Krebs-Henseleit Buffer Solution Research Articles

Active and passive mechanical characterization of a human descending thoracic aorta with Klippel-Trenaunay syndrome

A human aorta from a female donor affected by Klippel-Trenaunay syndrome was retrieved during a surgery for organ donation for transplant. The aorta was preserved in refrigerated Belzer UW organ preservation solution and tested within a few hours for mechanical characterization with and without vascular smooth muscle activation. KCl and Noradrenaline were used as vasoactive agents in bubbled Krebs-Henseleit buffer solution at 37 °C. A quasi-static and a dynamic mechanical characterization of the full wall and the three individual layers were carried out for strips taken in longitudinal and circumferential directions. The full wall in the descending portion of the aorta underwent mechanical tests with and without smooth muscle activation. Results were compared to data obtained from healthy aortas and show a reduced stiffness of the full wall in circumferential direction. Also, a significant reduction of the response to vasoactive agents in circumferential direction was observed, while the longitudinal response was similar to healthy cases.

Synthesis of an insulin-loaded mucoadhesive nanoparticle designed for intranasal administration: focus on new diffusion media.

Intranasal administration is a drug delivery approach to provide a non-invasive pharmacological response in the central nervous system with relatively small peripheral side effects. To improve the residence time of intranasal drug delivery systems in the nasal mucosa, mucoadhesive polymers (e.g., chitosan) can be used. Here, insulin-loaded chitosan nanoparticles were synthesized and their physiochemical properties were evaluated based on requirements of intranasal administration. The nanoparticles were spherical (a hydrodynamic diameter of 165.3nm, polydispersity index of 0.24, and zeta potential of +21.6mV) that granted mucoadhesion without any noticeable toxicity to the nasal tissue. We applied a new approach using the Krebs-Henseleit buffer solution along with simulated nasal fluid in a Franz's diffusion cell to study this intranasal drug delivery system. We used the Krebs-Henseleit buffer because of its ability to supply glucose to the cells which serves as a novel ex vivo diffusion medium to maintain the viability of the tissue during the experiment. Based on diffusion rate and histopathological endpoints, the Krebs-Henseleit buffer solution can be a substituent solution to the commonly used simulated nasal fluid for such drug delivery systems.

Subnormothermic isolated organ perfusion with Nicorandil increased cold ischemic tolerance of liver in experimental model.

The cold ischemia -reperfusion injury may lead to microcirculatory disturbances, hepatocellular swelling, inflammation, and organ dysfunction. Nicorandil is an anti-ischemic, ATP-sensitive potassium (KATP) channel opener drug and has proved its effectiveness against hepatic Ischemia/Reperfusion (I/R) injury. This study aimed to investigate the effect of Nicorandil on mitochondrial apoptosis, oxidative stress, inflammation, histopathological changes, and cold ischemic tolerance of the liver in an ex vivo experimental isolated-organ-perfusion model. We used an ex vivo isolated rat liver perfusion system for this study. The grafts were retrieved from male Wistar rats (n = 5 in each), preserved in cold storage (CS) for 2 or 4 hours (group 1, 2), or perfused for 2 or 4 hours (group 3, 4) immediately after removal with Krebs Henseleit Buffer (KHB) solution or Nicorandil containing KHB solution under subnormothermic (22-25°C) conditions (group 5, 6). After 15 minutes incubation at room temperature, the livers were reperfused with acellular, oxygenated solution under normothermic condition for 60 minutes. In the Nicorandil perfused groups, significantly decreased liver enzymes, GLDH, TNF-alpha, and IL-1ß were measured from the perfusate. Antioxidant enzymactivity was higher in the perfused groups. Histopathological examination showed ameliorated tissue deterioration, preserved parenchymal structure, decreased apoptosis, and increased Bcl-2 activity in the Nicorandil perfused groups. Perfusion with Nicorandil containing KHB solution may increase cold ischemic tolerance of the liver via mitochondrial protection which can be a potential therapeutic target to improve graft survival during transplantation.

Role of atrial natriuretic peptide in abrogated cardio protective effect of ischemic postconditioning in diabetic rat heart

Background: Diabetes decreased cardioprotective potential of ischemic postconditioning (IPOC), atrial natriuretic peptide (ANP) induced the cardioprotection against ischemic-reperfusion (I/R) injury. The present study has been designed to investigate the role of ANP induced postconditioning in diabetic rat heart. Methods: Isolated Langendorff perfused normal and diabetic rat hearts were stabilized for 10 min proceed by global ischemia further followed by four cycles of IPOC, each cycle comprised 5 min of reperfusion and 5 min of ischemia at onset of 120 min of reperfusion. Perfusion of ANP (0.1μM/l) with Krebs–Henseleit Buffer solution in isolated diabetic rat heart for four-cycle of IPOC significantly decreased I/R-induced myocardial infarct size and release of CK-MB and lactate dehydrogenase (LDH) level in coronary effluent. Results: Four cycles of IPOC-induced cardioprotection noted by decreased in infarct size and also in release of LDH and CK-MB in normal rat heart. However, IPOC-induced cardioprotection was completely attenuated in isolated heart obtained from diabetic rat. Perfusion of ANP (0.1μM/L) significantly restored the attenuated cardioprotection in diabetic rat heart, which was completely blocked by perfusion of L-NAME (100μM/L), an eNOS inhibitor. Conclusion: So that, ANP restored cardioprotective affect in diabetic rat heart, which was completely abolished by the perfusion of L-NAME (100μM/L), an eNOS inhibitor.

Effect of E‐liquid Base Solution (Vegetable Glycerin or Propylene Glycol) on Aortic Function in Mice

The effects of vaping with electronic cigarettes (e-cigs) on cardiovascular health are still under investigation. An important question that still remains unknown is the role of individual constituents within the e-liquid used for vaping. In this study, we examine the sole effect of either vegetable glycerin (VG) or propylene glycol (PG), without the presence of any flavors or nicotine, on aortic reactivity. Healthy C57BL/6J mice were exposed to e-cig vapor for 4 weeks (5d/wk, 1-hour/day, 60 puffs/day) to e-cig aerosol from either 100% VG or 100% PG e-liquid using a whole-body chamber exposure system (SCIREQ InExpose). Control mice were exposed to ambient air. E-cig aerosol was produced by a Joyetech eGRIP OLED device at 17.5 watts, with 5-second puff duration. Mice were sacrificed >24 hours after their final exposure, and thoracic aortas were excised, cleaned of perivascular adipose tissue, and were cut into 2mm ring segments. Aortic rings were mounted on wire myograph system (DMT, AD Instruments) containing warm aerated Krebs-Henseleit buffer solution. The vessels were pre-constricted with 50 µL of U46619 [7.5e-9 M], and then exposed to a serial dilution of methacholine [MCh 10-9 to 10-5 M] to assess endothelial-dependent (EDD) vasodilation, and separately to serial dilutions of sodium nitroprusside [SNP 10-9 to 10-5 M] to assess endothelium-independent (EID) vasodilation. In PG-exposed mice, max aortic EDD was reduced by 18±2% (P<0.05) compared to controls, and reduced by 14±2% (P<0.05) compared to VG-exposed mice. VG-exposed mice were not significantly different compared to controls. Maximal aortic EID was slightly impaired in PG- mice compared to control (8±2% P<0.05) and VG (5±1% P<0.05) groups. In summary, chronic exposure to e-cig aerosol from PG in the base solution resulted in aortic EDD and EID dysfunction, however VG-exposed mice were not affected. These data suggest that both endothelial-dependent and -independent mechanisms are adversely affected by PG, and therefore vaping with PG in the base solution alone poses a significant risk for adverse cardiovascular health effects.

A tissue preparation to characterize uterine fibroid tissue properties for thermal therapies.

Treating uterine fibroids with less invasive therapies such as magnetic resonance-guided focused ultrasound (MRgFUS) is an attractive alternative to surgery. Treatment planning can improve MRgFUS procedures and reduce treatment times, but the tissue properties that currently inform treatment planning tools are not adequate. This study aims to develop an ex vivo uterine fibroid model that can emulate the in vivo environment allowing for characterization of the uterus and fibroid MR, acoustic, and thermal tissue properties while maintaining viability for the necessary postsurgical histopathological assessments. Women undergoing a hysterectomy due to fibroid-related symptoms were invited to undergo a preoperative pelvic MRI and to permit postoperative testing of their uterine specimen. Patients that declined or could not be scheduled for a pre-operative MRI were still able to allow post-operative testing of their excised tissue. Following surgical removal of the uterus, nonmorcellated tissues were reperfused with a Krebs-Henseleit buffer solution. An MR-compatible perfusion system was designed to maintain tissue viability inside the MR suite during scanning. MR imaging protocols utilized preoperatively were repeated on whole sample, reperfused ex vivo uterus specimens. Thermal properties including thermal diffusivity and thermal conductivity of the uterus and fibroids were determined using an invasive needle sensor device in 50% of the specimens. Acoustic property measurements (density, speed of sound and attenuation) were obtained for approximately 20% of the tissue samples using both through-transmission and radiation force balance techniques. Differences between fibroid and uterus and in vivo and ex vivo measurements were evaluated with a two-tailed Student t test. Fourteen patients participated in the study and measurements were obtained from 22 unique fibroids. Of the 16 fibroids available for preoperative MRI testing, 69% demonstrated classic hypo-intensity relative to the myometrium, with the remainder presenting with iso- (25%) or hyper-intensity (6%). While thermal diffusivity was not significantly different between fibroid and myometrium tissues (0.217±0.047 and 0.204±0.039mm2 /s, respectively), the acoustic attenuation in fibroid tissue was significantly higher than myometrium (0.092±0.021 and 0.052±0.023Np/cm/MHz, respectively). When comparing in vivo with ex vivo MRI T1 and T2 measurements in fibroids and myometrium tissue, the only difference was found in the fibroid T2 property (P<0.05). Finally, the developed perfusion protocol successfully maintained tissue viability in ex vivo tissues as evaluated through histological analysis. This study developed an MR-compatible extracorporeal perfusion technique that effectively maintains tissue viability, allowing for the direct measurement of patient-specific MR, thermal, and acoustic property values for both fibroid and myometrium tissues. These measured tissue property values will enable further development and validation of treatment planning models that can be utilized during MRgFUS uterine fibroid treatments.

An investigation on cardioprotective potential of Marrubium vulgare aqueous fraction against ischaemia-reperfusion injury in isolated rat heart.

The aim of this study was to evaluate the cardioprotective effects of aqueous fraction of Marrubium vulgare hydroalcoholic extract on cardiac parameters in ischaemic-reperfused isolated rat hearts. The aerial parts of the plant were extracted with methanol 70% by maceration. The water-soluble portion of the total hydroalcoholic extract was prepared with liquid-liquid extraction (LLE). Afterwards, the antioxidant activity, total phenolic and flavonoids content of the aqueous fraction were determined. In order to evaluate the effects of the aqueous fraction on cardiac parameters and ischaemia-reperfusion (I/R) injury, the Langendroff method was used on male Wistar rats. Harvested hearts were cannulated immediately to the Langendroff apparatus and subjected into 30 min regional ischaemia and 2 h reperfusion, either by a modified Krebs-Henseleit buffer (KHB) solution or enriched KHB solution with plant extract (10, 20, 40 μg/mL). The aqueous fraction was found to be a scavenger of DPPH radical with RC50 value of 47 μg/mL. The total phenolic and flavonoids content of the fraction was 6.05 g gallic acid equivalent and 36.13 mg quercetin equivalent per 100 g of dry plant material. In addition, 40 μg/mL of Marrubium vulgare aqueous fraction significantly decreased infarct size in comparison to control group. All doses considerably reduced the total ventricular ectopic beats during 30 min of ischaemia. The extract at dose of 40 μg/mL noticeably decreased the arrhythmias during the first 30 min of reperfusion. The results of the study indicated aqueous fraction of Marrubium vulgare possesses a protective effect against I/R injuries in isolated rat hearts.

The Effects of Hesperidin on Ischemia/Reperfusion Induced Arrhythmias and Infarct Size in Isolated Rat Heart

Background: Hesperidin is a flavonoid and has strong anti-oxidant and anti-inflammatory activities. The aim of the present study is to investigate the effects of hesperidin on ischemic/reperfusion (I/R) induced injuries and arrhythmias. Methods: Male Wistar rats were anesthetized and then the hearts were removed and cannulated immediately to a langendorff apparatus and prepared for the left coronary artery ligation. The hearts were perfused with Krebs-Henseleit Buffer Solution (KHBS; control) or KHBS plus hesperidin (1, 2.5 & 5µg/ml; treated groups) 5 minutes before coronary occlusion, during the ischemia, and reperfusion period. After reperfusion, double staining strategy (Evans blue and TTC) were used. The percentage of infarct size was determined by Image-j software. Arrhythmia in control group and treated groups were analyzed and compared. Lactate concentration was measured in samples at the end of stabilization, 30 minute after ischemia, and 60 minute after reperfusion. Western blotting was performed for evaluation of pAMPK at the end of the ischemia in the heart tissues. Results: The results demonstrated that hesperidin caused a significant reduction in ventricular ectopic beats (VEBs) number during ischemia and reperfusion phase (p<0.01, p<0.05). The infarct size was reduced significantly by all concentration of hesperidin (p<0.001) and Lactate concentration at the end of ischemia had a significant reduction in the treatment groups (p<0.001). pAMPK/AMPK ratio was reduced by hesperidin at 5 µg/ml. Conclusion: The results of the study suggest that hesperidin has protective effects against I/R induced injuries and arrhythmias in isolated rat hearts that could be related to its effect on modulating of AMPK activity.

Lipopolysaccharide Induced Activation of Toll Like Receptor 4 in Isolated Rat Heart Suggests a Local Immune Response in Myocardium.

Myocardial dysfunction is one of the major complications in patients with sepsis where there is a relationship between the blood level of cytokines and the onset of myocardial depression. In many cases of sepsis, the presence of Lipopolysaccharide (LPS) has been established. LPS Binding Protein (LBP) bound endotoxin is recognized by CD14/toll-like receptor-4 (TLR4) complexes in innate immune cells which stimulates TNF-α release. To investigate whether isolated rat heart is capable of producing TNF-α locally through TLR4 activation by LPS. Using langendorff method, LPS in 120 mL of the modified Krebs-Henseleit buffer solution (KHBS) at final concentration of 1 µg/mL was perfused at recycling mode. The effect of LPS on cardiac function was evaluated. To assess the TLR4 activity and TNF-α release, western blotting, real time-PCR, and ELISA were used. Compared with control, coronary perfusion pressure (CPP) as well as left ventricular developed pressure (LVDP), maximum and minimum rates of the left ventricular developed pressure (dP/dtmax; dP/dtmin; p<0.001) were depressed to a maximum level after 180 minutes recycling with LPS. This myocardial depression was associated with a significant increase in TLR4 expression (p<0.01), MyD88 activity (p<0.01) and TNF-α (p<0.05) concentration in the heart tissue. The results of this study show that heart is capable of producing TNF-α through TLR4 and MyD88 activation independent of classic immune system and suggest a local immune response.

Hydroxyectoine ameliorates preservation injury in deceased after cardiac death donors in experimental liver grafts.

Due to the drastic shortage of organ donors, clinicians are increasingly considering the use of deceased after cardiac death donors (DCD). Compatible solutes like Ectoine and Hydroxyectoine are produced by extremophilic bacteria as a cell protectant to survive in harsh environments. We hypothesized that the addition of Hydroxyectoine to Histidine-Tryptophan-Ketoglutarate solution (HTK) could ameliorate cold ischemic preservation injury of DCD livers. Rat livers were harvested from male Wistar rats weighing 250-300 g. Three experimental groups (n=5 per group) were studied: (1) CONTROLS: cold static storage in HTK for 24 h, (2) DCD: 30-min warm ischemia time and 24-h cold static storage in HTK, and (3) DCD+Hydroxyectoine: like DCD, but with 24-h cold static storage in HTK+Hydroxyectoine. Viability of the livers was assessed after 24 h of preservation by isolated perfusion for 45 min with oxygenated Krebs-Henseleit buffer solution. (mean ±SEM, Control vs. DCD vs. DCD+Hydroxyectoine) Parenchymal enzyme release was significantly lower in DCD+Hydroxyectoine compared to DCD (AST: 9±0.54; 56.8±2.05; 32.2±7.25 U/L, ALT: 9.5±0.5; 37.75±9.6; 17.5±4.17 U/L). Bile production at the end of 45 min reperfusion was significantly higher in DCD+Hydroxyectoine (5.16±1.32; 1.36±0.34; 10.75±2.24 µL/g liver weight/45 min). Malondialdehyde values were significantly lower in DCD+Hydroxyectoine (0.8±0.09, 1.14±0.18, 0.77±0.08 nmol/mL). Intercellular adhesion molecule-1 showed significantly lower values in DCD+Hydroxyectoine (219.07±51.79, 431.9±35.70, 205.2±37.71 pg/mL) and the portal venous pressure at 45 min was lower compared to DCD (20.41±0.12, 27.47±0.45, 22.08±0.78 mmHg). Our data provide evidence for the beneficial role of Hydroxyectoine-modified HTK solution for the preservation of DCD livers compared to HTK.

The use of a perfluorochemical emulsion as a vascular perfusate in drug absorption.

In-vitro simultaneous luminal and vascular perfusion using the perfluorochemical emulsion, FC-43 emulsion, as a vascular perfusate, was examined for drug absorption in rat jejunum. The intestinal membrane in this system was found to retain its normal barrier functions for drug transport, as evident from the following: (i) stable absorption clearance of tritiated water and salicylic acid at steady-state, (ii) agreement of this clearance with that by in-situ single-pass luminal perfusion, (iii) active transport of D-glucose and its inhibition by phloridzin and (iv) normal glutamate pyruvate transaminase activity in the intestinal mucosa. FC-43 emulsion gave a more normal absorption site blood flow than the usual vascular perfusate containing erythrocytes and albumin in Krebs-Henseleit bicarbonate buffer solution. Consequently, this emulsion was useful for examining the contribution of blood flow resistance toward drug absorption. The rate-limiting steps of absorption of tritiated water, antipyrine and salicylic acid were examined by perfusion using FC-43 emulsion. The absorption of tritiated water was almost completely blood flow-limited and its absorption clearance may possibly be an approximated absorption site blood flow. The contribution of blood flow resistance to total resistance for antipyrine absorption exceeded that for salicylic acid absorption.

Effect of freezing on the passive mechanical properties of arterial samples

Little mechanical data is available on human arteries because of the difficulty of testing artery samples often obtained from autopsy, while arteries are still considered “fresh”. Various solutions mimicking the physiological environment have been used to preserve artery samples from harvesting to testing. Cryopreservation might provide a means to preserve the mechanical properties of arteries for days or weeks after harvesting. The objective of this study is to investigate the effect of several preservation methods, including simplified cryopreservation methods, on the passive mechanical properties of arteries. Eighteen fresh cruciform samples were mechanically tested. Samples were divided in three groups based on preservation medium and freezing method: isotonic saline solution, Krebs-Henseleit buffer solution with dimethyl sulfoxide (DMSO), and dipped in liquid nitrogen. In each group, half of the samples were stored at -20℃ and the other half at -80℃. Two months later, all the tissues were thawed at 4℃ and mechanical tests were repeated. Preservation of arteries for two months in Krebs solution with DMSO (at -20℃ or at -80℃) or in isotonic saline solution at -20℃ were the methods that least changed the mechanical properties of the arteries.

Protective effects ofdifferent concentration of L-carnitine on rabbit myocardium against ischemia/reperfusioninjury

：Objective To investigatethe protective effect of L-carnitine (L-CN) against the myocardial ischemia/reperfusioninjury in isolated rabbit hearts. Methods The experiment was performed on isolated rabbithearts perfused with Langendorff apparatus. Twenty four rabbit hearts were randomlydivided into ischemia/reperfusion (I/R) group, L-CN 2.5 group, L-CN 5.0 group and L-CN10.0 group (n=6). The I/R group was firstly perfused with Krebs-Henseleit buffer (K-H)solution for 25 min, followed with St. Thomas Ⅱsolutions untilcardiac arrest for 45 min and then reperfused with K-H solution for 20 min. Differentconcentration of L-CN groups were similarly treated to that of the I/R group, except thatevery group was firstly perfused with K-H solution for 10 min and then perfused withdifferent concentration of L-CN. The hemodynamic indexes were determined in the course ofperfusion. The heart was stained with TTC and photograph was taken to measure the ischemicarea. Results In contrast to the findings in the control group, the recovery of myocardialcontractility and heart rate was earlier in the L-CN 5.0 groups and the L-CN 10.0 groups (P＜0.05),the percentages of survival myocardium areas in the L-CN 5.0 groups and the L-CN 10.0groups were higher (P＜0.05). Conclusion L-CN pretreatment can increase the survival myocardium areasafter reperfusion and make cardiac function recover as soon as early afterischemia-reperfusion injury. L-CN has protection on isolated rabbit ischemia reperfusionmyocardium. Key words: L-carnitine; Ischemia/reperfusion injury; Preconditioning; Isolated heart; Rabbit

Effects of levosimendan on myocardial ischaemia-reperfusion injury

Levosimendan has a cardioprotective action by inducing coronary vasodilatation and preconditioning by opening KATP channels. The aim of this study was to determine whether levosimendan enhances myocardial damage during hypothermic ischaemia and reperfusion in isolated rat hearts. Twenty-one male Wistar rats were divided into three groups. After surgical preparation, coronary circulation was started by retrograde aortic perfusion using Krebs-Henseleit buffer solution and lasted 15 min. After perfusion Group 1 (control; n = 7) received no further treatment. In Group 2 (non-treated; n = 7), hearts were arrested with cold cardioplegic solution after perfusion and subjected to 60 min of hypothermic global ischaemia followed by 30 min reperfusion. In Group 3 (levosimendan treated; n = 7), levosimendan was added to the buffer solution during perfusion and the hearts were arrested with cold cardioplegic solution and subjected to 60 min of hypothermic global ischaemia followed by 30 min reperfusion. At the end of the reperfusion period, the hearts were prepared for biochemical assays and for histological analysis. Tissue malondialdehyde levels were significantly lower in the levosimendan-treated group than in the non-treated group (P = 0.019). The tissue Na+-K+ ATPase activity was significantly decreased in the non-treated group than in the levosimendan-treated group (P = 0.027). Tissue myeloperoxidase (MPO) enzyme activity was significantly higher in the non-treated group than in the levosimendan-treated group (P = 0.004). Electron microscopic examination of the hearts showed cardiomyocytic degeneration at the myofibril, mitochondria and sarcoplasmic reticulum in both non-treated and levosimendan-treated groups. The severity of these findings was more extensive in the non-treated group. Treatment with levosimendan provided better cardioprotection with cold cardioplegic arrest followed by global hypothermic ischaemia in isolated rat hearts.

Ozone Administration Reduces Reperfusion Injury in an Isolated Rat Heart Model

Accumulating clinical experience with ozone administration for conditions associated with ischemia has been encouraging. The aim of our study was to determine the effect of ozone on reperfusion injury in an isolated rat heart model. Isolated rat hearts were perfused with modified Krebs-Henseleit buffer solution via ascending aorta cannulation. After 15 minutes, perfusion was stopped and global ischemia was maintained for 30 minutes, following which perfusion was restarted, and continued for 40 minutes. Baseline hemodynamic measurements (heart rate, left ventricular developed pressure (LVDP), dP/dt, and coronary flow) were taken prior to ischemia, and every 10 minutes after reperfusion was started. Eleven hearts were treated with ozone during reperfusion and eight hearts served as controls. In the treatment group, after 5 minutes of reperfusion, ozone was administered in distilled water via a side arm for 5 minutes. Preischemic baseline hemodynamic measurements and coronary flow were similar in the two groups. Hearts treated with ozone during reperfusion exhibited better recovery than did controls. Mean (+/-SE) percent recovery for treatment and control groups, respectively, was: LVDP 69 +/- 2% vs 51 +/- 6% (p = 0.04); dP/dt 68.9 +/- 13.3% vs 53.7 +/- 20.4% (p = 0.05); and LVDPxHR 61.4 +/- 3.3% vs 44.4 +/- 3.5% (p = 0.02). In the isolated rat heart model, treatment with ozone during reperfusion enables better recovery than in controls. Although the mechanism by which ozone exerts its beneficial effect is not identified, it is possibly due to reduction in reperfusion injury.

Caffeic acid phenethyl ester (CAPE) supplemented St. Thomas’ hospital cardioplegic solution improves the antioxidant defense system of rat myocardium during ischemia-reperfusion injury

Background and aim of study: Cardioplegic arrest remains the method of choice for myocardial protection in cardiac surgery. Caffeic acid phenethyl ester (CAPE) prevents lipid peroxidation induced by ischemia-reperfusion injury and has a potent antioxidant property. We investigated the advantages of CAPE supplemented cardioplegic solution (St. Thomas’ Hospital cardioplegic solution No.: 2) on the antioxidant defense system of myocardium against ischemia-reperfusion injury. Material and methods: Isolated rat hearts were mounted on a nonrecirculating type of Langendorff apparatus. The hearts were arrested for 60 min with cardioplegic solution given at 20-min intervals and then reperfused for 15 min. The hearts were divided into three groups. Cold saline (0.9%, 4 °C) in group 1, St. Thomas’ Hospital solution in group 2 and CAPE added St. Thomas’ Hospital solution in group 3 were used as the cardioplegic solution. Krebs–Henseleit buffer solution was used for reperfusion. The tissues were examined biochemically for oxidative stress. Results: Significant differences among the three groups existed in tissue myeloperoxidase (MPO), catalase (CAT), Na +–K + ATPase activity and in the concentrations of malonydealdehyde (MDA) and 3-nitrotyrosine (3-NT). Group 2 showed significant changes in MPO ( P = 0.04), Na +–K + ATPase enzyme activity ( P = 0.02) and the levels of MDA ( P = 0.004) and 3-NT ( P = 0.01) in comparison with group 1. Group 3 efficiently reduced MDA levels ( P = 0.004) and also led to significant decrease in levels of MPO ( P = 0.006), 3-NT ( P = 0.01) and Na +–K + ATPase activity ( P = 0.01) and increase in the level of CAT ( P = 0.004) in comparison with group 1. Significant changes were also found in the levels of MDA ( P = 0.03), MPO ( P = 0.04) and CAT ( P = 0.009) in comparison between groups 2 and 3. Conclusions: We demonstrated that the administration of CAPE into cardioplegic solutions improves the antioxidant defense system of rat heart during the ischemia-reperfusion injury.

Perfluorohexane Vapor Has Only Minor Effects on Spatial Pulmonary Blood Flow Distribution in Isolated Rabbit Lungs

We tested the hypothesis that administration of perfluorohexane (PFH) vapor does not significantly affect the relative pulmonary blood flow (Qrel) distribution in isolated rabbit lungs. Fourteen isolated rabbit lungs were perfused with a Krebs-Henseleit buffer solution (flow 150 mL/min). Pulmonary afterload was set to 3 mm Hg. The lungs were ventilated with 4% CO(2) in room air using a small animal ventilator (respiratory rate, 30 breaths/min; tidal volume, 12 mL/kg body weight; positive end-expiratory pressure, 2 cm H(2)O). After a steady-state period, 18 vol. % of PFH vapor was administered to 9 lungs for 30 min. In a second set of experiments five lungs served as controls. Change in (Qrel) distribution was assessed using fluorescent-labeled microspheres. The unpaired Student's t-test was used to compare variables between groups. The paired Student's t-test, the one-sample Student's t-test, the Anderson-Hauck test of equivalence, and Pearson correlation were used to analyze changes within groups. The mean correlation coefficients of (Qrel) were 0.564 +/- 0.182 for the PFH group and 0.502 +/- 0.295 for the control group, respectively. No significant changes in (rel) distribution over time and between groups were found. However, in the PFH group a tendency towards redistribution of (Qrel) to more ventral lung areas was noted. Our results suggest that PFH vapor has no significant effects on redistribution of (Qrel) in isolated rabbit lungs.

Hypothermic machine perfusion of rat livers preserves endothelial cell function

This study was conducted to investigate the effect of starch in the preservation solution during hypothermic machine perfusion (HMP) on endothelial cell and hepatocyte functions in an isolated perfused rat liver model. Livers isolated from male Sprague-Dawley rats were perfused with the University of Wisconsin (UW) solution (HMP + starch group); modified UW solution (starch omitted) (HMP − starch group) at 0.4 mL/min per g liver; or simply stored in the UW solution (SCS group) at 4°C for 24 hours. Following preservation, livers from HMP + starch, HMP − starch, SCS, and control group (without preservation) were perfused with Krebs-Henseleit Buffer solution at 37°C for 30 minutes. Samples were taken every 10 minutes during 30-minute warm perfusion to assess hepatocyte and endothelial cell function and damage. After 24 hours of hypothermic preservation and 30 minutes rewarming, livers in the HMP + starch group displayed significantly lower lactate dehydrogenase levels and higher bile production. Endothelial cell function was also improved as indicated by hyaluronic acid uptake and shorter transient time for albumin observed in a multiple indicator dilution study. Liver wet and dry ratio and histological findings confirmed reduced edema formation in the tissue of the HMP + starch group livers compared with that of the HMP − starch and SCS group livers. These results suggest that HMP with the UW solution containing starch improve endothelial cell function and induce less hepatocellular damage following 24-hour preservation compared to SCS and HMP with the starch-free UW solution. These results also suggest that oncotic support may be an important component in preserving hepatic microcirculation in HMP.

Determining the tuning and matching requirements of RF coils using electromagnetic simulation and electric circuit analysis

Electromagnetic simulation using the transmission-line modelling method in conjunction with electric circuit analysis is applied to extract the tuning and matching requirements of RF coils for magnetic resonance imaging. Free-ringing microimaging RF coils were modelled in the unloaded and Krebs-Henseleit physiological buffer solution loaded condition. The simulations determined the frequency response and equivalent lumped-element circuit components of resistance, inductance, (fixed) capacitance, and coupling coefficient. Equivalent lumped-element electric circuit representations were derived for RF coils, and circuit analysis was applied to determine the tuning and matching requirements for the desired resonance frequency and characteristic impedance, respectively. Both capacitive and inductive matching schemes were considered. Experimental comparisons were performed with an agreement of less than 3 pF for the (variable) tuning and matching capacitances used in the tuning and matching networks, thus enabling component selection and validation of the methods. © 2005 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 25B: 27–41, 2005

Assessment of optical path length in tissue using neodymium and water absorptions for application to near-infrared spectroscopy

Quantitative analysis of blood oxygen saturation using near-IR spectroscopy is made difficult by uncertainties in both the absolute value and the wavelength dependence of the optical path length. We introduce a novel means of assessing the wavelength dependence of path length, exploiting the relative intensities of several absorptions exhibited by an exogenous contrast agent (neodymium). Combined with a previously described method that exploits endogenous water absorptions, the described technique estimates the absolute path length at several wavelengths throughout the visible/near-IR range of interest. Isolated rat hearts (n = 11) are perfused separately with Krebs-Henseleit buffer (KHB) and a KHB solution to which neodymium had been added, and visible/near-IR spectra are acquired using an optical probe made up of emission and collection fibers in concentric rings of diameters 1 and 3 mm, respectively. Relative optical path lengths at 520, 580, 679, 740, 800, 870, and 975 nm are 0.41+/-0.13, 0.49+/-0.21, 0.90+/-0.09, 0.94+/-0.01, 1.00, 0.84+/-0.01, and 0.78+/-0.08, respectively. The absolute path length at 975 nm is estimated to be 3.8+/-0.6 mm, based on the intensity of the water absorptions and the known tissue water concentration. These results are strictly valid only for the experimental geometry applied here.