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At least 811 records · Page 45Linked to original sources
PubMed1994

Cytomorphologic characterization of cell subsets isolated by density gradient centrifugation from tumor effusions of ovarian endometrioid carcinoma.

AIMS: Cytomorphologic characterization of tumor cell subsets, according to the stage of pathologic differentiation, and comparison of cellular composition in tumor cyst and ascitic fluids were carried out on individual patients with ovarian endometrioid carcinoma. METHODS: A density gradient centrifugation technique was applied to fractionate the cells from tumor effusions. RESULTS: The enrichment of cell forms representing individual stages of pathologic differentiation by gradient centrifugation facilitated their cytomorphologic characterization. According to cytomorphologic features, 5 discrete cell subpopulations were identified and catalogued. The cellular composition of tumor cyst and ascitic fluids in individual patients was similar, but the number of fractions and percentage of cell subsets differed. CONCLUSIONS: The estimation of precise cytomorphologic criteria for cell forms in tumor effusions facilitated the cytologic diagnosis of ovarian endometrioid carcinoma. The possibility to concentrate poorly differentiated, frankly malignant cell subsets in low densities could significantly improve the diagnosis of tumor effusions.

Carcinoma, Endometrioid↗
PubMed1986

Improved enrichment of functionally intact anterior pituitary cells by sequential centrifugal elutriation and density gradient sedimentation.

By centrifugal elutriation and subsequent Percoll density gradient centrifugation, we obtained highly enriched cell populations of the anterior pituitary of ovariectomized adult rats. Enrichment of somatotrophs, gonadotrophs and mammotrophs was 90%, 80% and 77%, respectively (determined by immunocytochemistry). 41% of the GH-cells showed a medium cell size and the highest density. 52% of the LH-cells and 44% of the FSH-cells were found within the population of the large and medium-dense cells. 69% of the prolactin-cells belonged to the small-sized cells with low density. Thyrotrophs were found within all of the size ranges. The majority of the corticotrophs (82%) showed a small cell size. The enriched somatotrophs, LH-gonadotrophs, and mammotrophs responded to GRF, LRH and TRH. Before and after enrichment, somatotrophs and mammotrophs showed the same responsiveness to releasing hormones. In contrast, enriched LH-gonadotrophs exhibited a higher responsiveness to LRH than unfractionated LH-gonadotrophs.

Animals↗
PubMed1975

Purification and concentration of influenza inactivated viruses by continuous-flow zonal centrifugation.

A mathod is described for the purification, on an industrial scale, of influenza viruses grown in allantoic cavity of embryonated eggs. The mehtod consists of combining continuous-flow centrifugation with zonal centrifugation in a sucrose (36.6 per cent-52.5 per cent w/v) density gradient. The sample flow rate is approximately 3.7 litres/h and the volumes treated vary between 3 and 33 litres of allantoic fluid. Both the recovery of the virus and the degree of concentration and purification result satisfactory.

Allantois↗
PubMed1989

[A comparison of the efficiency of density gradient and low-speed centrifugation methods for isolating Plasmodium sporozoites].

P. yoelii sporozoites(Sp) in Anopheles stephensi were first isolated with low-speed centrifugation and the Sp suspension was subsequently purified with the density gradient centrifugation. The recovery rates of Sp by the latter method is about 50 approximately 75% of that by the former, but few debris could be found in the Sp suspension and the infectivity of the Sp was not weakened as compared with the Sp obtained by low-speed method. Sp would retain partial infectivity, when its suspension was maintained in medium 199 at 4 degrees C for 48 hrs. When rats and mice were infected with these Sp, pathological changes of hepatocytes such as cloudy swelling or fatty degeneration, which had been evidenced to be induced by mosquito tissues, would be absent or present in the slightest degree.

Animals↗
PubMed1978

Centrifugal method of determining red cell deformability.

A recently developed technique for deforming red blood cells (RBC) in which they are centrifuged through buffer and into a glutaraldehyde solution was evaluated as a method of assessing cellular deformability (i.e., the ability of the entire RBC to form a new configuration). To accomplish this, RBC populations of differing cellular deformability were tested, using three generally accepted techniques to obtain these differences: partial fixation with low concentrations of glutaraldehyde, density fractionation, and suspension of RBC in nonisotonic media. Our results indicate that at a constant deforming force the mean deformed length of the RBC decreased under conditions where cellular deformability is known to decrease, thus suggesting the usefulness of this centrifugal method for the estimation of this cellular property.

Centrifugation↗
PubMed1984

Advantages of rubidium chloride gradients for isopycnic centrifugation of enzymes.

The isopycnic centrifugation of beta-amylase and the marker enzyme beta-galactosidase was carried out using four salts viz. rubidium chloride, potassium bromide, potassium acetate and lithium bromide. Lithium bromide inactivated both beta-galactosidase and beta-amylase. The high viscosity of potassium acetate gradients necessitated an extremely long centrifugation time. The density profiles obtained with rubidium chloride gradients were sharper and permitted better resolution than potassium bromide gradients. Both enzymes were stable in rubidium chloride gradients, while potassium bromide inactivated beta-galactosidase, even in the presence of 10 mM 2-mercaptoethanol.

Amylases↗
PubMed1981

Separation and concentration of murine hematopoietic stem cells (CFUS) using a combination of density gradient sedimentation and counterflow centrifugal elutriation.

To obtain concentrated suspensions of pluripotent hematopoietic stem cells *CFUS) from murine bone marrow, density gradient centrifugal sedimentation (DGCS) was combined with counterflow centrifugal elutriation (CE). This combination provided a 7.6 fold enrichment of the CFUS concentration. For DGCS, Percoll a suspension of silica particles coated with polyvinylpyrrolidone was used. For fractionation by the CE an elutriator rotor (JE-6, Beckman) was used for further concentration of the cells harvested from the DGCS. Bone marrow erythropoiesis was suppressed by transfusion plethora initiated 5-6 days before the bone marrow was harvested. These two physical separation procedures combined with transfusion plethora to suppress erythropoiesis are effective in producing an enriched fraction of CFUS without change in distribution of the histologic type of colonies.

Animals↗
PubMed1982

Centrifugal cytology of ocular fluids.

Centrifugal cytology is a new technique for the preparation of ocular fluids for cytologic examination. It differs from conventional cytocentrifuge techniques, since fixation is carried out simultaneously with centrifugation. It avoids air-drying artifacts and can be applied to small (50 microL) or large (200 mL or more) sample volumes and dilute cell suspensions, such as might be obtained by anterior chamber paracentesis, vitreous aspiration, or vitrectomy. The resultant preparation is a permanent, stained, well-preserved, flattened, homogeneous cell dispersion suitable for detailed cytologic evaluation.

Adult↗
PubMed1996

Cholesterol and phospholipid levels of washed and percoll gradient centrifuged mouse sperm: presence of lipids possessing inhibitory effects on sperm motility.

Levels of DNA, cholesterol, and phospholipids of mouse caudal epididymal and vas deferens sperm that were processed through simple washing and Percoll gradient centrifugation were measured. The DNA and cholesterol contents of washed sperm and Percoll gradient centrifuged (PGC) sperm (DNA = 3.6 +/- 0.3 pg/sperm and 3.4 +/- 0.3 pg/sperm, respectively; cholesterol = 0.219 +/- 0.057 nmole/microgram DNA and 0.224 +/- 0.030 nmole/microgram DNA, respectively, for washed and PGC sperm) were not significantly different from each other; however, the phospholipid level of PGC sperm was only one half of that of washed sperm (0.315 +/- 0.071 nmole/microgram DNA versus 0.720 +/- 0.075 nmole/microgram DNA, respectively). The presence of 0.3% bovine serum albumin (BSA) in the culture medium used in sperm washing did not change the cholesterol and phospholipid contents of washed sperm. Similarly, the cholesterol and phospholipid levels of washed sperm and PGC sperm that were further incubated in BSA-containing medium for 30 min remained the same. Interestingly, substantial amounts of lipids, as determined by the cholesterol and phospholipid levels, were released into the supernatants of the sperm washes, and sperm needed to be washed at least twice to ensure their stable levels of cholesterol and phospholipids. The lipid mixture in the first sperm wash supernatant was shown to have inhibitory effects on PGC sperm motility.

Animals↗
PubMed2001

Novel cell immobilization method utilizing centrifugal force to achieve high-density hepatocyte culture in porous scaffold.

Cell seeding is one of the key procedures in the construction of tissue-engineered organs. In our previous efforts to create a bioartificial liver, high-density cultures of hepatocytes (>1 x 10(7) cells/1 cm(3)-substrate) and long-term maintenance of metabolic function were achieved with a packed-bed reactor utilizing porous poly(vinyl formal) (PVF) resin as a scaffold. However, a low seeding efficiency of about 30% remains a major obstacle to the scaleup of the reactor. In the present study, a new cell seeding method, centrifugal cell immobilization (CCI), which is based on alternating centrifugation and resuspension, was used to achieve high-density seeding and improve the seeding efficiency. Using the CCI method, the maximum density of the immobilized hepatocytes reached 3.8 x 10(7) cells/1 cm(3)-PVF, and the seeding efficiency was improved to about 43% after a relatively short immobilization process (about 15 min). Moreover, further improvement of the seeding efficiency was obtained by serial immobilization procedures. Thus, we concluded that this method is useful and effective for seeding cells into 3-dimensional scaffolds.

Animals↗
PubMed1984

A method for the separation of erythrocytes on the basis of size using counterflow centrifugation.

A method has been developed for separation of erythrocytes on the basis of size using counterflow centrifugation. Human red blood cells with an original mean corpuscular volume (MCV) of 89.2 +/- 4.1 fl were isolated, free of plasma proteins and other cell contaminants, into seven fractions ranging in size from 77.0 +/- 2.7 fl to 98.5 +/- 4.8 fl. The ratio of the age-related enzyme, erythrocyte glutamic oxaloacetic transferase (EGOT), to hemoglobin (Hb) increased progressively through the fractions, suggesting a correlation between erythrocyte volume and age. Reticulocytes, though present in all fractions, were selectively enriched in the larger subpopulations. To verify the biochemical evidence that erythrocytes decrease in volume with aging, in vivo cohort labeling of red blood cells with 59Fe was performed in baboons. A similar relationship of EGOT to Hb was observed to that in the human subpopulations. The peak activity of 59Fe/RBC appeared initially in the red blood cells with the highest MCV and progressed from the erythrocytes with the largest MCV to the erythrocytes with the smallest MCV over the next 10-12 weeks, confirming the hypothesis that red blood cells decrease in volume as they age. The technique of counterflow centrifugation appears to provide a simple, rapid, and reproducible method for the separation of erythrocytes on the basis of size.

Adult↗
PubMed1981

Centrifugal separation of cells in sputum specimens from patients with adenocarcinoma.

A Ficoll density gradient centrifugation technique was used to separate fixed cells from the sputa of patients with bronchogenic adenocarcinoma. The selective enrichment of leukocytes, squamous or cancerous cells was achieved while retaining the diagnostically significant cell morphologic features. This technique is shown to typically eliminate most of the leukocytes (96.9%) macrophages (86.7%), squamous cells (70.0%) and necrotic debris from specimen fractions containing the majority of cancerous cells. The maximum purity of cancer cells (14.6%) occurs in high density (p = 1.35 g/ml) gradient fractions and results in an average 12.2-fold enrichment for cancer cells in contrast to their relative frequency of occurrence in unprocessed specimens. Differential cell count analyses of serial density centrifugation fractions show that this technique produces comparable enrichment rates for material from bronchogenic adenocarcinoma and squamous cell carcinoma.

Carcinoma, Bronchogenic↗
PubMed1989

Separation and concentration of phytoplankton populations using centrifugal elutriation.

Centrifugal elutriation is a technique for separating particles on the basis of their sedimentation velocity, an expression of size, shape, and specific gravity. Unialgal cultures, mixtures of two phytoplankton cultures, and natural seawater samples were elutriated to determine the feasibility of this technique for collecting fractions of different cell cycle phases, separating two phytoplankton species, and concentrating cells from dilute samples. Elutriation resulted in the separation of a culture of Dunaliella tertiolecta and Phaeodactylum tricornutum into homogeneous fractions of each species. Cells in the natural seawater sample were concentrated by nearly 2 orders of magnitude. Centrifugal elutriation provides an alternative cell separation and concentration technique when large numbers of cells are required.

Cell Separation↗
PubMed1995

The effects of centrifugation and titanium fiber reinforcement on fatigue failure mechanisms in poly(methyl methacrylate) bone cement.

The contributions to fatigue resistance in poly(methyl methacrylate) bone cement (PMMA) by centrifugation and titanium fiber addition were studied. Three modified bone cements were tested: porosity reduced cement (C-PMMA); titanium (Ti) fiber-reinforced cement (R-PMMA), using a novel method to incorporate fibers; and porosity reduced and Ti fiber-reinforced cement (C-R-PMMA). Specimens of untreated bone cement (PMMA) were included as controls. Non-notched and notched specimens were cyclically loaded in fully reversed bending. For the non-notched specimens, at all stress levels, C-R-PMMA had significantly greater fatigue life than either C-PMMA or R-PMMA (except C-PMMA at 30 MPa). R-PMMA had lower fatigue life than the control at 30 MPa (nominal maximum stress), but higher fatigue life at 20 and 15 MPa. At both 20 and 15 MPa, there was no statistical difference between the fatigue lives of C-PMMA and R-PMMA. Fractography revealed that, at 30 MPa, characteristics of rapid fracture predominated. At 20 and 15 MPa, in contrast, almost the entire fracture surface showed the characteristic fatigue morphology, indicating that subcritical crack growth was predominant. For the notched specimens, C-PMMA showed greater life than PMMA at the highest stress intensity, but the lifetimes converged with decreasing stress intensity. In contrast, the life-times for PMMA and R-PMMA diverged with decreasing stress intensity. The effect of centrifugation appeared to be strongest at higher stress intensities, and diminished with decreasing stress intensity. The reinforcing effect of Ti fiber addition increased the notched fatigue life at high initial stress intensities, and the reinforcing effect increased with decreased stress intensity.(ABSTRACT TRUNCATED AT 250 WORDS)

Biocompatible Materials↗
PubMed1983

Mononuclear cell (MNC) collection by continuous-flow centrifugation (CFC).

Mononuclear cell separation and collection by continuous-flow centrifugation relates to centrifugal acceleration, total blood processed, peripheral blood concentration, and probable mobilization from extravascular sites during the procedure. At low-G forces, 70-80% of mononuclear cells are cleared. As G forces are increased, 95-100% of mononuclear cells can be cleared, but excessive platelet depletion occurs. An average of three billion cells were harvested from 2-3 liters of blood, rising to nine billion when 6 liters were processed. The total blood processed is defined by citrate infusion rates and ionized calcium changes. Large quantities of mononuclear cells were collected from normal donors without any significant depletion. If the objective of harvesting mononuclear cells is depletion, intensive schedules may be needed.

Blood Component Removal↗
PubMed1984

Granulocyte collection by continuous-flow centrifugation using arteriovenous shunts.

Two thousand nine hundred twenty-seven granulocyte collections were made using continuous-flow centrifugation with the Aminco Celltrifuge I, the Fenwal Celltrifuge II, and the IBM 2997. There were 231 recipients and 246 donors. In 32 patients attempts to provide daily granulocyte transfusions from a single donor were unsuccessful owing to clotting of the silastic-Teflon arteriovenous shunt. Repeated granulocyte donations produced severe anemia requiring red cell transfusions in all the females and most of the males who had previously donated marrow for transplantation. Granulocyte collections were similar when collected with the Celltrifuge I or the IBM 2997, but collections with the Celltrifuge II were smaller. Infusion of hydroxyethyl starch directly into whole blood as it entered the centrifuge increased granulocyte collections. Granulocyte collections decreased with increasing number of daily collections.

Arteriovenous Shunt, Surgical↗
PubMed1994

Centrifugal and biochemical comparison of proteoglycan aggregates from articular cartilage in experimental joint disuse and joint instability.

Two models involving altered joint loading were compared with regard to their effects on the biochemical composition and proteoglycan aggregate structure of articular cartilage. Disuse atrophy was created in greyhound dogs by nonrigid immobilization of the right knee in 90 degrees of flexion, and joint instability was created by transection of the anterior cruciate ligament. Similarities and differences between the two experimental groups at two different time periods were examined to investigate why joint instability induces progressive and irreversible changes to the articular cartilage, whereas joint disuse induces changes that may be reversible when the joint is remobilized. The following studies were performed on the cartilage from all experimental and control groups: (a) compositional analyses to determine water, uronate, and hydroxyproline contents; (b) high performance liquid chromatography for detection of hyaluronan and chondroitin sulfates; and (c) centrifugation analyses of nondissociatively extracted and purified proteoglycans to isolate and quantify the populations of monomers and slow and fast-sedimenting families of aggregates. In general, all cartilage was found to have a decreased ratio of proteoglycan to collagen after 4 weeks of disuse, and this ratio returned to control values at 8 weeks. In contrast, cartilage had an elevated ratio of proteoglycan to collagen as well as increased hydration at 12 weeks after transection of the anterior cruciate ligament. The most striking contrast between the two models was the finding of an approximately 80% decrease in the content of hyaluronan at both time periods after transection of the anterior cruciate ligament, with no evidence of a change after disuse. The results of centrifugation analyses indicated a significant decrease in the quantity of proteoglycan aggregates in both models. However, this decrease was associated primarily with a loss of slow-sedimenting aggregates after disuse and a loss of both slow and fast-sedimenting aggregates after transection of the anterior cruciate ligament. Furthermore, the population of fast-sedimenting aggregates was depleted to a greater extent than that of the slow-sedimenting aggregates. The preservation of fast-sedimenting aggregates as well as hyaluronan after periods of joint disuse but not joint instability suggests a possible mechanism for the reversibility of cartilage changes. Although the proteoglycan aggregates were depleted after disuse atrophy, it is possible that an aggregate-depleted matrix could recover when normal proteoglycan synthesis is resumed. In contrast, although synthesis may be maintained or elevated after transection of the anterior cruciate ligament, the matrix may not be repopulated with aggregates because there is an insufficient amount of hyaluronan.

Analysis of Variance↗
PubMed1982

Separation of amniotic fluid cell types in primary culture by Percoll density gradient centrifugation.

Amniotic fluid cells obtained by transabdominal amniocentesis at 15-17 weeks of gestation and cultured for 15 and 21 days were separated into three fractions by density gradient centrifugation in Percoll. Each fraction (or peak) corresponded to the following densities: peak A, 1.02-1.03 g/ml; peak B, 1.04-1.05; peak C, 1.05-1.06. Peak A was composed of both non-viable and viable cells; the latter adopted the morphology of epithelial cells in culture. Peak B contained a mixture of fibroblasts and epithelioid cells and peak C had only epithelioid cells. The variability of N-acetyl-beta-hexosaminidase and alkaline phosphatase activities was reduced in peaks B and C as compared to that of peak A and of unseparated cells suggesting that more defined and homogeneous cell types for enzymatic determinations can be obtained by centrifugation in Percoll density gradient. In prenatal diagnosis of biochemical defects, the separation of cells would permit a more precise diagnosis by eliminating enzyme variability due to the presence of different cell types or non-viable cells.

Acetylglucosaminidase↗