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At least 1,099 records · Page 61Linked to original sources
PubMed1997

Effect of gemfibrozil on centrifugal behavior of rat peroxisomes and activities of peroxisomal enzymes involved in lipid metabolism.

The effect of gemfibrozil, and analogue of clofibric acid, on the centrifugal behavior of peroxisomes and activity of peroxisomal enzymes involved in lipid metabolism was studied. Rats were fed chow containing 0.2% gemfibrozil for 2 weeks. Nycodenz gradient centrifugation of the light mitochondrial fraction revealed that peroxisomes of gemfibrozil-treated rats were concentrated in fractions of higher density compared with control rats. The activity of fatty acyl-CoA oxidase, crotonase, beta-hydroxybutyryl-CoA dehydrogenase, and thiolase (individual enzymes of the peroxisomal fatty acid beta-oxidation system) were enhanced 9.6, 2.3, 3.4 and 9.1 times respectively compared with controls, by treatment. The hydroxymethylglutaryl-CoA (HMG-CoA) reductase (rate-limiting enzyme of cholesterol synthesis) activity of peroxisomes and microsomes was greatly increased by in vivo treatment with gemfibrozil, but was decreased by addition of the agent to the assay mixture of the enzyme. Gemfibrozil directly inhibited the reductase activity and did so at a lower concentration than clofibric acid. Peroxisomal reductase was more resistant to damage by the agent than the microsomal enzyme. The HMG-CoA reductase activity of peroxisomes and microsomes of hyperlipidemic rats was also increased by in vivo treatment with gemfibrozil, whereas the serum cholesterol level was hardly changed. These results indicate that the effect of gemfibrozil differs from that of clofibric acid, the main difference being the effect on HMG-CoA reductase. Gemfibrozil increased reductase activity in vivo, unlike clofibric acid, but inhibited the enzyme in vitro to a greater extent than clofibric acid.

Animals↗
PubMed1999

Comparative study of autologous fibrin glues prepared by cryo-centrifugation, cryo-filtration, and ethanol precipitation methods.

To establish a speedy preparation method for the fibrinogen-rich fraction (FRF) from autologous plasma using fibrin glue, we compared the concentrations and yields of coagulation factors in FRF prepared by 3 methods. Human plasma from healthy volunteers was divided into 3 samples. Two samples were frozen at -20 degrees C in a freezer and defrosted in a 4 degrees C water bath. One sample of defrosted plasma was centrifuged and FRF was obtained (C method). Another sample of defrosted plasma was filtered and FRF was obtained (F method). The last sample was treated with cold ethanol(1/10) in a 4 degrees C water bath and FRF was obtained after centrifugation (E method). The concentrations of fibrinogen, fibronectin, factor XIII, and plasminogen in each obtained FRF were measured and yields were calculated. (1) The volume of FRF obtained by the E method was greater than that by the C method, but less than that by the F method. While the variation in volume obtained by the E method was the lowest among the 3 methods; (2) the concentrations of fibrinogen obtained by the E and C method were similar, but the yield from the E method was the highest; (3) the concentration and yield of fibronectin from the E and C method were similar and were greater than those by the F method; (4) the concentration and yield of factor XIII from the E method were significantly higher than those from the other methods; (5) the E method preparation time was about 1 h, the shortest among the 3 methods. These results indicate that high quality FRF from autologous plasma can be prepared easily and within 1 h by the E method.

Adhesiveness↗
PubMed2006

Detection of a small number of Cryptosporidium parvum oocysts by sugar flotation and sugar centrifugation methods.

Detection rates from the samples including a small number of Cryptosporidium parvum oocysts were compared between the sugar flotation and the sugar centrifugal flotation methods. As the results, the oocysts were detected from 70 and 80 of 100 samples including 6.0x10(2) and 1.0x10(3) oocysts per 1 ml by the flotation method, respectively, whereas from 52 and 53 of the same samples by the centrifugal flotation method. Therefore, it was considered that the flotation method is the most suitable method for the detection from samples including a small number of Cryptosporidium oocysts. It is also suggested that results of the sugar flotation method were reliable for samples including more than 1.0x10(3) oocysts/ml.

Animals↗
PubMed1989

The effect of centrifuging bone cement.

We have tested the porosity and fatigue life of five commonly used bone cements: Simplex P, LVC, Zimmer regular, CMW and Palacos R. Tests were conducted with and without centrifugation and with the monomer at room temperature and, except for LVC, at 0 degrees C. We found that the fatigue life of different specimens varied by a factor of nearly 100. It did not depend on porosity alone, but was more influenced by the basic composition of the cement. Simplex P when mixed with monomer at 0 degrees C and centrifuged for 60 seconds had the highest fatigue life and was still sufficiently liquid to use easily.

Bone Cements↗
PubMed2005

Determining the subunit structure of phosphodiesterases using gel filtration and sucrose density gradient centrifugation.

Size-exclusion chromatography (gel filtration) is a widely used method to determine the molecular weight of a protein. Often, the elution volume of several standard proteins is plotted against their known molecular weight to generate a standard curve, which is then used to determine the molecular weight of the protein of interest by its elution volume. However, gel filtration does not measure the mass of a particle as such, but the Stokes radius (Rs), a property dependent on mass, shape, and hydration of a protein. Thus, this method works well only if the protein of interest has a spherical symmetrical shape and an average hydration level. For all other proteins, the use of gel filtration as the sole means to determine the molecular weight will be misleading. The molecular weight of any given protein can be calculated, however, using the method of Siegel and Monty. This method combines Stokes radii obtained from gel filtrations and sedimentation coefficients derived from density gradient centrifugations to calculate the mass of a protein independently of its shape or hydration. It has been shown previously that PDE4D3, a representative of the long PDE4 splice forms, behaves as a dimer, whereas PDE4D2, a prototype of the short PDE4 splice forms, is a monomer. Both proteins exhibit an anomalous behavior on gel filtration columns. For this reason, they are used in this study to demonstrate the necessity of performing both gel filtration and density gradient centrifugation to determine the molecular weight of a protein.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1987

[Centrifugal ultrafiltration method for determining the percent of free testosterone in serum].

Serum free testosterone (T) % in the follicular phase of 11 normal women, 11 normal men and 30 pregnant women of 5 to 39 weeks of gestation were determined by the centrifugal ultrafiltration method (CUF), which was performed at the centrifugation of 5 minutes, 1000 g and 37 degrees C, using the Amicon MPS-3 and YMT membrane. These conditions were shown to be appropriate for measuring the free T. There was a significant correlation between the percentage of free T due to the CUF and the equilibrium dialysis method (ED) (r = 0.88, p less than 0.01). Serum free T % and free T concentrations by the CUF method were, respectively, 2.89 +/- 0.09 (SE) % and 166.3 +/- 9.8 pg/ml in normal men, 1.76 +/- 0.09% and 9.4 +/- 0.7 pg/ml in non-pregnant women and 1.14 +/- 0.03%, 22.4 +/- 1.4 pg/ml in pregnant women. Serum free T % in non-pregnant women was significantly lower than in men (p less than 0.001) and higher than in pregnant women (p less than 0.001). In the CUF method the intra-assay CV was 4.9% in women, 6.0% in men and the inter-assay CV was 5.1% in women, 6.2% in men. The CUF method was more simple, rapid and accurate on the determination of the free T in serum than the ED method.

Centrifugation↗
PubMed1980

D-Glucose transport into suspended human fibroblasts. Rapid measurement of uptake by silicone oil filtration centrifugation, and comparison of different cell detachment procedures.

The uptake of 14C-labeled D-glucose into the cellular space of human diploid fibroblasts (Flow 2000)--grown to confluency and detached with trypsin-EDTA--was studied using silicone-oil-layerfiltering centrifugation. This method is rapid enough to enable the determination of initial transport rates, which are not complicated by subsequent metabolism of the hexose taken up into the cells. D-Glucose uptake shows saturation kinetics with a Km of 1.8mM and maximal transport capacity of 4--8 nmol/(10(6) cells x min) at 20 degrees C. This saturable transport system is responsible for at least 80% of the total glucose taken up into the cells in the concentration range tested (0.1--10mM D-glucose in incubation medium). The glucose carrier is stereo-specific, is independent of sodium and potassium ions, and is inhibited by cytochalasin B. Its temperature dependence reveals an activation energy of 3 1 kJ/mol (7.5 kcal/mol; Q10 approximately equal to 1.5). As detachment of the cells from the culture flasks is necessary for applying silicone-layer-filtering centrifugation, various detachment procedures were tested. In the enzymatic procedure cells were treated with either trypsin or pronase. In the chelating method, Ca2+ and Mg2+ ions were chelated by EDTA and K+ ions with sodium tetraphenylborate. For mechanical detachment, cells were grown initially on plastic foil. After each of these detachment procedures the transport of D-glucose was the same. It is therefore concluded that this method of rapid measurement of D-glucose uptake in suspended human fibroblasts may serve as an alternative to the uptake measurement with glucose analogues in attached cells when studying the hexose transport system in human diploid fibroblasts.

Biological Transport, Active↗
PubMed2004

The CentriMag: a new optimized centrifugal blood pump with levitating impeller.

PURPOSE: Blood pumps are routinely used for circulatory and pulmonary support. However, blood trauma and pump failure remain severe drawbacks of currently available pump models. This study evaluated the first clinical application of a new, totally bearingless centrifugal blood pump (CentriMag). MATERIAL AND METHODS: A centrifugal pump consisting of an electromagnetic suspended impeller was used as a blood pump during beating-heart coronary artery bypass grafting in 11 patients (mean weight, 77.4 kg). Heparin in a bolus of 150 IU/kg body weight was administered, and activated clotting time was maintained at approximately 180 to 250 seconds during extracorporeal circulation. Pump-induced blood trauma was evaluated by measurement of plasma free hemoglobin (PFH), lactate dehydrogenase (LDH), hematocrit, total bilirubin, and platelet levels. RESULTS: Mean pump flow was 3.3 +/- 0.62 L/min, and mean pressure gradient through the oxygenator was 69 +/- 4 mm Hg. No pump dysfunction occurred during a mean application time of 105 +/- 26 minutes. Inspection of the pump housings showed no internal thrombus formation despite low-dose heparinization. Only slight hemolysis was observed with a mean PFH level of 1.96 micromol/L; LDH, 460 U/L; hematocrit, 33%; total bilirubin, 25 micromol/L; and platelets, 191 x 10(3)/microL. CONCLUSIONS: The bearingless CentriMag blood pump is a safe and reliable new device that produces only minimal hemolysis. It seems to be suited for long-term evaluation as a blood pump for extracorporeal membrane oxygenation or as ventricular assist device.

Aged↗
PubMed1985

Biochemical and membrane functional alterations in red cells during preparation and storage of leukocyte- and platelet-poor red cell suspensions prepared by warm-centrifuge method.

A simple technique for effective removal of leukocytes and platelets from red blood cells (RBC) was reported. In that technique whole blood was incubated at 37 degrees C. In the modified procedure phosphate buffer was added to the starting RBC. Changes in red cells during preparation and storage at 4 degrees C of RBC suspensions were evaluated. Reconstituted RBC were incubated at 37 degrees C for 1 hr. After centrifugation, the lower compartment was separated with a special apparatus and diluted with 0.9% saline, which contained 78% red cells and 3% leukocytes and platelets of the starting RBC. In the incubation and subsequent preparation steps, 2,3-diphosphoglycerate levels were decreased, but not adenosine triphosphate. One-day storage caused no serious metabolic changes in red cells. Red cell osmotic fragility was not changed throughout. Stored RBC maintained sterility. The in vitro data indicate that red cells in leukocyte- and platelet-poor RBC suspensions processed with the warm-centrifuge method retained high biochemical and membrane functional abilities for 1 day.

2,3-Diphosphoglycerate↗
PubMed1996

Rapid and large-scale isolation of microsomal fraction of mouse liver by lyophilization and low speed centrifugation.

We could prepare the microsomal fraction of mouse liver, without using an ultracentrifuge but with a low speed centrifuge. The procedure includes 1) lyophilization of post-mitochondrial fraction (9,000 x g supernatant) of mouse liver, 2) powdering of the lyophilized sample, 3) the addition of 1.15 per cent potassium chloride solution or distilled water, which afforded microsomal aggregates, 4) sedimentation of microsomal fraction by low-speed centrifugation (20,000 x g, 20 min). The sedimented microsomal fraction showed normal contents of cytochrome P-450 and cytochrome b5, and gave a normal pattern on SDS polyacrylamide gel electrophoresis and normal electron microscopic feature. This method should be convenient for rapid and large-scale preparation of microsomes, especially for the preparation of cytochrome b5 and cytochrome P-450.

Animals↗
PubMed1982

Isolation of rat Leydig cells by density gradient centrifugation.

A rapid method for preparing Leydig cells from rat testes is described. An interstitial cell suspension, prepared by collagenase treatment of decapsulated testes, was centrifugal for 10 min over a cushion of 60% (v/v) Percoll to remove red blood cells, and then centrifuged for 20 min in a 0-60% linear density gradient of Percoll. Seventy-four per cent of the cells present in that fraction of the gradient comprising 35-50% Percoll were Leydig cells; the yield from each testis was about 1.5 x 10(6) cells. The Leydig cells appeared viable, excluded Trypan blue, possessed high-affinity binding sites for human chorionic gonadotrophin (hCG) and synthesized increased quantities of testosterone in response to hCG. The cells could be stored overnight in 20% (v/v) glycerol at -20 degrees C, with only minimal effect on the specific activities of a number of enzymes used as markers of subcellular components. Testosterone production in vitro by the cells after storage for 20 h was greater than that of hCG-stimulated fresh cells and was not further increased by hCG.

Animals↗
PubMed1986

Purification of dispersed rat adrenal zona glomerulosa cells by Percoll density gradient centrifugation and the isolation of a population of cells highly responsive to adrenocorticotrophin.

Percoll density gradient centrifugation is a simple, inexpensive and convenient method to eliminate contaminating zona fasciculata (ZF) cells from unpurified rat adrenal capsular glomerulosa (ZG) cell preparations (with less than 0.1% ZF cells in the final cell preparation). Basal steroid (aldosterone and corticosterone) output by the purified (PG) cells was unchanged. These purified cells, although free from ZF contamination, were more highly responsive than expected to ACTH (3 nmol/l). When PG cells were further separated by Sephadex column filtration, the filtered PG cells exhibited the steroidogenic response of ZG cells purified by unit gravity sedimentation and Sephadex column filtration, i.e. reduced basal steroid output and an ACTH response reduced to that stimulated by K+ (8.4 mmol/l). Although the cells retained in the column resembled the filtered PG cells ultrastructurally, they showed unchanged basal steroid output and a high ACTH response with increased late-pathway activity (the conversion of corticosterone to aldosterone). By combining Percoll density gradient centrifugation and Sephadex column filtration we have a method for the isolation and study of both the high- and low-response rat ZG cells which are free from ZF contamination.

Adrenal Cortex↗
PubMed1996

Relationship between response to interferon therapy and detection of hepatitis C virus RNA by differential flotation centrifugation.

Circulating hepatitis C virus (HCV) particles can be fractionated by means of differential flotation centrifugation. It is reported that in the bottom fraction HCV is in the form immune complexes, whereas in the top, it is free of antibodies. We evaluated the significance of circulating complex and free HCV in chronic hepatitis C, and assessed the relationship in terms of the response to interferon (IFN) therapy. We examined sera before, just after, and 1 year after administering IFN to 18 patients with chronic hepatitis C, 10 of whom responded (group CR), and 8 did not (group NR). The amounts of virus were similar between both groups before therapy. After differential flotation centrifugation with 1.063 g/ml of NaCl, the top and bottom fractions were assayed for HCV RNA. Before therapy, HCV RNA was detected in the top fraction in 1 of 10 in group CR, and in 6 of 8 in group NR (P < 0.05, chi-square test). HCV RNA was positive in the bottom fraction of all samples. In a follow-up study of group NR, HCV RNA was detected in the top fraction in 3 of 8 just after IFN therapy, and in 7 of 8 after 1 year. This study suggests that the presence of HCV in the top fraction can predict a poor response to IFN therapy.

Adult↗
PubMed2002

Creating arrays by centrifugation.

We describe afast, low-cost, and reliable way of creating arrays from sample molecules of interest present within microformatted sample vessels (such as 1536-well microplates). The principle involves simple centrifugal transfer of molecules of interest onto a solid planar or membrane surfaces placed over the initial sample vessel. Tools and procedures are presented that validate the robustness and precision of this facile solution to an otherwise difficult problem in modern molecular genetics. The availability of transferred DNA molecules for hybridization is also demonstrated. In conclusion, this "centrifugal-array" concept should help research studies to be applied on ever-greater scales with very simple machinery.

Centrifugation↗
PubMed1999

Centrifugal assay for fluorescence-based cell adhesion adapted to the analysis of ex vivo cells and capable of determining relative binding strengths.

Cell adhesion assays are widely used to identify novel cellular ligands, novel cell surface receptors for these ligands and to elucidate the mechanisms responsible for the underlying cellular and molecular interactions. We report here the development of a novel centrifugal assay for fluorescence-based cell adhesion (CAFCA) that offers a number of advantages over the currently available assays. CAFCA is based on two centrifugation steps: one to allow for the synchronization of the initial cell-substratum contact and one to enable both a defined removal force to be exerted onto the cells for displacement of unbound cells and determination of the relative binding strengths of adhering cells. The fluorescently tagged cells are monitored in specifically devised, disposable microplate assemblies by a two-sided fluorescence detection through the computer-interfaced SPECTRAFLUOR microplate fluorometer. The assay is rapid, accurate, reproducible and adaptable to small numbers of delicate primary cells that can ideally be labeled with the fluorochrome calcein AM (or analogous vital fluorescent dyes). Most uniquely, CAFCA provides (i) means of assessing the precise number of cells bound to a given substratum out of the total amount of cells contained within the population to be analyzed and (ii) a means of establishing the attachment strengths (i.e., dynes/cell) in a high number of samples/conditions simultaneously. CAFCA is therefore expected to make a substantial methodological and conceptual contribution to the range of available assays aimed at examining cellular interactions in vitro and promises the potential of being able to transpose automated versions of these tests for routine use in laboratories.

Animals↗
PubMed2001

[Proposal from space radiation biologists. Importance of Centrifuge Facility in the study of biological effect by space radiation].

In microgravity, astronauts were constantly exposed to space radiation containing various kinds of radiation with a low-dose rate during long-term stays in space. It is very difficult to define the relative biological effectiveness (RBE) of space radiation under microgravity. In order to understand correct the RBE of space radiation, therefore, utilization of Centrifuge Facility is desired as a control experiment at orbit for removing other factors such as microgravity except space radiation. Here, we summarized the importance of Centrifuge Facility in the study of biological effect of space radiation.

Aerospace Medicine↗
PubMed1989

Fluid distribution in pork, measured by x-ray diffraction, interference microscopy and centrifugation compared to paleness measured by fiber optics.

Moderately PSE (pale, soft, exudative) and moderately DFD (dark, firm, dry) pork was examined by x-ray diffraction for interfilament separation, by differential interference contrast microscopy for interfiber area, and was centrifuged to measure water holding capacity (WHC). Internal reflectance spectra were measured by fiber optics. For PSE to DFD pork, filament separation ranged from 39 to 48 nm, interfiber area from 42 to 3%, and WHC from 49 to 64%, respectively. The correlation of reflectance with interfilament separation varied considerably with wavelength (reaching r = -.83 at 680 nm, P less than .005). The correlation of reflectance with interfiber area was more uniform across the spectrum (reaching r = .90 at 450 nm, P less than .005), as was the correlation of reflectance with WHC (reaching r = -.80 at 400 nm, P less than .005). At 24 h postmortem, fiber-optic spectrophotometry may be used as a rapid, nondestructive method to predict WHC and potential fluid losses from commercial pork with a moderate range from PSE to DFD. Interfiber area was correlated negatively with filament lattice area and WHC, but no significant correlation was found between filament lattice area and WHC. Filament separation was decreased only slightly by centrifugation. These results indicate that at 24 h postmortem the extra fluid released from PSE pork already has been lost from the myofilament lattice and is awaiting release from compartments downstream such as interfiber and interfascicular spaces.

Animals↗
PubMed1988

Comparison of tube cultures of Madin Darby canine kidney cells with shell-vial cultures after low-speed centrifugation for influenza virus isolation.

The efficacy of isolation of influenza viruses was compared in two systems--conventional tube cultures of Madin Darby canine kidney cells, and shell-vial cultures after low-speed centrifugation. One hundred and fifty eight throat and nasal swabs were inoculated and cultures screened by hemagglutination on days 1, 2, 3 and 5 post-inoculation. Twenty-four shell-vial cultures (15.2%) and 6 tube cultures (3.8%) were positive for influenza virus type B, indicating that shell-vial cultures with low-speed centrifugation are superior to tube cultures for influenza virus type B isolation (p less than 0.005 by McNemar's test for analysis of matched pairs data).

Animals↗