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Biomedical subjects

W Isselhard

Publications and source records attributed to W Isselhard.

At least 37 records · Page 2Linked to original sources
PubMed1996

Resuscitation of cadaveric livers from non-heart-beating donors after warm ischemic insult: a novel technique tested in the rat.

Clinical liver transplantation has become the therapy of choice in end-stage liver disease, but the limited availability of suitable donor organs still impedes its widespread application. In order to increase the availability of donor organs for liver transplantation, it would be advantageous if ischemically damaged livers could be resuscitated from cadavers in which the heart has stopped beating. A method for doing this has been developed in a rat model. Compared to livers excised from rats in which the heart is still beating, severe deteriorations of tissue integrity and functional performance were evident in predamaged livers after cold preservation without supplementary treatment. A treatment of those livers which included an antioxidant rinse with superoxide dismutase, and venous vascular insufflation of gaseous oxygen during preservation, completely prevented tissue alterations upon reperfusion, and promoted a functional recovery of the livers, making them comparable to organs harvested from heart-beating donors.

Adenine Nucleotides↗
PubMed1996

Synthesis of high energy phosphates during cold ischemic rat liver preservation with gaseous oxygen insufflation.

The depletion of biochemical energy stores during anoxic ischemic preservation is a major problem affecting the viability of the graft in transplantation medicine. After cessation of blood flow and, thus, lack of metabolic substrates and oxygen supply, a swift decrease of energy-rich phosphates can be observed in the tissue, since endergonic metabolic processes continue, but no further oxidative regeneration of biochemical energy stores will take place. We investigated the effect of a continuous gaseous oxygen supply via the venous vessels during extended ischemic preservation of rat livers in University of Wisconsin preservation solution for 48 hr. Results showed that aerobic ischemic storage not only prevented the depletion of biochemical energy stores, but promoted a de novo synthesis of high energy phosphates, and significantly enhanced the functional recovery of the organs after postischemic reperfusion. The findings suggest that maintenance of oxidative energy metabolism largely protects the organ during ischemia and may enable organ viability even after extended preservation times.

Adenosine↗
PubMed1996

Taurine reduces experimental liver injury after cold ischemic preservation and a period of rewarming prior to reperfusion.

Livers of male Wistar rats (250-300 g) were isolated and flushed with 10 ml of Ringer's solution and 10 ml of UW preservation solution. Then the organs were stored for 24 h at 4 degrees C in UW solution. Livers of Group 1 were rinsed with 10 ml of Ringer's solution and reperfused after hypothermic storage with oxygenated Krebs-Henseleit solution (95% O2; 5% CO2) in a nonrecirculating system at constant pressure (10 mmHg) and 37 degrees C. Livers of Group 2 were incubated for 30 min at 37 degrees C prior to reperfusion, in order to simulate rewarming of the organ upon surgical implantation. Livers of Group 3 were treated like Group 2, but taurine was admixed to the UW solution (1 mM). Livers of Group 1 showed little signs of a preservation/reperfusion injury, with low enzyme activities of the parenchymal ALT and endothelial purine nucleoside phosphorylase (PNP) in the postischemic rinse solution (ALT: 19.9 +/- 12.4; PNP: 3.3 +/- 0.4 U/liter), adequate portal flow values about 3 ml/g/min and high O2 uptake at the end of the experiment (VO2: 3.2 +/- 0.4 ml/100g/min). Livers of Group 2 exhibited nearly tenfold higher enzyme activities in the rinse solution (ALT: 247.0 +/- 94.7*; PNP: 29.5 +/- 17.0* U/l) and disturbed tissue perfusion with significantly reduced flow values of about 2 ml/g/min during the first 10 min of reperfusion. As a result, the recovery of O2 uptake was only 2.2 +/- 0.3 ml/100 g/min*. Addition of taurine (Group 3) resulted in a significant reduction of the enzyme loss (ALT: 96.2 +/- 50.0#; PNP:12.4 +/- 7.0# U/liter) and improved portal flow values and O2 uptake at the end of reperfusion (2.7 +/- 0.3 ml/100 g/min#). The results give evidence for the importance of the rewarming period after hypothermic storage, which is inevitable during implantation of the organ in vivo. Taurine seems to exert a protective effect, affecting both the vascular endothelium and parenchymal tissue (*p < 0.05 vs Group 1; # p < 0.05 vs Group 2).

Adenosine↗
PubMed1996

Protective effect of taurine on hypoxia and reoxygenation-induced damage of human colon cells (HT 29).

In this experimental model, taurine administered during hypoxia markedly reduced the cell damage due to O2 deficiency, and the beneficial effect outlasted the period of reoxygenation. The mechanisms for the improved survival rates are postulated to be a reduced osmoregulatory disturbance of cellular integrity, improved Ca2+ homeostasis and induction of accelerated cellular growth processes. In our simplified cell culture model the UW solution seems to be the most appropriate solution for the cold (hypoxic) preservation of human colon cells. We conclude, that within this experimental model and under these experimental conditions, taurine supplementation of the conventionally used preservation solutions improved the solutions markedly. Considering our previous studies, taurine seems to be a potent endogenous protective agent against cellular deterioration due to hypoxia and reoxygenation.

Adenosine↗
PubMed1996

Reduction in nonparenchymal cell injury and vascular endothelial dysfunction after cold preservation of the liver by gaseous oxygen.

Reintroduction of oxygen to previously anoxic tissue may result in severe cell injury (oxygen paradox) and contribute to the so-called reperfusion damage of ischemic organs. Our study investigated the influence of simple gaseous oxygen supply during ischemia on nonparenchymal cell alterations upon reperfusion of the liver. Livers from male Wistar rats were isolated, rinsed blood-free and stored for 48 h at 4 degrees C in UW-preservation solution (group 1; n = 6). Gaseous oxygen was insufflated into a second group of livers (group 2; n = 6) during the storage period via the inferior caval vein at a pressure limited to 18 mmHg. To simulate the period of slow rewarming of the organ during surgical implantation in vivo, all livers were incubated at 25 degrees C in saline solution for 30 min prior to reperfusion. Reperfusion was carried out in vitro in a recirculating system with Krebs-Henseleit buffer. A control group was perfused immediately after harvest. The technique of aerobic storage (group 2) resulted in normal vascular perfusion characteristics without elevation of portal venous pressure (PVP) above control values, in contrast to group 1 livers which showed a significantly elevated PVP, averaging between 1.5 and 2 times the values of the control. Hepatic efflux of NO (nmol/ml) after 10 min of reperfusion was massively increased in group 1, while only low concentrations were found in group 2 and in control livers. Kupffer cell activation after ischemia was shown by a huge increase in acid phosphate release upon reperfusion compared with the control, with significantly lower values in group 2 after 10 min of reperfusion than in group 1. Thus, aerobic ischemia by gaseous oxygen persufflation seems an appropriate tool for long-term organ preservation, preventing vascular and parenchymal dysfunction upon reperfusion.

Alanine Transaminase↗
PubMed1996

Assessment of oxygen radicals during kidney transplantation--effect of radical scavenger.

In the present study, levels of free oxygen radicals, generated in the very early period of reperfusion during human kidney transplantation, were assessed by determination of malondialdehyde (MDA) levels using a high-pressure liquid chromatography (HPLC) method. Renal blood samples were obtained during reperfusion by intraoperative cannulation of the renal vein. Simultaneously, systemic MDA levels were determined. Furthermore, local and systemic levels of interleukin 6 (IL-6), tumor necrosis factor (TNF) receptors, p55 and p75, and vitamin E were measured. In a second group of patients, 500 mg of ascorbic acid were given prior to reperfusion. Renal MDA levels in the control group were always higher compared to systemic levels. IL-6 showed a marked increase shortly after reperfusion in the renal blood. In the scavenger group there was a diminution of these effects. TNF receptor levels and vitamin E remained largely unchanged. The results of this pilot study demonstrated clinically the moderate production of reactive oxygen species and the liberation of IL-6 shortly after reperfusion of human transplanted kidneys. Furthermore, the modulating effect of a radical scavenger on these effects was shown.

Adult↗
PubMed1996

No evidence for a protective effect of ascorbic acid on free radical generation and liver injury after hemorrhagic shock in rats.

Oxygen free radicals have been shown to be implicated in ischemic tissue injury, and free radical-induced reactions may also play an important role in the pathophysiology of circulatory shock. The present study was designed to investigate the potential use of ascorbic acid as an exogenous antioxidant on the liver's recovery from hemorrhagic shock in situ. Rats (fasted overnight) were subjected to 60 min of hemorrhagic shock (HS) (mean arterial pressure = 40 mmHg) under pentobarbital anesthesia, followed by retransfusion of the shed blood. One-half of the animals (n = 6) were injected with 10 mg/kg of ascorbic acid prior to induction of shock, while untreated animals (n = 6) received the same volume of saline solution. in untreated animals, systemic plasma levels of malondialdehyde rose from 1.07 +/- .08 during normotension (NT) to 1.36 +/- .18* 60 min after resuscitation (RS), documenting oxygen free radical-induced lipid peroxidation. Accordingly, plasma levels of alanine aminotransferase (16.5 +/- 2.5; 34.9 +/- 12.3*; 105.8 +/- 68.7* U/L; NT/HS/RS) and ammonia (127 +/- 40; 532 +/- 160*; 304 +/- 244* micrograms/dL) rose significantly during the experiment. Hepatic ATP content of the liver fell from 4.8 +/- .83 to .56 +/- .27* after HS and recovered partially to 2.7 +/- 1.6* mumol/g after RS. Leukocyte infiltration in the liver, indicated by tissue levels of myeloperoxidase, remained constant during HS but rose during RS (37.9 +/- 18.5; 38.6 +/- 16.4; 81.4 +/- 30.7*, arbitrary units), thus documenting an inflammatory reaction after HS. In the ascorbic acid group, plasma levels of malondialdehyde were comparable to those of untreated animals after RS, as were enzyme concentrations and ammonia. No differences were observed with regard to the tissue concentrations of ATP or myeloperoxidase. Mean arterial blood pressure as well as liver tissue perfusion, as measured by Laser Doppler flowmetry, did not show significant differences between the groups. It was concluded that, although an effect of oxygen free radicals on liver tissue could be found during and after HS, treatment with ascorbic acid alone, in our model, failed to ameliorate the recovery of the animals upon resuscitation (values are mean +/- SD; *, p < .05 vs. NT; one-way ANOVA).

Alanine Transaminase↗
PubMed1996

Long-lasting hypoxic preservation of porcine kidney cells. Beneficial effect of taurine on viability and metabolism in a simplified transplantation model.

Taurine administered during hypoxia reduced the cell damage due to O2 deficiency markedly. The beneficial effect outlasted the period of reoxygenation. The mechanisms for the improved survival rates are postulated in a reduced osmoregulatory disturbance of cellular integrity, improved Ca2+ homeostasis and induction of accelerated cellular growth processes. We conclude that taurine supplementation of the conventionally used kidney preservation solution (UW) improves this "gold standard" kidney preservation solution markedly.

Adenine Nucleotides↗
PubMed1995

Determination of plasma activities of purine nucleoside phosphorylase by high-performance liquid chromatography: estimates of nonparenchymal cell injury after porcine liver transplantation.

An assay is described for measurement of purine nucleoside phosphorylase (PNP) in plasma by high-performance liquid chromatography (HPLC). A plasma sample was incubated with hypoxanthine and ribose-1-phosphate in phosphate-free medium at pH 7.4 to catalyse the production of inosine by plasmatic PNP. The reaction was stopped by addition of perchloric acid to inactivate the enzyme and to precipitate plasma proteins. After centrifugation and neutralization of the supernatant with NaOH the increase in the substrate inosine was determined by HPLC. Plasma activities of PNP averaged 5.0 mU/ml before and 12.3 mU/ml (p < 0.001), 5 min after porcine liver transplantation. At the same time points, the plasma activities of the frequently used liver enzymes lactate dehydrogenase or alanine aminotransferase remained virtually unchanged. Thus, plasmatic activities of PNP may be a suitable and early indicator of ischemic alterations to the graft in vivo.

Alanine Transaminase↗
PubMed1995

Involvement of platelet activating factor in microcirculatory disturbances after global hepatic ischemia.

This study aimed at analyzing the involvement of platelet activating factor (PAF) in ischemia/reperfusion injury (I/R) of the liver. Male Wistar rats under pentobarbital anesthesia were subjected to 60 min of normothermic ischemia of the left and median liver lobes, followed by 30 min of reperfusion in vivo. Blood pressure and body temperature were controlled throughout the experiment. Preischemic injection of a specific PAF antagonist (BN52021, 5 mg/kg body mass) resulted in significant reduction of postischemic enzyme loss into the serum from the vascular endothelium (purine nucleoside phosphorylase: 56.9 +/- 11.4 vs 86.6 +/- 20.4 U/l**) and the hepatic parenchyme (alanine aminotransferase: 176 +/- 60 vs 519 +/- 180 U/l***), accompanied by a significant increase of hepatic bile production (1.28 +/- .32 vs 0.80 +/- 0.16 microliter/g/min*) and tissue levels of ATP (6.12 +/- 1.73 vs 4.21 +/- 1.30 mumol/g*). Laser Doppler flowmetry revealed a significant improvement by BN52021 of left lobular erythrocyte flux recovery from 27 +/- 25 to 78 +/- 19% of respective preischemic control values. The data give evidence for an implication of PAF in I/R damage to the vascular endothelium and in impaired parenchymal function of the liver, probably due to altered microvascular reperfusion. Treatment with PAF antagonists should improve results after liver surgery under ischemic conditions. (*;**;***: P < 0.05; 0.01; 0.001).

Adenosine Triphosphate↗
PubMed1995

Effects of taurine on liver preservation in UW solution with consecutive ischemic rewarming in the isolated perfused rat liver.

Taurine (2-aminoethane sulfonic acid) is a physiologic amino acid involved in cellular osmoregulation in various species including man. This study was intended to compare the respective effects of cold storage and consecutive ischemic rewarming of the liver postischemic hepatic flow and hepatocellular outcome upon reperfusion with or without the addition of taurine to the preservation medium. Livers from male Wistar rats were rinsed free of blood via the portal vein and stored ischemically at 4 degrees C in UW solution. Livers from group 1 were then rinsed again with 10 ml Ringer's solution and reperfused with Krebs-Henseleit buffer at a constant pressure of 10 mmHg for 45 min at 37 degrees C in a nonrecirculating manner. Livers from groups 2 and 3 were subjected to 30 min of warm ischemia subsequent to cold storage and prior to reperfusion with 10 mM taurine added to the UW solution in group 3. While there were only very few signs of hepatic injury in group 1, the additional period of warm ischemia (group 2) led to a significant reduction in early perfusate flow and enhanced enzyme leakage from the livers during postischemic rinse and reperfusion. Livers in group 3 exhibited an amelioration in hepatic circulation and significantly reduced enzyme release as compared to group 2. The results clearly demonstrate a remarkable impact of postischemic rewarming on graft viability. Furthermore, the addition of taurine to the preservation medium was shown to improve hepatic circulation and enhance viability of the liver upon reperfusion.

Adenosine↗
PubMed1995

Reduction of oxidative tissue injury and endothelial dysfunction by graduated reperfusion after cardioplegic arrest in isolated rat hearts.

The aim of this study was to investigate whether or not a graduated resumption of the perfusion pressure after cardioplegic ischaemic arrest will reduce the impact of oxygen free radicals on myocardium and the cardiovasculature. Langendorff-perfused rat hearts were subjected to cardioplegia and subsequent 40 min of global ischaemia at 25 degrees C. Reperfusion was carried out either abruptly (AR) or gradually (i.e., perfusion pressure stepwise increased from 40 to 75 mmHg within 30 min -GR). GR resulted in a significant improvement of percentage recovery of left ventricular systolic pressure as compared to AR. A marked increase of thiobarbituric acid reactive substances (TBARS) was detected in the effluent during AR, accompanied by an impaired release of the endothelial vasodilator NO and diminished coronary flow rates compared to the baseline values. GR resulted in a significant reduction of TBARS in the effluent and promoted a better recovery of coronary flow as well as endothelial release of NO during the later phase of reperfusion. It is concluded that graduated reperfusion is beneficial in reducing free radical mediated peroxidative tissue injury and endothelial dysfunction upon reoxygenation.

Animals↗
PubMed1995

Protective effect of heat shock pretreatment with heat shock protein induction before hepatic warm ischemic injury caused by Pringle's maneuver.

BACKGROUND: Induction of heat shock proteins is thought to have a > cytoprotective effect against environmental stress and to result in a better ischemic tolerance. The protective ability of heat exposure and heat shock protein 72 (HSP 72) induction before warm ischemia caused by Pringle's maneuver was evaluated in rats. METHODS: Heat exposed rats (HS) were compared with control animals (C). The gene expression (messenger RNA) of HSP 72 and HSP 72 were detected by Northern and Western blot analyses. During 40 minutes of in situ reperfusion, liver energy metabolism and levels of standard liver enzymes were evaluated. The survival rate was determined after postoperative day 7. RESULTS: After heat exposure and recovery, messenger RNA of HSP 72 and HSP 72 can be detected strongly in HS group but not in C group. During reperfusion HS group exhibited a significantly (p < 0.01) improved energy metabolism, and the release of liver enzymes was significantly (p < 0.001) reduced compared with C group. Seven-day survival rate was 100% in HS group but at 50% was significantly impaired (p < 0.05) in C group. CONCLUSIONS: Heat exposure associated with HSP induction has a significant protective effect against warm ischemic liver injury, which results in a relevant improvement of survival rate.

Adenosine Triphosphate↗
PubMed1995

Rapid determination of the membrane potential of mitochondria in small biopsy specimens of the liver.

In liver transplantation, graft viability is ideally to be determined before implantation. Integrity of mitochondria may be a prerequisite to a viable graft. A new method is presented, which allows for the determination of the membrane potential of mitochondria (MPM; mV) in state 4 respiration within 50 min in 40-mg specimens, employing rhodamine 123 as a probe. Normal control showed a MPM of 239.2 mV. Storage in saline at 37 degrees C yielded an impaired MPM of 153.5 mV within 3 h. The cold storage at 1 degree C could preserve MPM at quasi-normal after 3 h but reduced it significantly after 24 h to 222.2 mV in saline (p < 0.005 vs. control) and 231.0 mV in UW solution (p < 0.05 vs. control): the difference between the 24-hour values was significant (p < 0.05).

Animals↗
PubMed1995

Allopurinol effects in rat liver transplantation on recovery of energy metabolism and free radical-induced damage.

Rat livers were orthotopically transplanted after 90-min cold ischemia (group 1) or after 20-min warm and 70-min cold ischemia without (group 2) or with (group 3) allopurinol treatment (AT) (50 mg/kg i.v. 10 min prior to warm ischemia into the donor, flush perfusates with 1 mmol/l). Recovery processes were followed up for 60 min of reperfusion. Liver tissue levels of ATP and total adenine nucleotides were restored in group 1 to almost preischemic ranges within 15-30 min, remained significantly reduced by 30 and 20%, respectively, in group 2, and recovered with AT within 60 min in group 3 to almost the same extent as in group 1. A massive increase in the tissue malondialdehyde concentration, indicative of lipid peroxidation, occurred in the beginning of reperfusion of warm-ischemically damaged donor livers, which in group 3 with AT tended to be less pronounced than in group 2 without AT. The GSSG/GSH ratio reflecting intracellular oxidant stress averaged 3.3 x 10(-3) in group 1 between 15 and 60 min reperfusion. In group 3 AT resulted in comparably low values averaging 3.8 x 10(-3), while in warm-ischemically damaged livers without AT of group 2 this ratio was significantly and continuously elevated averaging 5.8 x 10(-3).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
PubMed1994

Protecting effect of taurine against hypoxic cell damage in renal tubular cells cultured in different transplant preservation solutions.

We conclude that, within this experimental model and under these experimental conditions, taurine supplementation of standard kidney preservation solutions improves survival of kidney cells during hypoxic preservation. The protective effect depends on the taurine concentration, the hypoxic preservation time and the used preservation solution. Physiological taurine concentrations are effective during short hypoxic periods, whereas pharmacological taurine concentrations seem to be needed for longer periods of hypoxia. Within this experimental model University of Wisconsin solution seems to be more effective than Euro collins solution.

Animals↗