PO2 Values Research Articles

Reappraisal of systemic venous chemoreceptors: might they explain the matching of breathing to metabolic rate in humans?

What is the topic of this review? One of the major unanswered questions in physiology is that of how breathing matches metabolic rate. Venous chemoreceptors seem to have been dismissed since the 1960s. What advances does it highlight? New evidence shows that their apparent dismissal needs reappraisal. The paper on which this depends has more than one interpretation, and another paper obtained the opposite result. Previous search ignored all locations between skeletal muscle and the right heart. Oxygen sensors other than the arterial chemoreceptors do exist. Heymans and colleagues originally demonstrated some residual breathing response to hypoxia in sino-aortically denervated animals. Similar results occur in humans. One of the major unanswered questions in physiology is that of how breathing matches metabolic rate. The existence in humans of venous chemoreceptors that might control breathing seems to have been dismissed since the 1960s. New evidence has emerged showing that this apparent dismissal needs reappraisal. First, the paper in humans on which this depends has more than one interpretation. Moreover, a previous paper obtained the opposite result and is not cited. Secondly, previous search for venous chemoreceptors failed to examine all venous locations between skeletal muscle and the right heart and lungs. Thirdly, oxygen sensors other than the arterial chemoreceptors do exist. Heymans himself originally demonstrated some residual breathing response to hypoxia in sino-aortically denervated animals. Others confirm a residual breathing response to hypoxia in mammals, including humans. There is now considerable interest in the importance of afferent feedback in controlling the cardiovascular and respiratory systems. Moreover, it is now clear that arterial, aortic and central chemoreceptors have no role in explaining how breathing matches metabolic rate during exercise. These together provide a timely reminder that venous chemoreceptors remain ideal candidates still to be considered as metabolic rate sensors to explain matching in humans. Firstly, this is because venous PO2 and PCO2 values do change appropriately in proportion to metabolic rate, so a metabolic rate signal sufficient to drive breathing might already exist. Secondly, chemoreceptor-like anatomical structures are present in the systemic venous system but remain unexplored. Finally, no extant experimental evidence precludes their existence.

Influence of oxygen availability on the metabolism and morphology of Yarrowia lipolytica: insights into the impact of glucose levels on dimorphism.

Dynamic behavior of Yarrowia lipolytica W29 strain under conditions of fluctuating, low, and limited oxygen supply was characterized in batch and glucose-limited chemostat cultures. In batch cultures, transient oscillations between oxygen-rich and -deprived environments induced a slight citric acid accumulation (lower than 29mgL-1). By contrast, no citric acid was detected in continuous fermentations for all stress conditions: full anoxia (zero pO2 value, 100% N2), limited (zero pO2 value, 75% of cell needs), and low (pO2 close to 2%) dissolved oxygen (DO) levels. The macroscopic behavior (kinetic parameters, yields, viability) of Y. lipolytica was not significantly affected by the exposure to DO fluctuations under both modes of culture. Nevertheless, conditions of oxygen limitation resulted in the destabilization of the glucose-limited growth during the continuous cultivations. Morphological responses of Y. lipolytica to DO oscillations were different between batch and chemostat runs. Indeed, a yeast-to-mycelium transition was induced and progressively intensified during the batch fermentations (filamentous subpopulation reaching 74% (v/v)). While, in chemostat bioreactors, the culture consisted mainly of yeast-like cells (mean diameter not exceeding 5.7μm) with a normal size distribution. During the continuous cultures, growth at low DO concentration did not induce any changes in Y. lipolytica morphology. Dimorphism (up to 80.5% (v/v) of filaments) was only detected under conditions of oxygen limitation in the presence of a residual glucose excess (more than 0.75gL-1). These data suggest an impact of glucose levels on the signaling pathways regulating dimorphic responses in Y. lipolytica.

Power Dissipation and Power Number Correlations for a Retreat-Blade Impeller under Different Baffling Conditions

Glass-lined tanks/reactors provided with a torispherical (dish) bottom and equipped with a retreat-blade impeller (RBI) are commonly used in the industrial syntheses of Active Pharmaceutical Ingredients (APIs). The power, P, dissipated by the RBI in the liquid in the tank is critical to many mixing processes, especially since the power per unit liquid volume, P/V, controls many mixing phenomena. Despite their common industrial use, limited information on P for RBIs and the corresponding nondimensional Power number, Po, is available. Here, P values for an RBI in liquids of very different viscosities at different agitation speeds and for different baffling configurations, i.e., unbaffled, partially baffled (with a single “beavertail” baffle), and fully baffled (four rectangular baffles), were measured experimentally in a scaled-down version of a typical reactor for API synthesis. The corresponding Po values were obtained for a large range of the Reynolds number, Re (1 < Re < 400,000). Po was found to vary s...

Noninvasive Absolute Electron Paramagnetic Resonance Oxygen Imaging for the Assessment of Tissue Graft Oxygenation

Oxygen is the single most important molecule for sustaining life and, therefore, an important variable in tissue engineering and regenerative medicine. It has been shown that the change in oxygen concentration in an artificial or tissue-engineered graft affects cell survival, differentiation, and tissue growth in profound ways. However, at present, there are no reliable methods to map partial oxygen pressure (pO2) in growing artificial tissues. Here, we adapt and test the suitability of electron paramagnetic resonance oxygen imaging (EPROI) in assessing tissue graft oxygenation in vitro. EPROI is an established method to assess absolute pO2 and has been widely applied to study tumor hypoxia in small animals. In this study, we demonstrate the feasibility of EPROI in evaluating oxygen dynamics in tissue grafts. We measured oxygen concentration in mesenchymal stem cell (MSC)-seeded polylactic-co-glycolic acid (PLGA) scaffolds with variable porosity. The pO2 maps of these scaffolds showed that the mean pO2 inside the scaffolds was smaller than the ambient air pO2 (21% oxygen, 160 torr) and was gradually increased with increasing pore size. We assessed the local oxygen dynamics of the MSC-seeded osteogenic scaffold made from collagen-chitosan hydrogels in a partially sealed Eppendorf tube. The change in pO2 values as a function of time inside the graft showed that the cells had used available oxygen within first 2 h of the experiment and then went to a dormant low oxygen consumption state until the oxygen supply was reestablished. Collectively, these data suggest that EPROI could be successfully used for mapping pO2 in tissue-engineered grafts. The knowledge of tissue graft oxygenation may be used to improve scaffold design and to assess the tissue viability and growth.

An innovative intermittent hypoxia model for cell cultures allowing fast Po2 oscillations with minimal gas consumption.

Performing hypoxia-reoxygenation cycles in cell culture with a cycle duration accurately reflecting what occurs in obstructive sleep apnea (OSA) patients is a difficult but crucial technical challenge. Our goal was to develop a novel device to expose multiple cell culture dishes to intermittent hypoxia (IH) cycles relevant to OSA with limited gas consumption. With gas flows as low as 200 ml/min, our combination of plate holders with gas-permeable cultureware generates rapid normoxia-hypoxia cycles. Cycles alternating 1 min at 20% O2 followed by 1 min at 2% O2 resulted in Po2 values ranging from 124 to 44 mmHg. Extending hypoxic and normoxic phases to 10 min allowed Po2 variations from 120 to 25 mmHg. The volume of culture medium or the presence of cells only modestly affected the Po2 variations. In contrast, the nadir of the hypoxia phase increased when measured at different heights above the membrane. We validated the physiological relevance of this model by showing that hypoxia inducible factor-1α expression was significantly increased by IH exposure in human aortic endothelial cells, murine breast carcinoma (4T1) cells as well as in a blood-brain barrier model (2.5-, 1.5-, and 6-fold increases, respectively). In conclusion, we have established a new device to perform rapid intermittent hypoxia cycles in cell cultures, with minimal gas consumption and the possibility to expose several culture dishes simultaneously. This device will allow functional studies of the consequences of IH and deciphering of the molecular biology of IH at the cellular level using oxygen cycles that are clinically relevant to OSA.

Thermodynamic stability, oxygen content, defect structure and related properties of YBaCo4 − xZnxO7 + δ (x = 0–3) oxides

Oxygen nonstoichiometry and thermodynamic stability of Zn–doped YBaCo4−xZnxO7+δ oxides were investigated by solid state coulometric titration and EMF-method, respectively. As a result, significant zinc doping was shown to increase the stability of YBaCo4−xZnxO7+δ oxides in oxidizing atmosphere. However enrichment of YBaCo4−xZnxO7+δ oxides by zinc results in increasing their reducibility since the low pO2 stability limit shifts towards higher pO2 values upon doping. Substitution of zinc for cobalt in YBaCo4−xZnxO7+δ oxides was also found to narrow their oxygen homogeneity region. Total conductivity and Seebeck coefficient of YBaCo4−xZnxO7+δ oxides were measured simultaneously using 4-probe dc-method. The defect structure of YBaCo4−xZnxO7+δ oxides was successfully analysed using Kröger-Vink approach. The data on oxygen nonstoichiometry, total conductivity and Seebeck coefficient of the thermodynamically stable YBaCo4−xZnxO7+δ (x=0, 1) oxides were found to be quite consistent with the proposed model of their defect structure.

Seasonal and maternal effects on acid-base, l-lactate, electrolyte, and hematological status of 205 dairy calves born to eutocic dams

In this study, we used linear mixed models to determine the effects of season, time of sampling relative to birth (factors), duration of the delivery process, duration of maternal grooming, calf body weight (BW) at birth, and time of day (covariates) on values of venous blood gas, acid-base and electrolyte parameters, and l-lactate concentrations in dairy calves born to eutocic dams in summer (SUM, n = 101) and winter (WIN, n = 104). Neonatal vitality was assessed at 0, 1, and 24 h after delivery in a linear scoring system using muscle tone, erection of the head, muscle reflexes, heart rate, and sucking drive as criteria. Simultaneously with vitality scoring, venous blood samples were collected by jugular venipuncture. Blood was tested for pH, partial pressure of CO2 (pCO2; mmHg) and oxygen (pO2; mmHg), l-lactate (mmol/L), hemoglobin (Hb; g/L), ionized calcium (Ca2+; mmol/L), sodium (Na+; mmol/L), potassium (K+; mmol/L) and chloride (Cl-; mmol/L). Bicarbonate (HCO3-; mmol/L), base excess (BE; mmol/L), total carbon dioxide (TCO2; mmol/L), and anion gap (mmol/L) were calculated. Electrolyte parameters were affected by none of the factors or covariates. Time of day at birth did not affect any of the parameters of interest. Vitality score tended to increase over time and it showed higher values in WIN calves than in SUM calves. Concentrations of HCO3-, BE, and l-lactate indicated a higher degree of metabolic acidosis in SUM calves; however, pH was not affected by season. Concentrations of Hb were higher in SUM calves than in WIN calves; however, covariates did not affect Hb concentrations. Blood pH, concentrations of pO2, HCO3-, and BE decreased, whereas l-lactate concentrations and values of pCO2, TCO2, and anion gap increased with longer duration of delivery. A shift in acid-base balance was also linked to BW of the calf at birth, with lower values of blood pH, HCO3-, and BE in calves with higher BW compared with those with lower BW at birth, whereas TCO2 and l-lactate concentrations increased with higher calf BW at birth. Values of pO2 increased and pCO2 decreased with longer duration of maternal grooming. Blood pH, HCO3-, and BE increased, whereas l-lactate concentrations and anion gap decreased with longer duration of licking the calf. Our results indicate that prolonged delivery can impair acid-base status and can cause slight lactic acidosis, even in calves born from spontaneous or eutocic calvings, and that high BW at birth predisposes calves to acidosis. The positive effect of maternal grooming on neonatal acid-base status should be considered in parturition management. Season, duration of the delivery process, calf BW at birth, and duration of maternal grooming are recommended for consideration in future studies on blood gas and acid-base parameters in dairy calves in the immediate neonatal period.

Assessing Passeriformes health in South Texas via select venous analytes.

The handheld point of care analyzer is a quick and feasible option to obtain hematology data from individuals. The iSTAT-1® was used to evaluate select venous blood analytes obtained via jugular venipuncture from 238 passerine birds from South Texas. These data were used to assess the health of birds in the area while taking into consideration life history (migratory or sedentary), locale, seasonality, sex, and age. We attributed increased values of pO2 and hematocrit, in addition to hemoglobin and glucose concentrations of migratory birds compared to sedentary birds as the increased need of oxygen carrying capacity and energy for long duration flights. Increased glucose and lower ionized calcium concentrations were observed in migratory birds likely based on breakdown of fat deposits in the body to fuel the muscular endurance of migration. During the hotter months of the year, birds' responses to handling were exhibited by relative respiratory acidosis. When sedentary birds sampled from South Texas were compared to a previous study from Central Texas, venous blood analytes differed by locale but were within the ranges of healthy populations. These findings lead us to conclude that sedentary avian communities can be used as ecosystem bioindicators.

Examination of the Relationship between Umbilical Cord Blood Gas Values and Hearing Function in Neonates.

The aim of the present study was to examine the relationship between the results of the transient otoacoustic emission (TEOAE) test used in neonatal hearing screening and the results of the umbilical cord blood (UCB) analysis in neonates. This retrospective study included 209 neonates born in the obstetric unit at the 37th gestational week. Based on the results of the TEOAE test, the neonates included in the study were divided into two groups as the study group composed of those "REFER" (n=141) and the control group consisting those "PASS" (n=68) the test. The UCB sampling procedure was performed on all neonates. In the blood samples, the pH parameters were evaluated by using glass electrodes, and the pCO2 and pO2 parameters were evaluated directly by using sensitive electrodes. When the additional maternal diseases were compared with the TEOAE results, the ratio of hypothyroidism was found to be statistically higher in the study group (p<0.05). In terms of the pO2, pCO2, HCO3, and pH values obtained as a result of analyzing the UCB samples, there was no statistically significant difference between the groups (p>0.05). The results of the present study showed that there was no statistically significant difference between the results of UCB analysis and the TEOAE test. However, we believe that conducting a larger study evaluating other parameters and employing UCB analysis would be useful, and UCB evaluation, which is an inexpensive, easy and effective method in determining hypoxia in neonates, might be a significant marker in cases at risk of hearing loss.

Peningkatan mutu blanket karet alam melalui proses predrying dan penyemprotan asap cair

Most of Indonesian rubber products SIR 20 are made from the material of raw rubber obtained from smallholders. However, the quality of this material is not good enough. Thus, quality improvement has to be carried out by manufacturers. The liquid smoke used during the blanket hanging process can improve the quality of the rubber products SIR 20. This research aimed to determine and study the effects of liquid smoke spraying and blanket-hanging duration on the drying factor, the dry rubber content, technical quality, vulcanization characteristics, and physical properties of vulcanized natural rubber. Treatments consisted of various hanging duration (6, 8, and 10 days, and without hanging) and spraying (with and without spraying of liquid smoke). The results showed that the spraying of liquid smoke on natural rubber blankets could improve the technical quality of the natural rubber, especially the values of Po and PRI. The spraying of liquid smoke could reduce the blanket hanging duration to 6-8 days. The blankets sprayed with liquid smoke had the optimum cure time of around 15 minutes and 19 seconds and the scorch time of around 3 minutes and 22 seconds. These values indicated that the vulcanization characteristics of blankets which were sprayed with liquid smoke were generally better than those of blankets which were not sprayed with liquid smoke. Keywords: liquid smoke, natural rubber, blanket quality, hanging.

Preoperative evaluation of bone quality for dental implantation using an ultrasound axial transmission device in an ex vivo model.

This study investigated the clinical utility of an ultrasound axial transmission device in preoperative evaluation of bone quality for dental implantation, by clarifying the relationship between cortical bone speed of sound (cSOS), insertion torque values (ITV), and implant stability quotient (ISQ) in porcine femur bone. Eleven fresh porcine femurs, without soft tissue, were prepared. The cSOS of these bones were measured using the axial transmission device. Bone mineral density (BMD) and porosity (Po) were measured in cortical bone samples obtained from the region of ultrasound measurements by X‐ray microcomputed tomography. Thirty‐three implants were inserted into these samples (three implants per bone sample), and ITV and ISQ were measured for all implants. Then, cortical bone thickness (CbTh) of the area for implantation was measured for all implants using a micrometer. The mean cSOS was 3962 m/s; mean BMD and Po were 0.822 g/cm2 and 0.185%, respectively. cSOS and BMD values were positively correlated, and cSOS values and Po values were negatively correlated. Mean ITV, ISQ, and CbTh were 37.95 Ncm, 71.172, and 2.869 mm, respectively. There was a positive correlation between cSOS values and ISQ values. The cSOS of each bone did not correlate with ITV for all of the bone samples. However, when the CbTh ranges from 3.0 to 3.5 mm, ITV are correlated with cSOS. These findings suggest that cSOS, which reflects the cortical bone quality, may be clinical utility as a preoperative diagnosis of the implant.

Dynamic EPR Oximetry of Changes in Intracerebral Oxygen Tension During Induced Thromboembolism.

Cerebral tissue oxygenation (oxygen tension, pO2) is a critical parameter that is closely linked to brain metabolism, function, and pathophysiology. In this work, we have used electron paramagnetic resonance oximetry with a deep-tissue multi-site oxygen-sensing probe, called implantable resonator, to monitor temporal changes in cerebral pO2 simultaneously at four sites in a rabbit model of ischemic stroke induced by embolic clot. The pO2 values in healthy brain were not significantly different among the four sites measured over a period of 4 weeks. During exposure to 15% O2 (hypoxia), a sudden and significant decrease in pO2 was observed in all four sites. On the other hand, brief exposure to breathing carbogen gas (95% O2 + 5% CO2) showed a significant increase in the cerebral pO2 from baseline value. During ischemic stroke, induced by embolic clot in the left brain, a significant decline in the pO2 of the left cortex (ischemic core) was observed without any change in the contralateral sites. While the pO2 in the non-infarct regions returned to baseline at 24-h post-stroke, pO2 in the infarct core was consistently lower compared to the baseline and other regions of the brain. The results demonstrated that electron paramagnetic resonance oximetry with the implantable resonator can repeatedly and simultaneously report temporal changes in cerebral pO2 at multiple sites. This oximetry approach can be used to develop interventions to rescue hypoxic/ischemic tissue by modulating cerebral pO2 during hypoxic and stroke injury.

Quantification of Tumor Hypoxic Fractions Using Positron Emission Tomography with [18F]Fluoromisonidazole ([18F]FMISO) Kinetic Analysis and Invasive Oxygen Measurements

The purpose of this study is to use dynamic [18F]fluoromisonidazole ([18F]FMISO) positron emission tomography (PET) to compare estimates of tumor hypoxic fractions (HFs) derived by tracer kinetic modeling, tissue-to-blood ratios (TBR), and independent oxygen (pO2) measurements. BALB/c mice with EMT6 subcutaneous tumors were selected for PET imaging and invasive pO2 measurements. Data from 120-min dynamic [18F]FMISO scans were fit to two-compartment irreversible three rate constant (K 1, k 2, k 3) and Patlak models (K i). Tumor HFs were calculated and compared using K i, k 3, TBR, and pO2 values. The clinical impact of each method was evaluated on [18F]FMISO scans for three non-small cell lung cancer (NSCLC) radiotherapy patients. HFs defined by TBR (≥1.2, ≥1.3, and ≥1.4) ranged from 2 to 85% of absolute tumor volume. HFs defined by K i (>0.004mlmincm-3) and k 3 (>0.008min-1) varied from 9 to 85%. HF quantification was highly dependent on metric (TBR, k 3, or K i) and threshold. HFs quantified on human [18F]FMISO scans varied from 38 to 67, 0 to 14, and 0.1 to 27%, for each patient, respectively, using TBR, k 3, and K i metrics. [18F]FMISO PET imaging metric choice and threshold impacts hypoxia quantification reliability. Our results suggest that tracer kinetic modeling has the potential to improve hypoxia quantification clinically as it may provide a stronger correlation with direct pO2 measurements.

Determination of oxygen nonstoichiometry in SrFeO3−δ by solid‐state Coulometric titration

AbstractThe oxygen nonstoichiometry of SrFeO3−δ was determined by solid‐state Coulometric titration at 750°C‐1040°C and 10−18≤pO2(atm)≤0.5. At T≤850°C, a hysteresis in the oxygen nonstoichiometry (δ) isotherms indicates the presence of a two‐phase region corresponding to a mixture of a perovskite and an oxygen vacancy ordered phase. The variation of δ with temperature at fixed pO2 values and the variation of log(pO2) with reciprocal temperature at fixed δ are reported. The pO2 at the p‐n transition in the electrical conductivity increases as the temperature increases, and the transition in the conductivity isotherm occurs at a composition of SrFeO2.505(1) at 950°C and SrFeO2.508(1) at 900°C. Since strontium exclusively occupies the A‐site, a simple point defect model that assumes noninteracting defects can describe the isotherms but only at 1040°C; nonideal behavior is observed at lower temperatures. The partial molar thermodynamic quantities for oxygen in SrFeO3−δ were determined.

Comparison and Agreement between Venous and Arterial Blood Gas Values for pH, pCO2, pO2, Bicarbonate and Oxygen Saturation in Patients with Acute Respiratory Illnesses

Comparison and Agreement between Venous and Arterial Blood Gas Values for pH, pCO2, pO2, Bicarbonate and Oxygen Saturation in Patients with Acute Respiratory Illnesses

Biochemical responses and physical performance during high-intensity resistance circuit training in hypoxia and normoxia.

The aim of this study was to analyze the effect of hypoxia on metabolic and acid-base balance, blood oxygenation, electrolyte, and half-squat performance variables during high-resistance circuit (HRC) training. Twelve resistance-trained subjects participated in this study. After a 6RM testing session, participants performed three randomized trials of HRC: normoxia (NORM: FiO2 = 0.21), moderate hypoxia (MH: FiO2 = 0.16), or high hypoxia (HH: FiO2 = 0.13), separated by 72h of recovery in normoxic conditions. HRC consisted of two blocks of three exercises (Block 1: bench press, deadlift and elbow flexion; Block 2: half-squat, triceps extension, and ankle extension). Each exercise was performed at 6RM. Rest periods lasted for 35 s between exercises, 3 min between sets, and 5 min between blocks. Peak and mean force and power were determined during half-squat. Metabolic, acid-base balance, blood oxygenation and electrolyte variables, arterial oxygen saturation (SaO2), and rating of perceived exertion (RPE) were measured following each block. During the first set, peak force and power were significantly lower in HH than MH and NORM; whereas in the second set, mean and peak force and power were significantly lower in HH than NORM. At the end of the HRC training session, blood lactate and RPE in HH were significantly higher than in MH and NORM. SaO2, pH, HCO3-, and pO2 values were significantly lower in all hypoxic conditions than in NORM. These results indicate that simulated hypoxia during HRC exercise reduce blood oxygenation, pH, and HCO3-, and increased blood lactate ultimately decreasing muscular performance.

Defining the hypoxic target volume based on positron emission tomography for image guided radiotherapy – the influence of the choice of the reference region and conversion function

Background: Hypoxia imaged by positron emission tomography (PET) is a potential target for optimization in radiotherapy. However, the implementation of this approach with respect to the conversion of intensities in the images into oxygenation and radiosensitivity maps is not straightforward. This study investigated the feasibility of applying two conversion approaches previously derived for 18F-labeled fluoromisonidazole (18F-FMISO)-PET images for the hypoxia tracer 18F-flortanidazole (18F-HX4).Material and methods: Ten non-small-cell lung cancer patients imaged with 18F-HX4 before the start of radiotherapy were considered in this study. PET image uptake was normalized to a well-oxygenated reference region and subsequently linear and non-linear conversions were used to determine tissue oxygenations maps. These were subsequently used to delineate hypoxic volumes based partial oxygen pressure (pO2) thresholds. The results were compared to hypoxic volumes segmented using a tissue-to-background ratio of 1.4 for 18F-HX4 uptake.Results: While the linear conversion function was not found to result in realistic oxygenation maps, the non-linear function resulted in reasonably sized sub-volumes in good agreement with uptake-based segmented volumes for a limited range of pO2 thresholds. However, the pO2 values corresponding to this range were significantly higher than what is normally considered as hypoxia. The similarity in size, shape, and relative location between uptake-based sub-volumes and volumes based on the conversion to pO2 suggests that the relationship between uptake and pO2 is similar for 18F-FMISO and 18F-HX4, but that the model parameters need to be adjusted for the latter.Conclusions: A non-linear conversion function between uptake and oxygen partial pressure for 18F-FMISO-PET could be applied to 18F-HX4 images to delineate hypoxic sub-volumes of similar size, shape, and relative location as based directly on the uptake. In order to apply the model for e.g., dose-painting, new parameters need to be derived for the accurate calculation of dose-modifying factors for this tracer.

Effect of Graft Weight to Recipient Body Weight Ratio on Hemodynamic and Metabolic Parameters in Pediatric Liver Transplant: A Retrospective Analysis.

To analyze how graft-weight-to-bodyweight ratio in pediatric liver transplant affects intraoperative and early postoperative hemodynamic and metabolic parameters. We reviewed data from 130 children who underwent liver transplant between 2005 and 2015. Recipients were divided into 2 groups: those with a graft weight to body weight ratio > 4% (large for size) and those with a ratio ≤ 4% (normal for size). Data included demographics, preoperative laboratory findings, intraoperative metabolic and hemodynamic parameters, and intensive care follow-up parameters. Patients in the large-graft-for-size group (>4%) received more colloid solution (57.7 ± 20.1 mL/kg vs 45.1 ± 21.9 mL/kg; P = .08) and higher doses of furosemide (0.7 ± 0.6 mg/kg vs 0.4 ± 0.7 mg/kg; P = .018). They had lower mean pH (7.1 ± 0.1 vs 7.2 ± 0.1; P = .004) and PO2 (115.4 ± 44.6 mm Hg vs 147.6 ± 49.3 mm Hg; P = .004) values, higher blood glucose values (352.8 ± 96.9 mg/dL vs 262.8 ± 88.2 mg/dL; P < .001), and lower mean body temperature (34.8 ± 0.7°C vs 35.2 ± 0.6°C; P = .016) during the neohepatic phase. They received more blood transfusions during both the anhepatic (30.3 ± 24.3 mL/kg vs 18.8 ± 21.8 mL/kg; P = .013) and neohepatic (17.7 ± 20.4 mL/kg vs 10.3 ± 15.5 mL/kg; P = .031) phases and more fresh frozen plasma (13.6 ± 17.6 mL/kg vs 6.2 ± 10.2 mL/kg; P = .012) during the neohepatic phase. They also were more likely to be hypotensive (P < .05) and to receive norepinephrine infusion more often (44% vs 22%; P < .05) intraoperatively. More patients in this group were mechanically ventilated in the intensive care unit (56% vs 31%; P = .035). There were no significant differences between the groups in postoperative acute renal dysfunction, graft rejection or loss, infections, length of intensive care stay, and mortality (P > .05). High graft weight-to-body-weight ratio is associated with adverse metabolic and hemodynamic changes during the intraoperative and early postoperative periods. These results emphasize the importance of using an appropriately sized graft in liver transplant.

The Human Erythrocyte Mechano Activated K+ Channel A (HEMKCA) a Partial Characterization of Conductance, Selectivity and Open Probability

Human Erythrocytes (HE) have a lifespan of 120 days, the control of this process has proven to be very rigorous. As the HE lacks nucleus and organelles, its lifespan is not controlled by a phenomena associated to classic apoptosis. How this process is controlled it's still under discussion: it's been proposed that this process is related to the fact that the membranes of these cells undergo a mechanical stress during microcirculation. Using the patch clamp technique we have characterized a K+ channel, which shows a sigmoid dependence of open probability (Po) on applied pressure, a mean conductance of 24 pS and is [Ca2+]i modulated; and we have proposed that this channel is the mechanical sensor that connects the mechanical stress on the cyclic passage through the capillaries with the process of senescence. We denominate this channel as: Human Erythrocyte Mechano-activated K+ Channel A (HEMKCA). Here we reviewed the behavior of this channel as an inward rectifier and the permeability of several ions. We study the selectivity in symmetrical conditions for K+, Rb+, Na+, Li+ and Cs+. In this condition we were unable to measure any conductance for Na+, Li+ or Cs+ through the channel. However, we determined that the conductance of HEMKCA for Rb+ is 0.59 times the conductance for K+. We also determined the selectivity sequence for these ions under bi-ionic conditions (PK/PX) with the test ion on the extracellular side: K+(1)>Rb+(1,49)>Cs+(16,36)>Li+(22,53)>Na+(34,95); and with the test ion on the intracellular side: K+(1)>Rb+(2,05)>Cs+(5,14)>Na+(11,89)> Li+(25,39). Finally we studied the effect of membrane potential on the channel's Po, and it was obtained that at negative membrane potentials the Po values are significantly higher than at positive potentials under the same experimental condition.

THE LAWS OF CAVITATION EROSION OF CONSTRUCTION MATERIALS

Objectives . The aim of the research is to find ways to use cavitation effects in the creation of new technologies and means of applying unique opportunities arising under conditions of developed bubble cavitation. Erosive destruction of concrete caused by a submerged cavitation jet is experimentally investigated in the present work in order to reveal the regularities of the extent of damage under different flow regimes. Methods. The tests were carried out using an specially constructed experimental bench, containing a receiving tank from which water was supplied to the plunger pump with an electric motor and pumped through a high-pressure hose into the cavitator. The criteria for assessing the intensity of cavitation impact were the dependence of the erosion zone depth on the test time and the relative distance to the cavitator's cut-off e for different values of the inlet pressure Po. Results. Experimental dependences and the analytical function of erosion penetration rate over time, as well as the relative distance between the sample and the cavitator's cut-off, obtained using the regression analysis method, are presented. For the selected parameters of jet flow, the optimum distance from the surface to be destroyed to the cavitator lies across the range of (10-40) e and reaches maximum effect across the pressure interval of 2.5-12.5 MPa on the average for 30 seconds. The relationship between the depth and the erosion penetration rate for given pressure parameters P0, the back pressure Pto, the distance from the cavitator's cut-off to the surface, as well as the cavitator's diameter, correspond to the maximum erosive effect of cavitation. Conclusion. The study of cavitation erosion opens up wide possibilities for estimating the service life of hydrotechnical facilities under the active influence of submerged cavitation jets. By varying the parameters of jet flow, it is possible to obtain a different intensity of erosive destruction of material for the application of this phenomenon in the purification and crushing of concrete.