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At least 775 records · Page 43Linked to original sources
PubMed1997

Fetoplacental vascular tone during fetal circuit acidosis and acidosis with hypoxia in the ex vivo perfused human placental cotyledon.

OBJECTIVES: Our purpose was to determine the effects of acidosis and acidosis-hypoxia on fetoplacental perfusion pressure and its response to angiotensin II. STUDY DESIGN: Perfused cotyledons from 14 placentas were studied with either an acidotic fetal circuit perfusate (n = 7) or an acidotic-hypoxic fetal circuit perfusate (n = 7). Each cotyledon's fetal vasculature was initially perfused under standard conditions and bolus injected with 1 x 10(-10) moles of angiotensin II. Fetoplacental perfusate was then replaced with either an acidotic medium (pH 6.90 to 7.00 and Po2 516 to 613 mm Hg) or an acidotic-hypoxic medium (pH 6.90 to 7.00 and Po2 20 to 25 mm Hg) followed by an angiotensin II injection. The vasculature was subsequently recovered with standard perfusate and again injected with angiotensin II. Perfusion pressures within each group were compared by one-way analysis of variance, and results were expressed as mean pressure +/- SEM. RESULTS: Resting fetoplacental perfusion pressure did not change when the fetal circuit perfusate was made acidotic (28 +/- 1 mm Hg vs 25 +/- 2 mm Hg) or acidotic-hypoxic (26 +/- 2 mm Hg vs 25 +/- 2 mm Hg). The maximal fetoplacental perfusion pressure achieved in response to angiotensin II did not differ with an acidotic perfusate (41 +/- 2 mm Hg vs 38 +/- 1 mm Hg) or with an acidotic-hypoxic perfusate (39 +/- 2 mm Hg vs 36 +/- 2 mm Hg). CONCLUSIONS: In the perfused placental cotyledon fetoplacental perfusion pressure and pressor response to angiotensin II are not affected by fetal circuit acidosis or acidosis-hypoxia. This suggests that neither fetal acidosis nor fetal acidosis combined with hypoxia has a direct effect on fetoplacental vascular tone.

Acidosis↗
PubMed1998

Cytostatic lung perfusion by use of an endovascular blood flow occlusion technique.

BACKGROUND: Different modalities of cytostatic lung perfusion were compared regarding plasma and tissue drug concentrations to assess the efficacy of an endovascular blood flow occlusion technique. METHODS: A cytostatic lung perfusion study with doxorubicin hydrochloride was performed on large white pigs (n = 12). Plasma and tissue concentrations of doxorubicin were compared for isolated lung perfusion with open cannulation (ILP), blood flow occlusion perfusion with open cannulation of the pulmonary artery alone (BFO), and intravenous drug administration (i.v.). In a fourth group, thoracotomy-free BFO perfusion was performed by endovascular balloon catheterization of the pulmonary artery (endovascular BFO). The 3 animals in this group were used to compare the doxorubicin-perfused pulmonary tissue with the contralateral nonperfused lobes after 1 month. RESULTS: The mean lung tissue doxorubicin concentration at the end of perfusion was 19.8 +/- 1.6 microg/g after ILP, 27.6 +/- 2.2 microg/g after BFO (p = not significant), and 3.0 +/- 0.8 microg/g after i.v. perfusion (p < 0.01). Whereas doxorubicin was not detectable in the plasma in the ILP group, concentrations ranged from not detectable to 0.44 microg/mL in the BFO group and from 0.31 to 0.84 microg/mL in the i.v. group (p < 0.05). Mean myocardial tissue concentration was not significantly different after BFO than i.v. perfusion (1.1 +/- 0.5 microg/g and 1.8 +/- 0.1 microg/g, respectively). In the endovascular BFO group, balloon-blocked pulmonary artery perfusion was successfully performed in all animals, and after 1 month, lung tissue showed no cytostatic-induced histologic changes. CONCLUSIONS: Compared with ILP, BFO cytostatic lung perfusion produced an insignificantly higher lung-tissue concentration, corresponding to a sixfold to ninefold higher level than after i.v. perfusion. Plasma drug levels during BFO perfusion were lower than during i.v. perfusion. Endovascular BFO may be a promising technique for repeated cytostatic lung perfusion.

Animals↗
PubMed1998

Removal of primate xenoreactive natural antibodies by extracorporeal perfusion of pig kidneys and livers.

Organ perfusion is one of the possible strategies to attenuate rejection of discordant xenografts by reducing the levels of the recipient's xenoreactive natural antibodies (XNA). Its efficacy in terms of XNA removal was studied in models of primate blood or plasma perfusion through porcine kidneys or livers, with special attention to haematological consequences and potential side-effects. We first perfused the blood of rhesus monkeys through pig kidneys and livers, and demonstrated that the perfusion of a pig liver resulted in higher XNA adsorption (72 +/- 13%) than the perfusion of a pig kidney (51 +/- 25%). However, when we normalized for the weight of the perfused organs and for levels of natural antibodies in individual monkeys, livers adsorbed less antibody (1.4 +/- 0.9 U antibody/g) than kidneys (7.2 +/- 7 U antibody/g). Histological signs of rejection were observed in perfused kidneys, but not in perfused livers. A major drawback of the perfusion of blood through livers was a considerable decrease in the primates' haemoglobin and platelet levels. To avoid this, we developed a plasma liver perfusion device. This method allowed a significant improvement in the haemodynamic state of primates and was particularly effective in preventing anaemia. Moreover, plasma liver perfusion was as effective as blood liver perfusion to remove natural antibodies and, resulted in a marked decrease in their functional activity as assessed by complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC). The level of other plasma proteins was not significantly affected, apart from a dilution effect. After xenoperfusion a strong antibody response was evidenced by ELISA, CDC and ADCC between days 7 and 14 and then decreased progressively. We conclude that the separation of blood to allow the perfusion of plasma through a pig organ is safer than the perfusion of unseparated blood and is associated with efficient natural antibody removal. However, organ perfusion is limited by a rebound in antibody levels after a few days, and thus will have to be associated with anti-B cell immunosuppressive therapy for long-term or repeated applications.

Animals↗
PubMed1996

Doppler grid surface scanning applications for pulmonary subsurface parenchymal perfusion assessment.

Subsurface perfusion to lung parenchyma underlying the pleura is difficult to assess in live ventilated animals. The purpose of this study was to assess applicability of a newly developed laser Doppler grid scanning imaging technology that measures perfusion of pleural subsurface lung regions in intact normal and abnormal animal lungs. Eighty-six Doppler grid perfusion measurements were performed in five New Zealand White Rabbits (3-5 kg); four with unilateral bullous lung disease, one normal control. Left upper lobe lung surface was exposed to 10 1-sec spot Nd:YAG exposures (70 W/cm2). One week following laser exposure, all rabbits underwent sequential bilateral open thoracotomy. Unaffected left lower lobes in these animals and all four lobes of a previously untreated rabbit were used as controls. Pleural subsurface perfusion measurements were recorded over a contiguous 900-pixel square surface grid using quantitative noncontact laser Doppler imaging during open thoracotomy procedures. Scans were obtained in a normal volume ventilation mode, at 30 cm of inspiratory hold airway pressure, and postinflation. A perfusion-pressure response curve was obtained in normal lung at 10-, 20-, and 30-cm static airway pressure. Post mortem measurements were used as 0 flow controls. Normal lung tissue was found to have relatively high pleural subsurface perfusion (1362 +/- 328 corrected units on a scale of 0-4095). Areas of atelectasis had decreased perfusion (659 +/- 512 U., 48.4 +/- 12.5% compared to normal lung, p < 0.02), but returned to normal levels after inflation of the lung (1253 +/- 363 U., p = 0.21 compared to normal). Pleural subsurface perfusion decreased uniformly and progressively as lung inflation pressure increased (p < 0.0001). Perfusion increased immediately to supranormal values following release of high inspiratory inflation pressure holds (1603 +/- 626 U., 117 +/- 18% compared to normal lung, p = 0.03). Bullae had markedly decreased perfusion (541 +/- 68 U.) that was not further reduced by increased inflation pressures. Noncontact laser Doppler grid perfusion imaging appears to provide a new tool for measuring pleural subsurface perfusion over a large area of lung surface in clinical experimental settings. Results are rapid, reproducible, and consistent. Sampling errors inherent in current point sampling Doppler flow techniques are reduced by the multiple contiguous measurements. We have used this technique to demonstrate inspiratory pressure-related reduction in pleural subsurface perfusion in normal lung, reversible decreased perfusion in atelectatic regions, and reduced perfusion in bullous and laser-treated lung regions.

Analysis of Variance↗
PubMed1999

Metabolism of [14C]phenol in the isolated perfused mouse liver.

A previous report from this laboratory focused on the metabolism of [14C]benzene (BZ) in the isolated, perfused, mouse liver (C. C. Hedli, et al., 1997, Toxicol. Appl. Pharmacol. 146, 60-68). Whereas administration of BZ to mice results in bone marrow depression (R. Snyder et al., 1993, Res. Commun. Chem. Pathol. Pharmacol. 20, 191-194), administration of phenol (P), the major metabolite of BZ, does not. It was, therefore, of interest to determine whether the metabolic fate of P produced during BZ metabolism differed from that of P metabolized in the absence of BZ. Mouse livers were perfused with a solution of [14C]P in both the orthograde (portal vein to central vein) and retrograde (central vein to portal vein) direction to investigate the metabolic zonation of enzymes involved in P hydroxylation and conjugation. Perfusate samples were collected, separated by HPLC, and tested for radioactivity. Unconjugated metabolites were identified by comparing their retention times with nonradiolabeled standards, which were detected by UV absorption. Conjugated metabolites were identified and collected on the basis of radiochromatogram results, hydrolyzed enzymatically, and identified by co-chromatography with unlabeled BZ metabolites. The objective was to compare and quantify the metabolites formed during the perfusion of P in the orthograde and retrograde directions and to compare the orthograde P-perfusion results with the orthograde BZ results reported previously. Regardless of the direction of P perfusion, the major compounds released from the liver were P. phenylgucuronide, phenylsulfate, hydroquinone (HQ), and HQ glucuronide. A comparison of the results of perfusing P in the orthograde versus the retrograde direction showed that more P was recovered unchanged and more HQ was formed during retrograde perfusion. The results suggest that enzymes involved in P hydroxylation are generally closer to the central vein than those involved in conjugation, and that during retrograde perfusion, P metabolism may be limited by the sub-optimal conditions of perfusion. Comparison of the orthograde perfusion studies of P and BZ revealed that a larger percentage of the radioactivity released from the liver was identified as unconjugated HQ after BZ perfusion than after P perfusion. In addition, the amount of radioactivity covalently bound to liver macromolecules was measured after each perfusion and determined to be proportional to the amount of HQ and HQG detected in the perfusate samples.

Animals↗
PubMed1979

Influence of potassium, sodium, perfusion pressure, and isoprenaline on renin release induced by acute calcium deprivation.

1. These studies were conducted in isolated perfused rat kidneys to determine the influence of perfusion pressure, isoprenaline, K, and Na on renin release stimulated by acute Ca deprivation.2. Removing Ca from the perfusion medium for 10 min stimulated renin release and reintroducing Ca returned it toward control values.3. Lowering concentration of Ca in the perfusion medium from 5 to 0 mM increased the effectiveness of low perfusion pressure (50 mmHg) and isoprenaline (2.43 muM) in stimulating renin release.4. At higher perfusion pressure (150 mmHg), renin release was inhibited in perfusion medium containing 2.5 mM-Ca but not in medium containing no Ca. In fact, high perfusion pressure stimulated renin release when the perfusion medium was without Ca.5. Raising concentration of K in the perfusion medium partially inhibited the renin release induced by Ca deprivation. Adding 5 mM-EGTA to Ca-deprived medium stimulated a greater rate of renin release than that of Ca-deprived medium alone. This greater renin release was also partially inhibited by raising K concentration in the perfusion medium.6. Lowering concentration of Na in the perfusion medium from 145 to 25 mM partially inhibited the renin release induced by Ca deprivation in the presence of low perfusion pressure or isoprenaline.7. These findings support the hypothesis that a decreased concentration of Ca in the cytoplasm of the juxtaglomerular cell stimulates renin release and increased Ca inhibits renin release. The sequence of events which leads to changes in cytoplasmic Ca might depend on the concentration of Ca in the perfusion medium, the renal perfusion pressure, the membrane potential of the juxtaglomerular cells, and Ca-Na exchange mechanisms.

Animals↗
PubMed1982

Isolated working rat heart perfusion with perfluorochemical emulsion Fluosol-43.

Isolated working rat hearts were perfused with the perfluorochemical emulsion Fluosol-43 to determine whether it would support prolonged, stable cardiac function. The perfluorochemical emulsion provides a controlled perfusate composition, relatively high oxygen capacity, and a colloid osmotic pressure that is similar to that of plasma. Electrically paced (325 beats/min) hearts were perfused for 6 h at 35 degrees C in a recirculating system. Hemodynamic and mechanical function of seven Krebs-Henseleit-perfused hearts declined significantly more than that of seven Fluosol-43-perfused hearts over the 6-h period. The percent of initial function remaining at 6 h for Krebs-Henseleit-perfused vs. Fluosol-43-perfused hearts was 70.3 +/- 5.0 vs. 95.4 +/- 1.1% (P less than 0.001) for left ventricular peak systolic pressure; 55.6 +/- 7.7 vs. 97.5 +/- 2.4% (P less than 0.001) for dP/dtmax; 27.1 +/- 7.2 vs. 60.6 +/- 5.2% (P less than 0.005) for cardiac output; 11.0 +/- 6.3 vs. 67.2 +/- 3.4% (P less than 0.001) for external work efficiency; and 17.4 +/- 8.4 vs. 67.7 +/- 4.5% (P less than 0.001) for stroke rhythmic than Fluosol-43-perfused hearts during the last 3 h of perfusion. Perfusate lactate concentration was 4.5-fold higher in the Krebs-Henseleit perfusate than in the Fluosol-43 perfusate at 6 h, reflecting greater anaerobic metabolism in the Krebs-Henseleit-perfused hearts. Thus isolated rat hearts perfused with Fluosol-43 have greater maintenance of hemodynamic and mechanical function over a longer time period than hearts perfused with Krebs-Henseleit bicarbonate buffer.

Animals↗
PubMed1989

Angiotensinogen's role in ANG formation, renin release, and renal hemodynamics in isolated perfused kidney.

Isolated perfused rat kidneys were used to investigate the effects of the addition of pure angiotensinogen or renin-free plasma to the perfusate on angiotensin I (ANG I) and angiotensin II (ANG II) generation, renal hemodynamics, and renin release. When no angiotensinogen or plasma is added, a very small amount of angiotensinogen is initially detected in the perfusate. Whereas renin secreted by the kidney accumulates in the perfusate, angiotensinogen disappears during the perfusion and immunoreactive ANG II cannot be detected. The addition of angiotensinogen reactivates the renin-angiotensin system. ANG I, [des-Asp1] ANG I, ANG II, and [des-Asp1] ANG II are progressively generated in the perfusate. At a constant perfusion pressure, as well as at a variable perfusion pressure, a progressive fall in renal perfusate flow is observed that is significantly correlated to the level of immunoreactive ANG II. ANG II significantly blunts the rise in renin, and renin release in the perfusate is negatively correlated to immunoreactive ANG II levels. Comparison of the ANG I and ANG II levels in in vitro incubated perfusates and circulated perfusates shows that in plasma-injected perfusates the level of immunoreactive ANG II is dependent on both the production of ANG I and its conversion to ANG II by renal and perfusate converting-enzyme activity, and on ANG I and ANG II degradation by the kidney and the perfusate.

Angiotensin I↗
PubMed2000

Computer-assisted ex vivo, normothermic small bowel perfusion.

BACKGROUND: In the present study, a technique for computer-assisted, normothermic, oxygenated, ex vivo, recirculating small bowel perfusion was established as a tool to investigate organ pretreatment protocols and ischemia/reperfusion phenomena. A prerequisite for the desired setup was an organ chamber for ex vivo perfusion and the use of syngeneic whole blood as perfusate. METHODS: The entire small bowel was harvested from Lewis rats and perfused in an organ chamber ex vivo for at least 2 h. The temperature was kept at 37 degrees C in a water bath. Three experimental groups were explored, characterized by different perfusion solutions. The basic perfusate consisted of syngeneic whole blood diluted with either NaCl, Krebs' solution or Krebs' solution and norepinephrine to a hematocrit of 30%. In addition, in each group l-glutamine was administered intraluminally. The desired perfusion pressure was 100 mm Hg which was kept constant with a computer-assisted data acquisition software, which measured on-line pressure, oxygenation, flow, temperature and pH and adjusted the pressure by changing the flow via a peristaltic pump. The viability of the preparation was tested by measuring oxygen consumption and maltose absorption, which requires intact enzymes of the mucosal brush border to break down maltose into glucose. RESULTS: Organ perfusion in group 1 (dilution with NaCl) revealed problems such as hypersecretion into the bowel lumen, low vascular resistance and no maltose uptake. In contrast a viable organ could be demonstrated using Krebs' solution as dilution solution. The addition of norepinephrine led to an improved perfusion over the entire perfusion period. Maltose absorption was comparable to tests conducted with native small bowel. Oxygen consumption was stable during the 2-hour perfusion period. CONCLUSIONS: The ex vivo perfusion system established enables small bowel perfusion for at least 2 h. The viability of the graft could be demonstrated. The perfusion time achieved is sufficient to study leukocyte/lymphocyte interaction with the endothelium of the graft vessels. In addition, a viable small bowel, after 2 h of ex vivo perfusion, facilitates testing of pretreatment protocols for the reduction of the immunogenicity of small bowel allografts.

Absorption↗
PubMed1985

Canine liver isolation-perfusion at normo- and hyperthermic temperatures with perfluorochemical emulsion (Fluosol-43).

A perfluorocarbon emulsion, Fluosol-43, was used as a blood substitute for oxygen transport during isolation-perfusion of the dog liver at 37 and 43 degrees C. Preservation of hepatic functional integrity was assessed through analysis of perfusate constituents and animal survival after perfusion. Flow to the liver during perfusion was greater than 1 ml/min/g with one-third of total flow provided through the hepatic artery and two-thirds through the protal vein. Perfusion duration was 3 h. The pO2 gradient across th liver indicated that oxygen was consumed during perfusion at both temperatures. The expected rise in pCO2 and decrease in pH of the outflow perfusate is consistent with active aerobic metabolism. Perfusate chemistries lactate, pyruvate, glucose, urea, total alpha-amino acids, ketone bodies and SGPT demonstrated that hepatic functional integrity was maintained during perfusion. Significant differences (p less than 0.05) between temperatures occurred in the perfusate levels of lactate, pyruvate, L/P ratios, glucose and total alpha-amino acids. Animal survival after a 3-hour perfusion was 3/4 at 37 degrees C, and 2/5 at 43 degrees C. After perfusion, SGPT levels were significantly higher in dogs subjected to perfusion at 43 degrees C. The success of these experiments demonstrates that perfusion of the liver with Fluosol-43 was not in itself hepatotoxic, and that Fluosol-43 may allow perfusion of the liver at 43 degrees C with only wild toxicity.

Alanine Transaminase↗
PubMed1983

Influence of perfusate PO2 on hypoxic pulmonary vasoconstriction in rats.

The purpose of these studies was to evaluate the influence of perfusate oxygen tension on hypoxic pulmonary vasoconstriction and to identify the site at which both alveolar and perfusate gas tensions stimulate hypoxic pulmonary vasoconstriction. Lungs from adult rats were ventilated and perfused in vitro at constant temperature, PCO2, and pH, with a perfusion circuit incorporating a membrane oxygenator that allowed independent control of the alveolar and perfusate gas tensions. Blood flow to the lung was constant (0.06 ml per g body weight per min), and pulmonary vascular resistance was therefore proportional to pulmonary artery pressure. In study 1, the pulmonary artery pressor response to zero or 22 mm Hg alveolar oxygen was measured when the perfusate oxygen tensions were approximately 8, 26, 41, 64, or 128 mm Hg. The pressor response as a percent of the maximum pressure change was progressively reduced as perfusate oxygen tension increased. For alveolar oxygen tension of zero; the pressor response = 128 -39 (Log PPO2) and r = 0.8 (P less than 0.01), the effect of perfusate gas tension on the response to alveolar gas tension of 22 mm Hg was similar. These results demonstrate that the stimulus for hypoxic pulmonary vasoconstriction is a function of both alveolar and perfusate oxygen tension. In study 2, the response to alveolar oxygen tension of 42 mm Hg was measured with mean perfusate oxygen tensions of 130, 52, and 17 mm Hg. In six animals with forward perfusion, the responses decreased with increasing perfusate oxygen tension, as in study 1. In another six animals, with retrograde perfusion, the responses to alveolar hypoxia were not altered when perfusate oxygen tension was increased. These results demonstrate that the sensor region for hypoxic pulmonary vasoconstriction is precapillary. These studies confirm and extend previous hypotheses that alveolar and perfusate oxygen tensions together, determine the PO2 at a precapillary site to stimulate hypoxic pulmonary vasoconstriction.

Animals↗
PubMed1976

Comparison of somatomedin activity in perfusates of normal and hypophysectomized rat livers with and without added growth hormone.

We compared the somatomedin (SM) activity of perfusates of livers from normal and hypophysectomized (hypox) rats with and without the addition of growth hormone (GH) to the perfusions. Livers were perfused for a total of 3 hours, with a change of Waymouth's medium MB 752/l every 30 min, in a continously recirculating system. SM activity was estimated by the stimulation of the incorporation of sulfate by hypox rat costal cartilage incubated in vitro. Endogenous SM activity (no addition of GH) in the perfusates of the livers of normal rats was initially 136 +/- 17% above buffer levels (mean +/- SE) and fell gradually to near-buffer levels over the first 2 1/2 hours. Endogenous SM activity in the perfusates of livers from hypox rats was initially 72 +/- 10% above buffer levels, significantly lower than that of the normal livers, and reached buffer levels with the fifth medium change. Pretreatment of hypox rats with GH in vivo increased their initial liver perfusate SM activity to 134 +/- 25%, comparable to that of normal livers and significantly greater than that of livers of untreated hypox rats. The addition of GH (25 mug/ml) to the perfusion of both normal and hypox rat livers led to significant increases in perfusate SM activity compared with that of control perfusates at the same time periods. The increase in SM activity was not significant until after 0-30 minutes with hypox livers, and after 30-90 minutes with normal livers. Although it has previously been reported that the direct addition of GH to livers perfusion systems led to an increase in perfusate SM activity, we have now established that in the absence of added GH, perfusates of normal rat livers contain significant SM activity, and that perfusates of normal rat livers contain more SM activity than perfusates of hypox rat livers. In addition, the observation that GH pretreatment increases the SM activity of perfusates of hypox rat livers constitutes the first evidence that SM activity of any body tissue may be altered by administration of GH in vivo.

Animals↗
PubMed1996

Nitric oxide regulation of corticotropin-releasing hormone release from the human perfused placenta in vitro.

We have investigated the regulatory role of nitric oxide (NO) in corticotropin-releasing hormone (CRH) release from the human perfused placental lobule in vitro. The effects of the NO donor sodium nitroprusside, the NO synthase inhibitor N omega-nitro-L-arginine, and the NO substrate L-arginine on human (h) placental CRH secretion have been studied. Single lobules of term placentae were bilaterally perfused with Krebs solution (5 mL/min; 95% O2-5% CO2; 37 C; pH 7.3). Fetal and maternal perfusates were collected at 4 C every 30 min for 3 h. CRH immunoreactivity (CRH-IR) in perfusates was measured by RIA using the 41-residue synthetic CRH as standard, 125I-labeled Tyr-hCRH as tracer, and a rabbit anti-CRH antibody Y2BO. The sensitivity of the assay was 0.13 pmol/L. Under basal conditions, human perfused placentae in vitro continuously secreted CRH-IR, which diluted in parallel to a synthetic hCRH-(1-41) standard curve. Size-exclusion chromatography of placental perfusates using a Sephadex G-50 column indicated that placental CRH-IR predominately coeluted with hCRH-(1-41) standard. Basal maternal perfusate CRH-IR levels (27 +/- 4 pmol/L) released from perfused placental lobules were nearly 10-fold greater than fetal perfusate CRH-IR levels (3.4 +/- 0.7 pmol/L; P < 0.05). Infusion of sodium nitroprusside (30-100 mumol/L) into the maternal and fetal placental circulations inhibited CRH-IR release into maternal perfusate in a concentration-dependent manner, but did not inhibit CRH-IR release into the fetal perfusate. N omega-nitro-L-arginine (100 mumol/L) increased placental CRH-IR secretion into fetal perfusate, and this effect was reversed by the infusion of L-arginine (100 mumol/L), which also reduced release below basal levels. In contrast, maternal perfusate CRH-IR levels were not affected by N omega-nitro-L-arginine or L-arginine. These results indicate that the human perfused placenta in vitro releases a substance of similar mol wt and hCRH-IR. Moreover, modulators of the NO signaling pathway differentially affect placental secretion of CRH-IR into the maternal and fetal perfusates. These data are consistent with the involvement of NO in the regulation of placental CRH release during pregnancy.

Adolescent↗
PubMed2002

Comparison of bone marrow cells harvested from various bones of cynomolgus monkeys at various ages by perfusion or aspiration methods: a preclinical study for human BMT.

Using cynomolgus monkeys, we have previously established a new method for harvesting bone marrow cells (BMCs) with minimal contamination of the BMCs with T cells from the peripheral blood. We originally conducted this new "perfusion method" in the long bones (the humerus, femur, and tibia) of cynomolgus monkeys. Here, we apply the perfusion method to obtain BMCs from the ilium of cynomolgus monkeys, since BMCs are usually collected from the ilium by the conventional aspiration method in humans. The perfusion method consists of two approaches: transverse iliac perfusion and longitudinal iliac perfusion. BMCs harvested by the perfusion method from the long bones and ilium were compared with those collected from the ilium by the aspiration method. The contamination of BMCs with peripheral blood, determined by the frequencies of CD4+ and CD8+ T cells, was significantly lower in BMCs obtained from the ilium or long bones by the perfusion method (CD4+ plus CD8+ T cells <4%) than in those obtained by the iliac aspiration method (CD4+ plus CD8+ T cells >20%). However, the numbers of immature myeloid cells, such as myeloblasts, promyelocytes, myelocytes, and metamyelocytes, were higher in BMCs obtained by the iliac perfusion method than in those obtained by the iliac aspiration method. The assays for in vitro colony-forming unit in culture revealed that progenitor activity was significantly higher in BMCs obtained by the perfusion method than in those obtained by the aspiration method. These findings suggest that the contamination of BMCs with peripheral blood is much less when using the perfusion method than when using the aspiration method. To determine the best site for harvesting BMCs by the perfusion method, age-dependent changes in BMCs harvested by the perfusion method from the long bones and ilium were examined. The numbers of BMCs varied in the long bones (humerus > femur > tibia) and showed age-dependent decreases, whereas they remained similar in the ilium of cynomolgus monkeys from 3 years to 6 years of age. However, in cynomolgus monkeys, BMC harvesting by the perfusion method from the ilium (but not from the long bones) is found to involve the risk of fat emboli, particularly when the BMCs are quickly perfused under high pressure. These findings suggest, even in humans, that the perfusion method is better than the aspiration method, and that the best site for collection of BMCs is the humerus.

Aging↗
PubMed1991

A comparison of lipoprotein secretion, bile production and hepatic morphology in isolated rat livers perfused with a perfluorocarbon emulsion or rat erythrocytes.

Isolated rat livers were perfused with an oxygenated perfluorocarbon emulsion, FC-43 emulsion for 1 to 4 hr. FC-43 emulsion contained 20% FC-43 (wt/vol) perfluorotributylamine (the fluorocarbon component for the transport of oxygen and carbon dioxide) emulsified with 2.56% Pluronic F-68 (a nonionic surfactant) in Krebs-Ringer bicarbonate buffer. FC-43 emulsion also contained 3% hydroxyethyl starch as an oncotic agent and 1.8 mg/ml glucose. The viability (oxygen consumption), bile secretion, structural integrity and secretion of nascent lipoproteins by FC-43-perfused rat livers was compared with livers perfused with Krebs-Henseleit bicarbonate buffer that contained rat erythrocytes (25% hematocrit) and 1.5 mg/ml glucose (red blood cell medium). Oxygen consumption was somewhat higher in livers perfused with FC-43 emulsion. Bile secretion of livers perfused with FC-43 emulsion for 4 hr was reduced significantly to 40% of that by red blood cell medium. The structural integrity of livers perfused with FC-43 emulsion varied from normal to marked cellular damage. Light-microscopical examination of rat livers perfused with FC-43 emulsion showed ballooning of sinusoids, presence of vacuoles in sinusoidal lining cells in some hepatocytes and detachment of endothelium in sinusoids. The number of vacuoles progressively increased in longer perfusions. Electron-microscopical studies showed the presence of small (60 to 100 nm) vesicles of varying electron density, presumably fluorocarbon particles inside the vacuoles in sinusoidal lining cells (Kupffer and endothelial) and hepatocytes. After 4 hr of perfusion with FC-43 emulsion, most of the sinusoidal endothelia were denuded, and the microvilli of the hepatocytes all but disappeared. In contrast, the ultrastructure of rat livers perfused with red blood cell medium for 4 hr was unaltered. The accumulation of nascent lipoproteins in perfusates of FC-43-perfused livers was markedly reduced, and no normal very-low-density lipoprotein, low-density lipoprotein or high-density lipoprotein were isolated. Chemical analysis showed the presence of Pluronic F-68 in all lipoprotein fractions. Our data strongly suggest that, during recirculating liver perfusions with FC-43 emulsion (between 1 and 4 hr), the nonionic surfactant detergent Pluronic F-68 dissociated from the emulsion and markedly affected hepatic structure, lipoprotein secretion and the composition of lipoproteins isolated from perfusate. Therefore FC-43 emulsion is not a suitable liver-perfusion medium for studies of lipoprotein metabolism.

Animals↗
PubMed1977

Regulation by insulin of amino acid release and protein turnover in the perfused rat hemicorpus.

Net changes in the concentrations of 18 amino acids in perfusate and skeletal muscle were followed during perfusion of hemicorpus preparations from fed rat. Perfusate levels of 16 amino acids showed little change from their initial concentrations during the 1st h, but increased dramatically during the 2nd and 3rd h. Aspartate and glutamate levels decreased continuously throughout the perfusion. Release of alanine and glutamine accounted for approximately 50% of the total change in perfusate amino acids. The increase in perfusate amino acids was derived from net breakdown of muscle proteins and not from leakage from the intracellular pool as evidenced by elevated concentrations of intracellular amino acids in perfused muscle. Addition of insulin to the perfusate did not change the pattern of amino acid release during the 1st h of perfusion. However, during the 2nd and 3rd h the hormone completely prevented the net release of most amino acids and maintained intracellular concentrations of most amino acids at levels found in upperfused tissue. Effects of time of perfusion and insulin on amino acid release were accounted for by changes in the rate of protein turnover. Protein synthesis in gastrocemius and psoas muscles in control perfusions decreased after 1 h to approximately 50% of the initial rate. This decrease was accompanied by a 2-fold increase in the level of ribosomal subunits, indicating development of a block in peptide chain initiation. Addition of insulin maintained the initial rate of synthesis and the in vivo level of ribosomal subunits, demonstrating that the hormone prevented the block in peptide chain initiation from forming. Addition of insulin after 2 h reversed the perfusion-induced block in initiation. Synthesis of the specific muscle protein myosin was increased 45% over the control rate in the presence of insulin. Insulin also produced a 50% decrease in the rate of protein degradation during the 2nd and 3rd h of perfusion. A similar effect was noted when protein synthesis was inhibited by addition of cycloheximide. Higher concentrations of insulin were required to maximally inhibit protein degradation than to increase protein synthesis. Involvement of lysosomal proteases in the effect of insulin on protein degradation was evaluated by measuring cathepsin D activity in psoas muscle homogenates. "Free" enzyme activity increased as a result of perfusion while addition of insulin maintained this activity at the unperfused level. Neither perfusion nor insulin had any effect on total cathepsin D activity. Alterations in protein degradation and lysosomal enzyme activity were not due to changes in levels of adenine nucleotides, GTP, or creatine phosphate.

Adenosine Diphosphate↗
PubMedDate not supplied

Pharmacokinetic studies of enalaprilat in the in vitro perfused human placental lobule system.

The objectives of this study were to evaluate the transplacental kinetics and effects on placental function of the angiotensin converting enzyme (ACE) inhibitor, enalaprilat, in the dually perfused human placental lobule system. When placed in the maternal perfusate at a high therapeutic serum concentration (150 ng/ml), enalaprilat was rapidly transferred from the maternal perfusate into placental tissue followed by a gradual release from the placenta into the fetal perfusate. Cmax and AUC values for enalaprilat in the maternal perfusate were approximately 3 times higher than in the fetal perfusate, and drug levels did not equilibrate between maternal and fetal perfusates during the 4-6 hours of perfusion. The more highly perfused regions of the placental lobule had higher drug levels than non-perfused areas. At the end of the perfusion period, the mean percent of total drug added in the maternal perfusate was 59%, with 23% in the fetal perfusate and the remainder (18%) in placental tissue. Despite the relatively high levels of drug found in placental tissue, there were no alterations in placental function as measured by fetal volume loss, fetal pressure, glucose utilization, lactate production, hCG release, net fetal oxygen transfer, and oxygen consumption. Results from this study clearly document placental transfer of enalaprilat in the perfused human placental lobule system. The lack of effect on placental function suggests that enalaprilat has no direct effect on fetoplacental vascular beds, and that fetal hypotension occurring from ACE inhibitor exposure may be due to direct effects on the fetal kidney and not to decreased perfusion of fetoplacental vascular beds; these findings require further validation in an in vivo model.

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PubMed1997

Contrast echocardiography for assessment of myocardial perfusion.

It has been suggested that the myocardial perfusion can be qualitatively and quantitatively assessed by different ultrasound contrast techniques. It has been reported that the intracoronary or intraaortic administration of the ultrasound contrast agents can be used to visualize perfusion defects or to analyze the coronary flow reserve. The perfusion analysis after intracoronary injection of ultrasound contrast agents seems to be established, but there are a lot of open questions. A topographic (qualitative) perfusion analysis with visualization of perfusion defects and perfusion areas or analysis of collaterals has been demonstrated. A quantitative analysis of myocardial blood flow has been described but the existing studies are inconsistent. It is not known which parameters of the contrast wash-out curves should be used for perfusion analysis and if the Stewart-Hamilton curve analysis can be transferred to all ultrasound contrast agents as a model for quantitative myocardial blood flow assessment. The development of the transpulmonary contrast agents for echocardiographic evaluation of left ventricular cavity has the impact for myocardial perfusion imaging. The increase of myocardial intensity does not mean that a qualitative or quantitative perfusion analysis can be clinically used. In this field we have to differentiate between the possibilities of qualitative discrimination of perfusion defects and quantitative perfusion (myocardial blood flow) analysis. The different scanning conditions, the poor transthoracic ultrasound window and insufficient enhancement of the myocardial intensity make it problematic to quantify the myocardial perfusion. At the moment myocardial intensity will be increased after intravenous injection of transpulmonary contrast agents, but the value for perfusion analysis has not been shown. New ultrasound technologies such as second harmonic imaging, power-mode and raw data analysis have to show the clinical importance of these techniques for perfusion analysis in daily clinical routine. The open questions of the perfusion analysis by contrast echocardiography will be discussed in this review article.

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