Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CENTRIFUGATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39Linked to original sources
PubMed1981

[Electron microscopic studies of striated muscles of the Japanese quail (Coturnix coturnix japonica) obtained from eggs centrifuged during incubation].

Reported in this paper are results obtained from investigations into the effect of hypergravitation on embryogenesis of striped muscles in Japanese quail. Specimens of striped muscles were excised from the birds after hatching and used in the study. The eggs had been centrifuged on zero day as well as on the first and 15th days of incubation. The muscle fibrils were found to proliferate in all groups, that is the control group, the group with centrifugation on zero day, and that with centrifugation on the first and 15th days. The process thus is characterised as physiological, known to occur prenatally and postnatally in developing individuals.

Animals↗
PubMed1980

Large scale fractionation of calf brain by double run zonal centrifugation.

A previously described method for the subfractionation of subcellular particles by zonal centrifugation (Spanner, 1972), gives an unsatisfactory resolution when applied to calf brain, particularly when large amounts of subcellular particles are required. We succeeded in subfractionating 30-45 g of gray matter by modifying the procedure for preparing the P2 fraction (crude mitochondrial fraction) and introducing a new stepwise sucrose gradient on double run zonal centrifugation. Satisfactory resolution can also be achieved by single run zonal centrifugation when the starting material does not exceed 15 g of gray matter. The following fractions were separated as characterized chemically morphologically and by their enzyme markers: a) light myelin (0.4-0.6 M sucrose); b) heavy myelin (0.7 M); c) plasmamembranes (0.9-1.0 M); d) nerve endings (1.0-1.2 M); e) mitochondria (1.3 M); f) lysosomes (1.4 M).

Animals↗
PubMed1978

Liquid preservation of canine granulocytes obtained by counterflow centrifugation-elutriation.

Granulocytes (PMN) were isolated from 120 ml of canine whole blood by a modification of the counterflow centrifugation-elutriation technique. Isolated cell suspensions of 96% granulocytes and 4% mononuclear leukocytes with a 21:1 PMN/RBC ratio were stored at 4 degrees C in 4:4:2 medium consisting of four parts HBSS minus Ca++ and Mg++, four parts MEM, twp parts autologous plasma, and 20 microgram/ml gentamicin for 15 days. Granulocytes were stored at concentrations of approximately 4 x 10(6) PMN/ml in polypropylene centrifuge tubes. The stored granulocyte suspensions were assayed in vitro 0, 1, 4, 8, and 15 days to monitor chemotaxis, bacterial growth inhibition, O2 consumption associated with phagocytosis, and enzyme activities. Cell volume analysis was used to evaluate cellular integrity of the liquid-stored granulocytes. Canine granulocytes isolated by the modified dilution technique of counterflow centrifugation-elutriation can be preserved for up to 15 days with 77 +/- 6% granulocyte survival with maintenance of morphological and organelle integrity, as well as retention of in vitro functions of recognition, migration, phagocytosis, and killing of gram-negative bacteria.

Animals↗
PubMed1995

Influence of centrifugation on the infectivity of Chlamydia pneumoniae IOL-207.

The influence of centrifugation on the infectivity of Chlamydia pneumoniae IOL-207 was compared with seven serovars of C. trachomatis biovar trachoma, the three serovars of C. trachomatis biovar lymphogranuloma and four C. psittaci strains. Prolonged centrifugation from 1 to 4 hours resulted in a 3-fold increase in the infectivity of C. pneumoniae and variable or no increase in the infectivity of the other Chlamydia strains studied. These findings indicate that a 4 hour centrifugation of C. pneumoniae is recommended to improve the isolation procedures of this organism in cell cultures.

Animals↗
PubMed1994

Monocyte isolation by flow cytometer-monitored centrifugal elutriation: a preparative tool for antibody-dependent cell-mediated cytotoxicity (ADCC) assays.

The value of isolating monocytes by flow cytometer-monitored centrifugal elutriation (CE) after initial density gradient centrifugation (DGC) was investigated. A pooled cell suspension prepared by DGC+CE had a monocyte purity of 90% while a pool prepared by DGC alone had a monocyte purity of only 30%. Monocyte suspensions prepared from 15 separate blood donations demonstrated that, despite wide variation in initial monocyte purity following DGC (i.e. 13-32%), CE consistently increased the purity to 85-92%. Antibody-dependent cell-mediated cytotoxicity (ADCC) studies showed that the most sensitive and reproducible assays were those performed with the DGC+CE pool. At a monocyte concentration of 2 x 10(6)/ml the DGC+CE pool was almost twice as active as the DGC pool (60.2% lysis vs 31.2% lysis, respectively). Considerable variation in ADCC activity was seen when using monocytes from individual donors. We conclude that centrifugal elutriation is a valuable tool for preparing effector cells for use in monocyte driven ADCC assays.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1994

[Clinical study of optimal bypass flow for temporary bypass with centrifugal pump in surgical treatment of aneurysm of the descending thoracic aorta].

Since 1987, 33 patients were operated on for aneurysm of the descending thoracic aorta using temporary bypass with a heparin-coated centrifugal pump and heparin-coated tubes at Kobe University Hospital. Sixteen patients had true aneurysms of the descending thoracic aorta, 7 had thoraco-abdominal aneurysms and 10 had aortic dissection (DeBakey's type III). Heat exchanger and oxygenator were not included in the bypass circuit in all cases. Perfusion time was from 42 to 205 minutes (average 90 minutes). Left heart bypass was established with 1 mg/kg of systemic heparinization in 5, 0.5 mg/kg in 5, and 0 mg/kg in 23 cases. There were no complications such as perioperative embolism, acidosis, or hypothermia. During aortic cross-clamping, the arterial pressure of the lower extremity was maintained over 70 mmHg, but there was no relationship between the distal perfusion pressure and bypass flow. The urine output during temporary bypass was significantly related to the distal perfusion flow by centrifugal pump (r = 0.455, p < 0.01). Seven out of 23 patients who were bypassed under 40 ml/kg/min of distal perfusion flow showed transient renal dysfunction postoperatively, and two developed postoperative renal failure, while the other patients bypassed over 40 ml/kg/min of pump flow stayed in the normal range of the renal function, where there were statistically differences (p < 0.05). Postoperative paresis occurred in 2 patients who were also perfused under 40 ml/kg/min of bypass flow. Therefore, it is concluded that temporary bypass with centrifugal pump is a safe and well acceptable circulatory support in the surgical treatment of aneurysm of the descending aorta.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Postural consequences of long duration centrifugation.

In the present paper a series of experiments will be described in which the postural consequences of long (up to 1.5 h) duration 3G-centrifugation have been subject to investigation. A vestibular model is presented in order to explain for the postural imbalance found in specific conditions after the centrifuge run, and for the often concomitant feelings of motion sickness (50% of the subjects suffer from Sickness Induced by long duration Centrifugation). Finally, the possible relation between SIC and the Space Adaptation Syndrome is discussed.

Adaptation, Physiological↗
PubMed1993

Incidence of cardiac dysrhythmias occurring during centrifuge training.

High-G training has been reported to provoke dysrhythmias in many subjects. These reports have been based on small subject groups. Students attending aeromedical professional courses at the USAF School of Aerospace Medicine are offered the opportunity to participate in high-G centrifuge training on the Armstrong Laboratory centrifuge, during which ECG monitoring is routinely performed. This study documents the incidence of dysrhythmias in this large group of subjects. The pertinent information from the records of 1,180 training sessions from 1984-91 were transcribed to a database on a personal computer. Dysrhythmias were recorded in 552 (47%) of the training sessions. Ventricular ectopy occurred in 480 (41%) of the sessions, and supraventricular dysrhythmias appeared in 127 (11%). In 53 (4.5%) of the sessions, training either was or would have been terminated because of the dysrhythmia. Session-terminating dysrhythmias included: 26 ventricular tachycardias (2.2%), including 18 triplets (1.5%); 9 ventricular couplets (0.8%); 8 episodes of too-frequent ventricular premature beats (0.7%); 4 of supraventricular tachycardia (0.3%), including 2 with aberrant conduction (0.2%); 2 of aberrantly conducted beats (0.2%); and 4 of anomalous bradycardia (0.3%). Centrifuge training can provoke serious dysrhythmias in ostensibly healthy individuals, and ECG monitoring of aircrew undergoing such training is recommended for their safety. Because some of these dysrhythmias are disqualifying for aircrew duties, the need for a more lenient aeromedical disposition policy must be considered.

Adult↗
PubMed1977

Microvascular pressure responses of second-generation rats chronically exposed to 2 G centrifugation.

The purpose of thses studies was to compare systemic arterial and microvascular pressures in the second generation of rats reared in a 2-G centrifuge with pressure data from animals subjected to 1 G centrifugation. Systemic arterial pressures were measured in anesthetized animals via carotid catheters and microvascular pressures were measured in mesenteric arterioles by a micropipette servo-null system. Systemic arterial pressures in the 1-G and 2-G groups were not significantly different from each other, but both were considerably higher than those reported for normal rats. In the microcirculation, pressures in the terminal arterioles (20 to 35 micron) were significantly higher in the 2-G animals, but pressures at the level of the smaller (10 to 15 micron) precapillary arterioles were not significantly different between the two groups. The pressure responses to intravenous infusion of norepinephrine were also compared in the two groups and found to be significantly less in the 2-G animals. It is concluded that both 1 G and 2 G chronic centrifugation will elevate arterial blood pressure, and that 2 G, of itself, will affect the pressure distribution in the microcirculation as well as attenuate the pressor effects of norepinephrine.

Animals↗
PubMed1996

Isolation of Mycobacterium tuberculosis from cerebrospinal fluid by the centrifugation & filtration methods.

Cerebrospinal fluid (CSF) samples were collected in 2 bottles each, from 112 children, examined clinically for tuberculous meningitis (TBM) One was processed by the centrifugation method and the other by the filtration method for the isolation of M. tuberculosis. Of these specimens, 11 and 13 yielded M. tuberculosis by the centrifugation method and the filtration method, respectively. In 7 specimens M. tuberculosis was isolated by both the methods; in 4, only by the centrifugation method, and in 6, only by the filtration method. Using both the methods, 17 (15.2%) of 112 specimens were culture positive for M. tuberculosis. The improvement in the rate of isolation, thus obtained, assumes importance as the confirmation of the diagnosis of TBM in all the clinically suspected cases is always desired. Moreover, the filtration method is simple and inexpensive and it can be carried out even in remote hospitals and the membranes, after filtration, can be transported to central mycobacteriology laboratory for culture of tubercle bacilli.

Bacteriological Techniques↗
PubMedDate not supplied

Development of a magnetically suspended centrifugal pump as a cardiac assist device for long-term application.

To overcome problems with the shaft seal in conventional centrifugal pumps, the authors have been developing a magnetically suspended centrifugal pump (MSCP) that operates as a valveless, sealless, and bearingless pump. The prototype of the MSCP was modified with respect to size of the volute diffuser and impeller blade profiles. A hemolysis test in vitro using a new version of the MSCP was performed in comparison with a commercially available centrifugal pump. The test circuit for the hemolysis test comprised a blood reservoir, a pump, and polyvinyl tubes, and was filled with fresh heparinized bovine blood. The pumping conditions were a flow rate of 5 L/min and a pump head afterload of 100 mmHg. The index of hemolysis in the MSCP was significantly lower than that in the Biomedicus pump (0.0035 +/- 0.0025 versus 0.0097 +/- 0.0056 g/100 L, p < 0.05). Reduction in the platelet count during pumping also was lower in the MSCP compared with the Biomedicus pump at both 6 hrs and 12 hrs of pumping (p < 0.01). This MSCP may be advantageous for extended use of assist devices, not only from the theoretical point of view, but in a practical sense after the results of the current hemolysis test.

Centrifugation↗
PubMed1996

Comparison of centrifugal and roller pump hemolysis rates at low flow.

We compared in vitro rates of hemolysis for a recently developed centrifugal pump with a conventional roller pump (10-10-00; Stöckert, Munich, Germany). Flow rates of 0.3 L/min and 1 L/min and a pressure of 200 mm Hg were chosen to simulate conditions during neonatal extracorporeal membrane oxygenation (ECMO). There was no significant difference in hemolysis rates between centrifugal and roller pumps (p = 0.57) nor between high and low flow (p = 0.86). The centrifugal pump caused no more blood trauma than the roller pump at the low-flow/high-pressure conditions required for neonatal ECMO. The Nikkiso pump is superior to roller pumps in size and priming volume (25 ml) and may permit development of a smaller and simpler ECMO system.

Animals↗
PubMed1996

Subchronic centrifugal mechanical assist in an unheparinized calf model.

The purpose of this study was to determine whether the major centrifugal pumps currently in use in the United States (Medtronic, BioMedicus BioPump and Carmeda-coated BioPump, Sarns 3M centrifugal pump, and St. Jude Medical Lifestream) could function as left mechanical assist devices in the subchronic (72 h) unheparinized calf model. Calves were instrumented for left atrial to aorta ex vivo assist, and the pump flow was set at 3.5 +/- 0.4 L/min. Two calves (Sarns 3M and St. Jude) survived 72 h of pumping without clinical complications. The other 2 calves died at 62 and 66 h (Medtronic BioPump and Carmeda-coated BioPump, respectively); both had pelvic limb paralysis. The seal of the Sarns 3M pump head ruptured after approximately 36 h of pumping and required replacement. On postmortem examination, pump-associated thromboembolic lesions were detected in 3 of the 4 calves in one or more of the following organs: kidneys, pancreas, abomasum, duodenum, ileum, spleen, and lumbar spinal cord. The calf with the Sarns 3M pump had no discernable lesions. Because of the clinical abnormalities and postmortem lesions in the unheparinized calf model, it was suggested that anticoagulation is necessary for conducting centrifugal mechanical assist studies in calves using presently available technology.

Analysis of Variance↗
PubMed1996

Clinical experience with the Nikkiso centrifugal pump.

The Nikkiso HPM-15 is a minimally sized centrifugal pump. Preliminary results regarding clinical use of this pump for cardiopulmonary bypass (CPB) procedures have been reported previously. Recently, we have managed some additional cases using a newly developed controller. This article reports our clinical experiences with the use of this pump. We have managed 23 cases with a Nikkiso centrifugal pump. Twenty-two patients underwent CPB and 1 patient with fulminant viral myocarditis underwent percutaneous cardiopulmonary support (PCPS). With this pump, the circuit was extremely easy to prepare and deaeration was achieved readily. Hemodynamics during CPB and PCPS were stable in all cases. The increase in serum-free hemoglobin levels during CPB with this pump was as low as that seen in preliminary tests. A decrease in the platelet count was observed after the initiation of CPB with this pump; however, platelet counts returned to preoperative values 7 days after surgery. Moreover, urine output during CPB with this pump was as high as that seen in preliminary tests. No abnormalities in renal or liver function occurred during CPB. It appears that this new centrifugal pump is safe and easy to operate, and we conclude that it is useful for CPB and PCPS.

Adult↗
PubMed1977

[Centrifugal analysis. History, general principles].

Three ideas were at the origin of the concept of rapid centrifugal analysis: automation, miniaturisation, suppleness. They led to the drawing up of a manuel for the development of a prototype including: simultaneity, miniaturisation, true time and reduction of data. The rapid centrifugal analyser may be described as a system of analysis based on the use of centrifugal force to add simultaneously in a discret way an aliquot of reagent to various aliquots of specimens and to displace the reactional mixtures in hollows equally distributed on the outer border of a rotor. The signals are detected optically. After showing the various forms of use of the rotors, the function of the module of analysis is described. The taking and treatment of data by the computer are described with special reference to their aspects in real time. Finally, a few applications are described.

Autoanalysis↗
PubMed1977

[Coordinate evaluation of three types of centrifugal analysers].

A coordinated evaluation effected under the control of French Society of Clinical Biochemistry has been with three centrifugal analysers. This evaluation involved two protocol patterns: --A type protocol: realized under ideal conditions. --B type protocol: realized under usual conditions. This study involved: --Evaluations of accuracy, reliability and thermostatisation, according to A type protocol. --Evaluation of contamination within the same transfer disc (Both A and B type). --Comparative survey of reliability performed every day, with the same transfer disc, through two months (B type). --Reliability analysis, through two years; the interest of this test in the control of the centrifugal systemes underlined (B type). --Comparative economical evaluation of the three centrifugal analysers, within two typical conditions.

Autoanalysis↗
PubMed1977

Femoral development in chronically centrifuged rats.

Groups of 30-d-old male and female rats were centrifuged at 2.00 G (RE, Rotation Experimental), 1.05 G (RC, Rotation Control) or exposed to the noise and wind of the centrifuge at 1.00 G (EC, Earth Control) for periods of 1, 2, 4, 8, and 16 weeks. Measurements of their femurs indicated that exposure to centrifugation a) decreased femoral length in tre animals, b) increased femoral length in RC animals, c) reduced femoral diameter in RE and RC animals, d) increased L/D ratios in RC animals, e) decreased L/D ratios in RE animals, f) increased femur length/body weight in RE animals, g) decreased cortical thickness (CT) in RE animals, h) increased relative CT in RE animals, and decreased it in RC animals, i) accelerated ossification in RC femoral heads, j) thinned and distorted RE epiphyseal plates, and k) thickened condylar cartilage in RE females. The effects tended to be strongly sexually dimorphic, with females more severely affected by the stress than males.

Animals↗
PubMedDate not supplied

The role of the centrifugal pump in hemolysis during neonatal extracorporeal support.

While the use of the centrifugal vortex ECMO pump as an alternative to a roller-occlusion pump offers distinct advantages, unacceptable hemolysis may occur during its use in newborn infants. The authors studied 87 consecutive neonatal patients with respiratory failure supported with venoarterial ECMO using a centrifugal vortex pump. Baseline mean plasma free hemoglobin level for all patients during the first 48 hours of bypass was 31.3 +/- 3.1 md/dl. In 51 patients, an abrupt rise in the plasma free hemoglobin occurred. In 48 of 51 patients, the pump head alone was changed at 91.9 +/- 6.6 hours after initiation of bypass. Mean plasma free hemoglobin decreased to baseline values following pump head change. The authors could not determine any factors that distinguish the infants who developed hemolysis from those who did not. Changing only the pump head provides a simple approach to hemolysis during use of the centrifugal vortex pump on newborn infants.

Centrifugation↗