PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “ISOLATION PERFUSION”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed2006

Phospholamban phosphorylation sites enhance the recovery of intracellular Ca2+ after perfusion arrest in isolated, perfused mouse heart.

OBJECTIVE: To investigate the importance of the phosphorylation of Ser16 and Thr17 sites of phospholamban (PLN) on intracellular Ca2+ (Cai2+) handling and contractile recovery of the stunned myocardium. METHODS: Cai2+ (Rhod-2, pulsed local-field fluorescence microscopy) and contractility (isovolumic left ventricular developed pressure, LVDP) were simultaneously measured in Langendorff perfused hearts from transgenic mice expressing either intact PLN (PLN-WT) or PLN with both phosphorylation sites mutated to Ala (PLN-DM), subjected to 12 min of global ischemia followed by a reperfusion period of 30 min. RESULTS: Pre-ischemic values of Cai2+ and LVDP were similar in both groups. In PLN-WT, a transient increase in Thr17 phosphorylation at early reperfusion preceded a recovery of Ca2+ transient amplitude, virtually completed by the end of reperfusion. LVDP at 30 min reperfusion was 67.9+/-7.6% of pre-ischemic values, n=14. In contrast, in PLN-DM, there was a poor recovery of Cai2+ transient amplitude and LVDP was significantly lower (28.3+/-6.7%, n=11, 30 min reperfusion) than in PLN-WT hearts. Although myofilament Ca2+ responsiveness and troponin I (TnI) degradation did not differ between groups, the episodes of mechanical alternans, typical of Cai2+ overload, were significantly prolonged in PLN-DM vs. PLN-WT hearts. CONCLUSIONS: PLN phosphorylation appears to be crucial for the mechanical and Cai2+ recovery during stunning and protective against the mechanical abnormalities typical of Cai2+ overload. The importance of PLN phosphorylation would primarily reside in the Thr17 residue, which is phosphorylated during the critical early phase of reperfusion. Our results emphasize that, although ablation of PLN phosphorylation does not affect basal contractility, it does alter Ca2+ handling and mechanical performance under stress situations.

Animals↗
PubMed1986

Cadmium toxicity in the isolated perfused rat liver.

Isolated perfused livers from male and female Sprague-Dawley rats were exposed to cadmium chloride (50 and 200 microM). Acute hepatotoxicity was investigated by measuring cadmium-induced changes in bile flow, urea synthesis and alanine aminotransferase (ALT) leakage. Cadmium-induced lipid peroxidation was estimated by formation of conjugated dieners and thiobarbituric acid (TBA) reactants. Cadmium, at both concentrations, caused a rapid decrease in bile flow (within 40 min) and complete cholestasis within 70 min exposure in livers perfused from both male and female rats. Cadmium exposure (50 and 200 microM) also resulted in the leakage of ALT into the perfusate within 60 min. In contrast, exposure of isolated rat hepatocytes to as high as 500 microM cadmium did not result in enzyme leakage until 180 min exposure. Sex differences in cadmium-induced cholestasis and ALT leakage were not observed at these concentrations. Malondialdehyde was not detected in the perfusate nor were conjugated dienes detected in liver tissue following 90 min cadmium exposure. These data demonstrate that the isolated perfused rat liver (IPRL) is a sensitive system in which to study chemically induced hepatotoxicity. Cadmium rapidly causes functional alterations and cellular damage in perfused livers from both male and female rats. Cadmium-induced liver injury was apparently not related to lipid peroxidation.

Alanine Transaminase↗
PubMed1984

Improved tissue perfusion during pressure-regulated hyperthermic regional isolated perfusion in dogs.

To achieve adequate tissue perfusion during regional isolated perfusion, hind limbs of dogs were perfused for 60 min, regulating the extracorporeal circuit on pressure. The dogs were divided into three groups. In groups I and II perfusions were performed at a delta pressure (systemic mean arterial pressure minus hind limb mean arterial pressure) of respectively 50 and 15 mm Hg; in group III delta pressure was also 15 mm Hg but the cytostatic drug Melphalan was added. Tissue perfusion was determined by means of a multiwire polarographic oxygen electrode. Adequate tissue perfusion was obtained only at subnormal perfusion pressures (groups II and III), although in all groups perfusion flow was higher than preoperative flow. At low perfusion pressures (group I), tissue perfusion was severely impaired. In all groups leakage remained less than 10%. During regional isolated perfusion the extracorporeal circuit must be regulated at a delta pressure of 15 mm Hg to achieve adequate tissue perfusion.

Animals↗
PubMed1985

Beneficial actions of two novel calcium entry blockers in the isolated perfused hypoxic cat liver.

The effects of two new calcium entry blockers, anipamil and ronipamil, were studied during 150 min of normoxic or hypoxic perfusion in isolated perfused cat livers. Hypoxic livers in which the vehicle for these inhibitors (i.e., ethanol) was injected intravenously prior to isolation of the liver, exhibited significantly higher increases in perfusion pressure, perfusate lactate dehydrogenase and cathepsin D activities, compared to control normoxic perfused livers. In contrast, the livers isolated from cats pretreated with calcium entry blocker anipamil and subsequently perfused under hypoxic conditions showed no significant difference in any of these variables from the control normoxic perfused livers. Ronipamil given intravenously 30 minutes prior to isolation also significantly protected the liver during hypoxia. The protection afforded by anipamil and ronipamil appears to be related to their inhibition of Ca++ influx which has been linked to cell death in hepatocytes.

Animals↗
PubMed1998

Endogenous or overexpressed cGMP-dependent protein kinases inhibit cAMP-dependent renin release from rat isolated perfused kidney, microdissected glomeruli, and isolated juxtaglomerular cells.

An overactive renin-angiotensin-aldosterone system (RAAS) has a central role in the pathogenesis of hypertension and cardiac hypertrophy, precursors of cardiac failure. Natriuretic peptides and NO acting through their second messenger, cGMP, increase natriuresis and diuresis, and inhibit renin release; however the mechanism by which this inhibition of the RAAS system functions is obscure. We recently reported cloning of the cDNA for type II cGMP-dependent protein kinase (cGK II), elucidated its first known function of inhibiting the cystic fibrosis transmembrane conductance regulator in rat intestine, and initially described its location in rat kidney juxtaglomerular (JG) cells, the ascending thin limb, and the brush border of proximal tubules. Here, we demonstrate inhibition of isoproterenol- or forskolin-stimulated renin release by 8-para-chlorophenylthio-cGMP (8-pCPT-cGMP), a selective activator of cGK, and prevention of this inhibition by a selective inhibitor of cGK, Rp-8-pCPT-cGMPS. In systems of differing complexity, inhibition by 8-pCPT-cGMP was nearly complete in isolated perfused kidney and microdissected afferent arterioles but only approximately 25% in isolated JG cells. Expression of either cGK II or cGK I in JG cells by using adenoviral vectors enhanced the inhibition of forskolin-stimulated renin release by 8-pCPT-cGMP to 50%. Our results indicate that cGK II, and possibly cGK I, can mediate cGMP inhibitory effects on renin release and are physiological components of the cGMP signal transduction system which opposes the RAAS.

Animals↗
PubMed1977

The metabolism of d-, l- and dl-methadone in the isolated perfused rat liver.

Five-milligram doses of d-, l- and dl-methadone were added to the perfusate of the isolated perfused rat liver and the disposition of each compound was monitored over a period of 120 minutes. There was an initial rapid decline in concentration of each drug in the perfusate, with approximately 70% disappearing in the first 10 minutes of the perfusion. Thereafter, the rate of decline of each compound slowed and the apparent half-life was about 100 minutes. In experiments with d- l- and dl-methadone the mean hepatic extraction from the perfusate at 10 minutes was 72, 66 and 69%, respectively. A comparison of the rate of disappearance of the d- and the l-isomers from the perfusate showed that the concentration of the d-isomer at each sampling time was lower than the concentration of the l-isomer and this concentration ratio ranged between 68 and 79%. A study of the disposition of dl-methadone in the isolated perfused liver indicated that the initial rapid decline of the drug in the perfusate in the first 10 minutes was caused primarily by the uptake of the unchanged drug into the liver. Thereafter, the concentration of methadone in the perfusate and liver declined slowly with time and was paralleled by an increase in the concentration of the primary mono-N-demethylated metabolite, which appeared in the liver, perfusate and bile. Smaller quantities of more polar metabolites, including hydroxylated compounds and conjugates, were also present in the liver and bile. Addition of SKF 525-A retarded the rate of decline of methadone from the perfusate and pretreatment of the rat with phenobarbital increased the rate of biotransformation of methadone in the isolated perfused liver.

Animals↗
PubMed1995

Continuous intraoperative external monitoring of perfusate leak using iodine-131 human serum albumin during isolated perfusion of the liver and limbs.

Regional isolated perfusion using tumor necrosis factor (TNF) shows significant promise for treatment of cancer which is limited to limbs or organs. The high toxicity of TNF requires very sensitive real time monitoring of leakage in order to avoid serious patient complications. Human serum albumin labeled with iodine-131 is used with an externally mounted and collimated NaI(Tl) detector to track the leakage of blood from the isolated perfusion blood circuit into the general systemic vascular space. Blood activity levels measured using the monitor demonstrated a very good correlation with blood serum samples taken concurrently with external monitoring. External monitoring can reduce the risks of perfusion leakage intraoperatively with the precision necessary to safely perform isolated perfusion using TNF.

Chemotherapy, Cancer, Regional Perfusion↗
PubMed1987

Inhibition by diltiazem of pressure-induced afferent vasoconstriction in the isolated perfused rat kidney.

The renal hemodynamic response to calcium entry blockade depends on the neural, hormonal and physiologic determinants influencing basal renal vascular tone. The effects of perfusion pressure per se on the renal vascular response of the rat kidney to diltiazem were evaluated using normal kidneys and hydronephrotic kidneys perfused extracorporally. In isolated perfused normal kidneys, diltiazem did not alter perfusate flow or glomerular filtration rate (GFR) when administered at a perfusion pressure of 100 mm Hg. In contrast, when diltiazem was administered at a perfusion pressure of 150 mm Hg, the calcium antagonists caused a striking increase in GFR, which was accompanied by an increase in renal perfusate flow. In the isolated perfused hydronephrotic rat kidney, elevation of perfusion pressure was associated with an increase in renal vascular resistance and a reduction in afferent arteriolar diameter. Diltiazem abolished the pressure-induced constriction of afferent arterioles and caused an increase in renal perfusate flow in hydronephrotic kidneys perfused at pressures above 100 mm Hg. These findings suggest that in the setting of increased renal perfusion pressure, diltiazem's effects on GFR are mediated in part by an inhibition of pressure-induced constriction of the afferent arteriole.

Animals↗
PubMed1988

The effect of norepinephrine on intestinal transport and perfusion pressure in the isolated perfused rabbit ileum.

Norepinephrine (NE) is an autonomic neurotransmitter and a potent vasoactive agent, with putative effects on intestinal absorption and secretion. To characterize the effects of NE on intestinal water and ion transport, independent of changes in intestinal blood flow, we studied the effects of three doses of NE (0.1, 0.4, and 2.0 microgram/min) on the isolated, vascularly perfused rabbit ileum at a constant vascular perfusion rate. Twenty-centimeter segments of New Zealand white rabbit distal ileum (n = 21) were vascularly perfused at a fixed rate of 1.5 ml/min using a modified Krebs buffer solution (37 degrees C) containing washed human red blood cells with a hematocrit of 15-20%. The intestinal lumen was perfused at 2 ml/min with a warm buffered isotonic electrolyte solution containing 10 microCi [14C]PEG as a nonabsorbable volume marker. Net fluxes of H2O, Na+, and Cl- were calculated during 20-min basal, NE infusion, and recovery periods. Perfusion pressure was monitored continuously. NE caused statistically significant graded increases in vascular resistance, as reflected by perfusion pressure, with increasing doses. NE stimulated absorption of H2O, Na+, and Cl- with a less distinct response to increasing dose. These data suggest that the separate effects of NE on absorption and hemodynamics may be mediated through different pathways or different receptors in the intestine.

Animals↗
PubMed1990

Alternative mechanisms for atriopeptin prohormone processing by isolated perfused rat hearts.

The isolated perfused rat heart releases atriopeptin-28 [AP28 (ANF99-126)], whereas the storage form of AP in the heart is the intact prohormone AP126 (ANF1-126). Right atrial stretch or phenylephrine (5 x 10(-5) M) stimulated the release of AP28. The processing of the prohormone during stretch was inhibited by infusion of the protease inhibitor aprotinin, resulting in the appearance of intact AP126 in the cardiac effluent. Other protease inhibitors including p-aminobenzamidine and soybean trypsin inhibitor did not alter prohormone processing by the isolated heart subjected to stretch. In contrast, aprotinin did not block the prohormone processing induced by phenylephrine. Ca+(+)-free medium markedly inhibited prohormone processing during stretch without a significant effect on AP release, whereas phenylephrine-stimulated AP release was completely suppressed by Ca+(+)-free medium. Exogenous AP126 could be cleaved by isolated rat hearts perfused either with Krebs-Henseleit solution or with Ca+(+)-free medium. However, amino acid sequence analysis revealed that the prohormone cleavage in Ca+(+)-free medium occurred at sites other than between Arg98 and Ser99 and that the resultant low molecular weight APs were not AP28. These findings suggest: 1) the characteristics of the enzyme(s) involved in the processing of AP prohormone in isolated perfused rat hearts are different from the described properties of purified enzymes; 2) in isolated perfused rat hearts the specific AP processing enzyme is Ca++ dependent, whereas nonspecific cleavage does not necessarily require Ca++ and 3) two independent AP processing pathways differentially activated by mechanical (stretch) and pharmacologic (alpha 1-adrenergic agonist) stimuli exist.

Animals↗
PubMed1982

Metabolism of prostaglandin E2 in the isolated perfused kidney of the rabbit.

In the Krebs-perfused rabbit isolated kidney, [3H]PGE2 (5 microCi, 165 Ci/mmole) was infused intra-artially for 5 min; venous and urinary effluents were collected every 2 min for 20 min. Efflux of radioactive material peaked at 8 min and declined thereafter. The kidney retained 35% of the infused 3H. Samples were extracted for acidic lipids; PGE2, PGF2 alpha and metabolites were separated by TLC and quantified by a radiometric method. Efflux of [3H]PGF2 alpha into urinary and venous outflows increased progressively over the first 12 min and then plateaued for the remaining 4 min. By 12 min, conversion of [3H]PGE2 to [3H]PGF2 alpha was 70 and 80% as determined by radiolabeled products recovered in the urinary and venous effluents respectively. Estimates of total conversion of [3H]PGE2 to [3H]PGE2 alpha were 62 and 52% of the radiolabeled material exiting in the urinary and venous effluents respectively. The 15-keto and 13,14-dihydro-15-keto metabolites of [3H]PGF2 alpha appeared in the urine but were not found in the venous outflow. We conclude that PGE-9-ketoreductase (PGE-9KRD) activity is high in the rabbit isolated perfused kidney. Further, the extent of conversion of PGE2 to PGF2 alpha and metabolism of newly formed PGF2 alpha may differ within the vascular and tubular compartments of the kidney. PGE-9KRD activity may be important in the regulation of renal vascular tone, compliance of veins, and salt and water balance.

Animals↗
PubMed2002

Vascular reactivity to angiotensin II alone or combined with a thromboxane A2 mimetic in the isolated perfused kidney of Lyon hypertensive rats.

The aim of this study was to evaluate whether thromboxane A2-prostaglandin H2 (TP) receptor activation potentiates the renal vasoconstrictor effect of Angiotensin II (Ang II) in genetically hypertensive rats of the Lyon strain (LH). Concentration-response curves (CRCs) to Ang II (5 pM to 10 nM), to the specific TP receptor agonist U46619 (7.5-960 nM) and to a mixture of Ang II + U46619 (fixed molar ratio of 1 : 9) were obtained in single-pass perfused kidneys isolated from 8 week-old LH and low blood pressure (LL) control rats. Baseline vascular resistance was significantly increased in LH compared to LL kidneys. Comparison of the CRCs obtained for Ang II and U46619 showed that, in both strains, Ang II was about 100 times more potent than U46619. For both drugs, the pD2 or slope values did not differ among the two strains. Co-activation of TP receptors, analyzed with the method of Pöch and Holzmann, tended to potentiate the effects of Ang II in LH but not in LL kidneys. In conclusion, isolated perfused kidneys of LH rat did not exhibit an increased vascular sensitivity to acute infusion of Ang II or U46619 compared to control LL ones. In addition, the results suggest that the interactions between Ang II and TP receptor agonist may differ among the two strains.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1975

Interaction between sedative premedicants and ketamine in man in isolated perfused rat livers.

Premedication with diazepam, hydroxyzine or secobarbital significantly increased ketamine-induced sleep time (137 +/- 3.5 min, 135 +/- 9.2 min, 128 +/- 4.7 min) over that of unpremedicated controls (98.5 +/- 4.4 min) in man. The corresponding mean plasma half-lives (t1/2) of ketamine were longer in patients premedicated with diazepam or seconbarbital (57.8 +/- 4.9 min, 46 +/- 3.2 min) than in controls (36 +/- 1.8 min). Ketamine t1/2 in the perfusate of isolated, perfused rat livers was prolonged 30 to 50 per cent by addition of diazepam, secobarbital, or hydroxyzine. The data suggest that these commonly used premedicants decrease the rate of ketamine metabolism.

Anesthetics↗
PubMed1988

Neutrophils accentuate ischemia-reperfusion injury in isolated perfused rat kidneys.

The contribution of neutrophils to reperfusion injury after ischemia is not known. To determine the effect of neutrophils on the function of ischemic kidneys, we added purified human neutrophils during perfusion of isolated ischemic or nonischemic rat kidneys. Reperfusion of ischemic kidneys with neutrophils caused a distinct morphological lesion of vascular endothelial and smooth muscle cells and more functional injury than reperfusion with buffered albumin alone; with neutrophils, glomerular filtration rate (GFR) was 113 +/- 7 microliter.min-1.g-1, tubular sodium reabsorption (TNa) was 72 +/- 2%; without neutrophils, GFR was 222 +/- 18 microliter.min-1.g-1; TNa was 90 +/- 2%; both P less than 0.01 vs. reperfusion with neutrophils. In contrast, addition of neutrophils did not injure control kidneys, unless the neutrophil activator, phorbol myristate acetate, was also added. Two experiments suggested that O2 metabolites contributed to neutrophil-mediated injury to ischemic kidneys. First, reperfusion of ischemic kidneys with O2 metabolite-deficient neutrophils from a patient with chronic granulomatous disease did not cause more injury than reperfusion with buffered albumin alone. Second, simultaneous addition of the O2 metabolite scavenger, catalase, prevented the GFR and TNa decreases caused by neutrophils but did not decrease injury in the absence of neutrophils. We conclude that neutrophils by an O2 metabolite-dependent mechanism contribute to ischemia-reperfusion injury in the isolated perfused kidney.

Animals↗
PubMed1992

Antithyrotropin-releasing hormone serum inhibits secretion of glucagon from isolated perfused rat pancreas: an experimental model for positive feedback regulation of glucagon secretion.

TRH is synthesized in the islets of Langerhans and was found in the perfusate of isolated rat pancreas. In the present study, designed to determine the role of endogenous TRH, we first characterized chromatographically the identity of immunoreactive TRH with synthetic pGlu-His-Pro-NH2. Since endogenous TRH secretion may mask the effects of exogenous TRH, we performed, in parallel to dose-response studies, immunoneutralization experiments using anti-TRH serum to neutralize the endogenous TRH secretion from isolated perfused rat pancreas. The data indicate that exogenous TRH enhances basal glucagon secretion; inversely, anti-TRH serum inhibits glucose plus arginine-induced glucagon secretion and produces a concomitant slight inhibition of somatostatin secretion. The present study shows a physiological contribution for endogenous TRH as a local modulator of intraislet hormone regulation; from these observations, we postulate a direct effect of pancreatic TRH on glucagon-containing (alpha) cell secretion, which, in turn, may produce the fluctuation in somatostatin secretion. Local TRH secretion provides a model for positive feedback regulation of glucagon secretion, frequently associated with diabetes.

Animals↗
PubMed1990

Cell volume regulatory responses of isolated perfused rat liver. The effect of amino acids.

1) Addition of glutamine, glycine, alanine, serine, phenylalanine, proline at a concentration of 3mM, each, or of an amino-acid mixture resembling the physiological amino-acid composition of portal venous blood, to influent perfusate of isolated perfused rat liver led to a 4-6% increase of liver mass without increase of the [3H]inulin space, and biphasic K+ movements across the plasma membrane. These K+ movements consisted of an initial net K+ uptake (0.4-0.9 mumol X g-1 liver) for about 2 min, being followed by a net K+ release (1.0-2.8 mumol X g-1 liver) during the next 10 min. Withdrawal of the amino acids from influent perfusate caused a slow net K+ reuptake by the liver and restored the initial liver mass. No effects on liver mass and K+ fluxes were observed following addition of glutamate or glucose at a concentration of 3mM, each. 2) Aminooxyacetate did not affect the alanine (3 mM) induced increase in liver mass. However, in presence of aminooxyacetate the alanine-induced net K+ release from the liver (i.e. K+ release from 2-10 min minus initial K+ uptake) increased from 0.1 to 2.2 mumol X g-1 liver, whereby simultaneously the alanine tissue level rose from 6.8 to 13.3 mumol X g-1 (corresponding to an increase of the intracellular alanine concentration from about 12 to 25 mM) in presence of aminooxyacetate. 3) When livers were perfused with different glutamine concentrations, a maximal increase in liver mass of 5-6% was observed at glutamine concentrations above 1.5-2mM. A halfmaximal increase in liver mass was observed at 0.6-1.0mM glutamine in influent, i.e. at the physiological portal glutamine concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗