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At least 271 records · Page 15Linked to original sources
PubMed1999

Can centrifugation at increased G be used to predict results of 0G?

Can physiologic research on the effects of weightlessness be conducted using a centrifuge providing an increased G environment? The answer to this question, if affirmative can have extraordinary implications regarding physiologic research in space that now begs the answer to the more general and basic question, what is the 'best environment' to differentiate the biological effects of mass from weight? In considering the best environment, there are several important factors in support of conducting human and animal physiologic 'gravitational' research on centrifuges here on Earth. Increased G research using a centrifuge can be conducted for a small fraction of the cost of research in space. It can be made available to more scientists as the number of centrifuges for this type of research increases. There are far less-detailed and therefore much easier preparation requirements for animal and human studies on a centrifuge compared with space research.

Acceleration↗
PubMed1999

[Technical consideration of setting up a specification for human centrifuge evaluation of anti-G equipment].

Anti-G equipment needs to be evaluated using human centrifuge before further developed. However, there isn't a general specification for human centrifuge evaluation of anti-G equipment. From related literature and from our over thirty years experience in this area, we sum up to five aspect technical consideration below: human centrifuge, medical specification for using human in +Gz stress experiment, anti-G equipment experimental assembly, principle should be abided by during human centrifuge evaluation of anti-G equipment. We hope that the technical considerations mentioned in the paper should be helpful to the work of setting up a specification for human centrifuge evaluation anti-G equipment. After we have a specification, the research will be conducted orderly and the anti-G [correction of an-G] equipment will be developed sequentially.

Acceleration↗
PubMed2003

[Effects of centrifugation-related artificial gravity on the human organism. Positive and negative effects].

Data of investigations of the artificial gravity issues in centrifuge experiments in Russian, USA and Japan over the past 40 years were analyzed. Periodic +Gz centrifugation was used to prevent or eliminate body deconditioning after 3- to 56-d simulated microgravity, and to increase the body functional reserve (orthostatic stability) in ordinary life. Positive effects included prevention of a decline of gravitational stability and reduction or averting the negative effects of simulated microgravity on various physiological systems. Better results can be achieved by combining artificial g-loads with the well-proven methods of combating deconditioning, i.e. physical training on bicycle ergometer and induced hydration. Human tolerance of g-loads on a short-arm centrifuge with a high (100%) gravitational gradient was found no worse than on a mid-arm centrifuge with a lower (20%) gravitational gradient. Negative effects of +Gz on a short-arm centrifuge were revealed and counteracting measures were determined.

Centrifugation↗
PubMed1992

Experience with the Sarns centrifugal pump in postcardiotomy ventricular failure.

The reported clinical use of the Sarns centrifugal pump (Sarns, Inc./3M, Ann Arbor, Mich.) as a cardiac assist device for postcardiotomy ventricular failure is limited. During a 25-month period ending November 1988, we used 40 Sarns centrifugal pumps as univentricular or biventricular cardiac assist devices in 27 patients who could not be weaned from cardiopulmonary bypass despite maximal pharmacologic and intraaortic balloon support. Eighteen men and nine women with a mean age of 60.4 years (28 to 83) required assistance. Left ventricular assist alone was used in 12 patients, right ventricular assist in 2, and biventricular assist in 13. The duration of assist ranged from 2 to 434 hours (median 45). Centrifugal assist was successful in weaning 100% of the patients. Ten of 27 patients (37%) improved hemodynamically, allowing removal of the device(s), and 5 of 27 (18.5%) survived hospitalization. Survival of patients requiring left ventricular assist only was 33.3% (4/12). Complications were common and included renal failure, hemorrhage, coagulopathy, ventricular arrhythmias, sepsis, cerebrovascular accident, and wound infection. During 3560 centrifugal pump hours, no pump thrombosis was observed. The Sarns centrifugal pump is an effective assist device when used to salvage patients who otherwise cannot be weaned from cardiopulmonary bypass. Statistical analysis of preoperative patient characteristics, operative risk factors, and postoperative complications failed to predict which patients would be weaned from cardiac assist or which would survive.

Adult↗
PubMed2004

The development of the International Space Station centrifuge.

Gravitational biology research facility "Centrifuge" is currently under development for the International Space Station. Research in the Complex Organism Biology, indispensable to the progress in Health Science, is only possible in the Centrifuge aboard the station. So, on-orbit 1 G controls for various specimens including small mammals, fish, and higher plants will be rigorously done in the Centrifuge. This facility is also capable of providing "reduced gravity" likely on the Moon or on Mars. Thus, it will play a key role in creating knowledge of space fundamental biology. As part of the offset of NASA's Shuttle launch services for the Japanese Experiment Module, JAXA is developing the Centrifuge Rotor (CR), the Life Sciences Glovebox (LSG) and the Centrifuge Accommodation Module (CAM). Critical Design Review (CDR) of LSG was conducted on July 2004, while the system CDRs of the CAM and CR are scheduled for December 2004 and August 2005, respectively. Their launch schedules are under review.

Animals↗
PubMed2005

Semicircular canal contribution to the perception of roll tilt during gondola centrifugation.

BACKGROUND: Spatial disorientation is an important problem in aviation. The mechanisms behind the sensation of roll tilt during coordinated turns are not well known. The present study aimed at elucidating what kind of semicircular canal information might cause tilts of the subjective horizontal during gondola centrifugation. METHODS: The subjective visual horizontal (SVH) was measured by means of an adjustable visual line in darkness. Subjects (n = 8) underwent four centrifuge runs (2 G, 5 min), sitting in different positions, i.e., heading forwards, backwards, centripetally, and centrifugally. The roll position of the gondola (60 degrees at 2 G) was controlled so that the subject was always upright with respect to the resultant gravitoinertial force vector. Thus, the semicircular-canal stimulus components in yaw, pitch, and roll were varied to some extent independently of each other. RESULTS: For the forward position the SVH was substantially tilted in a direction compensatory with respect to the inclination of the gondola. For the backward position there was also a tendency to a compensatory SVH tilt. In all subjects the magnitude of tilt was larger for the forward position than for the backward. The group means were +20.9 +/- 8.4 degrees and -6.9 +/- 10.5 degrees (positive sign designates a clockwise deviation of the SVH), p < 0.001, n = 8. There were no significant SVH tilts for the centripetal (+6.4 +/- 10.7 degrees) and centrifugal (+2.1 +/- 4.8 degrees) positions. The effects of deceleration of the centrifuge were very small for all positions. CONCLUSION: These findings suggest that the substantial SVH tilt after acceleration heading forwards is not directly related to any single component of semicircular canal stimulation but depends on the ability of the brain to expediently process complex stimulus patterns.

Adult↗
PubMedDate not supplied

Enhancement of sodium fluoride-induced cell death by centrifugal force.

As an initial step in the study of the influence of orthodontic force on cellular function in vitro, the effects of centrifugal force on the cytotoxicity induced by various apoptosis inducers were investigated. When human oral squamous cell carcinoma (HSC-2) and human promyelocytic leukemia (HL-60) cell lines were treated with increasing magnitudes of centrifugal force (evaluated by g-value), the viability assessed by the MTT method and trypan blue dye exclusion began to decline. Centrifugal force enhanced the cytotoxicity of sodium fluoride (NaF), but not that of redox compounds (hydrogen peroxide, sodium ascorbate, gallic acid) or chemotherapeutic agents (daunorubicin, doxorubicin, idarubicin, mitoxantrone, peplomycin, 5-FU). The combination of NaF and centrifugal force enhanced caspase-3 activity. The present study suggests that centrifugal force is an additional factor that modifies the biological activity of NaF.

Carcinoma, Squamous Cell↗
PubMed1991

Simulator sickness provoked by a human centrifuge.

Simulator sickness is now a well-recognized entity. It is recognized as a form of motion sickness, having a higher incidence in the more sophisticated simulators. Human centrifuges (dynamic simulators) are the newest innovation in aircrew training devices. Simulator sickness has never been reported in human centrifuges. We are reporting on a case of delayed simulator sickness in a pilot-subject after a centrifuge experience. A review of the "psycho-physiological" problems routinely experienced by subjects on human centrifuges indicates such problems are due to simulator sickness, although they are not reported as such. In this paper, we give a brief overview of simulator sickness and briefly discuss simulator sickness, as related to the human centrifuge experience.

Adult↗
PubMed1981

A high acceleration programmable centrifuge used in purification of myocardial and skeletal muscle myosins.

Protein purification can be improved by using high acceleration - deceleraton centrifugation. This study describes a high acceleration programmable centrifuge which reaches 5,000 x g in 3 sec and brakes from 5,000 to 0 x g in 4.3 sec. This study further describes the use of this centrifuge in myosin purification and thus demonstrates that protein purification can be improved by separating particles with a high acceleration - deceleration centrifuge for the following reasons: (1) biological and chemical equilibria are immediately terminated, (2) proteolysis is reduced, (3) working time is decreased, and (4) the native state of labile proteins are better preserved. Rapid acceleration and deceleration is advantageous in reducing centrifugation time for separation of particles because it decreases diffusion time of particles and non-desirable interactions.

Adenosine Triphosphatases↗
PubMedDate not supplied

[Effect of centrifugation on the early embryogenesis of the teleost Brachidanio rerio].

The early embryogenesis of the teleost Brachidanio rerio has been shown to be resistant to centrifugation. Beginning with the blastula stage, the development proceeds normally in 90% embryos centrifuged at 500 g for 1 h. Beginning with early developmental stages, embryos grow and develop normally when exposed to long-term centrifugation at 50 g. The exposure produces partial inhibition of cytotomy (with nuclear division continued). This effect changes the proportions of the cellular and syncytial fractions of the embryo (blastoderm and periblast). The exposure to centrifugation also reveals the dorsoventral asymmetry of egg surface tension. Resistance to centrifugation is attributed to the fact that the polarization control is beyond the cell embryonic fraction.

Animals↗
PubMed1978

Improved technique for increased granulocyte recovery from canine whole blood samples by counterflow centrifugation-elutriation. I. In vitro analysis.

Granulocytes were isolated from 120 ml of canine whole blood by a modification in counterflow centrifugation-elutriation technique. The leukocytes were concentrated in a buffy coat fraction and diluted to a fixed RBC density prior to entry into the rotor. Overall recovery of granulocytes from canine whole blood averaged 82% with 96% purity from contaminating mononuclear leukocytes. The purified cellular fraction was assayed in vitro to monitor O2 consumption, chemotaxis, bacterial growth inhibition, and enzyme activities. Cellular integrity was monitored by scanning and transmission electron microscopy as well as by cell volume analysis. The data suggest that the granulocytes isolated by counterflow centrifugation-elutriation suffered no noticeable morphological damage or loss of function in terms of recognition of a toxic agent, migration, phagocytosis, or bactericidal capacity. Granulocytes isolated by counterflow centrifugation-elutriation may be physiologically more active than cells obtained by filtration leukapheresis, continuous-flow centrifugal leukapheresis or discontinuous flow centrifugation both in vitro and in vivo.

Animals↗
PubMed1977

[Studies on the manufacture of hematological and cytological specimens using the centrifugation technic].

Centrifugal preparation (Cp) represents a method of creating haematological parameters which, in addition to a qualitative improvement of representing single cells, is suitable to produce reproducible haematological smear preparations. In qualitative and quantitative respect centrifugal preparations will reflect the intravasal conditions better than the common blood smear technique. Further advantages are the concentration of cellular elements and in connection with it the opportunity of finding cells rarely present. With a small amount of work centrifugal preparations enable counting values to be established as well as cytological and cytochemical findings from the venous blood to be obtained. As a result of the test it turned out that the common glass slides cannot be replaced by plastic foils ones without certain disadvantages appearing. First investigations of attempting to represent cells in culture medium as well as analyzing liquors and processing other biological liquids with the help of the centrifugal preparation technique brought unsatisfactory results. Centrifugal preparation provides the possibility of performing pre-programmed haematological examinations beginning with blood collection and ending up in the evaluation by a computer.

Blood Specimen Collection↗
PubMed1981

Effect of centrifugation on fluorescence polarization of amniotic fluid.

Fluorescence polarization was measured on amniotic fluids of different gestational ages before and after centrifugation at relative centrifugal forces of 34 to 4955 x g. Centrifugation significantly increased the fluorescence polarization values over those of uncentrifuged amniotic fluids. The greatest increase was observed in the most "mature" fluids centrifuged at 34 to 230 x g. Almost without exception, use of centrifugal forces greater than 1239 x g did not further increase fluorescence polarization values.

Amniotic Fluid↗
PubMed1995

[Observations on antibody determination and differentiation with papain test erythrocytes using the gel centrifugation technique (ID-Microtyping System)].

BACKGROUND: The gel centrifugation system (ID Microtyping System, Fa. Diamed, Bensheim, FRG) is one of several new methods, which has become commercially available within the last few years for the detection of antibodies against red blood cell antigens. MATERIALS AND METHODS: During 1 year we used the gel centrifugation method for antibody screening in our routine laboratory by performing 3 tests each time: 1. NaCl card (room temperature) with untreated red cells; 2. NaCl card (37 degrees C) with papain-treated red cells, and 3. Liss-Coombs card (37 degrees C) with untreated red cells. RESULTS: The two-stage papain test revealed some interesting phenomena: 1. In some cases the sensitivity of the papain gel test is higher than that of all other methods tested in this study, namely in the gel centrifugation technique and in the tube centrifugation technique. 2. There are reactions which seem to be directed against patients' own antigens (in the Rhesus or Kidd system), but there are no positive direct antiglobulin test and no clinical signs of hemolysis. 3. Some sera show reaction patterns which seem to have a distinct specificity, but they cannot be assigned to any of the antigens in the manufacturer's antigenogram. CONCLUSIONS: Before a general recommendation for antibody screening with the two-stage papain test in the gel centrifugation method can be given, further investigations about the clinical value of those antibodies which are detectable only by this technique are necessary. For antibody identification further declarations in the work sheet of the panel would be desirable.

Adult↗
PubMed1993

Rapid determination by centrifugal ultrafiltration of inter-mixed micellar/vesicular (non-lecithin-associated) bile salt concentrations in model bile: influence of Donnan equilibrium effects.

We have developed the technique of rapid (< 2 h) centrifugal ultrafiltration to measure the inter-mixed micellar/vesicular (non-lecithin-associated) bile salt (BS) concentrations (IMC) of individual BS in model biles. This methodology uses a centrifugal concentrator with a reinforced membrane, through which a small fraction (< 15% total volume) of model biles was ultrafiltered by low centrifugal forces (1500 g 5-60 min). Total and individual BS concentrations in the filtrate were measured by high performance liquid chromatography. However, non-filterable anions, in this case BS/lecithin/cholesterol mixed micelles and unilamellar vesicles, induce an asymmetric distribution of ions across the membrane. Therefore, BS concentrations in the filtrate exceeded the true IMC, which was estimated taking into account Donnan equilibrium effects. To confirm the hypothesis that a correction for Donnan forces was necessary, distributions of BS and another filterable anion, chloride, were measured in systems containing the non-filterable polyanion dextran sulfate as an analogue for non-filterable polyanionic mixed micelles and vesicles. An asymmetric distribution of the monovalent anions chloride and BS monomers as well as polyvalent simple BS micelles was indeed present during centrifugal ultrafiltration. This new methodology was validated by comparing IMC values with those obtained by modified equilibrium dialysis also corrected for Donnan equilibrium effects (Donovan, J.M., et al. 1991. J. Lipid Res. 32: 1501-1512). Centrifugal ultrafiltration, which utilizes < 1 ml of bile, determines the composition in the IMC necessary to separate micelles and vesicles of native biles by techniques that involve dilution of bile such as gel filtration chromatography.

Bile↗
PubMedDate not supplied

Vestibulo-ocular response of human subjects seated in a pivoting support system during 3 Gz centrifuge stimulation.

The vestibulo-ocular reflex (VOR) and spatial orientation perceptions were recorded in 15 subjects during 3 Gz centrifuge runs. These data were obtained to study two issues: (1) to gain insight into reports of asymmetrical disorientation and disturbance during acceleration and deceleration of centrifuge runs like those used to train pilots on the procedures to counteract G-induced loss of consciousness (G-LOC); (2) to study the effects of sustained vertical linear acceleration on the vestibular system. The centrifuge angular velocity profile consisted of a 19 s angular acceleration to 3 Gz that was sustained for 5 min during a period of constant angular velocity, and a 19 s deceleration to 1 Gz. The runs were repeated three times with the subject facing the motion and three times with the subject's back to the motion. The VOR and spatial orientation perceptions from the eight subjects who completed all six runs were analyzed. The total VOR response during acceleration and deceleration was composed of interacting angular (AVOR) and linear components (LVOR). Asymmetries in pitch orientation perception between centrifuge acceleration and decleration were not matched by asymmetries in the total VOR slow phase velocity. During the constant velocity high-G phase of the run, sustained up-beating LVOR (Lz nystagmus) was present in 14 of the 15 subjects. Significant individual differences in Lz nystagmus were found, but the maximum Lz response in our 15 subjects was probably of insufficient magnitude to degrade visual scan of cockpit instruments. Mean magnitudes ranged from 0 to 10 deg/s at 90 s from onset of centrifuge run.

Adult↗
PubMed1996

Clinical trials of a novel centrifugation method: axial separation.

Specimen centrifugation is one of the most time-consuming tasks associated with preanalytical specimen processing. We report the first clinical use and impact study of the novel centrifugation method, axial separation, using the Axial Separation Module (ASM). The ASM centrifuges medical specimens one at a time (in 1 min 9 s) in proprietary Axial Process Containers (APC). Here we report tests of the ASM in an outpatient clinical laboratory. Use of the ASM in the outpatient clinic laboratory led to an average total improvement (decrease in total bench time) of 8 min 9 s per specimen compared with conventional centrifugation. Laboratory analysis revealed no statistical difference between plasma obtained from the APC vs that from a Becton Dickinson Vacutainer Tube. We conclude the ASM offers a cost-effective alternative to conventional centrifugation. Further, the use of axial separation may allow specimen separation to become an integral part of the phlebotomy process.

Blood↗
PubMed1996

Clinical use of centrifugal pumps and the roller pump in open heart surgery: a comparative evaluation.

Centrifugal pumps have been used widely as the main pump in open heart surgery to reduce damage to blood elements and to reduce the activation of the coagulation system. The purpose of this study was the evaluation and comparison of the effects of two types of centrifugal pumps and of one type of roller pump on blood elements, the coagulation system, complements, and immunoglobulins. Two types of centrifugal pumps (Lifestream; St. Jude Medical, Chelmsford, Massachusetts; and BP-80: Medtronic, BioMedicus, Inc., Eden Prairie, Minnesota, U.S.A.) and one roller pump (Mera Co.) were used separately as the main pump for cardiopulmonary bypass (CPB) in 29 patients. Platelet counts, lactate dehydrogenase, antithrombin III, thrombin-antithrombin complex (TAT), complements (C3, C4, and CH50) and immunoglobulins G, A, and M values were measured before and after CPB and compared. Values, except those for TAT, showed no significant difference among the three groups. The TAT values increased less in each of the centrifugal pump groups than in the roller pump group. This finding suggests that thrombin synthesis might be suppressed by the use of a centrifugal pump.

Adult↗