.40, 95% CI: 1.09-1.80), hyperlactaemia (OR: 1.42, 95% CI: 1.05-1.93), and need for vasopressors/inotropes (OR: 5.29, 95% CI: 2.28-12.28), mechanical ventilation (OR: 3.76, 95% CI: 1.63-8.76) and renal replacement therapy (OR: 5.57, 95% CI: 1.25-24.76). Mortality rates at 3, 6 and 12 months were 17.5%, 27.6% and 39.0%, respectively. Connective tissue disease-associated PAH has lower 1-year survival compared to idiopathic PAH (51.4% versus 79.8%, log-rank test p=0.019).

Conclusions

RHF is the most common cause for ICU admission. In-hospital and 1-year mortality remain exceedingly high despite improved ICU care. Recognising specific risk factors on admission can help identifying patients at risk for poor outcomes.

Ventricular mass discriminates pulmonary arterial hypertension as redefined at the Sixth World Symposium on Pulmonary Hypertension

Cardiac magnetic resonance (CMR) measures of right ventricular (RV) mass, volumes, and function have diagnostic and prognostic value in pulmonary arterial hypertension (PAH). We hypothesized that RV mass-based metrics would discriminate incident PAH as redefined by the lower mean pulmonary arterial pressure (mPAP) threshold of >20 mmHg at the Sixth World Symposium on Pulmonary Hypertension (6th WSPH). Eighty-nine subjects with suspected PAH underwent CMR imaging, including 64 subjects with systemic sclerosis (SSc). CMR metrics, including RV and left ventricular (LV) mass, were measured. All subjects underwent right heart catheterization (RHC) for assessment of hemodynamics within 48 h of CMR. Using generalized linear models, associations between CMR metrics and PAH were assessed, the best subset of CMR variables for predicting PAH were identified, and relationships between mass-based metrics, hemodynamics, and other predictive CMR metrics were examined. Fifty-nine subjects met 6th WSPH criteria for PAH. RV mass metrics, including ventricular mass index (VMI), demonstrated the greatest magnitude difference between subjects with versus without PAH. Overall and in SSc, VMI and RV mass measured by CMR were among the most predictive variables discriminating PAH at RHC, with areas under the receiver operating characteristic curve 0.86 and 0.83. respectively. VMI increased linearly with pulmonary vascular resistance and with mPAP in PAH, including in lower ranges of mPAP associated with mild PAH. VMI ≥ 0.37 yielded a positive predictive value of 90% for discriminating PAH. RV mass metrics measured by CMR, including VMI, discriminate incident, treatment-naïve PAH as defined by 6th WSPH criteria.

Angiostatic Peptide, Endostatin, Predicts Severity in Pediatric Congenital Heart Disease-Associated Pulmonary Hypertension

Background Endostatin, an angiogenic inhibitor, is associated with worse pulmonary arterial hypertension (PAH) outcomes in adults and poor lung growth in children. This study sought to assess whether endostatin is associated with disease severity and outcomes in pediatric PAH. Methods and Results Serum endostatin was measured in cross-sectional (N=160) and longitudinal cohorts (N=64) of pediatric subjects with PAH, healthy pediatric controls and pediatric controls with congenital heart disease (CHD) (N=54, N=15), and adults with CHD associated PAH (APAH-CHD, N=185). Outcomes, assessed by regression and Kaplan-Meier analysis, included hemodynamics, change in endostatin over time, and transplant-free survival. Endostatin secretion was evaluated in pulmonary artery endothelial and smooth muscle cells. Endostatin was higher in those with PAH compared with healthy controls and controls with CHD and was highest in those with APAH-CHD. In APAH-CHD, endostatin was associated with a shorter 6-minute walk distance and increased mean right atrial pressure. Over time, endostatin was associated with higher pulmonary artery pressure and pulmonary vascular resistance index, right ventricular dilation, and dysfunction. Endostatin decreased with improved hemodynamics over time. Endostatin was associated with worse transplant-free survival. Addition of endostatin to an NT-proBNP (N-terminal pro-B-type natriuretic peptide) based survival analysis improved risk stratification, reclassifying subjects with adverse outcomes. Endostatin was secreted primarily by pulmonary artery endothelial cells. Conclusions Endostatin is associated with disease severity, disease improvement, and worse survival in APAH-CHD. Endostatin with NT-proBNP improves risk stratification, better predicting adverse outcomes. The association of elevated endostatin with shunt lesions suggests that endostatin could be driven by both pulmonary artery flow and pressure. Endostatin could be studied as a noninvasive prognostic marker, particularly in APAH-CHD.

The angiostatic peptide endostatin enhances mortality risk prediction in pulmonary arterial hypertension

Currently available noninvasive markers for assessing disease severity and mortality risk in pulmonary arterial hypertension (PAH) are unrelated to fundamental disease biology. Endostatin, an angiostatic peptide known to inhibit pulmonary artery endothelial cell migration, proliferation and survival in vitro, has been linked to adverse haemodynamics and shortened survival in small PAH cohorts. This observational cohort study sought to assess: 1) the prognostic performance of circulating endostatin levels in a large, multicentre PAH cohort; and 2) the added value gained by incorporating endostatin into existing PAH risk prediction models.

Endostatin ELISAs were performed on enrolment samples collected from 2017 PAH subjects with detailed clinical data, including survival times. Endostatin associations with clinical variables, including survival, were examined using multivariable regression and Cox proportional hazards models. Extended survival models including endostatin were compared to null models based on the REVEAL risk prediction tool and European Society of Cardiology/European Respiratory Society (ESC/ERS) low-risk criteria using likelihood ratio tests, Akaike and Bayesian information criteria and C-statistics.

Higher endostatin was associated with higher right atrial pressure, mean pulmonary arterial pressure and pulmonary vascular resistance, and with shorter 6-min walk distance (p<0.01). Mortality risk doubled for each log higher endostatin (hazard ratio 2.3, 95% CI 1.6–3.4, p<0.001). Endostatin remained an independent predictor of survival when incorporated into existing risk prediction models. Adding endostatin to REVEAL-based and ESC/ERS criteria-based risk assessment strategies improved mortality risk prediction.

Endostatin is a robust, independent predictor of mortality in PAH. Adding endostatin to existing PAH risk prediction strategies improves PAH risk assessment.

Endostatin is a robust, easily accessible biomarker of PAH severity and mortality that is mechanistically related to PAH pathogenesis. Incorporating endostatin into commonly used risk prediction strategies for PAH improves prediction of mortality.https://bit.ly/3kzGT0w

Right ventricular function as assessed by cardiac magnetic resonance imaging-derived strain parameters compared to high-fidelity micromanometer catheter measurements

Right ventricular function has prognostic significance in patients with pulmonary hypertension. We evaluated whether cardiac magnetic resonance-derived strain and strain rate parameters could reliably reflect right ventricular systolic and diastolic function in precapillary pulmonary hypertension. End-systolic elastance and the time constant of right ventricular relaxation tau, both derived from invasive high-fidelity micromanometer catheter measurements, were used as gold standards for assessing systolic and diastolic right ventricular function, respectively. Nineteen consecutive precapillary pulmonary hypertension patients underwent cardiac magnetic resonance and right heart catheterization prospectively. Cardiac magnetic resonance data were compared with those of 19 control subjects. In pulmonary hypertension patients, associations between strain- and strain rate-related parameters and invasive hemodynamic parameters were evaluated. Longitudinal peak systolic strain, strain rate, and early diastolic strain rate were lower in PAH patients than in controls; peak atrial-diastolic strain rate was higher in pulmonary hypertension patients. Similarly, circumferential peak systolic strain rate was lower and peak atrial-diastolic strain rate was higher in pulmonary hypertension. In pulmonary hypertension, no correlations existed between cardiac magnetic resonance-derived and hemodynamically derived measures of systolic right ventricular function. Regarding diastolic parameters, tau was significantly correlated with peak longitudinal atrial-diastolic strain rate (r = -0.61), deceleration time (r = 0.75), longitudinal systolic to diastolic time ratio (r = 0.59), early diastolic strain rate (r = -0.5), circumferential peak atrial-diastolic strain rate (r = -0.52), and deceleration time (r = 0.62). Strain analysis of the right ventricular diastolic phase is a reliable non-invasive method for detecting right ventricular diastolic dysfunction in PAH.

A novel approach to perioperative risk assessment for patients with pulmonary hypertension

Rationale

Pulmonary hypertension (PH) is associated with significant perioperative morbidity and mortality. We hypothesised that pulmonary arterial hypertension (PAH) composite risk assessment scores could estimate perioperative risk for PH patients when adjusted for inherent procedural risk.

Methods

We identified patients in the Johns Hopkins PH Center Registry that had noncardiac surgery (including endoscopies) between September 2015 and January 2020. We collected information on preoperative patient-level and procedural variables and used logistic regression to evaluate associations with a composite outcome of death within 30 days or serious postoperative complication. We generated composite patient-level risk assessment scores for each subject and used logistic regression to estimate the association with adverse surgical outcomes. We adjusted multivariable models for inherent procedural risk of major cardiovascular events and used these models to generate a numerical PH perioperative risk (PHPR) score.

Results

Among 150 subjects, 19 (12.7%) reached the primary outcome, including 7 deaths (4.7%). Individual patient-level and procedural variables were associated with the primary outcome (all p<0.05). A composite patient-level risk assessment score built on three noninvasive parameters was strongly associated with reduced risk for poor outcomes (OR=0.4, p=0.03). This association was strengthened after adjusting the model for procedural risk. A PHPR score derived from the multivariable model stratified patients into low (0%), intermediate (≤10%), or high (>10%) risk of reaching the primary outcome.

Conclusion

Composite PAH risk assessment scores can predict perioperative risk for PH patients after accounting for inherent procedural risk. Validation of the PHPR score in a multicentre, prospective cohort is warranted.

For patients with pulmonary hypertension undergoing noncardiac surgery, perioperative risk can be estimated using a model that combines inherent procedural risk with composite PAH risk assessment scoreshttps://bit.ly/3uTCibP

ST2 Is a Biomarker of Pediatric Pulmonary Arterial Hypertension Severity and Clinical Worsening

BACKGROUND

Pediatric pulmonary hypertension is a severe disease defined by sustained elevation of pulmonary artery pressures and pulmonary vascular resistance (PVR). Noninvasive diagnostic and prognostic markers that are more pulmonary vascular specific have been elusive because of disease heterogeneity and patient growth.

RESEARCH QUESTION

Is soluble suppressor of tumorigenicity (ST2) associated with pulmonary hemodynamic and functional changes in pediatric pulmonary hypertension? Does ST2 improve mortality risk models in pediatric pulmonary hypertension?

STUDY DESIGN AND METHODS

Two pediatric cohorts (age < 21 years) were assayed for ST2 and N-terminal prohormone B-natriuretic peptide: a cross-sectional cohort from the National Heart Lung and Blood Institute-funded National Biological Sample and Data Repository for PAH (PAHB) (N = 182), and a second longitudinal cohort from Children's Hospital of Colorado (N = 61). Adjusted linear regression was used for association with clinical variables. Clinical mortality models (the Registry to Evaluate Early and Long-Term PAH Disease Management [REVEAL] score) with and without ST2 were used to predict worsening outcomes and compared. Pulmonary artery endothelial and smooth muscle cell ST2 expression and secretion were assayed in vitro.

RESULTS

In an adjusted (age and sex) analysis in the PAHB, ST2 was significantly associated with shorter 6-min walk distance (P = .03) and increased PVR index (P = .02). In adjusted longitudinal regression in the Children's Hospital of Colorado cohort, ST2 was significantly associated with higher PVR index (P < .001), shorter 6-min walk distance (P = .01), and higher mean pulmonary artery pressure (P < .001). Although the REVEAL Risk Score Calculator 2.0 was predictive of clinical worsening in the PAHB (hazard ratio, 1.88), addition of ST2 significantly improved the model (hazard ratio, 2.05). In cell culture, ST2 was produced and secreted predominately by endothelial cells as opposed to smooth muscle cells (P < .0001).

INTERPRETATION

In two pediatric PAH cohorts, elevated ST2 was associated with unfavorable pulmonary hemodynamics and functional measures, clinical worsening, and significantly improved prediction of clinical worsening. Pulmonary artery endothelial cellular expression of ST2 suggests that ST2 is a more pulmonary vascular-specific marker for pulmonary hypertension.

Insulin-like growth factor binding protein-2: a new circulating indicator of pulmonary arterial hypertension severity and survival

BACKGROUND

Pulmonary arterial hypertension (PAH) is a fatal disease that results from cardio-pulmonary dysfunction with the pathology largely unknown. Insulin-like growth factor binding protein 2 (IGFBP2) is an important member of the insulin-like growth factor family, with evidence suggesting elevation in PAH patients. We investigated the diagnostic and prognostic value of serum IGFBP2 in PAH to determine if it could discriminate PAH from healthy controls and if it was associated with disease severity and survival.

METHODS

Serum IGFBP2 levels, as well as IGF1/2 levels, were measured in two independent PAH cohorts, the Johns Hopkins Pulmonary Hypertension program (JHPH, N = 127), NHLBI PAHBiobank (PAHB, N = 203), and a healthy control cohort (N = 128). The protein levels in lung tissues were determined by western blot. The IGFBP2 mRNA expression levels in pulmonary artery smooth muscle cells (PASMC) and endothelial cells (PAEC) were assessed by RNA-seq, secreted protein levels by ELISA. Association of biomarkers with clinical variables was evaluated using adjusted linear or logistic regression and Kaplan-Meier analysis.

RESULTS

In both PAH cohorts, serum IGFBP2 levels were significantly elevated (p < 0.0001) compared to controls and discriminated PAH from controls with an AUC of 0.76 (p < 0.0001). A higher IGFBP2 level was associated with a shorter 6-min walk distance (6MWD) in both cohorts after adjustment for age and sex (coefficient - 50.235 and - 57.336 respectively). Cox multivariable analysis demonstrated that higher serum IGFBP2 was a significant independent predictor of mortality in PAHB cohort only (HR, 3.92; 95% CI, 1.37-11.21). IGF1 levels were significantly increased only in the PAHB cohort; however, neither IGF1 nor IGF2 had equivalent levels of associations with clinical variables compared with IGFBP2. Western blotting shown that IGFBP2 protein was significantly increased in the PAH vs control lung tissues. Finally, IGFBP2 mRNA expression and secreted protein levels were significantly higher in PASMC than in PAEC.

CONCLUSIONS

IGFBP2 protein expression was increased in the PAH lung, and secreted by PASMC. Elevated circulating IGFBP2 was associated with PAH severity and mortality and is a potentially valuable prognostic marker in PAH.

Elevated Interleukin-6 Levels Predict Clinical Worsening in Pediatric Pulmonary Arterial Hypertension

OBJECTIVE

To assess whether circulating interleukin-6 (IL-6) is associated with measures of disease severity and clinical worsening in pediatric pulmonary arterial hypertension (PAH).

STUDY DESIGN

IL-6 was measured by enzyme-linked immunosorbent assay in serum samples from a cross-sectional cohort from the National Heart, Lung, and Blood Institute Pulmonary Arterial Hypertension Biobank (n = 175) and a longitudinal cohort from Children's Hospital Colorado (CHC) (n = 61). Associations between IL-6, disease severity, and outcomes were studied with regression and Kaplan-Meier analysis.

RESULTS

In analyses adjusted for age and sex, each log-unit greater IL-6 was significantly associated in the Pulmonary Arterial Hypertension Biobank cohort with greater pulmonary vascular resistance indices, lower odds of having idiopathic PAH or treatment with prostacyclin, and greater odds of having PAH associated with a repaired congenital shunt. In the CHC cohort, each log-unit greater IL-6 was significantly associated with greater mean pulmonary arterial pressure over time. Kaplan-Meier analysis in the CHC cohort revealed that IL-6 was significantly associated with clinical worsening (a composite score of mortality, transplant, or palliative surgery) (P = .037).

CONCLUSIONS

IL-6 was significantly associated with worse hemodynamics at baseline and over time and may be associated with clinical worsening. IL-6 may provide a less-invasive method for disease monitoring and prognosis in pediatric PAH as well as a potential therapeutic target.

Multi-Beat Right Ventricular-Arterial Coupling Predicts Clinical Worsening in Pulmonary Arterial Hypertension

Background Although right ventricular (RV) to pulmonary arterial (RV-PA) coupling is considered the gold standard in assessing RV dysfunction, its ability to predict clinically significant outcomes is poorly understood. We assessed the ability of RV-PA coupling, determined by the ratio of multi-beat (MB) end-systolic elastance (Ees) to effective arterial elastance (Ea), to predict clinical outcomes. Methods and Results Twenty-six subjects with pulmonary arterial hypertension (PAH) underwent same-day cardiac magnetic resonance imaging, right heart catheterization, and RV pressure-volume assessment with MB determination of Ees/Ea. RV ejection fraction (RVEF), stroke volume/end-systolic volume, and single beat-estimated Ees/Ea were also determined. Patients were treated with standard therapies and followed prospectively until they met criteria of clinical worsening (CW), as defined by ≥10% decline in 6-minute walk distance, worsening World Health Organization (WHO) functional class, PAH therapy escalation, RV failure hospitalization, or transplant/death. Subjects were 57±14 years, largely WHO class III (50%) at enrollment, with preserved average RV ejection fraction (RVEF) (47±11%). Mean follow-up was 3.2±1.3 years. Sixteen (62%) subjects met CW criteria. MB Ees/Ea was significantly lower in CW subjects (0.7±0.5 versus 1.3±0.8, P=0.02). The optimal MB Ees/Ea cut-point predictive of CW was 0.65, defined by ROC (AUC 0.78, P=0.01). MB Ees/Ea below this cut-point was significantly associated with time to CW (hazard ratio 5.1, P=0.001). MB Ees/Ea remained predictive of outcomes following multivariate adjustment for timing of PAH diagnosis and PAH diagnosis subtype. Conclusions RV-PA coupling as measured by MB Ees/Ea has prognostic significance in human PAH, even in a cohort with preserved RVEF.

Cellular sources of interleukin-6 and associations with clinical phenotypes and outcomes in pulmonary arterial hypertension

The pro-inflammatory cytokine interleukin (IL)-6 has been associated with outcomes in small pulmonary arterial hypertension (PAH) cohorts composed largely of patients with severe idiopathic PAH (IPAH). It is unclear whether IL-6 is a marker of critical illness or a mechanistic biomarker of pulmonary vascular remodelling. We hypothesised that IL-6 is produced by pulmonary vascular cells and sought to explore IL-6 associations with phenotypes and outcomes across diverse subtypes in a large PAH cohort.IL-6 protein and gene expression levels were measured in cultured pulmonary artery smooth muscle cells (PASMCs) and endothelial cells (PAECs) from PAH patients and healthy controls. Serum IL-6 was measured in 2017 well-characterised PAH subjects representing each PAH subgroup. Relationships between IL-6 levels, clinical variables, and mortality were analysed using regression models.Significantly higher IL-6 protein and gene expression levels were produced by PASMCs than by PAECs in PAH (p<0.001), while there was no difference in IL-6 between cell types in controls. Serum IL-6 was highest in PAH related to portal hypertension and connective tissue diseases (CTD-PAH). In multivariable modelling, serum IL-6 was associated with survival in the overall cohort (hazard ratio 1.22, 95% CI 1.08-1.38; p<0.01) and in IPAH, but not in CTD-PAH. IL-6 remained associated with survival in low-risk subgroups of subjects with mild disease.IL-6 is released from PASMCs, and circulating IL-6 is associated with specific clinical phenotypes and outcomes in various PAH subgroups, including subjects with less severe disease. IL-6 is a mechanistic biomarker, and thus a potential therapeutic target, in certain PAH subgroups.

Performance of Critical Care Outcome Prediction Models in an Intermediate Care Unit

BACKGROUND

Intermediate care units (IMCUs) are heterogeneous in design and operation, which makes comparative effectiveness studies challenging. A generalizable outcome prediction model could improve such comparisons. However, little is known about the performance of critical care outcome prediction models in the intermediate care setting. The purpose of this study is to evaluate the performance of the Acute Physiology and Chronic Health Evaluation version II (APACHE II), Simplified Acute Physiology Score version II (SAPS II) and version 3 (SAPS 3), and Mortality Probability Model version III (MPM₀III) in patients admitted to a well-characterized IMCU.

MATERIALS AND METHODS

In the IMCU of an academic medical center (July to December 2012), the discrimination and calibration of each outcome prediction model were evaluated using the area under the receiver-operating characteristic and Hosmer-Lemeshow goodness-of-fit test, respectively. Standardized mortality ratios (SMRs) were also calculated.

RESULTS

The cohort included data from 628 unique IMCU admissions with an inpatient mortality rate of 8.3%. All models exhibited good discrimination, but only the SAPS II and MPM₀III were well calibrated. While the APACHE II and SAPS 3 both markedly overestimated mortality, the SMR for the SAPS II and MPM₀III were 0.91 and 0.91, respectively.

CONCLUSIONS

The SAPS II and MPM₀III exhibited good discrimination and calibration, with slight overestimation of mortality. Each model should be further evaluated in multicenter studies of patients in the intermediate care setting.

Serum uric acid as a marker of disease risk, severity, and survival in systemic sclerosis-related pulmonary arterial hypertension

The object of this paper is to assess associations between serum uric acid (UA) and pulmonary arterial hypertension (PAH) risk, disease severity, and mortality in a well-characterized cohort of systemic sclerosis (SSc) patients referred for evaluation of possible PAH. Consecutive SSc patients aged >18 years with serum UA drawn within two weeks of a diagnostic right heart catheterization (RHC) were included. Associations between baseline serum UA and PAH at RHC were examined using logistic regression and receiver operating characteristic curves. Relationships between UA levels and metrics of disease severity were assessed using Pearson and Spearman correlation. Associations between UA and survival were assessed using Kaplan-Meier analysis and Cox proportional hazard modeling. A total of 162 SSc patients were included; 82 received a diagnosis of PAH at RHC. Patients found to have PAH had significantly higher UA than those without PAH. Elevated baseline UA was associated with significantly increased odds of PAH diagnosis at RHC (odds ratio [OR] = 4.07, 95% confidence interval [CI] = 2.11-7.87, P < 0.001). Each mg/dL higher UA was associated with a 14% increase in mortality (hazard ratio [HR] = 1.14, 95% CI = 1.02-1.28, P < 0.05). In multivariable models adjusting for potential confounders of the relationship between UA and survival, UA > 6.3 mg/dL remained significantly associated with increased mortality (HR = 1.84, 95% CI = 1.02-3.32, P < 0.05). Among SSc patients with suspected PAH, elevated serum UA is associated with increased risk of SSc-PAH. Among individuals diagnosed with SSc-PAH by RHC, UA is associated with disease severity and survival. These results indicate UA is a useful predictor of PAH risk and prognosis in SSc.

Hospital mortality prediction for intermediate care patients: Assessing the generalizability of the Intermediate Care Unit Severity Score (IMCUSS)

PURPOSE

The Intermediate Care Unit Severity Score (IMCUSS) is an easy to calculate predictor of in-hospital death, and the only such tool developed for patients in the intermediate care setting. We sought to examine its external validity.

MATERIALS AND METHODS

Using data from patients admitted to the intermediate care unit (IMCU) of an urban academic medical center from July to December of 2012, model discrimination and calibration for predicting in-hospital death were assessed using the area under the receiver operating characteristic (AUROC) and the Hosmer-Lemeshow goodness-of-fit chi-squared (HL GOF X²) test, respectively. The standardized mortality ratio (SMR) with 95% confidence intervals (95% CI) was also calculated.

RESULTS

The cohort included data from 628 unique admissions to the IMCU. Overall hospital mortality was 8.3%. The median IMCUSS was 10 (Interquartile Range: 0-16), with 229 (36%) patients having a score of zero. The AUROC for the IMCUSS was 0.72 (95% CI: 0.64-0.78), the HL GOF X² = 30.7 (P < 0.001), and the SMR was 1.22 (95% CI: 0.91-1.60).

CONCLUSIONS

The IMCUSS exhibited acceptable discrimination, poor calibration, and underestimated mortality. Other centers should assess the performance of the IMCUSS before adopting its use.

Outcomes of Emergency Medical Patients Admitted to an Intermediate Care Unit With Detailed Admission Guidelines

BACKGROUND

An important, but not well characterized, population receiving intermediate care is that of medical patients admitted directly from the emergency department.

OBJECTIVE

To characterize emergency medical patients and their outcomes when admitted to an intermediate care unit with clearly defined admission guidelines.

METHODS

Demographic data, admitting diagnoses, illness severity, comorbid conditions, lengths of stay, and hospital mortality were characterized for all emergency medical patients admitted directly to an intermediate care unit from July through December 2012.

RESULTS

A total of 317 unique patients were admitted (mean age, 54 [SD, 16] years). Most patients were admitted with respiratory (26.5%) or cardiac (17.0%) syndromes. The mean (SD) Acute Physiology and Chronic Health Evaluation score version II, Simplified Acute Physiology Score version II, and Charlson Comorbidity Index were 15.6 (6.5), 20.7 (11.8), and 2.7 (2.3), respectively. Severity of illness and length of stay were significantly different for patients who required intensive care within 24 hours of admission (n = 16) or later (n = 25), patients who continued with inter mediate care for more than 24 hours (n = 247), and patients who were downgraded or discharged in less than 24 hours (n = 29). Overall hospital mortality was 4.4% (14 deaths).

CONCLUSIONS

Emergency medical patients with moderate severity of illness and comorbidity can be admitted to an intermediate level of care with relatively infrequent transfer to intensive care and relatively low mortality.

Improving the utility of nematode resistance in groundnut

Host resistance to pests and pathogens, to be useful, must be introgressed into cultivars that possess the high yield potential and other important agronomic quality traits desired by the growers. The root-knot nematodes M. arenaria and M. javanica are only a subset of the several important pests and pathogens attacking groundnut. The resistance that was transferred from wild Arachis spp. to cultivated groundnut will provide nearly complete control of these important pathogens; however, growers have been reluctant to use this resistance because the resistant cultivars lack other desired traits. The introgression of nematode resistance into genotypes that have multiple disease resistance, higher yield potential, and the important agronomic trait of the high O/L ratio will provide growers with a cultivar that satisfies most of their needs. Our current efforts are aimed at providing growers with high quality cultivars with high levels of resistance to multiple diseases. Development of germplasm with these multiple traits will ensure that potential benefits of host resistance are realized.

Acetylecholinesterase-based biosensor electrodes for organophosphate pesticide detection. II. Immobilization and stabilization of acetylecholinesterase

The dry and wet stability of Drosophila acetylcholinesterase non-covalently immobilized onto polyethyleneimine modified screen-printed carbon electrodes was improved when compared to non-immobilized acetylcholinesterase, and acetylcholinesterase covalently immobilized onto dialdehyde and polyethyleneimine modified electrodes. Stabilizer mixtures were characterized for additional stabilization of acetylcholinesterase during storage in the dry state, with dextran-sulphate/sucrose and polygalacturonic acid/sucrose mixtures proving highly effective for long-term storage of biosensor electrodes.

A Recessive Gene for Resistance to Meloidogyne arenaria in Interspecific Arachis spp. Hybrids

A single dominant gene for resistance to Meloidogyne arenaria was identified previously in two peanut cultivars, Arachis hypogaea 'COAN' and 'NemaTAM'. The interspecific Arachis hybrid TxAG-6 was the source of this resistance and the donor parent in a backcross breeding program to introgress resistance into cultivated peanut. To determine if other resistance genes were present in TxAG-6 and derived breeding populations from the third backcross generation (BC), F individuals were evaluated for the resistance phenotype. The ratio of the resistant and susceptible individuals for all F populations fit the expected ratio for resistance being governed by one dominant gene and one recessive gene. Evaluation of the F generation from four susceptible F individuals (two from TxAG-6 x A. hypogaea and two from the BC population) confirmed that a recessive gene for resistance to M. arenaria was present in each of the tested populations. The identification of a second gene for resistance in the A. hypogaea germplasm may improve the durability of the resistance phenotype.

Acetylcholinesterase-based biosensor electrodes for organophosphate pesticide detection

Screen-printed carbon electrodes modified with the dialdehydes, glutaraldehyde and terephthaldicarboxaldehyde, and then polyethyleneimine have been utilized for production of pesticide biosensors based on acetylcholinesterase. To improve the extent of dialdehyde modification, the electrodes were NH2-derivatized, initially by electrochemical reduction of 4-nitrobenzenediazonium to a nitroaryl radical permitting attachment to the carbon surface. Subsequent reduction of the 4-nitrobenzene yields a 4-aminobenzene modified carbon surface. Drosophila melanogaster acetylcholinesterase was immobilized either covalently onto dialdehyde modified electrodes or non-covalently onto polyethyleneimine modified electrodes. Internal diffusion limitations due to the dialdehyde and polyethyleneimine modifications increased the apparent Km of the immobilized enzyme. The thiocholine sensitivity was about 90% for dialdehyde modified electrodes and about 10% for polyethyleneimine modified electrodes as compared with non-modified carbon electrodes. The detection limit of the biosensors produced by non-covalent immobilization of acetylcholinesterase onto polyethyleneimine modified carbon electrodes was found to be about 10(-10) M for the organophosphate pesticide dichlorvos.

Transmission genetics of chromatin from a synthetic amphidiploid to cultivated peanut (Arachis hypogaea L.). broadening the gene pool of a monophyletic polyploid species

Polyploidy creates severe genetic bottlenecks, contributing to the genetic vulnerability of leading crops. Cultivated peanut is thought to be of monophyletic origin, harboring relatively little genetic diversity. To introduce variability from diploid wild species into tetraploid cultivated Arachis hypogaea, a synthetic amphidiploid [[A. batizocoi K9484 x (A. cardenasii GKP10017 x A. diogoi GKP10602)](4x)] was used as donor parent to generate a backcross population of 78 progeny. Three hundred seventy RFLP loci were mapped onto 23 linkage groups, spanning 2210 cM. Chromatin derived from the two A-genome diploid ancestors (A. cardenasii and A. diogoi) comprised mosaic chromosomes, reflecting crossing over in the diploid A-genome interspecific F(1) hybrid. Recombination between chromosomes in the tetraploid progeny was similar to chromosome pairing reported for A. hypogaea, with recombination generally between chromosomes of the same subgenomic affinity. Segregation distortion was observed for 25% of the markers, distributed over 20 linkage groups. Unexpectedly, 68% of the markers deviating from expected segregation showed an excess of the synthetic parent allele. Genetic consequences, relationship to species origins, and significance for comparative genetics are discussed.

Genetics and Mechanism of Resistance to Meloidogyne arenaria in Peanut Germplasm

Segregation of resistance to Meloidogyne arenaria in six BCF peanut breeding populations was examined in greenhouse tests. Chi-square analysis indicated that segregation of resistance was consistent with resistance being conditioned by a single gene in three breeding populations (TP259-3, TP262-3, and TP271-2), whereas two resistance genes may be present in the breeding populations TP259-2, TP263-2, and TP268-3. Nematode development in clonally propagated lines of resistant individuals of TP262-3 and TP263-2 was compared to that of the susceptible cultivar Florunner. Juvenile nematodes readily penetrated roots of all peanut genotypes, but rate of development was slower (P = 0.05) in the resistant genotypes than in Florunner. Host cell necrosis indicative of a hypersensitive response was not consistently observed in resistant genotypes of either population. Three RFLP loci linked to resistance at distances of 4.2 to 11.0 centiMorgans were identified. Resistant and susceptible alleles for RFLP loci R2430E and R2545E were quite distinct and are useful for identifying individuals homozygous for resistance in segregating populations.

Resistance of Interspecific Arachis Breeding Lines to Meloidogyne javanica and an Undescribed Meloidogyne Species

Resistance to a peanut-parasitic population of Meloidogyne javanica and an undescribed Meloidogyne sp. in peanut breeding lines selected for resistance to Meloidogyne javanica was examined in greenhouse tests. The interspecific hybrid TxAG-7 was resistant to reproduction of Meloidogyne javanica, M. javanica, and Meloidogyne sp. An Meloidogyne javanica-resistant selection from the second backcross (BC) of TxAG-7 to the susceptible cultivar Florunner also was resistant to M. javanica but appeared to be segregating for resistance to the Meloidogyne sp. When reproduction of M. javanica and Meloidogyne javanica were compared on five BC4F3 peanut breeding lines, each derived from Meloidogyne javanica-susceptible BC4F2 individuals, all five lines segregated for resistance to M. javanica, whereas four of the lines appeared to be susceptible to Meloidogyne javanica. These data indicate that several peanut lines selected for resistance to Meloidogyne javanica also contain genes for resistance to populations of M. javanica and the undescribed Meloidogyne sp. that are parasitic on peanut. Further, differences in segregation patterns suggest that resistance to each Meloidogyne sp. is conditioned by different genes.

Additive Effects of Meloidogyne arenaria and Sclerotinin rolfsii on Peanut

Field observations have suggested that infection of peanut by Meloidogyne arenaria increases the incidence of southern blight caused by Sclerotium rolfsii. Three factorial experiments in microplots were conducted to determine if interactions between M. arenaria and S. rolfsii influenced final nematode population densities, incidence of southern blight, or pod yield. Treatments included four or five initial population densities of M. arenaria and three inoculum rates of S. rolfsii. Final nematode population densities were affected by initial nematode densities in all experiments (P = 0.01) and by S. rolfsii in one of three experiments (P = 0.01). Incidence of southern blight increased with increasing inoculum rates of S. rolfsii in all experiments and by the presence of the nematodes in one experiment (P = 0.01). Pod yield decreased with inoculation with S. rolfsii in all experiments (P = 0.05) and by M. arenaria in two of three experiments (P = 0.05). In no experiment was the interaction among treatments significant with respect to final nematode population densities, incidence of southern blight, or pod yield (P = 0.05). The apparent disease complex between M. arenaria and S. rolfsii on peanut is due to additive effects of the two pathogens.

Increasing the pool of qualified minority medical school applicants: premedical training at historically black colleges and universities

Historically black colleges and universities have educated significant numbers of black students preparing for careers in medicine. These institutions have the potential to make even greater contributions to the pool of black medical school applicants and ultimately to the supply of black physicians. The Division of Disadvantaged Assistance, Bureau of Health Professions, Health Resources and Services Administration within the Public Health Service, commissioned a study of the curriculums and other factors related to premedical education. The study was conducted at the historically black colleges and universities that graduate a large number of students who gain admission to medical school, and the historically black colleges and universities whose students are less successful in gaining admission to medical school. Nine historically black colleges and universities participated in a self-assessment of their undergraduate premedical curriculums. The findings from schools with higher acceptance rates were compared with those of schools with lower acceptance rates to identify factors contributing to the production of significant numbers of successful medical school applicants. Comparisons of data on these schools revealed several important factors that may be related to differences in acceptance rates: Those schools that devoted greater effort to premedical training (for example, advising students about how to prepare for medical school, curriculum development, maintaining premedical or pre-health professions offices and clubs--the staff of these offices provide students with information on medical or other health professions schools--to identify and recruit students) tended to have higher acceptance rates. * Schools with higher acceptance rates had larger proportions of biology and chemistry majors aspiring to medical and dental careers and stronger affiliations with medical schools than schools with lower acceptance rates.* Institutions with higher acceptance rates offered a broader range of externally sponsored enrichment programs; the highest medical school acceptance rates were found among those schools with continuing Health Careers Opportunity Program projects that served significant percentages of students interested in careers in medicine.* Mean Medical College Admission Test scores were somewhat lower for applicants from schools with lower acceptance rates, but the great variation in acceptance rates for these schools is not reflected in a comparable variation in the Medical College Admission Test scores.

RFLP variability in peanut (Arachis hypogaea L.) cultivars and wild species

RFLP variability was studied in eight U.S. peanut cultivars, representing the four market types, and in 14 wild Arachis species accessions, using random genomic clones from a PstI library. Very low levels of RFLP variability were found among the allotetraploids, which included the U.S. cultivars and Arachis monticola, a wild species. The diploid wild species were very diverse, however. RFLP patterns of the allotetraploids were more complex than the diploids, and the two constituent genomes could usually be distinguished. On the basis of RFLP band sharing, A. ipaensis, A. duranensis, and A. spegazzinii appeared most closely related to the diploid progenitor species of the allotetraploids. A dendrogram of relationships among the diploid wild species was constructed based on band sharing.

Resistance to Meloidogyne arenaria in Arachis spp. Germplasm

Field and greenhouse evaluations of 116 wild Arachis spp. genotypes demonstrated the presence of resistance to reproduction of the root-knot nematode Meloidogyne arenaria race 1. Resistance in greenhouse tests was based on test lines having </= 2.5% of the number of eggs per gram of roots as did the susceptible A. hypogaea cv. Tamnut 74. In field tests, resistant genotypes were identified on the basis of having lower (P = 0.05) final nematode population densities than did Tamnut 74. Resistance was identified in genotypes from 11 of 15 wild species tested and in 10 of 20 genotypes belonging to undescribed species. Results of field and greenhouse experiments were similar; 26 of 31 genotypes common to both tests gave similar responses in both tests. Resistance to M. arenaria was identified in the complex hybrid TP-135, which was derived from A. hypogaea cv. Florunner x (A. batizocoi K 9484 x [A. cardenasii GKP 10017 x A. chacoensis GKP 10602])x. In a single greenhouse test, three of six genotypes resistant to M. arenaria were also resistant to M. hapla. These data indicate that the Arachis spp. germplasm contains several sources of resistance to M. arenaria and possibly M. hapla. Some of this resistance is in germplasm that is genetically compatible with A. hypogaea. The complex hybrid TP-135 incorporates resistance from wild species into the genetic background of A. hypogaea. On the basis of these data, we believe it may be possible to develop peanut cultivars with high levels of resistance to M. arenaria and M. hapla.

Factors affecting the supply of minority physicians in 2000

There was a substantial increase in the number of black and Hispanic physicians between 1970 and 1985. During the next 15 years, 1985 to 2000, the increase is projected to continue. The factors that will determine the size of the increase and the changes in physician to population ratios include black and Hispanic population increases, medical school costs, availability of student support, minority enrollment in undergraduate schools and the pool of these students who will be applicants to medical school, attrition during medical school, competition from other professions for talented minority students, and the effects of intervention programs such as the Health Careers Opportunity Program. The most likely outcome would seem to be that the increases in black and Hispanic physicians will continue to 2000 at 1985 levels because the data show neither strong positive nor strong negative net influences for the factors examined.