Journal of Biorheology Vol. 30(2016) No. 1

We developed a hyperspectral imaging (HSI) method to image a rotary blood pump rotating at high speed, and we investigated the optical properties of blood associated with the blood clotting. In vitro antithrombogenic testing was conducted. Fresh porcine blood was circulated by a hydrodynamically levitated centrifugal blood pump while light pulsed at the same frequency as the rotational speed illuminated the bottom surface of the pump. Back scattering was captured with an HSI camera, and the spectral image in the wavelength range from 608 to 752 nm was constructed. Back scattering in the area of suspected thrombus formation decreased. The shape of the spectral image was consistent with that of the thrombus formed in the pump. Moreover, the hemoglobin concentration of the thrombus was quantified, and its value was significantly lower than the total hemoglobin concentration. Therefore, it is speculated that the decrease in back scattering is caused by a decrease in the number of red blood cells (RBCs) trapped in the thrombus area due to the surrounding blood flow. It was concluded that this optical technique is able to detect blood clotting using the behavior of RBCs as the optical marker for its detection.

The possibility of phase separation in the mixture of iota-carrageenan (IC) and kappa-carrageenan (KC) was elucidated by comparing rheological properties for carrageenan mixtures. In temperature sweeping experiments, lambda-carrageenan (LC) chain slightly lowered the aggregation temperature (T_agg) of IC and KC in the mixture solutions of IC-LC and KC-LC, respectively, by obstructing the aggregation. On the other hand, dextran chain largely lowered the T_agg of IC because of the strong interaction with IC chain, whereas dextran increased T_agg of KC. The IC-KC solutions showed two-step increases at the almost same temperatures with T_aggs in single component solutions of IC and KC. This exhibits independent aggregations of IC and KC chains in the mixture and suggesting the phase separation in the IC-KC solution. In the time courses of G', the IC-LC solution showed increases of G' by local aggregation of IC chain and by growing of aggregation of IC chain through the obstructive LC chains. The IC-dextran mixture solution showed a depressed increase of G' caused by a strong interaction between IC and dextran. The time courses of G' for the IC-KC solution showed two-step increases suggesting the induced aggregation of KC chains by the aggregation of IC chains.

Nitric oxide (NO) and shear stress modulates hepatocyte functions, including ammonia metabolism. This study investigated the simultaneous effects of NO and shear stress on hepatocyte functions. We developed a cell culture device to simultaneously apply NO and shear stress to hepatocytes, and measured changes in ammonia decomposition by hepatocytes in response to changes in NO concentration and shear stress. NO was supplied directly to cells at a constant rate at 0, 0.5, 5, and 25 ppm, and shear stress was either applied at 0.6 Pa or not (static culture). Ammonia decomposition in static culture was higher under all NO loads compared with 0 ppm NO, and was highest under 0.5 ppm NO and decreased under higher NO loads. In the absence of NO load, ammonia decomposition under shear stress was approximately double that in static culture. Under the simultaneous application of NO and shear stress load, ammonia decomposition under 0.5 ppm NO was approximately twice as high as under 0 ppm NO, but was almost the same under 25 ppm NO as under 0 ppm NO. These results indicate that both NO and shear stress enhance ammonia decomposition although the enhancement depends on the NO concentration in their immediate surroundings.

Kinetics of the orientation transition in the triblock copolymer lamellar phase is studied by viscometry. We find that the strain-controlled mechanism dominates the transition kinetics. We propose a possible scenario of the orientation transition from the viewpoint of the dislocation dynamics. We could also evaluate the critical shear rate of the orientation transition by assuming the limiting velocity of the dislocations under shear. Evaluated value is in good agreement with the experimental observation. The nucleation of the dislocations might be necessary for the orientation transition.