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K Niki

Publications and source records attributed to K Niki.

At least 19 recordsLinked to original sources
PubMed1997

Aortic blood momentum--the more the better for the ejecting heart in vivo?

OBJECTIVES: The aim of the present study was to test two hypotheses: (1) the momentum of the blood flowing out of the left ventricle toward the aorta (inertia force) plays an important role in the initiation of decay and the maximum rate of decay (peak (-dP/dt)) of left ventricular pressure (P); (2) a normal heart itself generates the inertia force which enhances its function. METHODS: The contribution of the inertia force to (-dP/dt) was theoretically given as rho c alpha, where rho is the blood density, c the pulse wave velocity, and alpha the deceleration rate of aortic blood flow. The correlations of peak (-dP/dt) with rho c alpha and with the time constant (tau) of the pressure decay during isovolumic relaxation, which was considered to represent myocardial relaxation characteristics, were compared in seven dogs. We developed a method of grading the strength of the inertia force, using the phase loop of left ventricular pressure (dP/dt vs. P relation). The method was applied to the records of 25 patients with ischemic heart disease, from which high fidelity left ventricular pressure recordings were available. RESULTS: The correlation of peak (-dP/dt) with rho c alpha was much higher than with tau (0.75 vs. -0.46). 16 of the 25 patients showed evidence of the inertia force. However, other patients showed no inertia force. The strength of the inertia force showed a significant (P < 0.05) correlation with left ventricular end-diastolic pressure (r = -0.46), cardiac index (r = 0.62), stroke volume index (r = 0.69), ejection fraction (r = 0.46), and peak (-dP/dt) (r = 0.56). CONCLUSION: The inertia force of late systolic aortic flow contributed to ventricular relaxation in the normal heart.

Aged↗
PubMed1997

[Transesophageal echocardiographic findings in patients after heart transplantation].

The diagnostic value of transesophageal echocardiography was investigated in heart transplant recipients, i.e., four patients who received orthotopic heart transplantation and one patient who received total heart transplantation. Donor-recipient atrial anastomosis was identified in the four patients with orthotopic heart transplantation, but not in the patient with total heart transplantation. Transthoracic and transesophageal echocardiography detected no thrombus or spontaneous echo contrast in any of the patients. Color Doppler transesophageal echocardiography showed trivial mitral regurgitation in all patients. Total heart transplantation resulted in no protruding suture line and normal atrial cavity size. The patient with total heart transplantation showed some difference in the peak flow velocity of the right and left pulmonary veins (left superior pulmonary vein: 48 cm/sec; right superior pulmonary vein: 86 cm/sec), possibly due to stenosis at the suture line between the left atrium and right superior pulmonary vein, or compression of the right superior pulmonary vein by the anastomosis between the superior vena cava and right atrium. Transesophageal echocardiography was helpful for detecting thrombus in the left atrium and left atrial appendage after heart transplantation, and allowed evaluation of the flow pattern in the pulmonary veins and left atrial appendage as well as abnormal flow in the atrium. In conclusion, transesophageal echocardiography is useful in the follow-up of heart transplant recipients.

Adult↗
PubMed1996

Regulation of the redox order of four hemes by pH in cytochrome c3 from D. vulgaris Miyazaki F.

The assignment of 1H-NMR signals of the heme methyl and propionate groups of cytochrome c3 of D. vulgaris Miyazaki F was performed. The heme assignment was revised for hemes 2 and 3 (sequential heme numbering). Namely, heme 4 is mainly reduced at first with hemes 1, 2 and 3 following it in this order. The p2H titration of heme methyl signals in four macroscopic oxidation states was performed in the p2H range of 5.2 to 9.0. While the heme methyl resonances in the fully oxidized state showed just small changes with p2H, most resonances in the intermediate oxidation states revealed clear p2H dependence. In particular, the methyl resonances of heme 1 shifted significantly in the acidic region. Then, the chemical shifts of beta-CH2 (next to the carboxyl group) of all propionate groups in the fully oxidized state were observed at various p2H in the range of 4.5 to 9.0. Only the propionate group at C-13 (IUPAC-IUB nomenclature) of heme 1 showed a clear change in this p2H range, its titration curve being similar to those of the methyl resonances of heme 1 in the intermediate oxidation states. pKa of the propionate group was 5.95 +/- 0.05. Analysis of the microscopic formal redox potentials was carried out for the observations at p2H 5.2, 7.1 and 9.0. The redox potentials of heme 1 showed the most remarkable p2H dependence, resulting in the change of the order of the redox potentials of four hemes. A significant change was also found in the interacting potential between hemes 1 and 2. In the light of the p2H-titration experiments, the propionate at C-13 of heme 1 was identified as the most plausible ionizable group responsible for the p2H dependence of microscopic redox potentials of heme 1 in the acidic region.

Cytochrome c Group↗
PubMed1995

[The characteristics of 123I-MIBG myocardial scintigraphy in patients with left ventricular pressure-overload diseases].

The purpose of this study was to clarify the clinical significance of 123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy in patients with left ventricular pressure-overload diseases. MIBG scintigraphy was applied to 10 pts with aortic valve stenosis (AS group), 11 pts with hypertrophic obstructive cardiomyopathy (HOCM group), 17 pts with hypertrophic non-obstructive cardiomyopathy (HCM group) and 6 control cases (C group). Mean pressure gradient in AS and HOCM groups was 62 +/- 21 mmHg and 38 +/- 18 mmHg, respectively. Initial myocardial uptake of MIBG (MU) was higher in the AS (1.92 +/- 0.46%) and HOCM (2.27 +/- 0.47%) groups than those in the HCM (1.61 +/- 0.29%) and C (1.50 +/- 0.23) groups. Myocardial clearance of MIBG (MC) was higher in the AS (39 +/- 11%), HOCM (37 +/- 19%) and HCM (28 +/- 17%) groups than that in the C (14 +/- 6%) groups. Heart/mediastinum count ratio (H/M) of AS, HOCM, HCM and C groups was 1.87 +/- 0.29, 2.09 +/- 0.19, 1.98 +/- 0.26, and 2.20 +/- 0.10, respectively. In the cases of AS, positive correlation was observed between mean pressure gradient and MU (r = 0.618, p < 0.05). In conclusion, MU was increased in the case of left ventricular pressure-overload state (AS and HOCM).

3-Iodobenzylguanidine↗
PubMed1995

[Clinical significance of transesophageal echocardiography for evaluation of patients after Bentall's operation: detection of graft failure].

Leakage from the composite graft at the site of coronary anastomosis into the perigraftal space (pseudoaneurysm) is an important complication of Bentall's operation. The clinical value of transesophageal echocardiography (TEE) for detecting this graft failure was evaluated in 30 patients who underwent Bentall's operation or Piehler's modification. Three patients (10%) had perigraftal leakage (pseudoaneurysm). TEE demonstrated the leakage site which was not clearly showed by computed tomography (CT) scan and aortography. The detection rate of the anastomosed native coronary artery was 89% (left: 100%, right: 67%). Interposition graft by Pichler's modification method was detected in 96% (left: 100%, right: 92%) of cases by TEE, but only in 43% (left: 57%, right: 29%) by CT scan (left: p < 0.005, right: p < 0.0001). The detection rate of the right coronary artery, interposition graft to right coronary artery, and their color signals were lower than those of the left coronary artery. TEE has considerable diagnostic value in evaluating patients after Bentall's operation.

Adult↗
PubMed1994

Novel FMN-binding protein from Desulfovibrio vulgaris (Miyazaki F). Cloning and expression of its gene in Escherichia coli.

A gene encoding a novel FMN-binding protein from Desulfovibrio vulgaris (Miyazaki F) was cloned, and its expression system was constructed in Escherichia coli. The 1.4-kilobase pair DNA fragment isolated from D. vulgaris (Miyazaki F) by double digestion with KpnI and SmaI was found to express a protein binding FMN as a prosthetic group under control of the lac promoter in E. coli. This DNA fragment contained several putative open reading frames. The partial amino acid sequence of the polypeptide portion of the purified FMN-binding protein and its tryptic peptides were completely consistent with those deduced from the nucleotide sequence of the third open reading frame in the cloned SmaI-SmaI fragment of D. vulgaris (Miyazaki F) DNA, which may include promoter and regulatory sequences. The nucleotide sequence of FMN-binding protein indicated that the protein is composed of 122 amino acids including an initiator Met residue and lacks a signal peptide for secretion. The main redox potential of the FMN-binding protein was measured as -325 mV using direct current cyclic and differential pulse voltammetric techniques and an electroreflectance method, suggesting that this FMN-binding protein functions as a redox protein like other FMN-binding proteins. Immunoblot analysis of the whole proteins from D. vulgaris (Miyazaki F) clearly indicated that this protein is expressed in this bacteria. However, the protein was found to have a primary structure distinct from those of other FMN-binding proteins and to be the smallest FMN-binding protein yet reported.

Amino Acid Sequence↗
PubMed1991

Full assignment of heme redox potentials of cytochrome c3 of D. vulgaris Miyazaki F by 1H-NMR.

Site-specific heme assignment of the 1H-NMR spectrum of cytochrome c3 of D. vulgaris Miyazaki F, a tetraheme protein, was established. The major reduction of the heme turned out to take place in the order of hemes I, III, IV and II (numbering in the crystal structure). The hemes with the smallest and greatest solvent accessibility were reduced at the highest and lowest potentials on average, respectively. A cooperative interheme interaction was attributed to a pair of the closest hemes, namely, hemes III and IV. This assignment can provide the physiochemical basis for the elucidation of electron transfer of this protein.

Cytochrome c Group↗
PubMed1991

1H NMR studies on ferricytochrome c3 from Desulfovibrio vulgaris Miyazaki F and its interaction with ferredoxin I.

The 1H NMR signals of the heme methyl, propionate and related chemical groups of cytochrome c3 from Desulfovibrio vulgaris Miyazaki F (D.v. MF) were site-specifically assigned by means of 1D NOE, 2D DQFCOSY and 2D TOCSY spectra. They were consistent with the site-specific assignments of the hemes with the highest and second-lowest redox potentials reported by Fan et al. (Biochemistry, 29 (1990) 2257-2263). The site-specific heme assignments were also supported by NOE between the methyl groups of these hemes and the side chain of Val18. All the results contradicted the heme assignments for D.v. MF cytochrome c3 made on the basis of electron spin resonance (Gayda et al. (1987) FEBS Lett., 217 57-61). Based on these assignments, the interaction of cytochrome c3 with D.v. MF ferredoxin I was investigated by NMR. The major interaction site of cytochrome c3 was identified as the heme with the highest redox potential, which is surrounded by the highest density of positive charges. The stoichiometry and association constant were two cytochrome c3 molecules per monomer of ferredoxin I and 10(8) M-2 (at 53 mM ionic strength and 25 degrees C), respectively.

Binding Sites↗
PubMed1990

Estimation of microscopic redox potentials of a tetraheme protein, cytochrome c3 of Desulfovibrio vulgaris, Miyazaki F, and partial assignments of heme groups.

The microscopic formal redox potentials of a tetraheme protein, cytochrome c3 from Desulfovibrio vulgaris, Miyazaki F, were estimated from the chemical shifts of the heme methyl signals in its 1H NMR spectrum. All chemical shifts in the five macroscopic oxidation states were determined for eight of the heme methyl protons by the saturation-transfer method. The electron-distribution probability at each heme in each oxidation state was estimated directly from the chemical shifts. To minimize errors due to interheme pseudocontact contributions, the average electron-distribution probability was used for calculation of the microscopic formal redox potentials. By introducing interacting potentials, 32 parameters were reduced to 10. The 10 parameters were determined analytically from the 9 independent electron-distribution probabilities and 2 macroscopic formal redox potentials. The results showed the presence of a strong positive interaction between a pair of particular hemes. The microscopic formal redox potential changes dramatically with the extent of reduction because of the intramolecular interheme interactions. NMR signals of two hemes were assigned to particular hemes in the crystal structures by nuclear Overhauser effect experiments. The results showed that the hemes with the highest and lowest redox potentials in the one-electron reduction process correspond to hemes I and IV in the crystal structure.

Cytochrome c Group↗
PubMed1990

Redox process of iron-sulfur clusters of the soluble-domain of the membrane-bound hydrogenase from Desulfovibrio vulgaris Miyazaki F studied by resonance Raman spectroscopy.

Resonance Raman spectra of the soluble-domain of a membrane-bound hydrogenase from Desulfovibrio vulgaris Miyazaki F were recorded in different oxidation states. In the oxidized state, the Raman band due to the totally symmetric stretching mode of the iron-sulfur cluster was observed at 341 cm-1, which was attributed to the 3Fe-4S cluster. In the hydrogen-reduced state, only a weak and broad band was observed in its vicinity. During the process of reoxidation, a Raman band assignable to the 4Fe-4S cluster was observed at 333 cm-1 in the first step. Then, the band at 341 cm-1 became stronger and eventually dominated the spectrum. Corresponding changes were observed in the visible absorption spectra of the same sample. It was concluded from these observations that this hydrogenase has both 3Fe-4S and 4Fe-4S clusters and takes on at least three oxidation states, namely, oxidized, intermediate, and hydrogen-reduced ones.

Binding Sites↗
PubMed1986

An epidermal factor which induces thyroid hormone-dependent regression of mesenchymal tissues of the tadpole tail.

Explants of tadpole tail skin secreted a factor which induces the thyroid hormone-dependent regression of the tail mesenchyme. The activity of the factor was not sensitive to digestion with trypsin or pronase. Heating at 120 degrees C but not at 100 degrees C for 20 min destroyed the activity. The factor came out gradually through a dialysis membrane. The factor was retarded on a Sephadex G-10 column and eluted with water after the salts fraction. We suggest that the active principle is a non-proteinaceous substance with a low molecular weight.

Animals↗
PubMed1986

Interrelationship between pituitary and ovarian hormones in normal and neoplastic growth of mammary glands of mice.

While prolactin is a key hormone for normal and neoplastic mammary gland growth, the participation of ovarian estrogen and progesterone is essential for these processes under the normal physiological conditions. Prolactin exerts its influence directly to the glands and indirectly through its luteotropic effects by stimulation of ovarian progesterone secretion. Furthermore, the action of prolactin, whether in promoting normal growth and function or enhancing the progression of neoplastic foci, depends upon the circulating levels of other mammotropic hormones as well as the level of prolactin itself. Presence of estrogen and prolactin is essential for manifestation of progesterone effects on mammary gland growth. Estrogen acts on the mammary glands directly by modulating mammary cell responsiveness to prolactin and indirectly by stimulating pituitary prolactin secretion. While data have been accumulated on the effects of growth hormone on mammary gland growth, the significance of these findings is still unknown. Neoplastic potential of mammary cells is largely dependent upon the susceptibility of the cells to mammotropic hormones.

Animals↗
PubMed1986

Development of pancreatic hyperplasia in female SHN mice receiving ectopic pituitary isografts.

The long-term effects on pancreas of ectopic pituitary grafting at various sites were studied in female SHN mice. Hyperprolactinemia induced by pituitary grafting resulted in an increase in the pancreatic weights, mainly due to hyperplastic proliferation of the pancreatic acinar glands. In addition, islet-cell hyperplasia and adenoma were found in the pituitary-grafted mice. Hyperplastic nodules resembling adenoma of the pancreatic acinar cells were also induced by pituitary grafting. The pancreata of mice with pituitary grafts frequently adhered to the uterus, ovary, and other organs; some of the pancreata further invaded these organs. Control mice bearing no pituitary grafts showed no pancreatic lesions. These results indicate the participation of prolactin in pancreatic tumorigenesis.

Animals↗
PubMed1985

Suppression of normal and preneoplastic mammary growth and uterine adenomyosis with reduced growth hormone level in SHN mice given monosodium glutamate neonatally.

As a step in the evaluation of the role of growth hormone (GH) in mammary tumorigenesis, the effects of neonatal treatment with monosodium glutamate (MSG) on normal and neoplastic mammary growth, plasma levels of GH and prolactin (PRL) and the pattern of estrous cycles were determined in SHN virgin mice. The development of uterine adenomyosis, which is under similar hormonal control, was also examined in these mice. The formation of precancerous mammary hyperplastic alveolar nodules (HAN) was markedly inhibited and the number of 'ghosts', the remnants of regressed HAN, was increased by the single injection of 4 mg MSG on the day of birth, although spontaneous mammary tumorigenesis was not inhibited. The incidence of adenomyosis was suppressed by MSG treatment. Plasma GH level was chronically lower in the MSG-treated mice than in the controls. In contrast, plasma PRL levels and the pattern of estrous cycles were little affected by the treatment. These results indicate an involvement of GH in the development of HAN and uterine adenomyosis in mice.

Animals↗
PubMed1985

Raman scattering from nucleic acids adsorbed at a silver electrode.

Adsorption of nucleic acids at a silver electrode polarized to -0.6 to -0.1 V (vs. Ag/AgCl) was investigated by means of surface enhanced Raman scattering (SERS) spectroscopy. Single-stranded polyriboadenylic acid and thermally denaturated DNA adsorbed at the silver electrode yield two intense bands at 734 and 1335 cm-1 on the SERS spectra. These bands, assigned to the vibrations of adenine residue rings, were much less intense if the SERS spectra were recorded for double-helical complex polyadenylic X polyuridylic acid and native DNA. Moreover, the courses of alkaline denaturation of DNA and its digestion by deoxyribonuclease I were observed by SERS spectroscopy. The results were interpreted as support for the view that intact double-helical segments of nucleic acids are not denatured or destabilized due to their adsorption at the positively charged and roughened surface.

Animals↗