PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Centrifugation, Density Gradient”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 19 recordsLinked to original sources
PubMed1976

Separation of megakaryocytes from mouse bone marrow by density gradient centrifugation.

The density profile of mouse bone marrow megakaryocytes, as determined by discontinuous albumin density gradient centrifugation, was characterized by a single density population (1.088 to 1.119 g/ml) with a peak density of 1.10 g/ml and a maximum enrichment of 15.5. This single population comprised both mature and immature megakaryocytes. The density profile of small, acetylcholinesterase-positive cells, a class of potential megakaryocyte precursors, was almost identical to that of morphologically recognizable megakaryocytes.

Animals↗
PubMed1978

Immobilization of immunoglobulins on polystyrene latex beads: characterization by density gradient centrifugation.

Isopycnic banding by density gradient centrifugation was used to measure density changes in complexes formed by the immobilization of each of four different immunoglobulins (IgG) (bovine, dog, rabbit, and sheep) on polystyrene latex beads (0.109 +/- 0.0025 micrometer diameter). Subtractive measurements of density changes allowed calculation of the mass of immobilized IgG under varying experimental conditions. The immobilization data were correlated with adsorption isotherms which incorporated charge repulsion forces. The effects of pH and NaCl concentration on the immobilization were studied for the latex-bovine IgG system. It was found that the mass of immobilized immunoglobulins was increased from 10 to 20% by removing the IgG from its isoelectric range.

Animals↗
PubMed1979

Colloidal silica--aluminum modified--PVP density gradient centrifugation: centrifuge tube wall cell adherence, aggregation, separation properties and comparison to BSA and Ficoll.

A method is described for the inexpensive and easy preparation of colloidal silica--aluminum modified--polyvinylpyrrolidone (CS-AM-PVP) density gradient centrifugation medium. Using density gradient centrifugation, several cell separation and biochemical characteristics were studied: centrifuge tube wall cell adherence, mouse spleen cell density distribution, rebanding properties, mitogen response and cell aggregation. Cell adherence to the centrifuge tube wall using density gradients of CS-AM-PVP was compared with density gradients of bovine serum albumin and Ficoll. Few cells adhered to the centrifuge tube wall when CS-AM-PVP was used as a gradient medium; whereas, significant cell adherence to the centrifuge tube cell wall occurred when bovine serum albumin or Ficoll was used as a gradient medium. The CS-AM-PVP gradient medium did not inhibit the response to mitogens of mouse spleen cells which had been separated into density subpopulations in a discontinuous CS-AM-PVP density gradient, caused a minimum amount of cell aggregation, and was found to be non-toxic.

Aluminum↗
PubMed1977

An analysis of the bovine genome by density gradient centrifugation: fractionation in Cs2SO4/3,6-bis(acetatomercurimethyl)dioxane density gradient.

The fractionation of calf thymus DNA by centrifugation in density gradients of Cs2SO4/BAMD, where BAMD = 3,6-bis(acetatomercurimethyl)dioxane, is described. A large-scale separation of (dG+dC)-rich DNA fractions has been obtained, allowing the relative amounts of minor and satellite components in the bovine genome to be precisely assessed.

Animals↗
PubMed1975

The effects of overloading in density-gradient centrifugation.

The effects of overloading of the sample zone in density gradient centrifugation have been studied by use of a three-component shelf-lavered sample in which the total protein concentration was increased by addition of different amounts of albumin. It is found that overloading of the gradient gives rise to particle movements which are not predictable from the Svedberg equation. The two typical effects of overloading are dislocation of the zone mass centres and changes in the zone shapes. It is found that the magnitude of the calculated sedimentation coefficients increases nearly linearly with increasing sample load. The changes in zone shapes are found to depend on the specific load and two different patterns may be distinguished. The zone of the sample component which causes the overloading is defined as primarily overloaded and the others as secondarily overloaded. In primarily overloaded zones the original Gaussian shape is lost, while in secondarily overloaded zones the Gaussian zone shape is maintained, although a zone broadening is seen. Extreme high loads are found to be able to divide single zones. As a whole these experiments show that evidence for a non-overloaded set of experimental conditions must be provided, when density gradient centrifugation is used for determination of sedimentation coefficients. For preparative gradient centrifugations the power of resolution will decrease with increasing sample load. A simple method to detect overloading in density gradient centrifugations is described.

Animals↗
PubMed1992

Detection of hypodense eosinophils by Percoll multilayer density gradient centrifugation in subjects with normal or slightly elevated eosinophilia. Poor reproducibility and eosinophils of density < 1.077 g/ml.

In patients with marked hypereosinophilia 'hypodense' and 'normodense' eosinophils have been found after density gradient centrifugation. Subsequently this terminology has also been used in studies of patients with milder eosinophilia. However, in these cases the differentiation between normo- and hypodense eosinophils was less clear. This might be due to the high imprecision of the test of density gradient centrifugation, as demonstrated in the first part of this study: the mean within-assay variance of the number of eosinophils in the different density layers was 35%. It was calculated that the test must be performed eight times to obtain an estimate of the true mean for the individual patient. In the second part of the study, the absolute number of 'hypodense eosinophils' in groups of patients with asthma (adults and children) and rheumatoid arthritis (adults) were compared to normal controls. Although a difference in the absolute number of hypodense eosinophils between groups of patients and controls could be demonstrated, the high imprecision of the test of density gradient centrifugation suggested that the technique used was not useful in an individual with normal or slightly elevated eosinophils in the peripheral blood.

Adult↗
PubMed1990

Separation of equine bronchopulmonary lavage cells by density gradient centrifugation and expression of procoagulant activity in unpurified cells and cell subpopulations.

Bronchopulmonary lavage was performed in 10 healthy horses and in 39 horses with chronic pulmonary disease. The predominant cell types were macrophages in healthy horses and neutrophils in severely diseased horses. Procoagulant activity (PCA) was detected in all 32 cell-free supernatants examined and in all 49 unpurified cell suspensions. Cells were separated by centrifugation on discontinuous gradients prepared either with Percoll or with Metrizamide. Macrophages were enriched in subpopulations of low density. Neutrophils could not be purified by density gradient centrifugation using either gradient medium. PCAs of cell subpopulations were plotted against their respective macrophage, neutrophil, and lymphocyte content. PCA was positively correlated with macrophage content (P less than 0.001) and negatively correlated with neutrophil (P less than 0.02) and lymphocyte (P less than 0.001) content. Therefore, PCA of equine lung cells most likely originates from macrophages as shown in other species. The density shift of lung neutrophils requires further investigation.

Animals↗
PubMed1992

RNA isolation from cartilage using density gradient centrifugation in cesium trifluoroacetate: an RNA preparation technique effective in the presence of high proteoglycan content.

An efficient method for the isolation of RNA from cartilage is described. The difficulties in obtaining RNA from cartilage, a tissue of low cell density and high proteoglycan content, were overcome by making several modifications to the guanidine thiocyanate/cesium chloride method of RNA extraction. Cartilage tissue is frozen, crushed, and homogenized in a 4 M guanidine thiocyanate lysis buffer. The RNA is then pelleted by ultracentrifugation through a cesium trifluoroacetate density gradient. The use of cesium trifluoroacetate, rather than cesium chloride, for density gradient centrifugation improves both the yield and purity of total RNA isolated from cartilage. The ultracentrifugation has been adapted to the Beckman TL100 tabletop centrifuge and is complete in 3 h. This fast, simple method produces high quality RNA, suitable for use in RNase protection assays, polymerase chain reaction analysis, and Northern analysis. This purification procedure may be applicable to other sources, from which RNA isolation is complicated by the presence of abundant cell wall or matrix components.

Animals↗
PubMed1985

Purification of thyroid lysosomes by colloidal silica density gradient centrifugation.

A procedure was devised for fractionating crude thyroid lysosomal particles (P750-15,000) by self-forming density gradient centrifugation with colloidal silica. Two discrete particle-containing peaks were observed, based on 131I-labeling and acid phosphatase activity: a heavy peak (density, 1.11-1.12) and a light peak (density, 1.05). Ultrastructural analysis revealed that the heavy peak consisted almost entirely of lysosomes, whereas the light peak represented a heterogeneous mixture of small vesicles and fragments of other intracellular organelles. In thyroids removed from rats 30 min after 131I injection, almost all of the 131I was present in the low density peak. This 131I appeared on sucrose density gradient centrifugation as a 19S peak, and it was almost completely insoluble in trichloroacetic acid. This was interpreted as indicating that the low density peak contained pinocytotic vesicles. In thyroids removed 4 days after 131I injection, the radioactivity appeared largely in the high density peak. Both the trichloroacetic acid solubility and the pattern on sucrose density gradient centrifugation indicated that the [131I] thyroglobulin had undergone extensive proteolysis. Thyroglobulin proteolytic activity was found primarily in the high density particles and to only a small extent in the low density particles. Studies performed at intervals after 131I injection combined with double labeling (131I and 125I) experiments provided evidence that radioactivity was transferred from the low density to the high density particles. Heterogeneity existed within the dense peak, related to the degree of thyroglobulin degradation, as it was observed that thyroid lysosomes become denser with increasing proteolysis of thyroglobulin. The acid phosphatase in the low density particles could be distinguished from that in the high density (lysosomal) particles by its elution pattern on Sephadex G-200 column chromatography, its response to freezing and thawing, and its reactivity with p-nitrophenylphosphate. It was concluded, therefore, that the acid phosphatase in the low density fraction was derived from prolysosomal structures such as vesiculated Golgi-endoplasmic reticulum-lysosomes. The prolysosomal acid phosphatase associated with the low density fraction appeared to be a large membrane-bound molecule which could be transformed into lysosomal acid phosphatase by incubation at pH 5.0.

Acid Phosphatase↗
PubMed1978

Density gradient centrifugation in urografin of Moraxella and Kingella cells and appendages.

Purification of fimbriae (pili) by density gradient banding in Urografin medium was attempted. Moraxella nonliquefaciens and Kingella kingae fimbriae were of higher density than their cells of origin, but fimbrial fractions obtained by homogenization and differential centrifugation still banded together with presumed outer membrane fragments and some whole cells in Urografin gradients. The cellular density of genetic variants with different fimbriation/competence levels was also studied. For one strain of M. nonliquefaciens and two strains of K. kingae, cells harvested from agar plates tended to show several bands on isopycnic density gradient centrifugation, with slightly higher general density of fimbriated variants than non-fimbriated. A single density band could be observed with cells from log phase broth cultures of selected strains which showed no distinct difference between fimbriation or competence variants of each strain. Cells of M. nonliquefaciens and M. bovis showed comparable buoyant densities, whereas those of K. kingae had a higher density.

Bacteriological Techniques↗
PubMed1975

Augmentation of marrow growth by thymocytes separated by discontinuous albumin density-gradient centrifugation.

Mouse thymocytes were separated by discontinuous albumin density-gradient centrifugation. The ability of B6 thymocytes from the gradient fractions to increase the number of spleen nodules formed by B6 marrow cells in B6D2F1 recipients was compared with that of similar numbers of B6 thymocytes from an unfractionated cell suspension. Thymocytes from any of the gradient fractions were not more effective than thymocytes from an unfractionated suspension in augmenting marrow-cell growth, indicating that the presumptive 'effective cell type' in this system cannot be separated from the total thymocyte population by its buoyant density properties.

Animals↗
PubMed1992

Extraordinarily low density of hepatitis C virus estimated by sucrose density gradient centrifugation and the polymerase chain reaction.

The genomic RNA of hepatitis C virus (HCV) in the plasma of volunteer blood donors was detected by using the polymerase chain reaction in a fraction of density 1.08 g/ml from sucrose density gradient equilibrium centrifugation. When the fraction was treated with the detergent NP40 and recentrifuged in sucrose, the HCV RNA banded at 1.25 g/ml. Assuming that NP40 removed a lipid-rich surface coat from HCV, the 1.08 g/ml and 1.25 g/ml HCV RNA may correspond to intact HCV virions and nucleocapsids, respectively. The extraordinarily low density of the virion is unusual in comparison to the density of classified viruses.

Base Sequence↗
PubMed1975

Use of iodinated organic compounds for the density gradient centrifugation of viruses.

Use of Urografin and Conray for the equilibrium centrifugation of viruses is described. These pharmaceuticals, which consist of iodinated arylic compounds, reach densities of 1.6 g/cm3 and have low intrinsic viscosities. Poliovirus, Newcastle disease virus, and lymphocytic choriomeningitis virus were centrifuged to equilibrium in gradients made of these substances. Viral infectivities were not measurably affected, which is especially noteworthy in the case of the very labile lymphocytic choriomeningitis virus. Buoyant densities were found to be significantly lower than densities obtained with gradients made of CsCl and sucrose.

Centrifugation, Density Gradient↗
PubMed1979

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↗
PubMed1978

Preparation of peroxisomes from carp liver by zonal rotor density gradient centrifugation.

Peroxisomes from carp liver can be separated by isopycnic density gradient centrifugation in sucrose. Without reaching complete sedimentation equilibrium, the purification by this method is quite successful. There is a 40-fold enrichment of catalase, the peroxisomal marker, with a total yield of 27%. No pretreatment of animals is necessary for separation from lysosomes, which, besides high fragility, show lower buoyant densities than peroxisomes. The enzyme content of carp liver peroxisomes is similar to that of rat liver, with the exception of alpha-glycerophosphate dehydrogenase, which in this tissue is a completely soluble cytoplasmic enzyme. Total activities are much lower than in the rat, for the characteristic peroxisomal oxidases the difference being in the range of one order of magnitude.

Alcohol Oxidoreductases↗
PubMed1977

Isolation of highly purified Leydig cells by density gradient centrifugation.

Purification of specific endocrine cells from mixed populations after dispersion of target tissues is important for detailed analysis of mechanisms of hormone action. A simple method for rapid isolation of endocrine cells with retention of biological integrity, has been developed by centrifugation in density gradients formed with Metrizamide. By this procedure, highly purified Leydig cells retaining morphological and biochemical characteristics were obtained. Such preparations bound 20, 300+/-3, 100 molecules of hCG per cell with affinity of 1.1+/-0.25 X 10(10) M-1. During incubation with hCG, cyclic AMP and testosterone responses of purified Leydig cells were considerably increased, and hCG concentrations as low as 0.2 pM caused activation of cAMP-dependent protein kinase.

Animals↗