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M Iwama

Publications and source records attributed to M Iwama.

88 records · Page 5Linked to original sources
PubMed1982

Modification of a glucoamylase from Aspergillus saitoi with 1-cyclohexyl-3-(2-morpholinyl-(4)-ethyl)carbodiimide.

1. In order to elucidate the structure-function relation of a glucoamylase [EC 3.2.1.3, alpha-D-(1 leads to 4)-glucan glucohydrolase] from Aspergillus saitoi (Gluc M1), the reaction of Gluc M1 with water-soluble carbodiimides was studied. 2. Gluc M1 was inactivated most effectively by 1-cyclohexyl-3-(2-morpholinyl-(4)-ethyl)carbodiimide (CMC) at pH 4.5. 3. Inactivation of Gluc M1 with [14C]CMC proceeded with the incorporation of about 12 CMC moieties. From the results of amino acid analysis, titration of SH group with Ellman's reagent and hydroxylamine treatment at pH 7.0, it was concluded that the crucial sites of modification were carboxyl groups of Gluc M1. 4. The CD spectrum of CMC-modified Gluc M1 (residual activity, ca. 9.8%) suggested that the gross conformation of the native enzyme was retained. 5. In the presence of maltose, when Gluc M1 was incubated with [14C]CMC, ca. 10 CMC moieties were incorporated with a simultaneous decrease in enzymatic activity (30%). The Gluc M1 modified in the presence of maltose was remodified with CMC after elimination of maltose. The CMC-modified Gluc M1 was inactivated completely with the incorporation of ca. 4 CMC moieties. 6. The logarithm of the half-life of the inactivation of Gluc M1 by CMC was a linear function of log [CMC] indicating that one carboxyl group among the modified ones was crucial for inactivation of Gluc M1. 7. The protection by maltose of Gluc M1 from inactivation and the increase in K1 values for maltose of CMC-modified Gluc M1's suggested that a crucial carboxyl group(s) was located near or on subsites 2 and 3.

Aspergillus↗
PubMed1982

The teratogenic mechanism of 6-aminonicotinamide on limb formation of chick embryos: abnormalities in the biosynthesis of glycosaminoglycans and proteoglycans in micromelia.

After a dose of 10 micrograms of 6-aminonicotinamide (6-AN) was administered to day-4- chick embryo in ovo, micromelia was obviously observed in the hind limbs of 7-day chick embryos. We examined the teratogenic mechanism of 6-AN by using the normal or micromelial hind limbs (buds) from day 5 to day 7, with special attention to the biosynthesis of glycosaminoglycan (GAG) and proteoglycan as an index of limb chondrogenesis. The present study provides evidence for abnormalities in the levels of GAG or proteoglycan biosynthesis in the micromelial hind limbs (buds). 1) Both [35S]sulfate and [3H]glucosamine incorporation into GAG per 10 limbs or mg DNA of the micromelia were inhibited, suggesting a decrease of GAG synthesis. 2) The micromelial limbs synthesized low-sulfated chondroitin sulfate (chondroitin) as judged by the 35S/3H ratio, the proportion of unsulfated disaccharide (delta Di-0S), and the result of cellulose acetate electrophoresis, although there were no significant differences in the approximate molecular size of 35S-chondroitin sulfates synthesized between the normal and micromelial limbs. 3) PAPS-synthesizing activity in the micromelial limbs was markedly inhibited, and this may result in the production of low-sulfated proteoglycan. 4) The transition from mesenchymal- to cartilage-specific proteoglycan synthesis did not appear in the micromelial limbs as judged by the sedimentation profiles. 5) 6-AN caused marked reductions in the oxygen consumption and ATP level of the micromelial limbs, thereby causing the defect in PAPS formation. We suggest that these 6-AN-induced sequential molecular defects (the reduction of respiratory activity, ATP and PAPS level, and concomitant interference with GAG and proteoglycan biosynthesis) in the limbs (buds) during the critical period of limb morphogenesis must be major factors resulting in the cartilage growth retardation or disorder, i.e., micromelia.

6-Aminonicotinamide↗
PubMed1982

[Correlation between local cerebral blood flow and EEG in experimental cerebral ischemia].

Varying degrees of cerebral ischemia were produced in adult Wistar rats by clipping of bilateral common carotid arteries with or without induced hypotension. Local cerebral blood flow was measured from bilateral caudate nuclei and parietal cortices using the hydrogen clearance method. EEG was recorded from the same electrode as used for the hydrogen clearance method. The delta power of EEG increased along with decreasing local cerebral blood flow. There was an inverse correlation between the delta power of EEG and local CBF values, ranging from normal to extremely low (10 ml/100 g/min). When local CBF was reduced below 6-8 ml/100 g/min, EEG became isoelectric. Continuous EEG recording might contribute to predict rCBF value in the ischemic lesion.

Animals↗
PubMed1981

Purification and properties of human urine ribonucleases.

1. Two RNases (RNase UL and RNase US) were purified from the urine of human adults by means of column chromatographies on SP-Sephadex C-50, phospho-cellulose and CM-cellulose and gel-filtration on Sephadex G-75 in homogeneous states obtained by SDS-disc electrophoresis. 2. Molecular weights of these RNases determined by gel-filtration were 38,000 and 13,000 for RNase UL and RNase US, respectively. 3. Optimal pH's of urine RNases were 8.0 and 6.75 for RNase UL and RNase US, respectively. 4. Chemical composition of urine RNases was determined. RNase UL contains about 20.7% of neutral sugar and 7.8% of hexosamine. RNase US contains a very small amount of carbohydrate moiety. 5. Base specificity of urine RNases studied with 2',3'-cyclic nucleotides and dinucleoside phosphates as substrates indicated that both RNases were pyrimidine specific and cytosine preferential enzyme, as is bovine pancreatic RNase A. Although base specificity of RNase UL was qualitatively similar to RNase A, that of RNase US was slightly different. That is, RNase US did not hydrolyze UpU and hydrolyzed UpC and 2',3'-cyclic UMP very slowly. 6. Antigenic properties of human urine RNases were studied by Ouchterlony's double diffusion analysis. RNase UL, RNase US, and RNase A were serologically distinguishable.

Adult↗
PubMed1977

Photooxidation and carbethoxylation of a minor ribonuclease from Aspergillus saitoi.

In order to investigate the nature of amino acid residues involved in the active in the active site of a ribonuclease from Aspergillus saitoi, the pH dependence of the rates of inactivation of RNase Ms by photooxidation and modification with diethylpyrocarbonate were studied. (1) RNase Ms was inactivated by illumination in the presence of methylene blue at various pH's. The pH dependence of the rate of photooxidative inactivation of RNase Ms indicated that at least one functional group having pKa 7.2 was involved in the active site. (2) Amino acid analyses of photooxidized RNase Ms at various stages of photooxidative inactivation at pH's 4.0 and 6.0 indicated that one histidine residue was related to the activity of RNase Ms, but that no tryptophan residue was involved in the active site. (3) 2',(3')-AMP prevented the photooxidative inactivation of RNase Ms. The results also indicated the presence of a histidine residue in the active site. (4) Modification of RNase Ms with diethylpyrocarbonate was studied at various pH's. The results indicated that a functional group having pKa 7.1 was involved in the active site of RNase Ms.

Aspergillus↗
PubMed1974

Case report. Fetal cardiac failure resulting from endocardial fibroelastosis.

An autopsy was performed on a female stillborn infant with generalized edema associated with ascites. On gross examination of the heart the pulmonary trunk was atretic from its origin of the heart to the bifurcation. The ductus arteriosus was abnormally wide. The right ventricle was hypoplastic and its endocardium was diffusely thickened. The inner surface of right ventricle appeared pale, obscuring the identification of trabeculae corneae and papillary muscles. At the posterior wall there was an extremely thin lesion where no apparnet cardiac muscle was contained. The tricuspid orifice was stenotic and the valve was hypoplactic. The right atrium was markedly enlarged and its wall was thickened. The foramen avale had patency of the valvular competent type. Atrial septal defect (ASD) was not present. The left ventricle was remarkably dilated with markedly thick wall. Ventricular septal defect (VSD) was present immediately beneath the right coronary cusp of the aortic valve. Light microscopic examination of the right ventricle revealed a marked increase of collagen and elastic fibers with extensive deposits of calcium not only in the endocardium but also in the deep portion of myocardium. Fibroelastosis appeared particularly prominent in the subendocardial layer. The muscle fibers surrounded by these penetrating fibers and deposits of calcium showed degeneration. The entire myocardial layer of the specific area in the right ventricle where the wall was paper-thin was fully replaced by fibers and calcium. Inflammatory cell infiltration was found only at some places of the pericardium. The left ventricular wall also showed fibroelastosis, although the degree of involvement was much less as compared to that seen in the right ventricle. There were no significant pathological changes in both atria.

Adult↗