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At least 451 records · Page 25Linked to original sources
PubMed2006

Bandwidth determines modulatory effects of centrifugal pathways on cochlear hearing desensitization caused by loud sound.

Centrifugal olivocochlear (OC) pathways modulate cochlear hearing losses induced in cats by loud sounds varying in bandwidth from tones to clicks and noise bands, in a variety of conditions. The general effect, always to reduce hearing damage, can be a net effect resulting from complex interactions between OC subcomponents (crossed and uncrossed OC pathways). The interactions between these subcomponents vary with type of loud sound, suggesting that sound bandwidth may be important in determining how OC pathways modulate loud sound-induced hearing loss. This dependency was examined and here it is reported that OC pathways do not alter cochlear hearing losses caused by loud noise with a 2-kHz-wide bandwidth intermediate between the loud sounds of previous studies. Increasing stimulus bandwidth even slightly more, to use a loud 3.5-kHz-wide bandwidth noise as the damaging sound, once again revealed OC modulation of cochlear hearing loss. The fact that OC pathways do not modulate cochlear hearing losses induced by loud 2-kHz-wide noise was demonstrated in three very different test conditions in which OC pathways modulate hearing losses caused by narrower or broader bandwidth sounds. This confirmed that the absence of centrifugal modulation of hearing loss to this particular sound was a robust phenomenon not related to test condition. The absence of overall centrifugal effects was also true at the level of subcomponent pathways; neither crossed nor uncrossed OC pathways individually modulated cochlear hearing losses to the loud 2-kHz-wide noise. This surprising frequency dependency has general implications for centrifugal modulation of cochlear responses.

Acoustic Stimulation↗
PubMed1993

A seal-less centrifugal pump (Baylor Gyro Pump) for application to long-term circulatory support.

We are developing a new centrifugal pump, the Baylor Gyro Centrifugal Pump (Gyro Pump), which can function for more than 2 weeks. The concept of the Gyro Pump is that a one-piece rotor-impeller with embedded permanent magnets, driven directly by a brushless direct current motor stator placed outside, rotates like a "gyroscope," and the rotor-impeller is supported by one pivot bearing at the bottom in accordance with the gyroscopic principle. This concept enables us to eliminate a driving shaft and a seal between the driving shaft and the blood chamber, which results in extending the life of the centrifugal pump. The blood passes through the space between the motor stator and the rotor to the impeller portion. In this preliminary phase, two pivot bearings were applied to support the rotor-impeller at the top and the bottom inside the blood chamber. Both pivot bearings showed less blood trauma and less thrombogenicity in in vitro and in vivo studies. The Gyro Pump is a promising second-generation centrifugal pump for long-term circulatory support in the near future.

Animals↗
PubMed2005

Quantification of the secondary flow in a radial coupled centrifugal blood pump based on particle tracking velocimetry.

Secondary flow in the centrifugal blood pump helps to enhance the washout effect and to minimize thrombus formation. On the other hand, it has an adverse effect on pump efficiency. Excessive secondary flow may induce hemolytic effects. Understanding the secondary flow is thus important to the design of a compact, efficient, biocompatible blood pump. This study examined the secondary flow in a radial coupled centrifugal blood pump based on a simple particle tracking velocimetry (PTV) technique. A radial magnetically coupled centrifugal blood pump has a bell-shaped narrow clearance between the impeller inner radius and the pump casing. In order to vary the flow levels through the clearance area, clearance widths of 0.25 mm and 0.50 mm and impeller washout holes with diameters of 0 mm, 2.5 mm, and 4 mm were prepared. A high-speed video camera (2000 frames per second) was used to capture the particle images from which radial flow components were derived. The flow in the space behind the impeller was assumed to be laminar and Couette type. The larger the inner clearance or diameter of washout hole, the greater was the secondary flow rate. Without washout holes, the flow behind the impeller resulted in convection. The radial flow through the washout holes of the impeller was conserved in the radial as well as in the axial direction behind the impeller. The increase in the secondary flow reduced the net pump efficiency. Simple PTV was successful in quantifying the flow in the space behind the impeller. The results verified the hypothesis that the flow behind the impeller was theoretically Couette along the circumferential direction. The convection flow observed behind the impeller agreed with the reports of other researchers. Simple PTV was effective in understanding the fluid dynamics to help improve the compact, efficient, and biocompatible centrifugal blood pump for safe clinical applications.

Biomedical Engineering↗
PubMed1992

Blood culture bottles are superior to lysis-centrifugation tubes for bacteriological diagnosis of spontaneous bacterial peritonitis.

The conventional method of ascitic fluid culturing was compared with the bedside inoculation of ascites into blood culture bottles and into lysis-centrifugation tubes. The conventional culture method was compared with the blood culture bottle method in 31 episodes of spontaneous bacterial peritonitis (SBP). Cultures were positive with the conventional culture method in 11 (35%) episodes and with the blood culture bottle method in 26 (84%) episodes (P less than 0.001). The lysis-centrifugation tube method was compared with the blood culture bottle method in 24 episodes of SBP. Cultures were positive with the lysis-centrifugation tube method in 11 (46%) episodes and with the blood culture bottle method in 19 (79%) episodes (P less than 0.05). Moreover, the blood culture bottle method also shortened the time needed for the detection of bacterial growth. In conclusion, bedside inoculation of ascites into blood culture bottles should be used routinely for patients with suspected SBP. Culturing of ascites in lysis-centrifugation tubes is more laborious than and inferior to that in blood culture bottles.

Ascites↗
PubMed1985

Effects of cytochalasin B on steroid-induced oocyte meiosis and centrifugally induced nuclear movement in the goldfish Carassius auratus.

In goldfish, 17 alpha, 20 beta-dihydroxyprogesterone (DHP) induced oocyte nucleus or germinal vesicle migration (GVM) and dissolution (GVD) in a dose-related fashion. Administration of cytochalasin B (CB) in the presence of DHP inhibited the steroid-induced GVM and GVD after 24 and 48 h of incubation. The presence of CB alone, at concentrations below 25 micrograms/mL, had no effect on GVM or GVD. Furthermore, CB, either alone or in combination with DHP, elicited significant increases in follicular diameter after 24 and 48 h of incubation. To test the effect of CB on ooplasmic viscoelasticity, fully grown follicles were centrifuged and the centrifugally induced germinal vesicle (GV) displacement was determined. Pretreatment (24 h) of follicles with high doses of CB (25 and 50 micrograms/mL) increased the movement of GV in a centripetal direction. However, at lower concentrations (0.005-5 micrograms/mL), CB treatment was without an effect on the centrifugally induced GV movement in the oocyte. The present study suggests involvement of microfilaments or other cytoskeletal components, sensitive to CB, in the mechanisms of GVM and GVD in goldfish oocytes. In addition, a simple technique has been described for testing ooplasmic viscoelasticity determined by movement of the GV under a centrifugal force.

Animals↗
PubMedDate not supplied

Somatosensory paths proceeding to spinal cord and brain--centripetal and centrifugal control for human movement.

The flow of fast-conducting somatosensory information proceeding from the human leg, and entering sensorimotor control processes, is modulated according to the demands of limb movement. Both centripetal (proceeding in from sensory receptor discharge) and centrifugal (proceeding out from motor control centres) convergences can cause modulation, as seen in human, dog, and cat studies. Spinal H-reflexes appear to be strongly centripetally modulated in magnitude, as do initial somatosensory-evoked potentials recorded from the scalp following transmission in fast-conducting afferents from the leg. From the brain and from locomotor pattern-generators, there is also centrifugal control onto fast-conducting somatosensory pathways from the leg, both serving spinal reflexes and ascending to the brain. One expression of the centrifugal control appears to be pattern-generator modulation of cutaneous reflexes. Centrifugal control also can be seen premovement, as spinal H-reflex facilitation. Further, it can be observed as reduction of reception at somatosensory cerebral cortex, when motor learning has occurred or when stimuli are less salient for the task. Fourteen research developments have been identified that involve the generalizability of effects, specific mechanisms, and somatosensory modulation in predictive control.

Animals↗
PubMed2001

Noise priming and the effects of different cochlear centrifugal pathways on loud-sound-induced hearing loss.

Priming/conditioning the cochlea with moderately loud sound can reduce damage caused by subsequent loud sound. This study examined immediate effects of short-term priming with monaural broadband noise on temporary threshold shifts (TTSs) in hearing caused by a subsequent loud high-frequency tone and the role of centrifugal olivocochlear pathways. Priming caused delay-dependent changes in tone-induced TTSs, particularly or only at frequencies higher than the peak tone-affected frequency, through two general effects: a short-lasting increase in cochlear susceptibility to loud sound and longer-lasting complex end effects of centrifugal pathways. The results indicated the following points. Priming noise had "pure" cochlear effects, outlasting its presentation and declining with delay, that exacerbated tone-induced TTSs at frequencies higher than the peak tone-affected frequency. The centrifugal uncrossed medial olivocochlear system (UMOCS) could prevent this noise exacerbation and as this noise effect declined, could even reduce tone-induced TTSs below those to the unprimed tone. For longer delays, when priming noise no longer had any exacerbative "pure" cochlear effects on TTSs, UMOCS exacerbated TTSs above those to the unprimed tone. The crossed medial olivocochlear system (CMOCS) appeared to show a gradual "build-up" of effects postpriming. A parallel study showed it exercised no end effect on TTSs when noise and tone were concurrent. With priming, CMOCS effects were observed. For the shortest priming delay, the CMOCS blocked a UMOCS effect preventing noise exacerbation of tone-induced TTSs. For longer delays, CMOCS end effects, when present, reduced tone-induced TTSs below those to the unprimed tone. The CMOCS may oscillate between producing these effects and exerting no end-effect. With increasing delay CMOCS protection occurred in a greater proportion of animals. Finally, with a delay of 600 s between primer and loud tone, all these systems appeared to have reset to normal so that TTSs were similar to those in the unprimed condition. Thus the effects of short-term priming are not simple and do not suggest that centrifugal pathways act automatically as a protective system during such priming.

Adaptation, Physiological↗
PubMed1997

Preclinical evaluation of the Kyocera Gyro centrifugal blood pump for cardiopulmonary bypass.

The Kyocera Gyro pump has been developed as a completely seal-less centrifugal pump to overcome the problems of the conventional centrifugal pumps. The Gyro pump is a double pivot bearing-supported centrifugal pump with several specific design features, including its eccentric inlet port. We investigated the feasibility of the Gyro pump for cardiopulmonary bypass (CPB) in a bovine model, comparing it with the BioMedicus pump (BP-80). Ten healthy calves (5: Gyro pump, 5: BP-80) underwent 6 h of mildly hypothermic CPB at approximately 33 degrees C. Both pumps provided more than 50 ml/kg/min without any incidents. The haemodynamics of both groups remained stable within the normal range. All haematology and biochemistry data demonstrated no significant differences between the two groups. However, values of plasma-free haemoglobin and lactate dehydrogenase were less throughout the experiments of the Gyro pump than those of the BP-80. To obtain flow equivalent to that of the BP-80, the Gyro pump needed less rotational speeds than the BP-80 (2749.7 +/- 233.3 versus 3170.6 +/- 300.8 rpm. p < 0.05). Less rotational speed in addition to the difference in operating principle may contribute to less blood damage during the CPB OF the Gyro pump. After pumping for CPB, no leakage or thrombus formation was observed in either pump. The present study indicated that the Kyocera Gyro pump can be applied as a centrifugal pump for CPB with the same performance as the BP-80 and with relatively less haemolysis than the BP-80.

Analysis of Variance↗
PubMed1992

Mechanical circulatory support with a centrifugal pump after open heart surgery.

Since December 1988, a centrifugal ventricular assist device (VAD) was used to support the circulation in 5 patients who could not be weaned from cardiopulmonary bypass (CPB) or developed cardiogenic shock after removal from CPB. Three patients required a left VAD, one needed a right VAD. One patient had biventricular support using a centrifugal left VAD and a diaphragm type right VAD. The duration of the centrifugal VAD support ranged from 6 to 136 (mean 72)h. All patients were weaned from the VAD, but only 2 patients were discharged from the hospital. Two patients died of multiple organ failure, and one died of cardiogenic shock caused by intractable arrhythmia. Infection occurred in all non-survivors, and 2 of them developed renal failure. We conclude that the centrifugal VAD is effective to recover a failing ventricle. The factors related to the unsuccessful recovery were delayed start of the VAD support and major complications such as infection as infection and renal failure.

Adult↗
PubMedDate not supplied

Centripetal and centrifugal family life cycle factors in long-term outcome following traumatic brain injury.

The family life cycle model categorizes stresses on family systems in terms of their source and their effects on family members. Centripetal forces bring members together while centrifugal forces lead to loosened intrafamilial ties. This study examined the association of normative, developmental and centripetal illness-related family forces with patient outcome. Hypothesized centripetal and centrifugal forces acting on 65 families of married male TBI patients were used as independent variables in stepwise multiple regressions with criterion measures of quality of life outcome used as dependent measures. Centripetal variables included measures of family coping, marital adjustment, and number of years married. Centrifugal variables included number of children, age of oldest child, and amount of perceived financial strain. Regression equations obtained had multiple R's ranging from 0.623 to 0.407 (p values < 0.017). Results suggest that families normatively dealing with the developmental stage of the family with young children may face unique challenges when a husband sustains a TBI, particularly when financial strain exists. Stages in family development involving conflict between centripetal and centrifugal forces may be most problematic for families to resolve, and potentially the most effective periods for intervention.

Adaptation, Psychological↗
PubMed1990

A comparative evaluation of pulmonary artery balloon counterpulsation and a centrifugal flow pump in an experimental model of right ventricular infarction.

To compare the efficiency of pulmonary artery balloon counterpulsation and a centrifugal flow pump in reversing the hemodynamic consequences of acute right-sided heart failure, we employed both devices in 14 Yorkshire pigs in which right ventricular infarction was created via surgical ligation of branches of the right coronary artery. Pulmonary artery balloon counterpulsation improved some of the indicators of right heart failure, as manifested by significantly decreased right atrial pressure and increased mean systemic blood pressure. In contrast, the centrifugal flow pump consistently and significantly reversed all of the hemodynamic consequences of right ventricular infarction. In comparison to pulmonary artery balloon counterpulsation, the centrifugal flow pump resulted in lower right atrial pressures (p=0.020), lower mean pulmonary pressures (p less than 0.0001), increased left atrial pressures (p=0.026), increased cardiac output (p less than 0.0001), and increased mean systemic blood pressures (p less than 0.0001). Possible mechanisms to explain the superiority of the centrifugal flow pump include better hemodynamic unloading of the failing myocardium and independence from right ventricular output.

Animals↗
PubMed1995

Proinflammatory mediator response in coronary bypass surgery using a centrifugal or a roller pump.

Major surgery, trauma, and infection induce a proinflammatory mediator response which, if excessive, may cause tissue injury. The response was measured during elective coronary bypass surgery when a centrifugal pump or a roller pump, differing in their basic working principles, was used for extracorporeal circulation (ECC). Eight patients were perfused with a centrifugal pump and eight patients with a roller pump during ECC. Plasma interleukin-1 beta (IL-1 beta), IL-2, IL-6, tumor necrosis factor alpha (TNF alpha), group II phospholipase A2, (PLA2), endotoxin, fibronectin and serum C-reactive protein (CRP) concentrations were measured. The operation increased plasma IL-6, group II PLA2, and serum CRP concentration and decreased plasma fibronectin concentrations. IL-1 beta and TNF alpha concentrations did not change. IL-2 occurred only occasionally, and endotoxin did not occur in any patient. No differences were seen between the group using a centrifugal pump and the group using the roller pump. Cardiac surgery with a perfusion time of less than two hours thus caused a proinflammatory mediator response which was similar whether a centrifugal or a roller pump was used for ECC.

Cardiopulmonary Bypass↗
PubMed1997

An under-occluded roller pump is less hemolytic than a centrifugal pump.

The purpose of this study is to measure and compare the hemolysis produced by roller pumps with varied occlusion settings and a centrifugal pump. The null hypothesis is that there is no difference in the Index of Hemolysis (IH = gm Hb/100 L pumped) produced by a roller pump (RP) at four different occlusion settings and a centrifugal pump (CP) at the same blood flow rate (4.5 L/min) and afterload (250 mmHg, +/-10 mmHg) over three hours. Five identical closed-loop circuits were assembled and primed with saline. The pumps were then calibrated and occlusions were set. In three circuits, the occlusion for the RP was opened at 5 RPMs to support 150, 225, or 300 mmHg (+/-10 mmHg) against a clamped line. In one circuit, a RP was adjusted to a barely non-occlusive setting (1 cm drop/30 inch gradient). The fifth circuit employed a CP. Prior to testing, the saline in each circuit was replaced with one liter of fresh bovine blood (Hct = 22 +/- 2%). The IH for each treatment was compared in six trials yielding a statistical power > 0.80. Analysis of variance with multiple comparison (p < or = 0.05) demonstrated that compared to the barely non-occlusive setting, the IH in the centrifugal pump was not significantly greater. Under-occluded RP settings yielded IHs significantly less than the CP. It appears that opening the occlusion on a roller pump allows a lower IH compared to traditional RP occlusion setting or centrifugal pumping.

Animals↗
PubMed2001

Ultrastructure of centrifuged bovine oocyte-cumulus complexes after pre-treatment with cytoskeletal relaxant.

The objective of this study was the electron microscope examination of the localization of lipid droplets, mitochondria and other intracellular organelles in bovine oocytes and cumulus cells after Cytochalasin B pre-treatment and ultra-centrifugation. Bovine (n = 180) oocyte cumulus complexes on a germinal vesicle stage were treated with 5 micrograms/ml Cytochalasin B at 38.5 degrees C for 10-15 min. They were then centrifuged at 15,800 g and fixed at 39 degrees C immediately after centrifugation in 3% glutaraldehyde with 0.5% formaldehyde for the microscopic examinations. The centrifugal pole of the oocytes was filled with mitochondria. The centripetal part contained lipid granules and vesicles. Cytoplasm of low density was located in the equatorial region. Hyaloplasm with spontaneously formed membrane and non-membrane vacuoles was located in a supra-equatorial zone of the oocytes. In the cumulus cells the lipid vesicles formed one dark mass in the centripetal pole. The nuclei of these cells were deformed and vacuolization of the cytoplasm was noted.

Animals↗
PubMed2001

Abnormal centrifugal axons in streptozotocin-diabetic rat retinas.

PURPOSE: To characterize the effects of diabetes on the expression of histidine decarboxylase mRNA and on the morphology of the histaminergic centrifugal axons in the rat retina. METHODS: Rats were made diabetic by streptozotocin. After 3 months, retinal histidine decarboxylase expression was analyzed by in situ hybridization in radial sections. Flatmount retinas from a second group of rats were labeled with an antiserum to histamine or an antibody to phosphorylated neurofilament protein. RESULTS: Histidine decarboxylase mRNA was expressed in cells in the inner and outer nuclear layers of diabetic retinas, but not in normal retinas. However, immunoreactive (IR) histamine was not localized to perikarya in either the normal or the diabetic retinas. Instead, a population of centrifugal axons was labeled. These axons emerged from the optic disc and had varicose terminal branches in the inner plexiform layer (IPL) of the peripheral retina. Some branches ended on large retinal blood vessels and others in dense clusters in the IPL. In rats with streptozotocin-induced diabetes, the centrifugal axon terminals developed many large swellings that contained neurofilament immunoreactivity; these swellings were rare in normal retinas. CONCLUSIONS: Diabetes perturbs the retinal histaminergic system, causing increases in histidine decarboxylase mRNA expression in neurons or glia and abnormal focal swellings on the centrifugal axons.

Animals↗
PubMed2000

[Design and optimization of a centrifugal pump for CPCR].

Requirements for an optimal centrifugal pump, the vital component in the equipment for cardiopulmonary cerebral resuscitation(CPCR), have been presented. The performance of the Sarns centrifugal pump (Sarns, Inc./3M, Ann arbor, MI, U.S.A) was tested. The preliminarily optimized model for CPCR was designed according to the requirements of CPCR and to the comparison and analysis of several clinically available centrifugal pumps. The preliminary tests using the centrifugal pump made in our laboratory(Type CPCR-I) have confirmed the design and the optimization.

Cardiopulmonary Bypass↗
PubMed2005

[Study on chondrogenesis of rabbit bone marrow-derived mesenchymal stem cells by centrifuge-tube culture in vitro].

OBJECTIVE: To investigate the feasibility of constructing tissue engineered cartilage by inducing bone marrow-derived mesenchymal stem cells (MSCs) in centrifuge-tube culture. METHOD: By Percoll density gradient centrifuge and monolaryer culture in vitro MSCs were isolated from rabbit bone marrow and were purified. Some MSCs were seeded into centrifuge tube culture and allowed to form three-dimensional aggregates in a chemically defined medium mainly including transforming growth factor- b1 (TGF-beta1, 10 ng/ml), dexamethasone (10-7), ascorbic acid (50 microg/ml), 1% insulin, 1% selenium and 1% transferring. At day 7, 14, 21, aggregates were take out and specific markers of differentiation of cartilage were detected by the appearance of toluiding blue merachromasia and the immunohistochemistry detection of type II collagen and in situ hybridization detection of collagen type II mRNA. RESULT: MSCs seeded into centrifuge tube culture became analogous cartilage tissue after 7-21 days, their specific markers of chondrogeneses were positive in the appearance of toluiding blue merachromasia and the immunohistochemistry detection of type II collagen and in situ hybridization detection of collagen type II mRNA. CONCLUSION: MSCs have the capacity to undergo chondrogenic differentiation.

Animals↗
PubMed1990

The electrocardiographic response of females to centrifuge +Gz stress.

Women continue to expand their participation in all areas of aviation, including flying high performance fighter aircraft. Acceleration (+Gz) stress is unique to fighter aviation, therefore it is important to thoroughly understand the electrocardiographic (ECG) response to +Gz stress since it reflects a portion of the cardiovascular +Gz tolerance. A comparison of the ECG response to centrifuge +Gz stress between 685 men and 94 women was made from data existing within a centrifuge data repository. The frequency of occurrence of specific types of atrial, ventricular, and the other most frequently observed ECG changes to +Gz stress were compared for females and males. Females had less atrial ectopy; essentially equivalent premature ventricular contractions (PVC's), multiformed PVC's, paired PVC's; less frequent ventricular and supraventricular tachycardia; and more frequent PVC's in a bigeminal pattern and QRS on T PVC's. Sinus arrhythmia, sinus bradycardia, and increased T-waves post +Gz stress were more frequent in males, with ectopic atrial rhythm and atrioventricular dissociation essentially equivalent in males and females. Although few women have participated in either simulated aerial combat maneuver type centrifuge profiles or centrifuge high-G training, they have shown similar ECG changes including conduction and rhythm disturbances infrequently seen in males, such as +Gz-induced right bundle branch block and high-G bradycardia. Based on the currently available ECG response data, women have no demonstrated unique susceptibility to +Gz-induced ECG changes. Therefore, no contraindication exists to initiating additional acceleration research to fully evaluate women's tolerance to the more stressful, higher levels of +Gz stress.

Acceleration↗