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Abstract Background Lactate is traditionally recognized as a by-product of anaerobic metabolism. However, lactate is a preferred oxidative substrate for stressed myocardium. Exogenous lactate infusion increases cardiac output (CO). The exact mechanism underlying this mechanism has yet to be elucidated. The aim of this study was to investigate the cardiovascular mechanisms underlying the acute haemodynamic effects of exogenous lactate infusion in an experimental model of human-sized pigs. Methods In this randomised, blinded crossover study in eight 60-kg-pigs, the pigs received infusions with one molar sodium lactate and a control infusion of tonicity matched hypertonic saline in random order. We measured CO and pulmonary pressures using a pulmonary artery catheter. A pressure–volume admittance catheter in the left ventricle was used to measure contractility, afterload, preload and work-related parameters. Results Lactate infusion increased circulating lactate levels by 9.9 mmol/L (95% confidence interval (CI) 9.1 to 11.0) and CO by 2.0 L/min (95% CI 1.2 to 2.7). Afterload decreased as arterial elastance fell by -1.0 mmHg/ml (95% CI -2.0 to -0.1) and systemic vascular resistance decreased by -548 dynes/s/cm5 (95% CI -261 to -835). Mixed venous saturation increased by 11 percentage points (95% CI 6 to 16), whereas ejection fraction increased by 16.0 percentage points (95% CI 1.1 to 32.0) and heart rate by 21 bpm (95% CI 8 to 33). No significant changes in contractility nor preload were observed. Conclusion Lactate infusion increased cardiac output by increasing heart rate and lowering afterload. No differences were observed in left ventricular contractility or preload. Lactate holds potential as a treatment in situations with lowered CO and should be investigated in future clinical studies. Graphical Abstract

Background: Lactate is traditionally recognized as a by-product of anaerobic metabolism. However, lactate is a preferred oxidative substrate for stressed myocardium. Exogenous lactate infusion increases cardiac output (CO). The exact mechanism underlying this mechanism has yet to be elucidated. The aim of this study was to investigate the cardiovascular mechanisms underlying the acute haemodynamic effects of exogenous lactate infusion in an experimental model of human-sized pigs. Methods: In this randomised, blinded crossover study in eight 60-kg-pigs, the pigs received infusions with one molar sodium lactate and a control infusion of tonicity matched hypertonic saline in random order. We measured CO and pulmonary pressures using a pulmonary artery catheter. A pressure–volume admittance catheter in the left ventricle was used to measure contractility, afterload, preload and work-related parameters. Results: Lactate infusion increased circulating lactate levels by 9.9 mmol/L (95% confidence interval (CI) 9.1 to 11.0) and CO by 2.0 L/min (95% CI 1.2 to 2.7). Afterload decreased as arterial elastance fell by -1.0 mmHg/ml (95% CI -2.0 to -0.1) and systemic vascular resistance decreased by -548 dynes/s/cm5 (95% CI -261 to -835). Mixed venous saturation increased by 11 percentage points (95% CI 6 to 16), whereas ejection fraction increased by 16.0 percentage points (95% CI 1.1 to 32.0) and heart rate by 21 bpm (95% CI 8 to 33). No significant changes in contractility nor preload were observed. Conclusion: Lactate infusion increased cardiac output by increasing heart rate and lowering afterload. No differences were observed in left ventricular contractility or preload. Lactate holds potential as a treatment in situations with lowered CO and should be investigated in future clinical studies. [ABSTRACT FROM AUTHOR]

Background and aimsLiving root tissues significantly constrain plant water uptake under drought, but we lack functional traits to feasibly screen diverse plants for variation in the drought responses of these tissues. Water stress causes roots to lose volume and turgor, which are crucial to root structure, hydraulics and growth. Thus, we hypothesized that root pressure-volume (p-v) curve traits, which quantify the effects of water potential on bulk root turgor and volume, would capture differences in rootstock drought tolerance.MethodsWe used a greenhouse experiment to evaluate relationships between root p-v curve traits and gas exchange, whole-plant hydraulic conductance and biomass under drought for eight grapevine rootstocks that varied widely in drought performance in field trials (101-14, 110R, 420A, 5C, 140-Ru, 1103P, Ramsey and Riparia Gloire), grafted to the same scion variety (Vitis vinifera 'Chardonnay').Key resultsThe traits varied significantly across rootstocks, and droughted vines significantly reduced root turgor loss point (πtlp), osmotic potential at full hydration (πo) and capacitance (C), indicating that roots became less susceptible to turgor loss and volumetric shrinkage. Rootstocks that retained a greater root volume (i.e. a lower C) also maintained more gas exchange under drought. The rootstocks that previous field trials have classified as drought tolerant exhibited significantly lower πtlp, πo and C values in well-watered conditions, but significantly higher πo and πtlp values under water stress, than the varieties classified as drought sensitive.ConclusionsThese findings suggest that acclimation in root p-v curve traits improves gas exchange in persistently dry conditions, potentially through impacts on root hydraulics or root to shoot chemical signalling. However, retaining turgor and volume in previously unstressed roots, as these roots deplete wet soil to moderately negative water potentials, could be more important to drought performance in the deep, highly heterogenous rooting zones which grapevines develop under field conditions.

Droughts in a warming climate have become more common and more extreme, making understanding forest responses to water stress increasingly pressing. Analysis of water stress in trees has long focused on water potential in xylem and leaves, which influences stomatal closure and water flow through the soil-plant-atmosphere continuum. At the same time, changes of vegetation water content (VWC) are linked to a range of tree responses, including fluxes of water and carbon, mortality, flammability, and more. Unlike water potential, which requires demanding in situ measurements, VWC can be retrieved from remote sensing measurements, particularly at microwave frequencies using radar and radiometry. Here, we highlight key frontiers through which VWC has the potential to significantly increase our understanding of forest responses to water stress. To validate remote sensing observations of VWC at landscape scale and to better relate them to data assimilation model parameters, we introduce an ecosystem-scale analog of the pressure-volume curve, the non-linear relationship between average leaf or branch water potential and water content commonly used in plant hydraulics. The sources of variability in these ecosystem-scale pressure-volume curves and their relationship to forest response to water stress are discussed. We further show to what extent diel, seasonal, and decadal dynamics of VWC reflect variations in different processes relating the tree response to water stress. VWC can also be used for inferring belowground conditions-which are difficult to impossible to observe directly. Lastly, we discuss how a dedicated geostationary spaceborne observational system for VWC, when combined with existing datasets, can capture diel and seasonal water dynamics to advance the science and applications of global forest vulnerability to future droughts.

Introduction: Measurement of the work of breathing (Wb) during exercise provides useful insights into the energetics and mechanics of the respiratory muscles across a wide range of minute ventilations. The methods and analytical procedures used to calculate the Wb during exercise have yet to be critically appraised in the literature. Purpose: The aim of this systematic review was to evaluate the quality of methods used to measure the Wb during exercise in the available literature. Methods: We conducted an extensive search of three databases for studies that measured the Wb during exercise in adult humans. Data were extracted on participant characteristics, flow/volume and pressure devices, esophageal pressure (Poes) catheters, and methods of Wb analysis. Results: A total of 120 articles were included. Flow/volume sensors used were primarily pneumotachographs (n = 85, 70.8%), whereas the most common pressure transducer was of the variable reluctance type (n = 63, 52.5%). Esophageal pressure was frequently obtained via balloon-tipped catheters (n = 114, 95.0%). Few studies mentioned calibration, frequency responses, and dynamic compensation of their measurement devices. The most popular method of measuring the Wb was pressure-volume integration (n = 51, 42.5%), followed by the modified Campbell (n = 28, 23.3%) and Dean & Visscher diagrams (n = 26, 21.7%). Over one-third of studies did not report the methods used to process their pressure--volume data, and the majority (60.8%) of studies used the incorrect Wb units and/or failed to discuss the limitations of their Wb measurements. Conclusions: The findings of this systematic review highlight the need for the development of a standardized approach for measuring Wb, which is informative, practical, and accessible for future researchers. [ABSTRACT FROM AUTHOR]

The cardiohemodynamics was studied 2 and 4 weeks after myocardial infarction modeling in Wistar rats. We compared the data obtained by echocardiography (echoCG) and catheterization of the left ventricle. The myocardial infarction was modeled by ligation of the left anterior descending coronary artery. EchoCG and the left ventricle catheterization were performed before and after myocardial infarction modeling. Similar results were obtained by both methods, namely the left ventricle dilatation, bradycardia, a reduced ejection fraction and delayed relaxation. According to echoCG, the end-diastolic left ventricle volume increased by 2 times, and initial diastolic left ventricle volume — by more than 5 times. The left ventricle catheterization showed lower rise, by 32 and 69%, respectively. The overestimated volume of the left ventricle in myocardial infarction according to echoCG data in comparison with catheterization can be explained by changes in the geometry of the ventricle (bulging of a part of the ventricular wall). [ABSTRACT FROM AUTHOR]

IntroductionThe pressure–volume (P-V) relationships of the left ventricle are the classical benchmark for studying cardiac mechanics and pumping function. Perturbations in the P-V relationship (or P-V loop) can be informative and guide the management of heart failure, hypovolemia, and aortic occlusion. Traditionally, P-V loop analyses have been limited to a single-beat P-V loop or an average of consecutive P-V loops (e.g., 10 cardiac cycles). While there are several algorithms to obtain single-beat estimations of the end-systolic and end-diastolic pressure–volume relations (i.e., ESPVR and EDPVR, respectively), there remains a need to better evaluate the variations in P-V relationships longitudinally over time. This is particularly important when studying acute and transient hemodynamic and cardiac events, such as active hemorrhage or aortic occlusion. In this study, we aim to investigate the variability in P-V relationships during hemorrhagic shock and aortic occlusion, by leveraging on a previously published porcine hemorrhage model.MethodsBriefly, swine were instrumented with a P-V catheter in the left ventricle of the heart and underwent a 25% total blood volume hemorrhage over 30 min, followed by either Zone 1 complete aortic occlusion (i.e., REBOA), Zone 1 endovascular variable aortic control (EVAC), or no occlusion as a control, for 45 min. Preload-independent metrics of cardiac performance were obtained at predetermined time points by performing inferior vena cava occlusion during a ventilatory pause. Continuous P-V loop data and other hemodynamic flow and pressure measurements were collected in real-time using a multi-channel data acquisition system.ResultsWe developed a custom algorithm to quantify the time-dependent variance in both load-dependent and independent cardiac parameters from each P-V loop. As expected, all pigs displayed a significant decrease in the end-systolic pressures and volumes (i.e., ESP, ESV) after hemorrhage. The variability in response to hemorrhage was consistent across all three groups. However, upon introduction of REBOA, we observed significantly high levels of variability in both load-dependent and independent cardiac metrics such as ESP, ESV, and the slope of ESPVR (Ees). For instance, pigs receiving REBOA experienced a 342% increase in ESP from hemorrhage, while pigs receiving EVAC experienced only a 188% increase. The level of variability within the EVAC group was consistently less than that of the REBOA group, which suggests that the EVAC group may be more supportive of maintaining healthier cardiac performance than complete occlusion with REBOA.DiscussionIn conclusion, we successfully developed a novel algorithm to reliably quantify the single-beat and longitudinal P-V relations during hemorrhage and aortic occlusion. As expected, hemorrhage resulted in smaller P-V loops, reflective of decreased preload and afterload conditions; however, the cardiac output and heart rate were preserved. The use of REBOA and EVAC for 44 min resulted in the restoration of baseline afterload and preload conditions, but often REBOA exceeded baseline pressure conditions to an alarming level. The level of variability in response to REBOA was significant and could be potentially associated to cardiac injury. By quantifying each P-V loop, we were able to capture the variability in all P-V loops, including those that were irregular in shape and believe that this can help us identify critical time points associated with declining cardiac performance during hemorrhage and REBOA use.

In recent years, attempts have been made in linking pressure–volume parameters and the leaf economics spectrum to expand our knowledge of the interrelationships among leaf traits. We provide theoretical and empirical evidence for the coordination of the turgor loss point and associated traits with net CO2 assimilation (An) and leaf mass per area (LMA). We measured gas exchange, pressure–volume curves and leaf structure in 45 ferns and angiosperms, and explored the anatomical and chemical basis of the key traits. We propose that the coordination observed between mass‐based An, capacitance and the turgor loss point (πtlp) emerges from their shared link with leaf density (one of the components of LMA) and, specially, leaf saturated water content (LSWC), which in turn relates to cell size and nitrogen and carbon content. Thus, considering the components of LMA and LSWC in ecophysiological studies can provide a broader perspective on leaf structure and function. [ABSTRACT FROM AUTHOR]

Fecobionics is an integrated device that has shown promise for assessment of anorectal function. We used a wireless Fecobionics prototype to visualize defecatory patterns and to compute volume–pressure, contraction work, and flow. Twelve normal subjects were studied. The probe was 10 cm-long and contained pressure sensors and electrodes for impedance planimetry. Pressures, diameters, and volume data during defecation were analyzed. The bag was distended inside rectum to the urge-to-defecate level where after the subjects were asked to evacuate. The contraction work and defecatory flow were computed from the volume changes during expulsion. The minimum anal diameter during the evacuation was 17.6 ± 1.5 mm. The middle diameter recording was 10–20% lower than the front diameter channels and 10–20% bigger than the rear channels. The bag volume at urge correlated with the minimum diameter (r = 0.63). The diameter-pressure and volume–pressure loops were counterclockwise with phases of bag filling, isometric contraction, ejection and anal passage. The defecatory contraction work was 3520 ± 480 mL × cmH2O. The maximum flow during defecation was 302 ± 33 mL/s. The flow was associated with the anal diameter (r = 0.84) but not with the rectoanal pressure gradient (r = 0.14). Volume–pressure loops have a tremendous impact on the understanding of cardiopulmonary pathophysiology. Future studies will shed light on potential clinical impact in defecatory pathophysiology. [ABSTRACT FROM AUTHOR]

Objectives: To describe hemodynamic effects of iVAC2L mechanical circulatory support (MCS).Background: MCS is increasingly used in the context of high-risk percutaneous coronary intervention (PCI). The effect of the pulsatile iVAC2L MCS on left ventricular loading conditions and myocardial oxygen consumption (MVO2) is unknown.Methods: This prospective single-arm two-center study included 29 patients who underwent high-risk PCI with iVAC2L MCS using simultaneous invasive pulmonary pressure monitoring and left ventricular pressure-volume analysis. Hemodynamic recordings were performed during steady state conditions with MCS off and on before and after PCI. Pressure-volume variations were analyzed to denote responders and non-responders.Results: The mean age was 74 (IQR: 70-81) years and the mean SYNTAX score was 31 ± 8.3. Left ventricular unloading with iVAC2L MCS was demonstrated in 22 out of 27 patients with complete PV studies. Patients with moderate or severe mitral regurgitation or presenting with acute coronary syndrome (ACS) had higher filling pressures and volumes and were most responsive to iVAC2L unloading (9/10 patients with moderate or severe MR and 11/11 patients with ACS). Pulsatile MCS activation reduced MAP (-4%), SBP (-9%), ESP (-11%), ESV (-15%) and EDV (-4%) among responders but not among non-responders. Responders experienced significant reductions in afterload (Ea: -19%) with increases in stroke volume (+11%) and cardiac output (+11%).Conclusions: Pulsatile iVAC2L MCS in patients with advanced coronary artery disease at high to prohibitive operative risk resulted in LV unloading and reduced myocardial oxygen consumption particularly in patients with ACS or significant MR with higher filling pressures at baseline.Clinical Trial Registration: NCT03200990. [ABSTRACT FROM AUTHOR]

Micro-scale models of lung tissue have been employed by researchers to investigate alveolar mechanics; however, they have been limited by the lack of biofidelic material properties for the alveolar wall. To address this challenge, a finite element model of an alveolar cluster was developed comprising a tetrakaidecahedron array with the nominal characteristics of human alveolar structure. Lung expansion was simulated in the model by prescribing a pressure and monitoring the volume, to produce a pressure-volume (PV) response that could be compared to experimental PV data. The alveolar wall properties in the model were optimized to match experimental PV response of lungs filled with saline, to eliminate surface tension effects and isolate the alveolar wall tissue response. When simulated in uniaxial tension, the model was in agreement with reported experimental properties of uniaxial tension on excised lung tissue. The work presented herein was able to link micro-scale alveolar response to two disparate macroscopic experimental datasets (stress-stretch and PV response of lung) and presents hyperelastic properties of the alveolar wall for use in alveolar scale finite element models and multi-scale models. Future research will incorporate surface tension effects, and investigate alveolar injury mechanisms. • Demonstrates agreement between stress-strain and pressure-volume data of lungs using alveolar finite element model. • Sensitivity study suggests an initial unloaded volume for the alveolar wall tissue of approximately 30 %TLC. • Presents hyperelastic properties of alveolar wall for use in alveolar models, and to inform multi-scale models of lung. [ABSTRACT FROM AUTHOR]

Mediterranean viticulture is highly dependent on soil water availability. Moreover, global warming is likely to increase average temperatures and the frequency of heat waves, thus leading to greater water scarcity. To cope with this situation, much research focused on the selection of genotypes with higher water use efficiency (WUE). Several previous studies indicated that WUE varies between genotypes of the Tempranillo cultivar with some showing interesting improvement in the leaf WUE. Here, we assessed the associations between the leaf WUE and physiological parameters in six selected Tempranillo clones. The plants were cultivated in pots and two water conditions were applied sequentially: a well-watered period followed by a moderate water stress and recovery phase. Growth parameters and intrinsic WUE were monitored during both periods. Pressure–volume and AN/Ci curves were measured after the plants were re-watered. At the end of the season, biomass accumulation and total irrigation water were used to calculate whole plant WUE (WUEWP). AN/Ci curves revealed significant differences in several photosynthetic parameters, including mesophyll conductance (gm), maximum velocity of carboxylation (Vcmax) and leaf respiration (R). Clones RJ51 and 1048 both exhibited high WUE, but presented distinct physiological traits: RJ51 had the highest gm, while genotype 1048, had the lowest R. This study confirms that physiological traits generally explain the intracultivar diversity in WUE observed in previous studies. [ABSTRACT FROM AUTHOR]

Animal models used by the pharmaceutical industry to define drug safety and efficacy are expensive, resource‐intensive, subject to interspecies differences, and often fail to predict human responses. Therefore, engineered human tissue preparations are gaining importance as in vitro models to address translation from preclinical data to clinical outcome. Methods that improve fabrication consistency, usability, and physiological relevance of tissues are crucial. For cardiac applications, the goal is to form a miniature 3D chamber that mimics the physiology and biomechanical properties of the ventricle, allowing the measurement of clinically relevant endpoints, such as pressure–volume relationships, which cannot be obtained with simpler constructs. Despite advances in biofabrication, a perfusable mini‐ventricle with a competent endocardium remains an unmet challenge, resulting in thin‐walled organoids that are fluid permeable. A novel method is developed and validated for improving the stability and performance of the herein described human mini‐heart model by creating an ultra‐compliant elastomer balloon for hollow‐organ engineering applications. Balloon properties, tissue formation, and biological data are examined. Findings demonstrate a thin permanent lining, which is retained during testing and permits tissue contraction, functions to eliminate leakage, increase uniformity, and enable multiday longitudinal measurements. Biological data presented herein show reduced variability across measured cardiac parameters when compared to our previously published fabrication method. [ABSTRACT FROM AUTHOR]

Impaired insulin synthesis is accompanied by hyperglycemia and the development of diabetic cardiomyopathy. Echocardiography and left-ventricular catheterization were employed for studying the contractile function of the left ventricle in 2 weeks after administration of streptozotocin (60 mg/kg). The results obtained by both methods were similar and indicated the development of systolic dysfunction with a 27% decrease in cardiac output. The invasive study showed that the maximum rate of left-ventricular pressure development, the contractility index, and systolic left-ventricular pressure were within the normal range, but the peak ejection rate was reduced by 28%. BP was normal, but the vascular stiffness index was increased by about 1.5 times and inversely correlated with the peak ejection rate (r=-0.69). The results showed that systolic dysfunction in type 1 diabetes model was due to reduced ejection from the left ventricle at normal rate of left-ventricular pressure development. [ABSTRACT FROM AUTHOR]

Objectives: Mechanical circulatory support (MCS) is often required to stabilize therapy-refractory cardiogenic shock patients. Left ventricular (LV) unloading by mechanical ventricular support (MVS) via percutaneous devices, such as with Impella® axial pumps, alone or in combination with extracorporeal life support (ECLS, ECMELLA approach), has emerged as a potential clinical breakthrough in the field. While the weaning from MCS is essentially based on the evaluation of circulatory stability of patients, weaning from MVS holds a higher complexity, being dependent on bi-ventricular function and its adaption to load. As a result of this, weaning from MVS is mostly performed in the absence of established algorithms. MVS via Impella is applied in several cardiogenic shock etiologies, such as acute myocardial infarction (support over days) or acute fulminant myocarditis (prolonged support over weeks, PROPELLA). The time point of weaning from Impella in these cohorts of patients remains unclear. We here propose a novel cardiovascular physiology-based weaning algorithm for MVS.Methods: The proposed algorithm is based on the experience gathered at our center undergoing an Impella weaning between 2017 and 2020. Before undertaking a weaning process, patients must had been ECMO-free, afebrile, and euvolemic, with hemodynamic stability guaranteed in the absence of any inotropic support. The algorithm consists of 4 steps according to the acronym TIDE: (i) Transthoracic echocardiography under full Impella-unloading; (ii) Impella rate reduction in single 8–24 h-steps according to patients hemodynamics (blood pressure, heart rate, and ScVO2), including a daily echocardiographic assessment at minimal flow (P2); (iii) Dobutamine stress-echocardiography; (iv) Right heart catheterization at rest and during Exercise-testing via handgrip. We here present clinical and hemodynamic data (including LV conductance data) from paradigmatic weaning protocols of awake patients admitted to our intensive care unit with cardiogenic shock. We discuss the clinical consequences of the TIDE algorithm, leading to either a bridge-to-recovery, or to a bridge-to-permanent LV assist device (LVAD) and/or transplantation. With this protocol we were able to wean 74.2% of the investigated patients successfully. 25.8% showed a permanent weaning failure and became LVAD candidates.Conclusions: The proposed novel cardiovascular physiology-based weaning algorithm is based on the characterization of the extent and sustainment of LV unloading reached during hospitalization in patients with cardiogenic shock undergoing MVS with Impella in our center. Prospective studies are needed to validate the algorithm.

Active upper-limb and passive lower-limb exercise are two interventions used in the spinal cord injury (SCI) population. Although the global cardiac responses have been previously studied, it is unclear how either exercise influences contractile cardiac function. Here, the cardiac contractile and volumetric responses to upper-limb (swim) and passive lower-limb exercise were investigated in rodents with a severe high-thoracic SCI. Animals were divided into control (CON), SCI no exercise (NO-EX), SCI passive hindlimb cycling (PHLC), or SCI swim (SWIM) groups. Severe contusion SCI was administered at the T2 level. PHLC and SWIM interventions began on day 8 postinjury and lasted 25 days. Echocardiography and dobutamine stress echocardiography were performed before and after injury. Cardiac contractile indexes were assessed in vivo at study termination via a left ventricular pressure-volume conductance catheter. Stroke volume was reduced after SCI (91 µl in the NO-EX group vs. 188 µl in the CON group, P < 0.05) and was reversed at study termination in the PHLC (167 µl) but not SWIM (90 µl) group. Rates of contraction were reduced in NO-EX versus CON groups (6,079 vs. 9,225 mmHg, respectively, P < 0.05) and were unchanged by PHLC and SWIM training. Similarly, end-systolic elastance was reduced in the NO-EX versus CON groups (0.67 vs. 1.37 mmHg/µl, respectively, P < 0.05) and was unchanged by PHLC or SWIM training. Dobutamine infusion normalized all pressure indexes in each SCI group (all P < 0.05). In conclusion, PHLC improves flow-derived cardiac indexes, whereas SWIM training displayed no cardiobeneficial effect. Pressure-derived deficits were corrected only with dobutamine, suggesting that reduced β-adrenergic stimulation is principally responsible for the impaired cardiac contractile function after SCI. [ABSTRACT FROM AUTHOR]

We present in-vivo study related to the use of our implantable RF telemetry system for pressure-volume (PV) cardiac monitoring in a animal subject. We implant a commercial MEMS PV sensor into the subject's heart left-ventricle (LV), while the telemetry system is implanted outside of the heart and connected to the sensor with a 7-microwires tether. The RF telemetry system is suitable for commercial application in medium sized subjects, its total volume of 2.475cm and a weight of 4.0g. Our designed system is 58 % smaller in volume, 44 % in weight and has a 55 % reduction in sampling power over the last reported research in PV telemetry. In-vivo data was captured in both an acute and a freely moving setting over a 24 hour period. We experimentally demonstrated viability of the methodology that includes the surgical procedure and real-time monitoring of the in-vivo data in a freely moving subject. Further improvements in catheter design will improve the data quality and safety of the subject. This real-time implantable technology allows for researchers to quantify cardiac pathologies by extracting real-time pressure-volume loops, wirelessly from within freely moving subjects. [ABSTRACT FROM AUTHOR]

Plantas jovens de S. amazonicum (paricá) e S. parahyba (guapuruvu) foram submetidas a dois ciclos de deficiência hídrica em casa de vegetação. O déficit hídrico induziu o aumento dos teores de aminoácidos solúveis totais, prolina, açúcares solúveis totais e K+ nos tecidos foliares, ocasionando o abaixamento do potencial osmótico em ambas as espécies. Porém, a análise dos resultados das curvas pressão-volume indica que as espécies respondem, de maneira diferente, ao estresse hídrico e o S. amazonicum apresenta maior capacidade de adaptação osmótica do que o S. parahyba.Juvenile plants of S. amazonicum (paricá) and S. parahyba (guapuruvu) were subjected to two cycles of water stress in greenhouse conditions. The water deficit induced the increase in total soluble amino acids, proline, total soluble sugars and K+ contents in the leaf tissues, lowering osmotic potential values in both species. However, the analysis of the pressure-volume curve results suggests that the species respond differently to water stress, and that S. amazonicum presents greater capacity of osmotic adaptation than S. parahyba.

Background This study examined the acute effect of intravenous S -nitroso human serum albumin ( S -NO-HSA) infusion on overall hemodynamics and oxidative stress in a chronic left-to-right shunt-induced pulmonary arterial hypertension model with right ventricle (RV) failure. Methods An aortocaval fistula (pulmonary-to-systemic blood flow ratio [Qp/Qs] > 2.0) was surgically created in 50 male Wistar rats. After 10 weeks, they were randomly treated with S -NO-HSA ( n = 20) or human serum albumin (HSA; n = 25) infusion (0.5 µmol/kg/h) for 60 minutes. A sham group ( n = 10) received S -NO-HSA. RV contractility, RV-vascular coupling, and ventricular interdependence were assessed in vivo at different pre-loads by biventricular conductance catheters. Heart and lung biopsy specimens were obtained for determination of high-energy phosphates, oxidative stress (oxidized glutathione/reduced glutathione), and endothelial nitric oxide synthase protein expression. Results S -NO-HSA, compared with HSA infusion, reduced RV afterload expressed by effective pulmonary arterial elastance (Ea; 0.49 ± 0.3 vs 1.2 ± 0.2 mm Hg/ml; p = 0.0005) and improved RV diastolic function (slope of end-diastolic pressure-volume relationship) as well as contractility indicated by slope of end-systolic pressure–volume relationship (Ees). Therefore an increase in efficiency of ventricular-vascular coupling (Ees/Ea) occurred after S -NO-HSA (0.35 ± 0.17 to 0.94 ± 0.21; p = 0.005), but not HSA infusion, leading to positive effect on ventricular interdependence with increased left ventricular stroke volume (56% ± 4% vs 19% ± 5%; p = 0.0013). S -NO-HSA, compared with HSA, treatment improved adenosine 5′-triphosphate (13.9 ± 1.1 vs 7.0 ± 1.8 µmol/g protein) and phosphocreatine (5.9 ± 3.3 vs 1.9 ± 0.6 µmol/g protein; p = 0.01) RV content and decreased the tissue oxidized glutathione/reduced glutathione ratio ( p = 0.001). Conclusions S -NO-HSA reduces pulmonary hypertension and improves RV systolic and diastolic function and RV-arterial coupling, with a positive effect on ventricular interdependence by increasing energetic reserve and reducing oxidative stress. [ABSTRACT FROM AUTHOR]

We present the discrete prototype version of our wireless telemetry system architecture, which is suitable for custom IC implementation and intended to eventually retrieve blood pressure and volume (PV) data from small animal subjects (e.g., mice, rats). The architecture consists of four system level blocks that are stacked in $$2.475\,{\hbox{cm}}^{3}$$ volume and it weights 4.0 g. The current prototype's size is well suited for commercial implementation inside medium sized animal subjects, for instance, rabbits and larger rats. Transmit power reported in this paper is tested between 0 to $$-$$ 20 dBm by using phantom tissue model. [ABSTRACT FROM AUTHOR]

In 1940, Scholander suggested that stiffened upper airways remained open and received air from highly compressible alveoli during marine mammal diving. There are few data available on the structural and functional adaptations of the marine mammal respiratory system. The aim of this research was to investigate the anatomical (gross) and structural (compliance) characteristics of excised marine mammal tracheas. Here, we defined different types of tracheal structures, categorizing pinniped tracheas by varying degrees of continuity of cartilage (categories 1-4) and cetacean tracheas by varying compliance values (categories 5A and 5B). Some tracheas fell into more than one category along their length; for example, the harbor seal (Phoca vitulina) demonstrated complete rings cranially, and as the trachea progressed caudally, tracheal rings changed morphology. Dolphins and porpoises had less stiff, more compliant spiraling rings while beaked whales had very stiff, less compliant spiraling rings. The pressure-volume (P-V) relationships of isolated tracheas from different species were measured to assess structural differences between species. These findings lend evidence for pressure-induced collapse and re-inflation of lungs, perhaps influencing variability in dive depth or ventilation rates of the species investigated. [ABSTRACT FROM AUTHOR]

Abstract: Optimization of fluid status, perfusion pressure and cardiac output in intraoperative and critical care settings improves clinical outcomes. Cardiac output is a measure of the blood pumped around the circulation. Modelling of the circulation facilitates estimation of cardiac output from readily measured variables. Methods include thermodilution, analysis of arterial pressure waveforms, Doppler measurements of blood flow velocity, electrical bioimpedance and regional oxygenation. Physical limitations of each measurement technique produce predictable as well as unquantifiable errors, leading to over- or underestimates of cardiac output. [Copyright &y& Elsevier]

Epidemiological studies have consistently linked inhalation of particulate matter (PM) to increased cardiac morbidity and mortality, especially in at risk populations. However, few studies have examined the effect of PM on baseline cardiac function in otherwise healthy individuals. In addition, airborne PM contain environmentally persistent free radicals (EPFR) capable of redox cycling in biological systems. The purpose of this study was to determine whether nose-only inhalation of EPFRs (20 min/day for 7 days) could decrease baseline left ventricular function in healthy male Sprague-Dawley rats. The model EPFR tested was 1,2-dichlorobenzene chemisorbed to 0.2-μm-diameter silica/CuO particles at 230°C (DCB230). Inhalation of vehicle or silica particles served as controls. Twenty-four hours after the last exposure, rats were anesthetized (isoflurane) and ventilated (3 l/min), and left ventricular function was assessed using pressure-volume catheters. Compared with controls, inhalation of DCB230 significantly decreased baseline stroke volume, cardiac output, and stroke work. End-diastolic volume and end-diastolic pressure were also significantly reduced; however, ventricular contractility and relaxation were not changed. DCB230 also significantly increased pulmonary arterial pressure and produced hyperplasia in small pulmonary arteries. Plasma levels of C-reactive protein were significantly increased by exposure to DCB230, as were levels of heme oxygenase-1 and SOD2 in the left ventricle. Together, these data show that inhalation of EPFRs, but not silica particles, decreases baseline cardiac function in healthy rats by decreasing cardiac filling, secondary to increased pulmonary resistance. These EPFRs also produced systemic inflammation and increased oxidative stress markers in the left ventricle. [ABSTRACT FROM AUTHOR]

In this study, a new computational method for modelling the contracting heart is described. Using this method, the cardiac wall is constructed from basic, repeating contractile units that represent individual myocardial units and collagen, each with its own set of parameters, including orientation, passive and active behaviour and stimulation propagation. The method allows individual control of each structural unit (e.g. at the level of a single myocardial unit). Feasibility of modelling dynamic heart contraction using this method is demonstrated using 2D cross-sections and simplified 3D geometries. Effects of non-contractile scar and myopathic tissue were also tested in these geometrical configurations. Results from the 2D and 3D simulations were, overall, in agreement with well-established physiological data. The present method holds promise for modelling complex heart pathologies, abnormal mechanical properties (e.g. myocardial infarcts) and electrical conduction properties (branch blocks), and their spatial distributions across the myocardial tissues. [ABSTRACT FROM AUTHOR]

Exposure to airborne particles is associated with increased cardiovascular morbidity and mortality. During the combustion of chlorine-containing hazardous materials and fuels, chlorinated hydrocarbons chemisorb to the surface of transition metal-oxide-containing particles, reduce the metal, and form an organic free radical. These radical-particle systems can survive in the environment for days and are called environmentally persistent free radicals (EPFRs). This study determined whether EPFRs could decrease left ventricular function before and after ischemia and reperfusion (I/R) in vivo. Male Brown--Norway rats were dosed (8 mg/kg, intratracheal) 24 h prior to testing with particles containing the EPFR of 1, 2-dichlorobenzene (DCB230). DCB230 treatment decreased systolic and diastolic function. DCB230 also produced pulmonary and cardiac inflammation. After ischemia, systolic, but not diastolic function was significantly decreased in DCB230-treated rats. Ventricular function was not affected by I/R in control rats. There was greater oxidative stress in the heart and increased 8-isoprostane (biomarker of oxidative stress) in the plasma of treated vs. control rats after I/R. These data demonstrate for the first time that DCB230 can produce inflammation and significantly decrease cardiac function at baseline and after I/R in vivo. Furthermore, these data suggest that EPFRs may be a risk factor for cardiac toxicity in healthy individuals and individuals with ischemic heart disease. Potential mechanisms involving cytokines/chemokines and/or oxidative stress are discussed. [ABSTRACT FROM AUTHOR]

Hydraulic dysfunction in leaves determines key aspects of whole-plant responses to water stress; however, our understanding of the physiology of hydraulic dysfunction and its relationships to leaf structure and ecological strategy remains incomplete. Here, we studied a morphologically and ecologically diverse sample of angiosperm's to test whether the water potential inducing a 50% loss in leaf hydraulic conductance (P50leaf) is predicted by properties of leaf xylem relating to water tension-induced conduit collapse.We also assessed the relationships between P50leaf and other traits considered to reflect drought resistance and ecological strategy. Across species, P50leaf was strongly correlated with a theoretical predictor of vulnerability to cell collapse in minor veins (the cubed ratio of the conduit wall thickness to the conduit lumen breadth). P50leaf was also correlated with mesophyll traits known to be related to drought resistance, but unrelated to traits associated with carbon economy. Our data indicate a link between the structural mechanics of leaf xylem and hydraulic function under water stress. Although it is possible that collapse may contribute directly to dysfunction, this relationship may also be a secondary product of vascular economics, suggesting that leaf xylem is dimensioned to avoid wall collapse. [ABSTRACT FROM AUTHOR]

The biomimetic formed solution of collagen reconstituted films into native fibers proved to be of high interest because of its regenerative medical applications. A variety of tests to characterize the mechanical properties of biomimetic engineered films are illustrated in this paper. Based on our previous results, the modulus of elasticity and the ultimate strain of reconstituted collagen films were compared to the reported stress-strain data in the literature on various tissues (animal material), correlating the achieved properties with possible use for artificial tissue implants. The results presented in this study, with great potential to provide reference data for future work, show that the mechanical properties of the biomimetically formed collagen films is close to that of several native collagen fibers, a fact which suggests their use in medical applications. [ABSTRACT FROM AUTHOR]

This paper presents a study on tabletting of Ficus deltoidea, a herb known as "Emas Cotek" in Malaysia and traditionally used for treating gout, hypertension and diabetes as well as to improve blood circulation and to reduce cholesterol and toxins levels in the body. Research has shown that this herb contains active compounds such as flavonoid, tetripenoids, tannins and phenols. For centuries, it was consumed at home through infusion and recently the herb was marketed in the form of tea sachet, capsules and tablets. The tablet is a universal form of delivery in modern medicine due to its ability to provide uniform product composition, particle size and density distributions, and to eliminate dust formation; and most importantly, it has a longer shelf life compared to the other forms of delivery. It is achieved by pressing a blend of ingredients into a tablet. In this study, a 13-mm-diameter cylindrical uniaxial die was used for tabletting. Pressures ranging from 7.5 to 75 MPa were applied to the herb powder. The effect of binder was investigated using Avicel, with compositions ranging from 10 to 60 % of the blend. The strength of the tabletted herb was then tested using an indirect tensile strength test, called diametrical compression test. The results were presented in the form of pressure-volume relationship and tensile strength. The experimental data was then compared to that of the prediction using a firs,t order model. The results indicated that this simple approach can be used to understand the tabletting behaviour of the herb. [ABSTRACT FROM AUTHOR]

Pulmonary ischemia resulting from chronic pulmonary embolism leads to proliferation of the systemic circulation within and surrounding the lung. However, it is not clear how well alveolar tissue is sustained during the time of complete pulmonary ischemia. In the present study, we investigated how pulmonary ischemia after left pulmonary artery ligation (LPAL) would alter lung mechanical properties and morphology. In this established mouse model of lung angiogenesis after chronic LPAL (10), we evaluated lung function and structure before (3 days) and after (14 days) a functional systemic circulation to the left lung is established. Age-matched naïve and sham-operated C57B1/6 mice and mice undergoing chronic LPAL were studied. Left and right lung pressure-volume relationships were determined. Next, lungs were inflated in situ with warmed agarose (25-30 cmH2O) and fixed, and mean chord lengths (MCL) of histological sections were quantified. MCL of naïve mice averaged 43.9 ± 1.8 µm. No significant changes in MCL were observed at either time point after LPAL. Left lung volumes and specific compliances were significantly reduced 3 days after LPAL. However, by 14 days after LPAL, lung pressure-volume relationships were not different from controls. These results suggest that severe pulmonary ischemia causes changes in lung mechanics early after LPAL that are reversed by the time a new systemic vasculature is known to perfuse pulmonary capillaries. The LPAL model thus affords a unique opportunity to study lung functional responses to tissue ischemia and subsequent recovery. [ABSTRACT FROM AUTHOR]

: ObjectivesWe investigated the interaction of heart rate (HR), temperature and contractility using a validated load independent method.: BackgroundTemperature manipulation is an integral part of cardiac surgery, and postoperative hypothermia is extremely common. Myocardial contraction is a series of enzymatic and physico-chemical reactions that may be differentially affected by temperature.: MethodsTen patients undergoing coronary artery bypass grafting were studied during moderately hypothermic cardiopulmonary bypass. After conduit procurement and heparinization but before grafting, the patient was placed on cardiopulmonary bypass and rewarmed to 37°C, and the left ventricle (LV) was instrumented with a conductance catheter allowing continuous pressure and volume measurement. The LV pressure volume relationship was examined to assess the contractility at 37, 35, 33 and 31°C, with fixed atrial pacing (100 beats/min) in five patients and at 80 and 120 beats/min, at 33 and 37°C in five patients.: ResultsAt a HR of 100 beats/min, lower temperature resulted in a highly significant decrease in maximal elastance (100% at 37°C, 29 ± 3.5% at 31°C, p < 0.0001). At 37°C, increasing HR increased contractility (80 beats/min 100%, 120 beats/min 205.9%, p = 0.0021); however, at 33°C contractility fell with increasing HR (80 beats/min 100%, 120 beats/min, 53.7%, p = 0.0014).: ConclusionAt normothermia LV contractility has a direct relationship with HR. In hypothermic conditions this relationship inverses. Clinical strategies maintaining higher HRs at colder temperatures result in reduced contractility. These factors are important in the management of cardiac surgical patients. [Copyright &y& Elsevier]

Two methods of rehydrating red pine (Pinus resinosa Ait.) shoots for pressure‐volume (PV) analysis were compared to clarify the effects of rehydration on estimated tissue water relations of shoots and fascicles. The commonly employed cut‐shoot method was compared to rehydration by means of water uptake through the roots of intact plants. Cut‐shoot rehydration and increased duration of rehydration significantly decreased estimates of tissue elasticity and relative water content at zero turgor for both shoots and fascicles. Rehydration of cut shoots for 2 days significantly increased the slope of the linear region of shoot pressure‐volume (PV) curves and decreased estimates of the apoplastic water fraction. Changes in these and estimates of other water relations attributes were correlated with increased initial water content during rehydration. Estimated apoplastic water fraction was higher for needle fascicles than shoots despite the large amount of woody stem tissue contained in shoots. Fascicle water status strongly influenced shoot water relations, in part due to apparent apoplastic loading with water of fascicles during rehydration. [ABSTRACT FROM AUTHOR]

Tissue elasticity can affect plant response to drought, in terms of turgor maintenance and water uptake from drying soils. The purpose of this study was to determine the effect of mycorrhizal colonization and drought acclimation on rose (Rosa hybrida L. cv. Samantha) leaf elasticity. Bulk elasticity was characterized by the pressure-volume method using plots of the elastic modulus as a function of leaf turgor pressure, total water potential and relative water content. The treatments, arranged in a 2 × 3 factorial design, included acclimated and unacclimated plants, and either Glomus intraradices Schenck and Smith, Glomus deserticola Trappe, Bloss and Menge, or a non-mycorrhizal control. Plants with root mycorrhizal colonization showed reduced leaf elasticity (i.e. higher elastic moduli) over a broad range of leaf water potential and water content. Both mycorrhizal colonization and acclimation facilitated the maintenance of positive values of turgor and elasticity at lower leaf water potential and water content than in controls. Mycorrhizal infections may aid plants in acclimating to water deficits through effects on leaf tissue elasticity. [ABSTRACT FROM AUTHOR]

Measures of leaf tissue elasticity were determined by analyzing the turgor pressure-water content relation developed from pressure-volume experiments in four naturally occurring forest tree species. The relation between the bulk tissue elastic modulus and tissue turgor pressure varied by spades and varied with state of leaf maturation through the growing season. Although the values of the elastic modulus reported here agree in magnitude with values reported in general for higher plant tissue, the functional dependency of the apparent elasticity on tissue water status was more complex in this study than can be accounted for by current models. [ABSTRACT FROM AUTHOR]

Using psychrometric pressure-volume analysis, root water relations following drought were characterized in Rosa hybrida L. plants colonized by the vesicular-arbuscular mycorrhizal fungus Glomus intraradices Schenck & Smith. Measurements were also made on uncolonized plants of similar size and adequate phosphorus nutrition. Under well-watered conditions mycorrhizal colonization resulted in lower solute concentrations in root symplasm, and hence lower root turgors. Following drought, however, mycorrhizal roots maintained greater turgor across a range of tissue hydration. This effect was apparently not due to increased osmotic adjustment (osmotic potentials at full turgor were similar in mycorrhizal and non-mycorrhizal roots after drought) or to altered elasticity but to an increased partitioning of water into the symplast. Symplast osmolality at full turgor was similar in mycorrhizal and non-mycorrhizal roots but, because of their higher symplastic water percentages, mycorrhizal roots contained a greater amount of osmotic (symplastic) solutes. Drought-induced changes in osmotic potential were observed only in mycorrhizal roots, where a 0.4 MPa decrease (relative to well-watered controls) brought the full turgor osmotic potential of mycorrhizal roots to the same level as that of non-mycorrhizal roots under either watering treatment. [ABSTRACT FROM AUTHOR]

Left ventricular chamber stiffness is determined by the level of operating pressure and the diastolic pressurevolume relation. This relation is curvilinear and the slope of a tangent to the pressure-volume curve (operative chamber stiffness) increases as the chamber progressively fills. Such preload dependent changes in compliance occur during any acute alteration in ventricular volume. At a given diastolic pressure, operative chamber stiffness is determined by the relative values for ventricular volume and muscle mass and by the stiffness of a unit of myocardium. Thus, there may be a leftward shift of the diastolic pressure-volume curve (increase in the modulus of chamber stiffness) as a consequence of ventricular hypertrophy or an increase in the stiffness of heart muscle itself (increase in the modulus of muscle stiffness). To assess the stiffness of heart muscle, the myocardial stressstrain and stiffness-stress relations must be defined.Although some controversy exists with regard to the stiffness of hypertrophied myocardium, clinical studies suggest that chamber stiffness and myocardial stiffness can be normal or increased in the presence of left ventricular hypertrophy. These studies also suggest that increased myocardial stiffness develops in the presence of increased interstitial fibrosis. Moreover, isolated cardiac muscle experiments indicate that the increase in myocardial stiffness can be prevented when the connective tissue response is prevented.Quantitative measures of left ventricular chamber and myocardial stiffness contribute to the understanding of the pathophysiology of cardiac dyspnea and provide insight into functional and structural defects of hypertrophied myocardium. [ABSTRACT FROM PUBLISHER]

Simple Summary: Cardiotoxicity is a serious side effect of doxorubicin in cancer patients due to the risk of development of heart failure. Early detection of doxorubicin-induced cardiomyopa-thy (DXR-ICM) has become a major objective to reduce heart failure in cancer patients. Echocar-diography is the gold standard method to diagnose cardiac diseases when cardiac dysfunction is prominent; however, it still cannot predict or early diagnose heart failure before functional de-cline. The intraventricular blood flow is characterized by intraventricular pressure gradients (IVPG) that created due to the suction of blood by the ventricles. Currently, advanced imaging techniques allow non-invasive assessment of IVPG from color M-mode echocardiography (CMME) after image processing for the clinical setting. Studies revealed that IVPG indices are promising for the early diagnosis of cardiac dysfunction. In this study, we aimed to investigate the usefulness of IVPG to detect cardiac function changes after DXR administration in dogs. Early detection of doxorubicin (DXR)-induced cardiomyopathy (DXR-ICM) is crucial to improve cancer patient outcomes and survival. In recent years, the intraventricular pressure gradient (IVPG) has been a breakthrough as a sensitive index to assess cardiac function. This study aimed to evaluate the usefulness of IVPG for the early detection of chemotherapy-related cardiac dysfunction. For this purpose, six dogs underwent conventional, speckle tracking, and color M-mode echocardiography concomitantly with pressure-and-volume analysis by conductance catheter. The cardiac function measurements were assessed before DXR administration (baseline, Pre), at the end of treatment protocol (Post), and at 1.5 years follow-up (Post2). The result showed a significant reduction in the left ventricular end-systolic pressure-volume (Emax: 4.4 ± 0.7, 6.1 ± 1.6 vs. 8.4 ± 0.8 mmHg/mL), total-IVPG (0.59 ± 0.12, 0.62 ± 0.15 vs. 0.86 ± 0.12 mmHg), and mid-IVPG (0.28 ± 0.12, 0.31 ± 0.11 vs. 0.48 ± 0.08 mmHg), respectively in Post2 and Post compared with the baseline (p < 0.05). Mid-to-apical IVPG was also reduced in Post2 compared with the baseline (0.29 ± 0.13 vs. 0.51 ± 0.11). Meanwhile, the fraction shortening, ejection fraction, and longitudinal strain revealed no change between groups. Total and mid-IVPG were significantly correlated with Emax (R = 0.49; p < 0.05, both) but only mid-IVPG was a predictor for Emax (R2 = 0.238, p = 0.040). In conclusion, this study revealed that impairment of contractility was the initial changes observed with DXR-ICM in dogs and only IVPG could noninvasively detect subclinical alterations in cardiac function. Color M-mode echocardiography-derived IVPG could be a potential marker for the early detection of doxorubicin cardiomyopathy. [ABSTRACT FROM AUTHOR]