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PubMed1979

Rat growth during chronic centrifugation.

Female weanling rats were chronically centrifuged at 4.15 g with controls at terrestrial gravity. Samples of 6 to 10 rats were sacrificed for body composition studies at 0, 28, 63, 105, 179 and 308 days of centrifugation and 57 days after centrifugation ended. The centrifuged group had a significantly lower mature body mass than the controls (251 vs 318 g) but the rate of approach to the mature values was the same in both groups. Retirement to 1 g on the 60th day resulted in complete recovery. Masses of muscle, bone, skin, CNS, heart, kidneys, body water and body fat were changed in the centrifuged group. However, an analysis of the growth in mass of individual components relative to growth of the total fat-free compartment revealed that only skin (which increased in mass) was responding to centrifugation per se.

Adipose Tissue↗
PubMed2001

Experimental analysis of centrifugal dewatering process of polyelectrolyte flocculated waste activated sludge.

The study experimentally investigated the centrifugal separation of moisture from activated sludge subject to cationic polyelectrolyte flocculation. An arm-suspended centrifuge was employed which allowed in-situ detection on all positions of interfaces of centrifuged sludge as functions of time. Experimental results revealed that, sludge flocculation would yield a significant sedimentation effect at the first phase of centrifugation. Therefore, not as suggested in conventional centrifugal-filtration models, the most significant moisture-removal stages included filtrate to flow through a wet cake. Moreover, an optimal rotational speed exists at which the moisture-removal rate reaches a maximum value. New theories/correlations are required to describe centrifugation dewatering of polyelectrolyte flocculated sludge.

Centrifugation↗
PubMed2000

Effect of centrifugation and partial removal of seminal plasma on equine spermatozoal motility after cooling and storage.

The objective of this study was to determine if centrifugation and partial removal of seminal plasma would improve spermatozoal motility in semen from stallions whose whole ejaculates have poor tolerance to cooling and storage. Stallions were divided into two groups (n = 5/group) based on the ability of their extended semen to maintain spermatozoal motility after cooling and storage. Group 1 stallions ("good coolers") produced semen in which progressive spermatozoal motility after 24 h of cooling and storage was reduced by < or = 30% of progressive motility prior to storage. Group 2 stallions ("poor coolers") produced semen in which progressive spermatozoal motility after 24 h of cooling and storage was reduced by > or = 40% of progressive motility prior to storage. The sperm-rich portion of each ejaculate was divided into 4 aliquots. Two aliquots underwent standard processing for cooled transported semen and were examined after 24 and 48 h of cooling and storage in an Equitainer. The remaining two aliquots were diluted 1:1 with semen extender, then centrifuged at 400 x g for 12 min at room temperature. After centrifugation, approximately 90% of the seminal plasma was removed, and the sperm pellet was resuspended in extender to a final concentration of 25 to 50 x 10(6) sperm/mL. These aliquots were then packaged as for the non-centrifuged aliquots and examined after 24 and 48 h of storage. The spermatozoal motion characteristics in fresh semen and after 24 and 48 h of cooling and storage was determined via computer-assisted semen analysis. Centrifugation and partial removal of seminal plasma increased the percentage of progressively motile spermatozoa and limited the reduction in progressive spermatozoal motility of "poor cooling" stallions after 48 h of cooling and storage. Results of this study indicate that centrifugation and partial removal of seminal plasma is beneficial for stallions whose ejaculates have poor tolerance to cooling and storage with routine semen dilution and packaging techniques, especially if the semen is stored for > 24 h.

Animals↗
PubMed1997

Proinflammatory cytokine release during pediatric cardiopulmonary bypass: influence of centrifugal and roller pumps.

OBJECTIVE: It has been proposed that nonocclusive centrifugal pumps may elicit less blood cell trauma and hence a reduced inflammatory response than standard roller pumps. However, there have been no reports describing the impact of such pumps on proinflammatory cytokine release in pediatric cohorts. DESIGN: A prospective randomized study was undertaken. SETTING: A regional cardiothoracic center of a university hospital. PARTICIPANTS: Thirty-four pediatric patients undergoing cardiopulmonary bypass (CPB) for the correction of complex congenital heart defects were recruited. INTERVENTIONS: Either standard twin roller (n = 17), or centrifugal vortex (Biopump, Medtronic Biomedicus Inc, MN) (n = 17) blood pumping. MEASUREMENTS AND MAIN RESULTS: Venous blood was drawn (1) on induction of anesthesia, (2) 5 minutes on bypass, (3) end of CPB, (4) 30 minutes post-protamine, (5) 2 hours and (6) 24 hours postoperation. Neutrophil count, level of plasma leukocyte elastase, terminal complement complex (C5b-9); interleukin-6 (IL-6) and interleukin-8 (IL-8) were increased during and after CPB compared with the postinduction baseline. C5b-9 levels in both groups peaked at the end of CPB before returning to baseline at 24 hours: (median [range]), 564 (16 to 1,136) ng/mL in centrifugal group versus 508 (0 to 1,128) ng/mL in the roller group. IL-6 in both groups reached its peak level at 2 hours postprotamine (208 [98 to 411] pg/mL in centrifugal versus 205 [60-327] pg/mL in the roller group), before coming back to baseline at 24 hours. Plasma leukocyte elastase and IL-8 reached their maximum level 15 minutes after protamine administration: 215 (64 to 375) pg/mL in centrifugal versus 235 (87 to 410) pg/mL in roller group; and 700 (90 to 5,925) ng/mL versus 362 (120 to 3,400) ng/mL, respectively. CONCLUSIONS: The current study confirms the proinflammatory nature of pediatric CPB surgery, but failed to show a significant advantage of centrifugal pumping over roller perfusion in terms of the inflammatory response.

Cardiopulmonary Bypass↗
PubMed2003

Human vestibular memory studied via measurement of the subjective horizontal during gondola centrifugation.

Measurements of the subjective visual horizontal (SVH) were made in a large swing-out gondola centrifuge. Rotation of the centrifuge was anti-clockwise, as seen from above. Test subjects were seated upright in the gondola, facing forwards. In front of the subject, at a straight-ahead eye-level position, there was a narrow luminous line, which could be rotated, by remote control, about the visual axis. At gravitoinertial force levels of 1.1-1.3G the subjects were asked to indicate, by repeatedly setting the line in darkness, what they perceived as horizontal (the SVH). During gondola centrifugation, the head and body length axis is always parallel with the resultant gravitoinertial force vector (vectorial sum of earth gravity force and the centrifugal force) i.e., the horizontal plane of the head or body does not change with respect to the gravitoinertial horizontal. Hence, the otolith organs, as well as the somatosensory system, continually signal upright position. However, the swing-out of the gondola during acceleration of the centrifuge (25 degrees at 1.1G) is a roll (frontal plane) change-in-position stimulus to the vertical semicircular canals, thus creating an otolith-semicircular canal conflict. After acceleration of the centrifuge, the SVH was initially tilted up to 20 degrees to the right relative to the gravitoinertial horizontal. Since there was no roll-tilt stimulus to gravity receptors, this SVH tilt must be related to stimulation of the semicircular canals. However, it decayed much more slowly than any known effects of angular-velocity stimulation of the semicircular canals. The decay was bi-phasic with two time constants, the smaller in the region of 1-2 min, the other being too large to be reliably estimated on the basis of data collected during only 10 min. This persistence of the SVH tilt suggests a memory for angular changes in roll head position detected by the semicircular canals-a position-storage mechanism. Further, the SVH seems to be dependent on two different mechanisms related to semicircular canal stimulation.

Adult↗
PubMed1998

Development of design methods of a centrifugal blood pump with in vitro tests, flow visualization, and computational fluid dynamics: results in hemolysis tests.

There are few established engineering guidelines aimed at reducing hemolysis for the design of centrifugal blood pumps. In this study, a fluid dynamic approach was applied to investigate hemolysis in centrifugal pumps. Three different strategies were integrated to examine the relationship between hemolysis and flow patterns. Hemolytic performances were evaluated in in vitro tests and compared with the flow patterns analyzed by flow visualization and computational fluid dynamic (CFD). Then our group tried to establish engineering guidelines to reduce hemolysis in the development of centrifugal blood pumps. The commercially available Nikkiso centrifugal blood pump (HPM-15) was used as a standard, and the dimensions of 2 types of gaps between the impeller and the casing, the axial and the radial gap, were varied. Four impellers with different vane outlet angles were also prepared and tested. Representative results of the hemolysis tests were as follows: The axial gaps of 0.5, 1.0, and 1.5 mm resulted in normalized index of hemolysis (NIH) values of 0.0028, 0.0013 and 0.0008 g/100 L, respectively. The radial gaps of 0.5 and 1.5 mm resulted in NIH values of 0.0012 and 0.0008 g/100 L, respectively. The backward type vane and the standard one resulted in NIH values of 0.0013 and 0.0002 g/100 L, respectively. These results revealed that small gaps led to more hemolysis and that the backward type vane caused more hemolysis. Therefore, the design parameters of centrifugal blood pumps could affect their hemolytic performances. In flow visualization tests, vortices around the impeller outer tip and tongue region were observed, and their patterns varied with the dimensions of the gaps. CFD analysis also predicted high shear stress consistent with the results of the hemolysis tests. Further investigation of the regional flow patterns is needed to discuss the cause of the hemolysis in centrifugal blood pumps.

Animals↗
PubMedDate not supplied

Standardization of blood product preparation by means of a "centrifugation index".

A centrifugation index for blood product preparation is proposed. This index, calculated from the domain of ultracentrifugation, is most applicable to describe the effects of centrifugation of large volumes than the relative centrifugal force and centrifugation time commonly used. The value of such an index is illustrated by the calculation of the minimum centrifugation time required for the preparation of platelet-poor plasma with seven different centrifuges.

Blood Banks↗
PubMed2005

Effect of centrifugation and electrical activation on male pronucleus formation and embryonic development of porcine oocytes reconstructed with intracytoplasmic sperm injection.

Oocyte centrifugation and electrical activation are commonly used in intracytoplasmic sperm injection (ICSI) of bovine and porcine oocytes, to facilitate visual identification of sperm release into the ooplasm and to support oocyte activation following injection with tail membrane-damaged sperm. The present study evaluated the necessity of these steps in porcine modified ICSI. In the first series of experiments, in vitro-matured gilt oocytes with or without centrifugation were injected with head membrane-damaged spermatozoa aspirated tail first. Oocytes without centrifugation exhibited a significantly higher normal fertilisation rate, defined as male pronucleus (MPN) and female pronucleus (FPN) formation and the presence of two polar bodies, than centrifuged oocytes (40% v. 9%, respectively; P < 0.05). The rate of MPN formation was significantly higher in uncentrifuged oocytes compared with centrifuged oocytes (48% v. 17%, respectively; P < 0.05). The rates of survival, cleavage, blastocyst formation and total cell number in blastocysts did not differ between the two groups of oocytes. Next, the effect of electrical activation after ICSI on uncentrifuged oocytes injected with head membrane-damaged spermatozoa was determined. No significant differences were observed in the rate of MPN formation in sperm-injected oocytes regardless of electrical activation. However, the survival rates of sperm-injected or control oocytes without electrical activation were significantly higher than those of sperm-injected or control oocytes with electrical activation (88% and 84% v. 77% and 64%, respectively; P < 0.05). The cleavage rates of sperm-injected oocytes were significantly higher than those of control oocytes, regardless of electrical activation (77% and 81% v. 47% and 61% in sperm-injected and control oocytes with or without electrical activation, respectively; P < 0.05). Although development to blastocysts was similar in all experimental groups, the total cell numbers in blastocysts from control oocytes were significantly higher than those in sperm-injected oocytes, regardless of electrical activation (40 and 44 v. 22 and 26 in control and sperm-injected oocytes with or without electrical activation, respectively; P < 0.05). In conclusion, the present study clearly demonstrated that oocyte centrifugation before sperm injection is not beneficial to normal fertilisation and that electrical activation is not necessary in the modified porcine ICSI.

Animals↗
PubMed2006

Directly observed reversible shape changes and hemoglobin stratification during centrifugation of human and Amphiuma red blood cells.

This paper describes changes that occur in human and Amphiuma red blood cells observed during centrifugation with a special microscope. Dilute suspensions of cells were layered, in a centrifuge chamber, above an osmotically matched dense solution, containing Nycodenz, Ficoll, or Percoll (Pharmacia) that formed a density gradient that allowed the cells to slowly settle to an equilibrium position. Biconcave human red blood cells moved downward at low forces with minimum wobble. The cells oriented vertically when the force field was increased and Hb sedimented as the lower part of each cell became bulged and assumed a "bag-like" shape. The upper centripetal portion of the cell became thinner and remained biconcave. These changes occurred rapidly and were completely reversible upon lowering the centrifugal force. Bag-shaped cells, upon touching red cells in rouleau, immediately reverted to biconcave disks as they flipped onto a stack. Amphiuma red cells displayed a different type of reversible stratification and deformation at high force fields. Here the cells became stretched, with the nucleus now moving centrifugally, the Hb moving centripetally, and the bottom of the cells becoming thinner and clear. Nevertheless, the distribution of the marginal bands at the cells' rim was unchanged. We conclude that centrifugation, per se, while changing a red cell's shape and the distribution of its intracellular constituents, does so in a completely reversible manner. Centrifugation of red cells harboring altered or missing structural elements could provide information on shape determinants that are still unexplained.

Animals↗
PubMed1990

Steady-state force-velocity relation in the ATP-dependent sliding movement of myosin-coated beads on actin cables in vitro studied with a centrifuge microscope.

To eliminate the gap between the biochemistry of actomyosin in solution and the physiology of contracting muscle, we developed an in vitro force-movement assay system in which the steady-state force-velocity relation in the actin-myosin interaction can be studied. The assay system consists of the internodal cells of an alga, Nitellopsis obtusa, containing well-organized actin filament arrays (actin cables); tosyl-activated polystyrene beads (diameter, 2.8 microns; specific gravity, 1.3) coated with skeletal muscle myosin; and a centrifuge microscope equipped with a stroboscopic light source and a video system. The internodal cell preparation was mounted on the rotor of the centrifuge microscope, so that centrifugal forces were applied to the myosin-coated beads moving along the actin cables in the presence of ATP. Under constant centrifugal forces directed opposite to the bead movement ("positive" loads), the beads continued to move with constant velocities, which decreased with increasing centrifugal forces. The steady-state force-velocity curve thus obtained was analogous to the double-hyperbolic force-velocity curve of single muscle fibers. The unloaded velocity of bead movement was 1.6-3.6 microns/s (20-23 degrees C), while the maximum "isometric" force generated by the myosin molecules on the bead was 1.9-39 pN. If, on the other hand, the beads were subjected to constant centrifugal forces in the direction of bead movement ("negative" loads), the bead also moved with constant velocities. Unexpectedly, the velocity of bead movement did not increase with increasing negative loads but first decreased by 20-60% and then increased towards the initial unloaded velocity until the beads were eventually detached from the actin cables.

Actins↗
PubMed1991

The slide centrifuge gram stain as a urine screening method.

A slide centrifuge Gram stain procedure was performed to screen for bacteriuria 4161 urine specimens submitted in urine preservative tubes for routine culture. For slide centrifuge Gram staining, each urine sample was mixed well. Thereafter, 0.2 mL of each sample was placed, using a pipette, into a slide centrifuge chamber and centrifuged at 2,000 rpm for 5 minutes. The slides were heat fixed, Gram stained, and read by laboratory personnel who scanned 12 consecutive oil-immersion fields using a set pattern. The presence of the same organism in six or more fields was defined as a positive urine screen. Urine samples were cultured using a 0.001-mL loop and a comparison of culture growth with slide centrifuge screening was made. When growth of 100,000 or more colony-forming units per milliliter (CFU/mL) was the reference for comparison, the screen had a sensitivity rate of 98%, a specificity rate of 90%, a negative predictive value of 99%, and a positive predictive value of 65%. When a lower colony count of 10,000 or more CFU/mL was the reference for comparison, the screen had a sensitivity rate of 88%, a specificity rate of 95%, a negative predictive value of 96%, and a positive predictive value of 84%. The slide centrifuge Gram stain is a very sensitive screening method to detect bacteriuria in an adult male population.

Adult↗
PubMed1985

Development of porcine ova that were centrifuged to permit visualization of pronuclei and nuclei.

The obscured pronuclei or nuclei in living one- and two-celled pig ova were revealed after centrifugation for 3 min at 15,000 X g. To determine viability of centrifuged ova, one- and two-celled pig ova were collected from superovulated gilts; half of the ova were centrifuged and all ova were transferred into recipient gilts. Prior to transfer all embryos were stained with tetramethylrhodamine isothiocyanate (TRITC) to distinguish the experimental embryos from the recipients's own ova. Centrifuged ova were transferred into one oviduct of recipient gilts and uncentrifuged ova were deposited into the opposite oviduct. Embryos were recovered 4 days after transfer and were stained with lacmoid or Hoechst 33342 to assess their stage of development. Centrifugation had no detectable influence on survival of the recovered embryos to 4 days. Centrifugation is a simple, reliable method for revealing pronuclei and nuclei of one- and two-celled pig ova and apparently does not alter subsequent preimplantation development.

Animals↗
PubMed1975

Deterioration of rat-liver mitochondria during isopycnic centrifugation in an isoosmotic medium.

We have investigated the effect of the centrifugation speed on the behavior of rat-liver mitochondria during isopycnic centrifugation in an isoosmotic medium. The gradient was made with a macromolecular compound, glycogen dissolved in 0.25 M aqueous sucrose. The distribution curves of several mitochondrial enzymes change when the centrifugation reaches a certain speed: they are shifted toward regions of lower density. The results are plausibly explained by supposing that the inner mitochondrial membrane becomes permeable to sucrose at high centrifugation speeds, and that the granules swell. The main causal agent of the phenomenon is the hydrostatic pressure the mitochondria are subjected to during centrifugation. Morphological observations show that mitochondria are markedly deteriorated when centrifuged at high speed in the glycogen gradient; they are swollen and the outer membrane is broken; also frequently, a large electron-dense granule is seen in the matrix near the inner mambrane.

Animals↗
PubMed1997

Control of centrifugal blood pump based on the motor current.

In this study, centrifugal pump performance was examined in a mock circulatory loop to derive an automatic pump rotational speed (rpm) control method. The pivot bearing supported sealless centrifugal pump was placed in the left ventricular apex to aorta bypass mode. The pneumatic pulsatile ventricle was used to simulate the natural ventricle. To simulate the suction effect in the ventricle, a collapsible rubber tube was placed in the inflow port of the centrifugal pump in series with the apex of the simulated ventricle. Experimentally, the centrifugal pump speed (rpm) was gradually increased to simulate the suction effect. The pump flow through the centrifugal pump measured by an electromagnetic flowmeter, the aortic pressure, and the motor current were continuously digitized at 100 Hz and stored in a personal computer. The analysis of the cross-spectral density between the pump flow and motor current waveforms revealed that 2 waveforms were highly correlated at the frequency range between 0 and 4 Hz, with the coherence and phase angles being close to 1.0 and 0 degree, respectively. The fast Fourier transform analysis of the motor current indicated that the second harmonic component of the motor current power density increased with the occurrence of the suction effect in the circuit. The ratio of the fundamental to the second harmonic component decreased less than 1.3 as the suction effect developed in the circuit. It is possible to detect and prevent the suction effect of the centrifugal blood pump in the natural ventricle through analysis of the motor current waveform.

Algorithms↗
PubMed1971

Standardization of human diploid fibroblast cultivation: centrifugation procedure.

The effect of varying centrifugal forces on the growth rate, longevity, and adsorption on glass of human embryonic diploid lung fibroblasts was studied. Cells centrifuged at 120, 500, or 1,500 x g at each passage had similar growth rates but their longevity decreased slightly with increasing force. These forces had no influence on the proportion of cells attaching to the glass. When the material in the first supernatant was recentrifuged at 2,000 x g for 30 min and added to the cells precipitated in the first centrifugation, the longevity of these cells was increased by several cell divisions. Cells which were not centrifuged but added directly from the cell suspension in trypsin to the new culture grew at a slightly slower rate than the centrifuged cells and became senescent at an earlier time. However, the noncentrifuged cells adsorbed to glass better than those centrifuged.

Cell Adhesion↗
PubMed1989

Detection of influenza virus by centrifugal inoculation of MDCK cells and staining with monoclonal antibodies.

Two methods for detection of influenza virus in 451 clinical respiratory specimens were compared: (i) 24-well-plate centrifugation with Madin-Darby canine kidney (MDCK) cells and staining with monoclonal antibody pools to influenza viruses A and B (Centers for Disease Control, Atlanta, Ga.) in an indirect immunofluorescence assay after incubation for 40 h, and (ii) conventional tissue cell culture with primary monkey cells and hemadsorption. For 100 of these specimens, direct examination of smears by the direct fluorescence assay with monoclonal antibodies (Boots Cell Tech/API Analytab Products, Plainview, N.Y.) was also performed. Influenza A virus was recovered from 28 specimens by tissue cell culture after incubation for an average of 4.75 days (range, 2 to 14 days). Influenza B virus was recovered from 35 specimens by tissue culture after incubation for an average of 5.4 days (range, 3 to 14 days). By the centrifugation assay, 23 specimens were positive for influenza A virus and 30 were positive for influenza B virus. All specimens positive by the centrifugation assay were also positive by conventional tissue cell culture. The sensitivities of the centrifugation assay were 82% for detection of influenza A virus and 86% for influenza B virus (84% overall); the specificity of the assay was 100%. Of the 100 specimens studied by direct examination, 15 were positive for influenza virus by both conventional culture and centrifugation assay; however, the direct-smear results for these 15 specimens were negative in 13 cases and inconclusive in 2. The centrifugation assay is a rapid and specific method for detection of influenza A and B viruses in clinical specimens, and it can serve as a valuable and cost-efficient adjunct to conventional culture methods.

Antibodies, Monoclonal↗
PubMed1989

Enhanced infectivity of bluetongue virus in cell culture by centrifugation.

The effects of centrifugation of the infection of cell culture with bluetongue virus (BTV) were investigated. Baby hamster kidney cells were infected with BTV with or without centrifugation. Viral antigen was detected by immunofluorescence at 24 h in both centrifuged and noncentrifuged cultures. However, after 24 h of infection, the production of PFU in centrifuged cell cultures was 10- to 20-fold greater than that seen in cultures not centrifuged. In addition, centrifugation enhanced the direct detection of PFU from blood samples collected from a sheep experimentally infected with BTV.

Animals↗
PubMed2004

Demonstration of altered signaling responses in bone marrow extracellular fluid during increased hematopoiesis in rats using a centrifugation method.

The composition and characteristics of the bone marrow extracellular fluid supposedly modify the transport of cytokines, drugs, and other signaling molecules involved in the regulation of bone marrow function. Direct access to the bone marrow extracellular fluid surrounding hematopoietic cells is complicated by the virtually noncompliant surrounding bone tissue. We examined the applicability of a centrifugation method to obtain representative samples of bone marrow extracellular fluid from rats and humans. Perforated rat bones or human bone marrow biopsies were wrapped in nylon mesh baskets before being centrifuged at 180-239 g. In the rats, we found an only minor contribution of fluid from other sources than the bone marrow extracellular fluid as indicated by the average ratio of centrifugate-to-plasma activity of the extracellular tracer fluid 51Cr-labeled EDTA of 0.85. The colloid osmotic pressure in the centrifugate was consistently lower than that in the corresponding plasma in both species. In rats and humans, high-performance liquid chromatography showed a protein elution pattern from the bone marrow fluid similar to that of plasma, except for a peak eluting in the approximately 40-kDa molecular mass range. Western blotting of the cytokines erythropoietin and granulocyte colony-stimulating factor revealed generally higher amounts in the centrifugate than in the plasma. This difference was augmented during increased hematopoietic activity induced by inflammation or bleeding in rats. We conclude that the centrifugation method provides representative samples of bone marrow extracellular fluid and that extracellular signaling responses to altered hematopoiesis are more clearly reflected locally in the bone marrow interstitium than in plasma.

Adult↗