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The effect of centrifugation on the mechanical properties of cement. An in vitro total hip-arthroplasty model.

An in vitro total hip-arthroplasty model was evaluated to determine if centrifugation of bone cement results in greater static strength and low-cycle fatigue strength than hand-mixing. The static-failure test of the stem, cement, and simulated bone composite demonstrated that the centrifuged cement had significantly greater static strength than the hand-mixed cement. However, under low-cycle fatigue tests on the same composite models, the centrifuged and hand-mixed specimens were not significantly different.

Biomechanical Phenomena↗

A comparative cytologic study of 100 urine specimens processed by the slide centrifuge and membrane filter techniques.

An evaluation of cytology preparations made by the slide centrifuge and membrane filter techniques was made on 100 consecutive urine specimens from 46 patients. The membrane filter technique gave better cellular recovery and produced slides qualitatively superior to those prepared by the slide centrifuge technique. The former, therefore, is the recommended method. The slide centrifuge might be of greater value with urine of low cellularity where the membrane filter has provided only a few to practically no cells. The diagnostic accuracy on clinical follow-up of the patients included in this study is 94% for both methods, with no false positive cases and a 6% false negative rate. This high degree of accuracy indicates that these concentrating methods may lead to clinically valuable information if used routinely in the cytology laboratory.

Adult↗

Side effects of therapeutic plasma exchange during treatment of polyarteritis nodosa. Comparison of filtration and centrifugation. 718 sessions in 63 patients.

Between 1981 and 1984, 72 patients (22-75 years) were included in a prospective study for treatment of Polyarteritis Nodosa (PN) which associated therapeutic plasma exchanges (TPE), corticosteroids (CS) 1 mg/kg/day, and a randomized trial of cyclophosphamide (CP) 2 mg/kg/day. We observed the incidence and analysed side effects (SE) occurring during TPE considering the technology of plasma removal. Full data were available for 63 patients. Seven hundred and eighteen TPE were performed. Centrifugation was used in 594 PE (82.7 per cent) with intermittent flow centrifugation (IFC) 320 times (44.5 per cent) and continuous flow centrifugation (CFC) 274 times (38.2 per cent). Filtration (F) was used in 124 sessions (17.3 per cent). Replacement fluid was 4 per cent albumin in 650 TPE and fresh frozen plasma (FFP) in 89 TPE. A total of two hundred and eleven SE were reported in 53 patients (84.1 per cent) during 173 TPE (24.1 per cent). Forty-six TPE were temporarily stopped because of SE (6.4 per cent). The mean volumes of removed plasma (ml/kg/TPE) were: 60.7 +/- 8.7 ml/kg when CFC was used 54.5 +/- 20 ml/kg with F and 52.5 +/- 9.6 ml/kg with IFC (n.s.) Main SE were: technical difficulties in 80 TPE, moderate or severe hypotension in 47, allergy to replacement fluid in 39. Hepatitis B antigen appeared in one patient. No death occurred during TPE and SE were usually minor and transient.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Hormones↗

A new multichamber counterflow centrifugation rotor with high-separation capacity and versatile potentials.

A new closed system for counterflow centrifugation (elutriation) is described. The system was developed to increase the capacity of counterflow centrifugation in order to be able to separate bone marrow intended for allogeneic bone marrow transplantation within 3 h. The rotor has the capacity for up to four separation chambers, offering the possibility of separating either a single-cell suspension under equal or differing conditions, or four different suspensions simultaneously. Profiles of low-density nucleated cells from normal blood were shown to be identical after elutriation in four different chambers. Leucocytes could be depleted from platelet concentrates without significant loss. Most (98%) of the lymphocytes were removed from donor marrow intended for transplantation within 3 h and the recovery of myeloid and erythroid clonogenic cells in the graft was similar to that obtained from the standard single chamber centrifuge.

Bone Marrow Cells↗

[Homogenization of samples for the culture of mycobacteria. A comparative study of samples with and without centrifugation].

A homogenization method for sputum samples for the culture of acid-fast bacilli that omits the use of centrifugation, passage test tubes and balances is described. 10% sodium phosphate was used as decontaminating substance. This method facilitates the laboratory work since the samples so treated are incubated at 37 degrees C up to the next day when they are then cultured. 676 samples prepared according to this method were compared with samples prepared according to the standard method; a 6,21% positivity in the former compared to a 5,47% in the latter as well as a lower percentage of contamination were obtained. Contamination occurred in 9,91% of samples without centrifugation and in 14,35% of centrifuged samples.

Bacteriological Techniques↗

Two-dimensional centrifugation for desk-top clinical chemistry.

We have developed a new system for clinical chemistry analysis, the Vision System, in which centrifugal force is used to separate whole blood, measure reagent and plasma volumes, and complete all steps required for a spectrophotometric analysis. The system is based on use of a multichambered plastic test pack containing liquid reagents, which can be centrifuged at 500 X g in two planes, oriented at right angles to each other. Alternating centrifugal fields allows liquid reagents and plasma to flow into highly precise measuring and mixing chambers. A unique flash lamp and diode array spectrometer provide for optical measurements of 10 test packs at as many as eight wavelengths simultaneously. The temperature of each individual test pack is controlled by using a flash lamp coupled to a liquid crystal temperature sensor. Microprocessor control allows as many as 10 different chemistry reactions to be measured simultaneously on whole-blood, plasma, or serum samples. Comparison with results by an established batch-photometric analyzer demonstrated excellent precision and accuracy for various clinical chemistry tests.

Blood Chemical Analysis↗

The calculation of some physical parameters of proteins from sucrose density gradient centrifugation data.

A simplified procedure is described for the calculation of protein physical parameters from data obtained by sucrose density gradient centrifugation. The position of an uncharacterized protein relative to standard proteins is determined after centrifugation through linear 5-20% sucrose gradients prepared in both H2O and D2O. From these data, together with the density of each 5% sucrose buffer, the partial specific volume and standard sedimentation coefficient can be calculated without knowledge of rotor dimensions, angular velocity, time of centrifugation, or solvent viscosity. In the absence of specific solvent-induced changes in protein composition or conformation, the magnitude of error due to the approximations inherent in the method is estimated to be less than 2.3% in partial specific volume or less than 10-15% in sedimentation coefficient.

Centrifugation, Density Gradient↗

Density gradient centrifugation for separation of different stages of Toxoplasma gondii.

Suitable procedures for separation of various stages of Toxoplasma gondii by density gradient centrifugation have been delineated using peritoneal exudate of infected mouse as a model. Separation from host cells was effected by gradient centrifugation at 450 g for 30 minutes. Using Ficoll, dextran and sucrose, average parasite recoveries by pooling up to and including the peak fraction of 73.65%, 66.18% and 65.68% respectively were obtained. Toxoplasma trophozoites peaked at density of 1.040 g/ml with Ficoll, 1.060 g/ml with dextran and 1.110 g/ml with sucrose. In view of successful separation of exo-enteric stages of Toxoplasma by density gradient centrifugation, possible application of this method to isolation of various endo-enteric stages is discussed.

Animals↗

Improved method for detecting hemagglutination by centrifugal analysis.

Centrifugal analysis can be used to detect hepatitis B surface antigen, antibody to rubella virus, and fibrin-related antigen. The procedure is performed with the same reagents used in conventional hemagglutination studies. Positive and negative reactions are distinguished by the rates of erythrocyte clearance in the centrifugal field (delta A/delta time); positive cells move more rapidly than negative cells, and this difference varies directly with the concentration of detectable antigen or antibody. This phenomenon is thought to be a result of the greater adhesion of negative cells to the cuvette's surface. Sensitivity and specificity are greater in the centrifugal analysis technique than in the more conventional hemagglutination tests. False-positive reactions are eliminated and the quantitative data are accurate and reproducible.

Antibodies↗

Centrifugal Cytology, IV. The Prearation of fixed stained dispersions of gynecological cells.

The Centrifugal Cytology technique has been utilized to produce glutaraldehyde fixed stained dispersions of both conventional Ayre scrapes and Davis pipet (PAPette) samples. Light microscope studies of dispersions of both types of cells on conventional microscope slides indicated that both the tinctorial and morphological appearance of the cells after Papanicolaou staining was very similar to that observed with conventional smears and that the same criteria could be utilized with the Centrifugal Cytology dispersions to screen the cells for cancer as had previously been used with the smears. A preliminary study indicated that six out of six positives with no false negatives or false positives were found. The Centrifugal Cytology technique appears to have promise as a method for preparing suspension samples such as pipets of gynecologic cells. Scanning electron microscope studies reveal that the squamous epithelial cells are very thin and at least some of them are covered by a network structure.

Carcinoma, Squamous Cell↗

Improved methodology for the quantitative analysis of mixtures by band centrifugation: reversible equilibration in immunoglobulin preparations.

Double-sector aluminium centerpieces are modified for use in analytical high-speed band centrifugation up to 60,000 rpm. A method has been developed for testing IG preparations according to administrative regulations with special regard to precision and reproducibility. The proposed band-forming centrifugation method with scanner registration in UV absorption optics and special evaluation of the curves gives values in comparison to well-known procedures by Svedberg and Pedersen. Subjective and systematic errors are especially estimated with this method and the sensitivity is best suited to automatic computerization and results are therefore readily available at the end of the centrifuge run within a few minutes. Investigations have been undertaken to analyze reversible equilibration in immunoglobulin preparations; the results are discussed.

Centrifugation, Density Gradient↗

Lecithin/sphingomyelin ratios centrifuged and uncentrifuged amniotic fluid.

The literature suggests that the presence of cellular debris and sediment in amniotic fluid samples may alter the value of the lecithin/sphingomyelin (L/S) ratios, with a loss of as much as 75 percent of the surface-active lecithin1 and consequently a marked change in the L/S ratio. We wish to report our findings on 22 amniotic fluids obtained by transabdominal amniocentesis and analyzed with and without preliminary centrifugation. We find the L/S ratio is indeed unaltered by centrifugation. However, the actual amounts of lecithin and sphingomyelin appear to be lower in centrifuged samples.

Amniotic Fluid↗

A rapid simple method of basophil purification by density centrifugation on Percoll.

This study describes simple and relatively rapid methods of purifying basophils from human peripheral blood. Our initial studies defined the densities of basophils in several donors and helped develop strategies for selectively concentrating basophils by isopyknic centrifugation over Percoll. We layered anticoagulated blood over Percoll of appropriate density, centrifuged these for 10 min, and collected the cells held in Percoll separately from the overlying band of mononuclear cells. Most of the basophils were distributed between densities of 1.072 and 1.078 g/ml, with a peak at approximately 1.074 to 1.076 g/ml. Basophil purity of 24.4 +/- 4% (range 5.6 to 50%) was achieved in a Percoll gradient of 1.076 g/ml due to both the increased numbers of basophils and the low numbers of mononuclear cells at this gradient. The cells isolated by this method are viable, appear morphologically normal, and release histamine to various stimuli in a normal manner. A second centrifugation of the cells obtained from this density over appropriate discontinuous gradients of Percoll leads to further enhancement of basophil purity. The main limitation of this technique appears to be the relatively low yield (percent of recovery) of the basophil (less than or equal to 20% for the two-step procedures).

Basophils↗

Measurements of some blood clotting factors using a centrifugal analyser (Multistat III).

Three coagulation tests are performed on a centrifugal analyser (Multistat III) and the results are compared with results from an ordinary coagulometer (Fibromat). The three tests are Quick's prothrombin time, prothrombin and proconvertin method (Owren's P & P) and activated partial thromboplastin time test (aPTT). The coefficients of correlation for the three methods between the two analysing systems are better than 0.90. The standard deviations of the three analyses are better than 0.60 sec on the centrifugal analyser compared to 1-2 sec on the coagulometer. The centrifugal analyser can perform up to 120 samples per hour.

Blood Coagulation Tests↗

Effects of castration and replacement of androgen on the separation of rat ventral prostate cells by Ficoll gradient centrifugation.

When regressing or growing (hypertrophic) cells from collagenase-digested ventral prostates were centrifuged on isokinetic Ficoll gradients for 6-8 min, they distributed into four fractions. Because of changes in epithelial cell morphology and density following castration to induce regression and replacement of androgens to cause cell growth, and contrary to results with normal rat ventral prostate, stromal cell fraction 2 was contaminated to a greater extent with regressing epithelial cells, as judged by their morphology and binding of radioactive androgens. However, centrifugation for 3 min increased the purity of epithelial cell fraction 4, although the yield of desired cells was reduced. Most cells from endocrine-manipulated rats were viable, as judged by exclusion of trypan blue and the initial incorporation of 3H-uridine. Cells centrifuged on a similar gradient of Percoll separated by a 'sieving' effect, which inverted the order of cellular fractions and removed red blood cells from fraction 2. Metrizamide offered no advantages, compared with Ficoll or Percoll. Neither physiologic nor pharmacologic amounts of testosterone returned the morphology of isolated epithelial cells to normal. To obtain consistent results with prostates from normal or hormone-manipulated rats, one should take care to select an active preparation of collagenase, avoid the use of very old animals, cool the tissue after it is dissociated, and do not apply undigested clumps of cells or overload the gradient. If attention is paid to these details, populations enriched in viable regressing or growing prostate epithelial or stromal cells can be obtained from hormonally manipulated rats.

Androgens↗

Effects of storage temperature and time before centrifugation on ionized calcium in blood collected in plain vacutainer tubes and silicone-separator (SST) tubes.

We studied the stability of ionized calcium and pH in samples stored at either room temperature or 4 degrees C, in centrifuged and uncentrifuged blood-collection tubes and in centrifuged tubes containing a silicone-separator gel (SST tubes). At room temperature, in uncentrifuged blood from healthy individuals, mean ionized calcium usually increased no more than 10 mumol/L per hour; at 4 degrees C it did not change detectably for 70 h. This stability was fortuitous, however: the concentrations of both hydrogen and lactate ions in these samples increased, apparently with offsetting effects on the concentration of ionized calcium. Blood stored for 70 h at 4 degrees C in centrifuged SST tubes, although showing a slightly greater change in ionized calcium, had less change of pH and no change in the ionized calcium corrected to pH 7.4. In 11 heparinized whole-blood samples from eight patients in intensive care, the mean change per hour in ionized calcium and pH after storage at room temperature was +10 mumol/L and -0.04 units, respectively.

Acute Disease↗

Isolation of human megakaryocytes by density centrifugation and counterflow centrigual elutriation.

Density centrifugation and counterflow centrifugal elutriation were utilized to prepare enriched fractions of megakaryocytes from human bone marrow aspirates. This separation method enriched megakaryocytes in initial marrow aspirates by 116- to 463-fold. Approximately 63% of megakaryocytes were recovered from the initial samples, composing 18.7% of the nucleated cells in the final preparations. Mean megakaryocyte diameters of 51.6 micron and 33.8 micron were obtained from fixed and unfixed cellular specimens, respectively. Smaller platelet glycoprotein-positive mononuclear cells with a mean diameter of 20.5 micron were found in the highest concentrations in this final fraction. These cells presumably represent immature megakaryocytic forms. Counterflow centrifugal elutriation provides a means of isolating enriched populations of marrow megakaryocytes. This accessibility to viable populations of human megakaryocytes will allow additional investigation of the terminal events of megakaryocyte development.

Bone Marrow↗

Evaluation of the Cornell-Wisconsin centrifugal flotation technique for recovering trichostrongylid eggs from bovine feces.

Several variables in the Cornell-Wisconsin centrifugal flotation technique were studied using helminthologically sterile bovine feces to which known numbers of Haemonchus contortus eggs had been added. Neither mode of mixing (levigation versus conventional), volume (15-60 mL) of water used for making the feces water suspension nor specific gravity (1.20-1.33) of the sucrose flotation solution affected egg recovery. Optimal times for centrifugation at 264 x g of first the feces water and then the feces sucrose suspension were three and five minutes respectively. Under these conditions 62.6% of the eggs were recoverable and there was a linear relationship between the number of eggs recovered and those added to the feces. About 30% of the unrecovered eggs were found in the fecal debris retained on the strainer. About 5% of the unrecovered eggs were found in the supernatant discarded after the feces water centrifugation and also in the matrix of the viscous sucrose solution. Addition of the detergent Triton X-100 caused a decrease in egg recovery. False negatives were not encountered between 3 to 70 epg; at 1.44 epg there was only one in 14 samples. Optimum procedures for the technique are presented.

Animals↗