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Biomedical subjects

Y Ohyama

Publications and source records attributed to Y Ohyama.

At least 163 records · Page 9Linked to original sources
PubMed1991

[Mechanism of the B-B' step formation in M-mode echocardiography].

This study analyzed the mechanism involved in the B-B' step formation of the mitral valve movement using pulsed Doppler and color Doppler echocardiography. We examined 24 patients with first degree atrioventricular block (AVB), 26 with old myocardial infarction (OMI), and 34 with a DDD-pacemaker (PM) (16 with complete AV block and 18 with sick sinus syndrome). In 19 of 24 AVB patients, the B-B' step was associated with diastolic mitral regurgitation (DMR). There was a significant positive correlation between the magnitude of the PQ interval and the B-B' step duration (r = 0.94, p less than 0.001). Intravenous administration of 1 mg of atropine shortened the B-B' step duration from 0.15 +/- 0.06 (SD) to 0.05 +/- 0.07 sec (p less than 0.001). Although changes in the PQ interval were well correlated with changes in the B-B' step duration, the P-B-B' step, or PC interval, did not change significantly. In 12 of the 26 OMI patients, the B-B' step and DMR were both observed. The QC intervals of these patients were longer than those of OMI patients without the B-B' step (0.088 +/- 0.03 vs. 0.066 +/- 0.021 sec, p less than 0.05). The P-B-B' step interval was shorter in the OMI patients than in the AVB patients (0.190 +/- 0.029 vs 0.232 +/- 0.033 sec, p less than 0.01). In 28 of 34 patients implanted with a DDD-pacemaker, the B-B' step and DMR were induced by prolonging the AV delay.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Circulation↗
PubMed1990

Structure of chicken 16-kDa beta-galactoside-binding lectin. Complete amino acid sequence, cloning of cDNA, and production of recombinant lectin.

The complete primary structure of chicken 16-kDa beta-galactoside-binding lectin (C-16) was determined. It was composed of 134 amino acid residues and has an acetylated NH2 terminus. A cDNA was also cloned, but no signal sequence was found in the initiator region. The initiator methionine remained as the NH2 terminus of the mature lectin. Although C-16 is distinct from chicken 14-kDa beta-galactoside-binding lectin (C-14), it proved to be a member of the vertebrate 14-kDa-type lectin family. Comparison of the primary structures between the vertebrate 14-kDa-type lectins suggests that C-14 and C-16 were produced by gene duplication of an ancestral lectin gene at a time close to the divergence of birds and mammals. Northern and Southern blot analysis indicated that these isolectins are encoded by individual genes which are differently regulated during the development of the embryo. A recombinant C-16 lectin was produced in Escherichia coli. The product was indistinguishable from the authentic C-16 lectin except that the NH2 terminus of the former was found to begin with free methionine.

Amino Acid Sequence↗
PubMed1990

Unique property of liver mitochondrial P450 to catalyze the two physiologically important reactions involved in both cholesterol catabolism and vitamin D activation.

The cDNA for vitamin D 25-hydroxylase in rat liver mitochondria was transfected in COS cells in order to confirm our previous postulation that both 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha-triol 27-hydroxylation and vitamin D 25-hydroxylation are catalyzed by a common enzyme. As a result it was found that both enzyme activities could be reconstituted from the solubilized extract of mitochondria of these cells, NADPH, NADPH-adrenodoxin reductase and adrenodoxin, giving unequivocal evidence that the two enzyme activities are catalyzed by a common enzyme.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed1990

Effect of chemical carcinogens on cholesterol biosynthetic pathways in the skin of mice.

The metabolism of zymosterol and mevalonic acid was studied in vitro using the skin homogenates of 3-methylcholanthrene (3MC), diazacholesterol-treated and untreated mice. In normal mouse skin only lathosterol was a major metabolite and the other metabolites, cholesta-5,7,24-trien-3 beta-ol, desmosterol, cholesterol and 7-dehydrocholesterol were much less abundant. However, in the skin homogenate of mice treated with 3MC lathosterol production was depressed, while the production of cholesta-5,7,24-trien-3 beta-ol and desmosterol was significantly increased, the cholesterol level being normal or a little higher. In contrast, in the skin homogenate of mice administered diazacholesterol the production of both lathosterol and cholesterol was almost completely blocked with the slightly increased production of cholesta-5,7,24-trien-3 beta-ol and desmosterol. The metabolism in vitro of [2-14C]-mevalonic acid was quite similar to that of zymosterol, and no additional product which might possibly have been produced by the Kandutsch-Russell pathway was observed. Two pathways for cholesterol biosynthesis, therefore, may exist in mouse skin; the first is lanosterol----zymosterol----5 alpha-cholesta-7,24-dien-3 beta-ol----lathosterol----7-dehydrocholesterol----cholesterol, and the second by Bloch: lanosterol----zymosterol----5 alpha-cholesta-7,24-dien-3 beta-ol----cholesta-5,7,24-trien-3 beta-ol----desmosterol----cholesterol. When mouse skin is treated with 3-MC the former pathway is virtually blocked and the latter is stimulated, keeping the level of cholesterol in the tissue constant or a little higher than normal, which seems to be a significant change in the early stage of chemical carcinogenesis.

Animals↗
PubMed1990

[Atrioventricular delay and diastolic mitral regurgitation in patient with DDD pacemaker implantation, and cardiac function].

We examined the mitral valve motion, the mitral valve flow pattern, and changing atrioventricular (AV) delay in 34 patients with DDD pacemaker implantation, using M-mode echocardiography and pulse Doppler echocardiography. In 28 patients, B-B' step and diastolic mitral regurgitation (DMR) were induced by extending the AV delay. 8 of 12 patients who showed B-B' step and DMR with the AV delay less than or equal to 165 mS had heart failures. In such patients, P-B-B' step (DMR) interval was 174 +/- 31 mS shorter than the other patients (216 +/- 26 mS, p less than 0.001), and Q-C interval was 131 +/- 26 mS longer than the other patients (63 +/- 31 mS, p less than 0.001). The minimal value of the AV delay that induces B-B' step and DMR can be decided under the influence of cardiac functions, and this echocardiographic examination is useful, giving us information about the cardiac function of the patients with DDD-PM. B-B' step is the mitral valve motion that corresponds with the DMR, so we can check the DMR through the B-B' step easily.

Aged↗
PubMed1989

Endogenous beta-galactoside-binding lectin expression is suppressed in retinol-induced mucous metaplasia of chick embryonic epidermis.

The fate of endogenous beta-galactoside-binding lectin of chick embryo (14K type) was investigated during the course of skin differentiation. Lectin (14K) was found in keratinized epidermis and was localized mainly in the basal and intermediate cells. However, the protein lectin in the epidermis disappeared when the cultured skin was treated with vitamin A and mucous metaplasia was observed. The synthesis of lectin mRNA was also strongly suppressed by vitamin A in a concentration-dependent manner. On the other hand, in the dermis, in which the lectin was localized in the extracellular matrix, lectin expression was scarcely affected by vitamin A. These results indicated that the lectin was expressed in the keratinized epidermis but that its expression was suppressed in vitamin A-induced mucous-secreting epithelium. The suppression may be a result of a transition of the epidermal regulatory system to one of mucous-secreting epithelium. This is the first finding that 14K lectin expression might be regulated during the course of the epidermal differentiation.

Animals↗
PubMed1989

Feasibility of using [18O2]11-dehydrothromboxane B2 as an internal standard of immunoaffinity purification followed by gas chromatography/selected ion monitoring.

[1,1-18O2]11-Dehydrothromboxane B2 (11-dehydro-TXB2) was prepared by repetitive base-catalyzed hydrolysis of the lactone ring of its [1,1,11-18O3]-analogue, and evaluated for its suitability as an internal standard in gas chromatography/selected ion monitoring (GC/SIM) of 11-dehydro-TXB2. Use of the present [18O2]-analogue as an internal standard may make it a suitable candidate for specific immunoaffinity purification followed by GC/SIM.

Adult↗
PubMed1989

[The clinical application of ultra-low field (0.02 T) MRI for the diagnosis of lung tumors].

Seventy-one patients with lung tumors were studied by thoracic Ultra-low field MRI (L-MRI) and the efficacy of L-MRI is evaluated as compared with the dynamic CT scan. In staging of lung cancer, L-MRI is not useful because of its poor spatial resolution. Both T1 (Inversion recovery) and T2 (long SE) weighted images can differentiate secondary atelectasis from central tumors in 15 out of 18 (78%). This sensitivity is almost equal as that of dynamic CT. IR images with short inversion time (STIR) are particularly useful for their differentiation.

Adult↗
PubMed1989

[Relationship between left atrial diameter and cardiac function in myocardial infarction--assessment of left ventricular end-diastolic pressure by the left atrial index].

To study the assessment of cardiac function in acute myocardial infarction (AMI), we measured left atrial diameter, left ventricular end-diastolic pressure (LVEDP), pulmonary capillary wedge pressure (PCWP), ejection fraction (EF) in 20 patients with acute myocardial infarction. Left atrial diameter was measured using echocardiography and was expressed as left atrial index (LAI, mm/m2) dividing by body surface area. LAI in AMI was 21.3 +/- 2.7 mm/m2 and significantly larger than LAI in normal subject (19.9 +/- 2.0 mm/m2) (p less than 0.05), In AMI, LVEDP was 13.3 +/- 3.4 mmHg, PCWP was 9.0 +/- 2.8 mmHg and EF was 52.3 +/- 14.8%, Relationship (r value) between LAI and LVEDP (r = 0.70, p less than 0.001, y = 0.87 x-5.4 x; LAI, y; LVEDP) was greater than PCWP and LVEDP (r = 0.60, p less than 0.01). LVEDP calculated from LAI using this method was directly measured LVEDP directly measured +/- 2.4 mmHg. In 9 patients, LAI was larger than 20.9 mm/m2, in 8 patients of them LVEDP was higher than 13 mmHg. In 11 patients LAI was smaller than 20.9 mmHg, only in 2 of them LVEDP was lower than 13 mmHg. It concluded that sensitivity was 88.9%, specificity was 81.8%, accuracy was 85.0%. Relationship between LAI and PCWP (r = 0.30), LAI and EF (r = -0.36) were not significant. We can measure LAI repeatedly in AMI non-invasively, and predict LVEDP. Thus, the measurement of LAI is useful in treatment of AMI.

Adult↗
PubMed1988

Purification and characterization of 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol 27-hydroxylase from female rat liver mitochondria.

5 beta-Cholestane-3 alpha,7 alpha,12 alpha-triol 27-hydroxylase (5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol, NADPH:oxygen oxidoreductase (26-hydroxylating), EC 1.14.13.15) was purified from female rat liver mitochondria based on its catalytic activity. The final preparation of the enzyme showed a single major band on the sodium dodecyl sulfate-polyacrylamide gel electrophoretogram. The content of purified enzyme was 12 nmol/mg of protein, and the specific activity was 431 nmol/min/mg of protein. The molecular weight of the enzyme was determined from sodium dodecyl sulfate-polyacrylamide gel electrophoresis as 52,500. The absorption spectra of the purified enzyme and that of the dithionite-reduced CO complex showed peaks at 417 and 450 nm, respectively, indicating the enzyme belongs to the cytochrome P-450 family. Upon reconstitution with the electron-transferring system of the adrenal (adrenodoxin and NADPH-adrenodoxin reductase), the enzyme showed high activity hydroxylating 5 beta-cholestane-3 alpha,7 alpha-12-triol at position 27 with a turnover number of 35.5 min-1 and Km of 6.3 microM. The enzyme activity was completely lost when the electron-transferring system was replaced by that of microsomes (NADPH-cytochrome P-450 reductase purified from rat liver microsomes), confirming that the P-450 enzyme was of the mitochondrial type, but not of the microsomal. The omission of cytochrome P-450, adrenodoxin, or NADPH-adrenodoxin reductase resulted in complete loss of enzyme activity. The specific activity toward 5 beta-cholestane-3 alpha, 7 alpha-diol was less than one-half that toward cholestanetriol and that toward cholesterol was about one-fiftieth. The enzyme showed no activity toward xenobiotics such as benzphetamine, 7-ethoxycoumarin, and benzo[a]pyrene. Its activity was not inhibited by metyrapone and slightly inhibited by aminoglutethimide. The enzyme activity was markedly lowered in an atmosphere of CO/O2/N2, 40/20/40.

Animals↗
PubMed1988

Purification and characterization of vitamin D 25-hydroxylase from rat liver mitochondria.

Vitamin D 25-hydroxylase was purified from female rat liver mitochondria based on the catalytic enzyme activity. The final preparation of cytochrome P-450 was homogeneous judging from sodium dodecyl sulfate-polyacrylamide gel electrophoresis (Mr = 52,500). The specific content of the purified enzyme was 12 nmol/mg of protein. The absorption spectrum of the purified enzyme showed a peak at 417 nm and that of the dithionite-reduced CO complex at 450 nm, indicating the enzyme belongs to the cytochrome P-450 family. Upon reconstitution with the electron-transferring system of the adrenal system (adrenodoxin and NADPH-adrenodoxin reductase), the enzyme showed a high activity in hydroxylating 1 alpha-hydroxycholecalciferol at position 25 with a turnover number of 3.8 min-1 and Km of 54 microM. The enzyme activity was completely lost when the electron-transferring system was repLaced by that of microsomes (NADPH-cytochrome P-450 reductase purified from rat liver microsomes), confirming that the P-450 enzyme was of the mitochondrial type, not the microsomal type. The omission of cytochrome P-450, adrenodoxin, or NADPH-adrenodoxin reductase resulted in complete loss of enzyme activity. The liver mitochondrial cytochrome P-450 hydroxylates vitamin D3 and 1 alpha-hydroxyvitamin D3 at position 25, but did not show any activity toward xenobiotics such as benzphetamine, 7-ethoxycoumarin, and benzo[a]pyrene. The enzyme activity was not inhibited by aminoglutethimide but slightly inhibited by metyrapone. The enzyme activity was markedly inhibited in an atmosphere of CO:O2:N2, 40:20:40.

Animals↗
PubMed1988

Alteration of cholesterol biosynthetic pathways in the skin of mice administered polycyclic aromatic hydrocarbons.

When polycyclic aromatic hydrocarbons were applied solely or together with a tumor promoter (12-O-tetradecanoylphorbol-13-acetate) to the skin of mice, a marked decrease in the level of lathosterol was observed, reflecting a significant change in the metabolism of sterols. Yet the total amount of cholesterol was not changed. When diazacholesterol (a metabolic inhibitor) was administered to mice, both desmosterol and 5 alpha-cholesta-7,24-dien-3 beta-ol accumulated in the skin, whereas the level of lathosterol decreased. These results seem to suggest that a significant portion of lathosterol is formed via 5 alpha-cholesta-7,24-dien-3 beta-ol in addition to the pathway through methostenol. When polycyclic aromatic hydrocarbon was applied to the skin of the mouse treated with diazacholesterol, a significant increase of desmosterol and a marked drop of the level of 5 alpha-cholesta-7,24-dien-3 beta-ol were observed. These results strongly suggest that polycyclic aromatic hydrocarbons perturb the metabolism of sterol in the skin of mice while keeping the total amount of cholesterol unchanged. A similar metabolism also seems to be operating in tumor tissue itself.

Animals↗