Large-volume multi-tined expandable RF ablation in pig livers: comparison of 2D and volumetric measurements of the ablation zone.

OBJECTIVES: To compare two-dimensional (2D) and three-dimensional (3D) computed tomography (CT) measurements of ablation zones (AZs) related to the shaft of two different large-volume monopolar multi-tined expandable electrodes. METHODS: Percutaneous radiofrequency (RF) ablation was performed in 12 pigs (81.6 +/- 7.8 kg) using two electrodes (LeVeen 5 cm, Rita XL 5 cm; n = 6 in each group). Contrast-enhanced CT with the electrode shaft in place evaluated the AZ. The largest sphere centred on the electrode shaft within the AZ was calculated (1) based on the 2D axial CT image in the plane of the shaft assuming rotational symmetry of the AZ and (2) using prototype software and the 3D volume data of the AZ measured with CT. RESULTS: The mean largest diameter of a sphere centred on the electrode shaft was always smaller using the 3D data of the AZ than using 2D CT measurements assuming rotational symmetry of the AZ (3D vs 2D): LeVeen 18.2 +/- 4.8 mm; 24.5 +/- 3.1 mm; p = 0.001; Rita XL 20.0 +/- 3.7 mm; 28.8 +/- 4.9 mm; p = 0.0002. All AZ showed indentations around the tines. CONCLUSIONS: Two-dimensional CT measurements assuming rotational symmetry of the AZ overestimate the largest ablated sphere centred on the electrode shaft compared with 3D CT measurements.

Poor cell survival limits the beneficial impact of mesenchymal stem cell transplantation on acute kidney injury.

BACKGROUND: Although renal tubular epithelium has a great capacity for repair it has been suggested that the administration of mesenchymal stem cells may accelerate the recovery following severe ischemic injury. METHODS: Here we analyzed the survival rate and organ distribution of transplanted mesenchymal stem cells as well as their contribution to kidney regeneration after ischemic renal injury using functional tests, histological examination as well as quantitative real-time PCR. RESULTS: Intravenously injected stem cells were mainly trapped in lungs and liver. One hour after injection, less than 1% of the injected stem cells could be detected in the injured kidneys. These cells disappeared within the first few days and did not replace renal epithelial cells precluding substantial transdifferentiation. To clarify whether reinforced stem cell delivery might promote sustained survival or conversion to tubular epithelia, stem cells were directly injected into the injured kidneys. Although these grafted cells also did not show sustained survival or contribute to structural renal repair, stem cell injection was associated with a significant but transient initial decrease in serum creatinine. CONCLUSION: These data suggest that mesenchymal stem cells do not significantly contribute to epithelial renewal after ischemic injury, promoting the idea that the major impact of cell-based therapy for acute kidney injury may result from paracrine or endocrine effects unrelated to stem cell transdifferentiation.

Ischemia-reperfusion injury activates early extracellular matrix processing and expression of endostatin in the heart with differential effects of temperature.

Acute ischemia is a well-known inductor of extracellular matrix (ECM) remodeling, which leads to the development of congestive heart failure and is associated with left ventricular dilatation. Here we investigate the timecourse of ECM processing with release of endostatin (ES) and other low-molecular-weight fragments during early ischemia-reperfusion of the heart. In this blinded study, 30 pigs were randomized to 60 min of global myocardial ischemia at either 4 or 37 degrees C or served as control. Five transmyocardial tissue samples were collected at baseline and after ischemia within 150 min of reperfusion. Collagen XVIII cleavage products of 10-75 kDa including ES (25 kDa) were analyzed using the Western blot and ELISA method, and creatin kinase as marker of myocardial injury was determined in samples collected from the coronary sinus. We demonstrate that processing of the extracellular matrix protein collagen XVIII starts during early reperfusion, as we observed a significantly increased expression of cleavage products at 10 and 75 kDa as well as ES at 150 min of normothermic ischemia-reperfusion. We further demonstrate a differential processing of collagen XVIII depending on temperature conditions during myocardial ischemia, as an increase in cleavage products was observed after normothermic ischemia only; however, expression of ES and other fragments remained unchanged after hypothermic ischemia-reperfusion and in controls. In conclusion, this blinded study first demonstrated that processing of extracellular matrix started early after ischemia-reperfusion and depends on temperature conditions. These findings may contribute to a broader understanding of matrix processing after ischemia-reperfusion.

Which parameters are needed for targeting a multitined radiofrequency device--an approach to a simple algorithm.

BACKGROUND: The use of radiofrequency ablation (RFA) for treatment of liver malignancies is limited by the high rate of local recurrences. The aim of this experimental study was to evaluate parameters describing the reproducible target volume of a RFA procedure in order to facilitate better applicator placement. MATERIALS AND METHODS: RFA was performed in perfused and nonperfused pig livers. The following parameters were measured: axial and transverse diameter, front margin, coagulation center, diameter of sphere ablated (D(S)), distance to center (DC), and volume. Graphic overlays were utilized to visualize variability. Parameters were evaluated for Rita XL (2 algorithms), LeVeen, and Rita Xli applicators. RESULTS: The best prediction of a reproducibly ablated target volume can be made by the diameter of the sphere ablated and the distance of the applicator tip to center of the sphere (DC). The spheres were significantly different in diameter (D(S)) depending on the applicator Rita XL 29 +/- 6 mm, Rita XL(wet) 35 +/- 5 mm, LeVeen 35 +/- 8 mm, Rita Xli 44 +/- 5 mm (perfused livers, p < 0.001). Graphic overlay demonstrated differences in variability that can influence the reliability of the system. CONCLUSIONS: D(S) and DC as specific values for each applicator and algorithm facilitate a placement of the applicator relative to the target volume that maximizes the chance of complete ablation.

Role of balloon occlusion for mononuclear bone marrow cell deposition after intracoronary injection in pigs with reperfused myocardial infarction.

AIMS: In clinical studies on cell therapy for acute myocardial infarction (MI), cells are usually applied by intracoronary infusion with balloon (IC/B). To test the utility of balloon occlusion, mononuclear bone marrow cell (MNC) retention after intracoronary infusion without balloon (IC/noB) was compared with IC/B and intramyocardial (IM) injection. METHODS AND RESULTS: Four hours after LAD ligation in male pigs, reperfusion was allowed (confirmed by coronary angiography). Five days later, 1 x 10(8) autologous (111)Indium-labelled MNC were injected IC/noB (n = 4), IC/B (n = 4), or IM (n = 4). At 1 h the fraction of injected MNC that was detected in the heart was 4.1 +/- 1.1% after IC/noB injection, 6.1 +/- 2.5% after IC/B injection (P = 0.19), and 20.7 +/- 2.3% after IM injection (P < 0.001 vs. IC/noB and IC/B). At 24 h it was 3.0 +/- 0.6% (IC/noB), 3.3 +/- 0.5% (IC/B, P = 0.43), and 15.0 +/- 3.1% (IM, P < 0.001 vs. IC/noB and IC/B). Dynamic scintigrammes during each of four consecutive IC/B injections showed a rapid 19.6 +/- 8.0% cell loss during balloon inflation (no-flow period, phase 1) and a rapid 36.6 +/- 17.8% cell loss after balloon deflation (re-flow period, phase 2). After each of four consecutive IC/noB injections the peak cell deposit was lower, followed by one phase of rapid cell loss (30.9 +/- 11.0% after 6 min). After IM injection only a slow linear cell loss was observed (9.7% per h). In histology, PKH-67 labelled cells only rarely had passed the endothelial barrier after 24 h after IC injection, while they were exclusively found in the interstitium after IM injection. CONCLUSION: The observation of a similar cell persistence after IC injections with and without balloon occlusion suggests that the balloon procedures currently applied in clinical studies are not necessary for cell deposit. If longer term persistence of cells plays a role for the clinical benefit of cardiac cell therapy, IM injection may be superior to IC applications.

Histological evidence for revascularisation of an autologous retinal pigment epithelium--choroid graft in the pig.

BACKGROUND: Translocation of a free autologous graft consisting of retinal pigment epithelium (RPE), Bruch's membrane, choriocapillaris and choroid in patients with exudative age-related macular degeneration is currently being evaluated in clinical practice. Angiographic studies in these patients suggest that their grafts become revascularised. AIM: To investigate the histological evidence of revascularisation of the graft in a porcine model. METHODS: In 11 pigs (11 eyes), an RPE-choroid graft was translocated from the mid-periphery to an intact or an intentionally damaged RPE and Bruch's membrane at the recipient site. The eyes were enucleated 1 week or 3 months after surgery. Tissue sections were evaluated using immunohistochemistry. RESULTS: Bridging vessels between recipient layer and graft were identified from 1 week to 3 months after surgery. This reconnection occurred regardless of whether the Bruch's membrane of the recipient site was left intact or intentionally damaged at the time of transplantation. The vasculature of the graft appeared open and perfused. Vessels with transcapillary pillars and conglomerates of small new vessels were present in the graft. CONCLUSIONS: This study showed histological evidence for revascularisation by angiogenesis of a free autologous RPE-choroid graft.

Biocompatibility of Beta-tricalcium phosphate root replicas in porcine tooth extraction sockets - a correlative histological, ultrastructural, and x-ray microanalytical pilot study.

This investigation studies porcine tissue response in tooth extraction sockets treated with root replicas made out of Beta-tricalcium phosphate (Beta-TCP; Beta-Ca(3)(PO(4))(2)) granules, molded and held together by thermal fusion of a thin film of polyglycolic-polylactic acid copolymer. Six left mandibular third incisors (n (1)/4 6) of experimental pigs are treated with the root replicas and four contralateral incisors are used as nontreated controls (n (1)/4 4). Two animals each were killed at 20, 40, and 60 weeks of observation periods. The mandibular jaw segments were prepared in toto for light microscopy by resin embedding and serial ground sectioning. Additionally, one Beta-TCP-treated socket at 60 weeks was thoroughly investigated by correlative light, electron microscopic and electron probe X-ray microanalysis to assess the bio-absorbability and host removal of the replica material from the implant site. The extraction wounds of the animals healed satisfactorily with very little histologically observable differences in the healing pattern of the test and control sites. The Beta-TCP was completely removed from extracellular sites, but at 60 weeks, remnants of it were found in the cytoplasm of multinucleated giant cells. The root replicas made out of Beta-TCP were biocompatible and bioabsorbable. Osseous healing occurred both in the test and control sockets, but the healing process was delayed due to the presence of Beta-TCP particles.

Effects of aprotinin on endothelium-dependent relaxation of large coronary arteries.

OBJECTIVE: Aprotinin is widely used in heart surgery for reduction of intraoperative blood loss. But recent reports presenting results from rat aorta experiments claimed that aprotinin selectively impairs endothelium-dependent relaxation (EDR) as well as basal NO availability in concentrations similar to doses routinely used in cardiovascular surgery. An impairment of coronary EDR by aprotinin would be a great danger for any cardiothoracic intervention. We therefore tested the influence of aprotinin in the coronary arteries of a non-rodent species. METHODS: Fresh coronary arteries of pigs were obtained from the local slaughterhouse and transported to our laboratory in cold oxygenated Krebs-Henseleit solution. Five-millimeter long rings were consecutively tested with or without aprotinin in concentrations of 500 KIU/ml (n=7) or 1000 KIU/ml (n=6) in oxygenated normothermic Krebs-Henseleit solution. PGF(2alpha) (10 micromol/l) was used for inducing contraction and substance P (10 nmol/l) for inducing EDR, which was calculated in percentage of the pre-contraction. Indomethacin (10 micromol/l) was added in all measurements to eliminate the influence of prostaglandins. In additional similar experiments (n=5), the influence of 1000 KIU/ml aprotinin on the EDR caused by the endothelium-derived hyperpolarizing factor (EDHF) was tested using l-NNA (300 micromol/l) to block all NO formation. RESULTS: The EDR of pig coronaries (82+/-5% or 80+/-5% of the pre-contraction in the control tests before and after aprotinin exposure) was not significantly changed by 500 KIU/ml aprotinin (78+/-7%). A small, but significant reduction of less than 1/10 of the EDR was induced by 1000 KIU/ml aprotinin (74+/-5%). After accounting for l-NNA for NO blockage, no aprotinin-related difference remained (59+/-6% vs 60+/-6% in controls). CONCLUSION: For clinically relevant concentrations of aprotinin up to 500 KIU/ml, no significant reduction of the EDR can be found in epicardial coronary arteries of the pig. For higher doses of 1000 KIU/ml, a reduction in NO production seems to be the cause of the small but significant reduction of the EDR by aprotinin. Therefore, danger for impairment of coronary EDR by aprotinin at clinical dosage levels, as suggested by studies on rat aortas, seems to be absent in coronary arteries of a large mammalian model.

Complications after cryosurgery with new miniature cryoprobes in long hollow bones: an animal trial.

BACKGROUND: In vitro studies show that new miniature cryoprobes are suitable for cryoablation of bone tissue. The aim of this animal trial on 24 sheep was to examine the perioperative complications, particularly the danger of embolism, of cryoablation when using miniature cryoprobes. METHODS: Cryoablations with 2 freeze-thaw cycles each were carried out in the epiphysis of the right tibia and the metaphysis of the left femur. Pulmonary artery pressure (PAP) and central venous pressure (CVP) were measured. Throughout the intra- and perioperative phase, heart rate and oxygen saturation by pulse oxymetry, blood gas and electrolytes were monitored regularly. Postoperative complications were examined up to 24 weeks postoperative. RESULTS: As result, no significant increase of PAP, CVP or heart rate were observed. Blood gases were unremarkable, with pO2 and pCO2 remaining constant throughout the operation. Regarding pH, standard bicarbonate and base excess, only a non-significant shift towards a slight acidosis was seen. There was a mean hemoglobin decrease of 0.5 g/dl. One animal showed postoperative wound infection and wound edge necrosis. No major peri- and postoperative complications associated with cryosurgery of bone were observed, especially regarding clinically relevant pulmonary embolism. CONCLUSION: Surgery with new types of miniature cryoprobes appears to be a safe alternative to or a complement to conventional resection of abnormal bone tissue.

Coronary oxygen persufflation for heart preservation in pigs: analyses of endothelium and myocytes.

BACKGROUND: Coronary oxygen persufflation (COP) has been shown to prolong heart preservation time up to 14 hr in a mature pig model, with excellent recovery after orthotopic transplantation. The aim of the present study was to assess the structural, metabolic, and functional myocardial and endothelial integrity after COP in mature pig hearts. METHODS: Cardioplegic arrest was induced by original crystalloid Bretschneider solution (HTK 3h, n=6), modified Bretschneider solution (mHTK+COP, n=6), or University of Wisconsin solution (UW+COP, n=6). Hearts were stored for 3 (HTK 3h) or 14 hr (mHTK+COP, UW+COP) at 0 degrees to 1 degrees C. In addition, COP hearts were persufflated. After heterotopic transplantation and reperfusion for 7 days, hearts were analyzed by light microscopy or electron microscopy for structural injuries. Endothelial function, cardiac enzymes, metabolic parameters, and myocardial water content (MWC) were determined. Six recipient hearts served as controls. RESULTS: Quantitative light microscopic analyses and semiquantitative electron microscopic analyses showed an equal amount of damage in all groups including HTK 3h hearts. No rejection was observed. Substance P induced an equal dilatation in all hearts. Serum levels of cardiac enzymes were similar in all groups, but energy-enriched phosphates were significantly reduced, and MWC was augmented in the HTK 3h hearts and in the UW+COP hearts, in contrast to the mHTK+COP transplants. CONCLUSIONS: The lack of structural defects related to the COP technique, similar endothelial function, and an even better metabolic state of the mHTK+COP hearts versus HTK 3h hearts demonstrate the efficacy of the COP technique for prolongation of myocardial preservation time up to 14 hr.

Maintenance of physiological coronary endothelial function after 3.3 h of hypothermic oxygen persufflation preservation and orthotopic transplantation of non-heart-beating donor hearts.

OBJECTIVE: The use of non-heart-beating donors (NHBD) might increase the number of grafts available for transplantation. Experiments on heart transplantation from NHBDs demonstrated the necessity for oxygenation during preservation to allow sufficient myocardial recovery. It has been shown that, after 16 min normothermic ischemia followed by 3.3-h hypothermic preservation, excellent myocardial and cardiovascular recovery is attained, if coronary oxygen persufflation (COP) is included in the preservation protocol. Here tests are presented on the recovery of coronary endothelium derived relaxation (EDR) of NHBD hearts after preservation including COP. METHODS: After 16 min normothermic ischemia, pig hearts were stored for 3.3 h at 0-1 degrees C in modified HTK plus COP (mBHTK+COP, n=6) or in two control groups without COP: (1) with mBHTK (n=6); and (2) with HTK (n=4). Following orthotopic transplantation and 3 h of reperfusion with full blood, coronary EDR was tested in vitro using Substance P (SP) under indomethacin for prostaglandin blockage. Additional tests were performed adding L-NIL to block the NO-production by iNOS or L-NNA to block total NO production. RESULTS: The EDR in percent of precontraction was 78 +/- 7% after mBHTK+COP and 77 +/- 20% (mBHTK) or 72 +/- 7% (HTK) in the controls without significant differences between the groups. Physiologic values of normal coronaries were 75 +/- 9%. L-NIL for blockage of NO-production by iNOS resulted in unchanged relaxations. After blockage of total NO production by L-NNA, the SP-induced dilation was significantly reduced to 58 +/- 8% (mBHTK+COP) and to 48 +/- 8% (mBHTK) or 55 +/- 13% (HTK) in the controls. CONCLUSIONS: Even after 16 min of warm ischemia followed by 3.3 h of preservation with gaseous oxygen persufflation, orthotopic transplantation, and reperfusion the endothelium derived coronary dilatation was unchanged from physiologic values and similar to the controls without COP. Blockage of NO production by L-NNA resulted in equal values of EDR with or without COP, while blockage of NO production by iNOS did not influence the EDR reaction. Thus COP preservation, which has been shown to allow excellent recovery of preserved NHBD hearts, caused no damage to the coronary EDR mechanisms.

Effect of pressure management during hypothermic selective cerebral perfusion on cerebral hemodynamics and metabolism in pigs.

OBJECTIVE: The effect of perfusion pressure on cerebral hemodynamics and metabolism during selective cerebral perfusion in patients undergoing aortic surgery is still unknown. This study explored cerebral blood flow, metabolic rate, and intracranial pressure at different pressure rates. METHODS: Twenty-five pigs (32-38 kg) were cooled during cardiopulmonary bypass to 25 degrees C. After 10 minutes of hypothermic circulatory arrest, the animals were randomized to 60 minutes of selective cerebral perfusion at 3 different perfusion pressures: group I (n = 8), 40 mm Hg; group II (n = 9), 60 mm Hg; and group III (n = 8), 80 mm Hg. Microspheres were injected at baseline, the coolest temperature, and 5, 15, 25, and 60 minutes of selective cerebral perfusion, respectively, to calculate cerebral hemodynamics. RESULTS: Cerebral blood flow decreased during cooling to 54% of baseline value (50 mL/min per 100 g) and recovered in all groups during the first 15 minutes of selective cerebral perfusion. In groups I and II it reached 110% to 113% of baseline values, whereas group III animals showed significantly higher values (P(25min) = .003) during the first 25 minutes of selective cerebral perfusion (360%; 153 mL/min per 100 g). Cerebral blood flow decreased in all groups over the following 35 minutes of selective cerebral perfusion to 57% of baseline value. Cooling to 25 degrees C decreased the intracranial pressure to 10 mm Hg (93%). During selective cerebral perfusion, groups I and II showed a further intracranial pressure decrease to 45% and 82%, respectively, whereas group III, with 15 mm Hg (128%), had significantly higher intracranial pressure values at the end of selective cerebral perfusion (P(25min) = .03 and P(60min) = .02). The metabolic rate decreased to 30% of the baseline value during cooling, reaching 34% to 38% after 60 minutes of selective cerebral perfusion, with no significant differences between groups. CONCLUSION: High-pressure perfusion provides no benefit during long-term selective cerebral perfusion at 25 degrees C. Higher cerebral blood flow during the initial 25 minutes of selective cerebral perfusion leads to cerebral edema, with no alteration in metabolic rate.

Temperature dependence of cerebral blood flow for isolated regions of the brain during selective cerebral perfusion in pigs.

BACKGROUND: Hypothermic circulatory arrest (HCA) and antegrade selective cerebral perfusion (ASCP) are utilized for cerebral protection during aortic surgery. However, no consensus exists regarding optimal ASCP-temperature showing a tendency toward higher values during the last years. This study investigates regional changes of cerebral blood flow (CBF) during ASCP at two temperatures. METHODS: In this blinded study, 20 pigs (35 to 37 kg) were randomized to two groups. Animals were cooled to 10 minutes of HCA followed by 60 minutes of ASCP. Afterward the animals were perfused at 25 degrees C and 30 degrees C according to the study group. Fluorescent microspheres were injected at seven time points during the experiment to calculate total and regional CBF. Hemodynamics, cerebrovascular resistance (CVR) and cerebral metabolic rate of oxygen (CMRO(2)) were assessed. Tissue samples from the cortex, cerebellum, hippocampus, and pons were taken for microsphere count. RESULTS: The CBF and CMRO(2) decreased significantly (p < 0.002) during cooling in both groups; it was significantly higher throughout ASCP in the 30 degrees C versus the 25 degrees C group (p = 0.0001). These findings were similar among all brain regions, certainly at different levels. The CBF increased significantly (p = 0.002) during the early period of ASCP for analyzed regions and decreased significantly (p = 0.034) below baseline after 60 minutes of ASCP, reaching critical levels in the hippocampus and neocortex. The hippocampus turned out to have the lowest CBF, while the pons showed the highest CBF. Thirty minutes and more ASCP provides less CBF compared with baseline values at both temperatures. CONCLUSIONS: Antegrade selective cerebral perfusion improves CBF in all regions of the brain for a limited time. Our study characterizes the brain specific hierarchy of blood flow during ASCP. These dynamics are highly relevant for clinical strategies of perfusion.

Degeneration of cholinergic rat basal forebrain neurons after experimental subarachnoid hemorrhage.

OBJECTIVE: The reasons for neuropsychological deficits after subarachnoid hemorrhage (SAH) are fairly unknown. Cholinergic basal forebrain (BFB) neurons are essential for attention, memory, and emotion. We investigated possible changes in the cholinergic BFB and its hippocampal and neocortical terminals after experimental SAH. METHODS: SAH was induced in 19 male Wistar rats by stereotactic injection of 150 microL of autologous blood into the prechiasmatic cistern. Five control animals received 150 microL of saline. Continuous monitoring of brain tissue oxygen tension, intracranial pressure, and cerebral perfusion pressure was performed. After 4 and 14 days, the BFB was analyzed for cholinergic and gamma-aminobutyric acid-ergic cell counts. The number of cholinergic terminals in the hippocampus and neocortex was calculated by optical densitometry. RESULTS: SAH resulted in a 20 to 30% decrease in cholinergic BFB neurons in the medial septum and diagonal band at 4 and 14 days. A similar decline in the density of hippocampal and neocortical cholinergic terminals was demonstrated. Animals treated with saline did not exhibit significant cholinergic cell loss, and gamma-aminobutyric acid-ergic neurons appeared unaffected by the SAH. Courses of intracranial pressure and cerebral perfusion pressure did not differ between animals injected with blood and saline, but brain tissue oxygen tension decreased considerably and continued to stay below baseline in SAH, although it returned to normal values after saline injection. CONCLUSION: The present study provides evidence for a decrease of cholinergic BFB neurons after SAH. The direct effect of blood in the basal cisterns seemed to result in an enduring tissue hypoxia as a significant mechanism for cholinergic degeneration.

Conspicuity of zones of ablation after radiofrequency ablation in porcine livers: comparison of an extracellular and an SPIO contrast agent.

PURPOSE: To compare conspicuity of zones of ablation on nonenhanced, gadopentetate dimeglumine-(Gd-DTPA) and ferucarbotran-(SPIO)-enhanced magnetic resonance (MR) images. MATERIALS AND METHODS: In all, 33 radiofrequency ablations (RFA) were performed in 17 healthy porcine livers at 1.5T MR imaging 1 day and 2 and 4 weeks after RFA: T2-weighted (w) ultra turbo spin echo (UTSE), proton density (PD)-w UTSE, T1-w gradient echo (GRE) pre- and 5 minutes postcontrast administration, dynamic T1-w GRE during Gd-DTPA (Magnevist) or SPIO (Resovist) administration, T2-w UTSE, and PD-w UTSE sequences 10 minutes after SPIO administration. Regions of interest (ROIs) for contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were drawn in consensus by two radiologists. RESULTS: PD-w SPIO-enhanced images (23.5 +/- 5.5) showed higher liver-to-lesion CNR than T1-w GRE Gd-DTPA-enhanced images (13.5 +/- 6.1) 1 day after RFA (P < or = 0.05). At all other timepoints, liver-to-lesion CNR of PD-w and T2-w SPIO-enhanced images did not differ significantly from T1-w GRE Gd-DTPA-enhanced images (P > or = 0.05). Nonenhanced T2-w images revealed lower liver-to-lesion CNR (7.0 +/- 7.5/6.5 +/- 5.9/6.8 +/- 5.0, 1 day/2 weeks/4 weeks, respectively) than T2-w SPIO-enhanced (17.4 +/- 4.8/15.3 +/- 4.5/14.2 +/- 5.7), PD-w SPIO-enhanced (23.5 +/- 5.5/16.9 +/- 3.6, 1 day/2 weeks), and T1-w Gd-DTPA-enhanced (15.3 +/- 3.6/12.7 +/- 3.5, 2/4 weeks) images (P < or = 0.05). Liver-to-lesion CNR of SPIO-enhanced dynamic T1-w GRE images after 30, 80, 150, and 240 seconds did not change significantly over time (P > or = 0.05). CONCLUSION: One day after RFA lesion conspicuity on PD-w ferucarbotran-enhanced images is better than on T1-w GRE Gd-DTPA-enhanced images. At all other timepoints, ferucarbotran is not superior to gadolinium. Ferucarbotran- and gadolinium-enhanced images improve lesion conspicuity compared with nonenhanced T2-w images at all timepoints.

Impaired mitochondrial Ca2+ homeostasis in respiratory chain-deficient cells but efficient compensation of energetic disadvantage by enhanced anaerobic glycolysis due to low ATP steady state levels.

Energy-producing pathways, adenine nucleotide levels, oxidative stress response and Ca(2+) homeostasis were investigated in cybrid cells incorporating two pathogenic mitochondrial DNA point mutations, 3243A>G and 3302A>G in tRNA(Leu(UUR)), as well as Rho(0) cells and compared to their parental 143B osteosarcoma cell line. All cells suffering from a severe respiratory chain deficiency were able to proliferate as fast as controls. The major defect in oxidative phosphorylation was efficiently compensated by a rise in anaerobic glycolysis, so that the total ATP production rate was preserved. This enhancement of glycolysis was enabled by a considerable decrease of cellular total adenine nucleotide pools and a concomitant shift in the AMP+ADP/ATP ratios, while the energy charge potential was still in the normal range. Further important consequences were an increased production of superoxide which, however, was neither escorted by major changes in the antioxidative defence systems nor was it leading to substantial oxidative damage. Most interestingly, the lowered mitochondrial membrane potential led to a disturbed intramitochondrial calcium homeostasis, which most likely is a major pathomechanism in mitochondrial diseases.

Respiratory chain deficiency slows down cell-cycle progression via reduced ROS generation and is associated with a reduction of p21CIP1/WAF1.

We have used HeLa cells without mitochondrial DNA (rho0-cells) and transient rho0-phenocopies, obtained from wild-type cells by short-term treatment with ethidium bromide, to analyze how the absence of a functional mitochondrial respiratory chain slows down proliferation. We ruled out an energetic problem (ATP/ADP content) as well as defective synthesis of pyrimidine, iron-sulfur clusters or heme as important causes for the proliferative defect. Flow cytometric analysis revealed that reactive oxygen species were reduced in rho0-cells and in rho0-phenocopies, and that, quite unusually, all stages of the cell cycle were slowed down. Specific quenching of mitochondrial ROS with the ubiquinone analog MitoQ also resulted in slower growth. Some important cell-cycle regulators were reduced in rho0-cells: cyclin D3, cdk6, p18INK4C, p27KIP1, and p21CIP1/WAF1. In the rho0-phenocopies, the expression pattern did not fully duplicate the complex response observed in rho0-cells, and mainly p21CIP1/WAF1 was downregulated. Activities of the growth regulatory PKB/Akt and MAPK/ERK-signaling pathways did not correlate with proliferation rates of rho0-cells and rho0-phenocopies. Our study demonstrates that loss of a functional mitochondrial electron transport chain inhibits cell-cycle progression, and we postulate that this occurs through the decreased concentration of reactive oxygen species, leading to downregulation of p21CIP1/WAF1.

Experimental radiofrequency ablation near the portal and the hepatic veins in pigs: differences in efficacy of a monopolar ablation system.

BACKGROUND: We sought to compare the efficacy of a monopolar radiofrequency ablation system in vivo near the portal vein and the hepatic veins in porcine liver. MATERIALS AND METHODS: Radiofrequency ablation of healthy livers near the portal vein and the hepatic veins was performed in 10 pigs with a multitined expandable electrode. Volumes and diameters of zones of ablation were assessed by magnetic resonance imaging. RESULTS: Volumes (16.0 +/- 5.5 mL, P = 0.001) and diameters (4.0 +/- 0.7 cm, 3.3 +/- 0.7 cm, 3.0 +/- 0.6 cm, P