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Biomedical subjects

S Ishiwata

Publications and source records attributed to S Ishiwata.

At least 73 records · Page 4Linked to original sources
PubMed1996

Synchronous behavior of spontaneous oscillations of sarcomeres in skeletal myofibrils under isotonic conditions.

An isotonic control system for studying dynamic properties of single myofibrils was developed to evaluate the change of sarcomere lengths in glycerinated skeletal myofibrils under conditions of spontaneous oscillatory contraction (SPOC) in the presence of inorganic phosphate and a high ADP-to-ATP ratio. Sarcomere length oscillated spontaneously with a peak-to-peak amplitude of about 0.5 microns under isotonic conditions in which the external loads were maintained constant at values between 1.5 x 10(4) and 3.5 x 10(4) N/m2. The shortening and yielding of sarcomeres occurred in concert, in contrast to the previously reported conditions (isomeric or auxotonic) under which the myofibrillar tension is allowed to oscillate. This synchronous SPOC appears to be at a higher level of synchrony than in the organized state of SPOC previously observed under auxotonic conditions. The period of sarcomere length oscillation did not largely depend on external load. The active tension under SPOC conditions increased as the sarcomere length increased from 2.1 to 3.2 microns, although it was still smaller than the tension under normal Ca2+ contraction (which is on the order of 10(5) N/m2). The synchronous SPOC implies that there is a mechanism for transmitting information between sarcomeres such that the state of activation of sarcomeres is affected by the state of adjacent sarcomeres. We conclude that the change of myofibrillar tension is not responsible for the SPOC of each sarcomere but that it affects the level of synchrony of sarcomere oscillations.

Animals↗
PubMed1996

Soft-X-ray damage to biological samples.

X-ray damage to biological samples was investigated in the wavelength region of 2.7-5 nm, which overlaps the so-called 'water-window', the wavelength range of 2.4-4.3 nm usually used in X-ray microscopy. Yeast cells and myofibrils were chosen as representatives of whole cell samples and motile protein systems, respectively. The samples were exposed to X-rays using an apparatus composed mainly of a laser-plasma X-ray source, a Wolter mirror condenser, and a sample cell. The yeast cells lost their dye exclusion ability when the X-ray flux was higher than 1 x 10(6) photons micron-2, while the myofibrils lost contractility when the X-ray flux was higher than 4 x 10(5) photons micron-2. These X-ray fluxes are lower than the flux required for the X-ray microscope observation of biological samples at a resolution higher than that of light microscopes.

Animals↗
PubMed1996

Direct determination of serum glycyrrhetic acid by a monoclonal antibody-based inhibition ELISA using ibuprofen for releasing serum albumin-bound glycyrrhetic acid.

We found that ibuprofen (IBU) had a potential for releasing serum albumin-bound glycyrrhetic acid (GA). Based on this observation, IBU was used to pretreat samples for the determination of serum GA levels by an inhibition ELISA. This method, termed IBU method was evaluated by the recovery of GA from human serum albumin (HSA) or normal human serum (NHS) that contained the exogeneously added GA (37-1000 ng/ml). The mean recovery of GA from HSA and NHS samples treated with IBU were 104.7 and 105.2%, respectively, whereas those without IBU pretreatment were 2.8 and 10.7%, respectively. Comparison of IBU method and chloroform extraction method revealed that the GA content of serum samples pretreated by each method were almost the same. These results suggest that IBU method is useful as a serum processing procedure for the determination of serum GA levels by an inhibition ELISA.

Antibodies, Monoclonal↗
PubMed1996

Causes of coronary events after successful coronary angioplasty.

OBJECTIVE: To determine the causes and incidence of coronary events after successful coronary angioplasty. METHODS: We evaluated retrospectively follow-up angiograms of 60 patients with coronary events (27 with myocardial infarction, 33 with new-onset angina pectoris) from among 930 consecutive patients who underwent successful elective angioplasty between February 1985 and April 1994. Patients who had undergone percutaneous transluminal coronary angioplasty to bypass grafts were excluded. RESULTS: No fatal cardiac events occurred within 6 months of percutaneous transluminal angioplasty; 10 occurred thereafter. Fifteen patients who developed early (3.9 +/- 1.8 months) restenosis showed non-Q-wave infarction resulting from severe restenosis at the previously dilated site. In patients without early restenosis, cardiac events developed not from the previously dilated site, but from previously undilated, non-obstructive sites. Furthermore, it was found that the patency of the previously dilated site remained good for a long period of time (41 +/- 23 months) in 96% (43 of 45) of these patients. These findings indicate that the vast majority of cardiac events in patients without early restenosis resulted from new lesions distant from the previous angioplasty site. CONCLUSIONS: Fatal cardiac events resulting from early restenosis were rare. In patients with no evidence of restenosis, long-term patency remained good. However, a proportion of these patients developed cardiac events resulting from lesions distant from the previous angioplasty site and hence careful long-term follow-up is essential.

Adult↗
PubMed1996

Preparation of a monoclonal antibody specific for 5-methyl-2'-deoxycytidine and its application for the detection of DNA methylation levels in human peripheral blood cells.

A monoclonal antibody specific for a modified nucleoside, 5-methyl-2'-deoxycytidine (m5dCyd), was prepared using 5-methylcytidine (m5Cyd)-keyhole limpet haemocyanin (KLH) conjugate, and was characterized. Termed FMC9, the antibody reacts with m5dCyd and slightly with m5Cyd and 5-methylcytosine (m5Cyt) but not with other nucleosides tested in this investigation. FMC-9 was used in an enzyme-linked immunosorbent assay (ELISA) system for the quantitation of m5dCyd levels. Sensitivity was in the picomole range. Methylation levels in peripheral blood cells of healthy donors were determined by inhibition ELISA. The percentage of m5dCyd in peripheral blood cells of 10 healthy donors was 5.08 +/- 0.50%. These results suggest that the inhibition ELISA using FMC9 is useful to monitor m5dCyd levels in the peripheral blood cells.

Adult↗
PubMed1996

Long-term outcome in single-vessel coronary artery disease in Japanese patients.

We assessed the long-term outcome of medical therapy in 453 patients who underwent coronary angiography in the period from September 1973 to February 1984, and who had a significant stenotic lesion (75% or more stenosis) in a single coronary artery. The mean follow-up period was 9.8 years. The 5- and 10-year survival rates were, respectively, 96.0% and 91.3% in these patients, and these survival rates were comparable to the cumulative survival rates in the age-matched healthy male controls determined on the basis of overall death. Cardiac death occurred in 35/453 patients (7.7%) with single-vessel disease (SVD), and non-fatal myocardial infarction occurred in 17 patients (3.8%) during the follow-up period. The incidence of cardiac events, which was defined as cardiac death and nonfatal myocardial infarction, was as low as 1.2% per year. The survival rates were compared in terms of the presence or absence of myocardial infarction, the type of the coronary artery with stenosis, and proximal versus distal location of the stenotic lesion in the left anterior descending artery (LAD). The survival rates were similarly high in both assessed groups, with no significant differences. Patients with SVD treated medically had a good prognosis, except for those patients with decreased left ventricular function (ejection fraction < or = 40%). These factors should be taken into consideration when selecting therapies for patients with SVD.

Case-Control Studies↗
PubMed1996

[Long-term recovery of regional wall motion in patients with medically treated anterior myocardial infarction: quantitative assessment of the post-infarction left ventriculograms].

The effect of medical treatment without reperfusion therapy on the long-term recovery of regional wall motion was evaluated retrospectively in 28 patients with transmural acute anterior myocardial infarction who had coronary angiography and left ventriculography at 1-6 months after the onset of the episode and were followed for a mean of 65 months. In all patients, initial coronary angiography revealed significant stenosis in only the left anterior descending artery (LAD). All patients were treated medically without reperfusion therapy (such as thrombolytic therapy, angioplasty, or bypass grafting). The regional wall motion in the LAD territory was measured by the centerline method using the right anterior oblique projection. Long-term improvement in anterior wall motion is unlikely in patients with patent LAD or underdeveloped collaterals to the LAD (38%). However, subsequent anterior wall motion frequently improved among patients with severely stenotic or occluded LAD (63%) and well-developed collaterals (73%). Therefore, the anterior wall motion of some LAD-related infarctions improves spontaneously, the extent of coronary collaterals is an important determinant of long-term improvement, and the improvement in wall motion is completed within the early period of acute anterior infarction in patients with patent LAD.

Angiocardiography↗
PubMed1995

Unbinding force of a single motor molecule of muscle measured using optical tweezers.

The unbinding and rebinding of motor proteins and their substrate filaments are the main components of sliding movement. We have measured the unbinding force between an actin filament and a single motor molecule of muscle, myosin, in the absence of ATP, by pulling the filament with optical tweezers. The unbinding force could be measured repeatedly on the same molecule, and was independent of the number of measurements and the direction of the imposed loads within a range of +/- 90 degrees. The average unbinding force was 9.2 +/- 4.4 pN, only a few times larger than the sliding force but an order of magnitude smaller than other intermolecular forces. From its kinetics we suggest that unbinding occurs sequentially at the molecular interface, which is an inherent property of motor molecules.

Actins↗
PubMed1995

Immunochemical detection of urinary 5-methyl-2'-deoxycytidine as a potential biologic marker for leukemia.

A monoclonal antibody against 5-methylcytidine was prepared and characterized. This antibody, termed AMC, was reactive with compounds that had 5-methylcytosine structure (i.e. 5-methyl-2'-deoxycytidine, 5-methylcytidine and 5-methylcytosine). AMC had the highest reactivity to 5-methyl-2'-deoxycytidine among reactive compounds and had no or very slight cross-reactivity to cytidine-related compounds and any other compounds. Analysis of immunoreactive materials in urine revealed that 5-methyl-2'-deoxycytidine rather than 5-methylcytidine was, contrary to our expectation, the major component. Then the inhibition ELISA system using AMC was established and urinary levels of 5-methyl-2'-deoxycytidine in healthy individuals and cancer patients were determined. The mean excretion levels of healthy individuals was 0.90 +/- 0.43 nmol/mumol creatinine and the cut-off value was set at the mean + 2 S.D. of healthy individuals (1.76 nmol/mumol creatinine). Among various types of cancer tested, elevated levels of 5-methyl-2'-deoxycytidine were detected in leukemia patients. From these results, urinary 5-methyl-2'-deoxycytidine might be applicable as a biologic marker for leukemia.

Animals↗
PubMed1995

Positron emission tomography (PET) study of the alterations in brain distribution of [11C]methamphetamine in methamphetamine sensitized dog.

[11C]Methamphetamine ([11C]MAP) was synthesized by an automated on-line [11C]methylation system for positron emission tomography (PET) study. We newly produced a MAP sensitized dog by repeated MAP treatment and studied the brain distribution of [11C]MAP in the normal and the MAP sensitized dog. The maximal level of accumulation of [11C]MAP in the sensitized dog brain was 1.4 times higher than that in the control. No difference was found in the metabolism of MAP between the two conditions. The significant increase of [11C]MAP in the MAP sensitized brain indicates that subchronic MAP administration causes some functional change in uptake site of MAP.

Animals↗
PubMed1995

Microscopic analysis of the elastic properties of nebulin in skeletal myofibrils.

The elastic properties of nebulin were studied by measuring the elasticity of single skeletal myofibrils, from which the portion of the thin filament located at the I band had been selectively removed by treatment with plasma gelsolin under rigor conditions. In this myofibril model, a portion of each nebulin molecule at the I band was expected to be free of actin filaments and exposed. The length of the exposed portion of the nebulin molecule was controlled by performing the gelsolin treatment at various sarcomere lengths. The relation between the passive tension and extension of the exposed portion of the nebulin showed a convex curve starting from a slack length, apparently in a fashion similar to that of wool. The slack sarcomere length shifted depending on the length of the exposed portion of the nebulin, however, the relation being represented by a single master curve. The elastic modulus of nebulin was estimated to be two to three orders of magnitude smaller than that of an actin filament. Based on these results, we conclude that nebulin attaches to an actin filament in a side-by-side fashion and that it does not significantly contribute to the elastic modulus of thin filaments. The relation between the passive tension and extension of connectin (titin) was obtained for a myofibril from which thin filaments had been completely removed with gelsolin under contracting conditions; this showed a concave curve, consistent with the previous results obtained in single fibers.

Actins↗
PubMed1995

[Serum 1-methyladenosine and pseudouridine as tumor markers in tumor-bearing mice].

It is known that in cancer patients elevated levels of modified nucleosides originated from RNA are excreted in the urine. Modified nucleosides in the serum are thought to be more useful than those in the urine as tumor markers because they are not influenced by other factors. However the determination of these nucleosides is difficult because of their low amounts. To examine the efficacy of the modified nucleosides in the serum as tumor markers, ascites and solid tumor mouse models were prepared, and the amounts of 1-methyladenosine and pseudouridine in the serum were determined. Along with the growth of ascites tumor, the amounts of 1-methyladenosine and pseudouridine in the serum increased. The modified nucleosides in the serum in a solid tumor model also increased. This is the first report on the variation in the amount of 1-methyladenosine in the serum of tumor models, and the results suggest the usefulness of measuring the amounts of 1-methyladenosine and pseudouridine in the serum as tumor markers.

Adenosine↗
PubMed1995

Comparison of long-term efficacy of medical treatment versus percutaneous transluminal coronary angioplasty (PTCA) in single-vessel disease.

The long-term outcome of PTCA and medical therapy were compared in patients with SVD. All patients were confirmed to have > or - 75% stenosis of a major coronary artery by coronary arteriogram. The 5-year survival rates were 96.0% for medical therapy and 98.9% for successful angioplasty. Both therapies achieved an equally good long-term outcome for SVD. The incidence of nonfatal cardiac events during follow-up was higher in patients treated by PTCA than in those on medical therapy, but there was no difference between the two groups in the incidence of nonfatal MI at 5 years (2.5% vs 1.8%). The most common cardiac event in patients undergoing successful PTCA was repeat intervention associated with restenosis. In view of the long-term efficacy of PTCA, the high restenosis rate remains an important problem and it is necessary to elucidate the causes of restenosis and develop countermeasures as soon as possible.

Adult↗
PubMed1995

Comparison of long-term efficacy of medical treatment versus coronary artery bypass grafting (CABG) in multivessel coronary artery disease.

The long-term results of medical therapy and coronary artery bypass grafting (CABG) were compared in patients with multivessel disease. All patients were confirmed to have > or = 75% luminal narrowing of major coronary arteries by coronary arteriogram. When multivessel disease was stratified into double- and triple- vessel disease, the outcomes varied. In triple-vessel disease, the outcome with CABG was good, but the outcome was unfavorable in those employing medical therapy, particularly in patients with decreased left ventricular (LV) function. In patients with double-vessel disease with good LV function, the long-term results with medical therapy were just as favorable as those with CABG. However, double-vessel disease complicated by reduced LV function (ejection faction < or = 40%) had a clearly less favorable outcome when treated with medical therapy than with CABG. Thus, it is important for patients with multivessel disease to undergo revascularization if indicated, to improve their prognosis. On the other hand, the incidence of cardiac events arising from vein graft occlusions tended to increase in CABG patients after 5 years or more following surgery.

Aged↗
PubMed1995

Comparison of serum and urinary levels of modified nucleoside, 1-methyladenosine, in cancer patients using a monoclonal antibody-based inhibition ELISA.

To evaluate the clinical usefulness of serum 1-methyladenosine, several modifications have been made in our previously established inhibition ELISA system. Horseradish peroxidase (HRP) labeled anti-mouse IgG and 3,3',5,5'-tetramethylbenzidine (TMBZ) were used as a secondary antibody and a substrate, respectively. The second blocking was done just before the addition of the secondary antibody. The standard curve of the modified ELISA system showed good linearity between 1 and 1,000 ng/ml, and the detection limit was 50 pg/well. Using the ultrafiltrated-serum samples, serum 1-methyladenosine levels in healthy individuals and cancer patients were determined. The mean level of 1-methyladenosine in 31 healthy individuals was 28.3 +/- 7.9 ng/ml, and cut off value was set at 44.1 ng/ml (Mean+ 2SD). In cancer patients, elevated levels of serum 1-methyladenosine above the cut off value were detected in 4 out of 25 cases tested, though 11 cases had elevated urinary 1-methyladenosine levels above the cut off value (3.23 nmol/mumol creatinine). Since 1-methyladenosine has no interaction with serum proteins and its molecular weight is quite low, it might be rapidly excreted into the urine.

Adenosine↗
PubMed1995

Mechanical measurements of single actomyosin motor force.

To elucidate the mechanism of force generation by actomyosin motor, a measuring system was constructed, in which an in vitro motility assay was combined with an optical trapping technique. An actin filament of several micron long was attached to a gelsolin-coated polystyrene bead, and was allowed to interact with a small number (approximately 1/1 micron actin filament) of rabbit skeletal heavy meromyosin (an active subfragment of myosin) molecules bound to a nitrocellulose-coated coverglass. The bead position was determined at 33-ms intervals. We measured the force generation event at relatively low (100-400 nM) ATP concentration so that the occurrence of individual force generation events could be detected with our time resolution. The actin-bound bead held in the optical trap moved in a stepwise manner in the direction of the actin filament only in the presence of ATP. At the trap strength of 0.3 pN/nm, the maximum size of the step was 11 nm, and the maximum force associated with the movement was 3.3 pN.

Actins↗