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PubMed1986

The effect of centrifugation on the fracture properties of acrylic bone cements.

In this study, centrifugation did not alter the static or cyclic fracture properties of bone cement. Tests of fracture toughness and fatigue-crack propagation of centrifuged specimens of commercial cements (with and without antibiotic additions) demonstrated no significant difference from control values. Among the cements tested, Palacos (with and without antibiotic) was found to have a significantly higher fracture toughness than either Simplex or Zimmer. We attributed this difference in fracture toughness to the higher molecular weight measured for the Palacos cements. For the tested cements, only Simplex had a significantly greater volume contraction on setting due to centrifugation. The results of our study demonstrate that centrifugation of bone cement does not improve the cement's resistance to fracture in the presence of surface imperfections, such as those found at the bone-cement interface.

Bone Cements↗
PubMed1984

Centrifugation as a method of improving tensile and fatigue properties of acrylic bone cement.

In this study centrifugation dramatically reduced the porosity and substantially increased the mechanical properties of bone cement. Monotonic tensile tests to failure of centrifuged specimens of cement demonstrated an increase of 24 per cent in the mean ultimate tensile strength compared with the control value. Mean ultimate tensile strain was improved by 54 per cent. In fully reversed tension-compression fatigue-testing, centrifugation resulted in a mean increase in fatigue life of 136 per cent. These strong advantages in mechanical properties were obtained without any detrimental changes. There was no change in elastic modulus, setting time, or peak temperature. Handling properties were improved. There was no increase in systemic toxicity as demonstrated in dogs by assessment of arterial blood-pressure response and peak levels of monomer in the serum during simulated total hip arthroplasty. We also present a practical system of cement centrifugation and delivery that is suitable for use in the operating room.

Acrylic Resins↗
PubMed1984

A comparison of centrifugal and membrane-based apheresis formats.

Membrane and centrifugal apheresis operate on different physical principles but are both capable of efficiently fractionating plasma proteins from whole blood. For therapeutic purposes, both formats yield about the same protein clearance per liter of solute exchanged and neither is significantly more rapid than the other. Only continuous centrifugation can be used to pherese cellular elements and only membrane filter can be deployed in 'spontaneous' circuits. Hardware for continuous centrifugation is more expensive and disposables less expensive than for the membrane methods; the 'crossover' occurs at 200 treatments. To date, only the centrifugal method is employed for donor apheresis; this may change in the future as membranes can yield a truly platelet-free product and appear to offer a much more rapid collection cycle.

Blood Donors↗
PubMedDate not supplied

Homogeneous enzyme immunoassay for theophylline with a centrifugal analyzer.

A rapid homogeneous enzyme immunoassay for theophylline has been adapted to a centrifugal analyzer. The sample volume used was 10 microliter and sera from as many as 28 patients could be measured in 180 seconds. The assay temperature was 30 degrees and the absorbance rates were measured at 340 nm. Within-run and run-to-run precision showed a coefficient of variation of less than 2.6 and 7.5 percent, respectively, for theophylline concentrations of 2.5 to 40 mg per liter. The method was linear to 50 mg per liter and the analytical recovery was quantitative. A comparison between high pressure liquid chromatography (X) and the centrifugal analyzer enzyme immunoassay method (Y) for 51 patient samples revealed a correlation coefficient of 0.976 with a regression line of Y = 1.07 X -1.05 mg per liter. Reagent costs were reduced three-fold by adapting the enzyme immunoassay procedure from a semi-automatic spectrophotometer to a centrifugal analyzer. An absorbance rate for each theophylline sample was obtained by a multipoint kinetic rate computer program by the centrifugal analyzer. Severe hemolysis and lipemia interfered in this assay.

Autoanalysis↗
PubMed1980

Subcellular fractionation of human intestinal mucosa by large-scale zonal centrifugation. Separation of the organelles in diseased ileum of a patient with Crohn's disease.

The subcellular organelles in diseased ileal mucosa of a patient with Crohn's disease have been separated by rate zonal density gradient centrifugation. Mucosal scrapings were obtained from a surgical specimen of diseased intestine and the cells disrupted by extrusion under controlled pressure. The homogenized cells were then centrifuged to prepare a cell extract and the extract fractionated in a single-step procedure by zonal centrifugation on a continuous sucrose gradient. The subcellular organelles (brush borders, basal-lateral membranes, lysosomes, mitochondria and endoplasmic reticulum) were located in the density gradient by assay of marker enzymes and their overall distribution compared with the distribution of organelles from a normal tissue. The centrifugal properties of individual organelles in the diseased tissue were largely unaffected but the lysosomes were more fragile than in the normal tissue. Since the fractionation technique used is on a large scale, each fraction of interest can be further analyzed for a variety of compounds. Therefore, the subcellular pathology and pathophysiology in this and other cases of Crohn's disease may eventually be studied and discussed in other than morphological and descriptive terms.

Aged↗
PubMed1993

Isolation and concentration of microfilariae from peripheral blood of Wuchereria bancrofti infected patients by density gradient centrifugation.

A Ficoll-Hypaque gradient centrifugation technique was used for isolation and concentration of microfilariae from peripheral blood of 30 subjects with clinically and parasitologically diagnosed Wuchereria bancrofti infections. 86% of the microfilariae were found in the Ficoll-Hypaque layer. None were detected in the plasma, leucocyte layer or lower erythrocyte layer. 14% of microfilariae were identified on the top part of the erythrocyte layer. A 35 fold concentration and 88% quantitative recovery of parasites was achieved by conventional centrifugation of microfilariae-rich Ficoll-Hypaque layer. Following the centrifugation procedures, living motile microfilariae were separated. These results indicate that Ficoll-Hypaque centrifugation technique could be an effective method for the detection of low levels of microfilaraemia, and for obtaining relatively pure suspensions of living microfilariae for metabolic studies, production of antigen-rich excretory-secretory products and antigen analysis.

Animals↗
PubMedDate not supplied

A magnetically suspended centrifugal pump. In vitro and in vivo assessment.

To overcome problems derived from the shaft within conventional centrifugal pumps, we have developed a new centrifugal pump, the magnetically suspended centrifugal pump (MSCP), which has no shaft and operates as a bearingless centrifugal pump. The impeller is suspended freely and centrally by magnetic force within the pump. Hemolysis tests were performed in comparison with the Biopump. Index of hemolysis and destruction of platelets were significantly lower in the MSCP than in the Biopump. Animal studies were designed to evaluate the durability and antithrombogenicity of the MSCP. Short-term animal studies were performed using two mongrel dogs. Left heart bypass was established with the MSCP. After 3 hr, the layer of thrombus adherent to the surface of the polycarbonate impeller impaired pumping efficiency. However, using the impeller coated with silicone, no thrombus was observed on the impeller after continuous pumping for 24 hr. In addition, long-term animal studies were performed using two sheep. Left heart bypass was established with the MSCP containing an impeller coated with silicone. In one sheep, the MSCP ran for 14 days without problems in pumping performance and showed no thrombus within the pump. In the other sheep, the MSCP ran for 15 days, and showed no thrombus on the impeller. During each experiment, plasma free hemoglobin levels were less than 15 mg/dl. The MSCP induced less hemolysis than did the Biopump, and the MSCP containing an impeller coated with silicone demonstrated the potential to run for 14 days without thrombus formation within the pump.

Animals↗
PubMedDate not supplied

Effects of long duration centrifugation on head movements and a psychomotor task.

Previous investigations suggest strong similarities between aftereffects of an 1.5-hour 3 gx centrifuge run (Sickness Induced by Centrifugation; SIC) and the Space Adaptation Syndrome (SAS). Head movements proved to be especially nauseogenic in both cases. Until recently, during SIC experimentation, the performance of head movements was not adequately operationalized, which hampered a statistical evaluation. For this purpose, a test was designed by which head movements in four directions (left, right, up, and down) were provoked and registered, once before and once after a 1-h 3 g centrifuge run. Subjects had to execute these head movements in order to perform well on a psychomotor task. The results indicate that the test described is sensitive in discriminating between subjects who are seriously affected after a long duration centrifugation and those who are not. Because differences in performance were found only on those parts of the task in which head movements were involved, objective evidence is obtained in favour of a vestibular cause in the etiology of SIC.

Centrifugation↗
PubMed1996

Filtration, centrifugation and mouse exposure for the detection of schistosome cercariae in water.

Three methods for detection of schistosome cercariae in water were studied under laboratory and simulated field conditions in Egypt. Water samples tested by filtration and centrifugation quantitatively reflected the density of cercariae in moderately turbid canal water (30 Nephelometry Turbidity Unites, NTU). When tested in waters of increasing turbidity, the centrifuge gave more consistent results than the filtration system. The centrifugation technique was more efficient in processing the water samples and took almost half the time of filtration. Mouse exposure was useful in detecting cercariae, but was not quantitative. However, there was a significant improvement in worm recovery when mice were more close together in the floatation device. Mouse exposure was also expensive and cumbersome to use. It appears from the present results that the technique of choice for further cercariometric work under Egyptian conditions may be centrifugation.

Animals↗
PubMed1996

Comparative hemolysis study of clinically available centrifugal pumps.

Centrifugal pumps have become important devices for cardiopulmonary bypass and circulatory assistance. Five types of centrifugal pumps are clinically available in Japan. To evaluate the blood trauma caused by centrifugal pumps, a comparative hemolysis study was performed under identical conditions. In vitro hemolysis test circuits were constructed to operate the BioMedicus BP-80 (Medtronic, BioMedicus), Sarns Delphin (Sarns/3M Healthcare), Isoflow (St. Jude Medical [SJM]), HPM-15 (Nikkiso), and Capiox CX-SP45 (Terumo). The hemolysis test loop consisted of two 1.5 m lengths of polyvinyl chloride tubing with a 3/8-inch internal diameter, a reservoir with a sampling port, and a pump head. All pumps were set to flow at 6 L/min against the total pressure head of 120 mm Hg. Experiments were conducted simultaneously for 6 h at room temperature (21 degrees C) with fresh bovine blood. Blood samples for plasma-free hemoglobin testing were taken, and the change in temperature at the pump outlet port was measured during the experiment. The mean pump rotational speeds were 1,570, 1,374, 1,438, 1,944, and 1,296 rpm, and the normalized indexes of hemolysis were 0.00070, 0.00745, 0.00096, 0.00066, 0.00090 g/100 L for the BP-80, Sarns, SJM, Nikkiso, and Terumo pumps, respectively. The change in temperature at the pump outlet port was the least for the Nikkiso pump (1.8 degrees C) and the most with the SJM pump (3.8 degrees C). This study showed that there is no relationship between the pump rotational speed (rpm) and the normalized index of hemolysis in 5 types of centrifugal pumps. The pump design and number of impellers could be more notable factors in blood damage.

Blood Flow Velocity↗
PubMed1996

[Effect of HLA antibodies on the gel centrifugation test].

We studied 39 samples of patients showing unexplainable but reproducibly positive indirect antiglobulin test (IAT) in the gel centrifugation (ID Micro Typing System, DiaMed) and negative auto-control test. Additionally 30 sera with defined red cell antibodies (control group) were tested. In 87.2% HLA antibodies could be found (none in the control group). After platelet absorption, 83.9% of the sera became negative in IAT. When IAT, microlymphocytotoxicity test (MLT) and platelet adhesion fluorescence antiglobulin test (PAFT) were performed with the cells of the same donors in parallel (n = 30) the IAT only became positive with the cells of donors (n = 21 = 70%) who also reacted in the MLT and/or PAFT. The tube test mostly was negative. The immunoglobulin class always was IgG. The specificity of the responsible HLA antibodies could be identified in 13 samples and was anti-HLA-B7, -B17, -A2, -A28 and mixed antibodies of these specificities. We conclude that unexplainable positive reactions in the IAT with gel centrifugation mainly are derived from HLA antibodies of high concentration which obviously play a greater role in the gel centrifugation than in other test methods. In cases of such unexplainable positive reactions the routine use of pooled platelets for absorption is recommended. In addition, test cells for antibody screening and identification by gel centrifugation should be typed at least for Bga (HLA-B7) in order to more easily recognize these irrelevant antibodies.

Blood Group Antigens↗
PubMed1994

[Antibody determination and differentiation using papain treated test erythrocytes in the gel centrifugation technique (ID-Microtyping System)].

For one year we have used the gel centrifugation method (ID-Microtyping System, Fa. Diamed, FRG) in our routine laboratory for antibody screening. The two-stage papain test in the gel centrifugation system revealed some interesting phenomena: 1) In some cases the sensitivity of the papain gel test is higher than that of all other methods in the gel centrifugation method or in the tube centrifugation method. 2) There are reactions which seem to be directed against the patient's own antigens (in the Rhesus or Kidd system), but there are no positive direct antiglobulin test and no clinical signs of hemolysis. 3) Some sera show reaction patterns which seem to have a distinct specificity, but they cannot be adjoined to any of the antigens in the manufacturer's antigenogram. Further declarations in the worksheet of the panel would be desirable.

Autoantibodies↗
PubMed1998

Evaluation of platelet damage in two different centrifugal pumps based on measurements of alpha-granule packing proteins.

Mechanical trauma caused by centrifugal pumps is usually evaluated in terms of hemolysis. However, platelet damage caused by centrifugal pumps has not been studied well. We evaluated platelet damage in 2 different centrifugal pumps, the Medtronic BioMedicus BP-80 and the Terumo Capiox, in vitro and compared the results in terms of hemolysis. To evaluate platelet damage, the rate of increase (RI) for beta-thromboglobulin (beta-TG) and platelet factor-4 (PF-4) were measured by enzyme immunoassay. RI was defined as follows: RI for beta-TG is deltabeta-TG/deltaN and RI for PF-4 is deltaPF-4/deltaN where deltabeta-TG is the increase in beta-TG, deltaPF-4 is the increase in PF-4, and deltaN is the increase of the passing number, which is defined in the following equation: N = Qt/V (t, time; V, priming volume; Q, flow rate). Each pump was tested in a mock circuit for 3 h under a flow rate of 5 L/min and a pressure head of 100 mm Hg using fresh human heparinized blood (n = 5). For comparison, the normalized index of hemolysis (NIH) values were calculated for both pumps. The NIH values did not indicate a significant difference between the Capiox and the BP-80 pumps (Capiox vs. BP-80, 0.0021 +/- 0.0004 vs. 0.0034 +/- 0.0007, NS). However, the RI values for beta-TG and PF-4 in the Capiox were significantly lower than in the BP-80 (beta-TG, 0.198 +/- 0.047 vs. 0.376 +/- 0.049; PF-4, 0.080 +/- 0.014 vs. 0.268 +/- 0.043, p < 0.05). In conclusion, although there was no significant difference between the 2 pumps in terms of hemolysis, the Capiox centrifugal pump induced less platelet damage than the BP-80. The results suggest that measurements of RI for beta-TG and PF-4 are more sensitive parameters than NIH values for evaluating blood cell damage.

Blood Platelets↗
PubMedDate not supplied

Purification of viruses by centrifugation in gradients of inert substances.

By using a reorienting gradient centrifuge rotor cut from a block of Nylon and fitted with eight septae, it was possible to separate the components of the haemolymph of the mollusc Turbo sarmaticus into three fractions in a sucrose gradient held in the bowl of the rotor. The fractions were (108 and 98)S, 44S and 16-22S. The success of the experiment was due to the large differences in the sedimentation coefficients of the components. When the rotor was applied to the natural mixture of the five viruses of the caterpillars of Nudaurelia cytheria only the main component could be isolated in a pure state. The viruses were separated by isopycnic centrifugation in "self formed" caesium chloride gradients, using a Beckman Model E analytical centrifuge in which a separation cell fitted with a centerpiece with two perforated partitions was used.

Animals↗
PubMed2003

A centrifugation cell adhesion assay for high-throughput screening of biomaterial surfaces.

A quantitative analysis of cell adhesion is essential in understanding physiological phenomena and designing biomaterials, implant surfaces, and tissue-engineering scaffolds. The most common cell adhesion assays used to evaluate biomaterial surfaces lack sensitivity and reproducibility and/or require specialized equipment and skill-intensive operation. We describe a modified centrifugation cell adhesion assay that uses simple and convenient techniques with standard laboratory equipment and provides reliable, quantitative measurements of cell adhesion. This centrifugation assay applies controlled and uniform detachment forces to a large population of adherent cells, providing robust statistics for quantifying cell adhesion. The applicability of this system to the design and characterization of biomaterial surfaces is shown by evaluating cell adhesion on substrates using different coating proteins, cell types, seeding times, and relative centrifugal forces (RCF). Results verify that this centrifugation cell adhesion assay represents a simple, convenient, and standard method for high-throughput characterization of a variety of biomaterial surfaces and conditions.

Biocompatible Materials↗
PubMed1996

Bio-Medicus centrifugal ventricular support for postcardiotomy cardiac failure: a review of 129 cases.

BACKGROUND: Bio-Medicus centrifugal ventricular support has been used widely for postcardiotomy cardiac failure. The purpose of this study was to review a large series of support patients examining complications and outcomes. METHODS: One hundred twenty-nine patients undergoing cardiac operations at The Methodist Hospital in Houston, Texas, were placed on Bio-Medicus centrifugal ventricular support for postcardiotomy cardiac failure; 102 were male and 27 were female with a mean age of 61.6 years. These patients were selected for ventricular support based solely on failure to be weaned from cardiopulmonary bypass or progressive postcardiotomy cardiac failure shortly after arrival in the intensive care unit. RESULTS: These patients experienced numerous complications including coagulopathy, renal insufficiency or failure, sepsis, neurologic deficits, ventricular failure, arrhythmias, and death; 56.3% of patients were weaned from mechanical support and 21.0% were discharged alive. Causes of death included ventricular failure (62.4%), arrhythmias (12.9%), triage (6.9%), perioperative myocardial infarction or cardiac arrest (5.0%), coagulopathy (4.0%), sepsis syndrome (4.0%), cardiac graft failure (3.0%), and device related (1.0%). The one device-related death was a venous cannula dislodgment in the intensive care unit with subsequent exsanguination. Device-related complications were seen in only 1.6% of patients. CONCLUSIONS: Bio-Medicus centrifugal ventricular support can be implemented rapidly and relatively easily. There are few device-related complications and the cost is relatively inexpensive compared with other assist systems. This series demonstrates that a substantial number of patients who experience reversible postcardiotomy myocardial injury will benefit from temporary centrifugal ventricular support.

Adolescent↗
PubMed1980

The origins of the centrifugal fibers to the olfactory bulb in the goldfish, Carassius auratus: an experimental study using the fluorescent dye primuline as a retrograde tracer.

The origin of the centrifugal fibers to the olfactory bulb in the goldfish was examined by injecting a fluorescent dye, primuline, into the olfactory bulb by means of hydraulic pressure. Three to five days after the primuline injection, which was confined to the unilateral olfactory bulb, a large number of primuline-labeled perikarya appeared in two telencephalic areas on the ipsilateral side: the area ventralis telencephali pars dorsalis (Vd) and the ventral part of the area dorsalis telencephali pars lateralis (Dlv). No labeled cells were observed in the other olfactory bulb or in the contralateral telencephalic hemisphere or more posterior part of the brain. A combination of the primuline injection and the transection of either the medial or lateral olfactory tract showed that the main course of the centrifugal fibers was through the medial olfactory tract. These results may support Sheldon's opinion that the so-called tractus olfactorius ascendens, which corresponds to the medial part of the medial olfactory tract, is a centrifugal bundle originating from the cells in the nucleus medianus. The areas of the telencephalic hemisphere into which the olfactory bulbar fibers projected were also examined and compared with the originating areas of the centrifugal fibers. There was a considerable overlap between these two areas. This suggests a reciprocal connection between the olfactory bulb and the telencephalon.

Animals↗
PubMed1984

An anatomical and electrophysiological study of the centrifugal visual system in the lamprey (Lampetra fluviatilis).

The centrifugal visual system of the lamprey Lampetra fluviatilis was investigated using various neurohistophysical methods: intraocular injections of [3H]adenosine, fluorescent tracer (Evans Blue) and the iontophoretic deposit of HRP on the optic nerve. Retrogradely labeled neurons were identified bilaterally within the nucleus M5 of Schober and contralaterally in the reticular mesencephalic area (RMA). Comparison of the various orthograde and retrograde labeling results indicated that the neurons of M5 and RMA were labeled via retrograde axonal transport of the different tracers in the retinopetal system and not by orthograde transneuronal processes or from extraretinal pathways. Part of the anatomical data regarding RMA as a site of origin of the centrifugal visual system was confirmed using electrophysiological techniques involving evoked potential and unit cell recordings in RMA following electrical stimulation of the optic nerve. The experiments were performed in the curarized animal under conditions of either normal blood circulation, perfusions of adapted physiological saline, or with a solution known to block chemical synaptic transmission. Various electrophysiological criteria, including the results obtained during the conditions of reversible chemical synaptic blockade, indicated that the responses in RMA reflect an antidromic process. The anatomical organization of the centrifugal visual system in the lamprey is compared to that found in different gnathostome vertebrate species. Several hypotheses concerning the marked interspecies differences related either to the number and the topographical location of the centrifugal neurons as well as the evolution of this system are advanced.

Animals↗