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Biomedical subjects

T Shimazu

Publications and source records attributed to T Shimazu.

At least 199 records · Page 11Linked to original sources
PubMed1984

Attenuated blood corticosterone rhythm in rats with jejunal resection.

Circadian rhythmic changes in blood corticosterone concentration were studied in rats after resection of the jejunum or the ileum. The rats with ileal resection showed a normal corticosterone rhythm, with a peak at the beginning of the dark period when they were fed ad libitum, and the phase of the rhythm shifted when the feeding time was restricted to a specific time of day during the light period. The rats with jejunal resection also showed a similar corticosterone rhythm, but its amplitude was lower compared to that of the rats with ileal resection. There were no differences in body weight and the circadian rhythm of blood urea concentration between two groups of rats. We conclude that the jejunum is an important site where the sense of food is received as an entraining signal for the corticosterone rhythm.

Animals↗
PubMed1984

[Non-invasive estimation of transmitral pressure gradient and mitral valve area in mitral stenosis by an ultrasonic pulsed Doppler technique].

We attempted to estimate transmitral pressure gradient and mitral valve area (MVA) noninvasively in mitral stenosis (MS) by a bi-directional pulsed Doppler flowmeter combined with an electronic two-dimensional echocardiograph. Eleven patients with MS in sinus rhythm were studied by cardiac catheterization. Fifteen healthy subjects (H) served as normal control. The pulsed Doppler flowmeter operated with a carrier frequency of 2.5 MHz, a pulse repetition rate of either 5 KHz or 10 KHz and a sample volume of 1 X 3 X 3 mm. The velocity of transmitral central flow was measured by this system, monitoring audible Doppler sounds and cardiac images which depict the anatomic location of the sampling site. The Doppler signal was analyzed by a sound spectrograph. In estimating the transmitral pressure gradient and MVA, we employed a Doppler parameter (half time) defined as the time for instantaneous maximal blood flow velocity to reduce to one-half from its rapid inflow peak, which is independent of the angle between the ultrasonic beam and blood flow. Transmitral pressure gradient (delta P100) was measured as the pressure gradient between either left atrial or pulmonary capillary pressure and left ventricular pressure at the point after 100 msec from the nadir of left ventricular early diastolic pressure [( LA or PC--LVDP]100). MVA was obtained using a Gorlin's formula. The transmitral blood flow velocity in both MS and healthy groups revealed a narrow frequency band pattern with two peaks, R and A, in diastole. The former peak occurred during rapid inflow phase and the latter following atrial contraction. In the healthy group, the descent rate of R wave was increased than that in the MS group. The square root of the pressure gradient also reduced linearly with transmitral flow velocity in the MS group. Thus in the MS group, the transmitral velocity was directly proportional to the square root of the pressure gradient as described by a Bernoulli theorem, and the half time was proportional to the transmitral velocity. The square of the half time (delta t2) was highly correlated with delta P100 (r = 0.97), and the inverse of the half time (delta t-1) was correlated with MVA (r = 0.76). There was no significant correlation between delta P100 and diastolic descent rate of anterior mitral leaflet (DDR). The present study indicates that the half time is useful in estimating transmitral pressure gradient and MVA in mitral stenosis.

Adult↗
PubMed1983

Effect of autonomic denervation on DNA synthesis during liver regeneration after partial hepatectomy.

The regulatory role of autonomic nerves in liver regeneration after partial hepatectomy was studied in rats by bilateral subdiaphragmatic vagotomy or splanchnicectomy. 1. In control rats the wet weight of the regenerating liver was restored to approximately 80% of the preoperative weight 72 h after partial hepatectomy. Restoration of the liver weight was significantly impaired in vagotomy rats, but not in splanchnicectomy. Increases in the DNA and protein contents of the regenerating liver were also suppressed by vagotomy. 2. Hepatic DNA synthesis, measured as the incorporation of [methyl-3H]thymidine into DNA at various times after partial hepatectomy, was significantly less in vagotomized rats, and slightly more in splanchnicectomized rats than in control rats. The onset of DNA synthesis triggered by partial hepatectomy was also delayed by vagotomy. 3. The increases in activities of hepatic aspartate transcarbamoylase and thymidine kinase, the key enzymes in synthesis of pyrimidine nucleotides via the de novo and salvage pathways respectively, during liver regeneration, were significantly suppressed and retarded in vagotomized rats. Conversely, splanchnicectomy tended to stimulate these enzyme inductions after partial hepatectomy. 4. During starvation the plasma insulin level decreased after partial hapatectomy in control and vagotomized rats, as in sham-operated rats, but showed a transient increase 6 h after partial hepatectomy in splanchnicectomized rats. It is concluded that vagotomy inhibits and delays DNA synthesis and proliferation of liver cells after partial hepatectomy, whereas splanchnicectomy tends to stimulate these processes. The data also suggest that parasympathetic innervation of the liver may play an important regulatory role in liver regeneration.

Animals↗
PubMed1983

Noninvasive evaluation of pulmonary hypertension by a pulsed Doppler technique.

We used a pulsed Doppler technique to examine the flow velocity pattern in the right ventricular outflow tract in 33 adults. In the patients with normal pulmonary artery pressure (mean pressure less than 20 mm Hg, 16 patients), ejection flow reached a peak level at midsystole (137 +/- 24 msec, mean +/- SD), producing a domelike contour of the flow velocity pattern during systole. In contrast, the flow velocity pattern in patients with pulmonary hypertension (mean pressure greater than or equal to 20 mm Hg, 17 patients) was demonstrated to accelerate rapidly and to reach a peak level sooner (97 +/- 20 msec, p less than .01); in 10 of the pulmonary hypertensive patients a secondary slower rise in flow velocity was observed during a deceleration, resulting in the midsystolic notching. The time to peak flow (acceleration time, AcT) and right ventricular ejection time (RVET) were measured from the flow velocity pattern. Either AcT or AcT/RVET decreased with increase in mean pulmonary artery pressure, and a very high correlation (r = -.90) was found between AcT/RVET and log10 (mean pulmonary artery pressure). The use of this technique permitted the noninvasive estimation of the pulmonary artery pressure.

Adolescent↗
PubMed1983

[Effect of diltiazem on diastolic performance of the hypertrophied left ventricle in patients with systemic hypertension and hypertrophic cardiomyopathy].

We studied the effect of a calcium antagonist, diltiazem, on left ventricular (LV) diastolic performance of hypertrophied hearts in five patients (pts) with systemic hypertension (HHD) and 6 pts with hypertrophic cardiomyopathy (HCM) by a combined phonoechocardiographic technique. Data were analyzed before and after the oral administration of diltiazem (90-180 mg/day). In HHD, the prolonged LV isovolumic relaxation time, measured from the onset of the aortic component of the second heart sound to the beginning of the mitral valve opening, decreased significantly from 112 +/- 17 to 90 +/- 9 msec (p less than 0.01) and normalized LV peak filling rate during rapid filling phase increased in all pts without a statistic significance. This filling rate during atrial contraction phase decreased (1.61 +/- 0.59 to 0.93 +/- 0.22 sec-1, p less than 0.05). In HCM, LV isovolumic relaxation time and normalized LV peak filling rate during rapid filling phase showed no significant change, although normalized LV peak filling rate during atrial contraction phase decreased significantly (1.20 +/- 0.27 to 1.05 +/- 0.24 sec-1, p less than 0.05). In both pts groups, no significant changes were observed in R-R interval, systolic blood pressure, LV end-systolic dimension, end-diastolic dimension and fractional shortening of the LV minor axis before and after the administration of diltiazem. These data indicate that diltiazem shortens abnormally prolonged LV diastolic relaxation time and improves LV diastolic filling in pts with HHD, whereas diltiazem failes to show such effects in pts with HCM except for a decrease in the normalized LV peak filling rate during atrial contraction phase.

Administration, Oral↗
PubMed1982

Hypothalamic regulation of lipid metabolism in the rat: effect of hypothalamic stimulation on lipogenesis.

The rates of fatty acid synthesis and syntheses of other lipids were measured in vivo by determining 3H-incorporation from tritiated water or 14C-incorporation from [U-14C]glucose into white adipose tissues (WAT), brown adipose tissue (BAT) and liver, during electrical stimulation of the ventromedial hypothalamic nucleus (VMH) and the lateral hypothalamic nucleus (LH) of female rats. Electrical stimulation of the VMH markedly increased the rate of fatty acid synthesis and the conversion of glucose to total lipids, glyceride glycerol and phospholipids in interscapular BAT, but not in parametrial or retroperitoneal WAT. Conversely, on VMH stimulation, the syntheses of total lipids, glyceride glycerol and phospholipids from glucose in the liver decreased slightly, though not significantly. Electrical stimulation of the LH had no such effect. Administration of insulin increased the rate of fatty acid synthesis in both brown and white adipose tissues and in the liver. The rate of disappearance of [14C]glucose and the concentration of insulin in the blood were not changed significantly by stimulation of the VMH. These data indicate that electrical stimulation of the VMH, but not the LH, enhances lipogenesis in BAT preferentially through a mechanism not involving insulin, but probably through activation of sympathetic innervation of BAT. The physiological significance of the findings is discussed in relation to hypothalamic function in controlling non-shivering thermogenesis and obesity.

Adipose Tissue↗
PubMed1982

Further studies on the mechanism of phosphorylase activation in rabbit liver in response to splanchnic nerve stimulation.

1. The mechanism of activation of liver phosphorylase after splanchnic nerve stimulation has been investigated in rabbits and compared with the effects of intraportal injections of noradrenaline.2. The increase in the activity of liver phosphorylase-a, the active form of this key glycogenolytic enzyme, in response to injections of noradrenaline was blocked by beta-adrenergic antagonists, but not by alpha-adrenergic antagonists, suggesting that the effect of noradrenaline is mediated mainly through beta-adrenoceptors in vivo. In contrast, the increase in phosphorylase activity in response to stimulation of the peripheral end of the splanchnic nerve was resistant to both alpha- and beta-adrenoceptor blockade.3. When diltiazem and verapamil, selective Ca(2+) antagonists that restrict calcium influx across the cell membrane, were infused intraportally, the phosphorylase response to splanchnic nerve stimulation was virtually abolished, while the response to noradrenaline was unaltered.4. Infusion of the prostaglandin-synthesis inhibitor indomethacin at a dose of 3.4 mug/min was found to block the activation of liver phosphorylase in response to stimulation of the splanchnic innervation.5. These results suggest that the mechanism whereby stimulation of the sympathetic innervation to the liver leads to activation of phosphorylase is not mediated by either alpha- or beta-adrenoceptors, but appears to depend upon prostaglandin formation and influx of Ca(2+) ions into the hepatocytes.

Adrenergic alpha-Antagonists↗
PubMed1982

Effects of acetylcholine injection into the hypothalamus on the insulin and glucagon release.

To evaluate the role of cholinergic neurones within the hypothalamus in modulating pancreatic-endocrine function, plasma levels of glucagon, insulin and glucose were measured after microinjection of acetylcholine into the ventromedial hypothalamic nucleus (VMH) of rabbits. Injection of acetylcholine (5 X 10(-8) mol in 2 microliter of saline) into the VMH of unanesthetized, unrestrained animals resulted in a prompt elevation of immunoreactive glucagon and glucose levels without any significant change in immunoreactive insulin level. The suppression of insulin secretion following cholinergic stimulation of the VMH was not counteracted by intravenous infusion of glucose (0.25 g/kg). Bilateral adrenalectomy prevented both hyperglucagonemia and hyperglycemia induced by the acetylcholine injection into the VMH. In adrenalectomized rabbits, exogenous glucose load was followed by a significant rise in the plasma insulin level despite the hypothalamic injection of acetylcholine. However, the response of insulin release to glucose load in these animals was much less than in adrenalectomized, saline-treated, control animals. These data support the conclusion that the action of acetylcholine within the hypothalamus on the pancreatic hormone secretions is mediated to a large part through sympatho-adrenomedullary activity. However, a part of the decreased insulin response to glucose may be mediated by direct innervation of the pancreas.

Acetylcholine↗
PubMed1982

Clinical evaluation of left ventricular performance in patients with myocardial infarction: comparison of hemodynamic responses to exercise and angiographic findings.

In order to evaluate the left ventricular performance during exercise in patients with myocardial infarction, we performed a symptom-limited multistage exercise test using a bicycle ergometer in the supine position on 82 patients with myocardial infarction, and their hemodynamic responses to exercise were analyzed. Patients were subdivided into three groups according to the levels of pulmonary capillary wedge pressure (PCWP) and cardiac index (CI) obtained at the end-point of the exercise: Group I (20 patients) with PCWP less than 18 mmHg and CI greater than or equal to 5.0 L/min/m2; Group II (32 patients) with PCWP greater than or equal to 18 mmHg and CI greater than or equal to 5.0 L/min/m2; Group III (30 patients) with PCWP greater than or equal to 18 mmHg and CI less than 5.0 L/min/m2. Exercise tolerance expressed as the duration of exercise was 11.9 +/- 0.5 (SEM) min in Group I, 10.6 +/- 0.4 in Group II and 7.8 +/- 0.5 in Group III, which was closely correlated with the left ventricular function observed at the end-point of the exercise. During exercise stroke volume index (SVI) decreased slightly in Group III, while it increased significantly in Groups I and II. The extent of coronary artery lesion in Group III was more severe than in Groups I and II. In 50 patients without prior myocardial infarction, infarct size estimated by total released CPK was larger in Group III than in Group I. These findings indicate that coronary artery lesion and infarct size are important factors contributing to left ventricular performance during exercise in patients with myocardial infarction.

Adult↗
PubMed1982

Clinical evaluation of left ventricular function in acute myocardial infarction--analysis of factors affecting left ventricular function.

The clinical significance of the possible factors which may affect the cardiac function and prognosis of the patients with acute myocardial infarction were evaluated in 112 patients with this disease. Patients were subdivided into 4 groups according to the levels of pulmonary capillary wedge pressure (PCWP) and left ventricular stroke work index (SWI): Group I (52 patients) PCWP less than 18 mmHg, SWI less than or equal to 30 g.m/m2; Group II (18 patients) PCWP greater than or equal to 18 mmHg, SWI greater than or equal to 30 g.m/m2; Group III (15 patients) PCWP less than 18 mmHg, SWI less than 30 g.m/m2; Group IV (27 patients) PCWP greater than or equal to 18 mmHg, SWI less than 30 g.m/m2. Immediate mortality rate (4 weeks after the onset of myocardial infarction) was 17.0% in all patients and Group IV had the highest mortality rate (48.1%), in contrast to the lowest mortality rate (3.8%) in Group I. The episodes of previous myocardial infarction were noted more frequently in Group IV (74.1%) than in Groups I (7.7%) and II (11.1%) (p less than 0.001). Mean age in Group IV (68.0 +/- 5.2 (SE) years) was also significantly higher than those of the remaining 3 groups (p less than 0.001). In 55 patients without previous myocardial infarction, mean infarct size estimated from total released creatine phosphokinase (CPK) (sigma CPK) in Group IV was largest among the 4 groups, although it was similar to that in Group II: 919.0 +/- 70.0 (SE) IU/ml in Group I, 1470.0 +/- 126.0 in Group II, 958.0 +/- 107.0 in Group III and 1493.0 +/- 145.0 in Group IV. The number of involved coronary arteries differed significantly between Groups I and IV: in Group I involved coronary artery (75% narrowing) was absent or one at most, while in Group IV all 9 patients had at least one coronary lesion and 3 of 9 had triple vessel disease. In this study no significant difference was observed between the incidence of anterior and inferior myocardial infarctions in Groups I, III and IV. Thus, we conclude that age, previous myocardial infarction, infarct size and the number of involved coronary arteries may determine the cardiac function in acute phase of myocardial infarction and hence, immediate mortality of this disease.

Adult↗
PubMed1982

[Visualization of intramyocardial blood flow distribution with contrast echomyocardiography].

To assess intramyocardial blood flow distribution by the contrast echocardiographic technique, we studied the effect of intracoronary injections of contrast agents on the echo intensity of the myocardium. As fundamental experiments, we made injections of ICG, urografin, artificial blood (FC-43) and microsphere into the coronary artery in open chest dogs and observed the changes in echo density of the myocardium. Bolus injection of 10 ml ICG into the coronary artery produced little change in the myocardial echo intensity, but bolus injection of 10 ml urografin, FC-43 and microsphere into the left circumflex coronary artery (LCX) and left anterior descending coronary artery (LAD) immediately increased the echo intensity of the left ventricular posterior wall (LVPW) and interventricular septum (IVS), respectively. Enhanced echo areas correlated well with the regions perfused by LCX and LAD, respectively. Clinically, we recorded two-dimensional echocardiograms during coronary arteriography (CAG) in 10 patients. In six of the 10 patients, the echo intensity of IVS increased during left CAG and in four of eight patients the echo intensity of LVPW increased during right CAG. Contrast echomyocardiography, contrast enhanced echocardiography of the myocardium, proved a useful technique for the evaluation of intramyocardial blood flow.

Animals↗
PubMed1981

Hypothalamic regulation of lipid metabolism in the rat: effect of hypothalamic stimulation on lipolysis.

In unanesthetized rats, electrical stimulation of the ventromedial hypothalamic nucleus (VMH) induced a marked increase in plasma concentration of glycerol, but did not increase the plasma free fatty acid (FFA) concentration, probably owing to a great elevation of plasma lactate which might inhibit the release of FFA from adipose tissue. In anesthetized rats, on stimulation of the VMH there was no remarkable increase in the plasma lactate, and the plasma glycerol and FFA concentrations were both elevated markedly. Electrical stimulation of the lateral hypothalamic nucleus (LH), on the other hand, had no significant effects on plasma glycerol and FFA levels. Bilateral adrenodemedullation did not prevent the lipolytic response to VMH stimulation, although it reduced slightly the increment of plasma glycerol and FFA. However, the lipolytic response was completely blocked by previous treatment of the animals with hexamethonium or propranolol, but not with phentolamine. These results suggest that sympathetic innervation of the adipose tissue is the dominant factor involved in VMH-induced lipolysis in the rat, while the role of the adrenal medulla is subdominant; the effect of VMH stimulation is mainly transmitted through the sympathetic nervous system to beta-adrenergic receptor of the adipose tissue.

Adrenal Medulla↗