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Biomedical subjects

N Itoh

Publications and source records attributed to N Itoh.

At least 541 records · Page 30Linked to original sources
PubMed1987

Molecular cloning and sequence analysis of cDNA for batroxobin, a thrombin-like snake venom enzyme.

Determination of the nucleotide sequence of a cDNA for batroxobin, a thrombin-like enzyme from Bothrops atrox, moojeni venom, allowed elucidation of the complete amino acid sequence of batroxobin for the first time for a thrombin-like snake venom enzyme. The molecular weight of batroxobin is 25,503 (231 amino acids). The amino acid sequence of batroxobin exhibits significant homology with those of mammalian serine proteases (trypsin, pancreatic kallikrein, and thrombin), indicating that batroxobin is a member of the serine protease family. Based on this homology and enzymatic and chemical studies, the catalytic residues and disulfide bridges of batroxobin were deduced to be as follows: catalytic residues, His41, Asp86, and Ser178; and disulfide bridges, Cys7-Cys139, Cys26-Cys42, Cys74-Cys230, Cys118-Cys184, Cys150-Cys163, and Cys174-Cys199. The amino-terminal amino acid residue of batroxobin, valine, is preceded by 24 amino acids. This may indicate that the amino-terminal hydrophobic peptide (18 amino acids) is a prepeptide and that the hydrophilic peptide (6 amino acids), preceded by the putative prepeptide, is a propeptide.

Amino Acid Sequence↗
PubMed1987

Messenger RNA guanylyltransferase from Saccharomyces cerevisiae. Large scale purification, subunit functions, and subcellular localization.

Messenger RNA capping enzyme (GTP:mRNA guanylyltransferase) purified from yeast Saccharomyces cerevisiae consisted of two polypeptides (45 and 39 kDa) and possessed two enzymatic activities, i.e. mRNA guanylyltransferase and RNA 5'-triphosphatase (Itoh, N., Mizumoto, K., and Kaziro, Y. (1984) J. Biol. Chem. 259, 13923-13929). In this paper, we describe an improved procedure suitable for the large scale purification of the enzyme. The steps include glass beads disruption of the cells and several ion-exchange and affinity column chromatographies. The enzyme was purified from kilogram quantities of yeast cells to apparent homogeneity. The purified enzyme had an approximate Mr of 180,000 and consisted of two heterosubunits of 80 and 52 kDa and had the same two enzymatic activities as above. We consider that this is the more intact form of the enzyme. Using the in situ assays on sodium dodecyl sulfate-polyacrylamide gels, RNA 5'-triphosphatase, and mRNA guanylyltransferase activities were located on the 80- and 52-kDa chains, respectively. In agreement with this, the 52-kDa enzyme-[32P]GMP complex was formed on incubation of the enzyme with [alpha-32P]GTP. Guinea pig antisera against purified yeast capping enzyme recognized both 80- and 52-kDa chains in Western blot analysis. The antibody did not cross-react with the enzymes from rat liver. Artemia salina, or vaccinia virus. Nuclear localization of the enzyme was demonstrated by immunofluorescence microscopy.

Acid Anhydride Hydrolases↗
PubMed1987

Involvement of inflammatory leukocytes in hepatic induction of T-kininogen in rat.

Hepatic synthesis as well as plasma levels of T-kininogen, a protein precursor of T-kinin (Ile-Ser-bradykinin), increase in rats following the induction of acute inflammation. Studies have been undertaken to elucidate an involvement of inflammatory leukocytes in the acute-phase response of T-kininogen. Peritoneal exudate cells (PEC) were prepared from rats six days after the intraperitoneal injection of Freund's complete adjuvant. By transfer of these leukocytes into the peritoneal cavity of normal rats, plasma kininogen levels of these recipients increased about threefold after one day. Secretion of kininogen from rat hepatocytes in primary culture was enhanced about twofold by coculturing with PEC. A similar effect was also obtained by adding culture supernatant of these leukocytes into hepatocytes, and the increased levels of kininogen in culture medium of hepatocytes was due to the increased levels of T-kininogen. From these results, it was concluded that leukocytes in the inflammatory site, probably macrophages, release some substance(s) which stimulate(s) the hepatic synthesis of T-kininogen.

Acute Disease↗
PubMed1987

Serial DST, TRH test, and TRH-like immunoreactivity measurements in major affective disorders.

Neuroendocrine functions in depressed patients with major affective disorders were serially investigated by the Dexamethasone Suppression Test (DST), the thyrotropin-releasing hormone (TRH) stimulation test, and the plasma TRH-like immunoreactivity (TRH-LI) measurement. Prior to antidepressant therapy, the sensitivity for nonsuppression to the DST was 36.0%, whereas that for blunted thyroid-stimulating hormone (TSH) response to TRH was 28.0%. Both DST nonsuppression and TSH blunting appeared to be state-related markers for depressed patients. Specifically, a significant increase of maximum TSH response to TRH after 4 weeks of antidepressant therapy was associated with clinical improvement. Plasma TRH-LI in depressed patients was significantly lower than that of healthy controls. It is possible that the lower plasma TRH-LI level is related to the pathophysiology of some depressed patients with major affective disorders.

Adult↗
PubMed1987

Comparison between pial and intraparenchymal vascular responses to sympathetic stimulation under hypercapnic conditions. With special reference to the mechanism for escape phenomenon.

We have shown that secondary vasodilation ('escape' phenomenon) during sympathetic nerve stimulation occurs in the intraparenchymal vessels but not remarkable in the pial vessels. To test a possible role of CO2 accumulation in the brain tissue in this phenomenon, the responses of pial and intraparenchymal vessels to sympathetic nerve stimulation were investigated during hypercapnia in 9 cats by using a video camera photoelectric system. The ipsilateral superior cervical ganglion was electrically stimulated for 5 min during hypercapnia (PaCO2 = 50 +/- 2 mm Hg). The intraparenchymal vessels as well as pial vessels remained constricted throughout the stimulation. Secondary dilation of the intraparenchymal vessels as seen at the later stage of sympathetic stimulation during normocapnia was not observed under the hypercapnic conditions. We assume that the arterial CO2 tension was so high that the constriction of inflow vessels could not result in accumulation of CO2 in the brain parenchyma. The accumulation of chemical metabolites as represented by CO2 is therefore considered to be the most probable mechanism underlying the escape phenomenon of the intraparenchymal vessels.

Animals↗
PubMed1987

Evolutionary origin of cholinergic macromolecules and thyroglobulin.

We have compared the amino acid sequences of proteins that are involved in acetylcholine (AcCho) metabolism and cholinergic neurotransmission: choline acetyltransferase (ChoAcTase), acetylcholinesterase (AcChoEase), and a neuronal alpha subunit of nicotinic AcCho receptor (AcChoR). A comparison of Drosophila ChoAcTase and rat neuronal alpha subunit of AcChoR shows a limited segmental type homology, which may suggest a similar acetylcholine binding site in the two proteins evolving by convergence. We note a global homology of 21-44% identity between Drosophila ChoAcTase and Torpedo AcChoEase. Six homologous segments of 40-60 amino acids cover 38% and 54% of the sequences, raising the possibility of a common evolutionary origin. We also note that mammalian thyroglobulin (TG), the precursor for thyroid hormones, contains an AcChoEase-like sequence at its carboxyl end. This homology raises the possibility that the gene for TG has evolved by gene fusion or condensation (i.e., recruiting a preexisting redundant copy of a gene for AcChoEase during vertebrate evolution). Our results demonstrate that the record of evolutionary history for nervous system proteins can be read across the boundaries of separation between vertebrates and invertebrates. They also provide molecular evidence for the common evolutionary origins of the nervous and endocrine systems in vertebrates--both evolving to make intercellular communication possible.

Acetylcholine↗
PubMed1987

Primary structure of rat liver mannan-binding protein deduced from its cDNA sequence.

cDNA clones encoding rat liver mannan-binding protein (MBP), a lectin specific for mannose and N-acetylglucosamine, were isolated from a rat liver cDNA library carried in lambda gt 11, by screening with affinity purified polyclonal rabbit anti-rat liver MBP antibodies. The nucleotide sequence of the cDNA determined by the dideoxy method revealed the complete amino acid sequence of the MBP (226 residues). The NH2-terminal residue of the MBP, glutamic acid, was preceded by a predominantly hydrophobic stretch of 18 amino acids, which was assumed to be a signal peptide. Near the NH2-terminal, there was a collagen-like domain, which consisted of 19 repeats of the sequence Gly-X-Y. Here, X and Y were frequently proline and lysine. Three proline and lysine residues were hydroxylated, and one of the latter appeared to link to galactose. Computer analysis of several lectins for sequence homology suggested that the COOH-terminal quarter of the MBP is associated with the calcium binding as well as carbohydrate recognition.

Amino Acid Sequence↗
PubMed1987

Treatment of pheochromocytoma with dilevalol.

Dilevalol, an alpha- and beta-blocking agent, has been evaluated in two patients with pheochromocytoma. Dilevalol could be a useful agent for the treatment of pheochromocytoma, especially for the adrenaline-dominant type.

Administration, Oral↗
PubMed1987

Amino acids and peptides. XV. Synthesis of Gln-Val-Val-Ala-Gly and derivatives, a common sequence of thiol proteinase inhibitors and their effects on thiol proteinase.

The Gln-Val-Val-Ala-Gly sequence, which occurs frequently in several natural thiol proteinase inhibitors, and derivatives were synthesized by conventional solution methods and their effect on thiol proteinases were examined. The studies led us to the conclusion that certain of these peptides exhibited a weak inhibitory effect on the thiol proteinase, papain. One of them, Z-Gln-Val-Val-Ala-Gly-OMe, showed a protective effect on papain from natural thiol proteinase inhibitor-induced inactivation. The relationship between structure and activity of these derivatives was studied and certain conclusions were derived on possible mode of action of these inhibitors. From these studies, it was concluded that Z-Gln-Val-Val-OMe was the smallest peptide to exhibit some effect on papain.

Amino Acid Sequence↗
PubMed1986

Na+-dependent p-aminohippurate transport at the basolateral side of the isolated perfused rat kidney.

The uptake of p-amino[3H]hippurate by isolated perfused rat kidney was studied to characterize the mechanism which was responsible for organic anion transport process. A rapid injection multiple indicator dilution technique and the distributed two-compartment model of Sawada et al. (Computer Methods Programs Biomed., 20 (1985) 51) were employed. Some characteristics of a carrier-mediated transport from the antiluminal space to the intracellular space for p-aminohippurate at the basolateral side were demonstrated: the uptake was stimulated by the countertransport effect and showed Na+ dependency. These findings are consistent with p-amino[3H]hippurate's being taken up into the isolated rat basolateral membrane vesicle by Na+-dependent carrier-mediated transport (J. Pharmacol. Exp. Ther. 227 (1983) 122). It is suggested that the multiple indicator dilution technique is a sensitive new method to study the mechanisms of renal tubular transport in the living kidney as an organ.

Aminohippuric Acids↗
PubMed1986

Characterization of nonheme type bromoperoxidase in Corallina pilulifera.

Bromoperoxidase was purified from the crude extract of Corallina pilulifera to be homogeneous upon polyacrylamide disc gel and sodium dodecyl sulfate-polyacrylamide gel electrophoreses according to the procedures previously reported (Itoh, N., Izumi, Y., and Yamada, H. (1985) Biochem. Biophys. Res. Commun. 131, 428-435). The enzyme had a molecular weight of approximately 790,000 and was composed of 12 subunits of identical molecular weights (Mr 64,000). Hexagonal molecular shapes of the enzyme were observed by electron microscopy. The isoelectric point of the enzyme was 3.0, and the predominance of acidic amino acids was revealed by amino acid analysis of the enzyme. The enzyme was specific for I- and Br- and inactive toward Cl- and F-. The optimum pH of the enzyme was 6.0, and the enzyme was stable in a range from pH 5.0 to 11.0. The enzyme had no hemeor flavin-like compounds as a prosthetic group. Plasma emission spectroscopy revealed that the enzyme contains 2.3 +/- 0.2 atoms of iron and 1.6 +/- 0.1 atoms of magnesium/molecule of protein. Hence, bromoperoxidase of C. pilulifera was distinct from other haloperoxidases and many peroxidases, which are hemoproteins.

Amino Acids↗
PubMed1986

[The effect of metoclopramide and dopamine on mineralocorticoid secretion--in vivo and in vitro studies].

There is considerable information suggesting that dopamine is a physiological regulator of aldosterone secretion. Metoclopramide, a specific dopamine antagonist, elicits a rapid rise in plasma aldosterone independent of the known aldosterone-regulating factors. However, the mechanism and the site of action of metoclopramide, whether adrenal or extra-adrenal, in stimulation of aldosterone production remain to be defined. The present studies were designed to investigate the mechanism of dopaminergic control of corticosteroid secretion and to determine at which step in the aldosterone biosynthetic pathway metoclopramide and dopamine exert their effect. Plasma concentrations of progesterone, 11-deoxycorticosterone (DOC), and cortisol were not altered by a bolus intravenous administration of 10 mg metoclopramide in 8 healthy male volunteers. Metoclopramide increased plasma aldosterone from 6.9 +/- 2.8 (Mean +/- 2SD) ng/100 ml to a maximum level of 18.2 +/- 4.7 ng/100 ml, 18-hydroxycorticosterone (18-OHB) from 12.6 +/- 6.5 ng/100 ml to a maximum of 41.3 +/- 7.3 ng/100 ml and corticosterone from 0.36 +/- 0.09 microgram/100 ml to a maximum of 0.85 +/- 0.22 microgram/100 ml. The aldosterone, 18-OHB and corticosterone responses displayed a parallel time course, with a significant response of each occurring within 5 minutes after metoclopramide administration. These data suggest that metoclopramide may modulate the activities of 18-hydroxylase and 11 beta-hydroxylase. Studies in vitro revealed that metoclopramide (10(-8)-10(-4) M had little effect on basal production of aldosterone, 18-OHB and corticosterone from human adrenal slices. Dopamine (10(-4) M) did not alter the basal secretion of aldosterone, 18-OHB and corticosterone, but suppressed the secretion of these 3 mineralocorticoids by ACTH, which were diminished by addition of 10(-4) M metoclopramide. There was a concentration-dependent inhibitory effect of dopamine on conversion of corticosterone to 18-OHB and DOC to corticosterone in vitro using bovine adrenal mitochondrial fractions. IC50 of dopamine inhibiting 18-hydroxylation and 11 beta-hydroxylation were 7.5 X 10(-7) M and 9.5 X 10(-4) M, respectively. It appears that physiological concentration of dopamine can modulate the activity of 18-hydroxylase enzyme. In summary, it can be concluded that the in vivo and in vitro studies are compatible with a view that dopamine has a physiological role in the regulation of aldosterone by modulating the activity of 18-hydroxylase enzyme.

18-Hydroxycorticosterone↗
PubMed1986

Neurological manifestations in xeroderma pigmentosum.

Xeroderma pigmentosum is an unusual neurocutaneous disorder. Recent studies have classified patients with xeroderma pigmentosum into 10 groups by somatic cell hybridization methods. In this report we describe 32 patients with Group A xeroderma pigmentosum, including 1 patient with an atypical case, who were assessed for neurological complications. Of these patients, 17 had microcephaly, 13 short stature, and 21 mental retardation. In patients over 7 years of age, sensorineural deafness and spinocerebellar signs such as nystagmus, dysarthria, tremor, and ataxia were frequently observed; no patients below 7 years of age had such neurological complications. Electroencephalographic studies revealed abnormal slow and low voltage background activity. Two patients had focal abnormal discharges, one of whom developed versive seizures. Cranial computed tomographic scans revealed abnormalities, including ventricular dilatation, cerebral atrophy, cerebellar and brainstem atrophy, and cranial bone thickening. A patient with an atypical case of Group A xeroderma pigmentosum had less skin and neurological involvement, and higher levels of postultraviolet colony-forming ability and host cell reactivation than did a typical Group A case. It is possible that these less severe cytological findings are responsible for the less severe skin lesions and neurological complications noted clinically.

Adolescent↗