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Biomedical subjects

S Usami

Publications and source records attributed to S Usami.

At least 163 records · Page 9Linked to original sources
PubMed1984

Arteriovenous distribution of hemodynamic parameters in the rat dental pulp.

A systematic investigation of the distribution of red cell velocity throughout the hierachy of the rat pulp microvascular network was performed. Luminal diameters (D) of microvessels ranging in size from 8 to 72 micron were measured in situ by an electronic video image shearing technique. Intravascular red cell velocities (Vrbc) were simultaneously measured by a variation of the "two-slit" photometric technique and intravascular volumetric flow rates (Q) were calculated. It was found that red cell velocity decreased monotonically throughout successive arteriolar divisions to attain capillary values of 1/10 those in the feeding arterioles. A slight rise in Vrbc was found in the venous confluences, however, a maximum value of Vrbc of only 1/5 large arteriolar values was evident in the large collecting venules. In contrast, the calculated volumetric flow rate distribution was found to be nearly parabolic from arterioles (40 micron) and their paired (72 micron) collecting venules. This behavior was attributed to the dominance of microvessel cross-sectional areas as a determinant of Q.

Animals↗
PubMed1984

Segmental and total microvascular resistances during hemorrhagic hypotension in rabbit omentum.

Single input-output microvascular modules in the rabbit omentum were studied to quantitate total modular resistance (RT) and the changes in resistance of successive serial segments (Rseg) during hemorrhagic hypotension (55 mmHg for 1 h). RT was calculated from the pressure drop between input and output vessels and the total flow through the module. Changes in Rseg were estimated from alterations in single microvessel hindrance (1/diam4) for selected microvessels within a module together with a correction for flow redistribution within each segment derived from changes in the proportion of total flow. Mean RT increased to 2.1 times control within the first 10 min of systemic hypotension and gradually declined over 1 h. Response of Rseg varied in different generations of microvessels (arterioles and venules subdivided by size). Rseg for arterioles and venules less than 30 microns, but not that for arterioles and venules greater than 30 microns, showed comparable or greater changes than RT. Calculated differences between RT and the summed Rseg of measured segments suggest that the unmeasured Rseg in capillaries and blood rheological parameters may have significantly influenced changes in RT during hemorrhagic hypotension.

Animals↗
PubMed1984

Influence of long-term repetitive rotatostimulations on lateral semicircular canals.

Sixty-five guinea pigs were used to investigate the influence of rotatostimulations on the lateral crista ampullaris. After repeated turning stimulations with the cupulometric mode (the terminal turning velocity: 180 degrees/sec) for 24-72 hours, the morphological changes in the crista ampullaris on the ampullopetal flow side were compared with those on the ampullofugal flow side by using scanning and transmission electron microscopy. Postrotatory nystagmus recorded by ENG during this experiment revealed the response decline phenomenon in all animals, and the caloric test performed after the rotatostimulation showed 'canal paresis' in the ear on the ampullopetal flow side. In a group stimulated for 24 hours, no particular damage on the crista ampullaris was noticed. However, in a group stimulated for 72 hours, local damage was dominant in the central part of the crista, which showed a tendency to extend towards the planum semilunatum according to an increment of changes. These findings were more remarkable on the ampullopetal flow side than on the ampullofugal flow side, suggesting the predominant effect of the ampullopetal endolymph flow in the lateral semicircular canal.

Animals↗
PubMed1984

Biorheological methods employing the Weissenberg rheogoniometer.

The theories and spatial concepts of Karl Weissenberg have been applied to the science of biorheology by employing the Weissenberg Rheogoniometer. Two main types of experimental methods have been used for the characterization of the bulk shear properties of biorheological fluids: (A) In continuous laminar shearing motion, the tangential and normal components of stress are measured at a series of rates of shear. From these parameters, the apparent viscosity, an elastic modulus and a recoverable strain, are calculated as functions of the rate of shear. In this continuous shear experiment, the physical structure present in the material at any given rate of shear may be quite different from the material in its rest state or at other rates of shear. (B) In harmonic oscillatory motion, the material is subjected to a harmonic laminar shear about its rest state at a number of frequencies and small strain amplitudes. From these experiments the dynamic moduli of viscosity and elasticity are calculated. Preparations of biological materials, such as whole blood and systems of blood components, both in health and disease states, have been investigated using methods A and B, together with studies of surface layers of plasma proteins at interfaces.

Blood Physiological Phenomena↗
PubMed1984

Rheologic measurements on small samples with a new capillary viscometer.

A newly developed capillary viscometer (capillary diameter 496 micron, length 10 cm) was tested and used for measurement of blood viscosity. The determination of pressure drop along the capillary during a constant flow allowed the calculation of the apparent viscosity. By changing the flow rate, the shear rate could be varied from 0.67 to 590 sec-1. A sample of 0.5 ml was sufficient for readings to be made at 10 shear rates in this range. Measurements of distilled water and standard oils were in good agreement with the expected values. Measurements on adult human plasma and umbilical cord blood were compared with simultaneous readings by Couette viscometer. For whole blood at various shear rates, regression analysis between the viscosity obtained from the capillary viscometer and that from the Couette viscometer yielded excellent correlation (r = 0.968, p less than 0.001). This capillary viscometer with high precision for very small samples is useful for various clinical applications.

Adult↗
PubMed1984

Evaluation of red blood cell filterability test: influences of pore size, hematocrit level, and flow rate.

To improve understanding of the basic principles of the red blood cell filtration test, we studied the influence of pore size, flow rate, and hematocrit level. Suspensions of washed red blood cells in Ringer's solution with hematocrit values of 5%, 10%, and 15% were pumped at flow rates of 0.42 and 0.82 ml/min through polycarbonate filters with pore sizes of 2.6 +/- 0.2, 4.5 +/- 0.6, and 6.9 +/- 0.8 micron (mean +/- SD). The initial pressure generated at the filter was normalized for pressure reading obtained with cell-free Ringer's solution at the same flow rate and used for the calculation of the relative resistance of one red blood cell in a pore. This measurement was independent of the flow rate and the hematocrit level, but it varied inversely with the pore size: 175.1 +/- 62.5, 5.2 +/- 1.2, and 2.4 +/- 0.8 for the 2.6, 4.5, and 6.9 micron pores, respectively. Plugging of filter pores as evidenced by progressive pressure rise at constant flow was a prominent feature for 2.6 micron filters, but was not significant for 6.9 micron filters. At the flow rates studied, less than 1% of the filtered red blood cells showed morphologic changes or underwent hemolysis. We found that 2.6 micron filters are most sensitive in detecting altered red blood cell filterability induced in vitro and occurring in vivo. These results may help to define an optimum filtration test for clinical investigations.

Adult↗
PubMed1983

Influence of red cell concentration on filtration of blood cell suspensions.

Pressure-time curves obtained by passing suspensions of blood cells in Ringer solution through a 5 microns polycarbonate filter at constant flow (1.6 ml/min) were evaluated for their ability to reflect the deformability of the erythrocytes. The initial pressure reading (Pi) obtained in a quasi-steady state during the first 1-2 sec of pumping was found to be reproducible for hematocrit values between 10 and 30 percent. This Pi value was normalized by the pressure generated by the cell-free suspending medium (PO) at the same flow rate. The ratio Pi/PO was found to be linearly proportional to hematocrit up to 30 percent but independent of leukocyte concentration up to 12,000/mm3. Later portions of the curve did vary with leukocyte count. By using the equations developed from theoretical modeling of cells passing through a filter, the experimentally determined relation of Pi/PO to hematocrit, and the known geometry of the filter pores, we were able to calculate parameters reflecting the deformability of red cells. These include beta, the ratio of resistance in a pore containing a red cell to that in a pore containing only the suspending medium, and alpha, the proportion of pores filled by erythrocytes in transit. The application of theoretical analysis to experimental data has provided quantitative insights into the behavior of red cells during filtration tests in normal and disease states.

Erythrocytes↗
PubMed1982

Influence of physicochemical factors on rheology of human neutrophils.

The effects of variations in temperature, pH, and osmolality on the rheological properties of human neutrophils were determined by studying the cell deformation in response to aspirational pressure applied via a micropipette. The time history of the deformation was analyzed by the use of a standard solid viscoelastic model consisting of an elastic element K1 in parallel with a Maxwell element (an elastic element K2 in series with a viscous element mu). With changes in temperature over a range of 9-40 degrees C, only mu varied inversely with temperature, while K1 and K2 did not show significant alterations. Variations in pH over the range of 5.4-7.8 did not significantly affect the viscoelastic coefficients, but K1 and mu rose at pH 8.4. An increase in osmolality caused all three coefficients to rise, but a decrease in osmolality had relatively little effect on the coefficients. These changes in response to physicochemical variations serve to provide insights into the viscoelastic properties of neutrophils and their possible roles in health and disease.

Adult↗
PubMed1982

Physiological significance of blood rheology.

The apparent viscosity (n) of blood is determined by plasma viscosity, hematocrit (Hct), cell deformation and cell aggregation. The optimum Hct for oxygen transport varies with shear conditions and shows regional differences. In circulation in vivo, the complex geometry causes inertial, in addition to viscous, losses. Microvessels have low Hct and correspondingly low n. Hydrodynamic interactions between red blood cells (RBCs) and white blood cells (WBCs) may contribute to WBC adhesion to the endothelium. Entry of WBC into diverging branches may cause redistribution of RBCs. There is some understanding of the relation between in vitro and in vivo blood rheology, but further investigations are needed.

Biological Transport↗
PubMed1982

Human SS red cell rheological behavior in the microcirculation of cremaster muscle.

The hemodynamic behavior of Hb SS erythrocytes introduced into the microcirculation of cremaster muscle (rat and mouse) was studied by intravital microscopy. Simultaneous measurements of intravascular pressure, pressure drop, red cell velocity, hematocrit and oxygen tensions were made to evaluate both regional resistance (arteriovenous) from 2nd order arterioles to venules, as well as the resistance to blood flow in single unbranched arterioles. Following the isovolemic exchange of 2 to 3 blood volumes with SS cells at 25% hematocrit, regional resistance remained within 20% of its control value due to compensatory vasodilation and shunting of blood through pathways parallel to capillaries occluded by sickled red cells. Prolonged exposure to circulating SS cells resulted in a degradation of microvascular function with an attendant four-fold rise in regional resistance. Transient resistance measurements during the passage of a bolus of SS cells through the cremasteric network demonstrated a 100% increase in regional resistance, which was rapidly abated by the subsequent SS cell washout and capillary recruitment. Computations of apparent viscosity in single unbranched arterioles (nominal diameter of 45 micrometer) revealed a four-fold rise in viscosity following the reduction in intravascular oxygen tension (PO2) from 40 mm HG to 7 mm Hg. Observations on the transient increase in viscosity concomitant with a rapid decrease in PO2, demonstrated a lag time of 2 to 3 s before the elevation of viscosity. To enhance the visualization of these processes, techniques for the fluorescent labelling of Hb SS cells with fluorescein isothiocyanate (FITC) were applied. Visual observations of the movement of SS-FITC red cells by fluorescence microscopy readily revealed the sequestration of sickled cells at the junction between 10 micrometer transverse arterioles and the smaller true capillaries, and the shunting of labelled cells around obstructed capillaries.

Abdominal Muscles↗
PubMed1982

Viscoelastic properties of sickle cells and hemoglobin.

The quantitative relationship between deoxygenation and rheological behavior of SS cell suspensions and concentrated HbS solutions has been studied under steady shear (viscosity eta) and oscillatory shear (complex viscosity with viscous component eta' and elastic component eta"). decrease of O2 saturation below 80-85% causes eta, eta' and eta" to increase progressively in SS cell suspensions and HbS solutions. These rheological parameters do not change in AA cell suspensions and HbA solutions following deoxygenation. The deoxygenation-induced increase in eta" of HbS solutions from the unmeasurable level when oxygenated reflects the gelation of HbS. At high O2 saturations, the rheological behavior of the intracellular fluid has relatively insignificant contribution to that of the SS cell suspension. As O2 saturation decreases, the viscoelastic properties of the SS cell suspension become increasingly dominated by that of the intracellular HbS. at a given degree of deoxygenation, eta, eta' and eta" of HbS solutions decrease with increasing shear rate, indicating that HbS aggregates can be dispersed by shear stress.

Anemia, Sickle Cell↗
PubMed1982

[Evaluation of clinical efficacy of sulbenicillin following surgery of malignant maxillary tumors. Transport of sulbenicillin to the exudates from the surgical wound of the maxilla and its therapeutic effects].

In order to know the amount of sulbenicillin (SB-PC) transported to the maxillary sinus through the blood supply after injecting by intravenous drip infusion, the authors measured SB-PC content of the exudate which was gathered from the exploratory operative maxillary sinus. This measurement was performed 3 times at 2, 4 and 6 hours after injecting 5 g of SB-PC by intravenous drip infusion. From results of these measurements, it became obvious that the SB-PC content reached to the maximum value (24.5 +/- 16.69 mcg/ml) at 2--4 hours after the injection. Next, the preventive and therapeutic effect on the postoperative maxillary infection was evaluated for 13 patients of maxillary cancer. The effect was excellent in 2 cases (16.7%), good in 8 cases (66.7%) and fair in 2 cases (16.7%). So, the ratio of effectiveness was 83.3%. The side effect of SB-PC was observed only in 1 patient who complained of palpitation, but it was not severe.

Adult↗
PubMed1981

Toxicity of aspartame and its diketopiperazine for Wistar rats by dietary administration for 104 weeks.

Aspartame (APM) or L-aspartyl-L-phenylalanine, and a 3 : 1 combination of APM with its decomposition product, 5-benzyl-3,6-dioxo-2-piperazine acetic acid (DKP), were incorporated at levels of up to 4 g/kg in the diet of male and female Wistar rats from 6 weeks to 104 weeks of age. There was a dose-dependent depression of body weight gain at 2 and 4 g/kg AMP and at 4 g/kg APM + DKP in males, and at all dose levels in females, correlated with decreased food consumption and attributed to liberation of amino acids from hydrolysis of APM. Increases in urinary specific gravity and pH, with increase of relative kidney weight, were attributed to the urinary excretion DKP and acidic metabolites of APM. A dose-related increase in urinary calcium probably reflected increased calcium absorption, as from high protein diets. A slight decrease in serum cholesterol and an increase in relative spleen weight appeared to be without adverse effect. It is concluded that the treatments were without toxic effect.

Animals↗