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 289 records · Page 16Linked to original sources
PubMed1997

A pivot bearing-supported centrifugal pump for a long-term assist heart.

A pivot bearing-supported centrifugal blood pump has been developed. It is a compact, cost effective, and anti-thrombogenic pump with anatomical compatibility. A preliminary evaluation of five paracorporeal left ventricular assist studies were performed on pre-conditioned bovine (70-100 kg), without cardiopulmonary bypass and aortic cross-clamping. The inflow cannula was inserted into the left ventricle (LV) through the apex and the outflow cannula affixed with a Dacron vascular graft was anastomosed to the descending aorta. All pumps demonstrated trouble free performance over a two-week screening period. Among these five studies, three implantations were subjected for one month system validation studies. All the devices were trouble free for longer than 1 month. (35, 34, and 31 days). After achieving one month studies, all experiments were terminated. There was no evidence of device induced thrombus formation inside the pump. The plasma free hemoglobin levels were within normal ranges throughout all experiments. As a consequence of these studies, a mass production model C1E3 of this pump was fabricated as a short-term assist pump. This pump has a Normalized Index of Hemolysis of 0.0007 mg/100L and the estimated wear life of the impeller bearings is longer than 8 years. The C1E3 will meet the clinical requirements as a cardiopulmonary bypass pump. For the next step, a miniaturized pivot bearing centrifugal blood pump P1-601 has been developed for use as a permanently implantable device after design optimization. The evolution from C1E3 to the PI-601 converts this pivot bearing centrifugal pump as a totally implantable centrifugal pump. A pivot bearing centrifugal pump will become an ideal assist pump for the patients with failing heart.

Animals↗
PubMed1994

Efficient antibody screening using gel centrifugation.

In a prospective study including 6,674 sera, antibody screening was performed (1) by tube test (saline/albumin/antiglobulin), (2) by gel centrifugation (Diamed) using two tests, saline/room temperature and antiglobulin/37 degrees C, and (3) by gel centrifugation using a single test antiglobulin (IAT)/ room temperature (RT). By gel centrifugation (saline RT + IAT 37 degrees C), compared to tube test, 40% more Coombs-reactive antibodies but 60% fewer cold-reactive antibodies were detected. Similar results were obtained by gel centrifugation using a single test IAT RT instead of the two tests saline RT + IAT 37 degrees C. A case of delayed hemolytic transfusion reaction was observed caused by anti-C demonstrable only by gel centrifugation. [table: see text]

Autoantibodies↗
PubMed1990

Electron microscopic study of immunocytochemically labeled centrifugal fibers in the goldfish retina.

The centrifugal fibers innervating the goldfish retina were studied quantitatively by light and electron microscopy. These fibers originating from cell bodies in the olfactory bulb were labeled by antiserum to the tetrapeptide Phe-Met-Arg-Phe-NH2 (FMRFamide). The number of FMRFamide-immunoreactive (ir) centrifugal fibers in each eye of the adult goldfish (body length: 12-15 cm) was 65 +/- 14 (mean +/- S.D., n = 7). All of these fibers in the optic nerve and the retina were unmyelinated. Each FMRFamide-ir centrifugal fiber runs along the optic fiber layer and gives several terminal arborizations in the outermost layer (layer 1) of the inner plexiform layer. Layer 1 is, therefore, densely covered by a plexus of terminal arborizations. Along these terminal arborizations, we found output synapses characterized by a cluster of small clear vesicles (40 nm in diameter) at the presynaptic site and a thickened membrane in the apposed retinal cell processes. In a sample area of 2,000 microns 2, such synapses occurred at a density of one per 105 microns 2, or about 13,000 per centrifugal fiber. Thus, the FMRFamide-ir centrifugal fibers are likely to modulate retinal cell activity through an estimated total of 840,000 output synapses per retina.

Animals↗
PubMed1983

The distribution of centrifugal terminals in the pigeon retina.

The terminals of the centrifugal fibres of the pigeon retina have been labelled by anterograde axonal transport or diffusion of horseradish peroxidase, and their distribution studied in whole amounts of the retina. Centrifugal terminal arborisations are concentrated in a band near the projection of the horizontal meridian on the retina. Within this band there are high density areas next to the area centralis and in the mid-temporal retina. The arborisations are largely absent from the red field and are nearly randomly arrayed. Their distribution resembles that of the displaced ganglion cells but not of other retinal neurons. We estimate that approximately 7,000 centrifugal terminal arborisations are present in each retina. Approximately two-thirds of these are convergent, with branches ending in large terminals clustered around a single cell in the amacrine sublayer; often penetrating up to 10 microns into the inner nuclear layer. The remainder are divergent endings which innervate a larger area of retina with widely spaced small terminals about 1 micron in diameter. Possible synaptic contacts between centrifugal terminals and displaced ganglion cells are occasionally seen; these contacts and the similarity in distribution suggest a link between the centrifugal and accessory optic systems.

Animals↗
PubMed2003

Performance prediction of industrial centrifuges using scale-down models.

Computational fluid dynamics was used to model the high flow forces found in the feed zone of a multichamber-bowl centrifuge and reproduce these in a small, high-speed rotating disc device. Linking the device to scale-down centrifugation, permitted good estimation of the performance of various continuous-flow centrifuges (disc stack, multichamber bowl, CARR Powerfuge) for shear-sensitive protein precipitates. Critically, the ultra scale-down centrifugation process proved to be a much more accurate predictor of production multichamber-bowl performance than was the pilot centrifuge.

Blood Cells↗
PubMed1996

Use of centrifugal pumps for postcardiotomy ventricular failure: technique and anticoagulation.

BACKGROUND: Centrifugal pumps have been employed most commonly for postcardiotomy mechanical support after intraaortic balloon pumping has failed. Despite their effectiveness in some patients, morbidity remains high. METHODS: Our clinical experiences with centrifugal pumps were reviewed with particular attention to common morbidity such as bleeding, coagulopathy, and thromboembolism. Evolution of cannulation techniques and anticoagulation strategies were defined. Morbidity during early and more recent experience was compared. RESULTS: Deranged coagulation and excessive mediastinal bleeding were commonly observed in patients undergoing centrifugal mechanical assist for postcardiotomy cardiogenic shock. Evolved strategies to reduce blood loss included meticulous cannulation techniques, early use of blood components, and an aggressive policy of mediastinal reexploration. Thromboembolism occurred with centrifugal mechanical assist, was underestimated by clinical events, and dictated pursuit of improved anticoagulation strategies and device refinement. A clinically significant trend of decreasing morbidity from early to recent experience was observed. CONCLUSIONS: Increasing clinical experience with centrifugal mechanical assist appears to result in a clinically relevant decrease in morbidity.

Anticoagulants↗
PubMed1976

The effects of centrifugation on the morphology of the lateral vestibular nucleus in the rat: a light and electron microscopic study.

Very little is known about structural changes in the central nervous system following exposure to increased g forces. Sprague-Dawley rats were centrifuged at Ames Research Center at 2.76-4.15 x g for periods ranging from 4 days to 21 months. The lateral vestibular nuclei were processed for electron microscopy and examined for evidence of structural alteration as a result of centrifugation. The number of filamentous nuclear inclusions, varicosities, and relative number of axosomatic synaptic terminals containing flattened vesicles (presumed inhibitory in function) increased in centrifuged rats. Altered mitochondria also were noted in that cell bodies of Deiters' neurons. Neuroaxonal dystrophy (NAD) was found in long-term centrifuged rats and was characterized by axons filled with reticulated mitochondria. The NAD found in the lateral vestibular nuclei of centrifuged rats is different from that seen in the dorsal column nuclei of aged mice.

Animals↗
PubMed1994

Very-fast ultracentrifugation of human plasma lipoproteins: influence of the centrifugal field on lipoprotein composition.

A short run-time in separation of lipoproteins by preparative ultracentrifugation is desirable for several reasons. Recently, a method was described that needs only 100 min for one run in a centrifugal field of 625,000 x g. It is assumed that lipoprotein separation depends on the rotor speed but this has not been systematically studied in centrifugal fields of this order. We performed such a study. Rotor speeds of 120, 90, 60 and 30 x 10(3) rev./min and run-times of 100 min, 3 h, 6.7 h and 27 h were selected in such a way that the product of centrifugal field and run-time remained constant. The first conditions correspond to the 'very fast ultracentrifugation' (VFU) procedure with a centrifugal field of 625,000 x g. The Optima tabletop ultracentrifuge, the rotor TLA-120.2 and thick wall open tubes for 1 ml were used. Thirteen different plasma samples covering a wide range of cholesterol and triglyceride concentrations were separated into VLDL, LDL and HDL in the course of two centrifugal runs at densities of 1.006 and 1.063. The constituents of the lipoproteins were calculated considering the mass of the tube contents after slicing. Recoveries of cholesterol, triglycerides and protein were 97%, 98% and 90%, respectively. The influence of the rotor speed on the apparent composition of the lipoproteins was small. With increasing rotor speed, VLDL-cholesterol became higher (by 14%, P < 0.001), VLDL-triglyceride became lower (by 6%, P < 0.012), LDL-cholesterol became lower (by 9%, P < 0.000). The effects on LDL-triglyceride and on HDL-cholesterol and HDL-triglyceride, did not reach statistical significance. Protein in VLDL and in LDL decreased and increased in 'HDL' (the subnatant of the LDL run). As checked by SDS-PAGE the protein effects were due to complete disappearance of albumin from VLDL and LDL while the apolipoproteins B-100, E and C-I to C-III remained unaffected. It is concluded that the main advantages of VFU are the short run-time and the disappearance of albumin from VLDL and LDL. The other compositional changes need to be further investigated.

Apolipoproteins↗
PubMed1985

Mechanism of chemical-induced toxicity. I. Use of a rapid centrifugation technique for the separation of viable and nonviable hepatocytes.

A major obstacle in defining the mechanism of chemical-induced toxicity has been the inability to distinguish between events that cause cell death and those that result from cell death. This problem results from measuring biochemical parameters in tissues or cell pellets containing both viable and nonviable cells. In the present study, we described a method for the rapid separation of viable hepatocytes from nonviable cells and medium prior to biochemical analysis. Separation of viable hepatocytes was accomplished in a microcentrifuge tube by layering a sample of isolated hepatocyte suspension over a dibutyl phthalate oil layer and centrifuging for several seconds. As a result, greater than 90% of the hepatocytes centrifuged through dibutyl phthalate were viable while greater than 90% of the cells recovered above the oil layer were nonviable. The separation of viable hepatocytes by the dibutyl phthalate method was not affected by the presence of the hepatotoxins, adriamycin (ADR) in combination with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) or ethyl methanesulfonate (EMS), though the ratio of viable to nonviable cells in the suspension was drastically reduced. The metabolic and morphological integrity of hepatocytes centrifuged through dibutyl phthalate was altered after cell suspensions were treated with the ADR-BCNU or EMS. These chemically treated viable hepatocytes showed degenerative ultrastructural changes and a greater than 80% reduction in intracellular K+ and glutathione concentrations. Because centrifugation through dibutyl phthalate does not significantly alter the concentration of intracellular constituents nor the ultrastructure of control hepatocytes, the signs of reversible injury observed in hepatocytes centrifuged through oil resulted from the chemical treatment. These data indicate that the dibutyl phthalate separation technique offers the advantage of monitoring only viable hepatocytes for changes in membrane integrity or metabolic performance during a toxic chemical insult.

Animals↗
PubMed1988

Detection of adenovirus by rapid 24-well plate centrifugation and conventional cell culture with dexamethasone.

Two methods for rapid detection of adenovirus were tested: (i) 24-well plate centrifugation followed by staining with a monoclonal antibody after incubation for 24 h and 48 h, and (ii) pretreatment of A549 cells used in conventional cell culture and 24-well plate centrifugation with 10(-5)M dexamethasone. Twenty-seven clinical isolates of adenovirus and 12 specimens from which adenovirus had been recovered were included in the analysis. Both isolates and specimens had been frozen at -70 degrees C for up to 6 months. By 24-well plate centrifugation both with and without dexamethasone, 21 (78%) and 27 (100%) isolates were positive for adenovirus at 24 h and 48 h, respectively. Of the specimens, 6 (50%) and 8 (67%) were positive by 24-well plate centrifugation without dexamethasone at 24 h and 48 h, respectively, whereas with dexamethasone 3 (25%) were positive at 24 h and 7 (58%) were positive at 48 h. Overall, combining isolates and specimens, the sensitivity of 24-well plate centrifugation for detection of adenovirus at 24 h was 69% without dexamethasone and 62% with dexamethasone, and at 48 h the sensitivity was 90% without dexamethasone and 87% with dexamethasone. The specificity under all conditions tested was 100%. In conventional tissue culture dexamethasone inhibited recovery of adenovirus. Without dexamethasone, adenovirus was recovered from all 39 samples within 7 days after inoculation; however with dexamethasone pretreatment, the virus was detected in only 31 (79%) of the samples tested in the same period of time.

Adenoviridae↗
PubMed2004

Identification of neurons with acetylcholinesterase and NADPH-diaphorase activities in the centrifugal visual system of the chick.

The isthmo-optic nuclei (ION) and ectopic neurons, which constitute the centrifugal visual system (CVS), are thought to be cholinoceptive and nitrergic. However, it is not clear which neurons express these markers, namely the ones that project to the retina rather than in neurons that only participate in a local circuit. Therefore, to characterize the neurochemical patterns of the centrifugal visual system in the post-hatched chick, retinopetal cells of the isthmo-optic nuclei and the ectopic region were identified via immunolabeling for cholera toxin, a neuronal tracer, which has been injected in the ocular globe. Then, double labeled with acetylcholinesterase histochemistry to reveal cholinergic synapses, or NADPH-diaphorase histochemistry as a nitrergic marker. Briefly, acetylcholinesterase activity was present mainly in cholera toxin labeled cell bodies of the isthmo-optic nucleus and the ectopic region indicating that retinal projecting neurons of centrifugal visual system comprise a cholinoceptive pathway. On the other hand, NADPH-diaphorase histochemistry was present in the neuropile and sparse cell bodies inside of the isthmo-optic nucleus and in ectopic neurons which were not cholera toxin positive suggesting their role in an intrinsic circuit of the centrifugal visual system. These data support the idea that these two neurochemical systems are present in distinct neuronal populations in the centrifugal visual system.

Acetylcholine↗
PubMed1994

A combined incision technique of radial keratotomy. A comparison to centripetal and centrifugal incision techniques in human donor eyes.

PURPOSE: To evaluate and compare the extent of corneal flattening and the anatomy of the incision grooves produced by centrifugal, centripetal, and combined incisions in a human donor eye model. METHODS: Twenty-seven eyes, divided into three groups of nine, received eight-incision radial keratotomy using the centrifugal, centripetal, or combined incision technique. Corneal curvature was evaluated using a topography system, and the anatomy of the incision was assessed by light microscopy and scanning electron microscopy. RESULTS: The average central corneal flattening at the 3-mm clear zone was 4.16 +/- 1.47 diopters (D) for centrifugal incisions; 7.71 +/- 2.77 D for centripetal incisions; and 9.26 +/- 1.75 D for combined incisions. The difference in corneal flattening between eyes that received centrifugal versus either centripetal or combined incisions was significant (P < 0.01), whereas the difference between combined and centripetal incisions was not significant (P = 0.174). Anatomic differences were observed within the incision grooves produced by the three techniques. CONCLUSION: The authors describe a novel combined incision technique of radial keratotomy that provides the potential safety of a centrifugal incision with the effect of a centripetal incision.

Aged↗
PubMed1998

An immunohistochemical study of putative neuromodulators and transmitters in the centrifugal visual system of the quail (Coturnix japonica).

The aim of the present study was to analyze the neurochemical properties of the centrifugal visual system (CVS) of the quail using an immunohistochemical approach by testing 16 neuropeptides (angiotensin: ANG, bradykinin: BK, cholecystokinin, dynorphin, L and M-enkephalin, beta-endorphin: beta-END, galanin, alpha-neoendorphin, neurokinin A, neuropeptide Y (NPY), ocytocin, somatostatin, substance P, vasopressin, vasoactive intestinal polypeptide) and three neurotransmitters or their synthetic enzymes (choline acetyltransferase: ChAT, tyrosine hydroxylase: TH, serotonin: 5-HT and nitric oxide synthase: NOS, including the histochemical nicotinamide adenine dinucleotide phosphate diaphorase technique). For each substance, the somatic and afferent fiber and terminal labeling was analyzed within the nucleus isthmo-opticus (NIO) and the ectopic area (EA) and compared with that of retinopetal cell bodies labeled retrogradely with RITC following its intraocular injection (double-labeling procedure). The results showed that none of the centrifugal neurons were reactive to any of the substances tested. In contrast, all with the exception of ANG, BK and beta-END, labeled fibers and terminals within the EA and only four (ChAT, 5-HT, NPY and NOS) within the NIO. Possible sources of these immunoreactive fibers terminating in the NIO and EA were investigated by mapping the somatic immunolabeling of the different substances within brainstem regions previously shown by Miceli and other authors to project upon the centrifugal neurons. The data suggests that, besides the rapid retino-tecto-NIO-retinal loop, which facilitates the transfer of meaningful or more relevant information within particular portions of the visual field, the multiple afferent input which stems from various brainstem regions utilizes a wide range of neuroactive substances. Some of these afferent projections upon the centrifugal neurons appear to belong to nonspecific systems which might play a role in modulating the excitability of centrifugal neurons as a function of arousal.

Animals↗
PubMedDate not supplied

The retinal targets of centrifugal neurons and the retinal neurons projecting to the accessory optic system.

In birds, neurons of the isthmo-optic nucleus (ION), as well as "ectopic" neurons, send axons to the retina, where they synapse on cells in the inner nuclear layer (INL). Previous work has shown that centrifugal axons can be divided into two anatomically distinct types depending on their model of termination: either "convergent" or "divergent" (Ramon y Cajal, 1889; Maturana & Frenk, 1965). We show that cytochrome-oxidase histochemistry specifically labels "convergent" centrifugal axons and target neurons which appear to be amacrine cells, as well as three "types" of ganglion cells: two types found in the INL (displaced ganglion cells) and one in the ganglion cell layer. Labeled target amacrine cells have distinct darkly labeled "nests" of boutons enveloping the somas, are associated with labeled centrifugal fibers, and are confined to central retina. Lesions of the isthmo-optic tract abolish the cytochrome-oxidase labeling in the centrifugal axons and in the target amacrine cells but not in the ganglion cells. Cytochrome-oxidase-labeled ganglion cells in the INL are large; one type is oval and similar to the classical displaced ganglion cells of Dogiel, which have been reported to receive centrifugal input; the other type is rounder. Rhodamine beads injected into the accessory optic system results in retrograde label in both types of cells, showing that two distinct types of displaced ganglion cells project to the accessory optic system in chickens. The ganglion cells in the ganglion cell layer that label for cytochrome oxidase also project to the accessory optic system. These have proximal dendrites that ramify in the outer inner plexiform layer.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Application of centrifugation to the large-scale purification of electric arc-produced single-walled carbon nanotubes.

We report a further advance in the bulk purification of nitric acid-treated single-walled carbon nanotubes (SWNTs) by use of high-speed centrifugation. We have already shown that low-speed centrifugation is effective in removing amorphous carbon (AC). In these earlier experiments, the AC preferentially suspends in aqueous dispersions on low-speed centrifugation (2000g), leaving the SWNTs in the sediment. In a surprising reversal, we now show that high-speed centrifugation (20000g) of well-dispersed preparations is effective in sedimenting carbon nanoparticles (CNP), while leaving the SWNTs suspended in aqueous media. Taken together, these two techniques allow the bulk scale (10 g) purification of SWNTs by efficiently separating the two main contaminants, in an industrially viable process. We show that the mechanism of these separations is based on the differential charging (zeta-potential) of the AC, CNPs, and SWNTs that comes about during the chemical processing. Due to their more robust structure, nitric acid oxidation leaves the CNPs with a surface charge density lower than that of the SWNTs, and thus the CNPs do not form stable dispersions in aqueous media during high-speed centrifugation. The efficiency of the process was confirmed by the high purification recovery factor (PRF = 90%), which is a measure of the fractional quantity of the product recovered after the purification. We demonstrate that the purity of SWNTs significantly affects their mechanical and electrical properties.

Journal Article↗
PubMedDate not supplied

Centrifugal fibres synapse on dopaminergic interplexiform cells in the teleost retina.

In teleost fish, centrifugal fibres originating in the olfactory bulb and containing FMRFamide-like and luteinizing hormone releasing hormone (LHRH)-like peptides project to the retina and terminate along the border of the inner nuclear and inner plexiform layers. Using a novel simultaneous two-colour immunolabelling technique, we have found that these centrifugal fibres are often closely apposed to the dopaminergic interplexiform cells. Contacts between centrifugal fibres and dopaminergic interplexiform cells were observed by electron microscopy to be conventional type synaptic junctions. Since the dopaminergic interplexiform cells make synapses on horizontal and bipolar cells, providing an intraretinal centrifugal pathway for information flow from the inner to the outer plexiform layers, we conclude that every neuron in the teleost retina is potentially susceptible to central influences via these centrifugal fibres and dopaminergic interplexiform cells.

Animals↗
PubMed2003

Comparison of the centrifugal and roller pump in elective coronary artery bypass surgery--a prospective, randomized study with special emphasis upon platelet activation.

Objective--Evaluation of the centrifugal pump vs roller pump concerning effects upon platelet function, hemolysis and clinical outcome in elective coronary artery bypass surgery. Design--Thirty-four patients were randomized to centrifugal or roller pump. Platelet activation was studied by flow cytometry before, during and up to 3 days after bypass. Results--Duration of bypass, ischemic period, peripheral anastomoses, hospital stay and mortality did not differ. In roller pump patients, platelet aggregates increased by 250% between end of bypass and 3 h postoperatively (p < 0.001). A secondary, fivefold increase in number of platelet aggregates was found on the 3rd postoperative day (p < 0.001). In the centrifugal pump group, these changes were not significant. Hemolysis increased (20%) at end of bypass and 3 h postoperatively (p < 0.005), and decreased to preoperative levels the next day without group difference. Conclusion--Platelet aggregation was significantly increased in roller compared with centrifugal pump patients, indicating higher susceptibility to postoperative thrombotic complications with the roller pump. Otherwise, there was no clinical evidence for superiority of the centrifugal pump.

Aged↗
PubMed1976

Isolation of plasma membranes from corn roots by sucrose density gradient centrifugation: an anomalous effect of ficoll.

An investigation was conducted into the isolation of plasma membrane vesicles from primary roots of corn (Zea mays L., WF9 x M14) by sucrose density gradient centrifugation. Identification of plasma membranes in cell fractions was by specific staining with the periodic-chromic-phosphotungstic acid procedure. Plasma membrane vesicles were rich in K(+)-stimulated ATPase activity at pH 6.5, and equilibrated in linear gradients of sucrose at a peak density of about 1.165 g/cc. It was necessary to remove mitochondria (equilibrium density of 1.18 g/cc) from the homogenate before density gradient centrifugation to minimize mitochondrial contamination of the plasma membrane fraction. Endoplasmic reticulum (NADH-cytochrome c reductase) and Golgi apparatus (latent IDPase) had equilibrium densities in sucrose of about 1.10 g/cc and 1.12 to 1.15 g/cc, respectively. A correlation (r = 0.975) was observed between K(+)-stimulated ATPase activity at pH 6.5 and the content of plasma membranes in various cell fractions. ATPase activity at pH 9 and cytochrome c oxidase activity were also correlated.A major peak of ATPase activity at pH 6.5 was observed at low density in Ficoll after nonequilibrium centrifugation in a combination Ficoll-sucrose gradient. Twenty to forty percent of the vesicles in this ATPase fraction stained positively for plasma membranes, and with equilibrium centrifugation the major portion of the ATPase activity shifted to densities in sucrose which were characteristic of plasma membranes. All major vesicular ATPase activities observed in Ficoll or sucrose contained substantial amounts of plasma membranes. For unknown reasons, mitochondria and plasma membranes equilibrated over a broader density range and at lower peak densities in sucrose as a result of equilibrium centrifugation through Ficoll.

Journal Article↗