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N Ohno

Publications and source records attributed to N Ohno.

At least 289 records · Page 16Linked to original sources
PubMed1981

Reaction of C-type cytochromes with the iron hexacyanides. Mechanistic implications.

The reaction of c-cytochromes with iron hexacyanides is similar in mechanism to the interaction of cytochromes with their physiological oxidants and reductants in that the formation of complexes precedes electron transfer. Analysis of the kinetics of oxidation and reduction of a number of c-cytochromes by solving the simultaneous differential equations defining the mechanism is possible, and allows assignment of all six rate constants describing a minimum three-step mechanism [cyto(Fe(+3)) + Fe(+2) right harpoon over left harpoon cyto (Fe(+3)) - Fe(+2) right harpoon over left harpoon cyto(Fe(+2)) - Fe(+3) right harpoon over left harpoon cyto(Fe(+2)) + Fe(+3)]. We find that the usual steady-state approximations are not valid. Furthermore, the ratio of first-order rate constants for electron transfer was approximately 1.0, and no correlation was found between any of the six rate constants and the differences in oxidation-reduction potential of the iron-hexacyanides and different cytochromes c. However, it was found that the ratio of the rate constants for complex formation between ferricytochrome c and potassium ferrocyanide and ferrocytochrome c and potassium ferricyanide was proportional to the difference in oxidation-reduction potentials. Thus the minimum three-step mechanism given above accurately describes the observed kinetic data. However, this mechanism leads to a number of conceptual difficulties. Specifically, the mechanism requires that the collision complexes formed [cyto(Fe(+3)) - Fe(CN)(6) (-4) and cyto(Fe(+2)) - Fe(CN)(6) (-3)] have very different equilibrium constants, and further requires that formation of the collision complexes be accompanied by "chemistry" to make the intermediates isoenergetic. A more complex five-step mechanism which requires that the reactants [Fe(CN)(6) (-4) and ferricytochrome c or Fe(CN)(6) (-3) and ferrocytochrome c] form a collision complex followed by a first-order process before electron transfer, was found to yield results similar to those of the three-step mechanism. However, describing the formation of the collision complex in terms of a rapid equilibrium circumvents conceptual difficulties and leads to a physically reasonable mechanism. In this mechanism the reactants are in rapid equilibrium with the collision complexes and the rate constants for complex formation are controlled by diffusion and accessibility. The collision complexes then rearrange, possibly through conformational changes and/or solvent reorganization, to yield isoenergetic intermediates that can undergo rapid reversible electron transfer. The five-step mechanism can be described by the same rate constants obtained from the three-step mechanism with the appropriate adjustments to account for rapid equilibrium. This more complex analysis associates the oxidation-reduction potential of a particular cytochrome with the relative magnitude of the first-order conversion of the oxidant and reductant collision complexes to their respective intermediates. Thus the cytochromes c control their oxidation-reduction potential by chemical and/or structural alterations. This mechanism appears to be general in that it is consistent with the observed kinetics of 11 different cytochromes c from a wide variety of sources with a range of oxidation-reduction potentials.

Animals↗
PubMed1981

Characterization of solubilized products from the cell wall of Streptococcus pneumoniae during autoplast formation.

The structure of the cell wall of Streptococcus pneumoniae R36a was investigated by means of chemical analysis of the solubilized products formed during autoplast formation. By autoplast formation, almost all of the cell wall components were solubilized as the end products within several hours. Analysis of the solubilized products revealed that the pneumococcal cell wall consists of three macromolecular components, teichoic acid-glycopeptide I (TA-GP I), teichoic acid-glycopeptide II (TA-GP II), and glycopeptide (GP-III). The molecular size of TA-GP I was larger than that of TA-GP II. TA-GP I and TA-GP II were constituted of similar components, galactosamine, 2-acetamido-4-amino-2, 4, 6-trideoxyhexose, glucose, ribitol, choline, phosphate, and peptidoglycan components, but the ratio of teichoic acid to glycopeptide in TA-GP II was higher than that in TA-GP I. TA-GP II was solubilized more slowly than TA-GP I and GP III during autoplast formation. The assembly of the cell wall by TA-GP I and II, and GP III is discussed in connection with the action of autolysin.

Cell Fractionation↗
PubMed1981

Vasopressin and CRF-ACTH in adrenalectomized and dexamethasone-treated rats.

Median eminence corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) and pituitary and peripheral plasma adrenocorticotropin (ACTH) and AVP were measured in male Wistar rats 1 and 2 weeks after bilateral adrenalectomy (ADX), sham operation (SHAM) or dexamethasone-treatment (DEX). Median eminence AVP content was unchanged 1 week after ADX but was significantly elevated 2 weeks after ADX, whereas CRF activity was reduced at 1 week after ADX and returned to control range at 2 weeks. Anterior pituitary ACTH content was elevated but posterior pituitary AVP content was reduced at 1 and 2 weeks after ADX. Plasma ACTH was greatly elevated in ADX rats and reduced in DEX rats, whereas plasma AVP did not differ significantly between these two groups or the control group. When ADX and SHAM rats were laparotomized under ether, plasma ACTH increased greatly, but this elevation was prevented by DEX treatment. The plasma AVP level was elevated in all three groups 2.5 min after onset of stress but returned to the basal range at 20 min. Median eminence CRF and AVP and pituitary ACTH and AVP were not significantly changed after onset of stress. These results indicate that the vasopressin and CRF-ACTH responses were not consistent in the median eminence, pituitary and peripheral plasma and suggest that vasopression is not involved in the feedback and acute stress mechanism of CRF-ACTH secretion. However, we have to measure CRF activity and AVP concentration in the hypophysial portal blood to confirm this conclusion.

Adrenalectomy↗
PubMed1981

Characterization of corticotropin releasing factor (CRF) and arginine vasopressin in median eminence extracts on sephadex gel-filtration.

Hypothalamic median eminence extracts (MEE) were subjected to gel filtration on Sephadex G-25 and G-75 columns to characterize the corticotropin releasing factor (CRF) in relation to arginine vasopressin (AVP). CRF activity was measured using monolayer cultured anterior pituitary cells, and AVP was measured by radioimmunoassay. Sephadex G-25 chromatography of AVP immunoreactivity of MEE (NIAMDD-Rat HE-RP-1) showed three peaks on elution with 0.1 N HCI and four peaks on elution with 0.2M acetic acid. But freshly prepared MEE showed only one peak on elution with 0.1 N HCI. These results suggest that AVP in NIAMDD-Rat HE-RP-1 is polymerized or aggregated on the Sephadex G-25 column, especially when eluted in 0.2M acetic acid. Two main peaks of CRF activity appeared consistently on both Sephadex G-25 and G-75 chromatography. One was near the void volume and the other was retarded. The small molecular CRF (small-CRF) peak was coeluted with immunoreactive AVP and 125I-AVP, on both chromatographies on elution with 0.1 N HCI. The large molecular CRF (big-CRF) appeared between the void volume and I-39 ACTH on Sephadex G-75 chromatography. Big-CRF from freshly prepared MEE had no AVP immunoreactivity. AVP showed CRF activity in pituitary cell cultures, but its CRF activity accounted for no more than 20% of the CRF activity of NIAMDD-Rat HE-RP-1. The log dose-response characteristics of the CRF activities of small-CRF and AVP differed. These results suggest that the median eminence has at least two substances with CRF activity: one is large molecular CRF, and the other is small molecular CRF which may have a vasopressin-like molecular weight. AVP may account for a part of the CRF activity of small molecular CRF but is not identical with genuine CRF.

Animals↗
PubMed1981

Effect of angiotensin II infusion into rat hepatic portal vessel on arginine vasopressin release.

The effects of intrahepatic portal infusion of hyperosmotic substances or angiotensin II (A II) on the plasma arginine vasopressin (pAVP) concentration were investigated. At the beginning of each experiment, rats anesthetized with sodium pentobarbital were infused with 0.9% NaCl at a rate of 0.037 ml/min via the hepatic portal vein for 30 min. Subsequent intraportal infusions of 1.4, 1.8 and 2.7% NaCl for 5 min at a rate of 0.052 ml/min raised pAVP levels from 15.6 +/- 5.2 pg/ml to 26.0 +/- 1.7, 61.5 +/- 8.8 and 37.5 +/- 6.6 pg/ml, respectively. However, subsequent intraportal infusions of 0.9 or 3.6% NaCl and intrajugular infusions of 1.8 or 3.6% NaCl did not further raise the pAVP levels. Intraportal infusions of 21 and 42% sucrose raised pAVP levels to 28.3 +/- 2.9 and 24 +/- 2.0 pg/ml, respectively, whereas glucose did not change the pAVP concentration. When A II was infused via the intraportal vessel at a rate of 30 ng/kg/min for 10, 15 or 30 min, pAVP levels became 29.3 +/- 2.7, 32.1 +/- 4.0 or 25.8 +/- 3.2 pg/kg/min respectively. PAVP levels did not change when the same dose of A II was infused into the jugular vein. The increase of pAVP induced by A II was prevented when angiotensin II analogue (A II A), 1Sar, 8Ileu-A II, was infused into portal vein simultaneously. These results not only suggest that the osmoreceptors exist in the area located somewhere within the hepatic portal vascular bed, but also that the osmoreceptors are somewhat different in nature from those of hypothalamic osmoreceptors. Furthermore, these results suggest that A II in the hepatic portal vein plays a part in controlling AVP release.

Angiotensin II↗
PubMed1981

Pulsatile arginine vasopressin release from the rat hypothalamo neurohypophyseal system during osmotic stimulation.

Arginine vasopressin (AVP) was released in vitro in a pulsatile pattern from the hypothalamo-neurohypophyseal system (HNS) and from the hypothalamus during continuous hyperosmotic stimuli with NaCl or fructose. No significant difference was found in the AVP pulse frequency between the two kinds of hyperosmotic agents. AVP was released from the HNS in a dose-related manner under NaCl stimulation. When the neural lobe was stimulated with NaCl or fructose, a clear AVP pulse pattern was not apparent. Urea failed to evoke a significant AVP release from the neural lobe or HNS. A stepwise increase in NaCl stimulation from 5 to 25 mEq induced a AVP response from the HNS and hypothalamus similar to that under constant stimulation at 25 mEq NaCl. This phenomenon was also found with fructose or sucrose. These results suggest that AVP release from the HNS during continuous osmotic stimulation has a pulsatile pattern regardless of the hyperosmotic substance or osmotic pressure. This AVP release accurately reflects the physiological function of the hypothalamus without modulation in the neural lobe. These results also suggest that the total amount of AVP was related to the osmotic pressure or the osmotic substance but that the frequency of the pulse release was not, moreover, that the AVP release depends not only on the absolute osmotic pressure, but also on the changing rate of osmotic pressure.

Animals↗
PubMed1981

A different distribution of corticotropin releasing factor and arginine vasopressin contents in the hypothalamic nuclei after estrogen administration.

The distribution of corticotropin releasing factor (CRF) and arginine vasopressin (AVP) in hypothalamic nuclei were examined in control and estrogen-treated female rats. CRF activity was measured using monolayer cultured rat anterior pituitary cells and AVP by radioimmunoassay. Hypothalamic nuclei were punched out according to the method of Palkovits. The distribution of CRF activity in 5 different hypothalamic nuclei was similar to that of AVP in intact female rats. CRF activity in hypothalamic nuclei, pituitary ACTH content and plasma ACTH levels in estrogen-treated rats were not significantly different from those in control rats. However, significant elevation of AVP content was observed in the supraoptic and paraventricular nuclei of estrogen-treated rats. These results indicate that CRF and AVP are distributed in similar hypothalamic nuclei, but that they are not identical.

Adrenocorticotropic Hormone↗
PubMed1981

A perifusion method for examining arginine vasopressin (AVP) release from hypothalamo-neurohypophyseal system.

A perifusion method has been developed using rat hypothalamo-neurohypophyseal system (HNS) or neural lobe to investigate the control mechanism of arginine vasopressin (AVP) release. A specific radioimmunoassay (RIA) for AVP was developed to measure AVP in perifusion medium employing anti-AVP serum which was obtained by immunizing rabbits. At a final dilution of 1/12,000, the antiserum showed less than 0.66 and 0.01% cross reactivity with lysine-vasopressin and oxytocin, respectively. But it did not cross reacted with other peptide hormones. The lowest detectable level of vasopressin was 0.5 pg/tube. The intra-assay coefficient of variation averaged 10.4%. The dilution curve of perifused medium was well paralled to the standard curve of AVP assay. AVP release from HNS or neural lobe gradually declined to the stable level in 90-120 min after the initiation of perifusion. Good repeatability of the AVP release from neural lobe was recognized by repeated stimulation with 10 min perifusion of 60 mM KCl at every 60 min. HNS released AVP in dose related manner to the osmotic challenge of sodium or glucose, and AVP release was stimulated from HNS by prostaglandin E2, but not by dopamine. These results show that the perifusion methods using AVP-RIA is a useful method to examine the AVP release from HNS or neural lobe.

Animals↗
PubMed1980

Conformational transitions of the hydrophobic polyacids.

The conformational transitions of the alternating maleic acid copolymers with styrene (MA-St)n, and alpha-methyl styrene (MA-MSt)(n) in aqueous solutions were studied by means of various methods. The following results were obtained: 1) The conformational transitions of (MA-St)n from the compact to extended coil form are observed in various salt solutions, as in aqueous NaCl, and the compact form is stabilized by Rb+ and Cs+, but destabilized by Li+. The coions, Br-, I-, ClO4- and SCN- affect scarcely the stability of the compact form. 2) The temperature coefficient of viscosity d In [eta]/dT of (MA-St)n in 0.09 M NaCl was positive for the compact form, but negative for the coil form, and it reflects the transition. 3) The difference between specific heats for the compact and coil forms of (MA-St)n in 0.03 M NaCl is determined to be about 15% of the corresponding heat of transfer of benzene to aqueous medium. 4) A remarkable dilution of the bound monomeric acridine orange to the compact form (MA-St)n is observed and the dimerization free energy of the dye in the compact form is about -2.1 kcal mole at 25 degrees C. 5) Potentiometric, dilatometric and viscometric titrations of (MA-MSt)n in aqueous NaCl at 25 degrees C show a similar conformational transition to that of (MA-St)n. Also, the difference in the molar extinction coefficient at 261 nm indicates the transition. The compact form of (MA-MSt)n is more unstable than that of (MA-St)n. From the results, the compact conformations and the transition mechanism of both the polyacids were discussed in comparison with the results for the maleic acid copolymers with n-alkyl vinyl ethers.

Journal Article↗
PubMed1979

On the phosphate linkages and the structure of a disaccharide unit of the type-specific polysaccharide of Pneumococcus type XIX.

The structure of the capsular polysaccharide (S-XIX) of Pneumococcus Type XIX, which contains residues of D-glucose, L-rhamnose, 2-acetamido-2-deoxy-D-mannose, and phosphate, has been investigated by acid hydrolysis, treatment with acid phosphatase, mass spectrometry, and 13C-n.m.r. spectroscopy. Phosphoric esters in S-XIX were largely resistant to hydrolysis (4M HCl, 100 degrees, 3 h). With M or 2M HCl at 100 degrees for 3 h, 4-O-(2-amino-2-deoxy-beta-D-mannopyranosyl)-D-glucose 4'-phosphate was liberated. More-drastic hydrolysis of S-XIX gave 2-amino-2-deoxy-D-mannose 3-, 4-, and 6-phosphates, and 4-O-(2-amino-2-deoxy-D-mannopyranosyl)-D-glucose and its 4'-phosphate.

Chemical Phenomena↗
PubMed1978

The frequency in Japanese of genetic variants of 22 proteins. IV. Acid phosphatase, NADP-isocitrate dehydrogenase, peptidase A, peptidase B and phosphohexose isomerase.

This paper presents the results of an electrophoretic survey of approximately 4000 individuals from Hiroshima and Nagasaki for four erythrocyte enzymes: isocitrate dehydrogenase, peptidase A, peptidase B, and phosphohexose isomerase. Also reported are the results for erythrocyte acid phosphatase for a subset of these individuals. The frequencies for the ACPA1 and ACPB1 alleles of the ACP1 locus are in agreement with previously reported results from Japanese populations. Rare variants of ICDS, PEPA, PEPB and PHI occur with frequencies varying from 0.25 to 7.2 per 1000 determinations. The relatively high frequency of the PHI 4HIR1 variant and some unusual features involving the effect of reducing agent on the electrophoretic pattern behaviour of some of the rare PHI variants detected during this study are discussed.

Acid Phosphatase↗
PubMedDate not supplied

Cytochrome oxidase activity and confocal laser scanning microscopic analysis of the hamster submandibular gland using microwave irradiated fixation.

Submandibular glands of the hamster were irradiated in 2% paraformaldehyde (pFA)-0.5% pure glutaraldehyde (PGA) with a microwave (MW) processor at temperatures of 10 degrees and 37 degrees C. Electron microscopy showed that cytochrome oxidase activity was taking place in the mitochondrial intermembrane-intracristal space of the granular duct cell when the temperature of the MW-irradiated fixatives was at 10 degrees C. However, a decrease of this activity was observed when we took care to keep the temperature of the MW-irradiated fixatives at 37 degrees C. The distinct reduction of cytochrome oxidase activity allowed by MW irradiation seems to be due the thermal affects of fixatives. Of course, the possibility cannot be excluded that MW irradiation caused other undetectable membrane damage. Then, we used confocal laser scanning microscopy for the preservation check of the mitochondrial membrane for cytochemistry with MW-irradiated fixation. The fluorescence of rhodamine 123 was observed in the inner spaces of the mitochondria at temperatures of 10 degrees and 37 degrees C. When the same tissues were fixed with 2% pFA using an MW processor as the sole fixative at 10 degrees C, no mitochondrial fluorescence was observed. Cytochrome oxidase activity, by contrast, could be seen in the mitochondrial intermembrane-intracristal spaces in the same condition. Formaldehyde is not the best aldehyde for the purpose of ultrastructural preservation. On the other hand, light and electron microscopy showed that the endogenous peroxidase activity was localized in the nuclear envelope, endoplasmic reticulum, secretory granules, and Golgi apparatus of the hamster submandibular gland using 2% pFA-0.5% PGA fixative with and without MW irradiations at temperatures of 10 degrees and 37 degrees C. Some of the same cells were fixed with only 2% pFA under MW irradiation at 10 degrees C; however, marked diffuseness of the peroxidase activity was observed. Therefore, these results indicated that cytochrome oxidase activity was sensitive to heat with MW-irradiated fixation. Peroxidase activity was very resistant to heat with MW-irradiated fixation but not with pFA solo fixation, therefore, PGA had to be used.

Animals↗
PubMedDate not supplied

Distribution profiles of fluoride in three different kinds of rat bones.

The study was performed to reveal the detailed distribution profiles of fluoride in three different kinds of rat bone--humerus, vertebral arch, and parietal bone--and to compare this with the histological appearance of each bone type. Two groups of Wistar rats were provided water ad libitum containing 0 and 100 ppm fluoride, respectively, for 24 weeks. The fluoride distribution profiles across the bone of the three different bones from the outer to the inner surface were determined by means of an abrasive micro-sampling technique. In control animals, both humerus and parietal bones showed higher concentrations at the periosteal and endosteal surfaces, while the vertebral arch showed additional high levels in the middle (containing trabecular bone) of the tissue. In exposed animals, fluoride levels increased greatly in all three bone types. The vertebral and parietal fluoride distribution profiles were relatively unchanged, although humerus fluoride increased from periosteum to endosteum. The differences in fluoride distribution profiles were apparently related to the histological appearances of these bones. The surface area of bone available and the extent of vascularity appear to affect fluoride uptake.

Animals↗