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O Inanami

Publications and source records attributed to O Inanami.

51 records · Page 3Linked to original sources
PubMed1994

Magnetic resonance imaging of young and aged rat brains under a magnetic field of 7.05 T.

Using a homemade MR imaging probe (Helmoholtz coil), MR images of brains of 5-week-old and 23- or 24-month-old Wistar rats were taken under a magnetic field of 7.05 T (Tesla). The probe was designed to fit the rat head and made by winding thin copper film round an acrylic tube with a 5-cm i.d., 10-cm length and 2-mm thickness. This was adjusted to resonate with the 300 MHz radiofrequency corresponding to the resonance frequency of 1H under a magnetic field of 7.05 T. MR images were obtained by T1-weighted and two-dimensional Fourier transformation techniques. The sagittal and coronal sections were imaged in 1-mm-thick slices. The size of the data matrix was 128 phase-encoded steps. Each image was obtained through eight acquisitions. A comparison of the MR images with those semi-microscopically taken at the same position of the coronal section revealed that the cerebral cortex, hippocampus, hypothalamus and thalamus were clearly imaged by this probe. With aging, MR images of cerebral cortices were observed with decreased signal intensities. Enlargement of the third ventricles and hypertrophy of cranical parietal bones were also recognized in sagittal MR images of aged rats. These observations were more marked in males than in females. From these observations it was concluded that this probe was applicable for MR imaging of rat brains under a magnetic field of 7.05 T.

Aging↗
PubMed1992

Responses of regional cerebral blood flow to intravenous administration of thyrotropin releasing hormone in aged rats.

The effects of i.v. administration of thyrotropin releasing hormone (TRH) on regional cerebral blood flow (rCBF) were examined in both healthy adult (3-5 months old) and healthy aged (24-25 months old) male Wistar rats under halothane anesthesia. The rCBFs in 9 different brain regions-cerebral cortex, caudate putamen, hippocampus, thalamus + hypothalamus, superior colliculus, inferior colliculus, cerebellum, pons, and medulla-were measured by [14C]iodoantipyrine method. In the adult rats, i.v. administration of TRH (300 micrograms/kg) produced significant increases in rCBFs in cerebral cortex, caudate putamen, hippocampus, thalamus + hypothalamus and superior colliculus. In the aged rats, the rCBFs in all brain regions measured did not change significantly by TRH administration. From these results, it is suggested that the system involved in TRH-induced vasodilatation of cerebral blood vessels was impaired with aging.

Aging↗
PubMed1992

Nitric oxide (NO) is involved in increased cerebral cortical blood flow following stimulation of the nucleus basalis of Meynert in anesthetized rats.

The effects of i.v. administration of a nitric oxide (NO) synthase inhibitor, L-NG-nitroarginine (L-NOArg), on the increase in cerebral cortical blood flow (cortical BF), following either electrical stimulation of the nucleus basalis of Meynert (NBM), whose cholinergic fibers project to the cortex, or hypercapnia with 10% CO2 inhalation, were studied in anesthetized rats. Cortical BF was measured using laser Doppler flowmetry. The threshold intensity of electrical stimulation of the NBM (0.5 ms, 50 Hz for 10 s) that induced an increase in regional cortical BF was defined as 1T. The cortical BF was increased on a stimulus intensity dependent manner at 1T-5T intensities tested. L-NOArg was administered cumulatively i.v. starting from 0.3 mg/kg, then 3 mg/kg, and 30 mg/kg. Time interval between each cumulative administration of L-NOArg was approximately 40 min. Three and 30 mg/kg of L-NOArg significant reduced the NBM stimulation-induced increase of cortical BF at intensities of 2T and 3T. The response at an intensity of 5T was reduced only by 30 mg/kg of L-NOArg to about half the control response. The reduced responses at 2T, 3T, and 5T were reversed following the i.v. administration of a physiological precursor of NO, L-arg (300 mg/kg). Inhalation of 10% CO2 for 15 s induced an increase in cortical BF which was not influenced by L-NOArg and L-Arg. These results suggest that NO is a necessary factor in the vasodilation of the cortical BF that is brought about by cholinergic fibers originating in the NBM.

Anesthesia↗
PubMed1990

Responses of regional cerebral blood flow following focal electrical stimulation of the nucleus basalis of Meynert and the medial septum using the [14C]iodoantipyrine method in rats.

The effects of focal electrical stimulation of the nucleus basalis of Meynert (NBM) and the medial septum (MS) on regional cerebral blood flow (rCBF) of the 14 brain regions were examined in halothane-anesthetized rats using the [14C]iodoantipyrine ([14C]IAP) method. The stimulation of the unilateral NBM (with parameters of 200 microA, 0.5 ms, 50 Hz for 60 s) produced significant increases in frontal, parietal and occipital cortical blood flows in the hemisphere ipsilateral to the stimulated NBM; no rCBFs in all other brain regions examined were influenced by the stimulation. The stimulation of the MS produced significant increases in bilateral hippocampal rCBFs, but rCBFs in other brain regions were not influenced by the stimulation. In summary, the response of increase in rCBF following focal electrical stimulation of the NBM or MS is restricted to regions that receive cholinergic nerve projections from the NBM or MS.

Animals↗
PubMed1990

Stimulation of the nucleus basalis of Meynert and substantia innominata produces widespread increases in cerebral blood flow in the frontal, parietal and occipital cortices.

The effect of a focal stimulation of the magnocellular nucleus of the basal forebrain at two different areas, the nucleus basalis of Meynert (NBM) and the substantia innominata (SI), on local cerebral blood flow (CBF) in the frontal, parietal and occipital cortices was examined in urethane-anesthetized rats. The stimulation, either electrically or chemically, of both the NBM and SI produced significant CBF increase in all these 3 cortices ipsilateral to the stimulation site. This fact suggests that activation of neurons originating in the NBM and SI produces widespread increases in local CBF in the ipsilateral cerebral cortex.

Animals↗
PubMed1989

Stimulation of the septal complex increases local cerebral blood flow in the hippocampus in anesthetized rats.

The effects of focal stimulation, either electrically or chemically, of the septal complex (i.e. the medial septal nucleus and the nucleus of the diagonal band) on the local hippocampal cerebral blood flow (Hpc CBF) measured by laser Doppler flowmetry were examined in anesthetized rats. Electrical stimulation of the septal complex produced a current-dependent increase in Hpc CBF that was accompanied by an increase in extracellular acetylcholine (ACh) release in the hippocampus. Microinjection of L-glutamate (50-100 nmol) into the septal complex also produced an increase in Hpc CBF. The L-glutamate-induced vasodilative response of Hpc CBF was markedly attenuated after administration of nicotinic cholinergic blocking agent, mecamylamine (2 mg/kg, i.v.). It was suggested that the cholinergic septohippocampal nerve fibers act as an intracerebral vasodilative neural system by releasing ACh from the nerve terminals in the hippocampus and by activating the nicotinic cholinergic receptor.

Anesthesia↗
PubMed1989

Stimulation of the nucleus basalis of Meynert increases cerebral cortical blood flow in rats.

Focal electrical stimulation of the magnocellular nucleus of the basal forebrain (nucleus basalis of Meynert; NBM) or a microinjection of L-glutamate (50 nmol) into the NBM increased cerebral cortical blood flow in the parietal lobe in urethane-anesthetized rats. The vasodilative responses were elicited only ipsilateral to the site of stimulation. Most of the vasodilative responses were abolished by intravenous administrations of muscarinic and nicotinic cholinergic blocking agents (atropine 0.5 mg/kg and mecamylamine 2 mg/kg). This suggests that the cholinergic projecting system sending fibers from the NBM to the parietal lobe contributes to the vasodilation of the cortex by activating muscarinic and nicotinic cholinergic receptors.

Animals↗
PubMed1988

Contribution of cholinergic vasodilators on the increase in cerebral cortical blood flow responses to the intravenous administration of thyrotropin releasing hormone in anesthetized rats.

The effect of an intravenous administration of thyrotropin-releasing hormone (TRH) on the regional cerebral blood flow in the sensory cortex was studied in halothane-anesthetized adult Wistar rats. The regional cerebral blood flow was continuously monitored with the laser Doppler flowmetry. The cerebral blood flow increased dose-dependently following the administration of 3 x 10(2) and 3 x 10(3) microns/kg TRH. The systemic blood pressure also increased simultaneously. After maintaining the systemic blood pressure at a constant level via a pressure reservoir system, the TRH-induced increases in the cerebral blood flow continued to be observed. In atropinized animals, the blood pressure increased as high as that indicated in non-atropinized animals following TRH administration, but the responses of the cerebral blood flow in the latter were much attenuated. It was suggested that the cholinergic vasodilative system contributed to the TRH-induced increase in cerebral blood flow.

Animals↗
PubMed1988

ESR and spin-trapping study of free radicals in gamma-irradiated solid lysozyme.

Free radicals produced by gamma-irradiation of solid lysozyme were investigated by a technique combining ESR, spin-trapping and enzymatic digestion. MNP and DMPO were used as spin-trapping reagents. The solid lysozyme was first gamma-irradiated and then dissolved in an aqueous solution containing the spin-trapping reagent to stabilize free radicals. The spin adducts of lysozyme were digested to oligopeptides to get ESR spectra having a well-resolved hyperfine structure. The ESR spectra obtained showed that carbon-centered radicals, -CH-, at the side chains of amino acids, and thiyl radicals, -CH2-S., at disulfide bridges were produced in gamma-irradiated solid lysozyme.

Electron Spin Resonance Spectroscopy↗
PubMed1987

Spin trapping of precursors of thymine damage in X-irradiated DNA.

A spin-trapping method combined with ESR spectroscopy was utilized to obtain evidence for the presence of precursor radicals leading to damage in X-irradiated DNA. Two technical improvements were introduced to the conventional spin-trapping method to make possible its application to large molecules such as DNA: prior to X irradiation, sonolysis of aqueous DNA solution by 19.5-kHz ultrasound was made to get a highly concentrated DNA solution and to lower the viscosity of the solution; after precursor radicals in X-irradiated DNA were trapped by a spin-trapping reagent, the DNA was digested to oligonucleotides by DNase I to get an ESR spectrum with a well-resolved hyperfine structure. Thus, it was recognized that the ESR spectrum obtained after X irradiation of the aqueous solution containing DNA and the nitroso spin-trapping reagent 2-methyl-2-nitrosopropane consisted of at least three sets of signals in the DNA. Identification of free radicals was made by comparing the spectrum with that of thymidine, which was precisely examined by a spin-trapping method combining two kinds of spin traps (nitroso and nitrone compounds) with liquid chromatography. As a result, all the signals were identified as the spin adducts of radicals produced at the thymine base moiety of DNA. The 5-hydroxy-5,6-dihydrothymin-6-yl radical was identified as a precursor of 5,6-dihydroxy-5,6-dihydrothymine (thymine glycol), the 6-hydroxy-5,6-dihydrothymin-5-yl radical as a precursor of 6-hydroxy-5,6-dihydrothymine, and the 5-methyleneuracil radical as a precursor of 5-(hydroxymethyl) uracil.

DNA↗
PubMed1987

OH-induced free radicals in 3'-UMP and poly(U): spin-trapping and radical chromatography.

Characterization of OH-induced free radicals using 3'-UMP and poly(U) was performed by a method combining spin-trapping and radical chromatography. A N2O-saturated aqueous solution containing 3'-UMP and 2-methyl-2-nitrosopropane as a spin-trap was X-irradiated. The spin adducts generated by the reactions of OH radicals with 3'-UMP were separated by paired-ion HPLC and the separated spin adducts were identified by ESR spectroscopy. In the case of poly(U), the spin adducts were digested to oligonucleotides with RNase A and then separated and identified in the same manner as 3'-UMP. The free radicals observed for poly(U) were identical to those for 3'-UMP. The 5-yl radical and the 6-yl radical were identified as precursors of various oxidized products of the base moiety, and the 4'-yl radical and 5'-yl radical, formed by H-abstraction at the C-4' and C-5' positions of the sugar moieties, respectively, were identified as precursors of strand breaks. The 1'-yl radical, produced by H-abstraction at the C-1' position of the sugar moiety, was also identified. From the similarity of the free radicals of 3'-UMP and poly(U), it is suggested that the reactivities of OH radicals with nucleotides are identical to those in polynucleotides.

Chromatography, High Pressure Liquid↗
PubMed1986

Reaction of the hydrated electron with histone H1 and related compounds studied by e.s.r. and spin-trapping.

The reactions of the hydrated electron with histone H1, protamine and related compounds (poly-L-lysine, poly-L-arginine and poly-D,L-alanine) were investigated by the spin-trapping technique. In order to identify the radical structure of the spin-adducts originating from macromolecules, the usual spin-trapping technique was developed as follows: N2-saturated aqueous solutions of proteins containing sodium formate were X-irradiated (4.5 kGy) in the presence of 2-methyl-2-nitrosopropane (MNP) as a spin-trap. The side-products due to the self trapping of MNP radicals were then removed from the spin-adducts of the proteins by a Sephadex G-25 column. Finally the spin-adducts were enzymatically digested to transform the broad e.s.r. signals due to slow tumbling of nitroxyl radicals to identifiable ones. The e.s.r. spectra obtained for all samples showed that the deaminated radical, R--CH--CO--NH--(R:amino acid side chain), was produced. Furthermore, polyacrylamide gel electrophoresis of the irradiated protamine and histone H1 indicated reduction of molecular size. These results confirm that hydrated electrons react with proteins and induce the deamination reaction which leads to main-chain scission.

Electron Spin Resonance Spectroscopy↗
PubMed1986

OH-induced free radicals in purine nucleosides and their homopolymers: e.s.r. and spin-trapping with 2-methyl-2-nitrosopropane.

Free radicals produced by X-irradiation of N2O-saturated aqueous solutions of purine nucleosides (2'-deoxyadenosine, adenosine, 2'-deoxyguanosine, 3'-deoxyadenosine, guanosine and inosine) and the corresponding homopolymers (poly A and poly I) have been investigated by the technique of spin-trapping and e.s.r. spectroscopy. 2-Methyl-2-nitrosopropane was used as a spin-trap. For 2'-deoxyadenosine and 2'-deoxyguanosine, the resulting spin-adducts were separated by Bio-Gel P-2 column chromatography and analysed by e.s.r. spectroscopy. For homopolymers, e.s.r. spectra were recorded at 50 degrees C after enzymatic digestion to obtain signals with narrower line width. The e.s.r. signal consisting of only a primary triplet without further splittings, which is consistent with assignment to the trapping of an H-abstraction radical at the C4' position of the sugar moiety, was observed in all cases. For 2'-deoxyguanosine an e.s.r. signal consisting of a secondary triplet was observed. Examinations using other spin-trapping reagents such as PBN, 4-PyOBN and DMPO provided no positive evidence supporting the proposal that this was due to an alpha-nitrogen. The e.s.r. signal consisting of a secondary doublet which further splits into a doublet was observed for 2'-deoxyadenosine, adenosine, 3'-deoxyguanosine, 2'-deoxyguanosine, and inosine, and tentatively associated with a radical centered in the sugar moiety.

Adenosine↗
PubMed1986

OH-induced free radicals in uridine studied by a method combining ESR, spin-trapping, and liquid chromatography.

Free radicals produced by the reactions of OH radicals with uridine were investigated by a method combining ESR, spin-trapping, and liquid chromatography. A N2O-saturated aqueous solution of uridine, containing 2-methyl-2-nitrosopropane as a spin-trap, was X-irradiated and the resulting spin-adducts were separated by gel permeation chromatography and reverse-phase HPLC. ESR and uv-absorbance spectra obtained from the separated spin-adducts show that 5-yl and 6-yl radicals are produced by OH addition to the 5,6 double bond of the base moiety. It is also shown that radicals due to H abstraction from the sugar moiety at the C-4' and C-5' positions are produced.

Chromatography, Gel↗