Regulation of endothelial nitric oxide synthase (eNOS) in myocardium subjected to cardioplegic arrest.

BACKGROUND: Nitric oxide (NO) production by both coronary endothelial cells and cardiomyocytes is thought to play a significant role in myocardial pathophysiology following ischemia/reperfusion (I/R). METHODS: In thirteen pigs subjected to 1 hour cardioplegic arrest (CA) on CPB, left ventricular (LV) biopsies were collected prior to CPB (baseline), at 60 min CPA, at 15 and 30 min reperfusion on CPB, and at 120 min post CPB. LV specimens were immunocytochemically stained against phospho-eNOS (Ser1177), phospho-eNOS (Thr495), phosphorylated ERK1/2, and AKT/PKB. Four additional pigs without CA served as controls. Cardiomyocytes were quantitatively investigated using TV densitometry (gray units: U). RESULTS: After 60 min CA phosphorylation of eNOS (Ser1177) increased significantly and remained elevated until 30 min of reperfusion. In contrast, eNOS (Thr495) phosphorylation remained unchanged during CA and throughout reperfusion. In control animals, eNOS phosphorylation remained unchanged. Akt/PKB activity significantly increased after 60 min CA and decreased thereafter. ERK1/2 activity remained unchanged during ischemia but increased during reperfusion. CONCLUSIONS: ENOS activation during ischemia occurs through phosphorylation at Ser1177 mediated by Akt/PKB. ERK1/2 does not seem to be involved in myocardial eNOS regulation especially not via phosphorylation at eNOS (Thr495).

Effects of thiopental on endothelium-dependent relaxation in porcine coronary arteries.

This study investigated the effects of thiopental on endothelium-dependent relaxation (EDR), and especially the effects on nitric oxide- and prostacyclin-independent EDR. Fresh porcine coronary artery rings (4 mm long), were consecutively tested with and without 20 microg/ml thiopental in Krebs-Henseleit solution. Indomethacin (10 micromol/l) was used in all experiments to eliminate prostacyclin effects. Prostaglandin F(2alpha) (10 micromol/l) was used to induce contractions and bradykinin (10(-10) - 10(-5) M) was used to induce EDR. Experiments were also carried out using 300 micromol/l N-nitro-L-arginine to block nitric oxide production and to assess the influence of thiopental on nitric oxide- and prostacyclin-independent EDR. Thiopental induced statistically significant increases in EDR at concentrations of 10(-6) - 10(-5) M bradykinin. Following nitric oxide production block, thiopental significantly reduced the relaxation response at concentrations of 10(-8) - 10(-5) M bradykinin. At a clinically relevant concentration of 20 microg/ml thiopental, a significant increase in EDR and a significant reduction in nitric oxide- and prostacyclin-independent relaxation was observed in porcine epicardial coronary arteries.

Electro-physiological parameters of hepatic radiofrequency ablation--a comparison of an in vitro versus an in vivo porcine liver model.

BACKGROUND: Radiofrequency ablation (RFA) is an inherent part of curative treatment within a multimodal therapy concept of malignant liver tumors. The biggest problem is the high rate of local recurrences in tumors with a diameter of more than 3 cm because of the high variability and poor reproducibility of the zone of ablation. No imaging modality facilitates monitoring during neither intraoperativ nor percutaneous RFA. This experimental study describes and compares an in vitro and in vivo porcine model by its electro-physiological parameters with the aim of monitoring RFA procedures. MATERIALS AND METHODS: RFA was performed in a perfused in vitro porcine (one RFA per liver) and in vivo porcine model (24 animals) with three different RFA systems (Rita XL 5 cm, Rita XLi 7 cm, LeVeen 5 cm). In the in vivo model, percutaneous placement of the RFA device was guided by native and contrast-enhanced CT scan. The electro-physical parameters during RFA were online (in real time) recorded by a dedicated software. After the RFA, the livers were explanted, sliced, and measured according to the consensus technique. RESULTS: The delivered energy was in vivo versus in vitro: Rita XL 238 +/- 135 kJ versus 135 +/- 53 kJ (p = 0.247); Rita XLi 711 +/- 180 kJ versus 159 +/- 54 (p = 0.016) and with LeVeen 212 +/- 71 kJ (in vivo). The LeVeen system was inconsistent in the in vitro model. This correlates to an energy consumption per ml of necrosis in vivo versus in vitro Rita XL of 8 +/- 3 kJ/ml versus 6.4 +/- 3.9 kJ/ml (p = 0.537), Rita XLi of 10 +/- 6 kJ/ml versus 1.8 +/- 0.2 kJ/ml (p = 0.016), and LeVeen of 14.0 +/- 12 kJ/ml (in vivo). The volume of ablation was in vivo versus in vitro Rita XL 30 +/- 10 ml versus 26 +/- 17 ml (p = 0.329), Rita XLi 90 +/- 58 ml versus 88 +/- 21 ml (p = 0.905), and LeVeen 22 +/- 11 ml versus 50 +/- 12 ml (p = 0.04). The impedance during RFA were in vivo versus in vitro Rita XL 39 +/- 4 Omega versus 50 +/- 14 Omega (p < 0.247), Rita XLi 33 +/- 5 Omega versus 61 +/- 16 Omega (p = 0.016) and LeVeen 31 +/- 2 Omega (in vivo). CONCLUSION: The volume of ablation showed analogue data in vivo and in vitro. The delivered energy and energy consumption was in vivo up to five times (Rita XLi) higher than in vitro and the impedance in vivo was always lower than in vitro. These differences observed between in vivo and in vitro were more pronounced than previously described. Thus the use of an in vitro model for research of the RFA technique must be challenged. The large deployment of the Rita XLi was a problem for percutaneous positioning of the device without direct contact to liver surface or major vessels in 80-kg pigs and to a lesser extent in in vitro liver originating from 130- to 140-kg pigs. Modern RFA systems which generate large volume of tissue necrosis can therefore only be adequately tested in a porcine model with a liver weight of at least 1.5-2 kg. Alternatively, a bovine liver model (with a liver weight up to 10 kg) should be developed in the future.

In-vivo measurements of coronary blood flow using 16-slice multidetector spiral computed tomography (MDCT) in a porcine model.

PURPOSE: To determine whether CTCA supplemented with CT flow measurements can be used to demonstrate and semiquantitatively evaluate poststenotic coronary blood flow in a porcine model. MATERIALS AND METHODS: In 10 thoracotomized pigs, transit time flow meter probes were attached to the aorta and left anterior descending artery (LAD) for real-time blood flow volumetry. A vascular silicone occluder was deployed around the LAD proximal to the probe to create medium-grade (MGS) and high-grade stenoses (HGS). The blood flow was measured by CT without vessel occlusion and distal to the stenoses. Time-density curves were generated from CT data. The curves were evaluated by calculating and cross-plotting the variables "slope of the density increase", "peak density" and "slope of the post-peak density decrease" from the LAD and aortic CT data. RESULTS: The flow in the LAD dropped to 41 % +/- 9 % (mean +/- SD) for MGS and 12 % +/- 6 % for HGS of the baseline. Coronary time-density curves plateaued proportional to luminal narrowing. Unimpaired flow could be differentiated statistically significant from poststenotic flow adjacent to MGS and HGS (p < 0.000 and p < 0.002, respectively). Flow adjacent to MGS and HGS was successfully differentiated for "slope of the density increase" and "slope of the post-peak density decrease" (p < 0.003 and p < 0.030, respectively). CONCLUSION: CT measurements allow semiquantitative evaluation of poststenotic coronary blood flow.

Healing of onlay mandibular bone grafts covered with collagen membrane or bovine bone substitutes: a microscopical and immunohistochemical study in the sheep.

The objective of this study was to evaluate the role of collagen membrane and Bio-Oss coverage in healing of an onlay graft to the mandible. Twelve adult sheep each received an onlay bone graft (experiment 1), bone graft+Bio-Gide (experiment 2), and bone graft+Bio-Oss/Bio-Gide (experiment 3) on the lateral surface of the mandible. The animals were euthanized at 4, 8, 12 or 16 weeks after surgery, and findings were analysed by routine microscopy and immunohistochemistry for proliferation (Ki67) and apoptotic (Caspase-3) markers. Grafts were fully incorporated in all specimens. Pronounced resorption was observed in experiment 1. Minimal loss of graft volume was seen in experiment 2 specimens without membrane displacement. A remarkable increase in the augmented region of the mandible was observed in experiment 3. A high number of osteoclasts were expressed within the grafts during the early healing period, and thereafter declined markedly. Osteoblasts within the grafts expressed a moderate level of Ki67 at 8 weeks, which thereafter declined markedly. The strongest expression of Caspase-3 on the bone surface was observed after 16 weeks. In conclusion, the effect of collagen membrane coverage on bone graft volume maintenance was dependent on membrane stability during healing. An autogenous bone graft covered with Bio-Oss particles resulted in a remarkable increase in augmented lateral surface of the mandible. The late stage of bone graft healing was associated with a high apoptotic induction pathway of osteoblasts lining the surfaces of the new bone, demonstrated by strong positive Caspase-3 immunoreactivity.

Regulation of UDP-glucuronosyltransferase (UGT) 1A1 by progesterone and its impact on labetalol elimination.

The authors recently reported the increased oral clearance of labetalol in pregnant women. To elucidate the mechanism of the elevated oral clearance, it was hypothesized that female hormones, at the high concentrations attainable during pregnancy, enhance hepatic metabolism of labetalol. Labetalol glucuronidation, which is the major elimination pathway of labetalol, was characterized by screening six recombinant human UGTs (UGT1A1, 1A4, 1A6, 1A9, 2B4, and 2B7) for their capacity to catalyse labetalol glucuronidation. The effect of female hormones (progesterone, oestradiol, oestriol, or oestrone) on the promoter activities of relevant UDP glucuronosyltransferases (UGT) was investigated using a luciferase reporter assay in HepG2 cells. The involvement of oestrogen receptor alpha (ERalpha) and pregnane X receptor (PXR) was examined by co-transfecting ERalpha- or PXR-constructs. UGT1A1 and UGT2B7 were identified as the major UGT enzymes producing labetalol glucuronides (trace amount of glucuronide conjugate was formed by UGT1A9). The activities of the UGT1A1 promoter containing PXR response elements were enhanced by progesterone, but not by oestrogens, indicating PXR-mediated induction of UGT1A1 promoter activity by progesterone. Results from semi-quantitative real-time polymerase chain reaction (PCR) assays are consistent with the above findings. This effect of progesterone on UGT1A1 promoter activities was concentration dependent. Promoter activities of UGT2B7 were not affected by either oestrogens or progesterone. The results suggest a potential role for progesterone in regulating labetalol elimination by modulating the expression of UGT1A1, leading to enhanced drug metabolism during pregnancy.

Monitoring cytosolic pH of carboxysome-deficient cells of Synechocystis sp. PCC 6803 using fluorescence analysis.

Disruption of the ccmM gene in the cyanobacterium Synechocystis sp. PCC 6803 causes a deficiency of carboxysomes and impairs growth in ambient CO2. The effect of this gene defect on cellular metabolism was investigated using electron microscopy, biochemical and fluorescence analysis. Mutant cells were devoid of the characteristic dense polyhedral bodies called carboxysomes. The photosynthetic oxygen evolution was considerably lower in mutant cells compared to wild type, while Rubisco activity in cell extracts was similar. During photosynthetic CO2-dependent oxygen evolution, Rubisco Vmax dropped from 142 micromol mg-1 chlorophyll h-1 (WT) to 77 micromol mg-1 chlorophyll h-1 in the mutant cells, and the Km for Ci (inorganic carbon) increased from 0.5 mM (WT) to 40 mM. The fluorescent indicator, acridine yellow, was used for non-invasive measurements of cytoplasmic pH changes in whole cells induced by addition of Ci, making use of the decrease in fluorescence yield that accompanies cytoplasmic acidification. The experimental results indicate that control of the cytoplasmic pH is linked to the internal carbon pool (Ci). Both wild-type and ccmM-deficient cells showed a linear response of acridine yellow fluorescence quenching and, thus, of internal acidification, with respect to externally added inorganic carbon. However, the fluorescence analysis of mutant (carboxysome-free) cells indicated slower kinetics of Ci accumulation.

Experimental bile duct protection by intraductal cooling during radiofrequency ablation.

BACKGROUND: The use of radiofrequency ablation (RFA) for liver tumours is limited by the proximity of large bile ducts to the targeted lesion. The aim of this randomized study was to evaluate intraductal cooling as a mean of protecting the bile ducts during RFA. METHODS: Twelve pigs underwent RFA adjacent to the right bile duct. After placement of an intraductal cooling catheter and a RFA probe, pigs were randomized to cooling or no cooling. Intraductal temperature was measured in all animals. The bile ducts were assessed by magnetic resonance imaging (MRI) and cholangiography 1 and 28 days after the procedure. RESULTS: Intraductal cooling abolished the increase of intraductal temperature seen in the absence of cooling. Concurrent cholangiography and MRI showed a biliary lesion in one of six pigs subjected to intraductal cooling and in five of six without cooling (P = 0.040). The biliary injuries were barely visible by MRI on day 1 but were clearly visible on day 28. CONCLUSION: Intraductal cooling can prevent biliary injury induced by RFA. The exact parameters for intraductal cooling require further investigation to establish the best compromise between bile duct protection and complete ablation of surrounding tissue.

Rate of perioperative complications in thermal ablation of bone: an animal trial.

INTRODUCTION: While only few data are available yet for radioablation of bone tissue, the occurrence of bone marrow embolisms during cryoablation has been documented. It was the aim of this study to assess perioperative complication rates of thermoablation in animals using state-of-the-art ablation probes. MATERIALS AND METHODS: Eight adult sheep were placed under general anaesthesia, and using a radioprobe, thermoablation was performed on the medial side of the head of the right tibia. In addition, freezing was performed with miniature cryoprobes on both femurs and the head of the left tibia. Haemodynamic monitoring and determination of blood gases and electrolytes were done intraoperatively. The animals were killed 1 week after surgery, and the ablation sites and lung tissue examined macroscopically and microscopically. RESULTS: None of the animals showed pathological changes in any of these parameters. Blood gases remained unremarkable throughout the operation. All eight animals showed an average drop in haemoglobin of 0.97 g/100 ml. Two animals showed fresh embolisms in the pulmonary vessels. CONCLUSION: Experimental thermoablation of bone tissue in large animals failed to show any significant perioperative complications following surgery. The lung embolisms which did occur were not clinically relevant. The use of mini-cryoprobes or radioprobes as alternative or complementary measures for treating pathologically altered bone tissue seems viable and does not involve any undue risks.

Efficacy and tolerability of the new antiepileptic drugs I: treatment of new onset epilepsy: report of the Therapeutics and Technology Assessment Subcommittee and Quality Standards Subcommittee of the American Academy of Neurology and the American Epilepsy Society.

OBJECTIVE: To assess the evidence demonstrating efficacy, tolerability, and safety of seven new antiepileptic drugs (AEDs) (gabapentin, lamotrigine, topiramate, tiagabine, oxcarbazepine, levetiracetam, and zonisamide-reviewed in the order in which these agents received approval by the US Food and Drug Administration) in the treatment of children and adults with newly diagnosed partial and generalized epilepsies. METHODS: A 23-member committee, including general neurologists, pediatric neurologists, epileptologists, and doctors in pharmacy, evaluated the available evidence based on a structured literature review including MEDLINE, Current Contents, and Cochrane library for relevant articles from 1987 until September 2002, with selected manual searches up until 2003. RESULTS: There is evidence either from comparative or dose-controlled trials that gabapentin, lamotrigine, topiramate, and oxcarbazepine have efficacy as monotherapy in newly diagnosed adolescents and adults with either partial or mixed seizure disorders. There is also evidence that lamotrigine is effective for newly diagnosed absence seizures in children. Evidence for effectiveness of the new AEDs in newly diagnosed patients with other generalized epilepsy syndromes is lacking. CONCLUSIONS: The results of this evidence-based assessment provide guidelines for the prescription of AEDs for patients with newly diagnosed epilepsy and identify those seizure types and syndromes where more evidence is necessary.

Efficacy and tolerability of the new antiepileptic drugs II: treatment of refractory epilepsy: report of the Therapeutics and Technology Assessment Subcommittee and Quality Standards Subcommittee of the American Academy of Neurology and the American Epilepsy Society.

OBJECTIVE: To assess the evidence demonstrating efficacy, tolerability, and safety of seven new antiepileptic drugs (AEDs) (gabapentin, lamotrigine, topiramate, tiagabine, oxcarbazepine, levetiracetam, and zonisamide) in the treatment of children and adults with refractory partial and generalized epilepsies. METHODS: A 23-member committee including general neurologists, pediatric neurologists, epileptologists, and doctors in pharmacy evaluated the available evidence based on a structured literature review including MEDLINE, Current Contents, and Cochrane library for relevant articles from 1987 until March 2003. RESULTS: All of the new AEDs were found to be appropriate for adjunctive treatment of refractory partial seizures in adults. Gabapentin can be effective for the treatment of mixed seizure disorders, and gabapentin, lamotrigine, oxcarbazepine, and topiramate for the treatment of refractory partial seizures in children. Limited evidence suggests that lamotrigine and topiramate are also effective for adjunctive treatment of idiopathic generalized epilepsy in adults and children, as well as treatment of the Lennox Gastaut syndrome. CONCLUSIONS: The choice of AED depends upon seizure and/or syndrome type, patient age, concomitant medications, AED tolerability, safety, and efficacy. The results of this evidence-based assessment provide guidelines for the prescription of AEDs for patients with refractory epilepsy and identify those seizure types and syndromes where more evidence is necessary.

The effect of an admixture of sodium hydrogen phosphate or heparin-coating to poly(D,L)lactide--results of an animal study.

The study was aimed at investigating the effect of an admixture of sodium hydrogen phosphate (NaP) on the pH value around degrading poly(D,L)lactide (PDLLA) and the possible improvement of PDLLA biocompatibility by coating its surface with heparin. PDLLA +/- NaP was injection-molded to form rods (20 x 3 x 2 (mm)) and cubes (3 x 2 x 2 (mm)). Half of the pure PDLLA samples were surface-coated using heparin. One rod and cube each of PDLLA, PDLLA + NaP and PDLLA/Hep were implanted into the dorsal muscles of 42 rats. From the 2nd to 52nd week after operation, pH measurements were performed in the environment around the implants. The samples were then harvested for histological and mechanical analyses. No significant decrease in pH-values was observed in the tissue around the implants. Pure PDLLA and PDLLA/Hep samples were macroscopically resorbed after 52 weeks, while the degradation of PDLLA + NaP was still in progress. Approximately 80% of the initial bending strength of PDLLA or PDLLA/Hep rods was present after six weeks, while the bending strength of PDLLA + Nap was reduced to 50% after 4 weeks. Heparin-coating of PDLLA did not improve its biocompatibility but did increase its resorption. While no significant effect of NaP on pH value was found, its admixture did reduce the mechanical characteristics of the implants.

Experimental evaluation of possible side effects of intra-operative photodynamic therapy on rabbit blood vessels and nerves.

BACKGROUND AND OBJECTIVES: Tumours of the head and neck show a high local tumour recurrence rate ranging between 7 and 30% despite combined treatment modalities. To improve these data, photodynamic therapy (PDT) might be used as an additional treatment besides surgery and radio-chemotherapy. Intra-operative PDT has been proposed to "sterilise" the tumour bed after surgical tumour resection in order to kill any remaining tumour cells which are responsible for local tumour recurrences. Often, during head and neck surgery, large blood vessels and important nerve structures are exposed and could potentially be harmed by intra-operative PDT. Despite the fact that mTHPC is the most commonly used photosensitiser for head and neck tumours, there are no data on potential detrimental side effects of intra-operative PDT onto these vital structures. The purpose of this study was to use a maximal treatment protocol in rabbit observing possible damage to the blood vessels and nerve structures and thus judge the most severe event that could happen in patients. STUDY DESIGN/MATERIALS AND METHODS: In rabbits the large blood vessels and nerve structures at the neck and at the groin area were surgically exposed and treated by mTHPC-mediated intra-operative PDT. Various treatment parameters (drug-light interval, light dosage, follow up interval) were modified in order to find the critical treatment parameters which might cause maximum tissue effects. The intention was to define the most severe clinical complications which could be expected from mTHPC mediated intra-operative PDT. RESULTS: The most severe tissue reactions were found at a drug dosage of 0.3 mg/kg, a drug-light interval of 24 hours and a light dosage of 20 J/cm(2). Complete necrosis was found for the muscles, fat and connective tissue within the entire treatment field. Blood vessels demonstrated severe oedema, media-hyperplasia or loosening of the endothelial layer leading to various degrees of local thrombosis but no break down of the vessel wall or any rupture was noted. Most nerves were altered by a 75% demyelisation but this did not result in any clinical symptoms. CONCLUSIONS: Our results have shown that mTHPC mediated intra-operative PDT used with a maximal treatment protocol (very high doses and very short drug-light intervals) has significant histological impact onto all tissue structures, but did not show any clinical symptoms in rabbits. mTHPC mediated intra-operative PDT seems to be a promising and a safe treatment option which could complement existing treatment modalities in order to improve total survival rate of tumour patients.

[In vivo study of degradation of poly-(D,L-) lactide and poly-(L-lactide-co-glycolide) osteosynthesis material]. / In-vivo-Untersuchung zur Degradation von Poly-(D,L-)Laktid- und Poly-(L-Laktid-co-Glykolid)-Osteosynthesematerial.

AIMS: Comparison of the degradation of poly(D,L)lactide (Resorb X) or poly(lactide-co-glycolide) (LactoSorb) in vivo. MATERIAL AND METHODS: LactoSorb and Resorb X osteosynthesis plates were fixed at the lateral aspect of the femora of 26 Chinchilla rabbits using the respective osteosynthesis screws. After intraperitoneal injection of fluorochromes the screw plate bone blocks were resected after 1, 6, 12, 14, 16, 21, 26 months and radiologic, histologic as well as fluorescence microscopic examinations were carried out. RESULTS: Newly formed bone was detectable above and beneath the polymers 1 month after the implantation. The implants were totally covered by newly formed bone after 6 months. While the LactoSorb screws were found to be as birefringent as after 1 month, in the Resorb X screws a continuous resorption by phagocytizing marrow cells starting from the periphery was detectable. Resorb X was totally resorbed in histologic slides 12 months after implantation, while total resorption of LactoSorb lasted 14 months; both polymers were replaced by marrow cells. Bone remodeling was not finished 26 months after implantation in both polymers. CONCLUSION: Resorption of Resorb X was finished earlier than the resorption of LactoSorb. Both materials were found by fluorescence microscope to be completely resorbed after 12 or 14 months, but bone remodeling of the screw holes was not yet finished 26 months after implantation.

Cryosurgery in long bones with new miniature cryoprobe: an experimental in vivo study of the cryosurgical temperature field in sheep.

AIM: The aim of this in vivo study was to determine whether new miniature cryoprobes provide adequate tissue cooling in long bones by measuring the field of temperature under various conditions. METHODS: Freezings were performed in femoral and tibial bones of 10 sheep under general anaesthesia. Applying one cryoprobe, temperatures of -75 degrees C resp. -51 degrees C could be reached within 0.75 cm resp. 1.00 cm of the probe. RESULTS: Histological examinations revealed compact bone and marrow necroses along the isotherm in all 10 sheep. Using two cryoprobes simultaneously, a mean temperature decrease to -71 degrees C between the two cryoprobes was achieved thanks to the synergistic freezing effect. Looking at consecutive freezes, it was apparent that with similar cryoprobe end temperatures, the temperature dropped faster if the number of freezing cycles was increased. CONCLUSION: In conclusion, it was seen that despite its small diameter, the new miniature cryoprobe delivers adequate in vivo tissue cooling in long tubular bones. Employing the synergistic freezing effect by using two or more cryoprobes simultaneously, efficient in vivo freezing of larger bone segments is also possible. Thus, cryosurgery with the new miniature probes can provide a valuable complement to conventional resection of long tubular bones, and offers a viable alternative to surgical treatment of neoplastic diseases of the skeletal system.

Microcirculatory changes associated with gastric tube formation in the pig.

The standard reconstruction after esophagectomy is the formation of a gastric tube with partial devascularization of the lesser curvature. The purpose of this experimental study was to establish an animal model in order to analyze microcirculation associated with the formation of a gastric tube. In 17 pigs tissue perfusion was measured with a laser Doppler imager (LDI) and partial tissue oxygen pressure (ptO(2)) with a Clark-type polarographic oxygen electrode before and after formation of a gastric tube in well-defined regions of the stomach. The operative procedure included the dissection of the left gastric and short gastric arteries; the left gastroepiploic artery along the greater curvature was preserved. LDI and ptO(2) baseline measurement were significantly lower in the fundus compared to the antrum and corpus. After formation of a gastric tube LDI and ptO(2) baseline values calculated from the mean measurements of the antrum, corpus and fundus decreased significantly (LDI: 1,099 PU +/- 228 SD to 601 PU +/- 125 SD, p < 0.0001; ptO(2): 50.8 mm Hg +/- 5.9 SD to 40.7 mm Hg +/- 9.3 SD, p = 0.0003). Microcirculatory changes did not correlate with changes of cardiac output and systemic vascular resistance. This study suggests that the pig is an appropriate model to investigate microcirculation associated with gastric tube formation. Its use for esophageal reconstruction by pull-up of the gastric interponate is limited.

[Detection of air embolism by a re-usable Doppler probe integrated in a central venous line--application in-vivo]. / Wiederverwendbare, in einen Zentralvenenkatheter integrierbare Dopplersonde zur Detektion von Luftembolien Anwendung in-vivo.

PROBLEM: Air embolism frequently occurs under neurosurgical operations performed in the sitting position. Recently we reported the idea of inserting a re-usable doppler probe into a blind-ending lumen of a central venous catheter (Schregel-Volk-Catheter, SVC). In vitro testing in a circulation model showed a high sensitivity: air bubbles as small as 0.5 microliter were reliably detected at a distance up to 4 cm from the tip of the SVC. METHOD: After approval by the local ethics committee pigs were anaesthetised and a cardiopulmonary bypass was connected. During the bypass period a 12 F SVC (Medex Medical, Germany) with one blind-ending lumen was positioned into the proximal vena cava cranialis or vena cava caudalis. An 8 MHz doppler probe (MTB Basler, Suisse) was introduced into the SVC and connected with the doppler device Multi-Dop T (DWL, Germany). Well defined air bubbles (3-6 microliter) were generated by a bubble generator and injected into the right femoral vein or the left vena jugularis interna. RESULTS: All bubbles were reliably detected by the re-usable doppler probe. Embolic events can be documented, counted and quantified by the Multi-Dop T. CONCLUSION: Using SVC's with a blind-ending lumen could improve and simplify the detection of air embolism. We see several advantages (e.g. sensitivity, costs) compared with established methods (precordial doppler, TEE) for detection of air embolism.

Endothelial function after prolonged coronary artery oxygen persufflation in a rabbit model of heart preservation.

Coronary oxygen persufflation may serve as a means to improve storage conditions and organ preservation time for cardiac transplantation. We examined whether coronary oxygen persufflation and prolonged preservation time alter the endothelium-dependent relaxation of isolated coronary arteries. Isolated rabbit hearts were subjected to four different protocols: control (no preservation), 3 h cold storage in Bretschneider's solution, 18 h cold storage in Bretschneider's or University of Wisconsin solution, combined with coronary oxygen persufflation. After 2 h parabiotic reperfusion, intramural segments of coronary arteries were isolated and isometric tension was recorded using a small-vessel myograph. Endothelial function was examined using carbachol and substance P, applied after vessel constriction using high (30 mmol/l) K(+) or U 46.619, a thromboxane receptor agonist. In another series, coronary flow was measured after Bretschneider's +/-18 h coronary oxygen persufflation, or in freshly isolated, retrogradely perfused Langendorff hearts. Flow responses to substance P, acetylcholine or bradykinin were recorded. In saline-reperfused intact hearts no change in the normal effects of endothelium-dependent relaxants was detected after 18 h, irrespective of coronary oxygen persufflation. However, after isolation of the resistance vessels endothelium-dependent relaxation was abolished after long-term preservation and persufflation. Similar results were obtained after mechanical removal of the endothelium using control hearts. Short-term preservation without persufflation resulted in relaxations similar to those in non-preserved control hearts. Long-term preservation of rabbit heart including coronary oxygen persufflation results in unchanged endothelium-dependent relaxation in intact heart, but abolishes the endothelium-dependent relaxation after isolation of the vessels.

The effect of an addition of sodium hydrogenphosphate to poly(D,L)lactide--results of in vitro examinations.

Aim of the study was to examine the influence of sodium hydrogenphosphate (NaP) on the pH value and the mechanical characteristics of degrading poly(D,L)lactide (PDLLA). Test rods of PDLLA with or without NaP amounting to 1, 10, 25 or 50 mol per 100 mol lactate, the degradation product of PDLLA, were produced by injection molding. Molecular weight and bending strength of the rods were measured before and after an accelerated in vitro-test (55 degrees C, Ringer's solution (RS)). For a long-time degradation test PDLLA-rods with or without 1 mol% NaP were placed in RS or Soerensen buffer solution (SB, pH 7.4) at 37 +/- 1 degrees C. Measurements of pH and determination of length, volume and weight of the samples were done in 2-4 week intervals up to the 52nd week after incubation. A pH-drop was measured in RS or SB containing pure PDLLA after 28 or 36 weeks respectively. Stabilization of the pH value due to admixed NaP delayed the degradation related pH drop for 8 weeks in RS or SB. A strong increase of length, volume and weight was measured in PDLLA + NaP-rods. In conclusion minimal stabilization of pH but also an increase of outer dimensions of the samples was found due to the admixture of NaP to PDLLA. Thus, an addition of substantially higher amounts than 1 mol% NaP in PDLLA can not be recommended, regardless of the positive effects on pH stabilization.

Degradation of poly(D,L)lactide implants with or without addition of calciumphosphates in vivo.

The study was aimed at examining the in vivo degradation of pure poly(D,L)lactide (PDLLA) or PDLLA with an admixture of calciumphosphates. One rod (20 x 3 x 2 mm) and one cube (3 x 2 x 2 mm) of pure PDLLA, PDLLA with tricalciumphosphate (PDLLA + TCP) or PDLLA with calciumhydrogenphosphate (PDLLA + CHP), respectively, were implanted into the dorsal muscles of 50 male Wistar Albino rats. After definite intervals (from 2nd to 72nd week), pH measurements were performed in the environment of the implants. Afterwards, the cubes with their surrounding tissues were excised for histological examinations, measurements of the outer dimensions and mechanical analyses of the explanted rods were performed. No drop of more than 0.1 pH units was detectable in the tissue surrounding any type of implants. No advantageous effect of the calciumphosphates could be proved. A mild foreign body reaction could be observed around PDLLA implants. After 72 weeks, pure PDLLA had been totally resorbed from the extracellular space, the degradation of calciumphosphate-enriched PDLLA was still in progress. A large amount of inflammations occurred in the tissues surrounding PDLLA with an admixture of slowly degrading TCP or CHP, leading to two abscesses and four fistulas at PDLLA + TCP, and two abscesses and three fistulas at PDLLA + CHP implantation site. Bending strength of pure PDLLA was constant up to the 4th week post-implantation and reduced to 60% of the initial value up to the 12th week. No traces of crystallinity could be observed during the degradation of PDLLA. As a conclusion of the study, complete resorption from the extracellular space and tissue tolerance of pure PDLLA is proved. An admixture of small calciumphosphate particles is not suitable to improve the biocompatibility of PDLLA but leads to a decrease in the mechanical characteristics.