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Biomedical subjects

A Wada

Publications and source records attributed to A Wada.

At least 433 records · Page 24Linked to original sources
PubMed1985

Synthesis of aldosterone by a reconstituted system of cytochrome P-45011 beta from bovine adrenocortical mitochondria.

When corticosterone was incubated with cytochrome P-45011 beta purified from bovine adrenocortical mitochondria in the presence of adrenodoxin, NADPH-adrenodoxin reductase and an NADPH generating system, aldosterone as well as 18-hydroxycorticosterone were formed with turnover numbers of 0.23 and 1.1 nmol/min/nmol P-450, respectively. Phospholipids extracted from adrenocortical mitochondria remarkably enhanced the activity of aldosterone formation by the cytochrome P-45011 beta-reconstituted system. The apparent Km and turnover number were estimated to be 6.9 microM and 2.0 nmol/min/nmol P-450 for aldosterone formation in the presence of the lipidic extract. When 18-hydroxycorticosterone was tested as a substrate, cytochrome P-45011 beta showed catalytic activity for aldosterone synthesis with an apparent Km and turnover number of 325 microM and 5.3 nmol/min/nmol P-450, respectively. Carbon monoxide and metyrapone inhibited the production of aldosterone from corticosterone and that from 18-hydroxycorticosterone. These results suggest that conversion of corticosterone and of 18-hydroxycorticosterone to aldosterone occurs through P-45011 beta-catalyzed reaction.

Adrenal Cortex↗
PubMed1985

Mechanism of the effect of droperidol to induce catecholamine efflux from the adrenal medulla.

The study was undertaken to determine whether droperidol had an effect to induce catecholamine efflux from the adrenal medulla as a mechanism for the possible pressor effect of droperidol in patients with pheochromocytoma and, if so, to ascertain the site of action of this compound. The efflux of catecholamines from perfused dog adrenals was increased from control level, 0.15 micrograms/min, to 0.66 micrograms/min by the administration of droperidol 6.6 microM. This effect of droperidol was not dependent on extracellular Ca++, in contrast to acetylcholine. The concomitant secretion of catecholamines and dopamine-beta-hydroxylase was observed in response to acetylcholine and caffeine. However, droperidol-, histamine-, and reserpine-induced catecholamine efflux was not accompanied by dopamine-beta-hydroxylase release. In additional studies, chromaffin granules were isolated with a Millipore filter technique from the bovine adrenal medulla and were incubated for 10 min in an isotonic medium to examine the direct effects of droperidol. Droperidol did not enhance the efflux of catecholamines from the granules in contrast to histamine. The uptake of 14C-norepinephrine into the granules was inhibited by droperidol in a manner comparable to reserpine. The results suggest that droperidol induces catecholamine efflux from adrenal medullary cells and the efflux probably is caused by a nonexocytotic mechanism. A contributing mechanism was an inhibition of catecholamine uptake into chromaffin granules, resulting in an increased diffusion of catecholamines out of the cell.

Acetylcholine↗
PubMed1985

Low activity of angiotensin-converting enzyme in cerebral microvessels of young spontaneously hypertensive rats.

Angiotensin-converting enzyme (ACE) activity was measured in microvessels prepared from cerebral cortices of 4-week-old spontaneously hypertensive rats (SHR). The Vmax value of the ACE activity in the cerebral microvessels of SHR was lower than that of Wistar Kyoto controls of the same age by 25% without difference in Km value for substrate. The low activity of ACE in the cerebral microvessels of young SHR indicates that in this animal model of hypertension the function of ACE is genetically altered in the cerebral microvessels, which may be correlated with the alteration of the cerebral microcirculation and pathogenesis of hypertension.

Animals↗
PubMed1985

alpha-Adrenergic receptors in cerebral microvessels of normotensive and spontaneously hypertensive rats.

In rat cerebral microvessels, we characterized alpha 1- and alpha 2-adrenergic receptors, using [3H]prazosin and [3H]-p-amino-clonidine as radioligands. [3H]Prazosin binding to the cerebral microvessels was saturable and of high affinity (dissociation constant of 78 pM), with a maximum binding of 48 fmol/mg protein. [3H]Prazosin binding reached equilibrium within 15 minutes and was dissociated by the addition of 10 microM phentolamine. The inhibitory effects of isomers of norepinephrine and epinephrine on the binding showed that l-isomers were over 10 times more potent than d-isomers. [3H]-p-Amino-clonidine binding to the cerebral microvessels was saturable and of high affinity (KD = 0.61 nM) with a Bmax of 73 fmol/mg protein. The binding reached equilibrium within 30 minutes, and was dissociated by the addition of 100 microM l-norepinephrine. l-Isomers of norepinephrine and epinephrine were over 10 times more potent than d-isomers in displacing the binding. Thus, both [3H]prazosin and [3H]-p-amino-clonidine bindings to the cerebral microvessels were characterized by saturability, high affinity, reversibility, and stereo-specificity. Furthermore, the specificity of both binding sites was pharmacologically evaluated by the inhibitory effects of various adrenergic agonists and antagonists on the bindings. These data indicate the existence of alpha-adrenergic receptors in the cerebral microvessels and are consistent with the hypothesis that the cerebral microcirculation is regulated by adrenergic innervation. Furthermore, the receptors were measured in cerebral microvessels of spontaneously hypertensive rats and Wistar-Kyoto controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Value of heparinized fine-needle aspiration biopsy in liver malignancy.

The accuracy of diagnosis of hepatic malignancy by percutaneous aspiration biopsy was compared using heparinized and nonheparinized 22-gauge needles. When a heparinized instrument was used, it was able to accurately diagnose malignancy and cytologic types of exfoliative cells. Heparinization also made it possible to recover small tissue fragments and make ultrathin sections for histologic examination. In this way, material suitable for cytologic and histologic examination was obtained from 100% and 95%, respectively, of 59 patients suspected of having hepatic malignancy. A correct diagnosis was made cytologically in 92.5% of patients with hepatic malignancy and in 89.5% of those from whom histologic material was obtained. From a combination of histologic and cytologic results, the overall diagnostic rate for hepatic malignancy was increased to 95%. This procedure proved to be a reliable method for diagnosis of hepatic malignancy.

Biopsy, Needle↗
PubMed1985

[A case of long-term survival of liver metastasis of breast cancer successfully treated with chemotherapy and endocrine therapy].

A 42-year-old woman was diagnosed as having hepatic metastasis two years after radical mastectomy for breast cancer. She was initially treated with oophorectomy and cytotoxic chemotherapy, which resulted in complete regression of the lesion within two years after the start of the treatment. She remained free of the disease until the fifth year thereafter, when she again developed a metastatic lesions in her liver. Since then, she has been treated sequentially with various kinds of chemotherapy and endocrine therapy with a certain degree of response to each treatment. She has survived 12 years and three months after the development of liver metastasis. This patient is the longest survivor of hepatic metastasis from breast cancer in the Japaneses literature.

Adenocarcinoma↗
PubMed1985

Fine structure in the B-A transition of native DNA.

The B-A transition caused by high ethanol concentrations has been studied by the multi-dimensional spectrophotometer equipped with the computer-controlled microbullet. When ethanol concentration is increased, the CD signal at 270 nm of linearized ColEl DNA exhibits a biphasic transition; the first broad one and the second sharp one. The B-A transition of the ColEl DNA is much broader than that of alternative copolymers with shorter lengths. In addition, each PvuII restriction fragment of ColEl DNA has a different transition curve. Therefore the stability of the B-A transition varies along a long DNA molecule. The second transition is speculated to be caused by aggregation. When ethanol concentration is decreased, on the other hand, only a single transition shifted to lower ethanol concentration is observed. Thus the B-A transition curve has a hysteresis. A slow dissociation rate of the aggregation seems to cause the hysteresis.

Bacteriocin Plasmids↗
PubMed1984

Cytohistologic diagnosis of neoplasms of the liver by ultrasonically guided fine-needle aspiration biopsy.

A procedure was developed for obtaining both cytologic and histologic specimens from patients suspected of having hepatic malignancy at the time of ultrasonically guided liver aspiration biopsy using a 22-gauge needle of 0.4 mm inner diameter. The fine needle and the syringe used were heparinized before use to avoid blood coagulation in the materials obtained. With heparinized needle and syringe it was possible to centrifuge the materials obtained and make good smears containing abundant tumor cells, and to obtain small tissue specimens. Histologic specimens obtained with the heparinized needle were fixed in 2.5% glutaraldehyde, postfixed in 1.0% osmium tetroxide, and embedded in epoxy Epon resin. Ultrathin sections were made and usually stained with Azan-Mallory stain. In 41 patients suspected of having hepatic malignancy, a correct diagnosis was made by a combination of these examinations. The sensitivity of this procedure for hepatic malignancy was 100%, and the specificity was 95.7%. Therefore, this procedure is a very reliable method for diagnosis of hepatic malignancy.

Aged↗
PubMed1984

Efflux of 45Ca from bovine adrenal medulla cells in culture caused by nicotinic receptor stimulation.

Efflux of 45Ca was investigated in cultured bovine adrenal medulla cells with its relation to Ca influx. Carbachol caused a rapid and transient efflux of 45Ca from 45C preloaded cells which proceeded with a similar time course to 45Ca influx. Nicotine also caused efflux of 45Ca that is completely antagonized by hexamethonium, while muscarine and pilocarpine did not cause 45Ca efflux. Nicotine-induced efflux of 45Ca was abolished by the Ca-antagonist, diltiazem, and was not observed in Ca-free medium. These observations show that in bovine adrenal medulla, not only the influx of Ca but also the efflux of Ca are caused by nicotinic receptor stimulation and that the efflux of Ca is dependent on the Ca in the medium.

Adrenal Medulla↗
PubMed1984

Involvement of Na influx in acetylcholine receptor mediated secretion of catecholamines from cultured bovine adrenal medulla cells.

The role of sodium (Na) in stimulus-secretion coupling of adrenal medulla was investigated in primary culture of bovine adrenal medulla cells. In Na-free medium, the secretion of catecholamines and influx of 45Ca induced by carbachol were decreased to 30% and 18% of control responses, respectively. Carbachol induced secretion of catecholamines and influx of 45Ca were not inhibited by tetrodotoxin, a highly selective blocker of voltage dependent Na-channels. Carbachol caused a rapid influx of 22Na which was inhibited by hexamethonium but not by tetrodotoxin. Nicotine but not muscarine could be a substitute for carbachol and caused catecholamine secretion, 45Ca influx 22Na influx. Veratridine caused continuous secretion of catecholamines and influxes of 45Ca and 22Na which were blocked by tetrodotoxin. These results indicate that in cultured bovine adrenal medulla cells, stimulation of nicotinic receptor causes the influx of Na through receptor-mediated Na-channels but not through voltage-dependent Na-channels, and that influxed Na may facilitate the influx of Ca which triggers the secretory process. The sodium ion seems to be involved in the stimulus-secretion coupling evoked by physiological secretagogue in adrenal medulla.

Adrenal Medulla↗
PubMed1984

Temperature-induced ultraviolet absorption changes of heavy meromyosin. An application of a computerized spectrophotometer system.

The UV absorption of HMM (heavy meromyosin) was measured at various temperatures with a computerized spectrophotometer system. HMM showed temperature-induced absorption changes in the presence and absence of nucleotides. The temperature-induced absorption change at 293 nm, which is due to conformational changes around the tryptophan residues of HMM, was enhanced in the presence of nucleotides. The temperature-induced difference spectra of HMM + AMPPNP relative to HMM obtained by using a conventional spectrophotometer [(1977) J. Biochem. (Tokyo) 81, 313-320] could be reproduced by subtracting the temperature-induced spectral changes of HMM from those of HMM + AMPPNP.

Adenylyl Imidodiphosphate↗
PubMed1984

Aldosterone biosynthesis by a reconstituted cytochrome P-45011 beta system.

[3H]Corticosterone was incubated with cytochrome P-45011 beta purified to electrophoretic homogeneity from bovine adrenocortical mitochondria, and the reaction products were analyzed by high performance liquid chromatography. The production of aldosterone (21.2 pmol/nmol P-450/min) and 18-hydroxycorticosterone (1.17 nmol/nmol P-450/min) was observed. When lipidic extracts from mitochondria of bovine adrenocortical zona glomerulosa were added to the reaction mixture, the rate of production of aldosterone was increased 28-fold. When [3H]18-hydroxycorticosterone was incubated with cytochrome P-45011 beta, the amount of aldosterone produced was 55.7 pmol/nmol P-450/min in the absence of the lipidic extracts and the enhancing effect of the lipidic extracts was 4-fold.

18-Hydroxycorticosterone↗
PubMed1984

A highly sensitive photometric method for proton release or uptake: difference protometry.

A highly sensitive quantitative method was developed to detect protons released or taken up upon ligand binding. A small change in pH due to proton release or uptake was detected by measuring the difference in the absorbance of a pH indicator upon ligand addition. Owing to the difference detection of protons, the uncertainty of pH due to CO2 dissolution and unknown buffering capacities of sample solutes could be compensated with easy manipulations. Precise calibration of the absolute amount of protons could also be made very easily. The amount of protons measurable by the method is as small as 0.5 nmol that is 10 to 30 times more sensitive than the pH-stat method. We measured the Mg2+ ion-induced proton releases of ADP to confirm the accuracy and reliability of the method and of Escherichia coli ribosomes to show the improvement in sensitivity. The method is useful for protometric studies of biomolecules that are difficult to obtain in large amount.

Acid-Base Equilibrium↗
PubMed1984

Liquid-like state of side chains at the intermediate stage of protein denaturation.

We propose a model for a conformational state of a partially denatured protein molecule which we call CMG (Compact Molten Globule) state. The CMG state is one where the freedom of motion of side chains is released while that of the backbone chain is restricted as in the native state; In other words, it is the state of fixed psi and phi, but of free chi in terms of the dihedral angles of the polypeptide chain. Experimental results of our study on the denatured state of cytochrome c in pH 2, 0.5 M KCl (IIb state) and those in the report of Dolgikh et al. (1981) on acid denatured state (A state) of alpha-lactalbumin support the present model. In IIb state, the 360 MHz 1H-NMR spectrum is similar to that of the fully denatured state, while intrinsic viscosity and diffusion coefficient are close to the native state. A diagram of the internal phase of cytochrome c in the course of acid denaturation is given, and discussions are presented as to whether this molten globule state might be comprehensively applied to other proteins.

Animals↗
PubMed1984

Mg2+-induced proton release from Escherichia coli ribosome and ribosomal RNA.

Escherichia coli ribosome released protons upon addition of Mg2+. The Mg2+-induced proton release was studied by means of the pH-stat technique. The number of protons released from a 70 S ribosome in the Mg2+ concentration range 1-20 mM was about 30 at pH 7 and 7.6, and increased to about 40 at pH 6.5. The rRNA mixture extracted from 70 S ribosome showed proton release of amount and of pH dependence similar to those of the 70 S ribosome but the ribosomal protein mixture released few. This indicates that rRNA is the main source of the protons released from ribosome. The pH titration of rRNA showed that the pKa values of nucleotide bases were downward shifted upon Mg2+ binding. This pKa shift can account for the proton release. The Scatchard plots of proton release from rRNA and ribosome were concave upward, showing that the Mg2+-binding sites leading to proton release were either heterogeneous or had a negative cooperativity. A model assuming heterogeneous Mg2+-binding sites is shown to be unable to explain the proton release. Electrostatic field effect models are proposed in which Mg2+ modulates the electrostatic field of phosphate groups and the potential change induces a shift of the pKa values of bases that leads to the proton release. These models can explain the main features of the proton release.

Binding Sites↗