Tissue-blood Partition Coefficient Research Articles

What contributes to the metal-specific partitioning in the chub-acanthocephalan system?

Physiologically based pharmacokinetic (PBPK) models have been applied to simulate the absorption, distribution, metabolism, and elimination of various toxicants in fish. This approach allows for considering metal accumulation in intestinal parasites. Unlike "semi" physiologically-based models developed for metals, metal accumulation in fish was characterised based on metal-specific parameters (the fraction in blood plasma and the tissue-blood partition coefficient) and physiological characteristics of the fish (the blood flow and the tissue weight) in our PBPK model. In the model, intestinal parasites were considered a sink of metals from the host intestine. The model was calibrated with data for the system of the chub Squalius cephalus and the acanthocephalan Pomphorhynchus tereticolliis. Metal concentrations in this fish-parasite system were monitored in Ag and Co treatments in duplicate during a 48-day exposure phase (Ag and Co were added to tap water at concentrations of 1 and 2µg/L, respectively) and a 51-day depuration phase. Their concentrations in the gills increased during the exposure phase and decreased in the depuration phase. A similar pattern was observed for Ag concentrations in other chub organs, while a relatively stable pattern for Co indicates regulations in the accumulation of essential metals by chubs. The metals were taken up by the acanthocephalans at similar rate constants. These results indicate that metal availability to parasites, which is determined by the internal distribution and fate, is critical to metal accumulation in the acanthocephalans. The high concentration of Ag in the liver as well as the high rate of Ag excretion from the liver to the intestine might contribute to higher concentrations of metals in the bile complexes in the intestine, which are available to the parasites, but not to the reabsorption by the host intestine. The opposite pattern might explain the lower availability of Co to the acanthocephalans.

Respirable aerosol exposures of nicotine dry powder formulations to in vitro, ex vivo, and in vivo pre-clinical models demonstrate consistency of pharmacokinetic profiles

Background: Nicotine, because of its volatility, has a complex dosimetry following inhalation as a vapor/aerosol mix. To better control the dosimetry, nicotine could be formulated with a suitable dry powder excipient for use in a clinical inhaler.Aim and Methods: The aim of this study was to investigate the pharmacokinetic PK profile of two dry powder formulations containing 2.5% or 5% nicotine using three experimental models associated to the PreciseInhale™ aerosolization system: the in vitro DissolvIt dissolution system; the ex vivo isolated, ventilated, and perfused lung (IPL) of the rat; and the in vivo intratracheally intubated rat. Results and Discussion: Following exposure, both nicotine formulations had very rapid and similar dissolution and absorption kinetics in both the DissolvIt and IPL exposure models, with an initial half-time of absorption to the single-pass perfusate of 34 and 72 seconds, respectively. In the intratracheally intubated rat, following a rapid initial equilibration between the lungs and systemic compartments, nicotine had a systemic elimination half-time of 2.3–2.4 hours for both formulations. The rapid pulmonary PK of nicotine was likely close to the theoretical equilibration of a low-binding substance with a tissue-blood partition coefficient close to 1. Conclusions: The data generated with the three experimental models provided a comprehensive picture of the inhalation PK of the two nicotine formulations. In particular, the results showed a very rapid dissolution and absorption of the two nicotine formulations and these results could be highly useful for improving the design and calibration of physiologically based PK models to produce more robust predictions. Abbreviations: AED: animal equivalent dose; BW: body weight; HPLC: high-performance liquid chromatography; IPL: isolated, ventilated, and perfused lung; PK: pharmacokinetics; SEM: scanning electron microscopy; USP: United States Pharmacopeia.

Myocardial Partition Coefficient of Gadolinium: A Pilot Study in Patients With Acute Myocarditis, Chronic Myocardial Infarction, and in Healthy Volunteers

BackgroundThe tissue-blood partition coefficient (PC) of gadolinium, derived from T1 measurements, reflects myocardial connective tissue fraction and tissue injury, increasing in proportion with edema or fibrosis. We determined the myocardial PC of gadolinium in patients with acute myocarditis, chronic myocardial infarction (MI), and healthy volunteers. We hypothesized that the characteristics of the injured myocardium in patients with MI and myocarditis may differ and that the PC will be higher in chronically injured myocardium (MI) compared with acutely injured myocardium (myocarditis). MethodsWe performed late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) imaging and T1 mapping before and after administration of gadolinium (0.1 mmol/kg Gd-BOPTA) at 3 Tesla in 10 healthy volunteers (47.1 ± 12.4 years), 18 patients with chronic MI (62.5 ± 8.1 years), and 16 patients with acute myocarditis (42.5 ± 13.9 years). ResultsIn patients with chronic MI and focal scar by LGE, the whole left ventricular myocardial PC (0.45 ± 0.05) was higher compared with patients with MI without focal scar (0.39 ± 0.03, P = 0.02) but not significantly different from whole myocardial PC in volunteers (0.40 ± 0.05) or patients with myocarditis (0.41 ± 0.05). The PC in myocarditis scars was lower than in chronic MI scars (0.60 ± 0.12 vs 0.77 ± 0.16, P = 0.016). The relationships of PC and scar burden, expressed as % LGE, were similar and significant for the 2 groups (P = 0.042). ConclusionThe tissue-blood partition coefficient of Gd-BOPTA is elevated in areas of acute and chronic myocardial injury and may serve as a marker for disease activity and density of scars, which was found to be higher in chronic MI than in acute myocarditis.

Diffuse Myocardial Fibrosis in Children After Heart Transplantations: A Magnetic Resonance T1 Mapping Study.

It is unclear whether the myocardium undergoes accelerated fibrotic remodeling in children after heart transplantation (HTx). In this prospective study, cardiac magnetic resonance (CMR) studies in 17 patients 1.3 years (median, range 0.03-12.6 years) after HTx (mean age, 9.8 ± 6.2 years; 8 girls) were compared to CMR studies in 9 healthy controls (mean age, 12.4 ± 2.4 years; 4 girls). T1 measurements were performed at a midventricular short axis slice before (ie, native T1 times) and after the application of 0.2 mmol/kg gadopentetate dimeglumine in the interventricular septum, left ventricular (LV) free wall and encompassing the entire LV myocardium. The tissue-blood partition coefficient (TBPC), reflecting the degree of diffuse myocardial fibrosis, was calculated as a function of the ratio of T1 change of myocardium compared to blood. Native T1 times and TBPC were correlated with echocardiographic parameters of diastolic function. Native T1 times were significantly higher in HTx patients compared to controls in all regions assessed (LV free wall 973 ± 42 vs 923 ± 12 ms; P < 0.005; interventricular septum 1003 ± 31 vs 974 ± 21 ms, P < 0.05; entire LV myocardium 987 ± 33 vs 951 ± 16 ms; P < 0.005) and correlated with LV E/e' as an echocardiographic marker of diastolic dysfunction (r = 0.54, P < 0.05). The TBPC was elevated in the LV free wall (0.45 ± 0.06 vs 0.40 ± 0.03, P < 0.005) and the entire LV myocardium (0.47 ± 0.06 vs 0.43 ± 0.03, P < 0.05). Evidence of diffuse myocardial fibrosis and is already present in children after HTx. It appears to be associated with diastolic dysfunction.

Myocardial T1 mapping in pediatric and congenital heart disease.

In addition to the depiction of anatomy and function, tissue characterization of the myocardium has emerged as an important asset of cardiac magnetic resonance (CMR). Among the tissue properties that are quantifiable by CMR is diffuse myocardial fibrosis. Diffuse fibrosis is regarded to be the common pathological pathway toward loss of myocardial function in many cardiac conditions, including congenital heart disease.1–4 As fibrosis seems to have a major role in myocardial failure and may be reversible,5–8 its assessment by CMR has the potential to transform the way we monitor and treat our patients.9 In this review, we describe the technical aspects of fibrosis quantification with CMR and outline past and potential applications in congenital and pediatric heart disease. Diffuse myocardial fibrosis, which is present to a varying degree in children with acquired and congenital heart disease, has been attributed to abnormal loading conditions, cyanosis, and genetic predisposition.1,7,10,11 Myocardial fibrosis manifests in the pressure-loaded left ventricle of infants and children with aortic stenosis and coarctation.1 In patients with tetralogy of Fallot right ventricular myofiber disorganization and interstitial fibrosis have been demonstrated histologically.2,12 Interestingly, right ventricular fibrosis not only occurs in late adult survivors, but is already present in infants with this condition.12 The changes in myocardial architecture observed with fibrotic remodeling can be detrimental to heart function: Fibrous endocardial thickening of the right ventricular infundibulum is a predictor of poor right ventricular function in patients after tetralogy of Fallot repair.3 In patients with tricuspid atresia myocardial fibrosis is associated with systolic ventricular dysfunction early in life.4,13 In addition to being a mediator of cardiac dysfunction, diffuse fibrosis is the substrate for electric instability and a risk factor for life-threatening ventricular arrhythmia.14 Antifibrotic drugs have …

Quantification and significance of diffuse myocardial fibrosis and diastolic dysfunction in childhood hypertrophic cardiomyopathy.

The purpose of this study was to evaluate the presence of diffuse myocardial fibrosis in children and adolescents with hypertrophic cardiomyopathy (HCM) and to assess associations with echocardiographic and clinical parameters of disease. While a common end point in adults with HCM, it is unclear whether diffuse myocardial fibrosis occurs early in the disease. Cardiac magnetic resonance (CMR) estimation of myocardial post-contrast longitudinal relaxation time (T1) is an increasingly used method to estimate diffuse fibrosis. T1 measurements were taken using standard multi-breath-hold spoiled gradient echo phase-sensitive inversion-recovery CMR before and 15 min after the injection of gadolinium. The tissue-blood partition coefficient was calculated as a function of the ratio of T1 change of myocardium compared with blood. An echocardiogram and blood brain natriuretic peptide (BNP) levels were obtained on the day of the CMR. Twelve controls (mean age 12.8 years; 7 male) and 28 patients with HCM (mean age 12.8 years; 21 male) participated. The partition coefficient for both septal (0.27 ± 0.17 vs. 0.13 ± 0.09; p = 0.03) and lateral walls (0.22 ± 0.09 vs. 0.07 ± 0.10; p < 0.001) was increased in patients compared with controls. Eight patients had overt areas of late gadolinium enhancement (LGE). These patients did not show increased partition coefficient compared with those without LGE (0.27 ± 0.15 vs. 0.27 ± 0.19 and 0.22 ± 0.09 vs. 0.22 ± 0.09; p = 0.95 and 0.98, respectively). However, patients who were symptomatic (dyspnea, arrhythmia and/or chest pain) had higher lateral wall partition coefficient than asymptomatic HCM patients (0.27 ± 0.08 vs. 0.17 ± 0.08; p = 0.006). Similarly, patients with raised BNP (>100 pg/ml) had raised lateral wall coefficients (0.27 ± 0.07 vs. 0.20 ± 0.07; p = 0.03), as did those with traditional risk factors for sudden death (0.27 ± 0.06 vs. 0.18 ± 0.08; p = 0.007). Diffuse fibrosis, measured by the partition coefficient technique, is demonstrable in children and adolescents with HCM. Markers of fibrosis show an association with symptoms and raised serum BNP. Further study of the prognostic implication of this technique in young patients with HCM is warranted.

Transfer of bromocriptine across the blood-brain barrier in man

The transfer of 14C-bromocriptine across the blood-brain barrier was studied in 10 patients using the double indicator single injection method. The extraction (E) of bromocriptine was 8 % (quartiles: 6 and 14 %). Based on the results the cerebral uptake velocity of bromocriptine was calculated assuming constant arterial drug concentration. Its T 1/2 was found to be 12--24 minutes, depending on the tissue-blood partition coefficient.

Determination of kinetic rate constants for 2-[18F]fluoro-2-deoxy-D-glucose and partition coefficient of water in conscious macaques and alterations in aging or anesthesia examined on parametric images with an anatomic standardization technique.

Kinetic rate constants for 2-[18F]fluoro-2-deoxy-d-glucose (FDG) and the tissue-blood partition coefficient of water were determined using dynamic positron emission tomography in conscious macaques, and alterations in these parameters in aging or anesthesia were also examined. The parameters were estimated on a pixel-by-pixel basis using an anatomic standardization technique; group differences were then examined on the parametric images from the young, aged, and anesthesia groups. For the conscious condition, seven young and seven aged male rhesus macaques were used; six young male rhesus macaques were used for the isoflurane anesthesia condition. H2 15O and FDG were used as tracers. The kinetic parameters were estimated by a nonlinear least-square fitting procedure with compartment models including terms for the cerebral blood volume (CBV) and time delay of the input function. Cerebral blood flow (CBF) and cerebral metabolic rate of glucose (CMRglc) were also calculated from the estimated parameters. In the aged group, glucose phosphorylation was decreased more than glucose transport, and the occipital cortex was the most affected region where reduction in CBV, CMRglc, and CBF were also observed. In the anesthesia group, glucose transport was decreased; however, glucose phosphorylation was not affected except for the occipital pole. The occipital cortex was also the most affected region. The tissue-blood partition coefficient of water was decreased globally.

A comparison of 1H8-and 2H8-toluene toxicokinetics in men

1. To examine the bioequivalence of an isotope-labelled tracer to study toxicant disposition, we conducted 33 controlled human exposures to a mixture of 50 ppm Htoluene and 50 ppm H-toluene for 2h, and measured concentrations in blood and breath, and metabolite levels in urine for 100h post-exposure. 2. A physiologically based kinetic (PBK) model found that compared with H-toluene, H-toluene had a 6.4 13% (mean SD) lower AUC, a 6.5 13% higher systemic clearance (1.46 0.27 versus 1.38 0.25 l h-kg), a 17 22% larger terminal volume of distribution (66.4 14 versus 57.2 10 l kg) and a 9.7 26% longer terminal half-life (38 12 versus 34 10h) (p0.05 for all comparisons). 3. The higher H-toluene clearance may have been due to an increased rate of ring oxidation, consistent with the 17% higher observed fraction of H- versus H-cresol metabolites in urine. 4. The larger terminal volume and half-lives for H-toluene suggested a higher adipose tissue blood partition coefficient. 5. Observed isotope differences were small compared with interindividual differences in H-toluene kinetics from previous studies. 6. The PBK model allowed us to ascribe observed isotope differences in solvent toxicokinetics to underlying physiologic mechanisms.

Characterisation of tumour blood flow using a 'tissue-isolated' preparation.

Tumour blood flow was characterised in a 'tissue-isolated' rat tumour model, in which the vascular supply is derived from a single artery and vein. Tumours were perfused in situ and blood flow was calculated from simultaneous measurement of (1) venous outflow from the tumour and (2) uptake into the tumour of radiolabelled iodo-antipyrine (IAP). Comparison of results from the two measurements enabled assessment of the amount of blood 'shunted' through the tumours with minimal exchange between blood and tissue. Kinetics of IAP uptake were also used to determine the apparent volume of distribution (VDapp) for the tracer and the equilibrium tissue-blood partition coefficient (lambda). lambda was also measured by in vitro techniques and checks were made for binding and metabolism of IAP using high-pressure liquid chromatography. VDapp and lambda were used to calculate the perfused fraction (alpha) of the tumours. Tumour blood flow, as measured by IAP (TBFIAP), was 94.8 +/- 4.4% of the blood flow as measured by venous outflow, indicating only a small amount of non-exchanging flow. This level of shunting is lower than some previous estimates in which the percentage tumour entrapment of microspheres was used. The unperfused fraction ranged from 0 to 20% of the tumour volume in the majority of tumours. This could be due to tumour necrosis and/or acutely ischaemic tumour regions. For practical purposes, measurement of the total venous outflow of tumours is a reasonable measure of exchangeable tumour blood flow in this system and allows for on-line measurements. Tracer methods can be used to obtain additional information on the distribution of blood flow within tumours.

Microcomputer programs for physiologically-based pharmacokinetic (PB-PK) modeling

Physiologically-based pharmacokinetic (PB-PK) models are each defined as a set of mathematical equations offering a fairly comprehensive time course of a chemical's disposition in several pre-selected anatomical compartments. Each of these compartments has its characteristic blood flow, volume, tissue-blood partition coefficient, and metabolic or clearance rate constants that together are deemed responsible for a chemical's disposition in that region. Numerous investigators have used these models to predict tissue dose in the animal or human body in recent years. This simulation technique, if proven effective, will eventually reduce the large number of animals that are required in the costly classic, in vivo studies to be conducted for chemical disposition or metabolism. This communication offers 2 affordable micro-computer programs which can be used as a practical simulation tool in further exploring the application of PB-PK modeling in chemical risk assessment. These 2 programs are written especially for investigators who prefer to have some appreciation of the required computer simulation first before committing themselves to using more advanced, expensive simulation software packages that are commercially available.

Skin blood flow in sheep: comparison of xenon-133 washout and radioactive microsphere techniques.

Blood flow was measured in leg and torso skin of conscious or anesthetized sheep by using 15-micron radioactive microspheres (Qm) and the 133Xe washout method (QXe). There was a good relationship between Qm in the cutaneous compartment and QXe calculated from the fast component of the biexponential washout curves (QXe = 0.40.Qm + 6.2, r = 0.90, P less than 0.001) with QXe values substantially below those determined with microspheres. Only at low blood flow levels was there a tendency for QXe to overestimate capillary blood flow as assessed with microspheres, but at higher blood flow levels the 133Xe washout method resulted in values substantially below those determined with microspheres. The slope of the slow component of the washout curves was inversely related to the tissue-blood partition coefficient in the subcutaneous tissue (r = 0.52, P less than 0.001), indicating an influence of the amount of subcutaneous fat on the washout rate. QXe calculated from the slow component of the washout curves was not significantly correlated with Qm in the subcutaneous compartment (r = 0.19, P greater than 0.10). In leg skin with dilated arteriovenous anastomoses, QXe was generally higher than in torso skin and leg skin with constricted arteriovenous anastomoses, indicating that shunt blood flow increases the washout of 133Xe.

Quantitation of local cerebral blood flow and partition coefficient without arterial sampling: theory and validation.

A new technique that requires neither arterial blood sampling nor prior knowledge of the indicator's tissue-blood partition coefficient has been developed for quantitation of local CBF. This technique arises from an existing method that uses the inert, freely diffusible gaseous tracer [18F]methyl fluoride (CH3(18)F) and positron computed tomography. The shape of the arterial blood curve is derived from continuous sampling of expired air. The concentration of CH3(18)F in the arterial blood is assumed to be proportional to the expired gas curve interpolated between end-tidal values. The absolute scale of the blood curve is determined by fitting a series of venous blood samples to a multicompartment model. Four validation studies were performed to compare values derived using the venous scaled expired breath input function with those derived using direct arterial samples. The proposed method gave higher flow values than the standard arterial sampling method by an average of 4.4%. These validation studies and data from both normal and patient scans suggest that the method provides the quantitation necessary for interstudy comparisons yet avoids the trauma of an arterial puncture.

The tissue-blood partition coefficient of iodoantipyrine in pig brain and its change with age.

The tissue-blood partition coefficient of 125I-labelled iodoantipyrine was measured in pig brain. The mean coefficient for 11 neonatal piglets (aged 0.5 to 4 days) was 0.718 mL/g (SD 0.083). Measurements in a further 11 animals up to 144 days old (at which time pigs are sexually mature), showed that the partition coefficient increased significantly with age, possibly as a result of the accumulation of brain lipid during growth. The change in partition coefficient with age was curvilinear, rising to unity as the animals reached maturity. There were significant differences between the partition coefficients in grey and in white matter, but these were so small relative to the differences between pigs that they could be neglected for all practical purposes. Since the accuracy of measurement of cerebral blood flow (CBF) by the Kety-Schmidt technique depends directly on the partition coefficient of the tracer, it is important to confirm that apparent changes of CBF do not simply reflect alterations in the partition coefficient rather than real changes in blood flow.

Measurement of blood flow in the dental pulp of dogs with the 133xenon washout method

Following rapid injection of 133Xe into the maxillary artery, the radioactivity from a dog canine tooth was monitored with a specially-designed scintillation probe connected to a multichannel analyser. With a PDP 11 10 municomputer, the semilogarithmic radioactivity-time curve was resolved into a fast component and a slow component using best fit least-square lines and the exponential rate constant ( k) was determined for each component. The blood flow per unit of pulp mass ( Q, in ml/min per 100g) was obtained using the equation: Q = k · λ tb′ , where λ tb is the tissue-blood partition coefficient of 133Xe in the pulp determined for the haematocrit value of the individual experiments. The fast-component blood flow was 53.12 ± 3.12 and the slow-component blood flow was 8.86 ± 0.53 ml/min per 100 g (mean ± SEM, n = 21). Although the exact anatomical areas for the fast and slow components are yet to be determined, the results show heterogeneity of blood flow in the pulp. The study showed that pulp blood flow in an intact tooth can be measured with the 133Xe washout method; the method enables study of circulatory physiology of the pulp in health and disease.

Effects of a Transfusion with a Blood Substitute (Fluosol-DA, 20%) on Cerebral Circulation in the Monkey

Local cerebral blood flow (lCBF) and electroencephalogram were monitored in six monkeys after a transfusion using a perfluorochemical suspension (Fluosol-DA, 20%) that has been manufactured as a blood substitute and is known to be synthetic, biologically inert, and nontoxic and to have a high capacity for carrying oxygen. The animals were mechanically ventilated, and blood gases were maintained at physiological levels. Fluosol-DA, 20% was administered either by an exchange transfusion of 20 ml/kg or by an infusion of 8 ml/kg followed by an exchange transfusion of 12 ml/kg. lCBF was measured using the hydrogen clearance technique. An equation was proposed to estimate the tissue-blood partition coefficient of hydrogen; this coefficient is considered to be dependent upon the amount of perfluorochemicals in the blood and was used to calculate lCBF. Systemic blood pressure, pulse rate, central venous pressure, electroencephalogram, and gas analysis of the blood from the femoral artery, the femoral vein, and the superior sagittal sinus showed little change throughout the experiment. lCBF was increased by 12% (p less than 0.005) after the infusion of Fluosol-DA, 20% of 8 ml/kg and by 31% (p less than 0.02) after the exchange transfusion. Hyperventilation reduced lCBF significantly (p less than 0.005), which implies that the reactivity of the cerebral blood vessels to hypocarbia was not impaired by the administration of FLuosol-DA, 20%. Both the results of this study and the physical properties of Fluosol-DA, 20% suggest that this blood substitute can safely be used for normal human brains and that it might also be effective for ischemic brains.

Tissue-blood partition coefficient for xenon: temperature and hematocrit dependence.

ARTICLESTissue-blood partition coefficient for xenon: temperature and hematocrit dependenceR. Y. Chen, F. C. Fan, S. Kim, K. M. Jan, S. Usami, and S. ChienR. Y. Chen, F. C. Fan, S. Kim, K. M. Jan, S. Usami, and S. ChienPublished Online:01 Aug 1980https://doi.org/10.1152/jappl.1980.49.2.178MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByUsing hyperpolarized 129Xe gas-exchange MRI to model the regional airspace, membrane, and capillary contributions to diffusing capacityZiyi Wang, Leith Rankine, Elianna. A. Bier, David Mummy, Junlan Lu, Alex Church, Robert M. Tighe, Aparna Swaminathan, Yuh-Chin T. Huang, Loretta G. Que, Joseph G. Mammarappallil, Sudarshan Rajagopal, and Bastiaan Driehuys11 May 2021 | Journal of Applied Physiology, Vol. 130, No. 5Safety, hemodynamic effects, and detection of acute xenon inhalation: rationale for banning xenon from sportJustin S. Lawley,* Hannes Gatterer,* Katrin A. Dias, Erin J. Howden, Satyam Sarma, William K. Cornwell, Christopher M. Hearon, Mitchel Samels, Braden Everding, Richard K. Bruick, Max Hendrix, Thomas Piper, Mario Thevis, and Benjamin D. Levine26 November 2019 | Journal of Applied Physiology, Vol. 127, No. 6Removal of hyperpolarized 129 Xe gas-phase contamination in spectroscopic imaging of the lungs12 June 2018 | Magnetic Resonance in Medicine, Vol. 262The Physics of Hyperpolarized Gas MRIInert gas clearance from tissue by co-currently and counter-currently arranged microvesselsY. Lu, C. C. Michel, and W. Wang1 August 2012 | Journal of Applied Physiology, Vol. 113, No. 3Laser-Polarized Xenon Nuclear Magnetic Resonance, a Potential Tool for Brain Perfusion Imaging: Measurement of the Xenon T1In VivoEffects of hyperthermia on cerebral blood flow and metabolism during prolonged exercise in humansLars Nybo, Kirsten Møller, Stefanos Volianitis, Bodil Nielsen, and Niels H. Secher1 July 2002 | Journal of Applied Physiology, Vol. 93, No. 1Hyperpolarized 129Xe MRI Using Gas-Filled LiposomesAcademic Radiology, Vol. 9, No. 1Unchanged Cerebral Blood Flow and Oxidative Metabolism after Acclimatization to High Altitude31 August 2016 | Journal of Cerebral Blood Flow & Metabolism, Vol. 22, No. 1Determination of regional ventilation and perfusion in the lung using xenon and computed tomographyThomas C. Kreck, Melissa A. Krueger, William A. Altemeier, Scott E. Sinclair, H. Thomas Robertson, Erin D. Shade, Jacob Hildebrandt, Wayne J. E. Lamm, David A. Frazer, Nayak L. Polissar, and Michael P. Hlastala1 October 2001 | Journal of Applied Physiology, Vol. 91, No. 4Transcranial doppler sonography and internal jugular bulb saturation during hyperventilation in patients with fulminant hepatic failureLiver Transplantation, Vol. 7, No. 4CEREBROVASCULAR METABOLIC AUTOREGULATION IS IMPAIRED DURING LIVER TRANSPLANTATION1Transplantation, Vol. 68, No. 10Pharmacologic Electroencephalographic Suppression During Cardiopulmonary BypassAnesthesia & Analgesia, Vol. 86, No. 2Isolated Cerebral Hypothermia by Single Carotid Artery Perfusion of Extracorporeally Cooled Blood in BaboonsNeurosurgery, Vol. 39, No. 3Phenylephrine Increases Cerebral Blood Flow during Low-flow Hypothermic Cardiopulmonary Bypass in BaboonsAnesthesiology, Vol. 85, No. 2Cerebral Physiologic Effects of Burst Suppression Doses of Propofol During Nonpulsatile Cardiopulmonary BypassAnesthesia & Analgesia, Vol. 81, No. 3β-adrenergic stimulation and abdominal subcutaneous fat blood flow in lean, obese, and reduced-obese subjectsMetabolism, Vol. 44, No. 2Periprandial regulation of lipid metabolism in insulin-treated diabetes mellitusMetabolism, Vol. 42, No. 4The assessment of cerebral function during paediatric cardiopulmonary bypass30 June 2016 | Perfusion, Vol. 8, No. 1Effects of muscle temperature on the V̇O2 kinetics at the onset of exercise in manRespiration Physiology, Vol. 88, No. 3Adipose tissue metabolism in obesity: Lipase action in vivo before and after a mixed mealMetabolism, Vol. 41, No. 3Validation of 133 Xe Clearance as a Cerebral Blood Flow Measurement Technique during Cardiopulmonary Bypass28 June 2016 | Journal of Cerebral Blood Flow & Metabolism, Vol. 12, No. 1Cerebral blood flow during cardiopulmonary bypass in a patient with occlusive cerebrovascular diseaseJournal of Cardiothoracic Anesthesia, Vol. 3, No. 1Xenon handling in the liver: red cell capacity effect.Circulation Research, Vol. 63, No. 4Skin blood flow from gas transport: Helium xenon and laser Doppler comparedMicrovascular Research, Vol. 35, No. 2Brain Luxury Perfusion during Cardiopulmonary Bypass in Humans. A Study of the Cerebral Blood Flow Response to Changes in CO 2 , O 2 , and Blood Pressure29 June 2016 | Journal of Cerebral Blood Flow & Metabolism, Vol. 6, No. 3Measurement of blood flow in the dental pulp of dogs with the 133xenon washout methodArchives of Oral Biology, Vol. 28, No. 6Local Cerebral Blood Flow Values as Estimated with Diffusible Tracers: Validity of Assumptions in Normal and Ischemic Tissue29 June 2016 | Journal of Cerebral Blood Flow & Metabolism, Vol. 1, No. 4 More from this issue > Volume 49Issue 2August 1980Pages 178-183 Copyright & PermissionsCopyright © 1980 the American Physiological Societyhttps://doi.org/10.1152/jappl.1980.49.2.178PubMed7400000History Published online 1 August 1980 Published in print 1 August 1980 Metrics

Measurement of regional blood flow with sulfanilamide (4-amino benzene sulfonamide).

A new technique utilising sulfanilamide (4-amino benzene sulfonamide) as a diffusible indicator is described for the measurement of organ blood flows in the rat. After a bolus injection the indicator is rapidly distributed in the tissue water and in most organs its tissue-blood partition coefficient corresponds to the relative water content of the organ. Sulfanilamide is, however, rapidly secreted by the renal tubules and slowly acetylated in the liver. This difficulty can be eliminated by the introduction of appropriate partition coefficients. The organ blood flows estimated with sulfanilamide were in the same animals compared with flows obtained by the 8Rb-uptake and by the radioactive microsphere techniques, and a high correlation was found between the flow values obtained by the different methods [sulfanilamide-86Rb; r = 0.992; sulfanilamide-MS: r = 0.995]. The merits and disadvantages of the individual methods are discussed.

Colon blood flow in the dog: effects of changes in arterial carbon dioxide tension.

A new method for measuring blood flow in the colon using a 133Xenon clearance technique has been developed in the greyhound. Values for 133Xe tissue blood partition coefficient for colon have been established. The mean basal colon blood flow in 35 animals was 39.8 cm3.min-1.100g-1 with a coefficient of variation for repeat measurements of 8.7%. Hypercapnia produced a significant rise in colon blood flow to a mean maximum level of 62.2 cm3.min-1.100g-1 and hypocapnia a significant fall to a mean level of 27.9 cm3.min-1.100g-1. For arterial carbon dioxide tension (PCO2) values between 2 and 12 kPa (15 and 90 mmHg) there was a straight line relationship between colon blood flow and arterial PCO2. When hypercapnia was prolonged for 75 min, the initial rise in colon blood flow was only partially sustained, while prolonged hypocapnia for a similar period resulted in sustained reduction in flow. Mean resting colon oxygen consumption in 35 animals was 1.17 cm3.min-1.100g-1 and this was not significantly affected by hypocapnia. Hypercapnia to arterial PCO2 levels between 8 and 14 kPa (60 and 105 mmHg), however, produced a significant rise in colon oxygen consumption. Since changes in colon blood flow during and after surgery may affect healing of colonic anastomoses, these results may be relevant when considering anaesthetic techniques for patients undergoing colon resection.

Partition Coefficient of 133Xe between Blood and Eye Tissues

The relative solubility coefficient of 133Xe and the tissue-blood partition coefficient for the aqueous humour vitreous body, conjunctiva and external eye muscles of the rabbit were determined in vitro at 37 degrees C and at various haematocrit values. The partition coefficient for haematocrit 40 was: for the aqueous humour 0,49 ml/ml, for the vitreous body 0,50 ml/ml, for the conjunctiva 0,81 ml/g and for the external eye muscles 0,77 ml/g. It was found that the solubility of 133Xe in rabbit erythrocytes is about 50 per cent higher than that in human red cells. The consequences of this fact for the precision of blood flow measurements by the method of tissue clearance are discussed.