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PubMed1991

Enhanced isolation of influenza virus in conventional plate cell cultures by using low-speed centrifugation from clinical specimens.

To determine whether low-speed centrifugation as a means of amplifying viral adsorption to target cells can enhance the sensitivity of conventional techniques for the isolation of influenza virus from clinical specimens, the authors conducted a simultaneous comparison between two conventional plate cell cultures--one with and one without centrifugation (700 X g, 60 minutes). Of 26 influenza virus isolates obtained from 528 clinical specimens, 17 were more efficiently isolated by the centrifugation assay compared with conventional culture methods. Centrifugation-assisted methods were found to be efficient in the recovery of 17 of 20 isolates (85%) not identified on first passage by conventional techniques. The number of isolates obtained with centrifugation was 1.5 times as high as that obtained with no centrifugation after three passages. The two assays were significantly different in the isolation of influenza virus (P less than 0.01). Since low-speed centrifugation may increase the infectivity of influenza virus in cell culture, this technique may prove useful in the efficient and rapid isolation of this virus from clinical specimens.

Animals↗
PubMed1997

Interstitial exclusion of macromolecules studied by graded centrifugation of rat tail tendon.

Mechanical compression of cartilage and tendon has been shown to expel fluid both from collagen fibrils and from the extrafibrillar space. As reported previously, albumin (Alb) concentration and colloid osmotic pressure in tendon fluid (TF) expelled by repeated centrifugations fell progressively at increasing centrifugation force (G = 600, 2,400, and 13,100), suggesting either molecular sieving in compressed tendon or mobilization of protein-free (excluded) fluid. The present experiments, including analysis of 51Cr-EDTA, aprotinin (Ap), Alb, immunoglobulin G (IgG), and hyaluronan (hyaluronic acid; HA) with molecular weight (MW) ranging from 341 to 5 x 10(6), strongly favored the exclusion hypothesis; the fraction of Alb, IgG, and HA-free fluid (excluded) was already 0.23-0.36 in the first centrifugate, increasing to 0.73-0.82 in the third. The corresponding numbers were, respectively, 0.11 and 0.43 for Ap (MW 6,500), and 0 and 0.08 for 51Cr-EDTA. These data, combined with calculated exclusion by collagen fibrils, proteoglycans, and HA, indicated that the first centrifugate was mainly derived from the extrafibrillar space, with increasing addition of macromolecular free intrafibrillar fluid in the second and third centrifugates, with each space contributing about equally to the total centrifugate volume. The calculations also indicated that Alb-, IgG-, and Ap-free fluid was mobilized from extrafibrillar space by increasing overlap of excluded territories. An excess of HA in tendon compared with that estimated from centrifugate concentrations suggests a large bound or immobilized HA fraction.

Animals↗
PubMed2000

Water balance in rats exposed to chronic centrifugation.

Changes in gravitational load have been shown to alter renal function, which could potentially affect water balance. Therefore, the present study was conducted to determine the effects of chronic centrifugation on water balance. Eight Sprague-Dawley rats were centrifuged (12 days at 2 G), and eight rats were used as a control group. Water balance over the course of the study was determined by quantifying the percentage (%) of total body water [TBW; (TBW/body mass)] and water flux (water consumption - urine volume). TBW was estimated, by means of deuterium oxide dilution, before the study and after 3 days of centrifugation and by means of desiccation after 12 days of centrifugation. %TBW did not change in the centrifuged rats from initial levels or relative to controls over the course of the study. Differences between the sum of water consumption and sum of urine volume for the 12-day period were the same in both groups. Although an initial period of negative water balance was observed, the lack of a change in %TBW among the three measurement periods or in water flux over the 12 days of centrifugation suggests that water balance is not negatively affected as a result of centrifugation at 2 G.

Animals↗
PubMed2004

Molecular and cellular reactions of retinal ganglion cells and retinal glial cells under centrifugal force loading.

PURPOSE: To investigate changes in retinal ganglion cell (RGC) survival and morphology, retinal glial cell effects on RGC survival, and changes in mRNA expression during centrifugal force loading using a newly developed device. METHODS: Changes in RGC survival and morphology were examined when isolated RGCs from 2-day-old rats were loaded with centrifugal force equivalent to 16, 28, or 33 mm Hg. The effects of cocultured retinal glial cells on RGC survival were studied in the presence of centrifugal force equivalent to 16 and 28 mm Hg for 48 hours. The microarray method and real-time polymerase chain reaction confirmed changes in mRNA expression when RGCs and retinal glial cells were loaded with centrifugal force equivalent to 28 mm Hg for 24 hours. RESULTS: The survival of isolated RGCs and the number of neurites were significantly decreased by centrifugal force loading. Conversely, there was no significant change in the survival of isolated retinal glial cells. The survival of cocultured RGCs was significantly better than that of isolated RGCs. In contrast to the numerous changes in the mRNA expression of retinal glial cells subjected to centrifugal force loading, there was no significant change in the mRNA expression of RGCs. CONCLUSIONS: The developed device may have potential for use as an in vitro model of RGC damage. The response to centrifugal force loading varies according to cell type, and the marked changes in the mRNA expression of retinal glial cells may be involved in the improvement of RGC survival.

Animals↗
PubMed1991

Extender and centrifugation effects on the motility patterns of slow-cooled stallion spermatozoa.

Slow-cooled stallion spermatozoa, with and without seminal plasma removed by centrifugation, were diluted in Kenney's extender (KE) containing nonfat dry skim milk with glucose and antibiotics or in KE supplemented by adding a modified high-potassium Tyrode's medium (KMT). Four ejaculates from each of four stallions were collected and divided factorially across these four treatments. Percentage of motile sperm, path velocity, and linearity immediately after treatment (0 h) and after storage at 4 degrees C for 24, 48, and 72 h were evaluated objectively by use of a HTM-2030 sperm motility analyzer. Stallions were a significant source of variation (P less than .01) throughout. After sperm had cooled, effects of stallion, extender, centrifugation, and their interactions were all found to be significant (P less than .01). The motility at 0, 24, 48, and 72 h for centrifuged KE was 74, 47, 39, and 24%; for uncentrifuged KE was 76, 56, 50, and 37%; for centrifuged KMT was 76, 75, 72, and 64%; and for uncentrifuged KMT was 80, 50, 26, and 13%, respectively. The extender x centrifugation interaction, after 24, 48, and 72 h of storage, accounted for half or more of the variation. Whereas centrifugation of semen extended in KE seemed to be harmful to sperm, motility of sperm extended in KMT after centrifugation was remarkably conserved for 72 h and was superior to all other treatments (P less than .05). This extender is promising for preserving liquid stallion semen when it must be transported before use in artificial insemination.

Analysis of Variance↗
PubMed1997

Effect of centrifugation on the ultrastructure of the parathyroid gland of the magnesium-treated golden hamster.

The ultrastructure of the parathyroid glands (PTG) of magnesium (Mg)-treated golden hamsters exposed to centrifugation at 1.2 G for 7 days was compared to that of the control, Mg-treated or centrifuged groups. In the PTG of the Mg-treated group exposed to centrifugation, the Golgi apparatus increased compared with that of the Mg-treated group, but was similar to that of the control and centrifuged groups. The cisternae of the rough endoplasmic reticulum (rER) increased compared with that of the Mg-treated group and decreased compared with that of the centrifuged group, but was the same as that of the control group. There were no significant differences among the 4 groups with regard to lysosomes, large vacuolar bodies, lipid droplets and secretory granules. These observations suggest that the rER is sensitive to centrifugation compared with the Golgi apparatus and more importantly the inhibitive effect of Mg on the synthesis of the hamster parathyroid hormone is enfeebled by centrifugation at 1.2 G.

Animals↗
PubMedDate not supplied

Effect of centrifuge speed, refrigeration medium, and sperm washing medium on cryopreserved sperm quality after thawing.

Cryopreservation and subsequent thawing of semen for assisted reproductive procedures decreases sperm motility; motility further reduces when the cryoprotectant medium is removed because of the osmotic shock and centrifugation done to prepare the sperm. To compare motility and thus pregnancy rates, this study examined the effects of adding an additional refrigeration medium and three different centrifugation speeds for sperm preparation. Semen samples from 16 healthy normal volunteers were obtained by masturbation after 48 h of abstinence. Sperm motility and other motion characteristics were analyzed with a computer-assisted semen analyzer before freezing, after thawing, and after centrifugation. Each sample was divided into 6 aliquots and frozen using the liquid nitrogen vapor method. After thawing, human tubal fluid (HTF) with 5% human serum albumin was added to 3 aliquots, and refrigeration medium (identical to freezing medium without glycerol) was added to the remaining 3 tubes for each specimen. The tubes containing the two media were then washed by centrifugation at 100 g, 300 g, and 500 g for 10 min. Aliquots with refrigeration medium did not significantly differ from those with HTF for percent motility, curvilinear velocity, straight-line velocity, and amplitude of lateral head displacement at any centrifugation speed. Motile sperm count was significantly greater only at 100 g and 300 g for refrigeration medium (p = .02 and .01) and HTF (p = 0.001); at 300 g, average path velocity in refrigeration medium aliquots (p = .01) and linearity in HTF (p = .01) were greater. The results indicated that the reduction in motility and other motion characteristics probably cannot be overcome by changing factors such as the sperm preparation medium or centrifugation speed. More effective cryopreservation techniques or preparation methods that eliminate centrifugation need to be developed.

Centrifugation↗
PubMed2001

Effect of centrifugal force on cellular activity of osteoblastic MC3T3-E1 cells in vitro.

The effects of centrifugal force on growth and differentiation of osteoblastic cells cultured in alpha-MEM containing 1% Fetal bovine serum were investigated by assays of DNA synthesis, alkaline phosphatase activity and osteocalcin-production in osteoblastic MC3T3-E1 cells. Centrifugation of the cells in low concentrations (1%) of fetal bovine serum caused a 1.9-fold increase of [3H]thymidine incorporation on day 3 from the start of centrifugation, and gradually decreased with culture up to day 9. Alkaline phosphatase activity was not affected by centrifugal force until day 5, and increased rapidly after day 7. Stimulation of DNA synthesis by centrifugation was abolished in the presence of H-7, an inhibitor of protein kinase C. These results suggest that centrifugal force stimulates the proliferation of osteoblastic cells through an autocrine secretion of some diffusable growth- promoting activity. Additional centrifugation of the cells also slightly stimulated alkaline phosphatase activity, although this did not directly influence the cell's osteocalcin-production activity.

Alkaline Phosphatase↗
PubMed1988

Centrifugation of antibiotic impregnated bone cement.

Centrifugation is used to increase the strength of bone cement in total joint arthroplasty. Antibiotics have been incorporated into cement for the treatment and prophylaxis of infection. To determine the effect of centrifugation on antibiotic containing cement, tobramycin and cefamandole impregnated Surgical Simplex P polymethylmethacrylate was centrifuged using manufacturers' techniques. The concentration of antibiotics was measured throughout the cement column by a zone of inhibition bioassay. No difference in the distribution of the antibiotics could be demonstrated as compared to hand mixed controls. Centrifugation decreased the number of large air inclusions overall, however, a significant number were noted to remain at the top of the centrifugation gradient. It was concluded that centrifugation of an antibiotic impregnated bone cement, utilizing this technique, may be used without disturbing the antibiotic distribution. Discarding the top 1 cm of liquid centrifuged column to remove residual air inclusions is recommended.

Biological Assay↗
PubMed1988

Effect of chronic centrifugation on mouse breeding pairs and their offspring.

Fetuses of chronically centrifuged mice are smaller than 1g fetuses, and have reduced areas of long bone ossification. Fewer pregnancies occurred in centrifuged mice. In this study, exposure of chronically centrifuged females to male bedding 48 hours prior to mating induced estrus as determined by vaginal smears. Females were paired with males on the centrifuge or at 1g, and were sacrificed at 18 days gestation. Fetuses were weighed, measured, and stained with alizarin red and methylene blue. This new mating method increased centrifuge pregnancies, but not to control levels. There were no pregnancies at 3.5 g. Weights and crown rump lengths of centrifuged 18-day fetuses were less than those of controls, significantly so at 2.6 and 2.9g. There was no effect on litter size, number of resorptions per litter or male/female ratio. Bones of centrifuged fetuses were found to be smaller and shaped differently from controls. Effects were mitigated by matings with 1g males. Results confirm our previous reports of decreased fetal size and areas of ossification in hypergravity, and demonstrate a reliable method for providing timed-pregnant mice in hyper-g conditions.

Animals↗
PubMed1997

Body mass change during altered gravity: spaceflight, centrifugation, and return to 1 G.

To assess the effect of gravity on growth, immature rats (130-200 g) were studied during chronic altered gravity exposure and while transitioning between gravity fields. Body mass gain of rats (n = 12) exposed to 14 days of microgravity (spaceflight) was evaluated and compared to mass gain of 1 G controls. Spaceflight did not affect mass gain. Six rats exposed to 1 G following spaceflight, when compared to controls, experienced a significant (0 < 0.05) post-flight mass loss over 48 h of 13 g. Over subsequent days, however, this loss was compensated for, and no difference from 1 G controls was noted after 5 days. Exposure to hypergravity (2 G) for 16 days was evaluated [(n = 6/group): Centrifuge (C); On Center Control (OCC); Centrifuge Control (CC)]. Body mass of centrifuged and OCC rats was reduced within 24 h, with OCCs regaining control mass within 13 days. The mass difference (44 g) in centrifuged animals persisted, however, with no subsequent difference in rate of mass gain between centrifuged animals and controls over Days 3-16 (3.7 +/- 0.1 vs. 3.9 +/- 0.1 g/day, respectively). Transitioning from 2 G to 1 G resulted in a mass increase within 48 hours for centrifuged animals. Over Days 3-16 at 1 G, the rate of gain for centrifuged animals continued to increase (3.1 +/- 0.1 g/day compared to 2.1 +/- 0.1 g/day for controls); differences from control, however, were still noted on Day 16. Transitioning to an increase in a gravity field causes acute losses in body mass. In hypergravity, the acute reduction in body mass persists but the rate of mass gain is normal. Animals returning to 1 G, after acute changes, adjust to attain control mass.

Adaptation, Physiological↗
PubMed2000

[Data analysis of 492 times centrifuge examination].

Objective. To sum up the experiences and to find the regularity of centrifuge examinations. Method. The data of nine years of centrifuge examination (from 1988 to 1996) of pilots who suffered from black out or LOC frequently were analyzed. Result. There were totally 492 times centrifuge examinations. First centrifuge examination included 229 pilots, 49 qualified, 180 unqualified. Second centrifuge examination included 263 pilots, 50 qualified, 213 unqualified. The pilots were all male. The average age of first centrifuge examination was 29.27 +/- 4.87 years. Average flying time was 1015.24 +/- 131.89 h. 68.7% of their plane was JJ-6 or above. Conclusion. Most pilots undergoing centrifuge examination these nine years were 26-35 year old, and had flown for 601-1200 h. The planes they flew are mostly high-performance fighter aircraft. Close attention must be paid to pilots under similar condition by the flight surgeon. It is recommended that the special equipment of G-tolerance training should be added to the fighter aircraft units.

Acceleration↗
PubMed2006

Semicircular canal influence on the visually perceived eye level during gondola centrifugation.

BACKGROUND: When exposed to an increased gravitoinertial force, a subject, sitting upright, experiences an illusion of being tilted backwards. This so-called "G-excess illusion" is generally ascribed to the otolith organs. The present study aimed at elucidating how stimulation of the semicircular canals may influence the development of the G-excess illusion. METHODS: The visually perceived eye level (VPEL) was measured by means of a visual indicator in a large swing-out gondola centrifuge. The roll position of the gondola was controlled so that the subject was always upright with respect to the resultant vector of the Earth gravity force and the centrifugal force. Subjects (n = 8) underwent four centrifuge runs (2 G, 5 min), sitting in different positions, i.e., heading forwards, backwards, centripetally, and centrifugally. RESULTS: At the 2-G plateau there was a depression of the VPEL which was initially small but increased with a time constant of 90 +/- 30 s toward an asymptote of -22.0 +/- 6.9 degrees (mean and 1 SD for all positions). The initial depression was significantly smaller for the centripetal (+2.0 +/- 14.6 degrees) than for the centrifugal position (-14.5 +/- 10.4 degrees). However, there was no difference between the forward (-5.6 +/- 4.8 degrees) and backward (-4.0 +/- 4.5 degrees) positions. Initially after deceleration of the centrifuge to 1 G there was still a significant depression of the VPEL (-13.5 +/- 7.9 degrees), decreasing with a time constant of 100 +/- 46 s. CONCLUSIONS: The considerable delay in the otolith-mediated changes in the VPEL is interpreted as due to the absence of adequate canal information for a change in head position. The difference in VPEL between the centripetal and centrifugal positions suggests an influence of canal change-in-position information. However, pitch-plane angular velocity, being of considerable magnitude but of opposite sign for the forward and backward positions, did not influence the VPEL.

Acceleration↗
PubMed1990

The electrocardiographic response to high +Gz centrifuge training.

The electrocardiographic (ECG) responses of 59 asymptomatic, healthy flight surgeons to the acceleration profiles included in current U.S. Air Force and U.S. Navy high-G centrifuge training programs are documented. ECG dysrhythmias were frequently observed during exposure to both gradual and rapid onset training profiles. Short self-limited episodes of ventricular tachycardia occurred in 5 subjects. Advanced Lown grade ventricular ectopy occurred in 13 subjects. The type of cardiac ectopy and the frequency of occurrence for each of the training profiles is described. The results suggest that significant ectopy frequently occurs during exposure of healthy, asymptomatic individuals to centrifuge training profiles. Since aircrew are expected to undergo high +Gz as part of their usual flying duties, ECG monitoring during high-G centrifuge training has not universally been a required part of the training exposures. Aircrew have not always accepted ECG monitoring during centrifuge training, fearing detection of certain cardiac dysrhythmias, which current aeromedical standards consider disqualifying for continued flying duties without clinical aeromedical evaluation. Based on the results of this study, and previous documentation of the occurrence of significant +Gz-induced cardiac dysrhythmias (both in flight and on the centrifuge), ECG monitoring might be considered appropriate to ensure optimum medical safety during high-G centrifuge training. The current inconsistency between 1) not monitoring ECG because of the aeromedical standards for flying qualification relating to the ECG response to +Gz stress, and 2) the need to monitor ECG to assure optimum safety during centrifuge training, deserves resolution.

Acceleration↗
PubMed1988

The effect of centrifugation on the fatigue life of bone cement in the presence of surface irregularities.

Reduction of the porosity of bone cement by centrifugation significantly improves the fatigue life of the cement when smooth, waisted specimens are tested. However, bone cement in vivo has surface irregularities at the interdigitation of the cement with the trabecular bone. The effect of centrifugation on the fatigue life of Simplex P in specimens containing surface irregularities was investigated by examining both composite specimens of trabecular bone and bone cement and specimens containing a sharp, circumferential notch. For the specimens with the sharp notch, the bone cement that had been centrifuged lasted significantly longer in fatigue (47,039 +/- 40,277 cycles) than the uncentrifuged specimens (3103 +/- 1950 cycles). Eleven of 15 uncentrifuged specimens broke at the location of a void, rather than the notch. In contrast, when the porosity was reduced by centrifugation, 13 of the 15 specimens broke at the notch. For the specimens that were a composite of bone cement and trabecular bone, the centrifuged specimens had a significant increase in fatigue life compared to the uncentrifuged specimens when tested at both 7 MPA (641,056 +/- 444,131 cycles vs. 237,969 +/- 124,153 cycles) and 15 MPA (8800 +/- 4673 cycles vs. 1534 +/- 719 cycles). Reduction of porosity in bone cement by centrifugation significantly extends its fatigue life even in the presence of trabecular bone or sharp surface notches as used in total joint replacements. These data support the concept that reduction of porosity of bone cement by centrifugation may extend the duration of fixation of the components in cemented total joint arthroplasties.

Animals↗
PubMed1981

Sedimentation of lung-derived phospholipid during low-speed centrifugation of amniotic fluid.

In most methods proposed for the assessment of fetal lung maturity, amniotic fluid is subjected to a preliminary low-speed centrifugation in an attempt to separate whole cells and cell debris from lung-derived surfactant phospholipid (lamellar body phospholipid). However, because lamellar body phospholipid is present in amniotic fluid in a membranous or particulate form, it is also partly sedimented by this procedure. The sedimentation of total phospholipid and lamellar body phospholipid by low-speed centrifugation has been quantitated for 49 samples of amniotic fluid from pregnancies of 30--41 weeks gestation. Isopycnic density-gradient centrifugation in a small air-driven ultracentrifuge was used to isolate lamellar body fractions from whole and centrifuged amniotic fluid. Centrifugation for 5 min at 1000 x g removed 0--70% of total phospholipid or lamellar body phospholipid, the mean values being 34 or 29%, respectively. There was an appreciable increase in lamellar body phospholipid relative to total phospholipid as a result of centrifugation in only 51% of the samples. In general, the effects of centrifugation were not related to gestational age of the fetus or the state of maturity of its lungs.

Amniotic Fluid↗
PubMed1996

Recovery of interphase nuclei from extreme structural alterations in centrifuged fern protonemal cells.

Nuclear ability to recover morphologically and physiologically from tremendous elongation induced by centrifugation was investigated in single-celled protonemata of the fern Adiantum capillus-veneris. Basipetal centrifugation at a strength of ca. 2000 g for more than 1 h caused an extremely long (more than 500 microns), thread-like chromatin-containing extension of the nuclear envelope in the centrifugal direction. The nucleolus was either located inside a terminal widening of the extension, or it was detached from the thread and located outside the nucleus. Such enucleolation occurred in about half of the nuclei during 3 h of basipetal centrifugation. After centrifugation, the nuclei recovered morphologically by completely reducing the chromatin thread. One day after the end of centrifugation, all nuclei again contained a nucleolus, indicating that nucleolar regeneration had taken place in the interphase nucleus. Almost all basipetally centrifuged cells were still able to divide under white light conditions. A strong delay in the division time course may be attributed to recovery processes of the nuclear internal order. The remarkable ability of the Adiantum interphase nuclei to recover morphologically and physiologically is assumed to be due to processes which also drive the maintenance of the functional nuclear structure during interphase.

Cell Fractionation↗
PubMed1981

Effect of centrifugation on herpes simplex virus isolation.

The effects of high-speed centrifugation on the isolation of herpes simplex virus (HSV) were studied. Aliquots of laboratory or clinical specimens were inoculated into test tubes and flat-bottomed tubes containing HEp2 monolayers. Test tubes were incubated at 35 degrees C on roller drums (standard method), and flat-bottomed tubes were centrifuged at 15,000g at 35 degrees C for 1 hr, before being incubated at 35 degrees C without rolling (centrifuged method). Centrifugation of clinical and laboratory specimens of HSV type 1 and HSV type 2 produced significantly increased isolation rates compared with the standard method. When clinical and laboratory specimens were diluted, the centrifuged method was more sensitive at all dilutions. When 20 specimens were used for end-point titrations, the centrifuged method was 10 times more sensitive for 15 specimens and 100 times more sensitive for five specimens. There was no difference in the time taken for the appearance of cytopathic effect (CPE) between the standard and centrifuged methods.

Cells, Cultured↗