Unit Mass Of Tissue Research Articles

Nonspecific eddy current heating in magnetic field hyperthermia

In this Perspective article, we explore the definition and use of clinical tolerability metrics associated with nonspecific eddy current heating in magnetic field hyperthermia (MFH). We revisit the origins of the “Brezovich criterion,” Hof ≤ 485 MA m−1s−1, as it is applied to axial time-varying magnetic fields H (t) = Ho sin(2πft) and the human torso. We then consider alternative metrics, including the “maximal specific absorption rate” (SARmax) of eddy-current-induced power absorbed per unit mass of tissue. With reference to previously published clinical data and the results of two volunteer studies in our laboratory, we show that the SARmax metric is both suitable and reliable. We also show how it may be extracted from in silico finite element models to cope with confounding effects such as anatomical hot spots and non-axial-field geometries. We note a parallel with a standardized metric, the “local SAR” used in magnetic resonance imaging (MRI). We suggest that the limits established in clinical MRI (that the local SAR, averaged over 10 g of tissue and 6 min of treatment, should not exceed 20 mW g−1 in the torso or head, and 40 mW g−1 in the limbs) might be regarded as a good starting point for the design of MFH interventions. We conclude with the recommendation that the SARmax metric is adopted for future use in the development of clinically safe and tolerable MFH equipment.

2018 ACC/HRS/NASCI/SCAI/SCCT Expert Consensus Document on Optimal Use of Ionizing Radiation in Cardiovascular Imaging: Best Practices for Safety and Effectiveness.

2018 ACC/HRS/NASCI/SCAI/SCCT Expert Consensus Document on Optimal Use of Ionizing Radiation in Cardiovascular Imaging: Best Practices for Safety and Effectiveness.

Flow versus permeability weighting in estimating the forward volumetric transfer constant (Ktrans) obtained by DCE-MRI with contrast agents of differing molecular sizes

PurposeTo quantify the differential plasma flow- (Fp-) and permeability surface area product per unit mass of tissue- (PS-) weighting in forward volumetric transfer constant (Ktrans) estimates by using a low molecular (Gd-DTPA) versus high molecular (Gadomer) weight contrast agent in dynamic contrast enhanced (DCE) MRI. Materials and methodsDCE MRI was performed using a 7T animal scanner in 14 C57BL/6J mice syngeneic for TRAMP tumors, by administering Gd-DTPA (0.9kD) in eight mice and Gadomer (35kD) in the remainder. The acquisition time was 10min with a sampling rate of one image every 2s. Pharmacokinetic modeling was performed to obtain Ktrans by using Extended Tofts model (ETM). In addition, the adiabatic approximation to the tissue homogeneity (AATH) model was employed to obtain the relative contributions of Fp and PS. ResultsThe Ktrans values derived from DCE-MRI with Gd-DTPA showed significant correlations with both PS (r2=0.64, p=0.009) and Fp (r2=0.57, p=0.016), whereas those with Gadomer were found only significantly correlated with PS (r2=0.96, p=0.0003) but not with Fp (r2=0.34, p=0.111). A voxel-based analysis showed that Ktrans approximated PS (<30% difference) in 78.3% of perfused tumor volume for Gadomer, but only 37.3% for Gd-DTPA. ConclusionsThe differential contributions of Fp and PS in estimating Ktrans values vary with the molecular weight of the contrast agent used. The macromolecular contrast agent resulted in Ktrans values that were much less dependent on flow. These findings support the use of macromolecular contrast agents for estimating tumor vessel permeability with DCE-MRI.

Assessment of vessel permeability by combining dynamic contrast-enhanced and arterial spin labeling MRI.

The forward volumetric transfer constant (K(trans)), a physiological parameter extracted from dynamic contrast-enhanced (DCE) MRI, is weighted by vessel permeability and tissue blood flow. The permeability × surface area product per unit mass of tissue (PS) in brain tumors was estimated in this study by combining the blood flow obtained through pseudo-continuous arterial spin labeling (PCASL) and K(trans) obtained through DCE MRI. An analytical analysis and a numerical simulation were conducted to understand how errors in the flow and K(trans) estimates would propagate to the resulting PS. Fourteen pediatric patients with brain tumors were scanned on a clinical 3-T MRI scanner. PCASL perfusion imaging was performed using a three-dimensional (3D) fast-spin-echo readout module to determine blood flow. DCE imaging was performed using a 3D spoiled gradient-echo sequence, and the K(trans) map was obtained with the extended Tofts model. The numerical analysis demonstrated that the uncertainty of PS was predominantly dependent on that of K(trans) and was relatively insensitive to the flow. The average PS values of the whole tumors ranged from 0.006 to 0.217 min(-1), with a mean of 0.050 min(-1) among the patients. The mean K(trans) value was 18% lower than the PS value, with a maximum discrepancy of 25%. When the parametric maps were compared on a voxel-by-voxel basis, the discrepancies between PS and K(trans) appeared to be heterogeneous within the tumors. The PS values could be more than two-fold higher than the K(trans) values for voxels with high K(trans) levels. This study proposes a method that is easy to implement in clinical practice and has the potential to improve the quantification of the microvascular properties of brain tumors.

Specific Absorption rate (SAR) Post-Processing Implementation: Numerical Approach [EM Programmer's Notebook

The accepted dosimetric measure of electromagnetic (EM) exposure is the specific absorption rate (SAR), which is defined as the power absorbed per unit mass of tissue. International standards for compliance testing of hand-held mobile communication devices define various cubical averaging schemes to obtain the spatial peak averaged specific absorption rate. In this paper, a numerical approach to illustrate the validation and uncertainty contributions of a SAR post-processing algorithm is described. Simplified interpolation and extrapolation techniques to calculate the 1g SAR for a 2.5 mm mesh grid are evaluated. Furthermore, using linear, nearest, and spline interpolation in MATLAB, the effects of the extrapolation order on the assessment of the resultant error are examined.

Counterpoint: There is a dose–response relationship in the low–dose rate brachytherapy management of prostate cancer

A dose response exists when higher doses of radiation (energy deposited per unit mass of tissue) delivered to cancer cells result in an increase in cell kill. Lower doses result in lower cell kill. In the laboratory, this is well documented by cell survival curves generated from in vitro experiments. In clinical practice, these relationships are usually demonstrated by correlating cancer control rates with various delivered radiation dose levels. In prostate cancer, a unique biochemical surrogate exists, prostate-specific antigen (PSA), which can be used to detect cancer recurrence at an early time frame.

MIRD Commentary: Proposed Name for a Dosimetry Unit Applicable to Deterministic Biological Effects—The Barendsen (Bd)

The fundamental physical quantity for relating all biologic effects to radiation exposure is the absorbed dose, the energy imparted per unit mass of tissue. Absorbed dose is expressed in units of joules per kilogram (J/kg) and is given the special name gray (Gy). Exposure to ionizing radiation may cause both deterministic and stochastic biologic effects. To account for the relative effect per unit absorbed dose that has been observed for different types of radiation, the International Commission on Radiological Protection (ICRP) has established radiation weighting factors for stochastic effects. The product of absorbed dose in Gy and the radiation weighting factor is defined as the equivalent dose. Equivalent dose values are designated by a special named unit, the sievert (Sv). Unlike the situation for stochastic effects, no well-defined formalism and associated special named quantities have been widely adopted for deterministic effects. The therapeutic application of radionuclides and, specifically, alpha-particle emitters in nuclear medicine has brought to the forefront the need for a well-defined dosimetry formalism applicable to deterministic effects that is accompanied by corresponding special named quantities. This commentary reviews recent proposals related to this issue and concludes with a recommendation to establish a new named quantity.

The Coronary Circulation in Cardiac Hypertrophy

Left ventricular hypertrophy is a common and important risk factor for cardiac mortality and morbidity. Cardiac hypertrophy adversely affects coronary perfusion because hypertension, its most frequent cause, is a major risk factor for coronary disease, and because cardiac hypertrophy may be associated with myocardial ischemia even in the absence of atheromatous coronary disease due to disturbances in coronary physiology. Several studies have demonstrated impairment of coronary reserve in human and experimental cardiac hypertrophy. Normal autoregulation of coronary flow may be disturbed in cardiac hypertrophy for many reasons, including (a) increased perfusion pressure in hypertension, (b) increased diastolic and systolic left ventricular pressures, in addition to disturbed coronary physiology. Studies undertake in the presence of maximal coronary vasodilatation indicate an increased minimal coronary vascular resistance in hypertrophied hearts. Because such measurements were determined in the presence of maximal coronary vasodilation, they are likely to indicate a reduced arteriolar lumenal cross-sectional area per unit mass of tissue. Studies of cardiac and coronary morphology support an imbalance in myocardial and coronary growth in cardiac hypertrophy, but further evidence is needed to confirm this. Myocardial contraction impairs coronary flow, and available evidence suggests that this systolic impairment may be greater in hypertrophied myocardium, and that this may be an additional factor in limiting coronary flow in hypertrophy. A further important feature of impaired coronary reserve in cardiac hypertrophy is its distribution. Studies using radiolabeled microspheres indicate that coronary reserve is reduced in endocardial regions to a much greater extent than epicardial regions. Previously, treatment of conditions such as hypertension, which are commonly associated with hypertrophy, have concentrated on correction of the main defect. It is important to bear in mind, however, that such treatments may have direct and indirect effects on the coronary circulation, which may have an important bearing on preserving myocardial function. An important aspect of future research will be to determine the effects of treatment on coronary perfusion.

Absorbed power deposition for various insertion depths for 915 MHZ interstitial dipole antenna arrays: Experiment versus theory

Dipole antennas are commonly used in interstitial clinical hyperthermia treatments because of their compatibility with brachytherapy techniques and their good power deposition patterns when used in arrays. For accurate treatment planning, however, there must be a comprehensive knowledge base to predict the power deposition patterns when insertion depth is a non-resonant length. This is especially true for insertion depths that result in significant power deposition outside of the antenna junction plane and presumably outside of the tumor volume. A computer controlled measurement system was used with a muscle equivalent phantom to make measurements of specific absorption rate (SAR) or absorbed power per unit mass of tissue at 598 points in a plane. The diagonal plane was the measurement plane of choice because it characterized the SAR profiles at the array center as well as areas in the proximity of the antennas. Dartmouth dipole antennas were used (0.9 mm O.D.) in brachytherapy catheters with inner catheters (2.2 mm O.D./1.2 mm I.D). The resonant half-wavelength of this dipole antenna/catheter combination is 7.8 cm. A choke modification of the dipole was also investigated. Four antennas were used in a boxlike configuration with 2.0 cm separation. Insertion depths of 5.9, 7.8, 9.8, 12.7, 15.6 and 17.6 cm were used. The h A subsection (junction to tip) was held constant at 3.9 cm. Plots were made of the experimental SAR data normalized to the maximum SAR measured in the plane. Theoretical plots were calculated in the same plane for each of the insertion depths. SAR comparisons were also made longitudinally along the central axis of the array and through the antenna junctions in the diiagonal plane for resonant half-wavelength insertion depth. Experimental results verified theoretical predictions of the existence of a secondary hot-spot in the center of the array, but outside of the antenna junction plane and approximately a quarter-wavelength from the insertion point. This secondary hot-spot appears for all insertion depths greater than 10 cm. At longer insertion depths approaching a full wavelength, however, this secondary peak is not dominant. Choke antennas demonstrated a solution to the problem of shifting SAR patterns with varying insertion depths by restricting the active length of the antenna.

Sources of amino acids for protein synthesis during early organogenesis in the rat. 1. Relative contributions of free amino acids and of proteins

Rat conceptuses on the 10th day of gestation were cultured for 27 h in whole rat serum. An addition of either [3H]leucine or [3H]leucine-labelled rat serum proteins was made once during the culture period, and the acid-soluble and acid-insoluble radioactivities of embryo and visceral yolk sac measured at harvesting. The extent of radiolabel incorporation into embryonic and yolk-sac proteins increased linearly with the duration of exposure of the conceptus to the radiolabelled leucine or radiolabelled serum proteins, indicating roughly constant rates of incorporation, per unit mass of tissue, throughout the culture period. The incorporation rates, expressed as clearances, were 0.73 and 0.78 microliter/mg tissue protein/h for embryo and yolk sac, respectively, when the source was [3H]leucine; and 1.8 and 1.3 microliters/mg tissue protein/h, for embryo and yolk sac, respectively, when the source was [3H]leucine-labelled serum proteins. It is estimated, from the known leucine and protein concentrations in serum, that protein contributed over 99 per cent of the leucine supplied to the conceptus for its protein synthesis. In parallel experiments, measurements were made on cultures conducted in the presence of an antiserum against rat visceral yolk sac (100 micrograms/ml). Antiserum profoundly inhibited incorporation of radioactivity into embryo and yolk-sac proteins, when the source was 3H-labelled protein, a result consistent with the known ability of the antiserum to inhibit pinocytosis in the yolk sac. Antiserum also decreased incorporation from [3H]leucine in the yolk sac, suggesting that a proportion of the free leucine entering the yolk sac does so by pinocytosis. The failure of antiserum to affect incorporation of [3H]leucine into the embryo probably indicates that leucine can enter the embryo without the mediation of yolk-sac pinocytosis. The primacy of protein, as a source of amino acids for the organogenesis-stage embryo, is consistent with the serious effects, in terms of embryonic death and malformation, that result from the interruption of amino acid supply when either pinocytosis or lysosomal proteolysis in the yolk sac is inhibited.

Measurement of liver haemodynamics.

The fundamental principle underlying static radionuclide imaging procedures is that concentration of radioactivity takes place following the intravenous administration of a radiopharmaceutical. Uptake of a radiopharmaceutical depends upon regional cardiac output to the tissue under examination and on the extraction efficiency by the tissue. The product of these two factors is often called the Effective Organ Blood Flow. It is important to make the distinction between blood perfusion, that is the pattern of relative blood flow to the organ, and the absolute blood flow, measured in millilitres of blood per minute flowing in a unit mass of tissue. Most radionuclide clinical investigations require only the perfusion pattern to be measured and absolute measurements are seldom necessary. Also it is usually difficult and unnecessary to measure the extraction efficiency of the radiopharmaceutical.

The effect of pregnancy on the metabolism of noradrenaline in reproductive organs of the rabbit.

The metabolites of (-)-3H-noradrenaline (1.2 mumol l-1) formed by uteri from non-pregnant mature rabbits were, in descending order of importance, 3H-DOPEG greater than 3H-MOPEG greater than 3H-NMN greater than 3H-VMA (3H-DOMA not measured). The pattern of metabolite formation per unit mass of tissue was markedly different in uteri from 28 day pregnant rabbits due to a fourfold increase in 3H-NMN formation and a fourfold decrease in 3H-DOPEG formation. The effects of cocaine indicated that 3H-NMN was largely extraneuronal in origin and 3H-DOPEG was both neuronal and extraneuronal in origin. The pattern of metabolite formation in pregnant rabbit uteri closely resembled the reported pattern in uteri from ovariectomized rabbits treated with 17 beta-oestradiol and progesterone. In the rabbit oviduct and ovary, the patterns of metabolite formation, and their modification by cocaine, indicated that (-)-3H-noradrenaline was metabolised mainly by intraneuronal deamination in the oviduct and mainly by extraneuronal O-methylation in the ovary. Pregnancy did not affect (-)-3H-noradrenaline metabolism in the oviduct, but decreased the metabolism in the ovary.

Effect of ovarian steroids on the metabolism of noradrenaline in rabbit uterus.

The metabolism of (-)-3H-noradrenaline was examined in uterine slices from ovariectomized rabbits which were either untreated or treated with 17 beta-oestradiol, alone or in combination with progesterone. 17 beta-oestradiol caused uterine enlargement which was not accompanied by a change in the formation per g of O-methylated metabolites (3H-NMN, 3H-VMA, 3H-MOPEG). Accumulation of unchanged 3H-noradrenaline and the formation of deaminated catechols (3H-DOMA and 3H-DOPEG) were decreased per g tissue, but increased per uterine horn. Progesterone produced further enlargement of the oestrogen-dominated uteri which was accompanied by (a) a decrease in deaminated catechol formation and (b) an increase in 3H-NMN formation per unit mass of tissue. In all uteri (control and hormone-treated), cocaine inhibited the formation of deaminated catechols, but not that of the O-methylated metabolites. It is suggested, therefore, that, per unit of uterine mass, the neuronal deamination of (-)-3H-noradrenaline is decreased by 17 beta-oestradiol and further decreased by progesterone, and that these changes reflect failure of the intraneuronal deaminating system in the whole uterus to increase in proportion to the increase in uterine mass. Since other agents which decreased the deamination of (-)-3H-noradrenaline (cocaine and nialamide) did not affect 3H-NMN formation in oestrogen-dominated uteri, it is suggested that stimulation of 3H-NMN formation represents a direct effect of progesterone on the extraneuronal O-methylation of noradrenaline.

The Spatial and Temporal Distribution of Inhaled UO 2 Particles in the Respiratory Tract of the Rat: II. The Relative Concentration of UO 2 between the Intrapulmonary Airways and the Pulmonary Tissue

In this experiment the relative masses of UO2 particles per unit mass of tissue are determined between intrapulmonary airways and pulmonary tissue in rat lungs. A mean value of 0.57 +/- 0.06 (SE) was determined in tissue sections taken at 3-mm or 5-mm intervals throughout the lobes of animals killed from 2 to 35 days after inhalation. The experimental results are compared with data derived from the ICRP Lung Model for man and indicate that in the rate approximately 4% of the lung burden as opposed to about 0.02% derived for man is associated with the intrapulmonary airways. The 4% figure, if also applicable to man, would have extremely important implications in radiological protection, since the basal cells of the bronchial epithelium are thought to be sensitive to the induction of bronchogenic carcinoma.

Left ventricular myocardial blood flow in multivessel coronary artery disease.

The relationship between resting left ventricular (LV) myocardial blood flow (MBF) and hemodynamic determinants of myocardial oxygen consumption was investigated in 15 patients with multivessel coronary artery disease (CAD) and in 10 patients with normal coronary arteriograms. Mean LV MBF per unit mass of tissue was measured with a multicrystal scintillation camera from the regional clearance rates of xenon-133 injected into the left main coronary artery. Peak LV wall stress, mean velocity of circumferential fiber shortening (Vcf), rate of ejection during the first third of systole (1/3 SV), LV ejection fraction (EF), and the ratio of peak LV systolic pressure to LV end-systolic volume were measured by contrast left ventriculography. Mean LV MBF per unit mass was significantly reduced (48 +/- 11 vs 67 +/- 12 ml/100 g.min; p less than 0.01) in patients with multivessel CAD. However, none of the patients with CAD experienced chest pain or had electrocardiographic evidence of myocardial ischemia during the resting MBF measurements. Ejection phase indexes were lower in the patients with CAD: LVEF (56 +/- 10% vs 64 +/- 7%, p less than 0.05); 1/3 SV (35 +/- 3 vs 44 +/- 4%, p less than 0.05); and mean Vcf (1.05 +/- 0.30 vs 1.19 +/- 0.27 circ/sec, NS). LV wall thickness (9.8 +/- 1.9 vs 7.5 +/- 1.4 mm, p less than 0.01) and LV mass index (94 +/- 32 vs 64 +/- 17 g/m2, p less than 0.05) were significantly increased in the patients with CAD, accounting for the reduction in peak LV wall stress (276 +/- 73 vs 373 +/- 91 dyn-cm-2 x 10(-3), p less than 0.05) observed in these patients. Multiple regression analysis indicated that indexes of three of the major determinants of myocardial oxygen consumption explained 65% of the variation in MBF in patients with CAD: peak LV stress, mean Vcf and heart rate. After adjustment for these three indexes, the average LV MBF rates were not significantly different in the two patient groups (54.8 +/- 1.8 vs 57.6 +/- 2.3 ml/100 g.min). In both groups, resting LV MBF/beat correlated most highly with peak LV wall stress (r = 0.79). Thus, the reduction in LV MBF per unit mass observed in patients with multivessel CAD at rest is related to lower levels of hemodynamic variables that determine myocardial oxygen consumption. Peak LV wall stress is the most important hemodynamic variable determining the level of resting MBF in patients with and without CAD.

Vascular permeability to macromolecules in rabbit paw and skeletal muscle: A lymphatic study with a mathematical interpretation of transport processes

Steady-state lymph:plasma ratios ( R ) of 131 I-human serum albumin (HSA), 125 I-fibrinogen, and 125 I-polyvinylpyrrolidone (PVP) (ranging in size from 4 to 11 nm molecular radius) were determined for lymph collected separately from rabbit skeletal muscle and the paw. In the same animal there was no consistent difference in the sieving curves obtained from muscle and paw although overall mean R was lower in muscle for molecules with radii greater than 6 nm. Lymph flow rates in the anaesthetised animal were approximately seven times greater from the paw than from muscle per unit mass of tissue. Lymphatic clearance ( R × lymph flow rate) of HSA was 25 μl/min/100 g for paw and 3.3 μl/min/100 g for muscle, R for HSA was 0.56 ± 0.02 and 0.58 ± 0.03 for paw and muscle, respectively, whilst R for fibrinogen was 0.22 ± 0.03 and 0.18 ± 0.03. Mathematical models, which included transport by ultrafiltration and diffusion through large pores combined with vesicular transport, showed compatibility to the data systems only for molecules of 7 nm radius or greater, suggesting that molecules less than this could pass through a small-pore system with a radius of about 6–7 nm. The proportion of transport through large pores or vesicles could not be resolved although maximal values were determined.

Effects of vasopressin and aldosterone on amiloride binding in toad bladder epithelial cells

Methods have been devised to measure the binding of [ 14 C]amiloride to isolated cells from bladders of toads, Bufo marinus . This agent blocks transepithelial sodium transport across bladders by preventing sodium entry to the transporting mechanism. A saturable binding component has been found with an affinity of 5.6 x 10 7 m -1 in the presence of 1.1 mM Na + , which corresponds to the affinity of amiloride when used as a transport inhibitor at the same sodium concentration. In freshly isolated cells the capacity of the binding sites is 3.6 x 10 5 sites/cell, but this value falls to about one third in aged suspensions. When cells are treated with vasopressin (100 mU/ml) somewhat less specific binding is measured at an amiloride concentration giving 50 % occupancy. The results are consistent with the view that vasopressin moves the binding curve to the right along the concentration axis, reducing the affinity of amiloride by a factor of approximately two, while leaving the total capacity unaffected. The affinity of amiloride when used as an inhibitor of transport is also found to be reduced by a factor of two by vasopressin, and complete inhibition of transport can still be achieved. d -Aldosterone in vitro increases the number of amiloride binding sites in isolated cells by approximately 115%, and results from transport studies indicate that there is no significant change in the affinity of amiloride after d -aldosterone treatment. Inhibitors of transcription and translation (actinomycin D and cycloheximide) prevent the increase in amiloride binding caused by d -aldosterone. In vivo the effects of d -aldosterone are more complex, but it is shown that the steroid increases the transport capacity of the tissue, when this is expressed as the number of amiloride binding sites per unit mass of tissue. The results are discussed in terms of the ways in which the two hormones may alter the entry of sodium into the epithelial cells, and so in turn affect transepithelial sodium transport.

Perfusion of the spleen with blood containing prostaglandin E1: transmitter liberation and uptake.

The cat’s spleen perfused with homologous blood containing prostaglandin E 1 provides an admirable preparation for the study of the liberation and uptake of the sympathetic transmitter. Obstruction of the circulation with platelet thrombi is eliminated; blood flow is high, and overflow of transmitter when the nerves are stimulated is higher than in other preparations. The high overflow of transmitter is attributed to adequate perfusion of a large mass of splenic tissue. There is no evidence that the amount of transmitter liberated per unit mass of tissue is increased. Uptake of liberated transmitter and of infused L-noradrenaline is no different from that observed in other preparations of the spleen.

Foliar nutrition and growth in red pine: the fate of photoassimilated carbon in a seedling tree

A 2- to 3-year-old red pine seedling was allowed to assimilate 14CO2 for 3 hours at 2000 ft-c and left under the same illumination for 6 days, then divided into segments and analyzed. Ethanol extracts were resolved by chromatography, insoluble residues by chemical methods. The radioactivity in various components was determined for all segments. Autoradiographs were made from stem sections at four levels.Radioactivity was found in all parts of the plant. Per unit mass of tissue, it was more or less uniformly apportioned among root, stem, and leaves, but the expanding terminal bud contained 5 times as much activity per gram of tissue. Overall, about one-third of the radioactivity was in insoluble compounds, mainly in cell wall constituents. In localities where conspicuous growth had occurred the proportion was higher. Autoradiographs of stem sections showed that 14C was concentrated in newly differentiated tracheids, and was still being incorporated after 6 days. About one-third of the activity in the ethanol extract was chloroform soluble, two-thirds water soluble. In the latter fraction, activity was largely in sugars and organic acids, little in amino acids. Activity in sugars, per unit weight of tissue, was more or less uniform throughout the plant, but activity in organic acids varied greatly. It was lowest in the stem, highest in the bud, where organic acids, almost exclusively quinic and shikimic, carried 75% of the label in the ethanol and water-soluble fraction, and 23% of all the activity in the bud.

Studies of the intrarenal distribution of blood flow using Xe133 in the diseased human kidney

In order to study the distribution of the blood flow in diseased human kidney, 133xenon clearance curves were obtained from the patients with chronic renal disease and hypertension. The results obtained from the xenon clearance curves were compared with those determined by the dye dilution method. Materials and Methods Observations were made in 34 kidneys of the patients including 21 chronic glomerulonephritis, 8 essential hypertension, 4 chronic pyelonephritis and I suspected polyarteritis nodosa. Through the catheter inserted into one renal artery, 1-5 mci of 133xenon dissolved in isotonic saline was injected and the clearance curve of 133xenon from the kidney was monitored externally by a scintillation probe positioned perpendicularly to the back for 30 to 45 minutes. The output of the probe was led to a ratemeter and thence to a printer. The counts per second were plotted against time on semilogarithm graph and the curves were analyzed graphically into several exponential components. The flow per unit mass of tissue (flow rate) and the percentage of the total renal blood flow (flow ratio) for each of these components were calculated. In 10 patients dye dilution curves were recorded and analyzed by the method introduced by TAKEUCHI and ISHIKAWA. The relationships between the results derived from 133xenon clearance curves recorded for 30 minutes and the values of blood urea nitrogen, RBF calculated from CCPH (RBFPAH), Cthio and of maximal urinary osmolality determined on Fishberg's concentration test were studied. Results The clearance curves of 133xenon recorded for 45 minutes were all resolved into 4 components, while 3 components were recognized in the curves recorded for 30 minutes. In the kidneys with normal function, the mean values of the flow rate and the flow ratio in component I and III calculated from the 30 minutes curves coincided closely with those of component I and IV obtained from the 45 minutes curves, respectively. The mean value of the flow rate of component II in the 30 minutes curves was similar to the average of those of component II and III in the 45 minutes curves. Analyzing in the same curves, statistically significant correlations were observed between the values of component I and III from the 30 minutes record and those of component I and IV from the 45 minutes record, respectively. Also, there was significant correlation between component II from the 30 minutes record and the average of component II and III from the 45 minutes record in the flow ratio but not in the flow rate.