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Biomedical subjects

S Maki

Publications and source records attributed to S Maki.

At least 37 records · Page 2Linked to original sources
PubMed1999

[A case report of concomitant operation of minimally invasive direct coronary artery bypass and left lower lobectomy].

A 72-year-old man was admitted complaining of laryngeal discomfort. A coronary angiogram showed a total occlusion of the LAD, a 90% stenosis of the 1st diagonal branch and well-developed collaterals from the LCX to the LAD. A chest X-ray showed a consolidation with unclear border at the left hilus of the lung. A lung biopsy through the bronchus revealed an adenocarcinoma of the left lower lung. He underwent a concomitant CABG operation without a cardiopulmonary bypass and a left lower lobectomy with lymph node dissection. The CABG was performed by left anterior small thoracotomy in the supine position and the lobectomy was performed by left posterolateral thoracotomy in the right lateral position. An intraoperative postural conversion was useful to obtain a good field in each operation and to prevent hemodynamic deterioration due to heart compression.

Adenocarcinoma↗
PubMed1998

Predictors of sudden cardiac death in hypertrophic cardiomyopathy.

Patients with hypertrophic cardiomyopathy (HC) die suddenly. Proposed risk factors for sudden cardiac death (SCD) in HC are youth, a family history of SCD, syncope, and ventricular tachycardia. Hemodynamic variables have not convincingly proved to be risk factors for SCD. Therefore, this study was designed to examine predictors of SCD in a large number of patients with HC during long-term follow-up periods. The relation of studied variables (clinical, electrocardiographic, echocardiographic, hemodynamic, and exercise test findings) to SCD in 309 patients with HC who were initially diagnosed during 1971 through 1994 (mean follow-up 9.4 years) was examined by multivariate analysis. SCD occurred in 28 patients. Independent predictors of SCD were a smaller difference between peak and rest systolic blood pressure during exercise testing (p=0.006), and higher left ventricular outflow tract pressure gradient at rest (p=0.003). Exercise-related SCD occurred in 8 patients and exercise-unrelated SCD in 20 patients (mean age 28 vs 47 years, p <0.05). Thus, patients of exercise-related SCD were younger and had smaller increases in systolic blood pressure during exercise testing, whereas patients with exercise-unrelated SCD were older and had higher left ventricular outflow tract pressure gradient.

Adolescent↗
PubMed1998

DNA polymerase II (epsilon) of Saccharomyces cerevisiae dissociates from the DNA template by sensing single-stranded DNA.

Two forms of DNA polymerase II (epsilon) of Saccharomyces cerevisiae, Pol II* and Pol II, were purified to near homogeneity from yeast cells. Pol II* is a four-subunit complex containing a 256-kDa catalytic polypeptide, whereas Pol II consists solely of a 145-kDa polypeptide derived from the N-terminal half of the 256-kDa polypeptide of Pol II*. We show that Pol II* and Pol II are indistinguishable with respect to the processivity and rate of DNA-chain elongation. The equilibrium dissociation constants of the complexes of Pol II* and Pol II with the DNA template showed that the stability of these complexes is almost the same. However, when the rates of dissociation of the Pol II* and Pol II from the DNA template were measured using single-stranded DNA as a trap for the dissociated polymerase, Pol II* dissociated 75-fold faster than Pol II. Furthermore, the rate of dissociation of Pol II* from the DNA template became faster as the concentration of the single-stranded DNA was increased. These results indicate that the rapid dissociation of Pol II* from the DNA template is actively promoted by single-stranded DNA. The dissociation of Pol II from the DNA template was also shown to be promoted by single-stranded DNA, although at a much slower rate. These results suggest that the site for sensing single-stranded DNA resides within the 145-kDa N-terminal portion of the catalytic subunit and that the efficiency for sensing single-stranded DNA by this site is positively modulated by either the C-terminal half of the catalytic subunit and/or the other subunits.

Amino Acid Sequence↗
PubMed1998

Plugging interactions of HAP2 pentamer into the distal end of flagellar filament revealed by electron microscopy.

Bacterial flagellum has a cap structure tightly attached to its distal end. The cap is an oligomeric assembly of HAP2 protein (also called FliD) and plays an essential role in the filament growth in vivo by preventing flagellin monomers from leaking out without polymerization. Electron micrographs of the HAP2 complex formed in solution showed exclusively a pentagonal shape, called "star-cap", which was thought to be the end-on view of the cap. The molecular mass roughly corresponded to a dodecamer of HAP2, and therefore a double-layered star-cap was modeled to be the cap. Here, we have observed the side view of the complex in electron micrographs. The images clearly show a rectangular shape, about 80 A wide and 180 A long, with a bipolar feature in its long axis, indicating that the complex is a bipolar pair of pentamers. A thin plate feature is identified at each end of the particle, which looks exactly like the one observed as the structure of the native filament cap. Together with the structure of the filament previously analyzed by electron cryomicroscopy, the results suggest that the cap is a pentamer with its thin plate exposed to the solvent and the other half plugged into the hole at the distal end of the filament, which is almost twice wider than its central channel. This also allows us to model the axial domain arrangement of flagellin subunit in the filament.

Bacterial Proteins↗
PubMed1998

A novel and practical route to A-ring enyne synthon for 1 alpha,25-dihydroxyvitamin D3 analogs: synthesis of A-ring diastereomers of 1 alpha,25-dihydroxyvitamin D2 and 3-methyl-1,25-dihydroxyvitamin D3.

A novel and practical route to the A-ring enyne synthon (2), which can be versatile for a variety of A-ring analogs of 1 alpha,25-dihydroxyvitamin D3 (1), was developed. This novel method led to an improved synthesis of the A-ring diastereomers of 1, the compounds 13-15, and synthesis of the new analogs, 2-methyl-1,25-dihydroxyvitamin D3 (4) with its all possible diastereomers. The biological evaluation of the 2-methyl analogs showed the alpha alpha beta-isomer to be more potent than 1.

Calcitriol↗
PubMed1998

The second subunit of DNA polymerase III (delta) is encoded by the HYS2 gene in Saccharomyces cerevisiae.

DNA polymerase III (delta) of Saccharomyces cerevisiae is purified as a complex of at least two polypeptides with molecular masses of 125 and 55 kDa as judged by SDS-PAGE. In this paper we determine partial amino acid sequences of the 125 and 55 kDa polypeptides and find that they match parts of the amino acid sequences predicted from the nucleotide sequence of the CDC2 and HYS2 genes respectively. We also show by Western blotting that Hys2 protein co-purifies with DNA polymerase III activity as well as Cdc2 polypeptide. The complex form of DNA polymerase III activity could not be detected in thermosensitive hys2 mutant cell extracts, although another form of DNA polymerase III was found. This form of DNA polymerase III, which could also be detected in wild-type extracts, was not associated with Hys2 protein and was not stimulated by addition of proliferating cell nuclear antigen (PCNA), replication factor A (RF-A) or replication factor C (RF-C). The temperature-sensitive growth phenotype of hys2-1 and hys2-2 mutations could be suppressed by the CDC2 gene on a multicopy plasmid. These data suggest that the 55 kDa polypeptide encoded by the HYS2 gene is one of the subunits of DNA polymerase III complex in S.cerevisiae and is required for highly processive DNA synthesis catalyzed by DNA polymerase III in the presence of PCNA, RF-A and RF-C.

Amino Acid Sequence↗
PubMed1998

A 4-year study of plasma ochratoxin A in a selected population in Tokyo by immunoassay and immunoaffinity column-linked HPLC.

Employing a competitive ELISA (cELISA) based on monoclonal antibody and a novel immunoaffinity-column (IAC)-linked HPLC-fluorometry, ochratoxin A (OTA) levels in the plasma of 184 healthy volunteers (130 males, 54 females) were surveyed in Tokyo during the 4 years from 1992 to 1996. It was found that 85% of the cases were positive for OTA except 38% in 1994, and an average value in the positives was estimated as 68 pg/ml. This suggests that the population in Tokyo is exposed to OTA at high frequency, although the level in plasma is far less than that reported in Europe and Canada. A partial contribution of fermented dietary foodstuffs, coffee and wine is suspected as the source of the OTA observed in the human plasma.

Chromatography, Affinity↗
PubMed1998

Exercise-induced abnormal blood pressure responses are related to subendocardial ischemia in hypertrophic cardiomyopathy.

OBJECTIVES: We examined by thallium-201 scintigraphy whether exercise-induced abnormal blood pressure response (BPR) is related to myocardial ischemia. BACKGROUND: Hemodynamic instabilities during exercise in patients with hypertrophic cardiomyopathy (HCM) are considered to be caused by abnormal reflex control of vascular resistance. METHODS: In 105 patients with HCM, exercise thallium scintigraphy was performed by means of a multistage, symptom-limited bicycle ergometer exercise test. RESULTS: Eighty-eight patients had normal BPR (> or = 25 mm Hg from baseline to peak exercise), and 17 had abnormal BPR (<25 mm Hg). Clinical characteristics including age, the prevalence of obstruction, New York Heart Association functional class and echocardiographic measurements were similar between the two groups. Left ventricular end-diastolic pressure was significantly higher in patients with abnormal BPR than in those with normal BPR (18+/-8 vs. 14+/-5 mm Hg, p < 0.05). Exercise-induced perfusion abnormalities including fixed and reversible perfusion defects, and left ventricular cavity dilatation (LVCD) were identified in 72 (69%) of 105 study patients. Left ventricular cavity dilatation indicates subendocardial hypoperfusion and is a marker of diffuse subendocardial ischemia. The prevalence of fixed or reversible perfusion defects was similar between the two groups. Patients with abnormal BPR had the higher prevalence of LVCD as compared to those with normal BPR (47.1 vs. 10%, p < 0.0002). Multiple logistic regression analysis revealed that LVCD was independently associated with abnormal BPR (odds ratio 3.76, 95% confidence interval 1.61 to 8.76). CONCLUSIONS: Exercise-induced abnormal BPRs in patients with HCM are related to subendocardial ischemia during exercise.

Adolescent↗
PubMed1998

Endothelin-1 expression in hearts of transgenic hypertensive mice overexpressing angiotensin II.

Cardiac myocytes and vascular endothelial cells produce endothelin (ET)-1, which has potent hypertrophic effects on cardiac myocytes. Although in cultured cardiomyocytes, angiotensin II (Ang II) was reported to enhance ET-1 production in vitro, it is not known whether ET-1 production is enhanced by Ang II in vivo. We investigated the production and pathophysiologic roles of ET-1 in 20-week-old male transgenic hypertensive mice (THM), in which the renin-angiotensin system (RAS) was markedly activated because of the presence of both human renin and angiotensinogen genes. Systolic blood pressure and the ratio of left ventricular weight to body weight were significantly higher in the THM than in control mice, indicating that THM developed cardiac hypertrophy. ET-1 production was significantly increased in the heart of THM because both ET-1 mRNA expression and peptide levels were significantly higher than in controls. However, circulating plasma ET-1 levels did not differ between the groups, and blood pressure did not change after i.v. injection with a high dose (3 mg/kg) of the ETA/B-nonselective receptor antagonist SB209670. These findings suggest that increased cardiac ET-1 production may contribute to the progression of cardiac hypertrophy and that endogenous ET-1 may not be involved in the short-term modulation of blood pressure in THM of this age.

Angiotensin II↗
PubMed1998

Hypotensive effects of an angiotensin II type 1 receptor antagonist differ between exercised and sedentary rats aged from 4 to 19 weeks.

The hypotensive effects of an angiotensin II type 1 receptor antagonist TCV-116 were accelerated by swimming training in the early period of chronic administration in young rats. In the latter period, however, a severe decrease in blood pressure that appeared during long-term administration of TCV-116 was prevented by swimming training. Therefore exercise may contribute to the stabilization of blood pressure in young rats treated with TCV-116.

Angiotensin Receptor Antagonists↗
PubMed1997

Does endothelin-1 participate in the exercise-induced changes of blood flow distribution of muscles in humans?

Endothelin-1 (ET-1) is an endothelium-derived potent vasoconstrictor peptide that potentiates contractions to norepinephrine in human vessels. We previously reported that the circulating plasma concentration of ET-1 is significantly increased after exercise (S. Maeda, T. Miyauchi, K. Goto, and M. Matsuda. J. Appl. Physiol. 77: 1399-1402, 1994). To study the roles of ET-1 during and after exercise, we investigated whether endurance exercise affects the production of ET-1 in the circulation of working muscles and nonworking muscles. Male athletes performed one-leg cycle ergometer exercise of 30-min duration at intensity of 110% of their individual ventilatory threshold. Plasma concentrations of ET-1 in both sides of femoral veins (veins in the working leg and nonworking leg) and in the femoral artery (artery in the nonworking leg) were measured before and after exercise. The plasma ET-1 concentration in the femoral vein in the nonworking leg was significantly increased after exercise, whereas that in femoral vein in the working leg was not changed. The arteriovenous difference in ET-1 concentration was significantly increased after exercise in the circulation of the nonworking leg but not of the working leg, which suggests that the production of ET-1 was increased in the circulation of the nonworking leg by exercise. The present study also demonstrated that the plasma norepinephrine concentrations were elevated by exercise in the femoral veins of both the working and nonworking legs, suggesting that the sympathetic nerve activity was augmented in both legs during exercise. Therefore, the present study demonstrates the possibility that the increase in production of ET-1 in nonworking muscles may cause vasoconstriction and hence decrease blood flow in nonworking muscles through its direct vasoconstrictive action or through an indirect effect of ET-1 to enhance vasoconstrictions to norepinephrine and that these responses may be helpful in increasing blood flow in working muscles. We propose that endogenous ET-1 contributes to the exercise-induced redistribution of blood flow in muscles.

Adolescent↗
PubMed1997

[Successful pulmonary thromboendarterectomy in a patient with chronic pulmonary thromboembolism].

A 63-year-old patient had been diagnosed with angina pectoris for 5 months and came to us complaining of progressive exertional dyspnea. Echo cardiography showed remarkable pulmonary hypertension and we were prompted to do cardiac catheterization. The catheterization showed the pressure of the main pulmonary artery (PA) as 84/14 (36) mmHg and PA angiography showed a massive embolus in the right main PA. Chest computed tomography and lung perfusion scintigraphy were also compatible with pulmonary embolism. The patient had been treated with anticoagulant for 1 month, but he was not doing well. We decided to remove the embolus surgically. In a median sternotomy, a cardiopulmonary bypass was established with ascending aortic and two caval cannulae. During cooling, the right PA was mobilized within the pericardial reflection. An incision was made in the right PA. An organized thrombus was located at the central PA and extended to the distal segmental PA. Thromboendarterectomy was carried out carefully. To obtain a better operative view, circulatory arrest was introduced intermittently. The left PA was opened and the organized thrombus, located at the bifurcation between the upper and lower branch, was removed. Post-operative PA angiography showed remaining thrombus in the right lower PA, but the pressure of the main PA fell to 27/12 (18) mmHg. Pulmonary thromboendarterectomy by median sternotomy with the aid of deep hypothermia and circulatory arrest was useful to remove the thrombus in the bilateral PA, and to obtain good hemodynamic and symptomatic results.

Endarterectomy↗
PubMed1997

[A case report on prosthetic valve dysfunction of the Carpentier-Edwards pericardial bioprosthesis in the tricuspid position associated with remarkable hypoproteinemia].

A 66-year-old woman underwent a second tricuspid valve replacement because of a malfunction of the Carpentier-Edwards pericardial bioprosthesis (CEP) in the tricuspid position 3.5 years after her first mitral and tricuspid valve replacement. The major symptom was lower leg edema and a serum albumin level ranging between 1.5 g/dl and 2.0 g/dl. The remarkable hypoproteinemia might have resulted from impaired albumin synthesis due to liver dysfunction, hemodilution, protein losing gastroenteropathy, and changes in albumin distribution due to edema. Although the explanted CEP showed neither dehiscence nor calcification of the leaflet, fibrous pannus mainly on the ventricular side restricted the mobility of the corresponding leaflet. Patients receiving a CEP in the tricuspid position should receive careful follow-up.

Aged↗
PubMed1996

Anticoagulant repertoire of the hookworm Ancylostoma caninum.

Hookworms are hematophagous nematodes that infect a wide range of mammalian hosts, including humans. There has been speculation for nearly a century as to the identity of the anticoagulant substances) used by these organisms to subvert host hemostasis. Using molecular cloning, we describe a family of potent small protein (75-84 amino acids) anticoagulants from the hookworm Ancylostoma caninum termed AcAP (A. caninum anticoagulant protein). Two recombinant AcAP members (AcAP5 and AcAP6) directly inhibited the catalytic activity of blood coagulation factor Xa (fXa), while a third form (AcAPc2) predominantly inhibited the catalytic activity of a complex composed of blood coagulation factor VIIa and tissue factor (fVIIa/TF). The inhibition of fVIIa/TF was by a unique mechanism that required the initial formation of a binary complex of the inhibitor with fXa at a site on the enzyme that is distinct from the catalytic center (exo-site). The sequence of AcAPc2 as well as the utilization of an exo-site on fXa distinguishes this inhibitor from the mammalian anticoagulant TFPI (tissue factor pathway inhibitor), which is functionally equivalent with respect to fXa-dependent inhibition of fIIa/TF. The relative sequence positions of the reactive site residues determined for AcAP5 with the homologous regions in AcAP6 and AcAPc2 as well as the pattern of 10 cysteine residues present in each of the inhibitors suggest that the AcAPs are distantly related to the family of small protein serine protease inhibitors found in the nonhematophagous nematode Ascaris lumbricoides var. suum.

Amino Acid Sequence↗
PubMed1996

Partner switching mechanisms in inactivation and rejuvenation of Escherichia coli DNA gyrase by F plasmid proteins LetD (CcdB) and LetA (CcdA).

Escherichia coli DNA gyrase, as well as a free form of its A subunit (GyrA), exists in an inactivated form in cells that overproduce the F plasmid protein LetD (CcdB). We found that the inactivated DNA gyrase and GyrA protein can be rejuvenated in vitro by another F plasmid protein, LetA (CcdA). Using this rejuvenation as an assay, we purified the inactivated GyrA protein to near homogeneity and found it to be complexed with the LetD protein. The complex has a molecular mass of 230 kDa and was suggested to be a complex of two molecules each of GyrA and LetD proteins. The GyrA-LetD complex, in the presence of purified GyrB protein, does not cause DNA cleavage. Therefore, the LetD protein in the GyrA-LetD complex inhibits the gyrase action by a mechanism different from one that involves trapping a covalently linked gyrase-DNA complex. In as much as a free form of the LetD protein has been shown to induce DNA cleavage by gyrase, the LetD protein seems to have two distinct modes of action on DNA gyrase. Rejuvenation of the inactivated GyrA protein by the LetA protein was achieved in vitro, and mechanisms governing this process were examined using the purified proteins. The rejuvenated GyrA protein sediments through sucrose gradients as a single protein species of 190 kDa and is indistinguishable from a free form of GyrA protein. In the same sedimentation experiment, the LetD protein was seen to be complexed with the added LetA protein. Thus, the LetA protein apparently rejuvenates the GyrA protein by removing the bound LetD protein from the inactivated form, followed by formation of a LetA-LetD complex.

Bacterial Proteins↗
PubMed1996

The role of CD11/CD18 integrins in the reverse passive Arthus reaction in rat dermal tissue.

The CD11/CD18 leukocyte integrins are necessary for tissue localization of neutrophils, an early requisite event in inflammation. We have analyzed the contribution of CD11a/CD18 and CD11b/CD18 to local neutrophil accumulation and tissue injury in the reverse passive Arthus reaction in the rat dermis. Experimental groups comprised animals that received an intravenous infusion of (1) recombinant neutrophil inhibitory factor (NIF), a hookworm-derived antagonist of CD11b/CD18; (2) monoclonal antibody to CD11a/CD18 (TA-3); (3) a combination of these agents; (4) a monoclonal antibody to CD18 (WT.3); or (5) saline. Administration of recombinant NIF or anti-CD11a/CD18 monoclonal antibody alone produced a slight reduction in neutrophil accumulation but did not affect edema formation. In contrast, a combination of these antagonists yielded a significant reduction in neutrophil accumulation and a modest reduction in edema, equivalent to levels observed with either anti-CD18 antibodies or animals that were rendered neutropenic. These results indicate that neutrophil infiltration in rat dermal tissue in the reverse passive Arthus reaction is dependent predominantly on the leukocyte integrins CD11a/CD18 and CD11b/CD18 and that either of these integrins is sufficient for neutrophil trafficking in this inflammatory setting.

Animals↗
PubMed1995

Increased soluble form of P-selectin in patients with unstable angina.

BACKGROUND: P-selectin in platelets and endothelial cells mediates adhesive interaction with leukocytes to form thrombi. The purpose of the present study was to investigate the plasma levels of P-selectin in patients with unstable angina and in those with stable effort angina of different pathophysiologies. METHODS AND RESULTS: Plasma P-selectin levels were determined by a monoclonal antibody-based enzyme immunoassay on plasma samples taken from 12 patients with unstable angina, 11 patients with stable effort angina, and 15 healthy volunteers. Patients with unstable angina had angina at rest associated with ECG changes. In patients with unstable angina, plasma P-selectin levels within 1 hour (361 +/- 90 ng/mL) and at 3 hours (282 +/- 56 ng/mL) after angina were significantly (P < .05) higher than those in volunteers (177 +/- 31 ng/mL). Plasma P-selectin levels at 5 hours after attack (242 +/- 46 ng/mL) did not differ from those in volunteers. Although patients with stable effort angina developed angina with ST-segment depressions by treadmill exercise, their plasma P-selectin levels did not change (before, 178 +/- 45; immediately after, 186 +/- 36; and 1 hour after the exercise, 179 +/- 34 ng/mL). CONCLUSIONS: Plasma P-selectin levels after angina increased significantly in patients with unstable angina but did not in patients with stable effort angina. These findings may contribute to understanding of the pathophysiology of the acute coronary syndrome of unstable angina.

Aged↗