Improved system for measuring rheological properties of thickened liquid using an inclined parallel plate and optical sensor.

The purpose of this study was to improve the method of using an inclined parallel plate (IPP) in directly estimating the yield stress τ iy and evaluating the properties of a thickened liquid. The flow curve of the relationship between the shear rate and shear stress of a liquid thickened with a xanthan gum agent was predicted using the Herschel-Bulkley fluid model ( τ = τ y + k γ ˙ n - 1 ). We supposed that the yield stress τ y and the result of a line spread test (LST) indicate the deformation state and the flow state of shear stress ( k γ ˙ n - 1 ), respectively. τ iy , the yield stress τ ry estimated adopting a rotational viscometer and LST, was investigated for three liquids thickened with xanthan gum at four concentrations (C) at intervals of 0.5 wt% within the range 0.5-2.0 wt%. Linear plots of the relations of C versus τ iy and τ ry and the LST show that with an increase in C , the resistance force ( τ ry and τ iy ) increases until flow starts, after which viscosity increases. We suggest that yield stress τ iy estimated with the IPP method effectively indicates the rheological properties of thickened liquids.

Improvement of simplified inclined plane test for evaluation of thickened liquids by using optical sensor.

The thickening management index for food for dysphagia is important in enabling recognition of the rheological properties of thickened liquids, including their static and dynamic properties. One of the static properties of these liquids is the yield stress. An improvement to the simplified inclined plane test is proposed here that involves use of an automatic system for measurement of the displacements of thickened liquids on an inclined plate. The aim of this study is to investigate the relationship between the displacements of the thickened liquids and the variable thickener concentrations using an optical sensor. To measure the displacement of each thickened liquid on a clear inclined plate, an optical sensor that has a 12-mm-long light receiving surface is selected to form a one-dimensional position-sensitive detector (1D-PSD) under the clear inclined plate. The relationship between the angle of inclination of the plate θ at which the maximum voltage occurred in the 1D-PSD and five thickener (xanthan gum) concentrations c, ranging from 1.0 to 3.0 wt% in steps of 0.5 wt%, was investigated. It was confirmed that an approximately linear plot was obtained under the condition that θ = 8.24 c + 0.18, with the correlation R = .99 (for n = 7). This result indicated that the optical sensor composed of the 1D-PSD can measure the displacements of thickened liquids with various thickener concentrations on the clear inclined plate automatically.

A proposed method of evaluating the yield stress of a thickened liquid using a simplified inclined plane test.

Managing the thickening index of food is important for dysphagia and helps in recognizing the static and dynamic rheological properties of the thickening agent. One dynamic property is the viscosity under a shear rate of 50 s-1 , and one static property is the yield stress at a shear rate of 0 s-1 . The purpose of this study is to design a simplified inclined plane test to identify the yield stress of a thickened liquid by observing flow behavior on an inclined plate. The yield angle (stress) is defined as the inclination angle of the plate just before the thickened liquid flows. The concentrations (yield stresses, yield angles) of a thickening agent containing xanthan gum are 1.0 (1.2, 3°), 1.5 (5.6, 13°), 2.0 (7.5, 26°), 2.5 (12.5, 26°), and 3.0 (19.1, 42°) wt% (Pa, degrees). We measured the time course of the displacement of the downstream edge (DDE) of the thickened liquid on the inclined plate. The discrete inclination angles were in the range of 0° to 42°. The DDE after 10 s was more than 4.5 mm for all concentrations of the thickening agent at an inclination greater than the yield angle of the plate. We confirmed that the yield angle identifies the yield stress for the thickened liquid via the DDE using the simplified inclined plane test with discrete inclination angles.

Proposal of a novel evaluation index for the effects of shear stress and exposure time on hepatocyte damage.

The purpose of this study was to propose a novel evaluation index for the effects of shear stress level and exposure time on hepatocyte damage. Suspensions of rat hepatocytes (0.5 mL) were subjected to shear stress from 1.2 to 3.1 Pa for 10 min (n = 3) using a rheoscope. We counted living and dead cells in photographs taken at 1-min intervals using a digital camera attached to the microscope. Living and dead cells were distinguished using a Trypan blue exclusion test. Under each level of shear stress, at each 1-min time interval, we measured the viability [living-cell number (t)/countable cell number (t)] and the ratio of living cells [RLC: living-cell number (t)/countable cell number in the initial condition]. The effects of shear stress and exposure time on viability and RLC were assessed by multiple regression analysis. As expected, we observed an increase in the number of dead cells and little change in the number of living cells when shear stress was increased. The coefficient of determination (R (2)) to predict the effectiveness of viability and RLC indicated a low to moderate correlation. Viability correlated with shear stress and exposure time (p < 0.001); however, RLC only correlated with exposure time of shear stress (p < 0.001). In this test condition, viability was strongly related not to living-cell damage but to dead-cell damage. Therefore, we propose RLC as a novel and effective index for investigating the effect of shear stress on living hepatocytes.

Comparison of allergenic properties of salmon (Oncorhynchus nerka) between landlocked and anadromous species.

BACKGROUND: Salmon is one of the most widely consumed seafoods in Japan and many other countries around the world. Due to the confirmed cases of salmon-induced allergy, the food sanitation law in Japan stipulates salmon as one of the specific food items for which labeling is recommended when used as an ingredient of processed foods. However, trout, the landlocked form of anadromous salmon, is not subject to the allergen-labeling requirements, even though both populations belong to a single species. Since no supporting data have been demonstrated to make a clear distinction between these two populations in terms of allergenicity, we comparatively examined their allergenic properties using sera from patients allergic to fish. METHODS: Extracts of Oncorhynchus nerka from different habitats were obtained: kokanee (landlocked) and red salmon (anadromous). Control extracts were derived from four other species. This study focused on the (1) IgE-binding capacity of the fish extracts in patients' sera (n = 50), (2) ELISA inhibition test (n = 6), and (3) inhibition immunoblot test (n = 8) between the kokanee and red salmon. RESULTS: The extracts from kokanee and red salmon showed the highest correlation with each other in terms of the IgE-binding capacity, and showed complete (100%) reciprocal cross-inhibition in the ELISA inhibition test. On immunoblotting, there was no marked difference in the staining pattern between the two extracts, and each IgE-binding band gradually disappeared when the patients' sera were preincubated with the counterpart antigen in a dose-dependent manner. CONCLUSIONS: These results suggest that kokanee has similar allergenic properties to red salmon.

Development of a reflected optical fiber system for measuring oxygen saturation in an integrated artificial heart-lung system.

The purpose of this study was to develop a blood oxygen saturation (OS) monitoring system for use with an integrated artificial heart-lung system (IAHLS). The OS monitoring system consists of two paired optical fiber probes (OFPs) and a measurement system. To investigate the effect of the OFP configuration and incident light wavelength on the relationship between OS and the reflectance ratio for wavelengths of 810 and 645 nm, we performed theoretical analyses of the relationship between OS and R810/R645 using a diffusion equation. The prototype OFP located on the blood outlet port of our IAHLS housing was evaluated using an in vitro test. An OS range of 65-100% was adjusted to supply oxygen and nitrogen gas to the IAHLS. The blood flow rate was maintained at 3 L/min by the rotational speed of an impeller in the IAHLS. The OS-corrected blood from the IAHLS was measured using a commercial gas analyzer. The correlation coefficients (r(2)) between the theoretical ratio of R810/R645 and OS, and between measured OS and the reflectance ratio of R810/R645 were 0.97 and 0.78, respectively. In conclusion, we confirmed that the development of this oximetry system is applicable for IAHLS.

Hemolytic performance of a MagLev disposable rotary blood pump (MedTech Dispo): effects of MagLev gap clearance and surface roughness.

Mechanical shaft seal bearing incorporated in the centrifugal blood pumps contributes to hemolysis and thrombus formation. In addition, the problem of durability and corrosion of mechanical shaft seal bearing has been recently reported from the safety point of view. To amend the shortcomings of the blood-immersed mechanical bearings, a magnetic levitated centrifugal rotary blood pump (MedTech Dispo Model 1; Tokyo Medical and Dental University, Tokyo, Japan) has been developed for extracorporeal disposable application. In this study, the hemolytic performance of the MedTech Dispo Model 1 centrifugal blood pump system was evaluated, with special focus on the narrow blood path clearance at the magnetic bearing between rotor and stator, and on the pump housing surface roughness. A pump flow of 5 L/min against the head pressure of 100 mm Hg for 4 h was included in the hemolytic test conditions. Anticoagulated fresh porcine blood was used as a working fluid. The clearance of blood path at the magnetic bearing was in the range of 100-250 micro m. Pump housing surface roughness was controlled to be around Ra = 0.1-1.5 micro m. The lowest hemolytic results were obtained at the clearance of 250 micro m and with the polished surface (Ra = 0.1 micro m) yielding the normalized index of hemolysis (NIH) of less than 0.001 g/100 L, which was 1/5 of the Biopump BP-80 (Medtronic Inc., Minneapolis, MN, USA, and 1/4 of the BPX-80. In spite of rough surface and narrow blood path, NIH levels were less than clinically acceptable level of 0.005 g/100 L. The noncontact, levitated impeller system is useful to improve pump performance in blood environment.

Grades of 43 fish species in Japan based on IgE-binding activity.

BACKGROUND: Hypersensitivity reactions to fish are a common food allergy, but IgE-binding activity to fish species have not been fully elucidated. The aim of this study was to identify fish with high binding activity to IgE in sera from Japanese fish-hypersensitive individuals. METHODS: 38 children with a history of at least one episode of hypersensitivity after ingestion of fish were enrolled and 34 children with no history of reactions and negative IgE results for at least five kinds of fish antigen were included as controls. Using a radioallergosorbent test, we examined IgE-binding to each fish species using sera from fish-hypersensitive subjects. Fish were then graded according to IgE-binding activity. RESULTS: Many fish species, including red salmon, silver salmon, yellowfin tuna, big eyed tuna, Atlantic tuna, saurel, skipper, yellowtail, Japanese sardine, bonita and mackerel had high IgE-binding activity. All of these fish are abundantly consumed in Japan. The hypersensitivity reactions experienced by many subjects occurred after ingestion of species with high IgE-binding activity. Only halibut (Osteichthyes) and sharks (Chondrichthyes) had low IgE-binding activity. CONCLUSIONS: A correlation was observed between IgE levels and expression of symptoms after fish ingestion. High consumption of salmon, tuna, scad (including saurel), skipper, yellowtail, sardine, bonita and mackerel in Japan might be the cause of the high IgE-binding activity of these species. The grades of fish species consumed widely in Japan are likely to be useful for nutritional instruction of fish-allergic patients.

Dynamic deformation and recovery response of red blood cells to a cyclically reversing shear flow: Effects of frequency of cyclically reversing shear flow and shear stress level.

Dynamic deformation and recovery responses of red blood cells (RBCs) to a cyclically reversing shear flow generated in a 30-microm clearance, with the peak shear stress of 53, 108, 161, and 274 Pa at the frequency of 1, 2, 3, and 5 Hz, respectively, were studied. The RBCs' time-varying velocity varied after the glass plate velocity without any time lag, whereas the L/W change, where L and W were the major and minor axes of RBCs' ellipsoidal shape, exhibited a rapid increase and gradual decay during the deformation and recovery phase. The time of minimum L/W occurrence lagged behind the zero-velocity time of the glass plate (zero stress), and the delay time normalized to the one-cycle duration remained constant at 8.0%. The elongation of RBCs at zero stress time became larger with the reversing frequency. A simple mechanical model consisting of an elastic linear element during a rapid elongation period and a parallel combination of elements such as a spring and dashpot during the nonlinear recovery phase was suggested. The dynamic response behavior of RBCs under a cyclically reversing shear flow was different from the conventional shape change where a steplike force was applied to and completely released from the RBCs.

New method for the detection of thrombus formation in cardiovascular devices: optical sensor evaluation in a flow chamber model.

We proposed a new method of detecting the onset of thrombus formation based upon the backscattered light intensity changes caused by the alteration of blood flow behavior in the cardiopulmonary devices. In an optical senor based upon the First Order Scattering theory, the relationship between the backscattered light intensity and hematocrit exhibited a monotonically decaying curve for the hematocrit level greater than 45%. To distinguish the effect either by thrombus formation or erythrocyte aggregation on the back-scattered light intensity with a flow chamber connected to a rabbit arterial-venous bypass model, we generated an oscillatory flow using a roller pump and analyzed the results using a Fast Fourier Transform (FFT) method. Our hypothesis was that the nonclotting blood flow would yield an unchanged fundamental spectral power density of the oscillation frequency generated by a roller pump, whereas the thrombus formation would attenuate its power. We measured the back-scattered light intensity in the flow chamber of high shear region and low shear region (n = 5). The blood flow rate was 40 ml/min with the roller pump. The activated clotting time and the hematocrit level were adjusted to 170 +/- 10 s with heparin and 35 +/- 5% with a phosphate buffered sulfate solution, respectively. As a result, the backscattered light intensity from the low shear rate region gradually diminished with time (p < 0.05; 0-5 minutes vs. more than 10-15 minutes), whereas that from the high shear rate region remained fairly constant. The experimental finding supported the hypothesis that the decrease of the backscattered light intensity and diminished spectral power density were caused by the aggregation or clotting erythrocytes. In conclusion, we found that the measurement of the average backscattered light intensity level together with FFT analysis of the backscattered light from the flowing blood is a valuable approach in detecting the onset of thrombus formation.

An investigation of blood damage induced by static pressure during shear-rate conditions.

Many investigators have studied the effect of a mechanical force (shear rate, pressure, or temperature) on hemolysis. However, there exists no investigation of a relationship between the interactions of mechanical forces and hemolysis. The purpose of this study is to investigate the interactions of mechanical forces on hemolysis. We performed in vitro tests by using bovine blood, applying shear rate (0, 500, 1,000, and 1,500 s-1), positive pressure (0, 200, 400, and 600 mm Hg), and temperature (21, 28, and 35 degrees C) simultaneously. In all temperatures at the shear rate of 1,500 s-1, there are statistically significant differences in the hemolysis rate between 0 and 600 mm Hg (p < 0.05). However, to investigate the effect of temperature on hemolysis, shear stress was calculated at each blood temperature. There were no statistically significant differences among them. The results suggested that erythrocyte trauma caused by pressure related to the level of shear rate. It was found that the causes of hemolysis included the shear rate as well as shear rate and pressure.