Optimizing Transcutaneous Oxygen Measurement Sites on Humans.

This study utilizes an optical method of transcutaneous oxygen sensing that has the potential to revolutionize at-home care. This technique is based on quenching the luminescence of a platinum porphyrin film. Since oxygen quenches luminescence, its lifetime is further measured to assess the partial pressure of transcutaneous oxygen diffusing through the skin. Unlike conventional transcutaneous oxygen monitors that use electrochemical sensors, the luminescence-based sensor allows the use of dry electrodes that do not require heating and reduce the risk of accidental skin irritations or burns. These properties not only improve patient safety but also allow the creation of miniature wearable transcutaneous oxygen sensors for continuous and accurate remote respiratory monitoring. To this end, it is critical to assess the efficiency of the wearable sensor by determining the optimal location for its placement on the body. Depending on the location on the body, physiological factors such as blood flow rate and skin thickness affect dermal perfusion of transcutaneous oxygen. In this work, four healthy volunteers participated in subject testing. We assessed each participant at the following locations: thumb, top of the wrist, forearm, thigh, and shin. All locations consistently reported accurate and reliable data. Among them, the thumb demonstrated shorter settling times and the most uniform luminescence lifetime values.

A Prototype Wearable Device for Noninvasive Monitoring of Transcutaneous Oxygen.

Transcutaneous oxygen monitoring is a noninvasive method for measuring the partial pressure of oxygen diffusing through the skin, which strongly correlates with changes in dissolved oxygen in the arteries. Luminescent oxygen sensing is one of the techniques for assessing transcutaneous oxygen. Intensity- and lifetime-based measurements are two well-known methods used in this technique. The latter is more immune to optical path changes and reflections, making the measurements less vulnerable to motion artifacts and skin color changes. Although the lifetime-based method is promising, the acquisition of high-resolution lifetime data is crucial for accurate transcutaneous oxygen measurements from the human body when skin is not heated. We have built a compact prototype along with its custom firmware for the lifetime estimation of transcutaneous oxygen with a provision of a wearable device. Furthermore, we performed a small experiment study on three healthy human volunteers to prove the concept of measuring oxygen diffusing from the skin without heating. Lastly, the prototype successfully detected changes in lifetime values driven by the changes in transcutaneous oxygen partial pressure due to pressure-induced arterial occlusion and hypoxic gas delivery. The prototype resolved a minimum change of 1.34 ns in a lifetime that corresponds to 0.031 mmHg in response to slow changes in the oxygen pressure in the volunteer's body caused by hypoxic gas delivery. The prototype is believed to be the first in the literature to successfully conduct measurements in human subjects using the lifetime-based technique.

Phase 1 pharmacogenetic and pharmacodynamic study of sorafenib with concurrent radiation therapy and gemcitabine in locally advanced unresectable pancreatic cancer.

PURPOSE: To define the safety, efficacy, and pharmacogenetic and pharmacodynamic effects of sorafenib with gemcitabine-based chemoradiotherapy (CRT) in locally advanced pancreatic cancer. METHODS AND MATERIALS: Patients received gemcitabine 1000 mg/m(2) intravenously weekly × 3 every 4 weeks per cycle for 1 cycle before CRT and continued for up to 4 cycles after CRT. Weekly gemcitabine 600 mg/m(2) intravenously was given during concurrent intensity modulated radiation therapy of 50 Gy to gross tumor volume in 25 fractions. Sorafenib was dosed orally 400 mg twice daily until progression, except during CRT when it was escalated from 200 mg to 400 mg daily, and 400 mg twice daily. The maximum tolerated dose cohort was expanded to 15 patients. Correlative studies included dynamic contrast-enhanced MRI and angiogenesis genes polymorphisms (VEGF-A and VEGF-R2 single nucleotide polymorphisms). RESULTS: Twenty-seven patients were enrolled. No dose-limiting toxicity occurred during induction gemcitabine/sorafenib followed by concurrent CRT. The most common grade 3/4 toxicities were fatigue, hematologic, and gastrointestinal. The maximum tolerated dose was sorafenib 400 mg twice daily. The median progression-free survival and overall survival for 25 evaluable patients were 10.6 and 12.6 months, respectively. The median overall survival for patients with VEGF-A -2578 AA, -1498 CC, and -1154 AA versus alternate genotypes was 21.6 versus 14.7 months. Dynamic contrast-enhanced MRI demonstrated higher baseline K(trans) in responding patients. CONCLUSIONS: Concurrent sorafenib with CRT had modest clinical activity with increased gastrointestinal toxicity in localized unresectable pancreatic cancer. Select VEGF-A/VEGF-R2 genotypes were associated with favorable survival.

FKBP12 is a critical regulator of the heart rhythm and the cardiac voltage-gated sodium current in mice.

RATIONALE: FK506 binding protein (FKBP)12 is a known cis-trans peptidyl prolyl isomerase and highly expressed in the heart. Its role in regulating postnatal cardiac function remains largely unknown. METHODS AND RESULTS: We generated FKBP12 overexpressing transgenic (αMyHC-FKBP12) mice and cardiomyocyte-restricted FKBP12 conditional knockout (FKBP12(f/f)/αMyHC-Cre) mice and analyzed their cardiac electrophysiology in vivo and in vitro. A high incidence (38%) of sudden death was found in αMyHC-FKBP12 mice. Surface and ambulatory ECGs documented cardiac conduction defects, which were further confirmed by electric measurements and optical mapping in Langendorff-perfused hearts. αMyHC-FKBP12 hearts had slower action potential upstrokes and longer action potential durations. Whole-cell patch-clamp analyses demonstrated an ≈ 80% reduction in peak density of the tetrodotoxin-resistant, voltage-gated sodium current I(Na) in αMyHC-FKBP12 ventricular cardiomyocytes, a slower recovery of I(Na) from inactivation, shifts of steady-state activation and inactivation curves of I(Na) to more depolarized potentials, and augmentation of late I(Na), suggesting that the arrhythmogenic phenotype of αMyHC-FKBP12 mice is attributable to abnormal I(Na). Ventricular cardiomyocytes isolated from FKBP12(f/f)/αMyHC-Cre hearts showed faster action potential upstrokes and a more than 2-fold increase in peak I(Na) density. Dialysis of exogenous recombinant FKBP12 protein into FKBP12-deficient cardiomyocytes promptly recapitulated alterations in I(Na) seen in αMyHC-FKBP12 myocytes. CONCLUSIONS: FKBP12 is a critical regulator of I(Na) and is important for cardiac arrhythmogenic physiology. FKPB12-mediated dysregulation of I(Na) may underlie clinical arrhythmias associated with FK506 administration.

Pancreatic cancer: utility of dynamic contrast-enhanced MR imaging in assessment of antiangiogenic therapy.

PURPOSE: To prospectively evaluate the utility of dynamic contrast material-enhanced magnetic resonance (MR) imaging in predicting the response of locally advanced pancreatic cancer to combined chemotherapy and antiangiogenic therapy. MATERIALS AND METHODS: This prospective, institutional review board-approved, HIPAA-compliant study with informed consent assessed dynamic contrast-enhanced MR imaging in 11 patients (mean age, 54.3 years; six men and five women) with locally invasive pancreatic cancer before and 28 days after combined chemotherapy and antiangiogenic therapy. Axial perfusion images were obtained after injection of 0.1 mmol gadopentetate dimeglumine per kilogram of body weight. Sagittal images of the upper abdominal aorta were obtained for arterial input function calculation. A two-compartment kinetic model was used to calculate the perfusion parameters K(trans) (the rate constant that represents transfer of contrast agent from the arterial blood into the extravascular extracellular space), K(ep) (the rate constant that represents transfer of contrast agent from the extravascular extracellular space to the blood plasma), and volume of distribution (v(e)). Semiquantitative measurements, peak tissue gadolinium concentration (C(peak)), maximum slope of gadolinium increase (slope), and area under the gadolinium curve at 60 seconds (AUC(60)) were also calculated. Perfusion parameters and tumor size changes were correlated with carbohydrate antigen 19-9 levels. Comparisons between pre- and posttreatment studies were performed by using the Wilcoxon signed rank test, and comparisons between responders and nonresponders were performed by using the Mann-Whitney test. RESULTS: After therapy, K(trans), v(e), C(peak), slope, and AUC(60) decreased significantly (P = .02, .001, .002, .007, and .01, respectively). Tumor size and K(ep) were not significantly changed. Pretreatment K(trans) and K(ep) were significantly higher (P = .02 and .006, respectively) in tumors that showed marker response than in those that did not. A pretreatment K(trans) value (milliliters of blood per milliliter of tissue times minutes) of more than 0.78 mL/mL . min was 100% sensitive and 71% specific for subsequent tumor response. Semiquantative parameters and tumor size were not different between the groups. CONCLUSION: Pretreatment K(trans) measurement in pancreatic tumors can predict response to antiangiogenic therapy. All perfusion parameters showed substantial reduction after 28 days of combined chemotherapy and antiangiogenic therapy.

Functional impact of the hyperpolarization-activated current on the excitability of myelinated A-type vagal afferent neurons in the rat.

1. The hyperpolarization-induced, cation-selective current I(h) is widely observed in peripheral sensory neurons of the vagal and dorsal root ganglia, but the peak magnitude and voltage- and time-dependent properties of this current vary widely across afferent fibre type. 2. Using patch clamp investigations of rat isolated vagal ganglion neurons (VGN) identified as myelinated A-type afferents, we established a compendium of functional correlates between changes in membrane potential and the dynamic discharge properties of these sensory neurons as a result of the controlled recruitment of I(h) using the current clamp technique. 3. Two robust responses were observed in response to hyperpolarizing step currents: (i) upon initiation of the negative step current, there was a rapid hyperpolarization of membrane potential followed by a depolarizing voltage sag (DVS) towards a plateau in membrane potential as a result of steady state recruitment of I(h); and (ii) upon termination of the negative step current, there was a rapid return to the pretest resting membrane potential that often led to spontaneous action potential discharge. These data were strongly correlated (r(2) > 0.9) with a broad compendium of dynamic discharge characteristics in these A-type VGN. 4. In response to depolarizing step currents of increasing magnitude, the discharge frequency of the A-type VGN responded with increases in the rate of sustained repetitive discharge. Upon termination of the depolarizing step current, there was a post-excitatory membrane hyperpolarization of a magnitude that was strongly correlated with action potential discharge rate (r(2) > 0.9). 5. Application of the selective hyperpolarization-activated cyclic nucleotide gated (HCN) channel blockers ZD7288 (10 micromol/L) or CsCl (1.0 mmol/L) abolished I(h) and all of the aforementioned functional correlates. In addition to reducing the excitability of the A-type VGN to step depolarizing currents. 6. Because there is increasing evidence that the HCN channel current may represent a valid target for pharmacological intervention, the quantitative relationships described in the present study could potentially help guide the molecular and/or chemical modification of HCN channel gating properties to effect a particular outcome in VGN discharge properties, ideally well beyond merely selective blockade of a particular HCN channel subtype.

Uniform action potential repolarization within the sarcolemma of in situ ventricular cardiomyocytes.

Previous studies have speculated, based on indirect evidence, that the action potential at the transverse (t)-tubules is longer than at the surface membrane in mammalian ventricular cardiomyocytes. To date, no technique has enabled recording of electrical activity selectively at the t-tubules to directly examine this hypothesis. We used confocal line-scan imaging in conjunction with the fast response voltage-sensitive dyes ANNINE-6 and ANNINE-6plus to resolve action potential-related changes in fractional dye fluorescence (DeltaF/F) at the t-tubule and surface membranes of in situ mouse ventricular cardiomyocytes. Peak DeltaF/F during action potential phase 0 depolarization averaged -21% for both dyes. The shape and time course of optical action potentials measured with the water-soluble ANNINE-6plus were indistinguishable from those of action potentials recorded with intracellular microelectrodes in the absence of the dye. In contrast, optical action potentials measured with the water-insoluble ANNINE-6 were significantly prolonged compared to the electrical recordings obtained from dye-free hearts, suggesting electrophysiological effects of ANNINE-6 and/or its solvents. With either dye, the kinetics of action potential-dependent changes in DeltaF/F during repolarization were found to be similar at the t-tubular and surface membranes. This study provides what to our knowledge are the first direct measurements of t-tubule electrical activity in ventricular cardiomyocytes, which support the concept that action potential duration is uniform throughout the sarcolemma of individual cells.

Smad7 is required for the development and function of the heart.

Transforming growth factor-beta (TGF-beta) family members, including TGF-betas, activins, and bone morphogenetic proteins, exert diverse biological activities in cell proliferation, differentiation, apoptosis, embryonic development, and many other processes. These effects are largely mediated by Smad proteins. Smad7 is a negative regulator for the signaling of TGF-beta family members. Dysregulation of Smad7 is associated with pathogenesis of a variety of human diseases. However, the in vivo physiological roles of Smad7 have not been elucidated due to the lack of a mouse model with significant loss of Smad7 function. Here we report generation and initial characterization of Smad7 mutant mice with targeted deletion of the indispensable MH2 domain. The majority of Smad7 mutant mice died in utero due to multiple defects in cardiovascular development, including ventricular septal defect and non-compaction, as well as outflow tract malformation. The surviving adult Smad7 mutant mice had impaired cardiac functions and severe arrhythmia. Further analyses suggest that Smad2/3 phosphorylation was elevated in atrioventricular cushion in the heart of Smad7 mutant mice, accompanied by increased apoptosis in this region. Taken together, these observations pinpoint an important role of Smad7 in the development and function of the mouse heart in vivo.

Cardiac restricted overexpression of kinase-dead mammalian target of rapamycin (mTOR) mutant impairs the mTOR-mediated signaling and cardiac function.

Mammalian target of rapamycin (mTOR) is a key regulator for cell growth through modulating components of the translation machinery. Previously, numerous pharmacological studies using rapamycin suggested that mTOR has an important role in regulating cardiac hypertrophic growth. To further investigate this assumption, we have generated two lines of cardiac specific mTOR transgenic mice, kinase-dead (kd) mTOR and constitutively active (ca) mTOR, using alpha-myosin heavy chain promoter. alpha-Myosin heavy chain (alphaMHC)-mTORkd mice had a near complete inhibition of p70 S6k and 4E-BP1 phosphorylation, whereas alphaMHC-mTORca had a significant increase in p70 S6k and 4E-BP1 phosphorylation. Although the cardiac function of alphaMHC-mTORkd mice was significantly altered, the cardiac morphology of these transgenic mice was normal. The cardiac hypertrophic growth in response to physiological and pathological stimuli was not different in alphaMHC-mTORkd and alphaMHC-mTORca transgenic mice when compared with that of nontransgenic littermates. These findings suggest that the mTOR-mediated signaling pathway is not essential to cardiac hypertrophic growth but is involved in regulating cardiac function. Additional analysis of cardiac responses to fasting-refeeding or acute insulin administration indicated that alphaMHC-mTORkd mice had a largely impaired physiological response to nutrient energy supply and insulin stimulation.

A single moving dipole model of ventricular depolarization.

Modeling abnormal depolarization of the ventricles may provide a means to localize sites of arrhythmia foci from the body surface recordings. In this paper, we present a single moving dipole (SMD) model of the ventricular depolarization. The model can reproduce characteristic QRS patterns comparable to the clinical recordings when it is located in an inhomogeneous torso model. Our approach involves estimating a series of dipole moments based on vectocardiograms and estimating trajectories based on the three-dimensional isochrone of the ventricular activation. The patterns of body surface potential isochrones are consistent with those from previous studies. The SMD model was also used to simulate posterior wall infarction, which matched the criteria for this diagnosis. In conclusion, our SMD model provided a base for further ventricular depolarization studies and this equivalent dipole approach might be useful in investigating ventricular arrhythmias and their site of origin.