In vivo evaluation of the pulsatile ECLS sysem

 Extracorporeal life support (ECLS) systems have been increasingly applied to groups of patients with cardiorespiratory failure, including pediatric and adult patients with respiratory failure. Current pulsatile ECLS systems use a single pulsatile blood pump that generates a high inlet pressure in the membrane oxygenator. To minimize this high inlet pressure, we have developed a new and improved ECLS system, twin pulse life support (T-PLS). To analyze the advantages of T-PLS, we have compared T-PLS with a single pulsatile ECLS system. An acute heart failure model was constructed by using a pulmonary artery banding technique. Fourteen pigs (22–31 kg) were used, with cardiac outputs of 2.0 l/min and a V/Q ratio set at 1. Cannulae of 28 Fr and 18 Fr were used in the right atrium and aorta, respectively. A polypropylene hollow-fiber membrane oxygenator and four polymer valves 30 mm in diameter were used in the T-PLS system. In the single pulsatile ECLS system, Medtronic Hall monostrut valves were used. To evaluate blood cell trauma in both pulsatile ECLS systems, plasma free hemoglobin (fHb) was measured while the systems were in use. The results show that fHb levels in T-PLS are lower than fHb levels in the single pulsatile ECLS system. There is a possibility that T-PLS could be used as an ECLS system for emergency situations. Received: June 7, 2002 / Accepted: December 10, 2002 Present address: Department of Artificial Organs, Research Institute, National Cardiovascular Center, 5-7-1 Fujishiro-dai, Suita 565-8565, Japan Tel. +81-6-6833-5012; Fax +81-6-6835-5406 e-mail: hslee@ri.ncvc.go.jp Correspondence to:H.S. Lee     

In vitro, ex vivo, in vivo veritas

In vitro assessments of inhaler performance are important in product development and quality control, but are not, as such, good predictors of performance in vivo . It is, however, possible to modify in vitro techniques so that they more closely resemble the in vivo situation. Measurements of fine-particle dose (defined as the amount of drug with an aerodynamic diameter less than 5 μm) by cascade impactor have shown that the measured fine-particle dose in vitro is highly dependent on the geometry of the inlet to the impactor, the fine-particle dose being considerably lower when the cast of a human throat (an "anatomical throat") is used than when a standard glass inlet is used. This difference is, however, less with a dry-powder inhaler such as Turbuhaler® than with a pressurized metered-dose inhaler (pMDI). Furthermore, there is a good correlation between fine-particle dose measured in vitro and in vivo lung deposition, provided that an anatomically correct inlet is used for the in vitro determination. Studies in children have shown that the degree of lung deposition of budesonide, delivered via Turbuhaler, is of the same order of size as the in vitro fine-particle dose. No comparable data are available for pMDIs; however, since children are smaller than adults, it is likely that differences in lung deposition between Turbuhaler and pMDIs are probably greater in children than in adults.     

In vivo evaluation of the pulsatile ECLS system.

Extracorporeal life support (ECLS) systems have been increasingly applied to groups of patients with cardiorespiratory failure, including pediatric and adult patients with respiratory failure. Current pulsatile ECLS systems use a single pulsatile blood pump that generates a high inlet pressure in the membrane oxygenator. To minimize this high inlet pressure, we have developed a new and improved ECLS system, twin pulse life support (T-PLS). To analyze the advantages of T-PLS, we have compared T-PLS with a single pulsatile ECLS system. An acute heart failure model was constructed by using a pulmonary artery banding technique. Fourteen pigs (22-31 kg) were used, with cardiac outputs of 2.0 l/min and a V/Q ratio set at 1. Cannulae of 28 Fr and 18 Fr were used in the right atrium and aorta, respectively. A polypropylene hollow-fiber membrane oxygenator and four polymer valves 30 mm in diameter were used in the T-PLS system. In the single pulsatile ECLS system, Medtronic Hall monostrut valves were used. To evaluate blood cell trauma in both pulsatile ECLS systems, plasma free hemoglobin (fHb) was measured while the systems were in use. The results show that fHb levels in T-PLS are lower than fHb levels in the single pulsatile ECLS system. There is a possibility that T-PLS could be used as an ECLS system for emergency situations.     

In vitro performance testing of a pediatric oxygenator with an integrated pulsatile pump

For different lung and heart diseases (e.g., acute respiratory distress syndrome, congenital heart failure, and cardiomyopathy) extracorporeal membrane oxygenation is a well-established therapy, particularly in the field of neonatal and pediatric medicine. To reduce the priming volume of the extracorporeal circuit, different components can be combined. In this study, an oval-shaped oxygenator (called ExMeTrA) with integrated pulsatile pump was tested in vitro using porcine blood. A feasibility study regarding the performance of collapsing and expanding silicone tubes within an oxygenator fiber bundle as a pulsatile pump was previously completed with successful results. The findings of this study improve upon the previous feasibility results, particularly in terms of gas exchange and filling volume. Five modules were manufactured in sizes of 20 ± 2.2 ml (priming volume) with fiber surface areas of 0.24 ± 0.027 m(2) and an analytically calculated volume pumping capacity of 692 ± 75 ml/min. The modules were made of polymethylpentene fibers with dense outer layer to permit long-term applications. The gas exchange rates at a gas/blood flow ratio of 2:1 were between 64 and 72.7 ml(O)(2)/l(blood) and between 62.5 and 81.5 ml/l(blood), depending on the blood flow. The individual module's pumping capacity ranged from 200-500 ml/min thus providing room for further improvements. In order to enhance the pumping capacity while maintaining sufficient gas exchange rates future optimization, adjustments will be made to the inlet and outlet geometries.     

In vitro and in vivo inactivation of reagins with mercaptans

The ability of a series of mercaptans, i.e. 2-mercaptoethanol, 1-cysteine, C-acetyl-cysteine, N-acetyl-cysteine, β-β-dimethyl-cysteine and cysteamine, to inactivate skin sensitizing antibodies in the serum of ragweed allergic individuals was studied. Following in vitro reductions and alkylations, 2-mercaptoethanol was shown to be the only mercaptan capable of destroying completely reaginic activity at 0.08–0.1 M. The other mercaptans, under similar conditions, were able to reduce only partially the skin-sensitizing activity. Some reaginic activity was restored if reoxidation of the reduced allergic serum was not prevented. However, it was shown that mixtures of allergic serum and mercaptan, when injected into monkey skin, did not regain skin sensitizing activity. Moreover, pre-treatment of monkey skin with mercaptan did not detectably affect the ability of the skin to fix human reagins. C-acetyl-cysteine was used for testing its efficacy of inactivating reagins in vivo in monkeys; it was demonstrated that the PCA titres of a human allergic serum were thus decreased by a factor of 8 following administration of the mercaptan to monkeys.     

In vitro and in vivo interactions of cells with biomaterials

The biocompatibility of materials at an implant site involves a complex interaction of cells and tissues with the biomaterial. This cell-cell and cell-polymer interaction evokes the release of mediators such as chemotactic and growth factors that elicit and sustain inflammatory responses at the implant site. In this review, we summarize the interaction of cells with biomaterials in vitro and in vivo.     

In vitro and in vivo methods in immunotoxicology

One approach to assessment of the immunotoxic effects of drugs and chemicals upon the immune system is briefly described. Appropriate in vivo and in vitro methods and techniques are delineated. It is likely that programs implemented at individual institutions will be modified to specific circumstances.     

In vitro and in vivo metal ion release

A series of experiments was conducted to study in vitro and in vivo metal ion release and the urine excretion of metal ions. Metal salts were injected and urine analyzed. Anodic potentials were applied to stainless steel and cobalt-chromium-molybdenum (CCM) specimens to cause an acceleration of corrosion rates. Corrosion experiments were done in saline, 10% serum and in a subcutaneous space in hamsters. Corrosion rates were determined by measurements of weight loss and calculations of net charge transfer. Metal ion concentrations were determined with graphite furnace atomic absorption spectroscopy, and were calculated from total charge using Faraday's law. The results with stainless steel showed that the weight loss and metal ion release from stainless steel in vitro and in vivo can be calculated using Faraday's Law, assuming release in proportion to alloy composition. The results with CCM indicated that release rates in vitro can be used to determine the proportionality of release in vivo. All the nickel and most of the cobalt was rapidly excreted, while less than 50% of the chromium was excreted. The excretion of metals following salt injection or in vivo corrosion were very similar.     

In vitro and in vivo susceptibility ofBorrelia burgdorferi

The antispirochetal activity in vitro and in vivo of several antibiotics against ten isolates ofBorrelia burgdorferi from human spinal fluids and skin biopsies was determined.Borrelia burgdorferi was most susceptible in vitro to erythromycin, ceftriaxone and cefotaxime (MIC90: 0.06, 0.06, 0.12 meg/ml respectively). Less activity was observed with tetracycline, amoxycillin and lincomycin (MIC90: 0.50 mcg/ml), imipenem and augmentin (MIC90. 0.25 mcg/ml), oxacillin (MIC90: 1 mcg/ml), ciprofloxacin (MIC90: 2 mcg/ml) and ofloxacin (MIC 90: 4 mcg/ml). Penicillin G, normally regarded as appropriate treatment for Lyme disease, had an MIC90 of only 4 mcg/ml. With the exception of erythromycin, activity in vitro corresponded to the activity in vivo. Erythromycin, however, was less active in vivo, and penicillin G showed poor activity both in vitro and in vivo.     

In vitro velocity measurements down strem from the lonescu-Shiley aortic bioprosthesis in steady and pulsatile flow

Velocity measurements were made in vitro using laser Doppler anemometry (LDA) downstream from an lonescu-Shiley (IS) bioprosthetic aortic heart valve. Velocity measurements were made in both steady and pulsatile flow. A systematic, flow mapping approach to the measurement methodology showed that the IS valve generated a large jetlike flow constriction. The acceleration ratio, defined as the maximum mean velocity for the IS valve divided by that for no valve obstructing the flow, was as high as 2·4 for steady flow and 2·6 for pulsatile flow. It was concluded that the IS valve generated a flow quite unlike that observed by other in vestigators for the natural human aortic valve, after which the leaflet design of the IS valve was modelled. In addition, a comparative analysis of steady and pulsatile results was undertaken. It was found that the pulsatile flow results for the systolic ejection interval could be divided into three phases, denoted early, mid, and late systole, as defined by the flow structure at the data plane location. Only during midsystole were the pulsatile flow results approximated by the steady flow results. Also, it was found that the magnitude of the flow disturbance measured in steady flow tended to be an upper bound on that measured for pulsatile flow.     

In vitro and in vivo studies of heparinized-collageno-elastic tubes

Heparin was covalently coupled to collageno-elastic grafts (CET) derived from lamb carotid arteries, by using the crosslinking agent 1-ethyl-3 (3-dimethyl-aminopropyl) carbodiimide (EDC). The collagenous grafts were pretreated with various aminating agents in order to enhance the number of available binding sites on the collagen surface. By varying the EDC/heparin weight ratio, the pH of the immobilization media, and the pretreatment agent, a global search pattern maximized heparin loading at 3.90 +/- 0.36 USP heparin/cm2 collagenous graft surface when the EDC/heparin ratio was 2:1 at a pH of 1.5 with 1 M hydroxylamine sulfate as the pretreatment agent. Heparinized CETs were superior to nonheparinized CETs by exhibiting both enhanced antiplatelet activity in using an in vitro differential recirculation reactor with chromium-51 tagged platelets and enhanced patency when interposed in canine carotid arteries. Both antiplatelet activity and patency duration for heparinized CETs were independent of heparin loading.     

可降解金属Mg-Nd-Zn-Zr镁合金的降解行为

背景：添加合金元素是改变镁合金微观结构和控制镁合金降解行为的有效方法。 目的：探讨Mg-Nd-Zn-Zr镁合金体内外的降解行为。 方法：①体外静态浸泡实验：在(37.0±0.5) ℃条件下,将Mg-Nd-Zn-Zr镁合金和纯镁各6个样品分别浸入 250 mL模拟体液中,浸泡过程中不搅拌振荡。静态浸泡第3,7,30天后从模拟体液中取出试样,扫描电镜及能谱分析分析Mg-Nd-Zn-Zr镁合金在模拟体液中的降解行为。②体内植入实验：在成年新西兰兔左侧股骨钻孔,实验组植入Mg-Nd-Zn-Zr镁合金,对照组植入钛合金,空白对照组不植入任何内植物。植入后1,2,4,8周,通过X射线观察内植物的位置及降解行为;植入后4,8周,通过扫描电镜观察Mg-Nd-Zn-Zr镁合金表面腐蚀产物,通过元素能谱分析腐蚀产物的成分,并计算材料降解速率。 结果与结论：①Mg-Nd-Zn-Zr镁合金浸泡于模拟体液中不同时间点的降解速率均低于纯镁组;浸泡30 d后,沉积于Mg-Nd-Zn-Zr镁合金表面的腐蚀产物主要是氧、碳、钠、镁、钙、磷和氯,去除腐蚀产物后Mg-Nd-Zn-Zr镁合金和纯镁表面均有腐蚀坑,但Mg-Nd-Zn-Zr镁合金表面腐蚀坑体积更小,分布更均匀,表明Mg-Nd-Zn-Zr镁合金和纯镁存在不同的腐蚀形式。②Mg-Nd-Zn-Zr镁合金植入动物体内后随时间延长逐渐降解,材料表面腐蚀产物及成分类似于体外浸泡实验。     

In vitro and in vivo antioxidant activity of ambroxol

In addition to a mucolytic action, ambroxol has antioxidant and anti-inflammatory properties. The antioxidant effects of ambroxol were studied both in vitro and in vivo. In vitro methods, such as (1) inhibition of hyaluronic acid degradation induced by hydroxy radicals and (2) standard lipid peroxidation assay in rat liver mitochondria and gastric mucosa, induced by tert-butyl hydroperoxide, were used. The in vivo approach was based on the study of the protective effect of pretreatment with ambroxol in a rat model of gastric corpus and antral lesions, induced by indomethacin. The inhibition of the degradation of hyaluronic acid was measured as a change of its viscosity; ambroxol (1,000 microl/l) reduced the degradation by 93%. Lipid peroxidation with tert-butyl hydroperoxide as a source of radicals was followed by the formation of thiobarbituric acid reactive substances. Ambroxol (10 mmol/l) inhibited lipid peroxidation by 96% in the rat liver mitochondria, and by 74% in the gastric mucosa. In vivo, ambroxol was administered p.o. at a dose of 10, 30, and 50 mg/kg, at 5, 30, and 60 min prior to indomethacin administration. The highest inhibition of the number of corpus gastric lesions and lowering of the lesion index (38% and 62%, respectively) was shown after the administration of 50 mg/kg, 30 min before indomethacin administration. Antral lesions were inhibited to a lesser extent by the same dose of ambroxol, administered 30 min before indomethacin treatment. Inhibition of the number of antral lesions reached 27% and the total area of the gastric damage was even larger (the ulcer index reached -5%).     

In vitro and in vivo evaluation of antifungal agents

The evaluation of any antifungal agent involves the determination of its in vitro and in vivo activity against pathogenic and/or opportunistic fungi. The in vitro evaluation is followed by an in vivo evaluation in animal models, and clinical trials in humans. From the first report of the efficacy of the iodides for the treatment of sporotrichosis (1903) until the introduction of the imidazoles (azoles, 1960s), the number of antifungal agents available was very limited, including griseofulvin (1939), nystatin (1950), amphotericin B (1956), and flucytosine (1964). This paper briefly reviews the status of the antifungal agents currently used, and gives a more in depth evaluation of progress during recent years in the search for new antifungal drugs. Efforts to improve the efficacy of the current antifungal agents are also reviewed.     

In vitro and in vivo antioxidant activity of ambroxol

Abstract In addition to a mucolytic action, ambroxol has antioxidant and anti-inflammatory properties. The antioxidant effects of ambroxol were studied both in vitro and in vivo. In vitro methods, such as (1) inhibition of hyaluronic acid degradation induced by hydroxy radicals and (2) standard lipid peroxidation assay in rat liver mitochondria and gastric mucosa, induced by tert-butyl hydroperoxide, were used. The in vivo approach was based on the study of the protective effect of pretreatment with ambroxol in a rat model of gastric corpus and antral lesions, induced by indomethacin. The inhibition of the degradation of hyaluronic acid was measured as a change of its viscosity; ambroxol (1,000 µl/l) reduced the degradation by 93%. Lipid peroxidation with tert-butyl hydroperoxide as a source of radicals was followed by the formation of thiobarbituric acid reactive substances. Ambroxol (10 mmol/l) inhibited lipid peroxidation by 96% in the rat liver mitochondria, and by 74% in the gastric mucosa. In vivo, ambroxol was administered p.o. at a dose of 10, 30, and 50 mg/kg, at 5, 30, and 60 min prior to indomethacin administration. The highest inhibition of the number of corpus gastric lesions and lowering of the lesion index (38% and 62%, respectively) was shown after the administration of 50 mg/kg, 30 min before indomethacin administration. Antral lesions were inhibited to a lesser extent by the same dose of ambroxol, administered 30 min before indomethacin treatment. Inhibition of the number of antral lesions reached 27% and the total area of the gastric damage was even larger (the ulcer index reached -5%).     

In vitro and in vivo Evaluation of TONGXIN LVAD

Background: Tongxin left ventricular assist device(LVAD), an implantable magnetic suspending VAD developed in China Heart Biomedical Incorporation aiming for clinical use, weighs about 350 g and can deliver 6 L/min for pressures of 145 mmHg at 2500 rpm. Objective: This study aims to investigate the implantation possibility, hemolysis and hemocompatibility of the LVAD before clinic use. Methods: The tests of implantation possibility, hemolysis and hemocompatibility to the LVAD were completed by fitting study, hemolysis test and in vivo experiments respectively. Meanwhile the hemolysis was evaluated by the amount of free hemoglobin in plasma and studied using the normalized index of hemolysis(NIH). Results: The fitting study showed that the blood pump could be implanted in the sheep heart chambers without squeezing the surrounding organs by comparing the preoperative and the postoperative chest X-ray. The NIH value of Tongxin LVAD was(0.00750±0017) g/100 L in vitro hemolysis test. Two sheep in vivo experiments showed the hemolysis in vivo was below 7.5 mg/dL. Hematologic and biochemical test results were within normal limits during the study period. There were no significant complications. Postmortem examination of the explanted organs revealed no evidence of microemboli, ischemia or infarction. The pump's inflow and outflow conduits were free of thrombus. Conclusion:These results indicated that the implantable magnetic suspending LVAD showed exceptional implantation possibility, hemolysis and hemocompatibility, which are crucial to the clinical success of this implantable LVAD.