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Biomedical subjects

S Miki

Publications and source records attributed to S Miki.

At least 91 records · Page 5Linked to original sources
PubMed1995

Left ventricular function after mitral valve replacement with or without chordal preservation.

The clinical significance of the chordae tendinae regarding postoperative left ventricular performance was evaluated in 148 patients with mitral regurgitation or mitral stenosis who underwent either mitral valve replacement using St. Jude Medical valve with complete chordal preservation, or with conventional mitral valve replacement, or valve repair. Mitral valve replacement preserving the autologous chordae tendinae (n = 28) or replacing them with Gore-Tex sutures (n = 16) was performed in 44 patients, 24 with mitral regurgitation and 20 with mitral stenosis. Their hemodynamic parameters were compared to those of patients who underwent conventional mitral valve replacement involving 25 with mitral regurgitation and 28 with mitral stenosis, or who underwent valve repair in 24 with mitral regurgitation, or commissurotomy in 27 patients with mitral stenosis. The LV performance was analyzed by cineangiography in the early (mean 1.2 months), and by multiple gated blood scintigraphy (MUGA), or echocardiography (UCG) in the late postoperative periods (mean 5.4 years) in the three groups of patients. In the mitral regurgitation group, the LV ejection fraction (EF) was unchanged in the chordal preserved group, but it was decreased in the conventional replacement and repair groups. The LV contractility index was better in the chordal preserved than in the conventional group. Both the LVEF by MUGA, and LV fractional shortening (FS) by UCG were significantly higher after chordal preservation or repair than after conventional valve replacement. The chordal preserved group exhibited superior LV performance than the conventional group, especially in those with mitral regurgitation and depressed preoperative left ventricular function (EF < 0.50). There were no significant difference between the three groups in patients with mitral stenosis. The results support the concept that maintenance of continuity between the mitral annulus and the papillary muscle has a beneficial effect on postoperative left ventricular performance, especially in patients with mitral regurgitation and depressed preoperative left ventricular function, but had no major effect in patients with mitral stenosis.

Adult↗
PubMed1994

Imposing deviant immunity on the presensitized state.

Delayed hypersensitivity (DH) is an important immune effector modality that successfully wards off intracellular pathogens and many parasites, but also causes immunopathogenic injury to vital tissues. Particularly in the eye, DH has devastating effects that can lead to blindness. Ags injected into the anterior chamber of the eye of naive mice elicit a deviant form of systemic immunity in which DH is selectively down-regulated. Expression of DH in this model system is curtailed by regulatory CD8+ T cells. At present, we have determined whether injection of Ag into the anterior chamber of eyes of specifically sensitized mice also impairs DH expression. Our results indicate that DH is blunted or eliminated in previously primed mice when heterologous proteins, retinal autoantigens, or minor histocompatibility Ags are injected into the anterior chamber. Suppression is achieved in this system by Ag-specific CD8+ T cells, and failed DH can be imposed on immunized mice by i.v. injections of peritoneal exudate cells pulsed with Ag in vitro in the presence of TGF-beta. Thus, the immune regulatory mechanisms that operate to protect the eye from immunogenic inflammation can be invoked in previously sensitized mice. In addition, tolerance could not be generated in presensitized mice by either i.v. injection of soluble Ag or painting of hapten on UVB-exposed skin. It seems that the strategies used by the eye to create a deviant state of immunity in the face of pre-existing conventional immunity may be unique.

Animals↗
PubMed1994

Modulation of substance P/neurokinin-1 receptor in human astrocytoma cells by antisense oligodeoxynucleotides.

1. An antisense oligodeoxynucleotide corresponding to the NH2-terminus of the substance P (SP)/neurokinin-1 (SP/NK1) receptor was constructed and added to cultures of human astrocytoma U-87 MG cells in vitro and rats in vivo. 2. Antisense oligodeoxynucleotide at a concentration of 30 microM progressively reduced the specific binding [3H][Sar9, Met(O2)11]-SP, selective SP/NK1 receptor agonist, in the U-87 MG astrocytoma cells by approx. 31% on the second day after treatment (control: 26.1 +/- 2.4 fmol/mg protein vs antisense oligodeoxynucleotide: 18.0 +/- 1.4 fmol/mg protein, P < 0.001). 3. Treatment with 30 microM antisense oligodeoxynucleotide for 2 days inhibited the SP/MK1 receptor-induced influx of 45Ca2+ into the U-87 MG cells by approx. 35%. 4. When the same antisense oligodeoxynucleotides were encapsulated in liposomes and injected into the lateral cerebral ventricle of rats, functional SP receptor was blocked.

Animals↗
PubMed1994

Successful repair of the right atrial isomerism, double outlet right ventricle, common atrioventricular canal, pulmonary stenosis, and total anomalous pulmonary venous connection.

A 6-year-old boy was successfully operated on for double outlet ventricle, common atrioventricular canal with severe valvular regurgitation, right atrial isomerism, L-loop ventricles, total anomalous pulmonary venous connection, and pulmonary stenosis with hypoplastic left pulmonary artery. The interventricular rerouting from the left ventricle to the ascending aorta was performed with a spiral patch, the interatrial switching was performed by a Mustard patch, the common atrioventricular orifice was partitioned and valve repair was performed, and an 18-mm valved conduit was inserted between the right ventricle and the pulmonary artery. Although the patient had a small residual ventricular septal defect and pulmonary stenosis, the patient is alive and well.

Abnormalities, Multiple↗
PubMed1994

Protective effect of continuous retrograde cerebral perfusion on the brain during deep hypothermic systemic circulatory arrest.

Deep hypothermic circulatory arrest has been widely used as an adjunct for surgery of the aortic arch to protect the brain and other vital organs. We introduced the use of continuous retrograde cerebral perfusion via the superior vena cava during deep hypothermic circulatory arrest in 1987 and have used it in 33 patients. Continuous retrograde cerebral perfusion times ranged from 10 to 89 minutes (mean 40.2 +/- 22.5), and minimal nasopharyngeal temperatures ranged from 14 to 25 degrees C (mean 17.4 +/- 2.0). Two patients with a ruptured aneurysm died during operation due to bleeding and two other patients, with continuous retrograde cerebral perfusion time of 24 and 35 minutes, died 1 month postoperatively due to preoperative liver cirrhosis and sepsis. Two patients suffered from stroke. The remaining 27 patients, including 6 with from 60 to 82 minutes of continuous retrograde cerebral perfusion, had no complications related to continuous retrograde perfusion. During continuous retrograde cerebral perfusion, 66 pairs of blood samples from the perfusate and from the drainage back to the arch vessels were obtained. Analysis of these samples revealed that partial pressure of oxygen, saturation of oxygen, and oxygen content significantly decreased (p < 0.001), and partial pressure of carbon dioxide (CO2) and CO2 content significantly increased (p < 0.001). The nasopharyngeal temperature gradually increased at the rate of 0.01 to 0.03 degree C/min, but was maintained below 20 degrees C. These results reflect the fact that the aerobic metabolism of the brain is maintained during continuous retrograde cerebral perfusion due to oxygen and substrate availability. This technique offers the potential of metabolic support to the brain during deep hypothermic circulatory arrest and prolongs the safe time limits of deep hypothermic circulatory arrest in surgery of the aortic arch.

Adult↗
PubMed1994

Large left-to-right shunt through a small atrial septal defect produced by progressive aortic stenosis in the elderly--a case report.

We present a 74-year-old female who showed a large left-to-right shunt through a small atrial septal defect presumably due to diastolic dysfunction of the left ventricle caused by the progression of aortic stenosis. Accordingly, elderly patients with even small atrial septal defect should be followed carefully, since diastolic dysfunction of the acquired left ventricular disorder could increase the left-to-right shunt.

Aged↗
PubMed1994

[Proliferation of pulmonary fibroblasts obtained from rats with bleomycin-induced pulmonary fibrosis and effects of rat rIL-1 alpha on this proliferation].

To clarify the mechanism of pulmonary fibrosis, the growth rate of fibroblasts obtained from bleomycin (BLM)-treated rats was compared with that of fibroblasts obtained from control rats. Proliferation of fibroblasts obtained from rats at 4 days after BLM instillation (BRF) was significantly more rapid than that of fibroblasts obtained from rats at 4 days after saline instillation (CRF), as assessed by cell counting and 3H-TdR incorporation. CRF and BRF were separated by the method of discontinuous Percoll gradients. Three fibroblast fractions of specific gravity (S.G.), S.G. < 1.036, 1.036 < or = S.G. < 1.050, 1.050 < or = S.G. < 1.062, were obtained. Percentages of the densest fibroblast fraction were 46.2 +/- 5.2 in BRF and 6.4 +/- 2.8 in CRF. The densest fibroblasts in BRF proliferated more rapidly than the least dense fibroblasts. Rat rIL-1 alpha suppressed the proliferation of CRF and BRF, dose dependently. These results suggest that an increase in the densest fibroblasts in the lung might correlate with BLM-induced pulmonary fibrosis and that IL-1 alpha suppresses the proliferation of pulmonary fibroblasts.

Animals↗
PubMed1994

[Intraoperative pulmonary angioscopy to undergo pulmonary embolectomy for acute massive pulmonary embolism].

An urgent pulmonary embolectomy on a patient under intraoperative angioscopy for the treatment of massive pulmonary embolism was performed and successfully saved the patient. The case was a 19-year-old man who had been bedridden over along period of time. He developed pulmonary embolism immediately after the initiation of walking rehabilitation. Although anticoagulation therapy was immediately carried out, hemodynamics deteriorated, and as a result, it became necessary to treat this patient with the urgent surgical procedure. Under extracorporeal circulation with the clamping of the aorta, the pulmonary artery was opened. Following embolectomy for the left pulmonary artery, the right pulmonary artery, where the presence of clots had not been confirmed with the naked eye, was inspected using an flexible fiberoptic choledochoscope 4.9 mm in diameter. Consequently, amount of clots were removed using forceps or an aspirating tube. The patient recovered from hypoxemia after surgery. The use of intraoperative angioscopy in the pulmonary artery proved to be very useful to examine the presence of emboli up to tertiary branches of pulmonary artery.

Acute Disease↗
PubMed1994

Reduction of homologous blood transfusion in reoperative valve surgery.

From April 1979 to October 1993, 126 adult patients underwent reoperative cardiac valve surgery. Patients were divided into two groups: 53 patients who underwent surgery before January 1990 (group 1) and 73 patients who underwent surgery after January 1990 (group 2). After January 1990, a clinical strategy for reducing homologous blood transfusions was implemented, including the use of predonation of autologous blood in the operating room, reduced heparin doses, an elevated threshold of indication for blood transfusion, and autotransfusion of shed, drained blood after surgery. In group 1, 44 patients (93.0%) received an average of 3785 +/- 1251 ml of homologous blood transfusions. In group 2, only 26 patients (35.6%) needed homologous blood transfusions and had a smaller amount (2985 +/- 1521 ml) on average. Furthermore, only seven patients needed fresh blood transfusion in group 2.

Adult↗
PubMed1994

Mitral valve replacement with maintenance of mitral annulopapillary muscle continuity in patients with mitral stenosis.

Postoperative left ventricular performance was evaluated in patients with mitral stenosis who underwent mitral valve replacement with maintenance of the continuity of the mitral anulus and papillary muscles. Mitral valve replacement with preservation of autologous chordae tendineae (n = 7) or their replacement with expanded polytetrafluoroethylene sutures (n = 14) was performed in 21 patients with mitral stenosis. Hemodynamic parameters were compared with those of 28 patients who underwent conventional mitral valve replacement and 27 patients who underwent open mitral valve commissurotomy. No deaths occurred in the early or late follow-up period. All hemodynamic parameters were improved after the operation, and no significant differences were detected among the three groups with regard to postoperative cardiac index or mitral valve area. No significant differences were observed in left ventricular end-diastolic volume index, end-systolic volume index, or contractility index, but the postoperative left ventricular ejection fraction in the chordal preservation and open commissurotomy groups was greater than that in the group having conventional mitral valve replacement. Postoperative regional shortening was greatest at the diaphragmatic portion in the chordal preservation group and at the long axis in the open commissurotomy group. In the mid-term postoperative period, although no differences were noted among the three groups in echocardiographic data or global ejection fraction measured by multigated equilibrium radionuclide angiography, the regional shortening at the anterolateral portion of the left ventricle in the chordal preservation and commissurotomy groups was greater than that in the group having conventional mitral valve replacement. Postoperative radionuclide angiography during exercise failed to demonstrate any difference between the ejection fraction in the chordal preservation group and that in the group having conventional mitral valve replacement.

Adult↗
PubMed1994

[Staggered intensive chemotherapy using arbekacin, fosfomycin and ceftazidime on polymicrobial infections involving MRSA].

Bacteriological and clinical studies were carried out on staggered intensive chemotherapy regimen for methicillin-resistant Staphylococcus aureus (MRSA) infections combined with Gram-negative opportunistic pathogens as polymicrobial infections. The regimen consisted of administering ceftazidime (CAZ) 30 minutes after infusion of arbekacin (ABK) and a bolus injection of fosfomycin (FOM). The combination of these drugs strongly inhibited the growth of MRSA and Pseudomonas aeruginosa. By this combination treatment, both of MRSA and P. aeruginosa in mixed culture became more susceptible to killing by macrophages. We evaluated the clinical efficacy and safety of combination of ABK, FOM and CAZ in the treatment of 15 patients with MRSA infections. The total efficacy rate was 80.0% and the bacterial eradication rate of MRSA was 60.0%. It is considered that staggered intensive chemotherapy with ABK, FOM and CAZ is useful for such polymicrobial infections involving MRSA.

Aged↗
PubMed1994

[Effect of low calcium diet on blood pressure and pressure natriuresis response in rats: role of the renin-angiotensin system].

Dietary Ca is an important modulator of arterial blood pressure in humans and rats. Since the kidney plays a key role in the pathogenesis of hypertension, the effect of a low Ca diet (0.01%Ca) on blood pressure and pressure natriuresis response was studied in Sprague-Dawley rats. In addition, a possible role of the renin-angiotensin system in the development of hypertension and an altered pressure natriuresis response resulting from low dietary Ca intake was investigated. In the low Ca diet group, systolic blood pressure determined by the tail-cuff method was significantly higher than in the normal Ca diet group (1.1%Ca) 1 week after the diet (113.0 +/- 7.1 vs. 105.0 +/- 9.5 mmHg, p < 0.05). Furthermore, low dietary Ca treatment significantly inhibited the water and sodium excretory responses to acute elevation of renal perfusion pressure. Treatment with an inhibitor of angiotensin converting enzyme, captopril (30 mg/kg/day), attenuated both the development of hypertension and the reduced pressure natriuresis response observed in Ca-deficient rats. Although plasma renin activity was not different between the low and normal Ca diet groups after the 2-week dietary regimen, the pressor response to angiotensin II injection was significantly greater in the low Ca diet group. These results indicate a possible involvement of the renin-angiotensin system in the development of hypertension and the inhibitory effects of the pressure natriuresis response caused by low dietary Ca intake, via enhanced sensitivity to angiotensin II.

Animals↗
PubMed1993

Expression of receptors for advanced glycosylation end products on renal cell carcinoma cells in vitro.

Proteins that have been modified by long-term expose to glucose accumulate advanced glycosylation end products (AGEs) as a function of protein age. In these studies, we have examined the interaction of AGE-protein with renal cell carcinoma cells (RCC) in vitro, using AGE-modified bovine serum albumin (AGE-BSA) as a probe. AGE-BSA showed tendency to induce in vitro cell growth of RCC cells and promoted the production of interleukin-6 (IL-6), an in vitro autocrine growth factor. Reverse transcriptase-polymerase chain reaction analysis revealed that RCC cells used here express mRNA for a receptor for AGEs (RAGE). These results suggested that AGEs taken up through RAGE on RCC cells might play a role in promoting the growth of RCC cells.

Adenocarcinoma, Clear Cell↗
PubMed1993

Age, sex and source of hamster affect experimental cholesterol cholelithiasis.

In the present study, we examined the effect of the following factors on a hamster model of cholesterol cholelithiasis: (i) the source of the golden Syrian hamsters (Sasco, Omaha, NE or Charles River, Wilmington, MA), (ii) the sex of the experimental animals and (iii) their age (4 wk vs. 8 wk of age). All hamsters were fed a semipurified diet which contained cholesterol (0.3%) and palmitic acid (1.2%). No cholesterol gallstones formed in any of the female hamsters regardless of age or source. The 4-week-old male hamsters from Sasco had the greatest incidence of gallstones (93%). The 8-week-old male hamsters tended to have a lower incidence of cholesterol gallstones than the younger ones, regardless of the commercial supplier (67 vs. 93% for Sasco and 27 vs. 40% for Charles River). Female hamsters had higher liver and serum cholesterol levels than the male hamsters; Charles River hamsters had lower serum cholesterol concentrations than the Sasco animals. Total biliary lipid concentrations were highest in Sasco male hamsters, but biliary cholesterol (mol%) was lower in the males than in the females (4.2-4.5% vs. 6.1-7.1%) regardless of age. The cholesterol saturation indices were higher in the Sasco females than the corresponding males; these values were lower in the Sasco hamsters than the Charles River animals, regardless of age or sex. The male Sasco hamsters had a higher total biliary bile acid concentration (98.9 mg/mL) than the Sasco females (58.9 mg/mL) and the Charles River animals (24.6 mg/mL for males and 38.2 mg/mL for females). The percentage of chenodeoxycholic acid in bile was significantly lower, and the percentage of cholic acid was higher in all females as compared to males.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1993

Replacement of chordae tendineae using expanded polytetrafluoroethylene (ePTFE) sutures during mitral valve replacement in patients with severe mitral stenosis.

Since September 1991, 20 patients with mitral stenosis underwent mitral valve replacement and chordal replacement with expanded polytetrafluoroethylene (ePTFE) sutures. The continuity between the papillary muscles and the mitral annulus was maintained by four mattress sutures of ePTFE, which connected the stumps of the papillary muscle heads to the mitral annulus at the 2, 4, 8, and 10 o'clock positions. Low profile bileaflet prosthetic valves were inserted. There was no mortality either in-hospital or during follow-up. There was no valve related morbidity, such as valve structural failure, thromboembolism, anticoagulant related hemorrhage, prosthetic valve endocarditis, or posterior left ventricular rupture. The technique of replacing chordae tendineae is described in detail.

Chordae Tendineae↗
PubMed1993

Ischemic preconditioning is associated with a delay in ischemia-induced reduction of beta-adrenergic signal transduction in rabbit hearts.

BACKGROUND: It has been reported that the A1-adenosine receptor mediates the cardioprotective effect of ischemic preconditioning. This receptor couples inhibitory guanine nucleotide-binding protein (Gi) and inhibits adenylate cyclase activity. However, the role of adenylate cyclase in preconditioning is unknown. METHODS AND RESULTS: We compared the effects of ischemia on the sarcolemmal beta-adrenergic receptor density (Bmax), the stimulatory guanine nucleotide-binding protein (Gs) activity as determined by reconstitution with S49 lymphoma cyc- membranes, and baseline and maximally stimulated adenylate cyclase activities (ACAs) in control and preconditioned rabbit hearts. The control population (n = 28) received 0, 10, 20, and 60 minutes of coronary occlusion (n = 6 to 8 per stage), and preconditioned rabbits (n = 24) received two cycles of alternating 5-minute occlusion and reperfusion before sustained ischemia (n = 6 per stage). In control hearts, occlusion induced rapid and progressive reductions in the Bmax, Gs, and ACAs after 10 to 60 minutes of ischemia. Preconditioning did not affect the reduction in Bmax, but it preserved reductions in Gs activity and ACAs after 10 to 20 but not 60 minutes of sustained ischemia. In another study, 18 rabbits were treated with pertussis toxin 48 hours before surgery to block Gi. During treatment, no significant difference was observed in the ischemia-induced reduction in ACAs in the ischemic region between control (n = 8) and preconditioned (n = 10) animals after 20 minutes of ischemia. CONCLUSIONS: Preconditioning delays ischemia-induced reductions in beta-adrenergic signal transduction. Inhibition of ACA is not the target effect of the A1-adenosine receptor-Gi pathway responsible for the cardioprotective role of preconditioning.

Adenylate Cyclase Toxin↗