Measurement of Pulmonary Flow Reserve and Pulmonary Index of Microcirculatory Resistance for Detection of Pulmonary Microvascular Obstruction

Background

The pulmonary microcirculation is the chief regulatory site for resistance in the pulmonary circuit. Despite pulmonary microvascular dysfunction being implicated in the pathogenesis of several pulmonary vascular conditions, there are currently no techniques for the specific assessment of pulmonary microvascular integrity in humans. Peak hyperemic flow assessment using thermodilution-derived mean transit-time (T_mn) facilitate accurate coronary microcirculatory evaluation, but remain unvalidated in the lung circulation. Using a high primate model, we aimed to explore the use of T_mn as a surrogate of pulmonary blood flow for the purpose of measuring the novel indices Pulmonary Flow Reserve [PFR = (maximum hyperemic)/(basal flow)] and Pulmonary Index of Microcirculatory Resistance [PIMR = (maximum hyperemic distal pulmonary artery pressure)×(maximum hyperemic T_mn)]. Ultimately, we aimed to investigate the effect of progressive pulmonary microvascular obstruction on PFR and PIMR.

Methods and Results

Temperature- and pressure-sensor guidewires (TPSG) were placed in segmental pulmonary arteries (SPA) of 13 baboons and intravascular temperature measured. T_mn and hemodynamics were recorded at rest and following intra-SPA administration of the vasodilator agents adenosine (10–400 µg/kg/min) and papaverine (3–24 mg). Temperature did not vary with intra-SPA sensor position (0.010±0.009 v 0.010±0.009°C; distal v proximal; p = 0.1), supporting T_mn use in lung for the purpose of hemodynamic indices derivation. Adenosine (to 200 µg/kg/min) & papaverine (to 24 mg) induced dose-dependent flow augmentations (40±7% & 35±13% T_mn reductions v baseline, respectively; p<0.0001). PFR and PIMR were then calculated before and after progressive administration of ceramic microspheres into the SPA. Cumulative microsphere doses progressively reduced PFR (1.41±0.06, 1.26±0.19, 1.17±0.07 & 1.01±0.03; for 0, 10⁴, 10⁵ & 10⁶ microspheres; p = 0.009) and increased PIMR (5.7±0.6, 6.3±1.0, 6.8±0.6 & 7.6±0.6 mmHg.sec; p = 0.0048).

Conclusions

Thermodilution-derived mean transit time can be accurately and reproducibly measured in the pulmonary circulation using TPSG. Mean transit time-derived PFR and PIMR can be assessed using a TPSG and adenosine or papaverine as hyperemic agents. These novel indices detect progressive pulmonary microvascular obstruction and thus have with a potential role for pulmonary microcirculatory assessment in humans.     

Lung respiration, somatic activity and gas metabolism in embryonic chicks prevented from hatching by thiourea

Treating chick embryos with high doses of thiourea (32.8 mumol) on day 17 of incubation resulted in prevention of hatching and of active breathing. Furthermore, thiourea also prevented the increase of O2 consumption and the marked increase of somatic activity associated with the final hatching act. These findings provide evidence for the importance of active breathing in the prenatal period to initiate pipping and hatching of the avian embryo.     

Essential role of phosphatidylinositol 3-kinase in insulin-induced activation and phosphorylation of the cGMP-inhibited cAMP phosphodiesterase in rat adipocytes studies using the selective inhibitor wortmannin

Incubation of rat adipocytes with wortmannin, a potent and selective phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, completely blocked the antilipolytic action of insulin (IC₅₀≈ 100 nM), the insulin-induced activation and phosphorylation of cGMP-inhibited cAMP phosphodiesterase (cGI-PDE) as well as the activation of the insulin-stimulated cGI-PDE kinase (IC₅₀≈ 10–30 nM). No direct effects of the inhibitor on the insulin-stimulated cGI-PDE kinase, the cGI-PDE and the hormone-sensitive lipase were observed. These data suggest that activation of PI 3-kinase upstream of the insulin-stimulated cGI-PDE kinase in the antilipolytic insulin signalchain has an essential role for insulin-induced cGI-PDE activation/ phosphorylation and anti-lipolysis.     

Bioenergetic profiling of zebrafish embryonic development

Many debilitating conditions are linked to bioenergetic defects. Developing screens to probe the genetic and/or chemical basis for such links has proved intractable. Furthermore, there is a need for a physiologically relevant assay of bioenergetics in whole organisms, especially for early stages in life where perturbations could increase disease susceptibility with aging. Thus, we asked whether we could screen bioenergetics and mitochondrial function in the developing zebrafish embryo. We present a multiplexed method to assay bioenergetics in zebrafish embryos from the blastula period (3 hours post-fertilization, hpf) through to hatching (48 hpf). In proof of principle experiments, we measured respiration and acid extrusion of developing zebrafish embryos. We quantified respiratory coupling to various bioenergetic functions by using specific pharmacological inhibitors of bioenergetic pathways. We demonstrate that changes in the coupling to ATP turnover and proton leak are correlated with developmental stage. The multiwell format of this assay enables the user to screen for the effects of drugs and environmental agents on bioenergetics in the zebrafish embryo with high sensitivity and reproducibility.