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At least 127 records · Page 7Linked to original sources
PubMed1997

Composite valve graft versus separate aortic valve and ascending aortic replacement: is there still a role for the separate procedure?

BACKGROUND: To ascertain if operative technique has any bearing on outcome, the surgical results after aortic root replacement using either a composite valve graft (CVG) or a separate graft and valve (GV) were analyzed. METHODS AND RESULTS: Three hundred and ninety consecutive, nonrandomized patients treated for aortic valve disease and ascending aortic aneurysm (n=278) or type A dissection (n=112 [45 acute]) between 1965 and 1995 were analyzed retrospectively. One hundred and thirty-five patients received a CVG, and 255 had separate GV replacement. Mean age was 52+/-16 years (+/-1 SD). Eighty-two patients (44% of the CVG group) had the Marfan syndrome (MFS). Follow-up (96% complete) totaled 2247 patient-years and extended to 27 years. The operative mortality rate was 10+/-3% (+/-70% confidence limits) for patients receiving a CVG and 15+/-2% for GV replacement (P=NS). The 15-year actuarial survival estimate was higher for the CVG group (53+/-14% [+/-SEM] versus 36+/-4%, P=.037). Seven patients in the CVG group required reoperation on the aortic valve or ascending aorta, as did 49 in the GV group. The probabilities of freedom from reoperation on the aortic rootwere 82+/-9% and 75+/-4% at 10 years for the CVG and GV group (P=NS). Thirty variables were analyzed in a multivariate model: pulmonary disease, higher New York Heart Association functional class, and longer cardiopulmonary bypass time were linked with higher operative mortality risk; older age, emergency operation, coronary artery disease, and liver dysfunction were independent determinants of late death. Younger age and use of a bioprosthesis were predictors of late reoperation. Type of procedure (GV versus CVG) was not a significant predictor of any outcome variable. CONCLUSIONS: The long-term results after CVG or GV were similar, which reflects proper patient selection. Use of a composite valve graft theoretically confers more protection against recurrent aortic root aneurysm, and, unless one opts for a valve-sparing aortic root replacement procedure, is most appropriate for younger patients, those with the MFS (including acute dissections), and others with marked pathological involvement of the sinuses. On the other hand, use of a separate GV should not be abandoned; in carefully selected patients (and if properly performed, eg, excision of the sinuses), GV also provides satisfactory results.

Adult↗
PubMed1980

Separation of granulocytes from peripheral blood in a single step using discontinuous density gradients of Ficoll-Urografin. A comparative study with separation by dextran.

A single-step method for separating granulocytes from peripheral blood using two different gradients of Ficoll-Urografin (F-U) density 1.075 and 1.097 g/ml) is described. The morphological, cytochemical and ultrastructural properties of neutrophils isolated by this method were compared to those isolated by dextran-enhanced sedimentation and neutrophils from the peripheral blood. These studies indicated fewer alterations in neutrophils separated by F-U centrifugation than in neutrophils concentrated by dextran. Finally, the granulocyte layer recovered by F-U fractionation was 98% pure (dextran 71%) and yielded 64% (dextran 79%) of total granulocytes.

Adult↗
PubMed1993

Improvement of separation efficiency and concentrate purity of the Fresenius cell separator AS 104: results of a multicenter study. Haemapheresis Scientific Workshop Group of DGTI.

The aim of this multicenter study, initiated by the Haemapheresis Scientific Workshop Group of the DGTI was to evaluate separation protocols for the cell separator AS 104, marketed by Fresenius, using modified software and parameters which were believed to allow a more effective platelet collection with a significantly lower leukocyte contamination of the concentrates. Plateletpheresis data from 950 runs in ten hemapheresis centers, using virtually the same equipment, identical pheresis protocols, and cell counting methods were registered and statistically analyzed for each center and machine-related differences. Additionally, the counting methods of the centers were controlled by bi-weekly external cell count trials, and the plateletpheresis data were corrected using the results of these cell count trials, to obtain a comparison of the two versions of the protocol independent of the center effect. For protocol (or software version) 4.1, 610 runs were registered. The results of cell countings (chamber) are (given as means+/-standard deviations) 3.452x10 11+/-1.009x10 11 for the platelet yield (or thrombocyte yield), 9x10 6+/-23x10 8 for leukocyte contamination, and 17x10 6+/-70x10 6 for the erythrocyte contamination, and 53%+/-13.5% for the extraction efficiency, respectively. For software version 4.4 with 340 runs, the results are 3.642x10 11+/-0.974x10 11 for the platelet yield, 15x10 6+/-74x10 8 for leukocyte contamination, 20x10 6+/-44x10 6 for erythrocyte contamination, and 59%+/-12.4% for the extraction efficiency, respectively. For the leukocyte and erythrocyte contaminations, the means and standard deviations must be interpreted carefully since the statistical distribution showed a considerable skewing of the data. From the automatic counts, marginally smaller means were found. The data were corrected by the values from the ring study; and for these mathematically corrected data, statistical tests showed a significant improvement in the extraction efficiency from software version 4.1 to 4.4. At the same time, the leukocyte contamination was significantly lower with version 4.4.

Blood Component Removal↗
PubMed1980

Surface affinity chromatographic separation of blood cells. I. Separation of human and rabbit peripheral granulocytes, lymphocytes and erythrocytes using polyethylene glycol-bonded column packings.

Two different types of column packings with bonded polyethylene glycol (PEG) as the stationary phase, PEG 20M-bonded Porasil AX and bisoxirane-coupled PEG 20M-Sepharose 6B, were prepared for chromatographing human and rabbit peripheral blood cells. The best separation, especially of granulocytes and lymphocytes (separation factor 2.65), was obtained with the latter packing and a phosphate-buffered solution (pH 7.5) of 8% (w/w) dextran as the mobile phase. The selectivity of the column for blood cells depended on the concentration and molecular weight of dextran and on the ionic composition of the electrolytes in the mobile phase. The recoveries of human granulocytes, lymphocytes and erythrocytes by this chromatographic system were about 67, 82 and 50%, respectively.

Animals↗
PubMed1999

Advances in cell separation: recent developments in counterflow centrifugal elutriation and continuous flow cell separation.

Cell separation by counterflow centrifugal elutriation (CCE) or free flow electrophoresis (FFE) is performed at lower frequency than cell cloning and antibody-dependent, magnetic or fluorescence-activated cell sorting. Nevertheless, numerous recent publications confirmed that these physical cell separation methods that do not include cell labeling or cell transformation steps, may be most useful for some applications. CCE and FFE have proved to be valuable tools, if homogeneous populations of normal healthy untransformed cells are required for answering scientific questions or for clinical transplantation and cells cannot be labeled by antibodies, because suitable antibodies are not available or because antibody binding to a cell surface would induce the cell reaction which should be investigated on purified cells or because antibodies bound to the surface hamper the use of the isolated cells. In addition, the methods are helpful for studying the biological reasons for, or effects of, changes in cell size and cellular negative surface charge density. Although the value of the methods was confirmed in recent years by a considerable number of important scientific results, activities to further develop and improve the instruments have, unfortunately, declined.

Animals↗
PubMed1997

The COBE Spectra cell separator is more effective than the Haemonetics MCS-3P cell separator for peripheral blood progenitor cell harvest after mobilization with cyclophosphamide and filgrastim.

BACKGROUND: Peripheral blood is rapidly replacing bone marrow as a source of hematopoietic progenitor cells for autologous transplantation. The advantages of peripheral blood progenitor cell transplantation are enhanced by the ability to collect sufficient progenitor cells to ensure rapid neutrophil and platelet recovery in a single procedure on some cell separators. STUDY DESIGN AND METHODS: A prospective randomized study was undertaken to compare peripheral blood progenitor cell yields from two cell separators (MCS-3P, Haemonetics and Spectra, COBE). Fifteen consecutive patients were mobilized with cyclophosphamide 2 g per m2 (Day 0) and filgrastim 10 micrograms per kg (Days 1-11). Consecutive collections (Day 10, Day 11) were performed with each machine once: patients were randomly assigned to either machine for the initial collection. RESULTS: Collection time was longer on the MCS-3P (p = 0.001), and the volume processed was greater with the Spectra (p < 0.0001). Despite similar nucleated cell yield (p = 0.62), the yield of CD34+ cells (p = 0.001) and colony-forming units-granulocytic-monocytic (p = 0.0001) was significantly higher with the Spectra. The yield of nucleated cells per unit of blood volume processed was higher for the MCS-3P (p = 0.0007), while the CD34+ cell yield (p = 1) and colony-forming units-granulocytic-monocytic yield (p = 1) per unit of blood volume processed were similar for the two machines. The collection of CD34+ cells at levels > 2 x 10(6) per kg (p = 0.063), 5 x 10(6) per kg (p = 0.031), and colony-forming units-granulocytic-monocytic > 1 x 10(5) per kg (p = 0.25) after a single collection was superior for the Spectra. CONCLUSION: The yield of progenitor cells after collection on the Spectra was superior to that achieved with the MCS-3P, because of the larger volume of blood processed per procedure. This would permit more patients to undergo only one collection.

Blood Volume↗
PubMed1986

Glycolytic activity in human red cell populations separated by a combination of density and counterflow centrifugation. Evidence for an improved separation of red cells according to age.

Human red blood cells were separated by a discontinuous Percoll density gradient into fractions of increasing density. Red cells comprising the lowest and highest density fractions, respectively, were subsequently separated according to mean cell volume (MCV) by means of counterflow centrifugation. The activities of 4 red cell age-dependent enzymes (hexokinase (HK), pyruvate kinase (PK), glucose-6-phosphate dehydrogenase (G6PD) and aspartate aminotransferase (ASAT) were highest in the red cell fraction with low density/large MCV, although the difference from red cell enzyme activities in the total low density fraction was not significant. These 4 enzyme activities were lowest in the fraction of red cells with high density/small MCV. The relative activities of the enzymes in the high density/small MCV fraction, as compared to the unseparated cell population, were: HK (58%), PK (49%), G6PD (53%) and ASAT (28%). These activities were all significantly lower than those measured in the total high density red cell fraction. The rates of lactate production in the low density/large MCV cells (0.89 +/- 0.15 mumol X min-1 X 10(-11) cells) is approximately 3-fold higher than in high density/small MCV cells (0.33 +/- 0.03 mumol X min-1 X 10(-11) cells). This latter value is 1.8-fold lower than the rate of lactate production in the total high density red cell fraction (0.59 +/- 0.14 mumol X min-1 X 10(-11) cells) and is, in contrast to lactate production in other density/size fractions, insensitive to phosphate as a metabolic stimulus. It is argued that the combination of density gradient and counter-flow centrifugation offers a greater potential for obtaining an old red cell population than classical red cell density centrifugation alone.

Cell Separation↗
PubMed1987

Improvement of the safety systems in cell separators. The new safety concept for the cell separator AS 104 (Fresenius).

The new, extended safety requirements for cell separators call for a new generation of machines to address current safety needs. In order to ensure safe treatment, the complete safety concept is of decisive importance - this includes closed seal-less systems, continuous operation, fractions collected externally to the centrifuge, and pump tubings, connections and clamps which are color and direction coded. 'Human failure' as a cause of fault should be excluded for these highly technical appliances - for example, through the use of 'fail-safe' circuits, drip-controlled ACD flow by a separate adjustable pump, detection of damages to blood components by hemolysis control.

Blood Component Removal↗
PubMed1975

Separation of human lymphoid cells by preparative cell electrophoresis. II. Free-flow electrophoretic separation of human blood cells.

By means of free-flow electrophoresis the different types of human blood leukocytes can be characterized by their electrophoretic distributions. In addition a separation of cells according to their electrophoretic mobility and at least an enrichment of certain cell types is achieved. The data given in this paper confirm that reproducible results can be obtained using this separation method and indicate that it can best be used to study populations of lymphocytes.

Cell Separation↗
PubMed1993

[Advance in the method of eosinophil separation--separation of human eosinophils in density gradients and measurement of density distribution].

To separate human eosinophils from peripheral blood, we used six discontinuous density gradients of Percoll solution (1.070, 1.080, 1.085, 1.090, 1.095 and 1.100 g/ml). Eosinophils isolated from patients with bronchial asthma or hypereosinophilic syndrome (HES) were shifted to the lighter density as compared with that from healthy subjects. Light-shift of density of eosinophils (hypodense eosinophils) was mimicked by several agents including chemical mediators such as histamine or platelet-activating factor (PAF), cytokines such as interleukin (IL)-3, IL-5 or GM-CSF. It has been reported that hypodense eosinophils survive, and the ability to generate leukotriene C4, superoxide anion or to secrete tissue injurious protein such as ECP or MBP augments as compared with that of normal density (normodense eosinophils). This separation method of eosinophils using a Percoll solution may contribute to accurate understanding a role of eosinophils in the pathogenesis of bronchial asthma or HES.

Animals↗
PubMed1997

[A new separation protocol (DRBCP-F) for automated blood component donation with the MCS 3p cell separator for collection of leukocyte depleted erythrocyte concentrates and plasma].

Previously published studies on automated blood component donation with the MCS 3p cell separator proved fairly good quality of the collected red blood cells (RBC) and fresh frozen plasma (FFP), with the disadvantage of a low hematocrit of the filtered RBC and a high platelet contamination of the FFP (RBCP-F protocol.) The DRBCP-F protocol was designed to eliminate the above-mentioned disadvantages and to provide 1 unit of leuko-depleted (filtered) RBC, 2 units of FFP, and additionally 1 platelet concentrate (PC) from the buffy coat. Twenty automated blood component collections (2 cycles, Latham bowl at 5,500 rpm, 230 ml isotonic saline for volume balance, PAGGS-M as additive solution) were performed. The RBC were filtered in a closed system after storage at 4 degrees C for 24 h. Blood cell counts and biochemical parameters of the RBC were determined initially and after 49 days. PC were separated from buffy coat after a soft spin. The volume of the RBC amounted to 293 +/- 12 ml (mean +/- SD) with a hematocrit of 0.61 +/- 0.05 l/l. Residual leukocytes after filtration were found to be 0.04 x 10(6) +/- 0.06 per unit. After storage, the following data were obtained: hemolysis 0.38%, ATP 2.1 +/- 0.4 mumol/g Hb, 2,3-diphosphoglycerate (2,3-DPG) 1.4 +/- 0.3 mumol/g Hb, ph 6.3 +/- 0.1, potassium 6.4 mmol per unit, and LDH in the supernatant was 219 U/l. None of the RBC showed bacterial growth after 49 days. The volume of the collected FFP was 398 +/- 32 ml, with 3.4 +/- 3.5 x 10(3) residual platelets and 5 +/- 12 leukocytes per microliter. Platelet concentrates contained 90.2 +/- 32 x 10(9) platelets in 88 +/- 14 ml plasma. Automated blood donation with the DRBCP-F protocol provided RBC with very low residual leukocyte counts, adequate hematocrit and good metabolic status up to 49 days, and FFP with low platelet contamination. The platelet concentrates were even superior to those prepared from whole blood using the buffy coat method. The storable leuko-depleted RBC are suitable for transfusion of chronically transfused patients in whom primary HLA sensitization should be prevented.

Adult↗
PubMed1999

Separation of double-stranded and single-stranded DNA in polymer solutions: II. Separation, peak width and resolution.

The electrophoretic separation of single-stranded and double-stranded DNA has been examined, using a matrix of linear poly-N,N-dimethylacrylamide (pDMA). The dependence of peak spacing, peak width and resolution on important parameters such as polymer concentration, polymer chain length and electric field strength, has been studied. This work complements our systematic study on electrophoretic mobility under different conditions (C. Heller, Electrophoresis 1999, 20, 1962-1977), and will help to further optimize and improve high performance DNA separation in capillary electrophoresis with entangled polymer solutions.

Acrylamides↗
PubMed1999

Ultrahigh-resolution capillary electrophoretic separation with indirect ultraviolet detection: isotopic separation of [14N]- and [15N]ammonium.

Separation of isotopically labeled [14N]/[15N] ammonium was performed with capillary electrophoresis. This ultrahigh-resolution separation was based on mobility counterbalance with precise control of the anodic electroosmotic flow. Mixtures of zwitterionic surfactant (Rewoteric AM CAS U) and cationic surfactant (cetyltrimethylammonium bromide) were used as buffer additives to modify the electroosmotic mobility. Indirect ultraviolet detection was used with benzyltributylammonium as the buffer coion. Baseline-resolved peaks of [14N]- and [15N]ammonium were obtained within 11 min. The detection limit was 0.01 mM for both [14N]-and [15N]ammonium. Linear calibration in concentration was observed up to 1.0 mM for [15N]ammonium and 2.0 mM for [14N]ammonium. Calibration of the isotopic ratio, [15N]ammonium concentration to total ([14N] and [15N])ammonium, was valid from 5 to 95%.

Betaine↗
PubMed2000

Enantiomeric separation by capillary electrochromatography. I. Chiral separation of dansyl amino acids and organochlorine pesticides on a diol-silica dynamically coated with hydroxypropyl-beta-cyclodextrin.

In this work, a commercially available diol-silica stationary phase was converted in situ to a chiral stationary phase by dynamically coating it with hydroxypropyl-beta-cyclodextrin (HP-beta-CD). This stationary phase was shown useful for the capillary electrochromatography (CEC) separation of neutral and anionic enantiomers such as some organochlorine pesticides and dansyl amino acids, respectively. The inclusion of HP-beta-CD in the mobile phase to produce the in situ chiral stationary phase allowed the rapid separation of the anionic dansyl amino acid enantiomers at relatively low electroosmotic flow (EOF). The formation of host-guest complexes between the dansyl amino acids and the neutral HP-beta-CD in the mobile phase lowered the actual charge-to-mass ratios of the anionic solutes, thus speeding up their transport by the EOF across the packed capillary column. Several parameters affecting enantioseparation were investigated, including the concentration of HP-beta-CD, ionic strength, pH, and organic modifier content of the mobile phase.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2000

Enantiomeric separation by capillary electrochromatography. II. Chiral separation of dansyl amino acids and phenoxy acid herbicides on sulfonated silica having surface-bound hydroxypropyl-beta-cyclodextrin.

A chiral silica-based stationary phase having surface-bound hydroxypropyl-beta-cyclodextrin (HP-beta-CD) with a relatively strong electroosmotic flow (EOF) was introduced for enantioseparation by capillary electrochromatography (CEC). The stationary phase contained a hydrophilic sulfonated sublayer to which a chiral top layer of HP-beta-CD was immobilized. While the sulfonated sublayer was to provide a relatively strong EOF, the top HP-beta-CD was to confer the desired chiral recognition towards enantiomeric solutes. This HP-beta-CD sulfonated silica (CDSS) stationary phase proved useful for the rapid separation of anionic enantiomers such as dansyl amino acids and phenoxy acid herbicides. The effects of the organic modifier content, pH, and ionic strength of the mobile phase on enantioseparation were investigated. Under the optimized separation conditions, ten dansyl amino acids and six phenoxy acid herbicides were enantioseparated with a resolution greater than unity.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMedDate not supplied

Chiral separation by high performance liquid chromatography. I. Review on indirect separation of enantiomers as diastereomeric derivatives using ultraviolet, fluorescence and electrochemical detection.

The increased attention on the therapeutic implications of stereoisomerism has provided an impetus for the development of analytical methods for enantiomeric separation. The indirect method of separation of enantiomers as diastereomers using high performance liquid chromatography (HPLC) has emerged as an efficient and versatile approach. This is due mainly to the availability of numerous chiral derivatization reagents (CDRs). This article reviews CDRs useful for the development of an indirect HPLC method using ultraviolet, fluorescence and electrochemical detection. In addition, factors crucial for the development of the indirect method are discussed.

Chromatography, High Pressure Liquid↗
PubMed2004

Separation-friendly Mitsunobu reactions: a microcosm of recent developments in separation strategies.

The Mitsunobu reaction is famous for its scope and power, but infamous for its separation headaches. Typically, the target product is enticed away from the reagent-derived byproducts by careful chromatography. The use of polymer-bound Mitsunobu reagents solves only half of the problem, because polymer-bound diethyl azodicarboxylate (DEAD) and phosphine reagents cannot be employed simultaneously. This article classifies, compares, and contrasts various emerging strategies for product isolation in Mitsunobu reactions. Because so many different strategies have been used, the Mitsunobu reaction is a microcosm for the new field of strategy level separations.

Alcohols↗
PubMed1984

Sequence of centromere separation: orderly separation of multicentric chromosomes in mouse L cells.

Mouse L cells have many dicentric chromosomes and one with eight centromeres. All eight centromeres behave similarly until midmetaphase when most centromeres split into two units each in apparently quick succession but out-of-phase. This premature separation leaves one or perhaps two closely located centromeres intact, which separate at late metaphase-anaphase, drawing the two chromatids to opposite poles. Such dominance of one centromere over all others, though unexplained, ensures the lack of any mitotic abnormality such as bridges or fragments. These observations show that all the centromeres are retained as functional primary constrictions except for a change in functional regulation when more than one centromere are located on a chromosome.

Animals↗