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PubMed1980

An Examination of Centrifugation as a Method of Extracting an Extracellular Solution from Peas, and Its Use for the Study of Indoleacetic Acid-induced Growth.

A technique of centrifuging pea epicotyl sections which extracts water-soluble cell wall polysaccharides with less than 1.5% cytoplasmic contamination as revealed by malate dehydrogenase activity determinations was developed. Tests for protein, hexose, pentose, and malate dehydrogenase indicate that significant damage to the cells occurs above 3,000g. Below this force, there is little damage, as evidenced by the similar growth rates of centrifuged and noncentrifuged sections. Centrifugation at 1,000g extracts polysaccharides containing rhamnose, fucose, arabinose, xylose, mannose, galactose, and glucose. An increase in xylose and glucose, presumably xyloglucan, is induced by treating sections with indoleacetic acid. Much of the alcohol-insoluble, water-soluble polysaccharide within the wall is extractable by centrifugation, since nearly as much arabinose and xylose are extractable by centrifugation as by homogenization. The utility of this method for the study of cell wall metabolism is discussed.

Journal Article↗
PubMed1984

Octopamine release from centrifugal fibers of the Limulus peripheral visual system.

Octopamine, a biogenic amine, is synthesized and stored within centrifugal (efferent) fibers that project from the brain to the lateral and ventral eyes of the horseshoe crab, Limulus polyphemus. The experiments described here show that depolarization of Limulus lateral and ventral eyes, produced by elevating the concentration of extracellular K+, causes the selective release of newly synthesized octopamine from centrifugal fibers in a manner that requires the influx of extracellular Ca2+. Conjugates of octopamine and tyramine that are also stored within centrifugal fibers are not released in response to K+-induced depolarization. These findings add further support to the hypothesis that octopamine is a neurotransmitter synthesized by and released from centrifugal fibers in Limulus eyes. This amine may be responsible for many of the alterations in lateral eye structure and function that are mediated by centrifugal innervation.

Animals↗
PubMed1988

Uptake and release of glycine in the guinea pig cochlear nucleus after axotomy of afferent or centrifugal fibers.

Glycine may be an inhibitory transmitter in the mammalian cochlear nucleus (CN). This study attempts to determine if cochlear and/or centrifugal projections to the CN use glycine as a transmitter. The high-affinity uptake and electrically evoked release of exogenous [14C]glycine were measured in vitro in the three major subdivisions of the guinea pig CN: the anteroventral, posteroventral, and dorsal cochlear nuclei (AVCN, PVCN, and DCN, respectively). [14C]Glycine (3.4 microM) was taken up by each subdivision, reaching tissue concentrations six to seven times that in the medium. Subsequent electrical stimulation evoked a Ca2+-dependent release of [14C]glycine from each subdivision. These activities were compared in subdivisions fr0m unlesioned animals, and from animals with lesions of centrifugal or cochlear projections to the CN. Two knife-cut lesions were made to interrupt centrifugal projections to the CN lying in the right acoustic striae and trapezoid body. In one group of animals, centrifugal fibers projecting mainly to the right AVCN and PVCN were severed, which reduced [14C]glycine uptake and release by 44-53% in these subdivisions, but not in the right DCN. In another group of animals, fibers projecting mainly to the right PVCN and DCN were severed, which reduced [14C]glycine uptake and release by 33-47% in these subdivisions, but not in the right AVCN. In CN subdivisions contralateral to either lesion there was no significant change in [14C]glycine uptake or release. Neither of these lesions altered the uptake or release of D-[3H]aspartate in the right or the left CN. Ablation of the left cochlea, which presumably destroyed cochlear nerve fibers unilaterally, had no effect on [14C]glycine uptake and release. These observations suggest that centrifugal projections contribute a proportion of the glycinergic synaptic endings in the CN. In addition, some glycinergic endings probably arise from neurons intrinsic to the CN. The cochlear nerve contains very few, if any, glycinergic fibers.

Afferent Pathways↗
PubMed1992

Development of an atraumatic small centrifugal pump for second-generation cardiopulmonary bypass.

A small and light direct-drive centrifugal pump has been developed for cardiopulmonary bypass. In the development process, blood compatibility studies including a hemolysis study, an in vitro fluid dynamic performance study, and in vivo durability and feasibility studies were performed. The centrifugal pump with a 50 mm diameter impeller resulted in almost the same index of hemolysis value as did a Bio-Medicus centrifugal pump. Heat dissipation from the motor was prevented by using a flexible drive cable. Forty-eight-hour sealing durability around the driving axis was accomplished by using a fluoro-rubber V-ring that connected to the hard chrome-plated stainless steel. In vitro and in vivo performances of the pump were satisfactory. Thrombus formation behind the impeller was prevented by using a holed impeller that generated blood flow from the back to the surface of the impeller. Elimination of air during priming procedures was also easier with this modification. This centrifugal pump has one-quarter of the priming volume, size, and weight of magnetically coupled centrifugal pump systems.

Animals↗
PubMed1995

In vitro evaluation of a pulsatile assist device for a centrifugal pump using a new principle.

To induce a pulsatile flow in a centrifugal pump, we developed a new device (pulsatile assist device for centrifugal pump: PADCP) using a new concept. This device consists of a flexible polyurethane tube with an air chamber which is connected to the arterial side of the centrifugal pump circuit directly. A mock circulation system was used for evaluation of this PADCP. Thirty to 40 mm Hg of pulse pressure was obtained under 3-6 L/min of flow rate. By increasing the driving pressure of the PADCP from 200 to 600 mm Hg in a mock system, 4-48 mm Hg of pulse pressure was gained accompanied by a decrease in pump flow and increased left atrial pressure. The decreased pump flow and increased left atrial pressure were recovered easily by increasing the flow rate of the centrifugal pump. Pressures at the proximal site of the PADCP were less than 500 mm Hg. The PADCP was useful to induce a pulsatile flow in a centrifugal pump.

Blood Flow Velocity↗
PubMed1990

Centrifugal motion bias in the cat's lateral suprasylvian visual cortex is independent of early flow field exposure.

1. Neurones in the postero-medial part of the cat's lateral suprasylvian visual cortex (area PMLS) show an overall preference for centrifugal motion, suggesting that the PMLS may be specialized in the analysis of expanding optic flow fields associated with forward locomotion. 2. We examined whether the visual experience young kittens normally receive during forward locomotion guides the development of the centrifugal preference in the PMLS. 3. Seven kittens were reared in the dark and exposed to either expanding or contracting flow fields for at least 100 h during their 4th-11th weeks of life. Specific experience was achieved by exposing kittens either to flow field patterns generated on a screen or by actually moving them forward or backward in a carousel. 4. Our results show that although the development of directional selectivity in the PMLS requires visual experience, the centrifugal bias is independent of specific visual exposure. The preference for centrifugal motion among PMLS cells was just as evident in kittens exposed to contracting as in kittens exposed to expanding flow fields. 5. We conclude that the preference for centrifugal motion in the PMLS is not the result of anisotropic stimulation kittens receive during locomotion in early ontogeny, but is probably innately determined as a phylogenetic adaptation.

Animals↗
PubMed1994

Quantitative centrifugation to extract benthic protozoa from freshwater sediments.

TWO METHODS FOR EXTRACTING PROTISTS FROM FRESHWATER SEDIMENT ARE DESCRIBED: (i) an adapted isopycnic centrifugation technique for sandy and gyttja-like sediments and (ii) a rate zonal centrifugation technique for sediments rich in particulate organic material (litter-like sediments). The recoveries of protists during isopycnic centrifugation in media of several densities were compared. No significant losses in sodium diatrizoate and Percoll were recorded. After known amounts of nanoflagellates were added to azoic sediments, the protists were extracted and counted. For sandy sediments, we found 100% recovery, and for the gyttja-like sediments we found a maximum recovery of 94%. The recovery of protozoa extracted from litter-like sediments, characteristic of littoral systems, depends on a given centrifugal force, on time, and on the dimensions of the flagellates. A recovery model which takes into account cell dimensions and centrifugation characteristics gives the minimum expected recovery.

Journal Article↗
PubMed2001

Discrepancy between dysmetric centrifugal movements and normometric centripetal movements in psychogenic ataxia.

A method to unravel an aberrant motor behaviour in psychogenic ataxia is reported. The kinematic features of fast reaching movements in the vertical plane are described in a patient presenting a psychogenic ataxia. The procedure compared centrifugal and centripetal movements. Path ratios were computed for each phase, as well as the ratios of the paths for centrifugal and centripetal directions. Trajectories of centrifugal phases were erratic but centripetal movements were very regular, whereas both centripetal and centrifugal movements were irregular in patients presenting an organic cerebellar syndrome. A similar incongruity between movements in opposite directions is also shown for a second patient exhibiting psychogenic ataxia. Discrepancies between the centrifugal phase and the centripetal phase of multi-joint reaching movements support the diagnosis of a psychogenic movement disorder.

Adult↗
PubMed2006

Effects of centrifugal and roller pumps on survival of autologous red cells in cardiopulmonary bypass surgery.

BACKGROUND: Either a roller pump or a centrifugal pump can be used in the extracorporeal circuit during surgery with cardiopulmonary bypass. In this study, we assessed the effect of these two pumps on the 24-h post-transfusion survival values of autologous red blood cells (RBC). STUDY DESIGN AND METHODS: Fourteen male patients subjected to extracorporeal bypass procedures were studied. In seven patients, the autologous red cells were collected following the cardiopulmonary bypass procedure using the roller pump, and in seven patients, autologous red cells were collected following the cardiopulmonary procedure using the centrifugal pump. The 24-h post-transfusion survival values of the autologous RBC were measured using the 51 disodium chromate/99m technetium double isotope procedure. The effects of the extracorporeal bypass procedures using the roller pump and the centrifugal pump were also assessed by the measurements of hematocrit, platelet count, plasma hemoglobin, and serum lactate dehydrogenase levels. RESULTS: The 51 disodium chromate 24-h post-transfusion survival values of the autologous RBC were similar whether the roller pump or the centrifugal pump was used in the extracorporeal circulation, as were the hematocrit, platelet count, plasma hemoglobin and serum lactate dehydrogenase levels. CONCLUSION: The 24-h post-transfusion survival values of autologous RBC, measured by the 51 disodium chromate/99m technetium double isotope procedure, were not significantly different, whether the roller pump or the centrifugal pump was used in the extracorporeal circuit using membrane oxygenators during cardiopulmonary surgical procedures.

Adult↗
PubMed1997

Neutrophil adhesion molecule expression during cardiopulmonary bypass: a comparative study of roller and centrifugal pumps.

The purpose of this study was to determine whether adhesion molecules and markers of cell activation were preferentially increased on blood neutrophils during cardiopulmonary bypass (CPB) and whether such effects were influenced by the use of a roller pump or a centrifugal pump. Forty-six patients undergoing open heart surgery were randomly allocated into either the roller or centrifugal groups. Blood (1 ml volumes) was removed from arterial and venous lines immediately before and 1 h after the start of bypass. Whole blood samples were immunolabelled and flow cytometry used to measure the distribution and expression of the adhesion molecules CD11b, CD18, CD62L on neutrophils, monocytes and lymphocytes, in addition to CD64 on neutrophils and monocytes, and CD14 on monocytes. The expression of CD11b was significantly enhanced on neutrophils in arterial and venous samples from both the roller pump (mean 84% and 100% increase, respectively; p < 0.001) and centrifugal pump (mean 74% and 73% increase, respectively; p < 0.001) groups. Neutrophil L-selectin expression increased to a small but significant extent in arterial and venous samples from the centrifugal pump group (mean 16% increase; p < 0.001) and in venous samples from the roller pump group (mean 10% increase; p < 0.01). Neither the percentage of neutrophils bearing CD11b/CD18, CD62L and CD64, nor the expression of adhesion molecules on lymphocytes and monocytes were modified by 1 h of bypass. These results suggest that patients subjected to CPB with roller or centrifugal pumps are equally at risk to neutrophil activation that could lead to increased interaction of these cells with blood vessel walls.

Antigens, CD↗
PubMed1999

Haemolysis during cardiopulmonary bypass: an in vivo comparison of standard roller pumps, nonocclusive roller pumps and centrifugal pumps.

Cardiopulmonary bypass (CPB) involves the use of either an occlusive roller pump or centrifugal pump. Damage to blood elements, including haemolysis, may arise from occlusion when using a roller pump; the appropriate degree of occlusion has not yet been determined scientifically. Centrifugal and nonocclusive roller pumps are reputed to reduce haemolysis. The objective of this study was to compare haemolysis caused by a standard roller pump with a dynamically set nonocclusive roller pump and with a centrifugal pump. We prospectively randomized 60 patients undergoing routine coronary artery surgery into three groups: standard roller pump (STD, n = 20), dynamically set roller pump (DYN, n = 20), or centrifugal pump (CEN, n = 20). The level of plasma free haemoglobin (FHb) was measured preoperatively, and the rate of formation of FHb (in mg/dl/min) was determined at the end of the ischaemic phase and at the end of CPB. Cardiotomy suction blood was isolated for the ischaemic phase and returned before the end of CPB. It was found that there were no differences between the groups in demographic or operative variables. The rate of formation of FHb at the end of the ischaemic phase was similar for all groups (STD 0.108 +/- 0.10, DYN 0.117 +/- 0.08, CEN 0.129 +/- 0.07). At the end of CPB, after return of the cardiotomy suction blood, there was a significant (< 0.001) increase in the rate of formation of FHb in all groups. The increase was similar for each of the groups (STD 0.424 +/- 0.17, DYN 0.481 +/- 0.20, CEN 0.471 +/- 0.18). We conclude that the rates of haemolysis are similar for each of the pump types, and no benefit is conferred by the use of either a dynamically set roller pump or a centrifugal pump compared with the standard roller pump. The return of the cardiotomy suction blood to the circulation is the principal source of plasma free haemoglobin.

Aged↗
PubMed1992

Physiologic validation of a short-arm centrifuge for space application.

A short-arm centrifuge (SAC) of 5-6 ft (1.5-1.8 m) radius may be useful in space to measure tolerances to acceleration (G) and to stimulate the cardiovascular system, thereby reducing cardiovascular decompensation that occurs in weightlessness. Relaxed rapid (1G/s onset rate, ROR) and gradual (0.1 G/s onset rate, GOR) G tolerances were measured on seven men using a 5-ft (1.5 m) radius centrifuge and compared with their G tolerances obtained on the 20-ft (6.1 m) radius human-use centrifuge at the Armstrong Laboratory, Brooks AFB, TX. Since the subjects were required to flex their legs to assume a squatting position on the SAC, a similar position was used on the 20 ft (6.1 m) centrifuge called feet up (FU), and compared with normal-seated +Gz tolerances (controls). The subjects tolerated the SAC exposures without any problems. ROR and GOR tolerances were as follows: control, 3.6 G and 4.2 G; FU, 4.5 G and 5.6 G; and SAC, 4.6 G and 6.4 G. We concluded that a 5-ft radius centrifuge can be used to measure G tolerances. The increases in the SAC GOR tolerances over ROR tolerances indicate that the baroreceptors were stimulated by the G, and the SAC exposure would be useful in preventing cardiovascular decompensation in microgravity.

Adult↗
PubMed2004

[Possibility of using cartilage cultured in centrifuge tube as a substitute for meniscus].

OBJECTIVE: To compare biological characteristics between articular chondrocyte and meniscal fibrochondrocyte cultured in vitro and to investigate the possibility of using cultured cartilage as a substitute for meniscus. METHODS: Chondrocytes isolated from articular cartilage and meniscus of rabbits aged 3 weeks were respectively passaged in monolayer and cultured in centrifuge tube. Cartilages cultured in centrifuge tube and meniscus of rabbit aged 6 weeks were detected by histological examination and transmission electron microscopy. Growth curves of articular chondrocytes and meniscal fibrochondrocytes were compared; meanwhile, cell cycles of articular chondrocytes and meniscal fibrochondrocytes in passage 2 and 4 were separately measured by flow cytometry. RESULTS: Articular chondrocytes in passage 4 were dedifferentiated. Articular chondrocytes formed cartilage 2 weeks after cultivation in centrifuge tube, but meniscal fibrochondrocytes could not generate cartilage. The differences in ultrastructure and histology obviously existed between cultured cartilage and meniscus; moreover, apoptosis of chondrocytes appeared in cultured cartilage. Proportion of subdiploid cells in articular chondrocytes passage 2 and 4 was markedly higher than that in passage 2 and 4 fibrochondrocytes (P < 0.05). CONCLUSION: Meniscal fibrochondrocytes can not form cartilage after cultivation in centrifuge tube, while cartilage cultured in centrifuge tube from articular chondrocytes can not be used as graft material for meniscus. Articular cartilage is markedly different from meniscus.

Animals↗
PubMedDate not supplied

Comparison of pressure-volume-flow relationships in centrifugal and roller pump extracorporeal membrane oxygenation systems for neonates.

Theoretical advantages and risks exist for the use of both the centrifugal and roller pump systems in neonatal extracorporeal membrane oxygenation (ECMO). The authors studied the pressure-volume-flow relationships in clinically configured ECMO systems using these two pumps and a simulated patient to characterize differences in the circuit mechanics of the two systems, and thereby improve the design of subsequent clinical comparative trials of the pumps themselves. The relationship between flow and pressure generated across the pump was identical for the two systems. Within the range of clinically used flows, there was a direct relationship between pump revolution and flow with the roller pump, and between pump revolution and pressure generated for the centrifugal pump. Flow was limited in both systems by restrictions on negative pressure generating capacity. In the roller pump circuit, the venous reservoir (bladder box) assembly interrupted flow when negative pressure exceeded -20 mmHg; in the centrifugal pump system, forward flow stopped when negative pressure exceeded -100 mmHg. Volume had no detectable effect on the patient-pump inlet pressure gradient until critically low volumes were reached. At that point, removal of a few milliliters of volume led to large increases in the pressure gradient. The authors conclude that differences in pressure-volume-flow relationships between roller and centrifugal pump ECMO systems are due to the presence of the bladder box in the roller pump circuit. The advantages and disadvantages of the greater negative pressure in the centrifugal pump system require further study.

Equipment Design↗
PubMed1991

[The role of the cytoskeletal elements during the return to the cell center of their nuclei displaced by centrifugation].

Living cells of the monolayer cultures of embryonal pig kidney epithelium (PKE-cells) and of embryonal bovine tracheal cells (FBT-cells) were ultracentrifuged at 20,000g. The centrifugal force was directed parallel to the surface of the culture slides. Just after centrifugation, the cellular nuclei were displaced to the centrifugal parts of cells. Centrifuged slides with cells were returned to the normal culture conditions, and 22 h later the nuclei were seen to restore their central position in the cells. The motion of the nuclei to the cell center was rather chaotic both in direction and speed. The speed of this motion never exceeded several microns per hour. After nocodasole treatment (0.1-10 mkg/ml) of the cells or in a hypotonic medium, the distance of nuclear dislocation during centrifugation was longer, and the nuclei returned to the cell centers faster than in the control ones. After cytochalasin B treatment (2 mkg/ml), the nuclei moved to the cell centers somewhat more slowly than they did in the control cells. Thus, the establishment of the central position of nuclei in the cells takes place in the absence of microtubules or intermediate filaments. Probably, the central position of nuclei depends mainly on the action part of the cytoskeleton.

Animals↗
PubMed1981

[Centrifugal blood pump (animal experiments) (author's transl)].

A new centrifugal blood pump (Medtronic 1861), suitable as an extracorporeal left ventricular assisting device was tested in vitro with respect to its efficiency and haemolysis. Cannulation was carried out by applying the Zwart technique. Additionally, comparative investigations into haemolysis were performed by using the centrifugal pump and an occlusive roller pump at equal output levels. Moreover, the haemodynamic efficiency of the centrifugal pump in combination with the Zwart cannulation technique was tested in landrace pigs. When the described centrifugal pump and tube system were used, a sufficient pump output and a low rate of early haemolysis could be observed. By applying the centrifugal pump together with the Zwart cannulation technique and conical tubes specially shaped, a complete relief of the left ventricle could be attained experimentally.

Assisted Circulation↗
PubMed1970

The use of conventional and zonal centrifugation to study the life cycle of mammalian cells. Phospholipid and macromolecular synthesis in neoplastic mast cells.

1. Conventional gradient centrifugation has been used to separate cells according to their position in the cell cycle, and to obtain synchronously growing cells. Analysis of prelabelled cells by gradient centrifugation confirms that phospholipid, protein and RNA synthesis is continuous throughout the cell cycle and shows that the rate of synthesis begins to increase already during the G(1) phase. The pattern of phospholipid degradation follows that of synthesis. 2. The limitations of conventional gradient centrifugation have been overcome by use of a zonal rotor. Analysis of prelabelled cells confirms the results obtained by conventional centrifugation and in addition shows that the rates of phospholipid, protein and RNA synthesis decrease during the G(2) phase. The mean cell volume and the net amount of phospholipid, protein and RNA, unlike that of DNA, are found to increase continuously throughout the intermitotic period. 3. These results show that the synthesis of macromolecules, and probably that of membranes also, is controlled by a mechanism other than that of gene dosage.

Cell Division↗
PubMed1973

Lysosomes in rat thoracic duct lymphocytes fractionated by zonal centrifugation.

A method of zonal centrifugation was developed which separates rat thoracic duct lymphocytes (TDL) mainly according to size. The validity of the fractionation method was supported by light microscope observations, Coulter Counter sizing, and in vivo and in vitro labeling of lymphocytes. The distributions of lysosomal acid hydrolases in TDL fractionated by zonal centrifugation are similar to the distribution obtained for the cells. This result indicates that the large lymphocyte is not the sole bearer of either lysosomes or the large amount of soluble cathepsin D found in homogenates of TDL. Both reside mainly in small lymphocytes. This point was clearly established by fractionating homogenates of purified small lymphocytes by means of differential centrifugation and isopycnic density gradient centrifugation.

Acetamides↗