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 469 records · Page 26Linked to original sources
PubMed1982

High concentration active enzyme centrifugation studies with pig kidney phosphofructokinase. Detection of 9.8 S, 25 S, and 53 S active polymeric forms.

This laboratory has carried out the first detailed studies of the active polymeric forms of phosphofructokinases over the concentration region of 1 to 1200 micrograms/ml. This includes the concentration range in which the enzymes exist in vivo and the concentration range in which their association-dissociation equilibria shift to yield various polymeric forms. Previously, active enzyme centrifugation experiments were limited to the concentration range below a few micrograms per ml. The present experiments were made possible by the recent development in this laboratory of a new technique called high concentration active enzyme centrifugation (Wei, G. J., and Deal, W. C., Jr. (1979) Biochemistry 18, 1129). We report here three new active polymeric forms of pig kidney phosphofructokinase which have been observed in high concentration active enzyme centrifugation experiments. These include: 1) a 9.8 S form (Mr = 2.6 X 10(5)); 2) a 25 S form (Mr = 1.01 X 10(6)); and 3) a 53 S form (too asymmetric to estimate Mr). In addition, a 5.4 S form is predicted from the Mr (8.8 X 10(4)) of the polypeptide chain obtained from sodium dodecyl sulfate gel electrophoresis; it is not known whether or not it is active. The 9.8 S value is the limiting sedimentation coefficient value observed in active enzyme centrifugation experiments. The 25 S form is indicated by a plateau in the 50 to 200 micrograms/ml region of the s versus c curve. The 53 S form is observed as a plateau in the 600 to 1000 micrograms/ml region of the s versus c curve.

Animals↗
PubMed1978

Centrifugal nerve fibers in the adult human optic nerve: 16 days after enucleation.

The optic nerve stump of a 56-year-old patient was removed 16 days after enucleation of the corresponding eyeball. The stumps of numerous centrifugal (efferent) nerve fibers are demonstrated histologically in this optic nerve central to the 16-day old surgical cut. Electron-microscopic views of the centrifugal nerve fibers are offered for the first time. The findings are further evidence for the existence of centrifugal fibers in the human optic nerve. The nerve fiber stumps exhibit reactive terminal swellings pointing towards the surgical cut indicating axoplasmic flow in that direction. It is of special interest that the centrifugal nerve fibers of this 56-year-old patient lack any evidence of attempted regeneration that has been observed under similar conditions in th optic nerve stump of a child.

Age Factors↗
PubMed1997

Usefulness of dark field microscopy after differential centrifugation in the early diagnosis of leptospirosis in dog and its human contacts.

1. We found leptospira in the blood of two out of three police dogs by dark field microscopic examination after high speed centrifugation. One dog had fever and the other was asymptomatic. Leptospira could not be seen in the urine of one police dog which died of jaundice. 11 out of 21 human contacts were found to be positive for leptospira after low speed centrifugation and 5 after high speed centrifugation. One child had jaundice and an another child had fever. Others had mild symptoms of headache to none. Dark field microscopy after differential centrifugation is useful in the early diagnosis of leptospirosis and thereby could prevent later complications like jaundice.

Adult↗
PubMed1998

Arm pain among Swedish fighter pilots during +Gz flight and centrifuge exposures.

BACKGROUND: The purpose was to survey the occurrence of arm pain among Swedish fighter or test pilots in connection with exposures to high +Gz load when flying or performing centrifuge tests. HYPOTHESIS: +Gz induced arm pain occurs in connection with high +Gz loads in flight as well as in centrifuge tests of high performance fighter pilots. METHODS: A questionnaire was used for data collection regarding +Gz induced arm pain. Respondents were 35 Swedish Air Force Viggen and Gripen fighter pilots who had previously participated as subjects in centrifuge tests between 1990 and 1995 at Brooks Air Force Base, TX, either with the standard anti-G suit or with extended coverage anti-G suit with pressure breathing during +Gz. RESULTS: Of the respondents, 55% reported that they had experienced arm pain during flight at least once and 42% experienced it more than three times. However, arm pain was more common in the centrifuge tests (82% once; and 42% more than 3 times). CONCLUSIONS: Presence of arm pain during high performance fighter aircraft flights is a phenomenon that should be taken into consideration when designing high performance aircraft or +Gz protective equipment.

Adult↗
PubMedDate not supplied

Enrichment of vital adult cardiac muscle cells by continuous silica sol gradient centrifugation.

A major improvement in the isolation of vital adult cardiocytes was achieved by isopycnic preformed continuous silica sol gradient centrifugation after perfusion of the heart with collagenase. Vital rat cardiocytes were enriched to 90-95% vital cells reproducibly and constantly by one- or two-step gradient centrifugations. The isolated cardiocytes were tolerant to calcium concentrations up to 0.03 mmol/l, to diluted human serum, and to human complement. Gentamycin (50 microgram/ml) exerted a cytotoxic effect on myocytes, whereas Penicillium and Streptomycin in concentrations of 50 IU/ml did not induce cytolysis of vital cells. Digoxin 15 ng/ml) decreased the natural decay of myocytes of 20% in 25 hours to 8%. Enriched of vital cardiocytes by silica sol gradient centrifugation following their isolation by perfusion with collagenase may be helpful for investigations depending on a high yield of vital myocardial cells.

Animals↗
PubMed1970

Fractionation of liver plasma membranes prepared by zonal centrifugation.

1. Plasma membranes were isolated from crude nuclear sediments from mouse and rat liver by a rate-dependent centrifugation through a sucrose density gradient contained in the ;A' type zonal rotor. 2. The membranes were further purified by isopycnic centrifugation, and characterized enzymically, chemically and morphologically. 3. When the plasma-membrane fraction of sucrose density 1.17g/cm(3) was dispersed in a tight-fitting homogenizer, two subfractions of densities 1.12 and 1.18 were obtained by isopycnic centrifugation. 4. The light subfraction contained 5'-nucleotidase, nucleoside diphosphatase, leucine naphthylamidase and Mg(2+)-stimulated adenosine triphosphatase activities at higher specific activities than unfractionated membranes. The heavy subfraction was deficient in the above enzymes but contained higher Na(+)+K(+)-stimulated adenosine triphosphatase activity. 5. The light subfraction contained twice as much phospholipid and cholesterol, and three times as much N-acetylneuraminic acid relative to unit protein weight as the heavy subfraction. Polyacrylamide-gel electrophoresis indicated differences in protein composition. 6. Electron microscopy showed the light subfraction to be vesicular. The heavy subfraction contained membrane strips with junctional complexes in addition to vesicles.

Adenosine Triphosphatases↗
PubMed1965

ISOLATION OF RELAXING PARTICLES FROM RAT SKELETAL MUSCLES IN ZONAL CENTRIFUGES.

Supernatants of rat skeletal muscle homogenates were fractionated by differential centrifugation and by zonal centrifugation in sucrose density gradients. Cytochrome oxidase was employed as an enzymatic marker for locating mitochondria. The subcellular fractions were also assayed for their ability to prevent the ATP-induced contraction of myofibrils. Both the mitochondrial and microsomal fractions obtained by differential fractionation were found to be rich in such relaxing activity, and the microsomal fraction was appreciably contaminated by mitochondria. In contrast to this, when fractionation was carried out by means of zonal centrifugation (4200 RPM x 205 min. to 40,000 RPM x 60 min.), relaxing activity was found to be associated only with particles having the sedimentation characteristics of microsomes (s(20,w) estimated to be between 370 and 1880S). Relaxing activity was not detected in the regions of the gradient containing either the starting sample zone (soluble phase) or the mitochondrial peak. The microsomal relaxing particles showed negligible cytochrome oxidase activity.

Adenosine Triphosphate↗
PubMed1971

Zonal centrifuge applied to the purification of Herpesvirus in the Lucké frog kidney tumor.

A series of "winter" and "summer" Lucké kidney tumors of the frog (Rana pipiens) were homogenized and fractionated by differential centrifugation into nuclear, mitochondrial, and mitochondrial supernatant fractions. Winter tumors often contained high concentrations of herpesvirus, whereas no virus was observed in any of the summer tumors. The crude tumor fractions were further purified by rate-zonal sucrose gradient centrifugation in a B-XV zonal rotor. Gradient fractions rich in an enveloped, nucleated form of the herpesvirus from certain winter tumors have induced renal tumors when injected into developing frog embryos. Zonal centrifugation was followed by isopycnic banding of the virus zones for further purification of the different morphological forms of the virus.

Animals↗
PubMed1972

Purification of bacterial endotoxins by zonal centrifugation.

In this paper, we describe a cultivation procedure in large-capacity fermentors (200 liters) and the purification of the Salmonella crude extracts by means of zonal centrifugation in a sucrose gradient. Briefly, the endotoxin has been extracted from salmonellae with hypertonic solutions. The crude endotoxin was shown to contain several antigens, mainly r(1), r(2), r(3), or heterologous antigen. The heavy endotoxin was isolated and purified previously by enzymatic digestion, followed by a series of gel filtrations on Sephadex or Sepharose columns. We report the isolation and purification of heavy endotoxin in sucrose gradients, with the use of a B XIV titanium zonal rotor. From 150 to 300 mg of the crude material resuspended in a solution containing 1 m sodium chloride, 0.1 m sodium citrate, and 2.5% (w/w) sucrose, has been submitted to zonal centrifugation in gradients consisting of 5 to 25% (w/w) sucrose, also containing 1 m sodium chloride and 0.1 m sodium citrate. An overlay of 200 ml of 1 m sodium chloride-0.1 m sodium citrate was introduced after the sample. The separations were obtained after centrifugation for 3.5 hr at 35,000 rev/min (integralw(2)dt = 1.66 x 10(11)) at 4 C; the heavy endotoxin sedimented as heterogeneous material, from the middle toward the distal portions of the gradient. The heterologous antigens (r(1), r(2), r(3)), as well as bacterial proteins, remained in the sample zone. The heavy endotoxin recovered from the gradients was quite pure, as revealed by immunodiffusion tests against several antibacterial sera.

Animals↗
PubMed1970

Density gradient centrifugation studies on lymphocytic choriomeningitis virus and on viral ribonucleic acid.

Lymphocytic choriomeningitis (LCM) virus, Traub strain, was purified from BHK-21 tissue culture medium. The virus was then analyzed by equilibrium centrifugation and rate zonal centrifugation in sucrose gradients. A buoyant density in sucrose of 1.18 g/ml was found and the S(20, w) value was estimated to be about 470 to 500S. Furthermore, the (3)H-uridine-labeled ribonucleic acid (RNA) from virus was extracted from LCM virus and analyzed by rate zonal centrifugation. Two major and one minor single-stranded RNA components were found with sedimentation coefficients of 28, 22, and 18S.

Animals↗
PubMed1978

Iodoamino acid composition of poorly iodinated human thyroglobulin fractionated by isopycnic centrifugation.

The distribution of iodotyrosines and iodothyroinines has been studied in poorly iodinated 19 S thyroglobulins isolated by sucrose gradient centrifugation from five human thyroid tissue. The 19 S thyroglobulins have been fractionated by isopycnic centrifugation and 34.5% rubidium chloride gradient. The distribution of iodoamino acids depends on the total iodine content of each fraction. The variations in MIT) and DIT residues with increasing levels of iodination are not identical, the elevation of DIT residues being higher than that of MIT. The number of T4 residues increases quite rapidly after 5 atoms of iodine while T3 increases slightly and slowly. It is shown here that, even after fractionation of poorly iodinated thyroglobulin, the synthesis of thyroid hormones is observed at a level of iodine content as low as 1.4 and 1.8 atoms per molecule of thyroglobulin. This shows that the thyroglobulin fractions obtained by isopycnic centrifugation are still heterogeneous, although less than the initial non-fractionated thyroglobulin. In order to explain our data, it must be admitted that a large proportion of thyroglobulin molecules are not iodinated.

Centrifugation, Density Gradient↗
PubMed1980

Subcellular fractionation of human intestinal mucosa by large-scale zonal centrifugation. I. Characterization of subcellular organelles in the distal part of the ileum.

The subcellular organelles in human ileal mucosa have been characterized by large-scale rate zonal and isopycnic density-gradient centrifugation. Mucosal scrapings were obtained from surgical specimens and the cells disrupted by extrusion under controlled pressure. The homogenized cells were then centrifuged to prepare a cell extract and the extract fractionated in a single-step procedure by zonal centrifugation on a continuous sucrose gradient. The subcellular organelles (brush borders, basal-lateral membranes, lysosomes, mitochondria, and endoplasmic reticulum) were located in the density gradient by assay of marker enzymes. Since a large number of analyses can be done on each fraction of interest, this fractionation technique may be used to study a variety of compounds and concepts involved in the subcellular physiology and pathology of human ileal mucosa.

Adult↗
PubMed1990

The evaluation of neutral density separation utilizing Ficoll-sodium diatrizoate and Nycodenz and centrifugal elutriation in the purification of bovine and canine islet preparations.

This study evaluates the potential of a neutral density separation technique using iodinated gradient media in combination with Ficoll or alone at two different densities for the purification of bovine and canine islets isolated by a continuous digestion-filtration technique. In addition, centrifugal elutriation is applied to the purification of isolated bovine islets. A single density layer of Ficoll-sodium diatrizoate or Nycodenz at densities of 1.080 g/ml or 1.085 g/ml resulted in an recovery of 47.4% to 77.4% bovine islet volume with bovine islet purities ranging from 43.5% to 49.0%. The use of a single density layer of Ficoll-sodium diatrizoate at 1.080 g/ml and Nycodenz at 1.085 g/ml resulted in recoveries of 86.4% and 56.2% canine islet volume with canine islet purities of 58% and 63.5%, respectively. The bovine islet enriched fraction (flow rates 50-90 ml/min at a rotor speed of 200 rpm) obtained by centrifugal elutriation was 20.0 +/- 3.5% pure, the average recovery of bovine islet volume obtained by centrifugal elutriation was 59.0 +/- 10.7%. It is suggest that a further refinement of factors like osmolality, viscosity, pH, ionic composition and temperature of iodinated density gradient media may allow continued improvement of islet purity and recovery obtained by the simple neutral density separation technique.

Animals↗
PubMed1996

Critical centrifugal forces induce adhesion rupture or structural reorganization in cultured cells.

Cultured epithelial cells were exposed to accelerations ranging from 9,000 to 70,000g for time periods of 5, 15, or 60 min, by centrifugation in a direction tangential to their plastic substrate. Three regimes describe the cellular response: (1) Cell morphology and density remain unaltered at forces below a threshold of about 10(-7) N; (2) Between this critical force and a second threshold of about 1.5 10(-7)N, the number of adherent cells decreases exponentially with time and acceleration, with no alteration of cell morphology. This behavior can be modeled by a constant probability of detaching and by an exponential distribution of cell-to-substrate adhesive forces; (3) Past the second threshold, cells that are still adherent exhibit elongated morphologies, the degree of elongation increasing linearly with the force. The fact that cells lose their vinculin-rich focal contacts past the first threshold and that cells cultured on gelatin-coated plastic show an increased resistance to detachment suggests a rupture of cell-to-substrate adhesions upon centrifugation. Immunofluorescent labeling of cells for actin and tubulin shows a reorganization of the cytoskeleton upon centrifugation, and treatment of cells with the drugs cytochalasin D and nocodazole demonstrates that cytoskeletal elements are actively involved in the structural deformation of cells past the second acceleration threshold, microtubules and microfilaments paying antagonistic roles.

Breast↗
PubMed1975

The total containment of a batch-type zonal centrifuge.

A batch-type zonal centrifuge has been modified and totally contained for use with biologically hazardous materials. A sealed cabinet encloses the centrifuge and the ancilliary equipment. It is operated with a flow of filtered air when the zonal system is on, decontaminated with ethylene oxide, and maintained at a negative pressure throughout. The centrifuge subsystems can be drained, flushed, and decontaminated with ethylene oxide before an engineer services the machine. The sample handling system within the cabinet is remotely controlled.

Centrifugation, Zonal↗
PubMed2002

Comparison of two density gradient centrifugation systems for the enrichment of disseminated tumor cells in blood.

BACKGROUND: The detection of disseminated tumor cells in peripheral blood is limited by the presence of very few tumor cells within a large number of blood cells. Therefore, tumor cell detection calls for enrichment systems with effective depletion of blood cells and high tumor cell recovery. METHODS: We compared the new density gradient centrifugation method OncoQuick with the standard method of Ficoll. The enriched cell fractions were quantified. Tumor cell spiking experiments examined the recovery of tumor cells as detected by immunocytochemistry and cytokeratin-20 reverse transcriptase-polymerase chain reaction (RT-PCR). Clinical application of OncoQuick was evaluated in 37 peripheral blood samples of patients with gastrointestinal carcinomas. RESULTS: The depletion of mononuclear cells (MNCs) in the enriched cell fraction after OncoQuick centrifugation was 632-fold, with an average cell number of 9.5 x 10(4), compared with Ficoll, with a depletion factor of 3.8 and a mean number of 1.6 x 10(7) MNCs. The mean tumor cell recovery rates were 87% for OncoQuick and 84% for Ficoll. The increased depletion of MNCs with OncoQuick centrifugation further simplified immunocytochemical evaluation by reducing the number of cytospins and increasing the tumor cell density. Due to the reduced number of co-enriched MNCs by OncoQuick, the blood volume, which could be analyzed in one RT-PCR reaction, was increased up to 30 ml. Examination of peripheral blood samples from 37 patients with gastrointestinal tumors showed a cytokeratin-20 detection rate of 30% and a significant correlation with the presence of distant metastases (P < 0.02). CONCLUSIONS: OncoQuick significantly reduced the co-enriched number of MNCs, with a high tumor cell recovery rate. Processing blood from tumor patients with OncoQuick increased the chance of detecting circulating tumor cells.

Cell Count↗
PubMed1993

Centrifuge-blotting of proteins after separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

A protein transfer method which allows elution and immobilization of polypeptides onto a polyvinylidene difluoride (PVDF) membrane has been developed. The protein band in a gel is eluted by centrifugation. The centrifuge-blotting procedure involves the following steps: (i) visualization of the protein in a sodium dodecyl sulfate (SDS)-polyacrylamide gel with 1 M KCl, (ii) excision of the protein band and equilibration for 15 min in a solution of 0.05% SDS/5% methanol/0.02% dithiothreitol in distilled water, (iii) placing the gel piece in direct contact with the PVDF membrane in the receptacle, (iv) centrifugation at 3000 g for 1 h. A 10 kDa cut-off dialysis membrane is placed beneath the PVDF membrane to retain nonimmobilized protein. The N-terminal sequence of the immobilized protein on the PVDF membrane was determined. For proteins with a molecular mass less than 30 kDa, an overall yield between 10%-30% has been obtained.

Centrifugation↗
PubMed1975

Centrifugal elutriation: separation of spermatogenic cells on the basis of sedimentation velocity.

Various types of cells from the testes of mice and hamsters were separated according to differences in sedimentation velocity by centrifugal elutriation, a counterflow centrifugation technique. Approximately 3 times 10(8) cells, prepared from six mouse testes or from one hanster testis, were separated into 11 fractions in less than two hours as compared to the 4--5 hours required for sedimentation at unit gravity ("Staput"). Fractions enriched in elongated spermatids and spermatozoa (100%), stages 1--8 spermatids (69%) and pachytene spermatocytes (58%) were obtained from mouse testis dispersions. Similarly enriched fractions were obtained from hamster cells. A single fraction enriched in stages 1--8 spermatids (mouse) was prepared in less than 30 minutes. As many as 2 times 10(9) cells were separated in a single procedure. Spermatogenic cells exhibited no evidence of structural damage with trypan blud and phase microscopy, and recovery was essentially 100%. Centrifugal elutriation had no effect on sperm motility or on the plating efficiency of CHO cells.

Animals↗