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Biomedical subjects

H Maeta

Publications and source records attributed to H Maeta.

At least 73 records · Page 4Linked to original sources
PubMed1997

Imaging of the orifice of the left ventricular outflow tract: technique and initial results.

The mechanism of left ventricular outflow tract (LVOT) obstruction in the patient after mitral valve replacement or repair was examined with the aid of 2D echocardiography. For the interpretation of the spatial relationship between the aortic root and mitral annulus, however, the 2D display is sometimes inadequate since it may not simultaneously capture these structures in each center. We developed a method to clarify this relationship in 3D based on magnetic resonance images. We defined the office of the left ventricular outflow tract (LVOT orifice), consisting of, in turn, a muscular region, i.e., edge of the interventricular septum, and an annular region, i.e., the annulus of the anterior mitral leaflet. In this paper we present image data obtained from one of eight normal subjects examined and compare this with data of one of two patients who preoperatively suffered degenerative mitral regurgitation and subsequently underwent chordal-preserving mitral valve replacement, in which anterior chordae were reattached to the anterior annulus. In the normal subject, the mitral annulus exhibited a flexible change in shape during the systole, maintaining sufficient LVOT orifice size. In the patient, the prosthetic valve exhibited translational motion during systole, resulting in dynamic LVOT obstruction. This phenomenon was also observed in one other case. Furthermore, the lateral view of the LVOT orifice revealed a projection of the prosthetic valve into the LVOT, causing mechanical LVOT obstruction. The finding that translational motion of the prosthetic valve with an inflexible mitral annulus results in dynamic LVOT obstruction may support the hypothesis that annular rigidity causes dynamic LVOT obstruction after mitral valve repair with a rigid prosthetic ring.

Adult↗
PubMed1997

[Surgery of aortic arch aneurysm combined with other cardiovascular lesion].

From 1995 to 1996, we performed aortic arch replacement using antegrade cerebral perfusion under deep hypothermia in 7 patients, in whom 4 cases accompanied with cardiac lesion which treated simultaneously and 3 cases had abdominal aortic aneurysm. We compared the surgical results between cases with (group II, n = 4) and without (group I, n = 3) combined cardiovascular lesion. There is no difference between two groups in the cerebral perfusion time and the amount of bleeding and blood transfusion. The cardiac ischemic time and bypass time were insignificantly longer in group II than in group I. We experienced no early death and no cardiac and brain complication in both groups. Three cases with abdominal aortic aneurysm had two-staged operation successfully after arch surgery within a half year. In conclusion, we successfully treated aortic arch aneurysm even in patients combined with other cardiovascular lesion as well as in patients without that.

Aged↗
PubMed1996

Intravenously-injected naloxone reverses the decrease in renal sympathetic nerve activity seen during hypotensive hemorrhage in conscious rabbits by acting through central mechanisms.

The response of renal sympathetic nerve activity (RNA) to hemorrhage was examined in chronically-instrumented conscious rabbits. Hemorrhage was induced at a rate of 5 ml/kg per min until the mean arterial pressure fell below 40 mmHg. The mean arterial pressure then remained at around 80 mmHg until 10 ml/kg of hemorrhage (normotensive hemorrhage) before falling to below the pre-hemorrhagic control level (hypotensive hemorrhage). The RNA response showed a biphasic pattern, i.e., it increased during normotensive hemorrhage, then fell below the control level during hypotensive hemorrhage. To examine the mechanism involved in this decrease in RNA, naloxone (7.5 mumol/kg), an opioidergic receptor antagonist, was intravenously injected 1 min after the end of hemorrhage. Intravenous injection of naloxone caused an increase in mean arterial pressure and RNA to the level seen during normotensive hemorrhage. These results indicate that the decrease in RNA induced by hypotensive hemorrhage is mediated by opioidergic receptors. To determine whether the effects of naloxone are mediated via central or peripheral opioidergic receptors, naloxone was replaced by an equimolar solution of methylnaloxone, a form unable to cross the blood-brain barrier. Neither the mean arterial pressure nor RNA was significantly altered by administration of methyl naloxone. These results suggest that the effects of naloxone on both the RNA and the mean arterial pressure are mediated via central opioidergic receptors, i.e., the sympathoinhibition induced by hypotensive hemorrhage is mediated via the stimulation of central opioidergic receptors.

Animals↗
PubMed1996

Effects of cold preservation and reperfusion on microsomal cytochrome P-450-linked monooxygenase system of the rat liver.

The effects of cold preservation and reperfusion of the liver on the hepatic microsomal cytochrome P-450-linked monooxygenase system (P-450 system) were investigated. Rat livers were preserved with cold University of Wisconsin solution for 0, 12, 24, 36, and 48 hr. Half of them in 0-, 24-, and 48-hr groups were reperfused for 1 hr at 37 degrees C with oxygenated Krebs-Henseleit buffer. After preservation or reperfusion, the liver microsomes were prepared and the concentration of each component of the P-450 system [NADPH-cytochrome b5 reductase (b5 reductase), cytochrome b5 (b5), NADPH-cytochrome P-450 reductase (P-450 reductase) and cytochrome P-450 (P-450)] and their drug metabolizing activities and concentration of apo-cytochrome P-450 2E1 (apo-P-450 2E1) were measured. After 48-hr preservation, b5 concentration did not decrease, whereas the concentration of P-450, P-450 reductase, and b5 reductase decreased from 0.865 to 0.676 nmole/mg protein, from 0.262 to 0.233 micromole/mg protein/min and from 5.34 to 4.86 micromole/mg protein/min, respectively. During cold preservation, the activities of p-nitroanisole O-demethylase and aniline p-hydroxylase did not change. Aminopyrine N-demethylase activity was inhibited from 4.45 to 3.34 nmole/mg protein/min after 48-hr cold preservation. Apo-P-450 2E1 was gradually decreased during cold preservation. Reperfusion caused a further decrease in the activities and concentration of the components of the P-450 system and concentration of apo-P-450 2E1 to 80-90% after 1-hr reperfusion. It was suggested that the prolonged preservation caused deterioration of the P-450 system and the loss of the abilities of metabolism and detoxication of xenobiotics.

Animals↗
PubMed1996

Increase in portal blood interleukin-6 soon after the commencement of digestive surgery.

To determine whether cytokines produced in the operative field during digestive surgery selectively spill over into the portal blood, the changes in interleukin-6 (IL-6) levels in portal and peripheral venous blood were assayed at several points in time from the commencement of surgery until 14 days later, in 11 patients. Similar changes in the IL-6 levels were observed in the portal and peripheral blood samples; however, the IL-6 levels in the portal blood reached a maximum 6-12h after the commencement of surgery, being earlier than in the peripheral venous blood. In fact, between 3 and 12h after the commencement of surgery, the IL-6 levels were higher in the portal blood by 33-81 pg/ml. By 24h or more after the commencement of surgery, the IL-6 levels did not differ significantly in the two types of blood samples. Moreover, the C-reactive protein levels 2 days after surgery were even more closely correlated to the maximum IL-6 levels in the portal blood than to those in the peripheral venous blood. These results suggest that IL-6 produced during intra-abdominal digestive surgery initially enters the portal blood, being trapped by IL-6 receptors in the liver, where it may regulate the synthesis of acute-phase proteins as a hepatocyte-stimulating factor.

Adult↗
PubMed1996

Comparison of University of Wisconsin and University of Pittsburgh solutions for heart transplantation.

The effectiveness of University of Wisconsin (UW) and University of Pittsburgh (UP) solutions for the preservation of rat hearts was compared. Lewis rat hearts were preserved with UW (group A, n = 45) or UP (group B, n = 45) solution for 0 or 24 h and then transplanted heterotopically into the recipients' abdomen. Ten recipients in each group were observed to obtain 1-week graft survival rates. Tissue water content and tissue content of adenine nucleotides were measured 2 h after transplantation in six grafts from each group. Six hearts preserved for 0 h and seven hearts preserved for 24 h were taken from each group 24 h after grafting for histopathology. The 1-week graft survival rates of groups A24 and B24 were 60% and 10%, respectively. In the 24-h preserved grafts, adenosine triphosphate (ATP) and energy charge [(ATP + adenosine diphosphate/2)/(ATP + adenosine diphosphate + adenosine monophosphate)] of groups A and B were 0.972 +/- 0.165 and 0.200 +/- 0.123 mg/g wet tissue (P < 0.05) and 74.4% and 61.1% (P < 0.05), respectively. The tissue water content of group A24 was 71.7%, whereas that of group B24 was 74.1% (P < 0.05). Histopathology revealed more severe muscle edema and necrosis and infiltration of polymorphonuclear cells in group B24 than in group A24. We conclude that UW solution is more appropriate for rat heart preservation than UP solution.

Abdomen↗
PubMed1996

Impact of adhesion molecules of the selectin family on liver microcirculation at reperfusion following cold ischemia.

We investigated the role of adhesion molecules in the early phase of reperfusion following cold ischemia. Livers of male Lewis rats were preserved for 0 h (group A) or 24 h in University of Wisconsin (UW) solution without additives (group B) or in UW solution with anti-ICAM-1 antibody (group C) or anti-E-selectin-1, SLe(x) and SLe(a) antibodies (group D). The livers were then reperfused with diluted rat whole blood (DWB; groups A and B). DWB containing anti-ICAM-1 and LFA-1 antibodies (group C) or DWB containing anti-L-selectin, SLe(x) and SLe(a) antibodies (group D). The reperfusion was performed at 37 degrees C for 1 h at 5 cm H2O of perfusion pressure. During reperfusion, hepatic microcirculation was assessed by monitoring portal and peripheral tissue blood flow. Bile production was significantly reduced in group B livers compared with those in group A. Anti-ICAM-1 and LFA-1 antibodies failed to improve hepatic microcirculation, whereas anti-LECAM-1, SLe(x) and SLe(a) antibodies significantly improved the microcirculation. Bile production in group C and D livers was comparable to that in group B livers. Preservation for 24 h significantly increased the release of TNF-alpha from 0.207 to 43.7 pg/g per hour during reperfusion. Monoclonal antibodies to the adhesion molecules did not suppress the release of TNF-alpha in groups C and D. Histological examination demonstrated a lack of leukocyte infiltration or thrombus in hetapic microvessels. The extent of hepatocyte necrosis did not differ among groups B, C, and D. We conclude that the microcirculatory disturbance in the early phase of reperfusion occurs as a result of the tethering of leukocytes through the interaction of the selectin family and their ligands, and that the ICAM-1-LFA-1 pathway is not involved in this step. The lack of improvement in bile production with antibodies to the selectin family and their ligands strongly suggests that other mechanisms participate in the deterioration of hepatic function.

Adenosine↗
PubMed1996

Protective effects of antithrombin III supplementation on warm ischemia and reperfusion injury in rat liver.

The effect of antithrombin III (AT III) supplementation on energy status, microcirculation, cytoprotection, and prostacyclin (PGI2) production during and after a period of warm ischemia of the rat liver was investigated. AT III supplementation (250 units/kg) stimulate prostaglandin I2 (PGI2) production from 1 hour after administration, with maximal production observed at 3 hours. Ischemia was induced by occluding the hepatoduodenal ligament for 30 minutes, and experiments were continued for 60 minutes after reperfusion. The rats received AT III (250 units/kg IC) 30 minutes before induction of liver ischemia (AT III group). In the AT III group, recovery of the beta-ATP/inorganic phosphate ratio measured by 31P nuclear magnetic resonance showed significant improvement (p < 0.01), and the recovery of tissue blood flow markedly improved (p < 0.01) compared to the saline-treated group (control group). Leakages of aspartame aminotransferase, alanine aminotransferase, and lactate dehydrogenase were mitigated in the AT III group (p < 0. 05). Ultrastructural alterations of sinusoidal endothelial cells were markedly reduced in the AT III group. The PGI2 level at the end of reperfusion was significantly elevated (p < 0.01) in the AT III group compared to the control group. The results of this study indicated that pretreatment with AT III significantly improved the energy status and microcirculation, as well as histologic damage, after liver ischemia and reperfusion. One of the fundamental effects of AT III might be mediated through the production of prostacyclin.

6-Ketoprostaglandin F1 alpha↗
PubMed1996

[A case of new stenosis in the distal portion following transaortic patch angioplasty for the left main coronary stenosis].

A 75-year-old man who had unstable angina underwent transaortic vein patch angioplasty for isolated 60% stenosis of the left main coronary artery. About four months after the operation, he developed effort angina and angiographycally new stenosis was detected in the distal portion of patch dilatation. So he underwent emergency aorto coronary bypass grafting. Transaortic patch angioplasty is attractive technique because of restoration of the original antegrade coronary flow, but this direct surgical approach may induce the stimulation of intima, and may injure the intima. It is important to bear this technique in the mind for selected patients with left main coronary lesions.

Aged↗
PubMed1995

Simultaneous occurrence of medullary carcinoma and papillary carcinoma of the thyroid.

We report a case of simultaneous occurrence of medullary carcinoma and papillary carcinoma of the thyroid in the same thyroid gland. Immunoreactivity of calcitonin, carcinoembryonic antigen, neuron specific enolase and thyroglobulin made a sharp distinction between both neoplasms of the thyroid. It appears reasonable to consider that simultaneous occurrence of medullary carcinoma and papillary carcinoma of the thyroid in this case does not have embryological or genetical significance.

Carcinoma, Medullary↗
PubMed1995

Effects of left intraatrial infusion of prostaglandin E1 after open-heart surgery.

The hemodynamic effects of a left intraatrial infusion of prostaglandin E1 (PGE1) given to ten patients after open-heart surgery (LA group), were compared with those following no treatment in a control group of ten patients, and to those following a right intraatrial infusion given to another ten patients (RA group). PGE1 was infused at a rate of 0.03 microgram/kg/min in the RA group and at 0.003 microgram/kg/min in the LA group, and hemodynamics were measured immediately after surgery, then 3, 6, and 12 h after the PGE1 infusion was commenced. The heart rate, right atrial pressure, left atrial pressure, and mean pulmonary arterial pressure remained almost unchanged in all three groups; however, the mean radial arterial pressure and systemic vascular resistance index decreased, and the cardiac index increased in the RA and LA groups. The pulmonary vascular resistance index decreased only in the LA group. Thus, a much smaller dose of PGE1, being one-tenth of that used for the right atrial infusion, administered directly into the left atrium yielded almost the same hemodynamic effects as the larger dose infused into the right atrium. Furthermore, this method of infusing PGE1 is safe, efficacious, and cost-efficient.

Adult↗
PubMed1995

Development of a fistula between an internal mammary artery graft and the pulmonary vasculature following coronary artery bypass grafting: report of a case.

We report herein the rare case of a 56-year-old man who gradually developed congestive cardiac failure 6 months after undergoing coronary artery bypass grafting and was found to have a fistula between the internal mammary artery and the pulmonary artery of the upper lobe diagnosed by selective left internal mammary arteriogram. A second sternotomy was performed and demonstrated dense adhesion between the fissure surrounding the internal mammary artery and the upper lobe, and the fistula was resected. We believe that the patient's increasing cardiac failure was almost certainly caused by coronary seal.

Arterio-Arterial Fistula↗
PubMed1995

Prediction of the early prognosis of the hepatectomized patient with hepatocellular carcinoma with a neural network.

The early prognosis of the hepatectomized patients with hepatocellular carcinoma was determined preoperatively with a perceptron-type neural network. The neural network was trained with the preoperative data of 54 example cases with the early prognosis, successful or died of hepatic dysfunction, as teaching signals. After learning these examples, the neural network came to give a precise prediction to the example data except for one case. With the learned neural network, the outcomes of the hepatectomy of 11 patients (10 successful; 1 died) were predicted prospectively with 100% precision. The usefulness of the neural network for the prediction was determined.

Adult↗