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PubMed2004

Evaluation of conventional castaneda and lysis centrifugation blood culture techniques for diagnosis of human brucellosis.

We investigated the role of the lysis centrifugation blood culture technique over the conventional Castaneda technique for the diagnosis of human brucellosis. The lysis centrifugation technique has been found to be more sensitive in both acute (20% higher sensitivity; P < 0.00001) and chronic (40% higher sensitivity; P = 0.087) forms of brucellosis. The major advantage of lysis centrifugation was in the mean detection time, which was only 2.4 days in acute and 2.7 days in chronic cases, with 103 out of 110 (93.6%) and 17 out of 20 (85%) cultures from acute and chronic brucellosis, respectively, detected before the conventional culture was positive. Our results confirmed the potential usefulness of the lysis technique in diagnosis and institution of appropriate antibiotic therapy.

Blood↗
PubMed1978

New centrifugation blood culture device.

A single-tube blood culture device designed for centrifugation in a tabletop centrifuge is described. Reconstruction experiments using 21 different organisms and human donor blood indicate that excellent recovery can be obtained by centrifugation for 30 min at 3,000 X g.

Bacteria↗
PubMed1993

Equilibrium centrifugation studies of hepatitis C virus: evidence for circulating immune complexes.

The buoyant density of hepatitis C virus (HCV), with high in vivo infectivity (strain H) or low in vivo infectivity (strain F), was determined by sucrose gradient equilibrium centrifugation. Viral RNA of strain H was detected in fractions with densities of < or = 1.09 g/ml (principally approximately 1.06 g/ml), while that of strain F was found in fractions with densities of approximately 1.06 and approximately 1.17 g/ml. The observed difference was confirmed by differential flotation centrifugation; in NaCl solution with a density of 1.063 g/ml, most of the HCV RNA of strain H was detected in the top fraction, while that of strain F appeared in the bottom. The same relationship between buoyant density and infectivity was observed in flotation centrifugation experiments with other HCV strains. In immunoprecipitation experiments with anti-human immunoglobulin, HCV (as measured by HCV RNA) was precipitated from the samples with low infectivity and high density but not from those with high infectivity and low density. Examination of serial sera from a chimpanzee infected with HCV revealed parallel changes in the buoyant density and immunoprecipitability of HCV-associated RNA during the course of infection. These data suggest that HCV is bound to anti-HCV antibodies as antigen-antibody complexes in chronic hepatitis C.

Animals↗
PubMed1984

Centrifugation of 2 g does not affect otoconial mineralization in chick embryos.

Chick embryos were grown on a rotating centrifuge for periods of 2 wk to study the effects of increased gravity on the relative growth of their otoliths and femurs. Embryos, 20-21 days of age, centrifuged at 2 g showed no difference in utricular otoconial CaCO3 weights and femur CaPO4 weights compared with stationary control embryos of the same age. In addition, control embryos rotated at the center of the centrifuge had otoconial CaCO3 weights and femur CaPO4 weights not significantly different from stationary controls or from embryos rotated at 2 g. Accordingly these data do not support the hypothesis that the weight of the embryonic otoconial membrane is involved in the feedback regulation of its growth.

Animals↗
PubMed1990

Centrifugal intensity and duration as countermeasures to soleus muscle atrophy.

Mechanical acceleration is a countermeasure that may be employed to prevent atrophy of slow-twitch muscle during non-weight bearing. In the present study, daily centrifugation of rats for different durations (1 or 2 h) and at different gravitational intensities (1.5 or 2.6 G) was used to test whether mechanical acceleration could ameliorate the atrophy of the soleus muscle induced by non-weight bearing (tail-traction model). The soleus muscle atrophied 32% during 7 days of non-weight bearing without countermeasures. Centrifugation treatment did not completely prevent atrophy relative to precontrol wet weight of the soleus muscle. Non-weight-bearing groups receiving 2-h daily treatments of 1, 1.5, or 2.6 G had 48, 56, and 65%, respectively, of the atrophy observed in the non-weight-bearing-only group compared with the precontrol group. No evidence was obtained that centrifugation at 2.6 G was more effective than exposure to 1 or 1.5 G as a countermeasure to non-weight-bearing-induced atrophy of the soleus muscle.

Animals↗
PubMed2003

Chronic centrifugation (hypergravity) disrupts the circadian system of the rat.

The present study was conducted to evaluate the response of rat deep body temperature (DBT) and gross locomotor activity (LMA) circadian rhythms to acute hypergravity onset and adaptation to chronic (14 day) hypergravity exposure over three gravity intensities (1.25, 1.5, and 2 G). Centrifugation of unanesthetized naive animals resulted in a dramatic acute decrease in DBT (-1.45, -2.40, and -3.09 degrees C for the 1.25, 1.5, and 2.0 G groups, respectively). LMA was suppressed for the duration of centrifugation (vs. control period); the percent decrease for each group on days 12-14, respectively, was 1.0 G, -15.2%, P = not significant; 1.25 G, -26.9%, P < 0.02; 1.5 G, -44.5%, P < 0.01; and 2.0 G, -63.1%, P < 0.002. The time required for DBT and LMA circadian rhythmic adaptation and stabilization to hypergravity onset increased from 1.25 to 2.0 G in all circadian metrics except daily means. Periodicity analysis detected the phenomenon of circadian rhythm splitting, which has not been reported previously in response to chronic hypergravity exposure. Our analysis documents the disruptive and dose-dependent effects of hypergravity on circadian rhythmicity and the time course of adaptation to 14-day chronic centrifugation exposure.

Adaptation, Physiological↗
PubMed1983

Platelet monoamine oxidase and plasma amine oxidase: effect of anticoagulant and centrifugation technique on platelet yield and enzyme activity.

Platelet recovery and activity of platelet monoamine oxidase (MAO) and plasma amine oxidase (PAO) were determined using different centrifugation procedures (125 g for 15 min vs. 600 g for 2.5 min) and anticoagulants. With either centrifugation procedure, the use of ethylenediaminetetraacetate (EDTA) as anticoagulant resulted in higher platelet yields and MAO activity compared to acid-citrate-dextrose (ACD). However, PAO activity was lower with EDTA as anticoagulant than with ACD. There was a trend toward higher platelet yields and higher activity levels of MAO and PAO with the 125 g centrifugation method than with the 600 g technique regardless of the anticoagulant used. The implications for MAO studies in psychiatric research were discussed.

Adult↗
PubMed2005

Postoperative mechanical circulatory support with Biomedicus centrifugal pump.

Despite advances in surgical techniques, myocardial protection, and management protocols, approximately 1% of patients undergoing open heart operations still need mechanical circulatory support for severe cardiac dysfunction. The Biomedicus centrifugal pump, available in most cardiovascular centers, is a highly effective and relatively inexpensive system compared to other more sophisticated devices for the same purpose. Of 10 patients aged 5 to 61 years who were supported for 22 to 168 hours with a Biomedicus centrifugal pump, 7 (70%) were weaned from support, there was one hospital death, and 6 patients were discharged from hospital. Two sudden deaths occurred in the first 8 months after discharge. Four patients (40%) were still alive after follow-up of 11-55 months, with no restriction in their daily activities. The centrifugal pump is a very cost-effective support system with survival rates comparable to those of more sophisticated devices in short-term ventricular assistance.

Adolescent↗
PubMed2006

Hemolysis evaluation of centrifugal pumps using microcapsule suspension.

OBJECTIVES: Bovine and human blood has been widely used for in vitro hemolysis testing to evaluate centrifugal cardiac assist pumps. However, results from such tests are complicated by variations in the susceptibility of individual red blood cells to shear. The objective of this study was to evaluate the use of microcapsule suspension as an alternative to bovine or human blood for hemolysis testing. METHODS: Microcapsule suspensions of 100 micro m maximal diameter (average 79.1 micro m) with a polyurethane membrane were used. Each microcapsule contained a leuco dye, which was used to measure "hemolysis" in the suspension after exposure to mechanical stress. Six centrifugal pumps were used to measure and compare the hemolysis values of microcapsule suspensions, bovine blood and human blood. RESULTS: Correlations were significant between the hemolysis values measured using microcapsule suspensions and those using bovine blood (R = 0.965, p = 0.002) and human blood (R = 0.940, p = 0.005). CONCLUSIONS: Microcapsule suspension can be successfully used instead of blood to compare the relative hemolytic performance of centrifugal blood pumps.

Animals↗
PubMed1984

Functional and morphological studies on isolated Leydig cells: purification by centrifugal elutriation and metrizamide fractionation.

Rat interstitial cells were fractionated by centrifugal elutriation to facilitate the purification of Leydig cells for analysis of mechanisms of gonadotropin action in vitro. By this procedure, 10(9) collagenase-dispersed interstitial cells from adult rat testes were separated into 12 fractions in about 1 h. Fractions 1-7 (sedimentation velocities, 1.9-12 mm/h.g) comprised 80-85% of the total cells applied, including erythrocytes, lymphocytes, germinal cells, macrophages, endothelial cells, damaged Leydig cells, and contained less than 4% intact Leydig cells. Fractions 8-12 (sedimentation velocities, greater than 12 mm/h.g) comprised 15-20% of the original cells and contained 90-95% intact Leydig cells. Despite their different sedimentation velocities, the Leydig cell-rich fractions were similar in their LH receptor content (mean +/- SD, 36,115 +/- 4,815 sites/cell) and showed similar 5-fold increases above the original cell preparation in testosterone and cAMP responses to hCG. The pooled Leydig cell-rich fractions (8-12) were further resolved on 16-24% Metrizamide gradients into 5 bands. Bands II-V (density range, 1.075-1.110 g/ml) contained pure Leydig cells, and band I (1.048 g/ml) contained pachytene spermatocytes, the contaminating cell type present in the Leydig cell-rich fractions obtained by elutriation. Each of the 4 Leydig cell-rich bands showed similar morphology and functional activity. Essentially similar results were observed using 14-32% Metrizamide gradients. Leydig cells desensitized in vivo by hCG treatment and isolated by elutriation were also resolved by Metrizamide gradients into 4 bands, but showed a redistribution in the gradient, due to the shift of about 50% of the cells originally present in the heaviest bands to lower density fractions. However, in spite of their changes in density, the Leydig cell bands still showed similar degrees of receptor down-regulation and impairment of the steroid responses to hCG in vitro. This study has demonstrated that centrifugal elutriation is a rapid and effective method for obtaining large quantities of purified (greater than 90%) and active Leydig cells. Further resolution of the Leydig cell-rich fractions in Metrizamide gradients has allowed complete Leydig cell purification, which is not achieved by density gradient centrifugation alone. Since less responsive or inactive Leydig cells displayed various degrees of structural damage, such cells should not be considered as a population of physiological significance.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Purification of thyroid lysosomes by colloidal silica density gradient centrifugation.

A procedure was devised for fractionating crude thyroid lysosomal particles (P750-15,000) by self-forming density gradient centrifugation with colloidal silica. Two discrete particle-containing peaks were observed, based on 131I-labeling and acid phosphatase activity: a heavy peak (density, 1.11-1.12) and a light peak (density, 1.05). Ultrastructural analysis revealed that the heavy peak consisted almost entirely of lysosomes, whereas the light peak represented a heterogeneous mixture of small vesicles and fragments of other intracellular organelles. In thyroids removed from rats 30 min after 131I injection, almost all of the 131I was present in the low density peak. This 131I appeared on sucrose density gradient centrifugation as a 19S peak, and it was almost completely insoluble in trichloroacetic acid. This was interpreted as indicating that the low density peak contained pinocytotic vesicles. In thyroids removed 4 days after 131I injection, the radioactivity appeared largely in the high density peak. Both the trichloroacetic acid solubility and the pattern on sucrose density gradient centrifugation indicated that the [131I] thyroglobulin had undergone extensive proteolysis. Thyroglobulin proteolytic activity was found primarily in the high density particles and to only a small extent in the low density particles. Studies performed at intervals after 131I injection combined with double labeling (131I and 125I) experiments provided evidence that radioactivity was transferred from the low density to the high density particles. Heterogeneity existed within the dense peak, related to the degree of thyroglobulin degradation, as it was observed that thyroid lysosomes become denser with increasing proteolysis of thyroglobulin. The acid phosphatase in the low density particles could be distinguished from that in the high density (lysosomal) particles by its elution pattern on Sephadex G-200 column chromatography, its response to freezing and thawing, and its reactivity with p-nitrophenylphosphate. It was concluded, therefore, that the acid phosphatase in the low density fraction was derived from prolysosomal structures such as vesiculated Golgi-endoplasmic reticulum-lysosomes. The prolysosomal acid phosphatase associated with the low density fraction appeared to be a large membrane-bound molecule which could be transformed into lysosomal acid phosphatase by incubation at pH 5.0.

Acid Phosphatase↗
PubMed1988

Purification of ovarian theca-interstitial cells by density gradient centrifugation.

The study of the biochemical mechanisms regulating the differentiation of the ovarian androgen-producing cells has been difficult because of the lack of a method for isolating the theca-interstitial cells (TIC) from the granulosa and other cell types. We report here a simple, rapid and reproducible method for obtaining large numbers of highly enriched TIC using density gradient centrifugation. When dispersed cells from ovaries of hypophysectomized immature rats were centrifuged in a Percoll gradient (20-70%), the cells were separated into five incompletely resolved bands. Of these, band V contained the androgen-producing cells. The band V cells produced 3.2- and 3.9-fold more cAMP and androgen, respectively, than the whole ovarian cells and contained 3.8- and 3.5-fold more 125I-hCG binding and 3 beta-HSDH labeled cells, respectively. These data indicated that the TIC were 65% pure. In order to improve the degree of purification, a discontinuous density procedure was used. When the ovarian cells were centrifuged in d = 1.055 g/ml Percoll, the purified TIC produced 4.7- and 5.9-fold more cAMP and androgen than the whole ovarian cells and they contained 5.3-fold more 125I-hCG binding. The TIC were cleanly separated from the granulosa cells and histochemical staining for 3 beta-HSDH activity revealed that the TIC were 93.0 +/- 1.3% pure. This method provides, for the first time, the opportunity to study TIC differentiation under defined conditions without granulosa cell contamination.

Animals↗
PubMed1993

Evaluation of STAT-CRIT hematocrit determination in comparison to Coulter and centrifuge: the effects of isotonic hemodilution and albumin administration.

The accuracy of the STAT-CRIT hematocrit (hct) was compared to Coulter and centrifuge methods in this study of the interrelationship between non-red cell blood constituents and accuracy of conductivity-based hct measurements. In the first part of the study, blood samples from 31 patients undergoing elective cardiac procedures were analyzed at three times: before induction of anesthesia (Time 1), during the rewarming period of cardiopulmonary bypass (CPB) (Time 2), and after transfusion of all cell-saver blood available after termination of CPB (Time 3). Laboratory evaluation included hct using the Stat-Crit, Coulter, and centrifuge methods, and sodium (Na), potassium (K), chloride (Cl), white blood cell count, total protein (TP), and albumin. In the second part of the study, patients were randomized to receive either 5% albumin (n = 14) or isotonic crystalloid (n = 14) after termination of CPB to determine the effect of protein colloid replacement on conductivity-based hct measurements. Blood samples were obtained before and after fluid volume replacement for multivariate analysis. Correlation of Coulter hct (absolute) with microhematocrit by centrifuge at all times (n = 93) was 0.95 (R2) with a bias and precision of -0.26 +/- 1.7%. Blood variables having the most significant effect on the Coulter-Stat-Crit difference (bias) were protein, Cl, and Na. Single regression analysis indicated that a 1-g/dL decrease in TP resulted in an absolute decrease in the hct reading by 1 hct% units. A 10-mmol/L change in either Cl or Na concentration resulted in a change in Stat-Crit accuracy of 3.5% and 2.5%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Proteins↗
PubMed2000

Separation of erythrocytes into age-related fractions by density or size? Counterflow centrifugation.

During the process of aging red blood cells become denser and smaller. Counterflow centrifugation separates particles of lower density and smaller diameter from those of higher density and bigger diameter. Thus, the question arises: which property of the red cells, density or size, governs the age-related separation by counterflow centrifugation? It is shown that it is the size which dominates the balance between sedimentation and streaming. Age-related separation of human red blood cells by counterflow centrifugation (elutriation) was analysed by the standard hematological parameters (hemoglobin, mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration), hemoglobin A1c and the membrane protein ratio 4.1a/(4.1a+4.1b). Red blood cells with a high hemoglobin A1c content and a high 4.1a/(4.1a+4.1b) ratio were found in the early fractions of the elutriation. This proves that old cells make up early fractions, while the "youngsters" constitute later ones. The elutriation technique used (yielding human red blood cells in a "healthy state") and the age parameters studied show that the membrane protein ratio 4.1a/(4.1a+4.1b) is another reliable age parameter for the assessment of red blood cell age.

Aging↗
PubMed2004

Calcium oxalate crystallization in untreated urine, centrifuged and filtered urine and ultrafiltered urine.

Centrifuged and filtered urine is often used to evaluate in vitro the crystallization processes of calcium oxalate (CaOx), but even such simple manipulations can alter the composition of the urine, as regards its protein and lipid concentrations. In urine samples taken from 17 normal male adults, we evaluated CaOx crystallization by simultaneously using three different types of urine: untreated (U), centrifuged at 2000 rpm (800 g) and filtered at 0.22 microm (CF), and centrifuged-filtered and ultrafiltered at 10 000 Da (CFU). The addition of 1.2 mmol/l of oxalate to each type of urine produced notably different results. The total amount of CaOx crystals (expressed as calcium oxalate dihydrate crystals (COD) + oxalate monohydrate crystals (COM) area/total area x 100) was on average 13.2% in U urine, 70.7% in CF urine and 11.1% in CFU urine (CF > U and CFU, U = CFU); the relative prevalence of COD and COM (expressed as COD area/COM area) was on average 71.4 in U urine, 0.0026 in CF urine and 5.5 in CFU urine (U > CF and CFU, CFU > CF); the diameter of COD (expressed in microns) was on average 15.2 in U urine, 3.7 in CF urine and 24.3 in CFU urine (CFU > U and CF, U > CF); the diameter of COM (expressed in microns) was on average 5.2 in U urine, 2.6 in CF urine and 8.9 in CFU urine (CFU > U and CF, U > CF); the total amount of CaOx aggregates (expressed as CaOxAgg area/total area x 100) was on average 8.5% in U urine, 22.1% in CF urine and 2.9% in CFU urine (CF > U and CFU, U > CF). We conclude that CaOx crystallization processes in manipulated urine are extremely different, probably due to changes in macromolecular compounds.

Adult↗
PubMed1994

Fertilizability and structural properties of boar spermatozoa prepared by Percoll gradient centrifugation.

Two techniques for the preparation of boar spermatozoa for in vitro fertilization were studied: a simple washing procedure and centrifugation on a discontinuous Percoll gradient. Their respective effects on motility of spermatozoa were analysed by computer-assisted sperm analysis. The Percoll density gradient technique selected spermatozoa with significantly (P < 0.0001) enhanced motility and movement characteristics. In vitro matured oocytes inseminated with spermatozoa prepared by Percoll gradient centrifugation had significantly (P < 0.0001) greater cleavage rates than did oocytes inseminated with washed spermatozoa. This increased penetration ability was not due to an increased proportion of acrosome-reacted spermatozoa. Transmission electron microscopy revealed no unique ultrastructural differences between the spermatozoa from either preparation. Spermatozoa prepared by Percoll gradient centrifugation are recommended for insemination and studies of porcine in vitro fertilization.

Animals↗
PubMed1996

Development of centrifugal phytotron to study the gravity effect on vegetable plant growth.

The present Spacetron is used to cultivate plants over a long term by controlling environment condition. The cultivation drum was rotated in perpendicular direction creating fluctuation in gravity. Centrifugal force plus 1 G ground gravity, are distributed unevenly over the cultivation drum. This fluctuation effect on plant growth was not clear. In the modified Spacetron the cultivation drum rotates horizontally whereas the plant stage rotated in the perpendicular direction. To find the basic information for design of centrifugal phytotron the two axes Spacetron Junior (clinostat) was developed to formulate the micro and hypergravity environment. It would be used to study the effect on a plant growth process of different gravity conditions. In order to produce the different values of gravity, the clinostat's axis was rotated with a stepping motor at different angular velocity. The axis rotated at 5.2 revolutions per minute (rpm) to create a centrifugal force equivalent to 0.01 G and the plant stage was rotated at 5.2 rpm. The chlorophyll value is higher in the plants under microgravity condition of 0.01 G whereas the fresh weight and dry weight are higher in the plants under control condition of 1 G earth gravity. The result of this study showed that the plant growth was affected by microgravity along with other known factors such as vibration and unknown factors.

Biomass↗
PubMed1995

Effect of lateral forces on the movement of myosin-coated beads on actin cables studied using a centrifuge microscope.

We developed an in vitro motility assay system, in which myosin-coated polystyrene beads were made to slide on actin filament arrays (actin cables) in giant algal cells and subjected to centrifugal forces, which were parallel to the direction of bead movement to serve as external loads on actin-myosin sliding (Oiwa et al. (1990) Proc Natl Acad Sci USA 87: 7893-7897), and succeeded in determining the steady-state force-velocity relation of ATP-dependent actin-myosin sliding. To give further information about the properties of actin-myosin sliding, we have applied centrifugal forces, in parallel with the plane of actin-myosin sliding but at right angles with the direction of bead movement, and have found that such "lateral" centrifugal forces reduced the velocity of bead movement. In addition, we have also found that the velocity of bead movement is reduced more markedly with lateral forces applied from the left side of the bead ("left" lateral forces) than those applied from the right side of the bead ("right" lateral forces). These results are discussed in connection with the direction of sliding force generated by the myosin heads on the bead which interact with the right-handed double helix of actin monomers constituting actin filaments.

Actins↗