Biomedical subjects
Publications and source records attributed to N Imai.
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The charge effect on the translational self-diffusion constant, D, of polyelectrolytes has been quantitatively analyzed based on dynamic light scattering experiments. Perfectly monodisperse bovine mercaptalbumin has been used at low pH as a positively charged polyelectrolyte sample. Completely linear plots of log{g2(t)-1} vs. time t have been obtained for uncharged states of the protein, for the cor relation function of the scattered light intensity, g2(t). The plots deviate from linearity as polyions bear the charges. The D values for various ionic states, obtained from the initial slopes of the plots, have been analyzed using the simple theory of Imai and Mandel (N. Imai and M. Mandel, Macromolecules 15 (1982) 1562) derived based on the Onsager-Navier-Stokes equation for solvent flow with counterion distribution around a polyion. It has turned out that the experimental D values coincide well with the theory and that the characteristic nature of D can be elucidated principally from the charge effect.
The charge effect on the translational self-diffusion constant, D, of polyelectrolytes has been quantitatively analyzed based on dynamic light scattering experiments. Perfectly monodisperse bovine mercaptalbumin has been used at low pH as a positively charged polyelectrolyte sample. Completely linear plots of log(g2(t)-1) vs. time t have been obtained for uncharged states of the protein, for the correlation function of the scattered light intensity, g2(t). The plots deviate from linearity as polyions bear the charges. The D values for various ionic states, obtained from the initial slopes of the plots, have been analyzed using the simple theory of Imai and Mandel (N. Imai and M. Mandel, Macromolecules 15 (1982) 1562) derived based on the Onsager-Navier-Stokes equation for solvent flow with counterion distribution around a polyion. It has turned out that the experimental D values coincide well with the theory and that the characteristic nature of D can be elucidated principally from the charge effect.
To clarify the relationship between the predisposing factors and malalignment of the patello-femoral joint, a study was conducted on the basis of roentgenograms of 621 cases in which a disorder of the dérangement was suspected in at least one knee. The degree of alignment was classified into four grade groups according to the dynamic skyline view arthrograms. Each predisposing factor was expressed by patellar tendon-patella ratio, patellar facet ratio, depth index, and femoro-tibial axis angle. As to each of the parameters each joint was categorized into three classes, on the basis of its mean and standard deviation. The frequency of occurrence of each of the three classes in each of the grade groups was then examined. For the patellar shape, the joints were categorized according to Baumgartl's taxonomy. The study indicates that there exists a causal relationship between the predisposing factors such as patella alta, narrow medial facet, shallow patellar groove of femur and unstable patellar shape, and the patello-femoral malalignment.
Dynamic sky-line view arthrography at 30, 60, and 90 flexion degrees was carried out on 1,242 knees of 621 cases who claimed trouble with at least one knee. The patient's age range was from 15 to 35 years. Alignment of the patello-femoral joint was classified into four groups; Grade I: The patello-femoral joint is congruent in all the three views. Grade II: The view taken at 30 degrees shows the joint space open in the medial facet but closed in the view at 60 degrees. Grade III: The medial interspace is open at 60 degrees but closed at 90 degrees. Grade IV: The medial joint space is open in all three views. Grade distribution of all cases studied was: Grade I, 62.1%; Grade II, 25.8%; Grade III, 6.7%; and Grade IV, 5.4%. Clinical disorders thus occur at high percentages in the groups of Grades III and IV. Based on this observation, the mechanism of the malalignment disorders of the patello-femoral joint is discussed.
To determine the hemodynamic effects of isomazole, an imidazopyridine, we administered isomazole (10 and 20 micrograms/kg/min) to 10 awake dogs with right-sided congestive heart failure produced by pulmonary artery constriction and tricuspid valve avulsion. Isomazole increased cardiac output, heart rate, right ventricular and left ventricular (LV) dP/dt, LVdP/dt/P and decreased aortic pressure and total peripheral vascular resistance. Simultaneously, blood flow increased to myocardium, quadriceps muscle, brain and splanchnic beds, whereas vascular resistance decreased. Furthermore, isomazole increased LV oxygen consumption and decreased transcoronary arteriovenous oxygen difference. Similar administration of normal saline had no effects. Angiotensin II was infused to restore mean aortic pressure to base-line values during isomazole infusion; however, despite the return of aortic pressure to base-line values, cardiac output, LVdP/dt and LVdP/dt/P remained elevated. The systemic and regional hemodynamic effects of isomazole were unaffected by pretreatment with propranolol and mecamylamine. Thus, isomazole exerted positive inotropic, chronotropic and vasodilator effects in congestive heart failure dogs. The inotropic effect of isomazole was independent of the decrease in aortic pressure, and the hemodynamic effects of isomazole were not mediated via the autonomic nervous system. Furthermore, the decrease in transcoronary arteriovenous oxygen difference suggests that isomazole exerted an active coronary vasodilator action which may improve myocardial oxygen demand/supply ratio.
To determine whether the increase in cardiac output during mild to moderate exercise is related to an increase in the tissue redox potential, we compared the responses of cardiac output, total body oxygen consumption, and arterial blood lactate-to-pyruvate ratio (a measure of NADH/NAD) to treadmill exercise between dogs treated with normal saline and those treated with a hydrogen acceptor, new methylene blue. Normal saline was infused into the left atrium in the first group of dogs at a rate of 0.38 ml/min throughout the treadmill exercise (2.5 mph and 5.0 mph on a 6% incline, each for 20 min). In the second group, methylene blue was administered as a loading dose (4 mg/kg) before exercise, followed by a continuous infusion (0.15 mg X kg-1 X min-1) throughout exercise. A similar infusion of methylene blue was given to a third group of dogs without exercise; it reduced the arterial lactate-to-pyruvate ratio from 6.70 +/- 0.35 to 4.12 +/- 0.27 but had no or little effects on cardiac output, heart rate, arterial pressure, and left ventricular dP/dt and (dP/dt)/P. Treadmill exercise doubled cardiac output and increased total body O2 consumption three- to fourfold in the first two groups but increased arterial blood lactate-to-pyruvate ratio only in group 1 (6.0 +/- 0.54 to 9.97 +/- 0.91). The relationship between cardiac output and total body O2 consumption was unaffected by the simultaneous administration of methylene blue during exercise. Groups 1 and 2 also did not differ in their heart rate, left ventricular dP/dt and (dP/dt)/P, and plasma catecholamine responses to exercise.(ABSTRACT TRUNCATED AT 250 WORDS)
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The treatment of fractures of the lateral tibial plateau is still a subject of controversy. Many authors have emphasized the importance of early mobilization of the knee joint following fractures of the tibial plateau. However, local depression fractures of the tibial plateau occur quite frequently in elderly patients and have presented many difficult problems in management. In 1982, the authors developed a new method of closed reduction using the spring action of Kirschner wires for severely displaced local depression fractures of the tibial plateau. The principle of this procedure is to apply continuous positive pressure to the depressed fragment for its reduction and retention. By re-establishing stability in the fracture, active knee mobilization can be allowed from the beginning. Seven patients were treated with this procedure, and the results of short-term follow-up, ranging from three to 26 months, were promising as to the range of motion, stability and relief of pain.
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A sensitive assay method to evaluate the inhibitor of Na+, K+-ATPase in human urine was developed by measuring the inorganic phosphate liberated from ATP in vitro using Na+, K+-ATPase from porcine cerebral cortex. Ouabain inhibited the Na+, K+-ATPase by competing with the potassium ion (an apparent Ki = 2.6 +/- 0.89 X 10(-8) M, n = 8) under the condition of 100 mM NaCl, 4.5 mM MgSO4 and 0.56 mM ATP. The apparent Km value of KCl was 0.4 mM. Factors inhibiting Na+, K+-ATPase were detected in the post-salt fraction on Sephadex G-15 chromatography following the ethanol extraction of lyophilized fresh urine of sodium loaded human subjects (300 meq Na+/day, for 4 days) with essential hypertension. Two active fractions around the 400 daltons following salt were eluted on Sephadex G-15 chromatography. The slower eluted factor competed kinetically with potassium ion, but the inhibitory activity was lost within two days during storage at 4 degrees C. The faster-eluted inhibitor lost its activity within a day. These results indicate that the unstable inhibiting factors of Na+, K+-ATPase exist in human urine and one of these factors inhibits ouabain sensitive Na+, K+-ATPase by binding to the potassium binding site (or very close to it), which exists at the outer surface of the cell membrane of this enzyme.
To clarify the effects of androgen on hemopoiesis in mice, we investigated changes in hemopoietic stem cells at various stages of differentiation after injection of 19-nandrolone decanoate (19-ND). 19-ND induced (a) a marked increase in the population of CFUe, especially in the spleen, and (b) a less significant increase in the number of CFUs, GM-CFC, and BFUe. The number of endogenous spleen colonies developed transiently on day 4 after irradiation (TE-CFU) increased significantly, and the initiation and induction of erythropoietic maturation was enhanced. Growth of the pluripotent stem cells (CFUs) assessed by endogenous spleen colony formation was influenced more than was the population size. Production of erythropoietin (Ep) in mice was not affected by the treatment with 19-ND. These results indicate that 19-ND affects mature precursors in erythroid cell lineage rather than pluripotent stem cells and that the effect is unlikely to be induced through an increase in the production of Ep.
It is well known that the entry of amniotic fluid into the mother's circulation may result in the occurrence of amniotic embolism, and aspiration of meconium by the neonate may cause meconium aspiration syndrome. To study meconium-like substances detected in the urine of mother and neonate during the perinatal period, the authors carefully assayed the Urinary Meconial Index (UMI) in subjects including 100 pregnant women, 171 parturient women, 171 neonates and 68 samples of amniotic fluid. Through the UMI assay, the frequency of the appearance of high UMI, the mode of delivery at high UMI and its effect upon both mother and neonate were studied and the following findings obtained. The entry of meconium into the mother's circulation occurs during labor pains and may be excreted into the mother's urine (6.4%). Labor pains enhance the entry of meconium into the mother's circulation and the entry takes place even in the absence of any clinical signs of rupture of the membranes (p less than 0.01). The entry of meconium into both mother and neonate occurs at a higher rate in dystocia and in cases with meconium-stained amniotic fluid (p less than 0.05). Even in the absence of marked symptoms such as those in meconium aspiration syndrome, the aspiration of meconium affects postnatal course of the newborn (positive CRP, early appearance of bilirubinemia: p less than 0.05).
The nature of the hormone-binding site of detergent-solubilized angiotensin II receptor from the bovine adrenal cortex has been characterized using diaminoalkanes. Their affinity for the hormone-binding site showed a dramatic alteration depending on their chain length; at the hexamethylene stage, a maximum and competitive inhibition was observed. These results indicate that the angiotensin II receptors have a definite hydrophobic binding groove limbed with diagonally located two negative charges, and those hydrophobic and electrostatic forces may play an important role in the proper register between the receptor and hormone.
A method for measurement of renin concentration (PRC) in human plasma has been developed and validated experimentally and theoretically. Like most of the previous methods, the present method is based on a radioimmunoassay of angiotensin I generated during incubation of plasma with an excess of renin substrate. In the present study we used, as the substrate, sheep angiotensinogen partially purified from anephric sheep plasma by ammonium sulfate fractionation and pepstatin-aminohexyl-agarose chromatography. The advantage of using sheep substrate is that it has an exceptionally high affinity for human renin. The partially purified substrate, which contained no detectable renin activity, improved the sensitivity, allowing quantification of renin in low-renin plasma. Possible interfering influences of plasma proteins on the radioimmunoassay were eliminated by the introduction of a simple deproteinization step. For determination of total renin concentration (TRC), inactive renin was activated by exposing plasma to low pH or trypsin. Normal values of PRC and TRC after careful selection of assay conditions were 2.9 +/- 0.4 and 33.9 +/- 6.1 ng angiotensin I X ml-1 X h-1, respectively. As an illustrative example of usefulness of the assay, PRC determination of a patient with a ectopic renin-secreting tumor is presented.
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