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At least 1,045 records · Page 58Linked to original sources
PubMed1997

Use of motor current in flow rate measurement for the magnetically suspended centrifugal blood pump.

Indirect measurement of the flow rate of a centrifugal blood pump using the driving motor current was studied. The pump flow rate can be expressed as a function of the motor current under a given motor speed in the absence of energy loss resulting from uncertain mechanical contact friction. The magnetically suspended centrifugal blood pump (MSCP), developed by the collaboration of Kyoto University and NTN Inc., was suitable for the application of this measuring method because the impeller is suspended magnetically inside the pump housing without any mechanical contact. The effect of fluid viscosity on the pump performance was investigated in detail, and it was possible to estimate the pump flow rate and the pressure difference through the pump (from inlet port to outlet port) accurately by monitoring the motor current and speed when the kinematic viscosity of working fluids was known. The kinematic viscosity of working fluids can also be measured with the MSCP. The motor current and motor speed were monitored in a chronic animal experiment, and the estimated flow rate and pressure difference showed good correlation with directly measured data.

Animals↗
PubMed1997

Chronic animal experiment with magnetically suspended centrifugal pump.

We have been developing a new type of centrifugal pump for long-term use. The magnetically suspended centrifugal pump (MSCP) contains no shaft and seal so that long life expectancy is predicted. Paracorporeal left ventricular (LV) assist circulation between the left atrium and the descending aorta was instituted using sheep. The flow rates ranged from 2.5-5.5 L/min. The sheep that lived the longest (46 days) died of an embolism as a result of the thrombus in the pump. No thrombus formation was observed in other pumps. Plasma free hemoglobin levels ranged from 9 to 18 mg/dl, which led to the conclusion that the hemolysis level remained within an acceptable range. Two driving modes were compared. The slope of the pressure-flow relationship plot under a constant motor current mode was steeper than that under a constant rotational speed mode, and thus, the flow fluctuation decreased. In conclusion, the MSCP is durable for more than a month at the current stage of development and is a promising device for long-term ventricular assist.

Animals↗
PubMed1997

Evaluation of hemolysis in a pulsatile assist device for centrifugal pump.

To evaluate the blood trauma caused by a new device for producing a pulsatile flow of the centrifugal pump, the pulsatile assist device for the centrifugal pump (PAD-CP) that we have developed, a hemolysis study was performed in vitro and in animal experimentation. For the in vitro testing, 2 identical sets of hemolysis test circuits were prepared with 2,400 ml of bovine blood. The 2 circuits were pumped simultaneously. Plasma total hemoglobin levels were less than 40 mg/dl after 3 h, under a pump flow of 2 L/min. Hemolysis increased to a severe level after 4 h of 4 L/min pump flow. The cause of this hemolysis was thought to be a vibration of the circuit because of incomplete compression of the polyurethane tube in the PAD-CP. Five adult sheep (average body weight, 47 kg) were used for in vivo evaluation of hemolysis. Hemolysis was less than 30 mg/dl of plasma hemoglobin after 4 h of open chest extracorporeal circulation with 3.0-3.6 L/min of flow rate using the PAD-CP. Other hematologic changes after PAD-CP driving were within normal limits. We conclude that the PAD-CP has proven to have possible clinical applications.

Animals↗
PubMed1997

Clinical evaluation of pulsatile flow mode of Terumo Capiox centrifugal pump.

The Terumo Capiox centrifugal pump system possesses an automatic priming function in which the motor repeatedly stops and runs intermittently to eliminate air bubbles in the circuit through the micropores of the hollow-fiber membrane oxygenator. By modifying this mechanism, we have developed a pulsatile flow mode. In this mode, maximum and minimum pump rotational speeds can be independently set every 20 rpm in the range of 0 to 3,000 rpm. The duration of the pump run at maximum and minimum speeds can also be independently set every 0.1 s in the range of 0.2 to 15 s. In a clinical trial, after obtaining the desired flow rate, 2.4 L/min/m2 in nonpulsatile flow mode, a pulsatile flow mode of 60 cycles/min (with 1 cycle being maximum speed for 0.4 s and minimum speed for 0.6 s) was obtained by adding and subtracting 500 rpm to and from the rotational speed in nonpulsatile flow mode. Pulse pressures in the femoral artery and in the circuit just proximal to the perfusion cannula (6.5 mm Sarns high flow cannula with metal tip) were measured in 5 patients who underwent pulsatile cardiopulmonary bypass (CPB) for a coronary artery bypass graft (CABG), and compared to pulse pressures obtained by intraaortic balloon pumping (IABP) in 3 patients and by the pulsatile mode of the 3M Delphin pump in 3 patients. The platelet count, free hemoglobin, and beta-thromboglobulin (beta-TG) were measured and compared with measurements from another 5 patients who underwent nonpulsatile CPB. Although the pulse pressure measured in the circuit was 180 mm Hg on average, the pressure in the femoral artery was only 15 to 40 mm Hg with a mean of 20 mm Hg. In the same patients, 60 to 80 mm Hg pulse pressure was obtained with IABP. The pulse pressure obtained with the Delphin pump was not more than that obtained with the Terumo pump. There were no significant differences in percents of preoperative levels of platelet counts (pulsatile, 87.6 +/- 15.8% and nonpulsatile, 72.4 +/- 40.6%), free hemoglobin (pulsatile, 18 +/- 8 mg/dl and nonpulsatile, 25 = 7 mg/dl), and beta-TG (pulsatile 298 +/- 28 ng/ml and nonpulsatile, 312 +/- 143 ng/ml). In conclusion, although the pulsatile mode of the Terumo centrifugal pump did not exhibit any adverse effects hematologically, the pulse pressure obtained was unsatisfactorily small, mainly because of dumping caused by the perfusion cannula.

Angina Pectoris↗
PubMed2004

Injury in organs after cardiopulmonary bypass: a comparative experimental morphological study between a centrifugal and a new pulsatile pump.

The aim of this investigation was to assess organ injury provoked by a new pulsatile pump for cardiopulmonary bypass (CPB) with respect to a conventional centrifugal pump. Eight pigs in the pulsatile group (PG) and five in the centrifugal group (CG) underwent a partial CPB lasting 180 min. The animals were sacrificed 180 min after CPB was suspended, and a morphological study of fragments of ventricular wall, liver, lung, and kidney was performed. In CG, centrilobular hepatic necrosis was observed accompanied by sinusoidal dilatation and congestion, multiple focuses of myocardial ischemia, and minor to moderate pulmonary interstitial edema. In PG, diffuse centrilobular sinusoidal congestion in the liver, congestion and capillary dilatation of low intensity in the ventricular wall, and nonsignificant pulmonary interstitial septal edema was observed. In the kidney, both groups showed degenerative changes of the tubular cells and nonsignificant tubular dilatation. These results suggest a better peripheral circulation in the pulsatile group.

Animals↗
PubMed2006

A review of leakage flow in centrifugal blood pumps.

This article presents a new approach in determining the functional relationship between the leakage flow in a centrifugal blood pump and various parameters that affect it. While high leakage flow in a blood pump is essential for good washout and can help prevent thrombus formation, excessive leakage flow will result in higher fluid shear stress that may lead to hemolysis. Dimensional analysis is employed to provide a functional relationship between leakage flow rate and other important parameters governing the operation of a centrifugal blood pump. Results showed that pump performance with a smaller gap clearance is clearly superior compared to those of two other similar pumps with larger gap clearances. It was also observed that the nondimensional leakage flow rate varies almost linearly with dimensionless pump head. It also decreases with increasing volume flow rate. A smaller gap clearance will also increase the flow resistance and hence, decrease the nondimensional leakage flow rate. Increasing surface roughness, length of the gap clearance passage, or loss coefficient of the gap geometry will increase losses and hence, decrease the leakage flow rate. It is also interesting to note that for a given pump and gap clearance geometry, the nondimensional leakage flow rate is almost independent of the Reynolds number when specific speed is constant.

Centrifugation↗
PubMedDate not supplied

A new centrifugal filtration device for free drug separation.

A new centrifugal membrane filtration device (Syva Corporation) has been evaluated to determine its capabilities for separation of free phenytoin for analysis. The device is a test tube-size cylinder with two compartments separated by the membrane. In serum samples from 70 patients at the Hospital of the University of Pennsylvania, free phenytoin was prepared by the new device and by equilibrium dialysis. Levels were assayed by gas chromatography and enzyme immunoassay with good agreement at all phenytoin levels. Although pH has a significant effect on the binding of some drugs to serum proteins, phenytoin binding increased to only a small extent as pH was increased from 7.0 to 7.8 (85-88.5% bound). Centrifugal filtration with this device is a reliable, fast, and easy way to prepare free drug from serum and does not include the dilution artifact inherent in equilibrium dialysis.

Centrifugation↗
PubMed2005

Effective storage of granulocytes collected by centrifugation leukapheresis from donors stimulated with granulocyte-colony-stimulating factor.

BACKGROUND: Donor stimulation with granulocyte-colony-stimulating factor (G-CSF) has increased the number of neutrophils (PMNs) that can be collected for granulocyte transfusion therapy. Clinical utility, however, has been limited by the inability to store functional PMNs ex vivo. This study was conducted to determine whether granulocyte products from G-CSF-stimulated donors could be effectively stored at reduced temperature (22 degrees C vs. 10 degrees C) with maintenance of functional properties in vitro and in vivo. STUDY DESIGN AND METHODS: Nine normal subjects received G-CSF (600 microg subcutaneously) 12 hours before centrifugation leukapheresis. Granulocyte products were divided and stored for 24 and 48 hours under four conditions: 1) 22 degrees C; 2) 22 degrees C, with supplemental G-CSF (100 ng/mL); 3) 10 degrees C; and 4) 10 degrees C, with supplemental G-CSF. Functional PMN activity during ex vivo storage was assessed in vitro and in vivo by the skin-window technique for granulocytes stored at 10 degrees C for 24 hours. RESULTS: Surface expression of CD11b/CD18, CD14, CD16, CD32, and CD64 was maintained during 48-hour storage at reduced temperature. Inducible respiratory burst activity, bactericidal activity, and fungicidal activity were preserved during storage for 48-hour storage at 10 degrees C. Proinflammatory cytokine production was decreased in product stored at 10 degrees C. Supplemental G-CSF ex vivo did not substantially improve functional activity during storage. After storage at 10 degrees C for 24 hours, in vitro chemotactic potential was maintained, and transfused granulocytes retained capacity to circulate and migrate appropriately in vivo. CONCLUSIONS: Granulocyte product collected by centrifugation leukapheresis from G-CSF-stimulated donors can be effectively stored at subphysiologic temperature for 24 hours with preservation of functional activity. Storage at 10 degrees C appears to be slightly superior to storage at 22 degrees C.

Adult↗
PubMed1999

Density gradient centrifugation of colonic fluid after segmental lavage: a method of purification of exfoliative epithelial colonic cells for cytological interpretation and image cytometry in patients with long-standing ulcerative colitis.

OBJECTIVES: Patients with extensive, long-standing ulcerative colitis (UC) have an increased risk for developing colorectal cancer. In this study, we wanted to establish a method for retrieving cytological material after segmental colonic lavage for further cytopathological investigations and for performing DNA image cytometry. METHODS: Ten patients with long-standing and extensive ulcerative colitis and 10 patients without macroscopic abnormalities were investigated. After segmental colonic lavage during routine colonoscopy a three-layer (1.146, 1.075, and 1.046 g/ml, respectively) density gradient centrifugation of the retrieved colonic fluid was performed for isolation and purification of the epithelial cells. For identification of the epithelial cells flow cytometry with monoclonal antibody against cytokeratin and counterstaining with propidium iodine was performed. The smears obtained were stained for routine cytopathological interpretation and for DNA image cytometry. RESULTS: In eight of 10 UC patients and in nine of 10 control group patients adequate cytological material could be obtained. The band on top of the density gradient at 1.046 g/ml could be identified as the epithelial cells. Atypical cells were found in smears of three UC patients. In these patients and in one additional patient aneuploid stemlines could be detected. In smears of control group patients neither atypical cells nor aneuploidy were present. CONCLUSIONS: Isolation and purification of epithelial cells after segmental colonic lavage by using density gradient centrifugation was performed. This cytological material is adequate for cytopathological interpretation and for DNA image cytometry. Information about atypical cells and DNA aneuploidy as an additional marker of malignant transformation in UC patients was obtained. The combination of cytological examination and DNA image cytometry might improve the detection of UC patients with high risk for colorectal cancer.

Aneuploidy↗
PubMed1978

Density gradient centrifugation in urografin of Moraxella and Kingella cells and appendages.

Purification of fimbriae (pili) by density gradient banding in Urografin medium was attempted. Moraxella nonliquefaciens and Kingella kingae fimbriae were of higher density than their cells of origin, but fimbrial fractions obtained by homogenization and differential centrifugation still banded together with presumed outer membrane fragments and some whole cells in Urografin gradients. The cellular density of genetic variants with different fimbriation/competence levels was also studied. For one strain of M. nonliquefaciens and two strains of K. kingae, cells harvested from agar plates tended to show several bands on isopycnic density gradient centrifugation, with slightly higher general density of fimbriated variants than non-fimbriated. A single density band could be observed with cells from log phase broth cultures of selected strains which showed no distinct difference between fimbriation or competence variants of each strain. Cells of M. nonliquefaciens and M. bovis showed comparable buoyant densities, whereas those of K. kingae had a higher density.

Bacteriological Techniques↗
PubMed1997

Purification of herpes simplex virus type 1 by density gradient centrifugation and estimation of the sedimentation coefficient of the virion.

Purification of herpes simplex virus type 1 (HSV-1) is often performed by centrifugation in gradients of various materials. A major problem with such procedures is a gradual decrease in the infectivity of the virus, probably due to the influence of the gradient material. In the present work we have compared Nycodenz gradients with Ficoll gradients for HSV-1 purification. Both gradient materials have low osmolarities. The purity of the preparations recovered from the two gradients was similar, as measured by electron microscopy and two-dimensional gel electrophoresis, and the yield of infectious virus was approximately the same. Szilágyi & Cunningham (22) reported previously that Ficoll gradients separate one band of complete virions and another band containing light particles devoid of nucleocapsids. In Nycodenz gradients we observed the same bands, and an additional third band which contained aggregates and disrupted particles. In this respect, the separation in Nycodenz is slightly superior to that in Ficoll. The purified HSV-1 virions were subjected to analytical differential centrifugation and an S-value of 670S was calculated for the virus.

Animals↗
PubMed1987

The effects of RPM and recycle on separation efficiency in a clinical blood cell centrifuge.

A COBE blood cell centrifuge, model 2997 with a single stage channel, was modified to allow computer controlled sampling, and to allow recycle of red blood cells (RBCs) and plasma streams using bovine whole blood. The effects of recycle of the packed RBC and plasma product streams, and of the centrifuge RPM on platelet and white blood cell (WBC) separation efficiencies were quantified using a central composite factorial experimental design. These data were then fit using second order models. Both the model for the WBC separation efficiency and the model for the platelet separation efficiency predict that RPM has the greatest effect on separation efficiency and that RBC and plasma recycle have detrimental effects at moderate to low RPM, but have negligible impact on separation efficiency at high RPM.

Animals↗
PubMed1975

New flow-through centrifuge without rotating seals applied to plasmapheresis.

The flow-through centrifuge eliminates complications arising from rotating seals. Preliminary studies on plasmapheresis demonstrated negligible platelet injury and no evidence of hemolysis during 12 hours of operation. Thus the system may provide a broad application to cell washing and elutriation, zonal centrifugation, and countercurrent chromatography.

Centrifugation↗
PubMed1968

Neuronal perikarya of rat brain isolated by zonal centrifugation.

Cerebral cortex and hippocampus of rat were disrupted in a specially designed tissue-press and prepared as a 2 percent suspension in 10 percent buffered Ficoll medium and fractionated by density-gradient centrifugation in the B XIV zonal rotor. The suspension was injected into a buffered 30 percent Ficoll, 58 percent sucrose discontinuous gradient previously loaded in the B XlV zonal rotor spinning at 3500 revolutions per minute. Intact neuronal perikarya were recovered as a discrete band in the dense sucrose zone of the gradient after centrifugation at 35,000 revolutions per minute for 45 minutes.

Animals↗
PubMed1971

Zonal-centrifuged purified duck embryo cell culture rabies vaccine for human vaccination.

Rabies virus produced in duck embryo cell culture was concentrated from volumes of 14 to 30 liters to 400 to 800 ml by zonal centrifugation. Virus titers of peak fractions were from 100- to 1,000-fold greater than those of the starting material. Vaccines were prepared by combining fractions with peak virus titers and diluting back to 10 times concentration. The resulting beta-propiolactone-inactivated vaccines, when prepared as lyophilized vaccines with AlPO(4) adjuvant diluents, were low in protein nitrogen (0.01 mg/ml), and three of four lots passed the National Institutes of Health potency test when tested as equivalent to a standard 10% suspension of duck embryo or mouse brain tissue vaccine. These vaccines also induced good sero-conversion in adult rabbits after a single 1-ml dose of vaccine. Guinea pigs sensitized with zonal-centrifuged purified duck embryo vaccine (with AlPO(4) adjuvant) did not exhibit anaphylactic shock reactions when challenged with homologous vaccine. Also, no anaphylactic shock reactions were observed when guinea pigs were sensitized with either a 10% experimental duck embryo vaccine or cell culture vaccine and then challenged with the zonal-purified vaccine. However, guinea pigs sensitized with cell culture or zonal-purified vaccine and then challenged with the 10% experimental vaccine did show slight transitory congestion. The 10% experimental whole duck embryo vaccine was responsible for all observed anaphylactic shock reactions whether homologous or heterologous.

Adjuvants, Immunologic↗
PubMed1972

Large-volume purification of tumor viruses by use of zonal centrifuges.

Large volumes of fluids from selected cell cultures producing ribonucleic acid tumor viruses were processed by a double sucrose density gradient procedure using zonal centrifuges. The primary recovery utilized a Model K continuous-flow zonal centrifuge at 9 to 11 liters/hr. The virus zone from the Model K gradient was further purified on a second gradient in a B-29 rotor. The resulting viral concentrates at 2 x 10(11) particles per ml showed high purity by electron microscopy and gel analysis and were useful reagents in biochemical and immunological studies of the reverse transcriptase enzyme, virus structure, complement fixation, and other virus properties. Similar recovery methods were applied to other tumor virus systems.

Animals↗