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PubMedDate not supplied

Testing of a centrifugal blood pump with a high efficiency hybrid magnetic bearing.

The purpose of this article is to present test results for a second generation, high efficiency, nonpulsatile centrifugal blood pump that is being developed for use as a left ventricular assist device (LVAD). The LVAD pump uses a hybrid passive-active magnetic bearing support system that exhibits extremely low power loss, low vibration, and high reliability under transient conditions and varying pump orientations. A unique feature of the second generation design configuration is the very simple and direct flow path for both main and washing blood flows. The pump was tested in both vertical and horizontal orientations using a standard flow loop to demonstrate the performance and durability of the second generation LVAD. Steady state and transient orientation pump operating characteristics including pressure, flow, speed, temperatures, vibration, and rotor orientation were measured. During the tests, pump performance was mapped at several operating conditions including points above and below the nominal design of 5 L/min at 100 mm Hg pressure rise. Flow rates from 2 to 7 L/min and pressure rises from 50 to 150 mm Hg were measured. Pump speeds were varied during these tests from 2,500 to 3,500 rpm. The nominal design flow of 5 L/min at 100 mm Hg pressure rise was successfully achieved at the design speed of 3,000 rpm. After LVAD performance testing, both 28 day continuous duty and 5 day transient orientation durability tests were completed without incident. A hydrodynamic backup bearing design feasibility study was also conducted. Results from this design study indicate that an integral hydrodynamic backup bearing may be readily incorporated into the second generation LVAD and other magnetically levitated pump rotors.

Centrifugation↗
PubMedDate not supplied

Total heart replacement with dual centrifugal ventricular assist devices.

In an ovine feasibility study, we implanted two HeartMate-III centrifugal ventricular assist devices (VADs) for total heart replacement. With cardiopulmonary bypass support, both ventricles were transected at the atrioventricular groove, preserving a rim of ventricular tissue. The atrioventricular valves were excised, and the aorta and pulmonary artery were transected above the ventriculoarterial valves. An interatrial septal window was created by excising the foramen ovale. The VADs' sewing rings were attached to the left and right ventricular remnants, respectively. Outflow grafts were anastomosed to the aorta and pulmonary artery. The left VAD operated continuously at 4,500 rpm. Right VAD speed increased from 2,000 to 4,500 rpm in 500 rpm increments. Outflow graft flow, pressure, oxygen saturation, and shunt direction were recorded. The pulmonary artery to aortic ratio of flow and pressure increased from 0.26 and 0.15 (at 2,000 rpm) to 1.21 and 0.53, respectively (at 4,500 rpm). The interatrial shunt, which was right to left at lower right VAD speeds, progressed to bidirectional, then to left dominant as right VAD speed increased. Outflow-graft oxygen saturation was reflective of the shunt direction. In this acute experiment, total heart replacement with continuous flow VADs satisfactorily balanced left and right ventricular flows and preserved the physiologic circulatory response.

Animals↗
PubMed1984

Purification of the scrapie agent by density gradient centrifugation.

Plasma membrane-enriched preparations from scrapie-infected and healthy hamster brains, as well as preparations of neural retina, were sonicated, then separated by rate-zonal sedimentation in 10 to 25% Nycodenz gradients. Gradient fractions were extracted with 0.5% Triton X-100 and re-fractionated by equilibrium density centrifugation in linear 25 to 40% CsCl gradients. Infectivity was highest in a fraction having a density of 1.280 g/ml and which contained a visible band of material. Digestion of the Nycodenz fractions with proteinase K before detergent extraction and CsCl fractionation resulted in a shift in the visible band to a density of 1.235 g/ml with most of the scrapie infectivity remaining at 1.280 g/ml. When labelled with 125I after 40-fold concentration, this 1.280 g/ml CsCl fraction from the proteinase K-treated gradients contained only a single band of protein(s) having a mol. wt. near 30 000. No differences were seen between proteins in healthy or scrapie-infected preparations.

Animals↗
PubMed1992

Extraordinarily low density of hepatitis C virus estimated by sucrose density gradient centrifugation and the polymerase chain reaction.

The genomic RNA of hepatitis C virus (HCV) in the plasma of volunteer blood donors was detected by using the polymerase chain reaction in a fraction of density 1.08 g/ml from sucrose density gradient equilibrium centrifugation. When the fraction was treated with the detergent NP40 and recentrifuged in sucrose, the HCV RNA banded at 1.25 g/ml. Assuming that NP40 removed a lipid-rich surface coat from HCV, the 1.08 g/ml and 1.25 g/ml HCV RNA may correspond to intact HCV virions and nucleocapsids, respectively. The extraordinarily low density of the virion is unusual in comparison to the density of classified viruses.

Base Sequence↗
PubMed1979

Differential neutralization of spontaneous and centrifuge-assisted chlamydial infectivity.

Neutralization by specific antibody of a fast-killing variant strain of Chlamydia trachomatis, which showed high spontaneous infectivity for cell monolayers, was examined. It appeared that in spontaneous infection antibody-treated chlamydiae were neutralized by inhibition of attachment to cells. Centrifugation imposed a different effect: infection was inhibited at some step at or subsequent to attachment.

Antibodies, Bacterial↗
PubMed1979

Germination and outgrowth of Schizosaccharomyces pombe spores isolated by a simple batch centrifugation technique.

Spores of the fission yeast Schizosaccharomyces pombe have been separated from vegetative cells by a simple and rapid centrifugation (800 g for 20 min) through a 35% Hypaque solution to a purity greater than 95%. Approximately 35% of the spores were recovered. Regrowth in EMM2 plus glucose showed that over 97% of the spores germinated within the first 2 h and outgrowth continued between 5 and 10 h. Sucrose induced germination in greater than 95% of the spores with a 1 h delay and outgrowth in 50% of the spores with a 3 h delay. There was little protein synthesis during germination but the protein content increased linearly coincident with outgrowth. The RNA content increased slightly during germination, but increased linearly 1 h before the onset of outgrowth and protein synthesis. After 8 h of regrowth, coincident with the onset of DNA synthesis, the rate of RNA synthesis was accelerated. The DNA content had increased 1.7-fold after 10 h of regrowth from a haploid level of 1.36 x 10(-8) microgram spore-1.

Ascomycota↗
PubMed2002

Preparation of crude subcellular fractions by differential centrifugation.

The employment of differential centrifugation to prepare crude fractions of subcellular particles from homogenates is often a necessary first step to a subsequent purification of one or more particles on a density gradient. Buoyant density gradient purification of peroxisomes or lysosomes for example is almost invariably carried out on a light mitochondrial fraction so as to eliminate smaller particles that may have similar densities. Unless they are first removed, large rapidly sedimenting particles in homogenates may also disturb shallow gradients designed to fractionate small low-density microsomes.

Animals↗
PubMed1990

A multiple disk centrifugal pump as a blood flow device.

A multiple disk, shear force, valveless centrifugal pump was studied to determine its suitability as a blood flow device. A pulsatile version of the Tesla viscous flow turbine was designed by modifying the original steady flow pump concept to produce physiological pressures and flows with the aid of controlling circuitry. Pressures and flows from this pump were compared to a Harvard Apparatus pulsatile piston pump. Both pumps were connected to an artificial circulatory system. Frequency and systolic duration were varied over a range of physiological conditions for both pumps. The results indicated that the Tesla pump, operating in a pulsatile mode, is capable of producing physiologic pressures and flows similar to the Harvard pump and other pulsatile blood pumps.

Assisted Circulation↗
PubMed1988

Enrichment of unlabeled human Langerhans cells from epidermal cell suspensions by discontinuous density gradient centrifugation.

In this report we introduce an alternative procedure for enrichment of human epidermal Langerhans cells (LC) from epidermal cell suspensions of normal skin. By means of discontinuous Ficoll-Metrizoate density gradient centrifugation, a fraction containing high numbers of viable, more than 80% pure LC was recovered, as judged by CD1a expression. The purity of the LC-enriched fraction appeared to be dependent on the percentage LC in the crude epidermal cell suspension. LC enriched by this method retained their accessory and antigen-presenting capacities, as determined in the Concanavalin-A induced T-cell response, in the allogeneic mixed leukocyte reaction and in the antigen-specific T-cell proliferation assay in vitro. The great advantage of this method is that it is simple and rapid and that the isolated LC are unlabeled.

Antigen-Presenting Cells↗
PubMed1982

Purification of Rickettsia tsutsugamushi by Percoll density gradient centrifugation.

Purification of Rickettsia tsutsugamushi has been achieved by Percoll density gradient centrifugation. The microorganisms purified showed good retention of infectivity and intracellular morphology. Budding rickettsiae in the egressing stage and intracellular rickettsiae in the multiplying process were harvested separately and purified by this technique. In electron microscopic observations, the intracellular rickettsiae obtained were surrounded with double membrane-layers of cell wall and cell membrane, and the budding rickettsiae were enveloped with an additional outermost membrane which may have originated from host cell membrane obtained in the budding process.

Animals↗
PubMed1975

Chamber centrifugation: a harvesting technique for estimation of the growth of human haemopoietic cells in diffusion chambers.

A harvesting technique which gives information about the spatial relationships between cells grown in diffusion chambers in mice has been designed. The principle is that cells are centrifuged directly from the chamber clot onto a slide during pronase treatment. The technique has been applied to normal human bone marrow cells grown in diffusion chambers. The slides show that the cells are situated in clusters. A limiting dilution assay of progenitor cells based on the presence of granulopoietic clusters in the chambers demonstrates the use of the method for quantitation of progenitor cells.

Animals↗
PubMed1976

Utilization of a new strength citrate anticoagulant during centrifugal plateletpheresis. I. Assessment of donor effects.

A reduction of donor effects during centrifugal plateletpheresis with the Haemonetics Blood Processor was achieved by reducing the concentration of the citrate anticoagulant. Serum citrate and ionized calcium levels, immediately and 1 h post-pheresis, were affected to a lesser extent by using 5.0 g total ionized citrate (TIC) THAN WITH EITHER 8.0 G OR 11.0 G. Total calcium, bicarbonate, prothrombin time, partial thromboplastin time, ECG, and platelet counts were affected to a similar degree by all three TIC formulations. The total number of platelets collected per litre of blood processed was not significantly different among the three TIC formulations. In vitro studies employing the screen filtration pressure (SFP) technique showed no evidence of platelet aggregates in whole blood collected into either 0.01 M or 0.005 M citrate and agitated or left stationary at room temperature for 5 h. The use of different citrate concentrations in plateletpheresis is discussed.

Anticoagulants↗
PubMed1978

Plateletpheresis by discontinuous centrifugation: effect of collecting methods on the in vitro function of platelets.

The in vitro function of platelets collected by two different methods during centrifugal plateletpheresis was compared. The RBC method involves collecting platelets with red cells followed by a supplementary spin to remove them, whereas the no-RBC method requires collecting platelets only from the buffy coat without red cells. Platelet response to adenosine diphosphate (ADP), epinephrine and collagen was slightly reduced in platelet-rich plasma (PRP) prepared by no-RBC technique and was markedly decreased in samples obtained by the RBC technique when compared to prepheresis controls. The decrease in platelet response to ADP, epinephrine and collagen was apparent in three testing systems: aggregation, release of serotonin and reptilase clot retraction. Both plasma and platelets appeared to be affected by the pheresis procedure. Platelet preparations obtained by both RBC and no-RBC techniques showed an increase of platelet factor 3 activity and an enhancement of aggregation, release of serotonin and clot retraction induced by thrombin as compared to prepheresis controls. Postpheresis platelet-poor plasma contains platelet membrane fragments which exhibit a high platelet factor 3 activity. The results showed that the RBC method, although providing a higher platelet yield, caused more qualitative alterations in platelets than in those obtained by no-RBC method, and that both methods of collecting platelets activated the procoagulant activity of platelets.

Blood Platelets↗
PubMed1978

Efficacy of platelets collected by semi-continuous flow centrifugation (Haemonetics Model 30).

The viability of both autologous and donor platelets collected by means of a semi-continuous flow centrifuge (Haemonetics Model 30) was measured. Radiochromium labelled pooled platelets harvested from six passes and reinfused into their normal donors showed recoveries and survivals of 58% +/- 8 and 9.6 d +/- 0.8 compared with normal values of 65% and 9.5 d +/- 0.6, respectively. When the viability in aplastic thrombocytopenic recipients of platelets collected from normal donors by the Haemonetics Model 30 was compared with that of platelets collected from the same donors by multiple bag plateletpheresis the results were very similar: recoveries of 82% +/- 18 and 80% +/- 25 and survivals of 3.9 d +/- 2.0 and 3.8 d +/- 1.3, respectively. The in vitro function of the collected platelets in response to aggregating agents was normal when measured within 60 min of collection at pH 7.4. The relationship between bleeding time and post-transfusion platelet count in aplastic, thrombocytopenic patients showed that in vivo function was maintained.

Blood Coagulation↗
PubMed1982

Fractionation of mammalian bone marrow by counterflow centrifugation-elutriation using a continuous albumin gradient: analysis of granulocyte-macrophage colony-forming units.

Bone marrow cells from murine, canine, primate and human donors were fractionated by counterflow centrifugation-elutriation (CCE) using a continuous albumin gradient. Fractionation of 9 x 10(8) nucleated bone marrow cells (without prior removal of the erythrocytes) can be done in less than 1.5 h with 92% nucleated cell recovery, depending on donor species. Murine bone marrow cell recovery after fractionation averaged 52% whereas cell recoveries for canine, primate and human donors averaged 85%, 92% and 89%, respectively. The fractions were evaluated for total nucleated cell counts and granulocyte-macrophage colony-forming units (GM-CFC). Each species studied presented a unique profile for nucleated cell recovery and associated GM-CFC activity. These profile variations may suggest significant differences in the modes of GM-CFC expression in the individual species that may depend on cell-to-cell interactions. Although CCE is unable to isolate a single population responsible for GM-CFC activity, CCE does permit a rapid, reproducible fractionation of a large numbers of cells with minimal manipulation of sample. This makes the isolated sample ideal for further purification of progenitor cell populations

Animals↗
PubMed1982

Bone marrow reconstitution of lethally irradiated canines using autologous bone marrow fractions obtained by counterflow centrifugation-elutriation.

Canine bone marrow fractionated by counterflow centrifugation-elutriation results in three areas of nucleated cell recovery. Fraction 1 accounts for 50% of the total nucleated cells and 25-40% of the total recovered CFU-GM activity. Fraction 2 contains less than 2% of the total nucleated cells and less than 0.2% of the CFU-GM activity. Fraction 3 accounts for approximately 50% of the total nucleated cell recovery and 60-75% of the total recovered CFU-GM activity. Animal survival was not directly correlated with the levels of CFU-GM activity in the transfused fractions. Autologous infusion of these fractions into irradiated canines (9 Gy, 0.1 Gy/min) resulted in distinct survival profiles. Canines receiving autologous fraction-2 cells showed no haematological reconstitution, with death occurring on days 10-11 post-irradiation. Canines receiving autologous fraction-3 cells showed limited myeloid repopulation of both the bone marrow and peripheral blood with a mean survival time for 24 d. Canines receiving autologous fraction-1 cells showed complete haematological reconstitution after 48 d and long-term survival. The data may indicate a separation or enrichment of pluripotential stem cells (fraction 1) from committed myeloid progenitor cells (fraction 3).

Animals↗

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