Publications

Fluorescence optical detection in sedimentation velocity analytical ultracentrifugation allows the study of macromolecules at nanomolar concentrations and below. This has significant promise, for example, for the study of systems of high-affinity protein interactions. Here we describe adaptations of the direct boundary modeling analysis approach implemented in the software SEDFIT that were developed to accommodate unique characteristics of the confocal fluorescence detection system. These include spatial gradients of signal intensity due to scanner movements out of the plane of rotation, temporal intensity drifts due to instability of the laser and fluorophores, and masking of the finite excitation and detection cone by the sample holder. In an extensive series of experiments with enhanced green fluorescent protein ranging from low nanomolar to low micromolar concentrations, we show that the experimental data provide sufficient information to determine the parameters required for first-order approximation of the impact of these effects on the recorded data. Systematic deviations of fluorescence optical sedimentation velocity data analyzed using conventional sedimentation models developed for absorbance and interference optics are largely removed after these adaptations, resulting in excellent fits that highlight the high precision of fluorescence sedimentation velocity data, thus allowing a more detailed quantitative interpretation of the signal boundaries that is otherwise not possible for this system.

BACKGROUND

Growth differentiation factor 15 (GDF-15) is a relatively new biomarker that predicts mortality in patients with chronic stable angina or acute coronary syndrome. However, the association of GDF-15 with cardiovascular (CV) events and the mechanisms of this association are not well understood.

METHODS

We measured plasma GDF-15 and cardiac disease severity in 984 patients with stable ischemic heart disease who were recruited for the Heart and Soul Study between September 2000 and December 2002. Subsequent CV events (myocardial infarction, stroke, and CV death), hospitalization for heart failure, and all-cause mortality were determined by chart review during an average of 8.9-year follow-up.

RESULTS

Each doubling in GDF-15 was associated with a 2.5-fold increased rate of CV events (hazard ratio [HR] 2.53, 95% CI 2.13-3.01, P < .001). This association persisted after extensive adjustment for covariates including comorbid conditions, measures of cardiac disease severity, cardiac function, inflammatory markers, and adipokines (HR 1.44, 95% CI 1.11-1.87, P < .01). Participants who had GDF-15 levels in the highest tertile had higher mortality compared with those in the lowest tertile (HR 2.73, 95% CI 1.80-4.15, P ≤ .001 adjusted for all covariates). Addition of GDF-15 to existing risk factors resulted in a 50% change in net reclassification of patients' risk for mortality.

CONCLUSIONS

Higher levels of GDF-15 are associated with major CV events in patients with stable ischemic heart disease. This suggests that GDF-15 is capturing an element of risk not explained by other known risk factors.

The pathology of pulmonary hypertension includes numerous abnormalities of the intima, media, and adventitia of the pulmonary vascular tree. A recently completed systematic analysis revealed high variability of morphologic measurements within a given pulmonary arterial hypertension (PAH) lung and among all PAH lungs, as well as distinct pathologic subphenotypes, and included a subset of lungs lacking intimal and medial remodeling. There was correlation between perivascular inflammation, remodeling, and hemodynamics. This article summarizes the pathologic features of the normal and abnormal pulmonary circulation, and correlations with animal models.