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Biomedical subjects

J Takagi

Publications and source records attributed to J Takagi.

At least 73 records · Page 4Linked to original sources
PubMed1993

Biplane transesophageal echo-Doppler studies of atrial septal defects: quantitative evaluation and monitoring for transcatheter closure.

Forty-four patients with atrial septal defects, aged 7 months to 18 years (median 8.9), underwent biplane transesophageal (TEE) and transthoracic (TTE) echocardiography. The size of the defect and the shunt flow volume were measured by TEE and compared with the actual size at surgery (N = 14) or the shunt volume measured by the Fick method (N = 34), respectively. In all cases the location and morphology of the defect were clearly demonstrated by TEE; on the other hand, two patients with sinus venosus-type and multiple-type defects, respectively, and one with a small ostium primum defect did not have a complete diagnosis by TTE. The defect size determined by TEE correlated well with the surgical measurement. Similarly a significant correlation was demonstrated between the shunt volume measured by TEE and that obtained by the Fick method. In three patients transcatheter closure of the atrial septal defect by means of a clamshell device was accomplished successfully with TEE monitoring. We conclude that biplane TEE provides a better appreciation of cardiac anatomy and hemodynamic evaluation than TTE in this setting, and TEE is essential for monitoring during transcatheter closure.

Adolescent↗
PubMed1992

Activation of phospholipases in platelets by polyclonal antibodies against a surface membrane protein.

In a previous paper we demonstrated using immunochemical techniques that propolypeptide of von Willebrand factor was present on the surface of resting platelets. In the present paper we show that polyclonal antibodies against propolypeptide of von Willebrand factor induce activation of phospholipase(s) in platelets and lead to platelet aggregation. The antibody-stimulation of platelets induced the synthesis of thromboxane A2 (TXA2). Furthermore, the aggregation was inhibited by aspirin and an antagonist of TXA2. Aspirin inhibited not only the aggregation but also the activation of arachidonic acid liberation from phospholipids, but the effect of aspirin on arachidonic acid liberation was cancelled by the combined effect of the antibodies and a TXA2 mimetic agonist, which itself did not activate arachidonic acid liberation. The antibody-induced activation of arachidonic acid liberation and the aggregation were blocked by cytochalasin B. All these results obtained with antibodies were quite similar to the results obtained with collagen.

Antibodies↗
PubMed1992

A collagen/gelatin-binding decapeptide derived from bovine propolypeptide of von Willebrand factor.

Propolypeptide of von Willebrand factor (pp-vWF) binds to type I collagen, and we have reported that a binding domain exists in a 21.5/21-kDa fragment originated from the C-terminal portion [Takagi, J., Fujisawa, T., Sekiya, F., & Saito, Y. (1991) J. Biol. Chem. 266, 5575-5579]. The collagen-binding property of the 21.5/21-kDa fragment was compared with that of the intact pp-vWF. Although pp-v WF preferentially binds to native type I collagen fibrils, the isolated fragment no longer has this specificity and binds well to collagen of other types in the native and heat-denatured states. In order to determine the critical site that mediates this collagen/gelatin binding, several peptides were synthesized based on the primary structure of the 21.5/21-kDa fragment. Among these, a 25-residue peptide strongly inhibited the binding of the 125I-labeled 21.5/21-kDa fragment to collagen. Using this inhibitory effect as an index, the binding site was defined to the sequence as follows: WREPSFCALS. Furthermore, a decapeptide of this sequence bound to collagen and gelatin, indicating that this sequence is responsible for the binding of the 21.5/21-kDa fragment to collagen/gelatin.

Amino Acid Sequence↗
PubMed1992

Propolypeptide and mature portions of von Willebrand factor of bovine origin recognize different sites on type-I collagen obtained from bovine tendon.

We compared the binding of propolypeptide and mature portions of von Willebrand factor of bovine origin to fibrillar type-I collagen obtained from bovine tendon. The propolypeptide (pp-vWF) and the mature portion (m-vWF) of human origin consist of 741 and 2050 amino acids, respectively, and are rather large proteins. The collagen-binding properties of the two proteins of bovine origin were similar in that both bound more avidly to native collagen than to heat-denatured collagen. Bindings was affected similarly by ionic strength but was not modified either by divalent cations or a synthetic peptide containing Arg-Gly-Asp. However, the binding sites in the fibrillar type-I collagen molecule for pp-vWF and m-vWF seem to be different: the two proteins did not effectively compete with each other for binding to collagen. Furthermore, pepsin treatment of fibrillar type-I collagen resulted in a drastic decrease in the binding of pp-vWF, while only a moderate decrease in the binding of m-vWF was observed after the treatment.

Amino Acid Sequence↗
PubMed1992

Vasodilatory response of the coronary arteries after Kawasaki disease: evaluation by intracoronary injection of isosorbide dinitrate.

OBJECTIVE: To determine coronary artery diameter change before and after an intracoronary infusion of isosorbide dinitrate in patients who have had Kawasaki disease, we performed coronary angiography in 188 such patients. PATIENTS AND METHODS: Four patient groups were studied. Groups 1 to 3 consisted of patients with Kawasaki disease: group 1 (the "normal" group; n = 65) had no coronary artery lesions; patients in group 2 had regression to normal of a coronary artery aneurysm after Kawasaki disease and were divided, according to the time since onset, into two subgroups, group 2-a (n = 20) being at an early stage after regression to normal (followed for 1.7 +/- 0.7 years) and group 2-b (n = 34) being at a later stage after regression (followed for 8.7 +/- 2.9 years); and group 3 (the "abnormal" group; n = 25) had persistent coronary artery aneurysm or stenosis or both. Group 4, the control group (n = 44), consisted of patients without Kawasaki disease who had congenital heart disease with normal coronary arteries. The coronary artery diameter change was calculated by the following formula: Percentage of change = (Diameter after infusion - Diameter before infusion)/Diameter before infusion x 100. RESULTS: The percentages of change in the coronary artery diameter after isosorbide dinitrate infusion were 16.2% +/- 13.4% (normal group), 11.3% +/- 7.2% (early-regression group), 7.8% +/- 8.3% (late-regression group), 6.8% +/- 7.8% (abnormal group), and 15.2% +/- 11.8% (control group). In the abnormal group, there was significantly poorer dilation than in the control and normal groups. The late-regression group also had significantly less change in diameter than did the control and normal groups (p < 0.05). CONCLUSIONS: These data suggest (1) that the coronary artery after Kawasaki disease becomes stiff not only in patients with persistent abnormal lesions but also in those with regressed aneurysms and (2) that stiffness of the coronary artery may be a risk factor for atherosclerosis.

Child↗
PubMed1992

Determination of fluconazole in human serum by solid-phase extraction and reversed-phase high-performance liquid chromatography.

A simple, rapid, and accurate reversed-phase octadecylsilyl high-performance liquid chromatographic method using solid-phase column extraction is described for measuring fluconazole in human serum. The column eluent was monitored by ultraviolet absorption at 210 nm. Fluconazole was extracted from diluted serum by adsorption on a small Bond-Elut C18 cartridge after the addition of UK48,134 as the internal standard and recovered by elution with methanol. The methanol was then evaporated to dryness and the residue reconstituted in 200 microliters of mobile phase and filtered prior to injecting an aliquot (50 microliters) onto an Adsorbosphere C18 column (4.6 x 250 mm, 5 microns particle size), using a mobile phase of 25 mM tris(hydroxymethyl)aminomethane-phosphate buffer (pH 7.0):acetonitrile (75:25, vol/vol). The retention times were 6.6 min for fluconazole and 9.0 min for the internal standard. The assay was precise, with inter- and intraassay coefficients of variation of less than or equal to 2.9% and less than or equal to 2.1%, respectively, and with good linearity (r = 1.000) in the range of 0.1 to 25 micrograms/ml. The duration of each analysis was 15 min and the minimum detectable serum concentration was 0.1 microgram/ml.

Administration, Oral↗
PubMed1992

Balloon valvuloplasty for congenital aortic valve stenosis in an infant and children.

Percutaneous balloon aortic valvuloplasty (BAV) was performed in 14 patients, including one critically ill infant with congenital valvular aortic stenosis (AS). BAV was effective in 13 patients (except the infant). The peak systolic pressure gradient between the left ventricle (LV) and the ascending aorta decreased from 76.6 +/- 21.6 to 29.5 +/- 15.3 mmHg (P less than 0.001). Follow-up cardiac catheterization was performed for eight patients between 1 and 3 years (1.6 +/- 1.1 years) after BAV. Restenosis was found in only one patient, and the efficacy of BAV continued significantly. Aortic regurgitation developed or increased in severity in 5 of 13 children immediately after BAV. Any other severe complication was not observed. Dilatation by BAV was not sufficient for the infant with critical AS, and acute myocardial infarction (AMI) in the lateral wall of the LV occurred during the BAV procedure. The infant died 3 days after the procedure due to AMI. It was concluded that the retrograde double balloon technique was superior to the retrograde single balloon technique. In two cases, the single balloon technique was ineffective because it was impossible to fix the balloon at the aortic annulus. However, the double balloon technique was effective in every patient. BAV is effective for AS in children, and an optional repeat trial may enable BAV to be the first choice for AS. Although BAV may be effective for neonates and infants with critical AS as an emergency treatment, much attention must be paid during the procedure.

Adolescent↗
PubMed1992

Stability of ranitidine hydrochloride with aztreonam, ceftazidime, or piperacillin sodium during simulated Y-site administration.

The stability of ranitidine hydrochloride after being mixed with commonly used i.v. beta-lactam antibiotics and administered by simulated Y-site injection was studied. Solutions of ranitidine 1 mg/mL (as the hydrochloride salt), aztreonam 16.7 mg/mL, ceftazidime 20 mg/mL (with sodium carbonate), and piperacillin 30 mg/mL (as the sodium salt) were prepared by reconstitution in i.v. mini-bags. To simulate Y-site injection, 2 mL of ranitidine hydrochloride was mixed with 2 mL of each antibiotic in glass test tubes. These admixtures were prepared in triplicate and stored at room temperature under fluorescent light. Concentrations of each drug in each admixture were determined by stability-indicating high-performance liquid chromatography immediately and after one, two, and four hours. Aztreonam, ceftazidime, and piperacillin each retained more than 95% of the original concentration for at least four hours when mixed 1:1 with ranitidine. Ranitidine retained more than 90% of its original concentration for at least four hours when combined with each of the other drugs. Ranitidine 1 mg/mL (as the hydrochloride salt) and aztreonam 16.7 mg/mL, ceftazidime 20 mg/mL (with sodium carbonate), or piperacillin 30 mg/mL (as the sodium salt) were stable for at least four hours during simulated Y-site administration.

Anti-Bacterial Agents↗
PubMed1991

12S-hydroxyeicosatetraenoic acid plays a central role in the regulation of platelet activation.

When platelets are activated by the recognition of exposed collagen fibers, they start synthesizing two major arachidonic acid metabolites, i.e. thromboxane A2 and 12S-hydroxyeicosatetraenoic acid (12-HETE) via cyclooxygenase and 12-lipoxygenase pathways, respectively. Although the physiological role of the former is well established, that of the latter has not been fully elucidated. Recently, we have revealed that 12-HETE interferes with collagen-induced platelet aggregation [Sekiya, F. et al. (1990) Biochim. Biophys. Acta 1044, 165-168]. In the present paper, we show that this substance enhances thrombin-induced aggregation of bovine platelets, in sharp contrast with the case of collagen. Additionally, 12-HETE is able to prevent the prostaglandin E1-induced elevation of platelet cAMP level and counteracts its inhibitory effect on platelet aggregations. With these observations, we propose a novel self-regulatory mechanism of platelets where 12-HETE plays a key role; it switches sensitivity of platelets from the primary agonist (collagen) to the secondary one (thrombin), and cancels the inhibitory effect of cAMP elevators.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1991

Immunological detection of propolypeptide of von Willebrand factor on platelet surface.

Recently we have found that propolypeptide of von Willebrand factor (pp-vWF) obtained from platelets binds to type I collagen. It is known that pp-vWF is present in platelet alpha-granules and is secreted upon activation. In this paper, we demonstrate the two following evidences to show that it is also present on the surface of resting platelets. [1] The antibody against pp-vWF bound to the surface of platelets. [2] The antibody induced aggregation of platelets. The binding of the antibody and the antibody-induced aggregation of platelets were inhibited in a dose-dependent manner by Fab fragment of the antibody. Platelets from von Willebrand disease patients bound less of the antibody and responded weakly to the antibody.

Antibodies↗
PubMed1991

Monoclonal antibodies that inhibit binding of propolypeptide of von Willebrand factor to collagen. Localization of epitopes.

We reported previously that bovine propolypeptide of von Willebrand factor (pp-vWF) binds to type I collagen. To determine the collagen-binding sites of pp-vWF we generated monoclonal antibodies (mAbs) against bovine pp-vWF. One mAb, designated TC8, very strongly inhibited the binding of pp-vWF to type I collagen; three other mAbs, designated TC2, TC6 and TC7, exhibited moderate inhibition. Competition between the mAbs for binding to intact pp-vWF revealed that the epitope for TC8 was structurally independent of that for TC6 and TC7. To determine directly the location of the epitope for each mAb on the bovine pp-vWF molecule, we tested the reactivity of mAbs by immunoblotting toward peptide fragments obtained by digestion with lysylendopeptidase. TC2 and TC8 recognized a fragment of mass 21 kDa, while TC6 and TC7 recognized a distinct fragment of 18 kDa. These two fragments were purified to homogeneity and their N-terminal amino acid sequences were determined. Comparing these sequences with the sequence of human pp-vWF, the locations of these fragments in the primary structure were estimated to be Phe570--Lys682 for the 21-kDa fragment and Glu281--Lys375 for the 18-kDa fragment. These data suggest that pp-vWF contains at least two collagen-binding sites which lie within or close to the regions between Phe570--Lys682 and Glu281--Lys375.

Amino Acid Sequence↗
PubMed1991

Collagen-binding domain within bovine propolypeptide of von Willebrand factor.

Two reduced/alkylated fragments of bovine propolypeptide of von Willebrand factor (pp-vWF) that inhibit pp-vWF binding to collagen were isolated. One is a tryptic fragment of molecular mass of about 30 kDa and inhibits the binding at a molar concentration about 20 times higher than the intact pp-vWF. Amino acid sequence of this fragment was determined almost completely, and it was revealed that this fragment corresponded to the carboxyl-terminal region of pp-vWF molecule beginning with Phe557. The other active fragment was obtained by lysyl endopeptidase digestion. This migrated as a 21.5/21-kDa doublet in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but deglycosylation of this doublet resulted in production of single species of 19 kDa. The difference between the doublet constituents, therefore, was of carbohydrate composition. The extent of inhibition of collagen-binding by this 21.5/21-kDa fragment was comparable to that of the 30-kDa fragment, and furthermore, location of this fragment in the molecule was established to be between Phe570 and Lys682. These were the only fragments among those obtained by proteolytic digestions that had significant competitive effect on the binding of intact pp-vWF to collagen. These results strongly suggest that at least one collagen-binding site should be present in the carboxyl-terminal region of bovine pp-vWF extending from residue 570 to 682.

Amino Acid Sequence↗
PubMed1991

Mitral valve prolapse in childhood: the incidence and clinical presentations in different age groups.

To elucidate the incidence and natural history of mitral valve prolapse (MVP) during childhood, we investigated a total of 4,238 children (aged from 1 day to 15 years) classified by age into 4 groups: Group 1:1 to 28-day-old full-term normal newborns (n = 108), Group 2: 6 to 18-month-old infants (n = 391), Group 3: 6 to 7-year-old children (n = 2,801), and Group 4: 12 to 15-year-old children (n = 938). The incidence of MVP was determined by videorecorded two-dimensional echocardiography in a double-blind method twice-over. There were 109 cases diagnosed as having MVP. The incidence rates of MVP were as follows: Group 1: 0%, Group 2: 0.25%, Group 3: 2.1% and Group 4: 5.1%. Arrhythmias were detected in 49% (27/55) by Holter ECG, and by exercise stress test in 4.7% (2/43). Eighty-three (77%) of 108 cases in Groups 3 and 4, excluding the 1 case in Group 2, showed no symptoms. Ventricular premature contraction (VPC) was the most common arrhythmia, and was benign in all cases. A mid-systolic click (MSC), late systolic murmur (LSM), MSC + LSM, and a pansystolic murmur were detected in 23.1%, 3.7%, 4.6% and 5.6%, respectively. Symptoms caused by MVP increased and appeared more apparently with age. Further prospective long-term follow-up studies to adulthood are necessary.

Adolescent↗
PubMed1991

[Cine magnetic resonance imaging for evaluating flow dynamics in congenital heart diseases with left-to-right shunts].

Cine magnetic resonance imaging (cine MRI) was used to evaluate the cardiac structures and blood flow in congenital heart diseases with left-to-right shunts. Fifteen children with left-to-right shunts which were confirmed by echocardiography or angiography were investigated in the present study. Five children each had atrial septal defect, ventricular septal defect, and complete endocardial cushion defect. Their ages ranged from 4 months to 13 years (mean 5.5 years). Prior to cine MRI, the ECG-gated cardiac imaging using multi-slice acquisition was performed in all the children to localize the optimal slice for cine MRI. To select the optimal imaging planes for various cardiac structures, we used axial, coronal, sagittal and four-chamber views. Cine MRI was demonstrated by a fast low 30 degree flip angle imaging technique, with a 15 msec echo time, a 30-40 msec pulse repetition time, and a 256 x 256 or 128 x 128 acquisition matrix. Abnormalities of cardiac structures were defined extremely well in all the children using ECG-gated cardiac imaging. In 14 of the 15 children (93%), cine MRI clearly detected a left-to-right shunt flow, which was visualized as a low signal intensity area compared to the surrounding blood flow. Noninvasively, cine MRI provides accurate images of the anatomy of the cardiac structures, makes functional assessments of the cardiac chambers and walls, and flow relationships. It has no limitations of imaging planes imposed bones and lung, and is not associated with technical difficulties as required with echocardiography which has small cardiac window.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

[Percutaneous balloon valvuloplasty for congenital aortic valve stenosis].

We performed percutaneous balloon aortic valvuloplasty for 10 patients with congenital aortic valve stenosis aged from 2 to 17 years and a 54-day-old infant with critical stenosis. The retrograde single balloon technique was used for 6 patients including the infant; the retrograde double balloon technique was used for 3 patients; and both techniques for 2 patients. The valvuloplasty was effective for 10 patients except for the infant in terms of the peak systolic pressure gradient between the left ventricle and aorta (from 80.6 +/- 21.9 to 29.4 +/- 17.0 mmHg). Follow-up cardiac catheterizations one year after valvuloplasty in 3 patients and 3 years after valvuloplasty in one patient disclosed no re-stenosis. Aortic regurgitation newly developed in one patient and advanced Sellers' classification I in 3 patients, however, all of them were asymptomatic and did not progress further. In the infant with critical stenosis, sufficient dilatation could not be achieved and acute myocardial infarction mainly at the lateral wall of the left ventricle developed during the valvuloplasty. He died 3 days after the valvuloplasty. The double balloon technique was found to be superior to the single balloon technique with the latter being ineffective in 2 cases, because the fixation of the balloon at the annulus was very difficult. Double balloon technique has low risk of vascular trauma and is applicable to a large sized annulus, because it enables blood supply between the 2 balloons during the inflation period.

Adolescent↗