HollyFrontier (United States)

Introduction: Turner syndrome (TS) is caused by the loss of the second sex chromosome, which occurs in approximately 1 in 2,000 female births. TS alone is an independent risk factor for aortic enlargement. 25 to 50% of those with TS also have a bicuspid aortic valve (BAV) which is present in most who have aortic dissection and rupture. Methods: We used whole exome sequencing to study the genes of 188 TS subjects with BAV (88 cases) or normal aortic valves (100 controls). Aorta diameters as markers of aortopathy severity converted into Z-scores were utilized as covariates with BAV status, and as a sole predictor of genetic variation. Enlarged aorta was defined as an ascending aorta Z-score > 2. Statistical analyses employed a kernel gene-based method, SKAT-O. Results: TS girls and women with BAV had significantly higher ascending aortic Z-scores than those without BAV (1.95 ± 1.97 vs 0.55 ± 1.01, t-test p= 1.6 x 10 -5 ).Mutations in TIMP3 and CHADL achieved exome-wide significance for association with BAV/aortic dilatation (p=1.6x10 -6 and 1.1x10 -6 , respectively). TIMP3 significance increased when aortic root Z-scores were included as a continuous covariant with BAV status (p=2.3x10 -7 ). Overall, 30.7% of those with aortic dilatation had mutations predicted by CADD scores to be deleterious in TIMP3 (8 individuals), CHADL (4 individuals), or both (4 individuals). Those with mutations in both genes were more likely to have enlarged aortas than those with 1 or none (chi-squared p=2.8x10 -3 ). Discussion and conclusions: BAV is known to be associated with aortopathy in TS. We found that TIMP3 and CHADL mutations occur commonly with those findings . TIMP3 is an inhibitor of several aortic matrix metalloproteinases, a group of peptidases that degrade extracellular matrix (ECM). CHADL is a collagen binding protein that regulates collagen fiber formation. Collagens are necessary for aortic structural integrity. We hypothesize that mutations in TIMP3 and CHADL disrupt the critical balance between ECM creation and degradation, thereby compromising aortic strength. There appears to be a synergy between TIMP3 and CHADL functions that may be involved in both BAV development and aortopathy. Both TIMP3 and CHADL may serve as biomarkers and pharmacologic targets for aortic disease in TS.

Lower limb peripheral vascular disease (PVD) results from the occlusion of arteries leading to reduced blood flow and limb ischemia. Compensatory growth of blood vessels may be sufficient to overcome limb ischemia but for some patients therapeutic intervention, even limb amputation, is required. To gain insight into the mechanisms regulating compensatory growth of blood vessels we used a mouse model of hindlimb ischemia. The ischemic lesions were confirmed and compensatory arteriogenesis was evaluated by high frequency power Doppler ultrasound. In this model, compensatory growth occurs mainly through arteriogenesis. While signaling by mitogen activated protein kinase kinases 1 and 2 (MEK 1 and 2) is required for developmental and tumor angiogenesis, it is unknown whether MEK1/2 activity drives other physiologic vascular growth such as arteriogenesis. We hypothesized that MEK 1/2 activity is necessary for hindlimb re-vascularization following femoral artery ligation. To test this we ligated the femoral artery in mice and then treated them with PD0325901, an allosteric MEK1/2 inhibitor. Following femoral artery ligation active MEK signaling was detected in spindle-shaped cells located within regions of intense angiogenesis and myocyte proliferation. MEK inhibition with PD0325901 reversibly blocked neovascularization, muscle regeneration, and caused extensive coagulative necropathy. MEK inhibition not only prevented arteriogenesis in ischemic limbs but also caused a reduction in arterial diameter. Finally, MEK inhibition prevented accumulation of CD68+ cells in ischemic tissues and skewed systemic cytokine expression towards a persistent, pro-inflammatory phenotype. Our investigation provides pharmacologic evidence demonstrating an essential role for MEK signaling in angiogenesis and arteriogenesis in response to hind limb ischemia. Further, we observed activation of MEK signaling is required for accumulation of macrophages in ischemic tissues and prevents down-regulation of systemic pro-inflammatory cytokines. Lastly, since the effects of MEK inhibition on reperfusion are reversible, we can use MEK inhibitors to create a mouse model of chronic limb ischemia that mimics aspects of PVD.

The objective of this study is to determine pharmacokinetics (PK) and pharmacodynamics (PD) of dabigatran and its antidote (a humanized Fab against dabigatran) in the monkey and to develop a combined mechanistic mathematical model to describe the data. Rhesus monkeys (n = 2/group) received either 12 mg/kg/day of dabigatran etexilate (DE) or vehicle orally on Days 1-4, 15-18 and 29-32 with a single IV dose of the antidote at 30, 90 and 175 mg/kg administered 90 minutes after DE on Days 4, 18 and 32. PK parameters of the antidote and sum dabigatran (dabigatran plus its glucuronides) were determined after measurements of plasma concentrations. Coagulation activity was measured using a diluted thrombin time assay. The PK of the antidote were not affected by dabigatran. Clearance of the antidote was low (0.87 mL/min/kg) and steady-state volume of distribution was small (0.06 L/kg), indicating that the antidote was mostly restricted to plasma. The plasma profile of the antidote was bi-phasic with a short initial phase t 1/2 of 0.4 hour (h) and a terminal phase t 1/2 of 4.3 h. Complete reversal of dabigatran’s anticoagulant activity was observed immediately after antidote dosing at all 3 dose levels as measured by the diluted thrombin time assay, and the degree to which this reversal effect was maintained over an extended period (24 h) was dose-dependent. A mechanistic ordinary differential equation model, based on the mass action kinetics for describing the distribution, binding and elimination of dabigatran and its antidote, was developed by combining the PK models for dabigatran and the antidote and adding the binding interaction (1:1 stoichiometry) between the two compounds. The combined PK/PD model of dabigatran and antidote was able to describe the in vivo PK/PD data observed in monkeys. In conclusion, the antidote successfully reversed the anticoagulant activity of dabigatran in the monkey in a dose-dependent manner, and our combined mathematical model accurately describes monkey PK/PD data of sum dabigatran and its antidote. Insights gained from this model will be used to guide model development for clinical trials.

Phosphorus (P) is the limiting nutrient controlling productivity in most inland freshwater systems. Several materials have been proposed for use to remove excess P from wastewater treatment, including volcanic lapilli and ash (tephra). There is limited data in using tephra as a P filter. There were two objectives of this study: 1) to determine the physical feasibility of tephra as a filter making sure the infiltration rate remains high enough to use under prolonged saturation, and 2) to test the suitability of volcanic tephra as a medium for removing P from an artificial solution on two different volcanic tephra materials: Okato and Papakai tephra. The experiment used a synthetic P influent solution (20.5 mg P/L) and a solution residence time in the columns of approximately 3 hours. By the end of the experiment infiltration in both tephras was adequate for use in wastewater treatment systems. The Okato tephra absorbed nearly 8 mg P/g tephra with 97% of the total amount of P added to the column over a 54 day period. The Papakai tephra absorbed only 4 mg P/g with a 52% of the total P added to the column.

Abstract Declines in amphibian species have become a worldwide concern. This concern is heightened by predicted global climatic changes that may result in shifts in current patterns of local precipitation. Because of the potential dependence of successful breeding by amphibians on rainfall patterns, we tested the relationship between breeding by the rare gopher frog (Rana capito) and rainfall. We used data collected from long-term (1988–2000) monitoring of breeding activity at two ponds (one ephemeral, one semi-permanent) located in the Lower Coastal Plain of Alabama. Egg-mass counts at both ponds showed a significant positive relationship between reproductive effort and rainfall during the breeding season. Individuals of R. capito disperse for considerable distances across a xeric landscape and wet conditions allow greater access to breeding sites for more distantly dispersed frogs. We did not find a significant trend in the number of egg masses laid over time at the ephemeral pond; however, there was a significant increase in egg masses deposited at the semi-permanent pond during the course of this study. Understanding the importance of environmental variables such as rainfall will hopefully lead to the successful conservation of this and other species of amphibians with similar environmental requirements.

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