A digital hematocrit-meter (DHM) was constructed for accurate determination of the hematocrit H by using a linear image sensor behind a tube holder: the holder and a tungsten lamp were settled on an optical bench. Intensity profiles from the sensor were fed into a computer through A/D converter vs. 1024 pixels along ca. 25mm length of a tube that is a coarse tube (id 1.1-1.2mm, Scientific Glass Inc.) or a fine tube (id 0.85±0.05mm, Nichiden Rika Glass Co.). Standard suspensions were prepared of swine red blood cell (RBC) in a physiological saline at H_s of ca. 8 to 60%. We determined three interfaces with 25μm resolution: air to medium, medium to packed RBC and packed RBC to patty at the bottom of the tube. The air-medium was located at minimal intensity (DHM-1) or at mean of two inflection points (DHM-2) near the end of the intensity profile, and the medium-RBC and the RBC-patty were given by inflection points. Data of H by DHM-1 and -2 were compared to the standard ones as well as H's with conventional turntable at 50mm and with cathetometer at 25mm and at 50mm full length of RBC suspensions in a tube. H's by DHM-2 in the fine tube were best correlated to the standard.

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The aim of present study was to evaluate cardiac lymph dynamics during a cardiac cycle by our CCD intravital microscopes. In anesthetized open-chest dogs, India ink or suspension fluid (Levovist) was injected into the myocardium of the left ventricular apex. The epicardial lymphatics were visualized by India ink using a regular speed (30 frames/s) needle-lens CCD intravital microscope. Velocities of Levovist flowing were calculated by frame-to-frame analysis using a high-speed CCD (200 frames/s) microscope based on the moving distance of Levovist suspension per 5 ms. The diameters of epicardial lymphatics showed an increasing trend from end-diastole to end-systole (6 ± 15%) without statistical significance. Either augmented or decreased contractility did not affect the end-systolic diameter increment (8 ± 12% and 3 ± 9%, respectively), compared with control conditions. Cardiac lymph flow velocity was accelerated in early systolic phase (1.01 ±0.26 mm/s). The mid-systolic dip was followed by late systolic and then early diastolic forward flow. A reverse flow was observed in some cases during late diastolic phase. In conclusions, cardiac lymph flow was slow, but exhibited a clear biphasic systolic forward pattern followed by an occasional small end-diastolic reverse flow, reflecting phasic changes in myocardial strain, pressure and stiffness due to myocardial contraction/relaxation during a cardiac cycle.

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We compared the spatial patterns of regional myocardial flows between crystalloid and blood perfused hearts, we measured within-layer regional myocardial flow distributions of Tyrode- and blood-perfused hearts using a molecular flow tracer, tritiated-desmethylimipramine (HDMI). Isolated rat hearts were perfused with Tyrode solution (Tyrd; n=7) or blood (Bld; n=14) at the 100 mmHg head pressure. After the peak reactive flow following 30 s flow-shutoff-reperfusion was measured, HDMI (2μCi) was injected into the perfusion line. A 60 s continuous injection was performed in seven and a bolus injection in seven hearts out of the fourteen Bld hearts and in Tyrd hearts. The left ventricular free wall was then sliced into 10 μm thick slices from subepi- to subendocardium. The distribution of HDMI density, i. e., within-layer relative flow, was measured in twenty-eight slices per heart by quantitative digital radiography with 100μm pixels. The coefficient of variation of flows (CV=SD of pixel tracer density/mean tracer density) was used to quantitate perfusion heterogeneity. In Tyrd and Bld, perfusion rates were 13.6±2.7 and 2.8±0.6 ml/min/g, respectively. The maximum percent increase of flow rate after the reperfusion was larger in Bld than in Tyrd (71±21% vs. 15±9%). CV was considerably higher in Bld than in Tyrd. In Bld, the continuous tracer injection yielded a smaller CV than the bolus injection. These CV differences were consistent over the resolution range of 100-800, μm. These data suggest that more preserved higher vasomotor tone and therefore higher flow resistance in blood-perfused hearts will be responsible for higher flow heterogeneity. The reduced CV under continuous tracer injection in blood-perfused hearts implies the short-term, temporal fluctuation of vasomotor tone and/or stochastic behaviors of the corpuscles in microvessels.

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