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At least 181 records · Page 10Linked to original sources
PubMed2001

Improving the rate of infectivity of Cryptosporidium parvum oocysts in cell culture using centrifugation.

Centrifugation was evaluated as a method to improve infectivity assays of Cryptosporidium parvum in cell culture using the focus detection method, an immunofluorescence-based method for detecting infectious C. parvum oocysts in vitro. Human ileocecal adenocarcinoma (HCT-8) cells were grown for 48 hr on 13-mm cover slips in 24-well microtiter plates and infected with bleach-treated C. parvum oocysts. Plates were centrifuged at 228 g for 10 min and incubated at 37 C for 5, 12, 18, 24, and 48 hr. Foci of infection were stained by immunofluorescence and enumerated using epifluorescent microscopy. Results were compared to noncentrifuged controls. Foci in centrifuged samples could be enumerated after 18 hr. According to most probable number (MPN) analysis, the number of infectious oocysts estimated at 48 hr (13,326 infectious oocysts) was reached by 18 hr in centrifuged samples. After 48 hr, there was no significant difference (P < 0.05) between centrifuged and noncentrifuged samples enumerated by number of foci or the MPN of infectious oocysts. Centrifugation may expedite detection during C. parvum infectivity assays. Furthermore, multiwell plate formats are more cost effective than traditional chamber slides.

Animals↗
PubMed2006

High-solids centrifuge is a boon and a curse for managing anaerobically digested biosolids.

High-solids centrifugation can reduce the cost of managing or disposing of anaerobically digested biosolids. High-solids centrifuges can increase relative cake solids by as much as 5% DS compared with other dewatering devices, such as belt filter presses, with a resulting 15-20% reduction in overall mass of hauled biosolids. Cost reductions can be similar (15-20%) or more, depending on the type of disposal or management involved. For example, the additional removal of water from the cake increases the energy content in the biosolids, thereby facilitating incineration or heat drying processes. For land application, the benefits are more mixed. As explained in this paper, increases in biosolids odours associated with high-solids centrifuges may increase digestion requirements and may compel producers to transport biosolids to more remote, distant sites, potentially increasing transportation costs. High-solids centrifuges shear anaerobically digested biosolids. The shear results in a net increase in labile protein, an odour precursor. Additionally, high-solids centrifugation also results in the inhibition of methanogenesis, a major mechanism for degradation of organosulphur odours. Therefore, the risks and benefits should both be weighed when considering high-solids centrifuges for land application of anaerobically digested biosolids.

Centrifugation↗
PubMed1997

Enhanced separation of X and Y bearing sperm cells by a combined density gradient centrifugation evaluated by fluorescence in situ hybridization of the Y-chromosome.

OBJECTIVES: Fluorescent in situ hybridization of decondensed sperm cells was used to evaluate the effectiveness of separating X- and Y chromosome bearing sperm cells using a combination of Percoll and NycoPrep media. MATERIAL AND METHODS: Semen samples from seven healthy men were divided into three equal aliquots. One aliquot served as an untreated control, the other two were either applied to a seven-step Percoll gradient (100%-40%), or to a seven-step Percoll gradient (100%-40%) underlayered with 100% NycoPrep for sperm purification. After centrifugation Y-bearing sperm cells in the pellet and in the control sample was determined by fluorescent in situ hybridization. RESULTS: A significantly reduction of Y-bearing sperm cells were observed in the pellet of the Percoll + NycoPrep centrifugation (39.3% Y-bearing sperm cells) compared to the control sample and to Percoll centrifugation without NycoPrep. The Percoll centrifugation without NycoPrep did not show a significant reduction of Y-bearing sperm cells in the pellet compared to the control sample. CONCLUSION: By the addition of a medium with a density higher than 100% Percoll a significantly increased separation of X and Y-bearing sperm cells can be achieved. This study opens new perspectives for improving separation of X- and Y-bearing spermatozoa by simple centrifugations. The described centrifugation technique can be applied in connection with preimplantation diagnosis in order to create more pre-embryos of the desired gender.

Cell Separation↗
PubMed1996

Centrifugal pump failures.

Centrifugal pumps will not pass gross quantities of gaseous emboli due to the nonocclusive nature of the pump. However, retrograde flow can occur under circumstances that include: product malfunctions, low flows, and human errors. Negative pressure created by falling arterial perfusate can draw air into the cannula. Food and Drug Administration (FDA) records about centrifugal pump malfunctions were obtained. Out of 350,000 cases completed with centrifugal pumps over a 23 month period, the FDA received reports of 68 malfunctions, 22 electrical burning smells, and three speed surges, yielding a failure rate of 1 in 3,763 cases. FDA records revealed five death reports and three serious injury reports. A survey was sent to 2,424 Society of Thoracic Surgeons' members to obtain more information; 285 who use centrifugal pumps responded. Sixty surgeons (21%) reported 108 malfunctions, including 46 complete pump failures. Fifty-one of 243 surgeons (21%) who use centrifugal pumps for bypass reported that perfusionists have forgotten to clamp the pump line, resulting in backflow. We conclude centrifugal pumps are generally safe, but malfunctions, low flows, and human errors can lead to retrograde flow and occasionally air embolization. There are valves that can be added to the bypass circuitry to prevent this risk.

Cardiopulmonary Bypass↗
PubMed1998

Effect of centrifugation at 2G for 14 days on metabolic enzymes of the tibialis anterior and soleus muscles.

BACKGROUND: The enzyme composition of different muscle types vary greatly, leading to different changes of enzyme level caused by exposure to various stimuli. METHODS: Male Wistar rats were centrifuged at 2G in a 12-ft radius centrifuge for 14 d. Tibialis anterior (TA) and soleus muscles from four centrifuge and four control rats were analyzed for three enzymes characteristic of fast twitch muscles (phosphofructokinase, glycerol-3-phosphate dehydrogenase, and pyruvate kinase), and four enzymes characteristic of slow twitch muscles (hexokinase, mitochondrial thiolase, B-hydroxyacyl CoA dehydrogenase, and citrate synthase). RESULTS: The centrifuged TA muscles lost 15% of their weight; the corresponding soleus muscles gained 4%. Calculated on the basis of dry weight, the fast twitch enzyme activities were reduced 3-15% in the TA muscles but increased 10-23% in the soleus muscles. The slow twitch enzymes were reduced 18-30% in TA muscles but were almost unchanged in the soleus muscles. When calculated on the basis of total muscle weight, all of the enzymes in TA muscles were significantly reduced by centrifugation. In contrast, in soleus muscles, on the basis of total muscle weight, centrifugation caused an average increase of 22% in the fast twitch enzymes but only marginal changes in the slow twitch enzymes.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1996

A human-powered, small radius centrifuge for space application: a design study.

The necessity of preventing physiologic deconditioning of astronauts exposed to long duration space flights is well known. A method under consideration to prevent this deconditioning is the use of periodic exposure to artificial gravity which could be provided by a centrifuge. This paper presents a design study for a human-powered centrifuge which could be used aboard the NASA Space Shuttle with analyses which quantify many of the forces produced. Consideration is given to managing reaction forces to changes in centrifuge angular velocity, centrifuge imbalance effects, the effects of gyroscopic moment on spacecraft orientation changes, and torque and power requirements as a function of centrifuge performance parameters. A design concept for a "human powered" centrifuge which could provide both exercise and artificial gravity exposure is also considered.

Acceleration↗
PubMed1991

Monitoring the centrifugal recovery of recombinant protein inclusion bodies.

The industrial processing of proteins expressed as insoluble inclusion bodies employs a reasonably standard sequence of unit operations. One of these is centrifugation, which serves to concentrate the inclusion bodies after disruption of the host microorganism, and also separates the inclusion bodies from other cellular debris. Monitoring the performance of the centrifuge is essential if excessive product and hence financial loss is to be avoided and a reasonable separation obtained. The analytical disc centrifuge may be used to monitor the centrifugation. This instrument returns the sample size distribution with high resolution and without fouling. By obtaining size distributions of the centrifuge feed, supernatant and concentrate, the fractional collection efficiency of the centrifuge may be determined as a function of the Stokes diameter, and a mass balance constructed.

Cell Fractionation↗
PubMed2004

[Separation of high-quality sperm by PureSperm centrifugation applied to intrauterine insemination cycles].

OBJECTIVE: To separate high-quality sperm by PureSperm centrifugation applied to intrauterine insemination (IUI) cycles. METHODS: We compared the separate results after washing the semen with one-layer and two-layer PureSperm gradient centrifugation methods and two-layer Percoll gradient centrifugation method, and used the recovered high-quality sperm for IUI. RESULTS: The density of the sperm washed with one-layer PureSperm centrifugation method was significantly higher than that washed with two-layer Percoll and two-layer PureSperm centrifugation methods(P < 0.01), but there were no differences in all the results between the use of two-layer Percoll and two-layer PureSperm(P > 0.05). No significant differences in the motility, teratozoospermia and IUI results were found when the three methods were used for sperm preparation(P > 0.05). The percentage of morphologically normal sperm was markedly increased, and the non-sperm components such as leucocytes, epithelial cells and cellular fragments were significantly reduced after washed by the two methods. CONCLUSION: PureSperm centrifugation is a safe, efficient and easy method for separating high-quality sperm on intrauterine insemination cycles.

Cell Separation↗
PubMed2004

Centrifugal force stretcher a new of in vitro mechanical cell stimulator.

A number of mechanical cell stimulators have been used to study the effect of mechanical stimulation on cells in vitro. But the efficiency of these devices is not fully desirable. We recently developed a new device for mechanical cell stimulation, the centrifugal force stretcher, and compared its efficacy with that of the traditional Flexercell Strain Unit. When the mechanical stretcher circumrotates with certain speed, cardiac myocytes attached on the plate are stretched and elongated by centrifugal force. Neonatal rat cardiac myocytes were isolated by enzymatic dissociation from the hearts of 3~5 d old Sprague Dawley rats, and were mechanically stimulated by traditional 20% stretch and 180 r/min centrifugal force for 12 and 24 h. The effects of mechanical stimulation on the hypertrophic response of neonatal rat cardiac myocytes and production of angiotensin II (Ang II) were examined. Compared with the non-stretch group, the radioactivity of (3)H-leucine incorporated into the stretch-stimulated cardiac myocytes in the centrifugal force stretch group was significantly higher [(1295.17+/-51.19) vs (1122.67+/-51.63) in 12 h; (1447.5+/-35.96) vs (1210.67+/-90.92) in 24 h, P<0.05]. Ang II was also dramatically increased by 128% in 12 h (P<0.05) and 139% in 24 h (P<0.01). After the myocytes was stretched for 24 h, the LDH level in the medium in the Flexercell Strain Unit group was significantly higher than that in the centrifugal force group [(14.5+/-8.7) U/L vs (7.8+/-4.3) U/L, P<0.05]. The centrifugal force stretcher is a new and improved mechanical cell stimulator with the same effects on the protein synthesis and Ang II secretion of the cardiac myocytes, and the damage to the cells bronght by this stimulator is relatively slighter in comparison with the Flexercell Strain Unit.

Angiotensin II↗
PubMed1992

[Hematologic and endocrinologic effects of pulsatile cardiopulmonary bypass using a centrifugal pump].

The effects of pulsatile and nonpulsatile flow during cardiopulmonary bypass (CPB) with of centrifugal pump (Sarns) and membrane oxygenator, on blood cells, hemodynamics, and hormonal response were studied. In the pulsatile group (group P) in which pulsatile flow was generated by centrifugal pump and a 20 Fr arterial cannula was used, hemolysis and reduction of platelet count during CPB were more marked than in the nonpulsatile group (group NP), in which the same type of circuit was used. When the 20 Fr arterial cannula was replaced with a 24 Fr cannula (group Pc), the rate of hemolysis during CPB was significantly reduced compared with that in group P (p less than 0.05). The rate of rise in plasma free hemoglobin from 10 to 70 minutes CPB in group Pc was 15.0 mg/dl/hr, this value did not exceed that in either group NP or in group Pr, in which a roller pump rather than centrifugal pump was used to generate pulsatile flow. These findings show that pulsatile CPB with a centrifugal pump produces no deleterious hematologic effect in clinical use. The rise in the level of angiotensin II in group P was significantly smaller than that in group NP (p less than 0.05), and the rise in plasma renin activity and levels of angiotensin I, adrenalin and noradrenaline were smaller than those in group NP, although these differences were no significance. These findings indicate that the centrifugal pump generates pulsatile flow effectively, although not so effectively as to prevent the rise in peripheral vascular resistance. During CPB, there was no change in levels of thyroid hormones, including free T3, free T4 and reverse T3, in either pulsatile groups P and Pc or nonpulsatile group. TSH level in group Pc was significantly elevated in contrast with that in the nonpulsatile group (p less than 0.05), in which no change in TSH level was seen. It is suggested that pulsatile perfusion using a centrifugal pump might maintain sufficient hypothalamic-pituitary function to permit secretion of TSH in response to various stimuli.

Aged↗
PubMedDate not supplied

[Rapid centrifugation for routine coagulation testing].

Routine coagulation assays are performed with platelet-poor plasma obtained after centrifugation of whole citrated blood. Usually clinical laboratories centrifuge blood from 2,000 to 2,500 g for 15-30 minutes. Thirty two blood samples routinely submitted to coagulation tests, were assayed for the prothrombin time, activated partial thromboplastin time, and fibrinogen level, in order to compare results obtained using 2 types of centrifugation : centrifugation at 2,500 g for 15 minutes and rapid centrifugation on StatSpin Express 2 at 4,440 g for 2 minutes. A good correlation was observed for the prothrombin time, activated partial thromboplastin time, and fibrinogen levels being respectively 1,009, 0,908 and 1. We concluded that rapid centrifugation at 4,440 g for 2 minutes does not modify results and contributes, by decreasing duration of the pre-analytical variable to reduce the completion time of these tests.

Blood Coagulation Tests↗
PubMed2006

Sensitivity of Ziehl-Neelsen method for centrifuged deposit smears of sputum samples transported in cetyl-pyridinium chloride.

BACKGROUND & OBJECTIVES: Sensitivity of Ziehl-Neelsen (ZN) method is known to be low for liquefied sputum smears. Information on the ZN sensitivity for centrifuged deposit smears is not known. This study was carried out to determine the sensitivity of ZN method for acid fast bacilli (AFB) in centrifuged deposit smears and liquefied sputum smears made from sputum samples transported in cetyl-pyridinium chloride (CPC) solution. METHODS: Liquefied sputum smears and the corresponding centrifuged deposit smears from each of the 607 consecutive sputum samples collected from tuberculosis patients admitted to receive treatment transported in CPC were read by the same readers and their results compared with culture results. RESULTS: A significantly (P<0.001) higher proportion of samples were positive in centrifuged deposit smears (40%) compared to liquefied sputum smears (30%). The results of 341 culture-positive specimens revealed that the sensitivity of ZN method was 47 per cent using liquefied sputum smears and 63 per cent using centrifuged deposit smears (P<0.001). INTERPRETATION & CONCLUSION: Our study demonstrated that the sensitivity of ZN method for AFB in centrifuged deposit smears and liquefied sputum smears was reduced if sputum samples are transported in CPC solution.

Bacteriological Techniques↗
PubMed1990

Bifurcation of the amphibian embryo's axis: analysis of variation in response to egg centrifugation.

Xenopus embryos have been reported to vary widely in their developmental response to centrifugation. Variation in response to centrifugation, as measured by embryo survival and twinning of axial structures, was monitored different spawnings of Xenopus laevis eggs. A convenient method for quantifying the egg cytoplasm's potential for displacement in a centrifugal field was employed. It involved testing small batches of eggs from each spawn under carefully controlled conditions for displacement of the cytoplasm while held in an inverted orientation. The cytoplasmic immobility (CIM) values thus measured in samples from each spawn were correlated with the spawning's developmental success (survival of embryos) and the twinning frequency after centrifugation. Those spawnings with high CIM values (i.e. a rigid or stiff cytoplasm) had the highest survival rates and the lowest frequency and severity of twinning in centrifuged eggs. Variations in CIM account for the broad variation in response to centrifugation previously noted in several reports and further emphasize the role cytoplasmic compartments play vis-à-vis egg organization and early embryonic pattern formation.

Animals↗
PubMed1983

Clinical evaluation of a lysis-centrifugation technique for the detection of septicemia.

A commercially available lysis-centrifugation blood culture system was compared with a two-bottle broth-culture system employing 100 mL of broth and 10 mL of blood per bottle to analyze 1,913 blood specimens. Of 154 clinically significant isolates, 89% were detected by the lysis-centrifugation technique, and 73% were detected by the broth-culture method. Twenty-seven percent of the organisms were detected only by the lysis-centrifugation technique, and 11% were detected only by the broth system. Fifteen polymicrobial cultures were encountered; the lysis-centrifugation technique detected 93% of the organisms in these cultures, while the broth-culture method detected only 20%. Isolated colonies of clinically important organisms were available 30 hours earlier with the lysis-centrifugation technique. These results suggest that the lysis-centrifugation technique may provide a substantial improvement over conventional methods for blood cultures.

Adult↗
PubMed1983

Platelet function, size and yield in whole blood and in platelet-rich plasma prepared using differing centrifugation force and time in domestic and food-producing animals.

The effects of centrifugation force and time upon platelets function, mean platelet volume and platelet yield were compared with whole blood platelet counts and size in citrated blood samples from the bovine, canine, caprine, equine, feline, ovine and porcine species. The results were similar, for a given species, irregardless of sample volume. Bovine, caprine, feline and ovine platelet yields and mean platelet volumes were maximal when platelet-rich plasma was prepared using longer centrifugation times and lower gravitational forces. Canine, equine and porcine platelet yields and mean platelet volumes were maximal when platelet-rich plasma was prepared using shorter centrifugation times and higher gravitational forces. Platelet aggregation to adenosine diphosphate or arachidonic acid was not effected by the method of platelet-rich plasma preparation in bovine, caprine, feline, ovine or porcine platelets. Equine platelet aggregation was maximal when platelet-rich plasma was prepared using longer centrifugation times and lower gravitational forces. Canine platelet aggregation, particularly arachidonic acid-induced aggregation, was maximal when platelet-rich plasma was prepared using short centrifugation times and higher gravitational forces. It appeared that the effects of centrifugation parameters upon platelet yield depended upon the relative difference between platelet and red blood cell volumes.

Animals↗
PubMedDate not supplied

[Hematological differences between the effects of roller vs, centrifugal pump].

A secondary complication in the utilization of the CPB (cardiopulmonary bypass) is post-op bleeding due to alterations in the red blood cells and the activation sequences between coagulation, fibrinolysis and complement. We did this study with the objective to evaluate the behavior of the blood cells and coagulation factors using centrifugal pump (n = 12) roller pump (n = 12); we evaluated the consumption of blood products as well as measuring the amount of blood products used. There were no demographic differences between the two groups, the time on CPB was less than 85 minutes, blood flow in the centrifugal pump was maintained at an average of 3.6 l Vs 3.37 l in the roller pump, this being statistically significant. The blood values were compared in each group there were no statistically significant differences, however factor VIII, fibrinogen and platelets presented a tendency (p < 0.05) to be higher in the centrifugal pump group than in the control group (roller pump). Thus 1. In patients in whom we used centrifugal pump there was a tendency for preservation of factor VIII, platelets and fibrinogen. 2. There was no significant difference in the number of blood units transfused between the centrifugal vs roller pump. 3. patients in the centrifugal group were better perfused during CPB.4. 24 hrs. post-op, both groups showed no difference in post-op bleeding.

Adult↗
PubMedDate not supplied

Three-dimensional baselines for perceived self-motion during acceleration and deceleration in a centrifuge.

Three-dimensional motion trajectories were computed, representing the motions that would be perceived by a perfect processor of acceleration information during the acceleration and deceleration stages of a centrifuge run. These motions serve as "baselines" for perceived self-motion in a centrifuge, and depend on the initial perception of orientation and velocity immediately preceding the acceleration and immediately preceding the deceleration. The baselines show that a perfect processor of acceleration information perceives self-motion during centrifuge deceleration significantly differently from self-motion during centrifuge acceleration, despite the fact that the angular accelerations have equal magnitude (with opposite direction). At the same time, the baselines can be compared with subjects' reported perceptions to highlight limitations of the nervous system; limitations and peculiarities of the nervous system are identified as deviations from a baseline. As a result, peculiarities of the nervous system are held responsible for any perception of pitch or roll angular velocity or change in tilt of the body-horizontal plane of motion during the centrifuge run. On the other hand, baselines explain perception of tilt position during deceleration, linear velocity, possible lack of significant linear velocity during deceleration, and yaw angular velocity, including on-axis angular velocity during centrifuge deceleration. The results lead to several experimental questions.

Acceleration↗
PubMed1996

Centrifugal processing of cell debris and inclusion bodies from recombinant Escherichia coli.

The settling characteristics of cell debris and inclusion bodies prior to, and following, fractionation in a disc-stack centrifuge were measured using Cumulative Sedimentation Analysis (CSA) and Centrifugal Disc photoSedimentation (CDS). The impact of centrifuge feedrate and repeated homogenisation on both cell debris and inclusion body collection efficiency was investigated. Increasing the normalised centrifuge feedrate (Q/sigma) from 1.32 x 10(-9) m s-1 to 3.97 x 10(-9) m s-1 leads to a 36% increase in inclusion body paste purity. Purity may also be improved by repeated homogenisation. Increasing the number of homogeniser passes results in smaller cell debris size whilst leaves inclusion body size unaltered. At a normalised centrifuge feedrate of 2.65 x 10(-9) m s-1, increasing the number of homogeniser passes from two (2) to ten (10) improved overall inclusion body paste purity by 58%. Grade-efficiency curves for both the cell debris and inclusion bodies have also been generated in this study. The data are described using an equation developed by Mannweiler (1989) with parameters of k = 0.15-0.16 and n = 2.5-2.6 for inclusion bodies, and k = 0.12-0.14 and n = 2.0-2.2 for cell debris. This is the first accurate experimentally-determined grade efficiency curve for cell debris. Previous studies have simply estimated debris grade efficiency curves using an approximate debris size distribution and grade efficiency curves determined with 'ideal particles' (e.g. spherical PVA particles). The findings of this study may be used to simulate and optimise the centrifugal fractionation of inclusion bodies from cell debris.

Cell Fractionation↗