Search PubMed⌕ Search

Biomedical subjects

N Itoh

Publications and source records attributed to N Itoh.

At least 559 records · Page 31Linked to original sources
PubMed1986

Responses of isolated and perfused dog coronary arteries to acetylcholine, norepinephrine, KCl, and diltiazem before and after removal of the endothelial cells by saponin.

The vascular responses to acetylcholine (ACh), norepinephrine (NE), KCl, and diltiazem were examined before and after removal of endothelial cells by an intraluminal bolus injection of saponin (1 mg) in isolated and perfused dog coronary arteries. Without any precontraction, ACh induced a long-lasting vasodilation in small doses (less than 1 microgram), and an initial brief vasoconstriction was occasionally accompanied in large doses. These vascular responses to ACh were not significantly affected by the pretreatment with propranolol (5 X 10(-6) mol/l). The endothelial removal by intraluminal saponin was confirmed electron microscopically. After 20-60 min of saponin treatment, the responses to drugs were observed and compared with the control. The ACh-induced vasodilation was significantly attenuated by saponin (P less than 0.01), but the ACh-induced vasoconstriction was not affected by it. The vasodilation was blocked by atropine. The NE- and KCl-induced vasoconstrictions and diltiazem-induced vasodilation were not affected by saponin treatment. It is suggested that: (1) ACh produced a vasodilation in the nonpreconstricted condition of dog coronary arteries; (2) the vasodilation caused by ACh is mostly endothelium-dependent, which is considered to be mediated by muscarinic receptors; and (3) the vascular responses to NE, KCl, and diltiazem and the vasoconstriction produced by ACh are not influenced by removal of the endothelium in a relatively large epicardial coronary artery of the dog.

Acetylcholine↗
PubMed1986

Amphibian metallothionein. Induction in the frogs Rana japonica, R. nigromaculata and Rhacophorus schlegelii.

Cadmium (Cd) was injected intramuscularly into three species of frogs to examine the number of isoforms in the induced metallothionein (MT). The induced MT was shown to consist of a single isoform in the three species of frogs Rana japonica, R. nigromaculata and Rhacophorus schlegelii. Native MT in the livers of R. japonica and R. nigromaculata was copper (Cu)-MT and the induced MT in the three species was Cd, Cu-MT, the Cd/Cu ratio in the induced MT being different from species to species. The effect of Cd injections on the concentrations of 10 elements in the livers and kidneys of the Rana species was not significant except for Cu.

Amphibians↗
PubMed1986

Cloning of Drosophila choline acetyltransferase cDNA.

Choline acetyltransferase (EC 2.3.1.6) is the biosynthetic enzyme for the neurotransmitter acetylcholine. To isolate choline acetyltransferase cDNA clones, a cDNA library was constructed from poly(A)+ RNA of Drosophila melanogaster heads, these being one of the richest known sources of the enzyme. By screening the cDNA library with a mixture of three different monoclonal antibodies to Drosophila choline acetyltransferase, we isolated 14 positive clones. Only 1 of these clones was identified to be a Drosophila choline acetyltransferase cDNA clone based on the following evidence. (i) The amino acid sequence deduced from the nucleotide sequence of the cDNA insert completely corresponded to that of several tryptic peptides from choline acetyltransferase. (ii) The cDNA insert hybridized specifically to only the region on Drosophila polytene chromosomes that had been identified as the site of the choline acetyltransferase (Cha) gene by cytogenetic analysis. The cDNA insert consisted of a coding region 2190 nucleotides long, a 3'-noncoding region 284 nucleotides long, and EcoRI linkers. RNA analysis of Drosophila head poly(A)+ RNA with the cDNA insert as a probe showed the choline acetyltransferase mRNA to be approximately equal to 4700 nucleotides long.

Amino Acid Sequence↗
PubMed1986

Vascular responses to intraluminal acetylcholine in isolated, perfused canine and simian basilar arteries.

ACh usually induced biphasic vascular responses, i.e. an initial vasodilation followed by a secondary constriction, in isolated and perfused basilar arteries from the dog. In dog vessels the vasoconstriction induced by ACh was not modified by treatment with phentolamine, at dose levels which suppressed noradrenaline-induced constriction, but was completely blocked by atropine. The dilation to ACh was also blocked by atropine. Physostigmine caused a potentiation of both ACh-induced dilator and constrictor responses. In dogs, ACh-induced constrictor responses were markedly potentiated, and the vasodilatation was slightly but insignificantly enhanced after treatment with intraluminal saponin which removed the endothelia of the arteries. In basilar arteries from monkeys, ACh usually induced a monophasic vasoconstriction in non-treated preparations. In monkey vessels, ACh-induced vasoconstriction was markedly potentiated and frequently vasodilatation appeared after intraluminal saponin treatment. From these results, it is concluded that ACh has primary vasoconstrictor and vasodilator properties in canine and simian cerebral basilar arteries.

Acetylcholine↗
PubMed1986

Kinetic analysis of rat renal tubular transport based on multiple-indicator dilution method.

New methods, based on the multiple-indicator dilution (MID) technique, to study the kinetic relations between the renal tubular cell entry process and the secretory process of drugs are proposed. [3H]Cimetidine was used as a model drug. T-1824-labeled albumin (a vascular reference), [14C]creatinine (an extracellular reference), and [3H]cimetidine were rapidly injected into the renal artery of isolated perfused rat kidney, and normalized outflow-time patterns were secured from rapidly sampled renal venous perfusate. A distributed two-compartment model was fitted to the dilution data by nonlinear least-squares regression, and the influx, efflux, and sequestration rate constants were estimated. Both the influx and the sequestration process (based on the unbound cimetidine concentration) had two transport systems (i.e., Michaelis-Menten-type saturable transport and linear-type passive transport), whereas the efflux process was independent of the intracellular cimetidine concentration. At the low dose of cimetidine the influx clearance was larger than those of the efflux and sequestration, whereas at the high dose no remarkable difference was observed among these three clearances due to the large decrease in the influx clearance. Thus the MID technique is a sensitive new method to study the rate-limited process of renal tubular transport in rats.

Animals↗
PubMed1986

A method for the determination of tritium in environmental water samples by electrolytic enrichment.

In order to determine the tritium concentration in environmental water samples, the electrolytic enrichment was carried out with (St) and without (S) addition of tritiated water of a certain concentration (deuterium-free) to the samples. With the use of the fundamental formulas on electrolytic enrichment, the deuterium concentration (Dit) before electrolysis for an environmental water sample is determined by liquid scintillation counting and densitometry for the sample St. Furthermore, the tritium concentration in the environmental water sample is determined by the above methods for the sample S, and by the substitution of Dit for Di in the formulas. Tritium concentrations in environmental water samples were found to be determined within an accuracy of 10% by this method when Vi/Vf was 14-25. It is considered that this method dispenses with the direct measurement of low deuterium concentrations (Di) before electrolysis, a special technique on the purification of water for densitometry, and moreover, excludes the possibility of cross contamination in the electrolytic enrichment by the spike cell method.

Densitometry↗
PubMed1985

Chloroperoxidase-catalyzed halogenation of trans-cinnamic acid and its derivatives.

Several 2,3-unsaturated carboxylic acids, such as trans-cinnamic acid and its derivatives, were found to be halogenated by chloroperoxidase of Caldariomyces fumago in the presence of hydrogen peroxide and either Cl- or Br-. Cinnamic acid, 4-hydroxycinnamic acid, 4-methoxycinnamic acid, and 3,4-dimethoxycinnamic acid were suitable substrates of chloroperoxidase, and were converted to 2-halo-3-hydroxycarboxylic acid, 2,3-dihydroxycarboxylic acid, decarboxylated halohydrin, or decarboxylated halocompound. However, 4-nitrocinnamic acid and 4-chlorocinnamic acid having electron-attracting groups did not serve as a substrate of the enzyme. The enzyme also did not act on acrylic acid, acrylamide, crotonic acid, fumaric acid, etc. From these data, the enzymatic reactions of chloroperoxidase, concerning the substrate specificity, stereoselectivity, and the reaction mechanism, are discussed on the basis of current knowledge regarding the reaction mechanism of the enzyme. Also they are compared with the chemical reactions of molecular halogen and hypohalous acid.

Carboxylic Acids↗
PubMed1985

Purification of bromoperoxidase from Corallina pilulifera.

Bromoperoxidase was purified from the crude extract of Corallina pilulifera (Corallinaeae, Rhodophyta) and found to be homogeneous upon disc gel electrophoresis by precipitation of ammonium sulfate and sequential column chromatographies of DEAE-Sepharose CL-6B, Sepharose 6B and Cellulofine GC-700m. The purified enzyme did not exhibit optical absorption spectra of a hemoprotein. Therefore, bromoperoxidase of C. pilulifera was completely distinguishable from other haloperoxidases which have heme-irons at the catalytic sites.

Ammonium Sulfate↗
PubMed1985

[The effects of o,p'-DDD on adrenal steroidogenesis and hepatic steroid metabolism].

O,p'-DDD is used for the treatment of adrenocortical carcinoma and Cushing's disease. The inhibitory effect of this drug on the adrenal steroid biosynthesis has been described by many authors, but there are very few reports about the sites of action of this drug on adrenal steroid synthesis. This paper presents in vitro studies on adrenal steroidogenesis and hepatic steroid metabolism. The effects of o,p'-DDD on adrenal 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), 11 beta-hydroxylase (11 beta-OHlase) and 18-hydroxylase (18-OHlase) were examined in vitro using mitochondrial and microsomal fractions prepared by standard centrifugation procedures from the homogenate of bovine adrenal cortices. The concentrations of o,p'-DDD inducing 50% inhibition of 3 beta-HSD, 11 beta-OHlase and 18-OHlase were 8 X 10(-6) M, 1 X 10(-5) M and 3 X 10(-6) M, respectively. This study clearly demonstrates the marked inhibitory effects of o,p'-DDD on 3 beta-HSD in vitro, which was not described previously. The inhibitory effects of o,p'-DDD on these 3 enzymes were diminished by an addition of 0.05 approximately 0.5 mM of cofactor (NADPH or NAD). The results indicate that o,p'-DDD may reduce NADPH or NAD utilization, resulting in the inhibition of steroidogenesis. The effects of o,p'-DDD on hepatic 5 beta-reductase were examined in vitro using rat liver homogenate. O,p'-DDD inhibits 5 beta-reductase, resulting in the decrease of conversion of cortisol to dihydrocortisol and tetrahydrocortisol at the concentration of 10(-3) M.

18-Hydroxycorticosterone↗
PubMed1985

Analysis of multiple indicator dilution curves for estimation of renal tubular transport parameters.

A model is developed to estimate the renal tubular secretory parameters by the multiple indicator dilution (MID) technique. The model allows the calculation of influx (from plasma space to tubular cell), efflux (from tubular cell to plasma space) and sequestration (from tubular cell to luminal side) rate constants. A program using the MID-statistical analysis with least squares fitting (SALS) system for the estimation of these parameters is presented. A trapezoid rule and a non-linear least squares regression were used to carry out definite integrals of cubic spline function and least squares fitting, respectively. The system presented seems to be useful for the precise and rapid estimation of the tubular secretory rate constants.

Animals↗
PubMed1985

Right-sided infective endocarditis combined with mitral involvement in a patient with ventricular septal defect.

An autopsy case of right-sided infective endocarditis combined with mitral valvular involvement in a 20-year-old male Japanese with ventricular septal defect (VSD) was reported. The vegetations were found on the endocardium bordering VSD, tricuspid valve, mural endocardium of the right ventricular outflow tract, and even the pulmonic valve, resulting in forming infective aneurysm of the pulmonary trunk. Streptococcus was morphologically identified in the vegetations obtained at autopsy. On the other hand, smaller vegetations were also noted on the mitral valve. The mechanisms of the mitral extending were discussed when right-sided infective endocarditis associated with VSD preceded that on the mitral valve. The authors think that mitral regurgitation in relation to VSD and right to left shunt through VSD which occur even temporarily may be the most important mechanism responsible for the mitral valvular involvement. Several differences between right-sided and left-sided infective endocarditis were also reviewed.

Adult↗
PubMed1985

Syringadenocarcinoma papilliferum.

A giant tumor developed on the right chest wall of a 52-year-old housewife over a 20-year period. It was accompanied by a spider-like invasion of skin, and a lymph node was palpated in the right axilla. Wide excision of the lesion was carried out. The cross-section of the tumor showed two different appearances. The tumor was histologically diagnosed as a syringadenocarcinoma papilliferum. The post-operative course was uncomplicated and without evidence of recurrence.

Adenocarcinoma, Papillary↗
PubMed1985

Permeability of materials in postglomerular capillary bed and distribution to interstitium of kidney in rats.

Extracellular reference materials are necessary to estimate tubular transport parameters for drugs which are secreted in the kidney. They must set up the flow-limited distribution between plasma and interstitial space, not be distributed to the intracellular space, and be nondegradable in the extracellular space. The capillary permeability of various molecular weight markers in the post glomerular circulation was investigated by performing pulse-injection multiple indicator dilution experiments on isolated rat kidney, using simultaneous injection of T1824-labeled albumin (the plasma reference) and creatinine (or inulin) as the extracellular reference materials. The permeability constants and the gamma values (ratio of the volume in the space of interstitium to that of capillary plasma) for creatinine and inulin were calculated by a nonlinear least squares regression. The gamma values for creatinine were greater than those for inulin, implying that the volume of distribution for creatinine is different from that for inulin. The capillary permeability clearance (CLinflux) for creatinine was 4 times higher than that of inulin, and was 3 times greater than the perfusion rate. Thus, creatinine satisfies the qualification for the flow-limited distribution between plasma and interstitial space. These findings suggest that in the rat kidney creatinine is more suitable for the extracellular reference material than inulin.

Animals↗