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Biomedical subjects

Y Imai

Publications and source records attributed to Y Imai.

At least 1,063 records · Page 59Linked to original sources
PubMed1988

Hypertensive episodes and circadian fluctuations of blood pressure in patients with phaeochromocytoma: studies by long-term blood pressure monitoring based on a volume-oscillometric method.

A new portable device for the indirect measurement of arterial blood pressure was successfully applied to detect paroxysmal hypertension and circadian fluctuation of blood pressure in patients with phaeochromocytoma. The device utilizes the volume-oscillometric technique, it is equipped with a microprocessor and allows long-term automatic monitoring of indirect blood pressure in the human finger. Compared with conventional fully automated portable devices of the arm-cuff type, our current equipment is lighter, less noisy, and causes less discomfort. With this device repeated measurements can be made without causing stress or discomfort, and without disturbing sleep. The arterial pressure measurement obtained using this device was reliable and reproducible. In some patients certain symptoms, possibly due to phaeochromocytoma, had been observed for several years before the study, although hypertension had not been identified. While these patients had consistently high circulating catecholamine levels, nocturnal falls in blood pressure were clearly documented. This suggests that plasma catecholamines released from the phaeochromocytoma, though excessive, may be of less physiological importance than other regulatory mechanisms concerned with circadian fluctuation of blood pressure, e.g. the sympathetic nervous system and/or hypothalamo-pituitary-adrenal system. This new device has proved to be a reliable means of monitoring long-term blood pressure and is useful in the diagnosis of paroxysmal hypertension in patients with phaeochromocytoma.

Adolescent↗
PubMed1988

Real-time measurement of tricuspid valve annular area for annuloplasty. Experimental study.

We used real-time measurement of the tricuspid valve annular area in anesthetized dogs to study the optimal size of the annular area for annuloplasty. During control conditions, the maximum tricuspid annular area appeared at the onset of ventricular systole. The minimum tricuspid annular area appeared between the ventricular isovolumic relaxation phase and the early ventricular filling phase. The maximum annular area varied in seven dogs between 2.18 and 3.10 cm2, and the minimum annular area ranged between 1.68 and 2.45 cm2. In regular sinus rhythm (heart rates 97 to 120 beats/min), the maximal decreases in tricuspid annular area during one cardiac cycle ranged from 14.3% to 23.6% of the maximum size. When the tricuspid annular area after the annuloplasty was kept larger than the minimum area that was observed during the cardiac cycle in the control study, cardiac output and right atrial pressure remained unchanged, as a result of unobstructed ventricular filling. On the other hand, when the annular area was reduced to smaller than the minimum area seen in the control study, a decrease in cardiac output and an elevation of right atrial pressure ensued. These findings suggest that the tricuspid annular area can be safely decreased by annuloplasty to the minimum area seen in the control study without causing a reduction of cardiac output or an elevation of right atrial pressure.

Animals↗
PubMed1987

Protein-protein and lipid-protein interactions in a reconstituted cytochrome P-450 dependent microsomal monooxygenase.

NADPH-cytochrome P-450 reductase and cytochrome P-450, both purified from liver microsomes of phenobarbital-treated rabbits, were incorporated into dimyristoylphosphatidylcholine vesicles. The reduction of cytochrome P-450 by NADPH in the reconstituted vesicles proceeded in a biphasic fashion, and 70-80% of the absorbance change was associated with the fast phase. The Arrhenius plot of the apparent first-order rate constant of the fast-phase reduction showed a marked discontinuity around the phase transition temperature of the synthetic phospholipid; an almost 10-fold change in rate constant was associated with this discontinuity. It was, therefore, suggested that the reduction of cytochrome P-450 by reductase in this system was a diffusion-limited reaction controlled by the viscosity of the phospholipid membrane. The Arrhenius plot of overall drug monooxygenase activity catalyzed by the reconstituted vesicles showed a break but in a different way from that observed for the reduction of cytochrome P-450. This break was accompanied only by a change of the slope of the plot but not by a change in reaction rate. This difference in the two Arrhenius plots was attributed to that in the rate-limiting step of the two reactions. NADPH-cytochrome c reductase activity of the reconstituted vesicles, an activity catalyzed by the reductase alone, and cumene hydroperoxide dependent N-methylaniline demethylation activity catalyzed by cytochrome P-450 alone did not show any break in the Arrhenius plots.

Animals↗
PubMed1987

Detection of platelet-activating factor in exudates of rats with phorbol myristate acetate-induced pleurisy.

PAF-likely activity, detected as aggregation of washed platelets, was found in the exudate of rats with pleurisy induced by phorbol myristate acetate (PMA, 1 nmol). At 30 min after the injection of PMA, 400-500 pg of PAF was detected in the pleural exudate. An extract of the exudate was made and analysed by HPLC and by rabbit platelet aggregation. The activity was characterized as that of PAF as a result of the inhibition seen with the PAF-antagonist CV-3988 and the loss of activity by treatment with phospholipase A2. Indirect evidence was previously reported in that CV-3988 suppressed the pleural fluid accumulation in the pleurisy induced by PMA. Taken together these facts it indicates that PAF could be an important mediator of acute inflammation, especially of the plasma exudation resulting from an increase in vascular permeability. Evidence that pleural cells produce PAF was also examined in an in vitro experiment. PAF was found in the supernatant and cellular fractions of the incubation mixture of the pleural cells from normal rats when stimulated by PMA (1 microM) or A23187 (5 microM), and the results indicate that the pleural cells produce PAF and release a portion of it.

Animals↗
PubMed1987

Characterization of a human osteosarcoma cell line (Saos-2) with osteoblastic properties.

This study examines the osteoblastic properties of the established human osteosarcoma cell line Saos-2. Saos-2 cells inoculated into diffusion chambers, which were implanted i.p. into nude mice, produced mineralized matrix in 4 of 6 chambers at 8 weeks. In 5 of 6 chambers there was a strong positive alkaline phosphatase reaction. In culture the alkaline phosphatase levels increased with time and cell density, reaching very high levels at confluence: 4-7 mumol/mg protein/min. The cells show a sensitive adenylate cyclase response to parathyroid hormone, 50% effective dose = 2.8 nM, which increases with cell density and is further raised by dexamethasone treatment. They also exhibit typical binding of 1-25-dihydroxyvitamin D3 to 3.2S receptor protein with an apparent Kd of 0.21 nM; the numbers of sites per cell were 3,300 at 50,000 cells/cm2 and 1,800 at 280,000 cells/cm2. The presence of osteonectin was visualized with a monoclonal antibody which revealed a reticular pattern on the cell surface. Osteonectin was also detected in the medium by Western blots, migrating at around Mr 40,000 in nonreduced gels and Mr 44,000 in reduced gels. The Saos-2 cells thus possess several osteoblastic features and could be useful as a permanent line of human osteoblast-like cells and as a source of bone-related molecules.

Adenylyl Cyclases↗
PubMed1987

Determination of valproic acid and its metabolites by gas chromatography-mass spectrometry with selected ion monitoring.

A modified method for the determination of valproic acid, its eleven metabolites and their conjugates in small samples of serum and urine by gas chromatography-mass spectrometry with selected-ion monitoring was developed. Valproic acid and its eleven metabolites were determined in serum and urine of epileptic patients treated with valproic acid. 2-Hydroxy-2-propylpentanoic acid was identified as a new metabolite of valproic acid in the urine of 11 of the 12 patients. The unsaturated metabolites, such as (Z)- and (E)-2-propyl-2-pentenoic acid, were found to be predominantly excreted as glucuronides. 3-Hydroxy-2-propylpentanoic acid and 2-propylglutaric acid were also excreted as glucuronides.

Adolescent↗