Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Separation”

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 1,117 records · Page 62Linked to original sources
PubMed1997

Sterol synthesis. A timely look at the capabilities of conventional and silver ion high performance liquid chromatography for the separation of C27 sterols related to cholesterol biosynthesis.

Sterol intermediates in the biosynthesis of cholesterol have recently assumed a very prominent position in a number of important problems in medicine and biology. In studies of these matters, the separation and identification of the sterol intermediates present formidable challenges, a situation which does not appear to be generally appreciated. High performance liquid chromatography (HPLC) is a simple and rapid approach for the separation of the concerned compounds. Reversed phase HPLC is very commonly used for this purpose. In the present studies, we have evaluated the capabilities of reversed phase, normal phase, and silver ion HPLC for the separation of sterols. Using an extensive collection of authentic sterols, our studies indicate very limited capabilities of reversed phase and normal phase HPLC for the separation of C27 sterols differing in the number and location of olefinic double bonds. In contrast, silver ion HPLC provided remarkable separations of the same compounds, either as the free sterols or their acetate derivatives. These findings, coupled with the results of recent studies of the properties of the same compounds by gas chromatography and by nuclear magnetic resonance and mass spectroscopy, have important implications regarding current application of methodologies for the separation, identification, and quantitation of sterol intermediates in cholesterol biosynthesis as critical portions of investigations on a number of current and emerging problems in biology and medicine.

Acetates↗
PubMed1994

[Flow cytometry quality control in stem cell separation].

Peripheral blood-derived haematopoietic stem cells (PBSC) are used as an alternative to bone marrow stem cells for autologous transplantation. One of the most important prerequisites for successful PBSC separation is the precise determination of the optimal separation days. As we previously demonstrated that neither PLT counts nor WBC counts in the peripheral blood (PB) are of predictive value for the amount of colony-forming cells (CFC) in the patients' PB, we started a daily monitoring of CD-34-positive cells to determine the beginning of the separation series. In addition to routine cell counts and CFU testing we assessed the number of CD 34+ in the PBSC concentrates to ascertain the number of separations needed for each patient. Due to the strong correlation of CD 34+ cells to CFC it is possible to predict the number of CFC collected within 2 h after finishing the PBSC separation and to calculate the efficiency of the separation for quality control.

Colony-Forming Units Assay↗
PubMed1996

Diagnosis of approximal caries in primary teeth: radiographic versus clinical examination using tooth separation.

PURPOSE: To compare the accuracy of clinical examination performed with bitewing radiographs or clinical examination using tooth separation to identify carious lesion activity. MATERIALS AND METHODS: 320 surfaces from 40 bitewing radiographs were examined for approximal caries on the maxillary and mandibular primary molars of 20 patients 3-10 years old. The patients were divided into three groups: (1) Absence of the permanent first molar; (2) Partial eruption of the permanent first molar; and (3) Full eruption of the permanent first molar. Two examiners evaluated the radiographs using a megascope, a magnifying glass (x2), and an amplifying image screen. Approximal radiolucencies were identified on 72 surfaces. Following the radiographic examinations, the two examiners performed conventional clinical inspection using a No. 4 dental mirror, a No. 5 dental explorer, and an air-water syringe, with artificial light and relative isolation. The separation method was performed with elastic bands, which were removed after 24 hours, and the clinical examination conducted as in the non-separation group. RESULTS: The correlation between the extension of interproximal radiolucent lesions in primary dentition and their clinical diagnoses following separation of the teeth, was similar to findings on literature evaluating the permanent dentition. On radiographic findings for enamel lesions, white spots predominated both in the inner (100%) and in the outer (94%) half of enamel upon clinical examination with separation of teeth. For radiolucent lesions in dentin, on the other hand, cavities predominated over white spot lesions (84%). In Groups 1 and 2 (young primary), white spots occurred in cases where the radiolucent lesions reached the dentin (15% and 25%), similar to findings for young permanent teeth. Clinical diagnosis performed with the mechanical separation of teeth cannot be considered conclusive for the primary dentition.

Child↗
PubMed1999

Evaluation of membrane physiology following fluorescence activated or magnetic cell separation.

BACKGROUND: Over the past decade, cell separation technology has become an important tool in various fields of cell biology allowing for the analysis or subsequent cultivation of specific cell subsets. The objective of the present study was to evaluate if the established sorting techniques fluorescence-activated (FACS) and magnetic cell separation (MACS) affect cell membrane physiology in order to define the most non-perturbing application for the separation of tumor and stromal cells. MATERIALS AND METHODS: Membrane physiology was monitored in single cell suspensions of adherently grown BT474 breast tumor cells and N1 normal skin fibroblasts using flow cytometry. Cell membrane integrity was evaluated by propidium iodide (PI) staining. Microviscosity within the lipophilic membrane layer was determined by a monomer/excimer method utilizing pyrene decanoic acid, membrane potential measurements were carried out using the fluorescence indicator DiBAC4(3), and Annexin-V-staining reflected transversal membrane asymmetry, and an altered phospholipid distribution. RESULTS: Not only the number of preparative cycles prior to cell separation but also the sort conditions during FACS resulted in loss of membrane integrity of a certain cell fraction. If these PI-positive cells were excluded from further analysis, neither MACS nor FACS affected membrane microviscosity while a clear hyperpolarization in both cell types after MACS resulting from exposure to the ferromagnetic matrix of the depletion column and the inhomogeneous magnetic field was shown. In addition, cell sorting of BT474 tumor cells by MACS and FACS was accompanied by the generation of an Annexin-V-positive/PI-negative cell fraction with altered phospholipid distribution. Data were discussed with regard to the sort-induced "stress" conditions such as exposure to hydrodynamic forces or magnetic fields. CONCLUSIONS: Both separation procedures modify cell membrane with neither technique being physiologically preferable for subsequent analysis or recultivation of the sorted cells.

Cell Line↗
PubMed1988

Some characteristics of human red blood cells separated according to their size: a comparison with density-fractionated red blood cells.

During their in vivo ageing, red blood cells (RBC) increase in density and become smaller. Age-defined RBC subpopulations are usually collected by centrifugation. A fractionation according to RBC volume has been proposed as an improved alternative to such age separation. Because a few data reported in the literature indicate some discrepancies between the two methods, blood samples were separated either by centrifugation or by counterflow centrifugation, and some characteristics of the RBC thus fractionated were studied. The enzyme activities decrease either when the density rises or when the volume (MCV) decreases. However, the comparison of other RBC characteristics strongly suggests that these two procedures do not lead to the collection of the same RBC subpopulations: for instance, the hemoglobin content increases when the MCV rises, whereas it remains constant whatever the RBC density is. With radiolabelled cells, it is shown 1) that the most dense RBC are recovered in all the size-separated RBC subpopulations, even though they tend to concentrate in the fractions with the largest MCV, and 2) that the smallest RBC are almost fairly distributed in all the RBC subpopulations, whatever their density, whereas the largest RBC are mainly, but not exclusively, present in the high-density fractions. Thus, fractionation according to size does not match separation according to density. Taken together with results from in vivo experiments carried out in mice and with the fact that reticulocytes are present in all the size-separated fractions, these data suggest that counterflow centrifugation may be a very questionable procedure to achieve a RBC fractionation according to age and therefore that RBC volume might not be a reliable criterion of RBC age.

Cell Separation↗
PubMed2001

Cell separation mediated by differential rolling adhesion.

Recently, we showed a correlation between the maturity of hematopoietic stem and progenitor cells during development and rolling efficiency on selectins. These findings motivated us to explore a novel separation that exploits differences in selectin-mediated rolling adhesion between populations of cells. We extend the use of a previously developed cell-free system to study the separation of populations of sialyl Lewis x (sLe(x))-coated microspheres designed to roll with different average velocities on L-selectin chimeric substrates under well-defined flow. Results show that a separation that exploits differences in average rolling velocities between cell or microsphere populations is attainable. Excellent recovery and purity values for the slower rolling, or more desirable, populations are obtained and can be estimated from rolling velocity measurements. We also assess the feasibility of a selectin-mediated separation of adult bone marrow cell populations using previously obtained rolling velocity and rolling flux data for CD34+ and CD34- adult bone marrow cells on L-selectin substrates. We believe that a cell separation mediated by differential rolling adhesion can be used to enrich populations of hematopoietic stem and progenitor cells from an adult bone marrow cell preparation and that this method possesses several major advantages over existing antibody-mediated cell-affinity chromatography technologies.

Adult↗
PubMed2003

Quantification of a novel h-shaped ultrasonic resonator for separation of biomaterials under terrestrial gravity and microgravity conditions.

A novel, h-shaped ultrasonic resonator was used to separate biological particulates. The effectiveness of the resonator was demonstrated using suspensions of the cyanobacterium, Spirulina platensis. The key advantages of this approach were improved acoustic field homogeneity, flow characteristics, and overall separation efficiency (sigma = 1 - ratio of concentration in cleared phase to input), monitored using a turbidity sensor. The novel separation concept was also effective under microgravity conditions; gravitational forces influenced overall efficiency. Separation of Spirulina at cleared flow rates of 14 to 58 L/day, as assessed by remote video recording, was evaluated under both microgravity (</=0.05 g) and terrestrial gravity conditions. The latter involved a comparison with 5- and 24-microm-diameter polystyrene microspheres. Influences of gravity on sigma were evaluated by varying the relative inclination angle (within a range of 120 degrees ) between the resonator and the gravitational vector. Cells of Spirulina behaved in a manner comparable to that of the 5-microm-diameter polystyrene microspheres, with a significant decrease in mean (+/-SE, n = 3) sigma from 0.97 +/- 0.03 and 0.91 +/- 0.02 at a flow rate of 14 L/day, to corresponding values of 0.53 +/- 0.05 and 0.57 +/- 0.03 (P < 0.05) at 58 L/day, respectively. During a typical microgravity period of ca. 22 s, achieved during the 29th ESA Parabolic Flight Campaign, sigma was unchanged at a flow rate of 14 L/day, compared with terrestrial gravity conditions; with increased flow rates, sigma was significantly reduced. Overall, these results demonstrate that, for optimum resonator performance under the relatively short microgravity period utilized in this study, flow rates of ca. 14 L/day were preferred. These data provide a baseline for exploiting noninvasive, compact, ultrasonic separation systems for manipulating biological particulates under microgravity conditions.

Cell Separation↗
PubMedDate not supplied

Antigen-specific electrophoretic cell separation for immunological investigations.

Preincubation of human blood lymphocytes with cell surface antigen specific antibodies under non-capping conditions reduces the electrophoretic mobility of the corresponding lymphocyte subpopulation. Antigen-positive and antigen-negative cells can be separated by free flow electrophoresis with high yield, purity and viability. The use of fluorescence-labelled second antibodies augments the induced decrease in net surface charge density, and allows rapid detection of antigen-positive cells in the fractions of electrophoresis. Carrier-free cell electrophoresis of human peripheral blood lymphocytes after reaction with anti-IgM-antibody or the monoclonal antibodies OKT4 or OKT8, and sandwich staining with tetrarhodamine isothiocyanate-labelled anti-IgG resulted in the large-scale separation of high pure human B and T lymphocyte subpopulations. Their functional integrity was shown in assays of lymphocyte transformation and of antigen-specific induction and regulation of antibody synthesis in vitro. These separate lymphocyte subpopulations are useful tools for immunological investigations. While, for instance, the effects of drugs on human lymphocytes are obscured by coincident changes in cell composition of the peripheral blood tested that do not by themselves reflect whole body immunocompetence, the cell separation and in vitro assays at a defined cell number and cell composition allow the recording of quantitative changes in the function of different cell subpopulations. We studied the influence of the anesthetic thiopental on separated human lymphocyte subsets. In both polyclonal lectin stimulation and in vitro antibody production, thiopental exhibited a noncytotoxic suppression of lymphocyte functions. B-Cells, T-helper and T-suppressor cells were equally affected and showed the same dose response.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1990

Free-flow electrophoresis under microgravity: evidence for enhanced resolution of cell separation.

A mixture of fixed rabbit, guinea pig and rat erythrocytes, suspended in a relatively conductive solution, was separated by means of continuous free flow electrophoresis (CFFE) under 1 g- and microgram- conditions using a specially designed electrophoretic module. Short duration microgram conditions were realized on board a sounding rocket. Due to the energy input and the associated thermal convection a separation of the three differently charged cell types in distinct peaks was not possible under 1 g-conditions as shown by reference experiments on the ground before launch. In contrast to the poor resolution under 1 g-conditions, clear separation of the cell mixture could be recorded after lift-off of the rocket under microgram-conditions. Repeated measurements demonstrated that the separation profile was completely stable during the entire microgram-phase of about 6 min. Since the CFFE experiment in space was an exact replica of the ground reference experiments, the results demonstrated unambiguously the potential of CFFE for cell separation under microgram-conditions in media of high ionic strength.

Animals↗
PubMed1988

Separation of human X and Y spermatozoa by free-flow electrophoresis.

Free-flow electrophoresis is a fast and promising method for gamete separation. Pretreated seminal plasma-free human spermatozoa were injected continuously as a fine stream into the buffer medium of the separation chamber flowing perpendicular to the forces of an electrical field, which separated the spermatozoa according to their differences in electrophoretic mobility. For characterization of the two classes of spermatozoa before and after separation, quinacrine mustard staining was used to identify the Y-chromosome-bearing spermatozoa carrying the fluorescent body (F-body). Human spermatozoa moved toward the anode and were separated into two main peaks. The faster moving fraction contained nearly 80% Y-bearing spermatozoa and the slower peak consisted mainly of pure X-bearing spermatozoa. Whereas sperm viability as determined by eosin staining was nearly unchanged, sperm motility was reduced after free-flow electrophoresis.

Cell Separation↗
PubMed1989

Employed mothers' concerns about separation from the first- and second-born child.

The effect of birth order on mothers' anxiety about separation from their infants was examined. Forty employed mothers were assessed in 1982 when their firstborns were 7 months old and again when their second-borns were 7 months old. Assessment included two measures: an Interview-Based Rating Scale (IBRS) and the Maternal Separation Anxiety Scale (MSAS). Findings revealed that mothers felt less guilt and anxiety about separation from their second-borns than they had from their first-borns at a similar age. They were more positive about the effects of separation on the child; however, their concerns about employment-related separation did not change.

Adult↗
PubMed1982

Enrichment of terminal deoxynucleotidyl transferase activity by cell separation.

Terminal deoxynucleotidyl transferase is a unique DNA polymerase that can carry out DNA synthesis on an initiator molecule in the absence of a template. The usefulness of this enzyme as a biological marker for following patients during treatment and remission has been suggested. The potential usefulness of this enzyme in predicting the onset of relapse before any morphological indications has been demonstrated in chronic myelogenous leukemia patients in blast phase of the disease. In order to be able to detect low levels of TdT activity especially during remission phase, we have used cell separation techniques which can enrich cell populations containing TdT activity. A number of cell separation techniques have been developed to separate different cell types. We have used the techniques of unit gravity sedimentation and free flow electrophoresis to achieve enrichment of TdT positive cell populations. Our results show that up to 20 fold enrichment of TdT activity in normal human bone marrow can be accomplished by using cell separation techniques. With the use of free flow electrophoresis, we have achieved enrichment of TdT positive cell populations from normal human bone marrow, cells from patients with acute lymphoblastic leukemia and chronic myelogenous leukemia in blast phase of the disease. No TdT positive cells were detected in patients with acute myelogenous leukemia. These cell separation techniques should prove to be useful in early detection of relapse in patients in remission.

B-Lymphocytes↗
PubMed1985

Magnetic separation techniques: their application to medicine.

Whilst separation techniques relying on gravitational forces have become relatively sophisticated in their application to biology the same is not true for magnetic separation procedures. The use of the latter has been limited to the few cells which contain paramagnetic iron. However with the development of several different types of magnetic particles and selective delivery system (e.g. monoclonal antibodies) the use of magnetic separation techniques is growing rapidly. This review describes the different types of particles currently available, the magnetic separation technique applied to the different magnetic compounds and illustrates major uses to which magnetic separation procedures are currently applied in the area of biology and medicine.

Animals↗
PubMed1982

Separation anxiety in mothers of latency-age fearful children.

The hypothesis that mothers of children who have symptoms indicative of separation anxiety are themselves separation-anxious was tested by scoring mothers' TAT themes for separation concerns. The stories of 15 mothers of fearful children were compared to the stories of 26 mothers of children manifesting behavior disorders and 21 mothers of children having had no psychiatric contact. Different kinds of separation concerns were found to differentiate the groups of mothers. The stories of mothers of fearful children expressed significantly more concerns about abandonment and rejection and more often expressed a desire to stay near the loved one; the mothers of children expressed significantly more concerns about abandonment and rejection and more often expressed a desire to stay near the loved one; the mothers of children with behavior disorders were found to tell significantly more stories with nurturance-succorance themes. The results lend support to the theory of anxious attachment in that mothers of fearful children seem to share the same concerns that have been ascribed to their children. On the other hand, it seems that separation anxiety may not be a unidimensional construct as different components seem to be more relevant to some symptom clusters than to others.

Adult↗
PubMed1983

[Thrombopoiesis, thrombocyte count and thrombocyte function before and following cell separation].

About 50% of the circulating platelets can be taken from healthy donors by means of the cell separation technique. In order to investigate the effect of cell separation on thrombopoesis bone marrow samples were taken from 12 voluntary donors up to 5 times. The megacaryocytes were analyzed before and after cell separation by morphometric measures and determinations of platelet count and platelet function (adhesion, aggregation, spreading, retraction) were carried out. Removing of large amounts of platelets form the circulation by stimulation of thrombopoesis resulted in an increase of the peripherical platelet count already 48 h after cell separation. Of the platelet functions tested only aggregation induced by collagen was found to be increased after cell separation as compared to that before the procedure.

Blood Platelets↗
PubMed1996

Retarded acquisition and reduced expression of conditioned locomotor activity in adult rats following repeated early maternal separation: effects of prefeeding, d-amphetamine, dopamine antagonists and clonidine.

Adult hooded rats exposed to a repeated maternal separation procedure during the neonatal period showed a blunted expression of locomotor hyperactivity conditioned to the presentation of the daily food ration. We have demonstrated that the expression of food-conditioned anticipatory hyperactivity is sensitive to the response-enhancing effects of systemic d-amphetamine (0.5; 1.0 mg/kg) and to the response-attenuating effects of the selective dopamine D2 antagonist sulpiride (8; 20 mg/kg), the selective dopamine D1 antagonist SCH 23390 (0.01; 0.022 mg/kg) and the mixed alpha 1/alpha 2 adrenoceptor agonist clonidine (5; 15 micrograms/kg) in a dose dependent manner. Animals from the early separation groups showed a reduced enhancement of activity in response to 0.5 mg/kg d-amphetamine and a greater attenuation of activity in response to 8 mg/kg sulpiride and 5 micrograms/kg clonidine. Female separated rats also exhibited an attenuated locomotor response to the unconditioned stimulant effects of 0.5 mg/kg systemic d-amphetamine. The experiments confirm that early maternal separation attenuates the response to conditioned appetitive cues in adult rats and implicate altered dopaminergic and noradrenergic function in the changes. It is possible that early maternal separation in the rat may offer a useful preparation for investigation of the neural substrates mediating affective development and affective psychopathology.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

Analysis of physical parameters of discrete cell populations. (Double data control by combining specific density and sedimentation velocity cell separation techniques).

Physical cell separations are employed in a number of investigations in cell biology, immunology, haematology, etc., when the study of homogeneous cell populations is required. Differences in physical characters are reflected in the various functions and differentiation stages of the individual cell lines, which can be concentrated and separated into discrete cell classes by these methods. The correct utilization of the separation techniques mainly depends on the knowledge of the physical laws on which they are based. This paper discusses the theoretical background and a practical application of a combined separation procedure which uses velocity sedimentation and linear density gradient and also gives a double check of the physical data obtained in the different experiments. As an example of this analysis, cells from the lymph nodes of Hodgkin's patients were separated, and the physical parameters as well as some sources of 'error' in the experimental results obtained with these 'Hodgkin's cells' are reported and discussed.

Cell Separation↗
PubMed2004

Biomagnetic separation of Escherichia coli by use of anion-exchange beads: measurement and modeling of the kinetics of cell-bead interactions.

Analyses of food-borne pathogens are of great importance in order to minimize the risk of infection for customers. These analyses should be as fast as possible. Any detection method requires enrichment and quantitative analysis of the enriched microbes. Conventional enrichment methods, which take several days, need to be replaced by faster techniques such as biomagnetic separation (BMS). This technique involves the use of paramagnetic microspheres coated with ligands that have special affinity to the microbes that have to be detected. In the studies reported here, enrichment experiments by BMS were carried out using the non-pathogenic E. coli DSM 498 as a model strain and beads coated with a polyethylenimine (PEI) anion-exchange material. The results show that the number of cells separated, as a proportion of the total, was positively correlated with the bead concentration and the length of the period they were mixed together. In addition, a mathematical model, based on the rate of impact between two different sorts of particles, was developed to describe the proportion of separated cells as a function of incubation time and the concentration, size and density of the beads and cells. This is the first mathematical description of cell-bead interactions to be based on well-understood physicochemical principles. The model was confirmed by separation experiments in which the concentration of beads and the incubation period were varied. The developed model enables optimization of the amount of beads added and the reaction period necessary for complete cell separation and thus minimization of costs in BMS.

Escherichia coli↗