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Biomedical subjects

T Sakamaki

Publications and source records attributed to T Sakamaki.

At least 127 records · Page 7Linked to original sources
PubMed1983

Characterization of left ventricular mechanical function during arrhythmias by two-dimensional echocardiography. II. Location of the site of onset of premature ventricular systoles.

Two-dimensional echocardiography was applied experimentally in a closed chest dog model with intact pericardium to determine the location, magnitude and extent of contractile response during pacing from discrete ventricular sites. Midventricular short-axis tomographic images obtained during regular sinus rhythm and subsequent premature ventricular beats provided comparative measurements of global and segmental systolic changes of cross-sectional luminal areas and myocardial wall thickness. Computer-assisted standardized analysis of segmental systolic fractional area change and wall thickening was used to map left ventricular contraction during normal rhythm and premature beats of 70% coupling interval, induced alternately from anterior and lateral aspects of the mid-left ventricular short-axis cross-sectional plane. A characteristic pattern consisting of early systolic contraction and wall thickening was followed by paradoxical motion and wall thinning in late systole in segments corresponding to the region of direct electrical stimulation. Statistical analysis of segment by segment function indicated a maximal amount of premature beat contractile derangement at the site of the stimuli. Pacing from a right ventricular wall site in the midventricular plane caused a similar premature beat response at the anterior aspect of the interventricular septum. It is concluded that two-dimensional echographic analysis of segmental ventricular function can identify the location of electrical stimuli, and thus might noninvasively characterize regional patterns of contraction associated with ectopic foci during arrhythmias.

Animals↗
PubMed1983

Diagnosis of coronary stenosis by two-dimensional echographic study of dysfunction of ventricular segments during and immediately after pacing.

The adequacy of two-dimensional echocardiography during right atrial pacing for the detection and characterization of coronary artery stenosis was examined in 10 closed chest dogs. Pacing at successively higher rates up to 210 beats/min was carried out in the control state and again during a 70% left anterior descending coronary artery stenosis-induced with intracoronary plugs. Left ventricular short-axis echographic cross sections were obtained at several levels of the left ventricle. After computer-aided standardized subdivision, contractile function of the global section and its subsegments was characterized by computed systolic fractional area change percent and wall thickening percent. Ventricular segments supplied from the site of the 70% coronary stenosis were delineated in a low papillary level cross section by a myocardial contrast echographic technique, and these segments demonstrated significant dysfunction during pacing at 150 to 210 beats/min. Echographic observation of the involved segments immediately after pacing revealed a maximal depression of function 5 seconds after pacing, equivalent to dysfunction at peak pacing, with function returning to control levels within about 2 minutes. Both maximal pacing and early postpacing studies facilitated satisfactory discrimination of ischemic from normally perfused myocardial segments. These experiments show that right atrial pacing study with quantitative two-dimensional echocardiography may serve to detect and assess a coronary stenosis associated with minor or no cardiac dysfunction in the rest state.

Animals↗
PubMed1983

Relation between myocardial injury and postextrasystolic potentiation of regional function measured by two-dimensional echocardiography.

An experimental study was designed to validate postextrasystolic potentiation assessment of myocardial viability or functional reserve of cardiac segments after acute coronary occlusion. Segmental systolic fractional area changes and wall thickening in pacing-induced postextrasystolic beats were mapped in 12 closed chest dogs by two-dimensional echocardiography during a control period and from 20 minutes to 3 hours after occlusion of the left anterior descending coronary artery. The extent of myocardial ischemic and necrotic zones was evaluated in left ventricular slices and subsegements corresponding to echographic cross sections. During two-dimensional echocardiography, left ventricular segments that were found to be neither ischemic nor necrotic always exhibited a significant augmentation of both fractional area change and wall thickening during the postextrasystolic beat that followed an induced premature contraction with a 42.4% coupling interval. In segments without necrosis but with varying degrees of ischemia, significant postextrasystolic potentiation was also demonstrated, even after 3 hours of occlusion. In contrast, segments that developed more than 80% necrosis failed to potentiate systolic fractional area change after 2 hours, and systolic wall thickening, even after 20 minutes of coronary occlusion. Statistical evaluation revealed a characteristic threshold at 41 to 60% necrosis, beyond which no potentiation of function could be elicited 3 hours after occlusion. Extrapolation from the experimental data suggests that when two-dimensional echographic studies in myocardial ischemia indicate postextrasystolic augmentation of segmental left ventricular function, the latter segments may be assumed to contain only small infarcts or to consist of reversibly ischemic and normal myocardium. Conversely, segments that fail to exhibit postextrasystolic potentiation can be assumed to be more than 60% necrotic.

Animals↗
PubMed1983

Body fluid distribution in the maintenance of DOCA-salt hypertension in rats.

Body fluid volumes and their relation to mean arterial pressure and plasma renin activity (PRA) were examined in heminephrectomized rats after 4 wk of treatment with deoxy-corticosterone acetate (DOCA) and placed on one of three levels of salt intake, either high (D-HS), normal (D-NS), or low (D-LS); sham-operated rats, which received heminephrectomy and no DOCA treatment, also received high (S-HS), normal (S-NS), or low (S-LS) intakes of salt. Body fluid volumes were measured as the distribution volumes of radioiodinated serum albumin, 35SO4, and tritiated water for plasma volume (PV), extracellular fluid volume (EFV), and total body water (TBW), respectively. Approximately the same degrees of hypertension occurred in the D-HS and D-NS rats, but the D-LS rats were normotensive. PV and EFV were increased only in the D-HS rats, with no prominent changes occurring in the D-NS rats. Intracellular fluid volume (ICF) was not changed in the D-NS rats when compared with the S-NS rats. The ratios of PV/EFV and EFV/TBW in the DOCA-treated groups on high or normal salt were not different from their controls. PRA was greatly suppressed in the D-HS and D-NS rats when compared with all other groups. In another group of D-HS rats, sodium was restricted for 2 wk; in this group the mean arterial pressure fell to control levels without significant changes in PV, but interstitial fluid volume was reduced to normal levels. These results demonstrated that 1) in DOCA-salt hypertensive rats there is expansion of body fluid volumes that are proportionally distributed among the PV, EFV, and ICF; 2) increases in body fluid volumes are not necessary for DOCA to maintain hypertension; 3) a certain minimal amount of dietary sodium is necessary for the development and maintenance of hypertension; and 4) following DOCA treatment the suppression of PRA is not due solely to expansion of body fluid volumes.

Animals↗
PubMed1983

Myocardial contrast echocardiography: a reproducible technique of myocardial opacification for identifying regional perfusion deficits.

The effects and reliability of a simple method of contrast two-dimensional echocardiographic delineation of myocardium after intracoronary injections were evaluated in closed-chest dogs. Multiple injections of an agitated saline-Renografin (meglumine diatrizoate) mixture (3:2 ratio, 2-ml bolus) into the left main coronary artery as well as at different sites of the left anterior descending and circumflex coronary arteries were studied in several short-axis and long-axis cross sections of the left ventricle. These contrast injections opacified specific regions of left ventricular myocardium depending on the site of injection. Contrast injection into the left main coronary artery provided a clear, echo-free outline (negative contrast) of underperfused myocardium distal to the coronary occlusion. Reproducibility studies of the extent of involved zones measured in echocardiographic cross sections indicated high intra- and interobserver correlation coefficients (r = 0.97 and 0.97). The effects of the intracoronary injection of contrast material appeared minor and brief. ECG ST-T changes lasted 49.4 +/- 36.7 seconds, aortic systolic pressure was reduced by 7.6 +/- 4.4% for 18.9 +/- 4.8 seconds, and the peak rate of left ventricular pressure rise decreased by 14.3 +/- 2.6%, but returned to control levels within 19.4 +/- 6.1 seconds. The zone of left ventricular asynergy after coronary occlusions was also delineated by cross-sectional echocardiography and corresponded to the contrast-outlined underperfused zone (negative contrast). This new intracoronary echocardiographic technique has only minor hemodynamic consequences and provides reliable quantitation of underperfused and dysfunctioning zones after experimental coronary occlusions. Further investigation and validation of this method may provide useful characterization of the extent and severity of myocardial ischemia and infarction.

Animals↗
PubMed1983

Mitral valve prolapse in short-term experimental coronary occlusion: a possible mechanism of ischemic mitral regurgitation.

Experimental coronary occlusions were carried out in 12 closed-chest dogs to investigate the functional anatomic characteristics of the mitral valve complex during acute myocardial ischemia. Two-dimensional echocardiography was used to assess left ventricular function, the mitral valve complex, and left atrial size. Presence of mitral regurgitation was assessed by left ventricular contrast echocardiography. Thirty-seven coronary occlusions of up to 10 min in duration were carried out in proximal or distal locations in the left anterior descending and the left circumflex coronary arteries. Mitral regurgitation, which was mild in severity as judged by a small rise in pulmonary artery wedge pressures, was observed in 15 of 37 brief coronary occlusion experiments. Mitral valve prolapse was noted in all 15 experiments, as well as in four additional studies in which mitral regurgitation was not seen. The development of experimental mitral valve prolapse was explained by measurements that demonstrated a relative displacement of the papillary muscle tips toward the mitral orifice. We conclude that mitral valve prolapse is a common sequela of short-term coronary occlusion and is often associated with mild mitral regurgitation. Relative displacement of ischemic papillary muscles toward the mitral orifice appears to be a likely mechanism of acute ischemic mitral valve prolapse.

Animals↗
PubMed1981

Effect of dexamethasone on the diurnal rhythm of plasma aldosterone in patients with congestive heart failure.

Diurnal rhythm studies were performed on 11 patients with congestive heart failure. Blood samples were taken for the determination of aldosterone, cortisol and plasma renin activity every 4 hours from 12:00 a.m. to 12:00 a.m. the following day. Following this control study, a second diurnal rhythm study was conducted under dexamethasone treatment (0.5 mg of dexamethasone every 4 hours for 48 hours). In the control study, aldosterone and cortisol fluctuated showing a diurnal rhythm with the lowest value in the evening and the highest value in the morning. Plasma renin activity rhythm was indistinct. Fluctuations in plasma renin activity were not parallel with aldosterone. Dexamethasone treatment suppressed cortisol to less than 1 microgram/100 ml. Aldosterone values decreased significantly in the morning (p less than 0.01); this was accompanied by the abolishment of aldosterone rhythm. Plasma renin activity rhythm remained indistinct following administration of dexamethasone. These results suggest that adrenocorticotrophic hormone plays an important role in the control of aldosterone diurnal rhythm in patients with congestive heart failure.

Adolescent↗
PubMed1979

[Clinical study on coxa magna during the treatment in congenital dislocation in the hip (author's transl)].

Enlargement of the femoral head is frequently observed in roentgenographs during the treatment of congenital dislocation of the hip. Clinical study was performed to clarify the definition, etiology and clinical entity of coxa magna. Three hundreds and three hip joints in 247 patients were examined roentgenographically and follow up for an average of 3.1 years. By measuring the longitudinal and cross-sectional lengths of both the femoral heads and necks, we felt that "coxa magna" should be defined as the condition with enlargement of all of these parameters. The incidence of coxa magna was 47% after open reduction, but only 5% after closed reduction. In most cases, coxa magna was roentgenographically evident approximately 10 months after open reduction. On the other hand, it was noticeable 18 months after closed reduction. In the hips without coxa magna, the acetabular index improved remarkably for 6 months following open reduction, but in the hips with coxa magna, it hardly improved. Coxa magna frequently developed femoral head deformity, unless persistent acetabular dysplasia had improved. The incidence of coxa magna appeared to be closely related to surgical intervention performed on acetabular dysplasia.

Age Factors↗
PubMed1978

Crystallization of arginine-, formylmethionine-tyrosine-, and glycine-transfer RNAs from Escherichia coli.

Crystals as large as 0.5 X 0.3 X 0.2 mm of purified arginine-transfer RNA from Escherichia coli have been prepared by a vapour diffusion method. X-ray diffraction photographs showed that the crystals gave reflections up to 3.7 A spacing. They have a trigonal space group P31 2 1 (OR P32 2 1) and cell-dimensions a=97.2, b=97.2, c=94.8A. Crystals of a mercury derivative of this transfer RNA have also been obtained, and an X-ray diffusion photography of one of them is presented. Formylmethionine-transfer RNA from E. coli was crystallized in various forms, and the appearance of the polymorphs was found to depend upon the amount of spermine in the solution from which the crystallization took place. Crystals of tyrosine-transfer RNA and glycine-transfer RNA have also been obtained.

Arginine↗
PubMed1977

Crystal structure of a protein proteinase inhibitor, Streptomyces subtilisin inhibitor, at 2.3 angstrom resolution.

The crystal structure of a protein proteinase inhibitor, Streptomyces subtilisin inhibitor which strongly inhibits bacterial alkaline proteinases, was determined at 2.3 angstrom resolution. The subunit (molecular weight, 11,485) of this dimeric molecule has a unique fold of polypeptide chain with a five-fold anti-parallel beta-sheet structure (about 21% of the 113 amino acid residues) and two small segments of alpha-helices (about 16%). The region around the apparent reactive site, Met(73)-Val(74), is held tight by a combination of various structural features. The conformation of this region seems to have close similarity to that found in substrate analogues of low molecular weight bound to subtilisin BPN'.

Crystallography↗
PubMed1977

The diurnal rhythm of plasma aldosterone and plasma renin activity in patients with congestive heart failure.

Study on a diurnal rhythm of plasma aldosterone (PA) and plasma renin activity (PRA) was performed in 8 patients with congestive heart failure. All patients had been digitalized and received diuretics under mild sodium restriction. An obvious diurnal rhythm of PA similar to the normal subjects, with the lowest value in the evening and the highest value in the morning, was observed in 7 of 8 cases, while a diurnal rhythm of PRA was obscure except in one case. The PA generally did not run parallel with PRA. Although the reason of the absence of PRA diurnal rhythm in congestive heart failure was not clear, it was considered that reninangiotensin system did not play a significant role for the development of PA diurnal rhythm in congestive heart failure. The determined PA values were entirely within normal range except in 2 cases, although they were administered the potent diuretics chronically. A high PA value was observed only in early morning in one case, while all determined PA values were extremely high in another case with severe congestive heart failure involved in cardiac liver cirrhosis. The PRA values were relatively low in 2 cases, normal in 5 and high in one.

Adult↗
PubMed1976

Double strandedness of nascent DNA of a higher plant (Vicia faba).

After a pulse of 5-10 min with [3H]thymidine, labeled DNA extracted from embryonic axes of Vicia seeds sedimented as a rather homogeneous peak at approx. 10S in an alkaline sucrose density gradient, as described in our previous paper ((1975) Biochim. Biophys. Acta 395, 314-321). The sedimentation pattern of the same pulse-labeled DNA in a neutral gradient showed a wide range of sizes from approx. 14 S to more than 40 S. However, most of these labeled DNA components, including the 14-20 S shorter fragments, were shown to have a double-stranded structure by hydroxyapatite column chromatography. Further investigations on neutral sucrose gradients revealed a decreased occurrence after a chase, and final disappearance after a longer chase period of these shorter double-stranded fragments. A possible secondary structure of the newly synthesized DNA in a higher plant (Vicia faba) is discussed.

Centrifugation, Density Gradient↗
PubMed1976

The diurnal rhythm of plasma aldosterone, plasma renin activity, plasma cortisol and serum growth hormone and subnormal responsiveness of aldosterone to angiotensin-II in the patients with normotensive acromegaly.

The diurnal rhythm of plasma aldosterone concentration (PA), plasma renin activity (PRA), plasma cortisol (PC) and serum growth hormone (GH) were examined in 5 cases of normotensive acromegaly and the results were compared with the observations in normal subjects. Moreover, the response of PA to angiotensin-II infusion was studied in 6 cases of normotensive acromegaly. A normal diurnal rhythm with the lowest values in the evening or midnight and the highest values in the morning was observed in 3 of 5 cases in PA and 3 of 4 cases in PC. On the other hand, no apparent rhythm of GH was observed in any cases and that of PRA in 4 of 5 cases. Although there was a significant positive correlation between PA and PC, no significant correlation was demonstrated between PA and PRA. The response of PA to angiotensin-II fusion was significantly suppressed in normotensive acromegaly as compared to the normal subjects in spite of normal levels of PRA except for 1 case. The above observations were interpreted to suggest that the aldosterone regulation system is slightly altered in a certain number of patients with normotensive acromegaly in contrast to the normal subjects in which PRA is the main contributing factor. The low PA and suppressed response of PA toangiotensin-II infusion may suggest the defective action of angiotensin-II infusion on the adrenal gland.

Acromegaly↗