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At least 253 records · Page 14Linked to original sources
PubMed2004

Brain perfusion in children: evolution with age assessed by quantitative perfusion computed tomography.

OBJECTIVE: The objective of this study was to assess the age-related variations of brain perfusion through quantitative cerebral perfusion computed tomography (CT) results in children without brain abnormality. METHODS: Brain perfusion CT examinations were performed in 77 children, aged 7 days to 18 years. These patients were admitted at our institution for both noncontrast and contrast-enhanced cerebral CT. Only children whose conventional cerebral CT and clinical/radiologic follow-up, including additional investigations, were normal were taken into account for this study (53 of 77). RESULTS: The average regional rCBF amounts to 40 (mL/100 g per minute) for the first 6 months of life, peaks at approximately 130 (mL/100 g per minute) at approximately 2 to 4 years of age, and finally stabilizes at approximately 50 (mL/100 g per minute) at approximately 7 to 8 years of age, with a small increase of rCBF values at approximately 12 years of age. The rCBF in the gray matter averages 3 times that in the white matter, except for the first 6 months of life. The global CBF represents 10% to 20% of the global cardiac output for the first 6 months of life, peaks at approximately 55% by 2 to 4 years of age, and finally stabilizes at approximately 15% by 7 to 8 years of age. Specific age-related evolution patterns were identified in the different anatomic areas of the cerebral parenchyma, which could be related to the development of neuroanatomic structures and to the emergence of corresponding cognitive functions. CONCLUSIONS: Quantitative perfusion CT characterization of brain perfusion shows specific age variations. Brain perfusion of each cortical area evolves according to a specific time course, in close correlation with the psychomotor development.

Adolescent↗
PubMed2003

Single photon emission computed tomography dual isotope myocardial perfusion imaging in women with systemic lupus erythematosus. II. Predictive factors for perfusion abnormalities.

OBJECTIVE: We have reported that 40% of patients with systemic lupus erythematosus (SLE) had abnormal myocardial perfusion studies. Here we investigated risk factors for abnormal myocardial perfusion in a cohort of women with SLE without history of coronary artery disease. METHODS: Consecutive women with SLE followed at a large lupus clinic underwent single photon emission computed tomography dual isotope myocardial perfusion imaging (DIMPI) following pharmacological stress using dipyridamole. At the time of study each patient had a clinical and laboratory assessment performed by a standard protocol. We compared traditional risk factors as well as disease and therapy related factors in those with and without perfusion abnormalities. RESULTS: A total of 129 patients were studied. The mean +/- SD age was 44.8 +/- 10.9 yrs, and mean SLE Disease Activity Index was 4.2 +/- 5.1. Forty-nine (38%) patients had an abnormality of myocardial perfusion. Factors associated with an abnormal DIMPI included current hypertension (OR 2.11, p = 0.05), elevated cholesterol ever (OR 2.51, p < 0.05), and total cholesterol:high density lipoprotein-cholesterol ratio (OR 1.96 for each increase of 1.0, p < 0.008). CONCLUSION: Myocardial perfusion abnormalities are common in women with SLE without known coronary artery disease (CAD), suggesting a high burden of subclinical CAD. Several metabolic and therapy related factors appear to be associated with the process of atherogenesis in SLE. These results suggest that SLE should be considered a predisposing factor for atherosclerosis.

Adult↗
PubMedDate not supplied

CT perfusion of the liver during selective hepatic arteriography: pure arterial blood perfusion of liver tumor and parenchyma.

PURPOSE: To quantify pure arterial blood perfusion of liver tumor and parenchyma by using CT perfusion during selective hepatic arteriography. METHODS: A total of 44 patients underwent liver CT perfusion study by injection of contrast medium via the hepatic artery. CT-perfusion parameters including arterial blood flow, arterial blood volume, and arterial mean transit time in the liver parenchyma and liver tumor were calculated using the deconvolution method. The CT-perfusion parameters and vascularity of the tumor were compared. RESULTS: A complete analysis could be performed in 36 of the 44 patients. For liver tumor and liver parenchyma, respectively, arterial blood flow was 184.6 +/- 132.7 and 41.0 +/- 27.0 ml/min/ 100 g, arterial blood volume was 19.4 +/- 14.6 and 4.8 +/- 4.2 ml/100 g, and arterial mean transit time was 8.9 +/- 4.2 and 10.2 +/- 5.3 sec. Arterial blood flow and arterial blood volume correlated significantly with the vascularity of the tumor; however no correlation was detected between arterial mean transit time and the vascularity of the tumor. CONCLUSION: This technique could be used to quantify pure hepatic arterial blood perfusion.

Aged↗
PubMed2003

Perfusion treatment algorithm: methods of improving the quality of perfusion.

The pathophysiological consequence associated with cardiopulmonary bypass (CPB) has generated a movement away from this technology in the treatment of heart disease. The negative outcomes are multifactorial in origin and may be associated both with the conduct of CPB and the instrumentation of extracorporeal flow. The purpose of this study was twofold. First, to develop a bedside patient risk assessment to aid in the development of a perfusion care plan. Second, to identify the controllable variables used during CPB that contribute to overall morbidity. Controllable perfusion-related variables that were positively linked to improved patient outcomes were identified from randomized, peer-reviewed human studies. Such variables as hematocrit, mean arterial pressure, thermic perfusion, blood lactate, colloid osmotic pressure, pulsatile perfusion, acid base homeostasis, oxygenation, and coated circuitry were included. Patient risk assessment was developed using the Society of Thoracic Surgeon database, where 61 variables affecting postoperative morbidity were identified. These variables were used to develop a bedside tool, Mortality Assessment Perfusion Score (MAPS), to guide the perfusion patient care plan. The MAPS generates a specific value that may predict patient morbidity and mortality based on past mortalities. In conclusion, the improvement in patient outcome may be associated with both the change in conduct of CPB and the quantitative assessment of patient risk stratification and a patient treatment algorithm.

Algorithms↗
PubMed2005

Effect of perfusion pattern and imaging sequence on gated perfusion SPECT evaluation of myocardial stunning.

UNLABELLED: The aim of this study was to determine the effect of perfusion defect and imaging sequence on the evaluation of myocardial stunning with gated perfusion SPECT. METHODS: A dynamic mathematic cardiac torso phantom was used to create 100 gated SPECT simulations (50 stress-rest and 50 rest-stress sequences) with a wide range of perfusion defects. No segmental wall motion abnormalities were created. After generating projection images, 2 additional acquisitions were simulated by thresholding the projected data to 25% and 75% of the maximum. Finally, gated SPECT projections were grouped by 2s to generate 2 series of phantoms corresponding to stress-rest and rest-stress imaging sequences. For each sequence, the first dataset was the 25% thresholded gated SPECT. Both 75% thresholded and 100% signal intensity were used as a second dataset. Each simulated gated SPECT image differed from others in the extent of myocardial scar or ischemia, but all had the same end-diastolic volume (EDV) (125 mL), end-systolic volume (ESV) (48 mL), and ejection fraction (EF) (62%). Left ventricular perfusion and function were each assessed using validated software. RESULTS: Mean stress EDV was decreased when compared with rest-simulated data (111 +/- 4.7 and 112.4 +/- 4.8 mL, respectively; P < or = 0.05), and mean stress ESV was increased when compared with rest-simulated data (44 +/- 4.2 and 42.7 +/- 4 mL, respectively; P < 0.02). The resulting mean stress EF was decreased in the same comparison (60.3% +/- 3.1% and 62% +/- 2.7%, respectively; P = 0.0001). After multivariate analysis, the difference between stress and rest EF was significantly influenced by myocardial infarction (P = 0.0027), severe extent of myocardial ischemia (P = 0.0017), and imaging sequence (P < 0.0001). A > or =5% decrease in EF on stress SPECT (i.e., myocardial stunning) was significantly associated with the stress-rest sequence (chi(2) = 26; P < 0.0001). CONCLUSION: Perfusion defects and imaging sequence had significant effects on the evaluation of myocardial stunning using gated perfusion SPECT.

Algorithms↗
PubMed2005

Attenuation correction of myocardial SPECT perfusion images with low-dose CT: evaluation of the method by comparison with perfusion PET.

UNLABELLED: In cardiac SPECT, specificity is significantly affected by artifacts due to photon absorption. As the success of attenuation correction depends mainly on high-quality attenuation maps, SPECT low-dose CT devices are promising. We wanted to evaluate the usefulness of a SPECT low-dose CT device in myocardial perfusion scintigraphy. For the evaluation of attenuation correction systems, primarily comparisons with coronary angiography are used. Because the comparison of a method showing myocardial perfusion with an investigation displaying the morphology of vessels yields some difficulties, we chose perfusion PET with (13)N-ammonia as the reference method. METHODS: We prospectively analyzed 23 patients (6 women, 17 men) with known or suspected coronary artery disease. Rest studies and studies under pharmacologic stress with adenosine were performed. After simultaneous injection of (13)N-ammonia and (99m)Tc-sestamibi, a dynamic PET acquisition was started. The SPECT study was performed about 2 h later. Based on 20-segment polar maps, SPECT with and without attenuation correction was compared with PET-derived perfusion values and ammonia uptake values. The PET uptake images were also smoothed to adjust their resolution to the resolution of the SPECT images. RESULTS: The concordance of SPECT and PET studies was improved after attenuation correction. The main effect was seen in the inferior wall. Especially in the apex and anterolateral wall, there were differences between SPECT and PET studies not attributable to attenuation artifacts. Because these differences diminished after smoothing of the PET studies, they might be due to partial-volume effects caused by the inferior resolution of the SPECT images. CONCLUSION: The x-ray-derived attenuation correction leads to SPECT images that represent myocardial perfusion more accurately than nonattenuation-corrected SPECT images. The benefit of the method is seen primarily in the inferior wall. The low resolution of the SPECT system may lead to artifacts due to partial-volume effects. This phenomenon must be considered when perfusion PET is used as a reference method to investigate the effect of attenuation correction.

Adult↗
PubMed1990

[The effects of pulsatile pumping on tissue perfusion and renal function during deep hypothermic low flow perfusion].

The effects of pulsatile pumping on tissue perfusion and renal function during deep hypothermic low flow perfusion were compared with non-pulsatile pumping. Twelve dogs were classified into 2 groups by the perfusion technique used. Animals were core cooled to 20 degrees C esophageal temperature with 80 ml/kg/min perfusion rate and maintained at the level for 2 hours with low flow perfusion (LFP) (30 ml/kg/min), then rewarmed to 35 degrees C with 80 ml/kg/min flow rate. As compared with the non-pulsatile group, pulsatile group demonstrated greater urine output during rewarming (p less than 0.05) and greater lymph flow during core cooling (p less than 0.05). The non-pulsatile group showed higher lymph/plasma protein concentration ratio (Lc/Pc) during LFP and rewarming (p less than 0.05), and greater plasma protein clearance during rewarming (p less than 0.05), and much higher increase of interstitial fluid pressure. The lesser water retention during bypass was also noted in the pulsatile group (28.6 +/- 27.6 ml/kg vs 85.4 +/- 52.1 ml/kg, p less than 0.05). These findings have suggested that the pulsatile perfusion may be useful for the infant cardiopulmonary bypass reducing tissue edema and preserving better renal function.

Animals↗
PubMed1988

[Utility of digital perfusion images of the lung in mitral stenosis: the pathophysiological significance of the distribution of pulmonary perfusion].

The relationship between pulmonary hemodynamics (cardiac index; CI and the mean pulmonary artery wedge pressure; mPw) and the redistribution of pulmonary perfusion were studied in 300 patients with mitral stenosis using computerized Tc99m-MAA perfusion images (digital perfusion images: DPI), which consisted of isocount areas. Various types of DPI were obtained and were classified in six grades according to patterns of 100-70% of the isocount area in the right anterior DPI, i.e. grade-0 (normal), grade-1 (increased perfusion in the upper zone), grade-2 (uniform distribution), grade-3 (disappearance of the basal hyperperfusion area), grade-4 (apical hyperperfusion area) and grade-5 (decrease of perfusion at the lower zone). The mPw was thought to be one of the factors determining distribution. Thus, it was not adequate to estimate the mPw from DPI. In patients with the mPw less than 20 mmHg, an increase in perfusion at the upper zone and disappearance of the basal hyperperfusion might be noted, however, the mPw more than 20 mmHg was necessary to cause an apical hyperperfusion area. The predictive values of grades 0 and 1 for the mPw less than 20 mmHg were 70% (54/77) and those of grades 4 and 5 for the mPw less than 20 mmHg and the mPw less than 25 mmHg were 86% (110/128) and 56% (71/128), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1997

Effects of hemodilution on splanchnic perfusion and hepatorenal function. I. Splanchnic perfusion.

Perfusion of intestinal organs increases in response to acute normovolemic hemodilution (ANH). However, detailed studies on distribution of regional splanchnic organ perfusion during ANH are lacking. We therefore carried out this study to test the hypothesis that ANH does not cause disturbance of physiologic patterns of regional splanchnic organ blood flow. After governmental permission, 22 anesthetized dogs were instrumented to allow invasive hemodynamic measurements and intracardial injection of radioactive microspheres (diameter 15 micro m) for determination of regional organ perfusion. Measurements were made at baseline (hematocrit 37 +/- 3%) and after ANH with 6% hydroxyethyl starch (mol. wt. 200000 / 0.5) to hct 20 +/- 1%. After completion of the protocol, splanchnic organs were removed and dissected into small samples according to anatomical and functional principles. Regional perfusion was determined based on the microsphere content of each sample. Hepatic, intestinal, and pancreatic blood flow increased with ANH. Hepatic arterial blood flow rose by 86%, whereas portal venous perfusion increased by 28%. Small intestine mucosal perfusion was augmented by 68% while the non-mucosal tissue compartment of the gut wall received 32% more blood flow after ANH which is in proportion to the increase in cardiac index after ANH. This redistribution of intestinal flow might be the basis for the preservation of tissue oxygenation during moderate isovolemic anemia.

Animals↗
PubMed1990

Isolated limb perfusion for localized melanoma of the extremity. A matched comparison of wide local excision with isolated limb perfusion and wide local excision alone.

The therapeutic efficacy of isolated limb perfusion in patients with localized melanoma of the extremity remains controversial. We compared patients treated at the University of Texas M.D. Anderson Cancer Center, Houston, with wide local excision and isolated limb perfusion using either melphalan or imidazole carboxamide with a group matched for prognostic factors from the University of Alabama at Birmingham and the University of Sydney (Australia) who were treated with wide local excision alone. No significant difference in disease-free or overall survival rates was found between patients treated with wide local excision with adjuvant isolated limb perfusion or wide local excision alone. However, a subset of patients with thicker lesions (greater than 2.0 mm) treated with wide local excision and isolated limb perfusion using melphalan had a significant improvement in both disease-free and overall survival rates. These data suggest that isolated limb perfusion using melphalan may improve survival rates in selected patients with localized melanoma of the extremity who are at increased risk for local and regional micrometastases, and justifies the continued study of this treatment approach in prospective clinical trials.

Aminoimidazole Carboxamide↗
PubMed1994

Influence of perfusion flow rate on uptake and pharmacodynamics of quinidine in isolated perfused rat heart.

With the single-pass isolated perfused rat heart preparation, we examined the effect of perfusate flow rate on the time course of quinidine output concentration (Cout) and the change in the QT interval (delta QT) on the electrocardiogram. Four hearts were perfused at 5.6 mL/min with quinidine (20 microM) for 25-45 min. This was followed by a 50-min washout period with drug-free perfusate. This procedure was repeated four times in each heart. Using a one-compartment model, the rate constants calculated from the time course of Cout (k) and delta QT (Ke) were similar (p > 0.05) and did not vary among the five phases. A zero-time intercept for Cout indicated shunting of perfusate (1.2-13.6%), from which the coronary output concentration (Ccor) and coronary flow rate were calculated. These experiments were repeated in another six hearts, except flow rates of 2, 4, 6, 8, and 2 mL/min were used in each phase. Equilibration of Cout and delta QT was faster with increasing flow rate, and ke and k were similar at each flow rate (p > 0.05). A modified Kety-Renkin-Crone equation was fitted to values for k and coronary flow rate. The mean permeability surface product estimate was 15.3 +/- 3.0 mL/min/g heart, which in comparison with the highest flow rate used (9 mL/min/g heart) suggests that quinidine has intermediate permeability. The excellent fit obtained indicates that a more complex model, incorporating heterogeneous flows or opening of capillaries at higher flows, was not necessary.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Influence of physicochemical parameters and perfusate flow rate on the distribution of solutes in the isolated perfused rat hindlimb determined by the impulse-response technique.

The relationship between solute distribution, physicochemical properties, and tissue physiology was determined by the impulse-response (IR) technique and statistical moment analysis in the isolated perfused rat hindlimb. The concentration of bovine serum albumin (BSA; 2, 4.7, and 7%, w/v), perfusate flow rate (4 and 8 mL/min), and solute physicochemical properties (lipophilicity, P, fraction unbound to protein, fu; fraction ionized, fi; and molecular weight MW) were varied to better understand the underlying determinants of solute distribution. An apparent low availability was found for a number of the solutes as a consequence of tissue sequestration. This low availability precludes the estimation of an apparent volume of distribution (V) for these solutes. The V of solute and tissue (skin, fat, and muscle) blood flow increased with perfusion flow rate (p < 0.01). The unbound distribution volume (Vu) of basic solutes was significantly linear with respect to P. Multiple linear regression analysis showed that the distribution volume of solute in tissue was significantly related to fu (p < 0.01), but not improved by including relationships to P, MW, and fi. Data obtained with this IR technique yield results consistent with in vivo studies in terms of the importance of fu as a determinant of V. This work has shown that the estimations of solute V by the IR technique in a single-pass preparation are unreliable for solutes with a low availability due to apparent solute sequestration into tissue. The parameter V may also be affected by changes in the perfused limb physiology associated with the perfusion conditions used. The Vs for lidocaine and diazepam vary with fu in accordance with deductions based on the results of steady-state studies.

Adrenergic beta-Antagonists↗
PubMed1989

Absorption and presystemic glucuronidation of 1-naphthol in the vascularly fluorocarbon emulsion perfused rat small intestine. The influence of 1-naphthol concentration, perfusate flow and noradrenaline.

Using the isolated vascularly fluorocarbon emulsion perfused rat small intestine some factors which determine the extent of the intestinal glucuronidation of 1-naphthol to 1-naphthol-beta-D-glucuronide were studied. Increasing the luminal 1-naphthol concentration resulted in a concomitant increase in the 1-naphthol appearance in the vascular perfusate. In contrast, the total appearance of 1-naphthol-beta-D-glucuronide increased less than proportional to the increase in the luminal 1-naphthol concentration. About 88% of the total amount of 1-naphthol-beta-D-glucuronide excreted was released into the vascular perfusate. The capacity-limited intestinal glucuronide efflux is most likely due to saturation of the excretory mechanism for 1-naphthol-beta-D-glucuronide. Decreasing the vascular flow rate influenced both the appearance of 1-naphthol and 1-naphthol-beta-D-glucuronide in the vascular perfusate, whereas the appearance of 1-naphthol-beta-D-glucuronide in the luminal perfusate was essentially flow-independent. A noradrenaline-induced change in the haemodynamic state of the vascular bed (with the total flow kept constant) resulted in a marked decrease in the naphthol vascular concentration. The vascular 1-naphthol-beta-D-glucuronide concentration was only slightly affected. These results indicate that changes in blood flow and blood flow distribution within the intestinal wall can affect the extent of presystemic intestinal metabolism by interfering with the absorption of the parent compound and the efflux of formed conjugates. These parameters can be of paramount importance for causing variable intestinal first-pass effects of drugs in vivo.

Animals↗
PubMed1988

Respiratory and cardiac responses to exercise-simulating peripheral perfusion in endurance trained and untrained rats. I. Reflex responses and changes in perfusion outflow.

Ventilatory and circulatory drives elicited by exercise-simulating perfusion of the circulatory isolated hindleg were examined in 10 trained (TR) and untrained (UTR) rats. TR were submitted to endurance training on a motordriven treadmill (30.min-1 at a grade of 10%, 5 days a week for 30 min). Exercise was simulated by perfusion with modified tyrode solutions: I.) hypoxic, enriched with lactic acid (15 mmol.l-1), II.) normoxic, enriched with lactic acid. III.) hypoxic without lactic acid. Perfusion was performed in anaesthetized animals through cannulae in the femoral artery and vein; the hindled was connected to the rest of the body only by nerve and bone. 10 min of control perfusion (normoxic tyrode solution) was followed by a 20 min test period and another 10 min control perfusion. Apart from heart rate (HR), respiratory rate (RR) and several outflow parameters were measured ([K+], [Na+], [lactate], pH, PO2, PCO2). During control period HR was slightly higher in UTR than in TR (375.5 +/- 3.9 (SE) vs. 364.1 +/- 5.5 beats/min-1, p less than 0.6 n.s.), and RR in UTR was significantly higher than those in TR (61.5 +/- 0.4 bpm vs. 55.5 +/- 3.9 breaths.min-1, p less than 0.001). During the test periods both HR and RR in UTR increased significantly while in TR they did not (e.g. in series I mean HR and RR in UTR increased by 8.9 +/- 1.2 beats.min-1 and 1.4 +/- 0.1 breaths.min-1 respectively, whereas in TR the changes were - 2.9 +/- 1.5 beats/min-1 and -0.8 +/- 0.2 breaths.min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Beneficial effect of coenzyme Q on myocardial slow action potentials in hearts subjected to decreased perfusion pressure-hypoxia-substrate-free perfusion.

Coenzyme Q, an important component of the electron transfer system in mitochondria, plays a central role in energy production aerobically. The effect of pretreatment with coenzyme Q10 (Co Q) on myocardial slow action potentials (APs) and accompanying contractions and on myocardial high energy phosphate content was studied in perfused hearts subjected to decreased perfusion pressure-hypoxia-substrate-free. Post-hatched chicks were treated i.p. with 10 mg/kg of Co Q daily for 5 days. To study the slow APs exclusively, the fast Na+ channels were voltage-inactivated by elevated K+ (25 mM) Tyrode solution. The Ca++-dependent slow APs were induced by elevating [Ca]o to 5.4 mM; hearts were paced at a rate of 40 per min. Hearts which had been pretreated with Co Q were protected against the deleterious effect of decreased perfusion pressure - hypoxia - substrate-free perfusion on mechanical performance accompanying the slow Ca++-Na+ APs. The slow APs in hearts pretreated with Co Q were also less affected than were non-treated hearts. However, the myocardial ATP and total adenine nucleotides were not affected by exogenous Co Q. It was suggested that exogenous Co Q could protect against the decline of cardiac contractions via improved availability of slow APs during decreased perfusion pressure - hypoxia - substrate-free, independently of the cellular high energy phosphate level.

Animals↗
PubMed1991

Use of an artificial oxygen carrier in isolated rat liver perfusion: first demonstration of net glucose uptake at physiological portal glucose concentrations using a hemoglobin-free perfusate.

A defect in isolated perfused rat-liver (IPRL) preparations has been proposed to explain discrepancies between in vivo and in vitro findings regarding hepatic glucose metabolism. The aim of the present study was to investigate whether a preparation of IPRL using a synthetic hemoglobin-free perfusate was capable of net glucose uptake and glycogen deposition at physiological portal substrate concentrations. Livers from fed anaesthetized rats were perfused in a recirculating system using a fluorocarbon emulsion as artificial oxygen carrier. Depending on the prevailing glucose concentration, livers exhibited net glucose uptake or release with a threshold value of 5.5-6.0 mM glucose. Net glucose uptake was associated with net glycogen deposition (+0.23 to +0.59 mumol C6 min-1 g-1). From 5.8 mM (n = 3) and 10.0 mM (n = 8), initial concentration glucose levels fell to 5.3 +/- 0.2 mM after 210 min (n = 3) and 6.3 +/- 0.9 mM after 120 min (n = 8), respectively. This was equivalent to a net glucose uptake of -0.16 and -0.45 mumol min-1 g-1. Anoxia reversibly switched hepatic glucose balance from net uptake (-0.42 mumol min-1 g-1) to release (+0.69 mumol min-1 g-1) followed by net uptake (-0.50 mumol min-1 g-1) after reinstitution of aerobic conditions. We conclude that the composition of perfusion media might play a pivotal role for studies of glucose metabolism in the isolated perfused rat liver. In our experimental model, using a hemoglobin-free synthetic medium, net glucose uptake was readily demonstrated at physiological portal substrate concentrations similar to the in vivo situation.

Aerobiosis↗
PubMed1984

Relative distribution of estrone, estradiol and estriol between fetal and maternal perfusates during perfusions of human term placentas with labelled C19 precursors.

Published results from in vivo experiments carried out in Rhesus monkeys and from in vitro perfusions of human term placentas have indicated that placental estradiol (E2) is preferentially released towards the mother whereas estrone (E1) is about evenly distributed between fetal and maternal circulation. In order to examine the distribution of estriol, relative to that of E1 and E2, we have now prepared [3H]16-hydroxyandrostenedione by incubation of [6,7-3H]androstenedione with Streptomyces roseochromogenus and perfused placental cotyledons with mixtures of these two labeled precursors. Measurement of the concentrations of tritiated E1, E2 and E3 in the maternal and fetal perfusates, flowing at approx 10 and 5 ml/min, respectively, indicated that the distribution of E3 is different from that of E2 and resembles the distribution of E1. The simple perfusion system being used shows differences in the distribution of various estrogens between fetal and maternal perfusates which may reflect the in vivo situation and offers the opportunity for experimental examination of various explanations for these differences, e.g. existence of specific carrier systems in the syncytial membranes, specific binding of the estrogens to secreted placental proteins, and actions of placental and decidual 17 beta-hydroxysteroid dehydrogenases.

Androstenedione↗
PubMed1989

The influence of perfusate viscosity, RBC deformability and drag on the function of an isolated perfused rat kidney.

There is increasing clinical interest in improving blood rheology to optimize organ function, but studies correlating the two are scarce. To study this, rat kidneys were perfused in vitro at 37 degrees C at a constant mean renal arterial pressure of 160 mm Hg. The perfusate consisted of an oxygenated Krebs HCO3 buffer containing 1 mg/ml glucose, 0.5 mg/ml creatinine, amino acids, [3H]inulin (marker for GFR), 2.5 g/dl albumin, and 10 or 20% hematocrit. In some experiments, RBC were made nondeformable by heating at 50 degrees C for 20 min. Deformability was measured by an ektacytometer. In other experiments, 0.001% of an anionic polyacrylamide (Separan), a drag-reducing agent, was added to the perfusate. Viscosity was measured with a cone and plate viscometer, [Na+] with a flame spectrophotometer, and perfusate flow with a Brooks in-line flowmeter. Other functional parameters, GFR, urine flow, RPF, and reabsorption of sodium and water, were also measured. The results indicate that (1) making RBC nondeformable or increasing viscosity by increasing hematocrit reduces renal function, and (2) addition of a drag-reducing agent improves renal function at 20% hematocrit. We conclude that rheologic manipulation of a perfusate solution can alter flow and renal function.

Absorption↗