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PubMedDate not supplied

Comparison of motility characteristics and normal sperm morphology of human semen samples separated by percoll density gradient centrifugation.

The aim of this study was twofold: to investigate the ability of Percoll gradient centrifugation (52, 68, 84%) to fractionate semen samples according to motility quality and percentage normal morphology and to determine whether there is an association between sperm motility quality and percentage normal morphology. Sperm motility was evaluated using a Hamilton Thorn analyzer and normal sperm morphology was manually assessed according to the strict criteria (< or = 4, 5-14, and >14%). The majority of motility parameters and the percentage normal morphology were found to be significantly improved in the 84% Percoll fraction. The greatest effect was on the < or = 4% group, shifting the mean normal morphology percentage from 2.6 to 5.2%. Curvilinear velocity (VCL) and average path velocity (VAP) were the only two motility parameters that were significantly associated with the percentage normal morphology. Using a combined VCL, VAP vector the >14% group was found to have a significantly different value as compared to the 5-14 and < or = 4% groups. Percoll (discontinuous) gradient centrifugation can therefore play a significant role in the improvement of semen samples for use in assisted reproduction procedures. The VCL, VAP vector identified may also serve as an additional tool in the prediction of the fertility potential of sperm samples.

Analysis of Variance↗
PubMed1986

The application of two-dimensional centrifugation to clinical chemistry testing.

We have developed a new clinical chemistry analyzer, the VISION System, which uses centrifugal force to separate whole blood, measure reagent and plasma volumes, and complete all steps required for a spectrophotometric analysis. The system is based on a multichambered test pack containing liquid reagents, which can be centrifuged in two planes oriented at right angles to each other. The analyzer regulates the temperature, timing and optical measurements for up to 10 different test packs in the same run. We have demonstrated good precision and accuracy on 6 clinical chemistry analytes, 2 enzymes, potassium and theophylline using this system.

Blood Chemical Analysis↗
PubMed1992

Mixing does not improve mechanical properties of all bone cements. Manual and centrifugation-vacuum mixing compared for 10 cement brands.

Contemporary mixing methods--centrifugation, vacuum mixing with or without precompression--were compared with manual mixing by testing strength characteristics in accordance with a proposed revision of the international standard for bone cements as applied to 10 cement brands. Simplex brands and low-viscosity cements were the strongest, and were not improved by any of the vacuum-mixing procedures. Centrifuging was found unsuitable for low-viscosity cements. Without attaining the strength of the former, the cements best suited for auxiliary mixing methods were CMW-1 and Palacos brands, which improved 6-11 percent by either of the methods. The Sterivac system was generally found unacceptable, because about 20 percent of a cement package was retained in the mixing gear, and the application of precompression had no additional effect on compressive and bending strengths.

Acrylic Resins↗
PubMed1990

Effects of centrifugation speed and freezing on composition of ruminal bacterial samples collected from defaunated sheep.

Triplicate ruminal samples from four rumen-cannulated defaunated sheep (50 kg BW) were used in a completely randomized design experiment with a 2 x 3 factorial arrangement of treatments to test effects of two pretreatments (fresh vs. freezing) and three centrifugation speeds (4640 x g for 30 min; 9820 x g for 20 min; 25,900 x g for 20 min) or quantity of ruminal bacteria harvested and composition of ruminal bacterial samples. There were no differences among centrifugation speeds on quantity of ruminal bacterial harvested, organic matter, total N, RNA, and diaminopimelic acid concentrations (% of DM), or RNA:N, RNA:organic matter, N:organic matter, and diaminopimelic acid:organic matter ratios. However, there were differences between fresh and frozen samples for all measurements except diaminopimelic acid concentration, and the diaminopimelic acid:organic matter ratio, suggesting that freezing ruminal fluid is not appropriate for obtaining truly representative bacterial samples.

Animals↗
PubMed1988

Separation of red blood cells at high volume concentration under low centrifugal accelerations.

The separation process of blood and RBC suspensions in a hematocrit range between 0.3-0.7 was investigated with a centrifuge allowed to run at low accelerations (100 xg-1000 xg). The position of the interface between the supernatant of plasma and the RBC column was continuously recorded by a new optoelectronic measuring system. The separation process could be mathematically described by an exponential decrease of the cell column approaching a final packing. At a given centrifugal acceleration the time constant is influenced by hematocrit, aggregation, deformation and plasma viscosity. The final packing depends linearly on the starting hematocrit (0.3-0.7) and can be used as a measure of deformability.

Blood Sedimentation↗
PubMed1975

A biological safety centrifuge.

The Washington State Public Health Laboratories has devised a metho to capture and remove aerosols produced during centrifugation. The method to adapt any centrifuge having an enclosed chamber with an air intake hole in the lid, and an exhaust hole in the bottom of the chamber, is discussed.

Aerosols↗
PubMed1998

Adaptation of rat gastrocnemius muscles to 2 weeks of centrifugation: myofibers and extracellular matrix.

BACKGROUND: The effect of 2 wk of exposure to centrifugation (2G) on gastrocnemius muscles of rats was investigated by morphometric and computer-assisted image analysis of muscle fiber areas and non-contractile tissue components (extracellular matrix). RESULTS: Muscle atrophy was seen in the myofibers from 2G rats which had decreased in cross-sectional area by 26%. In contrast, the non-contractile tissue component actually increased by 13%. These results were compared with soleus muscle atrophy seen following 2 wk of unloading by tail-suspension. In all cases, the extracellular matrix increased in proportion to the decrease in fiber area. A theoretical model was developed to assess the effect of changes in myofiber cross-sectional area on the relative content of the extracellular matrix. The experimental results from both rat gastrocnemius and soleus muscles were consistent with the model with slight variations due to the known differences in connective tissue content of different muscles in the rat. CONCLUSION: Thus, the gastrocnemius muscle atrophy seen after 2 wk of centrifugation results from loss of contractile and other myofiber specific proteins while the extracellular matrix remains relatively constant. The loss in myofiber content was greater than expected from changes in muscle wet weight and more than required to adapt to a decrease in body weight.

Adaptation, Physiological↗
PubMed2000

[Preparation of pellets with a centrifugal granulator].

It has been investigated how the centrifugal-granulator is applicable to form paracetamol pellets with good mechanical, powder rheological and dissolutional properties. During the preparation process the mechanical parameters were the same only the percentage of the effective material was changed. The authors found that the centrifugal-granulator is well applicable to form good pellet particles which have good dissolution and mechanical parameters to from needle shaped raw materials.

Centrifugation↗
PubMed2001

Theoretical and experimental analysis of the sedimentation kinetics of concentrated red cell suspensions in a centrifugal field: determination of the aggregation and deformation of RBC by flux density and viscosity functions.

The flow properties of blood are mostly determined using various viscometric approaches, and described in terms of a shear rate or shear stress dependent apparent viscosity. The interpretation of results are rather difficult, especially at low shear rates when particle sedimentation and migration within the viscometer gap are significant. By contrast, analysing the separation process in concentrated RBC suspensions in a centrifugal field also yields information about the viscosity function, including particle-particle interaction and deformation parameters. In this paper, the sedimentation process is approached by means of the theory of kinematic waves and theoretically described by solving the corresponding one-dimensional quasi-linear partial differential equation based on viscosity/flow function as a function of volume concentration. The sedimentation kinetics of rigid spherical RBC suspended in saline and normal RBC suspended in Dx-saline solutions were investigated by means of a separation analyser (LUMiFuge 114). The instrument detects the light transmission over the total length of the cell containing the suspension. During centrifugation the analyser automatically determines the position of the particle free fluid/suspension interface or the sediment by means of a special algorithm. The data obtained with sedimentation of rigid spherical RBC at different volume concentrations demonstrate that, in the case of suspensions rotated in containers of constant cross section, there is good agreement between the theory of kinematic waves developed by Anestis and Schneider (1983) and the results of the experiments. Such good agreement was obtained even though a restrictive one-dimensional model was used to obtain the theoretically derived sedimentation time course. In addition, we describe an algorithm enabling the experimental determination of the viscosity and related flux density function to be made for any suspension. Through this approach, we investigated in detail the rheological behavior of suspended rigid spheres at low Reynolds numbers ranging from 10(-6) to 10(-3). The method here introduced also enabled us to investigate RBC suspensions with respect to the deformability and interactions of the cells by means of the separation analysis. Normal, rigid as well as aggregating RBC exhibited marked differences in the sedimentation kinetics, which were quantified by means of the flux and viscosity functions based on the theory of kinematic waves.

Blood Sedimentation↗
PubMed1992

Centrifuges: evolution of their uses in plant gravitational biology and new directions for research on the ground and in spaceflight.

The use of centrifugation as a tool for exploring qualitative and quantitative features of plant responses to gravity and to other body forces can be traced to plant scientists' early 19th century experiments. To study how plants perceive and respond to gravitational stimuli requires experimental manipulation of the force or acceleration vector direction and magnitude. As technology advanced, especially during the past half-century, so did the sophistication of experimental designs and of the scientific questions that could be addressed. The most significant improvement in methodology probably will prove to be attainment of experimental access to the hypogravity range of inertial accelerations by the combination of centrifugation and spaceflight.

Acceleration↗
PubMed1993

The use of centrifugation to study early Drosophila embryogenesis.

By the end of 10th nuclear cycle, the somatic nuclei of the Drosophila embryo have migrated to the periphery of the egg. Centrifugation of embryos did not result in the displacement of these nuclei, since cytoskeletal elements anchor them to the cortex. But, mild centrifugal forces displace the centrally located, nascent yolk nuclei. If this increased sensitivity to hypergravity occurs before the beginning of nuclear differentiation during cycle 8, when the nascent yolk and somatic nuclei physically separate, then it would mark the earliest functional difference between these two lineages.

Animals↗
PubMed1998

Blastopore formation in the animal hemisphere: functional inversion of gastrulation by centrifugation of Xenopus laevis eggs.

Eggs of Xenopus laevis and many other amphibians contain a gradient of yolk platelets along the animal-vegetal axis. Small platelets predominate in the animal hemisphere, and a boundary between medium and large yolk platelets exists near the equator. The blastopore forms at this boundary at the beginning of gastrulation, in the vegetal hemisphere. Does this boundary have a role in determination of the position of the blastopore, or does cortical information predominate? Past experiments using 1g to invert the egg showed a distinct tendency to form the blastopore in the original vegetal hemisphere. Our experiments, however, have used 20g centrifugation to achieve a more complete inversion of the yolk gradient. The blastopore formed in the original animal hemisphere in >95% of surviving gastrulae, if centrifugation was begun at normalized time 0.20-0.25 of the first cell cycle. Nearly normal larvae (DAI grades 4 and 5) form in 64% of cases (ave. DAI = 3.2). These data support the idea that the position of the blastopore depends on the position of the egg's internal contents rather than cortical determinants.

Animals↗
PubMed1996

Centrifuge man-rating of a conceptual internal abdominal bladder restraint in an extended coverage anti-G suit.

An extended coverage anti-G suit, has been demonstrated to improve +Gz tolerance substantially. In some pilots/subjects, however, the abdominal bladder of the anti-G suit may expand excessively upward and inward causing discomfort and pain. This man-rating was performed to evaluate the effects on +Gz protection of an internal abdominal bladder restraint in the Swedish Tactical Flight Combat Suit (TFCS) used in conjunction with pressure breathing during G (PBG). The tests were executed in the Armstrong Laboratory Centrifuge at Brooks AFB with four Swedish test fighter pilots. The centrifuge profiles included gradual onset runs (GOR, relaxed) and rapid onset runs (ROR, with straining), as well as simulated aerial combat maneuver (SACM) runs up to +9 Gz until subjects experienced light loss or fatigue or surpassed 228 s. All subjects withstood 60 s at +9 Gz during GOR and ROR runs with and without abdominal bladder restraint. No difference There was no difference in SACM duration times. In three of four subjects, abdominal pain or discomfort experienced without abdominal bladder restraint disappeared with the addition of a bladder restraint. Ratings of perceived exertion (after 5 peaks at +9 Gz in the SACM), subjective +Gz tolerance, overall comfort, fatigue, and heat stress demonstrated no relevant differences with and without abdominal bladder restraint. Therefore, to enhance comfort, it seems possible to modify the TFCS by adding an abdominal bladder internal restraint without compromising its operational +Gz protection.

Abdomen↗
PubMed1999

Assessment of two methods to reduce simulated +Gz-induced arm pain using a non-centrifuge model.

Complaints of +Gz-induced arm pain have been expressed by centrifuge subjects and, to a lesser degree, by high performance fighter pilots, usually when the control stick and throttle are positioned below heart level; the pain may be higher during pressure breathing for +Gz protection. Elevated transmural pressure and overdistension of the blood vessels in the arms have been suggested as causal factors. An earlier-developed non-centrifuge model was used to provoke arm pain similar to that induced by +Gz exposure. Eleven healthy subjects placed inside a hyperbaric chamber with an arm externalized through a sealed opening. They were exposed to chamber pressures at 75, 100 and 125 mmHg fitted with elastic bandage of the arm, or a localized pressure of 50 mmHg applied to the vessels of the upper arm or were provided no protection (control). Arm pain was estimated using a modified Borg scale. The sizes of the ulnar, radial and interosseous arteries, and corresponding veins, at the elbow level were measured using a sonographic imaging system. No statistically significant differences in pain were detected comparing control to proposed (counteracting) devices. There were no statistical differences in arm arterial or venous vessel size with the different devices at the different pressures. Thus, the devices tested did not show any protection against the provoked arm pain.

Adult↗
PubMed2001

Effect of particle size on the performance of batchwise centrifugal filtration.

The effect of particle size distribution on the performance of batchwise centrifugal filtration is studied. By analyzing the velocity of particles in a filter, a numerical program is designed for simulating the migration and deposition of particles. The particle size distributions and the average specific filtration resistances of cake are then estimated under various rotating speeds of the centrifuge. A large deviation of particle concentration profiles in the filter chamber will occur if the particle size distribution is not taken into consideration. A more heterogeneous cake will form under a lower rotating speed due to the sedimentation effect of particles. The predicted results of particle size distribution and average specific filtration resistance of cake agree well with the available experimental data.

Centrifugation↗
PubMed2002

A prolonged time interval between blood sample collection and centrifugation causes an increase in serum carbohydrate-deficient transferrin.

BACKGROUND: Carbohydrate-deficient transferrin (CDT) is used for the laboratory diagnosis of chronic alcohol abuse. Non-optimal preanalysis can cause an increase in CDT and false positive results. The aim of our study was to determine whether CDT results change over time between collection of the blood sample and centrifugation, and whether shipment of whole blood samples is a potential source of false positive CDT reports. MATERIAL/METHODS: 152 blood samples were drawn from 38 persons (4 tubes per person, one venipuncture) and randomly assigned to 4 groups with different time intervals between blood sample collection and centrifugation (1h, 24h, 48h, 144h). CDT analysis was done using the ChronAlcoI.D. assay. The statistical analysis was based on box-plots, ANOVA and Kruskal-Wallis ANOVA. RESULTS: The means and medians of CDT increased with the time of whole blood storage. ANOVA analysis of between-group differences was significant for mean CDT concentrations between 1 and 144 hours of whole blood storage. There was no correlation between CDT and free hemoglobin as a measure of hemolysis. An interference of hemolysis with CDT measurement can be excluded as the main cause of increased CDT results with whole blood storage time. Whether an in vitro degradation of the transferrin N-glycan chains causes the CDT increase should be evaluated by isoelectric focusing of the transferrin isoforms in a further study. CONCLUSIONS: Storage or shipment of whole blood samples can shift initially normal CDT values to borderline and borderline to pathological CDT results.

Blood↗
PubMed2001

A centrifuge-less plasma separation method from whole blood anticoagulated with EDTA-2K for the use of clinical laboratory tests.

In the modern medical laboratory system, simple and rapid processing of specimens are required. In the current system with the transportation line, its centrifugation part would disturb smooth flow of the testing because it needs much time for the centrifugation. To solve the problems, a serum separation method was tried for the whole blood specimen using poly-L-lysine, concanavalin A and phyto-hemoagglutinin. Ploy-L-lysine with molecular weight 130,000 to 210,000 in a final concentration of 0.1% could accelerate blood sedimentation, although its supernatant contaminated platelets. Concanavalin and phytohemoagulutinin could accelerate the sedimentation and obtained plasma, but the method could yield enough amount of supernatant by 1 hour standing. As the purpose of this study is to develop a centrifugeless method, a sieve method using a steel mesh and a magnet was applied to the mixture of EDTA blood, red-cell adhesives and thrombin. The method was unique to separate plasma, but the yield was not so high and chemistry data were not fitted with serum data in some of tests. Thus, the trial would be a new technology, but it was judged that some further improvement will be needed technically.

Anticoagulants↗
PubMed1975

[Improvement in the granulocyte harvest from normal donors by means of a combination of "continuous flow" centrifugation and filter leukapheresis].

In 27 healthy donors a total of 30 leukaphreses were performed with the Aminco cellseparator. Pretreatment by steroids, anticoagulation by heparin and addition of fluid gelatin to the input line was performed in all runs. The combination of continuous flow centrifugation and filtration leukapheresis in 9 of the 30 runs resulted in highly significant increase in the yield of neutrophil granulocytes to a mean of 59.6x10(9) as compared with a mean of 30.8x10(9) obtained the conventional continuous-flow centrifugation alone. This significance is valid for the total yield of granulocytes as well as for the yield per hour of run or per liter of blood processed. No adverse reaction occurred.

Blood Transfusion↗