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At least 1,009 records · Page 56Linked to original sources
PubMed1990

Micro-centrifugation of human spermatozoa: its effect on fertilization of hamster oocytes after micro-insemination spermatozoal transfer.

Micro-centrifugation (MC) at 6500 r.p.m. (3352 g) has not been used previously for spermatozoal concentration and subsequent fertilization. We investigated MC for micro-insemination spermatozoal transfer (MIST) of human spermatozoa from normal donors into hamster oocytes. MC resulted in reduced penetration of hamster oocytes, both after MIST [77.4% (41/53) versus 87.8% (43/49) for control; NS] and after exposure to zona-free hamster oocytes [60.8% (79/130) versus 72.7% (88/121) for control; P less than 0.05]. However, MIST under the zona resulted in better incorporation of sperm nuclei when compared with zona-free hamster oocytes, for spermatozoa exposed to micro-centrifugation (77.4 versus 60.8%, P less than 0.05) and controls (87.8 versus 72.7%, P less than 0.05). Polyspermy was higher after MIST [22.0% (9/41) versus 13.9% (11/79); NS] for MC+, and [25.6% (11/43) versus 13.6% (12/88); NS] for MC-. We conclude that MC does have a negative, but minimal effect on the fertility of human spermatozoa with respect to hamster oocytes.

Animals↗
PubMed1993

Sperm selection by PD-10 sephadex columns: comparison with SpermPrep filtration and Percoll centrifugation.

The efficacy of a disposable, prepacked column (PD-10) containing Sephadex G-25, to select motile spermatozoa, was compared with another column for sperm filtration (SpermPrep) and centrifugation through Percoll gradients. Aliquots of washed sperm suspensions were processed by the three techniques. The number of motile cells and the proportion of total spermatozoa selected was similar for all methods. Recovery of spermatozoa showing optimal movement was 145.9 +/- 30% (mean +/- SEM) with PD-10 columns and 131.9 +/- 32% with Percoll, both significantly higher than SpermPrep (71.9 +/- 11%; P < 0.05). The straight line velocity of motile cells was lower in samples processed by SpermPrep (29.3 +/- 2 microns/S) compared to both PD-10 (34.7 +/- 1 micron/s) and Percoll (34.9 +/- 2 microns/s; P = 0.07). When whole semen was processed, total sperm recovery with PD-10 was 61.7 +/- 8% versus 47.7 +/- 7% with Percoll (P < 0.001). Percoll centrifugation improved the percentage of morphologically normal spermatozoa more than PD-10. Similar proportions of motile spermatozoa and cells with optimal motility were obtained by both methods. We conclude that PD-10 filtration columns can be used to prepare semen in the laboratory as a practical alternative to other methods.

Cell Separation↗
PubMed2004

Percoll gradient-centrifuged capacitated mouse sperm have increased fertilizing ability and higher contents of sulfogalactosylglycerolipid and docosahexaenoic acid-containing phosphatidylcholine compared to washed capacitated mouse sperm.

Although Percoll gradient centrifugation has been used routinely to prepare motile human sperm, its use in preparing motile mouse sperm has been limited. Here, we showed that Percoll gradient-centrifuged (PGC) capacitated mouse sperm had markedly higher fertilizing ability (sperm-zona pellucida [ZP] binding and in vitro fertilization) than washed capacitated mouse sperm. We also showed that the lipid profiles of PGC capacitated sperm and washed capacitated sperm differed significantly. The PGC sperm had much lower contents of cholesterol and phospholipids. This resulted in relative enrichment of male germ cell-specific sulfogalactosylglycerolipid (SGG), a ZP-binding ligand, in PGC capacitated sperm, and this would explain, in part, their increased ZP-binding ability compared with that of washed capacitated sperm. Analyses of phospholipid fatty acyl chains revealed that PGC capacitated sperm were enriched in phosphatidylcholine (PC) molecular species containing highly unsaturated fatty acids (HUFAs), with docosahexaenoic acid (DHA; C22: 6n-3) being the predominant HUFA (42% of total hydrocarbon chains of PC). In contrast, the level of PC-HUFAs comprising arachidonic acid (20:4n-6), docosapentaenoic acid (C22:5n-6), and DHA in washed capacitated sperm was only 27%. Having the highest unsaturation degree among all HUFAs in PC, DHA would enhance membrane fluidity to the uppermost. Therefore, membranes of PGC capacitated sperm would undergo fertilization-related fusion events at higher rates than washed capacitated sperm. These results suggested that PGC mouse sperm should be used in fertilization experiments and that SGG and DHA should be considered to be important biomarkers for sperm fertilizing ability.

Animals↗
PubMedDate not supplied

Hemodynamics on abrupt stoppage of centrifugal pumps during left ventricular assist.

A magnetically suspended centrifugal pump (MSCP), developed for long-term ventricular assist, is reliable and durable because it has no shaft or seal. However, with nonvalve pumps such as a MSCP, regurgitation occurs when they accidentally stop without cannula clamping. We investigated the hemodynamics during temporary stoppage of a MSCP being used as a left ventricular assist system (LVAS), comparing two inflow cannulation sites. In four sheep (weight, 35-45 kg), microspheres were injected into the left main coronary artery to induce heart failure. An outflow cannula was sutured onto the descending aorta, and two inflow cannulae were inserted into the left atrium and the left ventricle. The MSCP was stopped with both the left ventricular cannula and left atrial cannula clamped, and the hemodynamics and P-V loops were recorded. Each cannula was then unclamped in order, and similar parameters were recorded. LVEDP increased at unclamping of the left ventricular cannula (ULVC), and rose further at unclamping of the left atrial cannula (ULAC). Aortic pressure did not change at ULVC, but decreased at ULAC. The effective systemic flow that subtracted the regurgitant flow through the MSCP from left ventricular output was half at ULVC and almost 0 at ULAC. When stopping centrifugal pumps without circuit clamping, hemodynamic deterioration is less at ULVC than at ULAC. This finding suggests that left ventricular inflow cannulation is recommended to allow more time in emergency situations.

Animals↗
PubMedDate not supplied

Magnetically suspended centrifugal blood pump with a self bearing motor.

A magnetically suspended centrifugal blood pump with a self bearing motor has been developed for long-term ventricular assistance. A rotor of the self bearing motor is actively suspended and rotated by an electromagnetic field without mechanical bearings. Radial position of the rotor is controlled actively, and axial position of the rotor is passively stable within the thin rotor structure. An open impeller and a semiopened impeller were examined to determine the best impeller structure. The outer diameter and height of the impeller are 63 and 34 mm, respectively. Both the impellers indicated similar pump performance. Single volute and double volute structures were also tested to confirm the performance of the double volute. Power consumption for levitation and radial displacement of the impeller with a rotational speed of 1,500 rpm were 0.7 W and 0.04 mm in the double volute, while those in the single volute were 1.3 W and 0.07 mm, respectively. The stator of the self bearing motor was redesigned to avoid magnetic saturation and improve motor performance. Maximum flow rate and pressure head were 9 L/min and 250 mm Hg, respectively. The developed magnetically suspended centrifugal blood pump is a candidate for an implantable left ventricular assist device.

Centrifugation↗
PubMedDate not supplied

Purification of Treponema pallidum, Nichols strain, by Percoll density gradient centrifugation.

The purification of motile and virulent Treponema pallidum, Nichols strain, from rabbit testicular tissue is reported. Suspensions of T. pallidum were overlayed onto 20-ml cushions of 43% Percoll and in-situ density gradients were formed by centrifugation at 34,800 g for 30 min. Gradient fractionation indicated that T. pallidum banded at a density of 1.051 g/cc3 and that soluble proteineous testicular components remained in the upper portion of the gradient. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) confirmed the removal of host testicular and serum components. Purified suspensions of T. pallidum were greater than 95% actively motile and fully virulent, and greater than 50% motility could be maintained in vitro for up to five days. As determined by electron microscopy, Percoll-purified T. pallidum was structurally unaltered and contained much less tissue debris than did crude extracts or T. pallidum prepared by differential centrifugation. The Percoll purification method has been applied successfully to physiology, recombinant DNA, and antigenic structure studies, and to the preparation of antigen for the fluorescent treponemal antibody-absorbed (FTA-Abs) test for syphilis.

Animals↗
PubMed1984

Bone marrow repopulation capacity after transplantation of lymphocyte-depleted allogeneic bone marrow using counterflow centrifugation.

Bone marrow from six allogeneic HLA-matched and MCL nonreactive siblings was fractionated by means of isopycnic flotation centrifugation and subsequent counterflow centrifugation. The low density fraction (d less than or equal to 1.070 g/ml) obtained by IFC contained 20% of the nucleated cells and more than 90% of the myeloid and erythroid progenitors. The putative stem cell fraction obtained by CC showed a satisfactory recovery (88%) of the CFU-GM and BFU-E and only 3.5% of the original number of T lymphocytes. Bone marrow repopulation capacity was not impaired in comparison with a comparable group of patients. Despite the average high age of this group (29.6 years), only one of the four evaluable patients developed graft-versus-host disease.

Adolescent↗
PubMed1998

Relative sedimentation of hematopoietic progenitors in human cord blood, peripheral blood, and bone marrow as determined by counterflow centrifugal elutriation.

BACKGROUND: The current use of cord blood (CB) and peripheral blood (PB) stem cells as alternatives or adjunctives to bone marrow (BM) for hematopoietic reconstitution in the treatment of various diseases prompted an examination of the progenitors of these tissues by counterflow centrifugal elutriation (CCE). METHODS: The cells, obtained from normal donors not primed with colony-stimulating factors, were centrifuged at 3000 rpm in a Beckman Sanderson Chamber. Fractions (Frs.) were collected at (1) 18 ml/min, (2) 25 ml/min, (3) 32 ml/min, (4) 40 ml/min, and (5) the rotor-off fraction. RESULTS: Clonogenic assays revealed differences in the fraction localizations for CB and PB when compared to BM, i.e., recovery of the colony-forming units for CB and PB was greater in the small-medium cell size CCE fractions, and those from BM were found primarily among the medium-large cell size fractions. Thus, although colony-forming unit granulocyte/macrophage colonies were distributed throughout Frs. 2-5 of BM, CB and PB showed 80% of the total to be in Frs. 2 and 3. Further, although burst-forming unit erythroid colonies of BM were distributed equally in Frs. 2 and 3, greater than 70% of the total burst-forming unit erythroid colonies in CB and PB were found in Fr. 2. Distribution of the CD34 cells in the fractions correlated with the colony-forming units in that these were found primarily in Frs. 2 and 3 of CB and PB, whereas they were present in significant numbers throughout Frs. 1-5 of BM. CONCLUSIONS: We interpret these findings to indicate CB and PB to be qualitatively similar in their hematopoietic lineage development and to contain a greater proportion of early versus late progenitors relative to those found in BM.

Blood Cells↗
PubMedDate not supplied

Magnetically suspended centrifugal blood pump with a radial magnetic driver.

A new magnetic bearing has been designed to achieve a low electronic power requirement and high stiffness. The magnetic bearing consists of 1) radial passive forces between the permanent magnet ring mounted inside the impeller rotor and the electromagnet core materials in the pump casing and 2) radial active forces generated by the electromagnets using the two gap sensor signals. The magnetic bearing was assembled into a centrifugal rotary blood pump (CRBP) driven with a radial, magnetic coupled driver. The impeller vane shape was designed based upon the computational fluid dynamic simulation. The diameter and height of the CRBP were 75 mm and 50 mm, respectively. The magnetic bearing system required the power of 1.0-1.4 W. The radial impeller movement was controlled to within +/- 10 microm. High stiffness in the noncontrolled axes, Z, phi, and theta, was obtained by the passive magnetic forces. The pump flow of 5 L/min against 100 mm Hg head pressure was obtained at 1,800 rpm with the electrical to hydraulic efficiency being greater than 15%. The Normalized Index of Hemolysis (NIH) of the magnetic bearing CRBP was one fifth of the BioPump BP-80 and one half of the NIKKISO HPM-15 after 4 hours. The newly designed magnetic bearing with two degrees of freedom control in combination with optimized impeller vane was successful in achieving an excellent hemolytic performance in comparison with the clinical centrifugal blood pumps.

Biomedical Engineering↗
PubMedDate not supplied

Feasibility of a miniature centrifugal rotary blood pump for low-flow circulation in children and infants.

In this study, a seal-less, tiny centrifugal rotary blood pump was designed for low-flow circulatory support in children and infants. The design was targeted to yield a compact and priming volume of 5 ml with a flow rate of 0.5-4 l/min against a head pressure of 40-100 mm Hg. To meet the design requirements, the first prototype had an impeller diameter of 30 mm with six straight vanes. The impeller was supported with a needle-type hydrodynamic bearing and was driven with a six-pole radial magnetic driver. The external pump dimensions included a pump head height of 20 mm, diameter of 49 mm, and priming volume of 5 ml. The weight was 150 g, including the motor driver. In the mock circulatory loop, using fresh porcine blood, the pump yielded a flow of 0.5-4.0 l/min against a head pressure of 40-100 mm Hg at a rotational speed of 1800-4000 rpm using 1/4" inflow and outflow conduits. The maximum flow and head pressure of 5.25 l/min and 244 mm Hg, respectively, were obtained at a rotational speed of 4400 rpm. The maximum electrical-to-hydraulic efficiency occurred at a flow rate of 1.5-3.5 l/min and at a rotational speed of 2000-4400 rpm. The normalized index of hemolysis, which was evaluated using fresh porcine blood, was 0.0076 g/100 l with the impeller in the down-mode and a bearing clearance of 0.1 mm. Further refinement in the bearing and magnetic coupler are required to improve the hemolytic performance of the pump. The durability of the needle-type hydrodynamic bearing and antithrombotic performance of the pump will be performed before clinical applications. The tiny centrifugal blood pump meets the flow requirements necessary to support the circulation of pediatric patients.

Centrifugation↗
PubMed1977

Electron microscopy of herpes simplex virus DNA molecules isolated from infected cells by centrifugation in CsCl density gradients.

Herpes simplex virus (HSV) DNA molecules were isolated from infected BSC 1 cells and centrifuged in CsCl-ethidium bromide density gradients. Both newly labelled and mature virus DNA molecules were found to have a linear conformation. The morphology of virus DNA molecules at different stages of the virus growth cycle in BSC 1 cells, was studied by electron microscopy after separation of virus DNA from cellular DNA by centrifugation in CsCl gradients. In each sample, about 200 virus DNA molecules were photographed and the different morphological forms were studied. Four classes of virus DNA molecules were observed: (a) mature linear DNA molecules, 52-4 +/- 3-3 micronm in length, (b) DNA intermediates, (c) virus DNA molecules having one or more single-stranded filaments attached to them and (d) molecules with collapsed regions or with branches. A few circular molecules as well as linear DNA molecules longer than unit length were also observed. The virus DNA molecules resembling replicative intermediates gradually increased in number and reached a maximal amount of about 5% of the virus DNA population at 12 h after infection. The other forms of virus DNA were found to persist after the number of replicating DNA molecules decreased.

Cell Line↗
PubMed1984

Equilibrium density gradient centrifugation of the scrapie agent in Nycodenz.

Plasma membrane-enriched preparations from scrapie-infected and healthy hamster brains were detergent-extracted, then separated by equilibrium density centrifugation in continuous Nycodenz gradients. The highest level of infectivity was always associated with the insoluble residue which sedimented through 40% Nycodenz. The degree of aggregation in these insoluble complexes varied depending upon treatment. Centrifugation in gradients containing 2 M- to 8 M-urea resulted in the formation of large insoluble aggregates which seemed to retain a high level of infectivity when measured by the method of incubation interval assay. However, measurement of infectivity in these same samples by endpoint titration of tenfold dilutions resulted in values a thousand times lower. These observations reinforce previous findings that scrapie infectivity exists as a macromolecular complex and, furthermore, they emphasize the necessity for using non-denaturing conditions for purification of the scrapie agent.

Animals↗
PubMed1984

Purification by sucrose density gradient zonal centrifugation and affinity column chromatography of antigenic substances from the livers of mice infected with Tyzzer's disease.

Antigenic substances from livers of mice infected with Tyzzer's disease were purified by means of sucrose density gradient zonal centrifugation and affinity column chromatography using antiserum and checking antigenicity with the complement fixation test. Fractions obtained from zonal centrifugation fell into three main groups with different molecular weights, two of which (Fr. I and Fr. II) positively reacted with antiserum in the complement fixation tests. Both fractions were further purified by affinity column chromatography. The molecular weights of the main antigenic substances derived from Fr. I and Fr. II were determined to be about 52 000 and 66 000, respectively, by means of SDS-PAGE.

Animals↗
PubMed2005

Centrifugal force model for pedestrian dynamics.

In this paper, a centrifugal force model is developed for pedestrian dynamics. The effects of both the headway and the relative velocity among pedestrians are taken into account, which can be expressed by a "centrifugal force" term in dynamic equation. The jamming probability due to the arching at exits for crowd flows is provided. A quantitative analysis of the crowd flowing out of a hall shows that the average leaving time T is a function of the exit width W in negative power. The related simulation indicates that the proposed model is able to reproduce the self-organization phenomena of lane formation for sparse flows.

Behavior↗
PubMed1981

Density centrifugation of murine fibrosarcoma cells following in situ labelling with tritiated thymidine.

Murine fibrosarcoma (FSa) cells form at least five unique subpopulations after centrifugation in linear Renografin density gradients. Each of these subpopulations has been characterized with respect to selected kinetic parameters using pulse-labelling techniques and flow microfluorometry (FMF) analysis. Tumour-bearing mice were first injected intraperitoneally with a pulse label of tritiated thymidine ([3H]TdR, 50 microCi). Following 15, 30, 60 min or 24 hr these animals were injected with cold thymidine. Animals were killed, their tumours removed and made into suspension, and separated by density gradient centrifugation. Each gradient was fractionated and the density, cell number, tritium activity, and labelling index (LI) per fraction were determined. These data were then compared to FMF data for selected cell density, cell number, tritium activity, and labelling index (LI) per fraction were determined. These data were then compared to FMF data for selected cell density bands. The results indicated a relatively higher uptake of [3H]TdR in the cells recovered at the lighter (1.06-1.12 g/cm3) as compared to the heavier (greater than 1.12 g/cm3) densities. Following a 30-min pulse, the LI's of light cells (less than 1.12 g/cm3) ranged from 25 to 30%, while the heavier cells (greater than 1.12 g/cm3) had LI's between 10 and 15%. The unseparated control cells had an LI of 19%. comparable results were found at the other times tested. In contrast, the FMF profiles describing the DNA contents of the cells banding in the gradient showed no difference in proportion of S-phase cells among the separated subpopulations. This lack of correlation between the FMF determination of S-phase cells and labelling index for the denser cell populations implies that DNA content alone is not an effective measurement of the functional activity of cells in solid tumours. Finally, the relatively reduced uptake of [3H]TdR by these denser cells suggests that they may have resided at relatively large distances from the functional vasculature in the tumour.

Animals↗
PubMed2005

Are platelets activated after a rapid, one-step density gradient centrifugation? Evidence from flow cytometric analysis.

This procedure describes the preparation of platelets from whole blood of healthy donors and pregnancy-induced hypertensive (PIH) patients by a rapid, one-step density gradient centrifugation, and the direct immunofluorescence staining of obtained platelets (CD63). Platelets are relatively fragile structures. Consequently, for the investigation of their biochemical properties it is recommended to isolate them by a simple method that does not damage their functional parameters and induce their activation. During platelet activation, several changes occur at the platelet surface. CD63 is the receptor for a lysosomal glycoprotein expressed in activated platelets. Currently, flow cytometry (fluorescence-activated cell sorting) is the most sensitive method to detect increased surface exposure of activation antigens on the platelet surface. The present technical note describes that compared with other whole blood flow cytometric techniques, our one-step density-gradient centrifugation method using OptiPrep can also prevent artificial, sample manipulation-related platelet activation.

Blood Platelets↗
PubMed1984

Heterogeneity of alveolar surfactant in the rabbit: composition, morphology, and labelling of subfractions isolated by centrifugation of lung lavage.

Rabbit alveolar saturated phosphatidylcholine (SPC) can be separated by differential and density gradient centrifugation of lung lavage into three fractions. One fraction ('B'), which is analogous to conventionally prepared alveolar surfactant, contains 46.0 +/- 5.9% (SD) of lavage SPC, and is made of large multilamellar vesicles or sheet-like structures. A second fraction ('C') does not sediment after centrifugation at 80 000 g for 90 min, contains 29.8 +/- 14.0% of lavage SPC, and a uniform population of small vesicles. This fraction incorporates 3H-palmitate administered intravenously with a small delay with respect to fraction 'B'. A third fraction ('D') contains almost all the cells of lavage and less than 5% of lavage SPC. We conclude that alveolar SPC consists of more than one compartment. The possible significance of isolated fractions is discussed.

Animals↗
PubMed1984

Improved techniques for separating motile spermatozoa from human semen. II. An atraumatic centrifugation method.

A simple and atraumatic method for concentrating washed, motile spermatozoa from normal and subnormal semen specimens is described. It incorporates a modified technique of centrifugation in which sperm are spun onto a soft, fluid cushion, thereby minimizing mechanical damage. Following initial semen dilution to 5-10 ml in an artificial medium, the mixture is transferred to a test tube and layered onto 1 ml of oily contrast medium (Lipiodol). After centrifugation at 300 g for 10 min all but 0.5 ml of the supernatant is discarded, and the unshaken test tube is incubated at 37 degrees C for 15-20 min, during which time the motile sperm migrate into the upper 0.5 ml. After this incubation, 0.3 ml of the upper layer is removed which is sufficient for most IVF and AIH purposes. It contains concentrated, washed, motile spermatozoa that are free of debris and most abnormal forms. No change in pH or osmolarity and no diffusion of any iodine from the oil base into the top layer were detected.

Cell Separation↗